KR102537813B1 - Liquid crystalline medium and liquid crystal display - Google Patents

Abstract

상기 식에서, 파라미터는 제 1 항에 정의된 바와 같다.The present invention relates to a genetically positive nema comprising at least one compound of formula (I), at least one compound of formula (T), and at least one compound selected from the group of compounds of formulas (II) and (III), and optionally at least one chiral dopant. Tick media and liquid crystal displays comprising such media, in particular TN-displays, in particular active matrix displays:

In the above formula, the parameters are as defined in claim 1.

Description

Liquid crystal medium and liquid crystal display {LIQUID CRYSTALLINE MEDIUM AND LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystalline medium, preferably a dielectrically positive nema, comprising at least one genetically positive compound and at least one dielectrically neutral compound and preferably comprising at least one chiral dopant and preferably encapsulated in a polymer matrix. It relates to tick media and liquid crystal displays comprising said media, in particular to displays operated in a reflective mode and preferably addressed by an active matrix, which are also particularly well suited for cholesteric reflecting liquid crystals.

Liquid crystal displays (LCDs) are widely used to display information. LCDs are used in direct view displays and projection displays. The electro-optic method used in most displays is still a twisted nematic (TN) method and various modifications thereof. In addition to the above schemes, super twisted nematic (STN) schemes and more recently optically compensated bend (OCB) schemes and electrically controlled birefringence (ECB) schemes and their various modifications, such as vertically aligned nematic (VAN), patterns Polymer stabilized ITO vertically aligned nematic (PVA) mode and polymer stabilized vertically aligned nematic (PSVA) mode and multi-domain vertically aligned nematic (MVA) mode and others are increasingly used. All of these approaches use an electric field substantially perpendicular to the substrate or liquid crystal layer. In addition to these schemes, as in in-plane switching (abbreviated IPS) schemes (eg as disclosed in DE 40 00 451 and EP 0 588 568) and fringe field switching (FFS) schemes, substantially to the substrate or liquid crystal layer There are also electro-optical methods that use parallel electric fields. In particular, the electro-optical method, which corresponds to the latter of these, with good viewing angle characteristics and improved response time, has recently been increasingly used in LCDs for desktop monitors and even displays for TVs and multimedia products, and thus competes with TN-LCDs. there is.

Liquid crystals (LC) according to the present invention are preferably used in improved LCDs using cholesteric liquid crystals, also known as chiral nematic liquid crystals, having a short helical pitch and high dielectric anisotropy, especially for advanced products. . They are particularly useful to operate in a reflective manner, since cholesteric liquid crystals with appropriate cholesteric pitch selectively reflect light so that they are colored and avoid using color filters in LCDs.

The cholesteric liquid crystal can also be encapsulated in a polymer matrix, for example as PDLC or NCAP.

In such products, new liquid crystal media with improved properties are needed. Accordingly, there is a need for liquid crystal media with improved behavior. Their rotational viscosities should be as low as possible. In addition to the above parameters, the medium should exhibit an appropriately wide range of nematic phase, appropriate birefringence (Δn) (preferably in the range of 0.100 to 0.300, even up to 0.400) and a moderately high dielectric anisotropy (Δε). Δε must be high enough to allow for fairly low operating voltages. Preferably it should be 20 or more, preferably 30 or more to allow for easily accessible drivers with reasonably low operating voltages. However, since Δε is detrimental to at least some high resistivity, especially in the case of active matrix addressing, Δε should preferably be 60 or less, especially 55 or less. Most preferably, Δε should be in the range of 32 to 55.

The display according to the present invention is preferably an active matrix LCD (abbreviated AMD) addressed by an active matrix, preferably a matrix of thin film transistors (TFTs). However, the liquid crystals according to the invention can also advantageously be used in displays with other known addressing means.

Liquid crystal compositions suitable for LCDs, in particular for TN-displays, are already well known. However, these compositions have serious weaknesses. Most of these result, among other drawbacks, in many products unfavorably long response times and/or too low contrast ratios. They also most commonly have insufficient reliability and stability, particularly with respect to exposure to heat, moisture, or light (especially UV) irradiation (especially when one or more of these stressors are combined with one another).

Liquid-crystalline media for cholesteric liquid-crystal devices are known, for example, from WO 2010/022891 A1. However, this medium has significant disadvantages, such as the position of the wavelength of the center of selective reflection and/or the undesirable change in clarity (i.e., cholesteric pitch) as a function of temperature, and in many practical applications too high a switchable CLC. mode has an operating voltage (V _op ).

Thus, a wide nematic phase range, an appropriate optical anisotropy (Δn) depending on the type of display used, a high value of Δε, a low viscosity, especially a low rotational viscosity (γ ₁ ), a high contrast ratio in the display, and a particularly fast response time and liquid crystal media with improved properties suitable for practical products, such as good reliability, are highly desired.

Surprisingly, it has recently been found that liquid-crystalline media with suitable phase ranges, suitably high Δε and Δn, and suitably low viscosities can be realized while not exhibiting, or at least to a greatly reduced degree, the weaknesses of the materials of the prior art.

This improved liquid crystalline medium according to the present invention comprises at least the following components:

- at least one compound of formula I:

[In the above formula,

R ¹ is an alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, alkenyl, alkenyloxy, alkoxyalkyl, fluorinated alkenyl or fluorinated alkenyloxy, preferably having 1 to 7 carbon atoms, preferably preferably alkyl or alkoxyalkyl, most preferably n-alkyl;

는

이고,

Is

ego,

L ¹¹ and L ¹² are independently of each other H or F, preferably L ¹¹ and L ¹² are F,

X ¹ is CN or NCS, preferably CN;

i is 0 or 1, preferably 0],

- at least one compound of formula T:

[In the above formula,

R ^T1 and R ^T2 are, independently of each other, alkyl, alkoxy, alkenyl, alkenyloxy, alkoxyalkyl, or alkenyloxy, alternatively R ^T2 can alternatively be X ^T ;

X ^T is F, Cl, fluorinated alkyl or fluorinated alkoxy, fluorinated alkenyl or fluorinated CN or NCS;

When present, at least one of Z ^T1 and Z ^T2 is -C≡C-, when present, the other is independently of each other, and when Z ^T1 is present twice, they are also independently of each other -CH ₂ CH ₂ -; -COO-, trans -CH=CH-, trans -CF=CF-, -CH ₂ O-, -CF ₂ O-, -C≡C- or a single bond;

n is 0, 1 or 2, preferably 0 or 1;

는 서로 독립적으로, 그리고

가 2회 존재하는 경우에는 이들 또한 서로 독립적으로,

are independent of each other, and

When are present twice, they are also independently of each other,

am],

- at least one genetically positive compound having a dielectric anisotropy of greater than 3, preferably comprising at least one compound from each of them, selected from the group of compounds of formulas II and III:

[In the above formula,

R ² and R ³ independently of each other are alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, alkenyl having 2 to 7 carbon atoms, alkenyloxy, alkoxyalkyl or fluorinated alkyl represents kenyl, preferably R ² and R ³ are alkyl or alkenyl;

는 서로 독립적으로,

are independent of each other,

이고, 바람직하게는

and, preferably

이고,

ego,

L ²¹ , L ²² , L ³¹ and L ³² independently of each other are H or F, L ²¹ and/or L ³¹ are preferably F,

X ² and X ³ are independently of each other halogen, halogenated alkyl or alkoxy having 1 to 3 carbon atoms, or halogenated alkenyl or alkenyloxy having 2 or 3 carbon atoms, preferably F, Cl, -OCF ₃ or -CF ₃ , most preferably F, Cl or -OCF ₃ ;

Z ³ is -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O- or a single bond, preferably -CH ₂ CH ₂ -, -COO-, trans-CH=CH- or a single bond, most preferably -COO-, trans-CH=CH- or a single bond;

l, m, n and o independently of each other are 0 or 1], and optionally

- at least one genetically neutral compound, preferably comprising at least one compound from each of these groups, selected from the group of compounds of formulas IV and V:

[In the above formula,

R ⁴¹ to R ⁵² independently of each other have the meanings described for R ² in Formula II above, preferably R ⁴¹ is alkyl and R ⁴² is alkyl or alkoxy, or R ⁴¹ is alkenyl and R ⁴² is alkyl; preferably R ⁵¹ is alkyl and R ⁵² is alkyl or alkenyl, or R ⁵¹ is alkenyl and R ⁵² is alkyl or alkenyl, preferably alkyl;

는 서로 독립적으로, 그리고

가 2회 존재하는 경우에는 이들 또한 서로 독립적으로,

are independent of each other, and

When are present twice, they are also independently of each other,

and, preferably

중 하나 이상은

이고,

one or more of

ego,

는 서로 독립적으로, 그리고

가 2회 존재하는 경우에는 이들 또한 서로 독립적으로,

are independent of each other, and

When are present twice, they are also independently of each other,

and, preferably

중 하나 이상은

이고,

one or more of

ego,

Z ⁴¹ to Z ⁵² are independently of each other, and when Z ⁴¹ and/or Z ⁵¹ are present twice, they are also independently of each other, -CH ₂ CH ₂ -, -COO-, trans-CH=CH-, trans -CF=CF-, -CH ₂ O-, -CF ₂ O-, -C≡C- or a single bond, preferably at least one of Z ⁴¹ and Z ⁴² and at least one of Z ⁵¹ and Z ⁵² respectively is a single bond,

p and q are independently 0, 1 or 2

p is preferably 0 or 1],

At this time, the compound of formula T is excluded from the compound of formula V,

The medium preferably comprises 44 to 50% of a compound of formula I and 30 to 42% of a compound of formula T, or 25 to 40% of a compound of formula I and 45 to 65% of a compound of formula T .

In a preferred embodiment of the present invention, the medium comprises at least one compound of formula T selected from the group of compounds of formulas T-1 and T-2:

In the above formula, the parameters have the respective meanings given in formula T above,

L ^T1 to L ^T6 independently represent H or F, preferably 0, 1, 2 or 3 of them are F and the rest are H.

In a further preferred embodiment of the present invention, the medium is of at least one formula T-2 selected from the group of compounds of formulas T-2-1 and T-2-2, preferably of formula T-2-1 Contains compounds:

In the above formula, the parameters have the respective meanings given in formula T above,

L ^T4 is preferably F.

In a further preferred embodiment of the present invention, the medium, in addition to the compounds of formula T-2, is selected from the group of compounds of formulas T-1-1 and T-1-2, preferably of formula T-1-1 It includes one or more compounds of formula T-1 selected from:

In the above formula, the parameters have the respective meanings given in formula T above,

R ^T1 is preferably alkyl,

R ^T2 is preferably alkoxy.

Instead of or in addition to the compounds of formulas II and/or III, the medium according to the invention may comprise one or more genetically positive compounds of formula VI:

[In the above formula,

R ⁶ 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, preferably alkyl or alkenyl;

는 서로 독립적으로,

are independent of each other,

이고,

ego,

L ⁶¹ and L ⁶² are independently of each other H or F, L ⁶¹ is F;

X ⁶ is halogen, halogenated alkyl or alkoxy having 1 to 3 carbon atoms, or halogenated alkenyl or alkenyloxy having 2 or 3 carbon atoms, preferably F, Cl, -OCF ₃ or -CF ₃ , most preferably F, Cl or -OCF ₃ ,

Z ⁶ is -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF- or -CH ₂ O-, preferably -CH ₂ CH ₂ - , -COO- or trans-CH=CH-, most preferably -COO- or -CH ₂ CH ₂ -,

r is 0 or 1].

In a preferred embodiment of the present invention, the liquid crystalline medium according to the present invention comprises at least one polymerisable compound. The polymerizable compound is a well-known EHA, and a non-mesogenic compound such as 2EHA, or a mesogenic compound. These polymerizable mesogenic compounds are referred to herein as “reactive mesogens” (abbreviated RMs). These polymerisable compounds, whether mesogenic or non-mesogenic, may be mono-reactive or multi-reactive, preferably di-reactive. Preferably, the medium contains both at least one mono-reactive compound and at least one multi-reactive, preferably di-reactive compound. Most preferably, the medium comprises one or more RMs, but non-mesogenic compounds may additionally be present.

RMs can be chiral or achiral and can contain acrylate/methacrylate groups or another polymerizable group. In a particularly preferred embodiment, the RMs are chiral compounds (because the selective reflection wavelength can be tuned simply by polymerizing certain amounts of said chiral RMs), so there is no need to further twist the liquid crystal material, so that the cholesteric pitch is and consequently selective reflection at longer wavelengths. The resulting cholesteric pitch can be advantageously stabilized against further changes, for example by the use of suitable filters (eg UV filters) which protect the liquid crystals from ambient radiation.

If chiral reactive mesogens are used in the liquid-crystalline medium according to the invention, it is also preferred to use photoinitiators in the medium in many cases where it is exposed to UV radiation. The use of photoinitiators results in a significant reduction in the required UV radiation dose.

Chiral reactive mesogens can be used in the liquid-crystalline medium according to the present invention, since only chiral compounds are present in the medium. However, in a preferred embodiment of the present invention, chiral reactive mesogens are used together with conventional (non-reactive) chiral dopants. In this preferred embodiment, the preferred starting value of the cholesteric pitch, or else already somewhat close to said preferred value, can be fixed by means of one or more customary chiral dopant(s). The further use of one or more chiral reactive mesogens then allows further tuning of the cholesteric pitch by depleting said chiral reactive mesogens after exposing the medium to UV radiation.

In the latter of these embodiments, it is in many cases preferred to use conventional chiral dopants and chiral reactive mesogens having HTPs of the same sign with respect to each other. In this embodiment, only a small total concentration is required to achieve a short cholesteric pitch, and the overall physical properties of the mesogenic host material are altered only to a relatively small extent. This preferred embodiment results in relatively low requirements for the protection of the medium against further wavelength changes of selective reflection, after the desired values have been achieved by means of UV irradiation.

However, in some cases it is advantageous to use more than one chiral dopant and more than one chiral reactive mesogen, wherein the conventional chiral dopant has a different sign of HTP than the chiral reactive mesogen. In this case, the central wavelength of the selective reflection may be fixed by a conventional chiral dopant. This central wavelength can then be shifted to longer wavelengths by use of the chiral reactive mesogen. This effect can then be reversed by exposure of the medium to UV radiation. In particular, this latter preferred embodiment results in the lowest requirements necessary for the protection of the medium against further wavelength changes of selective reflection, after the preferred values have been achieved by means of UV irradiation.

It should be noted that, as a first approximation, the HTP of a mixture of chiral compounds, i.e., a conventional chiral dopant and a chiral reactive mesogen, is approximated by adding their respective HTP values weighed by their respective concentrations in the medium. .

RMs can be mono-reactive or bi- or multi-reactive. Particularly preferred is a material comprising at least one two-reactive compound (crosslinking agent) of liquid crystal or at least mesogenic, having a functional group at each end, which may be based on, for example, diacrylate-based RMs.

In case the medium comprises one or more polymerizable compounds, it preferably further comprises one or more polymerization initiators such as photoinitiators and/or thermal initiators.

The liquid-crystalline medium according to the invention may be stabilized, or in a preferred embodiment is stabilized, by polymerization of the respective polymer precursors consisting of said at least one polymerisable compound and optionally said at least one initiator. Preferably, the stabilizing polymer is in the form of a polymer network. That is, the non-polymerizable liquid crystal material/mesogenic material is present in a more or less continuous form in which more or less smooth strands of polymeric material are dispersed. Polymer network stabilized liquid crystals are described, for example, in Dierking, I., Adv. Mater. 12, no. 3, p. 167-181 (2000). In a preferred embodiment of the present invention, the liquid crystalline medium according to the present invention comprises at least one polymerisable compound, preferably an RM.

