U.S. patent application number 11/634262 was filed with the patent office on 2007-06-07 for display device and planar light source device.
This patent application is currently assigned to Hitachi Displays, Ltd.. Invention is credited to Hiroshi Kurihara.
Application Number | 20070126950 11/634262 |
Document ID | / |
Family ID | 38118356 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070126950 |
Kind Code |
A1 |
Kurihara; Hiroshi |
June 7, 2007 |
Display device and planar light source device
Abstract
The present invention relates to a technique which can make a
backlight used in a liquid crystal display device thin and
light-weighted. The present invention provides a liquid crystal
display device which includes a display panel and a backlight which
is arranged behind the display panel, wherein the backlight
includes a film-like light guide member, a film-like light
semi-transmissive member which is adhered to a first surface of the
light guide member which faces the display panel in an opposed
manner, a film-like reflective member which is adhered to a back
surface of the light guide member opposite to the first surface,
and a spot light source which is arranged at a position of the
light guide member at which light is incident on the light guide
member from the first surface or the back surface, and a refractive
index of the light semi-transmissive member is set smaller than a
refractive index of the light guide member.
Inventors: |
Kurihara; Hiroshi; (Mobara,
JP) |
Correspondence
Address: |
Stanley P. Fisher;Reed Smith LLP
Suite 1400
3110 Fairview Park Drive
Falls Church
VA
22042-4503
US
|
Assignee: |
Hitachi Displays, Ltd.
|
Family ID: |
38118356 |
Appl. No.: |
11/634262 |
Filed: |
December 6, 2006 |
Current U.S.
Class: |
349/65 |
Current CPC
Class: |
G02B 6/0023 20130101;
G02B 6/0055 20130101; G02B 6/0031 20130101; G02B 6/0068 20130101;
G02B 6/0035 20130101 |
Class at
Publication: |
349/065 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2005 |
JP |
2005-352167 |
Claims
1. A display device comprising: a display panel: and a backlight
which is arranged behind the display panel, wherein the backlight
includes a film-like light guide member, a film-like light
semi-transmissive member which is adhered to a first surface of the
light guide member which faces the display panel in an opposed
manner, a film-like reflective member which is adhered to a back
surface of the light guide member opposite to the first surface,
and a spot light source which is arranged at a position of the
light guide member at which light is incident on the light guide
member from the first surface or the back surface, wherein a
refractive index of the light semi-transmissive member is set
smaller than a refractive index of the light guide member.
2. A display device according to claim 1, wherein the backlight
includes a reflector which is arranged in the direction that the
spot light source radiates the light in the film surface direction
of the light guide member, and allows the light radiated from the
spot light source to be incident on the light guide member by
reflecting the light.
3. A display device according to claim 1, wherein the light
semi-transmissive member or the polarization reflective member
changes a ratio of transmissivity and reflectance of light which
propagates in the light guide member corresponding to a distance
from a position at which the light of the light guide member is
incident.
4. A display device according to claim 1, wherein a plurality of
through holes are formed in a plurality of portions of the light
semi-transmissive member or the polarization reflective member, and
the distribution density of the through holes is changed
corresponding to a distance from a position at which the light of
the light guide member is incident.
5. A display device according to claim 1, wherein the reflective
member changes reflectance thereof corresponding to a distance from
a position at which the light of the light guide member is
incident.
6. A display device according to claim 1, wherein the reflective
member has an irregular reflection pattern formed of a concave
shape or a convex shape at a plurality of portions of a surface of
the reflective member which is brought into close contact with the
light guide member, and the distribution density of the irregular
reflection pattern is changed corresponding to a distance from a
position at which the light of the light guide member is
incident.
7. A display device according to claim 1, wherein a total of a
thickness of the reflective member, a thickness of the light guide
member and a thickness of the light semi-transmissive member is set
to a value larger than 0 and equal to or smaller than 0.35 mm.
8. A display device according to claim 7, wherein the thickness of
the light guide member is larger than 0 and equal to or smaller
than 0.25 mm.
9. A display device according to claim 8, wherein the thickness of
the reflective member is larger than 0 and equal to or smaller than
0.05 mm.
10. A display device according to claim 1, wherein the light guide
member is polycarbonate, and the light semi-transmissive member is
made of polyethylene terephthalate or an acrylic resin.
11. A display device comprising: a display panel: and a backlight
which is arranged behind the display panel, wherein the display
panel adheres a polarizer to a surface thereof which faces the
backlight in an opposed manner and a back surface thereof opposite
to the surface, and the backlight includes a film-like light guide
member, a film-like polarization reflective member which is adhered
to a first surface of the light guide member which faces the
display panel in an opposed manner, a film-like reflective member
which is adhered to a back surface of the light guide member
opposite to the first surface, and a spot light source which is
arranged at a position of the light guide member at which light is
incident on the light guide member from the first surface or the
back surface, wherein a transmission axis of the polarization
reflective member is arranged in the same direction as a
transmission axis of the polarizer which is adhered to the surface
of the display panel which faces the backlight in an opposed
manner.
12. A display device according to claim 11, wherein the backlight
includes a reflector which is arranged in the direction that the
spot light source radiates the light in the film surface direction
of the light guide member, and allows the light radiated from the
spot light source to be incident on the light guide member by
reflecting the light.
13. A display device according to claim 11, wherein the light
semi-transmissive member or the polarization reflective member
changes a ratio of transmissivity and reflectance of light which
propagates in the light guide member corresponding to a distance
from a position at which the light of the light guide member is
incident.
14. A display device according to claim 11, wherein a plurality of
through holes are formed in a plurality of portions of the light
semi-transmissive member or the polarization reflective member, and
the distribution density of the through holes is changed
corresponding to a distance from a position at which the light of
the light guide member is incident.
15. A display device according to claim 11, wherein the reflective
member changes reflectance thereof corresponding to a distance from
a position at which the light of the light guide member is
incident.
16. A display device according to claim 11, wherein the reflective
member has an irregular reflection pattern formed of a concave
shape or a convex shape at a plurality of portions of a surface of
the reflective member which is brought into close contact with the
light guide member, and the distribution density of the irregular
reflection pattern is changed corresponding to a distance from a
position at which light of the light guide member is incident.
17. A planar light source device comprising: a light source; and a
film-like light guide member, wherein the light source includes a
film-like incident-light adjusting member which is arranged in the
direction at which light is radiated in the direction perpendicular
to a film surface of the light guide member, and changes the
incident direction of light to the light guide member is changed in
the propagation direction of light in the light guide member
between a region on which the light is incident and a surface to
which light of the light source is radiated, and the incident-light
adjusting member has one, two or more projections on a surface side
which faces the light guide member in an opposed manner, and distal
end surfaces of the projections are brought into close contact with
the light guide member.
18. A planar light source device according to claim 17, wherein a
radiation-light adjusting member which adjusts a radiation angle of
the light from the radiation surface is provided to a radiation
surface of the light of the light guide member.
19. A planar light source device according to claim 18, wherein a
reflective member is provided to a back surface of the light guide
member opposite to a surface on which the incident-light adjusting
member is arranged and to a region which is overlapped to the
incident-light adjusting member.
20. A planar light source device according to claim 18, wherein a
projection of the incident-light adjusting member is a columnar
projection having a curved bottom surface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The disclosure of Japanese Patent Application No.
2005-352167 filed on Dec. 6, 2005 including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a display device and a
planar light source device, and more particularly to a technique
which is effectively applicable to a planar light source device
which radiates light propagated through a light guide plate and a
display device which uses the planar light source device.
[0004] 2. Description of the Related Arts
[0005] Conventionally, as a display of a mobile phone or a
notebook-type PC (Personal Computer) or the like, a liquid crystal
display device (a liquid crystal display unit) having a liquid
crystal display panel is used.
[0006] The liquid crystal display device is roughly classified into
a transmissive-type liquid crystal display device which displays an
image (a video) by arranging a backlight (a light source) behind
the liquid crystal display panel and radiating light from the light
source to the liquid crystal display panel and allowing the light
to pass through the liquid crystal display panel, and a
reflective-type liquid crystal display device which displays an
image (a video) by reflecting light from outside a display device
on a liquid crystal display panel.
[0007] Further, the backlight of the transmissive-type liquid
crystal display device is roughly classified into, for example, a
direct-type backlight which arranges a light source such as a
fluorescent tube in a region which is overlapped to a display
region of a liquid crystal display panel, and an edge-light-type
(also referred to as a side-light-type) backlight which arranges a
light guide plate in a region which is overlapped to a display
region of a liquid crystal display panel and arranges a light
source on an end portion of the light guide plate.
