JP7718840B2 - Hard-coated film, optical member, and image display device - Google Patents

Description

The present invention relates to a hard-coated film, an optical component, and an image display device.

Hard-coated films are films that have a hard-coating layer on the surface to enhance scratch resistance, and are widely used in image display devices (see Patent Document 1, etc.).

Japanese Patent Application Laid-Open No. 2008-221746

However, increasing the hardness of the hard coat layer may cause the hard coat film to curl due to cure shrinkage. On the other hand, reducing the cure shrinkage may result in a decrease in the hardness of the hard coat layer. In other words, there is a problem with hard coat films: there is a trade-off between hardness and curl suppression.

In addition, other layers such as an anti-reflection layer may be laminated on the viewing side surface of the hard coat layer. However, increasing the hardness of the hard coat layer surface may reduce adhesion between the viewing side surface and other layers.

The present invention aims to provide a hard-coated film, optical component, and image display device that has high hardness, suppresses curling, and has high adhesion between the viewing-side surface and other layers.

In order to achieve the above object, the hard coat film of the present invention comprises:
a substrate, a first hard coat layer, a second hard coat layer, and a third hard coat layer;
the first hard coat layer, the second hard coat layer, the substrate, and the third hard coat layer are laminated in this order from the viewing side;
the first hard coat layer and the second hard coat layer each contain nanosilica particles;
The nanosilica particles contained in the first hard coat layer have a weight average particle diameter larger than the weight average particle diameter of the nanosilica particles contained in the second hard coat layer.

The optical member of the present invention is an optical member that includes the hard coat film of the present invention.

The image display device of the present invention is an image display device that includes the hard coat film of the present invention or the optical member of the present invention.

The present invention makes it possible to provide hard-coated films, optical components, and image display devices that have high hardness, suppress curling, and high adhesion between the viewing-side surface and other layers.

FIG. 1 is a cross-sectional view illustrating the structure of the hard coat film of the present invention. FIG. 2 is a cross-sectional view showing an example in which the hard coat film of the present invention is laminated on a glass plate. 3A to 3C are cross-sectional views illustrating the steps of producing the hard coat film of the present invention.

Next, the present invention will be explained in more detail using examples. However, the present invention is not limited in any way by the following explanation.

In the hard coat film of the present invention, for example, the third hard coat layer may not contain nanosilica particles.

In the hard coat film of the present invention, for example, the thickness of the third hard coat layer may be smaller than the total thickness of the first hard coat layer and the second hard coat layer.

In the hard coat film of the present invention, for example, the weight average particle diameter of the nanosilica particles contained in the first hard coat layer may be 30 to 50 nm, and the weight average particle diameter of the nanosilica particles contained in the second hard coat layer may be 5 to 30 nm.

The hard coat film of the present invention may have, for example, a light transmittance of 90% or more at a wavelength of 550 nm throughout the entire hard coat film.

The optical element of the present invention may be, for example, a polarizing plate.

In the present invention, unless otherwise specified, "weight" and "mass" may be read interchangeably. For example, "parts by mass" may be read as "parts by weight," "parts by weight" may be read as "parts by mass," "% by mass" may be read as "% by weight," and "% by weight" may be read as "% by mass."

[1. Hard-coated film]
As described above, in the hard coat film of the present invention, the weight average particle diameter of the nanosilica particles contained in the first hard coat layer is larger than the weight average particle diameter of the nanosilica particles contained in the second hard coat layer. That is, the weight average particle diameter of the nanosilica particles contained in the first hard coat layer and the weight average particle diameter of the nanosilica particles contained in the second hard coat layer satisfy the relationship of the following formula (1):

Ra>Rb (1)

In the formula (1), Ra is the weight average particle diameter [nm] of the nanosilica particles contained in the first hard coat layer, and Rb is the weight average particle diameter [nm] of the nanosilica particles contained in the second hard coat layer.

The cross-sectional view of Figure 1(a) shows an example of the configuration of a hard coat film of the present invention. As shown, this hard coat film 100a includes a substrate 110, a first hard coat layer 101, a second hard coat layer 102, and a third hard coat layer 103. As shown, the first hard coat layer 101, the second hard coat layer 102, the substrate 110, and the third hard coat layer 103 are laminated in this order from the viewing side. In other words, the second hard coat layer 102 and the first hard coat layer 101 are laminated in this order on one surface (the viewing side surface) of the substrate 110, and the third hard coat layer 103 is laminated on the other surface (the viewing back side surface) of the substrate 110. The first hard coat layer 101 contains nanosilica particles 101P. The second hard coat layer 102 contains nanosilica particles 102P. The weight average particle diameter (Ra in the above formula (1)) of the nanosilica particles 101P contained in the first hard coat layer 101 is larger than the weight average particle diameter (Rb in the above formula (1)) of the nanosilica particles 102P contained in the second hard coat layer 102.

The cross-sectional view of Figure 1(b) shows another example of the configuration of the hard coat film of the present invention. As shown, this hard coat film 100b is the same as the hard coat film 100a in Figure 1(a) except that the third hard coat layer 103 contains nanosilica particles 103P.

As described above, the hard-coated film of the present invention has high hardness and is also suppressed from curling. Specifically, for example, hard-coat layers are laminated on both sides of the substrate to suppress curling, and the first hard-coat layer and the second hard-coat layer are laminated on the front side (viewing side), thereby achieving high hardness. For this reason, the hard-coated film of the present invention can be used not only as a component of a polarizing plate, but also as a front panel, for example.

The hard coat film of the present invention can be used, for example, as a clear film or an anti-glare film (also referred to as an AG film). For example, to use it as an anti-glare film, the outermost layer on the viewing side (e.g., the first hard coat layer) can be given anti-glare properties (AG properties).

The hard coat film of the present invention may or may not include layers other than the substrate, the first hard coat layer, the second hard coat layer, and the third hard coat layer. For example, the substrate, the first hard coat layer, the second hard coat layer, and the third hard coat layer may be laminated directly to each other, or may be laminated via another layer such as an adhesive layer. Furthermore, for example, the first hard coat layer and the third hard coat layer may or may not have another layer laminated on their outer surfaces. Specifically, for example, an anti-reflection layer (also referred to as an AR layer) may be laminated on the outer surface of the first hard coat layer to impart an anti-reflection effect. The anti-reflection layer is not particularly limited, and may be, for example, a DRY-AR layer (an AR layer formed by a dry method such as sputtering or vapor deposition). Furthermore, for example, an adhesive layer may be formed on the outer surface of the third hard coat layer. The other layer may be formed, for example, by coating. As described above, the hard-coated film of the present invention exhibits high adhesion between the viewing-side surface and other layers. More specifically, the hard-coated film of the present invention is suitable for providing an anti-reflection layer (e.g., a DRY-AR layer) as another layer on the first hard-coat layer, due to the high adhesion between the surface of the first hard-coat layer (having nanosilica particles with a large weight-average particle diameter) and other layers. Furthermore, the hard-coated film of the present invention exhibits high hardness, due to the presence of the second hard-coat layer (having nanosilica particles with a small weight-average particle diameter) between the first hard-coat layer (having nanosilica particles with a large weight-average particle diameter) and the substrate. Furthermore, the hard-coated film of the present invention exhibits suppressed curling as described above, and therefore exhibits good transportability when forming other layers by coating.

