U.S. patent number RE39,082 [Application Number 10/244,662] was granted by the patent office on 2006-05-02 for half reflection type liquid crystal display device having matched phase of transmitted and reflected light.
This patent grant is currently assigned to Hitachi Device Engineering Co., Ltd., Hitachi, Ltd.. Invention is credited to Kiichirou Kubo, Yoshikuni Nagashima, Terunori Saitou, Masaru Suzuki.
United States Patent |
RE39,082 |
Kubo , et al. |
May 2, 2006 |
Half reflection type liquid crystal display device having matched
phase of transmitted and reflected light
Abstract
A liquid crystal display device is constructed such that a
liquid crystal layer is sandwiched between an upper substrate,
which is provided with upper transparent electrodes for forming
pixels, and a lower substrate, which is provided with lower
transparent electrodes disposed so as to intersect with the upper
transparent electrodes. The liquid crystal panel includes a half
reflection layer having a reflection function and a transmission
function which is formed on the inner surface of the lower
substrate as a lower layer of the lower transparent electrodes; an
upper retardation film, an upper polarizing plate, and a light
diffusing plate which are laminated on the upper substrate; and a
lower retardation film and a lower polarizing plate, which are
laminated on the surface of the lower substrate. Due to such a
construction, the half reflection type liquid crystal display
device is capable of providing an image display of high brightness
and high contrast.
Inventors: |
Kubo; Kiichirou (Mobara,
JP), Nagashima; Yoshikuni (Isumi-machi,
JP), Suzuki; Masaru (Mobara, JP), Saitou;
Terunori (Mobara, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
Hitachi Device Engineering Co., Ltd. (Mobara,
JP)
|
Family
ID: |
18025359 |
Appl.
No.: |
10/244,662 |
Filed: |
September 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
09432399 |
Nov 2, 1999 |
06124919 |
Sep 26, 2000 |
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Foreign Application Priority Data
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Nov 2, 1998 [JP] |
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10-312109 |
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Current U.S.
Class: |
349/114; 349/169;
349/162; 349/113; 349/117 |
Current CPC
Class: |
G02F
1/133555 (20130101); G02F 1/13338 (20130101); G02F
1/133557 (20210101); G02F 2413/02 (20130101); G02F
1/1397 (20130101); G02F 1/13363 (20130101) |
Current International
Class: |
G02F
1/1333 (20060101); G02F 1/1335 (20060101); C09K
19/02 (20060101) |
Field of
Search: |
;349/188,117,169,162,114,113 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Chowdhury; Tarifur R.
Assistant Examiner: Qi; Mike
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus, LLP
Claims
What is claimed is:
1. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate which is provided with upper
transparent electrodes for forming pixels, and a lower substrate,
which is provided with lower transparent electrodes disposed so as
to intersect with said upper transparent electrodes, said liquid
crystal panel comprising: a half reflection layer having a
reflection function and a transmission function which is formed on
the inner surface of said lower substrate as a lower layer of said
lower transparent electrodes; an upper retardation film, an upper
polarizing plate and a light diffusing plate, which are laminated
on said upper substrate; and a lower retardation film and a lower
polarizing plate, which are laminated on the surface of said lower
substrate; and wherein the phase of said reflected light at said
half reflecting layer and the phase of a transmitted light which
passes through said half reflection layer from said lower substrate
substantially agree with each other.
2. A liquid crystal display device according to claim 1, wherein
the transmission factor of said half reflection layer is made
uniform within a display range of said liquid crystal panel.
3. A liquid crystal display device according to claim 1, wherein a
back lighting device is disposed at the back side of said liquid
crystal panel.
4. A liquid crystal display device according to claim 3, wherein a
touch panel is disposed at the front surface side of said liquid
crystal panel.
5. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate, which is provided with upper
transparent electrodes for forming pixels and a lower substrate,
which is provided with lower transparent electrodes disposed so as
to intersect with said upper transparent electrodes, said liquid
crystal panel comprising: a half reflection layer having a
reflection function and a transmission function which is formed on
the inner surface of said lower substrate as a lower layer of said
lower transparent electrodes; an upper retardation film, an upper
polarizing plate and a light diffusing plate, which are laminated
on said upper substrate; and a lower retardation film and a lower
polarizing plate, which are laminated on the surface of said lower
substrate; said liquid crystal panel further including a color
filter layer of a plurality of colors which is formed on the inner
surface of said upper substrate as a lower layer of said upper
transparent electrodes, and a passivation film formed between said
color filter layer and said upper transparent electrodes, and the
retardation .DELTA.nd of said lower retardation film being
determined such that the phase of transmitted light which passes
through said lower polarizing plate, said lower retardation film
and said half reflection layer becomes equivalent to the phase of
reflected light by said half reflection layer.
6. A liquid crystal display device according to claim 5, wherein
the transmission factor of said half reflection layer is made
uniform within a display range of said liquid crystal panel.
7. A liquid crystal display device according to claim 5, wherein a
back lighting device is disposed at the back side of said liquid
crystal panel.
8. A liquid crystal display device according to claim 7, wherein a
touch panel is disposed at the front surface side of said liquid
crystal panel.
9. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate, which is provided with upper
transparent electrodes for forming pixels, and a lower substrate,
which is provided with lower transparent electrodes disposed so as
to intersect with said upper transparent electrodes, said liquid
crystal panel comprising: a half reflection layer having a
reflection function and a transmission function which is formed on
the inner surface of said lower substrate as a lower layer of said
lower transparent electrodes; an upper retardation film, an upper
polarizing plate and a light diffusing plate which are laminated on
said upper substrate; and a lower retardation film and a lower
polarizing plate, which are laminated on the surface, of said lower
substrate, said liquid crystal panel further including a color
filter layer of a plurality of colors which is formed on the inner
surface of said upper substrate as a lower layer of said upper
transparent electrodes, and a passivation layer formed between said
color filter layer and said upper transparent electrodes, and
wherein the phase difference between the phase of a transmitted
light which passes through said lower polarizing plate, said lower
retardation film and said half reflection layer and the phase of a
reflected light at said half reflection layer is set within
.+-..pi./4 .Iadd.when a bright display is performed.Iaddend..
