Double-sided adhesive tape and multilayer structure

Abstract

The invention provides a double faced adhesive tape and a multilayer structure. The double faced adhesive tape comprises a first adhesive layer and a second adhesive layer. The first adhesive layer is a product of a first adhesive composition, the first adhesive composition comprises a first acryl resin, a first cross-linking agent and a compound having a structure represented by formula (I), and R1 and R2 are as described in the specification. The second adhesive layer is a product of a second adhesive composition, wherein the second adhesive composition comprises a second acryl resin and a second cross-linking agent. The glass transition temperature of the first adhesive layer is Tg1, the glass transition temperature of the second adhesive layer is Tg2, Tg2 is smaller than or equal to-30 DEG C, and Tg2-Tg1 is larger than or equal to 10 DEG C. # imgabs0 #

Description

Technical Field

[0001] The present disclosure relates to a double-sided adhesive and a multi-layer structure. Background Art

[0002] The existing touch technology for touch displays includes using optical adhesives to bond and fix the cover plate and the touch panel of the touch display, and using optical adhesives to bond and fix the touch panel and the polarizer of the display module. To avoid the peeling of the two adhered panels, most existing optical adhesive products emphasize their strong adhesion, but the strong adhesion property also brings the drawback of inconvenient rework.

[0003] The panel rework process in panel factories can be mainly divided into two types. One is to use low-temperature treatment on the panel and then peel off the two panels adhered by the optical adhesive; the other is to mechanically cut the optical adhesive and then peel off the two panels. Since both panels in the two methods adhere to part of the optical adhesive at the same time, both methods require a lot of manpower and the use of solvents to remove the glue, which is quite time-consuming and not environmentally friendly, and the polarizer is extremely vulnerable to damage during the process of removing the residual glue.

[0004] In addition, when there is a step difference on the bonding surface of the touch panel, if the gap-filling ability of the used optical adhesive is insufficient, the step difference cannot be filled, reducing the display performance of the display. Summary of the Invention

[0005] The present disclosure provides a double-sided adhesive. According to an embodiment of the present disclosure, the double-sided adhesive includes a first adhesive layer and a second adhesive layer. The first adhesive layer is a product of cross-linking reaction of a first adhesive composition, wherein the first adhesive composition includes a first acrylic resin, a first cross-linking agent, and a compound having the structure shown in formula (I),

[0006]

[0007] wherein R 1 is hydrogen or methyl; and, R 2 is where n is 0, 1, 2, or 3; m is 0, 1, 2, or 3; i is 0, 1, 2, or 3; and, R 3 、R 4 and R 5 are independently hydrogen or C1-C4 alkyl. The second adhesive layer is a product of cross-linking reaction of a second adhesive composition, wherein the second adhesive composition includes a second acrylic resin and a second cross-linking agent. The glass transition temperature of the first adhesive layer is Tg 1 and the glass transition temperature of the second adhesive layer is Tg 2 wherein Tg 2 is less than or equal to -30 °C, and Tg 2-Tg 1 ≥10 °C.

[0008] According to an embodiment of the present disclosure, the present disclosure also provides a multi-layer structure. The multi-layer structure may include a first substrate, a second substrate, and the above-mentioned double-sided adhesive. The first adhesive layer of the double-sided adhesive has a first surface, and the second adhesive layer of the double-sided adhesive has a second surface, wherein the first surface contacts the first substrate and the second surface contacts the second substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a cross-sectional schematic view of the double-sided adhesive according to an embodiment of the present disclosure.

[0010] Figure 2 is a cross-sectional schematic view of the multi-layer structure according to an embodiment of the present disclosure.

[0011] Figure 3 is a cross-sectional schematic view of the multi-layer structure according to another embodiment of the present disclosure.

[0012] SYMBOL DESCRIPTION

[0013] 10 Double-sided adhesive;

[0014] 11 First surface;

[0015] 12 First adhesive layer;

[0016] 13 Second surface;

[0017] 14 Second adhesive layer;

[0018] 20 First substrate;

[0019] 25 Film layer;

[0020] 30 Second substrate; and

[0021] 100 Multi-layer structure. DETAILED DESCRIPTION

[0022] The following provides a detailed description of the double-sided adhesive and the multi-layer structure of the present disclosure. It should be understood that the following description provides many different embodiments or examples for implementing different aspects of the present disclosure. The specific elements and arrangements described below are only for a simple description of the present disclosure. Of course, these are only for illustration and not a limitation of the present disclosure. In the present disclosure, the term "about" means that the specified quantity may increase or decrease by an amount that can be recognized by those skilled in the art as being generally and reasonably sized.

[0023] Furthermore, the ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., which modify the elements of the claims, do not in themselves imply or represent that any of the claimed elements have any previous ordinal numbers, nor do they represent the order of one claimed element and another claimed element, or the order in the manufacturing method. The use of these ordinal numbers is only to clearly distinguish one claimed element with a certain name from another claimed element with the same name.

[0024] It must be understood that the elements specifically described or illustrated may exist in various forms well-known to those of ordinary skill in the art. In addition, when a layer is "on" another layer or substrate, it may mean "directly" on another layer or substrate, may mean a layer is on another layer or substrate, or may mean that a layer is interposed between other layers or substrates. In the drawings, the shape or thickness of the embodiments may be enlarged and simplified or conveniently labeled. Furthermore, the parts of each element in the drawings will be described separately. It should be noted that the elements not shown or described in the drawings are in forms well-known to those of ordinary skill in the art. In addition, the specific embodiments are only specific ways used to disclose the present disclosure content, and are not used to limit the present disclosure content.

[0025] The present disclosure provides a double-sided tape, such as a freeze-peel double-sided tape with high gap-filling ability. According to an embodiment of the present disclosure, the double-sided tape described in the present disclosure has a first adhesive layer and a second adhesive layer. By controlling the difference in the monomer content of the first adhesive layer and the second adhesive layer, the glass transition temperatures of the first adhesive layer and the second adhesive layer meet a specific relationship. In this way, a large difference in the adhesion between the first adhesive layer and the second adhesive layer of the double-sided tape can be generated after low-temperature treatment, so that the double-sided tape can be smoothly peeled off from the substrate (the substrate in contact with the second adhesive layer of the double-sided tape) during the rework process without causing residue of the adhesive material. In addition, due to the specific composition of the first adhesive layer, the first adhesive layer has better gap-filling ability. In this way, even if there is a step on the bonding surface of the substrate, the first adhesive layer of the double-sided tape described in the present disclosure can fill the step and avoid the generation of air hole defects in the adhesive layer.

[0026] According to an embodiment of the present disclosure, the present disclosure also provides a multi-layer structure including the double-sided adhesive, such as a display panel. According to an embodiment of the present disclosure, the first adhesive layer of the double-sided adhesive may have a first surface and the second adhesive layer of the double-sided adhesive has a second surface. The first surface may be used to adhere and fix a touchpad, and the second surface is used to adhere and fix a polarizer of a display module. After the double-sided adhesive is subjected to a low-temperature treatment, the adhesive forces of the first surface and the second surface of the double-sided adhesive decrease, and a large difference occurs between the adhesive force of the first surface of the first adhesive layer and the adhesive force of the second surface of the second adhesive layer. After a peeling process, in addition to being able to easily peel two adhered substrates, the double-sided adhesive described in the present disclosure will only remain on one substrate (such as a touchpad), and will not remain on both substrates at the same time (for example, no residual adhesive will be formed on the polarizer). In this way, the recycling rate of display panel components is improved and the efficiency of the rework process can be accelerated. In addition, since the first adhesive layer has better gap filling ability, it can closely fit with a substrate having a step difference (such as a touchpad having protrusions) (no voids will be generated).

[0027] According to an embodiment of the present disclosure, please refer to Figure 1 , the double-sided adhesive 10 may include a first adhesive layer 12 and a second adhesive layer 14, wherein the first adhesive layer has a first surface and the second adhesive layer has a second surface. The first adhesive layer 12 may be a product of a crosslinking reaction of a first adhesive composition. The second adhesive layer 14 may be a product of a crosslinking reaction of a second adhesive composition.

[0028] The first adhesive composition may include a first acrylic resin, a first crosslinking agent, and a compound having the structure shown in formula (I),

[0029]

[0030] wherein R 1 is hydrogen or methyl; and, R 2 is wherein n is 0, 1, 2, or 3; m is 0, 1, 2, or 3; i is 0, 1, 2, or 3; and, R 3 、R 4 and R 5Independently hydrogen or a C1-C4 alkyl group. According to an embodiment of the present disclosure, by means of a first adhesive composition having a specific composition and weight ratio, the first adhesive layer 12 prepared from the first adhesive composition can have better gap-filling ability. According to an embodiment of the present disclosure, the weight ratio of the compound having the structure shown in formula (I) to the first acrylic resin can be from 10:90 to 25:75, such as 11:89, 12:88, 13:87, 14:86, 15:85, 16:84, 17:83, 18:82, 19:81, 20:80, 21:79, 22:78, 23:77, or 24:76. When the weight ratio of the compound having the structure shown in formula (I) to the first acrylic resin is too high or too low, the first adhesive layer 12 has poor gap-filling ability. In addition, the second adhesive composition may include a second acrylic resin and a second crosslinking agent.

[0031] According to an embodiment of the present disclosure, the C1-C4 alkyl group can be a linear or branched alkyl group. For example, the C1-C4 alkyl group can be methyl, ethyl, propyl, butyl, or an isomer thereof.

[0032] According to an embodiment of the present disclosure, the compound having the structure shown in formula (I) can be

[0033]

[0034]

[0035] According to an embodiment of the present disclosure, the first resin composition can be a product of a copolymerization reaction of the first resin composition, wherein the first resin composition includes (A1) monomers (i.e., component (A1)), and the (A1) monomers can include a first monomer, a second monomer, and a third monomer. According to an embodiment of the present disclosure, the total weight of the first monomer, the second monomer, and the third monomer is 95 wt% to 100 wt%, based on the weight of the (A1) monomers.

