U.S. patent application number 13/461805 was filed with the patent office on 2012-11-08 for display device.
This patent application is currently assigned to UNIVERSITY OF CENTRAL FLORIDA RESEARCH FOUNDATION INC.. Invention is credited to Hui-Chuan Cheng, Takahiro Ishinabe, Ching-Huan Lin, Kang-Hung Liu, Shin-Tson Wu, Jin Yan.
Application Number | 20120280953 13/461805 |
Document ID | / |
Family ID | 47261439 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120280953 |
Kind Code |
A1 |
Cheng; Hui-Chuan ; et
al. |
November 8, 2012 |
DISPLAY DEVICE
Abstract
A display device including a display module, a light source
module, a turning optical film, a first compensation film and a
second compensation film is provided. The display module includes a
first substrate, a second substrate and a display medium. The light
source module generates directional light. The display module is
disposed above the light source module. The second substrate is
disposed opposite to the first substrate. The display medium is
disposed between the first substrate and the second substrate and
is optically isotropic. The turning optical film is disposed on the
second substrate of the display module. The directional light
enters the turning optical film and then exits the turning optical
film to form an output light. The first compensation film is
disposed on the first outer surface of the first substrate. The
second compensation film is disposed between the second substrate
and the turning optical film.
Inventors: |
Cheng; Hui-Chuan; (Taichung
City, TW) ; Yan; Jin; (Hsinchu, TW) ;
Ishinabe; Takahiro; (Hsinchu, TW) ; Wu;
Shin-Tson; (Oviedo, FL) ; Lin; Ching-Huan;
(Tainan City, TW) ; Liu; Kang-Hung; (Hsinchu
County, TW) |
Assignee: |
UNIVERSITY OF CENTRAL FLORIDA
RESEARCH FOUNDATION INC.
Orlando
FL
AU OPTRONICS CORPORATION
Hsinchu
|
Family ID: |
47261439 |
Appl. No.: |
13/461805 |
Filed: |
May 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61481295 |
May 2, 2011 |
|
|
|
Current U.S.
Class: |
345/204 ;
345/87 |
Current CPC
Class: |
G02F 1/1336 20130101;
G02B 6/0053 20130101; G02F 1/133524 20130101; G02F 2001/13793
20130101; G02F 1/1334 20130101; G02F 1/1393 20130101; G02F
2001/133562 20130101 |
Class at
Publication: |
345/204 ;
345/87 |
International
Class: |
G09G 3/36 20060101
G09G003/36; G06F 3/038 20060101 G06F003/038 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 24, 2012 |
TW |
101114566 |
Claims
1. A display device, comprising: a light source module generating a
directional light; a display module disposed above the light source
module, the display module comprising: a first substrate having a
first inner surface and a first outer surface; a second substrate
disposed opposite to the first substrate and having a second inner
surface and a second outer surface; and a display medium disposed
between the first substrate and the second substrate and is
optically isotropic, wherein the display medium is optically
anisotropic when driven with an electric field, the directional
light is not perpendicular to the first outer surface when the
directional light enters the display module, and the directional
light is not perpendicular to the second outer surface when the
directional light exits the display module; a turning optical film
disposed on the second outer surface of the second substrate of the
display module, the turning optical film having an incident surface
and an output surface, the directional light entering the turning
optical film from the incident surface and exiting the turning
optical film from the output surface so as to form an output light,
wherein an included angle is between the output light and the
output surface; a first compensation film disposed on the first
outer surface of the first substrate; and a second compensation
film disposed between the second substrate and the turning optical
film.
2. The display device as claimed in claim 1, further comprising: a
first optical film disposed on the first outer surface of the first
substrate, the first optical film having a plurality of first
optical structures allowing the directional light passing through
the first optical structures without generating total reflection;
and a second optical film disposed on the second outer surface of
the second substrate, wherein the second optical film has a
plurality of second optical structures substantially allowing the
directional light passing through the first optical structures
without generating total reflection.
3. The display device as claimed in claim 2, further comprising: a
bottom polarizer disposed on the first outer surface of the first
substrate; and a top polarizer disposed on the second outer surface
of the second substrate.
4. The display device as claimed in claim 3, wherein the bottom
polarizer is disposed between the first compensation film and the
first optical film, the top polarizer is disposed between the
second compensation film and the second optical film, and the
second optical film is disposed between the turning optical film
and the top polarizer.
5. The display device as claimed in claim 4, wherein an orientation
angle of the first compensation film is 20.degree..about.50.degree.
and Nz is 0.35.about.0.75; and an orientation angle of the second
compensation film is -20.degree..about.-50.degree. and Nz is
0.35.about.0.75.
6. The display device as claimed in claim 3, further comprising: a
third compensation film disposed between the first compensation
film and the bottom polarizer; and a fourth compensation film
disposed between the second compensation film and the top
polarizer; and
7. The display device as claimed in claim 6, wherein the third
compensation film and the fourth compensation film are respectively
a biaxial compensation film.
8. The display device as claimed in claim 7, wherein an orientation
angle of the first compensation film is 20.degree..about.40.degree.
and Nz is 0.25.about.0.55; an orientation angle of the second
compensation film is -20.degree..about.-40.degree. and Nz is
0.25.about.0.55; an orientation angle of the third compensation
film is 15.degree..about.35.degree. and Nz is 0.75.about.0.95; and
an orientation angle of the fourth compensation film is
-15.degree..about.-35.degree. and Nz is 0.75.about.0.95.
9. The display device as claimed in claim 6, wherein the bottom
polarizer is a wire-grid polarizer.
10. The display device as claimed in claim 9, wherein an
orientation angle of the first compensation film is
30.degree..about.60.degree. and Nz is 0.35.about.0.65; an
orientation angle of the second compensation film is
-30.degree..about.-60.degree. and Nz is 0.35.about.0.65; an
orientation angle of the third compensation film is
-10.degree..about.10.degree. and Nz is 0.71.about.0.91; and an
orientation angle of the fourth compensation film is
80.degree..about.100.degree. and Nz is 0.71.about.0.91.
11. The display device as claimed in claim 3, further comprising: a
third compensation film disposed between the first compensation
film and the first substrate; and a fourth compensation film
disposed between the second compensation film and the second
substrate.
12. The display device as claimed in claim 11, wherein the third
compensation film and the fourth compensation film are respectively
a biaxial compensation film.
13. The display device as claimed in claim 12, wherein an
orientation angle of the first compensation film is
25.degree..about.55.degree. and Nz is 0.45.about.0.75; an
orientation angle of the second compensation film is
-25.degree..about.-55.degree. and Nz is 0.47.about.0.67; an
orientation angle of the third compensation film is
80.degree..about.100.degree. and Nz is 0.4.about.0.6; and an
orientation angle of the fourth compensation film is
-10.degree..about.10.degree. and Nz is 0.4.about.0.6.
14. The display device as claimed in claim 3, wherein the first
compensation film and the second compensation film are respectively
a biaxial compensation film.
15. The display device as claimed in claim 14, further comprising:
a third compensation film disposed between the bottom polarizer and
the first compensation film, and the first optical film is disposed
between the third compensation film and the first compensation
film; and a fourth compensation film disposed between the second
compensation film and the top polarizer, and the second optical
film is disposed between the fourth compensation film and the top
polarizer.
16. The display device as claimed in claim 15, wherein the turning
optical film is disposed between the second optical film and the
top polarizer.
17. The display device as claimed in claim 16, wherein the third
compensation film is a biaxial compensation film, and the fourth
compensation film comprises an A-plate compensation film and a
C-plate compensation film.
18. The display device as claimed in claim 17, wherein an
orientation angle of the first compensation film is
100.degree..about.125.degree. and Nz is 0.55.about.0.8; an
orientation angle of the second compensation film is
10.degree..about.35.degree. and Nz is 0.8.about.1.0; an orientation
angle of the third compensation film is
-10.degree..about.10.degree. and Nz is 0.6.about.0.8; an
orientation angle of the A-plate compensation film is
-10.degree..about.10.degree., n.sub.o is 1.4.about.1.6, and n.sub.e
is 1.4.about.1.6; and n.sub.o of the C-plate compensation film is
1.4.about.1.6 and n.sub.e is 1.4.about.1.6.
19. The display device as claimed in claim 14, further comprising:
a third compensation film disposed between the bottom polarizer and
the first compensation film, and the bottom polarizer is disposed
between the first optical film and the third compensation film; and
a fourth compensation film disposed between the second compensation
film and the top polarizer, and the second optical film is disposed
between the fourth compensation film and the top polarizer.
20. The display device as claimed in claim 19, wherein the turning
optical film is disposed between the second optical film and the
top polarizer.
21. The display device as claimed in claim 20, wherein the third
compensation film is a biaxial compensation film, and the fourth
compensation film comprises an A-plate compensation film and a
C-plate compensation film.
22. The display device as claimed in claim 21, wherein an
orientation angle of the first compensation film is
-35.degree..about.-55.degree. and Nz is 0.4.about.0.6; an
orientation angle of the second compensation film is
35.degree..about.55.degree. and Nz is 0.4.about.0.6; an orientation
angle of the third compensation film is
-10.degree..about.10.degree. and Nz is 0.45.about.0.65; an
orientation angle of the A-plate compensation film is
-10.degree..about.10.degree., n.sub.o is 1.4.about.1.6, and n.sub.e
is 1.4.about.1.6; and n.sub.o of the C-plate compensation film is
1.4.about.1.6 and n.sub.e is 1.4.about.1.6.
23. The display device as claimed in claim 3, wherein the bottom
polarizer comprises an O-type polarizer, and the top polarizer
comprises an E-type polarizer.
24. The display device as claimed in claim 23, wherein an
orientation angle of the first compensation film is
-35.degree..about.-55.degree. and Nz is 0.4.about.0.6; and an
orientation angle of the second compensation film is
35.degree..about.55.degree. and Nz is 0.4.about.0.6.
25. The display device as claimed in claim 1, wherein the included
angle is 60.degree..about.120.degree..
26. The display device as claimed in claim 25, wherein the included
angle is 90.degree..
27. The display device as claimed in claim 1, further comprising a
diffusion film disposed on the turning optical film.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefits of U.S.
provisional application Ser. No. 61/481,295, filed on May 2, 2011
and Taiwan application serial no. 101114566, filed on Apr. 24,
2012. The entirety of each of the above-mentioned patent
applications is hereby incorporated by reference herein and made a
part of this specification.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a display device, and more
particularly to a liquid crystal display device.
[0004] 2. Description of Related Art
[0005] With vigorous development of display technologies,
consumers' requirements for favorable performance of displays have
been increasing. Specifically, consumers have high demands for the
response time of the displays in addition to the requirements for
resolution, contrast ratio, viewing angle, grey level inversion,
and color saturation.
[0006] To satisfy said requirements, blue phase liquid crystal
displays (LCDs) characterized by fast response speed have been
developed in the industry pertinent to displays. For instance, when
a positive blue phase liquid crystal material is applied, a
transverse electric field is required for operation, such that the
positive blue phase liquid crystal material can function as a light
valve. At this current stage, positive blue phase liquid crystal
molecules in the blue phase LCD are driven by adopting the
electrode design of an in-plane switching (IPS) display module.
