JP2018173564A - Optical film and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film having excellent scratch resistance and excellent wear resistance, and an image display device provided with the optical film. According to one aspect of the present invention, there is an optical film 10 including a resin base material 11 and a hard coat layer 12 provided on one surface 11A side of the resin base material 11. The surface 10A of the 10 is the surface 12A of the hard coat layer 12, and when a 5 μm square region of the surface 10A of the optical film 10 is three-dimensionally observed using an atomic force microscope, the diameter is 0.1 μm in the region. Provided is an optical film 10 characterized by the presence of 3 or more and 20 or less columnar protrusions having a height of 2.5 μm or less and a height of 20 nm or less. [Selection diagram] Fig. 1

Description

  The present invention relates to an optical film and an image display device.

  In recent years, not only smartphones and tablet terminals but also image display devices such as notebook personal computers have touch functions. The surface of an image display device having a touch function is usually made of a cover glass, but glass generally has a high thickness but a high film thickness and high cost. For this reason, using an optical film provided with a resin base material instead of a cover glass is examined (for example, refer to patent documents 1).

  On the other hand, an image display device having a touch function may be operated by rubbing the display surface with a touch pen instead of a finger. For this reason, in an optical film used in place of a cover glass, not only the scratch resistance is required, but also the component present on the surface of the optical film is not scraped off by rubbing with a touch pen or the like. Abrasion is also required.

JP 2016-126503 A

  Conventionally, optical films having scratch resistance have been known. However, since scratch resistance and abrasion resistance are completely different properties, an optical film having both excellent scratch resistance and excellent wear resistance can be obtained. The present situation is not yet obtained.

  The present invention has been made to solve the above problems. That is, an object is to provide an optical film having excellent scratch resistance and excellent wear resistance, and an image display device including the same.

  According to one aspect of the present invention, there is provided an optical film comprising a resin base material and a hard coat layer provided on one surface side of the resin base material, wherein the surface of the optical film is the hard coat. When the three-dimensional observation of a 5 μm square region on the surface of the optical film is performed using an atomic force microscope, the diameter is 0.1 μm or more and 2.5 μm or less and the height is 20 nm or less in the region. There is provided an optical film having 3 or more and 20 or less cylindrical protrusions.

  In the above optical film, when an eraser test is performed in which the surface of the optical film is rubbed 4000 times with a load of 500 g using an eraser, the eraser test with respect to a contact angle with water on the surface of the optical film before the eraser test. 80% or more of the contact angle maintenance rate which is the ratio of the contact angle with respect to the water in the surface of the said optical film after may be sufficient.

In the optical film, when a steel wool test is performed in which the surface of the optical film is rubbed back and forth 5000 times while applying a load of 1 kg / cm ² using steel wool, it is preferable that no scratch is confirmed on the surface.

  In the optical film, the hard coat layer is provided on a first hard coat layer containing particles, and on a surface opposite to the surface on the resin substrate side in the first hard coat layer, and the particles You may provide the 2nd hard-coat layer which does not contain.

  According to another aspect of the present invention, comprising: a display element; and the optical film according to claim 1 disposed closer to an observer than the display element, wherein the hard coat layer of the optical film includes the An image display device is provided that is located closer to the viewer than the resin substrate.

  In the image display device, a touch sensor may be further provided between the display element and the optical film.

  In the above image display device, the display element may be an organic light emitting diode element.

  According to one embodiment of the present invention, an optical film having excellent scratch resistance and excellent wear resistance can be provided. Moreover, according to the other aspect of this invention, the image display apparatus provided with this optical film can be provided.

FIG. 1 is a schematic configuration diagram of an optical film according to an embodiment. FIG. 2 is a diagram schematically showing how the number of protrusions is counted and how the diameter of the protrusion is obtained. FIG. 3 is a schematic configuration diagram of the image display apparatus according to the embodiment. FIG. 4 is a photograph when the surface of the optical film before the eraser test according to Example 1 is observed three-dimensionally using an atomic force microscope.

  Hereinafter, an optical film and an image display device according to an embodiment of the present invention will be described with reference to the drawings. In this specification, terms such as “film” and “sheet” are not distinguished from each other only based on the difference in designation. Therefore, for example, “film” is used to include a member that is also called a sheet. FIG. 1 is a schematic configuration diagram of an optical film according to the present embodiment, and FIG. 2 is a diagram schematically showing a state of counting the number of protrusions and determining a diameter of the protrusions.

<<< Optical film >>>
An optical film 10 shown in FIG. 1 has optical transparency, and includes a resin base material 11 and a hard coat layer 12 provided on one surface 11A side of the resin base material 11. The hard coat layer may have not only a single layer structure but also a multilayer structure of two or more layers. The hard coat layer 12 shown in FIG. 1 has a multilayer structure composed of a first hard coat layer 13 and a second hard coat layer 14. The surface of the optical film 10 is a surface 12 </ b> A of the hard coat layer 12.

  In the optical film 10, an atomic force microscope (AFM) (product name “WET-9100”, manufactured by Shimadzu Corporation) is used to three-dimensionally observe a 5 μm square (5 μm × 5 μm) region of the surface 10 A of the optical film 10. In this case, 3 to 20 columnar protrusions having a diameter of 0.1 μm to 2.5 μm and a height of 20 nm or less exist in the region. If the number of the protrusions is 3 or more and 20 or less, the dynamic frictional force between the eraser and the optical film 10 is reduced by the cylindrical protrusion, and the antifouling agent is prevented from falling off from the surface 10A of the optical film 10. It becomes possible. Further, if the number of columnar protrusions is less than 3, sufficient dynamic friction force cannot be obtained, and the contact angle with water may be reduced. If the number of protrusions exceeds 20, external haze starts to be generated by the protrusions, and the transparency may be lowered. Also, the protrusions themselves are soft, so that the protrusions are easily damaged and scratch-resistant. May deteriorate. Such a protrusion can be formed, for example, by including both the lubricant and the antifouling agent described later in the hard coat layer 12 although the reason is not clear. Moreover, the reason why the area to be observed is 5 μm square is that the area smaller than 5 μm square cannot be said to have sufficient resolution. The number of protrusions is the number of protrusions before performing an eraser test described later.

  The three-dimensional observation of the optical film 10 shall be performed as follows. Specifically, first, at least three locations that are not visually abnormal (location that is free of large foreign matter, scratches, etc.) are randomly selected on the optical film, and cut into 5 mm squares to obtain three samples. On the other hand, a plurality of flat circular metal plates having a diameter of 15 mm and a thickness of 1 mm are prepared, and a carbon double-sided tape manufactured by Nissin EM Co., Ltd. is attached to each metal plate. One sample is stuck on the tape so that the surface of the sample (the surface of the optical film) is on the upper side. Then, in order to ensure the adhesion between the tape and the sample, the sample-attached metal plate is left overnight in a desiccator. After standing overnight, the sample-attached metal plate is fixed with a magnet on a measurement table of an atomic force microscope (product name “WET-9400”, manufactured by Shimadzu Corporation), and in a tapping mode, a measurement area of 5 μm square is used. The surface shape is observed in three dimensions with an atomic force microscope.

