CN118302716A - Liquid crystal medium and liquid crystal display - Google Patents
Liquid crystal medium and liquid crystal display Download PDFInfo
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Abstract
The present invention relates to electro-optic devices and in particular energy efficient liquid crystal displays comprising a liquid crystal switchable layer containing a relatively small amount of one or more dichroic dyes; to a liquid crystal medium for use in said device; and to the use of said dichroic dyes in liquid crystal displays for reducing light leakage and improving contrast.
Description
The present invention relates to electro-optic devices and in particular energy efficient liquid crystal displays comprising a liquid crystal switchable layer containing a relatively small amount of one or more dichroic dyes; to a liquid crystal medium for use in said device and to the use of said dichroic dye in a liquid crystal display for reducing light leakage and improving contrast.
Liquid Crystals (LC) have been widely used since the first discovery of commercially available liquid crystal compounds. Liquid Crystal Displays (LCDs) are used in many fields for information display. LCDs are used for both direct view and projection type displays.
One liquid crystal display mode currently in use is the TN ("twisted nematic") mode. However, a disadvantage of TN LCDs is that the contrast ratio has a strong dependence on viewing angle.
In addition, so-called VA (vertical alignment) displays with a wider viewing angle are known. The LC cell of a VA display contains a layer of LC medium between two transparent electrodes, where the LC medium typically has a negative dielectric anisotropy. In the off-state, the molecules of the LC layer are aligned perpendicular to the electrode surface (homeotropically) or have an inclined homeotropic alignment. When a voltage is applied to both electrodes, a realignment of LC molecules parallel to the electrode surfaces occurs.
Also known are so-called IPS ("in-plane switching") displays which contain an LC layer between two substrates, wherein the two electrodes are arranged on only one of the two substrates and preferably have an intermeshed comb structure. When a voltage is applied to the electrodes, an electric field is thereby generated between them, having a significant component parallel to the LC layer. This results in a realignment of LC molecules in the layer plane.
In addition, so-called FFS (fringe field switching) displays have been reported, see inter alia s.h. jung et al, jpn.j.appl.Phys., volume 43, stage 3, 2004,1028, which contain two electrodes on the same substrate, one of which is structured in a comb-like manner and the other of which is unstructured. A strong so-called "fringe field", i.e. a strong electric field close to the edges of the electrodes, is thereby generated, and such an electric field in the whole cartridge has both a strong vertical component as well as a strong horizontal component. FFS displays have little contrast viewing angle dependence. FFS displays typically contain an LC medium with positive dielectric anisotropy, and an alignment layer, typically a polyimide, which provides planar alignment of the molecules of the LC medium.
FFS displays may operate as active matrix or passive matrix displays. In the case of active matrix displays, individual pixels are typically addressed by integrated nonlinear active elements such as transistors, e.g., thin film transistors or ("TFTs"), whereas in the case of passive matrix displays, individual pixels are typically addressed by multiplexing methods.
Typical applications for in-plane switching (IPS) and Fringe Field Switching (FFS) electro-optical modes are desktop monitors, notebook computers, TV, mobile phones, tablet PCs, etc., and multimedia applications. In general, dielectrically positive liquid-crystalline media having a comparatively low value of dielectric anisotropy are used in FFS displays, but in some cases liquid-crystalline media having a dielectric anisotropy of only about 3 or even lower are also used in IPS displays.
Further improvements have been achieved by the so-called "high brightness FFS" (HB-FFS) mode. One of the advantageous features of the HB-FFS mode is that it enables higher transmittance compared to conventional FFS technology, which allows the panel to operate with lower energy consumption.
Furthermore, FFS displays have been described in s.h.lee et al, appl.Phys.lett.73 (20), 1998, 2882-2883 and s.h.lee et al, liquid Crystals 39 (9), 2012, 1141-1148, which have similar electrode designs and layer thicknesses as FFS displays, but include layers of LC media with negative dielectric anisotropy, but not layers of LC media with positive dielectric anisotropy. LC media with negative dielectric anisotropy can exhibit more favorable director orientations with less tilt and more twist orientations than LC media with positive dielectric anisotropy, as a result of which these displays can have higher transmittance. The display further comprises an alignment layer, preferably a polyimide provided on at least one substrate, which is in contact with the LC medium and induces planar alignment of LC molecules of the LC medium. These displays are also referred to as "super-bright FFS" (UB-FFS) mode displays. These displays require LC media with high reliability.
Especially for monitors, mobile phones, video games and TV applications, it is desirable to advantageously obtain short response times, wide viewing angles, low power consumption, high transmittance and suitably high contrast of LC displays.
It is particularly desirable to provide a display having a high brightness while also giving a favorable contrast, also under ambient light conditions. In this regard, improving the image quality of the dark state can be considered in principle to help increase the contrast. For example, the retardation can generally be reduced by reducing the cell gap and/or by reducing the optical anisotropy of the LC medium to improve the dark state quality. However, such a configuration may adversely affect device transmittance or brightness. The dark state quality can in principle also be improved by adjusting the elastic constant of the LC medium. However, such adjustments may affect the operating voltage and response time of the device.
There remains a need in the art for LC displays having advantageous electro-optic properties and reliability that provide wide applicability under a variety of conditions (e.g., at different temperatures or under different ambient light conditions), or having reduced energy consumption, and for liquid crystal media that are applicable to such LC displays.
It is therefore an object of the present invention to provide an electro-optical device and in particular a display having advantageous electro-optical properties, in particular a high contrast ratio and a good black state, while enabling a high brightness or a high transmittance, a low threshold voltage, a fast addressing time and advantageous reliability and stability in one optical state, in particular at low and high temperatures. It is a further object of the invention to provide a liquid-crystalline medium which can give benefits in these displays and which is suitably advantageous for further optimizing the display. Other objects of the present invention will be readily apparent to those skilled in the art from the following detailed description.
The object is solved by the subject matter defined in the independent claims, while preferred embodiments are set forth in the respective dependent claims and further described below.
The invention provides, inter alia, the following items including main aspects, preferred embodiments and specific features, which individually and in combination help solve the above objects and ultimately provide additional advantages.
A first aspect of the invention provides an electro-optic device comprising:
A switchable layer interposed between two opposite transparent substrates,
Wherein each substrate is provided with an electrode structure or one of the substrates is provided with two electrode structures and the other substrate is not provided with an electrode, and
Two polarizers and optionally at least one optical retarder,
Wherein the switchable layer comprises a liquid crystal medium,
Wherein the liquid crystal medium comprises one or more dichroic dyes, and wherein the one or more dichroic dyes are contained in the medium in a total amount of 2.0 wt% or less.
It has now been recognized that light leakage, especially due to scattering, can detract from the image quality of the dark or black state and thus can also affect the obtainable contrast.
It has surprisingly been found that the addition of one or more dichroic dyes to a liquid crystalline medium in a relatively small amount, in particular in a total amount of 2.0 wt% or less and even more preferably in a total amount of 1.0 wt% or less, can significantly reduce unwanted light leakage in the dark or black state. Thus, providing one or more dichroic dyes as described herein may advantageously enhance the obtainable contrast ratio of an electro-optic device according to the present invention, while it has further been found that suitably high transmittance or brightness, fast response time, low operating voltage and low power consumption, and wide viewing angle of the device may be simultaneously maintained.
According to the present invention, one or more dichroic dyes are provided in a relatively small and limited but effective amount in a liquid crystal medium to effectively improve the dark state and overall contrast of the device and especially the display (e.g., FFS, HB-FFS and especially UB-FFS displays), while not affecting the desired device transmittance or brightness or reducing the device transmittance or brightness to a minimal or even negligible extent.
Thus, an energy efficient electro-optic device and in particular an energy efficient display is provided which advantageously exhibits a particularly high contrast ratio and at the same time exhibits an advantageous measure and a fast response time.
Other aspects of the invention relate to liquid-crystalline media comprising
One or more dichroic dyes in a total amount of 2.0 wt% or less, preferably 1.0 wt% or less; and one or more compounds of formula IV-1
The total amount thereof being at least 20 wt%, preferably at least 30 wt%,
Wherein in formula IV-1, R 41 and R 42 independently of each other represent an alkyl group, an alkoxy group, a fluorinated alkyl group or a fluorinated alkoxy group having 1 to 7C atoms, or an alkenyl group, an alkenyloxy group, an alkoxyalkyl group or a fluorinated alkenyl group having 2 to 7C atoms.
It has surprisingly been found that these liquid-crystalline media are particularly suitable for use in electro-optical devices according to the invention. In particular, these media may impart benefits in achieving improved dark states while also advantageously contributing to low operating voltages, fast response times, and reliability and stability, as well as reliability and stability at low and high temperatures.
Another aspect of the invention relates to the use of one or more dyes, and in particular a polychromatic dye or one or more pigments, in particular one or more dichroic dyes, in a liquid crystal switchable layer comprised in an electro-optical device to reduce light leakage and to improve the contrast of the device.
It has been advantageously recognized that the addition or doping of one or more dichroic dyes in a liquid crystal medium can improve the dark state as well as the overall contrast ratio, while other properties, including high device brightness and short response time, can be adequately maintained. In this regard, the use of one or more dyes may reduce unwanted light leakage, particularly light leakage that may otherwise occur due to scattering even in the presence of polarizers and retarders. Thus, such use according to the present invention makes it possible to provide a liquid crystal display having high contrast, high luminance and transmittance, and a short response time, particularly liquid crystal displays of FFS, UB-FFS, HB-FFS, and IPS modes.
Thus, in a further aspect of the invention, there is provided a method of operating an electro-optic device according to the invention, wherein one or more dichroic dyes are included in the switchable layer and light leakage in the dark state is reduced.
Without thereby limiting the invention, it is illustrated by the following detailed description of various aspects, embodiments and specific features, and specific embodiments are described in more detail.
Herein, halogen represents F, cl, br or I, preferably F or Cl, and more preferably F.
In the present invention, all atoms also include isotopes thereof. In particular, one or more hydrogen atoms (H) may be replaced by deuterium (D), which is particularly preferred in some embodiments; highly deuterated enables or simplifies analytical determination of the compounds, especially in the case of low concentrations.
Herein, alkyl and/or alkoxy means straight or branched alkyl or alkoxy, respectively. It is preferably straight-chain, has 2,3, 4, 5, 6 or 7C atoms and thus preferably represents ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, but also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decyloxy, undecoxy, dodecoxy, tridecyloxy or tetradecyloxy.
