Halogenated zinc phthalocyanine pigment as well as preparation method and application thereof

Abstract

The invention relates to the technical field of liquid crystal display pigments, in particular to a halogenated zinc phthalocyanine pigment as well as a preparation method and application thereof. The invention relates to a halogenated zinc phthalocyanine pigment, which has a structural formula as shown in formula (I), in which X1-X16 independently represent chlorine, bromine and hydrogen, the average substitution amount of chlorine is 4-5, and the average substitution amount of bromine is 6-12. The halogenated zinc phthalocyanine pigment prepared by the invention is used for a color filter, and has the advantages of thin film and high brightness during specific chromaticity display.

Description

Technical Field

[0001] This invention relates to the field of pigment technology for liquid crystal displays, and particularly to a zinc halide phthalocyanine pigment, its preparation method, and its application. Background Technology

[0002] In recent years, with the continuous development of liquid crystal display technology, there have been requirements for higher brightness and a wider color reproduction range for green colorants in liquid crystal display color filters.

[0003] In achieving high brightness, the key lies in selecting pigments with high backlight transmittance. For example, pigment green 58, due to its relatively high backlight transmittance, is used in color filters to enhance brightness.

[0004] To expand the color reproduction range, it is necessary to increase the chroma of the pigments contained in the color filter. Generally, Pigment Green 7, which is better suited for thin-film processing at specific chromaticities compared to Pigment Green 36 and Pigment Green 58, is chosen as the main pigment. Especially with the increasing standards for high color reproduction displays, Pigment Green 36 and Pigment Green 58 are insufficient to achieve the required pixel count. However, using Pigment Green 7 also presents significant problems. Compared to Pigment Green 36 and Pigment Green 58, Pigment Green 7 has lower transmittance, leading to reduced brightness in the resulting display. To compensate for insufficient brightness, the backlight intensity is usually increased, but this introduces a new problem of high power consumption.

[0005] Furthermore, Chinese Patent CN105829925A discloses a green pigment composition for color filters and a color filter, wherein the average number of chlorine atoms is 2-5 and the average number of halogen atoms is 10-14, providing a wide color reproduction range when the film thickness is set to 1.5µm-2.4µm. However, in order to achieve energy saving in displays and reduce manufacturing costs, there is still an urgent need to further improve the luminance of color filters.

[0006] In summary, in the field of green colorants for LCD color filters, no effective solution has yet been found that can perfectly balance high brightness and expanded color reproduction range while meeting the requirements of energy saving and cost reduction. Summary of the Invention To address the aforementioned technical problems in the prior art, this invention provides a zinc halide phthalocyanine pigment, its preparation method, and its application.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A first aspect of the present invention is to provide a zinc halide phthalocyanine pigment having the structural formula shown in formula (I):

[0008] Among them, X1-X 16 The three elements, chlorine, bromine, and hydrogen, are independent of each other. The average substitution amount of chlorine is 4-5, and the average substitution amount of bromine is 6-12.

[0009] The zinc halide phthalocyanine pigment provided by this invention has a high number of chlorine atom substitutions, and the number and position of chlorine atom substitutions in each phthalocyanine molecule are basically controllable, resulting in low product composition diversity and high pigment color purity. When used to prepare color filters, the zinc halide phthalocyanine pigment provided by this invention has the advantages of thin film thickness and high brightness when displaying specific color values.

