CN115136040A

CN115136040A - Optical laminate and display device provided with same

Info

Publication number: CN115136040A
Application number: CN202080096921.6A
Authority: CN
Inventors: 柳智熙; 张柱烈; 金东辉
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2020-02-21
Filing date: 2020-12-23
Publication date: 2022-09-30
Also published as: JP2021135505A; TW202132825A; KR20220137623A; WO2021166434A1

Abstract

The purpose of the present invention is to obtain an optical laminate that suppresses the repulsive force generated at the end portions even when used in an image display device in which the bending axis is not fixed to the center of the optical laminate, and an image display device provided with the optical laminate. According to the present invention, there is provided an optical laminate comprising a front plate, a polarizing plate, a back plate and at least one adhesive layer, wherein the optical laminate satisfies the following relational expression (1) when the bending stiffness of the optical laminate is K [ golley unit ]: k is more than or equal to 400 and less than or equal to 2000 (1).

Description

Optical laminate and display device provided with same

Technical Field

The present invention relates to an optical laminate and a display device provided with the optical laminate.

Background

Patent document 1 proposes an evaluation method capable of determining the usability as a substrate for a flexible touch screen panel, and describes that the relationship between toughness and bending stress, such as bending fatigue properties, of the substrate for a flexible touch screen panel is satisfied. Patent document 2 relates to a flexible display element in which flexibility of the structure is ensured. The flexible display element described in patent document 2 includes a base film and a display sheet formed on the base film, and further includes a structured pattern, and can prevent damage such as cracking and peeling from occurring on a display panel by transferring a neutral plane having a bending stress of 0 (zero) to a layer having a low breaking point.

Documents of the prior art

Patent document

Patent document 1: korean laid-open patent No. 10-2016-

Patent document 2: korean laid-open patent No. 10-2014-0108914

Disclosure of Invention

If the optical layered body is bent, a repulsive force acting in a direction in which the end portion of the optical layered body warps is generated. Therefore, when the optical laminate is incorporated into a flexible image display device, it is necessary to configure the optical laminate so as to reduce the warpage of the optical laminate. However, when the repulsive force of the optical laminate is large, there may be problems such as occurrence of cracks in the optical laminate and peeling of the optical laminate in the image display device.

The present inventors have obtained the following findings: the shorter the distance from the bending axis to the end portion, the larger the repulsive force acting in the direction in which the end portion of the optical laminate warps becomes. In the case where the optical laminate is applied to an image display device in which the bending axis is not the center of the optical laminate, an image display device in which the bending axis of the optical laminate changes, or the like, the repulsive force at the end portions becomes larger than that in the case where the bending axis is in the vicinity of the center of the optical laminate, and therefore the above-described problem is likely to occur.

The purpose of the present invention is to obtain an optical laminate having a small repulsive force generated at the end even when used in an image display device in which the bending axis is not fixed to the center of the optical laminate, and an image display device provided with the optical laminate.

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

[1] An optical laminate comprising a front sheet, a polarizer, a back sheet and at least one adhesive layer,

when the bending stiffness of the optical laminate is K [ golley unit ], the following relational expression (1) is satisfied:

400≤K≤2000 (1)。

[2] the optical laminate according to [1], wherein the total of the thickness of the front sheet and the thickness of the adhesive layer is 50 to 200 μm.

[3] The optical laminate according to [1] or [2], wherein the front sheet has a thickness of 60 μm or less.

[4] The optical laminate according to any one of [1] to [3], wherein the total thickness of the bonding layers is 3 μm to 130 μm.

[5] The optical laminate according to any one of [1] to [4], further comprising an impact-resistant layer,

the thickness of the impact-resistant layer is 100 μm or less.

[6] An image display device comprising the optical laminate according to any one of [1] to [5 ].

[7] The image display device according to item [6], wherein the front panel is outwardly bendable.

The present invention has an object to provide an optical laminate with a small repulsive force generated at an end portion even when used in an image display device in which a bending axis is not fixed to the center of the optical laminate, and an image display device including the optical laminate.

Drawings

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

Fig. 2 is a schematic cross-sectional view showing another example of the optical laminate of the present invention.

Fig. 3 (a) to (c) are photographs showing warpage of the end of the optical laminate during bending.

Fig. 4 is a schematic view showing a method of measuring a bending repulsive force of the optical layered body.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the drawings below, the scale of each component shown in the drawings is appropriately adjusted to facilitate understanding of each component, and the scale of each component does not necessarily match the scale of the actual component.

< optical laminate >

The optical laminate of the present invention comprises a front sheet, a polarizing plate, a back sheet, and at least one adhesive layer. Fig. 1 and 2 show an example of the layer structure of the optical laminate of the present invention.

Fig. 1 is a schematic cross-sectional view of an example of an optical laminate of the present invention. The optical laminate 100 shown in fig. 1 includes a front plate 10, a bonding layer 40, a polarizing plate 20, a bonding layer 41, and a back plate 30 in this order.