10. A liquid crystal display device according to claim 9, wherein
the transmission factor of said half reflection layer is made
uniform within a display range of said liquid crystal panel.
11. A liquid crystal display device according to claim 9, wherein a
back lighting device is disposed at the back side of said liquid
crystal panel.
12. A liquid crystal display device according to claim 11, wherein
a touch panel is disposed at the front surface side of said liquid
crystal panel.
.Iadd.13. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate and a lower substrate, said
liquid crystal panel comprising: a half reflection layer having a
reflection function and a transmission function, said half
reflection layer being disposed at an inner surface of said lower
substrate; an upper retardation film and an upper polarizing plate
being laminated on a surface of said upper substrate; and a lower
retardation film and a lower polarizing plate being laminated on a
surface of said lower substrate; wherein a phase difference of a
polarization condition of reflected light at said half reflection
layer and a phase difference of a polarization condition of
transmitted light which passes through said half reflection layer
from said lower substrate substantially agree with each
other..Iaddend.
.Iadd.14. A liquid crystal panel according to claim 13, wherein
said polarization condition of said reflected light at said half
reflection layer and said polarization condition of said
transmitted light at said half reflection layer are circular
polarization when a bright display is performed..Iaddend.
.Iadd.15. A liquid crystal panel according to claim 13, wherein
said upper substrate has upper transparent electrodes for forming
pixels, said lower substrate has lower transparent electrodes
disposed so as to intersect with said upper transparent electrodes,
and said half reflection layer is disposed between said lower
transparent electrodes and said lower substrate..Iaddend.
.Iadd.16. A liquid crystal panel according to claim 13, wherein
said liquid crystal panel is an active matrix type liquid crystal
panel..Iaddend.
.Iadd.17. A liquid crystal panel according to claim 13, further
comprising a color filter layer..Iaddend.
.Iadd.18. A liquid crystal panel according to claim 13, wherein a
transmission factor of the transmission function of said half
reflection layer is uniform within a display range of said liquid
crystal panel..Iaddend.
.Iadd.19. A liquid crystal display device comprising said liquid
crystal panel according to claim 13, and a back lighting device
disposed at a back side of said liquid crystal panel..Iaddend.
.Iadd.20. A liquid crystal display device according to claim 19,
further comprising a touch panel disposed at a front surface side
of said liquid crystal panel..Iaddend.
.Iadd.21. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate and a lower substrate, said
liquid crystal panel comprising: a half reflection layer having a
reflection function and a transmission function, said half
reflection layer being disposed at an inner surface of said lower
substrate; an upper retardation film and an upper polarizing plate
being laminated on said upper substrate; and a lower retardation
film and a lower polarizing plate being laminated on a surface of
said lower substrate; wherein a retardation .DELTA.nd of said lower
retardation film is determined so that a phase difference of a
polarization condition of transmitted light which passes through
said lower polarizing plate, said lower retardation film and said
half reflection layer becomes substantially equivalent to a phase
difference of a polarization condition of reflected light by said
half reflection layer..Iaddend.
.Iadd.22. A liquid crystal panel according to claim 21, wherein
said polarization condition of said reflected light at said half
reflection layer and said polarization condition of said
transmitted light at said half reflection layer are circular
polarization when a bright display is performed..Iaddend.
.Iadd.23. A liquid crystal panel according to claim 21, wherein
said upper substrate has upper transparent electrodes for forming
pixels, said lower substrate has lower transparent electrodes
disposed so as to intersect with said upper transparent electrodes,
and said half reflection layer is disposed between said lower
transparent electrodes and said lower substrate..Iaddend.
.Iadd.24. A liquid crystal panel according to claim 21, wherein
said liquid crystal panel is an active matrix type liquid crystal
panel..Iaddend.
.Iadd.25. A liquid crystal panel according to claim 21, further
comprising a color filter layer..Iaddend.
.Iadd.26. A liquid crystal panel according to claim 21, wherein a
transmission factor of the transmission function of said half
reflection layer is uniform within a display range of said liquid
crystal panel..Iaddend.
.Iadd.27. A liquid crystal display device comprising said liquid
crystal panel according to claim 21, and a back lighting device
disposed at a back side of said liquid crystal panel..Iaddend.
.Iadd.28. A liquid crystal display device according to claim 27,
further comprising a touch panel disposed at a front surface side
of said liquid crystal panel..Iaddend.
.Iadd.29. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate and a lower substrate, said
liquid crystal panel comprising: a half reflection layer having a
reflection function and a transmission function, said half
reflection layer being disposed at an inner surface of said lower
substrate; an upper retardation film and an upper polarizing plate
being laminated on said upper substrate; and a lower retardation
film and a lower polarizing plate being laminated on a surface of
said lower substrate; wherein a difference between a phase
difference of a polarization condition of transmitted light which
passes through said lower polarizing plate, said lower retardation
film and said half reflection layer and a phase difference of a
polarization condition of reflected light at said high reflection
layer is set within .+-..pi./4 when a bright display is
performed..Iaddend.
.Iadd.30. A liquid crystal panel according to claim 29, wherein
said polarization condition of said reflected light at said half
reflection layer and said polarization condition of said
transmitted light at said half reflection layer are circular
polarization when a bright display is performed..Iaddend.
.Iadd.31. A liquid crystal panel according to claim 29, wherein
said upper substrate has upper transparent electrodes for forming
pixels, said lower substrate has lower transparent electrodes
disposed so as to intersect with said upper transparent electrodes,
and said half reflection layer is disposed between said lower
transparent electrodes and said lower substrate..Iaddend.
.Iadd.32. A liquid crystal panel according to claim 29, wherein
said liquid crystal panel is an active matrix type liquid crystal
panel..Iaddend.
.Iadd.33. A liquid crystal panel according to claim 29, further
comprising a color filter layer..Iaddend.
