Acrylic adhesive, acrylic adhesive composition, adhesive film, and flexible device

Abstract

Provided are an acrylic adhesive that can balance excellent bendability and excellent recovery to a bending motion in a low-temperature environment, an acrylic adhesive composition that forms the acrylic adhesive, an adhesive film having an adhesive layer composed of the acrylic adhesive, and a flexible device provided with the adhesive film. The acrylic adhesive of the embodiment of the present invention is an acrylic adhesive having an adhesive strength of 5.0 N / 25 mm or more to a polyimide film at 23°C at a peeling rate of 300 mm / minute and a peeling angle of 180 degrees, a creep value of 70% or more at -20°C, and a recovery value of 70% or more at -20°C.

Description

Technical Field

[0001] This invention relates to acrylic adhesives, acrylic adhesive compositions, adhesive films, and flexible devices. Background Technology

[0002] Adhesive films are used for reinforcement and surface protection of components of various shapes.

[0003] For example, when bonding integrated circuits (ICs) or flexible printed circuit boards (FPCs) to a substrate of a semiconductor element (e.g., a TFT substrate), thermoforming is typically performed using an anisotropic conductive film (ACF). During such thermoforming, an adhesive film is sometimes pre-attached to the back side of the semiconductor element substrate for reinforcement (e.g., Patent Document 1).

[0004] Furthermore, in manufacturing methods for so-called flexible devices, such as foldable and rollable devices, which have been under development in recent years, a release layer and a flexible thin-film substrate are typically formed on a support substrate such as glass. A TFT substrate is then formed on this thin-film substrate, and subsequently, an organic EL layer is formed thereon. The support substrate is then peeled off to manufacture the flexible device. However, because the flexible display layer is very thin, defects can occur due to processing issues. Therefore, sometimes an adhesive film is pre-attached to the back side for reinforcement (e.g., Patent Document 2).

[0005] Semiconductor substrates and flexible devices are sometimes repeatedly bent. If the adhesive film attached to the substrate has poor bending characteristics, the recovery after bending may deteriorate, or in the worst case, breakage may occur due to repeated bending. Specifically, when an adhesive film is attached to a bent portion (e.g., a movable bent portion of a folding member), the following problems may occur.

[0006] When an adhesive film is bent at an angle, the compressive force acts on the inner diameter side of the bend, causing the adhesive film itself to deform in order to mitigate the force. Specifically, for example, it becomes more prone to wrinkling.

[0007] When an adhesive film is bent at an angle, tensile stress acts on the outer diameter side of the bend. Therefore, when this stress is relieved, levitation of the adhered material occurs.

[0008] When an adhesive film is bent at an angle, the thickness of the bent and stretched portions of the film changes significantly. Under such conditions, wrinkles or lifting may easily occur. For example, when an adhesive film is stretched, its thickness becomes significantly thinner, making it prone to lifting off the adhered object.

[0009] Thus, conventional adhesive films cannot fully achieve the desired contouring of diagonal and curved sections.

[0010] To address the issues mentioned above, adhesive films need to exhibit both excellent flexibility and resilience during bending. In particular, the application environments of flexible devices such as foldable and rollable devices, which are currently under development, are diverse, requiring adhesive films that can maintain excellent flexibility and resilience even in low-temperature environments where bending characteristics are difficult to demonstrate.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent No. 5600039

[0014] Patent Document 2: Japanese Patent No. 6376271 Summary of the Invention

[0015] The problem the invention aims to solve

[0016] The objective of this invention is to provide an acrylic adhesive that can achieve both excellent flexibility and excellent resilience in low-temperature environments, an acrylic adhesive composition forming the acrylic adhesive, an adhesive film having an adhesive layer composed of the acrylic adhesive, and a flexible device having the adhesive film.

[0017] Solution for solving the problem

[0018] The acrylic adhesive of the present invention exhibits an adhesion force of 5.0 N / 25 mm or more to a polyimide film at 23°C, a peel speed of 300 mm / min, and a peel angle of 180 degrees.

[0019] The creep value at -20℃ is over 70%, and the recovery value at -20℃ is over 70%.

[0020] In one embodiment, the acrylic adhesive of the present invention has a gelation rate of 50% or more.

[0021] In one embodiment, the acrylic adhesive of the present invention has a storage modulus G' of less than 150 kPa at -20°C.

[0022] The acrylic adhesive composition of the embodiments of the present invention forms the acrylic adhesive of the embodiments of the present invention.

[0023] The acrylic adhesive composition comprises an acrylic polymer (P) with a weight-average molecular weight (Mw) of less than 1.2 million.

[0024] In one embodiment, the acrylic polymer (P) in the acrylic adhesive composition comprises 50% by weight or more.

[0025] In one embodiment, the acrylic polymer (P) is obtained by polymerizing a monomer component (M), which comprises at least one selected from the group consisting of monomer (1) of general formula (1) and monomer (2) of general formula (2).

[0026]

[0027] (In general formula (1), R) 1 R is an alkyl group having 1 to 10 carbon atoms. 2 (The atom is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a -COOR group, where R is an alkyl group having 1 to 10 carbon atoms.)

[0028]

[0029] (In general formula (2), R) 3 R is an alkylene group having 1 to 10 carbon atoms. 4 R is an alkyl group having 1 to 10 carbon atoms. 5 (This can be a hydrogen atom or a methyl group.)

[0030] In one embodiment, the monomer component (M) comprises an alkyl (meth)acrylate.

[0031] The adhesive film of the embodiments of the present invention has an adhesive layer composed of an acrylic adhesive of the embodiments of the present invention.

[0032] The flexible device according to the embodiments of the present invention includes the adhesive film according to the embodiments of the present invention.

[0033] The effects of the invention

[0034] Using the present invention, it is possible to provide an acrylic adhesive that can achieve both excellent flexibility and excellent resilience in low-temperature environments, an acrylic adhesive composition forming the acrylic adhesive, an adhesive film having an adhesive layer composed of the acrylic adhesive, and a flexible device having the adhesive film. Attached Figure Description

[0035] Figure 1 A schematic cross-sectional view is provided to illustrate one embodiment of the flexible device of the present invention, showing one usage form of the adhesive film of the embodiment of the present invention. Detailed Implementation

[0036] In this specification, the term "(meth)acrylic acid" refers to "acrylic acid and / or methacrylic acid"; the term "(meth)acrylate" refers to "acrylate and / or methacrylate"; the term "(meth)allyl" refers to "allyl and / or methylallyl"; and the term "(meth)acrolein" refers to "acrolein and / or methacrolein". Furthermore, the term "acid (salt)" refers to "acid and / or its salt". Examples of salts include alkali metal salts and alkaline earth metal salts; specifically, examples include sodium salts and potassium salts.

[0037] Acrylic Adhesives

[0038] The acrylic adhesive of the present invention exhibits an adhesion strength of 5.0 N / 25 mm or more, more preferably 5.5 N / 25 mm or more, further preferably 6.0 N / 25 mm or more, and particularly preferably 6.5 N / 25 mm or more, to polyimide films at 23°C, a peel speed of 300 mm / min, and a peel angle of 180 degrees. Generally, a higher upper limit for the adhesion strength is preferable; however, considering the balance with other adhesive properties, it is preferably 30 N / 25 mm or less. When the adhesion strength is adjusted to the above range, sufficient adhesion to various substrates, such as foldable and rollable devices, can be achieved. The determination of the adhesion strength will be described later.

[0039] The acrylic adhesive of the embodiments of the present invention preferably has a creep value of 70% or more, more preferably 75% or more, further preferably 80% or more, and particularly preferably 85% or more at -20°C. The higher the upper limit of the above creep value, the better; however, considering the balance with other adhesive properties, it is preferably 160% or less. The creep value at -20°C is an indicator of the flexibility to bend in low-temperature environments; a higher value indicates better flexibility to bend in low-temperature environments. When the above creep value is adjusted to the above range, the acrylic adhesive of the embodiments of the present invention exhibits excellent flexibility to bend in low-temperature environments. The determination of the above creep value will be described later.

[0040] The acrylic adhesive of the embodiments of the present invention preferably exhibits a recovery value of 70% or more, more preferably 73% or more, further preferably 77% or more, and particularly preferably 80% or more at -20°C. The higher the upper limit of the above-mentioned recovery value, the better; however, considering the balance with other adhesive properties, it is preferably 95% or less. The recovery value at -20°C is an indicator of the resilience to bending at low temperatures; a higher value indicates better resilience to bending at low temperatures. When the above-mentioned recovery value is adjusted to the above range, the acrylic adhesive of the embodiments of the present invention exhibits excellent resilience to bending at low temperatures. The determination of the above-mentioned recovery value will be described later.

[0041] In embodiments of the present invention, the acrylic adhesive preferably has both its creep value at -20°C and its recovery value at -20°C adjusted to the aforementioned range. By making this adjustment, the acrylic adhesive of the present invention can achieve a better balance between bending performance and recovery performance in low-temperature environments. Conventionally, in adhesive design, bending performance and recovery performance are mostly inversely related. The acrylic adhesive of the present invention can effectively balance bending performance and recovery performance in low-temperature environments, exhibiting excellent bending characteristics.

