JPS62243682A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:A liquid crystal composition, obtained by blending a specific Nn liquid crystal with Np liquid crystal and further specific compound and having a wide nematic liquid crystal temperature range, improved steepness, low optical threshold voltage and excellent dynamic driving characteristic. CONSTITUTION:A composition obtained by blending (A) preferably 8-90wt% compound expressed by formula I with (B) preferably 2-80wt% compound expressed by formula (C) preferably 3-42.5wt% compound expressed by formula III, (D) preferably <=10wt% compound expressed by formula IV and (E) preferably 8-22.5wt% compound expressed by formula V. In the above-mentioned formulas I-V, R1, R2, R5, R6, R7 and R8 are 1-10C straight-chain alkyl; R3 and R4 are 1-12C straight-chain alkyl.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal composition for a display device, particularly to a liquid crystal composition having good dynamic drive characteristics in field effect mode.

[Traditional ri technique]

Conventionally, nematic compositions for display devices have the general formula R+C00-t, )ho-R' (R, l are also '
represents a straight-chain alkyl group having an arbitrary number of carbon atoms) (hereinafter abbreviated as ECH in the text).
A compound represented by O0-d-CN (R" represents a straight-chain alkyl group with any number of carbon atoms) (hereinafter referred to as P- in the text)
The optical threshold voltage is lowered by adding an Np liquid crystal such as (abbreviated as E). However, if the amount of Np liquid crystal added increases, the electro-optical properties such as steepness, which will be described later, will deteriorate, so it may be necessary to add more Np liquid crystal than necessary. It is not a good idea to add it.

Furthermore, in addition to the above Nn'M, crystal and Np liquid crystal, the general formula R''
By adding a compound represented by CN (R#' represents a straight alkyl group having an arbitrary number of carbon atoms), the clearing point can be lowered and the liquid crystal temperature range can be widened.

[Problem that the invention seeks to solve]

Today, the characteristics required for nematic liquid crystal compositions are: ■ The rise of the voltage-transmittance curve near the optical threshold voltage is steep (hereinafter abbreviated as steepness in the text) ■ The transmittance has a fast response speed to changes in voltage. ■ It can be driven in a wide temperature range mainly in the room.
That is, it must have a wide nematic liquid crystal range. It must be chemically stable and have excellent moisture resistance and light resistance. r9 The driving voltage (or optical threshold voltage) can be freely selected.

When a simple matrix display is dynamically driven, if the effective voltage applied by the IM drive circuit to the liquid crystal of the selected electrode part or the non-selected electrode part is von+Voff, and the number of scanning electrodes is n, then the ratio v is obtained. n/voff is Von/Voff==7 and 7"1"d2τ slow"door.
There is a relationship as follows, and as n increases, the ratio Von/
Voff also becomes smaller.

On the other hand, a twisted nematic mode liquid crystal cell, which is one type of liquid crystal display device, was placed between orthogonal polarizers, and the transmittance of the cell 4 was measured using the electro-optical property measuring device ity:x shown in FIG. By changing the effective voltage applied to the cell 4 by the drive circuit 6 while observing the cell under magnification, an effective voltage-relative transmittance curve as shown in FIG. 2 is obtained. The effective voltage at which the transmittance begins to change as the voltage is increased is the optical threshold voltage vth (in this specification, the effective voltage value required to change the transmittance by 10% is defined as vtb). , as the voltage is further increased, the transmittance increases the optical saturation voltage to vl' (
In this specification, if the effective voltage value necessary to change the transmittance is 90-Vast), then unselected 'f
At the L pole, if the applied effective voltage Voff is smaller than the optical threshold voltage vth, that is, if V o f f < V th = -・- (2), then no voltage is applied. In comparison, its transmittance does not change and it is not selected at all, and if the effective voltage Von applied to the selection electrode section is greater than the saturation voltage Vsat, that is, V o n > V a at - Science 9, part). If so, the transmittance will change sufficiently and it will be selected. Therefore, (3
) is divided by equation (2), the public t 〉%'sal2 ・・・・・・・・・(S Voff Vth ) When this relational expression holds true, the difference between the non-selected electrode and the selected electrode is The difference in transmittance is sufficient.Furthermore, (from equations In order to obtain sufficient contrast at the selective electrode, it is advantageous for vsat/Vth to be close to 1. In other words, the effective voltage-relative transmittance curve in Fig. 2 from the optical threshold voltage to the optical saturation voltage is advantageous. The steeper the slope of the curve, the more constant the contrast (
(or better) the number of scanning lines can be increased.