[0008] The edge-light-type backlight is a backlight which radiates
light to the liquid crystal display panel by propagating light from
the light source which is arranged on the end portion of the light
guide plate in the inside of the light guide plate, directing the
light in the direction toward the liquid crystal display panel by a
reflective portion formed on a back surface of the light guide
plate and by diffusing the light using a diffusion plate. The
edge-light-type backlight can reduce a thickness thereof compared
to a thickness of the direct-type backlight. Accordingly, the
liquid crystal display device having the edge-light-type backlight
has been often used in a display of a mobile phone or a
notebook-type PC.
[0009] Further, with respect to the edge-light-type backlight, to
uniformly radiate light to the display region of the liquid crystal
display panel, there has been known a backlight which uses a
combination of a light guide plate to which a shape which
efficiently reflects the propagating light (for example, grooves)
is applied and a reflective sheet (for example, see Japanese Patent
Laid-open No. 11599/2005 (patent document 1)).
[0010] Further, with respect to the edge-light-type backlight, to
achieve the reduction of thickness of the backlight, for example,
there has been known a backlight which is constituted of a light
guide body layer (a light guide plate), a reflection layer (a
reflective portion) and a diffusion layer (a diffusion plate) as
the integral structure, wherein each layer is formed of a thin film
sheet (for example, see Japanese Patent Laid-open Hei08-152526
(patent document 2)).
SUMMARY OF THE INVENTION
[0011] However, for example, in the backlight described in the
above-mentioned patent document 1, the reflection grooves or the
like are formed in the light guide plate and hence, a gap is
defined between the reflective sheets and light infiltrates into
the gap. Further, due to the formation of the grooves, there exists
light which reflects or refracts at an angle which does not
contribute to the front face brightness. Accordingly, there has
been a drawback that loss of light is increased. Further, in
general, the light guide plate is often formed by injection molding
and hence, there has been a drawback that it is difficult to form
the light guide plate into a shape as designed from a viewpoint of
forming accuracy.
[0012] Further, for example, the backlight described in the
above-mentioned patent document 2 makes use of the generation of a
total reflection on an interface between the sheets by combining
thin film sheets having different refractive indexes. However, no
consideration has been taken by the patent document 2 with respect
to an incident angle of light when the light is incident on the
light guide body layer from the light source. Accordingly, for
example, the light which is incident on the light guide plate at a
small incident angle which does not generate the total reflection
becomes dominant thus giving rise to a drawback that light cannot
be effectively radiated into the inside of a display region of the
liquid crystal display panel.
[0013] Further, in the liquid crystal display device (the liquid
crystal display unit) which is used in a mobile phone or the like,
recently, to achieve the reduction of weight of the liquid crystal
display device, for example, a spot light source such as an LED
(Light Emitting Diode) is used as the light source of the
backlight. However, the backlight described in the patent document
2 premises the use of a linear light source such as a fluorescent
tube as the light source. Accordingly, for example, when the spot
light source such as the LED is used, there has been a drawback
that it is difficult to make the brightness distribution of the
light which is radiated into the inside of the display region of
the liquid crystal display panel.
[0014] Accordingly, it is an object of the present invention to
provide a technique which can achieve the reduction of thickness
and the reduction of weight of a backlight used in a liquid crystal
display device, for example.
[0015] It is another object of the present invention to provide a
technique which can achieve the reduction of thickness, the
reduction of weight of a backlight used in a liquid crystal display
device, and the increase of brightness of the liquid crystal
display device, for example.
[0016] The above-mentioned and other objects and novel features of
the present invention will become apparent from the description of
this specification and attached drawings.
[0017] To explain the summary of typical inventions among the
inventions disclosed in this specification, they are as
follows.
[0018] (1) In a display device which includes a display panel and a
backlight which is arranged behind the display panel, the backlight
includes a film-like light guide member, a film-like light
semi-transmissive member which is adhered to a first surface of the
light guide member which faces the display panel in an opposed
manner, a film-like reflective member which is adhered to a back
surface of the light guide member opposite to the first surface,
and a spot light source which is arranged at a position of the
light guide member at which light is incident on the light guide
member from the first surface or the back surface, wherein a
refractive index of the light semi-transmissive member is set
smaller than a refractive index of the light guide member.
[0019] (2) In a display device which includes a display panel and a
backlight which is arranged behind the display panel, the display
panel adheres a polarizer on a surface thereof which faces the
backlight in an opposed manner and a back surface thereof opposite
to the surface, and the backlight includes a film-like light guide
member, a film-like polarization reflective member which is adhered
to a first surface of the light guide member which faces the
display panel in an opposed manner, a film-like reflective member
which is adhered to a back surface of the light guide member
opposite to the first surface, and a spot light source which is
arranged at a position of the light guide member at which light is
incident on the light guide member from the first surface or the
back surface, wherein a transmission axis of the polarization
reflective member is directed in the same direction as a
transmission axis of the polarizer which is adhered to the surface
of the display panel which faces the backlight in an opposed
manner.
[0020] (3) In the display device having the above-mentioned means
(1) or (2), the backlight includes a reflector which is arranged in
the direction that the spot light source radiates the light in the
film surface direction of the light guide member and allows the
light radiated from the spot light source to be incident on the
light guide member by reflecting the light.
[0021] (4) In the display device having the above-mentioned means
(1) or (2), the light semi-transmissive member or the polarization
reflective member changes a ratio of transmissivity and reflectance
of light which propagates in the light guide member corresponding
to a distance from a position at which the light of the light guide
member is incident.
[0022] (5) In the display device having the above-mentioned means
(1) or (2), a plurality of through holes are formed in a plurality
of portions of the light semi-transmissive member or the
polarization reflective member, and the distribution density of the
through holes is changed corresponding to a distance from a
position at which the light of the light guide member is
incident.
[0023] (6) In the display device having the above-mentioned means
(1) or (2), the reflective member changes reflectance thereof
corresponding to a distance from a position at which the light of
the light guide member is incident.
[0024] (7) In the display device having the above-mentioned means
(1) or (2), the reflective member has an irregular reflection
pattern formed of a concave shape or a convex shape at a plurality
of portions of a surface of the reflective member which is brought
into close contact with the light guide member, and the
distribution density of the irregular reflection pattern is changed
corresponding to a distance from a position at which the light of
the light guide member is incident.
[0025] (8) In a planar light source device having a light source
and a film-like light guide member, the light source includes a
film-like incident-light adjusting member which is arranged in the
direction that light is radiated in the direction perpendicular to
a film surface of the light guide member and changes the incident
direction of light to the light guide member to the propagation
direction of light of the light guide member between a region of
the light guide member which allows light to be incident thereon
and a surface of the light source from which light is radiated, and
the incident-light adj usting member has one, two or more
projections on a surface side thereof which faces the light guide
member in an opposed manner, and distal end surfaces of the
projections are brought into close contact with the light guide
member.
[0026] (9). In the planar light source device having the
above-mentioned means (8), a light radiation surface of the light
guide member has a radiation light adjusting member which adjusts a
radiation angle of the light from the light radiation surface.
[0027] (10) In the planar light source device having the
above-mentioned means (8) or (9), the light guide member includes a
reflective member on a back surface thereof opposite to a surface
thereof on which the incident-light adjusting member is arranged
and in a region thereof which is overlapped to the incident-light
adjusting member.
[0028] (11) In any one of the planar light source devices having
the above-mentioned means (8) to (10), the projections of the
incident-light adjusting member are columnar projections each of
which has a curved bottom surface.
[0029] (12) In a display device which includes a display panel and
a backlight which is arranged behind the display panel, the
backlight is formed of the planar light source device included in
any one of the planar light source devices having the
above-mentioned means (8) to (11).
[0030] The display device of the present invention adopts the
constitution in which the portion which propagates the light of the
backlight is integrally configured such that, as shown in the
above-mentioned means (1), the film-like light guide member is
sandwiched between the film-like light semi-transmissive member and
the film-like reflective member. Here, each member is integrally
formed by adhering film-like formed members having a thickness of
0.25 mm or less to each other, for example. Due to such a
constitution, the light guide plate can be made thin and
light-weighted. Further, by adopting the integral constitution
formed of a film-like light guide member, a semi-transmissive
member and a reflective member, light which is incident on the
light guide member propagates through the light guide member while
repeating the reflection between the semi-transmissive member and
the reflective member with high efficiency. Accordingly, loss of
the light which propagates through the light guide member is
decreased thus increasing the brightness of the light radiated to
the display region of the display panel.
[0031] Further, in the display device of the present invention, the
constitution of the portion which propagates the light of the
backlight may adopt a film-like polarization reflective member in
place of the semi-transmissive member as in the case of the
above-mentioned means (2).
[0032] Here, by adopting the above-mentioned constitution of the
means (3), the loss of light can be reduced and hence, the
brightness of light which is radiated to the display region of the
display panel can be increased. Here, it is preferable that the
above-mentioned reflector has a reflective surface having a convex
shape in the direction toward the spot light source, for
example.
