CN110978793A - Liquid discharge head - Google Patents

Abstract

A liquid discharge head is provided. The liquid discharge head includes a recording element configured to generate thermal energy and a discharge port provided at a position facing the recording element. Bubbles are generated in the liquid by thermal energy, the liquid between the bubbles and the discharge port is discharged from the discharge port by the pressure of the generated bubbles, and the bubbles communicate with the atmosphere outside the discharge port.

Description

Liquid discharge head

(this application is a divisional application filed on 2017, 1/6/2017, application No. 201710009956.1 entitled "liquid discharge head and liquid discharge method")

Technical Field

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.

Background

A droplet discharged from a liquid discharge head such as an ink jet head is generally separated into a main droplet and an accompanying sub droplet (hereinafter, also referred to as a "satellite droplet") at the time of discharge. The main droplets land on the recording medium at the intended positions, but it is difficult to control the landing positions of the satellite droplets. In the case of using a liquid discharge head requiring high throughput, satellite droplets may cause significant deterioration in the quality of recorded images. The particularly minute satellite droplets do not reach the recording medium and become floating ink droplets (hereinafter also referred to as "mist"). The mist contaminates the recording apparatus, and such contamination of the recording apparatus may be transferred to and contaminate the recording medium.

Japanese patent laid-open No. 2008-290380 discloses a method of reducing the occurrence of satellite droplets by forming discharge ports of a shape other than a circular shape to prevent deterioration of image quality due to satellite droplets. U.S. patent application publication No. 2011/0205303 discloses a method of shortening the distance between a recording element and a discharge port to reduce the length of a droplet (hereinafter also referred to as "tail length"), thereby reducing the occurrence of satellite droplets. However, studies conducted by the present inventors have shown that the configurations of Japanese patent laid-open No. 2008-290380 and U.S. patent application publication No. 2011/0205303 do not achieve a further reduction in the tail length. This lets us recognize a new problem as to how difficult it is to control satellite droplets.

It is desirable to provide a liquid discharge head and a liquid discharge method capable of reducing the tail length of a liquid droplet.

Disclosure of Invention

A liquid discharge head according to the present invention includes: a recording element configured to generate thermal energy for discharging liquid; a pressure chamber having the recording element therein; a discharge port configured to discharge liquid; and an exhaust port portion that communicates between the exhaust port and the pressure chamber, wherein bubbles are generated in the pressure chamber by the thermal energy, the generated bubbles enter into the exhaust port portion, and the liquid is discharged from the exhaust port by a pressure of the bubbles, and the bubbles that have entered into the exhaust port portion communicate with the atmosphere outside the exhaust port.

Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 is a diagram showing a schematic configuration of a recording apparatus according to a first application example of the present invention.

Fig. 2 is a diagram showing a first circulation path of liquid circulation in the recording apparatus.

Fig. 3 is a diagram showing a second loop path in the recording apparatus.

Fig. 4A and 4B are perspective views of a liquid discharge head according to a first application example of the present invention.

Fig. 5 is an exploded perspective view of the liquid discharge head in fig. 4.

Fig. 6A to 6F are diagrams illustrating the arrangement of first to third channel members included in the liquid discharge head in fig. 4.

Fig. 7 is a diagram for describing a connection relationship between channels in the channel member.

Fig. 8 is a sectional view taken along line VIII-VIII in fig. 7.

Fig. 9A and 9B are views showing the discharge module, fig. 9A is a perspective view, and fig. 9B is an exploded view.

Fig. 10A to 10C are diagrams illustrating the arrangement of the recording element board.

Fig. 11 is a perspective view showing a configuration of a recording element plate and a cover including sections XI-XI in fig. 10A.

Fig. 12 is a plan view showing a partially enlarged view of an abutting portion of the recording element plates in two abutting discharge modules.

Fig. 13 is a diagram showing a configuration of a recording apparatus according to a second application example of the present invention.

Fig. 14A and 14B are perspective views 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 discharge head in fig. 14.

Fig. 16A to 16E are diagrams illustrating the arrangement of first and second channel members included in a channel member which the liquid discharge head in fig. 14 has.

Fig. 17 is a diagram for describing a connection relationship of the recording element plate and the liquid in the passage member.

Fig. 18 is a sectional view taken along line XVIII-XVIII in fig. 17.

Fig. 19A and 19B are views showing the discharge module, fig. 19A is a perspective view, and fig. 19B is an exploded view.

Fig. 20A to 20C are diagrams showing the arrangement of the recording element boards.

Fig. 21A and 21B are conceptual diagrams illustrating the inside of the liquid discharge head according to the first embodiment.

Fig. 22A to 22G are schematic diagrams showing a transient process of the discharge phenomenon.

Fig. 23A to 23C are diagrams showing a relationship between the pressure distribution inside the bubbles and the internal pressure of the bubbles.

Fig. 24A to 24D are diagrams showing a relationship between a distance from the recording element to the discharge port and an atmospheric communication time.

Fig. 25 is a diagram showing a relationship among the thickness of the discharge port forming member, the height of the inlet passage, and the atmospheric communication time.

Fig. 26A and 26B are diagrams showing a relationship between a distance from the recording element to the discharge port and an atmospheric communication position of the bubble.

Fig. 27A and 27B are diagrams showing a relationship between a distance from the recording element to the discharge port and an atmospheric communication position of the bubble.

Fig. 28A to 28F are conceptual views illustrating liquid droplets discharged from the discharge ports.

Fig. 29 is a diagram showing the atmosphere communication time with respect to various discharge port shapes.

Fig. 30 is a diagram showing an atmosphere communication position with respect to various discharge port shapes.

Fig. 31A and 31B are conceptual diagrams illustrating the inside of a liquid discharge head according to another embodiment.

Fig. 32A and 32B are conceptual diagrams illustrating the inside of the liquid discharge head according to the second embodiment.

Fig. 33A and 33B are conceptual diagrams illustrating the inside of the liquid discharge head according to the reference example.

Fig. 34A to 34H are conceptual views illustrating discharge of droplets in the second embodiment and the comparative example.

Detailed Description

Liquid discharge heads according to application examples and embodiments of the present invention will be described below with reference to the accompanying drawings. Although various technically preferable conditions are associated with the application examples and embodiments described below, the present invention is not limited to the conditions in these application examples and embodiments as long as the idea of the present invention is followed. Note that the liquid discharge head according to the present invention which discharges a liquid such as ink or the like and the liquid discharge apparatus mounting the liquid discharge head are applicable to devices such as a printer, a copying machine, a facsimile apparatus having a communication system, a word processor having a printer unit, and the like, and further applicable to an industrial recording apparatus combined with various types of processing apparatuses in a complicated manner. For example, the invention may be used in the manufacture of biochips, in the printing of electronic circuits, in the manufacture of semiconductor substrates, and other such uses.

Embodiments of the present invention are described below with reference to the drawings. The following description is not intended to limit the scope of the present invention. Although the application examples and embodiments relate to an inkjet recording apparatus (or simply "recording apparatus") in a form in which liquid such as ink is circulated between an ink reservoir and a liquid discharge head, other forms may be used. For example, the following form may be adopted: wherein, instead of circulating the ink, two ink tanks are provided, one on the upstream side and the other on the downstream side of the liquid discharge head, and the ink within the pressure chamber is made to flow by causing the ink to travel from one ink tank to the other ink tank.

Further, the application examples and embodiments relate to a so-called line-type discharge head having a length corresponding to the width of the recording medium, but the present invention may also be a so-called serial liquid discharge head (page width) that performs recording while scanning the recording medium. An example of the serial liquid discharge head is a configuration having one recording element plate for recording black ink and recording color ink, respectively, for example. However, this is not limiting, and the following arrangement may be made: a plurality of recording element plates are arranged in a manner that the ports are overlapped in the discharge port row direction, and a stub type discharge head shorter than the width of the recording medium is formed, and the stub type discharge head is caused to scan the recording medium.

First application example

An application example to which the present invention can be suitably applied will be described below.

Description of ink jet recording apparatus

Fig. 1 shows a schematic configuration of an apparatus that discharges liquid, more specifically, an inkjet recording apparatus 1000 (hereinafter also simply referred to as "recording apparatus") that performs recording by discharging ink. The recording apparatus 1000 has a conveyance unit 1 that conveys a recording medium 2 and a line-type liquid discharge head 3 disposed substantially perpendicularly to the conveyance direction of the recording medium 2, and is a line-type recording apparatus that performs single-pass continuous recording while continuously or intermittently conveying a plurality of recording media 2. The recording medium 2 is not limited to a cut sheet, and may be a continuous roll sheet. The liquid discharge head 3 is capable of full-color printing using cyan, magenta, yellow, and black (abbreviated as "CMYK") inks. As described later, the liquid discharge head 3 has a liquid supply unit, a main tank, and a buffer tank (see fig. 2) connected by fluid connection, wherein the liquid supply unit serves as a supply path that supplies ink to the liquid discharge head 3. The liquid discharge head 3 is also electrically connected to an electric control unit that transmits electric power and a discharge control signal to the liquid discharge head 3. The liquid path and the electric signal path within the liquid discharge head 3 will be described later.

