TW202138843A - Antireflection film and image display device that comprises an antireflection layer comprising a plurality of thin films disposed on a film substrate - Google Patents

Abstract

An antireflection film (100) comprises, on a film substrate (1), an antireflection layer (5) that comprises a plurality of thin films. The antireflection layer is a multilayer thin film containing at least one layer of low refractive index layer and one layer of high refractive index layer as thin films. For the antireflection film, the positively reflected light of a D65 light source irradiating on the antireflection layer is preferable when satisfying: (A) luminance reflectance Y2 of positively reflected light of 2DEG incident light and luminance reflectance Y[theta] of positively reflected light of [theta]DEG incident light for any angle [theta] in the range of 5-50DEG being Y[theta]/Y2 ≤ 6.0; and (B) chromaticity index a*2 and b*2 of positively reflected light of 2DEG incident light and chromaticity index a*[theta] and b*[theta] of positively reflected light of [theta]DEG incident light for any angle [theta] in the range of 5-50DEG being {(a*2-a*[theta])<SP>2<SP> + (b*2-b*[theta])<SP>2<SP>}<SP>1/2<SP> ≤ 6.0.

Description

Anti-reflection film and image display device

The invention relates to an anti-reflection film and an image display device.

On the surface of image display devices such as liquid crystal displays and organic EL (Electroluminescence) displays, an anti-reflection film is sometimes provided to improve the visibility of the displayed image. The anti-reflection film is provided with an anti-reflection layer including a plurality of thin films with different refractive indexes on the film substrate.

The reflection characteristics of light brought by the anti-reflection layer are usually evaluated by the visual reflectance (Y value). By reducing the reflectance near the wavelength of 550nm, which is higher than the spectral luminous efficiency, the visual reflectance becomes smaller. For the anti-reflection film, not only the visual reflectance is required to be small, but also the hue of the reflected light is required to be neutral.

An anti-reflection film is proposed that not only controls the reflection characteristics when viewed from the front, but also controls the characteristics of the reflected light in the oblique direction. For example, Patent Document 1 discloses an anti-reflection film in which the hue of regular reflection light of incident light from all angles of 5 to 45° is within a predetermined range. Patent Document 2 proposes to reduce the chromatic aberration of reflected light in the range of 5 to 45° by performing optical design in such a way that the chromaticity in the range of incident angle of 20-30° is minimized. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2004-138662 [Patent Document 2] Japanese Patent Laid-Open No. 2016-177183

[The problem to be solved by the invention]

For the previous anti-reflection film, although the reflectance of a specific viewing direction can be reduced, it is difficult to make the change of the reflectance smaller in a wider viewing direction, and it is difficult to reduce the color change of the reflected light. [Technical means to solve the problem]

The anti-reflection film is provided with an anti-reflection layer including a plurality of thin films on the film substrate. The anti-reflection layer is a multilayer film including at least one of a low refractive index layer and a high refractive index layer as a thin film. In the anti-reflection film of the present invention, the regular reflection light of the D65 light source irradiated from the side of the anti-reflection layer satisfies the specified characteristics.

_{The visual reflectivity Y θ} of the regular reflection light of the incident light of θ° _{preferably satisfies: Y θ} /Y ₂ ≦6.0 at any angle θ in the range of 5 to 50°. Y ₂ is the visual reflectivity of the regular reflection of the incident light at 2°. ^{The chromaticity index a *} _θ and b ^* _θ of the regular reflection light of θ° is preferably satisfied: at any angle θ in the range of 5 to 50°, from Δa ^* b ^* = {(a ^* ₂ -a ^* _θ ) ² +(b ^* ₂ -b ^* _θ ) ² } The chromaticity difference Δa ^* b ^{* shown in 1/2} is Δa ^* b ^* ≦6.0. [Effects of Invention]

By using the anti-reflection film of the present invention, it is possible to realize image display with less changes in the characteristics of reflected light caused by the viewing direction.

[The composition of anti-reflective film] FIG. 1 is a cross-sectional view schematically showing the structure of an anti-reflection film according to an embodiment. The anti-reflection film 100 includes an anti-reflection layer 5 on the film substrate 1. The anti-reflection layer 5 is a laminate of a plurality of thin films. The anti-reflection layer 5 shown in FIG. 1 is a multilayer film including 6 layers of thin films formed by alternately laminating high refractive index layers 51, 53, 55 and low refractive index layers 52, 54, 56 from the film substrate 1 side.

＜Film base material＞ The film substrate 1 includes a flexible film 10. The thickness of the film substrate 1 is not particularly limited. From the viewpoints of strength, handleability, etc., workability, thin layer properties, etc., it is preferably about 5 to 300 μm, more preferably 10 to 250 μm, and still more preferably 20 to 200 μm.

As the film 10, a transparent film is generally 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, for example, a thermoplastic resin excellent in transparency, mechanical strength, and thermal stability can be cited. Specific examples of such thermoplastic resins include cellulose-based resins such as cellulose triacetate, polyester-based resins, polyether-based resins, poly-based resins, polycarbonate-based resins, polyamide-based resins, Polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (butene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol Resins, and their mixtures.

Preferably, a hard coat layer 11 is provided on the side of the film 10 where the anti-reflection layer 5 is formed. By providing the hard coat layer 11 on the surface of the film 10, the mechanical properties such as the hardness and elastic modulus of the anti-reflection film can be improved. The hard coat layer 11 is preferably one having high surface hardness and excellent scratch resistance.

Examples of curable resins include thermosetting resins, ultraviolet curing resins, electron beam curing resins, and the like. The types of curable resins include polyester, acrylic, urethane, acrylic urethane, amide, silicone, silicate, epoxy, and melamine. , Oxetane series, acrylic urethane series and other resins. One kind or two or more kinds of these curable resins can be appropriately selected and used.

The hard coat layer may contain fine particles. For example, by making the hard coating layer contain fine particles, irregularities can be formed on the surface of the hard coating layer 11 to provide anti-glare properties. The fine particles used for imparting anti-glare properties are preferably fine particles having a particle size of the μm order. The average particle size of the fine particles is preferably 0.5-10 μm, more preferably 1-5 μm. By forming fine unevenness on the surface of the hard coat layer 11, the adhesion with the anti-reflection layer 5 (or the undercoat layer 3) provided thereon tends to be improved. The fine particles used to form the surface of the hard coat layer 11 with the unevenness of the film such as the primer layer 3 and the anti-reflection layer 5 with excellent adhesion are preferably nano particles having a particle size of the nm order. The average particle size of the nano particles is preferably 10 to 150 nm, more preferably 20 to 100 nm, and still more preferably 25 to 80 nm.

The hard coat layer 11 can be formed by coating a solution containing a curable resin on the film 10, for example. It is preferable to prepare a polymerization initiator in the solution for forming the hard coat layer. In order to form an anti-glare hard coat layer containing fine particles, it is preferable to apply a solution containing the above fine particles in addition to the curable resin on the transparent film. The solution may contain additives such as leveling agents, thixotropic agents, and antistatic agents.

The thickness of the hard coat layer 11 is not particularly limited. In order to achieve high hardness, it is preferably 0.5 μm or more, and more preferably 1 μm or more. In consideration of the ease of formation by coating, the thickness of the hard coat layer is preferably 15 μm or less, and more preferably 10 μm or less.

＜Undercoating＞ A primer layer 3 can also be provided on the film substrate 1 to improve the adhesion of the anti-reflection layer 5 and the like. As the material constituting the undercoat layer 3, for example, metals such as silicon, nickel, chromium, indium, tin, gold, silver, platinum, zinc, titanium, tungsten, aluminum, zirconium, and palladium; alloys of these metals can be cited; Oxides, fluorides, sulfides or nitrides of these metals. Among them, the material of the undercoat layer is preferably an inorganic oxide layer, and may also be an oxide with less oxygen than the stoichiometric composition.