[0042] The acrylic adhesive of the embodiments of the present invention preferably has a gel rate of 50% or more, more preferably 55% or more, further preferably 60% or more, even more preferably 65% ​​or more, particularly preferably 70% or more, and most preferably 75% or more. The upper limit of the above gel rate is 100%. When the gel rate is adjusted to the above range, the acrylic adhesive of the embodiments of the present invention can achieve both excellent flexibility and excellent recovery in bending operations at low temperatures. If the gel rate exceeds the above range and is too small, there is a concern, especially at low temperatures, that the recovery in bending operations may be reduced. The determination of the above gel rate will be described later.

[0043] The storage modulus G' of the acrylic adhesive according to embodiments of the present invention at -20°C is preferably 150 kPa or less, more preferably 140 kPa or less, further preferably 130 kPa or less, even more preferably 120 kPa or less, particularly preferably 110 kPa or less, and most preferably 100 kPa or less. For the lower limit of the above-mentioned storage modulus G', considering the balance with other adhesive properties, it is preferably 70 kPa or more. When the storage modulus G' is adjusted to the above range, the acrylic adhesive according to embodiments of the present invention can achieve both excellent flexibility and excellent recovery in low-temperature environments. If the above-mentioned storage modulus G' exceeds the above range and is too large, there is a particular concern about a reduction in flexibility during bending. The determination of the above-mentioned storage modulus G' will be described later.

[0044] In embodiments of the present invention, the acrylic adhesive is preferably provided in which both the gel ratio and the storage modulus G' at -20°C are adjusted to the ranges described above. By making such adjustments, the acrylic adhesive of the present invention can achieve both superior flexibility and superior recovery in low-temperature environments.

[0045] The acrylic adhesives of the embodiments of the present invention are preferably formed from acrylic adhesive compositions.

[0046] Acrylic adhesives can be defined as being formed from acrylic adhesive compositions. This is because acrylic adhesive compositions become acrylic adhesives through cross-linking reactions caused by heating, ultraviolet irradiation, etc. Therefore, acrylic adhesives cannot be directly identified by their structure. Furthermore, since there are almost impractical situations ("impossible / unrealistic situations"), by defining them as "formed from acrylic adhesive compositions", acrylic adhesives are properly identified as "objects".

[0047] When the acrylic adhesive of the embodiments of the present invention is formed from an acrylic adhesive composition, any suitable method can be used as a method for forming such an acrylic adhesive without impairing the effects of the present invention. For example, a method for forming such an acrylic adhesive can be: applying the acrylic adhesive composition onto any suitable substrate, heating and drying it as needed, and curing it as needed to form the acrylic adhesive on the substrate. Any suitable means can be used as a coating method without impairing the effects of the present invention. Examples of such coating methods include gravure roller coating machines, reverse roller coating machines, contact roller coating machines, dip roller coating machines, bar coating machines, knife coating machines, air knife coating machines, spray coating machines, comma coating machines, direct coating machines, and roller brush coating machines. Any suitable means can be used for heating and drying the acrylic adhesive composition without impairing the effects of the present invention. For example, heating to approximately 60°C to 180°C can be used. Any suitable means can be used for curing the acrylic adhesive composition without impairing the effects of the present invention. Examples of such curing methods include ultraviolet irradiation, laser irradiation, alpha irradiation, beta irradiation, gamma irradiation, X-ray irradiation, and electron beam irradiation.

[0048] Acrylic Adhesive Compositions

[0049] The acrylic adhesive composition of the embodiments of the present invention is an acrylic adhesive composition that forms the acrylic adhesive of the embodiments of the present invention.

[0050] Acrylic polymers (P)

[0051] The acrylic adhesive composition of the embodiments of the present invention comprises an acrylic polymer (P). The acrylic polymer (P) may be only one type or may be two or more types.

[0052] The weight-average molecular weight (Mw) of the acrylic polymer (P) is preferably 1.2 million or less, more preferably 1.1 million or less, further preferably 1 million or less, even more preferably 900,000 or less, particularly preferably 800,000 or less, and most preferably 700,000 or less. The lower limit of the above-mentioned weight-average molecular weight (Mw) is preferably 500,000 or more. When the weight-average molecular weight (Mw) is adjusted to the above range, the acrylic adhesive of the embodiments of the present invention can exhibit both excellent flexibility and excellent recovery under bending conditions at low temperatures. If the weight-average molecular weight (Mw) exceeds the above range and is too large, there is a particular concern about a reduction in flexibility under bending conditions. The determination of the above-mentioned weight-average molecular weight (Mw) will be described later.

[0053] The acrylic polymer (P) in the acrylic adhesive composition of the embodiments of the present invention preferably contains 50% by weight or more, more preferably 70% by weight or more, further preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 97% by weight or more. The upper limit of the above-mentioned content ratio is preferably 100% by weight or less. When the above-mentioned content ratio is adjusted to the above range, the acrylic adhesive of the embodiments of the present invention can achieve both excellent flexibility and excellent recovery under bending conditions at low temperatures. If the above-mentioned content ratio exceeds the above range and is too small, there is a concern that the effects of the present invention may not be fully realized.

[0054] The acrylic polymer (P) is preferably obtained by polymerizing a monomer component (M), wherein the monomer component (M) comprises at least one selected from the group consisting of monomer (1) of general formula (1) and monomer (2) of general formula (2).

[0055]

[0056] (In general formula (1), R) 1 R is an alkyl group having 1 to 10 carbon atoms. 2 (The atom is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a -COOR group, where R is an alkyl group having 1 to 10 carbon atoms.)

[0057]

[0058] (In general formula (2), R) 3 R is an alkylene group having 1 to 10 carbon atoms. 4 R is an alkyl group having 1 to 10 carbon atoms. 5 (This can be a hydrogen atom or a methyl group.)

[0059] Acrylic polymers (P) can be defined as those obtained by polymerizing monomer components (M). This is because acrylic polymers (P) are formed by the polymerization reaction of monomer components (M), and acrylic polymers (P) cannot be directly identified by their structure. Furthermore, since there are almost impractical cases ("impossible / unrealistic cases"), by defining them as "those obtained by polymerizing monomer components (M), acrylic polymers (P) are properly identified as "objects".

[0060] The monomer component (M) comprises at least one selected from the group consisting of monomer (1) of general formula (1) and monomer (2) of general formula (2), and preferably comprises both monomer (1) of general formula (1) and monomer (2) of general formula (2) in order to further demonstrate the effects of the present invention.

[0061] The monomer (1) shown in general formula (1) can be only one type or more than two types.

[0062] The monomer (1) shown in general formula (1) has two polymerizable double bonds at the end and has a structure (C-CH2-O-CH2-C) that can be constructed by cyclization polymerization to form a furan ring structure. Furthermore, it has an alkyl ester group (COOR) on at least one of the second carbon atoms starting from the end of the two polymerizable double bonds at the end. 1 (Base), thereby promoting cyclization polymerization, and enabling the introduction of alkyl ester groups into the structure constructed by cyclization polymerization. Utilizing these characteristics, the resulting acrylic adhesive can achieve both superior flexibility and superior recovery in the face of bending action.

[0063] The monomer (2) shown in general formula (2) can be only one type or more than two types.

[0064] The monomer (2) shown in general formula (2) has a (meth)acrylate structure (CH2=C(R) 5 The characteristics of the COO- and carbamoyloxy structures (-O-CO-NH-) allow for the creation of acrylic adhesives that exhibit both superior flexibility and superior recovery during bending.

[0065] In monomer (1) represented by general formula (1), R 1 R is an alkyl group having 1 to 10 carbon atoms. From the perspective of further demonstrating the effects of the present invention, 1 Preferably, it is an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably methyl or ethyl, and most preferably methyl.

[0066] In monomer (1) represented by general formula (1), R 2 It consists of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a -COOR group. R 2 In the case of an alkyl group having 1 to 10 carbon atoms, from the perspective of further demonstrating the effects of the present invention, R 2 Preferably, it is an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and even more preferably an alkyl group having 1 to 3 carbon atoms. 2 In the case of a -COOR group, R is an alkyl group having 1 to 10 carbon atoms. From the perspective of further demonstrating the effects of the present invention, R is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably methyl or ethyl, and most preferably methyl. From the perspective of further demonstrating the effects of the present invention, R... 2 Hydrogen atoms are preferred.

[0067] In monomer (2) shown in general formula (2), R3 R is an alkylene group having 1 to 10 carbon atoms. From the perspective of further demonstrating the effects of the present invention, 3 Preferably, it is an alkylene group having 1 to 8 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, even more preferably an alkylene group having 1 to 3 carbon atoms, particularly preferably methylene (-CH2-) or ethylene (-CH2CH2-), and most preferably ethylene (-CH2CH2-).

