WO2025115576A1 - Hard coat film and optical laminate - Google Patents

Abstract

This hard coat film comprises a transparent base material and a hard coat layer formed on the transparent base material, wherein the hard coat layer contains a filler and has a black luminance, measured under the following conditions, of less than 5.0 × 10^-4 cd/m². (Conditions: The hard coat film is provided adhering to an organic EL display having a light emission angle of 180 degrees and a luminance of 360 cd/m²; a white region and a black region are displayed in a checkerboard pattern at the organic EL display; a shielding plate is provided so as to cover the surface except for the black region of the organic EL display; and the black luminance for the black region is measured by a spectroradiometer provided at a distance of 60 cm from the organic EL display.)

Description

Hard coat film and optical laminate

The present invention relates to a hard coat film and an optical laminate.
This application claims priority based on Japanese Patent Application No. 2023-200677, filed on November 28, 2023, the contents of which are incorporated herein by reference.

　Surface defects caused by scratches and fingerprints on displays lead to reduced visibility of the display. For this reason, hard coat films are often applied to the surface of displays to suppress surface defects. As various operating devices with displays are converted to touch panels, the importance of hard coat films is increasing, and it is said that the pencil hardness of the entire film formed on a display must be 3H or higher. Hard coat films with fillers dispersed therein to improve hardness are known.

In recent years, organic electroluminescence (EL) displays have become increasingly popular as a type of display. Organic EL displays use the self-luminescence of each pixel, so unlike LCD displays, which are illuminated by a backlight placed behind the LCD pixels, they do not require a backlight.

When expressing black on an LCD display, the LCD pixels are set to black, i.e., light from the backlight is blocked. However, the optical rotation properties of the liquid crystal molecules alone are not enough to block the light from the backlight, and some light may leak, resulting in poor brightness in the black region (black brightness). For this reason, a method is known in which a polarizing plate or a material with low retardation is used for the LCD display to eliminate leaked light through phase difference (for example, Patent Document 1).

In contrast, organic EL displays are known to have good black luminance because black can be displayed if each pixel is not made to emit light on its own. In recent years, there has been a demand for further improvement in contrast in organic EL displays. To improve contrast, improving black luminance is important. The key factors for improving black luminance are thought to depend on the materials and structure of the organic EL display and the film applied to the organic EL display.

JP 2005-301227 A

When a hard coat film with dispersed fillers is applied to an organic EL display, light from an emitting area adjacent to a black area may leak into the black area, resulting in high black luminance. Using a polarizing plate or a material with low retardation as disclosed in Patent Document 1 for an organic EL display was not effective in reducing black luminance. Furthermore, no hard coat film with dispersed fillers was known that could achieve black luminance that meets VESA's DisplayHDR500 True Black certification. Therefore, when applying a hard coat film with dispersed fillers to an organic EL display, another method for improving black luminance is needed.

The present invention was made in consideration of the above circumstances, and aims to provide a hard coat film and optical laminate that have high hardness and good black brightness when applied to an organic EL display.

The present invention provides the following means to solve the above problems.

(1) A hard coat film according to one aspect of the present invention comprises a transparent substrate and a hard coat layer formed on the transparent substrate,
The hard coat layer contains a filler,
The black luminance measured under the following conditions is less than 5.0×10 ⁻⁴ cd/m ² .
(Conditions: A hard coat film is placed in close contact with an organic EL display with a light emission angle of 180 degrees and a brightness of 360 cd/ ^m2 , white and black areas are displayed in a checkered pattern on the organic EL display, a shielding plate is placed so as to cover the surface of the organic EL display except for the black areas, and the black brightness in the black areas is measured with a spectroradiometer placed 60 cm away from the organic EL display.)

(2) In the hard coat film of (1) above, the hard coat layer contains an acrylic resin, the particle size of the filler is 20 nm or more and 50 nm or less, and the surface of the filler may be modified with a (meth)acrylic group.

(3) In the hard coat film of (1) or (2) above, the hard coat layer has a first layer separated from the transparent substrate and containing the filler, and a second layer provided between the transparent substrate and the first layer, and the second layer may contain a resin component of the transparent substrate and a resin component of the first layer.

(4) In the hard coat film of (3) above, the average particle size of the filler may be 20 nm or more and 50 nm or less, and the concentration of the filler in the first layer may be 25% or more and 65% or less.

(5) In the hard coat film of (1) or (2) above, the average particle size of the filler may be 20 nm or more and 50 nm or less, and the concentration of the filler in the hard coat layer may be 40% or more and 65% or less.

(6) An optical laminate according to one aspect of the present invention comprises a hard coat film according to any one of (1) to (5) above and an optical functional layer formed on the hard coat layer, the optical functional layer being made of an inorganic oxide or an inorganic nitride.

(7) In the optical laminate of (6) above, the optical functional layer may be a single layer film made of _SiO2 .

(8) The optical laminate of (6) or (7) above may further include an adhesive layer formed between the hard coat layer and the optical functional layer and in contact with the hard coat layer and the optical functional layer, and the optical functional layer may be formed by alternately stacking high refractive index material layers and low refractive index layers, and the adhesive layer may be in contact with the high refractive index material layer.

The present invention can provide a hard coat film and optical laminate that have high hardness and good black brightness when applied to an organic EL display.

FIG. 1 is a cross-sectional view of a hard coat film according to one embodiment of the present invention. FIG. 1 is a diagram illustrating interface reflection when a hard coat film is applied to an organic EL display. FIG. 1 is a diagram illustrating interface reflection when a hard coat film is applied to an organic EL display. FIG. 1 is a diagram illustrating scattering when a hard coat film containing a filler is applied to an organic EL display. FIG. 1 is a diagram illustrating scattering when a hard coat film containing a filler is applied to an organic EL display. FIG. 1 is a diagram illustrating scattering when a hard coat film containing a filler is applied to an organic EL display. FIG. 2 is a diagram illustrating the black luminance measured when the hard coat film of FIG. 1 is applied to an organic EL display. 1 is a graph showing a simulation of the correlation between the approximate luminance and the interparticle distance of the filler when light is incident laterally in the in-plane direction on a hard coat film 100A containing fillers with particle sizes of 22 nm, 42 nm, and 80 nm. FIG. 2 is a cross-sectional view showing a modified example of the hard coat film of FIG. 1 . FIG. 10(a) is a diagram illustrating the black luminance measured when the hard coat film of FIG. 1 is applied to an organic EL display, and FIG. 10(b) is a diagram illustrating the black luminance measured when the hard coat film of FIG. 9 is applied to an organic EL display. 1 is a graph showing a simulation of the correlation between the approximate luminance and the interparticle distance of the filler when light is incident laterally in the in-plane direction on hard coat films 100A and 100B containing a filler with a particle size of 42 nm. 1 is a graph showing a simulation of the correlation between the approximate luminance and the interparticle distance of the filler when light is incident laterally in the in-plane direction on hard coat films 100A and 100B containing a filler with a particle size of 22 nm. FIG. 1 is a cross-sectional view of an optical laminate according to one embodiment of the present invention. FIG. 14 is a cross-sectional view of an optical laminate according to a modified example of FIG. 13 . FIG. 14 is a cross-sectional view of an optical laminate according to another modified example of FIG. 13 . 4 shows a measurement pattern displayed on an organic EL display when measuring black luminance in the examples and comparative examples. 1 is a graph showing the results of filler concentration and luminance in Examples 5 to 7 and Comparative Example 4.

Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate.
The drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them, and can be modified as appropriate within the scope of the effects.

[Hard coat film]
Fig. 1 is a cross-sectional view of a hard coat film according to one embodiment of the present invention. The hard coat film 100A shown in Fig. 1 comprises a transparent substrate 1 and a hard coat layer 2 formed on the transparent substrate 1. The hard coat layer 2 contains a filler 21. The hard coat film 100A has a black luminance of less than 5.0 x ^10-4 cd/ ^m2 measured under the following conditions.
(Conditions for measuring black luminance: a hard coat film is provided on an organic EL display having a light emission angle of 180 degrees and a luminance of 360 cd/ ^m2 , and black luminance is measured with a spectroradiometer provided 60 cm away from the organic EL display.)
The conditions for measuring the black luminance will be described in detail later.