The above is the reason why condition (2) is necessary. However, since conventionally emphasis has been placed on eliminating temperature dependence in electro-optical characteristics, specific measures have been proposed to improve condition (P).
This is a problem. On the other hand, temperature dependence can now be easily removed by incorporating a degree compensation circuit into the drive circuit, as RCs have become cheaper.

Another problem is the response sequence.

When displaying still images, response speed variations are not so much of a problem. However, in cases where it is necessary to switch between images, such as in computer terminals and word processors, high-speed responsiveness is required. Needless to say, even faster response is required when displaying moving images such as television images.

The invention is intended to solve the above problems, and its purpose is to improve the steepness of nematic liquid crystal compositions for display devices, improve the dynamic drive characteristics, and widen the nematic liquid crystal temperature and curve. The object of the present invention is to provide a nematic liquid crystal composition '4f which has a wide range of m degrees and is chemically stable.

[Mediator to solve problems]

The liquid crystal composition of the present invention includes at least one compound whose general formula is represented by the following formula A, at least one compound whose general formula is represented by the following formula B, at least -fffl of a compound whose general formula is represented by the following formula C, and at least one compound whose general formula is represented by the following formula C. is characterized in that it consists of at least one compound represented by the following and at least one compound whose general formula is represented by the following E.

A--...--R1-@-c o o-o-o-RtB
......R3-Wanichi, TOOR4 C...R37-(Q)-0-R.

D......R,400÷F E---......R5-o-C0O-Q-CN However, R1 and R2 are linear alkyl groups of carbon X61-101 R1 and R1 are R3 and It are linear alkyl groups with 1 to 12 carbon atoms, R1 are linear alkyl groups with 1 to 10 carbon atoms, It is linear alkyl groups with 1 to 10 carbon atoms 1f represents an alkyl group.

The compound represented by the general formula A (hereinafter abbreviated as compound A in the text) is used to improve the steepness and widen the liquid crystal temperature range. The higher the content, the better. However, if it exceeds 90%, the deviation from the eutectic composition will be too large and the effect of lowering the freezing point will not be obtained and precipitation will occur at low temperatures.
8 weight S to 90 weight Itqk are beautiful.

Compound represented by general formula B (hereinafter referred to as compound W in the text)
(abbreviated as B) is a conventional simple Nn liquid crystal and NpWt,
It is used to improve steepness and widen the nematic liquid crystal temperature range by adding an additive to a nematic liquid crystal composition consisting of crystals, and it is ineffective if it is less than 2 tl, so the higher the content, the better. However, if it exceeds 80% by weight, the deviation from the eutectic composition becomes too large and #kb! Since the effect of lowering the d point cannot be obtained and precipitation occurs at low temperatures, 2% to 80% by weight is desired! Yes.

The compound represented by the general formula 〇 (hereinafter abbreviated as compound C in the text) is also effective for improving steepness when added to a conventional nematic liquid crystal composition consisting of a simple Nn crystal and an Np liquid crystal. It is a Nn liquid crystal, and if it is less than 5 times the effect is small, so the higher the content, the better. But 4
If it exceeds 2.5 double sacrificial temperature, the deviation from the eutectic composition will become too large and the effect of lowering the freezing point will not be obtained and precipitation will occur at a low iK.It is desirable that the weight is 5 to 42.5. .

The compound represented by the general formula (hereinafter abbreviated as "compound" in the text) is effective in improving the steepness and lowering the optical threshold voltage. However, compound @D has a low clearing point, so if it is added in a large amount, the clearing point of the nematic liquid crystal composition will increase. make low. Therefore, the content 1i of the compound is 15 times i
ts is desirable, and more preferably 10 weight leeward.

The compound represented by the general formula E (hereinafter abbreviated as compound E in the text) is an Np liquid crystal, and depending on its content, the optical threshold voltage can be lowered or increased. If the optical threshold voltage is low, the maximum constant power of the liquid crystal driving circuit will also be low, which is advantageous because inexpensive ICs can be used.

