Functional film formation method

Abstract

A method for forming a functional film that suppresses deterioration of an inkjet head member and improves the quality of the functional film. [Solution] The method for forming a functional film includes a preparation step of preparing a liquid containing an organic amine compound, a conductive material, and a solvent containing water, wherein the organic amine compound content is 0.02 mass % or more and 0.40 mass % or less relative to the total mass; an application step of applying the liquid to a medium by an inkjet method; and a removal step of removing the solvent and the organic amine compound from the liquid applied to the medium.

Description

[Technical Field]

[0001] The present invention relates to a method for forming a functional film. [Background technology]

[0002] Conventionally, inkjet printing has been used to apply a liquid to a medium to form various films. Some of these liquids contain a pH adjuster such as an organic amine compound. For example, Patent Document 1 discloses an inkjet ink containing an organic amine such as triethanolamine or triisopropanolamine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-105082 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the ink described in Patent Document 1 is used to form a functional film, it is difficult to improve the quality of the functional film. Specifically, triethanolamine and triisopropanolamine have relatively high boiling points and tend to remain in the film formed by the ink. Therefore, when the ink is used to form a functional film, the remaining organic amine can degrade the quality of the functional film. On the other hand, when an ink that does not contain a pH adjuster is used, there is also the problem that inkjet head components are prone to deterioration. In other words, there is a need for a method of forming a functional film that can suppress deterioration of inkjet head components and improve the quality of the functional film. [Means for solving the problem]

[0005] The method for forming a functional film includes a preparation step of preparing a liquid containing an organic amine compound, a conductive material, and a solvent containing water, wherein the content of the organic amine compound is 0.02 mass % or more and 0.40 mass % or less relative to the total mass; an application step of applying the liquid to a medium by an inkjet method; and a removal step of removing the solvent and the organic amine compound from the liquid applied to the medium. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a table showing the composition and pH of the material liquids used in Experiment 1. [Figure 2] 10 is a table showing the composition and pH of the material liquids used in Experiment 2. DETAILED DESCRIPTION OF THE INVENTION

[0007] The method for forming a functional film according to this embodiment includes a preparation step, a coating step, and a removal step. The method for forming a functional film according to this embodiment is an example and is not limited to this.

[0008] 1. Preparation process In the preparation step, a liquid that will be the material for the functional film is prepared. The liquid includes a solvent containing water, a conductive material, and an organic amine compound. Hereinafter, the liquid that will be the material for the functional film will also be referred to as a material liquid.

[0009] Water is the main solvent of the liquid material. In other words, the liquid material is aqueous. Water is a component that volatilizes after the liquid material is applied to the medium described below. Examples of water that can be used include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as ultrapure water, which has had ionic impurities removed as much as possible. Furthermore, using water sterilized by ultraviolet irradiation or the addition of hydrogen peroxide can prevent the growth of mold and bacteria when the liquid material is stored for a long period of time. The water content in the liquid material is adjusted appropriately depending on the type of functional film the liquid material forms, the material of the medium, the characteristics of the inkjet head used in the coating process, and other factors.

[0010] The liquid material may contain a solvent other than water. Examples of solvents other than water include 1,2-alkanediols such as 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol; polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,3-pentanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2,4-pentanediol, and glycerin; glycol ethers such as alkylene glycol monoethers and alkylene glycol diethers; and carbonate-based solvents.

[0011] The content of the organic solvent in the material liquid is adjusted appropriately depending on the type of functional film to be formed by the material liquid, the material of the medium, the characteristics of the inkjet head used in the coating process, and the like.

[0012] The conductive material functions as the functional film formed by the material liquid. The conductive material is selected depending on the application and purpose of the functional film. Applications of the functional film include, but are not limited to, fuel cells, solar cells, etc.

[0013] Examples of conductive materials for fuel cells include materials for forming polymer electrolyte membranes, such as tetrafluoroethylene-perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether] copolymers. The materials for forming polymer electrolyte membranes are also applicable to ion exchange membranes and hydrogen production.

