Liquid dispensing head

Abstract

Satellites and mist are generated in conjunction with the liquid dispensing operation of the liquid dispensing head. [Solution] A liquid dispensing head that dispenses liquid from a discharge port by imparting energy to the liquid from an energy generating element, wherein the discharge port includes an opening having a longitudinal direction and a transverse direction, the opening has a projection, a first region and a second region, the projection is positioned opposite to the discharge port in the longitudinal direction, the first region is the region of the discharge port other than the projection and is the region of the opening along the longitudinal direction separated by the projection, the second region is the region of the discharge port other than the projection and is the region of the opening bridging the first region between the opposing projections, and when the maximum length in the longitudinal direction is M, the maximum length in the transverse direction is L, and the half-width of the projection is a, the liquid dispensing head satisfies M / L > 1.0 (A) and (L - a) / 2L < 0.4 (B).

Description

Technical Field

[0001] The present disclosure relates to a liquid ejection head that ejects a liquid such as ink onto various media for recording.

Background Art

[0002] As a method of ejecting a liquid such as ink that is widely used today, an inkjet recording method is known. In this inkjet recording method, as a discharge energy generation element for discharging droplets, there are a method using an electrothermal conversion element (heater) and a method using a piezoelectric element (piezo). Any of these elements can control the ejection of droplets by an electrical signal.

[0003] With the recent increase in the density of ejection ports and the reduction in the size of droplets ejected from liquid ejection heads, the influence of droplets that do not contribute to the original printing cannot be ignored. Specific examples of the influence of such droplets include image degradation due to droplets such as ink landing on the recording medium being divided into a plurality (main droplets and satellites). In addition to this, the droplets lose their speed before reaching the recording medium and become floating droplets (also referred to as mist in this specification), which causes dirt on the recording device, and this dirt may be transferred to the recording medium.

[0004] To address the above problems, for example, there is a means of providing an opening having a specific shape at the ejection port as described in Patent Document 1. The means of Patent Document 1 provides a plurality of protrusions at the opening for ejecting the liquid, thereby accelerating the timing at which the liquid column ejected therefrom separates from the opening and shortening the length of the liquid column, thereby suppressing the generation of satellites and mist.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In order to achieve satellite suppression using the method described in Patent Document 1, a region between the protrusions that hold the liquid surface connected to the liquid, and regions formed on both sides of the other protrusions are necessary. To provide such openings, a certain amount of space is required in the openings depending on the amount of liquid being discharged, but due to the increasing density of discharge ports in recent years, it is sometimes not possible to secure sufficient space to provide them.

[0007] When attempting to install the discharge port described in Patent Document 1 in a limited space, it is conceivable to adopt a shape that is deformed to fit the available space. However, with such a deformed discharge port, the liquid discharge state may not be as originally intended, and the suppression of satellites and mist may not be fully achieved. [Means for solving the problem]

[0008] This disclosure is intended to solve the above problems. The liquid discharge head of this disclosure is a liquid discharge head that discharges liquid from a discharge port by imparting energy to the liquid from an energy generating element, wherein the discharge port includes an opening having a longitudinal direction and a transverse direction, the opening has a projection, a first region and a second region, the projection is arranged at opposing positions in the longitudinal direction of the discharge port, the first region is the region of the discharge port other than the projection and is the region of the opening along the longitudinal direction separated by the projection, the second region is the region of the discharge port other than the projection and is the region of the opening bridging the first region between the opposing projections, and when the maximum length in the longitudinal direction is M, the maximum length in the transverse direction is L, and the half-width of the projection is a, the following formulas (A) and (B) are satisfied. M / L > 1.0 (A) (L - a) / 2L < 0.4 (B) [Effects of the Invention]

[0009] According to this disclosure, a liquid discharge head can be provided that can effectively suppress satellites and mist even when the space for arranging the discharge port is small. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view of the liquid dispensing head of this disclosure. [Figure 2] Figure 2 is a perspective view showing the recording element substrate of the liquid ejection head of this disclosure. [Figure 3] Figure 3 is a cross-sectional view of the liquid dispensing head shown in Figure 2, cut along the line segment III-III. [Figure 4] Figure 4 shows the discharge port, foaming chamber, and liquid flow path of the liquid discharge section of the comparative example, where (a) is a front view, (b) is a cross-sectional view of (a) between IVb and IVb, and (c) is an enlarged view of the discharge port. [Figure 5] Figure 5 shows the discharge port, foaming chamber, and liquid flow path of the liquid discharge section of the first embodiment, where (a) is a front view, (b) is a Vb-Vb cross-sectional view of (a), and (c) is an enlarged view of the discharge port. [Figure 6] Figure 6 shows the liquid discharge process at a discharge port equipped with a protrusion. [Figure 7] Figure 7 shows the results of a simulation of the behavior of the liquid inside the outlet of the comparative example. [Figure 8] Figure 8 shows the results of a simulation of the behavior of the liquid inside the discharge port of the first embodiment. [Figure 9] Figure 9 shows the results of simulating the flight state of the liquid for the comparative example and the first embodiment. [Figure 10] Figure 10 illustrates an example of a discharge port shape applicable to this disclosure. [Figure 11] Figure 11 illustrates an example of a fluid flow path applicable to this disclosure, where (a) is a front view and (b) is a cross-sectional view of (a) from XIb-XIb. [Modes for carrying out the invention]

[0011] The liquid discharge heads of this disclosure will be described below with reference to the drawings. In this specification, directions may be defined by the X, Y, and Z axes. These axes are indicated by the directional axes with arrows shown in each drawing. In each of these directional axes, the direction in which the arrow points is defined as the "+" direction of the axis. When the direction of an axis is referred to without specifying the "+" or "-" direction, it is simply referred to as the "X-axis direction," "Y-axis direction," or "Z-axis direction." In the comparative examples and embodiments of discharge ports described herein, the direction along the long axis of the shape of the discharge port is referred to as the "longitudinal direction." In the comparative examples and embodiments of discharge ports described herein, the direction perpendicular (orthogonal) to the "longitudinal direction," i.e., the direction along the short axis of the discharge port, is referred to as the "short axis direction." In the comparative examples and embodiments described herein, the longitudinal direction is the direction along the liquid flow path in which the discharge port is formed, and the short axis direction is the direction perpendicular to this.

[0012] The following describes each embodiment of the liquid discharge head of this disclosure with reference to the drawings. First, the liquid discharge head of this disclosure will be described with reference to Figures 1 to 3. Next, (1) comparative examples (comparative) and (2) each embodiment of this disclosure will be described for the liquid discharge portion of the liquid discharge head. The liquid discharge head of this disclosure discharges liquid from the discharge port by imparting energy to the liquid from an energy generating element.

[0013] (Liquid dispensing head) Figure 1 is a perspective view showing the liquid discharge head of this disclosure. Figure 1(a) is an external perspective view of the liquid discharge head 100 as seen from the side of the recording element substrate 102. Figure 1(b) is an external perspective view of the liquid discharge head 100 as seen from the top side (opposite side of the recording element substrate). As shown in Figures 1(a) and 1(b), the liquid discharge head 100 has a housing 104. Liquid is stored inside this housing 104. This liquid is supplied to the recording element substrate 102 and discharged from a discharge port provided on the recording element substrate 102.

[0014] (Recording element substrate) The recording element substrate 102 of the present disclosure will be described with reference to FIGS. 2 and 3.

[0015] FIG. 2 is a perspective view showing the recording element substrate 102 of the present disclosure. FIG. 3 is a cross-sectional view of the recording element substrate 102 in the III-III cross-section shown in FIG. 2. The recording element substrate 102 of the present disclosure includes a substrate body 202, a flow path forming portion 204, and a discharge port plate 206. The substrate body 202 includes a liquid supply port 208, an electrothermal conversion element 212, and a common liquid chamber 214. As shown in FIG. 3, the flow path forming portion 204 includes a liquid flow path 302 and a foaming chamber 304. The discharge port plate 206 includes a discharge port 210. The liquid is supplied from the liquid supply port 208 formed in the substrate body 202 to the liquid flow path 302 of the flow path forming portion 204, and is supplied to the discharge port 210 through the foaming chamber 304. The liquid supplied to the discharge port 210 is given energy from the electrothermal conversion elements 212 formed on the substrate body and arranged in a row, and is discharged from the discharge port 210.

[0016] (Liquid discharge portion) The liquid discharge head of the present disclosure has a recording element substrate 102 including the substrate body 202, the flow path forming portion 204, and the discharge port plate 206 as shown in FIGS. 2 and 3. This recording element substrate 102 includes a liquid discharge portion composed of the liquid flow path 302, the discharge port 210, the electrothermal conversion element 212, and the foaming chamber 304 shown in FIG. 3 (details will be described later with reference to FIGS. 4 and 5). As shown in FIG. 3, the liquid flow path 302 of the liquid discharge portion is connected to the common liquid chamber 214 through the liquid supply port 208. Components such as the housing of the liquid discharge head of the present disclosure and the recording element substrate can be manufactured by known methods or in combination with known methods.

[0017] Hereinafter, the liquid discharge portion of the liquid discharge head will be described with (1) a comparative embodiment (comparative example) and (2) an embodiment of the present disclosure.

[0018] (1) Comparative example Below, as a comparative example to the present disclosure, we will describe the liquid discharge section with reference to Figure 4, using as an example a discharge port having a known shape (discharge port described in Patent Document 1) but with its aspect ratio changed so that it fits within the width W of the foaming chamber 304 of the present disclosure.

[0019] The comparative example liquid discharge unit shown in Figure 4 comprises an electric heat conversion element 212, a discharge port 210 as an opening for discharging liquid, a liquid flow path 302, and a foaming chamber 304. The foaming chamber 304 has a rectangular shape with a long side (longitudinal direction) and a short side (short direction). In this comparative example, the short side of the foaming chamber 304 has a width W. In Figure 4, the liquid discharge unit has one liquid flow path 302 on one of the short sides, which is the path through which the liquid flows into the foaming chamber 304. Figure 4(a) is a front view of the liquid discharge unit, Figure 4(b) is a cross-sectional view of Figure 4(a) from IVb-IVb, and Figure 4(c) is an enlarged view showing the shape of the discharge port in Figure 4(a).

[0020] The recording element substrate of this comparative example, shown in Figure 4(a), has liquid discharge ports arranged in a straight line at 1200 dpi, and the width W of the short side of the foaming chamber 304 is 17 μm. The liquid discharge section is provided with a discharge port 210 having an opening area capable of discharging a liquid volume equivalent to 3.5 pl. In order for the discharge port 210 to fit within the width W of the short side of the foaming chamber 304, the dimensions of the discharge port have the relationship M > L (i.e., M / L > 1.0) and are elongated along the longitudinal direction. Here, M is the length of the discharge port in the longitudinal direction, and L is the length of the discharge port in the short direction.

[0021] Figure 4(b) shows a cross-section of the liquid discharge section (the IVb-IVb cross-section in Figure 4(a)). As shown in Figure 4(b), in this comparative example, the distance from the electrothermal conversion element 212 to the discharge port surface is Dh, and this length is 23 μm. Also in this comparative example, the distance from the surface of the electrothermal conversion element 212 to the ceiling of the liquid flow path 302 is Di, and this length is 17 μm.

[0022] Figure 4(c) shows a discharge port with a modified aspect ratio, similar to the discharge port described in Patent Document 1, so that it fits within the width W of the short side of the foaming chamber 304.

[0023] The discharge port 210 of this comparative example has a flat bilobed shape as shown in Figure 4(c). The discharge port 210 has projections 402 and 402' facing each other in the longitudinal direction (Y-axis direction) of the discharge port 210. These projections have tip portions 408 and 408'. These projections 402 and 402' form a flat bilobed shape of the discharge port 210 having a longitudinal direction (Y-axis direction) and a short direction (X-axis direction). Furthermore, the discharge port 210 of this comparative example has longitudinal openings 404 and 404' of the flat bilobed shape and an opening 406 of a portion bridging these two openings of the bilobed (hereinafter also referred to as the bridging portion). In this comparative example, the region of the longitudinal openings 404 and 404' is referred to as the first region, and the opening 406 of the bridging portion is referred to as the second region. Specifically, the first region is the region of the opening along the longitudinal direction separated by the projections of the discharge port. The second region is the region of the discharge port other than the projections of the discharge port, and is the region that bridges the first region between the opposing projections (particularly between the two opposing projections 402 and 402'). The second region maintains the liquid surface that connects to the columnar liquid extending outside the discharge port when liquid is discharged from the discharge port. As shown in Figure 4(c), the second region is located between the tip portions 408 and 408' of the projections 402 and 402' of the discharge port. Furthermore, the region of the first region (the longitudinal opening portions 404 and 404') excluding the portion parallel to the projections 402 and 402' (in Figure 4(c), the region from the height indicated by M to the height indicated by H in the first region) is referred to as the "protrusion lateral region" or "protrusion lateral portion". As shown in Figure 4(c), the discharge port 210 has two ends 410 and 410' in the first region. In this comparative example, the discharge port 210 shown in Figure 4(c) has edges 412 and 412' along the longitudinal direction. In this comparative example, these edges are referred to as the "longitudinal edges" or "longitudinal outer edges".

[0024] In this comparative example, as shown in Figure 4(c), the lengthwise dimension of the flattened bilobed shape (the dimension between the two ends 410 and 410' of the first region) is M, and the widthwise dimension is L. The dimension between the protrusions 402 and 402' (the dimension along the lengthwise direction of the opening of the bridging portion) is H. In this embodiment, the half-width of the protrusions 402 and 402' is "a". In Figure 4, the respective dimensions are M=18.8μm, L=11.8μm, H=7.7μm, and a=2.0μm. In this case, the total width of the first regions 404 and 404' is (La), and the width of one of the first regions is (La) / 2. The ratio of this width of one of the first regions (La) / 2 to the width in the widthwise direction L, (La) / 2L, is 0.415. The discharge port in Figure 4(c) is a comparative example to the first embodiment of the present disclosure shown in Figure 5, which will be described below.

[0025] (2) Embodiments of the Disclosure (First embodiment) The liquid dispensing unit of the first embodiment of this disclosure will be described below.

[0026] Figure 5 shows a liquid discharge unit of the first embodiment in this disclosure. The configuration and dimensions other than the shape of the discharge port 210 are the same as those of the discharge port described in Figure 4. Specifically, the liquid discharge unit of this embodiment shown in Figure 5 comprises an electrothermal conversion element 212, a discharge port 210 as an opening for discharging liquid, a liquid flow path 302, and a foaming chamber 304. The foaming chamber 304 has a rectangular shape with a long side (longitudinal direction) and a short side (short direction). In this embodiment, the short side of the foaming chamber 304 has a width W. In this embodiment, the liquid discharge unit has one liquid flow path 302 on one of the short sides, which is the path through which the liquid flows into the foaming chamber 304. Figure 5(a) is a front view of the liquid discharge unit, Figure 5(b) is a Vb-Vb cross-sectional view of Figure 5(a), and Figure 5(c) is an enlarged view showing the shape of the discharge port of Figure 5(a).

