JPH0959631A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display comprising a pair of transparent base plates and a liquid crystal layer comprising a specified nematic liquid crystal composition and sandwiched between the plates and being useful as an electrooptical display material. SOLUTION: This liquid crystal display comprises a pair of base plates at least either of which is transparent and a liquid crystal layer sandwiched between the plates, wherein the liquid crystal layer comprises a liquid crystal composition being a nematic state and containing a compound of a cyclic enone structure. The compound of a cyclic neon structure is desirably a compound represented by the formula (wherein R<1> is an atomic group having a cyclic structure and substituted by a cyclic group having a long-chain hydrocarbon group; R<2> to R<4> are each H, F or a substituent having at least one carbon atom). R<1> in the formula is desirably an atomic group having a cyclic structure having at least one double bonds.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art In conventional liquid crystal display devices, there are many liquid crystal compositions containing a compound having a cyano group such as PCH (phenylcyclohexane) as an electron-withdrawing substituent as a compound having a high dielectric anisotropy. It is used.

[0003]

A liquid crystal composition having a high dielectric anisotropy is required to reduce the driving voltage of a liquid crystal display device. In a conventional liquid crystal display device, in order to realize this high dielectric anisotropy, a liquid crystal compound having a strong electron-withdrawing substituent such as a cyano group is added to a liquid crystal composition. However, the compound containing a cyano group is likely to contain impurities, and it is difficult to improve the purity by refining, which causes a decrease in the voltage holding ratio of the liquid crystal material and a deterioration in display quality such as afterimage and image sticking. In particular, this problem is large in an active matrix type liquid crystal display element. Further, a compound containing a cyano group may generate a toxic substance when decomposed, which is not preferable in terms of environmental protection and safety.

An object of the present invention is to provide a liquid crystal display device using a liquid crystal material which can be driven at a low voltage, has excellent display quality, and is highly safe.

[0005]

According to the liquid crystal display device of the present invention, the liquid crystal layer has a nematic state, and the liquid crystal composition contains a compound having a cyclic enone structure. It is desirable that the liquid crystal layer has a positive dielectric anisotropy.

A typical compound having this cyclic enone structure is a compound represented by the following formula [1].

[0007]

Embedded image

However, R1 is an atomic group having a cyclic structure, and R2, R3 and R4 are either hydrogen atoms, fluorine atoms or substituents containing at least one carbon atom. Examples of the atomic group having this cyclic structure include saturated hydrocarbon rings such as cyclohexane ring and cyclopentane ring, saturated heterocycles such as piperidine ring and thiolane ring, benzene ring, naphthalene ring, pyrrole ring, furan ring and pyrimidine ring. An aromatic ring, or a saturated hydrocarbon ring, an unsaturated hydrocarbon ring having at least one double bond in a saturated heterocycle,
An atomic group such as an unsaturated heterocycle may be mentioned. Particularly preferred is a cyclohexane ring, a cyclohexene ring, a cyclohexadiene ring, a benzene ring, a biphenyl ring, or a combination of two or more thereof.

As the compound having a cyclic enone structure, compounds represented by the following formulas [2] and [3] may be used.

[0010]

Embedded image

However, R1 is an atomic group having a 6-membered ring structure and having at least one double bond, and R2, R3, and R4 are either hydrogen atoms, fluorine atoms, or substituents containing at least one carbon atom. is there.

[0012]

[Chemical 6]

However, R1 is a phenyl ring or biphenyl ring having a long-chain alkyl group or alkoxyl group at the para position, and R2, R3 and R4 are either hydrogen atoms or alkyl groups.

An example of a compound having a cyclic enone structure used in the liquid crystal display device of the present invention is shown in FIG.

The inventors synthesized compounds having a cyclic enone structure and prepared a liquid crystal composition containing them.
As a result of the measurement, it was found that this liquid crystal composition had a high dielectric anisotropy sufficient for driving at a low voltage. Further, it has been found that a liquid crystal display device using this liquid crystal composition has a high display quality at the same time as driving at a low voltage.

In the compound having a cyclic enone structure contained in the liquid crystal composition used in the liquid crystal display device of the present invention, the conjugated structure of oxygen atom and double bond in the cyclic enone structure shown in FIG. 2 effectively acts. It has a high dielectric anisotropy.

