CN113359222A

CN113359222A - Optical laminate and display device

Info

Publication number: CN113359222A
Application number: CN202110224036.8A
Authority: CN
Inventors: 李昇祐; 金正熙
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2020-03-03
Filing date: 2021-03-01
Publication date: 2021-09-07

Abstract

The invention provides an optical laminate and a display device capable of suppressing generation of bubbles even when bent. The invention provides an optical laminate, which sequentially comprises a front panel, a1 st adhesive layer formed by using a1 st adhesive composition, a polarizing plate, a 2 nd adhesive layer formed by using a 2 nd adhesive composition and a back panel; in a1 st reference pressure-sensitive adhesive layer having a thickness of 200 μm formed using the 1 st pressure-sensitive adhesive composition, the shear recovery rates at a temperature of 25 ℃ before and after the deformation repetitive load test are R1A [% ] and R1B [% ], respectively, and in a 2 nd reference pressure-sensitive adhesive layer having a thickness of 200 μm formed using the 2 nd pressure-sensitive adhesive composition, the shear recovery rates at a temperature of 25 ℃ before and after the deformation repetitive load test are R2A [% ] and R2B [% ], respectively, and satisfy the following relational expressions (1) to (3). Δ R1 { (R1A) - (R1B) }/200 ≦ 0.2 … (1); Δ R2 { (R2A) - (R2B) }/200 ≦ 0.2 … (2); R1A > R2A … (3).

Description

Optical laminate and display device

Technical Field

The present invention relates to an optical laminate, and further relates to a display device including the optical laminate.

Background

Patent document 1 describes a laminate in which, when a laminate having a plurality of adhesive layers is folded, the storage modulus of the outermost adhesive layer on the convex side is substantially the same as or less than the storage modulus of the other adhesive layers.

Patent document 2 discloses a deformable adhesive composition for a display, which does not cause floating or breaking even at an ultra-low temperature of-20 ℃ while maintaining the adhesive properties at normal temperature and high temperature.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-28573

Patent document 2: korean laid-open patent No. 10-2019-0069334

Disclosure of Invention

When a display device including an optical laminate having a plurality of pressure-sensitive adhesive layers is bent, air bubbles may be generated in the pressure-sensitive adhesive layers in the optical laminate.

The invention aims to provide an optical laminate which can inhibit the generation of bubbles even if the optical laminate is bent, and a display device comprising the optical laminate.

The present invention provides an optical laminate and a display device exemplified below.

[ 1] an optical laminate comprising, in order: a front panel, a1 st adhesive layer formed using the 1 st adhesive composition, a polarizing plate, a 2 nd adhesive layer formed using the 2 nd adhesive composition, and a back panel,

in addition, in the 1 st reference pressure-sensitive adhesive layer having a thickness of 200 μm formed using the 1 st pressure-sensitive adhesive composition, the shear recovery rates at a temperature of 25 ℃ before and after the deformation repetitive load test are R1A [% ] and R1B [% ], respectively, and in the 2 nd reference pressure-sensitive adhesive layer having a thickness of 200 μm formed using the 2 nd pressure-sensitive adhesive composition, the shear recovery rates at a temperature of 25 ℃ before and after the deformation repetitive load test are R2A [% ] and R2B [% ], respectively, the following relational expressions (1) to (3) are satisfied.

ΔR1＝{(R1A)-(R1B)}/200≤0.2 (1)

ΔR2＝{(R2A)-(R2B)}/200≤0.2 (2)

R1A＞R2A(3)

[ 2] the optical laminate according to [ 1], further satisfying the following relational expression (4).

ΔR1≥ΔR2 (4)

[ 3] the optical laminate according to [ 1] or [ 2], wherein R2A [% ] is 20% or more.

The optical laminate according to any one of [ 1] to [ 3], wherein the back panel is a touch sensor panel.

A display device comprising the optical laminate according to any one of [ 1] to [ 4 ].

[ 6 ] according to the display device described above in [ 5 ], the display device can be bent with the front panel side as an outer side.

According to the present invention, an optical laminate and a display device can be provided in which bubble generation can be suppressed even when the optical laminate is bent.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of an optical laminate according to the present invention.

Fig. 2 is a sectional view schematically showing a method for producing an optical laminate according to the present invention.

Description of the reference numerals

100 laminate, 101 front panel, 102 1 st adhesive layer, 103 polarizer, 104 nd adhesive layer, 105 back panel.

Detailed Description

Hereinafter, embodiments of the optical laminate according to the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments below. In all the drawings below, the scale of each structural element is appropriately adjusted and shown in order to easily understand the structural element, and the scale of each structural element in the drawings does not necessarily coincide with the scale of the actual structural element.

< optical laminate >

Fig. 1 is a schematic cross-sectional view of an optical laminate according to an embodiment of the present invention. The optical laminate 100 includes a front panel 101, a1 st adhesive layer 102, a polarizing plate 103, a 2 nd adhesive layer 104, and a back panel 105 in this order. The 1 st adhesive layer 102 is formed of a1 st adhesive composition, and the 2 nd adhesive layer 104 is formed of a 2 nd adhesive composition. Hereinafter, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 are collectively referred to as an adhesive layer.

The thickness of the optical laminate 100 is not particularly limited, and is, for example, 30 to 1500 μm, preferably 40 to 1000 μm, and more preferably 50 to 500 μm, since it varies depending on the functions required for the optical laminate, the application of the optical laminate, and the like.

The planar view shape of the optical laminate 100 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 100 in the plane direction is rectangular, the length of the long side may be, for example, 10mm to 1400mm, and preferably 50mm to 600 mm. The length of the short side may be, for example, 5mm to 800mm, preferably 30mm to 500mm, and more preferably 50mm to 300 mm. In each layer constituting the optical laminate 100, the corner portion may be R-processed, and the end portion may be notched or perforated.

The optical laminate 100 can be used for a display device or the like, for example. The display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, and an electroluminescence display device. The optical stack 100 is suitable for a bendable display device.

[ shear recovery and reduction of shear recovery by deformation repeated load test ]

In the 1 st reference pressure-sensitive adhesive layer having a thickness of 200 μm formed using the 1 st pressure-sensitive adhesive composition, the shear recovery rates at a temperature of 25 ℃ before and after the deformation repetitive load test are R1A [% ] and R1B [% ], respectively, and in the 2 nd reference pressure-sensitive adhesive layer having a thickness of 200 μm formed using the 2 nd pressure-sensitive adhesive composition, the shear recovery rates at a temperature of 25 ℃ before and after the deformation repetitive load test are R2A [% ] and R2B [% ], respectively, the optical laminate 100 satisfies the following relational expressions (1) and (2).

