JP2008173915A - Recording head and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording head which can uniformize shearing rates of impact positions of main droplets and sub-droplets in both going and returning scannings by reducing the shearing rates of the main droplets and the sub-droplets discharged from the recording head by bringing about no deformation of the recording head and no heterogeneous ink discharge rate, etc. <P>SOLUTION: The nozzle of the recording head discharges the main droplets in a direction responding to the normal direction of the opening surface of the discharge port 4a at the time of the discharging operation, and discharges the sub-droplets in the direction crossing with the axial line L1 of the nozzle. The discharge port 4a is so formed that the normal line of the opening surface crosses the axial line L1 of the nozzle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a recording head capable of discharging a plurality of types of liquid and an ink jet recording apparatus that records an image using the recording head, and more particularly to an ink jet recording apparatus that discharges liquid in both reciprocating scans of the recording head and the recording head. .

  An ink jet recording apparatus that performs recording by ejecting a liquid such as ink from a nozzle as fine droplets (also referred to as ink droplets) and attaching it to a recording medium is low in running cost and quiet in recording. It has the advantage of being excellent. Furthermore, this type of recording apparatus has the advantage that it is possible to record in color relatively easily by using a plurality of colors of ink.

  As described above, an inkjet recording apparatus using an electrothermal conversion element (heater) or an electromechanical generation element (piezo) is known as an ejection energy generation element for ejecting droplets. Among these, a recording head using a heater is relatively easy to arrange nozzles including electrothermal conversion elements at a high density, and is an advantageous method for performing high-resolution recording.

  As a recording head using this electrothermal conversion element, one having a nozzle having a structure as shown in FIG. 15 has been proposed. The nozzles of the recording head h include a flow path 105 formed by a heater board 101 and a flow path forming member 103 having an upper surface nozzle 104 on the inner surface, a heater 102 provided on the heater board 101, and the like. A nozzle bank 107 made of a member having the same surface energy as that of the top plate nozzle 104 is formed at the inner surface end of the heater board 101. The end of the top plate nozzle 104 and the end of the nozzle bank 107 are Thus, an ejection port 106 for ejecting droplets is formed. In the figure, L1 is an axis that passes through the center of the discharge port and is parallel to the longitudinal direction of the flow path. Hereinafter, this axis L1 is referred to as the central axis of the nozzle.

  In such an ink jet recording head, ink droplets are ejected as shown in FIGS.

  As shown in FIG. 15A, when the electrothermal converter 101 is energized with the liquid channel 105 filled with ink, the ink In in the flow path 102 is generated by the heat generated by the electrothermal converter 101. Foams (see FIGS. 15B and 15C). Due to the foaming energy of the bubbles B generated at this time, the liquid in the flow channel is pushed outward from the discharge port 103, and then the bubbles B disappear as shown in FIGS. 15 (d) and 15 (e). As a result, a portion (hereinafter referred to as a “liquid column”) Ic between the liquid portion pushed out from the discharge port 103 and the liquid portion drawn into the flow path 102 is divided, and the liquid amount is large. Droplets Dm and small droplets (subdrops) Ds having a smaller liquid volume are formed. Then, when these droplets land on the recording medium, an image is recorded on the recording medium. The recording head H is provided with a movable valve 108 in the flow path 102 in order to effectively cause the foaming energy of the bubbles B to act in the direction of the discharge port 103.

  In such a recording head H, it is extremely important to maintain an appropriate ejection direction of ejected ink droplets in order to maintain image quality. Therefore, a nozzle bank 107 having the same surface energy as the top plate nozzle 106 attached to the flow path forming member 105 is used as a heater board so as to define the ink droplet ejection direction in a direction perpendicular to the opening surface of the ejection port. 101 is provided. According to this, the contact angle between the periphery of the ejection port 103 and the ink can be made equal, and the ejection direction of the main droplet Dm can be set to the normal direction of the opening surface of the ejection port 103.

  However, in the recording head H shown in FIG. 15, although the ejection direction of the main droplet Dm can be determined in the normal direction of the opening surface of the ejection port 106, the sub-droplet Ds is ejected in a direction different from the main droplet Dm. The problem has arisen. This is because the cross-sectional shape is different between the vicinity of the discharge port 106 and the inside of the nozzle.