[0033] Further, by constituting the light semi-transmissive member
or the polarization reflective member as in the case of the
above-mentioned means (4), it is possible to make the in-plane
brightness of the light radiated to the display region of the
display panel uniform. Here, in place of changing the ratio between
the transmissivity and the reflectance of the light
semi-transmissive member or the polarization reflective member as
in the case of the above-mentioned means (4), a plurality of
through holes may be formed in the light semi-transmissive member
or the polarization reflective member by changing the distribution
density of the through holes as in the case of the above-mentioned
means (5).
[0034] Further, in place of changing the ratio between the
transmissivity and the reflectance of the light semi-transmissive
member or the polarization reflective member as in the case of the
above-mentioned means (4), the reflectance of the reflective member
may be changed as in the case of the above-mentioned means (6).
Here, in place of changing the reflectance of the reflective member
as in the case of the above-mentioned means (6), a plurality of
irregular reflection patterns may be provided to a surface of the
reflective member which is laminated to the light guide member
while changing the distribution density of the irregular reflection
patterns as in the case of the above-mentioned means (7).
[0035] Further, when the light radiated from the spot light source
is directed toward the film surface of the light guide member as in
the case of the above-mentioned means (3), even when the light is
reflected on the reflector, there may be a case that among the
light which is incident on the light guide member, the light whose
incident angle does not exceed a critical angle becomes dominant.
With respect to the light which is incident with the angle which
does not exceed the critical angle and propagates through the light
guide member, there is no possibility that such a light is totally
reflected on an interface with the light semi-transmissive member
or the polarization reflective member or an interface with the
reflective member. Accordingly, the light leaks to the outside of
the light guide member on each interface, and the light does not
propagate through the inside of the light guide member.
[0036] To overcome such a drawback, for example, as in the case of
the above-mentioned means (8), it is desirable to use the planar
light source device which is arranged to radiate the light in the
direction perpendicular to the film surface of the light guide
member as the spot light source. Here, the above-mentioned incident
light adjusting member may be arranged between the spot light
source and the light guide member. Due to such a constitution, the
light of the spot light source which is radiated in the direction
perpendicular to the film surface of the light guide member is
allowed to be incident on the light guide member while converting
the incident angle thereof into an angle which exceeds the critical
angle in the inside of the light guide member using the incident
light adjusting member. Accordingly, it is possible to allow the
light of the spot light source to be effectively incident on the
light guide member thus acquiring the higher brightness
uniformity.
[0037] Further, for example, as in the case of the above-mentioned
means (9), the radiation light adjusting member which adjusts the
radiation angle of the light from the radiation surface may be
provided to the radiation surface of light of the light guide
member. The radiation light adjusting member may be constituted in
the same manner as the above-mentioned incident light adjusting
member, for example. Due to such a constitution, for example, even
when the light guide member is not sandwiched between the light
semi-transmissive member and the reflective member, it is possible
to radiate the light which is incident on the light guide member in
a planar shape while propagating the light through the light guide
member.
[0038] Further, by providing the reflective member as in the case
of the above-mentioned means (10), it is possible to allow the
light which is radiated to the outside of light guide member to be
reflected on the above-mentioned reflective portion without making
the incident angle exceed the critical angle using the incident
light adjusting member thus allowing the light to be incident on
the light guide member again.
[0039] Here, by adopting the constitution of the means (11), it is
possible to propagate the light of the spot light source in a
spreading manner in the inside of the light guide member.
[0040] In this manner, with the provision of the planer light
source device having any one of the above-mentioned means (8) to
means (11), it is possible to allow the light of the spot light
source to be effectively incident on and to propagate through the
light guide member thus acquiring the high brightness uniformity.
Further, by forming the light guide member, the incident light
adjusting member and the radiation light adjusting member in a film
shape, it is possible to realize the reduction of thickness and the
reduction of the weight of the planar light source device.
Accordingly, as in the case of the above-mentioned means (12), with
the use of the planar light source device having the any one of the
above-mentioned means (8) to means (11) as the backlight of the
display device, it is possible to realize the reduction of
thickness and the reduction of weight of the backlight and, at the
same time, the brightness uniformity of the display region can be
enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a schematic view showing the schematic
constitution of a display device of an embodiment 1 according to
the present invention;
[0042] FIG. 2 is an enlarged schematic view of an essential part of
FIG. 1;
[0043] FIG. 3 is a schematic view for explaining a modification of
the embodiment 1;
[0044] FIG. 4 is a schematic view showing the schematic
constitution of a backlight of an embodiment 2 according to the
present invention;
[0045] FIG. 5 is a cross-sectional view taken along a line A-A' in
FIG. 4;
[0046] FIG. 6 is a schematic view for explaining a modification of
the embodiment 2;
[0047] FIG. 7 is a schematic view for explaining a variation of the
embodiment 2;
[0048] FIG. 8 is a schematic view showing the schematic
constitution of a backlight of an embodiment 3 according to the
present invention;
[0049] FIG. 9 is a cross-sectional view taken along a line B-B' in
FIG. 8;
[0050] FIG. 10 is a schematic view for explaining a modification of
the embodiment 3;
[0051] FIG. 11 is a schematic view showing the schematic
constitution of a backlight of an embodiment 4 according to the
present invention;
[0052] FIG. 12 is a cross-sectional view taken along a line C-C' in
FIG. 11.
[0053] FIG. 13 is a cross-sectional view taken along a line D-D' in
FIG. 11;
[0054] FIG. 14 is a schematic view for explaining a modification of
the embodiment 4;
[0055] FIG. 15 is a cross-sectional view taken along a line E-E' in
FIG. 14;
[0056] FIG. 16 is a cross-sectional view taken along a line F-F' in
FIG. 14;
[0057] FIG. 17 is a schematic view for explaining one of
advantageous effects of the backlight of the embodiment 4;
[0058] FIG. 18 is a schematic view showing a constitutional example
of a display device which uses a conventional general backlight for
comparing with the backlight of the embodiment 4;
[0059] FIG. 19 is a schematic view showing the schematic
constitution of a backlight of an embodiment 5 according to the
present invention;
[0060] FIG. 20 is a cross-sectional view taken along a line G-G' in
FIG. 19;
[0061] FIG. 21 is a schematic view for explaining a mounting method
of an incident-light adjusting member;
[0062] FIG. 22 is a schematic view for explaining the manner of
operation of the backlight of the embodiment 5;
[0063] FIG. 23 is a schematic view showing one example of a method
for adhering a spot light source and the incident-light adjusting
member in the embodiment 5;
[0064] FIG. 24 is a cross-sectional view taken along a line H-H' in
FIG. 23;
[0065] FIG. 25 is a schematic view showing one example of the
arrangement of the backlight and the display panel of the
embodiment 5;
[0066] FIG. 26 is a schematic view showing another example of the
arrangement of the backlight and the display panel of the
embodiment 5;
[0067] FIG. 27 is a schematic view for explaining a first variation
of the embodiment 5;
[0068] FIG. 28 is a schematic view for explaining a second
variation of the embodiment 5;
[0069] FIG. 29 is a schematic view showing the schematic
constitution of a backlight of an embodiment 6 according to the
present invention; and
[0070] FIG. 30 is a cross-sectional view taken along a line J-J' in
FIG. 29.
DETAILED DESCRIPTION OF THE INVENTION
[0071] Hereinafter, the present invention is explained in detail in
conjunction with embodiments by reference to drawings. Here, with
respect to the whole drawings for explaining the embodiments, parts
having the same functions are given the same symbols and their
repeated explanation is omitted.
Embodiment 1
[0072] FIG. 1 is a schematic view showing the schematic
constitution of a display device of an embodiment 1 according to
the present invention, while FIG. 2 is an enlarged schematic view
showing an essential part of FIG. 1.
[0073] In FIG. 1, numeral 1 indicates a display panel, numeral 201
indicates a light radiation portion, numeral 201a indicates a light
guide member (a light guide film), numeral 201b indicates a light
semi-transmissive member (a light semi-transmissive film), numeral
201c indicates a reflective member (a reflective film), and
numerals 3A, 3B indicate polarizer films.
[0074] The display device of this embodiment 1 includes, for
example, as shown in FIG. 1, the light radiation portion 201 of a
backlight below the display panel 1.
[0075] The display panel 1 may be any kind of display panel
provided that the display panel 1 allows light radiated from the
light radiation portion 201 of the backlight to pass therethrough
and displays an image (a video). As one example of the display
panel 1, for example, a liquid crystal display panel in which a
liquid crystal material is sandwiched between a pair of substrates
may be named. Further, in the display panel 1, in general, as shown
in FIG. 1, polarizer films 3A, 3B are adhered to a surface of the
display panel 1 on which light radiated from the backlight is
incident and a surface of the display panel 1 from which light is
radiated respectively.
