Optical film and display device

Abstract

To provide an optical film which has antibacterial and antiviral properties and can suppress deterioration in characteristics including haze and appearance due to inclusion of functional particles, and to provide a display device.SOLUTION: The optical film 10 includes a base material 20 and a functional layer 21 containing a resin and functional particles which are at least one of an antibacterial agent and an antiviral agent. The average particle size Φ 1 of the functional particles is 1.0 μm or more, and the average thickness 11S between the front surface 21S of the optical film 10 and the back surface t1 of the functional layer 21 and the average particle size Φ 1 of the functional particles satisfy the following (formula 1): 0.2 * t1 ≤ Φ 1 ≤ 0.8 * t1 (formula 1). When a relationship between a mass ratio x of the functional particles to the resin contained in the functional layer 21 and a haze y of the optical film 10 is expressed by the following (Formula 2) by linear approximation, a ≤ 50 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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 to make the screen of the display device easier to view.

[0003] In addition to optical properties such as haze, optical films are required to have various properties such as hardness and scratch resistance depending on the application. Furthermore, due to recent increased awareness of hygiene, there is also 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.

[0004] Antibacterial and antiviral properties can be imparted to an optical film by adding an antibacterial and antiviral agent to a resin layer of the optical film. Inorganic functional particles containing silver or a silver compound are widely used as the antibacterial and antiviral agent (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6720639 Summary of the Invention [Problem to be solved by the invention]

[0006] 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 that constitutes 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.

[0007] 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.

[0008] 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.

[0009] Among the compounds that can be used as antibacterial and antiviral agents, there are some 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 can have a significant effect on the coating liquid and coating film, which can lead to problems such as bleed-out, reduced coating liquid stability, and changes in the mechanical properties and antireflection properties of the resin layer that forms the coating film. [Means for solving the problem]

[0010] Various aspects of the optical film and display device for solving the above problems will be described below. [Aspect 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, and 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, the average particle size Φ1 of the functional particles is 1.0 μm or more, the average film thickness t1 between the front 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 (Equation 1): 0.2 × t1 ≦ Φ1 ≦ 0.8 × t1 (Equation 1), and 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 to a first approximation by the following (Equation 2), a ≦ 50, y = ax + b (Equation 2).

[0011] According to the above configuration, since the functional particles are not too small relative to the average film thickness t1, the occurrence of functional particles that do not contribute to the expression of antibacterial and antiviral properties is suppressed. Furthermore, since the functional particles are not too large relative to the average film thickness t1, light scattering within the functional layer is suppressed, and the formation of convex portions on the surface of the optical film due to the functional particles is suppressed. Therefore, an increase in haze and deterioration of the appearance of the optical film are suppressed, and a decrease in the mechanical properties of the optical film is also suppressed.

[0012] Furthermore, by setting the slope a to 50 or less, an increase in haze can be suppressed even when functional particles having an average particle size Φ1 of 1 μm or more are used and the proportion of functional particles is increased to a level where antiviral properties are obtained in addition to antibacterial properties.

[0013] [Aspect 2] 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, and 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, the functional particles have an average particle size Φ1 of 1.0 μm or more, and the average film thickness t1 between the front 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 (formula 1), and for at least 75% of the functional particles extracted from a cross section of the optical film, the distance p between the front surface of the optical film and the functional particle at the location where the functional particle is located, the film thickness t2 between the front surface of the optical film and the back surface of the functional layer, and the particle size Φ2 of the functional particles satisfy the following formula (3): 0.3 ≦ p / (t2 - Φ2) (formula 3), optical film.

[0014] According to the above configuration, since the functional particles are not too small relative to the average film thickness t1, the occurrence of functional particles that do not contribute to the expression of antibacterial and antiviral properties is suppressed. Furthermore, since the functional particles are not too large relative to the average film thickness t1, light scattering within the functional layer is suppressed, and the formation of convex portions on the surface of the optical film due to the functional particles is suppressed. Therefore, an increase in haze and deterioration of the appearance of the optical film are suppressed, and a decrease in the mechanical properties of the optical film is also suppressed.

