JP7515646B1 - Anti-reflection film and image display device - Google Patents

Abstract

[Problem] To provide an anti-reflection film having high adhesion between a hard coat layer and an anti-reflection layer, exhibiting high anti-glare properties, and having good visibility with little white blurring of reflected light during black display. [Solution] An anti-reflection film 101 has a hard coat layer 11 on one main surface of a transparent film substrate 10, and has an anti-reflection layer 5 and an anti-fouling layer 7 provided in this order on the hard coat layer 11 of the hard coat film 1. The hard coat layer contains a binder resin, microparticles with an average primary particle diameter of 1 to 8 μm, and nanoparticles with an average primary particle diameter of 100 nm or less. The anti-reflection layer is a laminate of a plurality of thin films with different refractive indices. The anti-reflection film has an average spacing RSm of irregularities of 120 μm or more as determined from a roughness curve with a measurement length of 12 mm, and an arithmetic mean height Sa of 2.0 nm or more as determined from the three-dimensional surface properties of a 1 μm x 1 μm area. [Selected Figure] Figure 1

Description

The present invention relates to an anti-reflection film having an anti-reflection layer on a transparent film substrate. Furthermore, the present invention relates to an image display device having the anti-reflection film.

Anti-reflective films are used on the viewing side surfaces of image display devices such as liquid crystal displays and organic EL displays to prevent degradation of image quality due to reflection of external light and to improve contrast. Anti-reflective films have an anti-reflective layer made of a laminate of multiple thin films with different refractive indices on a transparent film.

Anti-glare treatment is used to prevent contrast loss caused by reflection of external light. For example, Patent Documents 1 to 3 disclose an anti-glare anti-reflection film in which an anti-reflection layer is provided on an anti-glare hard-coated film in which a hard-coat layer containing fine particles is formed on a transparent film. In anti-glare anti-reflection films, the hard-coat layer contains fine particles (microparticles) with particle diameters on the order of μm, forming surface irregularities, which scatter and reflect external light, thereby reducing reflection of external light.

Patent documents 1 to 3 disclose that the antiglare hard coat layer contains nanoparticles with an average primary particle diameter of 100 nm or less in addition to microparticles. Patent document 1 describes that silica particles with an average primary particle diameter of 20 nm are aggregated to form amorphous secondary particles, thereby improving light diffusion at the surface. Patent document 2 describes that surface-modified nanosilica particles have the effect of suppressing the sedimentation of organic fine particles (microparticles) and causing them to float to the surface, making it possible to adjust the antiglare properties. Patent document 3 (see Examples 6 to 8) describes that the inclusion of nanosilica particles in the antiglare hard coat layer results in the formation of fine irregularities on the surface of the hard coat layer, improving the adhesion between the hard coat layer and the antireflection layer.

JP 2008-40064 A JP 2009-204728 A International Publication No. 2021/106797

Conventional anti-glare anti-reflection films have poor adhesion between the hard coat layer and the anti-reflection layer, and when exposed to external light for long periods of time, the anti-reflection layer (and the anti-smudge layer provided on top of it) is prone to peeling, resulting in issues such as a deterioration in optical properties and anti-smudge properties with use.

As proposed in Patent Document 3, the presence of nanoparticles on the surface of the antiglare hard coat layer tends to improve adhesion between the hard coat layer and the antireflection layer. However, the antireflection films of Examples 6 to 8 of Patent Document 3 have good adhesion to the antireflection layer, but have problems in that when the image display device displays black, the reflected light of external light appears white and blurred (white blur), the color of the black display is not crisp, and the bright contrast is low.

In view of the above, the present invention aims to provide an anti-reflection film that has high adhesion between the anti-glare hard coat layer and the anti-reflection layer, has little white blurring of reflected light, and has good visibility.

The anti-reflection film of the present invention comprises an anti-reflection layer and an anti-fouling layer provided in this order on the hard coat layer of a hard coat film that has a hard coat layer on one main surface of a transparent film substrate. The hard coat layer contains a binder, fine particles (microparticles) with a particle size of 1 to 8 μm, and fine particles (nanoparticles) with an average primary particle size of 100 nm or less.

The anti-reflection layer is made of a laminate of multiple thin films with different refractive indices. The thin films constituting the anti-reflection layer are preferably made of an inorganic oxide. The anti-reflection layer may be a sputtered film formed by sputtering. A primer layer made of an inorganic oxide may be provided between the hard coat layer and the anti-reflection layer.

The surface of the anti-reflection film (surface of the anti-fouling layer) preferably has an average spacing between projections and recesses RSm of 120 μm or more as determined from a roughness curve with a measurement length of 12 mm, and an arithmetic mean height Sa of 2.0 nm or more as determined from the three-dimensional surface characteristics of an area of 1 μm x 1 μm. The arithmetic mean roughness Ra of the anti-reflection film surface as determined from a roughness curve with a measurement length of 12 mm may be 30 to 500 nm.

The microparticles contained in the hard coat layer preferably have a specific gravity of 1.25 or more. When the hard coat layer contains two or more types of microparticles, the average specific gravity of the microparticles is preferably 1.25 or more, and the ratio of particles having a specific gravity of 1.25 or more out of a total of 100 parts by weight of microparticles is preferably 85 parts by weight or more.

The amount of microparticles in the hard coat layer is preferably 0.5 to 12 parts by weight per 100 parts by weight of binder resin. The amount of nanoparticles in the hard coat layer is preferably 25 to 120 parts by weight per 100 parts by weight of binder. The average primary particle diameter of the nanoparticles is preferably 15 nm or more.

An anti-reflection film having the above Sa and RSm has high adhesion between the hard coat layer and the anti-reflection layer, exhibits high anti-glare properties, and has good visibility with little white blurring of reflected light. An image display device in which the anti-reflection film is arranged on the viewing side surface of an image display medium exhibits excellent anti-glare properties, has high contrast in bright areas, and is difficult for the anti-reflection layer and anti-fouling layer to peel off, so that it can maintain excellent optical properties and anti-fouling properties even after long-term use.

FIG. 2 is a cross-sectional view showing an example of a laminate structure of an antireflection film. 4 is a photograph showing the reflected light of the antireflection films of Examples and Comparative Examples.

