Optical film and display device

Abstract

This optical film comprises: a base material; and a functional layer that contains a resin and functional particles, which are an antimicrobial agent and / or an antiviral agent. The surface of the functional layer in contact with the base material is the rear surface of the functional layer, and the outermost surface of the optical film positioned on the opposite side of the base material with respect to the rear surface is the front surface of the optical film. The average particle diameter of the functional particles is 0.8 times or less than the average film thickness between the front surface of the optical film and the rear surface of the functional layer. The optical film is disposed on a display surface on which an image in the display device is displayed.

Description

Optical film and display device

[0001] The present disclosure relates to an optical film and a display device including the optical film.

[0002] Optical films have the function of controlling light reflection, transmission, etc. For example, optical films are disposed on the surface of a display device in order to improve the visibility of the screen of the display device (see, for example, Patent Document 1).

[0003] Patent No. 6720639

[0004] Due to the recent increase in awareness of hygiene, there is an increasing demand for optical films having antibacterial and antiviral properties. In particular, since the surfaces of display devices equipped with touch panels are frequently touched by users, optical films used in such display devices are required to have antibacterial and antiviral properties.

[0005] One aspect of the optical film is an optical film comprising a substrate and a functional layer containing functional particles that are at least one of an antibacterial agent and an antiviral agent and a resin, wherein the surface of the functional layer that contacts the substrate is the back surface of the functional layer, the outermost surface of the optical film located on the opposite side of the back surface to the substrate is the front surface of the optical film, and the average particle size of the functional particles is 0.8 times or less the average film thickness between the front surface of the optical film and the back surface of the functional layer.

[0006] Fig. 1 is a diagram showing the cross-sectional structure of a first example of the optical films of the first and second embodiments. Fig. 2 is a graph showing the relationship between the proportion of functional particles and haze. Fig. 3 is a diagram showing an example of the position of functional particles in the functional layer of the first embodiment. Fig. 4 is a diagram showing the cross-sectional structure of a second example of the optical films of the first and second embodiments. Fig. 5 is a diagram showing the configuration of the display devices of the first and second embodiments. Fig. 6 is a diagram showing an example of a load-displacement curve of the optical film of the second embodiment.

[0007] The phrase "at least one" as used herein means "one or more" of the desired options. As an example, the phrase "at least one" as used herein means "only one option" or "both of two options" when the number of options is two. As another example, the phrase "at least one" as used herein means "only one option" or "any combination of two or more options" when the number of options is three or more. As used herein, "antibacterial and antiviral" means at least one of antibacterial and antiviral.

[0008] First Embodiment A first embodiment of an optical film and a display device will be described with reference to the drawings.

[0009] Antibacterial and antiviral properties can be imparted to optical films by adding an antibacterial and antiviral agent to the resin layer of the optical film. Inorganic functional particles containing silver or silver compounds are widely used as antibacterial and antiviral agents.

[0010] In general, the particle size of functional particles used as antibacterial and antiviral agents is approximately several tens of nanometers to several micrometers. The functional particles have a refractive index different from that of the resin constituting the optical film. The inclusion of such functional particles tends to increase the scattering of light within the optical film, resulting in an increase in the haze of the optical film and poor appearance due to the functional particles being observed as bright spots.

[0011] In particular, when the particle size of the functional particles is equal to or greater than the film thickness of the resin layer containing the functional particles, light scattering tends to be large, resulting in a significant increase in haze even when the content of the functional particles is small. Furthermore, the formation of irregularities on the surface of the optical film due to the functional particles not only changes the surface scattering of the optical film, leading to haze and deterioration of the appearance, but also impairs glare resistance. Glare is a phenomenon in which the surface irregularities function as lenses, causing unevenness in the intensity of brightness as seen by the user of the display device, resulting in the image appearing to flicker.

[0012] On the other hand, when the particle size of the functional particles is sufficiently smaller than the film thickness of the resin layer, the effect on haze and appearance is small if the content of the functional particles is small. However, when the particle size of the functional particles is small, the functional particles are also arranged in the resin layer in areas away from the surface of the optical film, which tends to inhibit elution and result in functional particles that do not contribute to the development of antibacterial and antiviral properties. Therefore, in order to obtain sufficient antibacterial and antiviral properties, the content of the functional particles must be increased, which may result in deterioration of haze and appearance, and deterioration of the mechanical properties of the film due to a relative decrease in the resin component.

[0013] Compounds that can be used as antibacterial and antiviral agents include materials that are not particulate like organic materials but dissolve in the coating liquid used to form the resin layer. Such materials are less likely to cause an increase in haze. However, the chemical properties of the antibacterial and antiviral agents have a significant effect on the coating liquid and coating film, which can lead to problems such as bleed-out, reduced stability of the coating liquid, and changes in the mechanical properties and antireflection properties of the resin layer (coating film). The first embodiment aims to suppress the deterioration of properties, including haze and appearance, caused by the inclusion of functional particles in an optical film having antibacterial and antiviral properties.

[0014] [Optical Film Structure: First Example] Fig. 1 shows a first example of the layer structure of an optical film 10. An optical film 10A, which is the optical film 10 of the first example, includes a substrate 20 and a functional layer 21. The functional layer 21 is supported by the substrate 20. The functional layer 21 includes a resin and functional particles having at least one of antibacterial and antiviral properties.

[0015] Of the two surfaces of the functional layer 21, the surface in contact with the substrate 20 is the back surface 21S, and the surface opposite the back surface is the front surface. The outermost surface of the optical film 10A located on the opposite side of the substrate 20 from the back surface 21S of the functional layer 21 is the front surface 11S of the optical film 10A. The outermost surface opposite the front surface 11S, i.e., the back surface of the substrate 20, is the back surface of the optical film 10A. In the first example, the front surface of the functional layer 21 is the front surface 11S of the optical film 10A. The front surface 11S of the optical film 10A is an active surface that exhibits antibacterial and antiviral effects.

[0016] The structure of each layer will be described in detail below. <Substrate> The material and thickness of the substrate 20 may be any material and thickness that allows the functional layer 21 to be formed on the substrate 20. The substrate 20 is, for example, a resin film that is transparent to light in the visible range. Examples of materials for the resin film include polyester, polypropylene, polystyrene, nylon, polycarbonate, polyacrylonitrile, polyimide, triacetyl cellulose, etc. From the viewpoint of easy handling of the substrate 20, the thickness of the substrate 20 is preferably 12 μm or more, and more preferably 20 μm or more. If the thickness of the substrate 20 is 12 μm or more, the strength and quality of the substrate 20 are likely to be good. The substrate 20 may be a single-layer structure or a multi-layer structure.

[0017] <Functional Layer> The resin contained in the functional layer 21 may be an ultraviolet-curable resin or a thermosetting resin. The ultraviolet-curable resin is a cured product of a photopolymerizable compound. Examples of the photopolymerizable compound include monofunctional, bifunctional, trifunctional or higher functional (meth)acrylate compounds and urethane (meth)acrylate compounds. Note that "(meth)acrylate" is a general term for acrylate and methacrylate. Examples of thermosetting resins include acrylic resin, urethane resin, and epoxy resin. The resin contained in the functional layer 21 may be one type or two or more types.

[0018] The functional particles may be particles that function as either an antibacterial agent or an antiviral agent, or particles that function as both an antibacterial agent and an antiviral agent, or particles whose function as either an antibacterial agent or an antiviral agent changes depending on conditions such as the amount added.

[0019] The functional particles are composed of, for example, inorganic materials. Examples of inorganic materials include metals such as silver, copper, and zinc, metal oxides such as zinc oxide, and metal hydroxides such as calcium hydroxide. The functional particles may contain the metals as metal particles, or in the form of ions, complexes, or salts. The functional particles may also contain the metals supported on a carrier. In this case, the functional particles are composed of the metal and the carrier. Examples of the carrier include zeolite, phosphate-based carriers such as zirconium phosphate, silica gel, activated carbon, and glass materials.

[0020] Among the above, inorganic particles containing a metal or a metal oxide are preferably used as the functional particles, and particles containing silver are particularly preferably used. The functional layer 21 may contain light-scattering particles, which are fine particles for adjusting the light scattering properties of the optical film 10A. The inclusion of light-scattering particles makes it possible to adjust the surface roughness of the optical film 10A, thereby enabling control of the light scattering properties of the surface 11S of the optical film 10A. If the surface 11S of the optical film 10A has appropriate light scattering properties, it is possible to increase the diffuse reflection component of the light reflected at the surface 11S of the optical film 10A and suppress the specular reflection component, thereby suppressing the reflection of the surroundings on the optical film 10A.

[0021] Furthermore, the inclusion of light-scattering particles also makes it possible to control the light scattering properties within the functional layer 21. By controlling the light scattering properties on the surface 11S of the optical film 10A and within the functional layer 21, it is possible to control the haze of the optical film 10A, and thereby adjust the transparency of the optical film 10A.

[0022] The light-scattering particles are organic or inorganic particles. The functional layer 21 may contain one type of light-scattering particles, or two or more types that differ from each other in at least one of material and average particle size. The average particle size of the light-scattering particles is the volume-based median diameter (D50). The average particle size of the light-scattering particles is preferably 30% or more of the film thickness of the functional layer 21, and more preferably 50% to 80% of the film thickness of the functional layer 21.

[0023] The ratio of the light scattering particles to the resin contained in the functional layer 21 is preferably 3.0% by mass or more and 20% by mass or less. If the ratio of the light scattering particles is 3.0% by mass or more, the light scattering effect of the light scattering particles can be suitably obtained. If the ratio of the light scattering particles is 20% by mass or less, the amount of resin is not too small, and therefore deterioration of the mechanical properties of the functional layer 21 can be suppressed.

[0024] The organic fine particles are resin particles made of a light-transmitting resin material such as acrylic resin, polystyrene resin, styrene-(meth)acrylic acid ester copolymer, polyethylene resin, epoxy resin, silicone resin, polyvinylidene fluoride, or polyethylene fluoride resin.

[0025] Inorganic fine particles can be used as a material for controlling the sedimentation or aggregation of organic fine particles. Examples of inorganic fine particles include silica fine particles, metal oxide fine particles, and mineral fine particles. Examples of silica fine particles include colloidal silica and silica fine particles surface-modified with reactive functional groups such as (meth)acryloyl groups. Examples of metal oxides constituting metal oxide fine particles include aluminum oxide, zinc oxide, tin oxide, antimony oxide, indium oxide, titanium dioxide, and zirconium dioxide. Examples of minerals constituting mineral fine particles include mica, synthetic mica, vermiculite, montmorillonite, iron-montmorillonite, bentonite, beidellite, saponite, hectorite, stevensite, nontronite, magadiite, ilealite, kanemite, layered titanic acid, smectite, and synthetic smectite.

