JPS61290A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:To provide a nematic liquid crystal compsn. which enables time division driving at a duty ratio of 1/125, by mixing at least two cyclohexanecarboxylates so as to satisfy specified conditions. CONSTITUTION:At least two cyclohexanecarboxylates of formula I (wherein n, m are each an integer) are mixed with each other in such a proportion that the mean value [the value of formula II (wherein ml is the number of carbon atoms of -OCmH2m+1 groups in component l; Xl is the molar fraction of component l)] of carbon atoms of -OCmH2m+1 groups in components constituting liquid crystal compsn. is 4 or above, thus forming the desired liquid crystal compsn.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a nematic liquid crystal composition. A cyclohexanecarboxylic acid ester liquid crystal mixture with a value of -4 or more, with the addition of an appropriate amount of nematic liquid crystal exhibiting positive dielectric anisotropy, is an excellent method in which time-division driving at least at a duty ratio of V1251 can be performed. The present invention relates to a mixed liquid crystal composition having splitting characteristics.

[Prior art]

Recently, research and development efforts have been made to increase the display density and display capacity by improving the time division characteristics of liquid crystal displays, but at present the duty ratio is 1/1.
Only about 82 of them have been commercialized, and the display quality cannot be said to be sufficient.

Other methods for increasing display density and display capacity include arranging transistors on a silicone substrate and directly driving the liquid crystal, using the frequency characteristics of the liquid crystal to drive the liquid crystal, and improving the electrode structure and panel structure. There are two-layer and eight-layer systems, and recently announced methods include forming a thin film transistor on a glass substrate and driving it as a switching element, and forming a metal-insulator-metal M on a glass substrate.
Efforts are being made to develop a system that uses the nonlinearity of an M element to perform time-division driving with a small duty ratio by forming an M element.

However, these methods defeat the most excellent features of liquid crystals, such as low voltage, low power consumption, and low cost, and are not essentially desirable methods. For example, methods using silicon substrates are extremely costly;
Furthermore, the contrast is much lower than that of the two-polarizer method. ) The 2-frequency drive method consumes less power than the conventional method.
It goes without saying that a two-layer structure with a voltage of nearly 50V and a voltage of nearly 50V will be considerably expensive, considering the complexity of the structure and the yield. Also, although the display quality of the thin film transistor method is very good,
Due to the complexity of the structure, it is very difficult to reduce the price and make it difficult to make the screen larger.Although it is possible to make the MIM method larger,
After all, it is difficult to lower prices.

On the other hand, as an approach to increase display density and display capacity by improving the time division characteristics of liquid crystal compositions, JAPAN DISPLAY +
In 83, Suwa Seikosha reported that increasing the alkyl and alkoxy chain lengths improved the steepness of the voltage-contrast curve (P. 320-828).
) has been carried out for compound (1). Until then,
Compound (1) was widely used, but due to the nematic liquid crystal temperature range and viscosity, it was limited to components with n+m of 7 or less, and components with relatively large n were often used. Sara Busy JAPAN D Engineering 5PLAY
Even in the report of I133 by Suwa Seikosha, the steepness improves as n+m increases, but the (N-+8g1) point also increases, so there was a natural limit.

On the other hand, the present inventor paid attention to the above report and determined that n+m
We investigated the effects of i and 1 when keeping constant, and found that setting 4 or more leads to a marked improvement in time-sharing characteristics, and (N
-+E g ) point was found to be small, and the liquid crystal composition of the present invention was constructed.

〔the purpose〕

An object of the present invention is to provide a liquid crystal composition having excellent time-division characteristics capable of practically sufficient time-division driving with a duty ratio of at least 1/125.

Another object of the present invention is to provide a liquid crystal display device that can display a large capacity with high quality using such a liquid crystal composition.

Still another object of the present invention is to provide a compact and simplified liquid crystal display device using such a liquid crystal composition.

Still another object of the present invention is to provide a liquid crystal composition for a display device that has high contrast and is easy to see over a wide viewing angle range.

Still another object of the present invention is to provide a liquid crystal display device capable of bright display without the need for a color filter to prevent photodeterioration, and capable of displaying multiple colors.

