JP2023077835A - optical film - Google Patents

Abstract

To provide an optical film that is superior in low moisture permeability even when folded and suitable to a polarizing plate protective film for polarizing plate constituting a flexible display.SOLUTION: An optical film 10 has a lamination structure in which a resin layer 1 is laminated on one surface of the optical transmissive base material 2. The resin layer 1 is formed of a cured body of a curable composition including at least one kind of polymerizable compound selected from the group of a monomer having a polymerizable functional group and oligomer having a polymerizable functional group. The absolute value (|M2-M1|) of a difference between moisture permeability M1[g/m2 24h] of the optical film 10 in an environment of a temperature of 40°C and relative humidity of 92% before a bending test and moisture permeability M2[g/m2 24h] of the optical film 10 in an environment of a temperature of 40°C and relative humidity of 92% after the bending test is less than 10 g/m2 24h.SELECTED DRAWING: Figure 1

Description

The present invention relates to optical films. Specifically, it relates to an optical film suitable for a polarizing plate protective film.

Due to the image forming method of an image display device (for example, a liquid crystal display device, an organic EL display device, etc.), in many cases, a polarizing plate is arranged on at least one side of a display cell. The polarizing plate plays a role of passing only light with a plane of polarization in a certain direction, and the performance of the image display device is greatly influenced by the performance of the polarizing plate. A polarizing plate generally has a structure in which a polarizer made of a polyvinyl alcohol film or the like to which iodine or a dye is adsorbed and oriented and a transparent protective film (polarizing plate protective film) are attached to at least one surface of the polarizer. (For example, Patent Document 1).

JP-A-2000-338329

In recent years, there has been an increasing need for bendable flexible displays in mobile applications such as smartphones and tablet terminals. However, if damage such as cracks occurs on the surface of the polarizing plate protective film when the polarizing plate that constitutes the flexible display is folded, the permeability to moisture (moisture permeability) increases, and the polarization of the polarizer in a humid environment increases. The performance may be lost, and a phenomenon called "color loss" may occur.

The present invention was conceived under the circumstances as described above, and an object of the present invention is to provide a polarizing plate of a polarizing plate that has excellent low moisture permeability even when folded and constitutes a flexible display. An object of the present invention is to provide an optical film suitable for a protective film.

In addition, if the polarizing plate protective film is scratched during the manufacturing process, there is a problem that the performance of the polarizing plate deteriorates, such as the low moisture permeability. Therefore, the optical film used for the polarizing plate protective film is also required to have excellent surface hardness and scratch resistance.

A first aspect of the present invention provides an optical film in which a resin layer is laminated on one surface of a light-transmitting substrate. The resin layer imparts excellent low moisture permeability to the optical film of the first aspect of the present invention. The resin layer also imparts excellent surface hardness and scratch resistance to the optical film of the first aspect of the present invention. Furthermore, the resin layer imparts excellent bending resistance to the optical film of the first aspect of the present invention. Therefore, the optical film of the first aspect of the present invention having the resin layer in a laminated structure is suitable as a polarizing plate protective film for a polarizing plate constituting a flexible display.

In the optical film of the first aspect of the present invention, the resin layer has a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having a polymerizable functional group and oligomers having a polymerizable functional group. It is formed from a hardened material. This configuration is suitable for imparting excellent low moisture permeability to the optical film of the first aspect of the present invention. It is also suitable for imparting excellent surface hardness and scratch resistance to the optical film of the first aspect of the present invention. Furthermore, it is also suitable for imparting excellent bending resistance to the optical film of the first aspect of the present invention.

In the optical film of the first aspect of the present invention, the moisture permeability M ¹ [g/m ² ·24 h] of the optical film in an environment with a temperature of 40°C and a relative humidity of 92% before the bending test described below, and the following bending After the test, the absolute value of the difference (|M ² -M ¹ |) from the moisture permeability M ² [g/m ² ·24 h] in an environment of 40°C and 92% relative humidity was 10 g/. It is less than m ² ·24h.
Bending test:
In accordance with JIS K 5600-5-1, the optical film is tested using a mandrel with a diameter of 2 mm so that the resin layer faces outward.

The absolute value of the difference in moisture permeability (|M ² −M ¹ |) is less than 10 g/m ² ·24h, the optical film of the first aspect of the present invention can be used as a polarizing plate constituting a flexible display. When used as a polarizing plate protective film, it exhibits excellent low moisture permeability even when folded, and it is preferable from the viewpoint that the occurrence of "color loss" of the polarizer can be suppressed in a humidified environment.

In the optical film according to the first aspect of the present invention, the film thickness of the resin layer is preferably 1 to 10 μm. The configuration in which the film thickness of the resin layer is 10 μm or less is obtained when the optical film of the first aspect of the present invention is folded when used as a polarizing plate protective film for a polarizing plate constituting a flexible display. Even if there is, it is preferable from the viewpoint that excellent low moisture permeability can be exhibited and the occurrence of "color loss" of the polarizer can be suppressed in a humidified environment. Moreover, the configuration in which the film thickness of the resin layer is 1 μm or more is preferable from the viewpoint of achieving high levels of low moisture permeability, surface hardness, and scratch resistance.

In the optical film according to the first aspect of the present invention, the film thickness of the light-transmitting substrate is preferably 10-50 μm. The configuration in which the film thickness of the light-transmissive substrate is 50 μm or less is such that when the optical film according to the first aspect of the present invention is used as a polarizing plate protective film for a polarizing plate that constitutes a flexible display, it can be folded. Even in this case, it is preferable from the viewpoint that it exhibits excellent low moisture permeability and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. Moreover, the configuration in which the film thickness of the light-transmitting substrate is 10 μm or more is preferable from the viewpoint of achieving high levels of low moisture permeability, surface hardness, and scratch resistance.

In the optical film of the first aspect of the present invention, the product (H×T) of the hardness H (GPa) of the resin layer by the nanoindentation method and the thickness T (μm) of the optical film is 40. The following are preferable. The configuration in which the product (H×T) is 40 or less allows the optical film of the first aspect of the present invention to exhibit excellent surface hardness and scratch resistance, and the optical film of the first aspect of the present invention. , When used as a polarizing plate protective film for polarizing plates that make up flexible displays, it exhibits excellent low moisture permeability even when folded, and suppresses the occurrence of "color loss" in polarizers in humid environments. It is preferable in that it can be done.

In the optical film of the first aspect of the present invention, the product (Er×T) of the elastic modulus Er (GPa) of the resin layer obtained by the nanoindentation method and the thickness T (μm) of the optical film is 600. It is preferable to be the following. The configuration in which the product (Er×T) is 600 or less allows the optical film of the first aspect of the present invention to exhibit excellent surface hardness and scratch resistance, and to provide the optical film of the first aspect of the present invention. , When used as a polarizing plate protective film for polarizing plates that make up flexible displays, it exhibits excellent low moisture permeability even when folded, and suppresses the occurrence of "color loss" in polarizers in humid environments. It is preferable from the viewpoint that it can be done.

In the optical film of the first aspect of the present invention, the light-transmitting substrate may contain at least one selected from the group consisting of cellulose resins, polyester resins, acrylic resins, and cyclic olefin polymers. preferable. These resins can be suitably used as a base material for a polarizing plate protective film.

A second aspect of the present invention provides a polarizing plate in which a polarizer is arranged on the side of the optical film of the first aspect of the present invention opposite to the resin layer.
Furthermore, a third aspect of the present invention provides an image display device having the polarizing plate of the second aspect of the present invention. In the image display device according to the third aspect of the present invention, it is preferable that an adhesive layer and an optical member are laminated in this order on the resin layer. The image display device according to the third aspect of the present invention is preferably a flexible display.

Since the polarizing plate of the second aspect of the present invention uses the optical film of the first aspect of the present invention as a polarizing plate protective film, it exhibits excellent low moisture permeability, surface hardness, and scratch resistance, When used as a polarizing plate constituting a flexible display, it exhibits excellent low moisture permeability even when folded, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. Therefore, even when the image display device according to the third aspect of the present invention having the polarizing plate according to the second aspect of the present invention is folded, the polarizing plate is less likely to lose color in a humid environment. , suitable as a flexible display with excellent durability.

A polarizing plate obtained by using the optical film of the present invention as a polarizing plate protective film exhibits excellent low moisture permeability, surface hardness, and scratch resistance, and exhibits excellent low permeability even when folded. It exhibits wettability and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. Therefore, the optical film of the present invention can be suitably used as a polarizing plate protective film for a polarizing plate constituting a flexible display.