[0007] However, in the electrode design of a typical IPS display
module, many regions above the electrodes do not have transverse
electric fields. Consequently, a plurality of liquid crystal
molecules in the blue phase LCD cannot be properly driven, such
that the transmittance of the display module is low. Although the
transmittance of the IPS display module can be enhanced by
increasing the driving voltage, the resulting excess power
consumption is unfavorable. Accordingly, improving the low
transmittance and high driving voltage of the blue phase LCD demand
attention from research and developers. Moreover, further
enhancement of the contrast ratio and viewing angle of the blue
phase LCD is needed.
SUMMARY OF THE INVENTION
[0008] The invention provides a display device capable of solving
issues of low transmittance and high driving voltage when blue
phase liquid crystals are applied in a conventional IPS display
module.
[0009] The invention provides a display device including a light
source module, a display module, a turning optical film, a first
compensation film, and a second compensation film. The light source
module generates a directional light. The display module is
disposed above the light source module, and the display module
includes a first substrate, a second substrate, and a display
medium. The first substrate has a first inner surface and a first
outer surface. The second substrate is disposed opposite to the
first substrate and has a second inner surface and a second outer
surface. The display medium is disposed between the first substrate
and the second substrate and is optically isotropic. The display
medium is optically anisotropic when driven with an electric field.
The directional light is not perpendicular to the first outer
surface when the directional light enters the display module, and
the directional light is not perpendicular to the second outer
surface when the directional light exits the display module. The
turning optical film is disposed on the second outer surface of the
second substrate of the display module. The turning optical film
has an incident surface and an output surface. The directional
light enters the turning optical film from the incident surface,
and exits the turning optical film from the output surface so as to
form an output light. Moreover, an included angle is between the
output light and the output surface. The first compensation film is
disposed on the first outer surface of the first substrate. The
second compensation film is disposed between the second substrate
and the turning optical film.
[0010] In the display device according to an exemplary embodiment
of the invention, the compensation films are disposed between the
top polarizer and bottom polarizer. The configuration of the
compensation films can adjust the polarization state of the
directional light entering the display module, such that the
polarization state of the directional light matches the absorption
axis direction of the top polarizer. Accordingly, light leakage can
be minimized and the contrast ratio and viewing angle of the
display device can be enhanced.
[0011] In order to make the aforementioned and other features and
advantages of the invention more comprehensible, embodiments
accompanying figures are described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings are included to provide further
understanding, and are incorporated in and constitute a part of
this specification. The drawings illustrate exemplary embodiments
and, together with the description, serve to explain the principles
of the invention.
[0013] FIG. 1 is a schematic cross-sectional view of a display
device according to an embodiment of the invention.
[0014] FIG. 2A is a schematic view of an optically isotropic
display medium without an electric field.
[0015] FIG. 2B is a schematic view of an optically anisotropic
display medium in an electric field.
[0016] FIG. 3A and FIG. 3B are schematic cross-sectional views of a
display device according to an embodiment of the invention.
[0017] FIG. 4A is a schematic cross-sectional view of a first
optical film in a display device according to an embodiment of the
invention.
[0018] FIG. 4B is a perspective view of the first optical film
depicted in FIG. 4A.
[0019] FIG. 5A is a schematic cross-sectional view of a second
optical film in a display device according to an embodiment of the
invention.
[0020] FIG. 5B is a perspective view of the second optical film
depicted in FIG. 5A.
[0021] FIG. 6A is schematic cross-sectional view of an optical film
in a display device according to an embodiment of the
invention.
[0022] FIG. 6B is a perspective view of the optical film depicted
in FIG. 6A.
[0023] FIG. 7 is an optical path diagram of light passing through a
first optical film, a second optical film, and a turning optical
film according an embodiment of the invention.
[0024] FIG. 8A is schematic cross-sectional view of an optical film
in a display device according to another embodiment of the
invention.
[0025] FIG. 8B is a perspective view of the optical film depicted
in FIG. 8A.
[0026] FIG. 9A is schematic cross-sectional view of an optical film
in a display device according to another embodiment of the
invention.
[0027] FIG. 9B is a perspective view of the optical film depicted
in FIG. 9A.
[0028] FIG. 10A is schematic cross-sectional view of an optical
film in a display device according to another embodiment of the
invention.
[0029] FIG. 10B is a perspective view of the optical film depicted
in FIG. 10A.
[0030] FIG. 11 and FIG. 12 are schematic cross-sectional views of a
display device according to embodiments of the invention.
[0031] FIG. 13 is a relational diagram of a voltage of a transverse
electric field driving blue phase liquid crystals of a conventional
IPS display module and a transmittance.
[0032] FIGS. 14A and 14B are relational diagrams of a voltage of a
perpendicular electric field of a display device according to an
embodiment of the invention driving blue phase liquid crystals and
a light angle.
[0033] FIG. 15 is a relational diagram of a voltage of a transverse
electric field driving blue phase liquid crystals of a conventional
IPS display module and a transmittance.
[0034] FIG. 16 is a relational diagram of a voltage of a
perpendicular electric field of a display device according to an
embodiment of the invention driving blue phase liquid crystals and
a transmittance.
[0035] FIG. 17 depicts the measurement results of a hysteresis
phenomenon from a transverse electric field driving blue phase
liquid crystals of a conventional IPS display module.
[0036] FIG. 18 depicts the measurement results of a hysteresis
phenomenon from a perpendicular electric field of a display device
according to an embodiment of the invention driving blue phase
liquid crystals.
[0037] FIG. 19 is a relational diagram between display medium
thickness and voltage for a display device according to an
embodiment of the invention.
[0038] FIG. 20 is a relational diagram between voltage and
transmittance under different display thickness conditions for a
display device according to an embodiment of the invention.
[0039] FIG. 21 is a schematic cross-sectional view of a display
device according to a first embodiment of the invention.
[0040] FIG. 22 is a perspective view of a light source module and a
display module in a display device according to an embodiment of
the invention.
[0041] FIG. 23 is a schematic view of a Poincare sphere of a
compensation process during a dark state when a display device
according to the first embodiment of the invention employs
compensation films.
[0042] FIG. 24 is a contour map of the contrast ratios measured on
the display device of FIG. 21 with the parameter setting of Table
1.
[0043] FIG. 25 is a contour map of the contrast ratios measured on
the display device of FIG. 21 with the parameter setting of Table
2.
[0044] FIG. 26 is a contour map of the contrast ratios measured on
the display device of FIG. 21 with the parameter setting of Table
3.
[0045] FIG. 27 is a contour map of the contrast ratios measured on
the display device of FIG. 21 with the parameter setting of Table
4.
[0046] FIG. 28 is a contour map of the contrast ratios measured on
the display device of FIG. 21 with the parameter setting of Table
5.
[0047] FIG. 29 is a contour map of the contrast ratios measured on
the display device of FIG. 21 with the parameter setting of Table
6.
[0048] FIG. 30 is a schematic cross-sectional view of a display
device according to a second embodiment of the invention.
[0049] FIG. 31 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the second embodiment of the invention employs
compensation films.
[0050] FIG. 32 is a contour map of the contrast ratios measured on
the display device of FIG. 30 with the parameter setting of Table
7.
[0051] FIG. 33 is a schematic cross-sectional view of a display
device according to a third embodiment of the invention.
[0052] FIG. 34 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the third embodiment of the invention employs
compensation films.
[0053] FIG. 35 is a contour map of the contrast ratios measured on
the display device of FIG. 33 with the parameter setting of Table
8.
[0054] FIG. 36 is a contour map of the contrast ratios measured on
the display device of FIG. 33 with the parameter setting of Table
9.
[0055] FIG. 37 is a schematic cross-sectional view of a display
device according to a fourth embodiment of the invention.
[0056] FIG. 38 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the fourth embodiment of the invention employs
compensation films.
[0057] FIG. 39 is a contour map of the contrast ratios measured on
the display device of FIG. 37 with the parameter setting of Table
10.
[0058] FIG. 40 is a schematic cross-sectional view of a display
device according to a fifth embodiment of the invention.
[0059] FIG. 41 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the fifth embodiment of the invention employs
compensation films.
[0060] FIG. 42 is a contour map of the contrast ratios measured on
the display device of FIG. 40 with the parameter setting of Table
11.
[0061] FIG. 43 is a contour map of the bright state measurements on
the display device of FIG. 40 with the parameter setting of Table
11.
[0062] FIG. 44 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the fifth embodiment of the invention employs
compensation films.
[0063] FIG. 45 is a contour map of the contrast ratios measured on
the display device of FIG. 40 with the parameter setting of Table
12.
[0064] FIG. 46 is a contour map of the bright state measurements on
the display device of FIG. 40 with the parameter setting of Table
12.
[0065] FIG. 47 is a schematic cross-sectional view of a display
device according to a sixth embodiment of the invention.
[0066] FIG. 48 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the sixth embodiment of the invention employs
compensation films.
[0067] FIG. 49 is a contour map of the contrast ratios measured on
the display device of FIG. 47 with the parameter setting of Table
13.
[0068] FIG. 50 is a contour map of the bright state measurements on
the display device of FIG. 47 with the parameter setting of Table
13.
[0069] FIG. 51 is a schematic cross-sectional view of a display
device according to a seventh embodiment of the invention.
[0070] FIG. 52 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the seventh embodiment of the invention employs
compensation films.
[0071] FIG. 53 is a contour map of the contrast ratios measured on
the display device of FIG. 51 with the parameter setting of Table
14.
[0072] FIG. 54 is a contour map of the bright state measurements on
the display device of FIG. 51 with the parameter setting of Table
14.
DESCRIPTION OF EMBODIMENTS
[0073] FIG. 1 is a schematic cross-sectional view of a display
device according to an embodiment of the invention. With reference
to FIG. 1, a display device 100 of the present embodiment includes
a display module P, a light source module B, and a turning optical
film 25.
[0074] The display module P includes a first substrate 21b, a
second substrate 21a, and a display medium 20.
[0075] The first substrate 21b has an inner surface S1 and an outer
surface S2, and a pixel array 22b is disposed on the inner surface
S1 of the first substrate 21b. The first substrate 21b may be made
of glass, quartz, an organic polymer, or other suitable materials.
According to the present embodiment, the pixel array 22b includes a
plurality of scan lines, a plurality of data lines, and a plurality
of pixel units. Each of the pixel units includes an active element
and a pixel electrode electrically connected to the active element.
Moreover, the active element of the pixel unit is electrically
connected to a corresponding data line and a corresponding scan
line. The active element may a bottom-gate thin film transistor
(TFT) or a top-gate TFT.
[0076] The second substrate 21a is disposed opposite to the first
substrate 21b, and the second substrate 21a has an inner surface S3
and an outer surface S4. Moreover, an opposite electrode 22a is
disposed on the inner surface S3 of the second substrate 21a. The
second substrate 21a may also be made of glass, quartz, an organic
polymer, or other suitable materials. The opposite electrode 22a
completely covers the inner surface S3 of the second substrate 21a.
According to the present embodiment, the opposite electrode 22a is
a transparent electrode, and a material of the transparent
electrode includes a metal oxide such as indium tin oxide (ITO),
indium zinc oxide (IZO), aluminum tin oxide (ATO), aluminum zinc
oxide (AZO), indium germanium zinc oxide, other suitable metal
oxides, or a stacked layer having at least two of the above
materials.
