JP2017066402A - Ink containing pyrazole disazo compound, display containing the ink and pyrazole disazo compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dye compound having excellent light resistance while maintaining dissolubility to a low polar solvent, an ink and an electrowetting display containing the ink.SOLUTION: A pyrazole disazo compound is represented by the following general formula (1), where Rrepresents a fluoroalkyl group which may have a substituent, Rrepresents an alkyl group which may have a substituent or an aryl group which may have a substituent, Qrepresents an aryl group which may have a substituent and Qrepresents an arylene group which may have a substituent.SELECTED DRAWING: None

Description

  The present invention relates to an ink containing a pyrazole disazo compound, a display containing the ink, and a pyrazole disazo compound, and more specifically, a pyrazole disazo compound having a specific chemical structure, and a display material or optical shutter containing the compound. As a useful ink.

  In the electrowetting display, a plurality of pixels filled with two phases of an aqueous medium and oil-based colored ink are arranged on a substrate, and the affinity of the interface of the aqueous medium / oil-based colored ink is determined by on-off of voltage application for each pixel. This is an image display format performed by controlling oil and developing / aggregating oil-based colored ink on the substrate (Non-patent Document 1). A coloring compound contained in an ink used for an electrowetting display (hereinafter referred to as EWD) is required to have high solubility in a low polarity solvent (Patent Document 1).

  In the above-mentioned Patent Document 1, an azo dye compound that is widely known as a thermal transfer recording material is devised to enhance the solubility in a low-polarity solvent, thereby forming a dye compound for an EWD ink.

International Publication No. 2009/063880

“Nature”, (UK), 2003, Vol. 425, p. 383-385

However, according to the study by the present inventors, it has been found that the dye compound specifically described in Patent Document 1 is excellent in solubility in a low polarity solvent, but is decomposed by light.
An object of the present invention is to provide a dye compound having excellent light resistance while maintaining solubility in a low polarity solvent.

As a result of intensive studies to solve the above problems, the present inventors have found that a pyrazole disazo compound having a fluoroalkyl group in the pyrazole skeleton has excellent light resistance while maintaining solubility in a low-polar organic solvent. As a result, the present invention has been completed.
That is, the gist of the present invention is as follows.

[1] A solvent having a relative dielectric constant at 22 ° C. at a measurement frequency of 1 kHz of 3.0 or less and a water solubility at 25 ° C. of 20 mg / L or less, and a pyrazole represented by the following general formula (1) Ink containing a disazo compound.

(In the formula, R ¹ represents a fluoroalkyl group which may have a substituent, R ² represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and Q ¹ represents an aryl group which may have a substituent, and Q ² represents an arylene group which may have a substituent.

[2] The ink according to [1], wherein R ¹ is a fluoroalkyl group having 1 to 6 carbon atoms. [3] The ink according to [1] or [2], wherein R ² is an alkyl group having 1 to 20 carbon atoms which may have a substituent.
[4] The ink according to any one of [1] to [3], wherein Q ¹ is a phenyl group which may have a substituent or a naphthyl group which may have a substituent.
[5] Any of [1] to [4], wherein Q ² is a 1,4-phenylene group which may have a substituent or a 1,4-naphthylene group which may have a substituent. The ink described in 1.
[6] An electrowetting display including the ink according to any one of [1] to [5].
[7] A pyrazole disazo compound represented by the following general formula (1).

(In the formula, R ¹ represents a fluoroalkyl group having 1 to 6 carbon atoms, R ² represents an alkyl group having 3 to 6 carbon atoms which may have a substituent, and Q ¹ has a substituent. The substituent may be a further substituted alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, and Q ² may have a substituent. And may be a 1,4-phenylene group, and the substituent represents an alkyl group having 1 to 10 carbon atoms which may further have a substituent.

  The pyrazole disazo compound of the present invention and the ink containing the pyrazole disazo compound have particularly a certain degree of solubility in a low-polar solvent and are excellent in light resistance. It is useful for the ink produced. The display has a display part containing ink, a display that displays an image by controlling voltage application of the display part, a display that displays an image by changing a coloring state by voltage application, and electrophoresis in the display part It is particularly useful for displays and EWD that display using particles or aqueous media.

  Embodiments of the present invention will be specifically described below, but the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

1. About Pyrazole Disazo Compound Used in the Present Invention The pyrazole disazo compound used in the ink of the present invention is a compound represented by the following general formula (1).

