JP2007152665A - Liquid jetting head, and liquid jetting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid jetting device or the like which can expand the jetting range of liquid droplets without generating a cross talk first, and secondly, to suppress the generation of white stripes resulting from a gap between adjacent pixels in the subsidiary scanning direction, and to provide a liquid jetting head which can improve a recording quality, and a liquid jetting device equipped with the liquid jetting head. <P>SOLUTION: This recording head is equipped with a pressure chamber forming board 27 (pressure chamber-forming board) and a piezoelectric oscillator 20 (pressure generating means). In this case, on the pressure chamber forming board 27, a plurality of rows of pressure chambers 26 which communicate with nozzle openings are provided in the subsidiary scanning direction which is orthogonal to the head scanning direction. The piezoelectric oscillator 20 can generate a pressure variation in an ink (liquid) in the pressure chamber. In the recording head, a group of a plurality of nozzle openings 15 which are adjacent to each other is made a nozzle set 33, and 1 set each of the nozzle set 33 is arranged in each pressure chamber 26 while making the nozzle set 33 correspond to each pressure chamber 26, and the piezoelectric oscillator 20 is driven. Thus, the liquid jetting head is constituted in such a manner that liquid droplets are simultaneously discharged from each nozzle opening 15 of the nozzle set 33 corresponding to the pressure chamber 26 which is a driving object. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid ejecting head such as an ink jet recording head, and a liquid ejecting apparatus, and in particular, a pressure chamber forming substrate that forms a pressure chamber that communicates with a nozzle opening, and a pressure that can cause pressure fluctuations in liquid in the pressure chamber. A liquid ejecting head including a generating unit and operating a pressure generating source to cause a pressure fluctuation in the liquid in the pressure chamber to discharge the liquid in the pressure chamber as droplets from the nozzle opening, and a liquid ejecting apparatus including the same About.

  The liquid ejecting apparatus is an apparatus that includes a liquid ejecting head capable of ejecting liquid as droplets and ejects various liquids from the liquid ejecting head. As a typical example of this liquid ejecting apparatus, for example, an ink jet recording head (hereinafter simply referred to as a recording head) as a liquid ejecting head is provided, and recording paper is used as ink droplets from a nozzle opening of the recording head. Examples thereof include an image recording apparatus such as an ink jet printer that performs recording by forming dots by ejecting and landing on an ejection target such as the above. In recent years, liquid ejecting apparatuses have been applied not only to this image recording apparatus but also to various manufacturing apparatuses such as a manufacturing apparatus for color filters such as liquid crystal displays.

  In the ink jet printer (hereinafter simply referred to as a printer), the recording head is moved in the main scanning direction, and the recording paper as the recording medium (ejection target) is moved in the sub-scanning direction. To discharge. The ink droplets are ejected by selectively supplying ejection pulses from a drive signal including a plurality of ejection pulses to a pressure generating means (for example, a piezoelectric vibrator) and driving it. This is done by causing pressure fluctuations in the ink and controlling the pressure fluctuations. Some printers of this type are configured to perform multi-gradation recording by changing the size of dots formed on the recording paper according to the number of ejection pulses supplied to the pressure generating means. It has been proposed (see, for example, Patent Document 1).

In the printer of Patent Document 1, a series of drive signals are configured by including a plurality of ejection pulses generated at predetermined intervals within one recording period (one ejection period). When forming a large dot, three ejection pulses within the recording cycle are supplied to the pressure generating means. When forming a medium dot, two ejection pulses are supplied to the pressure generating means. Further, when forming small dots, one ejection pulse is supplied to the pressure generating means. As a result, recording is performed with four gradations of “large dots”, “medium dots”, “small dots”, and “non-recording”.
JP 2002-103619 A

  However, in the configuration of the above-mentioned Patent Document 1, when a large dot or a medium dot is recorded, when a plurality of ejection pulses are used to eject ink droplets continuously to form a dot in one pixel area. In order to land a plurality of ink droplets (dot elements) in the main scanning direction of the recording head, the pixels formed as an assembly of dot elements e are arranged in the main scanning direction as large dots L shown in FIG. It is long and short in the sub-scanning direction. For this reason, in the configuration of Patent Document 1, a gap G is generated between pixels adjacent in the sub-scanning direction, and this gap causes roughness or white streaks on the recorded image. There was a fear.

