JPH0549710B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to dichroic dyes that are dissolved in liquid crystals and used in liquid crystal devices such as liquid crystal display devices and liquid crystal light valves that utilize the guest-host effect. [Technical Background of the Invention] In general, liquid crystal devices such as display devices that utilize the guest-host effect can display images with good contrast, have fast response to display driving, and display colors that do not fade over a long period of time. is ideal. By the way, the display contrast of a guest-host type liquid crystal device is mainly determined by the dichroic ratio of the dichroic dye mixed into the liquid crystal, and the higher the dichroic ratio, the better the display contrast. Become. However, even if the dichroic ratio of the dye is high, if the coloring ability of the dye itself is low, the displayed color becomes pale and sufficient display contrast cannot be obtained. If the coloring ability of the dye is low, it is necessary to increase the amount of the dye added to the liquid crystal to make the displayed color darker, but this will have a negative effect on the liquid crystallinity of the liquid crystal molecules and reduce the responsiveness to display driving. Deteriorate. It is also important that the dichroic dye has sufficient compatibility with the liquid crystal. If the dichroic dye has low compatibility with the liquid crystal, the dye may precipitate into the liquid crystal (this dye precipitation is noticeable at low temperatures), causing color unevenness in the display area and deteriorating the display quality. It may cause a decline. In other words, the ideal guest as described above.
In order to obtain a host-type liquid crystal device, the guest dichroic dye mixed into the host liquid crystal must: 1) have a high dichroic ratio, 2) have high coloring ability, and display colors sufficiently deep even with a small amount of addition. 3. It must have sufficient compatibility with liquid crystals and not precipitate even at low temperatures. Conventionally used dichroic dyes include benzene-based azo dyes, stilbene-based dyes, and anthraquinone-based dyes, but none of these conventional dyes can be said to satisfy all of the above three requirements. It is something. [Object of the Invention] Therefore, the object of the present invention is to provide a dichroic device suitable for use in a liquid crystal device utilizing the guest-host effect, which has a high dichroic ratio and coloring ability, and has good compatibility with liquid crystal. An object of the present invention is to provide a colored dye. [Summary of the Invention] The dichroic dye of this invention has the general formula (Here, X is Y is each independently, base or Base; Z is R ¹ is a lower alkyl group, a cyano group, a fluorinated lower alkyl group, basis, base, or group; R ² is hydrogen; R ⁴ is base, or Group; Either one of R ⁵ and R ⁶ is a lower alkyl group,
When the other is a cyano lower alkyl group or a fluorinated lower alkyl group, and R ¹ is a cyano group or a fluorinated alkyl group, each is a lower alkyl group; R ¹⁰ is a lower alkyl group; i is each 0 or 1) Consists of at least one type of compound. In this specification and claims,
The term "lower" when used in reference to groups such as alkyl and alkylene groups refers to groups having from 1 to 8 carbon atoms. As can be seen from the definition of the above formula (), the dichroic dye of the present invention has the formula A disazo compound represented by the formula () (where W is Y), and a disazo compound represented by the formula It contains a trisazo compound represented by the formula (). In the above formulas (), (), (), R ¹ is
Preferably, a cyano group, a lower alkyl group, a fluorinated lower alkyl group, base, base, or group, R ² is hydrogen and R ⁴ is preferably base, or It is the basis. Especially In the case of a group, each of R ⁵ and R ⁶ is a lower alkyl group, the other is a cyano lower alkyl group or a fluorinated lower alkyl group, and when R ¹ is a cyano group or a fluorinated lower alkyl group, each R 5 and R 6 are independently is a lower alkyl group, and R ¹⁰ is preferably a lower alkyl group. Further, the dichroic dye of the present invention is preferably a disazo compound represented by the formula () and a trisazo compound represented by the formula (). In the case of a disazo compound, in formula (), W is 1,
4-phenylene group, and Z is group, and W is a 1,4-naphthylene group, and Z is Particularly preferred are groups. Further, in the case of a trisazo compound, in the formula (), X and Y are each a 1,4-phenylene group, and Z
but group, and X is a 1,4-phenylene group and Y is a 1,4-naphthylene group, and Z
