Liquid dispensing device

Abstract

To make damage to a projection of an ejection port less likely to occur during cleaning.SOLUTION: A liquid ejection head 2 has an ejection port 3 that ejects liquid, and the ejection port 3 has a plurality of projections 32 projecting toward a center 31 of the ejection port 3. Each of the plurality of projections 32 has a base portion 33, a tip portion 34, and two side portions 35 located between the base portion 33 and the tip portion 34. The plurality of projections 32 have a first projection 32A and a second projection 32B, respective angular positions of the tip portions 34 of which are farthest from each other. If the diameter of the minimum envelope circle 38 of the ejection port 3 is D, the minimum projection interval that is the minimum interval between the first projection 32A and the second projection 32B is d, the distance between two intersections of extension lines 39 of the two side portions 35 of the first projection 32A and the minimum envelope circle 38 is W, and the curvature radius of the base portion 33 of the first projection 32A is R, relations of 0.38≤d / D≤0.57, 0.34≤W / D≤0.51, and 0.0167≤R / D≤0.10 are satisfied.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head. Do The present invention relates to a liquid ejection device equipped with the same. [Background technology]

[0002] In recent years, liquid ejection heads that eject liquids such as ink have been required to suppress the generation of small droplets (hereinafter referred to as satellites) that are ejected alongside main droplets in response to demands for higher image quality and improved recording quality. Patent Document 1 proposes a method for achieving this, in which ejection ports have protrusions that protrude toward the center of the ejection port. Meanwhile, to prevent liquid from adhering to the ejection port surface, the ejection port surface is cleaned by a cleaning mechanism. Known cleaning mechanisms use fibers in the contact area with the ejection port surface. The fibers may penetrate the interior of the ejection port, potentially becoming caught on the protrusions and damaging them. Damage to the protrusions can result in an increase in satellites and changes in the landing position of droplets, potentially affecting recording quality. Patent Document 1 also discloses that the cleaning fibers have portions that are thicker than the minimum spacing between the protrusions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-130902 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the cleaning mechanism described in Patent Document 1 reduces the possibility of fibers getting inside the ejection orifice, there is still a possibility that fibers may get caught on the protrusions and damage the protrusions. Furthermore, the smaller the fiber diameter, the better the effect of removing liquid from the ejection orifice surface. Therefore, it is desirable to prevent damage to the protrusions regardless of the fiber diameter.

[0005] The present invention provides a liquid ejection head in which protrusions of ejection ports are less likely to be damaged during cleaning. A liquid ejection device equipped with The purpose is to provide. [Means for solving the problem]

[0006] The liquid ejection device of the present invention has a liquid ejection head and a cleaning member that cleans the ejection orifice surface of the liquid ejection head. The cleaning member contacts the ejection orifice surface while moving relative to the ejection orifice surface and has a contact portion that includes fibers. The liquid ejection head has an ejection orifice-forming member made of resin and provided with an ejection orifice through which liquid is ejected. The ejection orifice has two protrusions that protrude toward the center of the ejection orifice so as to face each other, and each of the two protrusions has a base, a tip, and two side portions located between the base and the tip. The two protrusions are a first protrusion and a second protrusion whose tip angular positions are furthest from each other in a polar coordinate system that has the center of the ejection orifice as the origin when the ejection orifice is viewed in plan. The first protrusion and the second protrusion have the same shape and dimensions, are both tapered, and are positioned symmetrically about the center of the ejection orifice. The diameter of the minimum enveloping circle of the discharge port is 20 to 30 μm, and when the diameter is D, the minimum protrusion interval that is the minimum interval between the first protrusion and the second protrusion is d, the distance between the two intersection points of the extension lines of the two sides of the first protrusion and the minimum enveloping circle is W, and the radius of curvature of the base of the first protrusion is R, the following relationships are satisfied: 0.38≦d / D≦0.57, 0.34≦W / D≦0.51, 0.0167≦R / D≦0.10, W≧10.1、 The relationship d>R is satisfied. [Effects of the Invention]

