Optical film

Abstract

To provide an optical film with excellent low moisture permeability, suitable for use as a protective film for polarizing plates. [Solution] The optical film 10 of the present invention has a laminated structure in which a resin layer 1 is laminated on one side of a light-transmitting substrate 2. The resin layer 1 is formed of a cured product of a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having polymerizable functional groups and oligomers having polymerizable functional groups. The thickness T [μm] of the resin layer 1 and the moisture permeability M of the optical film in an environment with a temperature of 40°C and a relative humidity of 92% 1 [g / m 2 Product of 24 hours (T × M) 1 ) is 1,500 or less.

Description

[Technical Field]

[0001] This invention relates to optical films, and more specifically, to optical films suitable for use as protective films for polarizing plates. [Background technology]

[0002] Image display devices (e.g., liquid crystal displays, organic EL displays, etc.) often have a polarizing plate on at least one side of the display cell, depending on their image forming method. The polarizing plate plays the role of allowing only light with a specific polarization plane to pass through, and the performance of the image display device is greatly affected by the performance of the polarizing plate. A polarizing plate generally consists of a polarizer made of a polyvinyl alcohol film on which iodine or dye is adsorbed and oriented, and a transparent protective film (polarizing plate protective film) laminated to at least one side of the polarizer (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2000-338329 [Overview of the project] [Problems that the invention aims to solve]

[0004] In recent years, the market for mobile applications such as smartphones and tablet devices has expanded, and the need for thinner image display devices has increased significantly. This has led to a demand for thinner components that make up polarizing plates, such as polarizing plate protective films. However, there is a problem in that as the thickness of the polarizing plate protective film decreases, its protective function against the polarizer deteriorates.

[0005] For example, if the protective film on a polarizing plate becomes thinner, its permeability to moisture (humidity) increases, and in humid environments, the polarization performance of the polarizer may disappear, resulting in a phenomenon known as "color fading."

[0006] The present invention was conceived under the circumstances described above, and its objective is to provide an optical film that is suitable for use as a protective film for polarizing plates, even when thin, and exhibits excellent low moisture permeability.

[0007] Furthermore, if the protective film for polarizing plates becomes thinner, surface hardness and scratch resistance decrease, making the polarizing plates more susceptible to scratches during the manufacturing process and reducing their moisture permeability, thus degrading their performance. Therefore, the optical film used in the protective film for polarizing plates is also required to have excellent scratch resistance. [Means for solving the problem]

[0008] In other words, the first aspect of the present invention provides an optical film in which a resin layer is laminated on one side of a light-transmitting substrate. The resin layer provides the optical film of the first aspect of the present invention with excellent low moisture permeability. The resin layer also provides the optical film of the first aspect of the present invention with excellent scratch resistance. Therefore, the optical film of the first aspect of the present invention having the resin layer in a laminated structure is suitable for use as a polarizing plate protective film.

[0009] In the first side optical film of the present invention, 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 polymerizable functional groups and oligomers having polymerizable functional groups. This configuration is suitable for imparting excellent low moisture permeability to the first side optical film of the present invention. It is also suitable for imparting excellent scratch resistance to the first side optical film of the present invention.

[0010] In the first aspect of the present invention, the thickness T [μm] of the resin layer and the moisture permeability M of the optical film in an environment with a temperature of 40°C and a relative humidity of 92% 1 [g / m 2 Product of 24 hours (T × M) 1 ) is 1,500 or less. The aforementioned product (T × M 1) being 1,500 or less is preferable in that, when the optical film of the first aspect of the present invention is used as a polarizer protection film, even when the resin layer is thin, it is possible to suppress the occurrence of "color leakage" of the polarizer in a humid environment. From the viewpoint of achieving both suppression of the occurrence of color leakage of the polarizer and further thinning of the resin layer at a higher level, the product (T×M 1 ) is preferably 1,400 or less, more preferably 1,300 or less, and may be 1,200 or less.

[0011] In the optical film of the first aspect of the present invention, the thickness T [μm] of the resin layer and the moisture permeability M of the optical film under the environment of a temperature of 60 ° C and a relative humidity of 90% 2 [g / m 2 ·24h] of the product (T×M 2 ) is preferably 3,000 or less. The configuration in which the product (T×M 2 ) is 3,000 or less is preferable in that, when the optical film of the first aspect of the present invention is used as a polarizer protection film, even when the resin layer is thin, it is possible to suppress the occurrence of "color leakage" of the polarizer in a humid environment. From the viewpoint of achieving both suppression of the occurrence of color leakage of the polarizer and further thinning of the resin layer at a higher level, the above product (T×M 2 ) is preferably 2,900 or less, more preferably 2,800 or less, and may be 2,700 or less.

[0012] In the optical film of the first aspect of the present invention, the product of the product (T×M 1 ) and the product (T×M 2 ), that is, the product ((T×M 1 )×(T×M 2 )) is preferably 4,500,000 or less. The configuration in which the product ((T×M 1 )×(T×M 2 )) is 4,500,000 or less is preferable in that, when the optical film of the first aspect of the present invention is used as a polarizer protection film, even when the resin layer is thin, it is possible to suppress the occurrence of "color leakage" of the polarizer in a humid environment. From the viewpoint of achieving both suppression of the occurrence of color leakage of the polarizer and further thinning of the resin layer at a higher level, the above product ((T×M1 )×(T×M 2 )) is preferably 4,000,000 or less, and more preferably 3,500,000 or less.

[0013] In the first side optical film of the present invention, it is preferable that the surface of the resin layer remains unscratched 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 / second, and 10 reciprocating motions. As described above, the resin layer also provides the first side optical film of the present invention with excellent scratch resistance. Therefore, when the first side optical film of the present invention is used as a polarizing plate protective film, the resin layer has excellent scratch resistance, making it less susceptible to scratches during the manufacturing process and suppressing a decrease in the performance of the polarizing plate, such as a decrease in low moisture permeability.

[0014] In the first side optical film of the present invention, the thickness of the resin layer is preferably 1.5 to 3.5 μm. As described above, even if the resin layer is thin, the first side optical film of the present invention can be given excellent low moisture permeability. When the first side optical film of the present invention is used as a polarizing plate protective film, the thickness of the resin layer is preferably 3.2 μm or less, and more preferably 3 μm or less, from the viewpoint of making the polarizing plate thinner. As a lower limit of the thickness of the resin layer, from the viewpoint of achieving both low moisture permeability and scratch resistance at a higher level, it is preferably 1.8 μm or more, and may be 2 μm or more.

[0015] In the first optical film of the present invention, it is preferable that the light-transmitting substrate contains at least one selected from the group consisting of cellulose resins, polyester resins, acrylic resins, and cyclic olefin polymers. These resins can be suitably used as substrates for polarizing plate protective films.

[0016] Furthermore, a second aspect of the present invention provides a polarizing plate in which a polarizer is arranged on the side of the optical film opposite to the resin layer of the first aspect of the present invention. Furthermore, a third aspect of the present invention provides an image display device having a polarizing plate as described in the second aspect of the present invention. In the image display device as described in the third aspect of the present invention, it is preferable that an adhesive layer and an optical member are laminated on the resin layer in that order.