Description of the first Loop Path

Fig. 2 is a schematic diagram showing a first loop path of a first form of loop paths as a recording apparatus applied to the present application example. Fig. 2 is a diagram showing a first circulation pump (high pressure side) 1001, a first circulation pump (low pressure side) 1002, a buffer reservoir 1003, and the like connected to the liquid discharge head 3 by fluid connection. Although fig. 2 shows only a path through which ink of one color of CMYK inks flows for the sake of simplicity of description, there are actually four-color circulation paths provided to the liquid discharge head 3 and the recording apparatus main unit. The buffer reservoir 1003, which is a sub-reservoir connected to the main reservoir 1006, has an atmosphere communication opening (not shown in the figure) so that the inside and the outside of the reservoir communicate, and bubbles in the ink can be discharged to the outside. The buffer reservoir 1003 is also connected to a make-up pump 1005. For example, in the case where ink is consumed at the liquid discharge head 3 when ink is discharged (ejected) from the discharge ports of the liquid discharge head 3 by discharging ink for recording, suction recovery, or the like, the replenishment pump 1005 is used to send the same amount of ink as the consumed amount from the main tank 1006 to the buffer tank 1003.

The two first circulation pumps 1001 and 1002 are used to extract ink from the liquid connection portion 111 of the liquid discharge head 3 and flow the ink to the buffer reservoir 1003. The first circulation pumps 1001 and 1002 are preferably volumetric pumps having a quantitative fluid delivery capability. Specific examples may include tube pumps, gear pumps, diaphragm pumps, syringe pumps, and the like. An arrangement may also be used in which a constant flow is ensured, for example by providing a common constant flow valve and pressure relief valve at the outlet of the pump. When the liquid discharge head 3 is driven, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 flow a constant amount of ink through the common supply channel 211 and the common recovery channel 212. It is preferable to set the flow rate to a level at which the temperature difference between the recording element plates 10 of the liquid discharge head 3 does not affect the quality of the recorded image or higher. On the other hand, if the flow rate is set too high, the influence of the pressure drop in the channel within the liquid discharge unit 300 causes the negative pressure difference between the recording element plates 10 to be too large, resulting in density unevenness in the image. Therefore, it is preferable to set the flow rate in consideration of the temperature difference and the negative pressure difference between the recording element plates 10.

The negative pressure control unit 230 is provided between the second circulation pump 1004 and the path of the liquid discharge unit 300. The negative pressure control unit 230 has the following functions: even in the case where the flow rate of the circulation system fluctuates due to the duty difference at the time of recording, the pressure downstream of the negative pressure control unit 230 (i.e., on the liquid discharge unit 300 side) is allowed to be maintained at the current constant pressure. Any mechanism may be used as the two pressure adjusting mechanisms included in the negative pressure control unit 230 as long as the pressure downstream of itself can be controlled to fluctuate within a constant range or a smaller range centered on the desired set pressure. As an example, a mechanism equivalent to a so-called "pressure reducing regulator" may be employed. In the case of using a pressure reducing regulator, the upstream side of the negative pressure control unit 230 is preferably pressurized by the second circulation pump 1004 via the liquid supply unit 220, as shown in fig. 2. This makes it possible to suppress the influence of the buffer memory 1003 on the water head pressure of the liquid discharge head 3, so that the buffer memory 1003 has a greater degree of freedom in layout in the recording apparatus 1000. The second circulation pump 1004 has a certain lift pressure or more within a range of the circulation flow rate of ink used when driving the liquid discharge head 3, and a turbo pump, a displacement pump, or the like may be used. Specifically, a diaphragm pump or the like may be used. Alternatively, instead of the second circulation pump 1004, a water head reservoir having a certain water head difference with respect to the negative pressure control unit 230, for example, may be used.

As shown in fig. 2, the negative pressure control unit 230 has two pressure adjusting mechanisms that are set with different control pressures from each other. In the two negative pressure adjusting mechanisms, a relatively high pressure setting side (denoted by H in fig. 2) and a relatively low pressure setting side (denoted by L in fig. 2) are connected to a common supply passage 211 and a common recovery passage 212 in the liquid discharge unit 300 via the liquid supply unit 220, respectively. An individual supply channel 213 and an individual recovery channel 214 communicating among the common supply channel 211, the common recovery channel 212, and the recording element plate 10 are provided to the liquid discharge unit 300. Since the individual supply channel 213 and the individual recovery channel 214 communicate with the common supply channel 211 and the common recovery channel 212, a flow (indicated by an arrow in fig. 2) of a part of the ink from the common supply channel 211 through the internal channels of the recording element plate 10 and toward the common recovery channel 212 occurs. The reason is that the pressure adjusting mechanism H is connected to the common supply passage 211, and the pressure adjusting mechanism L is connected to the common recovery passage 212, so that a pressure difference is generated between the two common passages.

Therefore, when the ink flows through each of the common supply channel 211 and the common recovery channel 212, a flow of a part of the ink through the recording element plate 10 occurs within the liquid discharge unit 300. Therefore, the heat generated at the recording element plate 10 can be discharged outward from the recording element plate 10 by the flow through the common supply passage 211 and the common recovery passage 212. This configuration also enables ink flow to be generated at the discharge ports and the pressure chambers which are not used for recording in the case of recording by the liquid discharge head 3, and therefore thickening of the ink at these portions can be suppressed. Further, the thickened ink and the foreign matter in the ink can be discharged to the common recovery passage 212. Therefore, the liquid discharge head 3 according to the present application example can perform high-speed recording with high image quality.

Description of the second Loop Path

Fig. 3 is a schematic diagram showing a second loop path belonging to a loop form different from the above-described first loop path among the loop paths applied to the recording apparatus according to the present application example. The main differences from the first circulation path are as follows. First, both pressure adjusting mechanisms included in the negative pressure control unit 230 have a mechanism for controlling the pressure on the upstream side of the negative pressure control unit 230 to fluctuate within a constant range centered on a desired set pressure (a mechanism component having an operation equivalent to a so-called "back pressure regulator"). Next, the second circulation pump 1004 functions as a negative pressure source, depressurizing the downstream side of the negative pressure control unit 230. In addition, a first circulation pump (high pressure side) 1001 and a first circulation pump (low pressure side) 1002 are provided on the upstream side of the liquid discharge head 3, and the negative pressure control unit 230 is provided on the downstream side of the liquid discharge head 3.

The negative pressure control unit 230 in fig. 3 is used to keep the pressure fluctuation on the upstream side of itself (i.e., the liquid discharge unit 300 side) within a constant range centered on a pressure set in advance even in the case where the flow rate fluctuates due to a difference in the recording duty at the time of recording using the liquid discharge head 3. As shown in fig. 3, the downstream side of the negative pressure control unit 230 is preferably pressurized by the second circulation pump 1004 via the liquid supply unit 220. This makes it possible to suppress the effect of the buffer memory 1003 on the water head pressure of the liquid discharge head 3, providing a wider range of choices for the layout of the buffer memory 1003 in the recording apparatus 1000. Alternatively, a water head reservoir provided with a certain water head difference with respect to the negative pressure control unit 230, for example, may be used instead of the second circulation pump 1004.

Like the arrangement shown in fig. 2, the negative pressure control unit 230 shown in fig. 3 has two pressure adjusting mechanisms in which control pressures different from each other are set. In the two negative pressure adjustment mechanisms, the opposite high pressure setting side (denoted by H in fig. 3) and the opposite low pressure setting side (denoted by L in fig. 3) are connected to the common supply passage 211 and the common recovery passage 212 in the liquid discharge unit 300 via the liquid supply unit 220, respectively. The pressure of the common supply passage 211 is made relatively higher than the pressure of the common recovery passage 212 by the two negative pressure adjusting mechanisms. Therefore, a flow (indicated by arrows in fig. 3) of ink from the common supply channel 211 through the individual channels 213 and 214 and the internal channels in the recording element plate 10 and to the common recovery channel 212 occurs. Therefore, the second circulation path generates the same ink flow state as the first circulation path in the liquid discharge unit 300, but has two advantages different from the case of the first circulation path.

One advantage is that, with the second circulation path, the negative pressure control unit 230 is disposed on the downstream side of the liquid discharge head 3, and therefore there is little risk that dust and foreign matter generated at the negative pressure control unit 230 will flow into the liquid discharge head. A second advantage is that the maximum value of the required flow rate to be supplied from the buffer tank 1003 to the liquid discharge head 3 can be smaller in the second circulation path than in the case of the first circulation path. The reason is as follows. In the case of circulation during the recording standby period, the total flow rate in the common supply channel 211 and the common recovery channel 212 will be represented by a. The value of a is defined as the minimum flow rate required to maintain the temperature difference in the liquid discharge unit 300 within a desired range in the case where temperature adjustment of the liquid discharge head 3 is performed during the recording standby. Further, a discharge flow rate in a case where ink is discharged from all the discharge ports of the liquid discharge unit 300 (full discharge) is defined as F. Therefore, 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, and thus the maximum value of the liquid supply amount to the liquid discharge head 3 required for full discharge is a + F.