In general formula (1), R ¹ represents a fluoroalkyl group which may have a substituent, and R ² represents an alkyl group which may have a substituent or an aryl group which may have a substituent. Q ¹ represents an aryl group which may have a substituent, and Q ² represents an arylene group which may have a substituent.

1-1. About R ^{1 In the} general formula (1), R ¹ represents a fluoroalkyl group which may have a substituent. By making R ¹ a uroalkyl group, the molecular orbital of the compound is likely to spread over the whole, so that the light resistance is considered to be improved.
Specific examples of R ¹ include trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, heptafluoroisopropyl group, nonafluorobutyl group, nonafluoroisobutyl group, nonafluoro-s-butyl group, nonafluoro-t-butyl. Group, undecafluoropentyl group, tridecafluorohexyl group, pentadecafluoroheptyl group, heptadecafluorooctyl group, nonadecafluorononyl group, henicosafluorodecanyl group and the like. Among these, a C1-C6 fluoroalkyl group is preferable, and a trifluoromethyl group or a pentafluoroethyl group is particularly preferable. This is because the solubility in the solvent used in the present invention can be improved.

The substituent for the fluoroalkyl group represented by R ¹ includes a halogen group, alkoxy group, aryl group, cyano group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, acylamino group, dialkylamino group, alkyl group. Examples thereof include an arylamino group, a diarylamino group, an alkylsulfonylamide group, an arylsulfonylamide group, a trialkylsilyl group, a trialkoxysilyl group, and a thioalkyl group.

1-2. For R ² R ² represents an aryl group which may have an alkyl group or a substituent which may have a substituent. As the alkyl group for R ² , methyl group, ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, sec-butyl group, isobutyl group, tert-butyl group, cyclobutyl group, pentyl group, isopentyl group, neopentyl group Straight chain, branched and cyclic alkyl groups such as tert-pentyl group and cyclopentyl group. The alkyl group for R ² is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 3 to 6 carbon atoms, and particularly preferably a branched alkyl group having 3 to 6 carbon atoms. By setting the number of carbon atoms in the alkyl group to an appropriate number, solubility in a low polarity solvent can be maintained.

Examples of the aryl group for R ² include hydrocarbon aryl groups such as a phenyl group and a naphthyl group, and heteroaryl groups such as a pyridyl group and a quinolinyl group.
R ² is preferably an alkyl group which may have a substituent rather than an aryl group which may have a substituent, from the viewpoint of solubility in a low polarity solvent.
The alkyl group or aryl group of R ² may have an arbitrary substituent. Substituents include halogen groups, alkoxy groups, aryl groups, cyano groups, alkoxy groups, aryloxy groups, alkoxycarbonyl groups, aryloxycarbonyl groups, acylamino groups, dialkylamino groups, alkylarylamino groups, diarylamino groups, alkyl groups. Examples thereof include a sulfonylamide group, an arylsulfonylamide group, a trialkylsilyl group, a trialkoxysilyl group, and a thioalkyl group.

1-3. Q ¹ Q ¹ represents an aryl group which may have a substituent. Examples of the aryl group of Q ¹ include hydrocarbon aryl groups such as a phenyl group and a naphthyl group; heteroaryls such as a pyridyl group, a quinolinyl group, a thiazolyl group, an isothiazolyl group, a pyrazolyl group, and an imidazolyl group. In view of solubility in a low polarity solvent, the aryl group of Q ¹ is preferably a hydrocarbon aryl group such as a phenyl group or a naphthyl group, and more preferably a phenyl group.

The aryl group of Q ¹ may have an arbitrary substituent. Examples of the optional substituent that the aryl group of Q ¹ may have include an alkyl group, an alkoxy group, an alkoxycarbonyl group, an acyloxy group, an alkylcarbamoyl group, a dialkylcarbamoyl group, an acylamino group, an N-alkylacylamino group, and a thioalkyl. Group, halogen atom, cyano group and the like. As the optional substituent that the aryl group of Q ¹ may have, an alkyl group, an alkoxy group, an alkoxycarbonyl group, and an acyloxy group are preferable from the viewpoint of solubility in a low-polarity solvent, and the carbon number thereof is 1 to 20 It is preferable that it is 3-10. As the optional substituent that the aryl group of Q ¹ may have, an alkyl group or an alkoxy group is more preferable. The optional substituent that the aryl group of Q ¹ may have may further have a substituent.
Incidentally, substituents for the aryl group for Q ¹ may be a plurality in one, if a plurality, may be the same or different.

