CN111748358A

CN111748358A - Liquid crystal composition and liquid crystal display element

Info

Publication number: CN111748358A
Application number: CN201911318024.0A
Authority: CN
Inventors: 斋藤将之; 高久里菜; 伊是名省吾
Original assignee: JNC Corp; JNC Petrochemical Corp
Current assignee: JNC Corp; JNC Petrochemical Corp
Priority date: 2019-03-26
Filing date: 2019-12-19
Publication date: 2020-10-09
Also published as: JP2020164784A; TW202100727A

Abstract

The present invention addresses the problem of providing a liquid crystal composition that sufficiently satisfies at least one of characteristics such as a high upper limit temperature, a smectic-nematic transition temperature lower than 0 ℃, a wide temperature range of a smectic phase, a low viscosity, an appropriate optical anisotropy, a large positive or negative dielectric anisotropy, a large specific resistance, a high stability to light, a high stability to heat, and a large elastic constant, or has an appropriate balance between at least two of these characteristics, and a liquid crystal display element. The method of the present invention is a liquid crystal composition which may contain a specific compound having a high upper limit temperature or a small viscosity as a component a, a specific compound having a large positive dielectric anisotropy as a component B, a specific compound having a large negative dielectric anisotropy as a component C, or a specific compound having a polymerizable group as an additive a, and has a smectic phase at a temperature lower than 0 ℃.

Description

Liquid crystal composition and liquid crystal display element

Technical Field

The present invention relates to a liquid crystal composition, a liquid crystal display element containing the same, and the like. In particular, it relates to a liquid crystal composition having positive or negative dielectric anisotropy and an element having the same. And to a polymer stabilized oriented device.

Background

In the liquid crystal display device, the operation modes based on the liquid crystal molecules are classified as follows: 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), Fringe Field Switching (FFS), field-induced photo-reactive alignment (FPA), and the like. The driving methods of the elements are classified into Passive Matrix (PM) and Active Matrix (AM). The PM is classified into a static type (static), a multiplexing type (multiplex), etc., and the AM is classified into a Thin Film Transistor (TFT), a Metal Insulator Metal (MIM), etc. TFTs are classified into amorphous silicon (amorphous silicon) and polycrystalline silicon (polysilicon). The latter is classified into a high temperature type and a low temperature type according to the manufacturing process. The light sources are classified into a reflection type using natural light, a transmission type using a backlight, and a semi-transmission type using both natural light and backlight.

The liquid crystal display element contains a liquid crystal composition having a nematic phase. The composition has suitable properties. By improving the characteristics of the composition, an AM element having good characteristics can be obtained. The correlation between these properties is summarized in table 1 below. The properties of the composition are further illustrated based on commercially available AM elements. The temperature range of the nematic phase is associated with the temperature range in which the element can be used. The upper limit temperature of the nematic phase is preferably about 70 ℃ or higher, and the lower limit temperature of the nematic phase is preferably less than 0 ℃. The viscosity of the composition correlates to the response time of the element. In order to display a moving image as an element, the response time is preferably short. Even a response time of 1 millisecond shorter than that of the other elements is desirable. Therefore, it is preferable that the viscosity of the composition is small. Further, it is preferable that the viscosity at low temperature is low. The elastic constant of the composition correlates to the contrast of the element. In order to improve the contrast of the element, it is preferable that the elastic constant of the composition is large.

The optical anisotropy of the composition correlates with the contrast of the element. Depending on the mode of the element, a large optical anisotropy or a small optical anisotropy, i.e., an appropriate optical anisotropy, is required. The product (Δ n × d) of the optical anisotropy (Δ n) of the composition and the cell gap (d) of the element is designed to maximize the contrast. The value of the appropriate product depends on the type of operation mode. The value is about 0.45 μm in a TN-or the like mode element, the value is in the range of about 0.30 μm to about 0.40 μm in a VA-mode element, and the value is in the range of about 0.20 μm to about 0.30 μm in an IPS-mode or FFS-mode element. In these cases, a composition having a large optical anisotropy is preferable for an element having a small cell gap. The large dielectric anisotropy of the composition contributes to a low threshold voltage, small power consumption, and large contrast of the element. Therefore, a large dielectric anisotropy is preferable. The large specific resistance of the composition contributes to a large voltage holding ratio and a large contrast ratio of the element. Therefore, a composition having a large specific resistance in the initial stage is preferable. Preferred are compositions which have a large specific resistance after a long period of use. The stability of the composition to light or heat is correlated to the lifetime of the element. When the stability is high, the life of the element is long. Such characteristics are preferable for AM elements used in liquid crystal monitors, liquid crystal televisions, and the like.

In a general-purpose liquid crystal display device, the vertical alignment of liquid crystal molecules can be achieved by a specific polyimide alignment film. In a liquid crystal display element of a Polymer Sustained Alignment (PSA) type, a polymer is combined with an alignment film. First, a composition to which a small amount of a polymerizable compound is added is injected into an element. Next, the composition was irradiated with ultraviolet rays while applying a voltage between the substrates of the element. The polymerizable compound is polymerized to form a network structure of the polymer in the composition. In the composition, the orientation of the liquid crystal molecules can be controlled by the polymer, so that the response time of the element is shortened, and the afterimage of the image is improved. Such effects of the polymer can be expected in devices having modes such as TN, ECB, OCB, IPS, VA, FFS, and FPA.

A composition having positive dielectric anisotropy is used for an AM element having a TN mode. A composition having negative dielectric anisotropy is used for an AM element having a VA mode. A composition having positive or negative dielectric anisotropy is used for an AM element having an IPS mode or an FFS mode. A composition having positive or negative dielectric anisotropy is used in an AM element of a Polymer Sustained Alignment (PSA) type.

The elements described in table 1 were driven in the temperature range of the nematic phase. The compositions described in table 1 sometimes have a smectic phase (smart phase) at low temperatures. The present inventors have focused on the smectic phase. If the temperature range of the smectic phase is wide, an element that is driven even in the temperature range of the phase can be expected. The present inventors have studied the desirability of using an element having a nematic phase and a smectic phase.

[ Prior art documents ]

[ patent document ]

[ patent document 1] International publication No. 2012-43145

[ patent document 2] International publication No. 1996-11897

[ patent document 3] Japanese patent laid-open No. Hei 10-204016

[ patent document 4] Japanese patent application laid-open No. 2000-53602

Disclosure of Invention

[ problems to be solved by the invention ]

The invention provides a liquid crystal composition which fully satisfies at least one of the characteristics of high upper limit temperature of a nematic phase, a smectic-nematic transition temperature lower than 0 ℃, a wide temperature range of a smectic phase, low viscosity, proper optical anisotropy, large positive dielectric anisotropy or large negative dielectric anisotropy, large specific resistance, high stability to light, high stability to heat, and large elastic constant. Another object is to provide a liquid crystal composition having an appropriate balance between at least two of these characteristics. Another object is to provide a liquid crystal display element containing such a composition. Still another object is to provide an AM element having characteristics such as a short response time, a high voltage holding ratio, a low threshold voltage, a high contrast ratio, and a long lifetime.

[ means for solving problems ]

The present invention mainly relates to a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃ and a liquid crystal display element having the same.

[ Effect of the invention ]

The present invention has an advantage of providing a liquid crystal composition that sufficiently satisfies at least one of characteristics such as a high upper limit temperature of a nematic phase, a smectic-nematic transition temperature of less than 0 ℃, a wide temperature range of a smectic phase, a small viscosity, an appropriate optical anisotropy, a large positive or negative dielectric anisotropy, a large specific resistance, a high stability to light, a high stability to heat, and a large elastic constant. Another advantage is to provide a liquid crystal composition having an appropriate balance between at least two of these characteristics. Another advantage is to provide a liquid crystal display element containing such a composition. Still another advantage is to provide an AM device having characteristics such as a short response time, a large voltage holding ratio, a low threshold voltage, a large contrast ratio, and a long lifetime.

Detailed Description

The usage of the terms in the present specification is as follows. The terms "liquid crystal composition" and "liquid crystal display element" may be abbreviated as "composition" and "element", respectively. The term "liquid crystal display element" is a generic term for liquid crystal display panels and liquid crystal display modules. The "liquid crystalline compound" is a general term for compounds having a liquid crystal phase such as a nematic phase or a smectic phase, and compounds which are not in a liquid crystal phase but are mixed in a composition for the purpose of adjusting characteristics such as a temperature range, viscosity, and dielectric anisotropy of a nematic phase. The compound has a six-membered ring such as 1, 4-cyclohexylene or 1, 4-phenylene, and the molecules (liquid crystal molecules) thereof are rod-like (rod-like). The "polymerizable compound" is a compound added for the purpose of forming a polymer in the composition. The liquid crystalline compound having an alkenyl group is not classified into a polymerizable compound in terms of its meaning.

The "liquid crystal composition" is prepared by mixing a plurality of liquid crystalline compounds. An additive such as an optically active compound or a polymerizable compound is added to the liquid crystal composition as needed. Even in the case where an additive is added, the proportion of the liquid crystalline compound is represented by a mass percentage (mass%) based on the liquid crystal composition containing no additive. The proportion of the additive is represented by a mass percentage based on the liquid crystal composition containing no additive. That is, the ratio of the liquid crystalline compound or the additive is calculated based on the total amount of the liquid crystalline compound. The ratio of the polymerization initiator and the polymerization inhibitor is calculated based on the total amount of the polymerizable compound. In some cases, the "mass" of "% by mass" is omitted.

The "upper limit temperature of the nematic phase" is sometimes abbreviated as "upper limit temperature". The "lower limit temperature of the liquid crystal phase" may be abbreviated as "lower limit temperature". The "lower temperature limit of the liquid crystal phase" means the transition temperature of the solid and the smectic phase. In the absence of a smectic phase, this refers to the transition temperature of the solid to the nematic phase. The expression "increase in dielectric anisotropy" means that the value increases positively in a composition having positive dielectric anisotropy, and increases negatively in a composition having negative dielectric anisotropy. The "large voltage holding ratio" means that the device has a large voltage holding ratio not only at room temperature but also at a temperature close to the upper limit temperature in the initial stage, and the device has a large voltage holding ratio not only at room temperature but also at a temperature close to the upper limit temperature after long-term use. The properties of the composition or the element are sometimes investigated by time-varying tests.

The compound (1z) is exemplified. In formula (1z), the symbols α and β surrounded by a hexagon correspond to ring α and ring β, respectively, and represent a six-membered ring, a condensed ring, and the like. Where the subscript 'x' is 2, there are two rings α. The two groups represented by the two rings a may be the same or may also be different. The rule applies to any two rings a where subscript 'x' is greater than 2. The rules also apply to other tokens such as the bonding base Z. The slash across one side of the loop β indicates that any hydrogen on the loop β may be substituted with a substituent (-Sp-P). The subscript 'y' indicates the number of substituents substituted. When subscript 'y' is 0 (zero), no such substitution is present. When the subscript 'y' is 2 or more, a plurality of substituents (-Sp-P) are present on the ring β. In that case, the rules "may be the same, or may also be different" also apply. Furthermore, the rules also apply to the use of the notation of Ra in a variety of compounds.

In formula (1z), for example, the expression "Ra and Rb are alkyl, alkoxy or alkenyl" means that Ra and Rb are independently selected from the group of alkyl, alkoxy and alkenyl. Here, the group represented by Ra and the group represented by Rb may be the same or may be different.

At least one compound selected from the compounds represented by the formula (1z) may be abbreviated as "compound (1 z)". The "compound (1 z)" means one compound, a mixture of two compounds or a mixture of three or more compounds represented by the formula (1 z). The same applies to the compounds represented by the other formulae. The expression "at least one compound selected from the group consisting of the compounds represented by the formula (1z) and the formula (2 z)" means at least one compound selected from the group consisting of the compound (1z) and the compound (2 z).

