JP2001164252A - Liquid crystal medium and liquid crystal display device containing the liquid crystal medium - Google Patents

Abstract

[PROBLEMS] To satisfy various characteristics required for an electro-optical display element, particularly the above-mentioned liquid crystal display element, and have a low threshold voltage, a wide nematic temperature range, and a low viscosity.
The present invention provides a liquid crystal composition and a liquid crystal display element using the liquid crystal composition, which have excellent high-speed response and can maintain a high retention rate up to a high temperature, or a liquid crystal composition and a liquid crystal display element (TN, STN) in which the above-mentioned disadvantages have been conventionally improved. , AM-LCD). SOLUTION: General formula (1), general formula (2) (R: Independently a C 1-15 alkyl, alkenyl, etc. ring
A, ring B, ring C, ring D: 1,4-phenylene, trans-1,4-cyclohexylene, etc., Z ₁ , Z ₂ , Z ₃ , Z ₄ : single bond, CH ₂ CH ₂ ,
COO, OCO, CH ₂ O or the like, n: 0,1, p: 0,1,2 , Y 1, Y 2: F atom, Cl atom, CN or the _{like, Q: OCH 2, OCF 2} , OCHF, single bond , C
A nematic liquid crystal composition containing a compound selected from the group of compounds such as F ₂ , OCF ₂ and OCHF is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal medium containing an indane derivative having a positive dielectric anisotropy, and to a display containing this medium.

[0002]

2. Description of the Related Art Since the appearance of liquid crystal display devices as calculator displays, the development of computers has been the same as that of TN (Twisted Nematic) mode.
The display capacity has been increased to istedNematic) mode, and it has become widely used as an interface between computers and people. In particular, active matrix liquid crystal display devices (AM-LCD) with thin film transistors in each pixel have high image quality that can be replaced by CRT, and are expected to be the most promising display with the backing of flattening and energy saving. Have been.

In the AM-LCD, to increase the contrast,
A voltage is supplied to each pixel by attaching a switching element such as a thin film transistor or a diode to each pixel.

[0006] Unlike the TN / STN passive drive system, the AM-LCD is driven by supplying electric charges to each pixel every several tens of msec through a switching element. For this reason, if the given charge cannot be completely held until the next writing time several tens of milliseconds after the supply of the charge, the display deteriorates. When the charge escapes, the potential between the electrodes decreases, the transmitted light intensity changes, and the contrast decreases. For this reason, a high voltage holding characteristic is required in the AM-LCD. In order to obtain a high voltage holding characteristic, it is necessary to select and use a material that easily maintains a high specific resistance for the liquid crystal composition for AM-LCD.

[0005] In recent years, the demand for notebook computers intended for portable use has been increased, and there has been an increasing demand for a wide operating temperature range that allows outdoor use and low power consumption that enables long-time battery operation. For low power consumption, a liquid crystal composition with a low threshold voltage that can be driven at a low voltage is required. In order to lower the threshold voltage, a material that increases the dielectric anisotropy Δε is necessary. However, in a system having a large dielectric anisotropy, the viscosity is increased and the response is deteriorated. There has been a problem that it is difficult to maintain high resistance because it is susceptible to surrounding contamination.
For this reason, liquid crystal compositions for liquid crystal display devices such as TN, STN, and AM-LCD include (1) a wide liquid crystal temperature range that can be used outdoors.
(2) Stability that can be used even at high temperature conditions (3) Low threshold voltage (4) High voltage holding ratio (5) Adjustable Δn is required to prevent coloring and obtain optimal contrast with a wide viewing angle I have.

Conventional liquid crystal compositions cannot always meet these demands, and have exhibited a decrease in contrast due to a decrease in voltage holding ratio at high temperatures, crystal precipitation at low temperatures, and the appearance of a smectic phase. In addition, when left outdoors at high temperatures or under exposure to UV light or sunlight, the retention rate decreased and display defects were observed.

