WO2024203781A1 - フレキシブルデバイス用粘着シート、フレキシブル積層体およびフレキシブルデバイス - Google Patents

フレキシブルデバイス用粘着シート、フレキシブル積層体およびフレキシブルデバイス Download PDF

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Publication number
WO2024203781A1
WO2024203781A1 PCT/JP2024/011167 JP2024011167W WO2024203781A1 WO 2024203781 A1 WO2024203781 A1 WO 2024203781A1 JP 2024011167 W JP2024011167 W JP 2024011167W WO 2024203781 A1 WO2024203781 A1 WO 2024203781A1
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Prior art keywords
adhesive layer
flexible
meth
pressure
adhesive
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Ceased
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PCT/JP2024/011167
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English (en)
French (fr)
Japanese (ja)
Inventor
広太郎 浦川
翔 小鯖
洋一 高橋
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Lintec Corp
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Lintec Corp
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Priority to KR1020257029179A priority Critical patent/KR20250166111A/ko
Priority to JP2025510679A priority patent/JPWO2024203781A1/ja
Priority to CN202480022597.1A priority patent/CN120958096A/zh
Publication of WO2024203781A1 publication Critical patent/WO2024203781A1/ja
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • C09J7/385—Acrylic polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
    • C08K3/013—Fillers, pigments or reinforcing additives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/0008—Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59
    • C08K5/0041—Optical brightening agents, organic pigments
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/04—Non-macromolecular additives inorganic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/06—Non-macromolecular additives organic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C09J133/062—Copolymers with monomers not covered by C09J133/06
    • C09J133/066—Copolymers with monomers not covered by C09J133/06 containing -OH groups
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • C09J133/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J201/00—Adhesives based on unspecified macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/133305—Flexible substrates, e.g. plastics, organic film
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K77/00—Constructional details of devices covered by this subclass and not covered by groups H10K10/80, H10K30/80, H10K50/80 or H10K59/80
    • H10K77/10—Substrates, e.g. flexible substrates
    • H10K77/111—Flexible substrates

Definitions

  • the present invention relates to an adhesive sheet for flexible devices, a flexible laminate, and a flexible device.
  • Display members having liquid crystal elements, light emitting diode (LED) elements, organic electroluminescence (OLED) elements, etc. are laminated with other members (such as a protective panel for protecting the display member) to form a display (display) for a device such as an electronic device.
  • Such a laminate of a display member and other members is generally formed by bonding the display member and other members together using the adhesive layer of an adhesive sheet.
  • bendable displays or so-called flexible displays
  • flexible displays have been proposed as displays for electronic devices.
  • Flexible displays are expected to have a wide range of applications, for example as stationary displays that are curved and installed on cylindrical pillars, or as mobile displays that can be folded or rolled up for easy portability.
  • Types of flexible displays include, for example, organic electroluminescence (OLED) displays, electrophoretic displays (electronic paper), and liquid crystal displays that use plastic film as a substrate.
  • OLED organic electroluminescence
  • electrophoretic displays electrophoretic paper
  • liquid crystal displays that use plastic film as a substrate.
  • Examples of such flexible displays include displays that are bent during molding and maintained in a bent state, and displays that are repeatedly bent during use.
  • Patent Document 1 discloses an adhesive sheet having an adhesive layer for bonding one flexible member to another flexible member that constitutes a flexible display.
  • One method to meet this requirement is to make the boundaries between the components that make up the flexible display less visible when the display is turned off, in order to give a sense of unity between the display and the surrounding components, such as the frame material, i.e., to make the display seamless.
  • One possible solution to satisfy this seamlessness requirement is to color the adhesive used to bond the components that make up the flexible display. This will improve the seamlessness of the flexible display, which is made up of multiple components, and therefore improve its design.
  • flexible displays are designed to be bent.
  • the inventors discovered that, particularly in the bent parts of a flexible display that are repeatedly bent during use, the optical properties of the adhesive change due to bending, causing the light that forms the image to be unintentionally colored as it passes through the bent parts, resulting in color unevenness in the displayed image.
  • the present invention has been made in consideration of these circumstances, and aims to provide an adhesive sheet that, even when used for bonding flexible materials, does not impair the design of a flexible display, suppresses lifting or peeling of the adhesive layer at bent sections, and suppresses color unevenness at bent sections.
  • a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer for bonding a first flexible member and a second flexible member,
  • the pressure-sensitive adhesive layer has a storage modulus of 0.12 MPa or less at 23° C.,
  • the lightness L * of the pressure-sensitive adhesive layer is 95 or less as defined by the CIE1976 L * a * b * color system;
  • the adhesive strength of the adhesive layer is 4 N/25 mm or more,
  • the pressure-sensitive adhesive sheet for flexible devices has a recovery rate of 80% or more of the pressure-sensitive adhesive layer.
  • a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer for bonding a first flexible member and a second flexible member,
  • the pressure-sensitive adhesive layer has a storage modulus of 0.12 MPa or less at 23° C.,
  • the lightness L * of the pressure-sensitive adhesive layer is 95 or less as defined by the CIE1976 L * a * b * color system;
  • the pressure-sensitive adhesive layer has a gel fraction of 84% or less,
  • the pressure-sensitive adhesive sheet for flexible devices has a recovery rate of 80% or more of the pressure-sensitive adhesive layer.
  • the (meth)acrylic acid ester polymer is an adhesive sheet for flexible devices according to [9], which contains an aromatic ring-containing monomer as a monomer unit constituting the (meth)acrylic acid ester polymer.
  • the (meth)acrylic acid ester polymer is an adhesive sheet for flexible devices according to [9] or [10], which contains a reactive functional group-containing monomer as a monomer unit constituting the (meth)acrylic acid ester polymer.
  • a flexible material laminate comprising a first flexible material, a second flexible material, and a pressure-sensitive adhesive layer that bonds the first flexible material and the second flexible material to each other,
  • the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for flexible devices according to any one of [1] to [11].
  • a flexible device comprising the flexible material laminate described in [12].
  • the present invention provides an adhesive sheet that, even when used for bonding flexible materials, does not impair the design of the flexible display, suppresses lifting or peeling of the adhesive layer at bent sections, and suppresses color unevenness at bent sections.
  • FIG. 1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention.
  • FIG. 2 is a cross-sectional view of a flexible component stack according to one embodiment of the present invention.
  • FIG. 3 is a cross-sectional view of a flexible device according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram for explaining the static bending test in the examples.
  • FIG. 5 is a schematic diagram for explaining the amount of deformation of a test piece in a static bending test in the examples.
  • FIG. 6 is a schematic diagram for explaining the deformation amount of a test piece in a dynamic bending test in the examples.
  • the adhesive sheet 1 for flexible devices has an adhesive layer 10 having a predetermined brightness, a first release sheet 11, and a second release sheet 12, as shown in FIG. 1. That is, in the present embodiment, the adhesive layer 10 is colored. The adhesive constituting the adhesive layer 10 will be described later.
  • two release sheets (first release sheet 11 and second release sheet 12) support the adhesive layer 10, and are arranged so that their release surfaces contact both main surfaces 10a and 10b of the adhesive layer, and are peelable from the adhesive layer. In other words, the adhesive layer 10 is sandwiched between two release sheets (first release sheet 11 and second release sheet 12) so as to be peelable.