  The number of the protrusions was obtained by randomly selecting 5 points for one sample and counting the number of protrusions existing in a 5 μm square area for 3 samples × 5 points (15 points in total). It is calculated by calculating the arithmetic average value of the number of 15 protrusions. Here, when a part, not all, of the protrusions exists in the region, the protrusions are observed as a circle when the 5 μm square region of the surface 10A of the optical film 10 is observed two-dimensionally with an atomic force microscope. Therefore, when the region is observed two-dimensionally, as shown by a dotted line in FIG. 2, a part of the protrusion 10B existing in the region is extrapolated to form a circle, and the protrusion 10B existing in the region. If the area of a part of the protrusion is equal to or more than half the area of the extrapolated circle, even a part of the protrusion is counted as a protrusion, and the area of a part of the protrusion 10B existing in the region is When the area is less than half of the extrapolated circle, it is not counted as a protrusion.

  As for the diameter of the protrusion, a 5 μm square region of the surface 10A of the optical film 10 is observed two-dimensionally with an atomic force microscope, and one protrusion has an arbitrary outer periphery on the periphery of the protrusion 10B as shown in FIG. It is calculated by drawing three lines with the longest length from the point A to any other point B existing on the outer periphery of the protrusion 10B, and calculating the arithmetic average value of the lengths of the lines. To do.

  In the optical film 10, when an eraser test is performed in which the surface 10A of the optical film 10 is rubbed back and forth 4000 times using an eraser, the optical film after the eraser test with respect to the contact angle with water on the surface 10A of the optical film 10 before the eraser test. It is preferable that the contact angle maintenance ratio which is the ratio of the contact angle with respect to water on the surface 10A of 10 is 80% or more. When the contact angle maintenance ratio is 80% or more, most of the antifouling agent remains on the surface 10A of the optical film 10 without being scraped off by the eraser test, so that the optical film 10 has excellent wear resistance. Thus, it can be determined that excellent antifouling properties can be obtained.

  In the above, the reason for testing using an eraser is that rubbing with an eraser is close to rubbing with a touch pen, and abrasion resistance against the touch pen can be evaluated by an eraser test. The scratch resistance of an optical film has been conventionally evaluated by a steel wool test in which the surface of the optical film is rubbed with steel wool. Steel wool is a thin metal wire and is significantly different from a touch pen. Abrasion resistance cannot be evaluated by a steel wool test.

  The above eraser test is performed by cutting the pencil at a position 5 cm from the tip of the eraser of a pencil with an eraser (product name “Office Pencil 9852 (with eraser)”, manufactured by Mitsubishi Pencil Co., Ltd.), and removing the pencil with the eraser on the eraser side. Insert the jig with the eraser from the opposite side into a jig having a hole with a diameter of 6 mm so that the tip of the eraser is completely exposed. 301 "(manufactured by Tester Sangyo Co., Ltd.), and the surface of the optical film is rubbed 4000 times with an eraser at a load of 500 g and a rubbing speed of 30 mm / sec. In the eraser test, an optical film cut into a size of 10 cm in the horizontal direction and 5 cm in the vertical direction is used.

  The contact angle with respect to water is measured using a microscopic contact angle meter (product name “DropMaster 300”, manufactured by Kyowa Interface Science Co., Ltd.) according to the sessile drop method described in JIS R3257-1999. Specifically, the contact angle with respect to water is obtained by dropping 1 μL of water onto the surface of the low refractive index layer, measuring 10 contact angles immediately after dropping, and calculating the arithmetic average value of the contact angle of the surface of the optical film. And

The contact angle maintenance rate is defined as A (%), the contact angle with water on the surface of the optical film before the eraser test is B, and the contact angle with water on the surface of the optical film after the eraser test is C. Is obtained by the following equation.
A = C / B × 100

  The contact angle with water on the surface of the optical film before the eraser test is preferably 100 ° or more. When the contact angle is 100 ° or more, the film has sufficient antifouling resistance, and adhesion of fingerprints and dirt can be suppressed, and even if fingerprints and dirt are attached, it is easy to wipe off. The lower limit of the contact angle of the surface 10A of the optical film 10 with respect to water is more preferably 95 ° or more, and the upper limit is preferably 120 ° or less.

In the optical film 10, the surface 10A of the optical film 10 (the surface 12A of the hard coat layer 12) is applied while applying a load of 1 kg / cm ² using steel wool (product name “Bonster # 0000”, manufactured by Nippon Steel Wool Co., Ltd.). It is preferable that no scratch is confirmed on the surface 10A of the optical film 10 when a steel wool test is performed by rubbing 5000 times. The steel wool test is performed in a state in which an optical film cut out in a size of 10 cm in the horizontal direction × 5 cm in the vertical direction is fixed on a glass plate with cello tape (registered trademark) manufactured by Nichiban Co., Ltd. so as not to be folded or wrinkled on the glass plate.

  The surface 10A of the optical film 10 preferably has a hardness (pencil hardness) of not less than 5H, more preferably 6H as measured by a pencil hardness test specified in JIS K5600-5-4: 1999. Preferably, it is more preferably 7H or more. However, in the pencil hardness test, an optical film cut out in a size of 10 cm in the horizontal direction × 5 cm in the vertical direction is fixed on a glass plate with cello tape (registered trademark) manufactured by Nichiban Co., Ltd. A load is applied and the scratching speed is set to 1 mm / second. The pencil hardness is the highest hardness at which the surface of the optical film was not damaged in the pencil hardness test. The pencil hardness is measured using a plurality of pencils having different hardnesses. The pencil hardness test is performed five times for each pencil, and the surface of the optical film is scratched four times or more out of the five times. If not, it is determined that the surface of the optical film was not scratched with the pencil having this hardness. The above-mentioned scratches refer to those that are visually observed through transmission observation of the surface of the optical film subjected to the pencil hardness test under a fluorescent lamp.

  In the optical film 10, according to the mandrel test described in JIS K5600-5-1: 1999 (a test in which a sample is wound around a metal cylinder of 2 mm to 32 mm), the optical film 10 with the hard coat layer 12 on the outside. It is preferable that the minimum diameter of the cylinder in which the crack (crack) does not occur when the is wound around the cylinder is 20 mm or less. The minimum diameter is determined by taking this measurement three times and making it the smallest of the three minimum diameters.

  The total light transmittance of the optical film 10 is preferably 90% or more. If the total light transmittance of the optical film 10 is less than 90%, the optical performance may be insufficient. The total light transmittance can be measured using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory) in accordance with JIS K7361-1: 1997. The total light transmittance is an arithmetic average value of values obtained by measuring three times with respect to an optical film cut into a size of 10 cm in the horizontal direction and 5 cm in the vertical direction. The total light transmittance of the optical film 10 is more preferably 91% or more, and further preferably 92% or more.

