JP2017124600A - Liquid discharge head and liquid discharge method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten tail lengths of liquid droplets.SOLUTION: The liquid discharge head comprises: a recording element 15 that generates heat energy which is used for discharging liquid; a pressure chamber 23 comprising the recording element 15 therein; a discharge port 13 for discharging liquid; and a discharge port portion 25 that communicates the discharge port 13 with the pressure chamber 23. Air bubbles B are generated in the pressure chamber 23 by heat energy, and the generated air bubbles enter the discharge port portion 25, so that liquid is discharged through the discharge port 13 by pressure of the air bubbles B. The air bubbles B entering the discharge port portion 25 communicate with atmospheric air G, outside the discharge port 13.SELECTED DRAWING: Figure 28

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 from which liquid is discharged.

  Liquid droplets discharged from a liquid discharge head typified by an ink jet head are generally divided into a main droplet and a sub-droplet (hereinafter also referred to as satellite) accompanying the droplet. The main droplet lands at a desired position on the recording medium, but the satellite is difficult to control the landing position. In a liquid discharge head that requires high image quality and high throughput, there may be a noticeable decrease in recording image quality due to satellites. 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 may contaminate the recording apparatus, and the recording apparatus may be transferred to the recording medium to contaminate the recording medium.

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

JP2008-290380 US Patent Application Publication No. 2011/0205303

As a result of investigations by the present inventors, the configurations of Patent Documents 1 and 2 have found a new problem that the tail length of a droplet cannot be further shortened 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.

  A liquid discharge head according to the present invention includes a recording element that generates thermal energy used to discharge a liquid, a pressure chamber that includes the recording element, a discharge port that discharges the liquid, a discharge port, and a pressure chamber. A discharge port portion that communicates with each other. Bubbles are generated in the pressure chamber by the thermal 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. Bubbles that enter 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 ejection head and a liquid ejection method capable of shortening the tail length of a droplet and suppressing satellites.

It is a figure which shows schematic structure of the recording device which concerns on the 1st application example of this invention. FIG. 3 is a diagram illustrating a first circulation path through which liquid of the recording apparatus circulates. It is a figure which shows the 2nd circulation path of a recording device. It is a perspective view of the liquid discharge head concerning the 1st example of application of the present invention. FIG. 5 is an exploded perspective view of the liquid ejection head in FIG. 4. FIG. 5 is a diagram illustrating a configuration of first to third flow path members that constitute a flow path member included in the liquid ejection head of FIG. 4. It is a figure for demonstrating the connection relation of each flow path in a flow path member. It is the EE sectional view taken on the line of FIG. It is the perspective view and exploded view of a discharge module. It is a figure which shows the structure of a recording element board | substrate. FIG. 11 is a perspective view illustrating a configuration of a recording element substrate and a lid member including a BB cross section in FIG. 10. FIG. 6 is a plan view showing a partially enlarged adjacent portion of a recording element substrate in two adjacent ejection modules. It is a figure which shows schematic structure of the recording device which concerns on the 2nd application example of this invention. FIG. 10 is a perspective view of a liquid discharge head according to a second application example of the present invention. FIG. 15 is an exploded perspective view of the liquid ejection head in FIG. 14. It is a figure which shows the structure of the 1st and 2nd flow path member which comprises the flow path member which the liquid discharge head of FIG. 14 has. FIG. 5 is a diagram for explaining a connection relationship between liquids in a recording element substrate and a flow path member. It is the FF sectional view taken on the line of FIG. It is the perspective view and exploded view of a discharge module. It is a figure which shows the structure of a recording element board | substrate. FIG. 3 is a conceptual diagram showing the inside of a liquid ejection head according to the first embodiment. It is a schematic diagram which shows the transient 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 printing element to an ejection opening, and atmospheric communication time Tth. It is a figure which shows the relationship between the thickness of a discharge port formation member, the height of an inlet flow path, and atmospheric communication time Tth. It is a figure which shows the relationship between the distance from a recording element to an ejection opening, and the air | atmosphere communication position dz of a bubble. It is a figure which shows the relationship between the distance from a recording element to an ejection outlet, and the air | atmosphere communication position dx of a bubble. It is a conceptual diagram which shows the droplet discharged from a discharge outlet. It is the figure which showed the atmosphere communication time Tth with respect to various discharge port shapes. It is the figure which showed the atmosphere 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. FIG. 6 is a conceptual diagram showing the inside of a liquid ejection head according to a second 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 discharge of the droplet in 2nd Embodiment and a reference example.

Hereinafter, liquid application heads according to application examples and embodiments of the present invention will be described with reference to the drawings. The application examples and embodiments described below are provided with various technically preferable conditions. However, the present invention is not limited to these application examples, embodiments, and conditions as long as the concept of the present invention is satisfied. Absent.
Hereinafter, 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 application example and the embodiment are an ink jet recording apparatus (recording apparatus) configured to circulate a liquid such as ink between a tank and a liquid discharge head, but may be in other forms. For example, the ink in the pressure chamber may be flowed by providing two tanks on the upstream side and the downstream side of the liquid discharge head without circulating the ink and flowing the ink from one tank to the other tank. .
The 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) that performs recording while scanning the recording medium. The present invention can also be applied to the liquid discharge head of FIG. As a serial type liquid discharge head, for example, there is a configuration in which one recording element substrate for black ink and one 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 that the ejection openings overlap in the ejection port array direction, and the recording head is used as the recording medium. It is also possible to scan the image with respect to the image.