〔overview〕

In view of the above objective, the present inventor focused on the carbon numbers of compound (1), ¥2 needle 1 and OCmH2m+ 1, and conducted various studies.
As a result of repeated studies, we have discovered a liquid crystal composition that satisfies all of the above objectives. That is, the present invention applies to general C? LH
2? L+1-J! D-Coo÷OCm1l yh+i
Contains two or more types of compound (1) represented by (1), and 100 mB @m of each component belonging to compound (1)
By blending the liquid crystal composition so that the average value of the number of +1 carbon atoms is 4 or more, a liquid crystal composition with dramatically improved time division characteristics was constructed.

All compounds (1) used in the button of the present invention are stable. In the present invention, compound (1) is formulated so that the cage is as large as possible, which leads to further improvement of time division characteristics, but at the same time, smecticity increases and response characteristics deteriorate. It is necessary to select and contain an appropriate amount. Therefore, approximately 4 to 7 is good.

Next is Ki-nii 1! AK - Specific examples of the compound (1) used are shown in Table 1.

Table 1 Examples Examples in which the liquid crystal composition of the present invention was constructed using the compounds shown in Table 1 are shown in Table 2, and Table 8 shows comparative examples.

The liquid crystal composition of the present application illustrated in Table 2 is used in a liquid crystal display device as shown in FIG. Time division drive circuit 11
applies a time division signal to the liquid crystal cell 12 to drive the liquid crystal cell 12. The liquid crystal cell 12 has an upper electrode substrate 18 and a lower electrode substrate 14 separated by a spacer 16 at a predetermined distance, and electrodes 17 and 18 are formed on the inner surfaces of the electrode substrates 13 and 14, respectively. In order to keep the distance between the electrode substrates 18 and 14 more constant, spacers such as glass fibers and glass poles may be interspersed within the liquid crystal cell.

In the liquid crystal cell 12, an upper photon 20 and a lower photon 21 are arranged above and below the cell, and a reflector 22 is placed below the lower photon 21.
will be arranged. If the liquid crystal display device is a transmission type, the reflector 2
2 is unnecessary. The liquid crystal composition 19 of the present application is placed between the upper and lower electrode substrates 18 and 14, and
] with a twisted orientation. And upper and lower electrode substrates 20
．． 21 has at least the surface in contact with the liquid crystal composition 19 covered with liquid crystal alignment layers 180 and 140. Drive signals are selectively applied to electrodes 13.14.

Then, the orientation of the liquid crystal changes due to the voltage selectively applied between the electrodes 13 and 14, and the state of light passing through the liquid crystal cell 12 changes between the parts where the orientation does not change, and the light is reflected (or transmitted). ] and a blocking part, and display is performed. At least one of the electrodes 17 and 18 is a transparent electrode. In a transmissive cell, at least the electrodes 17 and 18 of the display part are both transparent electrodes.

Note that at least light with a wavelength of 1380 nm or less is cut to prevent ultraviolet rays from reaching the liquid crystal, thereby preventing deterioration such as decomposition of the liquid crystal. In a reflective liquid crystal display device, a filter is placed between the liquid crystal and the light source. For example, a filter characteristic may be imparted to the electrode substrate 18 or the upper photon 20 itself, or a filter may be placed above the upper photon 20 or between the electrode substrate 18 and the upper photon 20. The adhesive used to bond the upper photons 20 together may have filter properties. A filter with these characteristics not only protects the liquid crystal from ultraviolet rays, but also has no coloration and provides high quality liquid crystal display.

In the case of a transmissive liquid crystal display device, a filter with similar characteristics is further installed between the backlight source and the liquid crystal.

Table 2-1 Table 2-2 Table 2-8 Table 2-4 Table 8-1 Table 8-2 Compounds ■ to ■ in Table 2 and Table 8 are the same compounds as in Table 1. show. In addition, in Tables 2 and 3,
The compounds indicated by symbols have the following structural formulas, and the composition ratios indicate wt%.

2ECN −+ C2H5-@-COo-@-c N4
E CN −+ C4Hg-o-C0O-o-CN5
- Q l -+ C3H11-@-Coope10cH
3602→C6H13-'B)-COo-o-o c2
a57-02→C7H15'■-COO-◎-RoC2H
58-02-+ 08H17-4t-GOCI-@-Q
C2H.