Further, this compound is relatively easy to be highly purified by purification, and excellent display quality with less afterimage can be obtained. In terms of safety, this compound is extremely unlikely to release a toxic substance upon decomposition. Therefore, the liquid crystal display device using the liquid crystal composition containing the compound having the cyclic enone structure in the molecule can be driven at a low voltage, exhibits excellent display characteristics, and is excellent in environmental protection and safety.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 Butyllithium (2.5M hexane solution 42
ml) to 4-nonyloxybromobenzene (18.5 g) /
Add to tetrahydrofuran solution at -78 ° C. After stirring for 2 hours, triisopropyl borate (34 m
l) / tetrahydrofuran solution is added. After stirring at room temperature for 10 hours, 150 ml of 10% hydrochloric acid is added and the mixture is stirred for 1 hour. The reaction solution was extracted with diethyl ether, the ether layer was concentrated, and the residue was recrystallized from petroleum ether to give 4-nonyloxyphenylboronic acid (16.9 g, yield 9
2%) was obtained. Triethylamine (1.33 g) and cyclohexane-1,3-dione (1.20 g) were added to a dibromotriphenylphosphorane (5.0 g) / benzene mixed solution, and the mixture was stirred at room temperature for 2 hours. After concentrating the reaction solution,
It was dissolved in diethyl ether, filtered through a silica gel column and then concentrated to give 3-bromo-2-cyclohexen-1-one (1.97 g, yield 97%). 4-Nonoxyphenylboronic acid (4.78 g) / ethanol solution and 3-bromo-2-cyclohexen-1-one (2.7
0 g) and a catalytic amount of tetrakis (triphenylphosphine) palladium in benzene were mixed with an aqueous solution of sodium carbonate, and the mixture was stirred for 24 hours while heating under reflux. The reaction solution was extracted with diethyl ether and the ether layer was concentrated,
The residue was purified by silica gel chromatography and recrystallized from petroleum ether to give 3- (4-nonyloxyphenyl) -2-cyclohexen-1-one (4.25).
g, yield 92%).

The fact that the above compound is synthesized can be seen from the following NMR spectrum and elemental analysis results.

¹ H-NMR (CDCl ₃ ); 7.44 (2
H, d), 6.83 (2H, d), 6.33 (1H,
m), 3.93 (2H, t), 2.67 (2H, d),
2.38 (2H, m), 2.17 (2H, q), 1.72
(2H, m), 1.45-1.16 (12H, m), 0.0.
82 (3H, t) Elemental analysis; C, 80.20%; H, 9.82% (calculated value C, 80.21%; H, 9.62%) The synthesized compound was a nematic liquid crystal composition manufactured by Merck & Co., Inc. Z
9.1 wt% was added to LI-4792, and the dielectric anisotropy was measured. The measurement temperature is (the temperature at which the liquid crystal composition is in an isotropic phase;
Tc)-(measured temperature; T) = 40 ° C. and 20 ° C. As a result of the measurement, Tc-T of ZLI-4792 = 40 ° C.
And the dielectric constant anisotropy at 20 ° C. are 3.57 and 2.63, respectively, whereas the dielectric anisotropy of the composition containing the compound is 3.90 and 2.97, respectively, which are clearly different from each other. It turned out that the direction was rising.

Next, ZLI-4792 and ZLI-4792
As shown in FIG. 3, S811 manufactured by Merck Ltd. was added as an optical rotatory substance to the liquid crystal composition containing 9.1% by weight of 3- (4-nonyloxyphenyl) -2-cyclohexen-1-one synthesized in Example 1. It was enclosed in an active matrix type liquid crystal display device. Here, the common electrode 5 is provided on the upper substrate 1.
And a pixel electrode 6 connected to the TFT is formed on the lower substrate 1. Further, a protective film 7 is formed on the pixel electrode. The TFT comprises a source / drain electrode 11, a gate electrode 8, a gate insulating film 9, and a semiconductor layer formed on the gate insulating film. A common voltage supply circuit 12 and a scanning voltage / signal supply circuit 13 are connected to the common electrode, source and drain electrodes, respectively, and these are connected to a control / data signal and power supply voltage supply source 14. An alignment film 2 is further formed on these substrates, and a liquid crystal layer 3 is sandwiched between them. Further, the liquid crystal cell thus configured is sandwiched between the polarizing plates 4.

This liquid crystal display device was driven by a drive circuit and the drive voltages were compared. As a result, the liquid crystal is ZLI-
The driving voltage of the liquid crystal display device in which the liquid crystal composition containing 3- (4-nonyloxyphenyl) -2-cyclohexen-1-one was encapsulated was reduced by about 4% as compared with the case of 4792 alone.

