U.S. patent application number 12/113448 was filed with the patent office on 2008-12-25 for light guide plate, method of manufacturing the same, and liquid crystal display device including the same.
This patent application is currently assigned to Samsung Electronics Co. Ltd.. Invention is credited to In-Sun Hwang, Heu-Gon Kim, Hyoung-Joo Kim, Taek-Sun Shin, Byung-Seo Yoon.
Application Number | 20080319715 12/113448 |
Document ID | / |
Family ID | 40137404 |
Filed Date | 2008-12-25 |
United States Patent
Application |
20080319715 |
Kind Code |
A1 |
Kim; Hyoung-Joo ; et
al. |
December 25, 2008 |
LIGHT GUIDE PLATE, METHOD OF MANUFACTURING THE SAME, AND LIQUID
CRYSTAL DISPLAY DEVICE INCLUDING THE SAME
Abstract
A light guide plate includes a light incident surface to which
light is incident as incident light, an opposite surface formed
opposite to the light incident surface, a light emitting surface
through which the incident light is emitted, a rear surface formed
opposite to the light emitting surface and including a prism
pattern which reflects the incident light to the light emitting
surface, and lateral surfaces, wherein a diffuse reflection pattern
is formed on at least any one of the light emitting surface and the
lateral surfaces to diffuse-reflect light incident to the lateral
surfaces, thus rendering a brightness at both the opposite surface
and the light incident surface substantially uniform.
Inventors: |
Kim; Hyoung-Joo; (Uiwang-si,
KR) ; Kim; Heu-Gon; (Yongin-si, KR) ; Hwang;
In-Sun; (Suwon-si, KR) ; Shin; Taek-Sun;
(Cheonan-si, KR) ; Yoon; Byung-Seo; (Incheon,
KR) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
Samsung Electronics Co.
Ltd.
Suwon-si
KR
|
Family ID: |
40137404 |
Appl. No.: |
12/113448 |
Filed: |
May 1, 2008 |
Current U.S.
Class: |
703/1 ;
359/599 |
Current CPC
Class: |
G02B 6/0061 20130101;
G02B 6/0038 20130101; G02B 6/0036 20130101; G02F 1/133615 20130101;
G02B 6/0025 20130101; G02B 6/0043 20130101; G02B 6/0068
20130101 |
Class at
Publication: |
703/1 ;
359/599 |
International
Class: |
G02B 5/02 20060101
G02B005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2007 |
KR |
10-2007-0061513 |
Claims
1. A light guide plate comprising: a light incident surface to
which light is incident as incident light; an opposite surface
formed opposite to the light incident surface; a light emitting
surface through which the incident light is emitted; a rear surface
formed opposite to the light emitting surface and including a prism
pattern to reflect the incident light to the light emitting
surface; and lateral surfaces, wherein a diffuse reflection pattern
is formed on at least any one of the light emitting surface and the
lateral surfaces to diffuse-reflect light incident to the lateral
surfaces, thus rendering a brightness adjacent both the opposite
surface and the light incident surface substantially uniform.
2. The light guide plate of claim 1, wherein an area of the diffuse
reflection pattern is reduced as a distance increases from the
light incident surface toward the opposite surface.
3. The light guide plate of claim 2, wherein the diffuse reflection
pattern has an average roughness decreased as a distance increases
from the light incident surface toward the opposite surface.
4. The light guide plate of claim 3, wherein the diffuse reflection
pattern is formed in a range of about 80% to about 95% of a length
from the light incident surface to the opposite surface.
5. The light guide plate of claim 1, wherein the prism pattern
comprises a plurality of intaglio prism lines extending
substantially parallel to the light incident surface.
6. The light guide plate of claim 5, wherein a size of the intaglio
prism lines gradually increases as a distance increases from the
light incident surface toward the opposite surface.
7. The light guide plate of claim 6, wherein the size of at least
any one of the intaglio prism lines formed in a region adjacent to
the opposite surface decreases as a distance increases from the
lateral surfaces to a central region thereof.
8. The light guide plate of claim 5, wherein the light emitting
surface further comprises a second prism pattern including a
plurality of relief prism lines, in which a groove and a projection
are repeatedly formed, and which extend in a direction crossing a
direction of extension of the intaglio prism lines.
9. The light guide plate of claim 1, wherein the rear surface
further comprises at least one reflection pattern formed in a prism
shape between prism lines of the prism pattern to reflect light to
the light emitting surface.
10. The light guide plate of claim 9, wherein the reflection
pattern is formed within a region of the rear surface occupying
about 10% of a length between the lateral surfaces, and the region
is disposed adjacent at least one of the lateral surfaces.
11. The light guide plate of claim 10, wherein the reflection
pattern is formed in any one of relief and intaglio patterns.
12. The light guide plate of claim 11, wherein the reflection
pattern has a vertex angle in a range of about 130.degree. to about
140.degree..
13. The light guide plate of claim 12, wherein the reflection
pattern has a height in a range of about 1 .mu.m to about 10 .mu.m
from the rear surface and a width in a range of several tens to
several hundreds of micrometers.
14. The light guide plate of claim 13, wherein a number of
reflection patterns increases as a distance increases from the
light incident surface toward the opposite surface.
15. The light guide plate of claim 13, wherein at least any one of
the height and the width of the reflection pattern gradually
increases as a distance increases from the light incident surface
toward the opposite surface.
16. A liquid crystal display device comprising: a liquid crystal
panel displaying an image; a light source generating light; and a
light guide plate including a light incident surface to which the
light supplied from the light source is incident as incident light,
an opposite surface formed opposite to the light incident surface,
a light emitting surface through which the incident light is
emitted, a rear surface formed opposite to the light emitting
surface and including a prism pattern which reflects the incident
light to the light emitting surface, and lateral surfaces, wherein
a diffuse reflection pattern is formed on at least any one of the
light emitting surface and the lateral surfaces to diffuse-reflect
light incident to the lateral surfaces, thus rendering a brightness
at both the opposite surface and the light incident surface
substantially uniform.
