JP2003342580A - Nematic liquid crystal composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition prevented against the generation of static electricity and decreasing electric voltage-holding rate exhibiting less change with time on making a liquid crystal element from the composition. <P>SOLUTION: This nematic liquid crystal composition contains a polyether compound expressed by following general formula (1): R<SB>1</SB>O(C<SB>2</SB>H<SB>4</SB>O)<SB>n</SB>R<SB>1</SB>[wherein, R<SB>1</SB>'s are each independently a 1-8C alkyl or a 6-18C aryl; and (n) is 4-10 integer], and has ≤30 ppm water content and at least 1.0×10<SP>11</SP>Ωcm specific resistance. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal composition for a display device, and more specifically, it contains a polyether compound having a specific structure and is charged by adjusting the water content and the specific resistance of the liquid crystal composition. The present invention relates to a nematic liquid crystal composition having an excellent prevention effect.

[0002]

2. Description of the Related Art In recent years,
Liquid crystal elements are used in various applications such as watches, calculators, measuring instruments, measuring instruments for automobiles, copying machines, cameras, office automation equipment, and portable personal computers, and the market is expanding rapidly. A liquid crystal composition used for a liquid crystal element is required to have a high specific resistance value. For this reason, when removing the resin film that is the protective film of the liquid crystal element, or when removing the dirt on the liquid crystal element with a cloth or the like, static electricity is easily generated inside and the lighting state is maintained without applying voltage. Therefore, there is a problem that the display does not disappear for a long time.

In order to solve this problem, it has been proposed to add a non-liquid crystal compound such as a surfactant to the liquid crystal composition to reduce the specific resistance value of the liquid crystal composition and obtain an antistatic effect. There is. For example, JP-A-4-180993 and JP-A-11-212070 disclose ethylene glycol dialkyl ethers, JP-A-8-337779 discloses a cyclic amine compound, and JP-A-9-67577 discloses polyoxyalkylene amines. However, none of them has a satisfactory effect.

On the other hand, in applications such as PDAs (Personal Digital Assistants) that require high voltage liquid crystal materials, it is required to reduce the voltage holding ratio to 40 to 85%. For example, the voltage holding ratio can be lowered by adding the antistatic agent as described above, but in that case, there is a drawback that the voltage holding ratio changes with time.

Therefore, an object of the present invention is to provide a liquid crystal composition which can prevent the generation of static electricity and can lower the voltage holding ratio when it is used as a liquid crystal element and has a small change with time. .

[0006]

Means for Solving the Problems As a result of extensive studies, the inventors of the present invention have contained a polyether compound having a specific structure, a water content of 30% by mass or less, and at least 1.0 ×
The inventors have found that the above problems can be solved by using a nematic liquid crystal composition having a specific resistance of 10 ¹¹ Ωcm, and have reached the present invention.

That is, the present invention has been made on the basis of the above findings, and contains a polyether compound represented by the following general formula (I) and has a water content of 30 ppm or less and at least 1.0. A nematic liquid crystal composition having a specific resistance of × 10 ¹¹ Ωcm is provided.

[Chemical 2]

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

In the polyether compound represented by the above general formula (I) according to the present invention, the carbon number represented by R ₁ is 1
~ 8 alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl,
Isobutyl, amyl, isoamyl, tertiary amyl, hexyl, cyclohexyl, heptyl, isoheptyl, tertiary heptyl, n-octyl, isooctyl, tertiary octyl,
2-ethylhexyl is mentioned, and examples of the aryl group having 6 to 18 carbon atoms include phenyl, naphthyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl and 4-
Vinylphenyl, 3-isopropylphenyl, 4-isopropylphenyl, 4-butylphenyl, 4-isobutylphenyl, 4-tert-butylphenyl, 4-hexylphenyl, 4-cyclohexylphenyl, 4-octylphenyl, 4- (2- Ethylhexyl) phenyl, 2,3
-Dimethylphenyl, 2,4-dimethylphenyl, 2,
5-dimethylphenyl, 2,6-dimethylphenyl,
3,4-dimethylphenyl, 3,5-dimethylphenyl, 2,4-di-tert-butylphenyl, 2,5-di-tert-butylphenyl, 2,6-di-tert-butylphenyl, 2,
4-ditertiary pentylphenyl, 2,5-ditertiary pentylphenyl, 2,4-dicumylphenyl, cyclohexylphenyl, biphenyl, 2,4,5-trimethylphenyl and the like are mentioned, and among them, carbon number 1 An alkyl group of 8 to 8 is preferable because it has an excellent antistatic effect.

In the above general formula (I), n is
4 to 10, preferably 4 to 6, especially tetraglyme can be preferably used. Here, when n is larger than 10, the viscosity of the liquid crystal composition increases and the display performance deteriorates, which is not preferable. When n is 1 to 3,
It is not preferable because the vapor pressure becomes large, which may adversely affect the cell filling.

Further, if the content of the above-mentioned polyether compound is less than 0.05% by mass with respect to the liquid crystal composition, a sufficient addition effect may not be obtained, and if it exceeds 10% by mass, display performance may be deteriorated. 0.
05 to 10 mass% is preferable.

The water content of the nematic liquid crystal composition of the present invention is 30 ppm or less, preferably 25 ppm or less. If the water content exceeds 30 ppm, the voltage holding ratio may change significantly, which is not preferable.

The specific resistance of the nematic liquid crystal composition of the present invention is at least 1.0 × 10 ¹¹ Ωcm, preferably 1.0 ×
10 ^{11 to} 1.0 × 10 ¹³ Ωcm and a specific resistance value of 1.
If it is less than 0 × 10 ¹¹ Ωcm, it may cause display unevenness, which is not preferable.

