JPS6254152B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electro-optical element that makes good color display possible by utilizing the guest-host effect of liquid crystal, and is expressed by the following general formula: (In the formula, X represents a hydrogen atom, a chlorine atom, or a bromine atom, Y represents an oxygen atom or a sulfur atom, and R represents an alkyl group, a cyclohexyl group, a 4-
Cyclohexyl represents a cyclohexyl group, an alkoxyalkyl group, a phenyl group, a p-hydroxyphenyl group, a p-cyclohexylphenyl group, a P-alkylphenyl group, a p-alkoxyphenyl group, a benzyl group, or a phenethyl group. This invention relates to an electro-optical element characterized in that a liquid crystal composition containing at least one kind of yellow pleochroic quinophthalone dye represented by the following formula is interposed between two opposing electrode substrates. Liquid crystals can be classified into three types depending on their molecular arrangement: nematic, cholesteric, and smectic liquid crystals.
Can be classified into types. Among these, in a nematic liquid crystal, all molecules are oriented so that their long axes are parallel to each other. When the long axes of liquid crystal molecules are perpendicular to the device or container wall, the arrangement is called homeotropic, and when they are parallel, the arrangement is called homogeneous. Further, nematic liquid crystals can be made to have a twisted alignment by appropriate alignment treatment. On the other hand, in a cholesteric liquid crystal, the molecules are arranged with their long axes parallel to each other, but they also form an extremely thin layer in a direction perpendicular to this long axis, and each layer is formed so that the long axis direction of the molecules is aligned as a whole. It shows a helical structure that appears to rotate sequentially around an axis that passes perpendicularly through the layers. Some cholesteric liquid crystals have the property that when an electric field is applied, the long axes of the liquid crystal molecules are aligned in the direction of the electric field and assume a nematic state with a homeotropic structure. Utilizing this property, it is possible to change from a cholesteric state to a nematic state, or from a nematic state to a cholesteric state, by performing parallel alignment treatment or perpendicular alignment treatment on the electrode surface of a liquid crystal element, or without any particular alignment treatment. A method of displaying by causing metastasis is known. In general, there are two types of liquid crystal display devices: those that utilize the electro-optical effect of the liquid crystal substance itself, and those that utilize the electro-optical effect that occurs as a result of interaction with other contaminants. The latter includes, for example, a liquid crystal display device using a nematic liquid crystal or a cholesteric liquid crystal in which a pleochroic dye is dissolved. By the way, in some pleochroic dyes, the direction of the transition moment of absorption of visible light is almost parallel to the long axis direction of the molecule, and when dissolved in the liquid crystal as a guest molecule, the dye molecular axis is in the same direction as the liquid crystal molecular axis. It is known that some materials are well oriented. The degree of alignment of dye molecules dissolved in a liquid crystal material can be expressed by an order parameter S, which will be described later. If a nematic liquid crystal containing such a pleochroic dye is interposed between two opposing electrode plates and a voltage is applied, the liquid crystal molecules will cause disturbance motion based on the dielectric and flow characteristics of the liquid crystal. Or it causes molecules to align in the direction of the electric field. At this time, the dye molecules move cooperatively with the liquid crystal molecules, which causes a direction change in the absorption transition moment of the dye molecules, making it possible to cause a change in the absorption characteristics of the liquid crystal display device. An electrically controlled color display device can be constructed. This phenomenon is widely known as the "guest-host effect." (A paper on such a device is “Guest-
Host Interaction in Nematic Liquid
Crystals: A New Electra-Optic Effect"G.
See H. Heilmeier, Applied Physics Letters, August 1, 1968, page 91. ) Furthermore, when pleochroic dyes are dissolved in a nematic liquid crystal that has a helical structure due to the addition of an optically active substance or a cholesteric liquid crystal that originally has a helical structure as a host material, these The molecules of the pleochroic dye are arranged by the helical structure of the host substance. When light propagates parallel to the helical axis of such a guest-host material, elliptic dichroism is sequentially induced due to the helical molecular arrangement. In the absence of an applied electric field, the guest-host material propagates the incident white light in two reference modes, which are clockwise and counterclockwise elliptically polarized, respectively. The direction of the electric vector of the light that displays these modes is closely related to the long axis of the guest molecule, and a specific wavelength region of the incident light is absorbed by the guest material, resulting in the guest-host material being colored. take a state. When an electric field is applied, the helical structure of the guest-host material is unwound, resulting in molecular orientation in the same direction (homeotropic orientation). In this arrangement, little incident light is absorbed by the guest molecules and therefore the guest-host material appears transparent. (Such a color display method is described in detail in, for example, Japanese Patent Laid-Open No. 49-127645.) Obtaining excellent contrast between the on state and off state in a liquid crystal display element that utilizes the guest-host effect In order to achieve this, the guest pleochroic dye must have the property of being strongly colored in one state and almost colorless and transparent in the other state. That is, in order to provide strong coloring, the long axis of the pleochroic pigment needs to be aligned parallel to the electric vector of the incident white light, i.e. perpendicular to the direction of light propagation; To provide this state, the long axes of the pleochroic dye molecules need to be aligned perpendicular to the electric vector of the incident white light, ie, parallel to the direction of light propagation. The direction of propagation of incident white light within a liquid crystal material is usually determined by the spatial configuration of the device. This direction is