The hard coat film 100A is composed of, for example, a transparent substrate 1 and a hard coat layer 2 formed in contact with the transparent substrate 1.

(Transparent base material)
The transparent substrate 1 may be formed of a transparent material capable of transmitting light in the visible light range. For example, a plastic film is preferably used as the transparent substrate 1. Specific examples of the constituent material of the plastic film include polyester-based resins, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyarylate-based resins, and polyphenylene sulfide-based resins.

In the present invention, the term "transparent material" refers to a material having a transmittance of 80% or more for light in the wavelength range used, provided that the effect of the present invention is not impaired.
In the present embodiment, "(meth)acrylic" means methacryl and acrylic.

The transparent substrate 1 may contain a reinforcing material as long as the optical properties are not significantly impaired. Examples of the reinforcing material include cellulose nanofiber and nanosilica. In particular, polyester-based resins, acetate-based resins, polycarbonate-based resins, and polyolefin-based resins are preferably used as the reinforcing material. Specifically, a triacetyl cellulose (TAC) substrate is preferably used as the reinforcing material.
The transparent substrate 1 may also be a glass film, which is an inorganic substrate.

The transparent substrate 1 may be a film that has optical and/or physical functions. Examples of films that have optical and/or physical functions include polarizing plates, phase difference compensation films, heat-blocking films, transparent conductive films, brightness-enhancing films, and barrier-enhancing films.

The thickness of the transparent substrate 1 is not particularly limited, but is preferably, for example, 25 μm or more, and more preferably 40 μm or more.
When the thickness of the transparent substrate 1 is 25 μm or more, the rigidity of the substrate itself is ensured, and wrinkles are unlikely to occur even when stress is applied to the optical laminate 10. In addition, when the thickness of the transparent substrate 1 is 25 μm or more, wrinkles are unlikely to occur even when the hard coat layer 2 is continuously formed on the transparent substrate 1, which is preferable because there are fewer concerns about production. When the thickness of the transparent substrate 1 is 40 μm or more, wrinkles are even less likely to occur, which is preferable.

When manufacturing is performed in a roll, the thickness of the transparent substrate 1 is preferably 1000 μm or less, and more preferably 600 μm or less. When the thickness of the transparent substrate 1 is 1000 μm or less, the optical laminate 10 during manufacturing and the optical laminate 10 after manufacturing can be easily wound into a roll, and the optical laminate 10 can be manufactured efficiently. Furthermore, when the thickness of the transparent substrate 1 is 1000 μm or less, the optical laminate 10 can be made thinner and lighter. When the thickness of the transparent substrate 1 is 600 μm or less, the optical laminate 10 can be manufactured more efficiently and can be made even thinner and lighter, which is preferable.

The surface of the transparent substrate 1 may be previously subjected to an etching treatment such as sputtering, corona discharge, ultraviolet irradiation, electron beam irradiation, conversion, oxidation, and/or an undercoat treatment. By previously performing these treatments, it is possible to improve adhesion with the hard coat layer 2 formed on the transparent substrate 1. In addition, it is also preferable to remove dust and clean the surface of the transparent substrate 1 by subjecting the surface of the transparent substrate 1 to solvent washing, ultrasonic washing, or the like, as necessary, before forming the hard coat layer 2 on the transparent substrate 1.

(Hard Coat Layer)
The hard coat layer 2 includes a binder resin 22 and a filler 21 as essential components, and may include other components such as a dispersant as optional components. A known material may be used as the binder resin 22. The filler 21 is contained in the binder resin to the extent that transparency is not impaired.
The filler 21 may be made of an organic material, an inorganic material, or a combination of an organic material and an inorganic material, but from the viewpoint of hardness and flex resistance, an inorganic material is preferred, and silica particles made of silica are more preferred. Furthermore, from the viewpoint of preventing the filler 21 from agglomerating and locally increasing the scattered light caused by the filler 21, surface-modified silica particles are particularly preferred because they have good dispersibility in the binder resin.

The binder resin used in the hard coat layer 2 is preferably transparent, and examples of resins that can be used include ionizing radiation curable resins that are cured by ultraviolet light or electron beams, thermoplastic resins, and thermosetting resins.

Examples of the ionizing radiation curable resin used as the binder resin of the hard coat layer 2 include ethyl (meth)acrylate, ethylhexyl (meth)acrylate, styrene, methylstyrene, and N-vinylpyrrolidone.
Examples of the compound that is an ionizing radiation curable resin having two or more unsaturated bonds include trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane ... Examples of the polyfunctional compounds include erythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, isocyanuric acid di(meth)acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate. Among them, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), and pentaerythritol tetraacrylate (PETTA) are preferably used. Incidentally, "(meth)acrylate" refers to methacrylate and acrylate. In addition, as the ionizing radiation curable resin, the above-mentioned compounds modified with PO (propylene oxide), EO (ethylene oxide), CL (caprolactone), etc. can also be used. In addition, urethane (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, etc. can also be used from the viewpoint of film formation of the hard coat layer and adjustment of viscoelasticity.

Thermoplastic resins used as the binder resin of the hard coat layer 2 include, for example, styrene-based resins, acrylic-based resins, (meth)acrylic-based resins, vinyl acetate-based resins, vinyl ether-based resins, halogen-containing resins, alicyclic olefin-based resins, polycarbonate-based resins, polyester-based resins, polyamide-based resins, cellulose derivatives, silicone-based resins, and rubber or elastomers. The above-mentioned thermoplastic resins are preferably non-crystalline and soluble in organic solvents (particularly common solvents capable of dissolving multiple polymers and curable compounds). In particular, from the viewpoints of transparency and weather resistance, styrene-based resins, acrylic-based resins, (meth)acrylic resins, alicyclic olefin-based resins, polyester-based resins, cellulose derivatives (cellulose esters, etc.), etc. are preferred.

The hard coat layer 2 contains, for example, a binder resin 22 and silica particles as fillers 21. As described above, the silica particles preferably contain silica particles that have been surface-modified in advance. The surface modification is preferably performed using a silane compound having a functional group. The surface of the filler 21 is preferably modified with a (meth)acrylic group.

Specific examples of silane compounds include vinyl group-containing silane compounds, (meth)acryloyl group-containing silane compounds, amino group-containing silane compounds, isocyanate group-containing silane compounds, isocyanurate group-containing silane compounds, epoxy group-containing silane compounds, and mercapto group-containing silane compounds. These may be used alone or in combination. The silane compound is appropriately selected depending on the type of binder resin, but when the binder resin contains a functional group, a silane compound having the same functional group as the binder resin is preferred. For example, when the binder resin contains a (meth)acrylate compound as an ionizing radiation curable resin, the silane compound is preferably a (meth)acryloyl group-containing alkoxysilane compound. Note that "(meth)acrylate" refers to methacrylate and/or acrylate. The silane compound used for surface modification preferably has an alkoxysilyl group or a silanol group at the end, since this improves the bond with the hydroxyl groups present on the surface of the silica particles.

By pre-modifying the surface of the silica particles, the dispersibility in the binder resin 22 is improved, and the reaction between the surface treatment agent used for the surface modification and the binder resin causes the particles to bond more firmly with the binder resin 22, improving hardness.

The average particle size of the filler 21 is, for example, 10 nm or more and 100 nm or less, preferably 20 nm or more and 50 nm or less, and more preferably 20 nm or more and 30 nm or less, depending on the concentration in the hard coat layer 2. In addition, from the viewpoint of suppressing unevenness in appearance in optical applications, the average particle size of the filler 21 is preferably 50 nm or less.

When the average particle size of the filler 21 in the hard coat layer 2 is within the above range, the haze value is at least 2%. When the haze value is 2% or less, the hard coat film 100A has high transparency and becomes a clear type hard coat film. In addition, taking into consideration the appearance and optical characteristics of the display, it is considered preferable that the haze value be 1% or less, and when the average particle size of the filler 21 is within the above range, this haze value can be achieved. Specifically, a low haze value suppresses contrast.

