CN110774761B

CN110774761B - Liquid ejection head, liquid ejection apparatus, and liquid ejection module

Info

Publication number: CN110774761B
Application number: CN201910694299.8A
Authority: CN
Inventors: 中川喜幸; 半村亚纪子
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2018-07-31
Filing date: 2019-07-30
Publication date: 2021-10-19
Anticipated expiration: 2039-07-30
Also published as: EP3603976A1; EP3603976B1; PH12019000273A1; CN110774761A

Abstract

The invention relates to a liquid ejection head, a liquid ejection apparatus, and a liquid ejection module. The liquid ejection head includes a pressure chamber configured to allow a first liquid and a second liquid to flow inside, a pressure generating element configured to apply pressure to the first liquid, and an ejection port configured to eject the second liquid. In a state where the first liquid flows in a crossing direction crossing an ejection direction in which the second liquid is ejected from the ejection openings while being in contact with the pressure generating element in the pressure chamber and the second liquid flows in the crossing direction along the first liquid, the second liquid is ejected from the ejection openings by causing the pressure generating element to apply pressure to the first liquid.

Description

Liquid ejection head, liquid ejection apparatus, and liquid ejection module

Technical Field

The present disclosure relates to a liquid ejection head, a liquid ejection module, and a liquid ejection apparatus.

Background

Japanese patent laying-open No. h6-305143 discloses a liquid ejecting unit configured to bring a liquid serving as an ejection medium and a liquid serving as a foaming medium into contact with each other on an interface, and eject the medium with the growth of bubbles generated in the foaming medium receiving the transferred thermal energy. Japanese patent laid-open No. h6-305143 describes a method of forming flows of an ejection medium and a foaming medium by applying pressure to the ejection medium and the foaming medium after ejecting the ejection medium, thereby stabilizing an interface between the ejection medium and the foaming medium in a liquid flow passage.

Disclosure of Invention

In a first aspect of the present disclosure, there is provided a liquid ejection head comprising: a pressure chamber configured to allow the first liquid and the second liquid to flow inside; a pressure generating element configured to apply pressure to a first liquid; and an ejection port configured to eject the second liquid, wherein the second liquid is ejected from the ejection port by causing the pressure generating element to apply pressure to the first liquid in a state in which the first liquid flows in a crossing direction crossing an ejection direction in which the second liquid is ejected from the ejection port while being in contact with the pressure generating element in the pressure chamber and the second liquid flows in the crossing direction along the first liquid.

In a second aspect of the present disclosure, there is provided a liquid ejection apparatus including a liquid ejection head including: a pressure chamber configured to allow the first liquid and the second liquid to flow inside; a pressure generating element configured to apply pressure to a first liquid; and an ejection port configured to eject the second liquid, wherein the second liquid is ejected from the ejection port by causing the pressure generating element to apply pressure to the first liquid in a state in which the first liquid flows in a crossing direction crossing an ejection direction in which the second liquid is ejected from the ejection port while being in contact with the pressure generating element in the pressure chamber and the second liquid flows in the crossing direction along the first liquid.

In a third aspect of the present disclosure, there is provided a liquid ejection module for configuring a liquid ejection head, the liquid ejection head including: a pressure chamber configured to allow the first liquid and the second liquid to flow inside; a pressure generating element configured to apply pressure to a first liquid; and an ejection port configured to eject the second liquid, wherein the second liquid is ejected from the ejection port by causing the pressure generating element to apply pressure to the first liquid in a state where the first liquid flows in a crossing direction crossing an ejection direction in which the second liquid is ejected from the ejection port while being in contact with the pressure generating element in the pressure chamber and the second liquid flows in the crossing direction along the first liquid, the liquid ejection head being formed by arranging a plurality of liquid ejection modules.

Other features of the present disclosure will become apparent from the following description of exemplary embodiments, which proceeds with reference to the accompanying drawings.

Drawings

FIG. 1 is a perspective view of a spray head;

fig. 2 is a block diagram for explaining a control configuration of the liquid ejection apparatus;

FIG. 3 is a cut-away perspective view of an element board in the liquid ejection module;

fig. 4A to 4D show enlarged details of the liquid flow channel and the pressure chamber in the first embodiment;

FIGS. 5A and 5B are graphs showing the relationship between the viscosity ratio and the water phase thickness ratio, and the relationship between the height of the pressure chamber and the flow rate;

FIG. 6 is a graph showing the relationship between the flow rate ratio and the water phase thickness ratio;

fig. 7A to 7E are diagrams schematically showing a transition state in the injection operation;

FIGS. 8A to 8G are diagrams showing ejected droplets at various water phase thickness ratios;

FIGS. 9A to 9E are more graphs showing ejected droplets at various water phase thickness ratios;

10A-10C are more graphs showing jetted droplets at various water phase thickness ratios;

FIG. 11 is a graph showing the relationship between the height of a flow channel (pressure chamber) and the thickness ratio of water;

FIGS. 12A and 12B are graphs showing the relationship between the water content and the foaming pressure;

fig. 13A to 13D show enlarged details of the liquid flow channel and the pressure chamber in the second embodiment;

fig. 14 is a sectional perspective view of an element plate in the third embodiment;

fig. 15A to 15C show enlarged details of the liquid flow channel and the pressure chamber in the third embodiment;

fig. 16A to 16H are diagrams schematically showing an injection state in the third embodiment;

FIGS. 17A and 17B are diagrams showing a case where the water phase thickness ratio is changed in the third embodiment;

fig. 18A to 18C show enlarged details of the liquid flow passage and the pressure chamber in the fourth embodiment;

fig. 19A to 19C are diagrams of the state of ejection at various water phase thickness ratios in the fourth embodiment;

fig. 20A to 20C show enlarged details of the liquid flow passage and the pressure chamber in the fifth embodiment; and

fig. 21A and 21B are diagrams of the state of ejection at various water phase thickness ratios in the fifth embodiment.

Detailed Description

However, in the configuration in which the interface between the ejection medium and the foaming medium is formed by applying pressure to the two media each time the ejection operation is performed as disclosed in japanese patent laid-open No. h6-305143, the interface is liable to be unstable during repeated ejection operations. As a result, the quality of the output obtained by depositing the ejection medium may deteriorate due to fluctuations in the medium components contained in the ejected droplets and fluctuations in the amount and speed of the ejected droplets.

The present disclosure has been made to solve the above-mentioned problems. Thus, it is an object of the present disclosure to provide a liquid ejection head capable of stabilizing an interface between an ejection medium and a foam medium in the case of performing an ejection operation, thereby maintaining good ejection performance.

(first embodiment)

(Structure of liquid Ejection head)

Fig. 1 is a perspective view of a liquid ejection head 1 that can be used in the present embodiment. The liquid ejection head 1 in the present embodiment is formed by arranging a plurality of liquid ejection modules 100 along the x direction. Each liquid ejection module 100 includes an element board 10 on which ejection elements are arrayed, and a flexible wiring board 40 for supplying electric power and an ejection signal to the respective ejection elements. The flexible wiring board 40 is connected to a commonly used electric wiring board 90, the electric wiring board 90 being provided with an array of power supply terminals and ejection signal input terminals. Each liquid ejection module 100 can be easily attached to and detached from the liquid ejection head 1. Therefore, any desired liquid ejection module 100 can be easily attached to the liquid ejection head 1 from the outside or detached from the liquid ejection head 1 without disassembling the liquid ejection head 1.

Assuming that the liquid ejection head 1 is formed by disposing multiple arrangements of the liquid ejection modules 100 (by an array of a plurality of liquid ejection modules) along the longitudinal direction as described above, even if a certain one of the ejection elements causes an ejection failure, only the liquid ejection module involved in the ejection failure needs to be replaced. Therefore, it is possible to improve the yield of the liquid ejection head 1 in the manufacturing process and reduce the cost of replacing the liquid ejection head.

(Structure of liquid ejecting apparatus)

Fig. 2 is a block diagram showing a control configuration of the liquid ejection apparatus 2 applied to the present embodiment. The CPU500 controls the entire liquid ejection apparatus 2 according to a program stored in the ROM501 while using the RAM 502 as a work area. For example, the CPU500 performs prescribed data processing on ejection data to be received from the externally connected host apparatus 600 in accordance with programs and parameters stored in the ROM501, thereby generating an ejection signal to enable the liquid ejection head 1 to perform ejection. Then, the liquid ejection head 1 is driven in accordance with the ejection signal while the target medium for depositing the liquid is moved in a predetermined direction by driving the conveyance motor 503. Therefore, the liquid ejected from the liquid ejection head 1 is deposited on the deposition target medium to be adhered.

The liquid circulation unit 504 is a unit configured to circulate and supply liquid to the liquid ejection head 1 and perform flow control of the liquid in the liquid ejection head 1. The liquid circulation unit 504 includes a sub tank for storing liquid, a flow passage for circulating liquid between the sub tank and the liquid ejection head 1, a pump, a flow rate control unit for controlling the flow rate of liquid flowing in the liquid ejection head 1, and the like. Therefore, under the instruction of the CPU500, these mechanisms are controlled so that the liquid flows in the liquid ejection head 1 at a predetermined flow rate.

(construction of element plate)

Fig. 3 is a sectional perspective view of the element board 10 provided in each liquid ejection module 100. The element plate 10 is formed by stacking an orifice plate 14 (ejection port forming member) on a silicon (Si) substrate 15. In fig. 3, the ejection ports 11 arrayed in the x direction eject the same type of liquid (e.g., liquid supplied from a common sub-tank or a common supply port). Fig. 3 shows an example in which the orifice plate 14 is also provided with the liquid flow passage 13. Alternatively, the element plate 10 may adopt a configuration in which the liquid flow passage 13 is formed by using a different member (flow passage forming member) and the orifice plate 14 provided with the ejection port 11 is placed on the member.

