JP2019218513A - Adhesive agent layer for flexible image display device, laminate body for flexible image display device, and flexible image display device - Google Patents

Abstract

To provide an adhesive agent layer for a flexible image display device that can satisfy bending resistance from low temperatures to high temperatures.SOLUTION: This adhesive agent layer for a flexible image display device according to the present invention is characterized by having a storage elastic modulus G' of 3.5×10-1.7×10Pa at -20°C, a storage elastic modulus G' of 1.0×10-5.0×10Pa at 23°C, and a difference of 5.2×10Pa or more between the storage elastic modulus G' at 23°C and a storage elastic modulus G' at 85°C.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a pressure-sensitive adhesive layer for a flexible image display device. The present invention also relates to a laminate for a flexible image display device to which, for example, an optical film including at least a polarizing film is applied together with the pressure-sensitive adhesive layer for a flexible image display device. The present invention also relates to a flexible image display device on which the laminate for a flexible image display device is arranged.

  As shown in FIG. 1, as a touch sensor-integrated organic EL display device, an optical laminate 20 is provided on the viewing side of the organic EL display panel 10, and a touch panel 30 is provided on the viewing side of the optical laminate 20. ing. The optical laminate 20 includes a polarizing film 1 having protective films 2-1 and 2-2 bonded on both sides thereof and a retardation film 3, and the polarizing film 1 is provided on the viewing side of the retardation film 3. In the touch panel 30, the transparent conductive films 4-1 and 4-2 having a structure in which the base films 5-1 and 5-2 and the transparent conductive layers 6-1 and 6-2 are laminated are provided with the spacer 7 interposed therebetween. It has an arranged structure (for example, see Patent Document 1).

  Further, the realization of a bendable organic EL display device which is more portable is expected. For example, it has been proposed to improve the flexibility and the like of a pressure-sensitive adhesive layer applied to an organic EL display device or the like by controlling the storage elastic modulus G '(for example, see Patent Documents 2 to 4).

JP 2014-157745 A JP-A-2006-108555 JP 2017-095657 A JP 2017-095559 A

  The conventional organic EL display device as shown in Patent Document 1 is not designed with bending in mind. If a plastic film is used for the organic EL display panel base material, the organic EL display panel can have flexibility. Further, even in a case where a plastic film is used for a touch panel and incorporated in an organic EL display panel, it is possible to impart flexibility to the organic EL display panel. However, there is a problem that an optical film including a conventional polarizing film and the like, which is laminated on the organic EL display panel, inhibits the flexibility of the organic EL display device.

  In addition, the conventional organic EL display device is repeatedly bent at normal temperature to cause minute distortion in layers and each layer such as an optical film and an adhesive layer constituting the organic EL display device, thereby causing peeling or cracking (breakage). ) Occur. Furthermore, in addition to the problem at room temperature, when bending is performed in a high-temperature environment, cohesive failure of the pressure-sensitive adhesive layer occurs, and peeling tends to be remarkable.

In Patent Literature 2, from the viewpoint of bending resistance and heat resistance, the storage elastic modulus G ′ at −20 ° C. is 1 × 10 ⁵ Pa or less, and the storage elastic modulus G ′ at 85 ° C. is 1 × 10 ⁴ Pa or more. It has been proposed to use an adhesive layer. Further, Patent Document 3 proposes to use a pressure-sensitive adhesive layer having a storage elastic modulus G 'of 3.0 × 10 ⁵ Pa or less at 23 ° C. from the viewpoint of adhesive strength and low-temperature bending resistance. Further, in Patent Document 4, from the viewpoint of bending resistance at low temperatures, the storage elastic modulus G ′ at −20 ° C. is 1.3 × 10 ⁵ Pa or more and 1 × 10 ⁶ Pa or less 3.0 × 10 ⁵ Pa or less. It has been proposed to use an adhesive layer. However, none of the pressure-sensitive adhesive layers satisfying the storage elastic modulus G ′ in the above range can satisfy the bending resistance from a low temperature to a high temperature.

  Therefore, an object of the present invention is to provide a pressure-sensitive adhesive layer for a flexible image display device, which can satisfy bending resistance from a low temperature to a high temperature.

  Further, the present invention provides a laminate for a flexible image display device to which an optical film including at least a polarizing film is applied, together with the pressure-sensitive adhesive layer for a flexible image display device, and further, the laminate for a flexible image display device is provided. It is an object of the present invention to provide an arranged flexible image display device.

  The present inventors have conducted intensive studies to solve the above problems, and as a result, have found the following pressure-sensitive adhesive layer for a flexible image display device, and have completed the present invention.

That is, the present invention has a storage elastic modulus G ′ at −20 ° C. of 3.5 × 10 ^{4 to} 1.7 × 10 ⁵ Pa,
The storage elastic modulus G ′ at 23 ° C. is 1.0 × 10 ^{4 to} 5.0 × 10 ⁴ Pa, and
The present invention relates to a pressure-sensitive adhesive layer for a flexible image display device, wherein the difference between the storage elastic modulus G ′ at 23 ° C. and the storage elastic modulus G ′ at 85 ° C. is 5.2 × 10 ³ Pa or more.

In the pressure-sensitive adhesive layer for a flexible image display device, the average value of the storage elastic modulus G ′ at −20 ° C. and the storage elastic modulus G ′ at 23 ° C. is 4.5 × 10 ^{4 to} 1.5 × 10 ⁵ Pa. It is preferable that

  In the pressure-sensitive adhesive layer for a flexible image display device, the gel fraction is preferably 70% by weight or more.

  The pressure-sensitive adhesive layer for a flexible image display device can be formed of a pressure-sensitive adhesive composition containing a (meth) acryl-based polymer containing an alkyl (meth) acrylate as a monomer unit.

  In the pressure-sensitive adhesive layer for a flexible image display device, the alkyl (meth) acrylate preferably contains an alkyl (meth) acrylate having an alkyl group having 10 or more carbon atoms.

  In the pressure-sensitive adhesive layer for a flexible image display device, the (meth) acryl-based polymer preferably contains an N-vinyl group-containing lactam-based monomer as a monomer unit in addition to the alkyl (meth) acrylate.

  The present invention also relates to a laminate for a flexible image display device, comprising the pressure-sensitive adhesive layer and an optical film including at least a polarizing film.

  Further, the present invention includes the laminate for a flexible image display device and an organic EL display panel, wherein the laminate for a flexible image display device is arranged on the viewing side with respect to the organic EL display panel. The present invention relates to a flexible image display device.

  In the flexible image display device, it is preferable that a window is arranged on a viewing side with respect to the flexible image display device laminate.

  The pressure-sensitive adhesive layer bonded to the base material needs a stress that follows minute deformation of the adjacent base material. In particular, in bending under a high-temperature environment, the cohesive force of the pressure-sensitive adhesive layer decreases at high temperatures, and when repeatedly bent, cohesive failure of the pressure-sensitive adhesive layer occurs due to repeated strain applied to the pressure-sensitive adhesive layer, and peeling occurs it is conceivable that. Since the pressure-sensitive adhesive layer of the present invention has a predetermined storage modulus at a predetermined temperature, the pressure-sensitive adhesive layer may be distorted even when exposed to any of low-temperature, normal-temperature, and high-temperature environments. The stress can be dispersed, and the strain applied to the substrate can be reduced. That is, the pressure-sensitive adhesive layer is easily deformed by minute distortion, and the distortion applied to the other layers (each layer) can be reduced. As a result, the pressure-sensitive adhesive layer of the present invention has no cracks, peeling or breakage of the substrate even with repeated bending, and can satisfy the bending resistance, and the peeling between the substrate and the pressure-sensitive adhesive layer can be achieved. This can be prevented from occurring and can be suitably applied to the use of the flexible image display device. In particular, when the optical laminate is bent, minute distortion is likely to occur in each layer, and there is a high possibility that cracks occur in the base material and peeling between the adhesive layer and the pressure-sensitive adhesive layer of the present invention is suitably applied. Is done.

FIG. 11 is a cross-sectional view illustrating a conventional organic EL display device. 1 is a cross-sectional view illustrating a flexible image display device according to an embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a flexible image display device according to another embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a flexible image display device according to another embodiment of the present invention. It is a figure which shows a bending test ((A) bending angle 0 degree, (B) bending angle 180 degree). It is sectional drawing which shows the sample for evaluation used in an Example. It is a figure showing the manufacturing method of the phase difference used in the example.

The pressure-sensitive adhesive layer for a flexible image display device of the present invention has a storage modulus G ′ at −20 ° C. of 3.5 × 10 ^{4 to} 1.7 × 10 ⁵ Pa, and a storage modulus G ′ at 23 ° C. Is 1.0 × 10 ^{4 to} 5.0 × 10 ⁴ Pa, and the difference between the storage elastic modulus G ′ at 23 ° C. and the storage elastic modulus G ′ at 85 ° C. is 5.2 × 10 ³ Pa That is all.

As described above, the pressure-sensitive adhesive layer of the present invention can control the storage elastic modulus G ′ at −20 ° C. in the range of 3.5 × 10 ^{4 to} 1.7 × 10 ⁵ Pa, so that the pressure-sensitive adhesive layer can operate in a low-temperature environment. Satisfies the bending resistance. The storage elastic modulus G ′ at −20 ° C. is preferably 5 × 10 ^{4 to} 1.6 × 10 ⁵ Pa, and more preferably 7.0 × 10 ⁴ to 1. 5 × 10 ⁵ Pa is preferred.

Further, the pressure-sensitive adhesive layer of the present invention controls the storage elastic modulus G ′ at 23 ° C. to be in a range of 1.0 × 10 ^{4 to} 5.0 × 10 ⁴ Pa, and the storage elastic modulus G at 23 ° C. By controlling the difference between 'and the storage elastic modulus G at 85 ° C to be 5.2 × 10 ³ Pa or more, the flex resistance under normal temperature and high temperature environments is satisfied. The range of the storage elastic modulus G ′ at 23 ° C. is preferably designed to be lower than the storage elastic modulus G ′ at −20 ° C., and is preferable in satisfying the bending resistance under a normal temperature environment. Further, by designing the storage elastic modulus G ′ at 85 ° C. to be lower than the storage elastic modulus G ′ at 23 ° C. by a predetermined amount, the bending resistance under a high-temperature environment is satisfied. That is, in addition to the control of the storage elastic modulus G ′ at −20 ° C., it is possible to satisfy the bending resistance in a wide temperature range from a low temperature to a high temperature where reliability is required.

The storage elastic modulus G ′ at 23 ° C. is preferably 1.3 × 10 ^{4 to} 4.0 × 10 ⁴ Pa, more preferably 1.5 × 10 ⁴ to 3.0 from the viewpoint of bending resistance under a normal temperature environment. 5 × 10 ⁴ Pa is preferred. The difference between the storage elastic modulus G ′ at 23 ° C. and the storage elastic modulus G ′ at 85 ° C. is 5.3 × 10 ³ Pa or more, more preferably 5 × 10 ³ Pa, from the viewpoint of bending resistance in a high-temperature environment. It is preferable to control the pressure to be 0.5 × 10 ³ Pa or more. If the difference in the storage elastic modulus G ′ is too large, the fluidity of the pressure-sensitive adhesive becomes high. Therefore, from the viewpoint of processing, 8.0 × 10 ³ Pa or less, and further 7.0 × 10 ³ Pa or less. It is preferable to control so that

Further, the storage elastic modulus G ′ at 85 ° C. is preferably 8.0 × 10 ^{3 to} 3.4 × 10 ⁴ Pa, and more preferably 1.0 × 10 ³ Pa, from the viewpoint of bending resistance under a high temperature environment. It is preferably 10 ^{4 to} 3.0 × 10 ⁴ Pa.

