Antiglare film, polarizer and image display device
Provided is an antiglare film having a hard coat property, capable of highly suppressing generation of a rainbow interference pattern and interference fringes in display images, preventing white muddiness and scintillation of a display screen, while giving high contrast in a bright room and a dark room. The antiglare film includes an antiglare layer having an uneven form on its surface and formed on one face of a transparent substrate having an in-plane birefringence and a retardation of 3000 nm or higher. The antiglare layer contains silica fine particles, organic fine particles, and a binder resin. The silica particles include particles forming agglomerates to be contained coarsely and densely in the antiglare layer. The agglomerates are distributed densely around the organic fine particles, and some agglomerates adhere to surfaces of the organic particles and/or some silica particles are impregnated in the inside of the organic particles.
1. An antiglare film comprising an antiglare layer having an uneven form on its surface and formed on one face of a transparent substrate having an in-plane birefringence, wherein
said transparent substrate having an in-plane birefringence has a retardation of 3000 nm or higher,
said antiglare layer contains silica fine particles, organic fine particles, and a binder resin,
said silica fine particles have an average primary particle diameter of 1 to 100 nm, and
said silica fine particles include particles forming agglomerates to be contained coarsely and densely in said antiglare layer, wherein the distributed coarsely and densely in the antiglare layer means that there are a plurality of regions where the agglomerates of the silica fine particles are distributed densely so that in the case where an arbitrary cross section in the thickness direction of the antiglare layer is observed at a 10000 magnification by an electron microscope, the regions in which the surface area ratio of the agglomerates of the silica fine particles occupying in the observation region of 2 μm square is 5% or higher and a plurality of regions where the agglomerates of the silica fine particles are distributed coarsely so that in the case where an arbitrary cross section in the thickness direction of the antiglare layer is observed at a 10000 magnification by an electron microscope, the regions in which the surface area ratio of the agglomerates of the silica fine particles occupying in the observation region of 2 μm square is less than 1%,
the agglomerates of said silica fine particles are distributed densely around said organic fine particles, wherein the agglomerates of the silica fine particles distributed densely around the organic fine particles means a state that the surface area ratio of the agglomerates of the silica fine particles to the region which is within a 200 nm outside the organic fine particles and from which the organic fine particles are removed is 10% or higher when a cross section in the thickness direction of the antiglare layer and in which the organic fine particles exist is observed with an electron microscope at a 20000 magnification,
and some of the agglomerates of the silica fine particles densely distributed around said organic fine particles adhere to the surfaces of said organic fine particles and/or some of the silica fine particles constituting said agglomerates are impregnated in the inside of said organic fine particle; and wherein
the uneven form is formed by agglomerates of the silica fine particles and the organic fine particles and
the uneven form satisfies the following expressions:
50 μm< Sm <600 μm
0.1 °<θa< 0.5°
0.02 μm< Ra< 0.25 μm
0.30 μm< Rz< 2.00 μm,
in which Sm is the average interval of the unevenness on the antiglare layer surface; θa is the average tilt angle of the uneven part; Ra is the arithmetic mean deviation of the unevenness; and Rz is a 10-point average roughness of the unevenness.
2. The antiglare film according to claim 1 , wherein the transparent substrate having an in-plane birefringence has a difference (nx−ny) of the refractive index (nx) in a slow axis direction, a direction with a high refractive index, and the refractive index (ny) in a fast axis direction, a direction orthogonal to said slow axis direction in a range of 0.05 to 0.20.
3. The antiglare film according to claim 1 , wherein the silica fine particles are surface-treated.
4. The antiglare film according to claim 1 , wherein the agglomerates of the silica fine particles have an average particle diameter of 100 nm to 1 μm.
5. The antiglare film according to claim 1 , wherein the binder resin is obtained from a polyfunctional acrylate monomer having no hydroxyl group in the molecule as a main material.
6. The antiglare film according to claim 1 , wherein the organic fine particles are surface-hydrophilized.
7. The antiglare film according to claim 1 , wherein the transparent substrate having an in-plane birefringence is a polyester substrate.
8. The antiglare film according to claim 1 , having a total haze according to JIS K7136 of less than 5.0.
9. A polarizer comprising a polarizing element, wherein
said polarizer has the antiglare film according to claim 1 , on the polarizing element surface.
10. An image display device comprising the antiglare film according to claim 1 .
11. The image display device according to claim 10 , which comprises a white light-emitting diode as a backlight light source.
12. The antiglare film according to claim 1 , wherein said silica fine particles have an average primary particle diameter of 5 to 50 nm.