TW202200740A - Adhesive sheet used for laminate within flexible image display device, laminate used for flexible image display device, and flexible image display device - Google Patents

Abstract

This invention provides an adhesive sheet which is, even when a flexible image display device having a display unit that can be wound is repeatedly used, able to prevent formation of trace such as curl and is also able to prevent a layer in the device from being peeled. The adhesive sheet of the present invention has a 1000% modulus of 0.01-0.6 N/mm2 and a gel fraction of 30% or more. The adhesive sheet is used for a laminate within a flexible image display device having a display unit that can be wound.

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, an image display panel and a laminate structure including an optical film (for example, Patent Document 1). Adhesive sheets are generally used for bonding the layers constituting 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 In recent years, bendable flexible image display devices have been put into practical use. According to the study by the inventors of the present application, when a flexible image display device having a rollable display portion is repeatedly used, traces such as roll marks are left on the device. If the image display device with traces is to be restored to a flat state forcibly, the layer bonded by the adhesive sheet may peel off or the display of the image may be uneven.

As a result of diligent investigations by the inventors of the present application, it was found that this is caused by the strain generated in each layer constituting the flexible image display device when the flexible image display device is bent due to marks such as curling marks. And it is predicted that this strain can be alleviated by using a soft adhesive sheet with a low gel fraction. However, when the gel fraction of the adhesive sheet is reduced, in a flexible image display device having a rollable display portion and a wide range of strain generation, the layer joined by the adhesive sheet becomes easy to peel off.

Therefore, an object of the present invention is to provide an adhesive sheet capable of suppressing the occurrence of traces such as roll marks, and suppressing the formation of The layers of the device peeled off.

MEANS TO SOLVE THE PROBLEM The present invention provides an adhesive sheet for use in a laminate in a flexible image display device having a reelable display portion; the 1000% modulus of the adhesive sheet is 0.01 to 0.6 N/mm ² , and the gel fraction is more than 30%.

Furthermore, the present invention provides a laminate for use in a flexible image display device having a rollable display portion; The laminate has: the above-mentioned adhesive sheet, and The substrate supporting 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 an image display panel; and The above-mentioned laminated body is located on the viewing side of the above-mentioned image display panel.

Invention effect According to the present invention, it is possible to provide an adhesive sheet capable of preventing traces such as roll marks from being left even when a flexible image display device having a reelable display portion is repeatedly used, and at the same time preventing the formation of the device. layer peeling off.

Form for carrying out the invention The present invention will be described in detail below, 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 this embodiment is used as a member of a laminated body in a flexible image display device having a reelable display portion, and the 1000% modulus of the adhesive sheet is 0.01~0.6N/ mm ² , and the gel fraction is 30% or more.

The 1000% modulus of an adhesive sheet is a property expressed by a numerical value obtained in the following manner: when a 1000% elongation is imparted to the adhesive sheet by a tensile force in one direction, stress (tensile stress) is generated in the adhesive sheet, A value is obtained by dividing the generated stress by the initial cross-sectional area of the adhesive sheet. The 1000% modulus of the adhesive sheet can be evaluated in the following manner.

The adhesive sheet of the evaluation object was cut into short sticks 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, the obtained test piece is installed in a tensile testing machine such as a universal testing machine (TENSILON), and a uniaxial extension test is carried out in the height direction thereof to obtain an elongation-stress curve of the adhesive sheet. In addition, the preparation of the test piece and the uniaxial elongation test were carried out at normal temperature (23° C.), the initial distance between the jigs in the uniaxial elongation test was 10 mm, and the tensile speed was 300 mm/min. From the obtained elongation-stress curve, the stress when the elongation was 1000% (the distance between the clamps was 110 mm at this time) was obtained, and it was divided by the initial cross-sectional area of the test piece to determine the 1000% modulus of the adhesive sheet.

The 1000% modulus of the adhesive sheet is 0.01~0.6N/mm ² , so the adhesive sheet can ensure sufficient cohesive force, even after the flexible image display device is wound, for example, the flexible image display device is being wound. When stored in the state of the shaft member (roller), the strain applied to the layer constituting the device, especially the layer to be bonded to the adhesive sheet, can be sufficiently relieved. Specifically, a flexible image display device having a retractable display portion is assumed to be wound around a shaft member when it is used. At this time, strain occurs in a wide range in the display portion. A large stress due to this strain will be generated in the laminate in the flexible image display device, and a large shear stress will also be generated in the adhesive sheet. If the 1000% modulus of the adhesive sheet is 0.01~0.6N/mm ² , the above strain can be relieved when a large shear stress is generated in the adhesive sheet. Therefore, the strain applied to the layer constituting the flexible image display device can be sufficiently relieved, and the stress generated in the layer can be reduced, so that traces such as roll marks and peeling of the layer can be suppressed sufficiently. In addition, according to the study by the inventors of the present application, in a foldable image display device having a bendable flexure, it is presumed that the stress generated in the flexure is relieved by the flat part other than the flexure. Therefore, little attention has been paid to the 1000% modulus of the adhesive sheet for the foldable image display device.

The 1000% modulus of the adhesive sheet should be 0.4N/ ^mm2 or less, preferably 0.25N/ ^mm2 or less, more preferably 0.2N/ ^mm2 or less, especially 0.15N/ ^mm2 or less, especially 0.12 N/mm ² or less, and may be 0.11 N/mm ² or less, or 0.10 N/mm ² or less. The 1000% modulus of the adhesive sheet can be 0.05N/ ^mm2 or more, 0.075N/ ^mm2 or more, 0.085N/ ^mm2 or more, 0.090N/ ^mm2 or more, or 0.095 N/mm ² or more.

