Liquid ejecting head and liquid ejecting apparatus

Abstract

The present application provides a liquid ejection head and a liquid ejection apparatus which can effectively eject a liquid having a viscosity of 2.5 cp or more at a high frequency. To this end, the relationship L ≤ H - 0.4D is satisfied, where D is the thickness of an ejection port plate, H is the distance from an electro-thermal conversion element to the outermost surface of the ejection port plate, and L is the height of a bubble.

Description

Technical Field

[0001] This invention relates to a liquid jet head and a liquid jetting device for spraying liquid. Background Technology

[0002] In recent years, there has been an increasing demand for liquid jetting heads capable of spraying high-viscosity liquids, with a particular preference for liquids with a viscosity of 2.5 cp or higher.

[0003] Japanese Patent Application Publication No. 2004-230811 discloses a bubble direct-flow injection method, which sets a short distance of 2μm to 8μm between the electrothermal conversion element and the opening of the injection port to reduce flow resistance in the direction toward the injection port (hereinafter also referred to as the injection port direction), and injects a high-viscosity liquid as droplets by communicating the bubble with the atmosphere.

[0004] In the bubble-through method, the short distance between the electrothermal conversion element and the surface of the injection port typically reduces the component of resistance that prevents the liquid from flowing towards the injection port. Therefore, good injection efficiency can be achieved even when using liquids with high viscosity.

[0005] However, in the method of Japanese Patent Application Publication No. 2004-230811, the short distance between the electrothermal conversion element and the opening of the jet port inevitably shortens the height of the liquid supply channel connected to the pressure chamber. As a result, the flow resistance in the liquid supply channel increases, and once a jetting operation is performed, it is difficult to perform rapid refilling for the next jetting operation. The higher the viscosity of the ink, the more pronounced this phenomenon becomes. Specifically, even when the electrothermal conversion element is driven at a high frequency, ink refilling cannot be completed in a timely manner, and therefore it is difficult to perform a good jetting operation at a high frequency. Summary of the Invention

[0006] Therefore, the present invention provides a liquid jetting head and a liquid jetting device that can effectively jet liquids with a viscosity of 2.5 cp or higher at high frequency.

[0007] For this purpose, the liquid jet head of the present invention includes a jet port and a pressure chamber, the jet port jetting liquid, the pressure chamber communicating with the jet port, and a heat-generating element disposed at a position facing the jet port. The liquid jet head generates and contracts bubbles by applying heat from the heat-generating element to a liquid with a viscosity of 2.5 [cp] or higher in the pressure chamber, thereby jetting a liquid with a volume of 4 [pl] or greater from the jet port. In the direction in which the liquid is jetted from the jet port, the relationship L ≤ H - 0.4D is satisfied, where D is the distance from a first opening portion to a second opening portion of the component forming the jet port, the first opening portion opening towards the pressure chamber, and the second opening portion being located on the side in which the liquid is jetted, H is the distance from the position where the heat-generating element is disposed to the second opening portion, and L is the distance from the heat-generating element to the gas-liquid interface of the bubble when the bubble is at its maximum volume during liquid jetting.

[0008] The present invention can provide a liquid jetting head and a liquid jetting device that can effectively jet liquids with a viscosity of 2.5 cp or higher at high frequency.

[0009] Other features of the invention will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1A This is a perspective view showing the liquid injection head;

[0011] Figure 1B This is a perspective view showing the liquid injection head;

[0012] Figure 2 This is a perspective view showing the printed component board;

[0013] Figure 3 yes Figure 2 A sectional view of section III-III' shown;

[0014] Figure 4A This is a cross-sectional view showing the area around the ejector port at the printing element board;

[0015] Figure 4B This is a cross-sectional view showing the area around the ejector port at the printing element board;

[0016] Figure 4C This is a cross-sectional view showing the area around the ejector port at the printing element board;

[0017] Figure 5 This is a schematic cross-sectional view illustrating the injection unit of a prior art liquid injection head;

[0018] Figure 6 This is a schematic cross-sectional view showing the injection unit of the liquid injection head;

[0019] Figure 7A It is a graph showing the experimental data;

[0020] Figure 7B It is a graph showing the experimental data;

[0021] Figure 8 It is a graph showing the relationship between distance and the height of the pressure chamber; and

[0022] Figure 9 This is a schematic diagram showing the area around the ejection port on the printing element board of the second embodiment. Detailed Implementation

[0023] (First Embodiment)

[0024] Figure 1A and Figure 1B This is a perspective view showing the liquid injection head 15 of this embodiment. Figure 1A This is an external perspective view of the liquid jet head 15 as seen from the side of the printed component board 11, and Figure 1B This is an external perspective view of the liquid jet head as seen from its upper surface side. Liquid is stored in the housing 14 and supplied to the print element board 11 and ejected from a plurality of ejection ports disposed on the print element board 11. The liquid jet head 15 is configured to be attached to a liquid jetting device.