Figure 1 is a cross-sectional view showing an example of the laminated structure of an anti-reflection film according to one embodiment of the present invention. The anti-reflection film 101 has an anti-reflection layer 5 on the hard coat layer 11 of the hard coat film 1, and has an anti-fouling layer 7 on the anti-reflection layer 5. The hard coat film 1 has a hard coat layer 11 on one main surface of a transparent film substrate 10. The anti-reflection layer 5 is a laminate of two or more inorganic thin layers with different refractive indices. A primer layer 3 may be provided between the hard coat layer 11 and the anti-reflection layer 5.

[Hard coat film]
The hard coat film 1 includes a hard coat layer 11 on one main surface of a transparent film substrate 10. By providing the hard coat layer 11 on the surface on which the antireflection layer 5 is formed, the mechanical properties such as surface hardness and scratch resistance of the antireflection film can be improved.

<Transparent film substrate>
The visible light transmittance of the transparent film substrate 10 is preferably 80% or more, more preferably 90% or more. As the resin material constituting the transparent film substrate 10, for example, a resin material excellent in transparency, mechanical strength, and thermal stability is preferable. Specific examples of the resin material include cellulose-based resins such as triacetyl cellulose, polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, cyclic polyolefin-based resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof.

The thickness of the transparent film substrate is not particularly limited, but from the viewpoints of workability such as strength and handling, thin layer property, etc., it is preferably about 5 to 300 μm, more preferably 10 to 250 μm, and even more preferably 20 to 200 μm.

<Hard Coat Layer>
The hard coat film 1 is formed by providing a hard coat layer 11 on the main surface of a transparent film substrate 10. The hard coat layer 11 contains a binder resin and fine particles, and the fine particles include microparticles having a particle diameter of 1 μm or more and nanoparticles having a particle diameter of 100 nm or less. The hard coat layer 11 exhibits antiglare properties due to the surface unevenness formed by the microparticles, and the fine surface unevenness formed by the nanoparticles contributes to improving the adhesion of the antireflection layer 5.

The thickness of the hard coat layer 11 is not particularly limited, but in order to achieve high hardness, it is preferably 2 μm or more, more preferably 4 μm or more, and even more preferably 5 μm or more. On the other hand, if the thickness of the hard coat layer 11 is excessively large, the surface unevenness of the hard coat layer may not be properly formed, or the film strength may decrease due to cohesive failure. Therefore, the thickness of the hard coat layer 11 is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 12 μm or less. In addition, the thickness of the hard coat layer 11 is preferably in the range of 1.2 to 4 times the average particle diameter of the microparticles, and more preferably in the range of 1.5 to 3 times. When the ratio of the particle diameter of the microparticles to the thickness of the hard coat layer is in the above range, the uneven shape formed on the surface of the hard coat layer is likely to have excellent anti-glare properties.

The haze of the hard coat film is preferably 1 to 35%, more preferably 2 to 30%, and may be 3 to 25%, 4 to 20%, 5 to 17%, or 6 to 15%. If the haze of the hard coat film is within the above range, it is possible to achieve both anti-glare properties and image clarity. If the haze is too small, the anti-glare properties may be poor, and if the haze is too large, the transmitted light will be significantly scattered, tending to reduce image clarity.

The arithmetic mean height Sa calculated from the three-dimensional surface characteristics of a 1 μm × 1 μm area on the surface of the hard coat layer 11 is preferably 2.0 nm or more. The average spacing RSm of irregularities calculated from a roughness curve of the surface of the hard coat layer 11 with a measurement length of 12 mm is preferably 120 μm or more.

The arithmetic mean height Sa is a value calculated in accordance with ISO 25178 from an observation image of 1 μm square using an atomic force microscope (AFM), and is an index that indicates the degree of formation of nano-scale fine unevenness. The larger the arithmetic mean height Sa of the hard coat layer 11, the more the adhesion of the anti-reflection layer 5 tends to improve. The larger the particle diameter of the nanoparticles contained in the hard coat layer 11 and the greater the content of nanoparticles, the larger Sa tends to be. The arithmetic mean height Sa of the hard coat layer 11 is more preferably 2.3 nm or more, even more preferably 2.5 nm or more, and may be 2.7 nm or more, 2.9 nm or more, or 3.0 nm or more.

On the other hand, if the surface unevenness formed by the nanoparticles becomes coarse, sufficient adhesion may not be achieved. In addition, if the surface unevenness formed by the nanoparticles becomes large, the shape of the microparticles is difficult to reflect in the surface shape of the hard coat layer 11, and the anti-glare properties may decrease. Therefore, the arithmetic mean height Sa of the hard coat layer 11 is preferably 10 nm or less, more preferably 8.0 nm or less, even more preferably 7.0 nm or less, and may be 6.0 nm or less, 5.5 nm or less, 5.0 nm or less, or 4.5 nm or less.

The average spacing between the irregularities RSm is the average length of the roughness curve elements calculated in accordance with JIS B0601:2001 from a roughness curve obtained by passing a 12 mm long cross-sectional curve measured with a stylus surface roughness measuring instrument through a wide-band filter with a cutoff value of 0.8 mm, and is an index representing the surface density of the irregularities on the μm scale. The smaller the average spacing between the irregularities RSm of the hard coat layer 11, the higher the density of the irregularities formed on the surface of the hard coat layer by the microparticles, and the better the anti-glare properties tend to be. On the other hand, if RSm is too small, when the image display device displays black, the reflected image of external light is likely to be viewed as white and blurred, the black color is poorly "tight," and the bright contrast tends to decrease (see "Comparative Example 2" in Figure 2).

By setting the average spacing RSm of the projections and recesses of the hard coat layer 11 to 120 μm or more, it is possible to realize a display with good black color density and high contrast in bright areas. The average spacing RSm of the projections and recesses of the hard coat layer 11 is preferably 130 μm or more, and may be 140 μm or more or 150 μm or more.

On the other hand, if the average spacing RSm of the irregularities in the hard coat layer 11 is too large, the antiglare properties may not be fully exhibited. Therefore, the average spacing RSm of the irregularities in the hard coat layer 11 is preferably 250 μm or less, more preferably 220 μm or less, even more preferably 200 μm or less, and may be 180 μm or less or 170 μm or less.

