JPH0116876B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to host-host combinations of pleochroic N-substituted cyclic derivatives of mono- and di-aminoanthraquinones and dielectrically positive nematic liquid crystals. The invention further relates to optoelectronic devices using the customer-host combination. Optoelectronic devices in which liquid crystals are used usually consist of two transparent flat plates with very thin transparent electrodes on their internally facing surfaces, separated by a distance of a few to tens of microns. Moreover, the space between these plates is filled with a liquid crystal composition. It is these plates that will be referred to below as the walls of the container. Imposing an electric field onto the liquid crystal affects the optical properties of the liquid crystal layer. Heilmeier and Zanoni (Applied Physics Letters, Vol. 13, page 91)
92 (1968)), that when a pleochroic dye is combined with a nematic liquid crystal in a device such as the one described above, the pleochroic color of the dye becomes manifest as an electric field is applied and released. was discovered. The nematic fluid is called the "host" and the pleochroic dye is called the "guest," and the composition is thus called a guest-master combination. This phenomenon is used in U.S. patents 3551026, 3597044 and
Used in No. 3960751. In order to be able to operate an optoelectronic device using a nematic liquid crystal, the liquid crystal must have an oriented structure that is adjusted by the direction of the applied electric field. Liquid crystals (mesomor-phic materials) tend to have rod-like molecules. If the long axis of the liquid crystal is perpendicular to the wall of the bath or container, the structure is called hemo-tropic. If the long axis of the liquid crystal is parallel to the wall of the bath or container, the structure is called homogeneous due to homogeneous boundary conditions. If two homogeneously oriented walls are perpendicular to the line of orientation, a twisted nematic liquid crystal structure is achieved. Many nematic liquid crystals, e.g. or (wherein the alkyl groups are activated amyl and activated heptyl) as a dopant.
Alternatively, by adding it as a chiral agent, it is possible to convert it to the cholesteric phase. In such cases, it is the axis of the homeotropically or homogeneously oriented cholesteric phase spiral. Homogeneous boundary conditions can be achieved by several techniques, each offering advantages for certain purposes. We believe that these matters are well known in the art and do not need to be described in detail. Suitable techniques and references for illustrating procedures include: 1 Unidirectional friction, for example in an aqueous suspension of very fine zirconium oxide. See "Nematic Liquid Crystal Device" by FJ Kahn, US Pat. No. 3,694,053. 2. Mechanical surface marking or deformation. D.W.
Berrgman, phys.Rev.Lett., Vol.28, page
See 1683 (1972). 3. Deposition of organic substances such as trimethoxysilane, R-Si (OCH ₃ ) and subsequent abrasion as described above. Appl.Phys.Lett.Vol.22 by FJKahn,
Page 11 (2/1/73) and by the same author
Appl.Phys.Lett.Vol.22, page 386 (4/15/
73). 4. Deposition of metal oxides or inorganic substances such as MgF ₂ deposited at an angle of 1 to 30° to the painted surface, or friction following deposition at an angle of more than 30°. App.Phys.Lett.Vol.21 by JLJanning,
See page 173 (1972). Homeotropic boundary conditions of less interest are generally obtained by coating with metal oxides at angles well above 30° or by treatment with surfactants. Dielectrically positive non-isotropy is exhibited by liquid crystals tending to align vertically with the imposed electric field. Such compounds are of particular interest for the host-host combinations of this invention. As the liquid crystal main body consists of a high percentage of dielectrically negative non-isotropic material and a small amount of highly dielectrically positive non-isotropic material, the overall effect is that of dielectrically positive non-isotropic material. Only one thing is usually necessary. Many pleochroic dyes useful in host-host combinations also tend to have molecules that are elongated in one direction, with little or no absorption along their long axes and no absorption along their short axes. They involve absorption of light in various parts of the visible spectrum. Other pleochroic dyes can be oppositely arranged, being colorless along the short axis and colored along the long axis. Thus they have two types. When combined with a homeotropic structure, i.e. a nematic liquid crystal with molecules perpendicular to the walls of the container, pleochroic dyes of the first type mentioned align their rods with those of the host liquid crystal, thus changing the color until an electric field is applied. unacceptable. Correspondingly, when the same pleochroic dye is combined with a nematic liquid crystal with a twisted structure, its molecules are aligned parallel to the walls of the container and increasingly at right angles, and thus the combination It looks colored until it is colored. A device is clearly possible that changes from one color to the other by combining two pleochroic dyes, each of the types mentioned above. By incorporating isotropic dyes, i.e., non-pleochroic dyes, so that the colors of the two are additive at one stage and isotropic dyes appear at other stages of the electric field cycle. The effect of this can be obtained. The use of dyes in amounts that can be aligned by the nematic liquid crystals, i.e. the amount of liquid crystals present, so that for a given device there is a cycle between colorless and colored or between two colors. It is clearly necessary to use the dye in an amount that does not exceed the proportions that can be aligned by. This is usually found to be up to about 5% by weight. In some cases, the solubility of the pleochroic dye in the liquid crystal is inadequate to achieve concentrations above 1-5% by weight. Prior art combinations range from zero to about 2:1 to about 4:1
It is possible to achieve contrasts up to a maximum electric field of up to 1. It is desirable to have greater solubility and higher contrast, and these are therefore goals and objectives of the present invention. In accordance with these goals and objectives, it has been found that a very useful group of pleochroic dyes for use in host-host combinations is provided by the anthraquinones of the following general formula: . [wherein the substituent (NRR') and Q are in positions 1 to 8, Q is F, Cl, NO ₂ , NH ₂ , NH (Alk), alkyl, or OH, and x is 0, 1 , 2 or 3, m is 1 or 2, R is independently H, and R′ is independently cyclohexane, bicyclohexyl, naphthyl or -(CH ₂ ) _p Ar {where p is 0, 1 or 2, and Ar is −
NHCOCH ₃ , CN, −C _o H _2o+1 , −OC _o H _2o+1 (n is 1 to 20, but when p=0, n is 2 to 20
), cyclohexyl, 4(-Alk)-cyclohexyl (Alk is alkyl with 1 to 8 carbon atoms), or

