JPS5829879A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:To provide a liquid crystal mixture suitable for time division driving of which the temperature and visual angle dependences of the threshod voltage are low, by mixing three specified compounds. CONSTITUTION:50-85wt% compound having formulaI(wherein R1 represens 2- 6C linear alkyl and R2 represents 1-5C linear alkyl), 5-30wt% compound having formula II (wherein R3 represents 2-4C linear alkyl) and 5-20wt% compound having formula III (wherein R represents 1-6C linear alkyl) are mixed. EFFECT:As this liquid crystal composition is less colored, is good in the contrast, has a visual angle capable of indicating bright indication, and exhibits a wide voltage margin, it can effectively be used in a display part in portable instruments including mainly a desktop electronic calculator, a watch, etc. that adopt a driving system of V-3V duty ratio of 1/4 wave form, V-2V duty ratio of 1/2 wave form, etc. or a wave form of a small duty ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nematic crystalline composition trap exhibiting positive dielectric anisotropy, and more specifically, an ester-based nematic liquid crystal mixture consisting of only two cyclic carbon bonds with t/'j,
The present invention relates to a mixed liquid crystal composition that allows time-divisional driving in addition to static driving.

Nematic liquid crystals, which exhibit positive dielectric anisotropy, can be produced by surface treatments such as rubbing the surface of the electrode plate in one direction with cotton, etc., or aligning it in one direction with steam, etc., to form a π orientation. ,
The long axes of the liquid crystal molecules are aligned in the processed direction. By placing a pair of electrode plates perpendicular to each other after such surface treatment, the f&product molecules are arranged in a twisted manner from one plate to the other. A transparent liquid crystal display device in which a polarizing plate is placed across a liquid crystal cell, a light source is placed on one side, and the other side is used for observation, and a liquid crystal cell is placed on one side with a polarizing plate and a light source is placed on one side and a light source is placed on the other side. 2. Description of the Related Art A reflective liquid crystal display pupil is known in which a light scattering plate is viewed from the light source side.

σ static drive and time-division drive are known as methods for driving this liquid crystal display device, but since time-division drive can reduce the number of drops and losses, This is advantageous in terms of reducing the number of coupling parts with the drive circuit output section, (1) simplifying the drive circuit, etc.

However, when time-division driving is performed, there is a problem that the drive voltage is limited due to the relationship with the liquid crystal.For example, the selection waveform frm1 (a) of the so-called V-5'V time-division drive waveform
, (b) - (c), and the half-selected waveform is shown in Figure 1 (b)
), (a), and the tth, IW (a) * (d
The solid line and broken line indicate the waveforms of the common and segment, respectively, and the potential difference between the common and the segment t-m1 diagram (C)
, (b)). FIG. 2 shows the relationship between the voltage of the liquid crystal cell and the light transmittance relative to this waveform. In Figure 2, vt
When h -t and Vth -2tlj are respectively applied to the selection waveform 1t and half-selection Lumi 2 to the liquid crystal cell, the display is turned on. The voltage 'Vd that can erase the light is Vth
-1<Va (limited to the range of Vth-2).

vth-t and Vth-2- are almost the same effective value voltage vt
The more V-3V shown in Figure 1 to wait for h.

Duty ratio? /N waveform The relationship is as follows.

Therefore, the smaller the duty ratio, the Vth-
1 and Vth-2 decreases. In practice, it would be desirable to be able to perform time-division driving with a small duty ratio over a wide temperature range including room temperature, but there is a limit to tS since it shows the temperature dependence of the threshold voltage. When driving within a predetermined temperature range, the threshold voltage on the high temperature side k vth
-t (E), vth -z Q(), low temperature side Te'
vth -1(d, vth -2(u-f),
vth-1(base<vth-t<u, vth-2(a
)< vth-2(I, 1, and the voltage V(L' that enables lighting-off display in this temperature range is vth-t (d<va'<vth-2@ .

In addition, in order to obtain a display contrast that is sufficient for practical use,
In the selected waveform shown in Fig. 142, the threshold voltage on the low temperature side of transmittance of 23 cm is vth -5 (Vd
' is vth -s (q<va'< vth -2(H)
It is desirable to limit the display device
) [Vth-5 (0°C) and 7th-2 (40
℃).

