JPS6149352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a liquid crystal composition and a dichroic dye.
The present invention relates to a composition for liquid crystal color display that utilizes electro-optic effects.

For more details, see the formula () used in display devices that utilize the electro-optic effect of liquid crystals. (In the formula (), X is a hydrogen atom or a halogen atom, and n represents an integer from 1 to 3), or a quinophthalone dye represented by the formula () (In formula (), R ₁ and R ₂ each independently represent a hydrogen atom or an alkyl group) is dissolved and included in a nematic liquid crystal having positive dielectric anisotropy. The present invention relates to a composition for liquid crystal color display.

It is well known that liquid crystal compositions containing dichroic dyes are used for "guest-host" display devices in the field of liquid crystal technology, and are attracting attention as display devices for watches, calculators, televisions, etc. There is.

These display devices utilize the fact that the absorption spectrum of dichroic dyes strongly depends on the angle between the long axis of the dye molecule and the vibration direction of incident polarized light. In other words, by dissolving a dichroic guest dye into a host liquid crystal with a fixed arrangement, and controlling the arrangement of the liquid crystal with an electric field, the arrangement of the dye is also controlled at the same time, and the change in color density at this time is utilized. .

In order to create and operate electro-optical devices using nematic liquid crystals, the liquid crystal must have a molecular orientation structure that is controlled in the direction of the applied electric field. In general, liquid crystal molecules tend to have rod-like molecules, and the orientation structure of the molecules has the following states.
If the long molecular axis of the liquid crystal is perpendicular to the container wall, the structure is called homeotropic. Furthermore, when the long axis of the liquid crystal molecules is parallel to the container wall, it is called homogeneous.
Furthermore, when the alignment lines of the two homogeneous alignment walls are at right angles, a twisted nematic liquid crystal structure is obtained.

Many nematic liquid crystals can be converted to the cholesteric phase by adding certain optically active substances or cholesteric liquid crystal compounds. In this case it is the helical axis of the cholesteric phase that is homeotropically or homogeneously oriented. The cholesteric liquid crystal substance transformed in this way undergoes a phase transformation upon application of an electric field.
Becomes in a nematic state.

In this way, the guest-host method currently has two methods: using nematic liquid crystals with positive or negative dielectric anisotropy, and adding optically active substances to these liquid crystals and converting them from the cholesteric phase by applying an electric field. There is a method of using a phase change type liquid crystal that undergoes a phase transition to a nematic phase.

Among these methods, the composition of the present invention can be used in a method that uses a nematic liquid crystal with positive dielectric anisotropy or a nematic liquid crystal that has been converted into a phase transition type by adding an optically active substance or the like to the nematic liquid crystal. This is a composition for liquid crystal color display.

In general, dichroic dyes used in liquid crystal color display devices that apply this principle are 1
゜゜It has sufficient coloring ability with a small amount. ２゜It has a large dichroism ratio, and when voltage is applied or not applied,
Conditions include: exhibiting large contrast, 3°, sufficient compatibility with liquid crystals, and 4°, being highly durable and stable, and not deteriorating the performance of the device even after long-term use. Basically, it is required to have the following.

The present invention is based on the result of extensive research into dyes that meet these requirements and the discovery that dyes of formula () or () have extremely excellent properties as dichroic dyes.

The dye represented by formula () or () is a compound that fully satisfies the requirements for dichroic dyes applied to the liquid crystal color display device. These dyes have extremely excellent properties, especially in terms of durability.

Representative examples of compounds represented by formula () or () include: These dyes are known and readily available for dyeing fibers or textiles or for coloring synthetic resins. The obtained or synthesized dye is used after being sufficiently purified by means such as recrystallization with an organic solvent or column chromatography.