Five and inkstone are shown by the following formula.

i=hat22. r* Here, nL and rnJ- are the carbon number of -CnH271,+1 and -o C711E 2. of component j belonging to compound (1), respectively. y, +1 carbon number, X
! is an ingredient! indicates the mole fraction of

Low-temperature characteristics indicate the temperature at which crystallization or smectic formation occurs when cooled from room temperature (20° C.).

All data below the cell thickness are measured at a measurement temperature of 20°C. Further, the cell thickness is 4 to 11μ, and #1 indicates the cell thickness at which the value of β is the minimum when measured at cell thicknesses of every 1μ, and vth, α, and β.

γ, iR, and iF indicate the characteristics depending on the cell thickness.

vth statically drives the liquid crystal cell, directly above (viewing angle 9
Graph IVc in FIG. 2, which shows the relationship between voltage and light transmittance when observed from 00), shows the threshold voltage at 90% light transmittance. Furthermore, if the relationship between voltage and light transmittance when observed from a viewing angle of 50° is shown in graph 2 in Figure 2, α,
β and γ are expressed by the following formulas.

vcL (visual angle 500, transmittance 90 cm) Vth (visual angle 90°, transmittance 90%) tR, tF are drive 11 pressure V th l!-V b
0 period "?" This is the response time required when OPi is turned off.

β5o is expressed by the following formula, vth (visual angle 90°, transmittance 90cm) If this value is less than the ratio of V○N and V OFF of the voltage averaging method at the optimal bias ratio, then the duty ratio 1
It is determined that time-division driving is sufficiently possible in practice,
The maximum value of 1 g was set as N mZ. That is, the elastic constant ratio of each liquid crystal composition, which is generally said to have a correlation with the β value, is 33/Kll (Kll : SI'1
(14/r Kll,', bend, ) was shown. Examples will be described in detail below.

Examples 1 to 8 of the liquid crystal compositions of the present invention all contain two or more types of compound (1), and 100? ? By blending so that the average number of carbon atoms in 1E 2m+ 1 is 4 or more, time-division driving with a duty ratio of at least 1/125 is made possible. Further, as shown in Examples 1 to 8, the liquid crystal compositions of the present invention have (N→T) points of 60° C. or higher, 3, 3, 4, 6, and 6. 1 Yua, 8, Examples 3 and 5 are highly practical, and have a wide liquid crystal temperature range. Easily improved.

On the contrary, in addition to its high practicality, this example shows that it contains two or more types of compound (1) of the present invention and that each component belonging to compound (1) is This is to simply express the novelty and superiority of the compounding method of compounding CrnE 2m+1 so that the average carbon number is 4 or more.

Examples 1 to 4 each contain two or more types of compound (1) in four different combinations, and the average value i of the carbon number of -OCtnE2m+1 of each component belonging to compound (1) is 4, The liquid crystal composition was prepared so that the average value i of the carbon number of -071H2n+L was 4, that is, n+m was 8. In addition, at this time, the compound (1
) The total ratio of components belonging to 9. III
CM and 4FiCN were each contained at 5 wt%. On the other hand, Comparative Examples 1 to 4 contain two or more types of the same compound (1), the blood component of the component belonging to compound (1) is 8, and i is 5 (Comparative Example 1 and 2) Or, like eggplant becomes 2 and π becomes 6 (Comparative Examples 8 and 4),
Again, this is a liquid crystal composition prepared so that n+m is 8. Total ratio of compound (1), 2'BC
Even though the N and 4BCMρ ratios are exactly the same,
As is clear from the β, β506 N m1LZ, and Ks3/KnO values, Examples 1 to 4 were lower than Comparative Examples 1 to 4.
shows extremely excellent time-sharing characteristics, and in NZ,
While the former is around 100, the latter is over 125. If this is replaced with the number of scanning lines in the liquid crystal display, if theta signals are input from the top and bottom, Comparative Example 1
-4 had 200 lines, Examples 1 to 4 had 250 lines, indicating that it is possible to increase the density and capacity by 50 lines with the same display quality, and has great practical value. There is.

Examples 5 and 6 contain two or more types of compound (1), such that aubergine is 5, i is 8, and n+m is 8.
This is a liquid crystal composition formulated to have the following properties. Comparative example 1
Not only in comparison with Examples 1 to 4, but also in comparison with Examples 1 to 4, the time sharing characteristics are equal to or better than those of Examples 1 to 4.

