Method for forming coating film

Abstract

To provide a method for forming a coating film by which the generation of a solid material in a coating film forming apparatus and the clogging of a head nozzle are suppressed and good injection properties and stable curability are obtained.SOLUTION: The method for forming a coating film is a method for forming a coating film using an inkjet head, wherein the inkjet ink contains a polymerizable monomer, a blocked isocyanate and a photopolymerization initiator, and the method comprises a step of dehydrating the ink and a step of heating the ink ejected from the inkjet head to a temperature of 40 °C or higher.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coating film forming method, and more particularly to a coating film forming method that suppresses the generation of solid matter in the apparatus and the clogging of the head nozzle, and that provides good ejection properties and stable curing properties. [Background technology]

[0002] Conventionally, photolithography and screen printing methods have been used to form etching resists, solder resists, and markings on printed wiring boards. As a method for utilizing the inkjet method in the production of printed wiring boards, for example, it has already been proposed to use inkjet ink containing a thermosetting agent on a copper-clad laminate for printed wiring boards, and then form a solder resist using an inkjet printer (see, for example, Patent Documents 1 to 3).

[0003] The inkjet method can significantly reduce the number of steps and labor compared to photolithography, which requires a photomask, and screen printing methods using resist ink or marking ink, which require a screen. Furthermore, the inkjet method can reduce consumables such as developers, various inks, and cleaning solvents, and can also reduce wastewater, which is expected to contribute to a cleaner environment.

[0004] However, in inks containing the above-mentioned heat curing agent, particularly blocked isocyanate, the blocked isocyanate reacts with water and hydroxy groups contained in the ink to generate solid matter, which can clog nozzles when the ink is ejected from a head using an inkjet method, resulting in the problem of ejection failure. In particular, in order to improve the inkjet ejection performance of curable inks, the ink is usually heated to reduce the ink viscosity before ejection, but heating further accelerates the generation of solids.

[0005] Therefore, a method has been proposed in which the water content is kept low at 500 ppm when producing ink containing an isocyanate group (see, for example, Patent Document 4). However, the method of limiting the water content to 500 ppm imposes a large manufacturing burden, is difficult to maintain and store, and leads to increased costs. Furthermore, this method is based on the premise that the ink will be used immediately after production. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 06069300 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-043565 [Patent Document 3] Patent No. 05969208 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-201593 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems and circumstances. The problem to be solved by the present invention is to provide a coating film forming method that suppresses the generation of solid matter in the device and the clogging of the head nozzle, and that achieves good ejection properties and stable curing properties. In the following description, "inkjet ink" will also be simply referred to as "ink." [Means for solving the problem]

[0008] The present inventors have investigated the causes of the above problems in order to solve the above problems, and have found that even when ink containing a blocked isocyanate is used, generation of solid matter in a film forming apparatus can be suppressed by performing a dehydration process on the ink before ejecting the ink. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] 1. A coating film forming method using an inkjet head, The inkjet ink contains a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, a dehydration step of the inkjet ink; a heating step of heating the ink-jet ink ejected from the ink-jet head to a temperature of 40° C. or higher. Paint film formation method.

[0010] 2. The heating step is performed in the ink supply path that supplies the inkjet ink to the inkjet head. 2. The method for forming a coating film according to claim 1.

[0011] 3. In the dehydration step, dry gas whose moisture content has been reduced by a drying device is injected into an ink supply path that supplies the inkjet ink to the inkjet head. 2. The method for forming a coating film according to claim 1.

[0012] 4. In the dehydration step, the dry gas is generated using a membrane filter or activated carbon. 4. The method for forming a coating film according to item 3.

[0013] 5. A degassing step for the inkjet ink is provided after the dehydration step. 2. The method for forming a coating film according to claim 1.

[0014] 6. The degassing step uses hollow fibers or ultrasonic waves. 6. The method for forming a coating film according to item 5.

[0015] 7. After the dehydration step, a second heating step is performed in addition to the heating step in the ink supply path that supplies the inkjet ink to the inkjet head. 3. The method for forming a coating film according to claim 2. [Effects of the Invention]

[0016] The above-described means of the present invention can provide a coating film forming method that suppresses the generation of solid matter and clogging of head nozzles in a coating film forming apparatus, even when an ink containing a blocked isocyanate is used, and that achieves good ejection properties and stable curing properties. The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows. Ink containing blocked isocyanate generates solids when the blocked isocyanate reacts with the water and hydroxyl groups in the ink. In particular, heating such ink accelerates the generation of solids. As a result, if solids are generated in the coating film forming equipment, it can lead to ejection failure. The estimated mechanism for solid formation is that the blocked isocyanate reacts with the water and hydroxyl groups contained in the ink, hydrolyzing the blocked isocyanate (NCO) moiety and generating an amine. Furthermore, the amino group reacts with the NCO moiety to form a polymer in which the bond site becomes urea. It is also speculated that the alcohol component generated by the hydrolysis of the acrylic monomer reacts with the NCO moiety and polymerizes. Therefore, in the present invention, a dehydration process is performed on the ink containing the blocked isocyanate before it is ejected. This reduces the water content of the ink, suppresses the reaction between the water and hydroxy groups in the ink and the blocked isocyanate, and also suppresses the generation of solids. As a result, the ink has good ejectability and stable curing properties. In particular, even when the ink ejected from the inkjet head is heated to a temperature of 40° C. or higher, the ejection properties are improved without accelerating the generation of solid matter. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating ink flow paths in an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] Schematic cross-sectional view of an external reflux type degassing module [Figure 3A] Schematic cross-sectional view showing the internal structure of the central tube of an external circulation type degassing module [Figure 3B]Schematic cross-sectional view showing the internal structure of the central tube of an external circulation type degassing module [Figure 4] Front view of a desiccant filter, another form of dehydration device DETAILED DESCRIPTION OF THE INVENTION

[0018] The coating film forming method of the present invention is a coating film forming method using an inkjet head, in which the ink contains a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, and the method includes a dehydration step of the inkjet ink in which the polymerizable monomer is a polymerizable monomer, and a heating step of heating the ink ejected from the inkjet head to a temperature of 40°C or higher. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0019] In an embodiment of the present invention, it is preferable to perform the heating step in the ink supply path that supplies the ink-jet ink to the ink-jet head, since this reduces the viscosity of the ink and improves the ejection properties.

[0020] In addition, in the dehydration step, it is preferable to inject dry gas, the moisture content of which has been reduced by a drying device, into the ink supply path that supplies the inkjet ink to the inkjet head, since this makes it easy to inject the dry gas and ensures that the ink can be dehydrated reliably.

[0021] In the dehydration step, it is preferable to use a membrane filter or activated carbon to generate the dry gas, since this does not change the ink properties and does not affect the ejection properties, and the device can be easily introduced.

[0022] It is preferable to provide a degassing step for the inkjet ink after the dehydration step, since this can remove air bubbles caused by the dehydration treatment, leading to improved ejection properties.

[0023] The degassing step is preferably carried out using hollow fibers or ultrasonic waves, since this improves the coating film performance by preventing the imbalance in curing and film deterioration due to oxygen inhibition, and also improves the ejection property by preventing the formation of bubbles.

[0024] After the dehydration step, it is preferable to perform a second heating step in addition to the heating step in the ink supply path that supplies the ink to the inkjet head, in order to further improve the ejection properties.

[0025] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0026] 1. Overview of the coating film forming method of the present invention The coating film forming method of the present invention is a coating film forming method using an inkjet head, in which the inkjet ink contains a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, and the method comprises a dehydration step of the inkjet ink, and a heating step of heating the ink ejected from the inkjet head to a temperature of 40°C or higher.

[0027] In the present invention, "(meth)acrylate" means acrylate or methacrylate, "(meth)acryloyl group" means acryloyl group or methacryloyl group, and "(meth)acrylic" means acrylic or methacrylic.

[0028] The ink used in the present invention functions as an insulating film (solder resist) by being applied to a substrate and cured with actinic rays in various fields, such as metal processing, electronic circuits, printed circuit boards, plate making, semiconductors, color filters, etc. Furthermore, since the ink can be removed with alkali after photo-curing, it also functions as an etching resist used when forming an etching pattern on a substrate. The ink can be used not only as an ink for forming the solder resist pattern described above, but also as an adhesive, a sealant, a circuit protectant, etc. for electronic components. In particular, the ink according to the present invention is preferably an ink for forming a solder resist pattern used on a printed wiring board. When a solder resist pattern (solder resist film) is formed using the ink according to the present invention, the ink has high curing properties, making it possible to prevent the penetration of oxygen and moisture into the solder resist film. Furthermore, the ink according to the present invention improves the adhesion between the copper foil and the solder resist film interface on the printed wiring board, preventing copper migration and suppressing a decrease in insulation properties.

[0029] The ink according to the present invention is an ink that can be cured by actinic radiation. "Actinic rays (also referred to as "active energy rays")" are rays that can impart energy to the ink by irradiation, generating reaction initiating species such as active radicals and ions, and include α-rays, γ-rays, X-rays, ultraviolet rays, electron beams, etc. Of these, ultraviolet rays and electron beams are preferred from the viewpoint of curing sensitivity and ease of equipment availability, with ultraviolet rays being more preferred.

[0030] <Dehydration process and heating process> The coating film forming method of the present invention comprises a dehydration step of the ink, and a heating step of heating the ink ejected from the inkjet head to a temperature of 40° C. or higher. The order of the dehydration step and the heating step does not matter, but performing the heating step after the dehydration step is preferable because it is effective in preventing the generation of solids in the ink due to heating. Since the ink according to the present invention contains a blocked isocyanate, the blocked isocyanate reacts with water and hydroxy groups contained in the ink to generate solids. In particular, heating of such ink accelerates the generation of solids. Therefore, dehydrating the ink before heating is effective in preventing the formation of solids. From the viewpoint of injectability, it is preferable to carry out the heating step multiple times. As will be described later, the heating step is preferably carried out immediately after the dehydration step and after the degassing step and immediately before injection. The dehydration step and the heating step will be described in detail later.

[0031] 2.Coating film formation method The coating film forming method of the present invention preferably includes the following steps (3) to (6) in addition to the dehydration step and heating step described above. The order of the dehydration step and heating step does not matter, but the following description will explain a preferred embodiment in which the heating step is performed after the dehydration step. Furthermore, a method for forming a resist film will be described as an example of the coating film forming method. (1) Ink dehydration process (2) Ink heating process (3) Ink degassing process (4) A process in which heated ink is ejected from the nozzle of an inkjet head and landed on a printed wiring board on which a circuit has been formed. (5) A process in which the ink is temporarily hardened by irradiating it with actinic light. (6) After the temporary curing, the ink is heated to fully cure it.

[0032] <Step (1)> In step (1), the ink is dehydrated before being ejected from the inkjet head. Dehydration prevents the water and hydroxyl groups in the ink from reacting with the blocked isocyanate, which would otherwise cause solids to form.

[0033] In the dehydration step, it is preferable to inject dry gas, the moisture content of which has been reduced by a drying device, into the ink supply path, thereby injecting the dry gas into the ink liquid and dehydrating it. The drying device may be a membrane filter or activated carbon. Examples of the device using activated carbon include a filter with activated carbon, and specifically, a desiccant filter, which will be described later, is preferred. The desiccant filter is configured such that the surface of a sheet-like substrate containing a corrugated nonwoven fabric is coated with a dehumidifying agent containing activated carbon, and details of this will be described later.

