CN113015928B

CN113015928B - Optical laminate and image display device provided with same

Info

Publication number: CN113015928B
Application number: CN201980074493.4A
Authority: CN
Inventors: 出崎光; 徐龙源; 姜大山; 金东辉; 金埈奭
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-11-16
Filing date: 2019-10-08
Publication date: 2023-02-28
Anticipated expiration: 2039-10-08
Also published as: CN113015928A; JP2020086429A; TW202030088A; KR20210091136A; JP7300906B2

Abstract

The invention provides an optical laminate having good bendability suitable for a flexible display and excellent impact resistance, and an image display device provided with the optical laminate. The optical laminate comprises a front panel, a circularly polarizing plate, and a 1 st adhesive layer for adhering the front panel and the circularly polarizing plate. The circularly polarizing plate includes a linearly polarizing plate and a retardation layer in this order from the 1 st bonding layer side. The front panel comprises an outer layer forming the outermost surface of the optical laminate, and an inner layer provided in contact with the outer layer and the 1 st adhesive layer, wherein the outer layer is a 1 st resin film, and the inner layer has a thickness of 100 [ mu ] m or less. The optical laminate has a load resistance value of 20g or more in a ball drop test.

Description

Optical laminate and image display device provided with same

Technical Field

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

Background

In recent years, flexible displays having flexibility have been attracting attention from the viewpoint of improving portability by being provided on a surface other than a flat surface such as a curved surface or a bent surface and being folded or formed in a roll shape. In such a flexible display, the front panel is also required to be flexible. Cover glass that has been used in image display devices that do not have flexibility cannot be mounted on flexible displays. Therefore, a front panel of a resin film is known as a front panel for a flexible display (patent document 1).

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2017-13492

Disclosure of Invention

The front panel having flexibility has the following problems: when compared with a cover glass used as a front panel of an image display device having no flexibility, impact resistance is insufficient.

The invention provides an optical laminate having good bendability suitable for a flexible display and excellent impact resistance, and an image display device provided with the optical laminate.

The invention provides an optical laminate and an image display device provided with the same.

[ 1] an optical laminate comprising a front plate, a circularly polarizing plate, and a 1 st adhesive layer for adhering the front plate and the circularly polarizing plate,

the circularly polarizing plate includes a linearly polarizing plate and a retardation layer in this order from the 1 st bonding layer side,

the front panel includes an outer layer forming an outermost surface of the optical laminate, and an inner layer provided so as to be in contact with the outer layer and the 1 st adhesive layer,

the outer layer is a 1 st resin film,

the thickness of the inner layer is 100 μm or less,

the load resistance value in the ball drop test (ball drop test) of the optical layered body is 20g or more.

The optical laminate according to [ 1], wherein the front sheet satisfies the relationship between the following expression (1) and expression (2) when an in-plane retardation value of the front sheet at a wavelength of 550nm is R0 (550) and a thickness direction retardation value of the front sheet at a wavelength of 550nm is Rth (550):

2000nm≤R0(550)≤15000nm (1)

5000nm≤Rth(550)≤15000nm (2)。

the optical laminate according to [ 1] or [ 2 ], wherein the product of the tensile modulus of 55% relative humidity at 23 ℃ of the inner layer and the thickness of the inner layer is 80MPa · mm to 700MPa · mm.

The optical laminate according to any one of [ 1] to [ 3 ], wherein the inner layer comprises a 2 nd resin film and a 2 nd adhesive layer for adhering the 2 nd resin film to the outer layer.

The optical laminate according to [ 5 ] or [ 4 ], wherein the relationship of the following formula (3) is satisfied where a [ MPa ] is a tensile elastic modulus of the 2 nd resin film at 23 ℃ and 55% relative humidity, b [ μm ] is a thickness of the 2 nd resin film, and c [ μm ] is a thickness of the 2 nd adhesive layer:

(a×b×10 ^－3 )+(c/2)≥55 (3)。

the optical laminate according to [ 4 ] or [ 5 ], wherein the tensile elastic modulus a [ MPa ] of the 2 nd resin film at 23 ℃ and 55% relative humidity is 7000MPa or less.

The optical laminate according to any one of [ 4 ] to [ 6 ], wherein the 2 nd adhesive layer is an adhesive layer.

The optical laminate according to any one of [ 1] to [ 7 ], wherein a product of a tensile elastic modulus of the outer layer at a temperature of 23 ℃ and a relative humidity of 55% and a thickness of the outer layer is 100MPa · mm to 800MPa · mm.

The optical laminate according to any one of [ 1] to [ 8 ], wherein the optical laminate has a limit number of bending times of 10 ten thousand or more in a bending test.

An optical laminate according to any one of [ 1] to [ 9 ], wherein the optical laminate is an antireflection film.

An image display device according to any one of [ 1] to [ 10 ] is provided with the optical laminate, wherein the front panel is disposed on a front surface.

According to the optical laminate of the present invention, an image display device having good bendability suitable for a flexible display and excellent impact resistance can be provided.

Drawings

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

Fig. 2 is a schematic cross-sectional view schematically showing an example of the image display device of the present invention.

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 is appropriately adjusted to show the component for easy understanding, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

(optical laminate)

Fig. 1 is a schematic cross-sectional view schematically showing an example of an optical laminate according to the present embodiment. The optical laminate 100 is composed of a front panel 10, a circularly polarizing plate 30, and a 1 st laminating layer 20, and as shown in fig. 1, includes the front panel 10, the 1 st laminating layer 20, and the circularly polarizing plate 30 in this order from the visible side. The 1 st adhesive layer 20 is a layer for adhering the front panel 10 and the circularly polarizing plate 30. The front panel 10 includes an outer layer 11 forming the outermost surface of the optical laminate 100, and an inner layer 12 provided so as to contact the outer layer 11 and the 1 st adhesive layer 20. The circularly polarizing plate 30 includes a linearly polarizing plate 31 and a retardation layer 32 in this order from the 1 st adhesive layer 20 side.

The optical laminate 100 may constitute an image display device as described later. Further, the optical laminate 100 may be used as an antireflection film since it includes the circularly polarizing plate 30.

The optical laminate 100 can be used for a foldable, rollable, or other image display device (flexible display) by forming the outer layer 11 of the front panel 10 as a 1 st resin film and forming the inner layer to have a thickness of 100 μm or less. The optical laminate 100 preferably has flexibility of 10 ten thousand or more times of ultimate bending determined in a bending test in examples described later, and the ultimate bending number is more preferably 15 ten thousand or more, and still more preferably 20 ten thousand or more. Thus, the optical laminate 100 can be suitably used for a flexible display. The bending test can be performed by the method of the example described later.

Light emitted from the display element side of the image display device having the optical laminate 100 passes through the optical laminate 100 and observed through a sunglass having a linear polarization characteristic (hereinafter, may be referred to as "polarized sunglasses") (light incident from the circularly polarizing plate 30 side of the optical laminate 100, emitted from the front panel 10 side, and transmitted through the polarized sunglasses) exhibits a specific transmitted color corresponding to the phase difference value of the front panel. Thus, even with the polarized sunglasses, the display image can be visually recognized. On the other hand, in the case where the image display device having the front panel with R0 (550) and Rth (550) of less than 10nm includes the linear polarizing plate, when the image display device is viewed through the polarized sunglasses, the luminance is greatly reduced by the angle formed by the absorption axis of the linear polarizing plate and the absorption axis of the polarizer of the polarized sunglasses, and a phenomenon such as light blocking (blackout) in which the display image is not easily visible occurs.