Figure 2 is a schematic cross-sectional view of another example of an optical stack of the present disclosure. The optical laminate 200 shown in fig. 2 includes a front plate 10, a bonding layer 40, an impact-resistant layer 50, a bonding layer 42, a polarizing plate 20, a bonding layer 41, and a back plate 30 in this order.

The thickness of the

optical laminates

100 and 200 is not particularly limited, and varies depending on the functions required for the optical laminate, the application of the optical laminate, and the like, but may be, for example, 30 to 2000 μm, 50 to 1500 μm, 70 to 1000 μm, 500 to 300 μm.

The optical

layered bodies

100 and 200 may have a square shape in plan view, for example, preferably a square shape having long sides and short sides, and more preferably a rectangular shape. When the optical

layered bodies

100 and 200 have a rectangular shape in the plane direction, the length of the long side may be, for example, 10mm to 1400mm, preferably 50mm to 600 mm. The length of the short side is, for example, 5mm to 800mm, preferably 30mm to 500mm, and more preferably 50mm to 300 mm. The respective layers constituting the optical

layered bodies

100 and 200 may be subjected to corner rounding, end notching, or hole forming.

The optical

layered bodies

100 and 200 can be used for, for example, an image display device. The image 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

layered bodies

100 and 200 are particularly suitable for an image display device in which the bending axis is not fixed to the center of the optical layered body.

[ bending rigidity of optical laminate ]

When the bending rigidity of the optical laminate is K [ Gurley units ], the following relational expression (1) is satisfied:

400≤K≤2000 (1)。

the flexural rigidity was measured according to TAPPI T543 om-00 by using a Gerley type tester. Note that 1mN is 9.807 × 10 ^－3 Gurley units.

When the bending rigidity K [ gurley unit ] of the optical laminate is 2000 or less, an optical laminate in which the repulsive force at the end portion is reduced at the time of bending can be obtained.

If the optical laminate is bent, the end of the optical laminate may warp as shown in fig. 3 (a). When the repulsive force acting in the direction in which the end portion is warped is large, if the optical layered body is housed in the image display device so as to suppress the warping of the end portion, a crack may occur in the optical layered body or separation may occur between the optical layered body and the image display element. The present inventors have obtained the following findings: the shorter the distance from the bending axis to the end portion, the larger the repulsive force acting in the direction in which the end portion of the optical layered body warps becomes. Therefore, when the optical laminate is applied to an image display device in which the bending axis is not the center of the optical laminate, an image display device in which the position of the bending axis of the optical laminate is changed, or the like, the repulsive force at the end portions may become larger than that in a case in which the bending axis is near the center of the optical laminate.

The present inventors have found that there is a correlation between the bending rigidity of the optical laminate and the repulsive force at the end, and if the bending rigidity of the optical laminate is large, the repulsive force becomes large. When the bending rigidity K [ golley unit ] of the optical laminate is 2000 or less, the repulsive force is reduced, and the optical laminate of the present invention can suppress the occurrence of cracks, peeling, and the like even when applied to an image display device in which the bending axis is not fixed near the center of the optical laminate or an image display device in which the position of the bending axis is variable. Examples of optical laminates having less warpage at the end portions when bent are shown in fig. 3 (b) and (c). In fig. 3, the optical laminate is bent with the front panel facing outward. In fig. 3 (b) and (c), the repulsive force at the end is also small, and the repulsive force at the end is 7.0gf or less, for example, as measured by the method described in the examples described later.

On the other hand, it is known that if the bending rigidity of the optical laminate is too small, the impact resistance of the optical laminate is lowered. If the impact resistance of the optical laminate is reduced, there is a risk that a defect (for example, malfunction of a touch sensor) due to impact occurs in a rear plate provided on the opposite side of the optical laminate from the front plate, or that the durability of an image display device provided with the optical laminate is reduced. When the bending rigidity K [ gurley unit ] of the optical laminate is 400 or more, the optical laminate can have sufficient impact resistance. The impact resistance of the optical laminate can be evaluated as the durability to a pen-drop test, for example. The durability in the pen-drop test can be evaluated by the method described in the examples described later.

In the present specification, the term "bent" includes a form of bending in which a curved surface is formed at a bent portion, and the radius of curvature of the inner surface of the bending is not particularly limited. In addition, bending also includes bending in which the bending angle of the inner surface is greater than 0 degrees and less than 180 degrees, and folding in which the bending radius of the inner surface is approximately zero or the bending angle of the inner surface is 0 degrees.

From the viewpoint of reducing the repulsive force of the optical layered body, the bending rigidity K [ gurley unit ] is preferably 1800 or less, and more preferably 1500 or less. From the viewpoint of improving the impact resistance of the optical laminate, the bending rigidity K [ gurley unit ] is preferably 600 or more, more preferably 800 or more, and still more preferably 1000 or more.

The bending rigidity of the optical laminate can be adjusted to a desired value by changing the type and thickness of the front panel, the type and thickness of the adhesive layer, the presence or absence and thickness of the impact-resistant layer, the thickness of the optical laminate, and the like.