However, if the content of P-E liquid crystal is too high, the performance of electro-optical characters such as steepness will deteriorate and the clear point will decrease. oT that has unfavorable effects such as narrowing the quasi-crystal range.
Because of its potential, it is best not to overdo this dragon content. That is, it is preferable to have 5-fold breakage to 60-60 t%, and more preferably 8-fold breakage to 22.5-fold breakage. .

〔Example〕

Below, regarding the present invention, actual Ni? This will be explained in detail based on IJ.

The characteristics of the liquid crystal composition were measured as follows.

Is Figure 1 a measurement system for electro-optical characteristics? It is an expression. The measurement cell 4 has a transparent IC electrode made of tin silica oxide on one side of a crushed glass substrate by steaming 4 or the like, and furthermore, that surface is covered with an organic thin film and subjected to an alignment treatment to serve as a spacer. The liquid crystal is sandwiched between frames made of nylon film which also serves as a frame, and the liquid crystal is sealed therein, and then the two glass spermatozoa are fixed facing each other so that the g-crystal layer has the desired thickness, and both sides of the cell are One polarizing plate is attached to each panel (the polarizing axes are aligned so that the light is transmitted when no pressure is applied, and the light is blocked when a voltage is applied).

In the text, the distance between the Gance substrate and the glass substrate (ie, the thickness of the liquid crystal layer) is abbreviated as cell thickness. The light beam emitted from the white light source 1 passes through the lens thread 5 and enters the nine cells 4 from the vertical direction, and the intensity of the transmitted light is measured by a detector provided at the rear. At this time, an alternating rectangular voltage having a frequency of 1 kilohertz and having an arbitrary effective value voltage is applied to the cell 4 by the driving circuit 5. 1 picture of my father-in-law? Liquid crystal cell using 1lIJ fixed system? Figure 2 shows the summed effective voltage-relative transmittance curve. In Figure 2, the transmittance is 1 when the trap is the brightest and when it is the darkest in the normal applied voltage range.
Applied voltage expressed as 00% and 0%? Transmittance 100%
Starting from the voltage and gradually increasing it, the effective value voltage when the transmittance changes by 10% is the original threshold 1rrL'F!
Transmittance is 100% by increasing the L voltage vtb or the applied voltage further.
The effective value voltage when the voltage changes by 90% from the time is defined as the optical saturation voltage vsat.

At this time, the rise (that is, the steepness) of the effective voltage-relative transmittance curve edge near the optical threshold 1 direct voltage is determined as the β value in the following formula ◇ β = vth When lighting (matrix In the cell, the effective voltage (denoted as Vow) of the cell when fL7 is selected is equal to Vast K, and the effective voltage (denoted as Voff) when the light is not turned on (when not selected) is equal to vth (c). When the "eye" is added, the transmittance becomes 90% and 10%, respectively, and the pixel turns on and off.Furthermore, Von becomes Vsat.
If Voff is f or smaller than vth, the respective transmittances will be 90% or more and 109b or less. At this time Vo n/Vo f f) V sat/Vth
= β. On the contrary, if Van is smaller than Vaat and Voff is larger than vth, the respective transmittances will be less than 90% and more than 10%, resulting in poor visibility. That is, Vo n/Vo f f (vs a t/v
When the force tb=β+1ftal is applied, visibility deteriorates. In this way, the β value is 1! If the effective voltage ratio Van/Voff of the signal is smaller, a pixel display with good visibility can be obtained, and to obtain the same image display, the smaller the β value, the smaller the Von/Voff ratio.

In a simple matrix display, the higher the number of scanning lines, the lower the Vo.
Since n/Voff becomes small, the β value also needs to be small (close to 1) $. The above pIl& is Yon/Voff
is the minimum value allowed? This is an indicator of multi-branch characteristics.

The response speed to changes in applied voltage shall be as follows. Transmission i4 for each effective value voltage in steady state when the applied effective value voltage is instantaneously switched from vth to Vaat
The time required for the transmittance to change by 90% of the difference between the rates (that is, the time required for the transmittance to change from 90% to 18%) is expressed in milliseconds as Ton, and similarly, Vsa
When the effective value voltage is instantaneously switched from t to vth, the difference in transmittance for each effective voltage in a steady state is 90
The time required for the attack transmittance to change (transmittance is 10
% to 82%) is expressed as Toff in milliseconds. I built Toll and Toff (
(in milliseconds) is used as an index of response speed.

