WO2022163165A1 - Acrylic adhesive agent, acrylic adhesive agent composition, adhesive film, and flexible device - Google Patents

Abstract

Provided are an acrylic adhesive agent capable of realizing both exceptional bending properties and exceptional recovery properties with respect to a bending motion in a low-temperature environment, an acrylic adhesive agent composition for forming the acrylic adhesive agent, an adhesive film having an adhesive agent layer configured from the acrylic adhesive agent, and a flexible device comprising the adhesive film.　The acrylic adhesive agent according to an embodiment of the present invention is such that the adhesive force with respect to a polyimide film is 5.0 N/25 mm or greater at a peel rate of 300 mm/min and a peel angle of 180 degrees at 23°C, wherein the creep value at -20°C is 70% or greater, and the recovery value at -20°C is 70% or greater.

Description

ACRYLIC ADHESIVE, ACRYLIC ADHESIVE COMPOSITION, ADHESIVE FILM, AND FLEXIBLE DEVICE

The present invention relates to acrylic pressure-sensitive adhesives, acrylic pressure-sensitive adhesive compositions, pressure-sensitive adhesive films, and flexible devices.

Adhesive films are used to reinforce and protect the surfaces of members of various shapes.

For example, when bonding an integrated circuit (IC) or flexible printed circuit board (FPC) to a substrate of a semiconductor element (for example, a TFT substrate), thermocompression bonding is usually performed using an anisotropic conductive film (ACF). When such thermocompression bonding is performed, an adhesive film may be adhered to the back side of the substrate of the semiconductor element in advance to reinforce the substrate (for example, Patent Document 1).

In addition, as a method for manufacturing so-called flexible devices such as foldable devices and rollable devices, which are being developed in recent years, generally, a release layer and a flexible film substrate are formed on a support substrate such as glass, A TFT substrate is formed on the film substrate, and an organic EL layer is formed thereon. Then, the support substrate is peeled off to manufacture the flexible device. However, since the flexible display layer is very thin, the device may be defective due to handling or the like. Therefore, in some cases, an adhesive film is adhered to the back side for reinforcement (for example, Patent Document 2).

Semiconductor element substrates and flexible devices may be repeatedly bent, and if the adhesive film laminated to the substrate, etc., has poor bending properties, the recovery after bending will deteriorate, and in the worst case, it will break due to repeated bending. It can be chilling. Specifically, when an adhesive film is attached to a bent portion (for example, a movable bent portion of a folding member), for example, the following problems occur.

When the adhesive film is bent at an angle, a compressive force acts on the bent inner diameter side, so the adhesive film itself deforms in an attempt to alleviate that force. Specifically, for example, wrinkles are likely to appear.

When the adhesive film is bent at an angle, a tensile stress acts on the bent outer diameter side. For this reason, when the stress is relaxed, it lifts from the adherend.

If the adhesive film is bent at an angle, the thickness of the area where the adhesive film is bent or pulled will change significantly, and even in such a state, wrinkles will easily appear or the film will float. do. For example, when the adhesive film is pulled, the thickness of the adhesive film is significantly reduced, and the film tends to be lifted from the adherend.

In this way, conventional adhesive films cannot sufficiently follow the unevenness of corners and bends.

In order to solve the above problems, it is necessary for the adhesive film to have both excellent flexibility and recovery properties against bending motion. In particular, flexible devices such as foldable devices and rollable devices, which are being developed in recent years, are used in a wide variety of environments, and even in low-temperature environments where bending characteristics are difficult to develop, they have excellent flexibility and excellent recovery from bending movements. There is a demand for an adhesive film that can achieve both.

Japanese Patent No. 5600039 Japanese Patent No. 6376271

An object of the present invention is to provide an acrylic pressure-sensitive adhesive that can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment, an acrylic pressure-sensitive adhesive composition that forms the acrylic pressure-sensitive adhesive, and the An object of the present invention is to provide an adhesive film having an adhesive layer composed of an acrylic adhesive, and a flexible device having the adhesive film.

The acrylic pressure-sensitive adhesive according to the embodiment of the present invention is
An acrylic pressure-sensitive adhesive having an adhesive force to a polyimide film of 5.0 N/25 mm or more at a peel speed of 300 mm/min and a peel angle of 180 degrees at 23° C.,
The creep value at -20°C is 70% or more, and the recovery value at -20°C is 70% or more.

In one embodiment, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention has a gel fraction of 50% or more.

In one embodiment, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention has a storage elastic modulus G' at -20°C of 150 kPa or less.

The acrylic pressure-sensitive adhesive composition according to the embodiment of the present invention is
An acrylic pressure-sensitive adhesive composition forming an acrylic pressure-sensitive adhesive according to an embodiment of the present invention,
An acrylic polymer (P) having a weight average molecular weight Mw of 1,200,000 or less is included.

In one embodiment, the content of the acrylic polymer (P) in the acrylic pressure-sensitive adhesive composition is 50% by weight or more.

（一般式（１）中、Ｒ^１は、炭素数１～１０のアルキル基であり、Ｒ^２は、水素原子、炭素数１～１０のアルキル基、または－ＣＯＯＲ基であり、Ｒは、炭素数１～１０のアルキル基である。）

（一般式（２）中、Ｒ^３は、炭素数１～１０のアルキレン基であり、Ｒ^４は、炭素数１～１０のアルキル基であり、Ｒ^５は、水素原子またはメチル基である。） In one embodiment, the acrylic polymer (P) is at least selected from the group consisting of monomers (1) represented by general formula (1) and monomers (2) represented by general formula (2) It is obtained by polymerizing a monomer component (M) containing one type.

(In the general formula (1), R ¹ is an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a —COOR group, and R is a carbon It is an alkyl group of numbers 1 to 10.)

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

In one embodiment, the monomer component (M) contains an alkyl (meth)acrylate.

The adhesive film according to the embodiment of the invention has an adhesive layer composed of the acrylic adhesive according to the embodiment of the invention.

A flexible device according to an embodiment of the present invention comprises an adhesive film according to an embodiment of the present invention.

According to the present invention, in a low-temperature environment, an acrylic pressure-sensitive adhesive that can exhibit both excellent flexibility and excellent recoverability against bending motion, an acrylic pressure-sensitive adhesive composition forming the acrylic pressure-sensitive adhesive, and the ADVANTAGE OF THE INVENTION The adhesive film which has an adhesive layer comprised from an acrylic adhesive, and a flexible device provided with this adhesive film can be provided.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the flexible device of the present invention, showing one usage pattern of the adhesive film according to the embodiment of the present invention.

When the expression "(meth) acrylic" is used in this specification, it means "acrylic and/or methacrylic", and when the expression "(meth) acrylate" is used, "acrylate and/or methacrylate ", and the expression "(meth)allyl" means "allyl and/or methallyl", and the expression "(meth)acrolein" means "acrolein and/or methacrolein". means rain. In addition, the expression "acid (salt)" in this specification means "acid and/or its salt". Examples of salts include alkali metal salts and alkaline earth metal salts, and specific examples include sodium salts and potassium salts.

≪≪Acrylic Adhesive≫≫
The acrylic pressure-sensitive adhesive according to the embodiment of the present invention preferably has an adhesive strength to a polyimide film of 5.0 N/25 mm or more at a peel speed of 300 mm/min and a peel angle of 180 degrees at 23° C., more preferably It is 5.5 N/25 mm or more, more preferably 6.0 N/25 mm or more, and particularly preferably 6.5 N/25 mm or more. Generally, the upper limit of the adhesive strength is preferably as high as possible, but it is preferably 30 N/25 mm or less in consideration of the balance with other adhesive properties. By adjusting the adhesive strength within the above range, sufficient adhesiveness to various adherends such as flexible devices such as foldable devices and rollable devices can be exhibited. The measurement of the adhesive force will be described later.

The acrylic pressure-sensitive adhesive according to the embodiment of the present invention preferably has a creep value at -20°C of 70% or more, more preferably 75% or more, still more preferably 80% or more, and particularly preferably 85%. % or more. Generally, the higher the creep value, the better. Considering the balance with other pressure-sensitive adhesive properties, the creep value is preferably 160% or less. The creep value at −20° C. is an index of flexibility in bending motion in a low-temperature environment, and the larger the creep value, the better the flexibility in bending motion in a low-temperature environment. By adjusting the above creep value within the above range, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention can exhibit excellent flexibility with respect to bending motion in a low-temperature environment. The measurement of the creep value will be described later.

The acrylic pressure-sensitive adhesive according to the embodiment of the present invention preferably has a recovery value at -20°C of 70% or more, more preferably 73% or more, still more preferably 77% or more, and particularly preferably 80%. % or more. Generally, the higher the upper limit of the recovery value, the better. Considering the balance with other pressure-sensitive adhesive properties, the upper limit of the recovery value is preferably 95% or less. The recovery value at −20° C. is an index of resilience to bending motion at low temperatures, and the higher the recovery value, the better the resilience to bending motion in a low temperature environment. By adjusting the recovery value within the above range, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention can exhibit excellent recovery from bending motion in a low-temperature environment. Measurement of the recovery value will be described later.

