Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-04-06
2004-02-10
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000
Reexamination Certificate
active
06690438
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color translucent liquid crystal display panel made by providing color filters in a translucent liquid crystal display panel which is reduced in power consumption and is made capable of a reflection display to improve visibility when light (external light) in an external environment is strong, and also capable of a temporary transmission display by providing an auxiliary light source to improve visibility when the external light is weak.
2. Description of the Related Art
At present, as liquid crystal display devices using liquid crystal display panels, there are a transmissive liquid crystal display device having an internal light source, a reflective liquid crystal display device using light of an external light source, and a transflective liquid crystal display device using light of an external light source when it is bright and turning on an auxiliary light source when the external light source is dim to be used in a transmission state. The reflective liquid crystal display device is effective in order to reduce the power consumption of and to thin the liquid crystal display device. A reflection display, however, can not be recognized when the external environment is dark, and thus a transflective display is hopeful.
Such a conventional transflective liquid crystal display device is explained using FIG.
16
.
FIG. 16
is a view schematically showing a cross section of the transflective liquid crystal display panel in this liquid crystal display device. Incidentally, it is assumed that a visible side by an observer is the upper side.
This liquid crystal display panel includes a liquid crystal layer
15
sandwiched between a first substrate
1
and a second substrate
5
each of which is transparent. Further, the liquid crystal display panel has scanning electrodes
2
in stripes parallel to the paper surface, each made of an indium tin oxide (ITO) film which is a transparent conductive film, on the first substrate
1
(inner surface) provided on the viewer side. On the other hand, on the second substrate
5
(inner surface), a color filter
9
is provided which is constituted of red (R) filters
6
, green (G) filters
7
and blue (B) filters
8
. In this color filter
9
, adjacent filters
6
,
7
and
8
slightly overlap one upon another or abut on each other.
On the color filter
9
, a protective insulating film
10
is formed to flatten levels of the color filters and prevent deterioration thereof. The protective insulating film
10
is provided thereon with data electrodes
11
in stripes perpendicular to the paper surface each made of an indium tin oxide (ITO) film that is a transparent conductive film. The scanning electrodes
2
and the data electrodes
11
are formed in directions perpendicular to each other to form pixel portions where they coincide as viewed in a plane view, and a plurality of the pixel portions form a display region.
Further, alignment films
12
are provided on the inner surface of the first substrate
1
including the scanning electrodes
2
and on the inner surface of the second substrate
5
including the data electrodes
11
respectively as treatment films for aligning the liquid crystal layer
15
in predetermined directions. The first and second substrates
1
and
5
are coupleed together with a fixed gap therebetween with a sealing material
16
so that the scanning electrodes
2
on the first substrate
1
and the data electrodes
11
on the second substrate
5
are opposed, a liquid crystal is injected from an opening (not shown) provided in the sealing material
16
, and sealed with a closing material (not shown), thereby forming the liquid crystal layer
15
.
Furthermore, a first polarizer
21
is provided on the visible side (upper side) of the first substrate
1
, and a second polarizer
22
is provided on the opposite side (lower side) to the visible side of the second substrate
5
. On the lower side of the second polarizer
22
, a transflective reflector
24
is provided which transmits a part of light and reflects almost all the remaining light. Moreover, a light source portion
31
is provided below the transflective reflector
24
as an auxiliary light source. The light source portion
31
is constituted of, for example, a cold-cathode fluorescent tube, a reflector, a prism sheet and a diffuser.
In such a transflective liquid crystal display panel, light from the outside, for example, passes through the first polarizer
21
and the first substrate
1
as a first incident light
35
, and is then made incident on the liquid crystal layer
15
. The liquid crystal layer
15
causes optical rotation or phase difference, and the light is made incident on the color filter
9
, passes through the second substrate
5
and the second polarizer
22
, and reaches the transflective reflector
24
. The first incident light
35
passes through such an optical path and is thus absorbed by the aforesaid members, resulting in attenuation of the light incident on the transflective reflector
24
. The path of light is explained in relation to major constituents, and additionally the scanning electrodes
2
and the like actually cause absorption.
The first incident light
35
is reflected by the transflective reflector
24
and goes out to an observer side as a first reflection light
36
, while absorbed by the second polarizer
22
, the second substrate
5
, the color filter
9
, the liquid crystal layer
15
, the first substrate
1
and the first polarizer
21
. Therefore, the first reflection light
36
passes through the color filter
9
twice, and thus it is greatly absorbed by the color filter
9
.
On the other hand, other light component from the external light source, as a second incident light
37
, passes through a path similar to that of the first incident light
35
to reach the transflective reflector
24
. The second incident light
37
, which is a component passing through the transflective reflector
24
, is slightly reflected by the constituent of the light source portion
31
disposed below the transflective reflector
24
. This reflection light goes out as a second reflection light
38
, but it becomes extremely weak reflection light because it is originally weak reflection light, and additionally, only a component of the light passes through the transflective reflector
24
when passing through it again, and it is absorbed by the constituents including the color filter
9
.
As described above, when the external light source is used, the first and second incident lights
35
and
37
passes through the color filter
9
twice and go out to the observer side as the first and second reflection lights
36
and
38
to be recognized as a display.
In contrast to the above, emitted light from the light source portion
31
disposed below the second substrate
5
becomes a transmission light
40
which passes through the transflective reflector
24
, the second polarizer
22
, the second substrate
5
, the color filter
9
, the liquid crystal layer
15
, the first substrate
1
and the first polarizer
21
to go out to the observer side. Accordingly, the transmission light
40
passes through the color filter
9
only once.
Consequently, brightness is important only in the case of the reflection display because the light going out to the observer side passes through the constituents twice and is thus absorbed greatly. It is particularly desired to use a color filter with little absorption because the light passes through the color filter twice.
Spectral characteristics of the color filter are explained here using FIG.
17
.
FIG. 17
is a graph showing spectral characteristics of the R, G and B color filters.
In
FIG. 17
, the horizontal axis represents optical wavelength in the unit nanometers (nm), and the vertical axis represents transmittance in the unit percent(%).
The spectral characteristic of the R, G and B filters used in the reflective liquid crystal display panel are represented by curved lines
66
,
67
and
68
, respectively. For exam
Citizen Watch Co. Ltd.
Parker Kenneth
Westerman Hattori Daniels & Adrian LLP
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