In general, the time required for the transmittance to change from 0 to 90 after instantaneously switching from an applied voltage of 0 to an arbitrary voltage ν (V) is t On, and the applied voltage is changed from ν to 0.
It is known that when the time required for the transmittance to change from 100 to 10%R after instantaneously switching to R is expressed by the following formula (Reference: M
, 5ehadt, Japan Society for the Promotion of Science 142nd Committee on Organic Materials for Information Science Subcommittee A (Liquid Crystal Group) 11th Study Group Materials 1978).

t6g=37 a. ΔaE"-K(-!-)")=d"
sv/(g,)-E”-!”)toff=η/K(d)! = d2・η/K

7g is the relative spinning rate anisotropy, zFi electric field, K.

Eight out of ten. -2 to □)/4, where d represents the cell thickness, 1+'ε and K are unique to the liquid crystal composition). Therefore, both ton and toff are d! becomes longer in proportion to

The response speed T fixed in this example is also F, which is closely related to the cell thickness.
There is a category A, and although it is qualitative, it was found that T tends to be shorter when the cell thickness is thinner, and longer when the cell thickness is thicker. These relationships are not difficult for those skilled in the art to understand. Therefore, a liquid crystal display using the same liquid crystal composition? The thinner the cell thickness is, the faster the response speed can be.

On the other hand, the steepness β is determined by the cell thickness d (/1) and the refractive index anisotropy Δ
It has been found that when Δnod, which is the core of n, is around 18 to 1.0, it becomes the smallest (fi is good) (References: Yoshio Yamazaki, Yutaka Takeshita, Mitsuo Nagata, Yukio Miyaji, P.
roc@edlngs of the 3rd Int
ernationalDl@play Rss*ar
eh Conferencenee 'JAPANDISP
LAY'83', 520 pages: 1985, ■5ID)
. Hence the contrast? If it is important, the cell thickness d should be Δn
It is best to make a liquid crystal display so that the od is around 18 to 1.0, and it is considered appropriate to compare the steepness of liquid crystal compositions using this cell thickness. . As mentioned above, in order to compare the response time of rounded liquid crystal compositions which are related to the cell thickness, it is necessary to measure the response time at an appropriate thickness.

In view of the above, in this example, the steepness, response speed, and optical threshold voltage were all measured using a cell with the minimum steepness β.

The measurement temperature was 20 degrees Celsius in all cases.

Further, in order to improve the uniformity of alignment, the nematic liquid crystal composition of the present invention to which a trace amount of presteric substance was added was sealed in a cell.

The stability of the nematic liquid crystal phase was expressed by high liquid crystallinity and low-temperature aII&apos; property when sealed in a cell.

In other words, the average annual temperature is 15℃ in Tokyo and 22℃ in Bugumi.
(Japanese Statistics, compiled by the Statistics Bureau of the Prime Minister's Office, 1980 edition, p. 6.7), assuming that the chamber m is 20°C, the cell is placed in a constant temperature bath, and the nematic phase is formed at a temperature 30°C higher than that. Whether the nematic phase is stable or not is referred to as high-temperature liquid crystallinity.If the nematic phase is stable, it is marked as an isotropic liquid.
e 1iquid) is expressed as 1. For low-temperature liquid crystallinity, start with the temperature of the constant temperature bath in which the cell is installed at 20℃, and increase the temperature at 5℃ per day.
When the temperature was lowered by 30°C from the assumed room temperature of 20°C (i.e., constant temperature 41 temperature - 10°C),
.

Is the nematic liquid crystal phase stable or not? It is called low-temperature liquid crystallinity, and if the nematic liquid crystal phase is stable, it is indicated by an O symbol, and if the smectic liquid crystal phase is in a 5ffi solid state or if precipitation occurs, it is indicated by an X symbol.