[0026] The functional layer 21 may contain various additives. Examples of additives include an ultraviolet absorber, an antistatic agent, a leveling agent, an antifouling agent, a thickener, etc. The inclusion of additives can enable the functional layer 21 to exhibit ultraviolet absorption functions, antistatic functions, etc., and improve coatability and quality.

[0027] The functional layer 21 is formed by applying a functional layer coating liquid, which is a coating liquid for forming the functional layer 21, to the surface of the substrate 20 and curing the film thus formed. The functional layer coating liquid contains compounds for forming the resin of the functional layer 21, functional particles, polymerization initiators, and other auxiliary agents as needed. When forming a functional layer 21 containing light-scattering particles, the functional layer coating liquid further contains light-scattering particles.

[0028] The functional layer coating liquid can be applied by any known method, such as bar coating, spin coating, offset coating, gravure coating, roll coating, die coating, etc. The method for curing the film after application may be any method appropriate for the curing type of the resin, and ultraviolet irradiation or heat drying may be used.

[0029] <Conditions of Optical Film> The optical film 10A satisfies the first condition and at least one of the second and third conditions described below.

[0030] [First Condition] The average particle diameter Φ1 of the functional particles is 1.0 μm or more, and the average film thickness t1 between the front surface 11S of the optical film 10A and the back surface 21S of the functional layer 21 and the average particle diameter Φ1 of the functional particles satisfy the following formula (1). In the optical film 10A of the first example, the average film thickness t1 is the average film thickness of the functional layer 21. 0.2×t1≦Φ1≦0.8×t1 (1)

[0031] By setting the average particle size Φ1 of the functional particles to 0.2 times or more the average film thickness t1, even when the functional particles are located near the substrate 20 in the functional layer 21, the functional particles are not too far away from the surface 11S of the optical film 10A. This prevents the generation of functional particles that do not contribute to the development of antibacterial and antiviral properties, thereby suppressing an increase in the content of functional particles necessary for the development of antibacterial and antiviral properties. This prevents an increase in haze and a deterioration in the appearance of the optical film 10A due to an increase in the content of functional particles, and also suppresses a decrease in the mechanical properties of the optical film 10A.

[0032] By setting the average particle size Φ1 of the functional particles to 0.8 times or less the average film thickness t1, scattering of light inside the functional layer 21 due to the inclusion of the functional particles is suppressed, and the functional layer 21 is prevented from swelling at the locations where the functional particles are located, thereby preventing the formation of convex portions on the surface 11S of the optical film 10A, thereby suppressing an increase in haze and a deterioration in the appearance of the optical film 10A.

[0033] The average film thickness t1 is the average value of sample thickness values ​​on the cross section of the optical film 10A. The sample thickness value is a measurement value of thickness measured at 10 points on the cross section of the optical film 10A at intervals of 1 mm or more, the difference between these measurement values ​​and the average value being within 50% of the average value.

[0034] The average film thickness of the functional layer 21 is preferably 1.5 μm or more from the viewpoints of improving the uniformity of the thickness of the functional layer 21, the applicability of the coating liquid for forming the functional layer 21, the mechanical strength, and the antibacterial and antiviral activities of the functional layer 21. The average film thickness of the functional layer 21 is preferably 15 μm or less, and more preferably 10 μm or less, from the viewpoints of improving the adhesion of the functional layer 21 to the substrate 20 and reducing the load required for curing the functional layer 21.

[0035] The average particle size Φ1 of the functional particles is the volume-based median diameter (D50). The particle size Φ1 of the functional particles is determined using a laser diffraction / scattering method. By setting the average particle size Φ1 to 1.0 μm or more, it is possible to easily satisfy the above formula (1) while keeping the film thickness of the functional layer 21 within the above-mentioned preferred range, and the range of selection for the average film thickness t1 and the average particle size Φ1 is expanded. From the viewpoint of improving the dispersibility of the functional particles in the coating liquid for forming the functional layer 21 and preventing the film thickness of the functional layer 21 from increasing, it is preferable that the average particle size Φ1 of the functional particles be 5 μm or less.

[0036] [Second Condition] When the relationship between the functional component ratio x, which is the ratio of the mass of the functional particles to the resin contained in the functional layer 21, and the haze y of the optical film 10A is expressed by the following formula (2) in a first approximation, a≦50: y=ax+b (2)

[0037] Here, the intercept b of the linear approximation formula (2) above is the haze value of the optical film 10A when no functional particles are contained in the functional layer 21. The slope a in the linear approximation formula above is obtained by preparing two or more samples of the optical film 10A with different functional component ratios x, measuring the haze y, and determining a linear approximation formula for the correlation between the functional component ratio x and the haze y. The haze y is measured in accordance with JIS K 7136.

[0038] Figure 2 shows an example of the relationship between the functional component ratio x and the haze y, which is a first-order approximation. In Figure 2, the same plotted points correspond to samples that have the same type of resin and the same type of functional particles, but different functional component ratios x.

[0039] 2, the slope a of the approximate line L1 is 21, the slope a of the approximate line L2 is 55, the slope a of the approximate line L3 is 76, and the slope a of the approximate line L4 is 165. The intercept b of each line is 0.23.

[0040] The slope a increases as the difference in refractive index between the resin and the functional particles in the functional layer 21 increases. Even when it is difficult to directly measure the refractive index between the resin and the functional particles, the tendency for the haze to increase due to the difference in refractive index can be accurately evaluated by obtaining a linear approximation for the correlation between the functional component ratio x and the haze y.

[0041] The ratio of the functional particles to the resin contained in the functional layer 21 is preferably 3% by mass or more from the viewpoint of enhancing antibacterial activity, and preferably 5% by mass or more from the viewpoint of enhancing antiviral activity. That is, the functional component ratio x is preferably 0.03 or more, and more preferably 0.05 or more. The ratio of the functional particles to the resin contained in the functional layer 21 is preferably 20% by mass or less, and more preferably 15% by mass or less, from the viewpoint of enhancing the dispersibility of the functional particles and minimizing the influence on the properties of the optical film 10A. That is, the functional component ratio x is preferably 0.20 or less, and more preferably 0.15 or less.

[0042] As shown in Figure 2, if the slope a is 50 or less, the increase in haze can be suppressed to 10% or less even if the functional component ratio x is increased to about 0.2. Conventionally, to suppress the increase in haze, it has been common to use small functional particles with an average particle size Φ1 of less than 1 μm. In contrast, if the slope a is 50 or less, the increase in haze can be suppressed even when functional particles with an average particle size Φ1 of 1 μm or more are used, as defined in the first condition.

[0043] Therefore, by satisfying the first and second conditions, it is possible to realize an optical film 10 in which an increase in haze is suitably suppressed while accurately avoiding the problem of a decrease in antibacterial and antiviral effect that occurs when functional particles with a small average particle size Φ1 are used.

[0044] The increase in haze due to the addition of functional particles, i.e., the difference between the haze of the optical film 10A and the haze of a resin film having the same configuration as the optical film 10A except that it does not contain functional particles, is preferably 5% or less, more preferably 3% or less. Furthermore, the difference in refractive index between the resin of the functional layer 21 and the functional particles is preferably 0.03 or less. This effectively suppresses the increase in haze in the optical film 10A.

[0045] [Third Condition] The following formula (3) is expressed by the distance p between the surface 11S of the optical film 10A and the functional particles in the thickness direction of the optical film 10A, the film thickness t2 between the surface 11S of the optical film 10A and the back surface 21S of the functional layer 21, and the particle diameter Φ2 of the functional particles. For 75% or more of a plurality of functional particles randomly sampled in the cross section of the optical film 10A, the distance p, film thickness t2, and particle diameter Φ2 at the location where the functional particles are located satisfy the following formula (3). The number of sampled functional particles may be 30 or more, and more preferably 50 or more. 0.3≦p / (t2-Φ2) (3)

[0046] 3, the measurement point in the cross section of the optical film 10A is a line Z1 that extends in the thickness direction and passes through the end of the functional particle 25 closest to the surface 11S of the optical film 10A. The distance p is the length between the end on the line Z1 and the surface 11S, in other words, the length along the thickness direction between the end of the functional particle 25 closest to the surface 11S and the surface 11S.

[0047] The film thickness t2 is the length on the line Z1 between the surface 11S and the back surface 21S of the functional layer 21, and in the optical film 10A of the first example, it is the thickness of the functional layer 21 on the line Z1. The particle diameter Φ2 of the functional particles 25 is the total length of the functional particles 25 on the line Z1.

[0048] A straight line Z1 is defined, and the distance p, film thickness t2, and particle size Φ2 are measured for each of the extracted functional particles 25. In other words, the straight line Z1 is defined in accordance with the measurement of the distance p, and the film thickness t2 and particle size Φ2 are measured on an extension of the measurement point of the distance p along the straight line Z1.

[0049] When the functional layer 21 contains light-scattering particles, the light-scattering particles may be present between the functional particles 25 and the surface 11S. The distance p is the length from the functional particles 25 to the surface 11S, including the region where the light-scattering particles are present.

[0050] Even when the average film thickness t1 and the average particle diameter Φ1 satisfy the first condition, if functional particles in the functional layer 21 are located near the surface 11S, irregularities may be formed on the surface 11S of the optical film 10A. Specifically, if the functional particles are located near the surface 11S, a difference in the degree of cure shrinkage of the resin may occur between this surface area and other areas, leading to the formation of irregularities. If the above formula (3) is satisfied, the formation of such irregularities is suppressed, and therefore haze and deterioration of the appearance of the optical film 10A are more effectively suppressed.

[0051] Furthermore, even if the above formula (3) is satisfied, the first condition is satisfied, and therefore the average particle size Φ1 of the functional particles is 0.2 times or more the average film thickness t1, and therefore the functional particles are prevented from being too far away from the surface 11S of the optical film 10A, which would result in a decrease in the antibacterial and antiviral properties.