[0036] According to an embodiment of the present disclosure, the (A1) monomers are composed of a main monomer and a minor monomer, wherein the main monomer is composed of a first monomer, a second monomer, and a third monomer, and the minor monomer is composed of monomers that can react with (meth)acrylate. Here, the weight of the main monomer is 95 wt% to 99.9 wt%, and the weight of the minor monomer is 0.1 wt% to 5 wt%. According to an embodiment of the present disclosure, the (A1) monomers can be composed of a first monomer, a second monomer, and a third monomer.

[0037] According to an embodiment of the present disclosure, the second resin composition may be a product of a copolymerization reaction of the second resin composition, wherein the second resin composition contains (B1) monomers (i.e., component (B1)), and the (B1) monomers may include a first monomer, a second monomer, and a third monomer. According to an embodiment of the present disclosure, the total weight of the first monomer, the second monomer, and the third monomer is 95 wt% to 100 wt%, based on the weight of the (B1) monomers.

[0038] According to an embodiment of the present disclosure, the (B1) monomers are composed of a main monomer and a minor monomer, wherein the main monomer is composed of a first monomer, a second monomer, and a third monomer, and the minor monomer is composed of monomers that can react with (meth)acrylate. Here, the weight of the main monomer is 95 wt% to 99.9 wt%, and the weight of the minor monomer is 0.1 wt% to 5 wt%. According to an embodiment of the present disclosure, the (B1) monomers may be composed of a first monomer, a second monomer, and a third monomer.

[0039] In the (A1) monomers, the weight percentage of the third monomer may be W1, based on the weight of the (A1) monomers (i.e., the total weight of the first monomer, the second monomer, and the third monomer in the first resin composition).

[0040] In the (B1) monomers, the weight percentage of the third monomer may be W2, based on the weight of the (B1) monomers (i.e., the total weight of the first monomer, the second monomer, and the third monomer in the second resin composition).

[0041] It should be noted that the weight percentage W1 and the weight percentage W2 satisfy the following relationship: 45 wt% ≥ 3W2 - W1 ≥ 37 wt% (for example: 40 wt% ≥ 3W2 - W1 ≥ 37 wt%, 35 wt% ≥ 3W2 - W1 ≥ 37 wt%, 32 wt% ≥ 3W2 - W1 ≥ 37 wt%, or 28 wt% ≥ 3W2 - W1 ≥ 37 wt%). According to an embodiment of the present disclosure, when the difference (W2 - W1) between the weight percentage W1 and the weight percentage W2 is less than 7, after the double-sided tape is treated at low temperature, the adhesion force between the first adhesive layer and the second adhesive layer does not show a significant difference.

[0042] According to an embodiment of the present disclosure, the first resin composition does not contain other reactive monomers (i.e., monomers that can be used to form the repeating units of the first resin composition) except for the first monomer, the second monomer, and the third monomer. According to an embodiment of the present disclosure, the second resin composition does not contain other reactive monomers (i.e., monomers that can be used to form the repeating units of the second resin composition) except for the first monomer, the second monomer, and the third monomer.

[0043] According to an embodiment of the present disclosure, the composition of the (A1) monomer of the first resin composition is the same as the composition of the (B1) monomer of the second resin composition. In other words, the first monomer of the first resin composition may be the same as the first monomer of the second resin composition, the second monomer of the first resin composition may be the same as the second monomer of the second resin composition, and the third monomer of the first resin composition may be the same as the third monomer of the second resin composition.

[0044] According to an embodiment of the present disclosure, the composition of the (A1) monomer of the first resin composition is different from the composition of the (B1) monomer of the second resin composition. In other words, the first monomer of the first resin composition is different from the first monomer of the second resin composition, the second monomer of the first resin composition is different from the second monomer of the second resin composition, and / or the third monomer of the first resin composition is different from the third monomer of the second resin composition.

[0045] According to an embodiment of the present disclosure, the first monomer may be a (meth)acrylate monomer having a hydroxyl group. According to certain embodiments of the present disclosure, the first monomer may be wherein R 6 may be hydrogen or methyl, and R 7 may be hydrogen, or a C1-C10 alkylol group. According to an embodiment of the present disclosure, the C1-C10 alkylol group may be a linear or branched alkylol group. For example, the C1-C10 alkylol group may be a methylol group, an ethylol group, a propylol group, a butylol group, a pentylol group, a hexylol group, or an isomer thereof. For example, the first monomer may be acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, or a combination thereof.

[0046] According to an embodiment of the present disclosure, the second monomer may be a soft monomer, where the soft monomer refers to a (meth)acrylate monomer whose homopolymer has a glass transition temperature less than or equal to -20 °C (for example, the glass transition temperature is -20 °C to -100 °C, the glass transition temperature is -20 °C to -90 °C, the glass transition temperature is -20 °C to -80 °C, or the glass transition temperature is -20 °C to -70 °C). In other words, the second monomer may be a (meth)acrylate monomer, where the homopolymer of the (meth)acrylate monomer has a glass transition temperature less than or equal to -20 °C. The glass transition temperature is measured by differential scanning calorimetry (DSC) (heating rate is 10 °C / min) or refers to literature values such as POLYMER HANDBOOK (Wiley-Interscience). For example, the second monomer may be n-butyl acrylate, sec-butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, ethoxyethyl acrylate, isononyl acrylate, lauryl methacrylate, or a combination of the above.

[0047] According to an embodiment of the present disclosure, the third monomer may be a hard monomer, where the hard monomer refers to a monomer having a terminal vinyl group and a glass transition temperature of the homopolymer greater than or equal to 0 °C (for example, the glass transition temperature is 0 °C to 200 °C, the glass transition temperature is 0 °C to 180 °C, the glass transition temperature is 0 °C to 150 °C, or the glass transition temperature is 0 °C to 130 °C). In other words, the third monomer may be a monomer having a terminal vinyl group, where the glass transition temperature of the homopolymer of the monomer having a terminal vinyl group is greater than or equal to 0 °C. For example, the third monomer may be tert-butyl acrylate, n-butylmethacrylate, sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, methylacrylate, methylmethacrylate, acrylonitrile, acrylamide, acryloylmorpholine, N-vinyl-2-pyrrolidone, or a combination of the above.

[0048] According to an embodiment of the present disclosure, in the (A1) monomer, the weight percentage of the first monomer may be 1 wt% to 10 wt% (e.g., 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 9 wt%), based on the weight of the (A1) monomer. In the (A1) monomer, when the weight percentage of the first monomer is 1 wt% to 10 wt%, the first resin composition has an appropriate number of hydroxyl groups that can further react with a crosslinking agent, and the resulting crosslinked product has weather resistance. According to an embodiment of the present disclosure, in the (B1) monomer, the weight percentage of the first monomer may be 1 wt% to 10 wt% (e.g., 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or 9 wt%), based on the weight of the (B1) monomer. In the (B1) monomer, when the weight percentage of the first monomer is 1 wt% to 10 wt%, the second resin composition has an appropriate number of hydroxyl groups that can further react with a crosslinking agent, and the resulting crosslinked product has weather resistance.

[0049] According to an embodiment of the present disclosure, in the (A1) monomer, the weight percentage of the first monomer may be 1 wt% to 10 wt%, based on the total weight of the first monomer, the second monomer, and the third monomer. According to an embodiment of the present disclosure, in the (B1) monomer, the weight percentage of the first monomer may be 1 wt% to 10 wt%, based on the total weight of the first monomer, the second monomer, and the third monomer.

[0050] According to an embodiment of the present disclosure, in the (A1) monomer, the weight percentage of the second monomer may be 50 wt% to 95 wt% (such as 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, or 94 wt%), based on the weight of the (A1) monomer. According to an embodiment of the present disclosure, in the (B1) monomer, the weight percentage of the second monomer may be 50 wt% to 95 wt% (such as 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, or 94 wt%), based on the weight of the (B1) monomer.

[0051] According to an embodiment of the present disclosure, in the (A1) monomer, the weight percentage of the second monomer may be 50 wt% to 95 wt%, based on the total weight of the first monomer, the second monomer, and the third monomer. According to an embodiment of the present disclosure, in the (B1) monomer, the weight percentage of the second monomer may be 50 wt% to 95 wt%, based on the total weight of the first monomer, the second monomer, and the third monomer.

[0052] According to an embodiment of the present disclosure, in the (A1) monomer, the weight percentage of the third monomer can be 4 wt% to 42 wt% (such as 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, or 41 wt%), based on the weight of the (A1) monomer. According to an embodiment of the present disclosure, in the (B1) monomer, the weight percentage of the third monomer can be 11 wt% to 49 wt% (such as 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, 46 wt%, 47 wt%, or 48 wt%), based on the weight of the (B1) monomer.

[0053] According to an embodiment of the present disclosure, in the first resin composition or the second resin composition, when the content of the soft monomer (i.e., the (meth)acrylate monomer whose glass transition temperature of the homopolymer is less than or equal to -20 °C) is high, the resulting acrylic resin has a low glass transition temperature. In addition, in the first resin composition or the second resin composition, when the content of the hard monomer (i.e., the monomer having a terminal vinyl group whose glass transition temperature of the homopolymer is greater than or equal to 0 °C) is high, the resulting acrylic resin has a high glass transition temperature.

[0054] According to an embodiment of the present disclosure, the glass transition temperature of the first acrylic resin used in the first adhesive layer described in the present disclosure is Tg 1 and the glass transition temperature of the second acrylic resin used in the second adhesive layer is Tg 2 where Tg 2 is less than or equal to -30 °C (such as less than or equal to -31 °C, or less than or equal to -32 °C), and Tg 2 -Tg 1 ≥10 °C (such as Tg2 -Tg 1 ≥11 °C, Tg 2 -Tg 1 ≥12 °C, or Tg 2 -Tg 1 ≥13 °C). Therefore, by adjusting the content of the hard monomer (i.e., the third monomer) in the first resin composition and the second resin composition, the glass transition temperatures (glass transition temperature) of the first adhesive layer and the second adhesive layer can be differentiated (i.e., Tg 2 -Tg 1 ≥10 °C). In this way, when the double-sided tape described in the present disclosure is subjected to low-temperature treatment, the difference in adhesive force between the first adhesive layer and the second adhesive layer can be further increased, so that the double-sided tape described in the present disclosure can be peeled off from the side of the second adhesive layer without causing adhesive residue.

