TW202214797A - Adhesive sheet used in layered product in flexible image display device, layered product used in flexible image display device, and flexible image display device - Google Patents

Abstract

The present invention provides an adhesive sheet that is capable of inhibiting layers, included in a flexible image display device that has a display part that can be rolled up, from coming off or undulating, even after the display part is held in a high-temperature environment while being rolled up around a shaft member and is returned back to a flat state. The adhesive sheet according to the present invention has a loss tangent tanδ of at most 0.32 at 85 DEG C and a gel fraction of at least 75%. The adhesive sheet is used in a layered product in a flexible image display device having a display part that can be rolled up.

Description

Adhesive sheet for laminated body in flexible image display device, laminated body for flexible image display device, and flexible image display device

The present invention relates to an adhesive sheet used for a laminate in a flexible image display device, a laminate used in a flexible image display device, and a flexible image display device.

Various thin image display devices such as liquid crystal displays and organic EL displays have, for example, a laminate structure including an image display panel and an optical film (eg, Patent Document 1). Adhesive sheets are generally used for bonding the layers used to form the image display device. prior art literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2014-157745

The problem to be solved by the invention When the inventors of the present invention developed a new type of flexible image display device having a display portion that can be taken up, they examined the adhesive sheet used in the device. According to the review by the inventors of the present invention, it has been clarified that, in the case of a flexible image display device having a display portion that can be taken up, when it is held in a state of being wound around a shaft member such as a roller and then returns to a flat state , the layer joined by the adhesive sheet will peel off or undulate on the layer. The problems of peeling and waviness tend to become particularly conspicuous in a high temperature environment.

Therefore, an object of the present invention is to provide an adhesive sheet which, for a flexible image display device having a display portion that can be rolled up, can return to a flat state even after being kept in a high temperature environment while being wound around a shaft member. At the same time, the adhesive sheet can still inhibit the occurrence of peeling and waviness of the layers constituting the device.

means of solving problems The present invention provides an adhesive sheet, which is used for a laminate in a flexible image display device having a reelable display portion; The loss tangent tanδ of the adhesive sheet at 85°C is 0.32 or less, and The gel fraction was 75% or more.

Furthermore, the present invention provides a laminate for use in a flexible image display device having a display portion that can be rolled up, and which includes: the above-mentioned adhesive sheet; and The base material supports the aforementioned adhesive sheet.

Furthermore, the present invention provides a flexible image display device, which has a display portion that can be rolled up, and which includes: the above-mentioned laminate; and image display panel; And the above-mentioned laminated body is located on the viewing side more than the above-mentioned image display panel.

Invention effect According to the present invention, it is possible to provide an adhesive sheet that, for a flexible image display device having a display portion that can be rolled up, even when the adhesive sheet is kept in a high-temperature environment in a state of being wound around a shaft member and then returned to a flat state. The adhesive sheet still inhibits the occurrence of peeling and waviness of the layers that make up the device.

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

(Embodiment of adhesive sheet) The adhesive sheet of the present invention is used as a member of a laminate in a flexible image display device having a reelable display portion, and has a loss tangent tanδ of 0.32 or less at 85° C. and a gel fraction of 75% or more.

The tanδ of the adhesive sheet at 85°C can be specified by the following method. First, a measurement sample composed of the material constituting the adhesive sheet is prepared. The shape of the sample for measurement is a disk shape. The diameter of the bottom surface of the sample for evaluation was 8 mm, and the thickness was 2 mm. The sample for measurement may be a laminate formed by laminating a plurality of adhesive sheets into a disc shape by punching. Next, the dynamic viscoelasticity measurement is performed on the sample for measurement. In the dynamic viscoelasticity measurement, for example, "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific can be used. The conditions for the dynamic viscoelasticity measurement are as follows. (measurement conditions) Frequency: 1Hz Deformation Mode: Twist Measurement temperature: -70℃~150℃ Heating rate: 5°C/min

The storage elastic modulus G' (MPa) and the loss elastic modulus G" (MPa) at 85°C are specified from the results of the dynamic viscoelasticity measurement. The loss elastic modulus G" can be compared with the storage elastic modulus G' The ratio G"/G' was regarded as the tanδ of the adhesive sheet at 85°C.

The tanδ of the adhesive sheet at 85°C is preferably 0.30 or less, preferably 0.28 or less, more preferably 0.25 or less, particularly preferably 0.20 or less, particularly preferably 0.18 or less, and may be 0.15 or less, or 0.13 or less. For a flexible image display device equipped with an adhesive sheet, from the viewpoint of suppressing the residual traces such as roll marks, the tanδ of the adhesive sheet at 85°C is preferably 0.07 or more, more preferably 0.08 or more, more preferably 0.09 or more, especially It is preferably 0.10 or more, particularly preferably 0.11 or more. The tanδ of the adhesive sheet at 85° C. may be 0.11 to 0.32, or 0.11 to 0.20.

The gel fraction of the adhesive sheet can be evaluated, for example, by the following method. First, scrape a portion of the adhesive sheet to obtain a small piece. Next, the obtained small pieces are covered with an extended porous film of polytetrafluoroethylene and tied with kite string. Thereby, a test piece can be obtained. Next, the total weight (weight A) of the small pieces of the adhesive sheet, the stretched porous film, and the kite string was measured. In addition, the total amount of the stretched porous film and kite string used is defined as weight B. Next, after immersing the test piece in a container filled with ethyl acetate, it was left to stand at 23° C. for one week. After standing, the test piece was taken out from the container and dried in a dryer set at 130° C. for 2 hours, and then the weight C of the test piece was measured. From the following formula, the gel fraction of the adhesive sheet can be calculated from the weight A, the weight B, and the weight C. Gel fraction (wt%)=(C-B)/(A-B)×100

The gel fraction of the adhesive sheet is preferably at least 80%, preferably at least 83%, more preferably at least 85%, particularly preferably at least 88%, particularly preferably at least 90%, and may be at least 92%. The upper limit of the gel fraction of the adhesive sheet is not particularly limited, and may be, for example, 99%, 97%, 95%, or 94%.

The adhesive sheet of the present embodiment has a tanδ of 0.32 or less at 85° C. and a gel fraction of 75% or more, thereby maintaining high cohesion and adhesion even in a high temperature environment. In addition, the adhesive sheet of the present embodiment is not easily deformed by the stress generated when the flexible image display device is wound around the shaft member. Therefore, according to the adhesive sheet of the present embodiment, in the case of a flexible image display device, even if it is kept in a high temperature environment in a state of being wrapped around a shaft member and then returned to a flat state, the layers constituting the device can still be Suppresses the occurrence of peeling and waviness.

The storage elastic modulus G' of the adhesive sheet at 25°C is not particularly limited. . The upper limit of the storage elastic modulus G' of the adhesive sheet at 25°C is not particularly limited, for example, it is 0.50 MPa, preferably 0.40 MPa, and more preferably 0.35 MPa. The storage elastic modulus G' of the adhesive sheet at 25°C can be specified from the results of the above-mentioned dynamic viscoelasticity measurement.

The storage elastic modulus G' of the adhesive sheet at 85°C is not particularly limited. . The upper limit of the storage elastic modulus G' of the adhesive sheet at 85°C is not particularly limited, and is, for example, 0.50 MPa, preferably 0.30 MPa, and more preferably 0.20 MPa. The storage elastic modulus G' of the adhesive sheet at 85°C can be specified from the results of the above-mentioned dynamic viscoelasticity measurement.

The 100% modulus of the adhesive sheet is, for example, 0.05 N/mm ² or more. The 100% modulus of the adhesive sheet refers to a property expressed by a value obtained in the following way: 100% elongation is imparted to the adhesive sheet by a tensile force in one direction, and the stress generated in the adhesive sheet at this time is changed. (tensile stress) divided by the initial cross-sectional area of the adhesive sheet. The 100% modulus of the adhesive sheet can be evaluated in the following manner.

First, the adhesive sheet of the evaluation object was cut into a short stick shape of 30mm×40mm. Next, the cut-out adhesive sheet was wound in the longitudinal direction so as not to mix air bubbles to obtain a cylindrical test piece having a height of 30 mm corresponding to the length of the short side. Next, after installing the obtained test piece in a tensile testing machine such as Tensilon, a uniaxial tensile test is performed on the height direction, and the elongation-stress curve of the adhesive sheet is obtained. In addition, the preparation of the test piece and the uniaxial tensile test were carried out at normal temperature (23° C.), and the initial distance between the jigs in the uniaxial tensile test was set to 10 mm, and the tensile speed was set to 300 mm/min. From the obtained elongation-stress curve, the stress at 100% elongation (the distance between the clamps at this time is 20 mm) was obtained and divided by the initial cross-sectional area of the test piece to obtain the 100% modulus of the adhesive sheet.

The 100% modulus of the adhesive sheet is preferably 0.10N/mm ² or more, more preferably 0.14N/mm ² or more, and may be 0.18N/mm ² or more, or 0.20N/mm ² or more. The upper limit of the 100% modulus of the adhesive sheet is not particularly limited, and it is, for example, 0.80 N/mm ² , 0.50 N/mm ² , or 0.30 N/mm ² .

The 500% modulus of the adhesive sheet is, for example, 0.05 N/mm ² or more. The 500% modulus of the adhesive sheet refers to a property expressed by a value obtained by: imparting 500% elongation to the adhesive sheet by a tensile force in one direction, and applying the stress generated to the adhesive sheet at this time (tensile stress) divided by the initial cross-sectional area of the adhesive sheet. The 500% modulus of the adhesive sheet can be evaluated as described above for the 100% modulus of the adhesive sheet.

The 500% modulus of the adhesive sheet is preferably 0.10N/ ^mm2 or more, preferably 0.20N/ ^mm2 or more, more preferably 0.30N/ ^mm2 or more, especially 0.35N/ ^mm2 or more, and can be 0.60 N/mm ² or more, and may be 1.0 N/mm ² or more. The upper limit of the 500% modulus of the adhesive sheet is not particularly limited, but is, for example, 10 N/mm ² .