[Formula] (where y is 0 or 1, Y is CH ₂ , O, S or -
CH ₂ O− (carbon atom is bonded to Ar) and Z
is 4-substituted H, NO ₂ , CN, -C _o H _2o+1 , -OC _o
phenyl substituted in the 4 position by H _2o+1 (n is 1 to 20), F or Cl;
Ar is CN, −C _o H _2o+1 , −OC _o H _2o+1 (n is 1 to 20),
0 to 2 other positions may be substituted by NH ₂ or OH}, and (i) x=1, m=1, Q=OH and NRR' is on the ring (ii) when x = 0, m = 2, the molecules are in para positions to each other or in positions 1,5 or 4,8
When substituted with two NRR′ groups, the above (i) and
In case (ii), NRR′ is

[Formula] (x is -C _o H _2o+1 , -OC _o H _2o+1 (n=2-20), cyclohexyl or

The substituted anthraquinone of the above general formula is a dielectrically positive non-isotropic, nematic compound such as n-pentylphenylcyclohexyl cyanide or p-heptyl-4-cyanobiphenyl or These compounds have been found to form particularly useful host-host combinations with compositions or compositions containing a predominant amount of these compounds, ie compositions that provide a net dielectrically positive anisotropy. It was done. Positive non-isotropy is understood herein to refer to dielectric positive anisotropy. The compositions of the present invention may be used alone and in combination in up to equimolar proportions with nematic compounds to obtain contrast ratios of up to about 20:1 or more. The pleochroic dye compounds of the present invention are further remarkable in providing exceptionally high values of the optical order variable S. This variable is a measure of the efficiency of dye orientation. This is measured by measuring the absorption of light as the reciprocal of the percent transmission at the maximum through a liquid crystal solution of the dye between the electrode-cladding plate in the aforementioned bath with or without an imposed electric field. be done. where A _l and A ₀ are the absorptions with and without electric field, respectively. S=A ₀ −A ₁ /A ₀ +2A ₁ The variable S is given as a decimal number below 1.
For a given dye, this can vary somewhat depending on the particular nematic liquid crystal used as host. Prior art pleochroic dyes provide S values on the order of about 0.3 to 0.5. Compounds of the above formula have an optical order variable of 0.5 and above and in preferred compounds 0.7
and above. Values of 0.9 and above are found for some particularly useful compounds. This is a very high range of values that could not be expected from the prior art. The unusual properties of the pleochroic dye of the present invention, in combination with net positive non-isotropic nematic liquid crystals, make it valuable in display devices for calculators, watches etc. and also in devices such as cameras and projectors. When used in a reflective arrangement, it helps provide a mirror that can pass from reflective to transparent, and thus can be used in applications where cameras or mirrors are used. The invention will now be described with reference to the accompanying drawings. FIG. 1 is a diagrammatic representation of a photovoltaic valve device using the pleochroic dye host-host combination of the present invention; FIG. Figure 3 is a diagrammatic representation of the homeotropic guest-host combination of Figure 2 with an imposed voltage; FIGS. 6, 7 and 8 show the combination of a homogeneous positive non-isotropic nematic liquid crystal and a dye of the invention in a customer-host relationship in the absence and presence of an applied voltage; FIGS. The figure shows a combination of FIGS. 4 and 5, but given a twisted nematic liquid crystal with orthogonal vessel wall orientation. FIG. 6 shows the case where no voltage is applied, and FIGS. 7 and 8 show the case where the voltage is applied. Figures 9, 10 and 11 show 1,5-bis(4-cyclohexylphenyl)anthraquinone, 1-methylamino-2-undecyl-4(-4-octylanilino)-anthraquinone and 1,4-bis(4-phenylanilino)
FIG. 2 is a diagram showing the transmittance curve of a 5% solution of anthraquinone. FIG. 12 shows a comparative curve of the decrease in optical density with increasing voltage applied to the test chamber. FIG. 1 shows walls 12 and 14 whose interior is coated with a conductive coating 16 of tin and/or indium oxide and a positive non-isotropic nematic liquid crystal and a pleochroic dye (this figure tank 8 containing guest-master combination 18 (not shown)
It is shown. The bath 8 is placed between the light source 10 and the observer 24, with a polarizer 28 and, for some applications, an analyzer 26. The vessel 8 is equipped with a DC power source 20, shown as a battery, but any suitable power source may be used.
The power supply is connected to the coating film 16 of the tank with a switch 22 in between.
connected to. 2 and 3 are enlarged views of the end of bath 8, in which the molecules of nematic liquid crystal material 30 and dissolved pleochroic dye 40 are diagrammatically shown. The cell walls of FIGS. 2 and 3 are in a homeotropic orientation when a voltage is applied as shown in FIG. 3 and molecules 30 and 40 become oriented perpendicular to the walls as shown. is processed as described above so that this occurs. The vessels in FIGS. 4 and 5 are shown facing each other. The internal vessel walls are preferably oriented in a parallel configuration as described herein by coating MgF ₂ at a low angle on the tin and/or indium oxide. The orientation of FIG. 4 at a bias voltage O is changed by an applied voltage of about 5 volts and molecules 30 and 40 are aligned with the electric field as shown in FIG. Figures 6, 7 and 8 show the behavior in a bath in a twisted orientation. The tank wall is shown in Figures 4 and 5.
Similar to the figure, but with a vertical orientation at the rear wall and a horizontal orientation at the front wall, without an applied voltage. It can be seen that the molecules become oriented in the electric field when a voltage is applied as in FIGS. 7 and 8. 6th
In the figure, a portion of the vessel and contents have been cut away to show orientation at the rear wall. As noted above, forming the host-host combinations of the present invention requires the use of dielectrically positive, non-isotropic nematic compounds or compositions. Representative compounds with positive anisotropy include the following, and the temperatures at which a change from crystalline to nematic state (CN) and from nematic to isotropic state (NI) occur are indicated.