Usually perpendicular to the planes of the pair of opposing electrodes. That is,
It is fixed in the direction in which the electric field is applied. However, liquid crystal molecules and dye molecules undergo random thermal fluctuations with respect to alignment, and cannot always be perpendicular or parallel to the direction of propagation of light. Therefore, the orderliness of the arrangement of dye molecules in a particular direction in the liquid crystal has a great effect on the contrast of the device. The degree of arrangement of dye molecules in a liquid crystal medium is usually expressed by a numerical value called an order parameter.
The order parameter S represents the degree of parallelism of the absorption transition moment of the dye molecule to the orientation direction of the liquid crystal molecules (usually expressed as a vector called a director), and is defined as follows. S = 1/2 (3 ² -1) In the formula, the term cos ² θ is time averaged, and θ is the angle between the absorption transition moment of the pleochroic dye and the orientation direction (director) of the liquid crystal. be. The order parameter S of the pleochroic dye dissolved in the liquid crystal can be determined using the following equation. S=A ₁₁ -A⊥/2A⊥+A ₁₁ In the formula, A ₁₁ and A⊥ represent the absorbance of the dye molecule with respect to light polarized parallel and perpendicular to the orientation direction (director) of the host liquid crystal, respectively.
Therefore, by measuring the absorption spectrum, A ₁₁ , A⊥
By determining this, the order parameter S of the dye in the host liquid crystal can be obtained, and the orientation of the dye can be evaluated. (For a paper on how to measure order parameters, see “Absorption and Pitch Relationships in
Dichroic Guest−Host Liquid Crystal System.
”HSCole, Jr., S.Aftergut, Journal of Chemical Physics, 1978, Vol. 68, No.
See page 896. ) In general, in electro-optical elements of the type in which a liquid crystal in which a pleochroic dye is dissolved is interposed between two opposing electrode plates to perform color display based on the guest-host effect, the pleochroic dye is In order to show a large contrast depending on the presence or absence of an electric field, the order parameter S must be large, and the extinction coefficient must be large to achieve clear colors.
It must have characteristics that satisfy conditions such as excellent stability against heat, water, oxygen, etc., high solubility in liquid crystals, and the ability to obtain any concentration within the required range. Furthermore, in addition to the conditions from these, in practice, yellow, red,
It is necessary to have a variety of pleochroic pigments with basic hues such as purple and blue. Known pleochroic dyes include merocyanine-based, azo-based, azomethine-based, and anthraquinone-based dyes, but in terms of hue, a practical dye that satisfies the above four conditions has not yet been found in terms of yellow color. Yellow pigments are used not only for yellow color, but also for
It is an indispensable component for blending colors such as orange, green, and black, and as a result of extensive study by the present inventors, the order parameters, extinction coefficient, stability,
The present invention has been completed by obtaining a yellow pleochroic quinophthalone dye that is excellent in all aspects of solubility. The yellow pleochroic quinophthalone dye used in the electro-optical element of the present invention has the following general formula [] (In the formula, X represents a hydrogen atom, a chlorine atom, or a bromine atom, Y represents an oxygen atom or a sulfur atom, and R represents an alkyl group, a cyclohexyl group, a 4-
Cyclohexyl represents a cyclohexyl group, an alkoxyalkyl group, a phenyl group, a p-hydroxyphenyl group, a p-cyclohexyl group, a p-alkylphenyl group, a p-alkoxyphenyl group, a verzyl group, or a phenethyl group. ) is a compound represented by In the above general formula, specific examples of the alkyl group represented by R include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, nonyl group, decyl group, dodecyl group, octadecyl group, etc. Examples include alkyl groups having 1 to 18 carbon atoms. Examples of the cycloalkyl group include a cyclohexyl group and a 4-cyclohexylcyclohexyl group. Examples of the alkoxyalkyl group include lower alkoxy lower alkyl groups such as methoxyethyl group and ethoxyethyl group. p-
Examples of the cycloalkylphenyl group include p-cyclohexylphenyl group. Examples of the p-alkylphenyl group include p-tolyl group, p-ethylphenyl group, p-propylphenyl group, p-butylphenyl group, p-pentylphenyl group, p-
hexyl phenyl group, p-octylphenyl group,
p-nonylphenyl group, p-decylphenyl group,
Examples include p _- alkyl ( _C1-18 ) phenyl groups such as p-dodecylphenyl group and p-octadecylphenyl group. Examples of the p-alkoxyphenyl group include p-methoxyphenyl group, P-ethoxyphenyl group, p-propoxyphenyl group, p-butoxyphenyl group, p-hexyloxyphenyl group,
p- such as p-heptyloxyphenyl group, p-octyloxyphenyl group, p-dodecyloxyphenyl group, p-octadecyloxyphenyl group, etc.
_Examples include alkoxy( _C1-18 ) phenyl groups.
Examples of the aralkyl group include a benzyl group and a phenethyl group. The pleochroic quinophthalone dye represented by the general formula [] can be obtained, for example, by heating and condensing 2-methyl-3-hydroxyquinoline-4-carboxylic acid with trimellitic anhydride [] Quinophthalone carboxylic acid represented by is obtained, which is reacted with a halogenating agent such as thionyl chloride or phosphorous oxychloride in an inert organic solvent to convert it into an acid halide, and then reacted with alcohols, phenols or thiols. When chlorine or bromine is introduced into the 4-position of the quinoline nucleus, it can be produced by halogenation using a conventional method. Examples of yellow pleochroic quinophthalone dyes used in the electro-optical device of the present invention and liquid crystal display devices using these dyes will be explained in more detail below using Examples. First, we will explain the maximum absorption wavelength and order of the pleochroic quinophthalone dye used in the present invention.
It is shown in Table 1 along with the parameters.

