Antireflection film and image display device

Abstract

The present application relates to an anti-reflection film and an image display device. An anti-reflection film (100) includes an anti-reflection layer (5) including a plurality of films on a film substrate (1). The anti-reflection layer is a multi-layer film including at least one of a low-refractive layer and a high-refractive layer as a film. For the anti-reflection film, the normal reflection light of a D65 light source irradiated from the anti-reflection layer side preferably satisfies: (A) the apparent reflectance Y2 of the normal reflection light of 2° incident light and the apparent reflectance Y θ of the normal reflection light of θ° incident light satisfy Y θ / Y2≤6.0; and (B) the chromaticity index a * 2 of the normal reflection light of 2° incident light and the chromaticity index a * 2 of the normal reflection light of θ° incident light satisfy a * θ 2≤6.0. * θ of the normal reflection light of 5° to 50° incident light satisfy {(a * 2-a * θ ) 2 +(b * 2-b * θ ) 2} 1 / 2 ≤6.0.

Description

Technical Field

[0001] This invention relates to anti-reflective films and image display devices. Background Technology

[0002] Anti-reflective films are sometimes applied to the surface of image display devices such as liquid crystal displays (LCDs) and organic EL displays to improve the visual legibility of displayed images. An anti-reflective film consists of an anti-reflective layer comprising multiple thin films with different refractive indices on a film substrate.

[0003] The light reflection characteristics imparted by an antireflective layer are typically evaluated using apparent reflectance (Y-value). Apparent reflectance is reduced by decreasing the reflectance near 550 nm, a wavelength with higher spectral luminous efficiency. For antireflective films, not only is low apparent reflectance required, but also a neutral hue of the reflected light.

[0004] Antireflective films have been proposed that control not only the reflective properties during frontal visual recognition but also the properties of reflected light in oblique directions. For example, Patent Document 1 discloses an antireflective film in which the hue of orthogonally reflected light from incident light at all angles from 5 to 45° is within a specified range. Patent Document 2 proposes reducing the chromatic aberration of reflected light in the 5 to 45° range by performing optical design to minimize the chromaticity in the range of incident angles from 20 to 30°.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-138662

[0008] Patent Document 2: Japanese Patent Application Publication No. 2016-177183 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Previous anti-reflective films could reduce reflectivity in specific visual recognition directions, but it was difficult to minimize the variation in reflectivity across a wide range of visual recognition directions and to reduce the variation in the color of reflected light.

[0011] Solution for solving the problem

[0012] The antireflective film has an antireflective layer comprising multiple thin films on a film substrate. The antireflective layer is a multilayer film comprising at least one low-refractive-index layer and one high-refractive-index layer as thin films. The positively reflected light from a D65 light source irradiated from the antireflective layer side of the antireflective film of the present invention meets the specified characteristics.

[0013] The apparent reflectance Y of the incident light at θ° is... θ Preferably, Y satisfies the following condition: within any angle θ in the range of 5–50°. θ / Y2≤6.0. Y2 is the perceived reflectance of the orthographically reflected light from a 2° incident light source. The chromaticity index a of the orthographically reflected light from a 2° incident light source. * θ and b * θ Preferably, it satisfies the following condition: within any angle θ in the range of 5–50°, Δa * b * ={(a * 2-a * θ ) 2 +(b * 2-b * θ ) 2} 1 / 2 The chromaticity difference Δa shown * b * Satisfy Δa * b * ≤6.0.

[0014] The effects of the invention

[0015] By using the anti-reflective film of the present invention, it is possible to achieve image display with minimal changes in the characteristics of reflected light caused by the direction of visual recognition. Attached Figure Description

[0016] Figure 1 A cross-sectional view showing the stacking method of the anti-reflective film.

[0017] Figure 2 For chroma C * and color difference Δa * b * The diagram is for illustrative purposes.

[0018] Explanation of reference numerals in the attached figures

[0019] 1. Thin film substrate

[0020] 3. Primer layer

[0021] 5 Anti-reflective layer

[0022] Low refractive index layers 51, 53, and 55

[0023] High refractive index layers 52, 54, and 56

[0024] 100% Anti-reflective film Detailed Implementation

[0025] [Composition of anti-reflective film]

[0026] Figure 1 A cross-sectional view schematically illustrating the structure of an antireflective film according to one embodiment is shown. The antireflective film 100 has an antireflective layer 5 on a film substrate 1. The antireflective layer 5 is a stack of multiple films. Figure 1 The antireflective layer 5 shown is a multilayer film consisting of six thin films, which are formed by alternately stacking high refractive index layers 51, 53, 55 and low refractive index layers 52, 54, 56 from the side of the thin film substrate 1.

[0027] <Thin Film Substrate>

[0028] The thin film substrate 1 includes a flexible thin film 10. The thickness of the thin film substrate 1 is not particularly limited, but from the viewpoints of strength, processability and other operability, as well as thinness, it is preferably about 5 to 300 μm, more preferably 10 to 250 μm, and even more preferably 20 to 200 μm.

[0029] As the film 10, a transparent film is typically used. The visible light transmittance of the transparent film is preferably 80% or more, more preferably 90% or more. As the resin material constituting the film 10, examples include thermoplastic resins with excellent transparency, mechanical strength, and thermal stability. Specific examples of such thermoplastic resins include cellulose resins such as cellulose triacetate, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof.