[0015] Furthermore, by satisfying formula 3 for 75% or more of the functional particles, the formation of irregularities on the surface of the optical film due to the presence of the functional particles can be more effectively prevented, thereby more effectively preventing an increase in haze and deterioration in the appearance of the optical film.

[0016] [Embodiment 3] 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 (Equation 3): 0.3≦p / (t2-Φ2)··· (Equation 3), an optical film according to [Embodiment 1].

[0017] According to the above configuration, since 75% or more of the functional particles satisfy (Equation 3), the formation of irregularities on the surface of the optical film due to the presence of the functional particles is more effectively prevented, and therefore, an increase in haze and deterioration in the appearance of the optical film are more effectively prevented.

[0018] [Aspect 4] The optical film according to any one of [Aspect 1] to [Aspect 3], wherein the mass ratio of the functional particles to the resin contained in the functional layer is 0.20 or less. According to the above-mentioned configuration, the influence of the inclusion of functional particles on the properties of the optical film can be reduced.

[0019] [Aspect 5] The optical film according to any one of [Aspect 1] to [Aspect 4], wherein the haze of the optical film is 5% or less. According to the above-mentioned configuration, high transparency can be obtained. Furthermore, since the conditions of [Mode 1] or [Mode 2] are satisfied, it is easy to keep the haze at 5% or less.

[0020] [Aspect 6] The optical film according to any one of [Aspect 1] to [Aspect 5], wherein the functional layer contains fine particles for scattering light. According to the above configuration, an optical film having antiglare properties can be realized.

[0021] [Aspect 7] The optical film according to any one of [Aspects 1] to [Aspect 6], wherein the pencil hardness of the surface of the optical film is 3H or more. According to the above configuration, good mechanical properties can be obtained.

[0022] [Aspect 8] The optical film according to any one of [Aspect 1] to [Aspect 7], wherein the haze of the optical film is 5% or more and 35% or less. The above-mentioned configuration provides good antiglare properties. Furthermore, since the conditions of [Aspect 1] or [Aspect 2] are satisfied, it is easy to keep the haze at 35% or less.

[0023] [Aspect 9] An optical film according to any one of [Aspect 1] to [Aspect 8], wherein in a first-order 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, when the glare contrast is 3.0, the pixel density is 150 ppi or more. According to the above configuration, good glare resistance can be obtained.

[0024] [Aspect 10] An optical film according to any one of [Aspect 1] to [Aspect 9], wherein 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 the functional particles is 5% or less. According to the above-described configuration, the deterioration of haze due to the addition of functional particles can be suitably suppressed.

[0025] [Aspect 11] The optical film according to [Aspect 10], wherein the difference between the haze of the optical film and the haze of the resin film is 3% or less. According to the above-described configuration, the deterioration of haze due to the addition of functional particles can be more suitably suppressed.

[0026] [Aspect 12] The optical film according to any one of [Aspects 1] to 11], wherein the difference in refractive index between the resin of the functional layer and the functional particles is 0.03 or less. According to the above-described configuration, the deterioration of haze due to the addition of functional particles can be suitably suppressed.

[0027] [Embodiment 13] A display device comprising the optical film according to any one of [Embodiment 1] to [Embodiment 12], wherein the optical film is positioned on a display surface on which an image is displayed.

[0028] According to the above configuration, good optical and mechanical properties can be obtained in addition to antibacterial and antiviral properties near the surface of the display device. [Effects of the Invention]

[0029] According to the present disclosure, in an optical film having antibacterial and antiviral properties, it is possible to suppress deterioration of properties including haze and appearance due to the inclusion of functional particles. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram showing a cross-sectional structure of a first example of an optical film according to an embodiment. [Figure 2] FIG. 2 is a graph showing the relationship between the proportion of functional particles and haze. [Figure 3] FIG. 3 is a diagram showing an example of the position of functional particles in a functional layer. [Figure 4] FIG. 4 is a diagram showing a cross-sectional structure of a second example of the optical film according to an embodiment. [Figure 5] FIG. 5 is a diagram showing the configuration of a display device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] An embodiment of an optical film and a display device will be described with reference to the drawings. [Optical film composition: Example 1] 1 shows a first example of the layer structure of an optical film 10. An optical film 10A, which is the first example of the optical film 10, 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.