"principal component" refers to the largest proportion of a component in a mixture or composition. For example, a mixture of 40% of the compound (1z), 35% of the compound (2z) and 25% of the compound (3z) contains the compound (1z) as a main component. When the component (1) is only the compound (1z), the compound (1z) is also referred to as a main component. When the compound (1z) is a single compound, the compound is also referred to as a main component.

The expression "at least one 'a'" means that the number of 'a's is arbitrary. The expression "at least one 'a' may be substituted with 'B' means that the position of 'a' is arbitrary when the number of 'a' is one, and the position thereof may be selected without limitation when the number of 'a' is two or more. Sometimes using "at least one-CH₂-may be substituted by-O-. In said case, -CH₂-CH₂-CH₂Can pass through non-contiguous-CH₂-conversion to-O-CH by-O-substitution₂-O-. However, there is no contiguous-CH₂-substituted by-O-. The reason is that: in said substitution-O-CH is formed₂- (peroxides).

The alkyl group of the liquid crystalline compound is linear or branched and does not include a cyclic alkyl group. Straight chain alkyls are preferred over branched alkyls. The same applies to terminal groups such as alkoxy groups and alkenyl groups. Regarding the configuration of 1, 4-cyclohexylene group-related stereo-configuration, the trans (trans) configuration is preferred over the cis (cis) configuration in order to increase the upper limit temperature. Since 2-fluoro-1, 4-phenylene is asymmetric to the left and right, it is present in the left (L) and right (R) directions.

The same applies to divalent radicals such as tetrahydropyran-2, 5-diyl. The same applies to a bonding group (-COO-or-OCO-) such as carbonyloxy.

The present invention is as follows.

Item 1. a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃.

Item 2. the liquid crystal composition of item 1, wherein a smectic phase is exhibited at-20 ℃.

Item 3. the liquid crystal composition according to item 1 or item 2, which contains a compound having a smectic phase.

Item 4. the liquid crystal composition according to any one of item 1 to item 3, which contains at least one compound selected from the compounds represented by formula (1) as component A.

In the formula (1), R¹And R²Is C1-12 alkyl, C1-12 alkoxy, C2-12 alkenyl or C2-12 alkenyl with at least one hydrogen substituted by fluorine; ring A and ring B are 1, 4-cyclohexylene, 1, 4-phenylene, 2-fluoro-1, 4-phenylene or 2, 5-difluoro-1, 4-phenylene; z¹Is a single bond, ethylene, vinylidene, methyleneoxy or carbonyloxy; a is 1 or 2.

Item 5. the liquid crystal composition according to item 4, which contains 40% or more of the following compounds: in the formula (1), R¹And R²Is alkyl of carbon number 1 to 12 or alkenyl of carbon number 2 to 12; ring A and ring B are 1, 4-phenylene, 2-fluoro-1, 4-phenylene or 2, 5-difluoro-1, 4-phenylene; z¹Is a single bond; a is 2.

Item 6. the liquid crystal composition according to any one of items 1 to 5, which contains at least one compound selected from the compounds represented by formulae (1-1) to (1-9) as the component A.

In the formulae (1-1) to (1-9), R¹And R²Is alkyl group with carbon number of 1 to 12, alkoxy group with carbon number of 1 to 12, alkenyl group with carbon number of 2 to 12 or alkenyl group with carbon number of 2 to 12, wherein at least one hydrogen is substituted by fluorine.

Item 7. the liquid crystal composition according to any one of items 3 to 6, wherein the proportion of the component A is in the range of 10% to 90%.

An item 8. the liquid crystal composition according to any one of items 1 to 7, which contains 50% or more of 3-HH-V.

Item 9. the liquid crystal composition according to any one of item 1 to item 7, which contains 20% or more of 4-HH-V.

Item 10 the liquid crystal composition according to any one of item 1 to item 7, which contains 10% or more of 3-HH-4.

Item 11. the liquid crystal composition according to any one of item 1 to item 10, which contains at least one compound selected from the compounds represented by formula (2) as the component B.

In the formula (2), R³Is alkyl group with carbon number of 1 to 12, alkoxy group with carbon number of 1 to 12 or alkenyl group with carbon number of 2 to 12; ring C is 1, 4-cyclohexylene, 1, 4-phenylene, 2-fluoro-1, 4-phenylene, 2, 3-difluoro-1, 4-phenylene, 2, 6-difluoro-1, 4-phenylene, pyrimidine-2, 5-diyl, 1, 3-dioxane-2, 5-diyl or tetrahydropyran-2, 5-diyl; z²Is a single bond, ethylene, vinylene, methyleneoxy, carbonyloxy or difluoromethyleneoxy; x¹And X²Is hydrogen or fluorine; y is¹Is fluorine, at least one alkyl group with 1 to 12 carbon atoms, at least one alkoxy group with 1 to 12 carbon atoms, or at least one alkenyloxy group with 2 to 12 carbon atoms, wherein the hydrogen is replaced by fluorine; b is 1,2, 3 or 4.

Item 12. the liquid crystal composition according to any one of items 1 to 11, which contains at least one compound selected from the compounds represented by formulae (2-1) to (2-36) as the component B.

In the formulae (2-1) to (2-36), R³Is alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms or alkenyl group having 2 to 12 carbon atoms.

Item 13. the liquid crystal composition of item 11, wherein, in formula (2), at least one of ring C is 1, 3-dioxane-2, 5-diyl.

Item 14 the liquid crystal composition of item 11, wherein, in the formula (2), R³Is an alkyl group having 1 to 12 carbon atoms, at least one of the ring C is 1, 3-dioxane-2, 5-diyl, Z²Is a single bond or difluoromethyleneoxy group, X¹And X²Is hydrogen or fluorine, Y¹Is fluorine.

Item 15. the liquid crystal composition of any one of items 11 to 14, wherein the proportion of component B is in the range of 10% to 90%.

Item 16. the liquid crystal composition according to any one of item 1 to item 15, which contains at least one compound selected from the compounds represented by formula (3) as the component C.

In the formula (3), R⁴And R⁵Is hydrogen, alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms, alkenyl group having 2 to 12 carbon atoms or alkenyloxy group having 2 to 12 carbon atoms; ring D and ring F are 1, 4-cyclohexylene, 1, 4-cyclohexenylene, tetrahydropyran-2, 5-diyl, 1, 4-phenylene in which at least one hydrogen is substituted by fluorine, naphthalene-2, 6-diyl in which at least one hydrogen is substituted by fluorine, chromane-2, 6-diyl or chromane-2, 6-diyl in which at least one hydrogen is substituted by fluorine; ring E is 2, 3-difluoro-1, 4-phenylene, 2-chloro-3-fluoro-1, 4-phenylenePhenyl, 2, 3-difluoro-5-methyl-1, 4-phenylene, 3,4, 5-trifluoronaphthalene-2, 6-diyl, 7, 8-difluorochromane-2, 6-diyl, 3,4,5, 6-tetrafluorofluorene-2, 7-diyl, 4, 6-difluorodibenzofuran-3, 7-diyl, 4, 6-difluorodibenzothiophene-3, 7-diyl, or 1,1,6, 7-tetrafluoroindan-2, 5-diyl; z³And Z⁴Is a single bond, ethylene, vinylidene, methyleneoxy or carbonyloxy; c is 0, 1,2 or 3, d is 0 or 1, and the sum of c and d is 3 or less.

Item 17. the liquid crystal composition according to any one of item 1 to item 16, which contains at least one compound selected from the compounds represented by formulae (3-1) to (3-33) as component C.

In the formulae (3-1) to (3-33), R⁴And R⁵Is hydrogen, alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms, alkenyl group having 2 to 12 carbon atoms or alkenyloxy group having 2 to 12 carbon atoms.

Item 18. the liquid crystal composition of item 16 or item 17, wherein the proportion of component C is in the range of 10% to 90%.

Item 19. the liquid crystal composition according to any one of item 1 to item 18, which contains at least one compound selected from polymerizable compounds represented by formula (4) as an additive A.

In the formula (4), the ring J and the ring L are cyclohexyl, cyclohexenyl, phenyl, 1-naphthyl, 2-naphthyl, tetrahydropyran-2-yl, 1, 3-dioxane-2-yl, pyrimidin-2-yl or pyridin-2-yl, and at least one hydrogen in these rings may pass throughFluorine, alkyl of carbon number 1 to 12, alkoxy of carbon number 1 to 12, or alkyl of carbon number 1 to 12 in which at least one hydrogen is substituted with fluorine; ring K is 1, 4-cyclohexylene, 1, 4-cyclohexenylene, 1, 4-phenylene, naphthalene-1, 2-diyl, naphthalene-1, 3-diyl, naphthalene-1, 4-diyl, naphthalene-1, 5-diyl, naphthalene-1, 6-diyl, naphthalene-1, 7-diyl, naphthalene-1, 8-diyl, naphthalene-2, 3-diyl, naphthalene-2, 6-diyl, naphthalene-2, 7-diyl, tetrahydropyran-2, 5-diyl, 1, 3-dioxane-2, 5-diyl, pyrimidine-2, 5-diyl or pyridine-2, 5-diyl, in these rings, at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine; z⁵And Z⁶Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -CO-, -COO-or-OCO-, at least one-CH₂CH₂-may be via-CH ═ CH-, -C (CH)₃)＝CH-、-CH＝C(CH₃) -or-C (CH)₃)＝C(CH₃) -substitution, of which at least one hydrogen may be substituted by fluorine; p¹、P²And P³Is a polymerizable group; sp¹、Sp²And Sp³Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -COO-or-OCO-, at least one-CH₂CH₂-may be substituted by-CH ═ CH-or-C ≡ C-, in which groups at least one hydrogen may be substituted by fluorine; f is 0, 1 or 2; g. h and j are 0, 1,2, 3 or 4, and the sum of g, h and j is 1 or more.

The liquid crystal composition according to the item 19, wherein, in the formula (4), the ring J and the ring L are cyclohexyl, phenyl, 1-naphthyl or 2-naphthyl, and in these rings, at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine; ring K is 1, 4-cyclohexylene, 1, 4-phenylene, naphthalene-1, 2-diyl or naphthalene-2, 6-diyl, in which at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine; z⁵And Z⁶Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂May be substituted by-O-, -CO-, -COO-or-OCO-, and at least one-CH₂CH₂-may be substituted by-CH ═ CH-, where at least one hydrogen may be substituted by fluorine; p¹、P²And P³Is a group selected from the polymerizable groups represented by the formulae (P-1) to (P-5):

here, M¹、M²And M³Hydrogen, fluorine, alkyl of 1 to 5 carbon atoms or alkyl of 1 to 5 carbon atoms wherein at least one hydrogen is substituted by fluorine; sp¹、Sp²And Sp³Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -COO-or-OCO-, at least one-CH₂CH₂-may be substituted by-CH ═ CH-, where at least one hydrogen may be substituted by fluorine; f is 0 or 1; g. h and j are 0, 1,2, 3 or 4, and the sum of g, h and j is 1 or more.

Item 21. the liquid crystal composition according to any one of items 1 to 20, which contains at least one compound selected from polymerizable compounds represented by formulae (4-1) to (4-29) as an additive A.

In formulae (4-1) to (4-29), P⁴、P⁵And P⁶Is a group selected from the polymerizable groups represented by the formulae (P-1) to (P-3):

here, M¹、M²And M³Hydrogen, fluorine, alkyl of 1 to 5 carbon atoms or alkyl of 1 to 5 carbon atoms wherein at least one hydrogen is substituted by fluorine; sp¹、Sp²And Sp³Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -COO-or-OCO-, at least one-CH₂CH₂-may be substituted by-CH ═ CH-or-C ≡ C-, at least one of these groups being substituted by fluorine.

Item 22. the liquid crystal composition of any one of items 19 to 21, wherein the proportion of additive a is in the range of 0.03% to 10%.