Other useful positive non-isotropic nematic liquid crystals include the following compounds:

【formula】

[expression] and (Wherein R is alkyl or alkoxy of 1 to 7 carbon atoms and x is alkyl or alkoxy of 1 to 9 carbon atoms.) Eutectic mixtures and combinations of all of the above are also useful. Illustrative eutectic mixtures of 4'-substituted 4-cyano-4'-alkylbiphenyls are shown in Table 2.

[Table] The above compounds with positive non-isotropy are
It may be used with compounds such as those representative of several useful groups of nematic liquid crystals with negative anisotropy as shown in the table.

[Table] Butylaniline

Table Some of the groups of compounds included are:

[expression] and (wherein R and R ¹ are C ₁ to C ₄ lower alkyl); (In the formula, R is C ₁ to C ₇ alkyl, and R ¹ is
_C1 - _C7 alkoxy or R is _C1 - _C7 alkoxy and ^R1 is _C1 - _C7 alkyl); (wherein R and R ¹ are C ₁ to C ₇ alkyl, and a or b is H or one of them is Cl
); (wherein R is alkyl or alkoxy of 1 to 10 carbon atoms); and eutectic mixtures of these compounds. The combined nematic compounds of Table 3 are
When together with those in Table 2 or Table 2, the combination must have a net positive non-isotropy. This could be accomplished using only a relatively low percentage of material with high positive anisotropy if the other material has relatively low negative non-isotropy. Such combinations include, for example, A shown as a percentage in Figure 4.
and B, both of which are at least −10
It is nematic from ℃ to +50℃.