[0014] Conductive materials for solar cell applications include conductive polymers such as a mixture of PEDOT (poly(3,4-ethylenedioxythiophene)) and PSS (polyanion poly(styrene sulfonate)). These conductive polymers can also be used in solid electrolytic capacitors, antistatic films, and light-emitting devices.

[0015] The content of the conductive material in the liquid material is adjusted appropriately depending on the type of functional film that the liquid material will form, the desired thickness of the functional film, and other factors.

[0016] The conductive material may be dissolved or dispersed in the liquid material. Among the conductive materials, those having a substituent such as a sulfo group in their molecular structure exhibit acidity when dissolved or dispersed in water. In other words, such a liquid material becomes acidic.

[0017] Inkjet heads used in inkjet printing use multiple types of components. Some of these components may be easily deteriorated by acidic liquids. Therefore, it is preferable to add a pH adjuster to the liquid material to increase the pH of the liquid material.

[0018] Examples of pH adjusters include inorganic bases and organic bases. Among these pH adjusters, those containing metal elements are difficult to remove from the formed functional film. If metal elements remain in the functional film, this may hinder quality improvement in the above-mentioned applications. In contrast, the method for forming a functional film of this embodiment uses an organic amine compound as a pH adjuster and removes the organic amine compound in the removal process.

[0019] The organic amine compound functions as a pH adjuster in the material liquid, increasing the pH of the material liquid and reducing its acidity. Examples of organic amine compounds include pyrrolidine, piperidine, pyridine, morpholine, and 4-methylmorpholine, and one or more of these compounds are used in the material liquid. These organic amine compounds have relatively large acid dissociation constants and have a strong effect of adjusting the material liquid toward alkaline. Furthermore, their respective characteristics, such as boiling point and vapor pressure at 20°C, make them easy to remove in the removal process. In this specification, boiling point refers to the standard boiling point.

[0020] The organic amine compound may be pyrrolidine, piperidine, a derivative of pyridine, or a derivative of morpholine other than 4-methylmorpholine. Also, the organic amine compound may be aziridine, 2-pyrrolidone, 3-pyrrolidone, ε-caprolactam, or the like.

[0021] When the organic amine compound is removed by reduced pressure in the removal step described below, an organic amine compound having a vapor pressure of 0.9 kPa or more and 10.0 kPa or less at 20°C is used. Examples of such organic amine compounds include pyrrolidine (6.51 kPa), piperidine (3.07 kPa), morpholine (1.06 kPa), 4-methylmorpholine (2.40 kPa), and pyridine. The numerical values ​​in parentheses following the names of the above compounds are vapor pressures at 20°C.

[0022] When the organic amine compound is removed by heating in the removal step described below, an organic amine compound having a boiling point of 80°C or higher and 150°C or lower is used. Examples of such organic amine compounds include pyrrolidine (89°C), piperidine (106°C), pyridine (115°C), morpholine (129°C), 4-methylmorpholine (114°C), 2-methylpyrazine (135°C), N-methylmorpholine (116°C), and 4-ethylmorpholine (139°C). The numbers in parentheses following the names of the above compounds are boiling points.

[0023] The content of the organic amine compound in the material liquid is 0.02% by mass or more and 0.40% by mass or less, based on the total mass of the material liquid. When the content of the organic amine compound is within this range, the organic amine compound exhibits its function and prevents the pH of the material liquid from increasing excessively. In particular, adding the organic amine compound in an appropriate amount within this range makes it easier to ensure stable dispersion of the conductive material in the material liquid.

[0024] The liquid material may contain other additives such as surfactants, resin emulsions, and moisturizers, etc. Known additives can be used as these additives.

[0025] In preparing the material liquid, the above components are mixed in any order. Then, filtration is performed as necessary to remove impurities and foreign matter. The components are mixed by adding them to a container equipped with a stirring device such as a mechanical stirrer, magnetic stirrer, or ultrasonic stirrer, and stirring and mixing them. Known methods such as centrifugal filtration and filter filtration can be used as the filtration method. The material liquid may also be degassed using a vacuum pump or the like. When degassing, the degree of vacuum is set to a level that does not remove the organic amine compound from the material liquid. While not particularly limited, for example, the degree of vacuum is set to 10.0 kPa or more at 20°C.