The gel fraction of the adhesive sheet can be evaluated, for example, by the following method. First, a small piece is obtained by scraping off a portion of the adhesive sheet. 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 piece of the adhesive sheet, the stretched porous film, and the kite string was measured. In addition, the total of the stretched porous film and kite string used is defined as weight B. Next, the test piece was immersed in a container filled with ethyl acetate and 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

When the gel fraction of the adhesive sheet is more than 30%, the adhesive sheet has sufficient cohesive force. Thereby, even if it is a flexible image display device which has a display part which can be taken up and has a wide range of generating strain, peeling of the layer joined by the adhesive sheet can be sufficiently suppressed. The gel fraction of the adhesive sheet may be more than 40%, may be more than 50%, may be more than 60%, may be more than 63%, may be more than 64%, may be more than 65%, or above 66%. The upper limit value of the gel fraction of the adhesive sheet is not particularly limited, for example, it may be 95% or less, may be 85% or less, may be 75% or less, may be 72% or less, may be 71% or less, or may be 70% or less, 69% or less, or 68% or less. The gel fraction of the adhesive sheet may be 55% or less depending on the situation.

The 500% modulus of the adhesive sheet is, for example, 0.2 N/mm ² or less. The 500% modulus of an adhesive sheet is a characteristic expressed by a numerical value obtained in the following manner: when a 500% elongation is imparted to the adhesive sheet by a tensile force in one direction, stress (tensile stress) is generated in the adhesive sheet, A value is obtained by dividing the generated stress by the initial cross-sectional area of the adhesive sheet. The 500% modulus of the adhesive sheet can be evaluated according to the method described above for the 1000% modulus of the adhesive sheet.

The 500% modulus of the adhesive sheet is preferably 0.15N/mm ² or less, preferably 0.1N/mm ² or less, more preferably 0.08N/mm ² or less, especially 0.05N/mm ² or less. The lower limit value of the 500% modulus of the adhesive sheet is not particularly limited, but is, for example, 0.01 N/mm ² or more.

The 700% modulus of the adhesive sheet is, for example, 0.3 N/mm ² or less. The 700% modulus of the adhesive sheet is a property expressed by a numerical value obtained in the following manner: When a 700% elongation is imparted to the adhesive sheet by a tensile force in one direction, stress (tensile stress) is generated in the adhesive sheet, A value is obtained by dividing the obtained stress by the initial cross-sectional area of the adhesive sheet. The 700% modulus of the adhesive sheet can be evaluated according to the method described above for the 1000% modulus of the adhesive sheet.

The 700% modulus of the adhesive sheet is preferably 0.2N/ ^mm2 or less, preferably 0.15N/ ^mm2 or less, more preferably 0.1N/ ^mm2 or less, and may be 0.08N/ ^mm2 or less, or 0.06 N/ ^mm2 or less. The lower limit value of the 700% modulus of the adhesive sheet is not particularly limited, but is, for example, 0.01 N/mm ² or more.

The upper limit of 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 (according to JIS K7136:2000) of the adhesive sheet in the visible light wavelength region is preferably 85% or more, and 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, and adhesion, 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 (meth)acrylic acid containing a (meth)acrylic monomer having a linear or branched alkyl group having 1 to 30 carbon atoms as a monomer unit system polymer. In addition, in this specification, "(meth)acrylic polymer" means acrylic polymer and/or methacrylic polymer, and "(meth)acrylate" means acrylate and/or methyl Acrylate.

Specific examples of the (meth)acrylic monomer having a linear or branched C1-30 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. The (meth)acrylic monomer having a linear or branched C6-C30 alkyl group (hereinafter sometimes referred to as "(meth)acrylic monomer having a long-chain alkyl group") is Preferably, 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 viewpoint 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, and among them, 2-ethyl acrylate is used. Hexyl esters are more preferred. (meth)acrylic-type monomers can be used 1 type or 2 or more types.

The (meth)acrylic monomer system having a straight-chain 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 50 (meth)acrylic monomers having a linear or branched alkyl group having 1 to 30 carbon atoms in the total monomers constituting the (meth)acrylic polymer. ~100% by weight, preferably 80~100% by weight, more preferably 90~99.9% by weight, especially preferably 94~99.9% by weight.

The monomer component constituting the (meth)acrylic polymer may contain a copolymerizable monomer ( comonomer). Moreover, a comonomer may be used individually or in combination of 2 or more types.

The comonomer 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 comonomers may contain monomers such as carboxyl group-containing monomers, amine group-containing monomers, and amide group-containing monomers with reactive functional groups. These monomers are preferably used from the viewpoint of adhesion in humidified and 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 and high-temperature environment. The carboxyl group-containing monomer 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 an adhesive sheet having excellent adhesion in a humidified and high-temperature environment. The amine group-containing monomer is a compound containing an amine group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group and a vinyl group.

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

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 a pressure-sensitive adhesive sheet excellent in adhesiveness. The amide group-containing monomer 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 -(meth)acryloyl pyrrolidine and other N-acryloyl heterocyclic monomers; N-vinyl pyrrolidone, N-vinyl-ε-caprolactam and other N-vinyl lactamide-containing systems Monomer, etc.

Moreover, a polyfunctional monomer (polyfunctional monomer) is mentioned as a comonomer. If a polyfunctional monomer is included, a cross-linking effect can be obtained after polymerization, and the gel fraction can be easily adjusted and the cohesive force can be improved. Therefore, cutting becomes easy, and it becomes easy to improve workability. In addition, peeling due to cohesive failure of the adhesive sheet 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, Neotaerythritol tri(meth)acrylate, Dipivalerythritol hexa(meth)acrylate, Trimethylolpropane tri(meth)acrylate, Tetramethylolmethane tri(meth)acrylate, Polyfunctional acrylates such as allyl (meth)acrylate, vinyl (meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, etc., or divinylbenzene, etc., among which polyfunctional acrylic acid As the ester, 1,6-hexanediol diacrylate and dipeotaerythritol hexa(meth)acrylate are preferable. Moreover, a polyfunctional monomer can be used individually or in combination of 2 or more types.

As the monomer unit 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 a monomer having a reactive functional group and a polyfunctional monomer, other copolymers may be introduced within a range that does not impair the effects of the present invention monomer.

