Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2003-10-31
2004-10-26
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299610, C252S299630, C252S299660, C252S299670
Reexamination Certificate
active
06808765
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates mainly to a liquid crystal composition suitable for use in an active matrix (AM) element and an AM element comprising the composition.
2. Related Art
Classification of a liquid crystal display element based on an operating mode of liquid crystals includes phase change (PC), twisted nematic (TN), super twisted nematic (STN), electrically controlled birefringence (ECB), optically compensated bend (OCB), in-plane switching (IPS), vertical alignment (VA) and so on. Classification based on a driving mode of liquid crystals includes passive matrix (PM) and active matrix (AM). PM is classified into static, multiplex and so on and AM is classified into thin film transistor (TFT), metal insulator metal (MIM) and so on. Classification of TFT includes amorphous silicon and polycrystal silicon. The latter is classified into a high temperature type and a low temperature type according to a production process. Classification based on a light source includes a reflection type using a natural light, a transmission type using a backlight and a semi-transmission type using both.
These liquid crystal display elements comprise liquid crystal compositions having appropriate characteristics. It is necessary to improve general characteristics of the compositions in order to obtain AM elements having good general characteristics. Relation between the general characteristics of the element and those of the composition is summarized in Table 1. The general characteristics of the compositions shall be explained further based on commercially available AM elements. A temperature range of a nematic phase is related to a temperature range usable for the element. Preferably, the upper limit temperature in a nematic phase is 70° C. or more and the lower limit temperature in a nematic phase is −20° C. or less. Viscosity of the compositions is related to response time of the elements. Short response time is preferable for displaying a moving picture on the elements. Consequently, a low viscosity of the composition is preferable, and a low viscosity at low temperatures is more preferable.
TABLE 1
General characteristics required for a liquid
crystal composition and an AM element
General characteristics
General characteristics
required for an AM
No.
of a composition
element
1
Wide nematic phase temperature range
Wide usable temperature
range
2
Low viscosity
1)
Short response time
3
Appropriate optical anisotropy
High contrast ratio
4
Low threshold voltage
Low power consumption
high contrast ratio
5
High resistivity
High voltage holding
ratio
High contrast ratio
1)
The composition can be put into a liquid crystal cell in shorter time.
Optical anisotropy of the compositions is related to a contrast ratio of the elements. A product (&Dgr;·d) of optical anisotropy (&Dgr;n) of the compositions and a cell gap (d) of the elements is designed to be approximately 0.45 &mgr;m to maximize a contrast ratio. Consequently, optical anisotropy of the compositions is mainly in the range of 0.08 to 0.12. A low threshold voltage of the compositions contributes to a low power consumption and a high contrast ratio of the elements. Consequently, a low threshold voltage is preferable. A high resistivity of the compositions contributes to a high voltage holding ratio and a high contrast ratio of the elements. Consequently, the compositions having a high resistivity in the initial stage are preferable. The compositions having a high resistivity even after using for a long time are preferable.
AM-TFT elements having polycrystal silicon produced at low temperature are driven at a very large frequency in comparison with AM-TFT elements having amorphous silicon. Accordingly, for the former elements, the compositions in which dielectric anisotropy has a low frequency dependence are preferable. The compositions having a low frequency dependence at low temperatures are more preferable. Especially desired are liquid crystal compositions which are also usable in the AM-TFT elements having polycrystal silicon produced at low temperatures. Related compositions hitherto known are disclosed in the following patents; JP 2-233626 A (1990) (EP 1179522 A), JP 8-73856 A (1996), JP 8-73857 A (1996), JP 10-204436 A (1998), JP 10-231482 A (1998), JP 10-298127 A (1998), JP 2000-144135 A (2000), JP 2001-3053 A (2001), JP 2001-123170 A (2001), JP 2001-288470 A (2001), JP 2001-335586 A (2001), JP 2001-342195 A (2001), and JP 2002-20344 A (2002).
SUMMARY OF THE INVENTION
The present invention comprises the following A and B.
A. A liquid crystal composition comprising; as a first component, at least one compound selected from a group of compounds represented by Formula (1); as a second component, at least one compound selected from a group of compounds represented by Formula (2); as a third component, at least one compound selected from a group of compounds represented by Formula (3); as a forth component, at least one compound selected from a group of compounds represented by Formula (4); and as a fifth component, at least one compound selected from a group of compounds represented by Formulas (5-1) and (5-2).
wherein R
1
is alkyl; R
2
is alkyl or alkenyl; R
3
is alkyl, alkoxy, or —CF
3
; R
4
is alkyl or alkoxy; R
5
is alkyl or alkoxymethyl; A
1
is 1,4-cyclohexylene or 1,4-phenylene in which any hydrogen may be replaced by fluorine; A
2
is 1,4-cyclohexylene or 1,4-phenylene; Z
1
is a single bond or —COO—; and X
1
is hydrogen or fluorine.
B. A liquid crystal display element comprising the liquid crystal composition described above.
DETAILED DESCRIPTION
An object of the present invention is to provide a liquid crystal composition which satisfies plural characteristics in the general characteristics of a composition, a low threshold voltage, a high resistivity, and a low frequency dependence. Low frequency dependence means that frequency dependence of dielectric anisotropy is low. Another object is to provide a liquid crystal composition having plural characteristics appropriately balanced. A further object is to provide a liquid crystal display element comprising the composition and especially having a high voltage holding ratio. A still further object is to provide an AM-TFT element having polycrystal silicon produced at low temperatures.
The present invention comprises the following items 1 to 20.
1. A liquid crystal composition comprising; as a first component, at least one compound selected from a group of compounds represented by Formula (1); as a second component, at least one compound selected from a group of compounds represented by Formula (2); as a third component, at least one compound selected from a group of compounds represented by Formula (3); as a forth component, at least one compound selected from a group of compounds represented by Formula (4); and as a fifth component, at least one compound selected from a group of compounds represented by Formulas (5-1) and (5-2).
wherein R
1
is alkyl; R
2
is alkyl or alkenyl; R
3
is alkyl, alkoxy, or —CF
3
; R
4
is alkyl or alkoxy; R
5
is alkyl or alkoxymethyl; A
1
is 1,4-cyclohexylene or 1,4-phenylene in which any hydrogen may be replaced by fluorine; A
2
is 1,4-cyclohexylene or 1,4-phenylene; Z
1
is a single bond or —COO—; and X
1
is hydrogen or fluorine.
2. The liquid crystal composition as described in the above item 1, wherein the fifth component is at least one compound selected from a group of compounds represented by Formula (5-1).
3. The liquid crystal composition as described in the above item 1, wherein the fifth component is at least one compound selected from a group of compounds represented by Formula (5-2).
4. The liquid crystal composition as described in the above item 1, wherein the first component is in the range of 5 to 30% by weight, the second component is in the range of 10 to 40% by weight, the third component is in the range of 10 to 50% by weight, the forth component is in the range of 3 to 30% by weight, and the fifth component is in the range of 3 to 40% by weight, e
Chisso Corporation
Wenderoth , Lind & Ponack, L.L.P.
Wu Shean C.
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