[0010] The design concept of this invention is that, in the preparation of color filters, the mass of pigment used is usually fixed. The smaller the average molecular weight of the pigment, the greater its molar number in the color filter, the higher the concentration, and the better the color rendering. Halogenated phthalocyanines are generally bromine-chlorine substituted zinc phthalocyanines, in which the molecular weight of the chlorine atom is lower than that of the bromine atom. Appropriately increasing the substitution amount of chlorine atoms can reduce the average molecular weight of the pigment, increase the pigment concentration, and increase the pigment chroma. For example, the chlorine substitution amount in the Pigment Green G7 molecule is 15-16, while the chlorine substitution amount in Pigment Green G36 and Pigment Green G58 is small, and the bromine substitution amount is large. Compared with Pigment Green G36 and Pigment Green G58, Pigment Green G7 has a smaller molecular weight. Under the condition of using the same amount of pigment, Pigment Green G7 has a larger molar number and higher chroma, and can achieve thin film formation better when displaying specific chroma. However, when the chlorine substitution amount is high, the pigment transmittance is low, so the chlorine substitution amount cannot exceed a certain range.

[0011] Furthermore, as the substitution rate of chlorine atoms in halophthalocyanine molecules increases, chlorine atoms become randomly distributed across various positions on the phthalocyanine ring, leading to a diversification of the composition of halophthalocyanine pigments and a broadening of the pigment's transmission spectrum. This, in turn, results in low color purity and decreased brightness in halophthalocyanine pigments. Therefore, the substitution positions of chlorine atoms should be appropriately controlled, and the distribution of chlorine atoms in each phthalocyanine molecule should be kept as narrow as possible.

[0012] Common methods for preparing halogenated phthalocyanines include solvent methods and melt methods.

[0013] As a solvent method, zinc phthalocyanine is typically dissolved in chlorosulfonic acid, and halogenation is carried out by introducing bromine and chlorine gas. The amount of bromine and chlorine substitution in the halophthalocyanine can be controlled by adjusting the amount of bromine and chlorine gas introduced. However, this method only controls the average number of chlorine and bromine atoms substituted in the molecule; the number of bromine and chlorine atoms substituted in each molecule cannot be controlled.

[0014] As a common melt reaction method, zinc phthalocyanine is added to a molten system consisting of thioyl chloride, aluminum trichloride, and sodium chloride, followed by the addition of liquid bromine, and reacted at 10-170°C to obtain zinc halophthalocyanine. By controlling the ratio of thioyl chloride to bromine, the reaction temperature, and the reaction time, zinc halophthalocyanine pigments with arbitrary amounts of bromine and chlorine substitution can be obtained. However, this method only allows control over the average number of chlorine and bromine atoms substituted in the molecule; the number of bromine and chlorine atoms substituted in each molecule cannot be controlled.

[0015] This invention provides a method for preparing zinc halophthalocyanine. First, chlorophthalic anhydride is reacted with zinc acetate in the presence of urea to prepare tetrachlorozinc phthalocyanine. Then, the tetrachlorozinc phthalocyanine is reacted with thioyl chloride and bromine in a molten system composed of aluminum trichloride and sodium chloride to prepare crude zinc halophthalocyanine. The obtained crude zinc halophthalocyanine is then subjected to pigmentation treatment to obtain zinc halophthalocyanine pigment.

[0016] First, tetrachlorozinc phthalocyanine is prepared so that each phthalocyanine molecule contains four chlorine atoms, and the substitution positions of the chlorine atoms are controllable, all located at the β-position. In the subsequent reactions of tetrachlorophthalocyanine, by controlling the feeding method, the amount of bromine added, the reaction temperature, and the reaction time, subsequent chlorine atom substitution reactions can be almost completely prevented, and the number of bromine atoms substituted can be controlled. The resulting zinc halide phthalocyanine pigment has a chlorine content of 4-5%, and the number of bromine atoms substituted can be controlled according to actual needs. The obtained zinc halide phthalocyanine pigment has low compositional diversity and high color purity. When preparing color filters for specific colorimetric displays, the obtained zinc halide phthalocyanine pigment has the advantages of thin film thickness and high brightness.