Item 23 the liquid crystal composition of any one of items 1 to 22, wherein an upper limit temperature of the nematic phase is 70 ℃ or more, an optical anisotropy at a wavelength of 589nm (measured at 25 ℃) is 0.07 or more, and a dielectric anisotropy at a frequency of 1kHz (measured at 25 ℃) is 2 or more or-2 or less.

The liquid crystal composition according to any one of claims 1 to 23, wherein a proportion of the compound having an alkenyl group is 50% or less.

Item 25. the liquid crystal composition according to any one of item 1 to item 24, which does not contain a compound having chlorine.

Item 26. the liquid crystal composition according to any one of item 1 to item 25, wherein a proportion of the compound represented by formula (1a) is in a range of 0% to 3%.

In the formula (1a), R¹And R²Is C1-12 alkyl, C1-12 alkoxy, C2-12 alkenyl or C2-12 alkenyl with at least one hydrogen substituted by fluorine; ring A and ring B are 1, 4-cyclohexylene, 1, 4-phenylene, 2-fluoro-1, 4-phenylene or 2, 5-difluoro-1, 4-phenylene; z¹Is a single bond, ethylene, vinylidene, methyleneoxy or carbonyloxy.

An item 27. a liquid crystal display element containing the liquid crystal composition according to any one of items 1 to 26.

The liquid crystal display device of item 27, wherein the liquid crystal display device operates in an IPS mode, a VA mode, an FFS mode, or an FPA mode, and the liquid crystal display device is driven in an active matrix mode.

Item 29. A polymer-stabilized alignment type liquid crystal display element, which contains the liquid crystal composition according to any one of items 19 to 22, and in which a polymerizable compound is polymerized.

Item 30. use of a liquid crystal composition according to any one of items 1 to 26 in a liquid crystal display element.

Item 31. use of a liquid crystal composition according to any one of items 19 to 22 in a polymer-stabilized alignment type liquid crystal display element.

Item 32. a method of developing a smectic phase at a temperature of less than 0 ℃ by preparing the liquid crystal composition of any one of items 1 to 26.

Item 33. a method of shortening a response time of a liquid crystal display element at a temperature below 0 ℃ by using the liquid crystal composition according to any one of items 1 to 26.

The present invention also includes the following items. (a) The composition contains one compound, two compounds or three or more compounds selected from additives such as an optically active compound, an antioxidant, an ultraviolet absorber, a delustering agent, a pigment, an antifoaming agent, a polymerizable compound, a polymerization initiator, a polymerization inhibitor and a polar compound. (b) An AM element comprising the composition. (c) The composition further contains a polymerizable compound, and a polymer-stabilized oriented (PSA) AM element containing the composition. (d) An AM element of Polymer Stable Alignment (PSA) type, comprising the composition, wherein a polymerizable compound in the composition is polymerized. (e) An AM element comprising the composition, wherein the composition comprises a polymer derived from a precursor, and the main component of the precursor is the polymerizable compound. (f) An element comprising said composition and having a pattern of PC, TN, STN, ECB, OCB, IPS, VA, FFS or FPA. (g) A permeable element comprising the composition. (h) Use of said composition as a composition having a nematic phase. (i) Use of an optically active composition obtained by adding an optically active compound to the composition.

The present invention also includes the following items. Combinations of the following with other items are also included. (j) A liquid crystal composition having a smectic-nematic transition temperature below 0 ℃ exhibiting a smectic phase at-20 ℃. (k) A liquid crystal composition having a smectic-nematic transition temperature below 0 ℃ exhibiting a smectic phase at-30 ℃. (l) A liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃ exhibiting a smectic phase at-20 ℃ or-30 ℃. (m) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃ showing a smectic phase at-25 ℃.

The present invention also includes the following items. Combinations of the following with other items are also included. (n) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃, the temperature range of the smectic phase being 10 degrees or more. (o) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃, the temperature range of the smectic phase being 20 degrees or more. (p) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃, the temperature range of the smectic phase being 30 degrees or more. (q) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃ and a temperature range of the smectic phase of 40 ℃ or more.

The present invention also includes the following items. Combinations of the following with other items are also included. (r) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃, exhibiting a smectic phase at-20 ℃, and having a temperature range of 10 ℃ or more. (s) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃, exhibiting a smectic phase at-20 ℃, and having a temperature range of the smectic phase of 20 ℃ or more. (t) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃, exhibiting a smectic phase at-30 ℃, and having a temperature range of the smectic phase of 10 ℃ or more. (u) a liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃, exhibiting a smectic phase at-30 ℃, and having a temperature range of the smectic phase of 20 ℃ or more.

The present invention is explained in the following order. First, the features of the present invention will be explained. Second, the composition is explained. Third, the main characteristics of the component compounds and the main effects of the compounds on the composition or element will be described. Fourth, the combination, preferred ratio and basis of the component compounds in the composition will be explained. Fifth, preferred forms of the component compounds will be described. Sixth, preferred component compounds are shown. Seventh, additives that can be added to the composition are explained. Eighth, a method for synthesizing the component compound will be explained. Finally, the use of the composition is illustrated.

First, the features of the present invention will be explained. The compositions described in table 1 have a nematic phase at room temperature. The preferred upper temperature limit of the nematic phase is about 70 ℃ or higher. The AM element with the composition has a short response time at room temperature. However, at low temperatures, such as-20 ℃, the response time is extremely long. This is a problem to be solved. Thus, various compositions were prepared and the response time of the element at low temperature was measured. A composition having a nematic phase at room temperature and a smectic phase at-20 ℃ was prepared. The composition is placed in the element and the response time is measured. The response time is shorter than that of an element having a composition that maintains a nematic phase even at-20 ℃. The results are unexpected as we predict that nematic phases are more favorable than smectic phases for achieving short response times.

Our prediction is consistent with the description of Japanese patent laid-open No. 2007-308707 (or US 5328644B). The publication relates to a nematic liquid crystal mixture having positive dielectric anisotropy, a liquid crystal display element containing the mixture, and the like. In paragraph 0007 of the publication (in the US publication, lines 2, 34 to 41), the following is described. "recently commercially available mixtures need to operate over a wide temperature range, and therefore crystallization at low temperatures or the formation of smectic phases must be excluded. In the development of nematic mixtures, one of the most important prerequisites for the usefulness of liquid-crystalline substances is good solubility. For the reasons mentioned, compounds having a high melting temperature or a tendency to form smectic phases are not suitable ".

The paragraph teaches: nematic mixtures which maintain a nematic phase even at low temperatures and do not undergo phase transition to the smectic phase are suitable for liquid crystal display elements. This is common knowledge. Our results show that: at low temperatures, smectic phases are more suitable than nematic phases. This is in contravention. Therefore, we have studied a composition having a nematic phase and a smectic phase and an element having the composition. We have also investigated the use of compounds in compositions which have a tendency to form smectic phases.

The present invention relates to a liquid crystal composition having the characteristics shown in table 1, having a smectic-nematic transition temperature of less than 0 ℃, and having a temperature range of a smectic phase of 10 degrees or more, a liquid crystal display element having the composition, and the like. The composition has a nematic phase at room temperature and a smectic phase at low temperatures. Elements that drive in the temperature range of the nematic phase are known and commercially available. However, elements that are also driven in the temperature range of the smectic phase appear to be unreported in the literature. We have studied compositions having a smectic phase at low temperatures, such as-10 c or-20 c or-30 c. We have studied a method of expanding the temperature range of the smectic phase. As a result, it has been found that a method of using a specific compound, increasing the proportion of a specific compound, not using a specific compound, or the like is effective. We have also found that a composition having a smectic a phase is preferable from the viewpoint of response time. It is also known that: several methods may be combined according to the kind of composition. Such a method is as follows.

(1) Use of specific component compounds

Various liquid crystalline compounds are known. Here, a rod-like compound may be used in the liquid crystal composition. The liquid crystalline compound preferably does not contain a hetero atom. The exception is fluorine and oxygen. The compound preferably has a smectic phase. Preferred are compounds having a smectic a phase. Even a compound having no smectic A phase can be used as required. It is preferable to use a compound having a wide temperature range of the smectic phase. Such compounds are preferably used in relatively large amounts. Examples of such compounds are shown below. 3-H-H-V, 4-H-H-V and 3-H-H-4 belong to component A. The remaining compounds belong to component B. The expression of the compounds by symbols is shown in Table 3.

Examples of the transition temperature of the compound are as follows.

(a) 3-HH-V: c (23.9) S33.9N 49.7I. This means that: the temperature for transition from the smectic phase (S) to the nematic phase (N) was 33.9 ℃ and the temperature for transition from the nematic phase (N) to the liquid (I) was 49.7 ℃. Brackets indicate that a phase transition is observed at reduced temperature. That is, it means that the temperature at which the smectic phase (S) is transformed into the crystal (C) is 23.9 ℃.

(b)4-HH-V：C<25.0S 54.5I。

(c)3-HH-4：C-7.7S 95.2I。

(d)3-GBB(F,F)XB(F,F)-F：C 90.9S 101.9N 124.3I。

These compounds have a smectic phase.

(2) Substituent of liquid crystalline compound

R for Compound (1)¹Or R²Alkyl or alkenyl groups are preferred over alkoxy or fluorinated alkenyl groups. Alkyl groups are preferred over alkenyl groups. From the viewpoint of stability against light or heat, a compound having an alkyl group is preferable. From the viewpoint of a wide temperature range of the near-crystal phase, a compound having an alkyl group is preferable. R¹Or R²In the above, the carbon number is preferably 5 or 7 to 2 or 3. The amount of the component compounds is preferably large. For example, a mixture of 10% of a compound and 10% of its homologues is better than 20% of a single compound.

R for Compound (2)³With R of the compound (1)¹Or R²The above description applies. The same applies to the number of component compounds. From the viewpoint of a wide temperature range of the near-crystal phase, a compound having 1, 3-dioxane-2, 5-diyl group is preferable. Further preferred are tetracyclic compounds having a 1, 3-dioxane-2, 5-diyl group.

In the compounds (1) to (3), there are cases where an alkenyl group is preferable to an alkyl group. From the viewpoint of short response time, a compound having an alkenyl group is preferable. From the viewpoint of good compatibility at low temperature, a compound having an alkenyl group is preferable. The preferable proportion of the compound is 50% or less. Further, the preferable ratio is 40% or less.

(3) Unsuitable liquid crystalline compounds

If desired, compounds having chlorine may also be added to the composition, but the proportion is preferably small. Chlorine is not said to be preferable from the viewpoint of a wide temperature range of the near-crystal phase. In the nematic phase, the liquid crystal molecules are oriented in one direction. Since the smectic phase also has a layer structure, liquid crystal molecules are regularly arranged as compared with the nematic phase. Chlorine is much larger than hydrogen or fluorine. Therefore, chlorine is not supposed to be suitable for the regular arrangement of molecules.

The compound (1a) has four rings. R¹The definition of the symbol such as ring A is described in item 26. The proportion of the tetracyclic compound is preferably in the range from 0% to 3%. Tetracyclic compounds are effective in increasing the upper temperature limit of the nematic phase. However, the smectic-nematic transition temperature is sometimes increased. Thus, tetracyclic compounds may be used as desired, but the proportion is preferably small. If there is no particular reason, the tetracyclic compound is preferably 0%.

Examples of tetracyclic compounds are described below.