[ front panel ]

The material and thickness of the front panel 10 are not limited as long as the front panel is a plate-like body capable of transmitting light. The front panel may be formed of only one layer or two or more layers. Examples of the front panel 10 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 10 can constitute the outermost surface of the image display device.

The thickness of the front panel 10 may be, for example, 10 to 500 μm. From the viewpoint of reducing the bending repulsive force, the thickness of the front panel 10 is preferably 100 μm or less, more preferably 80 μm or less, and further preferably 60 μm or less. The thickness of the front panel 10 is preferably 20 μm or more, and more preferably 30 μm or more, from the viewpoint of improving impact resistance. In the present invention, the thickness of each layer constituting the optical laminate can be measured by the thickness measurement method described in the following examples.

When the front panel 10 is a resin plate-like body, the resin plate-like body is not limited as long as it can transmit light. Examples of the resin constituting the plate-like body made of a resin include polymers such as triacetyl cellulose, cellulose acetate butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, levulinyl 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 two 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, polyamideimide, or the like.

From the viewpoint of hardness, the front panel 10 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 thereof. 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 contain additives for the purpose of improving strength. The additive is not particularly limited, and examples thereof include inorganic fine particles, organic fine particles, and a mixture thereof. When the resin film has hard coat layers on both surfaces thereof, the composition and thickness of each hard coat layer may be the same or different from each other.

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

When the optical laminate is used in an image display device, the front panel 10 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 cut-off function, a viewing angle adjustment function, and the like.

[ polarizing plate ]

The polarizing plate 20 may be, for example, a linear polarizing plate, a circular polarizing plate, an elliptical polarizing plate, or the like. Hereinafter, the circularly polarizing plate and the elliptically polarizing plate may be collectively referred to simply as a circularly polarizing plate. The circularly polarizing plate comprises a linearly polarizing plate and a retardation layer. Since the circularly polarizing plate can absorb external light reflected by the image display device, the optical laminate can be provided with a function as an antireflection film.

The thickness of the polarizing plate 20 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 20 is preferably 80 μm or less, and more preferably 60 μm or less.

(Linear polarizer)

The linearly polarizing plate has a function of selectively transmitting unidirectional linearly polarized light composed of unpolarized light rays such as natural light. The linearly polarizing plate may include, as the polarizer layer, a stretched film or a stretched layer having a dichroic dye adsorbed thereon, a liquid crystal layer containing a cured product of a polymerizable liquid crystal compound and a dichroic dye, in which the dichroic dye is dispersed and oriented in the cured product of the polymerizable liquid crystal compound, or the like. When the pigment is dispersed and oriented in a medium having anisotropy, coloration may be observed from a certain direction, and almost no color may be observed from a direction perpendicular thereto. A dye exhibiting such a phenomenon is called a dichroic dye. A linearly polarizing plate using a liquid crystal layer as a polarizer layer is preferable because it is not limited in the bending direction as compared with a stretched film or a stretched layer having a dichroic dye adsorbed thereon.

(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: the method for producing a polyvinyl alcohol film comprises a step of uniaxially stretching a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye such as iodine by dyeing the polyvinyl alcohol resin film with the dichroic dye, a step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution, and a step of washing the treated polyvinyl alcohol resin film with water after the treatment with the aqueous boric acid 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. The thickness of the polarizer layer is made thinner to facilitate the thinning of the polarizing plate 20. The thickness of the polarizer layer is usually 1 μm or more, and for example, may be 5 μm or more.

The polyvinyl alcohol resin is 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) acrylamide compounds having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is generally about 85 mol% to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and polyvinyl formal, polyvinyl acetal, or the like obtained by modifying aldehydes 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 having the dichroic dye adsorbed thereon can be generally produced through the following steps: a step of applying a coating liquid containing the polyvinyl alcohol resin onto a base film; a step of uniaxially stretching the obtained laminated film; a step of preparing a polarizer layer by dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminate film with a dichroic dye to adsorb the dichroic dye; 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 aqueous boric acid solution. The substrate film 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 as a linearly polarizing plate, or may be used as a linearly polarizing plate by 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 linearly polarizing plate 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 cellulose triacetate and cellulose diacetate; 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; polypropylene resin films and the like are known in the art. The polarizer layer and the protective layer may be laminated via an adhesive 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 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 or both surfaces of the thermoplastic resin film. 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 on the resin film.

(2) Polarizer layer as a cured layer of liquid crystals

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 participating in polymerization reaction, and is preferably a photopolymerizable reactive group. The photopolymerizable reactive group means a group capable of participating in a polymerization reaction by an active radical generated from a photopolymerization initiator, an acid, or the like. 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 an oxetanyl group. Among them, acryloxy, methacryloxy, vinyloxy, oxirane and oxetanyl groups are preferable, and acryloxy group is 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 thermotropic liquid crystal or lyotropic liquid crystal, and the phase-sequence structure may be nematic liquid crystal or smectic liquid crystal.