[0076] The light radiation portion 201 of the backlight is, for
example, as shown in FIG. 1 and FIG. 2, integrally configured such
that the light guide member 201a is sandwiched between the light
semi-transmissive member 201b and the reflective member 201c. Here,
the light semi-transmissive member 201b is made of a material
having a refractive index smaller than a refractive index of the
light guide member 201a.
[0077] Further, in the embodiment 1, the light guide member 201a,
the light semi-transmissive member 201b and the reflective member
201c are respectively formed of a film-like member. Hereinafter,
the light guide member 201a is referred to as a light guide film,
the light semi-transmissive member 201b is referred to as a light
semi-transmissive film and the reflective member 201c is referred
to as a reflective film. Here, a thickness Ta of the light guide
film 201a is set to 0.25 mm or less, for example. Further, a
thickness Tb of the light semi-transmissive film 201b and a
thickness Tc of the reflective film 201c are respectively set to
0.05 mm or less, for example.
[0078] The light guide film 201a is made of polycarbonate (PC)
having a refractive index of 1.59, for example, while the light
semi-transmissive film 201b is made of fluororesin having a
refractive index of 1.35, for example. Here, the light
semi-transmissive film 201b may be also made of polyethylene
terephthalate (PET) having a refractive index of 1.57 or an acrylic
UV curing resin having a refractive index of 1.49, for example.
Further, the reflective film 201c is formed of a polyester
multi-layered film or a silver sheet which is prepared by
sputtering silver to a PET substrate.
[0079] Further, in the embodiment 1, the light guide member 201a,
the light semi-transmissive member 201b and the reflective member
201c are formed into the integral structure by adhering them to
each other using an optical adhesive agent having a refractive
index which is substantially equal to a refractive index of the
light semi-transmissive member 201b, for example.
[0080] In the display device having such a constitution, for
example, as shown in FIG. 1 and FIG. 2, light 4 is incident on the
light radiation portion 201 of the backlight from an end portion of
a surface of the light guide film 201a which faces the display
panel 1 in an opposed manner (hereinafter, referred to as a film
surface). Then, the incident light 4 is propagated in the inside of
the light guide film while repeating the reflection between an
interface with the light semi-transmissive film 201b and an
interface with the reflective film 201c. Here, on the interface
with the light semi-transmissive film 201b, corresponding to the
relationship between a refractive index of the light guide film
201a and a refractive index of the light semi-transmissive film
201b, light having a shallow angle, that is, light having a large
incident angle with respect to the light semi-transmissive film
201b is reflected on the interface. On the other hand, light having
a deep angle, that is, light having a small incident angle with
respect to the light semi-transmissive film 201b is refracted on
the interface and is radiated in the direction toward the display
panel 1. The light which is reflected on the interface with the
light semi-transmissive film 201b is reflected on the interface
with the reflective film 201c and, again, is incident on the
interface with the light semi-transmissive film 201b. By allowing
the light which propagates through the light guide film 201a to
repeat this operation, the light 4 incident on the light guide film
201a is converted into a planar light and is radiated to the
display panel 1.
[0081] Here, although not shown in FIG. 1 and FIG. 2, a light
source of the light 4 which is incident on the light guide film
201a may be arranged at any position provided that the light 4
which is incident on the light guide film 201a propagates in the
direction toward a region which is overlapped to the display panel
1 from the light incident position.
[0082] In this manner, in the display device according to the
embodiment 1, the thickness Ta of the light guide film 201a is set
to 0.25 mm or less and the thickness Tb of the light
semi-transmissive film 201b and the thickness Tc of the reflective
film 201c are respectively set to 0.05 mm or less. Accordingly, a
total thickness of the thickness Ta of the light guide film 201a,
the thickness Tb of the light semi-transmissive film 201b and the
thickness Tc of the reflective film 201c can be, as a matter of
course, set to a value larger than 0 and equal to or less than 0.35
mm. Further, by forming these films into the integral structure,
the light radiation portion 201 of the backlight can be made thin
and light-weighted.
[0083] Further, by forming the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c into the
integral structure, it is possible to propagate the light 4 which
is incident on the light guide film 201a by repeating the
reflection of the light 4 with high efficiency on the interface
with the light semi-transmissive film 201b and the interface with
the reflective film 201c. Accordingly, loss of light attributed to
leaking of light on respective interfaces, particularly, on the
interface with the reflective film 201c can be reduced and hence,
it is possible to increase the brightness of light which is
radiated to the display panel 1.
[0084] FIG. 3 is a schematic view for explaining a modification of
the embodiment 1.
[0085] In the display device of the embodiment 1, by forming the
light guide film 201a, the light semi-transmissive film 201b and
the reflective film 201c into the integral structure, the light 4
which is incident on the light guide film 201a is propagated while
repeating the reflection of light with high efficiency between the
interface with the light semi-transmissive film 201b and the
interface with the reflective film 201c. Here, the light
semi-transmissive film 201b is a member which reflects or refracts
the light (allows the light to pass through) corresponding to an
incident angle of the light which is propagated through the light
guide film 201a and is incident on the interface with the light
semi-transmissive film 201b. That is, on the interface between the
light guide film 201a and the light semi-transmissive film 201b, a
portion of the light which is incident on the interface is
reflected and is continuously propagated through the light guide
film 201a and a remaining portion of the light is radiated to the
display panel 1. Accordingly, the light radiation portion 201 of
the backlight may be formed of a film having a function equal to a
function of the light semi-transmissive film 201b in place of the
light semi-transmissive film 201b. As a member which has the
function equal to the function of the light semi-transmissive film
201b, a polarization reflective film can be named, for example.
[0086] The polarization reflective film is, for example, a member
whose polarization surface allows only a component of the light
which is directed in a certain direction to pass through and
reflects remaining components of the light. Accordingly, with the
use of the polarization reflective film in place of the light
semi-transmissive film 201b, out of the light which propagates
through the light guide film 201a, only the component which agrees
with a transmission axis (a polarization axis) of the polarization
reflective film passes through the polarization reflective film and
is radiated to the display panel 1. Then, the remaining components
are reflected and continuously propagated through the light guide
film 201a. The light which is reflected on the interface with the
polarization reflective film 201b is reflected on the interface
with the reflective film 201c and, again, is incident on the
interface with the polarization reflective film 201b. By allowing
the light which propagates through the light guide film 201a to
repeat the operation, the light 4 which is incident on the light
guide film 201a is converted into a planar light and is radiated to
the display panel 1.
[0087] Here, the light which is radiated to the display panel 1
from the light guide film 201a after passing through the
polarization reflective film is a light whose polarization surface
agrees with the transmission axis of the polarization reflective
film. Accordingly, in using the polarization reflective film, for
example, as shown in FIG. 3, when the polarization reflective film
201d is adhered to a surface of the light guide film 201a which
faces the display panel 1 in an opposed manner, a transmission axis
AX1 of the polarization reflective film 201d is directed in the
same direction as a transmission axis AX2 of the polarizer 3A which
is adhered to a surface of the display panel 1 which faces the
light radiation portion 201 in an opposed manner. Due to such a
constitution, the polarization surface of the light which is
radiated to the display panel 1 from the light guide film 201a
after passing through the polarization reflective film 201d agrees
with the transmission axis AX2 of the polarizer 3A which is
positioned in front of the display panel 1 and hence, the light is
allowed to pass through the polarizer 3A and to be incident on the
display panel 1.
[0088] Further, by setting a thickness of the polarization
reflective film 201d to 0.05 mm or less, for example, in the same
manner as the light semi-transmissive film 201b and by forming the
polarization reflective film 201d, the light guide film 201a and
the reflective film 201c into the integral structure, the light
radiation portion 201 of the backlight can be made thin and
light-weighted.
[0089] Here, in FIG. 3, the transmission axis AX1 of the
polarization reflective film 201d is arranged parallel to a side of
the light guide film 201a on which the light is incident. However,
provided that the direction of the transmission axis AX1 agrees
with the direction of the transmission axis AX2 of the polarizer 3A
which is adhered to the display panel 1, the transmission axis AX1
may be directed in any direction.
Embodiment 2
[0090] FIG. 4 is a schematic view showing the schematic
constitution of a backlight of an embodiment 2 according to the
present invention. Further, FIG. 5 is a cross-sectional view taken
along a line A-A' of FIG. 4.
[0091] In the embodiment 2, on the premise of the constitution of
the embodiment 1, a constitutional example of a light radiation
portion 201 which can obtain the in-plane uniformity of the
brightness (the light quantity) of light radiated on the display
panel 1 is explained.
