Liquid spray head and one-component adhesive

Abstract

To provide a liquid spray head that has a low environmental impact, is acid-resistant, and is highly reliable. [Solution] A liquid spray head that sprays liquid from a nozzle comprises a first member, a second member, and a cured product of a one-component adhesive that adheres the first member and the second member, wherein the one-component adhesive comprises a bisphenol-free epoxy resin, a curing agent containing an aromatic amine polymer, and an alkylphenol, wherein the alkylphenol is (a) an alkylphenol having at least one ethyl group, or (b) an alkylphenol having 1 to 3 carbon atoms in the alkyl group and at least one methyl group and one isopropyl group.

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection head and a one-component adhesive.

Background Art

[0002] Conventionally, an epoxy resin has been used in the manufacture of a liquid ejection head. For example, in Patent Document 1, an epoxy resin composition is used to bond inkjet components to each other. When an epoxy resin is used for bonding components of a liquid ejection head that come into contact with ink, the epoxy resin is required to have sufficient resistance to the properties of the ink such as acidity and good adhesiveness. In Patent Document 1, the epoxy resin composition may be configured to include a liquid epoxy resin, a liquid curing agent, and a curing accelerator. It is described that an aliphatic amine can be used as the liquid curing agent and a phenol such as nonylphenol can be used as the curing accelerator.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, nonylphenol, which is listed as a curing accelerator, is not preferable because it is an endocrine disruptor. In addition, when an aliphatic amine is used, the resistance of the epoxy resin to the properties of the ink such as acid resistance may be insufficient.

Means for Solving the Problems

[0005] According to one embodiment of the present disclosure, a liquid spray head is provided for spraying a liquid from a nozzle. The liquid spray head comprises a first member, a second member, and a cured product of a one-component adhesive for bonding the first member and the second member, wherein the one-component adhesive comprises a bisphenol-free epoxy resin, a curing agent containing a polymer of aromatic amines, and an alkylphenol, wherein the alkylphenol is (a) an alkylphenol having at least one ethyl group, or (b) an alkylphenol having 1 to 3 carbon atoms in the alkyl group and at least one methyl group and one isopropyl group. [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic diagram showing the general configuration of the liquid injection device in the embodiment. [Figure 2] This is a perspective view of the head module. [Figure 3] This is a disassembled perspective view of the liquid spray head. [Figure 4] This is a cross-sectional view of the injection unit. [Figure 5] This is a diagram illustrating the process of adhesive curing. [Figure 6] This figure shows a list of the ingredients used in the experiment. [Figure 7] This diagram shows the chemical structural formulas from chemical formula (f1) to chemical formula (f3). [Figure 8] This is a diagram to explain the evaluation level A. [Figure 9] This is a diagram to explain evaluation level C. [Figure 10] This figure shows the equivalent ratio, mass ratio, and evaluation results for Experiment 1. [Figure 11] This figure shows the equivalent ratio, mass ratio, and evaluation results for Experiment 2. [Figure 12] This figure shows the equivalent ratio and mass ratio from Experiment 3. [Figure 13] This figure shows the evaluation results for Experiment 3 and Experiment 4. [Figure 14] This figure shows the equivalent ratio and mass ratio from Experiment 4. [Figure 15] This figure shows the equivalent ratio, mass ratio, and evaluation results for Experiment 5. [Figure 16] This figure shows the equivalent ratio, mass ratio, and evaluation results for Experiment 6. [Figure 17] This figure shows the equivalent ratio and mass ratio from Experiment 7. [Figure 18] This figure shows the evaluation results for Experiment 7 and Experiment 8. [Figure 19] This figure shows the equivalent ratio and mass ratio from Experiment 8. [Figure 20] This figure shows the equivalent ratio, mass ratio, and evaluation results for Experiment 9. [Modes for carrying out the invention]

[0007] A. Embodiments: A1. Overall configuration of the liquid injection device: Figure 1 is a schematic diagram showing the general configuration of the liquid injection device 100 in this embodiment. The liquid injection device 100 is an inkjet printing device that performs printing by spraying droplets of liquid ink onto a medium 12. The medium 12 can be any material, such as printing paper, resin film, or cloth. In the following description, the X, Y, and Z directions are mutually orthogonal. When specifying the direction, the positive direction is denoted as "+" and the negative direction as "-", and positive and negative signs are used in the direction notation. In this embodiment, the X direction is the main scanning direction, which is the direction of movement of the liquid injection head 30. The Y direction is the sub-scanning direction, which is the medium feeding direction, which is orthogonal to the main scanning direction. The -Z direction is the ink spraying direction. In the following description, the +Z direction may be referred to as up and the -Z direction as down.

[0008] The liquid injection device 100 comprises a head module 3, a head movement mechanism 20, a plurality of liquid storage sections 14, a plurality of sub-tanks 15, a transport mechanism 16, and a control unit 80. The head module 3 has a plurality of liquid injection heads 30.

[0009] Each liquid storage unit 14 stores ink to be supplied to the head module 3. As the liquid storage unit 14, a bag-shaped liquid pack formed of a flexible film, an ink tank capable of ink replenishment, a detachable ink cartridge, or the like can be used.

[0010] As the ink, a colored ink containing a coloring material, a treatment ink for improving the fixing property of the colored ink to the medium 12, or the like can be used. As the coloring material contained in the colored ink, a pigment or a dye can be used. The colored ink contains a coloring material, and other components such as a dispersant for dispersing the coloring material and a glycol ether.

[0011] The components contained in the treatment ink are adjusted according to the type of the medium 12. For example, when printing paper such as art paper or coated paper is used as the medium 12, the treatment ink is configured to contain a flocculant for flocculating a dye or a pigment which is a coloring material of the colored ink. As the flocculant, an organic acid such as citric acid, malic acid, or malonic acid, a cationic compound, or the like can be used. In addition to the flocculant, the treatment ink contains an organic solvent such as a surfactant or an alkanediol. The printing paper is difficult to absorb liquid. Therefore, by using the treatment ink, the components contained in the treatment ink react with the components contained in the colored ink, so that the fixing property and the color developing property of the colored ink can be enhanced. Further, by including a glycol ether in the colored ink, bleeding can be suppressed.

[0012] Each sub-tank 15 is connected to the liquid storage unit 14 by a tube through which ink flows. Further, each sub-tank 15 is connected to the head module 3 by a first tube for supplying ink to the head module 3 and a second tube for returning ink from the liquid injection head 30 to the sub-tank 15, respectively. Ink is supplied to each sub-tank 15 from the liquid storage unit 14 and is also returned to the sub-tank 15 from the head module 3. Then, the ink circulates between the sub-tank 15 and the head module 3.

[0013] The following description illustrates a case where the liquid injection device 100 comprises two liquid storage sections 14 and two sub-tanks 15. In this embodiment, each of the two liquid storage sections 14 contains ink of a different color. To distinguish between these two inks, the ink contained in one liquid storage section 14 is called the first ink, and the ink contained in the other liquid storage section 14 is called the second ink. The liquid injection device 100 may have one liquid storage section 14 or three or more. Furthermore, the inks contained in each of the two liquid storage sections 14 may be the same color.

[0014] The head module 3 has a plurality of nozzles N, which will be described later, for ejecting ink. The head module 3 ejects ink supplied from the liquid storage unit 14 from the plurality of nozzles N toward the medium 12.

[0015] The head movement mechanism 20 comprises a conveyor belt 21 and a carriage 22 that houses the head module 3. The carriage 22 is connected to the conveyor belt 21 and reciprocates in the X direction as the conveyor belt 21 is driven. The conveying mechanism 16 conveys the medium 12 in the +Y direction.

[0016] The control unit 80 includes processing circuits such as one or more CPUs (Central Processing Units) and FPGAs (Field Programmable Gate Arrays), and storage circuits such as semiconductor memory, and controls the operation of the entire liquid injection device 100. The control unit 80 is electrically connected to the transport mechanism 16, the head movement mechanism 20, and the liquid injection head 30, and controls each part. An image is printed on the medium 12 when liquid from the nozzle N is injected onto the medium 12 transported by the transport mechanism 16.

[0017] Figure 2 is a perspective view of the head module 3. As shown in Figure 2, the head module 3 has a support 301 and a plurality of liquid injection heads 30. In this embodiment, the head module 3 has eight liquid injection heads 30. However, the number of liquid injection heads 30 in the head module 3 is not limited to eight; for example, it may be one.

[0018] The support 301 is a plate-shaped member that supports multiple liquid spray heads 30. The support 301 has multiple mounting holes 302. Each liquid spray head 30 is supported by the support 301 while fitted into a mounting hole 302. The multiple liquid spray heads 30 are arranged in a matrix.

