JP3503751B2 - Nematic liquid crystal composition and liquid crystal display device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nematic liquid crystal composition useful as an electro-optical display material and a liquid crystal display device using the nematic liquid crystal composition.

[0002]

2. Description of the Related Art TN-LCD is a typical liquid crystal display device.
(Twisted nematic liquid crystal display element)
Used in clocks, calculators, electronic organizers, pocket computers, word processors, personal computers, etc. On the other hand, the amount of information displayed on one screen is increasing with the increase in processing information of OA devices.
ffer) et al. [SID '85 Digest, p. 120 (1985)] or Kinugawa et al. [SID '86 Digest, p. 122 (1986)]
STN (Super Twisted Nematic) -LCD has been developed and is beginning to be widely used in displays for high information processing such as word processors and personal computers.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In order to improve the electro-optical characteristics of STN-LCD, for example, the following compounds have been used.

[0004]

[Chemical 5]

(In the formula, R and R'independently,
It represents an alkyl group, an alkoxyl group, an alkoxyalkyl group or the like. ) However, even if these compounds can be used to improve the electro-optical characteristics, the chemical stability of the liquid crystal material, the low voltage drivability of the liquid crystal display device, and the characteristics such as the driving temperature range are still problematic. Remains.

For example, when any of the compounds represented by the general formulas (a) to (c) and the compound represented by the general formula (d) are mixed, a smectic phase tends to appear, and thus such compounds are likely to appear. Even if a nematic liquid crystal composition containing as a main component is used, it is very difficult to produce a liquid crystal display device which has excellent electro-optical characteristics and can be driven in a wide temperature range.

Further, for example, in the case of a conventional liquid crystal material used for STN-LCD having a large amount of information such as a word processor and a personal computer, it is generally known that the prepared resistance value after the initial or accelerated test is low. Has been. Therefore, a backlight type STN-LCD to which an auxiliary light source is added for the purpose of compensating for dark image quality needs a liquid crystal material having excellent chemical stability such as heat resistance and light resistance.

The problem to be solved by the present invention is to provide a nematic liquid crystal composition having a wide temperature range of a nematic phase, a low threshold voltage, excellent electro-optical steepness, and chemically stable. The present invention aims to provide a liquid crystal display device having improved electro-optical characteristics, which uses the nematic liquid crystal composition as a constituent material.

[0009]

In order to solve the above-mentioned problems, the present invention provides the following nematic liquid crystal compositions.

[First Nematic Liquid Crystal Composition of the Present Invention] (1) General formula (I) and general formula (II)

[0011]

[Chemical 6]

(Wherein R ¹ and R ² are each independently
Linear alkyl group having 2 to 7 carbon atoms or C _p H _{2p + 1} -O
-C _q H _2q , p and q are each independently 1 to
Represents an integer of 5, m and n each independently represents an integer of 0 or 1, and X ^{1 to} X ⁴ each independently represent H.
Or F. And a compound selected from the group consisting of compounds represented by the formula (2), and (2) the general formula (III) and the general formula (IV)

[0013]

[Chemical 7]

(In the formula, R ³ and R ⁴ are each independently
It represents a linear alkyl group or alkoxyl group having 2 to 7 carbon atoms. ) A nematic liquid crystal composition containing a compound selected from the group consisting of compounds represented by:

[Second Nematic Liquid Crystal Composition of the Present Invention] (1) A compound selected from the group consisting of compounds represented by the above general formulas (I) and (II), (2) the above general formula (III) And a compound selected from the group consisting of compounds represented by general formula (IV) and (3) general formula (V)

[0016]

[Chemical 8]

(In the formula, R ⁵ represents a linear alkyl group having 2 to 7 carbon atoms, R ⁶ represents a linear alkyl group or alkoxyl group having 1 to 7 carbon atoms, and m is 0 or 1
Represents an integer, and Y ¹ is a single bond, —COO— or —CH ₂
CH ₂ —, X ⁵ represents F or CH ₃ . The nematic liquid crystal composition containing the compound represented by these.

