Resin layer, optical film, and image display device

Abstract

Provided are a resin layer, an optical film, and an image display device. The optical film is a foldable optical film used for an image display device, and is provided with: a resin substrate; and a resin layer that is provided on one surface side of the resin base material and contains organic particles, the indentation hardness of the lower part of the resin layer being smaller than the indentation hardness of the upper part of the resin layer, and the surface of the resin layer being an uneven surface. The organic particles are unevenly distributed at a position closer to the resin base material side than a center line which divides the resin layer into two equal parts along the film thickness direction of the resin layer, and the ratio of the average particle diameter of the organic particles to the film thickness of the resin layer is more than 0.1 and less than 1; the resin layer is provided with a first resin layer and a second resin layer provided closer to the surface side than the first resin layer, the first resin layer contains the organic particles, and the second resin layer does not contain the organic particles.

Description

[0001] This application is a divisional application. The application number of the original application is 202080015091.X, the application date is February 27, 2020, and the name of the invention is “Resin layer, optical film and image display device”.

[0002] References to related applications

[0003] This application enjoys the benefit of priority of Japanese Patent Application No. 2019-37342 (filing date: March 1, 2019), Japanese Patent Application No. 2019-68027 (filing date: March 29, 2019), and Japanese Patent Application No. 2019-177178 (filing date: September 27, 2019), which are prior Japanese patent applications, and the disclosures of these patent applications are incorporated herein by reference in their entirety as a part of this specification. Technical Field

[0004] The present invention relates to a resin layer, an optical film and an image display device. Background Art

[0005] In the past, image display devices such as smartphones and tablet terminals were known, but foldable image display devices are currently being developed. Usually, smartphones, tablet terminals, etc. are covered with protective glass, but although glass is generally excellent in hardness, it is difficult to bend. Therefore, when the protective glass is used for an image display device, there is a high possibility of cracks when folded. Therefore, for a foldable image display device, research is being conducted on the use of a foldable optical film having a flexible resin substrate and a hard coating layer or a foldable optical film composed of a resin to replace the protective glass (for example, see patent documents 1 and 2). It should be noted that patent document 2 discloses that the hard coating layer contains organic particles to suppress external light reflection and glare.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2016-125063

[0009] Patent Document 2: International Publication No. 2017 / 14198 Summary of the invention

[0010] Problems to be solved by the invention

[0011] In addition to being required to have good foldability, the optical film used in this foldable image display device is also required to have impact resistance because impact is sometimes applied to the surface of the optical film. Here, if an impact is applied from the surface side of the optical film, the surface of the optical film is concave, and components (such as polarizers) that are located closer to the inside of the optical film in the image display device are sometimes damaged. Therefore, it is necessary to have impact resistance such that the surface of the optical film does not sag when an impact is applied to the surface of the optical film, or impact resistance such that the surface of the optical film does not sag when an impact is applied to the surface of the optical film, and components (such as polarizers) that are located closer to the inside of the optical film in the image display device are not damaged.

[0012] In addition, if such an optical film is kept in a folded state, a crease may be generated at the bent portion of the optical film. So far, optical films with good foldability have been proposed, but creases have not been considered at all. Here, foldability is an evaluation of cracks or breaks when folded, and is therefore an indicator completely different from the absence of creases. Therefore, even an optical film with good foldability may have creases.

[0013] In addition, the foldable optical film is used instead of the protective glass, so it may be pressed by fingers. However, it is softer than the protective glass, so it may be temporarily dented and leave a mark (pressing mark).

[0014] Currently, research is underway to add organic particles to the hard coat layer to make the pressure marks less noticeable. However, if organic particles are added, cracks may form at the interface between the organic particles and the binder resin when folded, causing cracks in the optical film.

[0015] The present invention is made to solve the above-mentioned problems. That is, the purpose is to provide a resin layer with good foldability and good impact resistance, an optical film and an image display device having the resin layer. In addition, the purpose is to provide a foldable optical film that is difficult to produce creases and has good impact resistance, and an image display device having the foldable optical film. In addition, the purpose is to provide a foldable optical film that is not easy to make obvious pressing marks and is difficult to break when folded, and an image display device having the foldable optical film.

[0016] Means for solving problems

[0017] The present invention includes the following aspects.

[0018] [1] A resin layer, which is a resin layer for an image display device and has light transmittance. Among them, the resin layer is trisected along the film thickness direction of the resin layer, and from the first surface of the resin layer to the second surface on the side opposite to the first surface, they are successively set as the first region, the second region, and the third region. When performing indentation tests in which a Berkovich indenter is indented into the first region, the second region, and the third region of the resin layer with a constant load respectively in the cross-section of the resin layer in the film thickness direction, when the displacement amount in the first region is set as d1, the displacement amount in the second region is set as d2, and the displacement amount in the third region is set as d3, the relationship d1 < d2 < d3 is satisfied.

[0019] [2] The resin layer as described in the above [1], wherein the ratio of the displacement amount d1 to the displacement amount d3 is 0.85 or less.

[0020] [3] The resin layer as described in the above [1] or [2], wherein the displacement amounts d1 to d3 are respectively 200 nm or more and 1000 nm or less.

[0021] [4] The resin layer as described in any one of the above [1] to [3], wherein the film thickness is 20 μm or more and 150 μm or less.

[0022] [5] An optical film, which is an optical film with a foldable laminated structure and at least includes the resin layer as described in any one of the above [1] to [4].

[0023] [6] The optical film as described in the above [5], which further includes a functional layer provided on either the first surface or the second surface side of the resin layer.

[0024] [7] The optical film as described in the above [5] or [6], which further includes a resin substrate provided on either the first surface or the second surface side of the resin layer.

[0025] [8] An optical film, which is a foldable light-transmissive optical film and includes: a resin substrate; and a resin layer provided on the first surface side of the resin substrate. The thickness of the resin substrate is 20 μm or less, the film thickness of the resin layer is 50 μm or more, the ratio of the film thickness of the resin layer to the thickness of the resin substrate is 4.0 or more and 12.0 or less. When performing an indentation test in which a Berkovich indenter is indented with a maximum load of 200 μN in the cross-section in the thickness direction of the resin substrate, the displacement amount of the resin substrate is 50 nm or more and 250 nm or less. When performing the indentation test in the cross-section in the film thickness direction of the resin layer, the displacement amount of the resin layer is 200 nm or more and 1500 nm or less.

[0026] [9] The optical film according to [8] above, wherein the resin substrate comprises at least one of a polyimide resin, a polyamide resin, and a polyamideimide resin.

[0027]

[10] The optical film according to [8] or [9], further comprising a hard coating layer provided on the second surface side of the resin substrate opposite to the first surface.

[0028]

[11] An optical film, which is a foldable optical film for an image display device, comprising: a resin substrate; and a resin layer disposed on one side of the resin substrate and containing organic particles, wherein the surface of the resin layer is a concave-convex surface, and the organic particles are located closer to the resin substrate side than a center line that bisects the resin layer in a film thickness direction of the resin layer.

[0029]

[12] The optical film according to

[11] above, wherein the resin substrate comprises one or more resins selected from the group consisting of polyimide resins, polyamideimide resins, polyamide resins, and polyester resins.

[0030]

[13] The optical film according to

[11] or

[12] above, wherein the resin layer has a thickness of 2 μm to 15 μm.

[0031]

[14] The optical film as described in any one of

[11] to

[13] above, wherein the indentation hardness of the lower portion of the resin layer is smaller than the indentation hardness of the upper portion of the resin layer.

[0032]

[15] An optical film as described in any one of

[11] to

[14] above, wherein the resin layer comprises a first resin layer and a second resin layer disposed at a position closer to the surface side than the first resin layer, and the first resin layer contains the organic particles.

[0033]

[16] An optical film as described in any one of [5] to

[15] above, wherein the optical film does not produce cracks or breaks when the optical film is repeatedly folded 180° 100,000 times with the opposing edges spaced 10 mm apart.

[0034]

[17] An image display device comprising: a display element; and the resin layer described in any one of [1] to [4] or the optical film described in any one of [5] to

[16] , which is arranged at a position closer to an observer than the display element.

[0035]

[18] The image display device as described in

[17] above, wherein the display element is an organic light emitting diode element.

[0036] Effects of the Invention

[0037] According to the first aspect of the present invention, a resin layer having good foldability and good impact resistance, an optical film having the resin layer, and an image display device can be provided. According to the second aspect of the present invention, a foldable optical film having good impact resistance and being difficult to produce creases can be provided, and an image display device having the foldable optical film can be provided. According to the third aspect of the present invention, a foldable optical film having a difficult pressing mark and being difficult to break when folded, and an image display device having the foldable optical film can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic structural diagram of the resin layer according to the first embodiment.

[0039] Figure 2 yes Figure 1 A local enlarged view of the resin layer.

[0040] Figure 3 This is a schematic structural diagram of the optical film according to the first embodiment.

[0041] Figure 4 (A)~ Figure 4 (C) is a diagram schematically showing the state of a continuous folding test.

[0042] Figure 5 This is a schematic structural diagram of another optical film according to the first embodiment.

[0043] Figure 6 This is a schematic structural diagram of the image display device according to the first embodiment.

[0044] Figure 7 It is a schematic structural diagram of the optical film of the second embodiment.

[0045] Figure 8 (A) and Figure 8 (B) is a diagram schematically showing the state of the folding static test.

[0046] Fig. 9 It is a schematic structural diagram of the optical film of the third embodiment.

[0047] Fig.10 yes Fig. 9 A partial enlarged view of the optical film.

[0048] Fig.11 This is a schematic structural diagram of another optical film according to the third embodiment.

[0049] Explanation of symbols

[0050] 10, 72, 82…resin layer

[0051] 30, 50, 70, 80...optical film

[0052] 31, 52, 85… Functional layers

[0053] 51, 71, 81…resin base material

[0054] 60…Image display device

[0055] 62…Display components

[0056] 73…Hard coating DETAILED DESCRIPTION

[0057] [First embodiment]

[0058] Hereinafter, the resin layer, optical film, optical film and image display device of the first embodiment of the present invention will be described with reference to the accompanying drawings. In this specification, the terms such as "film" and "sheet" are only different in terms of name and do not distinguish from each other. Therefore, for example, "film" is used to include a member called a sheet. Figure 1 is a schematic structural diagram of the resin layer of this embodiment, Figure 2 yes Figure 1 A partial enlarged view of the resin layer. Figure 3 It is a schematic structural diagram of the optical film of this embodiment. Figure 4 is a diagram schematically showing the situation of a continuous folding test, Figure 5 It is a schematic structural diagram of another optical film according to the embodiment.

[0059] <<<Resin layer>>>

[0060] Figure 1 The resin layer 10 shown is used for an image display device and has light transmittance. The "resin layer" in this embodiment refers to a layer of a single-layer structure containing a resin. The resin layer 10 is composed of a light-transmitting resin and has impact absorption. The resin layer 10 can be used as a single resin layer 10, and can also be assembled into an optical film 30, 50 of a laminated structure for use. In addition, a release film can be attached to the resin layer 10. The "light transmittance" in this specification refers to the property of transmitting light, for example, including a total light transmittance of 50% or more, preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more. Light transmittance does not necessarily need to be transparent, and can also be translucent.

[0061] For the resin layer 10, Figure 2As shown, the resin layer 10 is divided into three equal parts along the film thickness direction D1 of the resin layer 10, and the first area 10C, the second area 10D and the third area 10E are set in sequence from the first surface 10A of the resin layer 10 to the second surface 10B on the opposite side of the first surface 10A. In the cross section of the resin layer 10 in the film thickness direction D1, when the indenter is pressed into the first area 10C, the second area 10D and the third area 10E with a constant load, the displacement in the first area 10C is set to d1, the displacement in the second area 10D is set to d2, and the displacement in the third area 10E is set to d3, the following relationship (1) is satisfied. The resin layer of this embodiment is softer than the functional layer (hard coating) and the resin substrate described later, and the viscosity has a great influence, so the method of measuring the indentation hardness and Martens hardness by the nanoindentation method is not suitable. Therefore, the displacement is used as an indicator of hardness.

[0062] d1 <d2<d3…(1)

[0063] The displacements d1 to d3 can be obtained as follows using a nanoindenter (e.g., TI950 Tribo Indenter manufactured by Bruker). Specifically, first, a resin layer cut into 1 mm × 10 mm is embedded in an embedding resin to make a block, and a uniform slice having a thickness of 70 nm to 100 nm without holes is cut from the block using a general slice making method. Here, slices having a thickness of 70 nm to 100 nm are cut because the block remaining after the slices are cut is used for measurement, and the flatness of the cross section of the block remaining after the slices of this thickness are cut is good. It should be noted that if the flatness of the remaining block is poor, the measurement accuracy may deteriorate. For example, the Ultramicrotome EMUC7 of Leica Microsystems Co., Ltd. can be used to make the slices. Then, the block remaining after the uniform slice without holes is cut is used as a measurement sample. Next, in the cross section obtained by cutting out the above-mentioned slice in this measurement sample, under the following measurement conditions, the Berkovich indenter (triangular pyramid, such as TI-0039 manufactured by Bruker) as the above-mentioned indenter is vertically pressed into the center of the thickness direction of the cross section of the first region of the resin layer with a maximum load of 200μN for 40 seconds, and the displacement (indentation depth) d1 at this time is measured. Here, in order to avoid the influence of the side edge of the resin layer, the Berkovich indenter is pressed into the first region from the two side ends of the resin layer to the central side of the resin layer at a distance of more than 500nm. The displacement is the arithmetic mean of the values ​​obtained by measuring 10 locations. It should be noted that when the measured value contains a value that deviates from the arithmetic mean by more than ±20%, the measured value is removed and measured again. Regarding whether there is a value that deviates from the arithmetic mean by more than ±20% in the measured value, when the measured value is set as A and the arithmetic mean is set as B, it is judged by whether the value (%) calculated by (A-B) / B×100 is more than ±20%. The displacement amounts of the second region and the third region of the resin layer were measured in the same manner as the displacement amount of the first region.

[0064] (Measurement conditions)

[0065] Control method: load control (maximum load 200μN)

[0066] Lifting amount: 0nm

[0067] Preload: 0.5μN

[0068] Loading speed: 5μN / sec

[0069] Holding time under maximum load: 5 seconds

[0070] Unloading speed: 5μN / s

[0071] Temperature: 23±5℃

[0072] Relative humidity: 30% to 70%

[0073] The ratio of the displacement d1 to the displacement d3 (d1 / d3) is preferably 0.85 or less. If d1 / d3 is 0.85 or less, both excellent foldability and impact resistance can be achieved. In addition, the upper limit of d1 / d3 is more preferably 0.82 or less, or 0.80 or less, and the lower limit is preferably 0.40 or more, 0.50 or more, or 0.60 or more from the perspective of easily suppressing the generation of wrinkles during bending.

[0074] The ratio of the displacement d1 to the displacement d2 (d1 / d2) is preferably 0.70 or more and 0.99 or less. If d1 / d2 is 0.70 or more, wrinkles can be suppressed during bending, and if d1 / d2 is 0.99 or less, excellent foldability and impact resistance can be achieved. The lower limit of d1 / d2 is more preferably 0.75 or more, 0.80 or more, or 0.85 or more, and the upper limit is more preferably 0.95 or less, 0.92 or less, or 0.90 or less.

[0075] The ratio of the displacement d2 to the displacement d3 (d2 / d3) is preferably 0.70 or more and 0.99 or less. If d2 / d3 is 0.70 or more, wrinkles can be suppressed during bending, and if d2 / d3 is 0.99 or less, excellent foldability and impact resistance can be achieved. The lower limit of d2 / d3 is more preferably 0.75 or more, 0.80 or more, or 0.85 or more, and the upper limit is more preferably 0.95 or less, 0.92 or less, or 0.90 or less.

[0076] The displacement amounts d1 to d3 are preferably 1000 nm or less. If the displacement amounts d1 to d3 are 1000 nm or less, the resin layer 10 has sufficient hardness and can obtain excellent impact resistance. The upper limits of the displacement amounts d1 to d3 are more preferably 900 nm or less, 800 nm or less, or 700 nm or less, respectively. From the perspective of ensuring the foldability of the resin layer 10, the lower limits are more preferably 200 nm or more, 300 nm or more, or 350 nm or more.

[0077] The total light transmittance of the resin layer 10 is preferably 85% or more. If the total light transmittance of the resin layer 10 is 85% or more, sufficient image visibility can be obtained when the resin layer 10 is used in a mobile terminal. The total light transmittance of the resin layer 10 is more preferably 87% or more, or 90% or more.

[0078] The above-mentioned total light transmittance can be measured by a haze meter (for example, product name "HM-150", manufactured by Murakami Color Research Laboratory Co., Ltd.) in an environment of a temperature of 23±5°C and a relative humidity of 30% to 70% by a method in accordance with JIS K7361-1:1997. Regarding the above-mentioned total light transmittance, after the resin layer is cut into a size of 50 mm×100 mm, it is set in a state without curling or wrinkles, and without fingerprints or dust, and one resin layer is measured three times, and the arithmetic average of the values ​​obtained by the three measurements is adopted. The "measurement three times" in this specification does not mean that the same part is measured three times, but that three different parts are measured. In the resin layer 10, the first surface 10A and the second surface 10B are visually flat, and the deviation of the film thickness is also limited to the range of ±10%. Therefore, it is considered that by measuring the total light transmittance at three different parts of the cut resin layer, the average value of the total light transmittance in the entire surface of the resin layer can be roughly obtained. Even if the measured object is a 1m×3000m strip or a 5-inch smartphone, the deviation of the total light transmittance is within ±10%. It should be noted that when the resin layer cannot be cut into the above size, for example, the entrance opening of the HM-150 is Therefore, a sample size of 21 mm or more in diameter is required. Therefore, the resin layer can be appropriately cut into a size of 22 mm × 22 mm or more. When the size of the resin layer is small, the measurement points can be set to three locations by moving or changing the angle little by little within the range where the light source spot does not deviate.

[0079] The haze value (total haze value) of the resin layer 10 is preferably 3.0% or less. If the haze value of the resin layer is 3.0% or less, when the resin layer is used in a mobile terminal, whitening of the image display surface can be suppressed. The haze value is more preferably 2.0% or less, 1.5% or less, 1.0% or less, or 0.5% or less.

[0080] The haze value can be measured in an environment of a temperature of 23±5°C and a relative humidity of 30% to 70% using a haze meter (e.g., product name "HM-150", manufactured by Murakami Color Research Laboratory Co., Ltd.) by a method in accordance with JIS K7136: 2000. Specifically, the haze value is measured by the same method as the total light transmittance measurement method.

[0081] The film thickness of the resin layer 10 is preferably 20 μm or more and 150 μm or less. If the film thickness of the resin layer 10 is 20 μm or more, it can have excellent impact resistance. In addition, if the film thickness of the resin layer 10 is 150 μm or less, the resin layer 10 is difficult to break in 100,000 continuous folding tests and exhibits excellent performance. The lower limit of the film thickness of the resin layer 10 is more preferably 40 μm or more, or 50 μm or more. From the perspective of being suitable for thinning and having good processability, the upper limit of the resin layer 10 is more preferably 120 μm or less, 100 μm or less, 80 μm or less, or 60 μm or less.

[0082] The thickness of the resin layer 10 was determined by photographing a cross section of the resin layer 10 using a scanning electron microscope (SEM), measuring the thickness of the resin layer 10 at 10 locations in the cross-sectional image, and using the arithmetic mean of the thicknesses at the 10 locations.

[0083] The specific method for taking cross-sectional photographs is described below. First, a resin layer cut into a size of 1 mm × 10 mm is embedded in an embedding resin to make a block, and a uniform slice with a thickness of 70 nm to 100 nm without holes or the like is cut from the block using a general slice making method. The slices can be made using, for example, the Ultramicrotome EMUC7 of Leica Microsystems Co., Ltd. Then, the uniform slice without holes or the like is used as a measurement sample. Afterwards, a cross-sectional photograph of the measurement sample is taken using a scanning transmission electron microscope (STEM). As a scanning transmission electron microscope (STEM), the S-4800 manufactured by Hitachi High-Technologies Co., Ltd. can be cited. When taking cross-sectional photographs using the above-mentioned S-4800, the detector is set to "SE", the acceleration voltage is set to "5 kV", and the emission current is set to "10 μA" for cross-sectional observation. About magnification, adjust focal length, and observe whether each layer can be distinguished while appropriately adjusting contrast and brightness with 100 times to 100,000 times, preferably 500 times to 50,000 times, and more preferably 1000 times to 10,000 times. It should be noted that when using the above-mentioned S-4800 to take cross-sectional photos, the beam monitoring aperture can be further set to "3", the objective lens aperture is set to "3", and WD is set to "8mm". When measuring the film thickness of the resin layer, it is important to be able to clearly observe the interface contrast between the resin layer and other layers (such as embedding resin) as much as possible when performing cross-sectional observation. Assuming that the contrast is insufficient and it is difficult to see the interface, if dyeing is performed using osmium tetroxide, ruthenium tetroxide, phosphotungstic acid, etc., the interface between the organic layers is easy to see, so dyeing can also be performed. In addition, when the contrast of the interface is high magnification, it is sometimes difficult to distinguish. In this case, it is also observed at a low magnification. For example, observation is performed at two magnifications, 500 times and 10,000 times, 1000 times and 20,000 times, and the arithmetic mean is calculated at two magnifications, and the average is used as the film thickness of the resin layer.

[0084] The resin constituting the resin layer 10 is not particularly limited as long as it is a resin such as Hz that satisfies the above-mentioned relationship (1). As such a resin, a cured product (polymer) of an ionizing radiation curable compound (ionizing radiation polymerizable compound) and the like can be cited. As ionizing radiation in this specification, visible light, ultraviolet light, X-rays, electron beams, α-rays, β-rays and γ-rays can be cited. As a cured product of an ionizing radiation curable compound, a urethane resin, a silicone resin and the like can be cited.