That is, a high nematic-isotropic transition temperature, a low crystal (or smectic)
There has been no liquid crystal composition or liquid crystal display element which simultaneously satisfies a transition temperature, a low threshold voltage capable of driving at a low voltage, a low viscosity enabling a high-speed response, and a high retention at a high temperature. For example, WO9403558 discloses an example of a liquid crystal composition using a trifluoro compound and a difluoro compound, but has many problems such as a narrow liquid crystal temperature range and a high threshold voltage. That is the current situation.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to satisfy various characteristics required for an electro-optical display device, in particular, the above-mentioned liquid crystal display device, have a low threshold voltage, a wide nematic temperature range, Provided is a liquid crystal composition having a low viscosity, excellent in high-speed response, and capable of maintaining a high retention at a high temperature, and a liquid crystal display device using the same, or a liquid crystal composition and a liquid crystal in which the above-mentioned disadvantages have been improved compared to the prior art Display element
(TN, STN, AM-LCD).

[0009]

The present invention will be described in detail below.

According to a first aspect of the present invention, there is provided a liquid crystal medium based on a mixture of polar compounds having a positive dielectric anisotropy.
(1)

[0011]

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Wherein R is an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, and this group is unsubstituted or has at least one halogen as a substituent. cage, and -O as one or more CH ₂ groups are the O or S atoms each independently present in these groups are not linked directly to one another -, - S -, - CO -, - CO
It may be replaced by O-, -OCO-, or -OCO-O-. Ring A
And ring B are each independently of one another (a) trans-1,4-
Two or more CH ₂ groups xylene group (not one CH ₂ group or adjacent present in this group cycloheteroalkyl is -O- and or
May be replaced -S- in) (b) 1,4-phenylene group (one more CH ₂ groups not CH ₂ group or adjacent that present in the group replaced by -N- (C) 1,4-
Cyclohexenylene, 1,4-bicyclo (2.2.2) octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl,
A group selected from the group consisting of decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl, wherein the above group (a), group (b), group ( c) may be substituted by CN or halogen. n is 0 or 1, Z ₁
And Z ₂ are each independently -COO-, -OCO-, -CH ₂ O-, -O
_{CH 2 -, - CH 2 CH} 2 -, - CH = CH -, - C≡C -, - (CH 2) 4 -, - CH = CH-
CH ₂ CH ₂ —, —CH ₂ CH ₂ —CH = CH— or a single bond. X ₁ , X ₂
And X ₃ are each independently H, F, CF ₃ , OCF ₃ , OCHF ₂ , Cl
Or CN and Y ₁ is H, F, CF ₃ , OCF ₃ , OCHF ₂ , Cl or CN. One or more compounds of the formula
(2)

[0013]

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Wherein R is independently of one another as defined for R in formula (1), and ring C and ring D are each independently of each other, (d) trans-1,4-cyclo hexylene group (this one CH ₂ group or not adjoining present in group two or more CH ₂
Group may be replaced by -O- and / or -S-) (e)
1,4-phenylene group (the two or more CH ₂ groups not one CH ₂ group or adjacent present in the radical may be replaced by a-N-) (f) 1,4-cyclohexylene Senylene, 1,4-bicyclo (2.2.2) octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl and a group selected from the group consisting of decahydronaphthalene-2,6-diyl, Group (d) above, group
(e) and group (f) may be substituted with CN or halogen. Z ₃ and Z ₄ are each independently of each other Z ₁ and Z ₂ in the formula (1)
Has the same definition as X ₄ and X ₅ are each independently H or F
And p is 0, 1 or 2 and Y ₂ is F, Cl or C
N and Q is a single bond, -CF2-, -OCF2- or -OCHF-
It is. A) a liquid crystal medium characterized by containing one or more compounds.

In the second aspect of the present invention, at least two kinds of formulas
The present invention relates to the liquid crystal medium according to the first aspect, which comprises the compound of (1).

A third aspect of the present invention is that at least two kinds of formulas
The present invention relates to the liquid crystal medium according to the first aspect, which comprises the compound of (2).