On the other hand, in the case of the second circulation path (fig. 3), the liquid supply amount of the liquid discharge head 3 required at the time of the recording standby is the flow rate a. This means that the supply amount to the liquid discharge head 3 required for the full discharge is the flow rate F. Therefore, in the case of the second circulation path, the total value of the set flow rates of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002, that is, the maximum value of the required supply amount is the larger value of a and F. Therefore, as long as the liquid discharge unit 300 of the same configuration is used, the maximum value (a or F) of the required supply flow rate in the second circulation path is always smaller than the maximum value (a + F) of the required supply flow rate in the first circulation path. Therefore, in the case of the second circulation path, the degree of freedom of the applicable circulation pump is high, and for example, a low-cost circulation pump having a simple structure can be used, and the load on a cooler (not shown in the drawings) provided on the main unit side path can be reduced, thereby reducing the cost of the recording apparatus main unit. This advantage is more apparent for a line type discharge head in which the value of a or F is relatively large, and is more useful in the case where the length of the line type discharge head in the long side direction is longer.

On the other hand, however, there is a point that the first circulation path is more advantageous than the second circulation path. That is, with the second circulation path, the flow rate flowing through the liquid discharge unit 300 at the time of standby for recording is the largest, so the lower the recording duty of an image, the greater negative pressure is applied to the nozzles. Therefore, in particular, in the case of reducing the channel width (the length in the direction orthogonal to the ink flow direction) of the common supply channel 211 and the common recovery channel 212 to reduce the head width (the length in the lateral direction of the liquid discharge head), this may cause the influence of the satellite droplets to be larger. The reason is that, in a low-duty image in which unevenness is conspicuous, a high negative pressure is applied to the nozzles. On the other hand, when a high duty image is formed in the case of the first circulation path, a high negative pressure is applied to the discharge port, and therefore any generated satellite droplets are less noticeable, which is advantageous in forming a small influence on the image quality. Which of the two circulation paths is more preferable can be selected according to the specifications (discharge flow rate F, minimum circulation flow rate a, and channel resistance in the head) of the liquid discharge head and the recording apparatus main unit.

Description of configuration of liquid discharge head

The configuration of the liquid discharge head 3 according to the first application example will be described. Fig. 4A and 4B are perspective views of the liquid discharge head 3 according to the present application example. The liquid discharge head 3 is a line-type liquid discharge head in which fifteen recording element plates 10 capable of discharging C, M, Y and K four-color inks are aligned in a straight line (tandem layout). As shown in fig. 4A, the liquid discharge head 3 includes a recording element board 10, and a signal input terminal 91 and a power supply terminal 92 electrically connected via a flexible printed circuit board 40 and an electric wiring board 90. The signal input terminal 91 and the power supply terminal 92 are electrically connected to a control unit of the recording apparatus 1000, and each supply a discharge drive signal and electric power necessary for discharge to the recording element board 10. The merged wiring by the circuits in the electric wiring board 90 allows the number of the signal input terminals 91 and the power supply terminals 92 to be reduced compared to the number of the recording element boards 10. This reduces the number of electrical connection portions that need to be removed when assembling the liquid discharge head 3 to the recording apparatus 1000 or when replacing the liquid discharge head 3. The liquid connecting portions 111 provided at both ends of the liquid discharge head 3 are connected to a liquid supply system of the recording apparatus 1000, as shown in fig. 4B. Therefore, inks of four colors of CMYK are supplied from the supply system of the recording apparatus 1000 to the liquid discharge head 3, and the inks that have passed through the liquid discharge head 3 are recovered to the supply system of the recording apparatus 1000. In this way, the inks of the respective colors 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 components and units included in the liquid discharge head 3. The liquid discharge unit 300, the liquid supply unit 220, and the electric wiring board 90 are mounted to the housing 80. The liquid connection portion 111 (fig. 3) is provided to the liquid supply unit 220, and a filter 221 (fig. 2 and 3) for each color is provided inside the liquid supply unit 220, the filter 221 communicating with each opening of the liquid connection portion 111 to remove foreign substances in the supplied ink. The two liquid supply units 220 are each provided with filters 221 for two colors. The ink having passed through the filter 221 is supplied to the respective negative pressure control units 230 provided on the liquid supply unit 220 in correspondence with the respective colors. Each negative pressure control unit 230 is a unit having a pressure regulating valve for the corresponding color. The negative pressure control unit 230 significantly attenuates a change in pressure drop in the supply system of the recording apparatus 1000 (the supply system on the upstream side of the liquid discharge head 3) due to fluctuation in the flow rate of ink by operation of a valve and a spring member and the like provided therein. Therefore, the change in the negative pressure on the downstream side of the pressure control unit (on the side of the liquid discharge unit 300) can be stabilized within a certain range. As shown in fig. 2, each negative pressure control unit 230 has two pressure regulating valves built therein for each color, and sets the two pressure regulating valves to different control pressures, respectively. The two pressure regulating valves communicate with the common supply passage 211 in the liquid discharge unit 300 on the high pressure side and with the common recovery passage 212 on the low pressure side via the liquid supply unit 220.

The housing 80 is configured to include a liquid discharge unit supporting member 81 and an electric wiring board supporting member 82, support the liquid discharge unit 300 and the electric wiring board 90, and ensure the rigidity of the liquid discharge head 3. The electric wiring board support member 82 is for supporting the electric wiring board 90, and is fixed by being screwed to the liquid discharge unit support member 81. The liquid discharge unit supporting member 81 serves to correct warpage and deformation of the liquid discharge unit 300, thereby ensuring the relative positional accuracy of the plurality of recording element plates 10, thereby suppressing unevenness in recorded matter. Therefore, the liquid discharge unit support member 81 preferably has sufficient rigidity. Examples of suitable materials include metallic materials such as stainless steel and aluminum, and ceramics such as alumina. The liquid discharge unit supporting member 81 has openings 83 and 84 into which the joint rubber member 100 is inserted. The ink supplied from the liquid supply unit 220 passes through the joint rubber member 100 and is guided to the third passage member 70 as a part constituting the liquid discharge unit 300.

The liquid discharge unit 300 includes a plurality of discharge modules 200 and a channel member 210, and a cover member 130 is attached to a surface of the liquid discharge unit 300 facing the recording medium. The cover member 130 is a member having a frame-shaped face provided with an elongated opening 131. As shown in fig. 5, the recording element plate 10 and the sealing member 110 (fig. 9A) included in the discharge module 200 are exposed from the opening 131. The frame portion on the periphery of the opening 131 serves as a contact surface with a cover member that covers the liquid discharge head 3 at the time of standby for recording. Therefore, when the irregularities and gaps on the discharge port surface of the liquid discharge unit 300 are filled by coating the periphery of the opening 131 with an adhesive, a sealant, a filling material, or the like, a closed space is preferably formed at the time of covering.

Next, the configuration of the passage member 210 included in the liquid discharge unit 300 will be described. As shown in fig. 5, the tunnel member 210 is an article formed by laminating the first tunnel member 50, the second tunnel member 60, and the third tunnel member 70. The channel member 210 is a channel member that distributes the ink supplied from the liquid supply unit 220 to each of the discharge modules 200 and returns the ink recirculated from the discharge modules 200 to the liquid supply unit 220. The passage member 210 is fixed to the liquid discharge unit support member 81 by a screw member, thereby suppressing warping and deformation of the passage member 210.

Fig. 6A to 6F are diagrams illustrating the front and rear sides of the tunnel members constituting the first to third tunnel members. Fig. 6A shows the side of the first channel member 50 where the discharge module 200 is mounted, and fig. 6F shows the face of the third channel member 70 that contacts the liquid discharge unit support member 81. The first channel member 50 and the second channel member 60 have channel member contact surfaces that abut each other as shown in fig. 6B and 6C, and the second channel member 60 and the third channel member 70 have channel member contact surfaces that abut each other as shown in fig. 6D and 6E. The adjoining second and third passage members 60 and 70 have formed thereon common passage grooves 62 and 71, and when facing each other, the common passage grooves 62 and 71 form eight common passages extending in the longitudinal direction of the passage members. This forms a set of the common supply channel 211 and the common recovery channel 212 for each color within the channel member 210 (fig. 7). The communication port 72 of the third passage member 70 communicates with the hole in the junction rubber member 100 to communicate with the liquid supply unit 220 through a fluid connection. A plurality of communication ports 61 are formed on the bottom surface of the common passage groove 62 of the second passage member 60, communicating with one end of the individual passage groove 52 of the first passage member 50. The other end of the individual passage groove 52 of the first passage member 50 forms a communication port 51 to communicate with the plurality of discharge modules 200 through fluid connection via the communication port 51. The individual channel slots 52 allow the channels to merge in the middle of the channel member.

The first to third channel members are preferably resistant to corrosion by ink and are formed using a material having a low coefficient of linear expansion. Examples of suitable materials include alumina, Liquid Crystal Polymer (LCP), and composite materials (resin materials) in which an inorganic filler such as fine particles of silica or fibers or the like has been added to a base material such as polyphenylene sulfide (PPS), Polysulfone (PSF), or modified polyphenylene ether (PPE). The tunnel member 210 may be formed by laminating three tunnel members and bonding them with an adhesive, or in the case where a composite resin material is selected for the material, the three tunnel members may be joined by welding.

