U.S. patent application number 13/416571 was filed with the patent office on 2012-06-28 for optical sheet and method for fabricating the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Jin Sung CHOI, Dong Hoon KIM.
Application Number | 20120162773 13/416571 |
Document ID | / |
Family ID | 39148567 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120162773 |
Kind Code |
A1 |
KIM; Dong Hoon ; et
al. |
June 28, 2012 |
OPTICAL SHEET AND METHOD FOR FABRICATING THE SAME
Abstract
An optical sheet and a method for fabricating the optical sheet,
wherein a diffusion pattern is formed to diffuse and condense
light. The optical sheet includes a prism pattern having a
plurality of mountains and ravines to condense light generated from
a light source and a plurality of diffusion patterns irregularly
formed on the prism pattern to diffuse the light.
Inventors: |
KIM; Dong Hoon; (Seoul,
KR) ; CHOI; Jin Sung; (Cheonan-si, KR) |
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
39148567 |
Appl. No.: |
13/416571 |
Filed: |
March 9, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11933288 |
Oct 31, 2007 |
8158040 |
|
|
13416571 |
|
|
|
|
Current U.S.
Class: |
359/599 |
Current CPC
Class: |
B29L 2011/00 20130101;
B29C 33/3878 20130101; B29D 11/00278 20130101; G02B 6/0053
20130101; G02B 6/0065 20130101; G02B 5/02 20130101 |
Class at
Publication: |
359/599 |
International
Class: |
G02B 5/02 20060101
G02B005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2006 |
KR |
10-2006-0126026 |
Claims
1. An optical sheet for a display device, the optical sheet being
disposed between a light guide plate and a display panel, the
optical sheet comprising: a prism pattern including a plurality of
inclined surfaces defining a plurality of mountains and ravines to
condense light from the light guide plate; and a plurality of
diffusion patterns irregularly formed on the prism pattern to
diffuse the light from the light guide plate, wherein the optical
sheet transmits the diffused and condensed light to the display
panel.
2. The optical sheet of claim 1, wherein the plurality of diffusion
patterns have a concave or convex shape.
3. The optical sheet of claim 2, wherein the plurality of diffusion
patterns have a curved surface or a polyhedral surface.
4. The optical sheet of claim 3, wherein a diffusion pattern has a
different cross-sectional area size than an adjacent diffusion
pattern.
5. The optical sheet of claim 1, wherein the plurality of mountains
and ravines are extended in a first direction and arranged in a
second direction crossing the first direction.
6. The optical sheet of claim 5, wherein the plurality of mountains
of the prism pattern have a pitch of about 20 .mu.m to 200
.mu.m.
7. The optical sheet of claim 6, wherein the plurality of diffusion
patterns have a diameter of about 10 .mu.m to 20 .mu.m.
8. The optical sheet of claim 5, wherein the plurality of mountains
are arranged in a straight line or a curved line.
9. The optical sheet of claim 5, wherein the plurality of mountains
of the prism pattern are arranged at irregular intervals.
10. The optical sheet of claim 5, wherein the plurality of inclined
surfaces include a first inclined surface and a second inclined
surface defining a ravine of the plurality of ravines, and a ravine
line is defined along an intersection of the first inclined surface
and the second inclined surface.
11. The optical sheet of claim 10, wherein a part of the plurality
of diffusion patterns is irregularly arranged along the ravine
line.
12. The optical sheet of claim 11, wherein the part of the
plurality of diffusion patterns is disposed between the first
inclined surface and the second inclined surface.
13. The optical sheet of claim 12, wherein the part of the
plurality of diffusion patterns has a peak less than a peak of the
plurality of mountains in cross sectional view.
14. The optical sheet of claim 5, wherein each of the plurality of
mountains has a scalene triangular cross section in which two sides
are different in length.
15. The optical sheet of claim 5, wherein a peak of each of the
plurality of mountains is round.
Description
CROSS REFERERNCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/933,288, filed on Oct. 31, 2007 and claims priority
from and the benefit of Korean Patent Application No.
10-2006-0126026, filed on Dec. 12, 2006, both of which are hereby
incorporated by reference for all purposes as if fully set forth
herein.
BACKGROUND
[0002] 1. Field
[0003] The present invention relates to a prism sheet, and more
particularly to, a prism sheet having diffusing and condensing
functions that may prevent a moire phenomenon and a method for
fabricating the same.
