Inkjet Head and Inkjet Printer

Abstract

To provide an inkjet head having excellent repellency.SOLUTION: An inkjet head comprises a nozzle plate provided with a nozzle that discharges ink toward a recording medium. The nozzle plate includes a nozzle plate substrate, a primer layer, provided on a surface opposing to the recording medium, of the nozzle plate substrate, which is formed of a monomolecular film of a primer agent including a silicone atom and a carbon atom, and a repellent layer, provided on the primer layer, which is formed of a monomolecular film of a linear fluorine compound which has a perfluoroalkyl group as one terminal group at a surface side thereof and has the other terminal group coupled to the primer layer.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] Embodiments of the present invention relate to an inkjet head and an inkjet printer.

Background Art

[0002] For example, in an inkjet head that pressurizes ink by a piezoelectric element and discharges ink droplets from nozzles provided on a nozzle plate, a liquid repellency is imparted so that ink does not adhere to the surface of the nozzle plate. To impart liquid repellency to the surface of the nozzle plate, a liquid repellent film is formed by applying a fluorine-based compound to the surface of the nozzle plate substrate by a coating method or a vapor deposition method.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide an inkjet head having excellent liquid repellency and an inkjet printer including such an inkjet head.

Means for Solving the Problems

[0005] The inkjet head according to the embodiment includes a nozzle plate provided with nozzles for discharging ink toward a recording medium. The nozzle plate includes a nozzle plate substrate, a primer layer formed of a monomolecular film of a primer agent containing silicon atoms and carbon atoms provided on a surface of the nozzle plate substrate facing the recording medium, and a liquid repellent layer formed of a monomolecular film of a linear fluorine compound provided on the primer layer and having a perfluoroalkyl group as one terminal group on the surface side and the other terminal group bonded to the primer layer.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0007] Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a perspective view showing an on-demand type inkjet head 1 mounted on a head carriage of an inkjet printer according to an embodiment. In the following description, a rectangular coordinate system composed of an X-axis, a Y-axis, and a Z-axis is used. The direction indicated by the arrow in the figure is taken as the plus direction for convenience. The X-axis direction corresponds to the printing width direction. The Y-axis direction corresponds to the direction in which the recording medium is conveyed. The plus direction of the Z-axis is the direction facing the recording medium.

[0008] Briefly described with reference to FIG. 1, the inkjet head 1 includes an ink manifold 10, an actuator substrate 20, a frame 40, and a nozzle plate 50.

[0009] The actuator substrate 20 has a rectangular shape with its longitudinal direction along the X-axis. Examples of the material of the actuator substrate 20 include alumina (Al2O3), silicon nitride (Si3N4), silicon carbide (SiC), aluminum nitride (AlN), and lead zirconate titanate (PZT: Pb(Zr,Ti)O3).

[0010] The actuator substrate 20 is stacked on the ink manifold 10 so as to close the open end of the ink manifold 10. The ink manifold 10 is connected to an ink cartridge via an ink supply pipe 11 and an ink return pipe 12.

[0011] A frame 40 is attached to the actuator substrate 20. A nozzle plate 50 is attached to the frame 40. A plurality of nozzles N are provided at predetermined intervals along the X-axis direction so as to form two rows along the Y-axis on the nozzle plate 50.

[0012] FIG. 2 is an exploded perspective view of the actuator substrate 20, the frame 40, and the nozzle plate 50 that constitute the inkjet head 1 according to the embodiment. This inkjet head 1 is a so-called side shooter type of shear mode shared wall.

[0013] A plurality of ink supply ports 21 are provided at intervals along the X-axis direction on the actuator substrate 20 so as to form a row at the central portion in the Y-axis direction. Further, a plurality of ink discharge ports 22 are provided at intervals along the X-axis direction on the actuator substrate 20 so as to form rows in the Y-axis plus direction and the Y-axis minus direction with respect to the row of the ink supply ports 21, respectively.

[0014] A plurality of actuators 30 are provided between the column of the central ink supply port 21 and the column of one ink discharge port 22. These actuators 30 form a column extending in the X-axis direction. Also, a plurality of actuators 30 are provided between the column of the central ink supply port 21 and the column of the other ink discharge port 22. These actuators 30 also form a column extending in the X-axis direction.

[0015] Each of the columns composed of the plurality of actuators 30 is composed of a first piezoelectric body and a second piezoelectric body laminated on the actuator substrate 20. Examples of the materials of the first and second piezoelectric bodies include lead zirconate titanate (PZT), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), etc. The first and second piezoelectric bodies are polarized in opposite directions along the thickness direction.