[0017] A second aspect of the present invention is to provide a method for preparing the zinc halide phthalocyanine pigment provided in the first aspect of the present invention, comprising the following steps: S1. Zinc tetrachlorophthalocyanine is prepared by reacting chlorophthalic anhydride with zinc acetate in the presence of urea. S2, zinc tetrachlorophthalocyanine is reacted with thioyl chloride and bromine in a molten system composed of aluminum trichloride and sodium chloride to prepare crude zinc halide phthalocyanine; S3. The crude product of zinc halide phthalocyanine was subjected to pigmentation treatment to obtain zinc halide phthalocyanine pigment.

[0018] Based on the above technical solution, the present invention can also be improved as follows: Further, step S1 specifically includes the following process: adding chlorophthalic anhydride, urea, zinc acetate, and ammonium molybdate to the solvent, stirring evenly, raising the temperature of the reaction system to 180-220℃, turning off the heating after reacting for a period of time, filtering, and washing the filter cake successively with ethanol, alkali solution, acid solution, and water, and then drying to obtain tetrachlorozinc phthalocyanine.

[0019] Furthermore, the solvent is nitrobenzene, alkylbenzene, or trichlorobenzene, and the chlorophthalic anhydride is 4-chlorophthalic anhydride or 3-chlorophthalic anhydride; the reaction system temperature is 180-220℃, preferably 190-200℃; and the reaction time is 2-24h, preferably 6-10h.

[0020] Furthermore, the molar ratio of chlorophthalic anhydride to urea is 1:(1-10), and the molar ratio of chlorophthalic anhydride to zinc acetate is 1:(0.25-1).

[0021] Furthermore, the molar ratio of chlorophthalic anhydride to urea is 1:(4-6), and the molar ratio of chlorophthalic anhydride to zinc acetate is 1:(0.26-0.3).

[0022] Furthermore, the alkaline solution refers to a sodium hydroxide solution with a concentration of 1-5%, and the acid solution is a hydrochloric acid solution with a concentration of 1-5%.

[0023] Furthermore, step S2 specifically includes the following processes: Thionyl chloride, aluminum trichloride, and sodium chloride were added to a reaction flask and stirred until homogeneous. Liquid bromine was then slowly added and stirred until homogeneous again. Zinc tetrachlorophthalocyanine was then added and reacted at a certain temperature for a period of time. The material was then poured into water, washed, and dried to obtain crude zinc halophthalocyanine.

[0024] Furthermore, the mass ratio of zinc tetrachlorophthalocyanine to thiocyanate is 1:(2-4), the mass ratio of zinc tetrachlorophthalocyanine to aluminum trichloride is 1:(2-5), the mass ratio of aluminum trichloride to sodium chloride is (10-4):1, and the mass ratio of zinc tetrachlorophthalocyanine to bromine is 1:(2-5).

[0025] Furthermore, the reaction temperature is 60-140℃, and the reaction time is 2-20h.

[0026] Furthermore, the washing refers to washing the material several times with at least one of the following methods: cold water, hot water, 1-5% NaOH solution, 1-5% hydrochloric acid solution, acetone, and ethanol. There is no particular limitation on the number of washes, generally referring to 1-10 times, or washing the pigment until the acid, inorganic salts, or other impurities cannot be reduced further.

[0027] Furthermore, the pigment treatment described in step S3 refers to a method of mixing and kneading crude zinc halide phthalocyanine pigment with inorganic salts and organic solvents in a kneading device. The kneading device used can be a kneader, ball mill, bead mill, sand mill, ultrafine crusher, etc.

[0028] As an inorganic salt, it can be a water-soluble inorganic salt, such as sodium chloride, potassium chloride, sodium sulfate, etc. The particle size of the inorganic salt can be 0.5-50 μm. The amount of inorganic salt used relative to 1 part of zinc halocyanine pigment can be 1-100 parts, preferably 5-20 parts.

[0029] The organic solvent can be a water-soluble organic solvent, such as: ethylene glycol, diethylene glycol, propylene glycol, glycerol, liquid polyhexane glycol, liquid polypropylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, etc. The amount of organic solvent used, relative to 1 part of zinc halide phthalocyanine pigment, can be 0.01-20 parts, preferably 1-10 parts.