[0017] The polarizing plate on the second side of the present invention has excellent low moisture permeability and scratch resistance even with a thin resin layer, because the optical film on the first side of the present invention is used as a protective film for the polarizing plate. Therefore, the image display device on the third side of the present invention, which has the polarizing plate on the second side of the present invention, is thin, yet less prone to discoloration of the polarizing plate in humid environments and has excellent durability. [Effects of the Invention]

[0018] By using the optical film of the present invention as a protective film for polarizers, the resulting polarizer exhibits excellent low moisture permeability even when thin, is less prone to color fading of the polarizer, and has excellent durability. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a schematic diagram (cross-sectional view) showing one embodiment of the optical film of the present invention. [Figure 2] Figure 2 is a schematic diagram (cross-sectional view) showing one embodiment of a polarizing plate having the optical film shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram (cross-sectional view) showing one embodiment of an image display device having the polarizing plate shown in Figure 2. [Modes for carrying out the invention]

[0020] A first aspect of the present invention is to provide an optical film in which a resin layer is laminated on one side of a light-transmitting substrate. In this specification, the optical film of the first aspect of the present invention may be referred to as the "optical film of the present invention." Furthermore, the light-transmitting substrate and resin layer constituting the optical film of the present invention may be referred to as the "light-transmitting substrate of the present invention" and the "resin layer of the present invention," respectively. Also, "film" includes the meanings of "sheet" and "tape." That is, the optical film of the present invention may have a sheet-like or tape-like form.

[0021] 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. The polarizing plate of the second aspect of the present invention may be referred to as "the polarizing plate of the present invention" in this specification. Furthermore, a third aspect of the present invention provides an image display device having the polarizing plate of the present invention. The image display device of the third aspect of the present invention may be referred to as "the image display device of the present invention" in this specification.

[0022] The embodiments of the optical film of the present invention will be described below with reference to the figures, but the present invention is not limited thereto and is merely illustrative.

[0023] Figure 1 is a schematic diagram (cross-sectional view) showing one embodiment of the optical film of the present invention. In Figure 1, the optical film 10 has a laminated structure in which a resin layer 1 is laminated on one side of a light-transmitting substrate 2.

[0024] Figure 2 is a schematic diagram (cross-sectional view) showing one embodiment of the polarizing plate of the present invention. In Figure 2, the polarizing plate 20 has a laminated structure in which the polarizer 3 is positioned on the side of the optical film 10 opposite to the resin layer 1. In this embodiment, a second light-transmitting substrate 4 and an adhesive layer 5 are further laminated in this order on the side of the polarizer 3 opposite to the optical film 10.

[0025] Figure 3 is a schematic diagram (cross-sectional view) showing one embodiment of an image display device having the polarizing plate shown in Figure 2. In the image display device 30 shown in Figure 3, an image display panel 6 is laminated on the adhesive layer 5 of a polarizing plate 20. In this embodiment, the adhesive layer 7 and the optical member 8 are laminated on the resin layer 1 in this order. The following describes each component.

[0026] <Optical film> In the optical film of the present invention, "optical" means used for optical applications, and more specifically, it means used in the manufacture of products using optical components (optical products). Examples of optical products include image display devices and input devices such as touch panels, but it can be suitably used in the manufacture of liquid crystal image display devices, self-emissive image display devices (e.g., organic EL (electroluminescent) image display devices, LED image display devices), etc. More specifically, it can be suitably used as a protective film for polarizing plates that constitute an image display device.

[0027] The optical film of the present invention is not particularly limited in form, as long as a resin layer is laminated on one side of a light-transmitting substrate. For example, the optical film of the present invention may have a resin layer on only one side, or it may have resin layers on both sides. Furthermore, if the optical film of the present invention has resin layers on both sides, it may be configured such that both resin layers are provided by the resin layer of the present invention, or one resin 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, an optical film having a resin layer on only one side is preferred.

[0028] In addition to the light-transmitting substrate and resin layer of the present invention, the optical film of the present invention may also have other layers, such as substrates other than the light-transmitting substrate of the present invention, resin layers other than the resin layer of the present invention, intermediate layers, undercoat layers, antistatic layers, separators, surface protective films, etc., on the surface or between any of the layers, to the extent that the effects of the present invention are not impaired.

[0029] In the optical film of the present invention, the thickness T [μm] of the resin layer of the present invention and the moisture permeability M of the optical film of the present invention under conditions of 40°C and 92% relative humidity. 1 [g / m 2 Product of 24 hours (T × M) 1 ) is 1,500 or less. The resin layer of the present invention provides excellent low moisture permeability to the optical film of the present invention. Generally, moisture permeability tends to increase as the film thickness increases, and decreases as the film thickness decreases, inversely proportional to the resin layer thickness T [μm] and the moisture permeability M. 1 The product of (T × M) 1 ) can serve as an indicator of the moisture permeability of the resin layer itself in the present invention, and the lower the value, the better the low moisture permeability. Therefore, the above product (T × M) 1 The optical film of the present invention, having a laminated structure of the resin layer of the present invention having a value of 1,500 or less, is provided with excellent low moisture permeability even when the resin layer of the present invention is thin, thus combining both thinness and excellent low moisture permeability.

[0030] The preceding product (T × M 1 A configuration in which the product (T × M) is 1,500 or less is preferable because, when the optical film of the present invention is used as a polarizing plate protective film, it can provide excellent low moisture permeability even when the resin layer of the present invention is thin, and can suppress the occurrence of "color fading" of the polarizer in a humid environment. From the viewpoint of achieving a higher level of both suppression of color fading of the polarizer and thinning of the resin layer of the present invention, the product (T × M) is preferable. 1 The product (T × M) is preferably 1,400 or less, more preferably 1,300 or less, and may be 1,200 or less. 1 The lower limit of ) is not particularly limited, but from the viewpoint of allowing moisture inside the polarizing plate to escape to the outside and preventing the occurrence of "color fading" of the polarizer, it is preferably 500 or higher, more preferably 600 or higher, and may also be 700 or higher.

[0031] In the optical film of the present invention, the thickness T [μm] of the resin layer of the present invention and the moisture permeability M of the optical film of the present invention under conditions of 60°C and 90% relative humidity. 2 [g / m 2 Product of 24 hours (T × M) 2) is preferably 3,000 or less. Product (T × M 2 ) also, the above product (T × M 1 Similar to the above product (T × M), this can serve as an indicator of the moisture permeability of the resin layer itself in the present invention, and the lower the value, the better the low moisture permeability. Therefore, the above product (T × M) can be used as an indicator of the moisture permeability of the resin layer itself, and the lower the value, the better the low moisture permeability. 2 The optical film of the present invention, having a laminated structure of the resin layer of the present invention having a value of 3,000 or less, is preferable because it provides excellent low moisture permeability even when the resin layer of the present invention is thin, thus combining both thinness and excellent low moisture permeability.

[0032] The preceding product (T × M 2 A configuration in which the product (T × M) is 3,000 or less is preferable because, when the optical film of the present invention is used as a polarizing plate protective film, it can suppress the occurrence of "color fading" of the polarizer in a humid environment, even when the resin layer of the present invention is thin. From the viewpoint of achieving a higher level of both suppression of color fading of the polarizer and thinning of the resin layer of the present invention, the above product (T × M) is preferable. 2 The product (T × M) is preferably 2,900 or less, more preferably 2,800 or less, and may be 2,700 or less. 2 The lower limit of ) is not particularly limited, but from the viewpoint of preventing "color fading" of the polarizer by allowing moisture inside the polarizing plate to escape to the outside, it is preferably 500 or more, more preferably 1,000 or more, and may be 1,500 or more.