[0027] The recording element substrate of this embodiment shown in Figure 5(a) has liquid discharge ports arranged in a straight line at 1200 dpi, and the width W of the short side of the foaming chamber 304 is 17 μm. The liquid discharge section is also provided with a discharge port 210 having an opening area capable of discharging a liquid volume equivalent to 3.5 pl. The dimensions of the discharge port have the relationship M > L (i.e., M / L > 1.0) and are elongated vertically along the longitudinal direction. Here, M is the length of the discharge port in the longitudinal direction, and L is the length of the discharge port in the short direction.

[0028] Figure 5(b) shows a cross-section of the liquid discharge section (the Vb-Vb cross-section in Figure 5(a)). As shown in Figure 5(b), in this embodiment, the distance from the electrothermal conversion element 212 to the discharge port surface is Dh, and this length is 23 μm. Also in this embodiment, the distance from the surface of the electrothermal conversion element 212 to the ceiling of the liquid flow path 302 is Di, and this length is 17 μm.

[0029] The shape of the discharge port 210 shown in Figure 5(c) will be described in detail below.

[0030] The discharge port 210 of this embodiment has a substantially H shape as shown in Figure 5(c). The discharge port 210 has projections 502 and 502' that face each other in the longitudinal direction (Y-axis direction) of the discharge port 210. These projections have tip portions 508 and 508'. These projections 502 and 502' form a substantially H shape for the discharge port 210, which has a longitudinal direction (Y-axis direction) and a short direction (X-axis direction). Furthermore, the discharge port 210 of this embodiment has longitudinal openings 504 and 504' of the substantially H shape and an opening 506 that bridges these two openings (hereinafter also referred to as the bridging portion). In this embodiment, the region of the longitudinal openings 504 and 504' is referred to as the first region, and the region of the bridging portion opening 506 is referred to as the second region. That is, the first region is the region of the discharge port other than the projections, and is the region of the longitudinal opening separated by the projections. Furthermore, the second region is the region other than the projections of the discharge port, and is the region that bridges the first region between the opposing projections (particularly between the two opposing projections 502 and 502'). The second region maintains the liquid surface that connects to the columnar liquid extending outside the discharge port when liquid is discharged from the discharge port. As shown in Figure 5(c), the second region 506 is located between the tip portions 508 and 508' of the projections 502 and 502' of the discharge port. In addition, the region of the first region (the longitudinal openings 504 and 504') excluding the portion where the projections 502 and 502' are parallel (in Figure 5(c), the region from the height indicated by M to the height indicated by H in the first region) is referred to as the "protrusion lateral region" or "protrusion lateral portion". Furthermore, as shown in Figure 5(c), the discharge port 210 has two ends 510 and 510' in the first region. In this disclosure, the discharge port 210 shown in Figure 5(c) has edges 512 and 512' along its longitudinal direction. In this embodiment, these edges are referred to as "longitudinal edges" or "longitudinal outer edges".

[0031] The discharge port 210 of this disclosure is particularly preferably 2 in number of protrusions. Furthermore, the discharge port 210 of this disclosure is particularly preferably symmetrical in the longitudinal and transverse directions (up, down, left, and right symmetrical).

[0032] In this embodiment, as shown in Figure 5(c), the longitudinal dimension of the approximately H shape (the dimension between the two ends 510 and 510 of the first region) is M, and the transverse dimension is L. Also, the dimension between projections 502 and 502' (the dimension along the longitudinal direction of the opening of the bridging portion) is H. In this embodiment, the half-width of projections 502 and 502' is "a". In this embodiment, the total width of the first regions 504 and 504' is (La), and the width of one of the first regions is (La) / 2.

[0033] As shown in Figure 5(c), the dimensions of the discharge port 210 have the relationship M > L (i.e., M / L > 1.0) and are elongated along the longitudinal direction. The dimensions of M and L are 20.7 μm and 11.8 μm, respectively. The dimensions of H and a are 6.8 μm and 4.3 μm, respectively.

[0034] In a particularly preferred example of this embodiment, as shown in Figure 5(c), the width of the first region 504 or 504' [the width of one of the first regions in the direction perpendicular to the longitudinal direction (X-axis direction)] can be determined as (La) / 2. At this time, the ratio of the width (La) / 2 of one of the first regions (the longitudinal opening 504 or 504') to the width L in the short direction of the substantially H-shaped discharge port, (La) / 2L, is 0.318. Compared with the discharge port of the comparative example shown in Figure 4, the discharge port of this embodiment has a thicker projection, and consequently the area next to the projection in the first region is narrower. For this reason, the discharge port 210 of this disclosure has higher resistance to the discharged liquid in the opening region (the entire first and second regions) compared to the discharge port of the comparative example.

[0035] Next, referring to Figures 6 to 9, the liquid discharge process at the discharge port with the protrusion will be explained while comparing the discharge port of the first embodiment and the discharge port of the comparative example.

[0036] Figure 6 is a discharge process diagram showing the general liquid discharge process at a discharge port equipped with a protrusion. The dimensions of the liquid discharge section shown in Figure 6 are equivalent to those described in Figure 4. Figure 6(i) shows the state before the electric heat conversion element 212 is driven. In this state, the liquid is present in the discharge port and is not in a discharge state. Figure 6(ii) shows the state when the electric heat conversion element 212 is started to drive. In this state, bubbles 602 are generated in the liquid flow path 302, a liquid column 604 is formed, and liquid discharge begins (in this specification, the discharged or discharged liquid is also referred to as a droplet or liquid column). At this stage, bubbles grow in the direction of the discharge port and the direction of the liquid flow path. Figure 6(iii) shows the state in which bubbles 602 and liquid column 604 are growing. As shown in Figure 6(iii), the liquid is discharged as a liquid column 604, and the size of the bubbles 602 is maximized in the liquid flow path. The bubble 602 then transitions to the defoaming process, contracting while drawing liquid in from the discharge port side. Figure 6(iv) shows the process of the bubble 602 contracting. During this process, as the bubble 602 contracts, the tail portion 606 of the liquid column 604 adheres to the tip of the projection, and the liquid is discharged. Figure 6(v) shows the state when the series of discharge operations is completed. During this process, the tail portion 606 of the discharged liquid column separates from the projection, and the series of discharge operations is completed.

[0037] The characteristic of the discharge port with protrusions inside is shown between the processes in Figure 6(iii) and Figure 6(iv). Specifically, these processes are characterized by the fact that the meniscus of the second region falls toward the electrothermal conversion element 212, and the tail portion 606 of the liquid column is formed between the opposing protrusions of the discharge port. In a liquid discharge head, it is important to suppress satellites and mist of the discharged liquid. To enhance this suppression effect, it is important to make the meniscus of the second region fall quickly so that the tail portion 606 of the liquid column remaining between the opposing protrusions of the discharge port narrows early. This allows the protrusions and the tail portion of the liquid column to be separated at an early timing. As a result, the overall length of the liquid column is shortened, and satellites and mist are suppressed. Conversely, if the tail portion 606 of the liquid column remains between the protrusions of the discharge port, and separation from the discharge portion is delayed, the total length of the discharged liquid column increases, causing the liquid to split into a main droplet and numerous secondary droplets (satellites or mist) during flight, and increasing the amount of satellites and mist.

[0038] The movement of the liquid at the outlet of the liquid discharge head of this disclosure will be further explained with reference to Figures 7 and 8. The movement of the liquid at the outlet was analyzed using a fluid simulator. The fluid simulator used was Ansys Fluent. Figures 7 and 8 show the results of the simulation of the movement of the liquid during the liquid discharge operation, and illustrate the state of the liquid in the outlet at the timing between discharge steps (iii) and (iv) described using Figure 6.

[0039] Figure 7 shows the behavior of the liquid at the discharge port shown in Figure 4 (Comparative Example). Figures 7(a), 7(b), and 7(c) show the state of the liquid inside the discharge port at the same time, viewed from different directions. Figure 7(a) shows the state of the liquid inside the discharge port when viewed from the discharge port side toward the electric heat conversion element side. Figure 7(b) shows a cross-section of the liquid discharge port, which is the IVb-IVb cross-section of Figure 4(a). Figure 7(c) is the VIIc-VIIc cross-section of Figure 4(a), showing the foaming chamber 304 viewed toward the liquid flow path 302 side (towards the -Y direction in Figure 4).

[0040] As shown in Figure 7(a), as the bubbles 602 are defoamed, the meniscus m1 and m2 are drawn into the foaming chamber 304. In this specification, meniscus m1 refers to the meniscus in the central part of the first region of the discharge port (the region of the openings 504 and 504' along the longitudinal direction of the discharge port). Meniscus m2 refers to the meniscus other than the central part of the first region of the discharge port. Next, as shown in Figure 7(a), the meniscus in the central part of the first region indicated by meniscus m1 remains on the discharge direction side (the +Z direction in Figure 4) more than the meniscus m2 other than the central part of the first region of the discharge port. In addition, it can be seen that meniscus m2 is connected to the tail portion 606 of the discharged liquid.

[0041] As mentioned above, in a discharge port with protrusions, it is important to cause the meniscus m2 of the first region 504 and 504' (excluding the second region 506, the region between the protrusions) to fall into the foaming chamber at an early stage, thereby forming a narrow tail portion 606 of the discharged liquid. However, in Figure 7(a), the portion of the meniscus m1 in the first region remains on the discharge port side compared to the meniscus in other regions.

[0042] The situation shown in Figure 7(a) is better illustrated in the cross-sectional view in Figure 7(b). As shown in Figure 7(b), when comparing meniscus m1 and meniscus m2, meniscus m2 is drawn more into the foam chamber. On the other hand, meniscus m1 remains on the discharge side compared to meniscus m2.

[0043] As shown in the cross-sectional view in Figure 7(c), the tail portion of the discharged liquid is connected to the meniscus m1, and the area enclosed by the arrows in the figure indicates the narrowest part of the tail portion of the discharged liquid. It can be seen that the meniscus m2 is drawn deeper into the foaming chamber compared to the meniscus m1.

[0044] Figure 8 shows the behavior of the liquid at the discharge port of the first embodiment shown in Figure 5. Similar to Figure 7, Figures 8(a), 8(b), and 8(c) show the state of the liquid inside the discharge port at the same time, viewed from different directions. Similar to Figure 7, Figure 8(a) shows the state of the liquid inside the discharge port when the liquid discharge section is viewed from the discharge port side toward the electrothermal conversion element side. Figure 8(b) shows a cross-section of the liquid discharge section, which is the Vb-Vb cross-section of Figure 5(a). Figure 8(c) is the VIIIc-VIIIc cross-section of Figure 5(a), showing the foaming chamber 304 viewed toward the liquid flow path 302 side (towards the -Y direction in Figure 5).

[0045] As shown in Figure 8(a), there is no residual meniscus m1 in the central part of the first region of the discharge port, as seen in Figure 7(a). As shown in Figure 8(b), comparing meniscus m1 and meniscus m2, meniscus m1 is drawn into the foaming chamber more than meniscus m2. Thus, in this embodiment, the relationship between meniscus m1 and meniscus m2 shown in Figure 7(b) is reversed. This is due to the effect of increasing the half-width a of the projection of the discharge port, as shown in Figure 5(c), thereby reducing the area of ​​the region next to the projection in the first region 504 and 504' and increasing the resistance of the discharged liquid as it passes through the discharge port. By increasing the resistance of the region next to the projection, the resistance of the liquid as it passes through the discharge port becomes lower in the central part of the first region, resulting in the reversal of the relationship between meniscus m1 and meniscus m2.

[0046] Figure 8(c) shows that the meniscus m1 is drawn deeper into the foaming chamber 304 compared to the meniscus m1 in Figure 7(c). The area between the arrows in the figure is the narrowest part of the tail of the discharged droplet. This narrowest part is even narrower than that in Figure 7(c). If the tail of the discharged droplet narrows earlier from the start of liquid discharge, the timing of separation of the tail of the discharged droplet from the projection of the discharge port will also be earlier. If the separation timing is earlier, the total length of the discharged droplet can be shortened, and the generation of satellites and mist as the droplet flies can be suppressed.

[0047] Thus, in the discharge port provided with the protrusion of the present disclosure, by controlling the resistance distribution of the region in the discharge port with respect to the discharged liquid, it becomes possible to obtain the desired meniscus behavior. When examining the discharge port in the present disclosure, it was found that in order to obtain the meniscus behavior as shown in FIG. 8, it is desirable to satisfy the following conditions. That is, in the discharge port of the present disclosure, the ratio [(L-a) / 2L] of the width (L-a) / 2 of one of the first regions to the width L in the short direction of the substantially H-shaped discharge port is preferably less than 0.4 [(L-a) / 2L < 0.4]. Further, the ratio [(L-a) / 2L] of the width (L-a) / 2 of one of the first regions to the width L in the short direction of the substantially H-shaped discharge port is more preferably 2 / L or more and less than 0.4. That is, when arranging the discharge ports at a high density, it is necessary to shorten the length of L. Along with this, the outer edge in the longitudinal direction of the substantially H-shaped discharge port approaches the center of the discharge port (the width L in the short direction of the discharge port becomes shorter). When the width in the short direction of the discharge port becomes shorter and the outer edge in the longitudinal direction approaches the center of the discharge port, the resistance at the center of the first region increases accordingly. As a result, the behavior of the meniscus m1 may be inhibited as shown in FIG. 7. Therefore, when reducing the width L in the short direction of the discharge port due to the necessity of arranging the discharge ports at a high density, it is necessary to simultaneously reduce the width (L-a) / 2 of the first region to control the balance of the resistance in the discharge port. The balance is shown by the relationship of (L-a) / 2L < 0.4. As described above, the discharge port of the comparative example shown in FIG. 4 has (L-a) / 2L = 0.415 and does not satisfy this condition. In the discharge port of the embodiment of the present disclosure shown in FIG. 5, (L-a) / 2L = 0.318 and satisfies the condition.

[0048] Further, in the discharge port 210 of the present disclosure, when the distance between the tips of the protrusions of the discharge port is H, it is desirable to satisfy the relationship of (L-a) / 2 < H. By satisfying such a relationship, the balance between the first region and the second region in the discharge port becomes suitable for implementing the discharge method of the present disclosure.

[0049] Next, the flight state of the discharged liquid (droplet) 604 will be explained using Figures 9(a) and 9(b). Figure 9(a) shows the simulation results of the flight state with the nozzle shape of the comparative example shown in Figure 4. Figure 9(b) shows the simulation results of the flight state with the nozzle shape of the first embodiment of the present disclosure shown in Figure 5. Figures 9(a) and 9(b) show the passage of time from the start of firing at the top to the bottom, illustrating how the main droplet and satellites fly as time progresses. In each figure, the droplet 604 is flying in the direction indicated by the arrow in the figure [from the left side of the page where the symbols (a) and (b) are located to the right side of the page on the opposite side].

[0050] The droplet 604 shown in Figure 9(a) was simulated with a discharge velocity of 9.9 m / s and a discharge volume of 3.8 ng. When the foaming start time was measured as 0 μs, the time it took for the droplet 604 to separate from the discharge port 210 was 7.7 μs. The distance d between the front end of the main droplet 902 and the rear end of the terminal satellite 904 after 48 μs was 149.5 μm, and there were 2 satellites (see the flight diagram at the bottom of Figure 9(a)). In contrast, Figure 9(b) shows the discharge state of the discharge port in the first embodiment of this disclosure, with a discharge velocity of 9.6 m / s, a discharge volume of 3.5 ng, and a droplet separation time of 7.1 μs. The distance d between the main droplet and the satellite was 98.2 μm (see the flight diagram at the bottom of Figure 9(b)). The results for each are summarized in Table 1.

[0051] [Table 1]

[0052] Thus, with the nozzle shape of the first embodiment of this disclosure, the behavior of the meniscus can be controlled to accelerate the timing of the separation of the tail portion 606 of the ejected droplet from the nozzle. As a result, the total length of the droplet 604 when it separates from the nozzle can be shortened. This reduces the number of satellites in the subsequent flight state of the main droplet and satellites, and shortens the distance between the main droplet and satellites. As a result, when the ejected liquid lands on the recording medium, the difference in the landing positions of the main droplet and satellites is reduced, and good printing results can be obtained. With the nozzle shape of this disclosure, the number of satellites was 1 under the conditions of this simulation. However, with the nozzle shape of this disclosure, it is also possible to reduce the number of satellites to 0 by adjusting the ejection speed, the physical properties of the liquid (e.g., ink), the shape or dimensions of the nozzle, etc. To achieve zero satellites, it is desirable to set the liquid discharge rate to 12 m / s or less and the dynamic surface tension (γ) of the liquid (e.g., ink) to 40 mM / m or more.

[0053] In addition, in the first embodiment, the droplet discharge state was explained using a discharge volume equivalent to 3.5 pl for the discharge port shape shown in Figure 5, but the above results are not dependent on the discharge volume. For example, if the parameters of the discharge port shape are set to M=26.8, L=14.5, a=7.4, and H=10.3, the opening area becomes capable of discharging a 5.7 pl droplet, and the condition (La) / 2L < 0.4 is also satisfied.

[0054] When the ejection of a liquid (e.g., ink) was simulated using the nozzle shape based on this modified example, it was confirmed that the same effect as the present disclosure could be obtained. Thus, although the optimal relationship between M / L / a / H may change depending on the ejection volume, the effect of the present disclosure can be obtained if the overall parameter satisfies (La) / 2L < 0.4. For an ejection volume equivalent to 3.5 pl, the preferred numerical ranges for M / L / a / H are 18 μm to 23 μm, L 10 μm to 17 μm, a 3 μm to 7 μm, and H 4 μm to 11 μm. For an ejection volume equivalent to 5.7 pl, the preferred values ​​are 24 μm to 29 μm, L 12 μm to 17 μm, a 5 μm to 10 μm, and H 5 μm to 13 μm.

[0055] The simulation results described in Figures 7 and 8 are calculated assuming a viscosity of 1.8 mPa·s for the liquid (e.g., ink). Even if this viscosity is calculated as, for example, 4.0 mPa·s, the liquid behavior is similar to that described in Figure 7 for the comparative example and Figure 8 for the discharge nozzle of this disclosure. Therefore, it can be seen that even if the viscosity of the droplet (e.g., ink) is changed, the difference between the comparative example and the first embodiment will be about the same. This can be considered to be because the difference in liquid behavior is due to the difference in resistance between predetermined regions within the discharge nozzle as the liquid passes through the nozzle. Therefore, even if the physical properties of the liquid change, if the relationship of the resistance difference does not change, the relationship of the behavior of the liquid meniscus inside the discharge nozzle will not change. The preferred viscosity of the liquid (e.g., ink) in this disclosure is 1.0 mPa·s or more and 15.0 mPa·s or less.

[0056] (Second embodiment) This embodiment will be described with reference to Figure 10. Figure 10 shows a shape applicable to the discharge port of this disclosure. As mentioned in the first embodiment, in order to control the behavior of the meniscus, it is preferable to design the dimensions of the discharge port such that (La) / 2L < 0.4, taking into consideration the balance of resistance between predetermined regions within the discharge port. Figures 10(a), 10(b), and 10(c) all satisfy this condition.

[0057] Figure 10(a) shows a discharge port with a thicker projection compared to the discharge port shape of the comparative example described in Figure 4. In a discharge port of this shape, the resistance to the liquid being discharged is increased along the side of the projection. Furthermore, the discharge port of this disclosure may have a shape in which the tip of the projection is tapered and the wall of the side of the projection (first region side) is partially bent, as shown in Figure 10(b). Figure 10(b) differs from the discharge port of the first embodiment in that the wall of the side of the projection (first region side) is not smoothly connected. Figure 10(c) shows a discharge port with a shape in which ellipses are combined as the opening of the discharge port. A curved projection is formed in the portion where the ellipses are joined. As shown in Figure 10(c), it is particularly preferable that the discharge port of this example has a shape in which the major axes of the ellipses are joined adjacent to each other with their major axes parallel.

[0058] Other conditions regarding the shape, dimensions, etc. of the discharge port in this embodiment are as described in the first embodiment.

[0059] (Third embodiment) This embodiment will be described with reference to Figure 11. In the first and second embodiments described above, the configuration was assumed in which the liquid flow path 302 is connected to one side of the foaming chamber 304. In addition to these configurations, the discharge port of the liquid discharge head of this disclosure is also applicable to configurations in which the liquid flow paths 302 (first liquid flow path and second liquid flow path) are connected to opposite sides of the foaming chamber 304, as shown in Figures 11(a) and 11(b).

[0060] Other conditions regarding the shape, dimensions, etc. of the discharge port in this embodiment are as described in the first embodiment. [Explanation of symbols]

[0061] 210 Discharge port 502 protrusion 504, 504' 1st area (opening) 506 Second area (bridging opening)

[0062] <<Other Embodiments>> The disclosures described in each of the above embodiments include configurations represented by the following example of a liquid dispensing head.

[0063] (Composition 1) A liquid dispensing head that dispenses liquid from a discharge port by imparting energy to the liquid from an energy generating element, The discharge port includes an opening having a longitudinal direction and a transverse direction, The opening has a projection, a first region and a second region, The projections are arranged at opposing positions in the longitudinal direction of the discharge port. The first region is the region of the discharge port other than the projection, and is the region of the opening along the longitudinal direction separated by the projection. The second region is the region of the discharge port other than the projection, and is the region of the opening that bridges the first region between the opposing projections. If the maximum length in the longitudinal direction is M, the maximum length in the transverse direction is L, and the half-width of the projection is a, then the following equations (A) and (B): M / L > 1.0 (A) (La) / 2L<0.4 (B) A liquid dispensing head characterized by satisfying the following conditions.

[0064] (Configuration 2) The liquid discharge head according to configuration 1, wherein the discharge port is composed of two opposing protrusions and the discharge port has a symmetrical shape.

[0065] (Composition 3) If H is the distance between the protrusions of the discharge port, then the following formula (C): (La) / 2 <H (C) A liquid dispensing head according to configuration 1 or configuration 2, which satisfies the requirements.

[0066] (Composition 4) The liquid dispensing head according to any one of configurations 1 to 3, wherein the opening has a substantially H shape or a shape formed by joining adjacent ellipses.

[0067] (Composition 5) The liquid dispensing head according to any one of configurations 1 to 4, wherein the liquid dispensing head has a liquid dispensing section, the liquid dispensing section has a foaming chamber, and the foaming chamber has a first liquid flow path and a second liquid flow path located on the opposite side of the first liquid flow path.

Claims

1. A liquid dispensing head that dispenses liquid from a discharge port by imparting energy to the liquid from an energy generating element, The discharge port includes an opening having a longitudinal direction and a transverse direction, The opening has a projection, a first region and a second region, The projections are arranged at opposing positions in the longitudinal direction of the discharge port. The first region is the region of the discharge port other than the projection, and is the region of the opening along the longitudinal direction separated by the projection. The second region is the region of the discharge port other than the projection, and is the region of the opening that bridges the first region between the opposing projections. If the maximum length in the longitudinal direction is M, the maximum length in the transverse direction is L, and the half-width of the projection is a, then the following equations (A) and (B): M / L>1.0 (A) (L-a) / 2L<0.4 (B) A liquid dispensing head characterized by satisfying the following conditions.

2. The liquid dispensing head according to claim 1, wherein the dispensing port is composed of two opposing protrusions and the dispensing port has a symmetrical shape.

3. If H is the distance between the protrusions of the discharge port, then the following formula (C): (L-a) / 2<H (C) A liquid dispensing head according to claim 1, satisfying the requirements.

4. The liquid dispensing head according to claim 1, wherein the opening has a substantially H-shape or a shape formed by joining adjacent ellipses.

5. The liquid dispensing head according to claim 1, wherein the liquid dispensing head has a liquid dispensing section, the liquid dispensing section has a foaming chamber, and the foaming chamber has a first liquid flow path and a second liquid flow path located on the opposite side of the first liquid flow path.

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