A fourth feature of the present invention is that the compound of the formula (2) contains at least one compound selected from the following formulas (2-1) to (2-6). A liquid crystal medium according to the first, second or third aspect.

[0018]

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Wherein R is independently the same as R in formula (2), and Z is each independently -CH ₂ CH _2- , -CH = C
H-, -C≡C-,-(CH ₂ ) ₄ -or a single bond. A fifth aspect of the present invention is that the compound of the formula (2) includes at least two or more compounds selected from the formulas (2-1) to (2-6), A liquid crystal medium according to the second, third or fourth aspect.

A sixth aspect of the present invention is characterized in that the compound of the formula (1) includes at least one compound selected from the following formulas (1-1) to (1-14). The present invention relates to the liquid crystal medium according to the first, second, third, fourth or fifth aspect.

[0021]

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[0022]

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Wherein R is independently the same as R in formula (1), and Y ₃ is each independently F, OCF3 or CN
And X ₆ is each independently CN or F.

A seventh aspect of the present invention is the liquid crystal medium according to the first aspect of the present invention, which has a nematic-isotropic transition temperature of at least 65 ° C. and a nematic-crystal (or smectic) transition temperature lower than −20 ° C. , And 25
The first aspect of the present invention, wherein the optical anisotropy at 0 ° C is 0.07 to 0.20, the dielectric anisotropy at 25 ° C is 3 or more, and the viscosity at 20 ° C is 35 mPas or less. , Second, third, fourth,
A liquid crystal medium according to the fifth or sixth aspect.

The eighth aspect of the present invention relates to the first, second, third and third aspects of the present invention.
The present invention relates to an electro-optical display device including the liquid crystal medium according to the fourth, fifth, sixth or seventh aspect. Compounds of the general formula (2) used in the liquid crystal medium of the present invention are described in WO91 / 03450 and
33626. A compound according to 33626, which is a fluorochemically stable liquid crystal compound. However, with these compounds alone, the resulting composition has problems such as precipitation and smectic expression. Further, the compound represented by the general formula (1) is described in WO9
4/18245 is a low-viscosity compound having a relatively small Δn and being chemically stable. However, WO 94/18245 does not give a detailed description such as a composition example of a nematic composition and effects on TN, STN or AM-LCD. The present invention relates to TN, STN, A
As a result of intensive studies on the composition of a liquid crystal medium for a liquid crystal display device such as an M-LCD, the present invention has been made possible by combining these compounds.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A feature of the present invention is a liquid crystal medium comprising at least one kind of the compound represented by the formula (1) and at least one kind of the compound represented by the formula (2). As the compounds represented by the formulas (1) and (2), R is preferably an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, and ring C and ring D are trans-1, 4-cyclohexylene group,
1,4-phenylene group, naphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group is preferable, X ₃ and X ₄ is preferably either F, and more preferably both are F. n and p are preferably 0 or 1. Y ₁ is-
F, —CF ₃ , —OCF ₃ , —OCHF ₂ , and —OCH ₂ F are preferred. Y ₂ is preferably F, Q is a single bond, -OCHF-,
-OCF ₂ -and -CF ₂ -are preferred. The linking groups Z ₃ and Z ₄ are preferably a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, or —C≡C—, and a single bond is particularly preferable. The compound of the formula (2) is preferably contained at 10% or more, more preferably at 15% or more. Among the compounds of formula (2), formula (2-1)
To (2-6) are particularly preferable, and it is more preferable to use two or more of the compounds of formulas (2-1) to (2-6),
More preferably, the linking group Z in the formulas (2-1) to (2-6) is a single bond. Further, the compound of the formula (2) is preferably a compound having the group (3).

