JPH0132809B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid crystal compound containing an alicyclic ring and exhibiting low dielectric anisotropy, a liquid crystal material, and a device containing the compound. The use of liquid crystal materials to exhibit electro-optical effects in display devices such as digital calculators or watches is well known. One of the parameters of liquid crystal materials that is important with respect to electro-optical operation is the dielectric anisotropy (Δε) of the material. For a given frequency and temperature, the average permittivity measured parallel to the molecules of the material (ε ₁₁ ) and the average permittivity measured perpendicular to the molecules (ε⊥), for example, when oriented in a line, are This is the difference between The sign and strength of the dielectric anisotropy of a given liquid crystal material is one of the main parameters that determines the type of electro-optical device in which the material is used. For example, materials with positive dielectric anisotropy, referred to herein as "positive" materials, such as 4-alkyl or alkoxy-4'-cyanobiphenyl and 4"-alkyl or alkoxy-4-cyano-p-terphenyl, The mixture of Materials with negative dielectric anisotropy (with suitable resistivity), referred to as "negative" materials in the present invention, can be used in
It can be used in known dynamic scattering effect devices (in nematic cases) or cholesteric storage mode devices (in cholesteric cases). A material with a low dielectric anisotropy (e.g. Δε less than 1) can be mixed with a material with a positive or negative dielectric anisotropy so that the overall dielectric anisotropy is positive (but decreasing in value). ) may be produced. According to a first aspect of the invention, there is provided a novel liquid crystal compound exhibiting low dielectric anisotropy and having the following structural formula: (In the formula, R ₁ is an alkyl group; R ₂ is an alkyl group or an alkoxy group, and R ₁ and R ₂ are 18
Contains up to carbon atoms;