The pressure-sensitive adhesive layer of the present invention has an average value of the storage elastic modulus G ′ at −20 ° C. and the storage elastic modulus G ′ at 23 ° C., from the viewpoint of satisfying the bending resistance under any environment of low temperature and normal temperature. Is preferably 4.0 × 10 ^{4 to} 1.5 × 10 ⁵ Pa. The average value is more preferably from 4.5 × 10 ^{4 to} 1.0 × 10 ⁵ Pa.

Further, the pressure-sensitive adhesive layer of the present invention has a storage elastic modulus G ′ at −20 ° C. and a storage elastic modulus at 23 ° C. from the viewpoint of satisfying flex resistance under any of low temperature, normal temperature and high temperature environments. The average value of G ′ and the storage modulus G ′ at 85 ° C. is preferably from 5.0 × 10 ^{4 to} 4.0 × 10 ⁵ Pa. More preferably, the average value is from 8.0 × 10 ^{4 to} 3.0 × 10 ⁵ Pa.

  By controlling the average value of the storage elastic modulus G 'within the above range, a difference in elastic modulus for each temperature condition is reduced, which is preferable in exhibiting bending resistance in a wide temperature range.

  The gel fraction of the pressure-sensitive adhesive layer of the present invention is preferably 70% by weight or more, more preferably 70 to 95% by weight, more preferably 80 to 90% by weight, and still more preferably 82 to 90% by weight. Even more preferably, it is 85 to 90% by weight. When the gel fraction of the pressure-sensitive adhesive layer is within the above range, the cohesive force of the pressure-sensitive adhesive layer can be increased, and the appearance (e.g., a dent of glue), workability, durability, and flexibility can be improved. Flexibility under normal temperature and high temperature environments is easily compatible, which is a preferable embodiment.

  The glass transition temperature (Tg) of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but the upper limit is preferably 5 ° C. or lower. In consideration of the flexibility in a low-temperature environment or in a high-speed region, the temperature is more preferably −20 ° C. or less, and still more preferably −25 ° C. or less. When the Tg of the pressure-sensitive adhesive layer is in such a range, the pressure-sensitive adhesive layer is hardly hardened even in a low-temperature environment or at a bending speed in a high-speed region such as a bending speed exceeding 1 second / time, and is excellent in stress relaxation. A bendable or foldable laminate for a flexible image display device, and a flexible image display device on which the laminate for a flexible image display device is arranged can be realized. The glass transition temperature (Tg) is a theoretical value derived from the Fox equation.

  The total light transmittance (according to JIS K7136) in the visible light wavelength region of the pressure-sensitive adhesive layer used in the laminate for a flexible image display device of the present invention is preferably 85% or more, more preferably 90% or more.

  Hereinafter, the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer of the present invention, its composition, and the like will be described.

  Examples of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer of the present invention include an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a vinylalkyl ether-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a polyamide-based pressure-sensitive adhesive, and a urethane-based pressure-sensitive adhesive. , A fluorine-based adhesive, an epoxy-based adhesive, a polyether-based adhesive, and the like. The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is used alone or in combination of two or more. However, it is preferable to use an acrylic pressure-sensitive adhesive (composition) containing a (meth) acrylic polymer alone in terms of transparency, processability, durability, adhesion, and bending resistance.

<(Meth) acrylic polymer>
When an acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive composition, a (meth) acryl-based monomer containing, as a monomer unit, an alkyl (meth) acrylate having a linear or branched alkyl group having 1 to 30 carbon atoms. It preferably contains a polymer. By using the linear or branched alkyl (meth) acrylate having an alkyl group having 1 to 30 carbon atoms, a pressure-sensitive adhesive layer having excellent flexibility can be obtained. In the present invention, the (meth) acrylic polymer refers to an acrylic polymer and / or a methacrylic polymer, and the (meth) acrylate refers to acrylate and / or methacrylate.

  As specific examples of the alkyl (meth) acrylate having a linear or branched alkyl group having 1 to 30 carbon atoms, which constitutes the main skeleton of the (meth) acrylic polymer, methyl (meth) acrylate, ethyl ( (Meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, n- Hexyl (meth) acrylate, isohexyl (meth) acrylate, isoheptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (Meta) acri , N-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate (lauryl (meth) acrylate), n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate and the like. Can be

  Among the above-mentioned alkyl (meth) acrylates, from the viewpoint of flexibility due to a reduction in micro-deformation stress, an alkyl (meth) acrylate having a linear or branched alkyl group having 6 to 30 carbon atoms (hereinafter referred to as “length”). Alkyl (meth) acrylate having a chain alkyl group "). The alkyl (meth) acrylate having a long-chain alkyl group preferably contains an alkyl (meth)) acrylate having an alkyl group having 10 or more carbon atoms. In particular, n-dodecyl (meth) acrylate (lauryl (meth) acrylate) is more preferable as the alkyl (meth) acrylate having a long-chain alkyl group. By using the alkyl (meth) acrylate having the long-chain alkyl group, the entanglement of the polymer is reduced, and the polymer is easily deformed by a minute strain, which is a preferable embodiment for the flexibility. From the viewpoint of flexibility and adhesion at low temperatures, it is preferable to use an alkyl (meth) acrylate having a glass transition temperature (Tg) of a homopolymer of −70 to −20 ° C., and has 6 to 9 carbon atoms. It is more preferable to use an alkyl (meth) acrylate having an alkyl group of the formula (2), and among them, 2-ethylhexyl acrylate. As the alkyl (meth) acrylate, one or more kinds can be used. As the long-chain alkyl (meth) acrylate, a mixture of an alkyl (meth) acrylate having an alkyl group having 10 to 30 carbon atoms and an alkyl (meth) acrylate having an alkyl group having 6 to 9 carbon atoms is used. Is preferred. The mixture has a mixing weight ratio of (alkyl (meth) acrylate having an alkyl group having 10 to 30 carbon atoms): (alkyl (meth) acrylate having an alkyl group having 6 to 9 carbon atoms) = 40: It is preferably set to 60 to 90:10. A mixture of an alkyl (meth) acrylate having an alkyl group having 10 to 30 carbon atoms and an alkyl (meth) acrylate having an alkyl group having 6 to 9 carbon atoms is n-dodecyl (meth) acrylate and 2-ethylhexyl acrylate Is preferably used in combination.

  The alkyl (meth) acrylate having a linear or branched alkyl group having 1 to 30 carbon atoms is a main component in all monomers constituting the (meth) acrylic polymer. Here, the main component refers to 50 to 100% by weight of a linear or branched alkyl (meth) acrylate having an alkyl group having 1 to 30 carbon atoms in all monomers constituting the (meth) acrylic polymer. Is preferably 80 to 100% by weight, more preferably 90 to 99.9% by weight, and particularly preferably 94 to 99.9% by weight.

  The monomer component constituting the (meth) acrylic polymer may be a copolymerizable monomer (copolymer) in addition to the linear or branched alkyl (meth) acrylate having an alkyl group having 1 to 30 carbon atoms. (Polymerizable monomer). The copolymerizable monomers may be used alone or in combination of two or more.

  The copolymerizable monomer is not particularly limited, but is preferably a copolymerizable monomer having a reactive functional group having a polymerizable unsaturated double bond. As the copolymerizable monomer having a reactive functional group, a hydroxyl group-containing monomer is preferable. By using the hydroxyl group-containing monomer, a pressure-sensitive adhesive layer having excellent adhesion and flexibility can be obtained. The hydroxyl group-containing monomer is a compound containing a hydroxyl group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group or a vinyl group.

  Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxy Examples include hydroxyalkyl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate, such as octyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and 12-hydroxylauryl (meth) acrylate. Among the hydroxyl group-containing monomers, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable from the viewpoint of durability and adhesion. In addition, as the hydroxyl group-containing monomer, one type or two or more types can be used.

  Further, examples of the copolymerizable monomer having a reactive functional group include a carboxyl group-containing monomer, an amino group-containing monomer, and an amide group-containing monomer having a reactive functional group. These monomers are preferable from the viewpoint of humidification and adhesion in a high-temperature environment.

  By using the carboxyl group-containing monomer, a pressure-sensitive adhesive layer having excellent adhesion in a humidified or high-temperature environment can be obtained. The carboxyl group-containing monomer is a compound containing a carboxyl group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group or a vinyl group.

  Specific examples of the carboxyl group-containing monomer include, for example, (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and the like.

  By using the amino group-containing monomer, a pressure-sensitive adhesive layer having excellent adhesion in a humidified or high-temperature environment can be obtained. The amino group-containing monomer is a compound containing an amino group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group and a vinyl group.

  Specific examples of the amino group-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and the like.

  By using the amide group-containing monomer, a pressure-sensitive adhesive layer having excellent adhesion can be obtained. The amide group-containing monomer is a compound containing an amide group in its structure and containing a polymerizable unsaturated double bond such as a (meth) acryloyl group or a vinyl group.

  Specific examples of the amide group-containing monomer include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropylacrylamide, N-methyl (meth) acrylamide, -Butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylol-N-propane (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercapto Acrylamide monomers such as methyl (meth) acrylamide and mercaptoethyl (meth) acrylamide; N- such as N- (meth) acryloylmorpholine, N- (meth) acryloylpiperidine and N- (meth) acryloylpyrrolidine Acryloyl heterocyclic monomers; N- vinylpyrrolidone, N- vinyl-containing lactam monomers such as N- vinyl -ε- caprolactam.

  Among the copolymerizable monomers such as the carboxyl group-containing monomer, amino group-containing monomer, and amide group-containing monomer, amide group-containing monomers are preferable, and N-vinyl group-containing lactam monomers are particularly preferable. N-vinyl group-containing lactam monomers are preferred from the viewpoint of improving adhesion to adherends, particularly from the viewpoint of improving adhesion during heating.

  As the copolymerizable monomer having a reactive functional group, it is preferable to use a hydroxyl group-containing monomer and an amide group-containing monomer (in particular, an N-vinyl group-containing lactam monomer) in combination.

  In the monomer units constituting the (meth) acrylic polymer, the proportion of the copolymerizable monomer having a reactive functional group exemplified above is 20% by weight or less in all the monomers constituting the (meth) acrylic polymer. Is preferably 15% by weight or less, more preferably 10% by weight or less.

  When the hydroxyl group-containing monomer is contained, the mixing ratio is preferably 0.01 to 8% by weight, more preferably 0.01 to 5% by weight, and still more preferably 0.05 to 3% by weight.

  When the composition contains a copolymerizable monomer such as the carboxyl group-containing monomer, amino group-containing monomer, and amide group-containing monomer, the compounding ratio is preferably 0.01 to 15% by weight, and 0.1 to 12% by weight. %, More preferably 0.1 to 10% by weight. In particular, the N-vinyl group-containing lactam monomer is preferably used in an amount of 3 to 12% by weight, more preferably 4 to 10% by weight. If the proportion of the N-vinyl group-containing lactam monomer is too large, the glass transition temperature increases, and the storage modulus G ′ increases at room temperature (23 ° C.), which may cause peeling or cracking in a bending test. Therefore, the N-vinyl group-containing lactam monomer is preferably used in the above range.

  As the copolymerizable monomer, other than the copolymerizable monomer having a reactive functional group described above, other copolymerizable monomers can be used as long as the effects of the present invention are not impaired.