[0092] Here, the light radiation portion 201 of the backlight is,
for example, as shown in FIG. 4 and FIG. 5, formed into the
integral structure by sandwiching the light guide film 201a between
the light semi-transmissive film 201b and the reflective film 201c.
A thickness of the light guide film 201a is set to 0.25 mm or less.
Further, thicknesses of the light semi-transmissive film 201b and
the reflective film 201c are respectively set to 0.05 mm or less,
for example. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are
respectively made of materials explained in conjunction with the
embodiment 1. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are formed
into the integral structure by the method explained in conjunction
with the embodiment 1.
[0093] Further, in this embodiment 2, a plurality of through holes
(through holes) TH is formed in a plurality of portions of the
semi-transmissive film 201b. The through holes TH are formed by
etching the light semi-transmissive film 201b, for example.
[0094] Further, the through holes TH are, for example, as shown in
FIG. 4, formed in such a state that a plurality of rows in which a
plurality of through holes TH is arranged in parallel to a side of
the light guide film 201a on which a region L on which light is
incident is formed is arranged in the propagation direction of the
light. Here, it is preferable to set intervals G1, G2, G3, G4, G5,
G6, G7 between the respective through holes TH in a state that the
remoter the interval from the side of the light guide film 201a on
which light is incident, the smaller the interval becomes as shown
in FIG. 4. Further, although the number of rows of the through
holes TH is eight in the example shown in FIG. 4, it is needless to
say that the number of rows may be other than eight.
[0095] When these through holes TH are formed in the light
semi-transmissive film 201b, for example, as shown in FIG. 5, the
light 4 which is incident on the light guide film 201a from a
certain position of the light guide film 201a propagates through
the light guide film 201a following a path indicated by a
solid-line arrow. Here, the light which is reflected on the
reflective film 201c and is incident on the interface with the
light semi-transmissive film 201b is incident on a region where the
through holes TH are formed. The light which is incident on the
region where the through holes TH are formed is refracted and is
radiated into inner spaces formed in the through holes TH. Then,
the light is reflected or is refracted on side surfaces of the
through holes TH and is radiated in the direction where the display
panel 1 is arranged. That is, by forming the through holes TH, the
light is irregularly reflected on the side surfaces of the through
holes TH and is radiated in the direction where the display panel 1
is arranged. Accordingly, in comparison with the case of the
embodiment 1, the in-plane uniformity of the brightness (light
quantity) of the light radiated to the display panel 1 is
enhanced.
[0096] Further, the light which propagates through the light guide
film 201a exhibits a large light quantity in a region closer to the
side on which the light is incident and the light quantity is
gradually decreased as the region is away from the side on which
the light is incident. Accordingly, as shown in FIG. 4, by
increasing the distribution density of the through holes TH in the
region remote from the side on which the light is incident thus
facilitating the irregular reflection of the light, the in-plane
uniformity of brightness (light quantity) of the light which is
radiated to the display panel 1 is further enhanced.
[0097] FIG. 6 is a schematic view for explaining a modification of
the embodiment 2.
[0098] In the backlight of the embodiment 2, for example, when the
light source of the light 4 which is incident on the light guide
film 201a is formed of a plurality of spot light sources, for
example, even in a region closer to the side on which the light is
incident, the light quantity is decreased between two spot light
sources in the side direction. Accordingly, in the backlight which
uses the plurality of spot light sources, it is preferable to
arrange the through holes TH of the light semi-transmissive film
201b in a state as shown in FIG. 6, for example.
[0099] FIG. 6 shows a case in which the spot light sources are
arranged on two regions L of the light guide film. With respect to
a point that a plurality of rows in which a plurality of through
holes TH is arranged in parallel with a side of the light guide
film 201a on which light is incident is arranged in the
transmission direction of the light, the constitution of the
embodiment 2 is similar to the constitution of the embodiment 1.
Further, in a region closer to the side on which the light is
incident, spreading of light from the spot light source is
insufficient and hence, a region where the light quantity is small
is formed between the spot light sources. Accordingly, by providing
more plurality of through holes TH in the region to increase the
distribution density of the through holes TH, it is possible to
further enhance the in-plane uniformity of the brightness (light
quantity) of light which is incident on the display panel 1.
[0100] In this manner, in the backlight of the embodiment 2, even
when the spot light sources are used, it is possible to enhance the
in-plane uniformity of the brightness (light quantity) of the light
radiated on the display panel 1.
[0101] FIG. 7 is a schematic view for explaining a variation of the
embodiment 2.
[0102] The embodiment 2 is configured to enhance the in-plane
uniformity of light radiated on the display panel 1 with irregular
reflection of light which is radiated in the direction of the
display panel 1 from the light guide film 201a. Here, as an example
of a method of reflecting light irregularly, as shown in FIG. 4 or
the like, an example which forms the through holes TH in the light
semi-transmissive film 201b is shown. However, instead of forming
the through holes TH in the light semi-transmissive film 201b, for
example, as shown in FIG. 7, it is possible to obtain the similar
advantageous effect by forming a pattern which irregularly reflects
the light (hereinafter referred to as an irregular reflection
pattern) RP on the interface between the light guide film 201a and
the reflective film 201c.
[0103] When such an irregular reflection pattern RP is formed on
the interface between the light guide film 201a and the reflective
film 201c, for example, as shown in FIG. 7, the light 4 which is
incident from a certain position of the light guide film 201a
propagates through the light guide film 201a following a path
indicated by a solid-line arrow. Here, the light reflected on the
irregular reflection pattern RP of the reflective film 201c changes
the path and the incident angle to the interface with the light
semi-transmissive film 201b is changed before and after the light
is reflected on the irregular reflection pattern RP. Here, the
incident angle of the light is decreased after the light is
reflected on the irregular reflection pattern. When the light is
incident at a deep angle, a portion of the light is refracted with
the interface with the light semi-transmissive film 201b and
radiated in the direction where the display panel 1 is arranged.
Accordingly, in the same manner as the case in which the through
holes TH are formed in the light semi-transmissive film, the
in-plane uniformity of the brightness (light quantity) of the light
radiated to the display panel 1 is enhanced.
[0104] Further, here, the light guide film 201a and the reflective
film 201c have the integral structure by being adhered using a
transparent optical adhesive agent, for example, and there is no
gap on the interface. Accordingly, it is possible to prevent the
increase of the loss of light due to the leaking of light from the
interface between the light guide film 201a and the reflective film
201c.
[0105] Here, when the irregular reflection pattern RP is formed at
the interface between the light guide film 201a and the reflective
film 201c, the irregular reflection pattern RP may be arranged, in
the same manner as the arrangement of the through holes TH in the
light semi-transmissive film 201b shown in FIG. 4 or FIG. 6, in a
state that the distribution density is higher in a region remoter
from the side of the light guide film 201a on which light is
incident or in a region between the spot light sources.
[0106] Further, although, in the embodiment 2, the explanation is
made with respect to the example in which the light
semi-transmissive film 201b is used, it is needless to say that the
polarization reflective film 201d may be used in place of the light
semi-transmissive film 201b.
[0107] Further, although, in the embodiment 2, for example, as
shown in FIG. 4, the through holes TH are arranged in a row, it is
needless to say that the through holes TH may be arranged at
arbitrary positions.
Embodiment 3
[0108] FIG. 8 is a schematic view showing the schematic
constitution of a backlight of an embodiment 3 according to the
present invention. Further, FIG. 9 is a cross-sectional view taken
along a line B-B' in FIG. 8.
[0109] In the embodiment 3, a constitutional example of the light
radiation portion 201 which enables the in-plane uniformity of the
brightness (light quantity) of the light radiated on the display
panel 1 on the premise of the constitution of the embodiment 1 and
in a method different from the embodiment 2 is explained.
[0110] Here, the light radiation portion 201 of the backlight is,
as shown in FIG. 8 and FIG. 9, formed in the integral structure by
sandwiching the light guide film 201a between the light
semi-transmissive film 201b and the reflective film 201c. The
thickness of the light guide film 201a is set to 0.25 mm and less.
Further, the thicknesses of the light semi-transmissive film 201b
and the reflective film 201c are respectively set to 0.05 mm or
less. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are made
of the materials which are explained in the embodiment 1. Further,
the light guide film 201a, the light semi-transmissive film 201b
and the reflective film 201c are formed in the integral structure
in such a manner which is explained in conjunction with the
embodiment 1.
[0111] Further, in the case of embodiment 3, the light
semi-transmissive film 201b is provided with a pattern which blocks
light on a plurality of portions (hereinafter, referred to as a
light blocking pattern) BP. This light blocking pattern BP is, for
example, formed by printing the white ink or the like.