The 700% modulus of the adhesive sheet is, for example, 0.07 N/mm ² or more. The 700% modulus of the adhesive sheet refers to a property expressed by a value obtained by: imparting an elongation of 700% to the adhesive sheet by a tensile force in one direction, and applying the stress generated to the adhesive sheet at this time (tensile stress) divided by the initial cross-sectional area of the adhesive sheet. The 700% modulus of the adhesive sheet can be evaluated as described above for the 100% modulus of the adhesive sheet.

The 700% modulus of the adhesive sheet should be 0.10N/ ^mm2 or more, preferably 0.20N/ ^mm2 or more, more preferably 0.30N/ ^mm2 or more, especially 0.40N/ ^mm2 or more, or 0.60 N/mm ² or more. The upper limit of the 700% modulus of the adhesive sheet is not particularly limited, but is, for example, 10 N/mm ² .

The 1000% modulus of the adhesive sheet is, for example, 0.15 N/mm ² or more. The 1000% modulus of the adhesive sheet refers to a property expressed by a value obtained in the following way: 1000% elongation is imparted to the adhesive sheet by a tensile force in one direction, and the stress generated in the adhesive sheet at this time is changed. (tensile stress) divided by the initial cross-sectional area of the adhesive sheet. The 1000% modulus of the adhesive sheet can be evaluated as described above for the 100% modulus of the adhesive sheet.

The 1000% modulus of the adhesive sheet is preferably 0.20N/mm ² or more, more preferably 0.40N/mm ² or more, more preferably 0.50N/mm ² or more, especially 0.60N/mm ² or more. The upper limit of the 1000% modulus of the adhesive sheet is not particularly limited, but is, for example, 10 N/mm ² .

The glass transition temperature (Tg) of the adhesive sheet is preferably 5°C or lower, preferably -20°C or lower, and more preferably -25°C or lower. When the Tg of the adhesive sheet is within the above-mentioned range, the adhesive sheet is less likely to be hardened, and a flexible image display device having excellent stress relaxation properties can be realized.

The total light transmittance of the adhesive sheet in the visible light wavelength region (in compliance with JIS K7136:2000) is preferably 85% or more, more preferably 90% or more.

The adhesives constituting the adhesive sheet include acrylic adhesives, rubber-based adhesives, vinyl alkyl ether-based adhesives, polysiloxane-based adhesives, polyester-based adhesives, polyamide-based adhesives, urethane-based adhesives Ester-based adhesives, fluorine-based adhesives, epoxy-based adhesives, polyether-based adhesives, etc. Moreover, the adhesive which comprises an adhesive sheet can be used individually or in combination of 2 or more types. However, from the viewpoints of transparency, processability, durability, adhesion, etc., it is preferable to use an acrylic adhesive (composition) containing a (meth)acrylic polymer alone. In other words, the adhesive sheet preferably contains a (meth)acrylic polymer.

[(Meth)acrylic polymer] When an acrylic adhesive is used as the adhesive composition, it is preferable to contain a (meth)acrylic monomer having a linear or branched alkyl group having 1 to 30 carbon atoms as a monomer unit (meth) Acrylic polymer. In addition, in this specification, "(meth)acrylic polymer" refers to acrylic polymer and/or methacrylic polymer, and "(meth)acrylate" refers to acrylate and/or methyl ester Acrylate.

Specific examples of the (meth)acrylic monomer having a linear or branched C1-C30 alkyl group constituting the main skeleton of the (meth)acrylic polymer include methyl (meth)acrylate. ester, ethyl (meth)acrylate, n-butyl (meth)acrylate, tertiary butyl (meth)acrylate, tertiary butyl (meth)acrylate, isobutyl (meth)acrylate, (meth)acrylate base) n-amyl acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethyl (meth)acrylate Hexyl ester, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, (meth)acrylate base) isodecyl acrylate, n-dodecyl (meth)acrylate (lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, etc., among which A straight-chain or branched (meth)acrylic monomer having an alkyl group of 6 to 30 carbon atoms (hereinafter sometimes referred to as "(meth)acrylic monomer having a long-chain alkyl group") is preferable, N-dodecyl (meth)acrylate (lauryl (meth)acrylate) is more preferred. By using a (meth)acrylic monomer having a long-chain alkyl group, the entanglement of the polymer can be reduced and the polymer can be easily deformed to a small strain. From the point of view of adhesion at low temperature, it is also suitable to use a (meth)acrylic monomer whose glass transition temperature (Tg) of the homopolymer is -70~-20°C, among which 2-ethyl acrylate is used. Hexyl esters are preferred. (meth)acrylic-type monomers can be used 1 type or 2 or more types.

The (meth)acrylic monomer system having a linear or branched C1-30 alkyl group constitutes the main component of the total monomers of the (meth)acrylic polymer. Here, the main component refers to the (meth)acrylic monomer having a linear or branched C1-30 alkyl group among the total monomers constituting the (meth)acrylic polymer. 50 to 100% by weight, preferably 80 to 100% by weight, more preferably 90 to 99.9% by weight, particularly preferably 94 to 99.9% by weight.

The monomer component constituting the (meth)acrylic polymer may contain a copolymerizable monomer in addition to the (meth)acrylic monomer having a linear or branched C1-30 alkyl group. body (comonomer). Moreover, a comonomer can be used individually or in combination of 2 or more types.

The copolymerizable monomer is not particularly limited, but is preferably a hydroxyl-containing monomer having a reactive functional group. By using a hydroxyl-containing monomer, there exists a tendency for the adhesive sheet excellent in adhesiveness to be obtained. The hydroxyl group-containing monomer is, for example, a compound containing a hydroxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group and a vinyl group.

Specific examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate and other hydroxyalkyl (meth)acrylate or (4-hydroxyl methylcyclohexyl)-methacrylate, etc. From the viewpoint of durability or adhesion, among the hydroxyl group-containing monomers, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are also suitable. Moreover, 1 type or 2 or more types of hydroxyl-containing monomers can be used.

The comonomer may contain monomers such as carboxyl group-containing monomers, amine group-containing monomers, and amide group-containing monomers having reactive functional groups. It is preferable to use these monomers from the viewpoint of the adhesion in humidified or high temperature environments.

When an acrylic adhesive is used as the adhesive composition, the adhesive composition may contain a (meth)acrylic polymer containing a carboxyl group-containing monomer having a reactive functional group as a monomer unit. By using the carboxyl group-containing monomer, there is a tendency to obtain an adhesive sheet having excellent adhesion in a humidified or high-temperature environment. The carboxyl group-containing monomer system is a compound containing a carboxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group and a vinyl group.

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

When an acrylic adhesive is used as the adhesive composition, the adhesive composition may contain a (meth)acrylic polymer containing an amine group-containing monomer having a reactive functional group as a monomer unit. By using the amine group-containing monomer, there is a tendency to obtain a pressure-sensitive adhesive sheet having excellent adhesion in a humidified or high-temperature environment. The amine group-containing monomer system is a compound containing an amine group and a polymerizable unsaturated double bond such as a (meth)acryloyl group and a vinyl group in its structure.

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

When an acrylic adhesive is used as the adhesive composition, the adhesive composition may contain a (meth)acrylic polymer containing an amide group-containing monomer having a reactive functional group as a monomer unit. By using an amide group-containing monomer, there is a tendency to obtain an adhesive sheet excellent in adhesiveness. The amide group-containing monomer system is a compound containing an amide group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group and 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,N-diethyl(meth)acrylamide, and N,N-diethyl(meth)acrylamide. -Isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methylol(methyl)acrylamide base) acrylamide, N-methylol-N-propane (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaptomethyl (meth) acrylamide acrylamide-based monomers such as acrylamide, mercaptoethyl (meth) acrylamide, etc.; N-(meth) acryl morpholin, N-(meth) acryl piperidine, N -N-acryloyl heterocyclic monomers such as (meth)acryloyl pyrrolidine; N-vinyl lactamide-containing monomers such as N-vinyl pyrrolidone, N-vinyl-ε-caprolactam, etc. body etc.

In addition, polyfunctional monomers are mentioned as comonomers. If a polyfunctional monomer is contained, the crosslinking effect can be obtained by polymerization, and the gel fraction can be easily adjusted or the cohesive force can be improved. Therefore, the cutting of the adhesive sheet becomes easy, and it becomes easy to improve the workability. In addition, the peeling of the adhesive sheet due to cohesive failure can be further prevented. The polyfunctional monomer is not particularly limited, and examples thereof include hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, ( Poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentylerythritol di(meth)acrylate, new Pentaerythritol tri(meth)acrylate, Dipivalerythritol hexa(meth)acrylate, Trimethylolpropane tri(meth)acrylate, Tetramethylolmethane tri(meth)acrylate, ( Polyfunctional (meth)acrylates such as allyl meth)acrylate, vinyl (meth)acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate, or divinylbenzene, etc. The polyfunctional (meth)acrylates are preferably 1,6-hexanediol diacrylate and dipivalerythritol hexa(meth)acrylate. Moreover, a polyfunctional monomer can be used individually or in combination of 2 or more types.

Among the monomer units constituting the (meth)acrylic polymer, the blending ratio (total amount) of the monomer having a reactive functional group and the polyfunctional monomer is in the total monomer constituting the (meth)acrylic polymer Among them, it is preferably 20% by weight or less, more preferably 10% by weight or less, more preferably 0.01 to 8% by weight, particularly preferably 0.01 to 5% by weight, and most preferably 0.05 to 3% by weight. When it exceeds 20 weight%, since the crosslinking point increases and the adhesive agent (sheet) loses flexibility, there exists a tendency for stress relaxation property to become poor.

When an acrylic adhesive is used as the adhesive composition, as a monomer unit, in addition to the monomer having a reactive functional group and a polyfunctional monomer, other monomers may be introduced within a range that does not impair the effects of the present invention. comonomer.

