JPH052718B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid crystal composition used in a TN type liquid crystal display. In liquid crystal display devices, methods for increasing display density while maintaining display quality include active matrix methods such as thin film transistor (TFT) methods, and dual-frequency drive methods using dielectric dispersion of liquid crystal. The latter has problems in terms of reliability and price, and the latter has the disadvantage that it cannot take advantage of the characteristics of low voltage and low power consumption, which are characteristics of liquid crystal display devices. Therefore, in order to take advantage of the characteristics of high reliability, low cost, low voltage, and low power consumption of the voltage averaging method, which has been used in calculators since Jukyo, and to improve the display density, we used the voltage averaging method. Attempts have been made to multiplex using a time-division drive system. However, maintaining display quality in multiplexing and ensuring response speed that can withstand video display such as TV images is due to unsatisfactory physical properties of conventional liquid crystal compositions, namely, lack of steepness in voltage-luminance characteristics. However, it has been difficult due to insufficient viewing angle characteristics and high viscosity. In view of this situation, the present inventors conducted extensive research on a liquid crystal composition suitable for improving display density using a voltage averaging method, and arrived at the present invention. That is, an object of the present invention is to maintain display quality while
The purpose of the present invention is to provide a liquid crystal composition that improves display density, and more specifically, to increase the steepness of voltage-luminance characteristics, which are related physical property values of the liquid crystal composition, and to improve viewing angle characteristics. In order to improve response speed, reduce viscosity, and
The objective is to obtain a large refractive index anisotropy value under specific LCD usage conditions in order to prevent interference colors and improve contrast ratio. The present invention consists of at least the following three components ()()
A liquid crystal composition containing 50% or more of () in total. general formula (In the above formula, R ₁ and R ₂ each represent an alkyl group having 1 to 10 carbon atoms.)
%, general formula (In the above formula, R ₃ and R ₄ each represent an alkyl group having 1 to 10 carbon atoms.) One or more compounds represented by 5 to 50
%, general formula (In the above formula, R ₅ represents an alkyl group having 1 to 10 carbon atoms.)
%. In addition to the above three components, compounds included in this liquid crystal composition include nematic liquid crystal compounds (usually referred to as Nn) with a dielectric anisotropy value △ε of 5 or less or negative.
Among such compounds, the following three compounds () () () are preferred. general formula (In the above formula, R ₆ represents an alkyl group having 1 to 10 carbon atoms, and R ₇ represents an alkyl group or an alkoxy group having 1 to 10 carbon atoms.) A compound represented by the general formula (In the above formula, R ₈ represents an alkyl group having 1 to 10 carbon atoms, and R ₉ represents an alkyl group having 1 to 10 carbon atoms.) A compound represented by the general formula (In the above formula, R ₁₀ and R ₁₁ represent an alkyl group having 1 to 10 carbon atoms). The above three compounds may be used alone or in combination of two or more. The liquid crystal composition of the present invention is characterized by excellent steepness in voltage-luminance characteristics, good viewing angle characteristics, and low viscosity despite having a large refractive index anisotropy Δn. Helps speed up responsiveness. Generally, when setting the conditions of a display device, if △n・d<1.0 (d is the cell thickness), interference colors are likely to occur due to fluctuations in cell thickness and uneven thickness, resulting in a lack of quality in the display device. . Therefore, in order to prevent interference colors and increase the contrast ratio, it is considered desirable that Δn·d be 1 or more. On the other hand, the cell thickness is
In order to achieve low-voltage drive and high-speed response, the trend is to make the liquid crystal thinner and thinner.Thicknesses of 6 to 8 μm have begun to be put into practical use, and in order to make △n・d greater than 1, the △ of the liquid crystal composition used is becoming increasingly thinner. It is necessary to increase n. The liquid crystal composition of the present invention fully satisfies these requirements and can provide a display device with a high contrast ratio and no interference colors. For the reasons described above, when the liquid crystal composition of the present invention is used, it is possible to significantly increase the number of time divisions, that is, to improve display density while maintaining display quality. It is said that the conventional voltage averaging method has a duty of about 1/16th, which is the limit from the perspective of display quality. However, by using the liquid crystal composition of the present invention, one LSI
TN type liquid crystal display, which enables multi-digit display and therefore enables high time-division driving, which was previously considered difficult, and has improved display density; that is, information terminal display devices and television image display devices capable of multi-digit display. can be provided. The liquid crystal composition of the present invention will be explained in more detail below using Examples. In the table showing the properties of liquid crystal compositions, steepness (α) refers to the voltage at which the amount of change in light transmittance from the axial direction perpendicular to the display becomes 10% and 50%, respectively. When V _{is 10,0} ° and V _{is 50,0} °, the parameter α is defined as follows. α=V _50, °/V _10,0 ° Therefore, the closer α is to 1, the steeper the voltage-luminance characteristics are. The number of time divisions is obtained from α using the following formula. Nmax=(α ² +1/α ² −1) ² N _nax indicates that the larger the number, the higher the time division. Regarding viewing angle characteristics, if the voltage at which the transmittance of light from an axis tilted 40 degrees from the axis perpendicular to the liquid crystal display panel becomes 10% is V _10.40 degrees,
The parameter β indicating the viewing angle characteristic is defined as the following equation. β=V _10,40 °/V _10,0 ° The closer this β is to 1, the better the viewing angle characteristics are. As a parameter for evaluating the steepness of the voltage-luminance characteristic and the viewing angle characteristic, γ is defined as shown in the following equation. γ=α×β The closer both α and β are to 1, the closer to the ideal state it is, and the closer γ is to 1, the better the characteristics of the liquid crystal composition. In addition, the threshold voltage and other characteristic values are △n・d.
The cell used for the measurement had a PVA surface rubbed with a twist angle of 90°. Example 1 As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition having the following composition was prepared, and various properties as a liquid crystal were measured. The results are shown in Table 1 along with those of other examples.