[0112] Further, the light blocking patterns BP are, for example, as
shown in FIG. 8, formed in such a state that a plurality of rows in
which a plurality of light blocking patterns BP is arranged in
parallel to a side of the light guide film 201a on which a region L
on which light is incident is formed is arranged in the
transmission direction of the light. Here, as shown in FIG. 8 it is
preferable to set intervals between the respective light blocking
patterns BP G1, G2, G3, G4, G5, G6, G7 in a state that the remoter
the interval from the side of the light guide film 201a on which
the light is incident, the smaller the gap becomes. Further,
although the number of rows of the light blocking patterns BP is
eight in an example shown in FIG. 8, it is needless to say that the
number may be other than eight.
[0113] When the light blocking patterns BP are provided to the
light semi-transmissive film 201b, for example, as shown in FIG. 9,
the light 4 which is incident from a certain position of the light
guide film 201a propagates through the light guide film 201a
following a path indicated by a solid-line arrow. Here, the light
which is reflected on the reflective film 201c and is incident on
the interface with the light semi-transmissive film 201b is blocked
(reflected) with the light blocking patterns BP and hence, the
light is not radiated in the direction where the display panel is
arranged after propagating through the light transmissive film
201b. That is, by providing the light blocking patterns BP, it is
possible to limit the light quantity of the light radiated in the
direction where the display panel 1 is arranged. Accordingly,
compared to the case of the embodiment 1, the in-plane uniformity
of the brightness (light quantity) of the light radiated on the
display panel 1 is enhanced.
[0114] Further, here, the light which propagates through the light
guide film 201a exhibits a large light quantity in a region closer
to the side on which the light is incident and the light quantity
is gradually decreased as the region recedes from the side on which
the light is incident. Accordingly, as shown in FIG. 8, by
increasing the distribution density of the light blocking patterns
BP in the region close to the side on which the light is incident
and by decreasing the light quantity of the light radiated in the
direction where the display panel 1 is arranged, the in-plane
uniformity of the brightness (light quantity) of the light radiated
on the display panel is further enhanced.
[0115] FIG. 1 is a schematic view for explaining a modification of
the embodiment 3.
[0116] In the backlight of the embodiment 3, for example, when the
light source of the light 4 which is incident on the light guide
film 201a is formed of a plurality of spot light sources, for
example, even in the region closer to the side on which the light
is incident, the light quantity is decreased between two spot light
sources in the side direction. Accordingly, in the backlight which
uses the plurality of light sources, it is preferable to arrange
the light blocking patterns BP in a state as shown in FIG. 10, for
example.
[0117] FIG. 10 shows a case in which the spot light sources are
arranged on two regions L of the light guide film 201a. With
respect to a point that a plurality of rows in which a plurality of
light blocking patterns BP is arranged in parallel to a side of the
light guide film 201a on which the light is incident is arranged in
the propagating direction of the light, the constitution of the
embodiment 3 is similar to the constitution of the embodiment 1.
Further, in a region closer to the side on which the light is
incident, spreading of light from the spot light source is
insufficient and hence, a region where the light quantity is small
is formed between the spot light sources. Accordingly, by
increasing the distribution density of the light blocking pattern
in the region immediately front of the spot light source where the
light quantity is large in the region close to the side where the
light is incident, it is possible to further enhance the in-plane
uniformity of the brightness (light quantity) of light which is
incident on the display panel 1.
[0118] In this manner, in the backlight of the embodiment 3, even
when the spot light sources are used, it is possible to enhance the
in-plane uniformity of the brightness (light quantity) of the light
radiated on the display panel.
[0119] Further, although, in the embodiment 3, the explanation is
made with respect to the example in which the light
semi-transmissive film 201b is used, it is needless to say that the
polarization reflective film 201d may be used in place of the light
semi-transmissive film 201b.
[0120] Further, although, in the embodiment 3, for example, as
shown in FIG. 8, the light blocking patterns BP are arranged in a
row, it is needless to say that the light blocking patterns BP may
be arranged at arbitrary positions.
Embodiment 4
[0121] FIG. 11 is a schematic view showing the schematic
constitution of the backlight of the embodiment 4 according to the
present invention. Further, FIG. 12 is a cross-sectional view taken
along a line C-C' in FIG. 11. Further, FIG. 13 is across-sectional
view taken along a line D-D' in FIG. 11. Here, FIG. 11 shows a
front view of the backlight and a side view of the lower side of
the backlight.
[0122] In the embodiment 4, on the premise of the constitution of
the light radiation portion 201 of the backlight which is explained
in conjunction with the embodiment 1 to the embodiment 3, a
constitutional example of a backlight including a light source of
light which is incident on the light guide film 201a.
[0123] Here, the light radiation portion 201 of the backlight is,
as shown in FIG. 11 to FIG. 13, formed in the integral structure by
sandwiching the light guide film 201a between the light
semi-transmissive film 201b and the reflective film 201c. The
thickness of the light guide film 201a is set to 0.25 mm or less.
Further, the thicknesses of the light semi-transmissive film 201b
and the reflective film 201c are respectively set to 0.05 mm or
less, for example. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are
respectively made of materials explained in conjunction with the
embodiment 1. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are formed
in the integral structure in such a manner which is explained in
conjunction with the embodiment 1.
[0124] Further, here, the light radiation portion 201 may have, for
example, through holes TH formed in the light semi-transmissive
film 201b at a plurality of positions in the same manner as the
embodiment 2. Further, in place of the through holes TH, for
example, an irregular reflection pattern RP may be provided with
the interface between the light guide film 201a and the reflective
film 201c. Further, for example, in the same manner as the
embodiment 3, light blocking patterns BP may be provided with the
interface between the light semi-transmissive film 201b and the
light guide film 201a.
[0125] A light source of light 4 which is incident on the light
guide film 201a is formed of a spot light source 202 such as an
LED, for example. The spot light sources 202 are mounted on a
flexible circuit board 203, for example. Here, the flexible circuit
board 203 on which the spot light sources 202 are mounted is
arranged on, for example, on the light semi-transmissive film 201b
of the light radiation portion 201, and outside a region where the
light is radiated to a display region of the display panel 1
(hereinafter referred to as a radiation region) IR. Further, the
spot light sources 202 on the flexible circuit board 203 use a
side-view-type LED, for example, and are mounted in a state that
the light is radiated in the film surface direction of the light
guide film 201a and in the direction opposite to radiation region
IR.
[0126] Further, here, a reflector 204 is provided to an end portion
of the light guide film 201a on a side on which the spot light
sources 202 are arranged. The light 4 which is radiated from the
spot light source 202 is, as shown in FIG. 14 and FIG. 15,
reflected on a reflective surface 204a of the reflector 204 and
changes the direction thereof to the radiation region IR and,
thereafter, is incident on the light guide film 201a. The manner in
which the incident light 4 propagates through the light guide film
201a is the same manner as explained in conjunction with the
embodiments 1 to 3 and hence, the detailed explanation is
omitted.
[0127] Here, in the embodiment 4, the spot light source 202 such as
LED is used as the spot light source, and this LED is usually
configured such that the spreading of radiated light 4 is small to
enhance the brightness. Accordingly, out of the reflective surfaces
204a of the reflection plate 204, by forming the surface which
faces the light radiation surface of the spot light source 202 in
an opposed manner, for example, to project to the spot light source
202 side as shown in FIG. 13, it is possible to spread the light of
the spot light source 202. Due to such a constitution, it is
possible to effectively propagate the light to a region between two
spot light sources 202.
[0128] FIG. 14A and FIG. 14B are schematic views for explaining a
modification of the embodiment 4, wherein FIG. 14A is a front view
of a backlight and FIG. 14B is a side view of a lower portion of
the backlight. Further, FIG. 15 is a cross-sectional view taken
along a line E-E' in FIG. 14A, and FIG. 16 is a cross-sectional
view taken along a line F-F' in FIG. 14B.
[0129] The backlight of the embodiment 4 uses the spot light source
202 formed of a side-view-type LED, wherein light radiated toward
the film surface of a light guide film 201a from the spot light
source 202 is reflected on the reflector 204 and is incident on the
light guide film 201a. Here, for example, as shown in FIG. 13, by
forming a reflection surface 204a which forms a convex curved
surface on a spot-light-source-202 side of the reflector 204, the
light radiated from the spot light source 202 can be spread.
However, this embodiment is not limited to the reflective surface
204a having the convex curved surface shown in FIG. 13 and, it is
possible to spread the light radiated from the spot light source
202 by also using a reflective surface 204b which projects toward
the spot-light-source-202 side by combining planar surfaces shown
in FIG. 14 to FIG. 16, for example.
[0130] FIG. 17 is a schematic view for explaining one advantageous
effect of the backlight of the embodiment 4. Further, FIG. 18 is a
schematic view showing a constitutional example of a display device
which uses a conventional general backlight for comparison with the
backlight of the embodiment 4.