For the acrylic pressure-sensitive adhesive according to the embodiment of the present invention, both the creep value at -20°C and the recovery value at -20°C are more preferably adjusted within the above range. By adjusting in this way, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment. Conventionally, in the design of pressure-sensitive adhesives, there is often a trade-off relationship between flexibility and recoverability against bending motion. The acrylic pressure-sensitive adhesive according to the embodiment of the present invention can satisfactorily achieve both flexibility and recovery properties in a low-temperature environment with respect to bending motion, which are often in a trade-off relationship in the past. characteristics can be expressed.

The acrylic pressure-sensitive adhesive according to the embodiment of the present invention preferably has a gel fraction of 50% or more, more preferably 55% or more, still more preferably 60% or more, and still more preferably 65% or more. It is preferably 70% or more, and most preferably 75% or more. The upper limit of the gel fraction is 100%. By adjusting the gel fraction within the above range, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment. If the gel fraction is too small outside the above range, there is a risk that the recovery from bending motion will be reduced, especially in a low-temperature environment. The measurement of the gel fraction will be described later.

The acrylic pressure-sensitive adhesive according to the embodiment of the present invention has a storage modulus G' at -20°C of preferably 150 kPa or less, more preferably 140 kPa or less, still more preferably 130 kPa or less, and still more preferably 120 kPa. or less, particularly preferably 110 kPa or less, and most preferably 100 kPa or less. The lower limit of the storage elastic modulus G' is preferably 70 kPa or more in consideration of the balance with other adhesive properties. By adjusting the storage elastic modulus G′ within the above range, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention exhibits both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment. obtain. If the storage elastic modulus G' is too large outside the above range, there is a risk that the flexibility in particular for bending motion will be reduced. The measurement of the storage elastic modulus G' will be described later.

For the acrylic pressure-sensitive adhesive according to the embodiment of the present invention, both the gel fraction and the storage elastic modulus G' at -20°C are more preferably adjusted within the above ranges. By adjusting in this way, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment.

The acrylic pressure-sensitive adhesive according to the embodiment of the present invention is preferably formed from an acrylic pressure-sensitive adhesive composition.

The acrylic pressure-sensitive adhesive can thus be defined as being formed from an acrylic pressure-sensitive adhesive composition. This is because the acrylic pressure-sensitive adhesive becomes an acrylic pressure-sensitive adhesive when the acrylic pressure-sensitive adhesive composition causes a cross-linking reaction or the like by heating or ultraviolet irradiation, so that the acrylic pressure-sensitive adhesive can be directly specified by its structure. Due to the fact that it is impossible and almost impractical (“impossible / impractical circumstances”), the definition of “things formed from acrylic pressure-sensitive adhesive compositions” does not apply to acrylic It is a valid specification of the system adhesive as a "thing".

When the acrylic pressure-sensitive adhesive according to the embodiment of the present invention is formed from an acrylic pressure-sensitive adhesive composition, any suitable method for forming such an acrylic pressure-sensitive adhesive can be used as long as the effects of the present invention are not impaired. method can be adopted. As a method for forming such an acrylic pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive composition is applied onto any appropriate base material, heated and dried as necessary, and cured as necessary. and a method of forming an acrylic pressure-sensitive adhesive on the substrate. Any appropriate means can be adopted as such means for coating as long as the effects of the present invention are not impaired. Examples of such coating means include a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, an air knife coater, a spray coater, a comma coater, a direct coater, and a roll brush coater. mentioned. Any appropriate means can be employed for heating and drying the acrylic pressure-sensitive adhesive composition as long as the effects of the present invention are not impaired. As such heating/drying means, for example, heating at about 60° C. to 180° C. can be mentioned. Any appropriate means can be employed for curing the acrylic pressure-sensitive adhesive composition as long as the effects of the present invention are not impaired. Examples of such curing means include ultraviolet irradiation, laser beam irradiation, α-ray irradiation, β-ray irradiation, γ-ray irradiation, X-ray irradiation, and electron beam irradiation.

≪≪Acrylic adhesive composition≫≫
An acrylic pressure-sensitive adhesive composition according to an embodiment of the invention is an acrylic pressure-sensitive adhesive composition forming an acrylic pressure-sensitive adhesive according to an embodiment of the invention.

<<Acrylic polymer (P)>>
An acrylic pressure-sensitive adhesive composition according to an embodiment of the present invention contains an acrylic polymer (P). Only one type of acrylic polymer (P) may be used, or two or more types may be used.

The weight average molecular weight Mw of the acrylic polymer (P) is preferably 1,200,000 or less, more preferably 1,100,000 or less, even more preferably 1,000,000 or less, still more preferably 900,000 or less, and particularly preferably is 800,000 or less, most preferably 700,000 or less. The lower limit of the weight average molecular weight Mw is preferably 500,000 or more. By adjusting the weight-average molecular weight Mw within the above range, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment. . If the weight-average molecular weight Mw is too large outside the above range, there is a risk that the flexibility in particular for bending motion will be reduced. The measurement of the weight average molecular weight Mw will be described later.

The content of the acrylic polymer (P) in the acrylic pressure-sensitive adhesive composition according to the embodiment of the present invention is preferably 50% by weight or more, more preferably 70% by weight or more, and still more 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 content ratio is preferably 100% by weight or less. By adjusting the content ratio within the above range, the acrylic pressure-sensitive adhesive according to the embodiment of the present invention can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment. If the content is too small outside the above range, the effects of the present invention may not be sufficiently exhibited.

（一般式（１）中、Ｒ^１は、炭素数１～１０のアルキル基であり、Ｒ^２は、水素原子、炭素数１～１０のアルキル基、または－ＣＯＯＲ基であり、Ｒは、炭素数１～１０のアルキル基である。）

（一般式（２）中、Ｒ^３は、炭素数１～１０のアルキレン基であり、Ｒ^４は、炭素数１～１０のアルキル基であり、Ｒ^５は、水素原子またはメチル基である。） Acrylic polymer (P) is preferably a monomer containing at least one selected from the group consisting of monomer (1) represented by general formula (1) and monomer (2) represented by general formula (2). Obtained by polymerizing component (M).

(In the general formula (1), R ¹ is an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a —COOR group, and R is a carbon It is an alkyl group of numbers 1 to 10.)

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

The acrylic polymer (P) can thus be defined as one obtained by polymerizing the monomer component (M). This is because the acrylic polymer (P) becomes the acrylic polymer (P) by causing a polymerization reaction of the monomer component (M), and it is impossible to directly specify the acrylic polymer (P) by its structure. , In addition, due to the existence of circumstances that are almost impractical ("impossible / impractical circumstances"), the acrylic polymer (P) is defined as "obtained by polymerizing the monomer component (M)" is properly identified as a "thing".

The monomer component (M) contains at least one selected from the group consisting of the monomer (1) represented by the general formula (1) and the monomer (2) represented by the general formula (2), and the effects of the present invention are obtained. It is preferable to include both the monomer (1) represented by the general formula (1) and the monomer (2) represented by the general formula (2) in that it can express more.

The number of monomers (1) represented by general formula (1) may be one, or two or more.

The monomer (1) represented by the general formula (1) has two polymerizable double bonds at its terminals and a structure (C—CH ₂ —O— CH ₂ —C) and further having an alkyl ester group (COOR ¹ group) on at least one of the carbon atoms second from the end of the two terminal polymerizable double bonds, thereby promoting cyclization polymerization , it is possible to introduce an alkyl ester group into the structure constructed by cyclopolymerization, and these characteristics give the obtained acrylic pressure-sensitive adhesive better flexibility against bending motion and better Both resilience can be expressed.

The number of monomers (2) represented by general formula (2) may be one, or two or more.

The monomer (2) represented by the general formula (2) has a (meth)acrylate structure (CH ₂ =C(R ⁵ )COO-) and a carbamoyloxy structure (-O-CO-NH-). Due to these characteristics, the obtained acrylic pressure-sensitive adhesive can exhibit both excellent flexibility and excellent recovery property against bending motion.

In the monomer (1) represented by the general formula ( ¹ ), R ¹ is an alkyl group having 1 to 10 carbon atoms. an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably a methyl group or an ethyl group, most preferably is a methyl group.