(4) Method for adjusting characteristics

The composition has a broad temperature range of the smectic phase at temperatures below 0 ℃ when specific component compounds are used. The composition changes from a nematic phase to a smectic phase at a temperature below 0 ℃. The composition has an upper temperature limit of about 70 ℃ or greater. Examples of procedures for preparing such compositions are described below. First, the compositions described in table 1 were prepared. Next, 3-HH-V, 4-HH-V or 3-HH-4 is mixed in the composition. Several of these compounds may also be mixed. These compounds have the effect of lowering the viscosity, causing (developing) a smectic phase, or expanding the temperature range of an already existing smectic phase. However, these compounds also have the effect of lowering the upper limit temperature or lowering the dielectric anisotropy. Finally, in order to raise the upper limit temperature, the compounds (1-5) to (1-8) or the compounds (1-9) are mixed in the composition. In order to improve the dielectric anisotropy, the compound (2-23), the compound (2-24), the compound (2-25), the compound (2-29) or the compound (2-36) is mixed in the composition. A plurality of compounds may also be mixed as necessary.

Other examples are described below. First, the compositions described in table 1 were prepared. Next, the dioxane compound described in item 13 or 14 is mixed with the composition. Or, mixing said 3-GB (F) B (F, F) -F to 3-GB (F) B (F, F) XB (F, F) -F dioxane compounds. Several of these compounds may also be mixed. These compounds have the effect of increasing the dielectric anisotropy, inducing (developing) a smectic phase, and extending the temperature range of an existing smectic phase. However, these compounds also have an effect of increasing viscosity. Finally, compound (1-1), compound (1-2) or compound (1-3) is mixed in the composition in order to reduce the viscosity. For the purpose of adjusting the properties, the compounds (1-5) to (1-9), the compounds (2-29) or the compounds (2-36) are mixed in the composition. A plurality of compounds may also be mixed as necessary.

(5) Temperature range of smectic phase

Compositions having a temperature below 0 ℃ for the transition from the nematic phase to the smectic phase are produced by using specific component compounds. Preferred temperature ranges are as follows. The temperature range of the smectic phase is preferably 10 degrees or more, more preferably 20 degrees or more, particularly preferably 30 degrees or more, and most preferably 40 degrees or more. The temperature range of the smectic phase is preferably from a temperature lower than 0 ℃ to-10 ℃ or lower, more preferably from a temperature lower than 0 ℃ to-20 ℃ or lower, particularly preferably from a temperature lower than 0 ℃ to-30 ℃ or lower, and most preferably from a temperature lower than 0 ℃ to-40 ℃ or lower.

Second, the composition is explained. The composition contains a plurality of liquid crystalline compounds. The composition may also contain additives. The additive is an optically active compound, an antioxidant, an ultraviolet absorber, a matting agent, a coloring matter, an antifoaming agent, a polymerizable compound, a polymerization initiator, a polymerization inhibitor, a polar compound, or the like. From the viewpoint of the liquid crystalline compound, the compositions are classified into composition a and composition B. The composition a may contain other liquid crystalline compounds, additives, and the like in addition to the liquid crystalline compound selected from the compound (1), the compound (2), and the compound (3). The "other liquid crystalline compound" is a liquid crystalline compound different from the compound (1), the compound (2) and the compound (3). Such compounds are mixed in the composition for the purpose of further adjusting the properties.

The composition B substantially contains only a liquid crystalline compound selected from the group consisting of the compound (1), the compound (2) and the compound (3). "substantially" means that the composition B may contain additives but does not contain other liquid crystalline compounds. The amount of ingredients of composition B is low compared to composition a. From the viewpoint of cost reduction, composition B is superior to composition a. From the viewpoint that the properties can be further adjusted by mixing other liquid crystalline compounds, the composition a is superior to the composition B.

Third, the main characteristics of the component compounds and the main effects of the compounds on the composition or element will be described. The main properties of the component compounds are summarized in Table 2. In the notation of Table 2, L means large or high, M means medium, and S means small or low. The notation L, M, S is a classification based on qualitative comparisons between component compounds, with notation 0 (zero) meaning less than S.

TABLE 2 Properties of liquid crystalline Compounds

Characteristics of	Compound (1)	Compound (2)	Compound (3)
				Upper limit temperature	S～L	S～L	S～M
Viscosity of the oil	S～M	M～L	M
				Optical anisotropy	S～L	M～L	M～L
Dielectric anisotropy	0	S～L¹⁾	M～L²⁾
				Specific resistance	L	L	L

1) The value of the dielectric anisotropy is positive, and the symbol indicates the magnitude of the absolute value

2) The value of the dielectric anisotropy is negative, and the notation indicates the magnitude of the absolute value

The main effects of the component compounds are as follows. The compound (1) lowers the viscosity or raises the upper temperature. The compound (2) improves positive dielectric anisotropy. The compound (3) improves the negative dielectric anisotropy. Since the compound (4) is polymerizable, it forms a polymer by polymerization. The polymer stabilizes the alignment of liquid crystal molecules, thereby shortening the response time of the element and improving the afterimage of an image.

Fourth, the combination, preferred ratio and basis of the component compounds in the composition will be explained. Preferred combinations of the component compounds in the composition are compound (1) + compound (2), compound (1) + compound (3), or compound (1) + compound (2) + compound (3). The composition having positive dielectric anisotropy is prepared by mixing compound (2) with compound (1). A small amount of the compound (3) may also be added to the composition for the purpose of adjusting the elastic constant of the composition or adjusting the voltage-transmittance curve of the element. On the other hand, a composition having negative dielectric anisotropy is prepared by mixing compound (3) with compound (1). A small amount of the compound (2) may also be added to the composition for the purpose of adjusting the elastic constant of the composition or adjusting the voltage-transmittance curve of the element. Other liquid crystalline compounds may be added to these compositions as needed.

The preferable proportion of the compound (1) is about 10% or more for increasing the upper limit temperature or lowering the viscosity, and about 90% or less for increasing the dielectric anisotropy. Further preferred is a range of about 20% to about 80%. A particularly preferred ratio is in the range of about 30% to about 70%.

The preferable proportion of the compound (2) is about 10% or more for improving the positive dielectric anisotropy, and the preferable proportion of the compound (2) is about 90% or less for lowering the lower limit temperature. Further preferred is a range of about 20% to about 80%. A particularly preferred ratio is in the range of about 30% to about 70%.

The preferable proportion of the compound (3) is about 10% or more for improving the negative dielectric anisotropy, and about 90% or less for lowering the lower limit temperature. Further preferred is a range of about 20% to about 80%. A particularly preferred ratio is in the range of about 30% to about 70%.

The compound (4) is added to the composition for the purpose of being suitable for a polymer stable alignment type element. The preferable proportion of the compound (4) is about 0.03% or more for aligning liquid crystal molecules, and about 10% or less for preventing display defects of the device. Further preferred is a ratio ranging from about 0.1% to about 2%. A particularly preferred ratio is in the range of about 0.2% to about 1.0%.

Fifth, preferred forms of the component compounds will be described.

(a) Liquid crystalline compound

In the formulae (1), (2) and (3), R¹And R²Is alkyl group with carbon number of 1 to 12, alkoxy group with carbon number of 1 to 12, alkenyl group with carbon number of 2 to 12 or alkenyl group with carbon number of 2 to 12, wherein at least one hydrogen is substituted by fluorine. Preferred R for reducing viscosity¹Or R²R is an alkenyl group having 2 to 12 carbon atoms, and is preferably selected from the group consisting of¹Or R²Is an alkyl group having 1 to 12 carbon atoms. R³Is alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms or alkenyl group having 2 to 12 carbon atoms. Preferred R is for improving stability to light or heat³Is an alkyl group having 1 to 12 carbon atoms. R⁴And R⁵Is hydrogen, alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms, alkenyl group having 2 to 12 carbon atoms or alkenyloxy group having 2 to 12 carbon atoms. Preferred R is for improving stability to light or heat⁴Or R⁵Is an alkyl group having 1 to 12 carbon atoms, and R is preferably selected to improve dielectric anisotropy⁴Or R⁵Is alkoxy with 1 to 12 carbon atoms.

Preferred alkyl groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl or octyl. Further preferred alkyl groups for reducing the viscosity are methyl, ethyl, propyl, butyl or pentyl.

Preferred alkoxy groups are methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy. Further preferred alkoxy groups for reducing the viscosity are methoxy or ethoxy.

Preferred alkenyl groups are vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl or 5-hexenyl. Further preferred alkenyl groups for reducing the viscosity are vinyl, 1-propenyl, 3-butenyl or 3-pentenyl. The preferred steric configuration of-CH ═ CH-in these alkenyl groups depends on the position of the double bond. In order to reduce viscosity and the like, the trans configuration is preferable among alkenyl groups such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl, 3-hexenyl. Among alkenyl groups such as 2-butenyl, 2-pentenyl, 2-hexenyl, the cis configuration is preferred.

Preferred alkenyloxy groups are vinyloxy, allyloxy, 3-butenyloxy, 3-pentenyloxy or 4-pentenyloxy. Further preferred alkenyloxy groups are allyloxy or 3-butenyloxy groups in order to reduce the viscosity.

Preferred examples of alkyl groups in which at least one hydrogen is replaced by fluorine are fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl, 7-fluoroheptyl or 8-fluorooctyl. Further preferable examples of the compound include 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl and 5-fluoropentyl for improving the dielectric anisotropy.

Preferred examples of alkenyl groups in which at least one hydrogen is substituted by fluorine are 2, 2-difluorovinyl, 3-difluoro-2-propenyl, 4-difluoro-3-butenyl, 5-difluoro-4-pentenyl or 6, 6-difluoro-5-hexenyl. Further preferable examples for lowering the viscosity are 2, 2-difluorovinyl group and 4, 4-difluoro-3-butenyl group.

Ring A and ring B are 1, 4-cyclohexylene, 1, 4-phenylene, 2-fluoro-1, 4-phenylene or 2, 5-difluoro-1, 4-phenylene. For lowering the viscosity or for increasing the upper temperature limit, ring A or ring B is preferably a 1, 4-cyclohexylene group, and for lowering the lower temperature limit, ring A or ring B is preferably a 1, 4-phenylene group.

Ring C is 1, 4-cyclohexylene, 1, 4-phenylene, 2-fluoro-1, 4-phenylene, 2, 3-difluoro-1, 4-phenylene, 2, 6-difluoro-1, 4-phenylene, pyrimidine-2, 5-diyl, 1, 3-dioxane-2, 5-diyl or tetrahydropyran-2, 5-diyl. The ring C is preferably 1, 4-cyclohexylene for increasing the upper limit temperature, 1, 4-phenylene for increasing the optical anisotropy, and 2, 6-difluoro-1, 4-phenylene for increasing the dielectric anisotropy. Tetrahydropyran-2, 5-diyl in ring C is:

preferably:

ring D and ring F are 1, 4-cyclohexylene, 1, 4-cyclohexenylene, tetrahydropyran-2, 5-diyl, 1, 4-phenylene in which at least one hydrogen is substituted by fluorine, naphthalene-2, 6-diyl in which at least one hydrogen is substituted by fluorine, chromane-2, 6-diyl or chromane-2, 6-diyl in which at least one hydrogen is substituted by fluorine. Preferred examples of "1, 4-phenylene in which at least one hydrogen is substituted by fluorine" are 2-fluoro-1, 4-phenylene, 2, 3-difluoro-1, 4-phenylene or 2-chloro-3-fluoro-1, 4-phenylene. The ring D or F is preferably a 1, 4-cyclohexylene group for lowering the viscosity, a tetrahydropyran-2, 5-diyl group for improving the dielectric anisotropy, and a 1, 4-phenylene group for improving the optical anisotropy. The tetrahydropyran-2, 5-diyl in ring D and ring F is preferably:

ring E is 2, 3-difluoro-1, 4-phenylene, 2-chloro-3-fluoro-1, 4-phenylene, 2, 3-difluoro-5-methyl-1, 4-phenylene, 3,4, 5-trifluoronaphthalene-2, 6-diyl, 7, 8-difluorochromane-2, 6-diyl, 3,4,5, 6-tetrafluorofluorene-2, 7-diyl (FLF4), 4, 6-difluorodibenzofuran-3, 7-diyl (DBTF2), 4, 6-difluorodibenzothiophene-3, 7-diyl (DBTF2), or 1,1,6, 7-tetrafluoroindan-2, 5-diyl (InF 4).

