Light diffusion control member and reflective display body
A light diffusion control member includes a first light diffusion control layer and a second light diffusion control layer. The first light diffusion control layer and the second light diffusion control layer each has a regular internal structure that includes a plurality of regions having a relatively high refractive index in a region having a relatively low refractive index. The first light diffusion control layer and the second light diffusion control layer are laminated so that an angle between two respective vectors determined based on the regular internal structure in the first light diffusion control layer and the second light diffusion control layer is more than 0° and 90° or less.
1. A light diffusion control member comprising:
a first light diffusion control layer; and
a second light diffusion control layer laminated on one surface side of the first light diffusion control layer,
wherein the first light diffusion control layer and the second light diffusion control layer each have a regular internal structure comprising a plurality of regions having a relatively high refractive index in a region having a relatively low refractive index,
wherein when a first surface is defined as a surface of the light diffusion control member proximal to the first light diffusion control layer and a second surface is defined as a surface of the light diffusion control member proximal to the second light diffusion control layer, and wherein a thickness direction of the light diffusion control member is orthogonal to the first surface and the second surface, and wherein a surface direction is perpendicular to the thickness direction,
the regions having the relatively high refractive index each extend from the second surface side toward the first surface side in an extending direction, and wherein a straight line, which is parallel to the extending direction of the regions, is tilted with respect to the thickness direction of the light diffusion control member in each of the first light diffusion control layer and the second light diffusion control layer,
wherein the first light diffusion control layer has a first extending direction having a first surface-direction vector and a first thickness-direction vector, and the second light diffusion control layer has a second extending direction having a second surface-direction vector and a second thickness-direction vector, and wherein the first light diffusion control layer and the second light diffusion control layer are laminated so that, an angle between the first surface-direction vector and the second surface-direction vector is more than 0° and 90° or less.
2. The light diffusion control member according to claim 1 , wherein at least in one of the first light diffusion control layer and the second light diffusion control layer,
the regions having the relatively high refractive index are columnar bodies extending from the second surface side toward the first surface side, and
the regular internal structure is a column structure configured such that the columnar bodies are densely arranged to stand in the region having the relatively low refractive index.
3. The light diffusion control member according to claim 2 , wherein the columnar bodies are bent between one ends and other ends of the columnar bodies.
4. A reflective display body configured such that an up-down direction of display content on a display surface can be changed, the reflective display body comprising:
the light diffusion control member according to claim 3 ;
a display device provided on one surface side of the light diffusion control member; and
a reflective layer provided on a surface side of the display device opposite to the light diffusion control member or incorporated in the display device.
5. A reflective display body configured such that an up-down direction of display content on a display surface can be changed, the reflective display body comprising:
the light diffusion control member according to claim 2 ;
a display device provided on one surface side of the light diffusion control member; and
a reflective layer provided on a surface side of the display device opposite to the light diffusion control member or incorporated in the display device.
6. A reflective display body configured such that an up-down direction of display content on a display surface can be changed, the reflective display body comprising:
the light diffusion control member according to claim 1 ;
a display device provided on one surface side of the light diffusion control member; and
a reflective layer provided on a surface side of the display device opposite to the light diffusion control member or incorporated in the display device.
7. A light diffusion control member comprising a light diffusion control layer, the light diffusion control layer having a regular internal structure comprising a plurality of regions having a relatively high refractive index in a region having a relatively low refractive index,
wherein when preparing a measurement sample by laminating the light diffusion control member on a reflective surface of a mirror; irradiating an arbitrary one point on a surface of the measurement sample on the light diffusion control member side with light rays from each of four directions of orientation angles of 0°, 90°, 180°, and 270° around the one point to cause reflected light to be diffused and reflected from the one point at each of the orientation angles, the light rays forming an angle of 30° with a normal line of the surface of the measurement sample, the reflected light including reflected light directed in a front direction of the surface of the measurement sample; measuring, at the orientation angles, respective luminance values (cd/m 2 ) of the reflected light directed in the front direction of the surface of the measurement sample; and representing a minimum luminance value and a maximum luminance value among the obtained four luminance values as L min and L max , respectively, and
irradiating an arbitrary one point on one surface of any standard white plate with light rays from the orientation angle at which the L min is measured, the light rays forming an angle of 30° with a normal line of the one surface; and representing the luminance value (cd/m 2 ) of reflected light obtained by diffusion and reflection from the one point in the front direction as L STD ,
L 1 represented by L 1 =L min /L STD satisfies following expression (1):
L 1 >1.00 (1), and
L 2 represented by L 2 =L min /L max satisfies following expression (2):
0.6≤ L 2 ≤1.00 (2),
wherein when irradiating an arbitrary one point on a surface of the measurement sample on the light diffusion control member side with light rays from each of four directions of orientation angles of 0°, 90°, 180°, and 270° around the one point to cause reflected light to be diffused and reflected from the one point at each of the orientation angles, the light rays forming an angle of 30° with a normal line of the surface of the measurement sample, the reflected light including reflected light beams that travel in a plane including the one point and the nominal line and are perpendicular to the orientation angle of irradiation with the light rays, the reflected light beams forming an angle of 30° or less with the normal line; and representing a standard deviation value (cd/m 2 ) of luminance values of the reflected light beams as L 3 ,
the light diffusion control member satisfies following expression (3) in all the four directions:
L 3 <2.00 (3).
8. A reflective display body configured such that an up-down direction of display content on a display surface can be changed, the reflective display body comprising:
the light diffusion control member according to claim 7 ;
a display device provided on one surface side of the light diffusion control member; and
a reflective layer provided on a surface side of the display device opposite to the light diffusion control member or incorporated in the display device.