JPS60219262A - Dichroic dye for color liquid crystal - Google Patents

Abstract

PURPOSE:To provide the titled dichroic dye compd. which has absorption bands at the wavelengths of 650nm or above and suitable for use in a liquid crystal compsn. for guest-host type liquid crystal display, by introducing a dye skeleton having linear rigidity into an anthracene skeleton. CONSTITUTION:Dye compounds of formula I (wherein dye is a group of a dye having linear rigidity such as azo, azomethine or azoxy dye) such as a compd. of formula II. The dye compds. have max. absorption peak at the wavelengths of 650nm or above and has a high dichroic ratio and a long light-resistant life.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to dichroic dyes for color liquid crystals, and particularly to dichroic dyes for color liquid crystals.
The present invention relates to a dichroic dye suitable for host-type liquid crystal display devices (hereinafter abbreviated as G-HLCD).

[Background of the invention]

Conventionally, this type of dichroic dyes include azo, azomethine,
Anthraquinone-based organic compounds are known. The following four characteristics are required for this dichroic dye.

(1) The dichroic ratio (hereinafter abbreviated as CI'L) is large.

(The molecular extinction coefficient (hereinafter abbreviated as ξ) is large.

(It must have a long life.)

(High solubility in liquid crystal compounds.)

By the way, the azo and azomethine dyes are generally C'
Although R is large, the life is short. On the other hand, although anthraquinone dyes have a long lifespan, no conventional dichroic dye satisfies all of the above four characteristics, such as low CR9 and low ξ.

Furthermore, recently, G-HLCDs based on black have attracted attention, and in addition to the above-mentioned characteristics, hue has also become important. This is because, in order to achieve black color with good visibility, it is necessary to mix pigments with red, blue, and black hues so that they are absorbed uniformly over the entire visible range. However, at present, there is no dichroic dye that absorbs at wavelengths of 55 Qnm or more and has the above-mentioned characteristics, which is an obstacle to realizing black color with good visibility.

[Purpose of the invention]

The object of the present invention is to absorb at a wavelength of 650 nm or more,
Moreover, it is an object of the present invention to provide a dichroic dye for color liquid crystals having the above-mentioned properties.

[Summary of the invention]

In order to achieve this objective, the present invention proposes the use of an organic compound having the general structural formula shown below, in which a linearly rigid dye skeleton such as an azo type is introduced into an anthraquinone skeleton, as a dichroic dye for color liquid crystals. be a sign.

dye in the general structural formula is a straight, rigid group such as azo, azomethine, or azoxy dye.

What is particularly important in the above dye structure is that in the group 2,
The 3rd carbon is shared by both the anthraquinone benzene/ring and other rings. ), and a dye group having linear rigidity was introduced into this.

Most of the conventional anthraquinone dyes are mainly substituted at 2-position or 2,6-position, and the molecular axis (MP/
) and absorption axis (AA) do not match, resulting in low CR, etc. in many cases.

In this regard, the dye of the present invention shares the carbon at the 2° and 3rd positions of anthraquinone with the ring on the dye side into which it is introduced, and the molecular axis (M
M') and the absorption axis (A) coincide, and the CR value is large. Furthermore, the fact that the dye group introduced is also long and slender is also responsible for increasing the CR value.

Regarding the hue, the conventional one is anthraquinone 1,4
, 5. This is just a matter of placing an auxochrome at the 8th position.

Therefore, it has been difficult to obtain a deep blue blue pigment that absorbs at a wavelength of 65 Q nm or more. In this regard, the dye of the present invention uses -NH, as an auxochrome, and also has a strong color-forming,
A dye group such as an azo dye with an auxochrome is used. Therefore, deep coloring is easily possible, and by introducing an appropriate pigment group, the absorption maximum of deep fruits and vegetables, which absorb at wavelengths of 05Q nm or more, and the absorption maximum of yellow, which absorbs at wavelengths of 400 to 459 nm, coexist. Dyes with a 2 or only color and edge threads are also obtained.

[Embodiments of the invention]

Next, examples of the present invention will be described.

A transparent conductive film made of indium oxide and tin oxide is formed on a glass substrate by a known method, an insulating film made of silicon dioxide is provided on top of the transparent conductive film, and an organic silane-based homogeneity alignment agent is thinly coated on top of the insulating film. A liquid crystal cell is created by alignment treatment by rubbing.

On the other hand, 1% of the dichroic dye described below is dissolved in a cyanobiphenyl liquid crystal composition having positive dielectric anisotropy.

This was sealed in the liquid crystal cell to create a G-HLCD, and each characteristic value as shown in the figure was measured.

〔Effect of the invention〕

In the graph, λmax indicates the absorption maximum of the dye in the liquid crystal composition, and solubility indicates the value in the liquid crystal composition, respectively. Light-resistance life was tested by ultraviolet irradiation (approximately 42 times the irradiation intensity of normal light), fading is the time it takes for the color to change by 80% from the initial stage of manufacture, and the time for the current value to change is 3 times the initial value for manufacturing. are shown respectively. FIG. 1 shows the molecular structural formula and characteristic values of dichroic dyes according to each example of the present invention, and FIG. 2 shows the molecular structural formula and characteristic values of a comparative example.

The general formula of typical anthraquinone dyes is shown below. XI, X2. Y and Z each represent a substituent.

In the case of conventional anthraquinone dyes, the main substituent position is on the 1st or 2nd carbon atom, that is, the Xl or Y position, and Comparative Example 1.2 shows this example.

In Comparative Example 1, Xl is -NH〉〉2C,H, which not only causes a large steric hindrance, but also greatly shifts the molecular axis MxxMxt toward the absorption axis, resulting in a significant CR.
A decrease in value is observed.

Although Comparative Example 2 has less steric hindrance than Comparative Example 1, it shows a low CR value because the absorption axis A and the molecular axes MYMY' do not coincide. In addition, XLX2 is a hydrogen group, and no auxochrome has been introduced, so the hue is shallow and purple.

In the case of Comparative Example 3, the main substituents were Y and Z, and because they were placed in the same ring, the molecular axis coincided with the absorption axis, and the CR value increased compared to Comparative Examples 1 and 2. There is. Also xl, x2
The auxochrome -NH, is introduced into the
Since a dye group having an auxochrome is introduced into the Y and Z rings, the color becomes deep and has a large absorption at a wavelength of 684 nm. However, at the end of the introduced dye group, nonlinear and nonrigid -CO
Since the N H- group is introduced, the overall rigid rod-like property is lost, resulting in a molecular structure in which a larger CR value cannot be expected.

In this regard, the dichroic dye of the present invention has features such as having an absorption maximum at a wavelength of 650 nm or more, a large CR value, and a long light resistance life.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams showing the molecular structural formula and each characteristic value of a dichroic dye.

Claims (1)

[Scope of Claims] A dichroic dye for color liquid crystals, which is an organic compound having the following general structural formula in which a dye skeleton with linear rigidity is introduced into an anthraquinone skeleton. General Structural Formula However, in the formula, dye is a dye group having linear rigidity such as azo, azomethine, or azoxy dye.