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 no more good. When it exceeds 30 weight%, especially when using the thing other than a (meth)acrylic-type monomer, 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 be any form of adhesive composition, 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 preferably includes 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 have been partially polymerized. The "monomer mixture" includes only one monomer component.

The adhesive composition is preferably a mixture containing monomer components constituting a (meth)acrylic polymer (mono Active energy ray-curable adhesive composition with active energy ray-curable adhesive composition as an essential ingredient.

The (meth)acrylic polymer can be obtained by polymerizing monomer components. More specifically, it can be obtained by polymerizing a monomer component, a monomer mixture, or a partial polymer thereof by a known and usual 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 contact 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.

In the case of active energy ray polymerization (photopolymerization), the irradiated active energy rays include, for example, ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron rays, or ultraviolet rays, and ultraviolet rays are particularly preferred. The irradiation energy, irradiation time, irradiation method, etc. of the active energy rays are not particularly limited, as long as the photopolymerization initiator can be activated to react the monomer components.

When performing the 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; lipids such as cyclohexane and methylcyclohexane. Cyclic hydrocarbons; organic solvents such as methyl ethyl ketone, methyl isobutyl ketone and other ketones. Moreover, a solvent can be used individually or in combination of 2 or more types.

When performing the polymerization, a polymerization initiator such as a photopolymerization initiator (photoinitiator) and 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.

系光聚合起始劑。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 sulfonic acid chlorides. Photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, diphenylketone-based photopolymerization initiators, ketals It is a photopolymerization initiator, 9-oxysulfur 𠮿

It is a photopolymerization initiator.

系光聚合起始劑可舉例如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-dimethyl ether. Oxy-1,2-diphenylethan-1-one, anisole, 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 a photoactive oxime-based photopolymerization initiator, 1-benzene-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime etc. are mentioned, for example. As a benzoin type photopolymerization initiator, benzoin etc. are mentioned, for example. As a benzyl type photopolymerization initiator, benzophenone (benzil) etc. are mentioned, for example. For example, benzophenone-based photopolymerization initiators include benzophenone, benzoic acid, 3,3'-dimethyl-4-methoxy benzophenone, and polyvinyl benzophenone. , α-hydroxycyclohexyl phenyl ketone, etc. As a ketal type photopolymerization initiator, benzyl dimethyl ketal etc. are mentioned, for example. 9-oxysulfur 𠮿

As the photopolymerization initiator, for example, 9-oxothiocyanate is exemplified.

, 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.

The polymerization initiators used for solution polymerization include, for example, azo-based polymerization initiators, peroxide-based polymerization initiators (such as dibenzyl peroxide, tertiary butyl maleate peroxy, etc.), oxidative Reduction-based polymerization initiators, etc. Among them, the azo-based polymerization initiator disclosed in Japanese Patent Laid-Open No. 2002-69411 is preferable. The azo-based polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis( 2-methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanovaleric acid, etc.

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

In addition, polyfunctional monomers (polyfunctional acrylates) used as comonomers can also be used in solvent-based or active energy ray-curable adhesive compositions, but for example, when combining polyfunctional monomers (polyfunctional acrylates) with light When a polymerization initiator is mixed with a solvent-based adhesive composition and used, it is subjected to active energy ray curing 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 preferably 1.4 million to 1.8 million. When the weight-average molecular weight is less than 1 million, when the polymer chains are cross-linked to ensure durability, the number of cross-linking points increases compared to those with a weight-average molecular weight of 1 million or more, and the adhesive (sheet) Since the flexibility is lost, the strain on the outer side (convex side) and the inner side (concave side) of the curvature generated between the layers (films) constituting the image display device during winding cannot be relieved, and the layers may be prone to breakage in some cases. If the weight-average molecular weight is more than 2.5 million, a large amount of diluent solvent is required to adjust the viscosity suitable for coating, which increases the cost, which is unfavorable. In addition, the polymer chain of the obtained (meth)acrylic polymer is unfavorable. The entanglement of each other becomes complicated, so that the flexibility deteriorates, and each layer (film) may be easily broken during winding. In addition, the weight average molecular weight (Mw) means the value calculated by 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 is preferably a polymer with a smaller weight average molecular weight (Mw) than the (meth)acrylic polymer. By using the (meth)acrylic oligomer, (meth)acrylic oligomer can be used ( The meth)acrylic oligomer exists between the (meth)acrylic polymers, so that the entanglement of the (meth)acrylic polymers is reduced, and it becomes easy to deform against a small strain.