[0032] 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.

[0033] The structure of each layer will be described in detail below. <Base material> 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 region. 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, it is easy to obtain good strength and quality of the substrate 20. The substrate 20 may be a single-layer structure or a multi-layer structure.

[0034] <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 are monofunctional, difunctional, 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 are acrylic resin, urethane resin, epoxy resin, etc. The resin contained in the functional layer 21 may be one type or two or more types.

[0035] 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.

[0036] 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.

[0037] Among the above, inorganic particles containing a metal or a metal oxide are preferably used as 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 controlling 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 by 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.

[0038] 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.

[0039] The light scattering particles are organic or inorganic particles. The light scattering particles contained in the functional layer 21 may be of one type, or may be of 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.

[0040] The ratio of 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 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 light scattering particles is 20% by mass or less, the amount of resin is not too small, and deterioration of the mechanical properties of the functional layer 21 is suppressed.

[0041] 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.

[0042] 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.

[0043] The functional layer 21 may contain various additives. Examples of additives include ultraviolet absorbers, antistatic agents, leveling agents, antifouling agents, thickeners, etc. The inclusion of additives can enable the functional layer 21 to exhibit ultraviolet absorption functions, antistatic functions, etc., and improve coatability and quality.

[0044] 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.

[0045] 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.

[0046] <Optical film conditions> The optical film 10A satisfies the first condition and at least one of the second and third conditions described below.

[0047] (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 (Formula 1)

[0048] By setting the average particle size Φ1 of the functional particles to at least 0.2 times 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 deterioration of 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.

[0049] By setting the average particle size Φ1 of the functional particles to 0.8 times or less the average film thickness t1, light scattering within the functional layer 21 due to the inclusion of the functional particles is suppressed, and the functional layer 21 is prevented from swelling in the areas 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.

[0050] 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 spaced 1 mm or more apart on the cross section of the optical film 10A, where the difference from the average value of these measurements is within 50% of the average value.

[0051] 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.

[0052] The average particle diameter Φ1 of the functional particles is the volume-based median diameter (D50). By setting the average particle diameter Φ1 to 1.0 μm or more, it is possible to easily satisfy the above (Equation 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 diameter 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 becoming too thick, it is preferable that the average particle diameter Φ1 of the functional particles be 5 μm or less.

[0053] (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 first approximation, a≦50. y=ax+b (Equation 2)

[0054] Here, the intercept b of the linear approximation equation (Equation 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 equation 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 equation for the correlation between the functional component ratio x and the haze y. The haze y is measured in accordance with JIS K 7136.

[0055] 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 particle, but different functional component ratios x.

[0056] In Figure 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 intercepts b of all of them are 0.23.

[0057] The larger the difference in refractive index between the resin and the functional particles in the functional layer 21, the larger the slope a. Even when it is difficult to directly measure the refractive index between the resin and the functional particles, by finding a linear approximation for the correlation between the functional component ratio x and the haze y, it is possible to accurately evaluate how easily the refractive index difference affects the increase in haze.

[0058] The ratio of 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 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 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.

[0059] As shown in Figure 2, if the slope a is 50 or less, the increase in haze can be kept to 10% or less even if the functional component ratio x is increased to approximately 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 specified in the first condition.

[0060] Therefore, by satisfying the first and second conditions, an optical film 10 can be realized 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.

[0061] The increase in haze due to the addition of functional particles, i.e., the difference between the haze of optical film 10A and the haze of a resin film having the same configuration as optical film 10A except that it does not contain functional particles, is preferably 5% or less, and 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, which effectively prevents an increase in haze in the optical film 10A.

[0062] (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 on the cross section of the optical film 10A, the distance p, film thickness t2, and particle diameter Φ2 at the location where the functional particle is 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) (Equation 3)

[0063] 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.

[0064] The film thickness t2 is the length on the line Z1 between the front 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 particle 25 is the total length of the functional particle 25 on the line Z1.