[0033] In the optical film of the present invention, the product (T × M 1 ) and the aforementioned product (T × M 2 ) and the product ((T × M 1 )×(T×M 2 The product ((T × M) is preferably 4,500,000 or less. 1 )×(T×M 2 )) also, the aforementioned product (T × M 1 ), the aforementioned product (T × M 2 Similarly, the product ((T×M) can serve as an indicator of the moisture permeability of the resin layer itself in the present invention, and the lower the value, the better the low moisture permeability. 1 )×(T×M 2The optical film of the present invention, having a laminated structure of the resin layer of the present invention having a ratio of 4,500,000 or less, is preferable because it provides excellent low moisture permeability even when the resin layer of the present invention is thin, thus combining both thinness and excellent low moisture permeability.

[0034] Previous product ((T × M 1 )×(T×M 2 A configuration in which the product ((T×M)) is 4,500,000 or less is preferable because, when the optical film of the present invention is used as a polarizing plate protective film, it can suppress the occurrence of "color fading" of the polarizer in a humid environment, even when the resin layer of the present invention is thin. From the viewpoint of achieving a higher level of both suppression of color fading of the polarizer and thinning of the resin layer of the present invention, the above product ((T×M) 1 )×(T×M 2 The product ((T × M)) is preferably 4,000,000 or less, and more preferably 3,500,000 or less. 1 )×(T×M 2 The lower limit of )) is not particularly limited, but from the viewpoint of preventing the occurrence of "color fading" of the polarizer by allowing moisture inside the polarizing plate to escape to the outside, it is preferably 50,000 or more, more preferably 100,000 or more, and may be 150,000 or more.

[0035] In the optical film of the present invention, the thickness T [μm] of the resin layer of the present invention and the moisture permeability M of the optical film of the present invention under conditions of 65°C and 90% relative humidity. 3 [g / m 2 Product of 24 hours (T × M) 3 ) is preferably 4,000 or less. Product (T × M 3 ) also, the above product (T × M 1 ), product (T×M 2 Similar to the above product (T × M), this can serve as an indicator of the moisture permeability of the resin layer itself in the present invention, and the lower the value, the better the low moisture permeability. Therefore, the above product (T × M) can be used as an indicator of the moisture permeability of the resin layer itself, and the lower the value, the better the low moisture permeability. 3 The optical film of the present invention, having a laminated structure of the resin layer of the present invention having a value of 4,000 or less, is preferable because it provides excellent low moisture permeability even when the resin layer of the present invention is thin, thus combining both thinness and excellent low moisture permeability.

[0036] The preceding product (T × M 3 A configuration in which the product (T × M) is 4,000 or less is preferable because, when the optical film of the present invention is used as a polarizing plate protective film, it can suppress the occurrence of "color fading" of the polarizer in a humid environment, even when the resin layer of the present invention is thin. From the viewpoint of achieving a higher level of both suppression of color fading of the polarizer and thinning of the resin layer of the present invention, the above product (T × M) is preferable. 3 The product (T × M) is preferably 3,800 or less, more preferably 3,600 or less, and may be 3,400 or less. 3 The lower limit of ) is not particularly limited, but from the viewpoint of preventing the occurrence of "color fading" of the polarizer by allowing moisture inside the polarizing plate to escape to the outside, it is preferably 1,000 or more, more preferably 1,500 or more, and may be 2,000 or more.

[0037] The moisture permeability M of the optical film of the present invention under an environment of 40°C and 92% relative humidity. 1 [g / m 2 • 24h is 700g / m² 2 • Preferably 24 hours or less. 1 700g / m 2 The configuration of having a humidity of 24 hours or less is preferable because, when the optical film of the present invention is used as a polarizer protective film, it can suppress the occurrence of "color fading" of the polarizer in a humid environment. From the viewpoint of suppressing the occurrence of color fading of the polarizer to a higher level, the humidity permeability M 1 It is 600g / m 2 • Preferably 24 hours or less, 550 g / m² 2 • It may be less than 24 hours. 1 The lower limit is not particularly limited, but from the viewpoint of preventing "color fading" of the polarizer by allowing moisture inside the polarizer to escape to the outside, 100g / m 2 • Preferably 24 hours or more, 200g / m² 2 ・24 hours or more is preferable, 300g / m 2 • It can be more than 24 hours.

[0038] The moisture permeability M of the optical film of the present invention under conditions of 60°C and 90% relative humidity. 2 [g / m2 ·24h] is 1,500 g / m 2 ·24h or less is preferable. The moisture permeability M 2 being 1,500 g / m 2 ·24h or less is preferable in that when the optical film of the present invention is used as a polarizer protection film, the occurrence of "color bleeding" of the polarizer can be suppressed in a humid environment. From the viewpoint of suppressing the occurrence of color bleeding of the polarizer at a higher level, the moisture permeability M 2 is preferably 1,400 g / m 2 ·24h or less, more preferably 1,300 g / m 2 ·24h or less, and may even be 1,200 g / m 2 ·24h or less. The lower limit of the moisture permeability M 2 is not particularly limited, but from the viewpoint of preventing the occurrence of "color bleeding" of the polarizer by allowing the moisture in the polarizer to escape to the outside, 300 g / m 2 ·24h or more is preferable, 500 g / m 2 ·24h or more is more preferable, and may even be 800 g / m 2 ·24h or more.

[0039] The moisture permeability M of the optical film of the present invention at a temperature of 65°C and a relative humidity of 90% environment 3 [g / m 2 ·24h] is preferably 2,000 g / m 2 ·24h or less. The moisture permeability M 3 being 2,000 g / m 2 ·24h or less is preferable in that when the optical film of the present invention is used as a polarizer protection film, the occurrence of "color bleeding" of the polarizer can be suppressed in a humid environment. From the viewpoint of suppressing the occurrence of color bleeding of the polarizer at a higher level, the moisture permeability M 3 is preferably 1,800 g / m 2 ·24h or less, more preferably 1,600 g / m 2 ·24h or less, and may even be 1,400 g / m 2 ·24h or less. The lower limit of the moisture permeability M 3 is not particularly limited, but from the viewpoint of preventing the occurrence of "color bleeding" of the polarizer by allowing the moisture in the polarizer to escape to the outside, 500 g / m2 • Preferably 24 hours or more, 750 g / m² 2 ・More preferably 24 hours or longer, 1,000 g / m² 2 • It can be more than 24 hours.

[0040] The moisture permeability M in the optical film of the present invention 1 M 2 M 3 , and the thickness T of the resin layer and the moisture permeability M 1 M 2 , or M 3 The product of the above can be measured specifically by the method of the embodiment described below. The moisture permeability M in the optical film of the present invention 1 M 2 M 3 , and the thickness T of the resin layer and the moisture permeability M 1 M 2 M 3 The product of these factors can be adjusted by adjusting the type and thickness of the resin constituting the light-transmitting substrate of the present invention, the type, composition, and degree of crosslinking of the resin constituting the resin layer of the present invention, and so on.

[0041] The haze of the optical film of the present invention is not particularly limited, but from the viewpoint of obtaining good transparency, it is preferably 1.0% or less, and more preferably 0.8% or less. The haze can be determined in accordance with 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 constituting the light-transmitting substrate of the present invention, the type and thickness of the resin constituting the resin layer of the present invention, and so on.

[0042] The total light transmittance of the optical film of the present invention in the visible light wavelength range is not particularly limited, but is preferably 85% or higher, and more preferably 88% or higher. The visible light wavelength range can be determined in accordance with 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 constituting the light-transmitting substrate of the present invention, the type and thickness of the resin constituting the resin layer of the present invention, and so on.

