JPS6136559B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid crystal composition used in a liquid crystal display device. More specifically, the present invention relates to a novel liquid crystal composition that exhibits a vertical nematic liquid crystal phase over a wide temperature range and has excellent dynamic drive characteristics. This is a so-called twisted nematic display device that displays by applying an electric field to a nematic liquid crystal layer with twisted orientation, or by mixing a dichroic dye into the liquid crystal matrix and applying an electric field. Liquid crystal compositions used in displays using the so-called guest-host effect are stable against external factors such as moisture, air, light, and heat, and are easy to use. It is necessary that the liquid crystal temperature range is suitable for the conditions in which the liquid crystal is used, and that the driving characteristics are also excellent. In particular, as the use of liquid crystal displays has increased in recent years, dynamic driving of liquid crystal displays has become common in view of manufacturing and assembly costs of devices using liquid crystal displays. This is because static drive requires one lead wire for each display segment that performs display, but dynamic drive requires a very small number of lead wires, approximately 1/(duty ratio). This is because there will be less. Conventionally, the liquid crystal composition used for dynamically driven liquid crystal displays has the general formula So-called azoxy-based liquid crystal compositions, which are based on the compound represented by the formula [wherein R and R' represent alkyl and alkoxy groups] and mixed with other compounds;
general formula There are so-called biphenyl-based liquid crystal compositions which are based on a compound represented by the formula [wherein R represents an alkyl or alkoxy group] and mixed with other compounds. However, these liquid crystal compositions currently have the following drawbacks. That is, in the former azoxy liquid crystal composition, the driving margin is 1/2
12-13% for duty, 8-9 for 1/3 duty
%, and has the advantage of good dynamic drive characteristics.
The base azoxy compound has absorption in the visible region, and when used as a display, a yellow filter must be used to protect the liquid crystal and prevent it from deteriorating. As a result, the display becomes yellow, the apparent contrast decreases, and the display effect is significantly hindered. On the other hand, the latter biphenyl-based liquid crystal composition is stable against various external factors, and has the advantage of being able to provide a white display without the need for a yellow filter when used as a display. There are, but
Since the drive margin is as small as 6 to 7% at 1/2 duty and 3 to 4% at 1/3 duty, the dynamic drive characteristics are poor and multi-digit drive is difficult. If we focus only on the dynamic drive characteristics, it is possible to improve them by about 10 to 20% by adding some additives, but this increases viscosity and deteriorates low-temperature characteristics, making it impractical. lacking in quality and undesirable. The present invention eliminates the above-mentioned drawbacks, and provides a novel liquid crystal composition which is excellent in resistance to various external factors and has excellent dynamic characteristics having a nematic liquid crystal phase over a wide temperature range. That is, the dynamic driving liquid crystal composition of the present invention has at least the general formula: (In the formula, R ₁ is a straight-chain alkyl group having 3 to 5 carbon atoms, R ₂
represents a straight chain alkyl group having 1, 2, 4 or 5 carbon atoms. ) and one or more compounds represented by It is characterized by consisting of one or more types of compounds represented by: As a result, a liquid crystal composition having an extremely wide driving margin during dynamic driving can be obtained. In addition, this liquid crystal composition has an additional optical formula. By adding the compound represented by
A dynamic driving liquid crystal composition with an increased I point and a wide liquid crystal temperature range can be obtained. Examples will be described below, and then details will be explained according to the examples. Example

【table】

[Table] In the above examples, the formulas and physical property values of compounds 1 to 10 are as shown in the table below.

【table】

[Table] However, in the above table, the N-I point is the nematic liquid crystal phase-isotropic liquid phase transition temperature of each liquid crystal composition or compound. The center voltage and drive margin are defined as follows. That is, when a twisted-state nematic cell with a twist angle of 94° is made and an ON waveform as shown in Fig. 1 is applied while viewing from the front of the cell at an angle of 10° in the bright viewing direction at 0°C, 1. /2 duty,
For V-2V drive, 90% saturation, 1/3 duty, V
In the case of -3V drive, set the voltage required for 70% saturation to V _ON
40° from the front of the cell to the bright viewing direction at 40°C.
OFF as shown in Figure 2 when viewed from an angle of ゜.
When applying a waveform, if the voltage required for 10% saturation for both 1/2 duty, V-2V drive and 1/3 duty, V-3V drive is V _OFF , (center voltage) = V _ON + V _OFF /2 [V] (Drive margin) = 1/2・V _OFF - V _ON / (center voltage) x 100 = V _OFF - V _ON /V _ON +V _OF
F × 100 [%]. Next, details will be explained according to examples. As can be seen from the examples, by mixing appropriate amounts of the compound represented by the formula () and the compound represented by the formula (), a colorless liquid crystal composition having excellent dynamic characteristics characterized by an extremely wide driving margin can be obtained. I was able to get things. This has made it possible to create a white liquid crystal display that can easily perform three-digit dynamic driving, which has been strongly desired in the past. Moreover, as can be seen from Examples 2 to 4, by adding the compound represented by the formula (), N-1
The liquid crystal composition can be used under a wide range of usage conditions, and the temperature shift is also small, so that a more advantageous liquid crystal composition can be obtained, and its effects are very large. A high temperature aging test of a liquid crystal display using the liquid crystal composition according to the present invention was conducted at 125°C.
Several types of compounds represented by formulas () to (),
Cyclohexane ester compound with positive dielectric anisotropy (general formula,

[Formula] where R represents a straight chain alkyl group having 1 to 6 carbon atoms) from 35 to
Clearly better results were obtained compared to the liquid crystal composition obtained by mixing 70 wt%. As explained above, according to the present invention, a colorless liquid crystal with excellent dynamic characteristics that could not be obtained conventionally can be obtained, and its effects on liquid crystal displays are very large. Further, in this specification, the dynamic properties of the liquid crystal composition according to the present invention have been particularly described, but the static properties are also superior compared to conventional liquid crystal compositions (for example, at 0 to 40°C). The fluctuations in voltage required for 90% saturation in the temperature range are: 6 to 8 mV/°C for the liquid crystal composition of the present invention, 5 to 7 mV/°C for azoxy type, and 11 to 13 mV/°C for biphenyl type.
℃), the liquid crystal display according to the present invention has wide applicability as a liquid crystal composition for use in various liquid crystal displays.

[Brief explanation of the drawing]

FIGS. 1 and 2 show driving waveforms used to measure the dynamic characteristics of the liquid crystal composition in Examples of the present invention, and FIG. 1a...1/2 duty, V-2V, ON,
Figure 1b shows 1/3 duty, V-3V, ON, Figure 2 shows 1/2 duty, V-2V and 1/3 duty, V-3V OFF waveforms.

Claims (1)

[Claims] 1. At least the general formula is (In the formula, R ₁ is a straight-chain alkyl group having 3 to 5 carbon atoms, R ₂
represents a straight chain alkyl group having 1, 2, 4 or 5 carbon atoms. ) and one or more compounds represented by (In the formula, R ₃ represents a straight-chain alkyl group having 1 to 4 carbon atoms.) A dynamic driving liquid crystal composition comprising one or more compounds represented by the following formula. 2 The liquid crystal composition has a chemical formula A liquid crystal composition for dynamic driving according to claim 1, to which a compound represented by the following is added.