Patent Application
20150159087
The present invention relates to a liquid crystal composition having negative dielectric anisotropy (Δ∈) and useful as an electro-optic liquid crystal display material, and a liquid crystal display device that uses the liquid crystal composition.
Vertical alignment-liquid crystal displays (VA-LCDs) that use liquid crystal compositions having negative dielectric anisotropy (negative Δ∈) are capable of creating pure black and thus have high display quality. VA-LCDs are ubiquitous mainly in the liquid crystal television market as high-contrast liquid crystal display devices. In recent years, VA-LCDs have been increasingly employed in active-matrix driving systems such as liquid crystal televisions and in passive matrix driving systems used in displays to be mounted in vehicles and home electric appliances. Vehicle-mounted displays and the like are required to work in a wide temperature range and maintain high display quality; hence, the temperature dependence of the operation voltage of the liquid crystal composition is preferably as flat as possible.
It is relatively easy to make the temperature dependence of operation voltage flat for a liquid crystal composition having positive Δ∈ and this can be achieved by improving the temperature dependence of operation voltage in a high-temperature zone. The temperature dependence of the operation voltage in the high-temperature zone has been improved by increasing the nematic transition temperature (TNI) of the liquid crystal composition or increasing the specific resistivity of the liquid crystal composition. In contrast, in order to make the temperature dependence of the operation voltage flat for a liquid crystal composition having negative Δ∈, it is necessary to improve the temperature dependence of the operation voltage in a low-temperature zone but no effective means has been found to achieve this.
Although a large number of proposals related to liquid crystal compounds and liquid crystal compositions have been made for liquid crystal materials for VA-LCDs, there have been no reports related to combinations of liquid crystal compounds that can make the temperature dependence of the operation voltage flat.
PTL 1: Japanese Unexamined Patent Application Publication No. 2006-241214
PTL 2: Japanese Unexamined Patent Application Publication No. 2006-225450
PTL 3: Japanese Unexamined Patent Application Publication No. 2001-40354
An object of the present invention is to provide a liquid crystal composition that has negative dielectric anisotropy and in which the temperature dependence of the operation voltage is flat, and a liquid crystal display device that uses the liquid crystal composition.
The present invention provides a liquid crystal composition that contains one or more compounds represented by general formula (I) and one or more compounds represented by formula (II), and a liquid crystal display device that uses the liquid crystal composition.
(In the formulae, R11, R12, R21, and R22 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms and are each independently unsubstituted or have at least one halogen group as a substituent, and one or more —CH2— present in these groups may each be independently substituted with —O—, —S—, —CO—, —COO—, —OCO—, or —OCO—O—, provided that oxygen atoms are not directly bonded to each other;
A11, A12, A21, and A22 each independently represent a group selected from the group consisting of
(a) a trans-1,4-cyclohexylene group (where one —CH2— or two or more non-adjacent —CH2— present in this group may be substituted with —O— and/or —S—),
(b) a 1,4-phenylene group (where one —CH2— or two or more non-adjacent —CH2— groups present in this group may be substituted with —N—), and
(c) 1,4-cyclohexenylene, 1,4-bicyclo(2.2.2)octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, and 1,2,3,4-tetrahydronaphthalene-2,6-diyl,
where hydrogen atoms in the group (a), group (b), and group (c) may each be independently substituted with an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, an alkoxyl having 1 to 3 carbon atoms, an alkenyloxy group having 1 to 3 carbon atoms, a CN, or a halogen;
Z11, Z21, and Z22 each independently represent —COO—, —OCO—, —CH2O—, —OCH2—, —CF2O—, —OCF2—, —CH2CH2—, —CH═CH—, —C≡C—, —(CH2)4—, —CH═CH—CH2CH2—, —CH2CH2—CH═CH—, or a single bond; and a11, a21, and a22 each independently represent 0 or 1.)
