JP2004131705A - Liquid crystal medium and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal medium having preferable characteristics to practical applications, e.g., a wide range of a nematic phase, a low viscosity, an optical anisotropy Δn appropriate to a used display mode and, above all, a high Δε and the like. <P>SOLUTION: The liquid crystal medium contains one or more species of compounds expressed by formula I and having positive dielectric properties and one or more species of compounds selected from a group consisting of formula II to formula IV. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to liquid-crystal media and liquid-crystal displays containing these media, in particular displays driven by active matrices, and in particular displays of the in-plane switching (IPS) type.

Liquid crystal displays (LCDs) are widely used to display information. The electro-optical modes used are, for example, twisted nematic (TN) mode, super-twisted nematic (STN) mode, optical compensation bend (OCB) mode and voltage controlled birefringence (ECB) mode and various variants thereof. All of these modes use an electric field that is substantially perpendicular to the substrate and the liquid crystal layer, respectively. In addition, an electric field that is substantially parallel to the substrate and the liquid crystal layer is used, for example, an in-plane switching mode. (For example, disclosed in Patent Literature 1 and Patent Literature 2). In particular, this electro-optical mode is used in LCDs for the latest desktop monitors, and is considered to be applied to displays for multimedia applications. The liquid crystals of the present invention are preferably used for this type of display.

-These displays require new liquid crystal media with improved properties. In particular, the dielectric anisotropy (Δε) Δε should be high enough to allow a reasonably low operating voltage. Preferably, Δε should be higher than 8 and very preferably higher than 11, but preferably should be lower than or equal to 22, and especially lower than or equal to 20. Otherwise, the resistance of the mixture tends to be unacceptably low, even for IPS displays, having slightly less stringent requirements than TN-ADM in this regard. In addition to this parameter, the medium should exhibit a suitably wide range of nematic phase, slightly lower birefringence (Δn), slightly lower rotational viscosity, and, as noted above, at least moderately high resistivity.

The display of the present invention is preferably driven by an active matrix (active matrix LCD, AMD for short), preferably a thin-film transistor (TFT) matrix. However, the liquid crystals of the present invention can also be beneficially used in displays with other known driving means.

A variety of different display modes using a low molecular weight liquid crystal material as a composite system with a polymer material, such as a polymer dispersed liquid crystal (PDLC) system disclosed in US Pat. ) Systems and polymer network (PN) systems, or axially symmetric microdomain (ASM) systems. In contrast to these, it is particularly preferred according to the invention to use the liquid crystal medium, which is oriented on the surface, as is. These surfaces are typically pre-treated to achieve a uniform alignment of the liquid crystal material. The display mode according to the present invention preferably uses an electric field substantially parallel to the composite layer.

LCDs are used for both direct-view and projection displays.
Liquid crystal compositions suitable for LCDs and especially for IPS displays are known, for example, from US Pat. . However, these compositions have significant disadvantages. Many of these compositions have, among other disadvantages, too low resistivity values and / or require too high operating voltages. Many of them also have unnecessarily long response times.

German Patent Invention No. 4000451 European Patent No. 0588568 International Publication No. 91/05029 pamphlet JP-A-7-181439 European Patent No. 0667555 European Patent No. 0673986 German Patent Invention No. 19509410 German Patent No. 19528106 German Patent No. 19528107 WO 96/23851 pamphlet WO 96/28521 pamphlet

Therefore, there is a clear need for liquid crystal media having properties suitable for practical use, such as a wide nematic phase range, low viscosity, appropriate optical anisotropy Δn depending on the display mode used, and especially high Δε. Have been.

Surprisingly, it has been found that a suitably high Δε, a suitable phase range and a suitable Δn can be realized, this liquid-crystalline medium not exhibiting the disadvantages of the prior art materials or at least significantly lower Show it at the level.

The liquid crystal display including the liquid crystal medium according to the present invention can be suitably used for a display driven by an active matrix, particularly, an in-plane switching (IPS) display.