  In order to reduce the gap G, it is conceivable to reduce the feeding amount of a recording medium such as recording paper, but this cannot be adopted because the recording time becomes longer. It is also conceivable to increase the ejection from a plurality of nozzles by setting the pitch of nozzle openings in the sub-scanning direction to be small. However, in this case, the thickness of the partition wall that partitions adjacent pressure chambers is insufficient, and a new problem of crosstalk occurs.

  The present invention has been made in view of such circumstances, and a first object thereof is to provide a liquid ejecting apparatus and the like that can expand the droplet ejection range without causing the problem of crosstalk. Second, a liquid ejecting head capable of suppressing the occurrence of white streaks due to a gap between adjacent pixels in the sub-scanning direction and improving the recording quality, and a liquid including the same It is in providing an injection device.

The liquid ejecting head of the present invention has been proposed to achieve the above object, and a nozzle forming substrate in which a plurality of nozzle openings are arranged in a sub-scanning direction orthogonal to the head scanning direction, and a pressure leading to the nozzle openings. A liquid ejecting head comprising: a pressure chamber forming substrate in which a plurality of chambers are arranged in the sub-scanning direction; and a pressure generating means capable of causing a pressure fluctuation in the liquid in the pressure chamber,
A set of a plurality of adjacent nozzle openings is used as a nozzle set, and the nozzle set is arranged in correspondence with each pressure chamber,
By driving the pressure generating means, droplets are ejected simultaneously from the nozzle openings of the nozzle set corresponding to the pressure chamber to be driven.

  According to this configuration, since a set of a plurality of nozzle openings is arranged as a nozzle set in each pressure chamber, it is not necessary to thin the partition walls that partition adjacent pressure chambers, and the problem of crosstalk does not occur. A unit dot formed by a single ejection operation is composed of a plurality of dot elements, thereby expanding the droplet ejection range.

In this configuration, it is desirable that the nozzle sets are arranged at a specified pitch corresponding to the dot formation density, and the nozzle openings constituting the nozzle set are arranged at a pitch smaller than the specified pitch.
The pitch of the nozzle set means the distance from the center of the nozzle set to the center of the adjacent nozzle set.

  In the above configuration, it is desirable that the nozzle openings constituting the nozzle set are arranged in the sub-scanning direction.

  In such a configuration, a unit dot formed by one ejection operation is composed of a plurality of dot elements arranged in the sub-scanning direction, and thus has a longer shape in the sub-scanning direction than the conventional one. When a droplet larger than a unit dot is formed by continuously discharging droplets a plurality of times, the dot shape can be expanded in the sub-scanning direction compared to the conventional case, and the dot-shaped head scanning direction and sub-scanning direction can be expanded. The balance in the scanning direction can be improved. In other words, the aspect ratio of the dot shape can be made closer to 1. For this reason, when the present invention is applied to an image recording apparatus such as an ink jet printer, a gap between adjacent pixels in the sub-scanning direction can be suppressed. As a result, roughness, white streaks, etc. in the recorded image can be suppressed. Generation can be suppressed and image quality can be improved. Further, since the formation density of dots in the sub-scanning direction (including dot elements; hereinafter the same) is increased, the number of head scans, that is, the pass, is reduced in so-called solid recording in which a predetermined area is filled with dots without gaps. As a result, the recording speed can be increased.

  In this configuration, it is possible to employ a configuration in which the nozzle openings constituting the nozzle set are arranged at a pitch that is ½ of the specified pitch.

  According to this configuration, the dot formation density in the sub-scanning direction is apparently twice that of the prior art. Therefore, when the predetermined area of the ejection target is filled with the dots without gaps, the number of head scans is halved. As a result, the discharge operation speed can be further increased.

Furthermore, the structure which arrange | positions each nozzle opening which comprises the said nozzle set with a pitch smaller than 1/2 of the said regular pitch is employable.
Further, it is desirable to employ a configuration in which the nozzle openings constituting the nozzle set are arranged at a pitch smaller than the pitch corresponding to the dot formation density in the head scanning direction.

  According to these configurations, since the dot elements constituting each dot approach in the sub-scanning direction, the occurrence of white stripes can be effectively suppressed. As a result, it is possible to reduce the amount of dots required for solid recording, and as a result, it is possible to improve the recording speed with fewer passes.

  According to another aspect of the invention, a liquid ejecting apparatus includes the liquid ejecting head having any one of the above configurations.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet printer (hereinafter abbreviated as a printer) shown in FIG. 1 will be exemplified as the liquid ejecting apparatus of the invention.

