Optical laminate and polarizing plate, surface plate, image display panel, and image display device using said optical laminate

An optical laminate comprising a first side and a second side on the opposite side to the first side, wherein

• the optical laminate comprises a low refractive index layer and an anti-glare layer in this order, from the first side to the second side,
• the low refractive index layer comprises a binder resin and spherical particles having an average particle size of 20 nm or more,
• the first side has an uneven shape,
• an “average occupied area ratio of the spherical particles having an average particle size of 20 nm or more” calculated through the following Measurement 1 is 15.0% or more, and an “average film thickness of the low refractive index layer” is 200 nm or less and an “average standard deviation of a film thickness of the low refractive index layer” is 25.0 nm or less, calculated through the following Measurement 2:
• <Measurement 1>
• (1-1) a surface on the first side of the optical laminate is imaged with a scanning electron microscope;
• an imaging area is adjusted in such a manner that a region excluding a scale bar is 50.79 μm in width×38.10 μm in height;
• the region of 50.79 μm in width×38.10 μm in height is further adjusted to have a pixel number of 1280 pixels×890 pixels;
• (1-2) an image of the region of 50.79 μm in width×38.10 μm in height of the (1-1) is divided into 256 gradations, with a darkest part set to 0 and a brightest part set to 255;
• the image of the region of 50.79 μm in width×38.10 μm in height of the (1-1) is divided into “10 in width×10 in height=100” small regions;
• a standard deviation of the gradations is calculated for each of 64 small regions, excluding 36 small regions located on an outer periphery, out of the 100 small regions;
• a small region with a largest standard deviation of the gradations among the 64 small regions is specified;
• and among the 64 small regions, “3 in width×3 in height=9” small regions centered around the small region with the largest standard deviation of the gradations are regarded as a convex portion of the low refractive index layer and a neighboring region thereof;
• (1-3) the “convex portion and a neighboring region thereof” of the (1-2) is further divided into “10 in width×10 in height=100” fine regions;
• a standard deviation of the gradations is calculated for each of the 100 fine regions;
• the gradations for step (1-3) use the 256 gradations of the (1-2);
• and a fine region with a largest standard deviation of the gradations is specified among the 100 fine regions;
• (1-4) an image of a region of 1270 nm in width×890 nm in height, centered around a center part of the fine region specified in the (1-3), is captured with a scanning electron microscope;
• a portion of the low refractive index layer within the image of the region of 1270 nm in width×890 nm in height is regarded as a convex portion of the low refractive index layer;
• and a ratio of an area occupied by the spherical particles having an average particle size of 20 nm or more in the region of 1270 nm in width×890 nm in height is calculated;
• and
• (1-5) operations described above in the (1-1) to (1-4) are performed at 20 positions on a surface of the first side of the optical laminate;
• and an average of the ratios of the areas at 18 positions, excluding minimum and maximum values, is defined as the “average occupied area ratio of the spherical particles having an average particle size of 20 nm or more”;
• <Measurement 2>
• (2-1) a vertical cross-section of the optical laminate is imaged with a scanning transmission electron microscope;
• and an image is adjusted in such a manner that a region excluding a scale bar is 254 μm in width×178 μm in height;
• (2-2) in the image of the region of 254 μm in width×178 μm in height of the (2-1), a position where the low refractive index layer is thickest is specified;
• (2-3) an image of a region of 1270 nm in width×890 nm in height, centered around the position specified in the (2-2), is captured with a scanning transmission electron microscope;
• a portion of the low refractive index layer within the image of the region of 1270 nm in width×890 nm in height is regarded as a concave portion of the low refractive index layer;
• in the region of 1270 nm in width×890 nm in height, a film thickness of the low refractive index layer and a standard deviation of the film thickness of the low refractive index layer are calculated;
• the film thickness of the low refractive index layer is defined as an average value of film thicknesses at 25 positions;
• similarly, the standard deviation of the film thickness of the low refractive index layer is defined as a standard deviation of the film thicknesses at 25 positions;
• and the 25 positions are selected at 50 nm intervals within a range of the length of 1270 nm in width;
• and
• (2-4) operations described above in the (2-1) to (2-3) are performed at 20 positions on the vertical cross-section of the optical laminate;
• and an average of the film thicknesses and an average of the standard deviations of the film thicknesses at 18 positions, excluding minimum and maximum values, are defined respectively as the “average film thickness of the low refractive index layer” and the “average standard deviation of the film thickness of the low refractive index layer”.