[0025] Figure 2 This is a perspective view showing the printed component board 11, and Figure 3 yes Figure 2 The cross-sectional view shown is section III-III'. Flow channel forming units 4 and jet port plates (components forming jet ports) 8 are stacked on a printing element plate 11 for jetting liquid. Flow channel forming units 4 and jet port plates 8 are disposed on the printing element plate 11, and liquid is supplied from a common liquid chamber 10 formed in the printing element plate 11, and then from a liquid supply port 3 to each liquid flow channel 7 in the flow channel forming unit 4, and through a pressure chamber 5 to a jet port 2. The common liquid chamber 10 can supply liquid to multiple pressure chambers 5 together. The liquid supplied to the pressure chambers 5 is energized by an electrothermal conversion element (heat generating element) 1 and jetted from the jet port 2. Multiple sets of jet ports 2, pressure chambers 5, and electrothermal conversion elements 1 are disposed on the printing element plate 11 at predetermined intervals, forming a line.

[0026] The ejection port 2 is positioned correspondingly to the corresponding electrothermal conversion element 1. With the electrothermal conversion element 1 linearly arranged on the printing element plate 11, the ejection port 2 can be positioned at an equal distance from the liquid supply port 3, which helps prevent variations in the ejection operation throughout the liquid ejection head. Furthermore, it is desirable that the diameter of the ejection port 2 at its surface side be the same as or smaller than the diameter at the pressure chamber 5 side. Reversing this relationship could inhibit the effective transfer of energy generated by the electrothermal conversion element 1 to the liquid in the ejection port.

[0027] Figures 4A to 4C This is a cross-sectional view showing the area around the ejection port at the printing element board 11. Figure 4A This is a sectional view of the upper surface portion. Figure 4B and Figure 4C This is a cross-sectional view of the side surface portion. The liquid flow channel 7, which connects the pressure chamber 5 to the common liquid chamber 10, serves not only as a liquid flow channel but also as a means to efficiently transfer the energy of the bubbles generated by the electrothermal conversion element 1 to the injection port. This is because if the liquid flow channel 7 is branched or very short, the energy generated by the bubbles during liquid injection escapes to the liquid flow channel side, resulting in poor injection efficiency. Therefore, it is preferable that the liquid flow channel 7 is not branched. In this embodiment, the injection volume is set to 5 μm, and the length of the liquid flow channel is set to 15 μm, so that energy does not escape to the liquid flow channel side.

[0028] Figure 4B The state inside the injection unit is shown before voltage is applied to the electrothermal conversion element 1. Figure 4B In this context, the distance from the pressure chamber side opening of the injection port at the injection port plate 8 to its liquid injection opening is denoted as distance D, and the distance from the electrothermal conversion element 1 to the outermost surface of the injection port plate 8 is denoted as distance H. Then, Figure 4C The diagram shows the state when bubble 12 has reached its maximum volume. Bubble 12 is generated by being driven by electrothermal conversion element 1 and applying heat to the liquid. Figure 4C The letter L in the figure represents the distance from the electrothermal conversion element 1 to the gas-liquid interface of the bubble pointing in the direction of injection when the bubble 12 is at its maximum volume.

[0029] The liquid jet head 15 of this embodiment employs a bubble jetting method, which prevents the bubbles in the liquid jet head from communicating with the atmosphere during liquid jetting. In the bubble jetting method, unlike the bubble straight-through method, the bubbles generated for jetting contract and burst within the liquid chamber. Then, because liquid exists between the external air and the bubbles during this bubble bursting phase, the negative pressure generated by the bubble bursting makes it easier for liquid in the flow channel to be drawn into the pressure chamber. As a result, compared to the bubble straight-through method, which primarily relies on capillary forces for liquid refilling, the refilling time can be shortened, and the drive frequency can be increased.

[0030] As an example, the liquid jet head 15 of this embodiment is driven at a maximum jet frequency of 24 kHz and a jet volume of 5 plc. It should be noted that for liquid jet heads with a small jet volume of, for example, 1 plc to 3 plc, the refill time is therefore correspondingly shorter; therefore, it is easier to achieve a high frequency of 24 kHz as the maximum driving frequency.