Table: Minobenzonitrile One useful commercially available nematic liquid crystal composition includes approximately the following: 13.9% n-pentylphenyl cyclohexyl biphenyl cyanide 26.1% n-propylphenyl cyclohexyl cyanide 35.9% n-pentylphenyl cyclohexyl cyanide 24.1% n-heptyl phenyl cyclohexyl cyanide Customers of the present invention - The N-substituted aminoanthraquinones in which R is H used in the host composition are prepared by reactions known in the art to effect the conversion of groups on the anthraquinone molecule. Some of these reactions are illustrated in the Examples below. Other reactions will be obvious to those familiar with the chemistry of such molecules. The following examples illustrate the invention:
Temperatures in the examples are expressed in °C and melting points were determined in a capillary tube on a heating block with a Kahn Electro-thermal melting point apparatus using a National Bureau of Standards scale thermometer (uncorrected). Example 1 5 parts of 1,5-dichloroanthraquinone was added to a 4-hydrogen solution containing 5 parts of sodium acetate and 0.1 part of copper metal.
It was added to 20 parts of amino-1-cyclohexylbenzene. The mixture was stirred and refluxed to obtain a bright red slurry, which was cooled and mixed with petroleum ether. The sunken 1,5-
Bis(4-cyclohexylphenylamino)anthraquinone was recrystallized to obtain a light reddish powder. 10 mg of the above bis(1,5-cyclohexyl phenyl) anthraquinone was added to 13.9% of n-pentylphenyl cyclohexyl biphenyl cyanide, which has dielectrically positive non-isotropy.
-Pentyl, n-propyl and n-heptyl-
Phenylchlorohexyl cyanide (each
35.9, 36.1 and 24.1%) by gentle heating to obtain a customer-host composition. The vessel was constructed to provide orientation of the master nematic medium for measuring optical order variables.
Two glass plates, 5 mm thick and approximately 5 x 7 cm, were thoroughly cleaned by washing successively with acid, alcohol, aqueous ammonia and distilled water and dried in an oven at 65°C. One surface of each plate was then coated by vapor deposition of indium oxide, which rendered the surface electrically conductive. The indium oxide surface is oriented. It is rendered non-isotropic by rubbing about 20 times in a single direction under slight mild pressure with a cotton pad impregnated with an aqueous suspension of zirconium oxide. Each board is carefully rinsed with distilled water and placed edge down in an oven to dry at 65°C for 1 hour. Two strips of polytetrafluoroethylene sheet approximately 12 mm thick are cut to a length of approximately 5 cm and applied to the oriented surface of one board at a distance of approximately 5 cm and at right angles to the other board. It was applied in two plate orientation directions.
The assembly was then tied together. A solution of the pleochroic dye to be tested is prepared by heating approximately 0.5 g (10 drops) of the nematic combination of Table 4 to 65°C (i.e. above the isotropic melting point) and dissolving therein approximately 50 mg of the dye. Prepared by. This should provide an optical density of approximately 2 and 655 nm. With the solution still above the isotropic melting point, one edge of the bath was applied to the dye solution which was drawn up to fill the bath by capillary action. After cooling for a period of time, the temperature of the solution drops below the isotropic point into the nematic region and the test can then be continued. If desired, from about 0.1 to about 50% of a tyral agent such as cloesteryl nonanoate can be incorporated at this time. The amount used is determined by the desired effect. Small amounts (up to about 5-10%) are used to improve the spontaneous response of such host-host mixtures to electric field withdrawal. The large amount influences the composition to have a cholesteric structure instead of the more usual twisted nematic structure, so that the use of polarizers is not required. This phenomenon is known in the art. Electrical connections are made to the indium oxide coating on the exposed edges of the glass plates forming the bath using alligator clips and these are between 0.8 and 10
Volts or over a sufficiently high fixed voltage range
Connected to a direct current capable of providing 50-100 microamps. The bath is then connected to a spectrophotometer (e.g.