[0085] (Urethane resin)

[0086] The urethane resin is a resin having a urethane bond. Examples of the urethane resin include a cured product of an ionizing radiation curable urethane resin composition or a cured product of a thermosetting urethane resin composition. Among them, a cured product of an ionizing radiation curable urethane resin composition is preferred because it has high hardness, a fast curing speed, and excellent mass productivity.

[0087] The ionizing radiation curable urethane resin composition comprises urethane (meth) acrylate, and the heat curable urethane resin comprises a polyol compound and an isocyanate compound. The urethane (meth) acrylate, the polyol compound and the isocyanate compound may be any of a monomer, an oligomer and a prepolymer.

[0088] The number of (meth)acryloyl groups (number of functional groups) in urethane (meth)acrylate is preferably 2 or more and 4 or less. If the number of (meth)acryloyl groups in urethane (meth)acrylate is less than 2, the pencil hardness may decrease. If it exceeds 4, the curing shrinkage increases, the optical film may curl, and the resin layer may crack when bent. The upper limit of the number of (meth)acryloyl groups in urethane (meth)acrylate is more preferably 3 or less. It should be noted that "(meth)acryloyl" means both "acryloyl" and "methacryloyl".

[0089] The weight average molecular weight of urethane (meth) acrylate is preferably 1500 or more and 20000 or less. If the weight average molecular weight of urethane (meth) acrylate is less than 1500, the impact resistance may be reduced. If it exceeds 20000, the viscosity of the ionizing radiation curable urethane resin composition increases and the coating property may be deteriorated. The lower limit of the weight average molecular weight of urethane (meth) acrylate is more preferably 2000 or more, and the upper limit is more preferably 15000 or less.

[0090] Examples of the repeating unit having a structure derived from urethane (meth)acrylate include structures represented by the following general formula (1), (2), (3) or (4).

[0091] [Chemistry 1]

[0092]

[0093] In the above general formula (1), R 1 represents a branched alkyl group, R 2 represents a branched alkyl group or a saturated cyclic aliphatic group, R 3 represents a hydrogen atom or a methyl group, R 4represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0 or greater, and x represents an integer of 0-3.

[0094] [Chemistry 2]

[0095]

[0096] In the above general formula (2), R 1 represents a branched alkyl group, R 2 represents a branched alkyl group or a saturated cyclic aliphatic group, R 3 represents a hydrogen atom or a methyl group, R 4 represents a hydrogen atom, a methyl group or an ethyl group, n represents an integer of 1 or more, and x represents an integer of 0-3.

[0097] [Chemistry 3]

[0098]

[0099] In the above general formula (3), R 1 represents a branched alkyl group, R 2 represents a branched alkyl group or a saturated cyclic aliphatic group, R 3 represents a hydrogen atom or a methyl group, R 4 represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0 or greater, and x represents an integer of 0-3.

[0100] [Chemistry 4]

[0101]

[0102] In the above general formula (4), R 1 represents a branched alkyl group, R 2 represents a branched alkyl group or a saturated cyclic aliphatic group, R 3 represents a hydrogen atom or a methyl group, R 4 represents a hydrogen atom, a methyl group or an ethyl group, n represents an integer of 1 or more, and x represents an integer of 0-3.

[0103] It should be noted that the polymer chain (repeating unit) of which the resin constituting the resin layer 10 is formed can be determined by analyzing the resin layer 10 using, for example, pyrolysis gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FT-IR). In particular, pyrolysis GC-MS is useful for detecting monomer units contained in the resin layer 10 as monomer components.

[0104] The resin layer 10 may contain, in addition to the resin, an ultraviolet absorber, a spectral transmittance adjuster, an antifouling agent, inorganic particles and / or organic particles, and the like.

[0105] <<<Optical Film>>>

[0106] Figure 3 The optical film 30 shown is a film of a laminated structure, and at least has a resin layer 10. In addition to the resin layer 10, the optical film 30 further has a functional layer 31 disposed on either the first surface 10A or the second surface 10B of the resin layer 10. The "functional layer" in this specification refers to a layer that exerts a certain function. The functional layer 31 is a single-layer structure, but it can also be a multilayer structure of more than two layers. In addition, the optical film 30 does not have a substrate.

[0107] The optical film 30 is foldable. Specifically, it is preferred that the optical film 30 is subjected to the folding test (continuous folding test) described below 100,000 times, 200,000 times, 500,000 times, or 1,000,000 times under an environment of a temperature of 23±5°C and a relative humidity of 30% to 70%, and in this case, the optical film 30 does not produce cracks or breaks. If the optical film 30 produces cracks or breaks when the optical film 30 is subjected to 100,000 continuous folding tests, the foldability of the optical film 30 is insufficient. It should be noted that the evaluation of the folding number of the above-mentioned continuous folding test is set to at least 100,000 times for the following reasons. For example, if it is assumed that the optical film is assembled into a foldable smartphone, the frequency of folding (opening and closing frequency) is very high. Therefore, in the evaluation in which the folding number of the above-mentioned continuous folding test is set to, for example, 10,000 times or 50,000 times, it is sometimes impossible to evaluate at a practical level. Specifically, for example, if it is assumed that a person who often uses a smartphone opens and closes the smartphone 5 to 10 times only when commuting on the morning train or bus, it is assumed that the smartphone will be opened and closed at least 30 times in just one day. Therefore, if it is assumed that the smartphone is opened and closed 30 times a day, the continuous folding test with 10,000 folding times is 30 times × 365 days = 10950 times, that is, it is assumed that the test is used for 1 year. That is, even if the result of the continuous folding test with 10,000 folding times is good, after 1 year, the optical film may also have creases or cracks. Therefore, the evaluation of the number of folding times of 10,000 times in the continuous folding test can only confirm the level that cannot be used as a product. The situation that can be used but not sufficient will also become a good result and cannot be evaluated. Therefore, in order to evaluate whether it is a practical level, the number of folding times of the above-mentioned continuous folding test needs to be evaluated at least 100,000 times. When the optical film 30 is subjected to a continuous folding test, it is more preferred that the bending portion does not deform. The continuous folding test may be performed by folding the optical film 30 with the surface 30A facing outward, or by folding the optical film 30 with the surface 30A facing inward. In either case, it is preferred that the optical film 30 does not crack or break.

[0108] The continuous folding test was performed as follows. Figure 4As shown in (A), in the continuous folding test, first, a sample S having a size of 30 mm × 100 mm is cut out from the optical film 30. It should be noted that when it is impossible to cut out a sample S having a size of 30 mm × 100 mm from the optical film 30, for example, the sample S may be cut into a size of 10 mm × 100 mm. Then, the side S1 and the side S2 opposite to the side S1 of the cut sample S are respectively fixed by the fixing parts 40 and 45 of a parallel-arranged folding durability testing machine (for example, product name "U-shaped telescopic testing machine DLDMLH-FS", manufactured by YUASA SYSTEM Co., Ltd., in accordance with IEC62715-6-1). The fixing by the fixing parts 40 and 45 is performed by maintaining a portion of the sample S of approximately 10 mm on one side in the length direction of the sample S. In addition, when the sample S is smaller than the above-mentioned size, if the portion of the sample S required for the fixing is approximately 20 mm at most, it can be measured by sticking it to the fixing parts 40 and 45 with tape. In addition, as Figure 4 As shown in (A), the fixing part 40 can slide in the horizontal direction. It should be noted that the above device is preferred because it does not generate tension or friction on the sample, unlike the conventional method of winding the sample around a rod, and can perform durability evaluation of bending load.

[0109] Then, if Figure 4 As shown in (B), the fixing part 40 is moved so as to approach the fixing part 45, thereby folding the central part of the sample S to deform it, and then Figure 4 As shown in (C), the fixing unit 40 is moved to the interval between the two opposing sides S1 and S2 of the sample S fixed by the fixing units 40 and 45. After reaching the position of 10 mm, the fixing portion 40 is moved in the opposite direction to release the deformation of the optical film 30 .

[0110] Through Figure 4 By moving the fixing part 40 as shown in (A) to (C), the central part of the sample S can be folded 180 degrees. In addition, the bending part S3 of the sample S is not exposed from the lower end of the fixing parts 40 and 45, and the continuous folding test is carried out under the following conditions, and the interval when the fixing parts 40 and 45 are closest to each other is measured. By controlling the distance between the two opposing sides S1 and S2 of the sample S, In this case, the outer diameter of the curved portion S3 is 10 mm. In the sample S, it is preferred that the distance between the opposite sides of the sample S be 10 mm. The folding test of 180° is repeated 100,000 times without cracking or breaking. It is more preferable to adjust the interval between the opposite sides S1 and S2 of the sample S to 10 mm. When the continuous folding test of 180° is repeated 100,000 times in the form of 8mm or 6mm, no cracks or breaks occur.

[0111] (folding condition)

[0112] Reciprocating speed: 40rpm (times / minute)

[0113] Test stroke: 60mm

[0114] Bending angle: 180°

[0115] The surface 30A of the optical film 30 (the surface 31A of the functional layer 31) has a hardness (pencil hardness) of preferably 3H or more, more preferably 4H or more, when measured by a pencil hardness test specified in JIS K5600-5-4:1999. The pencil hardness test is performed by fixing the optical film 30 cut into a size of 30 mm×100 mm on a glass plate without folds or wrinkles using Cellotape (registered trademark) manufactured by Michiban Co., Ltd., and then, under an environment of a temperature of 23±5° C. and a relative humidity of 30% to 70%, applying a load of 750 g to a pencil (e.g., product name “Uni” manufactured by Mitsubishi Pencil Co., Ltd.) on the surface 30A of the optical film 30 using a pencil hardness tester (e.g., product name “Pencil Scratch Coating Hardness Tester (Electric)” manufactured by Toyo Seiki Seisaku-sho Co., Ltd.) and moving the pencil at a moving speed of 1 mm / sec. The pencil hardness is set to the highest hardness at which no scratch is produced on the surface of the optical film in the pencil hardness test. It should be noted that when measuring the pencil hardness, multiple pencils of different hardness are used, and the pencil hardness test is performed 5 times with each pencil. If no scratch is produced on the surface of the optical film in 4 or more of the 5 times, it is judged that no scratch is produced on the surface of the optical film under the pencil of the hardness. The above-mentioned scratches refer to the scratches observed on the surface of the optical film subjected to the pencil hardness test under fluorescent light.

[0116] The total light transmittance of the optical film 30 is preferably 85% or more, more preferably 87% or more, 88% or more, or 90% or more for the same reasons as described in the column of the resin layer 10. The total light transmittance of the optical film 30 is measured by the same method as the method for measuring the total light transmittance of the resin layer 10.

[0117] The haze value (total haze value) of the optical film 30 is preferably 3.0% or less, more preferably 2.0% or less, 1.5% or less, 1.0% or less, or 0.5% or less for the same reasons as those described in the column of the resin layer 10. The haze value of the optical film 30 is measured by the same method as the method for measuring the haze value of the resin layer 10.

[0118] When other films such as polarizers are provided on the surface 30A side or the back side 30B side of the optical film 30 via an adhesive layer or bonding layer, the other films are peeled off together with the adhesive layer or bonding layer, and then a folding test, a total light transmittance measurement, a haze value measurement, etc. are performed. It should be noted that even if there is such a peeling process, it will not have a great impact on these tests and these measurements. The haze value is measured after the adhesive layer or bonding layer is peeled off and the dirt on the adhesive layer or bonding layer is fully wiped off with alcohol.

[0119] The use of the optical film 30 is not particularly limited. Examples of the use of the optical film 30 include image display devices such as smartphones, tablet terminals, personal computers (PCs), wearable terminals, digital signage, televisions, and car navigation. In addition, the optical film 30 is also suitable for vehicle use. It is also preferred that the above-mentioned image display devices be used in applications that require flexibility such as foldable and retractable.

[0120] The optical film 30 can be cut into a desired size or in a roll. When the optical film 30 is cut into a desired size, the size of the optical film is not particularly limited and is appropriately determined according to the size of the display surface of the image display device. Specifically, the size of the optical film 30 can be, for example, 2.8 inches or more and 500 inches or less. Regarding the "inch" in this specification, when the optical film is a quadrilateral, it refers to the length of the diagonal, when the optical film is a circle, it refers to the diameter, and when the optical film is an ellipse, it refers to the average value of the sum of the short diameter and the long diameter. Here, when the optical film is a quadrilateral, the aspect ratio of the optical film when the above-mentioned inch is obtained is not particularly limited as long as there is no problem as a display screen of the image display device. For example, vertical: horizontal = 1:1, 4:3, 16:10, 16:9, 2:1, etc. can be cited. However, especially in design-rich vehicle-mounted uses or digital signage, it is not limited to such an aspect ratio. In addition, when the size of the optical film 30 is large, it is cut into the size of each measurement item after being cut out from an arbitrary position in A5 size (148 mm×210 mm). It should be noted that, for example, when the optical film 30 is in a roll, a predetermined length is drawn out from the roll of the optical film 30, and the desired size is cut out from the effective area near the center part where the quality is stable, rather than from the ineffective area including the two ends extending along the length direction of the roll.

[0121] The optical film 30 in the image display device can be disposed inside the image display device, but is preferably near the surface of the image display device. When used near the surface of the image display device, the optical film 30 functions as a protective film (window film) used instead of protective glass.

[0122] <<Functional Layer>>

[0123] The functional layer 31 is preferably provided on the first surface 10A side, that is, the first region 10C side, of the resin layer 10. By providing the functional layer 31 on the first region 10C side in this way, excellent scratch resistance is achieved while maintaining excellent foldability.

[0124] Figure 3 The functional layer 31 shown is a layer mainly used to impart hardness to the optical film 30, specifically, a layer that functions as a hard coating. However, the functional layer 31 may also be a layer having other functions. The "hard coating" in the present embodiment refers to a layer having a Martens hardness (HM) of 375 MPa or more at the center of the cross section of the functional layer. The "Martens hardness" in this specification refers to the hardness when the indenter is pressed into 500 nm by hardness measurement using the nanoindentation method. The above-mentioned measurement of the Martens hardness using the nanoindentation method is performed on an optical film cut into a size of 30 mm × 30 mm using the "TI950TriboIndenter" manufactured by Bruker. That is, under the following measurement conditions, the Bosch indenter (triangular pyramid, such as TI-0039 manufactured by Bruker) as the above-mentioned indenter is vertically pressed into 500 nm in the cross section of the functional layer. Here, in order to avoid the influence of the side edge of the resin layer or the functional layer, the Bosch indenter was pressed into the functional layer portion with a distance of 500 nm from the interface between the resin layer and the functional layer to the center of the functional layer, and a distance of more than 500 nm from both ends of the functional layer to the center of the functional layer. After that, the residual stress was kept constant to relax, and then unloaded, and the maximum load after relaxation was measured, and the maximum load P was used as the max and a depression area A with a depth of 500 nm, through P max / A calculates the Martens hardness. The Martens hardness is the arithmetic mean of the values ​​measured at 10 locations. It should be noted that when the measured value contains a value that deviates from the arithmetic mean by more than ±20%, the measured value is removed and the measurement is repeated. As to whether there is a value that deviates from the arithmetic mean by more than ±20% in the measured value, when the measured value is set to A and the arithmetic mean is set to B, it is judged by whether the value (%) calculated by (A-B) / B×100 is more than ±20%.

[0125] (Measurement conditions)

[0126] Control method: displacement control

[0127] Loading speed: 10nm / sec

[0128] Hold time: 5 seconds

[0129] Unloading speed: 10nm / sec

[0130] ·Measurement temperature: 23±5℃

[0131] ·Measurement humidity: 30%~70%

[0132] The Martens hardness of the functional layer 31 is preferably 375 MPa or more and 1500 MPa or less. If the Martens hardness of the functional layer 31 is 375 MPa or more, good hardness can be obtained, and if it is 1500 MPa or less, good folding performance can be obtained.

[0133] The thickness of the functional layer 31 is preferably 3 μm or more and 10 μm or less. If the thickness of the functional layer 31 is 3 μm or more, good hardness can be obtained, and if it is 10 μm or less, the deterioration of processability can be suppressed. In the case where the functional layer is a multilayer structure, the "thickness of the functional layer" in this specification refers to the thickness of the thickness of each functional layer combined (total thickness). The lower limit of the thickness of the functional layer 31 is more preferably 4 μm or more, or 5 μm or more, and the upper limit is more preferably 8 μm or less, or 7 μm or less.

[0134] Regarding the film thickness of the functional layer 31, a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM) is used to photograph the cross section of the functional layer 31, and the film thickness of the functional layer 31 at 10 locations is measured in the image of the cross section, and the arithmetic mean of the film thickness of the 10 locations is adopted. When measuring the film thickness of the functional layer 31, first, a measurement sample prepared by the same method as the resin layer 10 is prepared. Thereafter, a cross-sectional photograph of the measurement sample is taken using a scanning transmission electron microscope (STEM) (for example, product name "S-4800", manufactured by Hitachi High-Technologies Co., Ltd.). When taking a cross-sectional photograph using the above-mentioned S-4800, the detector is set to "TE", the acceleration voltage is set to "30kV", and the emission current is set to "10μA" for cross-sectional observation. Regarding the magnification, the focal length is adjusted, and the contrast and brightness are appropriately adjusted from 5000 times to 200,000 times while observing whether each layer can be distinguished. The preferred magnification is 10,000 times to 100,000 times, the more preferred magnification is 10,000 times to 50,000 times, and the most preferred magnification is 25,000 times to 50,000 times. It should be noted that when using the above-mentioned S-4800 to take cross-sectional photos, the beam monitoring aperture can be further set to "3", the objective lens aperture is set to "3", and WD is set to "8mm". When measuring the film thickness of the functional layer, it is important to be able to clearly observe the interface contrast between the functional layer and other layers (such as resin layer) as much as possible when performing cross-sectional observation. Assuming that the contrast is insufficient and it is difficult to see the interface, if dyeing is performed using osmium tetroxide, ruthenium tetroxide, phosphotungstic acid, etc., the interface between the organic layers is easy to see, so dyeing can also be performed. In addition, when the contrast of the interface is high magnification, it is sometimes difficult to distinguish. In this case, it is also observed at a low magnification. For example, observation is performed at two magnifications, 25,000 and 50,000, 50,000 and 100,000, and the arithmetic mean is calculated at two magnifications, and the average is used as the film thickness of the functional layer.

[0135] The functional layer 31 preferably further contains a resin and inorganic particles dispersed in the resin.

[0136] <Resin>

[0137] The resin contains a polymer (cured product) of a polymerizable compound (curable compound). A polymerizable compound is a compound having at least one polymerizable functional group in the molecule. Examples of the polymerizable functional group include ethylenically unsaturated groups such as (meth)acryloyl, vinyl, and allyl.

[0138] As the polymerizable compound, a multifunctional (meth)acrylate is preferred. Examples of the multifunctional (meth)acrylate include trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, tri ...propylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, Pentaerythritol octa(meth)acrylate, pentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, isocyanuric acid di(meth)acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerol tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, or those modified with PO, EO, caprolactone, etc.

[0139] Among them, because the above-mentioned Martens hardness can be appropriately satisfied, tri- to hexa-functional substances are preferred, for example, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), trimethylolpropane tri(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, etc. It should be noted that in this specification, (meth)acrylate refers to acrylate and methacrylate.

[0140] It should be noted that a monofunctional (meth)acrylate monomer may be further included in order to adjust the hardness or viscosity of the composition, improve adhesion, etc. Examples of the monofunctional (meth)acrylate monomer include hydroxyethyl acrylate (HEA), glycidyl methacrylate, methoxypolyethylene glycol (meth)acrylate, isostearyl (meth)acrylate, 2-acryloyloxyethyl succinate, acryloylmorpholine, N-acryloyloxyethyl hexahydrophthalimide, cyclohexyl acrylate, tetrahydrofuranyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, and adamantyl acrylate.

[0141] From the perspective of improving the hardness of the resin layer, the weight average molecular weight of the monomer is preferably less than 1000, more preferably 200 to 800. In addition, the weight average molecular weight of the polymerizable oligomer is preferably 1000 to 20,000, more preferably 1000 to 10,000, and further preferably 2000 to 7000.

[0142] <Inorganic particles>

[0143] As inorganic particles, there is no particular limitation as long as they can improve the hardness. From the perspective of obtaining excellent hardness, silica particles are preferred. Among the silica particles, active silica particles are preferred. The active silica particles are silica particles that can form a cross-linked structure with the multifunctional (meth)acrylate. By containing the active silica particles, the hardness of the functional layer 31 can be fully improved.

[0144] The active silica particles preferably have a reactive functional group on the surface thereof, and as the reactive functional group, for example, the polymerizable functional group described above is preferably used.

[0145] The above-mentioned active silica particles are not particularly limited, and conventionally known active silica particles can be used, and examples thereof include the active silica particles described in Japanese Patent Application Laid-Open No. 2008-165040. In addition, commercially available products of the above-mentioned active silica particles include, for example, MIBK-SD, MIBK-SD-MS, MIBK-SD-L, MIBK-SD-ZL (all manufactured by Nissan Chemical Industries, Ltd.), V8802, and V8803 (all manufactured by JGC Catalysts & Chemicals Co., Ltd.).

[0146] In addition, the above-mentioned silica particles can be spherical silica particles, but are preferably irregular silica particles. Spherical silica particles can also be mixed with irregular silica particles. It should be noted that the "spherical silica particles" in this specification refer to silica particles such as spherical, ellipsoidal, etc., and "irregular silica particles" refer to silica particles with irregular concave and convex shapes on the surface having a potato shape (the aspect ratio when observed in cross section is 1.2 or more and 40 or less). The above-mentioned irregular silica particles have a larger surface area than spherical silica particles, and thus by containing such irregular silica particles, the contact area with the above-mentioned multifunctional (meth) acrylates, etc. is increased, and the hardness of the above-mentioned hard coating can be improved. Whether the silica particles contained in the functional layer are irregular silica particles can be confirmed by observing the cross section of the functional layer using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM).