The concentration of the filler 21 in the hard coat layer 2 is, for example, more than 0% and not more than 80%. As will be described in detail later, the black luminance depends on the concentration (interparticle distance) of the filler 21 in the hard coat layer 2, which is the region in the hard coat film 100A where the filler 21 exists, and on the particle size of the filler 21.

When the average particle size of the filler 21 in the hard coat layer 2 is 30 nm or more and 50 nm or less, the concentration of the filler 21 in the hard coat layer 2 is preferably 23% or more and 50% or less, or more than 0% and 12% or less, and more preferably 30% or more and 45% or less. Also, when the average particle size of the filler 21 in the hard coat layer 2 is 10 nm or more and less than 30 nm, the concentration is preferably more than 0% and 30% or less. However, from the viewpoint of increasing the surface hardness of the hard coat film and the optical laminate described later, a higher concentration is preferable.

As a filler contained in the hard coat layer 2, various reinforcing materials can be used to impart toughness to the hard coat layer 2, as long as the optical properties are not impaired. An example of a reinforcing material is cellulose nanofiber.

The thickness of the hard coat layer 2 is preferably 0.5 μm or more, and more preferably 1 μm or more. The thickness of the hard coat layer 2 is preferably 100 μm or less, and more preferably 30 μm or less. When the thickness of the hard coat layer 2 is 0.5 μm or more, sufficient hardness is obtained, making it difficult for scratches to occur during production. Furthermore, when the thickness of the hard coat layer 2 is 100 μm or less, the hard coat film 100A can be made thinner and lighter. Furthermore, when the thickness of the hard coat layer 2 is 100 μm or less, microcracks in the hard coat layer 2 that occur when the hard coat film 100A is bent during production are unlikely to occur, and productivity is good.

The hard coat layer 2 may be a single layer or a laminate of multiple layers. When the hard coat layer 2 is a laminate of multiple layers, a filler may be dispersed in each layer, but may be contained only in the layer away from the transparent substrate 1. The hard coat layer 2 may further be provided with known functions such as ultraviolet absorbing performance, antistatic performance, refractive index adjusting function, and hardness adjusting function.
The function imparted to the hard coat layer 2 may be imparted to a single hard coat layer, or may be imparted to a plurality of separate layers.

The hard coat film 100A according to the above embodiment exhibits a high pencil hardness exceeding 3H, and has good black brightness when applied to an organic EL display. In other words, in an organic EL display, in a region (black region) where non-self-emitting pixels are located that is adjacent to a region where self-emitting pixels are located, light from each self-emitting pixel leaks due to interface reflection or scattering, which can prevent the black brightness from increasing.

The function of the hard coat film shown in FIG. 1 will be described below with reference to the appropriate drawings. FIGS. 2 and 3 are diagrams for explaining the interface reflection when the hard coat film is applied to an organic EL display. In FIGS. 2 and 3, as an example, the hard coat film 100A shown in FIG. 1 is formed on the organic EL display OLED, a shielding plate 30 having an opening is formed on the hard coat film 100A, and the luminance (black luminance) in the black area of the organic EL display OLED is measured by a spectroradiometer 40 through the opening, but the filler 21 is omitted to simplify the explanation of the interface reflection. In addition, in FIGS. 2 and 3, the hard coat film 100A is shown separated from the organic EL display OLED and the shielding plate 30 for convenience of explanation, but the hard coat film 100A is in contact with the organic EL display OLED and the shielding plate 30. In the following, we consider a case where the distance between the spectroradiometer 40 and the organic EL display OLED in the direction perpendicular to the surface of the organic EL display OLED is 60 cm (measurement angle 2°), and the distance between the white area W and the spectroradiometer 40 in the in-plane direction of the organic EL display OLED is 50 mm.

As shown in FIG. 2, in an organic EL display OLED, when each pixel is divided into a self-emitting region and a non-self-emitting region, and white regions W and black regions B are displayed in a checkerboard pattern, light L emitted from the white region W is reflected at the interface many times within the hard coat film 100A. With each interface reflection, photon energy is lost, and the light energy detected by the spectroradiometer 40 becomes a small value.

3, part of the light L emitted from the white region W passes through the hard coat film 100A as direct transmission light, and part of it is reflected at the interface to become internally reflected light, and passes through the opening of the shielding plate 30 with a smaller number of interface reflections than in the example shown in FIG. 2. However, because the angle is large, this light that passes through the opening of the shielding plate 30 is not detected as a signal by the spectroradiometer 40. In FIG. 2 and FIG. 3, the distance between the white region W and the spectroradiometer 40 in the in-plane direction of the organic EL display OLED is larger than the distance between the white region W and the spectroradiometer 40 in the perpendicular direction to the surface of the organic EL display OLED, so the effect of the light emitted from the white region W and reflected at the interface on the black region B is considered to be small. Note that FIG. 2 and FIG. 3 are figures for explaining the effect of interface reflection of the hard coat film without considering the effect of the filler, and in the actual hard coat film 100A, a phenomenon different from that in FIG. 2 and FIG. 3 occurs, and a detailed explanation will be given later with reference to FIG. 7 and subsequent figures.

Next, the effect of scattering by the filler when the filler is contained in the hard coat film will be described with reference to Figures 4 to 6. Figures 4 to 6 are diagrams for explaining scattering when a hard coat film containing a filler is applied to an organic EL display. In Figures 4 to 6, as an example, the hard coat film 100A shown in Figure 1 is formed on an organic EL display OLED, a shielding plate 30 is formed on the hard coat film 100A, and the luminance (black luminance) in the black area of the organic EL display OLED is measured by a spectroradiometer 40. However, to simplify the explanation of scattering by the filler 21, only one filler 21 is shown, and scattering by the filler 21 will be explained. In Figure 4, a filler located directly above the white area W is illustrated, and in Figures 5 and 6, a filler located directly below the opening of the shielding plate 30 and directly above the black area B is illustrated. These illustrated fillers are only illustrated for use in explaining the effect of the filler at that position on the black luminance, and the number of fillers included in the hard coat film 100A is not one but multiple.

As shown in FIG. 4, when the filler 21 is located above the white region W, the light L emitted from the white region W is scattered when it reaches the filler 21. When the particle size of the filler 21 is approximately 50 nm or less, visible light is scattered as Rayleigh light, and FIG. 4 shows how the scattered light spreads in a concentric pattern. Due to the positional relationship between the opening in the occlusion plate 30 and the spectroradiometer 40, the light scattered above the white region W is not detected as a signal by the spectroradiometer 40.

Here, the scattered light I of Rayleigh scattering for one particle is calculated by the following formula (1). As can be seen from formula (1), the scattered light I of Rayleigh scattering is highly dependent on the particle size. For example, with a refractive index of 1.5, a wavelength of 780 nm, and a particle size of 42 nm, the scattered light I of one particle is 1.3×10 ⁻⁷ times the incident light I ₀ , and most of the incident light does not become scattered light but travels straight (becomes transmitted light).

（式（１）中、Ｉ_０：入射光、Ｒ：粒子間距離、λ：光波長、ｎ：空間屈折率、ｄ：粒径）

(In formula (1), _I0 : incident light, R: interparticle distance, λ: light wavelength, n: spatial refractive index, d: particle size)

As shown in FIG. 5, when the filler 21 is located directly below the spectroradiometer 40, light L emitted at an angle from the white region W reaches the filler 21 directly and is detected as a signal by the spectroradiometer 40 through the aperture. In other words, such scattered light by the filler 21 leads to an increase in the luminance in the black region, which can be said to lead to an increase in black luminance.

As shown in FIG. 6, consider light L emitted from the white region W at a smaller angle than in the example shown in FIG. 5 when the filler 21 is located directly below the spectroradiometer 40. The light L is reflected at the interface of the hard coat film 100A, and each time it is reflected at the interface, photon energy is lost in the same principle as in the case shown in FIG. 3. However, when it reaches the filler 21, scattering occurs, and the scattered light is detected as a signal by the spectroradiometer 40. In other words, such scattered light by the filler 21 leads to an increase in the luminance in the black region B, leading to an increase in black luminance.