The thickness of the undercoat layer 3 is, for example, about 1-20 nm, preferably 2-15 nm, more preferably 3-15 nm. As long as the film thickness of the undercoat layer is in the above range, it is possible to achieve both improved adhesion and light transmittance.

＜Anti-reflective layer＞ The anti-reflection layer 5 is a laminate of a plurality of thin films with different refractive indexes. Furthermore, in this specification, the "refractive index" is the refractive index at a wavelength of 550 nm unless otherwise specified.

By laminating a plurality of thin films with different refractive indexes, the reflectance can be reduced in the wide wavelength range of visible light. As the thin film constituting the anti-reflection layer 5, a ceramic material containing metal or semi-metal oxide, nitride, fluoride, or the like is preferable. The film constituting the anti-reflection layer 5 may also be a film whose refractive index is adjusted by containing fine particles of high refractive index or low refractive index in the resin adhesive.

The low refractive index layers 52, 54, 56 have, for example, a refractive index of 1.6 or less, preferably 1.5 or less. Examples of the low refractive index material include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, and lanthanum fluoride.

The high refractive index layers 51, 53, 53 have, for example, a refractive index of 1.8 or more, preferably 1.9 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), silicon nitride, silicon oxynitride Wait.

The anti-reflection layer 5 is preferably an alternate laminate of a high refractive index layer and a low refractive index layer. In order to reduce the reflection at the air interface, the thin film 56 provided as the outermost layer of the anti-reflection layer 5 (the layer farthest from the film substrate 1) is preferably a low refractive index layer. In addition to the low refractive index layer and the high refractive index layer, the anti-reflection layer may also include a middle refractive index layer having a high refractive index layer and a low refractive index layer. The refractive index of the middle refractive index layer is, for example, about 1.6 to 1.9.

The film thickness of the high refractive index layer and the low refractive index layer are each about 5 to 200 nm, preferably about 10 to 150 nm. It is only necessary to design the film thickness of each layer in such a way that the reflectance of visible light becomes small according to the refractive index, the build-up layer structure, and the like.

The film forming method of the thin film constituting the anti-reflection layer 5 is not particularly limited, and may be either a wet coating method or a dry coating method. In terms of being able to form a thin film with a uniform thickness, dry coating methods such as vacuum evaporation, CVD (Chemical Vapor Deposition), sputtering, and electron beam evaporation are preferred. Among them, the sputtering method is preferred from the viewpoint of excellent film thickness uniformity.

＜Additional layer on the anti-reflective layer＞ The anti-reflection film may also have an additional functional layer on the anti-reflection layer 5. For example, in order to prevent pollution from the external environment or easily remove attached contaminants, an anti-fouling layer (not shown) may be provided on the anti-reflection layer 5.

When an anti-fouling layer is provided on the surface of the anti-reflective film, from the viewpoint of reducing the reflection at the interface, it is preferable that the difference in refractive index between the low-refractive index layer 56 on the outermost surface of the anti-reflective layer 5 and the anti-fouling 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 of the antifouling layer, fluorine-containing silane-based compounds, fluorine-containing organic compounds, etc. are preferred. The antifouling layer can be formed by a wet coating method such as a reverse coating method, a die coating method, and a gravure coating method, a vacuum vapor deposition method, a dry coating method such as a CVD method, or the like. The thickness of the antifouling layer is usually about 1-100 nm, preferably 2-50 nm, more preferably 3-30 nm.

[Characteristics of reflected light] The anti-reflection film preferably has a smaller change in the characteristics of the reflected light caused by the viewing angle. The characteristics of light can be evaluated by the three indicators of hue, chroma and brightness. The characteristics of reflected light depend on the spectrum of the irradiated light. Hereinafter, the characteristics of the reflected light when the surface of the anti-reflection film on the side of the anti-reflection layer 5 (the side opposite to the film base 1) is irradiated with the CIE standard light source D65 will be mentioned.

When light is incident from the side of the anti-reflection layer 5 and the reflected light is measured, the reflectance of visible light on the back side (the interface between the film substrate 1 and the air) is about 4%, and most of it is the reflected light from the back. In order to eliminate the influence of back reflection, a sample with a black film or a black plate attached to the back side of the film substrate 1 (the surface opposite to the surface where the anti-reflection layer 5 is formed) is used in the evaluation of the characteristics of the reflected light .

＜Vision reflectivity＞ The visual reflectance Y is an indicator of the brightness of the reflected light, which is the Y value in the XYZ color system (or Yxy color system). The visual reflectance Y is standardized so that the Y value of the complete reflector becomes 100%.

Generally, the anti-reflection film is designed in such a way that the reflectance of the light is reduced from the front, and the greater the incident angle θ, the greater the reflectance of the specular reflected light. From the viewpoint of reducing the difference in the amount of reflected light caused by the change in the incident angle (visual recognition direction) of the light, it is preferably the difference between the apparent reflectivity Y ₂ of the regular reflection light of the 2° incident light and the θ° incident light The ratio Y _θ /Y ₂ of the visual reflectance Y _θ of regular reflection light is 6.0 or less at any incident angle θ of θ=5-50°. Y _θ /Y _{2 is} more preferably 5.5 or less in the range of θ=5-50°, still more preferably 5.0 or less, and particularly preferably 4.5 or less.

_{The visual reflectance Y 2} of the regular reflection light of 2° incident light is preferably 1.0% or less, more preferably 0.9% or less, and still more preferably 0.8% or less. Y _{2 is} preferably as small as possible. However, if the optical design is performed in such a way that the reflectance of incident light in a specific direction is reduced, the change in reflectance may become larger when the incident angle θ changes. Therefore, Y ₂ may be 0.1% or more, 0.2% or more, or 0.3% or more.

From the viewpoint of reducing the reflection of ambient light and improving visibility regardless of the viewing direction, the visual reflectivity Y _θ of the regular reflection light of θ° incident light is preferably at any angle θ in the range of 5-50° It is 3.0% or less, more preferably 2.5% or less.

<Chromaticity Index> In the CIELAB color space (L ^* a ^* b ^* color space), L ^{* is used to} represent brightness, and chromaticity indices a ^* and b ^{* are used to} represent hue and saturation. When a ^* and b ^* are 0, it is achromatic, +a ^* indicates the red direction, -a ^* indicates the green direction, +b ^* indicates the yellow direction, and -b ^* indicates the blue direction. ^{In the a *} b ^* plane shown in Figure 2, the radial direction corresponds to the chroma, and the circumferential direction corresponds to the hue.

The chroma defined by C ^* = {(a ^* ) ² +(b ^* ) ² } ^1/2 indicates the degree of coloring. When C ^* is 0, it is achromatic. The ^{larger the C *, the} greater the coloring. When the color space is projected to a ^* b ^* plane space, the greater the distance between two points, the greater the difference between the colors of the two lights.

From the viewpoint of reducing the color difference of the reflected light caused by the change of the incident angle of the light (visual recognition direction), the chromaticity index of the regular reflected light of 2° incident light is a ^* ₂ and b ^* ₂ and θ° incident ^{The chromaticity indices a *} _θ and b ^* _{θ of} light specular reflection light are ^{preferably satisfying Δa *} b ^* ≦6.0 at any angle θ in the range of θ=5-50°. As shown in Figure 2, Δa ^* b ^* is the distance between the regular reflection light (A) of 2° incident light and the regular reflection light of θ° incident light in a ^* b ^* plane, which is defined by Δa ^* b ^* = {(a ^* ₂ -a ^* _θ ) ² +(b ^* ₂ -b ^* _θ ) ² ｝ ^1/2 . Hereinafter, Δa ^* b ^* may be referred to as "chromaticity difference". The chromaticity difference Δa ^* b ^{* is} more preferably 5.5 or less in the range of θ=5-50°, further preferably 5.0 or less, and particularly preferably 4.5 or less. Δa ^* b ^* may be 4.0 or less, 3.5 or less, or 3.0 or less.