Perkin Elmer model 350) sample beam. That filter gives a neutral gray color when crossed. Its transmittance is 400~
It is scanned over a range of 750 nm and recorded graphically with no voltage applied to the cell (switch off) and with a voltage exceeding the limit value for that particular host (switch on). The value of S is calculated from these transmission (or absorption) curves as described above. Its color goes from bright red to colorless with a transmittance curve as shown in Figure 9 with an absorption maximum at 555 nm. Example 2 By a procedure somewhat similar to that of Example 1, 5 parts of 1-butylamino-4-chloroanthraquinone are mixed with 20 parts of 4-aminodiphenyl, 0.1 g of copper and 5 g of sodium acetate and nitrobenzene.
It was added to 100 parts. 0.7 after refluxing for about 2 hours
A blue-green dye (1-butylamino-4-biphenylamino) anthraquinone was recovered with an optical order variable of . Its optical order variable is
It was 0.7. Example 3 5 parts of 1-(n-pentylanilino)-4-hydroxy-anthraquinone was dissolved in cyclohexylamine.
refluxed in the presence of a small amount of sodium hydrosulfite in 20 parts as a bright green dye.
-(n-pentylanilino-4-cyclohexylamino)anthraquinone was obtained. Integration of this pleochroic dye into a positive nematic liquid crystal mixture as in Example 1 above resulted in a blue guest-host mixture in which the dye had an optical order variable of 0.65. Reference Example 1 5 parts of leukoquinizarin were condensed with 20 parts of 4-n-butylcyclohexylamine to obtain bis(1,4-n-butylcyclohexylamino)anthraquinone as a bright sky blue dye. A 1% solution of this dye in a nematic liquid crystal mixture as in Example 1 gave a blue host-host mixture which subsequently became colorless. The optical order variable was 0.7. Example 4 Liukoquinizarin was prepared with ammonia.
conversion to amino-4-hydroxyanthraquinone and subsequent conversion of two amine bases, e.g. n-
Reacted with butylamine and p-toluidine. After heating at 90° for 2 hours and oxidizing with air and copper sulfate, 1-n-butylamino-4-p-toluidinoanthraquinone was obtained as a bright blue pleochroic dye with an optical order variable of 0.7. Obtained. Reference Example 2 1,5-diaminoanthraquinone was dissolved in o-dichlorobenzene and treated with sulfuryl chloride to obtain a 3,4,7,8-tetrachloroanthraquinone intermediate, which was then dissolved in 2 equivalents. was condensed with pn-hexylaniline. The chlorine atom was replaced to yield 4,8-bis-p-hexylphenylamino-1,5-diamino-2,6-dichloroanthraquinone as a pure blue dye with an optical order variable of 0.75. . Example 5 1 equivalent of p-n-octylaminoaniline to 4
-Bromo-1-methylaminoanthraquinone Cu
and 1-methylamino- by condensation with NaOAC
2-Undecyl-4-octylanilinoanthraquinone was prepared and the dye was then treated with nitrobenzene.
Alkylation was carried out by reaction with undecyl aldehyde in piperidine. This blue-red dye had an optical order variable of 0.7. The transmittance curve of the color transition is shown in FIG. Example 6 1-Nitroanthraquinone was refluxed with excess cyclohexylamine in o-dichlorobenzene to give 1-cyclohexylaminoanthraquinone. This product was further brominated in an aqueous pyridine solution to obtain the corresponding 1-cyclohexylamino-4-bromoanthraquinone. This compound was further condensed with p-aminoacetanilide to produce a bright green pleochroic dye with an optical order variable of 0.7, 1-cyclohexylamino-4-(p-
Acetaminoanilino) anthraquinone was obtained. Example 7 One equivalent (2.4 g) of 1,4-dihydroxyanthraquinone was added into a flask equipped with a reflux condenser, stirrer, and containing 1 g boric acid, 0.5 g stannous chloride, and 30 g 2-phenylethylamine. . Heating to 130° for 2 hours with stirring and pouring it into a 10% HCl solution yielded bis(1,4-phenethylamino)anthraquinone as a pleochroic blue dye with an optical order variable of 0.78. Ta. Examples 8-5, Reference Examples 3 and 4 A series of pleochroic dyes were prepared according to the procedure of Example 1. Q and color in the above general formula, x, R′,
m as well as the position on the anthraquinone nucleus are shown in Table 5 along with the optical order variables. 1,4
- A cyclohexylene radical is indicated by S in the ring.