In monomer (1) represented by general formula (1), R ² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a -COOR group. When R ² is an alkyl group having 1 to 10 carbon atoms, R ² is preferably an alkyl group having 1 to 8 carbon atoms, more preferably 1 to 1 carbon atoms, in that the effects of the present invention can be more exhibited. 6 alkyl group, more preferably an alkyl group having 1 to 3 carbon atoms. When R ² is a —COOR group, R is an alkyl group having 1 to 10 carbon atoms, and from the viewpoint that the effects of the present invention can be more expressed, R is preferably an alkyl group having 1 to 8 carbon atoms. , more preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably a methyl group or an ethyl group, most preferably a methyl group. R ² is preferably a hydrogen atom in that the effects of the present invention can be expressed more effectively.

In the monomer (2) represented by the general formula (2), R ³ is an alkylene group having 1 to 10 carbon atoms, and from the viewpoint that the effects of the present invention can be more expressed, R ³ preferably has a number of carbon atoms. an alkylene group having 1 to 8 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, still more preferably an alkylene group having 1 to 3 carbon atoms, and particularly preferably a methylene group ₍ --CH.sub.2--) or ethylene a group (--CH ₂ CH ₂ --), most preferably an ethylene group (--CH ₂ CH ₂ --).

In the monomer (2) represented by the general formula ( ² ), R ⁴ is an alkyl group having 1 to 10 carbon atoms. an alkyl group having 2 to 8 carbon atoms, more preferably an alkyl group having 3 to 6 carbon atoms, more preferably an alkyl group having 3 to 5 carbon atoms, particularly preferably a butyl group, most preferably n- butyl group.

In the monomer (2) represented by the general formula ( ² ), R ⁵ is a hydrogen atom or a methyl group, and is preferably a hydrogen atom from the viewpoint that the effects of the present invention can be exhibited more.

The content of at least one selected from the group consisting of the monomer (1) represented by the general formula (1) and the monomer (2) represented by the general formula (2) in the monomer component (M) is It is preferably 0.01 wt% to 30 wt%, more preferably 0.1 wt% to 20 wt%, still more preferably 0.5 wt% to 10 wt%, in terms of being able to express the effects of the invention more. % by weight, more preferably 1.0% by weight to 5.0% by weight, particularly preferably 1.5% by weight to 4.0% by weight, most preferably 2.0% by weight to 3.0% by weight. 5% by weight.

The content ratio of the monomer (1) represented by the general formula (1) in the monomer component (M) is preferably 0.01% by weight to 20% by weight, in order to further express the effects of the present invention. Yes, more preferably 0.1 wt% to 10 wt%, still more preferably 0.2 wt% to 5.0 wt%, still more preferably 0.3 wt% to 4.0 wt% , particularly preferably 0.4% to 3.0% by weight, most preferably 0.5% to 2.0% by weight.

The content ratio of the monomer (2) represented by the general formula (2) in the monomer component (M) is preferably 0.1% by weight to 20% by weight, in order to further express the effects of the present invention. , more preferably 0.5 wt% to 10 wt%, still more preferably 0.8 wt% to 8.0 wt%, still more preferably 1.0 wt% to 6.0 wt% , particularly preferably 1.2% to 4.0% by weight, most preferably 1.5% to 3.0% by weight.

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 as used herein does not include an alkyl group containing a polar group such as a hydroxyl group.

Only one type of alkyl (meth)acrylate may be used, or two or more types may be used.

The content of the alkyl (meth)acrylate in the monomer component (M) is preferably 50% to 99% by weight, more preferably 70% to 98% by weight, from the viewpoint of being able to exhibit the effects of the present invention. %, more preferably 80 wt % to 97 wt %, particularly preferably 85 wt % to 96 wt %, most preferably 90 wt % to 95 wt %.

Any appropriate alkyl (meth)acrylate can be employed as the alkyl (meth)acrylate as long as the effects of the present invention are not impaired. As such an alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.
_CH2 =C( ^R1 ) ^COOR2 (1)

Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group, and R ² is a C 1-20 alkyl group.

R ² is preferably an alkyl group having 1 to 16 carbon atoms, more preferably an alkyl group having 2 to 14 carbon atoms, and still more preferably a carbon It is an alkyl group having 4 to 14 carbon atoms, particularly preferably an alkyl group having 4 to 12 carbon atoms.

The above-mentioned alkyl group is preferably a chain alkyl group in that the effects of the present invention can be exhibited more effectively. The term "chain" as used herein means a straight-chain or branched chain.

Examples of alkyl (meth)acrylates in which R ² is a chain alkyl group having 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n - butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) ) acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate , tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, Eicosyl (meth)acrylates can be mentioned.

From the viewpoint that the effect of the present invention can be more expressed, the alkyl (meth)acrylate that can be contained in the monomer component (M) has a homopolymer glass transition temperature Tg of preferably −10° C. or lower. more preferably -12°C or lower, more preferably -15°C or lower, particularly preferably -18°C or lower, and most preferably -20°C or lower. The lower limit of the glass transition temperature Tg is preferably -80°C or higher. The glass transition temperature Tg of the alkyl (meth)acrylate homopolymer (homopolymer) that can be contained in the monomer component (M) can affect the adhesive properties and bending properties of the acrylic polymer (P). By adopting an alkyl (meth)acrylate whose homopolymer (homopolymer) has a glass transition temperature Tg within the above range as the alkyl (meth)acrylate that can be contained in the monomer component (M), an acrylic polymer ( The adhesive properties and bending properties of P) can be appropriately adjusted, and the effects of the present invention can be further expressed.

Here, as the glass transition temperature Tg of the alkyl (meth)acrylate homopolymer (homopolymer) that can be contained in the monomer component (M), a value described in a known document can be adopted. Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. In addition, when multiple numerical values are described in the above "Polymer Handbook", the conventional value is adopted. For alkyl (meth)acrylates not listed in the above "Polymer Handbook", the catalog values of monomer manufacturing companies are used. The Tg of the alkyl (meth)acrylate homopolymer, which is not described in the above "Polymer Handbook" and is not provided with the catalog value of the monomer manufacturing company, is the value obtained by the measurement method described in JP-A-2007-51271. shall be used.

Typical examples of the glass transition temperature Tg of the alkyl (meth)acrylate homopolymer that can be contained in the monomer component (M) are as follows.
2-ethylhexyl acrylate (2EHA): -70°C
Lauryl acrylate (LA): -23°C
n-butyl acrylate (BA): -55°C

The monomer component (M) is an alkyl (meth)acrylate having a homopolymer glass transition temperature Tg of −80° C. to −60° C. in the point that the effect of the present invention can be more expressed. preferably contains an alkyl (meth)acrylate (m1) in When the monomer component (M) contains the alkyl (meth)acrylate (m1), the content of the alkyl (meth)acrylate (m1) in the monomer component (M) is It is preferably 40% to 99% by weight, more preferably 45% to 90% by weight, still more preferably 50% to 80% by weight, particularly preferably 55% to 75% by weight. , most preferably 60% to 70% by weight.

As described above, the glass transition temperature Tg of the alkyl (meth)acrylate homopolymer (homopolymer) that can be contained in the monomer component (M) can affect the adhesive properties and bending properties of the acrylic polymer (P). . Then, as the alkyl (meth)acrylate that can be contained in the monomer component (M), the alkyl (meth)acrylate (m1) is adjusted so that the content ratio in the monomer component (M) is within the above range and adopted. By doing so, the adhesive properties and bending properties of the acrylic polymer (P) can be appropriately adjusted, and the effects of the present invention can be further exhibited.

Examples of the above alkyl (meth)acrylate (m1) include 2-ethylhexyl acrylate (2EHA) (the glass transition temperature Tg of its homopolymer (homopolymer) = -70°C).

The monomer component (M) is an alkyl (meth)acrylate having a homopolymer glass transition temperature Tg of −40° C. to −10° C. from the point of view that the effect of the present invention can be more expressed. preferably contains an alkyl (meth)acrylate (m2) in When the monomer component (M) contains the alkyl (meth)acrylate (m2), the content of the alkyl (meth)acrylate (m2) in the monomer component (M) is It is preferably 5% to 50% by weight, more preferably 7% to 40% by weight, still more preferably 10% to 30% by weight, particularly preferably 13% to 25% by weight. , most preferably between 15% and 22% by weight.

As described above, the glass transition temperature Tg of the alkyl (meth)acrylate homopolymer (homopolymer) that can be contained in the monomer component (M) can affect the adhesive properties and bending properties of the acrylic polymer (P). . Then, as the alkyl (meth)acrylate that can be contained in the monomer component (M), the alkyl (meth)acrylate (m2) is adjusted so that the content ratio in the monomer component (M) is within the above range and adopted. By doing so, the adhesive properties and bending properties of the acrylic polymer (P) can be appropriately adjusted, and the effects of the present invention can be further exhibited.

Examples of the above-mentioned alkyl (meth)acrylate (m2) include lauryl acrylate (LA) (the glass transition temperature Tg of its homopolymer (homopolymer) is -23°C).