  The printer 1 includes a recording head 2 that is a kind of liquid ejecting head, a carriage 4 to which an ink cartridge 3 is detachably attached, a platen 5 disposed below the recording head 2, and a recording head 2. A carriage moving mechanism 7 that moves the mounted carriage 4 in the paper width direction of the recording paper 6 (ejection target), a paper feeding mechanism 8 that transports the recording paper 6 in a paper feeding direction that is orthogonal to the paper width direction, and the like. In general, it is structured. Here, the paper width direction is the main scanning direction (head scanning direction), and the paper feeding direction is the sub-scanning direction (that is, the direction orthogonal to the head scanning direction). The ink cartridge 3 may be a type that is mounted on the carriage 4 or a type that is mounted on the housing side of the printer 1 and is supplied to the recording head 2 via an ink supply tube.

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction, and is configured to move in the main scanning direction along the guide rod 9 by the operation of the carriage moving mechanism 7. ing. The position of the carriage 4 in the main scanning direction is detected by the linear encoder 10, and a detection signal is transmitted to the printer controller 12 (see FIG. 4) as position information. Thus, the printer controller 12 can control the recording operation (discharge operation) by the recording head 2 while recognizing the scanning position of the carriage 4 (recording head 2) based on the position information from the linear encoder 10. .

  In addition, a home position serving as a scanning start point of the recording head 2 is set within the moving range of the recording head 2 and outside the platen 5. A capping mechanism 13 is provided at this home position. The capping mechanism 13 seals the nozzle surface of the recording head 2 with the cap member 14 to prevent evaporation of the ink solvent from the nozzle opening 15 (see FIG. 2). The capping mechanism 13 is used for a cleaning operation in which negative pressure is applied to the sealed nozzle surface to forcibly suck and discharge ink from the nozzle openings 15.

  FIG. 2 is a cross-sectional view of a main part for explaining the configuration of the recording head 2. The recording head 2 includes a head case 16, an actuator unit 17 accommodated in the head case 16, a flow path unit 18 joined to the bottom surface (tip surface) of the head case 16, and the like. The head case 16 is made of, for example, an epoxy resin, and a storage space 19 for storing the actuator unit 17 is formed in the head case 16. The actuator unit 17 includes a plurality of piezoelectric vibrators 20 (a kind of pressure generating means in the present invention) cut into comb teeth and a fixing plate 21 to which the piezoelectric vibrators 20 are joined. In addition, a flexible cable 22 is connected to each piezoelectric vibrator 20 of the actuator unit 17 so that a drive signal from a drive signal generation circuit 24 (see FIG. 4) is supplied through the flexible cable 22. Yes.

  The piezoelectric vibrator 20 in the present embodiment is a so-called longitudinal vibration mode piezoelectric vibrator that is displaced in a direction orthogonal to the electric field direction. When a drive signal is supplied, the piezoelectric vibrator 20 extends in a direction orthogonal to the stacking direction of the piezoelectric body and the electrodes. Displace (stretch). Further, each piezoelectric vibrator 20 is cut at the same pitch as the formation pitch of the pressure chambers 26 of the flow path unit 18, and is configured to correspond to one pressure chamber 26 (see FIG. 6) one by one. Has been.

  FIG. 3 is an exploded perspective view illustrating the configuration of the flow path unit 18 in the present embodiment. In this flow path unit 18, a nozzle plate 28 (a kind of nozzle forming substrate) is joined to one surface of the pressure chamber forming substrate 27, and a vibration plate 29 is joined to the other surface of the pressure chamber forming substrate 27. As shown in FIG. 2, a series of ink flow paths from the reservoir 30 to the ink supply port 31, the pressure chamber 26, the nozzle communication port 32, and the nozzle opening 15 are formed.

  The nozzle plate 28 is a thin metal plate having a plurality of nozzle openings 15 formed in a row in the sub-scanning direction. In the present embodiment, the nozzle plate 28 is made of a stainless steel plate, and a plurality of rows of nozzle openings 15 (nozzle rows) are provided. One nozzle row is composed of 360 nozzle openings 15. A set of a plurality of adjacent nozzle openings 15, for example, a set of two nozzle openings 15 adjacent in the sub-scanning direction is used as a nozzle set 33. The nozzle set 33 is arranged at 180 dpi in the sub-scanning direction corresponding to the pressure chamber 26 (the empty portion 38 of the pressure chamber forming substrate 27) one to one. Therefore, in this embodiment, one set of nozzles 33, that is, a set of two nozzle openings 15 is arranged for one pressure chamber 26. Details of this point will be described later.