In this context, oxaalkyl preferably means straight-chain 2-oxapropyl (=methoxymethyl); 2-oxabutyl (=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl); 2-, 3-, or 4-oxapentyl; 2-, 3-, 4-, or 5-oxahexyl; 2-, 3-, 4-, 5-or 6-oxaheptyl; 2-, 3-, 4-, 5-, 6-, or 7-oxaoctyl; 2-, 3-, 4-, 5-, 6-, 7-or 8-oxanonyl; 2-, 3-, 4-, 5-, 6-, 7-, 8-or 9-oxadecyl.
In this context, alkenyl groups (i.e. alkyl groups in which one CH 2 group is replaced by-ch=ch-groups) may be linear or branched. It is preferably linear and has 2 to 10C atoms. Thus, it represents in particular vinyl; prop-1-or-2-enyl; but-1-, -2-or-3-enyl; pent-1-, -2-, -3-or-4-enyl; hex-1-, -2-, -3-, -4-or-5-enyl; hept-1-, -2-, -3-, -4-, -5-or-6-enyl; oct-1-, -2-, -3-, -4-, -5-, -6-or-7-enyl; non-1-, -2-, -3-, -4-, -5-, -6-, -7-or-8-enyl; dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8-or-9-enyl.
In this context, the alkyl or alkenyl groups at least monosubstituted by halogen are preferably linear and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F. The resulting groups also include perfluorinated groups. In the case of mono-substitution, the fluorine or chlorine substituent may be located at any desired position, but is preferably at the ω position.
In this context, particularly preferably mono-or polyfluorinated alkyl or alkoxy groups having 1,2 or 3C atoms or mono-or polyfluorinated alkenyl groups having 2 or 3C atoms are F、Cl、CF3、CHF2、OCF3、OCHF2、OCFHCF3、OCFHCHF2、OCFHCHF2、OCF2CH3、OCF2CHF2、OCF2CHF2、OCF2CF2CHF2、OCF2CF2CHF2、OCFHCF2CF3、OCFHCF2CHF2、OCF2CF2CF3、OCF2CF2CClF2、OCClFCF2CF3、OCH＝CF2 or ch=cf 2, very particularly preferably F or OCF 3, also CF 3、OCF＝CF2、OCHF2 or och=cf 2.
In this context, the 1, 4-cyclohexylidene ring is depicted as follows:
Wherein the cyclohexylidene ring is a trans-1, 4-cyclohexylidene ring.
In this context, the 1, 4-phenylene ring is depicted as follows:
Electro-optic devices, particularly liquid crystal-based devices, according to the present invention may employ different optical states using electrical switching, in which voltage-controlled switching is applied. These devices can be used, for example, as light shutters and light intensity modulators, in particular liquid crystal-based light modulators, in which the transmission of light can be reversibly changed. Preferably, the electro-optical device is a display for displaying information, in particular an active matrix addressed display. Particularly preferably, the liquid crystal display is a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, UB-FFS, PS-HB-FFS, SA-HB-FFS, polymer stabilized SA-HB-FFS, VA or PS-VA display, more preferably IPS, FFS, HB-FFS or UB-FFS display.
According to the invention, in an electro-optical device, a switchable layer is arranged between two substrates, for example to provide an optical box that is operable in different optical states and that can be switched or actuated electrically. Suitable substrates are transparent substrates, which can preferably be made of glass or plastic.
Voltage application and electrical switching are achieved by providing electrodes. Preferably, the device and in particular the display has an electrode structure providing in-plane switching or fringe field switching, more preferably fringe field switching. In an alternative embodiment, electrodes are provided on both substrates to provide, inter alia, VA switching modes.
In addition to the electrodes, advantageously and preferably, one or both substrates are provided with an alignment or orientation layer made of, for example, polyimide, to influence or set the alignment of the liquid crystal medium at the interface. Rubbed polyimide or photo-aligned polyimide is preferably used as alignment layer, especially in FFS type applications, for example.
According to the invention, the electro-optical device comprises two polarizers, in particular two polarizer layers or polarizing layers. Both absorptive and reflective polarizers may be employed. It is preferable to use a polarizer in the form of an optical film. The polarizer is preferably a linear polarizer.
Optionally, at least one optical retarder, in particular at least one retarder layer, is provided in the device. In a preferred embodiment, there is at least one optical retarder, more preferably two optical retarders. In this regard, a retarder layer or plate may be used to compensate for phase dispersion so that a wider viewing angle may be obtained.
According to the invention, the liquid crystal medium contained in the liquid crystal medium, in particular in the switchable layer of an electro-optical device, contains one or more dichroic dyes in a total amount of 2.0 wt.% or less. In a preferred embodiment, the total amount of the one or more dichroic dyes in the liquid crystal medium is 1.0 wt% or less. It is further preferred that the total amount of the one or more dichroic dyes in the liquid crystal medium is 0.5 wt% or less, more preferably 0.2 wt% or less.
In this context, a dichroic dye means a light absorbing compound in which the absorption properties depend on the orientation of the compound with respect to the polarization direction of the light. The dichroic dye compounds according to the present invention generally have an elongated shape, i.e. the compounds are significantly longer in one spatial direction (i.e. along the longitudinal axis) than in the other two spatial directions. The dichroic dye absorbs or, respectively, preferentially absorbs light in one orientation such that the light transmission can be adjusted by changing the orientation of the dichroic dye.
According to the invention, the so-called liquid crystal host is doped with a relatively small, limited number of molecules of the dichroic dye. These dye doped LC media are particularly preferred for FFS and UB-FFS modes, however other display modes as described in the context may also be employed.
Preferably, the dichroic dye compound is present in the liquid crystal medium in solution. Thus, the dichroic dye molecules used according to the present invention preferably exhibit a suitable and sufficient solubility in the liquid crystal host. In addition, the dye compound preferably also advantageously contributes to the stability and reliability of the medium.
Each of the one or more dichroic dyes is preferably present in the liquid crystal medium in the following proportions, based on the total weight of the whole medium: from 0.002% to 2.0% by weight, more preferably from 0.003% to 1.0% by weight, still more preferably from 0.005% to 0.5% by weight, even more preferably from 0.01% to 0.3% by weight and particularly preferably from 0.02% to 0.2% by weight.
Preferably, the one or more dichroic dyes are generally present in the liquid crystal medium in a total concentration in the range of 0.003 to 2.0 wt%, more preferably 0.004 to 1.5 wt%, still more preferably 0.005 to 1.0 wt%, still more preferably 0.01 to 0.5 wt%, even more preferably 0.02 to 0.3 wt% and especially preferably 0.05 to 0.2 wt%.
The concentration of the dye(s) is advantageously selected so as to ensure proper performance of the resulting liquid crystal material, particularly in terms of the desired reduction of light leakage in the dark state and improved black image quality and overall contrast, while maintaining other device properties such as response time, operating voltage and brightness, as appropriate. The upper limit of dye concentration is provided, inter alia, in view of maintaining the bright state performance of the device such that the transmittance is not affected or only minimally affected.
Alternatively, it is also possible to use higher dichroic dye concentrations, for example in cases where the bright state properties are less relevant, for example in which case one or more dichroic dyes may also be present in the liquid crystal medium in a total concentration in the range of 2.0 to 5.0 wt%, or even above 5.0 wt% and up to 10.0 wt%.
The dichroic dye may preferably be selected from, for example, azo dyes, anthraquinones, thiophenoanthraquinone, methine compounds, azomethine compounds, azoquinone, tetrazine, pyrromethene dyes, malononitrile dyes, nickel dithiolenes, (metal) phthalocyanines, (metal) naphthalocyanines and (metal) porphyrins, rylenes (rylenes) (especially perylene and trinrylenes (terylenes)), thiadiazole dyes, thienothiadiazole dyes, benzothiadiazole, thiadiazoloquinoxaline and diketopyrrolopyrroles. Particularly preferred are azo compounds, anthraquinones, thiophenoanthraquinone, benzothiadiazoles, in particular as described in WO2014/187529 and WO 2020/104563A 1; diketopyrrolopyrroles, in particular as described in WO 2015/090497; thiadiazoloquinoxalines, in particular as described in WO2016/177449 and WO 2020/104563A 1; and rylenes, as described in particular in WO 2014/090373.
In a preferred embodiment, the one or more dichroic dyes are selected from azo compounds, benzothiadiazoles and thiadiazoloquinoxalines.
The liquid-crystalline medium preferably comprises one, two, three, four, five, six, seven, eight, nine or ten different dichroic dyes, particularly preferably two, three, four, five or six dichroic dyes. In a preferred embodiment, the medium contains at least three different dichroic dyes.
In one embodiment, the absorption spectra of the dichroic dyes contained in the medium or respectively the switchable layer are preferably complementary to each other in such a way that the eye gives the impression of a black or respectively a color neutral appearance. Preferably, two or more, more preferably three or more dichroic dyes are used in the liquid crystal medium, to preferably cover a large part of the visible spectrum. The exact manner in which dye mixtures which appear black or gray to the eye can be prepared is known in the art and is described, for example, in M.Richter, einf hrung in die Farbmetrik [ Introduction to Colorimetry ], 2 nd edition, 1981, ISBN 3 11-008209-8,Walter de Gruyter&Co.
The setting of the color position of the dye mixtures is described in the field of colorimetry. To this end, the spectra of the individual dyes are calculated using Lambert-Beer law (Lambert-Beer law) to obtain a total spectrum and converted into corresponding color positions and luminance values under the relevant illumination (e.g. daylight illuminant D65) according to the colorimetry rules. The location of the white point is fixed by the corresponding illuminant, e.g., D65, and is referenced in the table in the above reference, for example. The different color positions can be set by varying the proportions of the various dyes.
According to a preferred embodiment, the medium and the switchable layer comprise one or more dichroic dyes that absorb light in the visible spectrum, which is defined herein as light having a wavelength between 380nm and 780 nm.
In one embodiment, it is particularly preferred to include one or more dichroic dyes that sufficiently and effectively absorb green light.
In one embodiment, the dichroic dye provided in the medium and the switchable layer is preferably selected from the dye classes indicated in b.bahadur, liquid Crystals-Applications and Uses, volume 3, 1992,World Scientific Publishing, part 11.2.1, and particularly preferably from the exact compounds given in the tables present therein.