The monomer component (M) is an alkyl (meth)acrylate, and the glass transition temperature Tg of its homopolymer (homopolymer) is more than -60°C and less than -40°C in that the effect of the present invention can be more expressed. preferably contain alkyl (meth)acrylates (m3) in the range of When the monomer component (M) contains the alkyl (meth)acrylate (m3), the content of the alkyl (meth)acrylate (m3) in the monomer component (M) is It is preferably 0.1% to 30% by weight, more preferably 1% to 20% by weight, still more preferably 3% to 15% by weight, and particularly preferably 4% to 13% by weight. and most preferably 5% to 10% by weight.

As described above, the glass transition temperature Tg of the alkyl (meth)acrylate homopolymer (homopolymer) that can be contained in the monomer component (M) can affect the adhesive properties and bending properties of the acrylic polymer (P). . Then, as the alkyl (meth)acrylate that can be contained in the monomer component (M), the alkyl (meth)acrylate (m3) is adjusted so that the content ratio in the monomer component (M) is within the above range and adopted. By doing so, the adhesive properties and bending properties of the acrylic polymer (P) can be appropriately adjusted, and the effects of the present invention can be further exhibited.

Examples of the above-mentioned alkyl (meth)acrylate (m3) include n-butyl acrylate (BA) (the glass transition temperature Tg of its homopolymer (homopolymer) = -55°C).

The monomer component (M) is selected from the group consisting of alkyl (meth)acrylates (m1), alkyl (meth)acrylates (m2), and alkyl (meth)acrylates (m3) in order to further develop the effects of the present invention. It is preferable to include at least one selected, and at least two selected from the group consisting of alkyl (meth)acrylate (m1), alkyl (meth)acrylate (m2), and alkyl (meth)acrylate (m3) may be included. More preferably, it contains all of alkyl (meth)acrylate (m1), alkyl (meth)acrylate (m2), and alkyl (meth)acrylate (m3).

The monomer component (M) typically contains at least one selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate in order to further develop the effects of the present invention. It preferably contains at least two selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate, and more preferably contains all of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate. .

The monomer component (M) preferably contains a hydroxyl group-containing monomer (m4). Only one kind of hydroxyl group-containing monomer (m4) may be used, or two or more kinds thereof may be used.

From the point of view that the effect of the present invention can be more expressed, the hydroxyl group-containing monomer (m4) that can be contained in the monomer component (M) has a homopolymer glass transition temperature Tg of preferably −10° C. or lower. , more preferably -15°C or lower, still more preferably -20°C or lower, particularly preferably -25°C or lower, and most preferably -30°C or lower. The lower limit of the glass transition temperature Tg is preferably -80°C or higher. The glass transition temperature Tg of the homopolymer (homopolymer) of the hydroxyl group-containing monomer (m4) that can be contained in the monomer component (M) can affect the adhesive properties and bending properties of the acrylic polymer (P). As the hydroxyl group-containing monomer (m4) that can be contained in the monomer component (M), by adopting a hydroxyl group-containing monomer (m4) whose homopolymer (homopolymer) has a glass transition temperature Tg within the above range, acrylic Adhesive properties and bending properties of the polymer (P) can be appropriately adjusted, and the effects of the present invention can be further exhibited.

Here, the glass transition temperature Tg of the homopolymer (homopolymer) of the hydroxyl group-containing monomer (m4) that can be contained in the monomer component (M) is the value described in a known document, similar to the alkyl (meth)acrylate described above. can be employed, for example, the numerical values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. In addition, when multiple numerical values are described in the above "Polymer Handbook", the conventional value is adopted. For the hydroxyl group-containing monomer (m4) not listed in the "Polymer Handbook" above, the catalog value of the monomer manufacturing company is used. The Tg of the homopolymer of the hydroxyl group-containing monomer (m4), which is not described in the above "Polymer Handbook" and is not provided by the catalog value of the monomer manufacturing company, is obtained by the measurement method described in JP-A-2007-51271. values shall be used.

Representative examples of the glass transition temperature Tg of the homopolymer (homopolymer) of the hydroxyl group-containing monomer (m4) that can be contained in the monomer component (M) are as follows.
2-hydroxyethyl acrylate: -15°C
4-hydroxybutyl acrylate: -40°C

When the monomer component (M) contains the hydroxyl group-containing monomer (m4), the content ratio of the hydroxyl group-containing monomer (m4) in the monomer component (M) is preferably 0.00, from the viewpoint that the effects of the present invention can be exhibited more effectively. 01 wt% to 30 wt%, more preferably 0.1 wt% to 20 wt%, still more preferably 0.5 wt% to 15 wt%, particularly preferably 1 wt% to 10 wt% and most preferably 2% to 5% by weight.

Examples of hydroxyl group-containing monomers (m4) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxy hydroxyalkyl (meth)acrylates such as butyl (meth)acrylate; polypropylene glycol mono(meth)acrylate; N-hydroxyethyl (meth)acrylamide;

From the viewpoint that the effect of the present invention can be more expressed, the hydroxyl group-containing monomer (m4) preferably contains a hydroxyalkyl (meth)acrylate, more preferably a linear alkyl group having 2 to 4 carbon atoms in the alkyl group portion. hydroxyalkyl (meth)acrylate group. Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA). Butyl acrylate.

The monomer component (M) is preferably selected from alkyl (meth)acrylate (m1), alkyl (meth)acrylate (m2), and alkyl (meth)acrylate (m3) in order to further develop the effects of the present invention. At least one selected from the group consisting of, and a hydroxyl group-containing monomer (m4), more preferably alkyl (meth)acrylate (m1), alkyl (meth)acrylate (m2), alkyl (meth)acrylate (m3) At least two selected from the group consisting of and a hydroxyl group-containing monomer (m4), more preferably alkyl (meth)acrylate (m1), alkyl (meth)acrylate (m2), alkyl (meth)acrylate (m3 ) and a hydroxyl group-containing monomer (m4).

From the viewpoint that the effect of the present invention can be further expressed, the monomer component (M) is typically preferably at least one selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate. and a hydroxyl group-containing monomer (m4), more preferably at least two selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, n-butyl acrylate, and a hydroxyl group-containing monomer (m4), more preferably includes any of 2-ethylhexyl acrylate, lauryl acrylate, n-butyl acrylate, and a hydroxyl group-containing monomer (m4).

Alkyl (meth)acrylate (m1), alkyl (meth)acrylate (m2), alkyl (meth)acrylate (m3), hydroxyl group-containing in the monomer component (M) from the point of being able to further express the effects of the present invention The content of the total amount of the monomers (m4) is preferably 60% to 99% by weight, more preferably 70% to 99% by weight, still more preferably 80% to 99% by weight, Particularly preferred is 90% to 99% by weight, most preferred is 95% to 98% by weight.

The monomer component (M) includes the monomer (1) represented by the general formula (1), the monomer (2) represented by the general formula (2), the alkyl ( Other monomers other than meth)acrylate and the hydroxyl group-containing monomer (m4) may be included. Other monomers can be used, for example, for the purpose of adjusting the glass transition temperature (Tg) of the acrylic polymer (P), adjusting the adhesion performance, and the like. Only one kind of other monomer may be used, or two or more kinds thereof may be used.

Other monomers include, for example, carboxy group-containing monomers, nitrogen-containing monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, acid anhydride group-containing monomers, vinyl esters (for example, vinyl acetate ( VAc), vinyl propionate, vinyl laurate), aromatic vinyl compounds, amide group-containing monomers, epoxy group-containing monomers, (meth)acryloylmorpholine, and vinyl ethers.

Examples of carboxy group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. mentioned.

Examples of nitrogen-containing monomers include N-vinyl-2-pyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloyl. Nitrogen-containing vinyl monomers such as morpholine, N-vinylcarboxylic acid amides and N-vinylcaprolactam; Cyano group-containing acrylic monomers such as acrylonitrile and methacrylonitrile; Among these, N-vinyl-2-pyrrolidone is preferable because it has a high effect of improving adhesive strength by improving cohesive strength.

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

As a method for obtaining the acrylic polymer (P), various polymerization methods known as methods for synthesizing acrylic polymers, such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, etc., are appropriately used. can be adopted. Among these polymerization methods, the solution polymerization method can be preferably used. As a method of supplying the monomer during solution polymerization, a batch charging method, a continuous supply (dropping) method, a divided supply (dropping) method, or the like, in which the entire amount of the monomer component is supplied at once, can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is preferably 20°C or higher, more preferably 30°C or higher, and even more preferably 40°C. above, preferably 170° C. or lower, more preferably 160° C. or lower, and even more preferably 140° C. or lower. Methods for obtaining acrylic polymers include photopolymerization by irradiating with light such as UV (typically carried out in the presence of a photopolymerization initiator), and irradiation with radiation such as β rays and γ rays. Active energy ray irradiation polymerization such as radiation polymerization carried out using a method may also be employed.