but Particularly preferred are groups. That is, the most preferred dichroic dye of the present invention is one represented by the following general formula. (In the formula () to (), R ¹ ' and
R ⁴ ' represents the above-mentioned preferred R ¹ and R ⁴ groups, respectively. ) Now, the disazo and trisazo dichroic dyes of this invention have the formula It can be obtained by producing a monoazo compound represented by, coupling this monoazo compound with a primary amine to obtain an aminoazo compound, diazotizing this aminoazo compound, and repeating the same reaction. . First, the production of a monoazo compound will be explained. This monoazo compound has the formula It can be produced starting from diazotization of a 2-aminoethino[2,3-d]thiazole compound represented by the formula (). This diazotization is carried out by adding approximately equimolar amounts of the thienothiazole compound of formula () in a mineral acid such as sulfuric acid or phosphoric acid or an organic acid such as acetic acid or a propionic acid/acetic acid mixture. This can be carried out by reacting with sodium nitrate under ice cooling. This diazotization produces the corresponding thienothiazole diazonium salt. This diazonium salt is used in the next coupling step without being isolated from the reaction mixture. The monoazo compound represented by the formula () is prepared by combining the reaction mixture containing the thienothiazole diazonium salt with the coupling component represented by the formula H-Z (Z is as defined above) in acetic acid or a mixture of acetic acid and propionic acid. It can be obtained by reacting with This coupling reaction is carried out at relatively low temperatures (eg -30°C to 15°C). in general,
This coupling can be completed in 1 to 3 hours. The coupling component is preferably used in excess (for example, 2 to 4 times the molar amount) relative to the diazo component. In this reaction, when an aromatic primary amine such as aniline is used as a coupling component, more diazoamino compounds are produced than the desired aminoazo compound (i.e., when aniline is used as a coupling component, aniline's amino Coupling occurs more easily on the amino group itself than on the carbon that is para to the group). Therefore, in order to obtain the desired aminoazo compound in a higher yield, it is necessary to protect the amino group of the aniline with, for example, sodium methanesulfonate, as will be described in detail in the following examples. , it is preferable that coupling is preferentially performed on the carbon at the para position to the aniline amino group. After this coupling is completed, the coupling product is heated (for example, 60 to 90° C.) in, for example, an alkaline medium (for example, an aqueous sodium hydroxide solution) to remove the protecting group. Such a problem does not occur when α-naphthylamine is used as the coupling component. The disazo compound represented by formula () can be produced by the following method. That is, the reaction mixture containing the above thienothiazole diazonium salt is first converted to the formula H-W- _NH2 (where W is as defined above).
A coupling reaction is performed with the primary amine represented by The conditions for this coupling reaction are the same as those for producing the monoazo compound described above. With this coupling, the expression A gripping aminoazo compound represented by is obtained. This aminoazo compound is diazotized in the same manner as the diazotization reaction of thienothiazole described above. This diazotide is then coupled with a coupling component represented by the formula H-Z. This coupling is carried out in the same manner as the coupling reaction of the monoazo compound described above. In this way, a disazo compound represented by the formula () is obtained. The trisazo compound represented by the formula () is obtained by converting the above thienothiazole diazonium salt to the formula H-X- _NH2 (where X is as defined above).
The resulting aminoazo compound is diazotized, and the diazotized product is coupled with a primary amine of the formula H-Y- _NH2 (where Y is as defined above). It can be produced by diazotizing the obtained aminodisazo compound and coupling the diazotized product with a coupling component represented by the above formula H-Z. Each diazotization and coupling reaction in this production can be performed in the same manner as described above. Each final product obtained can be purified using a silica gel column or by recrystallization. The thienothiazole compound of formula (), which is the starting material for the dichroic dye of this invention, is, for example,
Journal fur praktische Chemie, 315 [3],
539-548 (1973) and British Patent No. 1549185, including its manufacturing method,