The pressure generating elements 12 (not shown in fig. 3) are arranged on the silicon substrate 15 at positions corresponding to the respective ejection openings 11. Each of the ejection ports 11 and the corresponding pressure generating element 12 are located at positions opposite to each other. In the case where a voltage is applied in response to an ejection signal, the pressure generating element 12 applies a pressure to the liquid along a z direction orthogonal to the flow direction (y direction) of the liquid. Therefore, the liquid is ejected in the form of droplets from the ejection port 11 opposed to the pressure generating element 12. The flexible wiring board 40 (see fig. 1) supplies electric power and a drive signal to the pressure-generating element 12 via the terminals 17 arranged on the silicon substrate 15.

The orifice plate 14 is provided with a plurality of liquid flow passages 13 extending in the y direction and connected to the respective ejection ports 11 one by one, respectively. Meanwhile, the liquid flow paths 13 arranged along the x direction are connected to a common first common supply flow path 23, a first common collection flow path 24, a second common supply flow path 28, and a second common collection flow path 29. The flow of liquid in the first common supply flow path 23, the first common collection flow path 24, the second common supply flow path 28, and the second common collection flow path 29 is controlled by the liquid circulation unit 504 described with reference to fig. 2. More specifically, the liquid circulation unit 504 performs control such that the first liquid flowing into the liquid flow passage 13 from the first common supply flow passage 23 is guided to the first common collection flow passage 24, and the second liquid flowing into the liquid flow passage 13 from the second common supply flow passage 28 is guided to the second common collection flow passage 29.

Fig. 3 shows an example in which the ejection ports 11 and the liquid flow passages 13 arrayed in the x direction, and the first common supply flow passage 23, the second common supply flow passage 28, and the first common collection flow passage 24, the second common collection flow passage 29 for supplying and collecting ink to and from these ejection ports and passages and used in common are defined as one set, and two sets of these are arrayed in the y direction. Fig. 3 shows a configuration in which each ejection port is located at a position opposite to the corresponding pressure-generating element 12 (or in other words, in the growth direction of the bubble). However, the present embodiment is not limited to this configuration only. For example, each ejection port may be located at a position orthogonal to the growth direction of the bubble.

(construction of flow channel and pressure Chamber)

Fig. 4A to 4D are diagrams for explaining the detailed configuration of each liquid flow channel 13 and each pressure chamber 18 formed in the element plate 10. Fig. 4A is a perspective view seen from the ejection port 11 side (from the + z direction side). Fig. 4B is a cross-sectional view taken along line IVB-IVB shown in fig. 4A. Meanwhile, fig. 4C is an enlarged view of the vicinity of each liquid flow channel 13 in the element plate shown in fig. 3. Further, fig. 4D is an enlarged view of the vicinity of the ejection opening in fig. 4B.

The silicon substrate 15 corresponding to the bottom of the liquid flow channel 13 includes a second inflow port 21, a first inflow port 20, a first outflow port 25, and a second outflow port 26 formed in this order along the y-direction. Further, the pressure chamber 18 communicating with the ejection port 11 and including the pressure generating element 12 is located substantially at the center between the first inflow port 20 and the first outflow port 25 in the liquid flow passage 13. The second inflow port 21 is connected to a second common supply flow channel 28, the first inflow port 20 is connected to a first common supply flow channel 23, the first outflow port 25 is connected to a first common collection flow channel 24, and the second outflow port 26 is connected to a second common collection flow channel 29 (see fig. 3).

In the above configuration, the first liquid 31 supplied from the first common supply flow path 23 to the liquid flow path 13 through the first inflow port 20 flows in the y direction (the direction indicated by the arrow). The first liquid 31 passes the pressure chamber 18 and is then collected in the first common collection flow channel 24 via the first outflow opening 25. At the same time, the second liquid 32 supplied from the second common supply flow path 28 to the liquid flow path 13 through the second inflow port 21 flows in the y direction (the direction indicated by the arrow). The second liquid 32 passes through the pressure chamber 18 and is then collected in the second common collection flow channel 29 via the second outflow opening 26. That is, in the liquid flow passage 13, both the first liquid and the second liquid flow in the y direction in the section between the first inflow port 20 and the first outflow port 25.

In the pressure chamber 18, the pressure generating element 12 is in contact with the first liquid 31, and the second liquid 32 exposed to the atmosphere forms a meniscus in the vicinity of the ejection port 11. The first liquid 31 and the second liquid 32 flow in the pressure chamber 18, so that the pressure generating element 12, the first liquid 31, the second liquid 32, and the ejection port 11 are arranged in this order. Specifically, assuming that the pressure generating element 12 is located on the lower side and the ejection port 11 is located on the upper side, the second liquid 32 flows above the first liquid 31. The first liquid 31 and the second liquid 32 flow in a fluid layer state. Further, the first liquid 31 and the second liquid 32 are pressurized by the pressure generating element 12 located below, and are ejected upward from the bottom. Note that this up-down direction corresponds to the height direction of the pressure chamber 18 and the liquid flow passage 13.

In the present embodiment, the flow rate of the first liquid 31 and the flow rate of the second liquid 32 are adjusted according to the physical properties of the first liquid 31 and the physical properties of the second liquid 32 so that the first liquid 31 and the second liquid 32 flow in contact with each other in the pressure chamber, as shown in fig. 4D. Although the first liquid, the second liquid, and the third liquid are allowed to flow in the same direction in the first embodiment and the second embodiment, the embodiments are not limited to this configuration. In particular, the second liquid may flow in a direction opposite to the flow direction of the first liquid. Alternatively, the flow channels may be arranged in such a way that the flow of the first liquid intersects the flow of the second liquid at right angles. Meanwhile, the liquid ejection head is configured such that the second liquid flows above the first liquid in the height direction of the liquid flow channel (pressure chamber). However, the present embodiment is not limited to this configuration only. Specifically, as in the third embodiment, both the first liquid and the second liquid may flow in contact with the bottom surface of the liquid flow passage (pressure chamber).

The above-described two-liquid mode includes not only a parallel flow in which two liquids flow in the same direction (as shown in fig. 4D), but also an opposite flow in which a second liquid flows in a direction opposite to the flow of a first liquid, and a flow in which the flow of the first liquid intersects with the flow of the second liquid. Hereinafter, the parallel flow in these modes will be described as an example.

In the case of parallel flow, it is preferable to keep the interface between the first liquid 31 and the second liquid 32 undisturbed, or in other words, to establish a laminar state of flow of the first liquid 31 and the second liquid 32 within the pressure chamber 18. Specifically, in the case where it is attempted to control the ejection performance so as to maintain a predetermined ejection volume, it is preferable to drive the pressure generating element in a state in which the interface is stable. However, the embodiment is not limited to this configuration only. Even if the flow in the pressure chamber 18 is to be changed to a turbulent flow state in which the interface between the two liquids is disturbed to some extent, the pressure generating element 12 can be driven in a state in which at least the first liquid flows mainly on the pressure generating element 12 side and the second liquid flows mainly on the ejection port 11 side. The following description will mainly focus on an example in which the flow in the pressure chamber is in a parallel flow state and in a laminar flow state.

(conditions for forming parallel flow simultaneously with laminar flow)

First, the conditions under which a laminar flow of liquid is formed in the tube will be described. The reynolds number, which represents the ratio of viscous force to interfacial force, is commonly referred to as the flow evaluation index.

Now, the density of the liquid is defined as ρ, the flow rate of the liquid is defined as u, the representative length of the liquid is defined as d, the viscosity is defined as η, and the surface tension of the liquid is defined as γ. In this case, the reynolds number may be expressed by the following formula (formula 1):

re ═ ρ ud/η (equation 1)

Here, it is known that as the reynolds number Re becomes smaller, laminar flow is more likely to be formed. More specifically, it is known that with reynolds numbers Re less than about 2200, the flow within the circular tube forms laminar flow, while with reynolds numbers Re greater than about 2200, the flow within the circular tube becomes turbulent.

In the case where the flow forms a laminar flow, the streamlines become parallel to the traveling direction of the flow without intersecting each other. Therefore, in the case where two liquids in contact constitute a laminar flow, the liquids can form a parallel flow while stably defining an interface between the two liquids.

Here, considering a general ink jet print head, in the vicinity of the ejection opening in the liquid flow channel (pressure chamber), the height of the flow channel (height of the pressure chamber) H [ μm]In the range of about 10 to 100 μm. In this regard, in water (density ρ of 1.0 × 10)³kg/m³Viscosity η ═ 1.0cP) at a flow rate of 100mm/s, the reynolds number Re being equal to ρ ud/η ≈ 0.1 to 1.0<<2200. As a result, it can be considered that a laminar flow is formed therein.

Here, even if the liquid flow channel 13 and the pressure chamber 18 of the present embodiment have a rectangular cross section as shown in fig. 4A to 4D, the height and width of the liquid flow channel 13 and the pressure chamber 18 in the liquid ejection head are sufficiently small. Therefore, the liquid flow passage 13 and the pressure chamber 18 may be regarded as the case of a circular pipe, or more specifically, the height of the liquid flow passage and the pressure chamber 18 may be regarded as the diameter of the circular pipe.