FIG. 1 is a schematic diagram (cross-sectional view) showing one embodiment of the optical film of the present invention. FIG. 2 is a schematic diagram (cross-sectional view) showing an embodiment of a polarizing plate having the optical film of FIG. FIG. 3 is a schematic diagram (cross-sectional view) showing an embodiment of an image display device having the polarizing plate of FIG.

A first aspect of the present invention provides an optical film in which a resin layer is laminated on one surface of a light transmissive substrate.
The optical film of the first aspect of the present invention may be referred to herein as "the optical film of the present invention". In addition, the light-transmitting substrate and the resin layer constituting the optical film of the present invention may be referred to herein as "the light-transmitting substrate of the present invention" and "the resin layer of the present invention", respectively. be. Also, the term "film" includes the meanings of "sheet" and "tape". That is, the optical film of the present invention may be in the form of a sheet or tape.

A second aspect of the present invention provides a polarizing plate in which a polarizer is arranged on the side of the optical film of the present invention opposite to the resin layer. In this specification, the polarizing plate of the second aspect of the present invention may be referred to as "the polarizing plate of the present invention".
Moreover, the 3rd side surface of this invention provides the image display apparatus which has a polarizing plate of this invention. The image display device according to the third aspect of the present invention may be referred to as "the image display device of the present invention" in this specification.

Hereinafter, embodiments of the optical film of the present invention will be described with reference to the drawings, but the present invention is not limited thereto and is merely an example.

FIG. 1 is a schematic diagram (cross-sectional view) showing one embodiment of the optical film of the present invention.
In FIG. 1, an optical film 10 has a laminated structure in which a resin layer 1 is laminated on one surface of a light transmissive substrate 2 .

FIG. 2 is a schematic diagram (cross-sectional view) showing one embodiment of the polarizing plate of the present invention.
In FIG. 2, the polarizing plate 20 has a laminated structure in which the polarizer 3 is arranged on the opposite side of the optical film 10 from the resin layer 1 . In this embodiment, on the opposite side of the polarizer 3 from the optical film 10, a second light-transmitting substrate 4 and an adhesive layer 5 are further laminated in this order.

FIG. 3 is a schematic diagram (cross-sectional view) showing an embodiment of an image display device having the polarizing plate of FIG.
The image display device 30 of FIG. 3 has the image display panel 6 laminated on the adhesive layer 5 of the polarizing plate 20 . The image display panel 6 may be a flexible display panel. In this embodiment, an adhesive layer 7 and an optical member 8 are laminated in this order on the resin layer 1 . The image display device 30 may be a flexible display. If the image display device 30 is a flexible display, the entire laminate structure is foldable.
Each configuration will be described below.

<Optical film>
The term “optical” in the optical film of the present invention means that it is used for optical purposes, and more specifically means that it is used for manufacturing products (optical products) using optical members. Examples of optical products include image display devices, input devices such as touch panels, and liquid crystal image display devices, self-luminous image display devices (eg, organic EL (electroluminescence) image display devices, LED image display devices, etc.). ), and in particular, it can be suitably used for the production of flexible displays. More specifically, it can be suitably used as a protective film for a polarizing plate that constitutes a flexible display.

The form of the optical film of the present invention is not particularly limited as long as the resin layer is laminated on one side of the light-transmitting substrate. For example, the optical film of the present invention may have a resin layer on only one side, or may have a resin layer on both sides. When the optical film of the present invention has resin layers on both sides, the optical film of the present invention may have a form in which both resin layers are provided by the resin layer of the present invention. A layer may be provided by the resin layer of the present invention, and the other resin layer may be provided by a resin layer other than the resin layer of the present invention (another resin layer). When the optical film of the present invention is used as a polarizing plate protective film, it is preferably an optical film having a resin layer only on one side.

The optical film of the present invention may include, in addition to the light-transmitting substrate of the present invention and the resin layer of the present invention, other layers, for example, other than the light-transmitting substrate of the present invention, as long as the effects of the present invention are not impaired. , a resin layer other than the resin layer of the present invention, an intermediate layer, an undercoat layer, an antistatic layer, a release liner, a surface protective film, etc. on the surface or between any layers.

In the optical film of the present invention, the moisture permeability M ¹ [g/m ² ·24 h] of the optical film in an environment with a temperature of 40 ° C. and a relative humidity of 92% before the bending test described below, and the optical film after the bending test described below. The absolute value (|M ² - M ¹ |) of the difference from the moisture permeability M ² [g/m ² · 24h] in an environment of a film temperature of 40°C and a relative humidity of 92% is less than 10g/m ² · 24h. is.
Bending test:
In accordance with JIS K 5600-5-1, the optical film is tested using a mandrel with a diameter of 2 mm so that the resin layer faces outward.

The optical film of the present invention exhibits excellent low moisture permeability, surface hardness, and scratch resistance. When such damage occurs, the low moisture permeability is lowered, and "color loss" of the polarizer may occur in a humidified environment.

In the optical film of the present invention, the absolute value of the difference in moisture permeability (|M ² −M ¹ |) is less than 10 g/m ² ·24h, the optical film of the present invention constitutes a flexible display. When used as a polarizer protective film for polarizers, even if it is bent, damage such as cracks is unlikely to occur on the surface, and it exhibits excellent low moisture permeability. is preferable from the viewpoint of suppressing the occurrence of ". The absolute value of the difference in moisture permeability (|M ² −M ¹ |) is preferably 9 g from the viewpoint that the occurrence of “color loss” of the polarizer can be suppressed in a humidified environment even when the polarizer is folded. /m ² ·24h or less, more preferably ^8g /m ² ·24h or less, still more preferably 7g/m 2 ·24h or less, 6g/m ² ·24h or less, or 5g/m ² ·24h or less, good too. The lower limit of the absolute value of the difference in moisture permeability (|M ² −M ¹ |) is not particularly limited, and the lower the better, but it may be 0.1 g/m ² ·24 h or more.

The moisture permeability M ¹ [g/m ² ·24h] of the optical film of the present invention in an environment of a temperature of 40°C and a relative humidity of 92% before the bending test is preferably 700 g/m ² ·24h or less. The configuration in which the moisture permeability M ¹ is 700 g/m ² ·24 h or less can suppress the occurrence of "color loss" of the polarizer in a humidified environment when the optical film of the present invention is used as a polarizing plate protective film. point is preferable. From the viewpoint of suppressing the color loss of the polarizer at a higher level, the moisture permeability M ¹ is preferably 600 g/m ² ·24h or less, and may be 550 g/m ² ·24h or less. Although the lower limit of the moisture permeability M ¹ is not particularly limited, it is preferably 100 g/m ² ·24 h or more from the viewpoint of preventing the occurrence of "color loss" of the polarizer by allowing the moisture in the polarizing plate to escape to the outside. It is more preferably 200 g/m ² ·24h or more, and may be 300 g/m ² ·24h or more.

Specifically, the absolute value of the difference between the moisture permeability M ¹ and M ² and the difference between M ¹ and M ² (|M ² −M ¹ |) in the optical film of the present invention can be determined by the method described in Examples below. can be measured by The absolute value of the difference between the moisture permeability M ¹ and M ² and the difference between M ¹ and M ² (|M ² −M ¹ |) in the optical film of the present invention is the resin constituting the light-transmitting substrate of the present invention. The type and thickness of the resin layer of the present invention can be adjusted by adjusting the type, composition, degree of cross-linking, thickness, and the like of the resin constituting the resin layer of the present invention.

In the optical film of the present invention, the product (H×T) of the hardness H [GPa] of the resin layer by the nanoindentation method and the thickness T [μm] of the optical film is 40 or less. preferable. When the hardness H of the resin layer according to the nanoindentation method is high, the surface hardness and scratch resistance of the resin layer are excellent. becomes more likely to occur. By controlling the product of the hardness H and the thickness T while adjusting the hardness H to a range in which the surface hardness and scratch resistance of the resin layer are excellent, excellent surface hardness and scratch resistance are exhibited, and bending Even when the polarizer is wetted, damage such as cracks is less likely to occur on the surface, exhibits excellent low moisture permeability, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment.

That is, the configuration in which the product (H×T) is 40 or less indicates that the optical film of the present invention exhibits excellent surface hardness and scratch resistance, and the optical film of the present invention is used as a polarizing plate constituting a flexible display. When used as a polarizing plate protective film, it exhibits excellent low moisture permeability even when folded, and is preferable in that it can suppress the occurrence of "color loss" of the polarizer in a humidified environment. In addition to exhibiting excellent surface hardness and scratch resistance, it exhibits excellent low moisture permeability even when folded, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. (H×T) is preferably 35 or less, more preferably 30 or less, still more preferably 25 or less, and may be 20 or less. The lower limit of the product (H×T) is not particularly limited, but may be 1 or more from the viewpoint of ensuring excellent surface hardness, scratch resistance, and low moisture permeability.

