JP6561519B2 - Antireflection film, display device using the antireflection film, and method for selecting antireflection film - Google Patents

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, development of display devices capable of displaying ultra-high definition images has been 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 that prevents external light from being reflected.
As means for preventing the reflection of external light, there are mainly anti-glare treatment for reducing the regular reflection light by making the surface uneven, and anti-reflection treatment for reducing the reflectance by the interference action of the multilayer thin film. In recent years, anti-reflection processing that tends to give a high-quality image has become mainstream.

  Multilayer thin films can reduce reflectivity and color as the thin films are stacked, but from the viewpoint of cost effectiveness, many of them use the interference action of two to four layers. As such an antireflection film, for example, one of Patent Document 1 can be mentioned.

In recent years, an anti-reflection film using an interference action of 2 to 4 layers is required to have an ultra-low reflectivity product having a reflectivity of 0.50% or less so as not to impair the image quality of an ultra-high-definition display device. ing.
In addition, due to the ultra-high definition of display devices in recent years, even if the display device has a large screen, pixels are no longer an issue, so the number of display devices with a large screen has further increased. In such a large screen display device, the left and right ends of the screen have large emission angles even when viewed from the front. Further, in a display device with a touch panel typified by a tablet-type portable information terminal, since the distance between the screen and the human eye is close, the left and right ends of the screen have a large emission angle even if the screen is not a large screen. In some cases (for example, when used sideways). In addition, even when the display device has a convex shape, the emission angles at the left and right ends are large. For this reason, color uniformity (hereinafter referred to as “color uniformity”) in a range where the emission angles are different has started to be regarded as important.
In order to reduce the reflectance and color in the front direction, the reflectance and color of the multilayer thin film antireflection film are managed by regular reflection light having an incident angle of 5 degrees. However, even if the specularly reflected light of light having an incident angle of 5 degrees shows a value in which the reflectance and color are suppressed, the color uniformity may not be sufficient.

JP 2010-152111 A

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

  The present inventors have intensively studied to solve the above problems, and an antireflection film that causes a problem of color tends to feel color when observed from an angle away from the front direction (around 30 to 45 degrees). And gained knowledge. As a result of further earnest studies, the present inventors have found that the angle dependency of the tint can be suppressed by managing the tint at an angle away from the frontal direction, rather than managing the tint at the frontal direction. The present invention has been completed.

The present invention provides the following antireflection films [1] to [11], 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 substrate, the antireflection film being opposite to the high refractive index layer side of the transparent substrate of the antireflection film Reflection satisfying the following conditions (1) and (2) where the luminous reflectance Y value and the a ^* value and b ^* value of the Lab color system measured from a sample having a black plate bonded to the surface through a transparent adhesive Prevention film.
<Condition (1)>
When the incident angle of light perpendicularly incident on the surface on the low refractive index layer side of the sample is 0 degree 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 perpendicularly incident on the surface of the low refractive index layer side of the sample is set to 0 degree, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and regular reflection of the incident light is performed. When the a ^* value and b ^* value of the Lab color system of light are measured and the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle is calculated, the minimum of the sum The incident angle x (degrees) indicating the value (S _min ) is 20 degrees ≦ x ≦ 30 degrees.

[2] When calculating the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle of 5 to 45 degrees, the cumulative value (SC _5-45 ) of the sum is calculated. The antireflection film according to [1], which satisfies the following condition (3).
SC _5-45 ≦ 34.0 (3)
[3] The antireflection film as described in [1] or [2] above, wherein the sum (S ₅ ) of the absolute value of the a ^* value and the absolute value of the b ^* value at an incident angle of 5 degrees satisfies the following condition (4).
2.0 ≦ S ₅ ≦ 5.0 (4)
[4] The reflection according to any one of [1] to [3], wherein a sum (S ₄₅ ) of an absolute value of a ^* values and an absolute value of b ^* values at an incident angle of 45 degrees satisfies the following condition (5): Prevention film.
S ₄₅ ≦ 8.0 (5)
[5] The above [1] to [4] in which the ratio of the sum of the absolute value of the a ^* value and the absolute value of the b ^* value (S ₅ ) at the incident angle of 5 degrees and the S _min satisfies the following condition (6) ] The antireflective film in any one of.
1.6 ≦ S ₅ / S _min (6)
[6] When the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value is calculated at each incident angle of 35 to 45 degrees, the standard deviation (Sσ _35-45 ) of the sum is calculated. The antireflection film according to any one of [1] to [5], wherein the following condition (7) is satisfied.
Sσ _35-45 ≦ 1.65 (7)

[7] The antireflection film as described in any one of [1] to [6], wherein a hard coat layer is provided between the transparent substrate and the high refractive index layer.
[8] A display device in which the antireflection film according to any one of the above [1] to [7] is disposed on a display element so that the transparent substrate side of the antireflection film faces the display element.
[9] The display device according to [8], including a touch panel on the display element, and the antireflection film disposed on the touch panel.
[10] The display device according to [8] or [9], wherein the number of pixels of the display element is 3840 × 2160 pixels or more.

[11] A black plate on a surface opposite to the high refractive index layer side 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 via a transparent adhesive. Is prepared, and the luminous 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) And a method for selecting an antireflection film.
<Condition (1)>
When the incident angle of light perpendicularly incident on the surface on the low refractive index layer side of the sample is 0 degree 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 perpendicularly incident on the surface of the low refractive index layer side of the sample is set to 0 degree, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and regular reflection of the incident light is performed. When the a ^* value and b ^* value of the Lab color system of light are measured and the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle is calculated, the minimum of the sum The incident angle x (degrees) indicating the value (S _min ) is 20 degrees ≦ x ≦ 30 degrees.