Other comonomers can be, for example, alkoxyalkyl (meth)acrylate [such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, (meth)acrylic acid) Methoxytriethylene glycol, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, (meth)acrylic acid 4-ethoxybutyl ester, etc.]; epoxy group-containing monomers [such as glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, etc.]; sulfonic acid group-containing monomers [such as ethylene Sodium sulfonate, etc.]; phosphoric acid group-containing monomers; (meth)acrylates with alicyclic hydrocarbon groups [such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, (meth)acrylic acid) (meth)acrylates with aromatic hydrocarbon groups [such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc.]; vinyl esters [such as vinyl acetate, vinyl propionate, etc.]; aromatic vinyl compounds [such as styrene, vinyltoluene, etc.]; olefins or dienes [such as ethylene, propylene, butadiene, isoprene, isobutylene, etc.]; vinyl ethers [eg vinyl alkyl ether, etc.]; vinyl chloride, etc.

The blending ratio of other comonomers is not particularly limited, but in the total monomers constituting the (meth)acrylic polymer, it is preferably 30% by weight or less, more preferably 10% by weight or less, and more preferably not contained. When it exceeds 30 weight%, especially when the thing other than a (meth)acrylic-type monomer is used, the reaction point of an adhesive sheet and other layers (film, base material) will become few, and there exists a tendency for adhesive force to fall.

The adhesive sheet is formed from an adhesive composition, and the adhesive composition can also be an adhesive composition in any form, such as emulsion type, solvent type (solution type), active energy ray hardening type, hot melt type (hot melt type), etc. Among them, the above-mentioned adhesive composition is preferably a solvent-based adhesive composition or an active energy ray-curable adhesive composition.

The solvent-based adhesive composition preferably includes an adhesive composition containing a (meth)acrylic polymer as an essential component. The active energy ray-curable adhesive composition preferably includes, as an essential component, a mixture (monomer mixture) of monomer components constituting the (meth)acrylic polymer or a partial polymer thereof. In addition, the "partial polymer" means a composition in which one or two or more of the monomer components contained in the monomer mixture are partially polymerized. The "monomer mixture" includes only one monomer component.

In particular, the adhesive composition is preferably a mixture ( A monomer mixture) or a partial polymer thereof as an essential component of an active energy ray-curable adhesive composition.

The (meth)acrylic polymer can be obtained by polymerizing monomer components. More specifically, the monomer component, or the monomer mixture or a partial polymer thereof can be polymerized by a known and conventional method. The polymerization method includes, for example, solution polymerization, emulsion polymerization, bulk polymerization, polymerization by heat or active energy ray irradiation (thermal polymerization, active energy ray polymerization), and the like. Among them, from the viewpoints of transparency, water resistance, cost, and the like, solution polymerization and active energy ray polymerization are preferred. In addition, from the viewpoint of suppressing the inhibition of polymerization by oxygen, the polymerization is preferably performed without contacting with oxygen. For example, it is preferable to carry out the polymerization in a nitrogen atmosphere, or to carry out the polymerization by blocking oxygen with a release film (separator). The obtained (meth)acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

Examples of active energy rays to be irradiated during active energy ray polymerization (photopolymerization) include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, and ultraviolet rays, among which ultraviolet rays are particularly preferred. The irradiation energy, irradiation time, irradiation method, etc. of the active energy rays are not particularly limited, and the photopolymerization initiator may be activated to promote the reaction of the monomer components.

When performing solution polymerization, various general solvents can be used. Examples of the 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, methylcyclohexane, etc. Alicyclic hydrocarbons; organic solvents such as methyl ethyl ketone, methyl isobutyl ketone and other ketones. Moreover, a solvent may be used individually or in combination of 2 or more types.

When performing the polymerization, a polymerization initiator such as a photopolymerization initiator (photoinitiator) or a thermal polymerization initiator may also be used according to the type of the polymerization reaction. Moreover, a polymerization initiator can be used individually or in combination of 2 or more types.

系光聚合引發劑。The photopolymerization initiator is not particularly limited, and examples thereof include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, and aromatic sulfonyl chloride-based photopolymerization initiators. , Photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzyl-based photopolymerization initiator, benzophenone-based photopolymerization initiator, ketal-based photopolymerization initiator, 9-oxysulfur 𠮿

It is a photopolymerization initiator.

系光聚合引發劑可舉例如9-氧硫𠮿

、2-氯9-氧硫𠮿

、2-甲基9-氧硫𠮿

、2,4-二甲基9-氧硫𠮿

、異丙基9-氧硫𠮿

、2,4-二異丙基9-氧硫𠮿

、十二烷基9-氧硫𠮿

等。Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy base-1,2-diphenylethan-1-one, anisole methyl ether, etc. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4 -Phenoxydichloroacetophenone, 4-(tertiary butyl)dichloroacetophenone, etc. As an α-ketoalcohol-based photopolymerization initiator, 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)benzene]-2-methylpropan-1-one, etc. are mentioned, for example. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride and the like. As the photoactive oxime-based photopolymerization initiator, 1-benzene-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime etc. are mentioned, for example. As a benzoin type photoinitiator, benzoin etc. are mentioned, for example. As a benzyl-type photoinitiator, a benzyl group etc. are mentioned, for example. For example, benzophenone-based photopolymerization initiators include benzophenone, benzoic acid, 3,3'-dimethyl-4-methoxy benzophenone, polyvinyl benzophenone, α-Hydroxycyclohexyl phenyl ketone, etc. As a ketal type photoinitiator, benzyl dimethyl ketal etc. are mentioned, for example. 9-oxysulfur 𠮿

The photopolymerization initiator may, for example, be 9-oxothio?

, 2-chloro-9-oxysulfur

, 2-methyl 9-oxothio

, 2,4-dimethyl 9-oxothio

, isopropyl 9-oxothioate

, 2,4-diisopropyl 9-oxothio

, dodecyl 9-oxysulfur

Wait.

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

Examples of polymerization initiators used in solution polymerization include azo-based polymerization initiators, peroxide-based polymerization initiators (for example, dibenzyl peroxide, tertiary butyl peroxymaleate, etc.), redox-based polymerization initiators, and the like. Polymerization initiators, etc. Among them, the azo-based polymerization initiator disclosed in Japanese Patent Laid-Open No. 2002-69411 is preferable. The above-mentioned azo-based polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2,2'-azobis(2) -methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanovaleric acid, etc.

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

In addition, polyfunctional monomers (polyfunctional (meth)acrylates) used as comonomers can also be used in solvent-based or active energy ray-curable adhesive compositions, but for example, when polyfunctional monomers (polyfunctional (meth)acrylates) are used When a functional (meth)acrylate) and a photopolymerization initiator are mixed in a solvent-based adhesive composition for use, active energy ray curing is performed after thermal drying.

The weight average molecular weight (Mw) of the (meth)acrylic polymer used in the solvent-based adhesive composition is usually in the range of 1 million to 2 million. If considering durability, especially considering heat resistance, it should be 1.2 million to 2 million, and 1.4 million to 1.8 million is better. If the weight average molecular weight is less than 1 million, when the polymer chains are cross-linked to each other in order to ensure durability, the number of cross-linking points will increase compared to those with a weight average molecular weight of 1 million or more, and the adhesive (sheet) will be lost. Due to its flexibility, the strain on the outer side (convex side) and the inner side (concave side) of the curvature that occurs between the layers (films) constituting the image display device during winding cannot be relieved, and each layer is prone to breakage. If the weight-average molecular weight is more than 2.5 million, a large amount of diluting solvent is required to adjust the viscosity suitable for coating, which increases the cost, which is unfavorable. Furthermore, the polymer chains of the obtained (meth)acrylic polymer are not connected to each other. Since the entanglement becomes complicated, the flexibility is deteriorated, and each layer (film) is likely to be broken during winding. In addition, the weight average molecular weight (Mw) means the value calculated by the polystyrene conversion measured by GPC (gel permeation chromatography; Gel Permeation Chromatography).

[(meth)acrylic oligomer] The (meth)acrylic oligomer may be contained in the adhesive composition. The (meth)acrylic oligomer preferably has a smaller weight average molecular weight (Mw) than the (meth)acrylic polymer. By using the (meth)acrylic oligomer, the (meth)acrylic oligomer can be ) Acrylic oligomers are present between (meth)acrylic polymers to reduce the entanglement of (meth)acrylic polymers, thereby making it easy to deform to small strains.

Examples of monomers constituting the (meth)acrylic oligomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, Butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, tertiary butyl (meth)acrylate, amyl (meth)acrylate, (meth)acrylic acid Isoamyl, 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, undecyl (meth)acrylate, dodecyl (meth)acrylate Such alkyl (meth)acrylates; (meth)acrylic acid and alicyclic esters of family alcohols; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylates obtained from terpene derivative alcohols, and the like. These (meth)acrylates may be used alone or in combination of two or more.

The (meth)acrylic oligomer preferably contains the following acrylic monomers having a relatively bulky structure as monomer units: isobutyl (meth)acrylate or tertiary butyl (meth)acrylate This kind of alkyl group has a branched chain structure (meth) acrylic acid alkyl ester; (meth)acrylates having a cyclic structure such as aryl (meth)acrylates such as phenyl (meth)acrylate or benzyl (meth)acrylate. By making the (meth)acrylic oligomer have such a bulky structure, the adhesiveness of the adhesive sheet tends to be further improved. In particular, from the viewpoint of a bulky structure, those having a cyclic structure are highly effective, and those containing polycyclic rings are more effective. In the synthesis of (meth)acrylic oligomers or the production of adhesive sheets, it is not easy to inhibit polymerization when ultraviolet rays are used. From this point of view, those having a saturated bond are suitable, and those having a branched structure with an alkyl group (methyl) are suitable. (meth)acrylic acid alkyl ester or ester with alicyclic alcohol is used as the monomer constituting the (meth)acrylic oligomer.

From this viewpoint, suitable (meth)acrylic oligomers include, for example, copolymers of butyl acrylate (BA), methyl acrylate (MA) and acrylic acid (AA), cyclohexyl methacrylate. Copolymer of ester (CHMA) and isobutyl methacrylate (IBMA), copolymer of cyclohexyl methacrylate (CHMA) and isobornyl methacrylate (IBXMA), cyclohexyl methacrylate (CHMA) Copolymer with Acrylomorphine (ACMO), Copolymer of Cyclohexyl Methacrylate (CHMA) and Diethyl Acrylamide (DEAA), 1-Adamantyl Acrylate (ADA) and Methacrylic Acid Copolymer of methyl ester (MMA), copolymer of dicyclopentyl methacrylate (DCPMA) and isobornyl methacrylate (IBXMA), dicyclopentyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isocampylate acrylate (IBXA), copolymer of cyclopentyl methacrylate (DCPMA) and methyl methacrylate (MMA), dicyclopentyl acrylate ( DCPA), 1-adamantyl methacrylate (ADMA), each homopolymer of 1-adamantyl acrylate (ADA), etc.