The load resistance value in the ball drop test of the optical laminate 100 is 20g or more, preferably 21g or more, more preferably 22g or more, and may be 25g or more, usually 50g or less, and may be 40g or less. When the load resistance value is within the above range, excellent impact resistance can be imparted to the optical laminate 100 even when the 1 st resin film is used as the outer layer 11 of the front panel 10. Therefore, a flexible display having flexibility and excellent impact resistance can be provided by using the optical laminate 100. The load-bearing value in the ball drop test is measured by the method described in the examples described later.

The load resistance value in the ball drop test of the optical laminate 100 can be adjusted by the rigidity (tensile elastic modulus, thickness), yield point elongation, yield stress, and the like of each layer constituting the optical laminate 100. For example, the rigidity of the inner layer 12 described later, the adhesive agent included in the inner layer 12 and forming the 2 nd bonded layer 12b described later, the type of the adhesive agent, the thickness of the 2 nd bonded layer 12b, the adhesive agent and the type of the adhesive agent forming the 1 st bonded layer 20, the thickness of the 1 st bonded layer 20, and the like can be adjusted.

When the optical laminate 100 is used as an antireflection film, the reflectance is preferably 10% or less, more preferably 7% or less, and still more preferably 5.5% or less. The reflectance was measured using a spectrophotometer (CM-2600 d, manufactured by Konikamet Co., ltd.).

The thickness of the optical laminate 100 is not particularly limited, but is preferably 220 μm or less, more preferably 180 μm or less, further preferably 150 μm or less, and usually 40 μm or more, and may be 70 μm or more in order to exhibit good flexibility.

The shape of the optical laminate 100 in the plane direction is not particularly limited, but is preferably a square shape, and more preferably a rectangular shape. When the optical laminate 100 has a rectangular shape, the length of the long side is preferably 50mm to 500mm, and may be 100mm to 400mm, and the length of the short side is, for example, preferably 30mm to 400mm, and may be 60mm to 300mm. The optical laminate 100 may have a rounded square shape obtained by performing R processing on at least 1 of the corners of the square shape, or may have a square shape with a cutout on at least one side. The optical laminate 100 may be provided with a hole penetrating in the lamination direction.

(front panel)

As shown in fig. 1, the front panel 10 includes an outer layer 11 forming the outermost surface of the optical laminate 100, and an inner layer 12 provided so as to contact the outer layer 11 and the 1 st adhesive layer 20. The front panel 10 is a plate-like body that transmits light. In an image display device including the optical laminate 100, the front panel 10 can function as a layer for protecting a display element and the like of the image display device. The front panel 10 may have a function as a touch sensor, a blue light cut-off function, and the like, in addition to a function of protecting the front surface of the image display device.

The front panel 10 may have a view angle adjusting function. In this case, when the in-plane retardation value of the front panel at a wavelength of 550nm is R0 (550) and the thickness direction retardation value of the front panel at a wavelength of 550nm is Rth (550), the front panel 10 preferably satisfies the relationship between the following expressions (1) and (2):

2000nm≤R0(550)≤15000nm (1)

5000nm≤Rth(550)≤15000nm (2)。

by making the front panel 10 satisfy the relationship between the formula (1) and the formula (2), color unevenness with rainbow colors due to retardation of the optical laminate is less likely to occur both when the image display device using the optical laminate 100 is viewed from the front direction by the polarized sunglasses and when the image display device using the optical laminate 100 is viewed from an oblique direction. This provides the optical laminate 100 having excellent impact resistance and bendability and excellent visibility.

The in-plane retardation value R0 (550) of the front panel 10 is more preferably 2500nm or more, and still more preferably 5000nm or more. The thickness direction retardation Rth (550) of the front panel 10 is more preferably 8000nm or more, still more preferably 9000nm or more, and still more preferably 10000nm or more.

The rigidity represented by the product of the tensile elastic modulus of the front panel 10 at 23 ℃ and 55% relative humidity and the thickness of the front panel 10 is preferably 100MPa · mm or more, may be 150MPa · mm or more, may be 300MPa · mm or more, and is preferably 5000MPa · mm or less, may be 4000MPa · mm or less, and may be 3000MPa · mm or less. Since the front panel 10 forms the outermost surface of the optical layered body 100, when the rigidity of the front panel 10 is small, the surface protection function of a display panel or the like included in the image display device is not easily obtained, and when the rigidity of the front panel 10 is large, the flexibility tends to be reduced.

The tensile modulus of the front panel 10 at 23 ℃ and 55% relative humidity is preferably 3000MPa or more, more preferably 5000MPa or more, and preferably 20000MPa or less, more preferably 15000MPa or less.

When the tensile elastic modulus of outer layer 11 is small, surface hardness tends to be difficult to obtain, and scratch resistance tends to decrease, and when the tensile elastic modulus of outer layer 11 is large, flexibility tends to decrease. The tensile modulus of the outer layer 11 at 23 ℃ and 55% relative humidity can be measured by the method described in the examples described later, and the value measured along the slow axis direction when the outer layer 11 has retardation characteristics.

The angle formed by the slow axis of the front panel 10 and the absorption axis of the linearly polarizing plate 31 is preferably 0 ° or more, more preferably 30 ° or more, further preferably 35 ° or more, and further preferably 65 ° or less, more preferably 60 ° or less, further preferably 55 ° or less, and most preferably 45 °.

The thickness of the front panel 10 is not particularly limited, but is preferably 250 μm or less, and may be 200 μm or less, and usually 40 μm or more, and may be 70 μm or more in order to exhibit good flexibility and good impact resistance.

(outer layer)

The outer layer 11 constituting the front plate 10 is a layer on the outermost surface of the optical laminate 100. The outer layer 11 has a function of imparting a desired surface hardness to the optical laminate 100, and a function of protecting other layers laminated on the outer layer 11. The 1 st resin film forming the outer layer 11 is not limited as long as it is a film that transmits light, and may be a resin film having a hard coat layer provided on at least one surface of a base film to improve surface hardness.

The rigidity represented by the product of the tensile elastic modulus of the outer layer 11 at a temperature of 23 ℃ and a relative humidity of 55% and the thickness of the outer layer 11 is preferably 90MPa · mm or more, more preferably 100MPa · mm or more, further preferably 250MPa · mm or more, and further preferably 2000MPa · mm or less, more preferably 1200MPa · mm or less, further preferably 800MPa · mm or less, and may be 600MPa · mm or less. Since the outer layer 11 forms the outermost surface of the optical laminate 100, when the rigidity of the outer layer 11 is low, it is difficult to obtain sufficient surface hardness of the optical laminate 100, and the abrasion resistance and the like tend to be low, and when the rigidity of the outer layer 11 is high, the flexibility tends to be low.

The rigidity of the outer layer 11 is preferably higher than the rigidity of the inner layer 12, the rigidity of the 1 st adhesive layer 20, and the rigidity of the circularly polarizing plate 30.