  The antireflection film and the 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 a suppressed reflectance and excellent color uniformity.

[Antireflection film]
The antireflective film of the present invention is an antireflective film having a high refractive index layer and a low refractive index layer on a transparent substrate, and is on the side opposite to the high refractive index layer side of the transparent substrate of the antireflective film. The luminous reflectance Y value measured from a sample with a black plate bonded to the surface through a transparent adhesive, the a ^* value and b ^* value of the Lab color system satisfy the following conditions (1) and (2) It is.
<Condition (1)>
When the incident angle of light perpendicularly incident on the surface on the low refractive index layer side of the sample is 0 degree 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 perpendicularly incident on the surface of the low refractive index layer side of the sample is set to 0 degree, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and regular reflection of the incident light is performed. When the a ^* value and b ^* value of the Lab color system of light are measured and the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle is calculated, the minimum of the sum The incident angle x (degrees) indicating the value (S _min ) is 20 degrees ≦ x ≦ 30 degrees.
In addition, in this invention, the refractive index of the transparent adhesive used for a sample uses that whose refractive index difference with the refractive index of a transparent base material and a black board is less than 0.05.

Condition (1)
Condition (1) indicates that the luminous reflectance Y value of the antireflection film is 0.50% or less under the above measurement conditions, in other words, the antireflection film is ultra-low reflection. When the luminous reflectance Y value of the antireflection film exceeds 0.50%, the angle dependency of the tint tends to be suppressed. However, due to the high luminous reflectance Y value, the super high definition The image quality of the display device is impaired.
In condition (1), the luminous reflectance Y value is preferably 0.30% or less, more preferably 0.20% or less, and preferably 0.15% or less.
In the measurement of the condition (1), it is preferable that the viewing angle, the light source, and the measurement wavelength are as follows.
Viewing angle: 2 degrees, light source: D65, measurement wavelength: 380 to 780 nm at 0.5 nm intervals Note that the luminous reflectance Y value refers to the Y value of the CIE 1931 standard color system.

Condition (2)
Condition (2) is an incidence indicating the minimum value (S _min ) of the sum of the absolute value of the a ^* value and the absolute value of the b ^* value (S) of the antireflection film under the above measurement conditions. The angle x (degrees) indicates that 20 degrees ≦ x ≦ 30 degrees. In other words, the condition (2) indicates that the incident angle x (degrees) indicating S _min is not located in the front direction but at an angle away from the front direction (incident angle 20 to 30 degrees). Yes. In the conventional antireflection film, the incident angle indicating S _min is located in the front direction, but in the present invention, the incident angle indicating S _min is deviated from the front direction.

When x (degrees) is less than 20 degrees, the color in the front direction can be suppressed, but the color feels strongly at angles exceeding 20 degrees (particularly 35 to 45 degrees), and the color uniformity cannot be improved. The reason is considered as follows.
The sum (S) of the absolute value of the a ^* value and the b ^* value of the antireflection film is either when the incident angle is smaller than x (degrees) or when the incident angle is larger than x (degrees). There is also a tendency to increase. Therefore, when x (degrees) is less than 20 degrees, the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value has a large value at an angle away from the front direction (around 35 to 45 degrees). The viewer will recognize a strong color. In addition, 45 degree | times intends that the frequency | count that a viewer observes a display apparatus at an angle exceeding 45 degree | times is low.
When x (degrees) exceeds 30 degrees, it becomes difficult to suppress the reflectance and color in the front direction.
On the other hand, the antireflection film of the present invention that satisfies the condition (2) can improve the color uniformity. Specifically, when observing a display device with a large screen (diagonal screen size of 106.7 cm or more) from the front direction, when observing a display device with a touch panel (diagonal screen size of more than 38.1 cm) from the front direction When observing a convex display device, the difference in color between the vicinity of the center of the screen and the vicinity of both ends of the screen can be suppressed. In addition, when changing the viewing angle of the display device, it is possible to suppress a difference in color near the center of the screen before and after the movement.

The a ^* value and b ^* value of the Lab color system in condition (2) are obtained by measuring the X value, Y value, and Z value of CIE XYZ of the regular reflection light of the incident light, and the obtained X value, Y It can be calculated by converting the value and the Z value by a general conversion equation. In the measurement of the condition (2), the viewing angle, the light source, and the measurement wavelength are preferably set as the following conditions.
Viewing angle: 2 degrees, light source: D65, measurement wavelength: 380 to 780 nm at 0.5 nm intervals Note that the measurement conditions in conditions (3) to (7) described later are the same as those in condition (2).

Condition (3)
When the antireflection film of the present invention calculates the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle with an incident angle of 5 to 45 degrees under the above measurement conditions, It is preferable that the cumulative value (SC _5-45 ) satisfies the following condition (3).
SC _5-45 ≦ 34.0 (3)
By setting SC _5-45 to 34.0 or less, it is possible to make it difficult to recognize the color in an angle range where the viewer frequently observes the display device, and to improve the color uniformity.
Condition (3) more preferably satisfies SC _5-45 ≦ 32.0, and more preferably satisfies SC _5-45 ≦ 30.0. The lower limit of SC _5-45 is about 15.0.