According to the liquid crystal composition of the present invention, the rate of change in operation voltage versus temperature ranging from 25° C. to −20° C. is within ±4% with respect to 25° C. This liquid crystal composition is effective for improving display quality in a low-temperature zone. Accordingly, the liquid crystal composition is suitable for use in vehicle-mounted displays and mobile appliances that are expected to be used in cold areas and outdoors.
Individual components will now be described.
A liquid crystal composition contains one or more compounds represented by general formula (I) and one or more compounds represented by general formula (II).
In the formulae, R11, R12, R21, and R22 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms and are each independently unsubstituted or have at least one halogen group as a substituent; and one or more —CH2— present in these groups may each be independently substituted with —O—, —S—, —CO—, —COO—, —OCO—, or —OCO—O—, provided that oxygen atoms are not directly bonded to each other. In the present invention, R11, R12, R21, and R22 preferably each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, and more preferably each independently represent an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms. These groups are preferably unsubstituted.
A11, A12, A21, and A22 each independently represent a group selected from the group consisting of the following:
(a) a trans-1,4-cyclohexylene group (where one —CH2— or two or more non-adjacent —CH2— present in this group may be substituted with —O— and/or —S—);
(b) a 1,4-phenylene group (where one —CH2— or two or more non-adjacent —CH2— groups present in this group may be substituted with —N—); and
(c) 1,4-cyclohexenylene, 1,4-bicyclo(2.2.2)octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, and 1,2,3,4-tetrahydronaphthalene-2,6-diyl.
Hydrogen atoms in the group (a), group (b), and group (c) may each be independently substituted with an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, an alkoxyl having 1 to 3 carbon atoms, an alkenyloxy group having 1 to 3 carbon atoms, a CN, or a halogen. In the present invention, A11, A12, A21, and A22 preferably each independently represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group, more preferably a trans-1,4-cyclohexylene group if low viscosity is desirable, and more preferably a 1,4-phenylene group if a large birefringence anisotropy is desirable. These groups are preferably unsubstituted.
Z11, Z21, and Z22 each independently represent —COO—, —OCO—, —CH2O—, —OCH2—, —CF2O—, —OCF2—, —CH2CH2—, —CH═CH—, —C≡C—, —(CH2)4—, —CH═CH—CH2CH2—, —CH2CH2—CH═CH—, or a single bond, but preferably a single bond in the present invention.
While a11, a21, and a22 each independently represent 0 or 1, a11, a21, and a22 in the present invention preferably each independently represent 0 if low viscosity is desirable and a11 preferably represents 1 and a21+a22 is preferably 1 or 2 if high transition temperature is desirable.
The liquid crystal composition of the present invention can contain one or more compounds represented by general formula (III).
In the formula, R31 and R32 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms and are each independently unsubstituted or have at least one halogen group as a substituent; and one or more —CH2— present in these groups may each be independently substituted with —O—, —S—, —CO—, —COO—, —OCO—, or —OCO—O—, provided that oxygen atoms are not directly bonded to each other. In the present invention, R31 and R32 preferably each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms and more preferably each independently represent an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms. These groups are preferably unsubstituted.
A31, A32, and A33 each independently represent a group selected from the group consisting of the following:
(a) a trans-1,4-cyclohexylene group (where one —CH2— or two or more non-adjacent —CH2— present in this group may be substituted with —O— and/or —S—);
(b) a 1,4-phenylene group (where one —CH2— or two or more non-adjacent —CH2— groups present in this group may be substituted with —N—); and
(c) 1,4-cyclohexenylene, 1,4-bicyclo(2.2.2)octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, and 1,2,3,4-tetrahydronaphthalene-2,6-diyl.