[0068] In monomer (2) shown in general formula (2), R 4 R is an alkyl group having 1 to 10 carbon atoms. From the perspective of further demonstrating the effects of the present invention, 4 Preferably, it is an alkyl group having 2 to 8 carbon atoms, more preferably an alkyl group having 3 to 6 carbon atoms, even more preferably an alkyl group having 3 to 5 carbon atoms, particularly preferably butyl, and most preferably n-butyl.

[0069] In monomer (2) shown in general formula (2), R 5 R can be a hydrogen atom or a methyl group, and from the perspective of further demonstrating the effects of the present invention, 5 Hydrogen atoms are preferred.

[0070] For the monomer component (M), the proportion of at least one selected from the group consisting of monomer (1) of general formula (1) and monomer (2) of general formula (2) is preferably 0.01 wt% to 30 wt%, more preferably 0.1 wt% to 20 wt%, further preferably 0.5 wt% to 10 wt%, further preferably 1.0 wt% to 5.0 wt%, particularly preferably 1.5 wt% to 4.0 wt%, and most preferably 2.0 wt% to 3.5 wt%, in order to further demonstrate the effects of the present invention.

[0071] Regarding the content of monomer (1) of general formula (1) in monomer component (M), in order to further demonstrate the effects of the present invention, it is preferably 0.01 wt% to 20 wt%, more preferably 0.1 wt% to 10 wt%, further preferably 0.2 wt% to 5.0 wt%, further preferably 0.3 wt% to 4.0 wt%, particularly preferably 0.4 wt% to 3.0 wt%, and most preferably 0.5 wt% to 2.0 wt%.

[0072] Regarding the content of monomer (2) of general formula (2) in monomer component (M), in order to further demonstrate the effects of the present invention, it is preferably 0.1 wt% to 20 wt%, more preferably 0.5 wt% to 10 wt%, further preferably 0.8 wt% to 8.0 wt%, further preferably 1.0 wt% to 6.0 wt%, particularly preferably 1.2 wt% to 4.0 wt%, and most preferably 1.5 wt% to 3.0 wt%.

[0073] The monomer component (M) preferably contains an alkyl (meth)acrylate. The alkyl group of the ester moiety is preferably an alkyl group having 1 to 16 carbon atoms. The alkyl group of the ester moiety referred to herein does not include alkyl groups having polar groups such as hydroxyl groups.

[0074] (Meth)acrylate alkyl esters can be of only one type or two or more types.

[0075] Regarding the proportion of alkyl (meth)acrylate in the monomer component (M), in order to further demonstrate the effects of the present invention, it is preferably 50% to 99% by weight, more preferably 70% to 98% by weight, further preferably 80% to 97% by weight, particularly preferably 85% to 96% by weight, and most preferably 90% to 95% by weight.

[0076] As an alkyl methacrylate, any suitable alkyl methacrylate may be used without impairing the effects of the present invention. For example, a compound represented by the following formula (1) may be used as such an alkyl methacrylate.

[0077] CH2=C(R 1 COOR 2 (1)

[0078] Here, R in equation (1) above 1 R is a hydrogen atom or a methyl group. 2 It is an alkyl group having 1 to 20 carbon atoms.

[0079] R 2 In aspects that can further demonstrate the effects of the present invention, alkyl groups having 1 to 16 carbon atoms are preferred, alkyl groups having 2 to 14 carbon atoms are more preferred, alkyl groups having 4 to 14 carbon atoms are even more preferred, and alkyl groups having 4 to 12 carbon atoms are particularly preferred.

[0080] The alkyl group described above is preferably a chain alkyl group, which further enhances the effects of the present invention. Here, "chain" means both straight-chain and branched-chain.

[0081] As R 2Alkyl (meth)acrylates comprising a chain of alkyl groups having 1 to 20 carbon atoms, examples of which include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptaethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, etc. Nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, isostearyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate.

[0082] In aspects that further demonstrate the effects of the present invention, the glass transition temperature (Tg) of the homopolymer of (meth)acrylate alkyl esters that may be included in the monomer component (M) is preferably -10°C or less, more preferably -12°C or less, further preferably -15°C or less, particularly preferably -18°C or less, and most preferably -20°C or less. The lower limit of the above-mentioned glass transition temperature Tg is preferably -80°C or more. The glass transition temperature Tg of the homopolymer of (meth)acrylate alkyl esters that may be included in the monomer component (M) can affect the adhesive and flexural properties of the acrylic polymer (P). By using (meth)acrylate alkyl esters that may be included in the monomer component (M) and whose homopolymer glass transition temperature Tg is within the above-mentioned range, the adhesive and flexural properties of the acrylic polymer (P) can be appropriately adjusted, thereby further demonstrating the effects of the present invention.

[0083] Here, the glass transition temperature (Tg) of the homopolymer of (meth)acrylate alkyl esters, which may be included in the monomer component (M), can be a value recorded in publicly available sources, such as the value recorded in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). It should be noted that if multiple values ​​are recorded in the aforementioned "Polymer Handbook," the conventional value is used. For (meth)acrylate alkyl esters not recorded in the aforementioned "Polymer Handbook," the values ​​listed in the monomer manufacturer's catalog are used. For the Tg of homopolymers of (meth)acrylate alkyl esters that are not recorded in the aforementioned "Polymer Handbook" and for which no monomer manufacturer's catalog is provided, the value obtained by the determination method described in Japanese Patent Application Publication No. 2007-51271 is used.

[0084] A representative example of the glass transition temperature Tg of a homopolymer of (meth)acrylate alkyl esters that may be included in the monomer component (M) is, for example, as described below.

[0085] 2-Ethylhexyl acrylate (2EHA): -70℃

[0086] Lauryl acrylate (LA): -23℃

[0087] n-Butyl acrylate (BA): -55℃

[0088] In aspects that further enhance the effects of the present invention, the monomer component (M) preferably contains an alkyl methacrylate (m1) whose homopolymer has a glass transition temperature (Tg) in the range of -80°C to -60°C, as an alkyl methacrylate. When the monomer component (M) contains an alkyl methacrylate (m1), in aspects that further enhance the effects of the present invention, the content of the alkyl methacrylate (m1) in the monomer component (M) is preferably 40% to 99% by weight, more preferably 45% to 90% by weight, further preferably 50% to 80% by weight, particularly preferably 55% to 75% by weight, and most preferably 60% to 70% by weight.

[0089] As mentioned above, the glass transition temperature (Tg) of the homopolymer of (meth)acrylate alkyl esters that may be included in the monomer component (M) can affect the adhesive and flexural properties of the acrylic polymer (P). Furthermore, by adjusting the proportion of (meth)acrylate alkyl ester (m1) in the monomer component (M) to be within the aforementioned range, the adhesive and flexural properties of the acrylic polymer (P) can be appropriately adjusted, further demonstrating the effects of the present invention.

[0090] As an alkyl methacrylate (m1) as described above, for example, 2-ethylhexyl acrylate (2EHA) (the glass transition temperature Tg of its homopolymer is -70°C) can be cited.

[0091] In aspects that further enhance the effects of the present invention, the monomer component (M) preferably contains alkyl methacrylates (m2) whose homopolymer has a glass transition temperature (Tg) in the range of -40°C to -10°C, as alkyl methacrylates. When the monomer component (M) contains alkyl methacrylates (m2), in aspects that further enhance the effects of the present invention, the content of alkyl methacrylates (m2) in the monomer component (M) is preferably 5% to 50% by weight, more preferably 7% to 40% by weight, further preferably 10% to 30% by weight, particularly preferably 13% to 25% by weight, and most preferably 15% to 22% by weight.

[0092] As mentioned above, the glass transition temperature (Tg) of the homopolymer of (meth)acrylate alkyl esters that may be included in the monomer component (M) can affect the adhesive and flexural properties of the acrylic polymer (P). Furthermore, by adjusting the proportion of (meth)acrylate alkyl esters (m2) in the monomer component (M) to fall within the aforementioned range, the adhesive and flexural properties of the acrylic polymer (P) can be appropriately adjusted, further demonstrating the effects of the present invention.

[0093] As an example of the alkyl methacrylate (m2) as described above, lauryl acrylate (LA) (whose homopolymer has a glass transition temperature Tg = -23°C) can be cited.

[0094] In aspects that further enhance the effects of the present invention, the monomer component (M) preferably contains alkyl methacrylates (m3) whose homopolymer has a glass transition temperature (Tg) in the range of more than -60°C and less than -40°C. When the monomer component (M) contains alkyl methacrylates (m3), in aspects that further enhance the effects of the present invention, the content of alkyl methacrylates (m3) in the monomer component (M) is preferably 0.1% to 30% by weight, more preferably 1% to 20% by weight, further preferably 3% to 15% by weight, particularly preferably 4% to 13% by weight, and most preferably 5% to 10% by weight.

[0095] As mentioned above, the glass transition temperature (Tg) of the homopolymer of (meth)acrylate alkyl esters that may be included in the monomer component (M) can affect the adhesive and flexural properties of the acrylic polymer (P). Furthermore, by adjusting the proportion of (meth)acrylate alkyl esters (m3) in the monomer component (M) to fall within the aforementioned range, the adhesive and flexural properties of the acrylic polymer (P) can be appropriately adjusted, further demonstrating the effects of the present invention.