Condition (4)
In the antireflection film of the present invention, it is preferable that the sum of the absolute value of the a ^* value and the absolute value of the b ^* value (S ₅ ) at an incident angle of 5 degrees satisfies the following condition (4) under the above measurement conditions.
2.2 ≦ S ₅ ≦ 5.0 (4)
With S ₅ 2.2 or more, it can easily obtain an antireflection film that satisfies the above-described conditions (1) and (2) at the same time, while suppressing the reflectance can be easily improving the color Uniformity. Further, by setting the S ₅ 5.0 or less, can easily suppressed color of the front direction, can be easily improving the color Uniformity.
The condition (4) more preferably satisfies 2.3 ≦ S ₅ ≦ 4.5, and more preferably satisfies 2.4 ≦ S ₅ ≦ 4.0.

Condition (5)
In the antireflection film of the present invention, it is preferable that, under the above measurement conditions, the sum (S ₄₅ ) of the absolute value of the a ^* value and the absolute value of the b ^* value at an incident angle of 45 degrees satisfies the following condition (5).
S ₄₅ ≦ 8.0 (5)
By satisfying the condition (5), it is difficult to recognize the color in an angle range where the viewer frequently observes the display device, and the color uniformity can be improved.
The condition (5) preferably satisfies S ₄₅ ≦ 7.5, and more preferably satisfies S ₄₅ ≦ 6.5. _The lower limit of the _{S 45} is about 4.0.

Condition (6)
In the antireflection film of the present invention, the ratio of the sum of the absolute value of the a ^* value and the absolute value of the b ^* value (S ₅ ) and S _min at the incident angle of 5 degrees under the above measurement conditions is the following condition (6): It is preferable to satisfy.
1.6 ≦ S ₅ / S _min (6)
Condition (6) indicates that the color in the front direction (incident angle of 5 degrees) is sufficiently larger than the minimum value of color (S _min ). By satisfying the condition (6), the effect of the condition (2) described above can be more easily exhibited.
The condition (6) more preferably satisfies 1.7 ≦ S ₅ / S _min, and more preferably satisfies 1.8 ≦ S ₅ / S _min . The upper limit of S ₅ / S _min is about 5.0.

Condition (7)
When the antireflection film of the present invention calculates the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle with an incident angle of 35 to 45 degrees under the above measurement conditions, The standard deviation (Sσ _35-45 ) preferably satisfies the following condition (7).
Sσ _35-45 ≦ 1.65 (7)
By satisfying the condition (7), when the viewer shifts the angle of observation in the range of 35 to 45 degrees, it is possible to suppress recognition of a sudden change in color tone, and to improve the color uniformity. it can.
Condition (7) more preferably satisfies Sσ _35-45 ≦ 1.60, and more preferably satisfies Sσ _35-45 ≦ 1.50. Note that if Sσ _35-45 is too small, the luminous reflectance Y value tends to be small, so Sσ _35-45 is preferably 0.50 or more, and more preferably 1.00 or more.

Configuration of Antireflection Film The antireflection film of the present invention has a basic configuration having a high refractive index layer and a low refractive index layer on a transparent substrate. The high refractive index layer and the low refractive index layer have a role of providing an antireflection function by the optical interference function of the multilayer thin film. The antireflection film may be further provided with an antireflection function by an optical interference function of three or more layers by providing a medium refractive index layer or the like. However, it is not preferable from the viewpoint of cost effectiveness if a multilayer structure is formed too much.
Therefore, the antireflection film of the present invention preferably has an antireflection function by an optical interference function in two layers of a high refractive index layer and a low refractive index layer. In addition, when it has the hard-coat layer mentioned later between a transparent base material and a high-refractive-index layer, a hard-coat layer is made into medium refractive index, a medium-refractive-index layer (hard-coat layer), a high-refractive-index layer, and It is preferable that three layers of the low refractive index layer provide an antireflection function by an optical interference function.

(Transparent substrate)
The transparent substrate of the antireflection film is not particularly limited as long as it is a transparent substrate generally used as the substrate of the antireflection film, but from the viewpoint of material cost, productivity, etc., preferably a plastic film, a plastic sheet, etc. Can be appropriately selected depending on the application.

  As a plastic film or a plastic sheet, what consists of various synthetic resins is mentioned. Synthetic resins include cellulose resins such as triacetyl cellulose resin (TAC), diacetyl cellulose, acetate butyrate cellulose, cellophane; polyethylene terephthalate resin (PET), polybutylene terephthalate resin, polyethylene naphthalate-isophthalate copolymer resin, polyester Polyester resins such as thermoplastic elastomers; low density polyethylene resins (including linear low density polyethylene resins), medium density polyethylene resins, high density polyethylene resins, ethylene α-olefin copolymers, polypropylene resins, polymethylpentene resins, polybutenes Polyolefin resins such as resins, ethylene-propylene copolymers, propylene-butene copolymers, olefinic thermoplastic elastomers or mixtures thereof; ) Acrylic resins such as methyl acrylate resin, poly (meth) ethyl acrylate resin, poly (meth) butyl acrylate resin; polyamide resin represented by nylon 6 or nylon 66; polystyrene resin; polycarbonate resin; polyarylate resin Or preferably a polyimide resin.