ΔR1＝{(R1A)-(R1B)}/200≤0.2 (1)

ΔR2＝{(R2A)-(R2B)}/200≤0.2 (2)

It is clear that: in an optical laminate in which a front plate, a1 st adhesive layer, a polarizing plate, a 2 nd adhesive layer, and a back plate are sequentially laminated, bubbles are likely to be generated in the adhesive layer during bending, and particularly, bubbles are likely to be generated in the adhesive layer on the inner diameter side. In the optical laminate 100 satisfying the above-described formulae (1) and (2), bubble generation can be suppressed even when the optical laminate 100 is bent, and in particular, bubble generation can be suppressed even when the optical laminate 100 is bent and maintained in this state for a certain period of time. In the present specification, the suppression of the generation of bubbles means that, for example, even when the optical laminate 100 is bent and left for 24 hours along a Mandrel bar (Mandrel) which is a cylindrical jig having a diameter of 10mm or less, bubbles are not generated in the pressure-sensitive adhesive layer and between the pressure-sensitive adhesive layer and the layer in contact with the pressure-sensitive adhesive layer. Hereinafter, such performance is referred to as excellent bending durability. The generation of bubbles can be judged by observation under an optical microscope.

In the present specification, "curved" includes a bent form in which a bent portion forms a curved surface, and the radius of curvature of the inner surface of the bend is not particularly limited. The term "curved" includes a refractive form in which the internal refraction angle is greater than 0 degrees and less than 180 degrees, and also includes a folded form in which the bending radius of the internal surface is approximately zero or the internal refraction angle is 0 degrees.

Δ R1 and Δ R2 were calculated by dividing the decrease in shear recovery before and after the deformation repetitive load test was performed by the thickness (200 μm) of the 1 st or 2 nd reference adhesive layer.

From this, the amount of decrease in shear recovery in the strain repeated load test can be determined with respect to the pressure-sensitive adhesive layer formed using the 1 st or 2 nd pressure-sensitive adhesive composition having a thickness of 1 μm. The small Δ R1 and Δ R2 mean that the shear recovery of the adhesive layer is difficult to decrease even when the deformation repetitive load test (acceleration test) is performed. That is, Δ R1 and Δ R2 are small, and it is considered that the cohesive force of the adhesive is hardly reduced even when repeated bending is performed, and the performance of the adhesive is easily maintained.

The optical laminate 100 preferably satisfies the following relational expressions (1') and (2').

ΔR1＝{(R1A)-(R1B)}/200≤0.1 (1')

ΔR2＝{(R2A)-(R2B)}/200≤0.1 (2')

If the optical laminate 100 satisfies the formulae (1') and (2'), the bending durability can be further improved. Δ R1 and Δ R2 may be, for example, 0.001 or more, or may be 0.003 or more.

The optical laminate 100 preferably satisfies the following relational expression (4).

ΔR1≥ΔR2 (4)

The optical laminate 100 more preferably satisfies the following relational expression (4').

ΔR1＞ΔR2 (4')

If the optical laminate 100 is bent with the front panel 101 as the outer side, a stress greater than that of the 2 nd adhesive layer 104 is generated in the 1 st adhesive layer 102, which is an adhesive layer on the inner diameter side. By disposing the pressure-sensitive adhesive layer having a small amount of change in shear recovery before and after the strain repetitive load test on the inner diameter side where the stress is larger, the bending durability of the optical laminate 100 can be further improved.

The optical laminate 100 satisfies the following relational expression (3).

R1A＞R2A (3)

If the shear recovery of the adhesive layer is large, the adhesive layer is likely to recover the original shape when the distortion is removed, and if the shear recovery of the adhesive layer is small, the adhesive layer is difficult to recover the original shape when the distortion is removed. In order to easily alleviate the strain, it is preferable that the shear recovery rate of the pressure-sensitive adhesive layer on the outer diameter side is higher than that of the pressure-sensitive adhesive layer on the inner diameter side. The optical laminate 100 satisfying the formula (3) is likely to suppress the generation of bubbles even when the front panel 101 is bent outward. The shear recovery of the pressure-sensitive adhesive layer was determined by the method described in the section of example.

From the viewpoint of improving the surface hardness of the optical laminate 100, the shear recovery rates R1A and R2A before the deformation repetitive load test are preferably 20% or more, more preferably 30% or more, and still more preferably 40% or more. The shear recovery rates R1B and R2B after the deformation repetitive load test are preferably 15% or more, more preferably 30% or more. The upper limit is not particularly limited, and the shear recovery rates R1A and R2A before the deformation repetitive load test are, for example, 100% or less, and may be 65% or less, or may be 60% or less, or may be less than 60%. The upper limit is not particularly limited as long as the formulas (1) and (2) are satisfied, and the shear recovery rates R1B and R2B after the deformation repetitive load test are, for example, 50% or less, or may be 40% or less.

The shear recovery rates R1A and R2A before the deformation repetition test and the shear recovery rates R1B and R2B after the deformation repetition test can be set to a desired range of values by adjusting the kind and amount of monomers constituting the base polymer contained in the adhesive composition, the kind and amount of polymerization initiator, the kind and amount of active energy ray, and the amount of irradiation.

[ front panel ]

The material and thickness of the front panel 101 are not limited as long as the front panel is a plate-like body that can transmit light. The front panel 101 may be composed of only 1 layer, or may be composed of 2 or more layers. Examples of the front panel 101 include a resin plate-like body (e.g., a resin plate, a resin sheet, a resin film, etc.), a glass plate-like body (e.g., a glass plate, a glass film, etc.), and a laminate of a resin plate-like body and a glass plate-like body. The front panel 101 constitutes the outermost surface of the display device.

The thickness of the front plate 101 may be, for example, 10 to 300. mu.m, preferably 20 to 200. mu.m, and more preferably 30 to 100. mu.m. In the present invention, the thickness of each layer constituting the optical laminate 100 can be measured by the thickness measurement method described in the examples described below.

Examples of the resin constituting the resin plate-like body include polymers such as triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic acid, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyetherketone, polyetheretherketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers may be used alone or in combination of 2 or more. From the viewpoint of improving strength and transparency, the resin plate-like body is preferably a resin film made of a polymer such as polyimide, polyamide, or polyamideimide.

From the viewpoint of hardness, the front panel 101 may be a resin film provided with a hard coat layer. The hard coat layer may be formed on one surface of the resin film or on both surfaces. By providing the hard coat layer, hardness and scratch resistance can be improved. 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, urethane resins, amide resins, and epoxy resins. The hard coating may also contain additives for strength enhancement. The additive is not particularly limited, and examples thereof include inorganic fine particles, organic fine particles, and a mixture thereof. In the case where the resin film has hard coat layers on both sides, the composition and thickness of each hard coat layer may be the same as or different from each other.