In the optical film of the present invention, the product (H×T ¹ ) of the hardness H [GPa] of the resin layer measured by the nanoindentation method and the thickness T ¹ [μm] of the resin layer is 9 or less. is preferred. By controlling the product of the hardness H and the thickness ^T1 while adjusting the hardness H to a range in which the surface hardness and scratch resistance of the resin layer are excellent, excellent surface hardness and scratch resistance are exhibited, Even when the polarizer is bent, damage such as cracks hardly occurs on the surface, exhibits excellent low moisture permeability, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. That is, when the product (H×T ¹ ) is 9 or less, the optical film of the present invention exhibits excellent surface hardness and scratch resistance, and at the same time, the optical film of the present invention can be used as a polarizer for composing a flexible display. When used as a polarizing plate protective film for a plate, it exhibits excellent low moisture permeability even when folded, and is preferable in that it can suppress the occurrence of "color loss" of the polarizer in a humidified environment. In addition to exhibiting excellent surface hardness and scratch resistance, it exhibits excellent low moisture permeability even when folded, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. (H×T ¹ ) is preferably 8 or less, more preferably 7 or less, still more preferably 6 or less, and may be 5 or less. The lower limit of the product (H×T ¹ ) is not particularly limited, but may be 0.5 or more from the viewpoint of ensuring excellent surface hardness, scratch resistance, and low moisture permeability.

In the optical film of the present invention, the hardness H [GPa] of the resin layer by the nanoindentation method is preferably 0.1 GPa or more, more preferably 0.2 GPa or more, from the viewpoint of excellent surface hardness and scratch resistance. , more preferably 0.3 GPa or more, and particularly preferably 0.4 GPa or more. On the other hand, the hardness H [GPa] is preferably 1 GPa or less, more preferably 0.9 GPa or less, and even more preferably 0.9 GPa or less, from the viewpoint that damage such as cracks is unlikely to occur on the surface even when bent. It is 8 GPa or less, particularly preferably 0.7 GPa or less.

In the optical film of the present invention, the product (Er×T) of the elastic modulus Er [GPa] of the resin layer obtained by the nanoindentation method and the thickness T [μm] of the optical film is 600 or less. preferable. When the elastic modulus Er of the resin layer obtained by the nanoindentation method is high, the surface hardness and scratch resistance of the resin layer are excellent. becomes more likely to occur. By controlling the product of the elastic modulus Er and the thickness T while adjusting the elastic modulus Er to a range in which the surface hardness and scratch resistance of the resin layer are excellent, excellent surface hardness and scratch resistance are exhibited, Even when the polarizer is wetted, damage such as cracks is less likely to occur on the surface, exhibits excellent low moisture permeability, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment.

That is, the configuration in which the product (Er×T) is 600 or less indicates that the optical film of the present invention exhibits excellent surface hardness and scratch resistance, and the optical film of the present invention is used as a polarizing plate constituting a flexible display. When used as a polarizing plate protective film, it exhibits excellent low moisture permeability even when folded, and is preferable in that it can suppress the occurrence of "color loss" of the polarizer in a humidified environment. In addition to exhibiting excellent surface hardness and scratch resistance, it exhibits excellent low moisture permeability even when folded, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. (Er×T) is preferably 550 or less, more preferably 500 or less, still more preferably 450 or less, and may be 400 or less. The lower limit of the product (Er×T) is not particularly limited, but may be 10 or more from the viewpoint of ensuring excellent surface hardness, scratch resistance, and low moisture permeability.

In the optical film of the present invention, the product (Er×T ¹ ) of the elastic modulus Er [GPa] of the resin layer obtained by the nanoindentation method and the thickness T ¹ [μm] of the resin layer is 130 or less. is preferred. By controlling the product of the elastic modulus Er and the thickness ^T1 while adjusting the elastic modulus Er within a range in which the surface hardness and scratch resistance of the resin layer are excellent, excellent surface hardness and scratch resistance are exhibited, Even when the polarizer is bent, damage such as cracks hardly occurs on the surface, exhibits excellent low moisture permeability, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. That is, when the product (elastic modulus Er×T ¹ ) is 130 or less, the optical film of the present invention exhibits excellent surface hardness and scratch resistance, and the optical film of the present invention constitutes a flexible display. When it is used as a polarizing plate protective film for a polarizing plate that is used as a polarizing plate protective film, it exhibits excellent low moisture permeability even when folded, and is preferable in that it can suppress the occurrence of "color loss" of the polarizer in a humidified environment. . In addition to exhibiting excellent surface hardness and scratch resistance, it exhibits excellent low moisture permeability even when folded, and can suppress the occurrence of "color loss" of the polarizer in a humidified environment. (Er×T ¹ ) is preferably 110 or less, more preferably 100 or less, still more preferably 80 or less, and may be 60 or less. The lower limit of the product (Er×T ¹ ) is not particularly limited, but may be 5 or more from the viewpoint of ensuring excellent surface hardness, scratch resistance, and low moisture permeability.

In the optical film of the present invention, the elastic modulus Er [GPa] of the resin layer measured by the nanoindentation method is preferably 1 GPa or more, more preferably 2 GPa or more, and still more preferably 2 GPa or more, from the viewpoint of excellent surface hardness and scratch resistance. It is 3 GPa or more, particularly preferably 4 GPa or more. On the other hand, the elastic modulus Er [GPa] is preferably 10 GPa or less, more preferably 9 GPa or less, still more preferably 8 GPa or less, particularly from the viewpoint that damage such as cracks is unlikely to occur on the surface even when bent. It is preferably 7 GPa or less.

The hardness H, the elastic modulus Er, and the product of these values and the thicknesses T and ^T1 of the optical film of the present invention according to the nanoindentation method are specifically measured by the method described in Examples below. can be done. The hardness H and elastic modulus Er obtained by the nanoindentation method in the optical film of the present invention, and the products thereof and the thicknesses T and ^T1 are determined by the type and thickness of the resin constituting the light-transmitting substrate of the present invention. In addition, it can be adjusted by adjusting the kind, composition, degree of cross-linking, thickness, etc. of the resin constituting the resin layer of the present invention.

Although the haze of the optical film of the present invention is not particularly limited, it is preferably 1.0% or less, more preferably 0.8% or less from the viewpoint of obtaining good transparency. Haze can be determined according to JIS K 7136 (2000). The haze of the optical film of the present invention can be adjusted by the type and thickness of the resin that constitutes the light-transmissive substrate of the present invention, the type and thickness of the resin that constitutes the resin layer of the present invention, and the like.

The total light transmittance of the optical film of the present invention in the visible light wavelength region is not particularly limited, but is preferably 85% or more, more preferably 88% or more. The visible light wavelength region can be determined according to JIS K 7361-1. The total light transmittance of the optical film of the present invention can be adjusted by the type and thickness of the resin that constitutes the light-transmitting substrate of the present invention, the type and thickness of the resin that constitutes the resin layer of the present invention, and the like. can.

Although the thickness of the optical film of the present invention is not particularly limited, it is preferably in the range of 11 to 100 μm, more preferably 20 to 80 μm in consideration of workability such as thinness, strength, and handleability. range, optimally in the range of 20-60 μm.

<Light transmissive substrate>
Materials constituting the light-transmitting substrate of the present invention include glass and plastic films. Examples of the plastic film include cellulose resins such as triacetyl cellulose (TAC), acrylic resins such as polymethyl methacrylate (PMMA), polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), Cyclic olefin-based polymer (COP) (e.g., trade name "Arton" (manufactured by JSR Corporation), trade name "Zeonor" (manufactured by Nippon Zeon Co., Ltd.), etc.), polycarbonate-based resin, polysulfone-based resin, polyarylate-based Plastic materials such as resins, polyimide resins, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymers, etc., are optically uniform and have a smooth surface. Cellulose resins, acrylic resins, polyester resins, and cyclic olefin polymers (COP) are preferred, and cellulosic resins are particularly preferred, from the viewpoint of good secondary workability. In addition, these plastic materials can be used individually or in combination of 2 or more types.

The haze of the light-transmitting substrate of the present invention is not particularly limited, but from the viewpoint of obtaining good transparency, it is preferably 1.0% or less, more preferably 0.8% or less. Haze can be determined according to JIS K 7136 (2000). The haze of the light-transmitting substrate of the invention can be adjusted by adjusting the type and thickness of the resin constituting the light-transmitting substrate of the invention.