.Iadd.34. A liquid crystal panel according to claim 29, wherein the
transmission factor of the transmission function of said half
reflection layer is uniform within a display range of said liquid
crystal panel..Iaddend.
.Iadd.35. A liquid crystal device comprising said liquid crystal
panel according to claim 29, and a back lighting device disposed at
a back side of said liquid crystal panel..Iaddend.
.Iadd.36. A liquid crystal display device according to claim 35,
further comprising a touch panel disposed at a front surface of
said liquid crystal panel..Iaddend.
.Iadd.37. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate and a lower substrate, said
liquid crystal panel comprising: a half reflection layer having a
reflection function and a transmission function, said half
reflection layer being disposed at an inner surface of said lower
substrate; an upper retardation film and an upper polarizing plate
being laminated on a surface of said upper substrate; and a lower
retardation film and a lower polarizing plate being laminated on a
surface of said lower substrate; wherein a phase difference of a
polarization condition of reflected light at said half reflection
layer and a phase difference of a polarization condition of
transmitted light which passes through said half reflection layer
from said lower substrate substantially agree with each other when
a bright display is performed. .Iaddend.
.Iadd.38. A liquid crystal panel according to claim 37, wherein
said upper substrate has upper transparent electrodes for forming
pixels, said lower substrate has lower transparent electrodes
disposed so as to intersect with said upper transparent electrodes,
and said half reflection layer is disposed between said lower
transparent electrodes and said lower substrate..Iaddend.
.Iadd.39. A liquid crystal panel according to claim 37, wherein
said liquid crystal panel is an active matrix type liquid crystal
panel..Iaddend.
.Iadd.40. A liquid crystal panel according to claim 37, further
comprising a color filter layer..Iaddend.
.Iadd.41. A liquid crystal panel according to claim 37, wherein a
transmission factor of the transmission function of said half
reflection layer is uniform within a display range of said liquid
crystal panel..Iaddend.
.Iadd.42. A liquid crystal device comprising said liquid crystal
panel according to claim 37, and a back lighting device disposed at
a back side of said liquid crystal panel..Iaddend.
.Iadd.43. A liquid crystal device according to claim 42, further
comprising a touch panel disposed at a front surface of said liquid
crystal panel..Iaddend.
.Iadd.44. A liquid crystal panel in which a liquid crystal layer is
sandwiched between an upper substrate and a lower substrate, said
liquid crystal panel comprising: a half reflection layer having a
reflection function and a transmission function, said half
reflection layer being disposed at an inner surface of said lower
substrate; an upper retardation film and an upper polarizing plate
being laminated on said upper substrate; and a lower retardation
film and a lower polarizing plate being laminated on a surface of
said lower substrate; wherein a retardation .DELTA.nd of said lower
retardation film is determined so that a phase difference of a
polarization condition of transmitted light which passes through
said lower polarizing plate, said lower retardation film and said
half reflection layer becomes substantially equivalent to a phase
difference of a polarization condition of reflected light by said
half reflection layer when a bright display is
performed..Iaddend.
.Iadd.45. A liquid crystal panel according to claim 44, wherein
said upper substrate has upper transparent electrodes for forming
pixels, said lower substrate has lower transparent electrodes
disposed so as to intersect with said upper transparent electrodes,
and said half reflection layer is disposed between said lower
transparent electrodes and said lower substrate..Iaddend.
.Iadd.46. A liquid crystal panel according to claim 44, wherein
said liquid crystal panel is an active matrix type liquid crystal
panel..Iaddend.
.Iadd.47. A liquid crystal panel according to claim 44, further
comprising a color filter layer..Iaddend.
.Iadd.48. A liquid crystal panel according to claim 44, wherein the
transmission factor of the transmission function of said half
reflection layer is uniform within a display range of said liquid
crystal panel..Iaddend.
.Iadd.49. A liquid crystal device comprising the liquid crystal
panel according to claim 44, and a back lighting device disposed at
a back side of said liquid crystal panel..Iaddend.
.Iadd.50. A liquid crystal device according to claim 49, further
comprising a touch panel disposed at a front surface of said liquid
crystal panel..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid crystal panel which is capable
of displaying a high quality image in both modes consisting of a
reflection mode which uses outdoor daytime light as an illumination
lighting source and a transmission mode which uses a backlight
incorporated in the panel as an illumination lighting source, and a
liquid crystal display device which uses this liquid crystal
panel.
2. Description of the Related Art
A liquid crystal display device which is used as display means of a
personal computer or a monitor of other devices is a device which
irradiates an illumination light to an image formed on a liquid
crystal panel and emits a transmitted light or a reflected light to
the display surface side so as to visualize the image.
That is, this type of liquid crystal display device, generally,
uses a liquid crystal panel which sandwiches a liquid crystal layer
in a space defined by adhering a pair of substrates having pixel
selecting electrodes and the like, and forms an image by changing
the orientation direction of liquid crystal molecules of selected
pixel portions. The formed image per se is not in a visible
condition so that the liquid crystal display device is constructed
such that light is given from the outside and is irradiated to the
liquid crystal panel and the transmitted light or the reflected
light is observed.
This type of liquid crystal panel is classified into a transmission
mode which uses a light source mounted behind the liquid crystal
panel, or a so-called backlight and a reflection mode which uses
outdoor daytime light which is present in the surroundings of the
liquid crystal panel.
Furthermore, its power source capacity is limited. For example,
with respect to PDA (small-sized portable data terminals), since
their respective power sources per se mounted thereon are small,
most of these terminals have a reflection display mode function
which takes in surrounding light as an illumination light while
excluding an active light source of the liquid crystal panel such
as a backlight as an illumination lighting source. However, to
assure the use of the liquid crystal panel in an atmosphere where
the surrounding light is small or there is no outdoor daytime light
at all, several liquid crystal display devices which are provided
with auxiliary light sources have been manufactured to assure the
use of the liquid crystal panel even in a dark environment.