【table】

【table】

【table】

【table】

【table】

[Table] The order parameter S listed in Table 1 is ZLI-1132, a phenylcyclohexane mixed liquid crystal manufactured by Merck & Co. (liquid crystal temperature range -6℃ to 70℃)
A host liquid crystal was prepared by adding 7% by weight of 4-(2-methylbutyl)-4'-cyanobiphenyl manufactured by BDH as an optically active substance, in which the above pleochroic quinophthalone dye was dissolved, and a transparent electrode was formed. The above-mentioned “Absorption and
Pitch Relationships in Dichroic Guest−Host
Liquid Crystal System”HSCole, Jr., S.
Aftergut, Journal of Chemical Physics, 1978, Vol. 68, p. 896. Since the value of the order parameter depends in part on the properties of the host liquid crystal and the concentration of the pleochroic dye, it may vary somewhat when the type of host liquid crystal or the dye concentration is changed. The pleochroic quinophthalone dyes shown in Table 1 have extremely good solubility in liquid crystals. It has solubility. In addition, each dye in Table 1 was used with ZLI-1132 manufactured by Merck & Co.
The solution was sealed in a liquid crystal device consisting of two transparent glass substrates with a thickness of 3 mm, and an accelerated deterioration test was conducted using a sunshine weather meter. As a result, after 100 hours of accelerated deterioration, the absorbance of all dyes decreased by 10% or less, indicating that the photostability of the dyes used in the present invention is extremely high. The nematic liquid crystal used in the present invention can be selected from a fairly wide range as long as it exhibits a nematic state within the operating temperature range. Further, by adding an optically active substance to be described later to such a nematic liquid crystal, it can be made to assume a cholesteric state. Examples of nematic liquid crystals include those shown in Table 2 and derivatives thereof.