In the present invention, "adhesive layer" means "sticky layer or adhesive layer." "Adhesive layer" means "layer formed from a pressure-sensitive adhesive." "Adhesive layer" means "layer formed from an adhesive." Generally, a material with relatively weak adhesive strength (adhesion strength) that allows the adherend to be removed is called an "adhesive," while a material with relatively strong adhesive strength (adhesion strength) that makes it impossible or difficult to remove is called an "adhesive." In the present invention, a material with relatively weak adhesive strength (adhesion strength) is called an "adhesive," and a material with relatively strong adhesive strength (adhesion strength) is called an "adhesive," but there is no clear distinction between the two.

In the hard coat film of the present invention, the materials of the substrate, the first hard coat layer, the second hard coat layer, and the third hard coat layer are not particularly limited and may be, for example, similar to or equivalent to those of general hard coat films. Specific examples are given in the method for producing the hard coat film of the present invention described below. The nanosilica particles are also not particularly limited and may be, for example, similar to or equivalent to those of general hard coat films. The hard coat film of the present invention can use, for example, materials similar to those of general hard coat films (no special materials, processing, etc. are required), thereby achieving both high hardness and curl suppression without sacrificing appearance, display properties, etc.

In recent years, even in large-sized displays, such as notebook PC displays, touch sensors have been incorporated into the liquid crystal cell (in-cell touch sensor technology). Furthermore, for notebook PC displays, glassless configurations (displays that do not use glass) are required from the standpoints of light weight, thinness, and processability. For example, the hard coat film of the present invention can meet these demands due to its high hardness.

The third hard coat layer in the hard coat film of the present invention may contain nanosilica particles, but as mentioned above, it does not have to contain nanosilica particles. It is preferable that the third hard coat layer does not contain nanosilica particles, as this tends to further increase the hardness of the hard coat film. If the third hard coat layer does not contain nanosilica particles, for example, the third hard coat layer is less likely to crack due to bending. Furthermore, if the third hard coat layer does not contain nanosilica particles, for example, even if a thick adhesive layer is formed on the outside of the third hard coat layer, the third hard coat layer is less likely to crack due to scratching, etc. Furthermore, the absence of nanosilica particles in the third hard coat layer has the advantages of significantly reducing material costs and improving the processability of the hard coat film.

In the present invention, the thickness of the substrate is not particularly limited, but from the viewpoints of strength, workability (e.g., ease of handling), thin layer properties, etc., it may be, for example, 80 μm or more, 90 μm or more, 100 μm or more, 110 μm or more, or 120 μm or more; for example, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less, and may be, for example, 10 to 40 μm, 40 to 70 μm, 70 to 100 μm, 100 to 130 μm, or 130 to 160 μm. It is preferable that the thickness of the substrate is not too large from the viewpoint of workability, and is preferably not too small from the viewpoint of maintaining hardness.

In the present invention, the thickness of the first hard coat layer is not particularly limited, but may be, for example, 0.1 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more, and may be, for example, 30 μm or less, 20 μm or more, 10 μm or more, 5 μm or less, 4 μm or less, 3 μm or less It may be 2 μm or less, or 1 μm or less, for example, 0.1 to 30 μm, 0.1 to 20 μm, 0.1 to 10 μm, 0.1 to 5 μm, 1 to 30 μm, 1 to 20 μm, 1 to 10 μm, 1 to 5 μm, 5 to 30 μm, 5 to 20 μm, 5 to 10 μm, 0.1 to 1 μm, 1 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 30 μm. The thickness of the first hard coat layer is preferably not too large from the viewpoints of processability and flexibility, and is preferably not too small from the viewpoint of hardness.

In the present invention, the thickness of the second hard coat layer is not particularly limited, but may be, for example, 0.1 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, and may be, for example, 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less. The thickness of the second hard coat layer may be, for example, 0.1 to 50 μm, 0.1 to 30 μm, 0.1 to 20 μm, 0.1 to 10 μm, 0.1 to 5 μm, 1 to 50 μm, 1 to 30 μm, 1 to 20 μm, 1 to 10 μm, 5 to 50 μm, 5 to 30 μm, 5 to 20 μm, 10 to 50 μm, 0.1 to 1 μm, 1 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. The thickness of the second hard coat layer is preferably not too large from the viewpoints of processability and flexibility, and is preferably not too small from the viewpoint of hardness.

In the present invention, the thickness of the third hard coat layer is not particularly limited, but may be, for example, 0.1 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, and may be, for example, 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less. The thickness of the third hard coat layer may be, for example, 0.1 to 50 μm, 0.1 to 30 μm, 0.1 to 20 μm, 0.1 to 10 μm, 0.1 to 5 μm, 1 to 50 μm, 1 to 30 μm, 1 to 20 μm, 1 to 10 μm, 5 to 50 μm, 5 to 30 μm, 5 to 20 μm, 10 to 50 μm, 0.1 to 1 μm, 1 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. The thickness of the third hard coat layer is preferably not too large from the viewpoints of processability and flexibility, and is preferably not too small from the viewpoint of hardness.

In the hard coat film of the present invention, if the thickness of any layer, including the substrate, is not uniform (for example, if the layer has an uneven surface), the "thickness" of that layer shall be the average thickness.

In the hard coat film of the present invention, for example, as described above, the thickness of the third hard coat layer may be smaller than the total thickness of the first hard coat layer and the second hard coat layer. That is, the thicknesses of the first hard coat layer, the second hard coat layer, and the third hard coat layer may satisfy the relationship of the following mathematical formula (2). By reducing the thickness of the third hard coat layer in this way, it is possible to reduce the overall thickness of the hard coat film, reduce the weight of the entire hard coat film, improve the processability of the hard coat film, reduce material costs, and suppress cracks when the hard coat film is folded, among other effects.

Tab>Tc (2)

In the formula (2), Tab is the sum [μm] of the thickness of the first hard coat layer and the thickness of the second hard coat layer, and Tc is the thickness [μm] of the third hard coat layer.

As described above, the hard coat film of the present invention has high adhesion between the hard coat layer and the anti-reflection layer (e.g., a DRY-AR layer) by forming an anti-reflection layer on the first hard coat layer, which contains nanosilica particles with a large weight-average particle diameter. Furthermore, the hard coat film of the present invention has high hardness by, for example, having the second hard coat layer, which contains nanosilica particles with a small weight-average particle diameter, between the first hard coat layer and the substrate.

In the present invention, "nanosilica particles" refers to silica particles having a weight-average particle diameter of approximately several hundred nanometers or less. The weight-average particle diameter of the "nanosilica particles" is not particularly limited, but may be, for example, 1 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, or 250 nm or more, or may be, for example, 300 nm or less, 250 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. , 1 to 300 nm, 1 to 250 nm, 1 to 200 nm, 1 to 100 nm, 1 to 50 nm, 10 to 300 nm, 10 to 250 nm, 10 to 200 nm, 10 to 100 nm, 50 to 300 nm, 50 to 250 nm, 50 to 200 nm, 50 to 100 nm, 100 to 300 nm, 100 to 250 nm, 1 to 10 nm, 10 to 50 nm, 50 to 100 nm, 100 to 200 nm, or 200 to 300 nm.