The host mixture contains a liquid crystal compound having a low molecular weight and preferably one or more chiral dopants in an amount sufficient to cause selective reflection of the electromagnetic spectrum in the visible range. These cholesteric phases with a relatively short cholesteric pitch are preferably stabilized by polymers. Stabilization of the (cholesteric) phase is achieved by adding to a chiral liquid crystal host mixture a mixture comprising one or more polymerizable compounds, preferably RMs, preferably mono-reactive and di-reactive RMs, and a suitable photo-initiator; This is done by polymerizing the polymerizable compound, for example by exposing it to UV radiation for a short period of time. Preferably, the polymerization is performed in an electro-optic cell maintained at a predetermined temperature in the cholesteric phase of the chiral liquid crystal host mixture.

The mesogenic mono-reactive compound according to the present invention preferably comprises one or more ring elements linked together by a direct bond or via a linking group, wherein two of these ring elements may optionally be directly or identical to or different from the linking group. They can be connected to each other through a possible linking group. The ring element is preferably selected from the group of 4, 5, 6 or 7 membered, preferably 5 or 6 membered ring members.

The RMs used according to the present invention are preferably selected from the group of compounds of the formulas VIIA and VIIB:

In the above formula,

R ⁷¹ is H, F, Cl, Br, I, CN, NO ₂ , NCS, SF ₅ , SO ₂ CF ₃ ; or straight-chain or branched, preferably having 1 to 20 C-atoms, unsubstituted, mono- or polysubstituted by F, Cl, Br, I or CN, optionally containing one or more non-adjacent CH ₂ groups -O-, -S-, -NH-, -NR 01 -, -SiR 01 R 02 -, -CO-, -O-, -S-, -NH-, -NR ⁰¹ -, -SiR ⁰¹ R ⁰² -, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -CY ¹ =CY ² - or alkyl replaced by -C≡C, preferably H, halogen; n-alkyl having 1 to 7, preferably 2 to 5 C-atoms, n-alkoxy; alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7, preferably 2 to 5 C-atoms; CN, NCS; halogen, preferably F, Cl; halogenated alkyl, alkenyl or alkoxy, preferably mono-, di- or oligo-fluorinated alkyl, alkenyl or alkoxy, particularly preferably CF ₃ , OCF ₂ H or OCF ₃ ,

이고,R ⁰¹ and R ⁰² independently of each other are H or alkyl having 1 to 12 C-atoms;

ego,

은 바람직하게는 하나 이상의 고리를 포함하는 메소젠성 잔기, 가장 바람직하게는 화학식

의 2가 라디칼이고,

is preferably a mesogenic moiety comprising one or more rings, most preferably of the formula

2 of is a radical,

은 서로 독립적으로 방향족 및/또는 지환족 고리, 또는 둘 이상의 융합된 방향족 또는 지환족 고리를 포함하는 기이며, 이때 이들 고리는 임의로 N, O 및/또는 S로부터 선택되는 하나 이상의 헤테로 원자를 함유하고 임의로 R⁷²에 의해 일치환 또는 다치환되고,

is independently of each other an aromatic and/or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more heteroatoms selected from N, O and/or S, optionally mono- or poly-substituted by R ⁷² ;

Z ⁷¹ to Z ⁷⁴ are each independently -O-, -S-, -CO-, -CO-O-, -O-CO-, -S-CO-, -CO-S-, -O-CO- O-, -CO-NR ⁰¹ -, -NR ⁰¹ -CO-, -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, -CH ₂ S-, -CF ₂ O-, -OCF ₂ -, -CF ₂ S-, -SCF-, -CH ₂ CH ₂ -, -CF ₂ CH ₂ -, -CH ₂ CF ₂ -, -CF ₂ CF ₂ -, -CH=N-, -N=CH-, -N=N-, -CH=CR ⁰¹ -, -CY ⁰¹ =CY ⁰² -, -C≡C-, -(CH ₂ ) ₄ -, -CH=CH-CO-O-, -O-CO- CH=CH- or a single bond;

Y ⁰¹ and Y ⁰² are independently of each other F, Cl or CN, alternatively one of them may be H;

R ⁷² is H or alkyl, preferably H or alkyl with 1 to 10 C-atoms;

PG ⁷¹ is a polymerizable or reactive group;

SP ⁷¹ is a spacer group or a single bond;

X ⁷¹ has one of the meanings described for Z ⁷¹ , preferably -O-, -CO-O-, -O-CO-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O- , -OCH ₂ - or a single bond;

는 상기 화학식 I에서

에 대해 기재된 의미를 갖고,

In Formula I above

have the meaning described for

PG ⁷² and PG ⁷³ independently of each other have one of the meanings described for PG ⁷¹ above;

SP ⁷² and SP ⁷³ independently of each other have one of the meanings described for SP ¹¹ above,

X ⁷² and X ⁷³ independently of each other have one of the meanings described for X ⁷¹ above.

In a preferred embodiment of the present invention, the precursor of said polymer comprises in addition to the compound(s) of formula VIIA at least one di-reactive mesogenic monomer, preferably of formula VIIB.

Compounds of formulas VIIA and VIIB according to the present invention may be chiral compounds.

Particularly preferred are polymer precursors comprising at least one compound of formula VIIA and/or formula VIIB having the following group definitions:

- Z ⁷¹ and/or Z ⁷⁴ is -O-, -CO-O-, -OCO-, -O-CO-O-, -CH ₂ -O-, -O-CH ₂ -, -CF ₂ -O -, -O-CF ₂ -, -C≡C-, -CH=CH- or a single bond, most preferably -CO-O-, -O-CO- or -O-;

- Z ⁷¹ is not a single bond;

- ring A ⁷¹ is phenylene, optionally substituted with one or more groups R;

- R ⁷¹ is alkyl or alkoxy having 1 to 12, preferably 1 to 8 C-atoms, or alkenyl, alkenyloxy or alkoxy having 2 to 12, preferably 2 to 7 C-atoms; is alkynyl and/or;

- SP ⁷¹ is optionally mono- or polysubstituted by F, and one or more non-adjacent CH ₂ may in each case independently of one another be replaced by -O-, -CH=CH- or -C≡C-, -O-, -CO-O-, -O-CO-, -O-CO-O- and a single bond of 1 to 12 carbon atoms connected to the ring, preferably to ring "A ⁷¹ " is an alkylene having atoms;

- SP ⁷¹ is a single bond.

MG ⁷² to X ⁷³ are preferably the same as for MG ⁷² to X ⁷¹ .

In a preferred embodiment, rings A ⁷¹ to A ⁷³ independently of each other are aromatic or cycloaliphatic rings, preferably 5, 6 or 7 membered rings, or two or more, preferably 2 or 3 fused aromatic or cycloaliphatic rings. wherein these rings optionally contain one or more heteroatoms selected from N, O and/or S and are optionally mono- or polysubstituted by L ⁷ , wherein L ⁷ is F, Cl, Br, CN , OH, NO ₂ , and/or an alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group having 1 to 12 C atoms, wherein one or more H atoms are optionally substituted with F or Cl.

L ⁷ is preferably F, Cl, CN, OH, NO ₂ , CH ₃ , C ₂ H ₅ , OCH ₃ , OC ₂ H ₅ , COCH ₃ , COC ₂ H ₅ , COOCH ₃ , COOC ₂ H ₅ , CF ₃ , OCF ₃ , OCHF ₂ or OC ₂ F ₅ , especially F, Cl, CN, CH ₃ , C ₂ H ₅ , OCH ₃ , COCH ₃ or OCF ₃ , most preferably F, Cl, CH ₃ , OCH ₃ or COCH ₃ .