  The pressure chamber forming substrate 27 disposed between the nozzle plate 28 and the vibration plate 29 is a portion that becomes an ink flow path, specifically, an opening portion 36 that becomes a reservoir 30, a groove portion 37 that becomes an ink supply port 31, In addition, in this embodiment, the silicon wafer which is a base material having crystallinity is subjected to an anisotropic etching process. It is made by doing. The empty portion 38 is a recess elongated in the main scanning direction, and one end communicates with the opening 36 through the groove portion 37 and the other end communicates with the nozzle opening 15 of the nozzle plate 28 through the nozzle communication port 32. It is configured. The empty portions 38 are provided in a plurality of rows in the sub-scanning direction on the pressure chamber forming substrate 27.

  The diaphragm 29 is made of a composite plate material in which a PPS (polyphenylene sulfide) resin film is laminated as an elastic thin film portion 40 on the surface of a metal support plate 39 such as stainless steel. The diaphragm 29 is formed with a diaphragm portion 41 that can be deformed in accordance with the expansion / contraction drive of the piezoelectric vibrator 20 to cause pressure fluctuation in ink (a kind of liquid) in the pressure chamber 26. The diaphragm portion 41 is configured by removing the supporting plate 39 around it by an etching process while leaving the portion to which the tip surface of the piezoelectric vibrator 20 is connected as an island portion 42, so that only the elastic thin film portion 40 is formed. Has been.

  In addition, a compliance portion 43 that seals one opening surface of the opening portion 36 of the pressure chamber forming substrate 27 and partitions a part of the reservoir 30 is formed on the vibration plate 29. The compliance portion 43 is made only of the elastic thin film portion 40 by removing the support plate 39 in the region corresponding to the reservoir 30 (opening portion 36) by etching. The compliance unit 43 functions as a damper that alleviates pressure fluctuations in the ink in the reservoir 30 when the piezoelectric vibrator 20 is driven.

  Reference holes 44 (44a, 44b, 44c) that can be inserted into positioning pins (not shown) are formed in the flow path unit constituent members, that is, the vibration plate 29, the pressure chamber forming substrate 27, and the nozzle plate 28. It is opened through the plate thickness direction. Then, each flow path unit constituting member is bonded with an adhesive or the like after the positioning pins are inserted into the respective reference holes 44, and then bonded with an adhesive or the like. It is fixed to the case 16.

  FIG. 4 is a block diagram showing the electrical configuration of the printer. The printer 1 according to the present embodiment is roughly configured by a printer controller 12 and a print engine 45. The printer controller 12 includes an external interface (external I / F) 46 that receives print data from an external device such as a host computer, a RAM 47 that is used as a work memory for temporarily storing various data, A ROM 48 that stores a control program for data processing, font data, graphic functions, and the like, a control unit 49 that controls each unit, an oscillation circuit 50 that generates a clock signal, and a drive signal that is supplied to the recording head 2 are generated. And a drive signal generation circuit 24 that performs printing, and an internal interface (internal I / F) 52 that outputs ejection data, drive signals, and the like obtained by developing print data for each dot to the recording head 2. .

  The control unit 49 performs integrated control of each unit based on a control program stored in the ROM 48, and also print data received from the external device through the external I / F 46 to eject data (used by the recording head 2) ( Dot pattern data). Specifically, the control unit 49 reads the print data once stored in the reception buffer of the RAM 47, converts it into intermediate code data, and stores it in the intermediate buffer of the RAM 47. Then, the converted intermediate code data is converted into ejection data corresponding to a dot pattern with reference to font data and graphic functions, and stored in the output buffer of the RAM 47. Then, if ejection data for one line that can be printed by one main scan of the recording head 2 is obtained, the control unit 49 converts the ejection data for one line stored in the output buffer to the internal I / O. Output to the recording head 2 through F52.

  The print engine 45 includes a recording head 2, a carriage moving mechanism 7, a paper feeding mechanism 8, and a linear encoder 10. The carriage moving mechanism 7 includes a carriage 4 to which the recording head 2 is attached and a drive motor (for example, a DC motor) that travels the carriage 4 via a timing belt or the like, and moves the recording head 2 in the main scanning direction. Let The paper feed mechanism 8 includes a paper feed motor, a paper feed roller, and the like, and sequentially feeds the recording paper 6 to perform sub-scanning. Further, the linear encoder 10 outputs an encoder pulse corresponding to the scanning position of the recording head 2 mounted on the carriage 4 to the control unit 49 through the internal I / F 52 as position information in the main scanning direction. Accordingly, the control unit 49 can grasp the position of the recording head 2 in the main scanning direction based on the encoder pulse received from the linear encoder 10 side.