[0055] According to an embodiment of the present disclosure, the Fox equation can be applied to calculate the estimated glass transition temperature of the acrylic resin used in the adhesive layer (such as the first adhesive layer or the second adhesive layer). The calculation formula of the Fox equation is as follows: 1 / Tg = W1 / Tg1 + W2 / Tg2 + W3 / Tg3 +... Wn / Tgn, where Tg is the glass transition temperature (K) of the acrylic resin; W1 is the weight fraction of monomer 1; Tg1 is the glass transition temperature (K) of the homopolymer of monomer 1; W2: the weight fraction of monomer 2; Tg2 is the glass transition temperature (K) of the homopolymer of monomer 2; Wn: the weight fraction of monomer N; Tgn is the glass transition temperature (K) of the homopolymer of monomer N, and monomers 1 to N refer to various monomers used to prepare the acrylic resin (such as the first resin composition or the second resin composition), and the acrylic resin is used to prepare the adhesive layer.

[0056] According to an embodiment of the present disclosure, when the double-sided tape is subjected to low-temperature treatment in the rework process, the temperature (T) of the low-temperature treatment can be less than the glass transition temperature (Tg 1 ) of the first acrylic resin used in the first adhesive layer and the glass transition temperature (Tg 2 ) of the second acrylic resin used in the second adhesive layer. In other words, the temperature (T) of the low-temperature treatment, the glass transition temperature (Tg 1 ) of the first acrylic resin used in the first adhesive layer, and the glass transition temperature (Tg 2 ) of the second acrylic resin used in the second adhesive layer can satisfy the following relationship: Tg 2 > Tg 1>T. In this way, after the double-sided adhesive described in the present disclosure undergoes low-temperature treatment, a significant difference in the adhesive force between the first adhesive layer and the second adhesive layer can be generated. According to an embodiment of the present disclosure, the glass transition temperature Tg of the second acrylic resin used in the second adhesive layer 2 and the glass transition temperature Tg of the first acrylic resin used in the first adhesive layer 1 The difference (i.e., Tg 2 -Tg 1 ) can be greater than or equal to 10 °C (i.e., Tg 2 -Tg 1 ≥10 °C).

[0057] According to an embodiment of the present disclosure, the time of the low-temperature treatment described in the present disclosure can be about 1 minute to 1 hour, such as 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, or 55 minutes. According to an embodiment of the present disclosure, the temperature of the low-temperature treatment can be about -10 °C to -130 °C, such as -15 °C, -20 °C, -25 °C, -30 °C, -40 °C, -50 °C, -60 °C, -70 °C, -80 °C, -90 °C, -100 °C, -110 °C, or -120 °C. According to an embodiment of the present disclosure, when the temperature (T) of the low-temperature treatment is lower, the time of the low-temperature treatment can be reduced.

[0058] According to an embodiment of the present disclosure, when the double-sided adhesive is subjected to low-temperature treatment in the rework process, the temperature (T) of the low-temperature treatment can be between the glass transition temperature (Tg 1 ) of the first acrylic resin used in the first adhesive layer and the glass transition temperature (Tg 2 ) of the second acrylic resin used in the second adhesive layer. In other words, the temperature (T) of the low-temperature treatment, the glass transition temperature (Tg 1 ) of the first acrylic resin used in the first adhesive layer, and the glass transition temperature (Tg 2 ) of the second acrylic resin used in the second adhesive layer can satisfy the following relationship: Tg 2 >T>Tg 1 . In this way, after the double-sided adhesive described in the present disclosure undergoes low-temperature treatment, the difference in the adhesive force between the first adhesive layer and the second adhesive layer can be further increased, and it can be ensured that the double-sided adhesive can be smoothly peeled off from the substrate (the substrate in contact with the second adhesive layer of the double-sided adhesive) during the rework process without causing the residue of the adhesive material. According to an embodiment of the present disclosure, when the temperature (T) of the low-temperature treatment is between the glass transition temperature (Tg 1 ) of the first acrylic resin used in the first adhesive layer and the glass transition temperature (Tg2 ) When it is between them, the energy loss during the low-temperature treatment can be reduced (that is, it is not necessary to lower the temperature below the glass transition temperature (Tg 1 ) of the acrylic resin used in the first adhesive layer).

[0059] According to an embodiment of the present disclosure, the time of the low-temperature treatment described in the present disclosure can be about 1 minute to 1 hour, such as 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, or 55 minutes. According to an embodiment of the present disclosure, the temperature of the low-temperature treatment can be about -10°C to -130°C, such as -15°C, -20°C, -25°C, -30°C, -40°C, -50°C, -60°C, -70°C, -80°C, -90°C, -100°C, -110°C, or -120°C. According to an embodiment of the present disclosure, when the temperature (T) of the low-temperature treatment is lower, the time of the low-temperature treatment can be reduced.

[0060] According to an embodiment of the present disclosure, the first resin composition may further comprise (A2) an initiator, wherein the weight ratio of the (A1) monomer to the (A2) initiator can be 10,000:1 to 100:3, such as 8,000:1, 6,000:1, 5,000:1, 3,000:1, 2,000:1, 1,750:1, 1,500:1, 1,250:1, 1,000:1, 750:1, 500:1, 200:1, 100:1, 100:2, or 100:2.5.

[0061] According to an embodiment of the present disclosure, the second resin composition may further comprise (B2) an initiator, wherein the weight ratio of the (B1) monomer to the (B2) initiator can be 10,000:1 to 100:3, such as 8,000:1, 6,000:1, 5,000:1, 3,000:1, 2,000:1, 1,750:1, 1,500:1, 1,250:1, 1,000:1, 750:1, 500:1, 200:1, 100:1, 100:2, or 100:2.5.

[0062] According to an embodiment of the present disclosure, the initiator (A2) and the initiator (B2) may be thermal initiators. According to an embodiment of the present disclosure, the selection of the initiator (A2) and the initiator (B2) is not particularly limited, and may be an azo compound, a cyanovaleric-acid-based compound, a peroxide, a benzoin-based compound, an acetophenone-based compound, a thioxanthone-based compound, a ketal compound, a benzophenone-based compound, an α-aminoacetophenone compound, an acylphosphine oxide compound, a biimidazole-based compound, a triazine-based compound, or a combination of the above.

[0063] According to an embodiment of the present disclosure, the azo compound may be 2,2'-azobis(2,4-dimethyl valeronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2-azobisisobutyronitrile (hereinafter referred to as AIBN), 2,2-azobis(2-methylisobutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 1-[(cyano-1-methylethyl)azo]formamide, 2,2'-azobis(N-butyl-2-methylpropionamide), or 2,2'-azobis(N-cyclohexyl-2-methylpropionamide). The peroxide may be benzoyl peroxide, 1,1-bis(tert-butylperoxy)cyclohexane, 2,5-bis(tert-butylperoxy)-2,5-dimethylcyclohexane, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-cyclohexene,5-dimethyl-3-cyclohexyne), bis(1-(tert-butylpeorxy)-1-methy-ethyl)benzene, tert-butyl hydroperoxide, tert-butyl peroxide, tert-butyl peroxybenzoate, cumene hydroperoxide, cyclohexanone peroxide, dicumyl peroxide, or lauroyl peroxide. The benzoin-based compound can be benzoin, benzoin methyl ether, or benzoin dimethyl ether; the acetophenone-based compound can be p-dimethylamino-acetophenone, α,α’-dimethoxyazoxy-acetophenone, 2,2’-dimethyl-2-phenyl-acetophenone, p-methoxy-acetophenone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, 2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone; the benzophenone-based compound can be benzophenone, 4,4-bis(dimethylamino)benzophenone, 4,4-bis(diethylamino)benzophenone, 2,4,6-trimethylaminobenzophenone, methyl-o-benzoyl benzoate, 3,3,3-dimethyl-4-methoxybenzophenone and 3,3,4,4-tetra(t-butylperoxycarbonyl)benzophenone; the thioxanthone-based compounds may be thioxanthone, 2,4-diethyl-thioxanthanone, thioxanthone-4-sulfone; the diimidazole-based compounds may be 2,2’-bis(o-chlorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-fluorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-methylphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-methoxyphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-ethylphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(p-methoxyphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(2,2’,4,4’-tetramethoxyphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(2-chlorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(2,4-dichlorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole; The phosphine oxide compound can be 2,4,6-trimethylbenzoyl diphenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; The triazine compound can be 3-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionic acid, 1,1,1,3,3,3-hexafluoroisopropyl-3-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionate, ethyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate, 2-epoxyethyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate, cyclohexyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate, benzyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate), 3-{chloro-4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionic acid, 3-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionamide, 2,4-bis(trichloromethyl)-6-p-methoxystyryl-s-triazine, 2,4-bis(trichloromethyl)-6-(1-p-dimethylaminophenyl)-1,3-butadienyl-s-triazine, or 2-trichloromethyl-4-amino-6-p-methoxystyryl-s-triazine.,

[0064] According to an embodiment of the present disclosure, the first resin composition may further comprise (A3) a solvent. The amount of the solvent used can be adjusted as needed to uniformly disperse the (A1) monomer and the (A2) initiator in the solvent. For example, the solid content of the first resin composition can be 20 wt% to 70 wt% (such as about 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or 65 wt%). Here, the solid content refers to the weight percentage of all components of the first resin composition except the solvent, based on the total weight of the first resin composition.