When the front plate 101 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, 10 to 1000 μm, or 10 to 100 μm. By using the glass plate, the front panel 101 having excellent mechanical strength and surface hardness can be constituted.

When the optical laminate 100 is used in a display device, the front panel 101 may have a function of protecting the front surface (screen) of the display device (a function as a window film), a function as a touch sensor, a blue light prevention function, a viewing angle adjustment function, and the like.

[ 1 st adhesive layer ]

The 1 st adhesive layer 102 is interposed between the front panel 101 and the polarizing plate 103, and they are bonded. The 1 st pressure-sensitive adhesive layer 102 may be formed of 1 layer or 2 or more layers, but is preferably formed of 1 layer.

The 1 st pressure-sensitive adhesive layer 102 may be composed of a pressure-sensitive adhesive composition containing a (meth) acrylic resin, a rubber-based resin, a urethane-based resin, an ester-based resin, a silicone-based resin, or a polyvinyl ether-based resin as a main component (base polymer). The pressure-sensitive adhesive composition constituting the 1 st pressure-sensitive adhesive layer 102 is preferably a pressure-sensitive 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 heat-curable type.

As the (meth) acrylic resin used in the adhesive composition, a polymer or copolymer in which 1 or 2 or more kinds of (meth) acrylic esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are used as monomers is preferably used. In the base polymer, it is preferable to copolymerize a polar monomer. 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 a (meth) acrylic acid compound, a 2-hydroxypropyl (meth) acrylate compound, a hydroxyethyl (meth) acrylate compound, an amide (meth) acrylate compound, an N, N-dimethylaminoethyl (meth) acrylate compound, and a glycidyl (meth) acrylate compound.

The active energy ray-curable 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 also has a property of having an adhesive property before the irradiation with the active energy ray, thereby being closely adhered to an adherend such as a film, and being cured by the irradiation with the 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 contains an active energy ray-polymerizable compound in addition to a base polymer and a crosslinking agent. If necessary, a photopolymerization initiator, a photosensitizer, and the like may be contained.

Examples of the active energy ray-polymerizable compound include (meth) acrylate monomers having at least 1 (meth) acryloyloxy group in the molecule; a (meth) acrylic compound such as a (meth) acryloyloxy group-containing compound such as a (meth) acrylate oligomer having at least 2 (meth) acryloyloxy groups in the molecule, which is obtained by reacting 2 or more kinds of functional group-containing compounds. When a (meth) acrylic compound having a cyclohexyl group or a (meth) acrylic compound having an ethoxy group is used as the active energy ray-polymerizable compound, the cohesive force in the adhesive layer is easily increased and the formula (1) and the formula (2) are satisfied. Examples of the (meth) acrylic compound having a cyclohexyl group include Miramer M1130 and Miramer M1150 from Miwon Specialty Chemical. Examples of the (meth) acrylic compound having an ethoxy group include Miramer M140, Miramer M142, and Miramer M144 from Miwon Specialty Chemical. The binder composition may contain the active energy ray-polymerizable compound in an amount of 0.1 part by mass or more, or 5 parts by mass or more, and may contain the active energy ray-polymerizable compound in an amount of 30 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 2 parts by mass or less, based on 100 parts by mass of the solid content of the binder composition.

Examples of the photopolymerization initiator include benzophenone, benzyl dimethyl ketal, and 1-hydroxycyclohexyl ketone. The photopolymerization initiator may contain 1 or 2 or more species. When the adhesive composition contains a photopolymerization initiator, the total content thereof may be 0.01 to 3.0 parts by mass per 100 parts by mass of the solid content of the adhesive composition.

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, anticorrosion agents, and photopolymerization initiators, which impart light scattering properties.

The 1 st adhesive layer 102 can be formed by applying a diluted solution of the adhesive composition in an organic solvent to a substrate and drying the applied solution. The 1 st adhesive layer 102 may be formed using an adhesive sheet formed using an adhesive composition. When an active energy ray-curable adhesive composition is used, the adhesive layer formed can be irradiated with active energy rays to form an adhesive layer having a desired degree of curing.

The thickness of the 1 st pressure-sensitive adhesive layer 102 is not particularly limited, and is, for example, preferably 1 μm to 100 μm, more preferably 3 μm to 50 μm, and may be 20 μm or more.

[ polarizing plate ]

The polarizing plate 103 may be, for example, a linear polarizing plate, a circular polarizing plate, an elliptical polarizing plate, or the like. The circular polarizing plate is provided with a linear polarizing plate and a phase difference layer. In the circularly polarizing plate, the optical laminate 100 may be provided with a function as an antireflection film so that external light reflected by the image display device can be absorbed.

The thickness of the polarizing plate 103 is usually 5 μm or more, and may be 20 μm or more, 25 μm or more, or 30 μm or more. The thickness of the polarizing plate 103 is preferably 80 μm or less, and more preferably 60 μm or less.

(Linear polarizing plate)

The linear polarizing plate has a function of selectively transmitting linearly polarized light in a certain direction from light of unpolarized light such as natural light. The linear polarizing plate may have as polarizer layers: a stretched film or a stretched layer having a dichroic dye adsorbed thereon; and a liquid crystal layer in which a dichroic dye is dispersed and aligned in a cured product of the polymerizable liquid crystal compound. If the pigment is dispersed and oriented in a medium having anisotropy, the pigment is colored when viewed from a certain direction and is substantially colorless when viewed from a direction perpendicular thereto. A dye showing such a phenomenon is referred to as a dichroic dye. A linear polarizing plate using a liquid crystal layer as a polarizer layer is preferable because the bending direction is not limited as compared with a stretched film or a stretched layer in which a dichroic dye is adsorbed.

(1) Polarizer layer as stretched film or stretched layer having dichroic dye adsorbed thereon

The polarizer layer as a stretched film having a dichroic dye adsorbed thereon can be generally produced through the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing a polyvinyl alcohol resin film with a dichroic dye such as iodine to adsorb the dichroic dye; treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the boric acid aqueous solution.

The thickness of the polarizer layer is usually 30 μm or less, preferably 18 μm or less, and more preferably 15 μm or less. It is advantageous to make the polarizing plate 103 thin when the thickness of the polarizer layer is made thin. The thickness of the polarizer layer is usually 1 μm or more, and may be 5 μm or more, for example.

The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith may be used. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acid compounds, olefin compounds, vinyl ether compounds, unsaturated sulfone compounds, and (meth) acrylic acid amide compounds having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually about 85 mol% to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and aldehyde-modified polyvinyl formals, polyvinyl acetals, and the like may be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.