[0016] The laminate composed of the first and second piezoelectric bodies is provided with a plurality of grooves each extending in the Y-axis direction and arranged in the X-axis direction. These grooves open on the second piezoelectric body side and have a depth greater than the thickness of the second piezoelectric body. Hereinafter, among this laminate, the portion sandwiched between adjacent grooves is referred to as a channel wall. These channel walls each extend in the Y-axis direction and are arranged in the X-axis direction. Note that the groove between two adjacent channel walls is an ink channel through which ink flows.

[0017] Electrodes are formed on the side walls and bottom of the ink channel. These electrodes are connected to a wiring pattern 31 extending along the Y-axis direction.

[0018] Except for the connection portion with the flexible printed circuit board described later, a protective film (not shown) is formed on the surface of the actuator substrate 20 including the electrodes and the wiring pattern 31. The protective film includes, for example, a plurality of layers of inorganic insulating films and organic insulating films.

[0019] The frame 40 has an opening. This opening is smaller than the actuator substrate 20 and larger than the area of the actuator substrate 20 where the ink supply port 21, the actuator 30, and the ink discharge port 22 are provided. The frame 40 is made of, for example, ceramics. The frame 40 is joined to the actuator substrate 20 by, for example, an adhesive.

[0020] The nozzle plate 50 includes a nozzle plate substrate, a primer layer provided on its medium-facing surface (the ejection surface from which the ink is ejected from the nozzles N), and a liquid-repellent layer provided on the primer layer. The nozzle plate substrate is made of, for example, a resin film such as a polyimide film. The primer layer and the liquid-repellent layer will be described in detail later.

[0021] The nozzle plate 50 is larger than the opening of the frame 40. The nozzle plate 50 is joined to the frame 40 by, for example, an adhesive.

[0022] A plurality of nozzles N are provided on the nozzle plate 50. These nozzles N form two rows corresponding to the ink channels. The diameter of the nozzles N increases as they proceed in the direction of the ink channels from the recording medium-facing surface. The dimensions of the nozzles N are set to predetermined values according to the ink ejection amount. The nozzles N can be formed, for example, by performing laser processing using an excimer laser.

[0023] The actuator substrate 20, the frame 40, and the nozzle plate 50 are integrated as shown in FIG. 1 and form a hollow structure. The area surrounded by the actuator substrate 20, the frame 40, and the nozzle plate 50 is an ink circulation chamber. Ink is supplied from the ink manifold 10 through the ink supply port 21 to the ink circulation chamber, passes through the ink channels, and circulates so that the excess ink returns from the ink discharge port 22 to the ink manifold 10. A part of the ink is ejected from the nozzles N while flowing through the ink channels and is used for printing.

[0024] On the wiring pattern 31, a flexible printed circuit board 60 is connected at a position outside the frame 40 on the actuator substrate 20. The flexible printed circuit board 60 is mounted with a drive circuit 61 for driving the actuator 30.

[0025] Hereinafter, the operation of the actuator 30 will be described. Here, the operation will be described by focusing on the central ink channel among three adjacent ink channels. Let the electrodes corresponding to the three adjacent ink channels be A, B, and C. When no electric field is applied in the direction perpendicular to the channel wall, the channel wall is in an upright state.

[0026] For example, a voltage pulse having a potential higher than the potentials of the adjacent electrodes A and C is applied to the central electrode B to generate an electric field in the direction perpendicular to the channel wall. In this way, the channel wall is driven in a shear mode, and a pair of channel walls sandwiching the central ink channel is deformed so as to expand the volume of the central ink channel.

[0027] Next, voltage pulses having a potential higher than the potential of the central electrode B are applied to the adjacent electrodes A and C to generate an electric field in the direction perpendicular to the channel wall. In this way, the channel wall is driven in a shear mode, and a pair of channel walls sandwiching the central ink channel is deformed so as to reduce the volume of the central ink channel. By this operation, pressure is applied to the ink in the central ink channel, and the ink is ejected from the nozzle N corresponding to this ink channel and landed on the recording medium.

[0028] For example, all the nozzles are divided into three groups, and the driving operations described above are controlled in a time division manner for three cycles to perform printing on the recording medium.