[0034] The dry gas preferably has a relative humidity of 10% RH or less, more preferably 5% RH or less, and the lower the better. Examples of the dry gas that can be used include air, nitrogen, helium, and argon. By injecting (supplying) the dry gas into the ink supply channel, the water content of the ink, as measured by the Karl Fischer method, is preferably in the range of 0.05 to 0.60% by mass relative to the total mass of the ink. The water content preferably falls within this range from after (1) the ink dehydration step until immediately before (4) the ink ejection step.

[0035] (Method for measuring moisture content) The water content according to the present invention can be measured by a known method such as the Karl Fischer method. The Karl Fischer method for determining water content in a substance utilizes the specific reaction of the Karl Fischer reagent, which contains iodine, sulfur dioxide, and pyridine, with water in the presence of methanol. In particular, volumetric titration involves placing a titration solvent in a titration flask, dissolving the sample in the titration solvent, extracting the water from the sample, and then titrating the sample with the Karl Fischer reagent, whose main components are iodine, sulfur dioxide, and a base, to determine the water content. Water reacts with iodine and sulfur dioxide in the presence of a base and an alcohol. H20+I2+SO2+CH3OH+3RN → 2RN・HI+RN・HSO4CH3 From the above equation, since the reaction ratio between H20 and I2 is 1:1, the number of milligrams of water (titer) per 1 ml of Karl Fischer reagent is determined in advance using water or a water standard substance, etc. Then, the amount of water (mg) is calculated from the titer (ml) of Karl Fischer reagent required to measure the sample. Water content (mg) = Karl Fischer reagent titer (ml) x titer (mgH2O / ml) Karl Fischer reagent is also called KF reagent. Then, the moisture content relative to the total mass of the ink is calculated from the calculated moisture amount. Water content (%) = (amount of water in ink / total mass of ink) x 100

[0036] The moisture content can be controlled within the range of 0.05 to 0.60% by mass by controlling the amount and duration of dry gas supply during the dehydration step. Other moisture content control methods include controlling the octanol / water partition coefficient (ClogP) of the polymerizable monomer contained in the ink and controlling the hydroxyl value of the ink. Another moisture content control method includes heating the ink.

[0037] The supply amount of the drying gas is set within a range of 0.3 to 1.5 L / min, and it is preferable to continue supplying the drying gas while the ink is being heated. The ClogP value of the polymerizable monomer is preferably within a range of 2.0 to 7.0. From the viewpoint of ejection stability, it is also preferable that the polymerizable monomer having a ClogP value within a range of 2.0 to 7.0 is contained in an amount of 30% by mass or more relative to the total ink. The hydroxy value in the ink is preferably within the range of 0.05 to 60 mgKOH / g. In order to keep the hydroxy value in the ink within this range, it is preferable to control the composition of the compound having a hydroxy value contained in the ink or to purify the compound having a hydroxy value. Examples of the compound having a hydroxy value include (meth)acrylate.

[0038] <Step (2)> In step (2), the dehydrated ink is heated. By heating, the ink droplets can be ejected from the inkjet head in a heated state, which improves ejection stability. The temperature of the ink during ejection is preferably 40°C or higher, with the upper limit being preferably 100°C or lower. To further improve ejection stability, the temperature of the ink during ejection is more preferably within the range of 40 to 90°C. In particular, it is preferable to eject the ink at an ink temperature such that the viscosity of the ink is within the range of 7 to 15 mPa·s, more preferably within the range of 8 to 13 mPa·s.

[0039] The ink is preferably heated in a flow path that supplies the ink to the inkjet head so that the ink temperature at the time of ejection is 40° C. or higher. As the heating method, for example, at least one of an ink supply system such as an ink tank of a head carriage, a supply pipe and a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head can be heated by an ink heater. In particular, in the present invention, it is preferable to perform the heating process multiple times before ejection. Specifically, as described below, in the ink supply system, it is preferable to heat the first sub-tank immediately after dehydration. Furthermore, in addition to heating the first sub-tank, it is also preferable to heat the second sub-tank after degassing and immediately before ejection, in order to improve ejection performance.

[0040] The ink heating section may be a panel heater, a rubber heater, a ribbon heater, or a heater for retaining heat. The specific configuration of the ink heating unit will be described later.

[0041] <Step (3)> Step (3) is a degassing step to remove air bubbles caused by dehydration of the ink. The degassing method preferably uses hollow fibers or ultrasonic waves. A degassing module (degassing device) using hollow fibers or ultrasonic waves will be described later.

[0042] The degassing step preferably adjusts the amount of dissolved oxygen in the ink at the temperature at which the ink is ejected to within a range of 0.1 to 10.0 mg / lppm, more preferably within a range of 0.1 to 5.0 mg / lppm, and particularly preferably within a range of 0.05 to 0.60 mg / lppm.

[0043] (Calculation method for dissolved oxygen amount by fluorescence method) The amount of dissolved oxygen can be measured by a known method such as a fluorescence method. For example, the fluorescence method for measuring dissolved oxygen is based on a phosphor electrode, which emits red fluorescence when exposed to blue excitation light. The fluorescent energy of the red fluorescence is absorbed by oxygen molecules, so the higher the oxygen molecular weight, the more fluorescent energy is absorbed, and the amount of fluorescent afterglow decreases in inverse proportion to the oxygen molecular weight. In other words, this method applies the principle that the more oxygen there is, the less afterglow there is.

[0044] As described above, it is preferable from the viewpoint of injectability to carry out the heating step (2) again after the degassing step and before the injection step described below.

[0045] <Step (4)> In the step (4), ink droplets are ejected from an inkjet head and landed on a printed wiring board, which is a recording medium, at positions corresponding to the resist film to be formed, thereby forming a pattern. The ejection method from the inkjet head may be either an on-demand method or a continuous method. The on-demand inkjet head may be of any of the following types: electro-mechanical conversion type, such as single cavity type, double cavity type, bender type, piston type, shear mode type, and shared wall type; and electro-thermal conversion type, such as thermal inkjet type and Bubble Jet (registered trademark) type (Bubble Jet is a registered trademark of Canon Inc.). The amount of ink droplets ejected is preferably within the range of 2 to 20 pL in terms of recording speed and image quality.

[0046] The printed wiring board is not particularly limited, but examples thereof include copper-clad laminates of all grades (FR-4, etc.) made of materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven cloth epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, copper-clad laminates for high-frequency circuits made of fluorine-polyethylene-PPO-cyanate ester, and other materials, as well as polyimide films, PET films, glass substrates, ceramic substrates, wafer plates, stainless steel plates, etc.

[0047] The printed wiring board is preferably subjected to a fine roughening treatment to increase the contact area with the ink in order to improve adhesion with the ink. When coating ink using the inkjet method, the viscosity of the ink must be low so that it can be ejected from an inkjet head. Therefore, inks that are primarily composed of polymerizable monomers before coating and that are cured by actinic radiation after coating are used. Such inks tend to shrink upon curing after coating, which can lead to poor adhesion between the ink and the printed wiring board. Therefore, in order to increase the contact area with the wiring board, it is necessary to perform a fine roughening treatment on the wiring board. Furthermore, because the ink has a low viscosity, there is a problem of bleeding occurring on the roughened wiring board. Therefore, it is preferable to perform a treatment to adjust the contact angle after roughening the wiring board. Therefore, when the ink of the present invention is used for the above-mentioned purposes, it is preferable to perform a roughening treatment or a treatment to prevent bleeding as a pretreatment for the wiring substrate.

[0048] Examples of roughening treatment methods include physical polishing, which involves forming irregularities on the surface of the wiring board using means such as buffing or scrubbing to form a rough surface. Other roughening treatment methods include chemical polishing treatments such as those based on copper chloride, persulfate, sulfuric acid / hydrogen peroxide, formic acid, and organic acids. As a roughening treatment method, from the viewpoint of adhesion, chemical polishing treatment is preferred, and organic acid treatment is more preferred.

[0049] Specific examples of chemical polishing treatments include copper chloride-based products such as MacDermid's MultiPrep 200, persulfate-based products such as MacDermid's Microclean, ME-301, and PR-820, sulfuric acid / hydrogen peroxide-based products such as Shikoku Kasei's GB1000F / 1400, G200, GB3100, and GB4300, MacDermid's Metex G-5, Metex G-6, ME-501, ME-602, ME-605, and ME-709, BOARDTEC's BTH-2066, and Mitsubishi Gas Chemical Company's CPE-900, EMR-5000, and EMR-7000, and organic acid-based products such as MEC's ​​CZ8100, CZ8101, and CZ8202, and BOARDTEC's BTH-2083 and BTH-2085. From the viewpoint of adhesion, sulfuric acid / hydrogen peroxide-based and organic acid-based compounds are preferred, and organic acid-based compounds are more preferred. As a treatment for preventing bleeding, CL8300 series from MEC and BTH-3066 from BOARDTEC are preferred.

[0050] The surface roughness of the copper plate roughened by the above pretreatment is preferably Ra 0.1 to 1.5 μm, more preferably 0.3 to 1.3 μm, and most preferably 0.4 to 1.1 μm. If Ra is 0.1 μm or more, adhesion is improved, and if it is 1.5 μm or less, bleeding is suppressed. The thickness of the copper plate roughened with the pretreatment agent is preferably 0.1 to 3.0 μm, more preferably 0.3 to 2.0 μm, and even more preferably 0.5 to 1.5 μm. If the roughening thickness is 0.1 μm or more, adhesion is improved due to the anchor effect, and if it is 3.0 μm or less, copper is not unnecessarily roughened or densified, thereby improving adhesion. The surface roughness can be controlled by adjusting the conditions such as the type of pretreatment agent, the treatment temperature, and the treatment time. The surface roughness can be measured using a laser microscope, a white light interference microscope, or the like.

[0051] <Step (5)> In the step (5), the ink deposited in the step (4) is irradiated with actinic rays to temporarily cure the ink. The actinic ray can be selected from, for example, electron beams, ultraviolet rays, α rays, γ rays, and X-rays, and is preferably ultraviolet rays. The ultraviolet light can be irradiated using, for example, a water-cooled LED manufactured by Phoseon Technology under conditions of a wavelength of 300 to 420 nm.

[0052] The ultraviolet irradiation is carried out such that the peak irradiance of the ultraviolet light on the surface of the resist film having a wavelength in the range of 300 to 420 nm is preferably 0.5 to 10 W / cm. 2 The irradiation of ultraviolet light is more preferably carried out so that the peak irradiance of the ultraviolet light on the surface of the resist film is in the range of 1 to 5 W / cm. 2 The measurement should be carried out so that it is within the range of From the viewpoint of suppressing the radiation heat from being irradiated onto the ink, the amount of light irradiated onto the resist film is set to 1000 mJ / cm 2 It is preferable that it is less than 10 ... The irradiation of actinic rays is preferably carried out within 0.001 to 300 seconds after the ink has landed, and more preferably within 0.001 to 60 seconds in order to form a highly precise resist film.

[0053] <Step (6)> In step (6), after the preliminary curing in step (5), the ink is further heated to fully cure it. The heating method is preferably, for example, placing the product in an oven set to a temperature in the range of 110 to 180° C. for 10 to 60 minutes.