The arithmetic mean roughness Ra calculated in accordance with JIS B0601:2001 from a roughness curve obtained by passing a cross-sectional curve of the surface of the hard coat layer 11 with a measurement length of 12 mm through a wide-band filter with a cutoff value of 0.8 mm is preferably 30 to 500 nm. The arithmetic mean roughness Ra is an index that represents the degree of formation of irregularities with heights on the submicron to μm scale that contribute to light scattering, and the larger the particle diameter of the microparticles contained in the hard coat layer 11 and the higher the content of the microparticles, the larger Sa tends to be.

The larger the arithmetic mean roughness Ra of the hard coat layer 11, the better the anti-glare properties tend to be. On the other hand, if the arithmetic mean roughness Ra of the hard coat layer 11 is excessively large, the light scattering is large, which may cause a decrease in image clarity and white out of reflected light. The arithmetic mean roughness Ra of the hard coat layer 11 is more preferably 50 to 400 nm, even more preferably 60 to 300 nm, and may be 70 to 250 nm or 80 to 200 nm.

The composition used to form the hard coat layer 11 contains a binder resin (or a curable resin as its precursor), microparticles with a particle diameter of 1 μm or more, and nanoparticles with a particle diameter of 100 nm or less.

(Binder resin)
As the binder resin of the hard coat layer 11, a curable resin such as a thermosetting resin, a photocurable resin, or an electron beam curable resin is preferably used. The types of curable resin include polyester, acrylic, urethane, acryl urethane, amide, silicone, silicate, epoxy, melamine, oxetane, and acryl urethane. Among these, acrylic resin, acryl urethane resin, and epoxy resin are preferred because of their high hardness and photocurability, and acrylic resin and acryl urethane resin are more preferred. The refractive index of the binder resin is generally about 1.4 to 1.6.

The photocurable binder resin component contains a polyfunctional compound having two or more photopolymerizable (preferably ultraviolet-polymerizable) functional groups. The polyfunctional compound may be a monomer or an oligomer. As the photopolymerizable polyfunctional compound, a compound containing two or more (meth)acryloyl groups in one molecule (polyfunctional (meth)acrylate) is preferably used.

(Microparticles)
By containing fine particles (microparticles) having a particle diameter of 1 μm or more in the hard coat layer 11, unevenness with a period of about 100 μm is formed on the surface of the hard coat layer, and anti-glare properties are imparted. The average particle diameter of the microparticles (particles having a particle diameter of 1 μm or more) contained in the hard coat layer is preferably 1 to 8 μm, more preferably 2 to 5 μm. When the particle diameter of the microparticles is small, the anti-glare properties tend to be insufficient. When the particle diameter of the microparticles is large, the clarity of the image tends to decrease. When two or more types of microparticles are contained in the hard coat layer, it is preferable that the average particle diameter of the entire microparticles (particles having a particle diameter of 1 μm or more) is within the above range. The average particle diameter is the weight average particle diameter measured by the Coulter count method.

The shape of the microparticles is not particularly limited, but from the viewpoint of reducing glare, spherical particles with an aspect ratio of 1.5 or less are preferred. The aspect ratio of the spherical particles is preferably 1.3 or less, more preferably 1.1 or less.

As materials for the microparticles, various metal oxide fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide, glass fine particles, and crosslinked or uncrosslinked organic fine particles made of various transparent polymers such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, polycarbonate, and silicone can be used without any particular restrictions. One or more of these fine particles can be appropriately selected and used. Silicone is particularly preferable as a material for the microparticles because it is possible to produce fine particles with a particle size on the order of μm, a small aspect ratio, and a high uniformity of particle size, and it has a high density.

It is preferable that the microparticles have a small refractive index difference with the binder resin of the hard coat layer. By reducing the refractive index difference between the binder and the microparticles, light scattering at the interface between the binder resin and the microparticles is reduced, and the haze is reduced, enabling a display with a high sense of clarity. On the other hand, if the haze of the hard coat layer is excessively small, the anti-glare properties may be insufficient. From the viewpoint of realizing a display with a high sense of clarity while providing the hard coat layer with an appropriate haze, the refractive index difference between the binder resin and the microparticles is preferably about 0.01 to 0.10, and may be 0.02 to 0.06.

The specific gravity of the microparticles is preferably 1.25 or more, more preferably 1.28 or more, and may be 1.30 or more. The specific gravity of the microparticles may be 2.0 or less, 1.70 or less, 1.50 or less, or 1.40 or less. The specific gravity of the microparticles is preferably greater than the specific gravity of the nanoparticles.

When the specific gravity of the microparticles is large, the microparticles tend to settle and become unevenly distributed near the transparent film substrate 10. As a result, the nanoparticles tend to become unevenly distributed near the surface of the hard coat layer 11 (the interface with the antireflection layer 5 or the primer layer 3), and fine irregularities are formed uniformly within the surface, which tends to improve the adhesion of the antireflection layer.

When microparticles and nanoparticles coexist in the hard coat layer 11, the presence of microparticles near the surface of the hard coat layer reduces the average spacing between the surface irregularities RSm, and the reflected light tends to cause white blurring, resulting in a decrease in bright contrast. By using microparticles that have a high specific gravity and tend to settle easily, the spacing between the irregularities formed on the surface of the hard coat layer becomes larger, reflecting the shape of the microparticles, and RSm tends to increase.

When the hard coat layer contains two or more types of microparticles, it is preferable that the average specific gravity of the microparticles (particles with a particle diameter of 1 μm or more) is in the above range. Even if the average specific gravity of the microparticles is 1.25 or more, if the ratio of microparticles with a specific gravity of less than 1.25 is large, the amount of microparticles present near the surface of the hard coat layer increases, and the RSm of the hard coat layer tends to decrease. Therefore, out of a total of 100 parts by weight of microparticles, the amount of particles with a specific gravity of 1.25 or more is preferably 85 parts by weight or more, more preferably 90 parts by weight or more, and may be 95 parts by weight or more, 99 parts by weight or more, or 100 parts by weight.