The tensile modulus of the outer layer 11 at 23 ℃ and 55% relative humidity is preferably 3000MPa or more, more preferably 5000MPa or more, and preferably 20000MPa or less, more preferably 15000MPa or less.

The thickness of the outer layer 11 is usually not less than 30 μm, but may be not less than 50 μm, and is usually not more than 100 μm, but may be not more than 80 μm. When the thickness of the outer layer 11 is small, the impact resistance tends to be low, and when the thickness of the outer layer 11 is large, the flexibility tends to be low.

The 1 st resin film forming the outer layer 11 may be a 1 st retardation film having a retardation characteristic. In this case, the in-plane retardation value of the outer layer 11 at a wavelength of 550nm may be, for example, 0nm or more, or 50nm or more, or 300nm or less, or 200nm or less. The phase difference in the thickness direction of the outer layer 11 at a wavelength of 550nm may be, for example, 0nm or more, or 100nm or more, or 3000nm or less, or 2000nm or less.

The 1 st resin film is not limited as long as it is a resin film that transmits light. Examples of the film include films formed of polymers such as cellulose triacetate, cellulose acetate butyrate, ethylene-vinyl acetate copolymer, cellulose propionate, cellulose butyrate, cellulose acetate propionate, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic acid, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyetheretherketone, polyethersulfone, poly (meth) acrylic acid methyl ester, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers may be used alone or in combination of 2 or more. When the image display device 300 is a flexible display, a resin film made of a polymer such as polyimide, polyamide, or polyamideimide, which has excellent flexibility and has high strength and high transparency, is preferably used.

The 1 st resin film may be a film having a hard coat layer provided on at least one surface of a base film to further improve hardness. The hard coat layer may be formed on one surface of the substrate film or on both surfaces. When the image display device to be described later is a touch panel type image display device, a resin film having a hard coat layer is preferably used because the surface of the outer layer 11 is a touch surface. By providing the hard coat layer, a resin film having improved hardness and scratch resistance can be formed.

The hard coat layer is a cured layer of, for example, an ultraviolet curable resin. Examples of the ultraviolet curable resin include (meth) acrylic resins, silicone resins, polyester resins, polyurethane resins, amide resins, and epoxy resins. The hard coating may contain additives to improve strength. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, and a mixture thereof.

(inner layer)

The inner layer 12 constituting the front panel 10 is provided between the outer layer 11 and the 1 st adhesive layer 20, and directly contacts both the outer layer 11 and the 1 st adhesive layer 20. The inner layer 12 may be provided to improve the impact resistance of the optical laminate 100. The thickness of the inner layer 12 is 100 μm or less, and thus, the optical laminate 100 is easily provided with bendability suitable for a flexible display. The inner layer 12 may have phase difference characteristics for giving the front panel 10 a phase difference value represented by the above formulas (1) and (2), and the inner layer 12 may have a phase difference value represented by the above formulas (1) and (2). As shown in fig. 1, the inner layer 12 may include a 2 nd resin film 12a and a 2 nd attaching layer 12b for attaching the 2 nd resin film 12a to the outer layer 11. The 2 nd bonding layer 12b may directly contact the 1 st bonding layer 20 on the opposite side of the 2 nd resin film 12 a. The inner layer 12 may further include 2 or more resin films and a bonding layer for bonding the 2 or more resin films.

The rigidity represented by the product of the tensile elastic modulus of the inner layer 12 at a temperature of 23 ℃ and a relative humidity of 55% and the thickness of the inner layer 12 is preferably 10MPa · mm or more, more preferably 40MPa · mm or more, further preferably 80MPa · mm or more, and further preferably 1000MPa · mm or less, more preferably 700MPa · mm or less, further preferably 640MPa · mm or less. When the rigidity of the inner layer 12 is in the above range, the flexibility of the optical laminate 100 can be easily ensured, and the impact resistance can be easily improved.

The rigidity of the inner layer 12 is preferably lower than the rigidity of the outer layer 11 and the rigidity of the circularly polarizing plate 30, and may be higher than the rigidity of the 1 st adhesive layer 20.

The tensile modulus of the inner layer 12 at 23 ℃ and 55% relative humidity is preferably 1000MPa or more, more preferably 1500MPa or more, and may be 2000MPa or more, and is preferably 10000MPa or less, more preferably 9000MPa or less, and may be 8000MPa or less. When the rigidity of the inner layer 12 is in the above range, the flexibility of the optical laminate 100 can be easily ensured, and the impact resistance can be easily improved. The tensile modulus of the inner layer 12 at 23 ℃ and 55% relative humidity can be measured by the method described in the examples described later, and the value measured along the slow axis direction when the inner layer 12 has retardation characteristics.

When the inner layer 12 includes the 2 nd resin film 12a and the 2 nd adhesive layer 12b, the tensile elastic modulus a [ MPa ] at 23 ℃ and 55% relative humidity of the 2 nd resin film 12a is preferably 1000MPa or more, more preferably 1500MPa or more, may be 2000MPa or more, may be 3000MPa or more, may be 3500MPa or more, is preferably 7000MPa or less, more preferably 6000MPa or less, and may be 5000MPa or less. The tensile elastic modulus of the 2 nd resin film 12a at a temperature of 23 ℃ and a relative humidity of 55% can be measured by the above-described method. When the inner layer 12 includes 2 or more resin films and a bonding layer for bonding the 2 or more resin films to each other, the tensile elastic modulus of the 2 nd resin film 12a refers to the tensile elastic modulus of the entire bonding layer including the 2 or more resin films.

The thickness of the inner layer 12 is 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, and preferably 20 μm or more, more preferably 40 μm or more. When the thickness of the inner layer 12 is small, the impact resistance tends to be low, and when the thickness of the inner layer 12 is large, the flexibility tends to be low.

The 2 nd resin film 12a may be a 2 nd retardation film having a retardation characteristic. In this case, the in-plane retardation value of the inner layer 12 at a wavelength of 550nm may be, for example, 100nm or more, 1000nm or more, or 3000nm or more. The thickness-direction phase difference of the inner layer 12 at a wavelength of 550nm may be, for example, 2500nm or more, or 3000nm or more. When the inner layer 12 includes 2 or more resin films and a bonding layer for bonding the 2 or more resin films to each other, the in-plane phase difference value and the thickness direction phase difference value of the 2 nd resin film 12a refer to the in-plane phase difference value and the thickness direction phase difference value of the entire bonding layer including the 2 or more resin films.

When the inner layer 12 includes the 2 nd retardation film and the outer layer 11 is the 1 st retardation film, it is preferable that the outer layer 11 and the inner layer 12 are laminated in the optical laminate 100 so that the slow axis direction of the 1 st retardation film coincides with the slow axis direction of the 2 nd retardation film.

This makes it possible to obtain excellent visibility when the image display device using the optical laminate 100 is visually recognized by the polarized sunglasses.

The angle formed by the slow axis of the 1 st retardation film and the absorption axis of the circularly polarizing plate 30 and the angle formed by the slow axis of the 2 nd retardation film and the absorption axis of the circularly polarizing plate 30 are preferably 25 ° or more, more preferably 30 ° or more, further preferably 35 ° or more, and further preferably 65 ° or less, more preferably 60 ° or less, further preferably 55 ° or less, and most preferably 45 °.