[0031] Figure 5 This is a schematic cross-sectional view of a liquid jetting unit of a prior art liquid jetting head employing a bubble jetting method. Figure 5 Parts (i) to (v) show the process of ejecting droplets in chronological order, and as an example, the ejection operation is shown when the cross-section of the ejection unit is H1 = 40 [μm] and D1 = 27 [μm] and the amount of liquid ejected is 5 pL.

[0032] Figure 5 Part (i) shows the state of the electrothermal conversion element 1 before it is driven. Figure 5 Part (ii) shows how the bubble 12 is generated by the drive of the electrothermal conversion element 1 and grows in the direction toward the injection port and the liquid flow channel. Figure 5 Part (iii) shows the time when bubble 12 has reached its maximum volume. Figure 5 L1 shown is the distance between the interface between the electrothermal conversion element 1 and the bubble 12 at this time. Even when the bubble 12 is at its maximum volume, there is still a distance between the bubble interface and the outermost surface of the injection port. Figure 5 In the H1-L1), the generated bubble 12 is also not connected to the atmosphere, including during the subsequent bubble bursting action.

[0033] After that, as Figure 5 As shown in section (iv), bubble 12 transitions to the bubble bursting stage and contracts, simultaneously drawing in liquid from two directions: the injection port side and the liquid flow channel side. Figure 5In part (v), bubble 12 collapses while it is not in communication with the atmosphere. After the bubble collapses, the liquid moves mainly towards the injection port due to capillary forces and reaches the surface of the injection port, completing the refilling process.

[0034] As previously mentioned, in liquid jetting heads using the bubble jetting method, a long distance exists between the electrothermal conversion element 1 and the outermost surface of the jetting port to prevent the bubbles from communicating with the atmosphere during jetting. However, this long distance from the electrothermal conversion element to the outermost surface of the jetting port results in a large resistance component for the liquid flow along that distance. Therefore, especially when jetting liquids with high viscosity, it is difficult to provide sufficiently large energy for jetting the droplets.

[0035] Figure 6 This is a schematic cross-sectional view showing the injection unit of the liquid injection head 15 of this embodiment employing a bubble injection method. Figure 6 Parts (i) to (v) show the process of ejecting droplets in chronological order, and as an example, the ejection operation is shown when the cross-section of the ejection unit is H2 = 35 [μm] and D2 = 15 [μm] and the amount of liquid ejected is 5 [pl].

[0036] As mentioned earlier, the existing injection unit using the bubble injection method has this structure, which results in a long distance between the electrothermal conversion element 1 and the outermost surface of the injection port, so that when the bubble has reached its maximum volume, there is sufficient distance between the bubble interface and the surface of the injection port in the direction toward the injection port. However, for the reasons mentioned above, it is difficult to inject liquids with high viscosity using the existing structure.

[0037] Therefore, the inventors of this invention investigated how to maintain a sufficient distance between the bubble interface and the surface of the injection port when the bubble reaches its maximum volume, by methods other than increasing the distance H. The inventors then discovered that it is effective if the height of the bubble interface in the direction toward the injection port is lower than its height in the prior art when the bubble is at its maximum volume. Even with a short distance H from the electrothermal conversion element 1 to the surface of the injection port, this method allows for rapid refilling by utilizing bubble collapse, while preventing the bubble 12 from communicating with the atmosphere, and thus enabling improved injection efficiency.

[0038] Through careful research, the inventors of this invention discovered that, in order to achieve this jetting operation, increasing the volume of the pressure chamber 5 (the region where bubbles grow and contract), especially the volume in the jetting port direction (height direction), can effectively reduce the maximum height of the bubbles. In other words, increasing the overall volume of the pressure chamber 5 in the jetting port direction increases the proportion of bubble growth in the pressure chamber 5 during the bubble growth stage, making it less likely for bubbles 12 to enter the jetting port. However, as the volume of the pressure chamber 5 increases, the distance H from the electrothermal conversion element 1 to the surface of the jetting port is shortened. This shortens the distance D (the thickness of the jetting port plate 8), which allows for a reduction in the component of resistance to the liquid flow towards the jetting port. As a result, even with a shorter distance H from the electrothermal conversion element 1 to the surface of the jetting port, communication between the bubbles and the atmosphere can be avoided. Consequently, the flow resistance in the jetting port direction can be reduced to improve jetting efficiency while maintaining the liquid refill rate achieved by the bubble jetting method.

