CN114641814A - Optical laminate and display device - Google Patents

Optical laminate and display device Download PDF

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Publication number
CN114641814A
CN114641814A CN202080075221.9A CN202080075221A CN114641814A CN 114641814 A CN114641814 A CN 114641814A CN 202080075221 A CN202080075221 A CN 202080075221A CN 114641814 A CN114641814 A CN 114641814A
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Prior art keywords
layer
adhesive layer
optical laminate
thickness
touch sensor
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Chinese (zh)
Inventor
姜大山
片宝蓝
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Sumitomo Chemical Co Ltd
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Sumitomo Chemical Co Ltd
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    • 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
    • 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
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • 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
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • 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
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/26—Layered products comprising a layer of synthetic resin characterised by the use of special additives using curing agents
    • 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
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)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
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • 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
    • B32B33/00—Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
    • 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
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/022—Mechanical properties
    • 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
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
    • 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
    • B32B7/03—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 with respect to the orientation of features
    • 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
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3025—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state
    • G02B5/3033—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid
    • G02B5/3041—Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state in the form of a thin sheet or foil, e.g. Polaroid comprising multiple thin layers, e.g. multilayer stacks
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0416—Control or interface arrangements specially adapted for digitisers
    • 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
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • 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
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/42—Polarizing, birefringent, filtering
    • 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
    • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
    • B32B2309/08—Dimensions, e.g. volume
    • B32B2309/10—Dimensions, e.g. volume linear, e.g. length, distance, width
    • B32B2309/105—Thickness
    • 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
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays

Abstract

The purpose of the present invention is to provide an optical laminate and a display device having excellent bendability and excellent impact resistance. The invention provides an optical laminate, which comprises a front panel, a3 rd adhesive layer, a protective film, a2 nd adhesive layer, a polarizing layer, a1 st adhesive layer and a touch sensor layer in sequence from a visual recognition side, wherein the impact resistance index A represented by the following formula (1) is more than 200. [ in the formula, tnDenotes the thickness (μm), G 'of the nth adhesive layer from the touch sensor layer'nRepresenting the storage elastic modulus (MPa), a, at 25 ℃ of the nth adhesive layer from the touch sensor layernDenotes the distance (μm) from the upper surface of the touch sensor layer to the lower surface of the nth adhesive layer divided by tnThe resulting value.]
Figure DDA0003618417350000011

Description

Optical laminate and display device
Technical Field
The present invention relates to an optical laminate and a display device, and more particularly, to an optical laminate covering a display surface of a flexible display panel and a flexible display device including the optical laminate.
Background
In recent years, a flexible display device has attracted attention. The display device may be provided on a surface other than a flat surface, such as a curved surface or a curved surface. In addition, the flexible display device can be folded or formed in a roll shape to improve portability. In the aforementioned flexible display device, flexibility is also required for the optical laminate covering the display surface thereof.
Patent document 1 describes a laminated film including a1 st base film, a hard coat layer on one surface of the 1 st base film, and a2 nd base film on the other surface, and can be preferably used for a cover window (cover window) substrate (abstract) of a flexible image display device. The laminate film of patent document 1 has high surface hardness and excellent scratch resistance.
Patent document 2 describes a transparent window covering a display surface of a flexible display. The window has a bendable glass layer and a functional coating layer (abstract) disposed between the glass layer and the display panel and having a smaller elastic coefficient than the glass layer. The window of patent document 2 has a glass layer, so that the surface hardness is high and the scratch resistance is excellent. In addition, when an impact is applied to a part of the glass layer, the functional coating layer counteracts the tensile stress generated in the glass layer to prevent the glass layer from being broken (paragraph [0086 ]).
Patent document 3 describes a cover window in which a bending pattern formed of a plurality of concave shapes is formed in a bendable portion (claim 1). The bendable portion of the cover window is provided with the bending pattern, so that the bendable portion can be slightly deformed and easily bent. The cover window of patent document 3 has a bending pattern in a bendable portion to ensure bendability, so that the non-bendable portion can be formed relatively thick from a material having high rigidity, and high impact resistance can also be ensured (paragraph [0009 ]).
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2017-13492
Patent document 2: U.S. patent publication No. 2018/0034001
Patent document 3: korean patent laid-open publication No. 10-2018-0079093
Disclosure of Invention
In the display device, the touch panel operates by touching the surface of the display device. Depending on the kind of operation, the surface of the display device is not only rubbed but also hit in some cases. There are also situations when an object hits the surface of the display device when the device is dropped. Therefore, the display device is required to have impact resistance capable of withstanding not only friction against the surface but also a force applied rapidly in a vertical direction from the visual recognition side.
The laminated film of patent document 1 does not consider a force applied in a direction perpendicular to a viewing side of a display device, and impact resistance is not sufficient.
In addition, the glass used for the window of patent document 2 is a material having poor flexibility, and since the glass layer is provided, the window of patent document 2 has insufficient bendability.
Further, in patent document 3, the operation of forming a plurality of concave shapes in the film bendable portion is complicated, and the manufacturing cost is high. When a portion of an optical film is patterned, the light transmittance of the portion changes, and the versatility as a film material is also reduced. In addition, since flexibility is required in a state where a bending pattern is formed, rigidity of a material cannot be improved so much, and it is difficult to achieve sufficiently high impact resistance.
The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide an optical laminate having excellent bendability and excellent impact resistance. It is also an object of the present invention to provide a display device having the optical laminate, which has excellent bendability and excellent impact resistance.
The invention provides an optical laminate, which comprises a front panel, a3 rd adhesive layer, a protective film, a2 nd adhesive layer, a polarizing layer, a1 st adhesive layer and a touch sensor layer in sequence from a visual recognition side,
has an impact resistance index A of 200 or more represented by the following formula,
Figure BDA0003618417330000021
[ in the formula, tnDenotes the thickness (μm), G 'of the nth adhesive layer from the touch sensor layer'nRepresenting the storage elastic modulus (MPa), a, at 25 ℃ of the nth adhesive layer from the touch sensor layernDenotes the distance (μm) from the upper surface of the touch sensor layer to the lower surface of the nth adhesive layer divided by tnThe resulting value.]
In one embodiment, the optical laminate has an impact resistance index a of 2000 or more.
In a certain mode, the No. 1, No. 2 and No. 3 adhesive layers have a thickness of 3 to 100 μm.
In a certain mode, the No. 1, No. 2 and No. 3 adhesive layers have a storage elastic modulus at a temperature of 25 ℃ of 0.005 to 1.0 MPa.
In one embodiment, the 1 st, 2 nd and 3 rd adhesive layers are formed from an adhesive composition containing a (meth) acrylic resin as a base polymer.
In certain forms, the 1 st, 2 nd, and 3 rd adhesive layers further comprise a crosslinking agent.
The present invention also provides any of the above optical layered bodies suitable for use in a display surface of a display panel.
The present invention also provides a display device including a display panel and any one of the above optical laminates applied to a display surface of the display panel.
According to the present invention, an optical laminate and a display device having excellent bendability and excellent impact resistance are provided.
Drawings
Fig. 1 is a cross-sectional view showing an example of the structure of an optical laminate of the present invention.
Fig. 2 is a cross-sectional view showing an example of the structure of the polarizing layer used in the optical layered body of the present invention.
Fig. 3 is a cross-sectional view showing an example of the structure of a touch sensor layer used in the optical laminate of the present invention.
Fig. 4 is a sectional view showing an example of the structure of the display device of the present invention.
Detailed Description
[ optical layered body ]
Fig. 1 is a cross-sectional view showing an example of the structure of an optical laminate of the present invention. The multilayer optical body 100 shown in fig. 1 includes a front panel 10, a3 rd adhesive layer 20, a protective film 30, a2 nd adhesive layer 40, a polarizing layer 50, a1 st adhesive layer 60, and a touch sensor layer 70 in this order from the viewer side.
The optical laminate 100 is preferably bendable at least in a direction in which the front panel 10 is inside. Bendable means bendable in a direction inward of the front panel 10 without causing cracks. The optical laminate of the present invention has excellent impact resistance, and can be an optical laminate having excellent impact resistance and excellent bending resistance. In one aspect, the optical laminate 100 is preferably bendable in a direction in which the front panel 10 is outward. In this case, the bendable means that the bendable panel can be bent in a direction in which the front panel 10 is outside without generating cracks.