[0065] 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.

[0066] 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.

[0067] 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, unevenness may form 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 unevenness. If the above formula 3 is satisfied, the formation of such unevenness is suppressed, and therefore haze and deterioration of the appearance of the optical film 10A are more effectively suppressed.

[0068] 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.

[0069] The position of the functional particles in the thickness direction of the functional layer 21 can be adjusted by adjusting the surface tension and 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.

[0070] [Optical film composition: Example 2] 4 shows a second example of the layer structure of the optical film 10. The optical film 10B of the second example of the optical film 10 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.

[0071] 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.

[0072] The low refractive index layer 22 contains an ultraviolet curable resin or a thermosetting resin. Such a resin can 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.

[0073] 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.

[0074] 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 improve coatability and quality.

[0075] 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 favorably. 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.

[0076] 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.

[0077] 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.

[0078] 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 thickness t1 in the first condition is the average thickness of the combined thickness of the functional layer 21 and the low-refractive-index layer 22. 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 thickness t2 is the combined thickness of the functional layer 21 and the low-refractive-index layer 22 on the line Z1. Because the thickness of the low-refractive-index layer 22 is sufficiently smaller than the thickness of the functional layer 21, the low-refractive-index layer 22 has little effect on the conditions related to the thickness.

[0079] 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.

[0080] [Optical film characteristics] The following describes the optical and mechanical properties of the optical film 10. The following properties are common to the optical films of the first and second examples.

[0081] 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, improving visibility through the optical film 10. In the optical film 10 of this 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.

[0082] 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. Since the optical film 10 of this embodiment satisfies the first condition and at least one of the second and third conditions, an increase in haze due to the inclusion of functional particles is suppressed, and the haze can 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.

[0083] 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 glare is an important issue.

[0084] Glare resistance can be evaluated using the glare contrast specified in JIS C 1006:2019. Specifically, the optical film 10 is placed on a metal mask having a grid pattern, and the glare contrast is measured for multiple metal masks having grid patterns with different pitches. The grid corresponds to the pixel arrangement, and 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 are used. The glare contrast is determined by single-image measurement using a glare measuring device in accordance with JIS C 1006:2019.

[0085] 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 where y = 3.0 is found and used as the glare tolerance value. In other words, the glare tolerance value is the maximum pixel density at which the glare contrast is 3.0 or less, and the higher 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 prevented from being clearly perceived.

[0086] 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 this 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, and thus reducing the decrease in the glare resistance value. In other words, good glare resistance is obtained.

[0087] 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. A pencil hardness of 3H or more makes the surface of the optical film 10 less susceptible to scratches. The pencil hardness is measured in accordance with JIS K 5600-5-4.

[0088] [Display device configuration] 5, the display device 100 includes an optical film 10 and a main body 30 having an image display function. The display surface 30S, which is the surface of the main body 30, is the 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.

[0089] In particular, when the display surface 30S is the surface of a touch panel, users will frequently touch the display device 100, and therefore it is highly beneficial for the optical film 10 to have antibacterial and antiviral properties.

[0090] Examples of display devices 100 include smartphones, tablet devices, personal computers, portable game consoles, music playback devices, televisions, monitors, e-book viewing devices, digital cameras, head-mounted displays, navigation devices, copiers, facsimiles, printers, multi-function printers, vending machines, automated teller machines (ATMs), personal authentication devices, optical communication devices, etc.

[0091] [Example] The above-mentioned optical film will be described using specific examples. <Preparation of Optical Film for Test Example> A photopolymerizable compound, a photopolymerization initiator, a functional component (antibacterial and antiviral agent), additives, and a solvent were mixed to prepare a functional layer coating liquid for forming the functional layer. A 40 μm-thick triacetyl cellulose film (TJ40, manufactured by Fujifilm) was used as the 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 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 of 200 mJ / cm. 2 In this way, an optical film of a test example including a substrate and a functional layer was obtained.

[0092] The optical films of Test Examples 1 to 41 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. The materials used in the functional layer coating liquid are as follows: The photopolymerizable compound, which is the material for the ultraviolet-curable 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.

