Adhesives and multilayer structures

Abstract

To provide a novel adhesive agent suitable for a cutting-edge wafer process.SOLUTION: An adhesive agent contains polyimide, and polyimide is a reaction product of reactant (a) and reactant (b). The reactant (a) is first diamine, or the reactant (a) consists of first diamine and second diamine, the reactant (b) consists of first dianhydride and second dianhydride. The first diamine is diamine containing a diphenyl ether part, the first dianhydride is dianhydride containing a diphenyl ether part, the second diamine is not diamine containing a diphenyl ether part, and the second dianhydride is not dianhydride containing a diphenyl ether part. The total weight percentage of the first diamine and the first dianhydride for the total weight of the reactant (a) and the reactant (b) is 55wt% to 94wt%.SELECTED DRAWING: Figure 1

Description

[Technical Field] 【0001】 This disclosure relates to adhesives and multilayer structures. [Background technology] 【0002】 Advanced wafer processing aims for miniaturization and finer linewidths. To avoid problems such as the formation of fragments and residues during wafer processing, it is necessary to enhance the dimensional stability and temperature resistance of adhesive materials used to temporarily protect wafers. [Prior art documents] [Patent Documents] 【0003】 [Patent Document 1] U.S. Patent Application Publication No. 2017 / 0306093A1 [Overview of the Initiative] [Problems that the invention aims to solve] 【0004】 Conventional temporary wafer protection materials include acrylic adhesives and polyamic acid adhesives. Acrylic adhesives have low heat resistance (≤150°C), which is unfavorable for semiconductor processes, and their more flexible nature makes them prone to leaving residue on the sidewalls of electrodes. Polyamic acid adhesives require a two-step process: applying the polyamic acid material to the substrate and then closing the polyamic acid rings by high-temperature treatment (above 300°C) to form a polyimide film. However, such high processing temperatures can generate significant stress due to the difference in thermal expansion coefficients between the polyimide and the substrate, potentially causing substrate bending, deformation, cracking, and even delamination, which can damage the device. 【0005】 Therefore, there is a need for novel adhesive materials suitable for advanced wafer processing. [Means for solving the problem] 【0006】 This disclosure provides an adhesive. The adhesive comprises a polyimide, which is a reaction product of reactant (a) and reactant (b), wherein reactant (a) is a first diamine, or reactant (a) consists of a first diamine and a second diamine, and reactant (b) consists of a first dianhydride and a second dianhydride, wherein the first diamine is a diamine containing a diphenyl ether moiety, the first dianhydride is a dianhydride containing a diphenyl ether moiety, the second diamine is not a diamine containing a diphenyl ether moiety, and the second dianhydride is not a dianhydride containing a diphenyl ether moiety. The total weight percentage of the first diamine and the first dianhydride is between 55 wt% and 94 wt% of the total weight of reactant (a) and reactant (b). 【0007】 According to embodiments of the present disclosure, the present disclosure provides a multilayer structure comprising a first substrate and an adhesive layer disposed on the first substrate, wherein the adhesive layer is a cured product of the adhesive of the present disclosure. [Effects of the Invention] 【0008】 This disclosure provides adhesives and multilayer structures, for example, adhesives that can be removed by laser light without leaving any residue. Multilayer structures include adhesive layers made from the adhesives of this disclosure. According to embodiments of this disclosure, the adhesives of this disclosure include polyimides. Polyimides can be obtained by reacting a specific diamine (e.g., a diamine containing a diphenyl ether moiety) as reactant (a) with a specific dianhydride (e.g., a dianhydride containing a diphenyl ether moiety and a dianhydride without a diphenyl ether moiety) as reactant (b). By controlling the total weight of the diamine containing a diphenyl ether moiety and the dianhydride containing a diphenyl ether moiety with respect to the total weight of reactant (a) and reactant (b) to satisfy a specific relationship, the glass transition temperature (Tg) of the polyimides of this disclosure can be made to be in the range of 180°C to 245°C and the UV transmittance at wavelengths from 260 nm to 355 nm to be 5% or less. As a result, the polyimide-containing adhesive of this disclosure can bond a first substrate (e.g., a transparent support) and a second substrate (e.g., an electronic component) at a lower processing temperature (e.g., below 300°C), avoiding substrate warping caused by high-temperature processing. Furthermore, since the adhesive of this disclosure can absorb UV light (i.e., has low UV transmittance), the first substrate and the second substrate can be separated by irradiating the adhesive with laser light. Therefore, it becomes possible to separate the electronic component from the substrate during processing or rework, and no adhesive residue is left behind. [Brief explanation of the drawing] 【0009】 This disclosure can be better understood by reading the following detailed description and examples while referring to the attached drawings. [Figure 1] This is a schematic diagram of a multilayer structure according to an embodiment of the present disclosure. [Figure 2] This is a schematic diagram of a multilayer structure according to another embodiment of the present disclosure. [Modes for carrying out the invention] 【0010】 The adhesives and multilayer structures of this disclosure are described in detail below. For illustrative purposes, numerous specific details and embodiments