2 to 6, when focusing on one filler, the black luminance becomes a high value due to scattering by the filler 21 located directly below the spectroradiometer 40. The light scattered by the filler increases as the particle size of the filler increases, but when a large number of fillers are contained in the hard coat film as in the hard coat film 100A, the possibility that the light emitted from the white region W will directly reach the filler 21 located directly below the spectroradiometer 40 without being affected by the other fillers 21 is extremely low, and it is necessary to take into consideration the influence of the multiple fillers 21. That is, it is necessary to take into consideration the value of (1+cos ² θ)/2R ² in the above-mentioned Rayleigh scattering formula (Formula (1)).

FIG. 7 is a diagram explaining the black luminance measured when the hard coat film of FIG. 1 is applied to an organic EL display. The spectroradiometer 40 detects, as a signal, the light scattered by the filler 21 located in the measurement region Ra located directly below the hard coat layer 2, but does not detect, as a direct signal, the light scattered by the filler 21 located in the intermediate region Rb located in the in-plane direction of the measurement region Ra.

On the other hand, as shown in FIG. 7, in the hard coat film 100A containing a large number of fillers, the scattered light from the fillers 21 located in the intermediate region Rb reaches the fillers 21 located in the measurement region Ra and is scattered, thereby being detected as a signal (scattered luminance signal). The light that reaches the fillers 21 located in the intermediate region Rb includes light emitted from the white region W and reaching the filler directly, light that reaches the filler after interfacial reflection, and scattered light from other fillers. Of these, light other than the light emitted from the white region W and reaching the filler directly loses photon energy due to scattering or interfacial reflection. The scattering loss, which is the loss due to scattering in the intermediate region Rb, is greater the higher the concentration of the fillers 21 and the larger the particle size of the fillers 21.

On the other hand, as described above, the black luminance increases due to the influence of the scattered light by the filler 21 in the measurement area Ra. Focusing on the measurement area Ra, the scattered light of the filler 21 in the measurement area Ra, which affects the black luminance, increases as the particle size of the filler 21 increases and as the concentration of the filler 21 increases. Therefore, it has been found that in order to achieve high hardness and low black luminance, it is important to optimize the particle size and concentration of the filler 21 in the hard coat layer 2.

To summarise, the measurement conditions of the present invention focus on the leakage light from the white area W to the black area B, and evaluation is performed by blocking direct light from the white area W. The light that reaches the measurement area Ra in front of the black area B is reflected and scattered inside the hard coat film 100A. The emission angle of the organic EL display OLED is wide (approximately 180°), and light is incident on the hard coat film at various angles. Light with a small angle of incidence reaches the front of the black area, so there are many interfacial reflections and the signal becomes extremely weak. Light with a large angle of incidence is mainly scattered by the filler 21 distributed in the hard coat layer 2 and is transmitted to the measurement area Ra in front of the black area B.

The occurrence of electric dipoles is the main cause of scattering, and the ease with which they occur is closely related to particle size. Particles that are relatively small relative to the wavelength qualify as Rayleigh scattering particles, while larger particles qualify as Mie scattering particles. In optical applications, a particle size of 50 nm or less is preferable from the standpoint of avoiding unevenness in appearance, and scattering at this particle size is generally classified as Rayleigh scattering. In this case, the scattered light from a single particle is related to the refractive index and particle size of the substance. Since the refractive index of the binder resin 22 in the hard coat layer 2 does not change significantly, the larger the particle size of the filler 21, the stronger the scattered light will be.

The amount of scattered light from a single filler 21 is very small compared to the incident light, and most of the light is transmitted without being scattered. The light that reaches the black region B is closely related to the optical path length and the filler concentration in the region where the filler 21 exists. In particular, the filler concentration is related to the probability of scattering, and is therefore a factor that determines the final scattering intensity. The optical path length here is the average length of transmission from the white region to the black region in the hard coat film. Scattering that occurs during the optical path becomes a loss and weakens the transmitted light. The transmitted light arrives in front of the black region (measurement area Ra), and the light scattered in this area becomes a luminance signal, which deteriorates the true black. When the filler concentration is high, the scattering intensity is strong and the transmitted light is weak, but the scattered luminance signal is strong. Therefore, depending on the filler concentration, there may be extreme values in the luminance of the black region. The relationship between particle size and scattering intensity has already been mentioned, but the relationship with the optical path length is also the reason why the leakage light of the black region close to the white region is strong and the leakage light of the black region far away is weak.

The inventors conducted a simulation to explore the correlation between the filler concentration (interparticle distance), filler particle size, and black luminance in the hard coat layer 2.

Fig. 8 is a graph showing the correlation between the approximate brightness and the interparticle distance of the filler when light is incident from the side in the in-plane direction on the hard coat film 100A containing the filler with a particle size of 22 nm, 42 nm, and 80 nm.The graph shown in Fig. 8 shows the simulation of the brightness measured by a spectroradiometer that is provided 60 cm away from the hard coat film through a shielding plate having an opening formed on the hard coat film, and the opening is provided at a position about 50 nm in the in-plane direction from the edge of the hard coat film.In addition, it is assumed that the incident light has a brightness of 360 cd/ ^m2 .

In Fig. 8, the horizontal axis represents the average distance between fillers, and the vertical axis represents the approximate luminance in the black region. That is, for example, in the graph of the simulation result of the particle size of 22 nm, the result of the filler distance of 22 nm is the result of the condition where the fillers in the hard coat layer 2 are in contact with each other. Note that the simulation result shown in Fig. 8 is a simulation result that takes into account Rayleigh scattering by the filler, but does not take into account scattering by the resin contained in the hard coat layer 2 and scattering by the transparent substrate, so it is considered that the black luminance will take a value higher than the approximate luminance value in Fig. 8 when actually measured under each condition. The value of increase is about 2.2 x ^10-4 cd/ ^m2 when a TAC film of 80 μm is used as the substrate.

As shown in FIG. 8, in the hard coat film in which the particle size of the filler contained is 22 nm, there is no maximum value in the graph of the estimated brightness against the filler distance. In other words, the larger the filler distance and the lower the concentration of the filler 21 in the hard coat layer 2, the lower the estimated brightness. On the other hand, in the hard coat film in which the particle size of the filler contained is 42 nm or 80 nm, a maximum value is confirmed. In other words, when the filler is a size equal to or larger than a predetermined value, the black brightness increases as the filler distance increases to a predetermined value and the concentration decreases, and when the filler distance exceeds a predetermined value, the black brightness decreases as the filler distance increases and the concentration decreases. The maximum value in the simulation result is considered to be due to the correlation between the magnitude of the scattering loss in the intermediate region Rb and the magnitude of the scattered light relative to the light that reaches the filler in the measurement region Ra. In addition, the filler distance at which the maximum value is reached is considered to depend on the particle size of the filler, the optical path length, which is the average length of the transmission in the hard coat film from the white region W to the black region B, and the thickness of the layer in which the filler is distributed.

It is difficult to strictly show the relationship between particle concentration and interparticle distance, but if the influence of particle size and interfiller distance on brightness is taken into consideration, in a hard coat film in which filler 21 with an average particle size of less than 30 nm is contained in the hard coat layer 2, the filler 21 concentration in the hard coat layer 2 is preferably set to a concentration at which the interfiller distance is 25 nm or more, and the simulation result shows that the concentration at this time is 44.5% or less in the hard coat layer 2. In a hard coat film in which filler 21 with an average particle size of 30 nm or more and 50 nm or less is contained in the hard coat layer 2, the filler concentration in the hard coat layer 2 is preferably a concentration at which the interfiller distance is 45 nm to 60 nm and a concentration at which the interfiller distance is 280 nm or more, and the simulation value of the former is 35% or more and 60% or less. Also, the simulation value of the concentration at which the interfiller distance is 280 nm or more is 0.3% or less. However, the concentration calculated in the simulation is the final filler concentration in the hard coat layer 2, not the concentration at the time of blending including the solvent.