In the present invention, the method for measuring the weight-average particle diameter is not particularly limited, but is, for example, as follows. For example, the average particle diameter of nanoparticles in a hard coat layer can be measured by TEM (Transmission Electron Microscope) analysis of a cross section of the hard coat layer, and this can be estimated as the weight-average particle diameter. Specifically, the weight-average particle diameter can be estimated by averaging the particle diameters (the sum of the major axis and minor axis divided by 2) of all particles observed in a 0.5 μm x 0.5 μm area in a TEM image of the cross section. Furthermore, when measuring the weight-average particle diameter of the nanoparticle system in a material (solution) in which nanoparticles are dispersed, it can be measured, for example, using a light scattering/diffraction method.

In the present invention, the weight average particle diameter of the nanosilica particles contained in the first hard coat layer is not particularly limited, but may be, for example, 1 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, or 250 nm or more, and may be, for example, 300 nm or less, 250 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. The weight average particle diameter of the nanosilica particles contained in the first hard coat layer may be, for example, 1 to 300 nm, 1 to 250 nm, 1 to 200 nm, 1 to 100 nm, 1 to 50 nm, 10 to 300 nm, 10 to 250 nm, 10 to 200 nm, 10 to 100 nm, 50 to 300 nm, 50 to 250 nm, 50 to 200 nm, 50 to 100 nm, 100 to 300 nm, 100 to 250 nm, 1 to 10 nm, 10 to 50 nm, 50 to 100 nm, 100 to 200 nm, or 200 to 300 nm. The weight average particle diameter of the nanosilica particles contained in the first hard coat layer is preferably not too large from the viewpoint of film transparency, and is preferably not too small from the viewpoint of adhesion to the antireflection layer (AR layer).

In the present invention, the weight average particle diameter of the nanosilica particles contained in the second hard coat layer is not particularly limited, but may be, for example, 1 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, or 250 nm or more, and may be, for example, 300 nm or less, 250 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. The weight average particle diameter of the nanosilica particles contained in the second hard coat layer may be, for example, 1 to 300 nm, 1 to 250 nm, 1 to 200 nm, 1 to 100 nm, 1 to 50 nm, 10 to 300 nm, 10 to 250 nm, 10 to 200 nm, 10 to 100 nm, 50 to 300 nm, 50 to 250 nm, 50 to 200 nm, 50 to 100 nm, 100 to 300 nm, 100 to 250 nm, 1 to 10 nm, 10 to 50 nm, 50 to 100 nm, 100 to 200 nm, or 200 to 300 nm. The weight average particle diameter of the nanosilica particles contained in the second hard coat layer is preferably not too large from the viewpoint of film transparency, and is preferably not too small from the viewpoint of film hardness.

As described above, the third hard coat layer may or may not contain nanosilica particles. When the third hard coat layer contains nanosilica particles, the weight average particle diameter of the nanosilica particles is not particularly limited, and may be, for example, 1 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, or 250 nm or more, or, for example, 300 nm or less, 250 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. The weight average particle diameter of the nanosilica particles contained in the third hard coat layer may be, for example, 1 to 300 nm, 1 to 250 nm, 1 to 200 nm, 1 to 100 nm, 1 to 50 nm, 10 to 300 nm, 10 to 250 nm, 10 to 200 nm, 10 to 100 nm, 50 to 300 nm, 50 to 250 nm, 50 to 200 nm, 50 to 100 nm, 100 to 300 nm, 100 to 250 nm, 1 to 10 nm, 10 to 50 nm, 50 to 100 nm, 100 to 200 nm, or 200 to 300 nm. The weight average particle diameter of the nanosilica particles contained in the third hard coat layer is preferably not too large from the viewpoint of film transparency, and is preferably not too small from the viewpoint of film hardness.

In the hard coat film of the present invention, for example, as described above, the weight average particle diameter of the nanosilica particles contained in the first hard coat layer may be 30 to 50 nm, and the weight average particle diameter of the nanosilica particles contained in the second hard coat layer may be 5 to 30 nm.

Furthermore, in the first hard coat layer, the content of the nanosilica particles may be, for example, 1% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, relative to the mass (weight) of the entire first hard coat layer; or, for example, less than 100% by mass, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less, and may be, for example, 1 to 90% by mass. %, 1-80% by mass, 1-70% by mass, 1-60% by mass, 1-50% by mass, 1-40% by mass, 20-90% by mass, 20-80% by mass, 20-70% by mass, 20-60% by mass, 20-50% by mass, 30-90% by mass, 30-80% by mass, 30-70% by mass, 30-60 Mass%, 30-50% by mass, 30-40% by mass, 40-90% by mass, 40-80% by mass, 40-70% by mass, 40-50% by mass, 60-90% by mass, 1-20% by mass, 20-40% by mass, 40-60% by mass, 60-80% by mass, or 80-90% by mass. In the first hard coat layer, the content of the nanosilica particles is preferably not too high from the viewpoints of processability and flexibility, and is preferably not too low from the viewpoint of hardness.

In the second hard coat layer, the content of the nanosilica particles may be, for example, 1% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, relative to the total mass (weight) of the second hard coat layer; or may be, for example, less than 100% by mass, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less, for example, 1 to 90% by mass , 1-80% by mass, 1-70% by mass, 1-60% by mass, 1-50% by mass, 1-40% by mass, 20-90% by mass, 20-80% by mass, 20-70% by mass, 20-60% by mass, 20-50% by mass, 30-90% by mass, 30-80% by mass, 30-70% by mass, 30-60 quality %, 30-50% by mass, 30-40% by mass, 40-90% by mass, 40-80% by mass, 40-70% by mass, 40-50% by mass, 60-90% by mass, 1-20% by mass, 20-40% by mass, 40-60% by mass, 60-80% by mass, or 80-90% by mass. In the second hard coat layer, the content of the nanosilica particles is preferably not too high from the viewpoints of processability and flexibility, and is preferably not too low from the viewpoint of hardness.

In the third hard coat layer, the content of the nanosilica particles may be, for example, 1% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, relative to the total mass (weight) of the third hard coat layer; or may be, for example, less than 100% by mass, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less, for example, 1 to 90% by mass , 1-80% by mass, 1-70% by mass, 1-60% by mass, 1-50% by mass, 1-40% by mass, 20-90% by mass, 20-80% by mass, 20-70% by mass, 20-60% by mass, 20-50% by mass, 30-90% by mass, 30-80% by mass, 30-70% by mass, 30-60 quality %, 30-50% by mass, 30-40% by mass, 40-90% by mass, 40-80% by mass, 40-70% by mass, 40-50% by mass, 60-90% by mass, 1-20% by mass, 20-40% by mass, 40-60% by mass, 60-80% by mass, or 80-90% by mass. In the third hard coat layer, the content of the nanosilica particles is preferably not too high from the viewpoints of processability and flexibility, and is preferably not too low from the viewpoint of hardness.