The preferred ring E is 2, 3-difluoro-1, 4-phenylene for decreasing viscosity, 2-chloro-3-fluoro-1, 4-phenylene for decreasing optical anisotropy, and 4, 6-difluorodibenzothiophene-3, 7-diyl for increasing dielectric anisotropy.

Z¹Is a single bond, ethylene, vinylidene, methyleneoxy or carbonyloxy. For reducing the viscosity, preferred is Z¹Is a single bond. Z²Is a single bond, ethylene, vinylene, methyleneoxy, carbonyloxy or difluoromethyleneoxy. For reducing the viscosity, preferred is Z²Is a single bond, and Z is preferably a single bond for improving positive dielectric anisotropy²Is difluoromethyleneoxy. Z³And Z⁴Is a single bond, ethylene, vinylidene, methyleneoxy or carbonyloxy. For reducing the viscosity, preferred is Z³Or Z⁴Is a single bond, and Z is preferably Z for lowering the lower limit temperature³Or Z⁴Is ethylene, and Z is preferably selected to improve negative dielectric anisotropy³Or Z⁴Is methyleneoxy.

Divalent radicals such as methyleneoxy are asymmetric to the left and right. In the methyleneoxy group, -CH₂O-is superior to-OCH₂-. In the carbonyloxy group, -COO-is preferable to-OCO-. Of difluoromethyleneoxy, -CF₂O-is superior to-OCF₂-。

X¹And X²Is hydrogen or fluorine. For improving positive dielectric anisotropy, X is preferable¹Or X²Is fluorine.

Y¹Is fluorine, alkyl of carbon number 1 to 12 with at least one hydrogen substituted by fluorine, or alkenyloxy of carbon number 2 to 12 with at least one hydrogen substituted by fluorine. For lowering the lower limit temperature, Y is preferable¹Is fluorine. A preferred example of an alkyl group in which at least one hydrogen is substituted with fluorine is trifluoromethyl. A preferred example of an alkenyloxy group substituted at least one hydrogen by fluorine is trifluoroethyleneoxy.

a is 1 or 2. In order to lower the viscosity, a is preferably 1, and in order to raise the upper limit temperature, a is preferably 2. b is 1,2, 3 or 4. In order to improve the positive dielectric anisotropy, b is preferably 2 or 3. c is 0, 1,2 or 3, d is 0 or 1, and the sum of c and d is 3 or less. For lowering the viscosity, c is preferably 1, and for raising the upper limit temperature, c is preferably 2 or 3. For lowering the viscosity, d is preferably 0, and for lowering the lower limit temperature, d is preferably 1.

(b) Polymerizable compound

In the formula (4), the ring J and the ring L are cyclohexyl, cyclohexenyl, phenyl, 1-naphthyl, 2-naphthyl, tetrahydropyran-2-yl, 1, 3-dioxane-2-yl, pyrimidin-2-yl or pyridin-2-yl, and in these rings, at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine. Preferred ring J or ring L is cyclohexyl, phenyl, 1-naphthyl or 2-naphthyl, in which at least one hydrogen may be substituted by fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine. Further preferably, ring J or ring L is a phenyl group.

Ring K is 1, 4-cyclohexylene, 1, 4-cyclohexenylene, 1, 4-phenylene, naphthalene-1, 2-diyl, naphthalene-1, 3-diyl, naphthalene-1, 4-diyl, naphthalene-1, 5-diyl, naphthalene-1, 6-diyl, naphthalene-1, 7-diyl, naphthalene-1, 8-diyl, naphthalene-2, 3-diyl, naphthalene-2, 6-diyl, naphthalene-2, 7-diyl, tetrahydropyran-2, 5-diyl, 1, 3-dioxane-2, 5-diyl, pyrimidine-2, 5-diyl or pyridine-2, 5-diyl, in these rings, at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine. Preferred ring K is 1, 4-cyclohexylene, 1, 4-phenylene, naphthalene-1, 2-diyl or naphthalene-2, 6-diyl, in which at least one hydrogen may be substituted by fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine. Further preferred ring K is 1, 4-phenylene or 2-fluoro-1, 4-phenylene.

Z⁵And Z⁶Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -CO-, -COO-or-OCO-, at least one-CH₂CH₂Can be-CH＝CH-、-C(CH₃)＝CH-、-CH＝C(CH₃) -or-C (CH)₃)＝C(CH₃) -substitution, of which at least one hydrogen may be substituted by fluorine. Preferred Z⁵Or Z⁶Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂May be substituted by-O-, -CO-, -COO-or-OCO-, and at least one-CH₂CH₂-may be substituted by-CH ═ CH-, where at least one hydrogen may be substituted by fluorine. Further preferred is Z⁵Or Z⁶Is a single bond, -CH₂CH₂-、-CH₂O-、-OCH₂-, -COO-or-OCO-. Particularly preferred Z⁵Or Z⁶Is a single bond.

P¹、P²And P³Is a polymerizable group. Preferred P¹、P²Or P³Is a group selected from the polymerizable groups represented by the formulae (P-1) to (P-5). Further preferred is P¹、P²Or P³Is a group represented by the formula (P-1), the formula (P-2) or the formula (P-5). Particularly preferred P¹、P²Or P³Is a group represented by the formula (P-1) or (P-2). Preferred formula (P-1) is-OCO-CH ═ CH₂or-OCO-C (CH)₃)＝CH₂. The wavy lines of the formulae (P-1) to (P-5) indicate the bonding positions.

In the formulae (P-1) to (P-5), M¹、M²And M³Hydrogen, fluorine, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms in which at least one hydrogen is substituted with fluorine. For the purpose of enhancing reactivity, M is preferred¹、M²Or M³Is hydrogen or methyl. Further preferred is M¹Is methyl, more preferably M²Or M³Is hydrogen.

In the formula (4), Sp¹、Sp²And Sp³Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -COO-or-OCO-, at least one-CH₂CH₂-may be via-CH ═ CH-or-C ≡ C-substitution, of which at least one hydrogen may be substituted by fluorine. Preferred is Sp¹、Sp²Or Sp³Is a single bond, -CH₂CH₂-、-CH₂O-、-OCH₂-, -COO-, -OCO-, -CO-CH-or-CH-CO-. Further preferred is Sp¹、Sp²Or Sp³Is a single bond.

f is 0, 1 or 2. Preferably f is 0 or 1. g. h and j are 0, 1,2, 3 or 4, and the sum of g, h and j is 1 or more. Preferably g, h or j is 1 or 2.

Sixth, preferred component compounds are shown. Preferred compound (1) is the compound (1-1) to the compound (1-9) described in the item 6. Of these compounds, it is preferable that at least one of the components A is a compound (1-1), a compound (1-3), a compound (1-5), a compound (1-6) or a compound (1-8). Preferably, at least two of the components A are a combination of the compound (1-1) and the compound (1-3), the compound (1-1) and the compound (1-5), or the compound (1-1) and the compound (1-8).

Preferred compound (2) is the compound (2-1) to the compound (2-36) described in the item 12. Of these compounds, it is preferable that at least one of the components B is a compound (2-4), a compound (2-12), a compound (2-14), a compound (2-15), a compound (2-17), a compound (2-18), a compound (2-21), a compound (2-22), a compound (2-23), a compound (2-24), a compound (2-26), a compound (2-27), a compound (2-29), a compound (2-30) or a compound (2-36). Preferably, at least two of the components B are a combination of the compounds (2-12) and (2-15), the compounds (2-14) and (2-27), the compounds (2-18) and (2-24), the compounds (2-18) and (2-29), the compounds (2-24) and (2-29), the compounds (2-29) and (2-30), the compounds (2-21) and (2-36), the compounds (2-22) and (2-36), the compounds (2-26) and (2-36), or the compounds (2-27) and (2-36).

Preferred compound (3) is the compound (3-1) to the compound (3-33) described in the item 17. Of these compounds, it is preferable that at least one of the components C is the compound (3-1), the compound (3-3), the compound (3-6), the compound (3-8), the compound (3-10), the compound (3-13) or the compound (3-32). Preferably, at least two of the components C are a combination of the compound (3-1) and the compound (3-8), the compound (3-1) and the compound (3-14), the compound (3-3) and the compound (3-8), the compound (3-3) and the compound (3-13), the compound (3-3) and the compound (3-32), the compound (3-6) and the compound (3-8), the compound (3-6) and the compound (3-10), or the compound (3-6) and the compound (3-13).

Preferred compound (4) is the compound (4-1) to the compound (4-29) described in the item 21. Of these compounds, it is preferable that at least one of the additives A is the compound (4-1), the compound (4-2), the compound (4-24), the compound (4-25), the compound (4-26) or the compound (4-27). Preferably, at least two of the additives A are a combination of the compound (4-1) and the compound (4-2), the compound (4-1) and the compound (4-18), the compound (4-2) and the compound (4-24), the compound (4-2) and the compound (4-25), the compound (4-2) and the compound (4-26), the compound (4-25) and the compound (4-26), or the compound (4-18) and the compound (4-24).

Seventh, additives that can be added to the composition are explained. Such additives include optically active compounds, antioxidants, ultraviolet absorbers, delustering agents, pigments, antifoaming agents, polymerizable compounds, polymerization initiators, polymerization inhibitors, polar compounds, and the like. An optically active compound is added to the composition for the purpose of inducing a helical structure of liquid crystal molecules to impart a twist angle (torsion angle). Examples of such compounds are compound (5-1) to compound (5-5). The preferable proportion of the optically active compound is about 5% or less. Further preferred is a ratio ranging from about 0.01% to about 2%.

In order to prevent a decrease in specific resistance caused by heating in the atmosphere or to maintain a large voltage holding ratio not only at room temperature but also at a temperature close to the upper limit temperature after the device is used for a long time, an antioxidant such as the compounds (6-1) to (6-3) may be added to the composition.

Since the compound (6-2) has low volatility, it is effective for maintaining a large voltage holding ratio not only at room temperature but also at a temperature close to the upper limit temperature after the device is used for a long time. In order to obtain the above effect, the preferable ratio of the antioxidant is about 50ppm or more, and in order not to lower the upper limit temperature or to raise the lower limit temperature, the preferable ratio of the antioxidant is about 600ppm or less. Even more preferred ratios range from about 100ppm to about 300 ppm.

In order to prevent deterioration caused by ultraviolet rays, an ultraviolet absorber may also be added to the composition. Preferable examples of the ultraviolet absorber include benzophenone derivatives, benzoate derivatives, triazole derivatives and the like. Light stabilizers such as sterically hindered amines are also preferred. Preferable examples of the light stabilizer are compound (7-1) to compound (7-16) and the like. The preferable proportion of these absorbents or stabilizers is about 50ppm or more in order to obtain the above effects, and about 10000ppm or less in order not to lower the upper limit temperature or not to raise the lower limit temperature. Even more preferred ratios range from about 100ppm to about 10000 ppm.

The matting agent is a compound that prevents decomposition of the liquid crystalline compound by receiving light energy absorbed by the liquid crystalline compound and converting the light energy into thermal energy. Preferable examples of the matting agent are a compound (8-1) to a compound (8-7), and the like. The preferable proportion of these matting agents is about 50ppm or more in order to obtain the above effects, and about 20000ppm or less in order not to raise the lower limit temperature. Even more preferred ratios range from about 100ppm to about 10000 ppm.

Dichroic dyes (dichromatic dye) such as azo-based pigments, anthraquinone-based pigments, etc. are added to the composition in order to be suitable for guest-host (GH) mode elements. The preferred proportion of pigment ranges from about 0.01% to about 10%. In order to prevent bubbling, an antifoaming agent such as dimethylsilicone oil or methylphenylsilicone oil is added to the composition. The preferable ratio of the defoaming agent is about 1ppm or more in order to obtain the above effects, and about 1000ppm or less in order to prevent display failure. Even more preferred ratios range from about 1ppm to about 500 ppm.