The dyes belong to the class of dichroic dyes known in the art and described in the literature. Thus, for example, anthraquinone dyes are described in EP 34832、EP 44893、EP 48583、EP 54217、EP 56492、EP 59036、GB 2065158、GB 2065695、GB 2081736、GB 2082196、GB 2094822、GB 2094825、JP A 55-123673、DE 3017877、DE 3040102、DE 3115147、DE 3115762、DE 3150803 and DE 3201120, naphthoquinone dyes in DE 3126108 and DE 3202761, azo dyes in EP 43904、DE 3123519、WO 82/2054、GB 2079770、JP-A 56-57850、JP-A 56-104984、US 4308161、US 4308162、US 4340973,T.Uchida、C.Shishido、H.Seki and M.Wada: mol. Cryst. Liq. Cryst.39,39-52 (1977) and H.Seki, C.Shishihido, S.Yasui and T.Uchida: jpn. J.appl. Phys.21,191-192 (1982), and perylene in EP 60895, EP 68427 and WO 82/1191. Rylene dyes are described, for example, in EP 2166040, U.S. Pat. No. 5,2011/0042651, EP 68427, EP 47027, EP 60895, DE 3110960 and EP 698649.
The compounds described herein are known or may be prepared analogously to known compounds or may be synthesized by methods known per se as described in the literature (e.g. in standard works such as Houben-Weyl,Methoden der organischen Chemie[Methods of Organic Chemistry],Georg-Thieme-Verlag,Stuttgart) and specifically under reaction conditions known and suitable for the particular reaction. In this connection, it is also possible to use variants known per se which are not mentioned in detail here. Furthermore, the starting materials are available via commonly accessible literature procedures or commercially.
The liquid-crystalline medium used according to the invention is a liquid-crystalline mixture which, in addition to the one or more dichroic dyes, further comprises one or more mesogenic compounds.
The liquid-crystalline medium used according to the invention may have a positive or negative dielectric anisotropy.
In order to achieve efficient electrical switching, the absolute value or magnitude of the dielectric anisotropy of the liquid-crystalline medium is preferably 1.5 or higher, more preferably 2.5 or higher and especially 3.0 or higher.
In this context, Δε represents the dielectric anisotropy, where Δε=ε/- ε ⊥. The dielectric anisotropy Δε is preferably measured at 20℃and 1 kHz.
In a preferred embodiment, a liquid crystalline medium with negative dielectric anisotropy is provided and used in the switchable layer. Preferred are liquid crystal mixtures having a dielectric anisotropy Δεranging from-8 to-1.5, more preferably-7 to-2.5, even more preferably-6 to-3.
In another embodiment, a liquid crystal medium having positive dielectric anisotropy is provided and used in the switchable layer. In this case, preferred are liquid crystal mixtures having a dielectric anisotropy Δεin the range of 1.5 to 30, more preferably 2.5 to 25, even more preferably 4 to 12.
The liquid-crystalline medium preferably has an optical anisotropy Δn of 0.06 or higher, more preferably 0.08 or higher, still more preferably 0.10 or higher and even more preferably 0.12 or higher.
In this context, Δn denotes the optical anisotropy, wherein Δn=n e-no, and wherein preferably the optical anisotropy Δn is measured at 20 ℃ and at a wavelength of 589.3 nm. The liquid-crystalline medium preferably has an optical anisotropy Δn in the range from 0.03 to 0.30, more preferably from 0.04 to 0.27, even more preferably from 0.06 to 0.21 and in particular from 0.09 to 0.16.
In addition, the liquid-crystalline medium preferably exhibits advantageous low-temperature stability without visible crystallization or decomposition, in particular a long shelf-life of more than 200 hours measured overall at-40 ℃.
Unless explicitly stated otherwise, all physical properties and physicochemical or electrooptical parameters are determined by generally known methods, in particular according to "Merck Liquid Crystals, physical Properties of Liquid Crystals", status 1997, month 11, MERCK KGAA, germany, and are given for temperatures of 20 ℃.
In this context, unless explicitly stated otherwise, all concentrations are given in weight percent and relative to the corresponding whole mixture. All temperatures are indicated in degrees celsius.
Preferably, the liquid-crystalline medium, in particular the liquid-crystalline medium contained in the switchable layer of the electro-optical device, comprises one or more compounds of the formula IV-1
Wherein the method comprises the steps of
R 41 and R 42 independently of one another represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms.
It is particularly preferred that the one or more compounds of formula IV-1 are contained in the liquid-crystalline medium in a total amount of at least 20 wt.%, preferably at least 30 wt.%, more preferably at least 40 wt.%, even more preferably at least 50 wt.%.
In a preferred embodiment, the liquid-crystalline medium comprises one or more compounds selected from the group consisting of the formulae B-1, B-2 and B-3
Wherein the method comprises the steps of
R 11 and R 12 are identical or different and represent H or a linear alkyl or alkoxy radical having 1 to 15C atoms, wherein one or more CH 2 groups in these radicals are optionally replaced independently of one another by-C.ident.C-, -CF 2O-、-OCF2 -, -ch=ch-, -O-, -CO-O-or-O-CO-is substituted in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen, preferably representing a linear alkoxy group having 1 to 7C atoms.
The compound of formula B-1 is preferably selected from the compounds of formulae B-1-a to B-1-e
Wherein R 11 and R 12 are identical or different and represent an alkyl group having 1 to 7C atoms, preferably ethyl, n-propyl, n-butyl or n-pentyl.
The compound of formula B-2 is preferably selected from the compounds of formulae B-2-a to B-2-e
Wherein R 11 and R 12 are identical or different and represent alkyl groups having 1 to 12C atoms, preferably alkyl groups having 1 to 7C atoms.
The compound of formula B-3 is preferably selected from the compounds of formulae B-3-a to B-3-j
Wherein R 12 represents an alkyl group having 1 to 7C atoms, preferably ethyl, n-propyl or n-butyl.
In ase:Sub>A preferred embodiment, one or more compounds selected from the group consisting of the formulae B-1, B-2 and B-3 are selected from the group consisting of the compounds B-A to B-J
The one or more compounds selected from the group consisting of formulae B-1, B-2 and B-3, in particular formula B-2, are preferably contained in the liquid-crystalline medium in a total amount of from 0.5% by weight to 20% by weight, more preferably 4% by weight or more and even more preferably 8% by weight or more.
In a preferred embodiment, the medium according to the invention comprises one or more compounds of the formula Y
Wherein the individual radicals have the following meanings:
And
Representation of
R 1、R2 independently of one another represents a linear, branched or cyclic alkyl or alkoxy radical which is unsubstituted or halogenated and has 1 to 15C atoms, wherein in addition thereto, one or more of these groups CH 2 groups may each, independently of one another, be replaced by-C.ident.C-, -CF 2 O-, -ch=ch-,-O-, -CO-O-or-O-CO-is replaced in such a way that O atoms are not directly connected to each other,
Z x、Zy independently of one another represents -CH2CH2-、-CH＝CH-、-CF2O-、-OCF2-、-CH2O-、-OCH2-、-CO-O-、-O-CO-、-C2F4-、-CF＝CF-、-CH＝CH-CH2O- or a single bond, preferably a single bond,
L 1、L2、L3 and L 4 independently of one another denote H, F or Cl, preferably H or F, more preferably F, and
X, y independently of one another represent 0,1 or 2, where x+y.ltoreq.3.
Preferably, the compound of formula Y contains at least one substituent L 1-4 which is F or Cl, preferably F, more preferably at least two substituents L 1-4 which are F.
In the compounds of the formula Y and its subformulae, R 1 and R 2 preferably represent straight-chain alkyl or alkoxy having 1 to 6C atoms, but also alkenyl having 2 to 6C atoms, in particular vinyl, 1E-propenyl, 1E-butenyl, 3-butenyl, 1E-pentenyl, 3E-pentenyl or 4-pentenyl.
In the compounds of the formula Y and its subformulae, preferably two radicals L 1 and L 2 represent F. In another preferred embodiment of the invention, in the compounds of the formula Y and its subformulae, one of the radicals L 1 and L 2 represents F and the other represents Cl.
In one embodiment, in the compounds of formula Y, each ring and preferably the phenylene ring may be optionally substituted with one or two alkyl groups, preferably with methyl and/or ethyl groups, preferably with one methyl group.
In a preferred embodiment of the invention, the medium contains one or more compounds of the formula Y selected from the following subformulae
Wherein R 1、R2、Zx、Zy、L1 and L 2 have one of the meanings given in formula Y or one of the preferred meanings given above and below,
A represents 0, 1 or 2, preferably 1 or 2,
B represents 0, 1 or 2, preferably 1 or 2,
Representation of
L 3、L4 independently of one another represents F or Cl, preferably F.
Preferably, in the compounds of formulae Y1 and Y2, L 1 and L 2 both represent F, or one of L 1 and L 2 represents F and the other represents Cl, or L 3 and L 4 both represent F or one of L 3 and L 4 represents F and the other represents Cl.
In one embodiment, in the compounds of the formulae Y1 and Y2, the individual rings, and preferably the phenylene rings, may each optionally be substituted by one or two alkyl groups, preferably by methyl and/or ethyl groups, preferably by one methyl group.
Preferably, the medium comprises one or more compounds of formula Y1 selected from the following subformulae
Wherein a represents 1 or 2, alkyl and alkyl each independently of the other represent a linear alkyl group having 1 to 6C atoms, and alkinyl represents a linear alkenyl group having 2 to 6C atoms, and (O) represents an O atom or a single bond. Alkenyl preferably represents CH2＝CH-、CH2＝CHCH2CH2-、CH3-CH＝CH-、CH3-CH2-CH＝CH-、CH3-(CH2)2-CH＝CH-、CH3-(CH2)3-CH＝CH- or CH 3-CH＝CH-(CH2)2 -.
Very preferably, the medium comprises one or more compounds of the formula Y1 selected from the formulae Y1-2 and Y1-10.
In certain embodiments, the medium comprises one or more compounds of the formulae Y1A-1 to Y1A-10:
Preferably, the medium comprises one or more compounds of formula Y2 selected from the following subformulae:
wherein alkyl and alkyl each independently represent a linear alkyl group having 1 to 6C atoms, and alkinyl represents a linear alkenyl group having 2 to 6C atoms, and (O) represents an oxygen atom or a single bond. Alkenyl preferably represents CH2＝CH-、CH2＝CHCH2CH2-、CH3-CH＝CH-、CH3-CH2-CH＝CH-、CH3-(CH2)2-CH＝CH-、CH3-(CH2)3-CH＝CH- or CH 3-CH＝CH-(CH2)2 -.