The thickness b [ μm ] of the 2 nd resin film 12a is not particularly limited, and is, for example, preferably 10 μm or more, more preferably 15 μm or more, further preferably 20 μm or more, and may be 30 μm or more, and may be 50 μm or more. The thickness b [ μm ] of the 2 nd resin film 12a may be 150 μm or less, or 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, and further preferably 50 μm or less. When the inner layer 12 includes 2 or more resin films and a bonding layer for bonding 2 or more resin films to each other, the thickness of the 2 nd resin film 12a is the thickness of the entire bonding layer including 2 or more resin films.

Tensile elastic modulus a [ MPa ] of 2 nd resin film 12a]And the thickness b [ mu ] m of the 2 nd resin film 12a]Rigidity expressed by the product of (a × b × 10 in the formula (3) described later) ^－3 ”)[MPa·mm]Preferably 10MPa · mm or more, more preferably 40MPa · mm or more, further preferably 80MPa · mm or more, and may be 150MPa · mm or more, and may be 200MPa · mm or more, and may be 300MPa · mm or more. The rigidity of the 2 nd resin film 12a is preferably 1500MPa · mm or less, more preferably 1000MPa · mm or less, may be 800MPa · mm or less, and may be 500MPa · mm or less. When the rigidity of the 2 nd resin film 12a is in the above range, the flexibility of the optical laminate 100 is easily ensured, and the impact resistance is easily improved.

The 2 nd resin film 12a is not limited as long as it is a film that transmits light, and examples thereof include a film made of a polymer exemplified as the 1 st resin film forming the outer layer 11. When the 2 nd resin film 12a is the 2 nd retardation film, a film made of a polymer such as polyethylene naphthalate, polyethylene terephthalate, or the like can be preferably used as the 2 nd resin film 12 a.

(second adhesive layer)

The 2 nd adhesive layer 12b may be an adhesive layer, preferably an adhesive layer. By using the 2 nd adhesive layer 12b as the pressure-sensitive adhesive layer, it becomes easy to adjust the rigidity of the inner layer 12 to the above range, and it becomes easy to improve the impact resistance of the optical laminate 100. The pressure-sensitive adhesive layer and the adhesive layer can be formed using the materials described later.

The thickness c [ μm ] of the 2 nd adhesive layer 12b is not particularly limited, and may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, and usually preferably 50 μm or less, and 30 μm or less.

The tensile elastic modulus a [ MPa ], the thickness b [ μm ] of the 2 nd resin film 12a and the thickness c [ μm ] of the 2 nd adhesive layer 12b constituting the inner layer 12 of the front panel 10 preferably satisfy the following formula (3):

(a×b×10 ^－3 )+(c/2)≥55 (3)。

by satisfying the relationship of the above expression (3), the durability of the optical laminate 100 in the pen-down test can be improved. It is considered that the pressure applied to the bottom surface side (circularly polarizing plate 30 side) of the optical laminate 100 can be reduced by improving the durability against the pen-drop test. Therefore, when a touch panel sensor or a display laminate is provided on the bottom surface side of the optical laminate 100 as in a composite optical laminate or an image display device described later, the durability of the composite optical laminate or the image display device can be improved by using an optical laminate satisfying the relationship of the above expression (3). For example, in the composite optical laminate, it becomes easy to suppress occurrence of malfunction in the touch panel sensor provided on the bottom surface side (circularly polarizing plate 30 side) of the optical laminate 100. Further, by satisfying the formula (3), the durability to the ball drop test can be improved. The durability in the pen-drop test can be evaluated by the method described in the examples described later.

The value on the left side of the above formula (3) is more preferably 60 or more, more preferably 80 or more, and may be 100 or more, or may be 200 or more, more preferably 250 or more, or may be 300 or more. The value on the left side of the above formula (3) is usually 500 or less, and may be 400 or less.

The tensile elastic modulus a [ MPa ] of the 2 nd resin film 12a in the above formula (3)]Thickness b [ mu ] m]The thickness c [ mu ] m of the 2 nd adhesive layer 12b]And a × b × 10 ^－3 The values of (b) may be, for example, in the ranges described above, respectively.

The pressure-sensitive adhesive layer forming the 2 nd adhesive layer 12b 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 of a heat-curable type.

As the (meth) acrylic resin (base polymer) used in the adhesive composition, for example, 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. It is preferred to copolymerize the polar monomer with the base polymer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The adhesive composition may contain only the above-mentioned base polymer, but usually further contains a crosslinking agent. Examples of the crosslinking agent include metal ions having a valence of 2 or more and a substance which forms a metal carboxylate salt with a carboxyl group; a polyamine compound which is a substance forming an amide bond with a carboxyl group; a polyepoxy compound, a polyhydric alcohol, and a substance forming an ester bond with a carboxyl group; a polyisocyanate compound and is a substance that forms an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.

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, defoaming agents, anticorrosion agents, and photopolymerization initiators for imparting light scattering properties.

The adhesive composition can be formed by applying a diluted solution of the above adhesive composition in an organic solvent to a substrate and drying the applied solution. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be formed by irradiating the pressure-sensitive adhesive layer formed with an active energy ray.

The adhesive layer forming the 2 nd adhesive layer 12b may be made of an adhesive composition. Examples of the adhesive composition include aqueous adhesive compositions such as aqueous polyvinyl alcohol resin solutions and aqueous two-pack polyurethane emulsion adhesives; and an active energy ray-curable adhesive composition which is cured by irradiation with an active energy ray such as ultraviolet ray.

(first adhesive layer 1)

The 1 st adhesive layer 20 is a layer interposed between the inner layer 12 of the front panel 10 and the circularly polarizing plate 30 to bond them, and is an adhesive layer or an adhesive layer. The pressure-sensitive adhesive layer and the adhesive layer may be formed using the above-mentioned materials. From the viewpoint of ensuring flexibility of the optical laminate 100 and improving impact resistance, the 2 nd lamination layer 12b is preferably an adhesive layer.

The storage elastic modulus of the 1 st adhesive layer 20 at 23 ℃ and 55% relative humidity is preferably 0.001MPa or more, may be 0.01MPa or more, may be 0.1MPa or more, and is preferably 0.5MPa or less, and may be 0.3MPa or less. When the storage elastic modulus of the 1 st adhesive layer 20 is in the above range, the flexibility of the optical laminate 100 can be easily ensured and the impact resistance can be easily improved. The storage elastic modulus of the 1 st adhesive layer 20 at 23 ℃ and 55% relative humidity can be measured by the method described in the examples described later.

The thickness of the 1 st adhesive layer 20 may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, and usually 100 μm or less, preferably 50 μm or less, and 30 μm or less.

(circular polarizing plate)

The circularly polarizing plate 30 includes a linearly polarizing plate 31 and a retardation layer 32 in this order from the 1 st adhesive layer 20 side. Further, since the circularly polarizing plate 30 can suppress the emission of reflected light of external light, the optical laminate 100 can be provided with a function as an antireflection film.