The polymerization method of the (meth)acrylic oligomer is the same as that of the (meth)acrylic polymer, and examples include solution polymerization, emulsion polymerization, bulk polymerization, emulsion polymerization, polymerization by heat or active energy ray irradiation ( thermal polymerization, active energy ray polymerization), etc. Among them, from the viewpoints of transparency, water resistance, cost, and the like, solution polymerization and active energy ray polymerization are preferred. The obtained (meth)acrylic oligomer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

The (meth)acrylic oligomer can be used for a solvent-based adhesive composition or an active energy ray-curable adhesive composition in the same manner as the (meth)acrylic polymer. For example, as an active energy ray-curable adhesive composition, a (meth)acrylic oligomer may be further mixed into a mixture (monomer mixture) of monomer components constituting a (meth)acrylic polymer or a partial polymer thereof. polymer to use. When the (meth)acrylic oligomer is dissolved in the solvent, it can be thermally dried to volatilize the solvent in the adhesive composition, and then the active energy ray hardening can be completed to obtain an adhesive sheet.

The weight average molecular weight (Mw) of the (meth)acrylic oligomer used in the solvent-based adhesive composition is preferably 1,000 or more, preferably 2,000 or more, 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, preferably 15,000 or less, more preferably 10,000 or less, and particularly preferably 7,000 or less. By adjusting the weight-average molecular weight (Mw) of the (meth)acrylic oligomer within the above range, for example, when used together with a (meth)acrylic polymer, the (meth)acrylic oligomer exists Between the (meth)acrylic polymers, the entanglement of the (meth)acrylic polymers will be reduced, and the adhesive sheet is easily deformed by small strains, which can reduce the application to other layers constituting the image display device. tendency to strain. Thereby, there exists a tendency for the crack of each layer, peeling between an adhesive sheet and another layer, etc. to be suppressed more. In addition, the weight-average molecular weight (Mw) of the (meth)acrylic oligomer is the same as that of the (meth)acrylic polymer, which is measured by GPC (gel permeation chromatography; Gel Permeation Chromatography) and measured by polyphenylene The value calculated in ethylene conversion.

When the (meth)acrylic oligomer is used in the adhesive composition, the blending amount thereof is not particularly limited, but is preferably 70 parts by weight or less, more preferably 70 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic polymer. 1 to 70 parts by weight, more preferably 2 to 50 parts by weight, still more preferably 3 to 40 parts by weight, and more preferably 20 parts by weight or less. By adjusting the blending amount of the (meth)acrylic oligomer within the above range, the (meth)acrylic oligomer is appropriately present between the (meth)acrylic polymers, so that (meth) The entanglement of the acrylic polymer is reduced, and the adhesive sheet tends to deform easily to small strains. Thereby, the strain applied to the other layers constituting the image display device can be reduced, and the tendency of cracking of each layer, peeling of the adhesive sheet and other layers, etc. can be suppressed.

[Crosslinking agent] A crosslinking agent may be contained in the adhesive composition. As a crosslinking agent, an organic type crosslinking agent or a polyfunctional metal chelate compound can be used in any of a solvent type or an active energy ray hardening type adhesive composition. The organic-based crosslinking agent includes an isocyanate-based crosslinking agent, a peroxide-based crosslinking agent, an epoxy-based crosslinking agent, an imine-based crosslinking agent, and the like. The polyfunctional metal chelate is a covalent bond or a coordinate bond between a polyvalent metal and an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, and the like. Examples of atoms that can be covalently or coordinately bonded in the organic compound include oxygen atoms and the like, and examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds, and the like. In the case of a solvent-based adhesive composition, a peroxide-based crosslinking agent or an isocyanate crosslinking agent is suitable. The peroxide-based crosslinking agent crosslinks the side chains of the (meth)acrylic polymer, for example, by removing hydrogen from the side chains of the (meth)acrylic polymer to generate free radicals Therefore, compared with the case of using an isocyanate-based cross-linking agent (such as a multifunctional isocyanate-based cross-linking agent) for cross-linking, the cross-linking state is relatively gentle, and it can maintain its ease of small strain deformation. while improving cohesion. Thereby, the cracking of each layer constituting the image display device, the peeling of the adhesive sheet and other layers, etc. tend to be suppressed. An isocyanate-based crosslinking agent (especially a trifunctional isocyanate-based crosslinking agent) is preferable from the viewpoint of durability. In addition, a peroxide-based crosslinking agent and an isocyanate-based crosslinking agent (especially a difunctional isocyanate-based crosslinking agent) are preferable from the viewpoint of windability. Peroxide-based cross-linking agents or difunctional isocyanate-based cross-linking agents will both form soft two-dimensional cross-links, while tri-functional isocyanate-based cross-linking agents will form stronger three-dimensional cross-links. Two-dimensional crosslinks, which are softer crosslinks, are advantageous when coiling. However, if only two-dimensional crosslinking is used, the durability may be poor and peeling is likely to occur. Therefore, hybrid crosslinking of two-dimensional crosslinking and three-dimensional crosslinking is preferable. Therefore, it is also preferable to use a trifunctional isocyanate-based crosslinking agent, a peroxide-based crosslinking agent or a difunctional isocyanate-based crosslinking agent in combination. In addition, in the active energy ray-curable adhesive composition, it is preferable to obtain a crosslinking effect by polymerization using a polyfunctional monomer from the viewpoint of productivity or thick film coating. However, the above-mentioned crosslinking agent may be used, or it may be used in combination with a multifunctional monomer. For example, a crosslinking agent may be mixed with a mixture of monomer components constituting a (meth)acrylic polymer (monomer mixture) or a partial polymer thereof, and before and after the adhesive composition is cured with active energy rays, The reaction of the crosslinking agent is completed by thermal drying.

The usage amount of the crosslinking agent is, for example, preferably 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer.

When the peroxide-based crosslinking agent is used alone, the blending amount of the peroxide-based crosslinking agent is preferably 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer. share. Within the above range, the adhesive sheet tends to increase the cohesive force sufficiently while maintaining the ease of deformation with respect to small strains, thereby improving the durability.

When the isocyanate crosslinking agent is used alone, the blending amount of the isocyanate crosslinking agent is preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer.

When a peroxide-based crosslinking agent and an isocyanate-based crosslinking agent are used together, the weight ratio of the peroxide-based crosslinking agent to the isocyanate-based crosslinking agent (peroxide-based crosslinking agent/isocyanate-based crosslinking agent) is lower than The limit is preferably 0.02 or more, preferably 1 or more, and more preferably 5 or more. The upper limit of the weight ratio is preferably 500 or less, preferably 100 or less, more preferably 50 or less, and even more preferably 40 or less. Within the above range, the adhesive sheet tends to sufficiently improve the cohesive force while maintaining the ease of deformation with respect to small strains.

When using a multifunctional monomer (especially a multifunctional (meth)acrylate) as a crosslinking agent, the blending amount of the multifunctional monomer is preferably 0.1 to 1 weight part relative to 100 parts by weight of the (meth)acrylic polymer parts, preferably 0.2 to 0.5 parts by weight.

[additive] In addition, the adhesive composition can also contain other well-known additives, such as various silane coupling agents, polyether compounds of polyalkylene glycols such as polypropylene glycol, powders such as colorants, pigments, etc., can be appropriately added according to the application. Dyes, surfactants, plasticizers, tackifiers, surface lubricants, levelers, softeners, antioxidants, antiaging agents, light stabilizers, UV absorbers, polymerization inhibitors, antistatic agents (ion (alkali metal salts of chemical compounds or ionic liquids, ionic solids, etc.), inorganic or organic fillers, metal powders, particles, foils, etc. A redox system to which a reducing agent is added can also be used within a controllable range.

The preparation method of the adhesive composition is not particularly limited, and a well-known method can be used. For example, as mentioned above, the solvent-based acrylic adhesive composition is prepared by adding (meth)acrylic polymer, components (such as (meth)acrylic oligomer, crosslinking agent, silane coupling agent, solvent, additives, etc.) are mixed and produced. As mentioned above, the active energy ray-curable acrylic adhesive composition is prepared by combining a monomer mixture or a partial polymer thereof, and components (such as photopolymerization initiators, multifunctional monomers, (meth)acrylic acid) added according to requirements. oligomers, crosslinking agents, silane coupling agents, solvents, additives, etc.) are mixed to produce.

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

The polymerization rate of the partial polymer can be obtained in the following manner. A part of the polymer was sampled as a sample. The sample was precisely weighed to obtain its weight, and this was taken as the "weight of the partial polymer before drying". Next, the sample was dried at 130° C. for 2 hours, and the weight of the dried sample was precisely weighed to obtain the weight, which was taken as the “weight of the partial polymer after drying”. Then, from the "weight of the partial polymer before drying" and the "weight of the partial polymer after drying", the weight of the sample that was reduced by drying at 130°C for 2 hours was obtained, and this was taken as the "weight loss" (volatile part, unreacted monomer weight). From the obtained "weight of the partial polymer before drying" and "weight loss", the polymerization rate (% by weight) of the partial polymer of the monomer component was obtained by the following formula. The polymerization rate of the partial polymer of the monomer component (% by weight)=1-(weight loss)/(weight of the partial polymer before drying)]×100

[Formation of adhesive sheet] The method of forming an adhesive sheet may include, for example, a method of applying a solvent-based adhesive composition to a separation member (peeling film) that has undergone peeling treatment, and drying and removing the polymerization solvent to form an adhesive sheet; polarizing films, etc. A method of coating a solvent-based adhesive composition, drying and removing the polymerization solvent, etc. to form an adhesive sheet on a polarizing film, etc. A method of forming by irradiating active energy rays, etc. In addition, heating and drying may be performed in addition to active energy ray irradiation as required. When coating the adhesive composition, other solvents other than the polymerization solvent may be newly added.