1-4. Q ² For Q ² is an arylene group which may have a substituent. Examples of the arylene group of Q ² include hydrocarbon-based arylene groups such as phenylene group and naphthylene group; heteroarylene groups such as pyridinediyl group, quinolinediyl group, thiazolediyl group, isothiazolediyl group, pyrazolediyl group, and imidazolediyl group Is mentioned. In view of solubility in a low polarity solvent, the arylene group of Q ² is preferably a hydrocarbon-based arylene group such as a phenylene group or a naphthylene group, and more preferably a 1,4-phenylene group or a 1,4-naphthylene group.

Examples of the substituent that the arylene group of Q ² may have include the same groups as those listed as the substituent of the aryl group of Q ^1. Particularly preferable substituents include, for example, a methyl group and an ethyl group. C1-C4 alkyl groups, such as these, are mentioned. By introducing these substituents, Q ² becomes non-planar, so that the solubility in a low polarity solvent is easily improved. In addition, examples of the substituent further included in the alkyl group include a halogen group, an alkoxy group, an aryl group, a cyano group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acylamino group, a dialkylamino group, and an alkylaryl. Examples thereof include an amino group, a diarylamino group, an alkylsulfonylamide group, an arylsulfonylamide group, a trialkylsilyl group, a trialkoxysilyl group, and a thioalkyl group. Especially, it is preferable that carbon number of the whole alkyl group including the substituent which further has is 1-8, and it is more preferable that it is C1-C6. This is because the solubility in the solvent used in the present invention can be improved.
Incidentally, the substituent of the arylene group Q ² 'may be a plurality in one, if a plurality, may be the same or different, Q ² from the ease of availability of raw materials, unsubstituted is particularly preferred.

1-5. Specific Examples of Pyrazole Disazo Compounds The following are specific examples of pyrazole disazo compounds used in the ink of the present invention, but the present invention is not limited to these unless it exceeds the gist.

1-6. Method for Producing Pyrazole Disazo Compound The pyrazole disazo compound used in the ink of the present invention can be synthesized as shown in the following reaction formula.

  The pyrazolone derivative on the right side of the above formula can be obtained by reacting a β-ketoester derivative with a hydrazine derivative.

  The pyrazole disazo compound on the right side of the above formula can be obtained by diazotizing a monoazo compound and coupling with the pyrazolone derivative.

1-7. Characteristics of Pyrazole Disazo Compound When the pyrazole disazo compound used in the ink of the present invention has a substituent, the molecular weight including the substituent is preferably 2000 or less, and more preferably 1000 or less. Moreover, it is preferable that it is 300 or more. When the molecular weight is in the above range, a good gram extinction coefficient can be obtained.

  The pyrazole disazo compound used in the ink of the present invention is excellent in solubility in a low polarity solvent, particularly in a hydrocarbon solvent, and has a solubility in n-decane of usually 0.1% by weight or more, preferably 0.8. 5% by weight or more, more preferably 1.0% by weight or more. The higher the solubility, the better, but it is usually about 80% by weight or less. When the solubility is in the above range, display in EWD or the like is likely to be possible.

Examples of the method for measuring the solubility in a low polarity solvent include the following methods. That is, a compound is added until a residue remains in a low polarity solvent, left at a certain temperature, and then filtered to obtain a saturated solution of the compound. The resulting solution is diluted to an appropriate concentration and the absorption spectrum is measured.
From the values of absorption maximum wavelength, gram extinction coefficient, molar extinction coefficient in the 350 to 800 nm wavelength region measured in advance at an appropriate concentration, and the previously measured dilution rate of the saturated solution and the absorption spectrum of the diluted solution, the solubility (wt% ) And the product of the molar extinction coefficient at the absorption maximum wavelength and the molar concentration of the saturated solution.

Note that the pyrazole disazo compound used in the ink of the present invention is desirably water-insoluble when used in an electrowetting display. Here, “water-insoluble” means that the solubility in water at 25 ° C. and 1 atm is usually 0.1% by weight or less, preferably 0.01% by weight or less.
The pyrazole disazo compound used in the ink of the present invention exhibits a yellowish color tone, and when dissolved in a low polarity solvent, usually has a maximum absorption wavelength of 350 to 500 nm, preferably 380 to 480 nm in a wavelength range of 350 to 800 nm. Is shown. Furthermore, it is preferable not to have an absorption maximum in a wavelength region other than 350 to 500 nm. The molar extinction coefficient is preferably 10,000 (L · mol ⁻¹ · cm ⁻¹ ) or more, and 15000 (L
More preferably, it is more than mol ⁻¹ · cm ⁻¹ ), and more preferably 20,000 (L · mol ⁻¹ · cm ⁻¹ ) or more in order to satisfy performance such as EWD.