  The drive signal generation circuit 24 generates a series of drive signals including a plurality of ejection pulses (ejection waveforms). This ejection pulse is a pulse that can eject the ink droplet (a kind of droplet) from the nozzle opening 15 by extending and contracting the piezoelectric vibrator 20, and the drive signal COM illustrated in FIG. Three ejection pulses (first ejection pulse P1, second ejection pulse P2, and third ejection pulse P3) are included. The drive signal generation circuit 24 repeatedly generates this drive signal COM every recording period T. The first ejection pulse P1 to the third ejection pulse P3 are all configured by signals having the same waveform, and are expansions that increase the potential with a constant gradient that does not eject ink droplets from the intermediate potential VM to the maximum potential VH. Element p1, an expansion hold element p2 that holds the maximum potential VH for a predetermined time, a discharge element p3 that drops the potential steeply from the maximum potential VH to the minimum potential VL, and a contraction hold element p4 that holds the minimum potential VL for a predetermined time And a damping element p5 for restoring the potential from the lowest potential VL to the intermediate potential VM.

  When these first ejection pulse P1 to third ejection pulse P3 are supplied to the piezoelectric vibrator 20, a predetermined amount of ink droplets are ejected from the nozzle opening 15 each time the ejection pulses P1 to P3 are supplied. Then, by changing the number of ejection pulse signals supplied within one recording period T, the size of dots recorded in one pixel formation region (virtual region in the recording paper 6) can be varied. . In the present embodiment, in the case of the ejection data (11), the ink droplet ejection operation is continuously performed three times by continuously supplying the three ejection pulses P1 to P3 within one recording period T to the piezoelectric vibrator 20. Thus, a large dot is recorded in the pixel formation area. In the case of the ejection data (10), the ink droplet ejection operation is performed by supplying the piezoelectric vibrator 20 with a total of two ejection pulses of the first ejection pulse P1 and the second ejection pulse P3 within one recording period T. Are performed twice in succession to record medium dots in the pixel formation region. In the case of ejection data (01), the second ejection pulse P2 within one recording cycle T is supplied to the piezoelectric vibrator 20 to record small dots in the pixel formation region. In the case of the ejection data (00), no ejection pulse is supplied to the piezoelectric vibrator 20, and no dot is formed in the pixel formation region.

  As described above, the printer 1 ejects a plurality of ink droplets continuously using a plurality of ejection pulses when forming a large dot or a medium dot. An ink droplet is landed. In the present embodiment, the design resolution (basic resolution) in the main scanning direction is set to 360 dpi. Therefore, for example, three ink droplets (unit dots) forming a large dot are arranged at 360 dpi in the main scanning direction (see FIG. 8B).

  Next, a first embodiment of the recording head 2 in the printer 1 will be described. In the recording head 2 in the present embodiment, a set of a plurality of adjacent nozzle openings 15 is used as a nozzle set 33, the nozzle set 33 is arranged corresponding to each pressure chamber 26, and the piezoelectric vibrator 20 is driven. Thus, the ink droplets are simultaneously ejected from the nozzle openings 15 of the nozzle set 33 corresponding to the pressure chamber 26 to be driven. In this way, since a set of a plurality of nozzle openings 15 is arranged in each pressure chamber 26 as a nozzle set 33, there is no need to thin the partition wall (partition wall 54) that partitions adjacent pressure chambers 26, and there is a problem of crosstalk. Does not occur. A unit dot formed by a single ejection operation is composed of a plurality of dot elements e, thereby expanding the ink droplet ejection range. Hereinafter, this point will be described in detail.

  FIG. 6 is a plan view of the main part of the pressure chamber forming substrate 27, and FIG. 7 is a cross-sectional view of the flow path unit 18 taken along the line YY. As shown in FIG. 6, in this embodiment, one nozzle set 33 is constituted by two adjacent nozzle openings 15, and each nozzle opening 15 constituting this nozzle set 33 is arranged in the sub-scanning direction. . For example, each nozzle set 33 is arranged in the sub-scanning direction at a specified pitch A corresponding to 180 dpi, and each nozzle opening 15 constituting the nozzle set 33 is arranged at a pitch B corresponding to 360 dpi smaller than the specified pitch A. Has been. That is, the nozzle openings 15 are arranged at a pitch that is ½ of the specified pitch A. As shown in FIG. 7, the island portion 42 of the vibration plate 29, the piezoelectric vibrator 20 of the actuator unit 17, and the pressure chamber 26 are in a one-to-one relationship with the nozzle set 33 (the combined nozzle opening 15). Is provided.