[0019] A2. Configuration of the liquid spray head: Figure 3 is an exploded perspective view of the liquid injection head 30. As shown in Figure 3, the liquid injection head 30 includes a cover member 31, a holder member 32, a flow path structure 33, a fixing plate 36, a reinforcing plate 37, a plurality of injection units 26, a wiring board 381, a wiring member 382, ​​a first circuit board 383u, and a second circuit board 383v. In this embodiment, the liquid injection head 30 has four injection units 26.

[0020] The fixing plate 36 is a plate member for fixing a plurality of injection units 26 to the holder member 32. In this embodiment, the material of the fixing plate 36 is stainless steel. The fixing plate 36 has a plurality of openings 361 for exposing the nozzles N formed on the lower surface of each injection unit 26.

[0021] The reinforcing plate 37 is a plate member for reinforcing the fixing plate 36. In this embodiment, the material of the reinforcing plate 37 is stainless steel. The reinforcing plate 37 is fixed to the fixing plate 36 by adhesive. Similar to the fixing plate 36, the reinforcing plate 37 has a plurality of openings 371 for exposing the nozzles N formed on the lower surface of each injection unit 26.

[0022] Each injection unit 26 has the nozzle N described above and four through holes 48a. Details of the injection unit 26 will be described later.

[0023] The holder member 32 has a plurality of housing sections 321, a plurality of first holder through holes 322, and a plurality of second holder through holes 323. The material of the holder member 32 is a metal, such as stainless steel. Each housing section 321 is formed to protrude downward from the plate-shaped flange 324 of the holder member 32. The lower side of each housing section 321 is open. An injection unit 26 is housed in each housing section 321. Each first holder through hole 322 communicates with one of the four first holder through holes 322 of each injection unit 26. Each second holder through hole 323 is a through hole for inserting a flexible substrate 51a, which will be described later.

[0024] The flow channel structure 33 includes a laminate 333, a first supply upper connection 331a, a first discharge upper connection 332a, a second supply upper connection 331b, and a second discharge upper connection 332b. The laminate 333 is composed of multiple flow channel members Su stacked together. Each flow channel member Su defines a flow channel through which the ink flows.

[0025] The laminate 333 is constructed by bonding two adjacent flow channel members Su together with an adhesive. In this embodiment, the material of each flow channel member Su is resin.

[0026] The laminate 333 has four structural channels (not shown) formed therein for circulating ink between the sub-tank 15 and the injection unit 26. Each structural channel consists of a groove formed on the upper or lower surface of each channel member Su and a through hole that penetrates through the thickness direction of each channel member Su.

[0027] The first supply upper connection 331a, the first discharge upper connection 332a, the second supply upper connection 331b, and the second discharge upper connection 332b are provided on the upper surface of the laminate 333. Each of the first supply upper connection 331a, the first discharge upper connection 332a, the second supply upper connection 331b, and the second discharge upper connection 332b is connected to one of the four structural flow channels.

[0028] The wiring board 381 and wiring member 382 are mounting components for electrically connecting the control unit 80 and the injection unit 26. Wiring and other connections are formed on the wiring board 381. The wiring member 382 is a connector to which a signal cable (not shown) is connected. Electronic circuits are formed on the first circuit board 383u and the second circuit board 383v. The first circuit board 383u and the second circuit board 383v are electrically connected to the wiring board 381.

[0029] The cover member 31 houses the laminate 333, the wiring board 381, the wiring member 382, ​​the first circuit board 383u, and the second circuit board 383. For the material of the cover member 31, for example, resin or metal can be used. The cover member 31 has two first connection holes 311, two second connection holes 312, and a first hole 313. The first hole 313 is for inserting the wiring member 382. A first supply upper connection 331a or a second supply upper connection 331b is inserted through each of the two first connection holes 311. A first discharge upper connection 332a or a second discharge upper connection 332b is inserted through each of the two second connection holes 312.

[0030] The materials for the cover member 31 and the holder member 32 are not limited to those described above. For example, the material for the holder member 32 may be resin. Also, the materials for the cover member 31 and the holder member 32 may be, for example, carbon steel or a material that combines resin and metal.

[0031] The laminate 333, wiring member 382, ​​first circuit board 383u, and second circuit board 383v are housed inside the cover member 31. The spray unit 26 is housed inside the holder member 32. A fixing plate 36 and a reinforcing plate 37 are placed on the underside of the holder member 32. The reinforcing plate 37, fixing plate 36, and holder member 32 are bonded together with adhesive. The spray unit 26 is fixed to the holder member 32 by bonding the fixing plate 36, which supports the spray unit 26 from below, to the holder member 32. The cover member 31, which houses the above-mentioned components, and the holder member 32, which houses the above-mentioned components, are connected to assemble the liquid spray head 30.

[0032] A3. Configuration of the injection unit: Figure 4 is a cross-sectional view of the injection unit 26, including the fixing plate 36, reinforcing plate 37, and holder member 32. As shown in Figure 4, the injection unit 26 includes a nozzle plate 62, two flow path sealing members 64, a flow path substrate 53, a pressure chamber substrate 34, a vibrating plate 54, a sealing body 46, a housing portion 48, and a flexible substrate 51a. The nozzle plate 62, flow path sealing members 64, flow path substrate 53, pressure chamber substrate 34, vibrating plate 54, and sealing body 46 are elongated plate-shaped members in the Y direction. Each of the nozzle plate 62, flow path substrate 53, pressure chamber substrate 34, vibrating plate 54, and sealing body 46 has a structure that is substantially symmetrical with respect to the center line in the X direction. The planar shapes of the pressure chamber substrate 34, vibrating plate 54, and sealing body 46 are smaller than the planar shapes of the flow path substrate 53 and housing portion 48. During assembly, the nozzle plate 62, the two flow path sealing members 64, the flow path substrate 53, the pressure chamber substrate 34, the diaphragm 54, the sealing body 46, and the housing portion 48 are stacked in this order and bonded to each other with a cured adhesive GL (not shown).

[0033] The nozzle plate 62 is a plate-shaped member on which multiple nozzles N are formed. Each nozzle N is a through-hole with a substantially circular planar shape. The multiple nozzles N are arranged along the Y direction. There are two rows of nozzles N, and these two rows are aligned in the X direction. The two flow path sealing members 64 are positioned in the X direction, flanking the nozzle plate 62.

[0034] The flow channel substrate 53 has two first openings 32a, a plurality of second openings 32b, and a plurality of third openings 32c. The planar shape of the first openings 32a is a rectangle that is elongated in the Y direction. The first openings 32a are formed along the side of the flow channel substrate 53 that is parallel to the Y direction. The plurality of second openings 32b are arranged in the Y direction. Similarly, the plurality of third openings 32c are arranged in the Y direction. There are two rows of second openings 32b and two rows of third openings 32c. In the X direction, the first openings 32a, a row of one second opening 32b, a row of one third opening 32c, a row of one third opening 32c, a row of one second opening 32b, and the first opening 32a are formed in this order. Furthermore, adjacent second openings 32b and third openings 32c in the X direction are formed so that their positions in the Y direction are approximately identical.

[0035] Multiple openings 34a are formed in the pressure chamber substrate 34. The planar shape of the openings 34a is a rectangle that is elongated in the X direction. The multiple openings 34a are arranged in the Y direction. There are two rows in which the multiple openings 34a are arranged, and these two rows are formed side by side in the X direction. The openings 34a are formed in a position that overlaps with the adjacent second opening 32b and third opening 32c formed in the flow channel substrate 53 when viewed from the Z direction.

[0036] A piezoelectric element 44 is formed on the diaphragm 54 at a position that overlaps with an opening 34a formed in the pressure chamber substrate 34 when viewed from the Z direction. The seal 46 reinforces the strength of the pressure chamber substrate 34 and the diaphragm 54 and protects the piezoelectric element 44. The seal 46 has a seal opening 46a. The planar shape of the seal opening 46a is a rectangle that is elongated in the Y direction.

[0037] The first circuit board 383u or the second circuit board 383v and the piezoelectric element 44 are electrically connected via the flexible substrate 51a.

[0038] The housing portion 48 is a case for storing ink and has a frame shape. The material of the housing portion 48 is resin. When laminated, the pressure chamber substrate 34, the diaphragm 54, and the sealing body 46 are arranged in the internal space of the housing portion 48. Through holes 48a are formed at each of the ends of the housing portion 48 in the X direction.