【table】

[Table] Examples 16-23, Reference Example 5 Substituted dichloroanthraquinones were condensed with various amines by refluxing in the presence of sodium acetate and cupric acetate in an inert solvent such as nitrobenzene. We have prepared several pleochroic dyes useful in host-host combinations. These dyes are shown in Table 6. Intermediates are known or can be easily obtained by known reactions.

[Table] Reference Example 6 Demonstrated by the formation of 1,5-bis(benzylamino)anthraquinone in the procedure of Examples 16-23. 1,5-dichloroanthraquinone to 20 g of benxylamine, 0.1 g of cupric acetate, 2.0 g of sodium acetate, and 10 g of nitrobenzene in a suitable container.
2.77g was added. The mixture was refluxed for 2 hours and the reaction mixture was poured into methanol. The crude dye was collected and treated with hot nitrobenzene containing a small amount of piperidine. The red dye was purified from alcohol and washed with ether. Its optical order variable was 0.75. Example 24 A convenient method for introducing a substituted amino group in place of a hydroxyl group is to heat the hydroxyl-substituted anthraquinone with an amine in the presence of boric acid, usually in an inert solvent such as nitrobenzene. This also applies to anthraquinones with two different substituents (e.g. Reference Example 1 above and Example 1 below).
24) promotes the formation of 1-Hydroxy-4-chloroanthraquinone was condensed with 1 equivalent of p-(n-decyl)aniline in the presence of boric acid to obtain 1-(p(n-decyl)anilino)-4-chloroanthraquinone. . This was then purified by condensation with 1 equivalent of 2-aminonaphthalene in the presence of copper acetate-sodium acetate as a blue-green pleochroic dye with an optical order variable of 0.72. -decyl)anilino-4-naphthylamino-anthraquinone was obtained. Examples 25-33 A series of pleochroic dyes were prepared using the boric acid condensation reaction described in Reference Example 6 and are shown in Table 7. Examples 31 and 32, marked with an asterisk, also contained stannous chloride as in Example 7 above.