[Formula] is a trans-1,4-disubstituted cyclohexane ring or 1,
It is a 4-disubstituted bicyclo(2.2.2)octane ring; Ar is a 1,4-disubstituted benzene ring, a 3-fluoro-1,4-disubstituted benzene ring or a 2,6-disubstituted naphthalene ring. ) R ₁ and R ₂ preferably contain up to 10 carbon atoms and may be straight chain or branched. In the case of branching, one or both of these groups may contain chiral centers, in which case the compound may be optically active. Preferably R ₁ is an n-alkyl group containing up to 10 carbon atoms;
_R2 is an n-alkyl or n-alkoxy group containing up to 10 carbon atoms. “Liquid crystal compound” means a compound belonging to one of the following two known categories: (i) compounds that normally exhibit a liquid crystal phase; (ii) compounds that do not normally exhibit a liquid crystal phase, but which are present in other liquid crystal compounds; When dissolved in the liquid crystal, it has some useful influence on the behavior of the liquid crystal. Compounds in category (ii) are “monotropic”
It exhibits a virtual or "virtual" transition from liquid crystal to isotropic liquid at temperatures below the melting point of the solid phase. A monotropic or hypothetical transition is a change in the transition of the material to an isotropic liquid phase by quenching the liquid phase or dissolving the compound in a material exhibiting a liquid crystalline phase, respectively, and adding the compound to the isotropic liquid phase. observed,
Then, it can be detected by calculating a virtual transition temperature by extrapolation. Compounds of category (ii) may, for example, be effectively dissolved in other liquid crystal compounds to extend or change the liquid crystal temperature range of the liquid crystal compound or (in the case of cholesteric liquid crystals) to change the helical pitch of the molecules. . One or more compounds of formula () may be used in any of the following applications: (i) for use with positive nematic materials to provide an overall positive nematic material and for use in twisted nematic effect devices, especially multiple (multiplexed) devices. Examples of such devices are described below. (ii) used alone (if Δε is large and negative) or together with another nematic material, preferably a negative material (for example if Δε is small), to provide an overall negative material, preferably a polychromatic dye; It is also used in Friedericks effect devices where the molecular orientation can change from a homeotropic orientation (OFF state) to a homogeneous orientation (ON state). Examples of such devices are described below. (iii) used with a nematic material, preferably also using a polychromatic dye, to provide an overall positive nematic material in which the electric field changes the molecular orientation from a homogeneous orientation (OFF state) to a homeotropic orientation (OFF state); Friederics effect devices that can be used. (iv) used with optically active materials to provide an overall negative cholesteric material with a suitable resistivity (approximately 10 ⁹ ohm-cm), where an electric field can twist the molecular orientation from a homogeneous orientation (OFF state) to turbulent scattering; Focal conic orientation (turbulent)
scattering focal conic texture) (ON state)
Used in cholesteric storage mode devices that can change to (v) used with an optically active material to provide an overall negative cholesteric material, preferably also with a polychromatic dye, to provide a weakly scattering surface oriented homeotropic orientation (OFF
used in cholesteric-nematic phase change effect devices that can change from a strongly scattering twisted homogeneous orientation (ON state) to a strongly scattering twisted homogeneous orientation (ON state). (vi) used in conjunction with optically active materials to provide an overall positive cholesteric material, preferably also with polychromatic dyes, in which the electric field changes the molecular orientation from a scattering focal conic orientation (OFF state) to a clear homeostatic orientation; Used in cholesteric-nematic phase change effect devices that can change to a tropic orientation (ON state). (vii) used with nematic materials to provide an overall negative nematic material with a suitable resistivity (approximately 10 ⁹ ohm-cm), where an electric field transforms the molecular orientation from a clear homeotropic orientation (OFF state) to turbulent scattering; It is used for dynamic scattering effect devices that can change their orientation (ON state). (viii) used with a positive nematic material to provide an overall positive nematic material, where the dielectric anisotropy of the material changes (at low frequencies) from positive (OFF state) to negative (ON state) by applying a high frequency electric field. For use in two frequency switching effect devices that change state). The construction and operation of such devices, as well as the general types of materials suitable for use in them, are known. It is clear to those skilled in the art that in the above applications of preparing mixtures, by adjusting the proportions of the materials to be mixed, these mixtures can be controlled to the desired dielectric anisotropy value and sign. When a material is added to one or more compounds of formula (), the material itself may be a mixture of two or more compounds. The mixture may be formed in a known manner. for example,
It may be formed by simply heating the component compounds to form a generally isotropic liquid, stirring the liquid, and allowing the liquid to cool. The compounds of formula () effectively reduce the operating voltage in the above applications and increase the negative value or decrease the positive value of the dielectric anisotropy. This may affect other properties such as multiplicity in twisted nematic effect devices or switching frequency in two frequency switching effect devices.
frequency). According to a second feature of the invention, there is provided a mixture of liquid crystal compounds comprising at least one of the compounds of formula () above. Such mixtures may be used in any of the applications (i) to (viii) above, depending on the composition and properties chosen. An example of a mixture of second characteristics that can be used in a multi-twisted nematic device is at least one compound of () above, plus one or more
4'-alkyl- or 4'-alkoxy-4-cyanobiphenyl and one or more of the following compounds: Preferably, the 4'-alkyl- or 4'-alkoxy-4-cyanobiphenyl accounts for about 10 to 90% by weight of the mixture, and the compounds selected from formulas () to () account for a total of no more than about 20% by weight. , the remainder is one or more compounds of the above formula (). Preferably, each 4'-alkyl- or 4'-alkoxy-4-cyanobiphenyl added to the mixture has no more than 5 carbon atoms in its alkoxy or alkyl group. Preferably, the carbon atoms are an odd number when the group is an alkoxy group and an even number when the group is an alkyl group. As a further example, a mixture according to the second characteristic may be used for one or more of the above-mentioned uses (the actual use depends on the nature of the mixture).
It may be a compound of formula () mixed with one or more of the following known groups of compounds: In the above formula,

[Formula] is a cyclohexane ring. the law of nature;