This transmission and reflection type liquid crystal panel (half
reflection type liquid crystal panel) which can be used in both the
reflection mode and the transmission mode is provided with a half
reflection plate on an outside surface of a substrate (lower
substrate) opposed to a display surface side substrate (upper
substrate). In such a liquid crystal panel, the outdoor daytime
light which enters through the observation side substrate as an
incident light is reflected and thereafter is emitted from the
upper substrate so as to visualize an image, and the light
irradiated from the backlight disposed behind the liquid crystal
panel is transmitted through the lower and upper substrates and is
emitted from the upper substrate so as to visualize the image.
FIG. 6 shows a cross sectional view schematically explaining the
construction of the conventional half reflection type liquid
crystal panel. The panel is constructed such that a liquid crystal
layer 7 is interposed between a lower substrate 1 made of a glass
plate or the like which is provided with a lower transparent
electrode 4 on an inner surface thereof and an upper substrate 5
made of a glass plate or the like which is provided with a lower
transparent electrode 6 on an inner surface thereof, the periphery
of the liquid crystal layer 7 is sealed by a seal member 8, a lower
polarizing plate 9 and a half reflecting plate 2' are laminated on
the surface of the lower substrate 1, and a retardation film 10, an
upper polarizing plate 11 and a light diffusing plate 15 are
laminated on the surface of the upper substrate 5.
Although FIG. 6 shows a liquid crystal panel for a monochromatic
display, the panel can be converted to the one for a color display
by merely providing three color filters to the inner surface of the
upper substrate or the lower substrate.
The upper polarizing plate 11 and the lower polarizing plate 9
which are disposed at the upper and lower portions of the liquid
crystal panel have a function to emit the modulated light which
transmits through the liquid crystal layer 7, that is, the light
which has its orientation direction controlled at selected pixels
toward the display surface side. The retardation film 10 corrects a
thickness of respective substrates and the liquid crystal layer of
the liquid crystal panel and .DELTA.nd (retardation) of other
constitutional members. Furthermore, the light diffusing plate 15
prevents lowering of the brightness by scattering light emitting
from the liquid crystal panel while preventing the reflection of
the outdoor daytime light.
With the type of the liquid crystal panel shown in FIG. 6, in the
reflection mode which uses the outdoor daytime light as the
illumination light, the light entered from the upper substrate 5
side which defines the display surface side to transmitted through
the lower substrate 1 and is reflected by the half reflection plate
2' and again is transmitted through the lower substrate 1 and the
upper substrate 5 and is emitted toward the display surface
side.
On the other hand, in the transmission mode which uses the
backlight as the illumination light, the light irradiated by the
backlight (not shown in the drawing) disposed at the rear side of
the liquid crystal panel, that is, on the rear surface of the half
reflection plate 2' is transmitted through the half reflection
plate 2', the lower substrate 1 and the upper substrate 5 and is
emitted toward the display surface side.
In case there is the outdoor daytime light by its level of
brightness is low, the display is performed using the
transmission-and-reflection mode where the backlight is turned on
so that the reflection mode and the transmission mode are both
used.
Furthermore, in the PDA and the like, there is a type which is
provided with a so-called touch panel (not shown in drawings) for
directly inputting data or the like from the display surface using
a pen, a finger or the like. Such a touch panel is laminated above
the upper substrate of the liquid crystal panel and upon pressing
the touch panel with a nib, given information is directly inputted
from a screen, is displayed on the liquid crystal panel, is stored
in memory means incorporated in the touch panel, and is used for
the reproduction.
With respect to the above-mentioned conventional liquid crystal
display device, however, in the reflection mode, for example, the
outdoor daytime light reaches the half reflection plate after
passing through the upper substrate and the lower substrate and the
light reflected by this half reflection plate again passes through
the lower substrate and the upper substrate and is emitted toward
the display surface side as the outgoing light and hence, the
utilization efficiency of the outdoor daytime light used as the
outgoing light is low so that there arises a problem that it is
difficult to enhance the brightness of the display screen.
Furthermore, in the transmission mode, the light irradiated from
the backlight suffers from a considerable loss at the half
reflection plate so that it is difficult to obtain the sufficient
brightness and the enhancement of the contrast is also limited.
Still furthermore, in the transmission mode, there has been a
problem that the sufficient brightness is not obtained when the
phase difference exists between the phase of the reflected light of
the outdoor daytime light emitted after being reflected by the half
reflection plate and the phase of the transmitted light which is
emitted after passing through the half reflection plate. .Iadd.As
utilized herein, the phase, "the phase of transmitted/reflected
light" means "the phase difference of the polarization condition of
transmitted/reflected light". .Iaddend.Furthermore, with respect to
the color display, in the reflection mode particularly, there exist
problems such that the light advances through the lower substrate
and then returns through the lower substrate so that the
deterioration of chroma occurs and the color mixture occurs due to
parallax.
Accordingly, it is an object of the present invention to provide a
half reflection type liquid crystal panel capable of displaying the
image having high brightness and high contrast and a liquid crystal
display device using such a liquid crystal panel.
.[.SUMMARY OF THE INVENTION.].
The above-mentioned object can be achieved by mounting a half
reflection film having high reflecting efficiency in the inside of
a liquid crystal panel in such a manner that in the reflection
mode, the incident outdoor daytime light does not receive the
influence of light absorption by a lower substrate and in the
transmission mode, the phase of the transmitted light passing
through the half reflection film substantially agrees with the
phase of the reflected outdoor daytime light and hence, the
brightness of both lights is amplified so that the image display of
high brightness and high contrast can be obtained.
That is, the present invention is characterized by having
constructions described in following (1) to (5).
(1) In the liquid crystal panel, a liquid crystal layer is
sandwiched between an upper substrate which is provided with upper
transparent electrodes for forming pixels and a lower substrate
which is provided with lower transparent electrodes such that they
intersect the upper transparent electrodes. The liquid crystal
panel includes a half reflection layer having a reflection function
and a transmission function which is formed on the inner surface of
the lower substrate as a lower layer of the under transparent
electrodes, an upper retardation film, an upper polarizing plate
and a light diffusing plate which are laminated on the upper
substrate, and a lower retardation film and a lower polarizing
plate which are laminated on the surface of the lower
substrate.