Very preferably, the medium contains one or more compounds of the formula Y2 selected from the group consisting of the compounds of the formulae Y2-2 and Y2-10, in particular one or more compounds of the formula Y2-10.
The proportion of the compounds of the formula Y1 or its subformulae in the medium is preferably from 1 to 10% by weight.
The proportion of the compounds of the formula Y2 or its subformulae, in particular of the formula Y2-10, in the medium is preferably from 1% to 15% by weight, more preferably from 2% to 10% by weight.
The total proportion of compounds of the formulae Y1 and Y2 or their subformulae in the medium is preferably from 0 to 20%, very preferably from 1 to 15%, most preferably from 1 to 10% by weight.
In particular embodiments, the medium contains 1,2 or 3 compounds of the formulae Y1 and Y2 or their subformulae, very preferably selected from the formulae Y1-2, Y1-10, Y2-2 and Y2-10.
In certain embodiments, the medium comprises one or more compounds of the formulae Y2A-1 to Y2A-5:
Preferably, the medium comprises one or more compounds of formula LY selected from the following formulas
Wherein the method comprises the steps of
R 1、R2、L1、L2, ring X, X and Z x have the meanings given in formula Y, wherein at least one of the rings X is cyclohexenylene. If X is 2, it is preferred that one ring X is cyclohexylidene-1, 4-diyl and the other ring X is cyclohexylidene-1, 4-diyl or cyclohexane-1, 4-diyl.
Preferably, in formula LY, x is 1 or 2, and
Representation ofAnd in the case where x is 2, a groupAlternatively represent
Preferably, both groups L 1 and L 2 represent F. In an alternative embodiment, one of the groups L 1 and L 2 represents F and the other represents Cl.
The compound of formula LY is preferably selected from the following subformulae
Wherein R 1 has the meaning indicated above for formula LY, (O) represents an oxygen atom or a single bond, and v represents an integer of 1 to 6. R 1 preferably represents a linear alkyl radical having 1 to 6C atoms or a linear alkenyl radical having 2 to 6C atoms, in particular CH3、C2H5、n-C3H7、n-C4H9、n-C5H11、CH2＝CH-、CH2＝CHCH2CH2-、CH3-CH＝CH-、CH3-CH2-CH＝CH-、CH3-(CH2)2-CH＝CH-、CH3-(CH2)3-CH＝CH- or CH 3-CH＝CH-(CH2)2 -.
Preferably, the medium contains 1, 2 or 3 compounds of formula LY. The proportion of the compounds of the formula LY or its subformulae in the medium is preferably from 0 to 15% by weight.
Particularly preferably, the medium contains one or more compounds of formula LY4, wherein the proportion of the compound of formula LY4 in the medium is preferably from 1 to 15% by weight, more preferably from 5 to 10% by weight.
In one embodiment, the medium comprises one or more compounds selected from the group consisting of the formulae Y4-1 to Y4-24
Wherein R represents a linear alkyl group having 1 to 7C atoms or an alkoxy group, R represents a linear alkenyl group having 2 to 7C atoms, (O) represents an oxygen atom or a single bond, and m represents an integer of 1 to 6. R preferably represents CH2＝CH-、CH2＝CHCH2CH2-、CH3-CH＝CH-、CH3-CH2-CH＝CH-、CH3-(CH2)2-CH＝CH- or CH 3-(CH2)3 -ch=ch-or CH 3-CH＝CH-(CH2)2 -. R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.
In particular embodiments, the medium contains one or more compounds of formula Y4-5, preferably in an amount of 0.5% by weight or more, more preferably 1% by weight or more.
Preferably, the total proportion of compounds of formula Y and in particular of the corresponding subformulae of formula Y in the medium is 5% by weight or more, more preferably 15% by weight or more and even more preferably 25% by weight or more.
In another preferred embodiment, the liquid-crystalline medium comprises one or more compounds selected from the group consisting of the formulae II-1 and II-2
Wherein the method comprises the steps of
R 2 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms,
Wherein optionally one or more CH 2 groups may be used independently of one another Instead of this, the first and second heat exchangers,
Independently of one another are
L 21、L22、L23 and L 24 independently of one another represent H or F,
L 25 represents H or CH 3, and
X 2 represents halogen, preferably F, halogenated alkyl or alkoxy having 1 to 3C atoms or halogenated alkenyl or alkenyloxy having 2 or 3C atoms.
The medium preferably comprises one or more compounds of the formulae II-1 and/or II-2 in a total amount of 5% by weight or more, more preferably 10% by weight or more.
In formulas II-1 and II-2, it is preferred that either both L 21 and L 22, or both L 23 and L 24 are F.
In another preferred embodiment, in formulas II-1 and II-2, L 21、L22、L23 and L 24 all represent F.
The compound of formula II-1 is preferably selected from the group consisting of compounds of formula II-1-a
Wherein the radicals present have the meanings given for the formula II-1, and wherein preferably X 2 is F.
Particularly preferably, the medium comprises one or more compounds of the formula II-1-a-1
Wherein R 2 has the meaning as explained for formula II-1.
The one or more compounds of formula II-1-a-1 are preferably contained in the liquid-crystalline medium in a total amount of 5% by weight or more, more preferably 10% by weight or more.
In another embodiment, the liquid-crystalline medium comprises one or more compounds selected from the group consisting of the formulae II-1-b to II-1-h
Wherein R 2 has the meaning as given in formula II-1.
The compound of formula II-2 is preferably selected from the group consisting of compounds of formulas II-2-a, II-2-b, II-2-c and II-2-d
Wherein the parameters have the corresponding meanings given above for formula II-2, and wherein preferably X 2 is F.
In a preferred embodiment of the invention, the medium comprises a compound of formula II-2-b, wherein L 21、L22、L23 and L 24 are all F, the total amount of which is preferably 5% by weight or more.
Particularly preferably, the medium comprises one or more compounds selected from the group consisting of the formulae II-2-d.
Particularly preferred compounds of the formula II-2 are compounds of the formulae II-2-i, II-2-II, II-2-iii and II-2-iv
Wherein R 2 has the meaning given above for formula II-2.
In a preferred embodiment, the medium contains at least one compound of the formula II-2-iii, preferably in a total amount of 2.5% by weight or more, more preferably 5% by weight or more.
In another embodiment, the liquid-crystalline medium comprises one or more compounds selected from the group consisting of the formulae II-2-A to II-2-L
Wherein R 2 has the meaning given above for formula II-2.
In one embodiment, the liquid-crystalline medium comprises one or more compounds selected from the group consisting of formulae III-1 to III-32
Wherein R 3 has the meaning given above for R 2 in formula II-2.
In one embodiment, the liquid-crystalline medium preferably comprises at least one compound of formula III-1, preferably in an amount of at least 2wt%, more preferably at least 5 wt%.
Preferably, the medium according to the invention comprises one or more compounds of formula IV
Wherein the method comprises the steps of
R 41 and R 42 independently of one another denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms, preferably R 41 is alkyl having 1 to 7C atoms and R 42 is alkyl having 1 to 7C atoms or alkoxy having 1 to 7C atoms, or R 41 is alkenyl having 2 to 7C atoms and R 42 is alkyl having 1 to 7C atoms,
The same or different representation at each occurrence
Preferably, the method comprises the steps of,At least one of which is
Z 41、Z42, identically or differently at each occurrence, represents-CH 2CH2 -, -COO-, trans-ch=ch-, trans-cf=cf-, -CH 2O-、-CF2 O-, -c≡c-, or a single bond, preferably a single bond, and
P is 0, 1 or 2, preferably 0 or 1, more preferably 0.
Preferably, the liquid-crystalline medium according to the invention, in particular the liquid-crystalline medium comprised in the switchable layer of an electro-optical device, comprises one or more compounds of formula IV selected from the compounds of formulae IV-1 to IV-5
Wherein R 41 and R 42 have the corresponding meanings given above under formula IV, and in formulae IV-1, IV-4 and IV-5R 41 is preferably alkyl or alkenyl, preferably alkenyl, and R 42 is preferably alkyl or alkenyl, preferably alkyl; in formula IV-2, R 41 and R 42 are preferably alkyl groups, and in formula IV-3, R 41 is preferably alkyl or alkenyl, preferably alkyl, and R 42 is preferably alkyl or alkoxy, preferably alkoxy.
Particularly preferably, the medium according to the invention comprises one or more compounds of the formula IV-1 and one or more compounds of the formula IV-4.
Optionally, the medium preferably further comprises one or more compounds of formula IV selected from the group consisting of compounds of formulas IV-6 through IV-13
Wherein the method comprises the steps of
R 41 and R 42 independently of one another denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms, and
L 4 represents H or F.
In a preferred embodiment, the liquid-crystalline medium comprises one or more compounds of formula IV-13, wherein L 4 is F.
In one embodiment, the medium may comprise one or more compounds of formula V
Wherein the method comprises the steps of
R 5 is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms, and is preferably alkyl having 1 to 7C atoms or alkenyl having 2 to 7C atoms,
To the point of
Independently of each other is
L 51 and L 52 independently of one another represent H or F, preferably L 51 represents F,
X 5 represents halogen, halogenated alkyl or alkoxy having 1 to 3C atoms or halogenated alkenyl or alkenyloxy having 2 or 3C atoms, preferably F, cl, -OCF 3 or-CF 3, most preferably F, cl or-OCF 3,
Z 5 represents-CH 2CH2-、-CF2CF2 -, -COO-, trans-CH=CH-, trans-cf=cf-or-CH 2 O, preferably-CH 2CH2 -; -COO-or trans-ch=ch-, and most preferably-COO-or-CH 2CH2 -, and
Q is 0 or 1.
Preferably, the medium according to the invention comprises one or more compounds of formula V selected from the compounds of formulae V-1 and V-2
Wherein the parameters have the corresponding meanings given above for formula V, and the parameters L 53 and L 54 are, independently of one another, H or F, and preferably Z 5 is-CH 2-CH2 -.
Preferably, the compound of formula V-1 is selected from compounds of formulae V-1a and V-1b
Wherein R 5 has the meaning given above for formula V.
Preferably, the compound of formula V-2 is selected from compounds of formulae V-2a to V-2d
Wherein R 5 has the meaning given above for formula V.