As described above, the hard coat film of the present invention may have, for example, a light transmittance of 90% or more at a wavelength of 550 nm throughout the entire hard coat film. The light transmittance of 550 nm throughout the entire hard coat film may be, for example, 90% or more, 92% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, or 99% or more. For example, it may be 100% or less, 99% or less, 98% or less, 97% or less, 96% or less, 95% or less, 94% or less, 93% or less, 92% or less, or 90% or less. For example, 90-100%, 90-99%, 90-98%, 90-97%, 90-96%, 90-95%, 90-94%, 90-93% , 90-92%, 92-100%, 92-99%, 92-98%, 92-97%, 92-96%, 92-95%, 92-94%, 92-93%, 94-100%, 94-99%, 94-98%, 94-97%, 94-96%, 94-95%, 95-100%, 95-99%, 95-98%, 95-97%, 95-96%, 96-100%, 96-99%, 96-98%, 96-97%, 97-100%, 97-99%, 97-98%, 98-100%, 98-99%, or 99-100%. The high light transmittance of the entire hard coat film has advantages such as not losing brightness when made into a polarizing plate, and its high transparency makes it easy to inspect the appearance.

In the present invention, the method for measuring light transmittance is not particularly limited, but it can be measured, for example, by the following measurement method.

[Method for measuring light transmittance]
・Device: Integrating sphere type spectral transmittance measuring instrument (Product name: DOT-3C, manufactured by Murakami Color Research Institute)
Measurement mode: Total light transmittance and color calculation Light source: D65 light source Viewing angle: 2 degree field of view With the above settings, the light transmittance is measured at a wavelength of 550 nm under measurement conditions of a temperature of 23°C and humidity of 50%.

[2. Method for producing hard coat film]
The method for producing the hard coat film of the present invention is not particularly limited, and can be carried out, for example, in the same manner as in the general method for producing a hard coat film. The method for producing the hard coat film of the present invention will be described below with reference to examples.

The cross-sectional process diagrams in Figures 3(a) to (d) show an example of a method for producing a hard coat film of the present invention.

First, as shown in Figure 3(a), a substrate 110 is prepared, and a third hard coat layer 103 is formed on one surface of the substrate.

The substrate 110 is not particularly limited, but may be, for example, a light-transmitting substrate, specifically, a transparent plastic film substrate. The transparent plastic film substrate is not particularly limited, but is preferably one that has excellent visible light transmittance (preferably a light transmittance of 90% or more) and excellent transparency (preferably a haze value of 1% or less), such as the transparent plastic film substrate described in JP 2008-90263 A. A transparent plastic film substrate with low optical birefringence is preferably used as the transparent plastic film substrate. The hard coat film of the present invention can also be used, for example, as a protective film in a polarizing plate. In this case, the transparent plastic film substrate is preferably a film formed from triacetyl cellulose (TAC), polycarbonate, an acrylic polymer, a polyolefin having a cyclic or norbornene structure, or the like. Furthermore, in the present invention, the transparent plastic film substrate may be the polarizer itself. This configuration eliminates the need for a protective layer made of TAC or the like, simplifying the polarizing plate structure, thereby reducing the number of manufacturing steps for polarizing plates or image display devices and improving production efficiency. Furthermore, with this configuration, the polarizing plate can be made thinner. When the transparent plastic film substrate is a polarizer, the non-transparent layer serves as a protective layer, for example. Furthermore, with this configuration, the hard coat film of the present invention also functions as a cover plate when attached to the surface of a liquid crystal cell, for example.

In the present invention, the thickness of the substrate is not particularly limited, but may be, for example, as described above. The refractive index of the substrate is not particularly limited, and may be, for example, in the range of 1.30 to 1.80 or 1.40 to 1.70.

In the present invention, "refractive index" refers to the refractive index at a wavelength of 550 nm unless otherwise specified. The method for measuring the refractive index in the present invention is not particularly limited. However, the refractive index of fine particles and other substances can be measured using, for example, the Becke method. The Becke method involves dispersing a sample in a standard refractive index solution on a glass slide and observing it under a microscope. The refractive index of the standard refractive index solution is determined as the refractive index of the sample when the sample's outline disappears or becomes blurred. The method for measuring the refractive index of objects whose refractive index cannot be measured using the Becke method (e.g., anti-glare films, anti-glare layers, or resins that make up anti-glare layers) is not particularly limited. For example, a general refractometer (a device for measuring refractive index) can be used. The refractometer is also not particularly limited. An example of an Abbe refractometer is the multi-wavelength Abbe refractometer DR-M2/1550 (product name) manufactured by Atago Co., Ltd.

The method for forming the third hard coat layer 103 on the substrate 110 is not particularly limited, but may be, for example, as follows. Hereinafter, the process for forming the third hard coat layer 103 may be referred to as the "third hard coat layer forming process." The third hard coat layer forming process may include, for example, a coating process in which a third hard coat layer forming coating liquid (hereinafter, sometimes simply referred to as the "coating liquid" or the "third hard coat layer forming material") is applied to the substrate 110, and a coating film forming process in which the applied coating liquid is dried to form a coating film. Furthermore, for example, the third hard coat layer forming process may further include a curing process in which the coating film is cured. The curing may be performed, for example, after the drying, but is not limited thereto. The curing may be performed, for example, by heating or light irradiation. The light may be, for example, ultraviolet light, etc., but is not particularly limited thereto. The light source for the light irradiation is also not particularly limited, but may be, for example, a high-pressure mercury lamp, etc.

The coating liquid (third hard coat layer-forming material) may be, for example, a coating liquid containing a resin material and a dilution solvent (hereinafter sometimes simply referred to as "solvent"). The coating liquid may or may not contain other components. Examples of such other components include, but are not limited to, a thixotropy-imparting agent and the nanosilica particles. Note that Figure 3 shows an example in which the third hard coat layer 103 contains nanosilica particles 103P. However, as described above, in the hard coat film of the present invention, the third hard coat layer may or may not contain nanosilica particles.

The resin material contained in the coating liquid may be, for example, the resin itself that forms the third hard coat layer 103, or a resin material that forms the resin by polymerization, curing, or the like. The resin is not particularly limited, but may be, for example, a thermosetting resin, an ionizing radiation curable resin, or the like. The resin may also include, for example, an acrylate resin (also called an acrylic resin), such as a urethane acrylate resin. The resin may also be, for example, a copolymer of a curable urethane acrylate resin and a polyfunctional acrylate.

The resin material may include, for example, an oligomer and a monomer having a functional group. For example, the resin forming the third hard coat layer 103 may be a copolymer of the oligomer having the functional group and the monomer. The oligomer having the functional group is not particularly limited, but examples thereof include curable urethane acrylate resins. Examples of curable urethane acrylate resins include those manufactured by Mitsubishi Chemical Corporation under the trade names "UV-1700TL" and "UT-7314." The monomer is not particularly limited, but examples thereof include multifunctional acrylates. Examples of multifunctional acrylates include those manufactured by Toa Gosei Co., Ltd. under the trade name "M-920."