As the transparent substrate, it can be used alone or in the form of a mixture of two or more of the above-described plastic film and plastic sheet. From the viewpoint of flexibility, toughness, transparency, and the like, a cellulose resin, A polyester resin is more preferable, and triacetyl cellulose resin (TAC) and polyethylene terephthalate resin are more preferable.
Although there is no restriction | limiting in particular about the thickness of a transparent base material, Although it selects suitably according to a use, Usually, it is 5-130 micrometers, and when durability, handling property, etc. are considered, 10-100 micrometers is preferable.

(Hard coat layer)
Between the transparent substrate and the high refractive index layer, it is preferable to have a hard coat layer for the purpose of improving the scratch resistance of the antireflection film. Here, a hard coat means what shows hardness more than "H" in the pencil hardness test prescribed | regulated by JISK5600-5-4: 1999.
A hard-coat layer can be formed from the hard-coat layer coating liquid containing a curable resin composition, for example. 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 necessary.

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 bond group such as a (meth) acryloyl group, a vinyl group, and an allyl group, 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 ethylenic unsaturated bond groups is more preferable, and among them, having two or more ethylenically unsaturated bond groups, Polyfunctional (meth) acrylate compounds are more preferred. As the polyfunctional (meth) acrylate compound, any of a monomer and an oligomer can be used.
The ionizing radiation means an electromagnetic wave or a charged particle beam having an energy quantum capable of polymerizing or cross-linking molecules, and usually ultraviolet (UV) or electron beam (EB) is used. Electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion beams can also be used.

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

Moreover, examples of the polyfunctional (meth) acrylate oligomer include acrylate polymers such as urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate.
Urethane (meth) acrylate is obtained by reaction of polyhydric alcohol and organic diisocyanate with hydroxy (meth) acrylate, for example.
A preferable epoxy (meth) acrylate is a (meth) acrylate obtained by reacting (meth) acrylic acid with a tri- or higher functional aromatic epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin or the like. (Meth) acrylates obtained by reacting the above aromatic epoxy resins, alicyclic epoxy resins, aliphatic epoxy resins and the like with polybasic acids and (meth) acrylic acid, and bifunctional or higher functional aromatic epoxy resins, It is a (meth) acrylate obtained by reacting an alicyclic epoxy resin, an aliphatic epoxy resin or the like with a phenol and (meth) acrylic acid.
The ionizing radiation curable compounds can 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 additives such as a photopolymerization initiator and a photopolymerization accelerator.
Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, 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, the photopolymerization initiator remaining due to the heat of the transparent conductive film formation or the crystallization process is sublimated to prevent the low resistance of the transparent conductive film from being impaired. can do. The same applies when a photopolymerization initiator is used in a high refractive index layer and a low refractive index layer described later.
The photopolymerization accelerator can reduce polymerization inhibition by air during curing and increase the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, etc. One or more selected may be mentioned.

The thickness of the hard coat layer is preferably in the range of 0.1 to 100 μm, and 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 it is difficult to break without occurrence of cracks or the like with respect to external impact.
The thicknesses of the hard coat layer and the high refractive index layer and the low refractive index layer, which will be described later, are measured using, for example, a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning transmission electron microscope (STEM). The thickness at 20 locations can be measured from the photographed cross-sectional image and calculated from the average value of the 20 locations. When the film thickness to be measured is on the order of μm, it is preferable to use SEM, and when it 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. 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 still more 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 middle 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 by the three layers is possible, it is preferable in that the above-described various conditions are easily satisfied. 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 means for imparting a role as a 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, so the former means (blending a resin having a high refractive index) is preferable.
Examples of the resin having a high refractive index include those obtained by introducing a sulfur-containing group, an aromatic ring, or the like into the thermosetting resin or ionizing radiation-curable compound described above. 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, for example, a reflection spectrum measured by a reflection photometer and a reflection spectrum calculated from an optical model of a multilayer thin film using a Fresnel coefficient. And can be calculated by fitting.

  The hard coat layer is prepared by adjusting the coating liquid for forming the hard coat layer by using the curable resin composition described above, additives such as an ultraviolet absorber and a leveling agent, and a diluting solvent, which are blended as necessary. It can be formed by coating on a material by a conventionally known coating method, drying, and curing by irradiation with ionizing radiation as required.

(High refractive index layer)
The high refractive index layer can be formed from, for example, a high refractive index layer coating solution 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 have a very low reflectance. However, in order to increase the refractive index, a large amount of high refractive index particles are required. Aggregates and causes whitening. For this reason, the refractive index is preferably 1.55 to 1.85, more preferably 1.56 to 1.70.
Further, the thickness of the high refractive index layer is preferably 200 nm or less, and more preferably 50 to 180 nm. In addition, when a high refractive index layer consists of 2 layer structure mentioned later, it is preferable that the total thickness of 2 layers satisfy | fills the said value.
The high refractive index layer may be formed from a plurality of layers satisfying the above refractive index range, but from the viewpoint of cost effectiveness, two or less layers are preferable, and a single layer is more preferable.

As high refractive index particles, antimony pentoxide (1.79), zinc oxide (1.90), titanium oxide (2.3 to 2.7), cerium oxide (1.95), 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. In addition, the inside of the said parenthesis shows 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 preferable refractive index with a small amount of addition. Further, conductive high refractive index 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, part of the light in the visible light region is also absorbed or reflected, and it may be difficult to suppress the color. For this reason, 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 suitable, and zirconium oxide is most suitable from the viewpoint of high durability stability such as light resistance. In addition, 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 that one layer contains conductive high refractive index particles.