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from any suitable organic solvent. Examples include aromatic compounds such as toluene (typically aromatic hydrocarbons), acetic esters such as ethyl acetate, and aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane.

The initiator (polymerization initiator) used for polymerization can be appropriately selected from any suitable polymerization initiator depending on the type of polymerization method. Only one polymerization initiator may be used, or two or more polymerization initiators may be used.

Examples of polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl- 2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis(2-methylpropionamidine) disulfate, 2,2′-azobis(N,N′-dimethyleneisobutyramidine), 2, 2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.) and other azo initiators; potassium persulfate, ammonium persulfate and other peroxides Sulfate, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butyl peroxyneodecanoate, t- Hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di Peroxides such as (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide physical initiators; redox initiators combining a peroxide and a reducing agent, such as a combination of persulfate and sodium bisulfite, a combination of peroxide and sodium ascorbate; substituted ethane-based initiators, such as phenyl-substituted ethane agents; aromatic carbonyl compounds;

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

Any other suitable additive may be included in the polymerization as long as it does not impair the effects of the present invention.

≪Crosslinking agent≫
The acrylic pressure-sensitive adhesive composition according to the embodiment of the invention may contain a cross-linking agent. The number of cross-linking agents may be one, or two or more.

By using a cross-linking agent, it is possible to impart moderate cohesion to the acrylic pressure-sensitive adhesive. The cross-linking agent may be included in the acrylic pressure-sensitive adhesive in a form after cross-linking reaction, a form before cross-linking reaction, a form in which partial cross-linking reaction has occurred, an intermediate or composite form thereof, and the like. The cross-linking agent is typically contained in the acrylic pressure-sensitive adhesive in the form after the cross-linking reaction.

The content ratio of the cross-linking agent in the acrylic pressure-sensitive adhesive composition is preferably 0.005 parts by weight to 10 parts by weight with respect to 100 parts by weight of the acrylic polymer (P) in order to further express the effects of the present invention. parts, more preferably 0.01 to 7 parts by weight, still more preferably 0.05 to 5 parts by weight, and particularly preferably 0.1 to 1 part by weight.

Examples of cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, silicone-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, silane-based cross-linking agents, alkyl-etherified melamine-based cross-linking agents, and metal chelate-based cross-linking agents. , peroxides and the like, preferably isocyanate-based cross-linking agents and epoxy-based cross-linking agents, more preferably isocyanate-based cross-linking agents, in that the effects of the present invention can be more expressed.

As the isocyanate-based cross-linking agent, a compound having two or more isocyanate groups (including an isocyanate-regenerating polar group temporarily protected by a blocking agent or by quantification of the isocyanate group) in one molecule can be used. Examples of isocyanate-based cross-linking agents include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate.

Examples of isocyanate-based crosslinking agents include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; and 2,4-tolylene diisocyanate. , 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, aromatic diisocyanates such as polymethylene polyphenyl isocyanate; trimethylolpropane/tolylene diisocyanate trimer adduct (for example, manufactured by Tosoh Corporation, trade name Coronate L), Trimethylolpropane/hexamethylene diisocyanate trimer adduct (e.g., manufactured by Tosoh Corporation, trade name: Coronate HL), isocyanate adduct of hexamethylene diisocyanate (e.g., manufactured by Tosoh Corporation, trade name: Coronate HX), etc. product; trimethylolpropane adduct of xylylene diisocyanate (e.g., Mitsui Chemicals, trade name: Takenate D110N), xylylene diisocyanate trimethylolpropane adduct (e.g., Mitsui Chemicals, trade name: Takenate D120N), Trimethylolpropane adduct of isophorone diisocyanate (e.g., Mitsui Chemicals, trade name: Takenate D140N), hexamethylene diisocyanate trimethylolpropane adduct (e.g., Mitsui Chemicals, trade name: Takenate D160N); polyether poly Isocyanates, polyester polyisocyanates, and adducts of these with various polyols; and polyisocyanates polyfunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, and the like. Among these, the aromatic isocyanate and the alicyclic isocyanate are preferable in terms of achieving a good balance between deformability and cohesive force.

As the epoxy-based cross-linking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule can be used. Examples of epoxy-based cross-linking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 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, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, penta erythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipate diglycidyl ester, o-phthalate diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, Examples include resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Examples of commercially available epoxy-based cross-linking agents include trade names "Tetrad C" and "Tetrad X" manufactured by Mitsubishi Gas Chemical Company, Inc.

≪Oligomer≫
The acrylic pressure-sensitive adhesive composition according to the embodiment of the present invention may contain an oligomer for adjusting adhesive properties and bending properties. Only one type of oligomer may be used, or two or more types may be used.

The weight average molecular weight Mw of the oligomer is preferably 1,000 to 30,000, more preferably 1,500 to 10,000, even more preferably 2,000 to 8,000, and particularly preferably 2,000 to 5,000. By using an oligomer having such a weight-average molecular weight Mw, the adhesive properties and bending properties of the acrylic pressure-sensitive adhesive can be improved.

　Acrylic oligomers are preferable as oligomers because they are easily compatible with acrylic polymers.

The glass transition temperature Tg of the acrylic oligomer is preferably 20°C or higher, more preferably 40°C or higher, still more preferably 60°C or higher, particularly preferably 80°C or higher, and most preferably 100°C. That's it. 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 still more preferably 160° C. or lower.

The glass transition temperature Tg of the acrylic oligomer is obtained from the Fox formula based on the Tg of the homopolymer of each constituent monomer (homopolymer) and the weight fraction (copolymerization ratio based on weight) of the monomer. It means the desired value. The Fox equation is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg=Σ(Wi/Tgi)

In the above Fox formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (weight-based copolymerization ratio), and Tgi is the homopolymer of the monomer i. represents the glass transition temperature (unit: K). As the Tg of the homopolymer, the values described in known materials can be adopted, for example, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. . If multiple numerical values are listed in the above "Polymer Handbook", the conventional value is adopted. For monomers not listed in the above "Polymer Handbook", the catalog values of the monomer manufacturing companies are used. As the Tg of a homopolymer of a monomer that is not described in the above "Polymer Handbook" and for which the catalog value of the monomer manufacturing company is not provided, the value obtained by the measurement method described in JP-A-2007-51271 shall be used. do.

　Acrylic oligomers contain alicyclic alkyl (meth)acrylates as the main constituent monomer components. Only one kind of alicyclic alkyl (meth)acrylate may be used, or two or more kinds thereof may be used.

Examples of alicyclic alkyl (meth)acrylates include cycloalkyl (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate; ) acrylates and other bicyclic aliphatic hydrocarbon ring-containing (meth)acrylic acid esters; dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth) (Meth) acrylic having a tricyclic or higher aliphatic hydrocarbon ring such as acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate acid esters.

As the alicyclic alkyl (meth)acrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferable in that the effects of the present invention can be further expressed.

The content of the alicyclic alkyl (meth)acrylate with respect to the total amount of the constituent monomer components of the acrylic oligomer is preferably 10% by weight to 99% by weight, more preferably 30% by weight, from the viewpoint that the effects of the present invention can be further expressed. % to 98% by weight, more preferably 40% to 97% by weight, particularly preferably 50% to 96% by weight.

The acrylic oligomer may contain a chain alkyl (meth)acrylate having a chain alkyl group as a constituent monomer component, and the chain alkyl (meth)acrylate having a chain alkyl group is only one. may be used, or two or more may be used. The term "chain" as used herein means a straight-chain or branched chain.

The chain alkyl (meth)acrylate is preferably a chain alkyl (meth)acrylate having a chain alkyl group having 1 to 20 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (Meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate , heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate , undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, iso stearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

As the chain alkyl (meth)acrylate, methyl methacrylate is preferable in that the effects of the present invention can be exhibited more effectively.

The content of the chain alkyl (meth)acrylate with respect to the total amount of the constituent monomer components of the acrylic oligomer is preferably 10% by weight to 90% by weight, more preferably 20% by weight, in order to further express the effects of the present invention. % to 80% by weight, more preferably 30% to 70% by weight.

The acrylic oligomer may contain (meth)acrylic acid as a constituent monomer component, and the number of (meth)acrylic acids may be one, or two or more.

As the (meth)acrylic acid, acrylic acid is preferable in that the effects of the present invention can be expressed more.

The content of (meth)acrylic acid with respect to the total amount of the constituent monomer components of the acrylic oligomer is preferably 0.1% by weight to 20% by weight, more preferably 1% by weight, from the viewpoint that the effects of the present invention can be further expressed. % to 10% by weight, more preferably 3% to 7% by weight.

　Oligomers are obtained by polymerizing constituent monomer components by various polymerization methods. Any appropriate additive may be used in the polymerization of the oligomer as long as the effects of the present invention are not impaired. Examples of such additives include polymerization initiators and chain transfer agents.