The polarizer layer as the stretched layer for adsorbing the dichroic dye can be generally produced through the following steps: a step of applying a coating liquid containing the polyvinyl alcohol resin to a base film; a step of uniaxially stretching the obtained laminated film; a step of dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminate film with a dichroic dye, and adsorbing the dichroic dye to form a polarizer layer; treating the film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the boric acid aqueous solution. The substrate film used for forming the polarizer layer may be used as a protective layer for the polarizer layer. The substrate film may be peeled off from the polarizer layer as necessary. The material and thickness of the base film may be the same as those of the thermoplastic resin film described later.

The polarizer layer as a stretched film or a stretched layer having a dichroic dye adsorbed thereon may be used as it is, or may be used as a linear polarizing plate after forming a protective layer on one or both surfaces thereof. As the protective layer, a thermoplastic resin film described later can be used. The thickness of the obtained linear polarizer is preferably 2 to 40 μm.

Examples of the thermoplastic resin film include a cyclic polyolefin resin film; cellulose acetate resin films made of resins such as triacetyl cellulose and diacetyl cellulose; polyester resin films made of resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; a polycarbonate-based resin film; a (meth) acrylic resin film; a polypropylene resin film and the like known in the art. The polarizer layer and the protective layer are laminated via a lamination layer described later.

From the viewpoint of thinning, the thickness of the thermoplastic resin film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, further preferably 40 μm or less, further preferably 30 μm or less, and further usually 5 μm or more, preferably 10 μm or more.

A hard coat layer may be formed on the thermoplastic resin film. The hard coat layer may be formed on one surface of the thermoplastic resin film or on both surfaces thereof. By providing the hard coat layer, a thermoplastic resin film having improved hardness and scratch resistance can be produced. The hard coat layer may be formed in the same manner as the hard coat layer formed in the resin film described above.

(2) Polarizer layer as a liquid crystal layer

The polymerizable liquid crystal compound used for forming the liquid crystal layer is a compound having a polymerizable reactive group and exhibiting liquid crystallinity. The polymerizable reactive group is a group involved in polymerization reaction, and is preferably a photopolymerizable reactive group. The photopolymerizable reactive group refers to a group associated with a polymerization reaction by an active radical, an acid, or the like generated from a photopolymerization initiator. Examples of the photopolymerizable functional group include a vinyl group, a vinyloxy group, a 1-chloroethenyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxirane group, and a glycidyloxy group. Among them, acryloxy, methacryloxy, vinyloxy, ethylene oxide and propylene oxide groups are preferable, and acryloxy groups are more preferable. The type of the polymerizable liquid crystal compound is not particularly limited, and a rod-like liquid crystal compound, a discotic liquid crystal compound, and a mixture thereof can be used. The liquid crystallinity of the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, and the phase order structure may be nematic liquid crystal or smectic liquid crystal.

The dichroic dye used for the polarizer layer as a liquid crystal layer preferably has a maximum absorption wavelength (λ MAX) in the range of 300 to 700 nm. Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, anthraquinone dyes, and the like, and among them, azo dyes are preferable. Examples of the azo dye include monoazo dyes, disazo dyes, trisazo dyes, tetraazo dyes, and stilbene azo dyes, and disazo dyes and trisazo dyes are preferable. The dichroic dye may be used alone or in combination of 2 or more, preferably 3 or more. It is particularly preferable to use 3 or more azo compounds in combination. A part of the dichroic dye may have a reactive group, and may have liquid crystallinity.

The polarizer layer as the liquid crystal layer can be formed, for example, by applying a composition for forming a polarizer layer containing a polymerizable liquid crystal compound and a dichroic dye to an alignment film formed on a base film, and polymerizing and curing the polymerizable liquid crystal compound. The composition for forming a polarizer layer may be applied to a base film to form a coating film, and the coating film may be stretched together with the base film to form a polarizer layer. The substrate film used for forming the polarizer layer may be used as a protective layer for the polarizer layer. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above.

Examples of the composition for forming a polarizer layer containing a polymerizable liquid crystal compound and a dichroic dye and the method for producing a polarizer layer using the composition include methods described in, for example, japanese patent laid-open nos. 2013-37353, 2013-33249, and 2017-83843. The composition for forming a polarizer layer may further contain additives such as a solvent, a polymerization initiator, a crosslinking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer in addition to the polymerizable liquid crystal compound and the dichroic dye. These components may be used in 1 kind, or 2 or more kinds may be used in combination.

The polymerization initiator that can be contained in the composition for forming a polarizer layer is a compound that can initiate the polymerization reaction of the polymerizable liquid crystal compound, and a photopolymerization initiator is preferable in that the polymerization reaction can be initiated at a lower temperature. Specifically, there may be mentioned photopolymerization initiators which generate active radicals or acids by the action of light, and among them, photopolymerization initiators which generate radicals by the action of light are preferred. The content of the polymerization initiator is preferably 1 to 10 parts by mass, more preferably 3 to 8 parts by mass, based on 100 parts by mass of the total amount of the polymerizable liquid crystal compound. When the amount is within this range, the reaction of the polymerizable group proceeds sufficiently, and the alignment state of the liquid crystal compound is easily stabilized.

The thickness of the polarizer layer as the liquid crystal layer is usually 10 μm or less, preferably 0.5 to 8 μm, and more preferably 1 to 5 μm.

The polarizer layer as the liquid crystal layer may be used as a linear polarizing plate without peeling and removing the base film, or may be used as a linear polarizing plate after peeling and removing the base film from the polarizer layer. The polarizer layer as the liquid crystal layer may or may not have an alignment film. The polarizer layer as the liquid crystal layer may be used as a linear polarizing plate after forming a protective layer on one or both surfaces thereof. The above thermoplastic resin film can be used as the protective layer.

For the purpose of protection of the polarizer layer, etc., the polarizer layer as the liquid crystal layer may have an overcoat layer on one surface or both surfaces of the polarizer layer. The overcoat layer can be formed, for example, by coating a material (composition) for forming the overcoat layer on the polarizer layer. Examples of the material constituting the overcoat layer include a photocurable resin and a water-soluble polymer. As a material constituting the overcoat layer, a (meth) acrylic resin, a polyvinyl alcohol resin, or the like can be used.

(retardation layer)

The retardation layer may be 1 layer or 2 or more layers. The retardation layer may have an overcoat layer for protecting the surface thereof, a substrate film for supporting the retardation layer, and the like. The phase difference layer includes a λ/4 layer, and may further include at least one of a λ/2 layer or a positive C layer. When the retardation layer includes a λ/2 layer, a λ/2 layer and a λ/4 layer are stacked in this order from the linear polarizer side. When the retardation layer includes the positive C layer, the λ/4 layer and the positive C layer may be stacked in this order from the linear polarizer side, or the positive C layer and the λ/4 layer may be stacked in this order from the linear polarizer side. The thickness of the retardation layer is, for example, 0.1 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 6 μm.