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

(Explanation of the first circulation path)
FIG. 2 is a schematic diagram showing a first circulation path which is one form of the circulation path applied to the recording apparatus of this application example. FIG. 2 is a diagram in which the liquid discharge head 3 is fluidly connected to a first circulation pump (high pressure side) 1001, a first circulation pump (low pressure side) 1002, a buffer tank 1003, and the like. In FIG. 2, for the sake of simplicity, only the path through which one color of CMYK ink flows is shown, but in reality, the circulation paths for four colors are the liquid ejection head 3 and the recording apparatus main body. Provided. A buffer tank 1003 serving as a sub tank connected to the main tank 1006 has an air communication port (not shown) that communicates the inside and outside of the tank, and can discharge bubbles in the ink to the outside. The buffer tank 1003 is also connected to a refill pump 1005. The replenishment pump 1005 discharges (discharges) ink from the discharge port of the liquid discharge head, such as recording by discharging the ink and recovery of suction, etc., when the ink is consumed by the liquid discharge head 3. 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, and the like. For example, a general constant flow valve or relief valve may be provided 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 through 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. The flow rate is preferably set to a level that does not affect the temperature difference between the recording element substrates 10 in the liquid ejection head 3. However, if the flow rate is set too high, the negative pressure difference is excessively increased in each recording element substrate 10 due to the pressure loss of the flow path in the liquid discharge unit 300, resulting in image density unevenness. For this reason, it is preferable to set the flow rate in consideration of 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 of the second circulation pump 1004 and the liquid discharge unit 300. The negative pressure control unit 230 maintains the pressure downstream of the negative pressure control unit 230 (that is, the liquid discharge unit 300 side) at a preset constant pressure even when the flow rate of the circulation system fluctuates due to the duty difference for recording. It has a function to operate. As the two pressure adjusting mechanisms constituting the negative pressure control unit 230, any mechanism can be used as long as it can control the pressure downstream of itself with a fluctuation 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 employed. When the pressure reducing regulator is used, it is preferable to pressurize the upstream side of the negative pressure control unit 230 via the liquid supply unit 220 by the second circulation pump 1004 as shown in FIG. In this way, the influence of the water head pressure on the liquid discharge head 3 of the buffer tank 1003 can be suppressed, so that the layout flexibility of the buffer tank 1003 in the recording apparatus 1000 can be increased. The second circulation pump 1004 may be any pump that has a head pressure higher than a certain pressure in the range of the ink circulation flow rate used when the liquid discharge head 3 is driven, and a turbo pump, a positive displacement pump, or the like can be used. Specifically, a diaphragm pump or the like is applicable. Further, instead of the second circulation pump 1004, for example, a water head tank arranged with a certain water head difference with respect to the negative pressure control unit 230 is also applicable.

  As shown in FIG. 2, the negative pressure control unit 230 includes two pressure adjustment mechanisms each having a different control pressure. 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. The common supply path 211 and the common recovery channel 212 in the liquid discharge unit 300 are connected. The liquid ejection unit 300 is provided with a common supply path 211, a common recovery path 212, and an individual supply path 213a and an individual recovery path 213b that communicate with each recording element substrate 10. Since the individual supply channel 213a communicates with the common supply channel 211 and the common recovery channel 212, a part of the ink passes from the common supply channel 211 through the internal channel of the recording element substrate 10 to the common recovery channel 211. A flow (arrow in FIG. 2) flowing to the path 212 is generated. This is because a pressure adjustment mechanism H is connected to the common supply flow path 211 and a pressure adjustment 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 ejection unit 300, a part of the ink passes through each recording element substrate 10 while flowing the ink so as to pass through the common supply channel 211 and the common recovery channel 212, respectively. Flow occurs. For this reason, the heat generated in each recording element substrate 10 can be discharged to the outside of the recording element substrate 10 through the flow of the common supply channel 211 and the common recovery channel 212. Further, with such a configuration, when recording is performed by the liquid discharge head 3, it is possible to cause an ink flow even in an ejection port or a pressure chamber where recording is not performed. Can be suppressed. Further, thickened ink and foreign matter in the ink can be discharged to the common recovery channel 212. For this reason, the liquid discharge head 3 of this application example can perform high-speed and high-quality recording.

(Explanation of second circulation path)
FIG. 3 is a schematic diagram showing a second circulation path having a circulation form different from the first circulation path described above, among the circulation paths applied to the recording apparatus of the present application example. The main differences from the first circulation path described above are as follows. First, both of the two pressure adjusting mechanisms constituting the negative pressure control unit 230 control a pressure upstream of the negative pressure control unit 230 with a fluctuation within a certain range around a desired set pressure (so-called “ It has a mechanical component that works in the same way as the back pressure regulator. Next, the second circulation pump 1004 functions as a negative pressure source for reducing the pressure on the downstream side of the negative pressure control unit 230. Further, a first circulation pump (high pressure side) 1001 and a first circulation pump (low pressure side) 1002 are arranged on the upstream side of the liquid ejection head, and a negative pressure control unit 230 is arranged on the downstream side of the liquid ejection head.

  The negative pressure control unit 230 shown in FIG. 3 preliminarily adjusts the pressure fluctuation on the upstream side (that is, the liquid ejection unit 300 side) in advance even if the flow rate varies due to the change in the recording duty when the liquid ejection head 3 performs the recording. It operates so as to be within a certain range around the set pressure. As shown in FIG. 3, it is preferable to pressurize the downstream side of the negative pressure control unit 230 through the liquid supply unit 220 by the second circulation pump 1004. In this way, since the influence of the water head pressure of the buffer tank 1003 on the liquid discharge head 3 can be suppressed, the selection range of the layout of the buffer tank 1003 in the recording apparatus 1000 can be widened. Instead of the second circulation pump 1004, for example, a water head tank arranged with a predetermined water 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 adjustment mechanisms each having a different control pressure. Of the two negative pressure adjusting 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, respectively, in the liquid discharge unit 300. Are connected to the common supply channel 211 and the common recovery channel 212. The pressure of the common supply channel 211 is made relatively higher than the pressure of the common recovery channel 212 by two negative pressure adjusting mechanisms. As a result, an ink flow that flows from the common supply channel 211 to the common recovery channel 212 via the individual channels 213 and the internal channels of each recording element substrate 10 is generated (arrow in FIG. 3). As described above, in the second circulation path, an ink flow state similar to that in the first circulation path can be obtained in the liquid ejection unit 300, but there are two advantages different from the case of the first circulation path.

  The first advantage is that since the negative pressure control unit 230 is arranged on the downstream side of the liquid discharge head 3 in the second circulation path, there is a concern that dust and foreign matters generated from the negative pressure control unit 230 may flow into the head. There are few. The second advantage is that the maximum value of the required flow rate supplied from the buffer tank 1003 to the liquid discharge head 3 is smaller in the second circulation path than in the first circulation path. The reason is as follows. A is the sum of the flow rates in the common supply channel 211 and the common recovery channel 212 when circulating during recording standby. The value A is defined as the minimum flow rate necessary for adjusting 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, F is defined as an ejection flow rate when ink is ejected from all ejection ports of the liquid ejection unit 300 (when all ejection is performed). 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 are A. 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 liquid supply amount to the liquid ejection head 3 required during recording standby is the flow rate A. The amount of supply to the liquid discharge head 3 required for full ejection 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 necessary supply flow rate is the larger of A or F It becomes the value of. For this reason, as long as the liquid discharge unit 300 having the same configuration is used, the maximum value (A or F) of the necessary supply amount in the second circulation path is greater than the maximum value (A + F) of the necessary 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 or a load of a cooler (not shown) installed in the main body side path is used. And the cost of the recording apparatus main body can be reduced. This advantage becomes larger as the line head has a relatively large value of A or F, and among the line heads, a line head having a long length in the longitudinal direction is more beneficial.

