JP2021039359A - Antireflection film, display device using antireflection film, and method for selecting antireflection film - Google Patents

Abstract

To provide an antireflection film that excels in color uniformity while suppressing reflection.SOLUTION: Provided is an antireflection film having a high refractive index layer and a low refractive index layer on a transparent substrate, the antireflection film being characterized in that the luminous reflectance Y value measured from a sample composed of a black plate pasted via a transparent adhesive to the face of transparent base material of the antireflection film on the side opposite to the high refractive index layer side, as well as the a* and b* values of a Lab color system, satisfy conditions (1) and (2). Condition (1): the luminous reflectance Y value of regular reflection light of incident light when light is entered to the sample at an incidence angle of 5 degrees from the low refractive index layer is 0.50% or smaller. Condition (2): an angle x (degrees) that indicates an inflection point where the gradient obtained from formula (A) by entering light to the sample at incidence angles of 5 degrees to 45 degrees in 5-degree increments from the low refractive index layer side changes from negative to positive is 25 degrees or smaller. (In the formula, n represents integers 1-8.)SELECTED DRAWING: None

Description

The present invention relates to an antireflection film, a display device using the antireflection film, and a method for selecting an antireflection film.

In recent years, with the shift to terrestrial digital broadcasting and the like, the development of display devices capable of displaying ultra-high-definition images is progressing. In order not to impair the image quality of such an ultra-high-definition display device, the surface of the display device is required to have a performance of preventing reflection of external light.
Examples of means for preventing reflection of external light include an anti-glare treatment in which the surface is made uneven to reduce specular reflected light, and an anti-reflection treatment in which the reflectance is reduced by the interference action of a multilayer thin film. In recent years, antireflection processing that tends to give a high-class feeling to images has become the mainstream.

The reflectance and color of the multilayer thin film can be reduced as the thin films are stacked, but from the viewpoint of cost effectiveness, many of them utilize the interference action of 2 to 4 layers. Examples of such an antireflection film include those of Patent Document 1.

Further, in recent years, even with an antireflection film utilizing the interference action of 2 to 4 layers, an ultra-low reflectance product having a reflectance of 0.5% or less has been required so as not to impair the image quality of an ultra-high-definition display device. ing.
Further, due to the ultra-high definition of display devices in recent years, the number of large screen display devices is further increasing because the pixels are no longer an issue even if the display device is enlarged. In such a large screen display device, the emission angles are large at both left and right ends of the screen even when observed from the front. Further, in a display device with a touch panel represented by a tablet-type personal digital assistant, the distance between the screen and the human eye is short, so that the emission angles are large on the left and right ends of the screen even if the screen is not large. In some cases (for example, when used sideways). Further, even when the display device has a convex shape, the emission angles at both the left and right ends become large. For this reason, color uniformity (hereinafter referred to as "color uniformity") in a range where the emission angles are different has begun to be emphasized.
The reflectance and tint of the antireflection film of the multilayer thin film are controlled by specularly reflected light of light having an incident angle of 5 degrees in order to reduce the reflectance and tint in the front direction. However, even if the specularly reflected light of the light having an incident angle of 5 degrees shows a value in which the reflectance and the tint are suppressed, the color uniformity may not be sufficient.

Japanese Unexamined Patent Publication No. 2010-152311

An object of the present invention is to provide an antireflection film having excellent color uniformity while suppressing reflectance, a display device using the antireflection film, and a method for selecting an antireflection film.

As a result of diligent research to solve the above problems, the present inventors have suppressed a sudden change in color due to an angle change by intentionally managing the color at an angle away from the front instead of managing the color in the front direction. We have found that it is possible and have completed the present invention.

The present invention provides the following antireflection films [1] to [7], a display device using the antireflection film, and a method for selecting the antireflection film.
[1] An antireflection film having a high refractive index layer and a low refractive index layer on a transparent base material, and the antireflection film is on the side opposite to the high refractive index layer side of the transparent base material of the antireflection film. The visual reflectance Y value measured from a sample in which a black plate is attached to the surface via a transparent adhesive, and the a ^* and b ^* values of the Lab color system satisfy the following conditions (1) and (2). Anti-reflective film.
<Condition (1)>
When the incident angle of light incident perpendicular to the surface on the low refractive index layer side of the sample is 0 degrees and the light is incident on the sample at an incident angle of 5 degrees, the specular reflection of the incident light is visible. The reflectance Y value is 0.50% or less.
<Condition (2)>
The incident angle of light incident perpendicular to the surface of the sample on the low refractive index layer side is set to 0 degrees, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and the incident light is positively reflected. ^{The a *} value and b ^* value of the Lab color system of light are measured, ^{the square root of the sum of squares of the a *} value and b ^* value at each incident angle is calculated, and further, from the following formula (A), between each measurement. When the slope of the square root of the sum of squares of the a ^* value and b ^* value of is calculated, the angle x (degree) indicating the turning point at which the slope changes from negative to positive is 25 degrees ≦ x.

(In the formula, "n" indicates an integer of 1 to 8.)

^{[2] The square root of the sum of squares of the a *} value and b ^* value at each incident angle of 5 to 45 degrees ^{is calculated, and the a *} value and b ^* value between each measurement are further calculated from the following formula (B). The antireflection film according to the above [1], wherein the maximum value of the absolute value is 17.3 or less when the absolute value of the slope of the square root of the sum of squares is calculated.

(In the formula, "n" indicates an integer of 1 to 8.)

[3] The antireflection film according to the above [1] or [2], which has a hard coat layer between the transparent base material and the high refractive index layer.
[4] A display device in which the antireflection film according to any one of [1] to [3] above is arranged on a display element so that the transparent base material side of the antireflection film faces the display element side.
[5] The display device according to the above [4], wherein the display device has a touch panel on the display element, and the antireflection film is arranged on the touch panel.
[6] The display device according to the above [4] or [5], wherein the number of pixels of the display element is 3840 × 2160 pixels or more.

[7] A black plate with a transparent adhesive on the surface of the transparent base material of the antireflection film having a high refractive index layer and a low refractive index layer on the transparent base material opposite to the high refractive index layer side. The determination condition is that the visual reflectance Y value measured from the sample and the a ^* value and b ^* value of the Lab color system satisfy the following conditions (1) and (2). How to select an antireflection film.
<Condition (1)>
When the incident angle of light incident perpendicular to the surface on the low refractive index layer side of the sample is 0 degrees and the light is incident on the sample at an incident angle of 5 degrees, the specular reflection of the incident light is visible. The reflectance Y value is 0.50% or less.
<Condition (2)>
The incident angle of light incident perpendicular to the surface of the sample on the low refractive index layer side is set to 0 degrees, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and the incident light is positively reflected. ^{The a *} value and b ^* value of the Lab color system of light are measured, ^{the square root of the sum of squares of the a *} value and b ^* value at each incident angle is calculated, and further, from the following formula (A), between each measurement. When the slope of the square root of the sum of squares of the a ^* value and b ^* value of is calculated, the angle x (degree) indicating the turning point at which the slope changes from negative to positive is 25 degrees ≦ x.

(In the formula, "n" indicates an integer of 1 to 8.)

The antireflection film and display device of the present invention are excellent in color uniformity while suppressing reflectance. In addition, the method for selecting an antireflection film of the present invention can accurately select an antireflection film having suppressed reflectance and excellent color uniformity.