[0065] According to an embodiment of the present disclosure, the second resin composition may further comprise (B3) a solvent. The amount of the solvent used can be adjusted as needed to uniformly disperse the (B1) monomer and the (B2) initiator in the solvent. For example, the solid content of the second resin composition may be 20 wt% to 70 wt% (such as about 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or 65 wt%). Here, the solid content refers to the weight percentage of all components of the second resin composition except the solvent, based on the total weight of the second resin composition.

[0066] According to an embodiment of the present disclosure, the (A3) solvent and the (B3) solvent may each independently be an aromatic hydrocarbon solvent, an alcohol solvent, an ether solvent, a ketone solvent, an ester solvent, a nitrogen-containing solvent, or a combination thereof.According to an embodiment of the present disclosure, the (A3) solvent and the (B3) solvent may each independently be benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, triethylbenzene, cyclohexane, cyclohexene, decahydronaphthalene, dipentene, pentane, hexane, heptane, octane, nonane, decane, ethylcyclohexane, methyl cyclohexane, cyclohexane, cyclohexene, p-menthane, dipropyl ether, dibutyl ether, anisole, ethyl acetate, butyl acetate, pentyl acetate, methyl isobutyl ketone, cyclohexylbenzene, cyclohexanone, cyclopentanone (CPN), triglyme, 1,3-dimethyl-2-imidazolidinone (DMI), N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK), N,N-dimethylacetamide (DMAc), γ-butyrolactone (GBL), N,N-dimethylformamide (DMF), propylene glycol methyl ether acetate (PGMEA), dimethyl sulfoxide (DMSO), or a combination thereof.

[0067] According to an embodiment of the present disclosure, the first resin composition may be composed of the (A1) monomer, (A2) initiator, and (A3) solvent. According to an embodiment of the present disclosure, the second resin composition may be composed of the (B1) monomer, (B2) initiator, and (B3) solvent.

[0068] According to an embodiment of the present disclosure, there is no particular limitation on the molecular weight of the first acrylic resin described in the present disclosure, and those of ordinary skill in the art can adjust it according to actual needs so that the first acrylic resin can undergo a crosslinking reaction with the first crosslinking agent to form a first adhesive layer. According to an embodiment of the present disclosure, the weight average molecular weight (Mw) of the first acrylic resin may be about 50,000 (g / mol) to 500,000 (g / mol), such as about 80,000 (g / mol), 100,000 (g / mol), 200,000 (g / mol), 300,000 (g / mol), or 400,000 (g / mol).

[0069] According to an embodiment of the present disclosure, there is no particular limitation on the molecular weight of the second acrylic resin described in the present disclosure, and those of ordinary skill in the art can adjust it according to actual needs so that the second acrylic resin can undergo a crosslinking reaction with the second crosslinking agent to form a second adhesive layer. According to an embodiment of the present disclosure, the weight average molecular weight (Mw) of the second acrylic resin may be about 50,000 (g / mol) to 500,000 (g / mol), such as about 80,000 (g / mol), 100,000 (g / mol), 200,000 (g / mol), 300,000 (g / mol), or 400,000 (g / mol). The weight average molecular weight (Mw) of the acrylic resin described in the present disclosure can be measured by gel permeation chromatography (GPC) (using polystyrene as a standard to prepare a calibration curve).

[0070] According to an embodiment of the present disclosure, the method for preparing the acrylic resin described in the present disclosure may include the following steps. First, a resin composition (such as the first resin composition or the second resin composition) is provided. Then, a heating process is performed on the resin composition, where the temperature of the heating process may be 60°C to 130°C, and the process time may be 5 hours to 24 hours.

[0071] According to an embodiment of the present disclosure, in the first adhesive composition, the weight ratio of the first crosslinking agent to the first acrylic resin may be from about 1:5,000 to 5:100, such as 2:5,000, 3:5,000, 4:5,000, 1:1,000, 2:1,000, 3:1,000, 4:1,000, 5:1,000, 8:1,000, 1:100, 2:100, 3:100, or 4:100. According to an embodiment of the present disclosure, in the second adhesive composition, the weight ratio of the second crosslinking agent to the second acrylic resin may be from about 1:5,000 to 5:100, such as 3:1,000, 4:1,000, 5:1,000, 8:1,000, 1:100, 2:100, 3:100, or 4:100.

[0072] According to an embodiment of the present disclosure, the first crosslinking agent and the second crosslinking agent may each independently be a compound having at least two crosslinkable functional groups (e.g., a compound having two crosslinkable functional groups, a compound having three crosslinkable functional groups, a compound having four crosslinkable functional groups, or a compound having five crosslinkable functional groups), wherein the crosslinkable functional group may be an isocyanate group, a carboxyl group, an aziridine group, an anhydride group, or a melamine group. For example, the first crosslinking agent and the second crosslinking agent may each independently be 2,4-toluenediisocyanate, 2,5-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate, isophorone diisocyanate, 4,4'-methylene dicyclohexyldiisocyanate, 4,4'-methylenediphenyldiisocyanate, or a combination of the foregoing.

[0073] According to an embodiment of the present disclosure, in the first adhesive composition, a photoinitiator may be further included to enhance adhesion. According to an embodiment of the present disclosure, in the first adhesive composition, the weight ratio of the photoinitiator to the first acrylic resin may be from 0.01:99.99 to 3:97, such as 0.05:99.95, 0.1:99.9, 0.2:99.8, 0.3:99.7, 0.5:99.5, 1:99, 1.5:98.5, 2:98, or 2.5:97.5. When the weight ratio of the photoinitiator to the first acrylic resin is too high, the first adhesive layer 12 is liable to deteriorate and turn yellow.

[0074] According to an embodiment of the present disclosure, in the first adhesive composition, a first solvent may be further included. The amount of the first solvent used can be adjusted as needed to uniformly disperse the first acrylic resin, the compound having the structure shown in formula (I), and the first crosslinking agent in the solvent. For example, the solid content of the first adhesive composition may be from 20 wt% to 70 wt% (such as about 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or 65 wt%). Here, the solid content refers to the weight percentage of all components of the first adhesive composition except the first solvent, based on the total weight of the first adhesive composition.

[0075] According to an embodiment of the present disclosure, in the second adhesive composition, a second solvent may be further included. The amount of the second solvent used can be adjusted as needed to uniformly disperse the second acrylic resin and the second crosslinking agent in the solvent. For example, the solid content of the second adhesive composition may be from 20 wt% to 70 wt% (such as about 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, or 65 wt%). Here, the solid content refers to the weight percentage of all components of the second adhesive composition except the second solvent, based on the total weight of the second adhesive composition.

[0076] According to an embodiment of the present disclosure, the first solvent and the second solvent may each independently be an aromatic hydrocarbon solvent, an alcohol solvent, an ether solvent, a ketone solvent, an ester solvent, a nitrogen-containing solvent, or a combination of the foregoing.According to embodiments of the present disclosure, the first solvent and the second solvent may each independently be benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, triethylbenzene, cyclohexane, cyclohexene, decahydronaphthalene, dipentene, pentane, hexane, heptane, octane, nonane, decane, ethylcyclohexane, methyl cyclohexane, cyclohexane, cyclohexene, p-menthane, dipropyl ether, dibutyl ether, anisole, ethyl acetate, butyl acetate, pentyl acetate, methyl isobutyl ketone, cyclohexylbenzene, cyclohexanone, cyclopentanone (CPN), triglyme, 1,3-dimethyl-2-imidazolidinone (DMI), N-methyl-2-pyrrolidone (NMP), methyl ethyl ketone (MEK), N,N-dimethylacetamide (DMAc), γ-butyrolactone (GBL), N,N-dimethylformamide (DMF), propylene glycol methyl ether acetate (PGMEA), dimethyl sulfoxide (DMSO), or a combination of the foregoing.

[0077] According to an embodiment of the present disclosure, the first adhesive composition may be composed of the first acrylic resin, a compound having the structure shown in formula (I), a first crosslinking agent, and a first solvent. According to an embodiment of the present disclosure, the first adhesive composition may be composed of the first acrylic resin, a compound having the structure shown in formula (I), a first crosslinking agent, a photoinitiator, and a first solvent. According to an embodiment of the present disclosure, the second adhesive composition may be composed of the second resin composition, a second crosslinking agent, and a second solvent.

[0078] According to an embodiment of the present disclosure, in the first adhesive composition, a first catalyst may be further included to accelerate the crosslinking reaction of the first adhesive composition. According to an embodiment of the present disclosure, the weight ratio of the first catalyst to the first acrylic resin may be about 1:10,000 to 1:100, such as 1:5,000, 2:5,000, 3:5,000, 4:5,000, 1:1,000, 2:1,000, 3:1,000, 4:1,000, 5:1,000, 6:1,000, 7:1,000, 8:1,000, or 9:1,000.

[0079] According to an embodiment of the present disclosure, in the second adhesive composition, a second catalyst may be further included to accelerate the crosslinking reaction of the second adhesive composition. According to an embodiment of the present disclosure, the weight ratio of the second catalyst to the second acrylic resin may be about 1:10,000 to 1:100, such as 1:5,000, 2:5,000, 3:5,000, 4:5,000, 1:1,000, 2:1,000, 3:1,000, 4:1,000, 5:1,000, 6:1,000, 7:1,000, 8:1,000, or 9:1,000.

[0080] According to embodiments of the present disclosure, the first catalyst and the second catalyst may each independently be bismuth nitrate, bismuth neodecanoate, lead 2-ethylhexoate, lead benzoate, neodecanoic acid, lithium salt, ferric chloride, antimony trichloride, antimony glycolate, stannous salts of carboxylic acids, zinc salts of carboxylic acids, dialkyl tin salts of carboxylic acids, glycine salts, tertiary amine trimerization catalysts, quaternary ammonium carboxylates, alkali metal carboxylic acid salts, potassium acetate, potassium octoate, potassium 2-ethylhexanoate, N-(2-hydroxy-5-nonylphenol)methyl-N-methylglycinate, tin(II) 2-ethylhexanoate, dibutyltin dilaurate, or a combination of the foregoing.