[0027]

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The compound of the formula (1) is preferably contained at 10% or more, more preferably at 15% or more. As the compound of the formula (1), ring A and ring B are trans-1,
4-cyclohexylene group, 1,4-phenylene group is preferred,
A trans-1,4-cyclohexylene group is particularly preferred. Further, the linking groups Z ₁ and Z ₂ are preferably a single bond, —CH ₂ CH ₂ —, and particularly preferably a single bond. Further, compounds represented by the formulas (1-1) to (1-14) are more preferable, and two or more of the compounds represented by the formulas (1-1) to (1-14) are more preferably used. The total number of components is preferably 10 or more. When R is an alkenyl group, it preferably has 2 to 5 carbon atoms, and particularly preferably has the following structure.

[0029]

Embedded image (In each of the above structures, the right end is bonded to the ring.) A combination of the following formulas (1) and (2) is preferred. formula
(2) Compound

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And a compound of formula (1)

[0031]

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[0032]

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[0033]

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[0034]

[0035]

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[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. The characteristics measured in the examples are as follows. Tni: Nematic-isotropic transition temperature (° C.) T-n: Crystal or smectic-nematic transition temperature (° C.) Vth: Threshold voltage (V) when injected into a TN-LCD with a cell thickness of 6 μm (no voltage applied電 圧: Dielectric anisotropy at 25 ° C (-) ｎn: Birefringence at 25 ° C (-) η: Viscosity at 20 ° C ( HR: Retention rate at 80 ° C (%) (Injection into TN-LCD with 6μm cell thickness, 5V applied, frame time 20ms, pulse width 64μs and measured voltage and initial applied voltage Resp: Response speed at 25 ° C (msec) (Injection into TN-LCD with a cell thickness of 6 μm, average value of rise time and fall time when 5 V is applied) Resp. Each composition of the following composition ratio was prepared,
The properties were measured. The composition ratio% means mass%. The characteristics measurement results are shown in Tables 1 to 6 below. (Example 1, Comparative Example 1)

[0037]

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[0038]

[Table 1]

(Example 2)

[0040]

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(Example 3, Comparative Example 3)

[0042]

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[0043]

[0044]

[Table 2]

(Embodiment 4)

[0046]

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(Embodiment 5)

[0048]

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[0049]

[0050]

[Table 3]

(Embodiment 6)

[0052]

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(Embodiment 7)

[0054]

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Example 8

[0056]

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[0057]

[Table 4]

(Embodiment 9)

[0059]

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(Embodiment 10)

[0061]

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(Embodiment 11)

[0063]

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(Embodiment 12)

[0065]

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[0066]

[0067]

[Table 5]

(Embodiment 13)

[0069]

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(Embodiment 14)

[0071]

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(Example 15)

[0073]

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[0074]

[0075]

[Table 6]

As is clear from each of the examples, a composition having a wide nematic temperature range and excellent electro-optical characteristics could be prepared by combining the indane derivative and the liquid crystal material shown in the examples.

[0077]

According to the combination of the liquid crystal materials of the present invention,
Satisfies various characteristics required for liquid crystal display elements, and
It is possible to provide a liquid crystal composition having a low threshold voltage, a wide nematic temperature range, a low viscosity, excellent high-speed response, and capable of maintaining a high retention at a high temperature, and a liquid crystal display device using the same. Was.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyofumi Takeuchi 1-67-12 Takashimadaira, Itabashi-ku, Tokyo (72) Inventor Tetsuo Kusumoto 3-11-2-A-202 Honmachi, Ageo-shi, Saitama F-term (reference) 4H027 BA01 BB03 BB04 BC04 BD02 BD03 BD05 BD08 BE04 BE05 CB01 CB02 CB04 CC01 CC04 CE04 CG04 CK01 CK04 CL01 CL04 CM04 CN01 CN04 CP04 CQ01 CQ04 CR04 CT01 CT02 CT03 CT04 CU01 CU04 CW01 CW05 DM04 04

Claims (8)