[Anti-reflective film]
The antireflection film of the present invention is an antireflection film having a high refractive index layer and a low refractive index layer on a transparent base material, and the antireflection film is on the high refractive index layer side of the transparent base material of the antireflection film. The visual reflectance Y value measured from a sample in which a black plate is attached to the surface opposite to the surface with a transparent adhesive, and the a ^* and b ^* values of the Lab color system are the following conditions (1) and It satisfies (2).
<Condition (1)>
When the incident angle of light incident perpendicular to the surface on the low refractive index layer side of the sample is 0 degrees and the light is incident on the sample at an incident angle of 5 degrees, the specular reflection of the incident light is visible. The reflectance Y value is 0.50% or less.
<Condition (2)>
The incident angle of light incident perpendicular to the surface of the sample on the low refractive index layer side is set to 0 degrees, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and the incident light is positively reflected. ^{The a *} value and b ^* value of the Lab color system of light are measured, ^{the square root of the sum of squares of the a *} value and b ^* value at each incident angle is calculated, and further, from the following formula (A), between each measurement. When the slope of the square root of the sum of squares of the a ^* value and b ^* value of is calculated, the angle x (degree) indicating the turning point at which the slope changes from negative to positive is 25 degrees ≦ x.

(In the formula, "n" indicates an integer of 1 to 8.)

In the above formula (A), the denominator "5" in parentheses indicates the measurement interval "5 degrees".
In the present invention, the refractive index of the transparent pressure-sensitive adhesive used for the sample is such that the difference in refractive index from the refractive index of the transparent base material and the black plate is within 0.05.

Condition (1)
Condition (1) indicates that the visual reflectance Y value of the antireflection film is 0.50% or less under the above measurement conditions, in other words, the antireflection film has ultra-low reflection. When the visual reflectance Y value of the antireflection film exceeds 0.50%, the angle dependence of the tint tends to be suppressed, but due to the high visual reflectance Y value, ultra-high definition The image quality of the display device is impaired.
In the condition (1), the visual reflectance Y value is preferably 0.30% or less, more preferably 0.20% or less, and preferably 0.15% or less.
The measurement of the condition (1) preferably has the following conditions of the viewing angle, the light source, and the measurement wavelength.
Viewing angle; 2 degrees, light source; D65, measurement wavelength: 380 to 780 nm at 0.5 nm intervals. The visual reflectance Y value refers to the Y value of the CIE1931 standard color system.

Condition (2)
In condition (2), ^{the square root of the sum of squares of the a *} value and b ^* value at each incident angle is calculated from the measurement results ^{of the a *} value and b ^* value under the above measurement conditions, and further, the above equation (A) is obtained. ), When ^{the slope of the square root of the sum of squares of the a *} and b ^* values between each measurement is calculated, the angle x (degree) indicating the turning point at which the slope changes from negative to positive is 25 degrees ≦. It shows that it is x.
Hereinafter, "the slope of the square root of the sum of squares ^{of the a *} value and b ^* value between each measurement" may be referred to as "SL of the ^{a *} value and b ^{* value".} Further, hereinafter, it may be referred to "square root of the sum of squares of a ^* and b ^* values" and "a ^* and b ^* values of SQ".

The angle x (degree) indicating the inflection point at which the SL of the ^{a *} value and the b ^* value changes from negative to positive means the angle at which the SQ ^{of the a *} value and the b ^{* value changes from decreasing to increasing.}
The SQ of a ^* value and b ^* value can also be called so-called "saturation", and in the conventional antireflection film, the product is designed so that the SQ ^{of a *} value and b ^{* value becomes small in the front direction.} There is. a ^* and ^{b *} values of SQ is the inflection point ^{of a *} and ^{b *} values of SL is changed from negative to positive is the minimum value. Therefore, in the conventional antireflection film, the product is designed by approaching the angle x (degree) indicating the inflection point at which the SL ^{of the a *} value and the b ^{* value changes from negative to positive in the front direction.}
On the other hand, in the present invention, the ^{angle x (degree) indicating the inflection point at which the SL of the a *} value and the b ^* value changes from negative to positive is intentionally shifted from the front direction so that 25 degrees ≦ x.

When x (degree) is less than 25 degrees, the color uniformity can be improved in the low angle region, but the color uniformity cannot be improved in the high angle region (particularly 35 to 45 degrees). The reason for this is considered as follows.
The SQ of the a ^* value and b ^* value of the antireflection film tends to increase monotonically in both the direction in which the incident angle is smaller than x (degrees) and the direction in which the incident angle is larger than x (degrees). The rate of increase in SQ of the a ^* value and b ^* value tends to be larger in the direction in which the incident angle is larger than in x (degrees). ^{Furthermore, the rate of increase in SQ of the a *} value and b ^* value in the direction in which the incident angle is larger than x (degrees) tends to reach a peak at an angle where the incident angle is more than 20 degrees away from x (degrees). .. That is, when x (degree) is less than 25 degrees, the angle at which the rate of increase in SQ of ^{the a *} value and b ^* value peaks in the region where the viewing angle is 45 degrees or less, where the viewer frequently observes the display device. The viewer will feel a sudden change in color. A sudden change in color due to this angle change leads to a decrease in color uniformity.
On the other hand, the antireflection film of the present invention satisfying the condition (2) can improve the color uniformity. Specifically, when observing a display device with a large screen (screen size diagonal of 106.7 cm or more) from the front direction, or when observing a display device with a touch panel (screen size diagonal of more than 38.1 cm) from the front direction. When observing a convex display device, it is possible to suppress the difference in color between the vicinity of the center of the screen and the vicinity of both ends of the screen. Further, when the viewing angle of the display device is changed, it is possible to suppress the difference in color tone near the center of the screen before and after the movement.

If x (degree) is too large, it becomes difficult to suppress the reflectance and color in the front direction. Therefore, x (degree) preferably satisfies the condition of 25 degrees ≤ x ≤ 40 degrees, more preferably satisfies the condition of 25 degrees ≤ x ≤ 35 degrees, and the condition of 25 degrees ≤ x ≤ 30 degrees. It is even more preferable to meet.

It is preferable that there is only one angle x (degree) indicating the inflection point at which the SL of the a ^* value and the b ^{* value changes from negative to positive, and there are not a plurality of angles x (degrees).} In other words, ^{it is preferable that the SQ of the a *} value and the b ^* value gradually decreases to the inflection point and gradually increases to 45 degrees from the inflection point.

^{The a *} value and b ^* value of the Lab color system of the condition (2) are the X value and the Y value obtained by measuring the X value, the Y value and the Z value of the CIE XYZ of the specularly reflected light of the incident light. It can be calculated by converting the value and Z value by a general-purpose conversion formula. Further, in the measurement of the condition (2), it is preferable that the viewing angle, the light source, and the measurement wavelength are the following conditions.
Viewing angle; 2 degrees, light source; D65, measurement wavelength: 380 to 780 nm at 0.5 nm intervals The measurement conditions of condition (3) described later are also the same as those of condition (2).

Condition (3)
^{The antireflection film of the present invention calculates the square root of the sum of squares of the *} value and the b ^* value at each incident angle of 5 to 45 degrees, and further, from the following formula (B), the a ^* value between each measurement is calculated. And b ^* When calculating the absolute value of the slope of the square root of the sum of squares, the maximum value of the absolute value is preferably 17.3 or less.

(In the formula, "n" indicates an integer of 1 to 8.)

The absolute SL values of the a ^* and b ^* values indicate the difference in the tint of the antireflection film between each measurement, and more specifically, the degree of change in the tint of the antireflection film due to the change in angle. There is. Therefore, satisfying the condition (3) means that the tint of the antireflection film does not suddenly change due to the change in angle, and the color uniformity can be improved.
_{The maximum value (SL max} ) of the absolute value of SL of the ^{a *} value and b ^* value calculated from the above formula (B) is preferably 17.0 or less, and more preferably 16.5 or less. ..