[0081] According to embodiments of the present disclosure, the first adhesive composition may be composed of the first resin composition, the first crosslinking agent, the first solvent, and the first catalyst. According to embodiments of the present disclosure, the second adhesive composition may be composed of the second resin composition, the second crosslinking agent, the second solvent, and the second catalyst.

[0082] According to an embodiment of the present disclosure, the first adhesive composition may be composed of the first acrylic resin, a compound having the structure shown in formula (I), a first crosslinking agent, a first solvent, and the first catalyst. According to an embodiment of the present disclosure, the first adhesive composition may be composed of the first acrylic resin, a compound having the structure shown in formula (I), a first crosslinking agent, a photoinitiator, a first solvent, and the first catalyst. According to an embodiment of the present disclosure, the second adhesive composition may be composed of the second resin composition, a second crosslinking agent, a second solvent, and the second catalyst.

[0083] The first adhesive composition described in the present disclosure may substantially be composed of a first acrylic resin, a compound having the structure shown in formula (I), a first crosslinking agent, a photoinitiator, a first solvent, and the first catalyst. In other words, the first acrylic resin, the compound having the structure shown in formula (I), the first crosslinking agent, the photoinitiator, the first solvent, and the first catalyst are the main components of the first adhesive composition. In addition to the main components, the first adhesive composition may optionally add additives (as secondary components), where the additives may be additives well-known in the adhesive layer, such as adhesion modifiers, leveling agents, surface treatment agents, viscosity modifiers, stabilizers, and antioxidants. According to an embodiment of the present disclosure, in the first adhesive composition, the weight ratio of the secondary component to the first acrylic resin may be about 1:10,000 to 1:10, such as about 1:5,000, 1:2,500, 1:2,000, 1:1,000, 1:500, 1:300, 1:200, 1:100, 1:50, 1:40, 1:30, 1:20, or 1:15.

[0084] According to an embodiment of the present disclosure, the photoinitiator may be a benzoin-based compound, an acetophenone-based compound, a thioxanthone-based compound, a ketal compound, a benzophenone-based compound, an α-aminoacetophenone compound, an acylphosphine oxide compound, a biimidazole-based compound, a triazine-based compound, or a combination of the above. Benzoin-based compounds, such as benzoin, benzoin methyl ether, or benzoin dimethyl ether; acetophenone-based compounds, such as p-dimethylamino-acetophenone, α,α’-dimethoxyazoxy-acetophenone, 2,2’-dimethyl-2-phenyl-acetophenone, p-methoxy-acetophenone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, 2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone; benzophenone-based compounds, such as benzophenone, 4,4-bis(dimethylamino)benzophenone, 4,4-bis(diethylamino)benzophenone, 2,4,6-trimethylaminobenzophenone, methyl-o-benzoyl benzoate, 3,3-dimethyl-4-methoxybenzophenone, and 3,3,4,4-Tetra(t-butylperoxycarbonyl)benzophenone (3,3,4,4-tetra(t-butylperoxycarbonyl)benzophenone); thioxanthone compounds, such as thioxanthone, 2,4-diethyl-thioxanthanone, thioxanthone-4-sulfone; diimidazole compounds, such as 2,2’-bis(o-chlorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-fluorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-methylphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-methoxyphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(o-ethylphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(p-methoxyphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(2,2’,4,4’-tetramethoxyphenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(2-chlorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(2,4-dichlorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole, 2,2’-bis(2,4-dichlorophenyl)-4,4’,5,5’-tetraphenyl-biimidazole]; acylphosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; triazine compounds such as 3-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionic acid, 1,1,1,3,3,3-hexafluoroisopropyl-3-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionate, ethyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate, methyl-2-epoxyethyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate, methyl-cyclohexyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate, methyl-benzyl-2-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}acetate, 3-{chloro-4-[2,(3-{chloro-4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionic acid), 3-{4-[2,4-bis(trichloromethyl)-s-triazine-6-yl]phenylthio}propionamide, 2,4-bis(trichloromethyl)-6-p-methoxystyryl-s-triazine, 2,4-bis(trichloromethyl)-6-(1-p-dimethylaminophenyl)-1,3,-butadienyl-s-triazine, or 2-trichloromethyl-4-amino-6-p-methoxystyryl-s-triazine.,

[0085] According to an embodiment of the present disclosure, the acetophenone-based compound may be a photoinitiator manufactured by Ciba Geigy and having a product number of Irgacure 2959, Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 379, Irgacure 907, or Darocur 1173.

[0086] According to an embodiment of the present disclosure, the acylphosphine oxide-based compound may be a photoinitiator manufactured by Ciba Geigy and having a product number of Irgacure 819 or Irgacure 1800, and a photoinitiator manufactured by BASF and having a product number of Lucirin TPO or Lucirin TPO-L.

[0087] According to an embodiment of the present disclosure, the initiator described in the present disclosure may also be a photoinitiator manufactured by LAMBSON and having product numbers Esacure 1001M, Esacure KIP150, Speedcure BEM, Speedcure EHA, Speedcure BMS, Speedcure MBP, Speedcure PBZ, Speedcure ITX, Speedcure DETX, Speedcure EBD, Speedcure MBB, Speedcure BP, or a photoinitiator manufactured by Ciba Geigy and having product numbers Irgacure 2100, Irgacure 250, or Irgacure 784.

[0088] According to an embodiment of the present disclosure, the molecular weight of the crosslinked reaction product (i.e., the first adhesive layer) obtained from the first adhesive composition described in the present disclosure is not particularly limited, and those with ordinary knowledge in the technical field can adjust it according to actual needs. According to an embodiment of the present disclosure, the weight average molecular weight (Mw) of the product obtained from the first adhesive composition may be about 50,000 (g / mol) to 2,000,000 (g / mol), such as about 80,000 (g / mol), 100,000 (g / mol), 200,000 (g / mol), 300,000 (g / mol), 400,000 (g / mol), 500,000 (g / mol), 800,000 (g / mol), 1,000,000 (g / mol), or 1,500,000 (g / mol).

[0089] According to an embodiment of the present disclosure, the molecular weight of the crosslinked reaction product (i.e., the second adhesive layer) obtained from the second adhesive composition described in the present disclosure is not particularly limited, and those with ordinary knowledge in the technical field can adjust it according to actual needs. According to an embodiment of the present disclosure, the weight average molecular weight (Mw) of the product obtained from the second adhesive composition may be about 50,000 (g / mol) to 2,000,000 (g / mol), such as about 80,000 (g / mol), 100,000 (g / mol), 200,000 (g / mol), 300,000 (g / mol), 400,000 (g / mol), 500,000 (g / mol), 800,000 (g / mol), 1,000,000 (g / mol), or 1,500,000 (g / mol). The weight average molecular weight (Mw) of the crosslinked reaction product described in the present disclosure can be measured by gel permeation chromatography (GPC) (using polystyrene as the standard to make the calibration curve).

[0090] According to an embodiment of the present disclosure, the method for preparing the adhesive layer (such as the first adhesive layer or the second adhesive layer) described in the present disclosure may include the following steps. First, provide an adhesive composition (such as the first adhesive composition or the second adhesive composition). Then, form a coating on the substrate by a coating process using the adhesive composition. Then, perform a heating process on the coating to obtain the adhesive layer. The temperature of the heating process may be 60°C to 120°C, and the process time may be 1 minute to 60 minutes.

[0091] According to an embodiment of the present disclosure, the method for preparing the double-sided adhesive described in the present disclosure may include the following steps. First, form a first coating on the first release film by a coating process using the first adhesive composition. Then, perform a heating process on the coating to obtain a first adhesive layer disposed on the first release film. Then, form a second coating on the second release film by a coating process using the second adhesive composition. Then, perform a heating process on the coating to obtain a second adhesive layer disposed on the second release film. Then, dispose the first adhesive layer on top of the second adhesive layer, and after a lamination process, form a laminate (structure: first release film / first adhesive layer / second adhesive layer / second release film).

[0092] The thickness of the double-sided adhesive described in the present disclosure is not particularly limited and can be selected according to actual needs. According to an embodiment of the present disclosure, the average thickness of the double-sided adhesive may be about 10 μm to 500 μm, such as 50 μm, 100 μm, 150 μm, 200 μm, 300 μm, or 400 μm. In addition, according to an embodiment of the present disclosure, the average thickness ratio of the first adhesive layer to the second adhesive layer may be about 5:1 to 1:5, such as 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, or 1:4.

[0093] According to an embodiment of the present disclosure, the present disclosure also provides a multi-layer structure 100, as Figure 2 shown. The multi-layer structure 100 includes the double-sided adhesive 10, the first substrate 20, and the second substrate 30 described in the present disclosure, wherein the double-sided adhesive 10 is disposed between the first substrate 20 and the second substrate 30. The double-sided adhesive 10 has a first adhesive layer 12 and a second adhesive layer 14. The first substrate 20 is disposed on the first surface 11 of the first adhesive layer 12 such that the first substrate 20 is in direct contact with the first adhesive layer 12. The double-sided adhesive 10 is directly disposed on the second substrate 30 such that the second surface 13 of the second adhesive layer 14 is in direct contact with the second substrate 30.

[0094] According to an embodiment of the present disclosure, the double-sided adhesive 10 is used to fix the first substrate 20 on the second substrate 30 to obtain the multi-layer structure 100. In addition, after the multi-layer structure 100 is subjected to a low-temperature treatment, the first substrate 20 can be peeled off from the second substrate 30 without any adhesive remaining on the second substrate 30. Specifically, after the double-sided adhesive 10 according to the present disclosure is subjected to a low-temperature treatment, the adhesive force of the first adhesive layer 12 and the second adhesive layer 14 of the double-sided adhesive 10 decreases, and a large difference in the adhesive force occurs between the first surface 11 of the first adhesive layer 12 and the second surface 13 of the second adhesive layer 14. Therefore, after the peeling process, not only can the first substrate 20 be easily peeled off from the second substrate 30, but also the double-sided adhesive 10 will only remain on the first substrate 20 and will not remain on the second substrate 30. In this way, the reuse rate of the display panel components is improved and the efficiency of the rework process can be accelerated.