(theoretical Condition for Forming parallel flow in laminar flow State)

Next, a condition in which a parallel flow in which the interface between the two types of liquids is stable is formed in the liquid flow passage 13 and the pressure chamber 18 will be described with reference to fig. 4D. First, the distance from the silicon substrate 15 to the ejection port surface of the orifice plate 14 is defined as H [ μm ]]And the distance from the ejection opening surface to the liquid-liquid interface between the first liquid 31 and the second liquid 32 (the phase thickness of the second liquid) is defined as h₂[μm]. Meanwhile, the distance from the liquid-liquid interface to the silicon substrate 15 (phase thickness of the first liquid) is defined as h₁[μm]. These definitions are such that H ═ H₁+h₂。

Regarding the boundary conditions in the liquid flow passage 13 and the pressure chamber 18, it is assumed that the velocity of the liquid on the wall surfaces of the liquid flow passage 13 and the pressure chamber 18 is zero. Further, it is assumed that the velocity and the shear stress of the first liquid 31 and the second liquid 32 at the liquid-liquid interface have continuity. Based on this assumption, if the first liquid 31 and the second liquid 32 form a stable flow of double layers and in parallel, the quartic equation defined in the following formula (formula 2) holds in the parallel flow section:

in (formula 2), η₁Denotes the viscosity, η, of the first liquid₂Denotes the viscosity, Q, of the second liquid₁Representing the flow rate (volume flow rate [ um ] of the first liquid³/us])，Q₂Indicating the flow rate of the second liquid (volume flow rate um³/us]). In other words, the first liquid and the second liquid flow in such a manner that a positional relationship is established according to the flow rate and the viscosity of each liquid in a range satisfying the above quartic equation (formula 2), thereby forming a parallel flow having a stable interface. In this embodiment, it is preferred that parallel flows of the first liquid and the second liquid are formed in the liquid flow channel 13 or at least in the pressure chamber 18. In the case where parallel flows are formed as described above, the first liquid and the second liquid are involved in mixing only due to molecular diffusion at the liquid-liquid interface therebetween, and the liquids flow in parallel in the y direction hardly causing any mixing. Note that the flow of the liquid does not always have to establish a laminar state in a certain region in the pressure chamber 18. In this case, the flow of the liquid at least in the region above the pressure generating element preferably establishes a laminar state.

Even in the case of using immiscible solvents (e.g., oil and water) as the first liquid and the second liquid, for example, as long as (equation 2) is satisfied, stable parallel flows are formed regardless of immiscibility. Meanwhile, even in the case of oil and water, if the interface is disturbed due to a slightly turbulent state of the flow in the pressure chamber, it is preferable that at least the first liquid mainly flows on the pressure generating element and the second liquid mainly flows in the ejection port.

FIG. 5A is a graph showing the flow rate ratio Q based on (equation 2)_r＝Q₂/Q₁Viscosity ratio eta when it becomes several grades_r＝η₂/η₁Phase thickness ratio of the first liquidh_r＝h₁/(h₁+h₂) Graph of the relationship between. Although the first liquid is not limited to water, the "phase thickness ratio of the first liquid" will be referred to as "water phase thickness ratio" hereinafter. The horizontal axis represents the viscosity ratio eta_r＝η₂/η₁The vertical axis represents the water phase thickness ratio h_r＝h₁/(h₁+h₂). With flow ratio Q_rBecomes higher and the water phase thickness ratio h_rBecomes lower. At the same time, at the flow rate ratio Q_rWith the viscosity ratio eta at each level of_rBecomes higher and the water phase thickness ratio h_rBecomes lower. In other words, by controlling the viscosity ratio η between the first liquid and the second liquid_rSum flow ratio Q_rThe ratio of the thickness of the water phase in the liquid flow path 13 (pressure chamber) to the thickness of the water phase h can be set_r(the position of the interface between the first liquid and the second liquid) is adjusted to a prescribed value. In addition, the viscosity ratio eta is_rTo flow rate ratio Q_rFor comparison, FIG. 5A teaches the ratio η to viscosity_rPhase to flow ratio Q_rThickness ratio to water phase h_rA greater effect is produced.

Note that condition a, condition B, and condition C shown in fig. 5A represent the following conditions, respectively:

condition a): at viscosity ratio eta _r1 and flow rate ratio Q_rIn the case of 1, the ratio of the thickness of the aqueous phase h_r＝0.50；

Condition B): at viscosity ratio eta _r10 and flow rate ratio Q_rIn the case of 1, the ratio of the thickness of the aqueous phase h_r0.39; and

condition C): at viscosity ratio eta _r10 and flow rate ratio Q_rIn the case of 10, the ratio of the thickness of the aqueous phase h_r＝0.12。

Fig. 5B is a graph showing flow velocity distributions in the height direction (z direction) of the liquid flow passage 13 (pressure chamber) with respect to the above-described conditions A, B and C, respectively. The horizontal axis represents a normalized value Ux normalized by defining the maximum flow rate value in the condition a as 1 (reference). The vertical axis represents the height from the bottom surface in the case where the height H of the liquid flow channel 13 (pressure chamber) is defined as 1 (reference). On each curve indicating the respective condition, the position of the interface between the first liquid and the second liquid is indicated with a marker. Fig. 5B shows that the position of the interface varies depending on the conditions, such as the position of the interface in condition a is higher than the positions of the interfaces in condition B and condition C. This variation is due to the fact that: in the case where two liquids having mutually different viscosities flow in parallel in the tube while forming laminar flows respectively (and also forming laminar flows as a whole), the interface between the two liquids is formed at a position where the pressure difference caused by the difference in viscosity between the liquids is balanced with the laplace pressure caused by the interfacial tension.

(relationship between flow ratio and thickness ratio of aqueous phase)

FIG. 6 is a graph showing the viscosity ratio eta _r1 and in the viscosity ratio η_rFlow rate ratio Q based on (formula 2) in the case of 10_rThickness ratio to aqueous phase h_rA graph of the relationship between. The horizontal axis represents the flow rate ratio Q_r＝Q₂/Q₁The vertical axis represents the water phase thickness ratio h_r＝h₁/(h₁+h₂). Flow rate ratio Q _r0 corresponds to Q₂The case of 0, where the liquid flow channel is filled with only the first liquid and there is no second liquid in the liquid flow channel. At this time, the water phase thickness ratio h_rEqual to 1. This state is shown by point P in fig. 6.

If the flow rate ratio Q_rSet to a position higher than point P (i.e. if the flow rate Q of the second liquid is₂Set to be greater than 0), the aqueous phase thickness ratio h_rI.e. the thickness h of the aqueous phase of the first liquid₁Becomes smaller and the thickness h of the aqueous phase of the second liquid is₂Becomes larger. In other words, only the state in which the first liquid flows is changed to a state in which the first liquid and the second liquid flow in parallel while defining the interface. Furthermore, the viscosity ratio η between the first liquid and the second liquid _r1 and viscosity ratio η_rThe above tendency can be confirmed in the case of 10.

In other words, to establish an interface in which the first liquid and the second liquid define therebetween while the liquid flowsThe state of flowing along each other in the moving passage 13 is required to satisfy the flow rate ratio Q_r＝Q₂/Q₁>0, or in other words, Q needs to be satisfied₁>0 and Q₂>0. This means that both the first liquid and the second liquid flow in the same direction, i.e. the y-direction.

(transition state in injection operation)

Next, a transition state in the ejection operation in the liquid flow passage 13 and the pressure chamber 18 in which the parallel flows are formed will be described. Fig. 7A to 7E are diagrams schematically showing that the height of the flow channel (pressure chamber) is H [ μm ] in the case where the thickness of the orifice plate is set to T6 μm]A viscosity ratio of η is formed in the liquid flow passage 13 of 20 μm_rGraph of the transition state in the case of the spraying operation performed in the state of the parallel flow of the first liquid and the second liquid of 4.

Fig. 7A shows a state before voltage is applied to the pressure generating element 12. Here, fig. 7A shows that the position of the interface is stabilized at the value Q of the first liquid flowing together by appropriately adjusting₁And value Q of the second liquid₂Thereby realizing the thickness ratio h of the water phase_r0.57 (i.e. the thickness h of the aqueous phase of the first liquid)₁[μm]6 μm).

Fig. 7B shows a state where the voltage application to the pressure generating element 12 is just started. The pressure generating element 12 of the present embodiment is an electrothermal transducer (heater). More specifically, the pressure generating element 12 rapidly generates heat upon receiving a voltage pulse in response to the ejection signal, and causes film boiling in the first liquid in contact therewith. Fig. 7B shows a state where the bubbles 16 are generated by film boiling. With the generation of the bubble 16, the interface between the first liquid 31 and the second liquid 32 moves in the z direction (the height direction of the pressure chamber), whereby the second liquid 32 is pushed out of the ejection orifice 11 in the z direction.

Fig. 7C shows a state in which the volume of the bubbles 16 generated by film boiling increases, whereby the second liquid 32 is further pushed out of the ejection port 11 in the z direction.

Fig. 7D shows a state where the air bubbles 16 communicate with the atmosphere. In the present embodiment, in the contraction phase after the bubble 16 grows to the maximum, the gas-liquid interface moving from the ejection port 11 toward the pressure generating element 12 communicates with the bubble 16.

Fig. 7E shows a state where the liquid droplets 30 are ejected. The liquid ejected from the ejection port 11 at the timing when the bubble 16 communicates with the atmosphere as shown in fig. 7D escapes from the liquid flow passage 13 due to its inertial force, and flies in the z direction in the form of the droplet 30. Meanwhile, in the liquid flow passage 13, the amount of liquid consumed by ejection is supplied from both sides of the ejection opening 11 by the capillary force of the liquid flow passage 13, thereby forming a meniscus at the ejection opening 11 again. Then, as shown in fig. 7A, a parallel flow of the first liquid and the second liquid flowing in the y direction is formed again.

As described above, in the present embodiment, the ejection operation as shown in fig. 7A to 7E is performed in a state where the first liquid and the second liquid flow as parallel flows. To describe in further detail, referring again to fig. 2, the CPU500 circulates the first liquid and the second liquid in the liquid ejection head 1 by using the liquid circulation unit 504 while maintaining constant flow rates of the first liquid and the second liquid. Then, the CPU500 applies voltages to the respective pressure generating elements 12 arranged in the liquid ejection head 1 according to the ejection data while maintaining the above-described control. Here, the flow rate of the first liquid and the flow rate of the second liquid may not be constant all the time depending on the amount of liquid to be ejected.

In the case where the ejection operation is performed in a state where the liquid is flowing, the flow of the liquid may adversely affect the ejection performance. However, in a typical inkjet printhead, the ejection velocity of each droplet is on the order of a few meters per second to tens of meters per second, which is much higher than the flow velocity in the liquid flow channel on the order of a few millimeters per second to a few meters per second. Therefore, even if the ejection operation is performed in a state where the first liquid and the second liquid are flowing in the range of several millimeters per second to several meters per second, the adverse effect on the ejection performance is small.