Furthermore, the molar extinction coefficient ε (L · mol ⁻¹ · cm ⁻¹ ) at the absorption maximum wavelength of the pyrazole disazo compound used in the ink of the present invention in the n-decane solution and the n ⁻ of the azo compound at 5 ° C. The value of the product εC with the saturated concentration C (mol·L ⁻¹ ) relative to decane is preferably 200 cm ⁻¹ or more, more preferably 500 cm ⁻¹ or more, and more preferably 1000 cm ⁻¹ or more. A higher εC value is preferable because the colorability is high, and there is no particular upper limit, but it is usually 100000 cm ⁻¹ or less.

2. About Ink of the Present Invention The ink of the present invention contains at least one pyrazole disazo compound described above. The ink of the present invention may contain only one kind of pyrazole disazo compound or two or more kinds, and the ratio thereof is also arbitrary.
In addition to the pyrazole disazo compound, the ink of the present invention may contain another coloring compound in order to obtain a desired color tone. For example, a pyrazole disazo compound may be mixed with red and blue pigments to make it black.

Furthermore, the ink of the present invention is used for displays such as EWD by dissolving the above-mentioned pyrazole disazo compound and other coloring compounds used as necessary in a low polarity solvent such as an aliphatic hydrocarbon solvent. Ink.
About the density | concentration of the pyrazole disazo type compound in the ink of this invention, it prepares by arbitrary density | concentrations according to the objective. For example, when used as a dye compound for EWD, it is usually used at a concentration of 1% by mass or more, diluted to a non-polar solvent according to the required concentration, preferably 3% by mass or more, more preferably 5%. It is at least mass%. Moreover, about 80 mass% or less is preferable normally.

2-1. Other dye compounds that the ink of the present invention may contain As other dye compounds that the ink of the present invention may contain, among dye compounds having solubility and dispersibility in the solvent to be used. , And can be arbitrarily selected within a range not impairing the effects of the compound of the present invention.
For example, when the ink of the present invention is used for EWD, the other dye compound that may be contained in the ink of the present invention is any dye selected from those soluble in a low polarity solvent such as an aliphatic hydrocarbon solvent. Can be used. Specific examples include oil blue N (alkylamine-substituted anthraquinone), Solvent Green, Sudan Red, Sudan Black, and the like.

2-2. Solvent used in the ink of the present invention A display or optical shutter to which the ink of the present invention is applied uses a low-polarity solvent as the ink solvent. The ink of the present invention has a layer such as a water layer or an oil layer, and can be used for a display device based on a break up or a move side. In order to make the display clear, it is necessary that the oil layer containing the ink does not mix with the water layer and stably split or move, so that the solvent has low compatibility with water and low polarity. Something is required. By including such a solvent and a pyrazole disazo compound in the ink, the oil layer can be stably split or moved.

The solvent used in the ink of the present invention has a relative dielectric constant of 3.0 or less measured at a frequency of 1 KHz and 22 ° C. Preferably it is 2.5 or less, More preferably, it is 2.2 or less. The lower limit of the relative dielectric constant is not particularly limited, but is usually 1.5 or more, preferably 1.8 or more. A method for measuring the relative dielectric constant of the solvent according to the present invention will be described below.
It is measured by an impedance meter method using an LCR meter. Equivalent parallel when a test signal voltage of 0.1 V is applied at room temperature (25 ° C.) and measurement frequency (1 kHz) after the solvent is sandwiched between parallel flat glass substrates with ITO electrodes facing each other with an electrode spacing of 30 μm. The capacitance is measured, and the relative dielectric constant is determined by calculation using the following formula.
Relative permittivity = Equivalent parallel capacitance × electrode spacing / electrode area / vacuum permittivity (ε0)

When a plurality of solvents are mixed and used as the solvent of the ink of the present invention, the relative dielectric constant indicates the relative dielectric constant of the entire mixed solvent.
When the relative dielectric constant of the layer containing the ink is in the above range, the display device tends to be driven without any trouble. For example, when the other layer that does not contain ink is a liquid such as water or a salt solution that is electrically conductive or polar, the relative dielectric constant of the solvent used in the layer that contains the ink is in the above range. The layers tend not to mix.