The shape of the optical laminate in the plane direction may be, for example, a square shape, preferably a square shape having a long side and a short side, and more preferably a rectangle. When the shape of the optical laminate in the plane direction is rectangular, the length of the long side may be, for example, 10 to 1400mm, preferably 50 to 600 mm. The length of the short side is, for example, 5 to 800mm, preferably 30 to 500mm, and more preferably 50 to 300 mm. Each layer constituting the optical laminate may be subjected to R processing on the corners, or to notch processing or hole forming on the ends.
The thickness of the optical laminate is not particularly limited, and is, for example, 20 to 1000 μm, preferably 50 to 500 μm, because the thickness varies depending on the function required for the optical laminate, the use of the laminate, and the like.
[ front panel ]
The front panel 10 constitutes the outermost surface of the optical layered body when viewed from the viewing side.
The front panel 10 is not limited in material and thickness as long as it is a plate-like body that transmits light, and may be formed of only 1 layer, or 2 or more layers. Examples thereof include a plate-like body made of resin (for example, a resin plate, a resin sheet, a resin film, etc.), and a plate-like body made of glass (for example, a glass plate, a glass film, etc.).
The thickness of the front panel 10 may be, for example, 30 to 2000 μm, preferably 50 to 1000 μm, more preferably 50 to 500 μm, and still more preferably 50 to 100 μm.
The tensile elastic modulus of the front panel 10 is preferably 3GPa or more, more preferably 4GPa or more, and further preferably 5GPa or more. The tensile elastic modulus of the front panel 10 is preferably 10GPa or less, and more preferably 9GPa or less. When the tensile modulus of elasticity is equal to or higher than the above-described lower limit, when an impact is applied from the outside, the front panel is less likely to have a defect such as a dent, and the strength of the front panel is likely to be improved. When the tensile elastic modulus is not more than the above upper limit, the bending resistance of the front panel is easily improved. The tensile modulus of elasticity may be in the range described above in at least one of MD (Machine Direction) and TD (Transverse Direction), and preferably in both directions.
When the front panel 10 is a resin plate-like body, examples of the material include acrylic resins such as polymethyl (meth) acrylate and ethyl (meth) acrylate; polyolefin resins such as polyethylene, polypropylene, polymethylpentene and polystyrene; cellulose resins such as triacetyl cellulose, acetyl cellulose butyrate, propionyl cellulose, butyryl cellulose and acetyl propionyl cellulose; polyethylene resins such as ethylene-vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and polyvinyl acetal; sulfone resins such as polysulfone and polyethersulfone; ketone resins such as polyether ketone and polyether ether ketone; a polyetherimide; a polycarbonate-based resin; a polyester resin; a polyimide-based resin; a polyamide imide resin; and polyamide resins. These polymers may be used alone or in combination of 2 or more. Among them, polycarbonate-based resins, polyester-based resins, polyimide-based resins, polyamideimide-based resins, or polyamide-based resins are preferably used from the viewpoint of improving strength and transparency. The thickness of the resin plate-like body may be, for example, 30 to 2000 μm, preferably 50 to 1000 μm, more preferably 50 to 500 μm, or 100 μm or less.
The front panel 10 may be a film having a hard coat layer provided on at least one surface of a base film to further increase the hardness. As the base film, a film made of the above resin can be used. The hard coat layer may be formed on one surface of the substrate film or on both surfaces. By providing the hard coat layer, a resin film having improved hardness and scratch resistance can be produced. The hard coat layer is a cured layer of, for example, an ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resins, silicone resins, polyester resins, polyurethane resins, amide resins, and epoxy resins. The hard coating may contain additives to improve strength. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, and a mixture thereof.
When the front panel 10 is a glass plate, a strengthened glass for display is preferably used as the glass plate. The thickness of the glass plate may be, for example, 50 to 1000 μm. By using the glass plate, the front panel 10 having excellent mechanical strength and surface hardness can be constituted.
In the case where the optical laminate is used for a display device, the front panel 10 may function as a window film in the display device. The front panel 10 may further have a function as a touch sensor, a blue light cut-off function, a viewing angle adjustment function, and the like.
[ adhesive layer ]
The adhesive layer is composed of a3 rd adhesive layer 20 between the front panel 10 and the protective film 30, a2 nd adhesive layer 40 between the protective film 30 and the polarizing layer 50, and a1 st adhesive layer 60 between the polarizing layer 50 and the touch sensor layer 70. More specifically, the 3 rd adhesive layer 20 is an adhesive layer in contact with the front panel 10 and the protective film 30, the 2 nd adhesive layer 40 is an adhesive layer in contact with the protective film 30 and the polarizing layer 50, and the 1 st adhesive layer 60 is an adhesive layer in contact with the polarizing layer 50 and the touch sensor layer 70. The adhesive layers may be made of the same material or different materials.
The pressure-sensitive adhesive layer may be composed of a pressure-sensitive adhesive composition containing a resin such as a (meth) acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin as a main component. Among them, preferred is an adhesive composition containing a (meth) acrylic resin as a base polymer, which is excellent in transparency, weather resistance, heat resistance and the like. The adhesive composition may be an active energy ray-curable type or a thermosetting type.
As the (meth) acrylic resin (base polymer) used in the pressure-sensitive adhesive composition, for example, a polymer or copolymer using 1 or 2 or more of (meth) acrylic esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate as monomers is preferably used. It is preferred to copolymerize the polar monomer with the base polymer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.
The adhesive composition may comprise only the above-mentioned base polymer, and typically further comprises a crosslinking agent. Examples of the crosslinking agent include metal ions having a valence of 2 or more and a metal carboxylate salt formed between the crosslinking agent and a carboxyl group; a polyamine compound and a substance forming an amide bond with a carboxyl group; a polyepoxy compound, a polyhydric alcohol, and a substance forming an ester bond with a carboxyl group; a polyisocyanate compound and a substance forming an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.
The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by irradiation with an active energy ray such as an ultraviolet ray or an electron beam, and has a property of being capable of adhering to an adherend such as a film with adhesiveness even before irradiation with an active energy ray, and being cured by irradiation with an active energy ray to adjust the adhesion force. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. The active energy ray-curable adhesive composition may further contain an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent.
Further, a photopolymerization initiator, a photosensitizer and the like may be contained as necessary.
The binder composition may contain additives such as fine particles, beads (resin beads, glass beads, and the like), glass fibers, resins other than the base polymer, adhesion-imparting agents, fillers (metal powders, other inorganic powders, and the like), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, anticorrosive agents, and photopolymerization initiators for imparting light scattering properties.
The adhesive composition can be formed by applying a diluted solution of the above adhesive composition in an organic solvent to a substrate and drying the applied solution. In the case of using an active energy ray-curable pressure-sensitive adhesive composition, a cured product having a desired degree of curing can be produced by irradiating the formed pressure-sensitive adhesive layer with an active energy ray.
The pressure-sensitive adhesive layer has high viscoelasticity and has a function of alleviating a shock applied to the optical laminate. In the optical laminate of the present invention, the impact resistance of the optical laminate against an impact applied to the outermost surface of the optical laminate is improved by appropriately adjusting the properties of the pressure-sensitive adhesive layer. That is, even when an impact is applied to the surface of the optical laminate, the touch sensor layer and the wiring, elements, and the like of the display panel covered by the optical laminate are not easily damaged.
According to the research of the inventor, the following steps are shown: the elasticity, thickness and location of the adhesive layer is related to the impact resistance of the optical stack. The lower the elastic modulus of the pressure-sensitive adhesive layer is, the greater the impact-relaxing effect by the pressure-sensitive adhesive layer is. In addition, the thicker the pressure-sensitive adhesive layer is, the greater the impact-relaxing effect by the pressure-sensitive adhesive layer is. Further, the closer the position of the pressure-sensitive adhesive layer is to the display panel, the more effective the above-described impact relaxing effect by the pressure-sensitive adhesive layer is.
Here, the elastic modulus of the adhesive layer is represented by a storage elastic modulus G' (MPa). The thickness of the adhesive layer is represented by an observed value t (μm). The elastic modulus and the thickness of the adhesive layer can be determined for each layer using their characteristic values.
The 1 st adhesive layer is closest to the position of the adhesive layer from the display panel, and the 2 nd adhesive layer and the 3 rd adhesive layer are sequentially distant. Each adhesive layer itself has a thickness, and the thickness thereof is independently determined appropriately. Therefore, when only the reference portion is specified and the distances from the reference portion of the lowermost layer to the reference portion of each pressure-sensitive adhesive layer are simply compared, it is difficult to indicate the position of the pressure-sensitive adhesive layer with respect to the display panel.