[0096] As an example of the alkyl methacrylate (m3) as described above, n-butyl acrylate (BA) (the glass transition temperature Tg of its homopolymer is -55°C) can be cited.

[0097] From the perspective of further demonstrating the effects of the present invention, the monomer component (M) preferably includes at least one selected from the group consisting of alkyl methacrylate (m1), alkyl methacrylate (m2), and alkyl methacrylate (m3), more preferably includes at least two selected from the group consisting of alkyl methacrylate (m1), alkyl methacrylate (m2), and alkyl methacrylate (m3), and even more preferably includes all three alkyl methacrylates (m1), alkyl methacrylate (m2), and alkyl methacrylate (m3).

[0098] From the perspective of further demonstrating the effects of the present invention, the monomer component (M) is preferably composed of at least one selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate, more preferably composed of at least two selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate, and even more preferably composed of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate.

[0099] The monomer component (M) preferably includes a hydroxyl-containing monomer (m4). The hydroxyl-containing monomer (m4) may be only one type or may be two or more types.

[0100] In aspects that further enhance the effects of the present invention, the glass transition temperature (Tg) of the homopolymer containing the hydroxyl-containing monomer (m4) that may be included in the monomer component (M) is preferably -10°C or less, more preferably -15°C or less, further preferably -20°C or less, particularly preferably -25°C or less, and most preferably -30°C or less. The lower limit of the above-mentioned glass transition temperature Tg is preferably -80°C or more. The glass transition temperature (Tg) of the homopolymer containing the hydroxyl-containing monomer (m4) that may be included in the monomer component (M) can affect the adhesive and flexural properties of the acrylic polymer (P). By using a hydroxyl-containing monomer (m4) whose homopolymer has a glass transition temperature (Tg) within the above-mentioned range as the hydroxyl-containing monomer (m4) that may be included in the monomer component (M), the adhesive and flexural properties of the acrylic polymer (P) can be appropriately adjusted, thereby further enhancing the effects of the present invention.

[0101] Here, the glass transition temperature (Tg) of the homopolymer containing hydroxyl-containing monomers (m4), which may be included in the monomer component (M), can be the same as that of the aforementioned alkyl methacrylates, using values ​​recorded in publicly available sources, such as those recorded in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). It should be noted that if multiple values ​​are recorded in the aforementioned "Polymer Handbook," the conventional value is used. For hydroxyl-containing monomers (m4) not recorded in the aforementioned "Polymer Handbook," the values ​​listed in the monomer manufacturer's catalog are used. For homopolymers containing hydroxyl-containing monomers (m4) that are not recorded in the aforementioned "Polymer Handbook" and for which no list of monomer manufacturers' catalogs is provided, the Tg value obtained using the measurement method described in Japanese Patent Application Publication No. 2007-51271 is used.

[0102] A representative example of the glass transition temperature Tg of a homopolymer that may contain hydroxyl-containing monomers (m4) in the monomer component (M) is, for example, as described below.

[0103] 2-Hydroxyethyl acrylate: -15℃

[0104] 4-Hydroxybutyl acrylate: -40℃

[0105] When the monomer component (M) contains a hydroxyl-containing monomer (m4), in order to further demonstrate the effects of the present invention, the content of the hydroxyl-containing monomer (m4) in the monomer component (M) is preferably 0.01% to 30% by weight, more preferably 0.1% to 20% by weight, further preferably 0.5% to 15% by weight, particularly preferably 1% to 10% by weight, and most preferably 2% to 5% by weight.

[0106] Examples of hydroxyl-containing monomers (m4) include, for example, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and other hydroxyalkyl methacrylates; polypropylene glycol mono(meth)acrylate; and N-hydroxyethyl(meth)acrylamide.

[0107] In terms of further demonstrating the effects of the present invention, the hydroxyl-containing monomer (m4) preferably comprises a hydroxyalkyl methacrylate, more preferably a hydroxyalkyl methacrylate comprising a straight-chain alkyl group having 2 to 4 carbon atoms. Examples of hydroxyalkyl methacrylates include 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA), and 4-hydroxybutyl acrylate is preferred in terms of further demonstrating the effects of the present invention.

[0108] From the perspective of further demonstrating the effects of the present invention, the monomer component (M) preferably includes at least one selected from the group consisting of alkyl methacrylate (m1), alkyl methacrylate (m2), and alkyl methacrylate (m3) and includes a hydroxyl-containing monomer (m4), more preferably includes at least two selected from the group consisting of alkyl methacrylate (m1), alkyl methacrylate (m2), and alkyl methacrylate (m3) and includes a hydroxyl-containing monomer (m4), and even more preferably includes alkyl methacrylate (m1), alkyl methacrylate (m2), and alkyl methacrylate (m3) and includes a hydroxyl-containing monomer (m4).

[0109] From the perspective of further demonstrating the effects of the present invention, the monomer component (M) is preferably composed of at least one selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate and contains a hydroxyl-containing monomer (m4), more preferably composed of at least two selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate and contains a hydroxyl-containing monomer (m4), and even more preferably composed of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate and contains a hydroxyl-containing monomer (m4).

[0110] From the perspective of further demonstrating the effects of the present invention, the total content of (meth)acrylate (m1), (meth)acrylate (m2), (meth)acrylate (m3), and hydroxyl-containing monomer (m4) in the monomer component (M) is preferably 60% to 99% by weight, more preferably 70% to 99% by weight, further preferably 80% to 99% by weight, particularly preferably 90% to 99% by weight, and most preferably 95% to 98% by weight.

[0111] The monomer component (M) may also include monomers other than monomer (1) shown in general formula (1), monomer (2) shown in general formula (2), alkyl methacrylate, and hydroxyl-containing monomer (m4) without impairing the effects of the present invention. Other monomers may be used, for example, for adjusting the glass transition temperature (Tg) of the acrylic polymer (P) or for adjusting the adhesive properties. There may be only one other monomer or two or more other monomers.

[0112] Other monomers include, for example, carboxyl-containing monomers, nitrogen-containing monomers, sulfonic acid-containing monomers, phosphate-containing monomers, cyano-containing monomers, acid anhydride-containing monomers, vinyl esters (e.g., vinyl acetate (VAc), vinyl propionate, vinyl laurate), aromatic vinyl compounds, amide-containing monomers, epoxy-containing monomers, (meth)acryloylmorpholine, and vinyl ethers.

[0113] Examples of carboxyl-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl methacrylate, carboxypentyl methacrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0114] Examples of nitrogen-containing monomers include N-vinyl-2-pyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazolium, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylcarboxylic acid amides, and N-vinylcaprolactam; and cyanoacrylate monomers such as acrylonitrile and methacrylonitrile. Among these, N-vinyl-2-pyrrolidone is preferred due to its high effect on improving adhesive strength resulting from increased cohesion.

[0115] The proportion of other monomers in the monomer component (M) is preferably 20% by weight or less, more preferably 10% by weight or less, further preferably 5% by weight or less, particularly preferably 3% by weight or less, and most preferably 1% by weight or less.

[0116] As a method for obtaining acrylic polymers (P), various polymerization methods known as synthetic techniques for acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization, can be appropriately employed. Among these polymerization methods, solution polymerization is preferred. As a monomer supply method for solution polymerization, a one-time feeding method that supplies the entire amount of monomer components at once, a continuous supply (dropleting) method, or a batch supply (dropleting) method can be appropriately employed. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., preferably 20°C or higher, more preferably 30°C or higher, even more preferably 40°C or higher, preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 140°C or lower. As a method for obtaining acrylic polymers, active energy line irradiation polymerization, such as photopolymerization by irradiation with UV light (typically carried out in the presence of a photopolymerization initiator) or radiation polymerization by irradiation with β-rays, γ-rays, etc., can be employed.

[0117] As a solvent used in solution polymerization (polymerization solvent), any suitable organic solvent can be appropriately selected. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons), acetates such as ethyl acetate, and aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane can be cited.

[0118] The initiator used in polymerization (polymerization initiator) can be appropriately selected from any suitable polymerization initiator depending on the type of polymerization method. There can be only one polymerization initiator or two or more.

[0119] Examples of polymerization initiators include, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, dimethyl 2,2'-azobis(2-methylpropionic acid) ester, 4,4'-azobis-4-cyanopentanoic acid, azobisisovalerate, 2,2'-azobis(2-amidinylpropane) dihydrochloride, and 2,2'-azobis[2-(5-methyl-2-imidazolium)] Azo-based initiators such as [azoline-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropanediamine) disulfide, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropanediamine] hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate; and peroxides... Peroxide-based initiators include di(2-ethylhexyl) dicarbonate, di(4-tert-butylcyclohexyl) dicarbonate peroxide, disec-butyl dicarbonate peroxide, tert-butyl neodecanoate peroxide, tert-hexyl peroxypentanoate peroxide, dilauroyl peroxide, dioctanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxide-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, benzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-di(tert-hexylperoxy)cyclohexane, tert-butyl hydroperoxide, and hydroperoxide; redox initiators combining peroxides and reducing agents, such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate; substituted ethane initiators, such as phenyl-substituted ethanes; and aromatic carbonyl compounds.