17. The liquid crystal display device of claim 16, wherein the
diffuse reflection pattern of the light guide plate is formed in a
range of about 80% to about 95% of a length from the light incident
surface to the opposite surface.
18. The liquid crystal display device of claim 17, wherein the
prism pattern is formed with a plurality of intaglio prism lines
extending substantially parallel to the light incident surface on
the rear surface, and wherein a height of the intaglio prism lines
formed in a region adjacent to the opposite surface decreases as a
distance increases from the lateral surfaces to a central region
thereof.
19. The liquid crystal display device of claim 18, wherein the
light guide plate further comprises at least one reflection pattern
projected in a prism shape from the rear surface.
20. A method of manufacturing a light guide plate, the method
comprising: forming a light incident surface to which light is
incident, an opposite surface formed opposite to the light incident
surface, a light emitting surface through which incident light is
emitted, a rear surface formed opposite to the light emitting
surface, and lateral surfaces; forming a prism pattern including a
plurality of intaglio prism lines on the rear surface; and forming
a diffuse reflection pattern on at least any one of the light
emitting surface and the lateral surfaces to diffuse-reflect light
incident to the lateral surfaces, thus rendering a brightness at
both the opposite surface and the light incident surface
substantially uniform.
21. The method of claim 20, where, in forming the diffuse
reflection pattern, the diffuse reflection pattern is formed in a
range of about 80% to about 95% of a length from the light incident
surface to the opposite surface.
22. The method of claim 20, wherein forming the prism pattern
including a plurality of intaglio prism lines on the rear surface
further comprises forming a reflection pattern in any one of relief
and intaglio patterns on the rear surface to reflect light incident
between the intaglio prism lines to the light emitting surface.
Description
[0001] This application claims priority to Korean Patent
Application No. 10-2007-0061513, filed on Jun. 22, 2007, and all
the benefits accruing therefrom under 35 U.S.C. .sctn.119, the
contents of which in its entirety are herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a light guide plate, a
method of manufacturing the same, and a liquid crystal display
("LCD") device including the same, and, more particularly, to a
light guide plate emitting light with uniform brightness, a method
of manufacturing the light guide plate, and an LCD device including
the light guide plate.
[0004] 2. Description of the Related Art
[0005] In general, an LCD device displays an image using a liquid
crystal. The liquid crystal has electrical characteristics in which
the alignment is changed according to the direction and intensity
of an electric field, and optical characteristics in which the
light transmittance is changed according to the alignment.
[0006] FIG. 1 is a plan view of a conventional LCD device in which
the positions of test points for measuring brightness are
shown.
[0007] The LCD device includes a liquid crystal panel 10 and a
backlight unit. The liquid crystal panel 10 displays an image using
light and a backlight unit provides the light to the liquid crystal
panel 10.
[0008] The liquid crystal panel 10 includes a color filter
substrate including a color filter array, a thin film transistor
("TFT") substrate including a TFT array, and a liquid crystal
disposed between the two substrates. The backlight unit includes a
light source generating light, such as lamp 28, a light guide plate
guiding the light from the light source to the liquid crystal panel
10, and a plurality of optical sheets.
[0009] The backlight unit is formed on the rear surface of the
liquid crystal panel 10 to provide light to the liquid crystal
panel 10. In the conventional backlight unit, the amount of emitted
light is reduced as a distance increases from the lamp 28 as the
light source. Accordingly, there occurs a defect such as a bright
line in which the region adjacent to the lamp 28 is displayed
brighter than the periphery in an effective display area displaying
an image. That is, as shown in FIG. 2, test points 1, 6, 11, 16 and
21 positioned at the right side of the liquid crystal panel 10 and
test points 5, 10, 15, 20 and 25 positioned at the left side of the
liquid crystal panel 10 have brightness lower than test points in
the center of the display area, such as test points 3, 8, 13, 18,
and 23.
[0010] Moreover, in the case where the lamp 28 is used as the light
source, there occurs a phenomenon in which the brightness measured
at an opposite surface such as test points 16, 20, 21 and 25 is
further lowered.
BRIEF SUMMARY OF THE INVENTION
[0011] It has been determined herein, according to the present
invention, that there occurs display nonuniformity due to low
brightness at both sides of a conventional liquid crystal panel. It
has been further determined herein, according to the present
invention, that brightness at opposite surfaces of a lamp is
restricted in a conventional backlight unit at both corners of a
light incident surface of a light guide plate due to a non-emissive
area of the lamp.
[0012] The present invention thus provides a light guide plate
including a diffuse reflection pattern to provide uniform
brightness, a method of manufacturing the same, and a liquid
crystal display ("LCD") device including the same.
[0013] In accordance with exemplary embodiments of the present
invention, there is provided a light guide plate including a light
incident surface to which light is incident as incident light, an
opposite surface formed opposite to the light incident surface, a
light emitting surface through which the incident light is emitted,
a rear surface formed opposite to the light emitting surface and
including a prism pattern which reflects the incident light to the
light emitting surface, and lateral surfaces, wherein a diffuse
reflection pattern is formed on at least any one of the light
emitting surface and the lateral surfaces to diffuse-reflect the
light incident to the lateral surfaces, thus rendering a brightness
at both the opposite surface and the light incident surface
substantially uniform.
[0014] The area of the diffuse reflection pattern may decrease as a
distance increases from the light incident surface toward the
opposite surface. The diffuse reflection pattern may have an
average roughness decreased as a distance increases from the light
incident surface toward the opposite surface. The diffuse
reflection pattern may be formed in a range of about 80% to about
95% of a length from the light incident surface to the opposite
surface.