Examples of monomers constituting the (meth)acrylic oligomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, (meth)acrylate Butyl meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, tertiary butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate Amyl ester, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylate base) nonyl acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (meth) acrylic acid alkyl esters; (meth) acrylic acid and cycloaliphatic Esters of alcohols; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylates obtained from terpene derivative alcohols, and the like. The (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 Alkyl (meth)acrylate with branched chain structure; (methyl) cyclohexyl (meth)acrylate, isobornyl (meth)acrylate (meth)acrylate and dicyclopentyl (meth)acrylate ) esters of acrylic acid and alicyclic alcohol; (meth)acrylates having a cyclic structure such as phenyl (meth)acrylate or aryl (meth)acrylates such as benzyl (meth)acrylate. When the (meth)acrylic oligomer has the bulky structure, the adhesiveness of the adhesive sheet tends to be further improved. In particular, in terms of size, those with a ring structure are more effective, and those with a plurality of rings are more effective. In the synthesis of (meth)acrylic oligomers or the production of adhesive sheets, if ultraviolet rays are used, the polymerization will not be easily inhibited. In this regard, those with saturated bonds are suitable, and (methyl) groups with branched alkyl groups can be suitably used. ) alkyl acrylate or ester with alicyclic alcohol 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 (CHMA) ) and isobutyl methacrylate (IBMA) copolymer, cyclohexyl methacrylate (CHMA) and isobornyl methacrylate (IBXMA) copolymer, cyclohexyl methacrylate (CHMA) and acrylonitrile Copolymer of mofolin (ACMO), copolymer of cyclohexyl methacrylate (CHMA) and diethylacrylamide (DEAA), 1-adamantyl acrylate (ADA) and methyl methacrylate ( MMA) copolymer, dicyclopentyl methacrylate (DCPMA) and isobornyl methacrylate (IBXMA) copolymer, dicyclopentyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA) , Isobornyl methacrylate (IBXMA), Isobornyl 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 in the solvent-based adhesive composition and the active energy ray-curable adhesive composition similarly to the (meth)acrylic polymer. For example, as an active energy ray-curable adhesive composition, (meth)acrylic acid may be further mixed into a mixture of monomer components constituting a (meth)acrylic polymer (monomer mixture) or a partial polymer thereof used as oligomers. When the (meth)acrylic oligomer is dissolved in the solvent, the solvent in the adhesive composition can be volatilized by thermal drying, 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 even more preferably 4,000 or more. The weight average molecular weight (Mw) of the (meth)acrylic oligomer is preferably 30,000 or less, more preferably 15,000 or less, 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 Existing between (meth)acrylic polymers will reduce the entanglement of (meth)acrylic polymers, and the adhesive sheet will be easily deformed by small strains, which can reduce the amount of stress applied to the image display device. Strain tendencies of other layers. Thereby, there exists a tendency for the crack of each layer, the peeling between an adhesive sheet and other layers, etc. to be suppressed more. In addition, the weight average molecular weight (Mw) of the (meth)acrylic oligomer is the same as the (meth)acrylic polymer, which is measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene. value.

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

[Crosslinking agent] The adhesive composition may contain a crosslinking agent. 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. In the polyfunctional metal chelate complex, the polyvalent metal system is covalently or coordinately bonded to the 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. When it is a solvent-based adhesive composition, it is suitable to be a peroxide-based crosslinking agent or an isocyanate-based crosslinking agent, and among them, a peroxide-based crosslinking agent is preferably used. The peroxide-based crosslinking agent crosslinks the side chains of the (meth)acrylic polymer with each other, for example, by removing hydrogen from the side chains of the (meth)acrylic polymer to generate free radicals Therefore, compared with the use of isocyanate-based cross-linking agents (such as polyfunctional isocyanate-based cross-linking agents) for cross-linking, the cross-linking state is gentler, and it can maintain its ease of small strain deformation, and at the same time Tendency to improve cohesion. Thereby, there exists a tendency for cracking of each layer which comprises an image display apparatus, peeling between an adhesive sheet and other layers, etc. to be suppressed. Isocyanate-based cross-linking agents (especially trifunctional isocyanate-based cross-linking agents) are desirable from the viewpoint of durability, and peroxide-based cross-linking agents and isocyanate-based cross-linking agents (especially difunctional isocyanate-based cross-linking agents) crosslinking agent) is preferable from the viewpoint of coilability. Both peroxide-based cross-linking agents and difunctional isocyanate-based cross-linking agents can form soft two-dimensional cross-links, while tri-functional isocyanate-based cross-linking agents can form stronger three-dimensional cross-links. Two-dimensional crosslinks, which are softer crosslinks, are more advantageous during coiling. However, if only two-dimensional crosslinking is used, durability may be poor, and peeling may easily occur. Therefore, mixed crosslinking of two-dimensional crosslinking and three-dimensional crosslinking is preferable. Therefore, it is preferable to use together a trifunctional isocyanate-based crosslinking agent, a peroxide-based crosslinking agent, or a difunctional isocyanate-based crosslinking agent. In addition, from the viewpoints of productivity and thick film coating of the active energy ray-curable adhesive composition, it is preferable to obtain a cross-linking effect by polymerizing using a polyfunctional monomer. However, the above-mentioned crosslinking agent may be used, or it may be used in combination with a multifunctional monomer. For example, a cross-linking agent may be mixed with a mixture of monomer components constituting a (meth)acrylic polymer (monomer mixture) or a partial polymer thereof, and a heat may be applied before and after the adhesive composition is cured with active energy rays. Dry to complete the reaction of the crosslinking agent.

The use amount of the crosslinking agent is, for example, preferably 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, more preferably 0.2 to 1 part by weight, relative to 100 parts by weight of the (meth)acrylic polymer.

When the peroxide-based crosslinking agent is used alone, it is preferably 0.5 to 5 parts by weight, and more preferably 1 to 3 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer. Within the above-mentioned range, the adhesive sheet tends to maintain the ease of deformation with respect to slight strains, and at the same time, the cohesive force can be sufficiently improved, and the durability can be improved.

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 above 0.02, preferably above 1, more preferably above 10, and particularly preferably above 15. The upper limit of the weight ratio is preferably 500 or less, preferably 100 or less, more preferably less than 50, and even more preferably 40 or less. Within the above-mentioned range, the adhesive sheet tends to sufficiently improve the cohesive force while maintaining the ease of deformation against slight strain.

[additive] In addition, the adhesive composition may also contain other known additives, such as various silane coupling agents, polyether compounds of polyalkylene glycols such as polypropylene glycol, powders and dyes such as colorants, pigments, etc., as appropriate according to the application. , surfactants, plasticizers, tackifiers, surface lubricants, levelers, softeners, antioxidants, antiaging agents, light stabilizers, UV absorbers, polymerization inhibitors, antistatic agents (ionic Compounds of alkali metal salts or ionic liquids, ionic solids, etc.), inorganic or organic fillers, metal powders, granules, foils, etc. Redox systems with added reducing agents 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, as required. (For example, a (meth)acrylic oligomer, a crosslinking agent, a silane coupling agent, a solvent, an additive, etc.) are mixed and produced. In addition, as described above, the active energy ray-curable acrylic adhesive composition is prepared by combining a monomer mixture or a partial polymer thereof, and optionally added components (such as a photopolymerization initiator, a multifunctional monomer, ( A meth)acrylic oligomer, a crosslinking agent, a silane coupling agent, a solvent, an additive, etc.) are mixed and produced.