[0026] The pH of the liquid material is preferably adjusted with an organic amine compound. The preferred pH of the liquid material is appropriately set depending on the components and equipment, such as the inkjet head, used in the method for forming the functional film. The pH of the liquid material can be measured using a commercially available measuring device. The surface tension of the liquid material is preferably 10 mN / m or more and 40 mN / m or less, and more preferably 20 mN / m or more and 40 mN / m or less, at 25°C. This improves the ejection stability from the inkjet head. The surface tension of the liquid material can be measured using Kyowa Interface Science's automatic surface tensiometer CBVP-Z.

[0027] From the same perspective as surface tension, the viscosity of the material liquid is preferably 2 mPa·s (millipascal seconds) or more and 15 mPa·s or less, and more preferably 2 mPa·s or more and 5 mPa·s or less, at 20°C. The viscosity of the material liquid can be measured using a viscoelasticity tester, MCR-300, manufactured by Pysica. Specifically, the viscosity of the material liquid at 20°C can be determined by adjusting the temperature of the material liquid to 20°C, increasing the shear rate from 10 to 1000, and reading the viscosity when the shear rate is 200.

[0028] The above-mentioned properties and characteristic values ​​of the material liquid are merely examples and are not limited to those mentioned above.

[0029] 2.Coating process In the coating process, the liquid material is applied to the medium using an inkjet method, which uses changes in the volume of a liquid storage chamber in an inkjet head to eject droplets from a nozzle and cause the liquid to adhere to the medium.

[0030] Known devices such as inkjet printers can be used in the inkjet method. Specific examples of inkjet printers include on-carriage or off-carriage serial printers and line head printers.

[0031] The inkjet head has an actuator as a driving means, which may be a piezoelectric element that utilizes the deformation of a piezoelectric body, an electromechanical transducer that utilizes the displacement of a vibration plate due to electrostatic adsorption, or an electrothermal transducer that utilizes bubbles generated by heating.

[0032] In the application process, any desired pattern can be formed on the surface of the medium by moving the inkjet head relative to the medium.

[0033] The medium to which the liquid material is applied is appropriately selected depending on the application of the functional film, etc. Examples of the medium include inorganic substrates such as quartz, silicon, and ceramic, resin sheets and plates such as polyvinyl chloride, polyethylene, polypropylene, and polyethylene terephthalate, metal or alloy plates such as iron, silver, copper, and aluminum, and fabrics made of natural or chemical fibers.

[0034] 3.Removal process In the removal step, the solvent and the organic amine compound are removed by volatilization from the liquid material adhered to the medium, using reduced pressure or heat.

[0035] When using reduced pressure as a removal method, the external pressure of the applied material liquid, i.e., the atmospheric pressure, is set lower than the vapor pressure of the water-containing solvent and the organic amine compound. This promotes evaporation of the solvent and organic amine compound from the applied material liquid. This method prevents heat from being applied to the functional film, thereby suppressing thermal deterioration of the functional film. Furthermore, using an organic amine compound whose vapor pressure at 20°C is in the range of 0.9 kPa to 10.0 kPa can reduce the time required for their removal.

[0036] The pressure reduction conditions, such as the external pressure and the time for applying the pressure reduction, are appropriately set based on the electrical properties of the formed functional film, or on the analysis of the residues in the functional film, etc. Examples of the analysis of the residues include gas chromatography mass spectrometry of the thermally desorbed gas from the functional film.

[0037] In the removal step, the external pressure may be changed stepwise. Specifically, for example, the external pressure may be first maintained at a pressure higher than the vapor pressure of the solvent and the organic amine compound for a certain period of time, and then maintained at a pressure lower than the vapor pressure for a certain period of time. Furthermore, when the external pressure is reduced from atmospheric pressure, the pressure may be reduced to the lowest vapor pressure among the vapor pressures of the solvent or the organic amine compound at 20°C relatively quickly, and then reduced relatively slowly after the lowest vapor pressure is reached.