Due to such a construction, in the reflection display mode as well
as in the transmission display mode, the brightness can be enhanced
and the image display having high contrast can be obtained.
Furthermore, the transmission factor or the transmittivity of the
half reflection layer is made uniform within a display range of the
liquid crystal panel, no irregularities of brightness occurs on the
displayed image.
(2) With respect to the construction of the feature (1), a color
filter layer made of a plurality of colors is formed on the inner
surface of the upper substrate as a lower layer of the upper
transparent electrodes and a passivation film is formed between
this color filter layer and the upper transparent electrodes.
Due to such a construction, in the reflection display mode as well
as in the transmission display mode, the brightness of the color
image can be enhanced so that the image display having high
contrast can be obtained.
(3) With respect to the construction of the feature (1) or (2), the
phase of the reflected light at the half reflection layer and the
phase of the transmitted light which passes through the half
reflection layer from the lower substrate side substantially agree
with each other.
Due to such a construction, lowering of brightness and color mixing
as a vision of an observer are suppressed so that in the reflection
display mode as well as in the transmission display mode,
brightness of the color image is enhanced so that image display
having high contrast can be obtained.
To be more specific, by setting the phase difference between the
phase of the transmitted light which passes through the half
reflection layer and the phase of the reflection light on the half
reflection layer within .+-..pi./4 (within .+-.45.degree.), the
difference of display between the reflection display mode and the
transmission display mode can be minimized.
(4) With respect to the construction of the feature (1) or (2), a
back lighting device is disposed at the rear side of the liquid
crystal panel so as to provide a back lighting type liquid crystal
display device.
The back lighting device, that is, the backlight is lit in an
environment with a little outdoor daytime light and mainly performs
the image display in the transmission mode thus enabling the image
display of high brightness and high contrast.
(5) With respect to the construction of the feature (4), a touch
panel is disposed on the surface side of the liquid crystal panel
so that information can be inputted by way of the screen.
Due to such a construction, with the provision of the touch panel,
information can be directly inputted by way of the screen thus
increasing the availability of the small-sized portable information
terminal.
The present invention is applicable to other types of liquid
crystal panel such as an active matrix type liquid crystal panel
adopting a thin film transistor system or the like. Furthermore,
the present invention is not limited to the above mentioned
constructions and various modifications thereof are considered
without departing from the technical spirit of the present
invention.
.[.BRIEF DESCRIPTION OF THE DRAWINGS.].
FIG. 1 is a cross sectional view explaining the first embodiment of
the liquid crystal panel according to the present invention.
FIG. 2 is a cross sectional view explaining the second embodiment
of the liquid crystal panel according to the present invention.
FIG. 3 is a cross sectional view explaining the construction of the
first embodiment of the liquid crystal display device according to
the present invention.
FIG. 4 is a cross sectional view explaining the construction of the
second embodiment of the liquid crystal display device according to
the present invention.
FIG. 5 is a perspective view showing one example of construction of
a portable information terminal as an example of an electronic
equipment on which the liquid crystal display device according to
the present invention is mounted.
FIG. 6 is a cross sectional view showing the schematic construction
of the conventional half reflection type liquid crystal panel.
FIG. 7(a) is a plan view of the liquid crystal panel explaining the
angular relationship among the absorption axis of an upper
polarizing plate, a stretching axis of an upper retardation film
and an orientation axis of liquid crystal according to one
embodiment of the present invention.
FIG. 7(b) is a plan view of the liquid crystal panel explaining the
angular relationship among the absorption axis of a lower
polarizing plate, a stretching axis of a lower retardation film and
an orientation axis of liquid crystal according to one embodiment
of the present invention.
FIG. 8 is a perspective view of a liquid crystal panel showing the
change of polarization of light in the reflection display mode and
the transmission display mode according to one embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The best mode for contemplating the present invention is explained
in conjunction with embodiments hereinafter.
FIG. 1 is a cross sectional view for explaining the first
embodiment of a liquid crystal panel of the present invention. In
the drawing, numeral 1 indicates a lower glass substrate which
constitutes a lower substrate, numeral 2 indicates a half
reflection layer, numeral 3 indicates a passivation film, numeral 4
indicates a lower transparent electrode which constitutes a lower
electrode, numeral 5 indicates an upper glass substrate which
constitutes an upper substrate, numeral 6 indicates upper
transparent electrodes which constitutes upper electrodes, numeral
7 indicates a liquid crystal layer made of liquid crystal
composition, and numeral 8 indicates a seal member made of epoxy
resin or the like which adheres the upper substrate and the lower
substrate after filling the liquid crystal layer between the upper
substrate and the lower substrate and secures them to form the
liquid crystal panel.
On the surface (upper side) of the upper glass substrate 5 side of
the liquid crystal panel, an upper retardation film 10, an upper
polarizing plate 11 and a light diffusing plate 15 are laminated.
The light diffusing plate 15 may preferably be formed by coating
silica fine particles on the surface of the upper polarizing plate
11.
In this embodiment, the half reflection layer 2 is made of an
aluminum thin film having a reflectance of 90% which is formed by a
vapor deposition method. On the surface of the aluminum thin film
having a half reflectivity, a passivation film 3 made of a
transparent organic material is formed. The passivation film 3 is
an oxidation prevention film made of SiO.sub.2 or the like provided
for preventing corrosion of aluminum and for flattening of the
aluminum thin film.
The material of this reflection layer is not limited to aluminum
and any material such as other metallic film or a non-metallic film
which has the mirror reflectivity while having half transmission
factor can be used. On this passivation film 3, the lower
transparent electrodes 4 for driving the liquid crystal panel are
mounted.
The degree of polarization and the polarization axis of the upper
polarizing plate laminated on the upper surface of the upper glass
substrate and .DELTA.nd of the upper retardation film are
respectively set to optimum values which are determined in view of
.DELTA.nd, the twist angle and the tilt angle of the liquid crystal
composition.