The solvent used in the present invention has a solubility in water at 25 ° C. of 20 mg / L or less. Preferably it is 10 mg / L or less, More preferably, it is 5 mg / L or less. When the solubility in water is not more than the above specific value, for example, the oil layer does not mix with the water layer and the display device tends to be driven without any trouble.
The method for measuring the solubility of the solvent according to the present invention in water is shown below.

30 g of pure water and 8 g of solvent are placed in a 110 mL vial and shaken at 25 times in a thermostatic bath at 25 ° C. for 4 hours. The liquid after shaking is centrifuged (6000 × g, 5 minutes), the aqueous layer is sampled, and the concentration of the dissolved solvent is quantified by gas chromatography.
In addition, when the solvent kind currently used is unknown, the solubility with respect to water can be measured by said method by identifying a solvent kind by mass spectrometry etc. When a plurality of solvents are mixed and used as a solvent, the solubility in water refers to the solubility of the entire mixed solvent.

  The boiling point of the solvent used in the ink of the present invention is not particularly limited, but is preferably 120 ° C. or higher, more preferably 150 ° C. or higher, and particularly preferably 170 ° C. or higher. Moreover, it is preferable that it is 300 degrees C or less. If the boiling point is not too high, the melting point and viscosity of the solvent do not become too high, and the drive tends to be smooth when used in a display device. Moreover, since the boiling point is not too low, it becomes difficult to volatilize, and stability and safety tend to be obtained.

  The viscosity of the solvent used in the ink of the present invention is not particularly limited, but the viscosity when the solvent temperature is 25 ° C. is preferably 0.1 mPa · s or more. Further, it is preferably 10000 mPa · s or less, more preferably 1000 mPa · s or less, and particularly preferably 100 mPa · s or less. When the viscosity of the solvent is not too high, the compound or the like is easily dissolved, and the drive tends to be smooth when used in a display device.

A solvent can be used individually or in mixture. Specific examples include hydrocarbon solvents, fluorocarbon solvents, fluorine inert liquids and silicone oils.
Examples of the hydrocarbon solvent include a linear or branched aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, an aromatic hydrocarbon solvent, and petroleum naphtha.
Examples of the aliphatic hydrocarbon solvent include n-decane, isodecane, decalin, nonane, dodecane, isododecane, tetradecane, hexadecane, and isoalkanes.

Examples of alicyclic hydrocarbon solvents include Isopar E, Isopar G, Isopar H, Isopar L, Isopar M (registered trademark, manufactured by Exxon Mobil Corporation), IP Solvent (registered trademark, manufactured by Idemitsu Petrochemical Co., Ltd.). ) And Saltol (manufactured by Philips Oil Co., Ltd.).
Examples of the aromatic hydrocarbon solvent include alkyl naphthalene and tetralin.

Examples of petroleum naphtha solvents include shell S.I. B. R. Shellzol 70, Shellzol 71 (manufactured by Shell Petrochemical Co., Ltd.), Pegasol (manufactured by Exxon Mobil Co., Ltd.), Hyzosol (manufactured by Nippon Oil Co., Ltd.)
The fluorocarbon solvent is mainly a fluorine-substituted hydrocarbon, and examples thereof include perfluoroalkanes represented by C _n F _{2n + 2} such as C ₇ F ₁₆ and C ₈ F ₁₈ . Examples of commercially available products include Fluorinert PF5080, Fluorinert PF5070 (manufactured by Sumitomo 3M), and the like.

Examples of the fluorinated inert liquid include Fluorinert FC series (manufactured by Sumitomo 3M). Examples of fluorocarbons include Crytox GPL series (registered trademark, manufactured by DuPont Japan Limited). Examples of chlorofluorocarbons include: Examples of iodinated fluorocarbons such as HCFC-141b (manufactured by Daikin Industries, Ltd.), F (CF ₂ ) ₄ CH ₂ CH ₂ I, F (CF ₂ ) ₆ I, etc. include I-1420, I-1600 (Daikin). Fine Chemicals Laboratory).