Preferably, the liquid-crystalline medium according to the invention additionally comprises one or more compounds of the formula VI
Wherein the method comprises the steps of
R 61 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms, preferably R 61 is alkyl having up to 7C atoms,
R 62 represents F, alkyl having 1 to 7C atoms, alkoxy, fluorinated alkyl or fluorinated alkoxy, or alkenyl having 2 to 7C atoms, alkenyloxy, alkoxyalkyl or fluorinated alkenyl,
To the point of
The same or different representation at each occurrence
Z 61 and Z 62, identically or differently at each occurrence, represent-CH 2CH2 -, -COO-, trans-CH=CH-, trans-CF=CF-, -CH 2O-、-CF2 O-, or a single bond, preferably at least one of them is a single bond, and
R is 0,1 or 2, preferably 0 or 1.
Preferably, the compound of formula VI is selected from the group consisting of compounds of formulas VI-1 to VI-4
Wherein R 61 and R 62 have the corresponding meanings given above for formula VI,
And R 61 is preferably alkyl having 1 to 7C atoms, and in formula VI-1R 62 is preferably alkenyl having up to 7C atoms, more preferably- (CH 2)2-CH＝CH-CH3), and in formula VI-2R 62 is preferably alkenyl having up to 7C atoms, more preferably- (CH 2)2-CH＝CH2), and in formulae VI-3 and VI-4R 62 is preferably alkyl having 1 to 7C atoms.
Preferably, the liquid-crystalline medium comprises one or more compounds of the formula VI-1 in a total amount of preferably at least 2.5% by weight, more preferably at least 4% by weight and especially at least 7.5% by weight.
In one embodiment, the medium comprises one or more compounds of the formula VI-2 in a total amount of preferably at least 5% by weight, more preferably at least 10% by weight and especially at least 15% by weight.
In a preferred embodiment, the liquid-crystalline medium comprises a compound of the formula
Which is also designated hereinafter and according to the abbreviations explained in tables a to C as compound CLP-V-1.
The liquid-crystalline medium according to the invention preferably maintains a nematic phase as low as-20 ℃, more preferably as low as-30 ℃ and even more preferably as low as-40 ℃. Preferably, the liquid-crystalline medium according to the invention has a clearing point of > 75 ℃, more preferably > 80 ℃ and especially > 85 ℃. In addition, the liquid-crystalline medium preferably exhibits a rotational viscosity gamma 1 of 110 mPas or less, particularly preferably 100 mPas or less, where the rotational viscosity is determined at 20 ℃. Thus, LC displays with fast response times can be advantageously provided.
The rotational viscosity gamma 1 of the liquid-crystalline medium is preferably less than or equal to 80 mPas, more preferably less than or equal to 70 mPas and even more preferably less than or equal to 60 mPas.
The ratio gamma 1/K11 of the liquid-crystalline medium (where gamma 1 is the rotational viscosity and K 11 is the elastic constant of the splay deformation) is preferably 4.5 Pa.s/pN or less, more preferably 4.2 Pa.s/pN or less, most preferably 4.0 Pa.s/pN or less.
The nematic phase range of the liquid-crystalline medium according to the invention preferably has a width of at least 90 ℃, more preferably at least 100 ℃, in particular at least 110 ℃. This range extends particularly preferably at least from-25℃to +80℃.
It has surprisingly been found that the liquid-crystalline medium provided at present can advantageously contribute to obtaining advantageous electro-optical device properties, for example in terms of achievable contrast and high-luminance transmittance, while also exhibiting functionality and reliability, also at high and low temperatures.
The electro-optic device preferably comprises a light source. For example, backlights conventionally used in LC displays may be used for illumination, such as LED backlights or cold cathode fluorescent lamp backlights.
Preferably, the polarizer used in the electro-optic device is a linear polarizer. In principle, linear polarizers are used to linearly polarize light such that the electric field of the light is confined to a single plane in the direction of propagation. In this regard, the linear polarizer has a transmission axis, also known as a polarizing axis (polarization axis), wherein the polarizer selectively transmits light that is linearly polarized parallel to this axis (i.e., aligned along the orientation).
In one embodiment, the two polarizers used in the electro-optic device are linear polarizers in a crossed configuration, wherein the polarizers are configured such that the polarization axes are orthogonal to each other.
In a preferred embodiment, the electro-optic device is operable in at least a bright state and a dark state and is electrically switchable between the bright state and the dark state, and the device comprises in the following order:
The light source is a light source which,
A first linear polarizer is provided which is arranged on the first substrate,
A switchable layer as described herein, and
A second linear polarizer is provided, which is arranged on the first substrate,
Wherein in the dark state, the absorption axis of the one or more dichroic dyes as described herein is parallel to the transmission axis of the second linear polarizer, or the absorption axis of the one or more dichroic dyes and the transmission axis of the second linear polarizer as described herein are configured at an angle of 25 ° or less.
The state of the switchable layer, and thus the optical state of the device, can be controlled by electrical switching, wherein an electric field can be applied by means of the electrodes. Although the switchable layer may have other switching states, particularly intermediate states, the device is preferably switchable between an optically bright state and an optically dark state, wherein the bright state has a greater degree of light transmission than the dark state. In particular, while intermediate or so-called gray-scale transmission states may be provided, the bright state gives maximum light transmission and the dark state gives minimum light transmission.
In a preferred embodiment, a dark state is provided wherein the absorption axis of the one or more dichroic dyes is parallel or substantially parallel to the transmission axis of the second linear polarizer, particularly when the first and second polarizers cross each other. In this regard, the second polarizer is a polarizer located distally of the light source. Although optimally, the absorption axis and the transmission axis are parallel to each other, in some cases a substantially parallel configuration may be provided with some deviation from the parallel configuration, which is still effective and desirable in this embodiment. In this case, the absorption axis of the one or more dichroic dyes described herein is disposed at an angle of 25 ° or less, especially an azimuth angle, preferably at an angle of 15 ° or less, even more preferably at an angle of 5 ° or less, and especially at an angle close to or about 0 ° with the transmission axis of the second linear polarizer.
In this embodiment, it is particularly preferred that in the dark state the liquid-crystalline medium has a homeotropic or parallel alignment.
For dichroic dyes, the light absorption properties depend on the orientation of the compound with respect to the polarization direction of the light. Dichroic dye compounds generally have an elongated shape, with a longitudinal or primary molecular axis significantly longer than the other two spatial dimensions. For positive dichroic dyes, the absorption axis and in particular the transition dipole moment is parallel or at least substantially parallel to this longitudinal axis. For negative dichroic dyes, the absorption axis and in particular the transition dipole moment is perpendicular or at least substantially perpendicular or transverse to this longitudinal axis. Thus, the absorption axis defines the orientation or direction in which light absorption, especially visible light absorption, occurs within the molecular framework.
The term light in this context preferably means visible light, in particular electromagnetic radiation with a wavelength of 380nm to 780 nm.
The orientation of the one or more dichroic dyes contained in the liquid crystal medium and thus the direction or orientation of the dye absorption axis is given herein as a spatial and temporal average.
The desired orientation of the dichroic dye and thus the direction of the dye absorption axis, especially in the dark state, can be provided and controlled by suitable electrical control using suitable alignment layers and/or switching at the cell substrate interface. Preferably, in the dark state, the liquid crystal molecules and the dichroic dye molecules in the liquid crystal medium contained in the switchable layer are aligned parallel to the substrate and thus exhibit parallel or in-plane alignment.
It has been found that even for electro-optical devices using two polarizers, undesirable light leakage can occur to some extent in the dark state. When a dichroic dye is comprised in the switchable layer according to the invention, and in addition the absorption axis of the dye molecules is set and aligned in view of the second polarizer, in particular aligned parallel or at least substantially parallel to the transmission axis of said second polarizer, unwanted light leakage can be effectively and significantly reduced or even avoided. Thus, setting the parallel alignment of the absorption axis and the transmission axis can help to further improve the dark state and the obtainable contrast.
In another embodiment, the absorption axis of the one or more dichroic dyes and the transmission axis of the second linear polarizer described herein are configured at an angle in the range of greater than 25 ° and up to and including 90 °. In this case, the use of one or more dichroic dyes according to the present invention may still suitably contribute to the benefits in terms of dark state and contrast compared to the case where no dye is included in the switchable layer.
In one embodiment, the medium may comprise one or more additives, in particular one or more stabilizers, one or more chiral dopants, one or more polymerizable compounds and/or one or more self-aligning additives.
The term "alkyl" or "alkyl" herein covers straight and branched alkyl groups preferably having 1 to 6 carbon atoms, especially the straight groups methyl, ethyl, propyl, butyl, pentyl and hexyl. Groups having 2 to 5 carbon atoms are generally preferred.
The branched alkyl groups may be selected from secondary and/or tertiary alkyl groups, preferably secondary alkyl groups.
The term "alkinyl" or "alkinyl" covers both straight and branched alkenyl groups, preferably having 2 to 6 carbon atoms, especially straight groups. Preferred alkenyl groups are C 2-C7 -1E-alkenyl, C 4-C6 -3E-alkenyl, in particular C 2-C6 -1E-alkenyl. Examples of particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl and 5-hexenyl. Groups having up to 5 carbon atoms are generally preferred, especially CH 2＝CH、CH3 ch=ch.
The term "fluorinated alkyl" preferably covers straight-chain groups with terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. However, other positions of fluorine are not excluded.
The term "oxaalkyl" or "alkoxy" preferably embraces straight-chain radicals of the formula C nH2n+1-O-(CH2)m, in which n and m each independently of the other represent 1 to 6.m may also represent 0. Preferably, n=1 and m=1-6, or m=0 and n=1-3.
In one embodiment of the invention, the liquid crystal medium additionally comprises one or more polymerizable compounds, for example in view of providing a PS-VA mode device. Preferably, the liquid-crystalline medium according to the invention comprises one or more polymerizable compounds selected from the following table G.
Preferably, the proportion of polymerizable compounds selected from table G in the liquid-crystalline medium is 0.01 to 5%, very preferably 0.05 to 1%, most preferably 0.1 to 0.5%.
The addition of one or more polymerizable compounds (e.g. selected from those of table G) to the liquid crystal medium may lead to advantageous properties, such as fast response times. Such liquid-crystalline media are particularly suitable for PSA displays, where they exhibit low image sticking, fast and complete polymerization, fast generation of stable low pretilt angles after UV exposure, high reliability, high VHR values after UV exposure and high birefringence. By a suitable choice of polymerizable compounds, the absorption of the liquid crystal medium at longer UV wavelengths can be increased, so that such longer UV wavelengths can be used for polymerization, which is advantageous for the display manufacturing process.