The average particle diameter of the primary particles of the high refractive index particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, and further preferably 10 to 80 nm.
The average particle diameter 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) A surface image of SEM, TEM, or STEM is taken for the particles themselves or those obtained by applying and drying a dispersion of particles on a transparent substrate.
(2) Ten arbitrary particles are extracted from the surface image, the major axis and minor axis of each particle are measured, and the particle diameter of each particle is calculated from the average of the major axis and 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 perpendicular to the midpoint of the line segment constituting the major axis is drawn and the perpendicular line segment intersects the particle. Shall.
(3) The same operation was performed five times in the imaging of another screen of the same sample, and the value obtained from the number average of the particle diameters of a total of 50 particles was defined as the average particle diameter.
In calculating the average particle diameter of the particles, it is preferable to use SEM when the average particle diameter to be calculated is on the order of μm, and it is preferable to use TEM or STEM when the average particle diameter to be calculated 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. 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 increasing the refractive index, suppressing tint, and suppressing whitening, and 50 More preferably, it is -200 mass parts, More preferably, it is 80-150 mass parts.

  The high refractive index layer is preferably dispersed and stabilized in order to suppress excessive aggregation of the high refractive particles. As a means for stabilizing the dispersion, for example, a means for adding another high refractive index particle having a smaller surface charge than that of the high refractive particle serving as a base to the base may be mentioned. According to this means, it is possible to suppress the high refractive index particles serving as the base from appropriately gathering around the other high refractive index particles and excessively aggregating the high refractive particles serving as the base. Further, as another means for stabilizing the dispersion, there may be mentioned means for using a surface treated as high refractive index particles or adding a dispersing agent to the high refractive index layer coating solution.

As the curable resin composition for forming the high refractive index layer, the same as those exemplified for the hard coat layer can be used, and an ionizing radiation curable resin composition is suitable.
Moreover, in order to obtain the refractive index mentioned above without making the addition amount of high refractive index particles excessive, 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.

The high refractive index layer may have a two-layer configuration 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 to make the refractive index of the high refractive index layer (B) higher than the refractive index of the high refractive index layer (A). By configuring the high refractive index layer as described above, the refractive index difference with the low refractive index layer can be increased, the reflectance can be lowered, and the refractive index difference between the high refractive index layer and the hard coat layer can be reduced, thereby interfering with the interference. Generation of fringes can be suppressed.
When the high refractive index layer has two layers, 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. Preferably there is.
Further, in the above two-layer configuration, 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 nonconductive high refractive index particles. And, it is preferable that [the thickness of the layer containing conductive high refractive index particles <the thickness of the layer containing nonconductive high refractive index particles]. By setting it as the said structure, antistatic property can be provided, suppressing the addition amount of electroconductive high refractive index particle | grains which can cause a color tint. Further, the conductive high refractive index particles are preferable in that they can be networked in the layer to impart antistatic properties with a small addition amount, and as a result, color and whitening can be suppressed.

  The high refractive index layer is prepared by adjusting the coating liquid for forming a high refractive index layer with a high refractive index particle, a curable resin composition, an additive such as an ultraviolet absorber or a leveling agent and a diluent solvent, if necessary. The coating solution can be formed on the hard coat layer by coating, drying, and curing by irradiating with 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 have an extremely low reflectance. More preferably, it is 30 to 1.32.
The lower the refractive index of the low refractive index layer, the lower the refractive index of the antireflection film without increasing the refractive index of the high refractive index layer. On the other hand, if the refractive index of the low refractive index layer is 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, the amount of the high refractive index particles added to the high refractive index layer can be suppressed while maintaining the strength of the low refractive index layer. 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 still more preferably 90 to 105 nm.
The low refractive index layer may be formed from a plurality of layers satisfying the above refractive index range, but from the viewpoint of cost effectiveness, two or less layers are preferable, and a single layer is more preferable.

Methods for forming the low refractive index layer can be broadly classified into wet methods and dry methods. As the wet method, a method of forming by a sol-gel method using a metal alkoxide, a method of forming by applying a low refractive index resin such as a fluororesin, and a low low refractive index particle in a resin composition. A technique of coating and forming a coating solution for forming a refractive index layer is exemplified. Examples of the dry method include a method in which particles having a desired refractive index are selected from low-refractive-index particles described later and formed by physical vapor deposition or chemical vapor deposition.
The wet method is excellent in terms of production efficiency. In the present invention, among the wet methods, the wet method is preferably formed by a coating solution for forming a low refractive index layer in which low refractive index particles are contained in a resin composition.

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

  A particle having a structure having a void itself has a fine void inside, and is filled with a gas such as air having a refractive index of 1.0, so that its own refractive index is low. It has become. Examples of such particles having voids include inorganic or organic porous particles, hollow particles, and the like. For example, porous polymer particles using porous silica, hollow silica particles, acrylic resin, or the like. And hollow polymer particles. As inorganic particles, silica particles having voids prepared by using the technology disclosed in Japanese Patent Application Laid-Open No. 2001-233611 are used, and as organic particles, technology disclosed in Japanese Patent Application Laid-Open No. 2002-80503. As a preferred example, hollow polymer particles prepared using Silica having voids as described above or porous silica 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 low from the viewpoint of reducing the refractive index of the low refractive index layer.