Alternatively, it can be produced by appropriately modifying the method described in that document. [Examples of the Invention] Next, the present invention will be explained in detail with reference to the following Examples. First, a monoazo compound is produced as follows. A monoazo compound in which Y is phenylene in the general formula () is produced as follows. formula 4.24 grams (0.02 mol) of 2-amino-5-n-butyl-thieno[2,3-d]thiazole
was added to 40 ml of 85% phosphoric acid and heated to 70°C to dissolve. After cooling this solution to -5 to 0°C, 5.9 g of 43% by weight nitrosyl sulfuric acid was gradually added dropwise over 30 minutes. After the dropwise addition, the reaction mixture was heated to -5
Diazotization was completed by stirring at ~0°C for 1 hour. On the other hand, a coupling component solution was prepared by dissolving 8.82 g (0.06 mol) of N-phenylpyrrolidine (coupling component) in 100 ml of acetic acid-propionic acid mixture with a weight ratio of 1:1. The reaction mixture containing the diazotized product was added dropwise to the coupling component solution at -5 to 0°C over 40 minutes while stirring, and the mixture was stirred at the same temperature for 2 hours. After that, this reaction mixture was poured into 300 ml of ice water, and the precipitate was filtered out.
It was washed with water and dried under vacuum. 2 grams of the obtained crude monoazo compound was dissolved in 50 ml of chloroform, and 20 grams of alumina powder was added with stirring, followed by filtration and washing with chloroform. Next, add 30ml of mother liquor.
The mixture was concentrated to 120 g and purified using chloroform as the eluent using a column with an inner diameter of 3 cm and a length of 30 cm packed with about 120 g of 300 mesh silica gel. The eluate was evaporated to dryness and subjected to two recrystallizations from a chloroform-methanol mixed solvent to obtain the desired dichroic dye. Example 1 First, the formula The disazo compound of is produced as follows. (A) 2-Amino-5-n-butyl-thieno [2,
3-d) 4.24 g (0.02 mol) of thiazole was diazotized in the same manner as the method for producing formula [). This diazotized reaction mixture was added dropwise to a solution of 8.58 g (0.06 mol) of α-naphthylamine dissolved in 150 ml of acetic acid at 10° C. over 30 minutes with stirring, and the mixture was stirred at the same temperature for 2 hours. This reaction mixture was poured into 400 ml of ice water, and the precipitate was separated and washed with water. The resulting cake was added to a 4% aqueous sodium carbonate solution, and after stirring for 30 minutes,
Filter, vacuum dry and 6.8 grams of a crude aminomonoazo compound represented by was obtained. (B) Add 3 grams of the above aminomonoazo compound to acetic acid.
After adding to 300 ml of propionic acid polymerization ratio 1:1 mixture, 43
% nitrosyl sulfate was added and stirred at the same temperature for 1 hour to achieve diazotization of the aminoazo compound. This diazotized reaction mixture is
6.2 grams of N,N-diethylaniline in acetic acid
It was added dropwise at -5 to 0°C into a solution dissolved in 100 ml of a mixture of propionic acid with a weight ratio of 1:1, and the mixture was stirred at the same temperature for 2 hours. Add 150 ml of ice water to this reaction mixture.
was added, and the precipitate was filtered off, washed with water, and dried under vacuum to obtain 2 grams of a crude bisazo compound. Purification of this crude bisazo compound yielded 0.4 grams of the desired dichroic dye. Here, for the disazo compound of Example 1, 2-amino-5-cyano-thieno[2,3-d]thiazole is used as the 2-aminothienothiazole compound, and the other methods are the production method of the disazo compound of formula (XI). A desired dichroic dye was obtained in the same manner as above. Example 2 First, the formula The disazo compound is produced as follows. (A) 2-Amino-5-n-butyl-thieno [2,
3-d] 4.24 g (0.02 mol) of thiazole was diazotized in the same manner as in Example 1. This diazotized reaction mixture can be expressed as 16.7 g (0.08 mol) of sodium aniline-ω-methanesulfonate represented by was dissolved in 100 ml of 50% acetic acid aqueous solution at 10° C.
The mixture was added dropwise over 30 minutes and stirred at the same temperature for 2 hours. This reaction mixture was stirred at 30° C. for 30 minutes, then poured into 500 ml of water, and the precipitate was filtered out and washed with water. The resulting cake was added to a 2% aqueous sodium carbonate solution and heated at 65°C for 2 hours and at 80°C.