Generally preferred are liquid-crystalline media having a nematic liquid-crystalline phase and preferably having no chiral liquid-crystalline phase.
The invention also relates to the use of a liquid-crystalline medium according to the invention as described above and below for electro-optical purposes, in particular in shutter glasses, 3D applications, TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, UB-FFS, HB-FFS, PS-FFS, VA and PS-VA displays, and to electro-optical displays, in particular of the type mentioned above, in particular IPS, FFS, HB-FFS and UB-FFS displays, containing a liquid-crystalline medium according to the invention as described above and below.
Preferably, the electro-optical device according to the present invention is used as or in desktop monitors, notebook computers, TVs, mobile phones, tablet PCs, etc. and multimedia applications. In one embodiment, the device is an AR or VR device, particularly a VR display with very high resolution.
The invention also relates to an electro-optical display, such as an STN or MLC display, having two planar parallel outer plates forming a cell together with a frame, an integrated nonlinear element for switching individual pixels on the outer plates, and a nematic liquid crystal mixture with negative or positive dielectric anisotropy and high specific resistance located in the cell, wherein the nematic liquid crystal mixture is a liquid crystal medium according to the invention as described above and below.
The liquid-crystalline medium according to the invention enables a significant widening of the parameter dimensions that can be obtained. The achievable combination of clearing point, viscosity at low temperature, thermal and UV stability and suitable optical anisotropy is superior to previous materials from the prior art.
Comparative measurements of Voltage Holding Ratio (VHR) are shown, for example, in S.Matsumoto et al ,Liquid Crystals 5,1320(1989);K.Niwa et al.,Proc.SID Conference,San Francisco,June 1984,p.304(1984);G.Weber, liquid crystals5,1381 (1989).
The construction of the MLC display according to the invention from the polarizers, electrode base plates and surface-treated electrodes corresponds to the usual design of displays of this type. The term common design is used herein in a broad sense and also covers all derivative and improved products of MLC displays, in particular including matrix display elements based on poly-Si TFTs or MIMs.
The liquid-crystalline media which can be used according to the invention are prepared in a manner which is conventional per se, for example by mixing the mesogenic compounds and optionally additives. In general, it is advantageous to dissolve a desired amount of the components used in smaller amounts in the components constituting the main ingredient at an elevated temperature. Solutions of the components in organic solvents (e.g., in acetone, chloroform or methanol) may also be mixed and after thorough mixing the solvent removed by, for example, distillation.
The liquid-crystalline medium may also comprise other additives known to the person skilled in the art and described in the literature, such as polymerization inhibitors, surface-active substances, stabilizers, antioxidants (e.g.BHT, TEMPOL), microparticles, radical scavengers, nanoparticles, etc. For example, a polychromatic dye or chiral dopant may be added. Suitable stabilizers and dopants are mentioned in tables E and F below.
In one embodiment, the liquid crystalline medium preferably contains one or more chiral dopants at a concentration of 0.01 wt% to 1 wt%, very preferably 0.05 wt% to 0.5 wt%. The chiral dopants are preferably selected from the compounds of the following Table E, very preferably from the group consisting of R-or S-811, R-or S-1011, R-or S-2011, R-or S-3011, R-or S-4011 and R-or S-5011.
In another embodiment, the liquid-crystalline medium contains racemates of one or more chiral dopants, which are preferably selected from the chiral dopants mentioned in the preceding paragraph.
In another embodiment, the LC medium according to the invention preferably contains self-alignment (SA) additives in a concentration of 0.1 to 2.5 wt%. The LC medium according to this embodiment is particularly suitable for polymer stabilized SA-FFS, SA-UB-FFS or SA-HB-FFS displays.
In a preferred embodiment, the SA-FFS, SA-UB-FFS or SA-HB-FFS display according to the present invention does not contain a polyimide alignment layer. In another preferred embodiment, the SA-FFS, SA-UB-FFS or SA-HB-FFS display contains a polyimide alignment layer.
Preferred SA additives for this embodiment are selected from compounds comprising mesogenic groups and linear or branched alkyl side chains terminated by one or more polar anchoring groups selected from hydroxyl, carboxyl, amine or thiol groups.
Further preferred SA additives contain one or more polymerizable groups, optionally linked to the mesogenic groups via spacer groups. These polymerizable SA additives can polymerize in LC media under conditions similar to those applied to RM in PSA processes.
Suitable SA additives to induce homeotropic alignment, in particular for SA-VA mode displays, are described for example in US2013/0182202 A1, US2014/0838581 A1, US 2015/0166890A1 and US2015/0252265 A1.
In another preferred embodiment, the LC medium or polymer stabilized SA-FFS, SA-UB-FFS or SA-HB-FFS display according to the invention contains one or more self-aligning additives selected from Table H below.
Furthermore, it is possible to add, for example, from 0 to 15% by weight of nanoparticles, conductive salts for improving the conductivity, preferably ethyldimethyldodecylammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenylborate or complex salts of crown ethers (see, for example, haller et al, mol. Cryst. Liq. Cryst.24,249-258 (1973)), or substances for adjusting the dielectric anisotropy, viscosity and/or alignment of the nematic phase to the liquid-crystalline medium. Materials of this type are described, for example, in DE-A22 09127, 22 40 864, 23 21 632, 23 38 281, 2450 088, 26 37 430 and 28 53728.
The display according to the invention is preferably addressed by an active matrix, preferably a matrix of TFTs. However, the liquid crystal of the invention can also be advantageously used in displays with other known addressing schemes.
In the present invention and in particular in the following examples, the structure of mesogenic compounds is indicated by means of abbreviations (also referred to as acronyms). In these acronyms, the following abbreviations for tables a to C are used. All radicals C nH2n+1、CmH2m+1 and C lH2l+1 or C nH2n-1、CmH2m-1 and C lH2l-1 denote straight-chain alkyl or alkenyl radicals, preferably 1E-alkenyl radicals, having n, m and l C atoms, where n, m and l independently of one another denote integers from 1 to 9, preferably from 1 to 7 or from 2 to 9, preferably from 2 to 7, respectively. C oH2o+1 represents a straight chain alkyl group having 1 to 7, preferably 1 to 4C atoms or a branched alkyl group having 1 to 7, preferably 1 to 4C atoms.
Table A shows the codes for the ring elements of the compound core structure, while Table B shows the linking groups. Table C gives the meaning of the codes for the left-hand or right-hand endgroups. Table D shows the illustrative structures of the compounds and their corresponding abbreviations.
Table a: ring element
Table B: linking groups
Table C: end group
Where n and m each represent an integer, and the three points "…" are placeholders from other abbreviations of this table.
The following table shows the illustrative structures and their corresponding abbreviations. These are shown to illustrate the meaning of the abbreviations rules. Which additionally represent the compounds preferably used.
Table D: illustrative Structure
The illustrative structures show compounds that are particularly preferred for use.
Wherein k, l, m and n are each independently of the other an integer, preferably 1 to 9, more preferably 1 to 7.
Table E
Table E indicates possible chiral dopants optionally added to the liquid-crystalline medium according to the invention. The liquid-crystalline medium preferably comprises from 0 to 10% by weight, in particular from 0.01 to 5% by weight, and particularly preferably from 0.01 to 3% by weight, of chiral dopants.
Table F
Stabilizers which may be added to the liquid-crystalline medium in an amount of preferably 0.005 to 3% by weight are shown below.
Table G
Table G shows illustrative reactive mesogenic compounds (RM) that can be used in the liquid crystal media according to the invention.
In a preferred embodiment, the liquid-crystalline medium according to the invention comprises one or more polymerizable compounds, preferably selected from the group consisting of the polymerizable compounds of the formulae RM-1 to RM 145. Of these, compounds RM-1、RM-4、RM-8、RM-17、RM-19、RM-35、RM-37、RM-39、RM-40、RM-41、RM-48、RM-52、RM-54、RM-57、RM-64、RM-74、RM-76、RM-88、RM-102、RM-103、RM-109、RM-117、RM-120、RM-121 and RM-122 are particularly preferable.
Table H
Table H shows self-aligning additives for vertical alignment, which can be used in LC media for SA-VA and SA-FFS displays according to the invention, optionally together with polymerizable compounds.
In a preferred embodiment, the LC medium comprises one or more SA additives selected from the formulae SA-1 to SA-34, preferably from the formulae SA-14 to SA-34, more preferably from the formulae SA-20 to SA-28, most preferably from the formula SA-20, especially in combination with one or more RMs.
The following examples are merely illustrative of the invention and they should not be construed as limiting the scope of the invention in any way. Embodiments and modifications or other equivalents thereof will become apparent to those skilled in the art in light of this disclosure.
However, the physical properties and compositions shown below illustrate which properties can be achieved and which ranges can be modified. In particular, the combination of properties that can be preferably achieved is thus well defined.
Working examples
Unless otherwise indicated, parts or percentages data refer to parts by weight or percentages by weight based on the mixture as a whole.
The symbols and abbreviations have the following meanings:
V o denotes the Freedericksz threshold voltage at 20 c, capacitive V,
V 10 represents the voltage of 10% transmittance V,
N e represents the extraordinary refractive index measured at 20℃and 589nm,
N o represents the ordinary refractive index measured at 20℃and 589nm,
Δn represents the optical anisotropy measured at 20℃and 589nm,
Epsilon ⊥ represents the dielectric polarizability (or "dielectric constant") perpendicular to the longitudinal axis of the molecule at 20 c and 1kHz,
Epsilon ‖ represents the dielectric polarizability (or "dielectric constant") parallel to the longitudinal axis of the molecule at 20 c and 1kHz,
Delta epsilon represents the dielectric anisotropy at 20 deg.c and 1kHz,
Cl.p. or
T (N, I) represents a clear light point [ DEGC ],
V represents the flow viscosity measured at 20 c [ mm 2·s-1 ],
Gamma 1 denotes the rotational viscosity [ mpa.s ] measured at 20c,
K 11 represents the elastic constant, the "splay" deformation [ pN ] at 20 ℃,
K 22 represents the elastic constant, the "twist" deformation [ pN ] at 20 ℃,
K 33 represents the elastic constant, the "bending" deformation [ pN ] at 20 ℃,
LTS means the low temperature stability of the phase as measured in its entirety, and
VHR represents the voltage holding ratio.