【table】

[Table] The liquid crystals in Table 2 all have positive dielectric anisotropy, but are known ester, azoxy, azo, Schiff, pyrimidine, diester, or biphenyl esters with negative dielectric anisotropy. The liquid crystal of the system can also be made positive as a whole by mixing liquid crystals with positive dielectric anisotropy. Furthermore, it goes without saying that even a liquid crystal with negative dielectric anisotropy can be used as is if an appropriate element configuration and driving method are used. As the optically active substance used in the present invention, chiral nematic compounds such as 2-methylbutyl group,
3-methylbutoxy group, 3-methylbentyl group,
There are compounds in which optically active groups such as 3-methylpentoxy, 4-methylhexyl, and 4-methylheptoxy groups are introduced into nematic liquid crystals. Also, alcohol derivatives such as l-menthol and d-borneol shown in JP-A-51-45546, d
- Ketone derivatives such as citrochloride, 3-methylcyclohexanone, carboxylic acid derivatives such as d-citronellaic acid and l-cilohexanone, aldehyde derivatives such as d-citronellal, alkene derivatives such as d-linonene, other amines, amides, and nitriles. Of course, optically active substances such as derivatives can be used. As the element used in the present invention, a known liquid crystal display element can be used. For elements that do not use a polarizing plate, such as the twisted nematic method, transparent electrodes in an arbitrary pattern are generally provided on a glass substrate with at least one side transparent, and the electrodes are arranged in parallel with an appropriate spacer interposed so that the electrode surfaces face each other. A configuration of elements is used. In this case, the gap of the element is determined by the spacer. The element gap is 3~
100 μm, particularly 5 to 50 μm is preferred from a practical standpoint. Hereinafter, the present invention will be explained by showing examples. Example 1 ZLI-1132, a phenylcyclohexane mixed liquid crystal manufactured by Merck & Co. (liquid crystal temperature range -6 to 70°C)
4 manufactured by BDH as an optically active substance.
-(2-Methylbutyl)-4'-cyanobiphenyl was added in an amount of 7% by weight, and the dye No. 8 in Table 1 was added as a pleochroic dye. 1% by weight of was added, heated to 70° C. or higher, thoroughly stirred in an isotropic liquid state, and then left to cool. This process was repeated to dissolve the dye. The above-mentioned liquid crystal composition thus prepared was sealed in an element having a gap of 10 μm and consisting of two glass substrates, upper and lower, each having a transparent electrode and whose surfaces in contact with the liquid crystal were coated with polyamide resin and rubbed. In the element subjected to the above alignment treatment, when no voltage is applied, the liquid crystal composition assumes a cholesteric state called Grangian alignment, in which the helical axis is perpendicular to the substrate surface.
The dye molecules also take a similar orientation according to the host liquid crystal. As a result, the light induced into the element appears strongly colored. FIG. 1 shows a sectional view of the above element when no voltage is applied. When a voltage above a certain level is applied to the above element, the liquid crystal composition assumes a homeotropic alignment in which the alignment direction is perpendicular to the substrate surface, and the dye molecules also take a similar alignment following the host liquid crystal, so the element exhibits a non-colored state. . FIG. 2 shows a cross-sectional view of the above element when voltage is applied. When the above-mentioned pleochroic dye was used, it exhibited a bright yellow color when no voltage was applied and a very pale yellow color when a voltage was applied, and a good contrast was obtained between the on state and the off state. FIG. 3 shows the absorption spectra of the above element when no voltage is applied and when no voltage is applied. The maximum absorption wavelength of the dye of this example in the host liquid crystal was 447 nm, and the order parameter was 0.66. Further, an accelerated deterioration test was conducted to obtain knowledge regarding the practical stability of the dye of this example. That is, the above-mentioned liquid crystal in which the above-mentioned dye had been dissolved was sealed in the above-mentioned device and left in a sunshine weather meter for 100 hours, and the rate of decrease in absorbance was monitored. For comparison, typical conventional dyes were simultaneously fabricated into devices, and an accelerated deterioration test was conducted in parallel with the above quinophthalone dye. The sunshine weather meter used in this example uses a carbon arc to continuously irradiate a sample with intense, nearly white light. Furthermore, by spraying
Water is sprayed directly onto the sample at a rate of 18 minutes in 120 minutes. The sample chamber of the weather meter is maintained at atmospheric pressure, temperature at 35-60°C, and humidity at 30-70%. The results of the accelerated deterioration test using the weather meter are shown in FIG. In the figure, curve 1 is the dye of this example, and curve 2 is the merocyanine dye. , curve 3 is the azo dye , curve 4 is azomethine dye It shows the change in absorbance of elements containing respectively. From FIG. 4, it can be seen that the stability of the dye used in the present invention is extremely high compared to conventional dichroic dyes. That is, the rate of decrease in absorbance of the quinophthalone dye of this example was 10% or less after 100 hours of accelerated deterioration measured by the weather meter. The transparent glass substrate used in this example was
The transmittance at wavelengths below 300 nm was almost 0. Example 2 The 15 dyes in Table 1 were added as pleochroic dyes to the same liquid crystal as used in Example 1 (7% by weight of optically active substance). A liquid crystal composition to which 1% by weight of was added was sealed in a device exactly the same as in Example 1, and the absorption spectra were measured when no voltage was applied and when a voltage was applied. In this case as well, good contrast was obtained between the on and off states. The maximum absorption wavelength of the dye of this example in the above liquid crystal was 448 nm, and the order parameter was 0.63. In addition, when a 100-hour accelerated deterioration test was conducted in the same manner as in Example 1, the absorbance reduction rate was 10
% or less, indicating extremely excellent stability. Example 3 22 of Table 1 was added as a pleochroic dye to the same liquid crystal as that used in Example 1 (7% by weight of optically active substance).
pigment of A liquid crystal composition to which 3% by weight of was added was encapsulated in a device exactly the same as in Example 1, and the absorption spectra were measured when no voltage was applied and when a voltage was applied. The results are shown in FIG. In this case as well, good contrast was obtained between the on and off states. The maximum absorption wavelength of the dye of this example in the liquid crystal was 448 nm, and the order parameter was 0.62. In addition, when a 100-hour accelerated deterioration test was conducted in the same manner as in Example 1, the absorbance reduction rate was 10%.
It was found that the stability is extremely excellent.