^{The chroma C*} of the regular reflection light of 2° incident light is preferably 5.0 or less, more preferably 4.0 or less, and still more preferably 3.0 or less. ^{The chroma C*} of the regular reflection light of 2° incident light can also be 2.5 or less or 2.0 or less.

Regardless of the visual recognition direction can have a neutral color light reflected thereby suppressing the coloration of view, the regular reflection light of incident light θ ° chroma C ^* of any angle in the range of 5 ~ 50 ° of θ is preferably in the 9.0 or less, more preferably 7.0 or less, and particularly preferably 5.0 or less.

＜Optical design of anti-reflection layer＞ By appropriately designing the film thickness of the film constituting the anti-reflection layer, an anti-reflection film having the above-mentioned characteristics can be obtained. The characteristics (spectrum) of the reflected light can be accurately evaluated by the calculation of the optical model. As a method for obtaining the reflection spectrum of a multilayer optical film by optical calculation, it is known to repeatedly apply a film interference formula to each interface of the film and add all the multiple reflected waves; and consider the boundary conditions of Maxwell's equation And the method of calculating the reflection spectrum by the transmission matrix, etc.

Calculate the reflectance spectrum of the specular reflection light when entering the D65 light source for a plurality of incident angles θ, and calculate the visual reflectance Y and the chromaticity index a ^* and b ^{* from} the reflectance spectrum for each θ. By repeatedly performing these optical calculations while changing the film thickness of the film constituting the anti-reflection layer, the optimization of the set film thickness of the film can be realized, and an anti-reflection film whose reflected light satisfies the above-mentioned characteristics can be obtained.

When the number of films constituting the anti-reflection layer is small, it is difficult to design the film thickness in such a way that both _{Y θ} /Y ₂ and Δa ^* b ^{* become smaller in an arbitrary range of θ=5-50°.} As shown in the following examples, when the number of layers of the anti-reflection layer (total number of films) is large, regardless of the material constituting the anti-reflection layer, both Y _θ /Y ₂ and Δa ^* b ^{* can be reduced} The way to design the film thickness of the film. The anti-reflection layer preferably includes a total of five or more layers of a low refractive index layer and a high refractive index layer, and preferably includes three or more low refractive index layers. The anti-reflection layer more preferably includes a total of 6 or more layers of a low refractive index layer and a high refractive index layer.

From the viewpoint of reducing the visual reflectance Y, it is preferable that the anti-reflection layer 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 still more preferably 0.40 or more.

The refractive index of the low refractive index layer is preferably 1.50 or less, more preferably 1.48 or less, and still more preferably 1.47 or less. The refractive index of the low refractive index layer is usually 1.00 or higher, but may also be 1.20 or higher, 1.30 or higher, or 1.35 or higher. The refractive index of the high refractive index layer is preferably 1.80 or higher, more preferably 1.84 or higher, and still more preferably 1.87 or higher. The refractive index of the high refractive index layer is usually 3.00 or less, and may also 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 1.84-2.55, more preferably 1.88-2.50. The refractive index of the high refractive index layer at a wavelength of 700 nm is preferably 1.78-2.35, more preferably 1.80-2.30.

If the reflectance near the wavelength of 550 nm is reduced, the visual reflectance Y tends to decrease. On the other hand, there is a tendency that if the optical design is performed in such a way that the reflectance near the wavelength of 550 nm is minimized, the reflectance at other wavelengths will increase, and the chromaticity index a ^* and/or b ^{* of the} reflected light will increase. , Reflected light coloring.

In order to reduce the coloration of the reflected light, it is preferable that the reflectance is the same in a wide wavelength range of visible light. When the wavelength dependence of the refractive index of the film constituting the anti-reflection layer is small, the change in reflectance caused by the wavelength becomes smaller, and the chroma of the reflected light becomes smaller (neutralized). In the case of using materials with large refractive index wavelength dispersion, optical design can also be implemented in a way that the color of the reflected light becomes smaller, but if the film thickness of the film is slightly different, the color of the reflected light may sometimes occur. From the viewpoint of increasing the degree of freedom of optical design and ensuring the allowable range of film thickness (Process Margin), the film constituting the anti-reflection layer is preferably the wavelength dispersion of the refractive index (the change of the refractive index caused by the wavelength change) )small.

_{The Abbe number ν D of the} high refractive index layer is preferably 20 or more, more preferably 23 or more, and still more preferably 25 or more. The Abbe number ν _D, a refractive index n _D at the wavelength of 589 nm, a refractive index n _F of the wavelength of 486 nm, a refractive index n _C, and at a wavelength of 656 nm, the _{ν D = (n D -1)} / (n _F -n _C ) means. The larger the Abbe number ν _D , the smaller the wavelength dispersion of the refractive index. The upper limit of the Abbe number ν _D of the high refractive index layer is not particularly limited. For ordinary ceramic materials, the _{larger the Abbe number ν D} (the smaller the wavelength dispersion of the refractive index), the smaller the refractive index becomes. . From the viewpoint of sufficiently increasing the refractive index of the high refractive index layer to reduce the reflectance, the Abbe number ν _{D of the} high refractive index layer is preferably 40 or less, more preferably 30 or less, and even more preferably 28 or less.

For the anti-reflection layer, considering the refractive index of each film, the number of layers, etc., the film thickness of each film may be set so that the reflected light satisfies the above-mentioned characteristics. As described above, by using the optical model to calculate the reflection spectrum of the anti-reflection film, the film thickness of the anti-reflection layer can be optimized.

[Use form of anti-reflective film] The anti-reflection film is disposed on the surface of image display devices such as liquid crystal displays and organic EL displays for use. For example, by disposing an anti-reflection film on the visible side surface of a panel containing image display media such as liquid crystal cells, organic EL cells, etc., the reflection of external light can be reduced and the visibility of the image display device can be improved. It is also possible to laminate the anti-reflection film with other films. For example, by bonding a polarizer on the side opposite to the surface where the anti-reflection layer of the film base 1 is formed, a polarizing plate with an anti-reflection layer can be formed.

The anti-reflection film of the present invention has a small difference in the characteristics of the reflected light caused by the viewing direction, so even when the viewing direction is changed, the change in the characteristics of the reflected light is small, and the image display device can be made uniform. [Example]

Hereinafter, an example of calculating the characteristics of the reflected light of the anti-reflection film by calculation with an optical model is shown.

[Evaluation method of reflected light characteristics] With the unit of 1 nm in the wavelength range of 380 ~ 780 nm, the optical model is used to calculate the normal reflectance of the anti-reflective film when the light of the wavelength λ is incident at the angle of incidence θ°, and the reflectance spectrum R(λ) is calculated .

Multiply the obtained spectra R(λ) by the spectrum of CIE standard light source D65 to obtain the spectrum of reflected light. The reflected light spectrum obtained, the luminous reflectance was calculated Y, and the color index of the CIELAB color system, a ^* and b ^*, chroma calculated ^{C * = {(a *)} 2 The values of a ^* and b ^* + (b ^* ) ² ｝ ^1/2 .

Carry out the above evaluation with the incident angle of 2° and the incident angle of θ=5～50° in the range of 5° as the unit, and calculate the apparent reflectance Y _{2 of the 2} ° incident light and the θ° incident light. The ratio of the apparent reflectance Y _θ of the _{regular reflected light Y θ} /Y ₂ , and the distance between the regular reflected light of 2° incident light and the regular reflected light of θ° incident light in a ^* b ^{* plane Δa *} b ^* = {(A ^* ₂ -a ^* _θ ) ² +(b ^* ₂ -b ^* _θ ) ² } ^1/2 .