The term "threshold voltage" refers to a capacitive threshold (V 0) for purposes of the present invention unless explicitly indicated otherwise. In an embodiment, as commonly used, the optical threshold may also be indicated for a relative contrast of, for example, 10% (V 10).
Reference mixture examples
Nematic host mixtures H1 to H13 were prepared as follows.
Reference mixture H1
Reference mixture H2
Reference mixture H3
The following compound B-2-B corresponds to the compound of formula B-2-B as specified and shown in the description above, wherein R 12 is ethyl.
Reference mixture H4
Reference mixture H5
Reference mixture H6
Reference mixture H7
The following compounds Y2A-1 and Y1A-5 correspond to the compounds of formula Y2A-1 and Y1A-5 as specified and shown in the description above.
Reference mixture H8
Reference mixture H9
Reference mixture H10
Reference mixture H11
Reference mixture H12
Reference mixture H13
Reference dye mixture DM1
Providing a dichroic Dye mixture DM1 comprising 18% Dye-1
38% Dye-2
And 44% Dye-3
Examples and comparative examples
Examples M1.1, M1.2, M1.3, M1.4, M1.5 and M1.6 and comparative examples CM1.1 and CM1.2
To the reference mixture H1 as indicated above was added 0.040% of a compound of the formula
Which will be referred to hereinafter as ST-1, to obtain mixture M1.
The dye mixtures DM1 as indicated above were added to the mixtures M1 in the respective amounts indicated in the table below to obtain mixtures M1.1, M1.2, M1.3, M1.4, M1.5 and M1.6 and comparative mixtures CM1.1 and CM1.2, respectively.
| Amount of DM1 added to M1 | |
| CM1.1 | - |
| M1.1 | 0.01 Wt% |
| M1.2 | 0.05 Wt% |
| M1.3 | 0.1 Wt% |
| M1.4 | 0.2 Wt% |
| M1.5 | 0.5 Wt% |
| M1.6 | 1.0 Wt% |
| CM1.2 | 2.5 Wt% |
The mixtures M1.1 to M1.6 have the same or very similar values of optical anisotropy, dielectric anisotropy, elastic constant and rotational viscosity compared to the comparative mixture CM1.1 without any dichroic dye. For the comparative mixture CM1.2 containing 2.5 wt% of the dichroic dye, the optical anisotropy was significantly changed.
The mixtures M1.1, M1.2, M1.3, M1.4, M1.5 and M1.6 and the comparative mixtures CM1.1 and CM1.2 were filled in FFS electro-optic boxes, respectively, and their electro-optic properties were evaluated.
The cartridges containing the comparative mixture CM1.2 exhibited less favorable operating voltages and response times than the cartridges containing the mixtures M1.1 to M1.6 and the comparative mixture CM1.1, respectively.
The difference in color coordinates between all FFS boxes is very small.
All other boxes have improved dark state with reduced scattering and reduced light leakage compared to the box containing the comparative mixture CM 1.1.
However, the cartridges containing the comparative mixture CM1.2 showed significantly reduced transmittance in the bright state compared to the cartridges containing the mixtures M1.1 to M1.6, respectively.
The cartridges containing the mixtures M1.1 to M1.6 exhibit an advantageous bright state transmittance, an advantageous contrast ratio and an advantageous response time.
Examples M2.1, M2.2, M2.3, M2.4, M2.5 and M2.6 and comparative examples CM2.1 and CM2.2
To the reference mixture H2 as indicated above was added 0.040% of compound ST-1 as indicated above and 0.005% of a compound of the formula
Which will be referred to hereinafter as ST-2, to obtain mixture M2.
The dye mixtures DM1 as indicated above were added to the mixtures M2 in the respective amounts indicated in the table below to obtain mixtures M2.1, M2.2, M2.3, M2.4, M2.5 and M2.6 and comparative mixtures CM2.1 and CM2.2, respectively.
| Amount of DM1 added to M2 | |
| CM2.1 | - |
| M2.1 | 0.01 Wt% |
| M2.2 | 0.05 Wt% |
| M2.3 | 0.1 Wt% |
| M2.4 | 0.2 Wt% |
| M2.5 | 0.5 Wt% |
| M2.6 | 1.0 Wt% |
| CM2.2 | 2.5 Wt% |
The mixtures M2.1 to M2.6 have the same or very similar values of optical anisotropy, dielectric anisotropy, elastic constant and rotational viscosity compared to the comparative mixture CM2.1 without any dichroic dye. For the comparative mixture CM2.2 containing 2.5 wt% of the dichroic dye, the optical anisotropy was significantly changed.
The FFS cells were filled with mixtures M2.1, M2.2, M2.3, M2.4, M2.5 and M2.6 and the comparative mixtures CM2.1 and CM2.2, respectively, and their electro-optical properties were evaluated.
The cartridges containing the comparative mixture CM2.2 show a less advantageous operating voltage and response time than the cartridges containing the mixtures M2.1 to M2.6 and the comparative mixture CM2.1, respectively.
The difference in color coordinates between all FFS boxes is very small.
All other boxes have improved dark state with reduced scattering and light leakage compared to the box containing the comparative mixture CM 2.1.
However, the cartridges containing the comparative mixture CM2.2 showed significantly reduced transmittance in the bright state compared to the cartridges containing the mixtures M2.1 to M2.6, respectively.
The cartridges containing the mixtures M2.1 to M2.6 exhibit an advantageous bright state transmittance, an advantageous contrast ratio and an advantageous response time.
Examples M3.1, M3.2, M3.3, M3.4, M3.5 and M3.6 and comparative examples CM3.1 and CM3.2
Mixtures M3.1, M3.2, M3.3, M3.4, M3.5 and M3.6 and comparative mixtures CM3.1 and CM3.2 were prepared similarly to mixtures M2.1, M2.2, M2.3, M2.4, M2.5 and M2.6 and comparative mixtures CM2.1 and CM2.2 as described above, wherein reference mixture H3 as indicated above was used instead of reference mixture H2.
The mixtures M3.1, M3.2, M3.3, M3.4, M3.5 and M3.6 give advantageous device properties, in particular advantageous contrast, transmittance and response time of the display.
Example 4
To the reference mixture H4 as indicated above was added 0.08% of a compound of the formula
Which will be referred to hereinafter as ST-3, to obtain mixture B4.
Mixture M4 was obtained by adding 0.16% Dye-1 as indicated above, 0.35% Dye-2 as indicated above and 0.43% Dye-3 as indicated above to mixture B4.
Mixture M4 gives advantageous device properties, in particular advantageous contrast, transmittance and response time of the display.
Example 5
To the reference mixture H5 as indicated above, 0.025% of compound ST-2 as indicated above and 0.150% of compound ST-3 as indicated above were added to obtain a mixture B5.
Mixture M5 was obtained by adding 0.047% Dye-1 as indicated above, 0.092% Dye-2 as indicated above and 0.110% Dye-3 as indicated above to mixture B5.
The mixture M5 gives advantageous device properties, in particular advantageous contrast ratio, transmittance and response time of the display.
Example 6
To a reference mixture H5 as indicated above was added 0.100% of compound ST-3 as indicated above, 0.032% Dye-4
Dye-5 at 0.063%
0.077% Dye-6
Dye-7 at 0.060%
0.073% Dye-8
And 0.037% Dye-9
To obtain a mixture M6.
Mixture M6 gives advantageous device properties, in particular advantageous contrast, transmittance and response time of the display.
Reference dye mixture DM2
A dichroic Dye mixture DM2 is provided comprising 9% Dye-4, 20% Dye-5, 17% Dye-6, 26% Dye-7 and 28% Dye-8.
Examples 7.1 and 7.2 and comparative example 7
To the mixture M1 as shown above, 0.2% of the dye mixture DM2 was added to obtain a mixture M7.
According to comparative example 7, a dye-free mixture M1 was filled in an electro-optic cell (ITO coated glass substrate with polyimide alignment layer), wherein the cell further comprised a first linear polarizer facing the light source and a second linear polarizer oriented opposite the light source and perpendicular to the first linear polarizer. The visible light transmittance in the dark state was measured, in which residual light leakage was observed.
According to example 7.1, the mixture M7 is filled in an electro-optical cell with crossed linear polarizers, in which in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. The visible light transmittance in the dark state was measured. Light leakage in the dark state was reduced as compared with the case in comparative example 7 and transmittance was only 81% with respect to the dark state transmittance of the case in comparative example 7.
According to example 7.2, the mixture M7 is filled in an electro-optical cell with crossed linear polarizers, wherein in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the second linear polarizer facing away from the light source, i.e. parallel to the polarizer located distally to the light source. The visible light transmittance in the dark state was measured. The light leakage in the dark state was even further reduced as compared to the case in comparative example 7 and the transmittance was only 74% with respect to the dark state transmittance of comparative example 7.
Examples 8.1 and 8.2 and comparative example 8
To the mixture M2 as shown above, 0.2% of the dye mixture DM2 was added to obtain a mixture M8.
According to comparative example 8, a dye-free mixture M2 was filled in an electro-optical cell with crossed polarizers. The visible light transmittance in the dark state was measured, in which residual light leakage was observed.
According to example 8.1, the mixture M8 is filled in an electro-optical cell with crossed polarizers, in which in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. The visible light transmittance in the dark state was measured. Light leakage in the dark state was reduced and transmittance was only 76% with respect to that of comparative example 8, as compared with the case of comparative example 8.
According to example 8.2, the mixture M8 is filled in an electro-optical cell with crossed polarizers, in which in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the second linear polarizer facing away from the light source. The visible light transmittance in the dark state was measured. The light leakage in the dark state was even further reduced as compared to the case of comparative example 8 and the transmittance was only 70% with respect to the dark state transmittance of comparative example 8.
Examples 9.1 and 9.2 and comparative example 9
To the reference mixture H10 as shown above, 0.04% of the compound ST-1 as shown above and 0.02% of the compound ST-2 as shown above were added to obtain a mixture B9.
To mixture B9 was added 0.2% of dye mixture DM2 to obtain mixture M9.
According to comparative example 9, a dye-free mixture B9 was filled in an electro-optical cell with crossed polarizers. The visible light transmittance in the dark state was measured, in which residual light leakage was observed.
According to example 9.1, the mixture M9 is filled in an electro-optical cell with crossed polarizers, in which in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. The visible light transmittance in the dark state was measured. Light leakage in the dark state was reduced and transmittance was only 80% with respect to that of comparative example 9, compared to the case of comparative example 9.