[0093] ·Resin materials (photopolymerizable compounds) A1: Acrylate monomer (a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate) (Viscoat #300, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 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 initiator (Omnirad 184, manufactured by IGM Resins BV) Functional ingredients B1: Silver-based antibacterial and antiviral agent (silver-loaded glass) (PMG721C, manufactured by Koa Glass, average particle size Φ1:3 μm) B2: Silver-based antibacterial and antiviral agent (silver-loaded glass) (PTC-NT ANV additive (ST), manufactured by Dainichiseika Chemicals, average particle size Φ1:3 μm) B3: Silver-based antibacterial and antiviral agent (silver-loaded glass) (PG721F, manufactured by Koa Glass, average particle size Φ1:1 μm) B4: Silver-based antibacterial and antiviral agent (silver-loaded zirconium phosphate) (Novalon AG1100, manufactured by Toa Gosei, average particle size Φ1:1 μm) B5: Quaternary ammonium salt antibacterial and antiviral agent (KBM-9418-40, Shin-Etsu Chemical Co., Ltd.) Additive: Leveling agent (GRANDIC PC4300, manufactured by DIC) Light scattering particles: organic fine particles (SSX-2035, Techpolymer) Solvent: Propylene glycol monomethyl ether

[0094] <Evaluation method> (exterior) The appearance of the test optical film was visually observed through two observations: a transmission observation in which the optical film was viewed through a three-wavelength fluorescent lamp, and a reflection observation in which the optical film was attached to a blackboard with an optical adhesive on its back side and viewed under a fluorescent lamp. Each observation checked for abnormalities in appearance, such as the presence 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. The appearance evaluation was performed as follows: no abnormalities were observed, which was rated as good (S); bright spots were observed, which was rated as poor (F1); uneven brightness or a foreign body sensation was observed, which was rated as poor (F2); whitish turbidity was observed, which was rated as poor (F3); and bleed-out, which was rated as poor (F4).

[0095] (Hayes) The haze of the optical film of the test example was measured using a haze meter (NDH7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136.

[0096] (Antibacterial) The optical film of the test example was subjected to antibacterial tests against Staphylococcus aureus and Escherichia coli in accordance with JIS Z 2801. Polyethylene film was used as the unprocessed sample. In the antibacterial evaluation, an antibacterial activity value of 2.0 or higher 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).

[0097] (antiviral) The optical film of the test example was subjected to antiviral tests against influenza A virus and feline calicivirus in accordance with ISO 21702. Polyethylene film was used as the unprocessed sample. In the antiviral evaluation, an antiviral activity value of 2.0 or higher 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).

[0098] (Pencil hardness) For the optical film of the 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 the 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.

[0099] (Anti-glare) The anti-glare properties of the optical film of the 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. It is determined by irradiating the surface of the optical film placed on a blackboard with light from a light source positioned at an incident angle of approximately 5.7° relative to the normal direction of the optical film surface through a slit, 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 reflection intensity at angles +θ and -θ relative to the reflection intensity in the specular reflection direction. The reflection clarity at angle θ is calculated by subtracting the reflection haze at the angle θ from 100.

[0100] To evaluate anti-glare properties, 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 with its backside attached to a blackboard with optical adhesive. Note that measurements were conducted under conditions other than those listed below in accordance with ASTM D5767. Light source slit width: 1mm Objective lens: 16mm Distance between the optical film surface and the receiving camera: 300mm

[0101] In the evaluation of anti-glare 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, while a film was 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 both cases where the surrounding image was clearly reflected on the optical film and cases where the image reflected on the optical film was too blurry.

[0102] (anti-glare) The optical film of the test example was placed on six types of metal masks with 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.

[0103] With the y-axis representing glare contrast and the x-axis representing pixel density, the pixel density indicated by the metal mask grid and the points corresponding to the obtained glare contrast were plotted, and a linear approximation (y = ax) was found for the correlation between these values ​​to calculate the slope. From this linear approximation, the value of x where y = 3.0 was found, and this was taken 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).