The content of microparticles in the hard coat layer is not particularly limited. From the viewpoint of forming uniform irregularities on the surface of the hard coat layer, the content of microparticles is preferably 0.5 to 12 parts by weight, more preferably 1 to 10 parts by weight, and may be 1.5 to 7 parts by weight or 2 to 5 parts by weight, relative to 100 parts by weight of the binder resin. If the content of microparticles is small, the RSm of the hard coat layer is large and the antiglare properties may be insufficient. On the other hand, if the content of microparticles is excessively large, even if high-density microparticles are used, the RSm becomes small and the bright contrast tends to decrease due to white blurring of reflected light.

As described above, by adjusting the specific gravity, particle size, and content of the microparticles, the surface shape of the hard coat layer 11 can be adjusted to impart anti-glare properties while reducing white blur. The greater the content of microparticles, the greater the number of protrusions formed by the microparticles, and therefore the smaller the RSm tends to be. In addition, the larger the average particle size of the microparticles and the greater the content of the microparticles, the larger the Ra tends to be. When the specific gravity of the microparticles is small and the proportion of microparticles present near the surface is large, the smaller the RSm tends to be and the larger the Ra tends to be.

(Nanoparticles)
When the hard coat layer 11 contains nanoparticles having a particle diameter of 100 nm or less in addition to microparticles having a particle diameter of 1 μm or more, fine irregularities smaller than the irregularities formed by the microparticles are formed on the surface of the hard coat layer, which tends to improve adhesion between the hard coat layer 11 and the antireflection layer 5 formed thereon.

As the material for the nanoparticles, inorganic oxides are preferred. Examples of inorganic oxides include metal or semimetal oxides such as silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, titanium oxide, niobium oxide, zinc oxide, tin oxide, cerium oxide, and magnesium oxide. The inorganic oxide may be a composite oxide of multiple (semi)metals. Among the inorganic oxides listed above, silicon oxide is preferred because it has a low refractive index, excellent transparency, and a high effect of improving adhesion. Among them, colloidal silica is particularly preferred as the material for the nanoparticles because it can produce fine particles with a high uniformity of particle size, has excellent dispersibility, and has a low density. Functional groups such as acrylic groups and epoxy groups may be introduced onto the surface of the nanoparticles for the purpose of improving affinity with the binder resin and improving the hardness of the hard coat layer.

The specific gravity of the nanoparticles is preferably smaller than that of the microparticles. The relatively low specific gravity of the nanoparticles makes them more likely to be concentrated near the surface of the hard coat layer 11, and fine irregularities are formed uniformly within the surface, which tends to improve the adhesion of the anti-reflection layer. The specific gravity of the nanoparticles is preferably less than 1.25, and may be 1.23 or less or 1.21 or less. The specific gravity of the nanoparticles may be 0.80 or more, 0.90 or more, 0.95 or more, or 1.00 or more. The specific gravity of colloidal silica is generally about 1.05 to 1.20.

The larger the particle diameter of the nanoparticles and the greater the content of nanoparticles, the greater the height and surface density of the nano-sized irregularities formed by the nanoparticles, and the greater the arithmetic mean height Sa of the hard coat layer 11, which tends to improve the adhesion of the anti-reflection layer 5.

From the viewpoint of increasing dispersibility in the binder and increasing the Sa of the hard coat layer to increase adhesion of the anti-reflection layer, the average primary particle diameter of the nanoparticles is preferably 15 nm or more, more preferably 20 nm or more, and may be 25 nm or more or 30 nm or more. On the other hand, from the viewpoint of forming a fine uneven shape that contributes to improving adhesion and suppressing coloring of reflected light on the surface of the hard coat layer, the average primary particle diameter of the nanoparticles is preferably 90 nm or less, more preferably 70 nm or less, and may be 60 nm or less, 55 nm or less, or 50 nm or less.

The content of nanoparticles in the hard coat layer is not particularly limited, but from the viewpoint of increasing the Sa of the hard coat layer and improving the adhesion of the anti-reflection layer, the content of nanoparticles is preferably 25 parts by weight or more, and may be 30 parts by weight or more or 35 parts by weight or more, relative to 100 parts by weight of binder resin. On the other hand, if the content of nanoparticles is excessively large, the RSm of the hard coat layer becomes small, and white blur of reflected light is likely to occur. Therefore, the content of nanoparticles in the hard coat layer is preferably 120 parts by weight or less, more preferably 100 parts by weight or less, and even more preferably 80 parts by weight or less, and may be 70 parts by weight or less, 60 parts by weight or less, 55 parts by weight or less, 50 parts by weight or less, or 45 parts by weight or less, relative to 100 parts by weight of binder resin.

(Formation of hard coat layer)
The hard coat composition comprises the above-mentioned binder resin component, microparticles and nanoparticles, and if necessary, comprises a solvent.When the binder resin component is a curable resin, it is preferable that the composition contains a suitable polymerization initiator.For example, when the binder resin component is a photocurable resin, it is preferable that the composition contains a photopolymerization initiator.

In addition to the above, the hard coat composition may contain additives such as leveling agents, viscosity modifiers (thixotropic agents, thickeners, etc.), antistatic agents, antiblocking agents, dispersants, dispersion stabilizers, antioxidants, UV absorbers, defoamers, surfactants, and lubricants.

Examples of thixotropic agents include organic clay, oxidized polyolefin, and modified urea. Among these, organic clay such as smectite is preferred. The amount of thixotropic agent is preferably about 0.3 to 5 parts by weight per 100 parts by weight of binder. Examples of leveling agents include fluorine-based or silicone-based leveling agents, and the amount of leveling agent is preferably about 0.01 to 3 parts by weight per 100 parts by weight of binder.

The above hard coat composition is applied onto a transparent film substrate 10, and the solvent is removed and the resin is cured as necessary to form a hard coat layer 11.

The hard coat composition may be applied by any suitable method such as bar coating, roll coating, gravure coating, rod coating, slot orifice coating, curtain coating, fountain coating, or comma coating. The heating temperature after application may be set to an appropriate temperature depending on the composition of the hard coat composition, for example, about 50°C to 150°C. When the binder resin component is a photocurable resin, photocuring is performed by irradiating it with active energy rays such as ultraviolet rays. The integrated light amount of the irradiated light is, for example, about 100 to 500 mJ/ ^cm2 .