The total light transmittance of the light-transmitting substrate of the present invention in the visible light wavelength region is not particularly limited, but is preferably 85% or more, more preferably 88% or more. The visible light wavelength region can be determined according to JIS K 7361-1. The total light transmittance of the light-transmitting substrate of the present invention can be adjusted by adjusting the type and thickness of the resin that constitutes the light-transmitting substrate of the present invention.

The film thickness of the light-transmitting substrate of the present invention is preferably 10 to 50 μm. The configuration in which the film thickness of the light-transmitting substrate is 50 μm or less is the case where the optical film of the present invention is folded when used as a polarizing plate protective film for a polarizing plate constituting a flexible display. Also, from the viewpoint of exhibiting excellent low moisture permeability and being able to suppress the occurrence of "color loss" of the polarizer in a humidified environment, it is preferable, more preferably 48 μm or less, further preferably 46 μm or less, and particularly preferably 44 μm or less. , 42 μm or less. In addition, the configuration in which the film thickness of the light-transmitting substrate is 10 μm or more is preferable, more preferably 15 μm or more, and still more preferably 15 μm or more, from the viewpoint of achieving high levels of low moisture permeability, surface hardness, and scratch resistance. 20 μm or more, particularly preferably 25 μm or more.

The refractive index of the light-transmitting substrate of the present invention is not particularly limited, but is, for example, in the range of 1.30-1.80, preferably in the range of 1.40-1.70. The surface of the light-transmitting substrate of the present invention (the surface on which the resin layer is formed and/or the surface opposite thereto) may be subjected to, for example, physical treatments such as corona discharge treatment and plasma treatment, undercoating treatment, and the like. A known and commonly used surface treatment such as chemical treatment may be applied as appropriate.

<Resin layer>
The resin layer of the present invention is laminated on one side of the light-transmitting substrate of the present invention, and imparts excellent low moisture permeability to the optical film of the present invention. Moreover, the resin layer of the present invention imparts excellent surface hardness and scratch resistance to the optical film of the present invention. Furthermore, the resin layer of the present invention also imparts excellent bending resistance to the optical film of the present invention. Therefore, the optical film of the present invention having the resin layer of the present invention in a laminate structure can be suitably used as a polarizing plate protective film for a polarizing plate constituting a flexible display. In this specification, the term “flex resistance” refers to a property that damage such as cracks is unlikely to occur on the surface (particularly, the surface of the resin layer) when the optical film of the present invention is folded.

The surface of the resin layer of the present invention is preferably not scratched when subjected to a scratch resistance test using steel wool under the conditions of a load of 0.98 N, a moving speed of 100 mm/sec, and 10 reciprocations. That is, since the optical film of the present invention is coated with the resin layer of the present invention having excellent surface hardness and scratch resistance, it is less likely to be scratched during the manufacturing process, and when used as a polarizing plate protective film, it has excellent durability. An excellent polarizing plate can be provided. The excellent surface hardness and scratch resistance of the resin layer of the present invention can be imparted by adjusting the composition and thickness of the resin layer, which will be described later.

The resin layer of the present invention is formed of a cured product of a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having a polymerizable functional group and oligomers having a polymerizable functional group. be. In this specification, the polymerizable compound constituting the resin layer of the present invention may be referred to as the "polymerizable compound of the present invention", and the curable composition containing the polymerizable compound of the present invention may be referred to as the "curable compound of the present invention." may be referred to as a "sexual composition". The configuration in which the resin layer of the present invention is formed of the cured product of the curable composition of the present invention containing the polymerizable compound of the present invention provides the optical film of the present invention with excellent low moisture permeability, surface hardness, and scratch resistance. It is preferable in that it can provide flexibility and flex resistance.

The "polymerizable functional group" of the polymerizable compound of the present invention is not particularly limited, but includes an unsaturated double bond group, an epoxy group, an oxetanyl group, etc., and has excellent low moisture permeability, surface hardness, and scratch resistance. An unsaturated double bond group is preferred from the viewpoint of flexibility and flexibility. The unsaturated double bond group includes a (meth)acryloyl group, a vinyl group, a styryl group, an allyl group, etc. Among them, a (meth)acryloyl group is preferable. In this specification, "(meth)acryloyl" represents either one or both of "acryloyl" and "methacryloyl", and "(meth)acrylic" also includes "acrylic" and "methacrylic ” represents either one or both.

The number of "polymerizable functional groups" possessed by the polymerizable compound of the present invention is not particularly limited as long as it is 1 or more. The curable composition of the present invention preferably has 2 or more polymerizable functional groups, more preferably 3 or more, still more preferably 4 or more, or 5 or more, or 6 or more polymerizable functional groups in that flexibility can be imparted. It is preferable that at least polymerizable compounds having 1 or more, 7 or more, 8 or more, 9 or more, or 10 or more are included. Although the upper limit of the number of "polymerizable functional groups" is not particularly limited, it may be 30 or less, 25 or less, or 20 or less.

In order to impart excellent low moisture permeability to the optical film of the present invention, the curable composition of the present invention contains, as the polymerizable compound of the present invention, a cyclic aliphatic hydrocarbon group and an unsaturated double bond in the molecule. It preferably contains a compound having a group (hereinafter sometimes referred to as "polymerizable compound A"). It is considered that the cycloaliphatic hydrocarbon group that the polymerizable compound A has in the molecule makes the resin layer of the present invention hydrophobic and reduces the moisture permeability. The curable composition of the present invention may contain one type of polymerizable compound A, or may contain two or more types of polymerizable compound A. In addition, the curable composition of the present invention may not contain the polymerizable compound A.

The polymerizable functional group of the polymerizable compound A is preferably an unsaturated double bond group such as a (meth)acryloyl group, a vinyl group, a styryl group, or an allyl group, and more preferably a (meth)acryloyl group. Especially preferred are the following compounds containing two or more (meth)acryloyl groups in one molecule.

The number of "polymerizable functional groups" that the polymerizable compound A has in the molecule is not particularly limited as long as it is 1 or more. From the viewpoint of imparting flexibility, it preferably has 2 or more, more preferably 3 or more, and still more preferably 4 or more polymerizable functional groups. Although the upper limit of the number of "polymerizable functional groups" possessed by the polymerizable compound A is not particularly limited, it may be 10 or less, 9 or less, or 8 or less.

The "cycloaliphatic hydrocarbon group" that the polymerizable compound A has in the molecule is preferably a group derived from an alicyclic compound having 7 or more carbon atoms, more preferably an alicyclic compound having 10 or more carbon atoms. It is a group derived from a compound, more preferably a group derived from an alicyclic compound having 12 or more carbon atoms. The cycloaliphatic hydrocarbon group is particularly preferably a group derived from a polycyclic compound such as bicyclic or tricyclic.

The cyclic aliphatic hydrocarbon group (including a linking group) is preferably a group represented by any one of the following general formulas (I) to (V), and the following general formulas (I), (II), or (IV) A group represented by is more preferable, and a group represented by the following general formula (I) is even more preferable.

In general formula (I), L and L' each independently represent a divalent or higher linking group. n represents an integer of 1 to 3;

In general formula (II), L and L' each independently represent a divalent or higher linking group. n represents an integer of 1-2.

In general formula (III), L and L' each independently represent a divalent or higher linking group. n represents an integer of 1-2.

In general formula (IV), L and L′ each independently represent a divalent or higher valent linking group, and L″ represents a hydrogen atom or a divalent or higher linking group.

In general formula (V), L and L' each independently represent a divalent or higher linking group.

Specific examples of cycloaliphatic hydrocarbon groups include monovalent to trivalent groups derived from norbornane, tricyclodecane, tetracyclododecane, pentacyclopentadecane, adamantane, diamantane, and the like.

The polymerizable compound A containing a group represented by any one of the general formulas (I) to (V) as a cycloaliphatic hydrocarbon group is represented by L, L′, and L″ via a linking group. It has a polymerizable functional group, and the linking group includes a single bond, an optionally substituted alkylene group having 1 to 6 carbon atoms, an optionally disubstituted amide group at the N-position, an N-substituted carbamoyl group, ester group, oxycarbonyl group, ether group and the like, and groups obtained by combining these.

The polymerizable compound A is, for example, a polyol such as a diol or triol having a cyclic aliphatic hydrocarbon group, and a (meth)acryloyl group, a vinyl group, a styryl group, a carboxylic acid derivative of a compound having an allyl group, or the like. , an epoxy derivative, an isocyanate derivative, etc., can be easily synthesized by a one-step or two-step reaction. Preferably, (meth)acrylic acid, (meth)acryloyl chloride, (meth)acrylic anhydride, glycidyl (meth)acrylate, 1,1-bis(acryloxymethyl)ethyl isocyanate, etc. are used to form the above cyclic It can be synthesized by reacting with a polyol having an aliphatic hydrocarbon group.