[0039] In this embodiment Figure 6 Part (i) and existing technology Figure 5 In the comparison between parts (i), H2 Figure 6 Part (ii) shows how bubble 12 grows in the direction toward the injection port and the liquid flow channel. Figure 5 In the prior art example shown in part (ii), regarding the growth of bubble 12 in the direction toward the injection port, because the height of the pressure chamber 5 is low and the volume inside the injection port is small, bubble 12 begins to enter the injection port. Therefore, in the subsequent stages shown... Figure 5 In part (iii), bubble 12 grows rapidly in the direction toward the injection port. In contrast, in Figure 6 In part (iii), even when the bubble is at its maximum volume, bubble 12 will not enter the injection port, and with Figure 5 Compared to the previous case, the distance between the interface of the generated bubble and the surface of the injection port ( Figure 6 The H2-L2 in the middle is long enough. Furthermore, in Figure 5 Parts (ii) to (iii) and Figure 6 In the comparison of liquid jetting observed between parts (ii) and (iii), the jetting efficiency was better. Figure 6 The liquid inside is sprayed out faster.

[0040] After that, Figure 6 Part (iv) shows the transition from bubble formation to bubble bursting, and Figure 6 ​Part (v) shows the time when bubble 12 bursts. From Figure 5 Part (v) and Figure 6 A comparison of the bubble bursting times between the parts (v) clearly shows that the states of the liquid surface are different.

[0041] exist Figure 5 In part (v), the negative pressure generated by bubble bursting causes the liquid surface to be forcefully drawn in from the injection port side, so that a portion of the liquid surface contacts the bottom surface of the injection unit after bubble bursting. In contrast, in this embodiment where the bubble height L2 is less than the bubble height L1, Figure 6 In part (v), less liquid surface is drawn in from the injection port side, and the higher height of the pressure chamber allows less contact between the liquid surface and the bottom surface of the injection port.

[0042] exist Figure 5 and Figure 6 In any case, after the bubble bursts, the liquid moves primarily due to capillary forces. For example... Figure 5 As shown in part (v), where the interface between air and liquid (hereinafter referred to as the gas-liquid interface) is closer to the bottom surface of the injection unit, the gas-liquid interface requires a longer time to move away from the bottom surface of the injection unit using the capillary force of the liquid flow channel 7. In contrast, as Figure 6 As shown in part (v), where the gas-liquid interface has minimal contact with the bottom surface of the injection unit, the gas-liquid interface does not require time to move away from the bottom surface of the injection unit immediately after the bubble bursts. Therefore, the gas-liquid interface moves smoothly in the direction toward the injection port, which greatly reduces the refill time.

[0043] As described above, shortening the distance H between the electrothermal conversion element 1 and the surface of the injection port reduces the flow resistance in the direction of the injection port, while simultaneously increasing the height of the pressure chamber 5 reduces the height L of the generated bubbles. This allows for both improved injection efficiency and faster refilling.

[0044] Figure 7A It is a graph showing the experimental data. Figure 7A The relationship between refill velocity (refill frequency) and droplet velocity (ejection velocity) relative to the height dimension of the pressure chamber is shown when the ejected droplet volume is 5 [pl] and the width of the liquid flow channel 7 is 11 [μm]. Figure 7AIn the diagram, the dashed line (f) represents the refill rate (refill frequency) relative to the height of the pressure chamber, and the solid line (v) represents the droplet ejection rate relative to the height of the pressure chamber. According to research conducted by the inventors of the present invention, a refill rate of 35 kHz or higher is required to achieve an ejection frequency of 24 kHz, and a droplet velocity of 10 m / s or higher is required for the droplet to land at a predetermined position on the printing medium. It should be noted that in the configuration of this embodiment, in order to effectively utilize the movement of liquid in the liquid flow channel 7 caused by the generation and contraction of bubbles during the ejection operation, it is preferable that the length of the liquid flow channel 7 connecting the individual pressure chambers 5 to the common liquid chamber 10 is 10 μm or more. In this embodiment, the length of the liquid flow channel 7 is 19 μm.

[0045] According to Figure 7, the longer the distance H and the higher the height of the pressure chamber 5, the faster the refilling rate and the slower the droplet velocity. Conversely, the shorter the distance H and the lower the height of the pressure chamber 5, the slower the refilling rate and the faster the droplet velocity.