  On the other hand, however, the first circulation path is advantageous over the second circulation path. That is, in the second circulation path, the flow rate that flows through the liquid ejection unit 300 during recording standby is maximized. Therefore, the lower the recording duty is, the higher the negative pressure is applied to each ejection port. For this reason, in particular, the flow width of the common supply flow path 211 and the common recovery flow path 212 (the length in the direction orthogonal to the ink flow direction) is reduced to reduce the head width (the length in the short 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 during high duty image formation, it is difficult to visually recognize even if satellites are generated, and the effect on the image is small. There is. The two circulation paths can be selected in light of the specifications of the liquid discharge head and the recording apparatus main body (discharge flow rate F, minimum circulation flow rate A, and in-head flow path resistance).

(Description of liquid discharge head configuration)
The configuration of the liquid ejection head 3 according to the first application example will be described. 4A and 4B are perspective views of the liquid ejection head 3 according to this application example. The liquid ejection head 3 is a line type liquid ejection head in which 15 recording element substrates 10 each capable of ejecting ink of four colors of C / M / Y / K are arranged in a straight line (arranged inline). As shown in FIG. 4A, the liquid ejection head 3 includes a signal input terminal 91 and a power supply terminal 92 electrically connected to each recording element substrate 10 via the flexible wiring board 40 and the electric wiring board 90. Is provided. The signal input terminal 91 and the power supply terminal 92 are electrically connected to the control unit of the recording apparatus 1000, and supply an ejection drive signal and electric power necessary for ejection 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. Accordingly, the number of electrical connection portions that need to be removed when the liquid discharge head 3 is assembled to the recording apparatus 1000 or when the liquid discharge head is replaced can be reduced. As shown in FIG. 4B, the liquid connection portions 111 provided at both ends of the liquid ejection head 3 are connected to the liquid supply system of the recording apparatus 1000. Thus, CMYK four color inks are supplied from the supply system of the recording apparatus 1000 to the liquid discharge head 3, and ink that has passed through the liquid discharge head 3 is collected into the supply system of the recording apparatus 1000. As described above, the ink of each color can be circulated through the path of the recording apparatus 1000 and the path of the liquid discharge head 3.

  FIG. 5 shows an exploded perspective view of each component or unit constituting the liquid ejection head 3. The liquid discharge unit 300, the liquid supply unit 220, and the electric wiring substrate 90 are attached to the housing 80. The liquid supply unit 220 is provided with a liquid connection portion 111 (FIG. 3), and each color communicating with each opening of the liquid connection portion 111 is provided inside the liquid supply unit 220 to remove foreign matters in the supplied ink. Another filter 221 (FIGS. 2 and 3) is provided. The two liquid supply units 220 are each provided with filters 221 for two colors. The ink that has passed through the filter 221 is supplied to the negative pressure control unit 230 disposed on the supply unit 220 corresponding to each color. The negative pressure control unit 230 is a unit composed of a pressure regulating valve for each color. The negative pressure control unit 230 is provided in the supply system of the recording apparatus 1000 (the supply system on the upstream side of the liquid ejection head 3) generated by the change in the ink flow rate by the action of a valve, a spring member, or the like provided therein. Significantly attenuates pressure loss changes. For this reason, it is possible to stabilize the negative pressure change on the downstream side (liquid ejection unit 300 side) from the pressure control unit within a certain range. In the negative pressure control unit 230 for each color, as described in FIG. 2, two pressure regulating valves for each color are built in, and are set to different control pressures. The two pressure regulating valves communicate with the common supply channel 211 in the liquid discharge unit 300 on the high pressure side and the common recovery channel 212 on the low pressure side via the liquid supply unit 220.

  The casing 80 includes a liquid discharge unit support part 81 and an electric wiring board support part 82, supports the liquid discharge unit 300 and the electric wiring board 90, and ensures the rigidity of the liquid discharge head 3. The electric wiring board support part 82 is for supporting the electric wiring board 90, and is fixed to the liquid discharge unit support part 81 by screws. 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 positional accuracy of the plurality of recording element substrates 10, thereby suppressing streaks and unevenness in the recorded matter. Therefore, the liquid discharge unit support portion 81 preferably has sufficient rigidity, and a metal material such as SUS or aluminum, or a ceramic such as alumina is preferable as the material. 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 through 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 included in the ejection module 200 and the sealing member are sealed from the opening 131. The stopper 110 (FIG. 9) is exposed. The frame portion around the opening 131 functions as a contact surface of a cap member that caps the liquid ejection head 3 during recording standby. For this reason, a closed space is formed at the time of capping by applying an adhesive, a sealing material, a filler, or the like along the periphery of the opening 131 and filling the irregularities and gaps on the discharge port surface of the liquid discharge unit 300. 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 laminate of the first flow path member 50, the second flow path member 60, and the 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 circulated 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, and thereby warpage and deformation of the flow path member 210 are suppressed.

  FIGS. 6A to 6F are views showing the front and back surfaces of each flow path member of the first to third flow path members. 6A shows the surface of the first flow path member 50 on the side where 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 FIG. 6B and FIG. 6C, which are contact surfaces of the respective flow path members, face each other. The member and the third flow path member are joined so that FIG. 6D and FIG. 6E, which are contact surfaces of the respective flow path members, face each other. By joining the second flow path member 60 and the third flow path member 70, eight common channel grooves 62 and 71 formed in the respective flow path members extend in the longitudinal direction of the flow path member. The common flow path is formed. As a result, a set of the common supply channel 211 and the common recovery channel 212 is formed in the channel 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 is in fluid communication with the liquid supply unit 220. A plurality of communication ports 61 are formed in the bottom surface of the common flow channel 62 of the second flow channel member 60 and communicate with one end of the individual flow channel 52 of the first flow channel member 50. A communication port 51 is formed at the other end of the individual flow channel 52 of the first flow channel member 50, and is in fluid communication with the plurality of discharge modules 200 via the communication port 51. The individual flow channel 52 enables the flow channels to be concentrated on the center side of the flow channel member.

  The first to third flow path members are preferably made of a material having corrosion resistance to ink and a low linear expansion coefficient. As a material, for example, a composite material (resin material) in which an inorganic filler such as silica fine particles or fibers is added to a base material can be suitably used. Examples of the base material include alumina, LCP (liquid crystal polymer), PPS (polyphenyl sulfide), 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. 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 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 the perspective view expanded. The flow path member 210 has a common supply flow path 211 (211a, 211b, 211c, 211d) and a common recovery flow path 212 (212a, 212b, 212c, 212d) extending in the longitudinal direction of the liquid ejection head 3 for each color. Is provided. A plurality of individual supply channels (213 a, 213 b, 213 c, and 213 d) formed by the individual channel grooves 52 are connected to the common supply channel 211 of each color via the communication port 61. In addition, 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 the communication port 61. With such a flow path configuration, it is possible to collect ink from each common supply flow path 211 via the individual supply flow path 213 to the recording element substrate 10 located at the center of the flow path member. Ink can be recovered from the recording element substrate 10 to each common recovery channel 212 via the individual recovery channel 214.