Polysiloxane release liners should be used for the separation parts that have been peeled off. When the adhesive composition is coated on the backing material and dried to form an adhesive sheet, the method of drying the adhesive may be an appropriate method depending on the purpose. A method of drying the above-mentioned coating film by heating is preferably employed. The heating and drying temperature is preferably 40 to 200°C, more preferably 50 to 180°C, and particularly preferably 70 to 170°C when preparing an acrylic adhesive using a (meth)acrylic polymer, for example. By setting the heating temperature to the above range, there is a tendency to obtain an adhesive sheet having excellent adhesive properties.

A suitable drying time can be adopted. The above drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, particularly preferably 10 seconds to 5 minutes, when preparing an acrylic adhesive using a (meth)acrylic polymer, for example.

Various methods can be used for the coating method of the adhesive composition. Specifically, for example, roll coating, touch roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, and air knife coating may be mentioned. Methods such as coating, curtain coating, lip coating, and extrusion coating using a die coater or the like are used.

The thickness of the adhesive sheet is preferably 1~200µm, more preferably 5~150µm, and more preferably 10~100µm. The adhesive sheet may have a single layer or a laminated structure. Within the above-mentioned range, the winding of the flexible image display device is not hindered, and it is also favorable from the viewpoint of adhesion (holding resistance).

As a method of producing the adhesive sheet of the present embodiment, the following methods are exemplified.

First, the method of using a solvent type adhesive composition (solvent type 1st method - 4th method) is demonstrated. The 1st method of a solvent type uses the (meth)acrylic-type polymer which copolymerized the (meth)acrylic-type monomer which has a long-chain alkyl group. Here, in the first method of the solvent type, the (meth)acrylic monomer having a long-chain alkyl group is preferably 40% by weight or more and 99% by weight with respect to the total monomers.

The solvent-based second method uses an isocyanate crosslinking agent alone as a crosslinking agent, and adds 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic polymer.

The third method of solvent type is to use a peroxide-based crosslinking agent and an isocyanate-based crosslinking agent as a crosslinking agent, and the weight ratio of the peroxide-based crosslinking agent to the isocyanate-based crosslinking agent (peroxide-based crosslinking agent) is used. Crosslinking agent/isocyanate type crosslinking agent) shall be 0.02 or more and 500 or less, and the addition amount of a peroxide type crosslinking agent shall be 0.1 weight part or more with respect to 100 weight part of (meth)acrylic-type polymers.

The fourth method of the solvent type is based on the first method to the third method of the solvent type, with respect to 100 parts by weight of the (meth)acrylic polymer, 1 part by weight or more and 70 parts by weight or less (methyl) is further added as described above. base) acrylic oligomers.

Next, the method of using the active energy ray hardening type adhesive composition (the first method to the third method of the active energy ray hardening type) will be described. The first method of the active energy ray hardening type uses a (meth)acrylic monomer having a long-chain alkyl group as a main component and a monomer having an alkyl group or a functional group having 1 to 5 carbon atoms. The mixture (monomer mixture), or a partial polymer of the mixture, is polymerized with polyfunctional monomers.

The second method of the active energy ray hardening type uses the first method of the active energy ray hardening type as the (meth)acrylic monomer having a long-chain alkyl group having an alkyl group having 10 or more and 30 or less carbon atoms. A mixture (monomer mixture) of a (meth)acrylic monomer and a (meth)acrylic monomer having an alkyl group with a carbon number of 6 or more and 9 or less, or a partial polymer of the mixture.

The third method of the active energy ray curing type is in the first method of the active energy ray curing type, using a polyfunctional (meth)acrylate as a polyfunctional monomer, and relative to 100 weight of the (meth)acrylic polymer parts, add 0.1 part by weight or more and 1 part by weight or less.

Here, in the first method to the third method of the active energy ray curing type, it is preferable to set the content of the (meth)acrylic monomer having a long-chain alkyl group to 50% by weight or more in the total monomers, and to set the 60 weight % or more is preferable, on the other hand, 100 weight % or less is preferable, and 99 weight % or less is preferable. In addition, when using a mixture of a (meth)acrylic monomer having an alkyl group having 10 to 30 carbon atoms and a (meth)acrylic monomer having an alkyl group having 6 to 9 carbon atoms, the mixing ratio It is preferable to set ((meth)acrylic monomer having an alkyl group having 10 or more carbon atoms and 30 or less): ((meth)acrylic monomer having an alkyl group having 6 to 9 carbon atoms)=40 : 60~90: 10.

(Embodiment of flexible image display device and laminate) As shown in FIG. 1 , the flexible image display device 100 of the present embodiment includes a laminate 10 and an image display panel 3 , and the laminate 10 is disposed on the viewing side with respect to the image display panel 3 .

[laminated body] The laminated body 10 is a member which can be used for the flexible image display device 100 , and includes the above-mentioned adhesive sheet 1 and the base material 2 . The base material 2 supports the adhesive sheet 1 , for example, is in contact with the adhesive sheet 1 . The base material 2 may not be in direct contact with the adhesive sheet 1 . The laminated body 10 is attached to the image display panel 3 via the adhesive sheet 1 . The layered body 10 does not include, for example, a polarizing film to be described later.

[Substrate] The base material 2 can also function as a protective film that protects members included in the laminate 10 . In FIG. 1, since the base material 2 is located in the outermost side of the laminated body 10, it can also function as a viewing window, for example.

The base material 2 is made of transparent resin, for example. Examples of the transparent resin include cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polyethylene and polypropylene, polyester-based resins, (meth)acrylic-based resins, and polyimide-based resins.

The thickness of the substrate 2 is, for example, 5 to 60 µm, preferably 10 to 40 µm, and more preferably 10 to 30 µm. If the thickness of the base material 2 is within the above-mentioned range, the base material 2 is less likely to hinder the winding of the flexible image display device. Surface treatments such as anti-glare, anti-reflection, and anti-static can also be applied to the substrate 2 .

[Image Display Panel] The image display panel 3 constitutes a display portion of the flexible image display device 100 . In the flexible image display device 100, the display portion constituted by the image display panel 3 can be rolled. The image display panel 3 is typically an organic EL display panel. A touch sensor may also be incorporated into the image display panel 3 . When the touch sensor is embedded in the image display panel 3 , the flexible image display device 100 is a so-called built-in flexible image display device.

In the flexible image display device 100 , the ratio of the area of the portion of the display portion that can be rolled up by the image display panel 3 to the area of the entire display portion is, for example, 50% or more and 90% or less.

[Transparent conductive layer] The laminated body 10 may further include a transparent conductive layer constituting a touch sensor. The transparent conductive layer can be located between the adhesive sheet 1 and the substrate 2 , or between the adhesive sheet 1 and the image display panel 3 . The transparent conductive layer is configured to be flexible, for example.

The constituent material of the transparent conductive layer is not particularly limited, and can be 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 metal or metal oxide in the group, or an organic conductive polymer such as polythiophene. The metal oxide may further include metal atoms shown in the above groups as required. For example, indium oxide (ITO) containing tin oxide, tin oxide containing antimony, etc. are preferably used, and ITO is particularly preferably used. ITO preferably contains 80-99 wt % of indium oxide and 1-20 wt % of tin oxide.

ITO includes crystalline ITO and amorphous (amorphous) ITO. Crystalline ITO can be obtained by increasing the temperature at the time of sputtering, or by further heating amorphous ITO.

The thickness of the transparent conductive layer is preferably 0.005~10µm, preferably 0.01~3µm, more preferably 0.01~1µm. If the thickness of the transparent conductive layer is less than 0.005 µm, there is a tendency that the change in the resistance value of the transparent conductive layer becomes large. On the other hand, if it exceeds 10 µm, the productivity of the transparent conductive layer will decrease, the cost will increase, and the optical properties will tend to decrease.

The total light transmittance of the transparent conductive layer is preferably more than 80%, preferably more than 85%, more preferably more than 90%.

The density of the transparent conductive layer is preferably 1.0-10.5 g/cm ³ , preferably 1.3-3.0 g/cm ³ .

The surface resistance of the transparent conductive layer is preferably 0.1~1000Ω/□, preferably 0.5~500Ω/□, and more preferably 1~250Ω/□.

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

A primer layer, an anti-oligomer layer, etc. can also be further provided between the transparent conductive layer and the substrate 2 according to requirements.

[Conductive layer (antistatic layer)] The layered body 10 may further have a conductive layer (conductive layer, antistatic layer). The layered body 10 can be formed with a very thin thickness, and thus is easily damaged by weak static electricity generated in the manufacturing process and the like. When the layered body 10 has a conductive layer, the load due to static electricity in the manufacturing process and the like tends to be greatly reduced.

During the winding operation of the flexible image display device 100 including the laminate 10, static electricity may be generated in the winding portion. When the layered body 10 has a conductive layer, there is a tendency that static electricity generated by winding can be quickly removed.

The conductive layer may be an undercoat layer with a conductive function, an adhesive containing an ionic compound of a conductive component or an antistatic agent, and a surface treatment layer containing a conductive component. The conductive layer may be formed of, for example, an antistatic agent composition containing a conductive polymer such as polythiophene and a binder. The layered body 10 preferably has one or more conductive layers, and may include two or more layers.

[Characteristics of flexible image display devices] As described above, according to the adhesive sheet 1, in the case of the flexible image display device 100, even when the flexible image display device 100 is wrapped around the shaft member and kept in a high temperature environment and then returned to a flat state, the layers constituting the device 100 can still be Suppresses the occurrence of peeling and waviness. For example, according to the adhesive sheet 1, in the case of the flexible image display device 100, in a state of being wound on a roller with a circular diameter of 20 mm defined by the side surface and kept at 85° C. for 48 hours, it returned to In the flat state, the components (eg, the base material 2 ) joined by the adhesive sheet 1 do not peel off.

[Application of flexible image display device] The flexible image display device 100 of the present invention can be suitably used as a flexible liquid crystal display device, an organic EL (electroluminescence) display device, an electronic paper and other image display devices. The flexible image display device 100 can be used regardless of a resistive film method or a capacitive method such as a touch panel.