As the nematic liquid crystal with positive dielectric anisotropy used in the present invention, for example, 4-cyano-4'-n
- Pesotilbiphenyl, 4-cyano-4'-n-propoxybiphenyl, 4-cyano-4'-n-pentoxybiphenyl, 4-cyano-4'-n-octoxybiphenyl, 4-cyano -Cyano-biphenyl liquid crystal mixtures such as -4'-n-pentylterphenyl (for example, Merck & Co. product code E-8), or trans-4-n-propyl-(4-cyanophenyl)-cyclohexane, trans-4-n ―
Pentyl-(4-cyanophenyl)-cyclohexane, trans-4-n-heptyl-(4-cyanophenyl)-cyclohexane, trans-4-
Cyclohexane-based liquid crystal mixtures such as n-pentyl-(4'-cyanobiphenyl)-cyclohexane (for example, Merck product code ZLI-1132, ZLI-
1840).

Furthermore, when an optically active substance such as cholesteryl nonanoate or optically active 4-cyano-4'-isopentyl biphenyl is added to the liquid crystal mixture, it is in a cholesteric phase state when no electric field is applied, and is in a nematic phase state when an electric field is applied. It is also possible to use so-called chiral nematic liquid crystal mixtures which undergo a phase transformation. The liquid crystals are not limited to the above examples, and may include other biphenyl liquid crystals, phenylcyclohexane liquid crystals, Schiff base liquid crystals, ester liquid crystals, pyrimidine liquid crystals, tetrazine liquid crystals, and other liquid crystals alone or in mixtures. Can be used.

The dyes according to the present invention may be used alone or in combination of two or more. The concentration of the dye to be used may be within the range where the dye can be dissolved in the liquid crystal and within the range where the dye molecules can be sufficiently controlled by the orientation of the liquid crystal molecules, but it is generally 0.01 to 0.01 to 0.01 to the liquid crystal. concentration of 5% by weight,
It is preferably used at a concentration of 0.01 to 3% by weight. It is also possible to mix the dichroic dye according to the present invention with another dichroic dye or a dye without dichroism and use the mixture to obtain a desired hue, and there is no limitation at all.

Furthermore, in producing a liquid crystal display device using the composition of the present invention, liquid crystal molecules and dichroic dye molecules are treated in advance so that they are aligned parallel to the surface of the transparent electrode. Examples of the treatment method include simply rubbing the surface of the transparent electrode in a certain direction with a cotton cloth, etc., applying a silane compound or polyamide compound and then rubbing it with a cotton cloth, etc., vapor depositing silicon oxide, etc. If a solution consisting of a nematic liquid crystal having a positive dielectric anisotropy and a dichroic dye of the present invention is used in a liquid crystal color display device treated so that the liquid crystal and dye molecules are parallel to the surface of the transparent electrode as described above, , the display device is of a type in which the coloring of the electrode portion disappears by application of an electric field.

As described above, there are a wide variety of liquid crystals and methods used in implementing a liquid crystal color display device using the composition according to the present invention, but essentially all of them are based on the electrical properties of nematic liquid crystals or chiral nematic liquid crystals. This can be regarded as a guest-host display method that uses optical effects. Although typical examples will be specifically described below, the present invention is not limited to these examples in any way.

Example 1 In a small beaker, 38% 4-cyano-4'-n-pentylbiphenyl, 8% 4-cyano-4'-n-pentoxybiphenyl, 4-cyano-4'-n-heptylbiphenyl. 23%, 4-cyano-4'-n-heptoxybiphenyl 8%, 4-cyano-4'-n-octoxybiphenyl 10%, 4-cyano-4'-n-pentylterphenyl 10% and To 9.9 parts of a liquid crystal mixture consisting of 3% of optically active 4-cyano-4'-isopentylbiphenyl was added 0.1 part of dye No. 2, which had been sufficiently purified by recrystallization, and heated to about 80°C. The solution should be completely clear. The contents are then left to cool and then introduced into a liquid crystal cell by a known method such as capillary action.

1 and 2 are schematic diagrams of a liquid crystal display device having a cell structure. The display device has a layer 1 partially filled with a liquid crystal material colored with a dye.