  Examples of the other copolymerizable monomers include, for example, alkoxyalkyl (meth) acrylates [eg, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and methoxytrimethyl (meth) acrylate. Ethylene glycol, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 4-ethoxybutyl (meth) acrylate, etc.]; an epoxy group-containing monomer [ For example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate]; a sulfonic acid group-containing monomer [for example, sodium vinyl sulfonate]; a phosphoric acid group-containing monomer; ) Acrylates [for example, (meth) acrylic acid Pentyl, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate); (meth) acrylate having an aromatic hydrocarbon group [for example, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, ( Vinyl esters [eg, vinyl acetate, vinyl propionate, etc.]; aromatic vinyl compounds [eg, styrene, vinyl toluene, etc.]; olefins or dienes [eg, ethylene, propylene, butadiene] , Isoprene, isobutylene, etc.]; vinyl ethers [for example, vinyl alkyl ethers]; vinyl chloride and the like.

  The mixing ratio of the other copolymerized monomer is not particularly limited, but is preferably 30% by weight or less, more preferably 10% by weight or less, and more preferably 10% by weight or less of all the monomers constituting the (meth) acrylic polymer. preferable. If it exceeds 30% by weight, especially when a material other than alkyl (meth) acrylate is used, the number of reaction points between the pressure-sensitive adhesive layer and other layers (films, substrates) tends to decrease, and the adhesion tends to decrease.

  Further, the monomer component constituting the (meth) acrylic polymer includes a multifunctional monomer having a plurality of the reactive functional groups in addition to the single functional monomer having a reactive functional group of the polymerizable unsaturated double bond described above. Functional monomers can be used.

  When a polyfunctional monomer is contained, a crosslinking effect is obtained by polymerization, and adjustment of the gel fraction and improvement of cohesion can be easily performed. For this reason, cutting becomes easy and workability is easily improved. Furthermore, peeling due to cohesive failure of the pressure-sensitive adhesive layer can be prevented during bending (particularly in a high-temperature environment). Although it does not specifically limit as a polyfunctional monomer, For example, hexanediol di (meth) acrylate (1,6-hexanediol di (meth) acrylate), butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate A) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylol Propane tri (meth) acrylate, tetramethylol methane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, epoxy acrylate, polyester acrylate Or polyfunctional acrylates such as urethane acrylate, divinyl benzene, and the like. Among them, the polyfunctional acrylate, 1,6-hexanediol diacrylate, dipentaerythritol hexa (meth) acrylate. The polyfunctional monomers may be used alone or in combination of two or more.

  The blending ratio of the polyfunctional monomer is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and more preferably 3 parts by weight or less, based on 100 parts by weight of the total amount of the monofunctional monomer constituting the (meth) acrylic polymer. More preferred. When the blending ratio of the polyfunctional monomer increases, the number of crosslinking points increases, and the flexibility of the pressure-sensitive adhesive (layer) is lost. Therefore, the stress relaxation property tends to be poor.

  The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition, and the pressure-sensitive adhesive composition may be a pressure-sensitive adhesive composition having any form, for example, an emulsion type, a solvent type (solution type). , Active energy ray curing type, hot melting type (hot melt type) and the like. Among them, the above-mentioned pressure-sensitive adhesive composition is preferably a solvent-type pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition.

  As the solvent-based pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition containing the (meth) acrylic polymer as an essential component is preferable. As the active energy ray-curable pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition containing a mixture of monomer components (monomer mixture) constituting the (meth) acrylic polymer or a partial polymer thereof as an essential component is preferable. No. The “partially polymerized product” refers to a composition in which one or more components among the monomer components contained in the monomer mixture are partially polymerized. Further, the “monomer mixture” includes the case where only one kind of monomer component is used.

  In particular, the pressure-sensitive adhesive composition is preferably a mixture of monomer components constituting a (meth) acrylic polymer in view of productivity, influence on the environment, and ease of obtaining a thick pressure-sensitive adhesive layer ( It is preferably an active energy ray-curable pressure-sensitive adhesive composition containing a monomer mixture) or a partially polymerized product thereof as an essential component.

  The (meth) acrylic polymer is obtained by polymerizing the monomer component. More specifically, it can be obtained by polymerizing the monomer component, the monomer mixture or a partial polymer thereof by a known and commonly used method. Examples of the polymerization method include solution polymerization, emulsion polymerization, bulk polymerization, and polymerization by irradiation with heat or active energy rays (thermal polymerization or active energy ray polymerization). Among them, solution polymerization and active energy ray polymerization are preferred in terms of transparency, water resistance, cost and the like. Note that the polymerization is preferably performed while avoiding contact with oxygen from the viewpoint of suppressing polymerization inhibition by oxygen. For example, it is preferable to carry out the polymerization under a nitrogen atmosphere, or to carry out the polymerization while blocking oxygen with a release film (separator). The (meth) acrylic polymer obtained may be any of a random copolymer, a block copolymer, a graft copolymer and the like.

  Examples of the active energy rays irradiated during the active energy ray polymerization (photopolymerization) include ionizing radiation such as α-rays, β-rays, γ-rays, neutron rays, and electron beams, and ultraviolet rays. Is preferred. The irradiation energy, irradiation time, irradiation method and the like of the active energy ray are not particularly limited as long as the photopolymerization initiator can be activated to cause a reaction of the monomer component.

  In the solution polymerization, various general solvents can be used. Examples of such a solvent include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane and methyl. Organic solvents such as alicyclic hydrocarbons such as cyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone; In addition, the said solvent may be used individually or in combination of 2 or more types.

  Further, upon polymerization, a polymerization initiator such as a photopolymerization initiator (photoinitiator) or a thermal polymerization initiator may be used depending on the type of the polymerization reaction. The polymerization initiator may be used alone or in combination of two or more.

  The photopolymerization initiator is not particularly limited, for example, benzoin ether-based photopolymerization initiator, acetophenone-based photopolymerization initiator, α-ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, light Active oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators are exemplified.

  Examples of the benzoin ether-based photopolymerization initiator include, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, Anisole methyl ether and the like can be mentioned. Examples of the acetophenone-based photopolymerization initiator include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl). ) Dichloroacetophenone and the like. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one. Can be Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime. Examples of the benzoin-based photopolymerization initiator include benzoin. Examples of the benzyl-based photopolymerization initiator include benzyl and the like. Examples of the benzophenone-based photopolymerization initiator include, for example, benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

  The amount of the photopolymerization initiator used is not particularly limited, but is preferably 0.01 to 1 part by weight, more preferably 0.05 to 0.5 part by weight, based on 100 parts by weight of the total amount of the monomer components.

  Examples of the polymerization initiator used in the solution polymerization include an azo polymerization initiator, a peroxide polymerization initiator (for example, dibenzoyl peroxide, tert-butyl permaleate, and the like), a redox polymerization initiator, and the like. Is mentioned. Among them, the azo-based polymerization initiator disclosed in JP-A-2002-69411 is preferable. Examples of the azo polymerization initiator include 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis-2-methylbutyronitrile, and 2,2′-azobis (2-methylpropionic acid). ) Dimethyl, 4,4'-azobis-4-cyanovaleric acid and the like.

  The amount of the azo polymerization initiator is not particularly limited, but is preferably 0.05 to 0.5 part by weight, more preferably 0.1 to 0.3 part by weight, based on 100 parts by weight of the total amount of the monomer components. It is.

  The polyfunctional monomer (polyfunctional acrylate) used as the copolymerizable monomer can be used for a solvent-type or active energy ray-curable pressure-sensitive adhesive composition. When a polyfunctional monomer (polyfunctional acrylate) and the photopolymerization initiator are mixed and used, active energy ray curing is performed after thermal drying.

  In the present invention, as the (meth) acrylic polymer used in the solvent-based pressure-sensitive adhesive composition, one having a weight average molecular weight (Mw) in the range of 1,000,000 to 2.5,000,000 is usually used. When durability, especially heat resistance and flexibility are taken into consideration, it is preferably 1.2 million to 2 million, more preferably 1.4 million to 1.8 million. When the weight average molecular weight is smaller than 1,000,000, the number of crosslinking points is increased as compared with those having a weight average molecular weight of 1,000,000 or more when the polymer chains are crosslinked to ensure durability. ), The strain on the outer side (convex side) and the inner side (concave side) of the bending generated between the layers (films) at the time of bending cannot be alleviated, and the layers easily break. On the other hand, when the weight average molecular weight is more than 2.5 million, a large amount of a diluting solvent is required to adjust the viscosity for coating, which is not preferable because the cost is increased. Since the entanglement of the polymer chains of the polymer is complicated, the flexibility is inferior, and each layer (film) is easily broken at the time of bending. The weight average molecular weight (Mw) is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

<(Meth) acrylic oligomer>
The pressure-sensitive adhesive composition may contain a (meth) acrylic oligomer. As the (meth) acrylic oligomer, it is preferable to use a polymer having a smaller weight average molecular weight (Mw) than that of the (meth) acrylic polymer. A) a preferred embodiment for the flexibility, in which the (meth) acryl-based oligomer is interposed between the acrylic polymers to reduce the entanglement of the (meth) acryl-based polymer, and to be easily deformed with respect to minute strain; Become.

  Examples of the monomer constituting the (meth) acrylic oligomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl (meth). Acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, Octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, unde Alkyl (meth) acrylates, such as cyclo (meth) acrylate and dodecyl (meth) acrylate; (meth) acrylic acids and fats, such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate Esters with cyclic alcohols; aryl (meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate; (meth) acrylates obtained from terpene compound derivative alcohols; Such (meth) acrylates can be used alone or in combination of two or more.

  Examples of the (meth) acrylic oligomer include alkyl (meth) acrylates having a branched alkyl group such as isobutyl (meth) acrylate and t-butyl (meth) acrylate; cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate. ) Acrylates such as dicyclopentanyl (meth) acrylates and esters of (meth) acrylic acid with alicyclic alcohols; cyclic structures such as aryl (meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate It is preferable to include, as a monomer unit, an acrylic monomer having a relatively bulky structure, represented by (meth) acrylate having the following. By giving such a bulky structure to the (meth) acrylic oligomer, the adhesiveness of the pressure-sensitive adhesive layer can be further improved. In particular, those having a ring structure are more effective in terms of bulkiness, and those having a plurality of rings are more effective. Further, when ultraviolet rays are employed in the synthesis of the (meth) acrylic oligomer or in the preparation of the pressure-sensitive adhesive layer, those having a saturated bond are preferable because polymerization inhibition is unlikely to occur, and the alkyl group is preferably used. An alkyl (meth) acrylate having a branched structure or an ester with an alicyclic alcohol can be suitably used as a monomer constituting the (meth) acrylic oligomer.

  From these points, suitable (meth) acrylic oligomers include, for example, a copolymer of butyl acrylate (BA), methyl acrylate (MA), and acrylic acid (AA), cyclohexyl methacrylate (CHMA), and isobutyl methacrylate ( (IBMA) copolymer, copolymer of cyclohexyl methacrylate (CHMA) and isobornyl methacrylate (IBXMA), copolymer of cyclohexyl methacrylate (CHMA) and acryloyl morpholine (ACMO), cyclohexyl methacrylate (CHMA) and diethyl acrylamide ( DEAA), 1-adamantyl acrylate (ADA) and methyl methacrylate (MMA), dicyclopentanyl methacrylate (DCPMA) and isobornyl methacrylate Copolymer (IBXMA), dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), cyclopentanyl methacrylate (DCPMA) and methyl Examples include methacrylate (MMA) copolymer, dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA) homopolymer.