The retardation layer may be formed of a resin film exemplified as a material of the protective layer, or may be formed of a layer in which a polymerizable liquid crystal compound is cured. The retardation layer may further include an alignment film. The phase difference layer may have a lamination layer to which the λ/4 layer, the λ/2 layer and the positive C layer are laminated.

When the polymerizable liquid crystal compound is cured to form the retardation layer, the retardation layer can be formed by applying a composition containing the polymerizable liquid crystal compound onto a substrate film and curing the composition. An alignment layer may be formed between the substrate film and the coating layer. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above. In the case where the retardation layer is formed from a layer obtained by curing a polymerizable liquid crystal compound, the retardation layer may be combined with the optical laminate in a form having an alignment layer and a base film. The retardation layer may be bonded to the surface of the linear polarizing plate opposite to the visual side thereof through a bonding layer described later.

[ 2 nd adhesive layer ]

The 2 nd adhesive layer 104 is interposed between the polarizing plate 103 and the back surface plate 105, and they are attached. The 2 nd adhesive layer 104 may be 1 layer or 2 or more layers, but is preferably 1 layer.

The composition and blending components of the pressure-sensitive adhesive composition constituting the 2 nd pressure-sensitive adhesive layer 104, the type of the pressure-sensitive adhesive composition (whether it is an active energy ray-curable type, a thermosetting type, or the like), additives that can be blended into the pressure-sensitive adhesive composition, the method for producing the 2 nd pressure-sensitive adhesive layer, the thickness of the 2 nd pressure-sensitive adhesive layer, and the like are the same as those described in the description of the 1 st pressure-sensitive adhesive layer 102.

The composition, blending components, thickness, and the like of the pressure-sensitive adhesive composition in the 2 nd pressure-sensitive adhesive layer 104 may be the same as or different from those in the 1 st pressure-sensitive adhesive layer 102.

[ adhesive layer ]

The optical laminate 100 includes a lamination layer for joining 2 layers. The adhesive layer is a layer made of an adhesive or a bonding agent. As the adhesive used as the material of the laminating layer, the same adhesive composition as that constituting the adhesive layer 102 of the 1 st adhesive layer can be used.

Other adhesives such as (meth) acrylic adhesives, styrene adhesives, silicone adhesives, rubber adhesives, urethane adhesives, polyester adhesives, and epoxy copolymer adhesives that are different from the adhesive constituting the adhesive layer 102 of the 1 st embodiment can be used for the adhesive layer.

The adhesive used as the material of the adhesive layer may be formed by combining 1 or 2 or more kinds of water-based adhesives, active energy ray-curable adhesives, and the like, for example. Examples of the aqueous adhesive include a polyvinyl alcohol resin aqueous solution and an aqueous two-pack polyurethane emulsion adhesive. The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as an ultraviolet ray, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable polyurethane monomer, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing active substances that generate neutral radicals, anionic radicals, and cationic radicals by irradiation with active energy rays such as ultraviolet rays.

The thickness of the adhesive layer may be, for example, 1 μm or more, preferably 1 to 25 μm, more preferably 2 to 15 μm, and still more preferably 2.5 to 5 μm.

The opposite surfaces bonded via the bonding layer may be subjected to corona treatment, plasma treatment, flame treatment, or the like in advance, or may have a primer layer or the like.

[ Back Panel ]

As the back plate 105, a plate-like body that can transmit light, a component that can be used in a general display device, or the like can be used.

The thickness of back plate 105 may be, for example, 5 μm to 2000 μm, preferably 10 μm to 1000 μm, and more preferably 15 μm to 500 μm.

The plate-like body that can be used for the back plate 105 may be constituted of only 1 layer, or may be constituted of 2 or more layers. Rear plate 105 may be a plate as exemplified in front plate 101.

Examples of the components that can be used in a typical display device include a touch sensor panel and an organic EL display element. Examples of the order of lamination of the components in the display device include a front panel, a circularly polarizing plate, a touch sensor panel, an organic EL display element, a front panel, a touch sensor panel, a circularly polarizing plate, and an organic EL display element. The back panel 105 is preferably a touch sensor panel.

(touch sensor panel)

The touch sensor panel is not limited as long as it is a panel having a sensor (i.e., a touch sensor) capable of detecting a touched position. The detection method of the touch sensor is not limited, and examples thereof include touch sensor panels of a resistive film method, a capacitive coupling method, an optical sensing method, an ultrasonic wave method, an electromagnetic induction coupling method, a surface acoustic wave method, and the like. From the viewpoint of low cost, a resistive-film type or capacitive-coupling type touch sensor panel is preferably used.

Examples of the resistive touch sensor include a pair of substrates arranged to face each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film provided on the front surface of the inner side of each substrate as a resistive film, and a touch position detection circuit.

In an image display device provided with a resistive touch sensor, if a surface of a front panel is touched, the opposing resistive films are short-circuited, and a current flows through the resistive films. The touch position detection circuit can detect the voltage change at this time and detect the touch position.

An example of the capacitive coupling type touch sensor includes a substrate, a position detection transparent electrode provided on the entire surface of the substrate, and a touch position detection circuit. In an image display device provided with a capacitive coupling type touch sensor, if the surface of the front panel is touched, the transparent electrode can be grounded at the touched point via the capacitance of the human body. The touch position detection circuit can detect the grounding of the transparent electrode and detect the touch position.

The thickness of the touch sensor panel is, for example, 5 to 2000 μm, preferably 5 to 100 μm, more preferably 5 to 50 μm, and may be 5 to 20 μm.

The touch sensor panel may be a member in which a pattern of a touch sensor is formed on a base film. Examples of the base film may be the same as those in the description of the thermoplastic resin film. In addition, the touch sensor panel may be transferred from the base material film to an adherend via an adhesive layer. That is, the touch sensor panel may have no substrate film. The thickness of the touch sensor pattern is, for example, 1 μm to 20 μm.

[ method for producing optical laminate ]

The optical laminate 100 can be manufactured by a method including the following steps: and a step of bonding the layers constituting the optical laminate 100 to each other via the pressure-sensitive adhesive layer. When the layers are bonded to each other via the pressure-sensitive adhesive layer and the bonding layer, it is preferable to apply a surface activation treatment such as corona treatment to one or both of the bonding surfaces for the purpose of adjusting the bonding force. The conditions of the corona treatment may be set as appropriate, and the conditions may be different between one surface of the bonding surface and the other surface.