[Third nematic liquid crystal composition of the present invention] (1) A compound selected from the group consisting of compounds represented by the above general formulas (I) and (II), (2) the above general formula (III) ) And a compound represented by the general formula (IV), (3) a compound represented by the general formula (V), and (4) general formulas (VI) to (VIII)

[0019]

[Chemical 9]

(In the formula, R ^{7 to} R ⁹ each independently represent a linear alkyl group or alkenyl group having 2 to 7 carbon atoms, and ring A and ring B are each independently 1,4 A nematic liquid crystal composition containing a compound selected from the group consisting of compounds represented by a cyclohexylene group or a 1,4-phenylene group.

Further, the present invention provides a twisted nematic or super twisted nematic liquid crystal display device using the above nematic liquid crystal composition.

Typical examples (Nos. 1 to 7) of the compounds represented by the general formulas (I) to (VI) according to the present invention and their phase transition temperatures are shown in Table 1 below and shown in the general formula (VII). ~ (VII
Examples of typical compounds represented by I) (No. 8)
~ 12) and their phase transition temperatures are shown in Table 2 below.

In the table below, mp is the temperature at which the crystal phase changes to the liquid crystal phase or the isotropic liquid phase, and cp is the temperature at which the liquid crystal phase changes to the isotropic liquid phase. Respectively.
In addition, each liquid crystal compound was used after being sufficiently purified by removing impurities by methods such as distillation, column purification, and recrystallization.

[0024]

[Table 1]

[0025]

[Table 2]

The liquid crystal composition of the present invention comprises (1) a compound selected from the group consisting of compounds represented by general formula (I) and general formula (II), and (2) general formula (III) and general formula (IV). ) A compound selected from the group consisting of compounds represented by Of these, the compounds represented by the general formulas (I) and (II) have the effect of lowering the threshold voltage of the liquid crystal composition. Also,
The compounds of the general formula (I) and the general formula (II) have excellent compatibility with other liquid crystal compounds because they have a fluorotolan structure.

The first nematic liquid crystal composition of the present invention is
The above-mentioned (1) general formula (I) and general formula (I
A nematic liquid crystal composition comprising a compound selected from the group consisting of compounds represented by I) and (2) a compound selected from the group consisting of compounds represented by general formulas (III) and (IV), The phase temperature range is wide, the driving voltage is low, and the electro-optical steepness (γ) useful for time-division driving is also excellent. Particularly, the compounds of the general formulas (III) and (IV) are conventionally known compounds, but like the compounds of the general formulas (I) and (II), the threshold voltage of the liquid crystal composition is lowered. Has the effect of Further, since it has excellent compatibility with the compounds represented by the general formula (I) and the general formula (II), a nematic liquid crystal composition having both excellent properties can be easily obtained.

The second nematic liquid crystal composition of the present invention is
The above-mentioned (1) general formula (I) and general formula (I
In addition to a compound selected from the group consisting of compounds represented by I) and (2) a compound selected from the group consisting of compounds represented by general formulas (III) and (IV),
(3) A nematic liquid crystal composition containing a compound represented by the general formula (V). Since the compound represented by the general formula (V) can easily adjust the elastic constant that plays an important role in the display characteristics, a nematic liquid crystal composition having an elastic constant ratio (K ₃₃ / K ₁₁ ) according to the application. You can get things. Furthermore, the birefringence (Δn) of the liquid crystal composition can be optimized according to the purpose, and it is possible to reduce color unevenness of the liquid crystal display device, improve viewing angle characteristics, increase contrast ratio, and the like.

The third nematic liquid crystal composition of the present invention is
The above-mentioned (1) general formula (I) and general formula (I
A compound selected from the group consisting of compounds represented by I), (2) a compound selected from the group consisting of compounds represented by general formulas (III) and (IV), and (3) represented by general formula (V) In addition to the compounds shown in (4)
A nematic liquid crystal composition containing a compound selected from the group consisting of compounds represented by I) to (VIII).