One set of adjacent nozzle openings 15 constituting the nozzle set 33 is arranged for one pressure chamber 26. The pressure chambers 26 corresponding to the nozzle set 33 are partitioned by a partition wall 54 as shown in FIG. In this way, by arranging the nozzle set 33 which is a set of a plurality of nozzle openings 15 corresponding to each pressure chamber 26, one pressure chamber 26 is provided for each nozzle opening 15 as in the prior art. There is no need to provide it. That is, in the nozzle row configured by the same number of nozzle openings 15, the pressure chambers 26 corresponding to these nozzle openings 15 are compared with the conventional configuration in which the pressure chambers 26 and the nozzle openings 15 correspond one-to-one. The number can be reduced. Alternatively, with respect to the nozzle row, the number of nozzle openings 15 can be increased without increasing the number of piezoelectric vibrators 20 and pressure chambers 26. In this embodiment, one nozzle row is composed of 360 nozzle openings 15, whereas the pressure chamber 26 corresponding to these nozzle openings 15 is composed of 180 halves. As a result, the partition walls 54 that partition the pressure chambers 26 can be made thicker than in the conventional configuration in which the same number of pressure chambers 26 as the nozzle openings 15 are provided. As a result, the rigidity of the partition wall 54 can be increased as compared with the conventional configuration, and the influence of the pressure wave generated by the discharge operation of the adjacent pressure chambers 26 can be prevented. For this reason, crosstalk can be prevented and the ejection characteristics can be stabilized.
In addition, since the plurality of nozzle openings 15 are arranged for the piezoelectric vibrator 20 serving as one pressure generation source, the width of the piezoelectric vibrator 20 in the sub-scanning direction cannot be made small due to manufacturing convenience. That is, even when the formation pitch of the piezoelectric vibrators 20 cannot be reduced, the number of nozzle openings 15 in the nozzle row can be increased without increasing the number of piezoelectric vibrators 20 in the sub-scanning direction.

  In the recording head 2 having the above configuration, as shown in FIG. 5, when an ejection pulse is supplied to the piezoelectric vibrator 20 through the flexible cable 22, first, the piezoelectric vibrator 20 contracts in the element longitudinal direction by the expansion element p1. Then, the island portion 42 is displaced in a direction away from the pressure chamber 26, whereby each pressure chamber 26 constituting the pressure chamber set 41 to be driven corresponds to the maximum potential VH from the reference volume corresponding to the intermediate potential VM. Expands to the expansion volume. Due to the expansion of the pressure chamber 26, ink is supplied into each pressure chamber 26 from the reservoir 30 side through the ink supply port 31. The expansion state of the pressure chamber 26 is maintained over the supply period of the expansion hold element p2.

  Thereafter, the discharge element p <b> 3 is supplied, the piezoelectric vibrator 20 is expanded, and the island portion 42 is displaced in the direction approaching the pressure chamber 26. Thereby, the pressure chamber 26 is rapidly contracted from the expansion volume to the contraction volume corresponding to the lowest potential VL. Due to the contraction of the pressure chamber 26, the ink inside is pressurized, and ink droplets are simultaneously ejected from the nozzle openings 15 of the nozzle set 33 corresponding to the pressure chamber 26 to be driven. The contraction state of the pressure chamber 26 is maintained over the supply period of the contraction hold element p4. During this period, the pressure in the pressure chamber 26 that has decreased due to the ejection of ink droplets rises again due to its natural vibration. The damping element p5 is supplied in accordance with this rising timing. By supplying the damping element p5, the pressure chamber 26 expands and returns to the reference volume, and the ink pressure fluctuation in the pressure chamber 26 is absorbed.