Examples 7 and 8 are liquid crystal compositions that contain two or more types of compound (1) and are prepared in such a way that the flight is 6 and the i is 8. In Examples 7 and 8, n+m is 9, but
Compared to Examples 1 to 6, the time division characteristics are clearly improved, and NmtLx is about 140, and it is thought that with future improvements, it will be possible to increase the number of scanning lines to 800. Despite this, no significant deterioration was observed in vth, low temperature characteristics, etc.

As mentioned above, as is clear from Examples 1 to 8 and Comparative Examples 1 to 4, the compound (1) is contained as two or more components, and the compound (1)
The liquid crystal composition of the present invention in which the average number of carbon atoms in -OCml-needle 1 of each component belonging to K is 4 or more has excellent steepness represented by the β value, but at the same time, the α It also has excellent viewing angle dependence as typified by the value. Comparative example 1
~4 has an α value of 1°127 to 1.168, whereas
Examples 1 to 8 are 1.106 to 1.122, and the examples are better in all cases. This shows that the liquid crystal composition of the present invention not only has good contrast but also enables a high-density, large-capacity liquid crystal display with a wide viewing angle.

Table 2 also shows the cell thicknesses and Δn of Examples 1 to 8.

△tLd (△n=ne-?L o , d: cell thickness), but in general, if △nd is 0.8 to 0.8 for time division characteristics,
It has also been confirmed in this example that the cylinder becomes the most cylindrical at about 1.0. Therefore, at present, the cell thickness is thin (6μ or less).
Considering that there are many difficulties in mass producing large panels in
The optimum cell thickness of a liquid crystal display in which the liquid crystal composition of the present invention is encapsulated is approximately 9 μm, and it is also excellent in mass production.

Furthermore, Tables 2 and 8 show Examples 1 to 8 and Comparative Examples 1 to 4.
K 337 K 11 was shown, but β, β5g,
It corresponds very well with Z for N, proving the high reliability of the data in this example and this comparative example.

1. In this Example 1 and this Comparative Example, in order to clearly explain the effect of the liquid crystal composition of the present invention, compound α)
It is composed only of positive esters (2BCN and 4BON), and the ratio of positive esters is kept constant at 10 wt%.
vth is relatively high and the response characteristics cannot be said to be excellent, but these points can be improved by increasing the amount of positive ester or by increasing the amount of P.
This can be easily improved by adding a thinner such as CH-based liquid crystal. In addition, nematic liquid crystals exhibiting positive dielectric anisotropy, liquid crystals other than positive esters (biphenyl, p
(CH, dioxane, etc.) or a mixture thereof.

〔effect〕

Above are Examples 1 to 8. In Comparative Examples 1 to 4, compound (1) was
At least a duty ratio of 1 can be achieved by blending so that the average value m of the carbon number of 100-2m+1 of each component belonging to compound (1) is 4 or more.
This shows that a liquid crystal composition that is practically capable of time-division driving of Δ25 can be obtained.

Further, the compound (1) used in the present invention does not absorb visible light. Therefore, there is no need to remove the color filter, and the display becomes brighter. Furthermore, when displaying in color, it is theoretically possible to make the display in full color.

Furthermore, compound (1) is easy to synthesize, has a high yield, and can be obtained at low cost, so when considering the increase in the amount of liquid crystal used due to the increase in the size of the panel, it also has a large cost advantage.

As explained above, the liquid crystal display device using the liquid crystal composition according to the present invention has excellent time-sharing characteristics that allow practical time-sharing driving up to at least a duty ratio of 1/125. It has the advantage of being able to display up to 250 lines at high capacity and high density with a wide viewing angle range and with high quality, and has great practical value7.

[Brief explanation of the drawing]

FIG. 1 shows a liquid crystal display device using the liquid crystal composition of the present application. FIG. 2 is a diagram for explaining the relationship between voltage and light transmittance. that's all

Claims (1)

[Claims] (1) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) Contains two or more types of compound (1) represented by and -OC_mH_2_m_+_ of each component belonging to compound (1)
Average value of carbon number of 1@m@(@m@=■(ml/Xl)
A liquid crystal composition characterized in that ml: number of carbon atoms in -OC_mH_2_m_+_1 of component 1, Xl: mole fraction of component 1) is 4 or more.