[0077] It should be noted that, a color filter array may be
disposed on the first substrate 21b or the second substrate 21a, so
that the display module P can display color images. However, the
invention is not limited thereto.
[0078] The display medium 20 is disposed between the pixel array
22b of the first substrate 21b and the opposite electrode 22a of
the second substrate 21a. Moreover, the display medium 20 is
optically isotropic when no electric field is applied thereto, as
shown in FIG. 2A. The display medium 20 is optically anisotropic
when a perpendicular electric field 201 is applied thereto, as
shown in FIG. 2B. In other words, when no electric field is
generated between the pixel array 22b and the opposite electrode
22a, the display medium 20 displays properties of optical isotropy.
When the perpendicular electric field 201 is generated between the
pixel array 22b and the opposite electrode 22a, the display medium
20 displays properties of optical anisotropy. According to the
present embodiment, the display medium 20 includes blue phase
liquid crystals, such as polymer-stabilized blue phase liquid
crystals or polymer-stabilized isotropic phase liquid crystals.
Since the display medium 20 switches between optically isotropic
and optically anisotropic by the generation of electric fields,
such that the display medium 20 functions as a light valve, the
response speed of this type of display medium 20 is preferably
faster than the twisting response speed of the conventional twisted
nematic liquid crystal molecules.
[0079] The light source module B is disposed below the outer
surface S2 of the first substrate 21b of the display module P.
Moreover, the light source module B generates a directional light
281. In other words, the directional light 281 projects along a
specific projected direction and distributes within a specific
angle. In the present embodiment, the directional light 281 is
concentrated within a specific range. That is, the directional
light 281 has directionality and is not like the conventional
scattered light source with light spreading in all directions
without any directionality. The light source module B is, for
example, a side incident type light source module, including a
light guide plate 26a and a light source 26b. It should be
appreciated that the light source module B may further include
elements such as an optical film set and a frame. In the present
embodiment, the side incident type light source module is used as
an example for description, although the invention is not limited
thereto. According to other embodiments, the light source module B
may be a light source module having other forms, such as the direct
type light source module, for example.
[0080] Since the display medium 20 is optically anisotropic when no
electric field is applied thereto, therefore, when the pixel array
22b of the display module P and the opposite electrode 22a form the
perpendicular electric field 201 therebetween, the display medium
20 not only display properties of optical anisotropy, but the
display medium 20 is also vertically aligned along the
perpendicular electric field 201, as shown in FIGS. 1 and 2B. In
order for the vertically aligned optically anisotropic display
medium 20 to be birefringent to the light from the light source
module B, in the present embodiment, the propagating direction of
the light from the light source module B has a specific design as
illustrated below.
[0081] According to the present embodiment, the directional light
281 generated by the light source module B propagates along an
incident direction D1 when the directional light 281 enters the
display module P. Moreover, the incident direction D1 is not
perpendicular to the outer surface S2 of the first substrate 21b.
In other words, the directional light 281 generated by the light
source module B does not perpendicularly enter into the display
module P, but the directional light 281 is incident at a specific
inclination angle into the display module P. In order for the
directional light 281 generated by the light source module B to
exit the light source module B at a specific angle, special optical
microstructures can be designed on the light guide plate 26a.
Alternatively, a layer of optical film having special optical
microstructures may be disposed on the light guide plate 26a.
Accordingly, when the light generated by the light source 26b
passes the light guide plate 26a (or optical film), the propagating
direction of the light changes, such that the directional light 281
generated by the light source module B exits at the specific
inclination angle. According to the present embodiment, since the
directional light 281 generated by the light source module B exits
at the specific inclination angle, therefore, an included angle
.theta.1 between the incident direction D1 of the directional light
281 and the outer surface S2 of the first substrate 21b is
5.degree..about.45.degree., for example. In other words, an
inclination angle .theta.1' of the directional light 281 generated
by the light source module B is 45.degree..about.85.degree., for
example. The inclination angle .theta.1' refers to the included
angle between the incident direction D1 of the directional light
281 and a perpendicular axial line V.
[0082] Accordingly, after the direction light 281 enters the
display module P at the inclination angle .theta.1', a directional
light 282 is formed. The directional light 282 in the display
module P maintains the same direction when passing through the
display medium 20. In other words, the directional light 281
generated by the light source module B becomes the directional
light 282 when entering the display medium 20. Moreover, the
directional light 282 propagates along an incident direction D2 not
perpendicular to the inner surface S1 of the first substrate 21b.
Therefore, the included angle .theta. between the incident
direction D2 of the directional light 282 and the inner surface S1
of the first substrate 21b is not equal to 90.degree.. According to
the present embodiment, the included angle .theta. between the
incident direction D2 of the directional light 282 and the inner
surface S1 of the first substrate 21b is
5.degree..about.45.degree., for example.
[0083] After the directional light 282 passes through the display
medium 20 and the second substrate 21a, the directional light 282
is guided by the turning optical film 25 to form an output light
283 propagating along a propagating direction D3. Moreover, an
included angle between the propagating direction D3 and a surface
(output surface) of the turning optical film 25 is substantially
60.degree..about.120.degree.. In the present embodiment, the output
light 283 exits the turning optical film 25 perpendicularly.
Therefore, the included angle between the propagating direction D3
and the surface (output surface) of the turning optical film is
substantially 90.degree., such that the output light 283 received
by a user's eye 29 is a light propagating along the normal
direction. Accordingly, an included angle .theta.2 between the
propagating direction D3 of the output light 283 and the surface
(output surface) of the turning optical film 25 is substantially
equal to 90.degree..
[0084] In the present embodiment, a first optical film 24b may be
further disposed on the outer surface S2 of the first substrate
21b, such that the directional light 282 maintains the same
propagating or transmitting direction as much as possible before
entering the display medium 20. Moreover, in order for the
directional light 282 to maintain the same propagating or
transmitting direction as much as possible after exiting the
display medium 20, a second optical film 24a may be further
disposed on the outer surface S4 of the second substrate 21a.
[0085] With reference to FIGS. 1, 4A, and 4B, the first optical
film 24b is disposed on the outer surface S2 of the first substrate
21b. To be specific, the first optical film 24b has a plurality of
first optical structures T1. Moreover, the first optical structures
T1 allow the directional light 281 passing through the first
optical structures T1 without generating total reflection. That is,
the directional light 281 directly passes through the first optical
structures T1 of the first optical film 24b. If the directional
light 281 is not being totally reflected or refracted when directly
passing through the first optical structures T1 of the first
optical film 24b, optical loss of the directional light 281 caused
by the first optical film 24b can be minimized. In other words,
optical loss of the directional light 281 at the interface of air
and the first substrate 21b due to reflection can be reduced.
Accordingly, the directional light 281 can pass through the first
optical film 24b in the same propagating direction as much as
possible.
[0086] According to the present embodiment, the first optical film
24b has a first surface S5 and a second surface S6 opposite to the
first surface S5. The first surface S5 faces the light source
module B, the second surface S6 faces the outer surface S2 of the
first substrate 21b, and the first optical structures T1 are
disposed on the first surface S5. That is, the second surface S6 of
the first optical film 24b is a smooth plane, although the
invention is not limited thereto. Moreover, the first optical
structures T1 on the first surface S5 of the first optical film 24B
can cause the directional light 281 of the light source module B to
pass through the first optical film 24b as directly as
possible.
[0087] According to the present embodiment, the first optical
structures T1 are grooves having a first side wall W1 and a second
side wall W2, as shown in FIG. 4A. The incident direction D1 is
substantially perpendicular to the first side wall W1, and the
incident direction D1 is substantially parallel to the second side
wall W2. To be specific, in the first optical structures (grooves)
T1 of the present embodiment, the first side wall W1 of the grooves
T1 is a short side wall, and the second side wall W2 is a long side
wall. Moreover, the short side wall W1 is substantially
perpendicular to the incident direction D 1. Furthermore, a
refractive index of the first optical film 24b is close to a
refractive index of the first substrate 21b. Accordingly, when the
directional light 281 passes through the first optical structures
(grooves) T1, the directional light 281 can directly pass through
the short side wall W1 without generating total reflection or
refraction, such that the directional light 281 can pass through
the first optical film 24b as directly as possible. In the present
embodiment, a width p1 of the first optical structures (grooves) T1
is approximately 5 .mu.m.about.100 .mu.m. An included angle
.theta.4 between the first side wall W1 of the first optical
structures (grooves) T1 and the perpendicular axial line V is
approximately 5.degree..about.45.degree.. An included angle
.theta.3 between the second side wall W2 of the first optical
structures (grooves) T1 and the perpendicular axial line V is
approximately 45.degree..about.85.degree..
[0088] With reference to FIGS. 1, 5A, and 5B, the second optical
film 24b is disposed on the outer surface S4 of the second
substrate 21a. To be specific, the second optical film 24a has a
plurality of second optical structures T2. Moreover, the second
optical structures T2 allows the directional light 282 passing
through the second optical structures T2 without generating total
reflection. That is, the directional light 282 directly passes
through the second optical structures T2 of the second optical film
24a. If the directional light 282 is not being totally reflected or
refracted when directly passing through the second optical
structures T2 of the second optical film 24a, optical loss of the
directional light 282 caused by the second optical film 24a can be
minimized. In other words, optical loss of the directional light
282 at the interface of air and the second optical film 24a due to
reflection can be reduced. Accordingly, the directional light 282
can exit the second optical film 24a in the same transmitting
direction as much as possible.
[0089] According to the present embodiment, the second optical film
24a has a first surface S7 and a second surface S8 opposite to the
first surface S7. The first surface S7 faces the outer surface S4
of the second substrate 21a, and the second optical structures T2
are disposed on the second surface S8. That is, the first surface
S7 of the second optical film 24a is a smooth plane, although the
invention is not limited thereto. Moreover, the second optical
structures T2 on the second surface S8 of the second optical film
24a can cause the directional light 282 to pass through the second
optical film 24a as directly as possible.
[0090] According to the present embodiment, the second optical
structures T2 are grooves having a first side wall W3 and a second
side wall W4, as shown in FIG. 5A. The incident direction D2 of the
directional light 282 when passing through the second optical film
24a is perpendicular to the first side wall W3, and the incident
direction D2 is parallel to the second side wall W4. To be
specific, in the second optical structures (grooves) T2 of the
present embodiment, the first side wall W3 is a short side wall,
and the second side wall W4 is a long side wall. Moreover, the
short side wall W3 is substantially perpendicular to the incident
direction D2 of the directional light 282. Furthermore, a
refractive index of the second optical film 24a is close to a
refractive index of the second substrate 21a. Accordingly, when the
directional light 282 passes through the second optical structures
(grooves) T2, the directional light 282 can directly pass through
the short side wall W3 without generating total reflection or
refraction, such that the directional light 282 can pass through
the second optical film 24a as directly as possible. In the present
embodiment, a width p2 of the second optical structures (grooves)
T2 is approximately 5 .mu.m.about.100 .mu.m. An included angle
.theta.6 between the first side wall W3 of the second optical
structures (grooves) T2 and the perpendicular axial line V is
approximately 5.degree..about.45.degree.. An included angle
.theta.5 between the second side wall W4 of the second optical
structures (grooves) T2 and the perpendicular axial line V is
approximately 45.degree..about.85.degree..
