Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2000-07-21
2002-06-04
Wu, Shean C (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299630, C252S299660
Reexamination Certificate
active
06399164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nematic liquid crystal composition having a negative dielectric anisotropic value and a liquid crystal display element using the said liquid crystal composition. More specifically, the present invention relates to a liquid crystal composition having a negative dielectric anisotropic value for an active matrix liquid crystal display element and a liquid crystal display element using the said liquid crystal composition.
2. Description of the Related Art
A liquid crystal display element (LCD) enables a low power consumption, a reduction in a size and a reduction in a weight as compared with CRT (Braun tube system display), therefore various LCD's such as a twist nematic (TN) mode, a super twist nematic (STN) mode and a thin film transistor (TFT) mode have been put to practical use. Among them, an active matrix LCD (AM-LCD) such as a thin film transistor (TFT) mode is advanced in conversion to color display and highly fine display, and therefore it attracts attentions as the most likely candidate of flat display.
Characteristics required to this liquid crystal composition for an AM-LCD includes:
1) a voltage-holding ratio (VHR) elevated in order to maintain a high contrast of LCD,
2) a nematic liquid crystal phase range expanded according to use environment,
3) a suitable optical anisotropic value (&Dgr;n) held according to a cell thickness, and
4) a suitable threshold voltage held according to a driving circuit.
A TN display mode in which alignment of liquid crystal molecules between the upper and lower electrode substrates is twisted by 90° has been the mainstream in an operating mode of an AM-LCD, but there has been the defect that the narrow angle of visibility thereof makes it difficult to apply it to a large picture plane. Then, proposed as modes for improving an angle of visibility are:
a) an IPS display mode in which a liquid crystal display element shows a homogeneous aligning state in applying no voltage and a liquid crystal molecule rotates by 45 to 90° in a face in applying voltage (R. Kiefer, B. Weber. F. Windscheid and G. Baur, “In-Plane Switching of Nematic Liquid Crystals”, JAPAN DISPLAY '92, p. 547), and
b) a VA display mode in which a liquid crystal display element shows a homeotropic aligning state in applying no voltage and changes to an aligning state of a horizontal direction in applying voltage (K. Ohmuro, S. Kataoka, T. Sasaki and Y. Koike “Development of Super-High-Image-Quality Vertical-Alignment-Mode LCD”, SID 97 DIGEST, p. 845).
These display modes not only can achieve a wide angle of visibility but also have the characteristics of a high speed response and a high contrast. Further, they have the large characteristic that a liquid crystal composition having a negative dielectric anisotropic value (&Dgr;∈) can be applied thereto.
These operating modes make use of a birefringence mode (electrically controlled birefringence mode). A product &Dgr;n·d of an optical anisotropic value (&Dgr;n) and a cell thickness (d) has to be set to some fixed value (for example, &Dgr;n·d: 0.275 &mgr;m) in order to obtain an optimum contrast. Accordingly, a value falling in the extent of roughly 0.05 to 0.13 is requested for the value of &Dgr;n applying to 2-6 &mgr;m of a cell thickness (d) . A response time is proportional to a viscosity (hereinafter abbreviated as &eegr;) of a liquid crystal composition, and therefore a liquid crystal composition having a small &eegr; is required. Further, the larger the absolute value of dielectric anisotropic value (hereinafter abbreviated as &Dgr;∈) is, the more the threshold voltage is lowered, and therefore a liquid crystal composition having a large negative &Dgr;∈ is required.
As described above, a liquid crystal compositions have intensively been investigated according to various purposes, but the existing state is that a novel improvement thereof is always required.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid crystal composition which has a suitable value of &Dgr;n, a low viscosity, a large negative &Dgr;∈, a wide nematic phase range and a high voltage-holding ratio while satisfying various characteristics required to the liquid crystal composition for AM-LCD described above so that it can be applied to the IPS display mode a) and the VA display mode b) described above which enable to achieve a wide angle of visibility.
The present inventors have intensively investigated compositions using various liquid crystal compounds in order to solve these problems, and as a result thereof, they have found that the expected object can be achieved by a liquid crystal composition comprising a component I comprising at least one compound selected from the group of compounds represented by Formula (I) and a component II comprising at least one compound selected from the group of compounds represented by Formulas (II-1) and (II-2). Thus, they have come to complete the present invention.
A first liquid crystal composition of the present invention is shown by the following items (1) and (2):
(1) A liquid crystal composition comprising a component I comprising at least one compound selected from the group of compounds represented by Formula (I) and a component II comprising at least one compound selected from the group of compounds represented by Formulas (II-1) and (II-2):
wherein R
1
, R
3
and R
5
each represent independently an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms; R
2
1
R
4
and R
6
each represent independently an alkyl group or alkoxy group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms; Z
1
and Z
2
each represent independently a single bond or —CH
2
CH
2
—; and rings A
1
and A
2
each represent independently trans-1,4-cyclohexylene, 1,4-phenylene or 1,4-phenylene in which at least one hydrogen atom is substituted with a fluorine atom.
(2) A liquid crystal composition as described in the above item (1), wherein the component I accounts for 3 to 40% by weight, and the component II accounts for 3 to 80% by weight each based on the whole weight of the liquid crystal composition.
A second liquid crystal composition of the present invention is shown by the following items (3) and (4):
(3) A liquid crystal composition as described in any one of the above items (1) and (2), comprising a component III comprising at least one compound selected from the group of compounds represented by Formulas (III-1), (III-2), (III-3) and (III-4):
wherein R
7
, R
9
, R
11
and R
13
each represent independently an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms; and R
8
, R
10
, R
12
and R
14
each represent independently an alkyl group or alkoxy group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms.
(4) A liquid crystal composition as described in the above item (3), comprising the component I of 3 to 40% by weight, the component II of 3 to 80% by weight and the component III of 1 to 80% by weight each based on the whole weight of the liquid crystal composition.
A third liquid crystal composition of the present invention is shown by the following item (5): (5) A liquid crystal composition as described in any one of the above items (3) and (4), comprising a component IV comprising at least one compound selected from the group of compounds represented by Formulas (IV-1), and (IV-2):
wherein R
15
and R
17
each represent independently an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms; R
16
and R
18
each represent independently an alkyl group or alkoxy group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms; Z
3
, Z
4
and Z
5
each represent independently a single bond or —CH
2
CH
2
—; and a ring B represents 1,4-phenylene or trans-1,4-cyclohexylene.
A liquid crystal display element of the present invention is shown by the following item (6):
(6) A liquid crystal display element comprising
Kubo Yasuhiro
Nakagawa Etsuo
Yanai Motoki
Chisso Corporation
Wenderoth , Lind & Ponack, L.L.P.
Wu Shean C
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