Preferred rings A ⁷¹ to A ⁷³ are, for example, furan, pyrrole, thiophene, oxazole, thiazole, thiadiazole, imidazole, phenylene, cyclohexylene, cyclohexenylene, pyridine, pyrimidine, pyrazine, julenes, indenes, naphthalenes, tetrahydronaphthalenes, decahydronaphthalenes, tetrahydropyrans, anthracenes, phenanthrenes and fluorenes.

Particularly preferably, at least one of these rings A ⁷¹ to A ⁷³ is furan-2,5-diyl, thiophene-2, wherein one or two non-adjacent CH ₂ groups are optionally replaced by O and/or S. ,5-diyl, thienothiophene-2,5-diyl, dithienothiophene-2,6-diyl, pyrrole-2,5-diyl, 1,4-phenylene, azulene-2, 6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, naphthalene-2,6-diyl, 1,2,3,4-tetrahydro-naphthalene-2,6- diyl, indenine-2,5-diyl or 1,4-cyclohexylene, wherein these groups are unsubstituted or mono- or polysubstituted with L as defined above.

는 서로 독립적으로 Preferably,

are independent of each other

또는 이들의 거울상이며, 상기 식에서

Or a mirror image thereof, in the above formula

R is alkyl having 1 to 12, preferably 1 to 7 C-atoms, or alkenyl or alkynyl having 2 to 12, preferably 2 to 7 C-atoms, in both One or more non-adjacent -CH ₂ - groups not adjacent to the phenyl ring may be replaced by -O- and/or -CH=CH- and/or one or more H-atoms may be replaced by halogen, preferably F and/or;

Preferably,

는

이다.

Is

am.

In a preferred embodiment of the present invention,

는 단지 단일환상 고리 A⁷¹ 내지 A⁷³만을 함유한다. 매우 바람직하게는, 이는 1 또는 2개의 5 및/또는 6원 고리를 갖는 기이다.energy

contains only monocyclic rings A ⁷¹ to A ⁷³ . Very preferably, it is a group having 1 or 2 5 and/or 6 membered rings.

Preferred subformulas of this group are listed below. For simplicity, in these groups Phe is 1,4-phenylene, PheL is a 1,4-phenylene group substituted with 1 to 4 L groups as defined above, and Cyc is 1,4-cyclohexylene , Pyd is pyridine-2,5-diyl, and Pyr is pyrimidine-2,5-diyl. The following list of preferred groups includes subformulas VII-1 to VII-20 and their mirror images:

In these preferred groups, Z has the meaning of Z ⁷¹ described in Formula VIIA. Preferably, Z is -COO-, -OCO-, -CH ₂ CH ₂ -, -C≡C- or a single bond.

는 하기 화학식 VIIa 내지 VIIj 및 이들의 거울상으로부터 선택된다:Very preferably,

is selected from Formulas VIIa to VIIj and their mirror images:

In the above formula,

L is F, Cl, Br, CN, OH, NO ₂ and/or an alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group having 1 to 12 C atoms, wherein one or more H atoms are optionally F or Cl is replaced,

r is 0, 1, 2, 3 or 4, preferably 0, 1 or 2.

는 매우 바람직하게는

, 뿐만 아니라

이며, 이때 L은 각각 독립적으로 상기 기재된 의미들 중 하나를 갖는다.In these preferred formulas

is very preferably

, As well as

, wherein L each independently has one of the meanings described above.

를 하나 이상 포함한다.Particularly preferred compounds of formula I are groups in which r is 1 or 2

contains one or more

를 둘 이상 및/또는 r이 2인 기

를 하나 이상 포함한다.More preferred compounds of formula I are groups in which r is 1

A group with two or more and/or r equals 2

contains one or more

는 매우 바람직하게는 하기 구조의 기들이다:

are very preferably groups of the structure:

In this case, the 1,4-phenylene ring may be optionally substituted by R, preferably by alkyl, preferably by methyl, and/or alkoxy, and/or by halogen, preferably by F.

More preferably,

는 하기 구조의 기들 또는 이들의 거울상이다:

are groups of the structure or their mirror images:

wherein R has the meaning given above, preferably one or more non-adjacent -CH ₂ - groups may optionally be replaced by -O- and/or -CH=CH- and/or one or more H atoms are halogen, preferably preferably an alkyl having 1 to 6 C-atoms which may be replaced by F, preferably n-alkyl.

In a preferred embodiment of the present invention, the liquid crystalline medium according to the present invention comprises compounds of the sub-formulas I-1 to I-5, preferably compounds of the sub-formulas I-2, I-4 and I-5, more preferably It includes at least one compound of formula I selected from the compounds of sub-formulas I-2 and/or the compounds of I-5, most preferably both the compounds of sub-formulas I-2 and I-5:

In the above formula,

R ¹ has each meaning described for formula (I) above, is preferably alkyl, most preferably n-alkyl, and X ¹ is preferably CN.

In a preferred embodiment of the present invention, the liquid crystalline medium according to the present invention comprises at least one compound selected from the group of compounds of formula II-1 and II-2, preferably of formula II-1:

In the above formula,

The variable has the respective meaning described for Formula II above, and X ² is preferably F or -OCF ₃ .

Preferably, the medium is selected from the group of compounds of Formulas II-1 and II-2, wherein both L ²¹ and L ²² are F.

Preferably, the medium contains at least one compound of formula II-1, which is preferably a compound selected from the group of compounds of formula II-1a to II-1c, preferably of formula II-1c:

In the above formula,

The variable has the respective meaning given above, preferably L ²¹ and L ²² are both F and L ²³ and L ²⁴ are both H, preferably L ²¹ , L ²² , L ²³ and L ²⁴ are all F .

In a preferred embodiment, the medium comprises at least one compound of Formula II-lc, wherein L ²¹ , L ²² , L ²³ and L ²⁴ are all F.

Preferably, the medium comprises, alternatively or additionally, at least one compound selected from the group of compounds of formula II-2a to II-2c, preferably of formula II-2c:

In the above formula,

The variable has each meaning given above, L ²³ to L ²⁷ are H or F independently of each other and other parameters, L ²¹ and L ²² are preferably both F, and two or three of L ²³ to L ²⁷ , most preferably L ²³ to L ²⁵ are F, the other of L ²¹ to L ²⁷ is H or F, preferably H, and X ² is preferably F or -OCF ₃ , most preferably F .

A particularly preferred compound of formula II-2 is a compound of formula II-2c-1:

In the above formula, R ² has the meaning described above.

In another preferred embodiment of the present invention, the medium comprises at least one compound selected from the group of compounds of formulas III-1 and III-2:

In the above formula, the parameters have the respective meanings described for formula III above.

The medium is preferably a compound of formula III-1, preferably a compound selected from the group of compounds of formulas III-1a to III-1f, preferably of formulas III-1a, III-1c and III-1d It comprises at least one compound selected from the group of compounds, most preferably each of formulas III-1a and/or III-1c and/or III-1d, preferably each of formulas III-1c and/or III-1f:

In the above formula, the parameters have the respective meanings described above, L ³³ to L ³⁷ are H or F independently of each other and other parameters, L ³¹ and L ³² are preferably both F, and among L ³³ to L ³⁷ Two or three, most preferably L ³³ to L ³⁵ are F, others of L ³¹ to L ³⁷ are H or F, preferably H, and X ³ is preferably F or -OCF ₃ .

Most preferred compounds of Formula III-1 are selected from the group consisting of compounds of Formulas III-1a-1, III-1c and III-1d-1:

In the above formula, R ³ has the meaning described above.

The compound of formula I is preferably selected from the group consisting of compounds of formulas IV-1 to IV-7, more preferably compounds of formulas IV-6 and/or IV-7:

In the above formula,

R ⁴¹ and R ⁴² have the respective meanings described in Formula IV above, particularly in Formulas IV-1 and IV-5, R ⁴¹ is preferably alkyl or alkenyl, preferably alkenyl, and R ⁴² is preferably preferably alkyl or alkenyl, preferably alkyl, alternatively in formula IV-2, R ⁴¹ and R ⁴² are preferably alkyl, and in formula IV-4, R ⁴¹ is preferably alkyl or alkenyl, preferably preferably alkyl, and R ⁴² is preferably alkyl or alkoxy, preferably alkoxy.

Preferably the medium contains at least one compound selected from the group consisting of compounds of formulas IV-6 and IV-7, most preferably at least one compound of each of formulas IV-6 and IV-7.

Preferred compounds of formula IV-6 are compounds of formula CPTP-n-m and CPTP-n-Om, more preferably compounds of formula CPTP-n-Om, and preferred compounds of formula IV-7 are compounds of formula CPGP-n-m. Definitions of these abbreviations (acronyms) are set forth in Tables A-C below and illustrated in Table D below.

In a preferred embodiment, the liquid crystalline medium according to the invention comprises at least one compound of formula V selected from the group of compounds of formulas V-1 to V-4:

In the above formula,

R ⁵¹ and R ⁵² have the respective meanings described in Formula V above, R ⁵¹ is preferably alkyl, more preferably n-alkyl, and R ⁵² in Formula V-1 is preferably alkenyl, preferably is 3-alkenyl, most preferably -(CH ₂ ) ₂ -CH=CH-CH ₃ , R ⁵² in formula V-3 is preferably alkyl or alkenyl, preferably n-alkyl or 3-alkenyl, most preferably -(CH ₂ ) ₂ -CH=CH-CH ₃ , R ⁵² in formulas V-3 to V-6 is preferably alkyl, and in formulas V-4 “F _0/1 " is preferably F.

Preferred compounds of formula V-1 are compounds of formula PP-n-2V and PP-n-2Vm, more preferably compounds of formula PP-1-2V1. Preferred compounds of formula V-2 are compounds of formulas PGP-n-m, PGP-n-2V and PGP-n-2Vm, more preferably compounds of formula PGP-2-m, PGP-3-m and PGP-n-2V am. Preferred compounds of formula V-3 are those of formula PGGIP-n-m. Preferred compounds of formula V-4 are those of formula PGIGP-n-m. Definitions of these abbreviations (acronyms) are set forth in Tables A-C and exemplified in Table D below.

Preferred compounds of formula T-1 are compounds of formula PTP-n-Om, particularly preferably compounds of formulas PTP-1-O2, PTP-2-O1 and PTP-3-O1. Preferred compounds of the formula T-2 are compounds of the formula PPTUI-n-m, particularly preferably compounds of the formulas PPTUI-3-2, PPTUI-3-3, PPTUI-3-4 and PPTUI-4-4.

The compound of formula VI is preferably a compound selected from the group consisting of compounds of formula VI-1 and VI-2, preferably a compound of formula VI-1:

In the above formula,

The variable has the respective meaning given above, the parameters L ⁵³ and L ⁶⁴ independently of each other and other parameters are H or F, preferably Z ⁶ is -CH ₂ -CH ₂ -, preferably X ⁶ is F.

Preferably, the liquid crystalline medium according to the present invention comprises compounds selected from the group consisting of compounds of formulas I to VI and VIIa and VIIb, more preferably compounds of formulas I to V and VIIa and/or VIIb, or more preferably compounds of formulas I to V and VIIa and/or VIIb It preferably consists mainly of these compounds, more preferably consists essentially of these compounds, and most preferably consists entirely of these compounds.

"Comprising" with respect to a composition herein means, unless expressly defined otherwise, that the associated entity such as a medium or component preferably contains at least 10%, more and most preferably, of the listed component or components or compound or compounds. It means containing at a total concentration of 20% or more.

As used herein, "consisting primarily of" means, unless expressly defined otherwise, that the related entity comprises at least 55%, preferably at least 60%, and even more and most preferably at least 70% of the listed ingredient or ingredients or compound or compounds. means to contain

As used herein, "consisting essentially of" means, unless expressly defined otherwise, that the related entity contains at least 80%, preferably at least 90%, more and most preferably 95% of the described ingredient or ingredients or compound or compounds. means containing more than

As used herein, "consisting entirely of" means, unless expressly defined otherwise, that the entity concerned contains at least 98%, preferably at least 99%, and even more and most preferably at least 100.0% of the listed ingredient or ingredients or compound or compounds. means to do

In addition, other mesogenic compounds not explicitly mentioned above may optionally and advantageously be used in the media according to the invention. Such compounds are known to those skilled in the art.

The liquid crystalline medium according to the present invention has a clearing point of greater than 85°C, preferably greater than 90°C.

Δn at 589 nm (Na ^D ) and 20° C. of the liquid crystal medium according to the present invention is preferably in the range of 0.150 or more and 0.350 or less, more preferably in the range of 0.170 or more and 0.250 or less, still more preferably in the range of 0.180 or more and 0.220 or less. is the range

Δ∈ at 1 kHz and 20° C. of the liquid crystal medium according to the present invention is preferably 10 or more, preferably 15 or more, more preferably 20 or more, most preferably 25 or more, preferably 40 or less, even more It is preferably 35 or less, more preferably 10 or more and 40 or less, and most preferably 20 to 30 (or 10 to 40).

The nematic phase of the medium according to the invention without chiral dopants is preferably at least 0°C or less to 80°C or more, more preferably at least -20°C or less to 85°C or more, most preferably preferably at least -20°C or less to 90°C or more, in particular at least -30°C or less to 95°C or more.

The liquid crystal medium is characterized for comparative purposes in a TN display operating at a second transition minimum according to Gooch and Tarry, preferably having an optical retardation (d Δn) in the range of greater than or equal to 1.0 μm and less than or equal to 1.1 μm. do. However, they are preferably used as cholesteric liquid crystals, also called chiral nematic liquid crystals, having a rather short cholesteric pitch, and preferably their cholesteric pitch is such that their selective reflection wavelength is in the visible light range of the electromagnetic spectrum. , i.e. between 400 and 800 nm.

The liquid crystal medium preferably has a helical twitch in the range of 20 μm ^-1 or more, preferably 40 μm ^-1 or more, more preferably 60 μm ^-1 or more, and most preferably 80 μm ^-1 or more and 260 μm ^-1 or less. It contains one or more chiral dopants with an absolute value of helical twisting power (HTP).

The liquid crystalline medium preferably comprises a total of 50 to 100%, more preferably 70 to 100%, more preferably 80 to 100%, in particular 90 to 100% of formulas I, T, II, III, IV, V and VI, preferably compounds of formulas I, T, II, III, IV and V.

The liquid crystalline medium more preferably comprises compounds of formulas I, T, II, III, IV, V and VI, preferably compounds of formulas I, T, II, III, IV and V, more preferably Consists primarily of them, more preferably consists essentially of them, and most preferably consists entirely of them.

The compound of formula I is preferably used in the medium at a total concentration of 1 to 35%, more preferably 2 to 30%, even more preferably 3 to 20%, most preferably 5 to 15% of the total mixture. do.

The compounds of formulas II and III are used together in a medium at a total concentration of 1 to 20%, more preferably 2 to 17%, still more preferably 3 to 16%, and most preferably 5 to 15% of the total mixture. do.

The compound of formula II is preferably used in the medium at a total concentration of 1 to 15%, more preferably 2 to 13% and most preferably 4 to 8% of the total mixture.

The compound of formula III is preferably used in the medium at a total concentration of 0 to 15%, more preferably 2 to 12% and most preferably 5 to 10% of the total mixture.

The compound of formula IV is preferably used in the medium at a total concentration of 0 to 10%, more preferably 0 to 8% and most preferably 0 to 5% of the total mixture.

The compound of formula V is preferably used in the medium at a total concentration of 0 to 10%, more preferably 0 to 8% and most preferably 0 to 5% of the total mixture.

The compound of formula VI is preferably used in the medium at a total concentration of 0 to 10%, more preferably 0 to 8% and most preferably 0 to 5% of the total mixture.

In the composition of the liquid crystal medium, the concentration applies only to the host mixture. Concentration(s) of various additives, in particular chiral dopants, polymerizable compounds and other additives such as stabilizers and dichroic dyes, are not taken into account unless explicitly stated otherwise.

The polymerizable compound, preferably a compound of formula VIIA and/or VIIB, is present in an amount of preferably 0 to 20%, more preferably 2 to 17%, most preferably 5 to 14% of the total mixture, relative to the host mixture. The total concentration is used in the medium.

Preferably at least one polymerization initiator is used, preferably at least one photoinitiator. The concentration of the initiator is 0.1 to 10%, more preferably 0.2 to 5%, most preferably 0.5 to 2% of the total concentration of the polymerizable compounds.

Preferably, the media according to the invention further comprise at least one chiral compound as a chiral dopant in order to adjust their cholesteric pitch. Their total concentration in the medium according to the present invention preferably ranges from 0.1 to 15%, more preferably from 1 to 10% and most preferably from 2 to 6% relative to the host mixture, where consideration of the polymerisable compounds is also not

Optionally, the medium according to the invention may contain additional liquid-crystalline compounds in order to adjust its physical properties. Such compounds are known to those skilled in the art. Their concentration in the medium according to the invention is preferably between 0 and 30%, more preferably between 0.1 and 20% and most preferably between 1 and 15%.

The liquid crystalline medium according to the present invention has a clearing point of greater than 85°C, preferably greater than 90°C, more preferably greater than 100°C, most preferably greater than 120°C and even greater than 130°C.

Preferably the liquid-crystalline medium according to the present invention has a birefringence in the range of greater than or equal to 0.150 and less than or equal to 0.400, preferably greater than or equal to 0.200 and less than or equal to 0.350, and most preferably greater than or equal to 0.240 and less than or equal to 0.330.

Preferably the liquid crystalline medium according to the present application has a dielectric anisotropy ranging from 10 or more to 70 or less, preferably 20 or more to 60 or less, most preferably 30 or more to 55 or less.

The medium according to the invention preferably comprises at least one compound of the formula:

- Formula I-2 (preferably at a concentration of 20 to 40%), and/or

- Formula I-5 (preferably at a concentration of 5 to 20%), and/or

- formula T (preferably at a concentration of 33 to 60%, preferably at a concentration of 35 to 42% or 45 to 70%), and of these

- formula T-1, preferably formula PTP-n-Om (preferably 33 to 41% concentration, preferably 38 to 41% or 50 to 70% concentration, preferably 55 to 65% concentration) ), and/or

- formula T-2, preferably formula PPTUI-n-m (preferably at a concentration of 1 to 10%, preferably at a concentration of 1 to 5%), and/or

- formula II-1c, preferably formula PUQU-n-F; and/or

- Formula II-2c, preferably Formula II-2c-1; and/or

- formula III-1c, preferably formula III-1c-1; and/or

- formula III-1d and/or III-1f, preferably formula III-1f, and/or

- formula IV-6, preferably formula CPTP-n-Om and/or CPTP-n-m, and/or

- formula IV-7, preferably formula CPGP-n-Om and/or CPGP-n-m, and/or

- formula V-1, preferably formula PP-n-mV and/or PP-n-ImVI, and/or

- formula V-2, preferably formula PGP-n-m and/or PGP-n-mV, and/or

- formula R-5011 or S-5011, and/or

- one or more reactive polymerizable compounds; and/or

- one or more polymerization initiators.

As used herein, the term "dielectrically positive" is used for a compound or component in which Δε exceeds 3.0, and the expression "dielectrically neutral" means a compound or component in which Δε is -1.5 or more and 3.0 or less. When used for components, the expression “dielectrically negative” is used for compounds or components with Δ∈ less than -1.5. Δε is determined at a frequency of 1 kHz and at 20 °C. The dielectrically anisotropy of each compound was determined from the results of a 10% solution of each individual compound in a nematic host mixture. If the solubility of each compound in the host mixture is less than 10%, the concentration is reduced by a factor of two until the resulting mixture is at least sufficiently stable to determine its properties. However, preferably the concentration is kept at least 5% to keep the significance of the result as high as possible. The capacity of the test mixture is determined both in cells with homeotropic orientation and cells with homogeneous orientation. The cell gap in both types of cells is about 20 μm. The applied voltage is a rectangular wave with a frequency of 1 kHz and is typically a root mean square (rms) of 0.5 to 1.0 V, but it is always chosen to be below the threshold of the capacity of each test mixture.

Δε is defined as (ε _│ -ε _⊥ ), and ε _av is defined as (ε _│ +2ε _⊥ )/3. Mixture ZLI-4792 for genetically positive compounds and mixture ZLI-3086 for genetically negative compounds as well as for genetic neutrality are used as host mixtures, respectively, both from Merck KGaA, Germany. . The dielectric constant of the compound is determined from the change in each value of the host mixture when the compound of interest is added. These values are extrapolated to 100% concentration of the compound of interest.

Components having a nematic phase at a measurement temperature of 20° C. are measured by themselves, and the others are treated like compounds.

Unless explicitly stated otherwise, the term “threshold voltage” herein refers to the optical threshold and is presented as 10% relative contrast (V 10 ), and the term “saturation voltage” refers to optical saturation and is presented as 90% relative contrast (V ₁₀ ). Contrast (V ₉₀ ). Also, the capacitance threshold voltage (V ₀ ), also referred to as the Freedericks-threshold (V _Fr ), is used only when explicitly stated.

Unless expressly stated otherwise, all ranges of parameters set forth herein are inclusive of the limits.

Unless expressly stated otherwise, throughout this application all concentrations are given in weight percent and are for the respective total mixture, all temperatures are given in degrees Celsius and all temperature differences are given in degrees Celsius. All physical properties are described in "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov. 1997, Merck KGaA, Germany] and, unless explicitly stated otherwise, are described for a temperature of 20°C. The optical anisotropy (Δn) is determined at a wavelength of 589.3 nm. Dielectric anisotropy (Δε) is determined at a frequency of 1 kHz. The threshold voltage as well as all other electro-optical characteristics were measured using a test cell manufactured by Merck KGaA, Germany. The test cell for measuring Δε has a cell gap of about 20 μm. The electrode was a circular ITO electrode with an area of 1.13 cm 2 and a guard ring. The orientation layer was lecithin for vertical orientation (ε _⊥ ) and polyimide AL-1054 from Synthetic Rubber, Japan for horizontal orientation (ε _⊥ ). Capacitance was determined with a frequency response analyzer Solatron 1260 using a sine wave with a 0.3 V _rms voltage. The test cell used had a cell gap selected to have an optical retardation suitable below the first transmission minimum according to Guchi and Terry, typically about 0.45 μm ⁻¹ . The light used for electro-optical measurements was white light. In this study, equipment commercially available from Autronic-Melchers, Karlsruhe, Germany was used. The characteristic voltage was determined under vertical observation. Threshold voltage (V ₁₀ ), mid-grey voltage (V ₅₀ ) and saturation voltage (V ₉₀ ) were determined for 10%, 50% and 90% relative contrast, respectively.

The response time is the increase time (τ _on ) for the change time (τ ₉₀ -τ ₀ ) of the relative contrast from 0 to 90% (ie, including the delay time (τ ₁₀ -τ ₀ )), again from 100%. It is written as the decay time (τ _off ), and the total response time (τ _total = τ _on + τ _off ) for the change time of the relative contrast to be 10%.