[Formula] is a bicyclo (2.2.2) octane ring Yes; X is 1,4 phenylene group

【Formula】Also is 4,4′biphenyl group

【Formula】Also is 2,6 naphthyl group

[Formula]; Y is CN or R' or OR' or COO-X-Y' (where Y' is CN or R' or OR',
R' is an alkyl group of up to 18 carbon atoms). According to a third aspect of the invention, there is provided a liquid crystal display device comprising two dielectric substrates, at least one of which is optically transparent, sandwiched between the substrates in a sandwich-like manner. The liquid crystal material layer has a liquid crystal material layer and an electrode provided on the inner surface of the substrate, and is configured so that an electro-optic effect can be obtained by applying an electric field to the liquid crystal material layer. The material is characterized in that it consists of or contains a compound of the above formula (). A device according to the third characteristic is a twisted nematic effect device, a cholesteric-nematic phase change effect device, a Friederix effect device, a two-frequency switching effect device, a cholesteric storage mode device, which can be operated in multiple ways or not. can be a dynamic scattering effect device;
All of these are constructed in a known manner. Various methods of using compounds of formula () in these devices have been outlined above and will be further apparent to those skilled in the art. Production examples and properties of the compound of the above formula () are shown below. Example 1 This example demonstrates the preparation of 4-(trans-4'-alkylcyclohexylmethoxy)-alkylbenzene and 4-(trans-4'-alkylcyclohexylmethoxy)-alkoxybenzene by the following route. In the above formula, R ₁ is an alkyl group, and Y is an alkyl or alkoxyl group. Step A1: Preparation of trans-4-alkylcyclohexylmethanol. Step B1: Preparation of trans-4-alkylcyclohexylmethyl bromide. Step C1: 4-(trans-4'-alkylcyclohexylmethoxy)-alkylbenzene or 4-
Production of (trans-4'-alkylcyclohexylmethoxy)-alkoxybenzene. To illustrate the specific steps of this production example,
The case where R ₁ is ethyl is shown. (This procedure is also used when R ₁ is other than ethyl.) Step A1 Known trans-4-ethylcyclohexane-
Production of trans-4-ethylcyclohexylmethanol from 1-carboxylic acid. Trans-4-ethylcyclohexane-1-carboxylic acid (10.9 g, 0.07 mol) is added to thionyl chloride (120 cm ³ ) and the mixture is heated under reflux for 90 minutes. Excess thionyl chloride is removed from the cooled solution under reduced pressure. Ether (50 cm ³ of sodium dry) is then added to the residue and the solvent is distilled off again under reduced pressure. This operation is carried out twice to remove the last traces of thionyl chloride. A solution containing the acid chloride in ether (100 cm ³ dry sodium) was added to a suspension of lithium aluminum hydride (3.42 g, 0.09 mol) in ether (80 cm ³ dry sodium) for 1 hour. Add in portions and after addition heat the whole under reflux for 20 minutes. Water (8 cm ³ ) is slowly added dropwise to the carefully cooled solution to decompose the excess lithium aluminum hydride, and then sulfuric acid (100 cm ³ of a 10% aqueous solution) is slowly added to the mixture. Shake the aqueous layer with ether (3 x 80 cm ³ );
Combined ether extracts with water (100 cm ³ and 50 cm ³ )
and dry with sodium sulfate.
The desired alcohol is obtained by removing the ether under reduced pressure and distilling the product under reduced pressure. Yield of trans-4-ethylcyclohexylmethanol: 8.95 g (90%), boiling point: 140°C at 3 mmHg. Step B1 Preparation of trans-4-ethylcyclohexylmethyl bromide from trans-4-ethylcyclohexylmethanol. Hydrochloric acid aqueous solution (48-50%, 15cm ³ ), concentrated sulfuric acid (4cm ³ )
An additional amount of concentrated sulfuric acid (2.5 cm ^<3> ) is added dropwise to a stirred solution of 100% and trans-4-ethylcyclohexylmethanol (9.94 g, 0.07 mol). The whole was then heated under reflux for 3 hours, cooled and iced (60
g) and then shaken with ether (3 x 60 cm ³ ). The combined ether extracts were diluted with water (3 x 60
cm ³ ), equal volumes of concentrated hydrochloric acid, water (3×60 cm ³ ), sodium bicarbonate (5% aqueous solution, 3×60 cm ³ ), and saturated sodium chloride solution (3×60 cm ³ ). The bromide solution is dried (CaCO ₃ ), the solvent is removed in vacuo, and the crude bromide is distilled in vacuo. Trans-4-
Yield of ethylcyclohexylmethyl bromide:
12.1g (84%), boiling point: 140°C at 15mmHg. Step C1 Preparation of 4-(trans-4'-ethylcyclohexylmethoxy)-alkyl- or alkoxy-benzene. Trans-4-ethylcyclohexylmethyl bromide (0.01 mol) was dissolved in aqueous 2-ethoxyethanol (95%, 5 cm ³ ) with the appropriate 4-alkyl- or 4-alkoxy-phenol (0.015 mol) and potassium hydroxide (0.0175 mol). ). The mixture was then heated under reflux for 2 hours, after which solid potassium hydroxide (0.0025 mol) was added and the mixture was heated again for 2 hours.
Reflux for an hour. Pour the reaction mixture into water (100cm ³ );
Shake the whole thing with ether (3 x 80 cm ³ ). The ether extract was dissolved in an aqueous sodium hydroxide solution (20%, 3
x 60 cm ³ ) and water and dried (Na ₂ SO ₄ ). The crude material was then combined with silica gel as the stationary phase and chloroform as the eluent: gas oil (boiling point 40-60
Column chromatography using a 2:1 mixture of 30° C.). Then vacuum distillation or the compound is heated to 30°C.
If the melting point is above, the final product is obtained by crystallization (using solid carbon dioxide as a coolant). Examples of the products of Example 1 are shown in Tables 1 and 2 below.