Before forming the anti-reflection layer 5 on the hard coat layer 11, the hard coat layer 11 may be subjected to a surface treatment in order to further improve the adhesion between the hard coat layer 11 and the anti-reflection layer 5. Examples of the surface treatment include surface modification treatments such as corona treatment, plasma treatment, frame treatment, ozone treatment, primer treatment, glow treatment, alkali treatment, acid treatment, and treatment with a coupling agent. Vacuum plasma treatment may be performed as the surface treatment. In dry etching treatment using vacuum plasma or the like, the resin component on the surface of the hard coat layer is easily selectively etched, and the proportion of nanoparticles on and near the surface of the hard coat layer increases, so that the arithmetic average height Sa of the hard coat layer surface tends to increase.

[Anti-reflection film]
An antireflection layer 5 is formed on the hard coat layer 11 of the hard coat film 1, optionally via a primer layer 3, and an antifouling layer 7 is formed on the antireflection layer 5, thereby obtaining an antireflection film.

<Primer layer>
A primer layer 3 is preferably provided between the hard coat layer 11 and the anti-reflection layer 5. Examples of materials for the primer layer 3 include metals such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, indium, tungsten, aluminum, zirconium, and palladium; alloys of these metals; and oxides, fluorides, sulfides, or nitrides of these metals. Among these, the material for the primer layer is preferably an inorganic oxide, and silicon oxide or indium oxide is particularly preferred. The inorganic oxide constituting the primer layer 3 may be a composite oxide such as indium tin oxide (ITO).

When the primer layer 3 is made of silicon oxide, it is particularly preferred that the amount of oxygen is less than that of the stoichiometric composition, since this has high light transmittance and high adhesive strength to both the organic layer (hard coat layer) and the inorganic layer (anti-reflection layer). The amount of oxygen in the primer layer 3 having a non-stoichiometric composition is preferably about 60 to 99% of that in the stoichiometric composition. For example, when a silicon oxide (SiO _x ) layer is formed as the primer layer 3, x is preferably 1.20 to 1.98.

The thickness of the primer layer 3 is, for example, about 1 to 20 nm, and preferably 3 to 15 nm. If the thickness of the primer layer is within the above range, it is possible to achieve both adhesion to the hard coat layer 11 and high light transmittance.

<Anti-reflection layer>
The antireflection layer 5 is made of two or more thin layers with different refractive indexes. In general, the optical film thickness (product of refractive index and thickness) of the thin film is adjusted so that the inverted phases of incident light and reflected light cancel each other out. By making the antireflection layer a multilayer laminate of two or more thin films with different refractive indexes, the reflectance can be reduced in a wide wavelength range of visible light.

Materials for the thin film constituting the anti-reflection layer 5 include metal oxides, nitrides, fluorides, etc. The anti-reflection layer 5 is preferably an alternating laminate of high-refractive index layers and low-refractive index layers. In order to reduce reflection at the interface with the anti-fouling layer, the thin film 54 provided as the outermost layer of the anti-reflection layer 5 is preferably a low-refractive index layer.

The high refractive index layers 51, 53 have a refractive index of, for example, 1.9 or more, preferably 2.0 or more. Examples of high refractive index materials include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, indium tin oxide (ITO), antimony-doped tin oxide (ATO), and the like. Among these, titanium oxide or niobium oxide is preferred. The low refractive index layers 52, 54 have a refractive index of, for example, 1.6 or less, preferably 1.5 or less. Examples of low refractive index materials include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, lanthanum fluoride, and the like. Among these, silicon oxide is preferred. In particular, it is preferred to alternately stack niobium oxide (Nb ₂ O ₅ ) thin films 51, 33 as high refractive index layers and silicon oxide (SiO ₂ ) thin films 52, 54 as low refractive index layers. In addition to the low refractive index layer and the high refractive index layer, a medium refractive index layer having a refractive index of about 1.6 to 1.9 may be provided.

The thickness of each of the high and low refractive index layers is about 5 to 200 nm, and preferably about 15 to 150 nm. The thickness of each layer can be designed so that the reflectance of visible light is small, depending on the refractive index and layer structure. For example, the layer structure of the high and low refractive index layers can be a four-layer structure consisting of, from the hard coat film side, a high refractive index layer 51 with an optical thickness of about 25 nm to 55 nm, a low refractive index layer 52 with an optical thickness of about 35 nm to 55 nm, a high refractive index layer 53 with an optical thickness of about 80 nm to 240 nm, and a low refractive index layer 54 with an optical thickness of about 120 nm to 150 nm.

The method for forming the thin film constituting the anti-reflective layer 5 is not particularly limited, and may be either a wet coating method or a dry coating method. Dry coating methods such as vacuum deposition, CVD, sputtering, and electron beam vapor deposition are preferred because they can form a thin film with a uniform thickness. Among these, sputtering is preferred because it has excellent uniformity in thickness and is easy to form a dense, high-strength film. By forming the anti-reflective layer by the sputtering method, the abrasion resistance of the antifouling layer 7 provided on the anti-reflective layer 5 tends to be improved.

In the sputtering method, a thin film can be continuously formed while transporting a long hard coat film in one direction (longitudinal direction) using a roll-to-roll method. In the sputtering method, the film is formed while introducing an inert gas such as argon, and if necessary, a reactive gas such as oxygen, into the chamber. The formation of an oxide layer by the sputtering method can be carried out by either a method using an oxide target or reactive sputtering using a metal target. In order to form a metal oxide film at a high rate, reactive sputtering using a metal target is preferred.

<Anti-stain layer>
The antireflection film includes an antifouling layer 7 as an outermost layer (topcoat layer) on an antireflection layer 5. By providing the antifouling layer on the outermost surface, the influence of contamination from the external environment (fingerprints, hand dirt, dust, etc.) can be reduced and contaminants attached to the surface can be easily removed.

In order to maintain the anti-reflection properties of the anti-reflection layer 5, it is preferable that the anti-smudge layer 7 has a small difference in refractive index from the low refractive index layer 54 on the outermost surface of the anti-reflection layer 5. The refractive index of the anti-smudge layer 7 is preferably 1.6 or less, and more preferably 1.55 or less.