[0091] With reference to FIGS. 1, 6A, and 6B, the turning optical
film 25 is disposed on the second optical film 24a. The turning
optical film 25 has a plurality of tuning optical structures T3,
such that the directional light 282 is totally reflected by the
tuning optical structures T3 to form the output light 283.
Moreover, an included angle between the propagating direction D3
after the output light 283 passes through the turning optical film
25 and a surface (output surface) S10 of the turning optical film
25 is 60.degree..about.120.degree.. In the present embodiment, the
propagating direction D3 after the output light 283 passes through
the turning optical film 25 is substantially perpendicular to the
surface (output surface) S10 of the turning optical film 25. That
is, the directional light 282 is totally reflected by the tuning
optical structures T3 of the turning optical film 25 as much as
possible to form the output light 283. In other words, the tuning
optical structures T3 of the turning optical film 25 is designed
mainly to redirect the propagating or transmitting direction of the
directional light 281 and 282 emitted from the light source module
B after passing through the turning optical film 25. Thereby, the
output light 283 can exit the turning optical film 25
perpendicularly to be received by the user's eye 29.
[0092] According to the present embodiment, the turning optical
film 25 has a first surface S9 (also referred to as the incident
surface) and a second surface S10 (also referred to as the output
surface) opposite to the first surface S9. The first surface S9
faces the outer surface S4 of the second substrate 21a, and the
tuning optical structures T3 are disposed on the first surface S9.
That is, the second surface S10 of the turning optical film 25 is a
smooth plane, although the invention is not limited thereto. The
directional light 282 is totally reflected by the tuning optical
structures T3 of the turning optical film 25 by the first surface
S9, so as to form the output light 283.
[0093] According to the present embodiment, the tuning optical
structures T3 are grooves having a first side wall W5 and a second
side wall W6, as shown in FIG. 6A. In the present embodiment, the
first side wall W5 and the second side wall W6 of the grooves T3
are planar side walls. To be specific, in the optical structures
(grooves) T3 of the present embodiment, an included angle .theta.7
between the first side wall W5 and the perpendicular axial line V
is approximately 5.degree..about.60.degree., and an included angle
.theta.8 between the second side wall W6 and the perpendicular
axial line V is approximately 15.degree..about.45.degree..
Therefore, when the directional light 282 enters the optical film
25, the directional light 282 is totally reflected by the first
side wall W5 of the tuning optical structures T3 so as to form the
output light 283, such that the output light 283 can exit the
turning optical film 25 perpendicularly. In the present embodiment,
a width p3 of the optical structures (grooves) T3 is approximately
5 .mu.m.about.100 .mu.m.
[0094] In FIG. 7, the optical paths of the directional light 281
and 282 passing through the first optical film 24b, second optical
film 24a, and the turning optical film 25 are illustrated. In order
to clearly depict the optical paths of the directional light 281,
the directional light 282, and the output light 283 respectively
passing through the first optical film 24b, the second optical film
24a, and the turning optical film 25, only the first optical film
24b, the second optical film 24a, and the turning optical film 25
are drawn in FIG. 7. That is, the display module P and other film
layers are omitted in the drawing.
[0095] As shown in FIG. 7, the directional light 281 passes through
the first optical film 24b as directly as possible without
generating total reflection or refraction. The directional light
282 then passes through the second optical film 24a also as
directly as possible without generating total reflection or
refraction. The directional light 282 is then totally reflected as
much as possible by the tuning optical structures T3 of the turning
optical film 25, so as to form the output light 283. By using the
afore-described configuration of the first optical film 24b, the
second optical film 24a, and the turning optical film 25, light
from the light source module B can obliquely enter into the display
module P and then exit the turning optical film 25 along the normal
direction.
[0096] With reference to FIG. 1, besides the display module P, the
light source module B, and the turning optical film 25, the display
device 100 of the present embodiment may further include a bottom
polarizer 23b and a top polarizer 23a. The bottom polarizer 23b is
disposed between the first substrate 21b and the first optical film
24b, and the top polarizer 23a is disposed between the second
substrate 21a and the second optical film 24a. Dichroic polymer
films, such as polyvinyl-alcohol-based films may be adopted for the
bottom polarizer 23b and the top polarizer 23a. An included angle
between a transmission axis of the bottom polarizer 23b and a
transmission axis of the top polarizer 23a may be
5.degree..about.175.degree..
[0097] Moreover, in order to achieve favorable display quality for
the display module P, the display module P of the present
embodiment further includes a compensation film 231 and a diffusion
film 27. The compensation film 231 is disposed between the bottom
polarizer 23b and the top polarizer 23a. In the present embodiment,
the compensation film 231 is disposed between the bottom polarizer
23b and the first substrate 21b as an example for description. In
other words, a compensation film (not drawn) may also be disposed
between the top polarizer 23a and the second substrate 21a.
Alternatively, the compensation film 231 may be disposed between
the bottom polarizer 23b and the first substrate 21b, and the
compensation film (not drawn) may be disposed between the top
polarizer 23a and the second substrate 21a. The configuration of
the compensation film 23a can enhance the contrast ratio of the
display module P as well as the viewing angle. Moreover, the
diffusion film 27 is disposed above the top polarizer 23a, so that
a diffusion effect is generated when the output light 283 passes
through the diffusion film 27, thereby achieving preferable display
quality for the display module P. However, the use of the diffusion
film 27 is not necessary in the invention.
[0098] Accordingly, since the display medium 20 of the display
module P of the present embodiment is driven by the perpendicular
electric field 201 between the pixel array 22b and the opposite
electrode 22a, the low transmittance and high driving voltage
issues of the conventional IPS display module can be resolved.
Moreover, since the incident direction D2 of the directional light
281 and the directional light 282 generated by the light source
module B in the present embodiment are not perpendicular to the
surface of the first substrate 21b when entering the display medium
20, the display medium 20 is still birefringent to the directional
light 282 of the light source module B when the display medium 20
is driven and becomes optically anisotropic. Accordingly, the
display module P can display images.
[0099] In the embodiment depicted in FIG. 1, the top polarizer 23a
is disposed between the second substrate 21a and the second optical
film 24a. Thereby, the effect from the second optical film 24a and
the turning optical film 25 on the polarization state of the
directional light 282 is minimized. However, the invention is not
limited thereto. According to other embodiments, the top polarizer
23a may also be disposed above the second optical film 24a or the
turning optical film 25, as shown in FIG. 3A.
[0100] Moreover, according to another embodiment, the second
optical film 24b may be omitted in the display module P, as shown
in FIG. 3B. Accordingly, the effect from the second optical film
24a on the polarization state of the directional light 282 is
minimized. However, the invention is not limited thereto.
[0101] Furthermore, in the embodiment depicted in FIG. 1, the
optical film 25 of the display module P are shown in FIGS. 6A and
6B, for example. However, the invention is not limited thereto.
According to other embodiments, the optical film 25 of the display
device 100 may also adopt other forms or structures, as further
elaborated below.
[0102] FIG. 8A is a schematic cross-sectional view of an optical
film in a display device according to another embodiment of the
invention. FIG. 8B is a perspective view of the optical film
depicted in FIG. 8A. With reference to FIGS. 8A and 8B, the tuning
optical structures T3' of the optical film 25 in the present
embodiment are grooves, a first side wall W5' of the optical
structures (grooves) T3 is a curved side wall, and a second side
wall W6' of the optical structures (grooves) T3' is a planar side
wall. Therefore, when the directional light 282 enters the optical
film 25, the directional light 282 is totally reflected by the
first side wall (curved side wall) W5' of the tuning optical
structures T3' so as to form the output light 283, such that the
output light 283 can exit the turning optical film 25
perpendicularly. It should be noted that, since the first side wall
W5' is a curved side wall, besides the directional light 282
generating total reflection at the first side wall (curved side
wall) W5', a part of the output light 283 generated by total
reflection has an incident angle that is less than a total
reflection angle. Therefore, after the part of the output light 283
is reflected to the first side wall (curved side wall) W5', the
part of the output light 283 is refracted out of the optical film
25. Therefore, when the curved side wall is adopted for the first
side wall W5' of the optical structures (grooves) T3', the included
angle between the propagating direction of the output light 283 and
the output surface can be 60.degree..about.120.degree.. That is,
the output light 283 can be diffused when emitted, thereby
enhancing the image quality. In the present embodiment, a width p4
of the optical structures (grooves) T3' is approximately 5
.mu.m.about.100 .mu.m.
[0103] In the embodiment depicted in FIGS. 8A and 8B, the radaii of
curvature of the curved side walls W5' of all the tuning optical
structures T3' in the turning optical film 25 are the same.
Therefore, each tuning optical structure T3' in the turning optical
film 25 of the embodiment depicted in FIGS. 8A and 8B has the same
pattern. However, the invention is not limited thereto. According
to other embodiments, the optical structures of the turning optical
film 25 may have different patterns, as shown in FIGS. 9A and
9B.
[0104] FIG. 9A is a schematic cross-sectional view of an optical
film in a display device according to another embodiment of the
invention. FIG. 9B is a perspective view of the optical film
depicted in FIG. 9A. With reference to FIGS. 9A and 9B, in the
present embodiment, each tuning optical structure T3' of the
turning optical film 25 has a planar side wall and a curved side
wall, but the radii of curvature of the curved side walls of the
tuning optical structures T3' are not all the same. For example, a
radius of curvature of the curved side wall W5' of the tuning
optical structure T3' in the present embodiment is different than a
radius of curvature of a curved side wall W5''. Moreover, the
tuning optical structure T3' having the curved side wall W5' with
the larger radius of curvature is alternatively arranged with the
optical structure T3' having the curved side wall W5' with the
smaller radius of curvature.
[0105] FIG. 10A is a schematic cross-sectional view of an optical
film in a display device according to another embodiment of the
invention. FIG. 10B is a perspective view of the optical film
depicted in FIG. 10A. With reference to FIGS. 10A and 10B, in the
present embodiment, each tuning optical structure T3' of the
turning optical film 25 has a planar side wall and a curved side
wall, and the curved side wall of each tuning optical structure T3'
has a plurality of radii of curvature. The radii of curvature of
the curved side wall progressively decrease as the bottom of the
groove T3' is approached. For example, the first side wall of the
grooves T3' in the turning optical film 25 is a curved side wall,
including a curved side walls W5-1 and a curved side wall W5-2.
Moreover, the radius of curvature of the curved side wall W5-1 is
smaller than the radius of curvature of the curved side wall W5-2.
In order to facilitate the description, the present embodiment uses
two different curvatures for the curved side walls W5-1 and W5-2 as
an illustrative example, although in actuality the first side wall
of the grooves T3' in the turning optical film 25 is a continuous
curved surface.
[0106] Based on the above, when the directional light 282 enters
the turning optical film 25, besides the directional light 282
generating total reflection at the curved side walls W5-1 and W5-2,
a part of the output light 283 can be refracted out of the optical
film 25 after being reflected to the curved side wall W5-1. Since
the radius of curvature of the curved side wall W5-1 progressively
decreases as the bottom of the grooves T3' is approached, an
included angle between a tangent of the curved side wall W5-1 and
the transmission direction of the output light 283 also decreases
gradually. Accordingly, the output light 283 can be easily
refracted out of the optical film 25 after being reflected to this
area. That is, the curved side wall W5-1 having the smaller radius
of curvature can refract more output light 283 out the optical film
25 at this area. In other words, the divergence angle and
distribution of light from the turning optical film 25 depicted in
FIGS. 10A and 10B is wider and broader than those of the embodiment
illustrated in FIGS. 8A and 8B.