[0046] With a distance H of 32 μm and a height of 17.3 μm in the pressure chamber 5, a minimum refill velocity of 35 kHz was obtained, which is required to achieve jetting at 24 kHz. Furthermore, when the distance H exceeds 40 μm, the droplet velocity drops below 10 m / s and does not reach the minimum droplet velocity required for the droplet to land at the predetermined position on the printing medium.

[0047] The inventors of this invention noted the value of the formula (H-MD-L) using the coefficient M, which represents the relationship between the distance H from the electrothermal conversion element 1 to the outermost surface of the injection port plate 8, the distance D between the pressure chamber side opening and the outermost surface side opening of the injection port plate 8, and the maximum height L of the bubble. The inventors then investigated the value of the coefficient M through which the most advantageous injection could be obtained, concluding that M = 0.4 was optimal. For example, when the value of M is M = 0.3 and L ≤ H - 0.3D, there exists a region where the refill rate of 35 kHz required for driving at 24 kHz is not achieved. Furthermore, when the value of M is M = 0.5 and L ≤ H - 0.5D, the structure of the injection unit is excluded, as there exists a region where driving at 24 kHz is possible.

[0048] Therefore, the inventors of this invention have discovered that, in order to achieve the required refill velocity of 35 kHz and droplet velocity of 10 m / s for jetting at a frequency of 24 kHz, it is advantageous to satisfy the following conditions:

[0049] L≤H-0.4D, and (I)

[0050] H < 40 [μm]. (II)

[0051] Figure 7B This is a graph showing the relationship between (I) obtained through simulation and the height of the pressure chamber. The viscosity of the liquid used for calculation was 3.4 [cp] at 25 [°C]. The height of the pressure chamber required to meet these conditions varies depending on the distance H for the following reasons: With a fixed height of the pressure chamber, the greater the distance H, the greater the distance D. Then, the greater the distance D, the higher the flow resistance during jetting, which reduces the bubble height L. To achieve effective jetting, it is necessary to minimize the increase in flow resistance, and regions where the distance H exceeds 40 [μm] are undesirable. As mentioned earlier, the greater the flow resistance, the slower the droplet velocity, and experiments have also confirmed that in regions where the distance H is 40 [μm] or greater, the droplet velocity drops below 10 [m / s]. Figure 7A The point in the equation where H = 32 and the height of the pressure chamber is 17.3 is... Figure 7B The point represented by (X) in the graph. In other words, with the value of (H-0.4DL) being 0, the minimum refill speed of 35 [kHz] required for driving at 24 [kHz] is achieved.

[0052] It should be noted that in this invention, the viscosity of the liquid is 2.5 [cp] or higher. The reason is as follows: When this invention is applied to liquids with low viscosity, the filling speed becomes too fast, resulting in increased oscillations on the liquid surface due to overshoot during liquid filling. This can cause liquid to overflow onto the surface of the jet port plate, thereby disrupting the trajectory of the ejected droplets or destabilizing the jetting operation during high-speed printing. It should be noted that in this invention, the viscosity of the liquid is measured using an E-type viscometer (RE-85L manufactured by TOKISANGYO) at 25 [°C].

[0053] Figure 8 This is a graph showing the relationship between distance H and the height of the pressure chamber. The specific structure of the jetting unit is described below to achieve efficient and high-speed printing using liquids with high viscosity.

[0054] Figure 8 Line (A) in the diagram represents the relationship between distance H and the height of the pressure chamber, which allows... Figure 7BIn this context, (H-0.4DL) is 0 (the height of the pressure chamber (HD) = -0.22H + 24.7). Furthermore, line (B) represents the relationship between distance H and the height of the pressure chamber (HD) when distance D = 5 [μm]. The smaller the value of distance D (i.e., the thickness of the injection port plate), the weaker the strength of the injection port plate. For the injection port plate, according to the research conducted by the inventors according to the present invention, D ≥ 5 is desirable.

[0055] Figure 8 The shaded area in the curve graph represents the region that satisfies conditions (I) and D≥5. The structure of the injection unit, which can be obtained from lines (A) and (B), satisfies the conditions shown in the following formula:

[0056] H<40[μm], ···(II)

[0057] D≥5[μm], and...(III)

[0058] HD≥-0.22H+24.7[μm]. ···(IV)

[0059] For example, Figure 5 The structure of the prior art injection unit shown, with H = 40 [μm] and D = 27 [μm], satisfies (III) but not (II) and (IV). However, for Figure 6 The structure of the injection unit in the embodiment of the present invention shown has H = 35 [μm] and D = 15 [μm], and satisfies conditions (II) to (IV).