Preferred specific examples of the polymerizable compound A are shown below, but the present invention is not limited thereto.

The content of the polymerizable compound A in the curable composition of the present invention is not particularly limited, but from the viewpoint of imparting excellent low moisture permeability to the resin layer of the present invention, the curable composition of the present invention 10% by weight or more, more preferably 15% by weight or more, or 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, or 35% by weight, based on 100% by weight of non-volatile solids Above, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, or 90% by weight or more. On the other hand, from the viewpoint that the resin layer of the present invention has low moisture permeability, surface hardness, scratch resistance, and flex resistance at a higher level, 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight Below, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight 25% by weight or less, 20% by weight or less, 15% by weight or less, or 10% by weight or less.

In order to impart excellent surface hardness, scratch resistance, and flex resistance to the optical film of the present invention, the curable composition of the present invention contains a polymerizable compound other than the polymerizable compound A, that is, It preferably contains a compound having no cycloaliphatic hydrocarbon group and having a polymerizable functional group (hereinafter sometimes referred to as "polymerizable compound B"). It is believed that the inclusion of the polymerizable compound B in the curable composition of the present invention increases the crosslink density and improves the surface hardness, scratch resistance, and flex resistance. In order to impart excellent low moisture permeability, surface hardness, scratch resistance, and flex resistance to the optical film of the present invention, the curable composition of the present invention contains both the polymerizable compound A and the polymerizable compound B. preferably included.

The polymerizable functional group possessed by the polymerizable compound B is preferably an unsaturated double bond group such as a (meth)acryloyl group, vinyl group, styryl group, or allyl group, and more preferably a (meth)acryloyl group. Especially preferred are the following compounds containing two or more (meth)acryloyl groups in one molecule.

The number of "polymerizable functional groups" possessed by the polymerizable compound B is not particularly limited as long as it is 1 or more, but the optical film of the present invention can be provided with excellent surface hardness, scratch resistance, and flex resistance. preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, or 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or 10 or more is preferred. Although the upper limit of the number of "polymerizable functional groups" possessed by the polymerizable compound B is not particularly limited, it may be 30 or less, 25 or less, or 20 or less.

As the polymerizable compound B, a monomer having no cyclic aliphatic hydrocarbon group in the molecule and having a polymerizable functional group (hereinafter sometimes referred to as "polymerizable monomer B"), a cyclic aliphatic Oligomers having no hydrocarbon group and having a polymerizable functional group (hereinafter sometimes referred to as "polymerizable oligomer B") are exemplified. The curable composition of the present invention may contain only the polymerizable monomer as the polymerizable compound B, may contain only the polymerizable oligomer B, or may contain both the polymerizable monomer B and the polymerizable oligomer B. You can stay. From the viewpoint of being able to form a high degree of crosslink density, it preferably contains at least the polymerizable oligomer B.

Examples of the polymerizable monomer B include hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, and neopentyl glycol. Di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipenta Erythritol (meth)hexaacrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate and the like. The curable composition of the present invention may contain one polymerizable monomer B, or may contain two or more polymerizable monomers B.

Polymerizable oligomer B is a compound containing two or more repeating units and having a polymerizable functional group. That is, the polymerizable oligomer B is a polymer having a polymerizable functional group in its molecule. Examples of the polymerizable oligomer B include urethane (meth)acrylate obtained by adding two or more (meth)acryloyl groups as functional groups to a urethane skeleton, and two or more (meth)acryloyl groups as functional groups to a polyester skeleton. and epoxy (meth)acrylate obtained by adding two or more (meth)acryloyl groups as functional groups to the epoxy skeleton. From the viewpoint of being able to form a high degree of crosslink density, it is preferable that at least urethane (meth)acrylate is included. The curable composition of the present invention may contain one type of polymerizable oligomer B, or may contain two or more types of polymerizable oligomer B.

Urethane (meth)acrylates are obtained, for example, by reacting polyols, isocyanates, and hydroxy (meth)acrylates.
As the polyol constituting the urethane (meth)acrylate, known polyols can be used without limitation. more preferably 6 or more), trimethylolpropane, ethoxylated isocyanuric acid, pentaerythritol, dipentaerythritol, tripentaerythritol, tetrapentaerythritol, and the like. These polyols may be used alone or in combination of two or more.

Polyisocyanates composed of chain saturated hydrocarbons, cyclic saturated hydrocarbons, and aromatic hydrocarbons can be used as isocyanates that constitute urethane (meth)acrylates. Examples of such polyisocyanates include chain saturated hydrocarbon isocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, methylenebis(4-cyclohexyl isocyanate), hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate and other cyclic saturated hydrocarbon isocyanates, 2,4-tolylene diisocyanate, 1,3-xylylene diisocyanate, p-phenylene diisocyanate, 3,3' -dimethyl-4,4'-diisocyanate, 6-isopropyl-1,3-phenyl diisocyanate, 1,5-naphthalene diisocyanate and other aromatic polyisocyanates. Preferred specific examples include isophorone diisocyanate, tetramethylene diisocyanate and hexamethylene diisocyanate. These polyisocyanates may be used alone or in combination of two or more.

Examples of hydroxy (meth) acrylates constituting urethane (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (meth) ) 6-hydroxyhexyl acrylate and the like. These hydroxy (meth)acrylates may be used alone or in combination of two or more.

As urethane (meth)acrylates, for example, Artresin UN series manufactured by Neagari Kogyo Co., Ltd., NK Oligo U series manufactured by Shin-Nakamura Chemical Co., Ltd., Shikou UV series manufactured by Mitsubishi Chemical Corporation, and Luxi manufactured by DIC Corporation. Dear series.

A polyester (meth)acrylate is obtained, for example, by reacting (meth)acrylic acid with a terminal hydroxyl group of a polyester obtained by polymerizing a polyol and a polyvalent carboxylic acid. Specific examples of polyester (meth)acrylates include Aronix M-6000, Aronix M-7000, Aronix M-8000, and Aronix M-9000 manufactured by Toagosei Co., Ltd.

Epoxy (meth)acrylate is obtained, for example, by reacting epoxy resin with (meth)acrylic acid. Specific examples of epoxy (meth)acrylates include Lipoxy SP and Lipoxy VR manufactured by Showa Polymer Co., Ltd., and epoxy ester series manufactured by Kyoeisha Chemical Co., Ltd.

The weight average molecular weight of the polymerizable oligomer B is not particularly limited, but from the viewpoint of improving the surface hardness, scratch resistance, and flex resistance of the resin layer of the present invention, it is preferably 400 or more, more preferably 500 or more, and more preferably 500 or more. It is preferably 600 or more, particularly preferably 700 or more. Moreover, the weight average molecular weight of the polymerizable oligomer B is preferably 10,000 or less, more preferably 7,000 or less, and still more preferably 5,000 or less, from the viewpoint of coatability of the curable composition of the present invention. The weight average molecular weight of the polymerizable oligomer B can be determined, for example, by high performance liquid chromatography (HPLC). For example, using HPLC8020 manufactured by Tosoh Corporation as an apparatus, using two TSKgelGMH-H (20) connected in series as a column, using tetrahydrofuran as a solvent, under the conditions of a flow rate of 0.5 mL / min, Weight average molecular weight measurements can be made.

The content of the polymerizable compound B in the curable composition of the present invention is not particularly limited, but from the viewpoint of imparting excellent surface hardness, scratch resistance, and bending resistance to the resin layer of the present invention, the present It is preferably 5% by weight or more, more preferably 10% by weight or more, still more preferably 15% by weight or more, or 20% by weight or more, or 25% by weight, based on 100% by weight of the non-volatile solid content of the curable composition of the invention. Above, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight It may be 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. On the other hand, from the viewpoint that the resin layer of the present invention has low moisture permeability, surface hardness, scratch resistance, and flex resistance at a higher level, 99% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight Below, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less.

When the curable composition of the present invention contains a polymerizable compound A and a polymerizable compound B, the ratio (polymerizable compound A / polymerizable compound B) imparts excellent low moisture permeability to the resin layer of the present invention. From the point of view of 50/50 or more, 55/45 or more, 60/40 or more, 65/35 or more, 70/30 or more, 75/25 or more, 80/20 or more, 85/15 or more, or 90/10 or more good too. On the other hand, from the viewpoint that the resin layer of the present invention has low moisture permeability, surface hardness, scratch resistance, and flex resistance at a higher level, 95/5 or less, 90/10 or less, 85/15 or less, 80/20 75/25 or less, 70/30 or less, 65/35 or less, 60/40 or less, 55/45 or less, 50/50 or less, 45/55 or less, 40/60 or less, 35/65 or less, 30/70 25/75 or less, 15/85 or less, or 10/90 or less.