<The refractive index of the thin film> In the examples and comparative examples, silicon _{oxide (SiO 2} ) was used as the low refractive index layer, and niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), and silicon nitride (Si _{3) were used as the low refractive index layer.} N ₄ ) and silicon oxynitride (SiON) are used as the high refractive index layer. For silicon oxynitride, the amount of oxygen introduced during sputtering film formation is changed to form two thin films of SiON(1) with relatively small oxygen content and SiON(2) with relatively large oxygen content, using a spectroscopic ellipsometer The measured refractive index. The refractive index of other films uses the value of the database. _{The refractive index n 400} , n ₅₅₀ , n ₇₀₀ and Abbe number ν _{D of} each film at wavelengths of 400 nm, 500 nm, and 700 nm are shown in Table 1.

[Table 1] Refractive index v _D n ₄₀₀ n ₅₅₀ n ₇₀₀ Low refractive index layer SiO ₂ 1.474 1.463 1.459 68.3 High refractive index layer Nb ₂ O ₅ 2.481 2.325 2.271 15.8 TiO ₂ 2.820 2.543 2.467 11.9 Si ₃ N ₄ 2.001 1.941 1.917 26.0 SiON(1) 1.895 1.845 1.826 27.9 SiON(2) 1.790 1.750 1.734 30.7

<Example 1> The anti-reflective film is implemented with the above-mentioned optical simulation. The anti-reflective film is provided with a 8.2 nm niobium oxide layer, 42.2 nm silicon oxide layer, 24.6 nm niobium oxide layer, and 18.6 nm acrylic hard coat on the hard coat film. A silicon oxide layer, a niobium oxide layer of 80.8 nm, a silicon oxide layer of 10.8 nm, a niobium oxide layer of 25.6 nm, and a silicon oxide layer of 25.6 nm are sequentially stacked to form an 8-layer anti-reflection layer, and the anti-reflection layer An antifouling layer made of fluorine-based resin with a thickness of 5 nm is provided on the layer. The refractive index of the hard coat film (acrylic hard coat) and the antifouling layer containing fluorine resin is measured by a spectroscopic ellipsometer (the refractive index of the hard coat at a wavelength of 550 nm is 1.54, and the antifouling The refractive index of the dirty layer at a wavelength of 550 nm is 1.32). In the optical simulation, in order to eliminate the influence of back reflection, the thickness of the film substrate of the hard coat film is set to ∞.

<Examples 2-7, Comparative Examples 1, 2> The same optical simulation as in Example 1 was performed on the material of the high refractive index layer, the multilayer structure (the total number of films constituting the anti-reflection (AR) layer), and the film thickness of each layer were changed to the anti-reflection film shown in Table 2.

[Evaluation results] Table 2 shows the structure of the anti-reflection film of Examples 1 to 7 and Comparative Examples 1 and 2 and the results of optical simulation. In Table 2, the numerical unit of the thickness of each layer is nm, and it is described as the first layer, the second layer, the third layer... from the side close to the film substrate. The characteristics of the reflected light show the results of θ=2° (front side), and θ=20°, 40°, and 50°.

[Table 2] Layered composition Reflected light characteristics Antifouling layer SiO ₂ High refractive index layer SiO ₂ High refractive index layer SiO ₂ High refractive index layer SiO ₂ High refractive index layer θ (°) Y (%) a* b* C* Y _θ /Y ₂ ∆a*b* Layer 8 Layer 7 Level 6 Layer 5 Level 4 Level 3 Level 2 Level 1 Example 1 High refractive index layer: Nb ₂ O ₅ AR 8 layers 5 87.5 25.6 10.8 80.8 18.6 24.6 42.2 8.2 2 0.50 0.45 0.00 0.45 - - 20 0.52 1.28 0.96 1.60 1.04 1.27 40 1.09 2.44 5.13 5.68 2.19 5.50 50 2.29 0.61 5.50 5.53 4.61 5.50 Maximum value 4.61 5.50 Example 2 High refractive index layer: Si ₃ N ₄ AR 8 layers 5 87.3 46.4 4.7 87.6 27.7 26.0 45.0 7.0 2 0.93 0.19 0.17 0.25 - - 20 0.96 -0.05 1.26 1.26 1.03 1.11 40 1.45 -0.79 3.33 3.42 1.55 3.31 50 2.51 -1.16 3.35 3.54 2.68 3.45 Maximum value 2.68 3.45 Example 3 High refractive index layer: Nb ₂ O ₅ AR 6 layers 5 - - 103 22.3 39.6 25.5 46.2 10.1 2 0.88 -0.95 1.25 1.57 - - 20 0.90 -2.52 2.80 3.77 1.02 2.20 40 1.29 -4.14 4.03 5.78 1.46 4.23 50 2.26 -2.51 2.54 3.57 2.56 2.02 Maximum value 2.56 4.23 Example 4 High refractive index layer: Si ₃ N ₄ AR 6 layers 5 - - 95 43 twenty one 49 36 16 2 0.84 0.50 0.08 0.50 - - 20 0.88 -0.66 1.65 1.78 1.04 1.95 40 1.34 -3.10 3.88 4.97 1.59 5.23 50 2.32 -2.71 2.82 3.91 2.76 4.22 Maximum value 2.76 5.23 Example 5 High refractive index layer: SiON(1)AR 6 layers 5 - - 85.9 69.1 5.0 65.8 29.4 18.2 2 1.10 0.01 0.25 0.25 - - 20 1.14 -0.46 1.22 1.30 1.03 1.08 40 1.61 -1.66 2.71 3.17 1.47 2.97 50 2.61 -1.45 2.16 2.60 2.38 2.41 Maximum value 2.38 2.97 Example 6 High refractive index layer: SiON(2)AR 6 layers 5 - - 86 79 5 65 28 19 2 1.46 -0.14 0.10 0.17 - - 20 1.49 -0.34 0.59 0.68 1.02 0.53 40 1.95 -0.81 1.40 1.62 1.34 1.46 50 2.96 -0.57 1.19 1.32 2.03 1.17 Maximum value 2.03 1.46 Example 7 High refractive index layer: TiO ₂ AR 6 layers 5 - - 100 19 37 twenty three 44 10 2 0.73 -3.45 2.99 4.57 - - 20 0.73 -5.46 4.48 7.06 1.00 2.50 40 1.10 -7.44 5.16 9.05 1.50 4.54 50 2.09 -3.33 2.48 4.15 2.86 0.52 Maximum value 2.86 4.54 Comparative Example 1 High refractive index layer: Nb ₂ O ₅ AR 4 layers 9 - - - - 83.5 105 27.5 10.1 2 0.16 1.64 -4.60 4.88 - - 20 0.14 1.51 -2.40 2.84 0.83 2.20 40 0.45 3.28 1.94 3.81 2.73 6.74 50 1.33 5.22 3.48 6.27 8.06 8.84 Maximum value 8.06 8.84 Comparative Example 2 High refractive index layer: Si ₃ N ₄ AR 4 layers 5 - - - - 101 33.4 38.2 23.4 2 1.06 -3.80 -0.06 3.80 - - 20 1.01 -1.30 -1.60 2.06 0.95 2.94 40 1.32 5.66 -1.80 5.94 1.24 9.62 50 2.34 7.22 1.17 7.31 2.20 11.09 Maximum value 2.20 11.09

For Example 1 and Example 2 in which the anti-reflection layer includes 4 layers of high refractive index layer and 4 layers of low refractive index layer in total, it can be seen that _{the maximum value of Y θ} /Y ₂ is small, and Δa ^* b ^* The maximum value is also smaller. For the anti-reflection layer including the high refractive index layer and the low refractive index layer, each of the three layers in the total of Examples 3 to 6 including 6 layers, it can also be seen that _{the maximum value of Y θ} /Y ₂ is small, and the maximum value of Δa ^* b ^* The value is also smaller. For Example 6 using SiON(2) with a large Abbe number ν _D (smaller wavelength dispersion of the refractive index) as the high refractive index layer, although a ^{tendency of Δa *} b ^{* to} decrease is observed, when viewed from the front The reflectivity becomes higher. This is considered 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, and therefore the reflectance cannot be sufficiently reduced.