(Variation of flexible image display device and laminate) The laminate 10 of the flexible image display device 100 may include a plurality of adhesive sheets 1 and a plurality of substrates 2, and may further include an optical film. The laminate 11 of the flexible image display device 110 shown in FIG. 2 includes a first adhesive sheet 1 a and a second adhesive sheet 1 b as the adhesive sheet 1 . The layered body 11 includes the first base material 2 a and the second base material 2 b as the base material 2 . The layered body 11 further includes an optical film 20 . Except for the above, the structure of the laminated body 11 is the same as that of the laminated body 10 of the flexible image display device 100 . Therefore, the common elements of the laminated body 10 of the flexible image display device 100 and the laminated body 11 of the present embodiment are given the same reference numerals, and the description thereof is omitted. In this specification, the laminated body 11 may be called an optical film with an adhesive layer.

As described later, the first base material 2 a is a member included in the optical film 20 . For example, the second base material 2b is located on the viewing side of the optical film 20 and is located on the outermost side of the layered body 11 . The first base material 2a and the second base material 2b may be the same or different from each other.

The first adhesive sheet 1a is located between the optical film 20 and the image display panel 3, and joins these members. The 2nd adhesive sheet 1b is located between the 2nd base material 2b and the optical film 20, and joins these members. The first adhesive sheet 1a and the second adhesive sheet 1b may be the same or different from each other.

[Optical Film] The optical film 20 has, for example, a first base material 2 a , a polarizing film 4 , and a retardation film 5 , and the polarizing film 4 is located between the first base material 2 a and the retardation film 5 . The first base material 2 a is located on the viewing side of the polarizing film 4 , for example, and functions as a protective film of the polarizing film 4 . The polarizing film 4 and the retardation film 5, for example, generate circularly polarized light in order to prevent the light incident from the viewing side of the polarizing film 4 from being internally reflected and then emitted to the viewing side, so as to compensate the viewing angle.

The thickness of the optical film 20 is preferably 92 µm or less, more preferably 60 µm or less, and more preferably 10-50 µm. Within the above range, the optical film 20 is less likely to hinder the winding of the flexible image display device 110 .

As long as the required characteristics of the polarizing film 4 can be maintained, the polarizing film 4 and the first base material 2a may be bonded together by an adhesive layer (not shown). Examples of the adhesive constituting the adhesive layer include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex, and water-based polyesters. The adhesive is usually used as an aqueous solution, for example, having a solid content concentration of 0.5 to 60% by weight. The adhesive constituting the adhesive layer may also be an ultraviolet curable adhesive, an electron beam curable adhesive, or the like. The electron beam curable adhesive exhibits good adhesion to the first base material 2a. The adhesive may also contain metal compound fillers.

[Polarizing film] As the polarizing film 4, for example, a polyvinyl alcohol (PVA)-based resin in which iodine is oriented by stretching by a stretching step such as air stretching (dry stretching) or a boric acid water stretching step can be used.

The manufacturing method of the polarizing film 4 is represented by the manufacturing method (monolayer stretching method) described in Unexamined-Japanese-Patent No. 2004-341515, and this manufacturing method includes the step of dyeing the monolayer of PVA resin and the step of stretching. The manufacturing method of the polarizing film 4 can also be mentioned in Japanese Patent Laid-Open No. 51-069644, Japanese Patent Laid-Open No. 2000-338329, Japanese Patent Laid-Open No. 2001-343521, International Publication No. 2010/100917, and Japanese Patent Laid-Open No. 2001-343521. The manufacturing method described in Japanese Unexamined Patent Application Publication No. 2012-073563 and Japanese Unexamined Patent Application Publication No. 2011-2816 includes a step of extending a laminate of a PVA-based resin layer and a resin substrate for drawing and a step of dyeing. According to this production method, since the PVA-based resin layer is supported by the resin base material for stretching, even if the PVA-based resin layer is thin, defects such as breakage due to stretching can be suppressed.

As the production method including the step of extending the layered body and the step of dyeing, the above-mentioned Japanese Patent Laid-Open No. 51-069644, Japanese Patent Laid-Open No. 2000-338329, and Japanese Patent Laid-Open No. 2001-343521 can be mentioned. The air extension (dry extension) method. From the viewpoint of being able to stretch at a high magnification and easily improving the polarization performance, the production method including the step of stretching in a boric acid aqueous solution described in International Publication No. 2010/100917 and Japanese Patent Laid-Open No. 2012-073563 is preferable. In particular, the production method (two-stage stretching method) described in Japanese Patent Laid-Open No. 2012-073563, which performs the step of performing in-air stretching before stretching in a boric acid aqueous solution, is preferred. Also preferred is the production method described in Japanese Patent Laid-Open No. 2011-2816 (excessive dyeing and decolorization method) in which the PVA-based resin layer is over-stretched after the laminate of the PVA-based resin layer and the stretching resin base is stretched. dyed and then depigmented. The polarizing film 4 may be, for example, a polarizing film formed of the above-mentioned polyvinyl alcohol-based resin having iodine oriented and stretched by two-stage stretching steps consisting of air-assisted stretching and boric acid water stretching. The polarizing film 4 may be, for example, a polarizing film composed of the above-mentioned polyvinyl alcohol-based resin in which iodine has been oriented, and the laminate of the stretched PVA-based resin layer and the stretched resin base material is over-dyed, and then It is made by decolorization.

The thickness of the polarizing film 4 is, for example, 20 µm or less, preferably 12 µm or less, preferably 9 µm or less, more preferably 1 to 8 µm, and particularly preferably 3 to 6 µm. Within the above range, the winding of the layered body 11 is hardly hindered.

[retardation film] As the retardation film 5, one obtained by extending a polymer film, or one obtained by orienting and immobilizing a liquid crystal material can be used. In this specification, the retardation film 5 has birefringence in the in-plane and/or thickness direction.

The retardation film 5 includes a retardation film for antireflection (refer to Japanese Patent Laid-Open No. 2012-133303 [0221], [0222], and [0228]), and a retardation film for viewing angle compensation (refer to Japanese Patent Laid-Open No. 2012- 133303 Nos. [0225], [0226]), a tilt-oriented retardation film for viewing angle compensation (refer to Japanese Patent Laid-Open No. 2012-133303 [0227]), and the like.

The retardation film 5 is not particularly limited, such as retardation value, arrangement angle, three-dimensional birefringence, single-layer or multi-layer, as long as it substantially has the above-mentioned functions, and a known retardation film can be used.

The thickness of the retardation film 5 is preferably 20 µm or less, preferably 10 µm or less, more preferably 1-9 µm, and particularly preferably 3-8 µm. Within the above range, the winding of the layered body 11 is hardly hindered.

The retardation film 5 is, for example, a retardation film composed of two layers of a 1/4 wavelength plate and a 1/2 wavelength plate in which the liquid crystal material is oriented and immobilized.

(Implementation form of image display system) As shown in FIG. 3 , the image display system 500 of the present embodiment includes a flexible image display device 100 (or 110 ) and a shaft member 45 . The flexible image display device 100 can be designed so that it can be rolled onto the shaft member 45 to bend and be pulled in at the same time. If the flexible image display device 100 is pulled in further than FIG. 3 , the device 100 will be rolled into a vortex. The shaft member 45 is, for example, a roller. The flexible video display device 100 functions as a so-called rollable video display device.

The image display system 500 may further include an accommodating portion (not shown) for accommodating the shaft member 45 . For example, the accommodating portion can accommodate the flexible image display device 100 that is wrapped around the shaft member 45 together with the shaft member 45 . The receptacle has, for example, an opening. When the flexible image display device 100 wrapped around the shaft member 45 is to be pulled out, for example, the device 100 can be pulled out from the accommodating portion through the opening of the accommodating portion.

The image display system 500 may further include a holding mechanism (not shown) for holding the flexible image display device 100 in a flat state when the flexible image display device 100 wound around the shaft member 45 is pulled out. The holding mechanism may be a plate supporting the flexible image display device 100 or a frame material surrounding the surface of the flexible image display device 100 . The holding mechanism can also be configured to be accommodated in the accommodating portion together with the device 100 when the flexible image display device 100 has been accommodated in the accommodating portion.

When the flexible image display device 100 is wound around the shaft member 45 , the minimum bending radius of the flexible image display device 100 is, for example, 50 mm or less, 30 mm or less, 20 mm or less, or 10 mm or less. The lower limit of the minimum deflection radius is not particularly limited, but is, for example, 5 mm. When the shaft member 45 is a roller, the minimum bending radius of the flexible image display device 100 is equivalent to the circle radius r defined by the side surface of the roller.

Example The present invention will be described in more detail below by means of examples. The present invention is not limited by the examples shown below.

[(Meth)acrylic polymer A1] A monomer mixture containing 99 parts by weight of butyl acrylate (BA) and 1 part by weight of 4-hydroxybutyl acrylate (HBA) was fed into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen introduction pipe, and a cooler. And relative to 100 parts by weight of the monomer mixture, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was fed together with ethyl acetate, and nitrogen was introduced while stirring slowly for nitrogen substitution. Then, the liquid temperature in the flask was maintained at around 55°C, and a polymerization reaction was performed for 7 hours. Then, ethyl acetate was added to the obtained reaction liquid, and the solution of the (meth)acrylic-type polymer A1 whose solid content concentration was adjusted to 30% and the weight average molecular weight of 1,600,000 was prepared.

[(Meth)acrylic polymers A2 and A4] The solutions of (meth)acrylic polymers A2 and A4 were prepared in the same manner as the (meth)acrylic polymer A1 except that the monomers used were changed as shown in Table 1.

[(Meth)acrylic monomer syrup A3] 100 parts by weight of the monomer mixture shown in Table 1, 2,2-dimethoxy-1,2-diphenylethan-1-one (trade name "Omnirad 651", IGM Resins B.V. Company) 0.4 parts by weight and 0.4 parts by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.) were put into a four-necked flask, and irradiated with ultraviolet rays in a nitrogen atmosphere until the viscosity became about 15Pa・It was photopolymerized until s, and the (meth)acrylic-type monomer syrup A3 containing a partial polymer of a monomer group was obtained. In addition, the viscosity was measured under the conditions of a rotation speed of 10 rpm and a temperature of 30 degreeC using a B-type viscometer (BH viscometer No. 5 rotor by TOKYO KEIKI CORPORATION).