  The haze value (total haze value) of the optical film 10 is preferably 1% or less. If the haze value of the optical film 10 exceeds 1%, the optical performance may be insufficient. The haze value can be measured using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory) in accordance with JIS K7136: 2000. The haze value is an arithmetic average value of values obtained by measuring three times with respect to an optical film cut into a size of 10 cm in the horizontal direction and 5 cm in the vertical direction. The haze value of the optical film 10 is more preferably 0.8% or less, and further preferably 0.5% or less.

  The arithmetic average roughness (Ra) in the 5 μm square region on the surface 10A of the optical film 10 may be 10 nm or less. The definition of Ra shall conform to JIS B0601: 2001. Ra is calculated as follows using an atomic force microscope (product name “WET-9100”, manufactured by Shimadzu Corporation). Specifically, first, at least three locations that are not visually abnormal (location that is free of large foreign matter, scratches, etc.) are randomly selected on the optical film, and cut into 5 mm squares to obtain three samples. On the other hand, a plurality of flat circular metal plates having a diameter of 15 mm and a thickness of 1 mm are prepared, and a carbon double-sided tape manufactured by Nissin EM Co., Ltd. is attached to each metal plate. One sample is stuck on the tape so that the surface of the sample (the surface of the optical film) is on the upper side. Then, in order to ensure the adhesion between the tape and the sample, the sample-attached metal plate is left overnight in a desiccator. After standing overnight, the sample-attached metal plate is fixed with a magnet on a measurement table of an atomic force microscope (product name “WET-9400”, manufactured by Shimadzu Corporation), and in a tapping mode, a measurement area of 5 μm square is used. The surface shape is observed with an atomic force microscope. Then, Ra is calculated from the observed data using surface analysis software built in the atomic force microscope. Note that the vertical scale during the surface analysis is 20 nm. Observation is performed at room temperature, and NCHR-20 manufactured by NanoWorld is used as a cantilever. For observation, five locations are selected at random for one sample, and the surface shape is observed for 3 samples × 5 locations (total of 15 points). Then, in all the obtained 15 points of data, Ra is calculated using the surface analysis software built in the atomic force microscope, and the arithmetic average value of 15 points is set as Ra of the sample.

<< Resin substrate >>
The resin base material 11 is a base material made of a resin having optical transparency. The “light transmittance” in the present specification means a property of transmitting light. For example, the total light transmittance is 50% or more, preferably 70% or more, more preferably 80% or more, and particularly preferably 90%. Including that. The light transmissive property does not necessarily need to be transparent, and may be translucent.

  The thickness of the resin substrate 11 is preferably 25 μm or more and 100 μm or less. When the thickness of the resin substrate is 25 μm or more, the optical film is difficult to curl and the hardness is not insufficient, and furthermore, when the optical film is produced by Roll to Roll, it is difficult to generate wrinkles. There is no risk of deterioration. On the other hand, when the thickness of the resin substrate is 100 μm or less, the bendability is not insufficient, and both hardness and flexibility can be achieved. The thickness of the resin base material 11 means the arithmetic mean value of the thickness of the resin base material 11 measured at 10 points using a thickness measuring device (product name “Digimatic Indicator IDF-130”, manufactured by Mitutoyo Corporation). Shall. The lower limit of the resin base material 11 is more preferably 30 μm or more, and the upper limit of the resin base material 11 is more preferably 90 μm or less.

  Although it does not specifically limit as the resin base material 11, An acetylcellulose base material, a cycloolefin polymer (COP) base material, a cycloolefin copolymer (COC) base material, a polycarbonate base material, an acrylic base material, a polyester base material, or these A composite of a base material is mentioned. Among these, an acetylcellulose base material is preferable from the viewpoint of adhesion of the resin to the resin base material and pencil hardness.

  Examples of the acetyl cellulose base material include a triacetyl cellulose (TAC) base material and a diacetyl cellulose base material. A triacetylcellulose base material is a base material which can make an average light transmittance 50% or more in a visible light region of 380 to 780 nm. The average light transmittance of the triacetyl cellulose base material is preferably 70% or more, and more preferably 85% or more.

  In addition, as a triacetyl cellulose base material, in addition to pure triacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like may be used in combination with components other than acetic acid as a fatty acid forming an ester with cellulose. Good. Moreover, various additives, such as other cellulose lower fatty acid esters, such as diacetylcellulose, or a plasticizer and an ultraviolet absorber, may be added to these triacetylcelluloses as necessary.

  Examples of the cycloolefin polymer substrate include a substrate made of a norbornene polymer, a monocyclic olefin polymer, a cyclic conjugated diene polymer, or a vinyl alicyclic hydrocarbon polymer. Examples of the cycloolefin copolymer substrate include a copolymer of ethylene and a norbornene-based monomer, a copolymer of ethylene and tetracyclododecene, and the like.

  Examples of the polycarbonate substrate include aromatic polycarbonate substrates based on bisphenols (bisphenol A and the like), aliphatic polycarbonate substrates such as diethylene glycol bisallyl carbonate, and the like.

  Examples of the acrylic base material include a poly (meth) methyl acrylate base material, a poly (meth) ethyl acrylate base material, and a (meth) methyl acrylate- (meth) butyl acrylate copolymer base material. .

  Examples of the polyester base material include a base material containing at least one of polyethylene terephthalate (PET), polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as a constituent component.

<< Hard coat layer >>
The “hard coat layer” in the present specification is a layer having a hardness (pencil hardness) of not less than “H” when measured by a pencil hardness test specified in JIS K5600-5-4: 1999. The pencil hardness test is performed in a state where a load of 500 g is applied to the pencil and the scratching speed is 1 mm / second. The pencil hardness is the highest hardness at which the surface of the optical film was not damaged in the pencil hardness test. The pencil hardness is measured using a plurality of pencils having different hardnesses. The pencil hardness test is performed five times for each pencil, and the surface of the optical film is scratched four times or more out of the five times. If not, it is determined that the surface of the optical film was not scratched with the pencil having this hardness. The above-mentioned scratches refer to those that are visually observed through transmission observation of the surface of the optical film subjected to the pencil hardness test under a fluorescent lamp.

  The hard coat layer 12 includes a first hard coat layer 13 and a second hard coat layer 14 provided on the surface of the first hard coat layer 13 opposite to the surface on the resin base material 11 side. ing.

<First hard coat layer>
The first hard coat layer 13 is a layer for increasing the hardness. The first hard coat layer 13 includes a binder resin and particles dispersed in the binder resin. By including particles in the first hard coat layer 13, higher pencil hardness can be achieved. The 1st hard coat layer 13 may contain various additives other than the above in the range which does not impair the effect of the present invention as needed other than binder resin. Examples of such additives include ultraviolet absorbers, antistatic agents, adhesion improvers, leveling agents, thixotropic agents, coupling agents, plasticizers, antifoaming agents, fillers, colorants, fillers, and the like. Is mentioned.