For Comparative Example 1, where the anti-reflection layer includes 2 layers each of the high refractive index layer and the low refractive index layer, which includes 4 layers in total, the reflectivity of the front side (2°) is reduced, but the maximum value of _{Y θ} /Y _{2 exceeds 6.} . In addition, for Comparative Example 1, ^{the maximum value of Δa *} b ^* also exceeds 6, and _{the maximum value of Y θ} /Y ₂ is 6 or less, but the change in ^{a *} of reflected light caused by the viewing direction is relatively large. , The maximum value of ^{Δa *} b ^{* is about 11.}

[Change of film thickness of anti-reflection layer] <Example 1A> The film thickness of the eight films constituting the anti-reflection layer in the anti-reflection film of Example 1 was changed layer by layer, and the same simulation was performed. The film thickness of the anti-reflection layer in each anti-reflection film, the characteristics of 2° regular reflection light, and _{the maximum values of Y θ} /Y ₂ and Δa ^* b ^{* in} the range of θ=5～45° are shown in Table 3. . In Table 3, the anti-reflection film of No. 1 is the same as that of Example 1. No. 2 to 5 changed the thickness of the first layer (high refractive index layer), No. 6 to 9 changed the thickness of the second layer (low high refractive index layer), and No. 10 to 13 changed the third layer ( The thickness of the high refractive index layer), No.14-17 changed the thickness of the fourth layer (low high refractive index layer), No.18-21 changed the thickness of the fifth layer (high refractive index layer), No.22 ～25 changed the thickness of the sixth layer (low high refractive index layer), No.26-29 changed the thickness of the seventh layer (high refractive index layer), and No.30～33 changed the eighth layer (low high refractive index) Rate layer) thickness.

[table 3] Layer 8 Layer 7 Level 6 Layer 5 Level 4 Level 3 Level 2 Level 1 2° regular reflection light Maximum value SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ Y a* b* C* Y _θ /Y ₂ ∆a*b* 1 87.5 25.6 10.8 80.8 18.6 24.6 42.2 8.2 0.5 0.45 0.00 0.45 4.6 5.5 2 87.5 25.6 10.8 80.8 18.6 24.6 42.2 7.4 0.5 3.34 -1.13 3.53 4.8 9.4 3 7.8 0.5 1.86 -0.54 1.94 4.7 7.2 4 9.0 0.5 -1.13 0.57 1.26 4.2 5.4 5 11.0 0.6 -10.26 3.31 10.78 3.1 15.5 6 87.5 25.6 10.8 80.8 18.6 24.6 38.0 8.2 0.4 2.54 -4.14 4.86 5.4 8.8 7 40.1 0.5 1.39 -1.90 2.35 5.0 7.0 8 44.3 0.5 -0.26 1.56 1.58 4.2 5.1 9 50.0 0.7 -1.02 3.95 4.08 3.3 8.4 10 87.5 25.6 10.8 80.8 18.6 18.0 42.2 8.2 1.1 -14.76 9.22 17.40 2.0 16.3 11 22.1 0.7 -2.41 2.68 3.61 3.3 4.3 12 25.8 0.4 3.28 -3.08 4.50 5.4 9.6 13 27.0 0.4 6.06 -6.53 8.91 6.2 13.9 14 87.5 25.6 10.8 80.8 16.7 24.6 42.2 8.2 0.6 1.51 2.75 3.14 4.3 7.3 15 17.7 0.5 1.01 1.41 1.73 4.5 6.1 16 19.5 0.5 -0.18 -1.46 1.47 4.6 5.8 17 20.5 0.5 -0.87 -2.97 3.10 4.6 6.7 18 87.5 25.6 10.8 72.7 18.6 24.6 42.2 8.2 0.4 0.38 -3.45 3.47 4.9 7.7 19 76.8 0.5 0.31 -1.72 1.75 4.7 6.5 20 88.9 0.5 0.82 1.61 1.80 4.6 5.8 twenty one 99.0 0.6 3.85 5.00 6.31 4.9 7.7 twenty two 87.5 25.6 9.7 80.8 18.6 24.6 42.2 8.2 0.4 1.74 -1.92 2.59 5.6 8.3 twenty three 10.2 0.4 1.09 -0.95 1.45 5.1 6.9 twenty four 15.0 1.0 -4.28 6.85 8.08 2.6 5.8 25 16.0 1.0 -4.28 6.85 8.08 2.6 6.1 26 87.5 23.0 10.8 80.8 18.6 24.6 42.2 8.2 0.5 0.72 -5.64 5.69 4.4 8.9 27 24.3 0.5 0.52 -2.69 2.74 4.5 7.1 28 28.1 0.6 0.53 2.41 2.46 4.6 5.0 29 38.0 1.0 7.48 9.36 11.98 3.8 13.0 30 70.0 25.6 10.8 80.8 18.6 24.6 42.2 8.2 1.4 0.94 4.58 4.68 2.9 2.2 31 78.7 0.8 0.55 2.96 3.01 4.0 2.0 32 91.9 0.5 0.40 -3.85 3.87 4.0 7.7 33 96.2 0.6 0.39 -8.44 8.45 2.9 9.7

According to the results shown in Table 3, _{the thickness of the first layer (Nb 2} O ₅ ) is 8-10 nm, the thickness of the second layer (SiO ₂ ) is 41-45 nm, and the third layer (Nb ₂ O ₅ ) The thickness is 21-25 nm, the thickness of the fourth layer (SiO ₂ ) is 18-20 nm, the thickness of the fifth layer (Nb ₂ O ₅ ) is 77-95 nm, and the thickness of the sixth layer (SiO ₂ ) is _{When the thickness of the 7th layer (Nb 2} O ₅ ) is 25-30 nm, and the thickness of the 8th layer (SiO ₂ ) is in the range of about 60 to 89 nm, 10.5～15 nm, θ=5～45° can be obtained. The Y _θ /Y _{2 in the range} is 6% or less, and Δa ^* b ^* is an anti-reflection film of 6 or less.

<Example 2A> The thickness of the eight films constituting the anti-reflection layer in the anti-reflection film of Example 2 was changed layer by layer and the same simulation was performed. Table 4 shows the film thickness of each layer and the evaluation results.