[0015] The prism pattern may include a plurality of intaglio prism
lines extending substantially parallel to the light incident
surface. A size of the intaglio prism lines may gradually increase
as a distance increases from the light incident surface toward the
opposite surface. The size of at least any one of the intaglio
prism lines formed in a region adjacent to the opposite surface may
decrease as a distance increases from the lateral surfaces to a
central region thereof.
[0016] The light emitting surface may further include a second
prism pattern including a plurality of relief prism lines, in which
a groove and a projection are repeatedly formed, and which extend
in a direction crossing a direction of extension of the intaglio
prism lines.
[0017] The rear surface may further include at least one reflection
pattern formed in a prism shape between prism lines of the prism
pattern to reflect light to the light emitting surface. The
reflection pattern may be formed within a region of the rear
surface occupying about 10% of a length between the lateral
surfaces, and the region is disposed adjacent at least one of the
lateral surfaces. The reflection pattern may be formed in any one
of relief and intaglio patterns. The reflection pattern may have a
vertex angle in a range of about 130.degree. to about 140.degree..
The reflection pattern may have a height in a range of about 1
.mu.m to about 10 .mu.m from the rear surface and a width in a
range of several tens or several hundreds of micrometers. A number
of the reflection patterns may increase as a distance increases
from the light incident surface toward the opposite surface. At
least any one of the height and the width of the reflection pattern
may gradually increase as a distance increases from the light
incident surface toward the opposite surface.
[0018] In accordance with other exemplary embodiments of the
present invention, there is provided an LCD device including a
liquid crystal panel displaying an image, a light source generating
light, and a light guide plate including a light incident surface
to which the light supplied from the light source is incident as
incident light, an opposite surface formed opposite to the light
incident surface, a light emitting surface through which the
incident light is emitted, a rear surface formed opposite to the
light emitting surface and including a prism pattern which reflects
the incident light to the light emitting surface, and lateral
surfaces, wherein a diffuse reflection pattern is formed on at
least any one of the light emitting surface and the lateral
surfaces to diffuse-reflect light incident to the lateral surfaces,
thus rendering a brightness at both the opposite surface and the
light incident surface substantially uniform.
[0019] The diffuse reflection pattern of the light guide plate may
be formed in a range of about 80% to about 95% of a length from the
light incident surface to the opposite surface.
[0020] The prism pattern may be formed with a plurality of intaglio
prism lines extending substantially parallel to the light incident
surface on the rear surface, and a height of the intaglio prism
lines formed in a region adjacent to the opposite surface may
decrease as a distance increases from the lateral surfaces to a
central region thereof.
[0021] The light guide plate may further include at least one
reflection pattern projected in a prism shape from the rear
surface.
[0022] In accordance with still other exemplary embodiments of the
present invention, a method of manufacturing a light guide plate
includes forming a light incident surface to which light is
incident, an opposite surface formed opposite to the light incident
surface, a light emitting surface through which incident light is
emitted, a rear surface formed opposite to the light emitting
surface, and lateral surfaces, forming a prism pattern including a
plurality of intaglio prism lines on the rear surface, and forming
a diffuse reflection pattern on at least any one of the light
emitting surface and the lateral surfaces to diffuse-reflect light
incident to the lateral surfaces, thus rendering a brightness at
both the opposite surface and the light incident surface
uniform.
[0023] In forming the diffuse reflection pattern, the diffuse
reflection pattern may be formed in a range of about 80% to about
95% of a length from the light incident surface to the opposite
surface.
[0024] Forming the prism pattern including a plurality of intaglio
prism lines on the rear surface may further include forming a
reflection pattern in any one of relief and intaglio patterns on
the rear surface to reflect light incident between the intaglio
prism lines to the light emitting surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and/or other aspects, features and advantages of
the present invention will now become more apparent from the
following detailed description when taken in conjunction with the
accompanying drawings, in which:
[0026] FIG. 1 is a plan view showing test points for measuring
brightness at respective points of a liquid crystal panel in a
conventional liquid crystal display ("LCD") device according to the
prior art;
[0027] FIG. 2 is a graph showing the brightness measured at the
test points of FIG. 1;
[0028] FIG. 3 is an exploded perspective view showing an exemplary
embodiment of an LCD device in accordance with the present
invention;
[0029] FIG. 4 is a perspective view showing a first exemplary
embodiment of a light guide plate in accordance with the present
invention in the exemplary LCD device of FIG. 3;
[0030] FIG. 5 is a perspective view showing a second exemplary
embodiment a light guide plate in accordance with the present
invention;
[0031] FIG. 6 is a perspective view showing a third exemplary
embodiment of a light guide plate in accordance with the present
invention;
[0032] FIG. 7 is a perspective view showing a fourth exemplary
embodiment of a rear surface of a light guide plate in accordance
with the present invention;
[0033] FIGS. 8 to 10 are cross-sectional views taken along lines
I-I', II-II', and III-III' of FIG. 7, respectively;
[0034] FIG. 11 is a perspective view showing a fifth exemplary
embodiment of a light guide plate in accordance with the present
invention;
[0035] FIG. 12 is a perspective view showing a sixth exemplary
embodiment of a rear surface a light guide plate in accordance with
the present invention;
[0036] FIG. 13 is an enlarged perspective view of an exemplary
reflection pattern shown in FIG. 12;
[0037] FIG. 14 is a cross-sectional view taken along line IV-IV' of
FIG. 13;
[0038] FIG. 15 is a perspective view showing an exemplary
reflection pattern engraved in intaglio; and
[0039] FIG. 16 is a cross-sectional view taken along line V-V' of
FIG. 15.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. In the drawings, the size
and relative sizes of layers and regions may be exaggerated for
clarity.