[0147] The average particle size of the silica particles is preferably 5 nm or more and 200 nm or less. If the average particle size of the silica particles is 5 nm or more, the manufacture of the particles themselves will not become difficult, the agglomeration of the particles can be suppressed, and it will not be difficult to form irregular shapes. On the other hand, if the average particle size of the irregularly shaped silica particles is 200 nm or less, the formation of large concave-convex surfaces in the functional layer can be suppressed, and the increase in haze can also be suppressed. In the case where the silica particles are spherical silica particles, the average particle size of the silica particles is measured by using a cross-sectional image of the particles taken using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), and the arithmetic mean of the particle sizes of the 20 particles is used. In addition, when the silica particles are irregular silica particles, the average particle size of the silica particles is determined by measuring the maximum value (long axis) and the minimum value (short axis) of the distance between two points on the periphery of the particles from a cross-sectional image of the hard coating layer taken using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), averaging the measured values ​​to determine the particle size, and using the arithmetic mean value of the particle sizes of 20 particles.

[0148] By controlling the size and amount of the inorganic particles, the hardness (Martens hardness) of the functional layer 31 can be controlled. For example, when forming the functional layer 31, the silica particles preferably have a diameter of 5 nm to 200 nm and are present in an amount of 25 to 60 parts by mass based on 100 parts by mass of the polymerizable compound.

[0149] Functional layer 31 may include materials other than the above materials within the range satisfying the above Martens hardness. For example, as a material of a resin component, a polymerizable monomer, a polymerizable oligomer, etc., which form a cured product by irradiation with ionizing radiation may be included. As the above polymerizable monomer or polymerizable oligomer, for example, a (meth) acrylate monomer having a free radical polymerizable unsaturated group in the molecule or a (meth) acrylate oligomer having a free radical polymerizable unsaturated group in the molecule may be cited. As the (meth) acrylate monomer having a free radical polymerizable unsaturated group in the above molecule or a (meth) acrylate oligomer having a free radical polymerizable unsaturated group in the molecule, for example, monomers or oligomers such as urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, melamine (meth) acrylate, polyfluoroalkyl (meth) acrylate, and silicone (meth) acrylate may be cited. These polymerizable monomers or polymerizable oligomers may be used in one or in combination of two or more. Among them, polyfunctional (hexafunctional or higher) urethane (meth)acrylates having a weight average molecular weight of 1,000 to 10,000 are preferred.

[0150] The functional layer 31 may further contain an ultraviolet absorber, a spectral transmittance adjuster and / or an antifouling agent.

[0151] <<<Other optical films>>>

[0152] Figure 3 The optical film 30 shown does not have a substrate, but may also be Figure 5 The optical film 50 shown in FIG. Figure 5 As shown, the optical film 50 includes a resin layer 10, a resin substrate 51, and a functional layer 52 in this order. The resin substrate 51 is preferably disposed on the first surface 10A side of the resin layer 10. It should be noted that in the optical film 50, the resin layer 10 is directly disposed on the resin substrate 51, but may also be attached to the resin substrate via an adhesive layer.

[0153] The surface 50A of the optical film 50 becomes the surface 52A of the functional layer 52. In this specification, the surface of the optical film is used to mean the surface of one side of the optical film, and the surface on the opposite side to the surface of the optical film is called the back surface to distinguish it from the surface of the optical film. The back surface 50B of the optical film 50 becomes the second surface 10B of the resin layer 10.

[0154] The optical film 50 is also foldable in the same manner as the optical film 30. Preferred number of folds and preferred spacing between the facing sides The conditions of the continuous folding test are the same as those of the optical film 30, so the description thereof is omitted here.

[0155] The hardness (pencil hardness) of surface 50A of optical film 50 (surface 52A of functional layer 52 ) measured by the pencil hardness test specified in JIS K5600-5-4:1999 is preferably 2B or more. The pencil hardness of optical film 50 is measured by the same method as the pencil hardness of optical film 30 .

[0156] The yellow index (YI) of the optical film 50 is preferably 15 or less. If the YI of the optical film 50 is 15 or less, the yellow tint of the optical film can be suppressed, and it can be applied to applications requiring transparency. The upper limit of the yellow index (YI) of the optical film 50 is more preferably 10 or less, 5 or less, or 1.5 or less. The yellowness index (YI) is a value calculated as follows: in an environment of a temperature of 23±5°C and a relative humidity of 30% to 70%, the optical film cut into a size of 50 mm×100 mm is placed in a spectrophotometer (e.g., product name “UV-2450”, manufactured by Shimadzu Corporation, light source: tungsten lamp and deuterium lamp), the chromaticity tristimulus values ​​X, Y, and Z are calculated according to the calculation formula described in JISZ8722:2009 from the transmittance of the optical film at a wavelength of 300 nm to 780 nm measured in accordance with the calculation formula described in ASTM D1925:1962, and the yellowness index (YI) is calculated from the tristimulus values ​​X, Y, and Z according to the calculation formula described in ASTM D1925:1962. The upper limit of the yellowness index (YI) of the optical film 50 is more preferably 10 or less. The yellowness index (YI) is as follows: one optical film is measured three times, and the arithmetic average of the values ​​obtained by the three measurements is taken as the yellowness index (YI). It should be noted that the yellow index is calculated as follows under UV-2450: on the monitor connected to UV-2450, read the above transmittance measurement data, confirm the "YI" item in the calculation items, and calculate the yellow index. The transmittance at a wavelength of 300nm to 780nm is measured as follows: under the following conditions, the transmittance of the lowest 5 points is measured between 1nm before and after each wavelength of 300nm to 780nm, and the average value is calculated to obtain the yellow index. In addition, if there is waviness in the spectrum of the spectral transmittance, it can be smoothed using Δ5.0nm.

[0157] (Measurement conditions)

[0158] Wavelength range: 300nm~780nm

[0159] Scanning speed: high speed

[0160] Slit width: 2.0

[0161] Sampling interval: automatic (0.5nm interval)

[0162] Lighting: C

[0163] Light source: D2 and WI

[0164] Field of view: 2°

[0165] Light source switching wavelength: 360nm

[0166] S / R switch: Standard

[0167] Detector: PM

[0168] Automatic zeroing: performed at 550nm after scanning the baseline

[0169] The total light transmittance of the optical film 50 is preferably 85% or more, preferably 87% or more, or 90% or more for the same reasons as described in the column of the resin layer 10. The total light transmittance of the optical film 50 is measured by the same method as the total light transmittance of the resin layer 10.

[0170] The haze value (total haze value) of the optical film 50 is preferably 3.0% or less, more preferably 2.0% or less, 1.5% or less, 1.0% or less, or 0.5% or less for the same reasons as those described in the column of the resin layer 10. The haze value of the optical film 50 is measured by the same method as the method for measuring the haze value of the resin layer 10.

[0171] <<Resin base material>>

[0172] The resin substrate 51 has light-transmitting properties and preferably includes one or more resins selected from the group consisting of, for example, polyimide resins, polyamide-imide resins, polyamide resins, and polyester resins (eg, polyethylene terephthalate resins and polyethylene naphthalate resins).

[0173] Among these resins, polyimide resins, polyamide resins or mixtures thereof are preferred because they are not easily cracked or broken in a continuous folding test, have excellent hardness and transparency, have excellent heat resistance, and can be given even better hardness and transparency by firing.

[0174] The polyimide resin is obtained by reacting a tetracarboxylic acid component with a diamine component. The polyimide resin is not particularly limited, and for example, from the viewpoint of having excellent light transmittance and excellent rigidity, it is preferred to have at least one structure selected from the group consisting of structures represented by the following general formula (5) and the following general formula (7).

[0175] [Chemistry 5]

[0176]

[0177] In the above general formula (5), R 5 represents a tetravalent group as a tetracarboxylic acid residue, R 6It represents at least one divalent group selected from the group consisting of trans-cyclohexanediamine residue, trans-1,4-dimethoxycyclohexanediamine residue, 4,4'-diaminodiphenyl sulfone residue, 3,4'-diaminodiphenyl sulfone residue, and divalent groups represented by the following general formula (6). n represents the number of repeating units, which is 1 or more. In this specification, "tetracarboxylic acid residue" refers to the residue after removing four carboxyl groups from tetracarboxylic acid, and represents the same structure as the residue after removing the dianhydride structure from tetracarboxylic dianhydride. In addition, "diamine residue" refers to the residue after removing two amino groups from diamine.

[0178] [Chemistry 6]

[0179]

[0180] In the above general formula (6), R 7 and R 8 Each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.

[0181] [Chemistry 7]

[0182]

[0183] In the above general formula (7), R 9 represents at least one tetravalent group selected from the group consisting of a cyclohexanetetracarboxylic acid residue, a cyclopentanetetracarboxylic acid residue, a dicyclohexane-3,4,3',4'-tetracarboxylic acid residue and a 4,4'-(hexafluoroisopropylidene)diphthalic acid residue, and R 10 represents a divalent group which is a diamine residue. n' represents the number of repeating units and is 1 or more.

[0184] In the above general formula (5), R 5 is a tetracarboxylic acid residue, and may be a residue obtained by removing the dianhydride structure from the above-mentioned tetracarboxylic dianhydride. 5 , wherein, from the perspective of improving light transmittance and improving rigidity, it is preferred to include at least one selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic acid residues, 3,3',4,4'-biphenyltetracarboxylic acid residues, pyromellitic acid residues, 2,3',3,4'-biphenyltetracarboxylic acid residues, 3,3',4,4'-benzophenonetetracarboxylic acid residues, 3,3',4,4'-diphenylsulfonetetracarboxylic acid residues, 4,4'-oxydiphthalic acid residues, cyclohexanetetracarboxylic acid residues and cyclopentanetetracarboxylic acid residues, and further preferably includes at least one selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic acid residues, 4,4'-oxydiphthalic acid residues and 3,3',4,4'-diphenylsulfonetetracarboxylic acid residues.

[0185] R 5The total amount of these preferred residues is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more.

[0186] In addition, as R 5 It is also preferred to mix the following group A and group B, wherein group A is a tetracarboxylic acid residue group selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic acid residues, 3,3',4,4'-benzophenonetetracarboxylic acid residues and pyromellitic acid residues, and at least one such tetracarboxylic acid residue group suitable for improving rigidity, and group B is a tetracarboxylic acid residue group selected from the group consisting of 4,4'-(hexafluoroisopropyl)diphthalic acid residues, 2,3',3,4'-biphenyltetracarboxylic acid residues, 3,3',4,4'-diphenylsulfonetetracarboxylic acid residues, 4,4'-oxydiphthalic acid residues, cyclohexanetetracarboxylic acid residues and cyclopentanetetracarboxylic acid residues, and at least one such tetracarboxylic acid residue group suitable for improving transparency.

[0187] In this case, regarding the content ratio of the tetracarboxylic acid residue group (group A) suitable for improving rigidity and the tetracarboxylic acid residue group (group B) suitable for improving transparency, the tetracarboxylic acid residue group (group A) suitable for improving rigidity is preferably 0.05 mol to 9 mol, more preferably 0.1 mol to 5 mol, and even more preferably 0.3 mol to 4 mol, per 1 mol of the tetracarboxylic acid residue group (group B) suitable for improving transparency.

[0188] As R in the above general formula (5) 2 In terms of improving light transmittance and rigidity, at least one divalent group selected from the group consisting of a 4,4'-diaminodiphenyl sulfone residue, a 3,4'-diaminodiphenyl sulfone residue and a divalent group represented by the general formula (6) is preferred, and more preferably selected from the group consisting of a 4,4'-diaminodiphenyl sulfone residue, a 3,4'-diaminodiphenyl sulfone residue, and R 7 and R 8 At least one divalent group selected from the group consisting of divalent groups represented by the above general formula (6) which is a perfluoroalkyl group.

[0189] As R in the above general formula (7) 9 Among them, from the viewpoint of improving light transmittance and rigidity, it is preferred to contain a 4,4′-(hexafluoroisopropylidene)diphthalic acid residue, a 3,3′,4,4′-diphenylsulfonetetracarboxylic acid residue, and an oxydiphthalic acid residue.

[0190] R 9 The preferred residues are preferably contained in an amount of 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more.

[0191] In the above general formula (7), R10 is a diamine residue, and may be a residue obtained by removing two amino groups from the above-mentioned diamine. 10 , wherein, from the perspective of improving light transmittance and rigidity, it is preferred to include a 2,2'-bis(trifluoromethyl)benzidine residue, a bis[4-(4-aminophenoxy)phenyl]sulfone residue, a 4,4'-diaminodiphenylsulfone residue, a 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane residue, a bis[4-(3-aminophenoxy)phenyl]sulfone residue, a 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether residue, a 1,4-bis[4-amino-2-(trifluoromethyl)phenoxy]benzene residue, a 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane residue, a bis[4-(3-aminophenoxy)phenyl]sulfone residue, a 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether residue, a 1,4-bis[4-amino-2-(trifluoromethyl)phenoxy]benzene residue, a 2,2-bis[4-(4- The present invention further preferably contains at least one divalent group selected from the group consisting of a 2,2'-bis(trifluoromethyl)benzidine residue, a bis[4-(4-aminophenoxy)phenyl]sulfone residue and a 4,4'-diaminodiphenyl sulfone residue.

[0192] R 10 The total amount of these preferred residues is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more.

[0193] In addition, as R 10 It is also preferred to use the following group C mixed with group D, wherein group C is a diamine residue group suitable for improving rigidity selected from the group consisting of bis[4-(4-aminophenoxy)phenyl]sulfone residue, 4,4'-diaminobenzanilide residue, N,N'-bis(4-aminophenyl)terephthalamide residue, p-phenylenediamine residue, m-phenylenediamine residue and 4,4'-diaminodiphenylmethane residue, and group D is a diamine residue selected from the group consisting of 2,2'-bis(trifluoromethyl)benzidine residue, 4,4'-diaminodiphenylsulfone residue, 2,2-bis[4-(4-aminophenyl)terephthalamide residue, p-phenylenediamine residue, m-phenylenediamine residue and 4,4'-diaminodiphenylmethane residue. The invention also provides a diamine residue group suitable for improving transparency, which comprises at least one of the group consisting of a bis[4-(3-aminophenoxy)phenyl]hexafluoropropane residue, a bis[4-(3-aminophenoxy)phenyl]sulfone residue, a 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether residue, a 1,4-bis[4-amino-2-(trifluoromethyl)phenoxy]benzene residue, a 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane residue, a 4,4'-diamino-2-(trifluoromethyl)diphenyl ether residue and a 9,9-bis(4-aminophenyl)fluorene residue.

[0194] In this case, regarding the content ratio of the above-mentioned diamine residue group (group C) suitable for improving rigidity and the diamine residue group (group D) suitable for improving transparency, the above-mentioned diamine residue group (group C) suitable for improving rigidity is preferably 0.05 mol to 9 mol, more preferably 0.1 mol to 5 mol, and even more preferably 0.3 mol to 4 mol, relative to 1 mol of the diamine residue group (group D) suitable for improving transparency.

[0195] In the structures represented by the general formula (5) and the general formula (7), n and n' each independently represent the number of repeating units and are 1 or more. The number of repeating units n in the polyimide can be appropriately selected according to the structure so as to exhibit the preferred glass transition temperature described later, and is not particularly limited. The average number of repeating units is usually 10 to 2000, and more preferably 15 to 1000.

[0196] The polyimide resin may contain a polyamide structure in part thereof. Examples of the polyamide structure that may be contained include a polyamideimide structure containing a tricarboxylic acid residue such as trimellitic anhydride, or a polyamide structure containing a dicarboxylic acid residue such as terephthalic acid.

[0197] From the viewpoint of heat resistance, the glass transition temperature of the polyimide resin is preferably 250° C. or higher, more preferably 270° C. or higher. On the other hand, from the viewpoint of ease of stretching or reduction of baking temperature, the glass transition temperature is preferably 400° C. or lower, more preferably 380° C. or lower.

[0198] Examples of the polyimide resin include compounds having a structure represented by the following chemical formula: In the following chemical formula, n is a repeating unit and represents an integer of 2 or more.

[0199] [Chemistry 8]

[0200]

[0201] [Chemistry 9]

[0202]

[0203] [Chemistry 10]

[0204]

[0205] [Chemistry 11]

[0206]

[0207] [Chemistry 12]

[0208]

[0209] [Chemistry 13]

[0210]

[0211] [Chemistry 14]

[0212]

[0213] [Chemistry 15]

[0214]

[0215] [Chemistry 16]

[0216]

[0217] [Chemistry 17]

[0218]

[0219] [Chemistry 18]

[0220]

[0221] [Chemistry 19]

[0222]

[0223] [Chemistry 20]

[0224]

[0225] [Chemistry 21]

[0226]

[0227] [Chemistry 22]

[0228]

[0229] [Chemistry 23]

[0230]

[0231] [Chemistry 24]

[0232]

[0233] Among the above-mentioned polyimide resins, polyimide resins or polyamide resins having a structure that is not prone to charge transfer within or between molecules are preferred because of their excellent transparency. Specifically, fluorinated polyimide resins such as those of the above-mentioned chemical formulas (8) to (15) and polyimide resins having an alicyclic structure such as those of the above-mentioned formulas (15) to (19) are included.

[0234] Furthermore, the fluorinated polyimide resins of the chemical formulas (8) to (15) have a fluorinated structure and therefore have high heat resistance. They are also not colored by heat during the production of a polyimide film containing the polyimide resin and therefore have excellent transparency.

[0235] Polyamide resin is a concept that includes not only aliphatic polyamide but also aromatic polyamide (aramid). Examples of polyamide resin include compounds having skeletons represented by the following chemical formulas (25) to (27). It should be noted that in the following formula, n is a repeating unit and represents an integer greater than 2.

[0236] [Chemistry 25]

[0237]

[0238] [Chemistry 26]

[0239]

[0240] [Chemistry 27]

[0241]

[0242] The substrate comprising the polyimide resin or polyamide resin represented by the chemical formulas (8) to (24) and (27) may be a commercially available substrate. Examples of commercially available substrates comprising the polyimide resin include Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd., and examples of commercially available substrates comprising the polyamide resin include Mictron (registered trademark) manufactured by Toray Industries, Inc.

[0243] In addition, the polyimide resin or polyamide resin represented by the above chemical formulas (8) to (24) and (27) may be a resin synthesized by a known method. For example, the synthesis method of the polyimide resin represented by the above chemical formula (8) is described in Japanese Patent Application Laid-Open No. 2009-132091, and specifically, it can be obtained by reacting 4,4'-hexafluoropropylene diphthalic anhydride (FPA) represented by the following chemical formula (28) with 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB).

[0244] [Chemistry 28]

[0245]

[0246] The weight average molecular weight of above-mentioned polyimide resin or polyamide resin is preferably the scope of more than 3000 and less than 500,000, more preferably the scope of more than 5000 and less than 300,000, more preferably the scope of more than 10,000 and less than 200,000.If weight average molecular weight is less than 3000, sufficient intensity can not be obtained sometimes, if it exceeds 500,000, then viscosity rises, solubility reduces, therefore can not obtain the substrate of surface smoothness, uniform film thickness sometimes.It should be noted that, in this specification, " weight average molecular weight " refers to the polystyrene conversion value measured by gel permeation chromatography (GPC).

[0247] As for the resin substrate 51, from the perspective of improving hardness, it is preferred to use a substrate comprising a fluorinated polyimide resin represented by the above chemical formulas (8) to (15) or a polyamide resin having a halogen group represented by the above chemical formula (27). Among them, from the perspective of further improving hardness, it is more preferred to use a substrate comprising a polyimide resin represented by the above chemical formula (8).

[0248] Examples of the polyester-based resin include resins containing at least one of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as a constituent component.

[0249] The thickness of the resin substrate 51 is preferably not less than 10 μm and not more than 100 μm. If the thickness of the resin substrate 51 is not less than 10 μm, the curling of the optical film can be suppressed, and sufficient hardness can be obtained, and even when the optical film is manufactured by a roll-to-roll method, wrinkles are difficult to form, and there is no need to worry about deterioration of the appearance. On the other hand, if the thickness of the resin substrate 51 is not more than 100 μm, the folding performance of the optical film 50 is good, and the conditions of the continuous folding test can be met. In addition, it is preferred in terms of lightweighting of the optical film 50. The thickness of the resin substrate 51 can be measured by the same method as the film thickness of the resin layer 10. The lower limit of the resin substrate 51 is more preferably not less than 20 μm, not less than 30 μm, or not less than 40 μm, and the upper limit of the resin substrate 51 is more preferably not more than 80 μm, or not more than 50 μm.

[0250] <Functional Layer>

[0251] The functional layer 52 is the same as the functional layer 31 , and therefore the description thereof is omitted here.

[0252] <<<Method for producing resin layer and optical film>>>

[0253] The resin layer 10 and the optical films 30 and 50 can be produced as follows: When producing the resin layer 10 and the optical film 30, first, a coating film is formed by applying the resin layer composition on one surface of a release film using a coating device such as a bar coater.

[0254] <<Resin layer composition>>

[0255] The resin layer composition contains at least an ionizing radiation curable compound. In addition to the ionizing radiation curable compound, it may further contain a solvent and a polymerization initiator. The ionizing radiation curable compound is described in the column of the resin layer 10, so the description thereof is omitted here.