[0043] The thickness of the optical film of the present invention is not particularly limited, but considering factors such as thinness, strength, and workability, it is preferably in the range of 1 to 500 μm, more preferably in the range of 10 to 300 μm, and optimally in the range of 20 to 200 μm.

[0044] <Light transparent base material> Examples of 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 triacetylcellulose (TAC), acrylic resins such as polymethyl methacrylate (PMMA), polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), cyclic olefin polymers (COP) (e.g., trade name "Arton" (manufactured by JSR Corporation), trade name "Zeonor" (manufactured by Hon-Zeon Corporation), etc.), polycarbonate resins, polysulfone resins, polyarylate resins, polyimide resins, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, and ethylene-propylene copolymers. From the viewpoint of being optically uniform, having a smooth surface, and having good secondary processability for manufacturing polarizing plates, cellulose resins, acrylic resins, polyester resins, and cyclic olefin polymers (COP) are preferred, and cellulose resins are particularly preferred. These plastic materials can be used individually or in combination of two or more.

[0045] 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, and more preferably 0.8% or less. The haze can be determined in accordance with JIS K 7136 (2000). The haze of the light-transmitting substrate of the present invention can be adjusted by the type and thickness of the resin constituting the light-transmitting substrate of the present invention.

[0046] 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 higher, and more preferably 88% or higher. The visible light wavelength region can be determined in accordance with JIS K 7361-1. The total light transmittance of the light-transmitting substrate of the present invention can be adjusted by the type and thickness of the resin constituting the light-transmitting substrate of the present invention.

[0047] The thickness of the light-transmitting substrate of the present invention is not particularly limited, but considering factors such as thinness, strength, and workability, a range of 1 to 500 μm is preferred, more preferably 10 to 300 μm, and optimally 20 to 200 μm.

[0048] 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 to 1.80, and preferably in the range of 1.40 to 1.70. Furthermore, the surface of the light-transmitting substrate of the present invention (the surface on which the resin layer is formed and / or the opposite surface) may be appropriately subjected to known and conventional surface treatments, such as physical treatments such as corona discharge treatment and plasma treatment, or chemical treatments such as undercoating.

[0049] <Resin layer> The resin layer of the present invention is laminated on one side of the light-transmitting substrate of the present invention, thereby imparting excellent low moisture permeability to the optical film of the present invention. Furthermore, the resin layer of the present invention also imparts excellent scratch 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 laminated structure can be suitably used as a polarizing plate protective film.

[0050] Preferably, the resin layer of the present invention remains scratch-free when its surface is 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 / second, and 10 reciprocating motions. In other words, because the optical film of the present invention is coated with the resin layer of the present invention, which has excellent scratch resistance, it is less prone to scratches during the manufacturing process even when thin, and when used as a polarizing plate protective film, it can provide a polarizing plate with excellent durability. The excellent scratch resistance of the resin layer of the present invention can be imparted by adjusting the composition and thickness of the resin layer, as described later.

[0051] The resin layer of the present invention is formed from a cured product of a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having polymerizable functional groups and oligomers having polymerizable functional groups. The polymerizable compound constituting the resin layer of the present invention may be referred to as "the polymerizable compound of the present invention" in this specification, and the curable composition containing the polymerizable compound of the present invention may be referred to as "the curable composition of the present invention." The configuration in which the resin layer of the present invention is formed from a cured product of the curable composition of the present invention containing the polymerizable compound of the present invention is preferable in that it can impart excellent low moisture permeability and scratch resistance to the optical film of the present invention.

[0052] The "polymerizable functional group" of the polymerizable compound of the present invention is not particularly limited, but examples include unsaturated double bond groups, epoxy groups, and oxetanyl groups. From the viewpoint of excellent low moisture permeability and scratch resistance, unsaturated double bond groups are preferred. Examples of unsaturated double bond groups include (meth)acryloyl groups, vinyl groups, styryl groups, and allyl groups, with (meth)acryloyl groups being preferred. In this specification, "(meth)acryloyl" refers to either or both of "acryloyl" and "methacryloyl," and "(meth)acrylic" also refers to either or both of "acrylic" and "methacrylic."

[0053] The number of "polymerizable functional groups" in the polymerizable compound of the present invention is not particularly limited as long as it is one or more. However, in order to impart excellent low moisture permeability and scratch resistance to the optical film of the present invention, it is preferable that the curable composition of the present invention contains at least one polymerizable compound having two or more, more preferably three or more, even more preferably four or more, or five or more, six or more, seven or more, eight or more, nine or more, or ten or more polymerizable functional groups. The upper limit of the number of "polymerizable functional groups" is not particularly limited, but it may be 30 or less, 25 or less, or 20 or less.

[0054] In order to impart excellent low moisture permeability to the optical film of the present invention, it is preferable that the curable composition of the present invention contains, as the polymerizable compound of the present invention, a compound having a cyclic aliphatic hydrocarbon group and an unsaturated double bond group in its molecule (hereinafter sometimes referred to as "polymerizable compound A"). It is believed that the cyclic aliphatic hydrocarbon group contained in polymerizable compound A in its molecule hydrophobicizes the resin layer of the present invention and reduces its moisture permeability. The curable composition of the present invention may contain one type of polymerizable compound A, or it may contain two or more types of polymerizable compound A.

[0055] The polymerizable functional groups of polymerizable compound A are preferably unsaturated double bond groups such as (meth)acryloyl groups, vinyl groups, styryl groups, and allyl groups, with (meth)acryloyl groups being particularly preferred. Particularly preferred are the following compounds containing two or more (meth)acryloyl groups in one molecule.

[0056] The number of polymerizable functional groups in polymerizable compound A is not particularly limited as long as it is one or more, but it is preferable that polymerizable functional groups be two or more, more preferably three or more, and even more preferably four or more, in order to impart excellent low moisture permeability and scratch resistance to the optical film of the present invention. The upper limit of the number of polymerizable functional groups in polymerizable compound A is not particularly limited, but it may be 10 or less, 9 or less, or 8 or less.

[0057] The "cyclic aliphatic hydrocarbon group" contained within the molecule of polymerizable compound A is preferably a group derived from an alicyclic compound having 7 or more carbon atoms, more preferably a group derived from an alicyclic compound having 10 or more carbon atoms, and even more preferably a group derived from an alicyclic compound having 12 or more carbon atoms. The cyclic aliphatic hydrocarbon group is particularly preferably a group derived from a polycyclic compound, such as a bicyclic or tricyclic compound.

[0058] The cyclic aliphatic hydrocarbon group (including the linking group) is preferably a group represented by any of the following general formulas (I) to (V), more preferably a group represented by the following general formulas (I), (II), or (IV), and even more preferably a group represented by the following general formula (I). [ka]

[0059] In general formula (I), L and L' each independently represent a linking group with two or more valencies. n represents an integer from 1 to 3. [ka]

[0060] In general formula (II), L and L' each independently represent a linked group with two or more valencies. n represents an integer between 1 and 2. [ka]

[0061] In general formula (III), L and L' each independently represent a linking group with two or more valencies. n represents an integer between 1 and 2. [ka]

[0062] In general formula (IV), L and L' each independently represent a divalent or higher linking group, and L'' represents a hydrogen atom or a divalent or higher linking group. [ka]

[0063] In general formula (V), L and L' each independently represent a linking group with two or more valent values.

[0064] Specific examples of cyclic aliphatic hydrocarbon groups include monovalent to trivalent groups derived from norbornane, tricyclodecane, tetracyclododecane, pentacyclopentadecane, adamantane, diamantane, and the like.