The adhesive composition preferably has a viscosity suitable for handling and 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 some polymers can be calculated in the following manner. A part of the polymer was sampled as a sample. The sample was precisely weighed to calculate its weight, and it was designated as "the weight of the partial polymer before drying". Next, the sample was dried at 130° C. for 2 hours, the dried sample was precisely weighed, and its weight was calculated, and it was defined as the “weight of the partial polymer after drying”. Then, the weight of the sample reduced by drying at 130°C for 2 hours was calculated from the "weight of the partial polymer before drying" and the "weight of the partial polymer after drying", and this was defined as the "weight loss" (volatile portion, 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 calculated 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

[Forming an adhesive sheet] The method of forming the adhesive sheet may include, for example, the following: a method of applying a solvent-based adhesive composition to a release member (release film) after peeling treatment, etc., and drying and removing the polymerization solvent and the like to form an adhesive sheet; A method of coating a solvent-based adhesive composition on a polarizing film, etc., and drying and removing the polymerization solvent, etc. to form an adhesive sheet on a polarizing film, etc.; A method of forming by separating parts, etc., and irradiating active energy rays. 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 also be added.

Polysiloxane release liner should be used for the separation piece after peeling treatment. 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 suitably used according to the purpose. Preferably, a method of drying the above-mentioned coating film by heating is employed. The heating and drying temperature is preferably 40 to 200°C, 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.

As the drying time, an appropriate time can be appropriately adopted. The drying time is preferably 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and 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, preferably 5~150µm, 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 preferable 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. In the 1st method of a solvent type, the (meth)acrylic-type polymer which copolymerized the (meth)acrylic-type monomer which has a long-chain alkyl group is used. Here, in the solvent-based first method, 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.

In the solvent-based second method, a peroxide-based crosslinking agent is used alone as a crosslinking agent, and is added in an amount of 0.1 part by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic polymer.

In the solvent-based third method, a peroxide-based cross-linking agent and an isocyanate-based cross-linking agent are used in combination, and the weight ratio of the peroxide-based cross-linking agent to the isocyanate-based cross-linking agent (peroxide-based cross-linking agent) (substance-based crosslinking agent/isocyanate-based crosslinking agent) is set to 0.02 or more and 500 or less, and the addition amount of the peroxide-based crosslinking agent is set to 0.1 weight part relative to 100 parts by weight of the (meth)acrylic polymer copies or more.

In the fourth method of the solvent type, in the second method or the third method of the solvent type, a (meth)acrylic oligomer was further added as described above with respect to 100 parts by weight of the (meth)acrylic polymer. 1 part by weight or more and not more than 70 parts by weight.

Next, the method of using the active energy ray-curable adhesive composition (the first method to the second method of the active energy ray-curable type) will be described. In the first method of the active energy ray hardening type, a (meth)acrylic monomer having a long-chain alkyl group as a main component and containing an alkyl group having a carbon number of 1 to 5 or a functional group is used. A mixture of monomers (monomer mixture), or a partial polymer of this mixture, is polymerized together with polyfunctional monomers.

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

Here, in the first method and the second method of the active energy ray hardening type, it is preferable to set the content of the (meth)acrylic monomer having a long-chain alkyl group to 60% by weight or more in the total monomers, and more It is preferable to set it as 70 weight% or more, on the other hand, it is preferable to set it as 100 weight% or less, and it is more preferable to set it as 99 weight% or less. 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 of the image display panel 3 .

[laminated body] The laminated body 10 is a member 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, and is in contact with the adhesive sheet 1, for example. 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 for protecting 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, 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 up. 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.

[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 bendable, 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, 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 during 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. When the thickness of the transparent conductive layer is less than 0.005 μm, the change in the resistance value of the transparent conductive layer tends to increase. On the other hand, when it exceeds 10 micrometers, the productivity of a transparent conductive layer will fall, the cost will also rise, and the optical characteristic will also tend to fall.

The total light transmittance of the transparent conductive layer is preferably more than 80%, more 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 , and more 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 conventionally known methods can be employed. Specifically, for example, a vacuum deposition method, a sputtering method, and an ion plating method can be exemplified. In addition, an appropriate method may be adopted according to the required film thickness.

Between the transparent conductive layer and the substrate 2, a primer layer, an anti-oligomer layer, etc. can be further provided as required.

[Conductive layer (antistatic layer)] The layered body 10 may further have a conductive layer (conductive layer, antistatic layer). Since the laminated body 10 has a very thin thickness structure, it is easily damaged by weak static electricity generated in a manufacturing process or 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.

When the winding operation of the flexible image display device 100 including the laminate 10 is continuously performed, static electricity may be generated at 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.

(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 . And the laminated body 11 is provided with the 1st base material 2a and the 2nd base material 2b 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, elements common to the laminated body 10 of the flexible image display device 100 and the laminated body 11 of the present embodiment are sometimes given the same reference numerals and their descriptions are 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 these members are joined. 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, for example, on the viewing side of the polarizing film 4 , and functions as a protective film of the polarizing film 4 . The polarizing film 4 and the retardation film 5 generate, for example, circularly polarized light for preventing the light incident from the viewing side of the polarizing film 4 from being internally reflected and then being emitted to the viewing side to compensate the viewing angle.

The thickness of the optical film 20 is preferably 92 µm or less, 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 properties of the polarizing film 4 are 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, and has, for example, 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 can exhibit good adhesiveness to the first base material 2a. The adhesive may also contain metal compound fillers.

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

The manufacturing method of the polarizing film 4 is represented by the manufacturing method (monolayer stretching method) described in Japanese Patent Laid-Open No. 2004-341515, and the manufacturing method includes the step of dyeing the monolayer of PVA-based 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 Publication No. 2012-073563 and Japanese Unexamined Patent 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, problems such as breakage due to stretching can be suppressed.

