JPH0465116B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to pleochroic dyes in organic materials, in particular liquid crystal material solutions used for example in electro-optical displays. Liquid crystal materials are well-known organic compounds that exhibit a phase known as a liquid crystal phase or meso phase with a degree of molecular alignment that is intermediate between a perfectly ordered liquid crystalline solid state phase and a completely disordered isotropic liquid state phase. It is a substance. Electro-optical devices incorporating liquid crystal materials are well known and widely used as digital displays in applications such as watches, calculators, and digital voltmeters. These devices take advantage of optical contrast when an electric field is applied across a thin insulating film of a suitable liquid crystal material. The molecules of this material (which are in the liquid crystalline phase at the operating temperature) are rearranged by the electric field, causing a change in the optical properties of the portion of the film to which the electric field is applied, such as the scattering or transmittance of ambient light. Many of the liquid crystal display devices commonly used in basic applications operate by the torsional nematic electro-optic effect. In this case, the optical activity of a film of nematic liquid crystal material with twisted molecular alignment is voltage dependent and, depending on the voltage, changes between various states of transmittance when said film is placed in the form of a cell between optical polarizers. The film can be switched.
Although this type of device would ideally be used in areas where low voltage and low power consumption are required, there are a number of limitations inherent in the mode of operation. In particular, the use of two polarizers is undesirable. Polarizers are relatively expensive, difficult to handle, degrade in moisture, and exhibit a cloudy appearance. Furthermore, the optical contrast of torsional nematic devices at wide viewing angles is poor. Liquid crystal materials have the property that the molecules of the liquid crystal material impose their alignment on the molecules of other suitable dopants incorporated into the liquid crystal material. This property forms the basis of so-called "guest-host" devices, such as display devices. In this display device, the host liquid crystal material and the guest material assume one molecular arrangement when no electric field is applied, and assume another molecular arrangement when an electric field is applied to the materials. The guest material is typically a pleochroic dye, a dye whose molecular absorption properties change with the direction of the electric vector of light incident on the molecule. Effect of electric field applied to liquid crystal molecules and guest −
The presence of such a dye can change the OFF state (no applied electric field) and ON state of a liquid crystal display, since the orientation of the dye molecules can actually be switched by reorientation of the dye molecules as a result of host effects. Contrast between states (applying an electric field) can be increased. As discussed further below, there are several types of liquid crystal effects that can utilize guest-host effects in electro-optical displays. These effects depend on the type of liquid crystal material used and the alignment of the liquid crystal material molecules in the off-state (as determined, for example, by the surface treatment of the substrate used to place the film of liquid crystal material). It changes depending on. Guest-host electro-optic displays, in particular electro-optic displays operating with the so-called phase-change electro-optic effect, have the following advantages. That is,
Two polarizers are not required, optical contrast at wide viewing angles can be improved, and liquid crystal cells can be deposited directly onto active substrates. To obtain maximum contrast between the on and off states of a guest-host liquid crystal display, it is important that the guest molecules be as close as possible to the time averaged orientation of the host molecules. However, this can only be achieved to a certain extent due to irregular thermal fluctuations. The degree to which the orientation deviates from the ideal is determined by the following formula: S = 1/2 (3cos ² θ−1) (1) (where cos ² θ is the time average term, and Q is the time average term of the host molecule. is the instantaneous angular orientation of the molecule with respect to its orientation. Determination of the value of the order parameter S is well understood in the art: for example, “A new absorptive mode
reflective liquid crystal display device”by
DLWhite and GNTaylor in the Journal of
See Applied Physics, 1974, 45 , 4718-4723. For perfect orientation, the order parameter S is 1 (ie θ is zero). In this way,
The pleochroic dye used in the guest-host device should have as high an order parameter as possible (ie less than 1 but as close to 1 as possible) in the liquid crystal host. However, pleochroic dyes also have suitable chemical, photochemical and electrochemical stability, such as stability when exposed to atmospheric pollutants, electric fields (in device operation) and ultraviolet radiation. Must be. The pleochroic dye must not be ionic or have any properties capable of ionizing (otherwise the liquid crystal material would lose its insulating properties and the device could not be used). ). Also, the pleochroic dye must have sufficient solubility in the host material; although the concentration of guest pleochroic dye required to achieve the desired effect is usually quite small (e.g. less than a few percent dye). However, many pleochroic dyes are unsuitable because they are virtually insoluble in liquid crystal materials. From British Patent Publication No. 2081736, general formula A _[ In _the formula _{, R 1} represents alkyl or _aryl ; NHCH ₃ ); one of R ₂ and R ₃ is H and the group ortho to the OH group is CH ₂ R ₁ ] is pleochroic and therefore They are known to be useful in conjunction with liquid crystal materials in electro-optic displays. It has been surprisingly found that certain anthraquinone compounds belonging to this class have high solubility in liquid crystal materials and high order parameters. Therefore,
It is particularly useful when used in electro-optic displays based on liquid crystal guest-host effects. A composition suitable for the guest-host liquid crystal device of the invention consists of a solution of a liquid crystal material and a pleochroic dye.
In this case, the pleochroic dye has no water soluble and ionic substituents and has the general formula: (wherein R and R ¹ each independently represent a C _4-7 -n-alkyl group, and R ² and R ³ each independently represent hydrogen or C _1-4 -alkyl) It consists of two anthraquinone compounds. Compounds in which R and R ¹ are the same group in the general formula are preferred, and compounds in which R and R ¹ are n-butyl or n-hexyl are particularly preferred. The latter compounds combine high solubility, high order parameters and good stability. Compounds in which both R ² and R ³ are H, or one of R ² and R ³ is H and the other is C _1-4 -alkyl are preferred. Compounds in which R ² and R ³ are H generally have higher order parameters compared to compounds in which one or both of R ² and R ³ is C _1-4 -alkyl. The latter compounds, especially
Compounds in which one or both of R ² and R ³ are methyl groups exhibit absorption maxima at higher wavelengths and thus have a greener ahade.
Compounds with green shades are mixed shades, in particular the yellow pleochroic dyes described in GB 2,082,196 and GB 8,203,421, the red pleochroic dyes and the blue pleochroic dyes described herein. Suitable for mixing with pleochroic dyes to create neutral black shades. Useful indicators of whether a dye can provide good contrast are its molecular extinction coefficient and solubility (moles/
liter). Liquid crystal composition solutions of dyes used in electrical displays preferably have a value of this product of at least 500 cm ^-1 and more preferably at least 750 cm ^-1 . Since the molecular extinction coefficient of a dye does not vary significantly between liquid crystal materials, the preferred product value allows one to calculate the minimum preferred solubility of a particular dye in any liquid crystal material to obtain good contrast. Therefore, 10000cm ²・
For dyes with a molecular extinction coefficient of moles ^-1 , the solubility is preferably at least 5.0 x 10 ^-2 mol/;
More preferably, it is at least 7.5×10 ⁻² mol/. For dyes with a molecular extinction coefficient of 15000 cm ² moles ^-1 , the solubility is preferably at least 3.3×
10 ⁻² mol/, more preferably at least 5.0×
10 ^-2 mol/. Molecular extinction coefficient ^20000cm2・
In the case of dyes with moles ^-1 , the solubility is preferably at least 2.5 x 10 ^-2 mol/, more preferably at least 3.7 x 10 ^-2 mol/. Compounds of the invention generally have high solubility and high extinction coefficient. The compounds used in liquid crystal displays are preferably free of inorganic substances and other ionizable substances or products that are sensitive to radiation and decompose within the display during operation, which would interfere with the operation of the display. Preferably it is as pure as possible. These compounds should also preferably be free of non-pleochroic or less performing pleochroic materials such as starting materials, intermediates and by-products. This is because these materials do not contribute to the perceived contrast of the display. To obtain the compound in pure form, i.e. substantially free of interfering or harmful substances, the dye is usually repeatedly recrystallized from organic solvents such as chloroform and/or subjected to chromatographic separation. is desirable. When the compounds of the invention are used in fields such as electro-optic displays, the addition of the compounds to liquid crystal materials tends to increase the viscosity of the liquid crystal composition and thus increase the response time of the display. Therefore, it is desirable to use as little amount as possible (sufficient to provide adequate electro-optic contrast). In this respect, compounds of the general formula are particularly important since many of them have very high extinction coefficients and therefore only small amounts, usually less than 7%, are required in liquid crystal compositions. . Although less than 7% by weight of each dye compound incorporated into the liquid crystal composition is sufficient for the guest-host device to operate at room temperature (20°C), the solubility of the dye in the liquid crystal composition decreases with decreasing temperature. and decrease,
To obtain adequate solubility at lower temperatures, the room temperature solubility of each compound used should be about 7% by weight, or more, such as 10% by weight. Dyes of the general formula exhibit high order parameters and solubility in a variety of liquid crystal host materials, including materials of positive and negative dielectric anisotropy. Examples of suitable liquid crystal host materials include: a Mixture of PECH compounds (50-80% by weight) General formula Q1 (In the formula, R _Q is preferably n- having 2 to 9 carbon atoms.
alkyl) and high clearing point substances (5-50%) such as general formula Q2 A mixture with one or more compounds having the general formula Compounds with Q2 are no.
It is disclosed in specification No. 2023136. b Preferably a few percent (5-40%)
BDH Chemicals Ltd., Broom Road, Poole
Substances E ₇ and E ₄₃ commercially available from Dorset, UK)
mixtures of cyanobiphenyls with substances having a high clearing point such as (e.g. cyano-P-terphenyl);
a mixture of a high clearing point material such as 1132 in a cyanophenylcyclohexane (PCH) compound; d preferably with a few percent of a high clearing point compound, such as a cyanophenylpyrimidine phenyl compound, such as the material ROTN30;
A mixture of at least one cyanobiphenyl and at least one cyanophenylpyrimidine compound; e General formula E (wherein R _A and R _B are alkyl or alkoxy groups, rings A and B are cycloaliphatic or aryl groups optionally bearing pendant substituents such as fluorine, e.g. R _A = alkyl,

