EP3116964A1

EP3116964A1 - Stretch releasable adhesive article, usage and manufacturing the same

Info

Publication number: EP3116964A1
Application number: EP14885414.4A
Authority: EP
Inventors: Jun Li; Jingjing Ma
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2014-03-11
Filing date: 2014-03-11
Publication date: 2017-01-18
Also published as: KR20160133476A; WO2015135134A1; EP3116964A4; CN106459683A

Abstract

A stretch releasable adhesive tape is described including a backing and a first layer of a pressure-sensitive adhesive composition coated on at least one surface of said backing, the adhesive tape having a thickness between 0.05 and 0.10mm, and elongation at break between 850% and 2200%), being capable of being firmly bonded to a substrate and thereafter being removable therefrom after being stretched at an angle at 90°degree or greater degree from the surface of a substrate without rupturing prior to the removal of the tape from the substrate and without leaving substantial pressure-sensitive adhesive residue on the substrate, wherein the pressure sensitive adhesive contains a functional group terminated polyurethane. An electronic device comprising a stretch releasable adhesive tape of the invention is also described.

Description

STRETCH RELEASABLE ADHESIVE ARTICLE, USAGE

AND MANUFACTURING THE SAME

Field of the Invention

The present invention relates to adhesive tapes, more particularly to a stretch releasable adhesive tapes.

Background of the Invention

Adhesive tapes, such as, for example, pressure-sensitive adhesive tapes, are usually firmly bonded to substrates because subsequent separation of the tapes from the substrates is neither intended nor desired. However, there are removable adhesive tapes wherein the adhesives are specifically formulated to allow clean and easy removal from substrates after use. U.S. Pat. No. 6,527,900 discloses a removable adhesive tape that can be applied to a substrate. The adhesive tape becomes firmly bonded after being attached to the substrate, but can be easily removed without damaging the substrate by simply stretching it in a direction substantially parallel, i.e., less than about 35 ° degree, to the surface of the substrate. In some occasions, it will not be workable to remove such an adhesive tape from a direction parallel or less than 35 ° degree if the tape is used in a highly compacted electronic device, for example, a mobile phone to adhere an inside placed battery with its recessed substrate.

SUMMARY OF THE INVENTION

Therefore, it is desirable to obtain a stretch releasable adhesive tape capable of being firmly bonded to a substrate and thereafter being removable there from after being stretched at an angle at 90°degree or greater degree from the surface of the substrate without the backing rupturing prior to the removal of the tape from the substrate and without leaving substantial pressure-sensitive adhesive residue on the substrate.

A first aspect relates to a stretch releasable adhesive tape including a backing having a first surface and a second surface, the backing being made of cross-linked thermoplastic polyurethane, and a pressure sensitive adhesive disposed on at least one of the first and second surfaces. The pressure sensitive adhesive is formed from an acrylic copolymer comprising a functional group terminated polyurethane. The adhesive tape has a thickness ranged between 0.05 and 0.10mm and a lengthwise elongation at break ranged between 850% and 2200%, the adhesive tape being capable of being firmly bonded to a substrate and thereafter being removable therefrom after being stretched at an angle at 90° degree or greater degree from the surface of the substrate without rupturing prior to the removal of the adhesive tape from the substrate and without leaving substantial pressure-sensitive adhesive residue on the substrate.

A second aspect relates to a A stretch releasable adhesive tape including a substrate having a first surface and a second surface, wherein the substrate includes cross-linked thermoplastic polyurethane and a pressure sensitive adhesive disposed on at least one of the first and second surfaces, wherein the pressure sensitive adhesive is formed from a reaction mixture comprising:

(i) 25 weight percent to 90 weight percent of acrylic copolymer based on a total weight of the reaction mixture;

(ii) 5 weight percent to 30 weight percent of functional group terminated polyurethane polymer based on a total weight of the reaction mixture;

(iii) 0 weight percent to 45 weight percent of tackifier based on a total weight of the reaction mixture, and

(iv) 0.02 weight percent to 0.1 weight percent of cross-linker based on a total weight of the reaction mixture.