The present embodiment shows a configuration in which the air bubbles 16 communicate with the atmosphere in the pressure chamber 18. However, the present embodiment is not limited to this configuration. For example, the bubble 16 may communicate with the atmosphere outside (atmosphere side) the ejection port 11. Alternatively, the bubbles 16 may be allowed to disappear without communicating with the atmosphere.

(ratio of liquid contained in ejected droplet)

FIGS. 8A to 8G are diagrams for comparison of height H [ μm ] of a flow channel (pressure chamber)]The water phase thickness ratio h was changed stepwise in a liquid flow channel 13 (pressure chamber) of 20 μm_rA pattern of ejected droplets in the case of (2). In FIGS. 8A to 8F, the water phase thickness ratio h_rEach increment is 0.10, and the water phase thickness ratio h is from the state of FIG. 8F to the state of FIG. 8G_rThe increase is 0.50. Note that each of fig. 8A to 8G ejects a droplet is shown based on a result obtained by performing simulation when the viscosity of the first liquid is set to 1cP, the viscosity of the second liquid is set to 8cP, and the ejection speed of the droplet is set to 11 m/s.

Following the aqueous phase thickness ratio h shown in FIG. 4D_r(＝h₁/(h₁+h₂) Closer to 0, the aqueous phase thickness ratio h of the first liquid 31₁Lower and with the thickness of the aqueous phase ratio h_rCloser to 1, the aqueous phase thickness ratio h of the first liquid 31₁And higher. Therefore, although the second liquid 32 near the ejection opening 11 is mainly contained in the ejected droplets 30, the proportion of the first liquid 31 contained in the ejected droplets 30 also follows the aqueous phase thickness ratio h_rIncreasing closer to 1.

In FIGS. 8A to 8G, the height of the flow channel (pressure chamber) was set to H [ μm ]]In the case of 20 μm, if the ratio of the thicknesses of the aqueous phases is h_r0.00, 0.10 or 0.20, only the second liquid 32 is contained in the ejected droplets 30, and the first liquid 31 is not contained in the ejected droplets 30. However, in the thickness ratio h of the aqueous phase_rIn the case of 0.30 or higher, the first liquid 31 is contained in the ejected droplet 30 in addition to the second liquid 32. In the thickness ratio h of the aqueous phase_rIn the case of 1.00 (i.e., the state where the second liquid is not present), only the first liquid 31 is contained in the ejected liquid droplets 30. As described above, the ratio between the first liquid 31 and the second liquid 32 contained in the ejected liquid droplets 30 is in accordance with the water phase thickness ratio h in the liquid flow passage 13_rBut may vary.

On the other hand, FIGS. 9A to 9E are diagrams for comparing the height H [ μm ] in the flow channel (pressure chamber)]The water phase thickness ratio h was changed stepwise in the liquid flow channel 13 of 33 μm_rA diagram of the ejected droplets 30 in the case of (1). In this case, if the aqueous phase thickness ratio h_r0.36 or lower, only the second liquid 32 is contained in the ejected droplets 30. At the same time, the thickness ratio h of the water phase_rIn the case of 0.48 or higher, the first liquid 31 is contained in the ejected droplets 30 in addition to the second liquid 32.

Meanwhile, FIGS. 10A to 10C are diagrams for comparing the height H [ μm ] in the flow channel (pressure chamber)]The water phase thickness ratio h was changed stepwise in the liquid flow channel 13 of 10 μm_rA diagram of the ejected droplets 30 in the case of (1). In this case, even in the thickness ratio h of the aqueous phase_rIn the case of 0.10, the first liquid 31 is also contained in the ejected liquid droplets 30.

FIG. 11 is a graph showing the ratio H of the height H of the flow channel (pressure chamber) to the thickness H of the water phase when the ratio R of the first liquid 31 contained in the ejected liquid droplets 30 is set to 0%, 20%, and 40% with the ratio R fixed_rGraph of the relationship between. In either ratio R, the desired water phase thickness ratio H increases as the flow channel (pressure chamber) height H becomes larger_rBecomes higher. Note that the ratio R of the first liquid 31 is included as a ratio of the liquid in which the first liquid 31 flows in the liquid flow channel 13 (pressure chamber) to the ejected liquid droplets. In this regard, even if each of the first liquid and the second liquid contains the same component (e.g., water), the water portion contained in the second liquid is not, of course, included in the above-described ratio.

In the case where the ejected droplet 30 contains only the second liquid 32 and the first liquid is eliminated (R ═ 0%), the flow channel (pressure chamber) height H [ μm ═ m]Thickness ratio to aqueous phase h_rThe relationship therebetween plots the locus as shown by the solid line in fig. 11. According to the study conducted by the inventors of the present disclosure, the height H [ μm ] of the flow channel (pressure chamber) can be represented by the following formula (formula 3)]Estimate the water phase thickness ratio h_r：

h_r= 0.1390+0.0155H (formula 3)

Further, in the case where the droplet 30 allowed to be ejected contains 20% of the first liquid (R ═ 20%), it is possible to pass through the height H [ μm ] of the flow channel (pressure chamber) shown in the following formula (formula 4)]Estimate the water phase thickness ratio h_r：

h_r= 0.0982+0.0128H (formula 4)

Further, in the case where the liquid droplet 30 allowed to be ejected contains 40% of the first liquid (R ═ 40%), according to the study of the inventors, it is possible to pass the height H [ μm ] of the flow channel (pressure chamber) shown in the following formula (formula 5)]Estimate the water phase thickness ratio h_r：

h_r= 0.3180+0.0087H (equation 5)

For example, in order for the ejected liquid droplet 30 not to contain the first liquid, the height H [ μm ] of the flow channel (pressure chamber)]In the case of a thickness equal to 20 μm, it is necessary to compare the thicknesses of the aqueous phases by h_rAdjusted to 0.20 or less. At the same time, the height H [ mu ] m of the flow channel (pressure chamber)]In the case of a thickness equal to 33 μm, it is necessary to compare the thicknesses of the aqueous phases by h_rAdjusted to 0.36 or less. In addition, the height H [ mu ] m of the flow channel (pressure chamber)]In the case of a thickness equal to 10 μm, it is necessary to compare the thicknesses of the aqueous phases by h_rAdjust to near zero (0.00).

However, if the water phase thickness ratio h_rIf the setting is too low, the viscosity η of the second liquid must be increased relative to the viscosity and flow rate of the first liquid₂Sum flow rate Q₂. This increase causes a fear of adverse effects associated with an increase in pressure loss. For example, referring again to FIG. 5A, to achieve the aqueous thickness ratio h_r0.20 at a viscosity ratio η_rEqual to 10, the flow ratio Q_rEqual to 5. At the same time, when the same ink is used (i.e., at the same viscosity ratio η)_rIn the case of (1), if the aqueous phase thickness ratio is set to h_rWhen the flow rate is 0.10, the flow rate ratio Q is_rEqual to 15 so that the first liquid is certainly not ejected. In other words, to compare the thickness of the aqueous phase to the thickness h_rAdjustment to 0.10 requires adjustment of the flow ratio Q_rIncreasing the thickness ratio h of the water phase_rFlow ratio of three in case of adjustment to 0.20And this increase may cause a fear of an increase in pressure loss and adverse effects associated therewith.

Therefore, in an attempt to eject only the second liquid 32 while reducing the pressure loss as much as possible, it is preferable to compare the water phase thickness h while satisfying the above conditions_rThe value of (b) is adjusted to be as large as possible. To describe this in detail, referring again to FIG. 11, at the height H [ μm ] of the flow channel (pressure chamber)]In the case of 20 μm, it is preferable to compare the thickness of the aqueous phase with h_rIs adjusted to a value of less than 0.20 and as close to 0.20 as possible. At the same time, the height H [ mu ] m of the flow channel (pressure chamber)]In the case of 33 μm, it is preferable to compare the thickness of the aqueous phase with h_rIs adjusted to a value of less than 0.36 and as close to 0.36 as possible.

Note that the above-described (formula 3), (formula 4), and (formula 5) define values suitable for a general liquid ejection head (i.e., a liquid ejection head that ejects liquid droplets with an ejection speed in a range of 10m/s to 18 m/s). In addition, these values are based on the assumption that the pressure generating element and the ejection port are located at positions opposite to each other and the first liquid and the second liquid flow such that the pressure generating element, the first liquid, the second liquid, and the ejection port are arranged in this order in the pressure chamber.

As described above, according to the present embodiment, by comparing the thickness of the aqueous phase in the liquid flow passage 13 (pressure chamber) with h_rSetting to a predetermined value and thus stabilizing the interface enables stable ejection operation of liquid droplets containing the first liquid and the second liquid in a predetermined ratio.

Incidentally, in order to repeat the above-described spraying operation in a stable state, regardless of the frequency of the spraying operation, it is necessary to obtain the target aqueous phase thickness ratio h_rWhile stabilizing the position of the interface.

Here, a specific method for obtaining the above state will be described with reference to fig. 4A to 4C again. For example, in order to adjust the flow rate Q of the first liquid in the liquid flow passage 13 (pressure chamber)₁It is only necessary to prepare the first pressure difference generating mechanism that sets the pressure at the first outflow port 25 lower than the pressure at the first inflow port 20. In this way, a secondary inflow can be created20 (in the y-direction) to the first outflow 25, and a flow of a first liquid 31. Meanwhile, it is only necessary to prepare the second pressure difference generating mechanism that sets the pressure at the second outflow port 26 lower than the pressure at the second inflow port 21. In this way, a flow of the second liquid 32 directed from the second inlet 21 to the second outlet 26 (in the y-direction) may be generated.

