Illumination device and display device incorporating the same
View Patent ↗Light emitted from a light source and incident on a light distributor of a light guide plate is partially emitted from the light guide plate as it is, and is predominantly reflected toward a prism section. Light incident on the prism section from the light distributor and light incident on the prism section directly from the light source are refracted and reflected by the prism section, and are then emitted from a light emission plane of the light guide plate in a region away from the light source in which the light distributor is not disposed, in a direction perpendicular to the light emission plane and substantially away from light source.
1. An illumination device comprising:
a light source; and
a light guide plate for receiving light from said light source on a light incident plane thereof and emitting the light from a light emission plane thereof, wherein:
said light guide plate includes a light distributor disposed on said light emission plane, and a prism section disposed on said light incident plane,
said light distributor is configured to cause part of the light incident from said light source to emit from said light guide plate as it is, and to reflect at least part of remaining light toward said prism section,
said prism section is configured to refract and reflect the light incident thereon from said light distributor and the light incident thereon directly from said light source to guide at least part of the light to said light emission plane, and
said illumination device satisfies the following equation:
D
≤
P
<
2
(
r
+
d
)
tan
{
90
°
-
sin
-
1
(
1
n
)
}
+
D
where r represents a distance between said light source and said light incident plane; d represents a thickness of said light guide plate; D represents a width of said light source in a direction parallel with said light emission plane; P represents a width of said light distributor in a direction parallel with said light emission plane; and n represents a relative refractive index of said light guide plate to air.
2. The illumination device according to claim 1 , wherein said light source is a linear light source which extends in the direction parallel with said light emission plane.
3. The illumination device according to claim 1 , wherein:
said light guide plate has said light incident plane and said light emission plane which are parallel with each other;
said light distributor has a reflection plane which forms an angle θ 3 with a direction perpendicular to said light emission plane; and
said angle θ 3 satisfies the following equations:
θ
3
-
sin
-
1
(
1
n
sin
x0
)
<
90
°
-
sin
-
1
(
1
n
)
tan
-
1
(
d
s
)
<
2
×
θ
3
-
sin
-
1
(
1
n
sin
x0
)
-
90
°
x0
<
tan
-
1
{
P
2
×
(
r
+
d
)
}
where x 0 represents an angle formed by the light incident on said light guide plate from said light source with a direction perpendicular to said light incident plane.
4. The illumination device according to claim 3 , wherein said angle θ 3 satisfies the following equation:
tan
-
1
(
2
×
d
s
)
≤
2
×
θ
3
-
sin
-
1
(
1
n
sin
x0
)
-
90
°
≤
tan
-
1
(
4
×
d
s
)
.
5. The illumination device according to claim 1 , wherein:
said light guide plate has said light incident plane and said light emission plane which are parallel with each other;
said light distributor has a reflection plane which forms an angle θ 3 with a direction perpendicular to said light emission plane, and a reflection plane which forms an angle θ 4 with a direction parallel with said light emission plane; and
said angles θ 3 and θ 4 satisfy the following equations:
θ
3
-
sin
-
1
(
1
n
sin
x0
)
<
90
°
-
sin
-
1
(
1
n
)
2
×
θ
3
-
θ
4
-
sin
-
1
(
1
n
sin
x0
)
>
sin
-
1
(
1
n
)
tan
-
1
(
d
s
)
<
90
°
-
2
×
θ
3
+
2
×
θ
4
+
sin
-
1
(
1
n
sin
x0
)
x0
<
tan
-
1
{
P
2
×
(
r
+
d
)
}
where x 0 represents an angle formed by the light incident on said light guide plate from said light source with a direction perpendicular to said light incident plane.
6. The illumination device according to claim 5 , wherein said angles θ 3 and θ 4 satisfy the following equation:
tan
-
1
(
2
×
d
s
)
≤
90
°
-
2
×
θ
3
+
2
×
θ
4
+
sin
-
1
(
1
n
sin
x0
)
≤
tan
-
1
(
4
×
d
s
)
.