[0052] The position of the functional particles in the thickness direction of the functional layer 21 can be adjusted by adjusting the surface tension or viscosity of the coating liquid used to form the functional layer 21, adjusting the specific gravity of the coating liquid material, changing the drying conditions for the film formed from the coating liquid, etc. The properties of the coating liquid, such as the surface tension, can be adjusted, for example, by adding an additive such as a leveling agent to the coating liquid.

[0053] 4 shows a second example of the layer structure of the optical film 10. An optical film 10B, which is the optical film 10 of the second example, includes a low refractive index layer 22 in addition to a substrate 20 and a functional layer 21. The low refractive index layer 22 has a lower refractive index than the functional layer 21 and has the function of suppressing surface reflection of the optical film 10B by utilizing light interference.

[0054] The low-refractive index layer 22 is located on the functional layer 21. When the surface of the functional layer 21 has irregularities, the low-refractive index layer 22 has a surface shape that follows the irregularities of the functional layer 21. In the second example, the surface of the low-refractive index layer 22 opposite to the surface that contacts the functional layer 21, i.e., the surface of the low-refractive index layer 22, is the surface 11S of the optical film 10B.

[0055] The low refractive index layer 22 contains an ultraviolet curable resin or a thermosetting resin. Such a resin may be any of the resins exemplified as the resin contained in the functional layer 21. The low refractive index layer 22 and the functional layer 21 may contain the same type of resin or different resins.

[0056] The low refractive index layer 22 may also contain a refractive index adjuster for lowering the refractive index of the low refractive index layer 22. Examples of the refractive index adjuster include fluoride fine particles such as lithium fluoride, magnesium fluoride, sodium hexafluoroaluminate, and aluminum fluoride, and silica fine particles. As the silica fine particles, it is effective to use fine particles having voids inside, such as porous silica fine particles or hollow silica fine particles, in order to lower the refractive index of the low refractive index layer 22.

[0057] The low refractive index layer 22 may contain various additives. Examples of additives include an ultraviolet absorber, an antistatic agent, a leveling agent, an antifouling agent, a thickener, etc. The inclusion of additives can enable the low refractive index layer 22 to exhibit ultraviolet absorption functions, antistatic functions, etc., and can improve coatability and quality.

[0058] The low refractive index layer 22 is thinner than the functional layer 21. The average film thickness of the low refractive index layer 22 is preferably 30 nm or more and 300 nm or less. If the average film thickness of the low refractive index layer 22 is 30 nm or more, light interference is likely to occur, and if the average film thickness of the low refractive index layer 22 is 300 nm or less, scratch resistance and adhesion to the functional layer 21 are likely to be maintained well. The average film thickness of the low refractive index layer 22 may be measured in the same manner as the average film thickness of the functional layer 21.

[0059] The low refractive index layer 22 is formed by applying a low refractive index layer coating liquid, which is a coating liquid for forming the low refractive index layer 22, to the surface of the functional layer 21 and curing the film thus formed. The low refractive index layer coating liquid contains compounds for forming the resin of the low refractive index layer 22, auxiliary agents as needed such as a polymerization initiator, and further contains a refractive index adjuster depending on the configuration of the low refractive index layer 22.

[0060] The coating liquid for the low refractive index layer can be applied by known methods such as bar coating, spin coating, offset coating, gravure coating, roll coating, die coating, etc. The method for curing the film after coating may be any method appropriate for the curing type of the resin, and ultraviolet irradiation or heat drying is used.

[0061] The optical film 10B of the second example also satisfies the first condition and at least one of the second and third conditions. In the second example, the average film thickness t1 in the first condition is the average film thickness of the combined thickness of the functional layer 21 and the low-refractive-index layer 22. Furthermore, in the second example, the distance p in the third condition is the length between the end of the functional particle 25 closest to the surface 11S, i.e., the end closest to the surface of the low-refractive-index layer 22, and the surface 11S, and the film thickness t2 is the combined thickness of the functional layer 21 and the low-refractive-index layer 22 on the line Z1. Because the film thickness of the low-refractive-index layer 22 is sufficiently smaller than the film thickness of the functional layer 21, the low-refractive-index layer 22 has little effect on the conditions related to film thickness.

[0062] In addition, the optical film 10 may have, in addition to the functional layer 21, a layer other than the low refractive index layer 22, and even in such a case, the average film thickness t1 is the average film thickness between the surface 11S of the optical film 10 and the back surface 21S of the functional layer 21, the distance p is the length along the thickness direction between the end of the functional particle 25 closest to the surface 11S and the surface 11S, and the film thickness t2 is the length between the surface 11S and the back surface 21S of the functional layer 21 on the straight line Z1.

[0063] [Optical Film Characteristics] The following describes the optical characteristics and mechanical characteristics of the optical film 10. The following characteristics are common to the optical films of the first and second examples.

[0064] When the functional layer 21 does not contain light-scattering particles, the haze of the optical film 10 is preferably 5% or less. This configuration provides high transparency for the optical film 10, thereby improving visibility through the optical film 10. In the optical film 10 of the first embodiment, the first condition and at least one of the second and third conditions are satisfied, thereby suppressing an increase in haze due to the inclusion of functional particles, and thus a haze of 5% or less can be suitably achieved.

[0065] When the functional layer 21 contains light-scattering particles, the haze of the optical film 10 is preferably 5% or more and 35% or less. This configuration reduces the reflection of the surroundings on the optical film 10 while preventing excessive deterioration of visibility through the optical film 10. In the optical film 10 of the first embodiment, the first condition and at least one of the second and third conditions are satisfied, thereby preventing an increase in haze due to the inclusion of functional particles, and thus allowing the haze to be controlled by the type and content of the light-scattering particles. In other words, because changes in haze due to factors other than the light-scattering particles are suppressed, the haze can be controlled by a single factor, the light-scattering particles, and the desired haze can be accurately obtained.

[0066] When the functional layer 21 contains light-scattering particles, unevenness caused by the light-scattering particles is formed on the surface of the optical film 10, and therefore glare resistance is required. Glare is a phenomenon in which the unevenness on the surface of the optical film functions as a lens, causing unevenness in the brightness seen by a user of a display device on which the optical film is laminated, causing the image on the display device to appear flickering. Glare is more likely to occur when there is a large difference between the size of the pixels in the display device and the size of the unevenness on the surface of the optical film. In recent years, as the resolution of display devices has increased, pixel size has become smaller, and the difference in size between the pixels and the unevenness is more likely to increase, so suppressing the occurrence of glare is an important issue.

[0067] Glare resistance can be evaluated using the glare contrast defined in JIS C 1006:2019. Specifically, the optical film 10 is placed on a metal mask having a grating pattern, and the glare contrast is measured for multiple metal masks having grating patterns with different pitches. The gratings correspond to the pixel arrangement, and six types of metal masks having grating patterns corresponding to pixel densities of 85 ppi, 106 ppi, 127 ppi, 169 ppi, 254 ppi, and 508 ppi are used. The glare contrast is determined by single image measurement using a glare measuring device in accordance with JIS C 1006:2019.

[0068] Then, a linear approximation equation is obtained for the measured value of glare contrast and the pixel density, with y representing the glare contrast and x representing the pixel density. From this linear approximation equation, the value of x at which y = 3.0 is found and used as the glare tolerance value. That is, the glare tolerance value is the maximum pixel density at which the glare contrast is 3.0 or less, and the larger the glare tolerance value, the more glare is suppressed for higher-resolution images. If the glare contrast is 3.0 or less, the glare is suppressed from being clearly perceived.

[0069] The glare resistance value is preferably 150 ppi or more. This reduces the occurrence of glare when the optical film 10 is used in a general display device. In the optical film 10 of the first embodiment, the first condition and at least one of the second and third conditions are satisfied, thereby preventing the formation of irregularities caused by the functional particles on the surface of the optical film, thereby preventing a decrease in the glare resistance value. In other words, good glare resistance is obtained.

[0070] The pencil hardness of the surface of the optical film 10, i.e., the scratch hardness measured using a pencil method, is preferably 3H or more. If the pencil hardness is 3H or more, the surface of the optical film 10 is less susceptible to scratches. The pencil hardness is measured in accordance with JIS K 5600-5-4.

[0071] 5, the display device 100 includes an optical film 10 and a main body 30 having an image display function. A display surface 30S, which is the surface of the main body 30, is a surface on which an image is displayed, and is the surface of a display panel such as a liquid crystal panel or an organic EL panel, or the surface of a touch panel laminated on the display panel. The optical film 10 is positioned on the display surface 30S, and the back surface of the optical film 10 is attached to the display surface 30S.

[0072] In particular, when the display surface 30S is the surface of a touch panel, users frequently touch the display device 100, and therefore it is highly beneficial for the optical film 10 to have antibacterial and antiviral properties.

[0073] Specific examples of the display device 100 include smartphones, tablet terminals, personal computers, portable game consoles, music playback devices, televisions, monitors, electronic book viewing terminals, digital cameras, head-mounted displays, navigation devices, copiers, facsimiles, printers, multi-function printers, vending machines, automatic teller machines (ATMs), personal authentication devices, optical communication devices, etc.

[0074] Second Embodiment A second embodiment of an optical film and a display device will be described. To improve the performance of an optical film, it is desirable to achieve both antibacterial and antiviral properties and other properties. Specifically, both antibacterial and antiviral properties and hardness are required. However, when an optical film contains an antibacterial and antiviral agent, it is difficult to increase hardness solely by selecting the resin material that is the main component of the optical film. For example, restrictions may be placed on usable materials due to the interaction between the antibacterial and antiviral agent and the resin, and precise control of the composition and manufacturing process may be required to achieve both properties. The second embodiment aims to improve antibacterial and antiviral properties and hardness in an optical film.

[0075] [Configuration of Optical Film: First Example] The optical film 50 of the second embodiment has the same layer configuration as the first or second example of the first embodiment. That is, the optical film 50A, which is the optical film 50 of the first example, includes a substrate 20 and a functional layer 21. In the second embodiment, the configuration of the substrate 20 is the same as in the first embodiment. The configuration of the functional layer 21 of the second embodiment will be described below.

[0076] The functional layer 21 includes a resin and functional particles having at least one of antibacterial and antiviral properties. The resin included in the functional layer 21 may be an ultraviolet-curable resin or a thermosetting resin. The ultraviolet-curable resin is a cured product of a photopolymerizable compound. Examples of the photopolymerizable compound include monofunctional, bifunctional, or trifunctional or higher functional (meth)acrylate compounds and urethane (meth)acrylate compounds. Examples of the thermosetting resin include acrylic resin, urethane resin, and epoxy resin. The resin included in the functional layer 21 may be one type or two or more types.