[ display device ]

The display device according to the present invention includes the optical laminate 100. The display device is not particularly limited, and examples thereof include image display devices such as an organic EL display device, an inorganic EL display device, a liquid crystal display device, and an electroluminescence display device. The optical laminate may further include a touch sensor, and the display device may have a touch panel function. The display device including the optical laminate 100 of the present invention has excellent bending durability and can be used as a flexible display capable of being bent, wound, or the like.

In the display device, the optical laminate 100 is disposed on the viewing side of the display element included in the display device, with the front panel 101 facing the outside (the side opposite to the display element side, i.e., the viewing side). The display device may be bent with the front panel 101 side as the outer side.

Examples of the image display element included in the image display device include an organic EL display element, an inorganic EL display element, a liquid crystal display element, a plasma display element, and a field emission type display element.

The display device of the present invention can be used as mobile devices such as smart phones and tablet computers, televisions, digital photo frames, electronic signboards, measuring instruments, office equipment, medical equipment, computer equipment, and the like.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[ measurement method ]

The measurement method and calculation method of each physical property value (layer thickness, adhesive layer property, etc.) used in the present example are as follows.

Thickness of layer

The film thickness was measured using a contact type film thickness measuring apparatus ("MS-5C" manufactured by Nikon K.K.). The polarizer layer and the alignment film were measured using a laser microscope ("OLS 3000" manufactured by olympus corporation).

< shear recovery >

The shear recovery was measured using a viscoelasticity measuring apparatus (MCR-301, Anton Paar Co.). The pressure-sensitive adhesive sheet was cut to a width of 20mm × a length of 20mm, the release film was peeled off, 8 pressure-sensitive adhesive layers having a thickness of 25 μm were laminated to form a reference pressure-sensitive adhesive layer having a thickness of 200 μm, and the pressure-sensitive adhesive layer was bonded to a glass plate. The shear strain amount in 1200 seconds was measured under the conditions of Normal force1N and Torque 1200. mu.Nm at a temperature of 25 ℃ in a state of being bonded to the measurement chip, and then the measurement was continued under the condition of Torque 0. mu.Nm, and the shear strain amount in 1206 seconds was measured. Based on these measured values, the shear recovery rate R was calculated according to the following equation.

R { (1200 sec shear deformation-1206 sec shear deformation)/1200 sec shear deformation } × 100 [% ]

< repeated load test on deformation >

The repeated strain load test as the acceleration test was carried out using a viscoelasticity measuring apparatus (MCR-301, Anton Paar Co.). The pressure-sensitive adhesive sheet was cut to a width of 20mm × a length of 20mm, the release film was peeled off, 8 pressure-sensitive adhesive layers having a thickness of 25 μm were laminated to form a reference pressure-sensitive adhesive layer having a thickness of 200 μm, and the pressure-sensitive adhesive layer was bonded to a glass plate. In the state of bonding to the measurement chip in the above-mentioned apparatus, loads of 0% and 1000% Strain were repeatedly applied to the reference adhesive layer on the glass plate at a temperature of 25 ℃, a Normal Force Free, and a frequency of 2Hz for 1000 seconds.

[ production of adhesive sheet comprising adhesive layer ]

A1-liter reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a temperature of , and a stirrer was charged with a monomer mixture solution of 2-ethylhexyl acrylate (2-EHA), Butyl Acrylate (BA), β -carboxyethyl acrylate (B-CEA), Acrylic Acid (AA), Glycidyl Methacrylate (GMA), and 2-hydroxyethyl methacrylate (2-HEMA) in the amounts shown in Table 1. Nitrogen was circulated for 1 hour to remove oxygen in the vessel and maintain the internal temperature at 60 ℃. The monomer mixture solution was uniformly mixed, and then the photopolymerization initiators, benzyldimethyl ketal (I-651) and 1-hydroxycyclohexylphenone (I-184), were added in the amounts shown in Table 1. (meth) acrylic polymers A1 to A6 were produced by irradiating a UV lamp (10mW) with stirring.

[ Table 1]

The obtained (meth) acrylic polymers A1 to A6, 3, 5-trimethylcyclohexyl acrylate (Miramer M1130), lauryl acrylate (Miramer M120), 2-phenoxyethyl acrylate (Miramer M140) and 1-hydroxycyclohexylphenylketone (I-184) were mixed in the blending amounts shown in Table 2 to prepare adhesive compositions B1 to B8.

[ Table 2]

The adhesive compositions B1 to B8 were coated to a thickness of 25 μm on a release film A (polyethylene terephthalate film, thickness 38 μm) coated with a silicon release agent. A release film B (polyethylene terephthalate film, 38 μm thick) was bonded thereto, and UV irradiation was performed to prepare a pressure-sensitive adhesive sheet composed of a release film A/a pressure-sensitive adhesive layer/a release film B. The condition of UV irradiation was a cumulative light amount of 400mJ/cm²Illuminance of 1.8mW/cm²(UVV reference).

The sources of the compounds in tables 1 and 2 are shown below.

2-EHA: tokyo chemical industry Co Ltd, Japan

BA: tokyo chemical industry Co Ltd, Japan

B-CEA: Sigma-Aldrich, USA

AA: tokyo chemical industry Co Ltd, Japan

GMA: Sigma-Aldrich, USA

2-HEMA: tokyo chemical industry Co Ltd, Japan

I-651: BASF corporation, Germany

I-184: BASF corporation, Germany

Miramer M1130: miwon specialty chemical Co., Korea

Miramer M120: miwon specialty chemical Co., Korea

Miramer M140: miwon specialty chemical Co., Korea

[ front panel ]

As the front panel 101, a film (50 μm) having a hard coat layer formed on one surface of a resin film was prepared. The resin film was a polyimide film having a thickness of 40 μm. The hard coat layer had a thickness of 10 μm and was formed from a composition containing a dendritic compound having a polyfunctional acrylic group at the terminal.

[ polarizer layer ]

1) As a base film, a triacetyl cellulose (TAC) film (KC2UA, manufactured by Konika Mentoda, thickness 25 μm) was prepared.

2) Polymer 1 shown below was dissolved in cyclopentanone at a concentration of 5% by mass. A solution was obtained, and the solution was prepared as a composition for forming an alignment film. The polymer 1 is formed of the following structural units and has a photoreactive group.

3) A composition for forming a polarizer layer is prepared.

First, as polymerizable liquid crystal compounds, a polymerizable liquid crystal compound represented by formula (1-1) [ hereinafter also referred to as compound (1-1) ] and a polymerizable liquid crystal compound represented by formula (1-2) [ hereinafter also referred to as compound (1-2) ] were prepared.