are provided in the following detailed description to ensure that the disclosure is fully understood. Certain elements and configurations in the following detailed description are provided to further illustrate the disclosure. However, it will be apparent that the exemplary embodiments shown herein are for illustrative purposes only, and the concepts of the invention can be embodied in various forms without being limited to these exemplary embodiments. In addition, for further illustration of the disclosure, similar and / or corresponding figures may be used in the figures of different embodiments to indicate similar and / or corresponding elements. However, the use of similar and / or corresponding figures in the figures of different embodiments does not imply any correlation between different embodiments. Where used herein, the term “about” in quantitative terms means adding or subtracting only a quantity that is common and reasonable to those skilled in the art. 【0011】 Furthermore, the use of sequential terms such as “first,” “second,” and “third” to modify elements in this disclosure does not in itself imply any priority, order, sequence, or temporal order in which the elements of one claim are formed relative to others, but is merely used as labels to distinguish one element of a claim having a specific name from another element having the same name (where no sequential terms are used), thus distinguishing the elements of the claims from each other. 【0012】 It should be noted that the elements or devices in the drawings of this disclosure may exist in any form or configuration known to those skilled in the art. Furthermore, the expressions “a layer covering another layer,” “a layer positioned above another layer,” “a layer positioned on another layer,” and “a layer positioned on another layer” may refer to layers that are in direct contact with other layers, or they may refer to layers that are separated from other layers by one or more intermediate layers and are not in direct contact with other layers. 【0013】 The disclosed figures are only schematic and non-limiting. In the figures, for the purpose of illustration, the size, shape or thickness of some elements may be exaggerated and not drawn to scale. Dimensions and relative dimensions do not correspond to the actual position of the implementation of the present disclosure. The present disclosure is described with reference to specific embodiments and specific drawings, but the present disclosure is not limited thereto. 【0014】 According to embodiments of the present disclosure, the present disclosure provides an adhesive, and the adhesive includes polyimide. According to embodiments of the present disclosure, the polyimide may be a reaction product of reactant (a) and reactant (b), reactant (a) may be a first diamine, or reactant (a) may consist of a first diamine and a second diamine. Reactant (b) consists of a first dianhydride and a second dianhydride. According to embodiments of the present disclosure, the first diamine may be a diamine containing a diphenyl ether moiety, and the first dianhydride may be a dianhydride containing a diphenyl ether moiety. The diphenyl ether moiety may have any of the following structures. 【0015】 【Chemical formula】 【0016】 Among the hydrogens bonded to the carbon of the above part, at least one may be optionally substituted with fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group or a C1-C4 alkoxy group. The second diamine does not contain a diphenyl ether moiety (i.e., the first diamine and the second diamine are different), and the second dianhydride does not contain a diphenyl ether moiety (i.e., the first dianhydride and the second dianhydride are different). It should be noted that the glass transition temperature (Tg) of the polyimide of the present disclosure can be in the range of 180°C to 245°C (for example, 190°C, 200°C, 210°C, 220°C, 230°C or 240°C), and the UV transmittance at wavelengths from 260 nm to 355 nm is 5% or less (for example, 4%, 3%, 2% or 1%). According to an embodiment of the present disclosure, with respect to the total weight of reactant (a) and reactant (b), the total weight percentage of the first diamine and the first dianhydride is in the range of 55 wt% to 94 wt% (for example, 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% or 93 wt%). When the weights of the first diamine and the first dianhydride are controlled within the above range, the glass transition temperature (Tg) of the polyimide of the present disclosure can be in the range between 180°C and 245°C, and the UV transmittance at wavelengths from 260 nm to 355 nm is 5% or less. 【0017】 According to embodiments of the present disclosure, when reactant (a) is a first diamine and reactant (b) consists of a first dianhydride and a second dianhydride, the amount of the second dianhydride may be in the range of 6 wt% to 45 wt% with respect to the total weight of reactant (a) and reactant (b) (i.e., all dianhydrides and diamines used to produce the polyimide). According to embodiments of the present disclosure, when reactant (a) consists of a first diamine and a second diamine and reactant (b) consists of a first dianhydride and a second dianhydride, the total weight percentage of the second diamine and the second dianhydride may also be in the range of 6 wt% to 45 wt% with respect to the total weight of reactant (a) and reactant (b). 【0018】 According to embodiments of the present disclosure, the first dianhydride may be at least one of dianhydrides having the structure represented by formula (I). 【0019】 [ka] 【0020】 In the formula, R 1 is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, a is independently 0, 1, 2 or 3, and A 1 ha-O-, [ka] And R 2 b is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, b is independently 0, 1, 2, 3 or 4, R 3 R is independently hydrogen, fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group, or C1-C4 alkoxy group, 4is independently fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group or a C1-C4 alkoxy group, and c is independently 0, 1, 2, 3, 4, 5 or 6. 