【formula】

[Formula] and R _B = alkyl). 4-n-alkyl- or alkoxy-4- forming a mixture of about 60% to 80% by weight with one or more substances having a high clearing point.
Cyanobiphenyl and 1-(4'-cyanophenyl)
A liquid crystal material containing a mixture of approximately equal weight proportions of -4-n-alkyl-cyclohexane has been found to be a particularly suitable host liquid crystal material. Generally, any other liquid crystal material incorporating one or more compounds selected from the following known groups may be mixed into the host material: however,

When [Formula] is a trans-1,4-substituted cyclohexane ring,

[Formula] is a 1,4-substituted bicyclo(2,2,2)octane ring, and X ₁ is a 1,4-phenylene group

[Formula] or 4,4' bipheni lyle group

[Formula] or 2,6 na thiful group

[Formula], Y is CN, or R ¹ , or OR ¹ or CO・O−X ₁ −Y ¹
(wherein Y ¹ is CN, R ¹ or OR ¹ ); R ¹ and R are alkyl, preferably n-alkyl having 1 to 9 carbon atoms. A solution of the dye and the liquid crystal material is prepared by simply mixing the dye and the liquid crystal material together, then heating the mixture with stirring at about 80° C. for about 10 minutes, and then allowing the mixture to cool. , can be prepared by conventional methods. The pleochroic dye compound of the above general formula may be mixed with other dye compounds (not necessarily dyes of the general formula) in order to improve the spectral absorption properties of the dye when dissolved in liquid crystal materials. good. For example, if a dye compound of the general formula is blue or blue/
In the case of green, neutral black mixtures can also be produced by mixing with yellow and red dye compounds or yellow, red and orange dye compounds. The components of suitable black dye mixtures are illustrated below. () General formula (preferably in the formula, both R ² and R ³ are H
A blue dye having the general formula P (In the formula, K ¹ and K ² are alkyl, preferably an n-alkyl group having 3 to 12 carbon atoms, S is sulfur, R ^A and R ^B are aryl, preferably phenyl or 4-alkyl substituted phenyl group) , R ^A
and one of R ^B is phenyl and the other has 3 to 3 carbon atoms
4-alkylphenyl having 8 branched alkyl groups)
Red dye; () General formula Y (In the formula, SR ^C and SR ^D are synonymous with SR ^A and SR ^B , respectively.) A yellow dye having the following formula: Dyes of other colors, such as general formula O (In the formula, SR ^A and SR ^B have the same meanings as above, and SR ^E
is a phenylthio or 4-alkyl phenylthio group) or a blue/green dye having the general formula in which one or both of R and R ¹ is a methyl group. It can be done. Suitable dye mixtures are illustrated below. The relative proportions of dyes mixed together are determined by the desired spectral response. If this spectral response is an absorption curve extending across the spectrum, it will exhibit a gray color. Furthermore, dye mixtures are used in combination with liquid crystal compositions as described above or as described below. The liquid crystal electro-optic display of the present invention comprises two electrically insulated substrates (at least one of which is optically transparent), an electrode on the inner surface of the substrate, and a space between the electrode and the substrate. an enclosed film of dielectric material, the dielectric material being a composition of the present invention. The liquid crystal/dye solution composition of the present invention can be used in any known electro-optic display. Known devices operating by the following effects are known to those skilled in the art: a. Twisted nematic effect In this case, a nematic liquid crystal material film with positive dielectric anisotropy assumes the off state. In this state, the liquid crystal molecules (long axes) are in the plane of the (usually mutually parallel) inner surfaces of the device substrates, or at a small angle to this plane, and the substrates are The orientation of the surface, caused by a treatment such as rubbing the surface in one direction, causes it to undergo a helical twist of approximately π/2, oriented from one substrate to the other. This is a twisted “homogeneous organization”
(homogeneous texture). When an electric field is applied between the electrodes on the inner surface of each substrate to provide an on state, the liquid crystal molecules rearrange and form a "homeotropic structure".
In fact (its long axis) is perpendicular to the inner surface of the substrate in the textured state. Changes in the optical activity (rotation power) of this film occur between the on and off states due to molecular rearrangement, which causes the observed optical effect to occur in the linear polarizer and liquid crystal material adjacent to one of the substrates. This can be enhanced by using pleochroic dyes dissolved in . This polarizer has a polarization axis parallel to the direction of the liquid crystal molecules on the inner surface of the adjacent substrate (or, more precisely, parallel to the average axis of the projection of the molecules onto the inner surface). The guest-host effect causes the dye to appear relatively dark or strongly colored in the off state, while appearing bright or weakly colored in the on state. b Fredericks Effect in Negative Nematics In this case, the nematic liquid crystal material with negative dielectric anisotropy assumes the off state. In this state, the liquid crystal molecules are (parallel) due to the surface treatment on the inner surface of the substrate prior to assembly.