[0054] 3.Coating film forming equipment The film-forming apparatus used in the film-forming method of the present invention will be described in detail below with reference to the drawings. However, the scope of the present invention is not limited to the illustrated example. In the following description, components having the same functions and configurations will be given the same reference numerals and their description will be omitted. An example of the coating film forming device is an inkjet recording device equipped with an inkjet head. The inkjet recording apparatus preferably has a dehydration device, an ink heating unit, a degassing device, and an inkjet head. Furthermore, the inkjet recording apparatus preferably has an actinic ray irradiation unit (UV irradiation unit) that irradiates the ink that has landed on the recording medium with actinic rays.

[0055] FIG. 1 is a diagram illustrating the ink flow path in an inkjet recording apparatus. In the inkjet recording apparatus 1, ink is pumped out from an ink tank 51 of an ink supply unit 50 by a supply pump 53 and supplied to each recording head 24a via an ink flow path 24b. The inkjet recording apparatus 1 is also configured to be able to return ink that was not ejected from each recording head 24a to the ink flow path 24b as needed.

[0056] On the ink flow path 24b, a dehydration device (dehydration means) 300, a first sub-tank 241, a degassing device 280, a liquid feed pump 243, a check valve 244, a second sub-tank 245, and the like are provided. The recording head 24a, the ink flow path 24b, and each component part located on the ink flow path 24b are heated and kept warm by an ink heating unit (ink heating means) 270, so that the ink temperature is maintained at an appropriate temperature. Specifically, the ink heating unit 270 heats the recording head 24a, the ink flow path 24b, and each component part located on the ink flow path 24b so that the ink ejection temperature is 40°C or higher.

[0057] <Ink heating unit> The ink heating unit 270 is preferably provided at least in one of the following locations among the recording head 24a and each component on the ink flow path 24b: before the dehydration device 300, between the dehydration device 300 and the degassing device 280 (degassing module 242), or between the degassing device 280 and the recording head 24a. The ink heating unit 270 may also be provided in the degassing device 280. From the viewpoint of preventing the formation of solids due to heating, the ink heating unit 270 is preferably provided after the dehydration device 300 , and is preferably provided between the dehydration device 300 and the degassing device 280 . In addition, the ink may be ejected from the recording head 24a immediately after being degassed, but in order to eject the ink more stably from the standpoint of preventing an increase in pressure loss, it is preferable to further provide an ink heating section 270 between the degassing device 280 and the recording head 24a. In the following explanation, we will explain the case where the ink heating unit 270 is installed in the first sub-tank 241 after the dehydration device, the second tank 247 between the dehydration device 300 and the degassing device 280, and the degassing device 280, but this is not limited to this.

[0058] The ink heating section 270 is configured by a heater, a heat transfer member that transfers heat from the heater, etc. The ink heating section 270 may also be configured using warm water. The heater may be, for example, an electric heating wire, which generates Joule heat when energized. Examples of such heaters include panel heaters, ribbon heaters, and rubber heaters. The heat transfer member may be a member with high thermal conductivity, such as a heat conduction plate made of various metals (alloys). The heater and heat transfer member are provided, for example, to cover the piping of the ink flow path 24b or to be in contact with the side walls of the first sub-tank 241 and the second sub-tank 245.

[0059] <Dehydration equipment> The dehydration device 300 dehydrates the ink pumped from the ink tank 51 by the supply pump 53, thereby preventing the formation of solids in the ink when heated in a subsequent process. That is, when the ink of the present invention is heated, the water and hydroxy groups contained in the ink react with the blocked isocyanate to generate solids, but dehydration prevents the generation of such solids. As a result, ink ejection failure is also prevented.

[0060] The dehydration device 300 may be configured to supply dry gas, the moisture content of which has been reduced by a drying device, to the ink. Specific examples of the drying device include those using a membrane filter or activated carbon. Examples of devices that use membrane filters include membrane dehumidifiers and general-purpose compressors. Commercially available dehumidifiers can be used, such as the SMC membrane dehumidifier IDG5-02B-PS. Examples of filters using activated carbon include filters with activated carbon, and more specifically, desiccant filters, which will be described later.

[0061] Then, by injecting the dry gas that has been dehydrated by such a drying device into the ink supply path, the dry gas is injected into the ink liquid, thereby dehydrating it. The relative humidity of the dry gas is preferably 10% RH or less. The flow rate of the dry gas supplied to the ink is preferably within the range of 0.3 to 1.0 ml / min, which is a balance between bubble formation and bubble destruction at the ink interface. The dry gas supply time is preferably 1 to 12 hours.

[0062] FIG. 4 is a front view of the desiccant filter. The desiccant filter 301 is made by coating the surface of a sheet-like substrate 302 with a dehumidifying agent 303 . The substrate 302 is made of a corrugated nonwoven fabric and a conductive polymer, which is a conductive material impregnated into the nonwoven fabric. The dehumidifying agent 303 contains activated carbon. A conductive wire 4, which is a conductive member for supplying power, is connected to the substrate 302 containing the conductive polymer. The conductive wire 4 is connected to an external power source 305. The conductive member is not limited to the conductive wire 304, and various known conductive members can be used. The desiccant filter 301 having such a configuration is disposed inside the dehydration device 300 together with an external power supply 305 .

[0063] The desiccant filter 301 absorbs the moisture in the ink with a dehumidifying agent 303 and then allows the ink with reduced moisture to pass through. When the amount of moisture adsorbed by the dehumidifying agent 303 of the desiccant filter 301 becomes large, it is preferable to perform a regeneration process for the desiccant filter 301.

[0064] In a method for regenerating desiccant filter 301, power is supplied from external power source 305 to the conductive polymer in base 302 via conductor 304. The supplied power causes the conductive polymer to generate heat, raising the temperature of base 302. When the temperature of base 302 reaches a temperature at which moisture can be desorbed, the moisture adsorbed in dehumidifying agent 303 is desorbed. As a result, the moisture adsorption capacity of dehumidifying agent 303 is restored, and the dehumidifying agent is regenerated to a state where it can fully adsorb moisture, i.e., can dehumidify.

[0065] The nonwoven fabric is preferably made of, for example, aramid fiber, cellulose fiber, nylon fiber, vinylon fiber, glass fiber, polyester fiber, polyethylene fiber, polypropylene fiber, polyolefin fiber, rayon fiber, or the like. Furthermore, the base 302 may be made of a sheet-like member other than nonwoven fabric (for example, woven fabric or resin film) and a conductive material.

[0066] An example of a conductive polymer is polythiophene, which is used in organic electronics. In the present invention, for example, PEDOT:PSS (a composite of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid) can be suitably used as the conductive polymer impregnated into the nonwoven fabric. Poly(3,4-ethylenedioxythiophene) doped with the conductive polymer poly(4-styrenesulfonic acid) can be colloidally dispersed in water, and it is known that the polymer alone can be formed into a film. Furthermore, to improve conductivity, approximately 1 to 3% of a high-boiling point solvent such as dimethyl sulfoxide, N-methyl-2-pyrrolidone, glycerin, or ethylene glycol can be added to the water-dispersed conductive material.

[0067] The desiccant 253 preferably contains activated carbon, such as activated carbon fused with zeolite 4A or an aluminosilicate-carbon composite, as disclosed in JP 2017-222547 A or JP 2018-30122 A. This activated carbon is obtained through the following steps (a) to (d). (a) A process for producing a silica-carbon composite by calcining a silica plant at 400°C or higher in an inert atmosphere. (b) preparing a mixture containing the silica-carbon composite, an Al compound, an alkali metal compound or an alkaline earth metal compound, and water so as to produce an aluminosilicate having a molar ratio of Si:Al in the range of 1:0.1 to 1.2; (c) subjecting the mixture to a hydrothermal reaction to obtain a porous aluminosilicate-carbon composite. (d) subjecting the porous aluminosilicate-carbon composite to an inert gas treatment at 600 to 800°C. This activated carbon can desorb moisture at temperatures of around 50°C to 100°C.

[0068] The desiccant filter is manufactured by first immersing a corrugated nonwoven fabric in an aqueous dispersion of the conductive polymer PEDOT:PSS. The nonwoven fabric is then removed from the solution and left to dry for approximately 10 to 20 hours. In this way, a substrate 302 made of nonwoven fabric impregnated with the conductive polymer is produced. Meanwhile, activated carbon is produced through steps (a) to (d) as described above.

[0069] The activated carbon produced in this way is ground in a mortar, mixed with a water-soluble binder, and stirred until evenly dispersed. Water is then added in multiple batches to produce a paste-like activated carbon solution. This activated carbon solution is applied to the surface of substrate 302, which is made of nonwoven fabric impregnated with a conductive polymer, to form a layer of dehumidifying agent (activated carbon). Thereafter, the substrate and the dehumidifying agent are dried at room temperature, and then a lead wire is connected to the substrate. In this manner, a desiccant filter having a large specific surface area is obtained, which has a configuration in which the surface of a corrugated nonwoven fabric impregnated with a conductive polymer is coated with activated carbon. The base 302 is not limited to a corrugated shape, and may have various shapes such as a pleated shape, a flat shape, etc. However, it is preferable that the base 302 has a shape that does not impair breathability.

[0070] <First sub-tank> The first sub-tank 241 is an ink chamber having a smaller volume than one or more ink tanks 51 that store ink dehydrated by the dehydration device 300. A first float sensor 241a is provided in the first sub-tank 241. A control unit (not shown) operates the supply pump 53 based on detection data of the liquid level position by the first float sensor 241a, thereby storing a predetermined amount of ink in the first sub-tank 241.

[0071] The first sub-tank 241 is preferably provided with an ink heating section 270. The ink in the first sub-tank 241 is heated by the ink heating section 270, so that the viscosity of the ink at the time of ejection can be adjusted. The ink heating section 270 preferably heats the ink so that the temperature of the ink when ejected is 40°C or higher, and preferably heats the ink in the first sub-tank 241 so that the temperature is 40 to 60°C. The ink heating section 270 is preferably provided in contact with the side wall, bottom wall, etc. of the first sub-tank 241.

[0072] The temperature of the ink heating unit 270 is controlled by the control unit. The control unit detects the temperature of the ink heating unit 270 using, for example, a thermocouple built into the ink heating unit 270, and performs on / off control using a target temperature that is set appropriately depending on the type of liquid.

[0073] <Degassing device> The degassing device 280 performs a degassing process to remove gases such as air from the ink that has flowed in, and then discharges the degassed ink. The degassing device is preferably one that uses a hollow fiber membrane or ultrasonic waves. Degassing devices that use hollow fiber membranes and degassing devices that use ultrasonic waves are described below. Note that although the degassing device 280 shown in Fig. 1 uses hollow fiber membranes, it can be changed to one that uses ultrasonic waves.

[0074] (Degassing device using hollow fiber membrane) The degassing device 280 is composed of a degassing module 242, a vacuum pump 249, a vacuum path 250, a pressure sensor 251, an air release valve 252, and the like. The degassing module 242 is an external reflux type degassing module having a hollow fiber membrane therein as a gas permeable membrane that allows the gas dissolved in the liquid to pass therethrough. Furthermore, a vacuum pump 249 , a vacuum path 250 , a pressure sensor 251 , and an air release valve 252 are connected to the degassing module 242 . The vacuum pump 249 reduces the air pressure inside the degassing module 242 . A vacuum line 250 connects the vacuum pump 249 with the degassing module 242 . The pressure sensor 251 measures the air pressure in the vacuum path 250 . The atmosphere release valve 252 is a valve that can switch the inside of the vacuum path 250 between an airtight state and an atmosphere open state.

