Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1999-01-27
2002-05-14
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S123000, C570S124000, C570S125000, C570S126000, C570S127000, C568S325000, C568S326000, C568S335000, C568S626000, C568S630000, C568S659000, C568S661000, C568S663000, C585S435000, C585S436000, C558S270000
Reexamination Certificate
active
06388146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device used by a single person or a plurality of people, such as a wordprocessor, a personal computer, or a mobile information terminal, a polymerizable compound suitable for such a liquid crystal display device, a polymerizable resin composition containing such a compound, and a cured polymer formed from such a composition. In this specification, a liquid crystal display device will be referred to as an “LCD device”.
2. Description of the Related Art
Conventionally, the following LCD devices using a composite of a liquid crystal material and a polymer are known.
Japanese National Phase PCT Laid-Open Publication No. 58-501631, for example, describes a polymer dispersed liquid crystal display device (hereinafter, referred to as a “PDLC display device”). The PDLC display device includes liquid crystal domains each surrounded by a polymer matrix. When no voltage is applied to the liquid crystal material, the refractive indices of the liquid crystal material and the polymer are not matched, resulting in a scattered state. When a voltage is applied to the liquid crystal material, the refractive index of the liquid crystal material changes so as to be matched with that of the polymer, resulting in a transparent state.
Japanese National Phase PCT Laid-Open Publication No. 61-502128, for example, describes an LCD device in which a mixture of the liquid crystal material and a photopolymerizable resin is irradiated with ultraviolet light, resulting in three-dimensional phase separation into a liquid crystal material and a polymer.
The above-described LCD devices perform display by electrically controlling the liquid crystal material so that it is in the scattered state or the transparent state.
Japanese Laid-Open Publication No. 1-269922 describes the following method. A mixture of a liquid crystal material and a photopolymerizable resin is subjected to a first exposure to ultraviolet light through a photomask. After the photomask is removed, the mixture is subjected to a second exposure with ultraviolet light, so that an area covered by the photomask during the first exposure is irradiated with ultraviolet light. Thus, areas having different display characteristics are formed. An LCD device produced by this method basically performs in a scattered mode.
Japanese Laid-Open Publication No. 5-257135 describes an LCD device produced by the following method. An alignment layer having an alignment restricting force is provided on each of two substrates. Into a gap between the two substrates, a mixture of a liquid crystal material and a photopolymerizable resin is injected. The mixture of the liquid crystal material and the photopolymerizable resin is irradiated with ultraviolet light through a photomask. The LCD device produced by this method is used for static driving, by which liquid crystal domains are patterned by a control performed outside the cell, utilizing that an area covered by the photomask and an area not covered by the photomask have different threshold characteristics.
As an attempt to improve the viewing angle characteristic of the LCD devices, use of a composite of a liquid crystal material and a polymer has been proposed. It is necessary that liquid crystal molecules are oriented in at least three directions in a pixel area in order to improve the orientation state of the liquid crystal molecules and thus the viewing angle characteristic.
With reference to
FIGS. 8A and 8B
, the viewing angle characteristic of a wide viewing angle mode LCD device are described.
FIG. 8A
schematically shows the relationship between a change in the orientation of liquid crystal molecules and the viewing angle characteristic in accordance with application of a voltage regarding a wide viewing angle mode LCD device
10
.
FIG. 8B
schematically shows such relationship regarding a conventional twisted nematic(TN) mode LCD device. In both
FIGS. 8A and 8B
, part (a) illustrates the state where no voltage is applied, part (b) illustrates an intermediate state where a voltage is applied to a certain degree less than full, and part (c) illustrates the state where the voltage is applied to a full degree.
As shown in
FIG. 8A
, the wide viewing angle mode LCD device
10
includes substrates
1
and
2
. A liquid crystal layer interposed between the substrates
1
and
2
includes a polymer wall
7
surrounding a liquid crystal domain
8
. Liquid crystal molecules
9
included in the liquid crystal domain
8
are oriented symmetrically with respect to an axis
6
. Accordingly, in the intermediate state shown in part (b), the apparent refractive indices of the liquid crystal molecules
9
when seen in directions A and B are averaged to be equal. As a result, the viewing angle characteristic is improved compared to the TN mode shown in FIG.
8
B.
In the conventional TN mode LCD device shown in
FIG. 8B
, the liquid crystal molecules have only one orientation direction in the intermediate state shown in part (b). Accordingly, display characteristics such as the levels of brightness and the apparent refractive indices of the liquid crystal molecules when seen in directions A and B are different. As a result, the viewing angle characteristic is inferior to that of the LCD device
10
.
The following LCD devices are disclosed as wide viewing angle mode LCD devices.
Japanese Laid-Open Publication Nos. 4-338923 and 4-212928 disclose a wide viewing angle mode LCD apparatus produced by combining the above-described PDLC display device and polarizers having polarizing axes perpendicular to each other.
Japanese Laid-Open Publication. No. 5-27242 discloses a method for improving the viewing angle characteristic of a non-scattering mode LCD device using polarizers. According to the method, a mixture of a liquid crystal material and a photopolymerizable resin is phase-separated, thereby forming a liquid crystal layer formed of a composite of the liquid crystal material and a polymer. Due to such a method, the orientation of liquid crystal domains becomes random by the resultant polymer. In other words, the liquid crystal molecules in different domains rise in different orientation directions when a voltage is applied. As a result, the transmittance of the liquid crystal molecules becomes equal when seen in a plurality of directions, thus improving the viewing angle characteristic in a half-tone display.
The applicant of the present invention discloses the following LCD device in Japanese Laid-Open Publication No. 6-301015. The LCD device is produced by controlling the amount of light using a photomask or the like during photopolymerization, so that the liquid crystal molecules are oriented in an all-direction state (axially symmetrical orientation) in a pixel area, and that the area which is not covered with the photomask forms a polymer wall mainly composed of a photocurable resin.
In the above-described LCD device, disclination is generated at the interface between the polymer wall and the liquid crystal domain due to a reverse tilt of the liquid crystal molecules in the liquid crystal domain. Such disclination is exhibited as a bright line on the display and thus the display characteristics degrade in a black state.
In order to overcome the problem of generation of disclination when a voltage is applied, the applicant of the present invention discloses, in Japanese Laid-Open Publication No. 7-120728, a technique where a polymerizable compound having a liquid crystal-like structure is added to a mixture of a liquid crystal composition and a photocurable resin.
By using the above polymerizable compound, however, the following two problems arise.
First, the pretilt of the liquid crystal molecules in the liquid crystal domain becomes large in a normally-white mode, reducing the brightness of the display when no voltage is applied.
Secondly, the response speed, the threshold characteristic and sharpness in the voltage vs. transmittance characteristic, and the like decrease due to the interaction between the p
Miyazaki Aya
Mizobe Hoyo
Onishi Noriaki
Suzuki Kenji
Yoshida Masahiko
Barts Samuel
Nixon & Vanderhye
Price Elvis O.
Sharp Kabushiki Kaisha
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