The compound (1-1) and the compound (1-2) were synthesized according to the method described in Lub et al, Recl, Trav, Chim, Pays-Bas, 115, 321-328 (1996).

As the dichroic dye, azo dyes described in examples of Japanese patent application laid-open publication No. 2013-101328 represented by the following formulae (2-1a), (2-1b), and (2-3a) were prepared.

The composition for forming a polarizer layer was prepared by mixing 75 parts by mass of the compound (1-1), 25 parts by mass of the compound (1-2), 2.5 parts by mass of each of the azo dyes represented by the above formulae (2-1a), (2-1b), and (2-3a) as dichroic dyes, 6 parts by mass of 2-dimethylamino-2-phenyl-1- (4-morpholinophenyl) butyl-1-one (Irgacure369, manufactured by BASF Japan) as a polymerization initiator, and 1.2 parts by mass of a polyacrylate compound (manufactured by BYK-361N, BYK-Chemie) as a leveling agent in 400 parts by mass of toluene as a solvent, and stirring the resulting mixture at 80 ℃ for 1 hour.

4) Composition for forming protective layer

The composition for forming a protective layer was prepared by mixing 100 parts by mass of water, 3 parts by mass of polyvinyl alcohol resin powder (manufactured by Kuraray Co., Ltd., average degree of polymerization 18000, trade name: KL-318), and 1.5 parts by mass of polyamide epoxy resin (cross-linking agent, manufactured by Sumika Chemtex Co., Ltd., trade name: SR650 (30)).

5) The polarizer layer was fabricated according to the procedure shown below.

First, corona treatment was applied 1 time to the TAC film side of the substrate film. The conditions of the corona treatment were an output of 0.3kW and a treatment speed of 3 m/min. Thereafter, the TAC film was coated with an alignment film-forming composition by a bar coating method, and dried by heating in a drying oven at 80 ℃ for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a1 st alignment film (AL 1). The polarized light UV treatment was performed under the following conditions: light irradiated from a UV irradiation apparatus (SPOT CURE SP-7; manufactured by Ushio Inc.) was transmitted through a wire grid (UIS-27132# #, manufactured by Ushio Inc.) and the cumulative quantity of light measured at a wavelength of 365nm was 100mJ/cm². The thickness of the 1 st alignment film was 100 nm.

Next, the composition for forming a polarizer layer was coated on the 1 st alignment film by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. Using the above UV irradiation apparatus, the cumulative light amount was 1200mJ/cm²The dried film was irradiated with ultraviolet light (365nm basis) to form a polarizer layer. The thickness of the resulting polarizer layer was 1.8 μm.

6) The protective layer-forming composition was applied to the polarizer layer by a bar coating method so that the thickness after drying was 1.0 μm, and dried at 80 ℃ for 3 minutes. In this manner, a linear polarizing plate formed of "substrate film/polarizer layer/overcoat layer" was obtained.

[ phase difference layer ]

1) As a substrate film, a polyethylene terephthalate (PET) film having a thickness of 100 μm was prepared.

2) The same composition as that used for the alignment film formation was used for the alignment film formation composition.

3) The following components were mixed, and the resulting mixture was stirred at 80 ℃ for 1 hour to obtain a composition for forming a retardation layer.

A compound (b-1) represented by the following formula: 80 parts by mass

A compound (b-2) represented by the following formula: 20 parts by mass

Polymerization initiator (Irgacure369, 2-dimethylamino-2-phenyl-1- (4-morpholinophenyl) butyl-1-one, manufactured by BASF Japan): 6 parts by mass

Leveling agent (BYK-361N, polyacrylate compound, BYK-Chemie Co., Ltd.): 0.1 part by mass

Solvent (cyclopentanone): 400 parts by mass.

4) The retardation layer was produced by the following procedure.

First, an alignment film-forming composition was applied to a base film by a bar coating method, and dried by heating in a drying oven at 80 ℃ for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a 2 nd alignment film. Polarized light UV treatment Using the UV irradiation device, the cumulative light amount measured at a wavelength of 365nm was 100mJ/cm²The conditions of (1) are carried out. The polarization direction of the polarized light UV is performed at 45 ° with respect to the absorption axis of the polarizer layer.

5) Is connected withNext, the retardation layer-forming composition was applied to the 2 nd alignment film by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. Using the above UV irradiation apparatus, the cumulative light amount was 1000mJ/cm²The obtained dried film was irradiated with ultraviolet light (365nm basis) to form a retardation layer. The thickness of the resulting retardation layer was 2.0. mu.m. The phase difference layer is a lambda/4 plate that shows a phase difference value of lambda/4 in the in-plane direction. In this way, a retardation layer formed of "substrate film/λ/4 retardation layer" was obtained.

[ adhesive sheet ]

The following components were stirred under a nitrogen atmosphere and reacted at 55 ℃ to obtain an acrylic resin.

Butyl acrylate: 70 parts by mass

Acrylic acid methyl group: 20 parts by mass

Acrylic acid: 2.0 parts by mass

Radical polymerization initiator (2,2' -azobisisobutyronitrile): 0.2 parts by mass.

Next, the following ingredients were mixed to obtain a composition for a laminate layer.

Acrylic resin: 100 parts by mass

Crosslinking agent (Tosoh Coronate L.): 1.0 part by mass

Silane coupling agent (product of shin-Etsu chemical Co., Ltd. "X-12-981"): 0.5 part by mass.

Ethyl acetate was added to the obtained composition for a pressure-sensitive adhesive layer so that the total solid content concentration was 10 mass%, to prepare a solution.

The prepared composition for a pressure-sensitive adhesive layer was applied to a release film a (polyethylene terephthalate film, thickness 38 μm) subjected to release treatment by using a coater so that the thickness after drying was 5 μm, to obtain a coated layer. The coated layer was dried at 100 ℃ for 1 minute to obtain a film having a pressure-sensitive adhesive layer. Thereafter, a release film B (polyethylene terephthalate film, 38 μm thick) was bonded to the exposed surface of the adhesive layer. The laminate was cured at 23 ℃ and 50% RH relative humidity for 7 days to obtain a laminate sheet having a layer structure of release film A/laminate layer/release film B.

[ Back Panel ]

As the rear panel 105, a touch sensor panel in which a transparent conductive layer, a separation layer, an adhesive layer, and a base material layer are laminated in this order was prepared. The transparent conductive layer contained an ITO layer, and the separation layer contained a cured layer of an acrylic resin composition, and the total thickness of both layers was 7 μm. The thickness of the adhesive layer was 2 μm. The substrate layer was a Cycloolefin (COP) film (ZF-14, manufactured by Nippon Ralskikai Co., Ltd., thickness: 23 μm).