【table】

EXAMPLE 34 The host-host combinations of the present invention are particularly useful because of their fastness to light. To demonstrate the stability of these combinations, a field effect device was assembled and 1% 1,4-bis(4-phenyl-anilino) anthraquinone (prepared as the 1,5 isomer in Example 9) was prepared. The containing nematic liquid crystal host-host mixture was used as the host-host nematic component. Test sample at 340nm
It was placed in an Atlas Weather-Ometer for 100 hours at 60° C. using a Zenon UV light source with an output of 0.115 nm/cm ² . The absorption spectra showed no decrease in the pleochroic dye maximum after 100 hours and less than a 10% increase in the current measured across the electrode surface. The transmittance curve for color transition is shown in FIG. Example 35 The improvement achieved by the compositions of the present invention over unsubstituted bis-phenylaminoanthraquinones in customer-host combinations in which each phenyl group is substituted with an octoxy group (of the general formula
Comparison of a composition of the invention (A) using the anthraquinone of Example 30 (at the 4 position of Ar) with a composition (B) in which there is no substituent at the same position. Solutions were prepared at the same concentration in the dielectrically positive nematic liquid crystal mixture used in Example 1 and the transmittance curves were measured as the voltage was increased. The results are shown in FIG. The higher optical order variable of about 0.7 for Composition B is indicative of the increased contrast ratio, lower colored background and increased brightness that can be achieved in optoelectronic devices using the compositions of the present invention. Optical order variables similar to those described in Examples 1-33 above are obtained when tyral agents such as cholesteryl nonanoate are included in varying amounts in the nematic liquid crystal material. It is observed that if the amount is small, i.e. about 0.5%, there is faster reordering when the imposed voltage is removed.

[Brief explanation of drawings]

FIG. 1 is a diagrammatic representation of a photoelectric valve device using the pleochroic dye host-host combination of the present invention, and FIG. Figure 3 is a diagrammatic representation of the homeotropic guest-host combination of Figure 2 with a voltage imposed; 6, 7 and 8 show the combination of a homogeneous positive non-isotropic nematic liquid crystal and a dye of the invention in a customer-host relationship in the absence and presence of an applied voltage; FIG. The figure shows a combination of FIGS. 4 and 5, but given a twisted nematic liquid crystal with orthogonal vessel wall orientation. FIG. 6 shows the case where no voltage is applied, and FIGS. 7 and 8 show the case where the voltage is applied. Figures 9, 10 and 11 show 1,5-bis(4-cyclohexylphenyl)anthraquinone, 1-methylamino-2-undecyl-4(-4-octylanilino)-anthraquinone and 5% of 1,4-bis(4-phenylanilino)anthraquinone
It is a figure which shows the transmittance curve of a solution.
FIG. 12 shows a comparative curve of the decrease in optical density with increasing voltage applied to the test chamber.

Claims (1)