  The hollow silica particles are particles having a function of lowering the refractive index while maintaining the coating strength of the low refractive index layer. The hollow silica particles used in the present invention are silica particles having a structure having a cavity inside. The hollow silica particles are silica particles whose refractive index decreases in inverse proportion to the occupancy of the internal cavities as compared with the original refractive index of silica particles (refractive index n = 1.45 or so). For this reason, 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 that have an outer shell and are porous or hollow inside, and are disclosed in JP-A-6-330606, JP-A-7-013137, and JP-A-7. -133105 and the silica particle prepared using the technique currently disclosed by Unexamined-Japanese-Patent No. 2001-233611.

  The average particle diameter of the primary particles of the low refractive index particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, and further preferably 10 to 80 nm. If the average particle diameter of the primary particles is within the above range, the transparency of the low refractive index layer is not impaired, and a good dispersion state of the particles can be obtained. In particular, when hollow particles are used as the low refractive index particles and the average particle diameter of the hollow particles is 70 to 80 nm, the refractive index is lowered by increasing the porosity while maintaining the thickness of the outer shell that does not cause insufficient strength. It is preferable in that it is excellent in balance with the thickness (about 100 nm) of an ideal low refractive index layer for reducing 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 preferably performed. By applying 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 agglomerate. The decrease in the transparency of the refractive index layer, the applicability of the composition for forming a low refractive index layer, and the decrease in the coating strength of the composition are suppressed.

  In addition, when the silane coupling agent has a (meth) acryloyl group, the silane coupling agent has ionizing radiation curability, and therefore easily reacts with a binder resin described later. Therefore, the composition for forming a low refractive index layer In the coating film, the low refractive index particles are satisfactorily fixed to the binder resin. That is, the low refractive index particles have a function as a crosslinking agent in the binder resin. Thereby, the tightening effect of the whole coating film is obtained, and it is possible to impart excellent surface hardness to the low refractive index layer while leaving the flexibility inherent to the binder resin. Therefore, since the low refractive index layer is deformed by utilizing its own flexibility, it has the ability to absorb and restore external impacts, so that the generation of scratches is suppressed and the surface hardness is excellent with excellent scratch resistance. It will have.

  Examples of the silane coupling agent preferably used in the surface treatment of the low refractive index particles include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, and 3- (meth) acryloxypropyl. Examples thereof include methyldimethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, 2- (meth) acryloxypropyltrimethoxysilane, 2- (meth) acryloxypropyltriethoxysilane 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 even more preferably 100 to 180 parts by mass with respect to 100 parts by mass of the resin of the low refractive index layer. preferable. If the content of the low refractive index particles is within the above range, good antireflection characteristics and surface hardness can be obtained.
Further, the ratio of the hollow particles and / or the porous particles in all the 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 80 to 95% by mass. preferable.

As a resin composition contained in the coating solution for forming a low refractive index layer, first, a curable resin composition is exemplified. As a curable resin composition, the thing similar to what was illustrated by the hard-coat layer can be used, and an 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 property is also preferably used. The fluorine-containing polymer is a polymer of a polymerizable compound containing at least a fluorine atom in the molecule, and is preferable in that it can impart antifouling property and slipperiness. The fluoropolymer preferably has a reactive group in the molecule and functions as a curable resin composition, and has an ionizing radiation curable reactive group and functions as an ionizing radiation curable resin composition. More preferred.

  As the fluorine-containing polymer, not only repels dirt on the surface of the low refractive index layer, but also preferably contains silicon together with fluorine in order to impart wiping property of the repelled dirt. For example, a silicone component is added to the copolymer. Preferred is a silicone-containing vinylidene fluoride copolymer. Examples of silicone components in this case include (poly) dimethylsiloxane, (poly) diethylsiloxane, (poly) diphenylsiloxane, (poly) methylphenylsiloxane, alkyl-modified (poly) dimethylsiloxane, azo group-containing (poly) dimethylsiloxane, , 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, Acrylic modified silicone, amino modified silicone, carboxylic acid modified silicone, carbinol modified silicone, epoxy modified silicone, mercapto modified silicone Corn, fluorine-modified silicones, polyether-modified silicone, and the like. Of these, those having a dimethylsiloxane structure are preferred.

  The low refractive index layer is prepared, for example, by adjusting the coating solution for forming a low refractive index layer with low refractive index particles, a resin composition, additives such as an ultraviolet absorber and a leveling agent, and a diluent solvent, if necessary. The coating liquid can be formed on the high refractive index layer by coating and drying by a conventionally known coating method, and curing by irradiation with ionizing radiation as necessary.

(Physical properties 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. In the antireflection film of the present invention, the haze (JISK7136: 2000) is preferably 1.0% or less, more preferably 0.5% or less, and further preferably 0.3% or less. preferable.
The light incident surface for measuring the total light transmittance and haze is on the transparent substrate side.

The arithmetic average 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, and more preferably 50 to 155 nm.
When Ra and Rz are within the above ranges, the surface is smooth and the scratch resistance is improved.

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

[Display device]
In the display device of the present invention, the above-described antireflection film of the present invention is arranged on a display element such that the transparent substrate 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, and an organic EL display element.
The specific configuration of the display element is not particularly limited. For example, in the case of a liquid crystal display element, the liquid crystal display element has a basic structure 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 patterned with high density.