[0030] Preferably, a hard coating layer 11 is provided on the side of the antireflective layer 5 of the film 10. By providing the hard coating layer 11 on the surface of the film 10, the mechanical properties of the antireflective film, such as hardness and elastic modulus, can be improved. The hard coating layer 11 preferably has high surface hardness and excellent scratch resistance.

[0031] Examples of curable resins include thermosetting resins, UV-curing resins, and electron beam curing resins. Types of curable resins include polyester-based, acrylic-based, urethane-based, acrylic urethane-based, amide-based, silicone-based, silicate-based, epoxy-based, melamine-based, oxetane-based, and acrylic urethane-based resins. One or more of these curable resins can be appropriately selected for use.

[0032] The hard coating may contain microparticles. For example, the surface of the hard coating 11 can be made uneven by including microparticles in the hard coating, thereby achieving anti-glare properties. The microparticles used to impart anti-glare properties are preferably microparticles with a particle size in the μm range. The average particle size of the microparticles is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. By forming fine unevenness on the surface of the hard coating 11, there is a tendency to improve the adhesion to the anti-reflective layer 5 (or primer layer 3) disposed thereon. The microparticles used to form unevenness on the surface of the hard coating 11 with excellent adhesion to films such as the primer layer 3 and the anti-reflective layer 5 are preferably nanoparticles with a particle size in the nm range. The average particle size of the nanoparticles is preferably 10 to 150 nm, more preferably 20 to 100 nm, and even more preferably 25 to 80 nm.

[0033] The hard coating 11 can be formed, for example, by coating a solution containing a curable resin onto the film 10. Preferably, a polymerization initiator is incorporated into the solution used to form the hard coating. To form an anti-glare hard coating containing microparticles, it is preferable to coat a transparent film with a solution containing not only the curable resin but also the aforementioned microparticles. The solution may contain additives such as leveling agents, thixotropic agents, and antistatic agents.

[0034] The thickness of the hard coating 11 is not particularly limited, but to achieve high hardness, it is preferably 0.5 μm or more, more preferably 1 μm or more. Considering the ease of coating formation, the thickness of the hard coating is preferably 15 μm or less, more preferably 10 μm or less.

[0035] <Primer layer>

[0036] A primer layer 3 may be provided on the thin film substrate 1 for purposes such as improving the adhesion of the antireflective layer 5. Examples of materials constituting the primer layer 3 include metals such as silicon, nickel, chromium, indium, tin, gold, silver, platinum, zinc, titanium, tungsten, aluminum, zirconium, and palladium; alloys of these metals; oxides, fluorides, sulfides, or nitrides of these metals; etc. Preferably, the primer layer is an inorganic oxide layer, which can be an oxide with a lower oxygen content than the stoichiometric value.

[0037] The thickness of the primer layer 3 is, for example, about 1 to 20 nm, preferably 2 to 15 nm, and more preferably 3 to 15 nm. When the thickness of the primer layer is within the above range, both improved adhesion and light transmittance can be achieved.

[0038] Anti-reflective layer

[0039] The antireflective layer 5 is a stack of multiple thin films with different refractive indices. It should be noted that, unless otherwise specified, "refractive index" in this specification refers to the refractive index at a wavelength of 550 nm.

[0040] By stacking multiple thin films with different refractive indices, reflectivity can be reduced over a wide wavelength range of visible light. The thin film constituting the antireflective layer 5 is preferably a ceramic material comprising oxides, nitrides, fluorides, or other metals or semi-metals. The thin film constituting the antireflective layer 5 can be a film whose refractive index is adjusted by including high- or low-refractive-index particles in the resin binder.

[0041] Low refractive index layers 52, 54, and 56 have, for example, a refractive index of 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, and lanthanum fluoride.

[0042] The high refractive index layers 51, 53, and 53 have a refractive index of 1.8 or higher, preferably 1.9 or higher. 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), silicon nitride, and silicon oxynitride.

[0043] The antireflective layer 5 is preferably an alternating laminate of a high-refractive-index layer and a low-refractive-index layer. To reduce reflection at the air interface, the thin film 56, which serves as the outermost layer (the layer furthest from the thin film substrate 1) of the antireflective layer 5, is preferably a low-refractive-index layer. In addition to the low-refractive-index and high-refractive-index layers, the antireflective layer may also include an intermediate-refractive-index layer having a refractive index between the high-refractive-index and low-refractive-index layers. The refractive index of the intermediate-refractive-index layer is, for example, approximately 1.6 to 1.9.

[0044] The thickness of the high-refractive-index layer and the low-refractive-index layer is approximately 5–200 nm, preferably approximately 10–150 nm. The thickness of each layer is designed based on the refractive index and layer composition to minimize the reflectivity of visible light.

[0045] The film formation method constituting the antireflective layer 5 is not particularly limited and can be either wet coating or dry coating. From the perspective of forming a film with uniform thickness, dry coating methods such as vacuum evaporation, CVD, sputtering, and electron beam evaporation are preferred. Among these, sputtering is preferred from the perspective of excellent film thickness uniformity.

[0046] <Additional layer on the anti-reflective layer>

[0047] The anti-reflective film may have additional functional layers on the anti-reflective layer 5. For example, for the purpose of easily preventing pollution from the external environment and easily removing attached pollutants, an anti-fouling layer (not shown) may be provided on the anti-reflective layer 5.