The dichroic dye used in the polarizer layer of the liquid crystal layer is preferably a dichroic dye having an absorption maximum wavelength (λ MAX) in the range of 300 to 700 nm. Examples of such dichroic dyes include acridine dyes,

Oxazine pigments, cyanine pigments, naphthalene pigments, azo pigments, anthraquinone pigments, and the like, and among them, azo pigments 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 two or more, but preferably three or more are used in combination. Particularly, three or more azo compounds are more preferably combined. A part of the dichroic dye may have a reactive group, and may have liquid crystallinity.

The polarizer layer of 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 onto an alignment film formed on a base film, and polymerizing and curing the polymerizable liquid crystal compound. The polarizer layer may also be formed by coating the composition for forming a polarizer layer on a base film to form a coating film and stretching the coating film together with the base film. The substrate film 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.

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 those described in jp 2013-a 37353, jp 2013-a 33249, and jp 2017-a 83843. The composition for forming a polarizer layer may 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 alone or in combination of two or more.

The polymerization initiator that can be contained in the composition for forming a polarizer layer is a compound capable of initiating a polymerization reaction of the polymerizable liquid crystal compound, and a photopolymerization initiator is preferable from the viewpoint of being capable of initiating a polymerization reaction under a lower temperature condition. Specifically, there may be mentioned photopolymerization initiators capable of generating an active radical or an acid by the action of light, and among them, a photopolymerization initiator capable of generating a radical by the action of light is preferable. 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 polarizer without peeling and removing the substrate film, or the substrate film may be peeled and removed from the polarizer layer to be used as a linear polarizer. The polarizer layer serving as the liquid crystal layer may be used as a linear polarizer by forming a protective layer on one or both surfaces thereof. As the protective layer, the above thermoplastic resin film can be used.

The polarizer layer as the liquid crystal layer may have an overcoat layer on one side or both sides of the polarizer layer in order to protect the polarizer layer and the like. The overcoat layer can be formed, for example, by coating the 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.

The polarizing plate 20 may be provided with a retardation layer on the surface of the linearly polarizing plate opposite to the visible side through a bonding layer described later.

(retardation layer)

The phase difference layer may be one layer or two or more layers. The retardation layer may include an overcoat layer for protecting the surface thereof, a base film for supporting the retardation layer, and the like. The phase difference layer includes a λ/4 layer, and may further include at least either a λ/2 layer or a positive C layer. When the retardation layer includes a λ/2 layer, the λ/2 layer and the 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 obtained by curing a polymerizable liquid crystal compound. The phase difference layer may further include an alignment film. The phase difference layer may have a lamination layer for laminating the λ/4 layer with the λ/2 layer and the positive C layer.

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 to 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 incorporated into the optical laminate in a form having an alignment layer and a substrate film. The retardation layer may be bonded to the linear polarizer via a bonding layer.

[ impact-resistant layer ]

In order to improve the impact resistance of the optical laminate, the optical laminate may be provided with an impact resistant layer 50. The impact-resistant layer 50 may be in direct contact with the front panel 10, or may be provided between the front panel 10 and the impact-resistant layer via the adhesive layer 40 or another layer.

The thickness of the impact-resistant layer 50 is, for example, 10 to 100 μm. The thickness of the impact-resistant layer 50 is preferably 80 μm or less, more preferably 50 μm or less, preferably 30 μm or more, and more preferably 40 μm or more. If the thickness of the impact-resistant layer 50 is small, the impact resistance tends to be low, and if the thickness of the impact-resistant layer 50 is large, the repulsive force of bending tends to be high.

When the optical laminate includes the impact-resistant layer 50, the total thickness of the front panel 10 and the impact-resistant layer 50 is, for example, 20 to 200 μm. The total of the thickness of the front panel 10 and the thickness of the impact-resistant layer 50 is preferably 50 μm or more, and preferably 100 μm or less.

The material and thickness of the impact-resistant layer 50 are not limited as long as they are plate-like bodies capable of transmitting light, and examples thereof include the plate-like bodies listed as the front panel 10. From the viewpoint of elastic properties and versatility, the resin plate-like body constituting the impact-resistant layer 50 is preferably a resin film made of a polymer such as polyethylene naphthalate, polyethylene terephthalate, or the like.

[ adhesive layer ]

The optical laminate has at least one adhesive layer. The number of the adhesive layers included in the optical laminate is preferably 2 or more, preferably 3 or more, and may be 10 or less, and may be 8 or less. The laminated layer is a layer which is interposed between two layers and is laminated, and may be a layer formed of, for example, an adhesive or a bonding agent, or a layer obtained by subjecting the layer to some treatment. Adhesives are also known as pressure sensitive adhesives. In the present specification, "adhesive" refers to an adhesive other than an adhesive (pressure-sensitive adhesive), and is clearly distinguished from an adhesive.

The thickness of each bonding layer constituting the optical laminate is, for example, 3 to 50 μm, and preferably 3 to 30 μm from the viewpoint of easily accommodating a bending repulsive force within a predetermined range. If the thickness of the adhesive layer is small, impact resistance tends to be low, and if the thickness of the adhesive layer is large, bending repulsive force tends to be high. The total thickness of the adhesive layers constituting the optical laminate is, for example, 3 to 130 μm, preferably 5 to 120 μm, and more preferably 10 to 100 μm.