[0095] According to an embodiment of the present disclosure, since the first adhesive layer 12 of the double-sided adhesive 10 according to the present disclosure has better gap-filling ability, it can be used to bond to the first substrate 20 with a step on the surface and fill the step.

[0096] Please refer to Figure 3 , the multi-layer structure 100 includes the double-sided adhesive 10, the first substrate 20, and the second substrate 30 according to the present disclosure. Here, any desired film layer 25 can be formed on the first substrate 20, so there is a step between the film layer 25 and the first substrate 20. As Figure 3 shown. Since the first adhesive layer 12 of the double-sided adhesive 10 according to the present disclosure has better gap-filling ability, when the double-sided adhesive 10 is disposed on the first substrate 20 with the first adhesive layer 12 and subjected to a pressing process (such as rolling or rolling), the first adhesive layer 12 can completely fill the gap between the film layer 25 and the first substrate 20 to avoid the generation of voids. According to an embodiment of the present disclosure, the ratio of the height of the step to the thickness of the first adhesive layer 12 can be from 1:1,000 to 1:1, such as 1:1,000, 1:500, 1:300, 1:200, 1:100, 1:50, 1:40, 1:30, 1:20, 1:15, 1:10, 1:8, 1:5, 1:3, 1:2, or 2:3.

[0097] According to an embodiment of the present disclosure, after the multi-layer structure 10 is subjected to a low-temperature treatment, the adhesion force (P1) between the first adhesive layer 12 and the first substrate 20 is greater than the adhesion force (P2) between the second adhesive layer 14 and the second substrate 30. According to an embodiment of the present disclosure, P1 and P2 meet the following conditions: P1 - P2 ≥ 200 gf / 25 mm (for example, 300 gf / 25 mm, 400 gf / 25 mm, 500 gf / 25 mm, 600 gf / 25 mm, 700 gf / 25 mm, 800 gf / 25 mm, 900 gf / 25 mm, 1,000 gf / 25 mm, or 1,500 gf / 25 mm). Here, the measurement method of the adhesion force is carried out according to the method specified in ASTM D3330. The measurement conditions of the adhesion force are as follows: using a tensile testing machine (QC-506B1, Guanglai Instrument Co., Ltd.), the pulling angle of the polyethylene terephthalate (PET) substrate is 180°, and the pulling speed is 300 mm / min.

[0098] According to an embodiment of the present disclosure, the first substrate 20 and the second substrate 30 may be two substrates that need to be bonded. According to an embodiment of the present disclosure, the substrate is not particularly limited and may be a metal sheet, a silicon substrate, glass, or a polymer film, and any required film layer may have been formed on the substrate. For example, the first substrate 20 and the second substrate 30 may each independently be glass, a transparent substrate, a release film, an optical protective film, a brightness enhancement film, a retardation film, a polarizer, a touch panel, an antireflection film, a light guide plate, or a diffusion film.

[0099] According to some embodiments of the present disclosure, the multi-layer structure 100 may be a display panel, the first substrate 20 may be a touch panel, and the second substrate 30 may be a polarizer, wherein the touch panel may include transparent glass or a transparent substrate, and a transparent conductive electrode is formed on at least one surface of the transparent glass or the transparent substrate.

[0100] According to an embodiment of the present disclosure, the method for manufacturing the multi-layer structure described in the present disclosure may include the following steps. First, provide a laminate having the double-sided tape described in the present disclosure (structure: first release film / first adhesive layer / second adhesive layer / second release film). Then, remove the first release film to expose the first surface of the first adhesive layer, dispose the first substrate on the first surface of the first adhesive layer, and perform a first lamination process. Then, remove the second release film to expose the second surface of the second adhesive layer, dispose the second adhesive layer on the second substrate, and perform a second lamination process to obtain the multi-layer structure described in the present disclosure. In addition, after the first lamination process, the first adhesive layer may be irradiated with a light source (such as ultraviolet light).

[0101] To make the above and other objects, features, and advantages of the present disclosure more apparent and understandable, several embodiments are specifically exemplified below in conjunction with the accompanying drawings and described in detail as follows:

[0102] Preparation of Acrylic Resin

[0103] Preparation Example 1

[0104] Add 388.19 grams of ethyl acetate to the reaction flask and introduce nitrogen. Then, add 18.96 grams of hydroxyethyl acrylate (Tg = 258K), 28.23 grams of acryloylmorpholine (Tg = 418K), 17.06 grams of acrylamide (Tg = 438K), 63.20 grams of n-butyl methacrylate (Tg = 293K), 387.13 grams of n-butyl acrylate (Tg = 219K), and 1.29 grams of azobisisobutyronitrile. After reacting at 85°C for 16 hours, a solution containing acrylic resin (1) with a solid content of approximately 57.1 wt% is obtained.

[0105] Preparation Example 2

[0106] Add 384.19 grams of ethyl acetate to the reaction flask and introduce nitrogen. Then, add 18.96 grams of hydroxyethyl acrylate (Tg = 258K), 45.17 grams of acryloylmorpholine (Tg = 418K), 27.29 grams of acrylamide (Tg = 438K), 86.18 grams of n-butyl methacrylate (Tg = 293K), 384.19 grams of n-butyl acrylate (Tg = 219K), and 1.27 grams of azobisisobutyronitrile. After reacting at 85°C for 16 hours, a solution containing acrylic resin (2) with a solid content of approximately 57.1 wt% is obtained.

[0107] The contents of the first monomer, second monomer, and third monomer used to prepare acrylic resin (1) and acrylic resin (2), as well as the estimated glass transition temperatures of acrylic resin (1) and acrylic resin (2), are shown in Table 1. The estimated glass transition temperatures are calculated using the Fox equation.

[0108] Table 1

[0109] First monomer (wt%) Second monomer (wt%) Third monomer (wt%) Estimated glass transition temperature (°C) Acrylic resin (1) 3.68 75.23 21.08 -35 Acrylic resin (2) 3.72 65.13 31.15 -25

[0110] Preparation of adhesive composition and adhesive layer

[0111] Preparation Example 3

[0112] 0.1 g of dibutyltin dilaurate (DBTDL) was mixed with 9.9 g of ethyl acetate to obtain a DBTDL solution. Next, 1 g of hexamethylene diisocyanate (HMDI) was mixed with 9 g of ethyl acetate to obtain an HMDI solution. Next, 175.25 g of a solution containing an acrylic resin (1) and 103.0 g of ethyl acetate were added to a reaction flask. After sufficient stirring and mixing, 1.33 g of the above HMDI solution and 0.25 g of the above DBTDL solution were added to the reaction flask. After stirring for 30 minutes, an adhesive composition (1) (solid content of about 35.8 wt%) was obtained.

[0113] Preparation Example 4

[0114] 0.1 g of dibutyltin dilaurate (DBTDL) was mixed with 9.9 g of ethyl acetate to obtain a DBTDL solution. Next, 1 g of hexamethylene diisocyanate (HMDI) was mixed with 9 g of ethyl acetate to obtain an HMDI solution. Next, 175.25 g of a solution containing an acrylic resin (2) and 103.0 g of ethyl acetate were added to a reaction flask. After sufficient stirring and mixing, 1.58 g of the above HMDI solution and 0.25 g of the above DBTDL solution were added to the reaction flask. After stirring for 30 minutes, an adhesive composition (2) (solid content of about 35.8 wt%) was obtained.

[0115] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (2) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number H338A, sold by Nan Ya Plastics Industry Co., Ltd.). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (1) (thickness approximately 90 μm) disposed on a heavy release PET substrate was obtained.

[0116] Preparation Example 5

[0117] 100 grams of the adhesive composition (1) and 5 grams of isobornyl acrylate were mixed to obtain the adhesive composition (3).

[0118] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (3) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industry Co., Ltd.). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (2) (thickness approximately 90 μm) disposed on a light release PET substrate was obtained.

[0119] Preparation Example 6

[0120] 100 grams of the adhesive composition (1) and 10 grams of isobornyl acrylate were mixed to obtain the adhesive composition (4).

[0121] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (4) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industry Co., Ltd.). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (3) (thickness approximately 90 μm) disposed on a light release PET substrate was obtained.

[0122] Preparation Example 7

[0123] Mix 100 g of the adhesive composition (1), 5 g of isobornyl acrylate, and 0.5 g of the photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (DOUBLE BOND CHEMICAL, product number 819) to obtain the adhesive composition (5).

[0124] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), coat the adhesive composition (5) onto a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industry Co., Ltd.). Then, place the release film in an oven and dry it at 100 °C for 5 minutes and cure it at 70 °C for 18 hours. After cooling to room temperature and standing still, obtain the adhesive layer (4) (thickness about 90 μm) disposed on the lightly release PET substrate.

[0125] Preparation Example 8

[0126] Mix 100 g of the adhesive composition (1), 5 g of isobornyl acrylate, and 1 g of the photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (DOUBLE BOND CHEMICAL, product number 819) to obtain the adhesive composition (6).

[0127] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), coat the adhesive composition (6) onto a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industry Co., Ltd.). Then, place the release film in an oven and dry it at 100 °C for 5 minutes and cure it at 70 °C for 18 hours. After cooling to room temperature and standing still, obtain the adhesive layer (5) (thickness about 90 μm) disposed on the lightly release PET substrate.

[0128] Comparative Example 1

[0129] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (1) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industry Co., Ltd.). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (6) (thickness approximately 90 μm) disposed on a lightly releasing PET substrate was obtained.

[0130] Comparative Example 2

[0131] 100 g of the adhesive composition (1) and 15 g of isobornyl acrylate were mixed to obtain an adhesive composition (7).