【0021】 According to an embodiment of the present disclosure, the first dianhydride may be any of the following, or a combination thereof. 【0022】 【Chemical formula】 【Chemical formula】 【0023】 wherein, R 1 is independently fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group or a C1-C4 alkoxy group, a is independently 0, 1, 2 or 3, R 2 is independently fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group or a C1-C4 alkoxy group, b is independently 0, 1, 2, 3 or 4, R 3 is independently hydrogen, fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group or a C1-C4 alkoxy group, R 4 is independently fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group or a C1-C4 alkoxy group, and c is independently 0, 1, 2, 3, 4, 5 or 6. 【0024】 According to an embodiment of the present disclosure, the first diamine may be at least one of the diamines having the structure represented by formula (II). 【0025】 【Chemical formula】 【0026】 wherein, R5 is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, d is independently 0, 1, 2, 3 or 4, A 2 ha-O-, [ka] And R 6 is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, e is independently 0, 1, 2, 3 or 4, R 7 R is independently hydrogen, fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group, or C1-C4 alkoxy group, 8 f is independently fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group, or a C1-C4 alkoxy group, and f is independently 0, 1, 2, 3, 4, 5, or 6. 【0027】 According to embodiments of this disclosure, the first diamine may be any of the following, or a combination thereof. 【0028】 [ka] [ka] [ka] 【0029】 In the formula, R 5 is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, d is independently 0, 1, 2, 3 or 4, R 6is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, e is independently 0, 1, 2, 3 or 4, R 7 R is independently hydrogen, fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group, or C1-C4 alkoxy group, 8 f is independently fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group, or a C1-C4 alkoxy group, and f is independently 0, 1, 2, 3, 4, 5, or 6. 【0030】 According to embodiments of the present disclosure, the alkyl group of the present disclosure may be linear or branched. According to embodiments of the present disclosure, the C1-C4 alkyl group may be methyl, ethyl, propyl, butyl, or isomers thereof. For example, the C1-C4 alkyl group of the present disclosure may be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, iso-butyl, or tert-butyl. 【0031】 According to embodiments of the present disclosure, the C1-C4 alkoxy group of the present disclosure may be linear or branched. For example, the C1-C4 alkoxy group may be methoxy, ethoxy, propoxy, butoxy, or isomers thereof. 【0032】 According to embodiments of the present disclosure, the C1-C4 fluoroalkyl group may be an alkyl group in which some or all of the hydrogen atoms bonded to a carbon atom are substituted with fluorine atoms. The C1-C4 fluoroalkyl group may be linear or branched, for example, fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or isomers thereof. Here, the fluoromethyl group may be a monofluoromethyl group, a difluoromethyl group, or a trifluoromethyl group, and the fluoroethyl group may be a monofluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a tetrafluoroethyl group, or a perfluoroethyl group. 【0033】 According to embodiments of the present disclosure, the C1-C4 fluoroalkoxy group of the present disclosure may be linear or branched. For example, the C1-C4 fluoroalkoxy group may be fluoromethoxy, fluoroethoxy, fluoropropoxy, fluorobutoxy, or isomers thereof. Here, the fluoromethoxy group may be a monofluoromethoxy group, a difluoromethoxy group, or a trifluoromethoxy group, and the fluoroethoxy may be a monofluoroethoxy group, a difluoroethoxy group, a trifluoroethoxy group, a tetrafluoroethoxy, or a perfluoroethoxy. 【0034】 According to embodiments of the present disclosure, the second dianhydride is different from the first dianhydride. The second dianhydride may be a dianhydride that does not contain a diphenyl ether moiety. According to embodiments of the present disclosure, the second dianhydride is not composed of cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), or the second dianhydride is not composed of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA). 【0035】 According to embodiments of the present disclosure, the second dianhydride may be an aromatic dianhydride or an aliphatic dianhydride. According to embodiments of the present disclosure, the second dianhydride may be bicyclo[2.2.2]octo-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (B1317), bicyclooctanetetracarboxylic acid dianhydride (BODA), dicyclohexyl-3,4,3',4'-tetracarboxylic acid dianhydride (H-BPDA), [3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride] (TCA-AH), 1,2,3,4-butanetetracarboxylic acid dianhydride (BDA), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (4,4'-BPDA), 2,3,3',4'-biphenyl The dianhydride may be tetracarboxylic acid dianhydride (3,4'-BPDA), 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione (1,4-PIB), 5-[3-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione (1,3-PIB), 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride (6FDA), 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), or a combination thereof. 