The solvent is not particularly limited, and various solvents can be used. One type may be used alone, or two or more types may be used in combination. For example, the optimal solvent type and solvent ratio may be appropriately selected depending on the composition of the resin, the type and content of the nanosilica particles and the thixotropy-imparting agent, etc. The solvent is not particularly limited, but examples include alcohols such as methanol, ethanol, isopropyl alcohol (IPA), butanol, t-butyl alcohol (TBA), and 2-methoxyethanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclopentanone; esters such as methyl acetate, ethyl acetate, and butyl acetate; ethers such as diisopropyl ether and propylene glycol monomethyl ether; glycols such as ethylene glycol and propylene glycol; cellosolves such as ethyl cellosolve and butyl cellosolve; aliphatic hydrocarbons such as hexane, heptane, and octane; and aromatic hydrocarbons such as benzene, toluene, and xylene. Furthermore, for example, the solvent may contain a hydrocarbon solvent and a ketone solvent. The hydrocarbon solvent may be, for example, an aromatic hydrocarbon. The aromatic hydrocarbon may be, for example, at least one selected from the group consisting of toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and benzene. The ketone solvent may be, for example, cyclopentanone, and at least one selected from the group consisting of acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, cyclohexanone, isophorone, and acetophenone. The solvent preferably contains the hydrocarbon solvent (e.g., toluene) to dissolve a thixotropy-imparting agent (e.g., a thickener). The solvent may be, for example, a mixture of the hydrocarbon solvent and the ketone solvent in a mass ratio of 90:10 to 10:90. The mass ratio of the hydrocarbon solvent to the ketone solvent may be, for example, 80:20 to 20:80, 70:30 to 30:70, or 40:60 to 60:40. In this case, for example, the hydrocarbon solvent may be toluene, and the ketone solvent may be methyl ethyl ketone. Furthermore, the solvent may include, for example, toluene and further include at least one selected from the group consisting of ethyl acetate, butyl acetate, IPA, methyl isobutyl ketone, methyl ethyl ketone, methanol, ethanol, and TBA.

When an acrylic film is used as the substrate 110 to form the intermediate layer (permeation layer), a good solvent for the acrylic film (acrylic resin) can be suitably used. As described above, the solvent may be, for example, a solvent containing a hydrocarbon solvent and a ketone solvent. The hydrocarbon solvent may be, for example, an aromatic hydrocarbon. The aromatic hydrocarbon may be, for example, at least one selected from the group consisting of toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and benzene. The ketone solvent may be, for example, at least one selected from the group consisting of cyclopentanone, acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, cyclohexanone, isophorone, and acetophenone. The solvent may be, for example, a mixture of the hydrocarbon solvent and the ketone solvent in a mass ratio of 90:10 to 10:90. The mass ratio of the hydrocarbon solvent to the ketone solvent may be, for example, 80:20 to 20:80, 70:30 to 30:70, or 40:60 to 60:40. In this case, for example, the hydrocarbon solvent may be toluene, and the ketone solvent may be methyl ethyl ketone.

When triacetyl cellulose (TAC) is used as the substrate 110, the solvent is not particularly limited, but examples include ethyl acetate, methyl ethyl ketone, MIBK (methyl isobutyl ketone), cyclopentanone, etc., and these may be used alone or in combination. In this case, the solvent may be, for example, a mixed solvent of MIBK and cyclopentanone. The mixing ratio of MIBK to cyclopentanone is not particularly limited, but may be, for example, 90:10 to 10:90, 80:20 to 20:80, or 70:30 to 30:70 by mass.

In addition, by appropriately selecting the solvent, it is possible to favorably impart thixotropy to the antiglare hard coat layer-forming material (coating liquid) when it contains a thixotropy-imparting agent. For example, when using an organoclay, toluene and xylene can be suitably used alone or in combination. For example, when using an oxidized polyolefin, methyl ethyl ketone, ethyl acetate, and propylene glycol monomethyl ester can be suitably used alone or in combination. For example, when using a modified urea, butyl acetate and methyl isobutyl ketone can be suitably used alone or in combination.

Various leveling agents can be added to the third hard coat layer-forming material. For example, fluorine-based or silicone-based leveling agents can be used as the leveling agent to prevent coating unevenness (uniformity of the coated surface). In the present invention, an appropriate leveling agent can be selected depending on whether antifouling properties are required on the surface of the third hard coat layer, or whether another layer, such as an antireflection layer (low refractive index layer) or a layer containing an interlayer filler, is formed on the third hard coat layer.

The amount of the leveling agent added is, for example, 5 parts by weight or less, preferably in the range of 0.01 to 5 parts by weight, per 100 parts by weight of the resin.

If necessary, pigments, fillers, dispersants, plasticizers, UV absorbers, surfactants, antifouling agents, antioxidants, etc. may be added to the third hard coat layer-forming material, provided that the additives do not impair performance. These additives may be used alone or in combination of two or more.

The third hard coat layer-forming material can be a conventionally known photopolymerization initiator, such as that described in JP-A-2008-88309.

Examples of methods that can be used to apply the third hard coat layer-forming material (coating liquid) to the substrate 110 to form a coating film include fountain coating, die coating, spray coating, gravure coating, roll coating, and bar coating.

Next, as described above, the coating film is dried and cured to form a third hard coat layer. The drying may be, for example, natural drying, air drying by blowing air, heat drying, or a combination of these methods.

The drying temperature of the third hard coat layer-forming material (coating liquid) may be, for example, in the range of 30 to 200°C. The drying temperature may be, for example, 40°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, or 100°C or higher, and may be 190°C or lower, 180°C or lower, 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, 135°C or lower, 130°C or lower, 120°C or lower, or 110°C or lower. The drying time is not particularly limited, and may be, for example, 30 seconds or higher, 40 seconds or higher, 50 seconds or higher, or 60 seconds or higher, or 150 seconds or lower, 130 seconds or lower, 110 seconds or lower, or 90 seconds or lower.

The means for curing the coating film is not particularly limited, but ultraviolet curing is preferred. The irradiation dose of the energy ray source is preferably 50 to 500 mJ/ ^cm2 as the cumulative exposure dose at an ultraviolet wavelength of 365 nm. If the irradiation dose is 50 mJ/ ^cm2 or more, curing tends to proceed sufficiently, and the hardness of the third hard coat layer formed tends to be high. Furthermore, if the irradiation dose is 500 mJ/ ^cm2 or less, coloration of the third hard coat layer formed can be prevented.

In this manner, the laminate of the substrate 110 and the third hard coat layer 103 shown in Figure 3(a) can be produced.

Next, as shown in FIG. 3(b), a protective film 120 is laminated on the surface of the third hard coat layer 103 (the surface opposite the substrate 110) (protective film lamination step). This protective film lamination step is not essential to the present invention and may or may not be performed. The protective film 120 is not particularly limited, but may be, for example, a polyethylene film, polyester film, PET film, etc., such as a product sold under the trade name "SPV" by Nitto Denko Corporation. Furthermore, although not shown, for example, an adhesive layer may be formed on the surface of the third hard coat layer 103, and the protective film 120 may be attached via the adhesive layer. The protective film 120 may then protect the surface of the adhesive layer from exposure. Furthermore, the protective film 120 may be peeled off immediately before use, and the hard coat film of the present invention may be attached to an adherend via the adhesive layer. The adherend may be, for example, a component other than the hard coat film of the present invention in an image display device. The method for forming the adhesive layer is not particularly limited, and any conventional method may be used, such as coating.