[0120] The amount of polymerization initiator relative to 100 parts by weight of monomer component (M) is preferably 0.005 parts by weight to 1 part by weight, more preferably 0.01 parts by weight to 1 part by weight.

[0121] Any other suitable additives may be added to the polymer without impairing the effects of the present invention.

[0122] Crosslinking Agent

[0123] The acrylic adhesive composition of the embodiments of the present invention may contain a crosslinking agent. The crosslinking agent may be only one type, or it may be two or more types.

[0124] By using crosslinking agents, acrylic adhesives can be endowed with appropriate cohesive strength. Crosslinking agents can be included in acrylic adhesives in various forms, including post-crosslinking, pre-crosslinking, partially crosslinked, intermediate, or composite forms. Typically, crosslinking agents are included in acrylic adhesives in their post-crosslinking form.

[0125] Regarding the proportion of the crosslinking agent in the acrylic adhesive composition, in order to further demonstrate the effects of the present invention, it is preferably 0.005 parts to 10 parts by weight, more preferably 0.01 parts to 7 parts by weight, further preferably 0.05 parts to 5 parts by weight, and particularly preferably 0.1 parts to 1 part by weight, relative to 100 parts by weight of the acrylic polymer (P).

[0126] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, organosilicon-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, and peroxides. In terms of further demonstrating the effects of the present invention, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred, and isocyanate-based crosslinking agents are more preferred.

[0127] Isocyanate-based crosslinking agents can be compounds having two or more isocyanate groups in one molecule (including isocyanate-regenerated polar groups that are temporarily protected by end-capping agents or by polymerization). Examples of isocyanate-based crosslinking agents include aromatic isocyanates such as toluene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate.

[0128] Examples of isocyanate-based crosslinking agents include, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, phenylenediamine diisocyanate, and polymethylene polyphenyl isocyanate; trimethylolpropane / toluene diisocyanate trimer adducts (e.g., manufactured by Tosoh Corporation, trade name CORONATEL), trimethylolpropane / hexamethylene diisocyanate trimer adducts (e.g., manufactured by Tosoh Corporation, trade name: CORONATE HL), and isocyanurate forms of hexamethylene diisocyanate (e.g., manufactured by Tosoh Corporation, trade name: CORONATE). Isocyanate adducts such as HX; trimethylolpropane adducts of dimethyl phthalate (e.g., manufactured by Mitsui Chemicals, trade name: TAKENATED110N), trimethylolpropane adducts of dimethyl phthalate (e.g., manufactured by Mitsui Chemicals, trade name: TAKENATE D120N), trimethylolpropane adducts of isophorone diisocyanate (e.g., manufactured by Mitsui Chemicals, trade name: TAKENATE D140N), trimethylolpropane adducts of hexamethylene diisocyanate (e.g., manufactured by Mitsui Chemicals, trade name: TAKENATE D160N); polyether polyisocyanates, polyester polyisocyanates, and their adducts with various polyols; polyisocyanates formed by multifunctionalization using isocyanurate bonds, biuret bonds, urethane bonds, etc. Among these, aromatic isocyanates and alicyclic isocyanates are preferred from the perspective of balancing deformability and cohesion.

[0129] As epoxy crosslinking agents, polyfunctional epoxy compounds having two or more epoxy groups in one molecule can be used. Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-phenylenediamine, diglycidyl aniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol polycondensate. Glyceryl ether, glyceryl polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, bisphenol-S-d-glycidyl ether, and epoxy resins having two or more epoxy groups within their molecules. Commercially available epoxy crosslinking agents include, for example, those manufactured by Mitsubishi Gas Chemical Co., Ltd. under the trade names "TETRAD C" and "TETRADX".

[0130] Oligomers

[0131] To adjust adhesive properties, bending properties, etc., the acrylic adhesive composition of embodiments of the present invention may include oligomers. There may be only one type of oligomer, or there may be two or more types.

[0132] The weight-average molecular weight (Mw) of the oligomer is preferably 1,000 to 30,000, more preferably 1,500 to 10,000, further preferably 2,000 to 8,000, and particularly preferably 2,000 to 5,000. By using oligomers with such a weight-average molecular weight (Mw), the adhesive properties and flexural properties of acrylic adhesives can be improved.

[0133] As oligomers, acrylic oligomers are preferred from the perspective of easy compatibility with acrylic polymers.

[0134] The glass transition temperature (Tg) of the acrylic oligomer is preferably 20°C or higher, more preferably 40°C or higher, even more preferably 60°C or higher, particularly preferably 80°C or higher, and most preferably 100°C or higher. The upper limit of the glass transition temperature (Tg) of the acrylic oligomer is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower.

[0135] The glass transition temperature (Tg) of acrylic oligomers is a value calculated using the Fox formula, based on the Tg of the homopolymer of each constituent monomer and the weight fraction of that monomer (copolymerization ratio on a weight basis). The Fox formula, shown below, expresses the relationship between the Tg of the copolymer and the glass transition temperature (Tgi) of the homopolymer formed by the homopolymerization of each monomer constituting the copolymer.

[0136] 1 / Tg=Σ(Wi / Tgi)

[0137] In the Fox formula above, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). The Tg of the homopolymer can be a value recorded in publicly available sources, for example, the value recorded in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). If multiple values ​​are recorded in the "Polymer Handbook," the conventional value is used. For monomers not recorded in the "Polymer Handbook," the values ​​listed in the monomer manufacturer's catalog are used. For the Tg of homopolymers of monomers not recorded in the "Polymer Handbook" and for which no manufacturer's catalog is provided, the value obtained by the measurement method described in Japanese Patent Application Publication No. 2007-51271 is used.

[0138] Acrylic oligomers contain (meth)acrylate cycloalkyl esters as their main monomer components. There may be only one (meth)acrylate cycloalkyl ester or two or more.

[0139] Examples of cycloalkyl methacrylates include cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, and other cycloalkyl methacrylates; isobornyl methacrylate and other methacrylates having a bicyclic aliphatic hydrocarbon ring; and dicyclopentyl methacrylate, dicyclopentoxyethyl methacrylate, tricyclopentyl methacrylate, 1-adamantyl methacrylate, 2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl methacrylate, and other methacrylates having three or more aliphatic hydrocarbon rings.

[0140] As cycloalkyl esters of (meth)acrylate, dicyclopentyl acrylate, dicyclopentyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferred in terms of further demonstrating the effects of the present invention.

[0141] Regarding the proportion of (meth)acrylate cyclic alkyl esters relative to the total amount of monomer components constituting acrylic oligomers, in order to further demonstrate the effects of the present invention, it is preferably 10% to 99% by weight, more preferably 30% to 98% by weight, further preferably 40% to 97% by weight, and particularly preferably 50% to 96% by weight.

[0142] Acrylic oligomers may contain alkyl (meth)acrylates with chain-like alkyl groups as constituent monomer components. There may be only one type of alkyl (meth)acrylate with chain-like alkyl groups, or there may be two or more types. Here, "chain-like" refers to both linear and branched chains.

[0143] As a chain alkyl ester of (meth)acrylate, a chain alkyl ester of (meth)acrylate having a chain alkyl group having 1 to 20 carbon atoms is preferred. Examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, and so on. (Meth)Octyl acrylate, (Meth)Nonyl acrylate, (Meth)Isononyl acrylate, (Meth)Decyl acrylate, (Meth)Isodecyl acrylate, (Meth)Undecyl acrylate, (Meth)Lauryl acrylate, (Meth)Tetrazyl acrylate, (Meth)Tetradecyl acrylate, (Meth)Venteyl acrylate, (Meth)Hexadecyl acrylate, (Meth)Heptadecanyl acrylate, (Meth)Octadecanyl acrylate, (Meth)Isostearyl acrylate, (Meth)Nondecyl acrylate, (Meth)Eicosyl acrylate.

[0144] As a chain alkyl ester of (meth)acrylate, methyl methacrylate is preferred in terms of further demonstrating the effects of the present invention.

[0145] Regarding the proportion of (meth)acrylate alkyl esters relative to the total amount of monomer components constituting acrylic oligomers, in order to further demonstrate the effects of the present invention, it is preferably 10% to 90% by weight, more preferably 20% to 80% by weight, and even more preferably 30% to 70% by weight.

[0146] Acrylic oligomers may contain (meth)acrylic acid as a constituent monomer component. (Meth)acrylic acid may be only one type or may be two or more types.

[0147] Acrylic acid is preferred as (meth)acrylic acid in terms of further demonstrating the effects of the present invention.

[0148] The proportion of (meth)acrylic acid relative to the total amount of monomer components constituting the acrylic oligomer is preferably 0.1% to 20% by weight, more preferably 1% to 10% by weight, and even more preferably 3% to 7% by weight, in order to further enhance the effects of the present invention.