Furthermore, on the surface of the lower glass substrate 1, a lower
retardation film 9 and a lower polarizing plate 14 are laminated.
The degree of polarization and the polarization axis of this lower
polarizing plate 14 and .DELTA.nd of the lower retardation film 9
are set such that the phase of the light which passes through the
lower polarizing plate 14 and the lower retardation film 9 and
further passes through the half reflection layer 2 substantially
agrees with the phase of the outdoor daytime light which is
reflected on the half reflecting layer 2.
To be more specific, the upper retardation film 10 is constructed
by two films which are comprised of a first upper retardation film
and a second upper retardation film. The angle made by a stretching
axis (optical axis) of a second upper retardation film 10 which
comes into contact with the second substrate (the upper substrate)
5 and the orientation axis of the upper-substrate-side liquid
crystal is set within a range of 70.degree.-120.degree.. The angle
made by a stretching axis (optical axis) of the first retardation
film (upper retardation film) 10 which comes into contact with the
upper polarizing plate 11 side and the orientation axis of the
upper-substrate-side liquid crystal layer 7 is set within a range
of 90.degree.-160.degree.. The angle made by an absorption axis
(optical axis, polarization axis or stretching axis) of the upper
polarizing plate 11 and the orientation axis of the
upper-substrate-side liquid crystal layer 7 is set within a range
of 100.degree.-180.degree.. The angle made by the orientation axis
of the upper-substrate-side liquid crystal layer 7 and the
orientation axis of lower-substrate-side liquid crystal layer is
set to not less than 240.degree.. The retardation .DELTA.nd of the
liquid crystal layer 7 is set to 0.7 .mu.m-0.95 .mu.m, the
retardation .DELTA.nd of the second retardation film is set to 130
nm-250 nm, and the retardation .DELTA.nd of the first upper
retardation film is set to 380 nm-500 nm. Due to such setting of
angles and retardations .DELTA.nd, the display having high contrast
is obtained.
FIG. 7(a) is a plan view of the liquid crystal panel which explains
the angular relationship between the absorption axis of the upper
polarizing plate, the stretching axis of the upper retardation film
and the orientation axis of the liquid crystal according to one
embodiment of the present invention.
FIG. 7(b) is a plan view of the liquid crystal panel which explains
the angular relationship between the absorption axis of the lower
polarization plate, the stretching axis of the lower retardation
film and the orientation axis of the liquid crystal according to
one embodiment of the present invention.
FIG. 7(a) and FIG. 7(b) are explained in view of an example which
uses the liquid crystal of STN mode.
In FIG. 7(a) and FIG. 7(b), e--e is a reference line, and to be
more specific, is a line parallel to a long side of the second
substrate 5 of the liquid crystal display panel and f--f is a line
perpendicular to the line e--e. In FIG. 7(a), numeral 37 indicates
an upper-substrate-side orientation axis of the liquid crystal
layer 7, numeral 36 indicates a lower-substrate-side orientation
axis of the liquid crystal layer 7, numeral 38 indicates an
absorption axis of the upper polarizing plate 11 (optical axis of
the polarizing plate) numeral 39 indicates a stretching axis of the
first upper retardation film 10 (optical axis of the first upper
retardation film), and numeral 40 indicates a stretching axis of
the second upper retardation film 10 (optical axis of the second
upper retardation film).
In FIG. 7(a), numeral 41 indicates an angle made by the absorption
axis of the polarizing plate 11 and the line c--c and is set to
125.+-.10.degree. to be more specific. Numeral 42 indicates an
angle made by the stretching axis 39 of the first upper retardation
film 10 and the line e--e and is set to 108.+-.10.degree. to be
more specific. Numeral 43 indicates an angle made by the stretching
axis 40 of the second upper retardation film 10 and the line e--e
and is set to 72.+-.10.degree. to be more specific. Numeral 44
indicates an angle made by the upper-substrate-side orientation
axis 37 of the liquid crystal layer 7 and the lower-substrate-side
orientation axis 36 (twist angle of liquid crystal display panel)
and it is set to not less than 240.degree. with the liquid crystal
in STN mode. Numeral 45 indicates an angle made by the
upper-substrate-side orientation axis 37 of the liquid crystal
layer 7 and the line c--c and is set to (360--twist angle
44)/2).degree. to be more specific. In TN mode, the twist angle 44
may be set to 90.+-.10.degree.. In case the liquid crystal in STN
mode is used, a sufficient contrast can be obtained even when the
number of display lines is increased so that the display having
high definition can be obtained.
In FIG. 7(b), numeral 46 indicates an absorption axis of the lower
polarizing plate 14 (optical axis of the lower polarizing plate)
and numeral 47 indicates a stretching axis of the lower retardation
film 9 (optical axis of the lower retardation film).
An angle made by the absorption axis of the lower polarizing plate
14 and the line c--c is set to 0.+-.10.degree.. The angle made by
the absorption axis of the lower polarizing plate 14 and the line
e--e may be set to 90.+-.10.degree.. Numeral 48 indicates an angle
made by the stretching axis 47 of the lower retardation film 9 and
the line e--e and is set to 45.+-.10.degree. to be more
specific.
In this embodiment, as a method for measuring the retardation
.DELTA.nd of the upper retardation film 10 and the lower
retardation film 9, a spectrum analysis method is used. For
example, the retardation film which is an object to be measured is
sandwiched between the first and second polarizing films which have
their polarizing axes intersept each other. The optical axis of the
object to be measured is arranged such that it makes an angle of
45.degree. relative to the polarizing axes of the first and second
polarizing films. Then, spectroscopic characteristics of the light
which passes through the object to be measured and the first and
second polarizing films are measured. In the spectroscopic
characteristics of the object to be measured and the first and the
second polarizing films, the transmission factor shows the minimum
value (valley value) at a specific wavelength .lamda.. Accordingly,
by measuring this specific wavelength .lamda., the retardation
.DELTA.nd of the object to be measured can be obtained. In the
above embodiment, although the first upper retardation film 10 is
measured by using one sheet of first retardation film 10, it is
difficult to measure the second upper retardation film 10 in case
one sheet of the second upper retardation film 10 is used.
