Inkjet head and inkjet recording device

Abstract

An inkjet head 100 includes a cover member 102 which accommodates therein a head tip 10 on which a nozzle 111 for discharging ink reversibly phase-transitioning at a phase transition temperature is formed, a common ink chamber 15, and a heater 105. The cover member 102 includes a first member 1021 and a second member 1022. The first member 1021 and the second member 1022 are connected by an adhesive 80 having a Young's modulus of 0.5-3 GPa.

Description

Technical Field

[0001] The present invention relates to an inkjet head and an inkjet recording device.Background Art

[0002] There has been known a conventional inkjet recording device that records an image by ejecting ink droplets onto a recording surface of a recording medium. The inkjet recording device ejects ink droplets from nozzles of an inkjet head at appropriate timings.

[0003] In this connection, for example, PTL 1 describes an inkjet recording device that ejects UV ink. The UV ink is phase transition ink that reversibly undergoes sol-gel phase transition depending on its temperature. The UV ink becomes gel-like, that is, highly viscous, at a low temperature. Therefore, the invention of PTL 1 heats the UV ink with a heater to turn it into a sol state. Thus, the invention of PTL 1 can efficiently eject the ink.Citation ListPatent Literature

[0004] PTL 1: Japanese Unexamined Patent Publication No. 2003-165217Summary of InventionTechnical Problem

[0005] However, the volume and the volume shrinkage rate of the phase transition ink change with the phase transition. With the change, physical distortion occurs in an adhesive portion between members forming the inkjet head. Furthermore, adhesion degradation due to the distortion may cause peeling of the adhesive portion between the members. If the phase transition ink is wax ink having a great volume shrinkage rate accompanying temperature change, the risk described above is greater. When the members are peeled from each other, the ink adhered to the nozzle forming surface of the inkjet head enters the inside of the inkjet head through a gap between the members. As a result, various failures, such as disconnection / breaking of an electrically connected portion, occur.

[0006] When the inkjet recording device is used, if the inkjet head is always maintained at a high temperature and the phase transition ink is prevented from returning to room temperature, the peeling of the adhesive portion between the members can be prevented. However, if the inkjet head is always maintained at a high temperature, power consumption increases. Therefore, it is not preferable to prevent the peeling between the adhesive members by always maintaining the phase transition ink at a high temperature, from the viewpoint of environment and cost.

[0007] The present invention has been made in view of such circumstances. An object of the present invention is to provide an inkjet head and an inkjet recording device excellent in durability against repeated cooling and heating.Solution to Problem

[0008] In order to solve the aforementioned problems, the invention described in claim 1 is an inkjet head including: a head chip in which a nozzle ejecting an ink that reversibly phase-transitions at a phase transition temperature is formed; and a cover member in which the head chip, a common ink chamber that supplies the ink to the head chip, and a heater that heats the ink from outside the common ink chamber are housed, wherein the cover member includes a first member having an exposure through hole that exposes a nozzle opening surface of the head chip, and a second member connected to a lower surface of the first member and covering a side surface portion of the head chip and a side surface portion of the common ink chamber, and wherein the first member and the second member are connected to each other with an adhesive having a Young's modulus of 0.5 GPa or more and 3 GPa or less after being cured.

[0009] The invention described in claim 2 is the inkjet head according to claim 1, wherein the adhesive is an epoxy resin-based adhesive.

[0010] The invention described in claim 3 is the inkjet head according to claim 2, wherein to the adhesive, hollow particles having an average particle diameter of 10 µm or more and 70 µm or less are added.

[0011] The invention described in claim 4 is the inkjet head according to claim 3, wherein the hollow particles are contained at a volume ratio of 45% or more and 85% or less to the adhesive.

[0012] The invention described in claim 5 is the inkjet head according to any one of claims 1 to 4, wherein a primer layer is provided between the adhesive and the first member.

[0013] The invention described in claim 6 is the inkjet head according to claim 5, wherein the primer layer has a film thickness of 0.1 µm or more.

[0014] The invention described in claim 7 is the inkjet head according to any one of claims 1 to 4, wherein the adhesive, with which the first member and the second member are connected to each other, comes into contact with the ink.

[0015] The invention described in claim 8 is the inkjet head according to any one of claims 1 to 4, wherein the heater heats the ink to 60°C or more and 120°C or less.

[0016] The invention described in claim 9 is an inkjet recording device including the inkjet head according to any one of claims 1 to 4.Advantageous Effects of Invention

[0017] According to the present invention, durability against repeated cooling and heating can be improved.Brief Description of Drawings

[0018] [FIG. 1] It is a perspective view of an inkjet recording device. [FIG. 2] it is a bottom view of a head unit. [FIG. 3] it is a perspective view of the inkjet head. [FIG. 4] It is an exploded perspective view of the main part of the inkjet head. [FIG. 5] It is an enlarged sectional view of a portion of the inkjet head including a head chip. [FIG. 6] It is a graph illustrating a measurement result of Example 1 of Test 1. [FIG. 7] It is a graph illustrating a measurement result of Comparative Example 1 of Test 1. [FIG. 8] It is a graph illustrating a measurement result of Test 3. Description of Embodiments

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description is an example of an embodiment of the present invention, and does not limit the present invention.[Inkjet Recording Device]

[0020] First, an example of the configuration of an inkjet recording device 1 including inkjet heads 100 will be disclosed.

[0021] FIG. 1 is a schematic configuration diagram of the inkjet recording device 1. The inkjet recording device 1 includes a conveyance section 2 and head units 3.(Conveyance Section)

[0022] The conveyance section 2 includes two conveyance rollers 2a and 2b that rotate in a Y direction (a conveyance direction) about rotation shafts extending in an X direction in FIG. 1. Furthermore, the conveyance section 2 includes a ring-shaped conveyance belt 2c.