[0060] In this way, the relationship L ≤ H - 0.4D is satisfied, where D is the thickness of the injection port plate 8, H is the distance from the electrothermal conversion element 1 to the outermost surface of the injection port plate 8, and L is the height of the bubble. This allows for the provision of liquid injection heads and liquid injection devices capable of efficiently injecting liquids with a viscosity of 2.5 cp or higher at high frequencies.

[0061] (Second Embodiment)

[0062] The second embodiment of the present invention will now be described with reference to the accompanying drawings. It should be noted that this embodiment has the same basic structure as the first embodiment, and therefore only the feature structures will be described below.

[0063] Figure 9 This is a cross-sectional view of the upper surface portion of the ejection port at the printing element board in this embodiment. (See image below.) Figure 9As shown, the injection port 92 in this embodiment is a non-circular injection port with two opposing protrusions. This type of non-circular injection port can be provided to reduce the injection of satellite droplets and mist by operating in the injection state. Even with this non-circular injection port, efficient and high-speed filling can be achieved by using a structure that allows the cross-section of the injection unit to meet the conditions described in the first embodiment.

[0064] While the invention has been described with reference to exemplary embodiments, it will be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be given the broadest interpretation in order to cover all such modifications and equivalent structures and functions.

Claims

1. A liquid injection head, the liquid injection head comprising: The injection port sprays liquid; as well as A pressure chamber, connected to the injection port, and having a heat-generating element positioned facing the injection port, the liquid injection head is configured to generate and contract bubbles by applying heat from the heat-generating element to a liquid with a viscosity of 2.5 [cp] or higher in the pressure chamber, thereby injecting a liquid volume of 4 [pl] or greater from the injection port. In the direction in which the liquid is ejected from the injection port, the relationship L ≤ H - 0.4D is satisfied, where D is the distance from a first opening portion to a second opening portion of the component forming the injection port, the first opening portion opening toward the pressure chamber, and the second opening portion located on the side in which liquid is injected. H is the distance from the location where the heat-generating element is arranged to the second opening, and L is the distance from the heat-generating element to the gas-liquid interface of the bubble when the bubble is at its maximum volume during liquid injection.

2. The liquid injection head according to claim 1, wherein... H<40[μm].

3. The liquid injection head according to claim 1, wherein... The diameter of the second opening is equal to or less than the diameter of the first opening.

4. The liquid injection head according to claim 1, further comprising: A common liquid chamber capable of supplying liquid to multiple pressure chambers; as well as Multiple liquid flow channels connect corresponding pressure chambers to the common liquid chamber, wherein... The length of the liquid flow channel is 10 μm or longer.

5. The liquid injection head according to claim 1, wherein... Multiple sets of the injection ports, the pressure chambers, and the heat-generating elements are arranged at predetermined intervals to form a line.

6. The liquid injection head according to claim 1, wherein... The shape of the injection port is non-circular.

7. A liquid injection head, the liquid injection head comprising: The injection port sprays liquid; as well as A pressure chamber, connected to the injection port, and having a heat-generating element positioned facing the injection port, the liquid injection head is configured to generate and contract bubbles by applying heat from the heat-generating element to a liquid with a viscosity of 2.5 [cp] or higher in the pressure chamber, thereby injecting a liquid volume of 4 [pl] or greater from the injection port. In the direction in which the liquid is ejected from the injection port, the relationships H < 40 [μm], D ≥ 5 [μm], and HD ≥ -0.22H + 24.7 [μm] are satisfied. D is the distance from a first opening portion to a second opening portion of the component forming the injection port, the first opening portion opening toward the pressure chamber, and the second opening portion located on the side in which liquid is injected. H is the distance from the location where the heat-generating element is arranged to the second opening.

8. A liquid jetting device, wherein a liquid jetting head is attachable to the liquid jetting device, the liquid jetting head comprising: The injection port sprays liquid; The liquid jet head is configured to generate and contract bubbles by applying heat from the heat-generating element to a liquid with a viscosity of 2.5 [cp] or higher in the pressure chamber, thereby jetting a liquid volume of 4 [pl] or greater from the jet port. In the direction in which the liquid is ejected from the injection port, the relationship L ≤ H - 0.4D is satisfied, where D is the distance from a first opening portion to a second opening portion of the component forming the injection port, the first opening portion opening toward the pressure chamber, and the second opening portion located on the side in which liquid is injected. H is the distance from the location where the heat-generating element is arranged to the second opening, and L is the distance from the heat-generating element to the gas-liquid interface of the bubble when the bubble is at its maximum volume during liquid injection.

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