  FIG. 8 is a view showing a cross section taken along line EE of FIG. As shown in this figure, each individual recovery channel (214a, 214c) communicates with the discharge module 200 via the communication port 51. Although only the individual recovery flow paths (214a, 214c) are shown in FIG. 8, the separate supply flow path 213 and the discharge module 200 communicate with each other in another cross section 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 includes a flow path for supplying ink from the first flow path member 50 to the recording element 15 (FIG. 10) provided on the recording element substrate 10, and part or all of the ink supplied to the recording element 15. Is recovered (circulated) to the first flow path member 50. Here, the common supply channel 211 of each color is connected to the corresponding negative pressure control unit 230 (high pressure side) via the liquid supply unit 220, and the common recovery channel 212 is connected to the negative pressure control unit 230 ( And a liquid supply unit 220. By this negative pressure control unit 230, a differential pressure (pressure difference) is generated between the common supply channel 211 and the common recovery channel 212. For this reason, as shown in FIGS. 7 and 8, in the liquid ejection head of this application example in which the respective flow paths are connected, 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 that flows in order from the channel 213b to the common recovery channel 212 is generated.

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

(Description of structure of 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 which the discharge port 13 is formed, FIG. 10B shows an enlarged view of the portion indicated by A in FIG. FIG.10 (c) shows the top view of the back surface of Fig.10 (a). As shown in FIG. 10A, the discharge port forming member 12 of the recording element substrate 10 is formed with four rows of discharge port rows corresponding to the respective ink colors. Hereinafter, the direction in which the discharge port array in which the plurality of discharge ports 13 are arranged is referred to as “discharge port array direction”.

  As shown in FIG. 10B, a recording element 15 that is a heating element for foaming ink with thermal energy is disposed at a position corresponding to each ejection port 13. A partition 22 defines a pressure chamber 23 having the recording element 15 therein. The recording element 15 is electrically connected to the terminal 16 in FIG. 10A by electrical 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 apparatus 1000 via the electric wiring board 90 (FIG. 5) and the flexible wiring board 40 (FIG. 9), and causes the ink to boil. Ink is ejected from the ejection port 13 by the force of foaming due to boiling. As shown in FIG. 10B, along each discharge port array, a liquid supply path 18 extends on one side, and a liquid recovery path 19 extends on the other side. The liquid supply path 18 and the liquid recovery path 19 are flow paths extending in the direction of the discharge port array provided in the recording element substrate 10 and communicate with the discharge port 13 through the supply port 17a and the recovery port 17b, respectively.

  As shown in FIGS. 10C and 11, a sheet-like lid member 20 is laminated on the back surface of the recording element substrate 10 on which the discharge ports 13 are formed. A plurality of openings 21 communicating with the liquid supply path 18 and the liquid recovery path 19 are provided. In this application example, three openings 21 are provided in the lid member 20 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 be 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 it is sufficient that at least two openings 21 are provided for any one of the liquid supply path 18 and the liquid recovery path 19. For example, the liquid supply path 18 may have a configuration of a liquid ejection head having two openings 21 and the liquid recovery path 19 having one opening 21. As shown in FIG. 10B, each opening 21 of the lid member 20 communicates with a plurality of communication ports 51 shown in FIG. As shown in FIG. 11, the lid member 20 has a function as a lid that forms part of the walls of the liquid supply path 18 and the liquid recovery path 19 formed in the substrate 11 of the recording element substrate 10. The lid member 20 is preferably one having sufficient corrosion resistance against ink, and high accuracy is required for the opening shape and opening position of the opening 21 from the viewpoint of preventing color mixing. For this reason, it is preferable to use a photosensitive resin material or a silicon plate as the material of the lid member 20 and provide the opening 21 by a photolithography process. As described above, the lid member converts the pitch of the flow path by the opening 21, and considering the pressure loss, it is desirable that the thickness is thin, 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. The recording element substrate 10 includes 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 grooves constituting a liquid supply path 18 and a liquid recovery path 19 extending along the ejection port array are 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 path 211 and the common recovery path 212 in the flow path member 210, respectively. A differential pressure is generated between the liquid recovery passageway 19 and the liquid recovery passageway 19. When ink is ejected from the plurality of ejection ports 13 of the liquid ejection head 3 and recording is performed, the following flow occurs in the ejection ports 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). The flow shown in). With this flow, in the ejection port 13 and the pressure chamber 23 where recording is paused, it is possible to collect the thickened ink generated by evaporation from the ejection port 13 and bubbles / foreign matter in the liquid recovery path 19. Further, it is possible to suppress the thickening of the ink in the ejection port 13 and the pressure chamber 23. The ink recovered into 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), the communication port 51 in the flow path member 210, the individual recovery flow path. 214 and the common recovery flow path 212 are recovered in this order. This ink is finally collected into the supply path of the recording apparatus 1000.

  That is, the ink supplied from the recording apparatus main body to the liquid discharge head 3 flows in the following order, and is supplied and recovered. The ink first flows into the liquid ejection head 3 from the liquid connection portion 111 of the liquid supply unit 220. The ink is then connected to the joint rubber 100, the communication port 72 and the common channel groove 71 provided in the third channel member, the common channel groove 62 and the communication port 61 provided in the second channel member, and the first channel. The individual flow channel 52 and the communication port 51 provided in the member are supplied in this order. Thereafter, the pressure 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 17 a in this order. Of the ink supplied to the pressure chamber 23, the ink that has not been ejected from the ejection port 13 passes through the recovery port 17 b and the liquid recovery path 19 provided in the substrate 11, the opening 21 provided in the lid member, and the support member 30. It flows through the provided liquid communication port 31 in order. Thereafter, the ink is provided in the communication port 51 and the individual flow channel 52 provided in the first flow channel member, the communication port 61 and the common flow channel 62 provided in the second flow channel member, and the third flow channel member 70. The common channel groove 71, the communication port 72, and the joint rubber 100 are sequentially flowed. Then, the ink flows from the liquid connection part 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 from the liquid connecting 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 collected from the pressure chamber 23 passes through the joint rubber 100 and then passes from the liquid connection unit 111 to the outside of the liquid ejection head via the negative pressure control unit 230. To flow.

  Further, as shown in FIGS. 2 and 3, not all ink that has flowed from one end of the common supply channel 211 of the liquid ejection unit 300 is supplied to the pressure chamber 23 via the individual supply channel 213a. . Some ink flows from the other end of the common supply channel 211 to the liquid supply unit 220 without flowing into the individual supply channel 213a. As described above, by providing a path that flows without passing through the recording element substrate 10, even if the recording element substrate 10 having a fine flow path having a high flow resistance is provided as in this application example, the ink can be used. The reverse flow of the circulating flow can be suppressed. In this way, in the liquid discharge head of this application example, it is possible to suppress the increase in the viscosity of the ink in the pressure chamber and the vicinity of the discharge port, so it is possible to suppress defects in the discharge direction and undischarge, and as a result, high-quality recording is performed Can do.

(Description of positional relationship between recording element substrates)
FIG. 12 is a plan view showing a partially enlarged adjacent portion of the recording element substrate in two adjacent ejection modules. As shown in FIG. 10, in this application example, a substantially parallelogram recording element substrate is used. As shown in FIG. 12, the ejection port arrays (14a to 14d) in which the ejection ports 13 in each recording element substrate 10 are arranged are arranged so as to be inclined at a certain angle with respect to the conveyance 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 conveyance 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 is slightly deviated from a predetermined position, the black streaks and white spots of the recorded image are made inconspicuous by driving control of the overlapping discharge ports. it can. The plurality of recording element substrates 10 can be arranged in a straight line (inline) instead of the staggered arrangement. In this case as well, it is possible to take measures against black streaks and white spots at the connecting portions of the recording element substrates 10 while suppressing an increase in the length of the recording medium transport direction of the liquid ejection head 10 with the configuration 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. For example, even when a rectangular, trapezoidal or other shape recording element substrate is used, the present invention is not limited thereto. The configuration can be preferably applied.

(Second application example)
The configurations of the ink jet recording apparatus 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.

(Description of inkjet recording apparatus)
FIG. 13 shows an ink jet recording apparatus according to a second application example of the present invention. The recording apparatus 1000 of the second application example is different from the first application example in that full-color recording is performed on a recording medium by arranging four monochromatic liquid ejection heads 3 corresponding to CMYK inks in parallel. In the first application example, the number of ejection port arrays that can be used per color is one, whereas in this application example 2, the number of ejection port arrays that can be used per color is 20 (FIG. 19). (A)). For this reason, it is possible to perform very high-speed recording by appropriately recording the recording data to a plurality of ejection port arrays. Furthermore, even if there is a discharge port that fails to discharge, reliability can be achieved by interpolating discharge from the discharge ports in other rows that are at positions corresponding to the transport direction of the recording medium with respect to that discharge port. It is improved and suitable for commercial printing. Similarly to the first application example, the supply system of the recording apparatus 1000, the buffer tank 1003, and the main tank 1006 (FIG. 2) are fluidly connected to each liquid ejection head 3. Each liquid discharge head 3 is electrically connected to an electric control unit that transmits power and a discharge control signal to the liquid discharge head 3.

(Explanation of circulation route)
As the liquid circulation path between the recording apparatus 1000 and the liquid discharge head 3, the first and second circulation paths shown in FIG. 2 or FIG. 3 can be used as in the first application example.
(Description of liquid discharge head structure)
The structure of the liquid ejection head 3 according to the second application example of the present invention will be described. 14A and 14B are perspective views of the liquid discharge head 3 according to this application example. The liquid discharge head 3 is an ink jet type line 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 perform recording with one color ink. Similar to the first application example, the liquid discharge head 3 includes a liquid connection portion 111, a signal input terminal 91, and a power supply terminal 92. However, since the liquid ejection head 3 of this application example has more ejection port arrays than the first application example, the signal output terminal 91 and the power supply terminal 92 are arranged on both sides of the liquid ejection head 3. This is to reduce 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 for each function. The role of each unit and member and the order of liquid circulation in the liquid discharge head are basically the same as those in the first application example, but the function of ensuring the rigidity of the liquid discharge head is different. In the first application example, the liquid discharge head rigidity is mainly secured by the liquid discharge unit support portion 81. However, 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 guaranteed. 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 apparatus 1000, so that the liquid discharge head 3 Perform positioning. The liquid supply unit 220 including the negative pressure control unit 230 and the electric wiring board 90 are coupled to the liquid discharge unit support portion 81. Each of the two liquid supply units 220 includes a filter (not shown). The two negative pressure control units 230 are set so as to control the pressure with different relatively high and low negative pressures. Further, when the negative pressure control unit 230 on the high pressure side and the low pressure side is 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 and The ink flows in the common recovery channel 212 face each other. In this way, heat exchange is promoted between the common supply channel 211 and the common recovery channel 212, and the temperature difference in the two common channels is reduced. Therefore, there is an advantage that a temperature difference in each of the recording element substrates 10 provided in a plurality along the common flow path is difficult to occur, and recording unevenness due to the temperature difference is less likely to occur.

  Next, 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 laminate 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 ejection module 200. . The flow path member 210 functions as a flow path member for returning ink circulated from the ejection 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 a common supply flow path 211 and a common recovery flow path 212 are formed, and has a function of mainly responsible for the rigidity of the liquid ejection head 3. Have. For this reason, as a material of the 2nd flow path member 60, what has sufficient corrosion resistance with respect to ink and high mechanical strength is preferable. Specifically, SUS, Ti, alumina or 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 that is in contact with the second flow path member 60. FIG. Unlike the first application example, the first flow path member 50 in the second application example has a plurality of members corresponding to each discharge module 200 arranged adjacent to each other. By adopting such a divided structure, it is possible to correspond to the length of the liquid discharge head by arranging a plurality of modules, so that, for example, a relatively long scale corresponding to a B2 size or longer. The present invention can be particularly preferably applied to the liquid discharge head. As shown in FIG. 16 (a), the communication port 51 of the first flow path member 50 is in fluid communication with the discharge module 200, and as shown in FIG. 16 (b), the individual communication of the first flow path member 50 is performed. The port 53 is in fluid communication 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 in contact with the first flow path member 50, and FIG. 15D shows the cross section of the central portion in the thickness direction of the second flow path member 60. FIG. 16 (e) is a diagram showing a surface of the second flow path member 60 on the side in 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 for one color in the first application example. One of the common flow channel grooves 71 of the second flow channel member 60 is a common supply flow channel 211 shown in FIG. 17 and the other is a common recovery flow channel 212, respectively, along the longitudinal direction of the liquid ejection head 3. Thus, 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 channel 211 and the common recovery channel 212 are opposite to each other.

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

  18 is a view showing a cross section taken along line FF in FIG. As shown in this figure, the common supply channel 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 apparent with reference to FIG. 17 that the individual recovery flow path is connected to the discharge module 200 through a similar path. As in 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 pauses the ejection operation. Through the discharge port 13 (pressure chamber 23), it is possible to circulate. Similarly to the first application example, the common supply channel 211 is connected to the negative pressure control unit 230 (high pressure side), and the common recovery channel 212 is connected to the negative pressure control unit 230 (low pressure side) and the liquid supply unit 220. It is connected. For this reason, the differential pressure causes a flow that flows from the common supply channel 211 to the common recovery channel 212 through the discharge port 13 (pressure chamber 23) of the recording element substrate 10.

(Description 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 respectively arranged on both sides (each long side of the recording element substrate 10) along the plurality of ejection port array directions of the recording element substrate 10 and electrically connected thereto. Two wiring boards 40 are also arranged for one recording element board 10. This is because the number of ejection port arrays provided on the recording element substrate 10 is 20, which is significantly larger than the 8 arrays of the first application example. That is, an object is to reduce the voltage drop and signal transmission delay that occur in the wiring portion in the recording element substrate 10 by suppressing the maximum distance from the terminal 16 to the recording element 15 provided corresponding to the ejection port array. It is said. Further, the liquid communication port 31 of the support member 30 is provided in the recording element substrate 10 and is opened so as to straddle all the ejection port arrays. The other points are the same as in the first application example.

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

(First embodiment)
(Relationship between tail length reduction and discharge port dimensions)
FIG. 21 shows the inside of the liquid ejection head, FIG. 21A is a plan view showing a recording element and a flow path, and FIG. 21B is a cross-sectional view taken along the line AA in FIG. It is. Between the substrate 11 of the recording element substrate 10 and the discharge port forming member 12, a plurality of pressure chambers 23 each having a discharge port 13, and an inlet channel 24a and an outlet channel 24b communicating with the pressure chambers 23, respectively. 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 channel 24 a branches from the liquid supply channel 18 at the supply port 17 a of the liquid supply channel 18, communicates with the pressure chamber 23, and supplies ink to the pressure chamber 23. The outlet channel 24 b communicates with the pressure chamber 23 on the side opposite to the inlet channel 24 a with respect to the pressure chamber 23, and the ink that has not been ejected from the ejection port 13 passes through the recovery port 17 b of the liquid recovery channel 19. 19 is discharged.

  The plurality of supply ports 17a form a supply port array, and the plurality of recovery ports 17b form a recovery port array. A discharge port row in which a plurality of discharge ports 13 are arranged is formed between the supply port row and the recovery port row. In the present embodiment, the discharge port array and the recovery port array are provided on both sides of the supply port array. 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 channel 24a, and a circulating flow is generated in which ink flows from the outlet channel 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 17 a, and the inlet channel 24 a and is discharged from the discharge port 13. The ink that has not been ejected is collected through the outlet flow path 24 b, the recovery port 17 b, and the liquid recovery path 19. The recovered ink is supplied again to the liquid supply path 18 via a circulation 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. A 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 from which ink is discharged. The ejection port portion 25 to the ejection 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 connects the discharge port 13 and the pressure chamber 23. It means a through hole that penetrates the discharge port forming member 12.

  FIG. 22 is a schematic diagram showing a transient process of the discharge phenomenon. 22A shows an enlarged view of a portion B in FIG. 21A, and FIGS. 22B to 22G are cross-sectional views taken along the line AA in FIG. 22A. In FIG. 22, the projection of the discharge port 13 shown in FIG. Ink is supplied to the pressure chamber 23 from the inlet channel 24a (see FIG. 22B). The recording element 15 generates thermal energy that is used to discharge the liquid when electric energy is applied thereto. The ink in the vicinity of the recording element 15 is heated and evaporated by this thermal energy, and a bubble B is formed (see FIG. 22C). 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. 22C). The bubble B enters the discharge port 25 while growing. As the bubble B grows, the internal pressure of the bubble B suddenly changes from a positive pressure to a negative pressure lower than the atmospheric pressure (see FIG. 22D). Due to the negative pressure, the trailing edge of the droplet is drawn toward the recording element 15 and the tail length is extended (see FIG. 22E). When the bubble B further proceeds inside the discharge port portion 25, the bubble B communicates with the atmosphere inside or outside the discharge port portion 25. As a result, the negative pressure of the bubble B is rapidly lost, and the tail length stops growing (see FIG. 22 (f)). Through the above steps, the ink between the generated bubble B and the discharge port 13 is discharged from the discharge port 13 by the pressure of the bubble B. The ejected ink is mainly ejected as a main droplet, but satellite S and mist are generated behind the main droplet (see FIG. 22G). In the present embodiment, the bubbles B communicate with the atmosphere when the internal pressure is in a negative pressure state and the volume increases (during expansion). This stabilizes the discharge volume of the droplets and improves the discharge speed. In the configuration in which the protrusion 27 is provided in 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, the droplets are ejected in communication with the atmosphere during the growth of the bubbles B, thereby suppressing the generation of satellites while suppressing a decrease in ejection speed.

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 a pattern A and a pattern B that are different in only the pressure profile inside the bubble with the same discharge port size. FIG. 23B schematically shows how the pattern A ink is ejected, and FIG. 23C schematically shows how the pattern B ink is ejected. In both the pattern A and the pattern B, the internal pressure of the bubble suddenly increases and then becomes a negative pressure. Thereafter, the bubble communicates with the atmosphere and increases to the 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. For this reason, as shown in FIG. 23C, the tail length of the droplet is longer than that of the pattern A, and satellites are easily generated. 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. For this reason, the tail length becomes relatively short, and the generation of satellites is suppressed as shown in FIG. Thus, shortening the duration of the negative pressure and allowing the bubbles to communicate with the atmosphere at an early stage is effective for suppressing tail length elongation, that is, suppressing satellites.

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

In any pattern, the effective diameter of OH and the discharge port 13 is the same, 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 desirably 100 μm ² or more. When the discharge port 13 has a circular shape (pattern 1), it can be seen that OH needs to be reduced in order to reduce Tth in order to shorten the tail length. In order to lower the OH, it is necessary to thin the discharge port forming member 12 (decrease H1) or reduce the height of the inlet channel 24a (height of the pressure chamber) (decrease H2). In the former, cracks or the like are likely to occur in the discharge port forming member 12, and the possibility that the reliability is lowered increases. 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 at the discharge port 13 (patterns 2 and 3), Tth is lower than that of the pattern 1. In particular, when the interval between the protrusions 27 is narrow (pattern 3), the decrease in Tth is significant. 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. However, 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. It 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 facing the tip of the discharge port), the tail length is shortened. Connection is preferable.

FIG. 25 shows the relationship between the thickness H1 of the discharge port forming member 12, the height of the inlet channel 24a (pressure chamber height) H2, and the atmosphere communication time Tth. The horizontal axis represents the inlet channel 24a. , The vertical axis indicates the thickness H1 of the discharge port forming member 12. 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 atmosphere communication time Tth when OH is fixed at 12 μm and the height H2 of the inlet channel 24a (or the thickness H1 of the discharge port forming member 12) is changed. Tth increases in the order of levels A, B, and C. Accordingly, when the OH is constant, the air communication time Tth can be further reduced when the height H2 of the inlet channel 24a is lower. The height H2 of the inlet channel 24a is preferably 7 μm or less, and is preferably half or less of OH. The distance OH between the ejection port 13 and the recording element 15 is desirably 12 μm or less.

(Reduction mechanism of atmospheric communication time Tth)
Next, a mechanism for reducing the atmosphere communication time Tth will be described.
26 and 27 show the relationship between the distance OH and the air communication position of the bubbles. FIG. 26A shows the definition of the dz and z directions. dz indicates the position in the z direction where 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. 26 (b), the horizontal axis represents OH and the vertical axis represents dz. When the shape of the discharge port 13 is circular (pattern 1), dz gradually approaches 0 as OH decreases. That is, when 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 protrusion 27 (patterns 2 and 3), OH ≦ 12 μm and dz> 0, and atmospheric communication is generated outside the discharge port 13. The pattern 3 having a narrow protrusion interval has a larger dz, and as a result, the Tth similarly decreases.

  FIG. 27A shows the definition of dx and x direction. dx indicates the position in the x direction where 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. 27B, the horizontal axis represents OH and the vertical axis represents dx. When the shape of the discharge port 13 is circular (pattern 1), dx hardly changes even if OH decreases. When the discharge port 13 has the protrusion 27 (patterns 2 and 3), dx approaches 0, and dx increases as OH decreases. The dx is larger in the pattern 3 where the protrusion interval is narrower.

FIG. 28 is a simulation view showing droplets ejected from the ejection port 13. FIG. 28A is a perspective view of ejection droplets when the shape of the ejection port 13 is circular (pattern 1), and FIG. (C) is the figure which showed the transient time change of the velocity distribution of a bubble and air | atmosphere. FIG. 28 (d) is a perspective view of a discharged droplet when the discharge port 13 has a protrusion 27, and FIGS. 28 (e) and 28 (f) show transient time changes in the velocity distribution of bubbles and air. FIG. FIGS. 28E and 28F are cross-sectional views regarding a straight line passing through the center of the two projections and the ejection port provided in the ejection port of FIG. x and z are defined in FIG. From FIG. 28B and FIG. 28C, the transient phenomenon inside the discharge port portion 25 when the shape of the discharge port 13 is circular (pattern 1) is as follows.
Step 1) The generated bubbles B enter the discharge port portion 25 and grow inside the discharge port portion 25. Accordingly, the bubble B has a velocity component toward the center of the discharge port 13 (x = 0) due to the influence of the wall surface of the discharge port forming member 12 (side surface of the discharge port portion 25) (see arrow A in FIG. 28B). )
Step 2) As the bubble B grows, 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) The air is drawn into the discharge port 13 by the negative pressure inside the bubble (see arrow D in FIG. 28C).
Step 4) Due to the negative pressure inside the bubble, the bubble itself is drawn toward the center of the discharge port 25, and further pulled toward the center of the discharge port 25 by the force of the ink interface (FIG. 28C). (See arrow C)
As a result, the atmosphere G and the bubbles B tend to communicate with each other inside the discharge port portion 25. There is a tendency that bubbles are difficult to communicate with the atmosphere outside the discharge port portion 25 and Tth becomes slow.

  On the other hand, when the ejection port 13 has the protrusion 27, the bubble B spreads outside the ejection port 13 by the force of the ink interface (see arrow C in FIG. 28 (f)). At least a part of the bubbles B that have entered the discharge port portion 25 has a velocity component from the center of the discharge port portion 25 toward the side wall. In particular, in the case of a discharge port shape in which the curvature is not constant by providing the protrusion 27, the surface tension acts so as to form a spherical shape with a stable gas-liquid interface. The atmosphere G is drawn into the discharge port portion 25, while the bubbles B expand in a direction away from the center of the discharge port portion 25. As a result, the atmosphere G and the bubbles B have velocity components opposite to each other and move in the direction in which they collide with each other. FIG. 28 (f) also shows that the atmosphere communication position is outside the discharge port portion 25 or the discharge port 13.

As described above, the following characteristics can be obtained by reducing the OH (the distance between the ejection port and the recording element is 12 μm or less) and providing the projection 27 on the ejection port 13.
Feature 1) Advancement of atmosphere communication time Tth Feature 2) Bubbles communicate with the atmosphere outside the discharge port 25 Feature 3) Bubbles before communicating with the atmosphere expand to the outside As a result, the tail length is shortened, and satellite and 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.
The discharge port shapes 1 to 6 have the following characteristics.
Discharge port shape 1: Circular discharge port discharge port shape 2: Two symmetrical projections 27, wide discharge port discharge port shape 3: Two symmetrical projections 27, having a projection spacing Narrow discharge port discharge shape 4: Four symmetrical projections 27, wide discharge port discharge port shape 5: One projection 27, and the distance between the projection and the opposite edge is Wide discharge port shape 6: One protrusion 27, and a narrow distance between the protrusion and the opposite edge The discharge port shapes 2-6 all have at least one protrusion 27, The protrusion 27 is located on a straight line passing through the center of the discharge port 13. In any of the discharge port shapes 2 to 6, Tth is smaller than that of the discharge port shape 1. Further, any of the discharge port shapes 2 to 6 has a positive dz, and atmospheric communication is generated outside the discharge port portion 25. Accordingly, the discharge port shapes 2 to 6 are preferable embodiments because the tail length can be shortened to suppress satellites and mist. However, in the discharge port shape 4, when the number of the protrusions 27 increases, the flow resistance of the discharge port 25 increases and the discharge efficiency deteriorates. For this reason, it is preferable that the protrusions 27 are not too many. 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 25, but the ejection port shape is asymmetrical, and ink droplets are inclined and easily fly. . From this point of view, the discharge port 13 is more preferably symmetrical. Therefore, particularly preferred embodiments are the discharge port shapes 2 and 3 having the two protrusions 27 provided at positions on both sides symmetrical with respect to the center of the discharge port 13. From the viewpoint of accelerating Tth, the discharge port shape 3 having two protrusions 27, a symmetrical discharge port shape, and a narrow protrusion interval is more preferable.

  In the embodiment described above, the liquid flow path is provided on both sides of the recording element 15, but as shown in FIGS. 31 (a) and 31 (b), the liquid flow path is 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)
FIG. 32 is a view showing a second embodiment of the present invention, FIG. 32 (a) is a plan view showing the recording element 15 and the flow path, and FIG. 32 (b) is an AA line in FIG. 32 (a). FIG. A circulating flow flows in a direction parallel to the protrusion 27 of the discharge port 13. Compared to the first embodiment shown in FIG. 21, the recovery path array is provided only on one side of the supply path array, and the others are the same. For details, refer to the first embodiment. I want.

  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 circulation flow. FIGS. 34A and 34B are views in which the vicinity of one pressure chamber 23 in FIGS. 32 and 33 is cut out. 34A, the extending direction of the circulating flow and the projection of the discharge port 13 is along (substantially parallel), and in FIG. 34B, the extending direction of the circulating flow and the projection of the discharge port 13 intersects (substantially). Are orthogonal). 34 (c) and 34 (d) show the numerical calculation results of droplet formation in the case of continuous ejection in FIGS. 34 (a) and 34 (b), respectively, when the influence of so-called pause time is small. FIGS. 34 (e) and (f) are numerical calculation results of droplet formation after a predetermined rest time in FIGS. 34 (a) and 34 (b), respectively. Ink thickening due to evaporation of ink from the ejection port 13 is shown in FIGS. The influence of is increasing.

  34 (e) and (f), the method (FIG. 34 (b)) in which the circulating flow is perpendicular to the configuration (FIG. 34 (b)) that flows in parallel with the protrusion 27 of the discharge port 13 is more ink. Less susceptible to thickening. This is because the ink evaporation rate is large in the portion where the radius of curvature at the base of the protrusion 27 is small (the portion surrounded by the circles in FIGS. 34 (g) and (h)), and therefore the direction where the circulating flow flows in that region is concentrated. It is thought that it is difficult to be affected by

Therefore, the present invention can be applied to any of the forms shown in FIGS. 34 (e) and 34 (f). However, in a configuration with a circulating flow, in order to further suppress the concentration inside the discharge port, the circulating flow is not discharged from the discharge port 13. A configuration that flows in a direction intersecting with the protrusion (more preferably perpendicular) is more preferable. In other words, it is desirable that the straight line on which the protrusion is located forms 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 sucrose.
In addition, the flying direction of the ejected liquid droplets may vary depending on the shape variation or deformation of the protrusion 27. In consideration of this point, it is preferable that the relative movement direction of the recording medium and the extending direction of the protrusions 27 are along (more preferably parallel) with respect to the liquid ejection head 3. This is because, with such a configuration, even if the flying direction of the droplet changes due to deformation of the projection 27, the influence on the recorded image is reduced.

13 Ejection port 15 Recording element 25 Ejection port B Bubble G Air

Claims (18)

A recording element that generates thermal energy used for discharging a liquid, a pressure chamber that includes the recording element therein, a discharge port that discharges liquid, and a discharge port that communicates the discharge port and the pressure chamber And
A bubble is generated in the pressure chamber by the thermal energy, the generated bubble enters the inside of the discharge port, and a liquid is discharged from the discharge port by the pressure of the bubble.
A liquid ejection head in which air bubbles entering the inside of the ejection port communicate with the atmosphere outside the ejection port. A recording element that generates thermal energy used for discharging a liquid, a pressure chamber that includes the recording element therein, a discharge port that discharges liquid, and a discharge port that communicates the discharge port and the pressure chamber And
A bubble is generated in the pressure chamber by the thermal energy, the bubble enters the inside of the discharge port, and a liquid is discharged from the discharge port by the pressure of the bubble;
The liquid discharge head, wherein at least a part of the bubbles entering 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, wherein a distance between the discharge port and the recording element is 12 μm or less.   The liquid supply path that communicates with the pressure chamber and supplies liquid to the pressure chamber, and the height of the liquid supply path in a direction perpendicular to the bottom surface of the pressure chamber is 7 μm or less. The liquid discharge head according to any one of the above. The liquid discharge head according to claim 1, wherein an opening area of the discharge port is 100 μm ² or more.   A liquid supply path that communicates with the pressure chamber and supplies liquid to the pressure chamber, and the height of the liquid supply path in a direction perpendicular to the bottom surface of the pressure chamber is the height between the ejection port and the recording element. The liquid discharge head according to claim 1, wherein the liquid discharge head is not more than half of the distance between them.   The liquid discharge head according to claim 1, wherein the discharge port has at least one protrusion that protrudes toward the center of the discharge port.   8. The liquid ejection head according to claim 7, wherein the liquid ejection head has two protrusions located on a straight line passing through the center and provided on both sides with respect to the center.   A liquid supply path that communicates with the pressure chamber and supplies 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 liquid ejection head according to claim 1, comprising: a liquid ejection head according to claim 1.   The discharge port has two protrusions protruding toward the center of the discharge port, the two protrusions are located on a straight line passing through the center, provided on both sides with respect to the center, and the straight line is The liquid discharge head according to claim 9, wherein the liquid discharge head forms an angle of 45 degrees or more with respect to a flow path axis connecting the liquid supply path and the liquid recovery path.   The liquid ejection head according to claim 10, wherein the straight line and the flow path axis intersect each other. A recording element that generates thermal energy used to discharge the liquid, a pressure chamber that includes the recording element therein, a liquid supply path that communicates with the pressure chamber and supplies the liquid to the pressure chamber, and a liquid A liquid discharge head comprising a discharge port for discharging,
The discharge port has at least two protrusions protruding toward the center of the discharge port,
The liquid discharge head, wherein the liquid supply path has a height of 7 μm or less.   The liquid discharge head according to claim 12, wherein a distance between the discharge port and the recording element is 12 μm or less.   The liquid ejection head according to claim 2, wherein bubbles that have entered the inside of the ejection port communicate with the atmosphere outside the ejection port.   The liquid discharge head according to claim 1, wherein the liquid in the pressure chamber is circulated between the outside of the pressure chamber. Generating bubbles in the liquid by a recording element that generates thermal energy;
Discharging the liquid from the discharge port provided at a position facing the recording element by the pressure of the generated bubbles;
Allowing the bubbles to communicate with the atmosphere outside the discharge port. A recording element that generates thermal energy used for discharging a liquid, a pressure chamber that includes the recording element therein, a discharge port that discharges liquid, and a discharge port that communicates the discharge port and the pressure chamber A liquid discharge method for a liquid discharge head comprising:
Generating bubbles in the liquid by the recording element;
Allowing the generated bubbles to enter the inside of the discharge port,
Causing the liquid to be discharged from the discharge port by the pressure of the generated bubbles,
The liquid discharge method, wherein at least a part of the bubbles that have entered the inside of the discharge port portion have a velocity component from the center of the discharge port portion toward the side wall. A recording element that generates thermal energy used for discharging a liquid, a pressure chamber that includes the recording element therein, a discharge port that discharges liquid, and a discharge port that communicates the discharge port and the pressure chamber A liquid discharge method for a liquid discharge head comprising:
Generating bubbles in the liquid by the recording element;
Allowing the generated bubbles to enter the inside of the discharge port,
Causing the liquid in the discharge port portion to be discharged from the discharge port by the generated pressure of the bubbles,
A liquid ejection method in which air bubbles that have entered the inside of the ejection port communicate with the atmosphere outside the ejection port.