The production method including the step of extending the layered body and the step of dyeing can include those described in 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. Air extension (dry extension) method. From the viewpoints 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 suitable, especially It is a production method (two-stage stretching method) of performing a step of in-air auxiliary stretching before stretching in a boric acid aqueous solution described in Japanese Patent Laid-Open No. 2012-073563. It is also suitable for the production method (excessive dyeing and decolorization method) described in Japanese Patent Laid-Open No. 2011-2816. Over-stained and then de-stained. The polarizing film 4 is, for example, a polarizing film formed of the above-described polyvinyl alcohol-based resin oriented with iodine, 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 oriented with iodine, and the laminate of the stretched PVA-based resin layer and the stretched resin base material is over-dyed, and then A polarizing film produced by decolorizing it.

The thickness of the polarizing film 4 is, for example, 20 µm or less, and 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-mentioned range, the winding up 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 Gazette [0225], [0226]), tilt alignment retardation film for viewing angle compensation (refer to Japanese Patent Laid-Open No. 2012-133303 Gazette [0227]), etc.

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

The thickness of the retardation film 5 is preferably 20 µm or less, preferably 10 µm or less, more preferably 1 to 9 µm, and particularly preferably 3 to 8 µm. Within the above-mentioned range, the winding up 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.

(Evaluation of adhesive sheets in flexible image display devices) As described above, the adhesive sheet 1 included in the flexible image display device 100 (or 110 ) can sufficiently relieve the strain applied to the layers constituting the device even after the device is wound. The extent to which the strain of each layer is relieved by the adhesive sheet 1 can be determined by the offset of each layer caused by the adhesive sheet when the flexible image display device 100 (or 110 ) is wound on the roller. evaluate. Hereinafter, as an example, a method of measuring the amount of displacement of each layer by the adhesive sheets 1 ( 1 a and 1 b ) in the flexible image display device 110 will be described. First, the laminated body 11 included in the flexible image display device 110 is attached to the support film 55 through the first adhesive sheet 1a, and is cut into a 320 mm×50 mm short strip shape to prepare the test piece 15 . FIG. 3A shows a cross-sectional view of the test piece 15 . As the support film 55, a resin film such as a polyethylene terephthalate (PET) film can be used, for example.

Next, the test piece 15 is wound around the roll 45 in a state where the support film 55 is in contact with the roll 45 . FIG. 3B is a side view of the test piece 15 after it has been completely wound by the roll member 45 . Next, the vicinity of the end portion (region C) of the test piece 15 after being completely wound up by the roller 45 is observed with a microscope or the like. FIG. 3C is an enlarged view of area C of FIG. 3B . Next, the distance between the end surface of the support film 55 and the end surface of the optical film 20 in the winding direction X of the test piece 15 is specified as the offset amount L1 by the first adhesive sheet 1a. And the distance between the edge surface of the optical film 20 in the winding direction X and the edge surface of the 2nd base material 2b is specified as the offset amount L2 by the 2nd adhesive sheet 1b. And the total value of the offset amount L1 and the offset amount L2 is specified as the offset amount L of the member by the adhesive sheet 1 in the laminated body 11. The larger the offset L is, the more the strain of each layer tends to be relieved by the adhesive sheet 1 . In addition, using the same method, it is also possible to measure the amount of displacement of each layer caused by the adhesive sheet 1 in the flexible image display device 100 .

When the radius r of the circle defined by the side surface of the roller 45 in contact with the test piece 15 is 5 mm, the offset amount L is, for example, 0.7 mm or more, preferably 1.0 mm or more, preferably 1.5 mm or more. At this time, the upper limit of the offset amount L is not particularly limited, but is, for example, 3.0 mm or less. In addition, the radius r corresponds to the minimum deflection radius of the test piece 15 . In this specification, the minimum deflection radius means the radius of curvature determined by the curved surface that can give the maximum curvature on the inner surface of the test piece 15 in a state where the test piece 15 is bent.

When the above-mentioned radius r is 10 mm, the offset amount L is, for example, 0.5 mm or more, preferably 0.8 mm or more, and preferably 1.0 mm or more. In this case, the upper limit value of the offset amount L is not particularly limited, but is, for example, 2.0 mm or less. When the above-mentioned radius r is 15 mm, the offset amount L is, for example, 0.3 mm or more, and preferably 0.5 mm or more. At this time, the upper limit value of the offset amount L is not particularly limited, but is, for example, 1.0 mm or less.

(Example of use of flexible image display device) As described above, in the flexible image display device 100 (or 110 ), the display portion constituted by the image display panel 3 can be rolled up. The flexible image display device 100 (or 110 ) having a display portion that can be taken up can be designed to be pulled in while being wound around the roller 45 as shown in FIG. 4 , for example. The flexible image display device 100 of FIG. 4 is a so-called rollable image display device. In addition, if the flexible image display device 100 is pulled in more than that shown in FIG. 4 , the device 100 will be rolled into a vortex.

In the flexible image display device 100 shown in FIG. 4 , the minimum bending radius may be, 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 or more. In the flexible image display device 100 shown in FIG. 4 , the minimum bending radius corresponds to the radius r of the circle defined by the side surface of the roller 45 in contact with the flexible image display device 100 .

In the flexible image display device 100 shown in FIG. 4 , the ratio of the area of the part of the display portion that can be taken up to the area of the entire display portion constituted by the image display panel 3 is, for example, 50% or more and 90% or less, and It should be greater than 50% and below 90%.

The flexible image display device 100 (or 110 ) of the present invention can be suitably used as a flexible liquid crystal display device, an organic EL (electroluminescence) display device, electronic paper and other image display devices. The flexible image display device 100 (or 110 ) can be used regardless of the resistive film method and the capacitive method such as the touch panel.