【0036】 According to embodiments of the present disclosure, when the second dianhydride includes cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) or 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA), the second dianhydride may be bicyclo[2.2.2]octo-7-ene-2,3,5,6-tetracarboxylic dianhydride (B1317), bicyclooctanetetracarboxylic dianhydride (BODA), dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride (H-BPDA), [3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride] (TCA-AH), 1,2,3,4-butanetetracarboxylic dianhydride (BDA), 3,3',4,4'-biphen The following may further be included: 4,4'- 【0037】 According to embodiments of the present disclosure, the second diamine is different from the first diamine. The second diamine may be a diamine that does not contain a diphenyl ether moiety. According to embodiments of the present disclosure, the second diamine is not composed of isophorone diamine (IPDA), or the second diamine is not composed of 4-methylcyclohexane-1,3-diamine (HTDA). 【0038】 According to embodiments of this disclosure, the second diamine may be an aromatic diamine or an aliphatic diamine. According to embodiments of the present disclosure, the second diamine is 4,4'-methylenebis(cyclohexylamine) (PACM), 4,4'-methylenebis(2-methylcyclohexylamine) (MACM), bis(aminomethyl)norbornane (NORB), adamantane-1,3-diamine (ADDA), octahydro-4,7-methanoindene-1(2),5(6)-dimethanamine, 2,2'-bis(trifluoromethyl)benzidine (TFMB), 4,4'-diamino-2,2'-dimethylbiphenyl (m-TBHG), O-tolidine, 4,4'-methylenedianiline (4,4'-DAPM), 3,4'-methylenedianiline (3,4'-DAPM), 4,4'-diamino-3,3'-dimethyldiphenylmethane (MDA), 4,4'-methylenebis(2 α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene (bisaniline P), 9,9-bis(4-aminophenyl)fluorene (DABP), or combinations thereof. 【0039】 According to embodiments of the present disclosure, if the second diamine is not isophorone diamine (IPDA) or if the second diamine is not 4-methylcyclohexane-1,3-diamine (HTDA), the second diamine may be 4,4'-methylenebis(cyclohexylamine) (PACM), 4,4'-methylenebis(2-methylcyclohexylamine) (MACM), bis(aminomethyl)norbornane ( NORB), adamantane-1,3-diamine (ADDA), octahydro-4,7-methanoindene-1(2),5(6)-dimethanamine, 2,2'-bis(trifluoromethyl)benzidine (TFMB), 4,4'-diamino-2,2'-dimethylbiphenyl (m-TBHG), O-tolidine, 4,4'-methylenedianiline (4,4'-DAPM), 3,4'-methylenedianiline (3,4'-DAPM), 4,4 '-Diamino-3,3'-dimethyldiphenylmethane (MDA), 4,4'-methylenebis(2-ethylbenzeneamine) (MOEA), 4,4'-methylenebis(2,6-diethylaniline) (MDEA), 9,10-bis(4-aminophenyl)anthracene (ADA), 2,6-naphthalenediamine, 2,6-anthracenediamine, 4,4''-diamino-p-terphenyl, 2,2-bis(4-aminophenyl) This may include hexafluoropropane (AAF), α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene (bisaniline P), 9,9-bis(4-aminophenyl)fluorene (FDA), 3,3',5,5'-tetramethylbenzidine (TMB), 4,4'-diamino-2,2'-dimethoxybiphenyl (m-DS), 4,4'-diaminobenzophenone (DABP), or combinations thereof. 【0040】 According to embodiments of the present disclosure, if reactant (a) consists of a first diamine and a second diamine, the weight ratio of the first diamine to the second diamine may be from 99.99:0.01 to 30:70, for example 99:1, 95:5, 90:10, 80:70, 60:40, 50:50, or 40:60. According to embodiments of the present disclosure, if reactant (b) consists of a first dianhydride and a second dianhydride, the weight ratio of the first dianhydride to the second dianhydride may be from 99.99:0.01 to 25:75, for example 99:1, 95:5, 90:10, 80:70, 60:40, 50:50, 40:60, or 30:70. 【0041】 According to embodiments of the present disclosure, the weight-average molecular weight (Mw) of the polyimide of the present disclosure may range from about 5,000 g / mol to 3,000,000 g / mol, for example, from about 8,000 g / mol to 2,500,000 g / mol, from 10,000 g / mol to 2,300,000 g / mol, from 15,000 g / mol to 2,000,000 g / mol, from 10,000 g / mol to 1,000,000 g / mol, from 10,000 g / mol to 500,000 g / mol, or from 10,000 g / mol to 300,000 g / mol. The weight-average molecular weight (Mw) of the polyimide of the present disclosure can be measured by gel permeation chromatography (GPC) based on a polystyrene calibration curve. 【0042】 According to embodiments of the present disclosure, the adhesive described above may contain the polyimide and solvent described above, thereby enabling the polyimide to be uniformly dispersed in the solvent. In addition, according to some embodiments of the present disclosure, the adhesive of the present disclosure may consist of the polyimide and solvent described above. 【0043】 In embodiments of this disclosure, the solids content of the adhesive may range from 2 wt% to 25 wt% (for example, about 3 wt%, 4 wt%, 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%, or 24 wt%). Here, solids content refers to the weight percentage of the adhesive components excluding the solvent relative to the total weight of the adhesive. According to embodiments of this disclosure, the thickness of the adhesive layer produced from the adhesive is proportional to the solids content of the adhesive. In other words, the thickness of the adhesive layer produced from the adhesive can be adjusted by changing the solids content of the adhesive. 【0044】 According to embodiments of the present disclosure, the solvent may be benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, triethylbenzene, cyclohexane, cyclohexene, decahydronaphthalene, dipentene, pentane, hexane, heptane, octane, nonane, decane, ethylcyclohexane, methylcyclohexane, p-menthane, dipropyl ether, dibutyl ether, anisole, butyl acetate, pentyl acetate, methyl isobutyl ketone (MEK), cyclohexylbenzene, cyclohexanone, cyclopentanone (CPN), triglycerides, 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), cresol, or a combination thereof. 