A third aspect relates to a stretch releasable adhesive tape being capable of being firmly bonded to a substrate and thereafter being removable therefrom after being stretched at an angle at 90° or greater degree from the surface of the substrate without leaving residue. The tape includes a backing layer having a first and second opposed major surfaces, wherein the backing layer comprises cross-linked polyurethane;

acrylic copolymer adhesive disposed on at least one of the first and second opposed major surfaces; wherein the acrylic adhesive comprises functional group terminated polyurethane polymer to increase bonding with the backing layer such that the cohesion between the backing layer and adhesive is greater than adhesion between the substrate and the adhesive.

A fourth aspect relates to a stretch releasable adhesive tape including a backing and a first layer of a pressure-sensitive adhesive composition coated on at least one surface of said backing, the adhesive tape having a thickness between 0.05 and 0.10mm, and elongation at break between 850% and 2200%) , being capable of being firmly bonded to a substrate and thereafter being removable therefrom after being stretched at an angle at 90°degree or greater degree from the surface of a substrate without rupturing prior to the removal of the tape from the substrate and without leaving substantial pressure-sensitive adhesive residue on the substrate, wherein the pressure sensitive adhesive contains a functional group terminated polyurethane. An electronic device comprising a stretch releasable adhesive tape of the invention is also described.

A fifth aspect relates to a method of making a stretch releasable adhesive tape. The method includes making a modified acrylic copolymer, making a cross-linked polyurethane layer, and then coating the modified acrylic copolymer on the polyurethane layer. The process of making modified acrylic copolymer includes preparing acrylic adhesive solution by mixing acrylic copolymer and functional group terminated polyurethane; providing a mixture of a cross-linking agent with the acrylic adhesive solution; coating the mixture on a liner; and curing the liner to form an adhesive layer by putting the coated liner into an oven. The functional group terminated polyurethane may be selected from aliphatic sulfonic acid terminated polyurethane, or aromatic hydroxyl terminated polyurethane, or their combinations. The process for making the polyurethane layer including the following steps of:

preparing a polyurethane solution by mixing aromatic polyester-based thermoplastic polyurethane with mehylethylketone; crosslinking the polyurethane solution; coating the polyurethane solution on a liner; and finally curing the liner under the condition of around 80°C for a predetermined period of time.

The present invention, a stretch releasable adhesive tape can be used in many electronic devices. An electronic device may be, for example, a cell phone, a personal assistance device, a music player such as, MP3, a MP4, and a laptop computer and so on. The electronic device is intended to represent one desirable end use application for the stretch releasable adhesive article, but it will be recognized that the stretch releasable adhesive article may be used in a wide variety of other end-use

applications.

As an exemplary embodiment, the electronic device may be a mobile phone. The phone includes a battery, a battery receiving surface, and a stretch releasable adhesive article for releasably bonding the battery to the battery receiving surface. When the battery is need to be separated from the battery receiving surface for fixture purpose or any other purpose, due to the space limitation of the electronic device, a stretch force is applied to pull the adhesive tape out at an angle around 90°degree or greater degree from the battery surface. It is desirable that the stretch releasable adhesive article can removed without rupturing prior to the removal thereof from the battery surface and without leaving adhesive residue on the battery surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows an exemplary structure of a stretch releasable adhesive tape;

Fig.2 shows an illustration of maximum bonding strength test being used to test the properties of the stretch releasable adhesive tape in Fig. 1;

Fig. 3 shows an illustration of stretch releasing test of the stretch releasable adhesive tape in Fig. 1;

Fig. 4 shows an illustration of adhesive tape drop resistance test of the stretch releasable adhesive tape in Fig. 1; and

Fig. 5 shows comparison of stretch releasing performance of the stretch releasable adhesive tape in Fig. 1.