  As the polymerization method of the (meth) acrylic oligomer, as in the case of the (meth) acrylic polymer, solution polymerization, emulsion polymerization, bulk polymerization, emulsion polymerization, polymerization by irradiation of heat or active energy rays (thermal polymerization, active energy Linear polymerization). Among them, solution polymerization and active energy ray polymerization are preferred in terms of transparency, water resistance, cost and the like. Further, the obtained (meth) acrylic oligomer may be any of a random copolymer, a block copolymer, a graft copolymer and the like.

  The (meth) acryl-based oligomer can be used for the solvent-based pressure-sensitive adhesive composition and the active energy ray-curable pressure-sensitive adhesive composition, similarly to the (meth) acryl-based polymer. For example, as the active energy ray-curable pressure-sensitive adhesive composition, the (meth) acrylic oligomer may be further added to a mixture (monomer mixture) of monomer components constituting the (meth) acrylic polymer or a partial polymer thereof. Can be mixed and used. When the (meth) acryl-based oligomer is dissolved in a solvent, the pressure-sensitive adhesive composition can be heated and dried to remove the solvent, and then the active energy ray curing can be completed to obtain a pressure-sensitive adhesive layer.

  The weight average molecular weight (Mw) of the (meth) acrylic oligomer used in the solvent-based pressure-sensitive adhesive composition is preferably 1,000 or more, more preferably 2,000 or more, still more preferably 3,000 or more, and particularly preferably 4,000 or more. . The weight average molecular weight (Mw) of the (meth) acrylic oligomer is preferably 30,000 or less, more preferably 15,000 or less, still more preferably 10,000 or less, and particularly preferably 7000 or less. By adjusting the weight average molecular weight (Mw) of the (meth) acrylic oligomer within the above range, for example, when used in combination with the (meth) acrylic polymer, the ) Acrylic oligomer intervenes, entanglement of (meth) acrylic polymer is reduced, adhesive layer is easily deformed by minute strain, strain on other layers can be reduced, cracks and adhesion of each layer The peeling between the agent layer and other layers can be suppressed, which is a preferable embodiment. The weight average molecular weight (Mw) of the (meth) acrylic oligomer is measured by GPC (gel permeation chromatography) in the same manner as the (meth) acrylic polymer, and the value calculated in terms of polystyrene is used. Say.

  When the (meth) acrylic oligomer is used for the pressure-sensitive adhesive composition, the amount thereof is not particularly limited, but is preferably 70 parts by weight or less based on 100 parts by weight of the (meth) acrylic polymer, More preferably, it is 1 to 70 parts by weight, more preferably 2 to 50 parts by weight, further preferably 3 to 40 parts by weight. By adjusting the blending amount of the (meth) acrylic oligomer within the above range, the (meth) acrylic oligomer is appropriately interposed between the (meth) acrylic polymers, and the entanglement of the (meth) acrylic polymer is reduced. Decrease, the pressure-sensitive adhesive layer is easily deformed by minute strain, the strain applied to the other layers can be reduced, and cracking of each layer and peeling between the pressure-sensitive adhesive layer and other layers can be suppressed, which is preferable. It becomes an aspect.

<Measurement of weight average molecular weight (Mw) of (meth) acrylic polymer and acrylic oligomer>
The weight average molecular weight (Mw) of the obtained (meth) acrylic polymer and acrylic oligomer was measured by GPC (gel permeation chromatography).
・ Analyzer: Tosoh Corporation, HLC-8120GPC
-Column: Tosoh Corporation, G7000H _XL + GMH _XL + GMH _XL
・ Column size: 7.8mmφ × 30cm each 90cm in total
-Column temperature: 40 ° C
・ Flow rate: 0.8ml / min
・ Injection volume: 100 μl
・ Eluent: tetrahydrofuran ・ Detector: differential refractometer (RI)
・ Standard sample: polystyrene

<Crosslinking agent>
The pressure-sensitive adhesive composition of the present invention may contain a crosslinking agent. As the cross-linking agent, an organic cross-linking agent or a polyfunctional metal chelate can be used in any of the solvent-type and active energy ray-curable pressure-sensitive adhesive compositions. Examples of the organic crosslinking agent include an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, and an imine crosslinking agent. Multifunctional metal chelates are those in which a polyvalent metal is covalently or coordinated with an organic compound. Examples of the polyvalent metal atom include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. No. The atom in the organic compound which forms a covalent bond or a coordinate bond includes an oxygen atom and the like, and the organic compound includes an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, a ketone compound and the like. In particular, in the case of a solvent-type pressure-sensitive adhesive composition, a peroxide-based crosslinking agent or an isocyanate crosslinking agent is preferred, and among them, a peroxide-based crosslinking agent is preferably used. The peroxide-based crosslinking agent generates radicals by, for example, extracting hydrogen from the side chains of the (meth) acrylic polymer, and promotes crosslinking between the side chains of the (meth) acrylic polymer. Using a cross-linking agent (for example, a polyfunctional isocyanate-based cross-linking agent) to increase the cohesive force while maintaining a relatively loose cross-linking state and maintaining the ease of deformation with respect to minute strain, as compared with the case of cross-linking. This is a preferred embodiment in terms of achieving both flexibility (suppression of cracking and peeling) under normal temperature and high temperature environments. Further, isocyanate-based cross-linking agents (particularly, trifunctional isocyanate-based cross-linking agents) are preferable in terms of durability, and a peroxide-based cross-linking agent and an isocyanate-based cross-linking agent (particularly, a bifunctional isocyanate-based cross-linking agent) Is preferred from the viewpoint of flexibility. Both peroxide-based crosslinkers and bifunctional isocyanate-based crosslinkers form flexible two-dimensional crosslinks, whereas trifunctional isocyanate-based crosslinkers form stronger three-dimensional crosslinks. When bending, two-dimensional crosslinking, which is a more flexible crosslinking, is advantageous. However, since only two-dimensional cross-linking has poor durability and peeling is apt to occur, hybrid cross-linking of two-dimensional cross-linking and three-dimensional cross-linking is good, so that a trifunctional isocyanate cross-linking agent and a peroxide cross-linking agent are used. In a preferred embodiment, a bifunctional isocyanate-based crosslinking agent is used in combination. In addition, as the active energy ray-curable pressure-sensitive adhesive composition, it is preferable to obtain a cross-linking effect by polymerization using the polyfunctional monomer from the viewpoint of productivity and thick film coating. Alternatively, it can be used in combination with the polyfunctional monomer. For example, a crosslinking agent is mixed with a mixture of monomer components (monomer mixture) or a partial polymer thereof constituting the (meth) acrylic polymer, and crosslinked by thermal drying before and after the active energy ray curing of the pressure-sensitive adhesive composition. The reaction of the agent can be completed.

  The amount of the crosslinking agent to be used is, for example, preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, and more preferably 0.3 to 3 parts by weight based on 100 parts by weight of the (meth) acrylic polymer. Part by weight is more preferred. Within the above range, excellent bending resistance is obtained, which is a preferable embodiment. In order to increase the cohesive force without changing the microdeformation stress, it is preferable to increase the amount of the crosslinking agent.

  When the peroxide crosslinking agent is used alone, it is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of the (meth) acrylic polymer. Within the above range, the cohesive force can be sufficiently increased while maintaining the ease of deformation with respect to minute strain, and the durability and bending resistance can be improved, which is a preferable embodiment.

  When the peroxide-based crosslinking agent and the isocyanate-based crosslinking agent are used in combination, the lower limit of the weight ratio of the peroxide-based crosslinking agent to the isocyanate-based crosslinking agent (peroxide-based crosslinking agent / isocyanate-based crosslinking agent). Is preferably 1.2 or more, more preferably 1.5 or more, and still more preferably 3 or more. The upper limit of the weight ratio is preferably 500 or less, more preferably 300 or less, and even more preferably 200 or less. When it is within the above range, the cohesive force can be sufficiently increased while maintaining the ease of deformation due to minute strain, which is a preferable embodiment.

<Other additives>
Further, the pressure-sensitive adhesive composition of the present invention may contain other known additives, for example, various silane coupling agents, polyalkylene glycol polyether compounds such as polypropylene glycol, coloring agents, pigments, and the like. Powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antioxidants, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic It can be added as appropriate depending on the use of an agent (such as an alkali metal salt or an ionic liquid as an ionic compound, or an ionic solid), an inorganic or organic filler, metal powder, particles, or a foil. Further, a redox system to which a reducing agent is added may be employed within a controllable range.

  The method for preparing the pressure-sensitive adhesive composition is not particularly limited, and a known method can be used. For example, as described above, a solvent-type acrylic pressure-sensitive adhesive composition includes a (meth) acryl-based polymer, It is produced by mixing components (for example, the (meth) acrylic oligomer, cross-linking agent, silane coupling agent, solvent, additive, etc.) added as necessary. In addition, as described above, the active energy ray-curable acrylic pressure-sensitive adhesive composition includes a monomer mixture or a partially polymerized product thereof, and components added as necessary (for example, the photopolymerization initiator, the polyfunctional monomer, (Meth) acrylic oligomer, crosslinking agent, silane coupling agent, solvent, additive, etc.).

  The pressure-sensitive adhesive composition preferably has a viscosity suitable for handling and coating. Therefore, the active energy ray-curable acrylic pressure-sensitive adhesive composition preferably contains a partially polymerized monomer mixture. The polymerization rate of the partial polymer is not particularly limited, but is preferably 5 to 20% by weight, and more preferably 5 to 15% by weight.

The conversion of the partially polymerized product is determined as follows.
A part of the partially polymerized product is sampled to obtain a sample. The sample is precisely weighed and its weight is determined to be "the weight of the partially polymerized product before drying". Next, the sample is dried at 130 ° C. for 2 hours, and the sample after drying is precisely weighed and its weight is obtained, which is referred to as “the weight of the partially polymerized product after drying”. Then, from the “weight of the partially polymerized product before drying” and “the weight of the partially polymerized product after drying”, the weight of the sample reduced by drying at 130 ° C. for 2 hours is obtained, and “weight loss amount” (volatility, Unreacted monomer weight).
From the obtained “weight of partial polymer before drying” and “weight loss amount”, the polymerization rate (% by weight) of the partial polymer of the monomer component is determined by the following formula.
Degree of polymerization of partial polymer of monomer component (% by weight) = [1- (weight loss) / (weight of partial polymer before drying)] × 100

<Formation of adhesive layer>
As a method of forming the pressure-sensitive adhesive layer, for example, a method of forming a pressure-sensitive adhesive layer by applying the solvent-type pressure-sensitive adhesive composition to a separator (release film) that has been subjected to a release treatment, and drying and removing a polymerization solvent and the like. A method of applying the solvent-based pressure-sensitive adhesive composition to a polarizing film or the like, drying and removing the polymerization solvent or the like to form a pressure-sensitive adhesive layer on the polarizing film or the like, and peeling off the active energy ray-curable pressure-sensitive adhesive composition And a method of applying the active energy ray to the applied separator and the like. Note that, if necessary, heat drying may be performed in addition to the active energy ray irradiation. In applying the pressure-sensitive adhesive composition, one or more solvents other than the polymerization solvent may be newly added as appropriate.

  As the separator subjected to the release treatment, a silicone release liner is preferably used. When the pressure-sensitive adhesive composition of the present invention is applied on such a liner and dried to form a pressure-sensitive adhesive layer, a method for drying the pressure-sensitive adhesive may be appropriately selected depending on the purpose. . Preferably, a method of heating and drying the coating film is used. The heating and drying temperature is, for example, preferably 40 to 200 ° C, more preferably 50 to 180 ° C, particularly preferably 70 to 180 ° C when preparing an acrylic pressure-sensitive adhesive using a (meth) acrylic polymer. 170 ° C. By setting the heating temperature in the above range, an adhesive having excellent adhesive properties can be obtained.

