U.S. patent application number 11/268027 was filed with the patent office on 2006-06-22 for light diffusion member, back light assembly including the same and display device including the same.
Invention is credited to Geun-Hyung Kim, Tae-Seok Kim, Jong-Dae Park.
Application Number | 20060133109 11/268027 |
Document ID | / |
Family ID | 36595498 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060133109 |
Kind Code |
A1 |
Kim; Geun-Hyung ; et
al. |
June 22, 2006 |
Light diffusion member, back light assembly including the same and
display device including the same
Abstract
The light diffusion member includes a light diffusing body and a
light diffusing layer. The light diffusing body includes a polymer
mixture obtained by uniformly blending a first polymer having a
first glass transition temperature and a second polymer having a
second transition temperature higher than the first transition
temperature. Alternatively, the light diffusing body includes a
copolymer prepared from the first and the second polymer. The light
diffusing body diffuses an incident light through a light exiting
surface. The light diffusing layer is formed on the light exiting
surface of the light diffusing body and includes a binder resin
having beads. A back light assembly including the light diffusion
member and a liquid crystal display device including the light
diffusion member exhibit an improved luminance and an improved
light diffusing efficiency.
Inventors: |
Kim; Geun-Hyung;
(Seongnam-si, KR) ; Park; Jong-Dae; (Seoul,
KR) ; Kim; Tae-Seok; (Suwon-si, KR) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
US
|
Family ID: |
36595498 |
Appl. No.: |
11/268027 |
Filed: |
November 7, 2005 |
Current U.S.
Class: |
362/615 |
Current CPC
Class: |
G02B 5/0226 20130101;
G02B 5/0278 20130101; Y10T 428/31507 20150401; C09K 2323/06
20200801; G02F 1/133606 20130101; Y10T 428/31786 20150401; G02B
5/0242 20130101; Y10T 428/26 20150115; G02F 1/133611 20130101; G02F
1/133317 20210101 |
Class at
Publication: |
362/615 |
International
Class: |
F21V 7/04 20060101
F21V007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2004 |
KR |
2004-90109 |
Claims
1. A light diffusion member comprising: a light diffusing body
including a polymer mixture having a first polymer having a first
glass transition temperature and a second polymer having a second
glass transition temperature higher than the first transition
temperature, the first and second polymers uniformly blended within
the polymer mixture, the light diffusing body diffusing an incident
light through a light exiting surface of the light diffusing body;
and a light diffusing layer formed on the light exiting surface of
the light diffusing body, the light diffusing layer including a
binder resin having beads.
2. The light diffusion member as claimed in claim 1, wherein the
light diffusing body is integrally formed with the light diffusing
layer forming a solitary unit for the light diffusion member and
eliminating gaps between the light diffusing body and the light
diffusing layer.
3. The light diffusion member as claimed in claim 1, wherein the
polymer mixture has a glass transition temperature higher than the
first glass transition temperature and a humidity absorbance lower
than the second polymer.
4. The light diffusion member as claimed in claim 1, wherein a
glass transition temperature of the polymer mixture is about or
greater than 100.degree. C.
5. The light diffusion member as claimed in claim 1, wherein a
humidity absorbance of the first polymer is lower than a humidity
absorbance of the second polymer.
6. The light diffusion member as claimed in claim 1, wherein the
first polymer includes polyester-based polymer.
7. The light diffusion member as claimed in claim 6, wherein the
polyester-based polymer is at least one polymer selected from a
group consisting of polyethylene terephthalate, polybutylene
terephthalate, and polyethylene naphtalate.
8. The light diffusion member as claimed in claim 1, wherein the
second polymer is at least one polymer selected from a group
consisting of polycarbonate, cyclic olefin copolymer, and
polymethyl methacrylate.
9. The light diffusion member as claimed in claim 1, wherein the
first glass transition temperature is in a range of from about 70
to about 80.degree. C. and the second glass transition temperature
is in a range of from about 130 to about 150.degree. C.
10. The light diffusion member as claimed in claim 1, wherein the
beads include at least one polymer selected from a group consisting
of polymethyl methacrylate and polyethylene terephthalate.
11. The light diffusion member as claimed in claim 1, wherein the
binder resin is an acryl-based resin.
12. The light diffusion member as claimed in claim 1, wherein a
thickness of the light diffusing body is in a range of from about
0.7 to about 1.2 mm.
13. The light diffusion member as claimed in claim 1, further
comprising an adhesion preventing layer facing the light exiting
surface of the light diffusing body.
14. The light diffusion member as claimed in claim 13, wherein the
adhesion preventing layer includes at least one polymer selected
from a group consisting of polymethyl methacrylate and polyethylene
terephthalate.
15. A light diffusion member comprising: a light diffusing body
including a polymer mixture of polyethylene
terephthalate/polycarbonate having polyethylene terephthalate and
polycarbonate uniformly blended within the polymer mixture, the
light diffusing body diffusing incident light through a light
exiting surface of the light diffusing body; and a light diffusing
layer formed on the light exiting surface of the light diffusing
body and including a binder resin including beads.
16. The light diffusion member as claimed in claim 15, wherein the
polymer mixture includes about 20-40% by weight of polyethylene
terephthalate and about 60-80% by weight of polycarbonate.
17. The light diffusion member as claimed in claim 16, wherein a
glass transition temperature of the polymer mixture is in a range
of from about 100 to about 121.degree. C.
18. A light diffusion member comprising: a light diffusing body
including a polymer mixture having a plurality of polymers
uniformly blended within the polymer mixture and diffusing an
incident light to a light exiting surface of the light diffusing
body; and a light diffusing layer formed on the light exiting
surface of the light diffusing body and including a binder resin
having beads.
19. The light diffusion member as claimed in claim 18, wherein the
polymer mixture exhibits a humidity absorbance proportional to a
glass transition temperature thereof.
20. A light diffusion member comprising a light diffusing body
including a copolymer having a first polymer having a first glass
transition temperature and a second polymer having a second glass
transition temperature higher than the first glass transition
temperature, the first and second polymers arranged as repeating
units, the light diffusing body diffusing an incident light through
a light exiting surface of the light diffusing body; and a light
diffusing layer formed on the light exiting surface of the light
diffusing body and including a binder resin having beads.