[Table] Example 2 As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition was prepared, and its properties were measured in the same manner as in Example 1. The results are shown in Table 1. Example 3 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition having the following composition was prepared and its characteristic values were measured. The results are shown in Table 1. Example 4 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition having the following composition was prepared and its characteristic values were measured. The results are shown in Table 1. Example 5 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition having the following composition was prepared and its characteristic values were measured. The results are shown in Table 1. Example 6 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition was prepared and its characteristic values were measured. The results are shown in Table 1. Example 7 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid phase composition consisting of the following was prepared and its characteristic values were measured. The results are shown in Table 1. Example 8 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition was prepared and its characteristic values were measured. The results are shown in Table 1. Example 9 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition was prepared and its characteristic values were measured. The results are shown in Table 1. Example 10 As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () As a compound of formula () A liquid crystal composition was prepared and its characteristic values were measured. The results are shown in Table 1. Comparative Examples 1 and 2 For the purpose of comparison, the compositions of two typical liquid crystals for high time division driving that have been commonly used are shown below, and their characteristic values are shown in Table 1. As a compound with negative Δε As a compound with positive Δε A liquid crystal composition having the following composition (Comparative Example 1). As a compound with negative △ε As a compound with positive △ε A liquid crystal composition having the following composition (Comparative Example 2). The results in Table 1 show that the liquid crystal composition of the present invention has higher voltage-luminance characteristic steepness (α), viewing angle characteristic (β), γ (α × β), and number of time divisions than the composition of the comparative example. Excellent in both ₍ N _nax ) and response speed (τ〓, τ _d ), compared to the comparative example with N _nax <60>
This clearly shows that more than 80 lines are possible and the response speed is also improved. In addition, as mentioned above, the composition of the present invention has a practical cell thickness of 6 to 6 to 1.0 in order to prevent the occurrence of interference colors and improve the contrast ratio. Since it is 8 μm, the refractive index anisotropy (△n) of the liquid crystal is required to be ≧0.125,
It has been shown that the liquid crystal composition of the present invention has a refractive index anisotropy value that fully satisfies this requirement, and the liquid crystal composition of the present invention is suitable as a liquid crystal for high-density display elements capable of high-time division driving. I understand that.

Claims (1)

[Scope of Claims] 1. A liquid crystal composition containing at least 50% or more of the following three components () () () () in total. general formula (In the above formula, R ₁ and R ₂ each represent an alkyl group having 1 to 10 carbon atoms.)
%, general formula (In the above formula, R ₃ and R ₄ each represent an alkyl group having 1 to 10 carbon atoms.)
%, general formula (In the above formula, R ₅ represents an alkyl group having 1 to 10 carbon atoms.)
%. 2. The liquid crystal composition according to claim 1, comprising a compound of the formula ()()() and a nematic liquid crystal compound (Nn) having a dielectric anisotropy value Δε of 5 or less or negative. 3 Nn is a general formula (In the above formula, R ₆ represents an alkyl group having 1 to 10 carbon atoms, and R ₇ represents an alkyl group or an alkoxy group having 1 to 10 carbon atoms.) liquid crystal composition. 4 Nn is a general formula (In the above formula, R ₈ represents an alkyl group having 1 to 10 carbon atoms, and R ₉ represents an alkoxy group having 1 to 8 carbon atoms.) The liquid crystal composition according to claim 2, which is a compound represented by: thing. 5 Compounds and general formulas where Nn is () formula (In the above formula, R ₁₀ and R ₁₁ represent an alkyl group having 1 to 10 carbon atoms.) The liquid crystal composition according to claim 2, comprising a compound represented by the following. 6. The liquid crystal composition according to claim 2, wherein Nn comprises a compound of formula () and a compound of formula ().