[0256] <Solvent>

[0257] Examples of the solvent include alcohols (e.g., methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, benzyl alcohol, PGME, ethylene glycol, and diacetone alcohol), ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, heptanone, diisobutyl ketone, diethyl ketone, and diacetone alcohol), esters (methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, methyl formate, and PGMEA), aliphatic hydrocarbons (e.g., hexane and cyclohexane), halogenated hydrocarbons (e.g., dichloromethane, chloroform, and carbon tetrachloride), aromatic hydrocarbons (e.g., benzene, toluene, and xylene), amides (e.g., dimethylformamide, dimethylacetamide, and N-methylpyrrolidone), ethers (e.g., diethyl ether, dioxane, and tetrahydrofuran), ether alcohols (e.g., 1-methoxy-2-propanol), and carbonates (dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate). These solvents may be used alone or in combination of two or more thereof. Among them, methyl isobutyl ketone and methyl ethyl ketone are preferred as the above-mentioned solvent from the viewpoint of dissolving or dispersing components such as urethane (meth)acrylate and other additives and being able to appropriately apply the resin layer composition.

[0258] <Polymerization Initiator>

[0259] The polymerization initiator is a component that is decomposed by ionizing radiation to generate radicals, thereby starting or advancing polymerization (crosslinking) of a polymerizable compound.

[0260] The polymerization initiator is not particularly limited as long as it can emit a material that initiates free radical polymerization by ionizing radiation. As the polymerization initiator, it is not particularly limited, and known polymerization initiators can be used, and specific examples include, for example, acetophenones, benzophenones, Michler's benzoyl benzoate, α-valeroxime ester, thioxanthones, phenylacetones, benzyls, benzoin, and acylphosphine oxides. In addition, preferably mixed photosensitizers are used, and as its specific example, for example, n-butylamine, triethylamine, poly-n-butylphosphine etc. can be mentioned.

[0261] After forming a coating film of the resin layer composition, when the resin layer composition contains a solvent, the coating film is dried by heating at a temperature of 30° C. to 120° C. for 10 to 120 seconds by various known methods to evaporate the solvent.

[0262] After the coating film is dried, it is irradiated with ionizing radiation such as ultraviolet rays to cure it. Then, the release film is peeled off to obtain the resin layer 10. The resin layer 10 satisfies the above-mentioned relationship (1), and such a resin layer 10 can also be obtained as follows: not only by adjusting the composition of the resin layer composition, but also by irradiating ionizing radiation from one side of the coating film, and appropriately adjusting the irradiation conditions of the ionizing radiation and / or the type and amount of the polymerization initiator, thereby obtaining it.

[0263] When forming the optical film 30, after drying the coating of the resin layer composition, the coating is irradiated with ionizing radiation such as ultraviolet rays to semi-cure the coating. "Semi-cure" in this specification means that curing substantially proceeds when further irradiated with ionizing radiation.

[0264] Thereafter, a functional layer composition for forming the functional layer 31 is applied onto the semi-cured coating film using a coating device such as a bar coater to form a coating film of the functional layer composition.

[0265] <<Composition for functional layer>>

[0266] The composition for the functional layer includes a polymerizable compound. In addition, the composition for the functional layer may include an ultraviolet absorber, a spectral transmittance modifier, an antifouling agent, inorganic particles, a leveling agent, a solvent, and a polymerization initiator as required. The solvent and the polymerization initiator are the same as those for the resin layer composition, so the description is omitted here.

[0267] After forming a coating film of the functional layer composition, the coating film is dried by heating at a temperature of 30° C. to 120° C. for 10 to 120 seconds by various known methods to evaporate the solvent.

[0268] After the coating of the functional layer composition is dried, ionizing radiation such as ultraviolet rays is irradiated to completely cure the coating (fully solidified) to form the functional layer 31. "Completely cured" in this specification means that even if more ionizing radiation is irradiated, curing does not substantially proceed. Thereafter, the anti-adhesive film is peeled off to obtain the optical film 30.

[0269] When forming the optical film 50, for example, the functional layer 52 is first formed on one surface side of the resin substrate 51. The functional layer 52 can be formed by the same method as the functional layer 31. Then, the resin layer 10 is formed on the surface of the resin substrate 51 opposite to the surface on which the functional layer 52 is formed in the same manner as described above. In this way, the optical film 50 can be obtained.

[0270] In the case where the resin layer is a single-layer structure composed of a soft resin layer with uniform hardness, good foldability can be obtained, but since the resin layer is soft, the impact resistance is poor. On the other hand, in the case where the resin layer is a single-layer structure composed of a hard resin layer with uniform hardness, good impact resistance can be obtained, but since the resin layer is hard, the foldability is poor. In addition, in the case where the resin layer is a multi-layer structure of a soft layer and a hard layer, peeling or cracks may occur at the interface between the soft layer and the hard layer during folding, and differences in deformation occur between the soft layer and the hard layer during folding, and wrinkles may occur. Based on this technical idea, the present inventors found that in order to obtain a resin layer having good foldability and good impact resistance in which the surface of the optical film does not dent when an impact is applied to the surface of the optical film and components (such as polarizers) existing inside the optical film in the image display device are not damaged, in the resin layer of the single-layer structure, it is necessary to make the hardness change slowly from one side to the other side. According to the present embodiment, since the displacement amounts d1 to d3 in the first region 10C to the third region 10E of the single-layer structure resin layer 10 satisfy the relationship of d1 < d2 < d3, good foldability and good impact resistance can be obtained.

[0271] <<<Image display device>>>

[0272] The optical film 30 can be assembled into a foldable image display device for use. Figure 6 is a schematic configuration diagram of the image display device of the present embodiment. As Figure 6 shown, the image display device 60 is mainly laminated in order toward the observer side with a housing 61 containing a battery or the like, a display element 62, a circular polarizer 63, a touch sensor 64, and an optical film 30. A light-transmissive adhesive layer 65 or an adhesive layer is disposed between the housing 61 and the display element 62, between the display element 62 and the circular polarizer 63, between the circular polarizer 63 and the touch sensor 64, and between the touch sensor 64 and the optical film 30, and these components are fixed to each other by the adhesive layer 65 or the adhesive layer. It should be noted that the adhesive layer 65 is disposed between the housing 61 and the display element 62, between the display element 62 and the circular polarizer 63, between the circular polarizer 63 and the touch sensor 64, and between the touch sensor 64 and the optical film 50, but the arrangement position of the adhesive layer is not particularly limited as long as it is between the optical film and the display element.

[0273] The optical film 30 is disposed such that the functional layer 31 is closer to the observer side than the resin layer 10. In the image display device 60, the surface 30A of the optical film 30 constitutes the surface 60A of the image display device 60.

[0274] In the image display device 60, the display element 62 is an organic light emitting diode element including an organic light emitting diode element. The touch sensor 64 is arranged at a position closer to the observer side than the circular polarizing plate 63, but can also be arranged between the display element 62 and the circular polarizing plate 63. In addition, the touch sensor 64 can be an external embedding method or an internal embedding method. As the adhesive layer 65, for example, OCA (Optical Clear Adhesive) can be used.

[0275] [Second embodiment]

[0276] Next, an optical film and an image display device according to a second embodiment of the present invention will be described with reference to the drawings. Figure 7 is a schematic structural diagram of the optical film of this embodiment, Figure 8 (A) and Figure 8 (B) is a diagram schematically showing the state of the folding static test.

[0277] <<<Optical Film>>>

[0278] Figure 7 The optical film 70 shown is foldable and has light transmittance. The optical film 70 has a surface 70A and a back surface 70B on the opposite side of the surface 70A. In addition, the optical film 70 includes a resin substrate 71, a resin layer 72, and a hard coating layer 73. In the optical film 70, the resin layer 72 is provided at a position closer to the back surface 70B side of the optical film 70 than the resin substrate 71, and the hard coating layer 73 is provided at a position closer to the surface 70A side of the optical film 70 than the resin substrate 71. Specifically, the optical film 70 includes a hard coating layer 73, a resin substrate 71, and a resin layer 72 in order from the surface 70A to the back surface 70B.

[0279] The optical film 70 is not prone to creases even when subjected to the folding and standing test. The folding and standing test and the confirmation of creases are performed as follows. First, the optical film 70 is cut into a size of 30 mm × 100 mm. Then, in order to reproduce the state inside the image display device, Figure 8 As shown in (A), the 30mm×48mm area of ​​the cut optical film 70 including the edges 70C and 70D on the two opposing short sides (30mm) is fixed to a glass plate 75 of size 50mm×100mm. The glass plate 75 is fixed to the back side 70B (resin layer 72 side) of the optical film 70. Thereafter, the glass plate 20 is arranged in parallel with the opposing edges 70C and 70D of the optical film 70 at a spacing of 2.5mm, and the optical film 70 is folded with the surface 70A facing the inside. In this state, it is placed at 25°C for 100 hours. Thereafter, the optical film 70 is opened with the glass plate 75, as shown in FIG. Figure 8As shown in (B), the surface of the optical film 70 is made flat. In this state, it is visually checked whether or not there is a crease on the optical film 70.

[0280] The optical film 70 is foldable in the same manner as the optical film 30. In the optical film 70, for example, it is preferred that the optical film 70 does not crack or break even when the optical film 70 is subjected to a folding test (continuous folding test) repeatedly for 100,000 times, more preferably, the optical film 70 does not crack or break even when the continuous folding test is repeated for 200,000 times, further preferably, the optical film 70 does not crack or break even when the continuous folding test is repeated for 300,000 times, and most preferably, the optical film 70 does not crack or break even when the continuous folding test is repeated for 1,000,000 times. The continuous folding test is performed by the same method as the continuous folding test described in the column of the first embodiment. It should be noted that in the optical film 70, it is more preferred that the optical film 70 does not crack or break even when the interval between the two opposing sides is increased. Even when the folding test was repeated 100,000 times with a thickness of 20 mm, 10 mm, 6 mm, or 3 mm, the optical film 70 did not produce cracks or breaks. The smaller the distance between the two opposing sides, the better.

[0281] When another film such as a polarizing plate is provided on one surface side of the optical film 70 via a pressure-sensitive adhesive layer or an adhesive layer, the other film is peeled off together with the pressure-sensitive adhesive layer or the adhesive layer, and then the folding static test or the folding test is performed.

[0282] The hardness (pencil hardness) of the surface 70A of the optical film 70 (the surface 73A of the hard coating layer 73) measured by the pencil hardness test specified in JIS K5600-5-4:1999 is preferably B or more, more preferably H or more. The pencil hardness test is performed by the same method as the pencil hardness test described in the first embodiment.

[0283] The yellow index of the optical film 70 and its measuring method are the same as those of the optical film 50. The haze value (total haze value), total light transmittance and their measuring methods of the optical film 70 are the same as those of the resin layer 10. The purpose, size and configuration position of the optical film 70 are the same as those of the optical film 30.

[0284] <<Resin base material>>

[0285] The resin substrate 71 is a substrate containing a resin having light transmittance. As the constituent material of the resin substrate 71, the same material as the constituent material of the resin substrate 51 can be cited. The thickness of the resin substrate 71 is 20 μm or less. If the thickness of the resin substrate 71 is 20 μm or less, the thickness of the resin substrate 71 is thin, so the elongation of the resin substrate 71 is small when the optical film 70 is folded. The thickness of the resin substrate 71 can be measured by the same method as the film thickness of the resin layer 72. From the perspective of further reducing the above-mentioned elongation, the upper limit of the resin substrate 71 is more preferably 18 μm or less, 16 μm or less, or 14 μm or less. In addition, from the perspective of ensuring the desired pencil hardness, the lower limit of the resin substrate 71 is preferably 2 μm or more, 4 μm or more, or 6 μm or more.

[0286] Regarding the film thickness of the resin substrate 71, a scanning transmission electron microscope (STEM) is used to photograph the cross section of the resin substrate 71 using the same method as the method for photographing the cross section of the functional layer 31. The film thickness of the resin substrate 71 at 10 locations is measured in the cross-sectional image, and the arithmetic average of the film thicknesses at the 10 locations is used.

[0287] When a pressure test is performed in which a Bosch indenter is pressed into a cross section in the thickness direction of the resin substrate 71 with a maximum load of 200 μN, the displacement d4 of the resin substrate 71 is greater than 50 nm and less than 250 nm. If the displacement d4 of the resin substrate 71 is greater than 50 nm, good bending properties can be obtained. If it is less than 250 nm, the desired pencil hardness can be ensured. From the perspective of obtaining excellent bending properties, the lower limit of the displacement d4 of the resin substrate 71 is preferably greater than 80 nm, greater than 100 nm, or greater than 110 nm. In addition, from the perspective of further ensuring the desired pencil hardness, the upper limit of the displacement d4 of the resin substrate 71 is more preferably less than 220 nm, less than 200 nm, or less than 180 nm. The method for measuring the displacement d4 of the resin substrate 71 is the same as the method for measuring the displacements d1 to d3 of the resin layer 10. It should be noted that in order to avoid the influence of the side edge of the resin substrate, the Glass indenter is pressed into a portion of the cross section of the resin substrate 71 in the thickness direction from both side ends of the resin substrate to the center of the resin substrate at a distance of more than 500 nm.

[0288] <<Resin layer>>

[0289] The resin layer 72 is a layer containing a light-transmitting resin and having impact absorption properties. The resin layer 72 is provided on the first surface 71A side of the resin substrate 71. Figure 7 In the optical film 70 , the resin layer 72 is adjacent to the first surface 71A of the resin base material 71 .

[0290] The film thickness of the resin layer 72 is 50 μm or more. If the film thickness of the resin layer 72 is 50 μm or more, good impact resistance can be obtained. The lower limit of the film thickness of the resin layer 72 is more preferably 60 μm or more, 65 μm or more, or 70 μm or more. From the perspective of achieving thinness and good processability, the upper limit of the film thickness of the resin layer 72 is more preferably 120 μm or less, 110 μm or less, or 100 μm or less. The film thickness of the resin layer 72 is measured by the same method as the thickness of the resin substrate 71.

[0291] The ratio of the film thickness of the resin layer 72 to the thickness of the resin substrate 71 (film thickness of the resin layer 72 / thickness of the resin substrate 71) is 4.0 or more and 12.0 or less. If the ratio is 4.0 or more, both crease suppression and impact resistance can be taken into account. In addition, if the ratio is 12.0 or less, the desired pencil hardness can be ensured. From the perspective of obtaining excellent crease suppression and excellent impact resistance, the lower limit of the ratio is more preferably 4.5 or more, 5.0 or more, or 6.0 or more, and from the perspective of obtaining excellent bendability, the upper limit is preferably 11.0 or less, 10.0 or less, or 8.0 or less.

[0292] When the indentation test of the glass indenter with a maximum load of 200 μN is carried out in the cross section of the film thickness direction of the resin layer 72, the displacement d5 of the resin layer 72 is more than 200nm and less than 1500nm. If the displacement d5 of the resin layer 72 is more than 200nm, the desired bending property can be ensured, and if it is less than 1500nm, the impact resistance required during the impact resistance test described later can be ensured. From the aspect of further suppressing the exposure of the resin layer 72 during folding, the lower limit of the displacement d5 of the resin layer 72 is preferably more than 300nm, more than 400nm, or more than 500nm. In addition, from the aspect of obtaining excellent impact resistance, the upper limit of the displacement d5 of the resin layer 72 is more preferably less than 1400nm, less than 1200nm, or less than 1100nm. The resin layer of the present embodiment is softer than the resin substrate and the hard coating layer, and the influence of viscosity is large, so the method of measuring the indentation hardness by the nanoindentation method is not suitable. Therefore, the displacement is used as an indicator of hardness. The displacement amount d5 of the resin layer 72 is measured by the same method as the displacement amount d4 of the resin base material 71 .

[0293] The ratio of the displacement d5 to the displacement d4 (d5 / d4) is preferably 1.5 or more. If d5 / d4 is 1.5 or more, both crease suppression and impact resistance can be achieved. In addition, from the perspective of obtaining excellent crease suppression and excellent impact resistance, the lower limit of d5 / d4 is more preferably 2.0 or more, 2.5 or more, or 3.0 or more, and from the perspective of ensuring the desired bendability, the upper limit is preferably 10.0 or less, 7.0 or less, or 5.0 or less.

[0294] The resin constituting the resin layer 72 is not particularly limited as long as the displacement d5 is 200 nm or more and 1500 nm or less. Such resins include cured products (polymers) of ionizing radiation curable compounds (ionizing radiation polymerizable compounds). Cured products of ionizing radiation curable compounds include urethane resins, acrylic gels, etc. "Gel" generally refers to a dispersion system with high viscosity and loss of fluidity.

[0295] (Urethane resin)

[0296] The urethane resin is the same as the urethane resin described in the column of the resin layer 10 .

[0297] (Acrylic gel)

[0298] As the acrylic gel, any polymer obtained by polymerizing monomers containing acrylic esters for use in adhesives and the like can be used, and various acrylic gels can be used. Specifically, as the acrylic gel, for example, acrylic gels obtained by polymerizing or copolymerizing acrylic monomers such as ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, isomyristyl (meth)acrylate, lauryl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate can be used. In the present specification, "(meth)acrylate" means both "acrylate" and "methacrylate". In addition, the acrylic acid ester used in the above (co)polymerization may be used alone or in combination of two or more.

[0299] <<Hard Coating>>

[0300] The hard coating layer 73 is provided on the second surface 71B side of the resin substrate 71. Figure 7 In the optical film 70, the hard coat layer 73 is adjacent to the second surface 11B of the resin substrate 11. The "hard coat layer" in the present embodiment refers to a layer having a pencil hardness of "H" or more in the above-mentioned pencil hardness test.

[0301] When the indentation test of the glass indenter with a maximum load of 500 μN is carried out in the cross section of the film thickness direction of the hard coating 73, the displacement d6 of the hard coating 73 is preferably less than 500 nm. If the displacement d6 of the hard coating 73 is less than 500 nm, the desired pencil hardness can be ensured. From the aspect of ensuring bending, the lower limit of the displacement d6 of the hard coating 73 is preferably more than 50 nm, more than 60 nm, or more than 70 nm. In addition, the upper limit of the displacement d6 of the hard coating 73 is more preferably less than 500 nm, less than 490 nm, or less than 480 nm. The above-mentioned displacement d6 of the hard coating 73 is measured by the same method as the above-mentioned displacement d4 of the resin substrate 71. It should be noted that the measurement conditions are as follows.

[0302] (Measurement conditions)

[0303] Control method: load control (maximum load 500μN)

[0304] Lifting amount: 0nm

[0305] Preload: 0.5μN

[0306] Loading speed: 20μN / sec

[0307] Hold time: 5 seconds

[0308] Unloading speed: 20μN / sec

[0309] ·Measurement temperature: 23±5℃

[0310] Relative humidity: 30% to 70%

[0311] The film thickness of the hard coating layer 73 is preferably 3 μm or more and 10 μm or less. If the film thickness of the hard coating layer 73 is 3 μm or more, good hardness can be obtained, and if it is 10 μm or less, the processability can be suppressed. In the case where the hard coating layer is a multilayer structure, the "thickness of the hard coating layer" in this specification refers to the thickness (total thickness) of the film thickness of each hard coating layer combined. The lower limit of the film thickness of the hard coating layer 73 is more preferably 5 μm or more, and the upper limit is more preferably 8 μm or less. The film thickness of the hard coating layer 73 is measured by the same method as the thickness of the resin substrate 71.

[0312] The hard coat layer 73 preferably further contains a resin and inorganic particles dispersed in the resin. The resin and inorganic particles of the hard coat layer 73 are the same as those described in the column of the functional layer 31 .

[0313] The hard coating layer 73 may include materials other than the above materials within the range satisfying the above displacement amount. For example, as a material of the resin component, a polymerizable monomer or a polymerizable oligomer that forms a cured product by irradiation with ionizing radiation may be included. The polymerizable monomer and the polymerizable oligomer are the same as those described in the column of the functional layer 31.

[0314] <<<Method for producing optical film>>>

[0315] The optical film 70 can be produced as follows: First, the hard coat composition is applied onto the second surface 71B of the resin substrate 71 using a coating device such as a bar coater to form a coating film of the hard coat composition.

[0316] <Hard Coat Composition>

[0317] The hard coating composition includes a polymerizable compound. In addition, the hard coating composition may include an ultraviolet absorber, a spectral transmittance modifier, an antifouling agent, inorganic particles, a leveling agent, a solvent, and a polymerization initiator as needed. The solvent and the polymerization initiator are the same as those described in the column of the resin layer composition of the first embodiment.

[0318] After forming a coating film of the hard coat composition, the coating film is dried by heating at a temperature of 30° C. to 120° C. for 10 to 120 seconds by various known methods to evaporate the solvent.

[0319] After the coating film of the hard coat composition is dried, it is irradiated with ionizing radiation such as ultraviolet rays to cure the coating film, thereby forming a hard coat layer 73 .

[0320] After forming hard coat layer 73 , a resin layer composition for forming resin layer 72 is applied to first surface 71A of resin substrate 71 using a coating device such as a bar coater to form a coating film of the resin layer composition. The coating film is then cured to form resin layer 72 .

[0321] <Resin Layer Composition>

[0322] When the resin layer 72 contains a urethane resin, for example, the ionizing radiation-curable urethane resin composition described in the section of the urethane resin can be used as the resin layer composition.

[0323] After forming the coating film of the resin layer composition, when the resin layer composition contains a solvent, the coating film is dried by heating at a temperature of 30° C. to 120° C. for 10 to 120 seconds by various known methods to evaporate the solvent.

[0324] After the coating film is dried, it is irradiated with ionizing radiation such as ultraviolet rays to cure the coating film, thereby forming the resin layer 12 and obtaining the optical film 70 .