The thickness of the circularly polarizing plate 30 is usually 5 μm or more, and may be 20 μm or more, or 25 μm or more, or 30 μm or more, or preferably 80 μm or less, or more preferably 60 μm or less. When the thickness of the circularly polarizing plate 30 is within the above range, the influence of the load resistance value in the ball drop test on the optical laminate 100 is smaller than that of the other layers forming the optical laminate 100, and the influence can be ignored.

(Linear polarizer)

The linearly polarizing plate 31 has a function of selectively transmitting linearly polarized light in a certain direction from light rays of unpolarized light such as natural light. Examples of the linearly polarizing plate 31 include a stretched film having a dye having absorption anisotropy adsorbed thereon, a film having a polarizer obtained by coating and curing a dye having absorption anisotropy, and the like. Examples of the dye having absorption anisotropy include dichroic dyes. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. The dichroic organic dye includes a dichroic direct dye composed of a bisazo compound such as c.i. direct red 39, and a dichroic direct dye composed of a compound such as triazole or tetrazole. Examples of the film coated with a dye having absorption anisotropy that can be used as a polarizer include a stretched film in which a dye having absorption anisotropy is adsorbed, and a film having a layer obtained by coating a composition containing a dichroic dye having liquid crystallinity or a composition containing a dichroic dye and a polymerizable liquid crystal and curing the composition. A film obtained by applying and curing a dye having absorption anisotropy is preferable because the bending direction is not limited as compared with a stretched film in which a dye having absorption anisotropy is adsorbed.

The polarizer included in the linearly polarizing plate 31 has a visual sensitivity correction polarization degree (Py) of usually 97% or more, preferably 98% or more, and more preferably 99% or more. The visual sensitivity corrected transmittance (Ty) of the polarizer is usually 40% or more, preferably 41% or more, more preferably 42% or more, and may be 44% or more.

(1) Polarizing plate having stretched film as polarizer

A linear polarizing plate including a stretched film having a dye having absorption anisotropy adsorbed thereon as a polarizer will be described. A stretched film as a polarizer, to which a dye having absorption anisotropy is adsorbed, is usually produced through a process of uniaxially stretching a polyvinyl alcohol resin film, a process of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with the dichroic dye, a process of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution, and a process of washing with water after the treatment with the aqueous boric acid solution. The polarizer may be used as it is as a linear polarizing plate, or an article having a transparent protective film attached to one or both surfaces thereof may be used as a linear polarizing plate. The thickness of the polarizer thus obtained is preferably 2 to 40 μm.

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 acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably 1500 to 5000.

The film formed from the polyvinyl alcohol resin can be used as a raw material film for a polarizer. The method for forming the film of the polyvinyl alcohol resin is not particularly limited, and the film can be formed by a known method. The thickness of the polyvinyl alcohol-based raw material film may be, for example, about 10 μm to 150 μm.

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing of the dichroic dye. When the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before the boric acid treatment or may be performed in the boric acid treatment. In addition, uniaxial stretching may be performed in a plurality of stages of these. In the case of uniaxial stretching, the stretching may be carried out uniaxially between rolls having different peripheral speeds, or uniaxially using a heat roll. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which a polyvinyl alcohol resin film is stretched in a state of being swollen with a solvent. The stretch ratio is usually about 3 to 8 times.

The material of the protective film to be attached to one or both surfaces of the polarizer is not particularly limited, and examples thereof include films known in the art, such as a cyclic polyolefin resin film, a cellulose acetate resin film made of a resin such as cellulose triacetate and cellulose diacetate, a polyester resin film made of a resin such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, a polycarbonate resin film, a (meth) acrylic resin film, and a polypropylene resin film. From the viewpoint of thinning, the thickness of the protective film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, and usually 5 μm or more, preferably 20 μm or more. The protective film may or may not have a phase difference.

(2) Polarizing plate having polarizer formed of film of liquid crystal layer

A linear polarizing plate including a film formed of a liquid crystal layer as a polarizer will be described. Examples of the film used as a polarizer coated with a dye having absorption anisotropy include a film obtained by applying a composition containing a dichroic dye having liquid crystallinity or a composition containing a dichroic dye and a liquid crystal compound to a substrate and curing the composition. The film may be used as a linear polarizer by peeling off or using a substrate together with the substrate, or may be used as a linear polarizer having a structure in which a protective film is provided on one surface or both surfaces thereof. Examples of the protective film include the same films as those of the linear polarizing plate having the stretched film as a polarizer.

The thinner the film obtained by applying and curing a coloring matter having absorption anisotropy, the better, but if too thin, the strength tends to decrease, and the processability tends to be poor. The thickness of the film is usually 20 μm or less, preferably 5 μm or less, and more preferably 0.5 to 3 μm.

Specific examples of the film obtained by applying the dye having the absorption anisotropy include films described in japanese patent application laid-open nos. 2013-37353 and 2013-33249.

(retardation layer)

The retardation layer 32 may be 1 layer or 2 or more layers. The retardation layer 32 includes a λ/4 layer, and may further include a λ/2 layer and a positive C layer. When the retardation layer 32 includes a λ/2 layer, a λ/2 layer and a λ/4 layer are stacked in this order from the linearly polarizing plate 31 side. When the retardation layer 32 includes a positive C layer, the λ/4 layer and the positive C layer may be stacked in this order from the linearly polarizing plate 31 side, or the positive C layer and the λ/4 layer may be stacked in this order from the linearly polarizing plate 31 side.

The retardation layer 32 may be formed of a resin film exemplified as a material of the protective film, or may be formed of a layer in which a polymerizable liquid crystal compound is cured. The retardation layer 32 may further include an alignment film, a base film, or a lamination layer for laminating the λ/4 layer with the λ/2 layer or the positive C layer. The adhesive layer is an adhesive layer or an adhesive layer, and the adhesive layer or the adhesive layer described above can be used.

(composite optical laminate)

The composite optical laminate includes an optical laminate 100 and a touch panel sensor. The touch panel sensor is provided on the circularly polarizing plate 30 side of the optical laminate 100. The optical laminate 100 and the touch panel sensor may be laminated via a bonding layer for the touch panel sensor, for example.

The adhesive layer includes an adhesive layer and an adhesive layer, and the adhesive layer can be formed using the above materials.

(image display device)

Fig. 2 is a schematic cross-sectional view schematically showing an example of the image display device according to the present embodiment. The image display device includes an optical laminate 100 including a front panel 10 disposed on the front surface (visible side) thereof, a display laminate 200 including a display cell, and a 3 rd adhesive layer 40, and the display laminate 200 is laminated on the circularly polarizing plate 30 side of the optical laminate 100 via the 3 rd adhesive layer 40. The 3 rd bonding layer 40 is used for bonding the circularly polarizing plate 30 and the display laminate 200 in the optical laminate 100. When the optical laminate 100 and the display laminate 200 are laminated, for example, the 3 rd bonding layer 40 may be provided on the circularly polarizing plate 30 of the optical laminate 100, and the display laminate 200 may be laminated on the 3 rd bonding layer 40. The adhesive layer for the display laminate is an adhesive layer or an adhesive layer, and the adhesive layer can be formed using the above materials.