The curable composition of the present invention preferably contains a polymerization initiator, and the polymerization initiator is preferably a photopolymerization initiator. Examples of photopolymerization initiators include benzyl, benzophenone, benzoylbenzoic acid, benzophenone compounds such as 3,3′-dimethyl-4-methoxybenzophenone; 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2- aromatic ketone compounds such as propyl)ketone, α-hydroxy-α,α.-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, α-hydroxycyclohexylphenyl ketone; methoxyacetophenone, 2,2-dimethoxy-2 Acetophenone compounds such as -phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropan-1-one; benzoin methyl ether, benzoin ethyl Benzoin alkyl ether compounds such as ether, benzoin isopropyl ether, benzoin butyl ether, and anisoin methyl ether; aromatic ketal compounds such as benzyl dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; 1-phenone- Photoactive oxime compounds such as 1,1_propanedione-2-(o-ethoxycarbonyl)oxime; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichloro thioxanthone compounds such as thioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone and dodecylthioxanthone; camphorquinone; halogenated ketone; acylphosphinate; These polymerization initiators may be used alone or in combination of two or more.

The content of the photopolymerization initiator in the curable composition of the present invention is not particularly limited, but from the viewpoint that the resin layer of the present invention sufficiently obtains low moisture permeability, surface hardness, scratch resistance, and flex resistance. is preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, and still more preferably It is 0.2 parts by weight or more. In addition, the content of the photopolymerization initiator in the curable composition of the present invention prevents the problem that the curable composition of the present invention is not sufficiently cured due to excessive radiation absorption by the photopolymerization initiator. From the viewpoint of suppression, it is preferably 10 parts by weight or less, more preferably 8 parts by weight or less, per 100 parts by weight of the polymerizable compound (the total when polymerizable compound A and polymerizable compound B are included).

Various leveling agents can be added to the curable composition of the present invention. As the leveling agent, for example, a fluorine-based or silicone-based leveling agent can be used for the purpose of preventing coating unevenness (uniformizing the coated surface). A leveling agent may also be blended as appropriate when antifouling properties are required for the surface of the resin layer of the present invention.
The amount of the leveling agent to be blended is, for example, 5 parts by weight or less, preferably 0.01 to 5 parts by weight, with respect to 100 parts by weight of the polymerizable compound (the total when polymerizable compound A and polymerizable compound B are included). part range.

The curable composition of the invention may contain a solvent. As the solvent, various solvents can be used in consideration of the solubility of the polymerizable compound (polymerizable compound A and/or polymerizable compound B), the drying property during coating, and the like. Examples of such organic solvents include dibutyl ether, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3-dioxolane, 1,3,5-trioxane, tetrahydrofuran, anisole, phenetole, dimethyl carbonate, carbonic acid. Methyl ethyl, diethyl carbonate, acetone, methyl ethyl ketone (MEK), diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl cyclohexanone, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, methyl 2-methoxyacetate, methyl 2-ethoxyacetate, ethyl 2-ethoxyacetate, ethyl 2-ethoxypropionate, 2-methoxyethanol, 2-propoxyethanol, 2-butoxy Ethanol, 1,2-diacetoxyacetone, acetylacetone, diacetone alcohol, methyl acetoacetate, ethyl acetoacetate, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, cyclohexyl alcohol, isobutyl acetate, methyl isobutyl ketone (MIBK) , 2-octanone, 2-pentanone, 2-hexanone, ethylene glycol ethyl ether, ethylene glycol isopropyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, ethyl carbitol, butyl carbitol, hexane, heptane, octane, cyclohexane, methylcyclohexane , ethylcyclohexane, benzene, toluene, xylene, etc., and can be used singly or in combination of two or more.

The curable composition of the present invention may optionally contain any suitable additives such as plasticizers, surfactants, antioxidants, ultraviolet absorbers, thixotropic agents, antistatic agents, etc., within the range not impairing the effects of the present invention. may further contain additives.

The film thickness of the resin layer of the present invention is preferably 1 to 10 μm. The configuration in which the thickness of the resin layer is 10 μm or less is excellent even when the optical film of the present invention is used as a polarizing plate protective film for a polarizing plate constituting a flexible display and is bent. It is preferably 9 μm or less, still more preferably 8 μm or less, and particularly preferably 7 μm or less from the viewpoint of exhibiting low moisture permeability and being able to suppress the occurrence of “color loss” of the polarizer in a humidified environment. In addition, the configuration in which the thickness of the resin layer is 1 μm or more is preferable, more preferably 1.5 μm or more, and even more preferably 2 μm, from the viewpoint of achieving high levels of low moisture permeability, surface hardness, and scratch resistance. 2.5 μm or more, particularly preferably 2.5 μm or more.

In the resin layer of the present invention, the polymerizable compound of the present invention (polymerizable compound A and/or polymerizable compound B) is optionally mixed with a photopolymerization initiator, a leveling agent, a solvent, other additives, and the like. to prepare a coating liquid (curable composition of the present invention), apply the coating liquid to one surface of a light-transmitting substrate, dry the coating, and cure the coating film.

The solid content concentration of the coating liquid is preferably 1 wt % to 70 wt %, more preferably 2 wt % to 50 wt %, even more preferably 5 wt % to 40 wt %.

Examples of methods for applying the coating solution include dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, die coating, extrusion coating, bar coating, and the like. be done.

Curing of the coating film is appropriately selected according to the type of the curable composition and the like. When the curable composition is photocurable, it can be cured by irradiating it with light using a light source that emits light of an appropriate wavelength. As the irradiation light, for example, light with an exposure amount of 150 mJ/cm ² or more, preferably 200 mJ/cm ² to 1000 mJ/cm ² can be used. Moreover, you may heat in the case of a photocuring process.
Examples of the light include ionizing radiation such as α-rays, β-rays, γ-rays, neutron beams and electron beams, and ultraviolet rays, with ultraviolet rays being particularly preferred. Moreover, the irradiation time, the irradiation method, and the like are not particularly limited as long as the photopolymerization initiator can be activated to cause the reaction of the polymerizable compound.

<Polarizing plate>
The polarizing plate of the present invention has a laminated structure in which a polarizer is arranged on the opposite side of the resin layer of the optical film of the present invention. In FIG. 2, the polarizing plate 20 has a laminated structure in which the polarizer 3 is arranged on the opposite side of the optical film 10 from the resin layer 1 . Since the optical film 10 is used as a polarizing plate protective film, the polarizing plate 20 exhibits excellent low moisture permeability, surface hardness, and scratch resistance. Even when the polarizer 3 is used, it exhibits excellent low moisture permeability, and quality deterioration such as color loss of the polarizer 3 is less likely to occur. In this embodiment, on the opposite side of the polarizer 3 from the optical film 10, a second light-transmitting substrate 4 and an adhesive layer 5 are further laminated in this order.

The polarizer 3 is an element that allows only light with a plane of polarization in a certain direction to pass through, and any known polarizer can be used without limitation. For example, a polyvinyl alcohol-based polarizing film can be used. The polyvinyl alcohol polarizing film may be a polyvinyl alcohol film dyed with iodine or a dichroic dye.

The polyvinyl alcohol-based polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol-based film and then dyeing it with iodine or a dichroic dye (preferably a film further subjected to durability treatment with a boron compound); A film obtained by dyeing an alcohol-based film with iodine or a dichroic dye and then uniaxially stretching the film (preferably, a film further subjected to a durability treatment with a boron compound) may be used. The absorption axis of the polarizer is parallel to the stretching direction of the film.

The thickness of the polarizer 3 is preferably 5 to 25 μm, and more preferably 10 to 15 μm from the viewpoint of thinning the polarizing plate 20 .

The second light-transmitting substrate 4 protects the opposite side of the polarizer 3 from the optical film 10 (polarizing plate protective film), and is similar to the light-transmitting substrate of the present invention, such as a glass or plastic film. Cellulose-based resins, cyclic olefin-based polymers (COP), and polycarbonate-based resins are preferred, and cyclic olefin-based polymers (COP) and polycarbonate-based resins are more preferred. The light transmissive substrate 4 may be made of the same material as the light transmissive substrate 2, or may be made of a different material. The light-transmitting base material 4 may be one in which the resin layer 1 is laminated, or may not have the resin layer 1 . Further, the light-transmissive base material 4 may be composed of a single layer, or may be a laminated structure of two or more layers that are the same or different.