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. Then, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was fed with ethyl acetate relative to 100 parts by weight of the monomer mixture, and nitrogen gas was introduced while stirring slowly. After nitrogen substitution, the liquid temperature in the flask was maintained at around 55° C. to carry out the polymerization reaction 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 A3] A solution of (meth)acrylic polymer A2 and a (meth)acrylic polymer were prepared in the same manner as (meth)acrylic polymer A1 except that the monomers used were changed as shown in Table 1. A3 solution.

[Acrylic oligomer (oligomer B1)] 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 into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction pipe, and a cooler, as the polymerization initiator. 0.1 parts by weight of 2,2'-azobisisobutyronitrile and 140 parts by weight of toluene as the starting agent, nitrogen was introduced while stirring slowly, and nitrogen substitution was carried out, and the liquid temperature in the flask was kept at around 70°C for 8 hours The polymerization reaction was carried out to prepare an acrylic oligomer (oligomer B1) solution. The weight average molecular weight of the above-mentioned oligomer B1 was 4500.

[Table 1]

The abbreviations in Table 1 are as follows. 2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate LA: Lauryl Acrylate MA: methyl acrylate NVP: N-Vinylpyrrolidone AA: Acrylic HBA: 4-hydroxybutyl acrylate AIBN: Azo-based polymerization initiator, 2,2'-azobisisobutyronitrile (manufactured by KISHIDA Chemical Co., Ltd.)

[Make adhesive sheet] (Examples 1 to 7 and Comparative Examples 1 to 2) 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 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 dried for 2 minutes in an air-circulating constant temperature oven set at 155° C. to form Examples 1 to 7. and the adhesive sheets of Comparative Examples 1-2. The coating of the adhesive composition was performed using a fountain coater.

[Table 2]

The abbreviations in Table 2 are as follows. D110N: Trimethylolpropane/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) Peroxide: Benzoyl peroxide (manufactured by NOF Corporation, trade name: NYPER BMT)

[Manufacture 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 quarter-wave plate (λ/4 plate) and a 1/2-wave plate were laminated in this order using the adhesive sheet. An optical film composed of a plate (λ/2 plate), a polarizing film and a base material (protective film), and an optical film A with an adhesive layer is obtained. 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, was produced by using a polymerizable liquid crystal material (manufactured by BASF Corporation, Paliocolor LC242) showing 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 (BASF, IRGACURE 907) in toluene, in order to improve the coating properties, 0.1 to 0.5% by weight of a fluorine-based surfactant (DIC) was further added depending on the thickness of the liquid crystal. MEGAFACE), 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. 5 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 rollers 231, molds 222, 229, 232, 239, and Ultraviolet irradiation devices 225, 227, 235, 237 for irradiating ultraviolet rays from 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 unscrewed from the supply turntable 221 by 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 the state of contact between the two, 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. On the conveying surface of the PET substrate 214 in the shaping roller 230, there are formed linear irregularities (75 to the MD direction of the PET substrate that can form a λ/4 plate after further forming the above-mentioned alignment film of the polymerizable liquid crystal material). ° direction extension), by the above-mentioned curing, a cured film of ultraviolet curable resin having a shape corresponding to the unevenness on the exposed surface can be formed. 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 ultraviolet curable resin and an oriented cured film of a polymerizable liquid crystal material can be formed on the PET substrate 214 .

Next, the PET base material 214 with 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. Then, 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. On the conveying surface of the PET substrate 214 in the shaping roller 240, there are formed linear irregularities (15 to 15° with respect to the MD direction of the PET substrate) that can form a λ/2 plate after further forming the alignment film of the polymerizable liquid crystal material. ° direction extension), by the above-mentioned curing, a cured film of ultraviolet curable resin having a shape corresponding to the unevenness on the exposed surface can be formed. 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 ultraviolet curable resin and a directional cured film of a polymerizable liquid crystal material can be further formed on the λ/4 plate of the PET base material 214 to obtain 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.

An amorphous IPA copolymerized PET film (thickness 100 µm) having 7 mol % isophthalic acid (IPA) units was prepared as a thermoplastic resin substrate, and corona treatment (58 W/m ² /min) was applied to its surface. In addition, 1% by weight 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%) will be added here. The PVA (degree of polymerization 4200, degree of saponification 99.2%) was dissolved in water to obtain a PVA coating solution 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 consisting of a base material and a PVA layer on the base material.

Next, the obtained layered body was subjected to free-end stretching (air-assisted stretching) at 130° C. in air at a stretching ratio of 1.8 times 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 insolubilized is dyed to obtain a colored laminate. The dyeing was carried out 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 within the range of making the monomer transmittance of the PVA layer constituting the polarizing film finally obtained to reach 40-44%. 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 staining solution was set to 7. Next, the colored layered body was immersed in a boric acid cross-linking aqueous solution at a liquid temperature of 30° C. for 60 seconds to perform a cross-linking treatment to form a cross-linked structure between PVA molecules in the iodine-adsorbed PVA layer. 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 layered body 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 layered body with a final stretching ratio of 5.50 times. The extension direction of the boric acid water extension is the same as the extension direction of the aerial auxiliary extension implemented at the beginning. 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 potassium iodide content was 4 parts by weight relative to 100 parts by weight of water). Then, the washed stretched laminate was dried with hot air at 60°C to obtain a laminate of the substrate and the polarizing film (thickness 5 µm) formed on the substrate.

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 laminate obtained above to obtain a laminate (c) of the substrate 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 laminated body (a) were bonded through the adhesive sheet of the laminated body (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 procedures were performed to obtain a PET layer|adhesive sheet|λ/4 plate|λ/2 plate|polarizing film| Protective film | Adhesive sheet | Optical film B with multi-layer structure of polyimide (PI) layer with 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 is bonded to the exposed adhesive sheet. Next, facing the exposed protective film on the opposite side (corona-treated), the PI layer (thickness 50µm, electro- 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 is based on It was measured by GPC (gel permeation chromatography).・Analysis device: Tosoh Corporation, HLC-8120GPC ・Column: Tosoh Corporation, G7000H _XL +GMH _XL +GMH _XL・Column size: 7.8mmφ×30cm each, 90cm in gauge ・Column temperature: 40°C ・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 produced adhesive sheet was carried out by the above-mentioned method. The weight of a small piece obtained by scraping off 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.

＜Modulus＞ The evaluation of the 1000% modulus of the produced adhesive sheet was carried out in the above-described method. The tensile testing machine used AG-IS manufactured by Shimadzu Corporation. In addition, the winding of the adhesive sheet was performed while peeling the adhesive sheet from the base film.

<Continuous coiling test> The continuous winding test was performed using the optical film B with the adhesive layer as a sample for evaluation. The continuous coiling test was carried out as follows using a testing machine manufactured by YUASA SYSTEM Co., Ltd. Also, as shown in FIGS. 6A and 6B, the testing machine has a mechanism for repeatedly winding the test piece 15B, which is a planar body, and can be adjusted by adjusting the side surface of the roller 45 in contact with the test piece 15B. The radius of the circle to change the deflection radius. The continuous winding test was performed in a state in which a load 54 of 100 gf was applied vertically downward to the test piece 15B.

As the test piece 15B, the optical film B with the adhesive layer was cut into a short strip of 320 mm×50 mm. The test piece 15B was fixed to the roll member 45 with the double-sided adhesive tape so that the PET layer was inside so as to be wound up in the longitudinal direction thereof. The test was carried out under the conditions of a bending radius of 10 mm and a coiling speed of 5.7 m/min in a gas atmosphere of 25°C. The test piece 15B was wound up from the state of FIG. 6A so that the roller 45 made 3.3 revolutions. The continuous winding test is evaluated according to the number of windings until the layer constituting the optical film B with the adhesive layer peels off, or until a significant winding mark is left on the optical film B with the adhesive layer the number of windings. In addition, the test was terminated when the number of coiling times reached 100,000.

Judgment criteria are as follows. AA: 100,000 or more coiling times until peeling or significant curling marks occur (no problem in practical use) A: 50,000 to less than 100,000 times of coiling until peeling or significant curling marks occur (no problem in practical use) B: 30,000 to less than 50,000 times of coiling until peeling or significant curling marks occur (no problem in practical use) C: 10,000 to less than 30,000 times of coiling until peeling or significant curling marks occur (no problem in practical use) D: The number of times of coiling until peeling or significant curling marks occurs is less than 10,000 times (practically problematic)

[table 3]

As can be seen from Table 3, the optical film B (Examples 1 to 7) with an adhesive layer with a 1000% modulus of 0.01 to 0.6 N/mm ² and an adhesive sheet with a gel fraction of 30% or more was used on a continuous roll. The occurrence of significant curl marks and layer peeling were successfully suppressed sufficiently in the extraction test. On the other hand, the adhesive layer-attached optical film B of Comparative Example 1 having an adhesive sheet with a 1000% modulus of more than 0.6 N/mm ² had significant curl marks at an early stage of the continuous winding test. In the optical film B with the adhesive layer of Comparative Example 2 having the adhesive sheet with a gel fraction of less than 30%, the layer of the optical film B constituting the adhesive layer peeled off in the early stage of the continuous winding test .

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 15,15B: Test piece 20: Optical Film 45: Roller parts 54: load 55: Support film 100,110: Flexible Image Display Devices 200: Manufacturing device of retardation film 214: PET substrate 221: Supply carousel 231: Conveyor Roller 210, 212: Solutions of UV-curable resins 224, 234: Pressure Roller 226, 236: Peeling Rollers 230, 240: Forming Roller 222, 229, 232, 239: Die 225, 227, 235, 237: Ultraviolet Irradiation Devices C: area L: The amount of displacement of the member caused by the adhesive sheet in the laminated body, the coating liquid L1: Offset caused by the first adhesive sheet L2: Offset caused by the second adhesive sheet X: winding direction r: the radius of the circle

1 is a cross-sectional view of a laminate for a flexible image display device and a flexible image display device according to an embodiment of the present invention. 2 is a cross-sectional view of a laminate for a flexible image display device and a flexible image display device according to another embodiment of the present invention. FIG. 3A is a diagram for explaining a method of measuring the amount of displacement caused by the adhesive sheet for each layer constituting the flexible image display device. 3B is a diagram for explaining a method of measuring the amount of displacement caused by the adhesive sheet for each layer constituting the flexible image display device. FIG. 3C is a diagram for explaining a method of measuring the amount of displacement caused by the adhesive sheet for each layer constituting the flexible image display device. FIG. 4 is a side view showing an example of a flexible image display device. FIG. 5 is a diagram for explaining a method of manufacturing a retardation film. FIG. 6A is a diagram for explaining a continuous coiling test. FIG. 6B is a diagram for explaining the continuous coiling test.

1: adhesive sheet

2: Substrate

3: Image display panel

10: Laminates for flexible image display devices

100: Flexible image display device

Claims (6)

An adhesive sheet, which is used for a laminated body in a flexible image display device having a display part that can be reeled; the 1000% modulus of the adhesive sheet is 0.01-0.6 N/mm ² , and the gel fraction is 30 %above. According to the adhesive sheet of claim 1, the aforementioned 1000% modulus is 0.1 N/mm ² or less. According to the adhesive sheet of claim 1 or 2, the aforementioned gel fraction is 50% or more. A laminated body is used for a flexible image display device having a display part that can be taken up; The laminate has: The adhesive sheet of any one of claims 1 to 3, and The substrate supporting the aforementioned adhesive sheet. The laminate of claim 4 further includes a polarizing film. A flexible image display device is provided with a rollable display portion, and has: If the laminate of claim 4 or 5, and an image display panel; and The above-mentioned laminated body is located on the viewing side of the above-mentioned image display panel.

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