[0149] Oligomers are obtained by polymerizing the constituent monomer components using various polymerization methods. During the polymerization of oligomers, any suitable additives may be used without impairing the effects of the present invention. Examples of such additives include polymerization initiators and chain transfer agents.

[0150] Regarding the proportion of oligomers in the acrylic adhesive composition, in order to further demonstrate the effects of the present invention, the proportion relative to 100 parts by weight of the acrylic polymer (P) is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, further preferably 1 to 10 parts by weight, and particularly preferably 1 to 5 parts by weight.

[0151] Tackifying Resins

[0152] To adjust adhesive properties, bending properties, etc., the acrylic adhesive composition of embodiments of the present invention may include a tackifying resin. The tackifying resin may be only one type or may be two or more types.

[0153] Examples of tackifying resins include rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastic system tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins.

[0154] Regarding the amount of tackifying resin used, in order to further demonstrate the effects of the present invention, it is preferably 5 to 70 parts by weight, more preferably 10 to 60 parts by weight, further preferably 15 to 50 parts by weight, even more preferably 20 to 45 parts by weight, particularly preferably 25 to 40 parts by weight, and most preferably 25 to 35 parts by weight, relative to 100 parts by weight of acrylic polymer (P).

[0155] For the tackifying resin, in order to further demonstrate the effects of the present invention, it is preferable to include a tackifying resin TL with a softening point below 105°C. The tackifying resin TL can effectively contribute to improving the deformability of the adhesive layer in the planar direction (shear direction). From the viewpoint of obtaining a greater improvement in deformability, the softening point of the tackifying resin used as the tackifying resin TL is preferably 50°C to 103°C, more preferably 60°C to 100°C, further preferably 65°C to 95°C, particularly preferably 70°C to 90°C, and most preferably 75°C to 85°C.

[0156] The softening point of the tackifying resin is defined as the value determined based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is rapidly melted at the lowest possible temperature, ensuring it is poured into a ring placed on a flat metal plate without creating bubbles. After cooling, the portion protruding from the upper plane containing the ring is cut off with a slightly heated knife. Next, a support (ring base) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerol is poured in until the depth is 90 mm or more. Then, a steel ball (9.5 mm in diameter, 3.5 g in weight) and the ring filled with the sample are immersed in glycerol without touching each other, and the temperature of the glycerol is maintained at 20 °C ± 5 °C for 15 minutes. Finally, the steel ball is placed in the center of the sample surface in the ring, and the ring is placed in a fixed position on the support. Next, maintaining a distance of 50 mm from the top of the ring to the glycerin surface, place a thermometer with the center of the thermometer's mercury bulb at the same height as the center of the ring, and heat the container. Position the Bunsen burner flame, used for heating, between the center of the container's bottom and the edge to ensure uniform heating. It should be noted that the rate of temperature increase from the start of heating until reaching 40°C must be 5.0 ± 0.5°C per minute. The sample gradually softens and flows off the ring; the temperature at which it finally contacts the bottom plate is recorded as the softening point. For softening point determination, at least two measurements should be taken simultaneously, and the average value should be used.

[0157] The amount of tackifying resin TL used, in order to further demonstrate the effects of the present invention, is preferably 5 to 50 parts by weight, more preferably 10 to 45 parts by weight, further preferably 15 to 40 parts by weight, particularly preferably 20 to 35 parts by weight, and most preferably 25 to 32 parts by weight, relative to 100 parts by weight of acrylic polymer (P).

[0158] As the tackifying resin TL, one or more suitable selections from the tackifying resins exemplified above with a softening point below 105°C may be used. The tackifying resin TL preferably includes a rosin-based resin.

[0159] For rosin-based resins that are preferably used as tackifying resins (TL), examples include unmodified rosin esters, modified rosin esters, and other rosin esters. Examples of modified rosin esters include hydrogenated rosin esters.

[0160] The tackifying resin TL preferably comprises hydrogenated rosin ester in a manner that further enhances the effects of the present invention. As a hydrogenated rosin ester, the softening point is preferably below 105°C, more preferably 50°C to 100°C, further preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C in a manner that further enhances the effects of the present invention.

[0161] Tackifying resins (TL) may contain non-hydrogenated rosin esters. Here, "non-hydrogenated rosin esters" is used broadly to refer to substances other than hydrogenated rosin esters in the aforementioned rosin ester category. Examples of non-hydrogenated rosin esters include unmodified rosin esters, disproportionated rosin esters, and polymerized rosin esters.

[0162] As a non-hydrogenated rosin ester, the softening point is preferably below 105°C, more preferably 50°C to 100°C, further preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C, in order to further demonstrate the effects of the present invention.

[0163] In addition to rosin-based resins, the tackifying resin TL may also contain other tackifying resins. As other tackifying resins, one or more suitable selections from those exemplified above with softening points below 105°C may be used. For example, the tackifying resin TL may contain rosin-based resins and terpene resins.

[0164] Regarding the proportion of rosin-based resin in the total tackifying resin TL, in order to further demonstrate the effects of the present invention, it is preferably more than 50% by weight, more preferably 55% to 100% by weight, further preferably 60% to 99% by weight, particularly preferably 65% ​​to 97% by weight, and most preferably 75% to 97% by weight.

[0165] In order to further enhance the effects of the present invention, the tackifying resin can be combined with a tackifying resin TL and a tackifying resin TH with a softening point of 105°C or higher (preferably 105°C to 170°C).

[0166] As the tackifying resin TH, one or more suitable selections from the tackifying resins exemplified above with a softening point of 105°C or higher may be used. The tackifying resin TH may include at least one selected from rosin-based tackifying resins (e.g., rosin esters) and terpene-based tackifying resins (e.g., terpene phenol resins).

[0167] Other Ingredients

[0168] The acrylic adhesive compositions of embodiments of the present invention may, as needed, contain various additives commonly found in the field of adhesives, such as leveling agents, crosslinking aids, plasticizers, softeners, fillers, antistatic agents, antioxidants, ultraviolet absorbers, antioxidants, light stabilizers, crosslinking catalysts, and crosslinking delay agents. Such additives can be obtained using conventionally known additives.

[0169] As a crosslinking catalyst, for example, can be cited as... Iron, tetrabutyl titanate, tetraisopropyl titanate, butyltin oxide, dioctyltin dilaurate, etc. As crosslinking delay agents, for example, compounds that generate keto-enol tautomers can be cited, specifically, β-diketones such as acetylacetone and 2,4-hexanedione; acetoacetate esters such as methyl acetoacetate and ethyl acetoacetate; propionyl acetate esters such as ethyl propionyl; isobutyryl acetate esters such as ethyl isobutyryl; malonates such as methyl malonate and ethyl malonate; etc.

[0170] "Adhesive Films"

[0171] The adhesive film of the embodiments of the present invention has an adhesive layer composed of an acrylic adhesive sheet of the embodiments of the present invention.

[0172] The adhesive film of the embodiments of the present invention can be a substrate-free film formed solely of an adhesive layer, or a substrate-supported film having a substrate layer and an adhesive layer. In addition to the substrate layer and the adhesive layer, the adhesive film of the present invention may also have any suitable other layers without impairing the effects of the present invention.

[0173] The substrate layer can be one layer or two or more layers. Preferably, the substrate layer is one layer, which can further enhance the effects of the present invention.

[0174] The adhesive layer can be one layer or two or more layers. Preferably, the adhesive layer is one layer, which can further enhance the effects of the present invention.

[0175] For purposes such as protection before use, the adhesive film of the present invention may have any suitable release liner on the surface opposite to the substrate layer of the adhesive layer.

[0176] Examples of release liner materials include, for instance, release liner materials whose surfaces (liner substrates) are treated with silicone; and release liner materials whose surfaces (liner substrates) are laminated with polyolefin resins. Examples of plastic films used as liner substrates include, for instance, polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, and ethylene-vinyl acetate copolymer films.

[0177] The thickness of the release liner is preferably 1 μm to 500 μm, more preferably 3 μm to 450 μm, further preferably 5 μm to 400 μm, and particularly preferably 10 μm to 300 μm.

[0178] The thickness of the adhesive film in the embodiments of the present invention is preferably 1 μm to 500 μm, more preferably 5 μm to 200 μm, further preferably 10 μm to 150 μm, particularly preferably 20 μm to 100 μm, and most preferably 30 μm to 80 μm. When the thickness of the adhesive film in the embodiments of the present invention is within the above range, the effects of the present invention can be further demonstrated.

[0179] The total light transmittance of the adhesive film in the embodiments of the present invention is preferably 20% or more, more preferably 30% or more, further preferably 40% or more, particularly preferably 50% or more, and most preferably 60% or more.

[0180] When the total light transmittance of the adhesive film of the present invention is within the above-mentioned range, it can further exhibit excellent transparency.

[0181] The haze of the adhesive film in the embodiments of the present invention is preferably 15% or less, more preferably 13% or less, further preferably 10% or less, particularly preferably 8% or less, and most preferably 6% or less. When the haze of the adhesive film of the present invention is within the above range, it can further exhibit excellent transparency.