[0131] The backlight of the embodiment 4 is integrally constituted
of the light guide film 201a, the light semi-transmissive film 201b
and the reflective film 201c thus reducing a thickness of the light
radiation portion 201. Further, the spot light source 202 of the
light which is incident on the light guide film 201a is formed on
the light guide film 201a, and is arranged outside a radiation
region IR which radiates the light to the display panel 1.
Accordingly, in the display device which uses the backlight of the
embodiment 4, for example, as shown in FIG. 17, it is possible to
arrange the spot light source 202 and the reflector 204 in the
direction toward the side surface of the display panel 1. Due to
such a constitution, it is possible to absorb an amount of
thickness corresponding to a height of the flexible printed circuit
board 203 and the height of the mounted spot light source 202 which
is arranged over the light semi-transmissive film 201b and hence, a
thickness Td of the structure obtained by overlapping the display
panel 1 and the backlight (the light radiation portion 201) to each
other can be reduced.
[0132] The conventional display device uses the light guide plate
formed by injection molding, for example, and the spot light source
202 is arranged on a side surface of the light guide plate 201e as
shown in FIG. 18. By providing such a constitution to the
backlight, the thickness of the light guide plate 201e becomes
approximately 0.4 mm, for example. Accordingly, a thickness Te of
the structure obtained by overlapping the display panel 1 and the
backlight (the light radiation portion 201) to each other becomes
approximately 1.06 mm, for example.
[0133] On the other hand, in case of the display device which uses
the backlight of the embodiment 4, the thickness of the light
radiation portion 201 of the backlight becomes 0.35 mm or less.
Accordingly, the thickness Td of the structure obtained by
overlapping the display panel 1 and the backlight (the light
radiation portion 201) to each other becomes approximately 0.95
mm.
[0134] In view of the above, with the use of the backlight of the
embodiment 4, the display device can be made thin and
light-weighted, and the in-plane uniformity of a light quantity of
the radiation region IR is enhanced.
[0135] Here, in this embodiment 4, a case which uses the light
semi-transmissive film 201b is exemplified. However, it is needless
to say that a polarization reflective film 201d may be used in
place of the light semi-transmissive film 201b.
Embodiment 5
[0136] FIG. 19 is a schematic view showing the schematic
constitution of a backlight of an embodiment 5 according to the
present invention, FIG. 20 is a cross-sectional view taken along a
line G-G' in FIG. 19, and FIG. 21 is a schematic view for
explaining a mounting method of an incident-light adjusting
member.
[0137] In the embodiment 5, on the premise of the constitution of
the light radiation portion 201 of the backlight explained in
conjunction with the embodiment 1 to embodiment 3, another
constitutional example of the backlight which includes the light
source of light incident on the light guide film 201a is
explained.
[0138] Here, the light radiation portion 201 of the backlight is,
as shown in FIG. 19 and FIG. 20, formed into the integral structure
in which the light guide film 201a is sandwiched between the light
semi-transmissive film 201b and a reflective film 201c. A thickness
of the light guide film 201a is set to 0.25 mm or less. Further,
thicknesses of the light semi-transmissive film 201b and the
reflective film 201c are respectively set to 0.05 mm or less, for
example. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are
respectively made of the material which has been explained in
conjunction with the embodiment 1, for example. Further, the light
guide film 201a, the light semi-transmissive film 201b and the
reflective film 201c are formed into the integral structure using
the method explained in conjunction with the embodiment 1.
[0139] Further, in the light radiation portion 201, through holes
TH may be formed in a plurality of portions of the light
semi-transmissive film 201b as in the case of the embodiment 2, for
example. Further, in place of the through holes TH, an irregular
reflection pattern RP may be provided to an interface between the
light guide film 201a and the reflective film 201c. Still further,
for example, as in the case of the embodiment 3, a light blocking
pattern BP may be provided to an interface between the light
semi-transmissive film 201b and the light guide film 201a.
[0140] Further, a light source of light 4 which is incident on the
light guide film 201a may be a spot light source 202 formed of an
LED, for example. The spot light source 202 may be mounted on the
flexible printed circuit board 203, for example. Here, the flexible
printed circuit board 203 on which the spot light source 202 is
mounted is arranged on a side of the light radiation portion 201
(the light guide film 201a) to which the reflective film 201c is
provided, for example and, at the same time, outside a radiation
region IR which radiates light to a display region of a display
panel 1. Here, the spot light source 202 on the flexible printed
circuit board 203 is formed of a top-view type LED, for example,
and is mounted so as to radiate light in the direction
perpendicular to the film-surface direction of the light guide film
201a.
[0141] Here, between the light guide film 201a and the spot light
source 202, an incident-light adjusting member 205 which forms a
plurality of projections 205a on a surface thereof which faces the
light guide film 201a in an opposed manner is interposed. The
incident-light adjusting member 205 is made of a material equal to
a material of the light guide film 201a. Further, the
incident-light adjusting member 205 has a distal end of the
projection 205a thereof formed in a flat surface shape and is
brought into close contact with a film surface of the light guide
film 201a.
[0142] The incident-light adjusting member 205 may preferably be
formed of a film having a thickness of 0.1 mm to 0.2 mm including
the projections 205a, for example. Further, the projections 205a
may be formed by photolithography, for example.
[0143] Further, distal end surfaces of the projections 205a of the
incident-light adjusting member 205 may be brought into close
contact with the light guide film 201a by, for example, as shown in
FIG. 21, applying an optical adhesive agent 206 to the distal end
surfaces of the projections 205a and adhering the distal end
surfaces of the projections 205a on the film surfaces of the light
guide film 201a.
[0144] Further, the projections 205a of the incident-light
adjusting member 205 may be formed of columnar projections having
curved bottom surfaces as shown in FIG. 19, for example. Further,
the projections 205a of the incident-light adjusting member 205
may, for example, as shown in FIG. 20, have side surfaces thereof
on a side opposite to the radiation region IR formed into a convex
curved shape.
[0145] Further, in the backlight shown in the embodiment 5, it is
preferable to provide a reflective sheet 207 which is overlapped to
the incident-light adjusting member 205 to a surface of the light
guide film 201a to which the light semi-transmissive film 201b is
provided.
[0146] FIG. 22 is a schematic view for explaining the manner of
operation of the backlight of the embodiment 5.
[0147] The manner of operation of the backlight of the embodiment 5
is explained in conjunction with FIG. 22. Here, FIG. 22 is an
enlarged cross-sectional view of a region AR1 shown in FIG. 20.
[0148] In the backlight of the embodiment 5, a spot light source
202 such as the LED is, as shown in FIG. 20, arranged such that the
spot light source 202 radiates light in the direction perpendicular
to the film surface of the light guide film 201a. Accordingly, in
such a state, a light from the spot light source 202 exhibits a
small incident angle with respect to the light guide film 201a and
hence, it is impossible to make the incident light 4 propagate into
the radiation region IR. Accordingly, between the spot light source
202 and the light guide film 201a, the incident-light adjusting
member 205 having the projections 205a shown in FIG. 22 is
interposed. Here, the light 4 which is radiated in the direction
perpendicular to the film surface of the light guide film 201a is,
for example, as shown in FIG. 22, reflected on the convex curved
surfaces of the projections 205a of the incident-light adjusting
member 205 on a side opposite to the radiation region IR thus
changing an advancing path thereof and, thereafter, the light 4 is
incident on the light guide film 201a. The manner in which the
incident light propagates through the light guide film 201a is
exactly as same as the manner of propagation of the incident light
explained in conjunction with the embodiment 1 to embodiment 3 and
hence, the detailed explanation is omitted.
[0149] Here, the convex curved surface of the projection 205a of
the incident-light adjusting member 205 adopts a shape which allows
a reflection angle .theta. of the light on the convex curved shape
to satisfy a following formula (1). .theta.=i/2>(arcsin(1/n))/2
(1)
[0150] Here, in the formula (1), "i" indicates an incident angle of
the light on the interface between the light guide film 201a and
the light semi-transmissive film 201b, and "n" indicates a
refractive index of the incident-light adjusting member 205 and the
light guide film 201a.
[0151] The light which is radiated from the spot light source 202
such as the LED exhibits the largest component in the direction
perpendicular to the film surface of the light guide film 201a.
However, by forming the light components other than the light
component in the perpendicular direction to have the shape which
satisfies the formula (1), it is possible to allow such light
components to be effectively incident on the light guide film
201a.
[0152] Further, for example, among the light which is radiated in
the direction perpendicular to the film surface of the light guide
film 201a, there exists light which passes through a portion
different from the convex curved shape of the projection 205a. In
this case, the light is incident perpendicular to the film surface
of the light guide film 201a and hence, the light is not reflected
on the interface with the light semi-transmissive film 201b whereby
the light passes through the light semi-transmissive film 201b.