Also, vth-2, vth-slxa shows Aneszl#UA
It shows viewing angle dependence that becomes smaller as the angle (viewing angle) t is made smaller with respect to the direction. When operating at a given temperature,
Threshold voltage on small viewing angle side +i Vth -2)vt
h -5 hood, large viewing angle side "74 vth -zφ), vt
h-Off), then vth -2ht< vth -2(β), vth
There is a relationship of -s < vth -5 (4), and the voltage va' that enables lighting-off display in this viewing angle range is vth -s (β) <va'< vth -2b)
It is. As shown in FIGS. 5(a) and 5(b), the direction in which the long axes of liquid crystal molecules are aligned with the surface of the upper substrate (1) and the direction (2) in which they are aligned with the surface of the lower substrate provides the highest display contrast. Vth-5C/ j> and Vth-2@) fX is respectively fifth-5 (80f) and vth-2 (50 degrees)@ Therefore, the drive voltage of the display cell @va'a Considering the temperature and viewing angle effect, Vth- 45 (0°C, 80[')8Vd"<Vth-2
(4(]℃, 50 degrees).

On the other hand, the driving voltage also fluctuates due to changes in battery voltage over time or variations in the circuit. Therefore, the voltage margin M is defined as a measure for allowing fluctuations in the driving voltage as shown in the following equation. However, the Top Fi driving center voltage can represent the suitability for time-division driving of the liquid crystal.

The voltage margin is practically 8 when the duty ratio is μ.
% or more.

The following compounds are known as conventional compounds exhibiting a nematic residue crystal phase that does not absorb visible light.

R Tsuu-ON 14) R Dan Hn C) 1 151 R-o-coo-o-cN (61 RO-O-Coosha R(7) R(Shin COO-Q-OR(8) R→◎G -OH(91 R-@0o-ON 顛Rbetato C00be)ON αDR-Q-coo
-Q-ooO-Q-Raz However, R represents a straight chain alkyl group.

The gap between display cells is d1, the refractive index of ordinary rays of liquid crystal molecules t-n
o, the refractive index of the extraordinary ray is no% Enoki refraction is Δn (=ne-
no), then the retardation R is Rxd
There is a relationship of (no - no)=dΔn. The cell gap for mass production is limited to a range of 8 to 11 μm, and in order to suppress coloring due to retardation and make the color close to white, σ refraction Δn f is required.
(It is necessary to maintain the range of 110 to (L15 or LL18 to α25.) Conventional nematic liquid crystal compositions aim to have a color very close to white, and the birefringence Δnt-α
Liquid crystal compounds with large ζ birefringence Δn 141, 161+s+ * fin to make it in the range of 18 to LIL23
*It was necessary to add a large amount of α-ri etc. However, in order to obtain the same contrast by increasing the birefringence Δn, the viewing angle in the range from the clear viewing direction to the direction of the left and right π forces has become smaller.

In addition, biphenyl liquid crystal compound (4), phenylcyclohexane liquid crystal compound 15+, liquid crystal compound 191 e (IQ eαυ, az
The synthesis of ester compounds * 161 @ 1711
Compared to synthesis by esterification such as 1B1, the reaction process is long and the yield is low, making it difficult to synthesize. Therefore, the cost of the compound is also high.

An object of the present invention is to provide a liquid crystal composition, particularly a liquid crystal composition for time-division driving, in which the temperature and viewing angle dependence of threshold voltage is small.

Another object of the present invention is to provide a liquid crystal composition with a wide viewing angle (hereinafter referred to as "viewing angle") that enables bright display with good contrast.

Still another object of the present invention is to provide a liquid crystal composition for a display device that reduces cost by 1.

Still another object of the present invention is to provide a liquid crystal composition that can be driven at low voltage.

In order to achieve the above object, the specific conditions required of the liquid crystal composition include: +11 Having a liquid crystal phase over a wide temperature range including room temperature.

121 Mtf! , suppress birefringence to the extent possible for bright display, minimize birefringence, and widen viewing angles.

(3) By adding a liquid crystal compound consisting of five or more cyclic carbon bonds, the cost can be significantly reduced compared to the Tc crystalline composition.

(4) Ensure a voltage margin of at least 8 inches or more in the waveform with a duty ratio of %.

is presented.