[0004] 2. Discussion of the Background
[0005] Liquid crystal display ("LCD") devices are widely used in
various industrial fields because they are generally lightweight
and compact and require low power consumption. Such an LCD device
includes a liquid crystal (LC) panel in which liquid crystal cells
are arranged in a matrix between two transparent substrates, a
driving circuit to drive the LC panel, and a backlight unit to
supply light to the LC panel.
[0006] The backlight unit includes a lamp to generate light, a
housing surrounding the lamp, a light guide plate to guide light
emitted from the lamp toward the LC panel, a reflector sheet
arranged below the light guide plate, and a plurality of optical
sheets stacked above the light guide plate.
[0007] The optical sheets include a diffuser sheet, a prism sheet,
and a protector sheet stacked sequentially above the light guide
plate. Here, two or more diffuser sheets and two or more prism
sheets may be arranged according to a desired product
characteristic. Multiple diffuser sheets result in a thicker
backlight unit. The prism sheet may have a prism pattern in which a
mountain and a ravine are formed in turn. However, if the pitch of
the prism mountain and the pixel pitch of the LC panel overlap, a
moire phenomenon, which is wave-like pattern interference, may
occur.
SUMMARY
[0008] The present invention provides an optical sheet having a
diffusion pattern to diffuse and condense light, which may prevent
a moire phenomenon and a method for fabricating the same.
[0009] Additional features of the invention will be set forth in
the description which follows, and in part will be apparent from
the description or may be learned by practice of the invention.
[0010] The present invention discloses an optical sheet including a
prism pattern having a plurality of mountains and ravines to
condense light generated from a light source and a plurality of
diffusion patterns irregularly formed on the prism pattern to
diffuse the light.
[0011] The present invention also discloses a method for
fabricating an optical sheet including preparing a sub master by
forming a prism pattern having a plurality of mountains and ravines
in turn and forming irregular diffusion patterns on sides of the
mountains. A main master having mountains, ravines, and irregular
diffusion patterns corresponding to the mountains and ravines and
irregular diffusion patterns of the sub master is formed, and a
film is pressurized using the main master to form an optical
sheet.
[0012] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention, and together with the description serve to explain
the principles of the invention.
[0014] FIG. 1 is a perspective view showing an LCD device that
includes a prism sheet according to an exemplary embodiment of the
present invention.
[0015] FIG. 2A is a perspective view showing a prism sheet
according to a first exemplary embodiment of the present
invention.
[0016] FIG. 2B, FIG. 2C, and FIG. 2D are cross sectional views
taken along line I-I' of FIG. 2A.
[0017] FIG. 3 is a perspective view showing a prism sheet according
to a second exemplary embodiment of the present invention.
[0018] FIG. 4 is a perspective view showing a prism sheet according
to a third exemplary embodiment of the present invention.
[0019] FIG. 5 is a cross-sectional view showing a prism sheet
according to a fourth exemplary embodiment of the present
invention.
[0020] FIG. 6 is a cross-sectional view showing a prism sheet
according to a fifth exemplary embodiment of the present
invention.
[0021] FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E, and FIG. 7F are
cross-sectional views showing a first method for fabricating the
prism sheet according to an exemplary embodiment of the present
invention.
[0022] FIG. 8A, FIG. 8B, FIG. 8C, FIG. 8D, FIG. 8E, and FIG. 8F are
cross-sectional views showing a second method for fabricating a
prism sheet according to an exemplary embodiment of the present
invention.
[0023] FIG. 9A is a photograph showing a result when the half width
of an LCD device with a conventional prism sheet is measured using
optical equipment.
[0024] FIG. 9B is a photograph showing a result when the half width
of an LCD device with a prism sheet according to an exemplary
embodiment of the present invention is measured using optical
equipment.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0025] The invention is 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 ser forth herein. Rather, these embodiments are
provided so that this disclosure is thorough, and will fully convey
the scope of the invention to those skilled in the art. In the
drawings, the size and relative size of layers and regions may be
exaggerated for clarity. Like reference numerals in the drawings
denote like elements.
[0026] It will be understood that when an element such as a layer,
film, region or substrate is referred to as being "on", "connected
to", or "coupled to" another element or layer, it can be directly
on, directly connected to, or directly coupled to the other element
or layer, or intervening elements or layers may also 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.
[0027] FIG. 1 is a perspective view showing an LCD device that
includes a prism sheet according to an exemplary embodiment of the
present invention. The LCD device of FIG. 1 includes an LC panel
100, panel driving portions 110 and 120, and a backlight unit
130.