[0182] The adhesive film of the present invention can maintain excellent flexibility and excellent recovery in low-temperature environments, and is therefore preferably used in flexible devices such as foldable devices and rollable devices.

[0183] Substrate Layer

[0184] The thickness of the substrate layer is preferably 1 μm to 500 μm, more preferably 5 μm to 300 μm, further preferably 10 μm to 100 μm, particularly preferably 15 μm to 80 μm, and most preferably 20 μm to 60 μm. When the thickness of the substrate layer is within the above range, the effects of the present invention can be further demonstrated.

[0185] The Young's modulus of the substrate layer at 23°C is preferably 6.0 × 10⁻⁶. 7 Pa or higher, more preferably 1.0 × 10 Pa 8 Pa or higher, more preferably 5.0 × 10 Pa 8 Pa or higher, with a preferred value of 8.0 × 10 Pa. 8 Pa or higher, with the optimal value being 1.0 × 10⁻⁶ Pa. 9 Pa or higher. The upper limit of the Young's modulus of the substrate layer at 23°C is typically preferably 1.0 × 10⁻⁶ Pa. 11Pa or less. When the Young's modulus of the substrate layer at 23°C is within the above-mentioned range, the effects of the present invention can be further demonstrated. If the Young's modulus of the substrate layer at 23°C is too low, if the adhesive film is bent at an angle, there is a concern that the compression relative to the inner diameter side may not adequately maintain the stretch of the outer diameter side, and there is a concern that the thickness may easily change and that the adhesive may easily lift off the adhered object. If the Young's modulus of the substrate layer at 23°C is too high, there is a concern that the adhesive film may not be easily deformable. The method for measuring the Young's modulus will be described in detail later.

[0186] As the material for the substrate layer, any suitable material may be used without impairing the effects of the present invention. Resin materials are representative examples of such substrate layer materials.

[0187] Examples of resin materials used as substrate layers include acrylic resins such as polyimide (PI), polyetheretherketone (PEEK), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polymethyl methacrylate (PMMA), as well as polycarbonate, cellulose triacetate (TAC), polysulfone, polyarylate, polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), fully aromatic polyamide (aromatic polyamide), polyvinyl chloride (PVC), polyvinyl acetate, polyphenylene sulfide (PPS), fluorinated resins, and cyclic olefin polymers.

[0188] Adhesive layer

[0189] The thickness of the adhesive layer is preferably 1 μm to 500 μm, more preferably 5 μm to 300 μm, further preferably 10 μm to 100 μm, particularly preferably 10 μm to 80 μm, and most preferably 10 μm to 60 μm. When the thickness of the adhesive layer is within the above range, the effects of the present invention can be further demonstrated.

[0190] The adhesive layer is formed by shaping the acrylic adhesive into a layer. Any suitable method can be used to form the adhesive layer without impairing the effects of the present invention. Examples of such methods include: applying an acrylic adhesive composition to any suitable substrate, heating and drying it as needed, and curing it as needed to form an acrylic adhesive layer on the substrate. Any suitable means can be used for such coating without impairing the effects of the present invention. Examples of such coating means include gravure roller coating machines, reverse roller coating machines, contact roller coating machines, dip roller coating machines, bar coating machines, knife coating machines, air knife coating machines, spray coating machines, comma coating machines, direct coating machines, and roller brush coating machines. Any suitable means can be used for heating and drying the acrylic adhesive composition without impairing the effects of the present invention. Examples of such heating and drying means include heating to approximately 60°C to 180°C. Any suitable means can be used for curing the acrylic adhesive composition without impairing the effects of the present invention. Examples of such curing methods include ultraviolet irradiation, laser irradiation, alpha irradiation, beta irradiation, gamma irradiation, X-ray irradiation, and electron beam irradiation.

[0191] Flexible Devices

[0192] The adhesive film of the present invention can maintain both excellent flexibility and excellent resilience in low-temperature environments, and is therefore suitable for use in flexible devices such as flexible devices, foldable devices, and rollable devices with movable bending portions.

[0193] That is, the flexible device according to the embodiments of the present invention includes the adhesive film according to the embodiments of the present invention. The flexible device according to the present invention includes the adhesive film according to the embodiments of the present invention. The foldable device according to the present invention, as long as it includes the adhesive film according to the embodiments of the present invention, may include any other suitable components.

[0194] Figure 1 This is a schematic cross-sectional view illustrating one embodiment of the flexible device of the present invention, which is a representative example of the use of the adhesive film as an embodiment of the present invention. Figure 1 In this embodiment of the invention, the foldable device 1000 includes: a cover film 10, an adhesive layer 20, a polarizing plate 30, an adhesive layer 40, a contact sensor 50, an adhesive layer 60, an OLED 70, and an adhesive film 100 according to the embodiment of the invention. The adhesive film 100 according to the embodiment of the invention... Figure 1The adhesive layer 80 and the substrate layer 90 are composed of an adhesive layer 20, an adhesive layer 40, and an adhesive layer 60. The adhesive layers 20, 40, and 60 may be adhesive layers containing an adhesive with the same composition as the adhesive layer 80 constituting the adhesive film 100 of the embodiments of the present invention, or they may be adhesive layers containing an adhesive with a different composition.

[0195] Example

[0196] The following examples and comparative examples illustrate the present invention in more detail. However, the present invention is not limited thereto. It should be noted that, unless otherwise specified, "parts" and "%" in the following description are based on weight.

[0197] The abbreviations and details of the raw materials used in the following manufacturing examples, embodiments, and comparative examples are as follows.

[0198] 2EHA: 2-Ethylhexyl acrylate

[0199] LA: Lauryl acrylate

[0200] BA: n-Butyl acrylate

[0201] 4HBA: 4-Hydroxybutyl acrylate

[0202] NVP: N-vinyl-2-pyrrolidone

[0203] AOMA (registered trademark): Cyclopolymerizable monomer manufactured by Nippon Shokubai Co., Ltd. (in general formula (1), R 1 Methyl, R 2 (It is a hydrogen atom.)

[0204] V#216: 2-Butylcarbamoyloxyethyl acrylate (VISCOAT#216, manufactured by Osaka Organic Chemical Industry Co., Ltd.) (in general formula (2), R 3 -CH2CH2-, R 4 n-Butyl, R 5 (It is a hydrogen atom.)

[0205] MMA: Methyl methacrylate

[0206] HEA: Hydroxyethyl acrylate

[0207] AIBN: 2,2'-azobisisobutyronitrile

[0208] Irgacure184: Photopolymerization initiator (manufactured by BASF)

[0209] Irgacure 651: Photopolymerization initiator (manufactured by BASF)

[0210] DCPMA: Dicyclopentyl methacrylate

[0211] C / HX: CORONATE HX (manufactured by Tosoh Corporation, an isocyanate-based crosslinking agent)

[0212] D110N: TAKENATE D110N (manufactured by Mitsui Chemicals, Ltd., isocyanate-based crosslinking agent)

[0213] HDDA: 1,6-Hexanediol diacrylate

[0214] Iron: Iron catalyst (manufactured by Nippon Chemical Industries, Ltd.)

[0215] IRGANOX 1010: Antioxidant (manufactured by BASF)

[0216] KBM403: Silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0217] <Adhesion to polyimide films>

[0218] After peeling off the separator with low peel strength (MRQ50T100J) from the adhesive film separators, a 25μm thick polyimide substrate (trade name "Upilex 25RN", manufactured by Ube Industries, Ltd.) is laminated to create an adhesive film with a polyimide substrate. The adhesive film with the polyimide substrate is cut into pieces 25mm wide and 100mm long. The separator (JT-50Wa) is peeled off to expose the adhesive. The adhesive is then bonded to the polyimide film (trade name "Upilex50S", manufactured by Ube Industries, Ltd.) by pressing a 2kg hand roller back and forth once, thus obtaining an evaluation sample.

[0219] The obtained evaluation samples were kept at room temperature for 30 minutes before being tested using a tensile testing machine. The tensile testing machine used was the Shimadzu Autograph AG-Xplus HS6000mm / min high-speed mode (AG-50NXplus), manufactured by Shimadzu Corporation. The evaluation samples were placed on the tensile testing machine, and the tensile test was started. The tensile test conditions were set as follows: peel angle: 180 degrees, peel speed (tensile speed): 300mm / min. The load at which the adhesive film was peeled from the polyimide film (Upilex 50S) was measured, and the average load at this point was taken as the adhesive force.

[0220] <Creep value at -20℃, recovery value at -20℃>

[0221] Only the adhesive layer is removed from the adhesive film, and then laminated to form a thickness of approximately 1 mm. This is then punched out. Cylindrical granules were prepared as samples for testing.

[0222] The obtained test sample was fixed using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, Inc., ARES). The jig for the parallel plate. The deformation strain (%) after applying a deformation stress of 10 kPa at -20°C and holding it for 600 seconds is set as value A. The deformation strain after applying a deformation stress of 0 and holding it for 600 seconds is set as value B. Value A is taken as the creep value at -20°C. The value calculated by [100 - {(value B × 100) / value A}] is taken as the recovery value at -20°C.