[0007] According to the present invention, a liquid ejection head in which the projections of the ejection ports are less likely to be damaged during cleaning is provided. A liquid ejection device equipped with can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic view of a liquid ejection device according to a first embodiment of the present invention. [Figure 2]FIG. 2 is a schematic diagram of a recording element substrate of the liquid ejection device shown in FIG. [Figure 3] FIG. 2 is a schematic view of a cleaning member. [Figure 4] FIG. [Figure 5] 1 is a schematic diagram showing the positional relationship between the discharge port and the fibers. [Figure 6] FIG. 10 is a diagram showing the relationship between the shape parameters of the protrusion and the stress generated at the base of the protrusion. [Figure 7] FIG. 4 is a plan view of a discharge port in second and third embodiments of the present invention. [Figure 8] FIG. 10 is a schematic diagram showing a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a liquid ejection head according to an embodiment of the present invention and a liquid ejection device using the same will be described with reference to the drawings. The liquid ejection head of the present invention is applicable to devices that eject liquids such as ink, such as printers, copiers, facsimiles with communication systems, word processors with printer units, and industrial recording devices combined with various processing devices. Furthermore, the liquid ejection head of the present invention can also be used in applications such as biochip fabrication, electronic circuit printing, semiconductor substrate fabrication, and 3D printers. The liquid ejection head of this embodiment is an inkjet head that ejects ink, but the ejected liquid is not limited to ink. This embodiment focuses on a thermal system that ejects liquid by generating bubbles using a heating resistor element, but the present invention can also be applied to liquid ejection heads using a piezo system or other liquid ejection methods. This embodiment focuses on a so-called serial scanning liquid ejection head that prints while scanning the recording medium, but the present invention can also be applied to a line-type liquid ejection head.

[0010] (First embodiment) A liquid ejection head and a liquid ejection device according to a first embodiment will be described below with reference to the drawings. Fig. 1 is a schematic diagram of a liquid ejection device 1 according to this embodiment. In Fig. 1, configurations other than a liquid ejection head 2 and a cleaning mechanism 5 are omitted. The liquid ejection device 1 has a liquid ejection head 2 and a cleaning mechanism 5 that cleans an ejection port surface 25 of the liquid ejection head 2.

[0011] FIG. 2(a) is a perspective view of a recording element substrate 21 and a support member 29, and FIG. 2(b) is a cross-sectional view of the recording element substrate 21. The liquid ejection head 2 has a recording element substrate 21 that ejects ink (liquid). The recording element substrate 21 includes an ejection port forming member 22, a substrate 23, and a heat generating resistor element 24. The ejection port forming member 22 is formed on the substrate 23 using, for example, resin. The ejection port forming member 22 has a top plate 26. The top plate 26 has an ejection port surface 25 that faces a recording medium (not shown). The ejection port surface 25 has a plurality of ejection ports 3 that eject ink. A pressure chamber 27 in which ink accumulates is provided between the top plate 26 and the substrate 23. A through hole 28 that penetrates the top plate 26 and has one end serving as an ejection port 3 is formed in the top plate 26. The through hole 28 is in communication with the pressure chamber 27. The substrate 23 is supported by a support member 29. The heating resistor element 24 is formed at a position facing the ejection port 3 on the substrate 23. When a voltage is applied to the heating resistor element 24, the ink on the heating resistor element 24 is instantaneously vaporized, generating bubbles. This causes ink droplets to be ejected from the ejection port 3, recording images, characters, etc.

[0012] Next, the cleaning mechanism 5 will be described. Referring to FIG. 1, the cleaning mechanism 5 includes a cleaning member 51, a supply roller 52 around which the cleaning member 51 is wound, and a take-up roller 53 around which the cleaning member 51 is taken up. The cleaning mechanism 5 further includes a pressing member 54 that presses the cleaning member 51 against the ejection port surface 25, and a biasing member 55 that presses the pressing member 54 toward the ejection port surface 25. The biasing member 55 is formed of a spring or the like. The cleaning member 51 has a contact portion 56 (see FIG. 3(a)) that comes into contact with the ejection port surface 25. The contact portion 56 of the cleaning member 51 moves relative to the ejection port surface 25 in the longitudinal direction of the cleaning member 51 due to the operation of the supply roller 52 and the take-up roller 53. At the same time, the contact portion 56 of the cleaning member 51 comes into contact with the ejection port surface 25 due to the operation of the pressing member 54 and the biasing member 55, thereby cleaning the ejection port surface 25. During cleaning, the cleaning member 51 is pressed against the ejection port surface 25, and then moved in the wiping direction D relative to the liquid ejection head 2. Cleaning is performed depending on the condition of the ejection port surface 25, the number of recording media that have been recorded on, and other factors. The ejection port surface 25 is cleaned entirely by moving the pressing member 54 over the ejection port surface 25. Cleaning can be performed by simply pressing the cleaning member 51 against the ejection port surface 25, but it is preferable to move the cleaning member 51 relative to the ejection port surface 25.

[0013] FIG. 3(a) is a schematic diagram of the cleaning member 51, and FIG. 3(b) is a cross-sectional view taken along line 3A-3A in FIG. 3(a). The cleaning member 51 can be made of rubber or a porous material, or a combination of rubber and a porous material. However, it is preferable for the cleaning member 51 to be made entirely of fibers 57. A cleaning member 51 made of fibers 57 is less likely to cause ink mixing because the fibers 57 absorb ink. Furthermore, the fibers 57 can scrape off adhered ink, improving cleaning performance. The cleaning member 51 may be made of woven fabric, but is preferably made of nonwoven fabric. Nonwoven fabrics have irregularly arranged fibers 57, which contact ink from various directions, improving ink removal efficiency. The cleaning member 51 does not need to be made entirely of fibers 57; it is sufficient that at least the contact portion 56 is made of fibers 57, or that at least the contact portion 56 contains fibers 57. The fiber diameter Φ of the fiber 57 in the contact portion 56 is the diameter of the smallest enveloping circle of the fiber 57 in a cross section perpendicular to the extending direction of the fiber 57 (see FIG. 3(b)). The fiber 57 may be a collection of short fibers or a single entangled long fiber. The fiber 57 may be a plurality of fibers twisted together so that it can be regarded as a single fiber. When the twisted fibers are frayed at the end of the fiber, each frayed fiber becomes the fiber 57 in this embodiment. The fiber diameter Φ does not have to be constant, and the thickness of each fiber 57 may be different as shown in FIG. 3(b).

[0014] FIG. 4(a) is a plan view of the ejection orifice 3 (viewed from above the recording medium), and FIG. 4(b) is an enlarged view of portion A in FIG. 4(a). The ejection orifice 3 has a center 31 of the ejection orifice 3 and multiple protrusions 32 protruding toward the center 31. Each of the multiple protrusions 32 has a base 33, a tip 34, and two side portions 35 located between the base 33 and the tip 34 and connecting the base 33 and the tip 34. The center 31 of the ejection orifice 3 coincides with the center of gravity of the figure defined by the periphery 36 of the ejection orifice 3, i.e., the center of gravity of the opening of the ejection orifice 3. In the following description, the multiple protrusions 32 include a first protrusion 32A and a second protrusion 32B whose tip portions 34 are furthest apart in angular position from each other. The angular positions are defined by an angle θ in polar coordinates with the center 31 of the ejection orifice 3 as the origin. In this embodiment, two protrusions 32 are provided facing each other. These protrusions 32 are a first protrusion 32A and a second protrusion 32B. The two protrusions 32 have the same shape and dimensions and are positioned symmetrically with respect to the center 31 of the ejection port 3. Therefore, the difference in angular position between the tip 34A of the first protrusion 32A and the tip 34B of the second protrusion 32B is 180 degrees. The region between the two protrusions 32 (hereinafter referred to as the inter-protrusion region 37) has higher fluid resistance than other regions. Due to this high fluid resistance, an ink liquid film is formed and maintained in the inter-protrusion region 37, forming an ink liquid column. Therefore, the liquid column is separated from the ink present inside the ejection port 3 at an early stage and ejected as a droplet. This shortens the tail-like portion following the trailing end of the ejected droplet, thereby suppressing the generation of satellites.

[0015] The angle formed by the extending (protruding) direction D1 of the protrusions 32 and the wiping direction D2 during cleaning (hereinafter referred to as the wiping angle) is preferably 0 degrees. When the extending direction D1 of the protrusions 32 and the wiping direction D2 during cleaning are parallel, the direction of the load acting on the protrusions 32 and the extending direction D1 of the protrusions 32 roughly coincide with each other, thereby reducing the stress acting on the bases 33 of the protrusions 32. When the wiping angle is 90 degrees, a force perpendicular to the protrusions 32 is applied, making the protrusions 32 most susceptible to damage. The wiping angle does not have to be 0 degrees. For example, when the wiping angle is 45 degrees or less, the component of force perpendicular to the extending direction D1 of the protrusions 32 is 1 / √2 times or less of the maximum value, which is expected to improve the effect of suppressing damage to the protrusions 32. However, the wiping angle is not limited to 90 degrees.

[0016] FIG. 5 shows the positional relationship between the fibers 57 included in the cleaning member 51 and the discharge port 3. Because FIG. 5 is a conceptual diagram, only one fiber 57 is shown; however, multiple fibers 57 may be present near the discharge port 3. FIGS. 5(a) to 5(c) illustrate a case where the fiber diameter Φ is greater than the minimum projection spacing d (described below) (Case 1). FIG. 5(a) is a plan view, FIG. 5(b) is a cross-sectional view taken along line 5B-5B in FIG. 5(a), and FIG. 5(c) is a cross-sectional view taken along line 5C-5C in FIG. 5(a). FIGS. 5(d) to 5(f) illustrate a case where the fiber diameter Φ is smaller than the minimum projection spacing d (Case 2). FIG. 5(d) is a plan view, FIG. 5(e) is a cross-sectional view taken along line 5E-5E in FIG. 5(d), and FIG. 5(f) is a cross-sectional view taken along line 5F-5F in FIG. 5(d). In Case 1, the fiber 57 is unlikely to penetrate the interior of the discharge port 3, whereas in Case 2, the fiber 57 is likely to penetrate the interior of the discharge port 3. Therefore, in case 2, the fibers 57 that have entered the interior of the ejection port 3 during cleaning are likely to get caught on the protrusions 32, causing large stress on the protrusions 32. Therefore, in order to prevent the fibers 57 from entering the interior of the ejection port 3, it is preferable that the fiber diameter Φ be larger than the minimum protrusion spacing d, but on the other hand, the smaller the fiber diameter Φ, the better the effect of removing ink. In this embodiment, the shape of the protrusions 32 is determined so that the protrusions 32 are less likely to be damaged, so this can be effectively used in not only case 1 but also case 2. In this way, in this embodiment, the fiber diameter Φ of the fibers 57 is not limited because it is possible to increase the effect of removing ink while suppressing the possibility of damage to the protrusions 32.

[0017] Here, the shape of the discharge port 3, and in particular the protrusions 32, will be described in more detail. As described above, the discharge port 3 has a plurality of (two in this embodiment) protrusions 32 that protrude toward the center 31 of the discharge port 3. The protrusions 32 have the same cross-sectional shape over the entire length of the through-hole 28 in the top plate 26 of the discharge port forming member 22. Therefore, although the following description will focus on the shape of the protrusions 32 at the position of the discharge port 3, the cross-sectional shape of the through-hole 28 and the shape of the protrusions 32 are the same at any position in the thickness direction of the protrusions 32.

[0018] The minimum distance between two protrusions 32 is referred to as the minimum protrusion distance d. In other words, the minimum protrusion distance d is the smallest distance between any point on the periphery 36 of the first protrusion 32A and any point on the periphery 36 of the second protrusion 32. In this embodiment, the minimum protrusion distance d is equal to the distance between the tip ends 34 of the two protrusions 32, but the minimum protrusion distance d may be determined at a position other than the tip ends 34. The minimum protrusion distance d is constant at any position in the thickness direction of the protrusions 32. Note that the shape of the protrusions 32 may vary in the thickness direction. In this case, the smallest value among the minimum distances between the protrusions 32 at each thickness direction position can be defined as the minimum protrusion distance d. For example, if the protrusions 32 protrude most toward the center of the through hole 28 at the center of the thickness direction of the protrusions 32, the distance between the two protrusions 32 at the center is the minimum protrusion distance d.

[0019] Below, several shape parameters that define the shape of the protrusion 32 will be described. The diameter D of the outlet 3 means the maximum distance between any two points on the periphery 36 of the outlet 3. In other words, the diameter D of the outlet 3 is equal to the diameter of the smallest circle (minimum enveloping circle 38) that contains the outlet 3. In this embodiment, the center of the minimum enveloping circle 38 coincides with the center 31 of the outlet 3, and the periphery 36 of the outlet 3, excluding the protrusion 32, overlaps with the minimum enveloping circle 38. In other words, without the protrusion 32, the outlet 3 would be circular, and the diameter of this circle is D. The width W of the base 33 of the protrusion 32 is the distance between two intersections 41 between extension lines 39 of the two side portions 35 of the protrusion 32 and the minimum enveloping circle 38. The side portions 35 of the protrusion 32 partially form straight portions 40, and the extension lines 39 are extensions of these straight portions 40. The radius of curvature R of the base 33 is the radius of curvature of a curve 44 that connects a point 42 where the protrusion 32 departs from the minimum enveloping circle 38 and a point 43 where the extension line 39 departs from the side 35 of the protrusion 32. The curve 44 has a constant radius of curvature R, but if the radius of curvature R varies depending on the position on the curve 44, then, for example, the average value can be used as the radius of curvature R of the curve 44.

[0020] The protrusions 32 are tapered. The first reason is to prevent droplets from splitting. Because the discharge port 3 is divided into two regions by the two protrusions 32, if the tip 34 of the protrusions 32 is made thicker, the discharged droplets are more likely to split into two regions. By tapering the protrusions 32, the tip 34 becomes thinner, preventing droplets from splitting. The tip 34 of the protrusions 32 is rounded, but to prevent droplets from splitting, it is preferable to make the minimum protrusion spacing d larger than the radius of curvature r of the tip 34A, 34B of the first and second protrusions 32A, 32B. The second reason is to increase the mechanical strength of the protrusions 32. When a fiber 57 gets caught on a protrusion 32, the force is concentrated on the base 33 of the protrusion 32. By tapering the protrusions 32, the width W of the base 33 is increased, dispersing stress at the base 33 and increasing mechanical strength.

[0021] In recent years, demand for higher printing speeds has led to a demand for inks with a higher solid content. The solid content of inks suitable for achieving higher printing speeds is, for example, 5 to 30% by weight. The solid content in ink includes emulsions of pigments, resins, and polymers. When using inks with such a high solid content, the ink tends to evaporate or thicken around the periphery 36 of the ejection orifice 3, causing solidification and resulting in ejection failures. This solidification is particularly likely to occur when the ejection orifice surface 25 heats up during ejection. To solve this problem, the diameter of the ejection orifice 3 can be increased. Increasing the diameter of the ejection orifice 3 increases the amount of ink ejected per ejection and the diameter of the ink dots that land on the recording medium. Therefore, for printing at the same density, the total amount of ink ejected can be reduced compared to a smaller-diameter ejection orifice 3. This reduces the frequency of ink ejection from the ejection orifice 3 per unit time, thereby reducing the ejection frequency. For these reasons, the temperature rise of the ejection orifice surface 25 can be suppressed. However, if an attempt is made to ensure a predetermined minimum projection spacing d for suppressing the generation of satellites while increasing the diameter of the ejection ports 3, the protrusion length of the projections 32 becomes relatively longer in the large-diameter ejection ports than in the small-diameter ejection ports. As a result, the stress applied to the bases 33 of the projections 32 during the wiping operation by the cleaning member 51 is greater in the large-diameter ejection ports than in the small-diameter ejection ports. Therefore, there is a demand for a large-diameter ejection port that can simultaneously suppress the stress on the bases 33 of the projections 32 and the generation of satellites.

[0022] Therefore, using three parameters—the radius of curvature R of the base 33 of the protrusion 32, the width W of the base 33, and the minimum protrusion spacing d—we conducted a simulation to determine the maximum principal stress (σ) generated at the base 33 of the protrusion 32 when wiping with the cleaning member 51. The small-diameter nozzles were shaped to ensure a discharge volume of approximately 4.5 pl per discharge, while the large-diameter nozzles were shaped to ensure a discharge volume of approximately 12 pl per discharge. The shape of the small-diameter nozzles was roughly similar to that of the large-diameter nozzles. We calculated the maximum principal stress generated at the base 33 of the protrusion 32 for the small-diameter nozzles and the maximum principal stress generated at the base 33 of the protrusion 32 for the large-diameter nozzles of levels 1 to 10, and then calculated the ratio (stress ratio) of the latter to the former (reference stress). Table 1 and Figure 6 show the simulation results. Table 1 shows the results of calculations where R, W, and d were changed from the standard values ​​of R = 0.5 μm, W = 3.2 μm, and d = 11.4 μm. Levels 1 to 3 changed only R (R = 0.5 / 1.0 / 2.0 μm), levels 4 to 6 changed only W (W = 6.8 / 8.5 / 10.1 μm), and levels 7 to 9 changed only d (d = 12.4 / 13.4 / 14.4 μm).

[0023] [Table 1]

[0024] Figures 6(a)-(c) each show R, W, and d on the horizontal axis and the stress ratios on the vertical axis. The dotted line in the figure indicates the maximum principal stress (reference stress = 1) generated at the base 33 of the protrusion 32 of the small-diameter outlet. The graph shows that as the stress ratio approaches 1, the stress generated at the base 33 of the protrusion 32 of the large-diameter outlet approaches the maximum principal stress generated at the base 33 of the protrusion 32 of the small-diameter outlet. The slope of the plotted line indicates the sensitivity of each parameter to the maximum principal stress of the base 33; the greater the slope, the higher the sensitivity of the base 33 to the maximum principal stress. Figure 6 shows that the width W of the base 33 of the protrusion 32 has the highest sensitivity to the maximum principal stress of the base 33, followed by the minimum protrusion spacing d and the radius of curvature R of the base 33 of the protrusion 32. Furthermore, at the point at the bottom right of Figure 6(b) (level 6), the stress ratio is 1.025, which is close to the reference stress.

[0025] The base 33 of the protrusions 32 generally generates stress (stress concentration) that is higher than the theoretically required stress by a certain factor (stress concentration coefficient). The stress concentration coefficient at the base 33 of the protrusions 32 increases as the R / W ratio decreases. Therefore, increasing W decreases R / W, making it difficult to suppress stress concentration. Furthermore, the minimum protrusion spacing d is an important parameter related to satellite suppression. Based on the above, the optimal combination of the three parameters is to keep the minimum protrusion spacing d as small as possible, increase W, which is the most sensitive, and increase the radius of curvature R of the base 33 of the protrusions 32 to suppress stress concentration. The stress ratio calculated using this combination is Level 10 (R = 2.0 μm, W = 10.1 μm, d = 11.4 μm). The stress ratio was 0.975, which is smaller than the reference stress for a small-diameter outlet and is even better than Level 6, in which only the width W was changed from the standard value.

[0026] Comparing levels 6 and 10, W and d are the same, and R is 0.5 μm (level 6) or 2.0 μm (level 10). Therefore, the preferred ranges for W, d, and R are R = 0.5 to 2.0 μm, W = 10.1 μm, and d = 11.4 μm, with R = 2.0 μm, W = 10.1 μm, and d = 11.4 μm (level 10) being particularly preferred. As shown in Table 2, the range of the diameter of the large-diameter outlet (diameter D of outlet 3) is approximately 20 μm (lower limit) to 30 μm (upper limit). Table 2 also lists the dimensional parameters R, W, and d for levels 6 and 10 normalized by the diameter D of outlet 3. Therefore, it is preferable that the dimensional parameters R, W, and d of outlet 3 satisfy the following relationship: 0.38≦d / D≦0.57, more preferably d / D=0.46 0.34≦W / D≦0.51, more preferably W / D=0.40 0.0167≦R / D≦0.10, more preferably 0.067≦R / D≦0.10, and even more preferably R / D=0.08

[0027] [Table 2]

[0028] By using the ejection ports 3 having the shapes described above, it is possible to suppress the occurrence of satellites while suppressing the stress generated in the bases 33 of the protrusions 32 when the ejection port surface 25 is wiped with the cleaning member 51. According to this embodiment, the ejection port surface 25 can be cleaned even when ink with a high solid content adheres to the ejection port surface 25, so that ink with a high solid content can be used in the liquid ejection device 1.

[0029] (Second embodiment) FIG. 7(a) shows a plan view of the ejection port 3 of a liquid ejection head 2 according to the second embodiment. The configuration and effects not described are the same as those of the first embodiment. The ejection port 3 has three protrusions 32. The three protrusions 32 have the same shape and dimensions, and the angular positions of the tips 34 of the three protrusions 32 differ by 120 degrees from each other. Therefore, any two protrusions 32 become a first protrusion 32A and a second protrusion 32B. The minimum protrusion spacing d is equal to the length of the shortest straight line connecting the peripheral edges 36 of adjacent protrusions 32. Having three protrusions 32 increases the proportion of the ejection port 3 occupied by the protrusions 32. Furthermore, the protrusions 32 extend around the ejection port 3 from multiple directions, not just one direction. As a result, fibers 57 are less likely to enter the interior of the ejection port 3, improving the effect of suppressing damage to the protrusions 32.

[0030] (Third embodiment) FIG. 7(b) shows a plan view of the ejection port 3 of the liquid ejection head 2 according to the third embodiment. The configuration and effects not described are the same as those of the first embodiment. The ejection port 3 has four protrusions 32. The four protrusions 32 have the same shape and dimensions, and the angular positions of the tips 34 of the four protrusions 32 are different by 90 degrees from each other. In this embodiment, two opposing protrusions 32 (two protrusions 32 whose angular positions are different by 180 degrees from each other) are the first protrusion 32A and the second protrusion 32B. In this embodiment, the minimum protrusion spacing d is equal to the length d2 of the shortest line connecting the peripheral edge 36 of the first protrusion 32A and the peripheral edge 36 of the second protrusion 32B, which are opposed to each other. When there are four or more protrusions 32, depending on the orientation of the fibers 57, the protrusion spacing d1 may be smaller than the minimum protrusion spacing d (= d2). This protrusion spacing d1 is equal to, for example, the length of the shortest line connecting the peripheral edges 36 of adjacent protrusions 32. 7(b), fibers 57 having a fiber diameter Φ larger than the protrusion spacing d1 may get inside the discharge port 3 when they extend in direction B, but are unlikely to get inside the discharge port 3 when they extend in direction A. Therefore, in this embodiment, the possibility of fibers 57 getting inside the discharge port 3 is reduced compared to the first embodiment, and the effect of suppressing damage to the protrusions 32 is improved.

[0031] (Variation) FIG. 8 shows another modified example. The configurations and effects not described are the same as those of the first embodiment. FIGS. 8(a) to 8(c) correspond to the cross sections shown in FIGS. 5(b) and 5(e) and show longitudinal cross sections of the protrusions 32. Referring to FIG. 8(a), the protrusions 32 are recessed toward the heating resistor element 24 toward the center 31 of the ejection port 3 (Modification 1). A certain distance can be provided in the thickness direction of the protrusions 32 between the ejection port surface 25 and the protrusions 32, making it difficult for fibers 57 to enter the inside of the ejection port 3, further reducing the possibility of damage to the protrusions 32. The surface of the protrusions 32 on the ejection port surface 25 side may be rounded into a bowl shape. Referring to FIG. 8(b), the end 321 of the protrusion 32 on the ejection port surface 25 side is recessed toward the heating resistor element 24 relative to the ejection port surface 25 (Modification 2). A step is formed between the end 321 of the protrusion 32 on the ejection port surface 25 side and the ejection port surface 25, so the same effect as in Modification 1 can be expected. 8(c), in Modification 2, the end 322 of the protrusion 32 on the heating resistor element 24 side protrudes from the top plate 26 of the ejection port forming member 22 toward the heating resistor element 24 (Modification 3). This modification is expected to have the same effect as Modification 2.

[0032] Although the present invention has been described above with reference to the embodiments and modifications, the present invention is not limited to these embodiments and modifications, and these embodiments and modifications can be combined as appropriate. [Explanation of symbols]

[0033] 2 Liquid ejection head 3 outlet 32 Protrusion D Diameter of outlet (diameter of minimum enveloping circle) d Minimum distance between the first and second protrusions (minimum protrusion distance) R Radius of curvature at the base of the first protrusion W Width of first protrusion

Claims

1. a liquid ejection head; a cleaning member that cleans the ejection port surface of the liquid ejection head, the cleaning member contacts the ejection port surface while moving relative to the ejection port surface, and has a contact portion including fibers, The liquid ejection head includes: a discharge port forming member made of resin having a discharge port for discharging a liquid; the ejection port has two protrusions that protrude toward a center of the ejection port so as to face each other, and each of the two protrusions has a base, a tip, and two side portions located between the base and the tip, the two protrusions are a first protrusion and a second protrusion, the angular positions of the tip ends of which are farthest from each other in a polar coordinate system having a center of the ejection port as an origin when the ejection port is viewed in a plane, the first protrusion and the second protrusion have the same shape and size, and both have a tapered shape, and are located symmetrically with respect to the center of the ejection port; The diameter of the minimum envelope circle of the discharge port is 20 to 30 μm, When the diameter is D, the minimum projection interval that is the minimum interval between the first projection and the second projection is d, the distance between two intersection points between extension lines of the two side portions of the first projection and the minimum enveloping circle is W, and the radius of curvature of the base of the first projection is R, 0.38≦d / D≦0.57 0.34≦W / D≦0.51 0.0167≦R / D≦0.10 W≧10.1 d>R A liquid ejection device characterized in that the following relationship is satisfied.

2. The liquid ejection device according to claim 1 , wherein the relationship 0.067≦R / D≦0.10 is satisfied.

3. 3. The liquid ejection device according to claim 1, wherein d / D=0.

46.

4. The liquid ejection device according to claim 1 , wherein W / D=0.

40.

5. The liquid ejection device according to claim 1 , wherein R / D=0.

08.

6. The discharge port forming member has a through hole formed in a top plate, one end of which is the discharge port, The liquid ejection device according to claim 1 , wherein the through-hole and the two protrusions have the same shape in a plane parallel to the top plate at any position in a direction perpendicular to the top plate.

7. A liquid ejection device described in any one of claims 1 to 6, wherein the protrusions of the ejection port are only the first protrusion and the second protrusion.

8. A liquid ejection device described in any one of claims 1 to 7, wherein the contact portion moves relative to the ejection outlet forming member of the liquid ejection head while being pressed against the ejection outlet forming member.

9. A liquid ejection device described in any one of claims 1 to 8, wherein the contact portion is a nonwoven fabric.

10. A liquid ejection device described in any one of claims 1 to 9, wherein the liquid is ink having a solid content of 5 to 30% by weight.

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