[0107] FIG. 11 and FIG. 12 are schematic cross-sectional views of a
display device according to embodiments of the invention. The
embodiment shown in FIGS. 11 and 12 is similar to the embodiment
shown in FIG. 1, and thus identical components denoted with the
same numerals and will not be repeated herein. A difference between
the embodiments in FIGS. 11 and 1 lies in that, a pixel array 221b
has a slit alignment pattern 60, and a protruding alignment pattern
70 is disposed on an opposite electrode 221a. By configuring the
slit alignment pattern 60 on the pixel array 221b and the
protruding alignment pattern 70 on the opposite electrode 221a, the
distribution of a perpendicular electric field 202 changes and
multi-domain alignment is achieved for the display medium 20,
accordingly. Similarly, a difference between the embodiments in
FIGS. 12 and 1 lies in that, the pixel array 221b has the slit
alignment pattern 60, and the opposite electrode 221a has a slit
alignment pattern 80. The distribution of the perpendicular
electric field 202 can also be changed by configuring the slit
alignment pattern 60 on the pixel array 221b and the slit alignment
pattern 80 on the opposite electrode 221a, thereby achieving
multi-domain alignment for the display medium 20.
[0108] Although the embodiments depicted in FIGS. 11 and 12
configure alignment patterns (e.g. slit alignment patterns or
protruding alignment patterns) on the pixel array 221b and the
opposite electrode 221a, the invention is not limited thereto.
According to other embodiments, alignment patterns (e.g. slit
alignment patterns or protruding alignment patterns) may only be
disposed on the pixel array 221b, or alignment patterns (e.g. slit
alignment patterns or protruding alignment patterns) may only be
disposed in the opposite electrode 221a. The combination of
alignment patterns on the pixel array 221b and the opposite
electrode 221a is also not limited to the embodiments depicted in
FIGS. 11 and 12. In other words, the protruding alignment pattern
may be disposed on the pixel array 221b and the slit alignment
pattern may be disposed on the opposite electrode 221a, or the
protruding alignment pattern may be disposed on the pixel array
221b and the protruding alignment pattern may be disposed on the
opposite electrode 221a
[0109] In order to illustrate that the display device according to
an exemplary embodiment has lower driving voltage and preferable
transmittance compared to the conventional IPS display device,
several examples with comparison to the conventional IPS display
device are set forth below.
Driving Voltage Comparison I
[0110] FIG. 13 is a relational diagram of a voltage of a transverse
electric field driving blue phase liquid crystals of a conventional
IPS display module and a transmittance. With reference to FIG. 13,
the horizontal axis of FIG. 13 represents voltage (V), while the
vertical axis represents the transmittance of the display module.
As shown in FIG. 13, when the conventional IPS display module
drives the blue phase liquid crystals, the driving voltage needs to
reach 52 V to achieve a preferable transmittance. That is, the
driving voltage needs to reach 52 V in order for the display module
to have a Kerr constant of 12.68 nm/V.sup.2.
[0111] FIGS. 14A and 14B are relational diagrams of a voltage of a
perpendicular electric field of a display device according to an
embodiment of the invention driving blue phase liquid crystals and
a light angle. The horizontal axis of FIGS. 14A and 14B represent
an inclination angle of light from a light source module (e.g. the
angle .theta.1' depicted in FIG. 1), and the vertical axis
represents voltage (V).
[0112] With reference to FIG. 14A, a display medium thickness (also
referred to as the cell gap) of the display module in this display
device is 3.5 .mu.m, and the display module of FIG. 14A has a Kerr
constant of 12.68 nm/V.sup.2. As shown in FIG. 14A, the driving
voltage (below 15 V) needed by the display module of FIG. 14A is
far lower than the driving voltage (52 V) needed by the IPS display
module of FIG. 13. Moreover, in the display device of FIG. 14A,
when the inclination angle of light from the light source module
increases, the driving voltage thereof decreases.
[0113] With reference to FIG. 14B, a display medium thickness (also
referred to as the cell gap) of the display module in this display
device is 5 .mu.m, and the display module of FIG. 14B has the same
Kerr constant of 12.68 nm/V.sup.2. As shown in FIG. 14B, the
driving voltage (below 18 V) needed by the display module of FIG.
14B is far lower than the driving voltage (52 V) needed by the IPS
display module of FIG. 13. Similarly, in the display device of FIG.
14B, when the inclination angle of light from the light source
module increases, the driving voltage thereof decreases.
Driving Voltage Comparison II
[0114] FIG. 15 is a relational diagram of a voltage of a transverse
electric field driving blue phase liquid crystals of a conventional
IPS display module and a transmittance. With reference to FIG. 15,
the horizontal axis of FIG. 15 represents voltage (V), while the
vertical axis represents the transmittance of the display module.
In FIG. 15, a laser light of 633 nm serves as the light from the
light source module, and the laser light enters the IPS display
module perpendicularly. As shown in FIG. 15, the display module has
the greatest transmittance when the driving voltage reaches 193
Vrms.
[0115] FIG. 16 is a relational diagram of a voltage of a
perpendicular electric field of a display device according to an
embodiment of the invention driving blue phase liquid crystals and
a transmittance. With reference to FIG. 16, the horizontal axis of
FIG. 16 represents voltage (V), while the vertical axis represents
the transmittance of the display module. In FIG. 16, the 633 nm
laser light serves as the light from the light source module, t
represents the display medium thickness (also referred to as the
cell gap), and .theta. represents the light inclination angle
(angle .theta.1' depicted in FIG. 1) of the light source module. As
shown in FIG. 16, under combinations of different display medium
thicknesses (also referred to as the cell gap) and different light
inclination angles, four relational curves of voltage and
transmittance can be obtained. However, in the four curves, the
driving voltages required for the display module to achieve the
highest transmittance condition are all far lower than the driving
voltage (193 Vrms) needed by the conventional IPS display
module.
Hysteresis Comparison
[0116] Blue phase liquid crystals typically exhibit the hysteresis
phenomeon. When blue phase liquid crystals are applied in the
display medium of the display device, hysteresis usually needs to
be suppressed or reduced to prevent the hysteresis of the blue
phase liquid crystals from affecting the gray level control
accuracy of the display module.
[0117] FIG. 17 depicts the measurement results of a hysteresis
phenomenon from a transverse electric field driving blue phase
liquid crystals of a conventional IPS display module. FIG. 18
depicts the measurement results of a hysteresis phenomenon from a
perpendicular electric field of a display device according to an
embodiment of the invention driving blue phase liquid crystals.
Generally speaking, the hysteresis phenomenon of blue phase liquid
crystals can be measured by gradually increasing voltage to measure
the voltage and transmittance curves M and M', and by gradually
decreasing voltage to measure the voltage and transmittance curves
N and N'. The voltage difference between the two curves M and N (M'
and N') under a half transmittance condition is then calculated. As
the voltage difference between the two curves M and N (M' and N')
increases, the hysteresis phenomenon is more apparent. On the other
hand, as the voltage difference between the two curves M and N (M'
and N') decreases, the hysteresis phenomenon is less apparent.
[0118] As shown in FIGS. 17 and 18, the voltage difference between
the curves M and N (FIG. 17) under the half transmittance condition
is significantly greater than the voltage difference between the
curves M' and N' (FIG. 18) under the half transmittance condition.
Therefore, the blue phase liquid crystals of the conventional IPS
display module driven by the transverse electric field exhibit high
hysteresis.
Effects of Display Medium Thickness on Driving Voltage
[0119] FIG. 19 is a relational diagram between display medium
thickness and voltage for a display device according to an
embodiment of the invention. The horizontal axis in FIG. 19
represents the display medium thickness (also referred to as the
cell gap), and the vertical axis represents voltage (V). In FIG.
19, the 550 nm laser light serves as the light from the light
source module, .theta. represents the light inclination angle
(angle .theta.1' depicted in FIG. 1) of the light source module,
and the four curves in FIG. 19 can all allow the display module to
have a Kerr constant of 10.2 nm/V.sup.2. As shown in FIG. 19, as
the display medium thickness (also referred to as the cell gap)
decreases, the required driving voltage is also reduced.
[0120] FIG. 20 is a relational diagram between voltage and
transmittance under different display medium thickness conditions
for a display device according to an embodiment of the invention.
The horizontal axis of FIG. 20 represents voltage (V), while the
vertical axis represents the transmittance. In FIG. 20, the display
medium thickness (also referred to as the cell gap) are
respectively 1, 2, and 5 .mu.m, the 550 nm laser light serves as
the light from the light source module, and the light inclination
angle (angle .theta.1' depicted in FIG. 1) of the light source
module is 70.degree.. As shown in FIG. 20, the driving voltage of
the display device according to an embodiment of the invention is
related to the display medium thickness.
[0121] Based on the above, in the display device according to an
embodiment of the invention, the display medium of the display
module is driven by the perpendicular electric field generated
between the pixel array and the electrode layer. In particular,
since the incident direction of the light generated by the light
source module when entering the display medium is not perpendicular
to the inner surface of the first substrate, the display medium
remains birefringent to the light from the light source module when
the display medium is driven to be optically anisotropic.
Accordingly, since the display device according to an exemplary
embodiment can adopt the perpendicular electric field to drive the
display medium, the issues of low transmittance and high driving
voltage from conventionally using the transverse electric field to
drive the blue phase liquid crystals can be resolved.
[0122] Moreover, the display device according to an exemplary
embodiment can further include a plurality of compensation films,
which can be configured to enhance the display quality of the
display device. Embodiments 1-7 provided below to further
illustrate the advantages of configuring the compensation films. It
should be noted that, the embodiments provided below are similar to
the embodiment shown in FIG. 1, and thus identical components
denoted with the same numerals and will not be repeated herein. The
omitted portions can be referenced to the earlier embodiments. The
differences between the embodiments are further described
below.
First Embodiment
[0123] FIG. 21 is a schematic cross-sectional view of a display
device according to a first embodiment of the invention. With
reference to FIG. 21, a difference between a display device 100a
and the embodiment of FIG. 1 lies in that, the display device 100a
includes a first compensation film 28b and a second compensation
film 28a, and does not include the compensation film 231. To be
specific, the first compensation film 28b is disposed on the outer
surface S2 of the first substrate 21b, and the second compensation
film 28a is disposed between the second substrate 21a and the
turning optical film 25.
[0124] In the present embodiment, the bottom polarizer 23b is
disposed on the outer surface S2 of the first substrate 21b, and
the top polarizer 23a is disposed on the outer surface S4 of the
second substrate 21a. According to the present embodiment, the
bottom polarizer 23b is disposed between the first compensation
film 28b and the first optical film 24b. The top polarizer 23a is
disposed between the second compensation film 28a and the second
optical film 24a, and the second optical film 24a is disposed
between the turning optical film 25 and the top polarizer 23a.
According to the present embodiment, the directional light 282
passes through the bottom polarizer 23b, the first compensation
film 28b, the second compensation film 28a, and the top polarizer
23a in sequence.