  The film thickness of the first hard coat layer 13 is preferably 10 μm or more and 40 μm or less. When the film thickness of the first hard coat layer is 10 μm or more, the hardness of the first hard coat layer does not become insufficient, and when it is 40 μm or less, deterioration of workability can be suppressed. The film thickness of the first hard coat layer 13 is obtained by photographing a cross section of the first hard coat layer 13 using a scanning electron microscope (SEM), and in the image of the cross section, the film of the first hard coat layer 13 The thickness is measured at 20 locations, and the arithmetic average value of the film thickness at the 20 locations is taken.

(Binder resin)
The resin contains a polymer (cured product) of a polymerizable compound (curable compound). The polymerizable compound has at least one polymerizable functional group in the molecule. Examples of the polymerizable functional group include ethylenically unsaturated groups such as a (meth) acryloyl group, a vinyl group, and an allyl group. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”.

  As the polymerizable compound, polyfunctional (meth) acrylate is preferable. Examples of the polyfunctional (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, trimethylolpropane tri (meth) acrylate , Ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate , Tetrapentaerythritol 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, di Glycerin tetra (meth) acrylate, adamantyl di (meth) acrylate, isobornyl di (meth) acrylate, dicyclopentane di (meth) acrylate, tricyclodecane di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and these Examples thereof include those modified with PO, EO, caprolactone and the like.

  Among these, since the pencil hardness described above can be suitably satisfied, those having 3 to 6 functionalities are preferable, 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 and the like are preferable. In the present specification, (meth) acrylate means acrylate and methacrylate.

  In addition, a monofunctional (meth) acrylate monomer may be further included for adjusting the hardness, viscosity of the composition, improving adhesion, and the like. 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, tetrahydrofuryl acrylate, isobornyl acrylate, phenoxyethyl acrylate, adamantyl acrylate and the like.

  From the viewpoint of improving the hardness of the resin layer, the weight average molecular weight of the monomer is preferably less than 1000, and more preferably 200 or more and 800 or less. The weight average molecular weight of the polymerizable oligomer is preferably 1000 or more and 20,000 or less, more preferably 1000 or more and 10,000 or less, and further preferably 2000 or more and 7000 or less.

(particle)
The particles are components that increase the hardness of the hard coat layer, and may be any of inorganic particles, organic particles, or a mixture thereof. Examples of the inorganic particles include inorganic oxide particles such as silica (SiO ₂ ) particles, alumina particles, titania particles, tin oxide particles, antimony-doped tin oxide (abbreviation: ATO) particles, and zinc oxide particles. Among these, silica particles are preferable from the viewpoint of further increasing the hardness. Examples of the silica particles include spherical silica particles and irregular silica particles. Among these, irregular silica particles are preferable. In this specification, “spherical particles” mean, for example, particles such as true spheres, ellipsoids, etc., and “irregular particles” are potato-shaped (the aspect ratio at the time of cross-sectional observation is 1.2 or more and 40 or less). It means particles having a shape having random irregularities on the surface. Since the irregular shaped particles have a surface area larger than that of the spherical particles, the inclusion of such irregular shaped particles increases the contact area with the binder resin and increases the pencil hardness of the first hard coat layer 13. It can be made better. Whether or not the silica particles contained in the first hard coat layer 13 are irregular-shaped silica particles is determined based on whether the cross section of the first hard coat layer 13 is a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). ) Can be confirmed by observing. When spherical silica particles are used, the smaller the particle diameter of the spherical silica particles, the higher the hardness of the light transmissive hard coat layer. On the other hand, the deformed silica particles can achieve the same hardness as that of spherical silica particles, even if they are not as small as the commercially available spherical silica particles having the smallest particle diameter.

  The average particle diameter of the silica particles is preferably 5 nm or more and 200 nm or less. If the thickness is less than 5 nm, it may be difficult to produce the particles themselves, the particles may aggregate together, and it may be extremely difficult to deform the ink. In some stages, the dispersible silica particles may be poorly dispersed and may aggregate. On the other hand, when the average particle diameter of the irregular shaped silica particles exceeds 200 nm, large irregularities may be formed in the first hard coat layer, or problems such as an increase in haze may occur. When the silica particles are spherical silica particles, the average particle diameter of the silica particles is 20 particles from the cross-sectional image of the particles taken using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). The particle diameter is measured to obtain the arithmetic average value of the particle diameters of 20 particles. When the silica particles are irregular-shaped silica particles, the average particle diameter of the silica particles is an image of a cross section of the hard coat layer taken using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). The maximum value (major axis) and the minimum value (minor axis) of the distance between two points on the outer periphery of the particle are measured and averaged to obtain the particle size, which is the arithmetic average value of the particle size of 20 particles.

  The content of the particles in the first hard coat layer 13 is preferably 20% by mass or more and 70% by mass or less. When the particle content is 20% by mass or more, sufficient hardness can be ensured, and when the particle content is 70% by mass or less, the filling rate does not increase too much, and the adhesion between the particles and the binder resin. The deterioration of the property can be suppressed, and the decrease in the hardness of the first hard coat layer can be suppressed.

  As the inorganic particles, it is preferable to use inorganic particles (reactive inorganic particles) having a polymerizable functional group on the surface. Such inorganic particles having a polymerizable functional group on the surface can be prepared by surface-treating the inorganic particles with a silane coupling agent or the like. As a method of treating the surface of the inorganic particles with a silane coupling agent, a dry method in which the silane coupling agent is sprayed on the inorganic particles, or a wet method in which the inorganic particles are dispersed in a solvent and then the silane coupling agent is added and reacted. Etc.

  Examples of the organic particles include plastic beads. Specific examples of the plastic beads include polystyrene beads, melamine resin beads, acrylic beads, acrylic-styrene beads, silicone beads, benzoguanamine beads, benzoguanamine / formaldehyde condensation beads, polycarbonate beads, polyethylene beads, and the like.

<Second hard coat layer>
The second hard coat layer 14 is a layer for improving scratch resistance and slipperiness. The second hard coat layer 14 contains a binder resin, a lubricant and an antifouling agent, and does not contain particles. The 2nd hard coat layer 14 may contain various additives other than the above in the range which does not impair the effect of the present invention as needed other than binder resin. Examples of such additives include ultraviolet absorbers, antistatic agents, adhesion improvers, leveling agents, thixotropic agents, coupling agents, plasticizers, antifoaming agents, fillers, colorants, fillers, and the like. Is mentioned.

  The film thickness of the second hard coat layer 14 is preferably 1 μm or more and 10 μm or less. When the thickness of the second hard coat layer is 1 μm or more, sufficient scratch resistance is exhibited, and when it is 10 μm or less, curling can be suppressed and flexibility can be maintained. The film thickness of the second hard coat layer 14 is measured by the same method as the film thickness of the first hard coat layer 13.