【table】

【table】

[Table] Example 2 This example shows the preparation of 4-(4'-alkyl-1'-bicyclo(2.2.2)octylmethoxy) by the following route.
-alkylbenzene and 4-(4'-alkyl-
The production of 1'-bicyclo(2.2.2)octylmethoxy)-alkoxybenzene is shown. In the above formula, R ₁ is an alkyl group, and Y is an alkyl or alkoxy group. Step A2: 4-alkyl-1-bicyclo (2.2.2)
Production of octyl methanol. Step B2: 4-alkyl-1-bicyclo (2.2.2)
Production of octylmethyltoluene-4-sulfonate. Step C2: 4-(4′-alkyl-1′-bicyclo(2.2.2)octylmethoxy)-alkylbenzene or 4-(4′-alkyl-1′-bicyclo(2.2.2)octylmethoxy)-alkoxybenzene Manufacture. An example of this route is shown for R ₁ =n-pentyl. Step A2 From the known 4-n-pentylbicyclo(2.2.2)octane-1-carboxylic acid to 4-n-pentyl-
Production of 1-bicyclo(2.2.2)octylmethanol. This step is identical to step A1 above, but here the known 4-n-pentylbicyclo (2.2.2)
Octane-1-carboxylic acid (2.6g, 0.0116mol)
(see UK Patent Application No. 32351/78.4)
Yield of -n-pentyl-1-bicyclo(2.2.2)octylmethanol: 2.2 g (90%), boiling point: 0.5
The temperature is 110°C at mmHg. Step B2 4-n-pentyl-1-bicyclo(2.2.2)octylmethanol to 4-n-pentyl-1-bicyclo(2.2.2)octylmethyltoluene-4-
Production of sulfonates. 4-n-Pentyl-1-bicyclo(2.2.2)octylmethanol (2.5 g, 0.0119 mol) was dissolved in toluene in pyridine (33 cm ³ sieve dried).
4-sulfonyl chloride (3.4g, 0.0179mol)
Heat at 40°C for 60 hours with stirring. The reaction mixture is poured into ice water (60 cm ³ ) and the product is extracted into ether (3×50 cm ³ ). The combined ether extracts were washed with dilute acid salt (50 cm ³ ) and water (3×50 cm ³ ),
Dry (CaCO ₃ ). The solvent is removed under reduced pressure and the crude tosylate is crystallized from light oil (boiling point 40-60°C). 4-n-pentyl-1-bicyclo (2.2.2)
The yield of octylmethyltoluene-4-sulfonate is 3.1 g (71%), melting point 67°C. Step C2 4-Alkyl-1-bicyclo(2.2.2)octylmethyltoluene-4-sulfonate to 4-
(4'-alkyl-1'-bicyclo(2.2.2)octylmethoxy)-alkylbenzene or 4-(4'-alkyl-1'-bicyclo(2.2.2)octylmethoxy)
-Production of alkoxybenzene. 4-Alkyl-1-bicyclo(2.2.2) octylmethyltoluene-4-sulfonate (0.007 mol) and potassium carbonate (2.9 g, 0.021 mol) were dissolved in dimethylformamide (12.5 cm ³ dry sieves) to give the required 4- Heat at reflux with stirring for 16 hours with alkyl- or 4-alkoxy-phenol (0.21 mol). The reaction mixture is poured into water (60 cm ³ ) and the organic products are extracted into ether (3×60 cm ³ ). The combined ether extracts are washed with aqueous sodium hydroxide (20%, 3 x 60 cm ³ ), water (2 x 60 cm ³ ) and dried (Na ₂ SO ₄ ). The solvent was removed under reduced pressure and the crude product was purified with silica gel as the stationary phase and chloroform as the eluent: gas oil (boiling point 40-60
Column chromatography using a 2:1 (volume ratio) mixture of The final product is obtained by vacuum distillation. Examples of products of step C2 are shown in Table 3 below.