21. The light diffusion member as claimed in claim 20, wherein each
repeating unit includes a layer of one of the first polymer or the
second polymer, wherein at least one layer of the first polymer is
arranged with at least one layer of the second polymer within the
copolymer.
22. The light diffusion member as claimed in claim 20, wherein the
light diffusing body is integrally formed with the light diffusing
layer forming a solitary unit for the light diffusion member and
eliminating gaps between the light diffusing body and the light
diffusing layer.
23. The light diffusion member as claimed in claim 20, wherein a
glass transition temperature of the copolymer is about or greater
than 100.degree. C.
24. The light diffusion member as claimed in claim 20, wherein a
humidity absorbance of the first polymer is lower than a humidity
absorbance of the second polymer.
25. The light diffusion member as claimed in claim 20, wherein the
first polymer includes polyester-based polymer.
26. The light diffusion member as claimed in claim 25, wherein the
polyester-based polymer is at least one polymer selected from a
group consisting of polyethylene terephthalate, polyethylene
naphthalate, and polybutylene terephthalate.
27. The light diffusion member as claimed in claim 20, wherein the
second polymer is at least one polymer selected from a group
consisting of polycarbonate, cyclic olefin copolymer, and
polymethyl methacrylate.
28. The light diffusion member as claimed in claim 20, wherein the
first glass transition temperature is in a range of from about 70
to about 80.degree. C. and the second glass transition temperature
is in a range of from about 130 to about 150.degree. C.
29. A light diffusion member comprising: a light diffusing body
including a copolymer including polyethylene terephthalate and
polycarbonate as repeating units and having a molecular weight of
from about 10,000 to about 100,000, the light diffusing body
diffusing an incident light through a light exiting surface of the
light diffusing body; and a light diffusing layer formed on the
light exiting surface of the light diffusing body and including a
binder resin having beads.
30. The light diffusion member as claimed in claim 29, wherein the
copolymer includes polyethylene terephthalate and polycarbonate
repeatedly by a 1:1.5-4.0 weight ratio.
31. The light diffusion member as claimed in claim 30, wherein a
glass transition temperature of the copolymer is in a range of from
about 100 to about 121.degree. C.
32. A light diffusion member comprising: a light diffusing body
including a copolymer including a plurality of polymers as
repeating units, the light diffusing body diffusing an incident
light through a light exiting surface of the light diffusing body;
and a light diffusing layer formed on the light exiting surface of
the light diffusing body and including a binder resin having
beads.
33. The light diffusion member of claim 32, wherein each repeating
unit includes at least one layer of each of the plurality of
polymers, wherein each layer is arranged within the copolymer.
34. The light diffusion member as claimed in claim 32, wherein a
humidity absorbance of the copolymer is proportional to a glass
transition temperature thereof.
35. A copolymer for a light diffusion member, the copolymer
including a first repeating unit of at least one polymer selected
from a group consisting of polyethylene terephthalate, polybutylene
terephthalate, and polyethylene naphthalate and a second repeating
unit of at least one polymer selected from a group consisting of
polycarbonate, cyclic olefin copolymer, and polymethyl methacrylate
in a mixing ratio of 2-4:6-8 by weight, the copolymer having a
glass transition temperature in a range of from about 100 to about
125.degree. C.
36. The copolymer for the light diffusion member as claimed in
claim 35, wherein a molecular weight of the copolymer is in a range
of from about 10,000 to about 100,000.
37. The copolymer for the light diffusion member as claimed in
claim 35, wherein a humidity absorbance of the copolymer is in a
range of from about 0.01 to about 1.0%.
38. A back light assembly comprising: a receiving container; a
light source generating light, the light source received in the
receiving container; and a light diffusion member provided on the
light source and including a light diffusing body and a light
diffusing layer, the light diffusing body including a polymer
mixture having a first polymer having a first glass transition
temperature and a second polymer having a second glass transition
temperature higher than the first glass transition temperature, the
first and second polymers uniformly blended within the polymer
mixture, the light diffusing body diffusing an incident light
through a light exiting surface of the light diffusing body, and
the light diffusing layer formed on the light exiting surface of
the light diffusing body and including a binder resin having
beads.
39. The back light assembly as claimed in claim 38, wherein the
first polymer is polyethylene terephthalate and the second polymer
is polycarbonate.
40. The back light assembly as claimed in claim 39, wherein the
polymer mixture includes about 20-40% by weight of polyethylene
terephthalate and about 60-80% by weight of polycarbonate.
41. The back light assembly as claimed in claim 38, wherein a glass
transition temperature of the polymer mixture is about or greater
than 100.degree. C.
42. The back light assembly as claimed in claim 38, wherein a
thickness of the light diffusing body is in a range of from about
0.7 to about 1.2 mm.
43. The back light assembly as claimed in claim 38, further
comprising a light collecting member improving a front side
luminance and a passivating layer protecting the light collecting
member.
44. A back light assembly comprising: a receiving container; a
light source generating light, the light source received in the
receiving container; and a light diffusion member provided on the
light source and including a light diffusing body and a light
diffusing layer, the light diffusing body including a copolymer
including a first polymer having a first glass transition
temperature and a second polymer having a second glass transition
temperature higher than the first glass transition temperature, the
first polymer and the second polymer within the copolymer as
repeating units, the light diffusing body diffusing an incident
light through a light exiting surface of the light diffusing body,
and the light diffusing layer formed on the light exiting surface
of the light diffusing body and including a binder resin having
beads.
45. The back light assembly as claimed in claim 44, wherein the
first polymer is polyethylene terephthalate and the second polymer
is polycarbonate.
46. The back light assembly as claimed in claim 45, wherein the
polyethylene terephthalate and polycarbonate are polymerized in a
mixing ratio of 1:1.5-4.0 by weight.
47. The back light assembly as claimed in claim 44, wherein a glass
transition temperature of the copolymer is about or greater than
100.degree. C.
48. The back light assembly as claimed in claim 44, wherein a
thickness of the light diffusing body is in a range of from about
0.7 to about 1.2 mm.