[0325] It is believed that the crease is caused by the following reasons: when the optical film is folded, the inner surface or outer surface of the resin substrate is stretched, thereby causing the resin substrate to exceed the elastic limit, causing plastic deformation, thereby generating creases. Therefore, if the resin substrate is thinned, the elongation of the resin substrate can be suppressed when the optical film is folded. However, if the resin substrate is thinned, the impact resistance is reduced. On the other hand, the resin layer whose displacement during the press-in test is more than 200nm and less than 1500nm has a wider elastic region than the resin substrate, so it is difficult to produce plastic deformation and creases compared to the resin substrate. In addition, if the film thickness of such a resin layer is thin, the impact resistance is reduced. Therefore, in order to obtain good impact resistance in which the surface of the optical film does not dent when an impact is applied to the surface of the optical film, a film thickness of a certain degree or more is required. In contrast, according to the present embodiment, a resin layer 72 having a displacement d5 of not less than 200 nm and not more than 1500 nm during a press-in test is provided on the first surface 71A side of a resin substrate 71 having a thickness of not more than 20 μm and a displacement d4 of not less than 50 nm and not more than 250 nm during a press-in test. The thickness of the resin substrate 71 is not more than 20 μm, the film thickness of the resin layer 72 is not less than 50 μm, and the ratio of the film thickness of the resin layer 72 to the thickness of the resin substrate 71 is not less than 4.0 and not more than 12.0. Therefore, creases are less likely to occur when the optical film 70 is folded, and good impact resistance can be obtained.

[0326] <<<Image Display Device>>>

[0327] The optical film 70 can be incorporated into a foldable image display device for use. The structure of the image display device incorporating the optical film 70 is the same as that of the image display device 60 except that the optical film 70 is incorporated instead of the optical film 30 .

[0328] [Third Embodiment]

[0329] Next, an optical film and an image display device according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 9 is a schematic structural diagram of the optical film of this embodiment, Fig.10 yes Fig. 9 A partial magnified view of the optical film. Fig.11 It is a schematic structural diagram of another optical film according to the present embodiment.

[0330] <<<Optical Film>>>

[0331] Fig. 9 The optical film 80 shown is used for an image display device and is foldable.

[0332] like Fig. 9 As shown, the optical film 80 includes a resin substrate 81 and a resin layer 82 disposed on the first surface 81A side, which is one surface of the resin substrate 81. In addition, the optical film 80 further includes a functional layer 85 disposed on the surface 82A of the resin layer 82. The "resin layer" in this embodiment refers to a layer containing a resin, which may be a single-layer structure or a multi-layer structure of more than two layers. As described later, the resin layer 82 is a multi-layer structure of more than two layers, specifically a two-layer structure, but may also be a single-layer structure. The functional layer 85 is a single-layer structure, but may also be a multi-layer structure of more than two layers.

[0333] The surface 80A of the optical film 80 is a concavoconvex surface. Fig. 9 In the embodiment, the surface 80A of the optical film 80 becomes the surface 85A of the functional layer 85. The back surface 80B of the optical film 80 becomes the second surface 81B on the opposite side to the first surface 81A of the resin substrate 81.

[0334] The optical film 80 is foldable in the same manner as the optical film 30. In the optical film 80, for example, it is preferred that the optical film 80 does not produce cracks or breaks even when the optical film 80 is subjected to a folding test (continuous folding test) 100,000 times repeatedly, more preferably the optical film 80 does not produce cracks or breaks even when the continuous folding test is repeated 200,000 times, further preferably the optical film 80 does not produce cracks or breaks even when the continuous folding test is repeated 300,000 times, and most preferably the optical film 80 does not produce cracks or breaks even when the continuous folding test is repeated 1 million times. In addition to making the interval between the two opposing sides The continuous folding test is performed by the same method as the continuous folding test described in the column of the first embodiment. In the optical film 80, it is more preferable that the interval between the two opposing sides is Even when the folding test was repeated 100,000 times with a thickness of 6 mm, 4 mm, or 2 mm, the optical film 80 did not crack or break.

[0335] The surface 80A of the optical film 80 (the surface 85A of the functional layer 85) is preferably made of #0000 steel wool (product name "BON STAR", manufactured by Japan Steel Wool Co., Ltd.) while applying 1 kgf / cm 2When the abrasion resistance test was conducted by rubbing the film back and forth 10 times at a speed of 60 mm / second while applying a load, no scratches were generated. The above test was conducted as follows: an optical film cut into a size of 50 mm × 100 mm was fixed on a glass plate in a manner without folds or wrinkles using Cellotape (registered trademark) manufactured by Michelbon Co., Ltd. with the surface of the optical film on the upper side, and the test was conducted in this state at a temperature of 23±5°C and a relative humidity of 30% to 70%. The above scratches refer to scratches observed visually under a three-wavelength fluorescent lamp by sticking a black polyvinyl chloride insulating tape (polyvinyl chloride insulating tape black NO200-38-21 manufactured by YAMATO Co., Ltd.) on the glass surface on the opposite side of the optical film.

[0336] The yellow index of the optical film 80 and its measuring method are the same as those of the optical film 50. The total light transmittance of the optical film 80 and its measuring method are the same as those of the resin layer 10. The purpose, size and arrangement position of the optical film 80 are the same as those of the optical film 30.

[0337] The haze value (total haze value) of the optical film 80 is preferably 20% or less. If the haze value of the optical film 80 is 20% or less, when the optical film 80 is used in a mobile terminal, whitening of the image display surface can be suppressed. The lower limit of the haze value may be 1% or more, and the upper limit is more preferably 15% or less, 10% or less, or 5% or less. The method for measuring the haze value of the optical film 80 is the same as the method for measuring the haze value of the resin layer 10.

[0338] The clarity of the transmitted image of the optical film 80 is preferably 40% or more and 90% or less under a 0.125mm comb (comb A), and 80% or more under a 2.0mm comb (comb B). If the clarity of the transmitted image under a 0.125mm comb (comb A) is 40% or more, glare (flare) can be suppressed, and if the clarity of the transmitted image under a 0.125mm comb (comb A) is 90% or less, the pressing marks can be made less obvious. In addition, if the clarity of the transmitted image under a 2.0mm comb (comb B) is 80% or more, the image can be clearly seen. The lower limit of the clarity of the transmitted image under the above-mentioned 0.125mm comb (comb A) is more preferably 45% or more, 50% or more, or 55% or more, and the upper limit is more preferably 85% or less. In addition, the lower limit of the clarity of the transmitted image under the above-mentioned 2.0mm comb (comb B) is more preferably 90% or more.

[0339] The above-mentioned transmission image clarity can be measured by using a clarity meter (for example, product name "ICM-IT", manufactured by SUGA TEST INSTRUMENTS Co., Ltd.) in an environment with a temperature of 23±5°C and a relative humidity of 30% to 70% by the transmission method of image clarity in accordance with JIS K7374:2007. The above-mentioned transmission image clarity is a value obtained as follows: After the optical film is cut into a size of 50mm×100mm, it is set in a clarity meter set for transmission measurement in a state where there is no curling or wrinkling, and no fingerprints or dust, etc., with the resin substrate being on the light source side. One optical comb is measured three times, and the arithmetic mean of the values ​​obtained by the three measurements is adopted. It should be noted that when the optical film cannot be cut into the above-mentioned size, for example, the opening of the sample stage during the measurement of ICM-1T is Therefore, a sample size of 26 mm or more in diameter is required. Therefore, the optical film can be appropriately cut into a size of 27 mm × 27 mm or more. When the size of the optical film is small, the measurement points can be set to three locations by moving or changing the angle little by little within the range where the light source spot does not deviate.

[0340] The surface 80A of the optical film 80 is a concavoconvex surface. The concavoconvexity constituting the surface 80A of the optical film 80 preferably satisfies the following relationship when the average interval is Sm, the average tilt angle is θa, the arithmetic mean roughness is Ra, and the maximum profile height is Ry.

[0341] 0.15mm≤Sm≤0.5mm

[0342] 0.02°≤θa≤0.50°

[0343] 0.01μm≤Ra≤0.15μm

[0344] 0.10μm≤Ry≤0.50μm

[0345] If the average interval Sm is 0.15 mm or more, the image can be less cloudy, and if Sm is 0.5 mm or less, glare can be less. The lower limit of Sm is more preferably 0.20 mm or more or 0.22 mm or more, and the upper limit is more preferably 0.45 mm or less or 0.40 mm or less.

[0346] If the average inclination angle θa is 0.02° or more, the pressing mark can be made less noticeable, and if θa is 0.05° or less, the white turbidity of the image can be suppressed. The lower limit of θa is more preferably 0.04° or more or 0.06° or more, and the upper limit is more preferably 0.30° or less or 0.20° or less.

[0347] The arithmetic mean roughness Ra is preferably 0.01 μm or more and 0.15 μm or less. If Ra is 0.01 μm or more, the pressing mark can be made less noticeable, and if Ra is 0.15 μm or less, the visibility of the image can be improved. The lower limit of Ra is more preferably 0.03 μm or more or 0.05 μm or more, and the upper limit is more preferably 0.12 μm or less or 0.10 μm or less.

[0348] The maximum height Ry of the profile is preferably 0.10 μm or more and 0.80 μm or less. If Ry is 0.10 μm or more, the pressing mark can be made less noticeable, and if Ry is 0.50 μm or less, glare can be suppressed. The lower limit of Ry is more preferably 0.15 μm or more or 0.20 μm or more, and the upper limit is more preferably 0.60 μm or less or 0.40 μm or less.

[0349] The definitions of "Sm", "Ra" and "Ry" are based on JIS B0601: 1994. The definition of "θa" is based on the operating instructions (revised on July 20, 1995) of SURFCORDER SE-3400 (manufactured by Kosaka Laboratory Co., Ltd.), which is a surface roughness measuring instrument. θa is represented by the following mathematical formula (A).

[0350] θa=tan -1 Δa…(A)

[0351] In formula (A), Δa is a value expressing the inclination in terms of the aspect ratio, and is a value obtained by dividing the sum of the differences between the minimum and maximum parts of each concavoconvexity (corresponding to the height of each convexity) by a reference length.

[0352] Sm, Ra, Ry and θa can all be measured using, for example, SURFCORDER SE-3400, SE-3500, or SE-500 (all manufactured by Kosaka Laboratory Co., Ltd.). Here, even if θa cannot be measured directly, when Δa can be measured, since θa and Δa have the relationship shown in the above mathematical formula (A), Δa can be measured and θa can be obtained from the measured Δa. It should be noted that the cutoff wavelength when measuring Sm, etc. is set to 0.8 mm.

[0353] When other films such as a polarizer are provided on the surface side of the optical film 80 via an adhesive layer or an adhesive layer, the other films are peeled off together with the adhesive layer and the adhesive layer, and then a folding test, yellow index measurement, total light transmittance measurement, haze value measurement, transmission image clarity, average interval Sm, etc. are performed.

[0354] The resin substrate 81 is a substrate containing a light-transmitting resin. The constituent material of the resin substrate 81 is the same as the constituent material of the resin substrate 51. The thickness of the resin substrate 81 is preferably greater than 10 μm and less than 100 μm. If the thickness of the resin substrate 81 is greater than 10 μm, the curling of the optical film can be suppressed, and sufficient hardness can be obtained, and even in the case of manufacturing the optical film 80 by a roll-to-roll method, wrinkles are difficult to generate, and there is no need to worry about the appearance being deteriorated. On the other hand, if the thickness of the resin substrate 81 is less than 100 μm, the folding performance of the optical film 80 is good, and the conditions of the continuous folding test can be met. In addition, it is preferred in terms of the lightweight of the optical film 80. Regarding the thickness of the resin substrate 81, a cross section of the resin substrate 81 is photographed using a scanning electron microscope (SEM), and the film thickness of the resin substrate 81 at 10 locations is measured in the image of the cross section, and the arithmetic average of the film thickness of the 10 locations is used. The lower limit of the resin base material 81 is 25 μm or more, 30 μm or more, or more preferably 35 μm or more, and the upper limit of the resin base material 81 is 80 μm or less, 75 μm or less, or more preferably 70 μm or less.

[0355] <<Resin layer>>

[0356] The surface 82A of the resin layer 82 is a concavoconvex surface. This is caused by the organic particles 83B described later. The Sm, θa, Ry, and Rz constituting the concavoconvex of the surface 82A are preferably in the same range as the Sm, θa, Ry, and Rz constituting the concavoconvex of the surface 80A. The Sm, etc. constituting the concavoconvex of the surface 82A can be measured by the same method as the Sm, etc. constituting the concavoconvex of the surface 80A.

[0357] The resin layer 82 is a layer that functions as a hard coating. In addition to hard coating properties, the resin layer 82 may also have functions other than hard coating properties. The "hard coating" in this embodiment refers to the indentation hardness (H) at the center of the cross section of the hard coating. IT ) is a layer with a hardness of 150 MPa or more. The "indentation hardness" in this specification refers to the value obtained from the load-displacement curve from the load of the indenter to the unloading. The indentation hardness is the arithmetic mean of the values ​​obtained by measuring 10 locations. The method for measuring the indentation hardness is described in detail below.

[0358] The indentation hardness of the lower portion 82B of the resin layer 82 is preferably smaller than the indentation hardness of the upper portion 82C of the resin layer 82. If the indentation hardness of the lower portion 82B of the resin layer 82 is smaller than the indentation hardness of the upper portion 82C of the resin layer 82, the organic particles 83B described later are present in the soft portion of the resin layer 82, so that the optical film 80 is more difficult to break when folded, and the hard portion is present on the surface 82A side of the organic particles 83B, so that a more excellent surface hardness can be obtained.

[0359] The indentation hardness (H) of the sample was measured using TI950 TriboIndenter manufactured by BRUKER. IT ) is measured. Specifically, first, an optical film cut into 1mm×10mm is embedded in an embedding resin to make a block, and a uniform slice with a thickness of 70nm to 100nm without holes or the like is cut from the block using a general slicing method. The slices can be made using, for example, the Ultramicrotome EMUC7 of Leica Microsystems Co., Ltd. Then, the block remaining after the uniform slice without holes or the like is cut out is used as a measurement sample. Next, in the cross-section obtained by cutting out the above-mentioned slice in this measurement sample, under the following measurement conditions, a Berkovich indenter (triangular pyramid, TI-0039 manufactured by BRUKER) as the above-mentioned indenter is vertically pressed into the lower cross-section of the resin layer with a maximum pressing load of 50μN for 10 seconds. Here, in order to avoid the influence of the side edge of the resin substrate or the resin layer, the Bosch indenter was pressed into the lower part of the resin layer, with a spacing of 500 nm from the interface between the resin substrate and the resin layer to the central side of the resin layer and a spacing of more than 500 nm from both side ends of the resin layer to the central side of the resin layer. After that, it was kept for 5 seconds and then unloaded for 10 seconds. The maximum indentation load P was used. max and contact projection area A p , through P max / A p Calculate the indentation hardness (H IT The contact projection area is the contact projection area corrected for the curvature of the indenter tip using the Oliver-Pharr method using a standard sample of fused quartz (5-0098 manufactured by BRUKER). Indentation hardness (H IT ) is the arithmetic mean of the values ​​obtained by measuring 10 locations. It should be noted that when the measured value contains a value that deviates from the arithmetic mean by more than ±20%, the measured value is removed and the measurement is performed again. As to whether there is a value that deviates from the arithmetic mean by more than ±20% in the measured value, when the measured value is set as A and the arithmetic mean is set as B, it is judged by whether the value (%) calculated by (A-B) / B×100 is more than ±20%. The indentation hardness of the upper part of the resin layer is also measured in the same way as the indentation hardness of the lower part of the resin layer, but in this case, in order to avoid the influence of the functional layer or the side edge of the resin layer, the Bosch indenter is pressed into the upper part of the resin layer at a distance of 500nm from the interface between the resin layer and the functional layer to the central side of the resin layer and at a distance of more than 500nm from the two side ends of the resin layer to the central side of the resin layer.

[0360] (Measurement conditions)

[0361] Control mode: load control mode

[0362] Loading speed: 5μN / sec

[0363] Hold time: 5 seconds

[0364] Unloading speed: 5μN / s

[0365] Temperature: 23℃~25℃

[0366] Relative humidity: 30% to 70%

[0367] The film thickness of the resin layer 82 is preferably 2 μm or more and 15 μm or less. If the film thickness of the resin layer 82 is 2 μm or more, a hardness sufficient for a hard coating layer can be obtained, and if it is 15 μm or less, the processability can be suppressed. In the case where the resin layer is a multilayer structure, the "film thickness of the resin layer" in this embodiment refers to the film thickness (total thickness) of the film thickness of each resin layer combined. The lower limit of the resin layer 82 is more preferably 3 μm or more, 4 μm or more, or 5 μm or more, and the upper limit of the resin layer 82 is more preferably 12 μm or less, 10 μm or less, or 8 μm or less.

[0368] Regarding the film thickness of the resin layer 82, a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM) is used to photograph the cross section of the resin layer 12 in the same manner as the method for photographing the cross section of the functional layer 31, and the film thickness of the resin layer 82 at 10 locations in the cross-sectional image is measured, and the arithmetic average of the film thicknesses of the 10 locations is used. It should be noted that a mixed layer containing components constituting the resin substrate 81 and components constituting the resin layer 82 sometimes exists between the resin substrate 81 and the resin layer 82, but the film thickness of the mixed layer is not included in the film thickness of the resin layer.

[0369] The resin layer 82 includes organic particles 83B described below. The organic particles 83B are located closer to the center line CL (see FIG. 1 ) than the imaginary line bisecting the resin layer 82 in the film thickness direction D2 of the resin layer 82. Fig.10) is closer to the resin substrate 81 side. As to whether the organic particles 83B are biased towards the position closer to the resin substrate 81 side than the center line CL, the center of each organic particle 83B is obtained from the cross-sectional photograph of the resin layer 12 obtained by using a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM), and it can be judged whether the average position of its center exists at a position closer to the resin substrate 81 side than the center line CL. Specifically, first, in the same way as the film thickness of the resin layer 82 is measured, the cross section of the resin layer 82 is photographed using a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM), and cross-sectional photographs of 10 parts are prepared. The film thickness of the resin layer 82 is measured in each cross-sectional photograph, and the position of the center line CL is obtained in each cross-sectional photograph. In addition, the center of the organic particle 83B that appears in each cross-sectional photograph is obtained. The midpoint of the imaginary line segment connecting the point closest to the organic particle and the resin substrate and the farthest point in the film thickness direction of the resin layer is obtained, and the center can be obtained. In addition, the distance between the center of the organic particle 83B and the center line CL is measured for each organic particle 83B in each cross-sectional photograph. At this time, the distance between the center of the organic particle 83B and the center line CL when the center of the organic particle 83B is located closer to the lower side (resin substrate 81 side) than the center line CL is set to "-", and the distance between the center of the organic particle 83B and the center line CL when the center of the organic particle 83B is located closer to the upper side (functional layer 85 side) than the center line CL is set to "+". Then, the average position of the center of the organic particle 83B is obtained by averaging the distances, and therefore, it is determined whether the obtained average position is "-" or "+" to determine whether the center of the organic particle 83B is located closer to the resin substrate 81 side than the center line CL.

[0370] The ratio of the average particle size of the organic particles 83B to the film thickness of the resin layer 82 (average particle size / film thickness) is preferably greater than 0.1 and less than 1. If the ratio is greater than 0.1, the desired concavoconvexity can be imparted. If it is less than 1, it is easy to make the organic particles 83B biased to a position closer to the resin substrate 11 side than the center line CL that divides the resin layer 82 in two equal parts along the film thickness direction D2. Regarding the average particle size of the organic particles 83B, the particle sizes of 20 organic particles are measured from a cross-sectional image of the organic particles taken at a magnification of 5000 to 20,000 times using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), which is the arithmetic mean of the particle sizes of the 20 organic particles. The particle size of the organic particles is measured as follows. First, the major diameter and the minor diameter are measured, and the particle size of each particle is calculated from the average of the major diameter and the minor diameter. Here, the major diameter is the longest diameter on the screen of each particle. In addition, a line segment is drawn that is perpendicular to the midpoint of the line segment constituting the major axis, and the minor axis is the distance between two points where the perpendicular line segment and the particle intersect.

[0371] The resin layer 82 includes a first resin layer 83 and a second resin layer 84 provided at a position closer to the surface 82A side than the first resin layer 83. Fig.10 In FIG. 8 , since the first resin layer 83 and the second resin layer 84 have the same film thickness, the center line CL exists near the interface between the first resin layer 83 and the second resin layer 84 .

[0372] <First Resin Layer>

[0373] The first resin layer 83 includes a binder resin 83A and organic particles 83B. By making the first resin layer 83 include organic particles 83B, the surface 82A of the resin layer 82 can be made into a concave-convex surface. The first resin layer 83 preferably further includes inorganic particles 83C. By making the first resin layer 83 include inorganic particles 83C, it is easy to control the concave-convex shape. In addition to the binder resin 83A, the first resin layer 83 may also include additives such as ultraviolet absorbers, adhesion improvers, leveling agents, thixotropy imparting agents, coupling agents, plasticizers, defoamers, fillers, colorants, etc. as needed within the range that does not impair the effect of the present invention.

[0374] The indentation hardness of the first resin layer 83 is preferably smaller than the indentation hardness of the second resin layer 84. If the indentation hardness of the first resin layer 83 is smaller than the indentation hardness of the second resin layer 84, the organic particles 83B are present in the soft first resin layer 83, so that the optical film 80 is more difficult to break when folded, and the hard second resin layer 84 is present on the surface 82A side of the organic particles 83B, so that a more excellent surface hardness can be obtained.

[0375] The indentation hardness of the first resin layer 83 is preferably 150 MPa or more and 350 MPa or less. If the indentation hardness of the first resin layer 83 is 150 MPa or more, a good pencil hardness can be obtained, and if the indentation hardness of the first resin layer 83 is 350 MPa or less, a good bendability can be obtained. The lower limit of the indentation hardness of the first resin layer 83 is more preferably 180 MPa or more, 200 MPa or more, or 220 MPa or more, and the upper limit is more preferably 330 MPa or less, 300 MPa or less, or 280 MPa or less. The indentation hardness of the first resin layer 83 is measured by the same method and the same measurement conditions as the indentation hardness of the lower part 82B of the resin layer 82.