【0045】 According to embodiments of the present disclosure, the polyimide described above can be prepared by the following steps. First, reactants (a) and (b) are added to a reaction bottle containing a solvent to obtain a mixture. The solid content of the mixture can be about 10 wt% to 50 wt% (for example, about 11 wt%, 12 wt%, 14 wt%, 15 wt%, 18 wt%, 20 wt%, 21 wt%, 22 wt%, 25 wt%, 27 wt%, 29 wt%, 30 wt%, 32 wt%, 34 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, or 48 wt%). Reactants (a) and (b) are as defined above. To enable the direct dissolution of the resulting polyimide in the solvent without the need for exchange, the solvent used to prepare the polyimide may be selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), γ-butyrolactone (GBL), N,N-dimethylformamide (DMF), cresol, cyclopentanone (CPN), and cyclohexanone. According to embodiments of this disclosure, the molar ratio of reactant (a) to reactant (b) may be about 1:1.05 to 1.05:1, for example, about 1:1. Furthermore, a catalyst may be optionally added to the solution to accelerate the polymerization process and form the polyimide. The amount of catalyst may be 0.1 wt% to 10 wt% (for example, about 0.2 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 5 wt%, 7 wt%, or 9 wt%) relative to the total weight of reactants (a) and (b). Next, the mixture is reacted at 180°C to 250°C for 4 to 12 hours to obtain a solution containing the polyimide of the present disclosure (i.e., a polyimide solution). According to embodiments of the present disclosure, the catalyst may be any catalyst suitable for use in the imidation reaction, such as a tertiary amine.Examples of tertiary amines include triethylenediamine (DABCO), N,N-dimethylcyclohexylamine, 1,2-dimethylimidazole, trimethylamine, triethylamine, tripropylamine, tributylamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, triethylenediamine, N-methylpyrrolidone, N-ethylpyrrolidone, N-methylpiperidine, N-ethylpiperidine, imidazole, pyridine, methylpyridine, dimethylpyridine, quinoline, or isoquinoline. 【0046】 According to embodiments of the present disclosure, the polyimide solution obtained from the reaction can be used directly as the adhesive of the present disclosure, or the obtained polyimide solution can be further diluted with a solvent and used as the adhesive of the present disclosure. The adhesive of the present disclosure consists substantially of the disclosed polyimide and solvent. Specifically, the polyimide and solvent are the main components of the adhesive, and the amounts of polyimide and solvent may be about 90 wt% to 99.99 wt% of the adhesive (e.g., 93 wt%, 95 wt%, 98 wt%, 99 wt%, or 99.5 wt%). In addition, the adhesive contains trace components other than the polyimide and solvent. These trace components may include catalysts used in the preparation of the polyimide, unreacted portions of reactant (a) and / or reactant (b), additives, or combinations thereof. The total weight of the trace components in the adhesive may be about 0.01 wt% to 10 wt%. According to embodiments of the present disclosure, the additive may be any additive known in the art, such as fillers, flame retardants, viscosity modifiers, thixotropic agents, defoamers, leveling agents, surface treatment agents, stabilizers, antioxidants, or combinations thereof. According to other embodiments of the present disclosure, the adhesive of the present disclosure may consist of the above-mentioned major and trace components. The viscosity of the adhesive of the present disclosure at 25°C may range from about 100 cP to 10,000 cP, for example, about 200 cP, 300 cP, 500 cP, 1,000 cP, 1,200 cP, 1,500 cP, or 1,800 cP. The viscosity of the adhesive of the present disclosure is measured using a viscometer (ViscoleadOne, Fungilab). 【0047】 Embodiments of this disclosure provide a multilayer structure 10 shown in Figure 1. The multilayer structure 10 includes a first substrate 20 and an adhesive layer 30 disposed on the first substrate 20. The adhesive layer 30 includes a cured product obtained by performing a baking process on the adhesive of this disclosure. The thickness of the adhesive layer 30 is not particularly limited and can be selected as required by practical needs. The average thickness of the adhesive layer 30 may be approximately 1 μm to 500 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 100 μm, 150 μm, 200 μm, 300 μm, or 400 μm. The first substrate 20 is not limited and can be modified as desired by those skilled in the art. The first substrate 20 may include a metal plate, a silicon substrate, glass, or a polymer film, such as polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, polyethylene (PE) film, polyethylene naphthalate (PEN) film, polypropylene (PP) film, polyvinyl chloride (PVC) film, or polyacrylate film. 【0048】 According to embodiments of the present disclosure, a multilayer structure 10 is formed by bonding a second substrate 40 to a first substrate 20 using an adhesive layer 30. According to embodiments of the present disclosure, the first substrate 20 and the second substrate 40 may be two substrates that need to be bonded together. As shown in Figure 2, the multilayer structure 10 further includes a second substrate 40, with the adhesive layer 30 positioned between the first substrate 20 and the second substrate 40. Furthermore, if the adhesive layer 30 of the multilayer structure 10 is irradiated with laser light (i.e., a laser separation process is performed), the adhesive strength of the adhesive layer 30 may decrease (for example, the adhesive strength between the first substrate 20 and the second substrate 40 may decrease to 40 gf or less). As a result, the second substrate 40 can be easily peeled off from the first substrate 20, and no adhesive residue remains on either the first substrate 20 or the second substrate 40, thereby improving the processing speed and reuse rate of electronic components, as well as increasing the efficiency of processing and rework processes. According to embodiments of the present disclosure, the second substrate 40 may be an electronic element. In other words, an electronic element may be temporarily fixed to the first substrate 20 using the adhesive layer 30 of the present disclosure. In addition, the electronic element is not limited to and may include, for example, semiconductor chips, touch panels, display elements, diodes, solar cells, organic light-emitting diodes (OLEDs), or other types of components. 