JP5381488B2 - Inkjet recording head driving method - Google Patents

Description

  The present invention relates to a method for driving an inkjet recording head.

  In an ink jet recording head (hereinafter referred to as a recording head) for recording an image using minute ink droplets, an ink droplet is ejected from a nozzle by applying pressure in a pressure generating chamber (hereinafter referred to as a channel). Land on a recording medium such as recording paper.

  Such an ink jet recording system has a relatively simple configuration and enables high-precision image recording, and has been rapidly developed in a wide range of fields from home use to industrial use. Particularly in recent years, various improvements have been proposed for speeding up ink jet recording and improving image quality.

  Along with the high performance of such an ink jet recording method, the ink itself has been improved, and ink containing solid components such as a polymer compound has been increased in the ink for the purpose of improving the scratch resistance after printing. ing. In addition, with the increase in printing speed, there is also a demand for quick-drying performance that allows ink to quickly dry after landing on the recording medium. For this reason, a large amount of volatile components are also contained in the ink.

  When printing is performed using ink containing such a polymer compound and a volatile component, the ink component volatilizes quickly from the meniscus surface, so that the solid component thickens in the vicinity of the nozzle and makes it difficult to eject ink droplets. In particular, there is a problem that some ink droplets are not likely to be ejected during intermittent ejection.

  In response to this problem, Patent Document 1 and Patent Document 2 describe a meniscus on a nozzle surface before ejecting ink droplets in a recording head that ejects ink droplets by deformation of a piezoelectric element provided on one partition wall of a channel. There has been proposed a method of stirring the ink in the vicinity of the nozzles by slightly vibrating the ink so as not to eject the ink.

  Further, Patent Document 3 discloses that a thickening of a solid component in the vicinity of a nozzle by fine vibration is applied to a recording head that ejects ink droplets by deforming partition walls on opposite sides of a channel to expand or contract a channel volume. In order to apply the technology to prevent and effectively cancel the residual vibration generated by this vibration, the pulse width is (2n) AL (AL is 1/2 of the acoustic resonance period of the channel, n is 1 or more There has been proposed a technique for applying a minute vibration pulse including at least one (integer) rectangular wave pulse at an appropriate timing before ink ejection.

  However, since the technique of Patent Document 3 generates micro vibrations by deforming the partition walls on both sides of the channel, the micro vibrations of the meniscus may be too strong, and it takes a long time to attenuate the micro vibrations. Injectability may become unstable.

JP-A-11-268264 JP 2000-94669 A JP 2004-262237 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for driving an ink jet recording head that has good stable ejection during high-speed driving and excellent intermittent ejection. .

  The present invention comprises a plurality of channels that are at least partially formed of a piezoelectric material and have partition walls facing each other, and expand or contract by application of a drive pulse to electrodes formed on the partition walls. In an ink jet recording head that discharges ink in a channel from a nozzle, the channel is slightly expanded by a fine vibration pulse that deforms only one wall of the channel from which the ink is discharged, thereby eliminating ink thickening.

Specifically, the object of the present invention is achieved by the following driving method.
(1) At least a part is formed of a piezoelectric material, has partition walls facing each other, and includes a plurality of channels that expand or contract by application of a drive pulse to electrodes formed on the partition walls. A method of driving an ink jet recording head that discharges ink from a nozzle,
Applying a first driving pulse for expanding the volume of the channel by deforming only one wall of the channel immediately before ejecting the ink to the channel to eject the ink,
Subsequently, a method of driving an ink jet recording head, wherein a second driving pulse for expanding the volume of the channel by deforming both walls of the channel is applied to eject ink.

  Further, in the present invention described above, the piezoelectric material is a material that deforms in a shear mode, and the channel includes a plurality of channels adjacent to each other as a set, and the channels in each set are sequentially driven to eject ink. The present invention can be applied to a shear mode type ink jet recording head that is driven and controlled as described above.

  Furthermore, the present invention comprises a plurality of channels separated from each other by at least a part of a partition formed of a piezoelectric material, and the plurality of channels have dummy channels and nozzles that do not have nozzles, and eject ink. Dummy channel type that is configured by alternately arranging ink discharge channels, and expands or contracts the volume of each channel by applying a drive pulse to the electrode formed on the partition wall, and discharges ink in the ink discharge channel from the nozzle The present invention can be applied to an inkjet recording head.

  Furthermore, the driving method of the present invention can be applied to either a so-called DR system or DRR system.

  According to the present invention, it is possible to provide a method for driving an ink jet recording head that has good stable ejection during high-speed driving and excellent intermittent ejection.