[0030] The kneading temperature can be between 20-150℃. The kneading time can be 2-30 hours.

[0031] After kneading, the material is put into a large amount of water, filtered, washed and dried to obtain halogenated zinc phthalocyanine pigment.

[0032] Furthermore, resin can be added as needed during the kneading process to coat the pigment surface.

[0033] There are no particular restrictions on the type of resin used; natural resins, modified natural resins, synthetic resins, and synthetic resins modified from natural resins can be used. The resin used is further preferably a solid at room temperature that is soluble or partially soluble in a solvent. The amount of resin used is 0.1-20 parts per 100 parts of pigment, preferably 1-5 parts.

[0034] Furthermore, yellow pigment can be added for color adjustment during the kneading process as needed. The preferred yellow pigments are pigments such as Y138, Y139, Y150, Y180, and Y185. The amount of yellow pigment used relative to 100 parts of phthalocyanine pigment can be 0.1-100 parts, preferably 1-20 parts.

[0035] A third aspect of the present invention is to provide a pigment paste comprising the zinc halide phthalocyanine pigment provided in the first aspect of the present invention.

[0036] Another aspect of the present invention is to provide the application of the zinc halide phthalocyanine pigment provided in the first aspect of the present invention in the color filter of a liquid crystal display device.

[0037] Compared with the prior art, the present invention has the following technical effects: A two-step method was used to prepare zinc halide phthalocyanines, which has a high chlorine atom substitution amount and the number and position of chlorine atoms in each phthalocyanine molecule are basically controllable. The product composition has low diversity and the pigment color purity is high. When used in color filters, it has the advantages of thin film thickness and high brightness under specific color development conditions. Attached Figure Description

[0038] Figure 1 The mass spectrum of the zinc tetrachlorophthalocyanine synthesized in Example 1 is shown. Figure 2 The mass spectra of crude zinc halide phthalocyanine pigment A1 and pigment green 58 synthesized in Example 1 are shown. Detailed Implementation

[0039] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a deep understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0040] Synthesis example 1 260 g nitrobenzene, 60 g 4-chlorophthalic anhydride, 88 g urea, 16 g zinc acetate, and 0.5 g ammonium molybdate were added to a 500 mL three-necked flask. The mixture was heated to 190 °C and reacted for 8 hours, after which the heating was turned off. The mixture was cooled to 80 °C and filtered. The filter cake was washed with ethanol until the nitrobenzene odor was eliminated, then further slurried with ethanol, filtered, and then washed twice successively with 5% NaOH solution and 5% hydrochloric acid solution. The filtrate was washed with water until neutral, filtered, and dried to obtain 50 g of zinc tetrachlorophthalocyanine, with a yield of 85%. The mass spectrum of zinc tetrachlorophthalocyanine is shown below. Figure 1 As shown, the theoretical molecular weight is 715.34, and the measured molecular weight is 713.88. 120g of thioyl chloride, 140g of aluminum trichloride, and 20g of sodium chloride were added to a 500mL four-necked flask and stirred until homogeneous. Then, 120g of bromine was added, and after further stirring, 40g of zinc tetrachlorophthalocyanine was slowly added. After the addition was complete, the temperature was slowly raised to 120℃, and the reaction was continued at 120℃ for 10 hours. The mixture was then poured into water, washed successively with water, acetone, and water, filtered, and dried to obtain crude zinc halide phthalocyanine pigment A1. The mass spectrum of A1 is shown below. Figure 2 As shown.

[0041] from Figure 2 It can be seen that the number of peaks in molecule A2 is small, indicating a low degree of compositional diversity. Based on the molecular weight analysis corresponding to the mass spectrometry peaks, the average chlorine substitution amount of A1 is 4.21, and the bromine substitution amount is 10.83. 100g of crude pigment A1, 1000g of sodium chloride, and 105g of diethylene glycol were kneaded at 80℃ for 20 hours. The mixture was then added to water, filtered, washed with water, and filtered again to obtain pigment G1.