It exists perpendicularly to the inner surface of the substrate (ie, in a homeotropic state). A single polarizer is placed adjacent one substrate with a transmission axis perpendicular to the inner surface. When an electric field is applied between the electrodes on the inner surface of each substrate to provide an on state, the liquid crystal molecules are rearranged to become parallel to the inner surface of the substrate (ie, a homogeneous structure). When pleochroic dyes are mixed into the liquid crystal material, the off-state appears relatively bright or weakly colored, while the on-state appears dark or strongly colored. The observed effect is enhanced by the presence of a polarizer. c Fredericks Effect in Positive Nematics In this case, a nematic liquid crystal material with positive dielectric anisotropy assumes the off state. In this state, due to the treatment of the inner surface of the board prior to assembly,
The liquid crystal molecules are approximately parallel and lie within the plane of the (parallel) inner surface of the substrate (ie, a homogeneous structure). A single polarizer is placed adjacent one substrate with a transmission axis parallel to the inner surface of the substrate. When an electric field is applied between the electrodes on the inner surface of each substrate to provide an on state, rearrangement of the liquid crystal molecules occurs, resulting in a homeotropic structure perpendicular to the inner surface of the substrate. Incorporation of pleochroic dyes in the liquid crystal material results in the off-state appearing relatively dark or strongly colored, while the on-state appears colorless or weakly colored, such as in the twisted nematic effect described above. The observed effect is enhanced by the presence of a polarizer. d Phase change effect (negative contrast type) In this case, a cholesteric liquid crystal material with a positive dielectric anisotropy and a long molecular helical pitch, typically 2 μm, assumes an off state. In this state,
Liquid crystal molecules are in an irregular helical state or "focal conic texture." When an electric field is applied between the electrodes on the inner surface of each substrate to give an on state, the liquid crystal molecules rearrange to become perpendicular to the inner surface of the substrate (i.e., like a positive nematic liquid crystal in the Fredericks effect). , homeotropic tissue). Incorporation of pleochroic dyes into liquid crystal materials provides an off state that appears relatively dark or strongly colored, and an on state that appears colorless or weakly colored. e Phase change effect (positive contrast type) In this case, the cholesteric liquid crystal material with negative dielectric anisotropy and long molecular helical pitch assumes the off state. In this state, the liquid crystal molecules exist perpendicularly to the inner surface of the substrate, that is, they are in a homeotropic state. When an electric field is applied between the electrodes on the inner surface of each substrate, the molecules are rearranged so that they are in a helical arrangement within the plane of the inner surface of the substrate, that is, a twisted homogeneous structure. Incorporation of pleochroic dyes into liquid crystal materials provides a relatively colorless or weakly colored off state and a relatively dark or strongly colored on state. f Frederiks effect in smectics In this case, the dielectric relaxation frequency c below about 10 kHz
A smectic A liquid crystal material with a positive dielectric anisotropy (ie, the material has a negative dielectric anisotropy above this frequency) assumes an off state. In this state, the liquid crystal molecules exist approximately parallel to the inner surface of the substrate together with the molecules on the two parallel inner surfaces, as in the Fredericks effect (c).
When an electric field is applied at a frequency less than c to provide an on-state, the liquid crystal molecules rearrange and become perpendicular to the inner surface of the substrate, resulting in a homeotropic structure. The on state is maintained when the electric field is removed. On-state clearing may be achieved by application of a high frequency electric field, ie, applying a frequency greater than c. If the molecular alignments on the inner surfaces of the two substrates are parallel in the off-state, a single polarizer is used, as is the case with the Fredericks effect (c) described above. Mixing pleochroic dyes into the liquid crystal material provides a relatively dark or strongly colored off state and a bright or weakly colored on state. Among the above effects, a phase change effect (negative contrast type) is preferred. The materials defined above are not limited to use in electro-optic displays. This material may be used in virtually any known use of dyed liquid crystal materials. An example of such a "non-electro-optical" application is a thermally addressed display. In this display, symbols are added to a smectic or cholesteric material by selectively heating the material, e.g. by a laser (e.g. He/Ne) beam, in order to produce local changes in the molecular structure of the material. Or a letter is given. The dye enhances the contrast between different areas of the display, ie, areas that are selectively heated and areas that are not heated. General formula (where R ² and R ³ are both hydrogen)
The method for producing the compound is based on the general formula (wherein R and R ¹ each independently represent C _4-7 -n-alkyl) is nitrated to give 2,7-
Di-(C _4-7 -n-alkyl)-4,5-dinitrocrisazine is produced, which is reduced to 2,7-di-
( _C4-7 -n-alkyl)-4,5-diaminocrisazine. This method is disclosed in a pending patent application. This two-step reaction, nitration and reduction, can be carried out using conventional reagents. For example, nitration may be carried out using a mixture of concentrated sulfuric acid and concentrated nitric acid, and reduction using a mixed sulfur/sodium sulfide reducing agent. A compound of the general formula (wherein R ² and/or R ³ is alkyl) is a compound of the general formula (wherein R ² and/or R ³ is alkyl).