DETAILED DESCRIPTION OF THE INVNETION

As used herein, the term "a", "an", and "the" are used interchangeably and mean one or more; "and/or" is used to indicate one or both stated cases may occur, for example A and/or B includes, (A and B) and (A or B); "at least two" includes all numbers of two and greater (e.g., at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.). "at least one" includes all numbers of one and greater (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.). "cross-linking" refers to connecting two pre-formed polymer chains using chemical bonds or chemical groups in order to increase the modulus of the material; "crosslinked" refers to two pre-formed polymer chains were connected using chemical bonds or chemical groups in order to increase the modulus of the material; "cross-linker" and/or "cross-linker" refers to crosslinking agents, "polymer" and "polymeric" and "polymerized product" refer to materials that are homopolymers, copolymers, terpolymers, and the like, "copolymer" and "copolymeric" refer to a polymeric material that is formed from at least two monomers. That is, a copolymer is a subset of polymers that excludes only homopolymers. "acrylate" refers to compounds containing either an acrylate or a methacrylate structure or combinations thereof. When referring to a range, the endpoints of the range are considered to be in the range. For example, the expressions "in a range from x to y", "in a range of x to y", "in an amount from x to y", "in an amount of x to y", or similar expressions include the endpoints x and y.

The term "glass transition temperature" or "Tg" refers to the temperature at which a material changes from a glassy state to a rubbery state. In this context, the term "glassy" means that the material is hard and brittle (and therefore relatively easy to break) while the term "rubbery" means that the material is elastic and flexible. For polymeric materials, the Tg is the critical temperature that separates their glassy and rubbery behaviors. If a polymeric material is at a temperature below its Tg, large-scale molecular motion is severely restricted because the material is essentially frozen. On the other hand, if the polymeric material is at a temperature above its Tg, molecular motion on the scale of its repeat unit takes place, allowing it to be soft or rubbery. The glass transition temperature of a polymeric material is often determined using methods such as Differential Scanning Calorimetry. Any reference herein to the Tg of a monomer refers to the Tg of a homopolymer prepared from that monomer.

Now referring to Fig. 1, a stretch releasable adhesive tape 2 includes a release liner 4, a first layer of adhesive 6 attached to the release liner, a backing layer 8 attached to the first layer of adhesive and a second layer of adhesive 10. In some embodiments, the first layer of adhesive and second layer of adhesive may be the same. In some embodiments, the tape may include a release liner, a layer of adhesive attached to the release liner, a backing layer attached to the layer of adhesive. In various embodiments, the adhesive tape may have a minimum thickness of at least about 0.05 millimeters(mm), about 0.07 millimeters, about 0.09 millimeters, or about 1.0 millimeters, and a maximum thickness of no greater than about 1.2 millimeters. In some embodiments, 180°peel strength of the adhesive tape using ASTM D3330 testing standard is at least 0.2 N/mm, at least 0.5 N/mm, at least 0.7 N/mm, at least 0.8 N/mm, but not exceeding 1.0 N/mm.

In some embodiments, backing layer 8 is made from a thermoplastic

polyurethane polymer. More particularly, the backing layer is made from a polyester based thermoplastic polyurethane polymer. Suitable polyester based thermoplastic polyurethane includes but not limited to aromatic polyester based thermoplastic polyurethane, aliphatic polyester based thermoplastic polyurethane. In some embodiments, the thermoplastic polyurethane is aromatic hydroxyl terminated. In some embodiments, the weight percent of aromatic hydroxyl group is between 0.3 and 3%wt, and glass transition temperature (Tg) of soft molecular chain of the

thermoplastic polyurethane is between -20 to 40 ^°C and glass transition

temperature/kofler melting temperature of hard molecular chain of the thermoplastic polyurethane is between 60 tol 10^°C . the thermoplastic polyurethane has tear strength above 35MPa and the shore hardness is from 55A to 70A, preferably 65 A.

In some embodiments, the thermoplastic polyurethane is cross-linked by adding cross-linkers. Suitable cross-linkers include isocyanate type cross-linkers. The amount of isocyanate cross-linker may be from 0.1 to 0.5 weight percent, may be from 0.15 to 0.3 weight percent . The the cross-linker comprises isophorondiisocyanate

homo-polymer. According to the invention, the backing layer for the adhesive article is usually selected to have suitable mechanical properties for use in a stretch release adhesive tape. For example, the backing layer is selected so that it can be stretched (elongated) in a first direction (e.g., a lengthwise direction) at least 850 percent without breaking. That is, at least one dimension such as the length of the backing layer can be increased through stretching at least 850 percent without breaking In other words, the backing layer has an elongation at break at least 850%, at least 1000%, at least 1200%, at least 1400%, at least 1600%, at least 1800%, at least 2000%), and at least 2200%). These relatively large elongation values facilitate stretch releasing of the adhesive tape 2 after being adhered to an object and/or substrate.