(Binder resin)
Since the binder resin contained in the second hard coat layer 14 is the same as the binder resin contained in the first hard coat layer 13, the description thereof will be omitted here.

(Lubricant)
The lubricant is for imparting slipperiness to the surface 10 </ b> A of the optical film 10. The lubricant preferably has a polymerizable functional group. When a lubricant having a polymerizable functional group is used as the lubricant, the lubricant is present in a state of being bonded to the binder resin in the second hard coat layer.

  As the lubricant, a silicone lubricant is preferable from the viewpoint of easily improving the slipperiness of the surface of the optical film. Although it does not specifically limit as a silicone type lubricant, Straight silicone and modified silicones, such as dimethyl polysiloxane, methylphenyl polysiloxane, and methylhydrogen polysiloxane, are mentioned.

  Examples of the modified silicone include ethylenically unsaturated group-modified silicone such as (meth) acryl-modified silicone, amino-modified silicone, amide-modified silicone, epoxy-modified silicone, carboxy-modified silicone, alcohol-modified silicone, carbinol-modified silicone, and mercapto-modified silicone. Examples include silicone.

  Examples of commercially available lubricants include BYK-313, BYK-322, BYK-331, BYK-333, BYK-345, BYK-377, BYK-378, BYK-UV3500, and BYK-UV3510 (all of which are Big Chemie Japan). Etc.).

  The weight average molecular weight of the lubricant is preferably 3000 or more and 20000 or less. When the weight average molecular weight of the lubricant is 3000 or more, the occurrence of surface problems can be suppressed, and when the weight average molecular weight of the lubricant is 20000 or less, the compatibility with the resin can be prevented from deteriorating.

  The content of the lubricant is preferably 0.01 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the polymerizable compound constituting the binder resin. When the content of the lubricant is 0.01 parts by mass or more, the dynamic friction coefficient of the surface of the second hard coat layer becomes low, and excellent slipperiness can be obtained, and when the content is 0.5 parts by mass or less. In addition, a decrease in scratch resistance can be suppressed.

  The content ratio of the lubricant and the antifouling agent is preferably 1: 9 to 5: 5. When the content ratio is within this range, an optical film having better scratch resistance and better wear resistance can be obtained.

(Anti-fouling agent)
The antifouling agent is for preventing dirt such as fingerprints from adhering to the surface 10 </ b> A of the optical film 10. The antifouling agent preferably has a polymerizable functional group. When an antifouling agent having a polymerizable functional group is used as the antifouling agent, the antifouling agent is present in a state of being bonded to the binder resin in the second hard coat layer.

  The antifouling agent is preferably a fluorine-containing antifouling agent such as a fluorine antifouling agent or a fluorine silicone antifouling agent. When the fluorine-containing antifouling agent is used, fingerprints are hardly attached (not easily noticeable), and wiping properties are good. Moreover, since the surface tension at the time of application | coating of the 2nd composition for hard-coat layers can be lowered | hung, leveling property is good and the external appearance of the 2nd hard-coat layer to form becomes a favorable thing. Among fluorine-containing antifouling agents, fluorine silicone antifouling agents are preferred from the viewpoint of reducing the frictional force with the eraser.

  Commercially available fluorine-based antifouling agents include, for example, OPTOOL DAC, OPTOOL DSX (all manufactured by Daikin Industries, Ltd.), Megafuck RS-56, Megafuck RS-71, Megafuck RS-74, Megafuck RS-75. (All manufactured by DIC), LINC152EPA, LINC151EPA, LINC182UA (all manufactured by Kyoeisha Chemical Co., Ltd.), 650, 601AD, 602, and 602.

  Commercially available fluorosilicone antifouling agents include, for example, MegaFac RS-851, MegaFac RS-852, MegaFac RS-853, MegaFac RS-854 (all manufactured by DIC), Opstar TU2225, Opstar TU2224. (Both manufactured by JSR).

  The weight average molecular weight of the antifouling agent is preferably 3000 or more and 20000 or less. When the weight average molecular weight of the antifouling agent is 3000 or more, the occurrence of problems on the surface quality can be suppressed, and when the weight average molecular weight of the antifouling agent is 20000 or less, the compatibility with the resin is deteriorated. Can be suppressed.

  The content of the antifouling agent is preferably 0.01 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the polymerizable compound constituting the binder resin. When the content of the antifouling agent is 0.01 parts by mass or more, excellent antifouling properties can be obtained, and when it is 0.5 parts by mass or less, a decrease in scratch resistance can be suppressed.

<< Optical Film Manufacturing Method >>
The optical film 10 can be produced as follows, for example. First, the first hard coat layer composition is applied on one surface 11A of the resin substrate 11 by a coating device such as a bar coater to form a first hard coat layer composition coating film. To do.

<First hard coat layer composition>
The 1st composition for hard-coat layers contains the polymeric compound and particle | grains which become binder resin after hardening. The 1st composition for hard-coat layers may contain the ultraviolet absorber, the leveling agent, the solvent, and the polymerization initiator as needed.

(solvent)
Examples of the solvent include alcohols (eg, methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol, diacetone alcohol), ketones (eg, acetone, methyl ethyl ketone, Methyl isobutyl ketone, cyclopentanone, cyclohexanone, heptanone, diisobutyl ketone, diethyl ketone, diacetone alcohol), ester (methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, methyl formate, PGMEA), aliphatic Hydrocarbons (eg, hexane, cyclohexane), halogenated hydrocarbons (eg, methylene chloride, chloroform, carbon tetrachloride), aromatic hydrocarbons (eg, benzene, toluene, xylene), Amide (eg, dimethylformamide, dimethylacetamide, n-methylpyrrolidone), ether (eg, diethyl ether, dioxane, tetrahydrofuran), ether alcohol (eg, 1-methoxy-2-propanol), carbonate (dimethyl carbonate, diethyl carbonate, Ethyl methyl carbonate), and the like. These solvents may be used alone or in combination of two or more. Among these, as the solvent, methyl isobutyl ketone can be suitably applied to the first hard coat layer composition by dissolving or dispersing components such as urethane (meth) acrylate and other additives. Methyl ethyl ketone is preferred.

(Polymerization initiator)
The polymerization initiator is a component that is decomposed by irradiation with ionizing radiation to generate radicals to initiate or advance polymerization (crosslinking) of the polymerizable compound.

  The polymerization initiator is not particularly limited as long as it can release a substance that initiates radical polymerization by irradiation with ionizing radiation. The polymerization initiator is not particularly limited, and known ones can be used. Specific examples include, for example, acetophenones, benzophenones, Michler benzoylbenzoate, α-amyloxime ester, thioxanthones, propiophenone. , Benzyls, benzoins, acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

  After forming the coating film of the first composition for hard coat layer, the coating film is dried by heating at a temperature of 30 ° C. or more and 120 ° C. or less for 10 seconds to 120 seconds, for example, by various known methods, Evaporate the solvent.