FIG. 9 is a cross-sectional view of a hard coat film according to a modified example of FIG. 1. The hard coat film 100B shown in FIG. 9 has a hard coat layer 2X separated from the transparent substrate 1, a first layer 2a containing a filler 21, and a second layer 2b provided between the transparent substrate 1 and the first layer 2a. The second layer 2b contains the resin component of the transparent substrate 1 and the resin component of the first layer 2a.

In the first layer 2a, the filler 21 is dispersed in the binder resin 22. The second layer 2b is, for example, an area that does not contain the filler 21, and the boundary between the first layer 2a and the second layer 2b is parallel to the transparent substrate 1 and is the surface where the filler 21 closest to the transparent substrate 1 is located. Specifically, the end of the filler 21 closest to the transparent substrate 1 on the transparent substrate 1 side can be used as the reference.

The thickness of the first layer 2a in the hard coat layer 2X is, for example, 5 μm to 15 μm, which is 40% to 80% of the thickness of the hard coat layer 2X. When the average particle size of the filler 21 is 20 nm to 30 nm, the filler concentration in the first layer 2a of the hard coat layer 2X is, for example, 10% to 80%, and preferably 25% to 65%. When the average particle size of the filler 21 is 30 nm to 50 nm, the filler concentration in the first layer 2a of the hard coat layer 2X is, for example, 10% to 80%, and preferably 25% to 65%.

The hard coat layer 2X is configured to have a first layer 2a containing a filler 21 and a second layer 2b provided between the transparent substrate 1 and the first layer 2a and containing the same resin components as those of the transparent substrate 1 and the first layer 2a, depending on the resin composition and transparent substrate 1 used to form the hard coat layer. The resin contained in the second layer 2b is not particularly limited, and may be a simple mixture (compatibility) of the resin constituting the transparent substrate 1 and the resin contained in the hard coat layer 2X. In addition, the resin contained in the second layer 2b may be a resin that has been chemically changed by heating, light irradiation, or the like, in at least one of the resin constituting the transparent substrate 1 and the resin contained in the first layer 2a.

The method of forming the second layer 2b includes a method in which, when forming the hard coat layer 2X on the transparent substrate 1, a solvent that dissolves/disperses the resin that constitutes the hard coat layer 2X is used that is also soluble in the transparent substrate 1. By selecting one of the group consisting of triacetyl cellulose (TAC), polyethylene terephthalate, polycarbonate, and acrylic as the transparent substrate 1, and selecting a solvent containing propylene glycol monomethyl ether acetate (PGMAC), butyl acetate, cyclohexanone (ANON), or the like as the resin composition used when forming the hard coat layer, the transparent substrate 1 can be dissolved, and a hard coat layer 2X as shown in FIG. 9 can be realized in which the second layer 2b is formed between the first layer 2a and the transparent substrate 1. When the hard coat layer 2 as shown in FIG. 1 contains the binder resin 22 and the filler 21, that is, when the hard coat layer is formed of the first layer, the above-mentioned materials are not used as the solvent when the hard coat layer is formed, and a resin composition composed of propylene glycol monomethyl ether (PGM) or the like is used as the solvent. The solvent is selected appropriately taking into consideration the type of transparent substrate 1 used and its solubility.

As described above, when a resin composition containing a solvent that dissolves the transparent substrate 1 is applied and cured by irradiation with light including UV, a hard coat layer 2X is formed on one surface of the transparent substrate, and a permeation layer (second layer) containing the binder resin 22 components that make up the hard coat layer 2X and the resin components of the transparent substrate 1 is formed by permeation. The thickness of the transparent substrate 1 becomes slightly smaller due to the dissolution of the hard coat layer 2X by the solvent and the permeation of the resin components.

By selecting a material that will form the second layer 2b, the overall thickness of the transparent substrate 1 and the hard coat layer 2X can be maintained at the desired design while adjusting the configuration of the first layer 2a, which is the region where the filler 21 is present, to obtain the desired optical characteristics. The thicknesses of the first layer 2a and the second layer 2b can be adjusted by the type and amount of the solvent. As a result of forming the penetration layer in this manner, the adhesion between the transparent substrate 1 and the hard coat layer 2 is improved, and the occurrence of interference fringes due to the difference in refractive index between the layers can be suppressed.

(a) of FIG. 10 is a diagram explaining the black luminance measured when the hard coat film of FIG. 1 is applied to an organic EL display, and (b) of FIG. 10 is a diagram explaining the black luminance measured when the hard coat film of FIG. 9 is applied to an organic EL display.

The content of filler 21 in the hard coat layer 2 of the hard coat film 100A shown in FIG. 10 is the same as the content of filler 21 in the hard coat film 100B shown in FIG. 10. On the other hand, the filler concentration is higher in the first layer 2a of the hard coat film 100B shown in FIG. 10 than in the hard coat layer 2 of the hard coat film 100A shown in FIG. 10, which is the region where the filler 21 exists. Specifically, the filler concentration is increased by {(thickness of the hard coat layer 2)/(thickness of the first layer 2a)} times. Accordingly, the filler concentration in the measurement region Ra measured by the spectroradiometer 40 is also increased by the same factor as above. Therefore, the transmitted light in the intermediate region Rb is changed to decrease, and in the hard coat film 100B, the optical characteristics can be changed without changing the total thickness of the transparent substrate and the hard coat layer.

Figure 11 is a graph showing a simulation of the correlation between the approximate brightness and the interparticle distance of the filler when light is incident in the in-plane direction from the side for hard coat films 100A and 100B containing filler with an average particle size of 42 nm. The simulation in Figure 11 uses a shielding plate with an opening similar to that in the simulation in Figure 8, and a spectroradiometer, and simulates the brightness of light incident from the side of the hard coat film and detected through the opening.

Figure 11 shows graphs of a hard coat film in which the hard coat layer is formed from the same material and has a uniform structure with a thickness of 10 μm due to its relationship with the transparent substrate, and a hard coat film in which the hard coat layer is made up of a first layer with a thickness of 6 μm and a second layer with a thickness of 4 μm. In other words, under the same filler distance, the filler concentration in the first layer of the latter is 1.67 times higher than that in the former hard coat layer.

FIG. 12 is a graph showing a simulation of the correlation between the approximate brightness and the distance between the filler particles when light is incident in the in-plane direction from the side for hard coat films 100A and 100B containing filler particles with a particle size of 22 nm. In FIG. 12, only the particle size of the filler is different from the simulation in FIG. 11, and the other conditions are the same.

From Figures 11 and 12, it was confirmed that regardless of the particle size of the filler in the range of 20 to 45 nm, the estimated luminance differs depending on whether the hard coat layer is homogeneous or has a first layer in which the filler is present and a second layer made of resin formed between the first layer and the transparent substrate. Specifically, it was confirmed that a hard coat film in which the hard coat layer is made of a first layer and a second layer shows a lower estimated luminance compared to a hard coat film in which the hard coat layer is made of a first layer. Furthermore, regardless of the particle size of the filler, the way in which the estimated luminance changes with respect to the filler distance is the same regardless of whether or not the second layer is present, and it was confirmed that when the filler particle size is 42 nm, the maximum value is reached when the filler distance is approximately 110 nm.

According to the hard coat films 100A and 100B of the above embodiment, the hard coat layers 2 and 2X contain the filler 21, and the concentration and particle size of the filler 21 are adjusted, so that when applied to an organic EL display, it is possible to realize a black luminance of less than 5.0×10 ⁻⁴ cd/m ² , which is the standard called True Black. Thus, according to the hard coat films 100A and 100B of the above embodiment, excellent black luminance can be realized.

[Optical laminate]
13 is a cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 200A shown in FIG. 13 includes the hard coat film 100A according to the above embodiment and an optical functional layer 50A formed on the hard coat layer 2, and the optical functional layer 50A is made of a layer made of an inorganic oxide or an inorganic nitride. Here, the "on the hard coat layer 2" is not limited to a configuration in which the hard coat layer 2 is in contact with the hard coat layer 2, and may be formed through another layer. The optical laminate 200A further includes, for example, an adhesion layer 3 formed between the hard coat layer 2 and the optical functional layer 50A and in contact with the hard coat layer 2 and the optical functional layer 50A, and an antifouling layer 6 formed on the optical functional layer 50A.