  • the release surface of the release sheet refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability even without being subjected to a release treatment.
  • the release sheet will be described later.
  • the adhesive sheet according to this embodiment is used to bond a first member and a second member.
  • the adhesive sheet according to this embodiment is suitable for use in bonding bendable members (flexible members).
  • a flexible member is a member that maintains its functionality even when it is bent, such as folded.
  • Examples of flexible members include members that are molded to bend during the manufacture of a device that includes the flexible member and that maintain a bent state, and members that are repeatedly bent during the use of a device that includes the flexible member.
  • the design is enhanced by creating a sense of unity between the display frame and the display when the display is turned off.
  • One method of enhancing the design is to color the adhesive used to bond the components that make up the display.
  • the optical properties of the adhesive may change due to bending. If the optical properties of the adhesive change, when an image generated on the flexible display passes through the adhesive and is observed by a user, the light forming the image may be unintentionally colored a color different from the original color. When such coloring occurs, the color at the bent portion is observed as a color unevenness that differs from the color in other portions, even when the same color is displayed. This results in a deterioration of the display quality.
  • the physical properties of the adhesive layer are controlled to have a predetermined brightness.
  • the components of the adhesive sheet according to this embodiment are described in detail below.
  • the adhesive layer having a predetermined brightness bonds the first member and the second member together.
  • the adhesive layer preferably bonds the first flexible member and the second flexible member together.
  • the adhesive layer may be composed of one layer (single layer), or may be composed of two or more layers. When the adhesive layer has multiple layers, these multiple layers may be the same or different, and there are no particular limitations on the combination of layers that make up these multiple layers.
  • the adhesive layer has the following physical properties, so that the design of the flexible device in which the first flexible member and the second flexible member are bonded together is not impaired, lifting or peeling of the adhesive layer at the bent portion is suppressed, and color unevenness at the bent portion is effectively suppressed.
  • the thickness of the adhesive layer 10 is preferably 5 to 1000 ⁇ m, more preferably 10 to 500 ⁇ m, even more preferably 20 to 250 ⁇ m, particularly preferably 30 to 100 ⁇ m, and most preferably 40 to 70 ⁇ m. This provides adhesion that allows the first flexible member and the second flexible member to be bonded well, and excellent flexibility. In particular, lifting and peeling of the adhesive layer at the bent portion is suppressed, and color unevenness at the bent portion is easily and effectively suppressed.
  • the pressure-sensitive adhesive layer 10 has the following physical properties.
  • the pressure-sensitive adhesive layer preferably has a storage modulus (G') of 0.12 MPa or less at 23°C and a frequency of 1 Hz.
  • the storage modulus is one of the indicators of the ease of deformation (hardness) of the pressure-sensitive adhesive layer. This allows the pressure-sensitive adhesive layer to sufficiently follow the bending even when repeatedly bent, and prevents lifting or peeling from the member to which it is attached.
  • the storage modulus of the adhesive layer is preferably 0.001 to 0.12 MPa, more preferably 0.003 to 0.1 MPa, even more preferably 0.005 to 0.09 MPa, and particularly preferably 0.01 to 0.08 MPa, and among these, 0.02 to 0.07 MPa is preferable, and 0.03 to 0.05 MPa is most preferable.
  • the storage modulus of the adhesive layer can be adjusted, for example, by changing the composition of the adhesive (type and amount of reactive functional groups, molecular structure and glass transition temperature of the monomer composition used, etc.), the molecular weight of the material constituting the adhesive, etc.
  • the storage modulus (G') may be measured by a known method.
  • the adhesive layer is treated as a sample of a given size, and a dynamic viscoelasticity measuring device is used to apply strain to the sample at a given frequency within a given temperature range, to measure the modulus. From the measured modulus, the storage modulus under the above conditions can be calculated.
  • the adhesive strength of the adhesive layer to the soda lime glass is preferably 4 N/25 mm or more. This ensures sufficient adhesion to the adherend to be bonded, excellent repeated bending resistance, and suppresses peeling of the adhesive layer from the bonded member. From the above viewpoint, the adhesive strength is more preferably 4 to 100 N/25 mm, even more preferably 6 to 50 N/25 mm, particularly preferably 8 to 30 N/25 mm, and of these, preferably 10 to 20 N/25 mm. The method for measuring the adhesive strength of the adhesive layer will be described in detail in the Examples below.
  • the pressure-sensitive adhesive layer according to the present embodiment preferably has a recovery rate of 80% or more.
  • the recovery rate indicates the percentage of the state of the pressure-sensitive adhesive layer 60 seconds after the pressure-sensitive adhesive layer is released from the bent state, which is recovered to the state of the pressure-sensitive adhesive layer when it is not bent. In other words, when the state of the pressure-sensitive adhesive layer 60 seconds after the pressure-sensitive adhesive layer is released from the bent state is the same as the state of the pressure-sensitive adhesive layer when it is not bent, the recovery rate is 100%.
  • the bent and unbent states of the adhesive layer are similar, which suppresses changes in the properties of the adhesive layer caused by bending and reduces color unevenness in the bent areas.
  • the lower limit of the recovery rate of the adhesive layer is preferably 84% or more, more preferably 88% or more, even more preferably 92% or more, and particularly preferably 95% or more.
  • the upper limit of the recovery rate of the adhesive layer is usually preferably 100%.
  • the recovery rate of the adhesive layer can be adjusted, for example, by changing the composition of the adhesive (the type and amount of reactive functional groups, the molecular structure and glass transition temperature of the monomer composition used, etc.), the molecular weight of the material that constitutes the adhesive, etc. Specific measurement methods are described in detail in the examples below.
  • the lightness L * of the pressure-sensitive adhesive layer according to the present embodiment is preferably equal to or less than 95. This makes it easy to color the pressure-sensitive adhesive layer, making the boundary between the display unit and the surrounding members (e.g., frame material) less visible, and providing a sense of unity between the display unit and the surrounding members (seamlessness).
  • the lightness L * is preferably 1 to 92, more preferably 10 to 88, even more preferably 30 to 84, particularly preferably 50 to 80, and of these, preferably 50 to 74.
  • the chromaticity a * defined by the CIE1976L * a * b * color system is preferably -30 to 30, more preferably -15 to 15, particularly preferably -5 to 5, even more preferably -2 to 2, and preferably -1 to 1.
  • the chromaticity b * defined by the CIE1976L * a * b * color system is preferably -30 to 30, more preferably -18 to 18, particularly preferably -10 to 10, even more preferably -3 to 3, and preferably -1.5 to 1.5.
  • the total light transmittance of the pressure-sensitive adhesive layer according to the present embodiment is preferably 3% or more, more preferably 10% or more, particularly preferably 30% or more, and even more preferably 40% or more. This improves the visibility of the display section.
  • the upper limit of the total light transmittance is usually 100% or less, but from the viewpoint of easily satisfying the lightness L * , it is preferably 97% or less, more preferably 90% or less, particularly preferably 80% or less, even more preferably 70% or less, and among them, it is preferably 60% or less, and most preferably 52% or less.