Hydrogen atoms in the group (a), group (b), and group (C) may each be independently substituted with an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, an alkoxyl having 1 to 3 carbon atoms, an alkenyloxy group having 1 to 3 carbon atoms, a CN, or a halogen but at least one of A31, A32, and A33 represents a 2,3-difluoro-1,4-phenylene group. In the present invention, A31, A32, and A33 preferably each independently represent a trans-1,4-cyclohexylene group if low viscosity is desirable, preferably each independently represent a 1,4-phenylene group or naphthalene-2,6-diyl if larger birefringence is desirable, and preferably each independently represent naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, or 1,2,3,4-tetrahydronaphthalene-2,6-diyl if large dielectric anisotropy /Δ∈/ is desirable.
Z31 and Z32 each independently represent —COO—, —OCO—, —CH2O—, —OCH2—, —CF2O—, —OCF2—, —CH2CH2—, —CH═CH—, —C≡C—, —(CH2)4—, —CH═CH—CH2CH2—, —CH2CH2—CH═CH—, or a single bond. In the present invention, Z31 and Z32 preferably each independently represent —CH2O—, —OCH2—, or a single bond.
The liquid crystal composition of the present invention can contain one or more compounds represented by general formula (IV).
In the formula, R41 and R42 each independently represent an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms and are each independently unsubstituted or have at least one halogen group as a substituent; and one or more —CH2— present in these groups may each be independently substituted with —O—, —S—, —CO—, —COO—, —OCO—, or —OCO—O—, provided that oxygen atoms are not directly bonded to each other. In the present invention, R41 and R42 preferably each independently represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, and more preferably each independently represent an alkyl group having 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms. These groups are preferably unsubstituted.
A41, A42, and A43 each independently represent a group selected from the group consisting of the following:
(a) a trans-1,4-cyclohexylene group (where one —CH2— or two or more non-adjacent —CH2— present in this group may be substituted with —O— and/or —S—);
(b) a 1,4-phenylene group (where one —CH2— or two or more non-adjacent —CH2— groups present in this group may be substituted with —N—); and
(c) 1,4-cyclohexenylene, 1,4-bicyclo(2.2.2)octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, and 1,2,3,4-tetrahydronaphthalene-2,6-diyl.
Hydrogen atoms in the group (a), group (b), and group (c) may each be independently substituted with an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, an alkoxyl having 1 to 3 carbon atoms, an alkenyloxy group having 1 to 3 carbon atoms, a CN, or a halogen. In the present invention, A41, A42, and A43 preferably each independently represent a trans-1,4-cyclohexylene group if low viscosity is desirable and preferably each independently represent a 1,4-phenylene group or naphthalene-2,6-diyl if large birefringence is desirable.
A41, A42, and A43 never represent a 2,3-dihalo-1,4-phenylene group; and
Z41 and Z42 each independently represent —COO—, —OCO—, —CH2O—, —OCH2—, —CF2O—, —OCF2—, —CH2CH2—, —CH═CH—, —C≡C—, —(CH2)4—, —CH═CH—CH2CH2—, —CH2CH2—CH═CH—, or a single bond. In the present invention, Z41 and Z42 preferably each independently represent a single bond if low viscosity is desirable and preferably each independently represent —C≡C— if large birefringence is desirable.
While a41 represents 0, 1, or 2, two A42 that are present when a41 represents 2 may be the same or different from each other and two Z32 that are present when a41 represents 2 may be the same or different from each other. In the present invention, a41 preferably represents 0 if low viscosity is desirable and preferably represents 1 or 2 if high transition temperature is desirable.
The liquid crystal composition of the present invention may further contain compounds represented by formulae V and VI.
In the formulae, R51 and R61 each independently denote the same as R31 in general formula (III) and R52 and R62 each independently denote the same as R32 in general formula (III).
A51, A52, A53, A61, A62, and A63 each independently represent a trans-1,4-cyclohexylene group, a 1,4-phenylene group, or 1,4-cyclohexenylene, where one or more hydrogen atoms in the 1,4-phenylene group may each be independently substituted with a halogen. In the present invention, A51, A52, A53, A61, A62, and A63 preferably each independently represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group, preferably a trans-1,4-cyclohexylene group if low viscosity is desirable, and preferably a 1,4-phenylene group if large birefringence is desirable.