is hydrogen) can be prepared by alkylation, for example by reacting boric acid with C _1-4 -alkanols in the presence of concentrated sulfuric acid. In this way, a C _1-4 -alkyl group can be introduced into one or both of the amino groups. This alkylation generally yields mixtures of compounds containing no, one or two C _1-4 -alkyl groups, which can be used as such or can be chromatographically and/or fractionally crystallized to separate the components. used separately. The shade of the mixture can be adjusted by blending other pleochroic dyes. General formula (wherein R and R ¹ are each independently C _4-7
-n-alkyl) is an intermediate compound of chrysazine or leuco-chrysazine and the formula RCHO or
It can be produced by reacting R ¹ CHO (wherein R and R ¹ are C _4-7 -n-alkyl) in the presence of pyridine. This alkylation reaction is preferably carried out using leucochrysazine, which is produced in situ by reducing chrysazine with alkaline dithionite. The reaction medium preferably consists of aqueous pyridine, especially water:pyridine in a weight ratio of 10:1. It is surprising that this reaction proceeds so effectively with n-alkyl aldehydes. This is because, in the absence of pyridine, n-alkyl aldehydes generally undergo aldol condensation reactions that compete with the desired alkylation reaction, resulting in a lower yield of the intermediate 2,7-dialkylchrysazine. be. This alkylation reaction is performed between 20 and 100
It may be carried out at a temperature of 1 to 24 hours, preferably 2 to 8 hours, at a temperature of 50 to 90 degrees Celsius. When two different aldehyde mixtures are used, the products are two symmetrical compounds with the general formula, one in which R and R 1 are the same, and the other in which R and R ¹ in the general formula are the ^same . consists of different compounds. If desired, the components can be chromatographically separated from the mixture and then converted into compounds of the general formula, or the mixture can be directly converted into a mixture of compounds of the general formula. R and
If a product with the same R ¹ is desired, per mole of chrysazine, the aldehyde, RCHO (where R is
at least 2 and preferably up to about 3 moles of C _4-7 -n-alkyl. If products in which R and R ¹ are different are desired, 1 to 1.5 moles of each aldehyde are used per mole of chrysazine. In the compound of the general formula, R and R ¹ are lower (<C ₄ )
Not only is it superior to similar compounds that are higher (>C ₇ ) alkyl groups, but it also has 1 OH group.
-NHR ² and NHR ³ groups are in the 4 and 8 positions, -CH ₂ R and -CH ₂ R ¹ groups are in the 2 and 6 positions
is superior to isomeric compounds derived from anthralfin in the position. In the following examples, examples of manufacturing compounds of the general formula,
and the properties of a mixture of the compound and the compound. In the examples, parts and percentages are generally by weight. Example 1 (a) Preparation of 2,7-di-n-pentylchrysazine Chrysazine (120 g) was dissolved in a solution of sodium hydroxide (120 g) in a mixture of water (1500 ml) and pyridine (220 ml). added to at 55℃,
Stirred. Sodium hydrosulfite (200g)
was added to the mixture and after stirring for 30 minutes under N ₂ another 100 g of sodium hydrosulfite was added.
Add n-pentanal (142 g) to this reaction mixture.
Add dropwise over 30 minutes and keep the mixture under N ₂
The mixture was stirred at 80° C. for 2 hours. The mixture is then cooled to room temperature and mixed with an acidified ice/water mixture (ice/
After stirring for 2 hours, the mixture was filtered and the filter cake was washed with water. The tarry cake was slurried in 400 ml of ethyl acetate, filtered, washed with methanol, and pulled until dry. When this paste is recrystallized using ethyl acetate, the dry product
56 g (yield 29.5%) was obtained. The melting point of the product was 127°C, and the elemental analysis values were as follows. C = 76.1% (75.8%) and H = 7.5% (7.4%) (b) Production of 2,7-di-n-pentyl-4,5-dinitrocrisazine 2,7-dipentylcrisazine (56 g) 98
% sulfuric acid at room temperature and stirred for 30 minutes,
Cooled to 0°C. To this cooled mixture, 160 ml of nitrating acid anhydride (33% nitric acid + 67% sulfuric acid) was added dropwise over a period of 30 minutes while maintaining the temperature below (<10°C), and the mixture was further heated to below 10°C. So 2
Stir for hours. The mixture was then poured into ice/water 4, stirred at room temperature for 30 minutes, filtered, washed until no longer acidic and dried to give 50.5 g (73% yield) of dry product. The melting point of the product was 140°C, and the elemental analysis values were as follows. C = 58.5% (61.3%), H = 5.4% (5.5%) and N = 5.5% (6.0%) (c) Production of 2,7-di-n-pentyl-4,5-diamino-chrysazine 2. 7-di-n-pentyl-4,5-dinitrocrisazine (6 g) was mixed with 200 ml of water and pyridine.
It was added to a mixture of 50 ml and stirred at 20°C. Add to this mixture a mixed sulfur/sulfide reducing solution (20% water
25 g of sodium sulfide and 3 g of sulfur in ml) and the mixture was stirred at 90° C. until the reaction was complete (1 hour). After another 30 minutes, 90℃
Heat the mixture at
4.6g (yield 88.4%) was obtained. The melting point of the product was 164-7°C. Example 2 (a) Preparation of 2,7-di-n-heptyl-chrysazine Example 1(a) was repeated. However, n-pentanal
171 g of n-heptanal was used instead of 142 g.
The yield of dry product was 103 g (yield 47.6%). The melting point of the product was 116-118°C, and the elemental analysis values were as follows. C=76.1% (75.8%) and H=7.5% (7.4%) (b) Preparation of 2,7-di-n-heptyl-4,5-dinitrocrisazine Example 1(b) was repeated. However, 2,7-G-
Instead of 56g of n-pentylcrisazine, 2,7
- 87.2 g of di-n-heptylcrisazine was used, and the amounts of other ingredients were also increased by 25%. The yield of dry product was 50.5 g (yield 69.1%). The melting point of the product was 140°C, and the elemental analysis values were as follows. C = 58.8% (61.3%) H = 5.4% (5.5%) and N = 5.5% (6.0%) (c) Production of 2,7-di-n-heptyl-4,5-diaminocrysazine Example 1 (c) was repeated. However, 2,7-G-