Example 2 Triethylamine (1.11)
g), 5,5-dimethyl-1,3-cyclohexanedione (1.40 g) and dibromotriphenylphosphorane (4.64 g) were used and 3-bromo-5,5-dimethyl was prepared in the same manner as in Example 1. -2-Cyclohexene-
1-one (1.57 g, 77% yield) was obtained. Using 4-nonyloxyphenylboronic acid (1.92 g), 3-bromo-5,5-dimethyl-2-cyclohexen-1-one (1.20 g) and a catalytic amount of tetrakis (triphenylphosphine) palladium In the same manner as in Example 1, 3- (4-nonoxyphenyl) -5,5-dimethyl-
2-Cyclohexen-1-one was obtained (1.99 g, yield 98%).

The fact that the above compound has been synthesized can be seen from the following NMR spectrum results.

¹ H-NMR (CDCl ₃ ); 7.56 (2
H, d), 6.92 (2H, d), 6.38 (1H,
m), 3.98 (2H, t), 2.61 (2H, d),
2.30 (2H, s), 1.76 (2H, q), 1.51
-1.25 (12H, m), 1.12 (6H, s), 0.9
1 (3H, t) The synthesized compound was added to ZLI-4792 in an amount of 9.2% by weight, and the dielectric anisotropy was measured by the same method as described in Example 1. As a result, T of the composition containing the compound
The dielectric anisotropies at c-T = 40 ° C. and 20 ° C. are 4.58 and 3.35, respectively, which clearly indicates that the dielectric anisotropy is increased.

Next, ZLI-4792 and ZLI-4792
3- (4-nonyloxyphenyl) -5,5-synthesized in
A liquid crystal composition containing 9.2% by weight of dimethyl-2-cyclohexen-1-one was added in the same manner as in Example 1,
When driving and comparing the driving voltage of the liquid crystal display device, the driving voltage was reduced by about 13%.

Example 3 Butyllithium (34.2 m
l), 4-decyloxybromobenzene (19.1 g) and triisopropyl borate (28.2 ml) were used in the same manner as in Example 1 to obtain 4-decyloxyphenylboronic acid (16.9 g). . Triethylamine (0.5
7 g), cyclopentane-1,3-dione (0.50)
g), dibromotriphenylphosphorane (2.34)
g) was used in the same manner as in Example 1 to obtain 3-bromo-
2-Cyclopenten-1-one (0.76 g, yield 96)
%) Was obtained. 4-decyloxyphenylboronic acid (0.48 g) and 3-bromo-2-cyclopentene-1
3- (4-decyloxyphenyl) -2-cyclopenten-1-one was obtained in the same manner as in Example 1 by using -one (0.22 g) and a catalytic amount of tetrakis (triphenylphosphine) palladium. (0.41 g, 97% yield).

The fact that the above compound has been synthesized can be seen from the following NMR spectrum results.

¹ H-NMR (CDCl ₃ ); 7.50 (2
H, d), 6.83 (2H, d), 6.35 (1H,
t), 3.90 (2H, t), 2.87 (2H, m),
2.42 (2H, m), 1.71 (2H, q), 1.45
-1.13 (14H, m), 0.81 (3H, t) 10% by weight of the synthesized compound was added to ZLI-4792, and the dielectric anisotropy was adjusted by the same method as that described in Example 1. It was measured. As a result, the Tc of the composition containing the compound was
The dielectric anisotropies at −T = 40 ° C. and 20 ° C. were 4.78 and 3.75, respectively, and it was found that the dielectric anisotropy was clearly increased.

Next, ZLI-4792 and ZLI-4792
The liquid crystal composition containing 10% by weight of 3- (4-decyloxyphenyl) -2-cyclopenten-1-one synthesized in Example 1 was filled and driven in the same manner as in Example 1, and the driving voltage of the liquid crystal display device was changed. As a result of comparison, the driving voltage was reduced by about 16%.

Example 4 Butyllithium (42 m
l), 4-octyloxybromobenzene (17.7 g),
4-Octyloxyphenylboronic acid (16.8 g, yield 95%) was obtained by the same method as in Example 1 using triisopropyl borate (34 ml). Triethylamine (1.29 g), 2-methylcyclopentane-1,
Using 3-dione (1.30 g) and dibromotriphenylphosphorane (5.38 g) in the same manner as in Example 1, 3-bromo-2-methyl-2-cyclopenten-1-one (1.67 g, Yield 82%) was obtained. 4-octyloxyphenylboronic acid (0.86g) and 3
-Bromo-2-methyl-2-cyclopenten-1-one
(0.46 g) and a catalytic amount of tetrakis (triphenylphosphine) palladium in the same manner as in Example 1, 3- (4-octyloxyphenyl) -2-methyl-2-
Cyclopenten-1-one was obtained (0.76 g, yield 9
6%).