[0023] The inner side of the conveyance belt 2c is supported by the conveyance rollers 2a and 2b. A recording medium M is placed on the conveyance surface of the conveyance belt 2c. The conveyance rollers 2a and 2b rotate in the Y direction in accordance with the operation of a not-shown conveyance motor. As a result, the conveyance belt 2c conveys the recording medium M in the Y direction.

[0024] The recording medium M is, for example, a sheet cut to be a certain size. The recording medium M is supplied onto the conveyance belt 2c by a not-shown sheet feed device. An image is recorded on the recording medium M by ejecting ink from the head units 3, and the recording medium M is discharged to a predetermined sheet ejection section.

[0025] The recording medium M may be a continuous roll sheet. The recording medium M to be used may be, other than plain paper or coated paper, textile or sheet-shaped resin. As described above, the recording medium M may be any of various media as long as the ink landed on the surface of the recording medium M can be fixed.(Head Unit)

[0026] The head units 3 record an image on the recording medium M conveyed by the conveyance section 2. The head units 3 record an image by ejecting ink at appropriate timings based on image data. The inkjet recording device 1 of the present embodiment includes four head units 3 corresponding to ink of four colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively. These four head units 3 are arranged at predetermined intervals in order of Y, M, C and K colors from the upstream side in the conveyance direction of the recording medium M. The number of head units 3 may be three or less or five or more.

[0027] The ink ejected from the head units 3 is phase transition ink that reversibly phase-transitions between gel and sol or between solid and liquid. The phase transition ink is heated to a phase transition temperature or higher by a heater 105 (see FIG. 5) and is ejected in a liquid state. After landing on the recording medium M, the phase transition ink is solidified by irradiation of energy rays, such as ultraviolet rays, or natural cooling. Specifically, the phase transition ink is solder resist ink, UV ink, wax ink, or the like.[Inkjet Head]

[0028] FIG. 2 is a plan view of one head unit 3 as viewed from the side facing the conveyance surface of the conveyance belt 2c, that is, from the Z direction perpendicular to the X direction and the Y direction. The head unit 3 includes a plate-like base section 3a and a plurality of inkjet heads 100. The inkjet heads 100 are fitted in and fixed to through holes of the base section 3a in a state in which surfaces provided with openings of nozzles 111 are exposed from the through holes of the base section 3a toward the -Z direction.

[0029] In the inkjet head 100, the nozzles 111 are arranged at equal intervals in the X direction. Each inkjet head 100 includes a nozzle row that is a row of nozzles 111 arranged one-dimensionally at equal intervals in the X direction.

[0030] Note that the inkjet head 100 may include a plurality of nozzle rows. In this case, the nozzle rows are arranged with the positions in the X direction shifted from each other so that the positions of the nozzles 111 in the X direction do not overlap each other.

[0031] In the head unit 3, the inkjet heads 100 are arranged in a houndstooth check pattern such that arrangement areas of the nozzles 111 in the X direction are continuous. The arrangement areas of the nozzles 111 in the head unit 3 in the X direction covers the width of an image recordable region in the X direction of the recording medium M conveyed by the conveyance belt 2c.

[0032] The head unit 3 is fixed in position during image recording and ejects the ink onto positions at predetermined intervals (intervals in the conveyance direction) as the recording medium M is conveyed. That is, the inkjet recording device 1 records an image by a single-pass method.

[0033] FIG. 3 is a perspective view of one inkjet head 100.

[0034] The inkjet head 100 includes an exterior member 101 and a cover member 102. The lower end of the exterior member 101 is engaged with the cover member 102. Main constituent elements of the inkjet head 100 are housed inside the exterior member 101 and the cover member 102. Of these, the cover member 102 is provided with an inlet 103a to which the ink is supplied from the outside, and an outlets 103b and 103c from which the ink is discharged to the outside. Furthermore, the cover member 102 is provided with a plurality of attachment holes 104 for attaching the inkjet head 100 to the base section 3a of the head unit 3.

[0035] FIG. 4 is an exploded perspective view of the main part of one inkjet head 100. In FIG. 4, each member is illustrated such that a nozzle opening surface 112 of the inkjet head 100 is directed upward, that is, so as to be turned upside down from FIG. 2. Hereinafter, a surface of each substrate on the -Z direction side is also referred to as an upper surface, and a surface on the +Z direction side is also referred to as a lower surface.

[0036] FIG. 4 shows, among the constituent members of the inkjet head 100, main constituent members housed inside the cover member 102. Specifically, FIG. 4 illustrates a head chip 10 including a nozzle substrate 11, a channel spacer substrate 12 (channel substrate), and a pressure chamber substrate 13. FIG. 4 also illustrates a wiring substrate 14 fixed to the head chip 10 and a FPC (Flexible Printed Circuit) 20 electrically connected to the wiring substrate 14. As shown in FIG. 5, a heater 105 is provided inside the cover member 102.

