US-12623456-B2 - Liquid ejection head and liquid ejection apparatus

Abstract

A liquid ejection head and a liquid ejection apparatus are capable of efficiently ejecting a liquid having a viscosity of 2.5 cp or above at high frequency. To this end, a relation L≤H−0.4D is satisfied, where D is the thickness of an ejection port plate, H is the distance from an electrothermal conversion element to the outermost surface of the ejection port plate, and L is the height of an air bubble.

Inventors

• Yasunori Takei

Assignees

• CANON KABUSHIKI KAISHA

Dates

Publication Date

20260512

Application Date

20240313

Priority Date

20230314

Claims (8)

1. 1 . A liquid ejection head comprising: an ejection port through which a liquid is ejected; and a pressure chamber that communicates with the ejection port and is provided with a thermal energy generating element at a position facing the ejection port, the liquid ejection head being configured to eject the liquid in a volume of 4 [pl] or more from the ejection port by generating and contracting an air bubble by application of heat from the thermal energy generating element to the liquid having a viscosity of 2.5 [cp] or higher in the pressure chamber, wherein in a direction in which the liquid is ejected from the ejection port, a relation L≤H−0.4D is satisfied, where D is a distance from a first opening portion to a second opening portion of a member forming the ejection port, the first opening portion opening toward the pressure chamber and the second opening portion being at a side where the liquid is ejected, H is a distance from the position where the thermal energy generating element is disposed to the second opening portion, and L is a distance from the thermal energy generating element to an air-liquid interface of the air bubble at a time when the air bubble is at a maximum volume in a liquid ejection process.
2. 2 . The liquid ejection head according to claim 1 , wherein H< 40 [μm].
3. 3 . The liquid ejection head according to claim 1 , wherein a diameter of the second opening portion is equal to or less than a diameter of the first opening portion.
4. 4 . The liquid ejection head according to claim 1 , further comprising: a common liquid chamber capable of supplying the liquid commonly to a plurality of pressure chambers; and a plurality of liquid flow channels connecting the respective plurality of pressure chambers to the common liquid chamber, wherein the liquid flow channels are 10 [μm] or longer in length.
5. 5 . The liquid ejection head according to claim 1 , wherein a plurality of sets of the ejection port, the pressure chamber, and the thermal energy generating element are provided at a predetermined interval, forming a line.
6. 6 . The liquid ejection head according to claim 1 , wherein the ejection port is non-circular in shape.
7. 7 . A liquid ejection head comprising: an ejection port through which a liquid is ejected; and a pressure chamber that communicates with the ejection port and is provided with a thermal energy generating element at a position facing the ejection port, the liquid ejection head being configured to eject the liquid in a volume of 4 [pl] or more from the ejection port by generating and contracting an air bubble by application of heat from the thermal energy generating element to the liquid having a viscosity of 2.5 [cp] or higher in the pressure chamber, wherein in a direction in which the liquid is ejected from the ejection port, relations H<40 [μm], D≥5 [μm], and H−D≥−0.22H+24.7 [μm] are satisfied, where D is a distance from a first opening portion to a second opening portion of a member forming the ejection port, the first opening portion opening toward the pressure chamber and the second opening portion being at a side where the liquid is ejected, and H is a distance from the position where the thermal energy generating element is disposed to the second opening portion.
8. 8 . A liquid ejection apparatus to which a liquid ejection head is attachable, the liquid ejection head including an ejection port through which a liquid is ejected and a pressure chamber that communicates with the ejection port and is provided with a thermal energy generating element at a position facing the ejection port, the liquid ejection head being configured to eject the liquid in a volume of 4 [pl] or more from the ejection port by generating and contracting an air bubble by application of heat from the thermal energy generating element to the liquid having a viscosity of 2.5 [cp] or higher in the pressure chamber, wherein in a direction in which the liquid is ejected from the ejection port, a relation L≤H−0.4D is satisfied, where D is a distance from a first opening portion to a second opening portion of a member forming the ejection port, the first opening portion opening toward the pressure chamber and the second opening portion being at a side where the liquid is ejected, H is a distance from the position where the thermal energy generating element is disposed to the second opening portion, and L is a distance from the thermal energy generating element to an air-liquid interface of the air bubble at a time when the air bubble is at a maximum volume in a liquid ejection process.