The adhesive layer may be, for example, an adhesive layer formed from an adhesive (adhesive composition). In the present invention, the adhesive layer may be, for example, a layer that allows the protective film 120 to be removably peeled from the third hard coat layer 103. The thickness of the adhesive layer is not particularly limited, but may be, for example, 5 μm or more, 10 μm or more, 20 μm or more, or 25 μm or more, or may be, for example, 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less. The adhesive is not particularly limited, but examples include (meth)acrylic polymers. These may be dissolved or dispersed in a solvent to form a solution or dispersion, which may be used as the adhesive (adhesive composition). Examples of the solvent include ethyl acetate, and these may be used alone or in combination. The concentration of the solute or dispersoid (e.g., the acrylic polymer) in the solution or dispersion may be, for example, 10% by mass or more, or 15% by mass or more, and may be, for example, 60% by mass or less, 50% by mass or less, 40% by mass or less, or 25% by mass or less. In the present invention, "(meth)acrylic polymer" refers to a polymer or copolymer of at least one monomer selected from (meth)acrylic acid, (meth)acrylic acid esters, and (meth)acrylamide. In the present invention, "(meth)acrylic acid" refers to "at least one of acrylic acid and methacrylic acid," and "(meth)acrylic acid ester" refers to "at least one of acrylic acid esters and methacrylic acid esters." Examples of the (meth)acrylic acid esters include linear or branched alkyl esters of (meth)acrylic acid. In the linear or branched alkyl ester of (meth)acrylic acid, the number of carbon atoms in the alkyl group may be, for example, 1 or more, 2 or more, 3 or more, or 4 or more, and may be, for example, 18 or less, 16 or less, 14 or less, 12 or less, 10 or less, or 8 or less. The alkyl group may be unsubstituted or substituted with, for example, one or more substituents. Examples of the substituent include a hydroxyl group, and when there are multiple substituents, the substituents may be the same or different. Specific examples of the (meth)acrylic acid ester include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and 4-hydroxybutyl acrylate. Furthermore, the pressure-sensitive adhesive may be used alone or in combination.

Furthermore, as shown in FIG. 3(c), a second hard coat layer 102 is formed on the other surface of the substrate 110 (the surface opposite the third hard coat layer 103) (second hard coat layer formation process). Thereafter, as shown in FIG. 3(d), a first hard coat layer 101 is formed on the surface of the second hard coat layer 102 (the surface opposite the substrate 110) (first hard coat layer formation process). The second hard coat layer formation process and the first hard coat layer formation process are not particularly limited and can be performed in the same manner as the third hard coat layer formation process described above, except that, for example, the composition of the coating liquid (hard coat layer-forming material) and the thickness of the hard coat layer are appropriately set according to the second hard coat layer 102 and the first hard coat layer 101. Specifically, for example, a coating liquid containing nanosilica particles is used, and the weight average particle diameter of the nanosilica particles is appropriately set according to the second hard coat layer 102 and the first hard coat layer 101. Other conditions can also be set appropriately depending on the second hard coat layer 102 and the first hard coat layer 101. Furthermore, for example, when the hard coat film of the present invention is used as an anti-glare film (anti-glare hard coat film), irregularities may be formed on the surface of the first hard coat layer 101. The method for forming these irregularities is not particularly limited, and for example, a general method can be used.

The hard-coated film of the present invention can be produced in the above manner. However, as mentioned above, this production method is merely an example, and the production method of the hard-coated film of the present invention is not limited thereto. For example, as mentioned above, the hard-coated film of the present invention may include layers other than the substrate, the first hard-coat layer, the second hard-coat layer, and the third hard-coat layer. Therefore, the production method of the hard-coated film of the present invention may further include a step of forming the other layers. More specifically, for example, as mentioned above, an anti-reflection layer may be formed on the outer side of the first hard-coat layer (the side opposite the second hard-coat layer). The method of forming the anti-reflection layer is not particularly limited, and a general method, for example, can be used.

The hard coat film manufacturing method of the present invention can also be, for example, a continuous manufacturing method. Specifically, for example, the hard coat film manufacturing method of the present invention may be a manufacturing method in which the substrate is long, and the third hard coat layer forming step, the second hard coat layer forming step, the first hard coat layer forming step, and other steps as necessary are continuously performed while the substrate is being transported. More specifically, for example, the long substrate is in the form of a roll, and the hard coat film manufacturing method of the present invention may be performed while the substrate is being unwound from the roll.

[3. Hard-coated film, optical member, and image display device]
The hard coat film of the present invention is not particularly limited, and may be, for example, a clear film or an antiglare film (antiglare hard coat film) as described above.

The optical member of the present invention is not particularly limited, and may be, for example, a polarizing plate. The polarizing plate is also not particularly limited, and may include, for example, the anti-glare film of the present invention and a polarizer, and may further include other components. The components of the polarizing plate may be bonded together, for example, with an adhesive or pressure-sensitive adhesive.

The image display device of the present invention is not particularly limited and may be any image display device, including, for example, a liquid crystal display device, an organic EL display device, an inorganic EL display device, and a plasma display device.

The configuration of the image display device of the present invention is not particularly limited, and may be the same as that of a general image display device. For example, in the case of an LCD, it can be manufactured by appropriately assembling each component, such as a liquid crystal cell, optical elements such as polarizing plates, and, if necessary, an illumination system (backlight, etc.), and incorporating a drive circuit.

The image display device of the present invention can be used for any application without particular limitations. Examples of applications include office automation equipment such as PC monitors, laptops, tablets, smartphones, and copiers; portable devices such as mobile phones, watches, digital cameras, personal digital assistants (PDAs), and portable game consoles; household electrical appliances such as video cameras, televisions, and microwave ovens; in-vehicle devices such as backup monitors, car navigation system monitors, and car audio; exhibition equipment such as commercial store information monitors; security equipment such as surveillance monitors; nursing and medical equipment such as nursing monitors and medical monitors; smart glasses; and virtual reality equipment. The image display device of the present invention may also be, for example, an image display device with a camera function. In this case, for example, as described above, the transparent layer in the hard coat film of the present invention may be a transparent layer for a camera hole in the image display device. According to the present invention, a hard coat film can be provided without impairing the transparency of the transparent layer, as described above. Therefore, it is possible to provide an image display device without impairing the image quality of camera images, for example.

Next, examples of the present invention will be described in conjunction with comparative examples. However, the present invention is not limited to the following examples and comparative examples.

In the following examples and comparative examples, the number of parts of a substance is in parts by mass (parts by weight) unless otherwise specified.

In the following examples and comparative examples, the first hard coat layer-forming material, second hard coat layer-forming material, and third hard coat layer-forming material were prepared with the following compositions.

[First Hard Coat Layer-Forming Material]
100 parts by mass of a polyfunctional acrylate containing nanosilica having a weight average particle size of 40 nm (trade name "NC035", manufactured by Arakawa Chemical Industries, Ltd.) and 2 parts by mass of a leveling agent (trade name "LE-303", manufactured by Shin-Etsu Chemical Co., Ltd.) were diluted with cyclopentanone as a dilution solvent to a solids concentration of 35% by mass. This was used as a first hard coat layer-forming material.

[Second Hard Coat Layer Forming Material]
100 parts by mass of a polyfunctional acrylate containing nanosilica having a weight average particle size of 10 nm (trade name "Opstar Z7540", manufactured by Arakawa Chemical Industries, Ltd.) and 2 parts by mass of a leveling agent (trade name "LE-303", manufactured by Shin-Etsu Chemical Co., Ltd.) were diluted to a solids concentration of 55% by mass using methyl ethyl ketone as a dilution solvent. This was used as a second hard coat layer-forming material.

[Third Hard Coat Layer-Forming Material (without Nanosilica Particles)]
100 parts by mass of a polyfunctional acrylate (trade name "Viscoat #300", manufactured by Osaka Organic Chemical Industry Ltd.) and 3 parts by mass of a photopolymerization initiator (trade name "OMNIRAD907", manufactured by BASF) were diluted with methyl ethyl ketone as a dilution solvent to a solids concentration of 55% by mass. This was used as a third hard coat layer-forming material (without nanosilica particles).

[Third Hard Coat Layer-Forming Material (Containing Nanosilica Particles)]
The third hard coat layer forming material (in the case where nanosilica particles are contained) was the same as the second hard coat layer forming material.

[Example 1]
A hard coat film was manufactured as follows using the manufacturing method described in FIG. 3 . First, an 80 μm-thick TAC substrate (manufactured by Konica Minolta, Inc., product name "KC8UA") was prepared as the substrate. Next, the third hard coat layer-forming material (without nanosilica particles) was coated on one side of the substrate and dried in an oven at 60°C for 60 seconds to form a coating film. The coating film was irradiated with ultraviolet light of 365 nm wavelength from a high-pressure mercury lamp at an integrated irradiation dose of 300 mJ/ ^cm² , and cured to form a third hard coat layer. In this example, the third hard coat layer-forming material (without nanosilica particles) was coated so that the thickness of the third hard coat layer was 5 μm. Furthermore, a protective film (manufactured by Toray Industries, Inc., product name "Tretec-7832C") was attached to the surface of the formed third hard coat layer opposite the substrate.

Next, the second hard coat layer-forming material was applied to the surface of the substrate opposite to the surface on which the third hard coat layer was formed, and dried for 60 seconds in an oven at 60 ° C. to form a coating film. The coating film was irradiated with ultraviolet light having a wavelength of 365 nm from a high-pressure mercury lamp so that the cumulative irradiation amount was 300 mJ / cm ² , and cured to form a second hard coat layer. In this example, the second hard coat layer-forming material was applied so that the thickness of the second hard coat layer was 10 μm.

Furthermore, the first hard coat layer-forming material was applied to the surface of the formed second hard coat layer opposite to the substrate, and dried for 60 seconds in an oven at 60 ° C. to form a coating film. The coating film was irradiated with ultraviolet light having a wavelength of 365 nm from a high-pressure mercury lamp so that the cumulative irradiation amount was 300 mJ / cm ² , and cured to form a first hard coat layer. In this example, the first hard coat layer-forming material was applied so that the thickness of the first hard coat layer was 5 μm.

The hard coat film of this example (Example 1) was produced in the above manner. Note that in the hard coat films of this example and the following examples and comparative examples, the protective film was peeled off from the third hard coat layer when attaching the film to a glass plate, as described below.

[Example 2]
The hard coat film of this example (Example 2) was produced in the same manner as in Example 1, except that the thickness of the second hard coat layer was changed to 20 μm and the thickness of the third hard coat layer was changed to 10 μm.

[Example 3]
The hard coat film of this example (Example 3) was produced in the same manner as in Example 1, except that the thickness of the first hard coat layer was changed to 10 μm and the thickness of the third hard coat layer was changed to 10 μm.

[Example 4]
The hard coat film of this example (Example 4) was produced in the same manner as in Example 1, except that the thickness of the first hard coat layer was changed to 10 μm, the thickness of the second hard coat layer was changed to 20 μm, and the thickness of the third hard coat layer was changed to 15 μm.

[Example 5]
The hard coat film of this example (Example 5) was produced in the same manner as in Example 1, except that the third hard coat layer-forming material (without nanosilica particles) was used to form a third hard coat layer containing nanosilica particles, and the thickness of the third hard coat layer was changed to 15 μm.

[Example 6]
A hard coat film of this example (Example 6) was produced in the same manner as in Example 5, except that the thickness of the second hard coat layer was changed to 20 μm and the thickness of the third hard coat layer was changed to 25 μm.

[Comparative Example 1]
A hard-coated film of this comparative example (Comparative Example 1) was produced in the same manner as in Example 1, except that the thickness of the first hard-coat layer was changed to 20 μm and the second hard-coat layer and the third hard-coat layer were not formed.

[Comparative Example 2]
A hard coat film of this comparative example (Comparative Example 2) was produced in the same manner as in Example 5, except that the first hard coat layer was not formed.

[Comparative Example 3]
A hard-coated film of this comparative example (Comparative Example 3) was produced in the same manner as in Comparative Example 2, except that the thickness of each of the second hard-coat layer and the third hard-coat layer was changed to 20 μm.

[Formation of antireflection layer]
An antireflection layer (DRY-AR layer) was formed on the surface opposite the substrate of the first hard coat layer (or the second hard coat layer if the first hard coat layer was not present) in the hard coat layer film of each of the Examples and Comparative Examples by the following method. First, an Nb target was set in a magnetron sputtering device, and reactive sputtering was performed to form a first Nb ₂ O ₅ layer (thickness 12 nm, refractive index 2.34) on the first hard coat layer (or the second hard coat layer if the first hard coat layer was not present). Next, an Si target was set in the magnetron sputtering device, and reactive sputtering was performed to form a first SiO ₂ layer (thickness 39 nm, refractive index 1.46) on the first Nb ₂ O ₅ layer. Next, a second Nb ₂ O ₅ layer (thickness: 119 nm, refractive index: 2.34) was formed on the first SiO ₂ layer using the same method as for forming the first Nb ₂ O ₅ layer. Furthermore, a second SiO ₂ layer (thickness: 78 nm, refractive index: 1.46) was formed on the second Nb ₂ O ₅ layer using the same method as for forming the first SiO ₂ layer. In this way, an anti-reflection layer (DRY-AR layer) was formed in which two Nb ₂ O ₅ layers and two SiO ₂ layers were alternately stacked.

[Thickness measurement method]
The thickness of each layer of the hard coat film was measured by observing the cross section with a TEM (transmission electron microscope).

[Method for measuring pencil hardness]
The pencil hardness was measured in accordance with the pencil hardness test of JIS K 5600-5-4, except that the load was 750 g. As described below, the pencil hardness of each of the hard-coated films of the Examples and Comparative Examples was measured under the following three conditions (1) to (3). The thickness of the glass plate in the following (1) to (3) was 1.5 mm. The 25 μm thick adhesive layer in the following (2) was formed using Nitto Denko Corporation's product name "CS9821UD" as an adhesive. The 5 μm thick adhesive layer in the following (3) was formed using Nitto Denko Corporation's product name "Monkey" as an adhesive.