Structure of Antireflection Film The antireflection film of the present invention has a basic structure having a high refractive index layer and a low refractive index layer on a transparent base material. The high refractive index layer and the low refractive index layer have a role of imparting an antireflection function by an optical interference function. The antireflection film may be further provided with an antireflection function having three or more layers of optical interference functions, such as by providing a medium refractive index layer, but it is not preferable from the viewpoint of cost effectiveness if the antireflection film has an excessively multilayer structure.
Therefore, it is preferable that the antireflection film of the present invention has two layers, a high refractive index layer and a low refractive index layer, to impart an antireflection function by an optical interference function. When a hard coat layer, which will be described later, is provided between the transparent base material and the high refractive index layer, the hard coat layer is made to have a medium refractive index to obtain a medium refractive index layer (hard coat layer), a high refractive index layer, and the like. It is preferable that the three layers of the low refractive index layer provide the antireflection function by the optical interference function.

(Transparent base material)
The transparent base material of the antireflection film is not particularly limited as long as it is a transparent material generally used as the base material of the antireflection film, but from the viewpoint of material cost, productivity, etc., a plastic film, a plastic sheet, etc. are preferable. Can be appropriately selected according to the intended use.

Examples of the plastic film or plastic sheet include those made of various synthetic resins. Examples of the synthetic resin include cellulose resins such as triacetyl cellulose resin (TAC), diacetyl cellulose, acetate butyrate cellulose, and cellophane; polyethylene terephthalate resin (PET), polybutylene terephthalate resin, polyethylene naphthalate-isophthalate copolymer resin, and polyester. Polyester resin such as based thermoplastic elastomer; low density polyethylene resin (including linear low density polyethylene resin), medium density polyethylene resin, high density polyethylene resin, ethylene α-olefin copolymer, polypropylene resin, polymethylpentene resin, polybutene Polyolefin resins such as resins, ethylene-propylene copolymers, propylene-butene copolymers, olefin-based thermoplastic elastomers, or mixtures thereof; poly (meth) methyl acrylate resin, poly (meth) ethyl acrylate resin, poly Acrylic resins such as (meth) butyl acrylate resin; polyamide resins typified by nylon 6 or nylon 66; polystyrene resins; polycarbonate resins; polyarylate resins; or polyimide resins are preferable.

As the transparent base material, one of the above-mentioned plastic films and plastic sheets can be used alone, or two or more kinds can be selected and used as a mixture. However, from the viewpoint of flexibility, toughness, transparency, etc., a cellulose resin is used. A polyester resin is more preferable, and a triacetyl cellulose resin (TAC) and a polyethylene terephthalate resin are more preferable.
The thickness of the transparent base material is not particularly limited, but is appropriately selected depending on the intended use, but is usually 5 to 130 μm, preferably 10 to 100 μm in consideration of durability, handleability, and the like.

(Hard coat layer)
It is preferable to have a hard coat layer between the transparent base material and the high refractive index layer for the purpose of improving the scratch resistance of the antireflection film. Here, the hard coat means a hardness of "H" or higher in the pencil hardness test defined by JIS K5600-5-4: 1999.
The hard coat layer can be formed from, for example, a hard coat layer coating liquid containing a curable resin composition. Examples of the curable resin composition include a thermosetting resin composition and an ionizing radiation curable resin composition, and an ionizing radiation curable resin composition is preferable from the viewpoint of scratch resistance.

The thermosetting resin composition is a composition containing at least a thermosetting resin, and is a resin composition that is cured by heating.
Examples of the thermosetting resin include acrylic resin, urethane resin, phenol resin, urea melamine resin, epoxy resin, unsaturated polyester resin, and silicone resin. In the thermosetting resin composition, a curing agent is added to these curable resins as needed.

The ionizing radiation curable resin composition is a composition containing a compound having an ionizing radiation curable functional group (hereinafter, also referred to as “ionizing radiation curable compound”). Examples of the ionizing radiation curable functional group include an ethylenically unsaturated group such as a (meth) acryloyl group, a vinyl group and an allyl group, and an epoxy group and an oxetanyl group. As the ionizing radiation curable compound, a compound having an ethylenically unsaturated bond group is preferable, a compound having two or more ethylenically unsaturated bond groups is more preferable, and a compound having two or more ethylenically unsaturated bond groups is particularly preferable. Polyfunctional (meth) acrylate compounds are more preferred. As the polyfunctional (meth) acrylate compound, either a monomer or an oligomer can be used.
Note that ionizing radiation means electromagnetic waves or charged particle beams that have energy quanta capable of polymerizing or cross-linking molecules, and usually ultraviolet rays (UV) or electron beams (EB) are used. Electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion rays can also be used.

Among the polyfunctional (meth) acrylate-based compounds, the bifunctional (meth) acrylate-based monomers include ethylene glycol di (meth) acrylate, bisphenol A tetraethoxydiacrylate, bisphenol A tetrapropoxydiacrylate, and 1,6-hexane. Examples thereof include diol diacrylate.
Examples of the trifunctional or higher functional (meth) acrylate-based monomer include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and di. Examples thereof include pentaerythritol tetra (meth) acrylate and isocyanuric acid-modified tri (meth) acrylate.
Further, the (meth) acrylate-based monomer may be one in which a part of the molecular skeleton is modified, and is modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol and the like. Can also be used.

Examples of the polyfunctional (meth) acrylate-based oligomer include acrylate-based polymers such as urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate.
Urethane (meth) acrylate is obtained, for example, by reacting a polyhydric alcohol or an organic diisocyanate with a hydroxy (meth) acrylate.
Further, the preferable epoxy (meth) acrylate is a (meth) acrylate obtained by reacting a (meth) acrylic acid with a trifunctional or higher functional aromatic epoxy resin, an alicyclic epoxy resin, an aliphatic epoxy resin or the like, and a bifunctional epoxy resin. (Meta) acrylate obtained by reacting the above aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, etc. with polybasic acid and (meth) acrylic acid, and bifunctional or higher functional aromatic epoxy resin, It is a (meth) acrylate obtained by reacting an alicyclic epoxy resin, an aliphatic epoxy resin or the like with phenols and (meth) acrylic acid.
The ionizing radiation curable compound may be used alone or in combination of two or more.

When the ionizing radiation curable compound is an ultraviolet curable compound, the ionizing radiation curable composition preferably contains an additive such as a photopolymerization initiator or a photopolymerization accelerator.
Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler ketone, benzoin, benzylmethyl ketal, benzoyl benzoate, α-acyloxime ester, thioxanthones and the like. These photopolymerization initiators preferably have a melting point of 100 ° C. or higher. By setting the melting point of the photopolymerization initiator to 100 ° C. or higher, it is possible to prevent the photopolymerization initiator remaining during the formation of the transparent conductive film or the heat of the crystallization step from sublimating and impairing the low resistance of the transparent conductive film. can do. The same applies when a photopolymerization initiator is used in the high refractive index layer and the low refractive index layer described later.
Further, the photopolymerization accelerator can reduce the polymerization inhibition by air at the time of curing and accelerate the curing rate. For example, from p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester and the like. One or more selected species can be mentioned.