[0125] According to the present embodiment, the first compensation
film 28b and the second compensation film 28a may be used to adjust
the polarization state of the directional light 282 located in the
display module P, such that the polarization state of the
directional light 282 after adjustment matches the absorption axis
direction of the top polarizer 23a. Thereby, the light leakage
generated when the directional light 282 forms the output light 283
can be reduced, and the contrast ratio of the display device 100a
in the dark state can be further enhanced.
[0126] In order to further describe the effects of the first
compensation film 28b and the second compensation film 28a, a
Poincare sphere is used to illustrate the compensation process of
the first compensation film 28b and the second compensation film
28a. To clearly define the directions of the directional light 281
and the directional light 282, as well as the absorption axis
angles of the top polarizer 23a, the bottom polarizer 23b, the
first compensation film 28b, and the second compensation film 28a,
a polar angle .theta. and an orientation angle .PHI. are used for
the definitions below.
[0127] FIG. 22 is a perspective view of a light source module and a
display module in the display device according to an embodiment of
the invention. With reference to FIG. 22, with the center of the
display module P as reference, the orientation angle .PHI. is an
included angle between a projection line on the XY plane of an
arbitrary direction D4 and the X direction. The polar angle .theta.
is an included angle between the arbitrary direction D4 and the Z
direction. For example, the polar angle .theta. of a direction D5
is 90.degree. and the orientation angle .PHI. is 0.degree.; the
polar angle .theta. of a direction D6 is 90.degree. and the
orientation angle .PHI. is 90.degree.; the polar angle .theta. of a
direction D7 is 90.degree. and the orientation angle .PHI. is
180.degree.; and the polar angle .theta. of a direction D8 is
90.degree. and the orientation angle .PHI. is 270.degree..
[0128] FIG. 23 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the first embodiment of the invention employs
compensation films. With reference to FIG. 23, when the polar angle
.theta. of the directional light 282 is 70.degree. and the
orientation angle .PHI. is 270.degree., an effective angle between
the bottom polarizer 23b and the top polarizer 23a changes.
Therefore, a transmissive state P.sub.1 of the directional light
282 and a state A.sub.1 of the absorption axis of the top polarizer
23a are separated, thereby causing the light leakage. According to
the present embodiment, the first compensation film 28b can rotate
the polarization state of the directional light 282 from the state
P.sub.1 to a state P.sub.0, and the second compensation film 28a
can rotate the polarization state of the directional light 282 from
the state P.sub.0 to the state A.sub.1. Accordingly, after the
directional light 282 passes through the first compensation film
28b and the second compensation film 28a, the polarization state of
the directional light 282 can be rotated from the state P.sub.1 to
the state A.sub.1, and thereby prevent light leakage.
[0129] Table 1 tabulates a parameter setting data of each component
in the display device 100a, in which Nz denotes the ratio of
refractive index anisotropy, and Nz can be represented by the
following equation:
Nz=(n.sub.x-n.sub.z)/(n.sub.x-n.sub.y)
[0130] in which is n.sub.x the x-axis refractive index, n.sub.y the
y-axis refractive index, n.sub.z the z-axis refractive index,
d(nx-ny) is the phase difference, and the incident light refers to
the directional light 281. FIG. 24 is a contour map of the contrast
ratios measured on the display device of FIG. 21 with the parameter
setting of Table 1.
TABLE-US-00001 TABLE 1 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 45.degree.
First Compensation Film .PHI. = 38.5.degree. Nz = 0.54 d(n.sub.x -
n.sub.y) = 256 nm Second Compensation Film .PHI. = -38.5.degree. Nz
= 0.54 d(n.sub.x - n.sub.y) = 256 nm Top Polarizer .PHI. =
-45.degree.
[0131] With reference to FIG. 24, the four contour lines from
outside to inside respectively represents the contour lines of
contrast ratios 100, 200, 500, and 1000. As shown in FIG. 24, the
viewing cone of contrast ratio greater than 1000:1 is approximately
20.degree., and the 20.degree. viewing cone is sufficient for the
straight directional light 282 in the vertical field switching blue
phase LCD. In order to widen the viewing angle, the front diffusion
film 27 or the turning optical film 25 can be used to diffuse the
straight backlight source, so as to achieve the wide viewing angle.
However, the invention is not limited thereto. An example of other
parameter settings is provided below to optimize the contrast
ratio.
[0132] Table 2 tabulates a parameter setting data of each component
in the display device 100a. FIG. 25 is a contour map of the
contrast ratios measured on the display device of FIG. 21 with the
parameter setting of Table 2.
TABLE-US-00002 TABLE 2 Incident Light .theta. = 60.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 45.degree.
First Compensation Film .PHI. = 42.degree. Nz = 0.63 d(n.sub.x -
n.sub.y) = 260 nm Second Compensation Film .PHI. = -42.degree. Nz =
0.63 d(n.sub.x - n.sub.y) = 260 nm Top Polarizer .PHI. =
-45.degree.
[0133] The contour line area of contrast ratio 1000:1 in FIG. 25 is
greater than the contour line area of contrast ratio 1000:1 in FIG.
24. However, the smaller polar angle of the incident light results
in higher driving voltage.
[0134] Table 3 tabulates a parameter setting data of each component
in the display device 100a. FIG. 26 is a contour map of the
contrast ratios measured on the display device of FIG. 21 with the
parameter setting of Table 3.
TABLE-US-00003 TABLE 3 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 40.degree.
First Compensation Film .PHI. = 36.degree. Nz = 0.506 d(n.sub.x -
n.sub.y) = 259 nm Second Compensation Film .PHI. = -36.degree. Nz =
0.506 d(n.sub.x - n.sub.y) = 259 nm Top Polarizer .PHI. =
-40.degree.
[0135] Table 4 tabulates a parameter setting data of each component
in the display device 100a. FIG. 27 is a contour map of the
contrast ratios measured on the display device of FIG. 21 with the
parameter setting of Table 4. FIG. 27 illustrates the contour lines
of the optimized contrast ratio for an incident light with a polar
angle .theta. of 70.degree. and an orientation angle .PHI. of
270.degree..
TABLE-US-00004 TABLE 4 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 30.degree.
First Compensation Film .PHI. = 29.75.degree. Nz = 0.399 d(n.sub.x
- n.sub.y) = 272 nm Second Compensation Film .PHI. = -29.75.degree.
Nz = 0.399 d(n.sub.x - n.sub.y) = 272 nm Top Polarizer .PHI. =
-30.degree.
[0136] Table 5 tabulates a parameter setting data of each component
in the display device 100a. FIG. 28 is a contour map of the
contrast ratios measured on the display device of FIG. 21 with the
parameter setting of Table 5. FIG. 28 illustrates the contour lines
of the optimized contrast ratio for an incident light with a polar
angle .theta. of 70.degree. and an orientation angle .PHI. of
270.degree..
TABLE-US-00005 TABLE 5 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 30.degree.
First Compensation Film .PHI. = 31.degree. Nz = 0.44 d(n.sub.x -
n.sub.y) = 264 nm Second Compensation Film .PHI. = -31.degree. Nz =
0.44 d(n.sub.x - n.sub.y) = 264 nm Top Polarizer .PHI. =
-30.degree.
[0137] Table 6 tabulates a parameter setting data of each component
in the display device 100a. FIG. 29 is a contour map of the
contrast ratios measured on the display device of FIG. 21 with the
parameter setting of Table 6. FIG. 29 illustrates the contour lines
of the optimized contrast ratio for an incident light with a polar
angle .theta. of 60.degree. and an orientation angle .PHI. of
270.degree..
TABLE-US-00006 TABLE 6 Incident Light .theta. = 60.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 30.degree.
First Compensation Film .PHI. = 32.5.degree. Nz = 0.4775 d(n.sub.x
- n.sub.y) = 264.5 nm Second Compensation Film .PHI. =
-32.5.degree. Nz = 0.4775 d(n.sub.x - n.sub.y) = 264.5 nm Top
Polarizer .PHI. = -30.degree.
Second Embodiment
[0138] FIG. 30 is a schematic cross-sectional view of a display
device according to a second embodiment of the invention. With
reference to FIG. 30, a display device 100b of the present
embodiment is similar to the display device 100a of the first
embodiment. A difference therebetween lies in that, the display
device 100b further includes a third compensation film 31b and a
fourth compensation film 31a. The third compensation film 31b is
disposed between the first compensation film 28b and the bottom
polarizer 23b, and the fourth compensation film 31a is disposed
between the second compensation film 28a and the top polarizer
23a.
[0139] According to the present embodiment, the third compensation
film 31b and the fourth compensation film 31a are respectively a
biaxial compensation film, for example. The third compensation film
31b and the fourth compensation film 31a may be designed in
accordance with different orientation angle .PHI., so as to
compensate for an angular difference between the top polarizer 23a
and the bottom polarizer 23b. According to the present embodiment,
the directional light 282 passes through the bottom polarizer 23b,
the third compensation film 31b, the first compensation film 28b,
the second compensation film 28a, the fourth compensation film 31a,
and the top polarizer 23a in sequence.
[0140] FIG. 31 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the second embodiment of the invention employs
compensation films. With reference to FIG. 31, in the present
embodiment, a P.sub.2 state is shifted from a P.sub.1 state. The
P.sub.2 state represents a polarization state when the orientation
angle .PHI. is 300.degree., and the P.sub.1 state represents a
polarization state when the orientation angle .PHI. is 270.degree..
In the present embodiment, the third compensation film 31b can
rotate the polarization state from the state P.sub.2 to the state
P.sub.1. The first compensation film 28b and the second
compensation film 28a can then rotate the polarization state from
the state P.sub.1 to a state A.sub.1. The fourth compensation film
31a can then rotate the polarization state from the state A.sub.1
to a state A.sub.2 matching the absorption axis of the top
polarizer 23a.
[0141] Table 7 tabulates a parameter setting data of each component
in the display device 100b. FIG. 32 is a contour map of the
contrast ratios measured on the display device of FIG. 30 with the
parameter setting of Table 7.
TABLE-US-00007 TABLE 7 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 30.degree.
Third Compensation Film .PHI. = 25.75.degree. Nz = 0.851 d(n.sub.x
- n.sub.y) = 281.5 nm First Compensation Film .PHI. = 29.72.degree.
Nz = 0.3984 d(n.sub.x - n.sub.y) = 272 nm Second Compensation Film
.PHI. = -29.72.degree. Nz = 0.3984 d(n.sub.x - n.sub.y) = 272 nm
Fourth Compensation Film .PHI. = -25.75.degree. Nz = 0.851
d(n.sub.x - n.sub.y) = 281.5 nm Top Polarizer .PHI. =
-30.degree.
Third Embodiment
[0142] FIG. 33 is a schematic cross-sectional view of a display
device according to a third embodiment of the invention. With
reference to FIG. 33, a display device 100c of the present
embodiment is similar to the display device 100b of the second
embodiment. A difference therebetween lies in that, in the display
device 100c, the third compensation film 31b is disposed between
the first compensation film 28b and the first substrate 21b, and
the fourth compensation film 31a is disposed between and the second
compensation film 28a and the second substrate 21a.