  As the drying time, an appropriate time can be appropriately used. The drying time is preferably, for example, 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, particularly preferably 10 seconds to 5 minutes when preparing an acrylic pressure-sensitive adhesive using a (meth) acrylic polymer. Minutes.

  Various methods are used for applying the pressure-sensitive adhesive composition. Specifically, for example, by roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. A method such as an extrusion coating method may be used.

  The thickness of the pressure-sensitive adhesive layer of the present invention is preferably 1 to 200 μm, more preferably 5 to 150 μm, and further preferably 10 to 100 μm. The pressure-sensitive adhesive layer may be a single layer or may have a laminated structure. Within the above range, a preferred embodiment is obtained without obstructing bending and also in terms of adhesion (holding resistance). When a plurality of pressure-sensitive adhesive layers are provided, all pressure-sensitive adhesive layers are preferably within the above range.

  Hereinafter, embodiments of an optical film, a laminate for a flexible image display device, and a flexible image display device according to the present invention will be described in detail with reference to the drawings and the like.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[Laminate for Flexible Image Display]
The laminate for a flexible image display device of the present invention is characterized by including an adhesive layer and an optical film.

[Optical film]
The laminate for a flexible image display device of the present invention is characterized by including an optical film including at least a polarizing film, and the optical film includes, in addition to the polarizing film, a protective film formed of, for example, a transparent resin material. And films including films such as retardation films. Further, in the present invention, as the optical film, the polarizing film, a protective film of a transparent resin material provided on the first surface of the polarizing film, and a second surface different from the first surface of the polarizing film. And a retardation film included in the above. Note that the optical film does not include a pressure-sensitive adhesive layer such as a first pressure-sensitive adhesive layer described later.

  The thickness of the optical film is preferably 92 μm or less, more preferably 60 μm or less, and still more preferably 10 to 50 μm. If it is in the said range, it will become a preferable aspect, without obstructing bending.

  As long as the characteristics of the present invention are not impaired, a protective film may be bonded to at least one side of the polarizing film with an adhesive (layer) (not shown in the drawings). An adhesive can be used for the bonding treatment between the polarizing film and the protective film. Examples of the adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl latex-based adhesive, and a water-based polyester. The adhesive is generally used as an adhesive composed of an aqueous solution, and usually contains a solid content of 0.5 to 60% by weight. In addition to the above, examples of the adhesive between the polarizing film and the protective film include an ultraviolet curable adhesive, an electron beam curable adhesive, and the like. The electron beam-curable adhesive for polarizing films exhibits suitable adhesiveness to the above various protective films. The adhesive used in the present invention can contain a metal compound filler. In the present invention, a polarizing film and a protective film bonded together with an adhesive (layer) may be referred to as a polarizing film (polarizing plate).

<Polarizing film>
The polarizing film (also referred to as a polarizer) contained in the optical film of the present invention is a polyvinyl alcohol (PVA) in which iodine is oriented, which is stretched in a stretching step such as an air stretching (dry stretching) or a boric acid in water stretching step. A system resin can be used.

  As a method for producing a polarizing film, typically, as described in JP-A-2004-341515, a production method including a step of dyeing a PVA-based resin monolayer and a step of stretching (single-layer stretching method) ). Also, JP-A-51-069644, JP-A-2000-338329, JP-A-2001-343521, WO 2010/100917, JP-A-2012-073563, JP-A-2011-2816 Described above, a production method including a step of stretching a PVA-based resin layer and a resin substrate for stretching in a state of a laminate and a step of dyeing the same. According to this production method, even if the PVA-based resin layer is thin, it can be stretched without any trouble such as breakage due to stretching, because it is supported by the stretching resin base material.

  The production method including the step of stretching and the step of dyeing in the state of a laminate include those described in JP-A-51-069694, JP-A-2000-338329, and JP-A-2001-343521. There is an air stretching (dry stretching) method. Then, in terms of being able to be stretched at a high magnification and improving the polarization performance, a step of stretching in a boric acid aqueous solution as described in WO 2010/100917 and JP-A-2012-073563 is described. In particular, a production method (two-stage stretching method) including a step of performing auxiliary in-air stretching before stretching in an aqueous boric acid solution as described in JP-A-2012-073563 is preferred. Further, as described in JP-A-2011-2816, after stretching a PVA-based resin layer and a stretching resin base material in a laminated state, excessively dye the PVA-based resin layer, and then decolorize the manufacturing method. (Excessive dyeing / decoloring method) is also preferable. The polarizing film included in the optical film of the present invention is made of a polyvinyl alcohol-based resin in which iodine is oriented as described above, and a polarizing film stretched in a two-stage stretching step including auxiliary stretching in air and stretching in boric acid in water. can do. Further, the polarizing film is made of a polyvinyl alcohol-based resin in which iodine is oriented as described above, by excessively dyeing the stretched body of the stretched PVA-based resin layer and the stretched resin base material, and then by decoloring. The manufactured polarizing film can be used.

  The thickness of the polarizing film is 20 μm or less, preferably 12 μm or less, more preferably 9 μm or less, further preferably 1 to 8 μm, and particularly preferably 3 to 6 μm. If it is in the said range, it will become a preferable aspect, without obstructing bending.

<Retardation film>
The optical film used in the present invention may include a retardation film, and the retardation film (also referred to as a retardation film) is obtained by stretching a polymer film or aligns and fixes a liquid crystal material. Can be used. In the present specification, the retardation film refers to a film having birefringence in a plane and / or a thickness direction.

  Examples of the retardation film include an anti-reflection retardation film (see JP-A-2012-133303 [0221], [0222], and [0228]), and a viewing-angle compensation phase difference film (JP-A-2012-133303 [0225]). ], [0226]), and an inclined alignment retardation film for viewing angle compensation (see JP-A-2012-133303, [0227]).

  As the retardation film, as long as the retardation film has substantially the above function, for example, the retardation value, the arrangement angle, the three-dimensional birefringence, whether a single layer or a multilayer is not particularly limited, and a known retardation film is used. Can be used.

  The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, further preferably 1 to 9 μm, and particularly preferably 3 to 8 μm. If it is in the said range, it will become a preferable aspect, without obstructing bending.

<Protective film>
The optical film used in the present invention may include a protective film formed of a transparent resin material. The protective film (also referred to as a transparent protective film) may be a cycloolefin resin such as a norbornene resin, polyethylene, An olefin resin such as polypropylene, a polyester resin, a (meth) acrylic resin, or the like can be used.

  The thickness of the protective film is preferably 5 to 60 μm, more preferably 10 to 40 μm, and still more preferably 10 to 30 μm, and appropriately providing a surface treatment layer such as an anti-glare layer or an anti-reflection layer. Can be. If it is in the said range, it will become a preferable aspect, without obstructing bending.

[Adhesive layer]
The laminate for a flexible image display device of the present invention is a laminate for a flexible image display device including an adhesive layer, wherein the adhesive layer has the predetermined storage modulus.

  The pressure-sensitive adhesive layer may be a single layer, but is used for laminating a transparent conductive film, an organic EL display panel, a window, a decorative printing film, a retardation layer, a protective film, and the like in addition to the optical film. (For example, when a plurality of pressure-sensitive adhesive layers are included in a laminate for a flexible image display device such as a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, for example, as shown in FIG. Etc.). When it has a plurality of pressure-sensitive adhesive layers, it is preferable to have two to five layers. If the number of layers is more than five, the thickness of the entire laminate increases, so that the difference in strain between the outermost layer and the innermost layer at the bent portion of the laminate increases, and peeling or breakage tends to occur.

[First pressure-sensitive adhesive layer]
Among the pressure-sensitive adhesive layers used in the laminate for a flexible image display device of the present invention, the first pressure-sensitive adhesive layer is disposed on the opposite side of the protective film from the surface in contact with the polarizing film. Is preferable (see FIG. 2).

[Other adhesive layers]
In the pressure-sensitive adhesive layer used for the laminate for a flexible image display device of the present invention, the second pressure-sensitive adhesive layer may be disposed on the side opposite to the surface in contact with the polarizing film with respect to the retardation film. (See FIG. 2).

  Among the pressure-sensitive adhesive layers used in the laminate for a flexible image display device of the present invention, a third pressure-sensitive adhesive layer is in contact with the second pressure-sensitive adhesive layer with respect to a transparent conductive layer constituting the touch sensor. On the side opposite to the surface, a third pressure-sensitive adhesive layer can be arranged (see FIG. 2).

  Among the pressure-sensitive adhesive layers used in the laminate for a flexible image display device of the present invention, the third pressure-sensitive adhesive layer is in contact with the first pressure-sensitive adhesive layer with respect to the transparent conductive layer constituting the touch sensor. It can be located on the opposite side of the surface (see FIG. 3).

  In addition, when using a 2nd adhesive layer and further another adhesive layer (for example, a 3rd adhesive layer etc.) in addition to a 1st adhesive layer, these adhesive layers are the same. Composition (identical pressure-sensitive adhesive composition), even those having the same properties, even those having different properties, are not particularly limited, but from the viewpoint of workability, economy, flexibility, all pressure-sensitive adhesives It is preferable that the layers are pressure-sensitive adhesive layers having substantially the same composition and the same characteristics.

[Transparent conductive layer]
The member having a transparent conductive layer is not particularly limited, and a known member can be used. However, a member having a transparent conductive layer on a transparent substrate such as a transparent film, or a transparent conductive layer and a liquid crystal A member having a cell can be given.

  The transparent substrate only needs to have transparency, and examples thereof include a substrate made of a resin film or the like (for example, a sheet-like, film-like, or plate-like substrate). The thickness of the transparent substrate is not particularly limited, but is preferably about 10 to 200 μm, and more preferably about 15 to 150 μm.

  The material of the resin film is not particularly limited, and examples thereof include various plastic materials having transparency. Examples of the material include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and (meth) acrylic resins. , A polyvinyl chloride resin, a polyvinylidene chloride resin, a polystyrene resin, a polyvinyl alcohol resin, a polyarylate resin, a polyphenylene sulfide resin, and the like. Of these, polyester resins, polyimide resins and polyethersulfone resins are particularly preferred.

  Further, the transparent substrate is subjected to an etching treatment or undercoating treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, oxidation or the like on the surface in advance, and the transparent conductive layer provided on this You may make it improve the adhesiveness with respect to a transparent base material. Before providing the transparent conductive layer, dust removal and cleaning may be performed by solvent cleaning or ultrasonic cleaning as necessary.

  The constituent material of the transparent conductive layer is not particularly limited, and is selected from the group consisting of indium, tin, zinc, gallium, antimony, titanium, silicon, zirconium, magnesium, aluminum, gold, silver, copper, palladium, tungsten, and molybdenum. At least one kind of metal or metal oxide to be used, or an organic conductive polymer such as polythiophene is used. The metal oxide may further contain the metal atom shown in the above group, if necessary. For example, indium oxide (ITO) containing tin oxide, tin oxide containing antimony, and the like are preferably used, and ITO is particularly preferably used. It is preferable that ITO contains 80 to 99% by weight of indium oxide and 1 to 20% by weight of tin oxide.

  Examples of the ITO include crystalline ITO and non-crystalline (amorphous) ITO. Crystalline ITO can be obtained by applying a high temperature during sputtering or by further heating amorphous ITO.