[0038] In the removal step, a degassing tank capable of accommodating a medium and being sealed, and a pressure reducing device such as a vacuum pump are used. Known devices and commercially available products can be used for these.

[0039] When heating is used as a removal method, the ambient temperature of the applied material liquid is set higher than the boiling point of the water-containing solvent and the organic amine compound. This promotes evaporation of the solvent and the organic amine compound from the applied material liquid. This method simplifies the removal process because heating can be performed with a relatively simple device. Furthermore, it becomes possible to remove the solvent and the organic amine compound in a relatively short process.

[0040] Heating conditions such as the atmospheric temperature and the heating time are appropriately set based on the electrical properties of the formed functional film or analysis of the residues in the functional film.

[0041] In the removal step, the ambient temperature may be changed stepwise. Specifically, for example, the ambient temperature may be first maintained at a temperature lower than the boiling points of the solvent and the organic amine compound for a certain period of time, and then the ambient temperature may be increased to a temperature higher than the boiling points and maintained at that temperature for a certain period of time.

[0042] In the removal step, the above-mentioned decompression and heating may be used in combination. The decompression and heating may be performed in parallel or sequentially. In addition, the medium on which the functional film is formed may be subjected to post-processing or post-treatment.

[0043] According to this embodiment, the following effects can be obtained.

[0044] This can suppress deterioration of the inkjet head member and improve the quality of the functional film. Specifically, since the organic amine compound is contained in the above-mentioned range, the pH of the material liquid is adjusted, thereby suppressing deterioration of the inkjet head member. Furthermore, since the solvent and organic amine compound are removed, components that do not contribute to the function of the functional film are reduced. As a result, it is possible to provide a method for forming a functional film that suppresses deterioration of the inkjet head member and improves the quality of the functional film.

[0045] 4. Working Example The effects of this embodiment will be described in more detail below with reference to examples and comparative examples. In these examples, the following experiments 1 to 3 were carried out. In the tables of FIG. 1 and FIG. 2 corresponding to experiments 1 and 2, the symbol "-" in the column for the composition of the liquid material means that the material is not contained.

[0046] In Experiment 1, tetrafluoroethylene-perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether] copolymer was used as the conductive material, and 4-methylmorpholine was used as the organic amine compound.

[0047] Specifically, in the preparation process, material liquids 1 to 6 were prepared according to the compositions shown in Fig. 1. Next, the pH of material liquids 1 to 6 was measured using a HORIBA, Ltd. pH meter LAQUA (registered trademark) F-74, and the measured values ​​were recorded in the pH column for each material liquid. Of material liquids 1 to 6, material liquid 4 containing 0.13 mass% of an organic amine compound was designated Example 1, and material liquid 1 containing no organic amine compound was designated Comparative Example 1.

[0048] Thereafter, in order to investigate the influence of Example 1 and Comparative Example 1 on the inkjet head members, the resistance to each material liquid was investigated using an inkjet head S800 manufactured by Seiko Epson Corporation.

[0049] Specifically, the liquid materials of Example 1 and Comparative Example 1 were individually placed in ink containers, and each ink container was connected to the inkjet head via a tube, and each liquid material was filled into the inkjet head. Next, the inkjet head was operated to print a nozzle check pattern. This confirmed that the nozzles ejecting Example 1 and Comparative Example 1 were ejecting droplets normally.

[0050] In this state, that is, with each liquid material filled inside the inkjet head, the head was left in an atmosphere of approximately 25° C. The leaving time was gradually extended from 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 1 day, 3 days, 1 week, and 2 weeks, and after each extension, a nozzle check was carried out in the same manner as above.

[0051] As a result, all nozzles continued to eject normally for more than two weeks with material liquid 4 of Example 1. On the other hand, with material liquid 1 of Comparative Example 1, non-ejecting nozzles began to appear after 30 minutes of standing, and the number of non-ejecting nozzles increased as the standing time increased.