[0048] When an antifouling layer is provided on the surface of the antireflective film, from the viewpoint of reducing reflection at the interface, it is preferable that the refractive index difference between the outermost low-refractive-index layer 56 of the antireflective layer 5 and the antifouling layer is small. The refractive index of the antifouling layer is preferably 1.6 or less, more preferably 1.55 or less. As the material for the antifouling layer, fluorine-based silane compounds, fluorine-based organic compounds, etc., are preferred. The antifouling layer can be formed by wet coating methods such as reverse coating, mold coating, and gravure coating, or dry coating methods such as vacuum evaporation and CVD. The thickness of the antifouling layer is typically about 1 to 100 nm, preferably 2 to 50 nm, more preferably 3 to 30 nm.

[0049] [Properties of reflected light]

[0050] The antireflective film is preferably characterized by minimal changes in the properties of reflected light caused by the visual viewing angle. The properties of light can be evaluated using three indicators: hue, chroma, and brightness. The properties of reflected light depend on the spectrum of the irradiated light. The following describes the characteristics of reflected light when the antireflective layer 5 side of the antireflective film (opposite to the film substrate 1) is irradiated with a CIE standard light source D65.

[0051] When incident light from the antireflective layer 5 side and measuring the reflected light, the reflectance of visible light on the back side (the interface between the thin film substrate 1 and air) is about 4%, with most of it being reflected light from the back side. To eliminate the influence of back reflection, a sample with a black film and a black plate bonded to the back side of the thin film substrate 1 (the side opposite to the formation surface of the antireflective layer 5) was used in the evaluation of the reflected light characteristics.

[0052] <Visual reflectivity>

[0053] Visual reflectance Y is an index representing the brightness of reflected light, and is the Y value in the XYZ color system (or Yxy color system). Visual reflectance Y is normalized such that the Y value of a perfectly reflective object is 100%.

[0054] Typically, antireflective films are designed to minimize reflectivity when light is incident from the front, and there is a tendency for the reflectivity of orthographically reflected light to increase as the incident angle θ increases. From the viewpoint of reducing the difference in the amount of reflected light accompanying changes in the incident angle (visual recognition direction), the perceived reflectivity Y2 of orthographically reflected light with 2° incident light and the perceived reflectivity Y of orthographically reflected light with θ° incident light are preferred. θ The ratio of Y θ / Y2 is less than 6.0 for any incident angle θ ranging from 5 to 50°. θ / Y2 is more preferably 5.5 or less, further preferably 5.0 or less, and particularly preferably 4.5 or less in the range of θ = 5 to 50°.

[0055] The perceived reflectance Y2 of the orthogonally reflected light from a 2° incident light source is preferably 1.0% or less, more preferably 0.9% or less, and even more preferably 0.8% or less. Y2 is preferably as small as possible, but if the optical design is carried out in a way that reduces the reflectance relative to the incident light from a specific direction, the change in reflectance with changes in the incident angle θ can sometimes be large. Therefore, Y2 can be 0.1% or more, 0.2% or more, or 0.3% or more.

[0056] From the perspective that reducing ambient light reflection and thus improving visual recognition can be achieved regardless of the direction of visual recognition, the visual reflectivity Y of the orthogonally reflected light of incident light at θ° is... θ The percentage is preferably 3.0% or less, more preferably 2.5% or less, in any angle θ within the range of 5 to 50°.

[0057] <Color Index>

[0058] In CIELAB color space (L * a * b * In the color space, L * Brightness is expressed using the chromaticity index α. * and b * Indicates hue and chroma. * and b * When the value is 0, there is no color; +a * Indicates the red direction, -a * Indicates the green direction, +b * Indicates the yellow direction, -b * Indicates the blue direction. In Figure 2 The a shown * b * In a plane, the radial direction corresponds to chroma, and the circumferential direction corresponds to hue.

[0059] By C * ={(a * ) 2 +(b * ) 2} 1 / 2 The defined chroma represents the degree of coloration, C * When C is 0, it is colorless. * The larger the value, the larger the shading. Project the color space onto a. * b * The greater the distance between two points in a two-dimensional space, the greater the difference in the colors of the two lights.

[0060] From the perspective of reducing the color difference of reflected light accompanying changes in the incident angle (visual recognition direction), the chromaticity index a of the orthogonal reflected light with a 2° incident angle is... * 2 and b *2. The chromaticity index a of the normally reflected light from the incident light at θ° * θ and b * θ Preferably, Δa is satisfied within any angle θ in the range of θ = 5 to 50°. * b * ≤6.0. For example... Figure 2 As shown, Δa * b * The positively reflected light (A) of the incident light at 2° and the positively reflected light of the incident light at θ°, at a * b * The distance in the plane is given by Δa * b * ={(a * 2-a * θ ) 2 +(b * 2-b * θ ) 2} 1 / 2 Indicated. Hereafter, Δa will sometimes be used. * b * This is called "chromaticity difference". Chromaticity difference Δa * b * More preferably, 5.5 or less, further preferably 5.0 or less, and particularly preferably 4.5 or less, within the range of θ = 5 to 50°. Δa * b * It can be below 4.0, below 3.5, or below 3.0.

[0061] The chroma C of the orthogonally reflected light from a 2° incident light * Preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. The chroma C of the orthotropically reflected light from a 2° incident light. * It can be below 2.5 or below 2.0.

[0062] From the perspective that reflected light can be a neutral color regardless of the direction of visual perception, thus suppressing chromaticity, the chroma C of the orthogonal reflected light of incident light at θ° is... * The angle θ is preferably 9.0 or less, more preferably 7.0 or less, and particularly preferably 5.0 or less, in any angle θ within the range of 5 to 50°.