The total thickness of the front plate 10 and the adhesive layer 40 bonded to the front plate may be, for example, 25 to 500 μm. From the viewpoint of reducing the bending repulsive force, the total thickness of the front panel 10 and the adhesive layer in contact with the front panel is preferably 200 μm or less, more preferably 100 μm or less, and still more preferably 80 μm or less.

From the viewpoint of improving impact resistance, the sum of the thickness of the front panel and the thickness of all the adhesive layers is preferably 50 μm or more, and more preferably 60 μm or more. From the viewpoint of reducing the bending repulsive force, the total of the thickness of the front panel and the thickness of all the adhesive layers is preferably 200 μm or less, and more preferably 150 μm or less. From the viewpoint of improving impact resistance, the optical laminate preferably satisfies at least one of (1) a thickness of the front sheet of 30 μm or more and (2) a total thickness of the adhesive layers of 20 μm or more.

The pressure-sensitive adhesive layer may be composed of one layer or two or more layers, but is preferably one layer. The adhesive layer may be formed of an adhesive composition. 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 heat-curable type.

As the (meth) acrylic resin (base polymer) used in the adhesive composition, a polymer or copolymer in which one or two 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 suitably 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, a (meth) acrylamide compound, an N, N-dimethylaminoethyl (meth) acrylate compound, and a glycidyl (meth) acrylate compound.

The adhesive composition may comprise only the above-mentioned base polymer, but usually also contains a crosslinking agent. Examples of the crosslinking agent include metal ions having a valence of 2 or more, which form a metal carboxylate with a carboxyl group; polyamine compounds forming amide bonds with carboxyl groups; polyepoxy compounds or polyols which form ester linkages with carboxyl groups; a polyisocyanate compound forming an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.

The active energy ray-curable adhesive composition is a pressure-sensitive adhesive composition having a property of being cured by irradiation with an active energy ray such as ultraviolet ray or electron beam, and has the following properties: the adhesive has adhesiveness even before irradiation with an active energy ray and can be adhered to an adherend such as a film, and the adhesive force can be adjusted by curing the adhesive by irradiation with an active energy ray. 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. Further, a photopolymerization initiator, a photosensitizer and the like may be contained as necessary.

The adhesive composition may contain additives such as fine particles, beads (resin beads, glass beads, and the like), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders, other inorganic powders, and the like), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, anticorrosion agents, and photopolymerization initiators for imparting light scattering properties.

The adhesive layer may be performed by: a method of dissolving or dispersing a pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a pressure-sensitive adhesive liquid, and directly applying the pressure-sensitive adhesive liquid to a target surface of a laminate film to form a pressure-sensitive adhesive layer; a method in which the pressure-sensitive adhesive layer is formed in a sheet form on the separation film subjected to the release treatment in advance, and the sheet is transferred to the target surface of the polarizing plate. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the pressure-sensitive adhesive layer formed with an active energy ray.

The thickness of the pressure-sensitive adhesive layer may be, for example, 1 μm to 100. mu.m. The thickness of the pressure-sensitive adhesive layer is preferably 3 μm or more, preferably 50 μm or less, and more preferably 30 μm or less. If the thickness of the pressure-sensitive adhesive layer is small, the impact resistance tends to be low, and if the thickness of the pressure-sensitive adhesive layer is large, the repulsive force of bending tends to be high.

The storage elastic modulus of the adhesive layer at a temperature of 25 ℃ is, for example, 0.01MPa to 0.2 MPa. It is considered that the impact resistance is improved when the storage elastic modulus is high. The storage elastic modulus can be measured using a viscoelasticity measuring apparatus ("MCR-301" (trade name) manufactured by Anton Paar Co., Ltd.). The adhesive layer was cut into a width of 20mm × a length of 20mm, and a plurality of adhesive layers were laminated so that the thickness became 150 μm. The laminated adhesive layer is bonded to the glass plate. In the state that the adhesive layer and the measuring chip are adhered, the measurement is carried out in the temperature range from-20 ℃ to 100 ℃ under the conditions of the frequency of 1.0Hz, the deformation amount of 1 percent and the temperature rising speed of 5 ℃/min, and the energy storage elastic modulus value of 25 ℃ is measured.

The adhesive layer is composed of a known aqueous composition (including an aqueous adhesive) in which a curable resin component is dissolved or dispersed in water, a known active energy ray-curable composition (including an active energy ray-curable adhesive) containing an active energy ray-curable compound, and the like.

Examples of the resin component contained in the aqueous composition include a polyvinyl alcohol resin and a urethane resin. In order to improve the adhesiveness and adhesiveness, the aqueous composition containing a polyvinyl alcohol resin may further contain a curing component such as a polyaldehyde, a melamine compound, a zirconium oxide compound, a zinc compound, glyoxal, a glyoxal derivative, a water-soluble epoxy resin, and a crosslinking agent. Examples of the aqueous composition containing a urethane resin include an aqueous composition containing a polyester ionomer urethane resin and a compound having a glycidyloxy group. The polyester ionomer urethane resin is a urethane resin having a polyester skeleton and a small amount of an ionic component (hydrophilic component) is introduced therein.