[0041] It will be understood that when an element or layer is
referred to as being "on," "connected to" or "coupled to" another
element or layer, it can be directly on, connected or coupled to
the other element or layer or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly connected to" or "directly coupled to"
another element or layer, there are no intervening elements or
layers present. Like numbers refer to like elements throughout. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items.
[0042] It will be understood that, although the terms first,
second, third etc. may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
components, regions, layers and/or sections should not be limited
by these terms. These terms are only used to distinguish one
element, component, region, layer or section from another element,
component, region, layer or section. Thus, a first element,
component, region, layer or section discussed below could be termed
a second element, component, region, layer or section without
departing from the teachings of the present invention.
[0043] Spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the figures.
For example, if the device in the figures is turned over, elements
described as "below" or "lower" other elements or features would
then be oriented "above" or "upper" relative to the other elements
or features. Thus, the exemplary term "below" can encompass both an
orientation of above and below. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein interpreted
accordingly.
[0044] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a," "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0045] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0046] Embodiments of the present invention are described herein
with reference to cross section illustrations that are schematic
illustrations of idealized embodiments of the present invention. As
such, variations from the shapes of the illustrations as a result,
for example, of manufacturing techniques and/or tolerances, are to
be expected. Thus, embodiments of the present invention should not
be construed as limited to the particular shapes of regions
illustrated herein but are to include deviations in shapes that
result, for example, from manufacturing. For example, a region
illustrated or described as flat may, typically, have rough and/or
nonlinear features. Moreover, sharp angles that are illustrated may
be rounded. Thus, the regions illustrated in the figures are
schematic in nature and their shapes are not intended to illustrate
the precise shape of a region and are not intended to limit the
scope of the present invention.
[0047] Hereinafter, the present invention will be described in
detail with reference to the accompanying drawings.
[0048] FIG. 3 is an exploded perspective view showing an exemplary
embodiment of liquid crystal display ("LCD") device in accordance
the present invention.
[0049] An exemplary embodiment of the LCD device in accordance with
the present invention includes a liquid crystal panel 30, a gate
driver 33 and a data driver 35 for driving the liquid crystal panel
30, a backlight unit 90 for supplying light to the liquid crystal
panel 30, and a bottom chassis 82 and a top chassis 81 for
accommodating the liquid crystal panel 30 and the backlight unit
90.
[0050] In particular, the liquid crystal panel 30 has a structure
in which a color filter substrate 31 including a color filter array
is bonded to a thin film transistor is ("TFT") substrate 32
including a TFT array with a liquid crystal disposed therebetween.
A plurality of sub-pixels independently driven by the TFTs is
arranged in a matrix form on the liquid crystal panel 30. Each
sub-pixel controls the liquid crystal alignment and the light
transmittance to display an image according to a difference between
a common voltage supplied to a common electrode and a pixel
electrode applied to a pixel electrode through the TFT. In this
case, since the liquid crystal panel 30 is a non-emissive display
device, the light generated from the backlight unit 90 is used.
[0051] The gate driver 33 drives a gate line formed on the TFT
substrate 32. The gate driver 33 may be mounted on a gate circuit
film 34, and the gate circuit film 34 equipped with the gate driver
33 may be connected to one side of the TFT substrate 32 to supply a
gate driving signal from the gate driver 33 to the gate line of the
liquid crystal panel 30.
[0052] The data driver 35 drives a data line formed on the TFT
substrate 32. The data driver 35 may be mounted on a data circuit
film 36. One side of the data circuit film 36 may be connected to
the TFT substrate 32 and the other side thereof is connected to a
printed circuit board ("PCB") 37. The gate circuit film 34 and the
data circuit film 36 shown in FIG. 3 are a chip-on-film ("COF") or
a tape carrier package ("TCP"). In an alternative exemplary
embodiment, the gate driver 33 and the data driver 35 may be
mounted on the TFT substrate 32 by a chip-on-glass ("COG") method
or directly mounted on the TFT substrate 32 during the formation of
the TFT.
[0053] The bottom chassis 82 accommodates the backlight unit 90. In
this case, the backlight unit 90 is accommodated in a mold frame 83
as shown.
[0054] The top chassis 81 is formed to surround the circumference
of the top of the liquid crystal panel 30, i.e., a non-display area
of the top surface of the liquid crystal panel 30, and fixes the
liquid crystal panel 30. For this, the top chassis 81 has a
substantially `L` shaped cross-section and is coupled to the bottom
chassis 82.
[0055] The backlight unit 90 includes a light source 40, a light
source cover 50, a light guide plate 100 for guiding light from the
light source 40, a reflection sheet 60 disposed at the bottom of
the light guide plate 100, and an optical sheet unit 70 disposed at
the top of the light guide plate 100.
[0056] The light source 40 is arranged on one side of the light
guide plate 100 and supplies light to the light guide plate 100. In
the illustrated embodiment, a lamp is used as the light source 40.
However, in an alternative exemplary embodiment, a light emitting
diode ("LED") may be used as the light source 40.
[0057] The light source cover 50 is arranged to at least partially
surround the circumference of the light source 40, thus protecting
the light source 40 from an external physical impact. An interior
of the light source cover 50 may include a reflective surface such
that the light source cover 50 reflects the light generated from
the light source 40 to a light incident surface of the light guide
plate 100, thus increasing the light emission efficiency.
[0058] The optical sheet unit 70 is provided on the top of the
light guide plate 100. The optical sheet unit 70 may include a
diffusion sheet, a prism sheet and a protective film. The optical
sheet unit 70 uniformly diffuses the light emitted from a light
emitting surface of the light guide plate 100 and collects the
diffused light to be supplied toward the liquid crystal panel
30.
[0059] The reflection sheet 60 is disposed on a rear surface 150 of
the light guide plate 100, as will be further described with
respect to the following figures, to reflect the light supplied to
the rear surface 150 of the light guide plate 100 toward the top of
the light guide plate 100, such that light may exit the light
emitting surface of the light guide plate 100.