In the nematic liquid crystal composition of the present invention, liquid crystal compounds used in ordinary nematic liquid crystal compositions can be used without limitation, provided that the above-mentioned conditions are satisfied. , Biphenyl, ester, azoxy, cyclohexanecarboxylic acid phenyl ester, phenylcyclohexane, phenylpyrimidine, phenylmetadioxane, cyanobiphenyl, cyanoterphenyl, cyanobiphenylcyclohexane, tolan, ethane, etc. These are used alone or in combination of two or more.

The above liquid crystal compounds can be exemplified by the following general formula (II) or (III).

[0016]

[Chemical 3]

Further specific examples of the above general formula (II) or (III) include the compounds shown below. still,
Y, Y ₁ , Y ₂ and Y ₃ in the following formula are the same as those in the above general formula (II) or (III).

[0018]

[Chemical 4]

[0019]

[Chemical 5]

The liquid crystal composition of the present invention is introduced into a liquid crystal cell by a method such as injection and is sandwiched between substrates with electrodes to form a liquid crystal element. The liquid crystal element is mainly used for display, but is also used for other purposes such as a light control window, an optical shutter and a polarization exchange element. Further, the liquid crystal composition is a TN system, an STN system, a TFT system, a guest-host (GH) system, a dynamic scattering system, a phase change system, a DAP system, a dual frequency drive system, a ferroelectric liquid crystal display system, and two colors. It can be used for a GH type liquid method using a sexual dye.

[0021]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

[Preparation Example of Liquid Crystal Composition] Liquid crystal compositions A to D were prepared by a conventional method according to the following formulation.

[0023]

[Chemical 6]

[0024]

[Chemical 7]

[0025]

[Chemical 8]

[0026]

[Chemical 9]

[Examples 1 to 4 and Comparative Examples 1 to 6] The above liquid crystal compositions A and B, and a liquid crystal composition in which a polyether compound was blended therein were vacuum-injected into a liquid crystal cell with electrodes to obtain a voltage holding ratio. (VHR) was measured. In addition, the characteristic values of the liquid crystal composition were also measured. These results are shown in Table 1.
Shown in.

The voltage holding ratio (VHR) was measured using a voltage holding ratio measuring device (VHR-AMP manufactured by Toyo Technica Ltd.), Pulse width 60 μsec, Aml.
5V, Frame freq 16, 67msec, A
Measurements were performed under the conditions of veraging 1 immediately after the liquid crystal cell was prepared and after the thermal acceleration test at 120 ° C. for 9 hours and 18 hours.

[0029]

[Table 1]

[Examples 5 to 8 and Comparative Examples 7 to 10] The above liquid crystal compositions C and D and the liquid crystal composition prepared by blending a polyether compound therein were sandwiched between substrates with electrodes to form a liquid crystal cell. Charging time (second), current consumption value (μA / cm
² ) was measured. In addition, the characteristic values of the liquid crystal composition were also measured. The results are shown in Table 2.

The charging time was evaluated by applying DC10V to the liquid crystal cell.
Was applied and the time until the display disappeared was measured. Moreover, the current consumption value is measured by a liquid crystal inspection device (Kawaguchiko Precision Co., Ltd.).
Manufactured by LC8DC tester), applied voltage 3V, 32
Immediately after the liquid crystal cell was created under the condition of Hz and 120 ° C
The thermal acceleration test was conducted for 9 hours and 18 hours.

[0032]

[Table 2]

As is clear from the results of Tables 1 and 2,
When no polyether compound is used, there is a drawback that the charging time is long (Comparative Examples 1 and 7). Further, when a low molecular weight polyether compound other than the present invention is used, foaming is large at the time of cell production and it is not practical (Comparative Examples 2 and 3). Further, in the case of using piperazine, when the voltage holding ratio was lowered to the range of 40 to 85%, even if the water content was suppressed to 30 ppm or less, the change in the voltage holding ratio with time was large, and the charging Although it has preventive ability, it has a drawback that the power consumption value increases with time (Comparative Examples 4 to 5 and 8 to 9). Further, tetrabutylammonium hydroxide can exhibit an excellent antistatic ability even if it is added in a small amount, but it has drawbacks that the specific resistance value decreases and the current consumption value is large (Comparative Example 10). Further, even when the polyether compound of the present invention is used, when the water content exceeds 30 ppm, the change in voltage holding rate due to heat is also large and the antistatic ability is small (Comparative Example 10). .

On the other hand, according to Examples 1 to 8 containing the polyether compound according to the present invention and suppressing the water content to 30 ppm or less, the change with time is small even if the voltage holding ratio is set to the target of 40 to 85%. Thus, a liquid crystal composition having excellent antistatic ability can be obtained.

[0035]

According to the present invention, it is possible to obtain a liquid crystal composition which can prevent the generation of static electricity and can reduce the voltage holding ratio when it is used as a liquid crystal element and its change with time is small.

Claims (5)

[Claims] 1. A water content of 30 ppm or less comprising a polyether compound represented by the following general formula (I):
A nematic liquid crystal composition having a specific resistance of at least 1.0 × 10 ¹¹ Ωcm. [Chemical 1] 2. In the general formula (I), R ₁ is 1 to
The nematic liquid crystal composition according to claim 1, which is an alkyl group of 8. 3. The nematic liquid crystal composition according to claim 1, wherein the polyether compound represented by the general formula (I) is tetraglyme. 4. The nematic liquid crystal composition according to claim 1, 2 or 3, wherein the absolute value of dielectric anisotropy (Δε) is smaller than 10. 5. A liquid crystal device composed of the nematic liquid crystal composition according to claim 1.