Optical laminate and article
This optical laminate contains a transparent substrate, an optical functional layer and an antifouling layer laminated in that order, wherein when a light with a wavelength of 380 nm to 780 nm from a standard light source D65 is incident upon the optical laminate at an incident angle within a range from 5° to 50° relative to the surface, the a* value and the b* value in the CIE-Lab color system of the reflected light are within the same quadrant of the a*b* plane.
1 . An optical laminate comprising:
a transparent substrate;
an optical functional layer; and
an antifouling layer, laminated in that order, wherein
when a light with a wavelength of 380 nm to 780 nm from a standard light source D65 is incident upon the optical laminate at an incident angle within a range from 5° to 50° relative to a surface of the optical laminate, an a* value and a b* value in a CIE-Lab color system of a reflected light are within a same quadrant of the a*b* plane, and
a maximum value of a difference between reflectance values when the light is incident at an incident angle of 10°, 20°, 30°, 40° and 50° relative to the surface, and a reflectance when the light is incident at an incident angle of 5°, expressed as an absolute value, is 1% or less.
2 . The optical laminate according to claim 1 , wherein the a* value and the b* value of the reflected light when the light is incident at an incident angle within a range from 5° to 50° relative to the surface are both less than zero.
3 . The optical laminate according to claim 1 , wherein the reflected light when the light is incident at an incident angle within a range from 5° to 50° relative to the surface has a ΔE*ab value represented by formula (1) of 10 or less:
Δ E*ab =√{square root over (Δ L* 2 +Δa* 2 +Δb* 2 )} Formula (1)
wherein in formula (1), ΔE*ab represents an amount of change in an L* value and the a* value and b* value in the CIE-Lab color system, ΔL* represents a maximum value of a difference between the L* values of the reflected light when the light is incident at an incident angle of 10°, 20°, 30°, 40° and 50°, and the L* value of the reflected light when the light is incident at an incident angle of 5°, Δa* represents a maximum value of a difference between the a* values of the reflected light when the light is incident at an incident angle of 10°, 20°, 30°, 40° and 50°, and the a* value of the reflected light when the light is incident at an incident angle of 5°, and Ab* represents a maximum value of a difference between the b* values of the reflected light when the light is incident at an incident angle of 10°, 20°, 30°, 40° and 50°, and the b* value of the reflected light when the light is incident at an incident angle of 5°.
4 . The optical laminate according to claim 1 , wherein
the optical functional layer is composed of a laminate comprising a low refractive index material layer and a high refractive index material layer formed from a material with a higher refractive index than the low refractive index material layer laminated in an alternating arrangement,
a first high refractive index material layer formed from the high refractive index material layer and having a thickness of at least 7.5 nm is disposed on the transparent substrate side of the laminate,
a first low refractive index material layer formed from the low refractive index material layer and having a thickness of 27 nm to 37 nm is disposed in contact with the first high refractive index material layer, and
a second low refractive index material layer formed from the low refractive index material layer and having a thickness of 85 nm to 103 nm is disposed on the antifouling layer side of the laminate.
5 . The optical laminate according to claim 4 , wherein
a second high refractive index material layer formed from the high refractive index material layer and having a thickness of at least 105 nm to 120 nm is disposed between the first low refractive index material layer and the second low refractive index material layer, and
the optical functional layer is composed of four layers: the first high refractive index material layer, the first low refractive index material layer, the second high refractive index material layer, and the second low refractive index material layer.
6 . The optical laminate according to claim 1 , further comprising an adhesive layer between the transparent substrate and the optional functional layer, wherein
the adhesive layer comprises at least one metal compound selected from the group consisting of a metal, an alloy, a metal oxide, a metal fluoride, a metal sulfide, and a metal nitride.
7 . The optical laminate according to claim 6 , wherein the adhesive layer comprises a metal oxide in an oxygen-deficient state.
8 . The optical laminate according to claim 6 , further comprising a hard coat layer between the transparent substrate and the adhesive layer.
9 . An article comprising the optical laminate according to claim 1 .
10 . The article according to claim 9 , further comprising an image display device, wherein the optical laminate is provided on a surface of the image display device.
11 . The optical laminate according to claim 1 , wherein the absolute value of the a* value is not more than 10.0 and the absolute value of the b* value is not more than 10.0, when light is incident at an incident angle of 5° to 50°.
12 . The optical laminate according to claim 1 , wherein the absolute value of the a* value is not more than 5.0 and the absolute value of the b* value is not more than 6.0, when light is incident at an incident angle of 5° to 50°.