Polymerizable compounds are used to adapt to polymer-stabilized alignment (PSA) type devices. The compounds (4) are suitable for this purpose. A polymerizable compound different from the compound (4) may be added to the composition together with the compound (4). Preferable examples of such polymerizable compounds are compounds such as acrylic acid esters, methacrylic acid esters, vinyl compounds, vinyloxy compounds, propenyl ethers, epoxy compounds (oxetane ) and vinyl ketones. Further preferred are derivatives of acrylic acid esters or methacrylic acid esters. The preferable proportion of the compound (4) is about 10% or more based on the total amount of the polymerizable compounds. A more preferable ratio is about 50% or more. Particularly preferred is a ratio of about 80% or more. The most preferred ratio is about 100%.

The polymerizable compound such as the compound (4) is polymerized by ultraviolet irradiation. The polymerization may be carried out in the presence of an appropriate initiator such as a photopolymerization initiator. Suitable conditions for carrying out the polymerization, suitable types of initiators, and suitable amounts are known to those skilled in the art and are described in the literature. For example, brilliant good solid (Irgacure)651 (registered trademark; BASF), brilliant good solid (Irgacure)184 (registered trademark; BASF) or Delocur (Darocur)1173 (registered trademark; BASF) as a photopolymerization initiator is suitable for radical polymerization. The preferable proportion of the photopolymerization initiator ranges from about 0.1% to about 5% based on the total amount of the polymerizable compound. Further preferred is a range of about 1% to about 3%.

When storing the polymerizable compound such as the compound (4), a polymerization inhibitor may be added to prevent polymerization. The polymerizable compound is usually added to the composition in a state where the polymerization inhibitor is not removed. Examples of the polymerization inhibitor are hydroquinone, hydroquinone derivatives such as methyl hydroquinone, 4-t-butyl catechol, 4-methoxyphenol, phenothiazine (phenothiazine), and the like.

Eighth, a method for synthesizing the component compound will be explained. These compounds can be synthesized by known methods. A synthesis method is exemplified. The compound (1-1) is synthesized by the method described in Japanese patent laid-open publication No. 59-176221. The compound (2-18) is synthesized by the method described in Japanese patent laid-open No. Hei 10-251186. The compound (3-1) is synthesized by the method described in Japanese patent laid-open No. Hei 2-503441. Antioxidants are commercially available. Compound (6-1) is available from Sigma Aldrich Corporation. The compound (6-2) and the like are synthesized by the method described in the specification of U.S. Pat. No. 3660505.

Compounds not described in the synthetic methods can be synthesized by methods described in the patent publications such as Organic Synthesis (John Wiley & Sons, Inc.), "Organic Reactions (Organic Reactions, John Wiley & Sons, Inc.)," Integrated Organic Synthesis (Pergamon Press), New Experimental chemistry lecture (Bolus), and the like. The compositions are prepared by known methods from the compounds obtained in the manner described. For example, the component compounds are mixed and then dissolved in each other by heating.

Finally, the use of the composition is illustrated. The composition has a substantial upper temperature limit above about 70 ℃ and an optical anisotropy in a range from about 0.07 to about 0.20. A composition having an optical anisotropy in the range of about 0.08 to about 0.25 may also be prepared by adjusting the ratio of the component compounds, or by mixing other liquid crystalline compounds. Compositions having optical anisotropy in the range of about 0.10 to about 0.30 may also be prepared by trial and error. The device containing the composition has a large voltage holding ratio. The composition is suitable for AM elements. The composition is particularly suitable for transmissive AM elements. The composition can be used as a composition having a nematic phase, and can be used as an optically active composition by adding an optically active compound.

The composition can be used in AM elements. And can also be used for PM elements. The composition can be used for AM elements and PM elements having modes such as PC, TN, STN, ECB, OCB, IPS, FFS, VA, FPA and the like. Particularly preferably for AM elements having TN, OCB, IPS mode or FFS mode. In an AM element having an IPS mode or an FFS mode, the alignment of liquid crystal molecules may be parallel or may be perpendicular to a glass substrate when no voltage is applied. These elements may be reflective, transmissive or transflective. Preferably for use in transmissive devices. It can also be used for an amorphous silicon-TFT element or a polysilicon-TFT element. The composition may be used for a device of a Nematic Curvilinear Aligned Phase (NCAP) type prepared by microencapsulation (microencapsulation) or a device of a Polymer Dispersed (PD) type in which a three-dimensional network polymer is formed in the composition.

[ examples ]

The present invention will be described in more detail by way of examples. The present invention is not limited to these examples. The invention comprises a mixture of the composition of example 1 and the composition of example 2. The invention also includes mixtures of at least two of the compositions of the examples. These mixtures or liquid crystal display elements having these mixtures belong to the present invention, and it is considered reasonable to have the effects of the present invention. The synthesized compound is identified by Nuclear Magnetic Resonance (NMR) analysis or the like. The properties of the compounds, compositions and devices were measured by the methods described below.

NMR analysis: DRX-500 manufactured by Bruker BioSpin was used for the measurement. In that¹In the measurement of H-NMR, the molecular weight of the polymer,dissolving the sample in CDCl₃The measurement was performed in a deuterated solvent at room temperature under conditions of 500MHz and 16 cumulative times. Tetramethylsilane was used as an internal standard. In that¹⁹In the measurement of F-NMR, CFCl was used₃As an internal standard, the number of times is accumulated to 24 times. In the description of the nmr spectra, s is a singlet (singlet), d is a doublet (doublt), t is a triplet (triplet), q is a quartet (quatet), quin is a quintet (quintet), sex is a sextant (sextet), m is a multiplet (multiplet), and br is a broad (broad).

Gas chromatographic analysis: for measurement, a GC-14B gas chromatograph manufactured by Shimadzu corporation was used. The carrier gas was helium (2 mL/min). The sample vaporizer was set at 280 ℃ and the detector (flame ionization detector, FID) was set at 300 ℃. The separation of the component compounds was carried out by using a capillary column DB-1 (length 30m, inner diameter 0.32mm, film thickness 0.25 μm; stationary liquid phase is dimethylpolysiloxane; non-polar) manufactured by Agilent Technologies Inc. After the column was held at 200 ℃ for 2 minutes, the temperature was raised to 280 ℃ at a rate of 5 ℃/min. After preparing the sample into an acetone solution (0.1%), 1. mu.L of it was injected into the sample vaporization chamber. The record is a chromatograph module (Chromatopac) model C-R5A manufactured by Shimadzu corporation or an equivalent thereof. The obtained gas chromatogram showed the retention time of the peak corresponding to the component compound and the area of the peak.

Chloroform, hexane, and the like can be used as a solvent for diluting the sample. To separate the constituent compounds, the following capillary column may be used. HP-1 (length 30m, inner diameter 0.32mm, film thickness 0.25 μm) manufactured by Agilent Technologies Inc., Rtx-1 (length 30m, inner diameter 0.32mm, film thickness 0.25 μm) manufactured by Rasteck Corporation, BP-1 (length 30m, inner diameter 0.32mm, film thickness 0.25 μm) manufactured by Australian SGE International Pty.Ltd. For the purpose of preventing overlapping of compound peaks, capillary columns manufactured by Shimadzu corporation CBP1-M50-025 (length 50M, inner diameter 0.25mm, film thickness 0.25 μ M) were used.

The ratio of the liquid crystalline compound contained in the composition can be calculated by the following method. The mixture of liquid crystalline compounds was analyzed by gas chromatography (FID). The area ratio of the peaks in the gas chromatogram corresponds to the ratio of the liquid crystalline compound. When the capillary column described above is used, the correction coefficient of each liquid crystalline compound can be regarded as 1. Therefore, the ratio of the liquid crystalline compound can be calculated from the area ratio of the peaks.

Measurement of the sample: in the measurement of the properties of the composition or the element, the composition is used as a sample as it is. In order to measure the characteristics of the compound, a sample for measurement was prepared by mixing the compound (15%) in a mother liquid crystal (85%). From the values obtained by the measurement, the characteristic values of the compounds were calculated by an extrapolation method (extrapolation method). (extrapolated value) { (measured value of sample) — 0.85 × (measured value of mother liquid crystal) }/0.15. When at said ratio, a smectic phase (or crystal) precipitates at 25 ℃, the ratio of the compound to the mother liquid crystal is set at 10%: 90% and 5%: 95%, 1%: the order of 99% was changed. The values of the upper limit temperature, optical anisotropy, viscosity and dielectric anisotropy relating to the compound were determined by the extrapolation method.

As the compound having positive dielectric anisotropy, the following mother liquid crystal a was used.

As the compound having negative dielectric anisotropy, the following mother liquid crystal B was used.

As for the compound having a dielectric anisotropy of substantially 0 (zero) represented by the compound (1), either the mother liquid crystal a or the mother liquid crystal B is used.

The determination method comprises the following steps: the characteristics were measured by the following methods. These methods are mostly described in JEITA standard (JEITA. ED-2521B) examined and established by the Japan electronic Information Technology Industries Association (JEITA), or modified. The TN element used for the measurement was not provided with a Thin Film Transistor (TFT).

The measurements (1) to (17) were used for samples having positive dielectric anisotropy. There are cases where the measurement method differs depending on whether the dielectric anisotropy is positive or negative. The measurement (18) to the measurement (22) are measurement methods exclusively used for samples having negative dielectric anisotropy.

(1) Upper limit temperature of nematic phase (NI;. degree. C.): the sample was placed on a hot plate of a melting point measuring apparatus equipped with a polarizing microscope, and heated at a rate of 1 ℃/min. The temperature at which a portion of the sample changes from a nematic phase to an isotropic liquid is measured. The upper limit temperature of the nematic phase is sometimes abbreviated as "upper limit temperature".

(2) Lower limit temperature (T) of nematic phase_C(ii) a C): the nematic phase was observed after placing the sample in a glass bottle and keeping the bottle in a freezer at 0 ℃, -10 ℃, -20 ℃, -30 ℃ and-40 ℃ for 10 days. For example, when the sample is kept in a nematic phase at-20 ℃ and changes to a crystalline or smectic phase at-30 ℃, it is described as T_C<-20 ℃. Further, the method is sometimes used to determine the lower limit temperature of the smectic phase.

(3) Viscosity (. eta.; measured at 20 ℃ C.; mPas): for the measurement, an E-type rotational viscometer manufactured by tokyo counter gmbh was used.

(4) Viscosity (rotational viscosity; γ 1; measured at 25 ℃; mPas): the measurement was carried out according to the method described in Molecular Crystals and Liquid Crystals (Molecular Crystals and Liquid Crystals), vol.259,37(1995) of M.J. well (M.Imai) et al. A sample was placed in a TN cell having a twist angle of 0 ℃ and a gap (cell gap) of 5 μm between two glass substrates. In the range of 16V to 19.5V, a voltage is applied to the element in stages in units of 0.5V. After 0.2 second of no voltage application, voltage application was repeated under the condition of applying only 1 square wave (square pulse; 0.2 second) and not applying (2 seconds). The peak current (peak current) and peak time (peak time) of the transient current (transient current) generated by the application are measured. The values of rotational viscosity were obtained from these measured values and the calculation formula (10) described on page 40 in the article by M. The value of the dielectric anisotropy required for the calculation was determined by the following method using an element for measuring the rotational viscosity.

(5) Optical anisotropy (refractive index anisotropy; Δ n; measured at 25 ℃): the measurement was performed by an Abbe refractometer having a polarizer attached to an eyepiece lens, using light having a wavelength of 589 nm. After rubbing the surface of the primary prism in one direction, the sample was dropped onto the primary prism. The refractive index n/is measured when the direction of polarization is parallel to the direction of rubbing. The refractive index n ″) is measured when the direction of the polarized light is perpendicular to the direction of the friction. The value of the optical anisotropy is calculated from the formula Δ n ═ n/n ″.