Examples of the silicone oil include low-viscosity synthetic dimethylpolysiloxane, and examples of commercially available products include KF96L (manufactured by Shin-Etsu Silicone) and SH200 (manufactured by Toray Dow Corning Silicone).
Among these solvents, in the use of the display to which the present invention is applied, an aliphatic hydrocarbon solvent is preferable from the viewpoint of preventing mixing with an aqueous layer, more preferably tetradecane, decalin, or n-decane, particularly preferably. Is n-decane.

  Moreover, although it is good also as a mixed solvent containing the solvent different from the said solvent, in that case, it is preferable that at least 1 chosen from the group which consists of a hydrocarbon type solvent, a fluorocarbon type solvent, and silicone oil is included. The content of the preferable solvent is usually 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more based on the whole solvent.

  When a mixed solvent is used in the present invention, it is considered that the interaction between the solvents is relatively small, and the relative permittivity of the mixed solvent is determined by adding the volume fraction of each to the relative permittivity of each solvent constituting the mixed solvent. Approximate by multiplying and totaling values. Similarly, the solubility of the mixed solvent in water is approximated by a total value obtained by multiplying the solubility of each solvent constituting the mixed solvent in water by each mole fraction.

The ink of the present invention contains the above-mentioned specific solvent and a pyrazole disazo compound, and is obtained by dissolving a pyrazole disazo compound and other compounds and additives used as necessary in a solvent. .
Here, the dissolution means that the pyrazole disazo compound does not need to be completely dissolved in the solvent, and the pyrazole disazo compound passes through a filter of about 0.1 micron and the extinction coefficient can be measured. It is sufficient that the fine particles of the compound are dispersed.

In addition, the ink of the present invention may contain an optional additive as necessary. Examples of these additives include dispersants, antistatic agents, antifoaming agents, antioxidants, viscosity adjusting agents and the like. The content of the additive is not particularly limited, but is usually used at about 20% by weight or less based on the total amount of ink.

(EWD of the present invention)
<Configuration of EWD of the Present Invention>
The configuration of the electrowetting display of the present invention may be a conventionally known configuration as appropriate. An example is as follows. A transparent electrode such as ITO is provided on a substrate, a water repellent (hydrophobic) insulating film is provided thereon, and a lattice-like partition is provided thereon. The portion surrounded by the partition walls is filled with the colored oil containing the ink of the present invention, and the upper portion thereof is bonded with the counter substrate on which the transparent electrode is formed by being filled with water.

<Method for producing EWD of the present invention>
The manufacturing method of the electrowetting display of the present invention may be a conventionally known manufacturing method as appropriate. An example is as follows. A suitable resin material is applied and formed on a substrate having a transparent electrode such as ITO formed by sputtering, and then patterned by photolithography to form a hydrophobic insulating film and a partition member. A colored hydrophobic ink containing the ink of the present invention is added to a portion surrounded by the partition walls, and a hydrophilic liquid is further added. Further, an EWD is manufactured by bonding a counter substrate having a transparent electrode such as ITO.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

[Example 1]
The dye 1 which is a pyrazole disazo compound used in Example 1 was synthesized as follows.

Concentrated hydrochloric acid (1.0 mL) was added dropwise to a mixed solution of ethyl 4,4,4-trifluoroacetoacetate (5.5 g) and tert-butylhydrazine hydrochloride (3.7 g) in ethanol (20 mL) and refluxed. Stirred under for 33 hours. The solvent was distilled off after standing_to_cool and ethyl acetate was added. Washing with water three times, the solvent was distilled off. The obtained crude product was washed with hexane and dried to obtain Compound 1 (3.4 g).

The above compound 2 (760 mg), N-methylpyrrolidone (12 mL) and concentrated hydrochloric acid (0.9 mL) were mixed and stirred at 0 to 5 ° C. Sodium nitrite (217 mg) aqueous solution (3
mL) was added slowly and stirred for 1 hour. Sulfamic acid (58 mg) was added to obtain a diazonium solution.
In a separate container, the obtained compound 1 (656 mg), potassium carbonate (311 mg) and 1M aqueous sodium hydroxide solution (3 mL) were mixed and stirred at 0 to 5 ° C. The diazonium solution synthesized earlier was slowly added thereto, and the temperature was raised to room temperature after the addition was completed. Toluene (20 mL) was added, liquid separation operation was performed 3 times with water (20 mL), and the solvent was distilled off. The obtained crude product was purified by silica gel column chromatography (hexane / ethyl acetate = 49/1 to 3/1). The obtained compound was dried to obtain the dye 1 (208 mg) corresponding to the pyrazole disazo compound represented by the general formula (1).