[0132] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (7) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industry Co., Ltd.). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (7) (thickness approximately 90 μm) disposed on a lightly releasing PET substrate was obtained.

[0133] Comparative Example 3

[0134] 100 g of the adhesive composition (1) and 20 g of isobornyl acrylate were mixed to obtain an adhesive composition (8).

[0135] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (8) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industry Co., Ltd.). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (8) (thickness approximately 90 μm) disposed on a lightly releasing PET substrate was obtained.

[0136] Comparative Example 4

[0137] 100 g of the adhesive composition (1), 5 g of isobornyl acrylate, and 2 g of the photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (DOUBLE BOND CHEMICAL, product number 819) were mixed to obtain the adhesive composition (9).

[0138] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (9) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industries). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (9) (thickness of about 90 μm) disposed on a lightly release PET substrate was obtained.

[0139] Preparation Example 9

[0140] 100 g of the adhesive composition (1), 5 g of tetrahydrofurfuryl acrylate, and 0.5 g of the photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (DOUBLE BOND CHEMICAL, product number 819) were mixed to obtain the adhesive composition (10).

[0141] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (10) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industries). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and aged at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (10) (thickness of about 90 μm) disposed on a lightly release PET substrate was obtained.

[0142] Preparation Example 10

[0143] 100 g of the adhesive composition (1), 5 g of 2-N-morpholinoethyl methacrylate, and 0.5 g of the photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (DOUBLE BOND CHEMICAL, product number 819) were mixed to obtain the adhesive composition (11).

[0144] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (11) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industries). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then cured at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (11) (thickness of approximately 90 μm) disposed on a lightly releasing PET substrate was obtained.

[0145] Preparation Example 11

[0146] 100 g of the adhesive composition (1), 5 g of cyclictrimethylolpropane formal acrylate, and 0.5 g of the photoinitiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (DOUBLE BOND CHEMICAL, product number 819) were mixed to obtain the adhesive composition (12).

[0147] Using a doctor blade with a gap of 420 μm and a width of 150 mm and a translational coater (model ZAA2300, sold by ZEHNTNER), the adhesive composition (12) was coated on a release film (polyethylene terephthalate (PET); thickness 38 μm; product number LA38A, sold by Nan Ya Plastics Industries). Subsequently, the release film was placed in an oven and dried at 100 °C for 5 minutes and then cured at 70 °C for 18 hours. After cooling to room temperature and standing still, an adhesive layer (12) (thickness of approximately 90 μm) disposed on a lightly releasing PET substrate was obtained.

[0148] Preparation of Double-Sided Adhesive

[0149] Example 1

[0150] The adhesive layer (2) disposed on the light release PET substrate is combined with the adhesive layer (1) disposed on the heavy release PET substrate, such that the adhesive layer (1) contacts the adhesive layer (2), to obtain a laminate comprising a double-sided tape (1) (the laminate structure is: light release PET substrate / adhesive layer (2) / adhesive layer (1) / heavy release PET substrate).

[0151] Example 2

[0152] Example 2 is carried out in the same manner as Example 1, except that the adhesive layer (3) is used to replace the adhesive layer (2), to obtain a laminate comprising a double-sided tape (2) (the laminate structure is: light release PET substrate / adhesive layer (3) / adhesive layer (1) / heavy release PET substrate).

[0153] Example 3

[0154] Example 3 is carried out in the same manner as Example 1, except that the adhesive layer (4) is used to replace the adhesive layer (2), to obtain a laminate comprising a double-sided tape (3) (the laminate structure is: light release PET substrate / adhesive layer (4) / adhesive layer (1) / heavy release PET substrate).

[0155] Example 4

[0156] Example 4 is carried out in the same manner as Example 1, except that the adhesive layer (5) is used to replace the adhesive layer (2), to obtain a laminate comprising a double-sided tape (4) (the laminate structure is: light release PET substrate / adhesive layer (5) / adhesive layer (1) / heavy release PET substrate).

[0157] Comparative Example 5

[0158] Comparative Example 5 is carried out in the same manner as Example 1, except that the adhesive layer (6) is used to replace the adhesive layer (2), to obtain a laminate comprising a double-sided tape (5) (the laminate structure is: light release PET substrate / adhesive layer (6) / adhesive layer (1) / heavy release PET substrate).

[0159] Comparative Example 6

[0160] Comparative Example 5 is carried out in the same manner as Example 1, except that the adhesive layer (7) is used to replace the adhesive layer (2), to obtain a laminate comprising a double-sided tape (6) (the laminate structure is: light release PET substrate / adhesive layer (7) / adhesive layer (1) / heavy release PET substrate).

[0161] Comparative Example 7

[0162] Comparative Example 5 is carried out in the same manner as Example 1, except that the adhesive layer (8) is used to replace the adhesive layer (2), to obtain a laminate comprising a double-sided tape (7) (the laminate structure is: light release PET substrate / adhesive layer (8) / adhesive layer (1) / heavy release PET substrate).

[0163] Comparative Example 8

[0164] Comparative Example 5 was carried out in the same manner as described in Example 1, except that the adhesive layer (9) was used to replace the adhesive layer (2), and a laminate containing a double-sided tape (8) was obtained (the laminate structure was: a light release PET substrate / adhesive layer (9) / adhesive layer (1) / heavy release PET substrate).

[0165] Adhesive layer evaluation

[0166] A glass plate (with dimensions of 45 mm x 75 mm and a thickness of 1.8 mm) was provided, and a polyethylene terephthalate (PET) pattern (with dimensions of 20 mm x 65 mm and a thickness of about 25 μm) was formed on the upper surface of the glass plate. The laminates containing double-sided tapes described in Examples 1-4 and Comparative Examples 5-8 above were respectively cut to obtain rectangular films (with dimensions of 45 mm x 75 mm). Then, the light release PET substrate of the rectangular film was peeled off to expose the adhesive layer of the rectangular film. Then, the adhesive layer of the rectangular film was pasted on the glass plate with the PET pattern, and a 2 kg heavy rolling roller was used to roll back and forth on the heavy release PET substrate of the rectangular film. Then, the interface between the PET pattern and the glass plate was observed with an optical microscope. If the adhesive layer could completely fill the step difference between the PET pattern and the glass plate, the step difference filling effect was recorded as O, otherwise it was recorded as X. The results are shown in Table 2.

[0167] Then, the rectangular film was irradiated with ultraviolet light (UV) (wavelength of about 365 nm) to cure it, and an optical microscope was used to observe whether there were air hole defects in the cured adhesive layer (i.e., the adhesive layer in contact with the glass plate). The results are shown in Table 2. In addition, the b* value of the adhesive layer in contact with the glass plate was measured, and the results are shown in Table 2. The b* value was measured by the method specified in JIS Z 8730:2009.

[0168] Table 2

[0169] Effect of compensating for step difference Porosity defect b* value Example 1 O None 0.15 Example 2 O None 0.15 Example 3 O None 0.16 Example 4 O None 0.18 Comparative Example 5 X Yes 0.15 Comparative Example 6 X None 0.16 Comparative Example 7 X None 0.16 Comparative Example 8 O None 0.31

[0170] As can be seen from Table 2, the first adhesive composition described in the present disclosure has a specific composition (for example, the first adhesive composition contains a first acrylic resin, a first crosslinking agent, and a compound having the structure shown in formula (I)) and content (for example, the weight ratio of the compound having the structure shown in formula (I) to the first acrylic resin is about 10:90 to 25:75). Therefore, the adhesive layer formed using the first adhesive composition has a gap filling ability and can completely fill the step difference between the PET pattern and the glass plate. When the adhesive composition does not contain the compound having the structure shown in formula (I), the resulting adhesive layer (i.e., the adhesive layer described in Comparative Example 5) does not have the gap filling ability and has air hole defects. In addition, when the weight ratio of the compound having the structure shown in formula (I) to the first acrylic resin is too high, the resulting adhesive layer (i.e., the adhesive layers described in Comparative Examples 6 and 7) also does not have the gap filling ability. Furthermore, when the content of the photoinitiator in the adhesive composition is too high, the resulting adhesive layer (i.e., the adhesive layer described in Comparative Example 8) is prone to yellowing after irradiation with ultraviolet light.

[0171] Example 5

[0172] Example 5 was carried out in the same manner as described in Example 1, except that adhesive layer (10) was used to replace adhesive layer (2), to obtain a laminate containing double-sided tape (9) (the laminate structure is: light release PET substrate / adhesive layer (10) / adhesive layer (1) / heavy release PET substrate).

[0173] Example 6

[0174] Example 6 was carried out in the same manner as described in Example 1, except that adhesive layer (11) was used to replace adhesive layer (2), to obtain a laminate containing double-sided tape (10) (the laminate structure is: light release PET substrate / adhesive layer (11) / adhesive layer (1) / heavy release PET substrate).

[0175] Example 7

[0176] Example 7 was carried out in the same manner as described in Example 1, except that adhesive layer (12) was used to replace adhesive layer (2), to obtain a laminate containing double-sided tape (11) (the laminate structure is: light release PET substrate / adhesive layer (12) / adhesive layer (1) / heavy release PET substrate).

[0177] Adhesive layer evaluation

[0178] A glass plate (with dimensions of 45 mm x 75 mm and a thickness of 1.8 mm) is provided, and a polyethylene terephthalate (PET) pattern (with dimensions of 20 mm x 65 mm and a thickness of approximately 25 μm) is formed on the upper surface of the glass plate. The laminates containing double-sided tape described in Examples 5 - 8 above are respectively cut to obtain rectangular films (with dimensions of 45 mm x 75 mm). Then, the light release PET substrate of the rectangular film is peeled off to expose the adhesive layer of the rectangular film. Next, the adhesive layer of the rectangular film is pasted on the glass plate with the PET pattern described above, and a 2 kg heavy rolling roller is used to roll back and forth on the heavy release PET substrate of the rectangular film. Then, the interface between the PET pattern and the glass plate is observed with an optical microscope. If the adhesive layer can completely fill the step difference between the PET pattern and the glass plate, the step difference compensation effect is recorded as O; otherwise, it is recorded as X. The results are shown in Table 3.