Accordingly, in this case, the wavelength .lamda.2 which
corresponds to the valley value of the three overlapped second
upper retardation films 10 is measured and then the mean value
which is obtained by dividing the wavelength .lamda.2 in three is
used.
According to the embodiment explained heretofore, no difference
takes place in the display characteristics between the reflection
display mode and the transmission display mode.
FIG. 8 is a perspective view showing the change of polarization
condition of the light in the reflection display mode and the
transmission display mode in this embodiment.
L1 is a outdoor daytime light such as solar light, L2 indicates the
reflected light reflected by the half reflecting layer 2, numeral
18 indicates a linear lamp (light source) and numeral 17 indicates
a light guide plate which introduces the light from the light
source 18 to the liquid crystal panel. The lighting device is
comprised of the light source 18 and the light guide plate 17.
L1' is the light irradiated from the lighting device before passing
through the half reflection layer 2 and L2' is the transmitted
light which is obtained by making the light L1' irradiated from the
lighting device pass through the half reflection layer 2.
Other symbols are as same as those of FIG. 1, FIG. 7(a) and FIG.
7(b).
First, the reflection display mode is explained. The outdoor
daytime light L1 which is the light of a circular polarization is
converted to the light of linear polarization when it passes
through the upper polarization plate 11. At #this point of time,
the phases of respective wavelengths .Iadd.(that is, the phase
difference of the polarization condition of respective wavelengths)
.Iaddend.are leveled. Subsequently, when the outdoor daytime light
of linear polarization passes through the upper retardation film
10, it is converted to the light of an elliptic polarization. At
this point of time, the phases of respective wavelengths are
different from each other. Thereafter, during its course of passing
through the liquid crystal layer 7, the outdoor daytime light L1 of
the elliptic polarization is converted to the light of the circular
polarization and reaches the half reflection layer 2. At the point
of time that the outdoor daytime light L1 reaches the half
reflection layer 2, the phases of respective wavelengths are
substantially leveled. This is because that the phases of
respective wavelengths which are shifted during the outdoor daytime
light L1 passes through the liquid crystal layer 7 are leveled by
the upper retardation film 10.
Upon reaching the half reflecting layer 2, the outdoor daytime
light L1 is reflected on the half reflecting layer 2 and turns out
to be the reflected light L2. At the point of time of reflection on
the half reflecting layer 2, the reflected light L2 is still the
light of circular polarization. At the point of time of reflection
on the half reflecting layer 2, the phases of respective
wavelengths of the reflected light L2 are leveled, while the phase
of the reflected light L2 is shifted 180.degree. relative to the
phase of the outdoor daytime light L1 right before being reflected
by the half reflecting layer 2. Thereafter, the reflected light L2
is converted to the light of the elliptic polarization during its
course of passing through the liquid crystal layer 7 and is emitted
from the upper substrate 5. At this point of time, the phases of
respective wavelengths are different from each other again.
Subsequently, when the reflected light L2 of elliptic polarization
passes through the upper retardation film 10, it is converted to
the light of the linear polarization. At this point of time, the
phases of respective wavelengths are leveled by the upper
retardation film 10 so that they substantially agree with each
other. The reflected light L2 having now the linear polarization
passes through the upper polarizing plate 11 and is diffused by the
light diffusing plate 15 not shown in the drawing and reaches eyes
of an observer. Accordingly, at the point of time of reaching the
eyes of the observer, the phases of the respective wavelengths of
the reflected light L2 are leveled, the display is not tinted in
colors of specific wavelengths and hence, the display is observed
as a display of natural colors by the observer.
Furthermore, in an optical system of the reflection display mode,
the retardations .DELTA.nd and the optical axes of the upper
polarizing plate 11, the upper retardation film 10 and the liquid
crystal layer 7 are determined such that the outdoor daytime light
L1 at the point of time of being reflected by the half reflecting
layer 2 has the circular polarization condition. By making the
outdoor daytime light L1 at the point of time of being reflected by
the half reflecting layer 2 have the circular polarization
condition, the reflected light L2 also becomes the circular
polarization so that the reflection is enhanced and the wavelength
dependency of the reflectance is minimized and there is no fear of
tinting in specific colors.
Subsequently, the transmission display mode is explained.
The illumination light L1' irradiated from the lighting device has
the phases of respective wavelengths thereof which are not leveled
and hence, it is the light having irregular phases. The
illumination light L1' irradiated from the lighting device is the
light having the circular polarization and it is directly converted
to the light having the linear polarization when it passes through
the lower polarizing plate 14. The illumination light L1' converted
to the light having the linear polarization is converted to the
light having the circular polarization upon passing through the
lower retardation film 9. That is, according to the present
invention, the illumination light L1' at the point of time of
reaching the half reflecting layer 2 becomes the light having the
circular polarization as in the case of the reflecting light L1.
The stretching axis and the retardation .DELTA.nd of the lower
polarizing plate 14 are determined such that the illumination light
L1' at this point of time becomes the light which has the phases of
respective wavelength leveled. Accordingly, the transmitted light
L2' which has passed through the half reflecting layer 2 follows
the same path as the reflected light L2 so that by making the
transmitted light L2' which has passed through the half reflecting
layer 2 have the same polarization condition and the phase
condition as the reflected light L2, no difference of display takes
place between the transmission display mode and the reflection
display mode. In case the phase difference between the transmitted
light L2' and the reflected light L2 .Iadd.(that is, the difference
between the phase difference of the polarization condition of the
transmitted light L2' and the phase difference of the polarization
condition of the reflected light L2) .Iaddend.is within .+-..pi./4,
no substantial difference is observed in displayed colors between
the transmission display mode and the reflection display mode.
The illumination light L1' at the point of time of reaching the
half reflecting layer 2 is the light of the circular polarization
which has the leveled polarization plane and is different from the
light of the circular polarization just after being irradiated from
the lighting device which has irregular polarization plane. The
reflected light L1 at the point of time of reaching the half
reflecting layer 2 also turns out to be the light of the circular
polarization which has the leveled polarization plane. Accordingly,
when the light of the lighting device is directly irradiated to the
half reflecting layer 2, the display different from the reflection
display mode can be obtained.