[0063] <Optical Design of Anti-reflective Layer>

[0064] By appropriately designing the thickness of the thin film constituting the antireflective layer, an antireflective film with the aforementioned properties can be obtained. The characteristics (spectrum) of the reflected light can be accurately evaluated through optical model calculations. Known methods for calculating the reflection spectrum of multilayer optical thin films through optical calculations include repeatedly applying the thin film interference formula to each interface of the film and summing up all the waves after multiple reflections; and considering the boundary conditions of Maxwell's equations and calculating the reflection spectrum using the transmission matrix.

[0065] Calculate the reflection spectrum of the normally reflected light when incident on a D65 light source at multiple incident angles θ, and calculate the perceived reflectance Y and chromaticity index a for each θ based on the reflection spectrum. * and b * By changing the thickness of the film constituting the antireflective layer and repeatedly performing these optical calculations, the set film thickness can be optimized to obtain an antireflective film that satisfies the aforementioned characteristics in terms of reflected light.

[0066] When the number of thin films constituting the antireflective layer is small, it is difficult to design the film thickness to be within any range of θ = 5 to 50°. θ / Y2 and Δa * b * Both of these decrease. As shown in the following embodiments, when the number of antireflective layers (the total number of films) is large, regardless of the materials constituting the antireflective layer, the film thickness can be designed to be Y. θ / Y2 and Δa * b * Both of these become smaller. The anti-reflective layer preferably comprises five or more layers, including low-refractive-index and high-refractive-index layers, and more preferably three or more low-refractive-index layers. More preferably, the anti-reflective layer comprises six or more layers, including low-refractive-index and high-refractive-index layers.

[0067] From the perspective of reducing the visual reflectivity Y, the anti-reflective layer preferably has a large refractive index difference between the low-refractive-index layer and the high-refractive-index layer. The refractive index difference between the low-refractive-index layer and the high-refractive-index layer is preferably 0.30 or more, more preferably 0.35 or more, and even more preferably 0.40 or more.

[0068] The refractive index of the low-refractive-index layer is preferably 1.50 or less, more preferably 1.48 or less, and even more preferably 1.47 or less. The refractive index of the low-refractive-index layer is typically 1.00 or more, and can be 1.20 or more, 1.30 or more, or 1.35 or more. The refractive index of the high-refractive-index layer is preferably 1.80 or more, more preferably 1.84 or more, and even more preferably 1.87 or more. The refractive index of the high-refractive-index layer is typically 3.00 or less, and can be 2.50 or less, 2.40 or less, or 2.30 or less. The refractive index of the high-refractive-index layer at a wavelength of 400 nm is preferably 1.84 to 2.55, more preferably 1.88 to 2.50. The refractive index of the high-refractive-index layer at a wavelength of 700 nm is preferably 1.78 to 2.35, more preferably 1.80 to 2.30.

[0069] If the reflectance near the wavelength of 550nm is reduced, there is a tendency for the perceived reflectance Y to decrease. On the other hand, there is a tendency that if the optical design is carried out in a way that minimizes the reflectance near the wavelength of 550nm, the reflectance at other wavelengths will increase, and the chromaticity index a of the reflected light will decrease. * and / or b * Enlarged, reflected light colored.

[0070] To reduce the coloration of reflected light, it is preferable to have a uniform reflectivity across a wide wavelength range of visible light. When the wavelength dependence of the refractive index of the thin film constituting the antireflective layer is small, there is a tendency for the change in reflectivity due to wavelength to be smaller, and the chroma of the reflected light to be reduced (neutralized). Even when using materials with large wavelength dispersion of the refractive index, optical designs can be implemented in a way that reduces the coloration of reflected light; however, if the film thickness varies slightly, coloration of reflected light can sometimes occur. From the viewpoint of increasing the freedom of optical design and ensuring the allowable range of film thickness (process margin), the thin film constituting the antireflective layer preferably has a small wavelength dispersion of the refractive index (the change in refractive index that varies with wavelength).

[0071] Abbe number ν of high refractive index layer D Preferably 20 or more, more preferably 23 or more, and even more preferably 25 or more. Regarding the Abbe number ν... D Using the refractive index n at a wavelength of 589nm D The refractive index n at a wavelength of 486nm F and the refractive index n at a wavelength of 656nm C , by ν D =(n D -1) / (n F -n C () represents the Abbe number ν. D The larger the Abbe number, the smaller the wavelength dispersion. The Abbe number ν of a high-refractive-index layer... D There is no specific upper limit; for common ceramic materials, there is the Abbe number ν.D The larger the refractive index (the smaller the wavelength dispersion), the smaller the refractive index tends to be. From the perspective of maximizing the refractive index of the high-refractive-index layer to reduce reflectivity, the Abbe number ν of the high-refractive-index layer... D Preferably 40 or less, more preferably 30 or less, and even more preferably 28 or less.

[0072] For the anti-reflective layer, the thickness of each film can be set by considering the refractive index, number of layers, etc., so that the reflected light meets the above-mentioned characteristics. As mentioned above, the film thickness of the anti-reflective layer can be optimized by calculating the reflection spectrum of the anti-reflective film using an optical model.

[0073] How to use anti-reflective film

[0074] Anti-reflective films are applied to the surface of image display devices such as liquid crystal displays (LCDs) and organic EL displays (OLEDs). For example, by applying an anti-reflective film to the visual recognition side surface of a panel containing image display media such as liquid crystal cells or organic EL cells, the reflection of external light can be reduced, thereby improving the visual recognition of the image display device. Anti-reflective films can also be laminated with other films. For example, by attaching a polarizing element to the side of the film substrate 1 opposite to the surface where the anti-reflective layer is formed, a polarizing plate with an anti-reflective layer can be formed.