After heating at 85℃ for 30 minutes, cool, filter, and vacuum dry. A crude aminomonoazo compound represented by was obtained. (B) A desired dichroic dye was obtained by coupling N,N-diethylaniline in the same manner as in Example 1(B) except that the above aminomonoazo compound was used. Here, the disazo compound of Example 2 was produced in the same manner as in the production method of formula (XII) except that the aminomonoazo compound obtained in (A) was coupled with N-methyl-N-cyanoethyl-aniline. A dichroic dye was produced. Example 3 A desired dichroic dye was produced in the same manner as in the production method of formula (XII) except that the aminomonoazo compound obtained in (A) was coupled with N-ethyl-N-cyanoethyl-aniline. Example 4 A desired dichroic dye was produced in the same manner as in the method for producing formula (XII) except that the aminomonoazo compound obtained in (A) was coupled with N-phenylmorpholine. Example 5 First, the formula The disazo compound of is produced as follows. (A) 2-amino-5-methyl-thieno[2,3-
d) 3.4 grams (0.02 mol) of thiazole were dissolved in 60 ml of a 1:1 mixture by weight of acetic acid-propionic acid. In this solution, add 43% nitrosyl sulfate 5.9
gram (0.02 mol) over 30 minutes and stirred at the same temperature for 1 hour to complete the disazotization.
This disazotized reaction mixture was added dropwise to a solution of 16.7 g (0.08 mol) of sodium aniline-ω-methanesulfonate dissolved in 100 ml of 50% aqueous vinegar solution at 10° C. over 30 minutes with stirring.
The mixture was stirred at the same temperature for 2 hours. Add this reaction mixture to 30
After stirring at ℃ for 30 minutes, it was poured into 500 ml of water.
It was filtered and washed with water. The obtained cake was added to 300 ml of 2% aqueous sodium hydroxide solution, and 65%
After heating at 85° C. for 30 minutes, it was cooled, filtered, washed with water, and dried in vacuum. Thus the formula 4.5 grams of the crude aminomonoazo compound represented by was obtained. (B) Add 4.5 grams of the above aminomonoazo compound to 200 ml of a 1:1 mixture by weight of acetic acid and propionic acid, cool to -10 to -5°C, and add 4.5 g of the above aminomonoazo compound to 43% of the mixture with stirring.
4.8 g of nitrosyl sulfuric acid was added dropwise over 10 minutes, and the mixture was further stirred at the same temperature for 1 hour to complete diazotization. This reaction mixture was mixed with α-naphthylamine.
12 grams were added dropwise in 1 hour to a solution of 100 ml of a 1:1 acetic acid-propionic acid mixture by weight,
The mixture was further stirred for 3 hours. water in this reaction mixture
Add 100ml, filter the precipitate, wash with water, wash with 2% sodium carbonate aqueous solution, further wash with water,
Vacuum dry, formula 3.8 grams of the crude aminodisazo compound represented by was obtained. (C) 3.8 grams of the above aminodisazo compound was ground in a mortar, and the weight ratio of acetic acid to propionic acid was 1:1.
The mixture was added to 200 ml, cooled to -5°C to 0°C, and 2.6 grams of 43% nitrosyl sulfuric acid was added dropwise over 10 minutes while stirring. This reaction mixture was stirred at the same temperature for 1 hour to complete diazotization. This diazotized reaction mixture was mixed with N,N-diethylaniline.
12 grams dissolved in 100 ml of acetic acid at 10°C.
After stirring for 3 hours, 200 ml of water was added. The precipitate was filtered off, washed with water, and dried in vacuum.
Two grams of this crude product was purified similarly to the method for producing formula (), yielding 0.3 grams of the desired dichroic dye. Here, the disazo compound of Example 5 has the formula (
), the aminodisazo compound obtained in (B) was coupled with N-methyl-N-cyanoethylaniline in (C), and the desired dichroic dye was obtained in the same manner as above. Example 6 Using 2-amino-5-n-butyl-thieno[2,3-d]thiazole in (A) of the production method of formula (), the obtained aminodisazo compound was converted into (C)
The desired dichroic dye was obtained in the same manner except for coupling with N-methyl-N-cyanoethylaniline. Example 7 Similarly to (A) of the method for producing formula (XII), the corresponding aminomonoazo compound was prepared using 2-amino-5-methyl-thieno[2,3-d]thiazole, and the aminomonoazo The compound was coupled with aniline to obtain the aminodisazo compound. This aminodisazo compound was coupled with N-methyl-N-cyanoethylaniline to obtain the desired dichroic dye. Table 1 lists the structural formulas and properties (maximum absorption wavelength (λmax), hue, and dichroic ratio) of the dichroic dyes produced in Examples 1 to 7 above. The characteristics shown in Table 1 are for each dichroic dye.
BDH Chemical's biphenyl liquid crystal E7 (nematic liquid crystal with positive dielectric anisotropy)
Using a liquid crystal material dissolved at a ratio of 0.2 to 1.0% by weight, this was incorporated into a negative display type guest-host type liquid crystal display device as shown in Figure 1, which will be described in detail below, and measurements were taken. It is something. Note that in guest-host liquid crystal devices of different formats, the characteristics of each dye may exhibit slightly different values.