The fact that the above compound has been synthesized can be seen from the following NMR spectrum results.

¹ H-NMR (CDCl ₃ ); 7.53 (2
H, d), 6.896 (2H, d), 4.00 (2H,
t), 2.89 (2H, m), 2.51 (2H, m),
1.98 (3H, t), 1.80 (2H, q), 1.50
-1.26 (10H, m), 0.89 (3H, t) 10% by weight of the synthesized compound was added to ZLI-4792, and the dielectric anisotropy was adjusted in the same manner as in Example 1. It was measured. As a result, the Tc of the composition containing the compound was
The dielectric anisotropies at −T = 40 ° C. and 20 ° C. were 4.93 and 3.65, respectively, indicating that the dielectric anisotropy was clearly increased.

Next, ZLI-4792 and ZLI-4792
The liquid crystal composition obtained by adding 10% by weight of 3- (4-octyloxyphenyl) -2-methyl-2-cyclopenten-1-one synthesized in Example 1 was filled and driven in the same manner as in Example 1 to obtain a liquid crystal display device. Comparing the driving voltages of the above, the driving voltage was reduced by about 17%.

Example 5 4-decyloxyphenylboronic acid (1.18 g), 3-bromo-2-methyl-2-cyclopenten-1-one (0.57 g) and a catalytic amount of tetrakis (triphenyl) Phosphine) palladium was used to obtain 3- (4-decyloxyphenyl) -2-methyl-2-cyclopenten-1-one in the same manner as in Example 1 (1.00 g, yield 93%).

It can be seen from the results of the following NMR spectra that the above compound has been synthesized.

¹ H-NMR (CDCl ₃ ); 7.44 (2
H, d), 7.38 (2H, d), 3.93 (2H,
t), 2.83 (2H, m), 2.45 (2H, m),
1.94 (3H, t), 1.73 (2H, q), 1.45
-1.12 (10H, m), 0.83 (3H, t) The synthesized compound was added to ZLI-4792 at 10% by weight, and the dielectric anisotropy was adjusted by the same method as that described in Example 1. It was measured. As a result, the Tc of the composition containing the compound was
The dielectric anisotropies at −T = 40 ° C. and 20 ° C. were 4.87 and 3.55, respectively, and it was found that the dielectric anisotropy was clearly increased.

Next, ZLI-4792 and ZLI-4792
The liquid crystal composition containing 10% by weight of 3- (4-decyloxyphenyl) -2-methyl-2-cyclopenten-1-one synthesized in Example 1 was encapsulated and driven in the same manner as in Example 1,
When the driving voltage of the liquid crystal display device was compared, the driving voltage was reduced by about 17%.

Example 6 Butyllithium (17 ml),
4'-decyloxy-4-bromobiphenyl (15 g),
4-Desiloxybiphenylboronic acid was obtained in the same manner as in Example 1 using triisopropyl borate (18.5 ml) (6.8 g). 4-decyloxybiphenylboronic acid (0.57 g) and 3-bromo-2-
Methyl-2-cyclopenten-1-one (0.20 g) and a catalytic amount of tetrakis (triphenylphosphine) palladium were used in the same manner as in Example 1 to obtain 3- (4-decyloxybiphenyl) -2-methyl. 2-Cyclopenten-1-one was obtained (0.68 g, yield 98%).

The fact that the above compound has been synthesized can be seen from the following NMR spectrum results.

¹ H-NMR (CDCl ₃ ); 7.56 (4
H, m), 7.48 (2H, d), 6.93 (2H,
d), 3.94 (2H, t), 2.87 (2H, m),
2.47 (2H, m), 1.96 (3H, t), 1.74
(2H, q), 1.45-1.12 (14H, m), 0.0.
83 (3H, t) The synthesized compound was added to ZLI-4792 at 10.9% by weight, and the dielectric anisotropy was measured in the same manner as in Example 1. As a result, the T of the composition containing the compound was
The dielectric anisotropies at c-T = 40 ° C. and 20 ° C. are 4.30 and 3.08, respectively, which clearly indicates that the dielectric anisotropy is increased.

Next, ZLI-4792 and ZLI-4792
Of 3- (4-decyloxybiphenyl) -2-methyl-2-cyclopenten-1-one synthesized in 10.9 wt%
The added liquid crystal composition was sealed and driven in the same manner as in Example 1, and the driving voltage of the liquid crystal display device was compared. As a result, the driving voltage was reduced by about 10%.