[Table] Example 3 In this example, 4-(trans-4'-alkylcyclohexylmethoxy)-3-
Fluoroalkylbenzene and 6-(trans-4'-alkylcyclohexylmethoxy)-2-
The production of alkylnaphthalenes is shown. In the above formula, R ₁ and R ₂ are alkyl groups as previously defined;

[Formula] is a trans-1,4-disubstituted cyclohexane ring, and Ar is a 3-fluoro-1,4-disubstituted benzene ring or a 2,6-disubstituted naphthalene ring. Step A3: Preparation of trans-4-alkylcyclohexylmethanol. Step B3: Preparation of trans-4-alkylcyclohexylmethyl bromide. Step C3: Preparation of 4-(trans-4'-alkylcyclohexylmethoxy)-3-fluoroalkylbenzene and 6-(trans-4'-alkylcyclohexylmethoxy)-2-alkylnaphthalene. Step A3 This step corresponds to step A1 described in the said UK application.
It can be carried out by the following method. An example of the product is trans-4-n-pentylcyclohexylmethanol, yield: 90%, boiling point: 3 mm
150℃ at Hg. Step B3 Preparation of trans-4-alkylcyclohexylmethyl bromide from trans-4-alkylcyclohexylmethanol. This step may be carried out by the method of step B1 above. An example of the product is trans-4-n-pentylcyclohexylmethyl bromide, yield: 84%, boiling point: 150° C. at 15 mmHg. Step C3 Preparation of 4-(trans-4'-alkylcyclohexylmethoxy)-3-fluoroalkylbenzene and 6-(trans-4'-alkylcyclohexylmethoxy)-2-alkylnaphthalene from trans-4-alkylcyclohexylmethyl bromide. This step may be carried out in essentially the same way as step C1 above (in place of the 4-alkyl or 4-alkoxyphenol in step C1, a suitable hydroxy compound