These improved liquid crystal media according to the present application comprise at least the following components:
Component A, which is a component having a positive dielectric property, comprising one or more compounds having a positive dielectric property represented by the formula I, and selected from the group consisting of the formulas II to IV Containing one or more compounds having a positive dielectric property,

Where:
R ¹ , R ² , R ³ and R ⁴ independently of one another are alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, alkenyl having 2 to 7 carbon atoms, Component A, wherein R ¹ is alkenyloxy, alkoxyalkyl or fluorinated alkenyl, and R ¹ is preferably alkenyl.
Optionally, additionally a component B having a positive dielectric property,
-Component C, which is optionally a component having neutral dielectric properties, and-Component D, which is optionally a component having negative dielectric properties.

Preferably, component A, a component having a positive dielectric property, comprises one or more compounds having a positive dielectric property, preferably Formulas I and II, more preferably Formulas I, II and III, Most preferably, it comprises the components of each of the formulas I, II, III and IV, more preferably predominantly from them, more preferably essentially from them, and particularly preferably all of them.

Preferably, the liquid crystal mixture of the present invention contains a second component having a positive dielectric property, component B. This component has a dielectric anisotropy of 3 or more, preferably in the range of 3 to 15. Preferably, it comprises a compound having a positive dielectric property, more preferably predominantly of them, more preferably essentially of them, and particularly preferably all of them. Preferably, this is a formula V with a positive dielectric
Where:

R ⁵ has the meaning indicated for R ^{2 in} formula II above,
But when there are two, they are also, independently of each other,
And preferably
And

Z ⁵¹ and Z ⁵² are, independently of each other, and when two Z ⁵¹ are present, and also independently of each other, —CH ₂ CH ₂ —, —COO—, trans—CH ＝ CH—, trans —CF ＝ CF—, —CH ₂ O—, —CF ₂ O— or a single bond, preferably at least one of them is a single bond, and most preferably at least one of them, if present. Are single bonds,
X ⁵ is F, Cl, alkyl halide, alkoxy halide, alkenyl halide or alkenyloxy halide, wherein the halogenation is preferably fluorinated and / or chlorinated, preferably fluorinated; And preferably, X ⁵ is F, OCF ₃ or OCF ₂ H;
n is 0, 1 or 2, preferably 1 or 2;
A compound comprising one or more compounds, preferably predominantly from them, more preferably essentially from them, and particularly preferably all consisting thereof, of the formula IV Is not included.

Preferably, the liquid-crystal mixtures according to the invention contain, in addition to component A, at least one further component. This second component may be any of component B, component C and component D; preferably, the second component of the present invention comprises component B or C, particularly preferably is there.
Obviously, the mixtures according to the invention can also optionally contain three of these components, preferably components A, B and C, and all four of them.

Preferably, the liquid crystal mixture of the present invention contains component C, which is a component having neutral dielectric properties. This component has a dielectric anisotropy in the range of -1.5 to +3. Preferably, it is of the formula VI with a neutral dielectric
Where:

R ⁶¹ and R ⁶² independently of one another have the meanings indicated for R ^{2 in} formula II above,
But when there are two, they are also, independently of each other,
And preferably
And

Z ⁶¹ and Z ⁶² are, independently of each other, and when two Z ⁶¹ are present, and also independently of each other, —CH ₂ CH ₂ —, —COO—, trans—CH ＝ CH—, trans —CFＣＦCF—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCO ₂ — or a single bond, preferably at least one of them is a single bond, and most preferably Is, if present, at least two of them are single bonds,
m is 0, 1 or 2;
And preferably comprises, mainly, from them, more preferably, essentially from them, and particularly preferably, all of them.