The image display device 300 may be a flexible display panel. The image display device as the flexible display may be configured to be foldable with the visible-side surface being the inner side, or may be configured to be rollable.

The image display device 300 may be configured as a touch panel type image display device. The touch panel type image display device may be configured using the composite optical laminate described above, and the touch panel sensor side of the composite optical laminate and the display laminate 200 may be laminated via a bonding layer for the display laminate, for example. The adhesive layer for the display laminate is composed of an adhesive layer and an adhesive layer, and the adhesive layer can be composed using the above materials. In the touch panel type image display device, the front panel 10 included in the optical laminate 100 of the composite optical laminate constitutes a touch surface.

Examples of the display unit included in the display laminate 200 include display units including display elements such as liquid crystal display elements, organic EL display elements, inorganic EL display elements, plasma display elements, and field emission type display elements.

The image display apparatus 300 can be used as a mobile device such as a smart phone or a tablet computer, a television, a digital photo frame, an electronic billboard, a measuring instrument, a meter, an office device, a medical instrument, a computer device, or the like.

Examples

The present invention will be described in more detail with reference to the following 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.

[ 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, co., ltd., counter TC101, MS-5C).

[ measurement of tensile elastic modulus ]

The tensile modulus was measured at a temperature of 23 ℃ and a relative humidity of 55% using a tensile tester (AG-1S, manufactured by Shimadzu corporation). When the object to be measured is a retardation film, the tensile modulus in the slow axis direction is measured.

[ measurement of in-plane phase Difference value and thickness-Direction phase Difference value ]

The in-plane retardation value and the thickness direction retardation value were measured using a birefringence measurement apparatus (Axo Sacn, manufactured by Axometrics).

[ falling ball test ]

A test sample (1) was prepared by bonding the circular polarization plate side of the optical laminates obtained in the examples and comparative examples to 0.7mm alkali-free glass with an acrylic adhesive (manufactured by Sumitomo chemical Co., ltd.) having a thickness of 5 μm. The test sample (1) was set on a steel table with the front panel side as the upper surface, and a ball drop test ball made of steel was allowed to freely drop vertically from a position of 50cm in height, and collided with the alkali-free glass via an optical laminate.

The test balls were used in 11 types of test balls having weights of 1g, 3g, 4g, 7g, 12g, 16g, 19g, 22g, 25g, 32g, and 36g, and the maximum value among the test ball weights at which cracks, scratches, and depressions were not observed in the test sample (1) (optical laminate, alkali-free glass) was referred to as a ball drop test load value (g), which was used as an index of impact resistance.

[ bending test ]

The circularly polarizing plate side of the optical laminates obtained in each example and each comparative example was fixed in a flat state (unbent state) to a bendability evaluation equipment (CFT-150ac, manufactured by covotech) via an acrylic adhesive (manufactured by sumitomo chemical corporation) having a thickness of 20 μm, and then bent at a speed of 30 times per 1 minute under a condition of a curvature radius of 3mm and a temperature of 25 ℃ so as to return to an original flat state with the front plate side as the inner side, and the above bending operation was repeated, and the number of bending times when cracking and whitening occurred at the bent position was counted as a limit number of bending times. When the number of times of bending reached 20 ten thousand, cracking in the bent region and lifting of the adhesive layer (pressure-sensitive adhesive layer) were not observed (the limit number of times of bending was 20 ten thousand or more) and when the number of times of bending was 10 ten thousand or more and less than 20 ten thousand, the above-described case (the limit number of times of bending was 10 ten thousand or more and less than 20 ten thousand) was denoted as B and when the number of times of bending was less than 10 ten thousand, the above-described case (the limit number of times of bending was less than 10 ten thousand) was denoted as C, and the bendability test was evaluated.

[ visibility test ]

The circular polarizer side of the optical laminate obtained in each of examples and comparative examples was disposed on a backlight unit (product name: light and aging LED Viewer5000A4, manufactured by koku corporation).

The optical laminate was visually recognized from the front panel side by the polarizing sunglasses, and the occurrence of color unevenness in the rainbow color with which the optical laminate was dyed was confirmed. The visibility test was conducted from two directions, i.e., a front direction perpendicular to the surface of the front panel and an oblique direction at 45 ° to the surface of the front panel, and the occurrence of color unevenness was confirmed. The case where the color unevenness was hardly visually recognized and good visibility was obtained was judged as "no" color unevenness, and the case where the apparent color unevenness was visually recognized was judged as "presence" color unevenness.

[ Pen-drop test ]

From the optical layered bodies obtained in the examples and comparative examples, rectangular pieces having a long side of 150mm × a short side of 70mm were cut out using a super cutter (supercout). The cut piece was bonded to the ITO layer side of the touch panel sensor through an adhesive layer to obtain a test sample (2). As the touch sensor panel, a panel composed only of a touch sensor pattern layer 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.

Next, under an environment of a temperature of 23 ℃ and a relative humidity of 55%, a pen point of an evaluation pen weighing about 5.6g (diameter of the pen point: 0.75 mm) was held at a distance of 10cm from the outermost surface of the front panel of the test sample (2) with the tip portion thereof facing downward, and the evaluation pen was dropped from this position toward the front panel side. The front panel of the test sample (2) was marked with bridge wiring (wiring for electrically connecting touch electrodes) of the conductive layer of the touch panel sensor, and the evaluation pen was dropped so that the pen tip was dropped to the marked bridge portion. The test sample (2) after the evaluation pen was dropped was observed with a Scanning Electron Microscope (SEM) (SU 8010, horiba, inc.) and the function of the touch panel sensor was confirmed. Based on the occurrence of cracks and the operation of the touch panel sensor, the pen-down test was evaluated by designating a case where there was no crack and the touch panel sensor was operating normally, B a case where there was a crack and the touch panel sensor was operating normally, and C a case where there was a crack and the touch panel sensor was operating abnormally.

[ example 1]

(preparation of front Panel)

As the outer layer, a 1 st resin film having a thickness of 60 μm, on which a hard coat layer was formed on one surface of a base film, was prepared. The substrate film was a polyimide resin film having a thickness of 50 μm. The hard coat layer is a layer having a thickness of 10 μm and formed of a composition containing a dendritic compound having a polyfunctional acrylic group at the end. The in-plane phase difference value at a wavelength of 550nm of the obtained outer layer was 133nm, the thickness direction phase difference value at a wavelength of 550nm was 1754nm, and the tensile elastic modulus was 8000MPa.

As the inner layer, a laminate in which the 2 nd adhesive layer was formed on the 2 nd resin film was prepared. The 2 nd resin film was a polyethylene naphthalate (PEN) film having a thickness of 34 μm ("Teonex", manufactured by Dishiitake K.K.), and the 2 nd adhesive layer was an acrylic adhesive having a thickness of 5 μm (manufactured by Sumitomo chemical Co., ltd.). The in-plane retardation value at a wavelength of 550nm of the 2 nd resin film was 6933nm, the retardation value in the thickness direction at a wavelength of 550nm was 8959nm, and the tensile elastic modulus was 2400MPa. The inner layer had a tensile modulus of 2500MPa and a rigidity of 98MPa mm.