[0075] The anti-reflective film of the present invention has a small difference in the characteristics of reflected light caused by the visual recognition direction. Therefore, even when the visual recognition direction is changed, the change in the characteristics of reflected light is small, which can make the image display device uniform.

[0076] Example

[0077] The following are examples of calculating the characteristics of reflected light from an anti-reflective film using optical models.

[0078] [Methods for evaluating the properties of reflected light]

[0079] Within the wavelength range of 380–780 nm, with 1 nm intervals, the normal reflectance of the antireflective film when incident at an incident angle θ° with wavelength λ is calculated using an optical model, and the reflectance spectrum R(λ) is obtained.

[0080] Multiply the obtained positive reflectance spectrum R(λ) by the spectrum of the CIE standard illuminant D65 to obtain the spectrum of the reflected light. Based on the obtained reflected light spectrum, calculate the visual reflectance Y and the chromaticity index a of the CIELAB colorimetric system. * and b * According to a * and b * The chroma C is calculated from the value. * ={(a * ) 2+(b * ) 2} 1 / 2 .

[0081] The above evaluation was performed at 5° intervals within the range of incident angles θ = 5 to 50°, with an incident angle of 2°. The apparent reflectance Y2 of the orthographically reflected light with an incident angle of 2° and the apparent reflectance Y of the orthographically reflected light with an incident angle of θ° were then calculated. θ The ratio of Y θ The positively reflected light of incident light at angles of y2 and 2° and the positively reflected light of incident light at angle θ° are reflected at a * b * Distance Δa in the plane * b * ={(a * 2-a * θ ) 2 +(b * 2-b * θ ) 2} 1 / 2 .

[0082] <Refractive index of thin films>

[0083] In each embodiment and comparative example, silicon oxide (SiO2) was used as the low refractive index layer, and niobium oxide (Nb2O5), titanium oxide (TiO2), silicon nitride (Si3N4), and silicon oxynitride (SiON) were used as the high refractive index layers. For silicon oxynitride, by changing the amount of oxygen introduced during sputtering, two thin films were formed: SiON (1) with relatively less oxygen and SiON (2) with relatively more oxygen. The refractive index was measured using a spectroscopic ellipsometry. The refractive indices of other thin films were obtained using values ​​from a database. The refractive indices n of each thin film at wavelengths of 400 nm, 500 nm, and 700 nm were used. 400 n 550 n 700 and Abbe number ν D As shown in Table 1.

[0084] [Table 1]

[0085]

[0086] <Example 1>

[0087] The above optical simulation was performed on an antireflective film consisting of an 8-layer antireflective layer (8.2 nm niobium oxide layer, 42.2 nm silicon oxide layer, 24.6 nm niobium oxide layer, 18.6 nm silicon oxide layer, 80.8 nm niobium oxide layer, 10.8 nm silicon oxide layer, 25.6 nm niobium oxide layer, and 25.6 nm silicon oxide layer) on an acrylic hard coating film, and a 5 nm thick antifouling layer formed of fluorine resin on top of the antireflective film. The refractive indices of the hard coating film (acrylic hard coating layer) and the antifouling layer of fluorine resin were measured using a spectroscopic ellipsometry (refractive index of the hard coating layer at 550 nm wavelength: 1.54, refractive index of the antifouling layer at 550 nm wavelength: 1.32). In the optical simulation, the thickness of the film substrate of the hard coating film was set to ∞ to eliminate the influence of back reflection.

[0088] <Examples 2-7, Comparative Examples 1 and 2>

[0089] The same optical simulation as in Example 1 was performed on an anti-reflective film with the material of the high refractive index layer, the stacked structure (the total number of films constituting the anti-reflective (AR) layer), and the film thickness of each layer changed to those shown in Table 2.

[0090] [Evaluation Results]

[0091] Table 2 shows the composition of the antireflective films of Examples 1-7 and Comparative Examples 1 and 2, and the results of optical simulations. In Table 2, the thickness values ​​of each layer are in nm, and are listed as layer 1, layer 2, layer 3, etc., starting from the side closest to the film substrate. The characteristics of reflected light are shown for θ = 2° (front side) and θ = 20°, 40°, and 50°.

[0092] [Table 2]

[0093]

[0094] For Examples 1 and 2, which contain a total of 8 layers (4 high-refractive-index layers and 4 low-refractive-index layers) in the anti-reflective layer, it can be seen that Y θ The maximum value of / Y2 is small, and Δa * b * The maximum value is also small. For embodiments 3-6, which contain a total of 6 layers (3 high-refractive-index layers and 3 low-refractive-index layers), it can also be seen that Y... θ The maximum value of / Y2 is small, and Δa * b * The maximum value is also small. For use as a high refractive index layer, the Abbe number ν... D Example 6 of large (low wavelength dispersion of refractive index) SiON(2) showed that although Δa * b* The reflectivity tends to decrease, but increases when viewed from the front. This is believed to be related to the fact that the refractive index difference between the high-refractive-index layer and the low-refractive-index layer is small, thus failing to sufficiently reduce reflectivity.

[0095] For Comparative Example 1, which contains four layers in total (two high-refractive-index layers and two low-refractive-index layers) in its anti-reflective layer, the reflectivity on the front (2°) is reduced, but the Y... θ The maximum value of / Y2 exceeds 6. Furthermore, for Comparative Example 1, Δa... * b * The maximum value also exceeded that of Comparison Example 2, which is 6. θ The maximum value of / Y2 is below 6, but the a of the reflected light caused by visual recognition direction * The change is large, Δa * b * The maximum value is approximately 11.