n-pentyl-4,5-dinitrocrisazine 6
2,7-di-n-heptyl-4,5 instead of g
- 27 g of dinitrocrisazine were used and the amount of water pyridine was also increased to 1 in the same proportion. The reducing solution is 100 g of sodium sulfide and 12 sulfur in 50 ml of water.
It was a liquid containing g. The yield of the product after recrystallization from toluene was 20.9 g (yield 88.2%). The melting point of the product was 140-2°C, and the elemental analysis values were as follows. C = 72.4% (72.1%), H = 8.5% (8.2%) and N = 6.0% (6.0%) Example 3 Example 1 is repeated using an equal amount of n-hexanal in place of n-pentanal. te, 2,7-j-n
-Hexyl-4,5-diaminocrisazine was produced. The melting point of the product was 138-9°C, and the elemental analysis values were as follows. C = 71.3% (71.2%) H = 7.8% (7.8%) and N = 5.9% (6.4%) The structure was confirmed by NMR and mass spectrometry, and the purity was confirmed by HPLC. Example 4 Example 1 is repeated using an equivalent amount of n-octanal in place of n-pentanal to produce 2,7-di-n
-Octyl-4,5-diaminocrisazine was produced. The melting point of the product was 112-4°C, and the production was confirmed by mass spectrometry and NMR analysis, and the purity was confirmed by HLPC. Example 5 (a) Preparation of partially methylated 2,7-di-n-heptyl-4,5-diaminocrysazine Boric acid (2.5 g) in 98% sulfuric acid (44 ml) at 20°C
and stirred for 30 minutes. Add 2,7 to this mixture
-di-n-heptyl-4,5-diaminocrisazine (8.63 g) was added and the whole was stirred for a further 1 hour.
Stir at 20°C. After adding a mixture of water (5g) and methanol (7.5g) dropwise over 10 minutes, the mixture was heated to 115°C. After being left at 115℃ for 3 hours, the temperature was raised to 120℃, and then at 120±5℃.
Stirred for 16 hours. The reaction mixture was then cooled to 20° C., poured into a mixture of ice and water, filtered, the solid washed free of acidity and dried to give 8.15 g of dry product. The product was reslurried in pyridine (80 ml), diluted with water (40 ml), cooled to 20°C, filtered, washed with water,
Dried (yield 7.3g). Finally, extraction with 100-120 petroleum ether yields partially methylated derivatives soluble in the solvent, namely 2,7-di-n-heptyl-4,5-diaminocrysazine, 2,7-
1.6 g of a derivative containing di-n-heptyl-4-amino-5-methylamino-chrysazine and 2,7-di-n-heptyl-4,5-di(methylamino)chrysazine was obtained. (b) 2,7-di-n-heptyl-4-amino-5
-Production of methylaminocrisazine (c) Production of 2,7-di-n-heptyl-4,5-di(methylamino)crisazine Partially methylated soluble in the solvent of Example 5(a) The derivative was dissolved in toluene and applied to a silica gel column. Separation was performed first by elution with toluene, and then recovery was performed by elution with toluene:chloroform (90:10). The fractions containing the two main products were evaporated to dryness and slurried separately in 40−60 petroleum ether, then
It was filtered and dried. The structure of the product in the first fraction was confirmed by mass spectrometry, and at 575 nm it was 22100.
2,7-di-n-heptyl-4,5-di(methylamino)chrysazine [5
(c)]. The structure of the product in the second fraction was confirmed by mass spectroscopy, and the melting point was 110-2℃.
It was 2,7-di-n-heptyl-4-amino-5-methylaminocrisazine [5(b)] with an extinction coefficient of 19522 at 675 nm. Example 6 2,7-di-n-heptyl-4,5-diaminocrisazine (2c) was replaced with an equivalent amount of 2,7-di-n
-Pentyl-4,5-diaminocrisazine (1c)
using an equal amount of 2,7-di-
A derivative of n-pentyl-4,5-diaminocrisazine was prepared. Mixtures of unmethylated, partially methylated and fully methylated derivatives (6a)
was separated in the same manner as in Example 5. The melting point of the monomethylated derivative (6b) is 142-5℃, and the extinction coefficient is
It was 23785 at 675nm. The melting point of the dimethylated derivative (6c) was 158-160°C. Example 7 2,7-di-n-pentyl-4,5-diaminocrysazine (1c: 11.74 g) was dissolved in 98% sulfuric acid (32.6
ml) at 20°C and stirred for 30 minutes. Add dimethyl sulfate (14.1 ml) to this mixture and bring the whole to 150 ml.
Stirred at -5°C for 12.5 hours. During this time, an additional 7.05 ml of dimethyl sulfate was added after 3 hours. The reaction mixture was poured into ice/water, and the product was filtered, washed with water until no longer acidic, and dried (yield: 11.9 g). The crude product was slurried in pyridine (220 ml) at 60 °C, diluted with water (110 ml), cooled to 20 °C,
It was filtered, washed successively with pyridine/water (50/50, 20 ml) and water, and dried (yield: 10.6 g). Successive extraction of the pyridine-treated material with 100-120 petroleum ether (200 ml) and ethyl acetate (50 ml) yields
5.6 g of insoluble material remained. The solvent extract (containing soluble material) was evaporated to dryness, washed with 40-60 petroleum ether, filtered and dried to yield 4.3 g of pure material (product 7a). 4.2 g of 7a in chloroform, 2,7-di-n-
Pentyl-4,5-diaminocrisazine (1c)
Dissolve 1.26 g to form a mixture and evaporate to dryness. Grind the mixture in 40-60 petroleum ether.
The solvent then evaporates and a fine powder (product 7b)5.3
g remained. Example 8 2,7-di-n-pentyl-4,5-diaminocrysazine (1c: 10.25 g) was dissolved in 98% sulfuric acid (250
g) and water (250 g) at 20°C.
The mixture was heated to 80-5°C. Formaldehyde solution (37%: 4 ml) was added in 0.5 ml portions at 30 minute intervals and the temperature was maintained at 80-5° C. for a further 3 hours. The reaction mixture was cooled to 20°C and poured onto ice/water (2). The product was filtered, washed with water until no longer acidic, and dried to obtain 10 g of product 8. HPLC analysis of products 7a, 7b and 8 revealed that the products had the following compositions.