(Adhesion layer)
The adhesion layer 3 is a layer formed to improve the adhesion between the hard coat layer 2, which is an organic film, and the optical function layer 50A, which is an inorganic film. The adhesion layer 3 is preferably made of a metal oxide or metal in an oxygen-deficient state. The metal oxide in an oxygen-deficient state refers to a metal oxide in a state in which the number of oxygen is deficient compared to the stoichiometric composition. Examples of the metal oxide in an oxygen-deficient state include SiOx, AlOx, TiOx, ZrOx, CeOx, MgOx, ZnOx, TaOx, SbOx, SnOx, and MnOx. Examples of the metal include Si, Al, Ti, Zr, Ce, Mg, Zn, Ta, Sb, Sn, Mn, and In. The adhesion layer 3 may be, for example, SiOx, where x is greater than 0 and less than 2.0. The adhesion layer may also be formed from a mixture of multiple metals or metal oxides.

The thickness of the adhesion layer is preferably more than 0 nm and not more than 20 nm, and particularly preferably 1 nm or more and not more than 10 nm, from the viewpoint of maintaining adhesion between the hard coat film and the optical functional layer and obtaining good optical properties.

(optical functional layer)
The optical functional layer 50A provided in the optical laminate 200A shown in FIG. 13 is a laminate that exhibits an anti-reflection function. The optical functional layer 50A is made of an inorganic oxide or an inorganic nitride. The optical functional layer 50A is a laminate of a total of four layers in which high refractive index layers 4 and low refractive index layers 5 are alternately laminated in order from the adhesive layer 3 side. In the optical functional layer 50A, the high refractive index layer and the low refractive index layer closest to the transparent substrate 1 are referred to as the first high refractive index layer 4a and the first low refractive index layer 5a, respectively, and the high refractive index layer and the low refractive index layer farthest from the transparent substrate 1 are referred to as the second high refractive index layer 4b and the second low refractive index layer 5b, respectively. The number of layers of the high refractive index layer 4 and the low refractive index layer 5 is not particularly limited, and the number of layers of the high refractive index layer 4 and the low refractive index layer 5 can be any number of layers.

In the optical laminate 200A shown in FIG. 13, the optical function layer 50A is made of a laminate in which low refractive index layers 5 and high refractive index layers 4 are alternately stacked, so that the light incident from the anti-fouling layer 6 side interferes with each other through the optical function layer 50A, thereby reducing the intensity of the reflected light and providing an anti-reflection function. Therefore, an anti-reflection function is obtained that prevents the light incident from the anti-fouling layer 6 side from being reflected in one direction.

The low refractive index layer 5 contains, for example, a metal oxide. The low refractive index layer 5 may contain an oxide of Si from the viewpoints of availability and cost, and is preferably a layer mainly composed of SiO ₂ (oxide of Si) or the like. The SiO ₂ single layer film is colorless and transparent. In this embodiment, the main component of the low refractive index layer 5 means a component contained in the low refractive index layer 5 at 50 mass % or more.
When the low refractive index layer 5 is a layer mainly composed of an oxide of Si, it may contain less than 50 mass% of another element. The content of the element other than the oxide of Si is preferably 10% or less. As the other element, for example, Na for improving durability, Zr, Al or N for improving hardness, and Zr, Al for improving alkali resistance may be contained.

The refractive index of the low refractive index layer 5 is preferably 1.20 to 1.60, and more preferably 1.30 to 1.50. Examples of the dielectric material used for the low refractive index layer 5 include magnesium fluoride (MgF ₂ , refractive index 1.38).

The refractive index of the high refractive index layer 4 is preferably 2.00 to 2.60, and more preferably 2.10 to 2.45. Examples of dielectric materials used in the high refractive index layer 4 include niobium pentoxide (Nb ₂ O ₅ , refractive index 2.33), titanium oxide (TiO ₂ , refractive index 2.33 to 2.55), tungsten oxide (WO ₃ , refractive index 2.2), cerium oxide (CeO ₂ , refractive index 2.2), tantalum pentoxide (Ta ₂ O ₅ , refractive index 2.16), zinc oxide (ZnO, refractive index 2.1), indium tin oxide (ITO, refractive index 2.06), zirconium oxide (ZrO ₂ , refractive index 2.2), and the like.
When it is desired to impart conductive properties to the high refractive index layer 4, for example, ITO or indium zinc oxide (IZO) can be selected.

In the optical function layer 50A, it is preferable to use, for example, a layer made of niobium pentoxide (Nb ₂ O ₅ , refractive index: 2.33) as the high refractive index layer 4 and a layer made of SiO ₂ as the low refractive index layer 5 .

The thickness of the low refractive index layer 5 may be in the range of 1 nm to 200 nm, and is appropriately selected depending on the wavelength range in which the anti-reflection function is required.
The thickness of the high refractive index layer 4 may be, for example, from 1 nm to 200 nm, and is appropriately selected depending on the wavelength range in which the anti-reflection function is required.
The thicknesses of the high refractive index layer 4 and the low refractive index layer 5 can be appropriately selected depending on the design of the optical function layer 50A.
For example, from the adhesive layer 3 side, the layers may be a high refractive index layer 4 of 5 to 50 nm, a low refractive index layer 5 of 10 to 80 nm, a high refractive index layer 4 of 20 to 200 nm, and a low refractive index layer 5 of 50 to 200 nm.

Among the layers forming the optical functional layer 50A, a low refractive index layer 5 is disposed on the side of the antifouling layer 6. It is preferable that the low refractive index layer 5 of the optical functional layer 50A is in contact with the antifouling layer 6, since this improves the antireflection performance of the optical functional layer 50A.

(Anti-stain layer)
The antifouling layer 6 is formed on the outermost surface of the optical functional layer 50A to prevent the optical functional layer 50A from being soiled or damaged. Furthermore, when the antifouling layer 6 is applied to a touch panel or the like, it suppresses wear of the optical functional layer 50A due to its abrasion resistance.
The antifouling layer 6 of this embodiment is made of a vapor-deposited film formed by vapor-depositing an antifouling material. In this embodiment, the antifouling layer 6 is formed by vacuum-depositing a fluorine-based organic compound as the antifouling material on one surface of the low refractive index layer 5 constituting the optical functional layer 50A. In this embodiment, since the antifouling material contains a fluorine-based organic compound, the optical laminate 10 has even better abrasion resistance and alkali resistance.

As the fluorine-based organic compound constituting the stain-resistant layer 6, a compound consisting of a fluorine-modified organic group and a reactive silyl group (e.g., alkoxysilane) is preferably used. Commercially available products include Optool DSX (manufactured by Daikin Corporation) and the KY-100 series (manufactured by Shin-Etsu Chemical Co., Ltd.).

When a compound consisting of a fluorine-modified organic group and a reactive silyl group (e.g., alkoxysilane) is used as the fluorine-based organic compound constituting the antifouling layer 6, and a layer consisting of SiO2 is used as the low refractive index layer 5 of the optical function layer 50A in contact with the antifouling layer ₆ , a siloxane bond is formed between the silanol group, which is the skeleton of the fluorine-based organic compound, and the _SiO2 . This results in good adhesion between the optical function layer 50A and the antifouling layer 6, which is preferable.

The optical thickness of the anti-fouling layer 6 may be in the range of 1 nm or more and 20 nm or less, and is preferably in the range of 3 nm or more and 10 nm or less. If the thickness of the anti-fouling layer 6 is 1 nm or more, sufficient abrasion resistance can be ensured when the optical laminate 10 is applied to touch panel applications, etc. If the thickness of the anti-fouling layer 6 is 3 nm or more, the liquid resistance, etc. of the optical laminate 10 is improved. If the thickness of the anti-fouling layer 6 is 20 nm or less, the time required for vapor deposition is short, allowing for efficient production.