In a preferred embodiment of the present invention, the liquid crystal mixture of the present invention comprises a compound of formulas Va to Vg

Where:
R ⁵ is alkyl having 1 to 7 carbon atoms, alkoxy, fluorinated alkyl or fluorinated alkoxy, alkenyl of 2-7 carbon atoms, alkenyloxy, alkoxyalkyl or fluorinated alkenyl,
X ⁵ are, independently of one another, F, Cl, or fluorinated alkyl or fluorinated alkoxy having 1 to 4 carbon atoms, respectively, or a fluorinated alkenyl or fluorine, respectively having 2 to 4 carbon atoms Alkenyloxy chloride, preferably F, OCF ₃ or OCF ₂ H;
L ^{51 to} L ⁵⁶ independently of one another are H or F, preferably at least one of them, preferably L ⁵¹ , more preferably two or more of them, preferably L ⁵¹ , L ⁵² and L ⁵³ are selected F.
At least one compound represented by the formula V selected from the group consisting of the compounds represented by the formula:

Particularly preferred are the formulas Va-1 to Va-4, Vb-1 to Vb-15, Vc-1 to Vc-6 and Vd-1 to Vd-8, Ve-1 to Ve-4, Vf-1. Vf-4 and Vg-1 to Vg-4

Where:
R ⁵ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms,
A liquid crystal mixture containing one or more compounds selected from the group of compounds represented by

In a further preferred embodiment of the invention, which may be the same or a different embodiment as described above, the liquid-crystal mixtures according to the invention have the formulas Vla to Vld and optionally Vle to Vlh

Where:
R ⁶¹ and R ⁶² independently of one another are alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, alkenyl having 2 to 7 carbon atoms, alkenyloxy, alkoxyalkyl or Is fluorinated alkenyl, and L ⁶ is H or F;
And preferably comprises component C, preferably predominantly from them, and most preferably all consisting of them.

The liquid crystal mixture is preferably a compound of the formula Va, wherein the following compounds -R ⁶¹ and R ⁶² are alkyl,
A compound of formula Va, wherein -R ⁶¹ is alkyl and R ⁶² is alkoxy;
A compound of formula Va, wherein -R ⁶¹ is alkyl and R ⁶² is alkenyl;
A compound of formula Vb, wherein R ⁶¹ and R ⁶² are alkyl; a compound of formula Vb, wherein R ⁶¹ is alkyl; and R ⁶² is alkoxyl.
A compound of formula Vc, wherein -R ⁶¹ and R ⁶² are alkyl;
Compounds of formula Vc, wherein -R ⁶¹ is alkyl and R ⁶² is alkoxyl, and compounds of formula Vc, wherein -R ⁶¹ is alkyl and R ⁶² is alkenyl And one or more compounds selected from the group of compounds of formula Vd, wherein -R ⁶¹ and R ⁶² are alkyl.
Particularly preferred liquid-crystal mixtures comprise, in addition to one or more compounds selected from the group of the formulas Vb to Vd, one or more compounds of the formula Va, particularly preferred A mixture containing a compound of Formula Va wherein R ⁶¹ is alkyl and R ⁶² is alkenyl.

Furthermore, the liquid-crystal mixtures according to the invention are a further optional component D, having a negative dielectric anisotropy and having the formula VII
Where:
R ⁷¹ and R ⁷² independently of one another have the meanings indicated for R ^{1 in} formula I above,

And

Z ⁷¹ and ^{Z 72} are, independently of one _{another, -CH 2 CH 2 -, -} COO-, trans -CH = CH-, trans _{--CF = CF -, - CH 2} O -, - CF 2 O- , or A single bond, preferably at least one of them is a single bond, and most preferably both are single bonds;
L ⁷¹ and L ⁷² , independently of one another, are CF or N, preferably at least one of them is CF, and most preferably both of them are CF , And k is 0 or 1,
And preferably comprises predominantly from them, more preferably essentially from them, and particularly preferably all the components D which consist of them.

Preferably, the liquid-crystalline media according to the invention comprise, preferably consist predominantly, and most preferably all, compounds selected from the group of components A to D and in particular the compounds of the formulas I to VII. Consists of
As used herein, the term "comprising" refers to the composition as a whole, for example, when the medium or component refers to one or more compounds or one or more components of interest. It means that it comprises preferably at least 10%, and most preferably at least 20%, by concentration.