[0060] The light guide plate 100 guides light from the light source
40 to be supplied to the liquid crystal panel 30 disposed at the
top thereof. As will be further described below, the light guide
plate 100 includes a diffuse reflection pattern 200 formed on at
least one of a light emitting surface 130 and lateral surfaces 140
in order to supply light from a light incident surface 110 to the
liquid crystal panel 30 with a uniform brightness distribution. The
diffuse reflection pattern 200 will be described in more detail
with reference to FIGS. 4 to 6.
[0061] FIG. 4 is a perspective view illustrating the exemplary
light guide plate shown in FIG. 3.
[0062] The first exemplary embodiment of the light guide plate 100
in accordance with the present invention includes a light incident
surface 110, an opposite surface 120, a light emitting surface 130,
a rear surface 150, and lateral surfaces 140. The opposite surface
120 is formed opposite to the light incident surface 110. The light
emitting surface 130 is formed opposite to the rear surface 150 to
supply light reflected from the rear surface 150 toward the liquid
crystal panel 30.
[0063] The rear surface 150 is formed opposite to the light
emitting surface 130. Moreover, the rear surface 150 includes a
prism pattern 151 formed to supply light, and the prism pattern 151
may be provided from the light incident surface 110 up to the
opposite surface 120.
[0064] The prism pattern 151 includes a plurality of intaglio prism
lines. In other words, the prism pattern 151 includes a plurality
of longitudinally extending lines that are indented from the rear
surface 150, and each of which extends in a direction substantially
parallel to the light incident surface 110. The size of the
intaglio prism lines is increased as it proceeds from the light
incident surface 110 toward the opposite surface 120. That is, a
size of a prism line adjacent the light incident surface 110 is
less than a size of a prism line further from the light incident
surface 110, such as adjacent the opposite surface 120. The light
emitted from the light source 40 to the light incident surface 110
is supplied up to the opposite surface 120. Moreover, with the
prism pattern 151, it may be possible to eliminate the diffusion
sheet disposed at the top of a conventional light guide plate, thus
reducing the thickness and cost of the backlight unit 90. The prism
pattern 151 will be described in more detail with reference to FIG.
7.
[0065] The light guide plate 100 includes a pair of opposing
lateral surfaces 140, one of which will be described herein. The
lateral surface 140 includes a first region in which the diffuse
reflection pattern 200 is formed and a second region in which the
diffuse reflection pattern 200 is not formed in order to increase
the brightness of both corners of the light guide plate 100
adjacent the opposite surface 120. The first region has a length of
about 80% to about 95% of the total length from the light incident
surface 110 to the opposite surface 120. The second region has a
length of about 5% to about 20% of the total length from the light
incident surface 110 to the opposite surface 120. If the second
region had a length 5% or less of the total length, i.e., if the
diffuse reflection pattern 200 is formed more than 95% of the total
length from the light incident surface 110 to the opposite surface
120, then the amount of light supplied toward the opposite surface
120 would be reduced and thus the brightness of both corners at the
opposite surface 120 would not be increased.
[0066] Moreover, if the diffuse reflection pattern 200 is formed
less than 80% of the total length from the light incident surface
110 to the opposite surface 120, then the brightness of both
corners adjacent the opposite surface 120 would be reduced. In
other words, the light that should be supplied toward the opposite
surface 120 would instead be applied to the light emitting surface
130 and thus the amount of light supplied to the opposite surface
120 would be reduced.
[0067] Here, the area of the diffuse reflection pattern 200 formed
in the first region is reduced as it proceeds from the light
incident surface 110 toward the opposite surface 120. The diffuse
reflection pattern 200 is formed with a predetermined shape such as
a triangle, a quadrangle, etc. on the first region.
[0068] Moreover, the average roughness of the diffuse reflection
pattern 200 may be reduced as it proceeds from the light incident
surface 110 toward the opposite surface 120. In other words, at
least any one of the density and size of fine dots is reduced as
the diffuse reflection pattern 200 proceeds from the light incident
surface 110 toward the opposite surface 120. For example, a greater
deal of fine dots may be formed on the lateral surface 140 adjacent
the light incident surface 110 and the amount decreases as it goes
away from the light incident surface 110 such that the diffuse
reflection pattern 200 diffuse-reflects a greater deal of light
adjacent the light incident surface 110 than adjacent to the
opposite surface 120.
[0069] Furthermore, the diffuse reflection pattern 200 has the same
effect as described above by forming the fine dots having a size
increasing as they proceed from the light incident surface 110
toward the opposite surface 120, thus increasing the brightness of
both corners of the light guide plate 100 adjacent the opposite
surface 120 of the light guide plate 100.
[0070] Accordingly, the diffuse reflection pattern 200 diffuses,
diffuse-reflects, or refracts the light from the lateral surface
140 adjacent the light incident surface 110 to supply a greater
deal of light to the lateral surface 140 adjacent the opposite
surface 120, thus increasing the brightness of both corners of the
light guide plate 100 adjacent the opposite surface 120.
[0071] The first exemplary embodiment of the diffuse reflection
pattern 200 in accordance with the present invention may be formed
by a surface roughness treatment such as sand blasting or any
methods capable of achieving the same effect.
[0072] For example, the diffuse reflection pattern 200 may be
formed on the lateral surfaces 140 of the light guide plate 100
directly by sand blasting. Moreover, the diffuse reflection pattern
200 may be formed on the light guide plate 100 by forming fine dots
such as a hemisphere, a cylindrical column, or a polygonal prism on
a mold used for manufacturing the light guide plate 100. In the
case where the fine dots are formed on the mold, they may be
engraved in relief or in intaglio. With the sand blasting method,
the fine dots are engraved in intaglio with indentations formed in
the mold such that the diffuse reflection pattern 200 is formed in
relief after the injection molding of the light guide plate 100.