[0223] <Gel content>

[0224] The adhesive film was cut into 50mm × 100mm pieces. The adhesive layer taken from the adhesive film was rolled into an arbitrary size as the test sample. It was then wrapped with a porous polytetrafluoroethylene (PTFE) membrane (NTF-1122 manufactured by Nitto Denko Corporation) with a pore size of 0.2μm and a cut size of 100mm × 100mm. The wrapped opening was tied with kite string. The weight of the test sample (B) was calculated by subtracting the total weight of the porous PTFE membrane and the kite string (A) from the weight of the test sample. The test sample wrapped with the porous PTFE membrane was immersed in about 50mL of ethyl acetate at 23°C for 7 days to allow the sol component of the adhesive to dissolve out of the porous PTFE membrane. After impregnation, the test sample wrapped in the porous polytetrafluoroethylene membrane was removed, dried at 130°C for 2 hours, and cooled for about 20 minutes. The dried weight (total weight of the sample, porous polytetrafluoroethylene membrane, and kite string) was then measured (C). The gelation rate of the adhesive was calculated using the following formula.

[0225] Gelation rate (%) = 100 × [(CA) / B]

[0226] <Storage Modulus G'>

[0227] Storage modulus G' is equivalent to the portion of elastic energy stored when a material deforms, and is an indicator of the degree of hardness.

[0228] Only the adhesive layer is removed from the adhesive film, and the layers are stacked to a thickness of approximately 1 mm. This is then punched out. Cylindrical granules were prepared as samples for testing.

[0229] The obtained test sample was fixed using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, Inc., ARES). Using a jig for parallel plates, the storage modulus G' was calculated. The measurement conditions are as follows.

[0230] Measurement: Shear Mode

[0231] Temperature range: -60℃~210℃

[0232] Heating rate: 5℃ / minute

[0233] Frequency: 1Hz

[0234] <Weight-average molecular weight Mw>

[0235] Weight-average molecular weight was determined by gel permeation chromatography (GPC). Specifically, an Agilent 1260 Infinity (manufactured by Agilent Technologies, Inc.) was used as the GPC measuring instrument. Taking into account the polymer concentration of the sample, a 0.1% by weight solution of tetrahydrofuran containing amine components was prepared, allowed to stand for 20 hours, filtered through a 0.45 μm membrane filter, and the filtrate was then subjected to GPC determination.

[0236] The determination was carried out under the following conditions and calculated using the standard polystyrene conversion value.

[0237] (Conditions for molecular weight determination)

[0238] • Sample concentration: 0.1% by weight (tetrahydrofuran solution with added amine components)

[0239] • Sample injection volume: 100 μL

[0240] • Pillar: Product name "TSK gel GMH-H(S)" (manufactured by Tosoh Corporation)

[0241] • Eluent: Contains tetrahydrofuran, an amine compound.

[0242] • Flow rate: 0.5 mL / min

[0243] • Detector: Differential refractometer (RI)

[0244] • Column temperature (measurement temperature): 40℃

[0245] • Standard sample: Polystyrene (PS)

[0246] [Manufacturing Example 1]: Manufacturing of acrylic polymer (1)

[0247] In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet pipe, and condenser, 66.6 parts by weight of 2EHA, 19.0 parts by weight of LA, 7.6 parts by weight of BA, 3.8 parts by weight of 4HBA, 1.0 part by weight of AOMA (registered trademark), 1.9 parts by weight of V#216, and 0.1 parts by weight of AIBN as a polymerization initiator were added to a total concentration of 30% by weight of ethyl acetate. The system was slowly stirred while nitrogen was replaced over 1 hour. The liquid temperature in the flask was maintained at approximately 58°C for 5 hours for the polymerization reaction. After the reaction was completed, ethyl acetate was added to adjust the polymer concentration to 28% by weight, resulting in a solution of acrylic polymer (1). The results are shown in Table 1.

[0248] [Manufacturing Examples 2-7]: Manufacturing of acrylic polymers (2)-(7)

[0249] The monomer composition and various conditions were changed to those described in Table 1, and the process was carried out in the same manner as in Manufacturing Example 1 to obtain solutions of acrylic polymers (2) to (7). The results are shown in Table 1.

[0250] [Manufacturing Example 8]: Manufacturing of acrylic oligomer (A)

[0251] 60 parts by weight of DCPMA and 40 parts by weight of MMA as monomers, 3.5 parts by weight of α-thioglycerol as a chain transfer agent, and 100 parts by weight of toluene as a polymerization solvent were mixed and stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by weight of AIBN as a thermal polymerization initiator were added, and the reaction was carried out at 70°C for 2 hours. The temperature was then raised to 80°C and the reaction was carried out for another 2 hours to obtain acrylic oligomer (A). The acrylic oligomer (A) has a weight-average molecular weight (Mw) of 5100 and a glass transition temperature (Tg) of 130°C.

[0252] [Example 1]

[0253] The following components were used: acrylic polymer (1): 100 parts by weight; C / HX as a crosslinking agent: 0.23 parts by weight; acrylic oligomer (A): 2 parts by weight; IRGANOX 1010 as an antioxidant: 0.3 parts by weight; and catalyst: Iron: 0.01 parts by weight were mixed and stirred thoroughly to make the total solid content 22% by weight. The mixture was then diluted with ethyl acetate and acetylacetone (2% by weight of solvent) to obtain a coating solution of acrylic adhesive composition (1). The obtained coating solution of acrylic adhesive composition (1) was coated onto the silicone-treated side of a 50μm thick polyester resin release sheet (product name: JT-50Wa, manufactured by Nitto Denko Corporation) with one side treated with silicone, to a thickness of 13μm after drying. The film was dried at a drying temperature of 130°C for 1 minute. Then, the silicone-treated side of the 50μm thick polyester resin release sheet (product name: MRQ50T100J, manufactured by Mitsubishi Chemical Corporation) was bonded to the surface of the obtained adhesive layer in contact to obtain an adhesive film (1). The film was cured at 50°C for 3 days and various evaluations were performed. The results are shown in Table 3.

[0254] [Examples 2-8]

[0255] The raw material composition and various conditions were changed as shown in Table 2. Otherwise, the process was the same as in Example 1 to obtain coating solutions and adhesive films (2) to (8) of acrylic adhesive compositions (2) to (8). They were cured at 50°C for 3 days and various evaluations were performed. The results are shown in Table 3.

[0256] [Comparative Examples 1-5]

[0257] The raw material composition and various conditions were changed as shown in Table 2. Otherwise, the process was the same as in Example 1 to obtain coating solutions and adhesive films (C1) to (C5) of acrylic adhesive compositions. These were cured at 50°C for 3 days, and various evaluations were performed. The results are shown in Table 3.

[0258] [Table 1]

[0259]

[0260] [Table 2]

[0261]

[0262] [Table 3]

[0263]

[0264] Industrial availability

[0265] The acrylic adhesives and the like of the embodiments of the present invention can be used in so-called flexible devices such as foldable devices and rollable devices.

[0266] Explanation of reference numerals in the attached figures

[0267] 1000 foldable devices

[0268] 100 adhesive film

[0269] 10. Covering film

[0270] 20 Adhesive layers

[0271] 30 polarizing plate

[0272] 40 Adhesive layer

[0273] 50 Contact Sensors

[0274] 60 Adhesive layer

[0275] 70 OLED

[0276] 80 Adhesive layer

[0277] 90 Substrate layer

Claims

1. An acrylic adhesive, which exhibits an adhesion force of 5.0 N / 25 mm or more to a polyimide film at 23°C, a peel speed of 300 mm / min, and a peel angle of 180 degrees. The creep value at -20℃ is over 70%, and the recovery value at -20℃ is over 70%. This acrylic adhesive is formed from an acrylic adhesive composition. This acrylic adhesive composition comprises an acrylic polymer (P) with a weight-average molecular weight (Mw) of less than 1 million. The acrylic polymer (P) is obtained by polymerizing a monomer component (M), which comprises at least one monomer selected from the group consisting of monomer (1) of general formula (1) and monomer (2) of general formula (2). In general formula (1), R 1 R is an alkyl group having 1 to 10 carbon atoms. 2 It consists of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a -COOR group, where R is an alkyl group having 1 to 10 carbon atoms. In general formula (2), R 3 R is an alkylene group having 1 to 10 carbon atoms. 4 R is an alkyl group having 1 to 10 carbon atoms. 5 It can be a hydrogen atom or a methyl group.

2. The acrylic adhesive according to claim 1, wherein the gelation rate is 50% or more.

3. The acrylic adhesive according to claim 1, wherein its storage modulus G' at -20°C is below 150 kPa.

4. The acrylic adhesive according to claim 1, wherein, The acrylic polymer (P) in the acrylic adhesive composition is present in an amount of 50% by weight or more.

5. The acrylic adhesive according to claim 1, wherein, The monomer component (M) comprises an alkyl (meth)acrylate.

6. An adhesive film having an adhesive layer made of an acrylic adhesive according to any one of claims 1 to 5.

7. A flexible device comprising the adhesive film of claim 6.

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