[0029] Figure 3 shows a schematic diagram of the inkjet printer 100. The inkjet printer 100 shown in Figure 3 includes a housing provided with a paper discharge tray 118. Inside the housing, cassettes 1011 and 1012, paper feed rollers 102 and 103, transport roller pairs 104 and 105, registration roller pair 106, transport belt 107, fan 119, negative pressure chamber 111, transport roller pairs 112, 113 and 114, inkjet heads 1151, 1152, 1153 and 1154, ink cartridges 1161, 1162, 1163 and 1164, and tubes 1171, 1172, 1173 and 1174 are installed.

[0030] Cassettes 1011 and 1012 accommodate recording media P of different sizes. The paper feed roller 102 or 103 takes out the recording media P corresponding to the selected size of the recording media from the cassette 1011 or 1012 and conveys it to the transport roller pairs 104 and 105 and the registration roller pair 106.

[0031] The transport belt 107 is tensioned by a drive roller 108 and two driven rollers 109. Holes are provided at predetermined intervals on the surface of the transport belt 107. Inside the transport belt 107, a negative pressure chamber 111 connected to the fan 119 is installed to adsorb the recording media P to the transport belt 107. Downstream in the transport direction of the transport belt 107, transport roller pairs 112, 113 and 114 are installed. In addition, a heater for heating the printing layer formed on the recording media P can be installed in the transport path from the transport belt 107 to the paper discharge tray 118.

[0032] Above the conveyor belt 107, four inkjet heads that eject ink onto the recording medium P according to image data are arranged. Specifically, an inkjet head 1151 that ejects cyan (C) ink, an inkjet head 1152 that ejects magenta (M) ink, an inkjet head 1153 that ejects yellow (Y) ink, and an inkjet head 1154 that ejects black (Bk) ink are arranged in this order from the upstream side. Each of the inkjet heads 1151, 1152, 1153, and 1154 is the inkjet head 1 described with reference to FIGS. 1 and 2.

[0033] Above the inkjet heads 1151, 1152, 1153, and 1154, cyan (C) ink cartridges 1161, magenta (M) ink cartridges 1162, yellow (Y) ink cartridges 1163, and black (Bk) ink cartridges 1164 that contain the corresponding inks are installed respectively. These cartridges 1161, 1162, 1163, and 1164 are connected to the inkjet heads 1151, 1152, 1153, and 1154 by tubes 1171, 1172, 1173, and 1174 respectively.

[0034] Next, the image forming operation of this inkjet printer 100 will be described. First, image processing means (not shown) starts image processing for recording, generates an image signal corresponding to the image data, and generates a control signal for controlling the operations of various rollers and the negative pressure chamber 111 and the like.

[0035] The paper feed roller 102 or 103 takes out the recording medium P of the selected size one by one from the cassette 1011 or 1012 under the control of the image processing means and conveys it to the pair of conveyance rollers 104 and 105 and the pair of registration rollers 106. The pair of registration rollers 106 corrects the skew of the recording medium P and conveys the recording medium P at a predetermined timing.

[0036] The negative pressure chamber 111 sucks air through the holes in the conveyor belt 107. Therefore, the recording medium P is adsorbed to the conveyor belt 107 and is sequentially conveyed to the positions below the inkjet heads 1151, 1152, 1153, and 1154 as the conveyor belt 107 moves.

[0037] The inkjet heads 1151, 1152, 1153, and 1154 eject ink in synchronization with the timing at which the recording medium P is conveyed under the control of the image processing means. Thereby, a color image is formed at a desired position on the recording medium P.

[0038] Thereafter, the transport roller pairs 112, 113, and 114 discharge the recording medium P on which the image is formed to the paper discharge tray 118. When a heater is installed in the transport path from the conveyor belt 107 to the paper discharge tray 118, the printing layer formed on the recording medium P may be heated by the heater. When heating is performed by the heater, in particular, when the recording medium P is non-permeable, the adhesion of the printing layer to the recording medium P can be enhanced.

[0039] FIG. 4 shows a perspective view of the main part of the inkjet printer 100. FIG. 4 depicts the inkjet head 1, the medium holding mechanism 110, the head moving mechanism 120, the blade moving mechanism 130, and the wiping blade 140 described above.

[0040] The medium holding mechanism 110 holds the recording medium P, for example, recording paper, facing the inkjet head 1. The medium holding mechanism 110 also has a function as a recording paper moving mechanism for moving the recording medium. The medium holding mechanism 110 includes the conveyor belt 107, the drive roller 108, the driven roller 109, the negative pressure chamber 111, and the fan 119 in FIG. 3. During printing, the medium holding mechanism 110 moves the recording medium P in a direction parallel to the printing surface of the recording medium P while facing the inkjet head 1. During that time, the inkjet head 1 ejects ink droplets from the nozzles to print on the recording medium P.

