Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-04-13
2003-05-20
Chow, Dennis-Doon (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S089000, C345S108000
Reexamination Certificate
active
06567060
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid crystal display device, more specifically, to a liquid crystal display device for performing a bright display using a reflection-type polarizing film by its reflection characteristic, or performing a display using a selective-reflection type film by its difference in color tones.
BACKGROUND TECHNOLOGY
Recently, a reflection-type liquid crystal display device for performing a display by an external light source has been developed as a liquid crystal display device for portable information processing devices, and improvement of brightness and multi-color display has progressed. As a method for improving brightness, a method is tried in which a reflection-type polarizing film is provided on the side of a liquid crystal cell opposite to the visible side, and a printed layer is formed on the rear face of the reflection-type polarizing film. The reflection-type polarizing film has a transmission axis and a reflection axis as two optical axes orthogonal to each other and has characteristics for transmitting a light linearly polarized in the direction parallel to the transmission axis but for reflecting an incident light linearly polarized in the direction parallel to the reflection axis.
Moreover, as another method for improving brightness of the liquid crystal display device, a method using a selective-reflection characteristic of a cholesteric liquid crystal polymer is also considered.
The polarizing film conventionally and widely used in a liquid crystal display panel is an absorption-type polarizing film. The absorption-type polarizing film has two optical axes, a transmission axis and an absorption axis, orthogonal to each other, and it has characteristics for transmitting a light linearly polarized in the direction parallel to the transmission axis but for absorbing an incident light linearly polarized in the direction parallel to the absorption axis.
Therefore, the absorption-type polarizing film is used in combination with the aforesaid reflection-type polarizing film, whereby the liquid crystal display device has a large transmission characteristic when the transmission axes of the polarizing films are parallel to each other and a large reflection characteristic when the transmission axes are orthogonal to each other.
Accordingly, the liquid crystal display device has a large absorption characteristic (a black display) when the two absorption-type polarizing films are disposed in such a manner that the transmission axes thereof are orthogonal to each other, different from a transmission characteristic when they are disposed in such a manner that the transmission axes are parallel to each other.
In the case of the liquid crystal display device using two absorption-type polarizing films, a reflector is disposed on the rear face side of the absorption-type polarizing film disposed on the side opposite to the visible side in relation to the liquid crystal cell, whereby a bright display is performed by reflecting incident light from the external light source to the visible side in a transmission state and a dark display is performed in an absorption state. In this case, however, since the reflected light which is viewed passes through the absorption-type polarizing film positioned on the reflector twice, the light is absorbed partly, resulting in a display of which brightness somewhat decreases.
Moreover, the reflector having light scattering properties is used, absorption by the absorption-type polarizing film occurs due to instability in polarization by the reflector, whereby brightness be come impaired.
Furthermore, in a dark environment without an external light source, since the visibility of the display of the liquid crystal display device extremely deteriorates, an auxiliary light source is provided in the liquid crystal display device in many cases. In that case, a reflector of a transflective-type is used in place of the reflector without a transmission characteristic.
In this case, the bright display by reflection of an incident light from the external light source, briefly explained except for the liquid crystal layer, corresponds to the case where the transmission axes of the two absorption-type polarizing films are parallel to each other, resulting in a bright display also in the case where the auxiliary light source is used. The converse dark display corresponds to the case where the transmission axes of the two absorption-type polarizing films are orthogonal to each other, resulting in a bright display also in the case where the auxiliary light source is used.
In contrast to the above, according to the liquid crystal display device using an absorption-type polarizing film and a reflection-type polarizing film in combination, in the case where the external light source is used, a bright state is a state where the transmission axis of the absorption-type polarizing film and the reflection axis of the reflection-type polarizing film are parallel to each other to obtain a reflection characteristic of the reflection-type polarizing film. Accordingly, the reflection-type polarizing film itself reflects incident light resulting in a bright display. Conversely, a dark state is a state where the transmission axis of the absorption-type polarizing film and the transmission axis of the reflection-type polarizing film are parallel to each other and uses the transmission characteristic, and thus it is required to dispose or print a light absorbing material on the rear face of the reflection-type polarizing film. As above, bright and dark displays with excellent contrast can be performed by means of the liquid crystal display device using the absorption-type polarizing film and the reflection-type polarizing film.
The structure of the conventional liquid crystal display panel of the liquid crystal display device as above is explained with reference to the drawings.
FIG. 16
is a plane view showing a plane structure of the principal portion thereof, and
FIG. 17
is a partly enlarged sectional view along the A—A line in FIG.
16
.
In the liquid crystal display panel, a first substrate
1
and a second substrate
5
made of a transparent material such as glass or the like are oppositely disposed to each other, a predetermined gap between them is kept by a spacer not shown, peripheries of the substrates are bonded together by a sealant
4
serving as an adhesive, and a liquid crystal layer
8
is filled in the gap and sealed by an end-sealing material
26
.
M pieces of scanning electrodes
2
made of a transparent electrode film are formed on the inner face of the first substrate
1
, N pieces of data electrodes
6
intersecting the scanning electrodes
2
are formed on the inner face of the second substrate
5
, and intersections of the scanning electrodes
2
and the data electrodes
6
form pixel portions
21
to form a liquid crystal cell of a matrix type liquid crystal display panel having an M×N piece of pixel portions.
In
FIG. 16
, since the second substrate
5
positioned on the uppermost side of this liquid crystal cell is transparent, the data electrodes
6
, the first substrate
1
and the scanning electrodes
2
, the sealant
4
, the end-sealing material
26
, and the like positioned thereunder are all shown by solid lines.
In the above liquid crystal display panel, there is a liquid crystal display panel of an active-matrix type having a switching element in each pixel portion
21
and a liquid crystal display panel of a passive-matrix type without providing a switching element, and the liquid crystal display panel as the passive-matrix type is explained here.
It should be noted that, as shown in
FIG. 17
, an alignment layer
3
and an alignment layer
7
are formed on the inner face of the first substrate
1
and the scanning electrodes
2
and on the inner face of the second substrate
5
and the data electrodes
6
respectively in order to align the liquid crystal molecules of the liquid crystal layer
8
regularly.
Moreover, a first polarizing film
11
is disposed on the rear face side of the firs
Armstrong Westerman & Hattori, LLP
Chow Dennis-Doon
Citizen Watch Co. Ltd.
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