When the fine dots are formed on the mold in the above-described
manner, it is possible to improve the reproducibility and reduce
the manufacturing cost during the mass production of the light
guide plate 100.
[0073] FIG. 5 is a perspective view showing a second exemplary
embodiment of a light guide plate in accordance with the present
invention.
[0074] The light guide plate of FIG. 5 may have substantially the
same components as that of FIG. 4, except for the diffuse
reflection pattern 200 being formed on the light emitting surface
130, and therefore a repeated description of the same elements
thereof will be omitted.
[0075] Referring to FIG. 5, the second exemplary embodiment of the
light guide plate 100 in accordance with the present invention
includes a diffuse reflection pattern 210 formed on opposing sides
of the light emitting surface 130 adjacent the lateral surfaces
140.
[0076] In particular, the diffuse reflection pattern 210 is formed
in a predetermined region of the light emitting surface 130 coming
in contact with or directly adjacent to both lateral surfaces 140
of the light guide plate 100. The area of the diffuse reflection
pattern 210 adjacent the light incident surface 110 is greater than
that adjacent the opposite surface 120. For example, the diffuse
reflection pattern 210 may be formed in a triangular or trapezoidal
shape, with a larger width of each shape formed adjacent the light
incident surface 110, and decreasing as the shape approaches the
opposite surface 120. In other words, the area of the diffuse
reflection pattern 210 adjacent to the light incident surface 110
is greater than that of the diffuse reflection pattern 210 adjacent
to the opposite surface 120. Such a diffuse reflection pattern 210
may be formed to have a uniform average roughness throughout the
diffuse reflection pattern 210. Alternatively, the diffuse
reflection pattern 210 may be formed to have an average roughness
adjacent the light incident surface 110 greater than that closer to
the opposite surface 120.
[0077] Meanwhile, the diffuse reflection pattern 210 is not formed
in the second region adjacent to the opposite surface 120. Similar
to the diffuse reflection pattern 200 of FIG. 4, the area of the
diffuse reflection pattern 210 is reduced as a distance increases
from the light incident surface 110 and the diffuse reflection
pattern 210 is not formed in the second region. Since the effect
thereof is the same as described with respect to FIG. 4, a detailed
description thereof will be omitted. Here, the first region is
defined as about 80% to about 95% of the total length between the
light incident surface 110 and the opposite surface 120, and the
second region is defined in the remaining length. Since the
description thereof has been given in detail with reference to FIG.
4, the repeated description thereof will be omitted.
[0078] As described above in the first exemplary embodiment and
shown in FIG. 4, the diffuse reflection pattern 210 may be formed
in such a manner that fine dots corresponding to the diffuse
reflection pattern 210 are formed on the surface of a mold
corresponding to the light emitting surface 130 and then the light
guide plate 100 may be injection molded.
[0079] FIG. 6 is a perspective view showing a third exemplary
embodiment of a light guide plate in accordance with the present
invention, in which the diffuse reflection pattern 200 is formed on
both the lateral surfaces 140 and the diffuse reflection pattern
210 is formed on the light emitting surface 130.
[0080] In this exemplary embodiment, the diffuse reflection pattern
includes a first diffuse reflection pattern 200 formed on the
lateral surfaces 140 and a second diffuse reflection pattern 210
formed on the light emitting surface 130.
[0081] The first diffuse reflection pattern 200 is formed on at
least any one of the lateral surfaces 140 of the light guide plate
100. The first diffuse reflection pattern 200 may be formed on both
lateral surfaces 140 of the light guide plate 100. The first
diffuse reflection pattern 200 is formed in the first region of the
light guide plate 100. As described with reference to FIG. 4, the
first diffuse reflection pattern 200 may be formed in a triangular
or quadrangular shape in the first region. The first diffuse
reflection pattern 200 may be formed to have a uniform average
roughness in the first region or to have an average roughness
decreased as it proceeds from the light incident surface 110 toward
the opposite surface 120.
[0082] The second diffuse reflection pattern 210 is formed on the
light emitting surface 130 of the light guide plate 100. The second
diffuse reflection pattern 210 is formed along the regions where
the light emitting surface 130 meets both the lateral surfaces 140
or adjacent to the lateral surfaces 140. The second diffuse
reflection pattern 210 may be formed in a triangular or
quadrangular shape in the first region. The second diffuse pattern
210 may be formed to have an area reduced gradually as it proceeds
from the light incident surface 110 toward the opposite surface
120. Moreover, the second diffuse reflection pattern 210 may be
formed to have an average roughness decreased as it proceeds from
the light incident surface 110 toward the opposite surface 120.
[0083] FIG. 7 is a perspective view showing a fourth exemplary
embodiment of a rear surface of a light guide plate in accordance
with the present invention, FIG. 8 is a cross-sectional view taken
along line I-I' of FIG. 7, FIG. 9 is a cross-sectional view taken
along line II-II' of FIG. 7, and FIG. 10 is a cross-sectional view
taken along line III-III' of FIG. 7.
[0084] Referring to FIGS. 7 to 10, the fourth exemplary embodiment
of the light guide plate 100 in accordance with the present
invention is formed on the rear surface 150 and includes a prism
pattern 151 having a plurality of intaglio prism lines formed in a
region adjacent to the opposite surface 120.
[0085] In particular, the prism pattern 151 is engraved in intaglio
on the rear surface 150 of the light guide plate 100, such that
each indentation is indented from a surface of the rear surface
150. The distance between the intaglio prism lines of the prism
pattern 151 may be the same. Moreover, the pitch of the intaglio
prism line of the prism pattern 151 is in the range from about
several tens to about several hundreds of micrometers.