[Table 4] Layer 8 Layer 7 Level 6 Layer 5 Level 4 Level 3 Level 2 Level 1 2° regular reflection light Maximum value SiO ₂ Si ₃ N ₄ SiO ₂ Si ₃ N ₄ SiO ₂ Si ₃ N ₄ SiO ₂ Si ₃ N ₄ Y a* b* C* Y _θ /Y ₂ ∆a*b* 1 87.3 46.4 4.7 87.6 27.7 26.0 45.0 7.0 0.9 0.19 0.17 0.25 2.7 3.5 2 87.3 46.4 4.7 87.6 27.7 26.0 45.0 4.0 0.9 6.37 -2.41 6.81 3.0 13.7 3 6.5 0.9 1.27 -0.30 1.30 2.7 5.1 4 7.5 0.9 -0.92 0.65 1.13 2.6 2.0 5 11.0 1.1 -9.41 4.45 10.41 2.1 12.5 6 87.3 46.4 4.7 87.6 27.7 26.0 35.0 7.0 0.8 0.88 -5.68 5.75 2.9 7.3 7 41.8 0.9 0.10 -1.31 1.31 2.7 3.9 8 48.1 1.0 0.57 1.39 1.50 2.6 4.5 9 55.0 1.1 2.37 2.87 3.73 2.5 9.2 10 87.3 46.4 4.7 87.6 27.7 20.0 45.0 7.0 1.4 -11.24 11.59 16.15 1.9 14.2 11 24.2 1.0 -3.18 4.10 5.19 2.4 2.0 12 27.8 0.8 3.41 -4.08 5.32 3.0 8.8 13 31.0 0.7 8.65 -12.30 15.04 3.6 18.1 14 87.3 46.4 4.7 87.6 21.0 26.0 45.0 7.0 1.1 2.38 7.66 8.03 2.6 12.7 15 25.8 1.0 1.07 2.32 2.55 2.7 4.8 16 29.6 0.9 -0.87 -1.80 2.00 2.6 3.5 17 35.0 0.9 -4.79 -7.42 8.83 2.3 9.3 18 87.3 46.4 4.7 73.0 27.7 26.0 45.0 7.0 0.7 2.93 -9.59 10.03 3.1 11.5 19 81.4 0.8 1.02 -4.14 4.27 2.8 6.6 20 102.0 1.1 0.88 8.96 9.00 2.7 3.5 twenty one 118.0 1.1 6.29 12.20 13.73 3.0 11.3 twenty two 87.3 46.4 1.0 87.6 27.7 26.0 45.0 7.0 0.7 3.36 -8.74 9.37 3.3 11.9 twenty three 3.0 0.8 1.60 -3.91 4.23 2.9 7.3 twenty four 6.0 1.0 -0.79 3.19 3.28 2.5 1.3 25 10.0 1.4 -3.39 12.22 12.68 2.2 8.0 26 87.0 36.0 4.7 87.6 27.7 26.0 45.0 7.0 0.8 1.64 -11.56 11.68 2.6 11.1 27 43.2 0.9 0.33 -2.98 3.00 2.6 5.1 28 58.0 1.0 2.35 8.74 9.05 3.0 7.4 29 62.0 1.0 4.07 9.98 10.78 3.1 9.7 30 74.2 46.4 4.7 87.6 27.7 26.0 45.0 7.0 1.4 -0.59 5.72 5.75 2.5 2.1 31 84.0 1.0 -0.12 2.56 2.56 2.7 1.9 32 90.0 0.9 0.44 -1.92 1.97 2.6 4.9 33 102.0 1.2 1.23 -9.50 9.58 1.7 7.8

According to the results shown in Table 4, _{the thickness of the first layer (Si 3} N ₄ ) is 5-10 nm, the thickness of the second layer (SiO ₂ ) is 48-60 nm, and the thickness of the third layer (Si ₃ N ₄ ) The thickness is 23-27 nm, the thickness of the fourth layer (SiO ₂ ) is 23-32 nm, the thickness of the fifth layer (Si ₃ N ₄ ) is 85-105 nm, and the thickness of the sixth layer (SiO ₂ ) is 4-7 nm, the thickness of the seventh layer (Si ₃ N ₄ ) is 40-50 nm, and the thickness of the eighth layer (SiO ₂ ) is in the range of 70-95 nm, θ=5～45° can be obtained The Y _θ /Y _{2 in the range} is 6% or less, and Δa ^* b ^* is an anti-reflection film of 6 or less.

<Example 3A> The film thickness of the six films constituting the anti-reflection layer in the anti-reflection film of Example 3 was changed layer by layer and the same simulation was performed. Table 5 shows the film thickness of each layer and the evaluation results.

[table 5] Level 6 Layer 5 Level 4 Level 3 Level 2 Level 1 2° regular reflection light Maximum value SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ Y a* b* C* Y _θ /Y ₂ ∆a*b* 1 103.1 22.3 39.6 25.5 46.2 10.1 0.9 -0.95 1.25 1.57 2.6 4.2 2 103.1 22.3 39.6 25.5 46.2 7.0 1.0 -10.93 -1.05 10.98 1.8 14.1 3 9.4 0.9 -3.32 1.26 3.55 2.4 1.8 4 10.8 0.9 1.70 0.92 1.94 2.7 9.8 5 13.0 0.9 10.35 -2.07 10.55 3.1 23.2 6 103.1 22.3 39.6 25.5 39.3 10.1 1.3 -10.34 13.84 17.28 1.9 14.7 7 42.0 1.0 -3.87 5.91 7.06 2.3 4.0 8 49.4 0.7 3.13 -6.05 6.81 3.0 9.7 9 54.5 0.6 8.66 -19.10 20.97 3.6 21.7 10 103.1 22.3 39.6 21.6 46.2 10.1 0.7 6.61 -1.65 6.81 3.6 16.0 11 23.7 0.8 2.57 0.05 2.57 3.0 10.3 12 27.2 1.1 -4.02 2.07 4.52 2.1 2.5 13 29.3 1.3 -6.82 2.46 7.25 1.8 6.5 14 103.1 22.3 33.6 25.5 46.2 10.1 0.5 5.71 -19.11 19.94 3.2 19.6 15 36.8 0.7 1.84 -7.73 7.95 2.8 9.5 16 41.4 1.0 -2.46 6.69 7.12 2.4 3.8 17 45.5 1.4 -4.88 16.89 17.58 2.1 11.3 18 103.1 18.9 39.6 25.5 46.2 10.1 1.2 -2.90 -4.71 5.53 1.8 1.8 19 20.7 1.0 -2.19 -1.36 2.57 2.2 2.7 20 23.8 0.8 0.77 2.77 2.87 3.0 7.7 twenty one 25.6 0.6 3.28 2.72 4.26 3.7 11.1 twenty two 87.6 22.3 39.6 25.5 46.2 10.1 1.4 -4.22 9.57 10.46 2.3 9.4 twenty three 95.8 1.0 -2.81 6.90 7.44 2.6 4.7 twenty four 110.3 1.0 1.14 -5.47 5.58 2.1 8.1 25 118.5 1.3 2.75 -10.71 11.06 1.6 11.1

According to the results shown in Table 5, _{the thickness of the first layer (Nb 2} O ₅ ) is 9 to 10.5 nm, the thickness of the second layer (SiO ₂ ) is 41 to 47 nm, and the thickness of the third layer (Nb ₂ O ₅ ) The thickness is 25-28 nm, the thickness of the fourth layer (SiO ₂ ) is 39-42 nm, the thickness of the fifth layer (Nb ₂ O ₅ ) is 17-23 nm, and the thickness of the sixth layer (SiO ₂ ) is _{In the range of about 90 to 106 nm, an anti-reflection film with Y θ} /Y _{2 in} the range of θ=5 to 45° of 6% or less and Δa ^* b ^* of 6 or less can be obtained.

<Example 4A> The film thickness of the six films constituting the anti-reflection layer in the anti-reflection film of Example 4 was changed layer by layer and the same simulation was performed. Table 6 shows the film thickness of each layer and the evaluation results.