[0376] (Binder resin)

[0377] The binder resin 83A contains a polymer (cured product) of a polymerizable compound (curable compound). The polymerizable compound is a compound having at least one polymerizable functional group in the molecule. The polymerizable functional group and the polymerizable compound are the same as those described in the column of the functional layer 31.

[0378] (Organic particles)

[0379] The organic particles 83B are particles mainly composed of organic components. In addition to the organic components, the organic particles 83B may also be mixed with inorganic components. Examples of the organic particles include polymethyl methacrylate particles, polyacrylic acid-styrene copolymer particles, melamine resin particles, polycarbonate particles, polystyrene particles, cross-linked polystyrene particles, polyvinyl chloride particles, benzoguanamine-melamine formaldehyde particles, silicone particles, fluorine resin particles, polyester resin particles, and the like.

[0380] The organic particles 83B are preferably spherical in terms of ease of control to the above-mentioned concavo-convex shape. The "spherical" in this specification includes, for example, a true sphere, an ellipsoid, etc., but does not include so-called amorphous shapes.

[0381] The average particle size of the organic particles 83B is preferably 0.5 μm or more and 10 μm or less. If the average particle size of the organic particles 83B is within this range, it is easy to control the desired concavo-convex shape. The lower limit of the average particle size of the organic particles is preferably 1.0 μm or more or 1.5 μm or more, and the upper limit is preferably 8 μm or less, 6 μm or less, or 4 μm or less.

[0382] (Inorganic particles)

[0383] Inorganic particles 83C are particles mainly containing inorganic components. The average particle size of inorganic particles 83C is preferably 1 nm or more and 50 nm or less. If the average particle size of inorganic particles 83C is 1 nm or more, it is easy to control the concave-convex shape. In addition, if the average particle size of inorganic particles 83C is 50 nm or less, the light diffusion caused by inorganic particles 83C can be suppressed, and excellent contrast can be obtained. The lower limit of the average particle size of inorganic particles 83C is preferably 3 nm or more, 5 nm or more, or 7 nm or more, and the upper limit is preferably 40 nm or less, 30 nm or less, or 20 nm or less. Regarding the average particle size of inorganic particles 83C, the particle size of 20 inorganic particles is measured by using a cross-sectional image of inorganic particles taken at a magnification of 50,000 to 200,000 times using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), and the arithmetic mean of the particle size of 20 inorganic particles is used.

[0384] The content of inorganic particles 83C in the first resin layer 83 is smaller than the content of inorganic particles 84B described later in the second resin layer 84. By making the content of inorganic particles 83C smaller than the content of inorganic particles 84B, the first resin layer 83 can be made softer than the second resin layer 84.

[0385] The inorganic particles 83C are not particularly limited, and examples thereof include inorganic oxide particles such as silicon dioxide (SiO 2 ) fine particles, aluminum oxide particles, titanium dioxide particles, tin oxide particles, antimony-doped tin oxide (ATO) particles, and zinc oxide particles.

[0386] When using silica particles as inorganic particles 83C, among the silica particles, gas phase silica particles are preferred from the aspect of being able to easily form a resin layer 82 with a smooth concave-convex surface. Gas phase silica refers to amorphous silica with a particle size of less than 200nm made by a dry method, which can be obtained by reacting volatile compounds containing silicon in the gas phase. Specifically, for example, substances generated by hydrolyzing silicon compounds such as silicon tetrachloride (SiCl4) in a flame of oxygen and hydrogen can be cited. As commercially available products of gas phase silica particles, AEROSIL (registered trademark) R805 manufactured by NIPPON AEROSIL Co., Ltd. can be cited.

[0387] When inorganic oxide particles are used as inorganic particles 83C, the inorganic oxide particles are preferably amorphous. This is because when the inorganic oxide particles are crystalline, the Lewis acid salt of the inorganic oxide particles becomes stronger due to lattice defects included in the crystal structure, and excessive aggregation of the inorganic oxide particles may not be controlled.

[0388] In addition, when using fumed silica particles as inorganic particles 83C, the fumed silica particles include substances showing hydrophilicity and substances showing hydrophobicity. Among these, substances showing hydrophobicity are preferred from the perspective of reducing water absorption and being easily dispersed in the resin layer composition. Hydrophobic fumed silica can be obtained by chemically reacting the above-mentioned surface treatment agent with the silanol group present on the surface of the fumed silica particles.

[0389] The inorganic particles 83C are preferably spherical in shape when they are single particles. When the inorganic particles 83C are spherical, an image with a higher contrast can be obtained when the optical film is disposed on the image display surface of an image display device.

[0390] <Second Resin Layer>

[0391] The second resin layer 84 includes a binder resin 84A and inorganic particles 84B. By making the second resin layer 84 include inorganic particles 84B, the hardness of the resin layer 82 can be improved. It should be noted that the second resin layer 84 does not include organic particles. In addition to the binder resin 84A, the second resin layer 84 may also include additives such as ultraviolet absorbers, adhesion improvers, leveling agents, thixotropy imparting agents, coupling agents, plasticizers, defoamers, fillers, colorants, etc. as needed within the range that does not impair the effects of the present invention.

[0392] The indentation hardness of the second resin layer 84 is preferably 250 MPa or more and 450 MPa or less. If the indentation hardness of the second resin layer 84 is 250 MPa or more, good pencil hardness and scratch resistance can be obtained. If the indentation hardness of the second resin layer 84 is 450 MPa or less, good bending can be obtained. The lower limit of the indentation hardness of the second resin layer 84 is more preferably 270 MPa or more, 300 MPa or more, or 320 MPa or more, and the upper limit is more preferably 420 MPa or less, 400 MPa or less, or 370 MPa or less. The indentation hardness of the second resin layer 84 is measured by the same method and the same measurement conditions as the indentation hardness of the upper part 82C of the resin layer 82.

[0393] (Binder resin)

[0394] The binder resin 84A includes a polymer (cured product) of a polymerizable compound (curable compound). As the polymerizable compound, a multifunctional (meth)acrylate is preferred. As the multifunctional (meth)acrylate, the same substances as the multifunctional (meth)acrylate in the column of the binder resin of the first resin layer 13 can be cited. In addition to the multifunctional (meth)acrylate, the binder resin may also include a multifunctional urethane (meth)acrylate, a multifunctional epoxy (meth)acrylate and / or a reactive polymer.

[0395] (Inorganic particles)

[0396] The inorganic particles 84B are the same as the inorganic particles described in the column of the functional layer 31 .

[0397] <<Functional Layer>>

[0398] The surface 85A of the functional layer 85 reflects the surface concavity and convexity of the resin layer 82. The functional layer 85 may be a single layer or a multilayer structure of two or more layers. Specifically, the functional layer 85 may have, for example, a laminated structure of an inorganic layer and an antifouling layer. By forming an antifouling layer, it is possible to suppress the adhesion of fingerprints and the like.

[0399] (Inorganic layer)

[0400] The inorganic layer is a layer mainly composed of inorganic substances. For example, if there are more than 55% by mass of inorganic substances in the inorganic layer, it meets the inorganic layer. The inorganic layer may also contain organic substances, but is preferably composed only of inorganic substances. Whether it meets the inorganic layer can be confirmed by X-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy: XPS or chemical analysis electron spectroscopy: ESCA).

[0401] As the constituent material of the inorganic layer, metals such as Ti, Al, Mg, and Zr, or silicon oxide (SiO x (x=1 to 2)), inorganic oxides such as aluminum oxide, silicon oxynitride, aluminum oxynitride, magnesium oxide, zinc oxide, indium oxide, tin oxide, and yttrium oxide, inorganic nitrides, and diamond-like carbon. Among them, silicon oxide is preferred from the perspective of improving transmittance and scratch resistance.

[0402] The inorganic layer preferably contains Si atoms. By making the inorganic layer contain Si atoms, a low refractive index can be achieved. Whether the inorganic layer contains Si atoms can be confirmed by X-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy: XPS or electron spectroscopy for chemical analysis: ESCA).

[0403] The thickness of the inorganic layer is preferably 10 nm or more and 300 nm or less. If the thickness of the inorganic layer is 10 nm or more, excellent scratch resistance can be given. If it is 300 nm or less, bending and optical properties will not be affected, and the adhesion with other layers is good. The lower limit of the thickness of the inorganic layer is more preferably 30 nm or more, 50 nm or more, or 80 nm or more, and the upper limit is more preferably 250 nm or less, 200 nm or less, or 150 nm or less. The thickness of the inorganic layer is obtained by the same method as the thickness of the resin layer 82.

[0404] The inorganic layer can be formed by a vapor deposition method such as a PVD method or a CVD method. Examples of the PVD method include a vacuum vapor deposition method, a sputtering method, and an ion plating method. Examples of the vacuum vapor deposition method include a vacuum vapor deposition method based on an electronic book (EB) heating method or a vacuum vapor deposition method based on a high-frequency dielectric heating method.

[0405] (Antifouling layer)

[0406] The antifouling layer is not particularly limited as long as it has water / oil repellency and can impart antifouling properties to the obtained optical film 80 , but is preferably composed of a fluorinated organosilicon compound layer obtained by curing a coating film of a fluorinated organosilicon compound.

[0407] The thickness of the antifouling layer is not particularly limited. When the antifouling layer is composed of a fluorine-containing organic silicon compound layer, the thickness of the antifouling layer is preferably 1 nm or more and 20 nm or less. If the thickness of the antifouling layer is 1 nm or more, the inorganic layer is uniformly covered by the antifouling layer, and the antifouling layer can withstand actual use from the aspect of scratch resistance. If the thickness of the antifouling layer is 20 nm or less, the optical properties such as the haze value of the optical film in the state where the antifouling layer is formed become good. The upper limit of the thickness of the antifouling layer is more preferably 15 nm or less or 10 nm or less.

[0408] As a method for forming a fluorinated organosilicon compound layer, there can be cited: a method of applying a composition of a silane coupling agent having a perfluoroalkyl group; a fluorinated alkyl group containing a perfluoro(polyoxyalkylene) chain, etc. to the surface of an inorganic layer by spin coating, dip coating, casting, slit coating, spray coating, etc., followed by heat treatment; a vacuum evaporation method in which a fluorinated organosilicon compound is vapor-deposited onto the surface of an inorganic layer and then heat treated; etc. In order to obtain a fluorinated organosilicon compound layer with high adhesion, it is preferred to form an antifouling layer by vacuum evaporation. When forming a fluorinated organosilicon compound layer by vacuum evaporation, it is preferred to use a film-forming composition containing a fluorinated hydrolyzable silicon compound.

[0409] The film-forming composition is not particularly limited as long as it contains a fluorine-containing hydrolyzable silicon compound and can form a film by vacuum evaporation. The film-forming composition may contain any component other than the fluorine-containing hydrolyzable silicon compound, or may consist only of the fluorine-containing hydrolyzable silicon compound. As the arbitrary component, a hydrolyzable silicon compound without fluorine atoms (hereinafter referred to as "non-fluorine hydrolyzable silicon compound"), a catalyst, etc., which can be used within the range that does not hinder the effect of the present invention, can be cited.

[0410] The fluorine-containing hydrolyzable silicon compound used for forming the fluorine-containing organosilicon compound coating is not particularly limited as long as the resulting fluorine-containing organosilicon compound coating has antifouling properties such as water repellency and oil repellency.

[0411] Specifically, the fluorinated hydrolyzable silicon compound may include a fluorinated hydrolyzable silicon compound having one or more groups selected from the group consisting of a perfluoropolyether group, a perfluoroalkylene group, and a perfluoroalkyl group. These groups exist in the form of fluorinated organic groups bonded to the silicon atom of the hydrolyzable silyl group via a linking group or directly. It should be noted that the perfluoropolyether group refers to a divalent group having a structure in which a perfluoroalkylene group and an etheric oxygen atom are alternately bonded.

[0412] Examples of commercially available fluorinated organosilicon compounds having one or more groups selected from the group consisting of a perfluoropolyether group, a perfluoroalkylene group, and a perfluoroalkyl group include KP-801, X-71, KY-130, KY-178, KY-185 (all manufactured by Shin-Etsu Chemical Co., Ltd.), OPTOOL (registered trademark) DSX (manufactured by Daikin Industries, Ltd.), etc. Among these, KY-185 and OPTOOL (registered trademark) DSX are preferred.

[0413] When a commercially available fluorinated hydrolyzable silicon compound is supplied together with a solvent, it is preferred to remove the solvent before using the commercially available fluorinated hydrolyzable silicon compound. The film-forming composition is prepared by mixing a fluorinated hydrolyzable silicon compound with optional components added as required, and subjected to vacuum deposition.

[0414] The film-forming composition containing such a fluorinated hydrolyzable silicon compound is attached to the surface of the inorganic layer and reacted to form a film, thereby obtaining a fluorinated organic silicon compound layer. In this case, the antifouling layer is composed of a cured product of the film-forming composition containing a fluorinated hydrolyzable silicon compound. It should be noted that, with regard to the specific vacuum evaporation method and reaction conditions, existing known methods and conditions can be applied.

[0415] <<Other optical films>>

[0416] Fig. 9 The optical film 80 shown has a functional layer 85, but may also be Fig.11 The optical film 90 does not include a functional layer as shown. The surface 90A of the optical film 90 is constituted by the surface 82A of the resin layer 82 .

[0417] <<<Image Display Device>>>

[0418] The optical films 80 and 90 can be incorporated into a foldable image display device for use. The structure of the image display device incorporating the optical films 80 and 90 is the same as that of the image display device 60 except that the optical film 30 is replaced by the optical films 80 and 90 .

[0419] According to this embodiment, since the resin layer 82 contains organic particles 83B, not only the surface 82A of the resin layer 82 but also the surface 80A of the optical film 80 can be made to have a concave-convex surface. Thus, the transmitted light and the reflected light can be blurred, so even if the surface is pressed with a finger and a dent is temporarily generated, the pressing mark is not easily noticeable.

[0420] According to the present embodiment, the organic particles 83B in the resin layer 82 are located closer to the resin substrate 81 side than the center line CL, so that it is difficult to apply pressure to the organic particles 83B near the curved portion S3 during folding, and it is difficult for the organic particles 83B to break. In particular, if the organic particles in the resin layer are present on the surface side of the resin layer, cracks are likely to occur when the optical film is folded so that the surface of the resin layer is on the outside (i.e., when it is bent outward), but in the present embodiment, since the organic particles 83B in the resin layer 82 are located closer to the resin substrate 81 side than the center line CL, cracks can be suppressed even when the optical film 80 is folded so that the surface 82A of the resin layer 82 is on the outside. Therefore, this optical film 80 is particularly effective when the optical film 80 is folded so that the surface 82A of the resin layer 82 is on the outside.

[0421] According to the present embodiment, since organic particles 83B in resin layer 82 are located closer to resin base material 81 than center line CL, organic particles 83B are not present near surface 82A of resin layer 82. Thus, surface hardness and scratch resistance can be improved.

[0422] Example

[0423] In order to explain the present invention in detail, the following examples are given for description, but the present invention is not limited to these descriptions.

[0424] <Preparation of Hard Coat Composition>

[0425] First, each component was mixed so as to have the following composition to obtain a composition for a hard coat layer.

[0426] (Hard Coat Composition 1)

[0427] A mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (product name "M403", manufactured by Toagosei Co., Ltd.): 25 parts by mass

[0428] Dipentaerythritol EO-modified hexaacrylate (product name "A-DPH-6E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 25 parts by mass

[0429] Irregularly shaped silica particles (average particle size 25 nm, manufactured by JGC Catalysts & Chemicals Co., Ltd.): 50 parts by mass (based on 100% solid content)

[0430] Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad 184", manufactured by IGM Resins BV): 4 parts by mass

[0431] Fluorine-based leveling agent (product name "F568", manufactured by DIC Corporation): 0.2 parts by mass (based on 100% solid content)

[0432] Methyl isobutyl ketone (MIBK): 150 parts by mass

[0433] (Hard Coat Composition 2)

[0434] · Multifunctional acrylate (product name "KAYARAD PET-30", manufactured by Nippon Kayaku Co., Ltd.): 18 parts by mass

[0435] EO modified acrylate (product name "ATM-35E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 12 parts by mass

[0436] Inorganic particles (fumed silica, octylsilane treated, average particle size 12 nm, manufactured by NIPPON AEROSIL Co., Ltd.): 0.6 parts by mass

[0437] Organic particles (particle size 2 μm, refractive index 1.555, spherical acrylic acid-styrene copolymer): 1.5 parts by mass

[0438] Silicone leveling agent: 0.075 parts by mass

[0439] Polymerization initiator (product name "Omnirad 184", manufactured by IGM Resins BV): 0.3 parts by mass

[0440] Toluene: 50 parts by mass

[0441] Propylene glycol monomethyl ether acetate: 17 parts by mass

[0442] Cyclohexanone: 1 part by mass

[0443] Isopropyl alcohol: 2 parts by mass

[0444] (Hard Coat Composition 3)

[0445] EO modified acrylate (product name "A-DPH18E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 15 parts by mass

[0446] Reactive acrylic polymer (product name "SMP220A", solid content 50%, diluent methyl isobutyl ketone, manufactured by Kyoeisha Chemical Co., Ltd.): 10 parts by mass

[0447] Inorganic particles (organic silica sol, product name "MIBK-SD", SiO2 solid content 30%, diluent methyl isobutyl ketone, particle size 10-15 nm, manufactured by Nissan Chemical Industries, Ltd.): 50 parts by mass

[0448] Silicone leveling agent: 0.15 parts by mass

[0449] Polymerization initiator (product name "Omnirad 184", manufactured by IGM Resins BV): 1 part by mass

[0450] Propylene glycol monomethyl ether: 24 parts by mass

[0451] (Hard Coat Composition 4)

[0452] · Multifunctional acrylate (product name "KAYARAD PET-30", manufactured by Nippon Kayaku Co., Ltd.): 18 parts by mass

[0453] EO modified acrylate (product name "ATM-35E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 12 parts by mass

[0454] Organic particles (particle size 3.5 μm, refractive index 1.540, spherical acrylic acid-styrene copolymer): 2.5 parts by mass

[0455] Organic particles (particle size 3.5 μm, refractive index 1.555, spherical acrylic acid-styrene copolymer): 0.4 parts by mass

[0456] Silicone leveling agent: 0.075 parts by mass

[0457] Polymerization initiator (product name "Omnirad 184", manufactured by IGM Resins BV): 0.3 parts by mass

[0458] Toluene: 50 parts by mass

[0459] Propylene glycol monomethyl ether acetate: 18 parts by mass

[0460] Cyclohexanone: 1 part by mass

[0461] Isopropyl alcohol: 2 parts by mass

[0462] (Hard Coat Composition 5)

[0463] Multifunctional acrylate (product name "KAYARAD PET-30", manufactured by Nippon Kayaku Co., Ltd.): 19 parts by mass

[0464] EO modified acrylate (product name "ATM35E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 16 parts by mass

[0465] Silicone leveling agent: 0.15 parts by mass

[0466] Polymerization initiator (product name "Omnirad 184", manufactured by IGM Resins BV): 1 part by mass

[0467] Propylene glycol monomethyl ether: 64 parts by mass

[0468] <Resin Layer Composition>

[0469] The components were mixed so as to have the following composition to obtain a composition for a resin layer.