  The thickness of the transparent conductive layer of the present invention is preferably 0.005 to 10 μm, more preferably 0.01 to 3 μm, and still more preferably 0.01 to 1 μm. If the thickness of the transparent conductive layer is less than 0.005 μm, the change in the electrical resistance of the transparent conductive layer tends to increase. On the other hand, if it exceeds 10 μm, the productivity of the transparent conductive layer tends to decrease, the cost increases, and the optical characteristics tend to decrease.

  The total light transmittance of the transparent conductive layer of the present invention is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more.

The density of the transparent conductive layer of the present invention is preferably 1.0 to 10.5 g / cm ³ , and more preferably 1.3 to 3.0 g / cm ³ .

  The surface resistance value of the transparent conductive layer of the present invention is preferably from 0.1 to 1000 Ω / □, more preferably from 0.5 to 500 Ω / □, and still more preferably from 1 to 250 Ω / □.

  The method for forming the transparent conductive layer is not particularly limited, and a conventionally known method can be employed. Specifically, for example, a vacuum deposition method, a sputtering method, and an ion plating method can be exemplified. Further, an appropriate method can be adopted according to a required film thickness.

  Further, an undercoat layer, an oligomer prevention layer, and the like can be provided between the transparent conductive layer and the transparent substrate, if necessary.

  The transparent conductive layer is required to constitute a touch sensor and be configured to be bendable.

  In the laminate for a flexible image display device of the present invention, the transparent conductive layer constituting the touch sensor is disposed on the side opposite to the surface in contact with the retardation film with respect to the second adhesive layer. (See FIG. 2).

  In the laminate for a flexible image display device of the present invention, the transparent conductive layer constituting the touch sensor may be arranged on the side opposite to the surface in contact with the protective film with respect to the first adhesive layer. (See FIG. 3).

  Further, in the laminate for a flexible image display device of the present invention, the transparent conductive layer constituting the touch sensor can be disposed between the protective film and the window film (OCA) (see FIG. 3).

  The transparent conductive layer can be suitably applied to a liquid crystal display device having a built-in touch sensor such as an in-cell type or an on-cell type when used in a flexible image display device. In particular, a touch sensor is built in an organic EL display panel. (Even if it is built in)

[Conductive layer (antistatic layer)]
Further, the laminate for a flexible image display device of the present invention may have a conductive layer (conductive layer, antistatic layer). Since the laminate for a flexible image display device has a bending function and has a very thin thickness configuration, the laminate has high reactivity to weak static electricity generated in a manufacturing process and the like, and is easily damaged. By providing a conductive layer on the substrate, a load due to static electricity in a manufacturing process or the like is greatly reduced, which is a preferable embodiment.

  One of the major features of the flexible image display device including the laminate is that it has a bending function. However, when the flexible image display device is continuously bent, static electricity is generated due to contraction between the films (base materials) at the bent portions. There are cases. Therefore, when conductivity is imparted to the laminate, the generated static electricity can be quickly removed, and damage to the image display device due to static electricity can be reduced, which is a preferable embodiment.

  Further, the conductive layer may be an undercoat layer having a conductive function, may be an adhesive containing a conductive component, or may be a surface treatment layer further containing a conductive component. For example, a method of forming a conductive layer between a polarizing film and a pressure-sensitive adhesive layer using an antistatic composition containing a conductive polymer such as polythiophene and a binder can be employed. Further, an adhesive containing an ionic compound as an antistatic agent can also be used. The conductive layer preferably has one or more layers, and may include two or more layers.

[Flexible image display device]
A flexible image display device of the present invention includes the above-described laminate for a flexible image display device and an organic EL display panel, and the laminate for a flexible image display device is arranged on the viewing side with respect to the organic EL display panel, and is bent. It is configured to be possible. Although optional, a window can be arranged on the viewing side with respect to the flexible image display device laminate (see FIGS. 2 to 4).

  FIG. 2 is a sectional view showing one embodiment of the flexible image display device according to the present invention. The flexible image display device 100 includes a laminate 11 for a flexible image display device and an organic EL display panel 10 that is configured to be foldable. The laminate 11 for a flexible image display device is arranged on the viewing side with respect to the organic EL display panel 10, and the flexible image display device 100 is configured to be bendable. Although optional, a transparent window 40 can be disposed on the viewing side of the laminate 11 for a flexible image display device via the first pressure-sensitive adhesive layer 12-1.

  The laminate 11 for a flexible image display device includes an optical laminate 20, and further, an adhesive layer constituting a second adhesive layer 12-2 and a third adhesive layer 12-3.

  The optical laminate 20 includes a polarizing film 1, a protective film 2 made of a transparent resin material, and a retardation film 3. The protective film 2 made of a transparent resin material is bonded to the first surface on the viewing side of the polarizing film 1. The retardation film 3 is bonded to a second surface different from the first surface of the polarizing film 1. The polarizing film 1 and the retardation film 3 generate, for example, circularly polarized light in order to prevent light that has entered inside from the viewing side of the polarizing film 1 from being internally reflected and emitted to the viewing side, or a viewing angle. Or to compensate for it.

  In the present embodiment, the protective film is provided on both surfaces of the conventional polarizing film, whereas the protective film is provided on only one surface, and the polarizing film itself is used in the conventional organic EL display device. The thickness of the optical laminate 20 can be reduced by using a polarizing film having a very thin thickness (20 μm or less) as compared with a polarizing film that is present. Further, since the polarizing film 1 is much thinner than a polarizing film used in a conventional organic EL display device, stress due to expansion and contraction generated under temperature or humidity conditions is extremely small. Therefore, the possibility that the stress generated by the shrinkage of the polarizing film causes deformation such as warpage in the adjacent organic EL display panel 10 is greatly reduced, and the deterioration in display quality and the destruction of the panel sealing material due to the deformation are greatly reduced. Can be suppressed. Further, the use of a polarizing film having a small thickness does not hinder bending, which is a preferable embodiment.

  When bending the optical laminate 20 with the protective film 2 side inside, the thickness (for example, 92 μm or less) of the optical laminate 20 is reduced, and the first having the characteristics of 100% modulus and 500% modulus as described above. By arranging the pressure-sensitive adhesive layer 12-1 on the side opposite to the retardation film 3 with respect to the protective film 2, it is possible to reduce the stress applied to the optical laminated body 20, whereby the optical laminated body 20 is bent. This makes it possible to suppress cracking of each layer and peeling of the pressure-sensitive adhesive layer at the bent portion, and finally, it is possible to bend the laminate 11 for a flexible image display device. Therefore, appropriate ranges of 100% modulus and 500% modulus may be set according to the environmental temperature in which the flexible image display device is used.

  Optionally, a foldable transparent conductive layer 6 constituting a touch sensor may be further disposed on the side opposite to the protective film 2 with respect to the retardation film 3. The transparent conductive layer 6 is configured to be directly bonded to the retardation film 3 by a manufacturing method as described in JP-A-2014-219667, for example, whereby the thickness of the optical laminate 20 is reduced. Can be further reduced when the optical laminate 20 is bent.

  Optionally, an adhesive layer constituting the third adhesive layer 12-3 can be further disposed on the side opposite to the retardation film 3 with respect to the transparent conductive layer 6. In the present embodiment, the second pressure-sensitive adhesive layer 12-2 is directly bonded to the transparent conductive layer 6. By providing the second pressure-sensitive adhesive layer 12-2, the stress applied to the optical laminate 20 when the optical laminate 20 is bent can be further reduced.

  The flexible image display device shown in FIG. 3 is almost the same as that shown in FIG. 2, but the flexible image display device shown in FIG. In the flexible image display device shown in FIG. 3, the foldable transparent conductive layer 6 is disposed, and the protective film 2 is opposite to the first adhesive layer 12-1. And a foldable transparent conductive layer 6 constituting the touch sensor. Further, in the flexible image display device of FIG. 2, the third pressure-sensitive adhesive layer 12-3 is disposed on the side opposite to the retardation film 3 with respect to the transparent conductive layer 2. The flexible image display device is different in that the second pressure-sensitive adhesive layer 12-2 is disposed on the side opposite to the protective film 2 with respect to the retardation film 3.

  Also, although optional, the third adhesive layer 12-3 can be disposed when the window 40 is disposed on the viewing side with respect to the flexible image display laminate 11.

  The flexible image display device of the present invention can be suitably used as an image display device such as a flexible liquid crystal display device, an organic EL (electroluminescence) display device, and electronic paper. Further, it can be used irrespective of a touch panel system such as a resistive film system or a capacitance system.

  Further, as shown in FIG. 4, the flexible image display device of the present invention is also used as an in-cell flexible image display device in which a transparent conductive layer 6 constituting a touch sensor is built in an organic EL display panel 10-1. It is possible to do.

  Hereinafter, some examples related to the present invention will be described, but it is not intended to limit the present invention to those shown in the specific examples.

Example 1
<Preparation of prepolymer>
A monomer mixture containing 59 parts by weight of lauryl acrylate (LA), 40 parts by weight of 2-ethylhexyl acrylate (2EHA), and 1 part by weight of 4-hydroxybutyl acrylate (4HBA) and 2,2-dimethoxy-1 which is a photopolymerization initiator. , 2-diphenylethan-1-one (trade name "Irgacure 651", BASF Japan Ltd.) and 1-hydroxy-cyclohexyl-phenyl-ketone (trade name "Irgacure 184", BASF Japan Ltd.) 0.05 parts by weight of each was put into a four-necked flask, and irradiated with ultraviolet light under a nitrogen atmosphere until the viscosity (BH viscosity system No. 5 rotor, 10 rpm, temperature 30 ° C.) became about 15 Pa · s. , By photopolymerization, partially polymerized monomer syrup (partial polymerized product of monomer component) It was obtained.

<Preparation of acrylic pressure-sensitive adhesive composition>
To 100 parts by weight of the obtained partially polymerized monomer syrup, 5 parts by weight of N-vinylpyrrolidone and 1,6-hexanediol diacrylate (trade name “A-HD-N”, manufactured by Shin-Nakamura Chemical Co., Ltd.) as additional monomers , HDDA, polyfunctional monomer) 0.15 parts by weight, photopolymerization initiator 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name “Irgacure 651”, manufactured by BASF Japan Ltd., added) (Initiator) 0.1 part by weight, and 0.3 part by weight of a silane coupling agent (trade name “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.) are uniformly mixed to prepare an acrylic pressure-sensitive adhesive composition. Obtained.

<Formation of adhesive layer>
The acrylic pressure-sensitive adhesive composition is applied onto a release-treated surface of a release film (trade name “MRF # 38”, manufactured by Mitsubishi Plastics, Inc.) so that the thickness after forming the pressure-sensitive adhesive layer is 70 μm. Then, a pressure-sensitive adhesive composition layer was formed, and then a release film (trade name “MRN # 38”, manufactured by Mitsubishi Plastics, Inc.) was bonded to the surface of the pressure-sensitive adhesive composition layer. Thereafter, ultraviolet irradiation was performed under the conditions of illuminance: 4 mW / cm ² and light amount: 1200 mJ / cm ² , and the pressure-sensitive adhesive composition layer was light-cured to form a pressure-sensitive adhesive layer. Then, an adhesive layer in which both surfaces of the adhesive layer were protected by a release film was obtained.

Examples 2-3, Comparative Examples 1-5
In the preparation of the prepolymer of Example 1, the monomer mixture (type, composition) of the prepolymer was changed as shown in Table 2, and in the preparation of the acrylic pressure-sensitive adhesive composition, the additional monomer (type, blending amount) was changed. The preparation of the prepolymer and the preparation of the acrylic pressure-sensitive adhesive composition were performed in the same manner as in Example 1 except for the change as shown in Table 2, and then the pressure-sensitive adhesive layer was formed.
In Comparative Examples 2 and 3, as shown in Table 2, the amount of 1,6-hexanediol diacrylate was changed to 0.3 parts by weight, so that 2,2- The blending amount of dimethoxy-1,2-diphenylethan-1-one (trade name “Irgacure 651”, manufactured by BASF Japan Ltd., additional initiator) was changed to 0.6 parts by weight.