The thickness of the hard coat layer is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.8 to 20 μm. If the thickness of the hard coat layer is within the above range, sufficient hard coat performance can be obtained, and cracks and the like are not generated due to an external impact, and cracks are less likely to occur.
The thickness of the hard coat layer and the high-refractive-index layer and low-refractive-index layer, which will be described later, can be determined by using, for example, a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning transmission electron microscope (STEM). It can be calculated from the average value of the values at 20 points by measuring the thickness at 20 points from the photographed cross-sectional image. When the film thickness to be measured is on the order of μm, it is preferable to use SEM, and when the film thickness is on the order of nm, it is preferable to use TEM or STEM. In the case of SEM, the acceleration voltage is preferably 1 to 10 kV and the magnification is preferably 1000 to 7000 times, and in the case of TEM or STEM, the acceleration voltage is preferably 10 to 30 kV and the magnification is preferably 50,000 to 300,000 times.

The refractive index of the hard coat layer is preferably smaller than the refractive index of the high refractive index layer described later, more preferably 1.45 to 1.70, and further preferably 1.45 to 1.60. .. If the refractive index of the hard coat layer is within such a range, the hard coat layer has a role as a medium refractive index layer, and the hard coat layer (medium refractive index layer), the high refractive index layer, and the low refractive index layer Since the interference action of the three layers is possible, it is preferable in that it is easy to satisfy the above-mentioned various conditions. Further, from the viewpoint of suppressing interference fringes, it is preferable to reduce the difference between the refractive index of the hard coat layer and the refractive index of the transparent substrate.

Examples of the means for imparting the role of the medium refractive index layer to the hard coat layer include a means for blending a resin having a high refractive index in the hard coat layer coating liquid and a means for blending particles having a high refractive index. When particles having a high refractive index are blended, whitening or coating defects may occur due to aggregation of the particles. Therefore, the former means (blended with a resin having a high refractive index) is preferable.
Examples of the resin having a high refractive index include those obtained by introducing a group containing sulfur, phosphorus, bromine, an aromatic ring, or the like into the above-mentioned thermosetting resin or ionizing radiation curable compound. As the particles having a high refractive index, the same particles as those used for the high refractive index layer described later can be used.

The refractive index of the hard coat layer, the high refractive index layer and the low refractive index layer, which will be described later, is determined from, for example, a reflection spectrum measured by a reflected photometric meter and a reflection spectrum calculated from an optical model of a multilayer thin film using a Fresnel coefficient. It can be calculated by fitting with.

For the hard coat layer, the coating liquid for forming the hard coating layer is prepared with the above-mentioned curable resin composition, additives such as an ultraviolet absorber and a leveling agent to be blended as necessary, and a diluting solvent, and the coating liquid is used as a transparent group. It can be formed by coating, drying, and if necessary, irradiating a material with ionizing radiation to cure it by a conventionally known coating method.

(High refractive index layer)
The high refractive index layer can be formed from, for example, a high refractive index layer coating liquid containing a curable resin composition and high refractive index particles.
The high-refractive index layer preferably has a high refractive index from the viewpoint of making the antireflection film ultra-low refractive index, but a large amount of high-refractive index particles are required to increase the refractive index, and the high-refractive index particles It causes agglomeration and causes whitening. Therefore, the refractive index is preferably 1.55 to 1.85, and more preferably 1.56 to 1.70.
The thickness of the high refractive index layer is preferably 200 nm or less, more preferably 50 to 180 nm. When the high refractive index layer has a two-layer structure described later, it is preferable that the total thickness of the two layers satisfies the above value.
Further, the high refractive index layer may be formed from a plurality of layers satisfying the above range of refractive index, but from the viewpoint of cost effectiveness, two or less layers are preferable, and a single layer is more preferable.

Examples of high refractive index particles include antimony pentoxide (1.79), zinc oxide (1.90), titanium oxide (2.3 to 2.7), cerium oxide (1.95), and tin-doped indium oxide (1. 95 to 2.00), antimony-doped tin oxide (1.75 to 1.85), yttrium oxide (1.87), zirconium oxide (2.10) and the like. The numbers in parentheses indicate the refractive index of the material of each particle.
Among these high refractive index particles, those having a refractive index of more than 2.0 are preferable from the viewpoint of achieving the above-mentioned suitable refractive index with a small amount of addition. Further, highly conductive particles such as antimony pentoxide, tin-doped indium oxide (ITO), and antimony-doped tin oxide (ATO) have free electrons whose plasma frequency is in the near-infrared region, and the free electrons. Due to the plasma oscillation of, part of the light in the visible light region is also absorbed or reflected, and it may be difficult to suppress the tint. Therefore, the high-refractive index particles are preferably non-conductive.
From the above, among the high-refractive index particles exemplified above, titanium oxide and zirconium oxide are preferable, and zirconium oxide is optimal from the viewpoint of high durability stability such as light resistance. When it is desired to impart antistatic properties to the antireflection film, it is preferable that the high refractive index layer has a two-layer structure as described later, and one layer contains conductive high refractive index particles.

The average particle size of the primary particles of the high refractive index particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, and even more preferably 10 to 80 nm.
The average particle size of the primary particles of the high refractive index particles and the low refractive index particles described later can be calculated by the following operations (1) to (3).
(1) An image of a surface image of SEM, TEM, or STEM is taken of the particles themselves or a dispersion of particles coated and dried on a transparent substrate.
(2) Arbitrary 10 particles are extracted from the surface image, the major axis and the minor axis of each particle are measured, and the particle size of each particle is calculated from the average of the major axis and the minor axis. The major axis is the longest diameter on the screen, and the minor axis is the distance between two points where a line segment orthogonal to the midpoint of the line segment constituting the major axis is drawn and the orthogonal line segment intersects the particle. It shall be.
(3) The same operation was performed 5 times in the imaging of the same sample on another screen, and the value obtained from the number average of the particle sizes of a total of 50 particles was taken as the average particle size.
When calculating the average particle size of the particles, it is preferable to use SEM when the calculated average particle size is on the order of μm, and it is preferable to use TEM or STEM when the calculated average particle size is on the order of nm. .. In the case of SEM, the acceleration voltage is preferably 1 to 10 kV and the magnification is preferably 1000 to 7000 times, and in the case of TEM or STEM, the acceleration voltage is preferably 10 to 30 kV and the magnification is preferably 50,000 to 300,000 times.

The content of the high refractive index particles is preferably 30 to 400 parts by mass with respect to 100 parts by mass of the curable resin composition from the viewpoint of the balance between high refractive index, suppression of color and whitening. It is more preferably about 200 parts by mass, and even more preferably 80 to 150 parts by mass.

The high refractive index layer is preferably dispersed and stabilized in order to suppress excessive aggregation of the high refractive index particles. Examples of the means for stabilizing the dispersion include means for adding another high-refractive index particle having a surface charge amount smaller than that of the high-refractive index particle as a base. According to the means, it is possible to prevent the base high-refractive index particles from appropriately gathering around the other high-refractive index particles and excessively agglomerate the base high-refractive index particles. Further, as another means for stabilizing the dispersion, a means for using surface-treated particles as high-refractive index particles or a means for adding a dispersant to the high-refractive index layer coating liquid can be mentioned.

As the curable resin composition for forming the high refractive index layer, the same curable resin composition as those exemplified in the hard coat layer can be used, and the ionizing radiation curable resin composition is suitable.
Further, in order to obtain the above-mentioned refractive index without excessively adding the high refractive index particles, it is preferable to use a curable resin composition having a high refractive index. The refractive index of the curable resin composition is preferably about 1.54 to 1.70.