Z51, Z52, Z61, and Z62 each independently represent —COO—, —OCO—, —CH2O—, —OCH2—, —CF2O—, —OCF2—, —CH2CH2—, —CH═CH—, —C≡C—, —(CH2)4—, —CH═CH—CH2CH2—, —CH2CH2—CH═CH—, or a single bond. In the present invention, Z51, Z52, Z61, and Z62 preferably each independently represent —CH2O—, —OCH2—, or a single bond.
While a51, a52, a61, and a62 each independently represent 0, 1, or 2, a51+a52 is 0, 1, or 2 and a61+a62 is 0, 1, or 2. Two A51 that are present when a51 represents 2 may be the same or different, two A52 that are present when a52 represents 2 may be the same or different, two Z51 that are present when a51 represents 2 may be the same or different, two Z52 that are present when a52 represents 2 may be the same or different, two A61 that are present when a61 represents 2 may be the same or different, two A62 that are present when a62 represents 2 may be the same or different, two Z61 that are present when a61 represents 2 may be the same or different, and two Z62 that are present when a62 represents 2 may be the same or different. In the present invention, a51, a52, a61, and a62 each preferably represent 0 if low viscosity is desirable and a51+a52 and a61+a62 are each preferably 1 or 2 if high transition temperature is desirable.
The liquid crystal composition according to the present invention may contain, as a compound represented by general formula (VII), one or more compounds represented by general formula (VII).
In the formula, R71 denotes the same as R41 in general formula (IV), R72 denotes the same as R42 in general formula (IV), and a71 represents 0 or 1. When low viscosity is desirable, a71 preferably represents 0 and when high transition temperature is desirable, a71 preferably represents 1.
The liquid crystal composition according to the present invention may contain nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, an antioxidant, a UV absorber, a polymerizable monomer, etc., that are common in the art in addition to the compounds described above as long as the advantages of the invention of the present application are not impaired. However, the liquid crystal composition according to the present invention preferably does not contain a liquid crystal compound that has a partial structure in which heteroatoms are directly bonded to each other, such as —O—O—, —O—S—, and —S—S—.
The polymerizable monomer that may be contained in the liquid crystal composition of the present invention is preferably a photopolymerizable monomer. In the case where the polymerizable monomer is contained, the photopolymerizable monomer content of the liquid crystal composition according to the present invention is preferably 500 to 5000 ppm. Examples of the photopolymerizable monomer include monomers having polymerizable unsaturated double bonds such as acrylate esters and methacrylate esters.
In the case where the liquid crystal composition according to the present invention is used in an active matrix driving liquid crystal display device, Tni of the liquid crystal composition according to the present invention is preferably 60 to 120° C. The lower limit is more preferably 65° C. and particularly preferably 70° C. The upper limit is more preferably 110° C. and particularly preferably 105° C. Δ∈ at 25° C. is preferably −1.5 to −6.0, more preferably −2.0 to −5.0, and particularly preferably −2.0 to −3.5. Δn at 25° C. is preferably 0.08 to 0.13 and more preferably 0.09 to 0.12. To be more specific, Δn at 25° C. is preferably 0.10 to 0.12 to be compatible with a small cell gap and is preferably 0.08 to 0.10 to be compatible with a large cell gap. The viscosity (η) at 20° C. is preferably 10 to 30 mPa·s, more preferably 10 to 25 mPa·s, and most preferably 10 to 20 mPa·s.