In this case, “consisting mainly of” means that the whole related compound contains one or more compounds or one or more components of interest as 55% or more, preferably 60% or more. Above, and most preferably 70% or more.
In this case, “consisting essentially of” means that the whole concerned relates to 80% or more, preferably 90% or more, of one or more compounds or one or more components of interest. %, And most preferably 95% or more.

In this case, the term “consisting entirely of” means that the whole related compound is one or more compounds, or one or two or more components, of 98% or more, preferably 99% or more. , And most preferably 100.0%.

Particularly preferred are liquid-crystalline media in which component A comprises, preferably consists essentially of, and most preferably consists entirely of, the compounds selected from the group of compounds of the formulas I to IV.

Component D comprises a compound of formula VII, preferably of formulas VIIa-VIIc
Where:
R ⁷¹ and R ⁷² each have the meaning shown in formula VII above,
Comprises, preferably consists essentially of, and most preferably consists entirely of, one or more compounds selected from the group of compounds represented by

In Formulas VIIa-VIIc, R ⁷¹ is preferably n-alkyl or 1-E-alkenyl, and R ⁷² is preferably n-alkyl or alkoxy.
Also, other mesogenic compounds not specifically mentioned above can optionally and beneficially be used in the media of the present invention. Such compounds are known to those skilled in the art.

Component A is preferably used at a concentration of 15-90%, preferably 20-80%, more preferably 25-70% and most preferably 30-60% of the total mixture.
Component B is preferably used at a concentration of 0 to 50%, preferably 2 to 20%, and most preferably 3 to 12% of the total mixture.

Component C is preferably used at a concentration of 0 to 70%, preferably 10 to 60%, more preferably 30 to 55%, and most preferably 40 to 50% of the total mixture.
Component D is preferably used at a concentration of 0-30%, preferably 0-20%, and most preferably 5-15% of the total mixture.

Optionally, the media of the present invention can include additional liquid crystal compounds to adjust physical properties. Such compounds are known to those skilled in the art. Their concentration in the media of the present invention is preferably 0-30%, more preferably 0-20%, and most preferably 5-15%.

The liquid-crystalline medium preferably comprises, preferably consists essentially of, one or more of the compounds of the formulas I, II, III, IV, V, VI and VII, respectively, and most preferably It comprises 50 to 100%, more preferably 70 to 100%, most preferably 80 to 100%, and especially 90 to 100%, of components A, B and C, all of which consist.
The liquid-crystalline media according to the invention are characterized by a clearing point above 65 ° C., preferably above 70 ° C., and especially above 75 ° C.
Δn of the liquid crystal medium of the present invention is 0.11 or less, preferably 0.060 to 0.135, more preferably 0.070 to 0.125, more preferably 0.080 to 0.115, And, most preferably, it is in the range of 0.090 to 0.110.

The [Delta] [epsilon] of the liquid crystal medium of the present invention at 1 kHz and 20 [deg.] C. is 8.0 or more, preferably 10.0 or more, most preferably 12.0 or more, and especially 12.0 to 15.0.
The nematic phase of the media of the present invention is preferably at least 0C to 70C, more preferably at least -20C to 70C, most preferably at least -30C to 75C, and especially at least -40C to 75C. ° C, where “at least” means preferably below the lower limit and above the upper limit.

As used herein, the term “having a positive dielectric” refers to a compound or component having Δε> 3.0, and the term “having a neutral dielectric” refers to a compound or a compound having −1.5 ≦ Δε ≦ 3.0 The term compound or component, and the term "having a negative dielectricity", refer to a compound or component where ?? <-1.5. Δε is determined at 1 kHz and 20 ° C. The dielectric anisotropy of the compounds is determined from the results in 10% solutions of the individual compounds in a nematic host mixture. The performance of these test mixtures is determined in both homeotropic and homogeneously oriented cells. The cell gap for both types of cells is about 10 μm. The applied voltage is a square wave with a frequency of 1 kHz, typically a root mean square of 0.5 V to 1.0 V, but less than the capacitive threshold capacity of each test mixture. It is always chosen to be low.