Therefore, how far the target adhesive layer is from the display panel is represented by a distance d (μm) from the upper surface of the touch sensor layer as the lowermost layer to the display panel side surface (lower surface) of the target adhesive layer, and in order to eliminate the influence of the thickness of the adhesive layer, a characteristic value a obtained by dividing the distance by the thickness t (μm) of the target adhesive layer is defined. Assuming an object adhesive layer of a unit thickness, the characteristic value a ═ d/t indicates how far the object adhesive layer is from the display panel. In addition, a of the 1 st adhesive layer is defined as 1.
When these characteristic values are used to express the tendency of the impact relaxation performance of the pressure-sensitive adhesive layer, the tendency is inversely proportional to the elastic modulus G' of the pressure-sensitive adhesive layer, proportional to the thickness t of the pressure-sensitive adhesive layer, and inversely proportional to the distance a from the display panel. Accordingly, as a characteristic value indicating the impact relaxation performance of the pressure-sensitive adhesive layer, t/(a × G') may be considered. The 1 st pressure-sensitive adhesive layer, the 2 nd pressure-sensitive adhesive layer, and the 3 rd pressure-sensitive adhesive layer were subjected to the total of the above characteristic values to obtain characteristic values indicating the impact-relaxing performance of the entire optical laminate. In the present specification, this characteristic value is hereinafter referred to as an impact resistance index a.
The pressure-sensitive adhesive layer may be present in the polarizing layer and in the touch sensor layer, but is generally as thin as 5 μm or less, and therefore is not considered to affect the impact resistance of the optical laminate. Therefore, the adhesive layer inside the polarizing layer and the adhesive layer inside the touch sensor layer are not considered in calculating the impact resistance index a.
Figure BDA0003618417330000081
[ in the formula, tnDenotes the thickness (. mu.m), G 'of the nth adhesive layer from the touch sensor layer'nRepresenting the storage elastic modulus (MPa), a, at 25 ℃ of the nth adhesive layer from the touch sensor layernDenotes the distance (μm) from the upper surface of the touch sensor layer to the lower surface of the nth adhesive layer divided by tnThe resulting value.]
In an optical laminate comprising a front panel, a3 rd adhesive layer, a protective film, a2 nd adhesive layer, a polarizing layer, a1 st adhesive layer and a touch sensor layer in this order from the viewing side, the quality of the impact relaxation performance has a correlation with the value of the impact resistance index a. That is, in the layer structure having the protective film between the front panel and the polarizing layer, the merit of the impact relaxation performance and the value of the impact resistance index a have a correlation. The optical laminate of the present invention has a value of 200 or more. This makes it possible to realize a good impact-relaxing performance of the optical laminate while having durability against bending.
In one aspect, a of the optical laminate is preferably 266 or more, more preferably 500 or more, more preferably 1500 or more, further preferably 2000 or more, and may be 2500 or more. In another aspect, a of the optical layered body is preferably 250 or more, more preferably 266 or more, more preferably 500 or more, more preferably 1500 or more, further preferably 2000 or more, and may be 2500 or more.
In one embodiment, a of the optical laminate may be, for example, 6000 or less, preferably 5000 or less, and more preferably 4658 or less. In another embodiment, a of the optical laminate may be 6000 or less, preferably 5000 or less, more preferably 4800 or less, more preferably 4658 or less, or 4000 or less, for example.
The optical laminate A is preferably 2013-4658. If the a of the optical laminate is increased beyond 6000, peeling and cohesive failure may occur at the interface between the adhesive layer and another member or inside the adhesive layer during bending.
In a preferred embodiment, the thicknesses of the 1 st, 2 nd and 3 rd adhesive layers are appropriately selected from the range of 3 to 100 μm. When the pressure-sensitive adhesive layer is too thin, the impact resistance of the optical laminate is lowered. When the pressure-sensitive adhesive layer is too thick, the flexibility of the optical laminate is reduced. The thickness of the No. 1, No. 2 and No. 3 adhesive layers is preferably 5 to 70 μm, and more preferably 10 to 50 μm.
In a preferred embodiment, the storage elastic modulus at 25 ℃ of the 1 st, 2 nd and 3 rd adhesive layers is appropriately selected from the range of 0.005 to 1.0 MPa. When the storage elastic modulus is too low, the impact resistance of the optical laminate is lowered. When the storage elastic modulus of the 1 st, 2 nd and 3 rd adhesive layers is too high, the flexibility of the optical laminate is reduced. The storage elastic modulus of the No. 1, No. 2 and No. 3 adhesive layers is preferably 0.01 to 0.5MPa, more preferably 0.01 to 0.2 MPa. In another embodiment, the storage elastic modulus of the 1 st, 2 nd and 3 rd adhesive layers is preferably 0.01 to 0.1MPa, more preferably 0.02 to 0.09MPa, and may be 0.02 to 0.06 MPa.
[ protective film ]
The protective film 30 is positioned between the 3 rd adhesive layer 20 and the 2 nd adhesive layer 40. The protective film may contribute to improvement of impact resistance of the optical laminate. The protective film 30 may also function as a protective layer for protecting the polarizing layer 50.
The tensile elastic modulus of the protective film 30 is preferably 3GPa or more, more preferably 4GPa or more, and further preferably 5GPa or more. The tensile elastic modulus of the protective film 30 is preferably 10GPa or less, and more preferably 9GPa or less. When the tensile elastic modulus is not less than the above lower limit, the impact resistance of the optical laminate is easily improved when an impact is applied from the outside. Further, if the tensile elastic modulus is equal to or less than the above upper limit, the bending resistance of the protective film 30 is easily improved. The tensile modulus of elasticity may be in the range described above in at least one of MD (Machine Direction) and TD (Transverse Direction), and preferably in both directions.
As the material of the protective film 30, for example, a thermoplastic resin having light transmittance (preferably optically transparent), a polyolefin resin such as a chain polyolefin resin (polypropylene resin or the like) or a cyclic polyolefin resin (norbornene resin or the like), a cellulose ester resin such as cellulose triacetate or cellulose diacetate, a polyester resin, a polycarbonate resin, (meth) acrylic resin, a polystyrene resin, or a mixture or copolymer thereof can be used.
The protective film 30 may be a protective film having an optical function such as a retardation film or a brightness enhancement film. For example, a retardation film to which an arbitrary retardation value is given can be produced by stretching a film made of the above thermoplastic resin (uniaxial stretching, biaxial stretching, or the like), or forming a liquid crystal layer or the like on the film.
Examples of the chain polyolefin resin include a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, and a copolymer of 2 or more kinds of chain olefins.
The cyclic polyolefin resin is a generic name of resins polymerized by using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene (typically random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids and derivatives thereof, and hydrogenated products of these. Among them, for example, norbornene-based resins obtained by using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.
The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Copolymers thereof and modified hydroxyl groups partially with other substituents may also be used. Among them, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.
The polyester resin is a resin other than the cellulose ester resin having an ester bond, and generally comprises a polycondensate of a polycarboxylic acid or a derivative thereof and a polyol. As the polycarboxylic acid or a derivative thereof, dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalenedicarboxylate, and the like. As the polyol, a diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, and the like.
Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, polypropylene naphthalate, polycyclohexanedimethanol terephthalate, and polycyclohexanedimethanol naphthalate.
The polycarbonate resin is composed of a polymer in which monomer units are bonded to each other through carbonate groups. The polycarbonate-based resin may be a resin called a modified polycarbonate in which a polymer skeleton is modified, a copolymerized polycarbonate, or the like.
The (meth) acrylic resin is a resin having a compound having a (meth) acryloyl group as a main constituent unit. Specific examples of the (meth) acrylic resin include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, methyl methacrylate- (meth) acrylate copolymers, methyl methacrylate-acrylate- (meth) acrylic acid copolymers, methyl (meth) acrylate-styrene copolymers (such as MS resins), and copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (such as methyl methacrylate-cyclohexyl methacrylate copolymers and methyl methacrylate-norbornyl (meth) acrylate copolymers). It is preferable to use a polymer containing a poly (meth) acrylic acid C1-6 alkyl ester such as polymethyl (meth) acrylate as a main component. More preferably, a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.
The thickness of the protective film 30 is preferably 10 μm to 200 μm, more preferably 10 μm to 100 μm, and still more preferably 15 μm to 95 μm. The protective film 30 has an in-plane retardation Re (550) of, for example, 0nm to 10nm, and a retardation Rth (550) in the thickness direction of, for example, -80 nm to +80 nm.