[0028] The LC panel 100 includes a color filter array substrate 102
and a thin film transistor ("TFT") array substrate 104 with a
liquid crystal layer to adjust the transmittance of light
interposed therebetween. The color filter array substrate 102 may
include a black matrix to prevent light leakage, a color filter to
realize a color image, a common electrode to form a vertical
electric field together with a pixel electrode, and an upper
alignment layer coated thereon to align the liquid crystal
molecules. The TFT array substrate 104 includes gate lines and data
lines arranged to cross each other, TFTs formed at crossing points
of the gate lines and data lines, a pixel electrode connected to
the TFTs, and a lower alignment layer coated thereon to align
liquid crystal molecules.
[0029] The panel driving portions 110 and 120 include a gate
driving portion to drive the gate lines of the LC panel 100 and a
data driving portion 120 to drive the data lines.
[0030] The gate driving portion 110 includes a gate PCB (Printed
Circuit Board) 114, a gate TCP (Tape Carrier Package) arranged
between the gate PCB 114 and the TFT array substrate 104, and a
gate IC (Integrated Circuit) 112 mounted on the gate TCP. The gate
IC 112 may sequentially supply the gate lines with a scan signal of
a high gate voltage. The Gate IC 112 may supply the gate lines with
a low gate voltage during the remaining time (i.e. except during a
time when the high gate voltage is supplied). The gate PCB 114 may
supply the gate IC 112 with a control signal and a power signal
from a timing control portion and a power portion mounted on a data
PCB 118.
[0031] The data driving portion 120 may include a data PCB 118 and
a data IC 116 mounted on a data TCP arranged between the data PCB
118 and the TFT array substrate 104. The data IC 116 may convert
pixel data into analog pixel signals and supply the data lines with
the analog pixel signals. The data PCB 118 may supply the data IC
116 with a control signal, a power signal, and the pixel data from
the timing control portion and the power portion.
[0032] The backlight unit 130 may be arranged below the LC panel
100 and supplies light to the LC panel 100. To this end, the
backlight unit 130 may include a light source 132, a light guide
plate 134, a prism sheet 140, a protector sheet 138, and a
reflector sheet 136.
[0033] A lamp or a light emitting diode may be arranged on one side
of the light guide plate 134 as the light source 132.
[0034] The light guide plate 134 guides light emitted from the
light source 132 to the LC panel 100. To this end, the light guide
plate 134 may have an uneven surface, a concave-convex form, or a
dot form so that light can be easily refracted and dispersed toward
the LC panel 100. The light guide plate 134 may be made of poly
methyl meta acrylate (PMMA), which is not easily transformed or
broken and has high transmittance.
[0035] The reflector sheet 136 may be arranged below or beneath the
light guide plate 134 and may reflect light emitted through a
bottom surface of the light guide plate 134 from the light source
132 toward the LC panel 100. The reflector sheet 136 may include a
reflective member having high reflectivity coated on a base
material. For example, stainless steel, brass, aluminum (Al),
polyethylene, or polyethylene terephthalate (PET) may be used as
the base material, and silver (Ag) or titanium (Ti) may be used as
the reflective member.
[0036] The prism sheet 140 may be located above or on the light
guide plate 134 and may refract and condense light coming from the
light guide plate 134 to improve brightness. The prism sheet 140
may convert inclinedly irradiated elements among light irradiated
from the light guide plate 134 to be vertically irradiated to the
LC panel 100. When light incident to the LC panel 100 is vertically
irradiated to the LC panel 100, the light efficiency may be
improved.
[0037] The inventive LCD device may optionally include the
protector sheet 138 above or on the prism sheet 140. The protector
sheet 138 may serve to prevent scratches which may occur when the
prism sheet 140 directly contacts the LC panel 100 if a prism
mountain of a prism pattern (see 142 in FIG. 2) is sharply formed
in a vertex form. However, if a prism mountain of the prism pattern
142 is round, there is no need to arrange the protector sheet 138
on the prism sheet 140, which will be described below.
[0038] The prism sheet 140 may include a prism pattern and a
plurality of irregular diffusion patterns. The pitch of the prism
mountain may be in a range of about 20 .mu.m to 200 .mu.m. If the
pitch of the prism mountain is less than about 20 .mu.m, a
brightness characteristic of light may be degraded. If the pitch of
the prism mountain greater than or equal to about 200 .mu.m, a
light condensing characteristic may be degraded. For these reasons,
it may be advantageous to form the prism mountain with a pitch of
about 20 .mu.m to 200 .mu.m. The diffusion pattern may be
irregularly dispersed on the prism sheet 140.
[0039] FIG. 2A is a perspective view showing the prism sheet
according to a first exemplary embodiment of the present invention,
and FIG. 2B, FIG. 2C, and FIG. 2D are cross sectional views taken
along line I-I' of FIG. 2A.
[0040] Referring to FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D, the
prism sheet 140 may include a prism pattern 142 having a plurality
of mountains and ravines formed in a straight line at regular
intervals and a plurality of diffusion patterns 144, which are
irregularly formed on the prism pattern 142.
[0041] In FIG. 2A and FIG. 2B, the prism mountain is formed with a
pitch of about 50 .mu.m, and the prism mountain is formed at a
height of about 25 .mu.m. In FIG. 2C, the prism mountain is formed
at a pitch of about 100 .mu.m, and the prism mountain is formed at
a height of about 50 .mu.m. In FIG. 2D, the prism mountain is
formed at a pitch of about 100 .mu.m, and the prism mountain is
formed at a height of about 25 .mu.m.
[0042] In order to improve a light condensing function of the prism
sheet 140, the pitch of the prism mountain should be minimized to
increase density. To the contrary, in order to improve the
diffusing function of the prism sheet 140, the pitch of the prism
mountain should be maximized to reduce density of the prism
mountain and increase density of the diffusion pattern 144. FIG. 2A
and FIG. 2B show cases where the light condensing characteristic is
high, and FIG. 2D show a case where the diffusion characteristic is
high. Therefore, it may be possible to adjust the condensing
function and the diffusing function according to product
characteristics.
[0043] FIG. 3 is a perspective view showing a prism sheet according
to a second exemplary embodiment of the present invention. The
prism sheet of FIG. 3 includes a prism pattern 142 having a
plurality of mountains and ravines formed in a curved line at
regular intervals and a plurality of diffusion patterns 144, which
are irregularly formed on the prism patterns 142. The pitch and the
height of the prism mountains of the prism pattern 142 may be
similar or identical to those described above in the first
exemplary embodiment of the present invention, and thus
descriptions of those are omitted.
[0044] FIG. 4 is a perspective view showing a prism sheet according
to a third exemplary embodiment of the present invention. The prism
sheet of FIG. 4 includes a prism pattern 142 having a plurality of
mountains and ravines formed in a curved line at irregular
intervals and a plurality of diffusion patterns 144, which are
irregularly formed on the prism patterns 142. For example, the
mountains of the prism pattern 142 may be formed in a curved line
at irregular intervals with a pitch of about 20 .mu.m to 70
.mu.m.
[0045] When the prism mountains form a curved line, it may be
possible to prevent a moire phenomenon that occurs due to
interference between the pixel pitch of the LC panel 100 and the
prism mountain pitch of the prism sheet 140.
[0046] FIG. 5 is a cross-sectional view showing a prism sheet
according to a fourth exemplary embodiment of the present
invention. The prism sheet 140 of FIG. 5 includes a prism pattern
142 and a plurality of diffusion patterns 144. Each prism mountain
of the prism pattern 142 may be formed in a scalene triangle in
which two sides are different in length and form an interior angle
.theta. of about 88.degree. to 93.degree..
[0047] FIG. 6 is a cross-sectional view showing a prism sheet
according to a fifth exemplary embodiment of the present invention.
The prism sheet 140 of FIG. 6 includes a prism pattern 142 and a
plurality of diffusion patterns 144. The vertex or peak of the
prism mountain of the prism pattern 142 may be round.
[0048] When the vertex of the prism mountain is round, the viewing
angle may be improved and a moire phenomenon may be prevented.
Further, friction between the LC panel 100 and the prism mountains
may be prevented. As a result, not only may light be condensed and
diffused but also, a moire phenomenon may be prevented using a
single prism sheet 140.
[0049] The prism sheet 140 of the present invention may be formed
using one of the first, second, third, fourth, and fifth
embodiments or a combination thereof.
[0050] Hereinafter, a method for fabricating the prism sheet 140
according to an exemplary embodiment of the present invention is
described. FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E, and FIG. 7F
are cross-sectional views showing a first method for fabricating
the prism sheet according to an exemplary embodiment of the present
invention, and FIG. 8A, FIG. 8B, FIG. 8C, FIG. 8D, FIG. 8E, and
FIG. 8F are cross-sectional views showing a second method for
fabricating the prism sheet according to an exemplary embodiment of
the present invention.
[0051] Methods for fabricating the prism sheet 140 according to
exemplary embodiments of the present invention include preparing a
sub master. The sub master includes a prism pattern in which
mountains and ravines are formed in turn and irregular diffusion
patterns formed on surfaces of the mountains. A main master
including mountains, ravines, and diffusion patterns corresponding
to the mountains and ravines and the diffusion patterns of the sub
master is formed, and a film is pressurized using the main master
to form a prism sheet.