As the material of the antifouling layer 7, a fluorine-containing compound is preferred. The fluorine-containing compound can impart antifouling properties and also contribute to lowering the refractive index. Among them, a fluorine-based polymer containing a perfluoropolyether skeleton is preferred because it has excellent water repellency and can exhibit high antifouling properties. From the viewpoint of enhancing antifouling properties, a perfluoropolyether having a main chain structure that can be rigidly arranged in parallel is particularly preferred. As the structural unit of the main chain skeleton of the perfluoropolyether, a perfluoroalkylene oxide having 1 to 4 carbon atoms that may have a branch is preferred, and examples thereof include perfluoromethylene oxide (-CF ₂ O-), perfluoroethylene oxide (-CF ₂ CF ₂ O-), perfluoropropylene oxide (-CF ₂ CF ₂ CF ₂ O-), and perfluoroisopropylene oxide (-CF(CF ₃ )CF ₂ O-).

The antifouling layer can be formed by a wet method such as reverse coating, die coating, or gravure coating, or a dry method such as vacuum deposition or CVD. The thickness of the antifouling layer is usually about 2 to 50 nm. The thicker the antifouling layer 7, the more the antifouling property tends to improve. In addition, the thicker the antifouling layer 7, the more the deterioration of the antifouling property due to wear tends to be suppressed. The thickness of the antifouling layer is preferably 3 nm or more, and may be 5 nm or more or 7 nm or more. On the other hand, from the viewpoint of forming a surface shape on the surface of the antifouling layer that reflects the uneven shape of the hard coat layer surface and enhancing the antiglare property, the thickness of the antifouling layer is preferably 30 nm or less, more preferably 20 nm or less, and may be 15 nm or less.

To improve contamination prevention and contaminant removal properties, the water contact angle of the antifouling layer 7 is preferably 100° or more, more preferably 102° or more, and even more preferably 105° or more. The larger the water contact angle, the higher the water repellency, and the more likely it is that the effect of preventing adhesion of contaminants and the ability to remove contaminants will improve. The water contact angle is generally 125° or less.

<Surface shape of anti-reflection film>
The arithmetic mean height Sa calculated from the three-dimensional surface properties of a 1 μm×1 μm region of the surface of the antireflection film, i.e., the surface of the antifouling layer 7, is preferably 2.0 nm or more. The arithmetic mean height Sa of the surface of the antifouling layer 7 is more preferably 2.3 nm or more, even more preferably 2.5 nm or more, and may be 2.7 nm or more, 2.9 nm or more, or 3.0 nm or more. The arithmetic mean height Sa of the surface of the antifouling layer 7 is preferably 10 nm or less, more preferably 8.0 nm or less, even more preferably 7.0 nm or less, and may be 6.0 nm or less, 5.5 nm or less, 5.0 nm or less, or 4.5 nm or less.

Because the antireflection layer 5 and the antifouling layer 7 formed on the hard coat layer 11 have a small thickness, the surface of the antifouling layer 7 is likely to have an uneven shape that reflects the surface shape of the hard coat layer 11. Therefore, by adjusting the particle size and blending amount of the particles contained in the hard coat layer 11 to adjust the surface shape of the hard coat layer, an antireflection film having the above Sa can be obtained. In addition, the surface shape may be adjusted by subjecting the hard coat layer 11 to a surface treatment such as vacuum plasma treatment.

When the arithmetic mean height Sa of the surface of the antifouling layer 7 is within the above range, the surface of the hard coat layer 11 also has a similar Sa, so that the antireflection film has excellent adhesion between the hard coat layer 11 and the antireflection layer 5 and the antifouling layer 7.

The average spacing RSm of the irregularities on the surface of the antifouling layer 7 calculated from a roughness curve with a measurement length of 12 mm is preferably 120 μm or more. The RSm of the surface of the antifouling layer 7 is more preferably 130 μm or more, and may be 140 μm or more or 150 μm or more. When the RSm of the surface of the antireflection film is in the above range, the white blur of reflected light during black display is reduced, and a display with excellent contrast in bright areas can be realized. The average spacing RSm of the irregularities on the surface of the antifouling layer 7 is preferably 250 μm or less, more preferably 220 μm or less, even more preferably 200 μm or less, and may be 180 μm or less or 170 μm or less.

The arithmetic mean roughness Ra of the surface of the antifouling layer 7 calculated from a roughness curve with a measurement length of 12 mm is preferably 30 to 500 nm, more preferably 50 to 400 nm, even more preferably 60 to 300 nm, and may be 70 to 250 nm or 80 to 200 nm. When the surface Ra of the antireflection film is in the above range, it tends to have excellent antiglare properties.

The surface of the antifouling layer 7 is prone to forming an uneven shape that reflects the surface shape of the hard coat layer 11, so by adjusting the particle size and amount of the particles contained in the hard coat layer 11, etc., it is possible to obtain an antireflection film having the above RSm and Ra.

[Usage of anti-reflection film]
Antireflection films are used by being disposed on the surface of image display devices such as liquid crystal displays, organic EL displays, etc. For example, by disposing an antireflection film on the viewing side surface of a panel including an image display medium such as a liquid crystal cell or an organic EL cell, the reflection of external light can be reduced and the visibility of the image display device can be improved.

The anti-reflection film may be used as is by attaching it to the surface of an image display device, or may be laminated with another film. For example, a polarizing plate with an anti-reflection layer can be formed by attaching a polarizer to the surface of the transparent film substrate 10 on which the hard coat layer is not formed.