The compounds of the general formulas (VI) to (VIII) are
It has the effect of raising the maximum temperature of the nematic phase of the liquid crystal composition, and the birefringence (Δn) can be optimized according to the purpose.

Further, the compound of the general formula (V) used in the second and third nematic liquid crystal compositions of the present invention has a similar structure to that of the general formula (d) or,
The compound of formula (VIII) is more compatible with the compounds of formulas (I) to (IV), which are essential components of the present invention, than the compound of formula (e) or (f) having a similar structure. It is excellent.

As described above, the nematic liquid crystal composition of the present invention has a wide temperature range of the nematic phase, and a liquid crystal display device which can be used in a wide temperature range can be manufactured.

The contents of the compounds of each group in the first to third nematic liquid crystal compositions of the present invention are represented by the general formulas (I) to (V
It is desirable that the content of the compound represented by III) be within the following range with respect to the total amount.

First, 5 to 6 compounds selected from the group consisting of compounds represented by the general formula (I) and the general formula (II) are used.
It is preferably contained in the range of 0% by weight, 10 to 50
A weight% range is particularly preferred. It is preferable that the compound selected from the group consisting of the compounds represented by the general formula (III) and the general formula (IV) is contained in the range of 5 to 75% by weight, and the range of 25 to 70% by weight is particularly preferable.

In the second and third nematic liquid crystal compositions of the present invention, the compound represented by the general formula (V) is 3 to
It is preferably contained in the range of 45% by weight, preferably 15 to 4
A range of 0% by weight is particularly preferred.

The third nematic liquid crystal composition of the present invention preferably contains a compound selected from the group consisting of compounds represented by the general formulas (VI) to (VIII) in the range of 5 to 30% by weight, The range of 5 to 20% by weight is particularly preferable, but it is preferable to contain the compounds represented by the general formulas (V) to (VIII) in the range of 10 to 70% by weight,
It is particularly preferable to contain it in the range of 25 to 60% by weight.

The liquid crystal composition of the present invention has the above general formula (I)
In addition to the compounds represented by (VIII) to (VIII), in order to improve the characteristics of the liquid crystal composition, a normal nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal or the like recognized as a liquid crystal compound may be contained. However, the use of a large amount of these compounds reduces the characteristics of the nematic liquid crystal composition, and therefore the addition amount is limited according to the required characteristics of the obtained nematic liquid crystal composition.

[0038]

The present invention will be described in detail below with reference to examples.
The invention is not limited to these examples. Moreover, "%" in the compositions of the following Examples and Comparative Examples means "% by weight".

The chemical stability of the composition is 2 g of the liquid crystal composition.
Was placed in an ampoule tube, vacuum degassed, and then nitrogen-filled and sealed, and a heat acceleration test at 150 ° C. for 1 hour and an ultraviolet irradiation acceleration test for 10 hours “SUNTEST” (manufactured by Original Hanau) were performed. The specific resistance of the liquid crystal composition was measured. The characteristics measured in the examples are as follows.

T _NI : Nematic phase-isotropic liquid phase transition temperature (° C.) T → _N : Solid phase or smectic phase-nematic phase transition temperature (° C.) V _th : When a TN-LCD having a cell thickness of 6 μm is constructed. Threshold voltage (V) γ: ratio of saturation voltage (V _sat ) to V _th

(Example 1)

[0042]

[Chemical 10]

A nematic liquid crystal composition No. Thirteen
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 84.1 ° C. V _th : 1.35 V γ: 1.13 Specific resistance before test: 1.2 × 10 ¹² Ω c
Specific resistance after m heating acceleration test: 7.6 × 10 ¹¹ Ω c
m Resistance after UV irradiation acceleration test: 3.9 × 10 ¹¹ Ω c
m

This nematic liquid crystal composition No. 13 is
Reference "High-speed liquid crystal technology" (CMC Publishing Co., 63
Limit value 1.1 of optical steepness of liquid crystal display shown in p)
The value is close to 2 and can be understood to be useful for a liquid crystal display device capable of high time division driving.