(6) Dielectric anisotropy (. DELTA.; measured at 25 ℃): a sample was placed in a TN cell having a cell gap of 9 μm and a twist angle of 80 degrees between two glass substrates. A sine wave (10V, 1kHz) was applied to the element, and the dielectric constant (/) in the long axis direction of the liquid crystal molecules was measured after 2 seconds. Sine wave (0.5V, 1kHz) was applied to the element, and the dielectric constant (#) in the short axis direction of the liquid crystal molecules was measured after 2 seconds. The value of the dielectric anisotropy is calculated according to the formula Δ ═/.

(7) Threshold voltage (Vth; measured at 25 ℃; V): for measurement, a luminance meter model LCD5100 manufactured by tsukamur electronics gmbh was used. The light source is a halogen lamp. A sample was placed in a TN element of normally white mode (normal white mode) in which the spacing (cell gap) between two glass substrates was 0.45/. DELTA.n (μm) and the twist angle was 80 degrees. The voltage (32Hz, square wave) applied to the element was increased from 0V to 10V in a stepwise manner in units of 0.02V. At this time, the element was irradiated with light from the vertical direction, and the amount of light transmitted through the element was measured. A voltage-transmittance curve was prepared in which the transmittance was 100% when the light amount reached the maximum and the transmittance was 0% when the light amount was the minimum. The threshold voltage is represented by a voltage at which the transmittance becomes 90%.

(8) Voltage holding ratio (VHR-9; measured at 25;%): the TN element used for the measurement had a polyimide alignment film, and the interval (cell gap) between the two glass substrates was 5 μm. The element is sealed with an adhesive hardened by ultraviolet rays after the sample is put in. The TN cell was charged by applying a pulse voltage (1V, 60 μ sec). The decayed voltage was measured by a high-speed voltmeter for 166.7 milliseconds, and the area a between the voltage curve per unit cycle and the horizontal axis was determined. The area B is the area when not attenuated. The voltage holding ratio is expressed by a percentage of the area a to the area B.

(9) Voltage holding ratio (VHR-10; measured at 60;%): the voltage holding ratio was measured in the same procedure as described except that the measurement was performed at 60 ℃ instead of 25 ℃. The obtained value is represented by VHR-10.

(10) Voltage holding ratio (VHR-11; measured at 60;%): after irradiation with ultraviolet light, the voltage holding ratio was measured to evaluate the stability to ultraviolet light. The TN cells used for the measurement had a polyimide alignment film and a cell gap of 5 μm. The sample was injected into the cell and irradiated with 5mW/cm²Ultraviolet ray of (1) for 167 minutes. The light source was black light (black light) manufactured by Kawasaki (EYEGRAPHICS) Inc., F40T10/BL (peak wavelength of 369nm), and the distance between the element and the light source was 5 mm. In the measurement of VHR-11, the voltage at which the voltage decayed was measured for 166.7 milliseconds. Compositions with large VHR-11 have a large stability to UV light.

(11) Voltage holding ratio (VHR-12; measured at 60;%): the TN cells impregnated with the samples were heated in a thermostatic bath at 120 ℃ for 20 hours, and then the voltage holding ratio was measured to evaluate the stability to heat. In the measurement of VHR-12, the voltage at which the voltage decayed was measured for 166.7 milliseconds. Compositions with large VHR-12 have a large stability to heat.

(12) Voltage holding ratio (VHR-13; measured at 60;%): the TN elements impregnated with the samples were heated in a thermostat at 100 ℃ for three weeks, and then the voltage holding ratio was measured to evaluate the stability to heat. In the measurement of VHR-13, the voltage at which the voltage decayed was measured for 166.7 milliseconds. Compositions with large VHR-13 have a large stability to heat.

(13a) Response time (. tau.a; measured at 25 ℃ C.; ms): for measurement, a luminance meter model LCD5100 manufactured by tsukamur electronics gmbh was used. The light source is a halogen lamp. The Low pass filter (Low-pass filter) was set to 5 kHz. The sample was placed in a TN element of normally white mode (normal white mode) in which the gap between two glass substrates (cell gap) was 3.4 μm and the twist angle was 80 degrees. A square wave (60Hz, 5V, 0.5 sec) was applied to the element. At this time, the element was irradiated with light from the vertical direction, and the amount of light transmitted through the element was measured. The transmittance was regarded as 100% when the amount of light reached the maximum, and 0% when the amount of light was the minimum. The rise time (τ r: rise time; millisecond) is the time required for the transmittance to change from 90% to 10%. The fall time (τ f: fall time; milliseconds) is the time required for the transmittance to change from 10% to 90%. The response time is represented by the sum of the rise time and the fall time found in the above manner.

(13b) Response time (. tau.b; measured at-20 ℃ C.; ms): the response time (. tau.b) was obtained in the same procedure as described except that the measurement was carried out at a temperature of-20 ℃ instead of 25 ℃.

(13c) Response time (. tau.c; measured at-30 ℃ C.; ms): the response time (. tau.c) was obtained in the same procedure as described, except that the measurement was carried out at a temperature of-30 ℃ instead of 25 ℃.

(14) Elastic constant (K; measured at 25 ℃ C.; pN): for the measurement, an LCR meter model HP4284A manufactured by Yokogawa Hewlett packard, Ltd was used. A sample was placed in a horizontally oriented cell having a gap (cell gap) of 20 μm between two glass substrates. A charge of 0 to 20 volts was applied to the element, and the electrostatic capacitance and applied voltage were measured. The values of the electrostatic capacitance (C) and the applied voltage (V) were fitted using the expressions (2.98) and (2.101) in page 75 of Handbook of Liquid Crystal Device (manufactured news), japan), and the values of K11 and K33 were obtained from the expressions (2.99). Next, the values of K11 and K33 obtained immediately before were used in expression (3.18) on page 171 of the "liquid crystal device manual" to calculate K22. The elastic constant is represented by the average value of K11, K22, and K33 obtained as described above.

(15) Specific resistance (. rho.; measured at 25 ℃ C.;. omega. cm): 1.0mL of the sample was injected into a container equipped with an electrode. A DC voltage (10V) was applied to the vessel, and a DC current after 10 seconds was measured. The specific resistance is calculated according to the following equation. (specific resistance) { (voltage) × (capacitance of container) }/{ (direct current) × (dielectric constant of vacuum) }.

(16) Pitch (P; measured at room temperature; μm): the pitch is measured using the wedge method. Refer to page 196 of "liquid Crystal Messaging" (published in 2000, Wanshan). The sample was poured into a wedge-shaped cell, and after standing at room temperature for 2 hours, the spacing (d2-d1) of the disclination lines was observed by polarized light microscope (Nikon (Strand), trade name MM40/60 series). The pitch (P) is calculated from the following equation which expresses the angle of the wedge element as θ. P is 2 × (d2-d1) × tan θ.

(17) Dielectric constant (. DELTA.; measured at 25 ℃) in the minor axis direction: a sample was placed in a TN cell having a cell gap of 9 μm and a twist angle of 80 degrees between two glass substrates. Sine wave (0.5V, 1kHz) was applied to the element, and the dielectric constant (#) in the short axis direction of the liquid crystal molecules was measured after 2 seconds.

The following is a method of measuring a sample having negative dielectric anisotropy.

(18) Viscosity (rotational viscosity; γ 1; measured at 25 ℃; mPas): for the measurement, a rotational viscosity ratio measuring system LCM-2 of Toyo technology (TOYOTechnica) Co., Ltd was used. A VA device having a gap (cell gap) of 10 μm between two glass substrates was used as a sample. A rectangular wave (55V, 1ms) was applied to the element. The peak current (peak current) and peak time (peak time) of the transient current (transient current) generated by the application are measured. The values of rotational viscosity were obtained using these measured values and dielectric anisotropy. The dielectric anisotropy was measured by the method described in measurement (6).

(19) Dielectric anisotropy (. DELTA.; measured at 25 ℃): the value of the dielectric anisotropy is calculated according to the formula Δ ═/. The dielectric constant (/ and ≠ T) was measured as follows.

1) Determination of dielectric constant (/): a solution of octadecyltriethoxysilane (0.16mL) in ethanol (20mL) was coated on the well-cleaned glass substrate. The glass substrate was rotated by a rotator and then heated at 150 ℃ for 1 hour. A VA cell having a gap (cell gap) of 4 μm between two glass substrates was loaded with a sample, and the cell was sealed with an adhesive cured by ultraviolet light. A sine wave (0.5V, 1kHz) was applied to the cell, and the dielectric constant (/) in the long axis direction of the liquid crystal molecules was measured after 2 seconds.

2) Determination of dielectric constant (. DELTA.): the polyimide solution was coated on the well-cleaned glass substrate. After the glass substrate is fired, the obtained alignment film is subjected to rubbing treatment. A sample was placed in a TN cell having a cell gap of 9 μm and a twist angle of 80 degrees between two glass substrates. Sine wave (0.5V, 1kHz) was applied to the element, and the dielectric constant (#) in the short axis direction of the liquid crystal molecules was measured after 2 seconds.

(20) Threshold voltage (Vth; measured at 25 ℃; V): for measurement, a luminance meter model LCD5100 manufactured by tsukamur electronics gmbh was used. The light source is a halogen lamp. A VA element of a normally black mode (normal black mode) in which the interval (cell gap) between two glass substrates was 4 μm and the rubbing directions were antiparallel was loaded with a sample, and the element was sealed using an adhesive hardened by ultraviolet rays. The voltage applied to the element (60Hz, square wave) was increased from 0V to 20V in a stepwise manner in units of 0.02V. At this time, the element was irradiated with light from the vertical direction, and the amount of light transmitted through the element was measured. A voltage-transmittance curve was prepared in which the transmittance was 100% when the light amount reached the maximum and the transmittance was 0% when the light amount was the minimum. The threshold voltage is represented by a voltage at which the transmittance becomes 10%.

(21a) Response time (. tau.; measured at 25 ℃ C.; ms): for measurement, a luminance meter model LCD5100 manufactured by tsukamur electronics gmbh was used. The light source is a halogen lamp. The Low pass filter (Low-pass filter) was set to 5 kHz.

1) Composition containing no polymerizable compound: the sample was placed in a VA element of a normally black mode (normal black mode) in which the interval (cell gap) between two glass substrates was 4 μm and the rubbing directions were antiparallel. The element is sealed using an adhesive hardened by ultraviolet rays. A square wave (60Hz, 10V, 0.5 sec) was applied to the element. At this time, the element was irradiated with light from the vertical direction, and the amount of light transmitted through the element was measured. The transmittance was regarded as 100% when the amount of light reached the maximum, and 0% when the amount of light was the minimum. The response time is represented by the time (fall time; millisecond) required for the transmittance to change from 90% to 10%.

(21b) Response time (. tau.b; measured at-20 ℃ C.; ms): the response time (. tau.b) was obtained in the same procedure as described except that the measurement was carried out at a temperature of-20 ℃ instead of 25 ℃.

(21c) Response time (. tau.c; measured at-30 ℃ C.; ms): the response time (. tau.c) was obtained in the same procedure as described, except that the measurement was carried out at a temperature of-30 ℃ instead of 25 ℃.