The active energy ray-curable composition is a composition that is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays.

The active energy ray-curable composition may contain an epoxy compound that is cured by cationic polymerization as a curable component, and is preferably an ultraviolet-curable composition containing the epoxy compound as a curable component. The epoxy compound is a compound having one or more, preferably two or more epoxy groups on average in a molecule. The epoxy compound may be used alone or in combination of two or more.

Examples of the epoxy compound include a hydrogenated epoxy compound (glycidyl ether of a polyol having an alicyclic ring) obtained by hydrogenating an aromatic ring of an aromatic polyol, which is obtained by reacting epichlorohydrin with the alicyclic polyol; aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof; and alicyclic epoxy compounds which are epoxy compounds having one or more epoxy groups bonded to alicyclic rings in the molecule.

The active energy ray-curable composition may contain a radically polymerizable (meth) acrylic compound as a curable component in place of or together with the epoxy compound. Examples of the (meth) acrylic compound include (meth) acrylate monomers having one or more (meth) acryloyloxy groups in the molecule; a (meth) acryloyloxy group-containing compound such as a (meth) acrylate oligomer having at least two (meth) acryloyloxy groups in a molecule, which is obtained by reacting two or more functional group-containing compounds.

When the active energy ray-curable composition contains an epoxy compound that is cured by cationic polymerization as a curable component, it preferably contains a photo cationic polymerization initiator. Examples of the photo cation polymerization initiator include aromatic diazonium salts; aromatic iodine

Salts, aromatic sulfonium salts and the like

Salt; iron-allene complexes, and the like.

When the active energy ray-curable composition contains a radical polymerizable component such as a (meth) acrylic compound, a photoradical polymerization initiator is preferably contained. Examples of the photo radical polymerization initiator include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone.

The thickness of the adhesive layer may be, for example, 1 μm to 25 μm. The thickness of the adhesive layer is preferably 2 μm or more, preferably 15 μm or less, and more preferably 5 μm or less. If the thickness of the adhesive layer is small, the impact resistance tends to be low, and if the thickness of the adhesive layer is large, the bending repulsive force tends to be high.

The storage elastic modulus of the adhesive layer at a temperature of 25 ℃ is, for example, 1000MPa or more. It is considered that the impact resistance is improved when the storage elastic modulus is high.

The opposite surfaces bonded via the adhesive 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 30, a plate-like body capable of transmitting light, a component used in a general display device, or the like can be used. Examples of the components used in a general display device used for the back panel 30 include a spacer, a touch sensor panel, and an organic EL display element.

Examples of the order of stacking the components in the display device include a front panel, a circularly polarizing plate, a spacer, a front panel, a circularly polarizing plate, an organic EL display element, 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.

Back panel 30 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 sensor method, an ultrasonic wave method, an electromagnetic induction coupling method, a surface acoustic wave method, and the like. Since the cost is low, a touch sensor panel of a resistive film type or a capacitive coupling type is suitably used.

As an example of the resistive film type touch sensor, there is a touch position detecting circuit including a pair of substrates arranged to face each other, an insulating spacer interposed between the pair of substrates, a transparent conductive film provided as a resistive film on an inner front surface of each of the substrates, and the touch position detecting circuit.

In an image display device provided with a resistive touch sensor, if a surface of a front panel is touched, opposing resistive films are short-circuited, and a current flows through the resistive films. The touch position detection circuit detects a change in voltage at that time, and detects the touched 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 a touch is made on the surface of a front panel, a transparent electrode is grounded at the touched point via the capacitance of a human body. The touch position detection circuit detects the grounding of the transparent electrode and detects the touched position.

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

The touch sensor panel may be a member in which a pattern of a touch sensor is formed on a base material film. Examples of the base film may be the same as those in the description of the thermoplastic resin film. The touch sensor panel may be a member that is transferred from a base film to an adherend via a pressure-sensitive adhesive layer. That is, the touch sensor panel may not have a substrate film. The thickness of the touch sensor pattern may be, for example, 1 μm to 20 μm.

[ method for producing optical laminate ]

The optical laminate can be produced by a method including the steps of: and a step of bonding the layers constituting the optical laminate to each other via the bonding layer. When the layers are bonded to each other via the bonding layer, it is preferable to perform surface activation treatment such as corona treatment on one surface or both surfaces of the bonding surface in order to adjust 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.

< image display device >

The optical

layered bodies

100 and 200 are disposed on the front surface (visible side) of the image display element, and can be used as a component of an image display device. An optical laminate as a circularly polarizing plate may be used as an antireflection polarizing plate for imparting an antireflection function to an image display device.

An image display device including the optical laminate of the present invention can be used as a flexible display that can be bent or wound. The image display device as a flexible display may be configured such that the front surface (visible side) of the front panel 10 can be bent outward, or may be configured such that the front surface (visible side) of the front panel 10 can be wound outward.