Further, the high refractive index layer may have a two-layer structure consisting of a high refractive index layer (A) located on the hard coat layer side and a high refractive index layer (B) located on the low refractive index layer side. At that time, it is preferable that the refractive index of the high refractive index layer (B) is higher than that of the high refractive index layer (A). By forming the high refractive index layer in this configuration, the refractive index difference from the low refractive index layer can be increased, the refractive index can be reduced, and the refractive index difference between the high refractive index layer and the hard coat layer can be reduced, resulting in interference. The occurrence of fringes can be suppressed.
When the high refractive index layer has a two-layer structure, the refractive index of the high refractive index layer (A) is 1.55 to 1.70, and the refractive index of the high refractive index layer (B) is 1.60 to 1.85. It is preferable to have.
Further, in the above two-layer structure, one of the high refractive index layer (A) and the high refractive index layer (B) contains conductive high refractive index particles, and the other contains non-conductive high refractive index particles. And, it is preferable that [thickness of the layer containing the conductive high refractive index particles <thickness of the layer containing the non-conductive high refractive index particles]. With this configuration, antistatic properties can be imparted while suppressing the amount of conductive high-refractive index particles that can cause color. Further, the conductive high refractive index particles are preferable in that they can impart antistatic properties with a small amount of addition by networking in the layer, and thus can suppress color tint and whitening.

For the high refractive index layer, the coating liquid for forming the high refractive index layer is prepared by adjusting the coating liquid for forming the high refractive index layer with high refractive index particles, a curable resin composition, additives such as an ultraviolet absorber and a leveling agent to be blended as necessary, and a diluting solvent. It can be formed by applying a coating liquid onto a hard coat layer by a conventionally known coating method, drying, and curing by irradiating ionizing radiation as necessary.

(Low refractive index layer)
The low refractive index layer is a layer provided on the high refractive index layer.
The low refractive index layer preferably has a refractive index of 1.26 to 1.36, more preferably 1.28 to 1.34, in order to make the antireflection film ultra-low reflectance. It is more preferably .30 to 1.32.
The lower the refractive index of the low refractive index layer is, the lower the refractive index of the antireflection film can be without having to increase the refractive index of the high refractive index layer so much. On the other hand, if the refractive index of the low refractive index layer is made too low, the strength of the low refractive index layer tends to decrease. Therefore, by setting the refractive index of the low refractive index layer within the above range, it is possible to suppress the amount of high refractive index particles added to the high refractive index layer while maintaining the strength of the low refractive index layer, resulting in tint and whitening. It is preferable in that it leads to suppression.
The thickness of the low refractive index layer is preferably 80 to 120 nm, more preferably 85 to 110 nm, and even more preferably 90 to 105 nm.
Further, the low refractive index layer may be formed from a plurality of layers satisfying the above range of refractive index, but from the viewpoint of cost effectiveness, two or less layers are preferable, and a single layer is more preferable.

The method for forming the low refractive index layer can be roughly divided into a wet method and a dry method. As the wet method, a method of forming by a sol-gel method using a metal alkoxide or the like, a method of forming by coating a resin having a low refractive index such as a fluororesin, or a method in which low refractive index particles are contained in a resin composition are low. A method of forming by applying a coating liquid for forming a refractive index layer can be mentioned. Examples of the dry method include a method of selecting particles having a desired refractive index from low refractive index particles described later and forming them by a physical vapor deposition method or a chemical vapor deposition method.
The wet method is excellent in terms of production efficiency, and in the present invention, among the wet methods, it is preferable to form the resin composition with a coating liquid for forming a low refractive index layer containing low refractive index particles.

The low refractive index particles are preferably used for the purpose of lowering the refractive index, that is, improving the antireflection property, and are used without limitation regardless of whether they are inorganic or organic such as silica and magnesium fluoride. However, from the viewpoint of further improving the antireflection property and ensuring good surface hardness, particles having a structure having voids themselves are preferably used.

Particles having a structure having voids themselves have fine voids inside, and are filled with a gas such as air having a refractive index of 1.0, so that the particles themselves have a low refractive index. It has become. Examples of the particles having such voids include inorganic or organic porous particles and hollow particles. For example, porous polymer particles using porous silica, hollow silica particles, acrylic resin and the like. And hollow polymer particles. As the inorganic particles, silica particles having voids prepared by using the technique disclosed in JP-A-2001-233611 are used, and as organic particles, the technique disclosed in JP-A-2002-80503. As a preferable example, hollow polymer particles prepared using the above can be mentioned. Silica having voids or porous silica as described above has a refractive index in the range of 1.18 to 1.44 and a refractive index higher than that of general silica particles having a refractive index of about 1.45. Is preferable from the viewpoint of reducing the refractive index of the low refractive index layer.

Hollow silica particles are particles having a function of lowering the refractive index while maintaining the coating film strength of the low refractive index layer. The hollow silica particles used in the present invention are silica particles having a structure having cavities inside. The hollow silica particles are silica particles whose refractive index decreases in inverse proportion to the occupancy rate of the internal cavity as compared with the original refractive index of the silica particles (refractive index n = about 1.45). Therefore, the refractive index of the hollow silica particles as a whole is 1.18 to 1.44.

The hollow silica particles are not particularly limited, and are, for example, particles having an outer shell and having a porous or hollow inside, and are JP-A-6-330606, JP-A-7-0131337, JP-A-7. Examples thereof include silica particles prepared by using the technique disclosed in 133105 and Japanese Patent Application Laid-Open No. 2001-233611.

The average particle size of the primary particles of the low refractive index particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, and even more preferably 10 to 80 nm. When the average particle size of the primary particles is within the above range, the transparency of the low refractive index layer is not impaired, and a good dispersed state of particles can be obtained. In particular, when hollow particles are used as low refractive index particles and the average particle size of the hollow particles is 70 to 80 nm, the void ratio is increased and the refractive index is decreased while maintaining the thickness of the outer shell that does not cause insufficient strength. It is preferable in that it can be made to grow and is excellent in balance with the ideal thickness of the low refractive index layer (about 100 nm) for lowering the reflectance.

The low refractive index particles used in the present invention are preferably surface-treated. As the surface treatment of the low refractive index particles, a surface treatment using a silane coupling agent is more preferable, and among these, a surface treatment using a silane coupling agent having a (meth) acryloyl group is preferable. By applying a surface treatment to the low refractive index particles, the affinity with the binder resin described later is improved, the dispersion of the particles becomes uniform, and the particles are less likely to aggregate with each other. The decrease in transparency of the rate layer, the coatability of the composition for forming a low refractive index layer, and the decrease in the coating strength of the composition are suppressed.

Further, when the silane coupling agent has a (meth) acryloyl group, the silane coupling agent has ionizing radiation curability and easily reacts with a binder resin described later. Therefore, a composition for forming a low refractive index layer. In the coating film of, the low refractive index particles are well fixed to the binder resin. That is, the low refractive index particles have a function as a cross-linking agent in the binder resin. As a result, the tightening effect of the entire coating film can be obtained, and it is possible to impart excellent surface hardness to the low refractive index layer while retaining the flexibility inherent in the binder resin. Therefore, since the low refractive index layer is deformed by utilizing its own flexibility, it has an absorbing force against an external impact and a restoring force, so that the occurrence of scratches is suppressed and the surface hardness is excellent in scratch resistance. Will have.

Silane coupling agents preferably used in the surface treatment of low refractive index particles include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, and 3- (meth) acryloxipropyl. Examples thereof include methyldimethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, 2- (meth) acryloxypropyltrimethoxysilane, 2- (meth) acryloxipropyltriethoxysilane, and the like.

The content of the low refractive index particles in the low refractive index layer is preferably 10 to 250 parts by mass, more preferably 50 to 200 parts by mass, and further 100 to 180 parts by mass with respect to 100 parts by mass of the resin in the low refractive index layer. preferable. When the content of the low refractive index particles is within the above range, good antireflection properties and surface hardness can be obtained.
Further, the ratio of the hollow particles and / or the porous particles to the total low refractive index particles contained in the low refractive index layer is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 80 to 95% by mass. preferable.