[ polarizing layer ]
The polarizing layer 50 is positioned between the 2 nd adhesive layer 40 and the 1 st adhesive layer 60. Fig. 2 is a cross-sectional view showing an example of the structure of the polarizing layer. The polarizing layer 50 shown in fig. 2 includes a polarizer 51, an adhesive layer 52, an 1/2 wavelength plate 53, an adhesive layer 54, and a 1/4 wavelength plate 55 in this order from the viewer side. The polarizing layer may be a so-called circular polarizer. The thickness of the circularly polarizing plate may be 10 to 100. mu.m, 15 to 70 μm, or 20 to 50 μm. In such a range, the optical laminate can easily have both the bending resistance and the impact resistance.
The polarizing layer 50 may have an additional protective film (not shown) between the polarizer 51 and the 2 nd adhesive layer 40. The additional protective film is made of the same material as exemplified as the material of the protective film 30, and is bonded to the surface of the polarizer 51 via an adhesive layer (not shown).
The polarizer 51 passes linearly polarized light having a polarization plane in a specific direction, and light passing through the polarizer 51 becomes linearly polarized light vibrating in the transmission axis direction of the polarizer. The thickness of the polarizer 51 is, for example, about 1 μm to 80 μm.
As the polarizer 51, for example, a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, a film obtained by subjecting a hydrophilic polymer film such as an ethylene-vinyl acetate copolymer partially saponified film to a dyeing treatment and a stretching treatment with a dichroic substance such as iodine or a dichroic dye, or a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol or a desalted product of polyvinyl chloride may be used. Among these, as a film having excellent optical properties, a film obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching the dyed film is preferably used.
The iodine-based dyeing is performed by, for example, immersing a polyvinyl alcohol-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment or may be performed together with the dyeing. In addition, dyeing may be performed after stretching.
The polyvinyl alcohol film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the polyvinyl alcohol film in water and washing it with water before dyeing, not only dirt and an antiblocking agent on the surface of the polyvinyl alcohol film can be washed but also the polyvinyl alcohol film can be swollen to prevent uneven dyeing and the like.
The polarizer 51 may be, for example, a polarizer in which a dichroic dye is oriented in a cured film obtained by polymerizing a liquid crystal compound, as described in Japanese patent laid-open publication No. 2016-170368. As the dichroic dye, a dichroic dye having an absorption in a wavelength range of 380 to 800nm can be used, and an organic dye is preferably used. Examples of the dichroic dye include azo compounds. The liquid crystal compound is a liquid crystal compound that can be polymerized in an aligned state, and may have a polymerizable group in a molecule.
The visibility-corrected polarization degree of the polarizer 51 is preferably 95% or more, more preferably 97% or more. The content may be 99% or more, or 99.9% or more. The visibility correction polarization degree of the polarizer 51 may be 99.995% or less, or may be 99.99% or less. The visibility correction polarization degree can be calculated by performing visibility correction on the obtained polarization degree using an integrating sphere spectrophotometer ("V7100" (trade name) manufactured by japan spectrophotometer by JIS Z8701 "with a 2-degree field of view (C light source).
By setting the visibility-corrected polarization degree of the polarizer 51 to 99.9% or more, the initial (before bending) color tone can be easily adjusted to a position away from neutrality. Therefore, the color tone of the reflected light before and after bending, which will be described later, is less likely to change in sign with the coordinate axis a and the coordinate axis b in the chromaticity coordinates a × b interposed therebetween. Further, by making the visibility correction polarization degree of the polarizer 51 99.9% or more, the durability of the polarizer 51 can be improved. On the other hand, when the visibility correction polarization degree of the polarizer 51 is less than 95%, the polarizer does not function as an antireflection film.
The visibility-corrected monomer transmittance of the polarizer 51 is preferably 42% or more, more preferably 44% or more, preferably 60% or less, and further preferably 50% or less. The visibility correction single transmittance can be calculated by correcting the visibility of the obtained transmittance with a 2-degree field of view (C illuminant) of JIS Z8701 using an integrating sphere spectrophotometer ("V7100" (trade name) manufactured by japan spectrophotometers).
By setting the visibility-corrected orthogonal transmittance of the polarizer 51 to 42% or more, the orthogonal color tone of the polarizer 51 can be easily adjusted to a position away from the neutral side, and therefore, a color change can be made inconspicuous before and after bending described later. If the amount exceeds 50%, the polarization degree is too low, and the function as an antireflection may not be achieved.
The adhesive layer 52 is formed of, for example, an acrylic adhesive.
The 1/2 wavelength plate 53 has a function of changing the direction (polarization direction) of linearly polarized light by giving a phase difference of pi (═ λ/2) to the electric field vibration direction (polarization plane) of incident light. Further, if circularly polarized light is incident, the rotation direction of the circularly polarized light can be reversed.
The 1/2 wavelength plate 53 has an in-plane retardation value Re (λ) at a specific wavelength λ nm that satisfies Re (λ) ═ λ/2. As long as the formula is realized at an arbitrary wavelength (for example, 550nm) in the visible light region. Among them, Re (550), which is an in-plane retardation value at a wavelength of 550nm, preferably satisfies 210 nm. ltoreq. Re (550). ltoreq.300 nm. Further, it is more preferable to satisfy 220 nm. ltoreq. Re (550). ltoreq.290 nm.
Rth (550), which is a retardation value in the thickness direction of the 1/2 wavelength plate 53 measured at a wavelength of 550nm, is preferably-150 to 150nm, more preferably-100 to 100 nm.
The thickness of the 1/2 wave plate 53 is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 0.5 to 5 μm, and still more preferably 0.5 to 3 μm, from the viewpoint of easily making the wrinkle preventing effect remarkable. The thickness of the 1/2 wave plate 53 is a value obtained by measuring the thickness at any 5 points in the plane and arithmetically averaging the measured values.
The 1/2 wavelength plate 53 may include a film made of a resin exemplified as a material of the protective film 51 described later, a layer obtained by curing a liquid crystal compound, and the like. When the 1/2 wave plate 53 is made of resin, polycarbonate resin, cycloolefin resin, styrene resin, and cellulose resin are preferable. In the present embodiment, the 1/2 wavelength plate 53 preferably includes a layer obtained by curing a liquid crystal compound. The type of the liquid crystal compound is not particularly limited, but the liquid crystal compound can be classified into a rod-like type (rod-like liquid crystal compound) and a discotic type (discotic liquid crystal compound ) according to its shape. Further, there are a low molecular type and a high molecular type, respectively. The polymer generally refers to a molecule having a polymerization degree of 100 or more (polymer physical-phase transition kinetics, native well, 2 p., rock book store, 1992).
In this embodiment, any liquid crystal compound may be used. Further, 2 or more kinds of rod-like liquid crystal compounds, 2 or more kinds of discotic liquid crystal compounds, or a mixture of rod-like liquid crystal compounds and discotic liquid crystal compounds may be used.
As the rod-like liquid crystal compound, for example, the liquid crystal compounds described in claim 1 of Japanese patent application laid-open No. 11-513019 or paragraphs [0026] to [0098] of Japanese patent application laid-open No. 2005-289980 can be preferably used. As the discotic liquid crystal compound, for example, the liquid crystal compounds described in paragraphs [0020] to [0067] of Japanese patent application laid-open No. 2007-108732 or paragraphs [0013] to [0108] of Japanese patent application laid-open No. 2010-244038 can be preferably used.
The 1/2 wave plate 53 is more preferably formed using a liquid crystal compound having a polymerizable group (rod-like liquid crystal compound or discotic liquid crystal compound). This can reduce temperature change and humidity change in the optical characteristics.
The liquid crystal compound may be a mixture of 2 or more kinds. In this case, at least 1 species preferably has 2 or more polymerizable groups. That is, the 1/2 wavelength plate 53 is preferably a layer formed by fixing a rod-like liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group by polymerization, and such a layer is included in a layer obtained by curing a liquid crystal compound. In this case, it is not necessary to exhibit liquid crystallinity even after the layer is formed.
The type of the polymerizable group contained in the rod-like liquid crystal compound or the discotic liquid crystal compound is not particularly limited, and for example, a functional group capable of undergoing an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a cyclopolymerizable group, is preferable. More specifically, for example, (meth) acryloyl group, vinyl group, styryl group, allyl group, and the like can be given. Among them, (meth) acryloyl groups are preferable. The term "meth (acryloyl group" refers to a concept including both a methacryloyl group and an acryloyl group.