[0077] The functional particles are solids containing metals or metal ions. The functional particles include, for example, metals such as silver, copper, and zinc, or ions thereof. The functional particles may also include a carrier that supports the metal or metal ions. The carrier is preferably an inorganic material. Examples of the carrier include zeolite, phosphate-based carriers such as zirconium phosphate, silica gel, activated carbon, and glass materials. The functional particles may also be metal oxides such as zinc oxide, or metal hydroxides such as calcium hydroxide.

[0078] The functional layer 21 may also contain light scattering particles and additives similar to those in the first embodiment. The functional layer 21 is manufactured by the same method as in the first embodiment.

[0079] The following describes the features of the functional layer 21 of the second embodiment. <Particle size of functional particles> The average particle size Φ3 of the functional particles is 0.8 times or less the average film thickness t3 of the functional layer 21. By having the average particle size Φ3 of the functional particles be 0.8 times or less the average film thickness t3, the formation of convex portions due to the functional particles on the surface of the functional layer 21 is suppressed. If the surface of the optical film is raised and convex portions are formed in the areas where the functional particles are located, the surface is likely to be scratched at the convex portions when the optical film is touched by an object such as a finger. As a result, the optical film is likely to crack. In other words, the hardness of the optical film is likely to decrease at the convex portions. In contrast, with the optical film 50A of the second embodiment, the formation of convex portions due to the functional particles is suppressed, thereby increasing the hardness of the optical film 50A.

[0080] Furthermore, because the functional particles are solids containing metal or metal ions, the functional component itself has a higher hardness than when the functional component having antibacterial and antiviral properties is an organic material. Therefore, the hardness of the optical film 50A can be improved. From the perspective of enhancing this effect, the hardness of the functional particles is preferably greater than the hardness of the resin constituting the functional layer 21. Specifically, the Vickers hardness of the functional particles is preferably greater than the Vickers hardness of the resin constituting the functional layer 21. Furthermore, the modulus of rigidity of the functional particles is preferably greater than the modulus of rigidity of the resin constituting the functional layer 21. Furthermore, by dispersing the hard functional particles within the functional layer 21, improved elasticity and toughness can be expected compared to when the entire functional layer 21 is uniformly hard.

[0081] In this way, the hardness of the optical film 50A is increased by the physical structure based on the relationship between the average particle diameter Φ3 and the average film thickness t3, and the functional particles contribute to improving both antibacterial, antiviral, and hardness properties. This increases the degree of freedom in selecting materials for the functional layer 21 while simultaneously achieving both antibacterial, antiviral, and hardness. Furthermore, the constraints on the composition and manufacturing conditions required to achieve the desired hardness along with antibacterial and antiviral properties are also reduced. This reduces the burden of material selection, composition adjustment, and manufacturing management.

[0082] The average film thickness t3 is the average value of sample values ​​of the thickness of the functional layer 21 on the cross section of the optical film 50A. The sample value of the thickness is a measurement value of the thickness measured at 10 points spaced 1 mm or more apart on the cross section of the optical film 50A, the difference between these measurement values ​​and the average value of these measurement values ​​being within 50% of the average value.

[0083] The average thickness t3 of the functional layer 21 is preferably 3 μm or more and 10 μm or less. When the average thickness t3 is 3 μm or more, the mechanical strength of the functional layer 21 is good. When the average thickness t3 is 10 μm or less, deformation such as curling of the optical film 50A during the manufacturing process is suppressed, and the functional particles located near the substrate 20 in the functional layer 21 are more likely to contribute to the development of antibacterial and antiviral properties on the surface of the optical film 50A.

[0084] The average particle size Φ3 of the functional particles is a volume-based median diameter (D50). The average particle size Φ3 of the functional particles is determined using a laser diffraction / scattering method. The average particle size Φ3 of the functional particles is preferably 0.5 μm or more and 5 μm or less. If the average particle size Φ3 is within the above range, the dispersibility of the functional particles in the coating liquid for forming the functional layer 21 is improved, and an increase in the thickness of the optical film 50A is suppressed.

[0085] Furthermore, from the viewpoint of enhancing the effect of suppressing the formation of convex portions, it is preferable that the average maximum diameter of the functional particles is 0.8 times or less the average film thickness t3. The maximum diameter of the functional particles is the diameter of a circle inscribed in the functional particles, and the average maximum diameter is the average of the maximum diameters of 10 functional particles observed in the cross section of the optical film 50A. Note that if the average particle diameter Φ3 of the functional particles is 0.8 times or less the average film thickness t3 of the functional layer 21, then the average particle diameter Φ3 also satisfies the requirement that it is 0.8 times or less the average film thickness t1 between the front surface of the optical film 50 and the back surface of the functional layer 21.

[0086] <Mechanical Properties> The following describes the composite elastic modulus, stress relaxation rate, and plastic deformation amount of the functional layer 21. These are determined using a nanoindentation method.

[0087] Conventionally, pencil hardness and indentation hardness have been used to evaluate the hardness of films. However, pencil hardness is not suitable for precise evaluation of hardness, and indentation hardness is a method for measuring the hardness of a minute region where an indenter makes contact, so in films containing particles, the measurement results vary depending on the presence or absence of particles in the minute region.

[0088] In contrast, the nanoindentation method continuously measures the deformation behavior of a very small region, and the measurement results may be affected by the structure immediately below and around the contact area of ​​the indenter. Furthermore, by averaging the measurement results of the composite elastic modulus, stress relaxation, and plastic deformation amount over a wide range of measurement points, it is possible to evaluate the hardness of the optical film 50A from a macroscopic perspective.

[0089] Each of the composite elastic modulus, stress relaxation rate, and plastic deformation amount is an average of values ​​calculated at 30 or more measurement points. The measurement points are set on the surface of the functional layer 21 at intervals of 20 μm or more. For example, it is preferable that three fields of view are set at intervals of 100 μm or more, and 10 measurement points are set in each field of view.

[0090] The measurement points may be set on a cross section of the functional layer 21. For example, when the functional layer 21 contains light-scattering microparticles, it is preferable to set the measurement points in areas where no light-scattering microparticles are present. When the area where no light-scattering microparticles are present on the surface of the functional layer 21 is small, the measurement points may be set on a cross section of the functional layer 21.

[0091] The composite elastic modulus is calculated using the Oliver-Pharr method based on a load-displacement curve obtained by nanoindentation. The higher the composite elastic modulus, the less the functional layer 21 deforms, i.e., the harder it is.

[0092] The composite elastic modulus of the functional layer 21 is preferably 5.5 GPa or more. When the composite elastic modulus is 5.5 GPa or more, the hardness of the functional layer 21 can be favorably obtained. The composite elastic modulus of the functional layer 21 is preferably 7.0 GPa or less. When the composite elastic modulus is 7.0 GPa or less, the flexibility of the optical film 50A can be favorably obtained.

[0093] The stress relaxation degree is calculated using the maximum load Fmax on the load curve in a load-displacement curve obtained by nanoindentation and the maximum load Pmax on the unload curve in the load-displacement curve, and is the ratio of the difference between the maximum load Fmax and the maximum load Pmax to the maximum load Fmax.

[0094] The stress relaxation rate indicates the change in stress when a certain strain is applied to an object and left to stand. The smaller the stress relaxation rate, the less the optical film 50A is likely to deform, i.e., the harder it is. The stress relaxation rate of the functional layer 21 is preferably 0.13 or less. If the stress relaxation rate is 0.13 or less, the functional layer 21 can have good hardness.

[0095] The amount of plastic deformation is the displacement value when the load changes from positive to negative on the unloading curve of the load-displacement curve obtained by the nanoindentation method. The amount of plastic deformation indicates the magnitude of permanent deformation that does not return to its original state even after the force is removed when an object is deformed beyond its elastic limit due to an external force.

[0096] The amount of plastic deformation of the functional layer 21 is preferably 60 nm or more. If the amount of plastic deformation is 60 nm or more, the toughness of the functional layer 21 is good and fractures such as cracks are less likely to occur. The amount of plastic deformation of the functional layer 21 is preferably 400 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. The smaller the amount of plastic deformation, the larger the elastic deformation region is likely to be secured and the easier it is for a depression to return to its original shape.

[0097] <Average Hydroxyl Value> The average hydroxyl value of the resin constituting the functional layer 21 is preferably 100 mgKOH / g or more. The average hydroxyl value is an actual measured value determined in accordance with JIS K0070 using the functional layer 21 or a material thereof as a sample, or a calculated value determined from the known hydroxyl value of the material.

[0098] For example, if the resin of the functional layer 21 is a polymer produced from multiple types of monomers, the average hydroxyl value can be determined by calculating the product of the hydroxyl value and the molar fraction of each monomer and then summing the products for all the monomers. The molar fraction of a monomer is the ratio of the amount of substance of that monomer to the total amount of monomers. Note that each of these monomers is either a monomer without a hydroxyl group or a monomer with a hydroxyl group that does not contribute to the polymerization reaction.

[0099] Furthermore, for example, if the resin of the functional layer 21 contains multiple polymers and the hydroxyl value of each polymer is known, the average hydroxyl value can be determined by calculating the product of the hydroxyl value of each polymer and the molar fraction, and then calculating the sum of these products for all polymers. The molar fraction of a polymer is the ratio of the amount of substance of that polymer to the total amount of polymers, and for each polymer, the value obtained by dividing the mass of the polymer by the number average molecular weight is treated as the amount of substance of the polymer.

[0100] The higher the affinity between the resin of the functional layer 21 and moisture, the more easily the components responsible for the antibacterial and antiviral properties will elute from the surface of the optical film 50A, making it easier to obtain high antibacterial and antiviral properties. The affinity between the resin and moisture can be evaluated by the average hydroxyl value of the resin and the moisture permeability of the functional layer 21. If the average hydroxyl value is 100 mgKOH / g or more, good antibacterial and antiviral properties are likely to be obtained.

[0101] On the other hand, resins with high hardness, i.e., resins with high crosslinking density, often have a low average hydroxyl value. Therefore, generally, using a resin with a high average hydroxyl value to enhance antibacterial and antiviral properties tends to reduce the hardness of the functional layer 21. In contrast, in the optical film 50A of the second embodiment, as described above, the functional particles contain a metal component, and the average particle diameter Φ3 of the functional particles is 0.8 times or less the average film thickness t of the functional layer 21, thereby increasing the hardness of the functional layer 21 from a perspective other than the properties of the resin. This increases the freedom in resin selection, making it possible to achieve both antibacterial and antiviral properties and hardness.