Examples of the resin composition contained in the coating liquid for forming a low refractive index layer include a curable resin composition. As the curable resin composition, the same ones as those exemplified in the hard coat layer can be used, and the ionizing radiation curable resin composition is suitable.
Further, as the resin composition, a fluorine-containing polymer or a fluorine monomer which itself exhibits a low refractive index is also preferably used. The fluoropolymer is a polymer of a polymerizable compound containing at least a fluorine atom in the molecule, and is suitable in that it can impart antifouling property and slipperiness. The fluorine-containing polymer preferably has a reactive group in the molecule and functions as a curable resin composition, and a fluoropolymer having an ionizing radiation-curable reactive group and functioning as an ionizing thermosetting resin composition is preferable. More preferred.

The fluoropolymer preferably contains silicon together with fluorine in order not only to repel stains on the surface of the low refractive index layer but also to impart wiping property of the repelled stains. For example, a silicone component is added to the copolymer. A silicone-containing vinylidene fluoride copolymer contained therein is preferably used. In this case, the silicone component includes (poly) dimethylsiloxane, (poly) diethylsiloxane, (poly) diphenylsiloxane, (poly) methylphenylsiloxane, alkyl-modified (poly) dimethylsiloxane, azo group-containing (poly) dimethylsiloxane, and the like. , Dimethyl silicone, phenylmethyl silicone, alkyl-aralkyl-modified silicone, fluorosilicone, polyether-modified silicone, fatty acid ester-modified silicone, methyl hydrogen silicone, silanol group-containing silicone, alkoxy group-containing silicone, phenol group-containing silicone, methacryl-modified silicone, Examples thereof include acrylic-modified silicone, amino-modified silicone, carboxylic acid-modified silicone, carbinol-modified silicone, epoxy-modified silicone, mercapto-modified silicone, fluorine-modified silicone, and polyether-modified silicone. Among them, those having a dimethylsiloxane structure are preferable.

For the low refractive index layer, for example, the coating liquid for forming the low refractive index layer is prepared with low refractive index particles, a resin composition, additives such as an ultraviolet absorber and a leveling agent to be blended as necessary, and a diluting solvent. It can be formed by coating a coating liquid on a high refractive index layer by a conventionally known coating method, drying it, and irradiating it with ionizing radiation as necessary to cure it.

(Physical characteristics of antireflection film)
The antireflection film preferably has a total light transmittance (JIS K7361-1: 1997) of 90% or more, and more preferably 92% or more. Further, the antireflection film of the present invention preferably has a haze (JIS K7136: 2000) of 1.0% or less, more preferably 0.5% or less, and preferably 0.3% or less. More preferred.
The light incident surface when measuring the total light transmittance and the haze is on the transparent substrate side.

The arithmetic mean roughness Ra (JIS B0601: 1994) of the surface of the antireflection film (the surface on the low refractive index layer side) is preferably 10 nm or less, and more preferably 1 to 8 nm. The ten-point average roughness Rz (JIS B0601: 1994) of the surface of the antireflection film (the surface on the low refractive index layer side) is preferably 160 nm or less, more preferably 50 to 155 nm.
When Ra and Rz are in the above range, it has smoothness and scratch resistance is improved.

The antireflection film of the present invention described above is excellent in color uniformity while suppressing reflectance. In particular, a large-screen display device having a screen size of 106.7 cm or more diagonally, a display device having a resolution of 3840 × 2160 pixels or more, a so-called 4K resolution or higher, a convex-shaped display device, and a display device with a touch panel ( When the antireflection film of the present invention is used for a screen size of more than 38.1 cm diagonally), the above effect can be easily exhibited.

[Display device]
The display device of the present invention is formed by arranging the above-mentioned antireflection film of the present invention on a display element so that the transparent base material side of the antireflection film faces the display element side.
Examples of the display element constituting the display device include a liquid crystal display element, a plasma display element, an organic EL display element, and the like.
The specific configuration of the display element is not particularly limited. For example, a liquid crystal display element has a basic configuration having a lower glass substrate, a lower transparent electrode, a liquid crystal layer, an upper transparent electrode, a color filter, and an upper glass substrate in this order. The upper transparent electrode is densely patterned.

The display element preferably has a resolution of 3840 × 2160 pixels or more, so-called 4K resolution or higher. An ultra-high-definition display element having a resolution of 4K or higher is easily affected by color because the amount of light per pixel is small. Further, a display device provided with a display element having a 4K resolution or higher has a large screen, and a problem of color uniformity is likely to occur. Therefore, a display element having a resolution of 4K resolution or higher is suitable in that the effect of the present invention can be easily exhibited.
Examples of the display element having a 4K resolution include those having a pixel count of 3840 × 2160 pixels and those having a pixel count of 4096 × 2160 pixels.
Further, even if the display device does not have a resolution of 4K resolution or higher, a large screen display device having a screen size of 106.7 cm or more diagonally is suitable in that the effect of the present invention can be easily exhibited.
Further, a convex-shaped display device is also suitable in that a problem of color uniformity is likely to occur and the effect of the present invention is easily exhibited.

The display device of the present invention may have a touch panel on the display element, and an antireflection film may be arranged on the touch panel. Also in this embodiment, it is necessary to arrange the antireflection film so that the transparent base material side faces the display element side. In the case of a display device with a touch panel, it is preferable in that the effect of the present invention can be easily exhibited when the screen size of the display device exceeds 38.1 cm diagonally.
Examples of the touch panel include a capacitive touch panel, a resistive touch panel, an optical touch panel, an ultrasonic touch panel, an electromagnetic induction touch panel, and the like.

The resistive touch panel has a basic configuration in which the conductive films of a pair of upper and lower transparent substrates having a conductive film are arranged via spacers so as to face each other, and a circuit is connected to the basic configuration. is there.
Examples of the capacitance type touch panel include a surface type and a projection type, and the projection type is often used. The projection type capacitance type touch panel is formed by connecting a circuit to a basic configuration in which an X-axis electrode and a Y-axis electrode orthogonal to the X-axis electrode are arranged via an insulator. More specifically, the basic configuration will be described as follows: (1) an embodiment in which an X electrode and a Y electrode are formed on separate surfaces on one transparent substrate, and (2) an X electrode, an insulator layer, and Y on the transparent substrate. Examples thereof include an embodiment in which the electrodes are formed in this order, (3) an X electrode is formed on a transparent substrate, a Y electrode is formed on another transparent substrate, and the electrodes are laminated via an adhesive layer or the like. Further, in addition to these basic modes, there is a mode in which another transparent substrate is laminated.

In a display device with a touch panel, the distance between the screen and the human eye is short, and even if the screen is not a large screen, the emission angles are large at the left and right ends of the screen, so color uniformity tends to be a problem. Therefore, when the antireflection film of the present invention is used for a display device with a touch panel, the effect of the present invention can be easily exhibited.

[How to select anti-reflective film]
In the method for selecting an antireflection film of the present invention, a surface of the transparent base material of the antireflection film having a high refractive index layer and a low refractive index layer on the transparent base material opposite to the high refractive index layer side. A sample in which a black plate is bonded via a transparent adhesive is prepared, and the visual reflectance Y value measured from the sample and the a ^* value and b ^* value of the Lab color system are the following conditions (1) and ( The determination condition is that 2) is satisfied.