[0052] Next, in the coating step, the liquid material 4 of Example 1 was coated onto a glass substrate. Specifically, the liquid material 4 was printed in a solid pattern of 30 mm square at a resolution of 1200 × 1200 dpi (dots per inch) and a droplet volume of 10 pL (picoliter).

[0053] Next, heating was employed as a removal step, and the glass substrate was placed in a thermostatic chamber and heated at 120° C. for 15 minutes, thereby removing water and methylmorpholine, and a functional film free of these substances was obtained.

[0054] In Experiment 2, tetrafluoroethylene-perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether] copolymer was used as the conductive material, and morpholine was used as the organic amine compound.

[0055] Specifically, in the preparation process, material liquids 10 to 14 were prepared according to the compositions shown in Fig. 2. Next, the pH of material liquids 10 to 14 was measured in the same manner as in Experiment 1, and the values ​​were recorded in the pH column for each material liquid. Of material liquids 10 to 14, material liquid 12 was designated as Example 2, material liquid 13 as Example 3, and material liquid 14 as Example 4.

[0056] Thereafter, the influence on the inkjet head member was investigated for Examples 2, 3, and 4 in the same manner as in Experiment 1. As a result, in Examples 2, 3, and 4, all nozzles ejected normally for more than two weeks.

[0057] In experiment 3, a mixture of PEDOT and PSS was used as the conductive material, and morpholine was used as the organic amine compound.

[0058] In the preparation process, material liquid 21 of Example 5 and material liquid 20 of Comparative Example 2 were prepared. Material liquid 21 of Example 5 contained 0.80 mass% of a mixture of PEDOT and PSS and 0.02 mass% of morpholine. Material liquid 20 of Comparative Example 2 contained 0.80 mass% of a mixture of PEDOT and PSS and did not contain an organic amine compound. The pH of each material liquid was measured in the same manner as in Experiment 1, and the pH of Example 5 was 5.0, and the pH of Comparative Example 2 was 3.5.

[0059] Thereafter, the effects on the inkjet head members of Example 5 and Comparative Example 2 were investigated in the same manner as in Experiment 1. As a result, with the liquid material 21 of Example 5, all nozzles continued to eject normally for more than two weeks. On the other hand, with the liquid material 20 of Comparative Example 2, non-ejecting nozzles began to appear after being left for four hours, and the number of non-ejecting nozzles increased as the leaving time increased.

[0060] Next, in the coating step, the liquid material 21 of Example 5 and the liquid material 20 of Comparative Example 2 were each coated onto a glass substrate under the same conditions as in Experiment 1.

[0061] Next, a removal step was performed by reducing the pressure, and the glass substrate was placed in a vacuum degassing tank and reduced for 10 minutes or more at a vacuum level of 100 Pa or less. In the functional film of Example 5, pure water and morpholine were removed.

[0062] Thereafter, the electrical conductivity was measured for the functional film of Example 5 and the functional film of Comparative Example 2. The functional film of Example 5 and the functional film of Comparative Example 2 both had a conductivity of 4×10 -3 It had a conductivity of Ωcm.

[0063] Experiments 1, 2, and 3 showed that the material liquid of the example suppresses the deterioration of the inkjet head member and improves the quality of the functional film.

Claims

1. a preparation step of preparing a liquid containing an organic amine compound, a conductive material, and a solvent containing water, wherein the content of the organic amine compound is 0.02 mass % or more and 0.40 mass % or less with respect to the total mass; an application step of applying the liquid to a medium by an inkjet method; a removing step of removing the solvent and the organic amine compound from the liquid applied to the medium.

2. the organic amine compound has a vapor pressure at 20°C of 0.9 kPa or more and 10.0 kPa or less; The method for forming a functional film according to claim 1 , wherein the organic amine compound is removed by reducing pressure in the removing step.

3. the boiling point of the organic amine compound is 80°C or higher and 150°C or lower, The method for forming a functional film according to claim 1 , wherein the organic amine compound is removed by heating in the removing step.

4. 2. The method for forming a functional film according to claim 1, wherein the organic amine compound is one or more of pyrrolidine, piperidine, pyridine, morpholine, and 4-methylmorpholine.

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