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a liquid ejection head and a liquid ejection apparatus that eject a liquid. Description of the Related Art In recent years, there have been increasing needs for a liquid ejection head capable of ejecting a liquid with high viscosity, and what is particularly desired is to use a liquid with a viscosity of 2.5 cp or above. Japanese Patent Laid-Open No. 2004-230811 discloses a bubble-through ejection method which sets a short distance, 2 μm to 8 μm, between an electrothermal conversion element and an opening portion of an ejection port in order to reduce resistance to the flow in a direction toward the ejection port (hereinafter also referred to as an ejection port direction), and ejects a liquid with high viscosity as a droplet by having an air bubble communicate with the atmosphere. In the bubble-through method, typically, the short distance between the electrothermal conversion element and the surface of the ejection port makes it possible to reduce a resistance component that inhibits the flow of liquid toward the ejection port. Thus, even with a liquid with high viscosity, favorable ejection efficiency can be achieved. However, in the method in Japanese Patent Laid-Open No. 2004-230811, the short distance between the electrothermal conversion element and the opening portion of the ejection port inevitably shortens the height of a liquid supply channel connecting to a pressure chamber. As a result, resistance to the flow in the liquid supply channel increases, and once an ejection operation is performed, it is difficult to perform a speedy refill for the next ejection operation. The higher the viscosity of the ink, the more noticeable such a phenomenon is. Specifically, ink refilling cannot be done in time even in a case where the electrothermal conversion element is driven at high frequency, and it is therefore difficult to perform favorable ejection operation at high frequency. SUMMARY OF THE INVENTION Thus, the present invention provides a liquid ejection head and a liquid ejection apparatus that can efficiently eject a liquid with a viscosity of 2.5 cp or above at high frequency. To this end, a liquid ejection head of the present invention includes an ejection port that ejects a liquid and a pressure chamber that communicates with the ejection port and is provided with a thermal energy generating element at a position facing the ejection port. The liquid ejection head ejects the liquid in a volume of 4 [pl] or above from the ejection port by generating and contracting an air bubble by application of heat from the thermal energy generating element to the liquid having a viscosity of 2.5 [cp] or above in the pressure chamber. In a direction in which the liquid is ejected from the ejection port, a relation L≤H−0.4D is satisfied, where D is a distance from a first opening portion to a second opening portion of a member forming the ejection port, the first opening portion opening toward the pressure chamber and the second opening portion being at a side where the liquid is ejected, H is a distance from the position at which the thermal energy generating element is disposed to the second opening portion, and L is a distance from the thermal energy generating element to an air-liquid interface of the air bubble at a time when the air bubble is at a maximum volume in a liquid ejection process. The present invention can provide a liquid ejection head and a liquid ejection apparatus that can efficiently eject a liquid with a viscosity of 2.5 cp or above at high frequency. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a perspective view showing a liquid ejection head; FIG. 1B is a perspective view showing the liquid ejection head; FIG. 2 is a perspective view showing a printing element board; FIG. 3 is a sectional view of a section III-III′ shown in FIG. 2; FIG. 4A is a sectional view showing an area around an ejection port at the printing element board; FIG. 4B is a sectional view showing an area around the ejection port at the printing element board; FIG. 4C is a sectional view showing an area around the ejection port at the printing element board; FIG. 5 is a schematic sectional view showing an ejection unit of a liquid ejection head of prior art; FIG. 6 is a schematic sectional view showing an ejection unit of the liquid ejection head; FIG. 7A is a graph showing experimental data; FIG. 7B is a graph showing experimental data; FIG. 8 is a graph showing the relation between the distance and the height of a pressure chamber; and FIG. 9 is a diagram showing an area around an ejection port at a printing element board of a second embodiment. DESCRIPTION OF THE EMBODIMENTS First Embodiment FIGS. 1A and 1B are perspective views showing a liquid ejection head 15 of the present em