  After the coating film is dried, the coating film is irradiated with ionizing radiation such as ultraviolet rays so that the coating film is semi-cured. The term “semi-curing” in the present specification means that the curing proceeds substantially upon further irradiation with ionizing radiation. However, at this stage, the coating film may be completely cured (full cure). “Complete curing” in the present specification means that curing does not substantially proceed even when ionizing radiation is further applied. Examples of the ionizing radiation in this specification include visible light, ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

  After the coating film is semi-cured, a second hard coat layer composition for forming the second hard coat layer is applied onto the coating film by a coating device such as a bar coater. A coating film of the composition for a hard coat layer is formed.

<Second composition for hard coat layer>
The 2nd composition for hard-coat layers contains the polymeric compound used as binder resin after hardening, a lubricant, and antifouling agent. The 2nd composition for hard-coat layers may contain the ultraviolet absorber, the solvent, and the polymerization initiator as needed. In the second hard coat layer composition, the solvent and the polymerization initiator are the same as the solvent and polymerization initiator described in the first hard coat layer composition, and therefore the description thereof will be omitted here. .

  After forming the coating film of the composition for the second hard coat layer, the coating film is dried by heating at a temperature of 30 ° C. or more and 120 ° C. or less for 10 seconds to 120 seconds, for example, by various known methods, Evaporate the solvent.

  After the coating film is dried, the coating film of the second hard coat layer composition is irradiated with ionizing radiation such as ultraviolet rays to form the first hard coat layer composition coating film and the second hard coat layer. The coating film of the composition for use is completely cured (full cure) to form the first hard coat layer 13 and the second hard coat layer 14 to obtain the hard coat layer 12. Thereby, the optical film 10 shown in FIG. 1 is obtained.

  The present inventors diligently researched about both excellent scratch resistance and excellent wear resistance. When an area of 5 μm square on the surface of the optical film was observed three-dimensionally using an atomic force microscope, In this region, cylindrical protrusions having a diameter of 0.1 μm or more and 2.5 μm or less and a height of 20 nm or less are mainly composed of a lubricant, and if there are 3 or more and 20 or less of these protrusions, excellent resistance It has been found that an optical film having scratch resistance and excellent abrasion resistance can be obtained. This is considered to be due to the following reasons. Since the protrusions are mainly composed of a lubricant, if the protrusions are present on the surface of the optical film, the surface of the optical film becomes slippery, and the frictional force between the surface of the optical film and the eraser may be reduced. it can. Here, if there are three or more protrusions, the antifouling agent can be prevented from dropping off from the surface of the optical film due to friction with the eraser, so that excellent wear resistance can be obtained. On the other hand, since the protrusion itself is soft, if the number of the protrusions is too large, the protrusions are scratched and the scratch resistance is lowered. For this reason, in order to obtain the outstanding abrasion resistance, it is necessary to be 20 or less. According to this embodiment, when an area of 5 μm square on the surface 10A of the optical film 10 is three-dimensionally observed using an atomic force microscope, a diameter of 0.1 μm to 2.5 μm and a height of 20 nm are included in this area. Since 3 or more and 20 or less of the following cylindrical protrusions are present, the optical film 10 having excellent scratch resistance and excellent wear resistance can be obtained.

<<<<< Image display device >>>>
The optical film 10 can be used by being incorporated in a foldable image display device. FIG. 3 is a schematic configuration diagram of the image display apparatus according to the present embodiment. As shown in FIG. 3, the image display device 30 mainly has a housing 31 in which a battery or the like is stored, a protective film 32, a display element 33, a touch sensor 34, and a circularly polarizing plate 35 toward the viewer. , And the optical film 10 are laminated in this order. Between the display element 33 and the touch sensor 34, between the touch sensor 34 and the circularly polarizing plate 35, and between the circularly polarizing plate 35 and the optical film 10, for example, optical transparency such as OCA (Optical Clear Adhesive). An adhesive layer 36 is disposed, and these members are fixed to each other by a light-transmitting adhesive layer 36.

  The optical film 10 is disposed such that the hard coat layer 12 is closer to the viewer than the resin base material 11. In the image display device 30, the surface 12 </ b> A of the hard coat layer 12 of the optical film 10 constitutes the surface 30 </ b> A of the image display device 30.

  The display element 33 is an organic light emitting diode (OLED) element, but the display element may be a liquid crystal display element, an inorganic light emitting diode element, or a quantum dot light emitting diode (QLED).

  The touch sensor 34 is disposed closer to the display element 33 than the circularly polarizing plate 35, but may be disposed between the circularly polarizing plate 35 and the optical film 10. The touch sensor 34 may be an on-cell method or an in-cell method.

  Although the use of the optical film 10 is not particularly limited, it can be particularly suitably used in an image display device such as a smartphone, a tablet terminal, or a personal computer having a touch function.

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited to these descriptions. In addition, the following “100% solid content conversion value” is a value when the solid content in the solvent diluted product is 100%.

<Preparation of composition for hard coat layer>
First, each component was mix | blended so that it might become the composition shown below, and the composition for hard-coat layers was obtained.

(Composition 1 for hard coat layer)
Dipentaerythritol polyacrylate (product name “A-9550”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 70 parts by mass Silica particles (product name “PGM-AC-2140Y”, manufactured by Nissan Chemical Industries, Ltd.): 30 parts by mass Fluorine-based leveling agent (product name “Megafac F-444”, manufactured by DIC Corporation): 0.1 parts by mass

(Composition 2 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-333”, manufactured by Big Chemie Japan): 0.1 . Part by mass / Fluorine-containing antifouling agent (product name “Megafac RS-56”, manufactured by DIC Corporation): 0.1 part by mass

(Composition 3 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-377”, manufactured by Big Chemie Japan): 0.1 Part by mass / Fluorine-containing antifouling agent (product name “Megafac RS-56”, manufactured by DIC Corporation): 0.1 part by mass

(Composition 4 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-378”, manufactured by Big Chemie Japan): 100 parts by mass Fluorine-containing antifouling agent (product name “Megafac RS-56”, manufactured by DIC Corporation): 0.1 parts by mass

(Composition 5 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-UV3510”, manufactured by Big Chemie Japan): 100 parts by mass Fluorine-containing antifouling agent (product name “Megafac RS-56”, manufactured by DIC Corporation): 0.1 parts by mass

(Composition 6 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-UV3500”, manufactured by Big Chemie Japan): 0.1 Part by mass / Fluorine-containing antifouling agent (product name “Megafac RS-56”, manufactured by DIC Corporation): 0.1 part by mass

(Composition 7 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-345”, manufactured by Big Chemie Japan): 0.1 Part by mass / Fluorine-containing antifouling agent (product name “Megafac RS-75”, manufactured by DIC): 0.1 part by mass / Lubricant (product name “H65”, manufactured by CIK Nanotech): 1.5 parts by mass

(Composition 8 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Fluorine-containing antifouling agent (product name “Megafac RS-75”, manufactured by DIC): 0 .1 part by mass