[0143] According to the present embodiment, the third compensation
film 31b and the fourth compensation film 31a are respectively a
biaxial compensation film, for example. The third compensation film
31b and the fourth compensation film 31a may be designed in
accordance with different orientation angles .PHI., so as to
compensate for an angular difference between the top polarizer 23a
and the bottom polarizer 23b. According to the present embodiment,
the directional light 282 passes through the bottom polarizer 23b,
the first compensation film 28b, the third compensation film 31b,
the fourth compensation film 31a, the second compensation film 28a,
and the top polarizer 23a in sequence.
[0144] FIG. 34 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the third embodiment of the invention employs
compensation films. With reference to FIG. 34, in the present
embodiment, the first compensation film 28b can rotate a
polarization state from a state P.sub.1 to a state P.sub.0. The
third compensation film 31b then rotates the polarization state
from a linear polarization state of the state P.sub.0 to a circular
polarization state of a state C.sub.1. The fourth compensation film
31a then rotates the polarization state from the circular
polarization state of the state C.sub.1 to the linear polarization
state of the state P.sub.0. The second compensation film 28a then
rotates the polarization state from the state P.sub.0 to a state
A.sub.1 matching the absorption axis of the top polarizer 23a.
Since circularly polarized light is not affected by the orientation
angles of the blue phase liquid crystal materials, circularly
polarized light can improve the viewing angle of the VFS blue phase
LCD.
[0145] Table 8 tabulates a parameter setting data of each component
in the display device 100c. FIG. 35 is a contour map of the
contrast ratios measured on the display device of FIG. 33 with the
parameter setting of Table 8.
TABLE-US-00008 TABLE 8 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 45.degree.
First Compensation Film .PHI. = 40.degree. Nz = 0.575 d(n.sub.x -
n.sub.y) = 256 nm Third Compensation Film .PHI. = 90.degree. Nz =
0.5 d(n.sub.x - n.sub.y) = 137 nm Fourth Compensation Film .PHI. =
0.degree. Nz = 0.5 d(n.sub.x - n.sub.y) = 137 nm Second
Compensation Film .PHI. = -40.degree. Nz = 0.575 d(n.sub.x -
n.sub.y) = 256 nm Top Polarizer .PHI. = -45.degree.
[0146] Table 9 tabulates a parameter setting data of each component
in the display device 100c. FIG. 36 is a contour map of the
contrast ratios measured on the display device of FIG. 33 with the
parameter setting of Table 9. FIG. 36 illustrates the contour lines
of the optimized contrast ratio for an incident light 281 with a
polar angle .theta. of 60.degree. and an orientation angle .PHI. of
270.degree..
TABLE-US-00009 TABLE 9 Incident Light .theta. = 60.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 45.degree.
First Compensation Film .PHI. = 42.degree. Nz = 0.63 d(n.sub.x -
n.sub.y) = 260 nm Third Compensation Film .PHI. = 90.degree. Nz =
0.5 d(n.sub.x - n.sub.y) = 137 nm Fourth Compensation Film .PHI. =
0.degree. Nz = 0.5 d(n.sub.x - n.sub.y) = 137 nm Second
Compensation Film .PHI. = -42.degree. Nz = 0.63 d(n.sub.x -
n.sub.y) = 260 nm Top Polarizer .PHI. = -45.degree.
Fourth Embodiment
[0147] FIG. 37 is a schematic cross-sectional view of a display
device according to a fourth embodiment of the invention. With
reference to FIG. 37, a display device 100d of the present
embodiment is similar to the display device 100b of the second
embodiment. A difference therebetween lies in that, in the display
device 100d, the bottom polarizer 23b is a wire-grid polarizer, for
example.
[0148] In the present embodiment, the first compensation film 28b,
the second compensation film 28a, the third compensation film 31b,
and the fourth compensation film 31a are all disposed between the
top polarizer 23a and the wire-grid bottom polarizer 23b. According
to the present embodiment, the directional light 282 passes through
the wire-grid bottom polarizer 23b, the third compensation film
31b, the first compensation film 28b, the second compensation film
28a, the fourth compensation film 31a, and the top polarizer 23a in
sequence.
[0149] FIG. 38 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the fourth embodiment of the invention employs
compensation films. With reference to FIG. 38, in the present
embodiment, an orientation angle .PHI. of the absorption axis of
the wire-grid bottom polarizer 23b is 90.degree., and an
orientation angle .PHI. of the absorption axis of the top polarizer
23a is 0.degree.. After the directional light 282 passes through
the wire-grid bottom polarizer 23b, the directional light 282
rotates from a state P.sub.1 to a linear polarization state of a
state P.sub.0.
[0150] The third compensation film 31b does not change the
polarization state when the orientation angle .PHI. is 270.degree..
The first compensation film 28b rotates the linear polarization
state of the state P.sub.0 to a circular polarization state of a
state C.sub.1. The second compensation film 28a rotates the
circularly polarized light from the state C.sub.1 to a state
A.sub.0 matching the absorption axis of the top polarizer 23a.
Accordingly, a preferable dark state performance can be
achieved.
[0151] However, when the orientation angle .PHI. of the directional
light 282 is not the same (e.g. 300.degree.), the polarization
state P.sub.1 shifts from the polarization state P.sub.0. Here, the
third compensation film 31b can employ different orientation angles
.PHI. (e.g. from 225.degree. to 315.degree.) in order to rotate the
state P.sub.1 back to the state P.sub.0. The first compensation
film 28b and the second compensation film 28a then rotate the
polarization state from the state P.sub.0 to a state P.sub.2
through the state C.sub.1. The fourth compensation film 31a then
polarizes the linearly polarized light from the state P.sub.2 to a
state A.sub.1 matching the absorption axis of the top polarizer
23a.
[0152] Table 10 tabulates a parameter setting data of each
component in the display device 100d. FIG. 39 is a contour map of
the contrast ratios measured on the display device of FIG. 37 with
the parameter setting of Table 10. FIG. 39 illustrates the contour
lines of the optimized contrast ratio for an incident light 281
with a polar angle .theta. of 70.degree. and an orientation angle
.PHI. of 270.degree..
TABLE-US-00010 TABLE 10 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 90.degree.
Third Compensation Film .PHI. = 90.degree. Nz = 0.81 d(n.sub.x -
n.sub.y) = 317.35 nm First Compensation Film .PHI. = 45.degree. Nz
= 0.5 d(n.sub.x - n.sub.y) = 137 nm Second Compensation Film .PHI.
= -45.degree. Nz = 0.5 d(n.sub.x - n.sub.y) = 137 nm Fourth
Compensation Film .PHI. = 0.degree. Nz = 0.81 d(n.sub.x - n.sub.y)
= 317.35 nm Top Polarizer .PHI. = 0.degree.
[0153] Since the wire-grid bottom polarizer 23b has a favorable
extinction ratio, preferably high and broad contour lines can be
obtained. Moreover, the wire-grid bottom polarizer 23b is not
sensitive to the incident light 281 angle and has minimal diffusion
effect. Therefore, the wire-grid bottom polarizer 23b is suitable
for the VFS blue phase LCD.
Fifth Embodiment
[0154] FIG. 40 is a schematic cross-sectional view of a display
device according to a fifth embodiment of the invention. With
reference to FIG. 40, a display device 100e of the present
embodiment is similar to the display device 100b of the second
embodiment. A difference therebetween lies in that, in the display
device 100e, the top polarizer 23a is disposed between the turning
optical film 25 and the diffusion film 27, and the fourth
compensation film 31a includes an A-plate compensation film 31a-1
and a C-plate compensation film 31a-2.
[0155] According to the present embodiment, the first compensation
film 28b, the second compensation film 28a, and the third
compensation film 31b are biaxial compensation films. The third
compensation film 31b is disposed between the bottom polarizer 23b
and the first compensation film 28b, and the first optical film 24b
is disposed between the third compensation film 31b and the first
compensation film 28b. Moreover, the fourth compensation film 31a
is disposed between the second compensation film 28a and the top
polarizer 23a, and the second optical film 24a is disposed between
the fourth compensation film 31a and the top polarizer 23a.
Specifically, the A-plate compensation film 31a-1 in the fourth
compensation film 31a is disposed between the C-plate compensation
film 31a-2 and the second optical film 24a. According to the
present embodiment, the directional light 282 passes through the
bottom polarizer 23b, the third compensation film 31b, the first
optical film 24b, the first compensation film 28b, the second
compensation film 28a, the C-plate compensation film 31a-2, the
A-plate compensation film 31a-1, and the second optical film 24a in
sequence. The output light 283 is formed after the directional
light 282 passes through the turning optical film 25, and then the
output light 283 passes through the top polarizer 23a.
[0156] FIG. 41 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the fifth embodiment of the invention employs
compensation films. With reference to FIG. 41, in the present
embodiment, the orientation angles .PHI. of the bottom polarizer
23b and the top polarizer 23a are respectively 0.degree. and
90.degree.. According to the present embodiment, for the
directional light 281 having a polar angle .theta. of 70.degree.
and an orientation angle .PHI. of 270.degree. as an incident angle,
when the directional light 281 passes through the bottom polarizer
23b, the polarization state of the directional light 281 is a state
P.sub.0. However, when the orientation angle .PHI. of the
directional light 281 changes (e.g. 300.degree.), the polarization
state of the directional light 281 shifts from the state P.sub.0 to
a state P.sub.1.
[0157] In the present embodiment, the third compensation film 31b
does not change the polarization state P.sub.0 when the orientation
angle .PHI. is 270.degree., but when the orientation angle .PHI. is
200.degree., the polarization state changes from the state P.sub.1
to the state P.sub.0. The first compensation film 28b rotates the
linearly polarized light from the state P.sub.0 to a circularly
polarized light of of a state C.sub.1. The second compensation film
28a rotates the circularly polarized light from the state C.sub.1
to the linearly polarized light of of the state P.sub.0. Since the
polarization state may change with the turning optical film 25
corresponding to the top polarizer 23a, therefore, the C-plate
compensation film 31a-2 is designed to rotate the polarization
state from the state P.sub.0 to a state P.sub.2, and the A-plate
compensation film 31a-1 is used to rotate the polarization state
from the state P.sub.2 to a state A.sub.1 matching the absorption
axis of the top polarizer 23a.
[0158] Table 11 tabulates a parameter setting data of each
component in the display device 100e, in which n.sub.o is the fast
axis refractive index, n.sub.e is the slow axis refractive index,
and d is the thickness. FIG. 42 is a contour map of the contrast
ratios measured on the display device of FIG. 40 with the parameter
setting of Table 11. FIG. 42 illustrates the contour lines of the
optimized contrast ratio for an incident light 281 with a polar
angle .theta. of 70.degree. and an orientation angle .PHI. of
270.degree., in which the contour lines from outside to inside
respectively represents the contour lines of contrast ratios 100,
200, 500, and 1000. FIG. 43 is a contour map for the bright state
measurements on the display device of FIG. 40 with the parameter
setting of Table 11, in which the contour lines from outside to
inside respectively represents the contour lines of transmittances
0.2, 0.25, 0.3, 0.35, and 0.4.
TABLE-US-00011 TABLE 11 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 0.degree.
Third Compensation Film .PHI. = 0.degree. Nz = 0.756 d(n.sub.x -
n.sub.y) = 254 nm First Compensation Film .PHI. = -45.degree. Nz =
0.501 d(n.sub.x - n.sub.y) = 137.5 nm Second Compensation Film
.PHI. = 45.degree. Nz = 0.501 d(n.sub.x - n.sub.y) = 137.5 nm
C-Plate Compensation Film n.sub.o = 1.5095 n.sub.e = 1.511 d = 48
.mu.m A-Plate Compensation Film .PHI. = 0.degree. n.sub.o = 1.5095
n.sub.e = 1.511 d = 70 .mu.m Top Polarizer .PHI. = 90.degree.