[Table] Hereinafter, "Dye 1(c)" refers to the product of Example 1(c), and "Dye 5(a)" refers to the product of Example 5(a). Example 9 8 parts of dye 1(c) (blue) and 2,7-di-n, the product of Example 5(d) of UK Patent Application No. 8223718 filed 18 August 1982 -Heptyl-
15 parts of 4-phenylthio-5-(4-t-butylphenylthio)chrysazine (violet) and 1-phenylthio-5-(4- t-Butyl-phenylthio)anthraquinone (yellow)
A black mixed dye was prepared by mixing 20 parts. Example 10 Using the same dye as Example 9, blue dye 12
A black mixed dye was prepared by mixing 20 parts of black dye, 20 parts of violet dye, and 30 parts of yellow dye. Example 11 10 parts of dye 1(c) (blue), 10 parts of the violet dye used in Example 9, 20 parts of the yellow dye used in Example 9, and GB 2094822A
1,5-di-, the product of Example 22 in the specification
(4-tert-butylphenylthio)-4-phenylthioanthraquinone (orange) 30 parts and dye 5(a)
(blue green), i.e., by mixing with 10 parts of the partially methylated derivative of the blue dye used in Example 9,
A black mixed dye was prepared. Comparative dyes with longer, shorter or branched alkyl chains or general formula B The comparative dye having C5-8 used in the example
-n- alcanal in place of a suitable alcanal,
and/or produced in the same manner using anthralfin as a starting material instead of chrysazine used in the examples. All products were recrystallized with petroleum ether or toluene until purity was greater than 95%. The properties of the products were investigated in various liquid crystal materials. The properties of compounds of the general formula in typical liquid crystal materials are shown in the table below.
For comparison, the properties of the branched isomers, short-chain and long-chain homologs, compounds of general formula B are also shown.