[0065] Polymerizable compound A, which contains a group represented by any of the above general formulas (I) to (V) as a cyclic aliphatic hydrocarbon group, has polymerizable functional groups via linking groups represented by L, L', and L''. Examples of linking groups include single bonds, optionally substituted alkylene groups having 1 to 6 carbon atoms, optionally disubstituted amide groups at the N position, optionally substituted carbamoyl groups at the N position, ester groups, oxycarbonyl groups, ether groups, and groups obtained by combining these.

[0066] Polymerizable compound A can be easily synthesized, for example, by a one- or two-step reaction between a polyol such as a diol or triol having the above-mentioned cyclic aliphatic hydrocarbon group and a carboxylic acid, carboxylic acid derivative, epoxy derivative, isocyanate derivative, etc., of a compound having a (meth)acryloyl group, vinyl group, styryl group, allyl group, etc. Preferably, it can be synthesized by reacting the above-mentioned polyol having the cyclic aliphatic hydrocarbon group with (meth)acrylic acid, (meth)acryloyl chloride, (meth)acrylic anhydride, (meth)acrylate glycidyl, 1,1-bis(acryloxymethyl)ethyl isocyanate, etc.

[0067] The following are preferred specific examples of polymerizable compound A, but the present invention is not limited to these. [ka] [ka] [ka] [ka] [ka] [ka]

[0068] The content of 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, it is preferably 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, 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 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 of achieving a higher level of both low moisture permeability and scratch resistance, the resin layer of the present invention may be 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 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 or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, or 10% by weight or less.

[0069] In order to impart excellent scratch resistance in addition to excellent low moisture permeability to the optical film of the present invention, it is preferable that the curable composition of the present invention further contains, in addition to polymerizable compound A, a polymerizable compound other than polymerizable compound A, that is, a compound that does not have a cyclic aliphatic hydrocarbon group in its molecule but has a polymerizable functional group (hereinafter sometimes referred to as "polymerizable compound B"). Polymerizable compound A tends to have a low crosslinking density due to the stereostructure of the cyclic aliphatic hydrocarbon group it contains in its molecule. It is believed that by including polymerizable compound B in addition to polymerizable compound A in the curable composition of the present invention, the crosslinking density becomes higher and the scratch resistance is improved.

[0070] The polymerizable functional groups of polymerizable compound B are preferably unsaturated double bond groups such as (meth)acryloyl groups, vinyl groups, styryl groups, and allyl groups, with (meth)acryloyl groups being particularly preferred. Particularly preferred are the following compounds containing two or more (meth)acryloyl groups in one molecule.

[0071] The number of polymerizable functional groups in polymerizable compound B is not particularly limited as long as there is one or more, but it is preferable to have two or more, more preferably three or more, even more preferably four or more, or five or more, six or more, seven or more, eight or more, nine or more, or ten or more, in order to impart excellent scratch resistance to the optical film of the present invention. The upper limit of the number of polymerizable functional groups in polymerizable compound B is not particularly limited, but it may be 30 or less, 25 or less, or 20 or less.

[0072] Examples of polymerizable compound B include monomers that do not have cyclic aliphatic hydrocarbon groups in their molecule but have polymerizable functional groups (hereinafter sometimes referred to as "polymerizable monomer B"), and oligomers that do not have cyclic aliphatic hydrocarbon groups in their molecule but have polymerizable functional groups (hereinafter sometimes referred to as "polymerizable oligomer B"). The curable composition of the present invention may contain only polymerizable monomers as polymerizable compound B, only polymerizable oligomer B, or both polymerizable monomer B and polymerizable oligomer B. From the viewpoint of forming a high crosslink density, it is preferable to contain at least polymerizable oligomer B.

[0073] Examples of polymerizable monomer B include hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, 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, dipentaerythritol (meth)hexaacrylate, tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, and propoxylated trimethylolpropane tri(meth)acrylate. The curable composition of the present invention may contain one polymerizable monomer B, or it may contain two or more polymerizable monomers B.

[0074] Polymerizable oligomer B is a compound that contains two or more repeating units and has polymerizable functional groups. In other words, polymerizable oligomer B is a polymer having polymerizable functional groups in its molecule. Examples of polymerizable oligomer B include urethane (meth)acrylate, which is obtained by adding two or more (meth)acryloyl groups as functional groups to a urethane backbone; polyester (meth)acrylate, which is obtained by adding two or more (meth)acryloyl groups as functional groups to a polyester backbone; and epoxy (meth)acrylate, which is obtained by adding two or more (meth)acryloyl groups as functional groups to an epoxy backbone. From the viewpoint of being able to form a high crosslink density, it is preferable to include at least urethane (meth)acrylate. The curable composition of the present invention may contain one type of polymerizable oligomer B, or it may contain two or more types of polymerizable oligomer B.

[0075] Urethane (meth)acrylates can be obtained, for example, by reacting a polyol, isocyanate, and hydroxy(meth)acrylate. As the polyol constituting the urethane (meth)acrylate, any known polyol can be used without limitation. However, from the viewpoint of improving crosslinking density, polyols having three or more hydroxyl groups (preferably four or more, more preferably five or more, and even more preferably six or more) are preferred. Examples include trimethylolpropane, ethoxylated isocyanuric acid, pentaerythritol, dipentaerythritol, tripentaerythritol, and tetrapentaerythritol. These polyols may be used individually or in combination of two or more.

[0076] As the isocyanate constituting the urethane (meth)acrylate, polyisocyanates composed of chain saturated hydrocarbons, cyclic saturated hydrocarbons, and aromatic hydrocarbons can be used. Examples of such polyisocyanates include linear saturated hydrocarbon isocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate; cyclic saturated hydrocarbon isocyanates such as isophorone diisocyanate, dicyclohexylmethane diisocyanate, methylenebis(4-cyclohexyl isocyanate), hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated toluene diisocyanate; and aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 1,3-xylylene diisocyanate, p-phenylene diisocyanate, 3,3'-dimethyl-4,4'-diisocyanate, 6-isopropyl-1,3-phenyl diisocyanate, and 1,5-naphthalene diisocyanate. Preferred examples include isophorone diisocyanate, tetramethylene diisocyanate, and hexamethylene diisocyanate. These polyisocyanates may be used individually or in combination of two or more types.

[0077] Examples of hydroxy(meth)acrylates that constitute urethane(meth)acrylate include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. These hydroxy(meth)acrylates may be used individually or in combination of two or more.

[0078] Examples of urethane (meth)acrylates include the Art Resin UN series from Negami Kogyo Co., Ltd., the NK Oligo U series from Shin Nakamura Chemical Industry Co., Ltd., and the Shiko UV series from Mitsubishi Chemical Corporation.

[0079] Polyester (meth)acrylates are obtained, for example, by reacting (meth)acrylic acid with the terminal hydroxyl groups of polyesters obtained by polymerizing polyols and polycarboxylic acids. Specific examples of polyester (meth)acrylates include Aronics M-6000, Aronics M-7000, Aronics M-8000, and Aronics M-9000, all manufactured by Toagosei Co., Ltd.

[0080] Epoxy (meth)acrylates can be 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 the epoxy ester series manufactured by Kyoeisha Chemical Co., Ltd.