[0470] (Resin layer composition 1)

[0471] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0472] Monofunctional acrylic monomer (product name "Viscoat #200", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 20 parts by mass

[0473] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 3 parts by mass

[0474] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0475] (Resin layer composition 2)

[0476] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0477] Monofunctional acrylic monomer (product name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass

[0478] Monofunctional acrylic monomer (product name "Viscoat #200", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass

[0479] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 3 parts by mass

[0480] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0481] (Resin layer composition 3)

[0482] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0483] Monofunctional acrylic monomer (product name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 20 parts by mass

[0484] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 3 parts by mass

[0485] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0486] (Resin layer composition 4)

[0487] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0488] Monofunctional acrylic monomer (product name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 20 parts by mass

[0489] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 1 part by mass

[0490] Polymerization initiator (product name "Ominirad 184", manufactured by IGM Resins BV): 2 parts by mass

[0491] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0492] (Resin layer composition 5)

[0493] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0494] Monofunctional acrylic monomer (product name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 20 parts by mass

[0495] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 6 parts by mass

[0496] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0497] (Resin layer composition 6)

[0498] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0499] Monofunctional acrylic monomer (product name "ACMO", manufactured by KJ Chemicals Co., Ltd.): 20 parts by mass

[0500] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 3 parts by mass

[0501] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0502] (Resin layer composition 7)

[0503] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0504] Monofunctional acrylic monomer (product name "IBXA", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 20 parts by mass

[0505] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 3 parts by mass

[0506] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0507] (Resin layer composition 8)

[0508] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0509] Monofunctional acrylic monomer (product name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass

[0510] Monofunctional acrylic monomer (product name "Viscoat #200", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 5 parts by mass

[0511] Monofunctional acrylic monomer (product name "ACMO", manufactured by KJ Chemicals Co., Ltd.): 5 parts by mass

[0512] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 5 parts by mass

[0513] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0514] (Resin layer composition 9)

[0515] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0516] Monofunctional acrylic monomer (product name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 20 parts by mass

[0517] Polymerization initiator (product name "Ominirad TPOH", manufactured by IGM Resins BV): 3 parts by mass

[0518] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0519] (Resin layer composition 10)

[0520] Urethane acrylate (product name "UV3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0521] Monofunctional acrylic monomer (product name "Viscoat #150D", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 20 parts by mass

[0522] Polymerization initiator (product name "Ominirad 127", manufactured by IGM Resins BV): 2 parts by mass

[0523] Polymerization initiator (product name "Ominirad 184", manufactured by IGM Resins BV): 2 parts by mass

[0524] Polymerization initiator (product name "Ominirad TPOH", manufactured by IGM Resins BV): 1 part by mass

[0525] Methyl isobutyl ketone (MIBK): 10 parts by mass

[0526] (Resin layer composition 11)

[0527] Urethane acrylate (product name "UV-3310B", manufactured by Mitsubishi Chemical Corporation): 90 parts by mass

[0528] Phenoxyethyl acrylate (product name "Viscoat #192", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass

[0529] Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad 184", manufactured by IGM Resins BV): 5 parts by mass

[0530] Methyl isobutyl ketone: 10 parts by mass

[0531] (Resin layer composition 12)

[0532] Urethane acrylate (product name "UV-3310B", manufactured by Mitsubishi Chemical Corporation): 50 parts by mass

[0533] Ethoxylated pentaerythritol tetraacrylate (product name "ATM-35E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 40 parts by mass

[0534] Dicyclopentanyl acrylate (product name "FA-513AS", manufactured by Hitachi Chemical Co., Ltd.): 10 parts by mass

[0535] Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad 184", manufactured by IGM Resins BV): 5 parts by mass

[0536] Methyl isobutyl ketone: 10 parts by mass

[0537] (Resin layer composition 13)

[0538] Urethane acrylate (product name "UV-3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0539] Ethoxylated pentaerythritol tetraacrylate (product name "ATM-35E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 10 parts by mass

[0540] Phenoxyethyl acrylate (product name "Viscoat #192", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass

[0541] Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad 184", manufactured by IGM Resins BV): 5 parts by mass

[0542] Methyl isobutyl ketone: 10 parts by mass

[0543] (Resin layer composition 14)

[0544] Urethane acrylate (product name "UV-3310B", manufactured by Mitsubishi Chemical Corporation): 80 parts by mass

[0545] A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (product name "KAYARAD PET-30", manufactured by Nippon Kayaku Co., Ltd.): 10 parts by mass

[0546] Phenoxyethyl acrylate (product name "Viscoat #150", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass

[0547] Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad 184", manufactured by IGM Resins BV): 5 parts by mass

[0548] Methyl isobutyl ketone: 10 parts by mass

[0549] (Resin layer composition 15)

[0550] Urethane acrylate (product name "UV-3310B", manufactured by Mitsubishi Chemical Corporation): 50 parts by mass

[0551] Ethoxylated pentaerythritol tetraacrylate (product name "ATM-35E", manufactured by Shin-Nakamura Chemical Industry Co., Ltd.): 40 parts by mass

[0552] Acryloylmorpholine (product name "ACMO", manufactured by KJ Chemicals Co., Ltd.): 10 parts by mass

[0553] Polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name "Omnirad 184", manufactured by IGM Resins BV): 5 parts by mass

[0554] Methyl isobutyl ketone: 10 parts by mass

[0555] <Preparation of Composition for Polyimide Substrate>

[0556] First, in a 5L detachable flask, the temperature of a solution containing 8960g of dehydrated dimethylacetamide and 16.0g (0.07mol) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (AprTMOS) was controlled to 30°C, and 14.6g (0.03mol) of 4,4'-(hexafluoroisopropyl)diphthalic anhydride (6FDA) was slowly added thereto in such a manner that the temperature rose below 2°C, and the solution was stirred for 30 minutes using a mechanical stirrer. 400 g (1.25 mol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was added thereto, and after confirming that it was completely dissolved, 565 g (1.27 mol) of 4,4'-(hexafluoroisopropyl)diphthalic anhydride (6FDA) was slowly added several times in such a manner that the temperature rose to below 2°C, thereby synthesizing a polyimide precursor solution 1 (solid content 10% by mass) in which the polyimide precursor 1 was dissolved.

[0557] <<Example A and Comparative Example A>>

[0558] <Example A1>

[0559] As a release film, a polyethylene terephthalate substrate having a thickness of 50 μm (product name "Cosmoshine (registered trademark) A4100", manufactured by Toyobo Co., Ltd.) was prepared, and the resin layer composition 1 was applied to the untreated surface of the polyethylene terephthalate substrate using a bar coater to form a coating film. Then, the formed coating film was heated at 70° C. for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb) was used to irradiate the film at a cumulative light intensity of 100 mJ / cm in air. 2 The coating film was semi-cured by irradiating ultraviolet rays from the coating film side in a manner to form a resin layer composed of a urethane resin with a film thickness of 50 μm.

[0560] Next, the hard coating composition 1 was applied to the surface of the resin layer using a bar coater to form a coating film. Thereafter, the formed coating film was heated at 70° C. for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by FusionUV Systems Japan, light source H bulb) was used to irradiate the film at a cumulative light intensity of 300 mJ / cm under the condition that the oxygen concentration was 200 ppm or less. 2 The coating film was completely cured (fully solidified) by irradiating ultraviolet rays from the coating film side in a manner of 100 μm. Thus, a hard coating layer with a film thickness of 5 μm was formed.

[0561] Thereafter, the resin layer is peeled off from the polyethylene terephthalate substrate, thereby obtaining an optical film composed of a resin layer composed of a urethane-based resin and a hard coat layer.

[0562] Regarding the film thickness of each layer, a scanning transmission electron microscope (STEM) (product name "S-4800", manufactured by Hitachi High-Technologies Co., Ltd.) was used to photograph the cross section of the optical film, and the film thickness of each layer at 10 locations was measured in the cross-sectional image, and the arithmetic mean of the film thickness of the 10 locations was used. The cross-sectional photograph of the optical film was taken as follows. First, an optical film cut into 1 mm × 10 mm was embedded in an embedding resin to make a block, and a uniform slice with a thickness of 70 nm to 100 nm without holes was cut from the block using a general slicing method. The slices were made using the Ultramicrotome EMUC7 of Leica Microsystems Co., Ltd. Then, the uniform slice without holes was used as a measurement sample. After that, a cross-sectional photograph of the measurement sample was taken using a scanning transmission electron microscope (STEM). When taking a cross-sectional photograph of the resin layer, the detector was set to "SE", the acceleration voltage was set to "5 kV", and the emission current was set to "10 μA" for SEM observation. Regarding the magnification, adjust the focal length, and observe whether each layer can be distinguished while appropriately adjusting the contrast and brightness at 1000 times to 10,000 times. When taking a cross-sectional photograph of the hard coating, set the detector to "TE", the acceleration voltage to "30kV", and the emission current to "10μA" for STEM observation. Regarding the magnification, adjust the focal length, and observe whether each layer can be distinguished while appropriately adjusting the contrast and brightness at 5000 times to 200,000 times. It should be noted that during SEM observation and STEM observation, the beam monitoring aperture is further set to "3", the objective lens aperture is set to "3", and the WD is set to "8mm". In Examples A2 to A15 and Comparative Examples A1 and A2, the film thickness of each layer is also measured by the same method as Example A1.

[0563] <Example A2>

[0564] In Example A2, except having used the composition 2 for resin layers instead of the composition 1 for resin layers, it carried out similarly to Example A1, and obtained the optical film.

[0565] <Example A3>

[0566] In Example A3, an optical film was obtained in the same manner as in Example A1 except that the composition 3 for a resin layer was used instead of the composition 1 for a resin layer.

[0567] <Example A4>

[0568] In Example A4, an optical film was obtained in the same manner as in Example A1 except that the composition 4 for a resin layer was used instead of the composition 1 for a resin layer.

[0569] <Example A5>

[0570] In Example A5, an optical film was obtained in the same manner as in Example A1 except that the composition 5 for a resin layer was used instead of the composition 1 for a resin layer.

[0571] <Example A6>

[0572] In Example A6, an optical film was obtained in the same manner as in Example A1 except that the composition 6 for a resin layer was used instead of the composition 1 for a resin layer.

[0573] <Example A7>

[0574] In Example A7, an optical film was obtained in the same manner as in Example A1 except that the composition 7 for a resin layer was used instead of the composition 1 for a resin layer.

[0575] <Example A8>

[0576] In Example A8, an optical film was obtained in the same manner as in Example A3 except that the thickness of the resin layer was 40 μm.

[0577] <Example A9>

[0578] In Example A9, an optical film was obtained in the same manner as in Example A3 except that the thickness of the resin layer was set to 25 μm.

[0579] <Example A10>

[0580] In Example A10, an optical film was obtained in the same manner as in Example A1 except that the resin layer composition 8 was used instead of the resin layer composition 1 and the thickness of the resin layer was set to 70 μm.

[0581] <Example A11>

[0582] In Example A11, an optical film was obtained in the same manner as in Example A10 except that the thickness of the resin layer was 80 μm.

[0583] <Example A12>

[0584] In Example A12, an optical film was obtained in the same manner as in Example A10 except that the thickness of the resin layer was 90 μm.

[0585] <Example A13>

[0586] In Example A13, an optical film was obtained in the same manner as in Example A10 except that the thickness of the resin layer was set to 100 μm.

[0587] <Example A14>

[0588] In Example A14, an optical film was obtained in the same manner as in Example A10 except that the thickness of the resin layer was 115 μm.

[0589] <Example A15>

[0590] In Example A15, an optical film was obtained in the same manner as in Example A10 except that the thickness of the resin layer was 140 μm.

[0591] <Comparative Example A1>

[0592] In Comparative Example A1, the resin layer composition 9 was used instead of the resin layer composition 1, and the resin layer was formed at a cumulative light intensity of 500 mJ / cm in air. 2 An optical film was obtained in the same manner as in Example A1 except that ultraviolet rays were irradiated from the coating film side.

[0593] <Comparative Example A2>

[0594] In Comparative Example A2, the resin layer composition 10 was used instead of the resin layer composition 1, and when forming the hard coat layer, the accumulated light intensity was 300 mJ / cm in the air as an additional treatment. 2 An optical film was obtained in the same manner as in Example A1 except that ultraviolet rays were irradiated from the release film side.

[0595] <Displacement measurement>

[0596] A test of pressing a Bosch indenter into the first to third regions of the resin layer of the optical film of Examples A1 to A15 and Comparative Examples A1 and A2 with a constant load was conducted, and the displacements d1 to d3 at this time were measured respectively. Specifically, first, an optical film cut into 1 mm × 10 mm was embedded in an embedding resin to make a block, and a uniform slice with a thickness of 70 nm to 100 nm without holes was cut from the block using a general slice making method. The slices were made using Ultramicrotome EMUC7 of Leica Microsystems Co., Ltd. Then, the block remaining after the uniform slice without holes was cut out was used as a measurement sample. Next, in this measurement sample, the resin layer was divided into three equal parts along the film thickness direction of the resin layer, and the first surface on the hard coating side of the resin layer to the second surface on the opposite side of the first surface were used as the first region, the second region, and the third region in sequence. Next, in the cross section obtained by cutting out the above-mentioned slice in this measurement sample, a nanoindenter (TI950TriboIndenter manufactured by Bruker) is used. Under the following measurement conditions, the Berkovich indenter (triangular pyramid, TI-0039 manufactured by Bruker) as the above-mentioned indenter is vertically pressed into the center of the cross section of the first region of the resin layer with a maximum load of 200μN for 40 seconds, and the displacement (indentation depth) d1 at this time is measured. Here, in order to avoid the influence of the side edge of the resin layer, the Berkovich indenter is pressed into the first region from the two side ends of the resin layer to the central side of the resin layer at a distance of more than 500nm. The displacement d1 is the arithmetic mean of the values ​​obtained by measuring 3 locations. It should be noted that when the measured value contains a value that deviates from the arithmetic mean by more than ±20%, the measured value is removed and the measurement is performed again. Whether there is a value that deviates from the arithmetic mean by more than ±20% in the measured value is determined by the formula described in the embodiment. In addition, the displacement amount d2 of the second region and the displacement amount d3 of the third region of the resin layer are measured in the same manner as the displacement amount d1 of the first region.

[0597] (Measurement conditions)

[0598] Control method: load control (maximum load 200μN)

[0599] Lifting amount: 0nm

[0600] Preload: 0.5μN

[0601] Loading speed: 5μN / sec

[0602] Holding time under maximum load: 5 seconds

[0603] Unloading speed: 5μN / s

[0604] Temperature: 23℃

[0605] Relative humidity: 50%

[0606] <Foldability>

[0607] The optical films of Examples A1 to A15 and Comparative Examples A1 and A2 were subjected to a continuous folding test to evaluate foldability. Specifically, first, a sample with a size of 30 mm × 100 mm was cut out from the optical film. The two opposing sides of the cut sample were fixed by the fixing part of a parallel-arranged folding durability tester (product name "U-shaped telescopic tester DLDMLH-FS", manufactured by YUASA SYSTEM Co., Ltd., in accordance with IEC62715-6-1). Afterwards, as Figure 4 (C) shows the minimum distance between two opposing sides. The folding test was performed 100,000 times under the following conditions in a manner where the surface side (hard coating side) of the optical film was 10 mm and the surface side (hard coating side) of the optical film was on the outside to investigate whether deformation, cracks or breaks occurred in the bent portion. The continuous folding test was performed at a temperature of 23°C and a relative humidity of 50%. The evaluation criteria are as follows. It should be noted that as long as there is no crack or break in the bent portion, the foldability is considered good.

[0608] A: In the continuous folding test, the bent portion did not deform, crack, or break.

[0609] B: In the continuous folding test, deformation at a level that does not cause practical problems was observed at the bent portion, but no cracks or breaks occurred.

[0610] C: In the continuous folding test, deformation was clearly observed at the bent portion, but no cracks or breaks occurred.

[0611] D: In the continuous folding test, cracks or breaks occurred in the bent portion.

[0612] <Impact Resistance>

[0613] The optical films of Examples A1 to A15 and Comparative Examples A1 and A2 were subjected to an impact resistance test. Specifically, the optical films of Examples A1 to A15 and Comparative Examples A1 and A2 were placed directly on the surface of a soda glass having a thickness of 0.7 mm in a manner such that the hard coating side was on the upper side, and an iron ball weighing 100 g and having a diameter of 30 mm was dropped from a height of 30 cm onto the surface of the hard coating of the optical film, and the impact resistance test was performed three times each. It should be noted that in the impact resistance test, the position where the iron ball fell was changed each time. Then, in the optical film after the impact resistance test, it was visually evaluated whether the surface of the hard coating was sunken or whether the soda glass was broken. The evaluation results are as follows. It should be noted that for impact resistance, as long as either the sunken evaluation of the surface of the hard coating or the crack evaluation of the soda glass is not "D", it is considered good.

[0614] (Evaluation of Depression on Hard Coat Surface)

[0615] A: In both cases where the hard coating layer was observed from the front and from an oblique direction, no depressions were observed on the surface of the hard coating layer.

[0616] B: In both the case of observing the hard coat layer from the front and from an oblique direction, depressions were observed on the surface of the hard coat layer, but the level was not a problem in practical use.

[0617] C: When the hard coating layer was observed from the front, no depressions were observed on the surface of the hard coating layer, but when observed from an oblique direction, depressions were confirmed on the surface of the hard coating layer.

[0618] D: In both cases where the hard coating layer was observed from the front and from an oblique direction, clear depressions were observed on the surface of the hard coating layer.

[0619] (Crack Evaluation of Soda Glass)

[0620] A: The soda glass is not broken and has no scratches.

[0621] B: The soda glass is scratched but not broken.

[0622] C: One crack occurred in the soda glass.

[0623] D: Soda glass has 2 to 3 cracks.

[0624] <Pencil Hardness>

[0625] The pencil hardness of the surface (hard coating surface) of the optical film of Examples A1 to A15 and Comparative Examples A1 and A2 was measured based on JIS K5600-5-4: 1999. Specifically, first, the optical film cut into a size of 30 mm × 100 mm was fixed on a glass plate of 2 mm thickness and 50 mm × 100 mm in a manner without folds or wrinkles using Cellotape (registered trademark) manufactured by Michibon Co., Ltd. Then, using a pencil hardness tester (product name "Pencil Scratch Film Hardness Tester (Electric)", manufactured by Toyo Seiki Seisaku-sho Co., Ltd.), a load of 750 g was applied to a pencil (product name "Uni", manufactured by Mitsubishi Pencil Co., Ltd.) and the pencil was moved at a speed of 1 mm / second under an environment of a temperature of 23°C and a relative humidity of 50%. The pencil hardness was set to the highest hardness at which the surface (hard coating surface) of the optical film was not scratched in the pencil hardness test. It should be noted that when measuring the pencil hardness, a plurality of pencils of different hardness are used, and the pencil hardness test is performed 5 times for each pencil. If no scratches are observed on the surface of the optical film when the surface of the optical film is observed through a fluorescent lamp 4 or more times out of 5 times, it is judged that the surface of the optical film is not scratched by the pencil of that hardness.

[0626] The results are shown in Table 1 below.

[0627] [Table 1]

[0628]

[0629] The results are described below. The optical film of Comparative Example A1 has poor foldability because the displacement d1 is greater than the displacement d2 and does not satisfy the above relationship (1). In addition, the optical film of Comparative Example A2 has poor foldability because the displacement d2 is greater than the displacement d3 and does not satisfy the above relationship (1). In contrast, the optical films of Examples A1 to A15 have good foldability and impact resistance because they satisfy the above relationship (1).

[0630] <<Example B and Comparative Example B>>

[0631] <Example B1>

[0632] Using the polyimide precursor solution 1 obtained above, a single-layer polyimide substrate with a thickness of 12 μm was prepared according to the following steps. First, the polyimide precursor solution 1 was applied to a glass plate and dried in a circulation oven at 120° C. for 10 minutes to form a coating. After the coating was formed, the glass plate with the coating was heated to 350° C. at a heating rate of 10° C. / min under a nitrogen flow (oxygen concentration of less than 100 ppm), maintained at 350° C. for 1 hour, and then cooled to room temperature. Thus, a single-layer polyimide substrate formed on the glass plate was obtained.

[0633] Next, the hard coating composition 1 was applied to the surface (second surface) of the polyimide substrate using a bar coater to form a coating film. The formed coating film was then heated at 70° C. for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb) was used to irradiate the film in air at a cumulative light intensity of 200 mJ / cm 2 The coating film was cured by irradiating ultraviolet rays in a manner of . Thus, a hard coating layer with a film thickness of 5 μm was formed on the polyimide substrate.

[0634] After forming the hard coating layer on the polyimide substrate, the glass plate was peeled off from the polyimide substrate, and the resin layer composition 11 was applied to the first surface of the polyimide substrate opposite to the second surface using a bar coater to form a coating film. Then, the formed coating film was heated at 70° C. for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by FusionUV Systems Japan, light source H bulb) was used to irradiate the film in air at a cumulative light intensity of 1200 mJ / cm 2 The coating film was cured by irradiating ultraviolet rays in a manner of 100 μm to form a resin layer composed of a urethane resin with a film thickness of 80 μm. Thus, an optical film was obtained.

[0635] Regarding the thickness of the polyimide substrate, a scanning electron microscope (SEM) was used to photograph the cross section of the polyimide substrate, and the thickness of the polyimide substrate at 20 locations was measured in the image of the cross section, and the arithmetic mean of the thickness of the 20 locations was used. The method for photographing the cross-sectional photograph is the same as the method for photographing the cross-sectional photograph when measuring the film thickness of the hard coating layer described in the column of Example A. The film thickness of the resin layer and the film thickness of the hard coating layer are also measured by the same method as the thickness of the polyimide substrate. In other Examples B2 to B7 and Comparative Examples B1 to B4, the thickness of the polyimide substrate, the film thickness of the resin layer, and the film thickness of the hard coating layer are also measured by the same method as Example B1.

[0636] <Example B2>

[0637] In Example B2, an optical film was obtained in the same manner as in Example B1 except that the thickness of the polyimide substrate was 8 μm.

[0638] <Example B3>

[0639] In Example B3, an optical film was obtained in the same manner as in Example B1 except that the thickness of the polyimide substrate was 18 μm.

[0640] <Example B4>

[0641] In Example B4, an optical film was obtained in the same manner as in Example B1 except that the thickness of the resin layer was set to 60 μm.

[0642] <Example B5>

[0643] In Example B5, an optical film was obtained in the same manner as in Example B1 except that the thickness of the resin layer was 100 μm.

[0644] <Example B6>

[0645] In Example B6, an optical film was obtained in the same manner as in Example B1 except that the composition 12 for a resin layer was used instead of the composition 11 for a resin layer.

[0646] <Example B7>

[0647] In Example B7, an optical film was obtained in the same manner as in Example B1 except that the composition 13 for a resin layer was used instead of the composition 11 for a resin layer.

[0648] <Comparative Example B1>

[0649] In Comparative Example B1, an optical film was obtained in the same manner as in Example B1 except that the thickness of the polyimide substrate was 30 μm.

[0650] <Comparative Example B2>

[0651] In Comparative Example B2, an optical film was obtained in the same manner as in Example B1 except that the thickness of the resin layer was 30 μm.

[0652] <Comparative Example B3>

[0653] In Comparative Example B3, an optical film was obtained in the same manner as in Example B1 except that the composition 14 for a resin layer was used instead of the composition 11 for a resin layer.

[0654] <Comparative Example B4>

[0655] In Comparative Example B4, an optical film was obtained in the same manner as in Example B1 except that the composition 15 for a resin layer was used instead of the composition 11 for a resin layer.

[0656] <Displacement measurement>

[0657] The indentation test was carried out by pressing the glass indenter into the cross-section of the polyimide substrate and the resin layer of the optical film of Examples B1 to B7 and Comparative Examples B1 to B4 with a maximum load of 200 μN, and the displacement d4 of the polyimide substrate and the displacement d5 of the resin layer were measured respectively. The displacement d4 was measured by the same method as the determination method of the displacements d1 to d3 described in the column of Example A. Among them, in order to avoid the influence of the side edge of the polyimide substrate, the glass indenter was pressed into the part with a spacing of more than 500 nm from the two side ends of the polyimide substrate to the central side of the polyimide substrate. The displacement d4 is the arithmetic mean of the values ​​obtained by measuring 3 parts. It should be noted that when the measured value contains a value that deviates from the arithmetic mean by more than ±20%, the measured value is removed and measured again. Whether there is a value that deviates from the arithmetic mean by more than ±20% in the measured value is judged by the formula described in the embodiment. In addition, the displacement d5 of the resin layer is also measured in the same way as the displacement d4 of the polyimide substrate.