[Brief explanation of the drawing]

FIG. 1 A schematic cross-sectional view of the display element of the present invention in a state where no voltage is applied. 1... Transparent glass substrate, 2... Pleochroic dye molecules, 3... Host liquid crystal molecules, 4... Transparent electrode, 5
. . . Incident light, FIG. 2 Schematic cross-sectional view of the voltage applied state of the display element of the present invention, 1 . . . Transparent glass substrate, 2 .
...Pleochroic dye molecule, 3...Host liquid crystal molecule, 4...
...Transparent electrode, 5... Incident light Fig. 3 Spectral characteristics of the display element of Example 1 of the present invention when no voltage is applied and when voltage is applied. The horizontal axis shows wavelength, and the vertical axis shows absorbance. 1... Spectral characteristics when no voltage is applied, 2...
Spectral characteristics when voltage is applied Fig. 4 Changes in absorbance over time of an element containing the quinophthalone dye of Example 1 of the present invention and an element containing a typical conventional dichroic dye. The horizontal axis is sunshine
The accelerated deterioration time measured by a weather meter is shown, and the vertical axis shows the ratio of the absorbance A at each time point to the initial absorbance Ai. 1... Time-dependent change in absorbance of the quinophthalone dye of Example 1, 2... Time-dependent change in absorbance of conventional pleochroic merocyanine dye, 3... Time-dependent change in absorbance of conventional pleochroic azo dye, 4... Time-dependent change in absorbance of conventional pleochroic azomethine dye Fig. 5 Spectral characteristics of the display element of Example 3 of the present invention when no voltage is applied and when voltage is applied. The horizontal axis shows wavelength, and the vertical axis shows absorbance. 1... Spectral characteristics when no voltage is applied, 2...
Spectral characteristics when voltage is applied.

Claims (1)

[Claims] 1. General formula (In the formula, X represents a hydrogen atom, a chlorine atom, or a bromine atom, Y represents an oxygen atom or a sulfur atom, and R represents an alkyl group, a cyclohexyl group, a 4-
Cyclohexyl represents a cyclohexyl group, an alkoxyalkyl group, a phenyl group, a p-hydroxyphenyl group, a p-cyclohexylphenyl group, a p-alkylphenyl group, a p-alkoxyphenyl group, a benzyl group or a phenethyl group. ) An electro-optical element comprising a liquid crystal composition containing at least one type of quinophthalone dye. 2 General formula (In the formula, X represents a hydrogen atom, a chlorine atom, or a bromine atom, and R ¹ represents a hydrogen atom, a hydroxyl group,
It represents a cyclohexyl group, an alkyl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 18 carbon atoms. 2. The electro-optical element according to claim 1, comprising a liquid crystal composition containing at least one type of quinophthalone dye represented by: 3 General formula (In the formula ^,
Represents a benzyl group or phenethyl group. 2. The electro-optical element according to claim 1, comprising a liquid crystal composition containing at least one type of quinophthalone dye represented by: 4 General formula (In the formula, X represents a hydrogen atom, a chlorine atom, or a bromine atom, and ^R3 represents an alkyl group having 1 to 18 carbon atoms.) An electro-optical element according to claim 1.