2) Composition containing polymerizable compound: the sample was placed in a Patterned Vertical Alignment (PVA) cell of a normally black mode (normal black mode) in which the interval (cell gap) between two glass substrates was 3.2 μm and the rubbing direction was antiparallel. The element is sealed using an adhesive hardened by ultraviolet rays. The element was irradiated with 60mW/cm while applying a voltage of 15V²Ultraviolet light of (1) for 500 seconds. When ultraviolet light was irradiated, an EXECURE4000-D mercury xenon lamp manufactured by HOYA CANDEO OPTRONICS GmbH was used. A square wave (60Hz, 10V, 0.5 sec) was applied to the element. At this time, the element was irradiated with light from the vertical direction, and the amount of light transmitted through the element was measured. The transmittance was regarded as 100% when the amount of light reached the maximum, and 0% when the amount of light was the minimum. The response time is represented by the time (fall time; millisecond) required for the transmittance to change from 90% to 10%.

(22) Elastic constant (K11: splay (splay) elastic constant, K33: bend (bend) elastic constant; measured at 25 ℃; pN): for the measurement, an EC-1 elastic constant measuring instrument manufactured by TOYO technical Co., Ltd was used. A sample was placed in a vertical alignment cell having a gap (cell gap) of 20 μm between two glass substrates. A charge of 20 to 0V was applied to the cell, and the electrostatic capacitance and applied voltage were measured. The values of the measured electrostatic capacitance (C) and the applied voltage (V) were fitted using the equations (2.98) and (2.101) on page 75 of the handbook of liquid crystal devices (journal industries, press), and the value of the elastic constant was obtained from the equation (2.100).

Examples of compositions are shown below. The component compounds are represented by symbols based on the definitions in table 3 below. In Table 3, the configuration of the 1, 4-cyclohexylene group-related solid is trans configuration. The numbers in parentheses following the marked compounds indicate the chemical formula to which the compound belongs. The symbol (-) indicates other liquid crystalline compounds. Finally, the values of the properties of the composition are summarized.

TABLE 3 formulation of Compounds Using symbols

R-(A₁)-Z₁-·····-Z_n-(A_n)-R’

[ example 1]

The following composition (M1) was prepared. The response time (. tau.a) of the composition at 25 ℃ was measured in accordance with measurement (13a) and found to be 23.2 msec. The nematic phase is maintained while the composition is stored at 0 ℃ according to the measurement (2). The composition is converted to the smectic phase at-10 ℃. Thus, the smectic-nematic transition temperature is between 0 ℃ and-10 ℃. The smectic phase was also maintained when stored at-40 ℃. The temperature range of the smectic phase is 30 degrees or more. The response time (. tau.b) measured at-20 ℃ and the response time (. tau.c) measured at-30 ℃ were 156.1ms and 304.3ms, respectively.

Composition (M1)

NI＝105.0℃；Δ＝3.8；γ1＝65.0mPa·s；τa＝23.2ms；τb＝156.1ms；τc＝304.3ms.

Comparative example 1

The following composition (C1) was prepared. The response time (. tau.a) of the composition at 25 ℃ was measured in accordance with measurement (13a) and found to be 23.0 msec. The nematic phase was maintained while the composition was stored at-40 ℃ according to the measurement (2). The response time (. tau.b) measured at-20 ℃ and the response time (. tau.c) measured at-30 ℃ were 172.3ms and 378.5ms, respectively.

Composition (C1)

NI＝99.6℃；η＝12.1mPa·s；Δn＝0.118；Δ＝3.3；Vth＝2.44V；γ1＝62.0mPa·s；τa＝23.0ms；τb＝172.3ms；τc＝378.5ms.

The characteristics of example 1 and comparative example 1 are summarized in Table 4. The response time of composition (M1) measured at 25 ℃ was of the same extent as that of composition (C1). However, at low temperatures, composition (M1) had a shorter response time than composition (C1).

TABLE 4 comparison of response times at Low temperatures

The response time tends to depend on the upper limit temperature or the dielectric anisotropy. The difference between the upper limit temperatures of the composition (M1) and the composition (C1) was 5.4 ℃. The liquid crystal composition has the following orientations: the response time (measured at 25 ℃) becomes longer as its upper temperature becomes higher. Therefore, the composition (M1) is disadvantageous in view of the upper limit temperature. The difference in dielectric anisotropy was 0.5. The liquid crystal composition has the following orientations: as its dielectric anisotropy becomes larger, the response time (measured at 25 ℃) becomes longer. Therefore, the composition (M1) is also disadvantageous from the viewpoint of dielectric anisotropy.

Surprisingly: although being a disadvantageous condition for composition (M1) compared to composition (C1), composition (M1) had a shorter response time at low temperatures compared to composition (C1). We conclude that a liquid crystal composition having a smectic phase, such as that of example 1, can be suitably used in a liquid crystal cell.

[ industrial applicability ]

The liquid crystal composition of the present invention can be used in liquid crystal monitors, liquid crystal televisions, and the like.

Claims

1. A liquid crystal composition having a smectic-nematic transition temperature of less than 0 ℃.

2. The liquid crystal composition of claim 1, wherein the smectic phase is exhibited at-20 ℃.

3. The liquid crystal composition according to claim 1, which contains a compound having a smectic phase.

4. The liquid crystal composition according to claim 1, which contains at least one compound selected from the group consisting of compounds represented by formula (1) as component a:

5. The liquid crystal composition according to claim 4, which contains 40% or more of the following compounds: in the formula (1), R¹And R²Is alkyl of carbon number 1 to 12 or alkenyl of carbon number 2 to 12; ring A and ring B are 1, 4-phenylene, 2-fluoro-1, 4-phenylene or 2, 5-difluoro-1, 4-phenylene; z¹Is a single bond; a is 2.

6. The liquid crystal composition according to claim 1, which contains at least one compound selected from the group consisting of compounds represented by formulae (1-1) to (1-9) as component a:

7. The liquid crystal composition according to claim 4, wherein the proportion of the component A is in the range of 10% to 90%.

8. The liquid crystal composition according to claim 1, which contains 50% or more of 3-HH-V:

9. the liquid crystal composition according to claim 1, which contains at least one compound selected from the compounds represented by formula (2) as component B:

in the formula (2), R³Is alkyl group with carbon number of 1 to 12, alkoxy group with carbon number of 1 to 12 or alkenyl group with carbon number of 2 to 12; ring C is 1, 4-cyclohexylene, 1, 4-phenylene, 2-fluoro-1, 4-phenylene, 2, 3-difluoro-1, 4-phenylene, 2, 6-difluoro-1, 4-phenylene, pyrimidine-2, 5-diyl, 1, 3-dioxane-2, 5-diyl or tetrahydropyran-2, 5-diyl; z²Is a single bond, ethylene, vinylene, methyleneoxy, carbonyloxy or difluoromethyleneoxy; x¹And X²Is hydrogen or fluorine; y is¹Is fluorine, at least one hydrogen being substituted by fluorineAn alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms wherein at least one hydrogen is substituted with fluorine, or an alkenyloxy group having 2 to 12 carbon atoms wherein at least one hydrogen is substituted with fluorine; b is 1,2, 3 or 4.

10. The liquid crystal composition according to claim 1, which contains at least one compound selected from the group consisting of compounds represented by formulae (2-1) to (2-36) as the component B:

11. The liquid crystal composition according to claim 9, wherein the proportion of the component B is in the range of 10% to 90%.

12. The liquid crystal composition according to claim 1, which contains at least one compound selected from the compounds represented by formula (3) as component C:

in the formula (3), R⁴And R⁵Is hydrogen, alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms, alkenyl group having 2 to 12 carbon atoms or alkenyloxy group having 2 to 12 carbon atoms; ring D andring F is 1, 4-cyclohexylene, 1, 4-cyclohexenylene, tetrahydropyran-2, 5-diyl, 1, 4-phenylene in which at least one hydrogen is substituted by fluorine, naphthalene-2, 6-diyl in which at least one hydrogen is substituted by fluorine, chromane-2, 6-diyl or chromane-2, 6-diyl in which at least one hydrogen is substituted by fluorine; ring E is 2, 3-difluoro-1, 4-phenylene, 2-chloro-3-fluoro-1, 4-phenylene, 2, 3-difluoro-5-methyl-1, 4-phenylene, 3,4, 5-trifluoronaphthalene-2, 6-diyl, 7, 8-difluorochromane-2, 6-diyl, 3,4,5, 6-tetrafluorofluorene-2, 7-diyl, 4, 6-difluorodibenzofuran-3, 7-diyl, 4, 6-difluorodibenzothiophene-3, 7-diyl, or 1,1,6, 7-tetrafluoroindan-2, 5-diyl; z³And Z⁴Is a single bond, ethylene, vinylidene, methyleneoxy or carbonyloxy; c is 0, 1,2 or 3, d is 0 or 1, and the sum of c and d is 3 or less.

13. The liquid crystal composition according to claim 1, which contains at least one compound selected from the group consisting of compounds represented by formulae (3-1) to (3-33) as component C:

14. The liquid crystal composition according to claim 12, wherein the proportion of the component C is in the range of 10% to 90%.

15. The liquid crystal composition according to claim 1, which contains at least one compound selected from polymerizable compounds represented by formula (4) as an additive a:

in the formula (4), the ring J and the ring L are cyclohexyl, cyclohexenyl, phenyl, 1-naphthyl, 2-naphthyl, tetrahydropyran-2-yl, 1, 3-dioxane-2-yl, pyrimidin-2-yl or pyridin-2-yl, and in these rings, at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine; ring K is 1, 4-cyclohexylene, 1, 4-cyclohexenylene, 1, 4-phenylene, naphthalene-1, 2-diyl, naphthalene-1, 3-diyl, naphthalene-1, 4-diyl, naphthalene-1, 5-diyl, naphthalene-1, 6-diyl, naphthalene-1, 7-diyl, naphthalene-1, 8-diyl, naphthalene-2, 3-diyl, naphthalene-2, 6-diyl, naphthalene-2, 7-diyl, tetrahydropyran-2, 5-diyl, 1, 3-dioxane-2, 5-diyl, pyrimidine-2, 5-diyl or pyridine-2, 5-diyl, in these rings, at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine; z⁵And Z⁶Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -CO-, -COO-or-OCO-, at least one-CH₂CH₂-may be via-CH ═ CH-, -C (CH)₃)＝CH-、-CH＝C(CH₃) -or-C (CH)₃)＝C(CH₃) -substitution, of which at least one hydrogen may be substituted by fluorine; p¹、P²And P³Is a polymerizable group; sp¹、Sp²And Sp³Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂-may be substituted by-O-, -COO-or-OCO-, at least one-CH₂CH₂-may be substituted by-CH ═ CH-or-C ≡ C-, in which groups at least one hydrogen may be substituted by fluorine; f is 0, 1 or 2; g. h and j are 0, 1,2, 3 or 4, and the sum of g, h and j is 1 or more.

16. The liquid crystal composition according to claim 15, wherein in formula (4),ring J and ring L are cyclohexyl, phenyl, 1-naphthyl or 2-naphthyl, in which at least one hydrogen may be substituted by fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine; ring K is 1, 4-cyclohexylene, 1, 4-phenylene, naphthalene-1, 2-diyl or naphthalene-2, 6-diyl, in which at least one hydrogen may be substituted with fluorine, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted with fluorine; z⁵And Z⁶Is a single bond or an alkylene group having 1 to 10 carbon atoms, in which at least one-CH group₂May be substituted by-O-, -CO-, -COO-or-OCO-, and at least one-CH₂CH₂-may be substituted by-CH ═ CH-, where at least one hydrogen may be substituted by fluorine; p¹、P²And P³Is a group selected from the polymerizable groups represented by the formulae (P-1) to (P-5):

17. The liquid crystal composition according to claim 1, which contains at least one compound selected from polymerizable compounds represented by formulae (4-1) to (4-29) as an additive a:

18. The liquid crystal composition according to claim 15, wherein the proportion of additive a is in the range of 0.03% to 10%.

19. The liquid crystal composition according to claim 1, wherein the proportion of the compound represented by formula (1a) is in the range of 0% to 3%,

20. A liquid crystal display element comprising the liquid crystal composition according to claim 1.