[Example-1] Table 1 shows the composition and properties of Example-1 according to the present invention. However, in this example, compound B has the general formula Rs -qr◎
-0-R, (wherein R1 and R1 represent a straight-chain alkyl group having 1 to 12 carbon atoms)
qb and compound C, the general formula Rs + ORs (in the formula R
1 and R6 are 1 having 1 to 10 carbon atoms! (representing a chain alkyl group) with 210% by weight and 11% of the compound represented by the general formula
A compound represented by 0 linear alkyl groups (shown) is 5
Table 2 shows the composition and properties of a liquid crystal composition containing ECH and PE as a conventional example.

While the β value representing steepness in Conventional Example-1 is 1265, the β value in Example-1 is t225, which is very good. That is, in a liquid crystal panel using half-open matrix electrodes, in order to reduce the transmittance to 10% or less with selective electrodes (gradation 'I) and to increase the transmittance to 90% or more with non-selective electrodes (4-shaped M4), In Conventional Example-1, only 17 or less scanning 'vL poles can be driven, whereas in Example-1, 25 or more scanning 'vL poles can be driven.

The response violation is 444 milliseconds in Conventional Example-1, whereas it is faster in 'C1 Implementation Series-1 at 296 milliseconds.

The optical threshold voltage vth is 2.59V in conventional example-1.
On the other hand, vth in Example-1 is 1.88 V
@Example-1, which has a very low temperature, has high-temperature liquid crystallinity at 50 degrees Celsius and low-temperature liquid crystallinity at minus 10 degrees Celsius, and is sufficiently stable and has a sufficiently wide nematic property to be used in ordinary display materials. It has a liquid crystal temperature range. More specifically, in Example-1, the high m1411 is in a nematic liquid crystal state even at -40 degrees Celsius or lower, and the low temperature side is in a nematic liquid crystal state even at 55 degrees Celsius, so it can be used for displays under fairly severe conditions. Is possible.

As mentioned above, while the β1 value of Conventional Example-1 is 1.265, Example-1 according to the present invention has a very good value of 1.223. Furthermore, the optical threshold voltage is low, the response speed is fast, and the nematic liquid crystal temperature range is sufficient.

Table 1 Table M2 [Effects of the Invention] As described above, according to the present invention, at least a compound represented by the general formula R1-@-COo-o-o-R1,
A compound represented by the general formula R1-q-G-OR4, a compound represented by the general formula R,? Compound represented by On-, general formula R, Beni b
A compound represented by coo→toF, general formula R, -Q-C
By constructing the nematic liquid crystal composition using the compound represented by OO-baycN, the temperature range of several cinematic products is wide from below -40 degrees Celsius to 55 degrees Celsius, with excellent steepness and optical threshold. We were able to obtain a nematic liquid crystal composition with low voltage, fast response speed, and excellent dynamic drive characteristics.

The use of the nematic liquid crystal composition according to the present invention is highly effective in obtaining excellent display contrast in display elements such as twisted nematic mode and guest-host effect mode (as host liquid crystal).

[Brief explanation of drawings]

Figure Ng1 is a hardware diagram showing the measuring device used in the examples, and Figure 2 is a curve diagram showing changes in relative transmittance versus effective voltage generally obtained using the measuring device. 1...Light source 2-, ,, rays 5...Lens and filter system 4...
Cell 5... Light receiving S (photomultiplier tube). that's all

Claims (1)

[Scope of Claims] At least one compound whose general formula is represented by the following A, at least one compound whose general formula is represented by the following B, at least one compound whose general formula is represented by the following C, and whose general formula is the following A liquid crystal composition comprising at least one compound represented by D and at least one compound represented by the following general formula E. A...▲There are mathematical formulas, chemical formulas, tables, etc.▼ B...▲There are mathematical formulas, chemical formulas, tables, etc.▼ C...▲There are mathematical formulas, chemical formulas, tables, etc.▼ D...▲There are mathematical formulas, chemical formulas, tables, etc. Yes▼ E...▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, R_1 and R_2 are straight chain alkyl groups with 1 to 10 carbon atoms R_3 and R_4 are straight chain alkyl groups with 1 to 12 carbon atoms R_5 and R_6 represents a straight chain alkyl group having 1 to 10 carbon atoms R_7 represents a straight chain alkyl group having 1 to 10 carbon atoms R_8 represents a straight chain alkyl group having 1 to 10 carbon atoms.