  After producing an optical laminate using each member produced by the following method, an optical laminate with an adhesive layer was produced using the adhesive layers obtained in the above Examples and Comparative Examples.

[Polarizing film]
As a thermoplastic resin substrate, an amorphous polyethylene terephthalate (hereinafter also referred to as “PET”) (IPA copolymerized PET) film (thickness: 100 μm) having an isophthalic acid unit of 7 mol% is prepared, and the surface is corona-treated ( 58 W / m ² / min). On the other hand, acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Gosefimer Z200 (average degree of polymerization: 1200, degree of saponification: 98.5 mol%, degree of acetoacetylation: 5 mol%)) 1% by weight of added PVA (polymerization degree 4200, saponification degree 99.2%) was prepared, and a coating solution of a PVA aqueous solution containing 5.5% by weight of a PVA-based resin was prepared. Was dried by hot air drying at 60 ° C. in an atmosphere at 60 ° C. for 10 minutes to prepare a laminate in which a PVA-based resin layer was provided on a substrate.

  Next, the laminate was first stretched in air at 130 ° C. 1.8 times at the free end (auxiliary in the air) to produce a stretched laminate. Next, a step of immersing the stretched laminate in a boric acid insolubilizing aqueous solution at a liquid temperature of 30 ° C. for 30 seconds to insolubilize the PVA layer in which the PVA molecules contained in the stretched laminate were oriented was performed. The boric acid insolubilizing aqueous solution in this step had a boric acid content of 3 parts by weight based on 100 parts by weight of water. A colored laminate was produced by dyeing the stretched laminate. The colored laminate is prepared by applying the stretched laminate to a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30 ° C. so that the PVA layer constituting the polarizing film finally formed has a single transmittance of 40 to 44%. The PVA layer contained in the stretched laminate was dyed with iodine by immersing the PVA layer in an arbitrary time. In this step, the dyeing solution used water as a solvent, the iodine concentration was in the range of 0.1 to 0.4% by weight, and the potassium iodide concentration was in the range of 0.7 to 2.8% by weight. The ratio of the concentrations of iodine and potassium iodide is 1: 7. Next, a step of subjecting the PVA molecules of the PVA layer to which iodine had been adsorbed to a crosslinking treatment by immersing the colored laminate in a 30 ° C. aqueous boric acid crosslinking aqueous solution for 60 seconds was performed. The boric acid crosslinking aqueous solution in this step had a boric acid content of 3 parts by weight with respect to 100 parts by weight of water and a potassium iodide content of 3 parts by weight with respect to 100 parts by weight of water.

  Further, the obtained colored laminate was stretched in a boric acid aqueous solution at a stretching temperature of 70 ° C., and stretched 3.05 times in the same direction as the stretching in the air (stretching in boric acid in water). An optical film laminate having a stretching ratio of 5.50 was obtained. The optical film laminate was taken out from the boric acid aqueous solution, and the boric acid attached to the surface of the PVA layer was washed with an aqueous solution having a potassium iodide content of 4 parts by weight with respect to 100 parts by weight of water. The washed optical film laminate was dried by a drying process using hot air at 60 ° C. The thickness of the polarizing film contained in the obtained optical film laminate was 5 μm.

[Protective film]
As the protective film, a methacrylic resin pellet having a glutarimide ring unit was extruded, formed into a film shape, and then stretched. This protective film was an acrylic film having a thickness of 20 μm and a moisture permeability of 160 g / m ² .

  Next, the polarizing film and the protective film were adhered to each other using an adhesive shown below to obtain a polarizing film.

As the adhesive (active energy ray-curable adhesive), each component was mixed according to the composition table shown in Table 1, and the mixture was stirred at 50 ° C. for 1 hour, and the adhesive (active energy ray-curable adhesive A) was used. Was prepared. Numerical values in the table indicate wt% when the total amount of the composition is 100 wt%. The components used are as follows.
HEAA: hydroxyethyl acrylamide M-220: ARONIX M-220, tripropylene glycol diacrylate), manufactured by Toagosei Co., Ltd. ACMO: acryloylmorpholine AAEM: 2-acetoacetoxyethyl methacrylate, manufactured by Nippon Synthetic Chemical Company, UP-1190: ARUFON UP- 1190, Toagosei IRG907: IRGACURE907, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, BASF DETX-S: KAYACURE DETX-S, diethylthioxanthone, Nippon Kagaku Yakusha

After laminating the protective film and the polarizing film via the adhesive, the adhesive was cured by irradiating ultraviolet rays to form an adhesive layer. For the irradiation of ultraviolet rays, a gallium-filled metal halide lamp (manufactured by Fusion UV Systems, Inc., trade name “Light HAMMER10”, bulb: V bulb, peak illuminance: 1600 mW / cm ² , integrated irradiation amount 1000 / mJ / cm ² (wavelength 380-440 nm)).

[Retardation film]
The retardation film (1/4 wavelength retardation plate) of this embodiment is composed of two layers, a 1/4 wavelength plate retardation layer and a 1/2 wavelength plate retardation layer, in which the liquid crystal material is aligned and fixed. The retardation film was constituted. Specifically, it was manufactured as follows.

(Liquid crystal material)
A polymerizable liquid crystal material exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name: Paliocolor LC242) was used as a material for forming the retardation layers for the 波長 wavelength plate and the 波長 wavelength plate. A photopolymerization initiator for the polymerizable liquid crystal material (manufactured by BASF, trade name: Irgacure 907) was dissolved in toluene. Further, for the purpose of improving coating properties, DIC Megafac series was added in an amount of about 0.1 to 0.5% depending on the liquid crystal thickness to prepare a liquid crystal coating liquid. The liquid crystal coating liquid was applied on an alignment base material using a bar coater, dried by heating at 90 ° C. for 2 minutes, and fixed by ultraviolet curing in a nitrogen atmosphere. As the base material, a material such as PET, which can transfer a liquid crystal coating layer later, was used. Further, for the purpose of improving coatability, a fluoropolymer, which is a Megafac series manufactured by DIC, is added in an amount of about 0.1% to 0.5% depending on the thickness of the liquid crystal layer, and MIBK (methyl isobutyl ketone), cyclohexanone, or MIBK is added. And a cyclohexanone mixed solvent to obtain a coating solution by dissolving to a solid concentration of 25%. This coating solution was applied to a substrate using a wire bar, a drying process was performed at 65 ° C. for 3 minutes, and the orientation was fixed by ultraviolet curing under a nitrogen atmosphere to produce a coating. As the base material, a material such as PET, which can transfer a liquid crystal coating layer later, was used.

(Manufacturing process)
With reference to FIG. 7, the manufacturing process of this embodiment will be described. Note that the numbers in FIG. 7 are different from the numbers in the other drawings. In this manufacturing process 20, the substrate 14 was provided by a roll, and the substrate 14 was supplied from a supply reel 21. In the manufacturing process 20, a coating liquid of the ultraviolet curable resin 10 was applied to the substrate 14 by the die 22. In this manufacturing process 20, the roll plate 30 was a cylindrical molding die in which the irregularities related to the quarter-wave plate alignment film of the quarter-wave retardation plate were formed on the peripheral side surface. In the manufacturing step 20, the base material 14 coated with the ultraviolet curable resin is pressed against the peripheral side surface of the roll plate 30 by the pressure roller 24, and the ultraviolet curable resin is irradiated with ultraviolet light by an ultraviolet irradiation device 25 composed of a high-pressure mercury lamp. Cured. Thereby, in the manufacturing process 20, the irregularities formed on the peripheral side surface of the roll plate 30 were transferred to the substrate 14 so as to be at an angle of 75 ° with respect to the MD direction. Thereafter, the base material 14 was peeled off from the roll plate 30 integrally with the ultraviolet curable resin 10 cured by the peeling roller 26, and a liquid crystal material was applied by a die 29. Thereafter, the liquid crystal material was cured by irradiating ultraviolet rays with the ultraviolet irradiating device 27, and thereby, a configuration relating to the retardation layer for a 波長 wavelength plate was prepared.
Subsequently, in step 20, the base material 14 is conveyed to the die 32 by the conveying roller 31, and the coating liquid of the ultraviolet curable resin 12 is applied to the quarter-wave plate retardation layer of the base material 14 by the die 32. did. In this manufacturing process 20, the roll plate 40 was a cylindrical molding die in which the irregularities related to the half-wave plate alignment film of the quarter-wave retardation plate were formed on the peripheral side surface. In the manufacturing step 20, the base material 14 coated with the ultraviolet curable resin is pressed against the peripheral side surface of the roll plate 40 by the pressure roller 34, and the ultraviolet curable resin is irradiated with ultraviolet light by an ultraviolet irradiation device 35 composed of a high-pressure mercury lamp. Cured. Thus, in the manufacturing process 20, the uneven shape formed on the peripheral side surface of the roll plate 40 was transferred to the base material 14 so as to be at an angle of 15 ° with respect to the MD direction. Thereafter, the base material 14 was peeled off from the roll plate 40 integrally with the ultraviolet curable resin 12 cured by the peeling roller 36, and a liquid crystal material was applied by a die 39. Thereafter, the liquid crystal material is cured by irradiating the liquid crystal material with ultraviolet light by the ultraviolet irradiation device 37, thereby forming a configuration relating to the retardation layer for the 波長 wavelength plate. A 7 μm thick retardation film composed of two retardation layers for a plate was obtained.

[Optical film (optical laminate)]
The retardation film obtained as described above and the polarizing film obtained as described above are continuously bonded using the above-mentioned adhesive by using a roll-to-roll method, and axes of a slow axis and an absorption axis. A laminated film (optical laminated body) was produced so that the angle was 45 °.

<Preparation of optical laminate with adhesive layer>
The separator on which the pressure-sensitive adhesive layer (second) obtained in the above Examples and Comparative Examples was formed was transferred to the protective film side (corona-treated) of the obtained optical laminate, and the optical laminate with the pressure-sensitive adhesive layer was transferred. Was prepared.

[First pressure-sensitive adhesive layer]
The same pressure-sensitive adhesive layer (first) as in each example was formed except that the thickness of the pressure-sensitive adhesive layer used in each example was changed to 50 μm. The separator on which the pressure-sensitive adhesive layer (first) was formed was transferred to the surface (corona-treated) of a 75 μm-thick polyimide film (PI film, manufactured by Dupont Toray, Kapton 300V, substrate), A PI film with an adhesive layer was formed.

[Third pressure-sensitive adhesive layer]
An adhesive layer (third) similar to each example was formed, except that the thickness of the adhesive layer used in each example was changed to 50 μm. A separator having the pressure-sensitive adhesive layer (third) formed thereon was transferred to the surface (corona-treated) of a 125 μm-thick PET film (transparent substrate, manufactured by Mitsubishi Plastics, Inc., trade name: diamond foil), A PET film with an adhesive layer was formed.

<Preparation of laminate for flexible image display device>
As shown in FIG. 6, the first to third pressure-sensitive adhesive layers (along with the respective transparent substrates) obtained as described above are applied to a PET film that is to be a 25 μm-thick transparent substrate 8-1 by a second method. , The third pressure-sensitive adhesive layer 12-3 on the retardation film 3, and the transparent substrate 8- on which the second pressure-sensitive adhesive layer 12-2 is further bonded. By laminating the first pressure-sensitive adhesive layer 12-1 to 1 (PET film), a laminate 11 for a flexible image display device was produced.