An anti-reflection film having a surface arithmetic mean height Sa and mean spacing RSm of irregularities within the above ranges is less likely to produce white blurring of reflected light, has excellent visibility, and has excellent adhesion between the hard coat layer 11 and the anti-reflection layer 5 and anti-fouling layer 7. An image display device equipped with this anti-reflection film has high contrast in bright areas and excellent visibility, and is less likely to suffer from peeling or wear of the anti-reflection layer and anti-fouling layer, so that excellent visibility and anti-fouling properties continue even when the device is used for a long period of time.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[Example 1]
<Preparation of Antiglare Hard Coat Film>
(Preparation of Hard Coat Composition)
A 60% by weight dispersion of colloidal silica (nanosilica) having an average primary particle size of 40 nm was added to a urethane acrylate-based photocurable resin composition (Beamset 577, manufactured by Arakawa Chemical Industries, Ltd.) so that the amount of silica particles per 100 parts by weight of the resin component was 40 parts by weight. 100 parts by weight of the solid content of this solution was mixed with 5.0 parts by weight of silicone particles ("Tospearl 130" manufactured by Momentive Performance Materials Japan, average particle size 3.0 μm, refractive index 1.43, true specific gravity 1.32); 2.0 parts by weight of organic smectite ("Sumecton SAN" manufactured by Kunimine Industries) as a thixotropic agent; 3.0 parts by weight of a photopolymerization initiator ("OMNIRAD907" manufactured by IGM Resins); and 0.15 parts by weight of a silicone-based leveling agent ("Polyflow LE303" manufactured by Kyoeisha Chemical Co., Ltd.), and diluted with ethyl acetate to prepare a hard coat composition with a solid content concentration of 30% by weight.

<Formation of hard coat layer>
The above hard coat composition was applied to a 60 μm-thick triacetyl cellulose (TAC) film (FUJITAC TG60UL, manufactured by FUJIFILM Corporation) using a Comma Coater (registered trademark) and heated at 60° C. for 1 minute. Thereafter, ultraviolet rays were irradiated from a high-pressure mercury lamp at an integrated light quantity of 300 mJ/cm ² to cure the coating layer, thereby forming an antiglare hard coat layer having a thickness of 6.0 μm.

<Formation of primer layer and antireflection layer>
The triacetyl cellulose film on which the hard coat layer was formed was introduced into a roll-to-roll sputtering deposition apparatus, and while the film was running, the surface of the hard coat layer was bombarded (plasma treatment with Ar gas), and then a 1.5 nm ITO layer was formed as a primer layer, and a 10.1 nm Nb ₂ O ₅ layer, a 27.5 nm SiO ₂ layer, a 105.0 nm Nb ₂ O ₅ layer, and an 83.5 nm SiO ₂ layer were formed thereon in this order. A Si target was used for the deposition of the primer layer and the SiO ₂ layer, and a Nb target was used for the deposition of the Nb ₂ O ₅ layer. In the deposition of the SiO ₂ layer and the Nb ₂ O ₅ layer, the amount of oxygen introduced was adjusted by plasma emission monitoring (PEM) control so that the deposition mode was maintained in the transition region.

<Formation of antifouling layer>
An antifouling coating agent having a solid content of 20% containing a perfluoropolyether group-containing alkoxysilane compound (manufactured by Shin-Etsu Chemical Co., Ltd., "KY1903-1") was dried and solidified and used as a deposition source to form an antifouling layer having a thickness of 8 nm on the antireflection layer by a vacuum deposition method at a heating temperature of 260°C.

[Example 2, Comparative Examples 1 to 5]
In the preparation of the hard coat composition, the type and amount of the microparticles, and the particle size and amount of the silica particles were changed as shown in Table 1, but the same procedures as in Example 1 were carried out to prepare an antiglare hard coat film, form a primer layer and an antireflection layer, and form an antifouling layer. In Comparative Example 2, crosslinked polymethylmethacrylate (PMMA) particles ("Technopolymer SSX-103" manufactured by Sekisui Chemical Co., Ltd.; average particle size 3.0 μm, refractive index 1.50, specific gravity 1.20) were used as the microparticles. In Comparative Examples 3 to 5, silicone particles and crosslinked PMMA particles were used in combination as the microparticles.

[evaluation]
<Surface shape measurement>
A 1.3 mm-thick slide glass ("MICRO SLIDE GLASS" 45 x 50 mm, manufactured by MATSUNAMI) was attached to the triacetyl cellulose film side of the antireflection film (the side on which the antireflection layer was not formed) via a 20 μm-thick acrylic adhesive to prepare a measurement sample.

The roughness curve of the antifouling layer surface was measured under the following conditions using a stylus-type surface roughness tester (high-precision microprofile tester "Surfcorder ET4000" manufactured by Kosaka Laboratory) having a measuring needle with a tip (diamond) having a radius of curvature R = 2 μm, and the arithmetic mean roughness Ra and the average length RSm of the roughness curve elements were determined in accordance with JIS B0601:2001.
Scanning speed: 0.1 mm/sec Measurement length: 12 mm
Cutoff value: 0.8 mm

The three-dimensional surface properties of the antifouling layer surface were measured using an atomic force microscope ("Dimension 3100" manufactured by Bruker, controller: Nanoscope V) under the following conditions, and the arithmetic mean height Sa was determined in accordance with ISO 25178.
Measurement mode: Tapping mode Cantilever: Si single crystal Measurement field of view: 1 μm x 1 μm

<Reflective visibility>
A black acrylic plate was attached to the triacetyl cellulose film side of the anti-reflection film (non-anti-reflection layer side) via an acrylic adhesive having a thickness of 20 μm. The anti-reflection film side of this sample was irradiated with light from a desk light at an illuminance of 1000 lux from a distance of 30 cm, and the reflected light from the anti-reflection film was visually confirmed. The area around the regular reflection light was visually observed as black (see "Example 1" in Figure 2), and the whole was visually observed as white and blurred (see "Comparative Example 2" in Figure 2).

<Adhesion>
A 1.3 mm thick glass plate was attached to the triacetyl cellulose film side of the antireflection film (the side on which the antireflection layer was not formed) via a 25 μm thick acrylic adhesive, and the sample was placed in an Iwasaki Electric Co., Ltd. weather resistance accelerated tester "Eye Super UV Tester SUV-W161" and subjected to an accelerated weather resistance test for 120 hours under the conditions of a black panel temperature of 80°C and a metal halide lamp irradiation intensity of 150 mW/ ^cm2 .

After the accelerated weathering test, the surface of the antifouling layer side of the sample was scored at 1 mm intervals to form a grid of 100 squares, and an adhesion test was carried out in accordance with the cross-cut test method (paint adhesion test) of JIS K 5400 8.5:1990. The number of squares where the antifouling layer and anti-reflective layer had peeled off over an area of 1/4 or more of the grid area was counted. If the number of peeled grids was 10 or more, it was marked as ×, and if it was 9 or less, it was marked as ◯.