[Table 6] Level 6 Layer 5 Level 4 Level 3 Level 2 Level 1 2° regular reflection light Maximum value SiO ₂ Si ₃ N ₄ SiO ₂ Si ₃ N ₄ SiO ₂ Si ₃ N ₄ Y a* b* C* Y _θ /Y ₂ ∆a*b* 1 95.0 43.0 21.0 49.0 36.0 16.0 0.8 0.50 0.08 0.50 2.8 5.2 2 95.0 43.0 36.0 11.0 1.2 -11.80 5.27 12.92 1.8 14.2 3 13.6 1.0 -5.52 3.23 6.40 2.2 5.1 4 17.1 0.8 3.35 -1.79 3.80 3.0 8.9 5 18.4 0.7 6.63 -4.23 7.86 3.4 13.9 6 95.0 43.0 21.0 49.0 30.6 16.0 1.1 -3.03 9.52 9.99 2.3 6.9 7 33.5 1.0 -0.98 4.62 4.72 2.6 4.8 8 38.5 0.8 1.67 -4.62 4.92 2.9 7.0 9 41.4 0.7 2.62 -10.14 10.48 3.0 10.6 10 95.0 43.0 21.0 41.7 36.0 16.0 0.6 6.26 -6.93 9.33 5.2 26.3 11 45.6 0.7 3.15 -3.35 4.59 3.2 9.3 12 52.4 1.0 -1.98 3.66 4.16 2.4 2.4 13 58.0 1.3 -5.40 9.49 10.92 2.1 8.3 14 95.0 43.0 16.0 49.0 36.0 16.0 0.6 4.13 -16.07 16.59 3.0 15.7 15 19.5 0.8 1.40 -4.41 4.63 2.8 7.0 16 22.5 0.9 -0.25 4.34 4.34 2.7 4.2 17 26.0 1.2 -1.40 13.44 13.52 2.5 8.7 18 95.0 33.0 21.0 49.0 36.0 16.0 1.0 -0.04 -11.20 11.20 1.9 6.4 19 36.6 1.0 -0.38 -7.26 7.27 2.2 5.1 20 46.0 0.8 1.66 2.60 3.08 3.1 8.2 twenty one 50.0 0.7 3.91 3.98 5.58 3.6 11.5 twenty two 80.8 43.0 21.0 49.0 36.0 16.0 1.4 -2.15 8.43 8.70 2.4 6.2 twenty three 88.4 1.0 -0.86 5.21 5.28 2.7 2.5 twenty four 101.7 0.9 1.89 -6.80 7.06 2.4 9.4 25 109.3 1.2 2.70 -10.70 11.03 1.8 10.4

According to the results shown in Table 6, _{the thickness of the first layer (Si 3} N ₄ ) is 13 to 16.5 nm, the thickness of the second layer (SiO ₂ ) is 32 to 40 nm, and the thickness of the third layer (Si ₃ N ₄ ) The thickness of the fourth layer (SiO ₂ ) is 20.5-24 nm, the thickness of the fifth layer (Si ₃ N ₄ ) is 34-44.5 nm, and the thickness of the sixth layer (SiO ₂ ) is 82 _{In the range of ~98 nm, an anti-reflection film with Y θ} /Y _{2 in} the range of θ=5 to 45° of 6% or less and Δa ^* b ^* of 6 or less can be obtained.

<Example 5A> The film thickness of the six films constituting the anti-reflection layer in the anti-reflection film of Example 5 was changed layer by layer and the same simulation was performed. Table 7 shows the film thickness of each layer and the evaluation results.

[Table 7] Level 6 Layer 5 Level 4 Level 3 Level 2 Level 1 2° regular reflection light Maximum value SiO ₂ SiON SiO ₂ SiON SiO ₂ SiON Y a* b* C* Y _θ /Y ₂ ∆ a*b* 1 85.9 69.1 5.0 65.8 29.4 18.2 1.1 0.01 0.25 0.25 2.4 3.0 2 85.9 69.1 5.0 65.8 65.8 14.0 1.3 -5.80 4.61 7.41 1.9 7.0 3 16.9 1.2 -1.83 1.75 2.53 2.2 0.9 4 19.5 1.0 1.91 -1.38 2.35 2.5 5.4 5 22.0 0.9 5.79 -4.90 7.58 2.9 11.5 6 85.9 69.1 5.0 65.8 23.0 18.2 1.3 -0.68 8.10 8.13 2.3 5.4 7 27.3 1.1 -0.02 2.48 2.48 2.4 3.5 8 35.0 1.0 -0.75 -5.14 5.19 2.3 4.8 9 37.0 1.0 -1.34 -6.72 6.85 2.3 6.0 10 85.9 69.1 5.0 54.0 65.8 18.2 0.8 3.71 -8.84 9.59 2.8 10.9 11 61.2 1.0 1.15 -3.03 3.24 2.5 5.0 12 70.4 1.2 -0.71 3.65 3.71 2.3 1.9 13 75.6 1.3 -1.33 8.35 8.45 2.3 4.7 14 85.9 69.1 1.0 65.8 65.8 18.2 1.0 1.00 -7.89 7.95 2.3 6.9 15 3.0 1.0 0.40 -3.90 3.92 2.4 4.6 16 7.0 1.2 -0.19 4.97 4.97 2.4 2.5 17 9.0 1.3 -0.17 9.32 9.32 2.4 5.1 18 85.9 55.0 5.0 65.8 29.4 18.2 0.9 1.92 -8.54 8.76 2.4 7.8 19 64.2 1.0 0.28 -2.83 2.85 2.4 3.8 20 73.9 1.1 0.16 3.23 3.24 2.4 2.9 twenty one 92.0 1.2 5.27 9.53 10.89 2.8 8.4 twenty two 73.0 69.1 5.0 65.8 29.4 18.2 1.5 -0.66 5.11 5.15 2.2 2.6 twenty three 79.9 1.2 -0.41 3.52 3.54 2.4 1.3 twenty four 91.9 1.1 0.51 -3.73 3.76 2.2 5.1 25 98.8 1.3 0.94 -7.66 7.72 1.8 6.8

According to the results shown in Table 7, the thickness of the first layer (SiON) is 13 to 16.5 nm, the thickness of the second layer (SiO ₂ ) is 22 to 37 nm, and the thickness of the third layer (SiON) is 58 to 80 nm, the thickness of the fourth layer (SiO ₂ ) is 2-10 nm, the thickness of the fifth layer (SiON) is 59-85 nm, and the thickness of the sixth layer (SiO ₂ ) is in the range of 65-95 nm. An anti-reflection film in which _{Y θ} /Y _{2 in} the range of θ=5 to 45° is 6% or less and Δa ^* b ^{* is 6 or less is obtained.}

<Comparative Example 1A> The film thickness of the four films constituting the anti-reflection layer in the anti-reflection film of Comparative Example 1 was changed layer by layer and the same simulation was performed. Table 8 shows the film thickness of each layer and the evaluation results.

[Table 8] Level 4 Level 3 Level 2 Level 1 2° regular reflection light Maximum value SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ Y a* b* C* Y _θ /Y ₂ ∆a*b* 1 83.5 105.0 27.5 10.1 0.2 1.64 -4.60 4.88 8.1 8.8 2 83.5 105.0 27.5 9.4 0.2 0.23 -2.60 2.61 6.0 7.5 3 10.8 0.1 3.06 -6.60 7.27 11.1 11.3 4 83.5 105.0 25.6 10.1 0.2 1.49 -4.20 4.46 7.8 7.4 5 29.4 0.2 1.70 -5.00 5.28 7.5 10.2 6 83.5 97.7 27.5 10.1 0.3 5.97 -8.90 10.72 4.2 17.0 7 112.4 0.2 0.75 -2.60 2.71 8.5 8.8 8 77.7 105.0 27.5 10.1 0.1 1.26 0.24 1.28 15.1 6.8 9 89.3 1.2 2.98 -10.10 10.53 2.4 11.9

<Comparative Example 2A> The film thickness of the four films constituting the anti-reflection layer in the anti-reflection film of Comparative Example 2 was changed layer by layer and the same simulation was performed. Table 9 shows the film thickness of each layer and the evaluation results.

[Table 9] Level 4 Level 3 Level 2 Level 1 2° regular reflection light Maximum value SiO ₂ Si ₃ N ₄ SiO ₂ Si ₃ N ₄ Y a* b* C* Y _θ /Y ₂ ∆a*b* 1 101.5 33.4 38.2 23.4 1.1 -3.80 -0.06 3.80 2.2 11.1 2 101.5 33.4 38.2 21.7 0.9 -1.20 8.46 8.54 2.5 11.7 3 25.0 1.2 -6.00 0.99 6.08 1.9 12.8 4 101.5 33.4 35.5 23.4 0.9 -2.20 -4.80 5.28 2.3 12.3 5 40.9 1.2 -4.80 4.62 6.66 2.1 10.9 6 101.5 31.1 38.2 23.4 1.2 -3.80 -2.30 4.44 2.0 11.6 7 35.7 1.0 -3.40 1.85 3.87 2.4 10.2 8 94.3 33.4 38.2 23.4 1.1 -0.48 1.41 1.49 2.5 8.7 9 108.6 1.2 -6.00 -1.90 6.29 1.7 12.0

As shown in Tables 8 and 9, when the number of films constituting the anti-reflection layer is 4, even if the thickness of the film is changed, Y _θ /Y cannot be obtained for any θ in the range of θ=5～45° ₂ is an anti-reflection film with 6% or less and Δa ^* b ^* of 6 or less.

According to the above results, it can be seen that by making the number of films constituting the anti-reflection film 5 layers or more, preferably 6 layers or more, a denser optical design can be realized, and the characteristic change of the reflected light can be obtained when the viewing direction is changed. Small anti-reflective film.

The optimal value of the film thickness of the film differs according to the refractive index of the material constituting the film, etc., so it is difficult to uniformly specify. On the other hand, as shown in Tables 3-7, by changing the thickness of the film constituting the anti-reflective film and repeatedly performing optical simulations, it is possible to find conditions where Y _θ /Y ₂ and Δa ^* b ^* are smaller. Therefore, when a thin film other than the material shown in the above-mentioned embodiment is used, it is also possible to design an anti-reflection film with a small change in the characteristics of reflected light when the viewing direction is changed.

[Insertion of undercoat layer] <Example 1B> In the anti-reflective film of Example 1 _{, add between the acrylic hard coat of the hard coat film and the anti-reflective layer (the Nb 2} O ₅ layer of the first layer) The SiOx primer layer with a thickness of 3 nm (x=0.65, the refractive index at a wavelength of 550 nm is 1.72), and the same simulation is performed. The results of the optical simulation of Example 1B and the results of Example 1 are shown in Table 10.

[Table 10] Layered composition Reflected light characteristics Antifouling layer SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ SiO ₂ Nb ₂ O ₅ SiO _x primer θ (°) Y (%) a* b* C* Y _θ /Y ₂ ∆a*b* Layer 8 Layer 7 Level 6 Layer 5 Level 4 Level 3 Level 2 Level 1 Example 1 No primer 5 87.5 25.6 10.8 80.8 18.6 24.6 42.2 8.2 - 2 0.50 0.45 0.00 0.45 - - 20 0.52 1.28 0.96 1.60 1.04 1.27 40 1.09 2.44 5.13 5.68 2.19 5.50 50 2.29 0.61 5.50 5.53 4.61 5.50 Maximum value 4.61 5.50 Example 1B Additional SiO _x primer layer 5 87.5 25.6 10.8 80.8 18.6 24.6 42.2 8.2 3.0 2 0.51 -1.66 0.69 1.80 - - 20 0.51 -0.43 1.06 1.14 1.01 1.28 40 1.03 2.36 3.64 4.34 2.03 4.99 50 2.21 1.27 4.10 4.29 4.35 4.49 Maximum value 4.35 4.99

In Example 1B, the chromaticity indices a ^* ₂ and b ^* ₂ of the specular reflected light are slightly changed from those in Example 1, but for Y _θ /Y ₂ and Δa which are indicators of changes in the reflected light characteristics when the angle θ is changed ^{The value of *} b ^* is not significantly different from that of Example 1. From this result, it can be seen that when a primer layer is provided between the film base material and the anti-reflection layer, by adjusting the build-up structure and film thickness of the anti-reflection layer in the same manner as in the above-mentioned embodiments, it is also possible to change the direction of visibility. Anti-reflective film with small changes in the characteristics of reflected light.

1: Film substrate 3: Undercoat 5: Anti-reflective layer 10: Membrane 11: Hard coating 51,53,55: low refractive index layer 52,54,56: high refractive index layer 100: Anti-reflective film

Fig. 1 is a cross-sectional view showing the laminated form of the anti-reflection film. Fig. 2 is a diagram for explaining the ^{chromaticity C *} and the chromaticity difference Δa ^* b ^*.

1: Film substrate

3: Undercoat

5: Anti-reflective layer

10: Membrane

11: Hard coating

51,53,55: low refractive index layer

52,54,56: high refractive index layer

100: Anti-reflective film

Claims (11)

An anti-reflection film comprising an anti-reflection layer comprising a plurality of thin films on a film substrate, the anti-reflection layer comprising a low refractive index layer and a high refractive index layer having a higher refractive index than the low refractive index layer as the For the film, the regular reflection light of the D65 light source irradiated from the side of the anti-reflection layer satisfies the following characteristics (A) and (B): (A) The apparent reflectivity of the regular reflection light of 2° incident light Y ₂ and θ° _{The visual reflectivity Y θ} of the regular reflection light of the incident light _{is Y θ} /Y ₂ ≦6.0 at any angle θ in the range of 5-50° (B) The chromaticity index of the regular reflection light of the 2° incident light a ^* ₂ and b ^* ₂ and the chromaticity index of the regular reflection light of θ° a ^* _θ and b ^* _θ at any angle θ in the range of 5 to 50° is {(a ^* ₂ -a ^* _θ ) ² + (b ^* ₂ -b ^* _θ ) ² } ^1/2 ≦6.0. Such as the anti-reflection film of claim 1, wherein the refractive index of the high refractive index layer at a wavelength of 550 nm is above 1.80, The refractive index of the low refractive index layer at a wavelength of 550 nm is 1.50 or less. The anti-reflection film of claim 1 or 2, wherein the high refractive index layer has a refractive index of 1.84-2.55 at a wavelength of 400 nm and a refractive index of 1.78-2.35 at a wavelength of 700 nm. The anti-reflection film of claim 1 or 2, wherein the Abbe number ν _D of the high refractive index layer is 20 or more. The anti-reflection film of claim 1 or 2, wherein the anti-reflection layer includes the low-refractive index layer and the high-refractive index layer totaling 5 or more layers. Such as the anti-reflection film of claim 1 or 2, wherein the visual reflectivity Y ₂ of the regular reflection light of 2° incident light is 1.0% or less. Such as the anti-reflection film of claim 1 or 2, wherein the visual reflectance Y _θ of the regular reflection light of θ° incident light is 3.0% or less at any angle θ in the range of 5-50°. Such as the anti-reflection film of claim 1 or 2, in which the chromaticity index a ^* ₂ and b ^* _{2 of the} 2° incident light of the regular reflection light satisfy {(a ^* ) ² +(b ^* ₂ ) ² } ^1/2 ≦ 5.0. Such as the anti-reflective film of claim 1 or 2, wherein the chromaticity index a ^* _θ and b ^* _θ ^{of the regular reflection light of θ° incident light satisfies {(a *} _θ ) at any angle θ in the range of 5-50° ² +(b ^* _θ ) ² } ^1/2 ≦9.0. The anti-reflection film of claim 1 or 2, wherein the plurality of thin films constituting the anti-reflection layer are all ceramic thin films. An image display device, which is provided with an anti-reflection film as in any one of Claims 1 to 10 on the visible side surface of an image display medium.

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