  • the haze value of the adhesive layer according to this embodiment is preferably 80% or less, more preferably 60% or less, particularly preferably 40% or less, even more preferably 25% or less, and most preferably 15% or less, most preferably 10% or less. This makes it easier to control the total light transmittance of the adhesive layer within the above range, and also makes it easier to give a sense of unity between the display unit and the surrounding members (e.g., frame material) in the flexible display.
  • the lower limit of the haze value is usually 0%.
  • the haze value in this specification is a value measured in accordance with JIS K7136:2000.
  • optical properties (brightness, chromaticity, total light transmittance, haze value, etc.) of the above adhesive can be adjusted, for example, by changing the type and content of the colorant, which will be described later, and the composition of the adhesive.
  • the method for measuring the optical properties of the adhesive will be described in detail in the examples, which will be described later.
  • the gel fraction of the pressure-sensitive adhesive layer according to the present embodiment is preferably 30% or more and 84% or less. This allows the pressure-sensitive adhesive to exhibit a suitable cohesive strength capable of withstanding repeated bending. As a result, the aforementioned repeated bending properties are more excellent.
  • the gel fraction of the adhesive layer is more preferably 34 to 80%, particularly preferably 38 to 75%, even more preferably 42 to 70%, and most preferably 45 to 66%.
  • the method for measuring the gel fraction of the adhesive will be described in detail in the Examples below.
  • the composition of the adhesive constituting the adhesive layer is not particularly limited.
  • it may be any of an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, etc.
  • the adhesive may be any of an emulsion type, a solvent type, or a solventless type.
  • the adhesive may have a crosslinked structure or may not have a crosslinked structure.
  • the adhesive may be active energy ray curable or may not be active energy ray curable.
  • an acrylic adhesive is preferred as the adhesive, and an acrylic adhesive having a crosslinked structure is more preferred.
  • the adhesive is preferably an adhesive obtained by crosslinking an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B).
  • adhesive composition P an adhesive obtained by crosslinking an adhesive composition
  • A a (meth)acrylic acid ester polymer
  • B a crosslinking agent
  • the adhesive may be made of a material with a high biomass content, may be made of a material that can be recycled or reused, or may be made of a recycled or reused material.
  • (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms.
  • copolymer is also included in "polymer”.
  • the (meth)acrylic acid ester polymer (A) preferably contains, as monomer units constituting the polymer, a (meth)acrylic acid alkyl ester and a monomer having a reactive functional group in the molecule (a reactive functional group-containing monomer), which makes it easier to obtain a pressure-sensitive adhesive having a crosslinked structure and good adhesion.
  • the (meth)acrylic acid ester polymer (A) contains an aromatic ring-containing monomer as a monomer unit constituting the polymer. This makes it easier to obtain the above-mentioned physical properties.
  • the (meth)acrylic acid ester polymer (A) contains a nitrogen atom-containing monomer as a monomer unit constituting the polymer. This makes it easier to obtain the above-mentioned physical properties.
  • the (meth)acrylic acid ester polymer (A) preferably contains, as monomer units constituting the polymer, an alkyl (meth)acrylic acid ester, a reactive functional group-containing monomer, and an aromatic ring-containing monomer, and also preferably contains an alkyl (meth)acrylic acid ester, a reactive functional group-containing monomer, an aromatic ring-containing monomer, and a nitrogen atom-containing monomer.
  • the resulting adhesive can exhibit desirable adhesiveness.
  • a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 20 carbon atoms is preferred.
  • the alkyl group may be linear or branched, or may have a cyclic structure.
  • Examples of (meth)acrylic acid alkyl esters having an alkyl group with 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.
  • (meth)acrylic acid esters having an alkyl group with 1 to 8 carbon atoms are preferred, and (meth)acrylic acid esters having an alkyl group with 4 to 8 carbon atoms are particularly preferred.
  • n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl (meth)acrylate are preferred, and n-butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate are particularly preferred. These may be used alone or in combination of two or more.
  • the (meth)acrylic acid ester polymer (A) preferably contains 60 to 99.9 mass % of (meth)acrylic acid alkyl esters having an alkyl group with 1 to 20 carbon atoms as monomer units constituting the polymer, more preferably 70 to 99 mass %, even more preferably 80 to 98.5 mass %, and particularly preferably 90 to 98 mass %.
  • This makes it possible to impart suitable adhesion to the (meth)acrylic acid ester polymer (A), and also makes it easy to adjust the storage modulus G' of the resulting adhesive to a lower value.
  • the (meth)acrylic acid ester polymer (A) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and the (meth)acrylic acid ester polymer (A) reacts with the crosslinking agent (B) described below via the reactive functional group derived from the reactive functional group-containing monomer, forming a crosslinked structure (three-dimensional network structure) in the adhesive.
  • the crosslinking agent (B) described below the reactive functional group derived from the reactive functional group-containing monomer
  • Preferred reactive functional group-containing monomers include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), and monomers having an amino group in the molecule (amino group-containing monomers). These reactive functional group-containing monomers may be used alone or in combination of two or more. Among these, hydroxyl group-containing monomers or carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are particularly preferred. By including a hydroxyl group-containing monomer, the physical properties related to the storage modulus G' described above are easily satisfied, and in addition, fine adjustment of the storage modulus G' is also made easier.
  • hydroxyl group-containing monomers examples include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.
  • (meth)acrylic acid hydroxyalkyl esters having a hydroxyalkyl group with 1 to 4 carbon atoms are preferred.
  • 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and in particular, 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate are preferred. These may be used alone or in combination of two or more.
  • carboxyl group-containing monomers examples include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid.
  • acrylic acid is preferred from the viewpoint of the adhesive strength of the resulting (meth)acrylic acid ester polymer (A). These may be used alone or in combination of two or more.
  • the (meth)acrylic acid ester polymer (A) preferably contains 0.1 to 30 mass % of reactive functional group-containing monomer as a monomer unit constituting the polymer, more preferably 0.3 to 20 mass %, even more preferably 0.6 to 10 mass %, particularly preferably 0.8 to 5 mass %, and of these, 0.9 to 2 mass % is preferred. This ensures that the adhesive obtained by the crosslinking reaction with the crosslinking agent (B) has an appropriate cohesive force, making it easier to satisfy the above-mentioned physical properties.
  • the (meth)acrylic acid ester polymer (A) does not contain a carboxy group-containing monomer as a monomer unit constituting the polymer. Since a carboxy group is an acid component, by not containing a carboxy group-containing monomer, even if the object to which the adhesive is applied contains something that may be damaged by acid, such as a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, or a metal mesh, such damage caused by acid (corrosion, change in resistance, etc.) can be suppressed.
  • a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, or a metal mesh
  • the carboxyl group-containing monomer is not substantially contained, and includes the case where the carboxyl group-containing monomer is contained to an extent that the transparent conductive film, metal wiring, etc. are not corroded by the carboxyl group, in addition to the case where the carboxyl group is not contained at all.
  • the (meth)acrylic acid ester polymer (A) may contain the carboxyl group-containing monomer as a monomer unit in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.
  • aromatic ring-containing monomers examples include phenyl (meth)acrylate, 2-phenylethyl (meth)acrylate, benzyl (meth)acrylate, naphthyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, ethoxylated-o-phenylphenol acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, biphenyl di(meth)acrylate, pentafluorobenzyl (meth)acrylate, etc.