The display element preferably has a so-called 4K resolution or higher resolution in which the number of pixels is 3840 × 2160 pixels or higher. An ultra-high-definition display element having a resolution of 4K or more is susceptible to the influence of color because the amount of light per pixel is small. In addition, a display device including a display element with 4K resolution or higher has a large screen and is likely to have a problem of color uniformity. For this reason, a display element having a resolution of 4K or higher is preferable in that the effect of the present invention is easily exhibited.
Note that examples of the 4K resolution display element include a display element having 3840 × 2160 pixels and a display element having 4096 × 2160 pixels.
In addition, a large-screen display device with a screen size of 106.7 cm or more is preferable in that the effect of the present invention is easily exhibited even when the resolution is not higher than 4K resolution.
A convex display device is also preferable in that the problem of color uniformity is likely to occur and the effects of the present invention are easily exhibited.

The display device of the present invention may have a touch panel on a display element, and an antireflection film may be disposed on the touch panel. In this embodiment as well, it is necessary to dispose the antireflection film so that the transparent substrate side faces the display element side. In the case of a display device with a touch panel, when the screen size of the display device is more than 38.1 cm diagonal, it is preferable in that the effect of the present invention is easily exhibited.
Examples of the touch panel include a capacitive touch panel, a resistive touch panel, an optical touch panel, an ultrasonic touch panel, and an electromagnetic induction touch panel.

A resistive touch panel has a basic configuration in which a conductive film of a pair of upper and lower transparent substrates having a conductive film is arranged with a spacer so as to face each other, and a circuit is connected to the basic configuration. is there.
The capacitive touch panel includes a surface type and a projection type, and a projection type is often used. A projected capacitive 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 electrode are arranged via an insulator. The basic structure will be described more specifically. (1) A mode in which X electrodes and Y electrodes are formed on separate surfaces on a single transparent substrate, (2) X electrodes, insulator layers, Y on a transparent substrate An embodiment in which the electrodes are formed in this order, (3) an embodiment in which an X electrode is formed on a transparent substrate, a Y electrode is formed on another transparent substrate, and laminated via an adhesive layer or the like are included. Moreover, the aspect which laminate | stacks another transparent substrate in these basic aspects is mentioned.

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

[Selection method of antireflection film]
The method for selecting the antireflection film of the present invention is such that the antireflection film having a high refractive index layer and a low refractive index layer on the transparent substrate has a surface opposite to the high refractive index layer side of the transparent substrate. A sample in which a black plate was bonded through a transparent adhesive was prepared, and the luminous reflectance Y value measured from the sample and the a ^* value and b ^* value of the Lab color system were the following conditions (1) and ( Satisfying 2) is a criterion.
<Condition (1)>
When the incident angle of light perpendicularly incident on the surface on the low refractive index layer side of the sample is 0 degree 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 perpendicularly incident on the surface of the low refractive index layer side of the sample is set to 0 degree, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and regular reflection of the incident light is performed. When the a ^* value and b ^* value of the Lab color system of light are measured and the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle is calculated, the minimum of the sum The incident angle x (degrees) indicating the value (S _min ) is 20 degrees ≦ x ≦ 30 degrees.

  In the method for selecting an antireflection film of the present invention, it is preferable that one or more selected from the above-described conditions (3) to (7) be an additional determination condition. Moreover, it is more preferable that all of the conditions (3) to (7) described above are set as additional determination conditions.

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 substrate. For example, you may have a hard-coat layer between a transparent base material and a high refractive index layer.
Embodiments of the transparent base material, the high refractive index layer, the low refractive index layer, and the hard coat layer provided as necessary according to the selection method of the antireflection film of the present invention are the antireflection film of the present invention. The transparent substrate, the high refractive index layer, the low refractive index layer, and the hard coat layer are the same as in the embodiment.

  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.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this example.

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. Luminous reflectance Y value of antireflection film A black plate (refractive index: on the surface opposite to the high refractive index layer side of the transparent base material of the antireflection film via a transparent adhesive (refractive index 1.49). A sample was prepared by bonding 1.49). When the incident angle of light perpendicularly incident on the surface on the low refractive index layer side of the sample is 0 degree 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) was used as a measuring device for the luminous reflectance Y value, the viewing angle was 2 degrees, the light source was D65, and the measurement wavelength was 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 of light incident perpendicularly to the surface on the low refractive index layer side of the sample prepared in 1-1 above is defined as 0 degree. 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 regular reflection light of the incident light were measured. Moreover, the numerical values of the above-mentioned conditions (2) to (7) were calculated from the measurement results of the a ^* value and the b ^* value.
The a ^* value and b ^* value measuring apparatus uses a spectrophotometer (trade name: V-7100, manufactured by JASCO Corporation), the viewing angle is 2 degrees, the light source is D65, and the measurement wavelength is 0 to 380 to 780 nm. .5 nm interval.

1-3. Evaluation of anti-reflection performance of anti-reflection film An anti-reflection film is installed on a liquid crystal display element having 3840 × 2160 pixels so that the surface of the anti-reflection film faces the liquid crystal display element side. A simulated liquid crystal display device was produced. In a bright room environment, without displaying an image on the display element, the image of the observer himself is reflected near the center of the surface (low refractive index layer) of the simulated liquid crystal display device from the vertical direction of the simulated liquid crystal display device. It was observed visually.
As a result, “A” indicates that the skin color of the reflected viewer cannot be recognized due to the strong black color, and “C” indicates that the skin color of the reflected viewer can be recognized.