In the case where the liquid crystal composition according to the present invention is used in a passive matrix driving liquid crystal display device, Tni of the liquid crystal composition according to the present invention is preferably 60 to 120° C. for consumer use. The lower limit is more preferably 65° C. and most preferably 70° C. The upper limit is more preferably 90° C. and most preferably 80° C. For vehicle-mounting usage, the lower limit is more preferably 90° C. and most preferably 100° C. The upper limit is more preferably 115° C. and most preferably 105° C. For low-duty driving, Δn at 25° C. is preferably 0.08 to 0.13 and more preferably 0.08 to 0.11. For high duty driving, Δn at 25° C. is preferably 0.13 to 0.20 and more preferably 0.15 to 0.18. For low duty driving, Δ∈ at 25° C. is preferably −2.0 to −7.0 and more preferably −2.5 to −5.5. Moreover, η at 20° C. is preferably 10 to 40 mPa·s, more preferably 10 to 30 mPa·s, and most preferably 10 to 25 mPa·s.
Tni, Δ∈, and Δn of the liquid crystal composition according to the present invention can be appropriately adjusted within the ranges suitable for the usage of the liquid crystal composition by adjusting the contents of various compounds including the first component and the second component. For the liquid crystal composition of the present invention, Tni is preferably 70° C. to 120° C., Δ∈ at 25° C. and 1 KHz is preferably −1.5 to −8.0, and Δn at 25° C. and 589 nm is preferably 0.080 to 0.250. When Tni, Δ∈, and Δn are within these ranges, the liquid crystal composition can be appropriately used in various usages.
A liquid crystal display device having a vertical aligning property can be produced by using the liquid crystal composition of the present invention. For example, a liquid crystal display device with a 80° to 90° pretilt angle can be produced by using the liquid crystal composition of the present invention.
The present invention will now be described in further detail by using Examples which do not limit the scope of the present invention. For the compositions of Examples and Comparative Examples below, “%” means “% by mass”.
The terminologies used in Examples are as follows:
Tni: nematic-isotropic transition temperature [° C.]
T→N: solid or smectic-nematic transition temperature [° C.]
Δn: refractive index anisotropy (589 nm, 25° C.)
n0: refractive index for ordinary rays (589 nm, 25° C.)
Δ∈: dielectric anisotropy (1 kHz, 25° C.)
∈⊥: dielectric constant in a direction perpendicular to a molecular axis (1 kHz, 25° C.)
η: bulk flow viscosity [mPa·s] (20° C.)
Response speed: The liquid crystal composition was poured into a vertical alignment cell having a 3.5 μm gap and 89° pretilt angle and response speed was measured at 5 V with 100 Hz square waves.
Voltage-temperature characteristic (temperature dependence of operation voltage): A value obtained by dividing Vth (threshold voltage (V)) at −20° C. by Vth at 25° C. was evaluated.
The following abbreviations are used in describing the compounds of Examples:
Abbreviations for side chains are as follows:
-n (numeral): —CnH2n+1 (an alkyl side chain is denoted by a numeral and represented by R)
-ndm: —(CnH2n+1—C═C—(CH2)m-1)
ndm-: CnH2n+1—C═C—(CH2)m-1—
-nOm: —(CH2)nOCmH2m+1
nOm-: CnH2n+1O(CH2)m—
-Od(m)n: —O(CnH2n+1—C═C—(CH2)m-2)
d(m)nO-: CnH2n+1—C═C—(CH2)m-2O—
Abbreviations for bonding groups are as follows:
Abbreviations for rings are as follows:
Liquid crystal compositions described in Table 1 are produced and compared in terms of temperature dependence of operation voltage.
In Comparative Example 1, the operation voltage (Vth) at −20° C. versus 25° C. was 93° C. In contrast, in Examples 1 and 2, the operation voltage at −20° C. versus 25° C. was 97 to 100%. Improvements of temperature dependence were thus observed.
A liquid crystal composition according to the present invention is useful for use in liquid crystal display devices, namely, active matrix driving liquid crystal display devices and passive matrix driving liquid crystal display devices, and is particularly useful for use in passive matrix driving liquid crystal display devices. The liquid crystal composition can also be used in VA-mode, PSVA-mode, IPS-mode, or ECB-mode liquid crystal display devices.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-120783 | May 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/064198 | 5/22/2013 | WO | 00 |
