Inkjet recording method and inkjet recording apparatus

Abstract

An inkjet recording method for ejecting ink from an inkjet head 24a to record an image comprises a main tank 51 that serves as an ink supply source, a first sub-tank 241 that is connected to the main tank 51 and to which ink is supplied, a degassing device that is connected to the first sub-tank 241 and degasses the ink supplied from the first sub-tank 241, a second sub-tank 245 that supplies the ink degassed by the degassing device to an inkjet head 24a and controls a negative pressure applied to the inkjet head 24a, and a heating device 270 that heats at least a flow path of the ink in the first sub-tank 241. The method further comprises a control unit 40 that feeds the ink so that the amount of ink freshly supplied from the main tank 51 to the first sub-tank 241 is greater than the amount of ink remaining inside the first sub-tank 241. The ink is a radical polymerizable ink containing a thermosetting component.

Description

[Technical field]

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus, and more particularly to an inkjet recording method and an inkjet recording apparatus which are excellent in coating durability, solder heat resistance and ejection stability. [Background technology]

[0002] Solder masks generally use radical-curing UV inks. Radical-curing UV inks can cause unintended polymerization due to radical species generated within the ink system (hereinafter referred to as "thermal polymerization"). Such radical species are captured by polymerization inhibitors or oxygen in the ink system, but if the amount of radical species generated continues to increase, there is a risk that they will not be able to be captured by these and will react with monomers, resulting in polymerization.

[0003] On the other hand, unlike the markings that preceded inkjet printing on printed circuit boards, solder masks are required to be printed with a high deposition amount and high duty, as in graphic printing, and are also required to be highly productive. In such inkjet recording devices, it is known that suppressing cavitation by degassing the ink is effective in improving the ejection reliability of the inkjet head (see, for example, Patent Document 1).

[0004] In addition, in order to improve the durability of the coating film as a solder mask, the ink usually contains a thermosetting component. If the amount of such a functional component added is increased in order to increase the durability of the coating film, the ink viscosity increases. Therefore, in order to adjust the viscosity range to the optimum range for ejection, the ink must be heated at a higher temperature than general UV inks. Also, as mentioned above, in order to improve ejection reliability, the ink must be degassed, and due to the need for heating and degassing, it is necessary to reduce the risk of thermal polymerization when handling solder mask ink. Although systems have been invented in which ink is supplied while degassing under high temperature conditions of about 60 to 90°C, no systems have been discovered in which the ink itself contains a thermosetting component (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-136957 A [Patent Document 2] Patent No. 6708128 [Patent Document 3] Patent No. 6036543 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems and circumstances, and an object of the present invention is to provide an inkjet recording method and an inkjet recording apparatus which have excellent coating film durability and solder heat resistance, and which are capable of stably ejecting ink for a long period of time without causing ink thickening or polymerization reaction even under ink deaeration. [Means for solving the problem]

[0007] In the course of investigating the causes of the above problems in order to solve the above-mentioned issues, the inventors discovered that by controlling the amount of ink newly supplied from the main tank to the first sub-tank so that it is greater than the amount of ink remaining in the first sub-tank, it is possible to achieve excellent coating durability, solder heat resistance and ejection stability even when using a radically polymerizable ink containing a thermosetting component, and thus arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. An inkjet recording method for recording an image by ejecting ink from an inkjet head, comprising: A main tank as an ink supply source; a first sub-tank connected to the main tank and supplied with ink; a degassing device connected to the first sub-tank and configured to degas the ink supplied from the first sub-tank; a second sub-tank that supplies the ink degassed by the degassing device to the inkjet head and controls a negative pressure applied to the inkjet head; a heating device that heats at least the ink flow path in the first sub-tank, a control unit that sends ink so that an amount of ink newly supplied from the main tank to the first sub-tank is greater than an amount of ink remaining in the first sub-tank, The ink jet recording method, wherein the ink is a radical polymerizable ink containing a thermosetting component.

[0009] 2. The ink jet recording method according to claim 1, wherein the control unit intermittently transfers the ink from the main tank to the first sub-tank.

[0010] 3. The ink-jet recording method according to item 1 or 2, wherein the thermosetting component contains a blocked isocyanate.

[0011] 4. An inkjet recording method described in any one of items 1 to 3, further comprising a heating device for heating the ink flow path in the second sub-tank, and wherein the surface area of ​​the tank inner wall heated by the heating device in contact with the ink in the first and second sub-tanks is larger in the first sub-tank than in the second sub-tank.

[0012] 5. The ink jet recording method according to any one of items 1 to 4, wherein the first sub-tank has a larger capacity than the second sub-tank.

[0013] 6. An inkjet recording device that records an image by ejecting ink from an inkjet head, A main tank as an ink supply source; a first sub-tank connected to the main tank and supplied with ink; a degassing device connected to the first sub-tank and configured to degas the ink supplied from the first sub-tank; a second sub-tank that supplies the ink degassed by the degassing device to the inkjet head and controls a negative pressure applied to the inkjet head; a heating device that heats at least the ink flow path in the first sub-tank, The inkjet recording apparatus further includes a control unit that sends the ink so that the amount of ink newly supplied from the main tank to the first sub-tank is greater than the amount of ink remaining in the first sub-tank.

[0014] 7. The ink jet recording apparatus according to claim 6, wherein the control unit intermittently transfers the ink from the main tank to the first sub-tank. Effect of the Invention

[0015] According to the above-mentioned means of the present invention, it is possible to provide an inkjet recording method and an inkjet recording apparatus which are excellent in coating film durability and solder heat resistance, and which are capable of stably ejecting ink for a long period of time without causing thickening of the ink or polymerization reaction even under ink deaeration. Although the mechanism by which the effects of the present invention are manifested or the mechanism by which the effects of the present invention are acted upon has not been clearly understood, it is speculated as follows. It was found that the most effective way to prevent thermal polymerization after degassing of ink in the ink supply system of an inkjet recording device is to keep the ink supplied to the degassing device as fresh as possible. In other words, it is presumed that if the ink remains in the first subtank for a long time, the polymerization inhibitor contained in the ink will gradually become inactive, making the ink more susceptible to thermal polymerization in the flow path downstream of the degassing device. For this reason, it is preferable to use up as much ink as possible in the first subtank, rather than consuming it by constantly refilling it. Therefore, in the present invention, by sending ink so that the amount of ink newly supplied to the first sub-tank is greater than the amount of ink stored in the first sub-tank, it is possible to shorten the residence time in the first sub-tank as much as possible and improve the stability of the ink in the ink supply system until it is supplied to the inkjet head. In other words, even when the ink is degassed, the ink does not thicken or polymerize, and the ink can be ejected from the inkjet head stably for a long period of time. As a result, a coating film formed by ejecting such an ink from an inkjet head has excellent durability because the ink residence time in the ink supply system is shortened, thereby suppressing thermal decomposition of the initiator, thermosetting components, etc., and improving the efficiency of photocuring and thermal curing after baking, which are the original purposes. Furthermore, since the ink is a radically polymerizable inkjet ink containing a thermosetting component, it is possible to obtain the coating durability and solder heat resistance required for a solder mask, for example. [Brief description of the drawings]

[0016] [Figure 1A] FIG. 1 is a front view illustrating a schematic configuration of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 1B] Plan view of an inkjet recording apparatus [Diagram 2] A block diagram showing the internal configuration of an inkjet printing apparatus. [Diagram 3] FIG. 1 is a diagram illustrating an ink path in an inkjet recording apparatus according to an embodiment of the present invention. [Figure 4] An enlarged view of a portion of the ink path shown in FIG. [Figure 5A] Top cross-sectional view showing the first sub-tank [Figure 5B] 5B is a cross-sectional view taken along a line VV in FIG. 5A. [Figure 6A] FIG. 5B is a top cross-sectional view showing a modification of the embodiment shown in FIG. [Figure 6B] FIG. 5B is a top cross-sectional view showing a modification of FIG. [Figure 6C] FIG. 5B is a top cross-sectional view showing a modification of the embodiment shown in FIG. [Figure 7]Schematic cross-sectional view of a cylindrical degassing module cut along a plane passing through the central axis. [Figure 8] 10 is a flowchart illustrating an example of an ink supply process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The inkjet recording method of the present invention is an inkjet recording method for recording an image by ejecting ink from an inkjet head, comprising: a main tank as an ink supply source; a first sub-tank connected to the main tank and supplied with ink; a degassing device connected to the first sub-tank and degassing the ink supplied from the first sub-tank; a second sub-tank that supplies the ink degassed by the degassing device to the inkjet head and controls the negative pressure applied to the inkjet head; and a heating device that heats at least the ink flow path in the first sub-tank, and further comprising a control unit that feeds the ink so that the amount of ink newly supplied from the main tank to the first sub-tank is greater than the amount of ink remaining in the first sub-tank, and the ink is a radically polymerizable ink containing a thermosetting component. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0018] In an embodiment of the present invention, the control unit intermittently sends the ink from the main tank to the first sub-tank, which can shorten the residence time in the first sub-tank and is preferable in terms of ink stability. Furthermore, it is preferable that the thermosetting component contains a blocked isocyanate, since this improves the resistance of the ink to high temperatures and high humidity.

[0019] It is preferable that the ink supply device further comprises a heating device for heating the ink flow path in the second sub-tank, and that the surface area of ​​the tank inner wall heated by the heating device in contact with the ink in the first and second sub-tanks is larger in the first sub-tank than in the second sub-tank, in that this can increase the ink heating efficiency and achieve the optimal viscosity for ejection.

[0020] It is preferable that the capacity of the first sub-tank is larger than that of the second sub-tank, because this makes it easier to control the ink temperature in the first sub-tank when performing high-productivity printing. Also, from the viewpoint of maintaining ink quality, it is preferable that the ink residence time in the flow paths and sub-tanks is as short as possible after degassing, so it is desirable to make the capacity of the first sub-tank larger than that of the second sub-tank.

[0021] The present invention, its components, and embodiments 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 the symbol "to" are included as lower and upper limits.

[0022] [Inkjet recording method of the present invention] Hereinafter, an inkjet recording method and an inkjet recording apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, the same reference numerals are used to designate components having the same functions and configurations, and the description thereof will be omitted.

[0023] Fig. 1A is a front view illustrating a schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention, and Fig. 1B is a plan view of the inkjet recording apparatus 1.

[0024] The inkjet recording apparatus 1 includes an inkjet head 24a (discharge operation section), a UV irradiation section 72, a scanning section 121, a scanning guide section 122, a transport stage 131, a transport guide section 132, and the like.

[0025] In the inkjet recording device 1 of this embodiment, the ink is discharged onto a wiring board S (substrate), for example. The wiring board S is placed on a conveying table 131. The conveying table 131 is capable of moving in a direction (conveying direction, sub-scanning direction) along a conveying guide portion 132 such as a rail with the wiring board S placed thereon. The wiring board S has a substantially flat conductor (wiring conductor) that forms signal wiring on an insulating board. The conductor is not particularly limited, but may be, for example, copper (copper foil). The signal wiring is positioned to protrude from the insulating board surface, so that the wiring board S has a stepped portion. In addition, the ink that has landed does not penetrate into the wiring board S, but rises on the surface, hardens, and is fixed. Here, the insulating board surface is flat, and the vertical outward direction with respect to this flat surface is considered to be upward.