49. A liquid crystal display device comprising: a) a back light
assembly comprising: a receiving container; a light source
generating light, the light source received in the receiving
container; and a light diffusion member provided on the light
source and including a light diffusing body and a light diffusing
layer, the light diffusing body including one of a polymer mixture
including a first polymer having a first glass transition
temperature and a second polymer having a second glass transition
temperature higher than the first glass transition temperature, the
first and second polymers uniformly blended within the polymer
mixture, and a copolymer of the first polymer and the second
polymer as repeating units, the light diffusing body diffusing an
incident light through a light exiting surface of the light
diffusing body, and the light diffusing layer formed on the light
exiting surface of the light diffusing body and including a binder
resin having beads; and b) a display unit provided on the light
diffusion member, the display unit changing diffused light into an
image light including information.
50. The liquid crystal display device as claimed in claim 49,
wherein the first polymer is polyethylene terephthalate and the
second polymer is polycarbonate.
51. The liquid crystal display device as claimed in claim 50,
wherein the polymer mixture includes about 20-40% by weight of
polyethylene terephthalate and about 60-80% by weight of
polycarbonate
52. The liquid crystal display device as claimed in claim 50,
wherein the copolymer includes polyethylene terephthalate and
polycarbonate polymerized in a mixing ratio of about 1:1.5-4.0 by
weight.
53. The liquid crystal display device as claimed in claim 49,
wherein a glass transition temperature of the polymer mixture and
the copolymer is about or greater than 100.degree. C.
54. The liquid crystal display device as claimed in claim 49,
wherein a thickness of the light diffusing body is in a range of
from about 0.7 to about 1.2 mm.
Description
[0001] This application claims priority to Korean Patent
Application No. 2004-90109, filed on Nov. 6, 2004 and all the
benefits accruing therefrom under 35 U.S.C. .sctn.119, and 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 diffusion member, a
back light assembly including the same, a display device including
the same, and a copolymer for the light diffusion member. More
particularly, the present invention relates to a light diffusion
member exhibiting an improved light luminance and an improved light
diffusing efficiency with a reduced manufacturing cost, a back
light assembly including the same, and a display device including
the same.
[0004] 2. Description of the Related Art
[0005] Generally, a display device transforms data having electric
signals after being processed by an information processing unit
into an image. A liquid crystal display device is one type of
display device and displays an image utilizing an electric
characteristic and an optical characteristic of liquid crystal.
[0006] The liquid crystal display device includes a liquid crystal
display panel and a device for providing light to display the
image. Light generated from the device for providing light passes
through liquid crystal included in the liquid crystal panel to
display the image on the liquid crystal display panel.
[0007] The quality of the displayed image on the liquid crystal
display device is largely dependent on the luminance and luminance
uniformity of the light generated from the device for providing
light.
[0008] In order to improve the luminance and the luminance
uniformity of the image, an optical membrane is provided between
the device for providing light and the liquid crystal display
panel. The optical membrane improves the uniformity of the
luminance and the luminance uniformity of the light generated from
the device for providing light to improve the quality of the image
displayed on the liquid crystal display panel.
[0009] A diffusion member, such as a diffusion plate and a
diffusion sheet, is used to induce the diffusion of light. The
diffusion plate is commonly used in a liquid crystal display device
for a television set, and the diffusion sheet is generally provided
on the diffusion plate. The diffusion plate is generally
manufactured using polymethyl methacrylate ("PMMA"). This material
functions to induce a light diffusing phenomenon when the light
passes there through to increase the uniformity of the non-uniform
light luminance of the light from a light source to some degree. In
general, the diffusion sheet includes PMMA beads coated on a base
matrix and diffuses light. The base matrix is generally obtained by
using polyethylene terephthalate ("PET").
[0010] However, the PET based material of the base matrix is
affected when the diffusion plate is deformed. Also, the PET base
itself might be deformed due to an applied heat that might then
induce a wrinkling phenomenon of the diffusion sheet.
[0011] In addition, the light diffusion member including the
diffusion plate and the diffusion sheet according to the
conventional method might generate luminance loss due to an air gap
present between the diffusion plate and the diffusion sheet.
BRIEF SUMMARY OF THE INVENTION
[0012] The present invention provides a light diffusion member
providing an improved light luminance and an improved light
diffusing efficiency, preventing a wrinkling phenomenon, and
reducing the manufacturing cost.
[0013] The present invention also provides a back light assembly
including the above light diffusion member.
[0014] The present invention still also provides a liquid crystal
display device including the above light diffusion member.
[0015] The present invention still also provides a copolymer
applicable for the above light diffusion member.
[0016] In accordance with an exemplary embodiment of the present
invention, there is provided a light diffusion member including a
light diffusing body and a light diffusing layer. The light
diffusing body includes a polymer mixture obtained by uniformly
blending a first polymer having a first glass transition
temperature and a second polymer having a second transition
temperature higher than the first transition temperature. The light
diffusing body diffuses an incident light through a light exiting
surface of the light diffusing body. The light diffusing layer is
formed on the light exiting surface of the light diffusing body and
includes a binder resin having beads.
[0017] In accordance with another exemplary embodiment of the
present invention, there is provided a light diffusion member
including a light diffusing body and a light diffusing layer. The
light diffusing body includes a polymer mixture of polyethylene
terephthalate/polycarbonate obtained by uniformly blending
polyethylene terephthalate and polycarbonate. The light diffusing
body diffuses incident light through a light exiting surface of the
light diffusing body. The light diffusing layer is formed on the
light exiting surface of the light diffusing body and includes a
binder resin including beads.
[0018] In accordance with still another exemplary embodiment of the
present invention, there is provided a light diffusion member
including a light diffusing body and a light diffusing layer. The
light diffusing body includes a polymer mixture obtained by
uniformly blending a plurality of polymers. The light diffusing
body diffuses an incident light towards a light exiting surface of
the light diffusing body. The light diffusing layer is formed on
the light exiting surface of the light diffusing body and includes
a binder resin having beads.
[0019] In accordance with still another exemplary embodiment of the
present invention, there is provided a light diffusion member
including a light diffusing body and a light diffusing layer. The
light diffusing body includes a copolymer having a first polymer
having a first glass transition temperature and a second polymer
having a second glass transition temperature higher than the first
glass transition temperature. The first and second polymers are
arranged as repeating units. The light diffusing body diffuses an
incident light through a light exiting surface of the light
diffusing body. The light diffusing layer is formed on the light
exiting surface of the light diffusing body and includes a binder
resin having beads.
[0020] In accordance with still another exemplary embodiment of the
present invention, there is provided a light diffusion member
including a light diffusing body and a light diffusing layer. The
light diffusing body includes a copolymer including polyethylene
terephthalate and polycarbonate as repeating units. The light
diffusing body diffuses an incident light through a light exiting
surface. The light diffusing layer is formed on the light exiting
surface of the light diffusing body and includes a binder resin
having beads.
[0021] In accordance with still another exemplary embodiment of the
present invention, there is provided a light diffusion member
including a light diffusing body and a light diffusing layer. The
light diffusing body includes a copolymer including a plurality of
polymers as repeating units. The light diffusing body diffuses an
incident light through a light exiting surface. The light diffusing
layer is formed on the light exiting surface of the light diffusing
body and includes a binder resin having beads.
[0022] In accordance with still another exemplary embodiment of the
present invention, there is provided a copolymer for a light
diffusion member, the copolymer including a first repeating unit of
at least one polymer selected from a group consisting of
polyethylene terephthalate, polybutylene terephthalate, and
polyethylene naphthalate and a second repeating unit of at least
one polymer selected from a group consisting of polycarbonate,
cyclic olefin copolymer, and polymethyl methacrylate in a mixing
ratio of 2-4:6-8 by weight. The copolymer has a glass transition
temperature in a range of from about 100 to about 125.degree.
C.
[0023] In accordance with still another exemplary embodiment of the
present invention, there is provided a back light assembly
including a receiving container, a light source generating light,
the light source received in the receiving container, and a light
diffusion member provided on the light source and including a light
diffusing body and a light diffusing layer. The light diffusing
body includes a polymer mixture obtained by uniformly blending a
first polymer having a first glass transition temperature and a
second polymer having a second glass transition temperature higher
than the first glass transition temperature. The light diffusing
body diffuses an incident light through a light exiting surface of
the light diffusing body. The light diffusing layer is formed on
the light exiting surface of the light diffusing body and includes
a binder resin having beads.
[0024] In accordance with still another exemplary embodiment of the
present invention, there is provided a back light assembly
including a receiving container, a light source generating light,
the light source received in the receiving container, and a light
diffusion member provided on the light source and including a light
diffusing body and a light diffusing layer. The light diffusing
body includes a copolymer including a first polymer having a first
glass transition temperature and a second polymer having a second
glass transition temperature higher than the first glass transition
temperature as repeating units. The light diffusing body diffuses
an incident light through a light exiting surface of the light
diffusing body. The light diffusing layer is formed on the light
exiting surface of the light diffusing body and includes a binder
resin having beads.
[0025] In accordance with still another exemplary embodiment of the
present invention, there is provided a liquid crystal display
device including a back light assembly and a display unit provided
on a light diffusion member of the back light assembly, the display
unit changing diffused light into an image light including
information. The back light assembly includes a receiving
container, a light source generating light, the light source
received in the receiving container, and a light diffusion member
provided on the light source and including a light diffusing body
and a light diffusing layer. The light diffusing body includes one
of a polymer mixture obtained by uniformly blending a first polymer
having a first glass transition temperature and a second polymer
having a second glass transition temperature higher than the first
glass transition temperature and a copolymer of the first polymer
and the second polymer as repeating units. The light diffusing body
diffuses an incident light through a light exiting surface of the
light diffusing body. The light diffusing layer is formed on the
light exiting surface of the light diffusing body and includes a
binder resin having beads.
[0026] According to the light diffusion member of the present
invention, a light luminance and a light diffusing efficiency of a
liquid crystal display device including the light diffusion member
can be improved and a wrinkling phenomenon of the light diffusion
member may be prevented. In addition, the manufacturing cost of the
liquid crystal display device may be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The above and other features and advantages of the present
invention will become more apparent by describing in detailed
exemplary embodiments thereof with reference to the accompanying
drawings, in which:
[0028] FIG. 1 is a schematic cross-sectional view showing an
exemplary embodiment of a light diffusion member according to the
present invention;
[0029] FIG. 2 is a schematic cross-sectional view showing an
exemplary embodiment of a back light assembly according to the
present invention;
[0030] FIG. 3 is an exploded perspective view showing an exemplary
embodiment of a liquid crystal display device according to the
present invention;
[0031] FIG. 4 is a graph illustrating an exemplary embodiment of
the change in the elastic modulus of PET/PC polymer mixture with
respect to the temperature according to the present invention;
[0032] FIG. 5 is a graph illustrating an exemplary embodiment of
the change in a glass transition temperature of a PET/PC polymer
mixture in the light diffusing body with respect to PET weight
fraction according to the present invention; and
[0033] FIG. 6 is a graph illustrating an exemplary embodiment of a
heat absorbing amount of a PET/PC polymer mixture in the light
diffusing body according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary 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.
[0035] In the drawings, the thickness of layers, films, and regions
are exaggerated for clarity. Like reference numerals refer to
similar or identical elements throughout. It will be understood
that when an element such as a layer, film, region, or substrate is
referred to as being "on" another element, it can be directly on
the other element or intervening elements may also be present.
[0036] Light Diffusion Member
EMBODIMENT 1
[0037] FIG. 1 is a schematic cross-sectional view showing an
exemplary embodiment of a light diffusion member according to the
present invention.
[0038] Referring to FIG. 1, a light diffusion member 100 includes a
light diffusing body 10 and a light diffusing layer 20 formed on
the light diffusing body 10. The light diffusion member 100
diffuses incident light from a light source 50 through a light
exiting surface of the light diffusing body 10, where the light
exiting surface may be a layer of the light diffusing body 10, or
may simply be the outermost surface of the light diffusing body 10
that faces the light diffusing layer 20. The light diffusion member
100 includes a polymer mixture obtained by uniformly blending a
first polymer and a second polymer.
[0039] Through the blending, two or more polymers having different
physical properties are uniformly mixed in a predetermined mixing
ratio. A complex material having a novel physical property can be
prepared through the blending process. The blending process is
preferably implemented until a uniform product is obtained. When
the mixture is non-uniformly blended, the glass transition
temperature or a humidity absorbance of the polymer mixture is not
constant and thus the obtained mixture would not be made
commercially available.
[0040] The polymers are preferably selected so that the polymer
mixture exhibits a high glass transition temperature and a low
humidity absorbance. Different polymers having complementary
properties can be selected to optimize the desired properties of
the polymer mixture. In addition, the price of each polymer also
might be considered as a factor in determining which polymers to
utilize in the polymer mixture. The preferred glass transition
temperature of the polymer mixture is about 100.degree. C. or
higher. The glass transition temperature of polymethyl methacrylate
("PMMA") included in the conventional light diffusing body is about
104.degree. C. Accordingly, a polymer mixture of which the glass
transition temperature is at least 100.degree. C. or higher is
required for the manufacture of the light diffusing body 10 in
place of the conventional light diffusing body of PMMA.
[0041] For the first polymer and the second polymer included in the
polymer mixture, polymers producing a polymer mixture having a
glass transition temperature of 100.degree. C. or higher and a
lower humidity absorbance than PMMA through the blending process
can be used. In an exemplary embodiment, the first polymer includes
a polyester-based polymer such as polyethylene terephthalate
("PET"), polyethylene naphthalate, and polybutylene terephthalate.
The polyester-based first polymer has an advantage of having a low
humidity absorbance. The second polymer includes polycarbonate
("PC"), cyclic olefin copolymer ("COC"), polymethyl methacrylate,
and the like. The glass transition temperature of the first polymer
is about 70 to about 80.degree. C. and the glass transition
temperature of the second polymer is about 130 to about 150.degree.
C. The first and second polymers are blended in a predetermined
mixing ratio to prepare the polymer mixture having the glass
transition temperature of about 100.degree. C. or higher.
[0042] The light diffusing layer 20 includes a binder resin 22
having a plurality of beads 24 distributed throughout the binder
resin 22. The beads 24 are formed using PMMA, PET, etc. For the
binder resin, an acryl-based resin such as PMMA can be used.
[0043] The light diffusing body 10 is manufactured as follows. The
first polymer and the second polymer are blended in a blending
apparatus and then the obtained product is cooled. The cooled
product is extruded and cut to a predetermined shape, such as, but
not limited to, a rectangular plate shape. The thickness of the
formed light diffusing body 10 is set when the light diffusing body
10 is passed through a T-Die after the blending. The preferred
thickness of the light diffusing body is from about 0.7 to about
1.2 mm. When the thickness of the light diffusing body 10 is less
than 0.7 mm, the elastic modulus of the light diffusing body 10 is
too low and a surface wrinkling due to the contraction of the
material may be generated. When the thickness of the light
diffusing body 10 exceeds 1.2 mm, a curvilinear motion of the light
diffusing body 10 while moving on a roll for coating the light
diffusing layer 20 becomes difficult.
[0044] On the light diffusion member 100, such as on the light
diffusing body 10, an adhesion preventing layer facing the light
exiting surface of the light diffusing body 10 may be formed. The
adhesion preventing layer functions to prevent the slip of the
light diffusing body 10 while moving on the roll for coating the
light diffusing layer 20. The adhesion preventing layer may be
formed using PMMA, PET, and the like.
[0045] The light diffusing body 10 is preferably formed using a
PET/PC polymer mixture obtained by uniformly blending PET with
PC.
[0046] PC is prepared by using a solvent polymerization method.
According to the solvent polymerization method, a reaction proceeds
at an interface of an aqueous layer in which bisphenol A ("BPA") is
dissolved and an organic solvent layer in which phosgene ("CDC") is
dissolved, under the presence of an acid binder and a solvent.
[0047] The polymer mixture includes about 20-40% by weight of PET
and about 60-80% by weight of PC. The mixing ratio is determined by
considering the high humidity absorbance of PET and the high glass
transition temperature of PC. The glass transition temperature of
the PET/PC polymer mixture is calculated by following Equation 1.
T.sub.g=(T.sub.g1T.sub.g2)/(w.sub.1T.sub.g2+w.sub.2T.sub.g1)
[Equation 1]
[0048] In Equation 1, T.sub.g, T.sub.g1 and T.sub.g2 respectively
represent the glass transition temperature T.sub.g of the polymer
mixture, the glass transition temperature T.sub.g1 of the first
polymer, and the glass transition temperature T.sub.g2 of the
second polymer. W.sub.1 and W.sub.2 represent the weight percents
of the first polymer and the second polymer, respectively.
[0049] The glass transition temperature T.sub.g1 of PET is about
78.degree. C. and the glass transition temperature T.sub.g2 of PC
is about 140.degree. C. Accordingly, the glass transition
temperature T.sub.g of the PET/PC polymer mixture obtained by
mixing 20% by weight of PET and 80% by weight of PC is
approximately 116.degree. C. Because this temperature T.sub.g is
higher than the glass transition temperature of PMMA, about 104 to
106.degree. C., the probability of generating deformation due to
heat, etc. can be reduced. In addition, since this PET/PC polymer
mixture includes PET having very low humidity absorbance, the
durability thereof is very good.
[0050] When considering the humidity absorbance of the PET/PC
polymer mixture, the preferred glass transition temperature T.sub.g
is about 100-121.degree. C.
[0051] While, thus far, the polymer mixture in the light diffusing
body 10 has been described as including a first polymer and a
second polymer, the polymer mixture included in the light diffusing
body 10 might include three or more polymers. Each polymer may have
different glass transition temperatures and humidity absorbances
from one another. Preferably, polymers that give a polymer mixture
having an optimized glass transition temperature T.sub.g, humidity
absorbance, and lower cost are selected.
[0052] Referring again to FIG. 1, the light diffusing layer 20 is
formed on the light diffusing body 10 by means of a coating method.
According to this embodiment, the light diffusing layer 20 is
directly coated on the light diffusing body 10 by means of the
coating method to produce the light diffusion member 100 and thus
does not require a base matrix as part of the light diffusion
member 100. Therefore, the wrinkling phenomenon due to a
deformation of the base matrix is not generated in the light
diffusion member 100. That is, in the light diffusion member 100,
the light diffusing body 10 and the light diffusing layer 20 are
formed in one integrally body, as a solitary unit rather than as
separate sheets. Therefore, the manufacturing efficiency is
improved and the unit manufacturing cost is reduced. Also, the
thickness of the liquid crystal display device may be reduced and a
gap between the light diffusing body 10 and the light diffusing
layer 20 is eliminated.
EXAMPLE 1
Manufacture of PET/PC Light Diffusing Body
[0053] 0.4 ton of chip-shaped PET and 1.6 ton of PC were put into a
blending apparatus, a twin screw extruder manufactured by Killon
Co., Ltd. The PET and PC were then blended at a temperature of
280.degree. C. Then, the blended product was extruded, allowed to
pass through a T-die, and then cooled in a cooling apparatus to a
temperature of 30.degree. C. The extruded and cooled light
diffusing body was transported on a roll and cut to a desired
size.
EMBODIMENT 2
[0054] The light diffusion member 100 according to this present
embodiment includes the same components described in Embodiment 1
except utilizes a different arrangement for the light diffusing
body 10. Therefore, the same reference numerals are given to the
same components and repeated explanation will be omitted.
[0055] The light diffusion member 100 according to this embodiment
includes a copolymer within the light diffusing body 10 having the
first and the second polymers arranged as repeating units. That is,
for example, instead of blending the first and second polymers to
form a polymer mixture as in Embodiment 1, at least one layer of
the first polymer and at least one layer of the second polymer form
the light diffusing body 10. The copolymer exhibits an improved
stability or uniformity of physical properties such as glass
transition temperature and humidity absorbance, when compared with
the polymer mixture prepared by Example 1.
[0056] The second polymer preferably has a higher glass transition
temperature (T.sub.g2) and a higher humidity absorbance than the
first polymer. The preferred glass transition temperature T.sub.g
of the copolymer is about 100.degree. C. or higher. The glass
transition temperature of PMMA included in the conventional light
diffusing body is about 104.degree. C. Therefore, in order to
replace PMMA for the preparation of the light diffusing body 10, a
copolymer having a glass transition temperature of at least
100.degree. C. is required.
[0057] For the first and the second polymers, polymers producing a
copolymer having the glass transition temperature T.sub.g of about
100.degree. C. or higher and the humidity absorbance lower than
that of PMMA can be used. As the first polymer, polyester-based
polymer such as PET, polyethylene naphthalate, and polybutylene
terephthalate can be used. Also, as the second polymer, PC, cyclic
olefin copolymer, and PMMA, and the like can be used. The preferred
glass transition temperature T.sub.g1 of the first polymer is about
70-80.degree. C. and the preferred glass transition temperature
T.sub.g2 of the second polymer is about 130-150.degree. C.
Preferably, a copolymer including the two polymers as repeating
units having the glass transition temperature of about 100.degree.
C. or higher is used.
[0058] The light diffusing body 10 preferably includes the
copolymer including PET and PC as repeating units.
[0059] The repeating units of PET and PC are linearly arranged in a
mixing ratio of 2-4:6-8 by weight. The units, or layers, of the
polymers may have varying thicknesses. The mixing ratio by weight
is determined so that the high humidity absorbance of PET and the
high glass transition temperature of PC can be maximized. The
transition temperature T.sub.g of the copolymer can be calculated
by following Equation 1.
T.sub.g=(T.sub.g1T.sub.g2)/(w.sub.1T.sub.g2+w.sub.2T.sub.g1)
[Equation 1]
[0060] In the equation 1, T.sub.g, T.sub.g1 and T.sub.g2,
respectively, represent the glass transition temperature T.sub.g of
the copolymer, the glass transition temperature T.sub.g1 of the
first polymer, and the glass transition temperature T.sub.g2 of the
second polymer. W.sub.1 and W.sub.2, respectively, represent the
weight percents of the first polymer and the second polymers
repeated in the copolymer.
[0061] The glass transition temperature T.sub.g1 of PET is about
78.degree. C. and the glass transition temperature T.sub.g2 of PC
is about 140.degree. C. When the copolymer includes 20% by weight
of PET and 80% by weight of PC, the glass transition temperature
T.sub.g of the copolymer becomes approximately 116.degree. C.
according to the above-described Equation 1. Since this temperature
T.sub.g is higher than the glass transition temperature of PMMA,
which is about 104 to 106.degree. C., the probability of
deformation due to heat can be reduced. In addition, since the
physical property of PET having a very low humidity absorbance is
exhibited, the durability thereof is also very good.
[0062] The glass transition temperature T.sub.g of the PET/PC
copolymer is preferably in the range of about 100 to 121.degree. C.
when considering the humidity absorbance.
[0063] The light diffusing body 10 may also include a copolymer
having three or more polymers arranged as repeating units or layers
according to this embodiment. Each polymer exhibits a different
glass transition temperature T.sub.g and humidity absorbance. By
considering the properties of polymers, appropriate polymers giving
the copolymer an optimized glass transition temperature T.sub.g and
humidity absorbance are selected.
[0064] Copolymer for Light Diffusion Member
[0065] The copolymer for the light diffusion member 100 includes
the first repeating unit of PET, polyethylene naphthalate, or
polybutylene terephthalate and the second repeating unit of PC,
cyclic olefin copolymer, or PMMA, and the first and second
repeating units are arranged repeatedly, that is, there may be a
plurality of each repeating unit or layer provided within the
copolymer and the first and second repeating units may be
alternatingly arranged in a pattern or irregularly. The copolymer
includes the first polymer and the second polymer in a mixing ratio
of 2-4:6-8 by weight and has a glass transition temperature of
about 100-125.degree. C.
[0066] The molecular weight of the copolymer for the light
diffusion member 100 is about 10,000 to 100,000. The humidity
absorbance of the copolymer is about 0.01-1.0%.
[0067] The preferred copolymer for the light diffusion member is a
block copolymer including the first repeating unit of PET and the
second repeating unit of PC in a mixing ratio of 2:8 by weight, and
the first and second repeating units are arranged repeatedly and
irregularly. The glass transition temperature T.sub.g of the block
copolymer is about 116.degree. C. and the molecular weight thereof
is about 10,000 to 100,000.