【0049】 According to embodiments of the present disclosure, the multilayer structure 10 can be fabricated by the following steps. First, a first substrate 20 is prepared. Next, the adhesive of the present disclosure is applied to the first substrate 20 using a coating process. The coating process may be screen printing, spin coating, bar coating, blade coating, roller coating, dip coating, spray coating, or brush coating. Next, a baking process is performed on the coating to form an adhesive layer 30. The temperature of the baking process may be approximately 50°C to 350°C, or 300°C or less (e.g., 150°C to 280°C), and the process time of the baking process may be 30 minutes to 8 hours. In embodiments, the baking process may be a single-stage or multi-stage process, for example, baking at 100°C to 200°C for 15 minutes to 2 hours, and then baking at 200°C to 350°C for 15 minutes to 6 hours. After the adhesive layer 30 is formed, a second substrate 40 can be placed on top of the adhesive layer 30. Next, a crimping process is performed on the obtained material to obtain a multilayer structure 10. The temperature of the crimping process may be approximately 50°C to 350°C, and the crimping time may be 3 minutes to 8 hours. 【0050】 The following describes exemplary embodiments in detail with reference to the accompanying drawings, in a manner easily understood by those with ordinary skill in the art. The concept of the present invention can be embodied in various forms, but is not limited to these exemplary embodiments shown herein. For clarity, descriptions of well-known parts are omitted, and similar reference figures throughout indicate similar components. 【0051】 Polyimide fabrication Table 1 lists the reagents used in the preparation examples of this disclosure. 【0052】 [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5] 【0053】 Examples 1-9 Preparation Examples 1-9 were carried out by adding reactant (a), reactant (b), and isoquinoline to a reaction bottle according to the components and amounts shown in Table 2. A mixture with a solid content of approximately 30 wt% was prepared using gamma-butyrolactone (GBL) as the solvent. Next, the mixture was reacted at 200°C for 6 hours under a nitrogen atmosphere to produce polyimide solutions (1)-(9) with a solid content of approximately 29 wt%. The weight percentage of the sum of the first diamine and the first dianhydride relative to the total weight of reactant (a) and reactant (b) was calculated and is shown in Table 2. After allowing the obtained polyimides (1)-(9) to stand for 30 minutes, it was observed that they were all homogeneous mixtures. 【0054】 [Table 2] 【0055】 Examples 10-15 Preparation Examples 10-15 were carried out by adding reactant (a), reactant (b), and isoquinoline to a reaction bottle according to the components and amounts shown in Table 3. A mixture with a solid content of approximately 30 wt% was prepared using gamma-butyrolactone (GBL) as the solvent. The mixture was then reacted at 200°C for 6 hours under a nitrogen atmosphere to produce polyimide products (10)-(15) with a solid content of approximately 29 wt%. The weight percentage of the sum of the first diamine and the first dianhydride relative to the total weight of reactant (a) and reactant (b) was calculated and is shown in Table 3. After the obtained polyimides (10)-(15) were allowed to stand for 30 minutes, phase separation was observed. 【0056】 [Table 3] 【0057】 Examples 16-23 Preparation Examples 16-23 were carried out by adding reactant (a), reactant (b), and isoquinoline to a reaction bottle according to the components and amounts shown in Table 4. A mixture with a solid content of approximately 30 wt% was prepared using gamma-butyrolactone (GBL) as the solvent. The mixture was then reacted at 200°C for 6 hours under a nitrogen atmosphere to produce polyimide products (16)-(23) with a solid content of approximately 29 wt%. The weight percentage of the sum of the first diamine and the first dianhydride relative to the total weight of reactant (a) and reactant (b) was calculated and is shown in Table 4. After allowing the obtained polyimides (16)-(23) to stand for 30 minutes, it was observed that the obtained polyimide products (16)-(23) exhibited the following states. The polyimide product (16) showed phase separation, the polyimide products (17) and (19) were turbid mixtures, and the products containing polyimides (18) and (20)-(23) were homogeneous mixtures. 【0058】 [Table 4] 【0059】 Examples 24-31 Preparation Examples 24-31 were carried out by adding reactant (a), reactant (b), and isoquinoline to a reaction bottle according to the components and amounts shown in Table 5. A mixture with a solid content of approximately 30 wt% was prepared using gamma-butyrolactone (GBL) as the solvent. The mixture was then reacted at 200°C for 6 hours under a nitrogen atmosphere to produce polyimide solutions (24)-(31) with a solid content of approximately 29 wt%. The weight percentage of the sum of the first diamine and the first dianhydride relative to the total weight of reactant (a) and reactant (b) was calculated and is shown in Table 5. After allowing the obtained polyimides (24)-(31) to stand for 30 minutes, it was observed that they were all homogeneous mixtures. 【0060】 [Table 5] 【0061】 Making adhesives Examples 1-22 Solutions (34.48 parts by weight) of polyimides (1)-(9), (18), and (20)-(31) obtained by preparation examples 1-9, 18, and 20-31 were mixed with gamma-butyrolactone (165 parts by weight), respectively. After stirring for 30 minutes, adhesives (1)-(22) with a solid content of approximately 5 wt% were obtained. 【0062】 The viscosity of adhesives (1) to (22) was measured at 25°C using a viscometer (Viscolead One, Fungilab), and the results are shown in Table 6. 【0063】 [Table 6] 【0064】 Preparation of test samples A 4-inch glass substrate (commercially available from William Optical Technology Corporation) was prepared. Next, adhesives (1) to (22) were spin-coated onto one 4-inch glass substrate at 1000 rpm for 60 seconds to form thin films on the glass substrate. A drying process was then performed on these thin films (baked at 200°C for 60 minutes, then baked at 280°C for 60 minutes). After the thin films cooled, samples (1) to (22) (having an adhesive layer / glass substrate structure) were obtained. 【0065】 Next, the average thickness, glass transition temperature (Tg), and transmittance at 355 nm of the adhesive layers (1) to (22) were measured, and the results are shown in Table 7. The average thickness was measured using a white light interferometer (commercially available from Agewell Technology Corp). These were obtained by measuring the thickness at six points in the adhesive layer and then averaging these values. The glass transition temperature was analyzed using a differential scanning calorimeter (Discovery DSC25) under a nitrogen atmosphere, with the temperature increased from room temperature to the onset decomposition temperature of the adhesive layer at a heating rate of 10°C / min. The transmittance of the adhesive layer was measured at a wavelength of 355 nm using a UV / Vis / NIR spectrophotometer (LAMBDA 1050). 【0066】 [Table 7] 【0067】 As shown in Tables 2-5 and 7, when polyimides are prepared using the specific diamines and dianhydrides of this disclosure, and the total weight percentages of the first diamine and the first dianhydride are controlled within the range of 55 wt% to 94 wt%, the resulting adhesive layer has a glass transition temperature (Tg) in the range of 180°C to 245°C and an ultraviolet transmittance of 5% or less at 355 nm. Conversely, if the total weight percentages of the first diamine and the first dianhydride are lower than 55 wt% or higher than 94 wt%, the resulting adhesive layer will have a glass transition temperature (Tg) outside the range of 180°C to 245°C, or an ultraviolet transmittance of 5% or more at 355 nm. In addition, when cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) alone or 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA) alone is used as the second dianhydride, the resulting reaction product is not a homogeneous mixture. Similarly, when isophorone diamine (IPDA) alone or 4-methylcyclohexane-1,3-diamine (HTDA) alone is used as the second diamine, the resulting reaction product is not a homogeneous mixture. These results indicate that the resulting polyimide has lower solubility in GBL. 【0068】 Fabrication of multilayer structures A 4-inch wafer was prepared, and then samples (1) to (22) were bonded to a single 4-inch wafer. The electrodes of the 4-inch wafer were in contact with the bonded layers of samples (1) to (22). A 5 kg load was applied to the edge of each resulting multilayer combination of 4-inch wafers, and then baked at 300°C for 60 minutes. After cooling to RT, multilayer structures (1) to (22) were obtained. Next, an adhesion test was performed on the 4-inch wafers bonded to the glass substrate in the multilayer structures (1) to (22). The adhesion test included the following step: Each of the multilayer structures (1) to (22) was inverted with the 4-inch wafer facing downwards and held in this position for 10 minutes. If the 4-inch wafer peeled off the glass substrate, the adhesion test for that multilayer structure was recorded as ×. If it did not peel off, it was recorded as ○. The results are shown in Table 8. 【0069】 Next, a peel test was performed to evaluate whether the 4-inch wafer could be separated from the glass substrate in the multilayer structure (1) to (22) after the laser separation process. The peel test included the following steps: A laser device (commercially available from Kin-Yo Optoelectronics) with a wavelength of 355 nm (output 2 kW, scanning speed 3 m / s) was used to irradiate the adhesive layer of the multilayer structure. After irradiation, the adhesive strength between the glass substrate and the 4-inch wafer was measured using a tensile tester (QC-506B1, Guang Rhenium Instrument Co.) with a tensile force of 90 degrees (upward tensile speed of 300 mm / min). The results are shown in Table 8. 【0070】 Next, 4-inch wafers with multilayer structures (1) to (22) were inspected to evaluate the adhesive residue after they were peeled off the glass substrate. The evaluation method included the following steps: The 4-inch wafers with multilayer structures (1) to (22) were removed from the glass substrate, and the 4-inch wafers were rinsed and cleaned with isopropanol (IPA). Then, the 4-inch wafers were examined using an optical microscope to evaluate the adhesive residue. The results are shown in Table 8. 【0071】 [Table 8] 【0072】 As shown in Table 8, if the glass transition temperature (Tg) of the resulting adhesive layer is in the range of 180°C to 245°C, the 4-inch wafer and the glass substrate will adhere via the adhesive layer in a thermocompression bonding process using relatively low temperatures. In addition, if the adhesive layer has low UV transmittance, it will absorb laser light more easily, which will facilitate the peeling of the wafer from the glass substrate. In multilayer structure (7), the total amount of the first diamine and first dianhydride used to form the polyimide is less than 55 wt%, so the glass transition temperature of the adhesive layer is higher, and therefore the adhesive layer does not soften easily during the thermocompression bonding process, making it difficult for the wafer and the glass substrate to adhere. In multilayer structure (8), the absorption of laser light at a wavelength of 355 nm is relatively weak in the adhesive layer, so the wafer and the glass substrate do not separate (adhesion strength > 50 gf). In multilayer structure (9), the glass transition temperature of the adhesive layer is lower (< 180°C), so the adhesive layer is more likely to be trapped on the sidewall of the electrode, and adhesive residue is more likely to form. 