<Condition (1)>
When the incident angle of light incident perpendicular to the surface on the low refractive index layer side of the sample is 0 degrees and the light is incident on the sample at an incident angle of 5 degrees, the specular reflection of the incident light is visible. The reflectance Y value is 0.50% or less.
<Condition (2)>
The incident angle of light incident perpendicular to the surface of the sample on the low refractive index layer side is set to 0 degrees, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and the incident light is positively reflected. ^{The a *} value and b ^* value of the Lab color system of light are measured, ^{the square root of the sum of squares of the a *} value and b ^* value at each incident angle is calculated, and further, from the following formula (A), between each measurement. When the slope of the square root of the sum of squares of the a ^* value and b ^* value of is calculated, the angle x (degree) indicating the turning point at which the slope changes from negative to positive is 25 degrees ≦ x.

(In the formula, "n" indicates an integer of 1 to 8.)

In the method for selecting the antireflection film of the present invention, it is preferable that the above-mentioned condition (3) is further used as a determination condition.

The antireflection film to be selected in the present invention may have a layer other than the high refractive index layer and the low refractive index layer on the transparent base material. For example, a hard coat layer may be provided between the transparent base material and the high refractive index layer.
The embodiment of the transparent base material, the high refractive index layer, the low refractive index layer, and the hard coat layer provided as needed of the antireflection film selected by the method for selecting the antireflection film of the present invention is the antireflection film of the present invention. It is the same as the embodiment of the transparent base material, the high refractive index layer, the low refractive index layer and the hard coat layer of.

According to the method for selecting an antireflection film of the present invention, an antireflection film having a low reflectance and excellent color uniformity can be accurately selected, and the quality of the antireflection film can be standardized.

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to this example.

1. 1. Physical Properties and Evaluation The following measurements and evaluations were performed on the antireflection films obtained in Examples and Comparative Examples. The results are shown in Tables 1 and 2.
1-1. Visual reflectance Y value of the antireflection film A black plate (refractive index: 1.49) is placed on the surface of the transparent base material of the antireflection film opposite to the high refractive index layer side via a transparent adhesive (refractive index 1.49). A sample was prepared by laminating 1.49). When the incident angle of light incident perpendicular to the surface on the low refractive index layer side of the sample is 0 degrees and the light is incident on the sample at an incident angle of 5 degrees, the specular reflection of the incident light is visible. The reflectance Y value was measured.
A spectrophotometer (manufactured by Shimadzu Corporation, trade name: UV-2450) is used as a measuring device for the visual reflectance Y value, the viewing angle is 2 degrees, the light source is D65, and the measurement wavelength is 380 to 780 nm. The interval was 5 nm.

1-2. ^{A *} value and b ^* value of the Lab color system of the antireflection film The incident angle is 0 degrees, where the incident angle of light incident perpendicular to the surface on the low refractive index layer side of the sample prepared in 1-1 above is 0 degrees. Light was incident on the sample at intervals of 5 degrees from 5 degrees to 45 degrees, ^{and the a *} value and b ^* value of the Lab color system of the specularly reflected light of the incident light were measured. Further, the numerical values of the above-mentioned conditions (2) and (3) were calculated from the measurement results of ^{the a *} value and the b ^{* value.}
A ^{spectrophotometer (manufactured by JASCO Corporation, trade name: V-7100) is used as the measuring device for the a *} and b ^* values, the viewing angle is 2 degrees, the light source is D65, and the measurement wavelength is 380 to 780 nm. The interval was set to 5.5 nm.

1-3. Evaluation of anti-reflection performance of anti-reflection film An anti-reflection film is installed on a liquid crystal display element with 3840 x 2160 pixels so that the surface of the anti-reflection film on the transparent substrate side faces the liquid crystal display element. , A simulated liquid crystal display device was manufactured. In a bright room environment, without displaying an image on the display element, the observer's own reflection is projected from the vertical direction of the simulated liquid crystal display device near the center of the surface (low refractive index layer) of the simulated liquid crystal display device. It was visually observed.
As a result, the one in which the reflected observer's skin color could not be recognized due to the strong black color was designated as "A", and the one in which the reflected observer's skin color could be recognized was designated as "C".

1-4. Color uniformity of antireflection film The color of the sample surface was visually observed from a position where specular reflected light could be confirmed by reflecting a fluorescent lamp on the sample prepared in 1-1 above. At the time of the observation, the sample was moved so as to gradually change from perpendicular (0 degree) to 45 degrees with respect to the fluorescent lamp directly under the fluorescent lamp.
The observation was carried out by 20 people, and one sample had no part where the color was strongly felt and no part where the sudden change in color was felt, and two samples had one of the two points. Each person evaluated the sample having both of the two locations as 3 points. The average score of 20 people is 1.1 points or less as "AA", more than 1.1 points and less than 1.5 points as "A", and more than 1.5 points and less than 2.0 points. "B", those with more than 2.0 points and 2.5 points or less were designated as "C", and those with more than 2.5 points and 3.0 points or less were designated as "D".

2. Fabrication of Antireflection Film [Example 1]
On a triacetyl cellulose film (refractive index 1.49) having a thickness of 80 μm, a coating liquid for forming a hard coat layer having the following formulation was applied, dried and irradiated with ultraviolet rays to obtain a thickness of 10 μm, a refractive index of 1.54, and a pencil hardness of 2H). A hard coat layer was formed. Next, a coating liquid for forming a high refractive index layer having the following formulation was applied onto the hard coat layer, dried and irradiated with ultraviolet rays to form a high refractive index layer having a thickness of 150 nm and a refractive index of 1.63). Next, a coating liquid for forming a low refractive index layer according to the following formulation is applied onto the high refractive index layer, dried and irradiated with ultraviolet rays to form a low refractive index layer having a thickness of 100 nm and a refractive index of 1.30) to form an antireflection film. Got

<Preparation of coating liquid for forming hard coat layer>
Photopolymerization initiator (BASF, Irgacure 127, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) benzyl] phenyl} -2-methylpropan-1-one) is 1 .6 parts by mass and 58.3 parts by mass of a diluting solvent (methyl isobutyl ketone / cyclohexanone = 8/2) were added, and the mixture was stirred until there was no undissolved residue. 20 parts by mass of a photocurable resin (Arakawa Chemical Co., Ltd., beam set 577) and 20 parts by mass of a high refractive index resin (DIC Corporation, Polylite RX-4800) are put therein and stirred until there is no undissolved residue. did. Finally, 0.1 parts by mass of a leveling agent (Seika Beam 10-28 (MB) manufactured by Dainichiseika Kogyo Co., Ltd.) was added and stirred to prepare a coating liquid for forming a hard coat layer.

<Preparation of coating liquid for forming a high refractive index layer>
0.1 part by mass of a photopolymerization initiator (Irgacure 127, manufactured by BASF) and 92.6 parts by mass of a diluting solvent (methyl isobutyl ketone / cyclohexanone / methyl ethyl ketone = 4/2/4) were added, and the mixture was stirred until there was no undissolved residue. .. A photocurable resin (manufactured by Arakawa Chemical Co., Ltd., beam set 577) was added thereto by 1.25 parts by mass, and the mixture was stirred until there was no undissolved residue. Furthermore, 6 parts by mass of zirconium oxide (MZ-230X, manufactured by Sumitomo Osaka Cement Co., Ltd., solid content 32.5% by mass, average primary particle size 15 to 50 nm), leveling agent (manufactured by Dainichiseika Kogyo Co., Ltd., Seika Beam 10-28) MB)) 0.05 parts by mass of each was added and stirred to prepare a coating liquid for forming a high refractive index layer.