FIG. 14 is a cross-sectional view of an optical laminate according to a modified example of FIG. 13. The optical laminate 200B shown in FIG. 14 is different from the optical functional layer 50A provided in the optical laminate 200A in that the optical functional layer 50B is an inorganic oxide or inorganic nitride monolayer. The optical functional layer 50B may contain an oxide of Si from the viewpoint of availability and cost. The optical functional layer 50B is, for example, a monolayer film containing SiO ₂ (oxide of Si) as a main component. The SiO ₂ monolayer film is colorless and transparent. In this embodiment, the main component of the optical functional layer 50B means a component contained in the optical functional layer 50B at 50% by mass or more. The optical functional layer 50B may be a layer made of SiO ₂ .

FIG. 15 is a cross-sectional view of an optical laminate according to another modified example of FIG. 13. The optical laminate 200C shown in FIG. 15 comprises an adhesion layer 3, an optical functional layer 50A, and an antifouling layer 6 on a hard coat film 100B. Like the optical laminate 200C shown in FIG. 15, the optical laminate according to this embodiment may have a configuration in which the optical functional layer is formed on a hard coat film having a hard coat layer 2X having a first layer 2a and a second layer 2b.

In the optical laminate according to the present embodiment, another layer may be provided on the surface of the transparent substrate 1 opposite to the surface on which the hard coat layer 2, 2X or the optical functional layer 50A, 50B is formed. For example, an adhesive layer to be attached to a display, a release layer provided on the adhesive layer, etc. may be provided.
The adhesive layer is a layer that is adhered to a display or the like. The adhesive layer is, for example, an acrylic adhesive, a silicone adhesive, or a urethane adhesive. The release layer is a layer that protects the adhesive layer, and is peeled off at the time of lamination, and the adhesive layer that is exposed by peeling can be attached. The release layer is, for example, paper or a film coated with a release agent. The adhesive layer may or may not have a separate substrate on the transparent substrate 1 side. That is, the adhesive layer may be formed directly on the transparent substrate 1 or may be formed via a substrate, but from the viewpoint of facilitating handling of the optical laminate and the display to which the optical laminate is attached, it is preferable to have a substrate layer on the transparent substrate 1 side.

The optical laminate according to this embodiment has high hardness, similar to the hard coat film according to the above embodiment, and can provide an optical laminate with good black brightness when applied to an organic EL display.

The following describes examples of the present invention. The present invention is not limited to the following examples.

<Preparation of composition for hard coat layer>
In order to prepare the hard coat films of Examples 1 to 4 and Comparative Examples 1 to 3 below, photocurable resin compositions mixed with fillers were prepared except for Comparative Example 1. The resin compositions were prepared by dissolving fillers, acrylates, leveling agents, and photopolymerization initiators in a solvent, as shown in Tables 1 and 2. Table 1 shows the blending ratios when the entire resin composition including the solvent is taken as 100%. Table 2 shows the blending ratios without the solvent. That is, Table 2 shows the blending ratios when the total solid content is taken as 100%. The percentages in the tables are blending ratios in the resin composition, and represent mass %.

[Example 1-1]
First, a triacetyl cellulose (TAC) substrate having a thickness of 80 μm was prepared as a transparent substrate. The resin composition of Example 1 shown in Table 1 was applied to the transparent substrate by a gravure coater so that the thickness of the hard coat layer before curing was 10 μm. Then, the resin composition applied to the transparent substrate was irradiated with light to cure the resin composition, thereby producing a hard coat film in which a hard coat layer composed of a second layer containing the resin component of the transparent substrate and the resin component of the hard coat layer and a first layer containing a filler was formed on the transparent substrate as shown in FIG. 9.
The PGMAC-4130Y (manufactured by Nissan Chemical Industries, Ltd.) used as the filler in Example 1-1 is a filler having an average particle size of 42 nm, in which the surface of the silica particles is modified with a (meth)acrylic group.

[Example 2-1]
A hard coat film was prepared in the same manner as in Example 1, except that the resin composition mixed with the filler was changed to that in Example 2 shown in Table 1.
In Example 2-1, the thickness of the first layer in the hard coat layer was made thinner than that of Example 1 by changing the solvent for the resin composition.

[Example 3-1]
A hard coat film was prepared in the same manner as in Example 1, except that the resin composition mixed with the filler was changed to that of Example 3 shown in Table 1.
In Example 3-1, the solvent of the resin composition was changed to PGM (propylene glycol monomethyl ether), so that a hard coat film was produced in which a hard coat layer containing a resin and a filler was provided in contact with a transparent substrate as shown in FIG.
PGMAC-3140Y (manufactured by Nissan Chemical Industries, Ltd.) used as the filler is a filler having an average particle size of 22 nm, in which the surface of the silica particles is modified with a (meth)acrylic group.

[Example 4-1]
A hard coat film was prepared in the same manner as in Example 1, except that the resin composition was changed to that of Example 4 shown in Table 1.
In Example 4-1, the compounding ratio of the resin composition was changed to adjust the thickness of the first layer and the second layer of the hard coat layer.

[Comparative Example 1-1]
A hard coat film was prepared in the same manner as in Example 1, except that the resin composition was changed to that of Comparative Example 1 shown in Table 1.
In Comparative Example 1-1, a resin composition containing no filler was used to prepare a hard coat film in which a hard coat layer containing no filler was formed on a transparent substrate.

[Comparative Example 2-1]
A hard coat film was prepared in the same manner as in Example 1, except that the resin composition was changed to that of Comparative Example 2 shown in Table 1.
In Comparative Example 2-1, a hard coat film was produced in which a hard coat layer having no first layer was formed on a transparent substrate by using PGM as a solvent.

[Comparative Example 3-1]
A hard coat film was prepared in the same manner as in Example 1, except that the resin composition was changed to that of Comparative Example 3 shown in Table 1.
In Comparative Example 3-1, the compounding ratio of was changed to make the first layer thinner and the second layer thicker, and IPA-ST-L (manufactured by Nissan Chemical Industries, Ltd.), i.e., silicon dioxide that was not surface-modified, was used as the filler.

Furthermore, in Examples 1-2, 2-2, 3-2, and 4-2 and Comparative Examples 1-2, 2-2, and 3-2, optical laminates (anti-reflection films) were produced by producing an adhesion layer, an optical functional layer, and an antifouling layer by the following method on the hard coat film layers produced in the above Examples 1-1, 2-1, 3-1, and 4-1 and Comparative Examples 1-1, 2-1, and 3-1. Examples 1-1 and 1-2 may be collectively referred to as Example 1. Other examples and comparative examples may also be collectively referred to in the same manner.

<Method of producing anti-reflection film>
The surface of the hard coat layer was treated by glow discharge treatment at 5 kW. Then, an adhesive layer and an optical functional layer were successively formed on the hard coat layer by reactive sputtering using a Si target and a Nb target as sputtering targets and a mixed gas of Ar gas and _O2 gas.
That is, on the hard coat layer, a 3 nm adhesion layer made of silicon oxide (SiOx, 0<x<2) which may have oxygen deficiency, _a first high refractive index material layer made of _Nb2O5 having a thickness of 10 nm, a first low refractive index material layer made of _SiO2 having a thickness of 26 nm, a second high refractive index material layer made of _Nb2O5 having a thickness of 110 _nm , and a second low refractive index material layer made of _SiO2 having a thickness of 85 nm were formed in this order.

Next, a 3 nm thick antifouling layer made of an alkoxysilane compound having a perfluoropolyether group (KY1903-1, manufactured by Shin-Etsu Chemical Co., Ltd.) was formed by deposition on the SiO ₂ film of the topmost layer of the optical functional layer at a pressure of 0.01 Pa in the deposition chamber, a deposition temperature of 230° C., and a retention time of 7.2 s to produce an optical laminate (antireflection film) of the example.

<Structural evaluation>
The cross section of the hard coat film produced in the above Examples and Comparative Examples was observed with an optical microscope to evaluate the laminate structure. In the observed cross section, the distance from the outermost surface of the filler closest to the transparent substrate was measured and defined as the thickness of the second layer.

