Light guide plate for image display
A light guide plate for image display can display clear images even when a resin base is used. The Sight guide plate configured for image display may include a first resin base and a hologram layer. The first resin base may have an MC value of 0.120 or less, obtained by evaluation using shadow contrast, according to expression (1): MC = Lmax - Lmin Lmax + Lmin , ( 1 ) wherein Lmax is a maximum value of brightness from a brightness distribution, Lmin is a minimum value of the lightness from the brightness distribution, and MC is an MC value that objectively represents a magnitude of a dip in low brightness portions in the brightness distribution.
1 . A light guide plate configured for image display, comprising:
a first resin base;
a hologram layer formed on one side of the first resin base in a thickness direction:
an incidence portion formed on another side of the first resin base in a thickness direction, an image light being incident on the incidence portion;
a display image emission portion formed on the another side of the first resin base at a position separated from the incidence portion in the plane direction which is a direction orthogonal to the thickness direction;
a second resin base; and
an external light incidence portion is provided on a side of the second resin base opposite to the hologram layer in the thickness direction,
wherein an arithmetic average roughness Ra of the surface of the first resin base is 2.6 nm or more but 5 nm or less,
wherein the hologram layer comprises a waveguide diffraction grating portion and a display diffraction grating portion,
wherein the display image emission portion comprises the display diffraction grating portion and a region of the first resin base facing the display diffraction grating portion in the thickness direction,
wherein the image light incident on the incidence portion is guided to the display diffraction grating portion through the waveguide diffraction grating portion and emitted to the outside of the light guide plate through the first resin base in the display image emission portion,
wherein at least a portion of an external light incident on the external light incidence portion is emitted to the outside of the light guide plate through the display image emission portion, and
wherein a first image on which a second image based on the image light and a third image based on the external light are superimposed is displayed,
wherein the first resin base has a maximum MC value in a range of from 0.020 to 0.110,
wherein the MC values are obtained by evaluation using shadow contrast according to Expression (1):
MC
=
Lmax
-
Lmin
Lmax
+
Lmin
,
(
1
)
wherein Lmax is a maximum value of brightness from a brightness distribution, Lmin is a minimum value of the brightness from the brightness distribution, and MC is an evaluated MC value that objectively represents a magnitude of a dip in low brightness portions in the brightness distribution,
wherein a measurement area of the evaluated MC value is provided at each of 41 points, which are shifted by 2 mm in a lateral direction in a rectangular region having a width of 180 mm in a vertical direction and a width of 80 mm in a horizontal direction,
wherein a measurement line is selected to divide the measurement area laterally into 40 equal parts in each measurement area, and
wherein each of the evaluated MC values is measured from the measurement line.
2 . The light guide plate of claim 1 , further comprising:
a first barrier layer.
3 . The light guide plate of claim 2 , wherein the first resin base, the first barrier layer, and the hologram layer are arranged in that order in a thickness direction.
4 . The light guide plate of claim 3 , further comprising:
a second barrier layer,
wherein the first resin base, the first barrier layer, the hologram layer, the second barrier layer, and the second resin base are arranged in that order in the thickness direction.
5 . The light guide plate of claim 3 , wherein a refractive index of the first barrier layer is higher than a refractive index of the first resin base.
6 . The light guide plate of claim 3 , wherein a refractive index of the first barrier layer is 1.48 or more.
7 . The light guide plate of claim 3 , wherein the first barrier layer comprises an inorganic material.
8 . The light guide plate of claim 3 , wherein the first barrier layer is disposed on a resin film.
9 . The light guide plate of claim 3 , wherein a steam barrier material is used as a material of the first barrier layer.
10 . The light guide plate of claim 2 , wherein a refractive index of the first barrier layer is higher than a refractive index of the first resin base.
11 . The light guide plate of claim 2 , wherein a refractive index of the first barrier layer is 1.48 or more.
12 . The light guide plate of claim 2 , wherein the first barrier layer comprises an inorganic material.
13 . The light guide plate of claim 12 , wherein the first barrier layer comprises silicon oxide, silicon nitrogen oxide, diamond-like carbon, aluminum oxide, and/or glass.
14 . The light guide plate of claim 2 , wherein a steam barrier material is used as a material of the first barrier layer.
15 . The light guide plate of claim 2 , wherein the first barrier layer is disposed on the hologram layer.
16 . The light guide plate of claim 1 , wherein a refractive index of the first resin base is in a range of from 1.48 to 1.70.
17 . The light guide plate of claim 1 , wherein the first resin base comprises a poly(meth)acrylic resin.
18 . The light guide plate of claim 1 , wherein a heat shrinkage rate measured based on annex A of JIS K 6718-1:2015 of the first resin base is less than 3%.
19 . The light guide plate of claim 1 , wherein an arithmetic average roughness Ra of a surface of the first resin base is 10 nm or less.
20 . An AR glass, comprising:
the light guide plate of claim 1 .
21 . The light guide plate of claim 1 , wherein the MC value of the first resin base is in a range of from 0.020 to 0.070.