The liquid-crystalline medium according to the invention may contain further additives in customary concentrations. The total concentration of these additional constituents ranges from 0 to 10%, preferably from 0.1 to 6%, based on the total mixture. The concentration of the individual compounds used is each preferably in the range of 0.1 to 3%. Where concentration values and ranges of liquid crystal components and compounds of a liquid crystal medium are recited herein, the concentrations of these components and similar additives are not taken into account. This is also effective with the concentration of the dichroic dye used in the mixture not being calculated when the concentrations of the compounds and components of the host mixture are not specified. The concentration of each of the above additives is always listed for the final doped mixture.

The liquid crystal medium according to the present invention consists of several compounds, preferably 3 to 30, more preferably 4 to 20 and most preferably 4 to 16 compounds. These compounds are mixed in a conventional manner. As a rule, compounds used in smaller amounts are dissolved in compounds used in larger amounts. When the temperature is above the clearing point of the compound used in higher concentration, it is particularly easy to observe the dissolution process to completion. However, other conventional methods are used, such as using so-called pre-mixtures, which can be homogeneous or eutectic mixtures of the compounds, or so-called multi-vessel systems, where the components themselves are ready-to-use mixtures. -bottle-systems) may be used to prepare the medium.

The liquid-crystalline medium according to the invention, which preferably comprises at least one chiral dopant, selectively reflects radiation in the visible range of the electromagnetic spectrum, ie in the range from 400 to 800 nm. Preferably, their band of selective reflection extends within said range of wavelengths, more preferably the center wavelength of this reflection band thereof lies within said range, most preferably their band of perfect reflection lies within said range. placed within Preferably they have a selective reflection at half width (1/2 FWHM) ranging from 15 to 60 nm, preferably from 20 to 55 nm and most preferably from 25 to 50 nm. In particular, the relative half width, i.e. the ratio of the half width of the reflection band to the center wavelength, is preferably 1 to 20%, more preferably 2 to 16%, more preferably 4 to 10%, most preferably 6 to 10%. 8% range.

The central wavelength of the selective reflection produced at the temperature described can be calculated from the actual concentration of the chiral dopant in the host used, through the approximation of polynomial (I):

λ _center [c(dop.)]=α [c(dop.)] ^-1 +β [c(dop.)] ^-2 +γ [c(dop.)] ^-3 + ... ( I)

In the above formula,

α, β and γ are the material constants specific for a given combination of chiral dopants in a given host mixture.

c(dop.) is the concentration of the chiral dopant in the host mixture.

In many practical cases, even considering only the first term, the linear term ("α·[c(dopant)] ^-1 ") gives sufficiently accurate results. The parameter "α" is analogous to the reciprocal of HTP (ie, HTP ^-1 ). However, here, in the determination of the selective reflection wavelength of the cholesteric LC similar to the "Bragg" reflection, the effective refractive index of the mixture should be further considered for more accurate numerical calculation.

Typically, the parameters α, β and γ depend more on the type of chiral dopant than on the particular liquid crystal mixture used.

Clearly, they depend on the enantiomeric excess of each chiral dopant. They have their respective maximum absolute values for pure enantiomers and zero for racemates. Herein, these stated values are for the pure enantiomer with an enantiomeric excess greater than 98%.

Preferably the absolute value of the parameter α of each chiral dopant in each liquid-crystalline medium according to the present invention ranges from 5 to 25 nm, more preferably from 10 to 20 nm and most preferably from 12 to 16 nm.

These media may contain one or more chiral dopants. If they contain two or more chiral dopants, they can advantageously be selected in one of the known ways to compensate for the temperature dependence of the cholesteric pitch and thus the selective reflection wavelength, for example. Here, according to the properties of the parameters of the higher order terms of the equation (I), in particular the parameters of the second order, the parameters β, in one host mixture, chiral dopants with the parameters α of the same sign as well as chiral dopants with the parameters of the opposite sign can be used

More preferably an embodiment of the present invention using a single chiral dopant, which shows a low temperature dependence of the derived chiral pitch in each host mixture, i.e. a small parameter β. Liquid-crystal media according to the invention, by adding suitable additives, use liquid-crystal media such as TN, TN-AMD, ECB-AMD, VAN-AMD, IPS and OCB LCDs, or PDLC, NCAP, PN LCDs, especially ASM- It can be modified to be used in all known types of liquid crystal displays using composite systems such as PA LCDs.

The melting point T(C,N), the transition from the smectic phase (S) to the nematic phase (N) T(S,N), and the clearing point T(N,I) of a liquid crystal are described in degrees Celsius.

In this application, particularly in the examples below, the structures of liquid crystal compounds are indicated by abbreviations, also called "acronyms". The transformation of an abbreviation into its corresponding formula is simplified according to the three Tables A-C below.

All of the groups C _n H _2n+1 , C _m H _2m+1 and C _l H _2l+1 are straight-chain alkyl groups having n, m and l carbon atoms, respectively, and C _n H _2n , C _m H _2m and C All of _{the l} H _2l groups are each preferably (CH ₂ ) _n , (CH ₂ ) _m and (CH ₂ ) _l , and -CH=CH- is preferably trans- or E- vinylene.

Table A lists the codes used for the ring elements, Table B lists the codes for the linking groups, and Table C lists the codes for the left and right terminal groups of the molecule.

Table D lists exemplary structures of the molecules together with their respective codes.

Table A: Ring Elements

Table B: Connectors

Table C: end group

In the above, n and m are each an integer, and "..." represents a spacing from other abbreviations in the table above.

The liquid-crystalline medium according to the present invention preferably comprises, in addition to the compound of formula I, at least one compound selected from the group consisting of compounds of the formulas in the table below.

Table D

Table E below lists the chiral dopants preferably used in the liquid crystal media according to the present invention.

Table E

In a preferred embodiment of the present invention, the medium according to the present invention comprises at least one compound selected from the group consisting of the compounds of Table E.

Table F below lists the stabilizers preferably used in the liquid crystalline medium according to the present invention.

Table F

In the table above, "n" means an integer from 1 to 12.

In a preferred embodiment of the present invention, the medium according to the present invention comprises at least one compound selected from the group consisting of the compounds of Table F.

The liquid crystal medium according to the present invention,

- at least 4, preferably at least 6 compounds selected from the group of compounds of table D, preferably

- at least 7, preferably at least 8 compounds selected from the group of compounds in table D, preferably at least 3 compounds of different formulas

includes

The examples provided below illustrate the present invention without limiting it in any way.

However, the physical properties and composition show those skilled in the art what properties can be obtained and to what extent they can be varied. In particular, the various combinations of properties that can be advantageously obtained are well defined for those skilled in the art.

A liquid crystal mixture was realized by the composition and properties given in the table below. Their optical performance was investigated. In particular, their reflectance spectra were recorded.

Example 1

Table 1: Composition and properties of liquid crystal mixture A-0

Examples 1.1 and 1.2

2.7% of the chiral dopant R-5011 (available from Merck KGaA, Darmstadt, Germany) was added to 97.3% of the mixture A-0 of Example 1 to form a circular in the blue-green spectral region at a wavelength of about 500 nm. Each cholesteric mixture with a relatively short cholesteric pitch that reflects polarized light of . The transition temperature from cholesteric liquid crystalline phase to isotropic phase (i.e., clearing point) was 82.6° C. for mixture A-1 with 2.7% R-5011.

Alternatively, 2.7% of the chiral dopant R-5011, the enantiomer of R-5011 (also available from Merck KGaA) was added to 97.3% of mixture A-0. The resulting mixture A-2 had the same properties as mixture A-1 with one exception. It reflects circularly polarized light with a twist in the opposite sense when compared to Mixture A-1 comprising the enantiomeric chiral dopant. This mixture (Mixture A-2), as expected, has the same clearing point as the aforementioned mixture, Mixture A-1.

