Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-08-27
2004-11-23
Thomas, Tom (Department: 2815)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S106000, C349S176000, C349S096000
Reexamination Certificate
active
06822712
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a reflection liquid crystal display such as a display for a mobile terminal device, a terminal display for utilizing various types of media for individuals, a display of a mobile telephone, and a display in an amusement device such as a game machine, a method for producing the same, and a method for driving the same. More specifically, this invention relates to a reflection liquid crystal display having excellent field-of-view angle characteristics, the production process of which is facilitated, a method for producing the same and a method for driving the same.
2. Description of the Related Art
Recently, demand for a reflection liquid crystal display, power consumption of which is reduced, has increased in line with development and diversification of mobile devices. Such a display that enables color display has been increasingly desired for use in, particularly, mobile telephone sets, mobile terminals, and office automation devices. A brighter display is further required in view of mobility, and reasonably wide field-of-view angle characteristics are required. Especially preferable, since narrow field-of-view angle characteristics are desired in an individual use although wide field-of-view angle characteristics are desired where a plurality of people observes a display, a reflection liquid crystal display that enables a changeover between a wide field-of-view angle and a narrow field-of-view angle is desired.
Conventionally, such types are widely used in reflection liquid crystal displays, in which a polarization plate is used as in a supertwisted nematic type (STN type) or twisted nematic type (TN type) that has been widely used in transmission type liquid crystal displays. In the case of reflection type, only a single polarization plate is used, differing from the transmission type. However, since it is necessary to switch reflection light, such a type is common, which is a so called single polarization plate used along with a quarter-wavelength plate as described in, for example, T. Sonehara et al., Japan Display 1989, Page 192 (1989).
A description is given of a display principle of a single polarization plate type, taking a normally white type, which has been most widely used, as an example (Prior art example 1). FIG.
1
A and
FIG. 1B
are views showing the display principle of a reflection type liquid crystal element of a prior art single polarization plate type, wherein
FIG. 1A
shows an example in the case of white display, and
FIG. 1B
shows an example in the case of black display. Also, FIG.
1
A and
FIG. 1B
show only optical elements of the reflection liquid crystal display.
As shown in
FIG. 1A
, incident non-polarized light
1107
is brought into collision with a reflection plate
1104
after having passed through a quarter-wavelength plate
1102
of a wide-band and passed through a liquid crystal layer
1103
and returns in its inverted optical route, and, when the light passes through the polarization plate
1101
, it enters eyes of people, wherein the light can be recognized as an image. At this time, by changing the state of polarization by utilizing electro-optical effects of liquid crystal, switching of the reflection light can be carried out. First, the incident non-polarized light
1107
enters the polarization plate
1101
and is converted to light polarization having a specified vibration direction. At this time, the polarization plate is set so that the outgoing light becomes P-polarized light
1105
. And, if the optical axis of the quarter-wavelength plate
1102
is disposed so that it forms 45 degrees with respect to the transmission axis of the polarization plate, the light that has passed through the quarter-wavelength plate
1102
becomes rightward circular-polarized light
1106
and enters the liquid crystal layer
1103
. In either the TN mode or the STN mode, retardation of the liquid crystal
1103
is set so that it gives &lgr;/4, that is, a phase difference &pgr;/2 when no voltage is applied. Therefore, light that has passed through the liquid crystal layer
1103
again becomes P-polarized light
1105
and reaches the reflection plate
1104
. In the reflection, since the P-polarized light
1105
is reflected as it is P-polarized light
1105
, it returns in a completely inverted optical path of the path along which it entered, and is converted to rightward circular-polarized light
1106
by the liquid crystal layer
1103
. Further, the light becomes P-polarized light
1105
by the quarter-wavelength plate
1102
and is caused to radiate from the polarization plate
1101
as it is P-polarized light
1105
. That is, white display is enabled in a state where no voltage is applied onto the liquid crystal.
As shown in
FIG. 1B
, if voltage is applied to the liquid crystal layer
1103
and liquid crystal is erected so that the liquid crystal molecules become perpendicular with respect to its substrate, the retardation of the liquid crystal layer
1103
becomes almost zero, and a phase difference 0 is given. That is, the liquid crystal layer
1103
does not give any influence to the state of polarization. In this state, where incident non-polarized light
1107
enters the polarization plate
1101
, light that has passed through the polarization plate
1101
and quarter-wavelength plate
1102
becomes rightward circular-polarized light
1106
as described above. Herein, since voltage is applied onto the liquid crystal layer
1103
, the liquid crystal layer
1103
does not change the state of polarization, and the rightward circular-polarized light
1106
passes through the liquid crystal layer
1103
as it is the rightward circular-polarized light
1106
and enters the reflection plate
1104
. Since the advancement direction of the light is inverted by reflection, the rightward circular-polarized light
1106
becomes a leftward circular-polarized light
1108
and returns. Since the liquid crystal layer
1103
also does not change the state of polarization, light that passed through the liquid crystal layer
1103
enters the quarter-wavelength plate
1102
as it is a leftward circular-polarized light, and it becomes S polarization
1109
whose direction of polarization is different by 90 degrees from the P-polarized light
1105
, wherein the light enters the polarization plate
1101
. Since the transmission axis of the polarization plate
1101
is set so that it can make the P-polarized light pass therethrough, wherein the S polarization
1109
cannot pass through the polarization plate
1101
, and it is displayed as black. Depending upon the intensity of application voltage, the retardation of the liquid crystal layer
1103
can be varied, wherein intermediate colors can be displayed.
Also, Japanese Unexamined Patent Application No. Hei-10-20323 (hereinafter called a “prior art example 2”) has disclosed a liquid crystal display whose production is facilitated and field-of-view angle characteristics are excellent. In the prior art example 2, a liquid crystal layer in which two or more types of slight areas coexist is placed between two substrates, and has an electrode having an opening formed on at least one substrate, and a second electrode (control electrode) secured in the opening, wherein a voltage that is higher than the voltage applied between the electrode having the opening and the electrode opposed thereto is applied between the control electrode and the electrode opposed thereto, thereby securing a wide field-of-view angle.
Further, Japanese Unexamined Patent Publication No. Hei-7-239471 (hereinafter called a “prior art example 3”) discloses the use of a cholesteric material layer and phase plate, that act as a reflection layer, for the purpose of improving the brightness and color purity of a reflection liquid crystal display. In the prior art example 3, the upper and lower substrates are disposed so as to be opposed to each other, a liquid crystal layer is placed and secured between these two substrates, and the prior art example 3 compris
Ishii Toshiya
Suzuki Masayoshi
Suzuki Teruaki
NEC Corporation
Richards N. Drew
Thomas Tom
Young & Thompson
LandOfFree
Reflection liquid crystal display, method for producing the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reflection liquid crystal display, method for producing the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflection liquid crystal display, method for producing the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3337382