The content of the oligomer in the acrylic pressure-sensitive adhesive composition is preferably from 0.1 to 20 parts by weight with respect to 100 parts by weight of the acrylic polymer (P), in order to further exhibit the effects of the present invention. , more preferably 0.5 to 15 parts by weight, still more preferably 1 to 10 parts by weight, and particularly preferably 1 to 5 parts by weight.

≪Tackifying resin≫
The acrylic pressure-sensitive adhesive composition according to the embodiment of the present invention may contain a tackifying resin in order to adjust adhesive properties and bending properties. Only one kind of tackifying resin may be used, or two or more kinds thereof may be used.

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, elastomer-based tackifying resins, and phenol-based tackifying resins. , and ketone-based tackifying resins.

The amount of the tackifying resin used is preferably 5 parts by weight to 70 parts by weight, more preferably 10 parts by weight, with respect to 100 parts by weight of the acrylic polymer (P), in order to further express the effects of the present invention. parts to 60 parts by weight, more preferably 15 parts to 50 parts by weight, still more preferably 20 parts to 45 parts by weight, particularly preferably 25 parts to 40 parts by weight, most preferably 25 to 35 parts by weight.

The tackifying resin preferably contains a tackifying resin TL having a softening point of less than 105°C, in order to achieve the effects of the present invention. The tackifying resin TL can effectively contribute to improving the deformability of the pressure-sensitive adhesive layer in the plane direction (shearing direction). From the viewpoint of obtaining a higher deformability improvement effect, the softening point of the tackifier resin used as the tackifier resin TL is preferably 50° C. to 103° C., more preferably 60° C. to 100° C., and still more preferably 65°C to 95°C, particularly preferably 70°C to 90°C, most preferably 75°C to 85°C.

The softening point of the tackifying resin is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate to avoid the formation of bubbles. After it cools down, cut off the raised part from the plane including the top of the ring with a slightly heated knife. Next, a supporter (ring base) is placed in a glass container (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured to a depth of 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin without touching each other, and the temperature of the glycerin is kept at 20° C.±5° C. for 15 minutes. . A steel ball is then centered on the surface of the sample in the ring and placed in position on the support. Next, the distance from the upper end of the ring to the glycerin surface is kept at 50 mm, a thermometer is placed, the center of the mercury ball of the thermometer is set at the same height as the center of the ring, and the container is heated. The Bunsen burner flame used for heating is directed halfway between the center and the rim of the bottom of the vessel to ensure even heating. The rate at which the bath temperature rises after reaching 40° C. from the start of heating must be 5.0±0.5° C. per minute. The temperature at which the sample gradually softens and flows down the ring and finally touches the bottom plate is read and taken as the softening point. Two or more softening points are measured at the same time, and the average value is adopted.

The amount of the tackifier resin TL to be used is preferably 5 parts by weight to 50 parts by weight, more preferably 5 parts by weight to 50 parts by weight, with respect to 100 parts by weight of the acrylic polymer (P), from the point of view that the effects of the present invention can be further expressed. 10 to 45 parts by weight, more preferably 15 to 40 parts by weight, particularly preferably 20 to 35 parts by weight, most preferably 25 to 32 parts by weight.

As the tackifier resin TL, one or more selected from among the tackifier resins exemplified above having a softening point of less than 105°C may be employed. The tackifying resin TL preferably contains a rosin-based resin.

Rosin-based resins that can be preferably employed as the tackifying resin TL include, for example, rosin esters such as unmodified rosin esters and modified rosin esters. Modified rosin esters include, for example, hydrogenated rosin esters.

The tackifying resin TL preferably contains a hydrogenated rosin ester in that it can further express the effects of the present invention. The hydrogenated rosin ester preferably has a softening point of less than 105°C, more preferably 50°C to 100°C, and even more preferably 60°C to 90°C, in order to further exhibit the effects of the present invention. , particularly preferably 70°C to 85°C, most preferably 75°C to 85°C.

The tackifying resin TL may contain a non-hydrogenated rosin ester. Here, the non-hydrogenated rosin ester is a concept that comprehensively refers to those other than the hydrogenated rosin ester among the rosin esters described above. Non-hydrogenated rosin esters include unmodified rosin esters, disproportionated rosin esters and polymerized rosin esters.

The non-hydrogenated rosin ester preferably has a softening point of less than 105° C., more preferably 50° C. to 100° C., and even more preferably 60° C. to 90° C., from the viewpoint that the effect of the present invention can be exhibited more effectively. °C, particularly preferably 70°C to 85°C, most preferably 75°C to 85°C.

The tackifier resin TL may contain other tackifier resins in addition to the rosin-based resin. As the other tackifying resin, one or more selected from those having a softening point of less than 105° C. among the tackifying resins exemplified above can be employed. The tackifying resin TL may contain, for example, a rosin-based resin and a terpene resin.

The content of the rosin-based resin in the entire tackifying resin TL is preferably more than 50% by weight, more preferably 55% to 100% by weight, and even more preferably, from the viewpoint that the effects of the present invention can be further expressed. is 60% to 99% by weight, particularly preferably 65% to 97% by weight, most preferably 75% to 97% by weight.

The tackifying resin may contain a combination of a tackifying resin TL and a tackifying resin TH having a softening point of 105° C. or higher (preferably 105° C. to 170° C.) in order to further express the effects of the present invention. good.

As the tackifying resin TH, one or more selected from those having a softening point of 105°C or higher among the tackifying resins exemplified above can be employed. The tackifying resin TH may contain at least one selected from rosin-based tackifying resins (eg, rosin esters) and terpene-based tackifying resins (eg, terpene phenolic resins).

≪Other ingredients≫
The acrylic pressure-sensitive adhesive composition according to the embodiment of the present invention may optionally contain a leveling agent, a cross-linking aid, a plasticizer, a softening agent, a filler, an antistatic agent, an antioxidant, an ultraviolet absorber, and an antioxidant. , a light stabilizer, a cross-linking catalyst, a cross-linking retarder, and the like, which are commonly used in the field of pressure-sensitive adhesives. As for such various additives, conventionally known ones can be used in a conventional manner.

Examples of cross-linking catalysts include Nasem ferric iron, tetra-n-butyl titanate, tetraisopropyl titanate, butyltin oxide, and dioctyltin dilaurate. Examples of crosslinking retarders include compounds that cause keto-enol tautomerism, and specific examples include β-diketones such as acetylacetone and 2,4-hexanedione; methyl acetoacetate and ethyl acetoacetate. propionyl acetate esters such as ethyl propionyl acetate; isobutyryl acetate esters such as ethyl isobutyryl acetate; malonic esters such as methyl malonate and ethyl malonate;

≪≪Adhesive film≫≫
An adhesive film according to an embodiment of the invention has an adhesive layer composed of an acrylic adhesive according to an embodiment of the invention.

The adhesive film according to the embodiment of the present invention may be a substrate-less film consisting only of an adhesive layer, or may be a substrate-attached film having a substrate layer and an adhesive layer. The pressure-sensitive adhesive film of the present invention may have any appropriate other layer in addition to the substrate layer and the pressure-sensitive adhesive layer as long as the effects of the present invention are not impaired.

The base material layer may be one layer, or may be two or more layers. The substrate layer is preferably a single layer in that the effect of the present invention can be exhibited more effectively.

The adhesive layer may be one layer, or two or more layers. The pressure-sensitive adhesive layer is preferably a single layer in that the effects of the present invention can be exhibited more effectively.

The pressure-sensitive adhesive film according to the embodiment of the present invention may be provided with any appropriate release liner on the surface of the pressure-sensitive adhesive layer opposite to the base layer for protection before use.

The release liner includes, for example, a release liner in which the surface of a base material (liner base material) such as paper or plastic film is treated with silicone, or a base material (liner base material) such as paper or plastic film whose surface is coated with a polyolefin resin. Examples include laminated release liners. Examples of plastic films as liner substrates include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, Polyurethane films, ethylene-vinyl acetate copolymer films and the like are included.

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

The thickness of the adhesive film according to the embodiment of the present invention is preferably 1 μm to 500 μm, more preferably 5 μm to 200 μm, even more preferably 10 μm to 150 μm, particularly preferably 20 μm to 100 μm, most preferably 30 μm to 80 μm. If the thickness of the pressure-sensitive adhesive film according to the embodiment of the present invention is within the above range, the effects of the present invention can be exhibited more effectively.

The adhesive film according to the embodiment of the present invention preferably has a total light transmittance of 20% or more, more preferably 30% or more, still more preferably 40% or more, and particularly preferably 50% or more. , most preferably 60% or more. If the total light transmittance of the pressure-sensitive adhesive film of the present invention is within the above range, excellent transparency can be exhibited.