  That is, as shown in FIG. 16A, in the liquid path 105 of the recording head h, the central axis L1 of the front portion where the nozzle bank 107 is provided and the center of the inner portion where the nozzle bank 107 is not provided. There is a deviation from the axis L2. For this reason, when the liquid is drawn inward from the nozzle bank 107 as shown in FIG. 15D, the liquid column Ic is inclined in a direction intersecting the nozzle axis L1, and the discharge direction of the sub-droplet Ds is thereby influenced. It tilts at a constant angle with respect to the central axis L1. That is, the sub-droplet Ds is discharged in a direction different from the main droplet Dm discharged in the direction orthogonal to the discharge port 106. As described above, when the recording operation is performed in both forward scanning and backward scanning using the recording heads h in which the ejection directions of the main droplet Dm and the sub-drop Ds are different, the landing of the main droplet Dm and the sub-drop Ds. The amount of positional deviation differs between forward scanning and backward scanning, and this is a factor that causes a reduction in image quality.

  Therefore, the present inventors have a recording head in which the nozzle bank 107 is extended inward of the liquid path 105 as shown in FIG. 16B in order to make the ejection directions of the main droplet Dm and the sub-droplet Ds coincide. h1 is also proposed. According to this, even when the subdroplet Ds is formed, the ink drawn inward of the liquid path is in contact with the nozzle bank. For this reason, the liquid column Ic can be kept in parallel with the central axis L1 of the nozzle even when the subdrop Ds is formed, and the subdrop Ds can be discharged in the same direction as the main droplet.

  However, in this case, the area where the heater board 101 and the ink are in direct contact decreases, and the amount of heat transmitted to the ink decreases. For this reason, the temperature rise in the region R (refer to FIG. 16B) on the heater board becomes intense, and there arises a new problem that the recording head h1 is deformed and the amount of ink discharged becomes uneven.

  The present invention reduces the deviation of the ejection direction of the main droplet and sub-droplet ejected from the recording head without causing deformation of the recording head or non-uniformity of the ink ejection amount, and the landing positions of the main droplet and sub-droplet are reduced. The purpose is to make the amount of deviation uniform in both reciprocating scans.

  In order to achieve the above object, the present invention has the following configuration.

  According to a first aspect of the present invention, there is provided a recording head that can be attached to a moving member that can reciprocate relative to a recording medium, and that discharges droplets from a nozzle outlet toward the recording medium. Ejects a main droplet as the droplet in a direction corresponding to the normal direction of the opening surface of the ejection port, and a sub-drop with a smaller liquid volume than the main droplet in a direction intersecting the axis of the nozzle. The discharge port is formed such that the normal line of the opening surface of the discharge port intersects the axis of the nozzle.

  According to a second aspect of the present invention, there is provided a recording head manufacturing method for ejecting liquid droplets from a nozzle ejection port toward a recording medium, wherein the ejection port forming portion that forms the ejection port is defined as an axis of the nozzle. A first step of forming an orthogonal plane, and a droplet composed of a main droplet and a sub-droplet from a discharge port in the discharge port forming portion formed by the first step; A second step of obtaining a distance between the main droplet and the sub-droplet that has landed on the surface, and a normal between the opening surface of the discharge port and the axis of the nozzle based on the distance obtained by the second step. A third step of determining an angle, and a first step of shaping the discharge port forming portion formed by the first step so that the discharge port forming portion has the angle determined by the third step. And 4 steps.

  The third aspect of the present invention can be mounted on a moving member that can move reciprocally relative to a recording medium, and uses a recording head that discharges liquid droplets from a nozzle outlet toward the recording medium. In the ink jet recording method for performing the recording, the nozzle ejects a main droplet as the droplet in a direction corresponding to a normal direction of the opening surface of the ejection port, and in a direction intersecting the axis of the nozzle. A sub-droplet having a smaller liquid volume than the main droplet is discharged, and the discharge port is formed so that the normal line of the opening surface of the discharge port intersects the axis of the nozzle, and the recording medium and the recording head are Recording is performed on a recording medium by ejecting ink from the nozzles while relatively reciprocating.