Also, the light-transmitting substrate 4 is preferably an optical compensation film (retardation film) having an optical compensation layer containing an optically anisotropic layer. An optical compensation film can improve the viewing angle characteristics of a liquid crystal display screen, for example. As the optical compensation film, known ones can be used without limitation, and for example, a retardation film described in JP-A-2014-194484 may be used.

The thickness of the light-transmissive substrate 4 is preferably 5 to 25 μm, and more preferably 10 to 15 μm from the viewpoint of thinning the polarizing plate 20 .

The adhesive layer 5 is made of any appropriate adhesive. Materials constituting the adhesive layer 5 include, for example, acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine polymers, rubber polymers, isocyanate polymers, polyvinyl alcohol polymers, and gelatin polymers. , vinyl-based polymers, latex-based polymers, water-based polyesters, and other polymer-based materials. Among them, a material having an acrylic polymer and/or a rubber polymer as a base polymer is preferable from the viewpoint of low moisture permeability. The adhesive layer 5 may contain a single base polymer, or may contain two or more base polymers.

The thickness of the adhesive layer 5 is preferably 5 to 25 μm, and more preferably 10 to 20 μm from the viewpoint of thinning the polarizing plate 20 .

The polarizing plate 20 can be obtained by bonding the polarizer 3 and the optical film 10 together with an adhesive. Also, the polarizer 3 and the light-transmitting base material 4 can be attached together with an adhesive. The adhesive used for bonding may be a completely saponified polyvinyl alcohol aqueous solution (water paste), or an active energy ray-curable adhesive.

The pressure-sensitive adhesive layer 5 can be formed by applying a pressure-sensitive adhesive composition containing a base polymer that constitutes the pressure-sensitive adhesive to the light-transmitting substrate 4, drying it, and then curing it as necessary. Alternatively, the pressure-sensitive adhesive layer 5 may be similarly formed on a release liner, attached to the light-transmitting substrate 4, and transferred.

The polarizing plate 20 may have layers other than the optical film 10, the polarizing plate 3, the light-transmitting substrate 4, and the pressure-sensitive adhesive layer 5 (e.g., surface protection film, release liner, etc.) on the surface or between any layers. good. For example, the surface of the adhesive layer 5 may be protected with a release liner, and the surface of the resin layer 1 of the optical film 10 may be protected with a surface protective film.

The thickness of the polarizing plate 20 (the total thickness including the light-transmitting substrate 4 and the adhesive layer 5) is preferably 50 to 100 μm, and from the viewpoint of thinning the polarizing plate 20, it is 60 to 75 μm. is more preferred.

<Image display device>
The image display device of the present invention has the polarizing plate of the present invention. Since the image display device of the present invention has the polarizing plate of the present invention in a laminated structure, it exhibits excellent low moisture permeability, surface hardness, and scratch resistance, and when used as a polarizing plate constituting a flexible display, Even when the polarizer 3 is folded, it exhibits excellent low moisture permeability, and quality deterioration such as color loss of the polarizer 3 is less likely to occur. Therefore, the image display device of the present invention is suitable as a flexible display excellent in flex resistance and durability, in which the polarizing plate is less likely to lose color in a humidified environment even when the display device is bent.

In FIG. 3 , an image display device 30 has an image display panel 6 laminated on an adhesive layer 5 of a polarizing plate 20 . In this embodiment, an adhesive layer 7 and an optical member 8 are laminated in this order on the resin layer 1 . If the image display device 30 is a flexible display, the entire laminate structure is foldable.

The image display panel 6 is not particularly limited. A bendable flexible display panel is preferred.

The image display panel 6 is formed by alternately arranging RGB elements, and the spaces between the RGB elements are preferably filled with a black matrix (BM) in order to improve the contrast.

The adhesive layer 7 can use a material containing a base polymer similar to those exemplified for the adhesive layer 5 . Among them, a material having an acrylic polymer and/or a rubber polymer as a base polymer is preferable from the viewpoint of low moisture permeability. The adhesive layer 7 may contain a single base polymer, or may contain two or more base polymers. The adhesive layer 7 may be made of the same material as the adhesive layer 5, or may be made of a different material.

The optical member 8 can be made of the same glass, plastic film, or the like as the light-transmitting substrate of the present invention. Acrylic resins, polyester resins, and cyclic olefin polymers (COP) are preferred, and polyester resins are particularly preferred. preferable. When the optical member 8 is positioned on the outermost surface of the image display device 30 on the viewing side, the optical member 8 functions as a cover member.

The image display device 30 includes an optical member other than the optical film 10, the polarizing plate 3, the light-transmitting substrate 4, the adhesive layer 5, the image display panel 6, the adhesive layer 7, and the optical member 8, on the surface or any It may be provided between layers. Examples of the optical member include, but are not particularly limited to, a polarizing plate other than the polarizing plate 3, a retardation plate, an antireflection film, a viewing angle adjusting film, an optical compensation film, and the like. Incidentally, the above-described optical members include members (design films, decorative films, surface protection plates, etc.) that play a role of decoration and protection while maintaining the visibility of the image display device and the input device.

The image display device 30 can be manufactured by laminating an optical film in which the image display panel 6, the polarizing plate 20, the optical member 8, and the adhesive layer 7 are laminated. / Or it can be carried out by laminating under pressure. Curing may be performed by irradiating active energy rays after lamination under heat and/or pressure. Irradiation with active energy rays can be performed in the same manner as in the formation of the resin layer of the present invention.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

Example 1
(Preparation of coating solution for forming resin layer)
As the resin contained in the resin layer, UV-curable acrylate resin (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “A-DCP”, solid content 100%) 50 parts by weight (solid content conversion), UV-curable acrylate resin ( Mitsubishi Chemical Corporation, trade name "UV-1700TL", solid content 80%) 50 parts by weight (solid content conversion) was prepared. Per 100 parts by weight of the resin solid content of the resin, 5 parts by weight of a photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD907"), a leveling agent (manufactured by Kyoeisha Chemical Co., Ltd., trade name "LE-303", solid 40% by weight) was mixed. This mixture was diluted with an MIBK/cyclopentanone mixed solvent (weight ratio: 60/40) so that the solid content concentration was 30%, to prepare a resin layer-forming coating solution.

(Preparation of optical film)
A transparent plastic film substrate (TAC, manufactured by FUJIFILM Corporation, trade name “TJ25UL”) was prepared as a light-transmitting substrate. A coating film was formed on one side of the transparent plastic film substrate using the coating solution for forming the resin layer prepared above using a bar coater #7. Then, the transparent plastic film substrate on which this coating film was formed was transported to a drying step. In the drying step, the coating film was dried by heating at 60° C. for 1 minute. Thereafter, the coating film was cured by irradiating ultraviolet light with an accumulated light quantity of 220 mJ/cm ² using a high-pressure mercury lamp to form a resin layer having a thickness of 2.5 μm.
Details of the resins used in Example 1 are as follows.
・A-DCP: tricyclodecanedimethanol dimethacrylate ・UV-1700TL: 10-functional urethane acrylate

Example 2
As the resin contained in the resin layer, per 100 parts by weight of an ultraviolet curable acrylate resin (manufactured by DIC Corporation, trade name “Luxidia 17-806”, solid content 80%), a photopolymerization initiator (manufactured by BASF, trade name 3 parts by weight of "OMNIRAD907") and 0.01 part by weight of a leveling agent (manufactured by DIC Corporation, trade name "PC4100", solid content 40%) were mixed. This mixture was diluted with a PGM/cyclopentanone mixed solvent (weight ratio: 63/37) so that the solid content concentration was 36%, to prepare a resin layer-forming coating solution.
An optical film 2 of Example 2 was obtained in the same manner as in Example 1, except that the resin layer-forming coating liquid prepared above was used to form a coating film having a thickness of 7 μm using a bar coater #14.
Details of the resins used in Example 2 are as follows.
・Lucidia 17-806: Multifunctional urethane acrylate

Example 3
The resin layer-forming coating solution prepared in Example 2 was applied to a transparent plastic film substrate (TAC, manufactured by Konica Minolta, Inc., trade name “KC2UA”) using a #14 bar coater to form a coating film having a thickness of 7 μm. An optical film 3 of Example 3 was obtained in the same manner as in Example 1, except that the was formed.

Example 4
The coating solution for forming a resin layer prepared in Example 2 was applied to one side of a transparent plastic film substrate (TAC, manufactured by Fuji Film Co., Ltd., trade name “TJ40UL”) using a bar coater #14 to a thickness of 7 μm. An optical film 4 of Example 4 was obtained in the same manner as in Example 1, except that the film was formed.