<Evaluation of Black Luminance>
The prepared sample was attached to an organic EL display (170 mm x 290 mm) of a notebook PC (ASUS ZenBook 13 OLED) equipped with an organic EL display. A predetermined measurement pattern was displayed on the organic EL display. The settings of the organic EL display were Brightness setting: MAX, HDR: Enable, light emission angle: 180°, and brightness: 360 cd/ ^m2 . FIG. 16 shows the measurement pattern displayed on the organic EL when measuring black brightness in the examples and comparative examples. As shown in FIG. 16, the measurement pattern has a white area W and a black area B located in a checkerboard pattern. A shielding plate was provided on the hard coat film so as to cover the organic EL display except for the black area B where the measurement area Ra is located. The black area B where the measurement area Ra is located is exposed through an opening provided in the shielding plate. The black area B where the measurement area is located has a size of 80 mm x 100 mm, and the measurement area is located at its center of gravity. Measurements were taken at a measurement angle of 2° using a spectroradiometer (TOPCON SR-UL1R) placed 60 cm away from the organic EL display. The measurement conditions met the VESA True Black measurement standard.
The black luminance was measured for each of the cases where the hard coat film was applied to the organic EL display and where the anti-reflection film was applied to the organic EL display.

<Pencil hardness>
The pencil hardness of the prepared hard coat film and anti-reflection film was measured by a method according to JIS K5600-5-4.

<Haze value>
The haze value of the prepared hard coat film was measured by a method according to JIS-K-7136.

In Table 3, the total thickness of the hard coat layer represents the total thickness of the hard coat layer before curing. The thickness of the second layer, the density of the first layer, the black brightness, the pencil hardness, and the haze values are the average values of the three samples prepared. In addition, the filler concentration in Table 3 is the mass % of the filler in the hard coat layer.

It was also confirmed that the black luminance was low in the hard coat films in which the particle size of the filler was in the range of 30 nm to 50 nm and the filler concentration in the first layer in which the filler was present was in the range of 25% to 65% as in Examples 1 and 2. It was also confirmed that the black luminance was low in the hard coat films in which the particle size of the filler was in the range of 30 nm or less and the filler concentration in the first layer in which the filler was present or in the homogeneous hard coat layer was in the range of 25% to 65% as in Examples 3 and 4. Furthermore, the pencil hardness was high in Examples 1 to 4, and both the hardness and the fulfillment of the standard called True Black in VESA were achieved. In particular, in Examples 1 to 4, the measurement results of black luminance when a hard coat film was applied were less than 3.5×10 ⁻⁴ (cd/m ² ), of which in Examples 1, 3, and 4 it was less than 3.0×10 ⁻⁴ (cd/m ² ), and in Example 4 it was less than 2.0×10 ⁻⁴ (cd/m ² ). In addition, the black luminance when an anti-reflection film was applied was 3.0×10 ⁻⁴ (cd/m ² ) or less in all of Examples 1 to 4.

In contrast, in a hard coat film in which the hard coat layer does not contain a filler, such as in Comparative Example 1, the absence of filler results in no scattering effect from the filler, and therefore the black luminance is low, but the pencil hardness is low. In Comparative Example 2, in which the particle size of the filler is 42 nm and the filler concentration in the 10 μm-thick hard coat layer without a second layer is 31.54%, the black luminance is insufficient.

In addition, Comparative Example 3, which uses a filler that is not surface-modified with (meth)acrylic groups, showed a significantly higher black luminance than Example 2, which was the same except for whether the filler was surface-modified or not. This is thought to be because the surface of the filler was not surface-modified with (meth)acrylic groups, the filler aggregated with itself, increasing the pseudo particle size, and the aggregated particles locally increased the scattered light.

[Examples 5 to 7, Comparative Example 4]
Based on the formulation shown in Table 4, the hard coat films described in Examples 5 to 7 and Comparative Example 4 were prepared. The resin composition was applied to a transparent substrate, TAC, by a gravure coater to a thickness of 10 μm, and cured by irradiating with light to prepare a hard coat film as shown in FIG.
The filler concentration in the hard coat layer of Example 5 corresponds to the data in the simulation of FIG. 8 where the filler distance is about 75 nm.
The filler concentration in the hard coat layer of Example 6 corresponds to the data for a filler distance of 120 nm in the simulation of FIG.
The filler concentration in the hard coat layer of Example 7 corresponds to the data of the filler distance of about 55 nm in the simulation of FIG.
The filler concentration in the hard coat layer of Comparative Example 4 is 0%, and the distance between fillers in the simulation of FIG. 8 is treated as being infinite.

(Brightness Evaluation)
For Examples 5 to 7 and Comparative Example 4, data corresponding to the simulation conditions shown in the graph in Figure 8 were actually measured. That is, the luminance of the hard coat film was measured using the same shielding plate and spectroradiometer as those used for measuring the black luminance in the above examples. The luminance was measured through the opening of the shielding plate by the spectroradiometer installed 60 cm away from the hard coat film.

FIG. 17 is a graph showing the filler concentration and brightness results for Examples 5 to 7 and Comparative Example 4. As shown in FIG. 17, between Examples 5 and 7, which have the same filler concentration, Example 7 showed lower brightness, while Example 6, which has a filler concentration between Examples 7 and Comparative Example 4, showed higher brightness than Example 5 and Comparative Example 4, suggesting the presence of a maximum value. In this way, a correlation was confirmed between the simulation results in FIG. 8 and the graph based on the actual measured values in FIG. 17, confirming the validity of the simulation results in FIG. 8.

1 Transparent substrate 2, 2X Hard coat layer 2a First layer 2b Second layer 3 Adhesion layer 4 High refractive index layer 4a First high refractive index layer 4b Second high refractive index layer 5 Low refractive index layer 5a First low refractive index layer 5b Second low refractive index layer 6 Antifouling layer 10 Optical laminate 21 Filler 22 Resin 30 Shielding plate 40 Spectroradiometer 50A, 50B Optical functional layer 100A, 100B Hard coat film 200A Optical laminate 200B Optical laminate 200C Optical laminate

Claims (8)

A transparent substrate and a hard coat layer formed on the transparent substrate,
The hard coat layer contains a filler,
A hard coat film having a black luminance measured under the following conditions of less than 5.0×10 ⁻⁴ cd/m ² .
(Conditions: A hard coat film is placed in close contact with an organic EL display with a light emission angle of 180 degrees and a brightness of 360 cd/ ^m2 , white and black areas are displayed in a checkered pattern on the organic EL display, a shielding plate is placed so as to cover the surface of the organic EL display except for the black areas, and the black brightness in the black areas is measured with a spectroradiometer placed 60 cm away from the organic EL display.) The hard coat layer contains an acrylic resin,
The particle size of the filler is 20 nm or more and 50 nm or less,
The hard coat film according to claim 1 , wherein a surface of the filler is modified with a (meth)acrylic group. the hard coat layer has a first layer separated from the transparent substrate and containing the filler, and a second layer provided between the transparent substrate and the first layer,
The hard coat film according to claim 1 , wherein the second layer comprises a resin component of the transparent substrate and a resin component of the first layer. The average particle size of the filler is 20 nm or more and 50 nm or less,
The hard coat film according to claim 3 , wherein the concentration of the filler in the first layer is 25% or more and 65% or less. The average particle size of the filler is 20 nm or more and 50 nm or less,
2. The hard coat film according to claim 1, wherein the concentration of the filler in the hard coat layer is 40% or more and 65% or less. The hard coat film according to any one of claims 1 to 5, and an optical functional layer formed on the hard coat layer,
The optical laminate, wherein the optical functional layer is a layer made of an inorganic oxide or an inorganic nitride. The optical laminate according to claim 6 , wherein the optical functional layer is a single layer film made of SiO ₂ . The optical functional layer further includes an adhesive layer formed between the hard coat layer and the optical functional layer and in contact with the hard coat layer and the optical functional layer,
The optical functional layer is formed by alternately laminating high refractive index material layers and low refractive index layers,
The optical laminate according to claim 6 , wherein the adhesion layer is in contact with the high refractive index material layer.

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