  As shown in FIG. 8A, the two ink droplets simultaneously ejected from the nozzle openings 15 of the nozzle set 33 corresponding to the pressure chamber 26 to be driven are aligned (spread) in the sub-scanning direction. A dot element e is landed on the recording paper 6, and one small dot S (unit dot) is formed by these two dot elements e. That is, the small dot S in the present embodiment is configured by two dot elements e arranged at 360 dpi in the sub-scanning direction. For example, by continuously supplying a total of three ejection pulses P1 to P3 within one recording period T to the piezoelectric vibrator 20, ink droplet ejection operations are performed three times in succession in one pixel formation region. When printing large dots, as shown in FIG. 8B, three unit dots are arranged in the main scanning direction to form one large dot L. In the drawing, a total of six large dots L are shown by arranging three in the main scanning direction at a pitch of 360 dpi and two in the sub-scanning direction at 180 dpi.

  As described above, the recording head 2 in the printer 1 is provided with the pressure chambers 26 corresponding to the nozzle sets 33 each including a plurality of nozzle openings 15 adjacent in the sub-scanning direction. 20 is driven so that ink droplets are simultaneously ejected from the nozzle openings 15 of the nozzle set 33 corresponding to the pressure chamber 26 to be driven, so that a plurality of ejection pulses in one recording cycle are used continuously. In the case where dots of a larger size are formed by ejecting ink droplets, the dot shape can be expanded in the sub-scanning direction compared to the conventional case, and the dot-shaped head scanning direction (main scanning direction) The balance in the sub-scanning direction can be improved. That is, the aspect ratio can be made closer to 1. For this reason, it is possible to suppress a gap between adjacent pixels in the sub-scanning direction, and as a result, it is possible to improve the image quality by suppressing the occurrence of roughness and white streaks in the recorded image. In the present embodiment, the dot formation density in the sub-scanning direction is apparently twice that in the case where the present invention is not applied, so that a predetermined area of the recording paper 6 is filled with dots without gaps, so-called solid recording. In this case, the number of head scans (pass) can be halved, and as a result, the recording speed can be increased.

  In addition, the present invention relates to the piezoelectric vibrator 20, and it is not necessary to change the formation pitch, and the conventional structure can be used as it is, which is convenient, and the size of each piezoelectric vibrator 20 is the same as before. As a result, the displacement efficiency does not decrease.

  By the way, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the description of the scope of claims.

  In the above-described embodiment, the configuration in which the nozzle openings 15 are arranged at a pitch that is ½ of the formation pitch of the nozzle set 33 is illustrated, but the present invention is not limited thereto. For example, the nozzle openings 15 of the nozzle set 33 are arranged at a pitch smaller than 1/2 of the formation pitch of the nozzle set 33, or a pitch based on the dot formation density corresponding to the basic resolution in the main scanning direction. It is also possible to adopt a configuration in which arrangement is made at a small pitch. Specifically, each nozzle set 33 is arranged in the sub-scanning direction at a specified pitch A corresponding to 180 dpi as in the above embodiment, and each nozzle opening 15 of the nozzle set 33 is set to 1/4 ( They can also be arranged at a pitch C corresponding to 720 dpi, which is 1/2 the pitch based on the dot formation density corresponding to the basic resolution in the main scanning direction (see FIG. 9). According to these configurations, as in the above embodiment, since the dot elements constituting each dot approach in the sub-scanning direction, it is possible to effectively suppress the occurrence of white stripes. This makes it possible to reduce the amount of dots required for solid recording, and as a result, the recording speed can be improved.

  Next, a modification of the above embodiment will be described. The recording head 2 in the above embodiment is exemplified by the configuration in which the nozzle set 33 is a set of two nozzle openings 15 adjacent in the sub-scanning direction, but is not limited thereto. For example, a configuration in which a set of a plurality of adjacent nozzle openings 15 is arranged in both the sub-scanning direction and the main scanning direction to form the nozzle set 33 can be employed. Specifically, as shown in FIG. 10, two nozzle openings 15 are arranged side by side in the sub-scanning direction and the main scanning direction around the center O serving as a reference for the specified pitch A, and these four nozzle openings are arranged. A configuration in which 15 sets are used as the nozzle set 33 can also be adopted. The nozzle openings 15 in the sub-scanning direction and the main scanning direction of the nozzle set 33 are arranged at a pitch smaller than the formation pitch of the nozzle set 33, that is, the specified pitch A. For example, it is desirable that the nozzle openings 15 of the nozzle set 33 are appropriately set at a pitch corresponding to 360 to 720 dpi. According to this configuration, as in the above embodiment, since the dot elements constituting each dot approach in the sub-scanning direction, it is possible to effectively suppress the occurrence of white stripes. In addition, since the dot elements constituting each dot approach not only in the sub-scanning direction but also in the main scanning direction, the dot shape can be expanded in the scanning direction. Accordingly, as shown in the upper column of FIG. 11, the dot shape can be broadened as a whole as compared with the conventional dot shape (lower column). This is suitable for solid recording without filling. Further, compared with the conventional case, when printing at the same resolution, since the dot elements are dispersed, it is possible to suppress roughness in a recorded image, particularly with small dots (low density). As a result, even when the basic resolution is lowered, it is possible to suppress the occurrence of white streaks and roughness in the recorded image, so that it is possible to increase the recording speed while suppressing deterioration in the image quality of the recorded image. Become.

  In the above description, the ink jet recording head 2 is described as an example of the liquid ejecting head, but the present invention can also be applied to other liquid ejecting heads. For example, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an electrode material ejecting head used for forming an electrode such as an organic EL (Electro Luminescence) display, an FED (surface emitting display), a biochip (biochemical element) The present invention can also be applied to bioorganic matter ejecting heads and the like used in the production of

FIG. 2 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view of a main part illustrating the configuration of a recording head. It is a disassembled perspective view explaining the structure of a flow path unit. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a figure explaining the structure of a drive signal. It is a principal part top view explaining the structure of a flow-path formation board | substrate. It is the YY sectional view taken on the line in FIG. (A) is a schematic diagram explaining the structure of a unit dot, (b) is a schematic diagram explaining the structure of a large dot. It is a principal part top view explaining the structure of a flow-path formation board | substrate. It is a principal part top view explaining the structure of a flow-path formation board | substrate. It is a schematic diagram explaining the structure of each dot in the modification of the prior art and this embodiment. It is a schematic diagram explaining the structure of the conventional large dot.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording head, 3 ... Ink cartridge, 4 ... Carriage, 5 ... Platen, 6 ... Recording paper, 7 ... Carriage mechanism, 8 ... Paper feed mechanism, 9 ... Guide rod, 10 ... Linear encoder, 12 ... Printer controller, 13 ... Capping mechanism, 14 ... Cap member, 15 ... Nozzle opening, 16 ... Head case, 17 ... Actuator unit, 18 ... Passage unit, 19 ... Storage space, 20 ... Piezoelectric vibrator, 21 ... Fixed plate , 22 ... Flexible cable, 24 ... Drive signal generation circuit, 26 ... Pressure chamber, 27 ... Pressure chamber forming substrate, 28 ... Nozzle plate, 29 ... Vibration plate, 30 ... Reservoir, 31 ... Ink supply port, 32 ... Nozzle communication port , 33 ... Nozzle set, 36 ... Opening part, 37 ... Groove part, 38 ... Empty part, 39 ... Support plate, 40 ... Elastic thin film part, 41 ... Diaphragm , 42 ... island part, 43 ... compliance part, 44 ... reference hole, 45 ... print engine, 46 ... external I / F, 47 ... RAM, 48 ... ROM, 49 ... control part, 50 ... oscillation circuit, 52 ... Internal I / F, 54 ... partition wall

Claims (7)

A nozzle forming substrate in which a plurality of nozzle openings are arranged in a sub-scanning direction orthogonal to the head scanning direction, a pressure chamber forming substrate in which a plurality of pressure chambers communicating with the nozzle openings are arranged in a sub-scanning direction, and the pressure in the liquid in the pressure chamber A liquid ejecting head comprising pressure generating means capable of causing fluctuations,
A set of a plurality of adjacent nozzle openings is used as a nozzle set, and the nozzle set is arranged in correspondence with each pressure chamber,
A liquid ejecting head, wherein the pressure generating unit is driven to simultaneously eject droplets from the nozzle openings of a nozzle set corresponding to a pressure chamber to be driven.   2. The liquid according to claim 1, wherein the nozzle sets are arranged at a specified pitch corresponding to a dot formation density, and the nozzle openings constituting the nozzle set are arranged at a pitch smaller than the specified pitch. Jet head.   The liquid jet head according to claim 2, wherein the nozzle openings constituting the nozzle set are arranged in a sub-scanning direction.   The liquid ejecting head according to claim 3, wherein the nozzle openings constituting the nozzle set are arranged at a pitch that is ½ of the specified pitch.   The liquid ejecting head according to claim 3, wherein the nozzle openings constituting the nozzle set are arranged at a pitch smaller than ½ of the specified pitch.   2. The liquid ejecting head according to claim 1, wherein the nozzle openings constituting the nozzle set are arranged at a pitch smaller than a pitch based on a dot formation density in a head scanning direction.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.

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