[0037] The head chip 10 has a structure in which the nozzle substrate 11, the channel spacer substrate 12, and the pressure chamber substrate 13 are stacked. The nozzle substrate 11, the channel spacer substrate 12, the pressure chamber substrate 13, and the wiring substrate 14 are all plate-like members each having a substantially rectangular columnar shape elongated in the X direction.(Nozzle Substrate)

[0038] The nozzle substrate 11 is a silicon substrate in which the nozzles 111, which are holes penetrating in the Z direction, are provided so as to form a row. Each of the nozzles 111 is provided at a position that coincides with a penetration channel 122 of an ink channel 121, which will be described later, of the channel spacer substrate 12 when viewed from the Z direction. The planar shape of the nozzle substrate 11 is substantially the same as those of the channel spacer substrate 12 and the pressure chamber substrate 13. The surface of the nozzle substrate 11 opposite to the channel spacer substrate 12 forms the nozzle opening surface 112 of the inkjet head 100. The thickness of the nozzle substrate 11 is, for example, about several tens of micrometers to several hundreds of micrometers.(Channel Spacer Substrate)

[0039] The channel spacer substrate 12 is a rectangular parallelepiped plate-like member having substantially the same size as the pressure chamber substrate 13 in plan view. The channel spacer substrate 12 is bonded (fixed) to the upper surface of the pressure chamber substrate 13. The channel spacer substrate 12 of the present embodiment is formed of a silicon substrate. The thickness of the channel spacer substrate 12 is not particularly limited, but is about several hundreds of micrometers.

[0040] The ink channels 121 provided in the channel spacer substrate 12 each have the penetration channel 122 and an individual ink discharge channel 123.

[0041] The penetration channel 122 is a channel that penetrates the channel spacer substrate 12 at a position that coincides with a formation position of a pressure chamber 131, which will be described later, when viewed from the Z direction. The sectional shape of the penetration channel 122 parallel to the X-Y plane is a rectangle which is substantially the same as the sectional shape of the pressure chamber 131. An opening of the penetration channel 122 on the pressure chamber substrate 13 side is connected to a pressure chamber 131. In addition, an opening of the penetration channel 122 on the nozzle substrate 11 side is connected to a nozzle 111.

[0042] The individual ink discharge channel 123 is a channel that branches from the penetration channel 122. The individual ink discharge channel 123 includes horizontal individual discharge channels 123a and vertical individual discharge channels 123b. The horizontal individual discharge channels 123a are a pair of groove-shaped channels each extending in the Y direction along the surface of the channel spacer substrate 12 from the opening of the penetration channel 122 on the nozzle substrate 11 side. The vertical individual discharge channels 123b are channels provided so as to penetrate the channel spacer substrate 12 from the ends of the horizontal individual discharge channels 123a. Openings of the vertical individual discharge channels 123b on the pressure chamber substrate 13 side are connected to horizontal common discharge channels 132a of common ink discharge channels 132, which will be described later. Therefore, the individual ink discharge channel 123 guides the ink that has flowed from the penetration channel 122 into the horizontal individual discharge channels 123a, to the common ink discharge channels 132 via the vertical individual discharge channels 123b.

[0043] In this manner, the individual ink discharge channel 123 provided in the channel spacer substrate 12 and the common ink discharge channels 132 provided in the pressure chamber substrate 13 constitute an ink discharge channel. The ink discharge channel discharges ink that has not been ejected from the nozzle 111 among the ink in the pressure chamber 131.(Pressure Chamber)

[0044] The pressure chamber substrate 13 is formed of a ceramic piezoelectric material. The piezoelectric material is a member that deforms in response to application of a voltage. The piezoelectric material is, for example, lead zirconate titanate (PZT), lithium niobate, barium titanate, lead metaniobate titanate, or the like.

[0045] The pressure chamber 131 in the pressure chamber substrate 13 is a through hole provided in the pressure chamber substrate 13 at a position that coincides with a nozzle 111 as viewed from the Z direction. A section of the pressure chamber 131 along the X-Y plane has a rectangular shape long in the Y direction. In the pressure chamber substrate 13 of the present embodiment, pressure chambers 131 are arranged in a row along the X direction.

[0046] Ink is supplied to each pressure chamber 131 via an ink supply port 141, which will be described later, of the wiring substrate 14. In addition, each pressure chamber 131 communicates with a nozzle 111 via an ink channel 121 of the channel spacer substrate 12. In addition, the pressure chambers 131 are partitioned by partition walls of the piezoelectric material, and drive electrodes are provided on the inner wall surfaces of the partition walls. In the pressure chamber substrate 13, the partition walls are repeatedly displaced in response to a drive signal(s) applied to the drive electrodes. Then, the pressure of the ink in the pressure chambers 131 varies, and the ink is ejected from the nozzles 111.

[0047] As illustrated in FIG. 4, the common ink discharge channels 132 are provided in the pressure chamber substrate 13. The common ink discharge channels 132 are provided at positions sandwiching the pressure chamber 131 in the Y direction, namely, one at a position. Among the ink supplied from the pressure chambers 131 to the ink channels 121 of the channel spacer substrate 12, ink not ejected from the nozzles 111 returns to the common ink discharge channels 132.

[0048] The common ink discharge channels 132 each include a horizontal common discharge channel 132a and a vertical common discharge channel 132b. The horizontal common discharge channel 132a is a groove-shaped channel extending in the X direction along the surface of the pressure chamber substrate 13 on the channel spacer substrate 12 side in the vicinity of an end in the Y direction. The vertical common discharge channel 132b is a channel that is connected to the horizontal common discharge channel 132a at the end on the +X direction side of the horizontal common discharge channel 132a and penetrates the pressure chamber substrate 13 in the Z direction. The ink that has returned to the horizontal common discharge channel 132a passes through the vertical common discharge channel 132b and a discharge hole 142 provided in the wiring substrate 14. Then, the ink is discharged to the outside of the inkjet head 100 from the outlet 103b or the outlet 103c.(Wiring Substrate)

[0049] The wiring substrate 14 is a plate-like member for connecting wires to apply a drive voltage from a not-shown drive circuit to the drive electrodes of the pressure chamber substrate 13. The wiring substrate 14 is a substrate made of, for example, glass, ceramics, silicon, or plastic. The wiring substrate 14 is preferably a flat plate-like substrate having an area larger than the area of the pressure chamber substrate 13 from the viewpoint of securing a bonding region with the pressure chamber substrate 13.