The haze of the adhesive film according to the embodiment of the present invention is preferably 15% or less, more preferably 13% or less, still more preferably 10% or less, particularly preferably 8% or less, and most preferably is 6% or less. If the haze of the pressure-sensitive adhesive film of the present invention is within the above range, more excellent transparency can be exhibited.

Since the pressure-sensitive adhesive film according to the embodiment of the present invention can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment, it is preferably used in flexible devices such as foldable devices and rollable devices. can be adopted.

<<Base material layer>>
The thickness of the substrate layer is preferably 1 μm to 500 μm, more preferably 5 μm to 300 μm, still more preferably 10 μm to 100 μm, particularly preferably 15 μm to 80 μm, most preferably 20 μm to 60 μm. . If the thickness of the base material layer is within the above range, the effects of the present invention can be exhibited more effectively.

The base layer preferably has a Young's modulus at 23° C. of 6.0×10 ⁷ Pa or more, more preferably 1.0×10 ⁸ Pa or more, and still more preferably 5.0×10 ⁸ Pa or more. , particularly preferably 8.0×10 ⁸ Pa or more, and most preferably 1.0×10 ⁹ Pa or more. The upper limit of Young's modulus of the substrate layer at 23° C. is typically preferably 1.0×10 ¹¹ Pa or less. If the Young's modulus of the base material layer at 23° C. is within the above range, the effects of the present invention can be exhibited more effectively. If the Young's modulus of the base layer at 23° C. is too low, and the pressure-sensitive adhesive film is bent at an angle, the tension on the outer diameter side may not be sufficiently maintained against the compression on the inner diameter side, and the thickness will change. It becomes easier, and there is a possibility that lifting from the adherend may easily occur. If the Young's modulus of the substrate layer at 23° C. is too high, the adhesive film may not be easily deformable. A method for measuring Young's modulus will be described in detail later.

Any appropriate material can be adopted as the material of the base material layer as long as it does not impair the effects of the present invention. A typical example of the material for such a base material layer is a resin material.

Examples of resin materials for the substrate layer include polyimide (PI), polyetheretherketone (PEEK), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polymethyl methacrylate. (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA) , polyamide (nylon), wholly aromatic polyamide (aramid), polyvinyl chloride (PVC), polyvinyl acetate, polyphenylene sulfide (PPS), fluorine resin, and cyclic olefin polymer.

≪Adhesive layer≫
The thickness of the adhesive layer is preferably 1 μm to 500 μm, more preferably 5 μm to 300 μm, still more preferably 10 μm to 100 μm, particularly preferably 10 μm to 80 μm, most preferably 10 μm to 60 μm. . If the thickness of the pressure-sensitive adhesive layer is within the above range, the effects of the present invention can be exhibited more effectively.

The adhesive layer is a layer of acrylic adhesive. As a method for forming the pressure-sensitive adhesive layer, any appropriate forming method can be adopted as long as the effects of the present invention are not impaired. As such a forming method, for example, an acrylic pressure-sensitive adhesive composition is applied onto any appropriate substrate, heated and dried as necessary, cured as necessary, and coated on the substrate. A method of forming an acrylic pressure-sensitive adhesive layer in . Any appropriate means can be adopted as such means for coating as long as the effects of the present invention are not impaired. Examples of such coating means include a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, an air knife coater, a spray coater, a comma coater, a direct coater, and a roll brush coater. mentioned. Any appropriate means can be employed for heating and drying the acrylic pressure-sensitive adhesive composition as long as the effects of the present invention are not impaired. As such heating/drying means, for example, heating to about 60° C. to 180° C. can be mentioned. Any appropriate means can be employed for curing the acrylic pressure-sensitive adhesive composition as long as the effects of the present invention are not impaired. Examples of such curing means include ultraviolet irradiation, laser beam irradiation, α-ray irradiation, β-ray irradiation, γ-ray irradiation, X-ray irradiation, and electron beam irradiation.

≪≪Flexible Device≫≫
The pressure-sensitive adhesive film of the present invention can exhibit both excellent flexibility and excellent recoverability against bending motion in a low-temperature environment. Flexible devices such as devices (foldable devices) and rollable devices (devices that can be rolled up) can be suitably provided.

That is, the flexible device according to the embodiment of the present invention includes the adhesive film according to the embodiment of the present invention. A flexible device of the present invention comprises an adhesive film according to embodiments of the present invention. A foldable device of the present invention may include any suitable other member as long as it comprises an adhesive film according to embodiments of the present invention.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the flexible device of the present invention as a representative example of one usage pattern of the adhesive film according to the embodiment of the present invention. In FIG. 1, a foldable device 1000 according to an embodiment of the present invention includes a cover film 10, an adhesive layer 20, a polarizing plate 30, an adhesive layer 40, a touch sensor 50, an adhesive layer 60, an OLED 70, and an embodiment of the present invention. The pressure-sensitive adhesive film 100 is provided by The adhesive film 100 according to the embodiment of the present invention is composed of an adhesive layer 80 and a substrate layer 90 in FIG. The adhesive layer 20, the adhesive layer 40, and the adhesive layer 60 are: The adhesive layer may contain an adhesive having the same composition as the adhesive layer 80 constituting the adhesive film 100 according to the embodiment of the present invention, or may contain an adhesive having a different composition.

The present invention will be described more specifically below with examples and comparative examples. However, the present invention is by no means limited to them. In the following description, "parts" and "%" are by weight unless otherwise specified.

Abbreviations and details of raw materials used in the following production examples, examples, and comparative examples are as follows.
2EHA: 2-ethylhexyl acrylate LA: lauryl acrylate BA: n-butyl acrylate 4HBA: 4-hydroxybutyl acrylate NVP: N-vinyl-2-pyrrolidone AOMA (registered trademark): Cyclopolymerization manufactured by Nippon Shokubai Co., Ltd. organic monomer (in general formula (1), R ¹ is a methyl group and R ² is a hydrogen atom.)
V#216: 2-butyl carbamoyloxyethyl acrylate (Viscoat #216, manufactured by Osaka Organic Chemical Industry Co., Ltd.) (in general formula (2), R ³ is —CH ₂ CH ₂ — and R ⁴ is n-butyl group, R ⁵ is a hydrogen atom.)
MMA: methyl methacrylate HEA: hydroxyethyl acrylate AIBN: 2,2'-azobisisobutyronitrile Irgacure 184: photopolymerization initiator (manufactured by BASF)
Irgacure 651: photopolymerization initiator (manufactured by BASF)
DCPMA: dicyclopentanyl methacrylate C/HX: Coronate HX (manufactured by Tosoh Corporation, isocyanate-based cross-linking agent)
D110N: Takenate D110N (manufactured by Mitsui Chemicals, isocyanate-based cross-linking agent)
HDDA: 1,6-hexanediol diacrylate Nathem ferric iron: iron catalyst (manufactured by Nippon Kagaku Sangyo Co., Ltd.)
Irganox 1010: antioxidant (manufactured by BASF)
KBM403: Silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.)

<Adhesive strength to polyimide film>
Of the adhesive film separators, after peeling off the separator (MRQ50T100J) with low peeling force, a 25 μm-thick polyimide base material (trade name “Upilex 25RN”, manufactured by Ube Industries, Ltd.) is pasted together, and an adhesive film with a polyimide base material is attached. was made. Cut the adhesive film with a polyimide base material into width 25 mm × length 100 mm, peel off the separator (JT-50Wa) to expose the adhesive, and apply 2 kg to the polyimide film (trade name "Upilex 50S", manufactured by Ube Industries). A sample for evaluation was obtained by adhering with one reciprocation of the roller.
The obtained evaluation sample was stored at room temperature for 30 minutes, and then measured with a tensile tester. As the tensile tester, a trade name "Autograph AG-Xplus HS 6000 mm/min high speed model (AG-50NX plus)" manufactured by Shimadzu Corporation was used. After setting the evaluation sample in the tensile tester, the tensile test was started. The conditions of the tensile test were a peeling angle of 180 degrees and a peeling speed (pulling speed) of 300 mm/min. The load when the adhesive film was peeled off from the polyimide film (Upilex 50S) was measured, and the average load at that time was taken as the adhesive strength.

<Creep value at -20°C, recovery value at -20°C>
Only the adhesive layer was taken out from the adhesive film, laminated to a thickness of about 1 mm, and punched out into a φ9 mm cylindrical pellet to prepare a sample for measurement.
Using a dynamic viscoelasticity measuring device (manufactured by Rheometrics Co., Ltd., ARES), the obtained measurement sample was fixed to a φ8 mm parallel plate jig. At -20 ° C., the deformation strain (%) after applying a deformation stress of 10 KPa and holding for 600 seconds is the A value, and the deformation strain after holding the deformation stress for 600 seconds with 0 is the B value, and the A value is A creep value at -20°C, a value calculated by [100-{(B value x 100)/A value}] was taken as a recovery value at -20°C.