(Composition 9 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-313”, manufactured by Big Chemie Japan): 0.1 Part by mass / Fluorine-containing antifouling agent (product name “Megafac RS-75”, manufactured by DIC Corporation): 0.1 part by mass

(Composition 10 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-322”, manufactured by Big Chemie Japan): 0.1 Part by mass / Fluorine-containing antifouling agent (product name “Megafac RS-75”, manufactured by DIC Corporation): 0.1 part by mass

(Composition 11 for hard coat layer)
Pentaerythritol triacrylate (product name “A-TMM-3”, manufactured by Shin-Nakamura Chemical Co., Ltd.): 100 parts by mass Silicone lubricant (product name “BYK-331”, manufactured by Big Chemie Japan): 0.1 Part by mass / Fluorine-containing antifouling agent (product name “Megafac RS-75”, manufactured by DIC Corporation): 0.1 part by mass

<Example 1>
As a resin substrate, a triacetyl cellulose substrate (product name “KC8UAW”, manufactured by Konica Minolta Co., Ltd.) having a thickness of 80 μm is prepared, and a hard coat layer composition is formed on one surface of the triacetyl cellulose substrate with a bar coater. 1 was applied to form a coating film. Then, the solvent in the coating film is evaporated by heating the formed coating film at 70 ° C. for 1 minute, and ultraviolet rays are removed from the air using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb). The coating film was semi-cured by irradiation so that the accumulated light amount was 100 mJ / cm ² . Next, the hard coat layer composition 2 was applied to the surface of the semi-cured hard coat layer composition 1 with a bar coater to form a coating film. The formed coating film is heated at 70 ° C. for 1 minute to evaporate the solvent in the coating film, and using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb), the ultraviolet ray has oxygen concentration. Irradiation was performed so that the integrated light amount was 200 mJ / cm ² under the condition of 200 ppm or less, and the coating film was completely cured (full cure). As a result, a hard comprising a first hard coat layer having a thickness of 15 μm and a second hard coat layer having a thickness of 5 μm laminated on the first hard coat layer on the triacetyl cellulose substrate. An optical film provided with a coat layer was obtained. The thickness of the triacetyl cellulose base material was measured at 10 points using the thickness measuring device (product name “Digimatic Indicator IDF-130”, manufactured by Mitutoyo Corporation), and the arithmetic average value thereof. It was. Further, the film thickness of the hard coat layer was measured by taking a cross section of the hard coat layer using a scanning electron microscope (SEM) and measuring the film thickness of the hard coat layer at 20 locations in the image of the cross section. It was set as the arithmetic average value of the film thickness of the location. In Examples 2 to 5 and Comparative Examples 1 to 5, the thickness of the base material and the thickness of the hard coat layer were measured by the same method as in Example 1.

<Example 2>
In Example 2, an optical film was obtained in the same manner as in Example 1 except that the composition 3 for hard coat layer was used instead of the composition 2 for hard coat layer.

<Example 3>
In Example 3, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 4 was used instead of the hard coat layer composition 2.

<Example 4>
In Example 4, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 5 was used instead of the hard coat layer composition 2.

<Example 5>
In Example 5, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 6 was used instead of the hard coat layer composition 2.

<Comparative Example 1>
In Comparative Example 1, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 7 was used instead of the hard coat layer composition 2.

<Comparative example 2>
In Comparative Example 2, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 8 was used instead of the hard coat layer composition 2.

<Comparative Example 3>
In Comparative Example 3, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 9 was used instead of the hard coat layer composition 2.

<Comparative example 4>
In Comparative Example 4, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 10 was used instead of the hard coat layer composition 2.

<Comparative Example 5>
In Comparative Example 5, an optical film was obtained in the same manner as in Example 1 except that the hard coat layer composition 11 was used instead of the hard coat layer composition 2.

<Check the number of protrusions>
In the optical films according to Examples and Comparative Examples, an atomic force microscope (AFM) (product name “WET-9100”, manufactured by Shimadzu Corporation) was used to three-dimensionally observe a 5 μm square region on the surface of the optical film. The number of cylindrical protrusions having a diameter of 0.1 μm to 2.5 μm and a height of 20 nm or less present in the region was counted. The number of protrusions was counted on an optical film before an eraser test described later. As a reference, when a 5 μm square region of the surface of the optical film before the eraser test according to Example 1 was observed three-dimensionally with an atomic force microscope (AFM) (product name “WET-9100”, manufactured by Shimadzu Corporation) The photograph of is shown in FIG.

  Three-dimensional observation of the surface of the optical film was performed as follows. Specifically, first, at least three locations that are not visually abnormal (location that is free of large foreign matter, scratches, etc.) are randomly selected on the optical film, and cut into 5 mm squares to obtain three samples. On the other hand, a plurality of flat circular metal plates having a diameter of 15 mm and a thickness of 1 mm are prepared, and a carbon double-sided tape manufactured by Nissin EM Co., Ltd. is attached to each metal plate. One sample is stuck on the tape so that the surface of the sample (the surface of the optical film) is on the upper side. Then, in order to ensure the adhesion between the tape and the sample, the sample-attached metal plate is left overnight in a desiccator. After standing overnight, the sample-attached metal plate is fixed with a magnet on a measurement table of an atomic force microscope (product name “WET-9400”, manufactured by Shimadzu Corporation), and in a tapping mode, a measurement area of 5 μm square is used. The surface shape was observed in three dimensions with an atomic force microscope.

  The number of the protrusions was obtained by randomly selecting 5 points for one sample and counting the number of protrusions existing in a 5 μm square area for 3 samples × 5 points (15 points in total). It calculated by calculating | requiring the arithmetic average value of the number of 15 processus | protrusions. Here, when not all of the protrusions but part of the protrusions are present in the region, the region of 5 μm square on the surface of the optical film is observed two-dimensionally with an atomic force microscope, and the dotted line shown in FIG. As described above, when a part of the protrusion existing in the region is extrapolated into a circle, and the area of a part of the protrusion existing in the region is equal to or larger than the half of the extrapolated circle Even if a part of the protrusion is counted as a protrusion, if the area of a part of the protrusion existing in the region is less than half of the extrapolated circle, it is not counted as a protrusion. did.

  As for the diameter of the protrusion, the 5 μm square region of the surface 10A of the optical film 10 is two-dimensionally observed with an atomic force microscope, and one protrusion is present on the outer periphery of the protrusion from an arbitrary point existing on the outer periphery of the protrusion. The calculation was performed by drawing three lines with the longest length up to an arbitrary point and calculating the arithmetic average value of the lengths of the lines.

<Contact angle maintenance ratio before and after the eraser test>
In the optical films according to Examples and Comparative Examples, the eraser test was performed by reciprocating 4000 times the surface of the optical film with an eraser, and the contact angle of the surface of the optical film with water before and after the eraser test was measured. The maintenance rate of the contact angle after the eraser test with respect to the corner was calculated.

  In the eraser test, first, a pencil with an eraser (product name “Office Pencil 9852 (with eraser)”, manufactured by Mitsubishi Pencil Co., Ltd.) is cut from the middle, and the cut pencil with an eraser is 6 mm in diameter from the side opposite to the eraser side. Insert the jig with a pencil with an eraser into a Gakken type wear fastness tester (product name “AB-301”, manufactured by Tester Sangyo Co., Ltd.). After mounting, the surface of the optical film was rubbed 4000 times with an eraser at a load of 500 g and a rubbing speed of 30 mm / sec.

In the contact angle measurement, the surface of the optical film (the surface of the second hard coat layer) in the optical films according to Examples and Comparative Examples before and after the eraser test cut out to a size of 10 cm in the horizontal direction and 5 cm in the vertical direction, respectively. The contact angle with water was measured. Specifically, according to the sessile drop method described in JIS R3257: 1999, using a microscopic contact angle meter (product name “DropMaster300”, manufactured by Kyowa Interface Science Co., Ltd.) at 25 ° C., 1 μL of water is added to the hard coat layer. It dropped on the surface, the contact angle after dripping was measured 10 points | pieces, and those arithmetic mean values were made into the contact angle with respect to the water of the surface of an optical film. Further, the contact angle maintenance rate is defined as A (%), the contact angle with water on the surface of the optical film before the eraser test is B, and the contact angle with water on the surface of the optical film after the eraser test is defined as B. When C, it was calculated by the following formula. In addition, the contact angle measurement after the eraser test was performed at a location rubbed with an eraser in the optical film.
A = C / B × 100

<Steel wool test>
A steel wool test was performed and evaluated on the surfaces of the optical films according to Examples and Comparative Examples (surface of the hard coat layer). Specifically, the optical film cut out in a size of 10 cm in the horizontal direction × 5 cm in the vertical direction was fixed with a cello tape (registered trademark) manufactured by Nichiban Co., Ltd. so as not to be folded or wrinkled on the glass plate. Using steel wool (product name “BON STAR”, manufactured by Nippon Steel Wool Co., Ltd.), while applying a load of 1 kg / cm ² , rubbing 5000 times at a speed of 50 mm / sec, and then checking the surface of the optical film for scratches It was confirmed visually. The evaluation criteria were as follows.
○: No scratch was confirmed.
X: Scratches were confirmed.

<Pencil hardness test>
The pencil hardness on the surface of the optical film according to the example and the comparative example (surface of the hard coat layer) was measured based on JIS K5600-5-4: 1999. When measuring the pencil hardness, the optical film cut out to a size of 5 cm × 10 cm is fixed to the pencil with a cello tape (registered trademark) manufactured by Nichiban Co., Ltd. so that there is no folding or wrinkle on the glass plate. While applying a load of 1 kg, the pencil was moved at a speed of 1 mm / second. The pencil hardness is the highest hardness at which the surface of the optical film was not damaged in the pencil hardness test. The pencil hardness is measured using a plurality of pencils having different hardnesses. The pencil hardness test is performed five times for each pencil, and the surface of the optical film is measured under a fluorescent lamp four times or more out of five times. In the case where no scratch is visually recognized on the surface of the optical film during the transmission observation, it is determined that the surface of the optical film is not scratched with the pencil having this hardness.

<Total light transmittance measurement>
The total light transmittance of the optical films according to Examples and Comparative Examples is measured using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory) in accordance with JIS K7361-1: 1997. did. The total light transmittance was an arithmetic average value of values obtained by measuring three times with respect to an optical film cut into a size of 10 cm in the horizontal direction and 5 cm in the vertical direction.

<Measurement of haze value>
Using the haze value (product name “HM-150”, manufactured by Murakami Color Research Laboratory) in accordance with JIS K7136: 2000, the haze value (total haze value) of the optical films according to Examples and Comparative Examples is It was measured. The haze value was an arithmetic average value of values obtained by measuring three times with respect to an optical film cut out in a size of 10 cm in the horizontal direction and 5 cm in the vertical direction.

The results are shown in Table 1.

  The results will be described below. In the optical films according to Comparative Examples 1 and 2, since the number of the protrusions was less than 3, the result of the steel wool test was good, but the contact angle maintenance rate was low and the wear resistance was poor. It was. In the optical film according to Comparative Example 1, since the second hard coat layer contained a lubricant, a large number of convex portions were present on the surface of the optical film, but the convex portions were not cylindrical. . For this reason, in the optical film according to Comparative Example 1, the contact area with the eraser is smaller than the cylindrical protrusion in the eraser test, so that the antifouling agent is scraped off and the contact angle maintenance rate is low. Conceivable. Further, in the optical films according to Comparative Examples 3 to 5, the number of the protrusions was more than 20, so the contact angle maintenance rate was high, but the results of the steel wool test were inferior and the scratch resistance was high. It was inferior. On the other hand, in the optical films according to Examples 1 to 5, the results of the steel wool test and the results of the contact angle maintenance rate were also good, so that the scratch resistance was excellent and the wear resistance was also excellent. .

DESCRIPTION OF SYMBOLS 10 ... Optical film 10A ... Surface 11 ... Resin base material 11A ... One surface 12 ... Hard coat layer 12A ... Surface 13 ... 1st hard coat layer 14 ... 2nd hard coat layer 30 ... Image display apparatus 33 ... Display element 34 ... Touch sensor

Claims (7)

An optical film comprising a resin substrate and a hard coat layer provided on one surface side of the resin substrate,
The surface of the optical film is the surface of the hard coat layer,
When an area of 5 μm square on the surface of the optical film is observed three-dimensionally using an atomic force microscope, cylindrical projections having a diameter of 0.1 μm to 2.5 μm and a height of 20 nm or less are formed in the area. An optical film having 3 or more and 20 or less.   When an eraser test is performed in which the surface of the optical film is rubbed 4000 times with a load of 500 g using an eraser, the optical film after the eraser test with respect to a contact angle with water on the surface of the optical film before the eraser test. The optical film according to claim 1, wherein a contact angle maintenance ratio, which is a ratio of a contact angle to water on the surface of the film, is 80% or more. ^2. The optical film according to claim 1, wherein a scratch is not confirmed on the surface when a steel wool test is performed in which the surface of the optical film is rubbed back and forth 5000 times while applying a load of 1 kg / cm ² using steel wool.   The hard coat layer is provided on a surface of the first hard coat layer containing particles and a surface of the first hard coat layer opposite to the surface of the resin base material, and does not contain particles. The optical film according to claim 1, comprising a hard coat layer. A display element;
The optical film according to claim 1, which is disposed closer to the viewer than the display element,
The image display apparatus in which the hard coat layer of the optical film is located closer to the viewer than the resin base material.   The image display device according to claim 5, further comprising a touch sensor between the display element and the optical film.   The image display device according to claim 5, wherein the display element is an organic light emitting diode element.

Images