[0050] The wiring substrate 14 is provided with a plurality of ink supply ports 141 at positions that coincide with the pressure chambers 131 of the pressure chamber substrate 13 when viewed from the Z-direction. In addition, a pair of discharge holes 142 is provided in the wiring substrate 14 at positions that coincide with the pair of vertical common discharge channels 132b. In addition, a plurality of wires 143 extending from ends of the ink supply ports 141 to an end of the wiring substrate 14 is provided on the bonding surface of the wiring substrate 14 with the pressure chamber substrate 13.

[0051] A common ink chamber 15 (shown in FIG. 5) is connected to the lower surface of the wiring substrate 14. Then, the ink is supplied from the common ink chamber 15 to the ink supply ports 141.

[0052] The pressure chamber substrate 13 and the wiring substrate 14 are bonded to each other with a conductive adhesive containing conductive particles interposed therebetween. Thus, connection electrodes on the surface of the pressure chamber substrate 13 and the wires 143 on the wiring substrate 14, which are electrically connected to the drive electrodes, are electrically connected to each other with the conductive particles interposed therebetween.

[0053] The FPC 20 is connected to the end of the wiring substrate 14 where the wires 143 are provided, for example, with an anisotropic conductive film (ACF) interposed therebetween. By the connection, the wires 143 of the wiring substrate 14 and wires 21 on the FPC 20 are electrically connected to each other in a one to-one correspondence.

[0054] FIG. 5 is a schematic sectional view of a portion of the inkjet head 100 including the head chip 10. FIG. 5 illustrates a section of the inkjet head 100 perpendicular to the X direction.(Cover Member)

[0055] As illustrated in FIG. 5, the cover member 102 is provided in such a manner as to cover a part of the head chip 10 while exposing the nozzle opening surface 112 of the nozzle substrate 11 of the head chip 10. The cover member 102 is bonded to the head chip 10 with an adhesive 80 interposed therebetween.

[0056] The cover member 102 includes a top plate (first member) 1021, a housing (second member) 1022, and a sealing plate 1023.{Top Plate}

[0057] The top plate 1021 is a rectangular plate-like member in which a recess formed surface 1021a as the upper surface has a shape in which a central portion is recessed so as to have a recess R. Further, the top plate 1021 is provided with an exposure through hole 1021b having an opening at the deepest part of the recess R. The nozzle substrate 11 is attached to the exposure through hole 1021b via the adhesive 80. Providing the nozzle substrate 11 in the recess R can prevent failures caused by contact between the nozzle opening surface 112 and the recording medium M or a foreign substance.

[0058] Note that the head chip 10 may be attached to the top plate 1021 such that the nozzle opening surface 112 protrudes within the range of the recess R. With the above-described structure, when the recess formed surface 1021a of the top plate 1021 and the nozzle opening surface 112 are wiped with a wiping member, it is easy to cause the wiping member to come into contact with the nozzle opening surface 112.{Housing}

[0059] The housing 1022 is a plate-like member that covers the side of the head chip 10. The housing 1022 is connected to the lower surface of the top plate 1021 via the adhesive 80. The housing 1022 is made of, for example, aluminum.{Sealing Plate}

[0060] The sealing plate 1023 is a plate-like member that extends along the side surfaces of the channel spacer substrate 12 and the pressure chamber substrate 13 of the head chip 10. The sealing plate 1023 is connected to the surface of the top plate 1021 on the + Z direction side. The head chip 10 is held in the housing 1022 by the sealing plate 1023. The sealing plate 1023 may use a member separate from the top plate 1021. The sealing plate 1023 may be provided integrally with the top plate 1021.{Heater}

[0061] The heater 105 is a member to heat the ink inside the housing 1022 and outside the head chip 10. The heater 105 is, for example, a heating wire or a heat transfer member. The heater 105 covers each member constituting the common ink chamber 15. Alternatively, the heater 105 is attached to an outer surface of each member constituting the common ink chamber 15.

[0062] The ink in the head chip 10 is heated and kept warm by the heater 105 and is kept at a predetermined temperature or higher. Specifically, the heater 105 heats the ink to 60°C or more and 120°C or less. Thus, the phase transition ink is brought into a state of being sufficiently phase-transitioned to a liquid state.{Adhesive}

[0063] As shown in FIG. 5, in the inkjet head 100, the top plate 1021, the housing 1022, and the head chip 10 are bonded and integrated by the adhesive 80.

[0064] Specifically, the lower surface of the top plate 1021 and the housing 1022 are bonded to each other with the adhesive 80. The housing 1022 is bonded to the inlet 103a, the outlets 103b and 103c with the adhesive 80. The side surface portion of the top plate 1021 and the side surface portion of the head chip 10 are bonded to each other with the adhesive 80.

[0065] As described above, the adhesive 80 according to the present invention adheres the members constituting the inkjet head 100 to each other. According to this, the adhesive 80 serves not only as a mere adhesive member but also as a sealing member to prevent inflow of ink from the outside of the cover member 102.

[0066] As the adhesive 80, an adhesive having resistance to ink, that is, solvent resistance, is used. That is, the adhesive 80 is preferably hard and has a high glass transition point (Tg). Specifically, the adhesive 80 preferably has a Tg of 80°C or more. Examples of such an adhesive 80 include an epoxy-based adhesive, a phenol-based adhesive, a polyurethane isocyanate-based adhesive, and an acrylic acid ester-based adhesive.

[0067] Among these, an epoxy-based adhesive is preferable because it is tough and has high adhesive strength. The epoxy-based adhesive is formed of a combination of an epoxy resin (main agent) and a curing agent. Examples of the main agent include a bisphenol A epoxy resin, a bisphenol F epoxy resin, a phenol novolac epoxy resin, a cresol novolac epoxy resin, a triazine skeleton epoxy resin, and a glycidyl amine epoxy resin. Examples of the curing agent include an amine-based curing agent, a polyaminoamide-based curing agent, an acid anhydride-based curing agent, a dicyandiamide-based curing agent, a polymercaptan-based curing agent, and an imidazole-based curing agent.

[0068] The adhesive 80 has a Young's modulus of 0.5 GPa or more and 3 GPa or less after being cured. The Young's modulus is measured and evaluated by Plastics-Determination of tensile properties (JIS K7161-1994). When the Young's modulus after being cured is 0.5 GPa or more and 3 GPa or less, the adhesive 80 has suitable elastic properties. As a result, mechanical stress can be uniformly dispersed, and mechanical strength against bending and impact can be increased. Then, the adhesive 80 can absorb the thermal stress while maintaining the adhesive force. Thus, in the inkjet recording device 1, peeling can be prevented from occurring between members even when the temperature of the phase transition ink is returned to normal temperature.

[0069] However, an epoxy-based adhesive having a Young's modulus of 3 GPa or less after being cured is rare. Therefore, in the case of using an epoxy-based adhesive, it is necessary to reduce the Young's modulus thereof after being cured.

[0070] Examples of a method of reducing the Young's modulus of the adhesive 80 after being cured to 3 GPa or less include a method of adding balloon-shaped hollow particles containing a gas. When the hollow particles are added to the adhesive 80, the density of the adhesive 80 decreases and the Young's modulus decreases.

[0071] Here, the balloon shape refers to a core / shell microcapsule shape in which a gas is enclosed in a shell. As the hollow particles, those generally called microballoons are preferably used. Specifically, for example, microballoons that are obtained by heating and expanding a rubber material having a thickness of 0.1 µm or less and containing ethylene gas inside to be spherical are used. More specifically, for example, a polymeric hollow microsphere composite (Matsumoto Microsphere MFL series, manufactured by Matsumoto Yushi - Seiyaku Co., Ltd) is used. Alternatively, hollow silica particles (Hipresica) are used.

[0072] The hollow particles preferably have an average particle diameter of 10 µm or more and 70 µm or less. When the average particle diameter is less than 10 µm, the stress relaxation effect by the hollow particles is not effectively exhibited. The thickness of the adhesive 80 for bonding the side surface portion of the top plate 1021 and the side surface portion of the head chip 10 is 50 µm to 100 µm. Therefore, when the average particle diameter of the hollow particles is more than 70 µm, the adhesive 80 does not have solvent resistance at the bonded portion, which is not preferable. In contrast, when the average particle diameter of the hollow particles is 10 µm or more and 70 µm or less, the adhesive 80 has the stress relaxation effect without deteriorating the sealing performance in the bonded portion so much. In particular, it is more preferable that the average particle diameter of the hollow particles is 10 µm to 30 µm.

[0073] The mixing ratio of the hollow particles in the adhesive 80 is preferably 45% to 85% in volume ratio with respect to the total amount of the adhesive 80. The volume ratio of the hollow particles to the adhesive 80 being less than 45% is not preferable because the Young's modulus of the adhesive 80 does not decrease, and thermal stress cannot be absorbed. The volume ratio of the hollow particles to the adhesive 80 being more than 85% is not preferable because the hollow particles are incompletely mixed with the adhesive 80, and the adhesive 80 does not have solvent resistance. In contrast, when the mixing ratio of the hollow particles is 45% or more and 85% or less in volume ratio with respect to the total amount of the adhesive 80, the adhesive 80 has the stress relaxation effect and the solvent resistance.

[0074] The Young's modulus of the adhesive 80 may be made to be 0.5 GPa or more and 3 GPa or less by adding acrylic rubber particles containing an elastic polymer containing an acrylate ester as a main component. Thus, the method for making the Young's modulus of the adhesive 80 be 0.5 GPa or more and 3 GPa or less is not particularly limited, and a known method may be used as appropriate.{Primer Layer}

[0075] As shown in FIG. 5, a primer layer 90 is preferably provided between the adhesive 80 and the top plate 1021.

[0076] Since the top plate 1021 is made of metal and its surface tension is low, the adhesion of the adhesive 80 thereto is low. Therefore, the primer layer 90 is provided on the surface of the top plate 1021 to improve the adhesion between the adhesive 80 and the top plate 1021. The primer layer 90 is not particularly limited as long as it is transparent and has a large amount of hydroxyl groups on the surface. For example, it is preferable to form the primer layer 90 with an inorganic layer such as silica, alumina, or zirconia. It is more preferable to form the primer layer 90 with polysilazane.

[0077] As the primer layer 90, for example, an ORGATIX organic titanium compound (TA-21 manufactured by Matsumoto Fine Chemical Co., Ltd) is used. The ORGATIX organic titanium compound has metal atoms or M-OH groups (alkoxide) and forms an amorphous (non-crystalline) titanium oxide film by hydrolysis through heat treatment. Then, these are bonded to the MOM groups or to the M-OH group included in the top plate 1021 in a covalent bond or a hydrogen bond, thereby improving the adhesion between the primer layer 90 and the top plate 1021.

[0078] The primer layer 90 can be formed by a vacuum film formation method, mainly a sputtering method, or a sol-gel method. When a film is formed by the sputtering method, the primer layer 90 becomes a thin film and may crack, and is unlikely to obtain desired characteristics. On the other hand, when a film is formed by the sol-gel method, the primer layer 90 becomes a thick film having a film thickness of 0.1 µm or more, which reduces its possibility of cracking, and is likely to obtain desired characteristics.Examples

[0079] Next, regarding Examples and Comparative Examples of the present invention, results of evaluations for preferred configurations by various tests will be described. Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.[Test 1. Comparison in Terms of Adhesive Type]

[0080] The peel strength with or without microballoons in the adhesive 80 was evaluated by Determination of 90° peel strength (JIS K6854-1 :1999).

[0081] To be specific, six sets of the top plate 1021 made of SUS 304 one day after plasma treatment and PI (polyimide) were prepared. First, the top plate 1021 and the PI were each bent at 90° so that their bonding margins became 10 mm widths. Then, the bonding margins of the top plate 1021 and the PI of each set were bonded to each other with an adhesive.

[0082] In a half of the sets, namely, a first set (Example 1), they were bonded with an adhesive A. In the other half of the sets, namely, a second set (Comparative Example 1), they were bonded with an adhesive B. As shown in Table I, the adhesive A is the adhesive 80 containing microballoons and having a Young's modulus of about 2.6 GPa when cured at 60°C for 6 hours. The adhesive B is an adhesive not containing microballoons and having a Young's modulus of about 5.41 GPa when cured at 60°C for 6 hours. Example 1 and Comparative Example 1 are shown in Table II.[Table I]

[0083] TABLE I NAME OF ADHESIVE MAIN AGENT CURING AGENT MICROBALLOON CURING CONDITION YOUNG' S MODULUS (GPa) *1 NOVOLAC AMINE ALCOHOL MAKER NAME * 3 ( µ m) MIXING RATIO (VOLUME; TO TOTAL AMOUNT OF ADHESIVE) ADHESIVE A TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 MFL-81GCA 10-30 50.00% 60°C 6 HOURS 2.6 ADHESIVE B TGAP (70) E3(30) H1(50) +H3(2) AL1(10) - - - - 60°C 6 HOURS 5.41 * 1 : POLYFUNCTIONAL EPOXY *2 : MATSUMOTO YUSHI-SEIYAKU *3: AVERAGE PARTICLE DIAMETER [Table II]

[0084] TABLE IIADHESIVE TOP PLATE MEMBER MATERIAL EXAMPLE 1 ADHESIVE A SUS304 COMPARATIVE EXAMPLE 1 ADHESIVE B SUS304

[0085] Next, a part of each of Example 1 and Comparative Example 1 was peeled off so that the PI was brought into a state of being folded back by 90°. Then, the peel strength of each adhered product was measured three times using a tensile tester (Strograph, manufactured by Toyo Seiki-Seisaku-Sho, Ltd).

[0086] FIG. 6 is a graph illustrating the measurement result of Example 1. FIG. 7 is a graph illustrating the measurement result of Comparative Example 1. In both figures, the horizontal axis represents the stroke (mm). In both figures, the vertical axis represents the peel strength (N / 10 mm).

[0087] As shown in FIG. 6, the peel strength of Example 1 in which the bonding was carried out with the adhesive A containing microballoons averaged 5.7 N / 10 mm. When the cohesive failure rate was visually checked, it was about 90%. On the other hand, as shown in FIG. 7, the peel strength of Comparative Example 1 in which the bonding was carried out with the adhesive B not containing microballoons averaged 2.1 N / 10 mm. When the cohesive failure rate was visually checked, it was 10% or less, and interfacial peeling occurred.

[0088] Thus, use of the adhesive 80 whose elastic modulus after being cured has been reduced by the addition of the microballoons relaxes the stress and increases the peel strength.[Test 2. Head Evaluation]

[0089] First, a top plate 1021 and a housing 1022 were connected by each of adhesives A to H shown in Table III, and inkjet heads 100 of Examples 2 to 8 and Comparative Examples 2 to 5 shown in Table IV were manufactured.[Table III]

[0090] TABLE III NAME OF ADHESIVE MAIN AGENT CURING AGENT MICROBALLOON CURING CONDITION YOUNG' S MODULUS (GPa) *1 NOVOLAC AMINE ALCOHOL MAKER NAME * 3 (µ m) MIXING RATIO (VOLUME; TO TOTAL AMOUNT OF ADHESIVE) ADHESIVE A TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 MFL-81GCA 10-30 50.00% 60°C 6 HOURS 2.6 ADHESIVE B TGAP (70) E3(30) H1(50) +H3(2) AL1(10) - - - - 60°C 6 HOURS 5.41 ADHESIVE C TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 MFL-81GCA 10-30 45.00% 60°C 6 HOURS 3.0 ADHESIVE D TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 MFL-81GCA 10-30 85.00% 60°C 6 HOURS 0.51 ADHESIVE E TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 MFL-100MCA 60-70 50.00% 60°C 6 HOURS 1.38 ADHESIVE F TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 F-80DE 30-13C 50.00% 60°C 6 HOURS 0.43 ADHESIVE G TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 MFL-81GCA 10-30 90.00% 60°C 6 HOURS 0.26 ADHESIVE H TGAP (70) E3(30) H1(50) +H3(2) AL1(10) * 2 MFL-81GCA 10-30 40.00% 60°C 6 HOURS 3.37 *1 : POLYFUNCTIONAL EPOXY *2: MATSUMOTO YUSHI-SEIYAKU *3: AVERAGE PARTICLE DIAMETER [Table IV]

[0091] TABLE IVADHESIVE PRIMER LAYER PRESCRIPTION YOUNG' S MODULUS (GPa) EXAMPLE 2 ADHESIVE A 2.6 TA-21 EXAMPLE 3 ADHESIVE A 2.6 - EXAMPLE 4 ADHESIVE C 3.0 TA-21 EXAMPLE 5 ADHESIVE C 3.0 - EXAMPLE 6 ADHESIVE D 0.51 TA-21 EXAMPLE 7 ADHESIVE D 0.51 - EXAMPLE 8 ADHESIVE E 1.38 - COMPARATIVE EXAMPLE 2 ADHESIVE B 5.41 - COMPARATIVE EXAMPLE 3 ADHESIVE F 0.43 - COMPARATIVE EXAMPLE 4 ADHESIVE G 0.26 - COMPARATIVE EXAMPLE 5 ADHESIVE H 3.37 -

[0092] Next, the inkjet heads 100 of Examples 2 to 8 and Comparative Examples 2 to 5 were subjected to Test 2-1 and Test 2-2 described below.(Test 2-1. Heat Cycle Test)

[0093] An operation in which the inkjet heads 100 of Examples 2 to 8 and Comparative Examples 2 to 5 are allowed to stand in a thermostatic bath at 100°C for 1 hour and then allowed to stand in a thermostatic bath at -20°C for 1 hour, which is one cycle, was repeatedly performed 10 cycles. Thereafter, the presence or absence of sealing leakage at the bonded portions of the inkjet heads 100 of Examples 2 to 8 and Comparative Examples 2 to 5 was checked. Specifically, the pressure in the ink channels 121 were reduced to 0.1 atm for 10 seconds, and air leakage was measured. The evaluation criteria of Test 2-1 are as follows. A: There is no air leakage. B: Air leakage is 0.2 ml or less. C: Air leakage is more than 0.2 ml. (Test 2-2. Solvent Ink Resistance Characteristic Test)

[0094] The inkjet heads 100 of Examples 2 to 8 and Comparative Examples 2 to 5 were immersed in 60°C test liquids for one week. The test liquids in this test were cyclohexane, ethyl lactate, xylene, and ethylene glycol monobutyl ether, which are solvents used in solvent ink. After the immersion in the test liquids, the pressure of the ink channels 121 was reduced to 0.1 atm for 10 seconds, and air leakage was measured. The evaluation criteria of Test 2-2 are as follows. G: Air leakage is 0.2 ml or less. NG: Air leakage is more than 0.2 ml.

[0095] Table V shows the results of Test 2-1 and Test 2-2. In Table V, if Test 2-1 is "A" and Test 2-2 is "G", the comprehensive evaluation is "A". If Test 2-1 is "B" and Test 2-2 is "G", the comprehensive evaluation is "B". If Test 2-1 is "C" or Test 2-2 is "NG", the comprehensive evaluation is "C".[Table V]

[0096] TABLE VADHESIVE PRIMER LAYER SEALING CHARACTERISTIC AFTER HEAT CYCLE TEST (TEST 2-1) SOLVENT INK RESISTANCE CHARACTERISTIC (TEST 2-2) COMPREHENSIVE EVALUATION PRESCRIPTION YOUNG' S MODULUS (GPa) EXAMPLE 2 ADHESIVE A 2.6 TA-21 A G A EXAMPLE 3 ADHESIVE A 2.6 - B G B EXAMPLE 4 ADHESIVE C 3.0 TA-21 A G A EXAMPLE 5 ADHESIVE C 3.0 - B G B EXAMPLE 6 ADHESIVE D 0.51 TA-21 A G A EXAMPLE 7 ADHESIVE D 0.51 - B G B EXAMPLE 8 ADHESIVE E 1.38 - B G B COMPARATIVE EXAMPLE 2 ADHESIVE B 5.41 - C G C COMPARATIVE EXAMPLE 3 ADHESIVE F 0.43 - C NG C COMPARATIVE EXAMPLE 4 ADHESIVE G 0.26 - C NG C COMPARATIVE EXAMPLE 5 ADHESIVE H 3.37 - C G C

[0097] Example 5 and Comparative Example 5 are compared, and Example 7 and Comparative Example 3 are compared. Then, it is found that connecting with the adhesive 80 having a Young's modulus of 0.5 GPa or more and 3 GPa or less after being cured results in the inkjet head 100 being able to withstand thermal stress and having solvent resistance.

[0098] Example 2 and Example 3 are compared, Example 4 and Example 5 are compared, and Example 6 and Example 7 are compared. Then, it is found that the thermal stress absorbability of the adhesive 80 is enhanced by providing the primer layer 90.

[0099] Comparative Examples 3 and 4 are compared to the other Examples and Comparative Examples. Then, it is found that use of the adhesive 80 in which the hollow particles are 70 µm or less and the mixing ratio is 85% or less in volume ratio to the total amount of the adhesive 80 results in the inkjet head 100 having solvent resistance.[Test 3. Comparison in Terms of Presence / Absence of Primer Layer]

[0100] The adhesion strength with or without the primer layer 90 was evaluated by Determination of 90° peel strength (JIS K6854-1:1999).

[0101] To be specific, two sets of the top plate 1021 made of SUS 430 one day after plasma treatment and PI (polyimide) were prepared. Then, the top plate 1021 and the PI of each set were bonded with the adhesive A. At this time, the top plate 1021 of a first set (Example 9) was not provided with the primer layer 90. The top plate 1021 of a second set (Example 10) was provided with the primer layer 90. The primer layer 90 in this test was made of an ORGATIX organic compound and had a thickness of 0.1 µm or more formed by the sol-gel method. Next, a part of each of these adhered products was peeled off so that the PI was brought into a state of being folded back by 90°. Then, the peel strength of each adhered product was measured using a tensile tester (Strograph, manufactured by Toyo Seiki-Seisaku-Sho, Ltd).