[Evaluation results]
The configurations of the hard coat layers of the antireflection films of the above-mentioned Examples and Comparative Examples (types of fine particles in the hard coat layer and amounts per 100 parts by weight of binder resin) and the evaluation results of the antireflection films are shown in Table 1. Observation photographs of reflected light of the antireflection films of Example 1 and Comparative Example 2 are shown in FIG.

Example 1, which used 5 parts by weight of silicone particles as microparticles and 40 parts by weight of silica particles with a particle diameter of 40 nm as nanoparticles, had high adhesion between the hard coat layer and the anti-reflection layer and the anti-fouling layer, and had good visibility without white blurring of reflected light. The same was true for Example 2, in which the amount of nanosilica particles was changed to 30 parts by weight. Example 1, which used 40 parts by weight of silica particles with a particle diameter of 10 nm as nanoparticles, had a small Sa and insufficient adhesion between the hard coat layer and the anti-reflection layer and the anti-fouling layer.

Comparative Example 4, which contained 3 parts by weight of silicone particles and 1 part by weight of PMMA particles as microparticles and 20 parts by weight of silica particles with a particle diameter of 40 nm as nanoparticles, had a small Sa and insufficient adhesion, similar to Comparative Example 1. Comparative Example 5, in which the amount of nanoparticles was changed to 10 parts by weight, had an even smaller Sa than Comparative Example 5 and insufficient adhesion.

In Comparative Example 1, the particle diameter of the nanoparticles was small, and in Comparative Examples 4 and 5, the amount of nanoparticles was small, so nanoscale irregularities were not sufficiently formed on the surface of the hard coat layer, and it is believed that the adhesion was inferior to that of Examples 1 and 2.

In Comparative Example 2, which contained 15 parts by weight of PMMA particles as microparticles and 40 parts by weight of silica particles with a particle diameter of 40 nm as nanoparticles, the adhesion between the hard coat layer and the anti-reflection layer and the anti-soiling layer was good, but white blur was observed in the reflected light, and visibility was inferior to Examples 1 and 2. In Comparative Example 2, the amount of microparticles was large, so the in-plane density of the microparticles in the hard coat layer was high and the average spacing RSm of the irregularities was small, which is thought to be the cause of the white blur in the reflected light.

In Comparative Example 3, in which 3 parts by weight of silicone particles and 1 part by weight of PMMA particles were blended as microparticles, white blur was observed in the reflected light, as in Comparative Example 2. In Comparative Example 3, as in Comparative Example 2, it is believed that the cause of the white blur is the small RSm. In Comparative Example 3, the blend of microparticles is the same as in Comparative Examples 4 and 5, and although the amount of microparticles is smaller than in Examples 1 and 2, the average spacing RSm of the irregularities was smaller. In Comparative Example 3, PMMA particles, which have a relatively small specific gravity, tend to be present near the surface of the hard coat layer, and PMMA microparticles and nanosilica particles are densely packed near the surface of the hard coat layer, which is thought to be why RSm was small.

Comparing the above examples and comparative examples, it can be seen that by having both microparticles and nanoparticles in the hard coat layer, adjusting the type, particle size, and blending amount of these particles, and increasing Sa, which is an index of surface unevenness on the nm scale, and increasing RSm, which is an index of the unevenness period on the μm scale, an anti-reflective film can be obtained that has excellent adhesion between the hard coat layer and the anti-reflection layer and anti-fouling layer, has little white blurring of reflected light, and is excellent in visibility.

REFERENCE SIGNS LIST 1 Hard coat film 10 Transparent film substrate 11 Hard coat layer 3 Primer layer 5 Anti-reflection layer 51, 53 High refractive index layer 52, 54 Low refractive index layer 7 Anti-soiling layer 101 Anti-reflection film

Claims (10)

A hard-coat film having a hard-coat layer on one main surface of a transparent film substrate, and an anti-reflection layer and an anti-fouling layer provided in this order on the hard-coat layer,
the antireflection layer is made of a laminate of a plurality of thin films having different refractive indices, each of which has a thickness of 5 to 200 nm;
the hard coat layer comprises a binder resin, microparticles having an average particle size of 1 to 8 μm, and nanoparticles having an average primary particle size of 100 nm or less;
The antifouling layer has a thickness of 2 to 50 nm,
The surface of the antifouling layer is
the average spacing between projections and recesses RSm calculated in accordance with JIS B0601 from a roughness curve of the antifouling layer measured by a stylus method over a measurement length of 12 mm is 120 to 250 μm ;
The arithmetic mean height Sa calculated in accordance with ISO 25178 from the three-dimensional surface properties of a 1 μm × 1 μm area of the antifouling layer measured by an atomic force microscope is 2.0 to 10 nm ;
Anti-reflective film. The anti-reflection film according to claim 1, wherein the specific gravity of the microparticles is 1.25 or more. The anti-reflection film according to claim 2, wherein the amount of particles having a specific gravity of 1.25 or more is 85 parts by weight or more out of a total of 100 parts by weight of the microparticles. The anti-reflection film according to any one of claims 1 to 3, wherein the amount of the microparticles in the hard coat layer is 0.5 to 12 parts by weight per 100 parts by weight of the binder resin. The anti-reflection film according to any one of claims 1 to 3, wherein the amount of the nanoparticles in the hard coat layer is 25 to 120 parts by weight per 100 parts by weight of the binder. The anti-reflection film according to any one of claims 1 to 3, wherein the average primary particle diameter of the nanoparticles is 15 nm or more. The antireflection film according to any one of claims 1 to 3, wherein the surface of the antifouling layer has an arithmetic mean roughness Ra of 30 to 500 nm calculated in accordance with JIS B0601 from a roughness curve of the antifouling layer measured by a stylus method over a measurement length of 12 mm. The anti-reflection film according to any one of claims 1 to 3, wherein the anti-reflection layer is a sputtered film. The anti-reflection film according to any one of claims 1 to 3, comprising a primer layer made of an inorganic oxide between the hard coat layer and the anti-reflection layer. An image display device, comprising an anti-reflection film according to any one of claims 1 to 3 disposed on a viewing side surface of an image display medium.

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