[Example 2]
The dye 2 corresponding to the pyrazole disazo compound represented by the general formula (1) used in Example 2 was synthesized as follows.

  The following compound 11 (6.0 g) was added dropwise to a mixture of the following compound 12 (5.1 g) and acetic acid (85 mL) at room temperature, and the mixture was stirred at room temperature for 2 hours, and then a mixture of water and methanol 1: 1 (40 mL) was added. The precipitate was separated by suction filtration, washed with cold methanol and dried to obtain Compound 13 (5.7 g).

  To a mixture of compound 13 (5.6 g) and ethanol (166 mL) was added a solution of sodium sulfide nonahydrate (10.8 g) in water (40 mL), and the mixture was heated to reflux for 1 hour. After cooling to room temperature, water (66 mL) was added, the mixture was cooled in an ice bath, the precipitate was separated by suction filtration, washed with a mixture of methanol and water 1: 1 (40 mL), dried and then compound 14 (3.79 g). )

  A mixture of compound 14 (3.79 g) and N-methylpyrrolidone (83 mL) was cooled in an ice bath, and a solution obtained by diluting concentrated hydrochloric acid (5.6 mL) with water (47 mL) was added. A solution of sodium nitrite (1.26 g) in water (10 mL) was added, and the mixture was stirred for 2 hours. Then, a 10 wt% aqueous sulfamic acid solution was added to eliminate excess nitrous acid to obtain a diazo solution. In a separate container, Compound 1 (2.94 g), sodium hydroxide (0.48 g), water (47 mL), sodium carbonate (1.19 g) were taken, cooled in an ice bath, and the diazo solution was added dropwise. During this time, a 1N aqueous sodium hydroxide solution was simultaneously added dropwise to keep the system at pH 8.8-9.2. The precipitate is separated by suction filtration, washed with an aqueous methanol solution, purified by silica gel column chromatography, the obtained solid is washed with methanol, and the obtained compound is dried to obtain a compound represented by the general formula (1). The following dye 2 (2.7 g) corresponding to the pyrazole disazo compound thus obtained was obtained.

[Example 3]
A dye 3 corresponding to the pyrazole disazo compound represented by the general formula (1) used in Example 3 was synthesized as follows.

  The following compound 4 (5.23 g), N-methylpyrrolidone (43 mL), potassium carbonate (4.46 g), 2-ethylhexyl bromide (6.24 g) and potassium iodide (0.357 g) were mixed, and at 80 ° C. After stirring for 3 hours, water was added, extracted with toluene, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. Methanol was added and the resulting solid was filtered off to obtain the following compound 5 (5.7 g).

  A solution of sodium sulfide nonahydrate (9.61 g) in water (40 mL) was added dropwise to a solution of the above compound 5 (5.7 g) in ethanol (150 mL), and the mixture was heated to reflux for 1 hour. The mixture was cooled to room temperature, water was added, and the mixture was extracted with ethyl acetate. The ethyl acetate layer was washed with water and concentrated under reduced pressure to obtain the following compound 6 as an oil.

  A mixture of the above compound 6 (1.3 g), N-methylpyrrolidone (16 mL) and 1N hydrochloric acid (14.4 mL) was cooled in an ice bath, an aqueous solution of sodium nitrite (0.29 g) was added, and the mixture was stirred for 2 hours. . An aqueous solution of sulfamic acid (0.078 g) was added to obtain a diazo solution. Compound 1 (0.833 g), sodium carbonate (0.318 g) and 1N aqueous sodium hydroxide solution (3 mL) were mixed in a separate container, cooled in an ice bath, and the diazo solution was added. After 2 hours, the temperature was raised to room temperature, water was added, the mixture was extracted with toluene, and concentrated under reduced pressure. The product was purified by silica gel column chromatography, and the obtained solid was washed with methanol to obtain Dye 3 (1.16 g) as an orange solid.

[Comparative Example 1]
Comparative dye 1 which is a dye compound used in Comparative Example 1 is an azo dye compound corresponding to Example 2 of Patent Document 1, and was synthesized by the method described in Patent Document 1.