The surface of the outer layer opposite to the side on which the hard coat layer was formed was bonded to the 2 nd adhesive layer of the inner layer to obtain a front panel. The outer layer and the inner layer are bonded so that the slow axis direction of the 1 st resin film forming the outer layer coincides with the slow axis direction of the 2 nd resin film forming the inner layer. The obtained front panel was measured for an in-plane retardation value R0 (550) at a wavelength of 550nm and a thickness direction retardation value Rth (550) at a wavelength of 550 nm. The results are shown in table 1.

(preparation of Linear polarizing plate)

A polyvinyl alcohol (PVA) film having an average polymerization degree of about 2400, a saponification degree of 99.9 mol% or more and a thickness of 20 μm was prepared. The PVA film was immersed in pure water at 30 ℃ and then immersed in an aqueous solution having a mass ratio of iodine/potassium iodide/water of 0.02/2/100 at 30 ℃ to perform iodine dyeing (iodine dyeing step). The PVA film subjected to the iodine dyeing step was immersed in an aqueous solution of potassium iodide/boric acid/water at a mass ratio of 12/5/100 at 56.5 ℃ to be subjected to boric acid treatment (boric acid treatment step). The PVA film subjected to the boric acid treatment step was washed with pure water at 8 ℃ and then dried at 65 ℃ to obtain a polarizer in which iodine was adsorbed and oriented to polyvinyl alcohol. The PVA film is stretched in the iodine dyeing step and the boric acid treatment step. The total draw ratio of the PVA film was 5.3 times. The thickness of the resulting polarizer was 8 μm.

The polarizer obtained above and a cycloolefin polymer (COP) film (ZF-14, manufactured by Nippon Ruizhiki K.K., having an in-plane retardation value of 1nm at a wavelength of 550 nm) having a thickness of 13 μm were bonded to each other with a kneading roll using a water-based adhesive. The obtained laminate was dried at 60 ℃ for 2 minutes while maintaining the tension of 430Nm, thereby obtaining a linear polarizing plate having a COP film on one side. The water-based adhesive was prepared by adding 3 parts of carboxyl-modified polyvinyl alcohol ("KURARAY KL318" manufactured by KURARAY corporation) and 1.5 parts of water-soluble polyamide epoxy resin ("Sumirez 650" (aqueous solution having a solid content of 30%) manufactured by takaki chemical industries, inc.) to 100 parts of water.

(preparation of retardation layer)

The following components were mixed, and the resulting mixture was stirred at a temperature of 80 ℃ for 1 hour to obtain a composition for forming a horizontally oriented film.

Photo-alignment material (5 parts) (weight average molecular weight: 30000):

solvent (95 parts): cyclopentanone

Further, the following components were mixed, and N-methyl-2-pyrrolidone (NMP) was further added so that the solid content concentration became 13%, and the mixture was stirred at 80 ℃ for 1 hour, thereby obtaining a composition for forming a horizontally aligned liquid crystal layer. The following polymerizable liquid crystal compound a is synthesized by the method described in jp 2010-31223 a, and the following polymerizable liquid crystal compound B is synthesized by the method described in jp 2009-173893 a.

Polymerizable liquid crystal compound a (90 parts):

polymerizable liquid crystal compound B (10 parts):

leveling agent (1 part):

f-556 (DIC corporation)

Polymerization initiator (6 parts):

2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one (Irgacure 369, manufactured by BASF Japan K.K.)

A cycloolefin resin (COP) film (ZF-14-50, manufactured by Nippon Ralskikusho Co., ltd.) was subjected to corona treatment. Corona treatment with TEC-4AX (Manufactured by niu-shou motor co., ltd.) was processed 1 time under conditions of an output of 0.78kW and a processing speed of 10 m/min. The horizontally oriented film-forming composition obtained above was applied to the corona-treated surface of the COP film by a bar coater, and dried at 80 ℃ for 1 minute. The cumulative quantity of light at a wavelength of 313nm of the coating film reached 100mJ/cm using a polarized UV irradiation apparatus ("SPOT CURE SP-9", manufactured by NIGHT MOTOR Co., ltd.) ² In such a manner that polarized light UV exposure was performed at an axial angle of 45 ℃ to obtain a horizontally oriented film having a thickness of 100 nm.

Subsequently, the composition for forming a horizontally aligned liquid crystal layer obtained above was applied to the horizontally aligned film by using a bar coater, and dried at 120 ℃ for 1 minute. The coating film was irradiated with ultraviolet rays (cumulative light amount at a wavelength of 365nm under a nitrogen atmosphere: 500 mJ/cm) using a high-pressure mercury lamp ("Unicure VB-15201BY-A", manufactured BY NIFI TAIL MOTOR Co., ltd.) ² ) Thus, a retardation layer was obtained by forming a λ/4 retardation layer as a horizontally aligned liquid crystal layer. The thickness of the lambda/4 phase difference layer was 2.3. Mu.m. The obtained retardation layer had a COP film, a horizontally oriented film, and a lambda/4 retardation layer in this order.

An acrylic pressure-sensitive adhesive (manufactured by Sumitomo chemical Co., ltd.) having a thickness of 5 μm was laminated on the λ/4 retardation layer side of the obtained retardation layer, and after the pressure-sensitive adhesive was bonded to glass, a COP film was peeled off to obtain a sample for measurement. Measuring the in-plane retardation value R0 at the wavelength λ of the sample _p (λ), the results are as follows: r0 _p (450)＝119nm，R0 _p (550)＝140nm，R0 _p (650)＝144nm，R0 _p (450)/R0 _p (550)＝0.85，R0 _p (650)/R0 _p (550) =1.03, λ/4 retardation layer exhibits reverse wavelength dispersion. The lambda/4 phase difference layer satisfies the relation that nx is larger than ny and is approximately equal to nz, and is a positive A plate.

Further, the above-mentioned measurement sample was measured for a retardation value Rth in the thickness direction at the wavelength λ _p

(λ), the results are as follows: rth _p (450)＝61nm，Rth _p (550)＝71nm，Rth _p (650)＝73nm。

(preparation of circular polarizing plate)

The polarizer side of the obtained linear polarizing plate and the λ/4 retardation layer side of the obtained retardation layer were bonded via an acrylic adhesive (manufactured by sumitomo chemical corporation) having a thickness of 5 μm, and the COP film of the retardation layer was peeled off to obtain a circular polarizing plate. The linearly polarizing plate and the retardation layer were bonded so that the angle formed by the absorption axis of the polarizer and the slow axis of the λ/4 retardation layer was 45 °. The circularly polarizing plate comprises a COP film (COP film of a linearly polarizing plate), a polarizer, an acrylic adhesive, and a lambda/4 retardation layer in this order.

(production of optical layered body)

The inner layer side of the front panel thus obtained was bonded to the linear polarizer side of the circularly polarizing plate via an acrylic pressure-sensitive adhesive (manufactured by Sumitomo chemical Co., ltd.) having a thickness of 5 μm, thereby obtaining an optical laminate having a thickness of 132 μm. The optical laminate thus obtained was subjected to a ball drop test, a bending test, a visual test, and a pen drop test. The results are shown in table 1.