(1) When the glass plate and the third hard coat layer are bonded with a 25 μm thick adhesive layer. (2) When the glass plate and the third hard coat layer are bonded with a 5 μm thick adhesive layer. (3) When the third hard coat layer is directly attached to the glass plate without providing an adhesive layer.

[Method for measuring and evaluating curl]
The hard-coated films of each of the Examples and Comparative Examples were cut into squares with sides of 15 cm from the center in the width direction of the original roll, and these were used as measurement samples. When cutting out the measurement samples, the diagonals of the squares were aligned with the MD and TD directions. The MD direction refers to the direction parallel to the conveying direction of the substrate (the longitudinal direction of the substrate) during the production of the hard-coated film on the surface of the substrate. The TD direction refers to the direction perpendicular to the MD direction on the surface of the substrate. A rod-shaped weight was placed on the diagonal line of the MD direction of the measurement sample to press it down, and the maximum height [mm] of the end of the TD direction of the measurement sample that rose was measured, and this was evaluated as the magnitude of curl in the TD direction. Similarly, a rod-shaped weight was placed on the diagonal line of the TD direction of the measurement sample to press it down, and the maximum height [mm] of the end of the MD direction of the measurement sample that rose up was measured, and this was evaluated as the magnitude of curl in the MD direction. The greater the height of the rise, the greater the curl.

[Method for measuring and evaluating adhesion of antireflection layer]
The hard coat films of each of the Examples and Comparative Examples with an anti-reflection layer formed thereon were cut into 5 cm squares, and the substrate side was attached to a 1.5 mm thick 5 cm square glass plate using Nitto Denko Corporation's adhesive, product name "CS9821UD." The film was then irradiated with UV light using a metal halide lamp. The irradiation conditions were an ambient temperature of 55°C, ambient humidity of 45%, light irradiation intensity of 830 W/ ^m² , irradiation time of 240 hours, and BPT temperature of 85°C. After UV irradiation, 1-2 mL of isopropyl alcohol was dropped onto the anti-reflection layer, and the anti-reflection layer was rubbed with a cloth (product name "Anticon Gold," manufactured by Contec Co., Ltd.) under a load. The presence or absence of scratches on the anti-reflection layer was confirmed visually and microscopically (100x magnification). If no scratches were observed on the anti-reflection layer either visually or microscopically, the adhesion was evaluated as "Good." If scratches were observed on at least one side, the adhesion was evaluated as "Poor."

The structure of the hard coat film in each of the examples and comparative examples and the evaluation results of its properties are shown in Tables 1 and 2 below. In Tables 1 and 2 below, "HC thickness" represents the thickness of each hard coat layer. "Glue" represents the adhesive layer used to bond the glass plate and the third hard coat layer. "MD" represents the aforementioned MD direction, i.e., the direction on the surface of the substrate that is parallel to the transport direction of the substrate (the longitudinal direction of the substrate) during the production of the hard coat film. "TD" represents the aforementioned TD direction, i.e., the direction perpendicular to the MD direction on the surface of the substrate.

As shown in Tables 1 and 2 below, the hard coat layers of Examples 1 to 4 have the same configuration as hard coat film 100a in Figure 1(a), except that the third hard coat layer does not contain nanosilica particles. The hard coat layers of Examples 5 and 6 have the same configuration as hard coat film 100b in Figure 1(b), except that the third hard coat layer contains nanosilica particles. Furthermore, as shown in Tables 1 and 2 below, pencil hardness was measured in three cases: (1) when the glass plate and the third hard coat layer were bonded together with a 25 μm-thick adhesive layer; (2) when the glass plate and the third hard coat layer were bonded together with a 5 μm-thick adhesive layer; and (3) when the third hard coat layer was directly attached to the glass plate without an adhesive layer. The cross-sectional views of Figures 2(a) to 2(d) show these configurations. Figures 2(a) and (b) show examples using the hard coat films of Examples 1 to 4 (where the third hard coat layer 103 does not contain nanosilica particles). Figure 2(a) shows an example in which the third hard coat layer 103 is directly adhered to the glass plate 210 without using an adhesive. Figure 2(b) shows an example in which the third hard coat layer 103 is directly bonded to the glass plate 210 with an adhesive 220. Figures 2(c) and (d) show examples using the hard coat films of Examples 5 and 6 (where the third hard coat layer 103 contains nanosilica particles 103P). Figure 2(c) shows an example in which the third hard coat layer 103 is directly adhered to the glass plate 210 without using an adhesive. Figure 2(d) shows an example in which the third hard coat layer 103 is directly bonded to the glass plate 210 with an adhesive 220.

As shown in Tables 1 and 2, the hard-coated films of Examples 1 to 6 all had high hardness (pencil hardness), suppressed curling (the edge lift of the hard-coated film was 0 mm in the curl measurement), and strong adhesion between the viewing-side surface and other layers (DRY-AR layers). In particular, the hard-coated films of Examples 1 to 4, in which the third hard-coated layer did not contain nanosilica particles, had high hardness (pencil hardness) even when attached to a glass plate using a 25 μm-thick adhesive layer. In contrast, Comparative Example 1, which did not have the second or third hard-coated layer, had low hardness (pencil hardness) and curled, resulting in the hard-coated film becoming cylindrical. Meanwhile, Comparative Examples 2 and 3, which had the second and third hard-coated layers but not the first hard-coated layer, had high hardness (pencil hardness) and suppressed curling, but had poor adhesion between the viewing-side surface and other layers (DRY-AR layers).

As explained above, the present invention can provide hard-coated films, optical components, and image display devices that have high hardness, suppress curling, and high adhesion between the viewing-side surface and other layers. As mentioned above, the hard-coated film of the present invention can be used as both a clear film and an anti-glare film (anti-glare hard-coated film), and can be used in a wide variety of optical components and image display devices, making it highly useful industrially.

100a, 100b Hard coat film 101 First hard coat layer 102 Second hard coat layer 103 Third hard coat layer 101P, 102P, 103P Nano silica particles 110 Substrate 120 Protective film 210 Glass plate 220 Adhesive layer

Claims (6)

a substrate, a first hard coat layer, a second hard coat layer, and a third hard coat layer;
the first hard coat layer, the second hard coat layer, the substrate, and the third hard coat layer are laminated in this order from the viewing side;
the first hard coat layer and the second hard coat layer each contain nanosilica particles;
the weight average particle diameter of the nanosilica particles contained in the first hard coat layer is larger than the weight average particle diameter of the nanosilica particles contained in the second hard coat layer;
the weight average particle diameter of the nanosilica particles contained in the first hard coat layer is 30 to 50 nm;
the weight average particle diameter of the nanosilica particles contained in the second hard coat layer is 5 to 30 nm;
A hard coat film, wherein the third hard coat layer does not contain nanosilica particles . 2. The hard coat film according to claim 1 , wherein the thickness of the third hard coat layer is smaller than the total thickness of the first hard coat layer and the second hard coat layer. 3. The hard coat film according to claim 1 , wherein the hard coat film as a whole has a light transmittance of 90% or more at a wavelength of 550 nm. An optical member comprising the hard coat film according to claim 1 . 5. The optical member according to claim 4 , which is a polarizing plate. An image display device comprising the hard coat film according to claim 1 or the optical member according to claim 4 or 5 .