[Evaluation of dye solution]
1 mg of each dye synthesized in Examples 1 to 3 and Comparative Example 1 was dissolved in 100 mL of n-decane. The obtained solution was added to a quartz cell having a measurement optical path length of 10 mm, and an absorption spectrum was measured with a Hitachi spectrophotometer U-4100. The absorption maximum wavelength λ _max [nm] and the molar extinction coefficient ε [L · mol ⁻¹ · cm ⁻¹ ] were determined from the obtained spectrum.
In addition, when the relative dielectric constant of n-decane and the solubility in water were measured by the above-mentioned method, the relative dielectric constant was 2.0 and the solubility in water was 1 mg / L or less.

[Measurement of saturation concentration]
The saturation concentration C with respect to n-decane of each dye was measured as follows.
Each dye synthesized in Examples 1 to 3 and Comparative Example 1 was added to n-decane until dissolved residue was generated, and sonicated at 30 ° C. for 30 minutes. After the addition, each was sonicated at 30 ° C. for 30 minutes. After standing at 5 ° C. for 24 hours, it was subjected to centrifugal filtration with a 0.1 micron filter using a microcentrifuge (centrifugal force 5200 × g). The obtained saturated solution is diluted to an appropriate concentration, and an absorption spectrum is measured with a Hitachi spectrophotometer U-4100 using a quartz cell having a measurement optical path length of 10 mm, and an absorption maximum wavelength and an absorption maximum wavelength λ _max are measured. The concentration of each compound was determined from the relationship between the absorbance at [nm] and the molar extinction coefficient ε [L · mol ⁻¹ · cm ⁻¹ ] measured in advance, and the saturated concentration C [mol·L ⁻¹ ] was calculated. Moreover, the value of the product ε · C of the molar extinction coefficient ε [L · mol ⁻¹ · cm ⁻¹ ] and the saturated concentration C [mol·L ⁻¹ ] was determined.

[Light resistance test]
Using each dye compound synthesized in Examples 1 to 3 and Comparative Example 1, a 0.2% by weight n-decane solution was prepared, put in a cell having an optical path length of 10 μm, and sealed with an epoxy resin. Samples for measurement were prepared. For these samples, xenon light using a weather meter (Atlas Ci4000) a (340 nm 0.55 W / ^{m 2} irradiance) was irradiated for 40 hours light. During irradiation, the temperature inside the test chamber of the weather meter was kept at 33 ° C. The residual ratio of each compound was calculated by the following formula.

  Table 1 shows a summary of the absorption maximum wavelength, molar extinction coefficient, and dye residual ratio. The saturation concentration and the value of ε · C are also shown.

  As shown in Table 1, it was found that Examples 1 to 3 had higher dye residual ratio after the light resistance test and improved light resistance as compared with Comparative Example 1. In Examples 1 to 3, the saturation density was a level usable as an ink such as EWD. That is, it has been found that the pyrazole disazo compound of the present invention can achieve better light resistance while maintaining a certain solubility in a low-polarity solvent, compared to conventional azo dye compounds.

  Since the pyrazole disazo compound of the present invention has solubility in a low polarity solvent and excellent light resistance, it is useful as a yellow dye compound such as EWD.

Claims (7)

A solvent whose relative dielectric constant at 22 ° C. is 3.0 or less at a measurement frequency of 1 kHz and whose solubility in water at 25 ° C. is 20 mg / L or less, and a pyrazole disazo compound represented by the following general formula (1) Ink containing.

(In the formula, R ¹ represents a fluoroalkyl group which may have a substituent, R ² represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and Q ¹ represents an aryl group which may have a substituent, and Q ² represents an arylene group which may have a substituent. The ink according to claim 1, wherein R ¹ is a fluoroalkyl group having 1 to 6 carbon atoms. The ink according to claim 1 or 2, wherein R ² is an alkyl group having 1 to 20 carbon atoms which may have a substituent. Wherein Q ¹ is, a phenyl group or a substituted group may have a substituent is also a naphthyl group, ink according to any one of claims 1 to 3. The Q ² is the 1,4-phenylene group which may have a substituent or the 1,4-naphthylene group which may have a substituent, according to any one of claims 1 to 4. ink.   An electrowetting display comprising the ink according to any one of claims 1 to 5. A pyrazole disazo compound represented by the following general formula (1).

(In the formula, R ¹ represents a fluoroalkyl group having 1 to 6 carbon atoms, R ² represents an alkyl group having 3 to 6 carbon atoms which may have a substituent, and Q ¹ has a substituent. The substituent may be a further substituted alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms, and Q ² may have a substituent. And may be a 1,4-phenylene group, and the substituent represents an alkyl group having 1 to 10 carbon atoms which may further have a substituent.