[0075] The degassing module 242 of the degassing device 280 will be described in detail with reference to Fig. 2. In the example shown in Fig. 2, an external reflux type degassing module 242 is shown. The degassing module 242 is formed, for example, in a cylindrical shape, removes (degasses) dissolved gases from the ink that has flowed in, and discharges the degassed ink. The degassing module 242 is configured such that a large number of hollow fiber membranes (gas permeable membranes) 2426 are arranged around a central tube 2424 inside an outer shell (chamber) 2421. One end of the central tube 2424 is connected to an ink inlet 2422, and the other end is sealed with a plug 2424a. Numerous fine holes (holes) 2424b (perforations) are provided on the outer wall of the central tube 2424. Ink flowing in from the ink inlet 2422 flows out from these fine holes 2424b to the surrounding area and then flows out from the ink outlet 2423. 2, the ink outlet 2423 is provided in a horizontal direction, and is configured so that ink flows out to the side of the degassing module 242. However, this configuration is not limited thereto, and the ink outlet 2423 may be provided in any direction, and the ink may be configured to flow out in any direction. Furthermore, it is preferable to provide the ink outlet 2423 at a position corresponding to the upper end of the hollow fiber membrane 2426 as shown in FIG. 2, because this prevents air from pooling in the chamber.

[0076] The hollow fiber membrane 2426 is a structure of many hollow fine fibers with one end closed, and its membrane surface is gas permeable. The other end of the fine fiber structure of the hollow fiber membrane 2426 is connected to a gas outlet 2425 to which a vacuum path 250 is connected. The pressure inside the hollow fiber membrane 2426 is reduced by suction with a vacuum pump 249. In this state, ink comes into contact with the membrane surface of the hollow fiber membrane 2426, and only the dissolved gas in the ink selectively permeates the membrane surface, degassing the ink. The dissolved gas that has passed through the hollow fiber membrane 2426 flows down the vacuum path 250.

[0077] Fig. 3A is a schematic cross-sectional view showing the internal configuration of the central tube of an external circulation type degassing module, and Fig. 3B is a cross-sectional view taken along line IVB-IVB in Fig. 3A. The degassing module 252 preferably has a heating section 2427 (ink heating section) inside the central tube 2424 . The heating unit 2427 is configured by having a heating wire and a thermocouple inside a rod-shaped member made of, for example, SUS. In this way, by arranging the heating unit 2427 in the center of the degassing module 242, the ink in the degassing module 242 can be heated uniformly and efficiently, and the ink can be heated to the target temperature in a short time. Furthermore, because the entire ink in the degassing module 242 can be heated uniformly, it is possible to prevent localized areas of unheated ink from occurring in the corners of the degassing module 242. In this way, because the ink can be heated uniformly and efficiently, it is possible to improve the degassing efficiency and the amount of ink sent, and to sufficiently reduce the viscosity of the ink, thereby suppressing the occurrence of ink non-ejection.

[0078] The temperature of the heating unit 2427 is controlled by the control unit. The control unit detects the temperature of the heating unit 2427 using, for example, a thermocouple built into the heating unit 2427, and performs on / off control using a target temperature that is set appropriately depending on the type of liquid. The shape and configuration of the heating unit 2427 may be any shape and configuration as long as it can heat the ink in the degassing module 242 and control the heating temperature. Furthermore, the shape and configuration of the heating unit 2427 may be configured so that the heating unit 2427 itself generates heat, as described above. The heating unit 2427 may be configured, for example, so that a heating element itself is provided outside the degassing module 242, and heat from the heating element is transferred to the heating unit 2427 to heat the inside of the degassing module 242.

[0079] Furthermore, on the outer surface of the degassing module 242, a second heating section 2428 (ink heating section) that heats the liquid inside the degassing module 242 is provided. That is, the second heating part 2428 is formed in a flat shape and is provided so as to cover the outer peripheral surface of the outer shell 2421 of the degassing module 242. As such second heating part 2428, for example, a rubber heater or the like is used. The second heating section 2428 is provided with a temperature sensor such as a thermistor (not shown), and is controlled to turn on and off by a control section in the same manner as the heating section 2427. By providing such a second heating section 2428, the ink in the degassing module can be heated to the target temperature in an even shorter time.

[0080] The vacuum pump 249 shown in FIG. 1 is a diaphragm pump that includes a pump chamber and a drive source. The pump chamber includes an expandable diaphragm. The drive source operates the diaphragm so that the volume of the pump chamber expands or contracts. The pump chamber is provided with an intake port equipped with a check valve that only allows fluid to flow in from the outside, and an outlet port equipped with a check valve that only allows fluid to flow out from the inside.

[0081] The pressure sensor 251 detects the air pressure in the vacuum path 250 and outputs the result to the control unit. The control unit controls the driving of the vacuum pump 249 based on the detection result from the pressure sensor 251.

[0082] The atmosphere release valve 252 is an electromagnetic valve that can switch the vacuum path 250 between an airtight state and an atmosphere-open state in accordance with an operation command from the control unit.

[0083] The liquid feed pump 243 sends the ink that flows out from the ink outlet 2423 of the degassing module 242 to the second sub-tank 245. A check valve 244 is provided between the liquid feed pump 243 and the second sub-tank 245 to prevent the ink that has been sent to the second sub-tank 245 from flowing back.

[0084] The above-mentioned degassing module 242 is an external reflux type hollow fiber membrane degassing module from the viewpoint of preferable degassing efficiency and processing flow rate, but is not limited to this and other types such as an internal reflux type may also be used. Commercially available products such as SEPAREL EF-002A-P and SEPAREL EF-004P from Dainippon Ink and Chemicals, Inc. can also be used as the external reflux type hollow fiber degassing module.

[0085] (Ultrasonic degassing device) The degassing device may be of a type that uses ultrasonic waves to degas. By using ultrasonic waves to degas the ink, it is possible to degas the ink without heating it, which makes it possible to prevent the generation of solids and also to increase the fluidity of the ink. The method of irradiating the ink with ultrasonic waves is not particularly limited. For example, an ultrasonic vibrator that generates ultrasonic waves is provided in an ink tank for degassing treatment. Then, by driving the ultrasonic vibrator with ink in the ink tank, ultrasonic waves can be irradiated to the ink. The ultrasonic waves may be applied directly to the ink by providing an ultrasonic vibrator inside the ink tank for degassing treatment, or may be applied indirectly through the wall of the tank or other liquid by providing an ultrasonic vibrator outside the ink tank for degassing treatment. When an ultrasonic vibrator is provided inside the ink tank where degassing is performed, if the ultrasonic vibrator is immersed entirely or partially in the ink when generating ultrasonic waves, the loss of ultrasonic waves is reduced, and therefore the ink can be degassed with less energy.

[0086] When ink is irradiated with ultrasonic waves, the ink vibrates, causing the gas dissolved in the ink to gather and precipitate as bubbles, a phenomenon known as cavitation. The bubbles precipitated by cavitation rise to the ink surface and exit the ink, reducing the amount of gas dissolved in the ink.

[0087] Furthermore, ink irradiated with ultrasonic waves has good fluidity even without heating. This is thought to be because the ink vibrates due to ultrasonic irradiation, which breaks down the gelling agent's aggregation and disperses it. In particular, when a crystalline gelling agent is used, the gelling agent may crystallize and form large lumps in the ink when the ink temperature is low, which can reduce the fluidity of the ink. In contrast, in the present invention, the crystalline structure of the gelling agent is broken down by ultrasonic irradiation, allowing the gelling agent to disperse in the ink, which is thought to improve the fluidity of the ink without heating.

[0088] To ensure the fluidity of the ink, the viscosity of the ink after being irradiated with ultrasonic waves is preferably within the range of 50 to 300 mPa·s at 30°C.

[0089] The oscillation frequency and irradiation energy of the ultrasonic waves can be appropriately set depending on the composition or viscosity of the ink. The entire ink can be sufficiently degassed by setting the ultrasonic oscillation frequency and irradiation energy so that the ultrasonic waves reach the entire ink without attenuation. The ultrasonic oscillation frequency and irradiation energy can also be set so that the viscosity of the ink after ultrasonic irradiation is in the range of 50 to 300 mPa·s at 30°C. The ultrasonic oscillation frequency and irradiation energy can also be set so that the dissolved oxygen content of the ink after degassing is in the range of 0.1 to 10.0 mg / lppm.

[0090] The oscillation frequency of the ultrasonic waves irradiated onto the ink can be in the range of 5 to 50 kHz, and preferably in the range of 10 to 30 kHz. By setting the oscillation frequency to 5 kHz or higher, sufficient degassing can be achieved, and by setting the oscillation frequency to 50 kHz or lower, aggregation of the coloring material due to vibration is less likely to occur. Furthermore, by setting the oscillation frequency of the ultrasonic waves in the range of 10 to 30 kHz, aggregation of the coloring material is even less likely to occur. This allows for uniform gloss in the image and makes it less likely for white streaks to occur in the image.

[0091] The ultrasonic energy irradiated to the ink is 1×10 4 ~1×10 5 J can be in the range of 2 x 10 4 ~8×10 4 It is preferable that the irradiation energy is in the range of 1×10 4 By setting the irradiation energy at 1×10 J or more, degassing can be performed sufficiently. 5 By setting the value to J or less, aggregation of the coloring material due to vibration can be prevented.

[0092] When ultrasonic waves are applied to the ink, the pressure inside the ink tank where degassing is performed may be normal pressure or may be reduced. By reducing the pressure inside the ink tank where degassing is performed, air bubbles are more likely to escape from the ink. The pressure inside the ink tank where degassing is performed when the ink is irradiated with ultrasonic waves can be set to, for example, a range of 0 to 1 atmosphere (a range of 0 to 101.3 kPa).

[0093] The temperature of the ink when irradiated with ultrasonic waves is preferably equal to or higher than the solidification point of the ink and lower than the gelling temperature of the ink. By setting the temperature of the ink when irradiating it with ultrasound lower than the gelation temperature, it is possible to prevent the photocurable compound from volatilizing from the ink that has been liquefied (sol) by heating, and to prevent the photocurable compound from deteriorating due to heating. The temperature of the ink is preferably at least 10° C. lower than the gelling temperature, and more preferably at least 20° C. lower.

[0094] By irradiating the ink with ultrasonic waves at a temperature equal to or lower than the gelling temperature, the ink can be degassed without including a step of heating the ink, even if the ink has been stored at near room temperature or cooled. In order to facilitate introduction of the ink before degassing into the ink tank where degassing is to be performed, the ink before degassing may be heated to impart fluidity. In this case, too, it is preferable to adjust the energy applied to the ink during heating so that the temperature of the ink does not rise above the gelation temperature. Furthermore, since the ink vibrates when exposed to ultrasonic waves, and the vibration energy may increase the temperature of the ink, it is preferable to adjust the ultrasonic oscillation frequency and irradiation energy so that the ink temperature does not exceed the gelation temperature.

[0095] <Second sub-tank> The second sub-tank 245 is a small ink chamber that temporarily stores ink that has been degassed by the degassing device 280. The second sub-tank has approximately the same capacity as the first sub-tank 241, although there is no particular limitation. The ink in the second sub-tank 245 is connected to the inlet 240a of each recording head 24a, and ink is supplied to each recording head 24a in an amount corresponding to the amount of ink ejected from the nozzles. A second float sensor 245a is provided in the second sub-tank 245. Based on the detection data of the liquid level position by the second float sensor 245a, the control unit operates the liquid feed pump 243 to store a predetermined amount of ink.

[0096] The second sub-tank 245 is preferably provided with an ink heating section 270, similar to the first sub-tank 241. The ink in the second sub-tank 247 is heated by the ink heating section 270, making it possible to adjust the viscosity of the ink when ejected. The ink heating section 270 preferably heats the ink so that the temperature of the ink when ejected is 40°C or higher, and preferably heats the ink in the second sub-tank 247 so that the temperature is 40 to 60°C. The ink heating section 270 is preferably provided in contact with the side wall, bottom wall, etc. of the second sub-tank 247.

[0097] The temperature of the ink heating unit 270 is controlled by the control unit. The control unit detects the temperature of the ink heating unit 270 using, for example, a thermocouple built into the ink heating unit 270, and performs on / off control using a target temperature that is set appropriately depending on the type of liquid.

[0098] Ink that is not ejected from the nozzles of the recording head 24a can be returned from the outlet 240b via the recovery path 241b and the valve 241c to the first sub-tank 241. For example, when it is necessary to drain ink from the ink flow path 24b during maintenance of the recording head 24a, the valve 241c can be opened to recover the ink from the recording head 24a without discarding it.

[0099] The control unit controls the operation of each unit of the inkjet recording apparatus 1 and supervises the overall operation. The control unit includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. In the control unit, various processing programs such as the system program stored in the ROM are read and loaded into the RAM, and the programs loaded into the RAM are executed by the CPU, thereby executing various control processes such as the image formation process and the temperature control described above.

[0100] In the inkjet recording apparatus having the above configuration, the ink in the ink path 24b is heated and kept warm by the ink heater 270, and is set so that the ink temperature is 40° C. or higher when ejected from the recording head.

[0101] In the inkjet recording apparatus 1 described above, the ink heating unit 270 is provided in the first sub-tank 241, the second sub-tank 247, and the degassing module 242, but this is not limiting and the ink heating unit 270 may be provided before the dehydration device 250. In addition, the ink heating unit 270 may be provided by incorporating a heater in the recording head 24a. Furthermore, the degassing device 280 is provided after the first sub-tank 241 and performs degassing after heating, but this is not limiting, and the device may be provided before the first sub-tank 241 and perform degassing before heating.

[0102] The ink ejected from the nozzle is irradiated with actinic rays by an actinic ray irradiating unit. The actinic ray irradiating section has, for example, a fluorescent tube such as a low-pressure mercury lamp, and irradiates energy rays such as ultraviolet rays by causing the fluorescent tube to emit light. Examples of fluorescent tubes that emit ultraviolet rays include low-pressure mercury lamps and mercury lamps with operating pressures of several hundred Pa to 1 MPa. Examples of such fluorescent tubes include light sources that can be used as germicidal lamps, cold cathode tubes, ultraviolet laser light sources, metal halide lamps, and light-emitting diodes. Among these, light sources that can irradiate ultraviolet rays with higher illuminance and consume less power (such as light-emitting diodes) are more desirable. The energy rays are not limited to ultraviolet rays, and any energy rays that have the property of curing ink depending on the properties of the ink may be used, and the light source may be changed depending on the wavelength of the energy rays, etc.

[0103] 4. Ink composition The ink used in the coating film forming method of the present invention contains a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator. The polymerizable monomer, blocked isocyanate, photopolymerization initiator, etc. will be described below.

[0104] <Polymerizable monomer> The polymerizable monomer according to the present invention is a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate. A monofunctional (meth)acrylate compound is a compound having one (meth)acrylate group in one molecule. Specific examples of the monofunctional (meth)acrylate compound include glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, methylglycidyl (meth)acrylate, 3-methyl-3-(meth)acryloxymethyloxetane, 3-ethyl-3-(meth)acryloxymethyloxetane, 3-methyl-3-(meth)acryloxyethyloxetane, 3-ethyl-3-(meth)acryloxyethyloxetane, 2-phenyl-3-(meth)acryloxymethyl ... Oxetane, 2-trifluoromethyl-3-(meth)acryloxymethyloxetane, 4-trifluoromethyl-2-(meth)acryloxymethyloxetane, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, iso-butyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, tricyclo[5.2.1.0 2,6 ]decanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, glycerol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (meth)acrylate of an ethylene oxide adduct of lauryl alcohol, succinic acid mono[2-(meth)acryloyloxyethyl], maleic acid mono[2-(meth)acryloyloxyethyl], 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 1,4-cyclohexanedimethanol mono(meth)acrylate, n-butyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, and 2-(2-ethoxyethoxy)ethyl (meth)acrylate.

[0105] In the present invention, the term "polyfunctional monomer" refers to a compound having two or more functional groups. From the viewpoint of curing by radical polymerization, examples of the functional group include an ethylenically unsaturated bond-containing acryloyl group, methacryloyl group, allyl group, vinyl group, vinyl ester group, etc. However, the functional group is not limited to the above. The polymerizable monomer used in the present invention preferably contains a polyfunctional monomer from the viewpoint of the physical properties of the coating film.

[0106] Examples of bifunctional acrylates include triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, bisphenol A PO (propylene oxide) adduct diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, polytetramethylene glycol diacrylate, tricyclodecane dimethanol dimethacrylate, and tricyclodecane dimethanol diacrylate.

[0107] Examples of tri- or higher functional acrylates include trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin propoxy triacrylate, and pentaerythritol ethoxy tetraacrylate.

[0108] Of the above acrylates, phenoxyethyl acrylate, o-phenylphenol acrylate, and 2-hydroxy-3-phenoxypropyl acrylate are preferred from the viewpoint of suppressing cure shrinkage.

[0109] From the viewpoint of rapid curing, neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, bisphenol A PO adduct diacrylate, and hydroxypivalic acid neopentyl glycol diacrylate are preferred.

[0110] The acrylate may be a modified product. Examples of modified acrylates include ethylene oxide-modified acrylates including ethylene oxide-modified trimethylolpropane triacrylate and ethylene oxide-modified pentaerythritol tetraacrylate, propylene oxide-modified acrylates including propylene oxide-modified trimethylolpropane triacrylate and propylene oxide-modified pentaerythritol tetraacrylate, caprolactone-modified acrylates including caprolactone-modified trimethylolpropane triacrylate, and caprolactam-modified acrylates including caprolactam-modified dipentaerythritol hexaacrylate.

[0111] (Multifunctional (meth)acrylate with a ClogP value in the range of 2.0 to 7.0) The ink of the present invention preferably contains a polymerizable monomer having an octanol / water partition coefficient (ClogP) value in the range of 2.0 to 7.0, i.e., a polyfunctional (meth)acrylate having a ClogP value in the range of 2.0 to 7.0. When the ClogP value is in the range of 2.0 to 7.0, the amines derived from the blocked isocyanates hydrolyzed by the water content in the ink and the hydrolyzates of the (meth)acrylates react with the components in the ink to form reaction products. The solubility of the reaction products thus formed is improved, which prevents the elution of solids such as cured products and foreign matter, improving ejection stability.

[0112] Examples of polyfunctional (meth)acrylate monomers having a ClogP value in the range of 2.0 to 7.0 include EO-modified trimethylolpropane triacrylate (ClogP 4.0), dipropylene glycol diacrylate (ClogP 2.0), 1,10-decanediol dimethacrylate (ClogP 5.75), tricyclodecane dimethanol diacrylate (ClogP 4.69), and tricyclodecane dimethanol dimethacrylate (ClogP 5.12).

[0113] Furthermore, as the polyfunctional (meth)acrylate according to the present invention, the polyfunctional (meth)acrylates shown below can also be used.

[0114] [ka]

[0115] From the viewpoint of ejection stability, it is preferable that the ink contains 30% by mass or more of a polyfunctional (meth)acrylate monomer having a ClogP value in the range of 2.0 to 7.0, based on the total mass of the ink. In particular, it is preferable that the ink of the present invention contains 30 to 50% by mass of a polyfunctional (meth)acrylate monomer having a ClogP value in the range of 2.0 to 7.0, based on the total mass of the ink.

[0116] In the present invention, the "ClogP value" is a logP value calculated by calculation. The ClogP value can be calculated by the fragment method, the atomic approach method, etc. More specifically, the ClogP value can be calculated using the fragment method described in the following document or the commercially available software package 1 or 2 listed below. Reference: C. Hansch and A. Leo, "Substituent Constants for Correlation Analysis in Chemistry and Biology" (John Wiley & Sons, New York, 1969) Software package 1: MedChem Software (Release 3.54, August 1991, Medicinal Chemistry Project, Pomona College, Claremont, CA), Software package 2: ChemDraw Ultra ver.20.0.0.47 (PerkinElmer Informatics) The numerical values ​​of the ClogP values ​​described in the present specification and elsewhere are "ClogP values" calculated using Software Package 2.

[0117] (bisphenol A structure) The polyfunctional (meth)acrylate preferably has at least one type of bisphenol A structure. Preferred examples of the polyfunctional (meth)acrylate monomer having a bisphenol A structure include the above-mentioned PO adduct diacrylate of bisphenol A, EO-modified bisphenol A diacrylate, and bisphenol A-type epoxy acrylate.

[0118] (hydroxy value) The total hydroxy value of the hydroxyl group-containing compounds contained in the ink of the present invention is preferably within the range of 0.05 to 60 mgKOH / g. When the hydroxy value is within this range, the generation of solid matter is suppressed even when the ink contains water, and the ink has excellent storage stability. Examples of means for adjusting the hydroxy value to be within the range of 0.05 to 60 mgKOH / g include appropriately selecting the compound having a hydroxy value contained in the ink, controlling the charging composition of the compound having a hydroxy value, and purifying the compound having a hydroxy value. In the present invention, the "hydroxy value" refers to the amount (mg) of potassium hydroxide (KOH) required to neutralize the acetic acid bonded to the hydroxy group when 1 g of the ink of the present invention is acetylated. The hydroxy value can be calculated according to the method described in JIS K0070-1992, or can be calculated from the charged composition of the compound having a hydroxy group in 1 g of ink.

[0119] The hydroxy value in the present invention is determined from the composition of the compound having a hydroxy group in 1 g of ink, among the above calculation methods. The specific calculation method is as shown in the following formula (a). Hydroxy value [mgKOH / g] = A [mol] × (number of hydroxyl groups in the compound with hydroxyl groups) × B [mg / mol] (a) In the above formula (a), "A" represents the number of moles of the compound having a hydroxy group in 1 g of ink, and "B" represents the molecular weight of 1 mole of potassium hydroxide (56,000 mg / mol). If the ink contains multiple types of compounds with hydroxy groups, the hydroxy value is calculated for each compound with a hydroxy group using the above formula (a), and the sum of the obtained hydroxy value values ​​is defined as the hydroxy value per 1 g of ink.

[0120] The compound having a hydroxy group is not particularly limited as long as it has a hydroxy group in its structure. Examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Furthermore, examples of hydroxy(meth)acrylates having an alicyclic structure include 1,4-cyclohexanedimethanol mono(meth)acrylate.

[0121] Examples of epoxy (meth)acrylates include aliphatic alcohol-based epoxy (meth)acrylates, aliphatic polyhydric alcohol-based epoxy (meth)acrylates, and phenol-based epoxy (meth)acrylates. Examples of epoxy (meth)acrylates include polyhydric phenol-based epoxy (meth)acrylates, alicyclic carboxylic acid-based epoxy acrylates, and aromatic carboxylic acid-based epoxy (meth)acrylates. Commercially available epoxy (meth)acrylates can be used. Examples of such commercially available products include DENACOL ACRYLATE DA-111, DA-141, DA-212, DA-250, DA-314, DA-721, DA-722, DA-911M, DA-920, and DA-931. All of these commercially available products are manufactured by Nagase ChemteX Corporation. These compounds having a hydroxy group may be used alone or in combination of two or more.

[0122] In the ink of the present invention, the content of the polymerizable monomer is preferably within a range of 40 to 90% by mass, and more preferably within a range of 60 to 85% by mass, based on the total mass of the ink. By keeping the content within this range, coating adhesion is improved.

[0123] <Blocked isocyanate> A blocked isocyanate is a compound having an isocyanate group, the isocyanate group of which is blocked with a blocking agent. Hereinafter, the compound having an isocyanate group will also be referred to as an "isocyanate compound." Heating dissociates the blocking agent from the blocked isocyanate, activating the isocyanate group.

[0124] The ink of the present invention has storage stability because the blocked isocyanate has blocked isocyanate groups and is non-reactive until it is applied to a recording medium. After application, heating the ink to a temperature above the temperature at which the blocking agent dissociates generates isocyanate groups. These groups then react with hydroxyl and / or carboxyl groups of the monomer contained in the ink, causing the ink to harden and form a coating film.

[0125] (Isocyanate compounds) The isocyanate compound is preferably a polyfunctional isocyanate from the viewpoint of curability. The polyfunctional isocyanate is not particularly limited as long as it is a compound having two or more isocyanate groups in the molecule. Specific examples of polyfunctional isocyanates include aromatic polyisocyanates such as 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI); hexamethylene diisocyanate; aliphatic polyisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6XDI (hydrogenated XDI), H12MDI (hydrogenated MDI), and H6TDI (hydrogenated TDI); polyisocyanates such as polymethylene polyphenylene polyisocyanate; and biuret, isocyanurate, and carbodiimide-modified products thereof. The ink of the present invention may use any one of these isocyanates alone or two or more of them in combination.

[0126] (blocking agent) As the blocking agent, known blocking agents can be used. Examples of blocking agents include alcohols such as ethanol, n-propanol, isopropanol, t-butanol, and isobutanol; phenols such as phenol, chlorophenol, cresol, xylenol, and p-nitrophenol; alkylphenols such as pt-butylphenol, psec-butylphenol, p-sec-aminophenol, p-octylphenol, and p-nonylphenol; basic nitrogen-containing compounds such as 3-hydroxypyridine, 8-hydroxyquinoline, and 8-hydroxyquinaldine; and active metal ions such as diethyl malonate, ethyl acetoacetate, and acetylacetone. Examples of suitable amines include ethylene compounds, acid amides such as acetamide, acrylamide, and acetanilide, acid imides such as succinimide and maleimide, imidazoles such as 2-ethylimidazole and 2-ethyl-4-methylimidazole, pyrazoles such as pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole, lactams such as 2-pyrrolidone and ε-caprolactam, oximes of ketones or aldehydes such as acetoxime, methyl ethyl ketone oxime, cyclohexanone oxime, butanone oxime, and acetaldoxime, ethyleneimine, and bisulfites.

[0127] The blocking agent is preferably at least one compound selected from the group consisting of oxime compounds, pyrazole compounds, and active ethylene compounds, in terms of ink storage stability and thermal dissociation properties. Examples of oxime compounds include formamide oxime, acetaldoxime, acetoxime, methyl ethyl ketone oxime, cyclohexanone oxime, and butanone oxime (MEKO). Examples of the pyrazole compounds include pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole. Examples of active ethylene compounds include dimethyl malonate, diethyl malonate (DEM), methyl acetoacetate, ethyl acetoacetate, and acetylacetone.

[0128] An example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate. Another example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3-butylidene)aminooxycarbonylamino]ethyl methacrylate. Another example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl acrylate. Another example of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent is 2-[(3-butylidene)aminooxycarbonylamino]ethyl acrylate.

[0129] The blocked isocyanate preferably has an aromatic ring from the viewpoint of ink storage stability and coating film performance. The blocked isocyanate having an aromatic ring is not particularly limited, but examples thereof include aromatic polyisocyanates such as 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI). The blocking agent for the blocked isocyanate may contain an aromatic group, and a blocking agent containing a benzene ring or a blocking agent containing a heteroaromatic ring is preferred. Dimethylpyrazole (DMP) is particularly preferred as a blocking agent for the blocked isocyanate containing an aromatic group.

[0130] The blocked isocyanate may contain a polyisocyanate structure. The polyisocyanate structure may be of three types: isocyanurate, biuret, and adduct. From the viewpoints of curability and coating film performance, the blocked isocyanate of the present invention is preferably of the isocyanurate or biuret type, and more preferably of the isocyanurate type.

[0131] The content of the blocked isocyanate is preferably within a range of 0.1 to 20 parts by mass, and more preferably within a range of 1 to 10 parts by mass, per 100 parts by mass of the polymerizable monomer. When the amount of the blocked isocyanate is 0.1 parts by mass or more, the ink is sufficiently cured by heat, and when the amount of the blocked isocyanate is 20 parts by mass or less, the ink has excellent storage stability at high temperatures.

[0132] The blocking agent may be used alone or in combination of two or more kinds. Alternatively, a plurality of blocked isocyanates blocked with a single blocking agent or two or more kinds of blocking agents may be used. Examples of commercially available blocked isocyanates include BI7774, BI7779, BI7950, BI7960, BI7961, BI7981, BI7982, BI7991, and BI7992 (all manufactured by LANXESS), MFK60X (manufactured by Asahi Kasei Chemicals Corporation), VPLS2253 and BL4265SN (both manufactured by Sumika Bayer Urethane Co., Ltd.), PU5211 and PU5210 (both manufactured by Leeson Polyurethanes), Karenz MOI-BP (2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate), and Karenz MOI-BM (2-(0-[1′-methylpropylideneamino]carboxyamino)ethyl methacrylate) (both manufactured by Showa Denko KK).

[0133] <Photopolymerization initiator> When the polymerizable monomer (polyfunctional (meth)acrylate monomer) is a radical polymerizable compound, the photopolymerization initiator according to the present invention preferably uses a photoradical initiator. When the polymerizable monomer is a cationically polymerizable compound, the photopolymerization initiator according to the present invention preferably uses a photoacid generator. The ink of the present invention may contain only one type of photopolymerization initiator, or may contain two or more types of photopolymerization initiators. The photopolymerization initiator may be a combination of both a photoradical initiator and a photoacid generator.

[0134] Photoradical initiators include cleavage-type radical initiators and hydrogen abstraction-type radical initiators. Examples of cleavage-type radical initiators include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, benzyl and methylphenyl glyoxyesters.

[0135] Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzil dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone.

[0136] Examples of benzoin-based initiators include benzoin, benzoin methyl ether, and benzoin isopropyl ether. Examples of acylphosphine oxide initiators include 2,4,6-trimethylbenzoindiphenylphosphine oxide. Examples of hydrogen abstraction radical initiators include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, and 10-butyl-2-chloroacridone, and examples of hydrogen abstraction radical initiators include 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone.

[0137] Examples of benzophenone initiators include benzophenone, o-benzoylmethylbenzoate-4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone. Examples of thioxanthone initiators include 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone. Examples of aminobenzophenone initiators include Michler's ketone and 4,4'-diethylaminobenzophenone. Examples of photoacid generators include the compounds described in Organic Electronics Materials Research Group, "Imaging Organic Materials," Bunshin Publishing (1993), pp. 187-192.

[0138] The content of the photopolymerization initiator may be in a range that allows the ink to be sufficiently cured, and may be, for example, in the range of 0.01 to 10% by mass relative to the total mass of the ink of the present invention. Examples of commercially available photopolymerization initiators include Omnirad TPO (manufactured by IGM), Omnirad 819 (manufactured by IGM), and Omnirad 379 (manufactured by IGM). Examples of commercially available photopolymerization initiators include Speedgure ITX (manufactured by Sartomer) and Speedcure EPD (manufactured by Sartomer).

[0139] <Polymerization inhibitor> The ink of the present invention preferably further contains a polymerization inhibitor, which can reduce the adhesiveness between multiple curable compounds. The term "polymerization inhibitor" includes all compounds added to inhibit polymerization reactions during preparation of ink containing polymerizable monomers or during storage after preparation.

[0140] In the present invention, various conventionally known polymerization inhibitors can be used. The polymerization inhibitor preferably contains any one of an N-oxyl-based polymerization inhibitor, a phenol-based polymerization inhibitor containing an ot-butyl group, or a polymerization inhibitor having two or more aromatic rings.

[0141] Among these, it is more preferable to contain an N-oxyl-based polymerization inhibitor from the viewpoint of adhesion to printed wiring boards. In the ink of the present invention, the content of the polymerization inhibitor is preferably within the range of 0.05 to 0.5% by mass relative to the total mass of the ink.

[0142] (N-oxyl polymerization inhibitor) Examples of the N-oxyl polymerization inhibitor include 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, Irgastab (registered trademark) UV10 (manufactured by BASF), and the like.

[0143] (Phenol-based polymerization inhibitor) Examples of phenolic polymerization inhibitors include 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, and 2-tert-butyl-4,6-dimethylphenol. Examples of phenolic polymerization inhibitors include 2,6-di-tert-butyl-4-methylphenol and 2,4,6-tri-tert-butylphenol. Examples of phenolic polymerization inhibitors include 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0144] (Quinone-based polymerization inhibitor) Examples of the quinone polymerization inhibitor include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0145] (amine-based polymerization inhibitor) Examples of the amine-based polymerization inhibitor include alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, and phenothiazine.

[0146] (Other polymerization inhibitors) Other examples of the polymerization inhibitor include copper dithiocarbamate polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0147] Only one of these may be contained, or two or more of them may be contained. Among these, N-oxyl and quinone polymerization inhibitors are preferred. As the inhibitor, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) is preferred. Furthermore, as the inhibitor, 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT) and 2,4-di-tert-butylphenol are preferred. As a polymerization inhibitor having two or more aromatic rings, naphthoquinone and the like are preferred.

[0148] <Other ingredients> (surfactant) The ink of the present invention may further contain a surfactant, if necessary. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, as well as silicone-based and fluorine-based surfactants. Examples of the anionic surfactant include dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers. Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts.

[0149] (coloring agent) The ink of the present invention may further contain a colorant, if necessary. The colorant may be a pigment or a dye, but is preferably a pigment from the viewpoints of having good dispersibility in the constituent components of the ink and excellent weather resistance. The pigment is not particularly limited, and examples thereof include organic pigments or inorganic pigments having the following numbers listed in the Color Index.

[0150] The ink of the present invention may contain only one type of colorant, or may contain two or more types of colorants, and may be toned to a desired color. The content of the colorant is preferably within a range of 0.1 to 20% by mass, and more preferably within a range of 0.2 to 10% by mass, relative to the total mass of the ink.

[0151] (pigment) Red or magenta pigment Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, and 257; Pigment Violet 3, 19, 23, 29, 30, 37, 50, and 88; and Pigment Orange. 13, 16, 20, 36 or a mixture thereof.

[0152] Blue or cyan pigment Examples of blue or cyan pigments include pigments selected from Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17:1, 22, 27, 28, 29, 36, and 60, or mixtures thereof.

[0153] Green Pigment Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, and 50, and mixtures thereof.

[0154] Yellow pigment Examples of yellow pigments include pigments selected from Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 147, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof.

[0155] Black pigment Examples of black pigments include pigments selected from Pigment Black 7, 28, and 26, and mixtures thereof.

[0156] <Examples of commercially available pigments> Examples of commercially available pigments include Black Pigment (manufactured by Mikuni), Chromofine Yellow 2080, 5900, 5930, AF-1300, 2700L, Chromofine Orange 3700L, 6730, Chromofine Scarlet 6750, Chromofine Magenta 6880, 6886, 6891N, 6790, 6887, Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, and Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seika Fast Red 8 040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B 1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B 800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (all manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.; "Chromofine" is a registered trademark of the company); KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (manufactured by DIC);Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow; T-13, T-05, Pigment Yellow1705, Colortex Orange 202, Colortex Red101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, 105C, USN, Colortex Maroon601, Colortex BrownB610N, Colortex Violet600, Pigment Red 122, Colortex Blue516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403, Colortex Black 702, U905 (all manufactured by Sanyo Dye Co., Ltd.; "Colortex" and "Finecol" are registered trademarks of the company); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (all manufactured by Toyo Ink Co., Ltd.; "Lionol" is a registered trademark of the company); Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapearm Blue B2G (all manufactured by Hoechst Industries); Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (all manufactured by Clariant; "Novoperm" and "Hostaperm" are registered trademarks of the company); carbon black #2600, #2400, #2350, #2200, #1000, #990, #980, #970, #960, #950, #850, MCF88, #750, #650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77, #52, #50, #47, #45, #45L, #40, #33, #32, #30, #25, #20, #10, #5, #44, and CF9 (all manufactured by Mitsubishi Chemical).

[0157] Pigment Dispersion The pigment can be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like.

[0158] The pigment is preferably dispersed so that the volume average particle size of the pigment particles is preferably within a range of 0.08 to 0.5 μm, and the maximum particle size of the pigment particles is preferably within a range of 0.3 to 10 μm, more preferably within a range of 0.3 to 3 μm. The dispersion of the pigment is adjusted by selecting the pigment, dispersant and dispersion medium, dispersing conditions, filtering conditions, and the like.

[0159] <Dispersant> The ink of the present invention may further contain a dispersant to improve the dispersibility of the pigment. Examples of dispersants include carboxylic acid esters having a hydroxy group, salts of long-chain polyaminoamides and high-molecular-weight acid esters, salts of high-molecular-weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high-molecular-weight unsaturated acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, naphthalene sulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Examples of commercially available dispersants include the Solsperse (registered trademark) series manufactured by Avecia and the PB series manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0160] <Dispersion aid> The ink of the present invention may further contain a dispersing aid, if necessary. The dispersing aid may be selected depending on the pigment. The total content of the dispersant and dispersion aid is preferably within the range of 1 to 50% by mass relative to the total mass of the pigment.

[0161] 《Dispersion medium》 The ink of the present invention may further contain a dispersion medium for dispersing the pigment, if necessary. The ink of the present invention may contain a solvent as a dispersion medium, but in order to prevent the solvent from remaining in the formed image, it is preferable to use the above-mentioned monomer as the dispersion medium. As the above-mentioned monomer, a monomer having a particularly low viscosity can be used.

[0162] Furthermore, when a solvent is used as a dispersion medium, the solvent is likely to volatilize when the ink is heated, which reduces the dispersibility of the pigment, from the viewpoint of ejection stability. However, by using the aforementioned polyfunctional (meth)acrylate monomer, the reduction in dispersibility of the pigment can be suppressed.

[0163] (Other additives) The ink of the present invention may further contain a coupling agent, a solvent, etc., as required.

[0164] Coupling Agents The ink of the present invention may further contain various coupling agents as needed, which can improve adhesion to printed wiring boards. Examples of various coupling agents include silane-based, titanium-based, and aluminum-based coupling agents.

[0165] <Curing accelerator> In the present invention, a curing accelerator may be contained as needed. The curing accelerator is not particularly limited as long as it accelerates the thermal curing of the resin component. Examples of the curing accelerator include imidazoles, dicyandiamide derivatives, dicarboxylic acid dihydrazides, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, 2-ethyl-4-methylimidazole-tetraphenylborate, and 1,8-diazabicyclo[5.4.0]undecene-7-tetraphenylborate.

[0166] <Ion scavenger> In the present invention, an ion scavenger may be contained as needed. The inclusion of an ion scavenger has the advantage that ionic impurities are adsorbed, improving the insulating properties of the cured film when it absorbs moisture. Examples of the ion trapping agent include inorganic ion adsorbents such as triazine thiol compounds, bisphenol-based reducing agents, zirconium compounds, and antimony-bismuth-based magnesium aluminum compounds.

[0167] Flame retardants In the present invention, a flame retardant may be contained as needed. Examples of flame retardants that can be used include hydrated metals such as aluminum hydroxide and magnesium hydroxide, red phosphorus, ammonium phosphate, ammonium carbonate, zinc borate, zinc stannate, molybdenum compounds, bromine compounds, and chlorine compounds.Furthermore, examples of flame retardants that can be used include phosphate esters, phosphorus-containing polyols, phosphorus-containing amines, melamine cyanurate, melamine compounds, triazine compounds, guanidine compounds, and silicone polymers.

[0168] "solvent" The ink of the present invention is preferably solvent-free from the viewpoint of rapid curing and ejection stability, but solvents may be added to adjust the ink viscosity.

[0169] 5. Inkjet ink manufacturing method The ink according to the present invention can be prepared by mixing the aforementioned polymerizable monomer, blocked isocyanate, photopolymerization initiator, and any other components. The resulting mixture is preferably filtered through a predetermined filter. When preparing an ink containing a pigment, it is preferable to prepare a pigment dispersion containing the pigment and polymerizable monomer, and then mix the pigment dispersion with other components. The pigment dispersion may further contain a dispersant.

[0170] The pigment dispersion can be prepared by dispersing a pigment in a polymerizable compound. The pigment can be dispersed using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, etc. In this case, a dispersant may be added.

[0171] 6. How to store inkjet ink The ink according to the present invention is preferably stored at a temperature within the range of -15 to 40°C and at a humidity of 60% RH or less. Specifically, in order to store the ink within the above temperature and humidity ranges, it is preferable to use the following ink container as a container for containing the ink according to the present invention.

[0172] [Ink container] The ink according to the present invention has a water vapor transmission rate of 0.05 to 1.50 g / m under conditions of 40°C and 90% RH. 2 It is preferable that the ink is contained in an ink container that satisfies the ink supply voltage range of 1000 V / day / atm. Hereinafter, the ink container may be simply referred to as the "container."

[0173] The container is a member that is filled with ink and substantially holds the ink. The form of the container in the present invention is not limited to the following, but examples include an ink cartridge, a pack, a bottle, a tank, a vial, and a can. Among these, ink cartridges, packs, bottles, and tanks are preferred, and packs are more preferred, because they are widely used and the water vapor transmission rate can be easily controlled to a desired value. Furthermore, the ink in the present invention can be contained in a bottle and then further contained in a pack.

[0174] A pack is a container made of flexible film. A pack is preferable because it is lightweight, can be easily placed in a box-shaped container, the volume of the container changes easily according to the amount of ink remaining, and the film can be heat-sealed to form a bag.

[0175] The container of this embodiment can be used in at least the following modes (A) to (C). (A) A form such as an ink cartridge that is separate from the inkjet recording device (film-coating device) and is attached to the recording device to sequentially supply the composition to the recording device. (B) A form that is separate from the recording device, and when ink is used, only the ink is transferred from the container to the recording device (C) A form such as a tank that is pre-installed in the recording device and contains ink

[0176] The above (A) and (B) can be said to be ink containers from the time of shipping until just before supplying (transferring) ink to the recording device. The above (C) can be said to be an ink container from the time the recording apparatus is shipped until the recording apparatus starts using ink for the first time. The above (A) and (C) can be said to be ink containers that perform printing in the recording device while ink is being supplied from the container to the recording device via a connection such as an ink tube. Furthermore, the above (B) can be said to be an ink container that transfers ink from the container to a recording device and then prints with the recording device. The object to which the ink is transferred in (B) can be a tank or the like attached to the recording device.

[0177] Examples of materials that can be used to form the container include polyethylene terephthalate (PET), polypropylene (PP), polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer (EVOH), and polystyrene. The container may also be a film made of these materials. The container may also be constructed by blending the above materials in an appropriate ratio or by stacking multiple materials. In the case of a film, the container may be obtained by laminating. When multiple types of films are stacked, it is not necessary for all of the multiple films to be the above-mentioned films, and a portion of the films may be made of other materials, such as metals and metal compounds.

[0178] In order to increase the flexibility of the container, the container may contain a plasticizer as a constituent material. Examples of plasticizers include fatty acid esters, epoxy compounds, and polyester compounds. Among these, fatty acid esters are preferred in terms of versatility as plasticizers. Examples of fatty acid esters include phthalates, adipates, trimellitates, and citrates. The fatty acid esters may be used alone or in combination of two or more.

[0179] During storage and transportation, the container may be agitated to release the sedimentation of components contained in the ink. This is because, if the sedimentation of components contained in the ink continues for a long period of time, the sediment may turn into cake, making it difficult to release. Furthermore, when supplying ink from the container to a recording device, it is preferable to agitate the container to release the sedimentation.

[0180] When the container is a container (pack) made of a flexible film, durability is particularly required so that cracks and tears do not occur during the stirring operation. Preferred examples of durable film materials include plastic films such as polyethylene terephthalate (PET), polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polystyrene, etc. Ethylene-vinyl acetate copolymer is more preferred as the film material. Preferred examples of the film include stretched plastic films such as high-density, low-density, or linear low-density polyethylene, polypropylene, ethylene-vinyl alcohol copolymer, and polystyrene. A laminated film in which multiple layers of films are bonded together may also be used.

[0181] When the container is the above-mentioned pack, if the components contained in the ink settle, the pack may be shaken left and right to agitate the ink and restore the ink. In this case, in order to prevent the pack from cracking or breaking, a plasticizer may be contained as a constituent material of the pack. The plasticizer may be any of those listed above, and fatty acid esters are preferred.

[0182] When the container is the above-mentioned pack, the water vapor transmission rate of the film constituting the pack is 0.05 to 1.50 g / m under conditions of 40°C and 90% RH. 2 The water vapor transmission rate is preferably in the range of 0.05 to 1.00 g / m. 2 It is more preferable that the range is 0.05 to 0.5 g / m 2 It is particularly preferred that the temperature is in the range of 1000 kJ / day atm. Water vapor permeability of 0.05 to 1.50 g / m 2 By using a film within the range of 1000 ppm / day, it is possible to prevent the moisture content of the ink filled in the pack from increasing even when the pack is stored for a long period of time. Water vapor permeability of 1.50g / m 2To achieve a value of 1.000 sq m / day atm or less, for example, the material constituting the film may be selected appropriately, or a layer composed of at least one of a metal and a metal compound may be provided on the film.

[0183] Among these, it is preferable to provide a layer made of at least one of a metal and a metal compound from the viewpoint of high versatility. Examples of metals include Al and Ti. Metal compounds are preferably metal oxides, such as alumina, silica, titania, and zirconia. These may be used alone or in combination of two or more. In this specification, metal oxides include silica.

[0184] The thickness of the film constituting the pack is preferably within the range of 50 to 200 μm. The lower limit of the film thickness is more preferably 70 μm or more, and even more preferably 80 μm or more. The upper limit of the film thickness is preferably 150 μm or less, and even more preferably 130 μm or less. When the film is a laminated film consisting of multiple layers, the film thickness is the total thickness. A film thickness within the above range is preferred in terms of the durability and flexibility of the film.

[0185] The volume of ink that can be stored in the container is not limited to the following, but is preferably in the range of 100 to 5000 mL. The lower limit of the ink volume is preferably 200 mL or more, and more preferably 500 mL or more. The upper limit of the ink volume is preferably 3000 mL or less, more preferably 2000 mL or less, and even more preferably 1000 mL or less. When the volume is within the above range, the curing property, storage stability, and ejection stability can all be further improved.

[0186] 5. Solder resist and printed wiring boards The solder resist preferably uses the ink according to the present invention described above. The method for forming the solder resist pattern involves first patterning an oxide film of conductive material such as copper or zinc formed on a substrate by inkjet printing using the ink according to the present invention. The ink is then cured with light to form a resist film. Next, the oxide film in the portion not covered with the resist film is removed with an acid etching solution. Furthermore, by removing the resist film covering the oxide film with alkali, it is possible to form precise circuits and patterns. In this way, a printed wiring board having a solder resist is formed. [Example]

[0187] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0188] <Preparation of Yellow Pigment Dispersion (Y Dispersion)> Dispersant 1 and Dispersant 2 shown below and the dispersion medium were placed in a stainless steel beaker, heated on a hot plate at 65°C for 1 hour while stirring and dissolving, and then cooled to room temperature. The pigment shown below was then added, and the mixture was placed in a glass bottle together with 200 g of 0.5 mm diameter zirconia beads and sealed. The mixture was dispersed in a paint shaker until the desired particle size was reached, after which the zirconia beads were removed. Dispersant 1: EFKA7701 (manufactured by BASF) 5.6 parts by mass Dispersant 2: Solsperse 22000 (manufactured by Lubrizol Japan) 0.4 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 80.6 parts by mass Pigment: PY147 (pigment yellow 147) (BASF Oracet® Yellow 140) 13.4 parts by mass

[0189] <Preparation of cyan pigment dispersion (C dispersion)> The yellow pigment dispersion was prepared in the same manner as in the preparation of the yellow pigment dispersion, except that the dispersant, dispersion medium, and pigment were changed as shown below. Dispersant: EFKA7701 (BASF) 7 parts by mass Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by mass Pigment: PB15:4 (pigment blue 15:4) (Dainichi Seika Chemicals, Chromofine Blue 6332JC) 23 parts by mass

[0190] <Blocked isocyanate> The blocked isocyanates used were as follows: Trixene BI7982 (manufactured by LANXESS, isocyanate compound: HDI) Trimer, Blocking Agent: DMP, Trifunctional BI) "HDI Trimmer" is C 24 H 36 It is N6O6 and has an isocyanurate structure. "DMP" is dimethylpyrazole, which has an aromatic ring structure.

[0191] <Photopolymerizable monomer> The photopolymerizable monomers used were those shown in Table I below.

[0192] [Table 1]

[0193] <Photopolymerization initiator> The photopolymerization initiator used was as follows: Omnirad 379EG (IGM) Omnirad TPO H (IGM) Speedcure 2-ITX (Sartomer, 2-isopropylthioxanthone)

[0194] <Preparation of Inkjet Ink> The inks were mixed according to the ink compositions shown in Table II below, and the mixture was filtered through a 3 μm Teflon (registered trademark) membrane filter manufactured by Advantec while heated to 60°C, yielding inks 1 to 7. Inks 1 to 7 have the same composition, but after preparation of the ink, a dehydration step (adjusting the drying gas injection time described below) was carried out to obtain inks 1 to 7 with different water contents.

[0195] [Table 2]

[0196] <Inkjet pattern formation> The ink prepared above was loaded into an ink jet recording apparatus having an ink jet recording head equipped with a piezoelectric ink jet nozzle. As shown in Figure 1, the ink supply system of the device consists of a dehydration device, an ink tank (first sub-tank), a degassing device, an ink flow path, a sub-ink tank (second sub-tank) located just before the inkjet recording head, piping with a metal filter, and a piezo head. In the dehydration device and degassing device, dehydration and degassing were carried out under the following conditions, and the ink from the ink tank to the head was heated to 55°C. Next, a heater was also built into the piezo head, and the ink temperature inside the piezo head was heated to 60° C. The piezo head used was KM1800i-SHC manufactured by Konica Minolta. Using this inkjet recording device, a voltage was applied so as to form dots with a droplet volume of 3.5 pL. A 70mm x 70mm solid pattern and a comb pattern with 100μm lines and spaces were printed on the substrate, each with a thickness of 30μm. Each pass was printed with 200mJ / cm using a Phoseon Technology LED lamp (365nm). 2 The ink layer was temporarily cured by irradiating it with light at a temperature of 2000 mJ / cm 2 after which it was placed in an oven set to 150°C for 60 minutes for full curing. 2After irradiation, a print sample was obtained.

[0197] <Ink dehydration process> Dry gas was generated using a membrane dehumidifier and a general-purpose compressor. The dehumidifier used was an SMC membrane dehumidifier IDG5-02B-PS. The relative humidity of the generated dry gas was measured and found to be 1.5% RH. Drying gas was injected into the ink in the dehydration device of the ink supply system. The flow rate of the drying gas was set to a range of 0.3 to 1.0 ml / min, which balanced the generation and defoaming of bubbles at the ink interface. The water content of the ink was adjusted by varying the drying gas injection time from 1 to 12 hours. After the dehydration process, the water content of the ink before it entered the head was measured using a Karl Fischer moisture meter (MKV-710, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). The measured water content of the ink is shown in Table II.

[0198] <Ink degassing process> The degassing device used was an external reflux type hollow fiber degassing module and a vacuum pump. After the dehydration process, ink flowing from the ink tank was passed through the ink inlet of the degassing module onto the outside of the hollow fibers. The vacuum pump was set to -90 kPa to reduce the pressure inside the hollow fibers, and degassing was performed to adjust the amount of dissolved oxygen in the ink. As the external circulation type hollow fiber degassing module, for example, SEPAREL EF-002A-P manufactured by Dainippon Ink and Chemicals, Inc. was used. After the degassing process, the amount of dissolved oxygen in the ink before it entered the head was measured using a fluorescent dissolved oxygen meter (Visifarm DO Arc, manufactured by Hamilton).

[0199] <Amount of solids generated> After the dehydration and degassing processes, the ink was stored at 40°C and 80% RH for four days before flowing into the head. After storing the ink for one day at the injection temperature of 55°C, 300 mL of ink was pressure filtered through a 5.0 μm PTFE filter (2.0 mm diameter). The 5.0 μm PTFE filter was then removed and washed with ethanol. The presence or absence of solid matter was checked using an optical microscope and evaluated according to the following criteria. "A" and "B" on the following criteria were deemed acceptable for practical use. (standard) A: No solid matter is present on the entire surface of the filter. B: Solid matter is present within 1% or less of the filter area. C: Solid matter is present in the area of ​​more than 1% but not more than 5% of the filter area. D: Solids present over more than 5% of the filter area.

[0200] <Ink ejection stability (large volume ejection)> (Number of missing nozzles after 200kg of ink is ejected) Using the piezo head, continuous ejection (driving) was performed under conditions of droplet volume of 3.5 pL, droplet speed of 7.0 m / sec, ejection frequency of 20 kHz, and printing rate of 100%. After ejecting 200 kg of ink, the number of nozzles that were not ejecting was counted and evaluated according to the following criteria. "A," "B," and "C" in the following criteria were deemed to be acceptable for practical use. (standard) A: The number of missing nozzles is 0. B: The number of missing nozzles is 1 or more and less than 3. C: The number of missing nozzles is 3 or more but less than 5. D: The number of missing nozzles is 5 or more and less than 10. E: The number of missing nozzles is 10 or more.

[0201] <Ink curing properties 1 (cross-cut resistance, substrate adhesion)> For the solid pattern print samples, grid-shaped cuts were made in the cured film according to the cross-cut method of JIS K5600, adhesive tape was applied, and the tape was peeled off to observe the peeling state of the cured film. "A" and "B" in the following criteria were deemed to be acceptable for practical use. (standard) A: The adhesion residual rate is 100%. B: The residual adhesion rate is 80% or more and less than 100%. C: The residual adhesion rate is 60% or more and less than 80%. D: The residual adhesion rate is less than 60%.

[0202] <Ink curing property 2 (hydrochloric acid resistance)> For solid pattern print samples, the cured film was immersed in 10% hydrochloric acid for 30 minutes, then washed with water and dried. Then, grid-shaped cuts were made in the cured film according to the cross-cut method of JIS K5600, and adhesive tape was applied and peeled off to observe the peeling state of the cured film. "A" and "B" on the following criteria were deemed acceptable for practical use. (standard) A: The adhesion residual rate is 100%. B: The residual adhesion rate is 80% or more and less than 100%. C: The residual adhesion rate is 60% or more and less than 80%. D: The residual adhesion rate is less than 60%.

[0203] [Table 3]

[0204] As shown by the above results, it is clear that the coating film forming method of the present invention prevents the generation of solid matter, has excellent injection stability after large-volume injection, and has good curing properties compared to the coating film forming method of the comparative example. [Industrial Applicability]

[0205] The present invention can be used in a coating film forming method that suppresses the generation of solid matter in the device and the clogging of the head nozzle, and that provides good ejection properties and stable curing properties. [Explanation of symbols]

[0206] 1. Inkjet recording device (film forming device) 24a recording head 24b Ink flow path 50 Ink supply unit 51 Ink Tank 53 Supply Pump 241 First Subtank 241a No. 1 float sensor 242 Degassing Module 243 Liquid transfer pump 244 Check valve 245 Second Subtank 245a Second float sensor 249 Vacuum Pump 270 Ink heating unit (heating means according to the present invention) 280 Degassing device 300 Dehydration device (dehydration means according to the present invention) 2421 Shell (Chamber) 2424 Central tube 2424b Small hole (hole) 2426 Hollow fiber membrane (gas permeable membrane) 2427 Heating unit (heating means according to the present invention) 2428 Second heating unit (heating means according to the present invention)

Claims

1. A coating film forming method using an inkjet head, comprising: The inkjet ink contains a polymerizable monomer, a blocked isocyanate, and a photopolymerization initiator, a dehydration step of the inkjet ink; a heating step of heating the ink-jet ink ejected from the ink-jet head to a temperature of 40° C. or higher. Paint film formation method.

2. The heating step is performed in an ink supply path that supplies the inkjet ink to the inkjet head. The method for forming a coating film according to claim 1.

3. In the dehydration step, dry gas whose moisture content has been reduced by a drying device is injected into an ink supply path that supplies the inkjet ink to the inkjet head. The method for forming a coating film according to claim 1.

4. In the dehydration step, the dry gas is generated using a membrane filter or activated carbon. The method for forming a coating film according to claim 3.

5. a degassing step for the inkjet ink after the dehydration step; The method for forming a coating film according to claim 1.

6. The degassing step uses hollow fibers or ultrasonic waves. The method for forming a coating film according to claim 5.

7. After the dehydration step, a second heating step is further performed in addition to the heating step in the ink supply path that supplies the inkjet ink to the inkjet head. The method for forming a coating film according to claim 2.

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