[Claims] A liquid crystal medium based on a mixture of polar compounds having a positive dielectric anisotropy, comprising a compound of the formula (1) Wherein R is an alkyl group having 1 to 15 carbon atoms or 2 to 15 carbon atoms.
Which is unsubstituted or has at least one halogen as a substituent and one or more of the alkenyl groups present in these groups.
CH ₂ groups each independently are those in which O or S atoms are not directly bonded to each other; -O-, -S-, -CO-, -COO-, -OCO-,-
It may be replaced by OCO-O-. Rings A and B are each, independently of one another, (a) trans-1,4-cyclohexylene group (not one CH ₂ group or adjacent present in this group two or more CH ₂ groups may be replaced by -O- and or -S-) (b) 1,4-phenylene group (the one CH ₂ group or not adjoining present in group two or more CH ₂ Group is
(C) 1,4-cyclohexenylene, 1,4-bicyclo (2.2.2) octylene, piperidine-1,
4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-
A group selected from the group consisting of 2,6-diyl,
(a), group (b) and group (c) may be substituted by CN or halogen. n is 0 or 1, and Z ₁ and Z ₂ are each independently -COO-, -OCO-, -CH ₂ O-, -OCH _2- , -CH ₂ CH _2- , -C
H = CH -, - C≡C - , - (CH 2) 4 -, - CH = CH-CH 2 CH 2 -, - CH 2 CH 2 -C
H = CH- or a single bond. X ₁ , X ₂ and X ₃ are each independently H, F, CF ₃ , OCF ₃ , OCHF ₂ , Cl or CN, and Y ₁
Is H, F, CF ₃ , OCF ₃ , OCHF ₂ , Cl or CN. )of
One or more compounds and a compound of formula (2) (Wherein, R is independently the same as defined for R in formula (1), and ring C and ring D are each independently of each other, (d) trans-1,4-cyclohexylene group (One C present in this group
More CH ₂ groups not H ₂ group or adjacent can be replaced by -O- and or -S-) (e) 1,4-phenylene group (one present in this group A CH ₂ group or two or more non-adjacent CH ₂ groups may be replaced by -N-)
(f) Consists of 1,4-cyclohexenylene, 1,4-bicyclo (2.2.2) octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl and decahydronaphthalene-2,6-diyl A group selected from the group, the above group (d), group (e), group (f) is C
It may be substituted with N or halogen. Z ₃ and Z ₄ have the same definitions as Z ₁ and Z ₂ in the formula (1) independently of each other. X ₄ and X ₅ are each independently H or F, and p is
0, 1 or 2, Y ₂ is F, Cl or CN, Q
Is a single bond, -CF2-, -OCF2- or -OCHF-. )
A liquid crystal medium comprising one or more compounds of the following. 2. The liquid crystal medium according to claim 1, comprising at least two or more compounds of the formula (1). 3. The liquid crystal medium according to claim 1, comprising at least two or more compounds of the formula (2). 4. A compound represented by the formula (2):
4. The liquid crystal medium according to claim 1, comprising at least one compound selected from (2-6). Embedded image (Wherein R is independently the same as R in formula (2), and Z is each independently -CH ₂ CH _2- , -CH = CH-, -C≡C
-,-(CH ₂ ) ₄ -or a single bond. ) 5. The compound of the formula (2), wherein the compound of the formula (2-1) to (2-6)
5. The liquid crystal medium according to claim 1, comprising at least two or more compounds selected from the group consisting of: 6. A compound represented by the formula (1):
6. The liquid crystal medium according to claim 1, comprising at least one compound selected from (1-14). Embedded image Embedded image (Wherein R is independently the same as defined for R in formula (1), Y ₃ is each independently F, OCF3 or CN, and X ₆
Is each independently CN or F. 7. The liquid crystal medium according to claim 1, wherein the nematic-isotropic transition temperature is at least 65 ° C.
A nematic-crystal (or smectic) transition temperature lower than -20 ° C, an optical anisotropy at 25 ° C of 0.07 to 0.20, a dielectric anisotropy at 25 ° C of 3 or more, 7. The liquid crystal medium according to claim 1, which has a viscosity at 35 ° C. of 35 mPa · s or less. 8. An electro-optical display device comprising the liquid crystal medium according to claim 1, 2, 3, 4, 5, 6, or 7.