[0081] The weight-average molecular weight of polymerizable oligomer B is not particularly limited, but from the viewpoint of improving the scratch resistance of the resin layer of the present invention, it is preferably 400 or more, more preferably 500 or more, even more preferably 600 or more, and particularly preferably 700 or more. Furthermore, from the viewpoint of the coatability of the curable composition of the present invention, the weight-average molecular weight of polymerizable oligomer B is preferably 10,000 or less, more preferably 7,000 or less, and even more preferably 5,000 or less. The weight-average molecular weight of polymerizable oligomer B can be determined, for example, by high-performance liquid chromatography (HPLC). For example, the weight-average molecular weight can be measured using an HPLC8020 manufactured by Tosoh Corporation, with two TSKgelGMH-H(20) columns connected in series, using tetrahydrofuran as the solvent, and under conditions of a flow rate of 0.5 mL / min.

[0082] The content of polymerizable compound B in the curable composition of the present invention is not particularly limited, but from the viewpoint of imparting excellent scratch resistance to the resin layer of the present invention, it is preferably 5% by weight or more, more preferably 10% by weight or more, even more preferably 15% by weight or more, or 20% by weight or more, 25% by weight or more, 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 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 of achieving a higher level of both low moisture permeability and scratch resistance in the resin layer of the present invention, the amount may be 90% by weight or less, 85% by weight or less, 80% by weight or less, 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 or less, 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.

[0083] If the curable composition of the present invention contains polymerizable compound A and polymerizable compound B, the ratio (polymerizable compound A / polymerizable compound B) is preferably 10 / 90 or more, more preferably 15 / 85 or more, or 20 / 80 or more, 25 / 75 or more, 30 / 70 or more, 35 / 65 or more, 40 / 60 or more, 45 / 55 or more, 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, from the viewpoint of imparting excellent low moisture permeability to the resin layer of the present invention. On the other hand, from the viewpoint of achieving a higher level of both low moisture permeability and scratch resistance, the resin layer of the present invention may be 95 / 5 or less, 90 / 10 or less, 85 / 15 or less, 80 / 20 or less, 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 or less, 25 / 75 or less, 15 / 85 or less, or 10 / 90 or less.

[0084] The curable composition of the present invention preferably contains a polymerization initiator, and a photopolymerization initiator is preferred as the polymerization initiator. Examples of photopolymerization initiators include benzophenone compounds such as benzyl, benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and α-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin Examples of polymerization initiators include benzoin alkyl ether compounds such as benzoin butyl ether and anisoin methyl ether; aromatic ketal compounds such as benzyldimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone; camphorquinone; halogenated ketones; acylphosphinoxides; and acylphosphonates. These polymerization initiators may be used individually or in combination of two or more.

[0085] The content of the photopolymerization initiator in the curable composition of the present invention is not particularly limited, but from the viewpoint of ensuring that the resin layer of the present invention has sufficient low moisture permeability and scratch resistance, it is preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, and even more preferably 0.2 parts by weight or more, per 100 parts by weight of the polymerizable compound (total of polymerizable compound A and polymerizable compound B). Furthermore, from the viewpoint of suppressing the problem that the curable composition of the present invention does not cure sufficiently due to excessive radiation absorption by the photopolymerization initiator, the content of the photopolymerization initiator in the curable composition of the present invention 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 (total of polymerizable compound A and polymerizable compound B).

[0086] Various leveling agents can be added to the curable composition of the present invention. For example, fluorine-based or silicone-based leveling agents can be used to prevent uneven coating (uniformity of the coated surface). Leveling agents can also be appropriately added when antifouling properties are required on the surface of the resin layer of the present invention. The amount of the leveling agent is, for example, 5 parts by weight or less, preferably in the range of 0.01 to 5 parts by weight, per 100 parts by weight of the polymerizable compound (total of polymerizable compound A and polymerizable compound B).

[0087] The curable composition of the present invention may contain a solvent. Various solvents can be used as the solvent, taking into consideration the solubility of the polymerizable compound (polymerizable compound A and / or polymerizable compound B), drying properties during coating, etc. Examples of such organic solvents include dibutyl ether, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3-dioxolane, 1,3,5-trioxane, tetrahydrofuran, anisole, phenethole, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, acetone, methyl ethyl ketone (MEK), diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butylolactone, methyl 2-methoxyacetate, methyl 2-ethoxyacetate, ethyl 2-ethoxyacetate, ethyl 2-ethoxypropionate, ethyl 2-methoxyethanol, 2-propoxyethanol, 2 Examples include butoxyethanol, 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., which can be used individually or in combination of two or more.

[0088] The curable composition of the present invention may further contain any suitable additives, such as plasticizers, surfactants, antioxidants, ultraviolet absorbers, thixotropic agents, and antistatic agents, as necessary, provided that the effects of the present invention are not impaired.

[0089] The thickness of the resin layer of the present invention is preferably 1.5 to 3.5 μm. As described above, even if the resin layer is thin, the optical film of the present invention can be given excellent low moisture permeability. When the optical film of the present invention is used as a protective film for a polarizing plate, the thickness of the resin layer is preferably 3.2 μm or less, and more preferably 3 μm or less, from the viewpoint of making the polarizing plate thinner. As a lower limit for the thickness of the resin layer, from the viewpoint of achieving both low moisture permeability and scratch resistance at a higher level, it is preferably 1.8 μm or more, and may be 2 μm or more. The resin layer of the present invention may be one layer or may consist of multiple layers. When the resin layer of the present invention consists of multiple layers, the thickness of the resin layer of the present invention is the sum of the thickness of each layer constituting the multiple layers.

[0090] The resin layer of the present invention can be formed by preparing a coating liquid (curable composition of the present invention) by mixing the polymerizable compound of the present invention (polymerizable compound A and / or polymerizable compound B) with a photopolymerization initiator, leveling agent, solvent, and other additives as needed, applying the coating liquid to one surface of a light-transmitting substrate and drying it to cure the coating film.

[0091] The solid content concentration of the coating solution is preferably 1% to 70% by weight, more preferably 2% to 50% by weight, and even more preferably 5% to 40% by weight.

[0092] Examples of coating methods include dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, die coating, extrusion coating, and bar coating.

[0093] The curing method for the coating film is appropriately selected depending on the type of curable composition. If the curable composition is photocurable, it can be cured by irradiating it with light using a light source that emits light of the required wavelength. For example, the light used for irradiation may have an exposure dose of 150 mJ / cm². 2 Light above, preferably 200 mJ / cm² 2 ~1000 mJ / cm 2Light can be used. Heating may also be performed during the photocuring process. Examples of light include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays, with ultraviolet rays being particularly preferred. Furthermore, the irradiation time and method are not particularly limited, as long as they can activate the photopolymerization initiator and cause a reaction of the polymerizable compound.

[0094] <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 Figure 2, the polarizing plate 20 has a laminated structure in which a polarizer 3 is arranged on the opposite side of the resin layer 1 of the optical film 10. Because the optical film 10 is used as a polarizing plate protective film, the polarizing plate 20 has excellent low moisture permeability and scratch resistance even if the resin layer 1 is thin, and quality deterioration such as discoloration of the polarizer 3 is less likely to occur. In this embodiment, a second light-transmitting substrate 4 and an adhesive layer 5 are further laminated in this order on the opposite side of the optical film 10 of the polarizer 3.

[0095] Polarizer 3 is an element that transmits only light with a specific polarization plane, and any known polarizer can be used without limitation. For example, a polyvinyl alcohol-based polarizing film can be used. The polyvinyl alcohol-based polarizing film may be a polyvinyl alcohol-based film dyed with iodine, or it may be a film dyed with a dichroic dye.