[Formula] or

(Use [Formula]). Examples of products are: Yield, 48%; C-I, 43°C; N-1, [-10°C] Yield, 59%; C-I, 99°C; N-1, [88°C] Examples of materials and devices embodying the invention of the second and third characteristics will be described with reference to the accompanying drawings. do. The display device of FIGS. 1 to 4 includes a cell 1 formed from two glass slides 2, 3, a front and a back, separated by about 7 m by a spacer 4, all held together by epoxy resin adhesive. . Liquid crystal material 12 fills the gap between slides 2, 3 and spacer 4. A front polarizer 5 is arranged in front of the windshield slide 2 with its polarization axis horizontal. A reflective material 7 is placed behind the slide 3. A rear polarizer 6 or analyzer is arranged between the slide 3 and the reflector 7. An electrode 8 typically made of tin oxide with a thickness of 100 Å,
9 is deposited in a complete layer on the inner surfaces of the slides 2, 3 and is etched into the shape shown in FIGS. The display has 7 bars per 10 digits and 11 decimal points between each digit. As shown in Figure 3, the rear electrode structure has three electrodes X ₁ , X ₂ ,
Formed into X ₃ . Similarly, the front electrode structure has three electrodes per digit and decimal points y ₁ , y ₂ , y ₃ .
It is formed into... Considering six electrodes per digit, each of the eight elements can have an applied voltage independently by applying the appropriate voltages to the appropriate x, y electrodes. Before assembly, the slides 2, 3 with electrodes are cleaned and immersed in a 0.2% by weight aqueous solution of polyvinyl alcohol (PVA). When dry, rub the slide with a soft fabric in a single direction, then rub the slide so that the directions of the rub are perpendicular to each other and parallel to the optical axis of each adjacent polarizer, i.e., the polarizers are crossed. , Assemble. When the nematic liquid crystal material 12 is introduced between the slides 2 and 3, the molecules on the slide surface are aligned so that twisting progresses between the slides along the respective rubbing directions. When zero voltage is applied to cell 1, light passes through cell 1, front polarizer 5 (during which the polarizations are rotated by 90°), passes through rear polarizer 6 and reaches reflector 7, where the light is It is reflected again and reaches the observer (at an angle of 45° with respect to the Z axis perpendicular to the X and Y axes in the planes of slides 2 and 3, as shown in Figure 1).
When a voltage above the limit value is applied between the two electrodes 8, 9, the liquid crystal layer 12 loses its optical activity and the molecules reorient themselves perpendicular to the slides 2, 3, i.e. along the Z axis. . Therefore, in this case no light reaches the reflector 7 and is not reflected to the observer, who sees a dark representation of one or more bars of the digit 10. The voltage was adjusted to 3 as shown in Figures 5, 6 and 7.
During two consecutive time intervals, linescan mode
fashion). A potential difference of 3/2V is applied (i.e., scanned) to each X electrode, while -
Apply V/2. Meanwhile, -3/2V or V/2 is y
Apply to the electrode. When 3/2V and -3/2V intersect at the intersection, a voltage of 3V is applied across the liquid crystal layer 12. Elsewhere the voltage is V or -V. In this way, when scanning is performed by applying -3/2V to the appropriate Y electrode and 3/2V to the X electrode, the selected intersection turns ON as shown by the solid line. The voltage V is, for example, a 100 Hz square wave AC signal, and its sign indicates the phase. The devices shown in Figures 1 to 7 have electrodes that are ON.
It is a multiple display device because it shares the OFF intersection or display element. A material embodying the second feature of the invention, suitable for use as material 12 in the above device,
As shown in Table 4 below (Mixture 1).

【table】

Table: A small amount of cholesteric material can be added to a nematic material to induce a favorable twist in the molecules in the liquid crystal layer. By this method and appropriate slide surface treatment, British Patent Application Nos. 1472247 and 1478592
The problem of patchiness of the display device taught in No. Suitable cholesteric materials include: C15: approx. 0.1~0.5% by weight, and CB15: approx. 0.1~
0.05% by weight C15 It is. CB15 is It is. Small amounts of polychromatic dyes can be added to increase the contrast of the display, for example one of the anthroquinone dyes described in GB 2011940A may be used. In another embodiment, mixtures embodying the second aspect of the invention may be used in Friederix effect cells. Such a cell may be constructed, like the devices described above, by sandwiching a liquid crystal material between glass slides with thin electrode films deposited on the inner surfaces. However, in this case a polarizer is not needed, the inner surface of the glass slide is treated with a coating of lecithin, and the liquid crystal material is placed in a negative polarizer with molecules aligned in the OFF state perpendicular to the slide substrate (homeotropic alignment) by the lecithin coating. It is the material.
Applying a suitable electric field across the material in the ON state reorients the molecules parallel to the slide surface (homogeneous orientation). By adding multicolor dyes to liquid crystal materials,
The contrast between ON and OFF states can be increased. The following mixture 2 can be added to the Friederics effect cells made by the above method, and the spacing of the cells is
It is 10 μm.