1-4. Color uniformity of antireflection film For the sample prepared in 1-1 above, a fluorescent lamp was reflected in a bright room, and the color of the sample surface was visually observed from a position where regular reflection light could be confirmed. During the observation, the sample was moved directly below the fluorescent lamp so as to gradually change from vertical (0 degrees) to 45 degrees with respect to the fluorescent lamp.
The observation was performed by 20 people, one point where there was no place where the color was strongly felt and where there was a sudden change in the color, and two samples having one of the two places, Each person evaluated the sample which has both out of 2 places as 3 points. 20 points with an average score of 1.1 or less are “AA”, 1.1 points to 1.5 points or less “A”, 1.5 points to 1.5 points or less “B”, more than 2.0 point and 2.5 point or less was “C”, and more than 2.5 point and 3.0 point or less was “D”.

2. Preparation of antireflection film [Example 1]
On a triacetyl cellulose film (refractive index: 1.49) having a thickness of 80 μm, a hard coat layer forming coating solution having the following formulation was applied, dried and irradiated with ultraviolet rays, having 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 solution for forming a high refractive index layer having the following formulation was applied on 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 solution for forming a low refractive index layer having the following formulation is applied on 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), and an antireflection film. Got.

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

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

<Preparation of coating solution for forming low refractive index layer>
A photopolymerization initiator (BASF, Irgacure 127) 0.2 parts by mass and a diluting solvent (MIBK / AN = 7/3) 91.1 parts by mass were added and stirred until there was no undissolved residue. Here, 1.0 part by mass of photo-curing resin (manufactured by Nippon Kayaku Co., Ltd., KAYARAD-PET-30), 7.6 parts by mass of hollow silica particles (solid content 20% by mass, average primary particle size 60 nm), leveling agent (large Nissei Kagaku Kogyo Co., Ltd., Seika Beam 10-28 (MB)) 0.1 parts by mass were added and stirred to prepare a coating solution 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 part by mass (the changed refractive index 1.51), and the high refractive index layer was changed to 2 parts. As a coating composition for the high refractive index layer (A) on the hard coat layer side, zirconium oxide in the coating liquid for forming a high refractive index layer in Example 1 was changed to antimony-doped tin oxide (solid content: 45% by mass). (The refractive index after change 1.59), the thickness is 70 nm, and the coating solution for forming the high refractive index layer of Example 1 is used as the coating solution for the high refractive index layer (B) on the low refractive index layer side. An antireflection film was obtained in the same manner as in Example 1 except that the thickness was 90 nm.

[Example 3]
An antireflection film was obtained in the same manner as in Example 2 except that the thickness of the high refractive index layer (B) on the low refractive index layer side in Example 2 was changed to 105 nm.

[Example 4]
Example 3 is the same as Example 3 except that the thickness of the high refractive index layer (A) on the hard coat layer side in Example 3 is changed to 60 nm and the thickness of the high refractive index layer (B) on the low refractive index layer side is changed to 120 nm. Thus, an antireflection film was obtained.

[Comparative Example 1]
The high refractive index layers (A) and (B) of Example 2 were not formed, and the photocurable resin of the low refractive index layer forming coating solution 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 was made (refractive index after change 1.36).

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

[Comparative Example 3]
Except for changing the photocurable resin of the coating liquid for forming a hard coat layer of Example 1 to 40 parts by mass and the high refractive index resin to 0 parts by mass (refractive index after change of 1.51), the same as Example 1. Thus, an antireflection film was obtained.

[Comparative Example 4]
For the high refractive index layer (A) on the hard coat layer side of Example 3, the coating solution was prepared by changing the antimony-doped tin oxide to antimony pentoxide (solid content 40% by mass) (refractive index 1 after change). 58) An antireflection film was obtained in the same manner as in Example 3 except that the thickness was changed to 50 nm.

As is apparent from the results of Tables 1 and 2, the antireflection films of Examples 1 to 4 that satisfy 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 the reflectance could not be suppressed. In addition, the antireflection films of Comparative Examples 3 and 4 have an incident angle x (degrees) indicating the minimum value (S _min ) of the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value, 20 degrees. Therefore, the sum (S) of the absolute values showed a large value at an angle away from the front direction (around 35 to 45 degrees), and the color uniformity could not be improved.

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

Claims (2)

A black plate is bonded to the surface opposite to the high refractive index layer side 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 via a transparent adhesive. The sample is prepared, and the luminous 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). Selection method of antireflection film.
<Condition (1)>
When the incident angle of light perpendicularly incident on the surface on the low refractive index layer side of the sample is 0 degree 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 0.20% or less.
<Condition (2)>
The incident angle of light perpendicularly incident on the surface of the low refractive index layer side of the sample is set to 0 degree, and light is incident on the sample at intervals of 5 degrees from an incident angle of 5 degrees to 45 degrees, and regular reflection of the incident light is performed. When the a ^* value and b ^* value of the Lab color system of light are measured and the sum (S) of the absolute value of the a ^* value and the absolute value of the b ^* value at each incident angle is calculated, the minimum of the sum The incident angle x (degrees) indicating the value (S _min ) is 20 degrees ≦ x ≦ 30 degrees. The refractive index of the high refractive index layer is 1.55-1.85, the thickness of the high refractive index layer is 50-180 nm, the refractive index of the low refractive index layer is 1.26-1.36, and the low refractive index. the thickness of the layer is 80 to 120 nm, the selection method of the antireflection film according to claim 1.