【table】

[Table] Examples 8 to 27 Dichroic dyes shown in Tables 2 to 5 below were produced according to each of the above Examples. The characteristics are also listed in Tables 2 to 5. The properties of the dichroic dyes of Examples 8 to 27 were also obtained in the same manner as those of the dichroic dyes of Examples 1 to 7.

【table】

【table】

【table】

【table】

〔Effect of the invention〕

According to the present invention, it is possible to provide a dichroic dye having a high dichroic ratio, high coloring ability, and excellent compatibility with liquid crystals.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a negative display type guest-host type liquid crystal display device, Figure 2 is a cross-sectional view of a White-Taylor type guest-host type liquid crystal display device,
FIG. 3 is a sectional view of a positive display type guest-host type liquid crystal display device. 11, 12, 21, 22, 31, 32... Electrode substrate, 13, 23, 33... Sealing material, 14, 2
4, 34... host liquid crystal, 15, 25, 35...
Dichroic dye, 16, 26, 36...External power supply, 1
7...Polarizing plate.

Claims (1)

[Claims] 1. General formula (Here, X is Y is each independently, base or Base; Z is R ¹ is a lower alkyl group, a cyano group, a fluorinated lower alkyl group, basis, base, or Group; R ² is hydrogen; R ⁴ is base, or Group; Either one of R ⁵ and R ⁶ is a lower alkyl group,
When the other is a cyano lower alkyl group or a fluorinated lower alkyl group, and R ¹ is a cyano group or a fluorinated alkyl group, each is a lower alkyl group; R ¹⁰ is a lower alkyl group; i is each 0 or 1) A dichroic dye for liquid crystals comprising at least one compound.