<Preparation of coating liquid for forming a low refractive index layer>
0.2 parts by mass of a photopolymerization initiator (Irgacure 127, manufactured by BASF) and 91.1 parts by mass of a diluent solvent (MIBK / AN = 7/3) were added, and the mixture was stirred until there was no undissolved residue. Here, 1.0 part by mass of a photo-curing resin (KAYARAD-PET-30 manufactured by Nippon Kayaku Co., Ltd.), 7.6 parts by mass of hollow silica particles (solid content 20% by mass, average primary particle diameter 60 nm), and a leveling agent (large). 0.1 parts by mass of Seika Beam 10-28 (MB) manufactured by Nisseika Kogyo Co., Ltd. was added and stirred to prepare a coating liquid for forming a low refractive index layer.

[Example 2]
The photocurable resin of the coating liquid for forming the hard coat layer of Example 1 was changed to 40 parts by mass, the high refractive index resin was changed to 0 parts by mass (refractive index after change 1.51), and the high refractive index layer was changed to 2 parts. As the coating liquid for the high refractive index layer (A) on the hard coat layer side, the zirconium oxide of the coating liquid for forming the high refractive index layer of Example 1 was changed to antimony-doped tin oxide (solid content 45% by mass). (Refractive index 1.59 after change) was used, the thickness was 70 nm, and the coating liquid for forming the high refractive index layer of Example 1 was used as the coating liquid for the high refractive index layer (B) on the low refractive index layer side. An anti-reflection film was obtained in the same manner as in Example 1 except that the thickness was 90 nm.

[Example 3]
The same as in Example 2 except that the thickness of the high refractive index layer (A) on the hard coat layer side of Example 2 was changed to 60 nm and the thickness of the high refractive index layer (B) on the low refractive index layer side was changed to 120 nm. Obtained an antireflection film.

[Comparative Example 1]
The high refractive index layers (A) and (B) of Example 2 were not formed, and the photocurable resin of the coating liquid for forming the low refractive index layer was 2.0 parts by mass and the hollow silica particles were 6.6 parts by mass. An antireflection film was obtained in the same manner as in Example 2 except that the change (refractive index after the change was 1.36).

[Comparative Example 2]
The high refractive index layer (B) of Example 2 was not formed, and the photocurable resin of the coating liquid was changed to 4.25 parts by mass and the antimony-doped tin oxide was changed to 3 parts by mass with respect to the high refractive index layer (A). (Refractive index after change 1.56), the film thickness was changed to 160 nm, and with respect to the low refractive index layer, 3.1 parts by mass of the photocurable resin of the coating liquid and 5.5 parts by mass of hollow silica particles. An antireflection film was obtained in the same manner as in Example 2 except that the refractive index was changed to 1.38 (refractive index after the change was 1.38) and the thickness was changed to 90 nm.

[Comparative Example 3]
The same as in Example 1 except that the photocurable resin of the coating liquid for forming the hard coat layer of Example 1 was changed to 40 parts by mass and the high refractive index resin was changed to 0 parts by mass (refractive index after change: 1.51). Obtained an antireflection film.

[Comparative Example 4]
Regarding the high refractive index layer (A) on the hard coat layer side of Example 2, the antimony-doped tin oxide of the coating liquid was changed to antimony pentoxide (solid content 40% by mass) (refractive index after change 1. 58) An antireflection film was obtained in the same manner as in Example 2 except that the thickness was changed to 50 nm and the thickness of the high refractive index layer (B) on the low refractive index layer side was changed to 105 nm.

As is clear from the results of Tables 1 and 2, the antireflection films of Examples 1 to 4 satisfying the conditions (1) and (2) have excellent antireflection performance and excellent color uniformity. It turns out that it is a thing.
On the other hand, the antireflection films of Comparative Examples 1 and 2 did not satisfy the condition (1) and could not suppress the reflectance. Further, since the antireflection films of Comparative Examples 3 and 4 do not satisfy the condition (2) while suppressing the reflectance, the color tone suddenly changes at an angle (around 35 to 45 degrees) away from the front direction. The color uniformity could not be improved.

The antireflection film and display device of the present invention are useful in that they have excellent color uniformity while suppressing reflectance.

Claims (10)

An antireflection film having a high refractive index layer and a low refractive index layer arranged on the high refractive index layer on a transparent base material.
The high refractive index layer has a two-layer structure, one high refractive index layer contains conductive high refractive index particles, and the other high refractive index layer contains non-conductive high refractive index particles. The refractive index of the high refractive index layer located on the material side is 1.55 to 1.70, and the refractive index of the high refractive index layer located on the low refractive index layer side is 1.60 to 1.85. The total thickness of the two layers of the high refractive index layer is 50 to 180 nm, the refractive index of the low refractive index layer is 1.26 to 1.36, and the thickness of the low refractive index layer is 80 to 120 nm.
The antireflection film has a visual reflectance Y value measured from a sample in which a black plate is attached to a surface of the transparent base material of the antireflection film opposite to the high refractive index layer side via a transparent adhesive. ^{An antireflection film in which the a *} value and b ^* value of the Lab color system satisfy the following conditions (1) and (2).
<Condition (1)>
When the incident angle of light incident perpendicular to the surface on the low refractive index layer side of the sample is 0 degrees and the light is incident on the sample at an incident angle of 5 degrees, the specular reflection of the incident light is visible. The reflectance Y value is 0.50% or less.
<Condition (2)>
The incident angle of light incident perpendicular to the surface of the sample on the low refractive index layer side is set to 0 degrees, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and the incident light is positively reflected. ^{The a *} value and b ^* value of the Lab color system of light are measured, ^{the square root of the sum of squares of the a *} value and b ^* value at each incident angle is calculated, and further, from the following formula (A), between each measurement. When the slope of the square root of the sum of squares of the a ^* value and b ^* value of is calculated, the angle x (degree) indicating the turning point at which the slope changes from negative to positive is 25 degrees ≦ x.

(In the formula, "n" indicates an integer of 1 to 8.) The antireflection film according to claim 1, wherein the total thickness of the two layers of the high refractive index layer is 50 to 160 nm. The antireflection film according to claim 1 or 2, wherein the thickness of the two layers of the high refractive index layer satisfies the following conditions.
Thickness of high refractive index layer containing conductive high refractive index particles <Thickness of high refractive index layer containing non-conductive high refractive index particles The antireflection film according to any one of claims 1 to 3, wherein the conductive high refractive index particles are antimony pentoxide or antimony-doped tin oxide. The antireflection film according to any one of claims 1 to 4 (however, the high refractive index layer located on the low refractive index layer side is a unit having a fluorine-containing alkyl group or a unit having a polydialkylsiloxane group. Except for those containing high refractive index particles which are surface-modified by a polymer having a unit having a reactive group which surface-modifies the high refractive index particles.) ^{The square root of the sum of squares of the a *} and b ^* values at each incident angle of 5 to 45 degrees ^{is calculated, and the sum of squares of the a *} and b ^* values between each measurement is further calculated from the following equation (B). The antireflection film according to any one of claims 1 to 5, wherein the maximum value of the absolute value is 17.3 or less when the absolute value of the slope of the square root of is calculated.

(In the formula, "n" indicates an integer of 1 to 8.) The antireflection film according to any one of claims 1 to 6, wherein a hard coat layer is provided between the transparent substrate and the high refractive index layer. A display device in which the antireflection film according to any one of claims 1 to 7 is arranged on a display element so that the transparent base material side of the antireflection film faces the display element side. The display device according to claim 8, wherein the display device has a touch panel on the display element, and the antireflection film is arranged on the touch panel. The display device according to claim 8 or 9, wherein the number of pixels of the display element is 3840 × 2160 pixels or more.