[0052] A first method for fabricating the prism sheet according to
an exemplary embodiment of the present invention is described with
reference to FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E, and FIG.
7F. Referring to FIG. 7A, beads 150 may be irregularly scattered on
a substrate 152. The substrate 152 may be made of a soft material,
and the beads 150 may be made of acrylic resin, urea resin, or
polyurethane. The beads 150 may have at least one of circular,
elliptical, and polyhedral shapes. Each bead 150 may have a size of
about 10 .mu.m to 12 .mu.m. The beads 150 may be irregularly
placed. Referring to FIG. 7B, the beads 150 may be pressurized so
that parts of the beads 150 can be inserted into the substrate 152.
The beads 150 may be removed and irregular diffusion patterns may
be formed in the substrate 152 as shown in FIG. 7C.
[0053] Next, referring to FIG. 7D, a sub master 154 may be prepared
by forming a prism pattern in the substrate 152 having the
irregular diffusion patterns using a diamond bite. Referring to
FIG. 7E, a main master 156 which has mountains, ravines, and
irregular diffusion patterns corresponding to the mountains,
ravines, and irregular diffusion patterns of the sub master 154 may
be prepared using the sub master 154. Finally, referring to FIG.
7F, a film may be pressurized using the main master 156, thereby
completing the prism sheet 140.
[0054] The prism sheets according to the first, second, third,
fourth, and fifth exemplary embodiments of the present invention
may be fabricated using the first method for fabricating the prism
sheet.
[0055] A second method for fabricating the prism sheet according to
an exemplary embodiment of the present invention is described with
reference to FIG. 8A, FIG. 8B, FIG. 8C, FIG. 8D, FIG. 8E, and FIG.
8F. Referring to FIG. 8A, a prism pattern may be formed in the
substrate 152. Then, the beads 150 may be irregularly scattered on
the substrate 152 with the prism pattern as shown in FIG. 8B. The
beads 150 may be made of acrylic resin, urea resin, or
polyurethane. The beads 150 may have at least one of circular,
elliptical, and polyhedral shapes. Each bead 150 may have a size of
about 10 .mu.m to 12 .mu.m. The beads 150 may be irregularly
placed. In FIG. 8C, the beads 150 may be pressurized so that parts
of the beads 150 can be inserted into the substrate 152.
[0056] Next, referring to FIG. 8D, the beads 150 may be removed,
and the sub master 154 may be prepared by forming irregular
diffusion patterns in the substrate 152 with the prism pattern.
[0057] Referring to FIG. 8E, the main master 156 which has
mountains, ravines, and irregular diffusion patterns corresponding
to the mountains, ravines, and irregular diffusion patterns of the
sub master 154 may be prepared using the sub master 154. Finally,
referring to FIG. 8F, a film may be pressurized by using the main
master 156to form the prism sheet 140. The prism sheets according
to the first, second, third, fourth, and fifth exemplary
embodiments of the present invention may be fabricated using the
second method for fabricating the prism sheet.
[0058] FIG. 9A is a photograph showing a result when the half width
of an LCD device with a conventional prism sheet is measured using
optical equipment. FIG. 9B is a photograph showing a result when
the half width of an LCD device with a prism sheet according to an
exemplary embodiment of the present invention is measured using
optical equipment.
[0059] Referring to FIG. 9A and FIG. 9B, the result of measuring
the half width is more than about 15 degrees when a prism sheet
according to an exemplary embodiment of the present invention is
used, whereas the result of measuring the half width is about 12
degrees when the conventional prism sheet is used. Here, the half
width is the angle at which the brightness is reduced by half. The
larger the half width is, the greater the brightness. It can be
seen in FIG. 9A and FIG. 9B that the brightness may be improved
when the prism sheet according to an exemplary embodiment of the
present invention is used than when the conventional prism sheet is
used.
[0060] The prism sheet and the method for fabricating the same
according to exemplary embodiments of the present invention have
the following advantages. Since the prism pattern and the diffusion
patterns may be formed in the prism sheet, the prism sheet may have
both diffusing and condensing functions, and thus it may be
possible to prevent a moire phenomenon through a single prism sheet
without using a diffusion sheet.
[0061] Further, since the diffuser sheet is not needed, the
backlight unit may be lightweight, thin, and small. Therefore, the
manufacturing process may be simplified and the manufacturing costs
may be decreased.
[0062] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *