Inkjet recording apparatus and inkjet recording method

Abstract

An object of the present invention is to provide a stainless steel nozzle plate for an inkjet head which has little deformation on the inner wall of the nozzle or at the nozzle tip, a method for manufacturing the same, and an inkjet head and an inkjet recording apparatus which use the nozzle plate for an inkjet head. [Solution] The nozzle plate for an inkjet head of the present invention is a nozzle plate for an inkjet head made of at least stainless steel, characterized in that the stainless steel is an austenitic stainless steel with a martensite phase content of 5.4% or less.

Description

[Technical field]

[0001] The present invention relates to stomach Inkjet recording device And inkjet recording method Regarding. More specifically, a stainless steel nozzle plate for an inkjet head with minimal irregularities on the nozzle inner wall and nozzle tip. Inkjet recording apparatus comprising: etc. [Background technology]

[0002] In the inkjet head, an actuator is disposed in each ink channel, and ink is ejected from a nozzle plate in which ink ejection ports, i.e. nozzles, communicating with each ink channel are formed.

[0003] Conventionally, stainless steel, which has excellent chemical stability against ink and durability against mechanical friction, has been used as the base material for nozzle plates for inkjet heads (hereinafter also simply referred to as "nozzle plates"). In particular, austenitic stainless steels such as SUS304 and SUS316 are often used. These steels are produced for general purposes and are more cost-effective than other steels. In addition, they have a relatively high Cr content and excellent corrosion resistance, so they have excellent chemical stability as the base material for nozzle plates that come into contact with ink.

[0004] Known methods for forming a nozzle in an austenitic stainless steel substrate such as the one described above include a laser processing method (Non-Patent Document 1) and a method in which a recess is formed by punching and then a convex portion on the back surface is polished and removed (Patent Document 1).

[0005] However, conventional nozzle plates in which nozzles are formed by laser machining using austenitic stainless steel as a base material have a problem in that minute recesses (needle holes) are easily generated in the inner wall of the nozzle.

[0006] Furthermore, even in the method of forming a recess by punching and then polishing and removing the convex portion on the back surface, when conventional austenitic stainless steel is used as the base material, there was a problem in that when the recess is formed, streak-like unevenness occurs on the inner wall of the nozzle from the flow path side toward the nozzle tip (tip in the discharge direction) due to plastic deformation, and when the convex portion on the back surface is polished and removed, the streak-like unevenness remains as burrs (protrusions) at the nozzle tip.

[0007] If irregularities such as the above-mentioned minute recesses and streaky irregularities exist on the inner wall of the nozzle, air bubbles generated in the ink become trapped, which makes the nozzle more likely to fail, and the frequency of maintenance increases, lowering the operating rate of the inkjet recording device. Also, if irregularities such as the above-mentioned minute recesses, streaky irregularities, and burrs exist near the tip of the nozzle, the ink ejection angle from the nozzle becomes curved, which makes it more likely to cause variations in landing position, uneven drawing, streaking, and pattern breaks, thereby lowering the drawing quality.

[0008] Therefore, a nozzle plate for an inkjet head made of stainless steel that has few irregularities such as minute recesses, streaky irregularities, and burrs on the inner wall of the nozzle and the tip of the nozzle is Inkjet recording apparatus comprising: What is required is... [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 3755332 [Non-patent literature]

[0010] [Non-Patent Document 1] Xinbing Liu "Industrial applications of ultrahigh precision short-pulse laser processing (Invited Paper)", Proc. SPIE 5713, Photon Processing in Microelectronics and Photonics IV, (12 April 2005) Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a nozzle plate for an inkjet head made of stainless steel, which has less deformation on the nozzle inner wall and nozzle tip. Equipped with Inkjet recording device And inkjet recording method The purpose of this project is to provide [Means for solving the problem]

[0012] In order to solve the above problems, the present inventors have studied the causes of the above problems and have found that by using stainless steel having a specific crystal structure ratio, it is possible to develop a stainless steel nozzle plate for an inkjet head that has fewer irregularities on the nozzle inner wall and nozzle tip. Inkjet recording apparatus comprising: The inventors have found that it is possible to provide the above-mentioned and have completed the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0013] 1. Nozzle plate for inkjet head made of at least stainless steel An inkjet recording apparatus that ejects ink, comprising: The stainless steel is an austenitic stainless steel having a martensite phase content of 5.4% or less. and the surface tension of the ink is within a range of 20 to 40 mN / m. Inkjet printer Recording device .

[0014] 2. Nozzle plate for inkjet head made of at least stainless steel An inkjet recording apparatus that ejects ink, comprising:The stainless steel has an area ratio of face-centered cubic crystals of 92.0% or more and an area ratio of body-centered cubic crystals of 5.4% or less, as measured by electron backscattering analysis. and the surface tension of the ink is within a range of 20 to 40 mN / m. Inkjet printer Recording device .

[0015] 3. The inkjet ink according to item 1 or 2, wherein the stainless steel has a frequency-average crystal grain size of 0.9 μm or less as measured by electron backscattering analysis. Recording device .

[0016] 4. The inkjet printer according to any one of claims 1 to 3, wherein the stainless steel has an area-weighted average crystal grain size of 2.3 μm or less as measured by electron backscattering analysis. Recording device .

[0017] 5. The inkjet printer according to any one of claims 1 to 4, wherein the stainless steel is a stainless steel having a ratio of the number-average crystal grain size measured by electron backscattering analysis to the nozzle tip opening diameter of 4.7% or less. Recording device .

[0018] 6. The inkjet printer according to any one of claims 1 to 5, wherein the stainless steel is a stainless steel having an area-weighted average crystal grain size ratio of 12.0% or less relative to the nozzle tip opening diameter as measured by electron backscattering analysis. Recording device . 7. The inkjet recording apparatus according to any one of items 1 to 6, wherein the stainless steel is SUS304L or SUS316L. 8. The inkjet recording apparatus according to any one of items 1 to 7, further comprising an ink degassing mechanism, and the ink is degassed ink. 9. An ink-jet recording method for ejecting ink using a nozzle plate for an ink-jet head made of at least stainless steel, comprising: The stainless steel is an austenitic stainless steel having a martensite phase content of 5.4% or less, and The inkjet recording method according to claim 1, wherein the surface tension of the ink is within a range of 20 to 40 mN / m. 10. An ink-jet recording method for ejecting ink using a nozzle plate for an ink-jet head made of at least stainless steel, comprising: The stainless steel has an area ratio of face-centered cubic crystals of 92.0% or more and an area ratio of body-centered cubic crystals of 5.4% or less, as measured by electron backscattering analysis, and The inkjet recording method according to claim 1, wherein the surface tension of the ink is within a range of 20 to 40 mN / m. 11. The ink jet recording method according to item 9 or 10, wherein the stainless steel has a frequency average crystal grain size of 0.9 μm or less as measured by electron backscattering analysis. 12. The inkjet recording method described in any one of items 9 to 11, wherein the stainless steel has an area-weighted average crystal grain size of 2.3 μm or less as measured by electron backscattering analysis. 13. The inkjet recording method described in any one of items 9 to 12, wherein the stainless steel is a stainless steel having a ratio of the frequency average crystal grain size to the opening diameter of the nozzle tip, as measured by electron backscattering analysis, of 4.7% or less. 14. The inkjet recording method described in any one of items 9 to 13, wherein the stainless steel is a stainless steel having an area-weighted average crystal grain size ratio measured by electron backscattering analysis to the nozzle tip opening diameter of 12.0% or less. 15. The ink jet recording method described in any one of items 9 to 14, wherein the stainless steel is SUS304L or SUS316L. 16. The ink jet recording method according to any one of items 9 to 15, further comprising a mechanism for degassing the ink, the ink being a degassed ink. Effect of the Invention

[0023] By the above-mentioned means of the present invention, a stainless steel nozzle plate for an inkjet head having little irregularities on the nozzle inner wall and nozzle tip is provided. Equipped with Inkjet recording device And inkjet recording method can be provided.

[0024] Although the mechanism by which the effects of the present invention are manifested or the mechanism by which the effects of the present invention are acted upon has not been clearly understood, it is speculated as follows.

[0025] The present inventors have found that the cause of the occurrence of deformities such as minute recesses, streak-like irregularities and burrs when forming a nozzle in austenitic stainless steel that has been used in the past is the presence of minute martensite phases. Specifically, the inventors have found that when an austenitic stainless steel having a martensite phase content of more than 5.4%, an area ratio of face-centered cubic crystals less than 92.0%, and an area ratio of body-centered cubic crystals more than 5.4% is used, deformities can occur significantly when forming a nozzle.

[0026] The austenite phase and the martensite phase have different crystal structures, with the austenite phase being a face-centered cubic structure and the martensite phase being a body-centered cubic structure. The body-centered cubic structure and the face-centered cubic structure have different space filling rates of the unit lattice, and therefore the material properties are also different, which can affect the occurrence of abnormalities on the inner wall and the nozzle tip.

[0027] For example, it is known that common martensitic stainless steels have lower melting points and higher thermal conductivity than austenitic stainless steels, and it is therefore believed that the martensite phase has higher thermal conductivity than the austenitic phase and therefore has a higher laser ablation rate during laser processing. Therefore, in laser processing, if martensite phase is present as a heterogeneous phase in austenitic stainless steel, the minute martensite phase present will be preferentially laser ablated, resulting in the formation of minute recesses (needle holes) on the inner wall of the nozzle.

[0028] As another example, since general martensitic stainless steels tend to have lower density and smaller elongation than austenitic stainless steels, they are less susceptible to plastic deformation under tensile loads, which suggests that the martensite phase is less susceptible to plastic deformation than the austenite phase. Therefore, if the martensite phase is included as a different phase in the austenitic stainless steel, when the stainless steel base material is plastically deformed by punching with a punch tool, there will be a difference in the plastic deformation response between the austenite phase and the martensite phase, which will result in striped irregularities on the inner wall of the nozzle from the flow passage side to the nozzle tip side.

[0029] Furthermore, if such stripe-like irregularities are formed on the inner wall of the nozzle, they may cause burrs to be formed on the edge of the nozzle tip when the rear surface protrusions are subsequently polished and removed.

[0030] Therefore, by using an austenitic stainless steel having a martensite phase content of 5.4% or less, as in the present invention, or by using a stainless steel having a face-centered cubic crystal area ratio of 92.0% or more and a body-centered cubic crystal area ratio of 5.4% or less, as measured by electron backscattering analysis, it is possible to suppress the occurrence of abnormalities during nozzle formation.

[0031] It is believed that these mechanisms of expression or action make it possible to provide a stainless steel nozzle plate for inkjet heads which has little abnormality on the inner wall of the nozzle or at the nozzle tip. [Brief description of the drawings]

[0032] [Figure 1A]Optical microscope image of stainless steel A [Figure 1B] Optical microscope image of stainless steel B [Figure 1C] Optical microscope image of stainless steel C [Figure 2A] Grain map of stainless steel A obtained by EBSD measurement [Figure 2B] Grain map of stainless steel B obtained by EBSD measurement [Figure 2C] Grain map of stainless steel C obtained by EBSD measurement [Figure 3A] SEM image of the entire nozzle of a nozzle plate made of stainless steel A [Figure 3B] SEM image of the entire nozzle of a nozzle plate made of stainless steel B [Figure 3C] SEM image of the entire nozzle of a nozzle plate made of stainless steel C [Figure 4A] SEM image of the nozzle inner wall of a nozzle plate made of stainless steel A [Figure 4B] SEM image of the nozzle inner wall of a nozzle plate made of stainless steel B [Figure 4C] SEM image of the nozzle inner wall of a nozzle plate made of stainless steel C [Diagram 5] SEM image of irregularly shaped micro recesses (needle holes) [Figure 6] Cross-sectional SEM image of a nozzle with irregular streaks and burrs [Figure 7] Cross-sectional SEM image of a nozzle without irregularities DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The present invention Related to In one embodiment, the nozzle plate for an inkjet head is made of at least stainless steel, and is characterized in that the stainless steel is an austenitic stainless steel having a martensite phase content of 5.4% or less.

[0034] In addition, the present invention Related to In one embodiment, the nozzle plate for an inkjet head is made of at least stainless steel, and is characterized in that the stainless steel has an area ratio of face-centered cubic crystals of 92.0% or more and an area ratio of body-centered cubic crystals of 5.4% or less, as measured by electron backscattering spectroscopy.

[0035] The present invention Related to In the nozzle plate for an inkjet head, it is preferable that the stainless steel has a frequency average crystal grain size of 0.9 μm or less as measured by electron backscattering analysis, in order to suppress the occurrence of irregularities.

[0036] The present invention Related to In the nozzle plate for an inkjet head, it is preferable that the stainless steel has an area-weighted average crystal grain size of 2.3 μm or less as measured by electron backscattering analysis, in order to suppress the occurrence of irregularities.

[0037] The present invention Related to In the nozzle plate for an inkjet head, it is preferable that the stainless steel used is a stainless steel having a ratio of the frequency average crystal grain size measured by electron backscattering analysis to the opening diameter of the nozzle tip of 4.7% or less, in order to suppress the occurrence of irregularities.

[0038] The present invention Related to In the nozzle plate for an inkjet head, it is preferable that the stainless steel used is a stainless steel having an area-weighted average crystal grain size ratio, measured by electron backscattering analysis, of 12.0% or less relative to the opening diameter of the nozzle tip, in order to suppress the occurrence of irregularities.

[0039] The present invention Related to In one embodiment, a method for manufacturing a nozzle plate for an inkjet head according to the present invention is Related toThe method for manufacturing a nozzle plate for an inkjet head includes a step of forming nozzles by laser processing.

[0040] In addition, the present invention Related to In one embodiment, a method for manufacturing a nozzle plate for an inkjet head according to the present invention is Related to The method for manufacturing a nozzle plate for an inkjet head is characterized by comprising the steps of forming a recess by punching, and then polishing and removing a protrusion on the back surface to form a nozzle.

[0041] The present invention Related to The nozzle plate for an inkjet head or an inkjet head using the same can be suitably used in an inkjet recording apparatus.

[0042] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as the lower and upper limits.

[0043] (1) The present invention Related to Outline of the nozzle plate for inkjet heads The present invention Related to In one embodiment, the nozzle plate for an inkjet head is made of at least stainless steel, and is characterized in that the stainless steel is an austenitic stainless steel having a martensite phase content of 5.4% or less.

[0044] In addition, the present invention Related to In one embodiment, the nozzle plate for an inkjet head is made of at least stainless steel, and is characterized in that the stainless steel has an area ratio of face-centered cubic crystals of 92.0% or more and an area ratio of body-centered cubic crystals of 5.4% or less, as measured by electron backscattering spectroscopy.

[0045] In the present application, the term "ink" is not limited to a liquid containing a dye or pigment, but refers to a liquid used for printing, recording, dyeing, etc., including, for example, a polymeric material such as varnish, or a liquid containing metal particles. Related to The ink ejected from the nozzle plate for an inkjet head is not limited to a liquid containing a dye or a pigment.

[0046] (2) Crystal structure of stainless steel In the present application, the term "austenitic stainless steel" refers to stainless steel that has austenite as the main structure at room temperature. Examples include austenitic steels specified in JIS G 4304, such as SUS301, SUS304, and SUS316. In the present invention, SUS304 is preferred in terms of its chemical stability against ink.

[0047] The "austenite phase" refers to the phase in stainless steel that has a face-centered cubic lattice (FCC) crystal structure, and the "martensite phase" refers to the phase in stainless steel that has a body-centered cubic lattice (BCC) crystal structure.

[0048] The composition ratio of stainless steel is not completely uniform microscopically, and even austenitic stainless steels contain regions that are thermodynamically metastable microscopically. In such regions, the free energy of the martensite phase is smaller than that of the austenite phase at room temperature, and when subjected to plastic deformation such as cold rolling, deformation-induced martensite transformation occurs, and the austenite phase may contain a small amount of martensite phase.

[0049] Whether the crystal structure of stainless steel is face-centered cubic or body-centered cubic can be determined by electron backscatter diffraction (EBSD).

[0050] "Electron backscattering analysis" is a method to obtain crystal information by analyzing the electron beam scattering pattern (Kikuchi line) according to the crystal orientation obtained by irradiating an electron beam on a tilted sample in a scanning electron microscope (SEM). Points with a certain degree of difference in orientation between adjacent measurement points can be identified as the boundaries of each crystal grain, and a crystal grain map can be created. It is also possible to measure the crystal structure and crystal grain size of each crystal grain.

[0051] Note that there are crystal grains whose crystal structure cannot be determined by electron backscattering diffraction analysis (hereinafter also referred to as "EBSD measurement"). However, the face-centered cubic area percentage [%] and the body-centered cubic area percentage [%] in the present invention are percentages relative to the area excluding crystal grains whose crystal structure cannot be determined.

[0052] The stainless steel according to one embodiment of the present invention is characterized in that the area ratio of face-centered cubic crystals is 92.0% or more and the area ratio of body-centered cubic crystals is 5.4% or less, as measured by the above method, which makes it possible to suppress the occurrence of deformed shapes during nozzle formation. In the present invention, the face-centered cubic crystal area percentage [%] and the body-centered cubic crystal area percentage [%] are values ​​rounded off to one decimal place.

[0053] In addition, the area percentage [%] of face-centered cubic crystals and the area percentage [%] of body-centered cubic crystals measured by electron backscattering analysis can be regarded as the austenite phase content [%] and the martensite phase content [%], respectively. In the present invention, the austenite phase content [%] and the martensite phase content [%] are values ​​rounded off to one decimal place.

[0054] That is, the stainless steel according to one embodiment of the present invention is an austenitic stainless steel having a martensite phase content of 5.4% or less, the martensite phase having a body-centered cubic crystal structure, which can suppress the occurrence of deformed shapes during nozzle formation.

[0055] In addition, the stainless steel according to the present invention may be a stainless steel having a low carbon concentration. In punching, deformation-induced martensitic transformation occurs, the grain size becomes fine, the stainless steel hardens, and the occurrence of deformed shapes becomes more likely. Since deformation-induced martensitic transformation is less likely to occur in stainless steel having a low carbon concentration, the occurrence of deformed shapes can be suppressed. Examples of stainless steel having a low carbon concentration include SUS304L and SUS316L.

[0056] (3) Grain size of stainless steel The stainless steel according to the present invention is preferably one having a small average grain size as measured by electron backscattering analysis, in order to suppress the occurrence of irregularities. Specifically, the frequency-average grain size is preferably 0.9 μm or less, or the area-weighted average grain size is preferably 2.3 μm or less. In the present invention, the frequency average crystal grain size [μm] and the area ratio weighted average crystal grain size [μm] are values ​​rounded off to one decimal place.

[0057] In addition, the stainless steel according to the present invention preferably has a ratio of the number-average crystal grain size measured by electron backscattering analysis to the opening diameter of the nozzle tip (end in the discharge direction) of 4.7% or less, or a ratio of the area-weighted average crystal grain size measured by electron backscattering analysis to the opening diameter of the nozzle tip (end in the discharge direction) of 12.0% or less, which can suppress the occurrence of irregular shapes during nozzle formation. The ratio [%] of the frequency average crystal grain size to the nozzle tip opening diameter and the ratio [%] of the area ratio weighted average crystal grain size to the nozzle tip opening diameter are rounded to one decimal place.

[0058] The "frequency average crystal grain size" is the total value of the crystal grain size in the measurement area divided by the frequency (number of particles).

[0059] The "area-weighted average crystal grain size" is calculated by weighting the data according to the proportion of the area occupied by the measurement region, and is the sum of the crystal grain size multiplied by the crystal grain area divided by the sum of the crystal grain areas.

[0060] Here, the "opening diameter of the nozzle tip" refers to the diameter of the nozzle tip opening if the opening shape of the nozzle tip is circular, and if the opening shape is not circular, it refers to the diameter of a circle having the same area as the opening area.

[0061] (4) Nozzle formation The present invention Related to In one embodiment, a method for manufacturing a nozzle plate for an inkjet head according to the present invention is Related to The method for manufacturing a nozzle plate for an inkjet head is characterized by comprising a step of forming nozzles by laser processing.

[0062] In addition, the present invention Related to In one embodiment, a method for manufacturing a nozzle plate for an inkjet head according to the present invention is Related to The method for manufacturing a nozzle plate for an inkjet head is characterized by comprising a step of forming a concave portion by punching, and then polishing and removing the convex portion on the back surface to form a nozzle.

[0063] From the viewpoint of ink ejection stability, the nozzle shape to be formed is preferably a funnel shape. For example, the shape described in paragraph

[0037] of JP2017-19174A can be used. By making the nozzle shape a funnel shape, it is possible to suppress the entrainment of air bubbles into the nozzle when the meniscus surface is retracted due to ink ejection.

[0064] <Nozzle formation by laser processing> Regarding a method for forming a nozzle by laser processing, for example, the methods described in paragraphs

[0014] to

[0035] of Japanese Patent No. 4455884 and paragraphs

[0016] to

[0036] of Japanese Patent Laid-Open No. 2017-19174 can be used.

[0065] Specifically, a nozzle is formed by laser ablation processing while focusing and scanning the laser light onto the stainless steel substrate using a laser light source that emits a laser light with a pulse width of 30 picoseconds or less, a piezo-controlled mirror for scanning the laser light, and a focusing lens for focusing the laser beam. The three-dimensional shape of the nozzle can be controlled by the scanning pattern of the laser beam.

[0066] The shorter the pulse width of the laser light, the less the thermal effect on the stainless steel. It is preferable to use femtosecond pulses rather than picosecond pulses. In addition, since dust of the stainless steel is generated during laser ablation processing, it is preferable to perform laser processing while blowing a gas such as air in order to remove the dust from the nozzle processing position. In addition, by splitting the laser beam using a diffractive optical element (DOE), it is possible to process multiple nozzles at the same time, improving the productivity of the nozzle processing process.

[0067] As the ablation process of the stainless steel substrate progresses, it is preferable to change the height of the stainless steel substrate or the height of the lens so that the focal position of the lens is on the substrate surface. By synchronously matching the nozzle processing height and the lens focal height, processing in a defocused state can be prevented, and the influence of lens aberration can be reduced, thereby reducing abnormalities in the nozzle processing shape.

[0068] <Nozzle formation by punching and polishing> The formation of the nozzle by punching and polishing can be carried out, for example, by the method described in paragraphs

[0008] to

[0014] of Japanese Patent No. 3755332.

[0069] A punch tool is used to form the recesses by punching. The punch tool is shaped to match the nozzle shape. By pressing the punch tool into the flow path side surface of the stainless steel substrate, the stainless steel substrate is plastically deformed, forming a recess shape to which the nozzle shape is transferred. In addition, a die formed with a punching die is used to receive and hold the stainless steel substrate that deforms and protrudes when the punch tool is pressed in.

[0070] Next, the convex portion formed on the ejection surface side is removed by polishing to form the nozzle. Specifically, the convex portion can be removed by polishing in two stages: rough polishing and finish polishing. For rough polishing, it is preferable to use tape polishing. Tape polishing is a method in which a film with fine abrasive grains attached is pressed against the surface to polish it. By feeding the film before the grains wear or become clogged, the finish is stable and the process can be automated. It is preferable to use chemical mechanical polishing (CMP) for the final polishing. By supplying a polishing solution containing an abrasive, pressing a polishing pad against the workpiece, and moving the workpiece relative to the workpiece, the combined action of chemical and mechanical polishing can remove the unevenness left by rough polishing to obtain a very flat surface.

[0071] (5) Use of nozzle plates for inkjet heads The present invention Related to The nozzle plate for an inkjet head can be used in an inkjet head, an inkjet recording apparatus, an inkjet recording method, and the like.

[0072] The present invention Related to Since the nozzle plate for an inkjet head has few irregularities in the nozzle inner wall and nozzle tip, an inkjet head using the nozzle plate is less likely to have missing nozzles, and the frequency of maintenance of an inkjet recording device using the inkjet head can be reduced. In addition, the printing quality is good because the variation in landing position, uneven printing, streaking, and pattern breaks are less likely to occur.

[0073] The ink-jet head of the present invention is Related to The configuration other than the use of a nozzle plate for an inkjet head is not particularly limited, and similar to a general inkjet head, it can be configured to include a pressure chamber, a piezoelectric actuator, a vibration plate, a wiring board, a common ink chamber, and a drive unit.

[0074] Furthermore, the inkjet recording device of the present invention is not particularly limited in terms of its configuration other than being equipped with the inkjet head of the present invention, and like a general inkjet recording device, it can be configured to include a head unit consisting of the inkjet head, as well as a conveying belt, conveying rollers, etc.

[0075] The present invention Related to When the nozzle plate for an inkjet head is used in an inkjet recording method, it is preferable to use ink having a surface tension in the range of 20 to 40 mN / m together with the nozzle plate. It is also preferable to use ink after reducing the amount of dissolved oxygen in the ink to 20% or less compared to atmospheric pressure by providing an ink degassing mechanism in the recording device or using degassed ink. It is more preferable to set the amount of dissolved oxygen to 3.0 g / mL or less. This makes it harder for air bubbles, which are the cause of nozzle missing, to form in the ink, further reducing the occurrence of nozzle missing. EXAMPLES

[0076] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.

[0077] (1) Example 1: Nozzle plate with nozzles formed by laser processing (1.1) Stainless steel The stainless steels used were the following austenitic stainless steels A to C, manufactured by Nippon Steel Chemical & Material Co., Ltd., with a thickness of 50 μm. Stainless steel A: SUS304-CSP-H-TA material Stainless steel B: SUS304-CSP-H material Lot 1 Stainless steel C: SUS304-CSP-H material Lot 2

[0078] The "H" in the above stainless steels means that it is a hard material. Also, "TA" means that it is a material that has been tension annealed, which removes stress and warping from stainless steel by rolling it. In other words, stainless steel A is a hard material that has been tension annealed, while stainless steel B and stainless steel C are hard materials that have not been tension annealed. "CSP" stands for cold-rolled steel strip for springs.

[0079] 1A to 1C are optical microscope images taken at a magnification of 100 times of stainless steels A to C, respectively. No difference was observed in the surface morphology of stainless steels A to C.

[0080] Next, the EBSD measurement results are explained. The EBSD measurement was performed using a JEOL SEM JSM-7001F and TSL OIM software Ver. 7.3, with the SEM acceleration voltage set to 15 kV, the sample tilt angle set to 70°, the measurement area set to 100 μm × 40 μm, the measurement step (measurement point interval) set to 0.2 μm, and the threshold value for the misorientation of the grain boundary set to 5°.

[0081] Figures 2A to 2C are crystal grain maps obtained by EBSD measurement for stainless steels A to C, respectively. In each of Figures 2A to 2C, the differences in crystal structure are mapped out into regions that are face-centered cubic, regions that are body-centered cubic, and regions where the crystal structure cannot be determined.

[0082] In the present invention, the face-centered cubic crystal area percentage [%] and the body-centered cubic crystal area percentage [%] are percentages relative to the area excluding crystal grains whose crystal structure cannot be determined, and therefore must be calculated using these values, rather than the percentages relative to the entire area including regions whose crystal structure cannot be determined (the values ​​of Iron bcc and Iron fcc shown in the figure), using the following calculation formula.

[0083] Area ratio of face-centered cubic crystal [%]=Iron fcc / (Iron bcc+Iron fcc)×100 Area ratio of body-centered cubic crystal [%]=Iron bcc / (Iron bcc+Iron fcc)×100

[0084] The area ratios [%] of face-centered cubic crystals and the area ratios [%] of body-centered cubic crystals obtained by the above calculations are shown in Table I below.

[0085] The area percentage [%] of face-centered cubic crystals and the area percentage [%] of body-centered cubic crystals in stainless steel can be regarded as the austenite phase content [%] and martensite phase content [%] in the stainless steel, respectively.

[0086] It is clear that the area ratio of face-centered cubic crystals exceeds 90% in all of stainless steels A to C, and that the austenite phase is the main phase. In addition, in all of stainless steels A to C, the area ratio of body-centered cubic crystals is considerably smaller than the area ratio of face-centered cubic crystals, so it can be said that the martensite phase is a different phase.

[0087] The frequency average grain size [μm] and area ratio weighted average grain size [μm] obtained by EBSD measurement are shown in Table I below.

[0088] (1.2) Fabrication of a nozzle plate with nozzles formed by laser processing Nozzles were formed in the above stainless steels A to C by laser processing, thereby producing nozzle plates No. 1 to 3.

[0089] The laser processing was performed using picosecond laser processing. Specifically, a laser beam with a wavelength of 1053 nm, pulse width of 25 ps, output of 1 W, and repetition frequency of 1 kHz emitted from a YLF (yttrium lithium fluoride) laser was split into 208 beams by a diffractive optical element (DOE), and focused on the flow path side of the stainless steel substrate by an f-sinθ lens with a focal length of 100 mm. The beam was then ablated while being scanned by a piezo-controlled mirror to form 208 nozzles. As the ablation process of the stainless steel substrate progressed, the height of the stainless steel substrate was changed so that the focal position of the lens was on the substrate surface.

[0090] The nozzle shape of all of nozzle plates No. 1 to 3 was a funnel shape in which the taper angle of the nozzle inner wall changed in two stages, with the opening diameter on the flow path side being 90 μm, the taper angle of the first stage being approximately 45°, the depth of the first stage taper being 30 μm, the taper angle of the connecting second stage being approximately 9°, the depth of the second stage taper being approximately 20 μm, and the opening diameter at the nozzle tip being 19.1 μm.

[0091] The frequency average crystal grain size / nozzle opening diameter [%] and area ratio weighted average crystal grain size / nozzle opening diameter [%] calculated based on the nozzle tip opening diameter of 19.1 μm are shown in Table I below.

[0092] (1.3) Evaluation of nozzle plate with nozzles formed by laser processing In order to evaluate the occurrence of abnormalities in nozzle plates No. 1 to 3, SEM observation was performed using a scanning electron microscope (SEM) S4800 manufactured by Hitachi High-Technologies Corporation.

[0093] Figures 3A to 3C and Figures 4A to 4C are SEM images of the nozzles of nozzle plates No. 1 to 3 taken from the flow path side. Figures 3A to 3C are SEM images of the entire nozzles of nozzle plates No. 1 to 3 taken at a magnification of 800x. Figures 4A to 4C are SEM images of the inner walls of the nozzles of nozzle plates No. 1 to 3 taken at a magnification of 8000x.

[0094] Nozzle plates Nos. 1 to 3 all had similar nozzle shapes, and it was confirmed that they were generally equivalent in terms of processability.

[0095] However, nozzle plate No. 1, made of stainless steel A, had micro-depressions (needle holes) that were irregular shapes on the inner wall of the nozzle. Figure 5 shows an SEM image of the micro-depressions. The size of the micro-depressions was approximately 1 μm, and the occurrence frequency of irregular shapes was 16 / 208 (16 irregular shapes out of 208 nozzles observed).

[0096] On the other hand, in nozzle plate No. 2 made of stainless steel B and nozzle plate No. 3 made of stainless steel C, the frequency of occurrence of abnormalities was both 0 / 208 (0 abnormalities were found out of 208 nozzles observed).

[0097] [Table 1]

[0098] The deformation that occurred in nozzle plate No. 1 made of stainless steel A is due to the influence of the body-centered cubic crystal, i.e., martensite phase, contained as a heterophase in stainless steel. Since the martensite phase has a lower melting point than the austenite phase, it is more easily ablated than the austenite phase in laser processing, which is the cause of the deformation.

[0099] From the results of Example 1, it is understood that when the content of the martensite phase is greater than 5.4%, as in the case of stainless steel A, the martensite phase becomes evident as deformed shapes such as minute recesses (needle holes).

[0100] On the other hand, it is understood that when the content of the martensite phase is 5.4% or less, as in the case of stainless steel B and stainless steel C, the martensite phase does not become apparent as a deformed shape.

[0101] The reason why stainless steel A has a larger martensite phase content than stainless steels B and C may be due to the presence or absence of tension annealing treatment and the amount of impurities contained in the raw materials.

[0102] In addition, in nozzle plate No. 2 made of stainless steel B and nozzle plate No. 3 made of stainless steel C, the frequency average crystal grain size of the stainless steel was 0.9 μm or less, and the area ratio weighted average crystal grain size was 2.1 μm or less, so it is believed that micro-depressions were less likely to occur.

[0103] (2) Example 2: Nozzle plate with nozzles formed by punching and polishing (2.1) Stainless Steel The stainless steel A and stainless steel C used in Example 1 were used.

[0104] (2.2) Fabrication of nozzle plate with nozzles formed by punching and polishing Nozzle plates No. 4 and No. 5 were produced by forming recesses in the above stainless steels A and C by punching, and then forming nozzles by polishing and removing the protrusions on the back surface.

[0105] The nozzle shape was the same as in the first embodiment.

[0106] The punching process was performed using a punch tool having a shape corresponding to the nozzle shape. The punch tool was pressed into the flow path side surface of the stainless steel substrate, causing plastic deformation of the stainless steel substrate, forming a recess shape that transferred the nozzle shape. In addition, a die formed with a punching die was used to receive and hold the stainless steel substrate that was deformed and protruding when the punch tool was pressed into place.

[0107] Next, the convex portion formed on the ejection surface side was removed by polishing to form a nozzle. Specifically, the convex portion was removed by polishing in two stages: rough polishing and finish polishing.

[0108] Rough polishing was performed using tape polishing. The polishing film used was a 75 μm thick polyester film with abrasive grains attached to one side. Finish polishing was performed using chemical mechanical polishing (CMP). By supplying a polishing solution containing an abrasive, pressing a polishing pad against the workpiece, and moving the workpiece relative to the workpiece, the combined action of chemical and mechanical polishing removed the unevenness left by the rough polishing, resulting in an extremely flat surface.

[0109] (2.3) Evaluation of nozzle plate with nozzles formed by punching and polishing Nozzle plates No. 4 and No. 5 were observed under an SEM in the same manner as in Example 1. Nozzle plates No. 4 and No. 5 had similar nozzle shapes, and it was confirmed that they were generally equivalent in terms of processability.

[0110] However, nozzle plate No. 4, made of stainless steel A, had stripe-like unevenness on the inner wall of the nozzle, and burrs on the edge of the nozzle tip. Figure 6 is an SEM image of a nozzle showing the stripe-like unevenness on the inner wall of the nozzle and the burrs on the nozzle tip. One of the nozzles in nozzle plate No. 4 was cut and a cross section near the nozzle tip was taken. The nozzle tip is at the bottom of the image.

[0111] On the other hand, no streaky irregularities or burrs were found in nozzle plate No. 5, which was made of stainless steel C. Figure 7 is an SEM image of a good nozzle with no streaky irregularities or burrs, taken by cutting one of the nozzles in nozzle plate No. 5 and photographing the nozzle tip of the cross section. The nozzle tip is at the bottom of the image.

[0112] The irregularities that occurred in nozzle plate No. 4, made of stainless steel A, are due to the influence of the body-centered cubic crystal, i.e., martensite phase, contained as a different phase in the stainless steel. When the stainless steel is plastically deformed by punching, the plastic deformation response of the surrounding austenite phase and martensite phase differs, causing streaky irregularities to occur on the nozzle inner wall from the flow channel side to the nozzle tip side.

[0113] From Example 2, it is clear that when the content of the martensite phase is greater than 5.4%, as in the case of stainless steel A, streaky irregularities are likely to occur.

[0114] Furthermore, in the case of nozzle plate No. 4 made of stainless steel A, stripe-like unevenness was formed on the inner wall of the nozzle, and when the convex portion on the back surface was subsequently polished away, a burr was formed on the edge of the nozzle tip.

[0115] On the other hand, it is clear that when the martensite phase content is 5.4% or less, as in the case of stainless steel C, no streaky irregularities are generated.

[0116] In addition, in nozzle plate No. 5 made of stainless steel C, the frequency average crystal grain size of the stainless steel is 0.9 μm or less, and further, the area ratio weighted average crystal grain size is 2.1 μm or less, so it is believed that streaky unevenness was less likely to occur. [Industrial Applicability]

[0117] The present invention can be applied to a stainless steel nozzle plate for an inkjet head which has little irregularities in the nozzle inner wall or nozzle tip, a method for manufacturing the same, and an inkjet head and an inkjet recording apparatus which use the nozzle plate for an inkjet head.

Claims

1. An inkjet recording apparatus that includes an inkjet head nozzle plate made of at least stainless steel and ejects ink, The stainless steel is an austenitic stainless steel having a martensite phase content of 5.4% or less, and The ink jet recording apparatus is characterized in that the surface tension of the ink is within a range of 20 to 40 mN / m.

2. An inkjet recording apparatus that includes an inkjet head nozzle plate made of at least stainless steel and ejects ink, The stainless steel has an area ratio of face-centered cubic crystals of 92.0% or more and an area ratio of body-centered cubic crystals of 5.4% or less, as measured by electron backscattering analysis, and The ink jet recording apparatus is characterized in that the surface tension of the ink is within a range of 20 to 40 mN / m.

3. 3. The ink jet recording apparatus according to claim 1, wherein the stainless steel has a frequency average crystal grain size of 0.9 [mu]m or less as measured by electron backscattering analysis.

4. 4. The inkjet recording apparatus according to claim 1, wherein the stainless steel has an area-weighted average crystal grain size of 2.3 μm or less as measured by electron backscattering analysis.

5. 5. The inkjet recording apparatus according to claim 1, wherein the stainless steel has a ratio of the number-average crystal grain size to the nozzle tip opening diameter, as measured by electron backscattering analysis, of 4.7% or less.

6. 6. The inkjet recording apparatus according to claim 1, wherein the stainless steel has an area-weighted average crystal grain size ratio of 12.0% or less to the nozzle tip opening diameter as measured by electron backscattering analysis.

7. An inkjet recording device described in any one of claims 1 to 6, characterized in that the stainless steel is SUS304L or SUS316L.

8. An inkjet recording device as described in any one of claims 1 to 7, characterized in that an ink degassing mechanism is provided, and the ink is degassed ink.

9. An inkjet recording method for ejecting ink using a nozzle plate for an inkjet head made of at least stainless steel, comprising: The stainless steel is an austenitic stainless steel having a martensite phase content of 5.4% or less, and The ink jet recording method according to claim 1, wherein the surface tension of the ink is within a range of 20 to 40 mN / m.

10. An inkjet recording method for ejecting ink using a nozzle plate for an inkjet head made of at least stainless steel, comprising: The stainless steel has an area ratio of face-centered cubic crystals of 92.0% or more and an area ratio of body-centered cubic crystals of 5.4% or less, as measured by electron backscattering analysis, and The ink jet recording method according to claim 1, wherein the surface tension of the ink is within a range of 20 to 40 mN / m.

11. The inkjet recording method according to claim 9 or claim 10, characterized in that the stainless steel is a stainless steel having a frequency average crystal grain size of 0.9 μm or less as measured by electron backscattering analysis.

12. An inkjet recording method described in any one of claims 9 to 11, characterized in that the stainless steel is a stainless steel having an area-weighted average crystal grain size of 2.3 μm or less as measured by electron backscattering analysis.

13. An inkjet recording method described in any one of claims 9 to 12, characterized in that the stainless steel is a stainless steel in which the ratio of the frequency average crystal grain size measured by electron backscattering analysis to the opening diameter of the nozzle tip is 4.7% or less.

14. An inkjet recording method described in any one of claims 9 to 13, characterized in that the stainless steel is a stainless steel in which the ratio of area-weighted average crystal grain size measured by electron backscattering analysis to the opening diameter of the nozzle tip is 12.0% or less.

15. The inkjet recording method according to claim 9, wherein the stainless steel is SUS304L or SUS316L.

16. The inkjet recording method according to claim 9, further comprising a mechanism for degassing the ink, the ink being a degassed ink.

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