[0042] Synthesis example 2 Zinc tetrachlorophthalocyanine was prepared using the process described in Synthesis Example 1.

[0043] 120 g of thioyl chloride, 140 g of aluminum trichloride, and 20 g of sodium chloride were added to a 500 mL four-necked flask and stirred until homogeneous. Then, 70 g of bromine was added, followed by further stirring. Finally, 40 g of zinc tetrachlorophthalocyanine was slowly added. After the addition was complete, the temperature was slowly raised to 120 °C, and the reaction was continued at 120 °C for 10 h. The mixture was then poured into water, washed successively with water, acetone, and water, filtered, and dried to obtain crude zinc halophthalocyanine pigment A2. Mass spectrometry analysis showed that the average chlorine substitution amount of A2 was 4.32, and the bromine substitution amount was 6.15. 100g of crude pigment A2, 1000g of sodium chloride, and 105g of diethylene glycol were kneaded at 80℃ for 20 hours. The mixture was then placed in water, filtered, washed with water, and filtered again to obtain pigment G2.

[0044] Synthesis example 3 Zinc tetrachlorophthalocyanine was prepared using the process described in Synthesis Example 1.

[0045] 120g of thioyl chloride, 140g of aluminum trichloride, and 20g of sodium chloride were added to a 500mL four-necked flask and stirred until homogeneous. Then, 90g of bromine was added, followed by further stirring. Finally, 40g of zinc tetrachlorophthalocyanine was slowly added. After the addition was complete, the temperature was slowly raised to 100℃, and the reaction was continued at 100℃ for 10 hours. The mixture was then poured into water, washed successively with water, acetone, and water, filtered, and dried to obtain crude zinc halophthalocyanine pigment A3. Mass spectrometry analysis revealed that the average chlorine substitution amount of A3 was 4.22%, and the bromine substitution amount was 9.14%. 100g of crude pigment A3, 1000g of sodium chloride, and 105g of diethylene glycol were kneaded at 80℃ for 20 hours. The mixture was then placed in water, filtered, washed with water, and filtered again to obtain pigment G3.

[0046] The bromochlorine substitution amounts of the zinc halophthalocyanines obtained in the synthetic examples are shown in Table 1.

[0047] Table 1. Bromochlorine substitution amount of zinc halophthalocyanines obtained in the synthetic examples

[0048] Examples 1-3, Comparative Examples 1-2: Pigments, dispersants, acrylic resin dispersions, and solvents were added to a glass bottle, with the proportions of each material shown in Table 2. 150g of 0.3mm zirconium balls were added to the glass bottle. The bottle was placed in a shaker and shaken for 24 hours. The zirconium balls were then filtered out, yielding the color pastes of Examples 1-3 and Comparative Examples 1 and 2.

[0049] Table 2. Pigment formulations for the examples and comparative examples

[0050] Take 1 mL of color paste and spin-coat it onto a glass slide at different speeds. Place the glass slide on a hot plate at 120℃ and bake for 3 min, then further bake it in an oven at 230℃ for 1 h to obtain filter sheets with different film thicknesses. The color coordinates and film thicknesses are shown in Table 3.

[0051] Table 3. Color coordinates and film thickness of color filters in the examples and comparative examples

[0052] Add 4g of Pigment Yellow Y138, 9.2g of BYK-161, 9.3g of acrylic resin dispersion (PMA solution, 30% solids content), and 27g of propylene glycol methyl ether acetate to a glass bottle in that order, along with 150g of 0.3mm zirconium balls. Place the glass slide in a shaker and shake for 24 hours. Filter out the zirconium balls to obtain yellow pigment dispersion Y1 for color mixing.

[0053] The color pastes from the examples and the comparative examples were mixed with yellow color paste in different proportions, and color filters were prepared with a film thickness of (x, y) = (0.210, 0.670). The brightness of the resulting color filters was tested. The test results are shown in Table 4.