Accordingly, by providing a reflective sheet 207 to a region on the
light semi-transmissive film 201b which is overlapped to the
incident-light adjusting member 205, the light which passes through
the light semi-transmissive film 201b is reflected on the
reflective sheet 207 thus allowing the incidence of the light on
the light guide film 201a again.
[0153] FIG. 23 is a schematic view showing one example of a method
for adhering the spot light source and the incident-light adjusting
member 205 in the embodiment 5. Further, FIG. 24 is a
cross-sectional view taken along a line H-H' in FIG. 23.
[0154] In the backlight of the embodiment 5, it is preferable to
adhere the spot light source 202 such as the LED to the
incident-light adjusting member 205 using an annular adhesive agent
208 as shown in FIG. 23 and FIG. 24, for example. Here, the annular
adhesive agent 208 may be provided to an outermost periphery of a
light radiation surface of the spot light source 202 for preventing
the blocking of light from the light emitting element (LED chip)
202a which the spot light source 202 possesses.
[0155] FIG. 25 is a schematic view showing one example of the
arrangement of the backlight and the display panel of the
embodiment 5. Further, FIG. 26 is a schematic view showing another
example of the arrangement of the backlight and the display panel
of the embodiment 5.
[0156] In the backlight of the embodiment 5, for example, as shown
in FIG. 20, the incident-light adjusting member 205 and the spot
light source 202 are arranged on a surface side of the light guide
film 201a on which the reflective film 201c is arranged. Here, the
display panel 1 is arranged on a surface side of the light guide
film 201a to which the light semi-transmissive film 201b is
provided. Accordingly, as shown in FIG. 25, the spot light source
202 is arranged on the back surface of the light radiation portion
201 of the backlight.
[0157] By adopting such an arrangement, for example, it is also
possible to arrange the incident-light adjusting member 205 such
that the incident-light adjusting member 205 is overlapped to the
display panel 1 partially or as a whole. Accordingly, a region of
the display device outside the display region, so-called a picture
frame region can be made small.
[0158] Here, in the backlight of the embodiment 5, the spot light
source 202 and the incident-light adjusting member 205 may be, for
example, as shown in FIG. 26, arranged on a surface side of the
light guide film 201a to which the light semi-transmissive film
201b is provided.
[0159] FIG. 27 is a schematic view for explaining a first variation
of the embodiment 5.
[0160] In explaining the constitution of the backlight of the
embodiment 5, the case in which one spot light source 202 is
arranged is exemplified as shown in FIG. 19, for example. However,
the present invention is not limited to such backlight constitution
and, for example, two spot light sources 202 may be arranged as
shown in FIG. 27. Further, although not shown in the drawing, it is
needless to say that three or more spot light sources 202 may be
arranged.
[0161] FIG. 28 is a schematic view for explaining a second
variation of the embodiment 5.
[0162] In explaining the constitution of the backlight of the
embodiment 5, for example, as shown in FIG. 20, the case in which
the reflective sheet 207 which is overlapped to the incident-light
adjusting member 205 is adhered to the light semi-transmissive film
201b is exemplified. However, the present invention is not limited
to the backlight constitution and, for example, as shown in FIG.
28, a prism sheet 209 may be arranged between the light
semi-transmissive film 201b and the reflective sheet 207. By
arranging the prism sheet 209 in such a manner, light which is
reflected on the reflective sheet 207 after passing through the
light semi-transmissive film 201b is allowed to be incident on the
light guide film 201a again by setting a certain incident angle
thus further enhancing the utilization efficiency of the light.
[0163] Further, although the explanation using drawings may be
omitted, it is needless to say that the arrangement of the
plurality of projections 205a of the incident-light adjusting
member 205 is not limited to the arrangement in a matrix array as
shown in FIG. 19, for example. With respect to the arrangement of
the projections, it may be possible to adopt a method in which a
plurality of projections 205a are arranged on curved lines which
project in the direction toward the radiation region IR such as
concentric circumferences about a certain point, for example.
Embodiment 6
[0164] FIG. 29 is a schematic view showing the schematic
constitution of a backlight of an embodiment 6 according to the
present invention. Further, FIG. 30 is a cross-sectional view taken
along a line J-J' in FIG. 29.
[0165] The backlight of the embodiment 6 is a backlight of another
modification of the embodiment 5, wherein the constitution of the
light source 202 and the vicinity of the light source 202 is equal
to the corresponding constitution of the backlight of the
embodiment 5. A point which makes this embodiment 6 different from
5 lies in the constitution of the radiation region IR of the light
guide film 201a.
[0166] In the backlight of this embodiment 6, for example, as shown
in FIG. 29 and FIG. 30, to a film surface of a light guide film
201a, a light semi-transmissive member 201b or a polarization
reflective film 201d, and a reflective film 201c are not adhered.
In place of such a constitution, a radiation-light adjusting member
201f is provided to one film surface of the light guide film 201a,
that is, the surface of the light guide film 201a which faces the
display panel 1 in an opposed manner. The radiation-light adjusting
member 201f is a member which adjusts a radiation angle of the
light which is radiated from the film surface of the light guide
film 201a and is radiated to the display panel 1.
[0167] Further, the radiation-light adjusting member 201f has
substantially the same constitution as the incident-light adjusting
member 205, for example, wherein the radiation-light adjusting
member 201f has one, two or more projections on a surface thereof
which faces the light guide film 201a in an opposed manner, and
distal-end surfaces of the projections are brought into contact
with a film surface of the light guide film 201a. Here, although
the projections are arranged only in a region close to the light
source 202, in an actual arrangement, the projections similar to
the projections shown in FIG. 29 and FIG. 30 are arranged over the
whole region of the radiation-light adjusting member 201f. Here,
the radiation-light adjusting member 201f may preferably be formed
of a film having a thickness of 0.05 mm including the projections,
for example. Further, the projections may be formed by
photolithography, for example.
[0168] Further, distal end surfaces of the projections of the
radiation-light adjusting member 201f may be brought into close
contact with the light guide film 201a by, for example, applying an
optical adhesive agent to the distal end surfaces of the
projections and adhering the distal end surfaces of the projections
on the film surfaces of the light guide film 201a.
[0169] Further, the projections of the radiation-light adjusting
member 201f may be formed of columnar projections having curved
bottom surfaces as shown in FIG. 29, for example. Further, the
projections of the radiation-light adjusting member 201f may, for
example, as shown in FIG. 30, have side surfaces thereof on a side
opposite to the light source 202 formed into a convex curved
shape.
[0170] Here, also in the backlight of the embodiment 6, a thickness
of the light guide film 201a is set to 0.25 mm or less. Further,
the light guide film 201a may be made of polycarbonate (PC) having
a refractive index of 1.59.
[0171] The backlight of the embodiment 6 does not use the light
semi-transmissive film 201b or the polarization reflective film
201d and the reflective member 201c. However, the refractive index
of the light guide film 201a is larger than the refractive index of
air and hence, the light 4 which is incident on the light guide
film 201a after passing through the incident-light adjusting member
205 repeats the total reflection on the film surface, that is, on
an interface between the light guide film 201a and air and
propagates in the inside of the light guide film 201a.
[0172] Here, at portions where the projections of the
radiation-light adjusting member 201f and the light guide film 201a
are brought into contact with each other, the refractive index is
substantially equal and hence, no total reflection occurs whereby
the light 4 advances to the inside of the projections of the
radiation-light adjusting member 201f directly. Then, the light 4
which enters the inside of the projections are reflected on the
interfaces between the side surfaces of the projections and air
and, thereafter, is radiated in the direction toward the display
panel 1.
[0173] In this manner, according to the backlight of the embodiment
6, with the use of the radiation-light adjusting member 201f in
place of the light semi-transmissive film 201b or the polarization
reflective film 201d and the reflective film 201c, it is possible
to obtain the advantageous effects substantially equal to the
advantageous effects obtained by the backlight of the embodiment 5.
Accordingly, it is possible to decrease kinds of sheets (films)
which are adhered to the light guide film 201a and hence, the light
guide film 201a can reduce the thickness thereof thus realizing the
backlight at a low cost.
[0174] Although the present invention has been specifically
explained in conjunction with the embodiments, it is needless to
say that the present invention is not limited to the
above-mentioned embodiments and various modifications are
conceivable without departing from the gist of the present
invention.
[0175] The backlights which have been explained in conjunction with
respective embodiments are thin and light-weighted and, at the same
time, exhibit high brightness uniformity of the radiation surface.
Accordingly, the constitutions of the backlights which are
exemplified in the respective embodiments may not be limited to the
light source of the display device such as the liquid crystal
display device and may be applicable to a planar light source
device (unit) such as illumination equipment, for example.
* * * * *