【table】

[Table] Comparative example isopropyl 0.63 * *

[Table] Comparative example isopropyl 0.54 * *

[Table] Comparative example isopropyl 0.63 * *

[Table] Notes to Table () The order parameters, solubility and stability in Table - are the results of measurements in liquid crystal material E43 at 20°C. The above E43 is published in British Patent Publication No.
The material is referred to as host B in specification no. 2081736 and is commercially available from BDH Ltd, Poole, Dorset. () Stability is expressed as the percentage decrease in absorption at maximum absorption after irradiation for a specified time at 30°C with an IKW phosphorus-coated mercury vapor lamp. () In the table, "S" and "Sol" are order parameters and solubility (wt%) in appropriate liquid crystal materials.
refers to () * indicates not measured. () The number in parentheses after the dye name in the table - for example, "(1c)" after "n-butyl" under the heading of the example (general formula) - is the dye of the example with that number. Shows a mixture. () ZLI 1132: Host C of UK Patent Publication No. 2081736 (EMerck, Darmstadt, West Germany)
ZLI 1695: Commercially available from Emerck Co.; FBCO Ester: Host 12 of UK Patent Publication No. 2093475 (this is a host with negative dielectric anisotropy); PECH: Has the following composition: . A specific example of a liquid crystal device embodying the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, a liquid crystal display of the Frederik effect (positive nematic) type includes a liquid crystal cell 3 consisting of two glass slides 4, 5 containing a layer 6 of liquid crystal material. This liquid crystal material is essentially a positive nematic material containing pleochroic dyes. Electrodes 7,8 made of tin oxide, for example, are arranged on the inner surface of the slides 4,5. A brushed aluminum reflector plate 27 may be placed after the slide 5. Before assembling the cell 3, the inner surfaces of the slides 4, 5 (which already carry the electrodes 7, 8) are coated with silicon monoxide or magnesium fluoride. This coating is formed, for example, by depositing a stream of silicon monoxide onto the slide at an angle of approximately 5° to the slide surface, as disclosed, for example, in GB 1454296. When assembling, the slides are arranged in accordance with the vapor deposition direction on the two slides 4 and 5 that are parallel to each other. With such a coating, the liquid crystal molecules on the coated surface are aligned in a single direction (parallel to the direction of deposition) and at an angle of about 25° to the adjacent slide surface.
They exist at an angle of 35°, typically 30°. As a result, the liquid crystal molecules exist in a parallel homogeneous organization as shown by arrows 13 (FIG. 1). The dye molecules, which are in a guest-host relationship with the liquid crystal molecules, are loosely present in a homogeneous structure that gives cell 3 a relatively strongly colored appearance (this appearance would occur if the dye absorbed uniformly across the visible spectrum). is black or gray). In this or "off" state, a single polarizer 1 (shown in front in FIG. 1) placed in front or behind the cell 3 with its transmission axis parallel to the alignment direction of the liquid crystal material 6 Enhances the color of the display. This arrangement confines the electric vector of the incident or reflected light to be approximately parallel to the changes in the dye molecules. When a suitable voltage, for example a few volts (greater than the threshold for effect) is applied between the electrodes 7 and 8 to give an "on" state, the liquid crystal material molecules are switched into a homeotropic organization, i.e. the slides 4, 5 lies parallel to the electric field along the axis perpendicular to . Due to the guest-host effect, dye molecules are also transformed into this tissue and have long axes substantially parallel to the light incident on the cell 3 in a direction perpendicular to the slides 4, 5 [i.e. The molecules are essentially in an "end-on" state], the absorption of ambient light is effectively reduced. This gives the cell 3 a relatively bright or weakly colored appearance. If electrodes 7 and 8 cover only part of the inner surface of slides 4 and 5, respectively, the entire cell 3 will appear strongly colored (i.e. highly reflective) in the "off" state, while in the "on" state In this state, only the area of the liquid crystal material 6 between the electrodes 7, 8 appears brightly or weakly colored. The remainder of the cell 3 in the "on" state is strongly colored, ie it appears to remain in the "off" state. (If the pleochroic dye absorbs uniformly across the visible spectrum, strong coloring will appear black or gray.) In this way, electrodes 7, 8 can be separated into
For example, symbols or letters may be displayed by being formed into bars of a digit that can be separately connected to a voltage source (not shown). This may be achieved by photoetching (in known manner) the layers used to form the electrodes 7, 8, for example _SnO2 , before assembly. For example, in the clock display of FIG. 3, the electrodes 7, 8 are formed with four sets of seven number bars to indicate the time; for example, the numbers 12.45 as shown in FIG. It shows. As in a conventional clock display, a pulsed period dot P is also included to indicate operation of the display. Examples of colored liquid crystal substances suitable for use as substance 6 above are the black dye mixtures described in Examples 9, 10 or 11 dissolved in host E43 (the layer thickness of substance 6 is 12 μm). . In another device embodying the invention, the cholesteric to nematic phase change effect is performed in a known manner. The inner surfaces of the power-bearing slides 4, 5 are not coated with MgF ₂ or SiO, no polarizer 1 is required, and the liquid crystal material 6 in this case is substantially elongated (containing a pleochroic dye). It is constructed in the same manner as described above with reference to FIGS. 1 to 3, except that it is a cholesteric substance (having a molecular helical pitch of about 2 μm). One of the host E43 containing dye mixtures 1, 2 or 3 as defined above (as used in the special Fredericks effect apparatus described with reference to Figures 1-3) is suitable. (The thickness of the layer of material 6 is 12 μm). In the "off" state (with no applied voltage), the cell 3 then appears strongly colored (as in a Frederik effect device). In this state, the liquid crystal substance 6 is in an undisturbed state of structure consisting of an irregular molecular helical arrangement. The dye molecules adopt the same arrangement due to the guest-host effect. Strongly colored due to the partial absorption of the ambient white light incident on the material 6 through the slide 4 by dye molecules oriented perpendicular or oblique to the direction of light propagation (this coloration is (can be black or dark gray). In the "on" state, a voltage (typically is 10-15 volts)
is applied between electrodes 7 and 8. The dye molecules between electrodes 7, 8 are reoriented into this arrangement by the guest-host effect. The dye molecules are substantially "end-" relative to ambient light propagating (through slides 4) in a direction perpendicular to cell 3, i.e. perpendicular to slides 4, 5.
In this state (as in the Fredericks effect device) the electrode 7,
The area between 8 appears bright or weakly colored. A suitable host in this case is E43 (96% by weight) as described above plus CB15 (4% by weight).
The dye mixtures described in Examples 9, 10 or 11 may be used as guest dyes. CB15 is a compound provided by BDH It is.

[Brief explanation of drawings]

FIG. 1 is an exploded view of a Fredericks effect display device embodying the present invention, and FIG.
A sectional view of the device shown in the figure, and FIG. 3 a front view of a watch with a liquid crystal display assembled as shown in FIGS. 1 and 2. 1... Polarizer, 3... Liquid crystal cell, 4, 5... Slide, 6... Liquid crystal substance, 7, 8... Electrode, 27
...Reflector, A...Reflected light, B...Ambient light.