[0054] Table 4. Brightness and thickness of glass substrates

[0055] As can be seen from the experimental results in Table 4, the prepared halophthalocyanine pigment has a thinner film and higher brightness compared with Pigment Green 7, and can exhibit excellent color reproduction when used in color filters.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A halogenated zinc phthalocyanine pigment, characterized in that, A structure shown in formula (I): wherein X1-X 16 each independently represents chlorine, bromine, hydrogen, the average substitution amount of chlorine is 4-5, and the average substitution amount of bromine is 6-12.

2. A process for the preparation of a halogenated zinc phthalocyanine pigment according to claim 1, characterized in that The method comprises the following steps: S1, chloranil reacts with zinc acetate under the action of urea to prepare zinc phthalocyanine tetrachloride; S2, zinc phthalocyanine tetrachloride reacts with sulfuryl chloride and bromine in a molten system composed of aluminum chloride and sodium chloride to prepare crude halogenated zinc phthalocyanine; S3, the crude halogenated zinc phthalocyanine obtained in step S2 is subjected to pigmentization treatment to obtain halogenated zinc phthalocyanine pigment.

3. The process for the preparation of halogenated zinc phthalocyanine pigments according to claim 2, characterized in that, Step S1 specifically comprises the following process: chloranil, urea, zinc acetate and ammonium molybdate are added into a solvent, the reaction system is stirred uniformly, and then the temperature of the reaction system is raised to 180-220 DEG C, after a period of reaction, the heating is turned off, the filter cake is washed with ethanol, lye, acid solution and water in sequence, and then dried to obtain zinc phthalocyanine tetrachloride.

4. The process for the preparation of halogenated zinc phthalocyanine pigments according to claim 3, characterized in that, The solvent is nitrobenzene, alkylbenzene or trichlorobenzene, the chloranil is 4-chloranil or 3-chloranil, the temperature of the reaction system is 180-220 DEG C, and the reaction time is 2-24 h.

5. The process for the preparation of halogenated zinc phthalocyanine pigments according to claim 2 or 3, characterized in that, The molar ratio of chloranil to urea is 1: (1-10), and the molar ratio of chloranil to zinc acetate is 1: (0.25-1).

6. The process for the preparation of halogenated zinc phthalocyanine pigments according to claim 2, characterized in that, Step S2 specifically comprises the following process: Sulfuryl chloride, aluminum chloride and sodium chloride are added into a reaction flask, stirred uniformly, and then liquid bromine is slowly added, after further stirring, zinc phthalocyanine tetrachloride is added, and after a period of reaction at a certain temperature, the material is poured into water, washed and dried to obtain crude halogenated zinc phthalocyanine.

7. The process for the preparation of halogenated zinc phthalocyanine pigments according to claim 6, characterized in that, The mass ratio of zinc phthalocyanine tetrachloride to sulfuryl chloride is 1: (2-4), the mass ratio of zinc phthalocyanine tetrachloride to aluminum chloride is 1: (2-5), the mass ratio of aluminum chloride to sodium chloride is (10-4): 1, and the mass ratio of zinc phthalocyanine tetrachloride to bromine is 1: (2-5); the reaction temperature is 60-140 DEG C, and the reaction time is 2-20 h.

8. The process for the preparation of halogenated zinc phthalocyanine pigments according to claim 2, characterized in that, Step S3 specifically comprises the following process: the crude halogenated zinc phthalocyanine obtained in step S2 is mixed with inorganic salt and organic solvent in a kneading device, the mixed material is poured into water, washed and dried to obtain the halogenated zinc phthalocyanine pigment.

9. A pigment paste, characterized in that The method comprises the halogenated zinc phthalocyanine pigment of claim 1.

10. The application of the halogenated zinc phthalocyanine pigment of claim 1 to a color filter of a liquid crystal display device.

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