The method for forming the 1/2 wave plate 53 is not particularly limited, and known methods can be used. For example, the first 1/2 wavelength plate 53 can be produced by applying a composition for forming an optically anisotropic layer (hereinafter, simply referred to as "composition") containing a liquid crystal compound having a polymerizable group to a predetermined substrate (including a temporary substrate) to form a coating film, and subjecting the obtained coating film to a curing treatment (irradiation of ultraviolet rays (light irradiation treatment) or heating treatment).
The composition can be applied by a known method such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method.
The composition may contain components other than the liquid crystal compound. For example, a polymerization initiator may be contained in the composition. The polymerization initiator used may be selected from, for example, thermal polymerization initiators and photopolymerization initiators depending on the form of the polymerization reaction. Examples of the photopolymerization initiator include α -carbonyl compounds, acyloin ethers, α -hydrocarbon-substituted aromatic acyloin compounds, polynuclear quinone compounds, combinations of triarylimidazole dimers and p-aminophenyl ketones, and the like. The amount of the polymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total solid content of the composition.
In addition, the composition may contain a polymerizable monomer in terms of uniformity of the coating film and strength of the film. Examples of the polymerizable monomer include a radically polymerizable or cationically polymerizable compound. Among them, polyfunctional radical polymerizable monomers are preferable.
As the polymerizable monomer, a polymerizable monomer copolymerizable with the polymerizable group-containing liquid crystal compound is preferable. Specific examples of the polymerizable monomer include polymerizable monomers described in paragraphs [0018] to [0020] in Japanese patent laid-open No. 2002-296423. The amount of the polymerizable monomer used is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total mass of the liquid crystal compound.
In addition, the composition may contain a surfactant in terms of uniformity of the coating film and strength of the film. Examples of the surfactant include conventionally known compounds. Among them, fluorine compounds are particularly preferable. Specific examples of the surfactant include compounds described in paragraphs [0028] to [0056] in Japanese patent application laid-open No. 2001-330725 and compounds described in paragraphs [0069] to [0126] in Japanese patent application laid-open No. 2003-295212.
The composition may contain a solvent, and an organic solvent is preferably used. Examples of the organic solvent include amides (e.g., N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), alkyl halides (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1, 2-dimethoxyethane). Among them, alkyl halides and ketones are preferable. In addition, 2 or more organic solvents may be used in combination.
The composition may contain various alignment agents such as a vertical alignment promoter such as a vertical alignment agent on the polarizer interface side and a vertical alignment agent on the air interface side, and a horizontal alignment promoter such as a horizontal alignment agent on the polarizer interface side and a horizontal alignment agent on the air interface side. In addition to the above components, the composition may contain an adhesion improving agent, a plasticizer, a polymer, and the like.
1/2 the wavelength plate 53 may contain an alignment film having a function of defining the alignment direction of the liquid crystal compound. The alignment film generally contains a polymer as a main component. As a polymer material for an alignment film, many documents have described that a large number of commercial products can be obtained. Among these, polyvinyl alcohol, polyimide, and derivatives thereof are preferably used as the polymer material, and particularly, modified or unmodified polyvinyl alcohol is preferably used.
The alignment film usable in this embodiment can be a modified polyvinyl alcohol described in international publication No. 2001/88574, page 43, line 24 to page 49, line 8, and japanese patent No. 3907735, paragraphs [0071] to [0095 ].
The alignment film is subjected to a generally known alignment treatment. For example, rubbing treatment, photo-alignment treatment by irradiation with polarized light, and the like are mentioned, and photo-alignment treatment is preferable from the viewpoint of surface roughness of the alignment film.
The thickness of the alignment film is not particularly limited, but is usually 20 μm or less, preferably 0.01 to 10 μm, more preferably 0.01 to 5 μm, and still more preferably 0.01 to 1 μm.
1/4 the wavelength plate 55 has a function of converting a linearly polarized light having a specific wavelength into a circularly polarized light (or converting a circularly polarized light into a linearly polarized light) by giving a phase difference of pi/2 (λ/4) to the electric field vibration direction (polarization plane) of the incident light.
1/4 the in-plane retardation value Re (λ) of the wavelength plate 55 at a specific wavelength λ nm satisfies the condition that Re (λ) ═ λ/4. As long as the formula is realized at an arbitrary wavelength (for example, 550nm) in the visible light region. Among them, Re (550), which is an in-plane retardation value at a wavelength of 550nm, preferably satisfies 100 nm. ltoreq. Re (550). ltoreq.160 nm. Further, it is more preferable that 110 nm. ltoreq. Re (550). ltoreq.150 nm be satisfied.
Rth (550), which is a retardation value in the thickness direction of the 1/4 wavelength plate 55 measured at a wavelength of 550nm, is preferably-120 to 120nm, more preferably-80 to 80 nm.
The thickness of the 1/4 wave plate 55 is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 0.5 to 5 μm, and still more preferably 0.5 to 3 μm, in terms of preventing wrinkles caused by a difference in dimensional change between the front and back surfaces of the film during bending. The thickness of the 1/4 wave plate 55 is a value obtained by measuring the thickness at any 5 points in the surface and arithmetically averaging the measured values.
1/4 the wavelength plate 55 preferably contains a layer obtained by curing a liquid crystal compound. The kind of the liquid crystal compound is not particularly limited, and the same materials as those exemplified as the material of the 1/2 wavelength plate 53 can be used. Among them, a layer formed by fixing a rod-like liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group by polymerization is preferable. In this case, it is not necessary to exhibit liquid crystallinity even after the layer is formed.
Of the layers included in the polarizer 51, the layer obtained by curing the liquid crystal compound is preferably 1 layer or 2 layers in addition to the polarizer 51. When the layer obtained by curing the liquid crystal compound includes 3 or more layers, the number of layers likely to cause wrinkles increases, and thus wrinkles are likely to occur during bending.
As the adhesive layer 54, an active energy ray-curable adhesive (preferably, an ultraviolet-curable adhesive) containing a curable compound that is cured by irradiation with an active energy ray such as ultraviolet ray, visible light, electron beam, or X-ray, or an aqueous adhesive obtained by dissolving or dispersing an adhesive component such as a polyvinyl alcohol resin in water can be used. In the polarizer 51, the 1/2 wavelength plate 53 and the 1/4 wavelength plate 55 are laminated via the adhesive layer 54, whereby wrinkles can be prevented from occurring at the time of bending.
Since the active energy ray-curable adhesive exhibits good adhesiveness, an active energy ray-curable adhesive composition containing a cationically polymerizable curable compound and/or a radically polymerizable curable compound can be preferably used. The active energy ray-curable adhesive may further contain a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.
Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having 1 or 2 or more epoxy groups in the molecule), an oxetane compound (a compound having 1 or 2 or more oxetane rings in the molecule), and a combination thereof. Examples of the radically polymerizable curable compound include a (meth) acrylic compound (a compound having 1 or 2 or more (meth) acryloyloxy groups in the molecule), another vinyl compound having a radically polymerizable double bond, and a combination thereof. The cationic polymerizable curable compound and the radical polymerizable curable compound may be used in combination.
The active energy ray-curable adhesive may contain additives such as a cationic polymerization accelerator, an ion scavenger, an antioxidant, a chain transfer agent, an adhesion imparting agent, a thermoplastic resin, a filler, a flow control agent, a plasticizer, an antifoaming agent, an antistatic agent, a leveling agent, and a solvent, if necessary.
When the 1/2 wavelength plate 53 and the 1/4 wavelength plate 55 are bonded to each other with an active energy ray-curable adhesive, the 1/2 wavelength plate 53 and the 1/4 wavelength plate are laminated with the active energy ray-curable adhesive serving as the adhesive layer 54 interposed therebetween, and then the adhesive layer is cured by irradiation with an active energy ray such as ultraviolet light, visible light, electron beam, or X-ray. Among them, ultraviolet rays are preferable, and as the light source in this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used. When an aqueous adhesive is used, the 1/2 wavelength plate 53 and the 1/4 wavelength plate 55 may be laminated via the aqueous adhesive, and then heated and dried.
The thickness of the adhesive layer 54 is preferably 0.5 to 5 μm, more preferably 0.5 to 3 μm.