[0104] <Evaluation results> Tables 1 to 4 show, for each test example, the type and amount of resin material and functional component 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 the second condition (Equation 2), and the evaluation results using each of the above evaluation methods.

[0105] 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.

[0106] 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.

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] [Table 4]

[0111] As shown in Table 1, Test Examples 1 to 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 of pencil hardness were also good. Furthermore, Test Examples 7 and 8, which contained light-scattering particles, also exhibited good antiglare and anti-glare properties.

[0112] In contrast, as shown in Table 2, in Test Examples 12 and 13, where 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 met, a foreign body sensation was observed in the appearance. In Test Example 13, where the amount of functional particles was increased to a level where sufficient antiviral properties were obtained, the haze was also greater than in Test Examples 1 to 6, 9, and 10.

[0113] In addition, in Test Examples 14 to 16, where the slope a exceeds 50 and the second condition is not satisfied, increasing the functional particles to a level where sufficient antiviral properties are obtained results in a significant increase in haze of over 5%. Furthermore, in Test Examples 17 to 19, where the slope a is even larger, not only does the haze increase significantly with increasing functional particles, as in Test Examples 14 to 16, but bright spots are also observed even when the functional particles are small. Furthermore, in Test Example 20, where the average film thickness t1 is increased compared to Test Examples 17 to 19, the haze and appearance do not improve significantly, and the first condition is no longer satisfied, resulting in a decrease in antiviral properties.

[0114] As shown in Table 3, Test Examples 21 to 23, which had even larger slopes a, also had poor haze and appearance. Furthermore, Test Example 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.

[0115] Test Examples 25 to 31 correspond to the configurations of Test Examples 11, 12, 13, 15, 18, 20, and 22, to which light-scattering particles were added. In these test examples, when the amount of functional particles was increased to a level sufficient to obtain antiviral properties, the haze increased to more than 30%, and the anti-glare and anti-glare properties were also poor. Test Example 28, in which the haze exceeded 40%, also exhibited a cloudy appearance.

[0116] As shown in Table 4, in Test Examples 32 to 34, where the slope a was even larger, exceeding 200, the haze and appearance were poor even though the amount of functional particles was so small that the antiviral properties were insufficient. In Test Examples 36 to 38 and Test Examples 39 to 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 the point where sufficient antiviral properties were obtained.

[0117] Furthermore, referring to Test Examples 11 and 35, it is suggested that when the ratio of 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 functional particles is 5% by mass, good antiviral properties are obtained.

[0118] Regarding the third condition, for each of Test Example 2 and Test Example 19, a cross section of the optical film was observed using a scanning electron microscope (SEM) to extract 50 functional particles contained in the cross section, and the distance p, film thickness t2, and particle size Φ2 were measured for each functional particle. The proportion of functional particles satisfying the third condition (Equation 3) was then calculated for the 50 populations. As a result, for Test Example 2, the proportion of functional particles satisfying (Equation 3) was 89%, and for Test Example 19, the proportion of functional particles satisfying (Equation 3) was 67%. In other words, Test Example 2 satisfied the third condition, while Test Example 19 did not. This suggests that satisfying the third condition can suppress haze and deterioration of appearance.

[0119] As described above, according to the above-described embodiment and example, the following effects can be obtained. (1) By satisfying the first condition, the functional particles are not too small relative to the average film thickness t1, thereby preventing the production 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, because 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.

[0120] (2) By satisfying the second condition, an increase in haze can be suppressed even when the proportion of functional particles is increased to the extent that antiviral properties are obtained in addition to antibacterial properties. In addition, in combination with the first condition, an increase in haze can be suppressed even when functional particles with an average particle size Φ1 of 1 μm or more are used.

[0121] (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 prevented, thereby more effectively preventing an increase in haze and deterioration in the appearance of the optical film.

[0122] (4) If the mass ratio of the functional particles to the resin contained in the functional layer is 0.20 or less, the influence of the inclusion of the functional particles on the properties of the optical film can be reduced. (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, the second condition, and the third condition, it is easy to achieve a haze of 5% or less.

[0123] (6) If the optical film contains light-scattering particles, it can be made into an optical film with 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.