[Table] The method for producing compound A is described in British patent application No. 7934129.
listed in the number. 1.2% by weight of a known polychrome dye, for example 1,5-bis-4'-n-butylphenylaminoanthraquinone, can be added to mixture 2 to obtain a dyeing mixture (mixture 2A). When a voltage is applied across the cell, the color changes from a weakly absorbing state to a strongly absorbing state. In another aspect of the invention, the (cholesteric-nematic) phase change effect device comprises the materials defined above. The cell, like the twisted nematic cell described above, is fabricated to contain a long helical pitch of cholesteric material sandwiched between glass slides with electrodes. However, polarizers and surface treatments for homogeneous alignment, such as treatment of the glass slide surface with SiO, are not used in this case. When the glass slide is untreated and the liquid crystal material has positive dielectric anisotropy (Δε), the liquid crystal material is in a state of twisted focal cone molecular orientation in the OFF state that scatters light. The effect of applying an electric field between a pair of electrodes on each inner surface of a glass slide is to convert the region of liquid crystal material between the electrodes into an ON state, which is a homeotropic nematic orientation that is less scattering than the OFF state. It is. This is a "negative contrast" type of phase change effect device. If the inner glass slide surfaces are treated, for example with lecithin, to align perpendicularly to these surfaces, and the liquid crystal material has a negative Δε, the material in the OFF state will have less scattering effect on the incident light. It is in a state of homeotropic orientation. When a voltage is applied between a pair of electrodes on each inner surface of a glass slide, the region of liquid crystal material between the electrodes transforms into a twisted homogeneous orientation (ON state) that scatters light. This is a "positive contrast" type of phase change effect device. The contrast between the two states in each case is determined by adding a small amount of a suitable polychromatic dye (e.g. 1% by weight of 1,5-bis-4'n-butylphenylaminoanthraquinone for positive Δε) to the liquid crystal material. It can be increased by adding. Suitable positive dielectric anisotropic materials embodying the invention for use in phase change effect devices are:

【table】

Table: Mixture 4, a suitable negative dielectric anisotropic material embodying the invention for use in phase change effect devices, is as follows:

【table】 [Brief explanation of drawings]

Figure 1 is a perspective view of a twisted nematic digital display, Figure 2 is a sectional view of the display in Figure 1, Figure 3 is a rear electrode arrangement of the display in Figure 1, and Figure 4 is the display in Figure 1. Figures 5, 6 and 7 are schematic diagrams of the front electrode arrangement when typical address voltages are applied to the device of Figures 1-4. 1... Cell, 2, 3... Glass slide, 4...
... Spacer, 5, 6... Polarizer, 7... Reflective material, 8, 9... Electrode, 12... Liquid crystal material.

Claims (1)

[Claims] 1. Structural formula (In the formula, R ₁ is an alkyl group, R ₂ is an alkyl group or an alkoxy group, and R ₁ and R ₂ are 18
is a trans-1,4-disubstituted cyclohexane ring or a 1,4-disubstituted bicyclo(2,2,2)octane ring; Ar is 1,4-disubstituted benzene ring [formula] 3-fluoro-1,4-disubstituted benzene ring [formula] or 2,6-disubstituted naphthalene ring [formula]. ) is a low dielectric anisotropy liquid crystal compound. 2 R ₁ is n-alkyl group containing up to 10 carbon atoms and R ₂ is n-alkyl group containing up to 10 carbon atoms
-Alkyl or n-alkoxy group, the liquid crystal compound according to claim 1. 3. The liquid crystal compound according to claim 1, wherein the group [formula] is a trans-1,4-disubstituted cyclohexane ring. 4. The liquid crystal compound according to claim 3, wherein the Ar group is a 1,4-disubstituted benzene ring. 5. The liquid crystal compound according to claim 3, wherein the Ar group is a 3-fluoro-1,4-disubstituted benzene ring. 6. The liquid crystal compound according to claim 3, wherein the Ar group is a 2,6-disubstituted naphthalene ring. 7. The liquid crystal compound according to claim 2, wherein the group [formula] is a bicyclo(2,2,2) octane ring. 8. The liquid crystal compound according to claim 7, wherein the Ar group is a 1,4-disubstituted benzene ring. 9 A liquid crystal material containing a mixture of liquid crystal compounds, in which at least one of the compounds has the structural formula (In the formula, R ₁ is an alkyl group, R ₂ is an alkyl group or an alkoxy group, and R ₁ and R ₂ are 18
is a trans-1,4-disubstituted cyclohexane ring or a 1,4-disubstituted bicyclo(2,2,2)octane ring; Ar is 1,4-disubstituted benzene ring [formula] 3-fluoro-1,4-disubstituted benzene ring [formula] or 2,6-disubstituted naphthalene ring [formula]. ) The liquid crystal material is a compound of: