JP6877970B2 - Liquid discharge head and liquid discharge method - Google Patents

Description

The present invention relates to a liquid discharge head and a liquid discharge method, and more particularly to a configuration in the vicinity of a discharge port for discharging a liquid.

The droplets ejected from the liquid ejection head represented by the inkjet head are generally divided into a main droplet and an auxiliary droplet (hereinafter, also referred to as satellite) accompanying the main droplet and ejected. The main drop lands at a desired position on the recording medium, but it is difficult for satellites to control the landing position. In a liquid discharge head that requires high image quality and high throughput, the deterioration of recording image quality due to satellites may be noticeable. Further, among the satellites, particularly minute satellites do not reach the recording medium and become floating ink droplets (hereinafter, also referred to as mist). The mist stains the recording device, and the dirt on the recording device may be transferred to the recording medium to stain the recording medium.

As a means for preventing such deterioration of image quality due to satellites, Patent Document 1 discloses a method of reducing the occurrence of satellites by forming the discharge port into a shape other than a circle. Patent Document 2 discloses a method of shortening the length of droplets (hereinafter, also referred to as tail length) by reducing the distance between the recording element and the discharge port to reduce the generation of satellites. ..

Japanese Patent Application Laid-Open No. 2008-290380 U.S. Patent Application Publication No. 2011/0205303

As a result of the examination by the present inventor, it has been found that the tail length of the droplet cannot be further shortened in the configurations of Patent Documents 1 and 2, and it is difficult to suppress satellites.
An object of the present invention is to provide a liquid discharge head and a liquid discharge method capable of shortening the tail length of a droplet.

The liquid discharge head of the present invention includes a recording element that generates heat energy used for discharging the liquid, a pressure chamber provided with the recording element inside, a discharge port for discharging the liquid, and a discharge port and a pressure chamber. A discharge port that communicates with the pressure chamber, a liquid supply path that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and a liquid recovery path that communicates with the pressure chamber on the opposite side of the liquid supply path with respect to the pressure chamber and collects the liquid. , the has. Bubbles are generated in the pressure chamber by the heat energy, the generated bubbles enter the inside of the discharge port, and the liquid is discharged from the discharge port by the pressure of the bubbles. The discharge port has two protrusions protruding toward the center of the discharge port, and the two protrusions are located on a straight line passing through the center and are provided on both sides with respect to the center, and the straight line is a liquid supply path. At an angle of 45 degrees or more with respect to the flow path axis connecting the liquid recovery path and the liquid recovery path, air bubbles that have entered the inside of the discharge port communicate with the atmosphere outside the discharge port.

According to the present invention, it is possible to provide a liquid discharge head and a liquid discharge method capable of shortening the tail length of a droplet and suppressing satellites.

It is a figure which shows the schematic structure of the recording apparatus which concerns on 1st application example of this invention. It is a figure which shows the 1st circulation path through which the liquid of a recording apparatus circulates. It is a figure which shows the 2nd circulation path of a recording apparatus. It is a perspective view of the liquid discharge head which concerns on 1st application example of this invention. It is an exploded perspective view of the liquid discharge head of FIG. It is a figure which shows the structure of the 1st | 3rd flow path member which comprises the flow path member which the liquid discharge head of FIG. 4 has. It is a figure for demonstrating the connection relation of each flow path in a flow path member. FIG. 7 is a cross-sectional view taken along the line EE of FIG. It is a perspective view and an exploded view of a discharge module. It is a figure which shows the structure of the recording element substrate. It is a perspective view which shows the structure of the recording element substrate and the lid member including the BB cross section of FIG. It is a top view which shows the adjacent part of the recording element substrate in two adjacent discharge modules partially enlarged. It is a figure which shows the schematic structure of the recording apparatus which concerns on the 2nd application example of this invention. It is a perspective view of the liquid discharge head which concerns on the 2nd application example of this invention. It is an exploded perspective view of the liquid discharge head of FIG. It is a figure which shows the structure of the 1st and 2nd flow path members which form the flow path member which the liquid discharge head of FIG. 14 has. It is a figure for demonstrating the connection relation of the liquid in a recording element substrate and a flow path member. FIG. 17 is a sectional view taken along line FF of FIG. It is a perspective view and an exploded view of a discharge module. It is a figure which shows the structure of the recording element substrate. It is a conceptual diagram which shows the inside of the liquid discharge head which concerns on 1st Embodiment. It is a schematic diagram which shows the transition process of a discharge phenomenon. It is a figure which shows the relationship between the pressure profile inside a bubble and the internal pressure of a bubble. It is a figure which shows the relationship between the distance from a recording element to a discharge port, and the atmospheric communication time Tth. It is a figure which shows the relationship between the thickness of the discharge port forming member, the height of an inlet flow path, and the atmospheric communication time Tth. It is a figure which shows the relationship between the distance from a recording element to a discharge port, and the atmospheric communication position dz of a bubble. It is a figure which shows the relationship between the distance from a recording element to a discharge port, and the atmospheric communication position dx of a bubble. It is a conceptual diagram which shows the droplet which is discharged from a discharge port. It is a figure which showed the atmospheric communication time Tth for various outlet shapes. It is a figure which showed the atmospheric communication position dx with respect to various discharge port shapes. It is a conceptual diagram which shows the inside of the liquid discharge head which concerns on other embodiment. It is a conceptual diagram which shows the inside of the liquid discharge head which concerns on 2nd Embodiment. It is a conceptual diagram which shows the inside of the liquid discharge head which concerns on a reference example. It is a conceptual diagram which shows the ejection of the droplet in the 2nd Embodiment and the reference example.

Hereinafter, the liquid discharge head according to the application example and the embodiment of the present invention will be described with reference to the drawings. Although various technically preferable conditions are attached to the application examples and embodiments described below, the present invention is not limited to these application examples, embodiments and conditions as long as the idea of the present invention is followed. Absent.
Hereinafter, examples of embodiments of the present invention will be described with reference to the drawings. However, the following description does not limit the scope of the present invention.
The present application example and the embodiment are inkjet recording devices (recording devices) in which a liquid such as ink is circulated between the tank and the liquid ejection head, but other forms may be used. For example, two tanks may be provided on the upstream side and the downstream side of the liquid discharge head without circulating the ink, and the ink in the pressure chamber may be flowed by flowing the ink from one tank to the other tank. ..
Further, the present application example and the embodiment are so-called line type heads having a length corresponding to the width of the recording medium, but the so-called serial type (page wide type) in which recording is performed while scanning the recording medium. ), The present invention can also be applied to the liquid discharge head. Examples of the serial type liquid ejection head include a configuration in which one recording element substrate for black ink and one recording element substrate for color ink are mounted. However, the present invention is not limited to this, and a short line head shorter than the width of the recording medium is created by arranging several recording element substrates so as to overlap the discharge ports in the discharge port row direction, and the recording medium is used. It may be in the form of scanning against.

(First application example)
Hereinafter, application columns to which the present invention can be preferably applied will be described.
(Explanation of inkjet recording device)
FIG. 1 shows a schematic configuration of a device for ejecting a liquid, particularly an inkjet recording apparatus 1000 (hereinafter, also referred to as a recording apparatus) for ejecting ink for recording according to the present invention. The recording device 1000 includes a transport unit 1 for transporting the recorded medium 2 and a line-type liquid discharge head 3 arranged substantially orthogonal to the transport direction of the recorded medium 2, and continuously transmits a plurality of recorded media 2. Alternatively, it is a line-type recording device that continuously records in one pass while carrying it intermittently. The recording medium 2 is not limited to cut paper, and may be continuous roll paper. The liquid discharge head 3 can perform full-color printing with CMYK ink (cyan, magenta, yellow, black). As will be described later, the liquid supply means, which is a supply path for supplying ink to the liquid discharge head, the main tank, and the buffer tank (see FIG. 2) are fluidly connected. Further, an electric control unit that transmits electric power and a discharge control signal to the liquid discharge head 3 is electrically connected to the liquid discharge head 3. The liquid path and the electric signal path in the discharge head 3 will be described later.

(Explanation of the first circulation route)
FIG. 2 is a schematic diagram showing a first circulation path, which is one form of a circulation path applied to the recording device of this application example. FIG. 2 is a diagram in which the liquid discharge head 3 is fluidly connected to the first circulation pump (high pressure side) 1001, the first circulation pump (low pressure side) 1002, the buffer tank 1003, and the like. Note that FIG. 2 shows only the path through which one color of the CMYK ink flows for the sake of simplification of the explanation, but in reality, the circulation path for four colors is the liquid ejection head 3 and the recording device main body. It is provided in. The buffer tank 1003 as a sub tank connected to the main tank 1006 has an air communication port (not shown) that communicates the inside and the outside of the tank, and can discharge air bubbles in the ink to the outside. The buffer tank 1003 is also connected to the replenishment pump 1005. The replenishment pump 1005 discharges (discharges) ink from the discharge port of the liquid discharge head, such as recording by discharging ink and recovering suction, and when the ink is consumed by the liquid discharge head 3, the amount of ink consumed. Is transferred from the main tank 1006 to the buffer tank 1003.
The two first circulation pumps 1001 and 1002 have a role of drawing ink from the liquid connection portion 111 of the liquid discharge head 3 and flowing it to the buffer tank 1003. As the first circulation pump, a positive displacement pump having a quantitative liquid feeding capacity is preferable. Specific examples include tube pumps, gear pumps, diaphragm pumps, syringe pumps, etc. For example, a general constant flow valve or relief valve may be placed at the pump outlet to ensure a constant flow rate. it can. When the liquid discharge head 3 is driven, a certain amount of ink flows in the common supply path 211 and the common recovery flow path 212 by the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002, respectively. It is preferable that the flow rate is set so that the temperature difference between the recording element substrates 10 in the liquid discharge head 3 does not affect the recording image quality. However, if an excessively large flow rate is set, the negative pressure difference becomes too large in each recording element substrate 10 due to the influence of the pressure loss of the flow path in the liquid discharge unit 300, and the density unevenness of the image occurs. Therefore, it is preferable to set the flow rate while considering the temperature difference and the negative pressure difference between the recording element substrates 10.

The negative pressure control unit 230 is provided between the path between the second circulation pump 1004 and the liquid discharge unit 300. The negative pressure control unit 230 maintains the pressure on the downstream side (that is, the liquid discharge unit 300 side) of the negative pressure control unit 230 at a preset constant pressure even when the flow rate of the circulation system fluctuates due to the difference in the recording duty. It has a function to operate as if it were. As the two pressure adjusting mechanisms constituting the negative pressure control unit 230, any mechanism can be used as long as the pressure downstream of itself can be controlled with fluctuations within a certain range around a desired set pressure. May be used. As an example, a mechanism similar to a so-called "decompression regulator" can be adopted. When a pressure reducing regulator is used, as shown in FIG. 2, it is preferable that the second circulation pump 1004 pressurizes the upstream side of the negative pressure control unit 230 via the liquid supply unit 220. In this way, the influence of the head pressure on the liquid discharge head 3 of the buffer tank 1003 can be suppressed, so that the degree of freedom in the layout of the buffer tank 1003 in the recording device 1000 can be expanded. The second circulation pump 1004 may be any pump having a lift pressure equal to or higher than a certain pressure within the range of the ink circulation flow rate used when driving the liquid discharge head 3, and a turbo type pump, a positive displacement type pump, or the like can be used. Specifically, a diaphragm pump or the like can be applied. Further, instead of the second circulation pump 1004, for example, a head tank arranged with a certain head difference with respect to the negative pressure control unit 230 can also be applied.

As shown in FIG. 2, the negative pressure control unit 230 includes two pressure adjusting mechanisms in which different control pressures are set. Of the two negative pressure adjustment mechanisms, the relatively high pressure setting side (denoted as H in FIG. 2) and the relatively low pressure setting side (denoted as L in FIG. 2) pass through the liquid supply unit 220, respectively. Therefore, it is connected to the common supply path 211 and the common recovery flow path 212 in the liquid discharge unit 300. The liquid discharge unit 300 is provided with a common supply path 211, a common recovery flow path 212, and an individual supply flow path 213a and an individual recovery flow path 213b communicating with each recording element substrate 10. Since the individual supply flow path 213a communicates with the common supply path 211 and the common recovery flow path 212, a part of the ink passes from the common supply flow path 211 through the internal flow path of the recording element substrate 10 and the common recovery flow. A flow (arrow in FIG. 2) flowing to the road 212 is generated. This is because the pressure adjusting mechanism H is connected to the common supply flow path 211 and the pressure adjusting mechanism L is connected to the common recovery flow path 212, so that a differential pressure is generated between the two common flow paths.

In this way, in the liquid discharge unit 300, some ink passes through each recording element substrate 10 while flowing ink so as to pass through the common supply flow path 211 and the common recovery flow path 212, respectively. A flow occurs. Therefore, the heat generated in each recording element substrate 10 can be discharged to the outside of the recording element substrate 10 by the flow of the common supply flow path 211 and the common recovery flow path 212. Further, with such a configuration, when recording is performed by the liquid discharge head 3, ink can be caused to flow even in a discharge port or a pressure chamber where recording is not performed, so that the ink thickens at that portion. Can be suppressed. Further, the thickened ink and foreign substances in the ink can be discharged to the common recovery flow path 212. Therefore, the liquid discharge head 3 of this application example enables high-speed and high-quality recording.

(Explanation of the second circulation route)
FIG. 3 is a schematic diagram showing a second circulation path, which is a circulation form different from the first circulation path described above, among the circulation paths applied to the recording device of this application example. The main differences from the above-mentioned first circulation path are as follows. First, the two pressure adjusting mechanisms constituting the negative pressure control unit 230 both control the pressure on the upstream side of the negative pressure control unit 230 with fluctuations within a certain range centered on a desired set pressure (so-called "" It has a mechanical component that has the same function as the "back pressure regulator". Next, the second circulation pump 1004 acts as a negative pressure source for reducing the pressure on the downstream side of the negative pressure control unit 230. Further, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are arranged on the upstream side of the liquid discharge head, and the negative pressure control unit 230 is arranged on the downstream side of the liquid discharge head.

The negative pressure control unit 230 of FIG. 3 preliminarily changes the pressure on its upstream side (that is, the liquid discharge unit 300 side) even if the flow rate fluctuates due to a change in the recording duty when recording is performed by the liquid discharge head 3. It operates so as to stay within a certain range around the set pressure. As shown in FIG. 3, it is preferable that the second circulation pump 1004 pressurizes the downstream side of the negative pressure control unit 230 via the liquid supply unit 220. In this way, the influence of the head pressure of the buffer tank 1003 on the liquid discharge head 3 can be suppressed, so that the layout selection range of the buffer tank 1003 in the recording device 1000 can be widened. Instead of the second circulation pump 1004, for example, a head tank arranged with a predetermined head difference with respect to the negative pressure control unit 230 can be applied.

Similar to the embodiment shown in FIG. 2, the negative pressure control unit 230 shown in FIG. 3 includes two pressure adjusting mechanisms in which different control pressures are set. Of the two negative pressure adjustment mechanisms, the high pressure setting side (denoted as H in FIG. 3) and the low pressure setting side (denoted as L in FIG. 3) pass through the liquid supply unit 220 and enter the liquid discharge unit 300, respectively. It is connected to the common supply path 211 and the common recovery flow path 212. The pressure of the common supply flow path 211 is made relatively higher than the pressure of the common recovery flow path 212 by the two negative pressure adjusting mechanisms. As a result, an ink flow is generated from the common supply flow path 211 to the common recovery flow path 212 via the individual flow path 213 and the internal flow path of each recording element substrate 10 (arrow in FIG. 3). As described above, in the second circulation path, the same ink flow state as in the first circulation path can be obtained in the liquid ejection unit 300, but there are two advantages different from those in the case of the first circulation path.

The first advantage is that the negative pressure control unit 230 is arranged on the downstream side of the liquid discharge head 3 in the second circulation path, so that there is a concern that dust and foreign matter generated from the negative pressure control unit 230 may flow into the head. Is less. The second advantage is that in the second circulation path, the maximum value of the required flow rate supplied from the buffer tank 1003 to the liquid discharge head 3 is smaller than in the case of the first circulation path. The reason is as follows. Let A be the total flow rate in the common supply flow path 211 and the common recovery flow path 212 when circulating during the recording standby. The value of A is defined as the minimum flow rate required to keep the temperature difference in the liquid discharge unit 300 within a desired range when the temperature of the liquid discharge head 3 is adjusted during recording standby. Further, the discharge flow rate when ink is discharged from all the discharge ports of the liquid discharge unit 300 (at the time of total discharge) is defined as F. Then, in the case of the first circulation path (FIG. 2), the set flow rates of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 become A, so that the liquid discharge required at the time of total discharge The maximum value of the liquid supply amount to the head 3 is A + F.

On the other hand, in the case of the second circulation path (FIG. 3), the amount of liquid supplied to the liquid discharge head 3 required during recording standby is the flow rate A. Then, the amount of supply to the liquid discharge head 3 required at the time of total discharge is the flow rate F. Then, in the case of the second circulation path, the total value of the set flow rates of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002, that is, the maximum value of the required supply flow rate is the larger of A or F. Is the value of. Therefore, as long as the liquid discharge unit 300 having the same configuration is used, the maximum value (A or F) of the required supply amount in the second circulation path is larger than the maximum value (A + F) of the required supply flow rate in the first circulation path. Will always be smaller. Therefore, in the case of the second circulation path, the degree of freedom of the applicable circulation pump is increased. For example, a low-cost circulation pump having a simple configuration can be used, or a load of a cooler (not shown) installed in the main body side path can be used. Can be reduced, and the cost of the recording device main body can be reduced. This advantage increases as the value of A or F becomes relatively large, and is more beneficial for line heads having a longer length in the longitudinal direction.

However, on the other hand, there is also a point that the first circulation path is more advantageous than the second circulation path. That is, in the second circulation path, since the flow rate flowing through the liquid discharge unit 300 during the recording standby is maximized, the lower the recording duty of the image, the higher the negative pressure is applied to each discharge port. Therefore, in particular, the flow path width (length in the direction orthogonal to the ink flow direction) of the common supply flow path 211 and the common recovery flow path 212 is reduced to reduce the head width (length in the lateral direction of the liquid discharge head). If the size is reduced, the effect of satellite droplets may increase. This is because a high negative pressure is applied to the discharge port in a low duty image in which unevenness is easily visible. On the other hand, in the case of the first circulation path, since a high negative pressure is applied to the discharge port when a high duty image is formed, it is difficult to visually recognize even if satellites are generated, and the influence on the image is small. There is. The selection of the two circulation paths can be made in light of the specifications of the liquid discharge head and the recording device main body (discharge flow rate F, minimum circulation flow rate A, and flow path resistance in the head).

(Explanation of liquid discharge head configuration)
The configuration of the liquid discharge head 3 according to the first application example will be described. 4 (a) and 4 (b) are perspective views of the liquid discharge head 3 according to this application example. The liquid discharge head 3 is a line-type liquid discharge head in which 15 recording element substrates 10 capable of discharging inks of four colors of C / M / Y / K are arranged in a straight line (arranged in-line). As shown in FIG. 4A, the liquid discharge head 3 has a recording element substrate 10, a signal input terminal 91 and a power supply terminal 92 electrically connected via the flexible wiring board 40 and the electrical wiring board 90. To be equipped. The signal input terminal 91 and the power supply terminal 92 are electrically connected to the control unit of the recording device 1000, and supply the discharge drive signal and the power required for discharge to the recording element substrate 10, respectively. By consolidating the wiring by the electric circuit in the electric wiring board 90, the number of signal output terminals 91 and power supply terminals 92 can be reduced as compared with the number of recording element boards 10. As a result, the number of electrical connections that need to be removed when assembling the liquid discharge head 3 to the recording device 1000 or when replacing the liquid discharge head can be reduced. As shown in FIG. 4B, the liquid connection portions 111 provided at both ends of the liquid discharge head 3 are connected to the liquid supply system of the recording device 1000. As a result, CMYK four-color ink is supplied from the supply system of the recording device 1000 to the liquid discharge head 3, and the ink that has passed through the liquid discharge head 3 is collected to the supply system of the recording device 1000. In this way, the inks of each color can be circulated through the path of the recording device 1000 and the path of the liquid ejection head 3.

FIG. 5 shows an exploded perspective view of each component or unit constituting the liquid discharge head 3. The liquid discharge unit 300, the liquid supply unit 220, and the electrical wiring board 90 are attached to the housing 80. The liquid supply unit 220 is provided with a liquid connection portion 111 (FIG. 3), and inside the liquid supply unit 220, each color communicating with each opening of the liquid connection portion 111 in order to remove foreign substances in the supplied ink. Another filter 221 (FIGS. 2 and 3) is provided. The two liquid supply units 220 are each provided with a filter 221 for two colors. The ink that has passed through the filter 221 is supplied to the negative pressure control unit 230 arranged on the supply unit 220 corresponding to each color. The negative pressure control unit 230 is a unit composed of pressure adjusting valves for each color. The negative pressure control unit 230 is located in the supply system of the recording device 1000 (the supply system on the upstream side of the liquid discharge head 3), which is generated when the ink flow rate fluctuates due to the functions of valves and spring members provided inside the negative pressure control unit 230. Significantly attenuates pressure loss changes. Therefore, it is possible to stabilize the negative pressure change on the downstream side (liquid discharge unit 300 side) of the pressure control unit within a certain range. As described with reference to FIG. 2, two pressure regulating valves for each color are built in the negative pressure control unit 230 for each color, and different control pressures are set for each. The two pressure regulating valves communicate with the common supply flow path 211 in the liquid discharge unit 300 on the high pressure side and the common recovery flow path 212 on the low pressure side via the liquid supply unit 220.

The housing 80 is composed of a liquid discharge unit support portion 81 and an electric wiring board support portion 82, supports the liquid discharge unit 300 and the electric wiring board 90, and secures the rigidity of the liquid discharge head 3. The electric wiring board support portion 82 is for supporting the electric wiring board 90, and is fixed to the liquid discharge unit support portion 81 by screwing. The liquid discharge unit support portion 81 has a role of correcting the warp and deformation of the liquid discharge unit 300 and ensuring the relative position accuracy of the plurality of recording element substrates 10, thereby suppressing streaks and unevenness in the recorded material. Therefore, the liquid discharge unit support portion 81 preferably has sufficient rigidity, and as the material, a metal material such as SUS or aluminum, or a ceramic such as alumina is preferable. The liquid discharge unit support portion 81 is provided with openings 83 and 84 into which the joint rubber 100 is inserted. The ink supplied from the liquid supply unit 220 is guided to the third flow path member 70 constituting the liquid discharge unit 300 via the joint rubber.

The liquid discharge unit 300 includes a plurality of discharge modules 200 and a flow path member 210, and a cover member 130 is attached to the surface of the liquid discharge unit 300 on the recording medium side. Here, as shown in FIG. 5, the cover member 130 is a member having a frame-like surface provided with a long opening 131, and the recording element substrate 10 and the sealing included in the discharge module 200 are sealed from the opening 131. The stopper 110 (FIG. 9) is exposed. The frame portion around the opening 131 has a function as a contact surface of a cap member that caps the liquid discharge head 3 during recording standby. Therefore, an adhesive, a sealing material, a filler, or the like is applied along the periphery of the opening 131 to fill the irregularities and gaps on the discharge port surface of the liquid discharge unit 300, so that a closed space is formed at the time of capping. It is preferable to do so.

Next, the configuration of the flow path member 210 included in the liquid discharge unit 300 will be described. As shown in FIG. 5, the flow path member 210 is a stack of a first flow path member 50, a second flow path member 60, and a third flow path member 70. The flow path member 210 is a flow path member for distributing the ink supplied from the liquid supply unit 220 to each discharge module 200 and returning the ink recirculated from the discharge module 200 to the liquid supply unit 220. The flow path member 210 is fixed to the liquid discharge unit support portion 81 with screws, whereby warpage and deformation of the flow path member 210 are suppressed.

6 (a) to 6 (f) are views showing the front surface and the back surface of each flow path member of the first to third flow path members. FIG. 6A shows the surface of the first flow path member 50 on the side on which the discharge module 200 is mounted, and FIG. 6F shows the liquid discharge unit support portion 81 of the third flow path member 70. The surface on the abutting side is shown. The first flow path member 50 and the second flow path member 60 are joined so that the contact surfaces of the flow path members, FIGS. 6 (b) and 6 (c), face each other, and the second flow path is formed. The member and the third flow path member are joined so that the contact surfaces of the flow path members, FIGS. 6 (d) and 6 (e), face each other. Eight extending in the longitudinal direction of the flow path member by the common flow path grooves 62 and 71 formed in the respective flow path members by joining the second flow path member 60 and the third flow path member 70. Common flow path is formed. As a result, a set of the common supply flow path 211 and the common recovery flow path 212 is formed in the flow path member 210 for each color (FIG. 7). The communication port 72 of the third flow path member 70 communicates with each hole of the joint rubber 100, and fluidly circulates with the liquid supply unit 220. A plurality of communication ports 61 are formed on the bottom surface of the common flow path groove 62 of the second flow path member 60, and communicate with one end of the individual flow path groove 52 of the first flow path member 50. A communication port 51 is formed at the other end of the individual flow path groove 52 of the first flow path member 50, and fluidly communicates with the plurality of discharge modules 200 via the communication port 51. The individual flow path groove 52 makes it possible to consolidate the flow paths toward the center of the flow path member.

The first to third flow path members are preferably made of a material having corrosion resistance to ink and a low coefficient of linear expansion. As the material, for example, a composite material (resin material) in which an inorganic filler such as silica fine particles or fibers is added to the base material can be preferably used. Examples of the base material include alumina, LCP (liquid crystal polymer), PPS (polyphenylsulfone), PSF (polysulfone), and modified PPE (polyphenylene ether). As a method for forming the flow path member 210, three flow path members may be laminated and bonded to each other, or when a resin composite resin material is selected as the material, a joining method by welding may be used.

Next, the connection relationship of each flow path in the flow path member 210 will be described with reference to FIG. 7. FIG. 7 shows a part of the flow path in the flow path member 210 formed by joining the first to third flow path members from the surface side of the first flow path member 50 on which the discharge module 200 is mounted. It is an enlarged perspective view. The flow path member 210 includes a common supply flow path 211 (211a, 211b, 211c, 211d) extending in the longitudinal direction of the liquid discharge head 3 for each color, and a common recovery flow path 212 (212a, 212b, 212c, 212d). It is provided. A plurality of individual supply channels (213a, 213b, 213c, 213d) formed by the individual channel grooves 52 are connected to the common supply channel 211 of each color via a communication port 61. Further, a plurality of individual recovery channels (214a, 214b, 214c, 214d) formed by the individual channel grooves 52 are connected to the common recovery channel 212 of each color via a communication port 61. With such a flow path configuration, ink can be concentrated on the recording element substrate 10 located at the center of the flow path member from each common supply flow path 211 via the individual supply flow path 213. Ink can be recovered from the recording element substrate 10 to each common recovery flow path 212 via the individual recovery flow path 214.

FIG. 8 is a view showing a cross section taken along the line EE of FIG. As shown in this figure, each individual collection flow path (214a, 214c) communicates with the discharge module 200 via a communication port 51. Although only the individual recovery channels (214a and 214c) are shown in FIG. 8, in another cross section, the individual supply channels 213 and the discharge module 200 communicate with each other as shown in FIG. A flow path is formed in the support member 30 and the recording element substrate 10 included in each discharge module 200. This flow path is a flow path for supplying the ink from the first flow path member 50 to the recording element 15 (FIG. 10) provided on the recording element substrate 10, and a part or all of the ink supplied to the recording element 15. Is collected (circulated) in the first flow path member 50. Here, the common supply flow path 211 of each color is connected to the negative pressure control unit 230 (high pressure side) of the corresponding color via the liquid supply unit 220, and the common recovery flow path 212 is the negative pressure control unit 230 (the negative pressure control unit 230 (high pressure side). It is connected to the low pressure side) via the liquid supply unit 220. The negative pressure control unit 230 creates a differential pressure (pressure difference) between the common supply flow path 211 and the common recovery flow path 212. Therefore, in the liquid discharge head of the present application example in which each flow path is connected as shown in FIGS. 7 and 8, the common supply flow path 211 to the individual supply flow path 213a to the recording element substrate 10 to the individual recovery flow for each color. A flow is generated in order from the path 213b to the common recovery flow path 212.

(Explanation of discharge module)
FIG. 9A shows a perspective view of one discharge module 200, and FIG. 9B shows an exploded view thereof. As a method of manufacturing the discharge module 200, first, the recording element substrate 10 and the flexible wiring substrate 40 are adhered to a support member 30 provided with a liquid communication port 31 in advance. After that, the terminal 16 on the recording element substrate 10 and the terminal 41 on the flexible wiring board 40 are electrically connected by wire bonding, and then the wire bonding portion (electrical connection portion) is covered with a sealing material 110 and sealed. .. The terminal 42 on the side of the flexible wiring board 40 opposite to the recording element board 10 is electrically connected to the connection terminal 93 (see FIG. 5) of the electrical wiring board 90. Since the support member 30 is a support that supports the recording element substrate 10 and is a flow path member that fluidly communicates the recording element substrate 10 and the flow path member 210, the flatness is high and sufficiently high. Those that can be reliably bonded to the recording element substrate are preferable. As the material, for example, alumina or a resin material is preferable.

(Explanation of the structure of the recording element substrate)
The configuration of the recording element substrate 10 in this application example will be described. FIG. 10A shows a plan view of the surface of the recording element substrate 10 on the side where the discharge port 13 is formed, and FIG. 10B shows an enlarged view of the portion shown by A in FIG. 10A. FIG. 10 (c) shows a plan view of the back surface of FIG. 10 (a). As shown in FIG. 10A, the ejection port forming member 12 of the recording element substrate 10 is formed with four rows of ejection ports corresponding to each ink color. Hereinafter, the direction in which the discharge port row in which the plurality of discharge ports 13 are arranged extends is referred to as the "discharge port row direction".

As shown in FIG. 10B, a recording element 15 which is a heat generating element for foaming ink by heat energy is arranged at a position corresponding to each ejection port 13. The partition wall 22 partitions the pressure chamber 23 including the recording element 15 inside. The recording element 15 is electrically connected to the terminal 16 of FIG. 10A by an electric wiring (not shown) provided on the recording element substrate 10. The recording element 15 generates heat based on a pulse signal input from the control circuit of the recording device 1000 via the electric wiring board 90 (FIG. 5) and the flexible wiring board 40 (FIG. 9) to boil the ink. Ink is ejected from the ejection port 13 by the force of foaming due to this boiling. As shown in FIG. 10B, a liquid supply path 18 extends on one side and a liquid recovery path 19 extends on the other side along each discharge port row. The liquid supply path 18 and the liquid recovery path 19 are flow paths extending in the discharge port row direction provided on the recording element substrate 10, and communicate with the discharge port 13 via the supply port 17a and the recovery port 17b, respectively.

As shown in FIGS. 10C and 11, a sheet-shaped lid member 20 is laminated on the back surface of the surface of the recording element substrate 10 on which the discharge port 13 is formed, and the lid member 20 will be described later. A plurality of openings 21 communicating with the liquid supply path 18 and the liquid recovery path 19 are provided. In this application example, the lid member 20 is provided with three openings 21 for one liquid supply path 18 and two openings 21 for one liquid recovery path 19. From the viewpoint of pressure loss, it is preferable that a plurality of openings 21 are provided for the flow path. In the present invention, it is not necessary for each flow path to have a plurality of openings 21, and at least two openings 21 may be provided for any of the flow paths of the liquid supply path 18 and the liquid recovery path 19. For example, the liquid discharge head may have a configuration in which the liquid supply path 18 has two openings 21 and the liquid recovery path 19 has one opening 21. As shown in FIG. 10B, each opening 21 of the lid member 20 communicates with the plurality of communication ports 51 shown in FIG. 6A. As shown in FIG. 11, the lid member 20 has a function as a lid forming a part of the walls of the liquid supply path 18 and the liquid recovery path 19 formed on the substrate 11 of the recording element substrate 10. The lid member 20 preferably has sufficient corrosion resistance against ink, and from the viewpoint of preventing color mixing, the opening shape and opening position of the opening 21 are required to have high accuracy. Therefore, it is preferable to use a photosensitive resin material or a silicon plate as the material of the lid member 20 and to provide the opening 21 by a photolithography process. As described above, the lid member changes the pitch of the flow path by the opening 21, and it is desirable that the lid member is thin in consideration of the pressure loss, and it is desirable that the lid member is composed of a film-like member.

Next, the flow of ink in the recording element substrate 10 will be described. FIG. 11 is a perspective view showing a cross section of the recording element substrate 10 and the lid member 20 on the BB plane in FIG. 10A. The recording element substrate 10 is formed by laminating a substrate 11 formed of Si and a discharge port forming member 12 formed of a photosensitive resin, and a lid member 20 is bonded to the back surface of the substrate 11. A recording element 15 is formed on one surface side of the substrate 11 (FIG. 10), and a groove forming a liquid supply path 18 and a liquid recovery path 19 extending along the discharge port row is formed on the back surface side thereof. Is formed. The liquid supply path 18 and the liquid recovery path 19 formed by the substrate 11 and the lid member 20 are connected to the common supply flow path 211 and the common recovery flow path 212 in the flow path member 210, respectively, and the liquid supply path 18 and A differential pressure is generated between the liquid recovery path 19 and the liquid recovery path 19. When ink is ejected from a plurality of ejection ports 13 of the liquid ejection head 3 and recording is performed, the following flow occurs at the ejection ports that are not performing the ejection operation. That is, due to this differential pressure, the ink in the liquid supply path 18 provided in the substrate 11 flows to the liquid recovery path 19 via the supply port 17a, the pressure chamber 23, and the recovery port 17b (arrow C in FIG. 10). Flow shown in). By this flow, in the discharge port 13 and the pressure chamber 23 where recording is suspended, thickening ink, bubbles, foreign substances, etc. generated by evaporation from the discharge port 13 can be collected in the liquid recovery path 19. Further, it is possible to suppress thickening of ink in the discharge port 13 and the pressure chamber 23. The ink collected in the liquid recovery path 19 passes through the opening 21 of the lid member 20 and the liquid communication port 31 of the support member 30 (see FIG. 9B), and the communication port 51 in the flow path member 210 and the individual recovery flow path. It is collected in the order of 214 and the common collection flow path 212. This ink is finally collected in the supply path of the recording device 1000.

That is, the ink supplied from the recording device main body to the liquid discharge head 3 flows in the following order, and is supplied and recovered. The ink first flows into the inside of the liquid discharge head 3 from the liquid connection portion 111 of the liquid supply unit 220. Next, the ink is applied to the joint rubber 100, the communication port 72 and the common flow path groove 71 provided in the third flow path member, the common flow path groove 62 and the communication port 61 provided in the second flow path member, and the first flow path. It is supplied in the order of the individual flow path groove 52 and the communication port 51 provided in the member. After that, the liquid is supplied to the pressure chamber 23 through the liquid communication port 31 provided in the support member 30, the opening 21 provided in the lid member, the liquid supply path 18 provided in the substrate 11, and the supply port 17a in this order. Of the ink supplied to the pressure chamber 23, the ink not discharged from the discharge port 13 is supplied to the recovery port 17b and the liquid recovery path 19 provided on the substrate 11, the opening 21 provided in the lid member, and the support member 30. It flows through the provided liquid communication ports 31 in order. After that, the ink is provided in the communication port 51 and the individual flow path groove 52 provided in the first flow path member, the communication port 61 and the common flow path groove 62 provided in the second flow path member, and the third flow path member 70. The common flow path groove 71, the communication port 72, and the joint rubber 100 flow in this order. Then, the ink flows from the liquid connection portion 111 provided in the liquid supply unit to the outside of the liquid discharge head 3. In the form of the first circulation path shown in FIG. 2, the ink flowing in from the liquid connection portion 111 is supplied to the joint rubber 100 after passing through the negative pressure control unit 230. In the form of the second circulation path shown in FIG. 3, the ink recovered from the pressure chamber 23 passes through the joint rubber 100 and then passes from the liquid connection portion 111 to the outside of the liquid discharge head via the negative pressure control unit 230. Flow to.

Further, as shown in FIGS. 2 and 3, not all the ink that has flowed in from one end of the common supply flow path 211 of the liquid discharge unit 300 is supplied to the pressure chamber 23 via the individual supply flow path 213a. .. There is also ink that flows from the other end of the common supply flow path 211 to the liquid supply unit 220 without flowing into the individual supply flow path 213a. In this way, by providing the path for flowing without passing through the recording element substrate 10, even when the recording element substrate 10 having a fine flow path having a large flow resistance as in this application example is provided, the ink is provided. It is possible to suppress the backflow of the circulating flow of. In this way, in the liquid discharge head of this application example, it is possible to suppress thickening of ink in the pressure chamber and the vicinity of the discharge port, so that it is possible to suppress defects in the discharge direction and non-discharge, and as a result, high-quality recording is performed. Can be done.

(Explanation of positional relationship between recording element substrates)
FIG. 12 is a plan view showing a partially enlarged view of an adjacent portion of the recording element substrate in two adjacent discharge modules. As shown in FIG. 10, in this application example, a substantially parallelogram-shaped recording element substrate is used. As shown in FIG. 12, each discharge port row (14a to 14d) in which the discharge ports 13 of each recording element substrate 10 are arranged is arranged so as to be inclined at a constant angle with respect to the transport direction of the recording medium. As a result, at least one discharge port in the adjacent portion between the recording element substrates 10 overlaps in the transport direction of the recording medium. In FIG. 12, the two discharge ports on the D line are in an overlapping relationship with each other. With such an arrangement, even if the position of the recording element substrate 10 deviates slightly from the predetermined position, the black streaks and white spots in the recorded image can be made inconspicuous by the drive control of the overlapping discharge ports. it can. It is also possible to arrange the plurality of recording element substrates 10 in a straight line (in-line) instead of in a staggered arrangement. Also in this case, it is possible to take measures against black streaks and white spots at the joints between the recording element substrates 10 while suppressing an increase in the length of the liquid discharge head 10 in the transport direction of the recording medium by the configuration as shown in FIG. it can. In this application example, the main plane of the recording element substrate is a parallelogram, but the present invention is not limited to this, and even when a rectangular, trapezoidal, or other shape recording element substrate is used, the present invention is not limited to this. The configuration can be preferably applied.

(Second application example)
The configuration of the inkjet recording device 1000 and the liquid ejection head 3 according to the second application example of the present invention will be described. In the following description, only the parts different from the first application example will be mainly described, and the description of the same parts as the first application example will be omitted.

(Explanation of inkjet recording device)
An inkjet recording apparatus according to a second application of the present invention is shown in FIG. The recording device 1000 of the second application example is different from the first application example in that full-color recording is performed on the recording medium by arranging four liquid ejection heads 3 for single colors corresponding to each ink of CMYK in parallel. In the first application example, the number of discharge port rows that can be used per color is one row, whereas in the present application example 2, the number of discharge port rows that can be used per color is 20 rows (FIG. 19). (A)). Therefore, by appropriately allocating the recorded data to a plurality of discharge port rows and recording the data, very high-speed recording becomes possible. Further, even if there is a discharge port that does not discharge, reliability can be improved by interpolating the discharge from the discharge port of another row located at a position corresponding to the transport direction of the recording medium with respect to the discharge port. Improved and suitable for commercial printing and the like. Similar to the first application example, the supply system of the recording device 1000, the buffer tank 1003, and the main tank 1006 (FIG. 2) are fluidly connected to each liquid discharge head 3. Further, an electric control unit that transmits electric power and a discharge control signal to the liquid discharge head 3 is electrically connected to each liquid discharge head 3.

(Explanation of circulation route)
As the liquid circulation path between the recording device 1000 and the liquid discharge head 3, the first and second circulation paths shown in FIG. 2 or 3 can be used as in the first application example.
(Explanation of liquid discharge head structure)
The structure of the liquid discharge head 3 according to the second application example of the present invention will be described. 14 (a) and 14 (b) are perspective views of the liquid discharge head 3 according to this application example. The liquid discharge head 3 is an inkjet type line-type recording head that includes 16 recording element substrates 10 arranged in a straight line in the longitudinal direction of the liquid discharge head 3 and can record with one color of ink. The liquid discharge head 3 includes a liquid connection portion 111, a signal input terminal 91, and a power supply terminal 92, as in the first application example. However, since the liquid discharge head 3 of this application example has more discharge port rows than the first application example, signal output terminals 91 and power supply terminals 92 are arranged on both sides of the liquid discharge head 3. This is to reduce the voltage drop and signal transmission delay that occur in the wiring portion provided on the recording element substrate 10.

FIG. 15 is a perspective exploded view of the liquid discharge head 3, and each component or unit constituting the liquid discharge head 3 is divided and displayed according to its function. The roles of each unit and member and the order of liquid flow in the liquid discharge head are basically the same as those in the first application example, but the functions for ensuring the rigidity of the liquid discharge head are different. In the first application example, the rigidity of the liquid discharge head was mainly secured by the liquid discharge unit support portion 81, but in the liquid discharge head of the second application example, the second flow path member 60 included in the liquid discharge unit 300 is used. The rigidity of the liquid discharge head is ensured. The liquid discharge unit support portion 81 in this application example is connected to both ends of the second flow path member 60, and the liquid discharge unit 300 is mechanically coupled to the carriage of the recording device 1000 to form a liquid discharge head 3. Perform positioning. The liquid supply unit 220 including the negative pressure control unit 230 and the electrical wiring board 90 are coupled to the liquid discharge unit support portion 81. A filter (not shown) is built in each of the two liquid supply units 220. The two negative pressure control units 230 are set to control the pressure with different, relatively high and low negative pressures. Further, when the negative pressure control units 230 on the high pressure side and the low pressure side are installed at both ends of the liquid discharge head 3 as shown in this figure, the common supply flow path 211 extending in the longitudinal direction of the liquid discharge head 3 The ink flows in the common recovery flow path 212 face each other. In this way, heat exchange is promoted between the common supply flow path 211 and the common recovery flow path 212, and the temperature difference between the two common flow paths is reduced. Therefore, there is an advantage that a temperature difference is less likely to occur in each of the plurality of recording element substrates 10 provided along the common flow path, and recording unevenness due to the temperature difference is less likely to occur.

Next, the details of the flow path member 210 of the liquid discharge unit 300 will be described. As shown in FIG. 15, the flow path member 210 is a stack of the first flow path member 50 and the second flow path member 60, and distributes the ink supplied from the liquid supply unit 220 to each discharge module 200. .. Further, the flow path member 210 functions as a flow path member for returning the ink recirculated from the discharge module 200 to the liquid supply unit 220. The second flow path member 60 of the flow path member 210 is a flow path member in which the common supply flow path 211 and the common recovery flow path 212 are formed therein, and also has a function of mainly carrying the rigidity of the liquid discharge head 3. Have. Therefore, as the material of the second flow path member 60, a material having sufficient corrosion resistance against ink and high mechanical strength is preferable. Specifically, SUS, Ti, alumina and the like can be preferably used.

FIG. 16A shows the surface of the first flow path member 50 on the side where the discharge module 200 is mounted, and FIG. 16B shows the back surface of the first flow path member 50, which is in contact with the second flow path member 60. It is a figure which showed the surface of. Unlike the first application example, the first flow path member 50 in the second application example is an array of a plurality of members corresponding to each discharge module 200 adjacent to each other. By adopting the structure divided in this way, it is possible to correspond to the length of the liquid discharge head by arranging a plurality of modules, so that it is a relatively long scale corresponding to, for example, B2 size and longer. It can be particularly preferably applied to the liquid discharge head of. As shown in FIG. 16A, the communication port 51 of the first flow path member 50 fluidly communicates with the discharge module 200, and as shown in FIG. 16B, individual communication of the first flow path member 50. The port 53 fluidly communicates with the communication port 61 of the second flow path member 60. FIG. 16C shows the surface of the second flow path member 60 on the side where it comes into contact with the first flow path member 50, and FIG. 15D shows a cross section of the central portion of the second flow path member 60 in the thickness direction. 16 (e) is a view showing a surface of the second flow path member 60 on the side that comes into contact with the liquid supply unit 220. The functions of the flow path and the communication port of the second flow path member 60 are the same as the functions of one color in the first application example. One of the common flow path grooves 71 of the second flow path member 60 is the common supply flow path 211 shown in FIG. 17, and the other is the common recovery flow path 212, respectively, along the longitudinal direction of the liquid discharge head 3. Ink is supplied from one end side to the other end side. In this application example, unlike the first application example, the ink flow directions of the common supply flow path 211 and the common recovery flow path 212 are opposite to each other.

FIG. 17 is a perspective view showing the connection relationship of the ink between the recording element substrate 10 and the flow path member 210. As shown in FIG. 17, a set of a common supply flow path 211 and a common recovery flow path 212 extending in the longitudinal direction of the liquid discharge head 3 are provided in the flow path member 210. The communication port 61 of the second flow path member 60 is connected in position with the individual communication port 53 of each first flow path member 50, and is a common supply flow path from the communication port 72 of the second flow path member 60. A liquid supply path is formed that communicates with the communication port 51 of the first flow path member 50 via 211. Similarly, a liquid supply path that communicates from the communication port 72 of the second flow path member 60 to the communication port 51 of the first flow path member 50 via the common recovery flow path 212 is also formed.

FIG. 18 is a view showing a cross section taken along the line FF of FIG. As shown in this figure, the common supply flow path is connected to the discharge module 200 via the communication port 61, the individual communication port 53, and the communication port 51. Although not shown in FIG. 18, in another cross section, it is clear with reference to FIG. 17 that the individual recovery channels are connected to the discharge module 200 by a similar path. Similar to the first application example, each ejection module 200 and the recording element substrate 10 are formed with a flow path communicating with each ejection port 13, and a part or all of the supplied ink suspends the ejection operation. It is possible to recirculate through the discharge port 13 (pressure chamber 23). Further, as in the first application example, the common supply flow path 211 is via the negative pressure control unit 230 (high pressure side), and the common recovery flow path 212 is via the negative pressure control unit 230 (low pressure side) and the liquid supply unit 220. It is connected. Therefore, due to the differential pressure, a flow is generated from the common supply flow path 211, passing through the discharge port 13 (pressure chamber 23) of the recording element substrate 10, and flowing to the common recovery flow path 212.

(Explanation of discharge module)
FIG. 19A shows a perspective view of one discharge module 200, and FIG. 19B shows an exploded view thereof. Unlike the first application example, a plurality of terminals 16 are arranged on both side portions (each long side portion of the recording element substrate 10) along a plurality of discharge port row directions of the recording element substrate 10, and are electrically connected to the plurality of terminals 16. Two wiring boards 40 are also arranged with respect to one recording element board 10. This is because the number of discharge port rows provided on the recording element substrate 10 is 20, which is significantly larger than the 8 rows of the first application example. That is, the purpose is to shorten the maximum distance from the terminal 16 to the recording element 15 provided corresponding to the discharge port row, and to reduce the voltage drop and signal transmission delay that occur in the wiring portion in the recording element substrate 10. It is supposed to be. Further, the liquid communication port 31 of the support member 30 is provided on the recording element substrate 10 and opens so as to straddle all the discharge port rows. Other points are the same as in the first application example.

(Explanation of the structure of the recording element substrate)
20 (a) is a schematic view of the surface of the recording element substrate 10 on the side where the discharge port 13 is arranged, and FIG. 20 (c) is a schematic view showing the back surface of the surface of FIG. 20 (a). 20 (b) is a schematic view showing the surface of the recording element substrate 10 when the lid member 20 provided on the back surface side of the recording element substrate 10 is removed in FIG. 20 (c). As shown in FIG. 20B, liquid supply paths 18 and liquid recovery paths 19 are alternately provided on the back surface of the recording element substrate 10 along the discharge port row direction. Although the number of discharge port rows is significantly increased from that of the first application example, the essential difference from the first application example is that the terminal 16 is along the discharge port row direction of the recording element substrate as described above. It is located on both sides. A set of a liquid supply path 18 and a liquid recovery path 19 are provided for each discharge port row, and the lid member 20 is provided with an opening 21 that communicates with the liquid communication port 31 of the support member 30. , The basic configuration is the same as that of the first application example.

(First Embodiment)
(Relationship between shortened tail length and discharge port size)
21 shows the inside of the liquid discharge head, FIG. 21 (a) is a plan view showing a recording element and a flow path, and FIG. 21 (b) is a cross-sectional view taken along the line AA of FIG. 21 (a). Is. Between the substrate 11 of the recording element substrate 10 and the discharge port forming member 12, there are a plurality of pressure chambers 23 each having a discharge port 13, and an inlet flow path 24a and an outlet flow path 24b communicating with each pressure chamber 23. And are provided. The pressure chamber 23 is partitioned by a wall member 26. The substrate 11 is provided with a liquid supply path 18 communicating with the inlet flow path 24a and a liquid recovery path 19 communicating with the outlet flow path 24b. The inlet flow path 24a branches from the liquid supply passage 18 at the supply port 17a of the liquid supply passage 18 and communicates with the pressure chamber 23 to supply ink to the pressure chamber 23. The outlet flow path 24b communicates with the pressure chamber 23 on the opposite side of the inlet flow path 24a with respect to the pressure chamber 23, and the ink not discharged from the discharge port 13 is passed through the recovery port 17b of the liquid recovery path 19 to the liquid recovery path. Discharge to 19.

The plurality of supply ports 17a form a supply port row, and the plurality of collection ports 17b form a collection port row. A discharge port row in which a plurality of discharge ports 13 are arranged is formed between the supply port row and the collection port row. In this embodiment, a discharge port row and a collection port row are provided on both sides of the supply port row. As described above, a pressure difference is provided between the liquid supply path 18 and the liquid recovery path 19. Due to this pressure difference, ink is introduced into the pressure chamber 23 from the supply port 17a through the inlet flow path 24a, and a circulation flow is generated in which the ink flows from the outlet flow path 24b to the recovery port 17b. That is, the ink is introduced into the pressure chamber 23 through the liquid supply path 18, the supply port 17a, and the inlet flow path 24a, and is discharged from the discharge port 13. The ink that has not been ejected is collected through the outlet flow path 24b, the recovery port 17b, and the liquid recovery path 19. The recovered ink is supplied to the liquid supply path 18 again via a circulation flow path (not shown).

A recording element 15 for generating thermal energy is provided on the bottom surface of the pressure chamber 23 facing the discharge port 13. The discharge port portion (nozzle) 25 penetrates the discharge port forming member 12 at a position facing the pressure chamber 23. The outer end of the discharge port 25, that is, the end opposite to the recording element 15, forms a discharge port 13 for ejecting ink. The discharge port 25 to the discharge port 13 are provided at positions facing the recording element 15. In the present specification, the discharge port 13 is an opening located on the outer surface of the discharge port forming member 12 facing the recording medium, and the discharge port portion 25 is a portion that communicates the discharge port 13 and the pressure chamber 23. It means a through hole penetrating the discharge port forming member 12.

FIG. 22 is a schematic view showing a transient process of the discharge phenomenon. 22 (a) shows an enlarged view of part B of FIG. 21 (a), and FIGS. 22 (b) to 22 (g) are cross-sectional views taken along the line AA of FIG. 22 (a). In FIG. 22, the protrusion of the discharge port 13 shown in FIG. 21A is not shown. Ink is supplied to the pressure chamber 23 from the inlet flow path 24a (see FIG. 22B). When electric energy is applied to the recording element 15, heat energy used for discharging a liquid is generated. The ink in the vicinity of the recording element 15 is heated and evaporated by this heat energy, and bubbles B are formed (see FIG. 22 (c)). The pressure at the initial stage of generation of the bubble B is very high, and the bubble B pushes the ink between the bubble B and the discharge port 13 toward the discharge port 13 (see the arrow in FIG. 22 (c)). The bubble B enters the inside of the discharge port 25 while growing. As the bubble B grows, the internal pressure of the bubble B rapidly changes from a positive pressure to a negative pressure lower than the atmospheric pressure (see FIG. 22 (d)). Due to the negative pressure, the rear end portion of the droplet is pulled toward the recording element 15 side, and the tail length is extended (see FIG. 22 (e)). When the bubble B further advances inside the discharge port 25, the bubble B communicates with the atmosphere inside or outside the discharge port 25. As a result, the negative pressure of the bubble B is rapidly lost, and the growth of the tail length also stops (see FIG. 22 (f)). Through the above steps, the ink between the generated bubbles B and the discharge port 13 is discharged from the discharge port 13 by the pressure of the bubbles B. The ejected ink is mainly ejected as a main droplet, but satellite S and mist are generated behind the main droplet (see FIG. 22 (g)). In the present embodiment, the bubble B communicates with the atmosphere when the internal pressure is in a negative pressure state and the volume increases (when expanding). As a result, the ejection volume of the droplet is stabilized and the ejection speed is also improved. In the configuration in which the protrusion 27 is provided on the discharge port as in the present embodiment, the area of the discharge port is reduced, so that the discharge speed generally tends to decrease. However, as in the present embodiment, by communicating the droplets with the atmosphere when the bubbles B grow, it is possible to suppress the generation of satellites while suppressing the decrease in the discharge rate.

FIG. 23A shows the relationship between the pressure profile inside the bubble and the internal pressure of the bubble. The horizontal axis shows time and the vertical axis shows the internal pressure of bubbles. FIG. 23A shows patterns A and B having the same discharge port dimensions but different only in the pressure profile inside the bubbles. FIG. 23 (b) schematically shows a state of ink ejection of pattern A, and FIG. 23 (c) schematically shows a state of ink ejection of pattern B. In both pattern A and pattern B, the internal pressure of bubbles rises sharply and then becomes negative pressure, and then the bubbles communicate with the atmosphere and rise to atmospheric pressure. Pattern B, because the bubble at time T _B is communicated with the atmosphere, the time the internal pressure of the bubble is maintained at a negative pressure is long. Therefore, as shown in FIG. 23 (c), the tail length of the droplet is longer than that of the pattern A, and satellites are likely to occur. Pattern A, since the air bubbles at the time T _B from earlier time T _A is communicated with the atmosphere, the time the internal pressure of the bubble is maintained at a negative pressure is short. Therefore, the tail length is relatively short, and as shown in FIG. 23 (b), the generation of satellites is suppressed. From this, it is effective to shorten the duration of the negative pressure and allow the bubbles to communicate with the atmosphere at an early stage in order to suppress the extension of the tail length, that is, to suppress the satellite.

FIG. 24 shows the distance OH from the recording element 15 to the discharge port 13 (FIG. 22 (b)) and the time from when the recording element 15 starts to generate heat until the bubbles communicate with the atmosphere (hereinafter, atmospheric communication time Tth). It shows the relationship with). The distance OH is the sum of H1 and H2, that is, the inlet flow in the direction perpendicular to the height H1 of the thick discharge port portion 25 of the discharge port forming member 12 and the bottom surface where the recording element 15 of the pressure chamber 23 is provided. The height of the path 24a (height of the pressure chamber) is equal to the sum of H2 (FIG. 22 (b)). The shape of the discharge port 13 is a circular shape (pattern 1: FIG. 24 (a)) and a shape having two protrusions 27 protruding toward the center of the discharge port 13 (patterns 2, 3: FIG. 24 (b)). , (C)). In the pattern 2 and the pattern 3, the two protrusions 27 are located on a straight line L passing through the center C of the discharge port 13, and are provided on both sides with the same shape with respect to the center C. Further, in the pattern 3, the length of the protrusions 27 is longer than that of the pattern 2, and the distance 28 between the protrusions 27 is smaller.

In both patterns, the effective diameters of OH and the discharge port 13 are the same, the OH is 12 μm or less, and the effective diameter of the discharge port 13 is 11 μm or more (opening area ≧ 100 μm ² ). The perforated diameter is defined as the diameter of a circle having an area equal to the actual area of the discharge port 13. The opening area of the discharge port 13 ^{is preferably 100 μm 2} or more. When the discharge port 13 has a circular shape (pattern 1), it can be seen that it is necessary to reduce the OH in order to reduce Tth in order to shorten the tail length. In order to reduce OH, it is necessary to thin the discharge port forming member 12 (decrease H1) or reduce the height of the inlet flow path 24a (height of the pressure chamber) (decrease H2). In the former case, the discharge port forming member 12 is liable to be cracked or the like, and the possibility that the reliability is lowered is increased. In the latter case, there is a concern that the throughput will decrease as the flow resistance increases.
On the other hand, when the protrusion 27 is provided on the discharge port 13 (patterns 2 and 3), the Tth is lower than that of the pattern 1. Especially when the distance between the protrusions 27 is narrow (pattern 3), the decrease in Tth is remarkable. Therefore, the tail length is shortened and the generation of satellites is suppressed. Although details will be described later, in the present embodiment, the configuration of the two protrusions 27 has been described, but the present invention is not limited to this, and the present invention can be applied to, for example, one protrusion or three or more protrusions. Is. As in the case of two protrusions, the narrower the distance between the protrusions 27 (in the case of one, the distance between the tip of the protrusion and the edge of the discharge port facing the tip) shortens the tail length. Connection is preferable.

FIG. 25 shows the relationship between the thickness H1 of the discharge port forming member 12, the height (height of the pressure chamber) H2 of the inlet flow path 24a, and the atmospheric communication time Tth, and the inlet flow path 24a is shown on the horizontal axis. The height H2 and the vertical axis show the thickness H1 of the discharge port forming member 12. The contour lines indicate Tth. The dimensions of levels A, B, and C in the figure are as follows.
Level A) OH = 12 μm, H1 = 7 μm, H2 = 5 μm, Tth ≈ 1.4 μs
Level B) OH = 12 μm, H1 = 6 μm, H2 = 6 μm, Tth ≈ 1.5 μs
Level C) OH = 12 μm, H1 = 5 μm, H2 = 7 μm, Tth ≈ 1.6 μs
Therefore, FIG. 25 shows the change in the atmospheric communication time Tth when the OH is fixed at 12 μm and the height H2 (or the thickness H1 of the discharge port forming member 12) of the inlet flow path 24a is changed. Tth increases in the order of levels A, B, and C. Therefore, when the OH is constant, the lower the height H2 of the inlet flow path 24a, the smaller the time Tth of atmospheric communication can be. The height H2 of the inlet flow path 24a is preferably 7 μm or less, and preferably half or less of OH. The distance OH between the discharge port 13 and the recording element 15 is preferably 12 μm or less.

(Mechanism for reducing atmospheric communication time Tth)
Next, a mechanism for reducing the atmospheric communication time Tth will be described.
26 and 27 show the relationship between the distance OH and the atmospheric communication position of bubbles. FIG. 26A shows the definitions in the dz and z directions. dz indicates the position in the z direction in which the bubbles communicate with the atmosphere when the discharge port 13 is the origin, and the direction away from the recording element 15 is positive. Therefore, when dz is positive, the atmospheric communication position is outside the discharge port 25 or outside the discharge port 13, and when dz is negative, the atmospheric communication position is inside the discharge port 25 or inside the discharge port 13. is there.
In FIG. 26B, OH is shown on the horizontal axis and dz is shown on the vertical axis. When the shape of the discharge port 13 is circular (pattern 1), dz gradually approaches 0 as the OH decreases. That is, when the OH decreases, atmospheric communication occurs at a position close to the discharge port 13. As a result, Tth decreases as shown in FIG. When the discharge port 13 has the protrusions 27 (patterns 2 and 3), dz> 0 when OH ≦ 12 μm, and atmospheric communication occurs outside the discharge port 13. The dz is larger in the pattern 3 in which the protrusion spacing is narrower, and as a result, the Tth is similarly reduced.

FIG. 27 (a) shows the definitions of dx and the x direction. dx indicates the position in the x direction in which the air bubbles communicate with the atmosphere when the edge of the discharge port 13 is the origin, and the direction away from the center of the discharge port 13 is positive. In FIG. 27 (b), OH is shown on the horizontal axis and dx is shown on the vertical axis. When the shape of the discharge port 13 is circular (pattern 1), dx hardly changes even if the OH decreases. When the discharge port 13 has the protrusions 27 (patterns 2 and 3), the dx approaches 0, and the dx increases as the OH decreases. The dx is larger in the pattern 3 in which the protrusion spacing is narrower.

FIG. 28 is a simulation diagram showing droplets discharged from the discharge port 13, and FIG. 28 (a) is a perspective view of the discharged droplets when the shape of the discharge port 13 is circular (pattern 1), FIG. 28 (b). , (C) is a diagram showing transient temporal changes in the velocity distribution of bubbles and the atmosphere. 28 (d) is a perspective view of the discharged droplet when the discharge port 13 has the protrusion 27, and FIGS. 28 (e) and 28 (f) show transient temporal changes in the velocity distribution of bubbles and the atmosphere. It is a figure shown. 28 (e) and 28 (f) are cross-sectional views of two protrusions provided at the discharge port of FIG. 28 (d) and a straight line passing through the center of the discharge port and in a direction along the protrusions. x and z are defined in FIG. From FIGS. 28 (b) and 28 (c), the transient phenomenon inside the discharge port 25 when the shape of the discharge port 13 is circular (pattern 1) is as follows.
Step 1) The generated air bubbles B enter the discharge port 25 and grow inside the discharge port 25. Along with this, the bubble B has a velocity component toward the center (x = 0) of the discharge port 13 due to the influence of the wall surface (side surface of the discharge port portion 25) of the discharge port forming member 12 (see arrow A in FIG. 28 (b)). )
Step 2) As the bubbles B grow, the atmosphere G outside the discharge port 13 is temporarily pushed out by the discharge ink in a direction away from the center of the discharge port 13 (see arrow B in FIG. 28B).
Step 3) Due to the negative pressure inside the bubbles, the atmosphere is drawn into the discharge port 13 (see arrow D in FIG. 28 (c)).
Step 4) The negative pressure inside the bubble causes the bubble itself to be drawn toward the center of the ejection port 25, and the force at the interface of the ink further draws the bubble toward the center of the ejection port 25 (FIG. 28 (c)). See arrow C)
As a result, the atmosphere G and the bubble B tend to communicate with each other inside the discharge port portion 25. Bubbles do not easily communicate with the atmosphere outside the discharge port 25, and Tth tends to be slow.

On the other hand, when the ejection port 13 has the protrusion 27, the bubble B spreads to the outside of the ejection port 13 due to the force at the interface of the ink (see arrow C in FIG. 28 (f)). At least a part of the bubbles B that have entered the discharge port 25 has a velocity component from the center of the discharge port 25 toward the side wall. In particular, in the case of a discharge port shape in which the curvature is not constant due to the provision of the protrusion 27, surface tension acts so as to form a spherical shape in which the gas-liquid interface has a stable shape. Then, the atmosphere G is drawn into the discharge port portion 25, while the bubble B spreads in the direction away from the center of the discharge port portion 25. As a result, the atmosphere G and the bubble B have velocity components opposite to each other and move in the direction of collision with each other, so that the bubble B is likely to communicate with the atmosphere. From FIG. 28 (f), it can be seen that the atmospheric communication position is outside the discharge port 25 to the discharge port 13.

From the above, the following features can be obtained by reducing the OH (the distance between the discharge port and the recording element is 12 μm or less) and providing the protrusion 27 on the discharge port 13.
Feature 1) Early atmospheric communication time Tth Feature 2) Bubbles communicate with the atmosphere outside the discharge port 25 Feature 3) Bubbles before communicating with the atmosphere spread outward As a result, the tail length is shortened, and satellites and satellites Mist is suppressed, and both high image quality and high throughput can be achieved.

29 and 30 are diagrams showing Tth and dz for various discharge port shapes.
Discharge port shapes 1 to 6 have the following features.
Discharge port shape 1: Circular discharge port Discharge port shape 2: Has two symmetrical protrusions 27 and has a wide protrusion interval Discharge port shape 3: Has two symmetrical protrusions 27 and has a protrusion spacing Narrow discharge port Discharge port shape 4: It has four symmetrical protrusions 27, and has a discharge port discharge port shape with a wide protrusion interval 5: 1. It has one protrusion 27, and the distance between the protrusion and the edge on the opposite side is large. Wide discharge port Discharge port shape 6: One protrusion 27, and the distance between the protrusion and the edge on the opposite side is narrow. Each of the discharge port shapes 2 to 6 has at least one protrusion 27. The protrusion 27 is located on a straight line passing through the center of the discharge port 13. All of the discharge port shapes 2 to 6 have a smaller Tth than the discharge port shape 1. Further, dz is positive in all of the discharge port shapes 2 to 6, and atmospheric communication occurs outside the discharge port portion 25. Therefore, the discharge port shapes 2 to 6 are preferable embodiments because the tail length can be shortened and satellites and mists can be suppressed. However, as the number of protrusions 27 increases in the discharge port shape 4, the flow resistance of the discharge port 25 increases and the discharge efficiency deteriorates. Therefore, it is preferable that the number of protrusions 27 is not too large. On the other hand, the ejection port shapes 5 and 6 have one protrusion 27, which is preferable from the viewpoint of the flow resistance of the ejection port portion 25. .. From this point of view, it is more preferable that the discharge port 13 has a symmetrical shape. Therefore, a particularly preferable embodiment is a discharge port shape 2 or 3 having two protrusions 27 provided at positions symmetrical with respect to the center of the discharge port 13. From the viewpoint of accelerating Tth, a discharge port shape 3 having two protrusions 27 and a symmetrical discharge port shape with a narrow protrusion interval is more preferable.

In the embodiment described above, the liquid flow paths are provided on both sides of the recording element 15, but as shown in FIGS. 31A and 31B, the liquid flow paths are provided only on one side of the recording element 15. But the same effect can be obtained.

(Second Embodiment)
(Relationship between flow path and circulation direction)
32 is a diagram showing a second embodiment of the present invention, FIG. 32 (a) is a plan view showing a recording element 15 and a flow path, and FIG. 32 (b) is a line AA of FIG. 32 (a). It is a cross-sectional view along. The circulating flow flows in the direction parallel to the protrusion 27 of the discharge port 13. Compared to the first embodiment shown in FIG. 21, the collection path row is provided on only one side of the supply path row, and the others are the same. Therefore, refer to the first embodiment for details. I want to.

The form shown in FIG. 33 is different from the form shown in FIG. 32 in that the protrusion 27 of the discharge port 13 extends in a direction orthogonal to the circulating flow. 34 (a) and 34 (b) are views cut out in the vicinity of one pressure chamber 23 in FIGS. 32 and 33, respectively. In FIG. 34 (a), the extending directions of the circulating flow and the protrusions of the discharge port 13 are along each other (substantially parallel), and in FIG. 34 (b), the extending directions of the circulating flow and the protrusions of the discharge port 13 intersect (substantially). Orthogonal). FIGS. 34 (c) and 34 (d) are numerical calculation results of drop formation in FIGS. 34 (a) and 34 (b), respectively, when the influence of the so-called pause time is small during continuous discharge. 34 (e) and 34 (f) are numerical calculation results of droplet formation after a predetermined pause time in FIGS. 34 (a) and 34 (b), respectively, and thickening of the ink due to evaporation of the ink from the ejection port 13. The influence of is increasing.

From FIGS. 34 (e) and 34 (f), the method (FIG. 34 (b)) in which the circulating flow flows vertically is more ink than the configuration in which the circulating flow flows parallel to the protrusion 27 of the discharge port 13 (FIG. 34 (a)). Less susceptible to thickening. This is because the evaporation rate of the ink is large in the portion where the radius of curvature at the base of the protrusion 27 is small (the portion circled in FIGS. 34 (g) and 34 (h)). It is thought that this is because it is not easily affected by.

Therefore, although the present invention can be applied to any of the forms of FIGS. 34 (e) and 34 (f), in order to further suppress the concentration inside the discharge port in the configuration with the circulation flow, the circulation flow is the discharge port 13. A configuration in which the flow flows in the direction (more preferably vertical) intersecting the protrusion is more preferable. In other words, it is desirable that the straight line where the protrusion is located is at an angle of 45 degrees or more with respect to the flow path axis connecting the supply flow path and the recovery flow path, and that the straight line and the flow path axis are perpendicular to each other inside the discharge port. It is particularly desirable in that it can suppress the concentration of eggplant.
In addition, the flight direction of the droplets ejected may be deviated due to the shape variation or deformation of the protrusion 27. Considering this point, it is preferable that the relative moving direction of the recording medium and the extending direction of the protrusion 27 are along (more preferably parallel) with respect to the liquid discharge head 3. This is because, with such a configuration, even if the flight direction of the droplet is deviated due to deformation of the protrusion 27 or the like, the influence on the recorded image is reduced.

13 Discharge port 15 Recording element 25 Discharge port B Bubble G Atmosphere

Claims (12)

A recording element that generates heat energy used to discharge a liquid, a pressure chamber having the recording element inside, a discharge port for discharging a liquid, and a discharge port that communicates the discharge port and the pressure chamber. A liquid supply path that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and a liquid recovery path that communicates with the pressure chamber on the opposite side of the liquid supply path with respect to the pressure chamber and collects the liquid. And have
A liquid discharge head in which bubbles are generated in the pressure chamber by the heat energy, the generated bubbles enter the inside of the discharge port portion, and the liquid is discharged from the discharge port by the pressure of the bubbles.
The discharge port has two protrusions protruding toward the center of the discharge port, and the two protrusions are located on a straight line passing through the center and are provided on both sides with respect to the center. At an angle of 45 degrees or more with respect to the flow path axis connecting the liquid supply path and the liquid recovery path,
A liquid discharge head in which air bubbles that have entered the inside of the discharge port communicate with the atmosphere outside the discharge port. A recording element that generates heat energy used to discharge a liquid, a pressure chamber having the recording element inside, a discharge port for discharging a liquid, and a discharge port that communicates the discharge port and the pressure chamber. A liquid supply path that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and a liquid recovery path that communicates with the pressure chamber on the opposite side of the liquid supply path with respect to the pressure chamber and collects the liquid. And have
A liquid discharge head in which bubbles are generated in the pressure chamber by the heat energy, the bubbles enter the inside of the discharge port portion, and the liquid is discharged from the discharge port by the pressure of the bubbles.
The discharge port has two protrusions protruding toward the center of the discharge port, and the two protrusions are located on a straight line passing through the center and are provided on both sides with respect to the center. At an angle of 45 degrees or more with respect to the flow path axis connecting the liquid supply path and the liquid recovery path,
A liquid discharge head in which at least a part of the bubbles that have entered the inside of the discharge port portion has a velocity component from the center of the discharge port portion toward the side wall. The liquid discharge head according to claim 1 or 2, wherein the distance between the discharge port and the recording element is 12 μm or less. Is the height of the liquid supply channel in the bottom surface perpendicular to the direction of the front Symbol pressure chamber is 7μm or less, the liquid discharge head according to any one of claims 1 to 3. The liquid discharge head according to any one of claims 1 to 4, wherein the opening area of the discharge port is 100 μm ^{2 or more.} Is the height of the liquid supply channel in the bottom surface perpendicular to the direction of the front Symbol pressure chamber, wherein the discharge port is less than half the distance between the recording element, according to any one of claims 1 5 Liquid discharge head. The liquid discharge head according to any one of claims 1 to 6 , wherein the straight line and the flow path axis intersect each other. The liquid discharge head according to claim 2, wherein the air bubbles that have entered the inside of the discharge port communicate with the atmosphere outside the discharge port. The liquid discharge head according to any one of claims 1 to 8 , wherein the liquid in the pressure chamber is circulated to and from the outside of the pressure chamber. A recording element that generates heat energy used for discharging a liquid, a pressure chamber having the recording element inside, a liquid supply path that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and the above. A liquid discharge method using a liquid discharge head having a liquid recovery path that communicates with the pressure chamber on the opposite side of the liquid supply path and collects the liquid with respect to the pressure chamber.
Using the recording element to generate bubbles in the liquid
By the pressure of the generated bubbles, the liquid is discharged from a discharge port provided at a position facing the recording element.
Have a, and be in communication with the atmosphere outside of the discharge port of the bubble,
The discharge port has two protrusions protruding toward the center of the discharge port, and the two protrusions are located on a straight line passing through the center and are provided on both sides with respect to the center. A liquid discharge method in which an angle of 45 degrees or more is formed with respect to a flow path axis connecting a liquid supply path and the liquid recovery path. A recording element that generates heat energy used to discharge a liquid, a pressure chamber having the recording element inside, a discharge port for discharging a liquid, and a discharge port that communicates the discharge port and the pressure chamber. A liquid supply path that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and a liquid recovery path that communicates with the pressure chamber on the opposite side of the liquid supply path with respect to the pressure chamber and collects the liquid. When, a liquid discharge head having the discharge port has two projections projecting toward the center of the discharge port, wherein two projections are located on a straight line passing through the center, the A liquid discharge method using a liquid discharge head provided on both sides with respect to the center and having an angle of 45 degrees or more with respect to the flow path axis connecting the liquid supply path and the liquid recovery path.
Using the recording element to generate bubbles in the liquid
And it is advanced the bubbles generated inside the discharge port portion,
The liquid is discharged from the discharge port by the pressure of the generated bubbles.
A liquid discharge method in which at least a part of the bubbles that have entered the inside of the discharge port portion has a velocity component from the center of the discharge port portion toward the side wall. A recording element that generates heat energy used to discharge a liquid, a pressure chamber having the recording element inside, a discharge port for discharging a liquid, and a discharge port that communicates the discharge port and the pressure chamber. A liquid supply path that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and a liquid recovery path that communicates with the pressure chamber on the opposite side of the liquid supply path with respect to the pressure chamber and collects the liquid. When, a liquid discharge head having the discharge port has two projections projecting toward the center of the discharge port, wherein two projections are located on a straight line passing through the center, the A liquid discharge method using a liquid discharge head provided on both sides with respect to the center and having an angle of 45 degrees or more with respect to the flow path axis connecting the liquid supply path and the liquid recovery path.
Using the recording element to generate bubbles in the liquid
And it is advanced the bubbles generated inside the discharge port portion,
The pressure of the generated bubbles causes the liquid in the discharge port to be discharged from the discharge port.
A liquid discharge method in which air bubbles that have entered the inside of the discharge port communicate with the atmosphere outside the discharge port.

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