[0026] The inkjet head 24a has a nozzle N (see FIG. 2) and ejects ink from the nozzle N onto the wiring board S. The amount of ink ejected onto each pixel range in each ink ejection cycle can be selected from a plurality of levels. The UV irradiation unit 72 irradiates the wiring board S on which the ink has landed with ultraviolet light (UV light). The inkjet head 24a and the UV irradiation unit 72 are fixed to the scanning unit 121 and are moved (scanned) in a direction along the scanning guide unit 122 (scanning direction, i.e., a direction intersecting the moving direction of the conveyance table 131, here a direction perpendicular thereto). For these movements, for example, a linear motor or the like may be used. The nozzles of the inkjet head 24a are aligned across the width of the wiring board S, and by setting the arrangement interval of the nozzles to be sufficiently small, it may be possible to complete printing in one scan (single pass). In addition, by repeating the scanning of the inkjet head 24a multiple times while moving the wiring board S, ink ejection in multiple passes (interlace) is possible.

[0027] FIG. 2 is a block diagram showing the functional configuration of the inkjet recording apparatus 1. As shown in FIG. The inkjet recording apparatus 1 includes a transport section 10, an inkjet head 24a (ink ejection section), a head drive control section 30, a fixing section 70, a control section 40, a storage section 60, an ink heating section (heating device) 270, a display section 81, an operation reception section 82, a communication section 90, a liquid delivery pump 243, a supply pump 53, a vacuum pump 249, a circulation pump 246, a float sensor 241a, a sensor 2427, a float sensor 245a, etc. The control section 40 and each section are connected for communication via a bus or the like.

[0028] The transport unit 10 relatively moves the inkjet head 24a and a medium on which an image (coating) is to be formed, here, the wiring substrate S. As described above, for example, the inkjet head 24a is movable in a predetermined direction (scanning direction) relative to the wiring substrate S, and the wiring substrate S is movable in a direction perpendicular to the scanning direction of the inkjet head 24a.

[0029] The transport unit 10 has a scan driver 12 and a transport driver 13. The scan driver 12 performs scanning by moving the inkjet head 24a through the scanning unit 121. The scan driver 12 has, for example, a linear motor, and moves the inkjet head 24a directly or indirectly via a fixing member for the inkjet head 24a.

[0030] The transport drive unit 13 moves a mounting member such as a base (transport table 131) on which the wiring board S is placed or a belt. The transport drive unit 13 is capable of reciprocating the mounting member.

[0031] The inkjet head 24a has a head drive unit 22 and a plurality of nozzles N, and ejects ink from the nozzles N in response to a drive signal output by the head drive unit 22. The head drive unit 22 has an ejection selection IC 28 (Integrated Circuit) and an electromechanical conversion element 223. The ejection selection IC 28 performs a switching operation to output a drive signal corresponding to the presence or absence of ink ejection and the ejection amount from each nozzle N based on image data to the electromechanical conversion element 223 corresponding to each nozzle N. The electromechanical conversion element 223 is, for example, a piezoelectric element, which changes shape in response to the input drive signal, and this shape change causes a pressure fluctuation in the ink in the ink flow path communicating with the nozzle N. The electromechanical conversion element 223 and the nozzle N constitute a recording element 26 .

[0032] The head drive control unit 30 includes a head control unit 31, a drive waveform signal generation circuit 32, etc., and outputs a drive waveform signal (analog signal) related to ink ejection and the like to the inkjet head 24a at a predetermined time period (ink ejection period) based on output data (digital data) from the drive waveform signal generation circuit 32. The drive waveform signal related to ink ejection may be a combination of multiple pulse signals. In addition, it may be possible to output drive waveform signals of multiple different waveform patterns (including not only waveforms but also changes in pulse length, amplitude, voltage value, etc.) according to the ink ejection amount. Alternatively, it may be possible to output continuous drive pulses the number of times according to the ink droplet amount per pixel (multi-pulse method). In this case, the ink droplets ejected by each drive pulse are merged during flight or landed within the same pixel range. The ink ejected from each nozzle to each pixel per pass (one cycle) may be an ink droplet amount that provides a minimum thickness (for example, 15 μm) of an insulating film, which will be described later, taking into consideration the surface characteristics of the wiring substrate S, the temperature (viscosity characteristics) when the ink is ejected, and the time interval from when the ink droplets land to when they are provisionally attached by UV light irradiation from the UV irradiation unit 72. Also, in addition to ejecting ink, a non-ejection waveform pattern for stirring the ink within the nozzle N may be output.

[0033] In addition to or instead of the above method, the ink ejection amount (landing amount) per pixel can be controlled by other methods, for example, by adjusting the state of the ink liquid surface (meniscus) in the nozzle N by adjusting the ink pressure (normally negative pressure is used to prevent ink leakage) when no drive pulse is applied, or by changing and adjusting the drive frequency. The ink droplet amount can also be adjusted by applying a drive pulse of a drive waveform pattern in a state in which a suitable non-ejection waveform pattern is applied before the ink ejection waveform pattern to vibrate the meniscus.

[0034] The fixing unit 70 performs an operation of fixing the ink that has landed on the wiring board S. The ink according to the present invention has a thermosetting property and a curing property by active energy rays (UV light), which will be described later, and accordingly the fixing unit 70 has a UV irradiation unit 72 and a heat fixing unit 73. Although not particularly limited, here, the UV irradiation unit 27 is fixed to the scanning unit 121 together with the inkjet head 24a as described above and scanned to temporarily fix the ink that has landed on the wiring board S. The UV irradiation unit 27 has, for example, a light-emitting diode (LED) that emits ultraviolet light, and emits ultraviolet light (UV light) by applying a voltage to the LED to pass a current through it. The UV irradiation unit 72 may have a light-shielding wall or the like to block leakage of UV light outside the desired irradiation range, as necessary.

[0035] The configuration for emitting UV light in the UV irradiation unit 72 is not limited to an LED. The UV irradiation unit 72 may have, for example, a mercury lamp. In addition, if the ink has a property of being cured and fixed by receiving active energy rays other than UV light, the UV irradiation unit 72 may have a known emission source (light source) that emits active energy rays that cure the ink, instead of the above-mentioned configuration for emitting UV light.

[0036] The heat fixing unit 73 has a heat generating unit such as an infrared heater or an electric heater, and directly or indirectly heats the wiring board S to fix the temporarily fixed ink. The heat fixing unit 73 is located so that the ink is landed and temporarily fixed by the inkjet head 24a and the UV irradiation unit 72, and then the wiring board S is transported downstream in the transport direction, and then the main fixing is performed. The heat fixing unit 73 may be located in a housing that surrounds the wiring board S and the area of ​​the transport member on which it is placed, so that the heat generated by the heat generating unit is retained inside the housing and the curing temperature is efficiently maintained at an appropriate temperature. In this case, it is not necessary to always operate the heat generating unit during heating, and it is sufficient that the temperature is maintained within the set range related to the curing temperature.

[0037] The heat fixing unit 73 may be provided in a separate heat fixing device, rather than being provided in the inkjet recording apparatus 1. The heat fixing device may be a post-processing device of the inkjet recording apparatus 1, and the transport unit 10 may be capable of directly feeding the wiring board S to the heat fixing device located on an extension of the moving direction of the transport table 131, or the wiring board S removed from the transport table 131 of the inkjet recording apparatus 1 may be configured to be set again in the heat fixing device, or the wiring board S may be moved manually by the user.

[0038] The control unit 40 comprehensively controls the operation of each part of the inkjet recording apparatus 1. The control unit 40 has a CPU 41 (Central Processing Unit) and a RAM 42 (Random Access Memory). The CPU 41 is a hardware processor that performs various arithmetic processing, and executes a program 61 stored in a storage unit 60. The RAM 42 provides a memory space for control to the CPU 41, and stores temporary data.

[0039] Specifically, the control unit 40 performs the following process on the inkjet recording apparatus 1. That is, based on detection data by a float sensor 241a provided in the first sub-tank 241 described later, the control unit 40 operates the supply pump 53 and the valve 55 to send ink from the main tank 51 to the first sub-tank 241 so that the amount of ink newly supplied from the main tank 51 to the first sub-tank 241 (supply amount) is greater than the amount of ink stored in the first sub-tank 241 (residual amount). In this way, the control unit 40 intermittently sends ink from the main tank 51 to the first sub-tank 241. Details will be described later.

[0040] The storage unit 60 includes at least a non-volatile memory, and stores the program 61 and setting data. An example of the non-volatile memory is a flash memory. In addition, a hard disk drive (HDD) may also be included in the non-volatile memory referred to here.

[0041] The ink heating unit 270 heats the ink in the inkjet head 24a and the ink supply path to the inkjet head 24a to maintain the ink at an appropriate temperature. As described later, the ink changes phase between sol and gel depending on the temperature, so if the ink remains in a gel state at room temperature, the ink lacks fluidity and is difficult to supply and eject. The ink heating unit 270 heats the ink to an appropriate temperature to maintain the ink in a sol state, enabling it to be supplied and ejected appropriately. The appropriate temperature may be determined so that the ink is quickly dissipated by the wiring board S after landing on the wiring board S and gels in an appropriate time. The ink heating section 270, which will be described later, may be, for example, an electric heating wire or a rubber heater. When electricity is passed through the electric heating wire or rubber heater, the electric heating wire or rubber heater comes into contact with the ink flow path, etc., and transfers heat to heat the ink.

[0042] The display unit 81 displays various statuses, menus, and the like on a display screen based on the control of the control unit 40. The display unit 81 has, for example, a display screen and LED (Light Emitting Diode) lamps. The display screen is not particularly limited, but is, for example, an LCD (Liquid Crystal Display). The LED lamps are turned on (including blinking) by the control unit 40 in a position and color corresponding to each situation, for example, depending on the power supply situation and the occurrence of an abnormality.

[0043] The operation reception unit 82 receives an input operation from an external user or the like, and outputs the input operation to the control unit 40 as an input signal. The operation reception unit 82 has, for example, a touch panel and a push button switch. The touch panel may be positioned so as to overlap with the display screen of the display unit 81. The operation reception unit 82 may also have various other operation switches and the like.

[0044] The communication unit 90 controls transmission and reception of data (signals) between the communication unit 90 and external devices in accordance with a predetermined communication standard. The communication unit 90 controls communication in accordance with a LAN (Local Area Network) standard, for example. The communication unit 90 may also be capable of connecting peripheral devices in accordance with the USB (Universal Serial Bus) standard.

[0045] Fig. 3 is a diagram illustrating the ink path in the inkjet recording apparatus 1 of this embodiment, and Fig. 4 is an enlarged view of a part of the ink path.

[0046] In the inkjet recording device 1 of this embodiment, ink is pumped out by a supply pump 53 from a main tank 51 as an ink supply source 50 through a filter 57, and is supplied to each inkjet head 24a through a valve (e.g., an electromagnetic valve) 55 and an ink path 24b. Also, the ink that is not ejected from each inkjet head 24a can be returned to the ink path 24b.