According to example 9.2, the mixture M9 is filled in an electro-optical cell with crossed polarizers, in which in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the second linear polarizer facing away from the light source. The visible light transmittance in the dark state was measured. The light leakage in the dark state was even further reduced as compared to the case of comparative example 9 and the transmittance was only 72% with respect to the dark state transmittance of comparative example 9.
Examples 10.1 and 10.2 and comparative example 10
To the reference mixture H11 as indicated above was added 0.04% of the compound ST-3 as indicated above to obtain a mixture B10.
To the mixture B10, 0.10% of the dye mixture DM2 was added to obtain a mixture M10.
According to comparative example 10, a dye-free mixture B10 was filled in an electro-optical cell with crossed polarizers. The visible light transmittance in the dark state was measured, in which residual light leakage was observed.
According to example 10.1, the mixture M10 is filled in an electro-optical cell with crossed polarizers, in which in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the first linear polarizer facing the light source. The visible light transmittance in the dark state was measured. Light leakage in the dark state was reduced and transmittance was only 97% with respect to that of the dark state of comparative example 10, as compared with the case of comparative example 10.
According to example 10.2, the mixture M10 is filled in an electro-optical cell with crossed polarizers, in which in the dark state the absorption axis of the dichroic dye is parallel to the transmission axis of the second linear polarizer facing away from the light source. The visible light transmittance in the dark state was measured. The light leakage in the dark state was even further reduced as compared to the case of comparative example 10 and the transmittance was only 79% with respect to the dark state transmittance of comparative example 10.
Example 11
To the reference mixture H12 as shown above was added 0.050% of the compound ST-1 as shown above to obtain a mixture M12.
M12 was treated similarly to mixture M1 as described above.
Example 12
To the reference mixture H13 as indicated above was added 0.050% of compound ST-1 as indicated above and 0.015% of a compound of the formula
Which will be referred to hereinafter as ST-4, to obtain mixture M13.
M13 is then treated similarly to mixture M1 as described above.
Example 13
Mixture M14 was prepared by including 0.25% Dye-5, 0.50% Dye-6 and 0.25% Dye-7 in the reference mixture H1 as indicated above.
The mixture M14 gives advantageous device properties, in particular advantageous contrast ratio, transmittance and response time of the display.
Example 14
Mixture M15 was prepared by including 1.00% Dye-6 and 1.00% Dye-7 in the reference mixture H1 as indicated above.
Mixture M15 gives advantageous device properties, in particular advantageous contrast, transmittance and response time of the display.
Claims (17)
1. An electro-optic device, comprising:
A switchable layer interposed between two opposite transparent substrates,
Wherein each substrate is provided with an electrode structure, or one of the substrates is provided with two electrode structures and the other substrate is not provided with an electrode, and
Two polarizers and optionally at least one optical retarder,
Wherein the switchable layer comprises a liquid crystal medium,
Wherein the liquid crystal medium comprises one or more dichroic dyes, and wherein the one or more dichroic dyes are contained in the liquid crystal medium in a total amount of 2.0 wt% or less.
2. The electro-optic device of claim 1, wherein the one or more dichroic dyes are included in the liquid crystal medium in a total amount of 1.0 wt% or less, preferably 0.5 wt% or less, more preferably 0.2 wt% or less.
3. The electro-optic device of claim 1 or 2, wherein the one or more dichroic dyes are selected from azo compounds, anthraquinone, thiophenoanthraquinone, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinone, tetrazine, pyrrole methylene dyes, malononitrile dyes, nickel dithioenes, phthalocyanines, naphthalocyanines, porphyrins, rylenes, thiadiazole dyes, thienothiadiazole dyes, benzothiadiazole, thiadiazoloquinoxaline and diketopyrrolopyrroles, preferably selected from azo compounds, benzothiadiazole and thiadiazoloquinoxaline.
4. An electro-optic device according to one or more of claims 1 to 3, wherein the device is a liquid crystal display, preferably a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, UB-FFS, PS-HB-FFS, SA-HB-FFS, polymer stabilised SA-HB-FFS, VA or PS-VA display, more preferably a IPS, FFS, HB-FFS or UB-FFS display.
5. The electro-optic device of one or more of claims 1-4, wherein the device is operable in at least a bright state and a dark state and is electrically switchable between the bright state and the dark state, and wherein the device comprises in the following order:
The light source is a light source which,
A first linear polarizer is provided which is arranged on the first substrate,
-A switchable layer, and
A second linear polarizer is provided, which is arranged on the first substrate,
Wherein in the dark state, the absorption axis of the one or more dichroic dyes is parallel to the transmission axis of the second linear polarizer, or the absorption axis of the one or more dichroic dyes and the transmission axis of the second linear polarizer are disposed at an angle of 25 ° or less.
6. The electro-optic device of one or more of claims 1-5, wherein the liquid crystal medium comprises one or more compounds of formula IV-1
Wherein the method comprises the steps of
R 41 and R 42 independently of one another represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms.
7. An electro-optic device according to claim 6 wherein the one or more compounds of formula IV-1 are included in the liquid crystal medium in a total amount of at least 20 wt%, preferably at least 30 wt%, more preferably at least 40 wt%, even more preferably at least 50 wt%.
8. The electro-optic device of one or more of claims 1-7, wherein the liquid crystal medium comprises one or more compounds selected from the group consisting of compounds of formulae B-1, B-2, and B-3
Wherein the method comprises the steps of
R 11 and R 12 are identical or different and represent H or a linear alkyl or alkoxy radical having 1 to 15C atoms, wherein one or more CH 2 groups in these radicals are optionally replaced independently of one another by-C.ident.C-, -CF 2O-、-OCF2 -, -ch=ch-, -O-, -CO-O-or-O-CO-is substituted in such a way that the O atoms are not directly connected to each other, and wherein one or more H atoms may be replaced by halogen, preferably representing a linear alkoxy group having 1 to 7C atoms.
9. The electro-optic device of one or more of claims 1-8, wherein the liquid crystal medium comprises one or more compounds selected from the group consisting of Y1, Y2, and LY compounds
Wherein the method comprises the steps of
R 1、R2 independently of one another represents a linear, branched or cyclic alkyl or alkoxy radical which is unsubstituted or halogenated and has 1 to 15C atoms, wherein in addition thereto, one or more of these groups CH 2 groups may each, independently of one another, be replaced by-C.ident.C-, -CF 2 O-, -ch=ch-,-O-, -CO-O-or-O-CO-is replaced in such a way that O atoms are not directly connected to each other,
Z x、Zy independently of one another represents -CH2CH2-、-CH＝CH-、-CF2O-、-OCF2-、-CH2O-、-OCH2-、-CO-O-、-O-CO-、-C2F4-、-CF＝CF-、-CH＝CH-CH2O- or a single bond, preferably a single bond,
L 1、L2、L3、L4 independently of one another represents H, F or Cl, preferably F,
A and b are identical or different and are 0, 1 or 2, preferably 1 or 2,
X is 1 or 2 and is preferably selected from the group consisting of,
Representation of
Wherein the method comprises the steps of
L 3 and L 4 are identical or different and denote F or Cl, preferably F, and
Representation ofAnd in the case where x is 2, a groupAlternatively represent
10. The electro-optic device of one or more of claims 1 to 9, wherein the liquid crystal medium comprises one or more compounds of formula VI
Wherein the method comprises the steps of
R 61 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms, preferably R 61 is alkyl having up to 7C atoms,
R 62 represents F, alkyl having 1 to 7C atoms, alkoxy, fluorinated alkyl or fluorinated alkoxy, or alkenyl having 2 to 7C atoms, alkenyloxy, alkoxyalkyl or fluorinated alkenyl,
To the point of
The same or different representation at each occurrence
Z 61 and Z 62, identically or differently at each occurrence, represent- -CH 2CH2 - -, - -COO- -, trans- -CH=CH- -, trans- -CF=CF- -, - -CH 2O-、-CF2 O- -or a single bond, preferably at least one of them is a single bond, and
R is 0,1 or 2, preferably 0 or 1.
11. The electro-optic device of one or more of claims 1 to 10, wherein the liquid crystal medium comprises one or more compounds selected from the group consisting of compounds of formulas II-1 and II-2
Wherein the method comprises the steps of
R 2 represents alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms,
Wherein optionally one or more CH 2 groups may be used independently of one another Instead of this, the first and second heat exchangers,
Independently of one another are
L 21、L22、L23 and L 24 independently of one another represent H or F,
L 25 represents H or CH 3, and
X 2 represents halogen, halogenated alkyl or alkoxy having 1 to 3C atoms or halogenated alkenyl or alkenyloxy having 2 or 3C atoms.
12. A liquid crystalline medium comprising:
One or more dichroic dyes in a total amount of 2.0 wt% or less,
And
-One or more compounds of formula IV-1
The total amount thereof being at least 20 wt%,
Wherein the method comprises the steps of
R 41 and R 42 independently of one another represent alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7C atoms.
13. The liquid-crystalline medium according to claim 12, wherein the one or more dichroic dyes are selected from azo compounds, anthraquinone, thiophenol anthraquinone, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinone, tetrazine, pyrrole methylene dyes, malononitrile dyes, nickel dithiolenes, phthalocyanines, naphthalocyanines, porphyrins, rylenes, thiadiazole dyes, thienothiadiazole dyes, benzothiadiazole, thiadiazoloquinoxaline and diketopyrrolopyrroles, preferably from azo compounds, benzothiadiazole and thiadiazoloquinoxaline.
14. The liquid-crystalline medium according to claim 12 or 13, wherein the liquid-crystalline medium contains at least three different dichroic dyes.
15. The liquid-crystalline medium according to one or more of claims 12 to 14, wherein the liquid-crystalline medium contains one or more stabilizers, one or more chiral dopants, one or more polymerizable compounds and/or one or more self-aligning additives.
16. Use of one or more dichroic dyes in a liquid crystal switchable layer comprised in an electro-optical device for reducing light leakage and improving the contrast of the electro-optical device.
17. The method of operation of an electro-optical device according to one or more of claims 1 to 11, wherein one or more dichroic dyes are included in the switchable layer and light leakage in the dark state is reduced.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP21210147 | 2021-11-24 | ||
| EP21210147.1 | 2021-11-24 | ||
| PCT/EP2022/082871 WO2023094404A1 (en) | 2021-11-24 | 2022-11-22 | Liquid crystal medium and liquid crystal display |
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| CN118302716A true CN118302716A (en) | 2024-07-05 |
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