[0068] Since the copolymer has a higher glass transition
temperature T.sub.g and a lower humidity absorbance than the
conventionally used PMMA, the probability of deformation of the
light diffusion member 100 due to heat and the change of the
physical properties due to humidity may be reduced, thereby
improving the performance of the light diffusion member 100.
[0069] Back Light Assembly
EMBODIMENT 3
[0070] FIG. 2 is a schematic cross-sectional view showing an
exemplary embodiment of a back light assembly according to the
present invention.
[0071] Referring to FIG. 2, a back light assembly 500 includes a
receiving container (not shown), a light source 50 and a light
diffusion member 100. In this embodiment, a plurality of vertically
downward radiating lamps is used as the light source 50, however
other types of lamps and lamp arrangements are within the scope of
these embodiments. The light source 50 is received in the receiving
container and generates light to radiate the light to the light
diffusion member 100. The light diffusion member 100 includes a
light diffusing body 10 and a light diffusing layer 20. Since the
light diffusion member 100 in this embodiment is illustrated and
described with respect to FIG. 1 and Embodiment 1, the same
reference numerals are given to the same components of the light
diffusion member 100 and the same explanation of the components
will be omitted.
[0072] The back light assembly 500 further includes a light
collecting member 110 and a passivation layer 120. The light
collecting member 110 is provided on the light diffusion member
100. The light collecting member 110 refracts light passed through
the light diffusion member 100 and collects the light toward a
displaying unit (not shown). Therefore, the light collecting member
110 improves a front side luminance. The passivation layer 120 is
provided on the light collecting member 110 and physically protects
the light collecting member 110.
[0073] As the light source 50, an edge-type lamp may alternatively
be used.
EMBODIMENT 4
[0074] A back light assembly according to this embodiment includes
the same components as described with respect to Embodiment 3
except for a different light diffusion member 100. Accordingly, the
explanation on the same components will be omitted.
[0075] The back light assembly 500 according to this embodiment
includes the light diffusion member 100. The light diffusion member
100 includes the light diffusing body 10 including the copolymer
described in Embodiment 2.
[0076] Liquid Crystal Display Device
EMBODIMENT 5
[0077] FIG. 3 is an exploded perspective view showing an exemplary
embodiment of a liquid crystal display device according to the
present invention. The explanation of the light diffusion member
100 will be omitted and the same reference numerals are given to
the same components because the same light diffusion member 100
illustrated in FIG. 1 and described with respect to Embodiments 1
and 2 is used.
[0078] Referring to FIG. 3, a liquid crystal display device 1000
includes a display unit 400 for displaying an image by an applied
image signal and a back light assembly 500 for providing light to
the display unit 400.
[0079] The display unit 400 includes a liquid crystal display panel
410, a data printed circuit board 420, a gate printed circuit board
430, a data tape carrier package ("TCP") 440, and a gate TCP 450.
The liquid crystal display panel 410 includes a TFT substrate 411
and a color filter substrate 413, and liquid crystal (not shown) is
injected between the TFT substrate 411 and the color filter
substrate 413.
[0080] The TFT substrate 411 is a transparent glass substrate on
which TFTs (not shown) are formed in a matrix shape. Although not
illustrated for clarity, a data line is connected to a source
terminal of the TFT, and a gate line is connected to a gate
terminal thereof. To a drain terminal, a pixel electrode includes a
transparent and conductive material such as, but not limited to,
indium tin oxide ("ITO"). When an electric signal is inputted to
the data line and the gate line, the electric signal is inputted
into the source terminal and the gate terminal of the TFT.
According to the input of the electric signal, the TFT is turned-on
or turned-off to output an electric signal necessary to form a
pixel through the drain terminal.
[0081] The color filter substrate 413 is a substrate on which color
pixels of red, blue, and green ("RGB") pixels are formed for
illustrating predetermined color when the light transmits. The
front surface of the color filter substrate 413 is coated with a
common electrode including a transparent and conductive material
such as, but not limited to, ITO.
[0082] When an electric power is applied to the gate terminal and
the source terminal of the transistor of the TFT substrate 411 and
the TFT is turned-on, an electric field is formed between the pixel
electrode of the TFT substrate 411 and the common electrode of the
color filter substrate 413. When the electric field is formed, the
arranging angle of the liquid crystal injected between the TFT
substrate 411 and the color filter substrate 413 is changed so that
the transmissivity of the liquid crystal is also changed to
accomplish a desired pixel.
[0083] As shown in the figures, a data TCP for determining the
applying time of a data driving signal is attached to the data line
of the liquid crystal display panel 410, and a gate TCP 450 for
determining the applying time of a gate driving signal is attached
to the gate line. The data printed circuit board 420 connects to
the data TCP 440, receives external image signals of the liquid
crystal display panel 410, and applies a driving signal to the data
line. The gate printed circuit board 430 connects to the gate TCP
450 and applies a driving signal to the gate line.
[0084] In FIG. 3, the liquid crystal display device 1000 separately
includes the data printed circuit board 420 and the gate printed
circuit board 430. However, the liquid crystal display device 1000
may alternatively include a combined printed circuit board (not
shown) of the data printed circuit board 420 and the gate printed
circuit board 430.
[0085] The back light assembly 500 includes a plurality of lamps 52
as the light source 50, a reflecting plate 40, a light diffusion
member 100, a light collecting member 110, a passivation layer 120
for protecting the light collecting member 110, and a receiving
container 30 for receiving the above components. In particular, the
lamps 52 generate light, and the light diffusion member 100 is
provided on the light source 50 to diffuse the light provided from
the light source 50 to output light having uniform luminance. The
light collecting member 110 collects the diffused light from the
light diffusion member 100 toward a display unit 400.
[0086] The liquid crystal display device 1000 includes a lower mold
frame 200 and an upper mold frame 300. The lower mold frame 200
includes two or more lower mold frame members 210, 220, 230, and
240 and the lower mold frame members 210, 220, 230, and 240 are
combined to form a rectangular frame shape. In the lower mold frame
200, a plurality of lamps 52 are received in parallel and within a
stepped portion formed on the lower mold frame 200. The light
diffusion member 100, the light collecting member 110, and the
passivation layer 120 are placed on the stepped portion of the
lower mold frame 200. The upper mold frame 300 is placed on the
passivation layer 120. The upper mold frame 300 has a rectangular
shape and presses the light diffusion member 100, the light
collecting member 110, and the passivation layer 120 towards the
lower mold frame 200. In addition, the liquid crystal display panel
410 is placed on the upper mold frame 300 for a stable support. On
the liquid crystal display panel 410, a top chassis 700 is
provided.