The storage elastic modulus of the adhesive layer 54 at 30 ℃ is preferably 600 to 4000MPa, more preferably 700 to 3500MPa, still more preferably 1000 to 3000MPa, and most preferably 1500 to 3000 MPa. By bonding the 1/2 wave plate 53 and the 1/4 wave plate 55 with the hard adhesive layer 54 exhibiting such a storage elastic modulus, the occurrence of wrinkles in the retardation layer during bending can be more easily prevented.
The storage elastic modulus at 30 ℃ of the adhesive layer 54 is a value measured when the storage elastic modulus at 30 ℃ of the adhesive layer 54 in the polarizer 51 is directly measured by the following method. On the other hand, when the measurement cannot be directly performed, it can be considered that the measurement is the same as the value of the storage elastic modulus measured by forming an adhesive layer test piece on a release paper under the same conditions (type of adhesive, curing conditions) as those for forming the adhesive layer 54, peeling the adhesive layer test piece from the release paper, and measuring the peeled adhesive layer test piece by the following method.
The storage elastic modulus of the adhesive layer 54 or the adhesive layer test piece can be measured by a commercially available dynamic viscoelasticity device, for example, "DVA-220" (trade name) manufactured by IT measurement control (ltd.).
[ touch sensor layer ]
The touch sensor layer 70 is located at the lowermost layer as viewed from the viewer side. Fig. 3 is a sectional view showing one example of the structure of the touch sensor layer. The touch sensor layer 70 shown in fig. 3 includes a transparent conductive layer 71, a separation layer 72, an adhesive layer 73, and a base material layer 74 in this order from the viewing side.
The touch sensor layer 70 is a sensor that can detect a position touched by the front panel 10, and the detection method is not limited as long as it has the transparent conductive layer 71, and examples thereof include a resistive film method, a capacitive method, an optical sensor method, an ultrasonic wave method, an electromagnetic induction coupling method, a surface acoustic wave method, and the like. Among them, a touch sensor layer of an electrostatic capacitance system is preferably used in terms of low cost, high response speed, and thin film. The touch sensor layer 70 preferably has a structure including a base material layer 74 and a transparent conductive layer 71 provided on the surface of the base material layer 74 on the adhesive layer 73 side, from the viewpoint of improving impact resistance. In the configuration in which the transparent conductive layer 71 is provided on the surface of the base material layer 74, the base material layer 74 and the transparent conductive layer 71 may be in contact with each other (for example, a touch sensor layer manufactured by the method 1 described later), or the base material layer 74 and the transparent conductive layer 71 may not be in contact with each other (for example, a touch sensor layer manufactured by the method 2 described later). The touch sensor layer 70 may include an adhesive layer, a separation layer, a protective layer, and the like in addition to the base material layer 74 and the transparent conductive layer 71. Examples of the adhesive layer include an adhesive layer and an adhesive layer. The thickness of the touch sensor layer 70 may be 1 μm to 100 μm, may be 5 μm to 50 μm, and may be 10 μm to 30 μm. In such a range, the optical laminate can easily have both the bending resistance and the impact resistance.
An example of the capacitive touch sensor layer includes a base material layer, a transparent conductive layer for position detection provided on a surface of the base material layer, and a touch position detection circuit. In a display device provided with an optical laminate having a capacitive touch sensor layer, when the surface of the front panel 10 is touched, the transparent conductive layer is grounded at the touched point via the capacitance of a human body. The touch position detection circuit detects grounding of the transparent conductive layer, thereby detecting a touched position. By having a plurality of transparent conductive layers separated from each other, more detailed positions can be detected.
The transparent conductive layer may be a transparent conductive layer made of a metal oxide such as ITO, or may be a metal layer made of a metal such as aluminum, copper, silver, gold, or an alloy thereof.
The separation layer may be a layer formed over a substrate such as glass for separating a transparent conductive layer formed over the separation layer from the substrate together with the separation layer. The separation layer is preferably an inorganic layer or an organic layer. Examples of the material for forming the inorganic layer include silicon oxide. As a material for forming the organic layer, for example, a (meth) acrylic resin composition, an epoxy resin composition, a polyimide resin composition, or the like can be used.
The touch sensor layer 70 may include a protective layer that is in contact with the transparent conductive layer 71 to protect the conductive layer. The protective layer includes at least one of an organic insulating film and an inorganic insulating film, and these films can be formed by spin coating, sputtering, vapor deposition, or the like.
The touch sensor layer 70 can be manufactured, for example, as follows. In the method 1, first, the base material layer 74 is laminated on the glass substrate via the adhesive layer. A transparent conductive layer 71 patterned by photolithography is formed on the base material layer 74. The glass substrate is separated from the base material layer 74 by heating, and the touch sensor layer 70 including the transparent conductive layer 71 and the base material layer 74 is obtained.
In the method 2, first, a separation layer is formed on a glass substrate, and a protective layer is formed on the separation layer as needed. A transparent conductive layer 71 patterned by photolithography is formed on the separation layer (or the protective layer). A protective film which can be peeled off is laminated on the transparent conductive layer 71, and the glass substrate is separated by transferring the protective film from the transparent conductive layer 71 to the separation layer. The substrate layer 74 and the release layer are bonded to each other through the adhesive layer, and the peelable protective film is peeled off, thereby obtaining the touch sensor layer 70 having the transparent conductive layer 71, the release layer, the adhesive layer, and the substrate layer 74 in this order. Note that a laminate including the transparent conductive layer 71 and the separation layer may be used as the touch sensor layer 70 without being bonded to the base material layer 74.
Examples of the substrate layer 74 of the touch sensor layer include resin films such as triacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, polyolefin, polycycloolefin, polycarbonate, polyethersulfone, polyarylate, polyimide, polyamide, and polystyrene. From the viewpoint of easily constituting a substrate layer having desired toughness, polyethylene terephthalate is preferably used.
The thickness of the base material layer 74 of the touch sensor layer is preferably 50 μm or less, and more preferably 30 μm or less, from the viewpoint of facilitating the formation of an optical laminate having excellent bending resistance. The thickness of the base material layer 74 of the touch sensor layer is, for example, 5 μm or more.
[ method for producing optical laminate ]
The optical laminate of the present invention is manufactured by combining the front panel and the protective film with the polarizing layer and the touch sensor layer using the adhesive layer. As a method of bonding the layers, a pressure-sensitive adhesive layer may be formed on the surface of one layer to be bonded and then the other layer may be stacked, or pressure-sensitive adhesive layers may be formed on the surfaces of both layers to be bonded and then the pressure-sensitive adhesive layers may be stacked. The pressure-sensitive adhesive layer may be formed on the surface to be bonded of the layers by using the pressure-sensitive adhesive composition as described above, or may be formed by preparing a sheet-like pressure-sensitive adhesive that can be handled independently and attaching the sheet-like pressure-sensitive adhesive to the surface.
The optical laminate may be disposed on a display surface of a display panel, for example, to constitute a display device. The optical laminate is particularly preferably used for a display surface of a flexible display panel. A display device comprising the optical laminate of the present invention has excellent impact resistance.
[ display device ]
Fig. 4 is a sectional view showing an example of the structure of the display device of the present invention. The display device 200 includes the optical laminate 100 disposed on the front surface (viewing side) thereof, and the display panel 80. The optical laminate 100 and the display panel 80 are typically bonded using an adhesive layer or an adhesive layer (not shown). The display panel may be configured to be foldable with the viewing side surface being an inner side, may be configured to be foldable with the viewing side surface being an outer side, or may be configured to be rollable. Specific examples of the display panel include a liquid crystal display element, an organic EL display element, an inorganic EL display element, a plasma display element, and a field emission type display element.
The display device 200 can be used for a mobile device such as a smart phone or a tablet, a television, a digital photo frame, an electronic signboard, a measuring instrument, an office machine, a medical machine, a computer machine, and the like.
Examples
The present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples. In the present example, the unit "part" of the ratio of the compounding materials is not particularly specified as a weight basis.
< production example 1 >
Manufacture of front panel
A Polyamideimide (PAI) film having a thickness of 50 μm was produced in the same manner as described in example 4 of Japanese patent application laid-open No. 2018-119141.
A composition for a hard coat layer was produced by mixing 30 parts of a polyfunctional acrylate ("MIRAMER M340" (trade name) manufactured by MIWON Specialty Chemical), 50 parts of a nano silica sol (average particle diameter 12nm, solid content 40%) dispersed in propylene glycol monomethyl ether, 17 parts of ethyl acetate, 2.7 parts of a photopolymerization initiator ("Irgacure 184" (trade name) manufactured by CIBA), and 0.3 part of a fluorine-based additive ("KY-product" manufactured by shin-Etsu Chemical Co., Ltd.) with a mixer and filtering the mixture with a filter made of polypropylene (PP).