[(Meth)acrylic monomer syrup A5] A (meth)acrylic monomer syrup A5 was prepared in the same manner as the (meth)acrylic monomer syrup A3 except that the monomers and polymerization initiators used were changed as shown in Table 1.

[(meth)acrylic oligomer B1] In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler, 95 parts by weight of butyl acrylate (BA), 2 parts by weight of acrylic acid (AA), and 3 parts by weight of methyl acrylate (MA) were fed as 0.1 part by weight of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.) as a polymerization initiator, 0.1 part by weight of 2,2'-azobisisobutyronitrile, and 140 parts by weight of toluene After the nitrogen substitution was sufficiently carried out by introducing nitrogen gas while stirring slowly, the liquid temperature in the flask was maintained at around 70° C. to carry out a polymerization reaction for 8 hours to prepare a solution of (meth)acrylic acid oligomer B1. The weight average molecular weight of the (meth)acrylic oligomer B1 was 4,500.

[(meth)acrylic oligomer B2] A (meth)acrylic oligomer B2 was prepared in the same manner as the (meth)acrylic oligomer B1 except that the monomers and polymerization initiators used were changed as shown in Table 1.

[Table 1]

The abbreviations in Table 1 are as follows. 2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate LA: Lauryl Acrylate MA: methyl acrylate BzA: benzyl acrylate NVP: N-Vinylpyrrolidone AA: Acrylic HBA: 4-hydroxybutyl acrylate HEA: 2-hydroxyethyl acrylate DCPM: Dicyclopentyl methacrylate MMA: methyl methacrylate Omnirad 651: Photopolymerization initiator, 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by IGM Resins B.V.) Omnirad 184: Photopolymerization initiator, 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins B.V.) AIBN: Azo-based polymerization initiator, 2,2'-azobisisobutyronitrile (manufactured by KISHIDA Chemical Co., Ltd.)

[Production of adhesive sheet] (Examples 1 to 5, Examples 7 to 8 and Comparative Example 1) A (meth)acrylic-type polymer, a (meth)acrylic-type oligomer, a crosslinking agent, and an additive were mixed so that it might become the composition shown in the following Table 2, and the solvent-type adhesive composition was obtained. Next, the obtained adhesive composition was coated on the surface of the PET film, which is a base film (separator), and then dried for 2 minutes in an air-circulating constant temperature oven set at 155° C. to form Examples 1 to 5. , the adhesive sheets of Examples 7-8 and Comparative Example 1. The coating of the adhesive composition was performed using a fountain coater.

(Example 6 and Comparative Example 2) A (meth)acrylic monomer syrup, a (meth)acrylic oligomer, a crosslinking agent, and an additive were mixed so as to have the composition shown in Table 2 below to obtain a mixture. Next, the above mixture was coated on the surface of a PET film (thickness 38µm) which is a base film (separator), and another above-mentioned PET film was placed on the coated film of the mixture, and a pair of PET films were sandwiched and coated. Cloth film. Next, the coating film was cured by irradiating ultraviolet rays under the irradiation conditions of an illuminance of 4 mW/cm ² and a light intensity of 1200 mJ/cm ² to form an adhesive sheet (thickness 50 µm). After the adhesive sheet was formed, the other PET film was peeled off to expose the adhesive sheet. Thereby, the adhesive sheets of Example 6 and Comparative Example 2 were formed.

[Table 2]

The abbreviations in Table 2 are as follows. D110N: Trimethylolpropane/stubble diisocyanate adduct (manufactured by Mitsui Chemicals, trade name: TAKENATE D110N) C/L: Trimethylolpropane/Tolyl diisocyanate (manufactured by Japan Polyurethane Industry Co., Ltd., trade name: CORONATE L) A-HD-N: 1,6-Hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: A-HD-N) Peroxide: Benzoyl peroxide (manufactured by NOF Corporation, trade name: NYPER BMT)

[Fabrication of Optical Film with Adhesive Layer] Next, with respect to the laminate (a) of the base film and the adhesive sheet obtained in each of the Examples and Comparative Examples, a 1/4 wavelength plate (λ/4 plate), a 1/2 wavelength plate, a 1/2 wavelength plate, and a A plate (λ/2 plate), a polarizing film, and an optical film formed by a substrate (protective film), to obtain an optical film A with an adhesive layer. The adhesive layer-attached optical film A has a multilayer structure of base film|adhesive sheet|λ/4 plate|λ/2 plate|polarizing film|protective film from the base film side. In addition, each layer constituting the optical film and the optical film were prepared as follows.

(λ/4 plate and λ/2 plate) The retardation film, which is a laminate of a λ/4 plate and a λ/2 plate, is produced using a polymerizable liquid crystal material (BASF Corporation, Paliocolor LC242) that exhibits a nematic liquid crystal phase after forming an alignment film. Specifically, it is as follows. After dissolving the above-mentioned polymerizable liquid crystal material and photopolymerization initiator (IRGACURE 907, manufactured by BASF) in toluene, in order to improve coatability, 0.1 to 0.5 wt% of a fluorine-based surfactant (MEGAFACE, manufactured by DIC) is further added depending on the thickness of the liquid crystal. , and the coating liquid L was prepared. The solid content concentration of the coating liquid L was set to 25% by weight.

Next, the manufacturing apparatus 200 of the retardation film shown in FIG. 4 is prepared. The manufacturing apparatus 200 includes: a supply turntable 221 for supplying a tape-shaped PET substrate 214, pressure rollers 224, 234, forming rollers 230, 240, peeling rollers 226, 236, conveying roller 231, molds 222, 229, 232, 239 and ultraviolet irradiation devices 225 , 227 , 235 and 237 for irradiating ultraviolet rays by a high pressure mercury lamp. Next, the solution 210 of the ultraviolet curable resin was applied to one surface of the PET base material 214 discharged from the supply turntable 221 using the mold 222 . Next, the above-mentioned coating film is brought into contact with the forming roller 230 by the pressing roller 224, and the PET substrate 214 is conveyed along the forming roller 230 in a state where the two are in contact, and at the same time, the ultraviolet irradiation device 225 is used to remove the The side of the PET substrate 214 is irradiated with ultraviolet rays to harden the coating film. The conveying surface of the PET substrate 214 in the shaping roller 230 is formed with linear concavities and convexities (extending in the direction of 75° with respect to the MD direction of the PET substrate), and the linear concavities and convexities are used to further form the orientation film of the polymerizable liquid crystal material. When a λ/4 plate is formed, a cured film of ultraviolet curable resin having a shape corresponding to the unevenness on the exposed surface is formed by the above curing. Next, after peeling off the PET base material 214 with the cured film formed thereon from the shaping roller 230 by the peeling roller 226, the coating liquid L is applied to the exposed surface of the cured film by the mold 229, and the ultraviolet rays are irradiated by the ultraviolet irradiation device 227. , to make the coating film directional hardening. In this way, a λ/4 plate (thickness 3 µm) composed of a cured film of an ultraviolet curable resin and an oriented cured film of a polymerizable liquid crystal material was formed on the PET substrate 214 .

Next, the PET base material 214 having the λ/4 plate formed thereon is conveyed by the conveying roller 231 , and the above-mentioned solution 212 of the ultraviolet curable resin is applied to the exposed surface of the λ/4 plate by the mold 232 to form a coating film. Next, the above-mentioned coating film is brought into contact with the forming roller 240 by the pressing roller 234, and the PET substrate 214 is conveyed along the forming roller 240 in the state of contact between the two, and at the same time, the ultraviolet irradiation device 235 is used to remove the The side of the PET substrate 214 is irradiated with ultraviolet rays to harden the coating film. The conveying surface of the PET substrate 214 in the shaping roller 240 is formed with linear concavities and convexities (extending in the direction of 15° with respect to the MD direction of the PET substrate), and the linear concavities and convexities are used to further form the orientation film of the polymerizable liquid crystal material. When a λ/2 plate is formed, a cured film of ultraviolet curable resin having a shape corresponding to the unevenness on the exposed surface is formed by the above curing. Next, after peeling off the PET base material 214 with the cured film formed thereon from the shaping roller 240 by the peeling roller 236, the coating liquid L is applied to the exposed surface of the cured film by the mold 239, and the ultraviolet rays are irradiated by the ultraviolet irradiation device 237. , to make the coating film directional hardening. In this way, a λ/2 plate (thickness 3 µm) composed of a cured film of an ultraviolet curable resin and a directional cured film of a polymerizable liquid crystal material was further formed on the λ/4 plate of the PET base material 214 to obtain a laminate ( b).

(Laminated body of polarizing film and protective film) The lamination system of the polarizing film and the protective film was produced in the following manner.

As the thermoplastic resin substrate, an amorphous IPA copolymerized PET film (thickness: 100 µm) having 7 mol% of isophthalic acid (IPA) units was prepared, and the surface was corona treated (58 W/m ² /min). ). In addition, 1 wt % of acetyl acetyl group-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., GOHSEFIMER Z200, average degree of polymerization 1200, degree of saponification 98.5 mol %, degree of acetoacetylation 5 mol %) was added. PVA (polymerization degree 4200, saponification degree 99.2%) was dissolved in water to obtain a PVA coating liquid with a concentration of 5.5% by weight. Next, the above-mentioned PVA coating solution was applied to the corona-treated surface of the IPA copolymerized PET film so that the film thickness after drying was 12 μm, and the coated film was dried by hot air drying at 60° C. for 10 minutes to obtain a A laminate composed of a substrate and a PVA layer on the substrate.