The layer 1 is sandwiched between two parallel rectangular glass slides 2,3. The slides 2 and 3
are separated from each other by a ring-shaped spacer 4 (not shown in FIG. 1) defining the lateral edges of the layer 1. The slides 2, 3 have electrodes 5, 6 on their respective inner surfaces. Electrode 5 is connected to external conductor 11 through strip 7 and contact 8. Similarly, electrode 6 is connected to strip 9 and contact 1.
It is connected to the external conductor 12° through 0. The electrodes 5 and 6 have the same M-shape and are arranged facing each other.

A voltage source 14 and a switch 13 connected in series with the voltage source are connected between external conductors 11 and 12. Voltage source 14 provides a direct current or low frequency alternating voltage sufficient to reorient the liquid crystal and dye molecules in layer 1 and place them in the plane of slides 2,3. Typically a voltage of 10-20 volts is required.

In the display device shown in FIGS. 1 and 2 as described above, silicon KF-99 (silicon-based compound manufactured by Shin-Etsu Chemical Co., Ltd. ), and then the colored liquid crystal solution, which is the liquid crystal composition according to the present invention, was sealed in one portion of the layer of the display element, which had been treated to make the liquid crystal alignment as homogeneous as possible. This display device appeared to be colored bright yellow when the switch 13 was open. switch 1
3 was closed and an AC voltage of 32 Hz and 10 V was applied, and the part of the letter M where the transparent electrodes 5 and 6 were facing became colorless. When the switch 13 was opened, the yellow color was displayed again. When the display device is placed in the optical path of a spectrophotometer, the maximum absorption wavelength is 452 nm, and at this wavelength, when the switch 13 is opened or closed, the absorbance ratio of the electrodes 5 and 6 is 1:3.0, indicating good dichroism. Indicated.

The dichroic ratio of this dye in liquid crystal E-8 (trade name of Nematic Liquid Crystal manufactured by Merck & Co.) was 8.1. The dichroic ratio is calculated by filling a 10 μm thick glass cell with a nematic liquid crystal solution containing dye at a concentration of 1% in a glass cell whose inner surface has been treated to make the liquid crystal alignment as homogeneous as possible, and using a spectrophotometer to measure polarized light parallel to the liquid crystal alignment. It is calculated by the following formula from the absorbance measured by applying polarized light (α ₁₁ ) and the absorbance measured by applying polarized light perpendicular to the liquid crystal alignment (α⊥), and is the magnitude of dichroism of a dichroic dye. This is a value that can be used as a guideline.

Dichroic ratio = α ₁₁ /α⊥ Example 2 0.1 part of dye No. 4, which was sufficiently purified by column chromatography, was dissolved in the same liquid crystal mixture as in Example 1, and the solution was sealed in the same cell as in Example 1. did. When the switch 13 was opened and closed, the absorbance ratio of the opposing portions of the electrodes 5 and 6 at the maximum absorption wavelength of 550 nm was 3.6, indicating good dichroism. Furthermore, the dichroic ratio of this dye in liquid crystal E-8 was as high as 9.2 (555 nm).

[Brief explanation of the drawing]

FIG. 1 is a front view of a liquid crystal display device, and FIG. 2 is a sectional view of the device taken along line a--a in FIG. 1, with a portion cut away for explanation. 1... Liquid crystal and dye layer, 2, 3... Glass slide, 4... Spacer, 5, 6... Electrode,
7, 9... Electrode strip, 8, 10... Contact,
11, 12... conductor, 13... switch, 14...
…power supply.

Claims (1)

[Claims] 1. For a nematic liquid crystal with positive dielectric anisotropy, the formula () (In the formula (), X is a hydrogen atom or a halogen atom, and n represents an integer from 1 to 3), or a quinophthalone dye represented by the formula () (In formula (), R ₁ and R ₂ each independently represent a hydrogen atom or an alkyl group) A composition for liquid crystal color display characterized by containing dissolved at least one thioindigo dye thing.