  • phenyl (meth)acrylate, 2-phenylethyl (meth)acrylate, benzyl (meth)acrylate, naphthyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and phenoxybutyl (meth)acrylate are preferred, and from the viewpoint of easily achieving favorable restorability, 2-phenoxyethyl (meth)acrylate is more preferred, and 2-phenoxyethyl acrylate is particularly preferred. These may be used alone or in combination of two or more.
  • the (meth)acrylic acid ester copolymer (A) preferably contains 0.1 to 30 mass% of an aromatic ring-containing monomer as a monomer unit constituting the polymer, more preferably 0.4 to 20 mass%, even more preferably 0.8 to 10 mass%, particularly preferably 1.2 to 6 mass%, and of these, preferably 1.5 to 3 mass%.
  • Nitrogen atom-containing monomers include monomers having an amino group, monomers having an amide group, and monomers having a nitrogen-containing heterocycle, among which monomers having a nitrogen-containing heterocycle are preferred. From the viewpoint of increasing the degree of freedom of the nitrogen atom-containing monomer-derived portion in the higher-order structure of the adhesive, it is preferred that the nitrogen atom-containing monomer does not contain a reactive unsaturated double bond group other than one polymerizable group used in polymerization to form the (meth)acrylic acid ester polymer (A).
  • the nitrogen atom-containing monomer may be used alone or in combination of two or more kinds.
  • Examples of monomers having an amino group include monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, monoethylaminopropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, etc.
  • Examples of monomers having an amide group include (meth)acrylamide, N-methyl(meth)acrylamide, N-methylol(meth)acrylamide, N-tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-phenyl(meth)acrylamide, N-(n-butoxymethyl)(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, and N-vinylcaprolactam.
  • Examples of monomers having a nitrogen-containing heterocycle include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, and N-vinylphthalimide.
  • N-(meth)acryloylmorpholine is preferred, and N-acryloylmorpholine is particularly preferred.
  • the (meth)acrylic acid ester polymer (A) preferably contains 0.1 to 20 mass % of a nitrogen atom-containing monomer as a monomer unit constituting the polymer, more preferably 0.5 to 12 mass %, and even more preferably 1 to 6 mass %. This makes it easier to satisfy the above-mentioned physical properties.
  • the (meth)acrylic acid ester polymer (A) contains a monomer having an alicyclic structure in the molecule (alicyclic structure-containing monomer) as a monomer unit constituting the polymer. Since the alicyclic structure-containing monomer is bulky, it is presumed that the presence of this in the polymer increases the distance between the polymers, and the resulting adhesive has excellent flexibility. This improves the physical properties described above.
  • the carbon ring of the alicyclic structure in the alicyclic structure-containing monomer may be a saturated structure or may have an unsaturated bond in part.
  • the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure (polycyclic structure) such as a bicyclic or tricyclic structure.
  • the alicyclic structure is preferably a polycyclic structure.
  • the polycyclic structure is particularly preferably a bicyclic to tetracyclic structure.
  • the number of carbon atoms in the alicyclic structure (meaning the total number of carbon atoms in the portion forming the ring, and in the case where multiple rings exist independently, the total number of carbon atoms) is preferably 5 to 15, more preferably 7 to 10.
  • alicyclic structure-containing monomers include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc.
  • dicyclopentanyl (meth)acrylate (alicyclic structure carbon number: 10), adamantyl (meth)acrylate (alicyclic structure carbon number: 10), or isobornyl (meth)acrylate (alicyclic structure carbon number: 7) are preferred, as they exhibit superior adhesion, with isobornyl (meth)acrylate being more preferred, and isobornyl acrylate being particularly preferred. These may be used alone or in combination of two or more.
  • the (meth)acrylic acid ester polymer (A) preferably contains 1 to 30 mass % of an alicyclic structure-containing monomer as a monomer unit constituting the polymer, more preferably 4 to 24 mass %, even more preferably 8 to 18 mass %, and particularly preferably 11 to 16 mass %. This makes it easier to satisfy the above-mentioned physical properties.
  • the (meth)acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, if desired.
  • monomers that do not contain reactive functional groups are preferred so as not to inhibit the above-mentioned action of the reactive functional group-containing monomer.
  • monomers include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.
  • the polymerization form of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.
  • the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 200,000 to 3,000,000, more preferably 400,000 to 2,400,000, even more preferably 650,000 to 2,000,000, particularly preferably 900,000 to 1,700,000, and most preferably 1,100,000 to 1,400,000. This makes it easier for the resulting adhesive to satisfy the physical properties related to the storage modulus G' described above.
  • the weight average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.
  • the (meth)acrylic acid ester polymer (A) may be used alone or in combination of two or more kinds.
  • crosslinker (B) The crosslinking agent (B) crosslinks the (meth)acrylic acid ester polymer (A) and forms a crosslinked structure (three-dimensional network structure) when the pressure-sensitive adhesive composition P containing the crosslinking agent (B) is heated, etc. As a result, the cohesive force of the resulting pressure-sensitive adhesive is improved, and the above-mentioned physical properties are easily satisfied.
  • the crosslinking agent (B) may be any that reacts with the reactive group possessed by the (meth)acrylic acid ester polymer (A). Examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Among these, it is preferable to use an isocyanate-based crosslinking agent that has excellent reactivity with the reactive functional group-containing monomer.
  • the crosslinking agent (B) may be used alone or in combination of two or more.
  • the isocyanate-based crosslinking agent contains at least a polyisocyanate compound.
  • polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and their biurets and isocyanurates, as well as adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil.
  • the content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 to 2 parts by mass, more preferably 0.05 to 1 part by mass or more, even more preferably 0.08 to 0.6 parts by mass, particularly preferably 0.10 to 0.3 parts by mass, and of these, preferably 0.12 to 0.21 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). This makes it easier to satisfy the above-mentioned physical properties.
  • the adhesive composition P according to the present embodiment preferably contains a colorant (C) for coloring the adhesive layer.
  • a colorant (C) for coloring the adhesive layer. This allows the total light transmittance, haze value, and lightness L * , chromaticity a * , and chromaticity b * defined by the CIE1976L * a * b * color system of the adhesive layer to be adjusted to desired ranges, thereby improving the design of the flexible device to which the adhesive layer is attached.
  • the colorant may be a pigment or a dye.
  • the pigment may be an inorganic pigment or an organic pigment. From the viewpoint of the durability of the resulting adhesive, inorganic pigments are preferred.
  • the color of the colorant can be appropriately selected to match the color of the flexible member from the viewpoints of seamlessness, screen color, etc., but generally, a dark or deep color such as black, brown, navy blue, purple, or blue is preferred, and black is particularly preferred.
  • inorganic pigments include carbon black, cobalt-based pigments, iron-based pigments, chromium-based pigments, titanium-based pigments, vanadium-based pigments, zirconium-based pigments, molybdenum-based pigments, ruthenium-based pigments, platinum-based pigments, ITO (indium tin oxide)-based pigments, and ATO (antimony tin oxide)-based pigments.
  • organic pigments and dyes examples include aminium dyes, cyanine dyes, merocyanine dyes, croconium dyes, squalium dyes, azulenium dyes, polymethine dyes, naphthoquinone dyes, pyrylium dyes, phthalocyanine dyes, naphthalocyanine dyes, naphtholactam dyes, azo dyes, condensed azo dyes, indigo dyes, perinone dyes, perylene dyes, dioxazine dyes, quinacridone dyes, isoindolinone dyes, quinophthalone dyes, pyrrole dyes, thioindigo dyes, metal complex dyes (metal complex dyes), dithiol metal complex dyes, indolephenol dyes, triarylmethane dyes, anthraquinone dyes, dioxazine dyes, naphthol dyes, azomethine dyes, benz
  • black pigments include carbon black, copper oxide, iron oxide, manganese dioxide, aniline black, and activated carbon.
  • black dyes include high-concentration vegetable dyes and azo dyes.
  • the above pigments or dyes can be mixed appropriately to obtain the desired physical properties in the adhesive layer.
  • carbon black nigrosine-based black dyes, and chromate-based black dyes are preferred because they are more likely to satisfy the above-mentioned physical properties and because they have advantages such as seamlessness and color on the screen.
  • the carbon black may or may not have been subjected to a specific treatment (e.g., a solvent-philic treatment) on its surface.
  • the above colorant (C) satisfies the following properties:
  • the colorant (C) is preferably one that has an average haze, which is the average of the haze value at a wavelength of 780 nm and the haze value at a wavelength of 380 nm, of a solution obtained by diluting the colorant 10,000 times with ethyl acetate, of 0.1 to 60%, more preferably 1 to 45%, particularly preferably 2 to 30%, even more preferably 3 to 20%, and of these, preferably 4 to 10%.
  • an average haze which is the average of the haze value at a wavelength of 780 nm and the haze value at a wavelength of 380 nm
  • a solution obtained by diluting the colorant 10,000 times with ethyl acetate of 0.1 to 60%, more preferably 1 to 45%, particularly preferably 2 to 30%, even more preferably 3 to 20%, and of these, preferably 4 to 10%.
  • the colorant (C) is preferably one in which the difference between the haze value at a wavelength of 780 nm and the haze value at a wavelength of 380 nm, when the colorant is diluted 10,000 times with ethyl acetate, is 0 to 30 points, more preferably 1 to 25 points, particularly preferably 3 to 20 points, and even more preferably 6 to 16 points.
  • the optical properties of the adhesive layer described above are easily satisfied.
  • the haze value at a wavelength of 780 nm of a solution obtained by diluting colorant (C) 10,000 times with ethyl acetate is preferably 0.1 to 50%, more preferably 0.5 to 24%, particularly preferably 1 to 12%, and even more preferably 2 to 5%.
  • the haze value at a wavelength of 380 nm of a solution obtained by diluting the above colorant 10,000 times with ethyl acetate is preferably 1 to 60%, more preferably 3 to 45%, particularly preferably 6 to 30%, and even more preferably 10 to 20%. This makes it easier to satisfy the optical properties of the adhesive layer.
  • the standard deviation of the haze value at each wavelength in the wavelength range of 380 nm to 780 nm at 5 nm intervals (i.e., 380 nm, 385 nm, 390 nm, ..., 775 nm, 780 nm) of a solution obtained by diluting colorant (C) 10,000 times with ethyl acetate is preferably 0.01 to 10, more preferably 0.1 to 8, particularly preferably 0.5 to 6, and even more preferably 1 to 5. This makes it easier for the optical properties of the pressure-sensitive adhesive layer to be satisfied.
  • the content of colorant (C) relative to 100 parts by mass of (meth)acrylic acid ester polymer (A) is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, even more preferably 0.1 to 1 part by mass, particularly preferably 0.2 to 0.8 parts by mass, and of these, preferably 0.3 to 0.6 parts by mass. This makes it easier for the optical properties of the pressure-sensitive adhesive layer to be satisfied.
  • the pressure-sensitive adhesive composition P according to the present embodiment preferably contains a silane coupling agent (D). This improves adhesion to the adherend and also suppresses lifting and peeling even when the composition is repeatedly bent.
  • the silane coupling agent is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, and is compatible with the adhesive component, particularly the (meth)acrylic acid ester polymer (A), and has optical transparency.
  • Such silane coupling agents include, for example, silicon compounds containing polymerizable unsaturated groups, such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; silicon compounds having an epoxy structure, such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; silicon compounds containing mercapto groups, such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane.
  • silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane
  • silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxy
  • Examples of such compounds include condensates of silicon compounds containing amino groups such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane, or condensates of at least one of these compounds with silicon compounds containing alkyl groups such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These compounds may be used alone or in combination of two or more.
  • the content of the silane coupling agent (D) is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 1 part by mass, even more preferably 0.15 to 0.7 parts by mass, and particularly preferably 0.18 to 0.4 parts by mass, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). This makes it easier to achieve the above-mentioned characteristics.
  • the pressure-sensitive adhesive composition P according to this embodiment also preferably contains an antistatic agent (E), which allows the pressure-sensitive adhesive layer to exhibit excellent antistatic properties.
  • the antistatic agent may be any agent capable of imparting antistatic properties to the adhesive layer, and examples thereof include ionic compounds and nonionic compounds, with ionic compounds being preferred.
  • the ionic compound may be a liquid (ionic liquid) or a solid (ionic solid) at room temperature.
  • an ionic compound refers to a compound in which a cation and an anion are primarily bound together by electrostatic attraction.
  • the antistatic agent may be used alone or in combination of two or more types.
  • nitrogen-containing onium salts nitrogen-containing onium salts, sulfur-containing onium salts, phosphorus-containing onium salts, alkali metal salts or alkaline earth metal salts are preferred, and from the viewpoint of blister resistance, nitrogen-containing onium salts or alkali metal salts are particularly preferred.
  • the nitrogen-containing onium salt is preferably an ionic compound composed of a nitrogen-containing heterocyclic cation and its counter anion.
  • the nitrogen-containing heterocyclic skeleton of the nitrogen-containing heterocyclic cation is preferably a pyridine ring, a pyrimidine ring, an imidazole ring, a triazole ring, an indole ring, etc., and among these, a pyridine ring or an imidazole ring is preferable.
  • the cation constituting the alkali metal salt is preferably a lithium ion, a potassium ion, or a sodium ion, and particularly preferably a lithium ion or a potassium ion.
  • preferred examples of the anion constituting the ionic compound include halogenated phosphate anions and sulfonylimide anions.
  • Preferred examples of halogenated phosphate anions include hexafluorophosphate.
  • Preferred examples of sulfonylimide anions include bis(fluoroalkylsulfonyl)imides and bis(fluorosulfonyl)imides.
  • the bis(fluoroalkylsulfonyl)imides may be bis(perfluoroalkylsulfonyl)imides, and among these, preferred examples include bis(trifluoromethanesulfonyl)imides.
  • nitrogen-containing onium salts having a pyridine ring and a halogenated phosphate anion include 1-butyl-4-methylpyridinium hexafluorophosphate, 1-hexyl-3-methylpyridinium hexafluorophosphate, 1-hexyl-4-methylpyridinium hexafluorophosphate, 1-octylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-dodecylpyridinium hexafluorophosphate, 1-tetradecylpyridinium hexafluorophosphate, 1-hexadecylpyridinium hexafluorophosphate, 1-dodecyl-4-methylpyridinium hexafluorophosphate, 1-tetradecyl-4-methylpyridinium hexafluorophosphate, 1-hexaxa
  • nitrogen-containing onium salts having a pyridine ring and a sulfonylimide anion include 1-decylpyridinium bis(fluorosulfonyl)imide, 1-ethylpyridinium bis(fluorosulfonyl)imide, 1-butylpyridinium bis(fluorosulfonyl)imide, 1-hexylpyridinium bis(fluorosulfonyl)imide, 1-butyl-3-methylpyridinium bis(fluorosulfonyl)imide, 1-butyl-4-methylpyridinium bis(fluorosulfonyl)imide, 1-hexyl-3-methylpyridinium bis(fluorosulfonyl)imide, 1-butyl-3,4-dimethylpyridinium bis(fluorosulfonyl)imide, 4-methyl-1-octylpyridinium bis(fluorosulfonyl)imide,
  • nitrogen-containing onium salts having an imidazole ring include 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-propyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-hexyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, etc.
  • alkali metal salts include potassium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, potassium bis(fluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.
  • the content of the antistatic agent in 100% by mass of the adhesive is preferably 0.1 to 10% by mass, more preferably 0.5 to 6% by mass, and even more preferably 1 to 3% by mass. This makes it easier to achieve excellent antistatic properties.
  • the adhesive composition P may contain additives that are commonly used in acrylic adhesives, if necessary.
  • additives include ultraviolet absorbers, infrared absorbers, tackifiers, antioxidants, light stabilizers, softeners, rust inhibitors, fillers, and refractive index adjusters. Note that the polymerization solvent and dilution solvent described below are not included in the additives that constitute the adhesive composition P.
  • the release sheets 11 and 12 protect the adhesive layer 10 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 10) is used.
  • the adhesive sheet 1 according to this embodiment, one or both of the release sheets 11 and 12 are not necessarily required.
  • the release sheets 11 and 12 may be, for example, polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, polyimide films, fluororesin films, etc. Crosslinked films of these may also be used. Furthermore, laminated films of these may also be used. From the perspective of the SDGs, the material constituting the release sheets may be a material with a high biomass content, a material that can be recycled or reused, or a recycled or reused material.
  • the release surfaces of the release sheets 11, 12 are preferably subjected to a release treatment.
  • release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. It is preferable that one of the release sheets 11, 12 is a heavy release type release sheet with a high release strength, and the other is a light release type release sheet with a low release strength.
  • the thickness of the release sheets 11 and 12 is usually about 20 to 150 ⁇ m.
  • the adhesive composition P can be produced, for example, by first producing a (meth)acrylic acid ester polymer (A) and then mixing the resulting (meth)acrylic acid ester polymer (A) with a crosslinking agent (B). If necessary, a colorant (C), a silane coupling agent (D), an antistatic agent (E), and additives may be added.
  • the (meth)acrylic acid ester polymer (A) can be produced, for example, by polymerizing a mixture of monomers that make up the polymer using a normal radical polymerization method.
  • the polymerization of the (meth)acrylic acid ester polymer (A) can be carried out by a solution polymerization method, using a polymerization initiator as necessary.
  • a solution polymerization method By polymerizing the (meth)acrylic acid ester polymer (A) using a solution polymerization method, it becomes easy to increase the molecular weight of the resulting polymer and adjust the molecular weight distribution, and it becomes possible to reduce the production of low molecular weight substances. As a result, it is easy to obtain an adhesive that is excellent in terms of resistance to repeated bending.
  • polymerization solvents used in the solution polymerization method include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone.
  • One type of polymerization solvent may be used, or two or more types may be used in combination.
  • polymerization initiators include azo compounds and organic peroxides, and two or more types may be used in combination.
  • a chain transfer agent such as 2-mercaptoethanol in the above polymerization process, the weight average molecular weight of the resulting polymer can be adjusted.
  • the crosslinking agent (B) is added to the obtained solution of the (meth)acrylic acid ester polymer (A) and mixed thoroughly to obtain a solvent-diluted adhesive composition P (coating solution). If necessary, a dilution solvent, a colorant (C), a silane coupling agent (D), an antistatic agent (E), and additives may be added.
  • any of the above components is a solid component, or if it is a component that will precipitate when mixed with other components in an undiluted state, that component may be dissolved or diluted in a dilution solvent before being mixed with the other components.
  • dilution solvents examples include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.
  • aliphatic hydrocarbons such as hexane, heptane, and cyclohexane
  • aromatic hydrocarbons such as toluene and xylene
  • halogenated hydrocarbons such as methylene chloride and
  • the concentration and viscosity of the prepared coating solution may be within the range that allows coating, and may be appropriately selected depending on the situation.
  • the adhesive composition P is diluted so that the concentration is 10 to 60% by mass. Note that the addition of a dilution solvent or the like is not a necessary condition for obtaining the coating solution, and if the adhesive composition P has a viscosity that allows coating, it is not necessary to add a dilution solvent. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent for the (meth)acrylic acid ester polymer (A) itself serves as the dilution solvent.
  • the adhesive constituting the adhesive layer is preferably obtained by crosslinking the above-mentioned adhesive composition P.
  • Crosslinking of the adhesive composition P can usually be performed by a heat treatment. This heat treatment can also serve as a drying treatment for volatilizing a diluting solvent and the like from a coating film of the adhesive composition P applied to a desired object.
  • the heating temperature for the heat treatment is preferably 50 to 150°C, and more preferably 70 to 120°C.
  • the heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes.
  • a curing period of about 1 to 2 weeks may be provided at room temperature (e.g., 23°C, relative humidity 50%), if necessary. If curing is required, an adhesive with a cross-linked structure will be obtained after the curing period has elapsed. If curing is not required, an adhesive with a cross-linked structure will be obtained after the heat treatment is completed.
  • the method for producing the adhesive sheet 1 is not particularly limited, and it may be produced by a known method.
  • the above-mentioned coating solution of the adhesive composition P is applied to the release surface of one of the first release sheets 11 (or the second release sheet 12), and the adhesive composition P is crosslinked by heat treatment to form a coating layer having a predetermined thickness.
  • the release surface of the other second release sheet 12 (or the first release sheet 11) is superimposed on the formed coating layer. If curing is required, the coating layer becomes the adhesive layer 10 after a predetermined curing period. Also, if curing is not required, the coating layer becomes the adhesive layer 10 as it is. In this way, the adhesive sheet 1 is obtained.
  • the above-mentioned coating liquid of the adhesive composition P is applied to the release surface of the first release sheet 11, and the adhesive composition P is crosslinked by heat treatment to form a coating layer, thereby obtaining the first release sheet 11 with the coating layer.
  • the above-mentioned coating liquid of the adhesive composition P is applied to the release surface of the other second release sheet 12, and the adhesive composition P is crosslinked by heat treatment to form a coating layer, thereby obtaining the second release sheet 12 with the coating layer.
  • the first release sheet 11 with the coating layer and the second release sheet 12 with the coating layer are bonded together so that both coating layers are in contact with each other. If curing is required, the coating layer becomes the adhesive layer 10 after a predetermined curing period. If curing is not required, the coating layer becomes the adhesive layer 10 as it is. In this way, the adhesive sheet 1 is obtained. According to this manufacturing method, it is possible to stably manufacture the adhesive layer 10 even if the adhesive layer 10 is thick.
  • Examples of methods for applying the adhesive composition P coating solution include bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.
  • the flexible material laminate 2 of this embodiment is composed of a first flexible member 21 (one flexible member), a second flexible member 22 (another flexible member), and an adhesive layer 10 located between them and bonding the first flexible member 21 and the second flexible member 22 to each other.
  • the adhesive layer 10 in the flexible material laminate 2 is the adhesive layer 10 of the adhesive sheet 1 described above.
  • the flexible material laminate 2 is a flexible device itself, or a material that constitutes part of a flexible device.
  • the flexible device may be a device that includes a material that has been bent once during manufacture and that maintains the bent state, or a device that includes a material that can be repeatedly bent (including folded).
  • the flexible device is preferably a display, but is not limited to this. Examples of flexible devices include organic electroluminescence (organic EL) displays, electrophoretic displays (electronic paper), liquid crystal displays that use a plastic substrate (film) as a substrate, light-emitting diode (LED) displays, foldable displays, stretchable displays, rollable displays, and the like. These may be touch panels.
  • the first flexible member 21 and the second flexible member 22 are, for example, members that can be repeatedly bent (including folded).
  • flexible members include cover films, barrier films, hard coat films, polarizing films (polarizing plates), polarizers, retardation films (retardation plates), viewing angle compensation films, brightness enhancement films, contrast enhancement films, diffusion films, semi-transmissive reflective films, electrode films, transparent conductive films, metal mesh films, film sensors (touch sensor films), liquid crystal polymer films, light-emitting polymer films, film-like liquid crystal modules, organic EL modules (organic EL films, organic EL elements), electronic paper modules (film-like electronic paper), TFT (Thin Film Transistor) substrates, etc.
  • the Young's modulus of the first flexible member 21 and the second flexible member 22 is preferably 0.1 to 10 GPa, more preferably 0.5 to 7 GPa, and even more preferably 1 to 5 GPa. Having the Young's modulus of the first flexible member 21 and the second flexible member 22 within the above ranges makes it easy to repeatedly bend each flexible member.
  • the thickness of the first flexible member 21 and the second flexible member 22 is preferably 10 to 3000 ⁇ m, more preferably 25 to 1000 ⁇ m, and even more preferably 50 to 500 ⁇ m. By having the thickness of the first flexible member 21 and the second flexible member 22 within the above range, it becomes easier to repeatedly bend each flexible member.
  • the interlayer adhesion (adhesive strength) between the first flexible member 21 and the second flexible member 22 is preferably 1 N/25 mm or more as a lower limit, particularly preferably 2 N/25 mm or more, and even more preferably 5 N/25 mm or more.
  • the interlayer adhesion is 1 N/25 mm or more, the flexible display has excellent bending resistance.
  • the interlayer adhesion is preferably 30 N/25 mm or less as an upper limit, more preferably 25 N/25 mm or less, and particularly preferably 20 N/25 mm or less.
  • the interlayer adhesion is 20 N/25 mm or less, the reworkability is excellent. As a result, even if a bonding error occurs between the flexible members, the two can be easily peeled off, and the flexible members (especially expensive flexible members) can be reused.
  • the interlayer adhesion basically refers to the adhesive strength measured by the 180-degree peel method in accordance with JIS Z0237:2009.
  • the measurement sample is 25 mm wide and 100 mm long, and a laminate consisting of a first flexible member/adhesive layer/second flexible member is prepared. It is pressurized at 0.5 MPa and 50°C for 20 minutes, and then left for 24 hours under conditions of normal pressure, 23°C, and a relative humidity of 50%, and then measured at a peel speed of 300 mm/min.
  • the other first release sheet 11 is peeled off from the adhesive layer 10 of the adhesive sheet 1, and the exposed adhesive layer 10 of the adhesive sheet 1 is bonded to the second flexible member 22 to obtain the flexible member laminate 2.
  • the bonding order of the first flexible member 21 and the second flexible member 22 may be reversed.
  • the flexible device according to the present embodiment includes the above-mentioned flexible material laminate 2, and may be composed of only the flexible material laminate 2, or may be configured to include one or more flexible material laminates 2 and other flexible materials.
  • the flexible device according to this embodiment has various components bonded together by the above-mentioned adhesive layer, so even when the device is repeatedly bent (e.g., 100,000 times), peeling of the adhesive layer from the bonded components is at least suppressed, and color unevenness in the bent portion is suppressed. Furthermore, the flexible device according to this embodiment has excellent design properties because various components are bonded together by the above-mentioned adhesive layer.
  • FIG. 3 shows a flexible device as an example of this embodiment. Note that the flexible device according to the present invention is not limited to this flexible device.
  • the flexible device 3 is constructed by laminating, from the top, a cover film 31, a first adhesive layer 32, a polarizing film 33, a second adhesive layer 34, a touch sensor film 35, a third adhesive layer 36, an organic EL element 37, a fourth adhesive layer 38, and a TFT substrate 39.
  • the cover film 31, polarizing film 33, touch sensor film 35, organic EL element 37, and TFT substrate 39 correspond to flexible members.
  • first adhesive layer 32, the second adhesive layer 34, the third adhesive layer 36, and the fourth adhesive layer 38 is the adhesive layer 10 of the adhesive sheet 1 described above. It is preferable that two or more of the first adhesive layer 32, the second adhesive layer 34, the third adhesive layer 36, and the fourth adhesive layer 38 are the adhesive layer 10 of the adhesive sheet 1 described above, and it is most preferable that all of the adhesive layers 32, 34, 36, and 38 are the adhesive layer 10 of the adhesive sheet 1.
  • Example 1 Preparation of (meth)acrylic acid ester polymer 48.6 parts by mass of n-butyl acrylate, 48.6 parts by mass of 2-ethylhexyl acrylate, 1.8 parts by mass of 2-phenoxyethyl acrylate, and 1 part by mass of 4-hydroxybutyl acrylate were copolymerized to prepare a (meth)acrylic acid ester polymer (A).
  • the molecular weight of the obtained (meth)acrylic acid ester polymer (A) was measured by the method described below, and the weight average molecular weight (Mw) was 1,200,000.
  • the weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement). (Measurement conditions) ⁇ GPC measurement device: Tosoh Corporation, HLC-8020 GPC columns (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation TSK gel GMHXL (x2) TSK gel G2000HXL Measurement solvent: tetrahydrofuran Measurement temperature: 40°C
  • the coating layer on the release sheet R1 obtained above was attached to a light release type release sheet R2, one side of which was a polyethylene terephthalate film treated with a silicone-based release agent, so that the release-treated surface was in contact with the coating layer, and the sheet was cured for 7 days under conditions of 23°C and 50% relative humidity to produce an adhesive sheet with an adhesive layer 50 ⁇ m thick.
  • This adhesive sheet had a structure of release sheet R1/adhesive layer (thickness: 50 ⁇ m)/release sheet R2.
  • the thickness of the adhesive layer was measured using a constant pressure thickness gauge (PG-02, manufactured by Tecrock Co., Ltd.) in accordance with JIS K7130. It was also confirmed that in the obtained adhesive sheet, release sheet R1 had a greater peel force from the adhesive layer than release sheet R2.
  • Examples 2 to 11, Comparative Examples 1 to 4 A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the composition and molecular weight of the (meth)acrylic acid ester polymer (A), the type and amount of the crosslinking agent (B), the type and amount of the coloring agent (C), the amount of the silane coupling agent (D), the type and amount of the antistatic agent (E) and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1.
  • the amounts of the crosslinking agent (B), the coloring agent (C), the silane coupling agent (D) and the antistatic agent (E) are amounts (solids equivalent) relative to 100 parts by mass (solids equivalent) of the (meth)acrylic acid ester polymer (A).
  • Table 2 shows the optical properties of the solutions in which colorants C1, C2 and C3 in Table 1 were diluted 10,000 times with ethyl acetate.
  • the optical properties shown in Table 2 were calculated from the haze values (%) obtained for the above-mentioned diluted solutions using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SH-7000") in accordance with JIS K7136:2000.
  • the difference from the haze value is the difference between the haze value at a wavelength of 780 nm and the haze value at a wavelength of 380 nm
  • the average haze is the average value of the haze value at a wavelength of 780 nm and the haze value at a wavelength of 380 nm
  • the standard deviation of the haze value is the standard deviation of the haze value at each wavelength at a 5 nm pitch in the wavelength range of 380 nm to 780 nm.
  • PET polyethylene terephthalate
  • Cosmoshine A4160 thickness: 50 ⁇ m
  • a composition containing an ultraviolet (UV) curable resin and reactive silica manufactured by Arakawa Chemical Industries Co., Ltd., product name "Opstar Z7530" was applied to one side (smooth surface not treated for easy adhesion) of the substrate with a Mayer bar to form a coating film, which was then dried at 70° C. for 1 minute.
  • a coating material containing perhydropolysilazane as the main component (Merck Performance Materials, product name "AZ-110a-20") was applied to the surface of the anchor coat layer by spin coating. It was then heated at 120°C for 1 minute to form a polysilazane layer containing perhydropolysilazane. The thickness of the formed polysilazane layer was 200 nm.
  • a plasma ion implantation device was used to implant argon (Ar) plasma ions into the surface of the polysilazane layer to form a gas barrier layer made of modified polysilazane.
  • argon (Ar) plasma ions into the surface of the polysilazane layer to form a gas barrier layer made of modified polysilazane.
  • a gas barrier film was obtained having a gas barrier layer made of modified polysilazane on one side of the substrate (PET film). Note that the modification of polysilazane progresses from the surface of the polysilazane layer. Therefore, the degree of modification does not affect the surface condition of the gas barrier layer, and therefore does not affect bending resistance, etc.
  • the storage modulus (G') (MPa) of the measurement sample was measured by a torsional shear method using a viscoelasticity measuring instrument (DYNAMICANALAYZER, manufactured by REOMETRIC) in accordance with JIS K7244-6, under the conditions of a measurement temperature of 23°C and a measurement frequency of 1 Hz.
  • the results are shown in Table 3.
  • the laminate consisting of the PI film/adhesive layer/gas barrier film obtained in this way was cut into a width of 50 mm and a length of 200 mm, which was used as a test piece S.
  • test piece S was held in a bent state between two holding plates P (distance between each plate: 4 mm) made of upright glass plates as shown in Figure 4, in an environment of 23°C and relative humidity of 50%, for 24 hours. At this time, the test piece S was bent so that the gas barrier film sides faced each other and the test was performed.
  • the adhesive layer produced in each of the examples and comparative examples was cut to a size of 80 mm x 80 mm, the adhesive layer was wrapped in a polyester mesh (product name: Tetron mesh #200), and the mass was weighed using a precision balance. The mass of the adhesive alone was calculated by subtracting the mass of the mesh alone from the weighed value. The mass at this time was designated as M1.
  • the release sheet R1 was peeled off from the above sample, and the exposed adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.), and then pressure was applied for 20 minutes at 0.5 MPa and 50°C in an autoclave manufactured by Kurihara Manufacturing Co., Ltd. After that, the sample was left for 24 hours under conditions of 23°C and 50% relative humidity, and then the adhesive strength (N/25 mm) was measured using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon”) at a peel speed of 300 mm/min and a peel angle of 180 degrees. Measurements were performed in accordance with JIS Z0237:2009 under conditions other than those described here. The results are shown in Table 3.
  • the release sheet R2 was peeled off from the adhesive sheet obtained in the examples and comparative examples, and the exposed adhesive layer was attached to one side of a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4160", thickness: 50 ⁇ m).
  • the release sheet R1 was peeled off, and the exposed adhesive layer was attached to one side of another polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4160", thickness: 50 ⁇ m).
  • the laminate was left for 24 hours under conditions of 23°C and 50% relative humidity.
  • the laminate thus obtained consisting of a PET film/adhesive layer/PET film, was used as a sample.
  • the obtained sample was placed immediately in front of a display (manufactured by Fujitsu, product name "LIFEBOOKA574/H", size 15.6 inches, resolution 1366 x 768) in an off state. At this time, the sample was placed so that the peripheral part of the sample was adjacent to the frame material of the display. Then, under a three-wavelength fluorescent lamp (distance from the fluorescent lamp: 200 cm), the color tone (blackness/whiteness) of the sample was visually judged, and the design regarding the color tone of the screen was evaluated according to the following criteria. The results are shown in Table 3. A: Deep black even under fluorescent light reflection. B: There is deep blackness without fluorescent light reflection. F: The whole thing looks whitish.
  • B Lifting or peeling of less than 1 mm occurred near the end of the bent portion, but the lifting or peeling did not spread to areas other than the bent portion, and was at a level sufficient for practical use.
  • C Lifting or peeling of 1 mm or more but less than 2 mm occurred near the end of the bent portion, but the lifting or peeling did not spread to areas other than the bent portion, and was at a level sufficient for practical use.
  • F Lifting or peeling was observed significantly at the bent portion and other than the bent portion.
  • the color unevenness of the adhesive layer at the bent portion was visually confirmed according to the following criteria.
  • the results are shown in Table 3. ⁇ Evaluation criteria for color unevenness> A: No change in color of the adhesive layer was visually observed at the bent portion. B: A slight change in color of the adhesive layer was visually observed at the bent portion, but was at a level that was barely noticeable. C: A change in color of the adhesive layer was visible at the bent portion, but was at a level that allowed practical use. F: A noticeable change in color of the adhesive layer was visually observed at the bent portion.
  • the adhesive sheet of the present invention can be suitably used, for example, to bond flexible materials.

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PCT/JP2024/011167 2023-03-29 2024-03-21 フレキシブルデバイス用粘着シート、フレキシブル積層体およびフレキシブルデバイス Ceased WO2024203781A1 (ja)

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JP2020007500A (ja) * 2018-07-11 2020-01-16 リンテック株式会社 粘着シートおよび表示体
JP2022156356A (ja) * 2021-03-31 2022-10-14 リンテック株式会社 粘着シート、繰り返し屈曲積層部材および繰り返し屈曲デバイス

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JP2020007500A (ja) * 2018-07-11 2020-01-16 リンテック株式会社 粘着シートおよび表示体
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