[0179] Next, the rectangular film is irradiated with ultraviolet light (UV) (wavelength of approximately 365 nm) to cure it, and an optical microscope is used to observe whether there are air hole defects in the cured adhesive layer (i.e., the adhesive layer in contact with the glass plate). The results are shown in Table 3. In addition, the b* value of the adhesive layer in contact with the glass plate is measured, and the results are shown in Table 3.

[0180] Table 3

[0181] Effect of compensating for step difference Porosity defect b* value Example 5 O None 0.16 Example 6 O None 0.17 Example 7 O None 0.15

[0182] Preparation and reworkability test of multi-layer structure

[0183] Example 9

[0184] A polarizing plate with a structure of protective film / polarizing film / pressure-sensitive adhesive / release film (with dimensions of 45 mm x 75 mm, and the polarizing film model is MIC25518, sold by Lite-On Optoelectronics) is provided, and the protective film is peeled off for standby. A laminate containing double-sided tape (1) described in Example 1 is provided, and after cutting, a rectangular film (with dimensions of 45 mm x 75 mm) is obtained. Then, the light release PET substrate of the rectangular film is peeled off to expose the adhesive layer (2) of the rectangular film. Next, a glass plate (with a thickness of 1.8 mm) is provided, the adhesive layer (2) of the rectangular film is pasted on the glass plate, and a 2 kg heavy rolling roller is used to roll back and forth on the heavy release PET substrate of the rectangular film. Then, the heavy release PET substrate of the rectangular film is peeled off to expose the adhesive layer (1) of the rectangular film. Next, the adhesive layer (1) of the rectangular film is pasted on the polarizing film of the polarizing plate (with a structure of polarizing film / pressure-sensitive adhesive / release film), and a 2 kg heavy rolling roller is used to roll back and forth on the release film of the polarizing plate to obtain a multi-layer structure (1) (with a structure of glass plate / adhesive layer (2) / adhesive layer (1) / polarizing film / pressure-sensitive adhesive / release film).

[0185] After subjecting the multi-layer structure (1) to a low-temperature treatment at -30°C for 30 minutes, the difference in the adhesive force between the glass plate and the adhesive layer (1) and the adhesive force between the adhesive layer (2) and the polarizing film was evaluated, and the results are shown in Table 4. The measurement method of the peel adhesive force was based on ASTM D3330.

[0186] In addition, after subjecting the multi-layer structure (1) to a low-temperature treatment at -30°C for 30 minutes, the glass plate of the multi-layer structure (1) was peeled from the polarizing plate, and then the residual situation of the double-sided adhesive (1) (adhesive layer (1) / adhesive layer (2)) on the glass plate and the polarizing film was examined, and the results are shown in Table 4.

[0187] Table 4

[0188] Multilayer structure (1) Low-temperature treatment temperature (°C) -30 Double-sided tape remains on the glass plate Yes Double-sided tape remains on the polarizing film None Adhesion (between glass plate and first adhesive layer) - Adhesion (between second adhesive layer and polarizing film) (gf / 25 mm) ～750

[0189] As can be seen from Table 4, for the multi-layer structure made of the double-sided adhesive described in the present disclosure, by adjusting the content (W1) of the third monomer (hard monomer) of the acrylic resin used to prepare the first adhesive layer and the content (W2) of the third monomer (hard monomer) of the acrylic resin used to prepare the second adhesive layer (i.e., W2 - W1 > 37 wt%), after the multi-layer structure is subjected to a low-temperature treatment, a large difference in the adhesive force between the first adhesive layer and the second adhesive layer can be generated. Therefore, the glass plate and the polarizing plate can be easily peeled off, and the double-sided adhesive will not remain on the polarizing film.

[0190] In summary, due to the specific composition of the first adhesive layer, the first adhesive layer has better gap filling ability. In this way, even if there is a step difference on the bonding surface of the substrate, the first adhesive layer of the double-sided adhesive described in the present disclosure can still fully fill the step difference and avoid generating air hole defects between the bonding surface of the substrate during the bonding process. In addition, by controlling the difference in the content of the hard monomer in the first adhesive layer and the hard monomer in the second adhesive layer, a large difference in the adhesive force between the first adhesive layer and the second adhesive layer of the double-sided adhesive can be generated after the low-temperature treatment.

[0191] Although the present disclosure has been disclosed above with several embodiments, it is not intended to limit the present disclosure. Any person with ordinary knowledge in the technical field can make any changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to that defined by the appended claims.

Claims

1. A double-sided adhesive tape, comprising: A first adhesive layer, which is a product of a cross-linking reaction of a first adhesive composition, wherein the first adhesive composition comprises a first acrylic resin, a first cross-linking agent, and a compound having the structure shown in formula (I), wherein R 1 is hydrogen or methyl; and, R 2 is where n is 0, 1, 2, or 3; m is 0, 1, 2, or 3; i is 0, 1, 2, or 3; and, R 3 , R 4 and R 5 are independently hydrogen or C1-C4 alkyl; and A second adhesive layer, which is a product of a cross-linking reaction of a second adhesive composition, wherein the second adhesive composition comprises a second acrylic resin and a second cross-linking agent, wherein the glass transition temperature of the first adhesive layer is Tg1, and the glass transition temperature of the second adhesive layer is Tg2, wherein Tg2 is less than or equal to -30 °C, and Tg2 - Tg1 ≥ 10 °C.

2. The double-sided adhesive tape according to claim 1, wherein the weight ratio of the compound having the structure shown in formula (I) to the first acrylic resin is 10:90 to 25:

75.

3. The double-sided adhesive tape according to claim 1, wherein the first acrylic resin is a product of a copolymerization reaction of a first resin composition, wherein the first resin composition comprises (A1) monomers, wherein the (A1) monomers comprise a first monomer, a second monomer, and a third monomer, wherein the first monomer is an acrylate monomer having a hydroxyl group; the second monomer is an acrylate monomer whose homopolymer has a glass transition temperature less than or equal to -20 °C; and the third monomer is a monomer having a terminal vinyl group whose homopolymer has a glass transition temperature greater than or equal to 0 °C.

4. The double-sided adhesive tape according to claim 3, wherein the second acrylic resin is a product of a copolymerization reaction of a second resin composition, wherein the second resin composition comprises (B1) monomers, wherein the (B1) monomers comprise the first monomer, the second monomer, and the third monomer.

5. The double-sided adhesive tape according to claim 4, wherein the weight percentage of the third monomer in the (A1) monomers is W1, based on the weight of the (A1) monomers; the weight percentage of the third monomer in the (B1) monomers is W2, based on the weight of the (B1) monomers; and 45 wt% ≤ 3W2 - W1 ≤ 7 wt%.

6. The double-sided adhesive tape according to claim 3, wherein the weight percentage of the first monomer in the (A1) monomers is 1 wt% to 10 wt%, the weight percentage of the second monomer in the (A1) monomers is 50 wt% to 95 wt%, and the weight percentage of the third monomer in the (A1) monomers is 4 wt% to 42 wt%.

7. The double-sided adhesive tape according to claim 4, wherein the weight percentage of the first monomer in the (B1) monomers is 1 wt% to 10 wt%, the weight percentage of the second monomer in the (B1) monomers is 50 wt% to 95 wt%, and the weight percentage of the third monomer in the (B1) monomers is 11 wt% to 49 wt%.

8. The double-sided adhesive according to claim 3, wherein the first monomer is wherein R 6 is hydrogen or methyl, and R 7 is hydrogen, or a C1-C10 alkanol group.

9. The double-sided adhesive tape according to claim 3, wherein the second monomer is n-butyl acrylate, sec-butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, ethoxyethyl acrylate, isononyl acrylate, lauryl methacrylate, or a combination thereof.

10. The double-sided adhesive according to claim 3, wherein the third monomer is tert-butyl acrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, methyl acrylate, methyl methacrylate, acrylonitrile, acrylamide, acryloylmorpholine, N-vinyl-2-pyrrolidone, or a combination thereof.

11. The double-sided adhesive according to claim 1, wherein the second adhesive composition contains a compound having the structure shown in formula (I), or the second adhesive composition does not contain a compound having the structure shown in formula (I).

12. The double-sided adhesive according to claim 1, wherein the first crosslinking agent and the second crosslinking agent are each independently a compound having at least two crosslinkable functional groups, and the crosslinkable functional group is an isocyanate group, a carboxyl group, an aziridinyl group, an acid anhydride group, or a melamine group.

13. The double-sided adhesive according to claim 1, wherein the weight ratio of the first crosslinking agent to the first acrylic resin is 1:5,000 to 5:100, and the weight ratio of the second crosslinking agent to the second acrylic resin is 1:5,000 to 5:

100.

14. The double-sided adhesive according to claim 3, wherein the first resin composition further contains an initiator (A2), and the second resin composition further contains an initiator (B2).

15. The double-sided adhesive according to claim 3, wherein the composition of the monomers (A1) of the first resin composition is the same as the composition of the monomers (B1) of the second resin composition, or the composition of the monomers (A1) of the first resin composition is different from the composition of the monomers (B1) of the second resin composition.

16. The double-sided adhesive according to claim 1, wherein the first adhesive composition further contains a photoinitiator, and the weight ratio of the photoinitiator to the first acrylic resin is 0.01:99.99 to 3:

97.

17. A multi-layer structure, comprising: a first substrate; a second substrate; and the double-sided adhesive according to claim 1, wherein the first adhesive layer has a first surface, the second adhesive layer has a second surface, the first surface is in contact with the first substrate, and the second surface is in contact with the second substrate.

18. The multi-layer structure according to claim 17, wherein the first substrate and the second substrate are each independently glass, a transparent substrate, a release film, an optical protective film, a brightness enhancement film, a retardation film, a polarizing plate, a touch panel, an anti-reflection film, a light guide plate, or a diffusion film.

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