Mixture A-1 exhibits reflection in the blue-green range of the spectral range of 460 nm to 540 nm (FWHM), the same holds for mixture A-2.

Examples 1.3 and 1.4

Similar to Example 1.1, now 3.0% of the chiral dopant R-5011 was added to 97.0% of the mixture A-0 of Example 1 to prepare a cholesteric mixture A-3. This mixture has selective reflection in the blue region of the visible spectrum at a wavelength of about 450 nm.

In the same way as in Example 1.2, 3.0% of the chiral dopant S-5011 was added here to 97.0% of the mixture A-0. The resulting mixture A-4 has the same properties as mixture A-3 except for one. It reflects circularly polarized light with a twist in the opposite sense when compared to Mixture A-3 comprising the enantiomeric chiral dopant.

The results of all examples are listed in Table 2 below. Also, the parameter "α" defined hereinafter is calculated for each individual embodiment. As expected, for the combination of the chiral dopant R-5011 or its enantiomer S-5011 with the host mixture A-0 this was nearly constant, (13.5±0.05) at the concentrations used here.

Table 2: Results of Example 1

main:

Color: color of optionally reflected light;

λ _min. and λ _max. : each given at 1/2 maximum,

Δλ/2 ≡ (λ _min. - λ _max. )/2, i.e. 1/2 FWHM (full width at 1/2 maximum),

λ _centroid ≡ (λ _min. + λ _max. )/2,

α ≡ c(R-5011)·λ _center and c(S-5011)·λ _center ,

t.b.d.: To be measured.

Example 2

Table 3: Composition and properties of liquid crystal mixture B-0

Example 2.1

2.65% chiral dopant R-5011 (available from Merck KGaA, Darmstadt, Germany) was mixed with 5.0% direactive mesogen RM1 (bis-methacrylate) of formula

and

5.0% direactive mesogen RM2 (also bis-methacrylate, but with slightly different structure, ie shorter spacer chain [using -(CH ₂ -) ₃ instead of -(CH ₂ -) ₆ in RM1) have)

was added to 87.35% of Mixture B-0 of Example 2 to prepare each cholesteric mixture B-1 having a relatively short cholesteric pitch. The transition temperature from the cholesteric liquid crystalline phase to the isotropic phase (i.e., the clearing point) was 122.2°C. Mixture B-1 showed reflection in the green range of the spectrum from 560 nm to 670 nm (FWHM).

The mixture was heated once to a temperature of 60° C. on a hot plate for 20 minutes to promote homogenization (series A) and its properties were investigated. It was then heated a second time to the same temperature on a hot plate for 20 minutes and irradiated again. Mixture (B-1) was investigated as described above. Thereafter, a small amount of a suitable photo-initiator (such as a photoinitiator of the known Irgacure® type) is added to the mixture, which is charged into a test cell, and then the reactive mesogen is polymerized by exposure to UV radiation. The crude mixture was again investigated as described above. The bandwidth of selective reflection typically increases after curing. Δλ/2 may be less than 150 nm, i.e. the reflection band may extend from 440 nm to 740 nm.

Claims (27)

- at least one compound of formula I:

[In the above formula,
R ¹ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy, alkenyl, alkenyloxy, alkoxyalkyl, fluorinated alkenyl or fluorinated alkenyloxy;

Is

ego,
L ¹¹ and L ¹² are independently of each other H or F;
X ¹ is CN or NCS;
i is 0 or 1],
- one or more compounds of formula T-2, wherein the total concentration of compounds of formula T-2 in the medium is in the range of at least 35% by weight and at most 70% by weight:

[In the above formula,
R ^T1 and R ^T2 are, independently of each other, alkyl, alkoxy, alkenyl, alkenyloxy, alkoxyalkyl, or alkenyloxy, alternatively R ^T2 can alternatively be X ^T ;
X ^T is F, Cl, fluorinated alkyl or fluorinated alkoxy, fluorinated alkenyl or CN or NCS;
L ^T1 to L ^T6 represent H or F independently of each other;
- at least one compound selected from the group of compounds of formulas II and III:

[In the above formula,
R ² and R ³ independently of each other are alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, alkenyl having 2 to 7 carbon atoms, alkenyloxy, alkoxyalkyl or fluorinated alkyl represents Kenil,

are independent of each other,

ego,
L ²¹ , L ²² , L ³¹ and L ³² are independently of each other H or F;
X ² and X ³ independently of each other are halogen, halogenated alkyl or alkoxy having 1 to 3 carbon atoms, or halogenated alkenyl or alkenyloxy having 2 or 3 carbon atoms,
Z ³ is -CH ₂ CH ₂ -, -CF ₂ CF ₂ -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH ₂ O- or a single bond;
l, m, n and o are each independently 0 or 1], and
- one or more chiral compounds
A liquid crystal medium containing a. According to claim 1,
Liquid-crystalline medium, wherein the total concentration of compounds of formula (I) in said medium is in the range of greater than or equal to 31% by weight and less than or equal to 58% by weight. delete According to claim 1,
Liquid-crystalline medium, wherein the liquid-crystalline medium comprises a compound of formula (I-2) in a concentration of 20 to 40% by weight:

In the above formula,
R ¹ and X ¹ each have the respective meanings described for Formula I above in claim 1 . According to claim 1,
Liquid-crystalline medium, wherein the liquid-crystalline medium comprises at least one compound of formula III according to claim 1 . According to claim 1,
Liquid-crystalline medium, wherein the liquid-crystalline medium comprises a compound of formula R-5011 or S-5011:

. delete According to claim 1,
Liquid-crystalline medium, wherein the liquid-crystalline medium comprises one or more polymerizable compounds. A liquid crystal display comprising a liquid crystal medium according to any one of claims 1, 2, 4 to 6 and 8. The method of any one of claims 1, 2, 4 to 6 and 8,
The liquid crystal medium used in liquid crystal displays. A mixture of at least one compound of formula I, at least one compound of formula T-2, at least one compound of formula II and/or III, and at least one chiral compound, all as described in claim 1, claims 1, 2 , A method for preparing a liquid crystal medium according to any one of claims 4 to 6 and 8. A composite material comprising a low molecular weight liquid crystalline medium obtainable from the medium according to claim 8 and a polymer. A liquid crystal display comprising the composite material according to claim 12 . A process for the preparation of a composite material according to claim 12 by polymerization of polymer precursors in a liquid crystalline medium. According to claim 1,
A liquid-crystalline medium comprising at least one compound having a nematic phase and at least one chiral reactive mesogen. According to claim 15,
A liquid-crystalline medium comprising one or more non-reactive chiral compounds (ie, chiral dopants). According to claim 15,
The liquid crystal medium further comprises a photoinitiator. According to claim 15,
The liquid-crystalline medium has a selective reflection wavelength in the near UV or visible range of the electromagnetic spectrum above 250 nm. delete A liquid crystal display comprising a liquid crystal medium according to claim 15 . According to any one of claims 15 to 18,
The liquid crystal medium used in liquid crystal displays. A process for preparing a liquid crystal medium according to any one of claims 15 to 18, wherein at least one compound having a nematic phase and at least one chiral reactive mesogen are mixed. A composite material comprising a low molecular weight liquid crystalline medium obtainable from a medium according to claim 15 and a polymer. A liquid crystal display comprising the composite material according to claim 23 . A process for the preparation of a composite material according to claim 23 by polymerization of polymer precursors in a liquid crystalline medium. A method for adjusting the color and/or bandwidth of selective reflection of a composite material according to claim 23 by exposing the medium to UV radiation. The method of any one of claims 1, 2, 4 to 6 and 8,
A liquid crystal medium having a dielectric anisotropy of greater than or equal to 30 and less than or equal to 55 when measured at a frequency of 1 kHz and at 20° C.