[0102] The average hydroxyl value of the resin constituting the functional layer 21 is preferably 250 mgKOH / g or less, and more preferably 150 mgKOH / g or less, so that the resin does not contain too many hydrophilic groups, thereby suppressing a decrease in the mechanical properties of the functional layer 21.

[0103] <Functional Particle and Resin Materials> As described above, from the viewpoint of increasing the hardness of the functional layer 21, the functional particles preferably have a structure in which a metal or metal ion is supported on a carrier. From the viewpoint of increasing the hardness of the functional layer 21, the carrier is preferably a phosphate-based, silica-alumina-based, or metal oxide-based carrier, and is particularly preferably a phosphate-based carrier. Examples of phosphate-based carriers include zirconium phosphate and phosphate glass.

[0104] In order to obtain good antibacterial and antiviral properties, hardness, and optical properties such as haze when used in combination with the functional particles, the resin constituting the functional layer 21 is preferably a polymer of one or more compounds selected from the group consisting of bifunctional, trifunctional, and tetrafunctional (meth)acrylate compounds. As described above, the average hydroxyl value of the resin constituting the functional layer 21 is preferably 100 mg KOH / g or more and 250 mg KOH / g or less, and more preferably 100 mg KOH / g or more and 150 mg KOH / g or less. The number of hydrophilic groups in the resin affects the antibacterial and antiviral properties, the crosslink density of the resin affects the hardness, and the difference in refractive index between the resin and the functional particles can affect the optical properties.

[0105] The ratio of the functional particles to the resin contained in the functional layer 21 is preferably 5% by mass or more, more preferably 10% by mass or more, from the viewpoint of enhancing antibacterial and antiviral activity. The ratio of the functional particles to the resin contained in the functional layer 21 is preferably 20% by mass or less, from the viewpoint of suppressing a decrease in adhesion of the functional layer 21 to the substrate 20 and minimizing the effect on the optical properties of the optical film 50A.

[0106] By using the above-mentioned functional particles and resin, it is easy to obtain a composite elastic modulus, stress relaxation rate, and plastic deformation amount within a suitable range. Meanwhile, the distribution of the functional particles within the functional layer 21 can also affect the composite elastic modulus, stress relaxation rate, and plastic deformation amount. To achieve a suitable range for the composite elastic modulus, stress relaxation rate, and plastic deformation amount, it is preferable that the distribution of the functional particles within the functional layer 21 is minimally biased. In other words, it is preferable that the functional particles are not unevenly distributed near the front or back surface of the functional layer 21. The distribution of the functional particles can be adjusted by the presence or absence and amount of a dispersant in the coating liquid used to form the functional layer 21, the viscosity of the coating liquid, the drying conditions for the coating film made from the coating liquid, and the like.

[0107] The functional layer 21 may contain an additive that contributes to improving hardness. Examples of such additives include silica particles and metal particles. The metal particles may function as an antistatic agent.

[0108] [Structure of Optical Film: Second Example] Optical film 50B, which is a second example of optical film 50, includes a substrate 20, a functional layer 21, and a low refractive index layer 22. In the second example of the second embodiment, the substrate 20 and the functional layer 21 have the same structure as in optical film 50A of the first example of the second embodiment, and the low refractive index layer 22 has the same structure as in the first embodiment.

[0109] By suppressing the formation of convex portions due to the functional particles on the surface of the functional layer 21, the formation of convex portions is also suppressed on the surface of the low refractive index layer 22. This increases the hardness of the optical film 50B. Furthermore, since the functional layer 21 is an extremely thin layer, increasing the hardness of the functional layer 21 also increases the hardness of the optical film 50B.

[0110] [Optical Film Characteristics] The optical characteristics and mechanical characteristics of the optical film 50 of the second embodiment will be described. The following characteristics are common to the optical films of the first and second examples.

[0111] When the functional layer 21 does not contain light-scattering particles, the haze of the optical film 50 is preferably 5% or less. With this configuration, high transparency can be obtained for the optical film 50, and visibility through the optical film 50 can be improved.

[0112] When the functional layer 21 contains light-scattering particles, the haze of the optical film 50 is preferably 5% or more and 35% or less. With this configuration, reflection of the surroundings on the optical film 50 is suppressed, while excessive deterioration of visibility through the optical film 50 is suppressed.

[0113] The glare resistance value of the optical film 50 is preferably 150 ppi or more. This reduces the occurrence of glare when the optical film 50 is used in a general display device. The glare resistance value is determined in the same manner as in the first embodiment.

[0114] The pencil hardness of the surface of the optical film 50 is preferably 3H or more. If the pencil hardness is 3H or more, the surface of the optical film 50 is less likely to be scratched. The scratch hardness of the surface of the optical film 50 is preferably 30g or more. If the scratch hardness is 30g or more, the surface of the optical film 50 is less likely to be scratched. The scratch hardness is measured in accordance with JIS K 7317.

[0115] The antibacterial activity value of the optical film 50 is preferably 2.0 or more. In particular, the antibacterial activity value for each of Staphylococcus aureus and Escherichia coli is preferably 2.0 or more. With this configuration, sufficient antibacterial properties can be obtained. The antibacterial activity value is determined in accordance with JIS Z 2801.

[0116] The antiviral activity value of the optical film 50 is preferably 2.0 or more. In particular, the antiviral activity value against at least one of influenza virus and feline calicivirus is preferably 2.0 or more. With such a configuration, sufficient antiviral properties can be obtained. The antiviral activity value is determined in accordance with ISO 21702. Note that the optical film 50 of the second embodiment can also be used in a display device, similar to the optical film 10 of the first embodiment.

[0117] EXAMPLES The above-mentioned optical film will be described using specific examples.

[0118] [First Example] The first example corresponds to the optical film 10 of the first embodiment. <Preparation of Optical Film for Test Example> A photopolymerizable compound, a photopolymerization initiator, a functional component serving as an antibacterial and antiviral agent, an additive, and a solvent were mixed to prepare a functional layer coating liquid for forming a functional layer. A 40 μm-thick triacetyl cellulose film (TJ40, manufactured by Fujifilm) was used as a substrate, and the functional layer coating liquid was applied to the surface of the substrate using a bar coater. The formed coating film was dried at 70°C for 1 minute using a dryer, and then irradiated with ultraviolet light in a nitrogen atmosphere (oxygen concentration of 500 ppm or less) to harden the coating film, thereby forming a functional layer. The ultraviolet light was applied using a high-pressure mercury UV device with an integrated exposure dose of 200 mJ / cm. ２In this way, an optical film of a test example including a substrate and a functional layer was obtained.

[0119] The optical films of Test Examples 1-1 to 1-41 were produced by changing the composition of the functional layer coating liquid and the film thickness of the functional layer. For some test examples, light-scattering particles were added to the functional layer coating liquid. The materials used in the functional layer coating liquid are as follows. The photopolymerizable compound, which is the material for the ultraviolet-curing resin, was selected from A1 to A4 below, and the functional component was selected from B1 to B5 below. Of the functional components, B1 to B4 are particulate, inorganic functional particles. Of the functional components, B5 is a non-particulate organic antibacterial and antiviral agent.

[0120] Resin materials (photopolymerizable compounds) A1: Acrylate monomer (mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate) (Viscoat #300, manufactured by Osaka Organic Chemical Industry) A2: Acrylate monomer (dipentaerythritol polyacrylate) (NK Ester A-DPHA, manufactured by Shin-Nakamura Chemical Co., Ltd.) A3: Acrylate monomer (di(meth)acrylate having a fluorene skeleton) (GA-5060P, manufactured by Osaka Gas Chemicals) A4: Acrylate monomer (polyethylene glycol diacrylate) (NK Ester A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.) Photopolymerization initiator: alkylphenone-based initiator (Omnirad 184, manufactured by IGM Resins B.V.)

[0121] Functional components B1: Silver-based antibacterial and antiviral agent (silver-supported glass) (PMG721C, manufactured by Koa Glass, average particle size Φ1:3 μm) B2: Silver-based antibacterial and antiviral agent (silver-supported glass) (PTC-NT ANV additive (ST), manufactured by Dainichiseika Color & Chemicals, average particle size Φ1:3 μm) B3: Silver-based antibacterial and antiviral agent (silver-supported glass) (PG721F, manufactured by Koa Glass, average particle size Φ1:1 μm) B4: Silver-based antibacterial and antiviral agent (silver-supported zirconium phosphate) (Novalon AG1100, manufactured by Toagosei, average particle size Φ1:1 μm) B5: Quaternary ammonium salt-based antibacterial and antiviral agent (KBM-9418-40, manufactured by Shin-Etsu Chemical Co., Ltd.) Additive: Leveling agent (GRANDIC PC4300, manufactured by DIC) Light scattering particles: organic fine particles (SSX-2035, manufactured by Techpolymer) Solvent: propylene glycol monomethyl ether

[0122] <Evaluation Method> [Appearance] The optical film of each test example was visually observed for its appearance through a transmission observation in which the optical film was observed through a three-wavelength fluorescent lamp, and through a reflection observation in which the optical film was attached to a blackboard on its back side with an optical pressure-sensitive adhesive and observed under a fluorescent lamp. In each observation, the presence or absence of abnormalities in appearance, such as the presence or absence of bright spots where functional particles are visible as dots, uneven brightness and a localized foreign body sensation due to surface irregularities, whitish turbidity, and bleed-out where powdered material appears on the surface, were confirmed. In the appearance evaluation, a case where no abnormalities in appearance were observed was rated as good (S), a case where bright spots were observed was rated as poor (F1), a case where uneven brightness or a foreign body sensation was observed was rated as poor (F2), a case where whitish turbidity was observed was rated as poor (F3), and a case where bleed-out was observed was rated as poor (F4).

[0123] [Haze] The haze of each optical film of each test example was measured using a haze meter (NDH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136.

[0124] [Antibacterial Property] Antibacterial tests were conducted on the optical films of each test example against Staphylococcus aureus and Escherichia coli in accordance with JIS Z 2801. Polyethylene film was used as the unprocessed sample. In the evaluation of antibacterial property, an antibacterial activity value of 2.0 or more against both Staphylococcus aureus and Escherichia coli was rated as good "S", and an antibacterial activity value of less than 2.0 against at least one of Staphylococcus aureus and Escherichia coli was rated as poor "F".