7. The illumination device according to claim 1 , wherein:
said light guide plate has said light incident plane and said light emission plane which are parallel with each other,
said prism section has two prism planes, and
said illumination device satisfies the following equations:
θ
1
>
γ
90
°
-
sin
-
1
(
1
n
)
<
2
×
θ
1
-
γ
<
90
°
+
sin
-
1
(
1
n
)
γ
=
sin
-
1
{
1
n
sin
(
θ
2
-
x0
)
}
-
θ
2
+
90
°
where
x0
≤
θ
2
γ
=
90
°
-
θ
2
-
sin
-
1
{
1
n
sin
(
θ
2
-
x0
)
}
where
x0
>
θ
2
x0
<
tan
-
1
(
s
r
)
where θ 1 represents an angle of the prism plane closer to the light source which is the closest to said prism section to said light incident plane, ; θ 2 represents an angle of the other prism plane further away from said closest light source to said light incident plane; n represents a relative refractive index of said light guide plate to air; s represents a distance between the adjacent light sources or a length of said light guide plate when there is one said light source; and x 0 represents an angle formed by the light incident on said light guide plate from said light source with a direction perpendicular to said light incident plane.
8. The illumination device according to claim 7 , wherein said angle x 0 satisfies the following equation:
tan
-
1
(
s
4
×
r
)
≤
x0
≤
tan
-
1
(
s
2
×
r
)
.
9. The illumination device according to claim 1 , wherein:
said light guide plate has said light incident plane and said light emission plane which are parallel with each other,
said prism section has two prism planes, and
said illumination device satisfies the following equations:
90
°
-
θ1
≥
α
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
>
90
°
where
α
>
tan
-
1
(
d
s
)
0
<
θ1
-
β2
<
90
°
-
sin
-
1
(
1
n
)
90
°
-
sin
-
1
(
1
n
)
<
2
×
θ1
-
β2
≤
90
°
+
sin
-
1
(
1
n
)
where
β1
=
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
-
90
°
β2
=
90
°
-
θ2
+
sin
-
1
{
1
n
×
sin
(
θ2
+
β1
-
90
°
)
}
where θ 1 represents an angle of the prism plane closer to the light source which is the closest to said prism section to said light incident plane; θ 2 represents an angle of the other prism plane further away from the closest light source to said light incident plane; α represents an angle formed by the light reflected by said light distributor with said light emission plane; and s represents a distance between the adjacent light sources or a length of said light guide plate when there is one said light source.
10. The illumination device according to claim 9 , wherein said angle α satisfies the following equation.
tan
-
1
(
2
×
d
s
)
≤
α
≤
tan
-
1
(
4
×
d
s
)
.
11. The illumination device according to claim 1 , wherein:
said light guide plate has said light incident plane and said light emission plane which are parallel with each other,
said prism section has two prism planes, and
said illumination device satisfies the following equations:
90
°
-
θ1
≥
α
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
>
90
°
where
α
>
tan
-
1
(
d
s
)
0
<
θ1
-
β4
<
90
°
-
sin
-
1
(
1
n
)
90
°
-
sin
-
1
(
1
n
)
<
2
×
θ1
-
β4
≤
90
°
+
sin
-
1
(
1
n
)
where
β1
=
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
-
90
°
β2
=
90
°
-
θ2
+
sin
-
1
{
1
n
×
sin
(
θ2
+
β1
-
90
°
)
}
β4
=
sin
-
1
[
1
n
sin
{
θ1
+
θ2
+
sin
-
1
{
n
×
sin
(
90
°
+
β2
-
θ1
)
}
-
180
°
}
]
+
90
°
-
θ2
where θ 1 represents an angle of the prism plane closer to the light source which is the closest to said prism section to said light incident plane; θ 2 represents an angle of the other prism plane further away from the closest light source to said light incident plane; α represents an angle formed by the light reflected by said light distributor with said light emission plane; and s represents a distance between the adjacent light sources or a length of said light guide plate when there is one said light source.
12. The illumination device according to claim 11 , wherein said angle α satisfies the following equation.
tan
-
1
(
2
×
d
s
)
≤
α
≤
tan
-
1
(
4
×
d
s
)
.