Claims (1)

[Scope of Claims] 1. A composition suitable for a guest-host liquid crystal device comprising a solution of a liquid crystal substance and a pleochroic dye, wherein the dye is water-soluble, contains no ionic substituents, and has the general formula (wherein R and R ¹ are each independently an n-alkyl group having 4 to 7 carbon atoms, and R ² and R ³ are each independently selected from the group consisting of hydrogen and an alkyl group having 1 to 4 carbon atoms. A composition comprising at least one anthraquinone compound having the following. 2. Composition according to claim 1, characterized in that at least 90% by weight of the solution is liquid crystal material. 3. The composition according to claim 1, wherein the liquid crystal material has positive dielectric anisotropy. 4. The composition according to claim 1, wherein the liquid crystal material has negative dielectric anisotropy. 5. The composition according to claim 1, wherein R and R ¹ in the general formula are the same. 6. The composition according to claim 5, wherein R ² and R ³ in the general formula are both hydrogen. 7 A compound of the general formula has the formula The composition according to claim 6, characterized in that it has the following. 8 A compound of the general formula has the formula The composition according to claim 6, characterized in that it has the following. 9 A compound of the general formula has the formula The composition according to claim 6, characterized in that it has the following. 10 The compound of the general formula has the formula The composition according to claim 6, characterized in that it has the following. 11 Claim 1, characterized in that at least one of R ² and R ³ is C _1-4 -alkyl.
The composition described in Section. 12 R and R ¹ in the general formula are the same and are either n-butyl or n-hexyl,
12. Composition according to claim 11, characterized in that ^R2 is H and ^R3 is _C1-4 -alkyl. 13 The pleochroic dye has the general formula where R and R ¹ are the same and are either n-butyl or n-hexyl, R ² is H and R ³ is C _1-4 -alkyl. 13. The composition according to claim 12, which is a mixture of compounds containing at least one compound. 14. The pleochroic dye is a mixture of compounds, at least one of which R and R ¹ are the same and is either n-butyl or n-hexyl,
R ² is H, R ³ is C _1-4 -alkyl, and at least one compound is a compound of the general formula in which R 2 is H and R ³ is C 1-4 -alkyl, and at least one compound is 14. The composition according to claim 13, wherein the composition is any of the following, and is a compound of the general formula in which one of ^R2 and ^R3 is hydrogen and the other is _C1-4 -alkyl. 15 The mixture further comprises at least one compound of the general formula in which R and R ¹ are the same and are either n-butyl or n-hexyl, and R ² and R ³ are both C _1-4 -alkyl. 15. A composition according to claim 14, characterized in that it comprises: 16 Both or all of the compounds of the general formula have the same R
and R ¹ , the composition according to claim 14 or 15. 17 Among the compounds of the general formula that are mixed into the composition,
R ² or R ³ or both are C _1-4 -alkyl groups,
17. The composition according to any one of claims 1 and 13 to 16, wherein the C _1-4 -alkyl group is a methyl group. 18. Composition according to claim 1, characterized in that the liquid crystal substance consists of a mixture of cyanobiphenyl and a substance having a clearing point of 80° C. or higher. 19. The composition according to claim 1, wherein the liquid crystal substance consists of a mixture of a cyanobiphenyl cyclohexane compound and a substance having a clearing point of 80°C or higher. 20 The liquid crystal substance has the formula (In the formula, R _A and R _B are alkyl or alkoxy groups, and [Formula] and [Formula] represent a six-membered aryl or alicyclic ring structure.) A composition according to claim 1. 21 The liquid crystal substance has the formula (wherein R _Q is C _2-9 -n-alkyl) and a substance having a clearing point of 80°C or higher. Compositions as described. 22. A composition according to claim 1, characterized in that the product of the molecular extinction coefficient and the solubility (mole/l) of the dye for each compound contained in the dye is at least 500 cm ^-1 . 23. The composition according to claim 1, wherein each compound contained in the pleochroic dye accounts for 0.5 to 10% by weight of the composition. 24 Each compound contained in the pleochroic dye
A composition according to claim 1, characterized in that the amount is from 0.5 to 5% by weight. 25. Composition according to claim 1, characterized in that the pleochroic dye consists of a mixture of dyes with different colors, and at least one of these dyes is a dye compound of the general formula . 26. Composition according to claim 25, characterized in that the pleochroic dye comprises a blue dye, a purple or a mixture of a red/purple dye and a yellow dye, said blue dye being a compound of the general formula . 27. A composition according to claim 26, characterized in that the mixture further comprises an orange dye and consists of a mixture of neutral colors. 28 Pleochroic dyes include yellow dyes, red or purple/red dyes, blue dyes and blue/red dyes.
28. A composition according to any of claims 25 to 27, consisting of a neutral color mixture of green dyes, wherein the blue dye and the blue/green dye are compounds of the general formula. 29 Yellow dye has general formula Y (In the formula, S is sulfur, and R ^C and R ^D are each an aryl group.) Claim 26
The composition according to any one of Items 28 to 28. 30 The dye mixture has the general formula P (In the formula, K ¹ and K ² are alkyl, S is sulfur,
29. A composition according to any one of claims 26 to 28, characterized in that it comprises a red/purple dye (R ^A and R ^B are aryl groups). 31. Claims 1, 18, 19 and 31, characterized in that the liquid crystal material is suitable for use in a cholesteric to nematic phase change effect device and consists of a chiral agent and a nematic liquid crystal material. 22. A composition according to any of paragraph 21. 32 A liquid crystal electro-optical device comprising two electrically insulated substrates, at least one of which is optically transparent, an electrode on the inner surface of the substrates, and a film made of a dielectric material housed between the substrates. A composition suitable for a guest-host liquid crystal device in which the dielectric material comprises a solution of a liquid crystal material and a pleochroic dye, the dye being water soluble and free of ionic substituents and having the general formula I. (wherein R and R ¹ are each independently an n-alkyl group having 4 to 7 carbon atoms, and R ² and R ³ are each independently selected from the group consisting of hydrogen and an alkyl group having 1 to 4 carbon atoms. 1. A device characterized in that it is a composition comprising at least one anthraquinone compound having the following: 33. Device according to claim 32, characterized in that the device is a cholesteric to nematic phase change effect device. 34. Device according to claim 32, characterized in that the device is a Fredericks effect device. 35. Device according to claim 32, characterized in that the device is a torsional nematic effect device.