[Scope of Claims] 1. At least one nematic liquid crystal material having dielectrically positive anisotropy, and a general formula; [wherein the substituent (NRR') and Q are in positions 1 to 8, Q is F, Cl, NO ₂ , NH ₂ , NH (Alk), alkyl, or OH, and x is 0, 1 , 2 or 3, m is 1 or 2, R is independently H, and R' is independently cyclohexyl, bicyclohexyl, naphthyl, or -( _CH2 ) _p Ar {where p is 0 , 1 or 2, and Ar is −
NHCOCH ₃ , CN, −C _o H _2o+1 , −OC _o H _2o+1 (n is 1 to 20, but when p=0, n is 2 to 20
), cyclohexyl, 4(-Alk)-cyclohexyl (Alk is alkyl having 1 to 8 carbon atoms), or [formula] where y is 0 or 1 and Y is CH ₂ , O, S or -CH ₂ O- (carbon atom is bonded to Ar), Z is 4-substituted H, NO ₂ , CN, -C _o H _2o+1 , -OC _o
phenyl substituted in the 4 position by H _2o+1 (n is 1 to 20), F or Cl;
Ar is CN, −C _o H _2o+1 , −OC _o H _2o+1 (n is 1 to 20),
0 to 2 other positions may be substituted by NH ₂ or OH}, and (i) x=1, m=1, Q=OH and NRR' is on the ring (ii) when x = 0, m = 2, the molecules are in para positions to each other or in positions 1, 5 or 4, 8
When substituted with two NRR′ groups, the above (i) and
In case (ii), NRR' is not [formula] (X is -C _o H _2o+1 , -OC _o H _2o+1 (n=2~20), cyclohexyl or [formula])] A dielectrically positive anisotropic composition comprising 0.01 to 50% by weight of a pleochroic dye. 2. In the composition according to claim 1,
A composition characterized in that about 0.1 to 10% by weight of an isotropic dye having a color contrast with respect to the normal color of the pleochroic dye is additionally present. 3. In the composition according to claim 1,
The nematic liquid crystal substance is N-p-alkoxybenxylidene-p'-amino-benzonitrile.
A composition characterized in that it consists of ~20% by weight. 4. In the composition according to claim 1,
The nematic liquid crystal substance is n-propyl-, n-
A composition characterized in that it consists of n-pentylphenylcyclohexyl biphenyl cyanide in combination with pentyl-, and n-heptyl-phenylcyclohexyl cyanide. 5. In the composition according to claim 1,
A composition characterized in that the nematic liquid crystal substance consists of a combination of 4-cyano-4'-alkylbiphenyls. 6. In the composition according to claim 4,
The pleochroic dye is 1,5-bis(p-(4-n-
A composition characterized in that it is anthraquinone (pentylcyclohexyl)-phenylamino). 7 In the composition according to claim 4,
A composition characterized in that the pleochroic dye is 1,5-bis(biphenylamino)anthraquinone. 8. In the composition according to claim 4,
The pleochroic dyes are such that their groups are 1,4-, 1,
Screw in 5- or 1,8-position (4-(p-
A composition characterized in that it is nitrophenylthio)-phenyl-amino)anthraquinone. 9. In the composition according to claim 4,
A composition characterized in that the pleochroic dye is 1,4-bis(4-n-desyloxyphenyl-amino)anthraquinone. 10. The composition of claim 1, wherein the composition additionally comprises a chiral agent in an amount of about 0.1 to about 50% by weight, based on the nematic liquid crystal material. 11. The composition according to claim 10, wherein the chiral agent is cloesteryl nonanoate. 12. In optoelectronic devices in which an electric field is imposed or withdrawn from the action on a bath consisting of a liquid crystal material in which a pleochroic dye is dissolved between transparent electroded glass plates, the liquid crystal material being dielectrically positively anisotropic. and at least one nematic liquid crystal material having positive dielectric anisotropy, the dissolved pleochroic dye having the following general formula: [wherein the substituent (NRR') and Q are in positions 1 to 8, Q is F, Cl, NO ₂ , NH ₂ , NH (Alk), alkyl, or OH, and x is 0, 1 , 2 or 3, m is 1 or 2, R is independently H, R' is independently cyclohexyl, bicyclohexyl, naphthyl or -(CH ₂ ) _p Ar {wherein P is 0, 1 or 2, and Ar is −
NHCOCH ₃ , CN, −C _o H _2o+1 , −OC _o H _2o+1 (n is 1 to 20, but when p=0, n is 2 to 20
), cyclohexyl, 4(-Alk)-cyclohexyl (Alk is alkyl having 1 to 8 carbon atoms), or [formula] where y is 0 or 1 and Y is CH ₂ , O, S or -
CH ₂ O− (carbon atom is bonded to Ar) and Z
is 4-substituted H, NO ₂ , CN, -C _o H _2o+1 , -OC _o
phenyl substituted in the 4 position by H _2o+1 (n is 1 to 20), F or Cl;
Ar is CN, −C _o H _2o+1 , −OC _o H _2o+1 (n is 1 to 20),
0 to 2 other positions may be substituted by NH ₂ or OH}, and (i) x=1, m=1, Q=OH and NRR′ is on the ring. (ii) when x = 0, m = 2, the molecules are in para positions to each other or in positions 1, 5 or 4, 8
When substituted with two NRR′ groups, in the above cases (i) and (ii), NRR′ is [Formula] (x is −C _o H _2o+1 , −OC _o H _2o+1 (n= 2-20), not cyclohexyl or [Formula]].