  In the present invention, the main droplet is ejected in a direction corresponding to the normal direction of the opening surface of the ejection port, and the sub-droplet is ejected in a direction intersecting with the axial direction of the nozzle. At this time, since the opening surface of the discharge port that defines the discharge direction of the main droplet intersects the axial direction of the nozzle, the discharge direction of the main droplet can be brought close to the discharge direction of the sub-droplet. As a result, even if there is a difference between the landing positions of the main droplet and the sub-droplet, the difference in landing position is made uniform between the forward movement and the backward movement, and it is possible to reduce the deterioration of the image quality. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment of inkjet recording apparatus)
Next, an embodiment of a recording apparatus using the ink jet recording head described in the above embodiment will be described with reference to FIGS.
FIG. 1 is a perspective view schematically showing an external configuration of a recording apparatus 20 in the present embodiment. The recording apparatus 20 shown here transports the recording medium P in a certain direction (Y direction) and performs recording while reciprocating the recording head H along the direction (X direction) intersecting the transport direction of the recording medium P. A so-called serial scan type recording apparatus is configured. In the figure, reference numeral 21 denotes a carriage on which the recording head H shown in the above embodiment and an ink tank 22 for storing ink to be supplied are mounted. The carriage 21 is in a direction orthogonal to the conveyance direction Y of the recording medium P ( Reciprocate along the X direction). Various transport mechanisms for transporting the recording medium can be applied. Here, a transport roller that rotates by a driving force such as a motor and a pinch roller (both illustrated) provided opposite to the transport roller. (Omitted).

  FIG. 2 is a block diagram illustrating a schematic configuration of a control device 200 that controls driving of the recording apparatus. The control device 200 includes an image controller 201 that processes recording data sent from the host computer 300. Further, the control device 200 includes an engine controller 202 that controls conveyance of the recording medium and movement of the carriage 21, a recording head controller 203 that controls ejection of ink droplets, and the like.

  The engine controller 202 includes a data rasterization unit 205, an ejection pulse generator 206, a transport control unit 207, a motor control unit 208, and the like. Among these, the data rasterizing unit 205 performs a rasterizing process for assigning serial recording data sent from the image controller 201 to each nozzle. Further, the ejection pulse generator 206 sends ejection pulses representing the drive timing of the recording head H to the recording head controller 203. The recording head controller 203 drives each nozzle (heater) of the recording head based on the ejection pulse from the ejection pulse generator 206 and the image data sent from the data rasterization unit 205.

  In addition, the conveyance control unit 207 controls the driving of the conveyance motor, and controls the rotation of a conveyance roller (not shown) that is rotated by the driving force of the conveyance motor 209. The motor control unit 208 detects the movement position of the carriage 22 based on a signal from the carriage scale encoder 204 and controls the carriage motor 210 to control the carriage 22 such as driving, stopping and acceleration, constant speed movement, and deceleration. Do.

  In the recording apparatus configured as described above, the recording medium P is intermittently Y pinched while being sandwiched between a transport roller that is rotated by the transport motor 209 and a pinch roller (not shown) provided opposite to the transport roller. It is conveyed in the direction. Further, the carriage 22 on which the recording head H is mounted performs forward scanning or backward scanning during the stop period of the recording medium P, and discharges ink from the recording head H during each scanning to record within the nozzle arrangement range. Do. By repeating this recording operation and the intermittent conveyance operation of the recording medium P, a predetermined image is formed on the recording medium P. Also, in both forward scanning and backward scanning, it is possible to form an image at high speed by performing so-called bidirectional recording, in which ink is ejected from the recording head and recording is performed.

  Next, an embodiment of the ink jet recording head H of the present invention used in the above embodiment will be described.

(First Embodiment of Recording Head)
FIG. 3 is a perspective view showing a recording head H to which the present invention is applied.
In FIG. 3, reference numeral 10 denotes a ceramic plate that forms the bottom of the recording head H. Disposed on the ceramic plate 10 are an ejection element 11 that ejects ink droplets, and a flow path forming member 12 that covers both the left and right side surfaces and the upper surface of the ejection element 11. In the ejection element 11, a plurality of nozzles that eject ink are arranged at a predetermined density. In the present specification and claims, a nozzle refers to an ink discharge port, which will be described later, a liquid path communicating therewith, and an electricity as a discharge energy generating element that generates discharge energy for discharging ink. It shall include a heat conversion element (heater).

4 is a partially cutaway perspective view showing the internal structure of the ejection element 11 in the recording head H. FIG.
A plurality of common liquid chambers 5 communicating with the nozzles are formed in the discharge element 11. In each common liquid chamber 5, a plurality of types of ink supplied from the ink tank 22 shown in FIG. 1 pass through an ink supply port 3a (see FIG. 3) formed in the flow path forming member 12 by anisotropic etching or the like. Supplied. The ink supplied into the common liquid chamber 5 is supplied into each flow path 3 communicating with the common liquid chamber 5.

  The flow path 3 is surrounded by the heater board 1, the nozzle wall 6, the nozzle bank 7 having a thickness of about 5 to 10 μm, and the top plate nozzle 8 having a thickness of about 2 μm to form a tubular shape. Further, a movable valve 9 is provided in the flow path 3, a free end 9 </ b> A is located on the discharge port 4 a side, and a base end thereof is a valve pedestal 10 (see FIG. 7) provided on the common liquid chamber 5 side. It is attached to the heater board 1 via.

  The heater board 1 is provided with a plurality of heaters (electrothermal converters) 2 for heating and foaming ink. As the heater 2, a resistor such as tantalum nitride is used. For example, the thickness is 0.01 to 0.5 μm, and the sheet resistance is 10 to 300Ω per unit square. The heater 2 is connected to an electrode (not shown) such as aluminum for energization. One of the electrodes is connected to a switching transistor (not shown) for controlling energization to the heater 2. The driving of the switching transistor is controlled by an IC composed of a circuit such as a control gate element, and the energization / interruption of the heater 2 is controlled in accordance with a signal from the recording apparatus. The heater 2 is formed in each of the plurality of flow paths 3. One end of each flow path 3 communicates with the corresponding discharge port 4 a and the other end communicates with the common liquid chamber 5.

  The ink supplied from the common liquid chamber 5 to the nozzle 4 is heated by the heater 2 disposed at a predetermined position in the nozzle 4 to be foamed. Accompanying this bubbling, the movement of ink in the nozzle 4 is started and the movable valve 9 is displaced to restrict the flow of ink to the common liquid chamber side. Thereby, the foaming energy is efficiently converted into the flow of ink toward the ejection port 4a and ejected from the ejection port 4a.

  By the way, in this embodiment, the nozzle wall 6, the nozzle bank 7, and the top plate nozzle 8 are formed with the photosensitive epoxy resin. For this reason, as shown in FIG. 5, the peripheral part of the discharge port in the discharge port surface F, which is the surface on which the discharge port 4a is formed, has a structure having the same surface energy. For this reason, the contact angle α of the ink with respect to the ejection port surface F is the same in any area around the ejection port 4a. Accordingly, the ejection direction of the main droplet Dm ejected from the ink ejection port 4a is ejected toward the normal direction of the opening surface of the ejection port 4a (the direction indicated by the broken line arrow in FIG. 5) A1, as shown in FIG. Is done.

  Further, in the present embodiment, the discharge port surface F is formed with an inclination of an angle θ1 (<π / 2) with respect to a surface f perpendicular to the nozzle axis L1 as shown in FIG. Here, the nozzle axis L1 refers to an axis that passes through the center of the discharge port 4a and extends in a direction parallel to the top nozzle 8 and the straight portion 6a of the nozzle wall 6. The angle θ1 is set to be the same (θ1 = θ2) as the angle θ2 formed by the central axis L1 and the discharge direction of the subdroplet Ds (the direction indicated by the dashed arrow in FIG. 6) A2. Accordingly, the discharge direction A1 of the main droplet Dm, which is the normal direction of the opening surface of the discharge port 4a, coincides with the discharge direction A2 of the sub-droplet Ds.

  As described above, as a method of processing the discharge port surface F in the direction intersecting with the nozzle axis L1, a polishing process can be used for the purpose of removing minute chips or small scratches on the discharge port surface F. It is. As this polishing step, for example, a step of contacting and sliding a polishing sheet (polishing member) S with abrasive grains fixed at a certain angle with respect to the discharge port surface F can be employed.

FIG. 7 is an explanatory diagram of the discharge process of ink droplets from the discharge port 4a.
FIG. 7A shows a state before the heater 2 is not energized and the ink in the flow path 3 is heated. The ink in the vicinity of the discharge port 4a forms a concave arcuate meniscus M.
FIG. 7B and FIG. 7C show a state in which bubbles B are generated with ink film boiling by heating the ink through the heater 2 and generating heat. At this time, the propagation direction of the pressure based on the generation of the bubbles B is guided in the ink ejection direction when the movable valve 9 is displaced with the valve pedestal 11 side as a fulcrum. The ink in the flow path 3 is pushed out from the discharge port 4a by the pressure generated at the time of foaming, and forms a liquid column Ic as shown in FIG.

  FIG. 7D shows a state where the heating of the ink by the heater 2 is completed and the bubbles B are in the contraction process. In this state, the ink is drawn into the flow path 3 as the bubbles B contract. At this time, the inertial force in the discharge direction is applied to the tip portion of the liquid column Ic, so that it is separated from the liquid column Ic. The separated liquid forms a main droplet Dm and a sub-droplet (satellite) Ds by the surface tension of the ink, and flies toward the recording medium.

At this time, in the present embodiment as well, as in the conventional recording head h shown in FIG. 15, the center of the cross section of the front portion where the nozzle bank 7 is provided in the flow path 3 and the nozzle bank 7 are Due to the difference from the center of the cross section of the inner part that is not provided, the liquid column Ic is inclined in a direction intersecting the nozzle axis L1. As a result, the subdrop Ds is ejected in a direction intersecting the central axis L1 at an angle θ2. This is also the same as the conventional recording head h shown in FIG.
However, in the present embodiment, the discharge port surface F that forms the opening surface of the discharge port 4a is inclined at an angle θ1 with respect to the surface f orthogonal to the central axis L1, and the angle θ1 is set to be the same as the angle θ2. Has been. For this reason, the main droplet Dm is also ejected in the same direction as the subdrop Ds (see FIG. 7E).

Next, the result of performing the recording operation using the recording head H shown in the first embodiment on the serial scan type ink jet recording apparatus as shown in FIG. 1 is recorded using the conventional recording head h. This will be described in comparison with the results of the above.
FIG. 8 is a diagram schematically showing an example of the ink droplet ejection direction and landing position when a recording operation is performed using the conventional recording head h shown in FIG. Here, (a) to (c) indicate the recording state during the forward scanning of the recording head h, and (a ′) to (c ′) indicate the recording state during the backward scanning.

In the conventional recording head h, as shown in FIG. 8, the main droplet Dm and the sub droplet Ds are ejected in different directions. FIG. 8 shows a recording head in which the sub-droplet Ds is discharged to the left with respect to the discharge direction of the main droplet Dm.
When the recording head h moves to the right during the forward scanning and lands so that the sub-drop Ds overlaps the main droplet Dm that has landed first on the recording medium, the main droplet Dm ejected from the recording head h in the backward scanning. And the subdrop Ds land with a deviation amount d. That is, there is a difference in the amount of deviation of the landing positions of the main droplet Dm and the sub-drop Ds between the forward scan and the backward scan.

  Here, the velocity vector of each droplet at the moment when the main droplet Dm and the sub droplet Ds are ejected from the recording head h will be described with reference to FIG. 9A shows the forward scanning of the recording head h, and FIG. 9B shows the backward scanning of the recording head h.

  In FIG. 9, Vm represents the ejection velocity vector of the main droplet Dm when the ink ejection operation is performed with the movement of the recording head h stopped. Vs indicates the ejection velocity vector of the sub-droplet Ds when the ink ejection operation is performed in a state where the movement of the recording head h is stopped. Further, Vh represents a moving speed vector of the recording head h. Θ represents an angle formed by the ejection direction of the main droplet Dm and the ejection direction of the sub-droplet Ds. Here, the main droplet Dm is discharged in the direction of the combined vector Vmh of the discharge velocity vector Vm and the moving velocity vector Vh, and the sub droplet Ds is discharged in the direction of the combined vector Vms of the discharge velocity vector Vs and the velocity vector Vh. Is done. Then, the intersection between the extended lines of the combined vectors Vmh and Vsh and the recording medium P is the landing position of each droplet. In the conventional recording head h in which the ejection directions of the main droplet Dm and the sub-drop Ds are different, the deviation amount of the landing positions of the main droplet and the sub-drop is greatly different between the forward scan and the backward scan. It is clear from

  FIG. 12A is a plan view schematically showing an example of a recording result when a recording operation is performed using the conventional recording head h. In FIG. 12A, E1 indicates a portion recorded during forward scanning, and E2 indicates a portion recorded during sub-scanning. In the recording results exemplified here, a portion E2 where the landing deviation between the main droplet and the sub-droplet has occurred and a portion E1 where no landing deviation has occurred are mixed in the output image. It can be recognized visually. Therefore, when image recording is performed in both forward scanning and backward scanning using the recording head h, the image quality is greatly reduced.

  On the other hand, FIG. 10 is a diagram schematically illustrating an example of the ejection direction and the landing state of ink droplets when a recording operation is performed using the recording head H in the present embodiment. Here, (a) to (c) indicate the recording state during the forward scanning of the recording head H, and (a ′) to (c ′) indicate the recording state during the backward scanning.

In the recording head H in this embodiment, as shown in FIG. 10, the main droplet Dm and the sub droplet Ds are ejected in the same direction.
When this recording head H is moved to the right and the forward scanning is performed, the main droplet Dm is landed on the recording medium P in advance, and then the sub droplet Ds is shifted to the right by the distance d1 from the main droplet Dm. Will land. Also in the backward scanning, the main droplet Dm and the sub droplet Ds sequentially land on the recording medium, and the sub droplet Ds reaches the position shifted by the distance d1 on the left side of the landing position of the main droplet Dm. That is, according to the recording head H in the present embodiment, the amount of deviation of the landing positions of the main droplet Dm and the sub-drop Ds is the same during forward scanning and backward scanning.

  Here, the velocity vector of each droplet at the moment when the main droplet Dm and the sub droplet Ds are ejected from the recording head H will be described with reference to FIG. 11A shows the forward scanning of the recording head H, and FIG. 11B shows the backward scanning of the recording head H.

  In FIG. 11, Vm represents the ejection velocity vector of the main droplet Dm when the ink ejection operation is performed in a state where the movement of the recording head H is stopped. Vs represents the ejection velocity vector of the sub-droplet Ds when the ink ejection operation is performed with the movement of the recording head stopped. Further, Vh represents a moving speed vector of the recording head H. Here, the main droplet Dm is discharged in the direction of the combined vector Dmh of the discharge speed vector Vm and the moving speed vector Vh, and the sub-drop Ds is discharged in the direction of the combined vector Dsh of the discharge speed Vs and the moving speed vector Vh. Is done. Then, the intersection between the extension line of each composite vector and the recording medium P becomes the landing position of each droplet. It is also clear from FIG. 11 that in the recording head H in the present embodiment, the amount of deviation between the landing positions of the main droplet Dm and the sub-drop Ds is uniform during forward scanning and backward scanning.

FIG. 12B is a plan view schematically showing an example of a recording result when a recording operation is performed using the recording head H in the present embodiment. In FIG. 12B, E1 indicates a portion recorded during forward scanning, and E2 indicates a portion recorded during sub-scanning.
As shown in the drawing, when the recording head H in the present embodiment is used, the area where the dots cover the recording medium is the same in the recording result in the forward scanning and the recording result in the backward scanning. There is no change in the visual density of the recorded result. Accordingly, even when image recording is performed in both forward scanning and backward scanning using the recording head H, a high-quality image can be recorded.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. In the drawings, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
In the first embodiment, the ejection port surface F of the recording head H is used while being inclined by an angle θ1 with respect to the upper surface (recording surface) of the recording medium P. In contrast, the recording head H1 according to the second embodiment has a configuration in which the ejection port surface F is used in a state parallel to the surface of the recording medium P. However, even in the recording head H1 in the present embodiment, as shown in FIG. 13, the angle formed by the discharge port surface F parallel to the top surface of the recording medium P and the nozzle axis L1 is the first. This is the same as the embodiment. Therefore, as shown in FIG. 11, in this embodiment as well, as in the first embodiment, the amount of deviation of the landing positions of the main droplet Dm and the sub-drop Ds is different between the forward scan and the backward scan. It becomes possible to make uniform.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.
The recording head H2 in the third embodiment is formed by two flat surface portions F1a and F1b whose discharge port surface F1 intersects at a predetermined angle. In the recording head H, the ink discharge ports are formed in the flat surface portion F1a located closer to the recording medium P. The flat portion F1a in which the discharge ports are formed may be a surface parallel to the upper surface of the recording medium P as in the second embodiment, but the upper surface of the recording medium P as in the first embodiment. May be inclined at an angle θ1. Therefore, the internal structure of the recording head H2 is the same as that in the first or second embodiment.

  When bidirectional recording is performed using the recording head H2 having such a bent ejection orifice surface F1, as shown in FIGS. 14 (a) and 14 (b), during the forward scanning and the backward scanning of the recording head, Then, there is a difference in the air flow generated between the recording head and the recording medium P. That is, when the moving direction of the recording head H is the direction shown in FIG. 14A, the air flow generated between the recording head H and the recording medium P is relatively slow, and FIG. In the case of the direction shown in b), on the contrary, the air flow becomes relatively fast. Due to the difference in the air flow velocity, the degree of influence on the landing positions of the main droplet and the sub-drop also changes between the forward scan and the sub-scan. For this reason, even if the ejection directions of the main droplet and the sub-droplet are matched as in the above embodiments, the amount of landing position deviation may not be uniform during forward scanning and backward scanning. Therefore, in the case of this recording head, the angle θ1 set with respect to the discharge port surface F in each of the above embodiments is further in accordance with the difference in air flow velocity between forward scanning and backward scanning. The angle of θ1 is adjusted. This makes it possible to equalize the amount of deviation between the landing positions of the main droplet and the sub-droplet. Note that the difference in the displacement of the landing position due to the difference in the air flow velocity is actually measured by performing bidirectional recording on the recording medium and measuring the displacement of the landing positions of the main droplet and the sub-droplet at that time. Can be confirmed. Based on the measurement result, the angle θ1 is set, that is, the angle between the normal line of the opening surface of the discharge port and the axial direction of the nozzle is set, thereby shifting the landing position of the main droplet and the sub-droplet. Can be made uniform in both reciprocating scans.

(Other embodiments)
In the first and second embodiments, the case where the normal line of the opening surface of the discharge port 4a and the discharge direction of the sub-droplet are matched is described as an example. However, it is also possible to set the angle between the nozzle axis and the normal line of the opening surface of the discharge port so that the normal line of the opening surface of the discharge port intersects the discharge direction of the sub-droplet. That is, the discharge port surface F may be formed such that the angle formed between the normal line of the opening surface and the sub-droplet discharge direction is smaller than the angle θ2 formed between the sub-droplet discharge direction and the central axis L1. According to this, compared with the conventional recording head in which the opening surface of the discharge port is orthogonal to the axis of the nozzle, it is possible to reduce the difference in the amount of deviation of the landing position between the sub-drop and the main droplet in both reciprocating scans, The intended object of the present invention can be achieved.

  The present invention can also be applied to a recording head (liquid ejection head) that ejects various liquids used directly or indirectly for image recording, and the liquid to be ejected is not particularly limited. Further, the liquid discharge method in the recording head may be a method using a piezo element or the like in addition to a method using an electrothermal transducer (heater). Further, even in the edge shooter type recording head as in the first embodiment, the movable valve 10 is not necessarily provided.

  In the above-described embodiment, the nozzle wall 6, the nozzle bank 7, and the top plate nozzle 8 that form the peripheral surface of the discharge port are made of the same material, and the surface energy thereof is made the same. However, at least only the portion located on the scanning direction side may be formed of the same material. Examples of factors that determine the surface energy include wettability with respect to a liquid and surface roughness. Further, as long as the surface energy is the same, the forming material of the peripheral portion of the discharge port may be different. In addition, an orifice plate in which a discharge port is formed may be attached to the opening of the liquid channel.

  Furthermore, it is possible to use materials having different surface energies (including wettability with respect to the liquid) as the forming material of the peripheral portion of the discharge port. In this case, a deviation occurs in the ejection direction of the main droplet with respect to the normal direction of the opening surface of the discharge port, but the amount of the deviation is obtained from an actual recording result. What is necessary is just to set the angle made with an axis.

  Note that the recording head 110 in the first embodiment described above is a so-called edge shooter type, and the ink ejection direction and the ink supply direction into the nozzles substantially coincide. However, the present invention can also be applied to a so-called side shooter type recording head. In the side shooter type recording head, the ink ejection direction and the ink supply direction into the nozzles are different. Therefore, in the side shooter type recording head, the nozzle axis is the direction in which the liquid is pushed out by the discharge energy generating element, and the angle between the nozzle normal and the normal of the opening surface of the discharge port with respect to the nozzle axial direction. Should be determined.

1 is a perspective view schematically showing an external configuration of a recording apparatus according to an embodiment. FIG. 2 is a block diagram illustrating a schematic configuration of a control device that controls driving of the recording apparatus illustrated in FIG. 1. 1 is a perspective view showing a recording head H to which the present invention is applied. FIG. 3 is a partially cutaway perspective view showing the internal structure of the ejection element of the recording head in the first embodiment of the present invention. FIG. 5 is a side sectional view showing a discharge direction and the like of a main droplet discharged from the discharge element shown in FIG. 4. FIG. 5 is a side sectional view showing a discharge direction and the like of subdroplets discharged from the discharge element shown in FIG. 4. FIG. 5 is a side sectional view showing a process in which ink is ejected in the ejection element shown in FIG. 4. FIG. 10 is a diagram schematically illustrating an example of an ink droplet ejection direction and a landing position when a recording operation is performed using a conventional recording head h. It is explanatory drawing which shows the velocity vector of each droplet at the moment when the main droplet and the sub-droplet were discharged from the conventional recording head h, (a) is at the time of forward scanning, and (b) is at the time of backward scanning. Show. FIG. 3 is a diagram schematically illustrating an example of an ink droplet ejection direction and a landing position when a recording operation is performed using the recording head according to the first embodiment of the present invention. FIG. 5 is an explanatory diagram showing velocity vectors of droplets at the moment when main droplets and sub droplets are ejected from the recording head according to the first embodiment of the present invention, in which (a) shows a forward scanning time and (b) shows. Indicates the time of backward scanning. (A) is a plan view schematically showing an example of a recording result when a recording operation is performed using a conventional recording head h, and (b) is a diagram using the recording head h in the first embodiment of the present invention. It is a top view which shows typically an example of the recording result at the time of performing recording operation. FIG. 6 is a side cross-sectional view illustrating an ejection element of a recording head in a second embodiment of the present invention. FIG. 10 is a side view schematically illustrating a recording head according to a third embodiment of the present invention, where (a) illustrates a forward scan and (b) illustrates a backward scan. FIG. 10 is a side cross-sectional view illustrating a process in which ink is ejected from a ejection element of a conventional recording head h. (A) is a sectional side view showing an axis of a nozzle in a discharge element of a conventional recording head h, and (b) is a side sectional view showing a discharge element of another conventional recording head h1.

Explanation of symbols

H, H1, H2 Recording head 1 Heater board 2 Heater 3 Flow path 4a Discharge port 6 Nozzle wall 7 Nozzle bank 8 Top plate nozzle 11 Discharge element F, F1 Discharge port surface θ1 angle L1 Nozzle axis A1 Normal direction Dm Main droplet Ds Subdrop B Bubble

Claims (11)

In a recording head that can be mounted on a moving member that can move reciprocally relative to a recording medium, and that discharges droplets from a nozzle outlet toward the recording medium
The nozzle discharges a main droplet as the droplet in a direction corresponding to a normal direction of the opening surface of the discharge port, and a sub-droplet having a smaller liquid volume than the main droplet in a direction intersecting the axis of the nozzle. Discharge
The recording head is characterized in that the ejection port is formed such that a normal line of an opening surface of the ejection port intersects with an axis of the nozzle.   2. The recording according to claim 1, wherein an angle formed between a normal line of the opening surface of the discharge port and an axis line of the nozzle is determined by an angle formed between the discharge direction of the sub-droplet and the axis line of the nozzle. head.   The opening surface of the discharge port and the nozzle so that the angle formed between the normal line of the opening surface of the discharge port and the axis line of the nozzle is smaller than the angle formed between the discharge direction of the subdroplet and the axis line of the nozzle. A recording head characterized in that an angle formed with the axis of is defined.   The angle formed between the normal line of the opening surface of the discharge port and the axial direction of the nozzle is determined by the velocity of the air flow generated between the recording medium and the periphery of the discharge port when the moving member moves forward, and the movement 4. The recording head according to claim 1, wherein the recording head is determined according to a difference between a velocity of an air flow generated between the recording medium and the peripheral portion of the ejection port when the member moves backward.   The angle formed between the normal line of the opening surface of the discharge port and the axis line of the nozzle is such that each of the main droplet and the sub-droplet discharged from the discharge port in which the opening surface is formed so as to be orthogonal to the axis line of the nozzle. A recording head obtained based on a difference in landing positions on a recording medium.   6. The nozzle according to claim 1, wherein a front portion located in a certain range extending from the discharge port to the inside of the nozzle is formed of a member having a uniform surface energy. A recording head according to claim 1.   The inner surface of the nozzle has a center of a cross section of a front portion extending in a certain range extending from the discharge port to the inside of the nozzle, and a cross section of an inner portion located inside the nozzle from the front portion. The sub-droplet ejection direction is deviated from the axis of the nozzle by moving the liquid from the front portion to the inward portion when forming the droplet. The recording head according to claim 1 or 2.   The recording head according to claim 1, wherein the nozzle includes an electrothermal converter that generates thermal energy for discharging a liquid.   The recording head according to claim 8, wherein the nozzle includes a movable plate that is displaced according to foaming of the liquid generated by the thermal energy. A moving means for reciprocally moving the recording head according to any one of claims 1 to 9 and the recording medium;
Control means for controlling the reciprocation of the recording head and the recording medium by the moving means, and for controlling the ejection of liquid from the recording head;
An ink jet recording apparatus comprising:   The inkjet recording apparatus according to claim 10, wherein a plurality of the nozzles in the recording head are arranged along a direction intersecting the main scanning direction.

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