[0125] [Antiviral Property] The optical film of each test example was subjected to an antiviral test against influenza A virus and feline calicivirus in accordance with ISO 21702. Polyethylene film was used as the unprocessed sample. In the evaluation of antiviral property, an antiviral activity value of 2.0 or more against at least one of influenza A virus and feline calicivirus was rated as good (S), and an antiviral activity value of less than 2.0 against both influenza A virus and feline calicivirus was rated as poor (F).

[0126] [Pencil Hardness] For the optical film of each test example, a hardness test was carried out in accordance with JIS K 5600-5-4 using a pencil (uni, manufactured by Mitsubishi Pencil Co., Ltd.) and a Clemens scratch hardness tester (HA-301, manufactured by Tester Sangyo Co., Ltd.) under conditions of a load of 750 g and a scratching speed of 0.5 mm / sec, thereby measuring the pencil hardness of the optical film surface. In the measurement, the test was repeated while changing the pencil hardness, and the surface of the optical film was visually observed, and the maximum hardness at which no scratches were observed was taken as the measurement result.

[0127] [Anti-glare Properties] The anti-glare properties of the optical film of each test example were evaluated by measuring the reflection clarity. The reflection clarity is a value obtained by subtracting the reflection haze (%) from 100. The reflection haze is a parameter indicating the degree of diffusion of reflected light, and is determined by irradiating the surface of the optical film on a blackboard through a slit from a light source position set at an incident angle of approximately 5.7° relative to the normal direction of the optical film surface, and measuring the intensity distribution of the reflected light near the specular reflection direction at the light receiving position in the specular reflection direction. The reflection haze at an arbitrary angle θ centered on the specular reflection direction is the percentage of the average value of the reflection intensity at angle +θ and the reflection intensity at angle −θ relative to the reflection intensity in the specular reflection direction, and the reflection clarity at angle θ is the value obtained by subtracting the reflection haze at the angle θ from 100.

[0128] In evaluating anti-glare properties, the reflection clarity at 1° and 5° was measured. Each reflection clarity was measured under the following conditions using a display measurement system (SMS-1000, manufactured by DM&S) for an optical film whose backside was attached to a blackboard with an optical adhesive. Note that the measurements were carried out in accordance with ASTM D5767 except for the following conditions: - Light source slit width: 1 mm - Objective lens: 16 mm - Distance between the surface of the optical film and the light-receiving camera: 300 mm

[0129] In the evaluation of antiglare properties, a film was rated as good (S) when the 1° reflection clarity was 90 or less and the 5° reflection clarity was 70 or more, and rated as poor (F) when at least one of the 1° reflection clarity was greater than 90 and the 5° reflection clarity was less than 70. Poor results include cases where the surrounding image was clearly reflected on the optical film and cases where the image reflected on the optical film was too blurred.

[0130] [Glare Resistance] For the optical film of each test example, the optical film was placed on six types of metal masks having grid patterns corresponding to pixel densities of 85 ppi, 106 ppi, 127 ppi, 169 ppi, 254 ppi, and 508 ppi, and the glare contrast was measured. The glare contrast was determined by single image measurement using a glare meter (SMS-1000, manufactured by DM&S) in accordance with JIS C 1006:2019.

[0131] With the y-axis representing the glare contrast and the x-axis representing the pixel density, points corresponding to the pixel density indicated by the metal mask grid and the obtained glare contrast were plotted, and a linear approximation (y = ax) was found for the correlation between them to calculate the slope. From this linear approximation, the value of x at which y = 3.0 was found and used as the glare resistance value. In the evaluation of glare resistance, a glare resistance value of 150 ppi or more was rated as good (S), and a glare resistance value of less than 150 ppi was rated as poor (F).

[0132] <Evaluation Results> Tables 1 to 4 show, for Test Examples 1-1 to 1-41, the types and amounts of resin materials and functional components used to form the functional layer, the amount of light-scattering particles, the average film thickness t1 (μm), the ratio of the average particle size Φ1 of the functional particles to the average film thickness t1, the ratio of functional components to resin, the slope a in equation (2) of the second condition, and the evaluation results obtained by each of the above evaluation methods.

[0133] The amount of each material in the functional layer coating liquid is expressed as a relative mass, with the resin material being 100 parts by mass. In all test examples, the amount of photopolymerization initiator was 5 parts by mass, the amount of additive was 0.05 parts by mass, and the amount of solvent was 110 parts by mass.

[0134] Furthermore, since anti-glare properties are a property imparted to optical films containing light-scattering particles, and anti-glare properties are a property required for optical films containing light-scattering particles, these properties were evaluated only for test examples containing light-scattering particles.

[0135]

[0136]

[0137]

[0138]

[0139] As shown in Table 1, Test Examples 1-1 to 1-10, which satisfied both the first and second conditions, exhibited good antibacterial and antiviral properties, good appearance, and suppressed excessive increases in haze. Furthermore, the mechanical properties, such as pencil hardness, were also good. Furthermore, Test Examples 1-7 and 1-8, which contained light-scattering particles, also exhibited good antiglare and anti-glare properties.

[0140] In contrast, as shown in Table 2, in Test Examples 1-12 and 1-13, in which the ratio of the average particle size Φ1 of the functional particles to the average film thickness t1 was greater than 0.8 and the first condition was not satisfied, a foreign body sensation was observed in the appearance. In Test Example 1-13, in which the amount of functional particles was increased to a level at which sufficient antiviral properties were obtained, the haze was also greater than in Test Examples 1-1 to 1-6, 1-9, and 1-10.

[0141] Furthermore, in Test Examples 1-14 to 1-16, in which the slope a exceeded 50 and the second condition was not satisfied, increasing the functional particles to a level at which sufficient antiviral properties were obtained significantly increased the haze by more than 5%. Furthermore, in Test Examples 1-17 to 1-19, in which the slope a was even greater, not only did the increase in haze with increasing functional particles be significant, as in Test Examples 1-14 to 1-16, but bright spots were also observed even when the amount of functional particles was small. Furthermore, in Test Example 1-20, in which the average film thickness t1 was increased compared to Test Examples 1-17 to 1-19, the haze and appearance did not improve significantly, and the first condition was no longer satisfied, resulting in a decrease in antiviral properties.

[0142] As shown in Table 3, Test Examples 1-21 to 1-23, which had even larger slopes a, also had poor haze and appearance. Furthermore, Test Example 1-24, which used a non-particulate antibacterial and antiviral agent as the functional ingredient, had good antibacterial and antiviral properties, haze, and pencil hardness, but bleed-out was observed.

[0143] Test Examples 1-25 to 1-31 correspond to the configurations of Test Examples 1-11, 1-12, 1-13, 1-15, 1-18, 1-20, and 1-22, to which light-scattering particles were added. In these test examples, too, when the amount of functional particles was increased to a level at which sufficient antiviral properties were obtained, the haze rose to more than 30%, and the anti-glare properties and anti-glare properties were also poor. Test Example 1-28, which had a haze of more than 40%, also exhibited cloudy appearance.

[0144] As shown in Table 4, in Test Examples 1-32 to 1-34, where the slope a was even larger and exceeded 200, the haze and appearance were poor even though the amount of functional particles was so small that the antiviral property was insufficient. Even in Test Examples 1-36 to 1-38 and Test Examples 1-39 to 1-41, when the slope a exceeded 50, it was suggested that at least one of the haze and the appearance would be poor if the amount of functional particles was increased to an extent that sufficient antiviral property was obtained.

[0145] Furthermore, referring to Test Examples 1-11, 1-35, etc., it is suggested that when the ratio of the functional particles to the resin contained in the functional layer is 3% by mass, antibacterial properties are obtained but antiviral properties are insufficient, and when the ratio of the functional particles is 5% by mass, good antiviral properties are obtained.

[0146] Regarding the third condition, for each of Test Examples 1-2 and 1-19, a scanning electron microscope (SEM) was used to observe the cross section of the optical film, and 50 functional particles contained in the cross section were extracted. The distance p, film thickness t2, and particle size Φ2 were measured for each functional particle. The proportion of functional particles satisfying the formula (3) of the third condition for the 50 populations was then calculated. As a result, for Test Example 1-2, the proportion of functional particles satisfying the formula (3) was 89%, and for Test Example 1-19, the proportion of functional particles satisfying the formula (3) was 67%. That is, Test Example 1-2 satisfied the third condition, and Test Example 1-19 did not. Therefore, it is suggested that satisfying the third condition suppresses deterioration of haze and appearance.

[0147] As described above, the first embodiment and the first example can achieve the following effects. (1-1) Since the first condition is satisfied, the functional particles are not too small relative to the average film thickness t1, thereby preventing the generation of functional particles that do not contribute to the development of antibacterial and antiviral properties. Therefore, the increase in the content of functional particles necessary for the development of antibacterial and antiviral properties is suppressed, thereby preventing an increase in haze and deterioration in the appearance of the optical film, and also preventing a decrease in the mechanical properties of the optical film. Furthermore, since the functional particles are not too large relative to the average film thickness t1, light scattering within the functional layer due to the inclusion of the functional particles is suppressed, and the formation of convex portions on the surface of the optical film due to the functional particles is suppressed. As a result, an increase in haze and deterioration in the appearance of the optical film are suppressed.

[0148] (1-2) By satisfying the second condition, an increase in haze can be suppressed even when the proportion of functional particles is increased to a level that provides antiviral properties in addition to antibacterial properties. In addition, by satisfying the first condition, an increase in haze can be suppressed even when functional particles having an average particle size Φ1 of 1 μm or more are used.

[0149] (1-3) By satisfying the third condition, the formation of irregularities on the surface of the optical film due to the presence of the functional particles can be more effectively suppressed, thereby more effectively suppressing an increase in haze and deterioration in the appearance of the optical film.

[0150] (1-4) If the mass ratio of the functional particles to the resin contained in the functional layer is 0.20 or less, the effect of the inclusion of the functional particles on the properties of the optical film can be reduced. (1-5) If the haze of the optical film is 5% or less, high transparency can be obtained. Furthermore, by satisfying at least one of the first condition and the second and third conditions, it is easy to keep the haze at 5% or less.