[0096] 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 treated for durability with a boron compound); or a film obtained by uniaxially stretching a polyvinyl alcohol-based film after dyeing it with iodine or a dichroic dye (preferably a film further treated for durability with a boron compound). The absorption axis of the polarizer is parallel to the stretching direction of the film.

[0097] The thickness of the polarizer 3 is preferably 5 to 25 μm, and more preferably 10 to 15 μm, from the viewpoint of making the polarizing plate 20 thinner.

[0098] The second light-transmitting substrate 4 protects the polarizer 3 on the side opposite to the optical film 10 (polarizer protective film), and can be made of glass, plastic film, etc., similar to the light-transmitting substrate of the present invention. Cellulose resin, cyclic olefin polymer (COP), and polycarbonate resin are preferred, and cyclic olefin polymer (COP) and polycarbonate resin are more preferred. The light-transmitting substrate 4 may be made of the same material as the light-transmitting substrate 2, or it may be made of a different material. The light-transmitting substrate 4 may have a resin layer 1 laminated on it, or it may not have a resin layer 1. Furthermore, the light-transmitting substrate 4 may be made of a single layer, or it may be a laminated structure of two or more identical or different layers.

[0099] Furthermore, the light-transmitting substrate 4 is preferably an optical compensation film (phase difference film) having an optical compensation layer comprising an optical anisotropic layer. The optical compensation film can, for example, improve the viewing angle characteristics of a liquid crystal display screen. Any known optical compensation film can be used without limitation; for example, a phase difference film described in Japanese Patent Application Publication No. 2014-194484 may be used.

[0100] The thickness of the light-transmitting substrate 4 is preferably 5 to 25 μm, and more preferably 10 to 15 μm from the viewpoint of thinning the polarizing plate 20.

[0101] The adhesive layer 5 is formed from any suitable adhesive. Examples of materials constituting the adhesive layer 5 include materials with polymers as base polymers, such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluoropolymers, rubber polymers, isocyanate polymers, polyvinyl alcohol polymers, gelatin polymers, vinyl polymers, latex polymers, and water-based polyesters. Among these, materials with acrylic polymers and / or rubber polymers as base polymers are preferred from the viewpoint of low moisture permeability. The adhesive layer 5 may contain a single base polymer or two or more base polymers.

[0102] 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.

[0103] The polarizing plate 20 can be obtained by bonding the polarizer 1 and the optical film 10 together with an adhesive. The polarizer 1 and the light-transmitting substrate 4 can also be bonded together with an adhesive. The adhesive used for bonding may be a fully saponified polyvinyl alcohol aqueous solution (water glue), or an active energy ray curable adhesive may be used.

[0104] The adhesive layer 5 can be formed by applying an adhesive composition containing the base polymer that constitutes the adhesive to the light-transmitting substrate 4, drying it, and then curing it as needed. Alternatively, the adhesive layer 5 may be formed on a separator in the same manner, and then attached and transferred to the light-transmitting substrate 4.

[0105] Layers other than the polarizing plate 20, optical film 10, polarizing plate 3, light-transmitting substrate 4, and adhesive layer 5 (e.g., surface protective film, separator, etc.) may be present on the surface or between any of the layers. For example, the surface of the adhesive layer 5 may be protected by a separator, and the surface of the resin layer 1 of the optical film 10 may be protected by a surface protective film.

[0106] The thickness of the polarizing plate 20 (total thickness including the light-transmitting substrate 4 and adhesive layer 5) is preferably 50 to 100 μm, and more preferably 60 to 75 μm from the viewpoint of making the polarizing plate 20 thinner.

[0107] <Image display device> The image display device of the present invention has a polarizing plate of the present invention. Because the image display device of the present invention has the polarizing plate of the present invention in a laminated structure, even if the resin layer 1 is thin, it has excellent low moisture permeability and scratch resistance, and quality deterioration such as discoloration of the polarizer 3 is less likely to occur.Therefore, even if the image display device of the present invention is thin, discoloration of the polarizing plate is less likely to occur in a humid environment and it has excellent durability. In Figure 3, the image display device 30 has an image display panel 6 laminated on the adhesive layer 5 of the polarizing plate 20. In this embodiment, the adhesive layer 7 and the optical member 8 are laminated on the resin layer 1 in this order.

[0108] The image display panel 6 is not particularly limited, but examples include liquid crystal image display panels, self-emissive image display panels (e.g., organic EL (electroluminescent) image display panels, LED image display panels), etc.

[0109] The image display panel 6 is formed by arranging RGB elements alternately, and it is preferable that the spaces between the RGB elements are filled with a black matrix (BM) in order to improve contrast.

[0110] The adhesive layer 7 can be made of a material containing a base polymer similar to that exemplified in the adhesive layer 5. Among these, materials using an acrylic polymer and / or a rubber polymer as the base polymer are preferred from the viewpoint of low moisture permeability. The adhesive layer 7 may contain a single base polymer or two or more base polymers. The adhesive layer 7 may be made of the same material as the adhesive layer 5 or of different materials.

[0111] The optical component 8 can be made of glass, plastic film, or the like, similar to the light-transmitting substrate of the present invention, and is preferably made of acrylic resin, polyester resin, or cyclic olefin polymer (COP), with polyester resin being particularly preferred. When the optical component 8 is located on the outermost surface of the viewing side of the image display device 30, it functions as a cover component.

[0112] The image display device 30 may have optical components other than the optical film 10, polarizing plate 3, light-transmitting substrate 4, adhesive layer 5, image display panel 6, adhesive layer 7, and optical component 8 on its surface or between any of the layers. The optical components are not particularly limited, but examples include polarizing plates other than the polarizing plate 3, phase difference plates, anti-reflective films, viewing angle adjustment films, and optical compensation films. The optical components also include components that serve a decorative or protective role while maintaining the visibility of the image display device or input device (such as design films, decorative films, and surface protection plates).

[0113] The image display device 30 can be manufactured by laminating an optical film in which an image display panel 6, a polarizing plate 20, an optical component 8, and an adhesive layer 7 are laminated. Specifically, this can be carried out by lamination under heating and / or pressure. After lamination under heating and / or pressure, curing may be performed by irradiation with active energy rays. Irradiation with active energy rays can be carried out in the same manner as the formation of the resin layer in the present invention. [Examples]

[0114] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0115] Example 1 (Preparation of coating liquid for resin layer formation) As resins to be included in the resin layer, 50 parts by weight (based on solids content) of UV-curable acrylate resin (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "A-DCP", 100% solids content) and 50 parts by weight (based on solids content) of UV-curable acrylate resin (manufactured by Mitsubishi Chemical Corporation, trade name "UV-1700TL", 80% solids content) were prepared. For every 100 parts by weight of the resin solids content of the above resins, 5 parts by weight of a photopolymerization initiator (manufactured by BASF, trade name "OMNIRAD907") and 0.2 parts by weight of a leveling agent (manufactured by Kyoeisha Chemical Co., Ltd., trade name "LE-303", 40% solids content) were mixed. This mixture was diluted with MIBK / cyclopentanone mixed solvent (weight ratio 60 / 40) to a solids content concentration of 30% to prepare a coating solution for forming the resin layer.