A composition for a hard coat layer is applied to a single surface of a PAI film, dried with a solvent, and UV-cured, thereby producing a front panel having a hard coat layer on one side of the PAI film. The resulting front panel had a thickness of 60 μm and a tensile elastic modulus of 6 GPa.
< production example 2 >
Manufacture of circular polaroid
A polyvinyl alcohol (PVA) film having an average polymerization degree of about 2400, a saponification degree of 99.9 mol% or more and a thickness of 20 μm was prepared. The PVA film was immersed in pure water at 30 ℃ and then immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.02/2/100 at 30 ℃ to carry out iodine dyeing (iodine dyeing step). The PVA film subjected to the iodine dyeing step was immersed in an aqueous solution having a potassium iodide/boric acid/water mass ratio of 12/5/100 at 56.5 ℃ to be subjected to boric acid treatment (boric acid treatment step). The PVA film subjected to the boric acid treatment step was washed with pure water at 8 ℃ and then dried at 65 ℃ to obtain a polarizer in which iodine was adsorbed and oriented to polyvinyl alcohol. The PVA film is stretched in the iodine dyeing step and the boric acid treatment step. The total draw ratio of the PVA film was 5.3 times. The thickness of the resulting polarizer was 7 μm.
The obtained polarizer and a cycloolefin polymer (COP) film (product name "ZF-14" manufactured by Nippon Ruiyaku Co., Ltd.) having a thickness of 13 μm were bonded to each other with an in-plane retardation value at a wavelength of 550nm of 1nm by a nip roll through a water-based adhesive. The obtained laminate was dried at 60 ℃ for 2 minutes while maintaining the tension per unit width of 430N/m, to obtain a linear polarizing plate having a COP film on one side. As the water-based adhesive, a solution obtained by adding 3 parts of carboxyl-modified polyvinyl alcohol ("Kuraray poval KL 318" (trade name) manufactured by Kuraray corporation) and 1.5 parts of water-soluble polyamide epoxy Resin ("Sumirez Resin 650" (trade name, aqueous solution having a solid content concentration of 30%) manufactured by takaki chemical industry (corporation)) to 100 parts of water was used.
As the 1/2 wavelength plate, a film composed of a layer obtained by curing a liquid crystal compound and an alignment film was used. 1/2 the thickness of the wavelength plate is 2 μm. As the 1/4 wavelength plate, a film composed of a layer obtained by curing a liquid crystal compound and an alignment film was used. 1/4 the wavelength plate has a thickness of 1 μm.
The 1/2 wavelength plate and the 1/4 wavelength plate were bonded using an ultraviolet curable adhesive. The laminate of the 1/2 wavelength plate and the 1/4 wavelength plate was bonded to the linear polarizing plate via a (meth) acrylic adhesive having a thickness of 5 μm, to obtain a circular polarizing plate. The thickness of the circularly polarizing plate was 30 μm.
< production example 3 >
Production of adhesive and production of adhesive layer
[ adhesive layer A1 ]
A500 ml four-necked reactor in which nitrogen was refluxed and a cooling device was provided to facilitate temperature adjustment was charged with 25 parts of 4-hydroxybutyl acrylate (4-HBA), 50 parts of 2-ethylhexyl acrylate (2-EHA), 15 parts of Methyl Acrylate (MA) and 10 parts of isobornyl acrylate (IBOA), and then 100 parts of ethyl acetate (EAc) was charged as a solvent. The nitrogen was purged for 1 hour to remove oxygen, and the temperature of the mixture was maintained at 60 ℃. At the stage when the mixture became homogeneous, 0.07 part of Azobisisobutyronitrile (AIBN) as a reaction initiator was added to 100 parts of the mixture. The reaction was carried out for about 5 hours to produce an acrylic copolymer 1 having a weight-average molecular weight of about 80 ten thousand.
An adhesive composition was obtained by mixing 100 parts by mass of the acrylic copolymer 1 with 0.5 part by mass of a crosslinking agent ("CORONATE-L" (trade name) manufactured by Tosoh corporation. This pressure-sensitive adhesive composition was applied to a release film coated with a silicon release agent, and dried at 100 ℃ for 1 minute to obtain a pressure-sensitive adhesive layer a 1. The adhesive layer a1 had a storage elastic modulus (G') of 0.3 MPa. In the examples described later, the thickness of the pressure-sensitive adhesive layer was adjusted by adjusting the coating thickness of the pressure-sensitive adhesive composition.
[ adhesive layer A2 ]
Acrylic copolymer 2 was produced in the same manner as acrylic copolymer 1 except that Butyl Acrylate (BA) was used instead of Methyl Acrylate (MA). In addition, an adhesive layer a2 was obtained in the same manner as the adhesive layer a 1. Adhesive layer a2 had a storage elastic modulus (G') of 0.08 MPa.
[ adhesive layer A3 ]
Acrylic copolymer 3 was produced in the same manner as acrylic copolymer 1 except that Hexyl Acrylate (HA) was used instead of Methyl Acrylate (MA). In addition, an adhesive layer A3 was obtained in the same manner as the adhesive layer a 1. Adhesive layer a3 had a storage elastic modulus (G') of 0.02 MPa.
< production example 3 >
Production of optical laminate
[ preparation of protective film ]
A polyethylene terephthalate (PET) film (SH 82 (trade name) manufactured by SKC) having a thickness of 80 μm was prepared as a protective film. The tensile modulus of elasticity of the PET film was 5GPa in the machine direction and 2GPa in the transverse width direction.
[ preparation of touch sensor Panel ]
A touch sensor panel was prepared in which a transparent conductive layer made of ITO, a separation layer made of an acrylic resin, an adhesive layer, and a base layer made of a COP film were laminated in this order from the viewing side. The total thickness of the transparent conductive layer, the separation layer, and the adhesive layer was 7 μm. The thickness of the substrate layer was 13 μm.
[ production of optical laminate ]
The PAI film side surface of the front panel, the surface and the back surface of the protective film, the surface and the back surface of the circularly polarizing plate, and the transparent conductive layer side surface of the touch sensor panel were subjected to corona treatment. The corona treatment was carried out at a frequency of 20 kHz/voltage of 8.6 kV/power of 2.5 kW/speed of 6 m/min. Referring to fig. 1, the respective layers were laminated in order of the front panel 10, the 3 rd adhesive layer 20, the protective film 30, the 2 nd adhesive layer 40, the polarizing layer 50, the 1 st adhesive layer 60, and the touch sensor layer 70 from the viewing side, and were bonded using a roll bonding machine, followed by curing with an autoclave to obtain an optical laminate.
< method for measuring layer thickness >
The thickness of each layer was measured using a contact type film thickness measuring instrument ("MS-5C" (trade name) manufactured by Nikon corporation. The polarizer and the alignment film were measured using a laser microscope ("OLS 3000" (trade name) manufactured by olympus corporation).
< storage elastic modulus (G') >)
The adhesive layers were laminated to 150 μm to prepare a sample. The storage elastic modulus (G') was measured using a rheometer ("MCR-301" (trade name) manufactured by Anton Parr). The measurement conditions were a temperature of 25 ℃, a stress of 1% and a frequency of 1 Hz.
< tensile elastic modulus >
Rectangular pieces having a long side of 110mm × a short side of 10mm were cut out from the parts using a super cutter. Next, both ends in the longitudinal direction of the measurement sample were clamped at a distance of 5cm by upper and lower clamps of a tensile tester ("AG-Xplus" (trade name) manufactured by shimadzu corporation, the measurement sample was stretched in the longitudinal direction of the measurement sample at a stretching speed of 4 mm/min under an environment of a temperature of 23 ℃ and a relative humidity of 55%, and the tensile elastic modulus (MPa) at the temperature of 23 ℃ and the relative humidity of 55% was calculated from the slope of a straight line between 20 and 40MPa of the obtained stress-strain curve. At this time, the thickness value of the layer measured as described above is used as the thickness for calculating the stress.
< evaluation of Performance of optical laminate >
[ impact resistance test ]
A rectangular chip having a long side of 150 mm. times.a short side of 70mm was cut out from the optical layered body using a super cutter. An adhesive layer is provided on the touch sensor layer side of the small piece, and is bonded to the acrylic plate. Then, the small piece was placed in an environment at 23 ℃ and 55% relative humidity, and the evaluation pen was held with its pen tip at a height of 10cm from the outermost surface of the front plate of the small piece and with its pen tip facing downward, and was dropped from this position.