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 display element.

The image display apparatus can be used as a mobile device such as a smart phone or a tablet computer, a television, a digital photo frame, an electronic signboard, a measuring instrument, an office machine, a medical machine, a computer machine, or the like.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In examples and comparative examples, "%" and "part(s)" are "% by mass" and "part(s) by mass" unless otherwise specified.

< example 1 >

[ preparation of front Panel ]

As the front panel 10, a resin film having a thickness of 50 μm, in which a hard coat layer is formed on one surface of a base film, was prepared. The substrate film was a polyimide resin film having a thickness of 40 μm. The hard coat layer is a layer having a thickness of 10 μm and formed of a composition containing a dendrimer compound having a polyfunctional acryl group at the end.

[ preparation of impact-resistant layer ]

As the impact resistant layer 50, a biaxially stretched polyethylene terephthalate (PET) film ("Lumirror", manufactured by Toray corporation) having a thickness of 45 μm was used.

[ preparation of polarizing plate ]

An alignment film composition was applied to one surface of a 25 μm thick TAC film (manufactured by konica minolta corporation), and the resultant was dried and irradiated with polarized UV light to form a photo-alignment film. A composition containing a dichroic dye and a polymerizable liquid crystal compound was applied to the photo-alignment film, dried, and then cured by ultraviolet irradiation to form a polarizer (thickness 2.5 μm). A protective layer composition comprising polyvinyl alcohol and water was applied to the surface of the polarizer opposite to the TAC film side and dried to form a protective layer (thickness: 1 μm, not shown). Thus, a linearly polarizing plate was obtained.

A circularly polarizing plate is obtained by laminating a retardation layer on the lambda/4 layer side described later on the protective layer of the linearly polarizing plate. The retardation layer had a thickness of 15 μm and had a structure in which a pressure-sensitive adhesive layer, a λ/4 layer, a pressure-sensitive adhesive layer and a positive C layer were sequentially laminated. The thickness of each adhesive layer was 5 μm. The lambda/4 layer had a layer obtained by curing a liquid crystal compound and an alignment film, and had a thickness of 2 μm. The positive C layer had a layer obtained by curing a liquid crystal compound and an alignment film, and had a thickness of 3 μm. Thus, a circularly polarizing plate having layers of "TAC film/optical alignment film/polarizer/protective layer/retardation layer" was prepared.

[ preparation of adhesive layer ]

An acrylic pressure-sensitive adhesive composition was applied to a release film and dried to form a pressure-sensitive adhesive layer, thereby preparing a pressure-sensitive adhesive layer with a release film.

[ preparation of Back Panel ]

A polyimide resin film (thickness: 50 μm, Kolon Co.) was prepared as the back plate 30.

[ production of optical laminate ]

The layers are laminated so as to form the front panel 10, the impact-resistant layer 50, the polarizing plate 20, and the back panel 30 in this order. The front plate 10 and the impact-resistant layer 50 were bonded via the bonding layer a, the impact-resistant layer 50 and the polarizer 20 were bonded via the bonding layer B, and the polarizer 20 and the back plate 30 were bonded via the bonding layer C, to obtain the optical laminate of example 1. As the laminating layers A, B and C, adhesive layers having thicknesses shown in table 1 were used. And carrying out corona treatment on the bonding surface. The optical laminate thus obtained had a structure as shown in fig. 2.

< example 2 >

An optical laminate of example 2 was obtained in the same manner as in example 1, except that adhesive layers having thicknesses shown in table 1 were used as the adhesive layers A, B and C.

< example 3 >

An optical laminate of example 3 was obtained in the same manner as in example 1 except that a resin film having a thickness of 32 μm, which had a polyimide-based resin film having a thickness of 25 μm and a hard coat layer having a thickness of 7 μm on one surface, was used as the front panel 10, adhesive layers having thicknesses shown in table 1 were used as the adhesive layers B and C, and an adhesive layer was used as the adhesive layer a. As the adhesive layer of the adhesive layer A, an adhesive layer having a thickness of 2.0 μm which is obtained by applying an active energy ray-curable composition and curing the composition by irradiation with ultraviolet rays was used.

< example 4 >

An optical laminate of example 4 was obtained in the same manner as in example 3, except that a pressure-sensitive adhesive layer having a thickness shown in table 1 was used as the bonding layer a.

< example 5 >

An optical laminate of example 5 was obtained in the same manner as in example 2, except that a resin film having a thickness of 32 μm, which includes a polyimide-based resin film having a thickness of 25 μm and a hard coat layer having a thickness of 7 μm on one surface, was used as the front plate 10.

< comparative example 1 >

An optical laminate of comparative example 1 was obtained in the same manner as in example 1, except that a resin film having a thickness of 62 μm, which had a polyimide-based resin film having a thickness of 50 μm and a hard coat layer having a thickness of 12 μm on one surface, and adhesive layers having thicknesses shown in table 1 were used as the adhesive layers A, B and C, as the front panel 10.