[0039] A space Rb extending in the Y direction is formed at each end of the housing portion 48 in the X direction. Space Rb communicates with the through hole 48a. Space Ra, the supply liquid chamber 26a, and the supply flow path 26b are formed by connecting the flow path substrate 53 and the flow path sealing member 64. Space Ra is the internal space of the first opening 32a. The supply liquid chamber 26a is the space enclosed by the partition wall 32d separating the first opening 32a and the second opening 32b, and the flow path sealing member 64. The supply flow path 26b is the internal space of the second opening 32b. Space Ra communicates with space Rb and the supply liquid chamber 26a, and the supply liquid chamber 26a communicates with the supply flow path 26b. A pressure chamber C is formed by connecting the pressure chamber substrate 34 and the diaphragm 54. The pressure chamber C is the space enclosed by the opening 34a and the diaphragm 54. The pressure chamber C is in communication with the supply channel 26b. The communication channel 26c is formed by the connection between the channel substrate 53 and the nozzle plate 62. The communication channel 26c is the internal space of the third opening 32c. The communication channel 26c is in communication with the pressure chamber C and the nozzle N.

[0040] Spaces Ra and Rb function as liquid storage chambers for storing ink supplied to the pressure chamber C. Space Rb communicates with multiple spaces Ra aligned in the Y direction, and the ink supplied through the through-hole 48a is stored in the multiple spaces Ra via space Rb. The ink stored in space Ra flows through the supply liquid chamber 26a and the supply channel 26b and is supplied to the pressure chamber C.

[0041] Each of the four through-holes 48a formed in the injection unit 26 communicates with each of the first holder through-holes 322 of the holder member 32. As a result, the first ink is stored in one of the two spaces Rb formed in the injection unit 26. The second ink is stored in the other of the two spaces Rb formed in the injection unit 26.

[0042] In a plan view from the Z direction, the piezoelectric element 44 is positioned to overlap with each of the two pressure chambers C. A drive signal and a reference voltage are input to the piezoelectric element 44 via the flexible substrate 51a. When the drive signal and reference voltage are input and voltage is applied, the piezoelectric element 44 deforms, and the diaphragm 54 vibrates in conjunction with the deformation of the piezoelectric element 44, causing the pressure in the pressure chamber C to fluctuate, which in turn causes ink to be ejected from the nozzle N.

[0043] As described above, the injection unit 26 is housed in the internal space of the holder member 32, and the reinforcing plate 37 and the fixing plate 36 are positioned below the injection unit 26, with each member being bonded together with adhesive.

[0044] In a plan view of the liquid spray head 30 from below along the Z direction, the fixing plate 36 is positioned inside the holder member 32. There is a gap between the fixing plate 36 and the holder member 32. The holder member 32 and the fixing plate 36 are bonded together by a cured adhesive GL. This cured adhesive GL fills the gap between the holder member 32 and the fixing plate 36, as well as the gap between the holder member 32 and the reinforcing plate 37. There is also a gap between the nozzle plate 62 and the fixing plate 36. The nozzle plate 62 and the fixing plate 36 are bonded together by a cured adhesive GL. This cured adhesive GL fills the gap between the nozzle plate 62 and the fixing plate 36. The holder member 32 is also called the first member PA1, and the fixing plate 36 is also called the second member PA2.

[0045] A4. Details of the adhesive: Figure 5 is a diagram illustrating the process from the time the adhesive is applied until it hardens. In Figure 4 above, the gaps between the holder member 32 and the fixing plate 36, and the gaps between the fixing plate 36 and the nozzle plate 62 are depicted in a simplified manner, but the actual gaps have a complex shape. As shown in Figure 5, in this disclosure, as a structural model in which the adhesive fills the gap, a structural model is used in which the gap formed in the first member PA1 and the second member PA2 includes a first adhesive flow path PG1, a second adhesive flow path PG2, and a third adhesive flow path PG3. The first adhesive flow path PG1 and the third adhesive flow path PG3 are flow paths along the Z direction. The cross-sectional area of ​​the third adhesive flow path PG3 is smaller than the cross-sectional area of ​​the first adhesive flow path PG1. The second adhesive flow path PG2 is a flow path that connects the first adhesive flow path PG1 and the third adhesive flow path PG3.

[0046] In the bonding process using adhesive, which is one step in the manufacturing process of the liquid spray head 30, the liquid spray head 30 is positioned so that the coating surface of the component to which the adhesive is applied faces upward in the vertical direction. Specifically, in the bonding process, the liquid spray head 30 is positioned so that the nozzle plate 62 faces upward.

[0047] As shown in (S1) of Figure 5, the adhesive is applied to the opening of the first adhesive channel PG1, for example, using a dispenser. In Figure 5, an example is shown where the opening width of the first adhesive channel PG1 is smaller than the minimum dispensing width of the dispenser.

[0048] As shown in (S2) of Figure 5, the adhesive moves downward through the first adhesive channel PG1 due to its own weight. After the adhesive is placed in the opening of the first adhesive channel PG1, the first member PA1 and the second member PA2 are held at a holding temperature that is higher than room temperature but lower than the curing temperature of the adhesive for a predetermined holding time. The holding temperature is, for example, around 40°C to 60°C. The holding time is, for example, several hours. Generally, the viscosity of the adhesive at the holding temperature is lower than its viscosity at room temperature. Therefore, as the temperature rises, the adhesive wets and spreads, moving through the second adhesive channel PG2 toward the third adhesive channel PG3.

[0049] Here, the inventors found that the movement of the adhesive in the third adhesive channel PG3 differs depending on the surface tension of the adhesive. That is, when the surface tension of the adhesive is relatively high, as shown in (S4) of Figure 5, the adhesive can crawl upward by capillary action and move upward in the third adhesive channel PG3. On the other hand, when the surface tension of the adhesive is relatively low, the adhesive cannot move upward in the third adhesive channel PG3. In this case, the adhesive hardens at the curing temperature set after the holding time has elapsed, and hardened material GL is formed with only the first adhesive channel PG1 and the second adhesive channel PG2 filled. Furthermore, in this case, excess adhesive spreads on the bonding surface of the first member PA1 and the second member PA2. In this case, the excess hardened material GL spoils the appearance. Furthermore, for example, if a water-repellent region PA2a is formed on the bonding surface of the second member PA2, and hardened material GL is formed on the water-repellent region PA2a, the hardened material GL on the water-repellent region PA2a will peel off or crack. Therefore, it is undesirable for the cured adhesive GL to form on the water-repellent region PA2a. Note that the cured adhesive GL shown by the dashed line in (S3) of Figure 5 represents the case where excess adhesive spreads and hardens on the bonding surface.

[0050] As shown in (S4) of Figure 5, if the adhesive can move through the third adhesive channel PG3, the adhesive will harden into product GL while filling the first adhesive channel PG1, the second adhesive channel PG2, and the third adhesive channel PG3. Therefore, there is a need for an adhesive that has a moderate surface tension that allows it to crawl up narrow gaps such as the third adhesive channel PG3 at a temperature lower than the curing temperature.

[0051] Furthermore, as described above, the liquid spray head 30 uses acidic liquids or liquids containing glycol ether as ink. The ink sprayed from the nozzle N becomes a mist and adheres to the exposed surfaces of the nozzle plate 62 and the fixing plate 36. Therefore, if the cured adhesive GL has low resistance to the properties of the ink, the cured adhesive GL is prone to deterioration. In particular, in adhesive areas where the cured adhesive GL is not filled into narrow gaps such as the third adhesive flow path PG3, ink leakage is likely to occur due to deterioration of the cured adhesive GL. For this reason, cured adhesive GL with acid resistance and glycol ether resistance is required. Here, "glycol ether resistance" refers to the property of not easily changing its chemical structure even when exposed to glycol ether. In the following explanation, acid resistance and glycol ether resistance will be collectively referred to as liquid resistance.

[0052] Furthermore, there is a demand for adhesives with a low environmental impact. For example, bisphenol A, which is used in the synthesis of glycidyl ether type epoxy resins commonly used as adhesives, and nonylphenol, which can be used as a curing accelerator in curing reactions, are known to have a high environmental impact. The inventors have discovered an adhesive that has appropriate surface tension, a low environmental impact, and liquid resistance.

[0053] Specifically, in this embodiment, the adhesive used for bonding the holder member 32 to the fixing plate 36 and for bonding the fixing plate 36 to the nozzle plate 62 is a one-component adhesive having the features of this disclosure. In the following description, the one-component adhesive having the features of this disclosure will be referred to simply as adhesive unless otherwise specified.

[0054] The one-component adhesive comprises a bisphenol-free epoxy resin, a curing agent containing an aromatic amine polymer, and an alkylphenol. The alkylphenol is (a) an alkylphenol having at least one ethyl group, or (b) an alkylphenol having 1 to 3 carbon atoms in the alkyl group and at least one methyl group and one isopropyl group.

[0055] A bisphenol-free epoxy resin refers to a resin in which bisphenol is not used in the synthesis of the epoxy resin. In this embodiment, the bisphenol-free epoxy resin is a tetrafunctional glycidylamine type epoxy resin, namely N,N,N',N'-tetraglycidyl-m-xylenediamine or 4,4'-methylenebis(N,N-diglycidylaniline). In this embodiment, the aromatic amine polymer is a 2-ethylaniline-formaldehyde polymer.

[0056] Furthermore, in this embodiment, (a) is an alkylphenol represented by the following formula (1), and (b) is an alkylphenol represented by the following formula (2). [ka] (However, R1, R2, and R3 in formula (1) represent hydrogen or an ethyl group, and at least one of R1, R2, and R3 represents an ethyl group.) [ka] (However, in formula (2), R1, R2, R3, R4, and R5 represent hydrogen or an alkyl group having 1 to 3 carbon atoms, at least one of R1, R2, R3, R4, and R5 represents a methyl group, and at least one of R1, R2, R3, R4, and R5 represents an isopropyl group.) In this embodiment, the alkylphenol represented by formula (1) is 4-ethylphenol, and the alkylphenol represented by formula (2) is carvacrol, orthocymen-5-ol, and thymol. Adhesives having the above characteristics have moderate surface tension, low environmental impact, and liquid resistance.

[0057] The epoxy resin contained in the adhesive is a so-called bisphenol-free epoxy resin, meaning it does not contain bisphenol. Therefore, it has a lower environmental impact compared to glycidyl ether-type epoxy resins, which contain bisphenol. Consequently, this adhesive is particularly useful when printing on a medium 12 used in food packaging materials using a liquid spray device 100.

[0058] The adhesive contains a polymer of aromatic amines. This improves the acid resistance of the cured product GL. Glycidylamine-type epoxy resins are known to have lower reactivity with amines compared to commonly used glycidyl ether-type epoxy resins. In general, aromatic amines have lower reactivity with epoxy resins than aliphatic amines or alicyclic amines. The inventors have found that the curing reaction can be accelerated by including the alkylphenol of (a) or the alkylphenol of (b) above in the adhesive, in addition to the glycidylamine-type epoxy resin and the polymer of aromatic amines.

[0059] Furthermore, in this embodiment, the adhesive contains 3,4-dihydrocoumarin. This improves acid resistance.

[0060] Furthermore, in this embodiment, the ratio of the phenol equivalent of the alkylphenol of (a) or the alkylphenol of (b) to the amine equivalent of the aromatic amine polymer is 0.05 or more and 0.22 or less. This makes it possible to provide an adhesive that has appropriate surface tension at the holding temperature and excellent liquid resistance, as will be described later in the experimental examples. Here, the amine equivalent is determined by the following formula (e1). The phenol equivalent is determined by the following formula (e2). Amine equivalent = Molecular weight of amine / Number of active hydrogen atoms in amine ···(e1) Phenol equivalent = Molecular weight of phenol / Number of hydroxyl groups ···(e2) Furthermore, the ester equivalent, which will be discussed later, can be calculated using the following formula (e3). Ester equivalent = Molecular weight of lactone / Number of ester groups ... (e3) Here, when an adhesive contains multiple types of phenol, the "ratio of phenol equivalents to amine equivalents" means that the adhesive is prepared such that the total equivalent weight, obtained by summing the equivalent weights of each phenol, matches the mass of phenol calculated using the ratio (phenol equivalents / amine equivalents). Further details will be explained in the experimental examples described later.

[0061] Furthermore, in this embodiment, the phenol equivalent of the alkylphenol in (a) or the alkylphenol in (b) is 0.6 or more relative to the amine equivalent of the aromatic amine polymer, which is 5.6. This further improves the liquid resistance of the adhesive.

[0062] Furthermore, in this embodiment, the equivalent weight of the intraring ester group of 3,4-dihydrocoumarin is 0.1 or more relative to the amine equivalent weight of the aromatic amine polymer (5.6). This further improves the acid resistance of the adhesive.

[0063] As described above, the one-component adhesive having the features described in this embodiment has a low environmental impact, moderate surface tension, and excellent liquid resistance. Because it has moderate surface tension at the holding temperature, the cured product GL of the one-component adhesive can fill the narrow gap between the first member PA1 and the second member PA2, thereby improving the reliability of the liquid spray head 30. Furthermore, because it has liquid resistance, even when acidic inks or inks containing glycol ethers are used as the liquid sprayed from the nozzle N, the deterioration of the cured product GL of the one-component adhesive can be suppressed, improving the reliability of the liquid spray head 30. In addition, because it has a low environmental impact, printed materials printed using the liquid spray device 100 can be used with peace of mind.

[0064] The one-component adhesive used in the manufacture of the liquid spray head 30 is not limited to the embodiments described above. Specifically, the bisphenol-free epoxy resin is not limited to a tetrafunctional glycidylamine type epoxy resin. The tetrafunctional glycidylamine type epoxy resin is not limited to N,N,N',N'-tetraglycidyl-m-xylenediamine or 4,4'-methylenebis(N,N-diglycidylaniline). The bisphenol-free epoxy resin may contain multiple types of epoxy resins. Furthermore, the aromatic amine polymer is not limited to 2-ethylaniline-formaldehyde polymer, but may be, for example, 2-ethyl-3ethylaniline-formaldehyde polymer. Even when these components are used, each of these components has the same chemical properties as the corresponding components in the embodiments described above, so a one-component adhesive exhibiting the same effects as in the embodiments described above can be produced.

[0065] Furthermore, the adhesive does not need to contain 3,4-dihydrocoumarin. If the adhesive contains 3,4-dihydrocoumarin, the equivalent amount of the intraring ester group of 3,4-dihydrocoumarin may be less than 0.1 relative to the amine equivalent amount of the aromatic amine polymer (5.6). The ratio of the phenol equivalent of the alkylphenol in (a) or (b) above to the amine equivalent amount of the aromatic amine polymer may be less than 0.05 and greater than 0.22. Even without containing 3,4-dihydrocoumarin, a one-component adhesive with appropriate surface tension, low environmental impact, and liquid resistance can be produced. Furthermore, regardless of the ratio values ​​described above, a one-component adhesive with appropriate surface tension, low environmental impact, and liquid resistance can be produced.

[0066] B. Experimental Examples: B1. List of ingredients: Figure 6 shows a list of the components used in the experiment. Figure 7 shows the chemical structures of chemical formulas (f1) to (f3). In this specification, each component is identified using a unique designation.

[0067] The CAS registry number for component CA-1 is 63738-22-7. As shown in the chemical formula (f1) in Figure 7, component CA-1 is N,N,N',N'-tetraglycidyl-m-xylenediamine, an epoxy resin having four functional groups. In the experiment, TETRAD-X (registered trademark / product name) manufactured by Mitsubishi Gas Chemical Company, Inc. was used as component CA-1. The CAS registry number for component CA-2 is 28768-32-3. As shown in the chemical formula (f2) in Figure 7, component CA-2 is 4,4'-methylenebis(N,N-diglycidylaniline), an epoxy resin having four functional groups. In the experiment, ELM434VL (product name) manufactured by Sumitomo Chemical Co., Ltd. was used as component CA-2.

[0068] The CAS registry number for component CB-1 is 69178-41-2. As shown in chemical formula (f3) in Figure 7, component CB-1 is a polymer of aromatic amines. In chemical formula (f3), n is an integer greater than or equal to 2. In the experiment, KAYAHARD® AA (product name), manufactured by Nippon Kayaku Co., Ltd., was used as component CB-1.

[0069] Component CC-1 is carvacrol, a phenol, with CAS registry number 499-75-2. In the experiment, a product manufactured by Tokyo Chemical Industry Co., Ltd. was used as component CC-1. Component CC-2 is 4-ethylphenol, a phenol, with CAS registry number 123-07-9. In the experiment, a product manufactured by Tokyo Chemical Industry Co., Ltd. was used as component CC-2. Component CC-3 is orthocymen-5-ol, a phenol, with CAS registry number 3228-02-2. In the experiment, a product manufactured by Tokyo Chemical Industry Co., Ltd. was used as component CC-3. Component CC-4 is thymol, a phenol, with CAS registry number 89-83-8. In the experiment, a product manufactured by Tokyo Chemical Industry Co., Ltd. was used as component CC-4. Component CC-5 is 2,4,6-tris(dimethylaminomethyl)phenol, a phenol, with CAS registry number 90-72-2. In the experiment, a product manufactured by Tokyo Chemical Industry Co., Ltd. was used as component CC-5.

[0070] Component CD-1 is the lactone 3,4-dihydrocoumarin, with CAS registry number 119-84-6. In the experiment, a product manufactured by Tokyo Chemical Industry Co., Ltd. was used as component CD-1.

[0071] Component CE-1 is the aliphatic amine polyoxypropylenediamine, with CAS registry number 9046-10-0. In the experiment, a product manufactured by Mitsui Chemicals Fine Chemicals, Inc. was used as component CE-1. Component CE-2 is the aromatic amine 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, with CAS registry number 19900-72-2. In the experiment, a product manufactured by Tokyo Chemical Industries, Ltd. was used as component CE-2. Component CE-3 is the imidazole compound 1-benzyl-2-methylimidazole, with CAS registry number 13750-62-4. In the experiment, a product manufactured by Tokyo Chemical Industries, Ltd. was used as component CE-3.

[0072] The molecular weight, reactive groups, number of reactive groups, and equivalent weights of each component are shown in Figure 6. In each experiment described later, the mass was calculated using the equivalent weights shown in Figure 6 to obtain the desired equivalent ratio.

[0073] In each of the experiments from Experiment 1 to Experiment 9, evaluation A was performed to assess the acid resistance of the cured adhesive, evaluation B was performed to assess the glycol ether resistance of the cured adhesive, and evaluation C was performed to assess the surface tension of the adhesive.

[0074] Figure 8 is a diagram illustrating evaluation A. Figures 10 to 20 show the equivalent ratios and mass ratios of the components and the evaluation results for each experiment. Note that the mass ratio is equal to the mass of each component that satisfies the equivalent ratio when the total mass of all components is 100g. Note that the mass ratios shown in Figures 10 to 20 are substantially the same as the equivalent ratios. In this specification, mass ratios are also shown for reference.

[0075] B2. Explanation of Rating A (Acid Resistance): B2-1. Preparation of evaluation samples: First, a dumbbell-shaped hardened material was fabricated as shown in Figure 8. This dumbbell shape is based on the Japanese Industrial Standard JIS K 7139, Plastic - Test piece type CP. In detail of the fabrication method, a dumbbell-shaped mold was first created on a 3 mm thick PTFE (polytetrafluoroethylene) sheet using cutting.

[0076] Next, an adhesive was prepared. Here, we will explain the method for preparing the cured product using Experimental Example 1 as an example. An adhesive was prepared by mixing component CA-1, which is an epoxy resin, component CB-1, which is an amine, and component CC-2, which is a phenol, in the equivalent and mass ratios shown in Figure 10.

[0077] Adhesive was poured into the fabricated dumbbell-shaped mold, and the excess adhesive was removed with a PTFE squeegee. The PTFE sheet containing the adhesive in the mold was placed in a room temperature constant temperature bath, and the temperature of the bath was raised to 80°C after 30 minutes. The adhesive was then cured by heating at 80°C in the constant temperature bath for 10 hours. After stopping the heating, the cured material was left in the constant temperature bath for 5 hours, and after the temperature of the bath had dropped to about 40°C, the cured material was removed to room temperature. The PTFE sheet was then deformed to remove the cured material.

[0078] Next, the prepared cured material was immersed in the first evaluation solution at 60°C for one week. Specifically, the cured material was placed in a 30 ml Labolan® screw-cap bottle, the evaluation solution was poured in so that the entire cured material was submerged, the bottle was sealed, and it was left in a 60°C constant temperature bath for one week. The first evaluation solution is a liquid that mimics the acidic processing ink used in the liquid spray device 100 described above. The components of the first evaluation solution and the mass ratio of each component are as follows. The lactic acid contained in the first evaluation solution is an organic acid, and the pH of the first evaluation solution is approximately 2. (First evaluation solution) Component: Mass ratio 3-methyl-1,5-pentanediol (MPD): 10 Orphine (registered trademark) E1010:1 Water:84 Lactic acid: 5

[0079] Next, the cured material was separated from the evaluation solution using an aspirator-type filtration device. A PTFE membrane filter with a pore size of 10 μm was used as the filtration filter. The cured material remaining on the funnel side, including the minute particles of cured material, was washed with pure water and ethanol, and then dried at 25°C for one day. The dried cured material was evaluated using the following evaluations A-1, A-2, and A-3. In the following explanation, the dried cured material may be referred to as the evaluation material.

[0080] B2-2. Evaluation A-1 (Weight change rate): When the weight of the cured material before immersion in the first evaluation solution is W1 and the weight of the evaluation material is W2, the swelling rate was calculated using the following formula (e4). Swelling rate [%] = (W2 - W1) / W1 × 100 ... (e4) In the case of cured materials with poor acid resistance, that is, those whose chemical structure is easily altered by acids, they swell and increase in mass when immersed in the evaluation solution. Therefore, using the determined swelling rate, the acid resistance was evaluated using three ranks: A, B, and C, as described below. The ranks C, B, and A indicate the order of acid resistance, from best to worst. Note that cured materials with poor acid resistance typically lose their shape and break into multiple small pieces when immersed in the evaluation solution. Therefore, evaluation A-2, described later, was performed on cured materials that maintained their dumbbell shape. A: Swelling rate is less than 15% B: Swelling rate of 15% or more but less than 20% C: Swelling rate of 20% or more

[0081] B2-3. Evaluation A-2 (Tensile breaking strength): The tensile strength of the evaluated material was measured using a tensile testing apparatus. The tensile testing apparatus used was the STB-1225S manufactured by A&D Corporation. Specifically, parallel clamping jaws were attached to each of the wide ends of a dumbbell-shaped hardened material, and the evaluation material was pulled at a speed of 0.5 mm / min until it fractured. The tensile load at the time of fracture was measured. The area of ​​the fracture surface was measured and obtained using a digital microscope VHX-6000 manufactured by Keyence Corporation. Using the obtained tensile load and the area of ​​the fracture surface, the fracture strength was calculated using the following formula (e5). Breaking strength [MPa] = Tensile load [N] / Area of ​​the fracture [mm²] 2 ] ···(e5)

[0082] The greater the acid resistance of the cured material, the greater its tensile strength. Therefore, the tensile strength was evaluated using three ranks, A, B, and C, as shown below. The ranks C, B, and A indicate the order of acid resistance, from best to worst. A: Breaking strength of 30 MPa or more B: Breaking strength of 20 MPa or more but less than 30 MPa C: Breaking strength less than 20 MPa

[0083] B2-4. Evaluation A-3 (Visual Observation): The acid resistance of the evaluated samples was assessed by visual inspection. Hardened materials with poor acid resistance undergo a change in chemical structure due to acid, resulting in cracks. Furthermore, this change in chemical structure causes a brownish discoloration. Cracks and discoloration are more likely to occur at the edges of the dumbbell-shaped samples. Therefore, the appearance was evaluated using four ranks: A, B, C, and D, as shown below. The ranks indicate acid resistance in the order of D, C, B, and A. A: There is no discoloration or cracks on the edges. B: There is discoloration on the edges, but no cracks. C: Discoloration and cracks on the edges. D: Cracks are present in areas other than the edges, and the shape is not maintained.

[0084] B3. Explanation of Evaluation B (Glycol ether resistance): Evaluation B differs from Evaluation A in the composition of the evaluation solution used to immerse the cured material and in the rank threshold for evaluating the weight change rate. Therefore, the differences will be explained, and the explanation of the parts that are the same as Evaluation A will be omitted.

[0085] B3-1. Rating B: The components of the second evaluation solution used in evaluation B and the mass ratio of each component are as follows. The second evaluation solution is a liquid that mimics the colored ink containing glycol ether used in the liquid spray device 100 described above. The second evaluation solution contains diethylene glycol monobutyl ether instead of lactic acid, which is present in the first evaluation solution. (Second evaluation solution) Component: Mass ratio 3-methyl-1,5-pentanediol (MPD): 10 Orphine (registered trademark) E1010:1 Water:84 Diethylene glycol monobutyl ether: 5

[0086] B3-2. Evaluation B-1 (Percentage change in weight): The threshold values ​​for the swelling rate rank in evaluation B-1 are as follows: A: Swelling rate is less than 5% B: Swelling rate of 5% or more but less than 10% C: Swelling rate of 10% or more

[0087] B4. Explanation of Grade C (Surface Tension): Figure 9 illustrates the evaluation method for Evaluation C. Similar to the adhesive preparation method in Evaluation A, the components were mixed to prepare the adhesive. Two hours after mixing, 2.5 g of the prepared adhesive was placed in a 4 ml Labolan glass screw-cap bottle. Next, a 0.46 mm diameter capillary tube was inserted to the bottom of the Labolan glass screw-cap bottle containing the adhesive. The Labolan glass screw-cap bottle with the capillary tube inserted was left in a 40°C constant temperature chamber for two hours. After two hours, the upper end of the capillary tube protruding from the Labolan glass screw-cap bottle was covered with a finger, and the capillary tube was removed from the bottle. The filling length h, which is the length along the axial direction of the capillary tube where the adhesive is filled, was then measured. Note that 40°C corresponds to the holding time required to allow the adhesive to spread throughout the gaps of the liquid spray head 30.

[0088] The longer the filling length h, the greater the surface tension. Therefore, the surface tension was evaluated using three ranks: A, B, and C. The ranks C, B, and A indicate increasing surface tension. A: Filling length h is 46 mm or more B: Filling length h is 42mm or more and less than 46mm C: Filling length h is less than 42 mm

[0089] B5. Experiment 1: As described above, the inventors found that by including an epoxy resin, a polymer of aromatic amine, and the alkylphenol of (a) or (b) above in the adhesive, a one-component adhesive with appropriate surface tension and liquid resistance can be produced. In Experiment 1, the alkylphenol content and the effectiveness of 3,4-dihydrocoumarin were evaluated.

[0090] Figure 10 shows the equivalent ratio, mass ratio, and evaluation results for Experimental Examples 1 to 6 of Experiment 1. Figure 10 shows the value of the ratio (C / B). The ratio (C / B) is the ratio of the phenol equivalent of the alkylphenol (a) or the alkylphenol (b) above to the amine equivalent of the aromatic amine polymer. In Experimental Example 3, the adhesive contains two phenols: component CC-1 and component CC-2. If the amine equivalent of component CB-1 is Ae(CB-1), the phenol equivalent of component CC-1 is Ae(CC-1), and the phenol equivalent of component CC-2 is Ae(CC-2), then the ratio (C / B) can be calculated using the following formula (e6). Ratio (C / B)= (Ae(CC-1)+Ae(CC-2)) / Ae(CB-1) ···(e6) In Experiment 1, the ratio (C / B) was set to either "0.0536" or "0.1071".

[0091] Experimental Examples 1 to 3 include an epoxy resin (component CA-1), an aromatic amine polymer (component CB-1), and at least one of carvacrol (component CC-1) and 4-ethylphenol (component CC-2). In Experimental Examples 1 and 2, although evaluation A-3 was rank C, evaluation B-3 was rank A, and evaluations A-1, A-2, B-1, B-2, and C were all rank B, indicating good results. Therefore, it can be seen that good evaluation results can be obtained by setting the ratio (C / B) to at least 0.0536 or in the range of 0.1071.

[0092] Such favorable results are thought to be obtained because the alkylphenol in (a) or (b) above promotes the curing reaction to an extent that does not cause the viscosity of the adhesive to become excessively high, while also imparting appropriate surface tension to the adhesive. Furthermore, when the viscosity of the adhesive does not become excessively high, it is preferable because it spreads more easily into the gap between the first member PA1 and the second member PA2. In addition, many of the alkylphenols in (a) or (b) above, such as carvacrol, are highly safe compounds. Therefore, adhesives can be manufactured without including nonylphenol, an endocrine disruptor, as a curing accelerator.

[0093] Furthermore, focusing on the evaluation results for evaluations A-1, A-2, B-1, and B-2, the evaluation result for Experimental Example 3 is rank A, which is better than the evaluation results for Experimental Examples 1 and 2. Therefore, it can be seen that using a phenol equivalent of 0.6 yields better evaluation results for the weight change rate of liquid resistance and tensile breaking strength than using a phenol equivalent of 0.3.

[0094] Experimental Examples 4 through 6 differ from Experimental Examples 1 through 3 in that they contain the component CD-1 (3,4-dihydrocoumarin). The evaluation results for Experimental Examples 4 through 6 are rank B, which is better than the rank C of Experimental Examples 1 through 3. Therefore, it can be seen that including component CD-1 improves acid resistance, preventing cracking and discoloration even when exposed to acid.

[0095] B6. Experiment 2: Figure 11 shows the equivalent ratio, mass ratio, and evaluation results for Experimental Examples 7 to 12 of Experiment 2. From the results of Experiment 1, it was found that a phenol equivalent of 0.6 was better than 0.3 in terms of liquid resistance. Therefore, in Experiment 2, the phenol equivalent was set to 0.6 or 1.2. In other words, the equivalent ratio of alkylphenol was increased.

[0096] Focusing on the evaluation results for ratings A-1, A-2, B-1, and B-2, the evaluation results for Experimental Examples 7, 8, 10, and 11 are rank A, which is better than the evaluation results for Experimental Examples 1, 2, 4, and 5, where the phenol equivalent was 0.3. Therefore, it can be seen that using a phenol equivalent of 0.6 rather than 0.3 results in better evaluation results for the weight change rate of liquid resistance and tensile breaking strength.

[0097] Furthermore, focusing on the evaluation results for evaluation C, the evaluation result for Experimental Example 9 is rank A, which is good compared to the evaluation results for Experimental Examples 7 and 8, where the phenol equivalent is 0.6. Therefore, it can be seen that even without including component CD-1 (3,4-dihydrocoumarin), a good evaluation result for surface tension can be obtained by setting the phenol equivalent to 1.2. Also, focusing on the evaluation results for evaluation A-3, the evaluation result for Experimental Example 9 is rank B, which is good compared to the evaluation results for Experimental Examples 7 and 8, where the phenol equivalent is 0.6. Therefore, it can be seen that even without including component CD-1 (3,4-dihydrocoumarin), a good evaluation result for acid resistance regarding cracking and discoloration can be obtained by setting the phenol equivalent to 1.2.

[0098] Experimental Examples 10 to 12 differ from Experimental Examples 7 to 9 in that they contain the component CD-1 (3,4-dihydrocoumarin). The evaluation results for Experimental Examples 10 to 12 (A-3) are rank A, which is comparable to the rank C or rank B of Experimental Examples 7 to 9. Therefore, as with the results of Experiment 1, it can be seen that including component CD-1 improves acid resistance in terms of cracking and discoloration.

[0099] B7. Experiment 3: Figure 12 shows the equivalent ratio and mass ratio for Experimental Examples 13 to 17 of Experiment 3. Figure 13 summarizes the evaluation results of Experiment 3 and Experiment 4. From the results of Experiment 2, it was found that a phenol equivalent of 1.2 yielded better evaluation results for surface tension than a phenol equivalent of 0.6. Therefore, in Experiment 3, the phenol equivalent was fixed at 1.2, and the types of phenol included in the adhesive were increased.

[0100] As shown in the evaluation results for Experiment 3 in Figure 13, for all of Experiment Examples 13 to 17, the evaluation results for all evaluations except A-3 were rank A, and the evaluation result for A-3 was rank B, indicating good results. This shows that good results are obtained regardless of whether component CC-1 (carvacrol), component CC-2 (4-ethylphenol), component CC-3 (orthocymen-5-ol), or component CC-4 (thymol) is included as the phenol.

[0101] B8. Experiment 4: Figure 14 shows the equivalent ratios and mass ratios for Experimental Examples 18 to 22 of Experiment 4. Experiment 4 differs from Experiment 3 in that it includes component CD-1 (3,4-dihydrocoumarin).

[0102] As shown in the evaluation results of Experiment 4 in Figure 13, all experimental examples from Experiment 18 to Experiment 22 in Experiment 4 received a rank of A. Therefore, as with the results of each of the experiments described above, it can be seen that including component CD-1 improves acid resistance in terms of cracking and discoloration.

[0103] B9. Experiment 5: Figure 15 shows the equivalent ratios, mass ratios, and evaluation results for Experimental Examples 23 to 28 of Experiment 5. Experiment 5 differs from Experiment 1 in that it includes component CA-2 instead of component CA-1, which is an epoxy resin. As can be seen by comparing Figure 10 and Figure 15, each of Experimental Examples 18 to 22 corresponds to each of Experimental Examples 1 to 6 of Experiment 1.

[0104] Aside from the fact that the result for evaluation C in Experimental Example 28 is rank B, and the result for evaluation C in Experimental Example 6 is rank A, the results for Experimental Example 5 are the same as those for Experimental Example 1. Therefore, it can be seen that the same results as in each of the above experiments can be obtained even when component CA-2 is used instead of component CA-1 in the epoxy resin.

[0105] B10. Experiment 6: Figure 16 shows the equivalent ratios, mass ratios, and evaluation results for Experimental Examples 29 to 33 of Experiment 6. Experiment 6 differs from Experiment 4 in that it includes component CA-2 instead of component CA-1, which is an epoxy resin. As can be seen by comparing Figure 16 with Figure 14, each of Experimental Examples 29 to 33 corresponds to each of Experimental Examples 18 to 22 of Experiment 4.

[0106] The results of Experiment 6 are the same as those of Experiment 4. Therefore, it can be seen that the same results as in each of the above experiments can be obtained even when component CA-2 is used instead of component CA-1 in the epoxy resin.

[0107] B11. Experiment 7: Figure 17 shows the equivalent ratio and mass ratio for experimental examples 34 to 41 of Experiment 7. Figure 18 shows the combined evaluation results of Experiment 7 and Experiment 8. In each of the above experiments, the ratio (C / B) is between 0.0536 and 0.2143. In Experiment 7, the ratio (C / B) was set to "0.0357" and "0.2321", which are outside this range. In addition, the phenols used were components CC-1 (carvacrol), CC-2 (4-ethylphenol), CC-3 (orthocymen-5-ol), and CC-4 (thymol). Furthermore, Experiment 7 does not contain component CD-1 (3,4-dihydrocoumarin).

[0108] As shown in the evaluation results for Experiment 7 in Figure 18, the evaluation results for Experiments 34 to 37, where the ratio (C / B) is "0.0357", were the same as those for Experiments 1 and 2, where the ratio (C / B) is "0.0537", as shown in Figure 10.

[0109] As shown in the evaluation results for Experiment 7 in Figure 18, the evaluation results for Experiments 38 to 41, where the ratio (C / B) was "0.2321", were favorable, with evaluation results A-3 receiving a rank of B, and all other evaluation results receiving a rank of A.

[0110] From the evaluation results of Experiments 1 to 7 described above, in the experimental examples where the ratio (C / B) is in the range of 0.0357 to 0.2321, the rank of each evaluation, except for evaluation A-3, is rank B or higher, which is sufficiently good. Therefore, it can be seen that by satisfying the range of 0.05 to 0.22 for the ratio (C / B), it is possible to produce adhesives with appropriate surface tension and excellent liquid resistance.

[0111] Furthermore, if the ratio (C / B) is outside the above range, it is considered undesirable for the following reasons: The smaller the ratio (C / B), the less phenol there is relative to the amine. Since phenol promotes the curing reaction, if there is little phenol, it becomes necessary to raise the curing temperature to promote the curing reaction. In each of the above experiments, the curing temperature was set to 80°C, but if the amount of phenol is reduced, it becomes necessary to raise the temperature to a higher level, such as 100°C. Raising the curing temperature is undesirable because it generates stress when bonding dissimilar materials with different coefficients of thermal expansion. Conversely, the larger the ratio (C / B), the more phenol there is relative to the amine. The higher the temperature, the greater the rate of phenol consumption by the chemical reaction. This may lead to a higher swelling rate when exposed to acid.

[0112] B12. Experiment 8: Figure 19 shows the equivalent ratios and mass ratios for Experimental Examples 42 to 49 of Experiment 8. Experiment 8 differs from Experiment 7 in that it includes component CD-1 (3,4-dihydrocoumarin). Each of Experimental Examples 42 to 49 in Experiment 8 corresponds to each of Experimental Examples 34 to 41 in Experiment 7. In addition, the ester equivalent of component CD-1 was increased to 0.5 in Experiment 8.

[0113] As can be seen by comparing the evaluation results of Experiment 7 and Experiment 8 in Figure 18, including component CD-1 (3,4-dihydrocoumarin) improves the evaluation result A-3. This indicates that including 3,4-dihydrocoumarin is beneficial. Furthermore, it can be seen that the same evaluation results can be obtained even when the ester equivalent of 3,4-dihydrocoumarin is increased to 0.5.

[0114] Furthermore, since component CD-1 (3,4-dihydrocoumarin) has an odor, it is not desirable to increase its equivalent ratio. Also, if the equivalent ratio of component CD-1 (3,4-dihydrocoumarin) is high, the viscosity of the adhesive will decrease. In addition, since component CD-1 promotes the curing reaction, including a large amount in the adhesive will cause it to cure quickly. Therefore, it is preferable that the equivalent amount of component CD-1 (3,4-dihydrocoumarin) be between 0.1 and 0.5 equivalents relative to the amine equivalent amount of 5.6.

[0115] B13. Experiment 9: Figure 20 shows the equivalent ratio, mass ratio, and evaluation results for Experimental Examples 50 to 54 of Experiment 9. Experimental Examples 50 and 51 are experimental examples that include component CA-1 (epoxy resin) and component CB-1 (polymer of aromatic amine), and component CE-3, which is an imidazole known as a curing accelerator, or component CC-5, which is a phenol that is neither the alkylphenol of (a) above nor the alkylphenol of (b) above. Comparing Experimental Example 50 with Experimental Example 1 of Experiment 1, the evaluation results A-1 and A-2 of Experimental Example 50 are rank C, which is worse than the evaluation results of Experimental Example 1. Similarly, comparing Experimental Example 51 with Experimental Example 1 of Experiment 1, the evaluation results A-1 and A-2 of Experimental Example 51 are rank C, which is worse than the evaluation results of Experimental Example 1. From the above, it can be seen that including 2,4,6-tris(dimethylaminomethyl)phenol as a curing accelerator improves acid resistance.

[0116] Experimental Examples 52 and 53 are examples in which component CA-1 is included along with either component CE-1, which is an aliphatic amine, or component CE-2, which is an aromatic amine. Comparing Experimental Example 52 with Experimental Example 1 of Experiment 1, the evaluation results for Experimental Example 52 (A-1 and A-2) are rank C, which is worse than the evaluation results for Experimental Example 1. Similarly, comparing Experimental Example 53 with Experimental Example 1 of Experiment 1, the evaluation results for Experimental Example 53 (A-1 and A-2) are rank C, which is worse than the evaluation results for Experimental Example 1. From the above, it can be seen that including a polymer of an aromatic amine as the amine improves acid resistance.

[0117] Experimental Example 54 is an experiment that includes only components CA-1 (epoxy resin) and CB-1 (aromatic amine polymer). Because Experimental Example 54 does not contain a curing accelerator, it did not cure under the curing conditions set in the experiment.

[0118] From the above results, it can be seen that the adhesive containing epoxy resin, a curing agent containing an aromatic amine polymer, and 2,4,6-tris(dimethylaminomethyl)phenol has appropriate surface tension at the holding temperature and excellent liquid resistance.

[0119] C. Other embodiments: (C1) In the above embodiment, an embodiment in which a one-component adhesive is applied to a liquid spray head 30 is shown, but the member to which the one-component adhesive is applied is not limited to the liquid spray head 30. Also, in the above embodiment, the adhesive does not contain a filler, but it may contain a filler for viscosity adjustment.