On the front panel of the small piece, the position of the bridge in the pattern of the transparent conductive layer of the touch sensor layer was marked, and the evaluation was performed by dropping a pen so that the pen point contacted the mark. As the evaluation pen, a pen having a mass of 5.6g and a pen tip diameter of 0.75mm was used. The small piece after dropping with the evaluation pen was visually observed and the function of the touch sensor layer was confirmed, and evaluated according to the following criteria.
Excellent: has no crack. The touch sensor layer functionality is maintained.
Good (good): there was a crack. The touch sensor layer functionality is maintained.
X (not): there was a crack. No touch sensor layer function.
[ calculation of impact resistance index A ]
The impact resistance index A was calculated from the formula (1).
[ inside bending test ]
The flexural test was carried out at a temperature of 25 ℃. The optical laminate obtained in each of the examples and comparative examples was set in a flat state (unbent state) in a bending tester ("CFT-720C" (trade name) manufactured by Covotech corporation), and the optical laminate was bent 180 ° so that the front panel side was the inside and the distance between the opposing front panels was 4.0mm (bending radius 2 mm). Then, the original flat state is restored. The number of bending times was 1 in the case of 1 series of operations, and the bending operation was repeated. The bending speed was 60 rpm. The number of bending times when cracks were generated in the region subjected to bending in the bending operation and the adhesive layer was floated was recorded as the limit number of bending times. The number of limit bending times was evaluated according to the following criteria.
Excellent: the limit bending times is more than 10 ten thousand,
good (good): the limit bending times are more than 5 ten thousand and less than 10 ten thousand,
Δ (poor): the limit bending times is more than 1 ten thousand and less than 5 ten thousand,
x (not): the limit bending times are less than 1 ten thousand,
[ outside bending test ]
The optical layered bodies obtained in the examples and comparative examples were set in a flat state (unbent state) in a bending tester ("CFT-720C" (trade name) manufactured by Covotech corporation) and bent so that the front panel side was outward, and the limit number of times of bending was recorded and evaluated in the same manner as in the inward bending bendability test.
< example 1 >
An optical laminate was obtained by using an adhesive layer A3 (thickness 50 μm, G ' ═ 0.02MPa) for the 3 rd adhesive layer 20, an adhesive layer A3 (thickness 50 μm, G ' ═ 0.02MPa) for the 2 nd adhesive layer 40, and an adhesive layer A3 (thickness 50 μm, G ' ═ 0.02MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 1.
< example 2 >
An optical laminate was obtained by using an adhesive layer A3 (thickness 25 μm, G ' ═ 0.02MPa) for the 3 rd adhesive layer 20, an adhesive layer A3 (thickness 25 μm, G ' ═ 0.02MPa) for the 2 nd adhesive layer 40, and an adhesive layer A3 (thickness 50 μm, G ' ═ 0.02MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 1.
< example 3 >
An optical laminate was obtained by using an adhesive layer A3 (thickness 25 μm, G ' ═ 0.02MPa) for the 3 rd adhesive layer 20, an adhesive layer A3 (thickness 25 μm, G ' ═ 0.02MPa) for the 2 nd adhesive layer 40, and an adhesive layer A3 (thickness 25 μm, G ' ═ 0.02MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 1.
< example 4 >
An optical laminate was obtained by using an adhesive layer A3 (thickness 10 μm, G ' ═ 0.02MPa) for the 3 rd adhesive layer 20, an adhesive layer a2 (thickness 25 μm, G ' ═ 0.08MPa) for the 2 nd adhesive layer 40, and an adhesive layer a2 (thickness 25 μm, G ' ═ 0.08MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 1.
< example 5 >
An optical laminate was obtained by using an adhesive layer a1 (thickness 10 μm, G ' ═ 0.3MPa) for the 3 rd adhesive layer 20, an adhesive layer a2 (thickness 25 μm, G ' ═ 0.08MPa) for the 2 nd adhesive layer 40, and an adhesive layer a1 (thickness 50 μm, G ' ═ 0.3MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 1.
< example 6 >
An optical laminate was obtained by using an adhesive layer A3 (thickness 10 μm, G ' ═ 0.02MPa) for the 3 rd adhesive layer 20, an adhesive layer a1 (thickness 25 μm, G ' ═ 0.3MPa) for the 2 nd adhesive layer 40, and an adhesive layer a1 (thickness 50 μm, G ' ═ 0.3MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 1.
< comparative example 1 >
An optical laminate was obtained by using an adhesive layer a1 (thickness 10 μm, G ' ═ 0.3MPa) for the 3 rd adhesive layer 20, an adhesive layer a1 (thickness 10 μm, G ' ═ 0.3MPa) for the 2 nd adhesive layer 40, and an adhesive layer a1 (thickness 50 μm, G ' ═ 0.3MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 2.
< comparative example 2 >
An optical laminate was obtained by using an adhesive layer a1 (thickness 25 μm, G ' ═ 0.3MPa) for the 3 rd adhesive layer 20, an adhesive layer a1 (thickness 25 μm, G ' ═ 0.3MPa) for the 2 nd adhesive layer 40, and an adhesive layer a1 (thickness 25 μm, G ' ═ 0.3MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 2.
< comparative example 3 >
An optical laminate was obtained by using an adhesive layer a1 (thickness 10 μm, G ' ═ 0.3MPa) for the 3 rd adhesive layer 20, an adhesive layer a1 (thickness 10 μm, G ' ═ 0.3MPa) for the 2 nd adhesive layer 40, and an adhesive layer a1 (thickness 10 μm, G ' ═ 0.3MPa) for the 1 st adhesive layer 60. The impact resistance index a was calculated for the obtained optical laminate, and an impact resistance test and a bending test were performed. The results are shown in Table 2.
[ Table 1]
Figure BDA0003618417330000261
[ Table 2]
Figure BDA0003618417330000262
The laminate of the example having the impact resistance index a of 200 or more exhibits excellent performance in all of the impact resistance test, the inner bend bending test, and the outer bend bending test. In contrast, the laminate of the comparative example having an impact resistance index a of less than 200 had poor performance in some of the impact resistance test, the inner-side bending flexibility test and the outer-side bending flexibility test.
Description of the symbols
10 … front panel
20 … adhesive layer No. 3
30 … protective film
40 … adhesive layer 2
50 … polarizing layer
51 … polarizer
52 … adhesive layer
53 … 1/2 wavelength plate
54 … adhesive layer
55 … 1/4 wave plate
60 … adhesive layer 1
70 … touch sensor layer
71 … transparent conductive layer
72 … separating layers
73 … adhesive layer
74 … base material layer
80 … display panel
100 … optical laminate
200 … display device

Claims (8)

1. An optical laminate comprising, in order from the viewer side, a front panel, a3 rd adhesive layer, a protective film, a2 nd adhesive layer, a polarizing layer, a1 st adhesive layer, and a touch sensor layer,
has an impact resistance index A represented by the following formula of 200 or more,
Figure FDA0003618417320000011
in the formula, tnDenotes the thickness, G ', of the nth adhesive layer from the touch sensor layer'nRepresenting the storage elastic modulus at a temperature of 25 ℃ of the nth adhesive layer from the touch sensor layer, anDenotes the distance from the upper surface of the touch sensor layer to the lower surface of the nth adhesive layer divided by tnThe obtained values are in units of μm for the thickness and distance and in units of MPa for the storage modulus of elasticity.
2. The optical stack of claim 1, wherein the impact resistance index A is 2000 or greater.
3. The optical stack of claim 1 or 2, wherein the 1 st, 2 nd and 3 rd adhesive layers have a thickness of 3 to 100 μm.
4. The optical laminate according to any one of claims 1 to 3, wherein the storage elastic modulus at a temperature of 25 ℃ of the 1 st, 2 nd and 3 rd adhesive layers is from 0.005 to 1.0 MPa.
5. The optical laminate according to any one of claims 1 to 4, wherein the 1 st, 2 nd and 3 rd adhesive layers are formed from an adhesive composition containing a (meth) acrylic resin as a base polymer.
6. The optical stack of claim 5, wherein the 1 st, 2 nd and 3 rd adhesive layers further comprise a crosslinker.
7. The optical laminate according to any one of claims 1 to 6, wherein the optical laminate is applied to a display surface of a display panel.
8. A display device comprising a display panel and the optical laminate according to any one of claims 1 to 7 applied to a display surface of the display panel.
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