[0124] (7) If the pixel density of the optical film is 150 ppi or more when the glare contrast is 3.0, good glare resistance can be obtained. (8) If the pencil hardness of the surface of the optical film is 3H or more, good mechanical properties can be obtained.

[0125] (9) If the difference in haze between the optical film and a resin film having the same configuration as the optical film but excluding the functional particles is 5% or less, the deterioration of haze due to the addition of functional particles is suitably suppressed. Furthermore, if the difference in haze between the optical film and the resin film is 3% or less, the deterioration of haze due to the addition of functional particles is even more suitably suppressed.

[0126] (10) If 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 can be suitably suppressed. (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 can be highly beneficial. [Explanation of symbols]

[0127] 10, 10A, 10B...Optical film 20...Base material 21...Functional layer 22...Low refractive index layer 25…Functional particles 100…Display device

Claims

1. A substrate; An optical film comprising a functional layer containing functional particles that are at least one of an antibacterial agent and an antiviral agent and a resin, a surface of the functional layer in contact with the substrate is a back surface of the functional layer, and an outermost surface of the optical film located on the opposite side of the back surface from the substrate is a front surface of the optical film, the average particle diameter Φ1 of the functional particles is 1.0 μm or more, an average film thickness t1 between the front surface of the optical film and the back surface of the functional layer, and the average particle diameter Φ1 of the functional particles satisfy the following (Formula 1): 0.2×t1≦Φ1≦0.8×t1 (Formula 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 (Equation 2) in first approximation, a≦50. y=ax+b...(Formula 2) Optical film.

2. A substrate; An optical film comprising a functional layer containing functional particles that are at least one of an antibacterial agent and an antiviral agent and a resin, a surface of the functional layer in contact with the substrate is a back surface of the functional layer, and an outermost surface of the optical film located on the opposite side of the back surface from the substrate is a front surface of the optical film, the average particle diameter Φ1 of the functional particles is 1.0 μm or more, an average film thickness t1 between the front surface of the optical film and the back surface of the functional layer, and the average particle diameter Φ1 of the functional particles satisfy the following (Formula 1): 0.2×t1≦Φ1≦0.8×t1 (Formula 1) For 75% or more of the functional particles extracted from the cross section of the optical film, a distance p between the surface of the optical film and the functional particle in the thickness direction at a location where the functional particle is located, a film thickness t2 between the surface of the optical film and the back surface of the functional layer, and a particle diameter Φ2 of the functional particle satisfy the following (Equation 3): 0.3≦p / (t2-Φ2) ... (Formula 3) Optical film.

3. For 75% or more of the functional particles extracted from the cross section of the optical film, a distance p between the surface of the optical film and the functional particle in the thickness direction at a location where the functional particle is located, a film thickness t2 between the surface of the optical film and the back surface of the functional layer, and a particle diameter Φ2 of the functional particle satisfy the following (Equation 3): 0.3≦p / (t2-Φ2) ... (Formula 3) The optical film according to claim 1 .

4. The mass ratio of the functional particles to the resin contained in the functional layer is 0.20 or less. The optical film according to claim 1 or 2.

5. The haze of the optical film is 5% or less. The optical film according to claim 1 or 2.

6. The functional layer contains particles for light scattering. The optical film according to claim 1 or 2.

7. The pencil hardness of the surface of the optical film is 3H or more. The optical film according to claim 1 or 2.

8. The haze of the optical film is 5% or more and 35% or less. The optical film according to claim 1 or 2.

9. 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, when the glare contrast is 3.0, the pixel density is 150 ppi or more. The optical film according to claim 1 or 2.

10. 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 the functional particles is 5% or less. The optical film according to claim 1 or 2.

11. The difference between the haze of the optical film and the haze of the resin film is 3% or less. The optical film according to claim 10.

12. The difference in refractive index between the resin of the functional layer and the functional particles is 0.03 or less. The optical film according to claim 1 or 2.

13. A display device comprising the optical film according to claim 1 or 2, The optical film is positioned on a display surface on which an image is displayed. Display device.

Images