[0041] During printing, the head movement mechanism 120 moves the inkjet head 1 to the printing position. Also, during cleaning, the head movement mechanism 120 moves the inkjet head 1 to the cleaning position.

[0042] The wiping blade 140 wipes the surface of the nozzle plate of the inkjet head 1 that faces the recording medium, i.e., the recording medium facing surface, to remove deposits from this recording medium facing surface. Here, the deposits are, for example, ink, dust, and dirt such as dust.

[0043] The blade movement mechanism 130 moves the wiping blade 140. Specifically, after the head movement mechanism 120 moves the inkjet head 1 to the cleaning position, the blade movement mechanism 130 moves the wiping blade 140 while pressing it against the recording medium facing surface of the nozzle plate 50 and moving it thereon. Thereby, deposits such as ink adhering to the recording medium facing surface of the nozzle plate 50 are removed. Note that the wiping blade 140 and the blade movement mechanism 130 may be omitted.

[0044] In the above inkjet head 1, liquid repellency is imparted to the medium facing surface of the nozzle plate 50. To impart liquid repellency, a primer layer and a liquid repellent layer are provided on the medium facing surface of the nozzle plate substrate. This will be described with reference to FIG. 5.

[0045] FIG. 5 is a cross-sectional view schematically showing the structure of the nozzle plate 50 of FIGS. 1 and 2. The nozzle plate 50 includes the nozzle plate substrate 51, the primer layer 52, and the liquid repellent layer 53 as described above.

[0046] The primer layer 52 is provided on the surface of the nozzle plate substrate 51 that faces the recording medium P. The primer layer 52 is composed of a monomolecular film of a primer agent. The primer agent contains silicon atoms and carbon atoms.

[0047] The primer agent contains, for example, a first and a second reactive functional group, a carbon skeleton, and an alkoxysilyl group.

[0048] The first reactive functional group binds the primer agent to the nozzle plate substrate 51 by reacting with the functional group present on the surface of the nozzle plate substrate 51. The first reactive functional group is, for example, a hydroxyl group, an epoxy group, an amino group, a methacryl group, an unsaturated hydrocarbon group such as a vinyl group, or a mercapto group. The functional group present on the surface of the nozzle plate substrate 51 is, for example, a hydroxyl group, an ester bond, an amino group, or a thiol group.

[0049] The second reactive functional group binds the linear fluorine compound to the primer agent by reacting with the linear fluorine compound used for forming the liquid repellent layer 53. The linear fluorine compound will be described later. The second reactive functional group is, for example, a hydroxyl group, or an alkoxy group such as a methoxy group and an ethoxy group.

[0050] The carbon skeleton connects the first reactive functional group and the second reactive functional group. The carbon skeleton contains one or more carbon atoms. The number of carbon atoms in the carbon skeleton is preferably in the range of 4 to 30, and more preferably in the range of 4 to 22. The carbon skeleton preferably further contains one or more fluorine atoms. When the carbon skeleton has fluorine atoms, the liquid repellency is excellent.

[0051] The alkoxysilyl group is connected to the carbon skeleton. When the alkoxysilyl group is hydrolyzed, a silanol group is generated. By causing dehydration condensation of the silanol groups between the molecules of the primer agent adjacent to each other on the nozzle plate substrate 51, intermolecular bonding can be generated in the primer agent. Thus, it is preferable that the molecules of the primer agent are bonded to each other. According to an example, the molecules of the primer agent adjacent to each other on the nozzle plate substrate 51 are bonded to each other by a siloxane bond (Si-O-Si). Thereby, the primer agent forms a bond substantially parallel to the medium-facing surface of the nozzle plate substrate 51.

[0052] Among the silanol groups generated by hydrolysis, the silanol groups not used for intermolecular bonding of the primer agent can be used for bonding between the primer agent and the linear fluorine compound.

[0053] As the primer agent, for example, a compound represented by the following general formula (1) can be used.

[0054] [Chemical formula]

[0055] In the general formula (1), n is a natural number from 1 to 10. In the general formula (1), R1 and R2 are the above-described first and second reactive functional groups, respectively. The compound represented by the general formula (1) contains the first and second reactive functional groups, a carbon skeleton, and an alkoxysilyl group.