[0086] The size of the prism pattern 151 is increased as a distance
increases from the light incident surface 110 toward the opposite
surface 120. The size/height of the intaglio prism line of the
prism pattern 151 adjacent to the light incident surface 110 is
relatively small and the size/height gradually increases as a
distance increases from the light incident surface 110 toward the
opposite surface 120. Accordingly, the light guide plate 100
reduces the amount of light reflected toward the light emitting
surface 130 by the intaglio prism lines adjacent to the light
incident surface 110 and increases the amount of light closer to
the opposite surface 120 by supplying the remaining light toward
the opposite surface 120.
[0087] Moreover, the height of the prism pattern 151, at least
adjacent to the opposite surface 120, is reduced towards the center
and is increased towards both ends of each line. As shown in FIGS.
8 to 10, a height H1 of both sides of the intaglio prism line is
greater than a height H2 of the center thereof. In other words, the
height H1 of the prism pattern 151 adjacent to the lateral surface
140 of the light guide plate 100 is greater than the height H2 of
the prism pattern 151 formed in the center or central region of the
light guide plate 100. Since the prism pattern 151 forms an
inclined surface for reflecting light to the light guide plate 100,
the area of the inclined surface is varied according to the height
of the prism pattern 151. In the cross-sectional view of FIG. 8,
the slanted lines show the inclined surface. The area of the
inclined surface at the lateral surface 140, in which the prism
pattern 151 is formed larger in height, is larger than that of the
center. Moreover, since the size of the prism pattern 151 is
gradually reduced as it proceeds from the lateral surfaces 140 to
the center or central region, the area of the inclined surface is
also gradually reduced. Accordingly, since the amount of light
reflected from the lateral surface 140 is greater than that
reflected from the center or central region, the brightness of both
corners of the light guide plate 100 adjacent the opposite surface
120 of the light guide plate 100 is increased.
[0088] The above-described prism pattern 151 may be formed in such
a manner that prism patterns are engraved in relief with a prism
shape on the surface of a mold corresponding to the rear surface
150 and then the light guide plate 100 is injection molded.
[0089] FIG. 11 is a perspective view showing a fifth exemplary
embodiment of a light guide plate in accordance with the present
invention.
[0090] The fifth exemplary embodiment of the light guide plate 100
in accordance with the present invention further includes a second
prism pattern 230 formed on the light emitting surface 130.
[0091] In particular, the second prism pattern 230 includes a
plurality of relief prism lines in which a groove 232 and a
projection 231 are repeatedly formed and extend from the light
incident surface 110 to the opposite surface 120. The second prism
pattern 230 collects light supplied from the light emitting surface
130 and supplies the collected light to the liquid crystal panel 30
disposed at the top of the backlight unit 90. The relief prism
lines of the second prism pattern 230 may be formed
perpendicularly, or substantially perpendicularly, to the intaglio
prism lines in the prism pattern 151 formed on the rear surface 150
of the light guide plate 100. The second prism pattern 230 formed
on the light emitting surface 130 of the light guide plate 100
provides the same effect without using the optical sheets such as
the diffusion sheet and the prism sheet employed in the
conventional backlight unit. Accordingly, it is possible to reduce
the thickness, weight, and cost of the backlight unit 90.
[0092] The above-described second prism pattern 230 may be formed
in such a manner that prism lines are engraved in intaglio with a
prism shape on the surface of a mold corresponding to the second
prism pattern 230 and then the light guide plate 100 is injection
molded.
[0093] FIG. 12 is a perspective view showing a sixth exemplary
embodiment of a light guide plate in accordance with the present
invention, FIG. 13 is an enlarged perspective view of an exemplary
reflection pattern in the exemplary light guide plate of FIG. 12,
and FIG. 14 is a cross-sectional view taken along line IV-IV' of
FIG. 13.
[0094] Referring to FIGS. 12 to 14, the sixth exemplary embodiment
of the light guide plate 100 in accordance with the present
invention includes a reflection pattern 240 formed on the rear
surface 150 adjacent to the lateral surfaces 140.
[0095] In particular, the reflection pattern 240 is formed in at
least any one of both sides of the rear surface 150 adjacent to the
lateral surfaces 140. The reflection pattern 240 is formed between
intaglio prism lines of the prism pattern 151. Moreover, the
reflection pattern 240 is form on the flat surface between the
intaglio prism lines repeatedly arranged. In other words, the prism
lines and the reflection patterns 240 are alternately arranged.
Such a reflection pattern 240 may be formed in a third region and a
fourth region, which are disposed adjacent the opposing lateral
surfaces 140, respectively. The third and fourth regions are
positioned within 10% of the total length between lateral surfaces
140 of the light guide plate 100. For example, in a case where the
length between the lateral surfaces 140 of the light guide plate
100 is about 30 cm, the third and fourth regions correspond to the
regions positioned within 3 cm from the lateral surfaces 140.
[0096] As shown in FIGS. 12 to 14, the reflection pattern 240 is
engraved in relief from the rear surface 150. As shown in FIG. 14,
light incident along a fourth light path L4 is reflected by the
inclined surface of the prism pattern 151 and thus supplied
vertically to the light emitting surface 130. Light incident along
first to third light paths L1 to L3 is reflected by the reflection
pattern 240 and thus emitted vertically to the light emitting
surface 130. At this time, the reflection pattern 240 may supply
light incident along other light paths than the first to third
light paths L1 to L3 vertically to the light emitting surface
130.
[0097] The reflection pattern 240 has a vertex angle .theta.1 in
the range of about 130.degree. to about 140.degree.. As shown in
FIG. 14, the vertex angle .theta.1 of triangle ABC is formed about
130.degree. to about 140.degree.. The reflection pattern 240 has
the maximum reflection efficiency when the vertex angle .theta.1 is
136.degree., or about 136.degree..