< comparative example 2 >

An optical laminate of comparative example 2 was obtained in the same manner as in comparative example 1, except that a polyimide resin film having a thickness of 80 μm and a resin film having a thickness of 90 μm, which is a hard coat layer having a thickness of 10 μm, were used as the front panel 10.

[ measurement of thickness ]

The thickness of each layer was measured using an ellipsometer (M-220, manufactured by Nippon spectral Co., Ltd.) or a contact film thickness meter (MH-15M, manufactured by Nikon, Ltd., counter TC101, MS-5C).

[ measurement of flexural rigidity ]

The flexural Stiffness of a test piece of 2.54cm by 8.89cm optical laminate was measured according to TAPPI T543 om-00 using a Bending Stiffness Tester from Gurley corporation.

[ measurement of bending repulsive force ]

The repulsive force of the optical laminate was measured according to the method shown in fig. 4. First, the optical laminate was cut into a test piece of 2.54cm × 8.89 cm. The test piece was bent so that the front panel was outside and was wound around a bending jig 500 having a thickness of 8mm, fixed with an adhesive tape, and set on a table 501. The tape fixing length 504 of the bottom surface of the bending jig 500 was 35mm, and the tape fixing length 505 of the upper surface of the bending jig 500 was 30 mm. The end of the test piece is warped by a warp amount 503 in a direction away from the bending jig 500. The maximum repulsive force during the period was measured as a bending repulsive force by using SurTA system (bending model, manufactured by Chemilab corporation) after the height moving plate 502 moved from the height 35mm above the stage 501 to a height of 8mm from the stage 501 so as to bring the warped portion of the optical layered body 200 closer to the folding jig 500 and then returned to the height of 35 mm. The moving speed of the plate 502 is 5 mm/sec. The optical laminate had a bend radius of 4mm (4R).

When the measured bending repulsive force exceeds 7.0gf, cracks and peeling easily occur in the optical laminate when the optical laminate is used in an image display device in which the bending axis is not fixed in the vicinity of the center, and therefore the bending repulsive force was evaluated in the following criteria, and the results are shown in table 1.

A: the bending repulsive force is 7.0gf or less.

B: the bending repulsive force exceeds 7.0 gf.

[ impact resistance test ]

As the impact resistance test, an optical laminate having a polyimide resin film as a back sheet having a touch sensor panel in place of the optical laminate of the above examples and comparative examples was used. The front plate and the circularly polarizing plate were bonded to each other with a bonding layer to obtain a laminate, and the laminate was cut into rectangular small pieces each having a length of 150mm in the long side by 70mm in the short side using a super cutter. The small circular polarizer side was bonded to the ITO layer side of the touch panel sensor via an adhesive layer, to obtain an optical laminate for testing. As the touch sensor panel, a touch sensor panel composed only of a touch sensor pattern layer and having no base film is used. The touch sensor pattern layer included an ITO layer as a transparent conductive layer and a cured layer of an acrylic resin composition as a separation layer, and had a thickness of 7 μm.

Then, the evaluation pen was held with the pen tip at a distance of 10cm from the outermost surface of the front panel of the small chip and with the pen tip facing downward, and was dropped from this position, under an environment of 23 ℃ and a relative humidity of 55%. In the front panel of the small piece, a mark is written at a position where the pattern of the transparent conductive layer of the touch sensor panel is located, and the evaluation pen is dropped so that the pen point comes into contact with the mark. As the evaluation pen, a pen having a weight of 11g and a pen tip diameter of 0.7mm was used. The small piece after dropping with the evaluation pen was visually observed and the touch sensor panel function was confirmed, and evaluated according to the following criteria. Table 1 shows the evaluation results.

A: no crack. The touch sensor panel function is maintained.

B: there is a crack. The touch sensor panel function is maintained.

C: there is a crack. No touch sensor panel function.

[ Table 1]

Description of the symbols

100. 200 optical laminated body, 10 front panel, 20 polaroid, 30 back panel, 40, 41, 42 laminating layers, 500 bending clamp, 501 worktable, 502 panel, 503 warping amount, 504 bottom tape fixed length, 505 top tape fixed length.

Claims

1. An optical laminate comprising a front sheet, a polarizer, a back sheet and at least one adhesive layer,

when the bending stiffness of the optical laminate is K, the following relational expression (1) is satisfied:

k is 400-2000 (1), wherein the unit of K is Gerlai unit.

2. The optical stack of claim 1, wherein the sum of the thickness of the front face sheet and the thickness of all of the applied layers is from 50 μm to 200 μm.

3. The optical stack according to claim 1 or 2, wherein the front sheet has a thickness of 60 μm or less.

4. The optical stack according to any one of claims 1 to 3, wherein the total thickness of the adhesive layers is from 3 μm to 130 μm.

5. The optical laminate according to any one of claims 1 to 4, further comprising an impact resistant layer,

the thickness of the impact-resistant layer is less than 100 μm.

6. An image display device comprising the optical laminate according to any one of claims 1 to 5.

7. The image display device according to claim 6, which can bend the front panel side outward.