<Gel fraction>
The adhesive film was cut into a size of 50 mm × 100 mm, and the adhesive layer taken out from the adhesive film was rolled into an arbitrary size to be used as a measurement sample. It was wrapped with a membrane (“NTF-1122” manufactured by Nitto Denko Co., Ltd.), and the opening of the wrap was tied with octopus thread. The weight (B) of the measurement sample was calculated by subtracting the total weight (A) of the porous polytetrafluoroethylene membrane and the octopus thread, which had been measured in advance, from the weight of this sample. The measurement sample wrapped with the porous polytetrafluoroethylene film was immersed in about 50 mL of ethyl acetate at 23° C. for 7 days to elute the sol component of the adhesive out of the porous polytetrafluoroethylene film. After immersion, the measurement sample wrapped with the porous polytetrafluoroethylene membrane was taken out, dried at 130 ° C. for 2 hours, and left to cool for about 20 minutes. The total yarn weight) (C) was measured. The gel fraction of the adhesive was calculated by the following formula.
Gel fraction (%) = 100 × [(CA) / B]

<Storage elastic modulus G'>
The storage elastic modulus G' corresponds to the portion stored as elastic energy when the material is deformed, and is an index representing the degree of hardness.
Only the adhesive layer was taken out from the adhesive film, laminated to a thickness of about 1 mm, and punched out into a φ9 mm cylindrical pellet to prepare a sample for measurement.
Using a dynamic viscoelasticity measuring device (manufactured by Rheometrics Co., Ltd., ARES), the obtained measurement sample was fixed to a φ8 mm parallel plate jig, and the storage elastic modulus G′ was calculated. The measurement conditions are as follows.
Measurement: Shear mode Temperature range: -60°C to 210°C
Heating rate: 5°C/min Frequency: 1Hz

<Weight average molecular weight Mw>
A weight average molecular weight was measured by a gel permeation chromatography (GPC) method. Specifically, "Agilent 1260 Infinity" (manufactured by Agilent Technologies) was used as a GPC measurement device, and a tetrahydrofuran solution containing 0.1% by weight of an amine-based component was prepared in consideration of the polymer concentration of the sample. After allowing to stand and filtering through a 0.45 μm membrane filter, the filtrate was subjected to GPC measurement.
It was measured under the following conditions and calculated from standard polystyrene conversion values.
(Molecular weight measurement conditions)
・Sample concentration: 0.1% by weight (tetrahydrofuran solution with amine component added)
・Sample injection volume: 100 μL
・ Column: Product name “TSKgel GMH-H (S)” (manufactured by Tosoh Corporation)
・Eluent: tetrahydrofuran with amine-based component ・Flow rate: 0.5 mL/min
・Detector: Differential refractometer (RI)
・Column temperature (measurement temperature): 40°C
・ Standard sample: polystyrene (PS)

[Production Example 1]: Production of acrylic polymer (1) Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 2EHA: 66.6 parts by weight, LA: 19.0 parts by weight parts, BA: 7.6 parts by weight, 4HBA: 3.8 parts by weight, AOMA (registered trademark): 1.0 parts by weight, V#216: 1.9 parts by weight, AIBN as a polymerization initiator: 0.1 parts by weight Ethyl acetate was charged so that the total concentration of these was 30% by weight, the system was replaced with nitrogen over 1 hour while gently stirring, and the liquid temperature in the flask was maintained at around 58 ° C. A polymerization reaction was carried out for 5 hours, and after completion of the reaction, ethyl acetate was added to adjust the polymer concentration to 28% by weight, thereby obtaining a solution of acrylic polymer (1). Table 1 shows the results.

[Production Examples 2 to 7]: Production of Acrylic Polymers (2) to (7) The procedure of Production Example 1 was repeated except that the monomer components and various conditions were changed as shown in Table 1, and acrylic polymers ( Solutions of 2) to (7) were obtained. Table 1 shows the results.

[Production Example 8]: Production of acrylic oligomer (A) DCPMA: 60 parts by weight and MMA: 40 parts by weight as monomer components, α-thioglycerol: 3.5 parts by weight as a chain transfer agent, and toluene as a polymerization solvent 100 parts by weight were mixed and stirred at 70° C. for 1 hour under nitrogen atmosphere. Next, 0.2 parts by weight of AIBN was added as a thermal polymerization initiator, reacted at 70°C for 2 hours, then heated to 80°C and reacted for 2 hours to obtain an acrylic oligomer (A). . The acrylic oligomer (A) had a weight average molecular weight Mw of 5100 and a glass transition temperature (Tg) of 130°C.

[Example 1]
Acrylic polymer (1): 100 parts by weight, C/HX as a cross-linking agent: 0.23 parts by weight, Acrylic oligomer (A): 2 parts by weight, Irganox 1010 as an antioxidant: 0.3 parts by weight, catalyst Nasem ferric as: 0.01 parts by weight, mixed well and diluted with ethyl acetate to a total solids content of 22% by weight and acetylacetone to a solvent content of 2% by weight. Thus, a coating solution of the acrylic pressure-sensitive adhesive composition (1) was obtained. A release sheet (product name: JT-50Wa, manufactured by Nitto Denko Co., Ltd.) made of a polyester resin having a thickness of 50 μm and having one surface subjected to silicone treatment is applied to the obtained coating solution of the acrylic pressure-sensitive adhesive composition (1). It was applied to the treated surface so that the thickness after drying was 13 μm, and dried under the conditions of a drying temperature of 130° C. and a drying time of 1 minute. Next, the silicone-treated surface of a release sheet (product name: MRQ50T100J, manufactured by Mitsubishi Chemical Co., Ltd.) made of a polyester resin having a thickness of 50 μm and having one surface silicone-treated was brought into contact with the surface of the obtained pressure-sensitive adhesive layer. They were laminated to obtain an adhesive film (1). This was aged at 50° C. for 3 days and various evaluations were made. Table 3 shows the results.

[Examples 2 to 8]
Except for changing the raw material composition and various conditions as shown in Table 2, the same procedure as in Example 1 was performed, and the coating solutions of the acrylic pressure-sensitive adhesive compositions (2) to (8) and the pressure-sensitive adhesive films (2) to (8) were prepared. got This was aged at 50° C. for 3 days and various evaluations were made. Table 3 shows the results.

[Comparative Examples 1 to 5]
Except for changing the raw material composition and various conditions as shown in Table 2, the same procedure as in Example 1 was performed, and the coating solutions of the acrylic pressure-sensitive adhesive compositions (C1) to (C5) and the adhesive films (C1) to (C5) were prepared. got This was aged at 50° C. for 3 days and various evaluations were made. Table 3 shows the results.

The acrylic pressure-sensitive adhesive and the like according to the embodiment of the present invention can be used for so-called flexible devices such as foldable devices and rollable devices.

1000 foldable device 100 adhesive film 10 cover film 20 adhesive layer 30 polarizing plate 40 adhesive layer 50 touch sensor 60 adhesive layer 70 OLED
80 Adhesive layer 90 Base layer

Claims (9)

An acrylic pressure-sensitive adhesive having an adhesive force to a polyimide film of 5.0 N/25 mm or more at a peel speed of 300 mm/min and a peel angle of 180 degrees at 23° C.,
The creep value at -20°C is 70% or more, and the recovery value at -20°C is 70% or more.
Acrylic adhesive. The acrylic pressure-sensitive adhesive according to claim 1, which has a gel fraction of 50% or more. The acrylic pressure-sensitive adhesive according to claim 1 or 2, wherein the storage elastic modulus G' at -20°C is 150 kPa or less. An acrylic pressure-sensitive adhesive composition that forms the acrylic pressure-sensitive adhesive according to any one of claims 1 to 3,
including an acrylic polymer (P) having a weight average molecular weight Mw of 1,200,000 or less,
Acrylic adhesive composition. The acrylic pressure-sensitive adhesive composition according to claim 4, wherein the content of the acrylic polymer (P) in the acrylic pressure-sensitive adhesive composition is 50% by weight or more. The acrylic polymer (P) contains at least one monomer component ( 6. The acrylic pressure-sensitive adhesive composition according to claim 4, obtained by polymerizing M).

(In the general formula (1), R ¹ is an alkyl group having 1 to 10 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a —COOR group, and R is a carbon It is an alkyl group of numbers 1 to 10.)

(In general formula (2), R ³ is an alkylene group having 1 to 10 carbon atoms, R ⁴ is an alkyl group having 1 to 10 carbon atoms, and R ⁵ is a hydrogen atom or a methyl group. ) The acrylic pressure-sensitive adhesive composition according to claim 6, wherein the monomer component (M) contains an alkyl (meth)acrylate. An adhesive film having an adhesive layer composed of the acrylic adhesive according to any one of claims 1 to 3. A flexible device comprising the adhesive film according to claim 8.

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