13. The illumination device according to claim 1 , wherein:
said light guide plate has said light incident plane and said light emission plane which are parallel with each other,
said prism section has two prism planes, and
said illumination device satisfies the following equations:
90
°
-
θ1
≥
α
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
>
90
°
where
α
>
tan
-
1
(
d
s
)
0
<
θ1
-
β7
<
90
°
-
sin
-
1
(
1
n
)
90
°
-
sin
-
1
(
1
n
)
<
2
×
θ1
-
β7
≤
90
°
+
sin
-
1
(
1
n
)
where
β1
=
90
°
-
θ1
-
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
β5
=
θ2
+
sin
-
1
{
1
n
×
sin
(
90
°
+
β1
-
θ2
)
}
-
90
°
β6
=
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
β5
-
θ1
)
}
-
90
°
β7
=
90
°
-
θ2
+
sin
-
1
{
1
n
×
sin
(
θ2
+
β6
-
90
°
)
}
where θ 1 represents an angle of the prism plane closer to the light source which is the closest to said prism section to said light incident plane; θ 2 represents an angle of the other prism plane further away from the closest light source to said light incident plane; α represents an angle formed by the light reflected by said light distributor with said light emission plane; and s represents a distance between the adjacent light sources or a length of said light guide plate when there is one said light source.
14. The illumination device according to claim 13 , wherein said angle α satisfies the following equation.
tan
-
1
(
2
×
d
s
)
≤
α
≤
tan
-
1
(
4
×
d
s
)
.
15. The illumination device according to claim 1 , wherein:
said light guide plate has said light incident plane and said light emission plane which are parallel with each other,
said prism section has two prism planes, and
said illumination device satisfies the following equations:
90
°
-
θ1
≥
α
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
≤
90
°
where
α
>
tan
-
1
(
d
s
)
0
<
θ1
-
β9
<
90
°
-
sin
-
1
(
1
n
)
90
°
-
sin
-
1
(
1
n
)
<
2
×
θ1
-
β9
≤
90
°
+
sin
-
1
(
1
n
)
where
β1
=
90
°
-
θ1
-
sin
-
1
{
n
×
sin
(
90
°
-
α
-
θ1
)
}
β5
=
θ2
+
sin
-
1
{
1
n
×
sin
(
90
°
+
β1
-
θ2
)
}
-
90
°
β6
=
θ1
+
sin
-
1
{
n
×
sin
(
90
°
-
β5
-
θ1
)
}
-
90
°
β7
=
90
°
-
θ2
+
sin
-
1
{
1
n
×
sin
(
θ2
+
β6
-
90
°
)
}
β9
=
sin
-
1
[
1
n
sin
{
θ1
+
θ2
+
sin
-
1
{
n
×
sin
(
90
°
+
β7
-
θ1
)
}
-
180
°
}
]
+
90
°
-
θ2
where θ 1 represents an angle of the prism plane closer to the light source which is the closest to said prism section to said light incident plane; θ 2 represents an angle of the other prism plane further away from the closest light source to said light incident plane; α represents an angle formed by the light reflected by said light distributor with said light emission plane; and s represents a distance between the adjacent light sources or a length of said light guide plate when there is one said light source.
16. The illumination device according to claim 15 , wherein said angle α satisfies the following equation.
tan
-
1
(
2
×
d
s
)
≤
α
≤
tan
-
1
(
4
×
d
s
)
.
17. The illumination device according to claim 1 , wherein said prism sections are bilaterally symmetric about said light source when there is one said light source, and about a midpoint between said light sources when there are two said light sources.
18. The illumination device according to claim 1 , wherein said light distributor is formed of repetitions of a plane which transmits the light from said light source and a plane which reflects the light from said light source.
19. A liquid crystal display device comprising the illumination device according to claim 1 .
20. An illumination device comprising:
a light source; and
a light guide plate for receiving light from said light source on a light incident plane thereof and emitting the light from a light emission plane thereof, wherein:
said light guide plate includes a light distributor disposed on said light incident plane, and a prism section disposed on said light incident plane in a region in which said light distributor is not disposed,
said light distributor is configured to cause part of the light incident from said light source to emit from said light guide plate as it is, and to refract at least part of remaining light so that said light is reflected by said light emission plane,
said prism section is configured to refract and reflect the light reflected by said light emission plane and incident thereon and the light incident thereon directly from said light source to guide at least part of the light to said light emission plane, and
said illumination device satisfies the following equation:
D
≤
P
<
2
r
tan
{
90
°
-
sin
-
1
(
1
n
)
}
+
D
.
where r represents a distance between said light source and said light incident plane; D represents a width of said light source in a direction parallel with said light emission plane; P represents a width of said light distributor in a direction parallel with said light emission plane; and n represents a relative refractive index of said light guide plate to air.
21. The illumination device according to claim 20 , wherein said light source is a linear light source which extends in the direction parallel with said light emission plane.