[Evaluation]
The following evaluation was performed on the pressure-sensitive adhesive layer and the laminate for a flexible image display device obtained in Examples and Comparative Examples. Table 2 shows the results.

<Storage modulus G 'of pressure-sensitive adhesive layer>
The separator was peeled off from the pressure-sensitive adhesive layer obtained in each of the examples and comparative examples, and a plurality of pressure-sensitive adhesive layers were laminated to produce a test sample having a thickness of about 2 mm. This test sample was punched out into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to dynamic viscoelasticity measurement under the following conditions using "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific, under the following conditions. From the results, the storage elastic modulus G ′ of the pressure-sensitive adhesive layer at −20 ° C., 23 ° C., and 85 ° C. was read.
(Measurement condition)
Deformation mode: torsion Measurement temperature: -70 ° C to 150 ° C
Heating rate: 5 ° C / min

<Measurement of gel fraction of adhesive layer>
Sample 1 was obtained by scraping about 0.2 g from the pressure-sensitive adhesive layer formed on the release-treated surface of the separator film one week after the preparation. After wrapping the sample 1 in a Teflon (registered trademark) film having a diameter of 0.2 μm (trade name “NTF1122”, manufactured by Nitto Denko Corporation), the sample was tied with a kite string, and this was designated as sample 2. The weight of Sample 2 before being subjected to the following test was measured, and this was designated as Weight A. The weight A is the total weight of Sample 1 (adhesive layer), Teflon (registered trademark) film, and kite string. The total weight of the Teflon (registered trademark) film and the kite string was defined as weight B. Next, the sample 2 was placed in a 50 ml container filled with ethyl acetate, and allowed to stand at 23 ° C. for one week. Thereafter, the sample 2 was taken out of the container, dried in a dryer at 130 ° C. for 2 hours to remove ethyl acetate, and the weight of the sample 2 was measured. The weight of the sample 2 after the test was measured, and this was defined as a weight C. Then, the gel fraction (% by weight) was calculated from the following equation.
Gel fraction (% by weight) = (CB) / (AB) × 100

  The gel fraction of the pressure-sensitive adhesive layer is preferably from 55 to 90% by weight, more preferably from 57 to 90% by weight, still more preferably from 60 to 88% by weight, and still more preferably from 62 to 88% by weight. Preferably it is 65-86% by weight, most preferably 70-86% by weight. When the gel fraction of the pressure-sensitive adhesive layer is within the above range, appearance (e.g., glue dents), workability, durability, and flexibility are improved, and both flexibility under a normal temperature environment and a high temperature environment is compatible. This is a preferred embodiment.

<Measurement of thickness>
The thicknesses of the polarizing film, the retardation film, the protective film, the optical laminate, and the pressure-sensitive adhesive layer were measured using a dial gauge (manufactured by Mitutoyo).

<Folding resistance (continuous bending) test method>
FIGS. 5A and 5B are schematic diagrams of a bending test based on a U-shaped expansion / contraction tester (Yuasa System Equipment Co., Ltd.).
The testing machine has a mechanism of repeating 180 ° bending in a U-shape with no load on a planar workpiece in a constant temperature bath, and adjusting a distance between the surfaces bent in a U-shape to reduce a bending radius. Can be changed.
In the test, the laminate for a flexible image display device of 2.5 cm × 10 cm obtained in each of the examples and comparative examples was set on a testing machine so that it could be bent in the long side direction. Evaluation was performed at RH and 85 ° C. under the conditions of a bending angle of 180 °, a bending radius of 3 mm, and a bending speed of 1 second / time.
In addition, as a sample for measurement (evaluation), the structure shown in FIG. 6 is adopted, the transparent substrate 8-2 (PET film) is on the concave side (inside), and the substrate 9 (PI film) is on the convex side (outside). ) And evaluated by bending in the long side direction near the center. The bending strength was evaluated by the number of times until cracking or peeling between layers occurred at the bent portion of the laminate for a flexible image display device. Here, when the number of times of bending reached 200,000 times, the test was terminated.
<Peeling / cracking>
◎: No defect after 200,000 operations (no problem in practical use)
：: defective in less than 100,000 to 200,000 times (no problem in practical use)
△: Less than 50,000 to 100,000 times, defective (no problem in practical use)
×: defective if less than 50,000 times (practical problem)

<Measurement of modulus stress>
Using the same pressure-sensitive adhesive composition as in Examples and Comparative Examples, a pressure-sensitive adhesive layer having a release film (trade name “MRF # 38”, manufactured by Mitsubishi Plastics, Inc.) having a thickness of 50 μm was prepared on both sides. After the pressure-sensitive adhesive layer was cut into a width of 30 mm and a length of 100 mm, the release films on both sides were peeled off, and the film was rolled up so as to prevent air bubbles from entering, thereby obtaining a columnar sample. Using a Tensilon-type tensile tester, this sample was subjected to a stress (N / D) at an elongation of 100%, 500%, and 700% modulus from a load-elongation curve measured under the conditions of 10 mm between chucks and a tensile speed of 300 mm / min. mm ² ). Here, 100% elongation refers to a state where the distance between chucks is 20 mm, 500% elongation refers to a state where the distance between chucks is 60 mm, and 700% elongation refers to a state where the distance between chucks is 80 mm.

<Adhesion>
The PI film, the optical laminate, and the PET film used above were bonded and fixed on a glass plate via a general-purpose double-sided tape (No. 500, manufactured by Nitto Denko Corporation) to produce an adherend.
Using the same pressure-sensitive adhesive composition as in Examples and Comparative Examples, a pressure-sensitive adhesive layer having a release film (trade name “MRF # 38”, manufactured by Mitsubishi Plastics, Inc.) having a thickness of 50 μm was prepared on both sides. The adhesive layer was cut into a size having a width of 25 mm and a length of 100 mm, and one of the release films was peeled off and bonded to a PET film having a thickness of 25 μm (manufactured by Toray, Lumirror S10). Then, the other separator was peeled off. The one with the adhesive layer surface exposed was used as a sample. The sample was bonded to the adherend prepared earlier. Crimping was performed at a linear pressure of 78.5 N / cm and a speed of 0.3 m / min. After leaving this in an environment of 23 ° C. and 50% RH for 30 minutes, a sample was obtained from the adherend under the same environment at a peeling speed of 0.3 m / min and a peeling angle of 180 ° using a universal tensile tester. Was peeled off, and the peeling force at this time was evaluated as adhesion (N / 25 mm).

Abbreviations in Table 2 are as follows.
LA: lauryl acrylate 2EHA: 2-ethylhexyl acrylate 4HBA: 4-hydroxybutyl acrylate NVP: N-vinylpyrrolidone A-HD-N: 1,6-hexanediol diacrylate (trade name, manufactured by Shin-Nakamura Chemical Co., Ltd.) : A-HD-N)

From the evaluation results in Table 2, in all the examples, the storage elastic modulus G ′ at −20 ° C. of the pressure-sensitive adhesive layer was 3.5 × 10 ^{4 to} 1.7 × 10 ⁵ Pa,
The storage elastic modulus G ′ at 23 ° C. is 1.0 × 10 ^{4 to} 5.0 × 10 ⁴ Pa, and
The difference between the storage modulus G ′ at 23 ° C. and the storage modulus G ′ at 85 ° C. is not less than 5.2 × 10 ³ Pa, and according to a folding endurance (continuous bending) test, −20 ° C. Even when exposed to 25 ° C. × 50% RH and 85 ° C. (under low temperature, normal temperature or high temperature environment), it was confirmed that cracking (breaking) or peeling was at a level that does not cause any practical problem. . That is, in the laminate for a flexible image cover device of each embodiment, by using the pressure-sensitive adhesive layer having a storage elastic modulus G ′ in a predetermined range, the layer may be cracked (bent) or peeled with repeated bending. Thus, it was confirmed that a laminate for a flexible image display device having excellent bending resistance and adhesion was obtained.

  On the other hand, since Comparative Examples 1 to 4 are not included in the storage elastic modulus G ′ in the predetermined range, according to the bending resistance (continuous bending) test, −20 ° C., 25 ° C. × 50% RH, and 85 ° C. ( When exposed to a low-temperature, normal-temperature, or high-temperature environment), cracking (breaking) or peeling was at a practically problematic level, and inferior in either bending resistance or adhesion.

DESCRIPTION OF SYMBOLS 1 Polarizing film 2 Protective film 2-1 Protective film 2-2 Protective film 3 Retardation layer 4-1 Transparent conductive film 4-2 Transparent conductive film 5-1 Base film 5-2 Base film 6 Transparent conductive layer 6 1 Transparent conductive layer 6-2 Transparent conductive layer 7 Spacer 8 Transparent substrate 8-1 Transparent substrate (PET film)
8-2 Transparent substrate (PET film)
9 Base material (PI film)
10 Organic EL display panel 10-1 Organic EL display panel (with touch sensor)
11 Laminate for Flexible Image Display (Laminate for Organic EL Display)
12 pressure-sensitive adhesive layer 12-1 first pressure-sensitive adhesive layer 12-2 second pressure-sensitive adhesive layer 12-3 third pressure-sensitive adhesive layer 13 decorative printing film 14 double-sided pressure-sensitive adhesive tape 20 optical laminate 30 touch panel 40 window 100 flexible Image display device (organic EL display device)
P Bending point UV UV irradiation L Liquid crystal material

Claims (9)

Storage elastic modulus G ′ at −20 ° C. is 3.5 × 10 ^{4 to} 1.7 × 10 ⁵ Pa;
The storage elastic modulus G ′ at 23 ° C. is 1.0 × 10 ^{4 to} 5.0 × 10 ⁴ Pa, and
A pressure-sensitive adhesive layer for a flexible image display device, wherein a difference between a storage elastic modulus G ′ at 23 ° C. and a storage elastic modulus G ′ at 85 ° C. is 5.2 × 10 ³ Pa or more. The average value of the storage elastic modulus G 'at -20 ° C and the storage elastic modulus G' at 23 ° C is 4.5 × 10 ^{4 to} 1.5 × 10 ⁵ Pa. Pressure-sensitive adhesive layer for flexible image display devices.   3. The pressure-sensitive adhesive layer for a flexible image display device according to claim 1, wherein the gel fraction is 70% by weight or more.   The flexible image display device according to any one of claims 1 to 3, wherein the flexible image display device is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic polymer containing an alkyl (meth) acrylate as a monomer unit. Pressure-sensitive adhesive layer.   The pressure-sensitive adhesive layer for a flexible image display device according to claim 4, wherein the alkyl (meth) acrylate contains an alkyl (meth)) acrylate having an alkyl group having 10 or more carbon atoms.   6. The flexible image display device according to claim 4, wherein the (meth) acrylic polymer contains, as a monomer unit, an N-vinyl group-containing lactam monomer in addition to the alkyl (meth) acrylate. 7. Adhesive layer.   A laminate for a flexible image display device, comprising: the pressure-sensitive adhesive layer according to claim 1; and an optical film including at least a polarizing film.   A laminate for a flexible image display device, comprising: the laminate for a flexible image display device according to claim 7; and an organic EL display panel, wherein the laminate for a flexible image display device is arranged on a viewing side with respect to the organic EL display panel. Flexible image display device. 9. The flexible image display device according to claim 8, wherein a window is arranged on the viewing side with respect to the flexible image display device laminate.

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