[0102] FIG. 8 is a graph illustrating the measurement result of Test 3. In FIG. 8, the vertical axis represents the peel strength (N / 10 mm) of Example 9 and Example 10.

[0103] As illustrated in FIG. 8, the peel strength of Example 10 in which the primer layer 90 was provided is about 20% higher than the peel strength of Example 9 in which the primer layer 90 was not provided.

[0104] Thus, providing the primer layer 90 on the top plate 1021 increases the peel strength.[Technical Effects]

[0105] As described above, the inkjet head 100 according to the present embodiment includes the cover member 102 in which the head chip 10, the common ink chamber 15, and the heater 105 are housed. The cover member 102 includes the first member 1021 and the second member 1022 that are connected to each other by the adhesive 80 having a Young's modulus of 0.5 GPa or more and 3 GPa or less after being cured.

[0106] According to the above configuration, the adhesive 80 has elasticity, and the thermal stress can be absorbed while the adhesive force of the adhesive 80 is maintained. Therefore, even when the thermal stress is generated due to the change in the volume and the volume shrinkage rate caused by the temperature change of the phase transition ink, the inkjet head 100 can withstand the thermal stress.

[0107] Further, in the inkjet head 100 according to the present embodiment, the adhesive 80 is an epoxy resin-based adhesive.

[0108] According to the above-described configuration, the first member 1021 and the second member 1022 can be strongly bonded to each other.

[0109] Further, in the inkjet head 100 according to the present embodiment, hollow particles having an average particle diameter of 10 µm or more and 70 µm or less are added to the adhesive 80.

[0110] According to the above-described configuration, the stress relaxation effect can be provided without significantly reducing the adhesive sealing performance at the bonded portion of the adhesive 80, and the solvent resistance can also be achieved.

[0111] Further, in the inkjet head 100 according to the present embodiment, the hollow particles are contained at a volume ratio of 45% to 85% to the adhesive 80.

[0112] If the volume ratio of the hollow particles to the adhesive 80 is great, the curability of the adhesive 80 becomes worse, and the solvent resistance and the adhesion performance decrease. With the above-described configuration, both the solvent resistance and the reduction effect of the Young's modulus can be achieved.

[0113] Further, in the inkjet head 100 according to the present embodiment, the primer layer 90 is provided between the adhesive 80 and the first member 1021.

[0114] According to the above-described configuration, the adhesive strength of the first member 1021 can be further increased.

[0115] Further, in the inkjet head 100 according to the present embodiment, the primer layer 90 has a film thickness of 0.1 µm or more.

[0116] According to the above-described configuration, the primer layer 90 becomes a thick film, so that cracks are less likely to occur, and desired characteristics are more likely to be obtained.

[0117] Further, in the inkjet head 100 according to the present embodiment, the adhesive 80, with which the first member 1021 and the second member 1022 are bonded to each other, comes into contact with the ink.

[0118] In the conventional invention, when the adhesive 80 contacts the ink, the ink enters from the peeled portion when peeling between members occurs, and comes into contact with an electric connection portion, such as the FPC 20, to cause disconnection. However, in the present invention, peeling between members can be prevented, so that even with the above-described configuration, disconnection of the electrical connection portion can be prevented.

[0119] Further, in the inkjet head 100 according to the present embodiment, the heater 105 heats the ink to 60°C or more and 120°C or less.

[0120] According to the above-described configuration, it is possible to eject the ink that has been sufficiently phase-changed to the liquid state onto the recording medium M.

[0121] Although one embodiment of the present invention has been described above, the scope of the present invention is not limited to the above-described embodiment. The scope of the present invention includes the scope of the invention described in claims and the scope of equivalents thereof.Industrial Applicability

[0122] The present invention can be used for an inkjet head and an inkjet recording device that are excellent in durability against repeated cooling and heating.Reference Signs List

[0123] 1 Inkjet Recording Device 10 Head Chip 102 Cover Member 1021 Top Plate (First Member) 1021B Exposure Through Hole 1022 Housing (Second Member) 105 Heater 111 Nozzle 112 Nozzle Opening Surface 15 Common Ink Chamber 80 Adhesive 90 Primer Layer 100 Inkjet Head

Claims

1. An inkjet head comprising: a head chip in which a nozzle ejecting an ink that reversibly phase-transitions at a phase transition temperature is formed; and a cover member in which the head chip, a common ink chamber that supplies the ink to the head chip, and a heater that heats the ink from outside the common ink chamber are housed, wherein the cover member includes a first member having an exposure through hole that exposes a nozzle opening surface of the head chip, and a second member connected to a lower surface of the first member and covering a side surface portion of the head chip and a side surface portion of the common ink chamber, and wherein the first member and the second member are connected to each other with an adhesive having a Young's modulus of 0.5 GPa or more and 3 GPa or less after being cured.

2. The inkjet head according to claim 1, wherein the adhesive is an epoxy resin-based adhesive.

3. The inkjet head according to claim 2, wherein to the adhesive, hollow particles having an average particle diameter of 10 µm or more and 70 µm or less are added.

4. The inkjet head according to claim 3, wherein the hollow particles are contained at a volume ratio of 45% or more and 85% or less to the adhesive.

5. The inkjet head according to any one of claims 1 to 4, wherein a primer layer is provided between the adhesive and the first member.

6. The inkjet head according to claim 5, wherein the primer layer has a film thickness of 0.1 µm or more.

7. The inkjet head according to any one of claims 1 to 4, wherein the adhesive, with which the first member and the second member are connected to each other, comes into contact with the ink.

8. The inkjet head according to any one of claims 1 to 4, wherein the heater heats the ink to 60°C or more and 120°C or less.

9. An inkjet recording device comprising the inkjet head according to any one of claims 1 to 4.

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