Although the lower retardation film 9 is made of a single sheet of
film in the previously mentioned embodiment, the lower retardation
film 9 may be made of two overlapped retardation films.
In case the lower retardation film 9 is made of two retardation
films, as shown in FIG. 7(b) in a dotted line, in place of the
stretching axis 47 of the lower retardation film 9, a stretching
axis of the first lower retardation film 9 which comes into contact
with the lower substrate is denoted as 51, and a stretching axis of
the second lower retardation film 9 which comes into contact with
the lower polarization plate 14 is denoted as 49, and an angle 52
made by the stretching axis 51 of the first lower retardation film
9 and the line e--e is preferably set to 100.+-.10.degree. and an
angle 50 made by the stretching axis 49 of the second lower
retardation film 9 and the line e--e is preferably set to
162.5.+-.10.degree.. The other conditions are as same as those of
the previously mentioned embodiment.
According to the embodiment of the present invention, both the
reflection display mode and the transmission display mode can
enhance the brightness and can obtain the image display having the
high contrast.
FIG. 2 is a cross sectional view explaining the second embodiment
of the liquid crystal panel according to the present invention,
wherein the same numerals which also appear in FIG. 1 denote the
same parts and numeral 12 indicates a color filter made of three
colors (R, G, B).
Between respective colors R, G, B which constitute the color filter
12, a grid-like light blocking film (black matrix) may be formed if
necessary, and a passivation film 13 preferably made of a
transparent organic material is formed on the color filter 12. This
passivation film 13 prevents the liquid crystal layer 7 from being
contaminated by the color filter 12 and also makes the surface of
the electrode flattened and smooth. Other remaining constructions
and functions of this embodiment are as same as those of the first
embodiment.
According to this embodiment, both the reflection display mode and
the transmission display mode can enhance the brightness and can
obtain the color image display of high contrast, no color mixing
and high chroma.
FIG. 3 is a cross sectional view explaining the construction of the
first embodiment of the liquid crystal display device according to
the present invention, wherein a case that the liquid crystal
display device uses the liquid crystal panel explained previously
in view of FIG. 2 is shown. In the drawing, numeral 20 indicates
half reflection type liquid crystal panel and a backlight 16 is
disposed on a planar surface of the liquid crystal panel 20 so as
to construct the liquid crystal display device.
The backlight 16 is comprised of a light guide plate 17 which is
made of a transparent acrylic plate provided with a surface
treatment for giving the light directivity to the plate, a linear
lamp 18 such as a cold cathode fluorescent tube arranged along one
side of the light guide plate 17, and a reflection sheet 19.
According to this liquid crystal display device, in an environment
which has a sufficient outdoor daytime light, the backlight 16 is
turned off and the display of the image is performed in the
reflection mode which uses the outdoor daytime light which enters
from the upper glass substrate 5 side as the illumination light. On
the other hand, in a condition where there is a little or no
outdoor daytime light, the backlight 16 is turned on so as to
perform the image display in the transmission mode.
Here, in case the outdoor daytime light is insufficient, when the
backlight 16 is turned on, the degree of polarization and the
polarization angle of respective retardation films and respective
polarizing plates and .DELTA.nd of respective constitutional
members are determined such that the phase of the light which has
passed through the half reflection layer 2 from the backlight 6 and
the phase of the outdoor daytime light which is reflected by the
half reflecting layer 2 substantially agree with each other thus
providing high brightness and high contrast.
According to the liquid crystal display device of the present
embodiment, the half reflection type liquid crystal display device
which enables the image display of high brightness and high
contrast can be obtained.
FIG. 4 is a cross sectional view showing the construction of the
second embodiment of the liquid crystal display device according to
the present invention. This drawing shows the liquid crystal
display device equipped with the liquid crystal panel explained
previously in view of FIG. 2. In this embodiment, a touch panel 21
is mounted on the display surface side of the liquid crystal
display device as shown in FIG. 3.
This touch panel 21 has a function to directly input information by
tracing the surface of the screen with a nib or the like and
inputted data is displayed on the liquid crystal panel 20 or is
stored in memory means not shown in the drawing and is
utilized.
According to the liquid crystal display device of the present
embodiment, the half reflection type liquid crystal display device
which enables the direct screen inputting and the image display of
high brightness and high contrast can be obtained.
FIG. 5 is a perspective view explaining an example of the
construction of the portable type information terminal as an
example of an electronic equipment on which the liquid crystal
display device of the present invention is mounted. This portable
type information terminal (PDA) is comprised of a body portion 30
and a cover 31 which is mounted on the body portion 30 by means of
a hinge such that it can be opened or closed and the liquid crystal
display device according to the present invention is mounted on the
body portion 30.
This liquid crystal panel 20 of the liquid crystal display device
is of the above-mentioned half reflection type and can provide a
favorable image recognition in both the reflection mode and the
transmission mode and can obtain the image display of high
brightness, high contrast and no color mixing irrespective of the
presence of the environmental outdoor daytime light. Furthermore,
in case the touch panel 21 is mounted on the upper surface of the
liquid crystal panel 20, letters and symbols can be inputted by
tracing the input portion on the display screen with a pen 32
accommodated in an accommodating portion 33 formed on a portion of
the cover 31.
The shape and the structure of this kind of portable type
information terminal are not limited to those shown in the drawing
and the terminal can have other various shapes, construction and
functions.
Furthermore, the present invention is not limited to the liquid
crystal display device equipped with the above-mentioned touch
panel and is applicable to the liquid crystal display device having
no backlight or other general reflection-type liquid crystal
display device in the same manner, as has been described
heretofore, according to the present invention, it becomes possible
to provide the half reflection type liquid crystal panel capable of
performing the image display of high brightness and high contrast
and the liquid crystal display device equipped with this liquid
crystal panel.
* * * * *