Further, the nematic liquid crystal composition of the present invention is
Since the specific resistance value after the initial or accelerated test is high,
For example, it is useful for a backlight type liquid crystal display device to which an auxiliary light source is added for the purpose of compensating for dark image quality.

(Comparative Example 1)

[0047]

[Chemical 11]

A mixed liquid crystal h consisting of was prepared and various properties of this composition were measured. The results were as follows. T _NI : 69.8 ° C. V _th : 1.45 V γ: 1.17 Specific resistance before test: 1.5 × 10 ¹¹ Ω c
m Specific resistance after accelerated heating test: 5.3 × 10 ¹⁰ Ω c
m Specific resistance after UV irradiation acceleration test: 8.8 × 10 ⁹ Ω c
m This mixed liquid crystal h is the nematic liquid crystal composition N of Example 1.
o. Compared with No. 13, the threshold voltage is high, and the specific resistance value at the initial stage or after the accelerated test is low, so that it is clear that it is not a practical nematic liquid crystal composition.

(Example 2)

[0050]

[Chemical 12]

A nematic liquid crystal composition No. 14
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 68.9 ° C. V _th : 1.28 V γ: 1.16 This nematic liquid crystal composition No. 14 as a constituent material
When TN-LCD was manufactured, it was 100 at low temperature of -25 ℃.
It was confirmed that the drive was good even after storage for 0 hours.

(Example 3)

[0053]

[Chemical 13]

A nematic liquid crystal composition No. 15
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 74.5 ° C. V _th : 1.54 V γ: 1.15 This nematic liquid crystal composition No. 15 as a constituent material
When a TN-LCD was produced, it was confirmed that it could be driven even at a low temperature of -40 ° C.

(Example 4)

[0056]

[Chemical 14]

A nematic liquid crystal composition No. 16
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 83.5 ° C. γ: 1.15

(Example 5)

[0059]

[Chemical 15]

A nematic liquid crystal composition No. 17
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 81.9 ° C. V _th : 1.37 V γ: 1.15

(Example 6)

[0062]

[Chemical 16]

A nematic liquid crystal composition No. 18
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 84.7 ° C. V _th : 1.33 V γ: 1.14

A chiral substance "S-811" (manufactured by Merck) was added to this nematic liquid crystal composition to prepare a mixed liquid crystal. On the other hand, on the opposite flat transparent electrode,
An organic film of "150" (manufactured by Nissan Kagaku Co., Ltd.) was rubbed to form an alignment film, and an STN-LCD display cell with a twist angle of 220 degrees was produced. The above-mentioned mixed liquid crystal was injected into this cell to construct a liquid crystal display device, and display characteristics were measured. As a result, a liquid crystal display device having a low threshold voltage, excellent high time division characteristics, and STN-LCD display characteristics with improved display screen flicker and crosstalk phenomenon was obtained.

The chiral substance is added so that the inherent helical pitch P of the mixed liquid crystal and the cell thickness d of the display cell due to the addition of the chiral substance are Δn · d = 0.85 and d / P = 0.53. did.

(Example 7)

[0067]

[Chemical 17]

A nematic liquid crystal composition No. 19
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 79.7 ° C. V _th : 1.32 V γ: 1.14

(Example 8)

[0070]

[Chemical 18]

A nematic liquid crystal composition No. 20
Was prepared and various properties of this composition were measured. The results were as follows. T _NI : 84.2 ° C. γ: 1.14

[0072]

INDUSTRIAL APPLICABILITY The nematic liquid crystal composition of the present invention has a wide temperature range of the nematic phase, a low threshold voltage, excellent electro-optical steepness, and high chemical stability. Therefore, the liquid crystal display device of the present invention using this, it is possible to improve the flicker of the display screen, the crosstalk phenomenon, therefore good driving characteristics and display characteristics in TN-LCD, STN-LCD with a large amount of information. can get.