【0073】 As described above, by controlling the total weight of the diamine containing the diphenyl ether moiety and the dianhydride containing the diphenyl ether moiety, as well as the total weight of reactant (a) and reactant (b), and satisfying a specific relationship, the glass transition temperature (Tg) of the polyimide of this disclosure is in the range of 180°C to 245°C, and the UV transmittance of the polyimide at wavelengths from 260 nm to 355 nm is 5% or less. As a result, the adhesive containing the polyimide of this disclosure can bond the first substrate and the second substrate at a lower processing temperature, and substrate warping caused by high-temperature processing is avoided. In addition, because the UV light is absorbed by the adhesive containing the polyimide, the first substrate and the second substrate can be separated by laser irradiation. As a result, separation of electronic elements from the substrate is possible during processing or rework, and no adhesive residue is formed. 【0074】 While the present disclosure has been described in terms of preferred embodiments by the examples, it should be understood that the present disclosure is not limited to those disclosed embodiments. Rather, it is intended to cover various modifications and similar configurations (which would be obvious to those skilled in the art). Therefore, the scope of the appended claims should be given the broadest possible interpretation to encompass all such modifications and similar configurations. [Explanation of Symbols] 【0075】 10...Multilayer structure 20. First circuit board 30...adhesive layer 40...Second circuit board

Claims

[Claim 1] An adhesive comprising a polyimide, wherein the polyimide is a reaction product of reactant (a) and reactant (b), and reactant (a) is a first diamine, or reactant (a) consists of the first diamine and a second diamine, and reactant (b) consists of a first dianhydride and a second dianhydride, wherein the first dianhydride is a dianhydride containing a diphenyl ether moiety, the second diamine is not a diamine containing a diphenyl ether moiety, and the second dianhydride is not a dianhydride containing a diphenyl ether moiety, the total weight percentage of the first diamine and the first dianhydride is 55 wt% to 94 wt% with respect to the total weight of reactant (a) and reactant (b), the molar ratio of reactant (a) to reactant (b) is 1:1.05 to 1.05:1, and the first diamine is at least one of diamines having a structure represented by formula (II). 【Chemistry 1】 (wherein R5 is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, d is independently 0, 1, 2, 3 or 4, and A2 is 【Chemistry 2】 R6 is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, e is independently 0, 1, 2, 3 or 4, R7 is independently hydrogen, fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, R8 is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, and f is independently 0, 1, 2, 3, 4, 5 or 6. [Claim 2] The adhesive according to claim 1, wherein the first dianhydride is at least one of dianhydrides having the structure represented by formula (I). 【Transformation 3】 (In the formula, R １ is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, a is independently 0, 1, 2 or 3, A １ Ha-O-, 【Chemistry 4】 And R ２ b is independently fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, b is independently 0, 1, 2, 3 or 4, R ３ R is independently hydrogen, fluorine, C1-C4 alkyl group, C1-C4 fluoroalkyl group, C1-C4 fluoroalkoxy group or C1-C4 alkoxy group, ４ c is independently fluorine, a C1-C4 alkyl group, a C1-C4 fluoroalkyl group, a C1-C4 fluoroalkoxy group, or a C1-C4 alkoxy group, and c is independently 0, 1, 2, 3, 4, 5, or 6. [Claim 3] The adhesive according to claim 1, wherein the second dianhydride is not composed of cyclobutane-1,2,3,4-tetracarboxylic dianhydride, or the second dianhydride is not composed of 1,2,4,5-cyclohexanetetracarboxylic dianhydride. [Claim 4] The second dianhydride is bicyclo[2.2.2]octo-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, bicyclooctanetetracarboxylic acid dianhydride, dicyclohexyl-3,4,3',4'-tetracarboxylic acid dianhydride, [3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride], 1,2,3,4-butanetetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid The adhesive according to claim 1, wherein the adhesive is a dianhydride, 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, 5-[3-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, or a combination thereof. [Claim 5] The adhesive according to claim 1, wherein the second diamine is not composed of isophoronediamine, or the second diamine is not composed of 4-methylcyclohexane-1,3-diamine. [Claim 6] The second diamine is 4,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(2-methylcyclohexylamine), bis(aminomethyl)norbornane, adamantane-1,3-diamine, octahydro-4,7-methanoindene-1(2),5(6)-dimethaneamine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-diamino-2,2'-dimethylbiphenyl, O-tolidine, 4,4'-methylenedianiline, 3,4'-methylenedianiline, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4,4'-methylenebis(2-ethylbenzeneamine), 4,4 The adhesive according to claim 1, wherein the adhesive is '-methylenebis(2,6-diethylaniline), 9,10-bis(4-aminophenyl)anthracene, 2,6-naphthalenediamine, 2,6-anthracenediamine, 4,4''-diamino-p-terphenyl, 2,2-bis(4-aminophenyl)hexafluoropropane, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, 9,9-bis(4-aminophenyl)fluorene, 3,3',5,5'-tetramethylbenzidine, 4,4'-diamino-2,2'-dimethoxybiphenyl, 4,4'-diaminobenzophenone, or a combination thereof. [Claim 7] The adhesive according to claim 1, wherein the weight-average molecular weight of the polyimide is 5,000 g / mol to 3,000,000 g / mol.

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