[0098] If the vertex angle .theta.1 is smaller than 130.degree. or
greater than 140.degree., then the amount of light incident to the
inclined surface of the reflection pattern 240 and supplied
vertically to the light emitting surface 130 would be reduced.
[0099] Moreover, the reflection pattern 240 has a height H3 in the
range of about 1 .mu.m to about 10 .mu.m with respect to the flat
surface of the rear surface 150. If the height H3 of the reflection
pattern 240 is less than 1 .mu.m, then the size of the reflection
pattern 240 would become too small, and thus the amount of light
reflected toward the light emitting surface 130 would be reduced.
If the height H3 of the reflection pattern 240 is more than 10
.mu.m, then the amount of light reflected toward the light emitting
surface 130 would be increased, however, it may cause a defect such
as scratch on a reflection sheet to be formed on the rear surface
150 when coming in contact with the reflection sheet. Moreover, the
reflection pattern 240 has a width W of several or several tens of
micrometers.
[0100] In an exemplary embodiment, the size of the reflection
pattern 240 may be increased as a distance increases from the light
incident surface 110 toward the opposite surface 120, and thus it
is possible to increase the brightness of both sides of the light
guide plate 100. For example, the width W of the reflection pattern
240 may be increased as a distance increases from the light
incident surface 110 toward the opposite surface 120. That is, if
the width W of the reflection pattern 240 adjacent the opposite
surface 120 is greater than that of the reflection pattern 240
adjacent the light incident surface 110, the area for reflecting
the incident light is increased towards the opposite surface 120,
and thus it is possible to supply a greater deal of light toward
the light emitting surface 130.
[0101] In an alternative exemplary embodiment, the reflection
patterns 240 formed at the light incident surface 110 and the
opposite surface 120 may have the same width W, and the reflection
pattern 240 formed adjacent the opposite surface 120 may have a
height H3 greater than that of the reflection pattern 240 formed
adjacent the light incident surface 110.
[0102] In yet another exemplary embodiment, the number of the
reflection patterns 240 may be increased as a distance increases
from the light incident surface 110 toward the opposite surface
120, and thus it is possible to increase the brightness of both
sides of the light guide plate 100. For example, since the
brightness adjacent the light incident surface 110 adjacent to the
light source 40 is greater than that adjacent the opposite surface
120, a greater number of reflection patterns 240 may be formed
adjacent the opposite surface 120 in order to maintain a uniform
brightness across the opposite surface 120. Accordingly, it is
possible to supply a greater deal of light toward the light
emitting surface 130 from an area adjacent the opposite surface 120
than from an area adjacent the light incident surface 110.
[0103] Meanwhile, as shown in FIGS. 15 and 16, the reflection
pattern 240 may be formed to have an intaglio prism shape engraved
from the rear surface 150.
[0104] The reflection pattern 240 having the intaglio prism shape
may have a vertex angle .theta.2, a height H4 and a width W', which
may be the same or substantially the same as the vertex angle
.theta.1, the height H3 and the width W of the reflection pattern
240 engraved in relief shown in FIGS. 13 and 14. As shown in FIG.
16, the vertex angle .theta.2 of triangle A'B'C' is formed in the
range of about 130.degree. to about 140.degree., which may be the
same as the vertex angle .theta.1 of triangle ABC shown in FIG. 14.
Moreover, the height H4 of the reflection pattern 240 engraved in
intaglio has a value in the range of about 1 .mu.m to about 10
.mu.m, which may be the same as the height H3 of the reflection
pattern 240 engraved in relief as shown in FIG. 14.
[0105] The size or the number of such reflection patterns 240 may
be increased as a distance increases from the light incident
surface 110 toward the opposite surface 120, and thus it is
possible to increase the brightness of both sides of the light
guide plate 100. Since the method of increasing the size and number
of reflection patterns 240 for the exemplary embodiment described
with respect to FIGS. 15 and 16 may be the same as described above
with respect to the exemplary embodiment described with respect to
FIGS. 12 to 14, a detailed description thereof will be omitted.
[0106] A fine intaglio or relief pattern is formed on a mold to
form such a reflection pattern 240. In this case, the fine intaglio
or relief pattern formed on the mold may have a size corresponding
to that of the reflection pattern 240. Here, since the size of the
intaglio or relief pattern is very small, a mechanical indentation
method may be used.
[0107] Another exemplary embodiment of the light guide plate 100 in
accordance with the present invention may include the diffuse
reflection pattern 200 shown in FIGS. 4 to 6 formed on any one of
both lateral surfaces 140 and the light emitting surface 130.
Moreover, it will be understood by those skilled in the art that
the second prism pattern 230 shown in FIG. 11 may be further formed
on the light emitting surface 130 of the light guide plate 100. In
other words, any combinations of the above-described exemplary
embodiments of the light guide plate 100 are also within the scope
of these embodiments.
[0108] As described above, the light guide plate and the backlight
unit in accordance with the exemplary embodiments of the present
invention include the diffuse reflection pattern subjected to the
surface roughness treatment formed on any one of the lateral
surface and the light emitting surface of the light guide plate to
increase the brightness of both corners adjacent the opposite
surface, thus achieving the uniform brightness of the entire light
guide plate.
[0109] Moreover, the brightness of both corners adjacent the
opposite surface may be increased by forming the prism pattern on
the rear surface and forming the height of the prism pattern in a
central region thereof adjacent to the opposite surface greater
than that of the prism pattern at the lateral surface.
[0110] Furthermore, the brightness of both sides of the light guide
plates may be increased by forming the reflection pattern between
the prism patterns on the rear surface.
[0111] While the present invention has been shown and described
with reference to some exemplary embodiments thereof, it should be
understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and the scope of the present invention as defined
by the appended claims.
* * * * *