─────────────────────────────────────────────────── Continued from the front page (56) References JP-A-4-234828 (JP, A) JP-A-60-155142 (JP, A) JP-A-2-233626 (JP, A) European Patent Application Publication 393443 (EP, A 1) German patent application publication 4027840 (DE, A 1) Mitsuharu Okano, Shunsuke Kobayashi, Liquid Crystal = Basic, 1987, 194-199 (58) Fields investigated (Int.Cl. ⁷ , DB) Name) C09K 19/02-19/46

Claims (4)

(57) [Claims] 1. A general formula (I) and a general formula (II): (In the formula, R ¹ and R ² are each independently a carbon atom number of 2 to 7
Represents a linear alkyl group or CpH2p + 1-O-CqH2q, p and q each independently represent an integer of 1 to 5, m and n
Each independently represent an integer of 0 or 1, and X ^{1 to} X ⁴ each independently represent H or F. ) And a compound selected from the group consisting of compounds represented by (2) the general formula (III)
And the general formula (IV): (In the formula, R ³ and R ⁴ are each independently C ² to C 7
Represents a linear alkyl group or an alkoxyl group. ) Containing a compound selected from the group consisting of compounds represented by the general formula (I) and the compound represented by the general formula (II)
Content of 5 to 60 wt% der compound selected from the group consisting of
A compound represented by the general formula (III) or the general formula (IV)
The content of the compound selected from Ranaru group of 5 to 75 wt% der
A nematic liquid crystal composition. (1) General formula (I) and general formula of claim 1.
A compound selected from the group consisting of compounds represented by (II), (2) a compound selected from the group consisting of compounds represented by the general formula (III) and general formula (IV) according to claim 1, and (3)
General formula (V) (In the formula, R ⁵ represents a linear alkyl group having 2 to 7 carbon atoms, R ⁶ represents a linear alkyl group or an alkoxyl group having 1 to 7 carbon atoms, and l is an integer of 0 or 1. the stands, Y ¹ represents a single bond, -COO- or -CH ₂ CH ₂ -. represents, X ⁵ contains a compound represented by representing) a F or CH _3, the general formula (I) and one
Of selected from the group consisting of compounds represented by general formula (II)
The content of the compound is 5 to 60 % by weight , and the content of general formula (III) and
Of selected from the group consisting of compounds represented by general formula (IV)
The content of the compound is 5 to 75 % by weight , represented by the general formula (V) .
Nematic liquid crystal composition The content of the compound is 3 to 45 wt%. (1) The general formula (I) and the general formula according to claim 1.
A compound selected from the group consisting of compounds represented by (II), (2) a compound selected from the group consisting of compounds represented by the general formula (III) and general formula (IV) according to claim 1, (3) claim A compound represented by the general formula (V) according to item 2 and (4) the general formulas (VI) to (VIII) (In the formula, each of R ^{7 to} R ⁹ independently represents a linear alkyl group or an alkenyl group having 2 to 7 carbon atoms, and ring A and ring B are each independently 1,4-cyclohexylene. Basis or
Represents a 1,4-phenylene group. ) Contains a compound selected from the group consisting of compounds represented by the general formula (I) and one
Of selected from the group consisting of compounds represented by general formula (II)
The content of the compound is 5 to 60 % by weight , and the content of general formula (III) and
Of selected from the group consisting of compounds represented by general formula (IV)
The content of the compound is 5 to 75 % by weight , represented by the general formula (V) .
Which is 3 to 45% by weight content of the compound of general formula (VI) ~
A compound selected from the group consisting of the compounds represented by (VIII)
A nematic liquid crystal composition having a content of 5 to 30 % by weight . 4. A twisted nematic or super twisted nematic liquid crystal display device using the nematic liquid crystal composition according to claim 1.