Silicon compound, liquid crystal composition and liquid...

Details Silicon compound, liquid crystal composition and liquid... Silicon compound, liquid crystal composition and liquid...

2002-02-28

2004-03-09

Wu, Shean C (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299610, C252S299630, C252S299640, C252S299650, C252S299660, C252S299670, C556S436000, C556S445000, C556S465000, C556S487000, C556S488000, C556S489000

Reexamination Certificate

active

06703083

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel liquid crystalline compound and a liquid crystal composition (hereinafter referred to merely as a composition according to circumstances). More specifically, it relates to a liquid crystalline compound having a SiH
3
group at an end, a composition comprising the same and a liquid crystal display constituted using this composition. The term “liquid crystalline compound” used in the present invention is a general term for a compound showing a liquid crystal phase and a compound which does not show a liquid crystal phase but is useful as a component for a liquid crystal composition.
2. Description of the Related Art
A liquid crystal display (LCD) making use of characteristics of a nematic liquid crystal phase is widely used for various uses including monitors for personal computers and portable telephones, and demand therefor has been growing large year by year. In accordance with it, improvement items for performances required for LCD have come to extend over many divergences such as an expansion in an operable temperature range, a shift to a high density and coloring of a display picture plane, an acceleration in response and an expansion in a viewing angle. Various display modes using electro-optical effects, such as a DS (Dynamic Scattering) mode, a TN (Twisted Nematic) mode, a GH (Guest Host) mode, an STN (Super Twisted Nematic) mode, an IPS (In-Plane switching) mode, a VA (Vertical Alignment) mode and OCB (Optically Compensated Bend) have been proposed in order as means for solving them.
In such situation, various characteristics are required to a composition used for LCD according to the respective display modes. First, the physical property values such as a birefringence (&Dgr;n), a dielectric anisotropy (&Dgr;∈), a viscosity (&eegr;), a conductivity and an elastic constant ratio K
33
/K
11
(K
33
: bend elastic constant and K
11
: spray elastic constant) of a liquid crystal composition are required to have values which are optimum for a display mode and a form of an element. Further, in order to achieve high-speed response in any of the LCD's shown above, a composition having a low viscosity is required, and a liquid crystalline compound has to be indispensably reduced as well in a viscosity. In addition thereto, given as common items of characteristics required to a composition are stability against moisture, light, heat and air which are usually present under an use environment and stability against an electric field and electromagnetic irradiation. Further, it is important that a liquid crystalline compound constituting a composition is chemically stable under use conditions and that they have a good solubility with each other.
In the existing state, however, it is very difficult to solve these problems only with the existing liquid crystal compounds and compositions, and it is an urgent matter to develop a novel liquid crystalline compound and composition which can meet the various requirements described above.
In recent years, development of various techniques in a liquid crystal display has been tried for the purpose of an enlargement in a picture plane. Especially, liquid crystal compositions which contribute largely to a reduction in power consumption and high speed response are desired to be developed. It is essential for a reduction in power consumption to further reduce a threshold voltage of a composition (E. Jakeman et al., Phys. Lett., 39A. 69 (1972)). Also, a low viscosity is important as well for high speed response. Various compounds have so far been developed in order to achieve these objects. For example, compounds having a silyl group in a molecule represented by the following formulas (a), (b) and (c) are known respectively according to Japanese Patent Application Laid-Open No. 9653/1994, Japanese Patent Application Laid-Open No. 2878/1995 and Japanese Patent Application Laid-Open No. 2879/1995:
In these compounds, silicon is substituted with three alkyl groups. For example, the present inventors measured the physical property values of a compound having a propyldimethylsilyl group represented by the following formula (d) to find the problem that it had not only a markedly high viscosity but also an unsatisfactory mutual solubility with other components constituting a composition:
Physical property measurement: a nematic phase-isotropic phase transition temperature (NI) and a viscosity (&eegr;) at 20° C. of a liquid crystal composition ZLI-1132 manufactured by Merck Co., Ltd. were 72.6° C. and 26.7 mPa·s respectively. Then, 15% by weight of the compound represented by the formula (d) was added to 85% by weight of this composition, and NI and &eegr; of the resulting composition were determined to find that they were 15° C. or lower and 39.7 mPa·s respectively. It has been found from this result that a composition prepared using the compound represented by the formula (d) is not only notably increased in a viscosity but also reduced in NI by 50° C. or lower. Further, the compound represented by the formula (d) was inferior in mutual solubility with the other compositions.
SUMMARY OF THE INVENTION
An object of the present invention is to solve problems on conventional techniques and provide a novel silicon compound which has a low viscosity and a low threshold voltage and which is improved in mutual solubility, a composition comprising the same and a liquid crystal display using the above composition.
In order to achieve the objects described above, the following inventions are claimed for the grant of a patent in the present application.
[1] A silicon compound represented by formula (1):
wherein Y
1
is alkylene having 1 to 10 carbon, in which any —CH
2
— in this alkylene may be replaced by —O—, —S—, —CO—, —CH═CH— or —C≡C—, but —O— and —O—, —S— and —S—, —O— and —S—, —O— and SiH
3
, or —S— and SiH
3
are not adjacent, and at least one hydrogen in the alkylene may be replaced by halogen or —CN; Y
2
is hydrogen, halogen, —CN, —C≡C—CN, or alkyl having 1 to 10 carbon, in which any —CH
2
— in the alkyl may be replaced by —O—, —S—, —CO—, —CH═CH—, or —C≡C—, but —O— and —O—, —S— and —S—, or —O— and —S— are not adjacent, and any hydrogen in the alkyl may be replaced by halogen or —CN; A
1
, A
2
, A
3
, and A
4
each are independently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene, or 1,4-phenylene in which any hydrogen is replaced by halogen; in which any hydrogen in 1,4-cyclohexylene or 1,4-cyclohexenylene may be replaced by halogen, any —CH
2
— in these rings may be replaced by —O—, but —O— and —O— are not adjacent, and any —CH═ in 1,4-phenylene may be replaced by —N═; Z
1
, Z
2
and Z
3
each are independently a single bond, —(CH
2
)
2
—, —OCH
2
—, —CH
2
O—, —CH═CH—, —C≡C—, —(CH
2
)
4
—, —O(CH
2
)
3
—, —(CH
2
)
3
O—, —COO—, —OCO—, —OCF
2
—, or —CF
2
O—; and p and q each are independently 0 or 1.
[2] The silicon compound defined in the above item [1], wherein in formula (1) described above, p and q are 0; A
1
and A
2
each are independently 1,4-cyclohexylene, 1,4-cyclohexylene in which one or more non-adjacent —CH
2
— are replaced by —O—, 1,4-phenylene, 1,4-phenylene in which any hydrogen is replaced by halogen, or pirimidine-2,5-diyl; and Z
1
is a single bond, —(CH
2
)
2
—, —CH=CH—, —C=C—, —(CH
2
)
4
—, —COO—, —OCO—, —OCF
2
—, or —CF
2
O—.
[3] The silicon compound defined in the above item [1], wherein in formula (1) described above, p is 1, and q is 0; A
1
, A
2
and A
3
each are independently 1,4-cyclohexylene, 1,4-cyclohexylene in which one or more non-adjacent —CH
2
— are replaced by —O—, 1,4-phenylene, 1,4-phenylene in which any hydrogen is replaced by halogen, or pirimidine-2,5-diyl; and Z
1
and Z
2
each are independently a single bond, —(CH
2
)
2
—, —CH═CH—, —C≡C—, —COO—, —OCO—, —(CH
2
)
4
—, —OCF
2
—, or —CF
2
O—.
[4] The silicon compound defined in the above item [1], wherein in formula (

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