[0658] <Foldability>

[0659] The optical films of Examples B1 to B7 and Comparative Examples B1 to B4 were subjected to a continuous folding test to evaluate foldability. The continuous folding test was performed in the same manner as the continuous folding test described in the column of Example A. In addition, the evaluation criteria were also the same as the evaluation criteria of the continuous folding test described in the column of Example A.

[0660] <Crease Evaluation>

[0661] In the optical films of Examples B1 to B7 and Comparative Examples B1 to B4, evaluate whether creases are confirmed during the folding and standing test. Specifically, first, an optical film cut into a size of 30 mm × 100 mm is obtained. Then, the 30 mm × 48 mm area of ​​the cut optical film including the sides of the two opposing short sides (30 mm) is fixed to glass plates of 50 mm × 100 mm in size. The glass plate is fixed to the resin layer side of the optical film. Thereafter, the glass plates are arranged in parallel so that the interval between the opposing sides of the optical film is 2.5 mm, and the optical film is folded so that the hard coating layer is on the inside. In this state, a folding and standing test is performed at a temperature of 25°C and a relative humidity of 50% for 100 hours. Thereafter, the optical film is opened with the glass plate so that the surface of the optical film is flat. Then, confirm whether creases are generated on the surface of the optical film. The evaluation criteria are as follows.

[0662] A: In both cases of observing the optical film from the front and from an oblique direction, no crease was observed in the optical film.

[0663] B: In both the case of observing the optical film from the front and from an oblique direction, some creases were observed in the optical film, but the level was not a problem in practical use.

[0664] C: When the optical film is observed from the front, no fold is observed on the optical film, but when the optical film is observed from an oblique direction, a fold is confirmed on the optical film.

[0665] D: In both cases where the optical film is observed from the front and from an oblique direction, clear creases are observed on the optical film.

[0666] <Impact Resistance Evaluation>

[0667] The optical films of Examples B1 to B7 and Comparative Examples B1 to B4 were subjected to an impact resistance test. Specifically, first, an optical film cut into a size of 50 mm × 50 mm was obtained. Then, the optical film was directly placed on the surface of a soda glass having a thickness of 0.7 mm and a size of 50 mm × 50 mm in such a way that the hard coating side was on the upper side, and a ballpoint pen (orange 0.7 manufactured by BIC Japan) weighing 100 g and having a pen tip with a diameter of 0.7 mm was dropped from a height of 30 cm with the pen tip facing downward onto the surface of the hard coating of the optical film, and the impact resistance test was performed three times each. It should be noted that in the impact resistance test, the position where the pen fell was changed each time. Then, in the optical film after the impact resistance test, whether the surface of the hard coating layer was concave was visually evaluated. The evaluation results are as follows.

[0668] A: In both cases where the hard coating layer was observed from the front and from an oblique direction, no depressions were observed on the surface of the hard coating layer.

[0669] B: In both the case of observing the hard coat layer from the front and from an oblique direction, depressions were observed on the surface of the hard coat layer, but the level was not a problem in practical use.

[0670] C: When the hard coating layer was observed from the front, no depressions were observed on the surface of the hard coating layer, but when observed from an oblique direction, depressions were confirmed on the surface of the hard coating layer.

[0671] D: In both cases where the hard coating layer was observed from the front and from an oblique direction, clear depressions were observed on the surface of the hard coating layer.

[0672] <Pencil Hardness>

[0673] The pencil hardness of the surface (hard coat surface) of each of Examples B1 to B7 and Comparative Examples B1 to B4 was measured in accordance with JIS K5600-5-4: 1999. The pencil hardness was measured by the same method as the pencil hardness described in the column of Example A.

[0674] The results are shown in Table 2 below.

[0675] [Table 2]

[0676]

[0677] The results are described below. In the optical film of Comparative Example B1, since the thickness of the polyimide substrate was too thick, creases were confirmed after the folding static test. In the optical film of Comparative Example B2, since the film thickness of the resin layer was too thin, good impact resistance was not obtained. In the optical film of Comparative Example B3, since the displacement of the resin layer caused by the press-in test was too small, good foldability was not obtained. In the optical film of Comparative Example B4, since the displacement of the resin layer caused by the press-in test was too large, impact resistance could not be ensured. In contrast, in the optical films of Examples B1 to B7, the thickness of the polyimide substrate is less than 20 μm, the thickness of the resin layer is greater than 50 μm, the ratio of the thickness of the resin layer to the thickness of the polyimide substrate is greater than 4.0 and greater than 12.0, the displacement d4 of the polyimide substrate during the press-in test is greater than 50 nm and less than 250 nm, and the displacement d5 of the resin layer during the press-in test is greater than 200 nm and less than 1500 nm. Therefore, no creases were confirmed during the folding static test, and good impact resistance was obtained.

[0678] <<Example C and Comparative Example C>>

[0679] <Example C1>

[0680] As a resin substrate, a polyimide substrate with a thickness of 50 μm (product name "Neoprim (registered trademark)", manufactured by Mitsubishi Gas Chemical Co., Ltd.) is prepared. It should be noted that the above-mentioned Neoprim (registered trademark) used in Examples C1 to C5 and Comparative Examples C1 to C3 is a commercially available polyimide film. Then, the hard coating composition 2 is applied to one surface of the polyimide substrate using a rod coater to form a coating film. Thereafter, the formed coating film is heated at 70°C for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb) is used to irradiate the film in air at a cumulative light intensity of 200 mJ / cm 2 The coating film was cured by irradiating ultraviolet rays in a manner to form a first hard coating layer with a film thickness of 3 μm.

[0681] Next, the hard coating composition 3 was applied to the surface of the first hard coating layer using a bar coater to form a coating film. The formed coating film was heated at 70° C. for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by FusionUV Systems Japan, light source H bulb) was used to irradiate the film at a cumulative light intensity of 200 mJ / cm under the condition that the oxygen concentration was 200 ppm or less. 2The coating film was cured by irradiating ultraviolet rays in a manner. Thus, a hard coating layer consisting of a first hard coating layer with a film thickness of 3 μm and a second hard coating layer with a film thickness of 3 μm stacked on the first hard coating layer was formed on the polyimide substrate to obtain an optical film.

[0682] Regarding the film thickness of each layer, a scanning transmission electron microscope (STEM) (product name "S-4800", manufactured by Hitachi High-Tech Co., Ltd.) was used to photograph the cross section of the optical film, and the film thickness of each layer at 10 locations was measured in the image of the cross section, and the arithmetic mean of the film thickness of the 10 locations was used. The cross-sectional photograph of the optical film was taken as follows. First, an optical film cut into 1mm×10mm was embedded in an embedding resin to make a block, and a uniform slice with a thickness of 70nm to 100nm without holes was cut from the block using a general slicing method. The slices were made using the Ultramicrotome EMUC7 of Leica Microsystems Co., Ltd. Then, the uniform slice without holes was used as a measurement sample. After that, a cross-sectional photograph of the measurement sample was taken using a scanning transmission electron microscope (STEM). When taking the cross-sectional photograph, the detector was set to "TE", the acceleration voltage was set to "30kV", and the emission current was set to "10μA" for STEM observation. Regarding the magnification, the focal length was adjusted, and the contrast and brightness were appropriately adjusted at 5000 to 200,000 times while observing whether each layer could be distinguished. It should be noted that when taking cross-sectional photographs, the beam monitoring aperture was further set to "3", the objective lens aperture was set to "3", and the WD was set to "8 mm". In Examples C2 to C5 and Comparative Examples C1 to C3, the film thickness of each layer was also measured by the same method as in Example C1.

[0683] <Example C2>

[0684] In Example C2, an optical film was obtained in the same manner as in Example C1 except that the film thickness of the first hard coat layer was 4 μm and the film thickness of the second hard coat layer was 4 μm.

[0685] <Example C3>

[0686] In Example C3, an optical film was obtained in the same manner as in Example C1 except that the composition 4 for a hard coat layer was used instead of the composition 2 for a hard coat layer.

[0687] <Example C4>

[0688] In Example C4, an optical film was obtained in the same manner as in Example C1 except that the composition 5 for a hard coat layer was used instead of the composition 3 for a hard coat layer.

[0689] <Example C5>

[0690] In Example C5, a 100 nm thick SiO2 film was formed on the surface of the second hard coating layer of the optical film of Example C1 by sputtering. x An optical film was obtained in the same manner as in Example C1 except that an inorganic layer composed of (x=1 to less than 2) was formed and an antifouling layer composed of a fluorinated organic silicon compound was further formed to have a thickness of 2 nm by vacuum deposition.

[0691] <Comparative Example C1>

[0692] As a resin substrate, a polyimide substrate with a thickness of 50 μm (product name "Neoprim (registered trademark)", manufactured by Mitsubishi Gas Chemical Co., Ltd.) was prepared, and the hard coating composition 2 was applied to the first surface, which is one surface of the polyimide substrate, using a bar coater to form a coating film. Thereafter, the formed coating film was heated at 70° C. for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb) was used to irradiate the film at an oxygen concentration of 200 ppm or less at a cumulative light intensity of 400 mJ / cm 2 The coating film was cured by irradiating ultraviolet rays in a manner to form a hard coating layer with a film thickness of 6 μm, thereby obtaining an optical film.

[0693] <Comparative Example C2>

[0694] In Comparative Example C2, an optical film was obtained in the same manner as in Example C1 except that hard-coat composition 3 was used instead of hard-coat composition 2, and hard-coat composition 2 was used instead of hard-coat composition 3. That is, the optical film of Comparative Example C2 has a second hard-coat layer containing organic particles on the first hard-coat layer.

[0695] <Comparative Example C3>

[0696] As a resin substrate, a polyimide substrate with a thickness of 50 μm (product name "Neoprim (registered trademark)", manufactured by Mitsubishi Gas Chemical Co., Ltd.) was prepared, and the hard coating composition 3 was applied to the first surface, which is one surface of the polyimide substrate, using a bar coater to form a coating film. Thereafter, the formed coating film was heated at 70° C. for 1 minute to evaporate the solvent in the coating film, and an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb) was used to irradiate the film at a cumulative light intensity of 200 mJ / cm in air. 2 The coating film was cured by irradiating ultraviolet rays in a manner to form a hard coating layer with a film thickness of 6 μm, thereby obtaining an optical film.

[0697] <Biased Evaluation of Organic Particles>

[0698] In the optical films of Examples C1 to C5 and Comparative Examples C1 and C2, it is investigated whether the organic particles are biased towards a position closer to the polyimide-based substrate side than the center line that bisects the hard coating layer in the film thickness direction of the hard coating layer. Specifically, first, a scanning transmission electron microscope (STEM) (product name "S-4800", manufactured by Hitachi High-Tech Co., Ltd.) is used to photograph the cross section of the hard coating layer under the same conditions as when the film thickness of each layer is measured, and cross-sectional photographs of 10 parts are prepared. In each cross-sectional photograph, the film thickness of the hard coating layer is measured, and the center line is obtained in each cross-sectional photograph. In addition, the center of the organic particles appearing in each cross-sectional photograph is obtained. The midpoint of the imaginary line segment connecting the organic particles and the polyimide-based substrate closest point and the farthest point in the film thickness direction of the hard coating layer is obtained, thereby obtaining the center. In addition, the distance between the center and the center line of the organic particles is measured in each cross-sectional photograph. At this time, the distance between the center of the organic particle and the center line when the center of the organic particle is located closer to the lower side (polyimide substrate side) than the center line is set to "-", and the distance between the center of the organic particle and the center line when the center of the organic particle is located closer to the upper side is set to "+". The average position of the center is obtained by averaging the distances, and whether the average position is "-" or "+" is used to determine whether the center is located closer to the polyimide substrate side than the center. The evaluation criteria are as follows. It should be noted that the optical film of Comparative Example C3 is not the subject of this evaluation because it does not contain organic particles.

[0699] A: The organic particles are located more toward the polyimide-based substrate side than the center line.

[0700] B: The organic particles are not biased toward the polyimide-based substrate side relative to the center line.

[0701] <Foldability>

[0702] The optical films of Examples C1 to C5 and Comparative Examples C1 to C3 were subjected to a continuous folding test to evaluate foldability. Specifically, first, the optical film cut into a size of 30 mm × 100 mm was fixed at the short sides of the optical film to a durability tester (product name "DLDMLH-FS", manufactured by YUASA SYSTEM Co., Ltd.) using a fixing portion, as shown in FIG. Figure 4 As shown in (C), the film was installed with a minimum interval of 8 mm between the two opposing sides, and the surface side of the optical film (the hard coating side in Examples C1 to C4 and Comparative Examples C1 to C3, and the antifouling layer side in Example C5) was placed on the outside. The film was folded 180° 100,000 times to investigate whether cracks or breaks occurred in the bent part. The evaluation criteria are as follows.

[0703] A: In the continuous folding test, no cracks or breaks occurred in the bent portion.

[0704] B: In the continuous folding test, some cracks occurred in the bent portion, but the level was not a problem in practical use.

[0705] C: In the continuous folding test, cracks or breaks were clearly generated in the bent portion.

[0706] <Haze value measurement>

[0707] The haze values ​​(total haze values) of the optical films of Examples C1 to C5 and Comparative Examples C1 to C3 were measured in an environment of a temperature of 23° C. and a relative humidity of 50% using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K7136: 2000. The haze values ​​were measured by placing an optical film cut into a size of 50 mm×100 mm in a state where there were no curls or wrinkles and no fingerprints or dust, etc., with the polyimide-based substrate side facing the light source side, and measuring the value three times for one optical film, and adopting the arithmetic average of the values ​​obtained by the three measurements.

[0708] <Transmission Image Clarity>

[0709] The optical films of Examples C1 to C5 and Comparative Examples C1 to C3 were measured for transmission image clarity using a clarity meter (product name "ICM-1T", manufactured by SUGA TEST INSTRUMENTS Co., Ltd.) in an environment of a temperature of 23° C. and a relative humidity of 50% or more in accordance with JIS K7374: 2007. Regarding the transmission image clarity, an optical film cut into a size of 50 mm×100 mm was placed in a state where there was no curling or wrinkling, and no fingerprints or dust, etc., with the polyimide-based substrate side facing the light source side in the clarity meter with the optical axis rotating table and the sample stage set to "transmission", and one optical comb was measured three times, and the arithmetic average of the values ​​obtained in the three measurements was used.

[0710] <Evaluation of pressure marks>

[0711] For the optical films of Examples C1 to C5 and Comparative Examples C1 to C3, the appearance was observed under an environment with a temperature of 23°C and a relative humidity of 50% or more. Specifically, a colorless transparent glass with a thickness of 1 mm was bonded to the polyimide substrate side of the optical film by two transparent adhesive layers with a thickness of 100 μm (product number "8146-4", manufactured by 3M Company), and an evaluation sample with a size of 5 cm×10 cm was produced. Then, the optical film was placed on a black table with the upper side facing up. Next, a polyethylene terephthalate film (PET film) with a thickness of 250 μm and a size of 20 mm×200 mm (product name "A4300", Toyobo Co., Ltd.) was placed on the evaluation sample, and a cylindrical 300 g weight with a diameter of 35 mm was placed on the PET film. After standing for 1 minute, the weight and PET film were removed. Then, after 3 seconds, observe whether the pressing marks of the weight were confirmed on the PET film. The evaluation criteria are as follows.

[0712] (Press mark evaluation)

[0713] A: No pressure marks were found.

[0714] B: Some marks of pressure were observed, but the level was not a problem in practical use.

[0715] C: The pressing mark is clearly confirmed.

[0716] <Indentation hardness (H IT ) determination>

[0717] The indentation hardness (H) of the lower and upper parts of the hard coating layers of the optical films of Examples C1 to C5 was measured. IT). Specifically, first, an optical film cut into 1mm×10mm is embedded with an embedding resin to prepare a block, and a uniform slice with a thickness of 70nm to 100nm without holes is cut from the block using a general slicing method. The slices are prepared using Ultramicrotome EMUC7 of Leica Microsystems Co., Ltd. Then, the block remaining after the uniform slice without holes is cut out is used as a measurement sample. Next, in the cross-section obtained by cutting out the above-mentioned slice in this measurement sample, a TI950TriboIndenter manufactured by BRUKER (Bruker) is used, and under the following measurement conditions, a Berkovich indenter (triangular pyramid, TI-0039 manufactured by BRUKER) as the above-mentioned indenter is vertically pressed into the lower cross-section of the hard coating with a maximum indentation load of 50μN for 10 seconds. Here, the Bosch indenter is pressed into the lower part of the hard coating layer with a spacing of 500 nm from the interface between the polyimide substrate and the hard coating layer to the central side of the hard coating layer and a spacing of more than 500 nm from both side ends of the hard coating layer to the central side of the hard coating layer. After that, it is kept for 5 seconds and then unloaded for 10 seconds. Using the above maximum indentation load P max and contact projection area A p , through P max / A p Calculate the indentation hardness (H IT The contact projection area is the contact projection area corrected for the curvature of the indenter tip using the Oliver-Pharr method using a standard sample of fused quartz (5-0098 manufactured by BRUKER). Indentation hardness (H IT ) is the arithmetic mean of the values ​​obtained by measuring 10 locations. It should be noted that when the measured value contains a value that deviates from the arithmetic mean by more than ±20%, the measured value is removed and the measurement is performed again. As to whether there is a value that deviates from the arithmetic mean by more than ±20% in the measured value, when the measured value is set as A and the arithmetic mean is set as B, it is judged by whether the value (%) calculated by (A-B) / B×100 is more than ±20%. The indentation hardness of the upper part of the hard coating is also measured in the same way as the indentation hardness of the lower part of the hard coating, but in this case, the Bosch indenter is pressed into the upper part of the hard coating at a distance of 500nm from the surface of the hard coating to the center side of the hard coating and at a distance of more than 500nm from the two side ends of the hard coating to the center side of the hard coating.

[0718] (Measurement conditions)

[0719] Control mode: load control mode

[0720] Loading speed: 5μN / sec

[0721] Hold time: 5 seconds

[0722] Unloading speed: 5μN / s

[0723] Temperature: 23℃

[0724] Relative humidity: 50%

[0725] <Scratch resistance>

[0726] The surface of the optical film of Examples C1 to C5 was subjected to a scratch resistance test and evaluated. Specifically, the optical film cut into a size of 50 mm × 100 mm was fixed on a glass plate in a manner without folds or wrinkles using Cellotape (registered trademark) manufactured by Michibon Co., Ltd. with the surface of the optical film facing up. In this state, #0000 steel wool (product name "BON STAR", manufactured by Japan Steel Wool Co., Ltd.) was used to apply 1 kgf / cm 2 The glass was rubbed back and forth 10 times at a speed of 60 mm / sec under a load of 23°C and a relative humidity of 50%. After that, a black polyvinyl chloride insulating tape (polyvinyl chloride insulating tape black NO200-38-21 manufactured by YAMATO Co., Ltd.) was pasted on the glass surface opposite to the surface pasted with the optical film, and the presence or absence of scratches was visually confirmed under a three-wavelength fluorescent lamp. The evaluation criteria are as follows.

[0727] A: No scratches were found.

[0728] B: Some scratches were observed, but the level was not a problem in practical use.

[0729] C: More scratches than ○ were observed.

[0730] D: Many scratches were confirmed.

[0731] The results are shown in Tables 3 and 4 below.

[0732] [Table 3]

[0733]

[0734] [Table 4]

[0735]

[0736] The results are described below. The optical films of Comparative Examples C1 and C2 have poor continuous foldability because the organic particles are located closer to the polyimide substrate side than the center line. This is believed to be because cracks and ruptures occur at the interface between the organic particles and the binder resin near the surface of the hard coating layer in the curved portion of the optical film during the continuous folding test. In addition, since the optical film of Comparative Example C3 does not contain organic particles in the hard coating layer, the pressure marks of the weights are clearly confirmed. This is believed to be because the surface of the hard coating layer is a flat surface. In contrast, the optical films of Examples C1 to C5 have excellent continuous foldability and no obvious pressure marks because the organic particles are located closer to the polyimide substrate side than the center line.

Claims

1. An optical film, which is a foldable optical film for an image display device, comprising: a resin substrate; and a resin layer provided on one surface side of the resin substrate and containing organic particles, The indentation hardness of the lower portion of the resin layer is smaller than the indentation hardness of the upper portion of the resin layer, The surface of the resin layer is a concave-convex surface, The organic particles are located closer to the resin substrate than a center line bisecting the resin layer in a film thickness direction of the resin layer. The ratio of the average particle size of the organic particles to the film thickness of the resin layer is 0.1 or more and 1 or less, The resin layer includes a first resin layer and a second resin layer provided at a position closer to the surface side than the first resin layer. The first resin layer contains the organic particles, and the second resin layer does not contain the organic particles.

2. The optical film according to claim 1, wherein: The resin substrate includes one or more resins selected from the group consisting of polyimide resins, polyamideimide resins, polyamide resins, and polyester resins.

3. The optical film according to claim 2, wherein: The resin layer has a thickness of 2 μm or more and 15 μm or less.

4. The optical film according to any one of claims 1 to 3, wherein In the optical film, when a test of folding the optical film by 180° was repeated 100,000 times so that the interval between the opposing sides of the optical film was 10 mm, no crack or breakage occurred.

5. An image display device comprising: display element; and The optical film according to any one of claims 1 to 4, arranged at a position closer to the viewer than the display element.

6. The image display device according to claim 5, wherein: The display element is an organic light emitting diode element.

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