For the compound having a positive dielectric property, the mixture ZLI-4792 is used. For the compound having a neutral dielectric property and the compound having a negative dielectric property, the mixture ZLI-3086 (both mixtures are manufactured by Merck KGaA, Germany) is used. Each is used as a host mixture. The dielectric constant of a compound is determined from the change in the relative value of the host mixture due to the addition of the compound of interest and is extrapolated for a 100% concentration of the compound of interest. At the measurement temperature of 20 ° C., the component having the nematic phase is measured as it is, and all other components are treated in the same manner as the compound.

Both unless otherwise stated, the term "threshold voltage" as used herein, indicates an optical threshold, given by 10% relative contrast (V _10), and "saturation voltage The term "" indicates optical saturation and is given at 90% relative contrast ( _V90 ). The capacitive threshold voltage (V ₀ , also called Frederick threshold V _Fr ) is used only when explicitly described.
All parameter ranges given herein include limiting values, unless expressly stated otherwise.

Throughout this specification, all concentrations are given in weight percent relative to each complete mixture, all temperatures are given in degrees Celsius (Celsius), and all temperature differences, unless explicitly stated otherwise, Is given in degrees Celsius. All physical properties are determined by “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, Status Nov. 1997, Merck KGaA, Germany and are given for a temperature of 20 ° C., unless explicitly stated otherwise. Optical anisotropy (Δn) is determined at a wavelength of 589.3 nm. The dielectric anisotropy (Δε) is determined at a frequency of 1 kHz. The threshold voltage as well as all other electro-optical properties were determined by test cells prepared by Merck KGaA, Germany. The test cell for the determination of Δε has a cell gap of 22 μm. The electrode is a circular ITO electrode with an area of 1.13 cm ² and a protective ring. The alignment layer for homeotropic alignment (ε‖) is lecithin, for homogeneous orientation (epsilon _⊥) is a polyimide AL-1054 of Japan Synthetic Rubber Co., Ltd.. The capacity was determined at a voltage of 0.3 V _rms using a sine wave with a frequency characteristic analyzer Solatron 1260. The light used for the electro-optical measurement is white light. The setup used is equipment commercially available from Otsuka (Otsuka, Japan). Characteristic voltages were determined by perpendicular observation. Threshold voltage _{(V 10)} - mid gray (mid gray) Voltage _{(V 50)} - and saturation voltage _{(V 90),} respectively, 10%, was determined for 50% and 90% relative contrast.

液晶 The liquid crystal medium of the present invention may contain further additives and chiral dopants in usual concentrations. The total concentration of these further constituents ranges from 0% to 10%, preferably from 0.1% to 6%, based on the total mixture. The concentrations of the individual compounds used are each preferably in the range from 0.1% to 3%. These and similar additive concentrations are not considered herein in the values and ranges for the concentrations of the liquid crystal components and compounds of the liquid crystal medium.

The novel liquid crystal medium of the present invention comprises several compounds, preferably 3 to 30, more preferably 8 to 20, and most preferably 10 to 16 compounds. These compounds are mixed in a conventional manner. Generally, a given amount of a compound used in a smaller amount is dissolved in a larger amount of the compound used. When the temperature is above the clearing point of the compound used at high concentration, it is especially easy to observe the completion of the dissolution process. However, also by other conventional methods, such as so-called premixing, which can be a homologous or eutectic mixture of compounds, or the so-called multi-bottom system, in which the contents are ready to use the mixture itself. It is also possible to prepare a medium.

With the addition of suitable additives, the liquid crystal medium of the present invention allows the liquid crystal medium to remain intact, such as all known types of liquid crystal displays, TN-, TN-AMD, ECB-AMD, VAN-AMD, IPS LCD and OCB LCD. It can be modified to be usable for any of the used systems, and especially for complex systems such as PDLC, NCAP, PN LCD, and especially ASM-PA LCD.
The melting point T (C, N) of the liquid crystal, the transition temperature T (S, N) from the smectic (S) phase to the nematic (N) phase, and the clearing point T (N, I) are given in degrees Celsius.