Next, the connection relationship of the channels within the channel member 210 will be described with reference to fig. 7. Fig. 7 is a partially enlarged perspective view of the channel in the channel member 210 formed by joining the first to third channel members, as viewed from the side of the first channel member 50 where the discharge module 200 is installed. The channel member 210 has, for each color, a common supply channel 211(211a, 211b, 211c, and 211d) and a common recovery channel 212(212a, 212b, 212c, and 212d) extending in the longitudinal direction of the liquid discharge head 3. A plurality of individual supply channels 213(213a, 213b, 213c, and 213d) formed by the individual channel grooves 52 are connected to the common supply channel 211 of each color via the communication port 61. A plurality of individual recovery channels 214(214a, 214b, 214c, and 214d) formed by the individual channel grooves 52 are connected to the common recovery channel 212 of each color via the communication port 61. This channel configuration enables the inks to merge at the recording element plate 10 located in the middle of the channel member from the common supply channel 211 via the individual supply channels 213. It is also possible to cause the ink to be recovered from the recording element board 10 to the common recovery channel 212 via the individual recovery channels 214.

Fig. 8 is a sectional view taken along line VIII-VIII in fig. 7, which shows that the individual recovery channels (214a and 214c) communicate with the discharge module 200 via the communication port 51. Although fig. 8 shows only individual recovery channels (214a and 214c), the individual supply channel 213 and the exhaust module 200 communicate at different cross sections, as shown in fig. 7. A passage is formed in the support member 30 and the recording element plate 10 included in the discharge module 200. These channels are used to supply ink from the first channel member 50 to the recording elements 15 (fig. 10B) provided to the recording element plate 10 and to collect (recirculate) part or all of the ink supplied to the recording elements 15 to the first channel member 50. The common supply channel 211 of each color is connected to the negative pressure control unit 230 (high pressure side) of the corresponding color via the liquid supply unit 220 thereof, and the common recovery channel 212 is connected to the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220. The negative pressure control unit 230 generates a differential pressure (pressure difference) between the common supply passage 211 and the common recovery passage 212. Therefore, in the liquid discharge head 3 according to the example of the present application in which the channels are connected as shown in fig. 7 and 8, the following sequence of flows occurs for each color: the common supply passage 211 → the individual supply passage 213 → the recording element plate 10 → the individual recovery passage 214 → the common recovery passage 212.

Description of expelling modules

Fig. 9A shows a perspective view of one of the ejection modules 200, and fig. 9B shows an exploded view thereof. The manufacturing method of the discharge module 200 is as follows. First, the recording element board 10 and the flexible printed circuit board 40 are adhered to the support member 30 in which the liquid communication port 31 has been formed in advance. Subsequently, the terminals 16 on the recording element board 10 are electrically connected to the terminals 41 on the flexible printed circuit board 40 by wire bonding, and then the wire bonding portions (electrical connection portions) are covered and sealed with a sealant 110. The terminal 42 at the other end of the flexible printed circuit board 40 opposite to the recording element board 10 is electrically connected to the connection terminal 93 of the electric wiring board 90 (fig. 5). The support member 30 is a support member that supports the recording element plate 10, and is also a passage member that communicates between the recording element plate 10 and the passage member 210 by fluid connection. Therefore, the support member 30 should have high flatness, and should also be able to be bonded to the recording element board 10 with high reliability. Examples of suitable materials include alumina and resin materials.

Description of the structure of the recording element board

The configuration of the recording element board 10 according to the present application example will be described. Fig. 10A is a plan view of the side of the recording element plate 10 where the discharge ports 13 are formed, and fig. 10B is an enlarged view of a portion indicated by XB in fig. 10A. Fig. 10C is a plan view of the back surface of the recording element board 10 opposite to the side surface of fig. 10A. As shown in fig. 10A, the recording element board 10 has a discharge port forming member 12 that forms four discharge port rows corresponding to the ink colors. Note that, hereinafter, a direction in which the discharge port rows in which the plurality of discharge ports 13 are arrayed extend is referred to as "discharge port row direction".

As shown in fig. 10B, a recording element 15 as a heating element that foams ink due to thermal energy is provided at a position corresponding to the discharge port 13. The pressure chambers 23 containing the recording elements 15 are separated by partitions 22. The recording element 15 is electrically connected to the terminal 16 in fig. 10A through an electric wiring (not shown in the figure) provided to the recording element board 10. The recording element 15 generates heat to boil ink based on a pulse signal from a control circuit of the recording apparatus 1000 and input via the electric wiring board 90 (fig. 5) and the flexible printed circuit board 40 (fig. 9B). The bubbling force due to this boiling causes the ink to be discharged from the discharge port 13. As shown in fig. 10B, the liquid supply channel 18 extends along one side of each discharge port row, and the liquid recovery channel 19 extends along the other side. The liquid supply channel 18 and the liquid recovery channel 19 are channels extending in the direction of the discharge port row provided on the recording element plate 10, and communicate with the discharge port 13 via the supply port 17a and the recovery port 17b, respectively.

As shown in fig. 10C and 11, a sheet-like cover member 20 is laminated on the back surface of the face of the recording element plate 10 where the discharge ports 13 are formed, the cover member 20 having a plurality of openings 21 communicating with the liquid supply channel 18 and the liquid recovery channel 19 as will be described later. In the present application example, three openings 21 are provided in the cover member 20 for each liquid supply channel 18, and two openings 21 are provided for each liquid recovery channel 19. The number of the openings 21 provided for the passage is preferably plural from the viewpoint of pressure drop. In the present embodiment, it is not necessary to provide a plurality of openings 21 for each channel, and it suffices to provide at least two openings 21 for any one of the liquid supply channel 18 and the liquid recovery channel 19. For example, the configuration of the liquid discharge head 3 having two openings 21 for the liquid supply channel 18 and one opening 21 for the liquid recovery channel 19 is sufficient. As shown in fig. 10B, the openings 21 of the cover member 20 are each communicated with a plurality of communication ports 51 shown in fig. 6A. As shown in fig. 11, the cover member 20 serves as a cover that forms a part of the side surfaces of the liquid supply channel 18 and the liquid recovery channel 19 formed in the substrate 11 of the recording element plate 10. The cover member 20 preferably has sufficient corrosion resistance to ink, and must have high accuracy with respect to the opening shape and the opening position of the opening 21 from the viewpoint of preventing color mixing. Therefore, a photosensitive resin material or a silicon plate in which the opening 21 is formed by a photolithography process is preferably used as the material for the cover member 20. Thus, the cover member 20 serves to switch the pitch of the channels through the opening 21. The cover member 20 is preferably thin in view of pressure drop, and is preferably formed using a film-like resin material.

Next, the flow of ink within the recording element plate 10 will be described. Fig. 11 is a perspective view showing a cross section of the recording element plate 10 and the cover member 20 taken along a plane XI-XI in fig. 10A. The recording element board 10 is formed by laminating a substrate 11 formed using silicon (Si) and a discharge port forming member 12 formed of a photosensitive resin, with a cover member 20 bonded on the back surface of the substrate 11. The recording element 15 is formed on the other surface side of the substrate 11 (fig. 10B) in which grooves constituting the liquid supply channel 18 and the liquid recovery channel 19 extend along the discharge port row formed on the back surface side thereof. The liquid supply channel 18 and the liquid recovery channel 19 formed by the substrate 11 and the cover member 20 are connected to a common supply channel 211 and a common recovery channel 212, respectively, in the channel member 210, and there is a pressure difference between the liquid supply channel 18 and the liquid recovery channel 19. When ink is discharged from the plurality of discharge ports 13 of the liquid discharge head 3 and recording is being performed, the following flow is generated at the discharge ports 13 where the discharging operation is not performed. That is, the ink in the liquid supply path 18 provided in the substrate 11 flows from the liquid supply channel 18 to the liquid recovery channel 19 via the supply port 17a, the pressure chamber 23, and the recovery port 17b due to the pressure difference (flow indicated by arrow C in fig. 11). This flow causes ink, bubbles, foreign matter, and the like thickened due to evaporation from the discharge port 13 to be recovered from the discharge port 13 and the pressure chamber 23 where no recording is performed to the liquid recovery channel 19. This also makes it possible to suppress thickening of the ink at the discharge port 13 and the pressure chamber 23. The ink recovered to the liquid recovery channel 19 is recovered via the opening 21 of the cover member 20 and the liquid communication port 31 (see fig. 9B) of the support member 30 in the order of the communication port 51 in the channel member 210, the individual recovery channel 214, and the common recovery channel 212. The ink is finally recovered to the supply path of the recording apparatus 1000.

That is, the ink supplied from the recording apparatus main unit to the liquid discharge head 3 is supplied and recovered by flowing in the order described below. First, ink flows into the liquid discharge head 3 from the liquid connecting portion 111 of the liquid supply unit 220. Next, the ink is supplied to the joint rubber member 100, the communication port 72 and the common channel groove 71 provided to the third channel member 70, the common channel groove 62 and the communication port 61 provided to the second channel member 60, and the individual channel groove 52 and the communication port 51 provided to the first channel member 50 in this order. Then, the ink is supplied to the pressure chambers 23 in the order of the liquid communication port 31 provided to the support member 30, the opening 21 provided to the cover member 20, and the liquid supply channel 18 and the supply port 17a provided to the substrate 11. The ink that has been supplied to the pressure chamber 23 but has not been discharged from the discharge port 13 flows in the order of the recovery port 17b and the liquid recovery channel 19 provided to the substrate 11, the opening 21 provided to the cover member 20, and the liquid communication port 31 provided to the support member 30. Then, the ink flows in the order of the communication port 51 and the individual passage groove 52 provided to the first passage member 50, the communication port 61 and the common passage groove 62 provided to the second passage member 60, the common passage groove 71 and the communication port 72 provided to the third passage member 70, and the junction rubber member 100. The ink also flows from the liquid connecting portion 111 provided in the liquid supply unit to the outside of the liquid discharge head 3. In the first circulation path shown in fig. 2, the ink flowing from the liquid connection portion 111 passes through the negative pressure control unit 230, and then is supplied to the junction rubber member 100. In the second circulation path as shown in fig. 3, the ink recovered from the pressure chamber 23 passes through the joint rubber member 100, and then flows from the liquid connecting portion 111 to the outside of the liquid discharge head 3 via the negative pressure control unit 230.

Further, as shown in fig. 2 and 3, not all the ink flowing in from one end of the common supply channel 211 of the liquid discharge unit 300 is supplied to the pressure chambers 23 via the individual supply channels 213 a. There is ink that flows from the other end of the common supply channel 211 and through the liquid supply unit 220 without entering the individual supply channels 213 a. Therefore, providing a passage through which ink does not flow through the recording element plate 10 enables suppression of backflow in the ink circulation flow even in the case where the recording element plate 10 has a minute passage with a large flow resistance, as in the case of the present application example. Therefore, the liquid discharge head according to the present application example can suppress thickening of ink in the pressure chamber and in the vicinity of the discharge port, thereby suppressing a defective discharge direction and non-discharge of ink, and thus can perform high image quality recording as a result.

Description of positional relationship between recording element boards

Fig. 12 is a partially enlarged plan view showing an abutting portion of the recording element plate 10 for two abutting discharge modules. As shown in fig. 10A to 10C, the recording element plate 10 according to the present application example is shaped into a substantially parallelogram. As shown in fig. 12, the discharge port rows (14a to 14d) in which the discharge ports 13 are arranged on the recording element plate 10 are inclined at a certain angle with respect to the transport direction of the recording medium. Therefore, at least one discharge port of the discharge port rows at the adjoining portion of the recording element plate 10 overlaps in the conveying direction of the recording medium. In fig. 12, the two discharge ports on the line D are in an overlapping relationship with each other. This layout makes it possible to make black streaks and blank portions in a recorded image inconspicuous by overlapping drive control of the discharge ports even in the case where the position of the recording element board 10 is slightly deviated from a predetermined position. The plurality of recording element boards 10 may be laid out in a linear arrangement (in series) instead of in a staggered arrangement. In this case, due to a configuration such as that shown in fig. 12, it is also possible to treat black stripes and blank portions at the connecting portions between the recording element plates 10 while suppressing an increase in the length of the liquid discharge head 3 in the conveying direction of the recording medium. Although the shape of the main surface of the recording element board 10 according to the present embodiment is a parallelogram, this is not limitative. The configuration of the present invention can be suitably applied even in the case where, for example, the shape is a rectangle, a trapezoid, or other shapes.

Second application example

Configurations of the ink jet recording apparatus 1000 and the liquid discharge head 3 according to a second application example to which the present invention is applicable will be described. Note that only portions different from the first application example will be mainly described below, and description of portions identical to the first application example will be omitted.

Description of ink jet recording apparatus

Fig. 13 shows an inkjet recording apparatus according to a second application example of the present invention. The recording apparatus 1000 according to 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 single-color liquid discharge heads 3 (each liquid discharge head corresponds to one of CMYK inks). Although the number of discharge port rows usable per color in the first application example is one row, the number of discharge port rows usable per color in the second application example is 20 rows (fig. 19A). This enables extremely high-speed recording by appropriately allocating the recording data to a plurality of discharge port rows. Even if there is a discharge port exhibiting no ink discharge, reliability is improved by performing compensation discharge with respect to the discharge port of another line at a corresponding position of the discharge port in the conveying direction of the recording medium, and therefore this arrangement is suitable for industrial printing. As in the first application example, the supply system, the buffer storage tank 1003, and the main storage tank 1006 (fig. 2) of the recording apparatus 1000 are connected to the liquid discharge head 3 through fluid connections. Each liquid discharge head 3 is also electrically connected to an electric control unit that transmits electric power and a discharge control signal to the liquid discharge head 3.

Description of Cyclic paths

As in the first application example, the first circulation path and the second circulation path shown in fig. 2 and 3 can be used as the liquid circulation paths between the recording apparatus 1000 and the liquid discharge head 3.

Description of the structure of a liquid discharge head

A structure of a liquid discharge head 3 according to a second application example of the present invention will be described. Fig. 14A and 14B are perspective views of the liquid discharge head 3 according to the present application example. The liquid discharge head 3 has 16 recording element plates 10 aligned in a line in the longitudinal direction of the liquid discharge head 3, and is an ink jet type line recording head that can record with ink of one color. As in the first application example, the liquid discharge head 3 has a liquid connection portion 111, a signal input terminal 91, and a power supply terminal 92. The liquid discharge head 3 according to the present application example is different from the first application example in that the signal input terminal 91 and the power supply terminal 92 are provided on both sides of the liquid discharge head 3 because the number of discharge port rows is large. This is to reduce a voltage drop and a signal transfer delay occurring in the wiring portion provided in the recording element board 10.

Fig. 15 is an exploded perspective view of the liquid discharge head 3, which shows each member or unit included in the liquid discharge head 3 according to functional decomposition. The roles of the members and the units and the order of liquid flowing through the liquid discharge head are basically the same as the first application example, but the function of ensuring the rigidity of the liquid discharge head is different. In the first application example, the rigidity of the liquid discharge head is mainly ensured by the liquid discharge unit supporting member 81, but in the second application example, the rigidity of the liquid discharge head is ensured by the second channel member 60 included in the liquid discharge unit 300. In the present application example, the liquid discharge unit support members 81 are connected to both ends of the second passage member 60. The liquid discharge unit 300 is mechanically joined to a carriage of the recording apparatus 1000, thereby positioning the liquid discharge head 3. The liquid supply unit 220 having the negative pressure control unit 230 and the electric wiring board 90 are joined to the liquid discharge unit support member 81. Filters (not shown in the drawings) are built in the two liquid supply units 220. The two negative pressure control units 230 are arranged to control the pressure by a high negative pressure and a low negative pressure which are different with respect to each other. When the high-pressure side negative pressure control unit 230 and the low-pressure side negative pressure control unit 230 are provided on the end of the liquid discharge head 3 (as shown in fig. 14A to 15), the ink flows on the common supply channel 211 and the common recovery channel 212 extending in the longitudinal direction of the liquid discharge head 3 are opposite to each other. This promotes heat exchange between the common supply passage 211 and the common recovery passage 212, so that the temperature difference between the two common passages can be reduced. This is advantageous because a temperature difference is less likely to occur between the plurality of recording element plates 10 disposed along the common channel, and therefore recording unevenness due to the temperature difference is less likely to occur.

The channel member 210 of the liquid discharge unit 300 will be described in detail next. As shown in fig. 15, the passage member 210 is the first passage member 50 and the second passage member 60 which are laminated, and distributes the ink supplied from the liquid supply unit 220 to the discharge modules 200. The passage member 210 also functions as a passage member that returns the ink recirculated from the discharge module 200 to the liquid supply unit 220. The second channel member 60 of the channel member 210 is a channel member in which the common supply channel 211 and the common recovery channel 212 have been formed, and also mainly bears the rigidity of the liquid discharge head 3. Therefore, the material of the second passage member 60 is preferably sufficient in corrosion resistance to ink and high in mechanical strength. Specific examples of suitably used materials include stainless steel, titanium (Ti), alumina, and the like.

Fig. 16A shows a surface of the first passage member 50 on the side where the discharge module 200 is mounted, and fig. 16B is a view showing a reverse surface of the surface in contact with the second passage member 60. Unlike the case of the first application example, the first passage member 50 according to the second application example adopts an arrangement in which a plurality of members corresponding to the discharge module 200 are arranged adjacently. The use of such a dividing structure enables a length corresponding to the length of the liquid discharge head to be realized by arranging a plurality of modules, and is therefore particularly suitable for a relatively long-sized liquid discharge head corresponding to a sheet of B2 size or more, for example. As shown in fig. 16A, the communication port 51 of the first passage member 50 communicates with the discharge module 200 by fluid connection, and as shown in fig. 16B, the individual communication port 53 of the first passage member 50 communicates with the communication port 61 of the second passage member 60 by fluid connection. Fig. 16C shows a surface of the second passage member 60 that contacts the first passage member 50, fig. 16D shows a cross section of an intermediate portion of the second passage member 60 taken in the thickness direction, and fig. 16E is a view showing a surface of the second passage member 60 that contacts the liquid supply unit 220. The functions of the passage and the communication port of the second passage member 60 are the same as those of one color in the first application example. One of the common channel grooves 71 of the second channel member 60 is a common supply channel 211 shown in fig. 17, and the other is a common recovery channel 212. Both supply ink from one end side to the other end side in the longitudinal direction of the liquid discharge head 3. In the present embodiment, the difference from the case in the first application example is that the flow directions of the inks for the common supply channel 211 and the common recovery channel 212 are opposite to each other.

Fig. 17 is a perspective view illustrating a connection relationship between the recording element plate 10 and the passage member 210 with respect to ink. As shown in fig. 17, a set of a common supply channel 211 and a common recovery channel 212 extending in the longitudinal direction of the liquid discharge head 3 is provided in the channel member 210. Each of the communication ports 61 of the second channel member 60 is positionally aligned with and connected to the individual communication port 53 of the first channel member 50, thereby forming a fluid supply path from the communication port 72 of the second channel member 60 to the communication port 51 of the first channel member 50 via the common supply channel 211. In the same manner, a liquid supply path from the communication port 72 of the second passage member 60 to the communication port 51 of the first passage member 50 via the common recovery passage 212 is also formed.

Fig. 18 is a sectional view taken along XVIII-XVIII in fig. 17. Fig. 18 shows how the common supply channel 211 is connected to the discharge module 200 through the communication ports 61, the individual communication ports 53, and the communication ports 51. Although illustration is omitted in fig. 18, another cross-section will show the individual recovery channels 214 connected to the exhaust module 200 by similar paths, as is clear from fig. 17. As in the first application example, channels are formed on the discharge module 200 and the recording element board 10 to communicate with the discharge ports 13, and a part or all of the supplied ink is recirculated through the discharge ports 13 (pressure chambers 23) which are not subjected to the discharge operation. As in the first application example, the common supply passage 211 is connected to the negative pressure control unit 230 (high pressure side) via the liquid supply unit 220 and the common recovery passage 212 is connected to the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220. Therefore, by the pressure difference thereof, a flow from the common supply passage 211 to the common recovery passage 212 through the discharge port 13 (pressure chamber 23) of the recording element plate 10 is generated.

Description of expelling modules

Fig. 19A is a perspective view and fig. 19B is an exploded view of one of the discharge modules 200. Unlike the first application example, a plurality of terminals 16 are arranged at both side portions of the recording element board 10 (long side portions of the recording element board 10) in the direction of the rows of the plurality of discharge ports, and two flexible printed circuit boards 40 are provided to one recording element board 10 and electrically connected to the terminals 16. The reason is that the number of discharge port rows provided on the recording element board 10 is 20 rows, which is greatly increased compared to the eight rows in the first application example. The purpose is to keep the maximum distance from the terminals 16 to the recording elements 15 arranged corresponding to the discharge port rows short, thereby reducing the voltage drop and signal transfer delay occurring at the wiring portions provided to the recording element board 10. The liquid communication port 31 of the support member 30 is provided to the recording element plate 10, and is opened across all the discharge port rows. Other points are the same as the first application example.

Description of the structure of the recording element board

Fig. 20A is a schematic view showing a face of the recording element plate 10 on the side where the discharge ports 13 are provided, and fig. 20C is a schematic view showing a back face of the face shown in fig. 20A. Fig. 20B is a schematic view showing a face of the recording element plate 10 in a case where the cover member 20 provided on the back face side of the recording element plate 10 is removed in fig. 20C. As shown in fig. 20B, the liquid supply channels 18 and the liquid recovery channels 19 are alternately arranged on the back surface of the recording element plate 10 in the discharge port row direction. Although the number of discharge port rows is larger than that of the first application example, the substantial difference from the first application example is that the terminals 16 are provided at both side portions of the recording element plate 10 in the discharge port row direction as described above. The basic structure is the same as that of the first application example, such as providing a set of the liquid supply channel 18 and the liquid recovery channel 19 for each discharge port row, providing the opening 21 communicating with the liquid communication port 31 of the support member 30 for the cover member 20, and the like.

First embodiment

Relationship between tail length reduction and discharge port size

Fig. 21A and 21B illustrate the inside of the liquid discharge head. Fig. 21A is a plan view of the recording element 15 and the channel, and fig. 21B is a sectional view taken along line XXIB-XXIB in fig. 21A. A plurality of pressure chambers 23 each having a discharge port 13, and an inlet passage 24a and an outlet passage 24b communicating with each pressure chamber 23 are provided between the substrate 11 of the recording element plate 10 and the discharge port forming member 12. The pressure chambers 23 are separated by wall members 26. A liquid supply channel 18 communicating with the inlet channel 24a and a liquid recovery channel 19 communicating with the outlet channel 24b are provided on the substrate 11. The inlet channel 24a branches off from the liquid supply channel 18 at the supply port 17a of the liquid supply channel 18 and communicates with the pressure chamber 23, supplying ink to the pressure chamber 23. The outlet channel 24b communicates with the pressure chamber 23 on the side of the pressure chamber 23 opposite to the inlet channel 24a, and causes ink that is not discharged from the discharge port 13 to be led to the liquid recovery channel 19 via the recovery port 17b of the liquid recovery channel 19.

The plurality of supply ports 17a form a supply port row, and the plurality of recovery ports 17b form a recovery port row. A discharge port row in which a plurality of discharge ports 13 are arranged is formed between the supply port row and the recovery port row. In the present embodiment, the discharge port row and the recovery port row are provided on both sides of the supply port row. As previously described, a pressure difference is provided between the liquid supply passage 18 and the liquid recovery passage 19. This pressure difference generates a flow in which ink is guided from the supply port 17a into the pressure chamber 23 through the inlet channel 24a, and from the outlet channel 24b to the recovery port 17 b. That is, the ink passes through the liquid supply channel 18, the supply port 17a, and the inlet channel 24a, enters the pressure chamber 23, and is discharged from the discharge port 13. The ink that is not discharged is recovered through the outlet channel 24b, the recovery port 17b, and the liquid recovery channel 19. The recovered ink is supplied again to the liquid supply channel 18 through a circulation channel not shown in the drawing.

The recording element 15 generating thermal energy is disposed on the bottom surface of the pressure chamber 23 facing the discharge port 13. The discharge port portion (nozzle) 25 passes through the discharge port forming member 12 at a position facing the pressure chamber 23. A discharge port 13 for discharging ink is formed at an outer end of the discharge port 25, that is, an end opposite to the recording element 15. The discharge port portion 25 and the discharge port 13 are provided at positions facing the recording element 15. In this specification, the discharge port 13 is an opening located on the outer face of the discharge port forming member 12 facing the recording medium, and the discharge port portion 25 is a portion that communicates the discharge port 13 and the pressure chamber 23, serving as a through hole that passes through the discharge port forming member 12.

Fig. 22A to 22G are schematic diagrams illustrating a transient process of the discharge phenomenon. Fig. 22A is an enlarged view of XXIB in fig. 21A. Fig. 22B to 22G are sectional views taken along lines XXIIB to XXIIG-XXIIB to XXIIG in fig. 22A. The projections of the discharge port 13 shown in fig. 21A are omitted in fig. 22A to 22G. Ink is supplied from the inlet passage 24a to the pressure chamber 23 (see fig. 22B). The recording element 15 generates thermal energy for discharging the liquid by electric energy applied thereto. The ink near the recording element 15 is heated and evaporated by the thermal energy, forming a bubble B (see fig. 22C). The pressure of the bubble B at the initial stage of generation 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 an arrow in fig. 22C). The bubbles B enter the discharge port portion 25 while continuing to grow. The internal pressure of the bubble B rapidly changes from the positive pressure to the negative pressure lower than the atmospheric pressure due to its growth (see fig. 22D). This negative pressure pulls the trailing end of the droplet back toward the recording element 15 side, forming an extended tail (see fig. 22E). When the air bubbles B further advance through the discharge port portion 25, the air bubbles B communicate with the atmosphere inside or outside the discharge port portion 25. As a result, the negative pressure of the bubble B is suddenly lost, and the growth of the tail length is also stopped (see fig. 22F). Through the above-described process, 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 discharged ink is mainly discharged as a main ink droplet, but a satellite droplet S and mist also appear behind the main ink droplet (see fig. 22G). In the present embodiment, the air bubbles B communicate with the atmosphere in a state where the internal pressure is negative and the volume is increased (expanded). Therefore, the discharge amount of the liquid droplets is stable, and the discharge speed is faster. In the structure in which the projection 27 is provided at the discharge port 13 as in the present embodiment, the area of the discharge port is small, and therefore the discharge speed generally tends to decrease. However, the air bubbles B communicate with the atmosphere to discharge liquid droplets at the time of growth so that the occurrence of satellite droplets can be suppressed while suppressing a decrease in the discharge speed.

Fig. 23A shows the relationship between the pressure distribution in the bubble and the internal pressure in the bubble. The horizontal axis represents time, and the vertical axis represents internal pressure. Fig. 23A shows mode a and mode B in which the discharge port size is the same and only the pressure distribution within the bubbles is different. Fig. 23B schematically shows a manner of discharging ink according to the pattern a, and fig. 23C shows a manner of discharging ink according to the pattern B. Both mode a and mode B exhibit a rapid rise in the internal pressure of the bubble, followed by a transition to negative pressure, followed by a rise to atmospheric pressure when the bubble is vented to atmosphere. In mode B, the bubble is at time T_BIs open to the atmosphere and therefore the internal pressure within the bubble remains at a negative pressure for a long amount of time. As can be seen from fig. 23C, the tail of the droplet is longer than mode a, and the satellite is easily formed. Ratio T of bubbles in mode A_BEarly time T_AIs open to the atmosphere and therefore the amount of time that the internal pressure within the bubble remains at negative pressure is short. Therefore, as shown in fig. 23B, the tail is relatively short, and the occurrence of satellite droplets is suppressed. Therefore, reducing the amount of time of the negative pressure and making the air bubble communicate with the atmosphere at an early stage is effective for suppressing the tail from becoming long, and is therefore effective for suppressing the satellite droplets.

Fig. 24A to 24D show the relationship between the distance OH (fig. 22B) from the recording element 15 to the discharge port 13 and the amount of time from the start of heating of the recording element 15 until the bubbles communicate with the atmosphere (hereinafter referred to as "atmosphere communication time Tth"). The distance OH is equal to the sum of the height H1 of the discharge port forming member 12 (which is also the height of the discharge port portion 25) and the height H2 of the inlet passage 24a in the direction perpendicular to the bottom surface of the pressure chamber 23 where the recording element 15 is provided, that is, OH ═ H1+ H2 (see fig. 22B). Three patterns are considered here for the shape of the discharge port, pattern 1 having a circular shape (fig. 24A) and patterns 2 and 3 having two protrusions 27 protruding toward the center of the discharge port 13 (fig. 24B and 24C). The two protrusions 27 in the patterns 2 and 3 are located on a straight line L passing through the center Cn of the discharge port 13, are disposed on both sides of the center Cn, and have the same shape. In pattern 3, the protrusions 27 are formed longer and the gaps 28 between the protrusions 27 are smaller, as compared to pattern 2.

In either pattern, OH is the same as the effective diameter of the discharge port 13, OH is 12 μm or less, and the effective diameter of the discharge port 13 is 11 μm or more (opening area 100 μm or more)²). The effective diameter is defined as the diameter of a circle having an area equal to the actual area of the discharge port 13. Note that the opening area of the discharge port 13 is preferably 100 μm²The above. In the case where the shape of the discharge port 13 is circular (pattern 1), it can be seen that it is necessary to reduce OH to reduce Tth, thereby shortening the tail. In order to reduce OH, the discharge port forming member 12 needs to be formed thinner (reduction H1) or the height of the inlet passage 24a needs to be reduced (reduction H2). Both of these have problems in that the former causes the discharge port forming member 12 to be more easily broken or the like, and reliability may be lowered. The latter may give rise to a concern that throughput may deteriorate due to increased flow resistance.

On the other hand, in the case where the projection 27 is provided at the discharge port 13 (patterns 2 and 3), Tth is lower than pattern 1. In particular, in the case where the gap between the protrusions 27 is narrow (pattern 3), Tth is significantly reduced. This results in a shorter tail and inhibits the occurrence of satellite droplets. Although the configuration in which two protrusions 27 are provided is described in the present embodiment, it is not limited thereto, and the present invention may also be applied to a case in which one protrusion or three or more protrusions are provided, which will be described later. In these cases, it is preferable to have a narrow gap between the projections 27 (in the case of one projection, a gap between the tip of the projection and the edge of the discharge port) as in the case of two projections 27, because this results in a shorter tail.

Fig. 25 shows the relationship among the thickness H1 of the discharge port forming member 12, the height H2 of the inlet passage 24a, and the atmospheric communication time Tth. The horizontal axis represents the height H2 of the inlet passage 24a, and the vertical axis represents the thickness H1 of the discharge port forming member 12. The contour lines indicate Tth. The sizes of the standard a, standard B, and standard C in fig. 25 are as follows.

Standard a: OH 12 μm, H1 7 μm, H2 5 μm, Tth 1.4 μ s

Standard B: OH 12 μm, H1 6 μm, H2 6 μm, Tth 1.5 μ s

Standard C: OH 12 μm, H1 5 μm, H2 7 μm, Tth 1.6 μ s

Therefore, fig. 25 shows a change in the atmospheric communication time Tth when OH is fixed at 12 μm and the height H2 of the inlet passage 24a (or the thickness H1 of the discharge port forming member 12) is changed. Tth increases in the order of criteria A, B and C. Therefore, with OH constant, the atmospheric communication time Tth can be further reduced by lowering the height H2 of the inlet passage 24 a. The height H2 of the inlet channel 24a is preferably 7 μm or less, and preferably half OH or less. The distance OH between the discharge port 13 and the recording element 15 is preferably 12 μm or less.

Mechanism for reducing atmosphere communication time

Next, a mechanism of reducing the atmospheric communication time Tth will be described. Fig. 26A to 27B show the relationship between the distance OH and the atmospheric communication position of the bubble. The directions dz and z are defined in FIG. 26A. The dz represents a position where the bubble communicates with the atmosphere in the z direction with the discharge port 13 as the origin, when the direction of moving away from the recording element 15 is the positive direction. Therefore, in the case where dz is positive, the atmosphere communication position is outside the discharge port portion 25 or outside the discharge port 13, and in the case where dz is negative, the atmosphere communication position is inside the discharge port portion 25 or inside the discharge port 13.

In fig. 26B, the horizontal axis represents OH and the vertical axis represents dz. When the shape of the discharge port 13 is circular (pattern 1), decreasing OH gradually approaches dz to 0. That is, decreasing OH causes atmospheric communication to occur at a position near the discharge port 13. Therefore, as can be seen from fig. 23A, Tth decreases. In the case where the discharge port 13 has the projection 27 (patterns 2 and 3), dz >0 when OH.ltoreq.12 μm, atmospheric communication occurs outside the discharge port 13. In the pattern 3 in which the protrusion gap is narrow, dz is larger, and thus Tth decreases accordingly.

The directions dx and x are defined in fig. 27A. The dx represents a position where the bubble communicates with the atmosphere in the x direction with the edge of the discharge port 13 as the origin when the direction away from the center of the discharge port 13 is the positive direction. In fig. 27B, the horizontal axis represents OH and the vertical axis represents dx. In the case where the shape of the discharge port 13 is circular (pattern 1), lowering OH hardly causes any change in dx. In the case where the discharge port 13 has the projection 27 (patterns 2 and 3), dx is close to 0, and dx increases as OH decreases. The dx is larger in the pattern 3 in which the protrusion gap is narrower.

Fig. 28A to 28F are simulation diagrams showing liquid droplets discharged from the discharge port 13, in which fig. 28A is a perspective view of a discharged liquid droplet in the case where the shape of the discharge port 13 is a circle (pattern 1), and fig. 28B and 28C are diagrams showing transient changes in velocity distribution of bubbles and the atmosphere with time. Fig. 28D is a perspective view of a discharged liquid droplet in the case where the discharge port 13 has the projection 27, and fig. 28E and 28F are diagrams showing transient changes in velocity distribution of air bubbles and atmospheric air with time. Fig. 28E and 28F are sectional views taken along a line passing through the centers of the two protrusions 27 and the discharge port 13 provided in the discharge port 13 in fig. 28D. The directions x and z are as defined in fig. 27A. In the case where the shape of the discharge port 13 is circular (pattern 1), the transient phenomenon in the discharge port portion 25 is as follows, as shown in fig. 28B and 28C.

In stage 1, the generated bubbles B enter the discharge port portion 25 and grow in the discharge port portion 25. Therefore, the bubble B has a velocity component toward the center (x ═ 0) of the discharge port 13 due to the action of the wall of the discharge port forming member 12 (the side wall of the discharge port portion 25) (see arrow (i) in fig. 28B).

In phase 2, as the bubbles grow, the atmosphere G outside the discharge port 13 is temporarily pushed out in a direction away from the center of the discharge port 13 due to the discharged ink (see arrow (ii) in fig. 28B).

In stage 3, the atmosphere G is pulled into the discharge port 13 due to the negative pressure inside the bubble B (see arrow (iv) in fig. 28C).

In stage 4, the bubble B itself is also pulled toward the center of the discharge port portion 25 due to the negative pressure inside the bubble B, and is further pulled toward the center of the discharge port portion 25 due to the force of the interface of the ink (see arrow (iii) in fig. 28C).

Therefore, the atmosphere G and the bubbles B tend to communicate inside the discharge port portion 25. The bubbles B are not easily communicated with the atmosphere G outside the discharge port portion 25, and Tth tends to be long.

On the other hand, in the case of the configuration in which the discharge port 13 has the projection 27, the bubbles B are expanded toward the outside of the discharge port 13 due to the force of the interface of the ink (see arrow (iii) in fig. 28F). At least part of the bubbles B that have entered the discharge port portion 25 have a velocity component from the center of the discharge port portion 25 toward the side wall. In particular, in the case where the discharge port 13 is not constant in curvature due to the presence of the projection 27, the surface tension acts so that the gas-liquid interface forms a sphere having a stable shape. The atmosphere G is pulled into the discharge port portion 25, and the bubbles B are expanded in a direction away from the center of the discharge port portion 25. Therefore, the atmosphere G and the bubbles B have mutually opposite velocity components, acting in the direction of colliding with each other, thereby promoting the atmosphere communication of the bubbles B. As can also be seen from fig. 28F, the atmosphere communication position is outside the discharge port portion 25 or the discharge port 13.

Therefore, by reducing OH (making the distance between the discharge port 13 and the recording element 15 12 μm or less), and also providing the projection 27 to the discharge port 13, the following characteristics are obtained:

the method is characterized in that: short atmospheric vent time Tth

And (2) feature: the air bubbles B and the atmosphere G communicate with the feature 3 at the outside of the discharge port portion 25: the bubbles B expanding outwards before communicating with the atmosphere G

Therefore, the tail is shorter, the occurrence of satellite droplets and fog is suppressed, and high image quality and high throughput can be achieved.

Fig. 29 and 30 are diagrams showing Tth and dz with respect to the discharge port 13 of various shapes. The discharge port shapes 1 to 6 have the following features.

Discharge port shape 1: circular discharge port

Discharge port shape 2: discharge port having two symmetrical projections 27 and a wide gap between the projections 27

Discharge port shape 3: discharge port having two symmetrical projections 27 and narrow gap between projections 27

Discharge port shape 4: discharge port having four symmetrical projections 27 and wide gap between projections 27

Discharge port shape 5: discharge port having one projection 27 and wide gap between projection 27 and opposite edge

Discharge port shape 6: discharge port having one projection 27 with narrow gap between projection 27 and opposite edge

The discharge port shapes 2 to 6 each have at least one projection 27, wherein the projections 27 are located on a straight line passing through the center of the discharge port 13. All the discharge port shapes 2 to 6 have smaller Tth than the discharge port shape 1. Furthermore, all the discharge port shapes 2-6 have a positive dz, which means that atmospheric communication occurs outside the discharge port portion 25. Accordingly, the discharge port shapes 2-6 are preferred embodiments because they can shorten the tail and suppress satellite droplets and fog. Note, however, that in the discharge port shape 4 in which the number of the protrusions 27 is increased, the flow resistance at the discharge port portion 25 is increased, and the discharge efficiency is deteriorated. Therefore, the number of the protrusions 27 should not be too large. On the other hand, the discharge port shapes 5 and 6 have one projection 27, which is preferable from the viewpoint of flow resistance at the discharge port portion 25. However, the discharge port shape is asymmetric, and therefore, a situation where ink droplets are ejected in an inclined state occurs more easily. From this viewpoint, the discharge port 13 is more preferably of a symmetrical shape. Therefore, the most preferred embodiment is the discharge port shapes 2 and 3 having two protrusions 27 symmetrically disposed on both sides of the discharge port 13 across the center of the discharge port 13. The discharge port shape 3 is more preferable from the viewpoint of shorter Tth because it has two protrusions 27 symmetrically disposed on the discharge port 13 and the gap between the protrusions 27 is narrow.

Although the liquid channels are provided on both sides of the recording element 15 as in the above-described embodiment, the same effect can be obtained by a structure in which the liquid channels are provided only on one side of the recording element 15 as shown in fig. 31A and 31B.

Second embodiment

Relationship between passage and circulation direction

Fig. 32A and 32B are diagrams showing a second embodiment of the present invention. Fig. 32A is a plan view showing the recording element 15 and the passage, and fig. 32B is a sectional view taken along line XXXIIB-xxxib in fig. 32. The circulating flow is in a direction parallel to the projection 27 of the discharge port 13. This arrangement differs from the first embodiment shown in fig. 21A and 21B only in that the recovery port row is provided only on one side of the supply port row, and all other points are the same. Therefore, reference should be made to the first embodiment for details.

The arrangement shown in fig. 33A and 33B is different from that in fig. 32A and 32B in that the projection 27 of the discharge port 13 extends in a direction orthogonal to the circulating flow. Fig. 34A and 34B are diagrams focusing on one of the pressure chambers 23 in each of fig. 32A and 32B. In fig. 34A, the direction in which the circulating flow and the protrusion 27 of the discharge port 13 extend is the same (substantially parallel), whereas in fig. 34B, the direction in which the circulating flow and the protrusion 27 of the discharge port 13 extend intersects (substantially orthogonal). Fig. 34C and 34D show numerical calculation results regarding droplet formation in the case where the continuous discharge, i.e., the influence of the interruption period is small with respect to fig. 34A and 34B. Fig. 34E and 34F show numerical calculation results regarding droplet formation when the influence of thickening of the ink due to evaporation of the ink from the discharge ports 13 is large after a predetermined interruption period with respect to fig. 34A and 34B, respectively.

As can be seen from fig. 34E and 34F, the arrangement of the circulating flow perpendicular to the protrusion 27 (fig. 34B) is less susceptible to ink thickening than the configuration in which the circulating flow is parallel to the protrusion 27 (fig. 34A). It is considered that this is because the evaporation rate is large at the portion of the base of the projection 27 having a small radius of curvature (the portion surrounded by a circle in fig. 34G and 34H), and therefore the arrangement of the circulating flow flowing through this region is not easily affected by the concentration.

Therefore, although the present embodiment can be applied to either of fig. 34E and 34F, in order to further suppress the concentration within the discharge port 13 in the configuration having the circulating flow, an arrangement in which the circulating flow flows in a direction intersecting (more preferably, orthogonal to) the projection 27 of the discharge port 13 is more preferable. In other words, it is preferable that the straight line on which the projection 27 is located is at an angle of 45 degrees or more with respect to the channel axis connecting the supply channel and the recovery channel, and in order to suppress concentration in the discharge port 13, it is particularly preferable that the straight line on which the projection 27 is located is perpendicular to the channel axis.

There is also a case where the discharge direction of the discharged liquid droplets is deviated due to the change and deformation of the shape of the projection 27. In view of this, an arrangement is preferable in which the relative movement direction of the recording medium with respect to the liquid discharge head 3 and the direction in which the projection 27 extends coincide (more preferably, are parallel). According to this configuration, even if the ejection direction of the liquid droplets is deviated due to deformation of the projection 27 or the like, the influence on the recorded image will be reduced.

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

Claims (14)

1. A liquid discharge head, comprising:

a substrate;

a recording element configured to generate thermal energy for discharging liquid;

a pressure chamber having the recording element therein;

an inlet channel connected to the pressure chamber and configured to supply liquid to the pressure chamber; and

a discharge port configured to discharge the liquid,

characterized in that the liquid discharge head includes two protrusions located on a straight line passing through a center of the discharge port and disposed on both sides of the center,

wherein the pressure chamber and the inlet channel are provided on a face of the substrate and the inlet channel extends along the face,

wherein the liquid discharge head includes a liquid supply channel communicating with the pressure chamber and configured to supply liquid to the pressure chamber, and a liquid recovery channel communicating with the pressure chamber on a side of the pressure chamber opposite to the liquid supply channel and configured to recover liquid,

wherein a direction in which the liquid flows from the liquid supply passage to the liquid recovery passage through the pressure chamber is the same as a direction in which the two protrusions extend, an

Wherein a distance between the discharge port and the recording element is 12 μm or less.

2. The liquid discharge head according to claim 1,

the height of the liquid supply channel in a direction perpendicular to the bottom surface of the pressure chamber is less than half of the distance between the discharge port and the recording element.

3. The liquid discharge head according to claim 1,

the height of the liquid supply channel in a direction perpendicular to the bottom surface of the pressure chamber is 7 μm or less.

4. The liquid discharge head according to claim 1,

the opening area of the discharge port is 100 μm²The above.

5. The liquid discharge head according to claim 1,

the straight line is at an angle of 45 degrees or more with respect to a channel axis connecting the liquid supply channel and the liquid recovery channel.

6. The liquid discharge head according to claim 5,

the straight line and the passage axis intersect each other.

7. The liquid discharge head according to claim 1,

the liquid within the pressure chamber circulates between the interior of the pressure chamber and the exterior of the pressure chamber.

8. A liquid discharge head, comprising:

a substrate;

a recording element configured to generate thermal energy for discharging liquid;

a pressure chamber having the recording element therein;

an inlet channel connected to the pressure chamber and configured to supply liquid to the pressure chamber;

a discharge port configured to discharge liquid; and

an exhaust port portion that communicates between the exhaust port and the pressure chamber,

characterized in that the liquid discharge head includes two protrusions located on a straight line passing through a center of the discharge port and disposed on both sides of the center,

wherein the liquid discharge head includes a liquid supply channel communicating with the pressure chamber and configured to supply liquid to the pressure chamber, and a liquid recovery channel communicating with the pressure chamber on a side of the pressure chamber opposite to the liquid supply channel and configured to recover liquid,

wherein the pressure chamber and the inlet channel are provided on a face of the substrate and the inlet channel extends along the face,

wherein a direction in which the liquid flows from the liquid supply passage to the liquid recovery passage through the pressure chamber is the same as a direction in which the two protrusions extend, an

Wherein a distance between the discharge port and the recording element is 12 μm or less.

9. The liquid discharge head according to claim 8,

the height of the liquid supply channel in a direction perpendicular to the bottom surface of the pressure chamber is 7 μm or less.

10. The liquid discharge head according to claim 8,

the opening area of the discharge port is 100 μm²The above.

11. The liquid discharge head according to claim 8,

the straight line is at an angle of 45 degrees or more with respect to a channel axis connecting the liquid supply channel and the liquid recovery channel.

12. The liquid discharge head according to claim 11,

the straight line and the passage axis intersect each other.

13. The liquid discharge head according to claim 8,

the bubbles that have entered the discharge port portion communicate with the atmosphere outside the discharge port.

14. The liquid discharge head according to claim 8,

the liquid within the pressure chamber circulates between the interior of the pressure chamber and the exterior of the pressure chamber.

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