[0056] In the general formula (1), the alkoxysilyl group is a trimethoxysilyl group, but the alkoxysilyl group may be a functional group such as a triethoxysilyl group. Further, in the general formula (1), the number of CF2 groups contained in the carbon skeleton is 2, but the number of CF2 groups may be 1 or may be 3 or more. Also, the number of carbon atoms contained in the repeating unit of the carbon skeleton is 2, but the number of carbon atoms may be 1 or may be 3 or more.

[0057] When a self-assembled monolayer is formed using the above primer agent, a primer layer 52 with a thickness of usually 0.7 nm to 1 nm is obtained.

[0058] The liquid-repellent layer 53 is provided on the primer layer 52. The liquid-repellent layer 53 is composed of a self-assembled monolayer of a linear fluorine compound. The linear fluorine compound is a linear molecule having a perfluoroalkyl group as one terminal group on the surface side and the other terminal group bonded to the primer layer 52.

[0059] The liquid-supplying layer 53 can be formed, for example, using a linear fluorine compound in which one terminal group is a perfluoroalkyl group and the other terminal group is a third reactive functional group.

[0060] The perfluoroalkyl group is linear. The number of carbon atoms in the perfluoroalkyl group can be selected within the range of 4 or less (C1 to C4). The perfluoroalkyl group is preferably upright along the direction perpendicular to the surface of the nozzle plate substrate 51. Increasing the number of carbon atoms in the perfluoroalkyl group makes it easier to make the perfluoroalkyl group stand upright, but it has adverse effects on the human body such as carcinogenicity.

[0061] The third reactive functional group reacts with the second reactive functional group to bond the linear fluorine compound to the primer agent. The third reactive functional group is, for example, a hydroxyl group or an alkoxy group such as a methoxy group and an ethoxy group. Note that the third reactive functional group can also bond the linear fluorine compound to the primer agent by reacting with the silanol group that has not been used for intermolecular bonding among the silanol groups generated by the hydrolysis of the alkoxysilyl group.

[0062] The linear fluorine compound has, for example, a spacer linking group that links the perfluoroalkyl group and the third reactive functional group. The presence of the spacer linking group is advantageous for the perfluoroalkyl group to take a structure that stands upright along the direction perpendicular to the surface of the nozzle plate substrate 51. The spacer linking group is, for example, a perfluoropolyether group.

[0063] As the linear fluorine compound, for example, a compound represented by the following general formula (2) can be used.

[0064]

Chemical formula

[0065] In general formula (2), p is a natural number from 1 to 50, and R3 is a third reactive functional group.

[0066] When a monomolecular film is formed using the above linear fluorine compound, a liquid-repellent layer 53 with a thickness of usually 9 nm to 10 nm is obtained.

[0067] The nozzle plate 50 shown in FIG. 5 can be obtained, for example, as follows. Here, as an example, it is assumed that the nozzle plate substrate 51 is made of polyimide and the primer agent contains an alkoxysilyl group.

[0068] First, a nozzle plate substrate 51 made of polyimide is prepared. The surface of the nozzle plate substrate 51 facing the recording medium P may have almost no functional groups necessary for bonding with the primer agent, such as hydroxyl groups. In such a case, prior to the formation of the primer layer 52, it is preferable to perform the following pretreatment on the nozzle plate substrate 51.

[0069] For example, the surface of the nozzle plate substrate 51 is subjected to ion plasma treatment in an argon-oxygen mixed gas to modify the surface. The ion plasma treatment is performed, for example, as follows. That is, the nozzle plate substrate 51 is placed in a vacuum chamber, and the air in the chamber is evacuated. Then, the atmosphere surrounding the nozzle plate substrate 51 is switched to an argon-oxygen mixed gas, and then plasma is generated.

[0070] By performing ion plasma treatment in an atmosphere containing oxygen, a ring-opening reaction occurs in the polyimide on the surface of the nozzle plate substrate 51 to modify this surface with hydroxyl groups. In addition to this, by performing ion plasma treatment in an atmosphere containing argon, the dust adhering to the nozzle plate substrate 51 is removed.

[0071] The ion plasma treatment is preferably performed in an argon-oxygen mixed gas with an oxygen concentration of 50% by volume or less, more preferably in an argon-oxygen mixed gas with an oxygen concentration in the range of 20 to 50% by volume. When the oxygen concentration is too high, the surface of the nozzle plate substrate 51 may be damaged and surface roughness may occur. If roughness occurs on the surface of the nozzle plate substrate 51, the bonding with the primer agent may be insufficient.

[0072] The ion plasma treatment is preferably performed for 100 seconds or more, more preferably for 200 seconds or more. If the plasma irradiation time is too short, there is a risk that the surface modification of the nozzle plate substrate 51 will not be sufficiently performed.

[0073] Next, a solution containing a primer agent is applied to the surface of the nozzle plate substrate 51. As the solution containing the primer agent, for example, a solution obtained by dissolving the primer agent in an organic solvent can be used. Also, for the application of the solution, ordinary methods such as the spray method, spin coating method, and blade coating method can be used.

[0074] Next, the laminate including the coating film containing the primer agent and the nozzle plate substrate 51 is heated. In this way, the primer agent is bonded to the polyimide and the coating film is dried. The heating is performed, for example, at 200 °C for 15 minutes.

[0075] Next, the alkoxysilyl group of the primer agent is hydrolyzed. When the alkoxysilyl group of the primer agent is hydrolyzed, a silanol group is generated. Then, dehydration condensation of the silanol groups occurs between the molecules of the primer agent adjacent on the nozzle plate substrate 51. Thereby, an intermolecular bond of the primer agent is formed.

[0076] In this way, a primer layer 52 is formed on the nozzle plate substrate 51.

[0077] Next, a solution containing a linear fluorine compound is applied to the surface of the primer layer 52 to form a liquid-repellent layer 53. As the solution containing the linear fluorine compound, for example, a solution in which the linear fluorine compound is dissolved in an organic solvent can be used. Also, for applying the solution, the method described above for the solution containing the primer agent can be used.

[0078] Next, a laminate including a coating film containing a linear fluorine compound, the primer layer 52, and the nozzle plate substrate 51 is heated. In this way, a reaction is caused between the linear fluorine compound and the primer agent, and the linear fluorine compound is bonded to the surface of the primer layer 52. Thereby, a monomolecular film made of a linear fluorine compound is formed as the liquid-repellent layer 53. The heating is performed, for example, at 200 °C for 15 minutes.

[0079] As described above, the nozzle plate 50 shown in FIG. 5 is obtained.

[0080] The nozzle plate 50 described above has excellent liquid repellency. Therefore, the inkjet head 1 including the nozzle plate 50 described above also has excellent liquid repellency.

[0081] A nozzle plate having a structure similar to the nozzle plate 50 described above can be obtained, for example, by omitting the primer layer and forming a liquid-repellent layer on the nozzle plate substrate using a material having the structure described above for the primer agent and the structure described above for the linear fluorine compound in one molecule.

[0082] However, the molecules used for forming such a liquid-repellent layer are long because they have the structure described above for the primer agent and the structure described above for the linear fluorine compound in one molecule. Therefore, it is difficult to arrange these molecules densely and orderly on the nozzle plate substrate.

[0083] On the other hand, the primer agents used in the production of the nozzle plate 50 described above have relatively short molecular lengths. Therefore, the molecules of these primer agents can be easily arranged densely and orderly on the nozzle plate substrate 51. Also, the linear fluorine compounds used in the production of the nozzle plate 50 described above also have relatively short molecular lengths. Therefore, the molecules of these linear fluorine compounds can also be easily arranged densely and orderly on the primer layer 52. Accordingly, the nozzle plate 50 having the two-layer structure of the primer layer 52 and the liquid-repellent layer 53 on the nozzle plate substrate 51 can achieve better liquid repellency than the above-described nozzle plate without a primer layer.

[0084] Also, since the nozzle plate 50 described above has a two-layer structure of the primer layer 52 and the liquid-repellent layer 53 on the nozzle plate substrate 51, the number of moles of the primer agent and the number of moles of the linear fluorine compound do not have to match. Therefore, for example, the number of moles of the linear fluorine compound contained in the liquid-repellent layer 53 can be made larger compared to the number of moles of the primer agent contained in the primer layer 52. Specifically, the second reactive functional group and the silanol group not used for intermolecular bonding each bind to the molecules of another linear fluorine compound, whereby the number of moles of the linear fluorine compound contained in the liquid-repellent layer 53 can be made larger than the number of moles of the primer agent contained in the primer layer 52. Thus, with the nozzle plate 50 described above, the desired liquid repellency can be easily achieved.

[0085] The nozzle plate 50 described above includes a primer layer 52 made of a single molecular film. Such a nozzle plate 50 is superior in the adhesion between the liquid-repellent layer and the nozzle plate substrate and in scratch resistance compared to a nozzle plate in which the primer layer is composed of a laminate of a plurality of single molecular films. Scratch resistance is a property in which deterioration of liquid repellency due to scratching using a wiping blade 140 or the like hardly occurs.

[0086] In addition, to determine whether the primer layer 52 is composed of a monolayer, an X-ray photoelectron spectroscopy (XPS) method can be used. For example, an X-ray photoelectron spectroscopy (XPS) spectrum of the nozzle plate 50 obtained by etching the nozzle plate 50 including the liquid repellent layer 53, the primer layer 52, and the nozzle plate substrate 51 from the surface of the liquid repellent layer 53 can be examined to make the above determination.

Example

[0087] Hereinafter, examples and comparative examples will be described. (Example) In this example, a nozzle plate having a primer layer and a liquid repellent layer was manufactured. The primer layer and the liquid repellent layer were formed by the following method.

[0088] As the nozzle plate substrate, a polyimide film was prepared. This nozzle plate substrate was subjected to plasma treatment in a reduced pressure atmosphere containing an argon-oxygen mixed gas. As a result, a ring-opening reaction occurred in the polyimide on the substrate surface, and hydroxyl groups were imparted to this surface.

[0089] A solution of the primer agent was applied to the above surface of the nozzle plate substrate by the blade coating method. As the primer agent, one represented by the above general formula (1) in which R1 is a hydroxyl group, R2 is a hydroxyl group, and n is 10 was used. This coating film was heated at 200°C for 15 minutes. In this way, the primer agent was bonded to the polyimide, and the coating film was dried. Further, the alkoxysilyl group of the primer agent was hydrolyzed, and dehydration condensation of silanol groups occurred between adjacent primer agent molecules. As a result, a monolayer composed of the primer agent was formed as the primer layer.

[0090] Thereafter, a solution of a linear fluorine compound was applied to the primer layer by the blade coating method. As the linear fluorine compound, one represented by the above general formula (2) in which R3 is a hydroxyl group and p is 1 was used. This coating film was heated at 200 °C for 15 minutes. In this way, the third reactive functional group of the linear fluorine compound was reacted with the second reactive functional group of the primer layer. As a result, a monomolecular film made of a fluorine compound was formed as the liquid-repellent layer.

[0091] (Comparative Example) A nozzle plate was manufactured by the same method as in the above Example, except that the formation of the primer layer was performed twice.

[0092] (Liquid-repellent property test) Each of the nozzle plates according to the Example and the Comparative Example was cut to a width of 15 mm. Each of these samples was immersed in the inkjet ink for several seconds so that its main surface was parallel to the gravitational direction. Then, each sample was pulled up from the ink by 45 mm, and the time required for the ink to disappear from the pulled-up portion was measured. As a result, in all samples, the ink disappeared from the pulled-up portion immediately after being pulled up from the ink. From this, it was found that both the nozzle plates according to the Example and the Comparative Example had excellent liquid-repellent properties.

[0093] (Adhesion and abrasion resistance test) The nozzle plate according to the Example was rubbed 6000 times with a wiping blade. As a result, even after being rubbed 6000 times, the liquid-repellent layer did not peel off from the nozzle plate substrate in the Example. Also, the nozzle plate after rubbing had excellent liquid-repellent properties. Thus, the nozzle plate according to the Example was excellent in the adhesion between the liquid-repellent layer and the nozzle plate substrate, and in abrasion resistance.

[0094] When the nozzle plate according to the Comparative Example was rubbed with a wiping blade, the liquid-repellent layer immediately peeled off from the nozzle plate substrate. Thus, the nozzle plate according to the Comparative Example was not excellent in the adhesion between the liquid-repellent layer and the nozzle plate substrate, and therefore, was not excellent in abrasion resistance either.

[0095] (XPS analysis) XPS spectra were measured for each of the nozzle plates according to the examples and comparative examples. In addition to the measurement of the above XPS spectra, each of the nozzle plates according to the examples and comparative examples was etched, and XPS spectra were also measured for the nozzle plates obtained by etching. Further, XPS spectra were measured for the nozzle plates obtained by changing the etching time. The etching was performed such that the etching rate was 1.7 pm / second.

[0096] Figures 6 and 7 are graphs showing the XPS spectra obtained for the nozzle plates according to the examples and comparative examples, respectively. As shown in Figures 6 and 7, for example, when etching was performed for 6000 seconds, the nozzle plate according to the example had a smaller peak value of the energy intensity within the range of binding energies of 680 to 690 eV compared to the nozzle plate according to the comparative example. Thus, the difference between the structure of the nozzle plate according to the example and the structure of the nozzle plate according to the comparative example appears in the XPS spectrum.