[0120] D. Other forms: This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each of the embodiments described below can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0121] (1) According to a first embodiment of the present disclosure, a liquid spray head is provided which sprays a liquid from a nozzle. The liquid spray head comprises a first member, a second member, and a cured product of a one-component adhesive that adheres the first member and the second member, wherein the one-component adhesive comprises a bisphenol-free epoxy resin, a curing agent containing an aromatic amine polymer, and an alkylphenol, wherein the alkylphenol is (a) an alkylphenol having at least one ethyl group, or (b) an alkylphenol having 1 to 3 carbon atoms in the alkyl group and at least one methyl group and one isopropyl group. According to this embodiment, the environmental burden can be reduced by using an epoxy resin that does not use bisphenol. Furthermore, by using an aromatic amine polymer, the acid resistance and resistance to organic solvents such as glycol ethers of the cured product can be improved. Furthermore, by using the alkylphenol described in (a) or (b) above, an adhesive is formed that has sufficient surface tension to crawl up narrow gaps at a temperature lower than the curing temperature, and that hardens at the curing temperature. This fills the gap between the first and second members, improving adhesion and enhancing the reliability of the liquid spray head. (2) In the liquid spray head of the above form, the epoxy resin that does not contain bisphenol may also include a tetrafunctional glycidylamine type epoxy resin. (3) In the liquid spray head of the above form, the tetrafunctional glycidylamine type epoxy resin may contain at least one of N,N,N',N'-tetraglycidyl-m-xylenediamine and 4,4'-methylenebis(N,N-diglycidylaniline). (4) In the liquid spray head of the above form, the polymer of the aromatic amine may include a 2-ethylaniline-formaldehyde polymer. (5) In the liquid spray head of the above configuration, the one-component adhesive may contain 3,4-dihydrocoumarin. This configuration can suppress the occurrence of cracks and discoloration even when exposed to acidic liquids. (6) In the liquid spray head of the above embodiment, the alkylphenol may include at least one of carvacrol, 4-ethylphenol, orthocymen-5-ol, and thymol. This embodiment provides a highly safe adhesive. (7) In the liquid spray head of the above embodiment, the ratio of the phenol equivalent of the alkylphenol to the amine equivalent of the aromatic amine polymer may be 0.05 or more and 0.22 or less. This embodiment provides an adhesive that has high resistance to the properties of liquids and has appropriate surface tension. (8) In the liquid spray head of the above embodiment, the phenol equivalent of the alkylphenol may be 0.6 or more relative to the amine equivalent of the aromatic amine polymer of 5.6. This embodiment provides an adhesive that has high resistance to the properties of liquids and has appropriate surface tension. (9) In the liquid spray head of the above embodiment, the phenol equivalent of the alkylphenol may be 1.2 or more relative to the amine equivalent of the aromatic amine polymer of 5.6. This embodiment provides an adhesive with further improved acid resistance. (10) In the liquid spray head of the above form, the ester equivalent of 3,4-dihydrocoumarin may be 0.1 or more relative to the amine equivalent of the aromatic amine polymer of 5.6. This form provides an adhesive that is less prone to cracking or discoloration even when exposed to acidic liquids. (11) In the liquid spray head of the above embodiment, (a) is an alkylphenol represented by the above formula (1) (wherein R1, R2, and R3 of formula (1) represent hydrogen or an ethyl group, and at least one of R1, R2, and R3 represents an ethyl group), and (b) is an alkylphenol represented by the above formula (2) (wherein R1, R2, R3, R4, and R5 of formula (2) represent hydrogen or an alkyl group having 1 to 3 carbon atoms, at least one of R1, R2, R3, R4, and R5 represents a methyl group, and at least one of R1, R2, R3, R4, and R5 represents an isopropyl group). (12) According to a second embodiment of the present disclosure, a one-component adhesive can be provided. This one-component adhesive comprises a bisphenol-free epoxy resin, a curing agent containing a polymer of aromatic amine, and an alkylphenol, wherein the alkylphenol is (a) an alkylphenol having at least one ethyl group, or (b) an alkylphenol having 1 to 3 carbon atoms in the alkyl group and at least one methyl group and one isopropyl group. According to this embodiment, an adhesive can be provided that has excellent acid resistance and excellent resistance to organic solvents such as glycol ethers, while reducing the environmental impact. Furthermore, an adhesive can be provided that has a moderate surface tension that allows it to crawl through narrow gaps at a temperature lower than the curing temperature, and that cures at the curing temperature. (13) In the above-described form of a one-component adhesive, (a) is an alkylphenol represented by the following formula (1) (wherein R1, R2, and R3 of formula (1) represent hydrogen or an ethyl group, and at least one of R1, R2, and R3 represents an ethyl group), and (b) is an alkylphenol represented by the following formula (2) (wherein R1, R2, R3, R4, and R5 of formula (2) represent hydrogen or an alkyl group having 1 to 3 carbon atoms, at least one of R1, R2, R3, R4, and R5 represents a methyl group, and at least one of R1, R2, R3, R4, and R5 represents an isopropyl group). (14) The above-described form of a one-component adhesive may contain 3,4-dihydrocoumarin. This form provides an adhesive that is less prone to cracking or discoloration even when exposed to acidic liquids. [Explanation of Symbols]

[0122] 3...Head module, 12...Media, 14...Liquid container, 15...Sub-tank, 16...Transport mechanism, 20...Head movement mechanism, 21...Transport belt, 22...Carriage, 26...Injection unit, 26a...Supply liquid chamber, 26b...Supply channel, 26c...Communication channel, 30...Liquid injection head, 31...Cover member, 32...Holder member, 32a...First opening, 32b...Second opening, 32c...Third opening, 32d...Partition wall, 33...Channel structure, 34...Pressure chamber substrate, 34a...Opening, 36...Fixing plate, 37...Reinforcement plate, 44...Piezoelectric element, 46...Sealing body, 46a...Sealing body opening, 48...Housing part, 48a...Through hole, 51a...Flexible substrate, 53...Channel substrate, 54...Vibrating plate, 62...Nozzle plate, 64...Channel sealing member, 80...Control unit, 100...Liquid injection device, 301...Support, 3 02...Mounting hole, 311...Hole for first connection part, 312...Hole for second connection part, 313...First hole, 321...Housing part, 322...First through hole for holder, 323...Second through hole for holder, 324...Flange, 331a...First upper connection part for supply, 331b...Second upper connection part for supply, 332a...First upper connection part for discharge, 332b...Second upper connection part for discharge, 333...Laminate, 361...Opening, 371...Open Mouth section, 381...Wiring board, 382...Wiring member, 383u...First circuit board, 383v...Second circuit board, 383...Second circuit board, C...Pressure chamber, GL...Cured material, N...Nozzle, PA1...First member, PA2...Second member, PA2a...Water-repellent region, PG1...First adhesive channel, PG2...Second adhesive channel, PG3...Third adhesive channel, Ra...Space, Rb...Space, Su...Channel member, h...Filling length

Claims

1. A liquid spray head that sprays liquid from a nozzle, The device comprises a first member, a second member, and a cured product of a one-component adhesive for bonding the first member and the second member. The aforementioned one-component adhesive is Epoxy resin that does not contain bisphenol, A curing agent containing a polymer of aromatic amines, Alkylphenols and Includes, The alkylphenol is (a) an alkylphenol having at least one ethyl group, (b) an alkylphenol having 1 to 3 carbon atoms in the alkyl group and having at least one methyl group and one isopropyl group, A liquid spray head characterized by the following features.

2. The bisphenol-free epoxy resin includes a tetrafunctional glycidylamine type epoxy resin. The liquid spray head according to feature 1.

3. The aforementioned tetrafunctional glycidylamine-type epoxy resin comprises at least one of N,N,N',N'-tetraglycidyl-m-xylenediamine and 4,4'-methylenebis(N,N-diglycidylaniline). The liquid spray head according to feature 2.

4. The polymer of the aromatic amine includes a 2-ethylaniline formaldehyde polymer. The liquid spray head according to feature 1.

5. The aforementioned one-component adhesive contains 3,4-dihydrocoumarin, The liquid spray head according to feature 1.

6. The alkylphenol comprises at least one of carvacrol, 4-ethylphenol, orthocymen-5-ol, and thymol. The liquid spray head according to feature 1.

7. The ratio of the phenol equivalent of the alkylphenol to the amine equivalent of the aromatic amine polymer is 0.05 or more and 0.22 or less. The liquid spray head according to feature 1.

8. The phenol equivalent of the alkylphenol is 0.6 or more relative to the amine equivalent of the aromatic amine polymer, which is 5.

6. The liquid spray head according to feature 1.

9. The phenol equivalent of the alkylphenol is 1.2 or more relative to the amine equivalent of the aromatic amine polymer, which is 5.

6. The liquid spray head according to feature 1.

10. The ester equivalent of the 3,4-dihydrocoumarin is 0.1 or more relative to the amine equivalent of the polymer of the aromatic amine, which is 5.

6. The liquid spray head according to feature 5.

11. (a) is an alkylphenol represented by the following formula (1), and (b) is an alkylphenol represented by the following formula (2). The liquid spray head according to feature 1. 【Chemistry 1】 (However, R in equation (1) １ , R ２ , and R ３ R represents a hydrogen or ethyl group. １ , R ２ , and R ３ At least one of them represents an ethyl group. 【Chemistry 2】 (However, R in formula (2) １ , R ２ , R ３ , R ４ , and R ５ represent hydrogen or an alkyl group having 1 to 3 carbon atoms, and at least one of R １ , R ２ , R ３ , R ４ , and R ５ represents a methyl group, and at least one of R １ , R ２ , R ３ , R ４ , and R ５ represents an isopropyl group.)

12. Epoxy resin that does not contain bisphenol, A curing agent containing a polymer of aromatic amines, Alkylphenols and Includes, The alkylphenol is (a) an alkylphenol having at least one ethyl group, (b) an alkylphenol having 1 to 3 carbon atoms in the alkyl group and having at least one methyl group and one isopropyl group, A one-component adhesive characterized by the following features.

13. (a) is an alkylphenol represented by the following formula (1), and (b) is an alkylphenol represented by the following formula (2). The one-component adhesive according to feature 12. 【Transformation 3】 (However, R in equation (1) １ , R ２ , and R ３ R represents a hydrogen or ethyl group. １ , R ２ , and R ３ At least one of them represents an ethyl group. 【Chemistry 4】 (However, R in equation (2) １ , R ２ , R ３ , R ４ , and R ５ R represents hydrogen or an alkyl group having 1 to 3 carbon atoms. １ , R ２ , R ３ , R ４ , and R ５ At least one of them shows a methyl group, R １ , R ２ , R ３ , R ４ , and R ５ At least one of them shows an isopropyl group.

14. Containing 3,4-dihydrocoumarin, The one-component adhesive according to feature 12.

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