[0096] [Change in the thickness of the anti-reflective layer]

[0097] <Example 1A>

[0098] The thicknesses of the eight thin films constituting the antireflective layer in the antireflective film of Example 1 were varied layer by layer, and the same simulation was performed. The film thickness of the antireflective layer in each antireflective film, the characteristics of 2° positive reflection, and the Y-axis within the range of θ = 5–45° were compared. θ / Y2 and Δa * b * The maximum values ​​are shown in Table 3. In Table 3, the antireflective film of No. 1 is the same as that of Example 1. The thickness of the first layer (high refractive index layer) was changed for No. 2 to 5, the thickness of the second layer (low high refractive index layer) was changed for No. 6 to 9, the thickness of the third layer (high refractive index layer) was changed for No. 10 to 13, the thickness of the fourth layer (low high refractive index layer) was changed for No. 14 to 17, the thickness of the fourth layer (low high refractive index layer) was changed for No. 18 to 21, the thickness of the fifth layer (high refractive index layer) was changed for No. 22 to 25, the thickness of the sixth layer (low high refractive index layer) was changed for No. 26 to 29, the thickness of the seventh layer (high refractive index layer) was changed for No. 30 to 33, and the thickness of the eighth layer (low high refractive index layer) was changed for No. 30 to 33.

[0099] [Table 3]

[0100]

[0101] According to the results shown in Table 3, when the thickness of the first layer (Nb₂O₅) is approximately 8–10 nm, the thickness of the second layer (SiO₂) is approximately 41–45 nm, the thickness of the third layer (Nb₂O₅) is approximately 21–25 nm, the thickness of the fourth layer (SiO₂) is approximately 18–20 nm, the thickness of the fifth layer (Nb₂O₅) is approximately 77–95 nm, the thickness of the sixth layer (SiO₂) is approximately 10.5–15 nm, the thickness of the seventh layer (Nb₂O₅) is approximately 25–30 nm, and the thickness of the eighth layer (SiO₂) is approximately 60–89 nm, the Y value in the range of θ = 5–45° can be obtained. θ / Y2 is below 6%, and Δa * b * Anti-reflective film with a resolution of 6 or lower.

[0102] <Example 2A>

[0103] The thicknesses of the eight thin films constituting the antireflective layer in the antireflective film of Example 2 were varied layer by layer, and the same simulation was performed. The film thicknesses of each layer and the evaluation results are shown in Table 4.

[0104] [Table 4]

[0105]

[0106] According to the results shown in Table 4, when the thickness of the first layer (Si3N4) is approximately 5–10 nm, the thickness of the second layer (SiO2) is approximately 48–60 nm, the thickness of the third layer (Si3N4) is approximately 23–27 nm, the thickness of the fourth layer (SiO2) is approximately 23–32 nm, the thickness of the fifth layer (Si3N4) is approximately 85–105 nm, the thickness of the sixth layer (SiO2) is approximately 4–7 nm, the thickness of the seventh layer (Si3N4) is approximately 40–50 nm, and the thickness of the eighth layer (SiO2) is approximately 70–95 nm, the Y value in the range of θ = 5–45° can be obtained. θ / Y2 is below 6%, and Δa * b * Anti-reflective film with a resolution of 6 or lower.

[0107] <Example 3A>

[0108] The thicknesses of the six thin films constituting the antireflective layer in Example 3 were varied layer by layer, and the same simulation was performed. The film thicknesses of each layer and the evaluation results are shown in Table 5.

[0109] [Table 5]

[0110]

[0111] According to the results shown in Table 5, when the thickness of the first layer (Nb₂O₅) is approximately 9–10.5 nm, the thickness of the second layer (SiO₂) is approximately 41–47 nm, the thickness of the third layer (Nb₂O₅) is approximately 25–28 nm, the thickness of the fourth layer (SiO₂) is approximately 39–42 nm, the thickness of the fifth layer (Nb₂O₅) is approximately 17–23 nm, and the thickness of the sixth layer (SiO₂) is approximately 90–106 nm, the Y value in the range of θ = 5–45° can be obtained. θ / Y2 is below 6%, and Δa * b * Anti-reflective film with a resolution of 6 or lower.

[0112] <Example 4A>

[0113] The thicknesses of the six thin films constituting the antireflective layer in the antireflective film of Example 4 were varied layer by layer, and the same simulation was performed. The film thicknesses of each layer and the evaluation results are shown in Table 6.

[0114] [Table 6]

[0115]

[0116] According to the results shown in Table 6, when the thickness of the first layer (Si3N4) is approximately 13–16.5 nm, the thickness of the second layer (SiO2) is approximately 32–40 nm, the thickness of the third layer (Si3N4) is approximately 47–55 nm, the thickness of the fourth layer (SiO2) is approximately 20.5–24 nm, the thickness of the fifth layer (Si3N4) is approximately 34–44.5 nm, and the thickness of the sixth layer (SiO2) is approximately 82–98 nm, the Y value in the range of θ = 5–45° can be obtained. θ / Y2 is below 6%, and Δa * b * Anti-reflective film with a resolution of 6 or lower.

[0117] <Example 5A>

[0118] The thicknesses of the six thin films constituting the antireflective layer in Example 5 were varied layer by layer, and the same simulation was performed. The film thicknesses of each layer and the evaluation results are shown in Table 7.

[0119] [Table 7]

[0120]

[0121] According to the results shown in Table 7, when the thickness of the first layer (SiON) is approximately 13–19.5 nm, the thickness of the second layer (SiO2) is approximately 22–37 nm, the thickness of the third layer (SiON) is approximately 58–80 nm, the thickness of the fourth layer (SiO2) is approximately 2–10 nm, the thickness of the fifth layer (SiON) is approximately 59–85 nm, and the thickness of the sixth layer (SiO2) is approximately 65–95 nm, the Y value in the range of θ = 5–45° can be obtained. θ / Y2 is below 6%, and Δa * b * Anti-reflective film with a resolution of 6 or lower.

[0122] <Comparative Example 1A>

[0123] The thicknesses of the four thin films constituting the antireflective layer in Comparative Example 1 were varied layer by layer, and the same simulation was performed. The film thicknesses of each layer and the evaluation results are shown in Table 8.

[0124] [Table 8]

[0125]

[0126] <Comparative Example 2A>

[0127] The thicknesses of the four thin films constituting the antireflective layer in Comparative Example 2 were varied layer by layer, and the same simulation was performed. The film thicknesses of each layer and the evaluation results are shown in Table 9.

[0128] [Table 9]

[0129]

[0130] As shown in Tables 8 and 9, when the number of thin films constituting the antireflective layer is 4, even if the thickness of the films is changed, it is still not possible to obtain any θ within the range of θ = 5 to 45°. θ / Y2 is below 6%, and Δa * b * Anti-reflective film with a resolution of 6 or lower.

[0131] Based on the above results, it can be seen that by making the number of films constituting the anti-reflective film 5 or more, preferably 6 or more, a denser optical design can be achieved, and an anti-reflective film with small changes in the characteristics of reflected light when the visual recognition direction is changed can be obtained.

[0132] The optimal thickness of the thin film varies depending on factors such as the refractive index of the materials constituting the film, and therefore cannot be uniformly defined. On the other hand, as shown in Tables 3-7, by varying the thickness of the thin film constituting the antireflective film and repeatedly performing optical simulations, the optimal value for Y can be found. θ / Y2、Δa * b *Even with less stringent requirements, it is possible to design anti-reflective films that exhibit minimal changes in the characteristics of reflected light when the visual recognition direction is altered, even when using films other than those shown in the above embodiments.

[0133] [Installation of the primer layer]

[0134] <Example 1B>

[0135] In the antireflective film of Example 1, a 3 nm thick SiOx primer layer (x = 0.65, refractive index at 550 nm: 1.72) was added between the acrylic hard coating layer of the hard coating film and the antireflective layer (the first Nb2O5 layer), and the same simulation was performed. The results of the optical simulation of Example 1B are shown together with the results of Example 1 in Table 10.

[0136] [Table 10]

[0137]

[0138] In Example 1B, the chromaticity index a of the positively reflected light * 2 and b * 2. Several changes have occurred compared to Example 1, but for Y, which serves as an indicator of the change in the characteristics of reflected light when the angle θ is changed... θ / Y2 and Δa * b * The values ​​were not significantly different from those in Example 1. Based on these results, it can be concluded that by providing a primer layer between the film substrate and the antireflective layer, and by adjusting the lamination structure and film thickness of the antireflective layer in the same manner as in the aforementioned examples, an antireflective film with minimal changes in the characteristics of reflected light when the visual recognition direction is altered can also be obtained.

Claims

1. An antireflection film having an antireflection layer on a film substrate, the antireflection layer comprising a plurality of thin films, the antireflection layer comprising, from the film substrate side, a total of 8 thin films of a Nb2O5 layer having a film thickness of 8 to 10 nm, a SiO2 layer having a film thickness of 41 to 45 nm, a Nb2O5 layer having a film thickness of 21 to 25 nm, a SiO2 layer having a film thickness of 18 to 20 nm, a Nb2O5 layer having a film thickness of 77 to 95 nm, a SiO2 layer having a film thickness of 10.5 to 15 nm, a Nb2O5 layer having a film thickness of 25 to 30 nm, and a SiO2 layer having a film thickness of 60 to 89 nm, forward reflection light of a D65 light source irradiated from the antireflection layer side satisfies the following characteristics (A) and (B): (A) the apparent reflectance Y2 of the regular reflection light of 2° incident light and the apparent reflectance Y of the regular reflection light of 0° incident light θ satisfies Y θ / Y2≤6.0 (B) Colorimetric index a of regular reflection light of 2° incident light * 2 and b * (B) Colorimetric index a of regular reflection light of 2° incident light * θ 2 and b * θ In any angle θ in the range of 5 to 50°, {(a * 2-a * θ ) 2 +(b * 2-b * θ 2} 1 / 2 ≤ 6.0.​ 2. An antireflection film having an antireflection layer on a film substrate, the antireflection layer comprising a plurality of thin films, the antireflection layer comprising, from the film substrate side, a total of 8 thin films of a Si3N4 layer having a film thickness of 5 to 10 nm, a SiO2 layer having a film thickness of 48 to 60 nm, a Si3N4 layer having a film thickness of 23 to 27 nm, a SiO2 layer having a film thickness of 23 to 32 nm, a Si3N4 layer having a film thickness of 85 to 105 nm, a SiO2 layer having a film thickness of 4 to 7 nm, a Si3N4 layer having a film thickness of 40 to 50 nm, and a SiO2 layer having a film thickness of 70 to 95 nm, forward reflection light of a D65 light source irradiated from the antireflection layer side satisfies the following characteristics (A) and (B): (A) the apparent reflectance Y2 of the regular reflection light of 2° incident light and the apparent reflectance Y of the regular reflection light of 0° incident light θ satisfies Y θ / Y2≤6.0 (B) Colorimetric index a of regular reflection light of 2° incident light * 2 and b * 2 and colorimetric index a of regular reflection light of 2° incident light * θ 2 and b * θ In any angle θ in the range of 5 to 50°, {(a * 2 - a * θ ) 2 + (b * 2 - b * θ ) 2} 1 / 2 ≤ 6.

0.

3. An antireflection film having an antireflection layer on a film substrate, the antireflection layer comprising a plurality of thin films, the antireflection layer comprising, from the film substrate side, a total of 6 thin films of a Nb2O5 layer having a film thickness of 9 to 10.5 nm, a SiO2 layer having a film thickness of 41 to 47 nm, a Nb2O5 layer having a film thickness of 25 to 28 nm, a SiO2 layer having a film thickness of 39 to 42 nm, a Nb2O5 layer having a film thickness of 17 to 23 nm, and a SiO2 layer having a film thickness of 90 to 106 nm, forward reflection light of a D65 light source irradiated from the antireflection layer side satisfies the following characteristics (A) and (B): (A) the apparent reflectance Y2 of the regular reflection light of 2° incident light and the apparent reflectance Y of the regular reflection light of 0° incident light θ satisfies Y θ / Y2≤6.0 (B) Colorimetric index a of regular reflection light of 2° incident light * 2 and b * (B) Colorimetric index a of regular reflection light of 2° incident light * θ 2 and b * θ In any angle θ in the range of 5 to 50°, {(a * 2 - a * θ ) 2 + (b * 2 - b * θ ) 2} 1 / 2 ≤ 6.

0.

4. An antireflection film having an antireflection layer on a film substrate, the antireflection layer comprising a plurality of thin films, the antireflection layer comprising, from the film substrate side, a total of 6 thin films of a Si3N4 layer having a film thickness of 13 to 16.5 nm, a SiO2 layer having a film thickness of 32 to 40 nm, a Si3N4 layer having a film thickness of 47 to 55 nm, a SiO2 layer having a film thickness of 20.5 to 24 nm, a Si3N4 layer having a film thickness of 34 to 44.5 nm, and a SiO2 layer having a film thickness of 82 to 98 nm, forward reflection light of a D65 light source irradiated from the antireflection layer side satisfies the following characteristics (A) and (B): (A) the apparent reflectance Y2 of the regular reflection light of 2° incident light and the apparent reflectance Y of the regular reflection light of 0° incident light θ satisfies Y θ Y2≤ 6.0 (B) Colorimetric index a of regular reflection light of 2° incident light * 2 and b * (B) Colorimetric index a of regular reflection light of 2° incident light * θ 2 and b * θ In any angle θ in the range of 5 to 50°, {(a * 2 - a * θ ) 2 + (b * 2 - b * θ ) 2} 1 / 2 ≤ 6.

0.

5. An antireflection film having an antireflection layer on a film substrate, the antireflection layer comprising a plurality of thin films, The antireflection layer comprises, from the side of the film substrate, a total of six thin films of a SiON layer having a film thickness of 13 to 19.5 nm, a SiO2 layer having a film thickness of 22 to 37 nm, a SiON layer having a film thickness of 58 to 80 nm, a SiO2 layer having a film thickness of 2 to 10 nm, a SiON layer having a film thickness of 59 to 85 nm, and a SiO2 layer having a film thickness of 65 to 95 nm, The normal reflection light of a D65 light source irradiated from the side of the antireflection layer satisfies the following characteristics (A) and (B): (A) the apparent reflectance Y2 of the regular reflection light of 2° incident light and the apparent reflectance Y of the regular reflection light of 0° incident light θ satisfies Y θ / Y2≤6.0 (B) Colorimetric index a of regular reflection light of 2° incident light * 2 and b * (B) Colorimetric index a of regular reflection light of 2° incident light * θ 2 and b * θ In any angle θ in the range of 5 to 50°, {(a * 2 - a * θ 2 + (b * 2 - b * θ 2} 1 / 2 ≤ 6.0.​​ 6. The antireflection film according to any one of claims 1 to 5, wherein The normal reflection light of a 2° incident light of a D65 light source irradiated from the side of the antireflection layer has a visual sensation reflectance Y2 of 1.0% or less.

7. The antireflection film according to any one of claims 1 to 5, wherein Y of the regular reflection light of the θ° incident light of a D65 light source irradiated from the side of the antireflection layer θ 3.0% or less at any angle θ in the range of 5 to 50°.

8. The antireflection film according to any one of claims 1 to 5, wherein The chromaticity index a of the regular reflection light of the 2° incident light of a D65 light source irradiated from the antireflection layer side * 2 and b * 2 satisfy {(a * 2) 2 +(b * 2) 2} 1 / 2 ≤ 5.

0.

9. The antireflection film according to any one of claims 1 to 5, wherein The chromaticity index a of the regular reflection light of the θ° incident light of a D65 light source irradiated from the side of the antireflection layer * θ and b * θ In any angle θ in the range of 5 to 50°, {(a * θ ) 2 + (b * θ ) 2} 1 / 2 ≤ 9.

0.

10. An image display device provided with the antireflection film according to any one of claims 1 to 9 on the visually recognized side surface of an image display medium.

Images