[ production of optical layered body ]

The optical laminates of examples 1 to 3 and comparative examples 1 to 3 were produced according to the steps shown in FIGS. 2(a) to (e). Adhesive sheets formed from the adhesive compositions shown in table 2 were used as the 1 st adhesive layer or the 2 nd adhesive layer as shown in table 3.

First, a linear polarizing plate 410 including a polarizer layer [ base film 301/polarizer layer 302/overcoat layer 303] and the above adhesive sheet 420 (release film a 304/adhesive layer 305/release film B306) were prepared (fig. 2 (a)). The linear polarizing plate 410 including the polarizer layer was attached to the outer coating 303 side and the surface of the attachment sheet 420 from which the release film a304 was peeled by corona treatment (output 0.3KW, speed 3 m/min), and then the laminate a430 was obtained. Further, a retardation layer 440[ base material film 308/λ/4 retardation layer 307] was prepared. (FIG. 2 (b)).

The λ/4 retardation layer 307 side of the retardation layer 440 and the surface of the laminate a430 from which the release film B306 was peeled were subjected to corona treatment (output 0.3KW, speed 3 m/min), followed by lamination to obtain a circularly polarizing plate 450. The adhesive sheet prepared above was prepared as an adhesive sheet 460 (release film a309, adhesive layer 310, and release film B311) (fig. 2 (c)).

The adhesive layer 310 of the adhesive sheet 460 corresponds to the 2 nd adhesive layer.

The circularly polarizing plate 450 and the adhesive sheet 460 were bonded to each other after the substrate film 308 was peeled and the release film a309 was peeled by corona treatment (output 0.3KW and speed 3 m/min), to obtain a laminate B470. Further, the psa sheet prepared above was prepared as psa sheet 490 (release film a314, psa layer 315, release film B316). The surface of the front panel 480 (resin film 313/hard coat layer 312) from which the release film a314 was peeled was subjected to corona treatment (output 0.3KW, speed 3 m/min), and then laminated to obtain a laminate C500 (fig. 2 (d)). The adhesive layer 315 of the adhesive sheet 490 corresponds to the 1 st adhesive layer.

The laminate C500 was subjected to corona treatment (output 0.3KW, speed 3 m/min) on the side from which the release film B316 was released and on the side of the base film 301 of the laminate B470, and then laminated to obtain a laminate D510 (fig. 2 (e)).

An optical laminate was obtained by applying corona treatment (output 0.3KW, speed 3 m/min) to the transparent electrode layer 317 side of the touch sensor panel 520 in which the transparent conductive layer 317, the separation layer 318, the adhesive layer 319, and the base layer 320 were laminated, and the surface of the laminate D510 from which the release film B311 was peeled.

The optical laminates of examples 1 to 3 and comparative examples 1 to 3 were subjected to the following bending property test and surface hardness test. The results are shown in Table 3.

< bendability evaluation test >

The optical layered bodies of the examples and comparative examples were bent with the front panel 101 side as the outer side (bending radius 1.5mm), that is, with the distance between the surfaces opposite to the front panel being 3.0mm, and left at 60 ℃ and 90% RH for 24 hours, then taken out and left at room temperature for 30 minutes (durability test).

After the end of the durability test, the optical layered body was released from being bent. Test pieces having a length of 100mm and a width of 10mm were cut out from the optical laminate after the durability test using suppercutter with the bend at the center. The test piece was wound around a cylindrical Mandrel (Mandrel) so that the front panel of the test piece was positioned outside, and the test piece was bent in the longitudinal direction at a temperature of 25 ℃ using a bending resistance tester (cylindrical Mandrel method) manufactured by TP technical research corporation, and a bending resistance evaluation test (Mandrel test) was performed.

From this, the minimum diameter of the plug in which no bubble was generated in the pressure-sensitive adhesive layer of the test piece was determined, and the grade was determined based on the following criteria. In the bending property evaluation test, the smaller the value of the minimum diameter, the more excellent the bending durability of the adhesive layer can be evaluated.

A: when the core rod is wound up to a diameter (phi) of 10mm or less, bubbles are generated in the adhesive layer.

B: when the core rod is wound over a diameter of 10mm to 15mm, bubbles are generated in the adhesive layer.

C: when the core rod is wound over a diameter of 15mm to 20mm, bubbles are generated in the adhesive layer.

D: after winding to exceed

In the case of the mandrel (2), air bubbles are generated in the adhesive layer.

< evaluation test of surface hardness >

The surface of the optical laminate after the durability test on the front panel 101 side in the bent portion was measured at a temperature of 25 ℃ using a pencil hardness tester (PHT, manufactured by SUKBO SCIENCE, korea). A pencil (manufactured by Mitsubishi Pencil) loaded with 100g of load had a hardness of 6B, and had a concave mark formed on the surface. Thereafter, the time until the recessed portion mark disappeared was measured, and the surface hardness of the optical layered body of each example and each comparative example was evaluated based on the following reference scale. In this surface hardness test, the shorter the time until the dent mark disappears, the more excellent the surface hardness property can be evaluated.

A: the dent mark disappeared in less than 30 minutes.

B: when the time is 30 minutes or more and less than 60 minutes, the dent mark disappears.

C: when the time is 60 minutes or more and less than 90 minutes, the dent mark disappears.

D: even after 90 minutes, the dent mark did not disappear.

[ Table 3]

Claims

1. An optical laminate comprising, in order: a front panel, a1 st adhesive layer formed using the 1 st adhesive composition, a polarizing plate, a 2 nd adhesive layer formed using the 2 nd adhesive composition, and a back panel,

in a1 st reference adhesive layer having a thickness of 200 μm formed using the 1 st adhesive composition, when shear recovery rates at a temperature of 25 ℃ before and after a repeated deformation load test are respectively defined as R1A and R1B, and in a 2 nd reference adhesive layer having a thickness of 200 μm formed using the 2 nd adhesive composition, when shear recovery rates at a temperature of 25 ℃ before and after a repeated deformation load test are respectively defined as R2A and R2B, the following relational expressions (1) to (3) are satisfied:

ΔR1＝{(R1A)-(R1B)}/200≤0.2 (1)

ΔR2＝{(R2A)-(R2B)}/200≤0.2 (2)

R1A＞R2A (3)

wherein R1A, R1B, R2A and R2B are in%.

2. The optical stack of claim 1, further satisfying the following relationship (4):

ΔR1≥ΔR2 (4)。

3. the optical laminate according to claim 1 or 2, wherein R2A is 20% or more.

4. The optical stack of any of claims 1-3, wherein the back panel is a touch sensor panel.

5. A display device comprising the optical stack of any of claims 1-4.

6. The display device according to claim 5, wherein the front panel can be bent with the front panel side as an outer side.