[ example 2 ]

An optical laminate was obtained in the same manner as in example 1 except that a highly birefringent polyethylene terephthalate (PET) film ("Cosmoshine SRF", manufactured by toyobo co., ltd.) having a thickness of 80 μm was used as the 2 nd resin film forming the inner layer. The in-plane phase difference value at a wavelength of 550nm of the above-mentioned 2 nd resin film was 6187nm, the thickness-direction phase difference value at a wavelength of 550nm was 6320nm, and the tensile elastic modulus was 3800MPa. The tensile modulus of elasticity of the inner layer was 3900MPa, and the rigidity was 332MPa mm.

The obtained front panel was measured for an in-plane retardation value R0 (550) at a wavelength of 550nm and a thickness direction retardation value Rth (550) at a wavelength of 550 nm. The optical laminate thus obtained was subjected to a ball drop test, a bending test, a visual test, and a pen drop test. The results are shown in Table 1.

[ example 3 ]

An optical laminate was obtained in the same manner as in example 1, except that a biaxially stretched polyethylene terephthalate (PET) film ("Lumirror", manufactured by tokyo corporation) having a thickness of 45 μm was used as the 2 nd resin film forming the inner layer. The in-plane retardation value at a wavelength of 550nm of the 2 nd resin film was 2655nm, the thickness-direction retardation value at a wavelength of 550nm was 3455nm, and the tensile elastic modulus was 4000MPa. The tensile modulus of elasticity of the inner layer was 4100MPa, and the rigidity was 205MPa mm.

The obtained front panel was measured for an in-plane retardation value R0 (550) at a wavelength of 550nm and a thickness direction retardation value Rth (550) at a wavelength of 550 nm. The optical laminate thus obtained was subjected to a ball drop test, a bending test, a visual test, and a pen drop test. These results are shown in table 1.

[ example 4 ]

A front plate was obtained in the same manner as in example 1 except that a uniaxially stretched cycloolefin polymer (COP) film ("ZF-14-23", manufactured by japan regent corporation) having a thickness of 23 μm was used as the 2 nd resin film forming the inner layer, and an acrylic adhesive (manufactured by sumitomo chemical) having a thickness of 20 μm was used as the 2 nd bonding layer forming the inner layer, to obtain an optical laminate. The 2 nd resin film has an in-plane retardation value at a wavelength of 550nm of less than 1nm, a thickness-direction retardation value at a wavelength of 550nm of less than 1nm, and a tensile elastic modulus of 2100MPa. The inner layer had a tensile modulus of elasticity of 2300MPa and a rigidity of 99MPa mm.

[ comparative example 1]

A front plate was obtained in the same manner as in example 1 except that the inner layer was not provided, and an optical laminate was obtained. The obtained front panel was measured for an in-plane retardation value R0 (550) at a wavelength of 550nm and a thickness direction retardation value Rth (550) at a wavelength of 550 nm. The optical laminate thus obtained was subjected to a ball drop test, a bending test, a visual test, and a pen drop test. The results are shown in Table 1.

[ comparative example 2 ]

An optical laminate was obtained in the same manner as in example 1, except that a uniaxially stretched cycloolefin polymer (COP) film ("ZF-14-23", manufactured by japan regen corporation) having a thickness of 23 μm was used as the 2 nd resin film forming the inner layer. The 2 nd resin film has an in-plane retardation value at a wavelength of 550nm of less than 1nm, a thickness-direction retardation value at a wavelength of 550nm of less than 1nm, and a tensile elastic modulus of 2100MPa. The inner layer had a tensile modulus of elasticity of 2200MPa and a rigidity of 62MPa mm.

[ comparative example 3 ]

An optical laminate was obtained in the same manner as in example 1 except that a front plate was obtained as the 2 nd resin film forming the inner layer, using a film obtained by coating a uniaxially stretched cycloolefin polymer (COP) film ("ZF-14-23", manufactured by kushoku corporation) having a thickness of 23 μm with an acrylic soft coat layer ("UF 8003G", manufactured by cohniki chemical corporation) having a thickness of 80 μm. The 2 nd resin film has an in-plane retardation value at a wavelength of 550nm of less than 1nm, a thickness-direction retardation value at a wavelength of 550nm of less than 1nm, and a tensile elastic modulus of 2100MPa. The inner layer had a tensile modulus of elasticity of 2300MPa and a rigidity of 248MPa mm.

[ Table 1]

Description of the symbols

10 front panel, 11 outer layer, 12 inner layer, 12a 2 nd resin film, 12b 2 nd adhesive layer, 201 st adhesive layer, 30 circular polarizing plate, 31 linear polarizing plate, 32 retardation layer, 40 rd adhesive layer, 100 optical laminate, 200 display laminate, 300 image display device.

Claims

1. An optical laminate comprising a front plate, a circularly polarizing plate and a 1 st adhesive layer for adhering the front plate and the circularly polarizing plate,

the circularly polarizing plate comprises a linearly polarizing plate and a retardation layer in this order from the 1 st adhesive layer side,

the front panel includes an outer layer forming an outermost surface of the optical laminate and an inner layer provided so as to be in contact with the outer layer and the 1 st adhesive layer,

the outer layer is a 1 st resin film,

the thickness of the inner layer is less than 100 μm,

the inner layer comprises a 2 nd resin film and a 2 nd bonding layer for bonding the 2 nd resin film and the outer layer,

assuming that a is a tensile modulus at a temperature of 23 ℃ and a relative humidity of 55% of the 2 nd resin film, a MPa is a unit, b is a unit of μm is a unit, and c is a unit of μm is a unit of the 2 nd bonding layer, the relationship of the following formula (3) is satisfied:

(a×b×10 ^－3 )+(c/2)≥80 (3)

the optical laminate has a load resistance value of 20g or more in a ball drop test.

2. The optical laminate according to claim 1, wherein the front sheet satisfies the relationship between the following expression (1) and expression (2) when an in-plane phase difference value of the front sheet at a wavelength of 550nm is R0 (550) and a thickness direction phase difference value of the front sheet at a wavelength of 550nm is Rth (550):

2000nm≤R0(550)≤15000nm (1)

5000nm≤Rth(550)≤15000nm (2)。

3. the optical laminate according to claim 1 or 2, wherein the product of the tensile elastic modulus of the inner layer at a temperature of 23 ℃ and a relative humidity of 55% and the thickness of the inner layer is 80MPa · mm to 700MPa · mm.

4. The optical laminate according to any one of claims 1 to 3, wherein the tensile elastic modulus a of the 2 nd resin film at 23 ℃ and 55% relative humidity is 7000MPa or less.

5. The optical stack of any one of claims 1-4 wherein the 2 nd conforming layer is an adhesive layer.

6. The optical laminate according to any one of claims 1 to 5, wherein the product of the tensile elastic modulus of the outer layer at a temperature of 23 ℃ and a relative humidity of 55% and the thickness of the outer layer is 100 MPa-mm to 800 MPa-mm.

7. The optical laminate according to any one of claims 1 to 6, which has a limit number of bending times of 10 ten thousand or more in a bending test.

8. The optical laminate according to any one of claims 1 to 7, wherein the optical laminate is an antireflection film.

9. An image display device comprising the optical laminate according to any one of claims 1 to 8, wherein the front panel is disposed on the front surface.