[0097] Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof at the implementation stage. Also, the embodiments may be implemented in appropriate combinations, and in that case, combined effects can be obtained. Furthermore, the above embodiments include various inventions, and various inventions can be extracted by combinations selected from a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiments, if the problem can be solved and the effects can be obtained, the configuration from which these constituent elements are deleted can be extracted as an invention. The invention originally described in the claims is appended below. [1] An inkjet head comprising a nozzle plate provided with nozzles for ejecting ink toward a recording medium, wherein the nozzle plate comprises a nozzle plate substrate, a primer layer provided on a surface of the nozzle plate substrate facing the recording medium and consisting of a monomolecular film of a primer agent containing silicon atoms and carbon atoms, and a liquid-repellent layer provided on the primer layer and consisting of a monomolecular film of a linear fluorine compound having a perfluoroalkyl group as one terminal group on the surface side and the other terminal group bonded to the primer layer. [2] The inkjet head according to claim 1, wherein the molecules of the primer agent are bonded to each other. [3] The inkjet head according to claim 1 or 2, wherein the nozzle plate substrate is made of polyimide. [4] An inkjet printer comprising the inkjet head according to any one of claims 1 to 3, and a medium holding mechanism for holding the recording medium facing the inkjet head. [5] The inkjet printer according to claim 4, further comprising a wiping blade for removing deposits from the surface of the nozzle plate facing the recording medium by rubbing the surface.

Description of Symbols

[0098] 1... Inkjet head, 10... Ink manifold, 11... Ink supply tube, 12... Ink return tube, 20... Actuator substrate, 21... Ink supply port, 22... Ink discharge port, 30... Actuator, 31... Wiring pattern, 40... Frame, 50... Nozzle plate, N... Nozzle, 51... Nozzle plate substrate, 52... Primer layer, 53... Liquid-repellent layer, 60... Flexible printed circuit board, 61... Driving circuit, 100... Inkjet printer, 1011... Cassette, 1012... Cassette, 102... Paper feed roller, 103... Paper feed roller, 104... Pair of conveyance rollers, 105... Pair of conveyance rollers, 106... Pair of resist rollers, 107... Conveyance belt, 108... Driving roller, 109... Driven roller, 111... Negative pressure chamber, 112, Pair of conveyance rollers, 113... Pair of conveyance rollers, 114... Pair of conveyance rollers, 1151... Inkjet head, 1152... Inkjet head, 1153... Inkjet head, 1154... Inkjet head, 1161... Ink cartridge, 1162... Ink cartridge, 1163... Ink cartridge, 1164... Ink cartridge, 1171... Tube, 1172... Tube, 1173... Tube, 1174... Tube, 118... Paper discharge tray, 119... Fan, P... Recording medium, 110... Medium holding mechanism, 120... Head movement mechanism, 130... Blade movement mechanism, 140... Wiping blade.

Claims

1. A nozzle plate provided with nozzles for ejecting ink toward a recording medium, wherein the nozzle plate comprises a nozzle plate substrate, a primer layer provided on a surface of the nozzle plate substrate facing the recording medium and consisting of a monomolecular film of a primer agent, and a liquid-repellent layer provided on the primer layer and consisting of a monomolecular film of a linear fluorine compound having a perfluoroalkyl group as one terminal group on the surface side and the other terminal group bonded to the primer layer, and the nozzle plate substrate is made of a resin film, the primer agent includes a first reactive functional group selected from the group consisting of a hydroxyl group, an epoxy group, an amino group, a methacrylic group, an unsaturated hydrocarbon group, and a mercapto group, a second reactive functional group selected from the group consisting of a hydroxyl group and an alkoxy group, a carbon skeleton connecting the first reactive functional group and the second reactive functional group, and an alkoxysilyl group connected to the carbon skeleton, and the first reactive functional group reacts with a functional group present on the surface of the nozzle plate substrate to bond the primer agent to the nozzle plate substrate, and molecules of the primer agent are bonded to each other by siloxane bonds. An inkjet head.

2. The inkjet head according to claim 1, wherein the nozzle plate substrate is made of polyimide.

3. An inkjet printer comprising the inkjet head according to claim 1 or 2, and a medium holding mechanism for holding the recording medium facing the inkjet head.

4. The inkjet printer according to claim 3, further comprising a wiping blade for removing deposits from a surface of the nozzle plate facing the recording medium by rubbing the surface of the nozzle plate facing the recording medium. ​

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