Next, the obtained layered body was subjected to free-end stretching (air-assisted stretching) at 130° C. at a stretching ratio of 1.8 times in the air to obtain a stretched layered body. Next, the stretched laminate was immersed in a boric acid-insoluble aqueous solution having a liquid temperature of 30° C. for 30 seconds to insolubilize the PVA layer. The boric acid content in the boric acid-insoluble aqueous solution was set to 3 parts by weight with respect to 100 parts by weight of water. Next, the stretched laminate in which the PVA layer has been insoluble is dyed to obtain a colored laminate. Dyeing was performed by immersing the stretched laminate in a dyeing solution containing iodine and potassium iodide at a temperature of 30°C. In the above dyeing, the PVA layer contained in the extended laminate is dyed with iodine. The dyeing time is adjusted so that the monomer transmittance of the PVA layer constituting the finally obtained polarizing film is in the range of 40 to 44%. As the dyeing liquid, an aqueous solution having an iodine concentration of 0.1 to 0.4% by weight and a potassium iodide concentration of 0.7 to 2.8% by weight is used. The ratio of the potassium iodide concentration to the iodine concentration in the dyeing solution was set to 7. Next, the colored layered body was immersed in a boric acid cross-linking aqueous solution having a liquid temperature of 30° C. for 60 seconds, whereby a cross-linking treatment for forming a cross-linked structure between the PVA molecules of the iodine-adsorbed PVA layer was performed. Both the boric acid content and the potassium iodide content in the boric acid crosslinking aqueous solution were set to 3 parts by weight with respect to 100 parts by weight of water.

Next, the colored laminate after the crosslinking treatment was stretched in a boric acid aqueous solution at a stretching temperature of 70° C. and a stretching ratio of 3.05 times (stretching in boric acid water) to obtain a stretched laminate with a final stretching ratio of 5.50 times. Make the extension direction of the boric acid water extension consistent with the extension direction of the initially implemented aerial auxiliary extension. Next, the stretched layered body after stretching was taken out from the boric acid aqueous solution, and the boric acid adhering to the surface of the PVA layer was washed with a potassium iodide solution (the content of potassium iodide was 4 parts by weight relative to 100 parts by weight of water). Next, the washed stretched laminate was dried by hot air drying at 60° C. to obtain a laminate of the base material and the polarizing film (thickness 5 μm) formed on the base material.

Next, a stretched film (thickness 20 µm, moisture permeability 160 g/m ² ) of a methacrylic resin having a glutarimide ring unit was prepared as a protective film. Next, the prepared protective film was bonded to the exposed surface of the polarizing film in the obtained laminate to obtain a laminate (c) of the base material and the polarizing film having the polarizing film and the protective film. A known acrylic adhesive is used for the bonding of the polarizing film and the protective film.

Next, using the laminated body (a), laminated body (b), and laminated body (c) obtained above, the optical film A with an adhesive bond layer was produced as follows. First, the base material is peeled off from the layered body (c) to expose the polarizing film. Next, the exposed polarizing film and the λ/2 plate of the laminate (b) were bonded with a known acrylic adhesive. Next, the PET base material 214 was peeled off from the laminated body (b) to expose the λ/4 plate. Next, the exposed λ/4 plate and the laminate (a) were joined by the adhesive sheet of the laminate (a) to obtain an optical film A with an adhesive layer.

From the adhesive layer-attached optical films A produced using the adhesive sheets of the Examples and Comparative Examples, the following methods were obtained, respectively, having a PET layer|adhesive sheet|λ/4 plate|λ/2 plate|polarizing film|protection Film | Adhesive Sheet | Optical Film B with Multi-layer Structure of Polyimide (PI) Layer Adhering to the Adhesive Layer. First, the base film (separator) is peeled off from the optical film A of the adhesive layer to expose the adhesive sheet. Next, a PET layer (corona treated) with a thickness of 125 µm was bonded to the exposed adhesive sheet. Next, to the protective film (corona-treated) on the exposed side on the opposite side, a PI layer (thickness 50 µm, electro-treated) was bonded with the same adhesive sheet as the one used between the PET layer and the λ/4 plate. halo treatment) to obtain an optical film B with an adhesive layer.

[Evaluation] <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 determined by using determined by GPC (gel permeation chromatography).・Analysis device: HLC-8120GPC manufactured by Tosoh Corporation ・Column: G7000H _XL +GMH _XL +GMH _XL manufactured by Tosoh Corporation ・Column size: 7.8mmφ×30cm each, 90cm in total ℃ ・Flow rate: 0.8ml/min ・Injection volume: 100µl ・Eluent: Tetrahydrofuran ・Detector: Differential refractometer (RI) ・Standard sample: Polystyrene

＜Thickness＞ The thickness of the adhesive sheet and the like is measured using a dial gauge (manufactured by Mitutoyo).

<Gel fraction> The evaluation of the gel fraction of the obtained adhesive sheet was carried out by the above-mentioned method. The weight of the small piece obtained by scraping a part of the adhesive sheet is about 0.2 g. The stretched porous membrane of PTFE was NTF1122 (average pore diameter: 0.2 µm) manufactured by Nitto Denko.

<tanδ and storage elastic modulus G'> The evaluation of the tanδ at 85°C, the storage elastic modulus G' at 25°C, and the storage elastic modulus G' at 85°C of the obtained adhesive sheet was carried out by the above-mentioned methods. The dynamic viscoelasticity measurement was performed using "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific.

＜Modulus＞ The evaluation of the 100% modulus, 500% modulus, 700% modulus and 1000% modulus of the obtained adhesive sheet was carried out by the above-mentioned method. As the tensile testing machine, AG-IS manufactured by Shimadzu Corporation can be used. In addition, the winding of the adhesive sheet is performed while peeling the adhesive sheet from the base film.

< Coil retention test > The optical film B with the pressure-sensitive adhesive layer was used as a sample for evaluation, and the winding retention test was carried out. The coiling retention test was carried out in the following manner. First, the optical film B with the adhesive layer was cut into a 320 mm×25 mm short strip shape, and the test piece 15 was produced. Next, as shown in FIG. 5A , the test piece 15 is wound in the longitudinal direction thereof by the shaft member 45 . At this time, the end portion 15a of the test piece 15 in contact with the shaft member 45 was fixed to the shaft member 45 using an adhesive tape. Similarly, the end portion 15b of the test piece 15 in contact with the surface of the test piece 15 was fixed to the test piece 15 using an adhesive tape. The shaft member 45 is a roller, and the diameter R of the circle defined by the side surface is 20 mm.

Next, in the state in which the test piece 15 was wound up, the test piece 15 was kept under the condition of 85° C. for 48 hours. After cooling to room temperature (23° C.), the test piece 15 returned to a flat state as shown in FIG. 5B . At this time, the presence or absence of peeling and waviness of the layer of the optical film B constituting the adhesive layer was visually confirmed.

Judgment criteria are as follows. A: No peeling or waviness occurred (no problem in practical use) B: Some microwave-like undulations occurred at the end of the test piece (no problem in practical use) C: Some microwave-like undulations occurred in the whole test piece (no problem in practical use) D: Peeling occurred or waviness occurred in the entire test piece (practically problematic)

[table 3]

As can be seen from Table 3, the optical film B (Examples 1 to 8) having an adhesive layer with a tanδ at 85°C of 0.32 or less and a gel fraction of 75% or more of the pressure-sensitive adhesive sheet (Examples 1 to 8) was held during the winding process. In the test, the occurrence of peeling and waviness was successfully suppressed sufficiently.

industrial availability The adhesive sheet of the present invention can be suitably used for a flexible image display device having a display portion that can be taken up.

1: adhesive sheet 1a: 1st adhesive sheet 1b: 2nd adhesive sheet 2: Substrate 2a: 1st substrate 2b: 2nd substrate 3: Image display panel 4: polarizing film 5: retardation film 10,11: Laminates for flexible image display devices 15: Test piece 15a, 15b: end 20: Optical Film 45: Shaft member 100,110: Flexible Image Display Devices 200: Manufacturing Device 210, 212: Solutions of UV-curable resins 214: PET substrate 222, 229, 232, 239: Die 221: Supply carousel 224, 234: Pressure rollers 225, 227, 235, 237: Ultraviolet Irradiation Devices 226, 236: Stripping Rollers 230, 240: Forming rollers 231: Conveyor Roller 500: Image Display System L: coating liquid R: circle diameter r: circle radius

1 is a cross-sectional view of a laminate and a flexible image display device used in a flexible image display device according to an embodiment of the present invention. 2 is a cross-sectional view of a laminate and a flexible image display device used in a flexible image display device according to another embodiment of the present invention. FIG. 3 is a schematic diagram showing an example of a video display system. FIG. 4 is a diagram for explaining a method of manufacturing a retardation film. FIG. 5A is a diagram for explaining the coiling holding test. FIG. 5B is a diagram for explaining the coiling holding test.

1: adhesive sheet

2: Substrate

3: Image display panel

10: Laminates for flexible image display devices

100: Flexible image display device

Claims (10)

An adhesive sheet used for a laminate in a flexible image display device having a reelable display portion; The loss tangent tanδ of the adhesive sheet at 85°C is 0.32 or less, and The gel fraction was 75% or more. The adhesive sheet according to claim 1, wherein the aforementioned tanδ is 0.11 or more. The adhesive sheet according to claim 1 or 2, wherein the aforementioned tanδ is 0.20 or less. The adhesive sheet according to any one of claims 1 to 3, wherein the gel fraction is 90% or more. The adhesive sheet according to any one of claims 1 to 4, whose storage elastic modulus G' at 25°C is 0.05 MPa or more. According to the adhesive sheet of any one of claims 1 to 5, its 100% modulus is 0.05N/mm ² or more. A laminated body is used for a flexible image display device having a display portion that can be taken up, and has: such as the adhesive sheet of any one of claims 1 to 6; and The base material supports the aforementioned adhesive sheet. The laminate of claim 7 further includes a polarizing film. The laminated body of claim 7 or 8, when the state of being wrapped around a roller with a circle diameter of 20 mm defined by the side surface is kept at 85° C. for 48 hours and then returned to a flat state, by the aforementioned adhesion There was no peeling of the sheet-bonded members. A flexible image display device is provided with a rollable display portion, and has: A laminate as claimed in any one of Claims 7 to 9; and image display panel; And the above-mentioned laminated body is located on the viewing side more than the above-mentioned image display panel.

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