[0087] The light diffusing body 10 of the light diffusion member
100 of the liquid crystal display device 1000 may include either
the polymer mixture prepared as described with respect to
Embodiment 1 or the copolymer prepared as described with respect to
Embodiment 2.
[0088] Performance Test of Light Diffusion Member
[0089] For the light diffusion member 100 having a thickness of
about 0.8 mm and including the polymer mixture prepared by the
Example 1, haze value, transparency, diffraction degree, and
straight light ratio were evaluated and the results are illustrated
in Table 1.
COMPARATIVE EXAMPLE 1
[0090] A conventional light diffusing body was used as Comparative
Example 1. The light diffusing body included a diffusion plate
having a thickness of about 2 mm and comprised PMMA and a diffusing
sheet formed by coating PMMA beads on a base matrix formed using
PET.
[0091] The haze value was calculated using the following equation.
HAZE VALUE=(diffused and transmitted amount of light/total
transmitted amount of light).times.100 [Equation 2] TABLE-US-00001
TABLE 1 Item Example 1 Comparative Example 1 Haze value (%) 93.3
93.4 Transparency (%) 62.76 47.99 Diffraction degree (%) 58.56
58.26 Straight light ratio (%) 4.2 3.17
[0092] Referring to Table 1, the light diffusion member of the
present invention exhibits similar optical characteristics when
compared with PMMA and even better result for the transparency and
diffraction degree.
[0093] Measurements on Elastic Modulus
[0094] FIG. 4 is a graph illustrating an exemplary embodiment of
the change in elastic modulus of PET/PC polymer mixture with
respect to the temperature according to the present invention.
[0095] In order to measure the elastic modulus, the light diffusing
body 10 including the PET/PC polymer mixture prepared by Example 1
was used. As a control, the diffusing plate manufactured by
Comparative Example 1 was used.
[0096] The elastic modulus was measured using a dynamic mechanical
thermal analyzer (vibration number 1 hz, strain 1%).
[0097] Generally, the bending stiffness of a material is
proportional to Et.sup.3 of a plate-shaped structure, where E
represents the elastic modulus of a material and t represents the
thickness of the material. Accordingly, as the thickness and
elastic modulus decrease, the stiffness also decreases. When the
stiffness is small, not much force is applied when contacting with
the display panel 410 of the liquid crystal display device 1000,
thereby reducing the generation of strain on the panel.
[0098] Referring to FIG. 4, since the degree of lowering of the
elastic modulus according to the increase of temperature is weak
for PET/PC when comparing with PMMA, the stiffness of PET/PC is
large when considering the elasticity. However, when considering
the thickness, the stiffness is small and so the generation of
strain of the panel is relatively small.
[0099] Measurements on the Changing Ratio of Glass Transition
Temperature
[0100] FIG. 5 is a graph illustrating an exemplary embodiment of
the change of a glass transition temperature T.sub.g of a PET/PC
polymer mixture in the light diffusing body 10 with respect to PET
weight fraction according to the present invention.
[0101] Referring to FIG. 5, the glass transition temperature
T.sub.g of the PET/PC polymer mixture decreases as the amount of
PET increases. When the amount of PET increases, the humidity
absorbance increases, however, the deformation due to external heat
becomes easier. Therefore, the preferred amount of PET is about 20%
by weight. As shown in FIG. 5, the glass transition temperature
T.sub.g of the polymer mixture is about 116.degree. C. when the
amount of PET is 20%. This temperature is higher than the glass
transition temperature of PMMA, about 106.degree. C. Therefore, the
heat resistance of the light diffusing body 10 of the present
invention is better than that of the conventional light diffusing
plate.
[0102] Measurements on Heat Absorbing Amount
[0103] FIG. 6 is a graph illustrating an exemplary embodiment of a
heat absorbing amount of a PET/PC polymer mixture in the light
diffusing body 10 according to the present invention.
[0104] In order to measure the heat absorbing amount, the light
diffusing body 10 including a PET/PC polymer mixture prepared by
Example 1 was used. As a control, the PMMA light diffusing plate
manufactured by the Comparative Example 1 was used.
[0105] The temperature of the point of inflection for PMMA was
about 109.2.degree. C. and that of the PET/PC polymer mixture was
about 117.6.degree. C. The temperature of the point of inflection
corresponds to the glass transition temperature T.sub.g of each
material.
[0106] As opposed to the conventional light diffusion member that
includes a light diffusing plate separate from a diffusing sheet,
the light diffusion member 100 of the present invention includes
the components in one body, such as one body formed in a solitary
unit. Therefore, the efficiency of the manufacturing process is
improved and the manufacturing cost is lowered.
[0107] Since the light diffusion member of the present invention is
thinner than the conventional light diffusing plate, the
manufacturing of a thinner liquid crystal display device can be
accomplished. Also, the light transparency is good and the
luminance can be improved.
[0108] In addition, the light diffusion member of the present
invention has a good durability with respect to heat or humidity.
In particular, since the light diffusion member has a high glass
transition temperature, the deformation thereof due to heat is
rarely generated. Accordingly, the wrinkling phenomenon exhibited
by the conventional diffusing sheet can be effectively
prevented.
[0109] Further, a problem of a luminance loss due to an air gap
between a diffusing plate and a diffusing sheet can be
prevented.
[0110] Although the exemplary embodiments of the present invention
have been described, it is understood that the present invention
should not be limited to these exemplary embodiments but various
changes and modifications can be made by one ordinary skilled in
the art within the spirit and scope of the present invention as
hereinafter claimed. Moreover, the use of the terms first, second,
etc. do not denote any order or importance, but rather the terms
first, second, etc. are used to distinguish one element from
another. Furthermore, the use of the terms a, an, etc. do not
denote a limitation of quantity, but rather denote the presence of
at least one of the referenced item.
* * * * *