[0151] (1-6) If the optical film contains fine particles for scattering light, it can be made to have antiglare properties. Furthermore, if the haze of the optical film is 5% or more and 35% or less, good antiglare properties can be obtained. By satisfying at least one of the first condition, the second condition, and the third condition, it is easy to achieve a haze of 35% or less.

[0152] (1-7) When the optical film has a pixel density of 150 ppi or more when the glare contrast is 3.0, good anti-glare properties can be obtained. (1-8) When the optical film has a surface pencil hardness of 3H or more, good mechanical properties can be obtained.

[0153] (1-9) When the difference between the haze of the optical film and the haze of a resin film having the same configuration as the optical film except that it does not contain functional particles is 5% or less, the deterioration of haze due to the addition of functional particles is suitably suppressed. Furthermore, when the difference between the haze of the optical film and the haze of the resin film is 3% or less, the deterioration of haze due to the addition of functional particles is even more suitably suppressed.

[0154] (1-10) When the difference in refractive index between the resin of the functional layer and the functional particles is 0.03 or less, the deterioration of haze due to the addition of the functional particles is suitably suppressed. (1-11) By providing a display device with the optical film, good optical and mechanical properties as well as antibacterial and antiviral properties can be obtained near the surface of the display device. In particular, in a display device equipped with a touch panel, the antibacterial and antiviral properties of the optical film are highly beneficial.

[0155] [Second Example] The second example corresponds to the optical film 50 of the second embodiment. <Preparation of Optical Film for Test Example> A photopolymerizable compound, a photopolymerization initiator, a functional component serving as an antibacterial and antiviral agent, an additive, and a solvent were mixed to prepare a functional layer coating liquid for forming a functional layer. A 40 μm-thick triacetyl cellulose film (TJ40, manufactured by Fujifilm) was used as a substrate, and the functional layer coating liquid was applied to the surface of the substrate using a bar coater. The formed coating film was dried at 70°C for 1 minute using a dryer, and then irradiated with ultraviolet light in a nitrogen atmosphere (oxygen concentration of 500 ppm or less) to harden the coating film, thereby forming a functional layer. The ultraviolet light was applied using a high-pressure mercury UV device with an integrated exposure dose of 200 mJ / cm. ２ In this way, an optical film of a test example including a substrate and a functional layer was obtained.

[0156] Optical films of Test Examples 2-1 to 2-15 were produced by changing the composition of the functional layer coating liquid and the film thickness of the functional layer. In some test examples, light-scattering particles were added to the functional layer coating liquid, and in some test examples, no functional component was added to the functional layer coating liquid. The materials used in the functional layer coating liquid are as follows. The photopolymerizable compound, which is a material for the ultraviolet-curable resin, was selected from A1 to A3 below, and the functional component was selected from B1 to B3 below. Of the functional components, B1 and B2 are functional particles containing a metal component. Of the functional components, B3 is a non-particulate organic antibacterial and antiviral agent.

[0157] Resin materials (photopolymerizable compounds) A1: Acrylate monomer (mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate) (Viscoat #300, manufactured by Osaka Organic Chemical Industry) A2: Acrylate monomer (dipentaerythritol acrylate) (NK Ester A-DPH, manufactured by Shin-Nakamura Chemical Co., Ltd.) A3: Acrylate monomer (mixture of glycerin diacrylate and glycerin triacrylate) (M-920, manufactured by Toagosei) Photopolymerization initiator: alkylphenone-based initiator (Omnirad 184, manufactured by IGM Resins B.V.)

[0158] Functional ingredients B1: Silver-based antibacterial and antiviral agent (silver-supported zirconium phosphate) (Novalon AG1100, manufactured by Toagosei, average particle size Φ3: 1 μm) B2: Silver-based antibacterial and antiviral agent (silver-supported phosphate glass) (PMG721C, manufactured by Koa Glass, average particle size Φ3: 3 μm) B3: Quaternary ammonium salt-based antibacterial and antiviral agent (KBM-9418-40, manufactured by Shin-Etsu Chemical Co., Ltd.) Additive: Leveling agent (GRANDIC PC4300, manufactured by DIC) Light scattering particles: Organic fine particles (SSX-2035, manufactured by Techpolymer) Solvent: Propylene glycol monomethyl ether

[0159] <Evaluation Method> [Nanoindentation Test: Sample Preparation] For each test example, the back surface of the optical film was subjected to corona treatment at 0.20 kW using a corona treatment machine (CT-0212, manufactured by Kasuga Electric Co., Ltd.). The back surface of the optical film was then attached to a sample stage (AFM / STM sample disk, manufactured by EM Japan, diameter: 12 mm) with an instant adhesive (Aron Alpha, manufactured by Toa Gosei Co., Ltd.) to prepare a sample with the surface of the functional layer exposed, which was the measurement surface.

[0160] [Nanoindentation Test: Composite Elastic Modulus and Stress Relaxation] Using a nanoindenter (Hysitron TI-Premier, manufactured by Bruker Japan) in displacement control mode, the measurement surface of the sample was indented at a speed of 100 nm / sec to a depth of 500 nm, and then held at the maximum depth for 5 seconds. Thereafter, the load was released at a speed of 100 nm / sec to obtain a load-displacement curve. A Berkovich-type diamond indenter (manufactured by Bruker Japan) was used as the indenter. Figure 6 shows an example of the obtained load-displacement curve.

[0161] The measurement points were set at 30 points spaced at least 20 μm apart by using the shape measurement function of a nanoindenter, which scans the sample surface with an indenter, to obtain a shape image of the measurement surface, and specifying points on the functional layer based on the shape image.

[0162] The composite elastic modulus Er was calculated by using the Oliver-Pharr method, correcting the relationship between the contact depth and the contact projected area between the indenter and the sample based on the test results for fused quartz, a standard sample, and then analyzing the unloading curve in the range of 60% to 95% of the maximum load at the time of unloading. Then, for each test example, the average value of the composite elastic modulus Er calculated at 30 measurement points was taken as the composite elastic modulus for that test example.

[0163] The specific procedure for calculating the composite elastic modulus Er is as follows: First, the contact depth hc is calculated using the following formula (4).

[0164]

[0165] In the above formula (4), ε is a constant related to the indenter shape, and for a Berkovich indenter, the constant ε is 0.75. Pmax is the maximum load of the unloading curve, and hmax is the maximum displacement. S is the contact stiffness. The contact stiffness S is the slope immediately after pulling out of the approximate curve obtained by fitting the range of 60% to 95% of the maximum load of the unloading curve with the function of the following formula (5). A, hf, and m in the following formula (5) represent fitting parameters used in the fitting.

[0166]

[0167] Next, the contact projected area Ac is calculated based on the shape of the indenter and the contact depth hc. The contact projected area Ac can be expressed as a function of the contact depth hc, as shown in the following formula (6). Formula (6) corrects for the influence of the roundness of the indenter tip using correction terms C1 to C5. The correction terms C1 to C5 are set so that the composite elastic modulus calculated at each maximum load from test results using fused silica samples at maximum loads in the range of 20 μN to 10 mN matches the composite elastic modulus Er of fused silica, which is 69.6 GPa.

[0168]

[0169] Next, the composite elastic modulus Er is calculated using the contact projected area Ac and the contact stiffness S according to the following formula (7).

[0170]

[0171] The stress relaxation degree Rs was calculated by the following formula (8) using the maximum load Fmax of the load curve and the maximum load Pmax of the unload curve obtained from the load-displacement curve: Rs=(Fmax-Pmax) / Fmax (8) Then, for each test example, the average value of the stress relaxation degree Rs calculated at 30 measurement points was taken as the stress relaxation degree of that test example.

[0172] [Nanoindentation test: plastic deformation amount] Using a nanoindenter (Hysitron TI-Premier, manufactured by Bruker Japan) in displacement control mode, the measurement surface of the sample was indented at a speed of 100 nm / sec to a depth of 1000 nm, and then held at the maximum depth for 10 seconds. Thereafter, the load was released at a speed of 100 nm / sec to obtain a load-displacement curve. A Berkovich-type diamond indenter (manufactured by Bruker Japan) was used as the indenter.

[0173] The measurement points were set at 30 points spaced at least 20 μm apart by using the shape measurement function of a nanoindenter, which scans the sample surface with an indenter, to obtain a shape image of the measurement surface, and specifying points on the functional layer based on the shape image.

[0174] The amount of plastic deformation h1 was determined from the unloading curve of the load-displacement curve. The amount of plastic deformation h1 is the displacement value when the load on the unloading curve changes from positive to negative, i.e., the displacement value at the intersection of the unloading curve and the horizontal axis showing the displacement. For each test example, the average value of the amount of plastic deformation h1 calculated at 30 measurement locations was used as the amount of plastic deformation for that test example.

[0175] [Pencil Hardness] For the optical film of each test example, a hardness test was conducted using a pencil (uni, manufactured by Mitsubishi Pencil Co., Ltd.) and a Clemens scratch hardness tester (HA-301, manufactured by Tester Sangyo Co., Ltd.) under conditions of a load of 500 g and a scratching speed of 0.5 mm / sec, thereby measuring the pencil hardness of the surface of the optical film. In the measurement, the test was repeated while changing the pencil hardness, and the surface of the optical film was visually observed, and the maximum hardness at which no scratches were observed was taken as the measurement result. Note that the measurement was conducted under conditions other than those mentioned above in accordance with JIS K 5600-5-4.

[0176] [Scratch Hardness] The scratch hardness of the surface of the optical film of each test example was measured in accordance with JIS K 7317.

[0177] [Antibacterial and Antiviral Properties] Antibacterial tests against Staphylococcus aureus and Escherichia coli were carried out for the optical films of each test example in accordance with JIS Z 2801. Polyethylene film was used as the unprocessed sample. In the evaluation of antibacterial properties, an antibacterial activity value of 2.0 or more against both Staphylococcus aureus and Escherichia coli was rated as good, and an antibacterial activity value of less than 2.0 against at least one of Staphylococcus aureus and Escherichia coli was rated as poor.

[0178] For the optical film of each test example, antiviral tests against influenza A virus and feline calicivirus were conducted in accordance with ISO 21702. Polyethylene film was used as the unprocessed sample. In the evaluation of antiviral properties, an antiviral activity value of 2.0 or more against at least one of influenza A virus and feline calicivirus was rated as good, and an antiviral activity value of less than 2.0 against both influenza A virus and feline calicivirus was rated as poor.

[0179] In the evaluation of antibacterial and antiviral properties, a good antiviral evaluation was rated as "S", a poor antiviral evaluation and a good antibacterial evaluation were rated as "G", and a poor antibacterial and antiviral evaluation were rated as "F". Generally, when antiviral properties are good, antibacterial properties are also good. In Test Examples 2-1 to 2-15, Test Examples that were good in antiviral evaluation also had good antibacterial evaluations.

[0180] [Haze] The haze of the optical film of each test example was measured. The haze measurement was performed using a haze meter (NDH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136. In the evaluation, for test examples in which the functional layer did not contain light-scattering microparticles, a haze of 5% or less was rated as good (S), a haze of more than 5% and less than 20% was rated as fair (G), and a haze of more than 20% was rated as poor (F). For test examples in which the functional layer contained light-scattering microparticles, a haze of 35% or less was rated as good (S), a haze of more than 35% and less than 40% was rated as fair (G), and a haze of more than 40% was rated as poor (F).

[0181] [Anti-glare Property] The anti-glare property of the optical film of each test example was evaluated by measuring the reflection clarity in the same manner as in Example 1. In the evaluation of anti-glare property, when the reflection clarity at 1° was 90 or less and the reflection clarity at 5° was 70 or more, it was rated as good "S", and when at least one of the reflection clarity at 1° was greater than 90 and the reflection clarity at 5° was less than 70, it was rated as poor "F".

[0182] <Evaluation Results> Tables 5 and 6 show, for each test example, the type of resin material used to form the functional layer and the average hydroxyl value (mgKOH / g), the type of functional component used to form the functional layer and the ratio of the functional component to the resin, whether or not light-scattering particles were added, the average film thickness t3 (μm) of the functional layer, the ratio of the average particle diameter Φ3 of the functional particles to the average film thickness t3, and the evaluation results using each of the above evaluation methods.

[0183] In each of the test examples, the blending amounts of each material in the functional layer coating liquid were 5 parts by mass of the photopolymerization initiator, 0.05 parts by mass of the additive, and 110 parts by mass of the solvent, based on 100 parts by mass of the resin material. In test examples 2-3 and 2-4, the blending amount of the light scattering particles was 8 parts by mass, based on 100 parts by mass of the resin material.

[0184] Furthermore, since antiglare properties are a property imparted to optical films containing light-scattering particles, evaluation was carried out only on test examples containing light-scattering particles.

[0185]

[0186]

[0187] As shown in Tables 5 and 6, high hardness was obtained in Test Examples 2-1 to 2-7, 2-10, 2-11, 2-13, and 2-14, in which the functional component contained a metal component and particles had an average particle size Φ3 of 0.8 times or less the average film thickness t3 of the functional layer. Comparing Test Examples 2-1 to 2-7 with Test Examples 2-8 and 2-15, it can be confirmed that the inclusion of functional particles can improve hardness compared to cases in which functional particles are not contained. Furthermore, comparing Test Examples 2-1 to 2-6 with Test Example 2-9, it can also be confirmed that the inclusion of functional particles can improve hardness compared to cases in which the functional component is not particulate.

[0188] Furthermore, Test Examples 2-12 to 2-14 show that although it is possible to improve hardness by using a resin with a low average hydroxyl value, the amount of functional particles required to obtain antibacterial and antiviral properties increases, resulting in a deterioration of optical properties. All of the Test Examples confirm that antibacterial and antiviral properties can be adequately obtained when the average hydroxyl value of the resin is 100 mgKOH / g or more, and that hardness can be further increased when the average hydroxyl value of the resin is 150 mgKOH / g or less.

[0189] Test Examples 2-1 to 2-7, 2-10, and 2-11, which have good hardness and antibacterial and antiviral properties, have a composite elastic modulus of 5.5 GPa or more, a stress relaxation rate of 0.13 or less, and a plastic deformation amount of 60 nm or more.

[0190] As described above, the second embodiment and second example can achieve the following effects. (2-1) The functional particles contain a metal or metal ions, and the average particle size Φ3 of the functional particles is 0.8 times or less the average film thickness t3 of the functional layer. This allows the functional particles to have high hardness and prevents the formation of convex portions on the surface of the optical film at the positions of the functional particles, thereby improving the hardness of the optical film. Furthermore, because the hardness of the functional layer is increased from a perspective other than the properties of the resin, the freedom in resin selection is increased and the burden of managing composition and production is reduced in order to achieve both antibacterial and antiviral properties and hardness.

[0191] (2-2) A composite elastic modulus of 5.5 GPa or more provides suitable hardness. A stress relaxation rate of 0.13 or less provides suitable hardness. A plastic deformation amount of 60 nm or more provides suitable hardness.

[0192] (2-3) When the resin contained in the functional layer has an average hydroxyl value of 100 mgKOH / g or more, good antibacterial and antiviral properties are easily obtained. (2-4) When the functional particles contain a phosphate-based carrier, the hardness of the optical film is easily increased.

[0193] (2-5) If the pencil hardness of the surface of the optical film is 3H or more, sufficient hardness can be obtained. If the scratch hardness of the surface of the optical film is 30g or more, sufficient hardness can be obtained. (2-6) If the mass ratio of the functional particles to the resin contained in the functional layer is 20% or less, deterioration of the optical properties of the optical film can be suppressed.

[0194] (2-7) If at least one of the antibacterial activity value and the antiviral activity value of the optical film is 2.0 or more, sufficient antibacterial and antiviral properties can be obtained. (2-8) If the haze of the optical film is 5% or less, high transparency can be obtained.

[0195] (2-9) If the optical film contains fine particles for scattering light, the optical film can have antiglare properties. If the haze of the optical film is 5% or more and 35% or less, good antiglare properties can be obtained.

[0196] (2-10) When the optical film has a pixel density of 150 ppi or more when the glare contrast is 3.0, good anti-glare properties can be obtained. (2-11) By including the optical film in a display device, antibacterial and antiviral properties and hardness can be obtained near the surface of the display device. In particular, in a display device equipped with a touch panel, the antibacterial and antiviral properties of the optical film are highly beneficial.

Claims

1. An optical film comprising a substrate and a functional layer containing functional particles that are at least one of an antibacterial agent and an antiviral agent and a resin, wherein the surface of the functional layer that contacts the substrate is the back surface of the functional layer, the outermost surface of the optical film located on the opposite side of the back surface to the substrate is the front surface of the optical film, and the average particle size of the functional particles is 0.8 times or less the average film thickness between the front surface of the optical film and the back surface of the functional layer.

2. The optical film according to claim 1, wherein the average particle size Φ1 of the functional particles is 1.0 μm or more, and the average film thickness t1 between the surface of the optical film and the back surface of the functional layer and the average particle size Φ1 of the functional particles satisfy the following formula (1): 0.2×t1≦Φ1≦0.8×t1 ... (1). When the relationship between the mass ratio x of the functional particles to the resin contained in the functional layer and the haze y of the optical film is expressed by the following formula (2) to a first approximation, a≦50: y=ax+b ... (2).

3. The optical film according to claim 1, wherein the average particle size Φ1 of the functional particles is 1.0 μm or more, and the average film thickness t1 between the surface of the optical film and the back surface of the functional layer and the average particle size Φ1 of the functional particles satisfy the following formula (1): 0.2×t1≦Φ1≦0.8×t1 ... (1). For 75% or more of the functional particles extracted from the cross section of the optical film, the distance p between the surface of the optical film and the functional particle in the thickness direction at the location where the functional particle is located, the film thickness t2 between the surface of the optical film and the back surface of the functional layer, and the particle size Φ2 of the functional particle satisfy the following formula (3): 0.3≦p / (t2-Φ2) ... (3).

4. The optical film according to claim 2, wherein for 75% or more of the functional particles extracted from the cross section of the optical film, the distance p between the surface of the optical film and the functional particle in the thickness direction at the location of the functional particle, the film thickness t2 between the surface of the optical film and the back surface of the functional layer, and the particle diameter Φ2 of the functional particle satisfy the following formula (3): 0.3≦p / (t2-Φ2) ... (3).

5. An optical film according to claim 2 or 3, wherein the difference in haze between the optical film and a resin film having the same configuration as the optical film except that it does not contain the functional particles is 5% or less.

6. The optical film according to claim 5, wherein the difference between the haze of the optical film and the haze of the resin film is 3% or less.

7. The optical film according to claim 2 or 3, wherein the difference in refractive index between the resin of the functional layer and the functional particles is 0.03 or less.

8. The optical film according to claim 1, wherein the functional particles contain a metal or metal ions, and the average particle size of the functional particles is 0.8 times or less the average film thickness of the functional layer.

9. The optical film according to claim 8, wherein the functional layer has a composite elastic modulus of 5.5 GPa or more as measured by nanoindentation.

10. The optical film according to claim 8, wherein the stress relaxation degree of the functional layer measured by nanoindentation is 0.13 or less.

11. The optical film according to claim 8, wherein the amount of plastic deformation of the functional layer measured by nanoindentation is 60 nm or more.

12. The optical film according to claim 8, wherein the resin contained in the functional layer has an average hydroxyl value of 100 mgKOH / g or more.

13. The optical film according to claim 8, wherein the functional particles include a phosphate-based carrier.

14. The optical film according to claim 8, wherein the scratch hardness of the surface of the optical film is 30 g or more.

15. The optical film according to any one of claims 2, 3 and 8, wherein the mass ratio of the functional particles to the resin contained in the functional layer is 0.20 or less.

16. The optical film according to any one of claims 2, 3 and 8, wherein the haze of the optical film is 5% or less.

17. The optical film according to any one of claims 2, 3 and 8, wherein the functional layer contains fine particles for scattering light.

18. The optical film according to any one of claims 2, 3 and 8, wherein the haze of the optical film is 5% or more and 35% or less.

19. The optical film according to any one of claims 2, 3 and 8, wherein the pencil hardness of the surface of the optical film is 3H or more.

20. An optical film described in any one of claims 2, 3, and 8, wherein, in a linear approximation of the correlation between the glare contrast and pixel density obtained by measuring the glare contrast of the optical film arranged on a grid pattern corresponding to the pixel arrangement, the pixel density is 150 ppi or more when the glare contrast is 3.

0.

21. A display device comprising the optical film according to any one of claims 2, 3 and 8, wherein the optical film is positioned on a display surface on which an image is displayed.

Images