Further, by controlling the first pressure difference generating mechanism and the second pressure difference generating mechanism while maintaining the relationship defined in the following formula (formula 6), it is possible to obtain a desired water phase thickness ratio h in the liquid flow passage 13_rParallel flows of the first liquid and the second liquid are formed flowing along the y-direction so as not to cause any reverse flow in the liquid channel:

P2_in≥P1_in>P1_out≥P2_out(equation 6).

Here, P1_inIs the pressure at the first inlet 20, P1_outIs the pressure at the first outflow opening 25, P2_inIs the pressure at the second inlet 21, P2_outIs the pressure at the second outlet 26. If the predetermined water phase thickness ratio h can be maintained in the liquid flow path (pressure chamber) by controlling the first pressure difference generating means and the second pressure difference generating means as described above_rEven if the position of the interface is disturbed with the ejection operation, the preferable parallel flow can be restored in a short time, and the next ejection operation can be immediately started.

(specific examples of the first liquid and the second liquid)

In the configuration of the above-described embodiment, functions required for the respective liquids are explained, for example, the first liquid serves as a foaming medium causing film boiling, and the second liquid serves as an ejection medium to be ejected from the ejection port to the outside. According to the configuration of the present embodiment, the degree of freedom of the components contained in the first liquid and the second liquid can be increased more than in the related art. Now, the foaming medium (first liquid) and the ejection medium (second liquid) in such a configuration will be described in detail based on specific examples.

The foaming medium (first liquid) in the present embodiment needs to induce film boiling in the foaming medium in the case where the electrothermal converter generates heat and needs to rapidly increase the size of the generated bubbles, or in other words, the foaming medium (first liquid) in the present embodiment needs to have a high critical pressure that can efficiently convert thermal energy into foaming energy. Water is particularly suitable for this medium. Although the molecular weight of water is small (18), water has a high boiling point (100 ℃) and a high surface tension (58.85 dynes/cm at 100 ℃), and thus has a high critical pressure of about 22 MPa. In other words, water causes an extremely high boiling pressure at film boiling. In general, inks prepared by making water contain a coloring material (e.g., a dye or a pigment) are suitable for use in an inkjet printing apparatus that ejects the ink by using film boiling.

However, the foaming medium is not limited to water. Other materials may also be used as the foaming medium as long as such materials have a critical pressure of 2MPa or more (or preferably 5MPa or more). Examples of foaming media other than water include methanol and ethanol. Mixtures of any of these alcohols and water may also be used as the foaming medium. In addition, a material prepared by allowing water to contain the coloring materials (e.g., dyes and pigments) as described above and other additives can be used.

On the other hand, unlike the foaming medium, the ejection medium (second liquid) in the present embodiment does not need to satisfy the physical properties for causing film boiling. Meanwhile, adhesion of the char material to the electrothermal transducer (heater) is liable to deteriorate foaming efficiency by damaging the flatness of the heater surface or reducing the thermal conductivity of the heater. However, the ejection medium is not in direct contact with the heater, and therefore the risk of coking of components of the ejection medium is lower. In particular, with the ejection medium in the present embodiment, the conditions of the physical properties that cause film boiling or avoid scorching are relaxed as compared with the ink used for the conventional thermal head. Thus, the ejection media in this embodiment enjoys greater freedom of the components contained therein. Thus, the ejection medium can more efficiently contain components suitable for the purpose after ejection.

For example, in the present embodiment, the ejection medium can be made to effectively contain a pigment that has not been used before because the pigment is prone to scorch on the heater. Meanwhile, a liquid other than the aqueous ink having an extremely low critical pressure may be used as the ejection medium in the present embodiment. In addition, various inks which are difficult to handle with a conventional thermal head and have special functions, such as ultraviolet-curable inks, conductive inks, Electron Beam (EB) -curable inks, magnetic inks, and solid inks, can also be used as the ejection medium. Meanwhile, the liquid ejection head in the present embodiment can also be used in various applications other than image formation by using any of blood, cultured cells, and the like as an ejection medium. Liquid ejection heads are also suitable for other applications including biochip fabrication, electronic circuit printing, and the like.

In particular, a mode of using water or a liquid similar to water as a first liquid (foaming medium) and using a pigment ink having a higher viscosity than that of water as a second liquid (ejection medium), and ejecting only the second liquid is one of effective uses of the present embodiment. Also in this case, it is effective to set the flow rate ratio Q_r＝Q₂/Q₁To compare the thickness of the water phase with h_rAs low as possible, as shown in fig. 5A. Since there is no limitation on the second liquid, the second liquid may employ the same one of the liquids cited as examples of the first liquid. For example, even if both the liquids are inks containing a large amount of water, one of the inks may be used as the first liquid and the other ink as the second liquid depending on the situation such as the usage pattern.

(spraying media requiring parallel flows of two liquids)

In the case where the liquid to be ejected has been determined, the necessity of causing two liquids to flow in the liquid flow channel (pressure chamber) in such a manner as to form a parallel flow can be determined based on the critical pressure of the liquid to be ejected. For example, the second liquid may be determined as the liquid to be ejected, while the foaming material serving as the first liquid may be prepared only in the case where the critical pressure of the liquid to be ejected is insufficient.

Fig. 12A and 12B are graphs showing the relationship between the water content and the foaming pressure at film boiling in the case where diethylene glycol (DEG) is mixed with water. The horizontal axis in fig. 12A represents the mass ratio (in mass percentage) of water to the liquid, and the horizontal axis in fig. 12B represents the molar ratio of water to the liquid.

As is apparent from fig. 12A and 12B, as the water content (content percentage) decreases, the foaming pressure at film boiling becomes lower. In other words, as the water content becomes lower, the foaming pressure is more reduced, and as a result, the ejection efficiency is reduced. However, the molecular weight of water (18) is significantly less than the molecular weight of diethylene glycol (106). Therefore, even if the mass ratio of water is about 40 wt%, the molar ratio of water is about 0.9, and the foaming pressure ratio is maintained at 0.9. On the other hand, if the mass ratio of water is less than 40 wt%, the foaming pressure ratio is drastically decreased with the molar concentration, as is apparent from fig. 12A and 12B.

As a result, in the case where the mass ratio of water is less than 40 wt%, it is preferable to separately prepare the first liquid as the foaming medium and form parallel flows of the two liquids in the liquid flow passage (pressure chamber). As described above, in the case where the liquid to be ejected has been determined, the necessity of forming a parallel flow in the flow passage (pressure chamber) can be determined based on the critical pressure of the liquid to be ejected (or based on the foaming pressure at the time of film boiling).

(ultraviolet curing ink as an example of an ejection medium)

Preferred components of the ultraviolet-curable ink usable as the ejection medium in the present embodiment will be described as examples. The ultraviolet curable ink is 100% solid. Such ultraviolet curable inks can be classified into inks formed of polymerization reaction components and containing no solvent, and inks containing solvent-based water or a solvent as a diluent. The ultraviolet curable ink actively used in recent years is a 100% solid type ultraviolet curable ink formed of a nonaqueous photopolymerization reaction component which is a monomer or an oligomer and does not contain any solvent. As for the components, the exemplary ultraviolet curable ink contains a monomer as a main component, and also contains a small amount of a photopolymerization initiator, a coloring material, and other additives including a dispersant, a surfactant, and the like. Generally, the components of such an ink include a monomer in the range of 80 to 90 wt%, a photopolymerization initiator in the range of 5 to 10 wt%, a coloring material in the range of 2 to 5 wt%, and the remaining other additives. As described above, even in the case of an ultraviolet curing ink which is difficult to handle by a conventional thermal head, it is possible to use such an ultraviolet curing ink as an ejection medium in the present embodiment and eject the ink to a liquid ejection head by performing a stable ejection operation. This enables printing of an image excellent in image fastness and rubbing resistance as compared with the prior art.

(use of a mixed liquid as an example of ejecting liquid droplets)

Next, a case where the ejected liquid droplets 30 are ejected in a state where the first liquid 31 and the second liquid 32 are mixed at a predetermined ratio will be described. For example, in the case where the first liquid 31 and the second liquid 32 are inks having different colors from each other, these inks form a laminar flow in the liquid flow channel 13 and the pressure chamber 18 without mixing as long as the liquids satisfy a relationship in which the reynolds numbers calculated based on the viscosities and flow rates of the two liquids are smaller than a predetermined value. In other words, by controlling the flow ratio Q between the first liquid 31 and the second liquid 32 in the liquid flow passage and the pressure chamber_rThe thickness ratio h of the water phase can be adjusted_rAnd thus the mixing ratio between the first liquid 31 and the second liquid 32 in the ejected droplets is adjusted to a desired ratio.

For example, assuming that the first liquid is a colorless ink and the second liquid is a cyan ink (or a magenta ink), it is possible to control the flow ratio Q_rAnd light cyan ink (or light magenta ink) is ejected at various coloring material concentrations. Alternatively, assuming that the first liquid is yellow ink and the second liquid is magenta ink, it is possible to control the flow ratio Q_rAnd the red ink is ejected at various hue levels that are gradually different. In other words, if it is feasible to eject droplets prepared by mixing the first liquid and the second liquid at a desired mixing ratio, the range of color reproduction expressed on the printing medium can be expanded more than in the related art by appropriately adjusting the mixing ratio.

Further, the configuration in the present embodiment is effective also in the case of using two types of liquids that need to be mixed together immediately after ejection, rather than mixing the liquids immediately before ejection. For example, in image printing, there are cases where: it is desirable to simultaneously deposit a high-concentration pigment ink having excellent color developability and a resin emulsion (resin EM) having excellent image fastness (e.g., scratch resistance) on a printing medium. However, the pigment component contained in the pigment ink and the solid component contained in the resin EM tend to form aggregates at close interparticle distances, resulting in deterioration of dispersibility. In this regard, if high-concentration EM (emulsion) is used as the first liquid of the present embodiment and high-concentration pigment ink is used as the second liquid of the present embodiment, and parallel flows are formed by controlling the flow rates of these liquids, the two liquids are mixed with each other after ejection and aggregated on a printing medium. In other words, it is possible to maintain an ideal ejection state with high dispersibility, and to obtain an image having high color developability and high fastness after droplet deposition.

Note that, in the case where mixing after ejection is desired as described above, the present embodiment exerts an effect of generating flows of two kinds of liquids in the pressure chamber regardless of the mode of the pressure generating element. In other words, the present embodiment effectively functions also in the case of a configuration using a piezoelectric element as a pressure generating element (for example, a configuration in which the restriction of the critical pressure or the problem of scorching is not feared first).

As described above, according to the present embodiment, by maintaining the predetermined water phase thickness ratio h in the liquid flow passage (pressure chamber)_rWhile driving the pressure generating element 12 in a state where the first liquid and the second liquid are stably made to flow, the ejection operation can be favorably and stably performed.

By driving the pressure generating element 12 in a state where the liquid is made to flow stably, a stable interface can be formed when the liquid is ejected. If the liquid does not flow during the ejection operation of the liquid, the interface is liable to be disturbed by the generation of bubbles, and the print quality is also affected in this case. By driving the pressure generating element 12 while allowing the liquid to flow as described in the present embodiment, the disturbance of the interface due to the generation of the bubbles can be suppressed. Since a stable interface is formed, for example, the content ratios of various liquids contained in the ejected liquid are stable and the print quality is also improved. Further, since the liquid is made to flow before the pressure generating element 12 is driven and the liquid is made to flow continuously even during ejection, it is possible to reduce the time for the meniscus to be formed again in the liquid flow passage (pressure chamber) after the liquid is ejected. Meanwhile, before the driving signal is input to the pressure generating element 12, the flow of the liquid is generated by using a pump or the like loaded in the liquid circulation unit 504. Therefore, the liquid flows at least immediately before the liquid is ejected.

The first liquid and the second liquid flowing in the pressure chamber may be circulated between the pressure chamber and the external unit. If not circulated, a large amount of any first liquid and second liquid that have formed parallel flows in the liquid flow channel and the pressure chamber but have not been ejected will remain inside. Thus, the circulation of the first and second liquids with the external unit makes it possible to use the liquid that has not been ejected to form a parallel flow again

(second embodiment)

The present embodiment also uses the liquid ejection head 1 and the liquid ejection apparatus shown in fig. 1 to 3.

Fig. 13A to 13D are diagrams showing the configuration of the liquid flow channel 13 of the present embodiment. The liquid flow passage 13 of the present embodiment differs from the liquid flow passage 13 described in the first embodiment in that: in addition to the first liquid 31 and the second liquid 32, a third liquid 33 is allowed to flow in the liquid flow passage 13. By allowing the third liquid 33 to flow in the pressure chamber, it is possible to use a foaming medium having a high critical pressure as the first liquid, and use any of inks of different colors, high-concentration resin EM, and the like as the second liquid and the third liquid.

In the present embodiment, the silicon substrate 15 corresponding to the bottom of the liquid flow channel 13 includes a second inflow port 21, a third inflow port 22, a first inflow port 20, a first outflow port 25, a third outflow port 27, and a second outflow port 26 formed in this order along the y-direction. Further, the pressure chamber 18 including the ejection port 11 and the pressure generating element 12 is located substantially at the center between the first inflow port 20 and the first outflow port 25.

The first liquid 31 supplied to the liquid flow channel 13 through the first inflow port 20 flows in the y direction (direction indicated by the arrow) and then flows out of the first outflow port 25. Meanwhile, the second liquid 32 supplied to the liquid flow path 13 through the second inflow port 21 flows in the y direction (direction indicated by the arrow) and then flows out of the second outflow port 26. The third liquid 33 supplied to the liquid flow path 13 through the third inlet 22 flows in the y direction (direction indicated by the arrow) and then flows out of the third outlet 27. That is, in the liquid flow passage 13, the first liquid 31, the second liquid 32, and the third liquid 33 all flow in the y direction in the section between the first inflow port 20 and the first outflow port 25. The pressure generating element 12 is in contact with the first liquid 31, and the second liquid 32 exposed to the atmosphere forms a meniscus near the ejection port 11. The third liquid 33 flows between the first liquid 31 and the second liquid 32.

In the present embodiment, the CPU500 controls the flow rate Q of the first liquid 31 by using the liquid circulation unit 504₁The flow rate Q of the second liquid 32₂And the flow rate Q of the third liquid 33₃And three layers of parallel flows are stably formed as shown in fig. 13D. Then, in a state where three-layer parallel flows are formed as described above, the CPU500 drives the pressure generating elements 12 of the liquid ejection head 1 and ejects liquid droplets from the ejection ports 11. In this way, even if the position of each interface is disturbed with the ejection operation, the three-layer parallel flow is restored in a short time (as shown in fig. 13D), so that the next ejection operation can be immediately started. As a result, it is possible to maintain a good ejection operation of the droplets containing the first to third liquids at a predetermined ratio and obtain an excellent output product.

(third embodiment)

A third embodiment will be described with reference to fig. 14 to 17B. Note that the same components as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted. The present embodiment is characterized in that: the pressure generating element 12 is driven in a state where the first liquid and the second liquid flow side by side in the x direction in the pressure chamber 18. The present embodiment also uses the liquid ejection head 1 and the liquid ejection apparatus shown in fig. 1 and 2.

Fig. 14 is a sectional perspective view of the element plate 50 in the present embodiment. Although the element plate 50 actually has the structure shown in fig. 15A and 15B, fig. 14 shows the element plate 50 with the structures around the second inflow port 21 and the second outflow port 26 partially omitted to describe the general outline of the flow in the element plate 50. The first common supply flow path 23, the first common collection flow path 24, the second common supply flow path 28, and the second common collection flow path 29 are connected to the common liquid flow path 13. Also in the present embodiment, the flow of the liquid in the first common supply flow path 23, the first common collection flow path 24, the second common supply flow path 28, and the second common collection flow path 29 is controlled by the liquid circulation unit 504 described with reference to fig. 2. More specifically, the liquid circulation unit 504 performs control such that the first liquid flowing into the liquid flow path 13 from the first common supply flow path 23 is guided to the first common collection flow path 24, and the second liquid flowing into the liquid flow path 13 from the second common supply flow path 28 is guided to the second common collection flow path 29.

(construction of liquid flow channel in third embodiment)

Fig. 15A to 15C are diagrams for describing details of one of the liquid flow channels 13 formed in the silicon substrate 15. Fig. 15A is a perspective view of the liquid flow passage viewed from the ejection orifice 11 side (+ z direction), and fig. 15B is a perspective view showing a cross section taken along an XVB line in fig. 15A. Also, fig. 15C is an enlarged view of a cross section taken along the XVC line in fig. 15A.

The silicon substrate 15 includes a first inflow port 20, a second inflow port 21, a second outflow port 26, and a first outflow port 25 formed in this order along the y-direction. Further, the first inflow port 20 and the second inflow port 21 are formed in the silicon substrate 15 at positions offset from each other in the x direction. Likewise, the second outflow port 26 and the first outflow port 25 are formed in the silicon substrate 15 at positions offset from each other along the x-direction. The first inflow port 20 is connected to a first common supply flow channel 23, the first outflow port 25 is connected to a first common collection flow channel 24, the second inflow port 21 is connected to a second common supply flow channel 28, and the second outflow port 26 is connected to a second common collection flow channel 29 (see fig. 14).

According to the above configuration, the first liquid 31 supplied from the first common supply flow path 23 to the liquid flow path 13 through the first inflow port 20 flows in the y direction (indicated by a solid arrow), and then is collected from the first outflow port 25 into the first common collection flow path 24. Meanwhile, the second liquid 32 supplied from the second common supply flow passage 28 to the liquid flow passage 13 flows once in the-x direction and then flows while changing its direction to the y direction (indicated by a dotted arrow). The second liquid 32 is then collected from the second outflow openings 26 into the second common collection flow channel 29.

At a position on the upstream side of the second inflow port 21 in the y direction, the first liquid flowing in from the first inflow port 20 occupies the entire area in the width direction (x direction). By flowing the second liquid 32 from the second inflow port 21 once in the-x direction, the flow of the first liquid 31 can be partially pushed to reduce the width of the flow. As a result, a state in which the first liquid 31 and the second liquid 32 flow side by side in the x direction in the liquid flow passage can be established, as shown in fig. 15A and 15C.

Here, the pressure generating element 12 and the ejection port 11 are formed so as to be offset from each other in the x direction. More specifically, the pressure generating element 12 is formed at a position offset from the ejection orifice 11 toward the flow of the first liquid 31. As a result, the first liquid 31 mainly flows on the pressure generating element 12 side, and the second liquid 32 mainly flows on the ejection port 11 side. Therefore, by applying pressure to the first liquid 31 using the pressure generating element 12, the second liquid pressurized through the interface can be ejected from the ejection opening 11.

In the present embodiment, the flow rate of the first liquid 31 and the flow rate of the second liquid 32 are adjusted in accordance with the physical properties of the first liquid 31 and the physical properties of the second liquid 32, so that the first liquid 31 flows on the pressure generating element 12, and the second liquid 32 flows in the ejection port 11, as described above.

(theoretical condition for forming parallel flow in laminar flow state in the third embodiment)

Next, a condition for forming a parallel flow in which the first liquid and the second liquid flow side by side in the x direction will be described with reference to fig. 15C. In fig. 15C, the distance in the x direction (width of flow) of the liquid flow channel 13 is defined as W. Meanwhile, the distance from the wall surface of the liquid flow channel 13 to the liquid-liquid interface between the first liquid 31 and the second liquid 32 (the water phase thickness of the second liquid) is defined as w₂And the distance from the liquid-liquid interface to the opposite wall surface of the liquid flow channel (the thickness of the aqueous phase of the first liquid) is defined as w₁. These definitions lead to W ═ W₁+w₂. At this time, regarding the boundary conditions in the liquid flow passage 13 and the pressure chamber 18, as in the first embodiment, the velocities of the liquids on the wall surfaces of the liquid flow passage 13 and the pressure chamber 18 are assumed to be zero, and the velocities and the shear stresses of the first liquid 31 and the second liquid 32 at the liquid-liquid interface are assumed to have continuity. Based on this assumption, if the first liquid 31 and the second liquid 32 form parallel stable flows flowing side by side in the x direction, the quartic equation described previously in (equation 2) holds in the section of the parallel flow. In the present embodiment, the value H shown in (formula 2) corresponds to the value W, in which the value H₁Corresponding to the value w₁And the value h therein₂Corresponding to the value w₂. Thus, as in the first embodiment, it may be based on the viscosity ratio η_r＝η₂/η₁Sum flow ratio Q_r＝Q₂/Q₁(which are the viscosities eta of the first liquid, respectively)₁Sum flow rate Q₁Viscosity eta relative to the second liquid₂Sum flow rate Q₂Ratio of (d) to adjust the aqueous phase thickness ratio h_r＝w₁/(w₁+w₂). Further, as in the first embodiment, in order to establish a state in which the first liquid and the second liquid flow in the liquid flow passage 13 while defining the interface therebetween, it is necessary to satisfy the flow rate ratio Q_r＝Q₂/Q₁>0, or in other words, Q needs to be satisfied₁>0 and Q₂>0。

(transitional state in the injection operation in the third embodiment)

Next, a transition state in the injection operation in the third embodiment will be described with reference to fig. 16A to 16H. Fig. 16A to 16H are schematic diagrams showing that the viscosity ratio is η when the thickness of the orifice plate is set to T6 μm_rThe first liquid and the second liquid of 4 were H [ μm ] in the height of the flow channel (length in z direction)]A diagram of a transition state in the case where the ejection operation is performed in a state of flowing in the liquid flow channel 13 of 20 μm. Fig. 16A to 16H show the sequence of the injection process over time. Here, by adjusting the layer thicknesses of the first liquid 31 and the second liquid 32, only the first liquid 31 is brought into contact with the effective area of the pressure generating element 12. Meanwhile, the inside of the ejection port 11 is filled with only the second liquid 32. If the ejection operation is performed in this state, bubbles are generated from the first liquid 31 in contact with the pressure generating element 12, and the bubbles 16 thus generated can eject the liquid from the ejection port 11. Although the second liquid 32 filling the ejection opening is dominant in the ejected droplets 30, the ejected droplets 30 also contain a certain amount of the first liquid 31 pushed out by the bubbles 16. The amount of the first liquid 31 pushed out by the bubbles 16 can be changed by changing the water phase thickness ratio h_rTo adjust.

Next, a ratio between the first liquid and the second liquid contained in the ejected droplets will be described with reference to fig. 17A and 17B. According to the thickness ratio h of the water phase_r(＝w₁/(w₁+w₂) Close to 0, the thickness w of the aqueous phase of the first liquid 31₁The size is reduced; and the ratio h is dependent on the thickness of the aqueous phase_rApproximately 1, the thickness w of the aqueous phase of the first liquid 31₁Becomes larger. According to the thickness ratio h of the water phase_rNear 0, the amount of the first liquid 31 pushed out by the bubbles 16 becomes small. Therefore, the ejected droplets 30 mainly contain the second liquid 32 occupying the inside of the ejection opening 11. On the other hand, in the thickness ratio h of the aqueous phase_rWith a reasonably large size, the first liquid starts to enter the ejection openings 11 (as shown in fig. 17A), and the amount of the first liquid 31 pushed out by the bubbles 16 also increases. As a result, the percentage of the first liquid 31 contained in the ejected liquid droplets 30 increases. Note thatFig. 17A shows a simplified interface between the first liquid 31 and the second liquid 32.

As described above, the ratio between the first liquid 31 and the second liquid 32 contained in the ejected liquid droplets 30 is dependent on the water phase thickness ratio h in the liquid flow passage 13_rBut may vary. In the case where the first liquid 31 is used as the foaming medium and it is desirable that the second liquid 32 is the main component of the ejected liquid droplets 30, for example, it is necessary to adjust the water phase thickness ratio h_rSo that the ejection openings 11 are filled with only the second liquid, as shown in fig. 15C. However, if the aqueous phase thickness ratio h_rSet too low, the percentage of the pressure-generating element 12 in contact with the second liquid 32 increases (as shown in fig. 17B), which leads to a fear of instability in foaming due to adhesion of the coked portion of the second liquid 32 to the pressure-generating element 12. Further, if the contact area of the pressure generating element 12 with the first liquid 31 is reduced, foaming energy is reduced, whereby ejection efficiency is lowered, thus causing a fear of occurrence of adverse effects associated therewith. Therefore, in order to maintain stable ejection, it is necessary to adjust the water phase thickness ratio h_rTo suppress the amount of the second liquid 32 that comes into contact with the pressure generating element 12.

(fourth embodiment)

A fourth embodiment will be described with reference to fig. 18A to 18C and fig. 19A to 19C. Note that the same components as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted. The present embodiment is characterized in that: the first liquid 31 and the second liquid 32 flow in such a manner that the second liquid 32 is sandwiched by a layer of the first liquid 31. The present embodiment also uses the liquid ejection head 1 and the liquid ejection apparatus shown in fig. 1 and 2. Fig. 18A is a perspective view of the liquid flow passage of the present embodiment viewed from the ejection opening 11 side (+ z direction side), and fig. 18B is a perspective view showing a cross section taken along line xviib in fig. 18A. Further, fig. 18C is an enlarged view of a cross section taken along line XVIIIC in fig. 18A.

In the present embodiment, in the case where the first liquid 31 flows into the liquid flow passage 13 from the first inflow port 20 and meets the second liquid 32 flowing in from the second inflow port 21, the first liquid 31 bypasses the flow of the second liquidFlows between the second liquid 32 and the walls of the flow passage, as indicated by the arrow a in fig. 18A. The second liquid 32 flows from the second inflow port 21 toward the second outflow port 26. As a result, a liquid-liquid interface is formed in the order of the first liquid 31, the second liquid 32, and the first liquid 31 from one wall of the flow channel, so that the second liquid 32 is sandwiched by the layer of the first liquid 31, as shown in fig. 18C. The pressure generating elements 12 are arranged on the silicon substrate 15 in a symmetrical manner with respect to the ejection opening 11 in the x direction. Therefore, the two pressure generating elements 12 are in contact with the respective layers of the first liquid 31, and the ejection openings 11 are mainly filled with the second liquid 32. If the pressure generating elements 12 are driven in this state, the first liquid 31 in contact with each pressure generating element 12 forms bubbles to cause liquid droplets mainly containing the second liquid 32 to be ejected out of the ejection ports. Meanwhile, since the pressure generating elements 12 are symmetrically arranged with respect to the ejection opening 11, the ejected droplets 30 can be ejected in a shape symmetrical in the x direction to achieve high-quality printing. According to the interface form shown in fig. 18C, the second liquid 32 is sandwiched by a layer of the first liquid 31. In this regard, the relationship between the thickness of the aqueous phase and the flow rate as defined in (equation 2) does not apply in a strict sense to this configuration. However, the aqueous phase thickness tends to vary in proportion to the flow rate of each liquid phase. Specifically, if it is necessary to increase the phase thickness of the second liquid 32 in the case where the viscosity of the first liquid 31 is substantially the same as the viscosity of the second liquid 32, it is possible to increase the flow rate ratio Q by increasing the flow rate of the second liquid 32_rTo make the phase thickness of the second liquid 32 thicker.

Next, an ejection process of liquid in the present embodiment will be described with reference to fig. 19A to 19C. Fig. 19A to 19C are diagrams showing the ejection process in the case where the phase thickness ratio between the first liquid 31 and the second liquid 32 was changed while the height of the flow channel was set to 14 μm, the thickness of the orifice plate was set to 6 μm, and the diameter of the ejection orifice was set to 10 μm. In each of fig. 19A to 19C, the injection process over time is shown from the top to the bottom.

Fig. 19A shows an ejection process in the case where the phase thickness of the second liquid 32 is adjusted to be less than 10 μm (the diameter of the ejection orifice is equal to 10 μm). Both the second liquid 32 and the first liquid 31 exist in the ejection openings 11. If the ejection operation is performed in this state, the liquid can be ejected by forming bubbles of the first liquid 31 in contact with the pressure generating element 12. Since both the first liquid and the second liquid exist in the ejection opening 11, the ejected liquid droplets 30 are a mixed liquid of these liquids.

Fig. 19B shows the ejection process in the case where the phase thickness of the second liquid 32 is adjusted to coincide with the diameter of the ejection opening (equal to 10 μm). If the ejection operation is performed in this state, the liquid can be ejected by forming bubbles of the first liquid 31 in contact with the pressure generating element. Although the ejected liquid droplets 30 mainly contain the second liquid 32 occupying the inside of the ejection port, a part of the first liquid 31 is also ejected as a part of the ejected liquid droplets due to foaming. Therefore, such liquid droplets are a mixed liquid of the second liquid and the first liquid, and the percentage of the first liquid is smaller than that in the case of fig. 19A.

Fig. 19C shows the ejection process in the case where the phase thickness of the second liquid 32 is adjusted to 12 μm, which is larger than the diameter of the ejection opening 11. The pressure generating element 12 is located at a position in contact with only the first liquid, so that the liquid can be ejected by generating bubbles of the first liquid. A part of the second liquid 32 located inside and around the ejection openings is pushed out of the ejection openings 11, and the droplets 30 thus ejected are substantially composed of the second liquid 32. The percentage of the component in the ejected droplets 30 may be controlled by adjusting the phase thickness of the second liquid 32, as described above. In particular, in the case where the ejected droplets 30 are formed only from the second liquid, it is effective to set the phase thickness of the second liquid to be larger than the diameter of the ejection opening, as shown in fig. 19C. However, if the second liquid 32 comes into contact with the pressure generating elements 12 due to an increase in its phase thickness, there is a fear that foaming is not stabilized due to adhesion of a scorched portion of the second liquid 32 to any of the pressure generating elements 12. Further, if the contact area of each pressure generating element 12 with the first liquid 31 is reduced, foaming energy is reduced, so that ejection efficiency is lowered, thus causing a fear of occurrence of adverse effects associated therewith. Therefore, it is preferable to position the position of each liquid-liquid interface between the second liquid 32 and the first liquid 31 at a position from the ejection port to the corresponding pressure generating element, as shown in fig. 19C.

(fifth embodiment)

A fifth embodiment will be described with reference to fig. 20 to 21B. Note that the same components as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted. The present embodiment is characterized in that: the first liquid 31 and the second liquid 32 flow in such a manner that the second liquid 32 is sandwiched by a layer of the first liquid 31. In this case, the two pressure-generating elements 12 are provided on the wall surface near the ejection opening 11, not on the wall surface near the silicon substrate 15. Fig. 20A is a perspective view of the liquid flow channel 13 of the present embodiment viewed from the ejection opening 11 side (+ z direction side), and fig. 20B is a perspective view showing a cross section taken along the line XXB in fig. 20A. Further, fig. 20C is an enlarged view of a cross section taken along the line XXC in fig. 20A.

The difference between the present embodiment and the fourth embodiment is in the location of the pressure generating element 12. In the present embodiment, the pressure generating element 12 is arranged within the pressure chamber 18 and at a position on the orifice plate 14 that is symmetrical with respect to the ejection port 11 in the x direction. As shown in fig. 20C, the pressure generating elements 12 are in contact with the respective layers of the first liquid 31, and the ejection openings 11 are mainly filled with the second liquid 32. If the pressure generating element 12 is driven in this state, the first liquid 31 in contact with the pressure generating element 12 forms bubbles, and droplets mainly containing the second liquid 32 are ejected from the ejection openings 11. Since the pressure generating elements 12 are symmetrically arranged with respect to the ejection opening 11, the ejected droplets can be ejected in a shape symmetrical in the x direction to achieve high-quality printing.

In the case where the pressure generating elements 12 are provided on the silicon substrate 15 as in the fourth embodiment, if the distance between the ejection opening 11 and each pressure generating element 12 is set too large, there is a case where the pressure at the time of generating bubbles in the first liquid cannot be sufficiently transmitted to the second liquid and the liquid cannot be appropriately ejected. On the other hand, by providing the pressure generating elements 12 on the orifice plate 14 as in the present embodiment, even if the distance between the ejection port 11 and each pressure generating element 12 is increased, it is possible to avoid a situation in which the pressure due to the generation of bubbles cannot be sufficiently transmitted to the second liquid. As a result, according to the present embodiment, it is possible to eject the liquid without being affected by the distance between the ejection port 11 and each pressure generating element 12 (or in other words, the height of the liquid flow passage). Therefore, the height of the liquid flow passage can be increased. Therefore, the present embodiment is capable of not only stably ejecting liquid but also reducing deterioration of the refill speed, which is generally problematic in the case of using a very viscous liquid, by increasing the height of the liquid flow passage.

Fig. 21A and 21B are diagrams showing the ejection process in the case where the phase thickness ratio between the first liquid 31 and the second liquid 32 was changed while the height of the flow channel was set to 14 μm, the thickness of the orifice plate was set to 6 μm, and the diameter of the ejection orifice was set to 10 μm. In each of fig. 21A and 21B, the injection process over time is shown from top to bottom.

In fig. 21A, the phase thickness ratio is adjusted so that the ejection opening 11 is filled only with the second liquid 32, while the first liquid 31 is mainly in contact with each pressure-generating element 12. If the ejection operation is performed in this state, the ejected liquid droplets 30 are substantially composed of the second liquid 32, so that the first liquid 31 in the liquid droplets can be minimized. Fig. 21B shows an example in which the phase thickness of the second liquid 32 is set to be smaller than the diameter of the ejection opening. At this time, the first liquid 31 is included in the ejection port 11. If the ejection operation is performed in this state, the ejected droplets 30 mainly contain the first liquid 31, but at the same time also partially contain the second liquid 32. As described above, by adjusting the water phase thickness ratio, the components to be contained in the ejected liquid droplets 30 can be controlled, and thus the content ratio can be adjusted according to the intended purpose.

Note that in any of the third, fourth, and fifth embodiments, the third liquid described in the second embodiment may also be caused to flow in the pressure chamber. Further, the ejection method is not limited to a configuration in which the pressure generating element and the ejection port are located at positions opposing each other. It is also possible to employ a so-called side shooter mode in which the ejection port is located at a position at an angle equal to or smaller than 90 degrees with respect to the direction in which the pressure generating element generates the pressure.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A liquid ejection head comprising:

a pressure chamber configured to allow the first liquid and the second liquid to flow inside;

a pressure generating element configured to apply pressure to a first liquid;

an ejection port configured to eject a second liquid,

a first inflow port through which a first liquid flows into the pressure chamber; and

a second inlet port through which a second liquid flows into the pressure chamber, wherein

The liquid ejection head is configured to eject the second liquid from the ejection port by causing the pressure generating element to apply pressure to the first liquid in a state where the first liquid flows in a flow direction intersecting an ejection direction in which the second liquid is ejected from the ejection port while being in contact with the pressure generating element in the pressure chamber and the second liquid flows in the flow direction along the first liquid, and the first liquid and the second liquid are caused to stably flow.

2. The liquid ejection head according to claim 1, wherein the liquid ejection head is configured to cause the first liquid and the second liquid to form a laminar flow in the pressure chamber.

3. The liquid ejection head according to claim 1, wherein the liquid ejection head is configured to form the first liquid and the second liquid into parallel flows in the pressure chamber.

4. The liquid ejection head according to claim 1, wherein the liquid ejection head is configured to flow the first liquid and the second liquid side by side in an ejection direction of the second liquid in the pressure chamber.

5. The liquid ejection head according to claim 1, wherein the liquid ejection head is configured to flow the first liquid and the second liquid side by side in the pressure chamber in a direction intersecting with an ejection direction of the second liquid and intersecting with a flow direction of the first liquid and the second liquid in the pressure chamber.

6. The liquid ejection head according to claim 4, wherein the liquid ejection head satisfies an expression defined as follows:

h₁/(h₁+h₂)≤-0.1390+0.0155H，

wherein, H [ mu ] m]Is the height of the pressure chamber in the direction of ejection of the second liquid, h₁[μm]Is a thickness of the first liquid in the pressure chamber in an ejection direction of the second liquid, and h₂Is the thickness of the second liquid in the pressure chamber in the ejection direction of the second liquid.

7. The liquid ejection head according to claim 1, wherein the liquid ejection head is configured such that a flow rate of the second liquid is equal to or greater than a flow rate of the first liquid in the pressure chamber.

8. The liquid ejection head according to claim 1, wherein the liquid ejection head is configured to prevent the first liquid from being included in the liquid to be ejected from the ejection ports.

9. The liquid ejection head according to claim 4,

the third liquid also flows in the pressure chamber, and

the third liquid flows along the first liquid and the second liquid in the pressure chamber in such a way that the first liquid, the third liquid and the second liquid are arranged in the listed order.

10. The liquid ejection head according to claim 1, wherein the first liquid is any one of water and an aqueous liquid having a critical pressure equal to or greater than 2 MPa.

11. The liquid ejection head according to claim 1, wherein the second liquid is any one of an emulsion and an aqueous ink containing a pigment.

12. The liquid ejection head according to claim 1, wherein the second liquid is a solid type ultraviolet curable ink.

13. The liquid ejection head according to claim 1, further comprising:

a first outflow port through which the first liquid flows out of the pressure chamber; and

a second outlet through which the second liquid flows out of the pressure chamber.

14. The liquid ejection head according to claim 13, wherein the second flow inlet, the first flow outlet, and the second flow outlet are formed by being arranged in the listed order along the flow direction of the first liquid and the second liquid in the pressure chamber.

15. The liquid ejection head according to claim 13, wherein the second inflow port and the second outflow port are formed at positions offset from the first inflow port and the first outflow port in a direction intersecting an ejection direction of the second liquid and intersecting a flow direction of the first liquid and the second liquid in the pressure chamber.

16. The liquid ejection head according to claim 15, wherein the pressure generating element is formed at a position deviated from the ejection orifice in a direction intersecting an ejection direction of the second liquid and intersecting a flow direction of the first liquid and the second liquid in the pressure chamber.

17. The liquid ejection head according to claim 13, wherein the first liquid, the second liquid, and the first liquid flow in the pressure chambers side by side along a direction intersecting an ejection direction of the second liquid and intersecting a flow direction of the first liquid and the second liquid in the pressure chambers while being arranged in the listed order.

18. The liquid ejection head according to claim 1, wherein the first liquid flowing in the pressure chamber circulates between the pressure chamber and an external unit.

19. A liquid ejection apparatus comprising a liquid ejection head, the liquid ejection head comprising:

a pressure generating element configured to apply pressure to a first liquid;

an ejection port configured to eject a second liquid,

20. A liquid ejection module for configuring a liquid ejection head, the liquid ejection head comprising:

a pressure generating element configured to apply pressure to a first liquid;

an ejection port configured to eject a second liquid,

The liquid ejection head is configured to eject the second liquid from the ejection port by causing the pressure generating element to apply pressure to the first liquid in a state where the first liquid flows in a flow direction intersecting an ejection direction in which the second liquid is ejected from the ejection port while being in contact with the pressure generating element in the pressure chamber and the second liquid flows in the flow direction along the first liquid, and the first liquid and the second liquid are caused to stably flow, and

the liquid ejection head is formed by arranging a plurality of liquid ejection modules.