The present invention σ In view of the above-mentioned objects, as a result of various studies and tests, the present invention provides a crystalline composition gold that satisfies all the above-mentioned conditions. That is, the present invention is based on the general formula % formula %, where R1 is a linear alkyl group having 2 to 6 carbon atoms R, #
Compounds of each group represented by 1 to 51 Ra 12 or Id4 z R, # 1 or 61 +11, (2), +31'
This relates to liquid crystal compositions each containing at least one component.

Compounds used in the present invention ill, f2+, +
All of No. 31 are easier to synthesize and have higher yields than liquid crystal compounds consisting of three or more cyclic lazy bonds, resulting in very low costs. Can create cost reductions.

In the present invention, as the concentration of the compound Fll increases, it is desirable to have a large amount of the compound in order to widen the voltage margin, improve the liquid crystal clearing point, and expand the upper limit of the operating temperature range, but if it is added too much, low-voltage driving becomes impossible. Therefore, a concentration range of 50-85 wt % of the compound (() is preferable).

In addition, when compound (21) is used, the Zc current value tends to decrease after being opened for a long time at high temperature.
The concentration range is S0 because it affects the lifespan of the display panel.
It is best to reduce it to 1% or less.

Since the viscosity of compound* +31 slows down the response, it is desirable to set the concentration to Jd-old J20 or higher.

Historically, in the above concentration range of compounds (2) and (3),
In order to achieve a skin tone due to retardation with a cell gap of 8 to 11 μm for FIk Ukawa surface, and to have a wide viewing angle,
Birefringence [preferably in the range of 110 to 013, and the concentration range of compounds +21 and 131? 5-5 each
0wt excellent, 5-20wt1Kf is desirable.

Next, the present invention r (such compound (1) used, +2
1.

(Specific example of 3:? Shown in Table I!41.

Table 1 Example Examples according to the invention are all shown in Table 2.

Table 2 Is the 0 mark in Table 2 a non-inventive composition? No abnormality was observed even after the sealed cell was left at 20° C. for 4 days, and the fc was completely maintained. TR and TF indicate the rise and fall response times of liquid crystal molecules, respectively. Vop,
M, response time is v-y; v in Examples 1 to 8, when driven with a waveform of duty ratio μ, and V- in Example 9.
2V, the waveform of the duty ratio rod is driven and the characteristics at the time of hole are shown.O Example 3ilr compound 11+, +21,
+31 thick Hts, 71wt, 19wt, and 10wt, the voltage margin is wide at over 10%, and the response time is 180 m5ec for both rise and fall.
and very short.

Also, in Example 5, the degree of # of compound il+ was 5w from Example 5.
Although this is a mixed liquid crystal composition with increased t%, the voltage margin is widened to 13 inches or more.

As described above, in all Examples, excellent n7 responsiveness was exhibited, and a display with good contrast was obtained. Further, the birefringence is in the range of 0.10 to 0.13, and the viewing angle is wide. Compounds A to H in Table 2 represent the same compounds as in Table 1.

As described above, the liquid crystal display device according to the present invention has a wide viewing angle, a wide voltage margin, a V-5V duty ratio waveform, a -2V duty ratio waveform, etc. Furthermore, the present invention can be used for the display section Km of portable instruments, mainly calculators and watches, which use a waveform drive system with a small duty ratio.

[Brief explanation of drawings]

Fig. 1 ra)-(e) tiv-57 time division drive waveform, (
b). (d) shows a half-selected waveform, and FIG. 2 shows the relationship between the voltage of the liquid crystal cell and the light transmittance corresponding to the waveform of FIG. 1. FIGS. 3(a) and 3(b) are diagrams showing the clear viewing direction of the frame liquid crystal display device. Applicant Shinshu Seiki Co., Ltd. Agent Mogami Patent Attorney (G) (j)) (C)
(d) Figure 1 tJE -m1 l Figure 2 Figure 3

Claims (1)

[Claims] (1) Represented by the general formula % formula % (21 (3), each group of compounds (1), 121, 131
A mixed liquid crystal composition containing at least one component of each of Iiii in a predominant %. However, Rstff carbon a2-6 straight chain alkyl group R1 is a straight chain alkyl group R having 1 to 5 carbon atoms, ri carbon a straight chain alkyl group R4 is 4 carbon atoms
1 or 6 direct alkyl group (2) All range of the previous ge compound... is 50 to 85 wt% f of the compound (2)
The concentration of the compound (3) in the Ik degree range is 5 to 3 Oat
The liquid crystal composition according to claim 1, characterized in that the f range is 5 to 20 wt%.