[0159] However, the invention is not limited thereto. Another type
of compensation process described below may be adopted by using the
framework of the present embodiment.
[0160] FIG. 44 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the fifth embodiment of the invention employs
compensation films. With reference to FIG. 44, in the present
embodiment, the third compensation film 31b is used in different
orientation angles to compensate the polarization state from the
state P .sub.1 to the state P.sub.0. The first compensation film
28b shifts the state P.sub.0 to the state P.sub.2. The second
compensation film 28a shifts the state P.sub.2 back to the state
P.sub.0. The C-plate compensation film 31a-2 shifts the state
P.sub.0 to a state P.sub.3, and the A-plate compensation film 31a-1
shifts the state P.sub.3 to the state A.sub.1 matching the
absorption axis of the top polarizer 23a.
[0161] Table 12 tabulates a parameter setting data of each
component in the display device 100e. FIG. 45 is a contour map of
the contrast ratios measured on the display device of FIG. 40 with
the parameter setting of Table 12. FIG. 45 illustrates the contour
lines of the optimized contrast ratio for an incident light 281
with a polar angle .theta. of 70.degree. and an orientation angle
.PHI. of 270.degree., in which the contour lines from outside to
inside respectively represents the contour lines of contrast ratios
100, 200, 500, and 1000. FIG. 46 is a contour map for the bright
state measurements on the display device of FIG. 40 with the
parameter setting of Table 12, in which the contour lines from
outside to inside respectively represents the contour lines of
transmittances 0.2, 0.25, 0.3, 0.35, and 0.4.
TABLE-US-00012 TABLE 12 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 0.degree.
Third Compensation Film .PHI. = 0.degree. Nz = 0.756 d(n.sub.x -
n.sub.y) = 254 nm First Compensation Film .PHI. = 112.5.degree. Nz
= 0.6738 d(n.sub.x - n.sub.y) = 275 nm Second Compensation Film
.PHI. = 22.5.degree. Nz = 0.9328 d(n.sub.x - n.sub.y) = 275 nm
C-Plate Compensation Film n.sub.o = 1.5095 n.sub.e = 1.511 d = 65
.mu.m A-Plate Compensation Film .PHI. = 0.degree. n.sub.o = 1.5095
n.sub.e = 1.511 d = 70 .mu.m Top Polarizer .PHI. = 90.degree.
[0162] As shown in FIGS. 43 and 46, the bright state area in FIG.
43 is larger than the bright state area in FIG. 46. The foregoing
result is because during the compensation process of FIG. 41, the
polarization state of the directional light 282 in the blue phase
liquid crystal materials is circularly polarized. Since the
circularly polarized light is not affected by the orientation
angle, the contour lines of the contrast ratio can be improved.
Sixth Embodiment
[0163] FIG. 47 is a schematic cross-sectional view of a display
device according to a sixth embodiment of the invention. With
reference to FIG. 47, a display device 100f of the present
embodiment is similar to the display device 100e of the fifth
embodiment. A difference therebetween lies in that, in the display
device 100f, the third compensation film 31b is disposed between
the bottom polarizer 23b and the first compensation film 28b, and
the bottom polarizer 23b is disposed between the first optical film
24b and the third compensation film 31b.
[0164] According to the present embodiment, the fourth compensation
film 31a is disposed between the second compensation film 28a and
the top polarizer 23a, and the second optical film 24a is disposed
between the fourth compensation film 31a and the top polarizer 23a.
In the present embodiment, the first compensation film 28b, the
second compensation film 28a, and the third compensation film 31b
are biaxial compensation films. Moreover, the fourth compensation
film 31a includes the A-plate compensation film 31a-1 and the
C-plate compensation film 31a-2. According to the present
embodiment, the directional light 282 passes through the bottom
polarizer 23b, the third compensation film 31b, the first
compensation film 28b, the second compensation film 28a, the
C-plate compensation film 31a-2, the A-plate compensation film
31a-1, and the second optical film 24a in sequence. The output
light 283 is formed after the directional light 282 passes through
the turning optical film 25, and then the output light 283 passes
through the top polarizer 23a.
[0165] FIG. 48 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the sixth embodiment of the invention employs
compensation films. With reference to FIG. 48, in the present
embodiment, a polar angle of the directional light 281 is
70.degree. and an orientation angle .PHI. is 270.degree., for
example. After the backlight passes through the bottom polarizer
23b, the polarization state of the directional light 282 is a state
P.sub.0. When the orientation angle .PHI. of the directional light
282 changes, such as when the orientation angle .PHI. becomes
300.degree., the polarization state of the directional light 282
shifts from the state P.sub.0 to a state P.sub.1. The third
compensation film 31b does not change the polarization state
P.sub.0 when the orientation angle .PHI. is 270.degree., but when
the orientation angle .PHI. is 300.degree., the polarization state
of the polarized light can be changed from the state P.sub.1 to the
state P.sub.0. The first compensation film 28b shifts a linearly
polarized light of the state P.sub.0 to a circularly polarized
light of a state C.sub.1. The second compensation film 28a shifts
the circularly polarized light of the state C.sub.1 to the state
P.sub.0. By using the turning optical film 25 for depolarization,
the absorption axis of the top polarizer 23a is shifted to the
state A.sub.1. The C-plate compensation film 31a-2 shifts the
directional light 282 from the state P.sub.0 to a state P.sub.2,
and the A-plate compensation film 31a-1 shifts from the state
P.sub.2 to the state A.sub.1 matching the absorption axis of the
top polarizer 23a.
[0166] Table 13 tabulates a parameter setting data of each
component in the display device 100f. FIG. 49 is a contour map of
the contrast ratios measured on the display device of FIG. 47 with
the parameter setting of Table 13. FIG. 49 illustrates the contour
lines of the optimized contrast ratio for an incident light 282
with a polar angle .theta. of 70.degree. and an orientation angle
.PHI. of 270.degree., in which the contour lines from outside to
inside respectively represents the contour lines of contrast ratios
100, 200, 500, and 1000. FIG. 50 is a contour map for the bright
state measurements on the display device of FIG. 47 with the
parameter setting of Table 13, in which the contour lines from
outside to inside respectively represents the contour lines of
transmittances 0.2, 0.25, 0.3, 0.35, and 0.4. The ideal maximum
transmittance after passing the bottom polarizer 23b and the top
polarizer 23a is 0.5.
TABLE-US-00013 TABLE 13 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm Bottom Polarizer .PHI. = 0.degree.
Third Compensation Film .PHI. = 0.degree. Nz = 0.568 d(n.sub.x -
n.sub.y) = 209.6 nm First Compensation Film .PHI. = -45.degree. Nz
= 0.501 d(n.sub.x - n.sub.y) = 137.5 nm Second Compensation Film
.PHI. = 45.degree. Nz = 0.501 d(n.sub.x - n.sub.y) = 137.5 nm
C-Plate Compensation Film n.sub.o = 1.5095 n.sub.e = 1.511 d = 40
.mu.m A-Plate Compensation Film .PHI. = 0.degree. n.sub.o = 1.5095
n.sub.e = 1.511 d = 60 .mu.m Top Polarizer .PHI. = 90.degree.
Seventh Embodiment
[0167] FIG. 51 is a schematic cross-sectional view of a display
device according to a seventh embodiment of the invention. With
reference to FIG. 51, a display device 100g of the present
embodiment is similar to the display device 100a of the first
embodiment. A difference therebetween lies in that, in the display
device 100g, the bottom polarizer 23b is an O-type polarizer, and
the top polarizer 23a is an E-type polarizer, for example.
[0168] Typically speaking, the absorption axis of the O-type
polarizer follows an orientation angle .PHI. of 0.degree..
Moreover, the c-axis (i.e. transmission axis) of the E-type
polarizer follows the orientation angle .PHI. of 0.degree..
Compared to the bottom polarizer 23b (O-type polarizer), the top
polarizer 23a (E-type polarizer) transmits the extraordinary ray
and absorbs the ordinary ray. The top polarizer 23a (E-type
polarizer) weakens light which is not perpendicular to any
transmission direction of the c-axis. According to the present
embodiment, the first compensation film 28b and the second
compensation film 28a are disposed between the top polarizer 23a
and the bottom polarizer 23b.
[0169] FIG. 52 is a schematic view of a Poincare sphere for a
compensation process during a dark state when a display device
according to the seventh embodiment of the invention employs
compensation films. With reference to FIG. 52, in the present
embodiment, the polarization state of the directional light 181
after passing through the bottom polarizer 23b is a state P.sub.1.
The first compensation film 28b rotates a linearly polarized light
from the state P.sub.1 to a circularly polarized light of of a
state C.sub.1. Since circularly polarized light is not affected by
the orientation angles, circularly polarized light is applied in
the display medium 20 to improve the contrast ratio and bright
state performance. After the directional light 282 passes through
the display medium 20 materials, the second compensation film 28a
shifts the circularly polarized light of the state C.sub.1 to a
state A.sub.1 matching the absorption axis of the top polarizer
23a, in which the display medium 20 is optically isotropic and no
voltage is applied.
[0170] Table 14 tabulates a parameter setting data of each
component in the display device 100g. FIG. 53 is a contour map of
the contrast ratios measured on the display device of FIG. 51 with
the parameter setting of Table 14. FIG. 53 illustrates the contour
lines of the optimized contrast ratio for an incident light 281
with a polar angle .theta. of 70.degree. and an orientation angle
.PHI. of 270.degree., in which the contour lines from outside to
inside respectively represents the contour lines of contrast ratios
500, 1000, 2000, and 5000. FIG. 54 is a contour map for the bright
state measurements on the display device of FIG. 51 with the
parameter setting of Table 14, in which the contour lines from
outside to inside respectively represents the contour lines of
transmittances 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, and 0.4.
TABLE-US-00014 TABLE 14 Incident Light .theta. = 70.degree. .PHI. =
270.degree. .lamda. = 550 nm O-Type Polarizer .PHI. = 0.degree.
First Compensation Film .PHI. = -45.degree. Nz = 0.5 d(n.sub.x -
n.sub.y) = 137.5 nm Second Compensation Film .PHI. = 45.degree. Nz
= 0.5 d(n.sub.x - n.sub.y) = 137.5 nm C-Axis of the E-Type
Polarizer .PHI. = 0.degree.
[0171] In view of the foregoing, compensation films are disposed
between the top and bottom polarizers in the display device
according to an exemplary embodiment of the invention. The
configuration of the compensation films can adjust the polarization
state of the directional light entering the display module, such
that the polarization state of the directional light matches the
absorption axis direction of the top polarizer. Accordingly, light
leakage can be minimized and the contrast ratio of the display
device can be enhanced. Moreover, the configuration of the
compensation films can convert the polarization state of the
directional light from the linear polarization state to the
circular polarization state for transmission in the display medium.
Since the circularly polarized light is not affected by the
orientation angle, the viewing angle of the display device can be
increased.
[0172] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
invention cover modifications and variations of this invention
provided they fall within the scope of the following claims and
their equivalents.
* * * * *