The backing layer has a Young's modulus at least 25MPa, at least 30MPa, at least 35MPa, at least 45MPa, and not exceeding 50MPa. The Young's Modulus can be measured, for example, using method ASTM D790-07 or ASTM D882-02. The backing layer may have a thickness between 35 micron and 70 micron. The backing layer may be of any suitable construction. For example, the backing layer can be in the form of a film any suitable thickness, composition, and opaqueness or clarity. The backing layer can be a single layer of film, and/or multiple layers of film.

The adhesive layer is made of a pressure sensitive adhesive with further modification. In some embodiments, the pressure sensitive adhesive is formed from a reaction mixture which includes below components:

25 weight percent to 90 weight percent of acrylic copolymer based on a total weight of the reaction mixture;

5 weight percent to 30 weight percent of functional group terminated

polyurethane polymer based on a total weight of the reaction mixture; 0 weight percent to 45 weight percent of tackifier based on a total weight of the reaction mixture, 0.02 weight percent to 0.1 weight percent of cross-linker based on a total weight of the reaction mixture; and

0 weight percent to 3 weight percent of pigment.

Suitable acrylic copolymer is described in US Pub. No. 20110104486A1 which is hereby incorporated by reference. The weight percent of the acrylic copolymer may be from 25 to 90, from 30 to 90, from 40 to 80, from 50 to 70, from 60 to 65 weight percent, based on a total weight of the reaction mixture. In some embodiments, the acrylic copolymer includes 3 weight percent to 10 weight percent of acrylic acid monomer based on a total weight of the acrylic copolymer.

In some embodiments, the functional group terminated polyurethane polymer includes aliphatic sulfonic acid terminated polyurethane, or aromatic hydroxyl terminated polyurethane, or their combinations. The Tg of the functional group terminated polyurethane is between 60 and 80 ^°C . The weight percent of the functional group terminated polyurethane varies from 5 to 30, varies from 10 to 25, varies from 10 to 15, based on a total weight of the reaction mixture. In some embodiments, functional group terminated polyurethane polymer includes aliphatic sulfonic acid terminated polyurethane and the weight percent of sulfonic acid group is between 2 and 5%.

The tackifier used in the present invention includes but not limited to rosin resins, terpene resins. The weight percent of the tackifier varies from 0 to 45, varies from 4-45, varies from 10-35, varies from 15 to 30, varies from 20 to 30, based on a total weight of the reaction mixture.

The cross-linker used in the present invention includes but not limited to polyisocynate. The amount of the cross-linker varies from 0.02 to 0.1, 0.05 to 0.09, 0.06 to 0.08 weight percent based on a total weight of the reaction mixture. The NCO (isocyanate group) content of the cross-linker is from 5 to 12% and the viscosity of cross-linker is from 400 to 800cP. Suitable cross-linker includes but not limited to aliphatic polyisocyanate (IPDI trimer, HDI trimer).

The reaction mixture may include 0-3 weight percent of pigment if it is desired to change the color of the adhesive tape.

EXAMPLES

The object and advantages of the present invention will be further illustrated with reference to the following examples. The specific materials, amounts, and other conditions and details recorded in those examples are merely used to describe the present invention and should not be construed to limit the present invention in any way. The percents, ratios, parts and the like quoted in the present invention are all by weight, unless otherwise specified.

All amounts are stated as weight percent unless otherwise indicated.

Table 1: Raw materials of the stretch releasable tape

Test Methods

The performance testing and characterization for the samples of the present invention are carried out according to the following test methods.

Peel Adhesion Test (ASTM D 3330/D 3330M-04)

180 Degree peel adhesion was performed as described in the ASTM

International standard, D3330 using an IMASS SP-200 slip/peel tester (available from IMASS, Inc., Accord, MA) at speed of 12 inch/min.

Tensile Test (ASTM D 3759)

Tensile test was performed as described in the ASTM International

standard,D3759 on an Instron (model4465) using 12.7mmX25.4mm tape strip at cross head speed of 304.8mm/min.

Tensile Test (ASTM D1876)

T-peel was performed according to ASTM D1876 using an an Instron

(model4465) using 25.4mmX150mm tape strip at cross head speed of 304.8mm/min.

Maximum bonding strength was tested on a 60mmX20mmx0.1mm (thickens) tape sample using an Instron (model 4465) at cross head speed of 12 inch/min as shown in Fig.2.

Stretch releasing test was performed on a sample of 90mmx20mmx0.1mm (thickness) using an Instron (model 4465) at cross head speed of 12 inch/min and at 90 degree pulling angle as shown in Fig.3. Reliability of stretch-release was recorded as a percentage of clean removal samples over total samples tested. The stretch releasing test was performed on 1) the original sample and 2) the sample after aging at 65 ^°Cand RH95% for 72hrs.

Drop Resistance Test

Drop resistance test was performed on a sample of 60mmx20mm as shown in Fig.4. The testing device includes a plate 14, a support 16 connected with the plate, and testing blocks 18, and a base 20 used to support the testing blocks via a rod with a certain height. When testing, an article with the present invention of tape is dropped from the surface of the plate to test its drop resistance with adhered to the testing blocks 18. Drop height was increased at 5 cm increment from the initial height and the height of failure (HOFF) was observed. Any partial adhesive failure/peeling was counted as failure.

Measure of Residue

The residue on a substrate which the adhesive is removed from is measured by visibility, i.e. by eyes.

Releasing Reliability Test

Preparatory Examples

The detailed formulation of the stretch releasable tape example (El and E2) is shown in below.

Table 2: Formulation of the stretch releasable tape and related products

Examples El and E2

Modified acrylic adhesive layer

The preparation of the acrylic copolymer of acrylic copolymer is followed. A bottle of 2-ethyl hexyl acrylate (2-EHA) was taken from Dow Chemical Co., 4.5 grams of butyl acrylate (BA), and 4.5grams of acrylic acid (AA, obtained from BASF Corp.) The bottle also contained 177 grams of ethyl acetate (EtOAc, a solvent) and 0.200 grams of VAZO-67 (an azonitrile polymerization initiator obtained from DuPont). This mixture was purged with nitrogen to remove all oxygen and the bottle was then sealed. This sealed bottle was placed in a water bath and heated at 58oC for 24hours. The resulting sample was further diluted with an additional 56 grams of EtOAc. The final sample was a clear, viscous solution.

Adhesive solution with 40% solids was prepared by mixing the components (except cross-linker) as listed in Tab.2 under Modified Acrylic Adhesive to yield a coatable solution having a viscosity of about 8,000cps. The adhesive solution is then mixed with DESMODUR DN cross-linker and coated on a polyolefin coated Kraft (PCK) release liner using a solvent coater and dried in a continuous heating oven at 105 °C for 2 minutes to yield a 21 micrometer adhesive layer.

PU Layer

Polyurethane solution was prepared by first mixing 25 parts aromatic polyester-based thermoplastic polyurethane (ESTANE 5702) with 75 parts methylethylketone (MEK) and then introducing Z4470 cross-linker. The PU solution was coated on a PCK liner using a solvent coater and dried in a continuous heating oven at 80 °C for 5 minutes to yield a 58 micrometer thickness of PU layer. The multilayer adhesive tape of this invention is prepared by laminating adhesive skin layer to both surfaces of PU layer as shown in Fig 1. Such adhesives may be coated onto the backing layer 8 to form the adhesive tape 2, or such adhesives may be used to form an adhesive article in the form of a single homogeneous layer of adhesive (i.e. without a backing layer). The construction of the stretch releasable tape includes the polyolefin coated KRAFT (PCK) release liner, first layer of modified acrylic adhesive, specific polyurethane core and second layer of modified acrylic adhesive just as shown in Fig.1. The formulation of 1 st layer and 2nd layer of modified acrylic adhesive may be the same. A hot melt process is also suitable to prepare the stretch release tape by extruder and multi-layer co-extrusion die to form the adhesive layer and core layer.

Comparative examples (CI, C2, C3 and C4)

Comparative examples are shown in Tab.2. Comparatives CI (T company 0.1mm Bond & Detach DC tape) and C2 (M company 0.9mm) are commercial products as described in Table 2. Comparatives C3 & C4 were prepared using the same procedure described in El & E2 except the adhesive contains no thermoplastic PU addition as shown in Table 2.

Table 3: Construction of the related stretch releasable tapes

Tab. 3 shows construction of the stretch-releasable adhesive tapes of the present invention in comparison with the competitive tapes.

Table 4: Performance comparison of the related stretch releasable tapes 180° Max.bonding Drop

Tensile T-peel Releasing reliability

peel to SS strength height

Max. Elongatio

ID# Stress n N/mm N/m m N % Residue cm

/M Pa /%

E1 48.2 1100 0.733 1.070 657 100 N 15

C3 47.3 1090 0.805 0.431 556 100 Y 5

E2 50.3 1105 0.570 0.781 613 100 N 10

C4 48.1 1010 0.621 0.350 432 100 Y 5

C8 49.2 1100 0.510 0.675 575 100 N 10

C5 29.5 1500 0.050 0.150 89 100 N 5

C6 26.9 2196 0.165 0.310 165 100 N 5

C7 18.5 2044 0.670 0.710 436 70 Y 15

C9 21.3 1630 0.350 0.400 213 70 N 10

C1 13.0 1508 0.900 NA 502 70 N 5

C2 4.8 810 1.200 1.600 867 0 Y 5

As summarized in Table 4, comparatives CI and C2 show poor releasing reliability: 70% for CI and 0% for C2 as these are conventional stretch-releasable tapes originally designed for in-plane stretch-release. The adhesive tape of the present invention examples El & E2 comprising a modified acrylic adhesive with aliphatic sulfonic acid terminated polyurethane, i.e. SINOCHEM and crosslinked aromatic hydroxyl terminated polyurethane, show >1000% elongation at break and >40 MPa maximums stress. Comparing the testing results of El vs. C3 and E2 vs. C4, it indicates that blending the special polyurethane as listed in the table with acrylic copolymer, tackifier, and cross-linker provides the modified acrylic PSA with balanced adhesion, holding power, improved adhesion to the crosslinked polyurethane layer, and therefore enables the final tape with reliable vertical stretch-release performance and improved drop resistance over the comparatives.

Fig. 5 shows the vertical stretch-release performance of El, CI and C2 where CI and C2 have significantly lower elongation at break and maximum stress compared to El . After heat -humidity aging at 65 ^°C and RH95% for 72hrs, C2 shows noticeably reduced elongation at break and tensile while E2 maintains high elongation at break and tensile strength. This demonstrates the adhesive tape made from the

composition as invented not only has advantages in balanced adhesion, vertical stretch-release performance and drop resistance, but also has improved heat-humidity aging resistance over the completive tapes on the market.

Claims

Claims:

1. A stretch releasable adhesive tape comprising: a backing having a first surface and a second surface, wherein said backing is made of cross-linked thermoplastic polyurethane; a pressure sensitive adhesive disposed on at least one of said first and second surface, wherein the pressure sensitive adhesive is formed from an acrylic copolymer comprising a functional group terminated polyurethane, wherein the adhesive tape has a thickness ranged between 0.05 and 0.10mm and a lengthwise elongation ranged between 850% and 2200%, the adhesive tape being capable of being firmly bonded to a substrate and thereafter being removable therefrom after being stretched at an angle at 90° degree or greater degree from the surface of the substrate without said backing rupturing prior to the removal of the adhesive tape from the substrate and without leaving substantial pressure-sensitive adhesive residue on the substrate.

2. A stretch releasable adhesive tape as defined in claim 1, wherein the functional group terminated polyurethane comprises aliphatic sulfonic acid terminated polyurethane, or aromatic hydroxyl terminated polyurethane, or their combinations.

3. A stretch releasable adhesive tape as defined in claim 1 or claim 2, wherein said backing comprises aromatic hydroxyl terminated thermoplastic polyurethane.

4. A stretch releasable adhesive tape as defined in claim 3, wherein said thermoplastic polyurethane is polyester based thermoplastic polyurethane polymer.

5. A stretch releasable adhesive tape as defined in claim 1, wherein said thermoplastic polyurethane has a shore hardness ranged from 55A to 70A, the glass transition temperature (Tg) of soft molecular chain of the thermoplastic polyurethane is between -20 to 40 ^°C and glass transition temperature/kofler melting temperature of hard molecular chain of the thermoplastic polyurethane is between 60 tol l0^°C, and tear strength is above 35MPa.

6. A stretch releasable adhesive tape as defined in claim 1, wherein the functional group terminated polyurethane is compatible with said acrylic copolymer.

7. A stretch releasable adhesive tape as defined in claim 1 or claim 2, wherein the adhesive tape has a tensile strength from 25MPa to 50MPa.

8. A stretch releasable adhesive tape as defined in claim 1 , wherein 180° peel strength of the adhesive tape is ranged from 0.2 N/mm to 1.0 N/mm.

9. A stretch releasable adhesive tape comprising: a substrate having a first surface and a second surface, wherein the substrate comprises cross-linked thermoplastic polyurethane;

a pressure sensitive adhesive disposed on at least one of said first and second surface, wherein the pressure sensitive adhesive is formed from a reaction mixture comprising:

(v) 25 weight percent to 90 weight percent of acrylic copolymer based on a total weight of the reaction mixture;

(vi) 5 weight percent to 30 weight percent of functional group terminated polyurethane polymer based on a total weight of the reaction mixture;

(vii) 0 weight percent to 45 weight percent of tackifier based on a total weight of the reaction mixture, and

(viii) 0.02 weight percent to 0.1 weight percent of cross-linker based on a total weight of the reaction mixture.

10. A stretch releasable adhesive tape as defined in claim 9, wherein 180° peel strength of the adhesive tape is ranged from 0.2 N/mm to 1.0 N/mm and the thickness of the adhesive tape is ranged between 0.05 and 0.10mm.

11. A stretch releasable adhesive tape as defined in claim 9, wherein the functional group terminated polyurethane comprises aliphatic sulfonic acid terminated polyurethane, or aromatic hydroxyl terminated polyurethane, or their combinations

12. A stretch releasable adhesive tape as defined in claim 11, wherein the amount of functional group terminated polyurethane varies from 5 to 30 weight percent based on a total weight of the reaction mixture.

13. A stretch releasable adhesive tape as defined in claim 11, wherein the amount of functional group terminated polyurethane varies from 10 to 25 weight percent based on a total weight of the reaction mixture.

14. A stretch releasable adhesive tape as defined in claim 11, wherein the amount of functional group terminated polyurethane varies from 10 to 15 weight percent based on a total weight of the reaction mixture.

15. A stretch releasable adhesive tape as defined in claim 9, wherein the acrylic copolymer comprises 3 weight percent to 10 weight percent of acrylic acid monomer based on a total weight of the acrylic copolymer.

16. A stretch releasable adhesive tape as defined in claim 9, wherein the reaction mixture comprises 10 weight percent to 40 weight percent of tackifier based on a total weight of the reaction mixture.

17. A stretch releasable adhesive tape as defined in claim 9, wherein the reaction mixture comprises 15 weight percent to 30 weight percent of tackifier based on a total weight of the reaction mixture.

18. A stretch releasable adhesive tape as defined in claim 9, wherein the thermoplastic polyurethane is aromatic hydroxyl terminated, the weight percent of aromatic hydroxyl group is between 0.3 and 3%, and glass transition temperature (Tg) of soft molecular chain of the thermoplastic polyurethane is between -20 to 40 ^°C and glass transition temperature/kofler melting temperature of hard molecular chain of the thermoplastic polyurethane is between 60 tol l0^°C .

19. A stretch releasable adhesive article as defined in claim 9, wherein the thermoplastic polyurethane is cross-linked by adding 0.1 weight percent to 0.5 weight percent of isocyanate cross-linker.

20. A stretch releasable adhesive article as defined in claim 9, wherein the thermoplastic polyurethane is cross-linked by adding 0.15 weight percent to 0.3 weight percent of isocyanate cross-linker.

21. A stretch releasable adhesive article as defined in claim 19 or claim 20, wherein the cross-linker comprises isophorondiisocyanate homo-polymer.

22. A stretch releasable adhesive tape as defined in claim 9, wherein the reaction mixture comprises 0.02-0.1 weight percent of the cross-linker based on a total weight of the reaction mixture.

23. A stretch releasable adhesive tape being capable of being firmly bonded to a substrate and thereafter being removable therefrom after being stretched at an angle at 90° or greater degree from the surface of the substrate without leaving residue, the tape comprising:

a backing layer having a first and second opposed major surfaces; wherein the backing layer comprises cross-linked polyurethane;

24. A stretch releasable adhesive tape as defined in claim 23, wherein the adhesive tape has a thickness between 0.05mm and 0.10mm, lengthwise elongation at break greater than 1000%, and tensile strength greater than 25MPa.

25. A stretch releasable adhesive tape as defined in claim 23, wherein the acrylic adhesive layer is formed from a reaction mixture comprising:

5 weight percent to 30 weight percent of functional group terminated polyurethane based on a total weight of the reaction mixture;

0 weight percent to 45weight percent of tackifier based on a total weight of the reaction mixture, and

0.02 weight percent to 0.1 weight percent of cross-linker based on a total weight of the reaction mixture.

26. A stretch releasable adhesive tape as defined in claim 26, wherein the reaction mixture comprises 0 weight percent to 3 weight percent of pigment.

27. A stretch releasable adhesive tape as defined in any one of claims 1 to 27, further comprising a liner to which the adhesive is attached.

28. An electronic device comprising a first component and second component which are adhered to each other by using a stretch releasable adhesive tape as defined in any one of claim 1 to claim 28.

29. A stretch releasable adhesive tape comprising a backing and a first layer of a pressure-sensitive adhesive composition coated on at least one surface of said backing, the adhesive tape having a thickness between 0.05 and 0.10mm, said tape being capable of being firmly bonded to a substrate and thereafter being removable therefrom after being stretched at an angle at 90°degree or greater degree from the surface of said substrate without said backing rupturing prior to the removal of said tape from said substrate and without leaving substantial pressure-sensitive adhesive residue on said substrate, wherein the pressure sensitive adhesive comprises a functional group terminated polyurethane and the tape has an elongation at break between 850% and 2200%.

30. A stretch releasable adhesive tape as defined in claim 30, wherein the functional group terminated polyurethane comprises aliphatic sulfonic acid terminated polyurethane.

31. A method of making a stretch releasable adhesive tape comprising following steps:

(1) Providing an adhesive made from a functional group terminated polyurethane and acrylic copolymer;

(2) providing a cross-linked polyurethane layer;

(3) disposing the adhesive on at least one of the surfaces of the polyurethane layer.

32. A method of making a stretch releasable adhesive tape as defined in claim 32, wherein step (1) comprises: preparing acrylic adhesive solution by mixing acrylic copolymer functional group terminated polyurethane;

b) providing a mixture of a cross-linker into the acrylic adhesive solution;

c) coating the mixture on a liner; and

d) drying the liner to form an adhesive layer.

33. A method of making a stretch releasable adhesive tape as defined in claim 32, wherein step (2) comprises:

a) preparing a polyurethane solution by mixing aromatic polyester-based thermoplastic polyurethane with mehylethylketone;

b) introducing a cross-linker into the polyurethane solution;

c) coating the polyurethane solution on a liner;

d) drying the liner under the condition of around 80°C for a predetermined period of time to form a backing layer.

34. A method of making a stretch releasable adhesive tape as defined in claim 1 to claim 30 comprising a hot melt process suitable to prepare the stretch release tape by extruder and multi-layer co-extrusion die to form the adhesive layer and a backing layer to which the adhesive is attached.