[0047] In the ink path 24b, there are provided a first sub-tank 241, a filter 241d, a degassing module 242, a liquid feed pump 243, a check valve 244, a second sub-tank 245, a filter 245c, etc. These are connected by, for example, a member having a hollow ring-shaped tube structure, though this is not particularly limited.

[0048] It is also preferable that a circulation pump 246 is provided in parallel to the degassing module 242, so that ink flowing out of the degassing module 242 can be returned to just before the ink inlet 2422 (see Figure 7) of the degassing module 242 via a circulation path 24c connected to both ends of the degassing module 242.

[0049] The inkjet head 24a, the ink path 24b and the circulation path 24c are heated and kept warm by an ink heating unit 270 such as a heater or a heat transfer member that transfers heat from the heater, so that the temperature of the ink is kept at an appropriate level. The heater of the ink heating section 270 may be, for example, a rubber heater 272 or an electric heating wire 271 (see FIG. 4), which generates heat when electricity is applied. The heat transfer member is preferably a heat conductive plate made of a material with high thermal conductivity, such as various metals (alloys), and is provided to cover the piping of the ink path 24b and the circulation path 24c.

[0050] In the degassing module 242, a check valve 247, a trap 248, a vacuum pump (degassing pump) 249, and the like are connected in series to form a degassing device.

[0051] The ink in the main tank 51 of the ink supply source 50 is maintained at room temperature (25° C.).

[0052] <First sub-tank> The first sub-tank 241 is one or more ink chambers that store the ink pumped from the main tank 51 by the supply pump 53 and the valve 55 . It is preferable that the capacity of the first sub-tank 241 is smaller than the capacity of the main tank 51 and larger than the capacity of a second sub-tank 245 described later. Specifically, the capacity of the first sub-tank 241 is preferably larger than the capacity of the second sub-tank 245 within the range of 1.1 to less than 2.0 times, although this varies depending on the number of inkjet heads mounted and the design.

[0053] In the first sub-tank 241 and the second sub-tank 245, the surface area of ​​the tank inner wall heated by the ink heating unit 270 that comes into contact with the ink (also referred to as the "liquid contact surface area") is preferably larger in the first sub-tank 241 than in the second sub-tank 245. Specifically, it is preferable that the surface area in the first sub-tank 241 is larger than that in the second sub-tank 245 by a range of 1.1 times or more and less than 5.0 times.

[0054] Here, "the surface area (liquid contact surface area) of the tank inner wall heated by the ink heating section 270 in the first sub-tank 241" refers to the surface area of ​​contact between the ink and the inner surface of the side wall section 2411 or the bottom section 2412 when, for example, a rubber heater 272 is provided on the outer surface (outer wall surface) of the side wall section 2411 or the bottom section 2412 of the first sub-tank 241 as shown in Figures 4, 5A and 5B, and heat is transferred to the ink in the tank via the side wall section 2411 or the bottom section 2412 heated by the rubber heater 272. In addition to this case, as shown in Figures 5A and 5B, in addition to the rubber heater 272 provided on the outer surface of the side wall portion 2411 or the bottom portion 2412 of the first sub-tank 241, a partition plate 2415 is provided in the first sub-tank 241, and heat is transferred to the ink in the tank via the partition plate 2415 heated by the rubber heater 272, the surface area of ​​the partition plate 2415 in contact with the ink is also included. The second sub-tank 245 has the same definition as above. In addition, the "tank inner wall" refers to, for example, the inner surface of the side wall portion 2411 or the bottom portion 2412 of the first sub-tank 241, or the surface of the partition plate 2415 provided within the first sub-tank 241, and the same definition applies to the second sub-tank 245.

[0055] In order to increase the liquid contact surface area of ​​the first sub-tank 241, it is preferable that the first sub-tank 241 be configured, for example, as shown in Figures 5A and 5B, with partition plates 2415 provided on the outer surface of the side wall portion 2411 of the first sub-tank 241, the outer surface of the bottom portion 2412, and within the first sub-tank 241. The arrangement pattern of the ink heating portion 270 and the partition plate 2415 provided in the first sub-tank 241 will be described below.

[0056] 5A and 5B are schematic diagrams showing the first sub-tank, in which FIG. 5A is a cross-sectional view taken along line VV in FIG. 5A. The first sub-tank 241 is provided with a rubber heater 272 as an ink heating unit 270 on the outer surfaces of a side wall 2411 and a bottom 2412. A partition plate 2415 is provided in the first sub-tank 241 and has a generally rectangular shape in top view so as to spiral counterclockwise from the left side wall 2411 toward the center when viewed from above, thereby forming an ink flow path. The partition plate 2415 is thermally connected to the rubber heater 272. Further, an inlet 2413 through which the ink supplied from the main tank 51 flows is provided on the left side wall 2411 of the first sub-tank 241, and the inlet 2413 communicates with an ink flow path. In addition, an outlet 2414 communicating with a degassing module (degassing device) 242 is provided at the most downstream position of the ink flow path in the first sub-tank 241, i.e., near the center of the first sub-tank 241, and ink flowing in from the inlet 2413 flows counterclockwise along the ink flow path in the first sub-tank 241 and is sent to the degassing module 242 via the outlet 2414.

[0057] A float sensor 241a is provided as a liquid level sensor in the first sub-tank 241. There are no particular limitations on where the float sensor 241a is provided, but it is preferable to provide it at the most downstream position of the ink flow path in the first sub-tank 241. In FIG. 5A, the float sensor 241a is provided near the center of the first sub-tank 241.

[0058] The arrangement pattern of the partition plates 2415 in the first sub-tank 241 is not limited to that shown in FIGS. 5A and 5B, and may be, for example, the arrangement patterns shown in FIGS. 6A to 6C. 6A to 6C are top cross-sectional views of a first sub-tank showing a modification of FIG. 5A and FIG. 5B.

[0059] 6A, a plurality of partition plates 2415 are alternately installed between the opposing left and right side wall portions 2411 and 2411 inside the first sub-tank 241. This forms a serpentine ink flow path inside the first sub-tank 241. An outlet 2414 communicating with the degassing module 242 is provided at the most downstream position of the ink flow path in the first sub-tank 241, and the ink flowing in from the inlet 2413 flows in a serpentine manner through the ink flow path in the first sub-tank 241 and is sent to the degassing module 242 via the outlet 2414. In addition, in the vicinity of the degassing module 242 of the first sub-tank 241, a float sensor 241a is provided. In addition, rubber heaters 272 are also provided on the outer surfaces of the side wall portion 2411 and the bottom portion 2412 of the first sub-tank 241.

[0060] 6B has a partition plate 2415 disposed in the center of the first subtank 241 so as to be approximately parallel to the left and right side wall portions 2411 and 2411, so as to divide the inside of the first subtank 241 into left and right spaces. This divides the inside of the first subtank 241 into two spaces, left and right, forming an ink flow path. An outlet 2414 communicating with the degassing module 242 is provided in the space on the right side of the first sub-tank 241, and ink flowing in from the inlet 2413 flows from the left to the right side of the first sub-tank 241 and is sent to the degassing module 242 via the outlet 2414. In addition, in the vicinity of the degassing module 24 of the first sub-tank 241, a float sensor 241a is provided. In addition, rubber heaters 272 are also provided on the outer surfaces of the side wall portion 2411 and the bottom portion 2412 of the first sub-tank 241.

[0061] 6C has a partition plate 2415 disposed in the center of the first sub-tank 241 so as to form a cross shape when viewed from above. This forms ink flow paths in the clockwise and counterclockwise directions in the first sub-tank 241. An outlet 2414 communicating with the degassing module 242 is provided at the most downstream position of the ink flow path in the first sub-tank 241, and the ink flowing in from the inlet 2413 flows clockwise or counterclockwise through the ink flow path in the first sub-tank 241 and is sent to the degassing module 242 via the outlet 2414. In addition, in the vicinity of the degassing module 242 of the first sub-tank 241, a float sensor 241a is provided. In addition, rubber heaters 272 are also provided on the outer surfaces of the side wall portion 2411 and the bottom portion 2412 of the first sub-tank 241.

[0062] It should be noted that the first sub-tank 241 shown in FIGS. 6A, 6B, and 6A to 6C is merely an example of an embodiment of the present invention, and the present invention is not limited to these. 5A, 5B, and 6A to 6C are configured to have the rubber heater 272 provided on the outer surfaces of the side wall 2411 and the bottom 2412, but the rubber heater 272 may be provided on the inner surfaces of the side wall 2411 and the bottom 2412. In this case, in terms of durability, etc., it is preferable to cover the surface of the rubber heater 272 with another member so that the rubber heater 272 does not come into direct contact with the ink. In addition, the first sub-tank 241 shown in Figures 5A, 5B, and 6A to 6C is configured so that a partition plate 2415 is provided inside the first sub-tank 241 and the partition plate 2415 is thermally connected to a rubber heater 272 provided on the outside of the first sub-tank 241, but this is not limited to the above and the rubber heater may be provided inside two partition plates (not shown).

[0063] Furthermore, it is preferable to use a metal with high thermal conductivity, such as aluminum or copper, for the flow path members and partition plate 2415 after the first sub-tank 241, and aluminum is more preferable from the viewpoints of cost and workability.

[0064] A float sensor 241a provided in the first sub-tank 241 detects the ink level. The control unit 40 opens and closes the valve 57 and operates the supply pump 53 based on the detection data of the ink level by the float sensor 241a. Specifically, the control unit 40 operates the valve 55 and the supply pump 53 based on the detection data by the float sensor 241a so that the amount of ink newly supplied from the main tank 51 to the first sub-tank 241 is greater than the amount of ink stored (residual) in the first sub-tank 241. This shortens the retention time of ink in the first sub-tank 241.

[0065] As the liquid level sensor, in addition to the float sensor 241a that detects the liquid level based on the position of the float, an ultrasonic sensor that measures the reflection of ultrasonic waves at the liquid surface, a dielectric capacitance sensor that detects the liquid level based on the dielectric constant difference between the gas and liquid, and a pressure sensor that detects the weight and pressure of the liquid at the bottom of the tank can be used.

[0066] <Degassing module> The degassing module 242 performs a degassing process to remove gas such as air from the ink that has flowed in, and then discharges the degassed ink. The degassing module 242 can usually reduce the air concentration in the ink to a level that does not adversely affect the ink ejection with a single degassing, but by performing degassing multiple times, the air concentration can be further reduced.

[0067] FIG. 7 is a schematic cross-sectional view of the cylindrical degassing module 242 taken along a plane passing through the central axis thereof. The degassing module 242 has a shape in which a central tube 2424 is surrounded by a number of hollow fiber membranes (transparent member) 2426 inside the outer shell 2421. One end of the central tube 2424 is connected to the ink inlet 2422, and the other end is sealed by a plug 2424a. The outer wall of the central tube 2424 is provided with numerous fine holes 2424b (perforations), and ink that flows into the central tube 2424 from the ink inlet 2422 flows out from these fine holes 2424b to the surroundings, passes between the hollow fiber membranes 2426, and flows out from the ink outlet 2423. An ink flow path 2428 is formed by the ink inlet 2422, the inside of the central tube 2424, the gap between the numerous hollow fiber membranes 2426 outside the central tube 2424, the ink outlet 2423, etc.

[0068] The hollow fiber membrane 2426 has a structure of many hollow fine fibers with one end closed, and the 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, and the inside of the fine fiber structure of the hollow fiber membrane 2426 is depressurized by sucking air with a vacuum pump 249. In this state, ink comes into contact with the membrane surface of the hollow fiber membrane 2426, and only gas such as air in the ink selectively permeates the membrane surface, degassing the ink. A gas flow path 2429 is formed by the inside of the fine fiber structure of the hollow fiber membrane 2426, the gas outlet 2425, etc.

[0069] From the standpoint of degassing efficiency and processing flow rate, it is preferable that the degassing module 242 is an external reflux type hollow fiber membrane degassing module in which the inside of the hollow fiber membrane 2426 is degassed and ink is circulated to the outside of the hollow fiber membrane 2426, but other types such as an internal reflux type may also be used.

[0070] In addition, it is preferable to provide a sensor 2427 for detecting when the ink flow path 2428 is filled with ink at a position within the ink flow path 2428 of the degassing module 242 that is the most difficult for ink flowing in from the ink inlet 2422 to reach. The position in the ink flow path 2428 where it is most difficult for ink to reach is a position where the entire area in the ink flow path 2428 can be said to be filled with ink if the ink reaches that position, and examples of such positions include a position between the base ends of a number of hollow fiber membranes 2426, and a position farthest from the ink inlet 2422 and also from the ink outlet 2423. When the sensor 2427 detects that the ink has reached the position where the sensor 2427 is provided, the detection result is output to the control unit 40.

[0071] The liquid feed pump 243 feeds the ink flowing 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, once fed to the second sub-tank 245, from flowing back. Although the liquid delivery pump 243 is described as being provided between the degassing module 242 and the second sub-tank 245, this is not limited to this and the liquid delivery pump 243 may be provided between the first sub-tank 241 and the degassing module 242.

[0072] <Second sub-tank> The second sub-tank 245 is a small ink chamber in which the ink degassed in the degassing module 242 is temporarily stored, and it is preferable that the second sub-tank 245 has a smaller capacity than the first sub-tank 241 .

[0073] Furthermore, it is preferable that the surface area of ​​the inner wall heated by the ink heating unit 270 in the second sub-tank 245 that comes into contact with the ink (liquid contact surface area) is smaller in the second sub-tank 245 than in the first sub-tank 241.

[0074] In order to reduce the liquid contact surface area of ​​the second sub-tank 245, it is preferable that the second sub-tank 245 is not configured to have a partition plate 2415 like the first sub-tank 241, but rather is configured to have a rubber heater 272 only on the outer surface of the side wall or bottom of the second sub-tank 245 (see Figure 4).

[0075] The second sub-tank 245 is connected to the inlet 240a of each inkjet head 24a, and ink corresponding to the amount of ink ejected from the nozzles is supplied from the second sub-tank 245 to each inkjet head 24a. The second sub-tank 245 is provided with a float sensor 245a, and a predetermined amount of ink is stored in the second sub-tank 245 by the control unit 40 operating the liquid feed pump 243 based on detection data of the liquid level position by the float sensor 245a. The second sub-tank 245 is provided with a floating lid 245b, which covers the surface of the degassed ink. Since the second sub-tank 245 is open to the atmosphere, the floating lid 245b reduces the contact area between the atmosphere and the degassed ink, thereby preventing air from re-mixing with the ink. In an inkjet recording device 1 used for industrial purposes, ink degassed by continuous image formation or the like is not stored for a long time in the second sub-tank 245, so the amount of air re-mixed is often small. Therefore, the second sub-tank 245 may be configured without the floating lid 245b.

[0076] Ink that is not ejected from the nozzles of the inkjet head 24a can be returned from the outlet 240b through the recovery path 241b and the valve 241c to the first sub-tank 241. When it is necessary to drain ink from the inkjet head 24a during maintenance of the inkjet head 24a, the valve 241c is opened, making it possible to recover the ink from the inkjet head 24a without wasting it.

[0077] A trap 248 is provided between the degassing module 242 and the vacuum pump 249 via a check valve 247. The hollow fiber membrane 2426 normally does not allow liquid ink to pass through, but a small amount of ink may pass through depending on the level of negative pressure by the vacuum pump 249. If this permeated ink reaches the vacuum pump 249, the vacuum pump 249 will deteriorate, so the trap 248 collects the ink before that happens. The ink collected by the trap 248 can be extracted by opening a valve (not shown) connected to the trap 248.

[0078] As described above, the ink in the ink path 24b is heated and kept warm by the ink heating unit 270. It is preferable to heat the ink to a temperature within a range of 70 to 80°C, for example. In particular, in this embodiment, a rubber heater 272 is provided in the first sub-tank 241. By providing such a rubber heater 272, the ink sent from the main tank 51 can be sufficiently heated to a predetermined temperature before being sent to the degassing module 242. In particular, in the case of gel ink, it is necessary to completely dissolve the ink by heating.

[0079] In addition, the degassing module 242 is provided with a heating wire 271. Since heat from the heater or heat transfer plate covering the outside is difficult to transfer inside the degassing module 242, by separately heating the ink in this manner and transferring the heat to the inside, the ink is heated more efficiently inside the degassing module 242, where the ink stays for a longer time than inside the normal ink path 24b.

[0080] Furthermore, in the inkjet recording apparatus 1 of this embodiment, even when the supply of ink to the inkjet head 24a is stopped, the ink in the degassing module 242 is circulated appropriately by the circulation pump 246, so that the ink flowing through the degassing module 242 and the circulation path 24c is heated and kept warm appropriately and in a balanced manner. Even if the ink has cooled down when the inkjet recording apparatus 1 is turned on, the ink can be quickly heated so that it can be circulated and ejected at an appropriate temperature.

[0081] Next, an example of the ink supply process performed by the control unit 40 in the inkjet recording apparatus 1 configured as above will be described below with reference to Fig. 8. Fig. 8 is a flow chart showing an example of the ink supply process.

[0082] First, the control unit 40 determines whether or not the float sensor 241a in the first sub-tank 241 has detected that the amount of ink stored in the first sub-tank 241 (remaining ink amount) has reached a lower limit (step S1).

[0083] If it is determined that the remaining ink amount has not reached the lower limit (step S1; NO), the valve 55 between the main tank 51 and the first sub-tank 241 is closed (step S5), and the transfer of ink from the main tank 51 to the first sub-tank 241 is stopped (step S6).

[0084] When it is determined that the remaining amount of ink has reached the lower limit (step S1; YES), the control unit 40 opens the valve 55 between the main tank 51 and the first sub-tank 241 (step S2). Next, the control unit 40 causes the supply pump 53 to send ink from the main tank 51 to the first sub-tank 241 (step S3). Then, the float sensor 241a in the first sub-tank 241 detects the upper limit of the remaining amount of ink in the first sub-tank 241 and determines whether the first sub-tank 241 is filled with ink (step S4).

[0085] If it is determined that the remaining amount of ink in the first sub-tank 241 has not reached the upper limit (step S4: NO), the supply pump 53 continues to pump ink (step S3). When it is determined that the remaining amount of ink in the first sub-tank 241 has reached its upper limit (step S4; YES), the control unit 40 closes the valve 55 between the main tank 51 and the first sub-tank 241 (step S5) and stops the transfer of ink from the main tank 51 to the first sub-tank 241 (step S6).

[0086] In this way, the control unit 40 constantly controls the operation of the valve 55 and the supply pump 53 based on the detection results of the float sensor 241a of the first sub-tank 241, and by intermittently pumping ink, the amount of ink newly supplied to the first sub-tank 241 is made greater than the amount of ink stored in the first sub-tank 241.

[0087] <Ink> The ink used in the inkjet recording method of the present invention is a radical polymerization type inkjet ink containing a thermosetting component, that is, a compound having a thermosetting functional group. The ink according to the present invention preferably contains a gelling agent and undergoes a sol-gel phase transition depending on temperature. Furthermore, the ink according to the present invention preferably contains a compound having a photopolymerizable functional group and a photopolymerization initiator. The ink according to the present invention is not limited to the gel-like ink described above, but may be a water-based ink or ink having other physical properties.

[0088] (1) Compounds having thermosetting functional groups Examples of the thermosetting functional group according to the present invention include functional groups cited in reviews such as "Refinition of Thermosetting Polymers" (Endo Tsuyoshi, CMC Co., Ltd., 1986), "Latest Binder Technology Handbook" Chapter II-I (Harasaki Yuji, General Technology Center, 1985), "Synthesis, Design and New Application Development of Acrylic Resins" (Otsu Takayuki, Chubu Business Development Center Publishing Division, 1985), and "Functional Acrylic Resins" (Omori Eizo, Techno System, 1985). Specifically, from the viewpoint of thermosetting properties, the thermosetting functional group is preferably at least one selected from the group consisting of a hydroxy group, a carboxy group, an isocyanate group, an epoxy group, a (meth)acrylic group, a maleimide group, a mercapto group, and an alkoxy group.

[0089] (Hydroxy group) Examples of the compound having a hydroxy group include various hydroxy group-containing (meth)acrylates (e.g., 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, etc.), addition reaction products of the above various hydroxy group-containing (meth)acrylates with ε-caprolactone, various hydroxy group-containing vinyl ethers (e.g., 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 4-hydroxybutyl vinyl ether, 5-hydroxybutyl vinyl ether, 6-hydroxybutyl vinyl ether, 7-hydroxybutyl vinyl ether, 8-hydroxybutyl vinyl ether, 9-hydroxybutyl vinyl ether, 10-hydroxybutyl vinyl ether, 11-hydroxybutyl vinyl ether, 12-hydroxybutyl vinyl ether, 13-hydroxybutyl vinyl ether, 14-hydroxybutyl vinyl ether, 15-hydroxybutyl vinyl ether, 16-hydroxybutyl vinyl ether, 17-hydroxybutyl vinyl ether, 18-hydroxybutyl vinyl ether, 19-hydroxybutyl vinyl ether, 20-hydroxybutyl vinyl ether, 21-hydroxybutyl vinyl ether, 22-hydroxybutyl vinyl ether, 23-hydroxybutyl vinyl ether, 24-hydroxybutyl vinyl ether, 25-hydroxybutyl vinyl ether, 26-hydroxybutyl vinyl ether, 27-hydroxybutyl vinyl ether, 28-hydroxybutyl vinyl ether, 29-hydroxybutyl vinyl ether, 30-hydroxybutyl vinyl ether, 31-hydroxybutyl vinyl ether, 32-hydroxybutyl vinyl ether, 33-hydroxybutyl vinyl ether, 34-hydroxybutyl vinyl ether, 35-hydroxybutyl vinyl ether, 36 ethyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, etc.), addition reaction products of the above-mentioned various hydroxy group-containing vinyl ethers with ε-caprolactone, various hydroxy group-containing allyl ethers (for example, 2-hydroxyethyl(meth)allyl ether, 3-hydroxypropyl(meth)allyl ether, 2-hydroxypropyl(meth)allyl ether, 4-hydroxybutyl(meth)allyl ether, 3-hydroxybutyl(meth)allyl ether, 2-hydroxy-2-methylpropyl(meth)allyl ether, 5-hydroxypentyl(meth)allyl ether, 6-hydroxyhexyl(meth)allyl ether, etc.), addition reaction products of the above-mentioned various hydroxy group-containing allyl ethers with ε-caprolactone, and the like.

[0090] (Carboxy group) Examples of the compound having a carboxy group include various carboxy group-containing monomers (e.g., (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc.), various monoesters of α,β-unsaturated dicarboxylic acids with monohydric alcohols having 1 to 18 carbon atoms (e.g., monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monoisobutyl fumarate, monotert-butyl fumarate, monohexyl fumarate, monooctyl fumarate, mono 2-ethylhexyl fumarate, monomethyl itaconate, monoethyl maleate, monobutyl maleate, monoisobutyl maleate, mono-tert-butyl maleate, monohexyl maleate, monooctyl maleate, mono-2-ethylhexyl maleate, etc.), monoalkyl itaconate esters (for example, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, monoisobutyl itaconate, monohexyl itaconate, monooctyl itaconate, mono-2-ethylhexyl itaconate, etc.). Further examples include carboxyl group-containing acrylate compounds, which can be obtained by copolymerizing an unsaturated carboxylic acid, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, or anhydrides thereof, with an acrylic monomer, and among the unsaturated carboxylic acids, acrylic acid and methacrylic acid are preferably used. Examples of the acrylic monomer constituting the carboxylic acid group-containing acrylic copolymer include isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isomyristyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, N-methylol (meth)acrylamide, glycidyl (meth)acrylate, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, (meth)acryloylmorpholine, (meth)acetonitrile, vinylpyrrolidone, N-cyclohexylmaleimide, itaconimide, and N,N-dimethylaminoethyl (meth)acrylamide. In addition, vinyl acetate, styrene, etc. may also be used. These monomers may be used alone or in combination of two or more.

[0091] (isocyanate group) The compound having an isocyanate group is not particularly limited as long as it has two or more isocyanate groups in the molecule. Specific examples of the compound having an isocyanate group include aromatic isocyanates 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). aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and methyl norbornane diisocyanate (NBDI); alicyclic 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 derivatives, isocyanurate derivatives, and carbodiimide-modified derivatives of these.

[0092] The acrylate or methacrylate compound having an isocyanate group may be any compound having an isocyanate group and an acryloyl group or a methacryloyl group in the molecule, and examples of such compounds include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, 2-isocyanatoethyl acrylate, 3-isocyanatopropyl acrylate, 2-isocyanatoethyl methacrylate, 3-isocyanatopropyl methacrylate, and reaction products of hydroxyalkyl acrylates or methacrylates such as hydroxyethyl acrylate with polyisocyanates such as tolylene diisocyanate.

[0093] Among the compounds having an isocyanate group, a polyfunctional isocyanate compound having an isocyanate group protected with a thermally dissociable blocking agent (blocked isocyanate group) is preferred in terms of improving resistance to high temperatures and high humidity. In the case of a polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent, the isocyanurate ring generated from the trimerization reaction of isocyanate has higher thermal stability of the bond compared to urethane or urea bonds and has excellent heat resistance. However, when a more polyfunctional isocyanate compound is used, a network structure having further isocyanurate rings is formed, which further improves heat resistance and makes the compound less susceptible to the effects of humidity at high temperatures.

[0094] The thermally dissociable blocking agent is preferably at least one compound selected from the group consisting of oxime compounds, pyrazole compounds, and active ethylene compounds, from the viewpoints of ink storage stability and thermal dissociability.

[0095] Examples of the oxime compounds include formamide oxime, acetaldoxime, acetoxime, methyl ethyl ketone oxime, and cyclohexanone oxime.

[0096] Examples of the pyrazole-based compounds include pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole.

[0097] Examples of active ethylenic compounds include dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone.

[0098] Examples of the polyfunctional isocyanate compound having an isocyanate group protected with a blocking agent include 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate, 2-[(3-butylidene)aminooxycarbonylamino]ethyl methacrylate, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl acrylate, and 2-[(3-butylidene)aminooxycarbonylamino]ethyl acrylate.

[0099] (epoxy group) Examples of the compound having an epoxy group include various chain epoxy group-containing monomers (e.g., glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, glycidyl vinyl ether, allyl glycidyl ether, etc.), various (2-oxo-1,3-oxolane) group-containing vinyl monomers (e.g., (2-oxo-1,3-oxolane)methyl (meth)acrylate, etc.), various alicyclic epoxy group-containing vinyl monomers (e.g., 3,4-epoxycyclohexyl (Meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, etc.), bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers; polyglycidyl ethers of polyether polyols obtained by adding one or more alkylene oxides to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin; diglycidyl esters of aliphatic long-chain dibasic acids; monoglycidyl ethers of aliphatic higher alcohols; monoglycidyl ethers of polyether alcohols obtained by adding phenol, cresol, butylphenol, or these with alkylene oxides; and glycidyl esters of higher fatty acids.

[0100] Further, examples of the compound having an epoxy group include a compound having a (meth)acryloyl group and an epoxy group, and a partial (meth)acrylic compound of an epoxy compound. Examples of the compound having a (meth)acryloyl group and an epoxy group include glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether. The partially (meth)acrylated epoxy compound can be obtained by reacting the epoxy compound with (meth)acrylic acid in the presence of a catalyst according to a conventional method. Examples of the epoxy compound that can be used for the partially (meth)acrylated epoxy compound include novolac type epoxy compounds and bisphenol type epoxy compounds. Examples of the novolac type epoxy compounds include phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, biphenyl novolac type epoxy compounds, trisphenol novolac type epoxy compounds, and dicyclopentadiene novolac type epoxy compounds. Examples of the bisphenol type epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, 2,2'-diallyl bisphenol A type epoxy compounds, hydrogenated bisphenol type epoxy compounds, and polyoxypropylene bisphenol A type epoxy compounds. By appropriately changing the blending amount of the epoxy compound and (meth)acrylic acid, it is possible to obtain an epoxy compound with a desired acrylate ratio.

[0101] ((Meth)acrylic group) "(Meth)acrylic group" means an acrylic group or a methacrylic group. Examples of compounds having a (meth)acrylic group include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstyryl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobutyric acid, methyl acrylate ... Monofunctional acrylates including, for example, propanyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, and t-butylcyclohexyl (meth)acrylate, as well as triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, and tricyclodecane dimethanol diacrylate, etc., including bifunctional acrylates, and trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate, etc., including polyfunctional acrylates.

[0102] Among the compounds having a (meth)acrylic group, a (meth)acrylate compound having an imide group is preferred in terms of improving resistance to high temperatures and high humidity. In the case of (meth)acrylate compounds having imide groups, the imide groups have high polarity, so they can provide strong metal adhesion. In addition, because they themselves have strong cohesive power, they have little effect on metal adhesion even under high humidity conditions.

[0103] Examples of the (meth)acrylate compound having an imide group include the imide acrylates and imide methacrylates described in JP-A-10-36462 and JP-A-11-21470.

[0104] (Maleimide group) Examples of the compound having a maleimide group include N-methylmaleimide, N-ethylmaleimide, N-hexylmaleimide, N-propylmaleimide, N-butylmaleimide, N-octylmaleimide, N-dodecylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, Np-carboxyphenylmaleimide, Np-hydroxyphenylmaleimide, Np-chlorophenylmaleimide, Np-tolylmaleimide, Np-xylylmaleimide, No-chlorophenylmaleimide, No-tolylmaleimide, N-benzylmaleimide, N-2,5-diethylphenylmaleimide, N-2,5-dimethylphenylmaleimide, Nm-tolylmaleimide, N-α-naphthylmaleimide, No-xylylmaleimide, Nm-xylylmaleimide, amide, bismaleimide methane, 1,2-bismaleimide ethane, 1,6-bismaleimide hexane, bismaleimide dodecane, N,N'-m-phenylene dimaleimide, N,N'-p-phenylene dimaleimide, 4,4' bismaleimide diphenyl ether, 4,4'-bismaleimide diphenyl methane, 4,4'-bismaleimide-di(3-methylphenyl) methane, 4,4'-bismaleimide-di(3-ethylphenyl) methane, 4,4'-bismaleimide-di(3-methyl-5-ethyl-phenyl) methane, N,N'-(2,2-bis-(4-phenoxyphenyl) propane) dimaleimide, N,N'-2,4-tolylene dimaleimide, N,N'-2,6-tolylene dimaleimide, N,N'-m-xylylene dimaleimide, bisphenol A diphenyl ether bismaleimide, and the like.

[0105] (Mercapto group) Examples of compounds having a mercapto group include ethyl thioacrylate, ethyl thiomethacrylate, biphenyl thioacrylate, biphenyl thiomethacrylate, nitrophenyl thioacrylate, nitrophenyl thiomethacrylate, triphenylmethyl thioacrylate, triphenylmethyl thiomethacrylate, 1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane trisacrylate, 2-(mercaptomethyl)-methyl ester of 2-propenoic acid, and 2-[(2-mercaptoethyl)thio]ethyl ester of methacrylic acid, 1,4-bis(3-mercaptobutyryloxy)butane, and 1,3,5-tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

[0106] (alkoxy group) Examples of compounds having an alkoxy group include methoxymethyl acrylate, methoxymethyl methacrylate, dimethoxymethyl acrylate and dimethoxymethyl methacrylate, 1-methoxyethyl acrylate, 1-methoxyethyl methacrylate, 2-methoxyethyl acrylate, 2-methoxyethyl methacrylate, 1,1-methoxyethyl acrylate and 1,1-methoxyethyl methacrylate, 1-ethoxyethyl acrylate, 1-ethoxyethyl methacrylate, 2-ethoxyethyl acrylate and 2-ethoxyethyl methacrylate, N-ethoxymethyl acrylamide, N-ethoxymethyl methacrylamide, ethoxymethyl acrylate and ethoxymethyl methacrylate, and acrylic-modified alkylated melamine.

[0107] (Other functional groups) In addition to the above-mentioned functional groups, compounds having an oxetanyl group or an oxazoline group can be used as the thermosetting functional group. Examples of compounds having an oxetanyl group include oxetane (meth)acrylate, etc. Commercially available products of such compounds include trade names: OXE-10 and OXE-30 manufactured by Osaka Organic Chemical Industry Co., Ltd. Examples of compounds having an oxazoline group include 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and monomers having a substituent on the oxazoline group of these oxazoline group-containing monomers.

[0108] (2) Gelling agent The gelling agent contained in the ink according to the present invention is preferably maintained in a uniformly dispersed state in the cured film cured by light and heat, which makes it possible to prevent the penetration of moisture into the cured film. Such a gelling agent is preferably at least one of the compounds represented by the following general formula (G1) or (G2), in that it is dispersed in the cured film without inhibiting the curing of the ink, and is also preferable in that it has good pinning properties in inkjet printing, can be drawn with both fine lines and a thick film, and has excellent fine line reproducibility. General formula (G1): R1-CO-R2 General formula (G2): R3-COO-R4 [In the formula, R1 to R4 each independently have a linear moiety having 12 or more carbon atoms, and represents an alkyl chain which may be branched.

[0109] The ketone wax represented by the general formula (G1) or the ester wax represented by the general formula (G2) has a linear or branched hydrocarbon group (alkyl chain) with 12 or more carbon atoms, which enhances the crystallinity of the gelling agent, improves water resistance, and creates more sufficient spaces in the house-of-cards structure described below. This makes it easier for ink media such as solvents and photopolymerizable compounds to be fully enclosed in the spaces, improving the pinning ability of the ink. In addition, the number of carbon atoms in the linear or branched hydrocarbon group (alkyl chain) is preferably 26 or less. If the carbon number is 26 or less, the melting point of the gelling agent will not be excessively high, and therefore it is not necessary to excessively heat the ink when ejecting it. From the above viewpoint, it is particularly preferable that R1 and R2, or R3 and R4, are linear hydrocarbon groups having 12 to 23 carbon atoms. In addition, from the viewpoint of increasing the gelation temperature of the ink and gelling the ink more rapidly after it has landed, it is preferable that either R1 or R2, or either R3 or R4, is a saturated hydrocarbon group having 12 to 23 carbon atoms. From the above viewpoint, it is more preferable that both R1 and R2, or both R3 and R4, are saturated hydrocarbon groups having 11 or more and less than 23 carbon atoms.

[0110] Examples of the ketone wax represented by the general formula (G1) include dilignoceryl ketone (C24-C24), dibehenyl ketone (C22-C22), distearyl ketone (C18-C18), dieicosyl ketone (C20-C20), dipalmityl ketone (C16-C16), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12), lauryl myristyl ketone ( These include: lauryl palmityl ketone (C12-C14), myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl behenyl ketone (C14-C22), palmityl stearyl ketone (C16-C18), palmityl behenyl ketone (C16-C22), and stearyl behenyl ketone (C18-C22). The number of carbons in the parentheses above indicates the number of carbons in each of the two hydrocarbon groups separated by the carbonyl group.

[0111] Commercially available examples of the ketone wax represented by general formula (G1) include Stearonne (manufactured by Alfa Aeser; Stearon), 18-Pentatriacontanone (manufactured by Alfa Aeser), Hentriacontan-16-one (manufactured by Alfa Aeser), and Kaowax T-1 (manufactured by Kao Corporation).

[0112] Examples of fatty acid or ester waxes represented by general formula (G2) include behenyl behenate (C21-C22), icosanoic acid icosyl (C19-C20), stearyl stearate (C17-C18), palmityl stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C18), myristyl myristate (C13-C14), cetyl myristate (C13-C16), octyldodecyl myristate (C13-C20), oleyl stearate ... These include stearyl ester (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), behenyl oleate (C18-C22), and arachidyl linoleate (C17-C20). Note that the number of carbon atoms in the parentheses above indicates the number of carbon atoms in each of the two hydrocarbon groups separated by the ester group.

[0113] Commercially available examples of the ester wax represented by general formula (G2) include Unistar M-2222SL and Sperm Acetate, manufactured by NOF Corporation ("Unistar" is a registered trademark of the company), Exepar SS and Exepar MY-M, manufactured by Kao Corporation ("Exepar" is a registered trademark of the company), EMALEX CC-18 and EMALEX CC-10, manufactured by Nippon Emulsion Co., Ltd. ("EMALEX" is a registered trademark of the company), and Amureps PC, manufactured by Kokyu Alcohol Kogyo Co., Ltd. ("Amureps" is a registered trademark of the company). These commercially available products are often mixtures of two or more types, and therefore may be separated and purified as necessary before being added to the ink. Of these gelling agents, ketone wax, ester wax, higher fatty acid, higher alcohol, and fatty acid amide are preferred from the viewpoint of further enhancing pinning properties.

[0114] The content of the gelling agent according to the present invention is preferably within the range of 0.5 to 5.0% by mass based on the total mass of the ink. By setting the content of the gelling agent within the above range, the solubility of the gelling agent in the solvent component and the pinning effect are improved, and further, the water resistance of the cured film is improved. From the above viewpoint, the content of the gelling agent in the inkjet ink is more preferably within the range of 0.5 to 2.5% by mass.

[0115] From the following viewpoint, it is preferable that the gelling agent crystallizes in the ink at a temperature equal to or lower than the gelling temperature of the ink. The gelling temperature is the temperature at which the gelling agent undergoes a phase transition from sol to gel and the viscosity of the ink suddenly changes when the ink that has been solated or liquefied by heating is cooled. Specifically, the solated or liquefied ink is cooled while its viscosity is measured using a viscoelasticity measuring device (e.g., MCR300, manufactured by Physica), and the temperature at which the viscosity suddenly increases can be regarded as the gelling temperature of the ink.

[0116] (3) Compounds having photopolymerizable functional groups The compound having a photopolymerizable functional group (also referred to as a photopolymerizable compound) contained in the ink according to the present invention may be any compound that undergoes a polymerization or crosslinking reaction when irradiated with actinic rays, thereby polymerizing or crosslinking, thereby curing the ink. Examples of the photopolymerizable compound include radically polymerizable compounds and cationic polymerizable compounds. The photopolymerizable compound may be any one of a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof. The photopolymerizable compound may be contained in the inkjet ink alone or in combination of two or more kinds. The radical polymerizable compound is preferably an unsaturated carboxylic acid ester compound, more preferably a (meth)acrylate, and examples of such compounds include the above-mentioned compounds having a (meth)acrylic group. The cationically polymerizable compound may be an epoxy compound, a vinyl ether compound, an oxetane compound, etc. The inkjet ink may contain only one type of cationically polymerizable compound, or may contain two or more types of cationically polymerizable compounds.

[0117] (4) Photopolymerization initiator As the photopolymerization initiator used in the ink according to the present invention, when the photopolymerizable compound is a radical polymerizable compound, it is preferable to use a photoradical initiator, and when the photopolymerizable compound is a cationically polymerizable compound, it is preferable to use a photoacid generator. The ink of the present invention may contain only one type of photopolymerization initiator, or may contain two or more types. The photopolymerization initiator may be a combination of both a photoradical initiator and a photoacid generator. The photoradical initiator includes a cleavage type radical initiator and a hydrogen abstraction type radical initiator.

[0118] Examples of cleavage type radical initiators include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, benzyl and methylphenyl glyoxyesters. Examples of acetophenone-based initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl 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-methylphenyl)propan-1-one. phenyl)-butanone. 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.

[0119] Examples of the hydrogen abstraction type radical initiator include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthrenequinone, and camphorquinone. Examples of benzophenone-based 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.

[0120] Examples of photoacid generators include the compounds described in Organic Electronics Materials Research Group (ed.), "Organic Materials for Imaging," Bunshin Shuppan (1993), pp. 187-192. The content of the photopolymerization initiator may be within a range that allows the ink to be sufficiently cured, and may be, for example, within a 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 Irgacure TPO (manufactured by BASF), 819 (manufactured by BASF), Irgacure 379 (manufactured by BASF), Genocure ITX (manufactured by Rahn AG), Genocure EPD (manufactured by Rahn AG), and the like.

[0121] The ink according to the present invention may further contain a photopolymerization initiator assistant, a polymerization inhibitor, and the like, if necessary. The photoinitiator coagent may be a tertiary amine compound, preferably an aromatic tertiary amine compound. Examples of aromatic tertiary amine compounds include N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, N,N-dimethylamino-p-benzoic acid ethyl ester, N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N,N-dihydroxyethylaniline, triethylamine, and N,N-dimethylhexylamine. Among them, N,N-dimethylamino-p-benzoic acid ethyl ester and N,N-dimethylamino-p-benzoic acid isoamyl ethyl ester are preferred. These compounds may be used alone or in combination of two or more.

[0122] (5) Coloring agent The ink according to the present invention may further contain a colorant, if necessary. The colorant may be a dye or a pigment, but a pigment is preferred because it has good dispersibility in the components of the ink and has excellent weather resistance. The pigment is not particularly limited, but examples thereof include the organic pigments or inorganic pigments listed in the Color Index as follows:

[0123] 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, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, and 36 or a mixture thereof.

[0124] 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.

[0125] Examples of green pigments include pigments selected from Pigment Green 7, 26, 36, 50, or mixtures thereof. 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, 153, 154, 155, 157, 166, 167, 168, 180, 185, and 193, or mixtures thereof. Examples of black pigments include pigments selected from Pigment Black 7, 28, and 26, or mixtures thereof.

[0126] 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, and 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, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Chromofine Black A-1103, Seika Fast Yellow Low 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400(B), 2500, 2600, ZAY-260, 2700(B), 2770, Seika Fast Red 8040, C405(F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmy 6B1476T-7, 1483LT, 3840, 3870, Seika Fast Bordeaux 10B-430, Seika Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C718, A612, Cyanine Blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seika Chemicals Co., Ltd.); 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 (Sanyo Dye Co., Ltd.); Lionol Yellow 1405G, Lionol Blue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (Toyo Ink Co., Ltd.); Toner Magenta E02, Permanent Rubin F6B, Toner Yellow HG, Permanent Yellow GG-02, Hostapearm Blue B2G (Hoechst Industries Co., Ltd.); Novoperm P-HG, Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant); 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 (manufactured by Mitsubishi Chemical) are listed.

[0127] The pigment can be dispersed by 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. 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 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, and by adjusting the dispersion conditions and filtration conditions.

[0128] The ink according to the present invention may further contain a dispersant to enhance the dispersibility of the pigment. Examples of dispersants include carboxylates having a hydroxyl 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, naphthalenesulfonic acid-formaldehyde condensate salts, aromatic sulfonic acid-formaldehyde condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate, etc. Examples of commercially available dispersants include the Solsperse series from Avecia and the PB series from Ajinomoto Fine-Techno Co., Ltd.

[0129] The ink according to the present invention may further contain a dispersing agent, if necessary. The dispersing agent may be selected depending on the pigment. The total amount of the dispersant and the dispersion aid is preferably within the range of 1 to 50% by mass relative to the pigment.

[0130] The ink according to the present invention may further contain a dispersion medium for dispersing the pigment as necessary. Although a solvent may be contained in the ink as the dispersion medium, in order to suppress the solvent from remaining in the formed image, it is preferable to use a photopolymerizable compound (particularly a monomer having a low viscosity) as described above as the dispersion medium.

[0131] The dye may be an oil-soluble dye. Examples of oil-soluble dyes include the following dyes. Examples of magenta dyes include MS Magenta VP, MS Magenta HM-1450, MSMagenta HSo-147 (all manufactured by Mitsui Chemicals), AIZENSOT Red-1, AIZEN SOTRed-2, AIZEN SOTRed-3, AIZEN SOT Pink-1, SPIRON Red GEH SPECIAL (all manufactured by Hodogaya Chemical), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (all manufactured by Bayer Japan), KAYASET Red B, KAYASET Red 130, KAYASET Red 802 (all manufactured by Nippon Kayaku), PHLOXIN, ROSE BENGAL, ACID Red (all manufactured by Daiwa Kasei), HSR-31, DIARESIN Red K (all manufactured by Mitsubishi Kasei), and Oil Red (manufactured by BASF Japan).

[0132] Examples of cyan dyes include MS Cyan HM-1238, MS CyanHSo-16, Cyan HSo-144, and MS Cyan VPG (all manufactured by Mitsui Chemicals), AIZEN SOT Blue-4 (manufactured by Hodogaya Chemical), RESOLIN BR.Blue BGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ.Blue Z-BGL, and SIRIUS SUPRA TURQ.Blue FB-LL 330% (manufactured by Bayer Japan), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq.Blue GL-5 200, and Light Blue BGL-5200 (manufactured by Nippon Kayaku), DAIWA Blue 7000, and OleosolFast Blue GL (manufactured by Daiwa Kasei), DIARESIN Blue P (manufactured by Mitsubishi Kasei), and SUDAN Blue. 670, NEOPEN Blue 808, and ZAPON Blue 806 (all manufactured by BASF Japan Ltd.).

[0133] Examples of yellow dyes include MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (manufactured by Mitsui Chemicals), AIZENSOT Yellow-1, AIZEN SOT Yellow W-3, AIZEN SOT Yellow-6 (all manufactured by Hodogaya Chemical Co., Ltd.), MACROLEX Yellow 6G, MACROLEX FLUOR.Yellow 10GN (all manufactured by Bayer Japan Ltd.), KAYASET Yellow SF-G, KAYASET Yellow 2G, KAYASET Yellow AG, KAYASET Yellow EG (all manufactured by Nippon Kayaku Co., Ltd.), DAIWA Yellow 330HB (manufactured by Daiwa Kasei Co., Ltd.), HSY-68 (manufactured by Mitsubishi Kasei Corporation), SUDAN Yellow 146, and NEOPEN Yellow 075 (all manufactured by BASF Japan Ltd.).

[0134] Examples of black dyes include MS Black VPC (manufactured by Mitsui Chemicals, Inc.), AIZEN SOT Black-1, AIZEN SOT Black-5 (all manufactured by Hodogaya Chemical Co., Ltd.), RESORIN Black GSN 200%, RESOLIN Black BS (all manufactured by Bayer Japan KK), KAYASET Black AN (manufactured by Nippon Kayaku Co., Ltd.), DAIWA Black MSC (manufactured by Daiwa Kasei Co., Ltd.), HSB-202 (manufactured by Mitsubishi Kasei Corporation), NEPTUNE Black X60, and NEOPEN Black X58 (all manufactured by BASF Japan KK).

[0135] The ink according to the present invention may contain one or more types of colorant, 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, more preferably within a range of 0.4 to 10% by mass, based on the total amount of the ink.

[0136] (5) Other ingredients The ink according to the present invention may further contain other components including a polymerization inhibitor and a surfactant, as long as the effects of the present invention can be obtained. Only one type of these components may be contained in the ink according to the present invention, or two or more types may be contained.

[0137] (Polymerization inhibitor) Examples of polymerization inhibitors include (alkyl)phenols, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupferron, aluminum N-nitrosophenylhydroxyamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime. Examples of commercially available polymerization inhibitors include Irgastab UV10 (manufactured by BASF) and Genorad 18 (manufactured by Rahn AG).

[0138] The amount of the polymerization inhibitor can be set arbitrarily within the range in which the effects of the present invention can be obtained. The amount of the polymerization inhibitor can be, for example, not less than 0.001% by mass and less than 1.0% by mass with respect to the total mass of the ink.

[0139] (Surfactant) Examples of the surfactant include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surfactants such as alkylamine salts and quaternary ammonium salts; and silicone-based and fluorine-based surfactants.

[0140] Examples of silicone surfactants include polyether-modified polysiloxane compounds, specifically, Tego rad 2250 manufactured by Evonik, KF-351A, KF-352A, KF-642 and X-22-4272 manufactured by Shin-Etsu Chemical Co., Ltd., BYK307, BYK345, BYK347 and BYK348 manufactured by BYK-Chemie ("BYK" is a registered trademark of the company), and TSF4452 manufactured by Momentive Performance Materials.

[0141] The fluorosurfactant refers to a surfactant in which some or all of the hydrogen atoms bonded to the carbon atoms of the hydrophobic group of a normal surfactant are substituted with fluorine. Examples of fluorine-based surfactants include Megafac F, manufactured by DIC Corporation ("Megafac" is a registered trademark of the company), Surflon, manufactured by AGC Sei Chemical Co., Ltd. ("Surflon" is a registered trademark of the company), Fluorad FC, manufactured by 3M Corporation ("Fluorad" is a registered trademark of the company), Monflor, manufactured by Imperial Chemical Industries, Zonyls, manufactured by E.I. duPont Nemelas and Company, Licowet VPF, manufactured by Lubenberge-Hoechst, and FTERGENT, manufactured by Neos Corporation ("FTERGENT" is a registered trademark of the company).

[0142] The amount of the surfactant can be set arbitrarily as long as the effects of the present invention can be obtained. The amount of the surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass with respect to the total mass of the ink.

[0143] (Cure accelerator) The ink according to the present invention may contain a curing accelerator as required. There are no particular limitations on the curing accelerator 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.

[0144] (Coupling Agent) The ink according to the present invention may contain various coupling agents as necessary. By containing a coupling agent, the adhesion to the copper foil can be improved. The various coupling agents include, for example, silane-based, titanium-based, and aluminum-based coupling agents.

[0145] (Ion scavenger) The ink according to the present invention may contain an ion scavenger as necessary. 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.

[0146] (solvent) In the ink according to the present invention, it is essentially preferable that the ink be solvent-free from the viewpoint of curability, but a solvent may be added to adjust the ink viscosity.

[0147] <Ink properties> The ink according to the present invention can be suitably used as an inkjet ink so long as the ink has a viscosity of 3 to 20 mPa·s, more preferably 5 to 15 mPa·s, when heated in the range of 30 to 100° C. The ink according to the present invention is an ink containing a gelling agent and having an ink viscosity of 1 to 1×10 at 25° C. 4It is more preferable to use an ink having a viscosity in the Pa s range, which is preferable because the ink is sufficiently gelled when it lands and is cooled to room temperature, resulting in good pinning properties.

[0148] The ink according to the present invention preferably has a phase transition point in the range of 40° C. or more and less than 100° C. If the phase transition point is 40° C. or more, the ink quickly gels after landing on a recording medium, resulting in higher pinning properties. If the phase transition point is less than 100° C., the ink is easier to handle and has higher ejection stability. From the viewpoint of enabling the ink to be discharged at a lower temperature and reducing the load on the image forming apparatus, the phase transition point of the ink of the present invention is more preferably within the range of 40 to 60°C.

[0149] The viscosity and phase transition point of the ink according to the present invention can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink using a rheometer. In the present invention, the viscosity and phase transition point are values ​​obtained by the following method. It is preferable to perform the measurement by appropriately adjusting the measurement temperature depending on the ink. The ink according to the present invention is heated to 100°C, and the viscosity is measured using a stress-controlled rheometer Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0°) manufactured by Anton Paar. The ink is then cooled to 20°C under conditions of a shear rate of 11.7 (1 / s) and a temperature drop rate of 0.1°C / s to obtain a temperature change curve of the viscosity. For example, the viscosity at a discharge temperature of 80°C and the viscosity at the temperature of 25°C when the ink hits the substrate can be determined by reading the viscosities at 80°C and 25°C on the viscosity temperature change curve. The phase transition point can be determined as the temperature at which the viscosity becomes 200 mPa s on the viscosity temperature change curve.

[0150] From the viewpoint of improving ejection properties from an inkjet head, the average dispersed particle size of the pigment particles according to the present invention is preferably within a range of 50 to 150 nm, and the maximum particle size is preferably within a range of 300 to 1000 nm, and more preferably within a range of 80 to 130 nm. The average dispersed particle size of pigment particles in the present invention means a value determined by dynamic light scattering using a Datasizer Nano ZSP manufactured by Malvern. Note that inks containing colorants have high concentrations and light is not transmitted through this measuring device, so the ink is diluted 200 times before measurement. The measurement temperature is room temperature (25°C).

[0151] <Method of forming solder resist film> The ink according to the present invention is preferably an ink for forming a solder resist pattern used on a printed circuit board. When a solder resist pattern (solder resist film) is formed using the ink according to the present invention, it is possible to prevent moisture from penetrating into the solder resist film, resulting in good adhesion at the interface between the copper foil and the solder resist film on the printed circuit board, and also preventing copper migration and suppressing deterioration of insulation properties.

[0152] A method for forming a solder resist film using the ink of the present invention preferably includes the steps of: (1) ejecting the ink of the present invention from the nozzles of an inkjet head and causing it to land on a printed circuit board on which a circuit is formed; and (3) heating the ink to fully cure it. When the ink according to the present invention contains a compound having a photopolymerizable functional group and a photopolymerization initiator, it is preferable to include a step (step (2)) of temporarily curing the ink by irradiating the deposited ink with actinic rays between the above steps (1) and (3).

[0153] Step (1) In the step (1), droplets of the ink of the present invention are ejected from an inkjet head and landed on a printed circuit 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.).

[0154] The ejection stability can be improved by ejecting the ink droplets from the inkjet head in a heated state. The temperature of the ink when ejected is preferably within a range of 40 to 100°C, and more preferably within a range of 40 to 90°C in order to further improve the ejection stability. In particular, it is preferable to eject the ink at an ink temperature such that the viscosity of the ink is within a range of 7 to 15 mPa·s, more preferably within a range of 8 to 13 mPa·s.

[0155] In order to improve the ejection properties of the sol-gel phase transition ink from the inkjet head, it is preferable that the temperature of the ink when filled into the inkjet head is set to (gelation temperature + 10)°C to (gelation temperature + 30)°C. If the temperature of the ink inside the inkjet head is less than (gelation temperature + 10)°C, the ink will gel inside the inkjet head or on the nozzle surface, and the ejection properties of the ink will tend to decrease. On the other hand, if the temperature of the ink inside the inkjet head exceeds (gelation temperature + 30)°C, the ink will become too hot, which may cause the ink components to deteriorate.

[0156] The method for heating the ink is not particularly limited. For example, at least one of an ink supply system such as an ink tank constituting the head carriage, a supply pipe, and an anterior ink tank immediately before the head, a pipe with a filter, and a piezo head can be heated by a panel heater, a ribbon heater, or warm water. The amount of ink droplets ejected is preferably within the range of 2 to 20 pL in terms of recording speed and image quality.

[0157] The printed circuit board is not particularly limited, but examples thereof include copper-clad laminates for high frequency circuits made of materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluorine-polyethylene-PPO-cyanate ester, and the like, and are preferably copper-clad laminates of all grades (such as FR-4), as well as polyimide films, PET films, glass substrates, ceramic substrates, wafer plates, and stainless steel plates.

[0158] Step (2) In the step (2), the ink deposited in the step (1) is irradiated with actinic rays to provisionally cure the ink. The actinic ray can be selected from, for example, an electron beam, an ultraviolet ray, an α ray, a γ ray, an X-ray, and the like, and is preferably an ultraviolet ray. The ultraviolet light can be irradiated at a wavelength of 395 nm using, for example, a water-cooled LED manufactured by Phoseon Technology Co., Ltd. By using an LED as the light source, it is possible to prevent poor curing of the ink caused by the ink melting due to the radiant heat of the light source.

[0159] The ultraviolet irradiation is performed such that the peak illuminance of the ultraviolet light having a wavelength in the range of 370 to 410 nm on the surface of the resist film is preferably 0.5 to 10 W / cm 2 within the range of 1 to 5 W / cm 2 From the viewpoint of suppressing the radiation heat from being irradiated to the ink, the amount of light irradiated to the resist film is set to 500 mJ / cm 2 It is preferable that it is less than 1000 .mu.m. Irradiation with actinic rays is preferably carried out within 0.001 to 300 seconds after the ink has landed, and in order to form a highly precise resist film, it is more preferably carried out within 0.001 to 60 seconds.

[0160] Step (3) In step (3), after the provisional curing in step (2), the ink is further heated to completely cure it. The heating method is preferably, for example, placing the product in an oven set at a temperature within the range of 110 to 180° C. for 10 to 60 minutes.

[0161] The ink according to the present invention can be used not only as an ink for forming the above-mentioned solder resist pattern, but also as an adhesive, sealant, circuit protectant, etc. for electronic components. EXAMPLES

[0162] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, unless otherwise specified, the operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0163] <Preparation of Yellow Pigment Dispersion> Dispersant 1 and Dispersant 2 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, cooled to room temperature, and then the pigment below was added, placed in a glass bottle together with 200 g of zirconia beads with a diameter of 0.5 mm and sealed. This was dispersed in a paint shaker until the desired particle size was reached, and the zirconia beads were then removed. Dispersant 1: EFKA7701 (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) Yes) 80.6 parts by mass Pigment: PY185 (BASF, Paliotol Yellow D1155) 13.4 parts by mass

[0164] <Preparation of Cyan Pigment 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 weight Dispersion medium: Dipropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by mass Pigment: PB15:4 (Dainichi Seika Chemicals, Chromofine Blue 6332JC) 23 parts by mass

[0165] <Gelling agent> The gelling agents used were as follows: Distearyl ketone Behenyl behenate

[0166] <Compounds having thermosetting functional groups> The materials used are shown in Table I below.

[0167] [Table 1]

[0168] <Compound having a photopolymerizable functional group> As the compound having a photopolymerizable functional group, the following compounds were used. DPGTA (Product name: M222 (Miwon)) ·TMP(EO)9TA (Product name: EM2382 (manufactured by Choko Chemical Co., Ltd.))

[0169] <Photopolymerization initiator> As the photopolymerization initiator, the following was used. · TPO (manufactured by BASF)

[0170] <Photosensitizer assistant> As the photosensitizing assistant, the following was used. ITX (Lambson)

[0171] <Preparation of Inkjet Inks 1 and 2> The inks were prepared according to the ink compositions shown in Table II below, and filtered through a 3 μm Teflon (registered trademark) membrane filter manufactured by ADVATEC Corp. Ink 1 contains an unblocked isocyanate, and ink 2 contains a pyrazole-based blocked isocyanate.

[0172] [Table 2]

[0173] <Inkjet pattern formation> Each of the prepared inkjet inks was loaded into an inkjet recording device having an inkjet recording head equipped with a piezoelectric inkjet nozzle. Using this device, a pattern was formed on a copper-clad laminate for printed wiring boards (FR-4, thickness 1.6 mm, size 150 mm x 95 mm). The ink supply system used was composed of a main tank, a first sub-tank, a degassing device, a second sub-tank, an ink flow path, piping with a metal filter, and a piezo head, as shown in FIG. Furthermore, as shown in the flow chart of FIG. 8, the ink is supplied from the main tank to the first sub-tank using the valve (solenoid valve) 55, the supply pump 53, and the float sensor 241a. The second sub-tank used had a capacity of 100 mL, and was shaped as shown in FIG. 4, with rubber heaters 272 provided on the side walls and the outer surface of the bottom of the second sub-tank 245.

[0174] Furthermore, the capacity of the first sub-tank was 200 mL, and the shape of the first sub-tank was as follows, as shown in Table III below. Subtank A: The first subtank does not have a partition, and a rubber heater is provided on the outer surface of the side wall and bottom of the first subtank. The surface area of ​​the tank inner wall heated by the rubber heater that comes into contact with the ink is approximately the same as the surface area of ​​the tank inner wall heated by the rubber heater that comes into contact with the ink in the second subtank. Subtank B: Same configuration as the first subtank shown in Figures 5A and 5B. That is, rubber heaters are provided on the outer surfaces of the side walls and bottom of the first subtank, and a partition plate is provided inside the first subtank, so that the surface area of ​​the tank inner walls (side walls 2411, bottom 2412, and partition plate 2415) heated by the rubber heater that comes into contact with the ink is larger than the surface area of ​​the tank inner walls heated by the rubber heater that comes into contact with the ink in the second subtank.

[0175] The ratio of the amount of ink newly supplied from the main tank to the first sub-tank (supplied amount) to the amount of ink remaining in the first sub-tank (residual amount) was set to be as shown in Table III below. Furthermore, the ink from the first sub-tank to the head was heated to 85°C, and a heater was also built into the piezo head, heating the ink temperature in the recording head to 80°C. The piezo head used was a Konica Minolta KM1024iSHE-C with a nozzle resolution of 360 dpi, and the heads were arranged in a staggered pattern to provide a nozzle resolution of 360 dpi and a print width of 140 mm. Using this inkjet recording device, a voltage was applied so that a dot with a droplet volume of 6.0 pl was formed. A solid pattern of 20 mm × 50 mm and a comb pattern with lines and spaces of 100 μm were printed on the substrate with a print resolution of 1440 dpi × 1440 dpi in 4 passes, each with a thickness of 20 μm. After that, the ink was printed using an LED lamp (395 nm, 8 W / cm) manufactured by Phoseon Technology. 2 , water cooled unit) at 500mJ / cm 2 The ink layer was temporarily cured by irradiating the ink so that the ink layer was cured. The ink layer was then placed in an oven set at 150°C for 60 minutes for full curing, and a print sample was obtained.

[0176] [evaluation] <Adhesion to substrate> For the solid pattern print sample, the cured film was cut in a checkerboard pattern according to the cross-cut method of JIS K5600, and adhesive tape was attached and peeled off to observe the peeling state of the cured film, and the adhesion residual rate was obtained by the following method and evaluated according to the following criteria. Here, the adhesion residual rate is calculated by using the number of squares created by cutting as the denominator and the number of squares remaining after tape peeling as the numerator. ◎, ○, and △ were considered to be acceptable. (standard) ◎: Adhesion remaining rate 100% ○: Adhesion remaining rate is 80% or more but less than 100% △: Adhesion remaining rate is 60% or more but less than 80% ×: Adhesion remaining rate is less than 60%

[0177] <Solder heat resistance> The solid pattern print sample was immersed in a 260° C. solder bath for 10 seconds three times, and then the above-mentioned evaluation of substrate adhesion was performed, and the peeling state of the cured film was observed.

[0178] <Injection stability> The inkjet recording device was used to print 100 printed wiring boards for 8 hours per day for 5 consecutive days. Head maintenance was performed at the start and end of each operation day, and 10 cc of ink was discharged per head. After 8 hours of operation on the fifth operation day, a nozzle check pattern was printed, and the frequency of non-ejecting nozzles out of the total number of nozzles was evaluated according to the following criteria. For ejection stability, ◯ and ◎ were considered to be acceptable. (standard) ◎: No non-ejecting nozzles at all ○: A few non-ejecting nozzles were observed, but this was resolved by maintenance. △: Several non-ejecting nozzles were observed, and the problem could not be solved even by maintenance. ×: Several dozen or more non-ejecting nozzles are observed, and the problem cannot be solved even by maintenance.

[0179] [Table 3]

[0180] As shown by the above results, in the embodiment in which the amount of ink newly supplied from the main tank to the first sub-tank is set to be greater than the amount of ink remaining in the first sub-tank, it is found that the embodiment has superior substrate adhesion, solder heat resistance, and ejection stability compared to the comparative example. In addition, the reason why the results when the shape of subtank B was used for the first subtank were better than when the shape of subtank A was used is presumably because by increasing the contact surface area between the ink and the rubber heater, the heating time required for the ink inside the first subtank to reach a specified temperature could be shortened, which led to improved ejection stability and substrate adhesion (coating film strength). Furthermore, it can be seen that when ink 2 containing a blocked isocyanate is used, the solder heat resistance is superior to when ink 1 containing an unblocked isocyanate is used. [Industrial Applicability]

[0181] The present invention can be used in an inkjet recording method and an inkjet recording apparatus. [Explanation of symbols]

[0182] 1 Inkjet recording device 24a Inkjet head 40 Control section 51 Main Tank 53 Supply Pump 55 Valve 241 First Subtank 241a Float sensor 2411 Side wall 2412 Bottom 2413 Inlet 2414 Outlet 242 Deaeration device 245 Second Subtank 270 Heating device 272 Rubber Heater

Claims

1. An inkjet recording method for recording an image by ejecting ink from an inkjet head, comprising: A main tank as an ink supply source; a first sub-tank connected to the main tank and supplied with ink; a degassing device connected to the first sub-tank and configured to degas the ink supplied from the first sub-tank; a second sub-tank that supplies the ink degassed by the degassing device to the inkjet head and controls a negative pressure applied to the inkjet head; a heating device that heats at least the ink flow path in the first sub-tank, a control unit that sends ink from the main tank to the first sub-tank so that an amount of ink newly supplied to the first sub-tank is greater than an amount of ink remaining in the first sub-tank, The ink jet recording method, wherein the ink is a radical polymerizable ink containing a thermosetting component.

2. The inkjet recording method according to claim 1 , wherein the control unit intermittently transfers the ink from the main tank to the first sub-tank.

3. The inkjet recording method according to claim 1 or 2, wherein the thermosetting component comprises a blocked isocyanate.

4. a heating device for heating the ink flow path in the second sub-tank; and 4. An inkjet recording method according to claim 1, wherein the surface area of ​​the inner wall of the tank heated by the heating device in contact with the ink in the first and second sub-tanks is larger in the first sub-tank than in the second sub-tank.

5. 5. The ink jet recording method according to claim 1, wherein the first sub-tank has a larger capacity than the second sub-tank.

6. An inkjet recording apparatus that records an image by ejecting ink from an inkjet head, A main tank as an ink supply source; a first sub-tank connected to the main tank and supplied with ink; a degassing device connected to the first sub-tank and configured to degas the ink supplied from the first sub-tank; a second sub-tank that supplies the ink degassed by the degassing device to the inkjet head and controls a negative pressure applied to the inkjet head; a heating device that heats at least the ink flow path in the first sub-tank, an ink jet recording apparatus further comprising a control unit that sends the ink so that the amount of ink newly supplied from the main tank to the first sub-tank is greater than the amount of ink remaining in the first sub-tank;

7. The inkjet recording apparatus according to claim 6 , wherein the control unit intermittently transfers the ink from the main tank to the first sub-tank.

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