[0116] (Preparation of optical film) A transparent plastic film substrate (TAC, manufactured by Fujifilm Corporation, product name "TJ25UL") was prepared as a light-transmitting substrate. A coating film was formed on one side of the transparent plastic film substrate using a bar coater #7 with the resin layer forming coating liquid prepared above. The transparent plastic film substrate with this coating film was then transported to the drying process. In the drying process, the coating film was dried by heating at 60°C for 1 minute. After that, a high-pressure mercury lamp was used to apply an integrated light intensity of 220 mJ / cm². 2 The coating film was cured by irradiating it with ultraviolet light to form a resin layer with a thickness of 2.5 μm, thereby obtaining the optical film 1 of Example 1. The details of the resin used in Example 1 are as follows. A-DCP: Tricyclodecane dimethanol dimethacrylate • UV-1700TL: 10-function urethane acrylate

[0117] Example 2 Optical film 2 of Example 2 was obtained in the same manner as in Example 1, except that the resins included in the resin layer were 70 parts by weight (solid content) of A-DCP and 30 parts by weight (solid content) of UV-1700TL.

[0118] Example 3 The resin layer contains 0.1 parts by weight of a leveling agent, resulting in an integrated light intensity of 260 mJ / cm². 2 Except for the difference made, the optical film 3 of Example 3 was obtained in the same manner as in Example 1.

[0119] Comparative Example 1 As the resin to be included in the resin layer, 40 parts by weight (based on solid content) of UV-curable acrylate resin (manufactured by Toagosei Co., Ltd., trade name "M-920", 100% solid content) and 60 parts by weight (based on solid content) of UV-1700TL were prepared and mixed with 3 parts by weight of OMNIRAD907 and 0.2 parts by weight of LE-303. This mixture was diluted with MIBK / cyclopentanone mixed solvent (weight ratio 70 / 30) to a solid content concentration of 30% to prepare a coating solution for forming the resin layer. The optical film 4 of Comparative Example 1 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 using a bar coater #6.

[0120] (evaluation) The optical films obtained in the above examples and comparative examples were used for the following evaluations. The evaluation method is shown below. The results are shown in Table 1.

[0121] (1) Film thickness measurement The film thickness of the optical films in the examples and comparative examples was measured at five points relative to their width using a digital linear gauge (product name "MODELD-10HS," manufactured by Ozaki Seisakusho Co., Ltd.), and the average of the five film thicknesses was taken as the total thickness. The film thickness of the light-transmitting substrates used in the examples and comparative examples was measured using the same measurement method, and the average of the five film thicknesses 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.

[0122] (2) Moisture permeability measurement In accordance with JIS Z0208, the water vapor permeability of the optical films of the examples and comparative examples was measured at a temperature of 40°C and a relative humidity of 92%. The water vapor permeability of the optical films of the examples and comparative examples was measured under the temperature and humidity conditions of 60°C and 90% relative humidity, or 65°C and 90% relative humidity, in the same manner as under the temperature and humidity conditions of 40°C and 92%.

[0123] (3) Evaluation of color loss in polarizers After storing the optical films of the examples and comparative examples at a temperature of 60°C and a relative humidity of 90% for 120 hours, the films were observed in a darkroom with the backlight intensity set to 8000 candelas. If color fading such as unevenness or streaks was visible, it was determined that there was color fading in the polarizer.

[0124] (4) Scratch resistance measurement The optical films of the examples and comparative examples were cut to a size of 5 cm x 15 cm, and a diameter of 2.5 cm and a contact area of ​​6.25 x π cm were applied to the surface of the resin layer. 2 Steel wool of #0000 was brought into contact with the film in this manner. A load of 100 gf (0.98 N) was applied to the steel wool, and the surface of the resin layer was rubbed back and forth 10 times at a moving speed of 100 mm / s in the direction of the long side of the film. The presence or absence of scratches was visually inspected in the central 5cm x 5cm area of ​​the film after testing under fluorescent and LED light source conditions.

[0125] [Table 1]

[0126] Variations of the present invention are listed below. [Note 1] An optical film in which a resin layer is laminated on one side of a light-transmitting substrate, The resin layer is formed from a cured product of a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having polymerizable functional groups and oligomers having polymerizable functional groups. The thickness T [μm] of the resin layer and the moisture permeability M of the optical film in an environment with a temperature of 40°C and a relative humidity of 92%. 1 [g / m 2 Product of 24 hours (T × M) 1 Optical film with a value of 1,500 or less. [Note 2] The thickness T [μm] of the resin layer and the moisture permeability M of the optical film under conditions of 60°C and 90% relative humidity. 2 [g / m2 Product of 24 hours (T × M) 2 The optical film specified in Appendix 1 has a value of 3,000 or less. [Note 3] The product (T × M) described in Note 1 1 ) and the product (T × M) described in Appendix 2. 2 ) and the product ((T × M 1 )×(T×M 2 An optical film as described in Appendix 1 or 2, wherein the value of )) is 4,500,000 or less. [Note 4] An optical film as described in any one of Notes 1 to 3, wherein the surface of the resin layer is 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 / second, and 10 reciprocating motions. [Note 5] The optical film according to any one of Notes 1 to 4, wherein the thickness of the resin layer is 1.5 to 3.5 μm. [Note 6] The optical film according to any one of Notes 1 to 5, wherein the light-transmitting substrate comprises at least one selected from the group consisting of cellulose resins, polyester resins, acrylic resins, and cyclic olefin polymers. [Note 7] A polarizing plate in which a polarizer is arranged on the side opposite to the resin layer of the optical film described in any one of Notes 1 to 6. [Note 8] An image display device having the polarizing plate described in Note 7. [Note 9] The image display device according to Note 8, wherein an adhesive layer and an optical component are laminated on the resin layer in that order. [Explanation of Symbols]

[0127] 10 Optical film 1. Resin layer 2 Light-transparent base material 20 Polarizing plates 3 Polarizer 4. Light-transmitting substrate (optical compensation film) 5. Adhesive layer 30 Image display devices 6. Image display panel 7. Adhesive layer 8 Optical components

Claims

1. An optical film in which a resin layer is laminated on one side of a light-transmitting substrate, The resin layer is formed from a cured product of a curable composition containing at least one polymerizable compound selected from the group consisting of monomers having polymerizable functional groups and oligomers having polymerizable functional groups. The thickness of the resin layer is 1.5 to 3.5 μm. The thickness T [μm] of the resin layer and the moisture permeability M of the optical film in an environment with a temperature of 40°C and a relative humidity of 92%. １ [g / m ２ • Product of 24h (T × M) １ ) is between 700 and 1,500, An optical film with a thickness of 1 to 500 μm.

2. The thickness T [μm] of the resin layer and the moisture permeability M of the optical film under conditions of 60°C and 90% relative humidity. ２ [g / m ２ • Product of 24h (T × M) ２ The optical film according to claim 1, wherein the value of ) is 3,000 or less.

3. The product (T × M) according to claim 1 １ ), and the product (T × M) according to claim 2 ２ ), and the product ((T × M) １ ) × (T × M) ２ ) is 4,500,000 or less, The optical film according to claim 1 or 2.

4. The optical film according to any one of claims 1 to 3, wherein the surface of the resin layer remains unscratched 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 / second, and 10 reciprocating motions.

5. The optical film according to any one of claims 1 to 4, wherein the light-transmitting substrate comprises at least one selected from the group consisting of cellulose resins, polyester resins, acrylic resins, and cyclic olefin polymers.

6. A polarizing plate having a polarizer arranged on the side opposite to the resin layer of the optical film according to any one of claims 1 to 5.

7. An image display device having a polarizing plate as described in claim 6.

8. The image display device according to claim 7, wherein an adhesive layer and an optical member are laminated on the resin layer in this order.

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