Comparative Example 1 As a comparative example, a PCH-based liquid crystal compound S1115 having a cyano group manufactured by Merck & Co., Inc. was used.
1% by weight was added, and the dielectric anisotropy was measured by the same method as that described in Example 1. As a result, the dielectric anisotropy at Tc-T = 40 ° C. and 20 ° C. of the composition containing S1115 was 4.82 and 3.59, respectively. From these results, the dielectric anisotropy of the compound having a cyclic enone structure used in the liquid crystal display device of the present invention is
It was found that it was almost the same as that of the CH-based liquid crystal compound.

[Embodiment 7] An afterimage generated in a liquid crystal display device depending on whether or not an electric field is applied is applied to a liquid crystal layer by applying a predetermined electric field to the liquid crystal layer.
After applying for a minute, it was evaluated by measuring the time from when the electric field was removed to when the afterimage disappeared visually. For the evaluation, the liquid crystal display device shown in FIG. 3 was used, and as the liquid crystal composition, the compound having the cyclic enone structure described in Examples 1 to 6 and the liquid crystal composition in which S1115 was added to ZLI-4792 were used. As a result of the evaluation of the afterimage, no afterimage was generated in the liquid crystal display device using the liquid crystal composition to which the compound having the cyclic enone structure was added, but the afterimage was observed in the liquid crystal display device using the liquid crystal composition to which S1115 was added. There has occurred.

[0045]

In the liquid crystal display device of the present invention, the compound having a cyclic enone structure contained in the liquid crystal composition has a high dielectric anisotropy, so that it can be driven at a low voltage and, at the same time, has a high afterimage. Has display quality. Furthermore, since a compound having a cyclic enone structure is less likely to release a toxic substance by decomposition, a liquid crystal display device having excellent safety can be provided.

[Brief description of drawings]

FIG. 1 is an example of a compound having a cyclic enone structure used in the liquid crystal display device of the present invention.

FIG. 2 is a schematic diagram showing a conjugated structure of a cyclic enone portion of a compound having a cyclic enone structure used in the liquid crystal display device of the present invention.

FIG. 3 is a liquid crystal display device of the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... Alignment film, 3 ... Liquid crystal layer, 4 ... Polarizing plate, 5 ...
Common electrode, 6 ... Pixel electrode, 7 ... Protective film, 8 ... Gate electrode, 9 ... Gate insulating film, 10 ... Semiconductor layer, 11 ... Source and drain electrode, 12 ... Common voltage supply circuit, 13 ...
Scan voltage / signal supply circuit, 14 ... Control / data signal and power supply source.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Omura 7-1-1 Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Katsumi Kondo 7-chome, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Incorporated company Hitachi Ltd. Hitachi Research Laboratory (72) Inventor David Allen Dummer S 3 7 UK F Sheffield (no address) University of Sheffield (72) Inventor Jane Morel UK S 3 7 HFC Field (no street number) at University of Sheffield

Claims (5)

[Claims] 1. A pair of substrates, at least one of which is transparent, and a liquid crystal layer sandwiched between the substrates, the liquid crystal layer being a nematic liquid crystal composition, wherein the liquid crystal composition has a ring structure. A liquid crystal display device comprising a compound having an enone structure. 2. A liquid crystal display device according to claim 1, wherein the compound having a cyclic enone structure is a compound represented by the formula [1]. Embedded image [However, R1 is an atomic group having a cyclic structure and is substituted with a substituent containing a long-chain hydrocarbon. R2, R3, R4
Is either a hydrogen atom, a fluorine atom or a substituent containing at least one carbon atom. ] 3. The liquid crystal display device according to claim 2, wherein R 1 in the formula [1] is an atomic group having a cyclic structure having at least one double bond. 4. The liquid crystal display device according to claim 1, wherein the compound having a cyclic enone structure is a compound represented by the formula [2]. Embedded image [However, R1 is an atomic group having a 6-membered ring structure and having at least one double bond, and is substituted with a substituent containing a long-chain hydrocarbon. R2, R3 and R4 are each a hydrogen atom, a fluorine atom or a substituent containing at least one carbon atom. ] 5. The liquid crystal display device according to claim 1, wherein the compound having a cyclic enone structure is a compound represented by the formula [3]. Embedded image [However, R1 is a substituent containing a long-chain hydrocarbon. R2, R
3, R4 is either a hydrogen atom or an alkyl group. ]