Comparative example 1
As the resin contained in the resin layer, per 100 parts by weight of an ultraviolet curable acrylate resin (manufactured by Arakawa Chemical Industries, Ltd., product name "Opstar Z7540", solid content 56%), a leveling agent (manufactured by Kyoeisha Chemical Co., Ltd., product LE-303, solid content 40%) was mixed in an amount of 0.1 part by weight. This mixture was diluted with MEK to a solid content concentration of 55% to prepare a resin layer-forming coating solution.
The coating liquid for forming the resin layer prepared above was applied to one side of a transparent plastic film substrate (TAC, manufactured by Konica Minolta, Inc., trade name “KC8UAW”) using a #36 bar coater to form a 20 μm-thick coating film. An optical film 5 of Comparative Example 1 was obtained in the same manner as in Example 1, except that the was formed.
Details of the resin used in Comparative Example 1 are as follows.
Opstar Z7540: Particle-containing polyfunctional urethane acrylate

Comparative example 2
The coating solution for forming a resin layer prepared in Example 2 was coated on one side of a transparent plastic film substrate (TAC, manufactured by Konica Minolta, Inc., trade name “KC8UAW”) to a thickness of 20 μm using a #50 bar coater. An optical film 6 of Comparative Example 2 was obtained in the same manner as in Example 1, except that a coating film was formed.

(evaluation)
The following evaluations were performed using the optical films obtained in the above Examples and Comparative Examples. The evaluation method is shown below. Table 1 shows the results.

(1) Film thickness measurement A digital linear gauge (trade name “MODEL D-10HS”, manufactured by Ozaki Seisakusho Co., Ltd.) was used to measure the film thickness of the optical films of Examples and Comparative Examples at five points across the width. , and the average value of the film thickness at 5 points was taken as the total thickness. The film thickness of the light-transmitting substrates used in Examples and Comparative Examples was measured by the same method, and the average value of the film thicknesses at 5 points was taken as the substrate thickness. The difference between the total thickness and the substrate thickness was taken as the thickness of the resin layer.

(2) Measurement of moisture permeability The optical films of Examples and Comparative Examples were measured for moisture permeability at a temperature of 40°C and a relative humidity of 92% according to JIS Z0208.
The optical films of Examples and Comparative Examples were subjected to the following bending test, and then measured for moisture permeability in the same manner.
·Bending test In accordance with JIS K 5600-5-1, the optical films of Examples and Comparative Examples were tested using a mandrel with a diameter of 2 mm so that the resin layer was on the outside.

In addition, the presence or absence of cracks on the surface of the resin layer after the bending test was visually inspected under an LED lighting environment.
In addition, the appearance of the optical film after the bending test was evaluated according to the following criteria.

〇・・・Cracks cannot be visually recognized ×・・・Cracks can be visually recognized, or the film is broken

(3) Hardness and elastic modulus by nanoindentation method The optical films of Examples and Comparative Examples were cut into pieces of about 1 cm square. Using a sample for nanoindentation measurement, nanoindentation measurement was performed under the following conditions to obtain a load-displacement curve.

・Nanoindentation measurement conditions Apparatus: Hysitron Inc. Triboindenter manufactured by
Indenter used: Berkovich (triangular pyramid)
Measurement method: single indentation measurement Measurement temperature: room temperature Indentation depth: 100 nm

The hardness H is calculated by the following formula (1) from the applied load (maximum load P _max ) when the indenter is pushed to the above-described indentation depth and the contact area (contact projected area Ac) between the indenter and the sample at that time. bottom.

In addition, the elastic modulus Er is obtained from the slope of the tangent line (contact stiffness S) at the maximum load of the unloading curve of the applied load-displacement curve and the contact area (contact projected area Ac) between the indenter and the sample at that time, as follows. It was calculated by the formula (2).

(4) Evaluation of color loss of polarizer after bending test After the optical films of Examples and Comparative Examples after the bending test were stored in an environment at a temperature of 60°C and a relative humidity of 90% for 120 hours, the backlight was placed in a dark room. When the illuminance of the film was set to 8000 candela and color loss such as unevenness or streaks was visually observed, it was determined that the polarizer had color loss.

Variations of the present invention are appended below.
[Appendix 1] An optical film in which a resin layer is laminated on one surface of a light-transmitting substrate,
The resin layer is formed of a cured product of a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having a polymerizable functional group and oligomers having a polymerizable functional group,
The moisture permeability M ¹ [g/m ² · 24 h] of the optical film in an environment with a temperature of 40 ° C. and a relative humidity of 92% before the following bending test, and the temperature of 40 ° C. and relative humidity of the optical film after the following bending test. An optical film whose absolute value (|M ² -M ¹ |) of the difference from the moisture permeability M ² [g/m ² ·24h] in an environment of 92% humidity is less than 10 g/m ² ·24h.
Bending test:
In accordance with JIS K 5600-5-1, the optical film is tested using a mandrel with a diameter of 2 mm so that the resin layer faces outward.
[Appendix 2] The optical film according to Appendix 1, wherein the film thickness of the resin layer is 1 to 10 μm.
[Appendix 3] The optical film according to Appendix 1 or 2, wherein the film thickness of the light-transmitting substrate is 10 to 50 μm.
[Appendix 4] The product (H×T) of the hardness H [GPa] of the resin layer obtained by the nanoindentation method and the thickness T [μm] of the optical film is 40 or less. Appendices 1 to 3 The optical film as described in any one of .
[Appendix 5] Appendices 1 to 3, wherein the product (Er×T) of the elastic modulus Er (GPa) of the resin layer obtained by the nanoindentation method and the thickness T (μm) of the optical film is 600 or less. The optical film as described in any one of .
[Appendix 6] Any one of Appendices 1 to 5, wherein the light-transmitting substrate contains at least one selected from the group consisting of cellulose-based resins, polyester-based resins, acrylic-based resins, and cyclic olefin-based polymers. The optical film described in .
[Appendix 7] A polarizing plate in which a polarizer is arranged on the side of the optical film according to any one of Appendices 1 to 6 opposite to the resin layer.
[Appendix 8] An image display device comprising the polarizing plate according to Appendix 7.
[Appendix 9] The image display device according to Appendix 8, wherein an adhesive layer and an optical member are laminated in this order on the resin layer.
[Appendix 10] The image display device according to appendix 8 or 9, which is a flexible display.

10 optical film 1 resin layer 2 light transmissive substrate 20 polarizing plate 3 polarizer 4 light transmissive substrate (optical compensation film)
5 adhesive layer 30 image display device 6 image display panel 7 adhesive layer 8 optical member

Claims (10)

An optical film in which a resin layer is laminated on one surface of a light-transmitting substrate,
The resin layer is formed of a cured product of a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having a polymerizable functional group and oligomers having a polymerizable functional group,
The moisture permeability M ¹ [g/m ² · 24 h] of the optical film in an environment with a temperature of 40 ° C. and a relative humidity of 92% before the following bending test, and the temperature of 40 ° C. and relative humidity of the optical film after the following bending test. An optical film whose absolute value (|M ² -M ¹ |) of the difference from the moisture permeability M ² [g/m ² ·24h] in an environment of 92% humidity is less than 10 g/m ² ·24h.
Bending test:
In accordance with JIS K 5600-5-1, the optical film is tested using a mandrel with a diameter of 2 mm so that the resin layer faces outward. 2. The optical film according to claim 1, wherein the resin layer has a thickness of 1 to 10 μm. 3. The optical film according to claim 1, wherein the film thickness of the light-transmitting substrate is 10 to 50 μm. 4. The product (H×T) of the hardness H [GPa] of the resin layer by the nanoindentation method and the thickness T [μm] of the optical film is 40 or less. 2. The optical film according to item 1. 4. The product (Er×T) of the elastic modulus Er (GPa) of the resin layer obtained by the nanoindentation method and the thickness T (μm) of the optical film is 600 or less. 2. The optical film according to item 1. 6. The light-transmitting substrate according to any one of claims 1 to 5, wherein the light-transmitting substrate contains at least one selected from the group consisting of cellulose-based resins, polyester-based resins, acrylic-based resins, and cyclic olefin-based polymers. optical film. A polarizing plate, comprising a polarizer disposed on the side of the optical film according to any one of claims 1 to 6 opposite to the resin layer. An image display device comprising the polarizing plate according to claim 7 . 9. The image display device according to claim 8, wherein an adhesive layer and an optical member are laminated in this order on the resin layer. 10. The image display device according to claim 8, which is a flexible display.

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