In this specification, and especially in the following examples, the structures of the liquid crystal compounds are indicated by abbreviations, also called initials. The conversion of abbreviations to the corresponding structures is easy according to the following two tables, A and B. All C _n H _{2n + 1} and C _m H _{2m + 1} groups are straight-chain alkyl groups having n or m carbon atoms, respectively. The interpretation of Table B is self-evident. Table A lists only the abbreviation for the core of the structure. Individual compounds are represented by an abbreviation for the core followed by a hyphen and the following codes identifying the substituents R ¹ , R ² , L ¹ and L ² .

Table A:

Table B:

The liquid crystal medium of the present invention is preferably
-7 or more, preferably 8 or more compounds, selected from the group of compounds described in Tables A and B, preferably represented by different formulas, and / or-from the group of compounds described in Table A Selected, preferably one or more, preferably two or more, more preferably three or more compounds represented by different formulas, and / or-selected from the group of compounds described in Table B, preferably Includes three or more, preferably four or more, more preferably five or more compounds represented by different formulas.

(Example)
The following examples illustrate the invention but do not limit it in any way.
However, the configuration of the physical properties tells a person skilled in the art what properties can be achieved and to what extent they can be changed. In particular, the combinations of the various properties that can preferably be achieved are thus made clear for the person skilled in the art.

(Example 1)
A liquid crystal mixture having the composition and properties given in the following table was prepared.
This mixture has advantageously low Δn and high Δε values and is very suitable for displays operating in IPS mode.

(Example 2)
A liquid crystal mixture having the composition and properties given in the following table was prepared.
This mixture has advantageously low Δn and high Δε values and is very suitable for displays operating in IPS mode.

By using the liquid crystal medium of the present invention having properties suitable for practical use, for example, a suitably high Δε, a suitable phase range, and a suitable Δn, it can be applied to a wide range of applications, so that it can be used in related industries. It is a place that contributes to the development.

Claims (10)

In liquid crystal media,
Component A, which is a component having a positive dielectric property, comprising one or more compounds having a positive dielectric property represented by the formula I, and selected from the group consisting of the formulas II to IV Containing one or more compounds having a positive dielectric property,
Where:
R ¹ , R ² , R ³ and R ⁴ independently of one another are alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, alkenyl having 2 to 7 carbon atoms, Component A, wherein R ¹ is alkenyloxy, alkoxyalkyl or fluorinated alkenyl, and R ¹ is preferably alkenyl.
Optionally, additionally a component B having a positive dielectric property,
-Component C, optionally a component having a neutral dielectric property, and-component D, optionally a component having a negative dielectric property.
The liquid crystal medium, comprising: The composition according to claim 1, characterized in that it comprises a component A having a positive dielectric property, comprising one or more compounds having a positive dielectric property represented by the formula I, wherein R ¹ is alkenyl. Liquid crystal medium. The composition according to claim 1, further comprising a component B that is a component having a positive dielectric property and includes one or more compounds represented by Formula V described in the present specification. Liquid crystal medium. The composition according to any one of claims 1 to 3, further comprising a component C which is a component having a neutral dielectric property and comprises one or more compounds represented by the formula VI described in the present specification. A liquid crystal medium according to any one of the above. The composition according to any one of claims 1 to 4, further comprising a component D which is a component having a negative dielectric property and comprising one or more compounds represented by the formula VII described in the present specification. The liquid crystal medium according to item 1. The liquid crystal medium according to claim 1, comprising one or more compounds represented by the formula II according to claim 1. The liquid crystal medium according to claim 1, comprising one or more compounds represented by the formula III according to claim 1. A liquid crystal display comprising the liquid crystal medium according to claim 1. The liquid crystal display according to claim 8, wherein the liquid crystal display is driven by an active matrix. Use of a liquid crystal medium according to any of claims 1 to 7 in a liquid crystal display.