1 is a diagram illustrating an overall configuration of an ink jet recording apparatus according to the present invention. 1A and 1B are a perspective view and a cross-sectional view showing a structure of a recording head according to a first embodiment of the invention. The figure which shows typically the deformation | transformation of the drive pulse and channel of the drive method of DR system. The figure which shows the state of the channel deformation | transformation at the time of time-division drive by the drive method of DR system. FIG. 5 is a timing chart of the drive pulse in FIG. 4. The figure which shows typically the deformation | transformation of the drive pulse and channel of the drive method of a DRR system. The figure which shows the state of the channel deformation | transformation at the time-division drive using only a positive voltage with the drive method of a DRR system. FIG. 8 is a timing chart of the drive pulse in FIG. 7. FIG. 6 is a perspective view and a cross-sectional view showing a structure of a recording head according to a second embodiment of the invention. FIG. 6 is a diagram schematically illustrating a recording head driving method according to a second embodiment.

  An overall configuration of an inkjet recording apparatus equipped with an inkjet recording head to which the present invention can be applied will be described with reference to FIG.

  In the ink jet recording apparatus 1 of FIG. 1, the recording medium P is sandwiched between the transport roller pair 31 of the transport mechanism 3 and further transported in the Y direction in the figure by the transport roller 33 that is rotationally driven by the transport motor 32. ing.

  The recording head 2 is provided between the conveying roller pair 31 and the conveying roller 33 so as to face the recording surface of the recording medium P. The recording head 2 is mounted on a carriage 5 provided so as to be reciprocally movable along a guide rail 4 spanned across the width direction of the recording medium P. The carriage 5 is driven by driving means (not shown). Then, the recording medium P is reciprocated in the XX ′ direction (main scanning direction) perpendicular to the conveyance direction (sub-scanning direction) of the recording medium P. The recording head 2 is arranged so that the nozzle surface side faces the recording surface of the recording medium P, and is electrically connected to the drive pulse generating means 100 (see FIG. 2) via the flex cable 6. Yes.

  As the carriage 5 moves, the recording head 2 moves the recording surface of the recording medium P in the X-X ′ direction in the figure, and ejects ink droplets in this movement process to record a desired inkjet image.

  In the figure, reference numeral 7 denotes an ink receiver. When the recording head 2 is at the home position during non-recording, a small amount of ink droplets are discarded toward the ink receiver 7. When the recording head 2 has stopped operating for a long time at this standby position, although not shown, the nozzle surface of the recording head 2 is protected by covering it. Reference numeral 8 denotes another ink receiver provided at a position opposite to the ink receiver 7 across the recording medium P. When recording in both reciprocating directions, the same as described above when switching from forward movement to backward movement. Accepts ink drops discarded.

  The driving method according to the present invention includes a plurality of channels that are formed of a piezoelectric material and have partition walls facing each other and expand or contract by application of a drive pulse to electrodes formed on the partition walls. Can be applied to any type of recording head, as long as it is an ink jet recording head that discharges ink in an ink discharge channel from a nozzle by driving, and what kind of liquid is filled in the channel? Also good.

  In the following description, a shear mode (share mode) type ink jet recording head 2 will be described as means for expanding or contracting the volume in the channel. In a shear mode type recording head, a partition wall of a channel is constituted by a piezoelectric element, and an ink droplet is ejected from a nozzle by deforming the piezoelectric element.

[Recording head of the first embodiment]
2A and 2B are diagrams showing a schematic configuration of the first form of the recording head 2, wherein FIG. 2A is a perspective view showing a partial cross section, FIG. 2B is a cross-sectional view showing a state where an ink supply unit is provided, ) Is a cross-sectional view seen from a direction orthogonal to the cross-sectional view of (b). The recording head 2 in FIG. 2 is a type of head in which channels are continuous across a partition wall and ink droplets can be ejected from all channels.

  In FIG. 2, 100 is a drive pulse generating means, 2 is a recording head, 21 is an ink tube, 22 is a nozzle forming member, 23 is a nozzle, 24 is a cover plate, 25 is an ink supply port, 26 is a substrate, and 27 is a partition wall. is there. A channel 28 that is an ink channel is formed by the partition wall 27, the cover plate 24, and the substrate 26.

  As shown in FIG. 2C, the recording head 2 has a large number of channels 28 between a cover plate 24 and a substrate 26 separated by a plurality of partition walls 27A, 27B, 27C, 27D made of a piezoelectric material such as PZT. This is a shear mode type recording head arranged side by side. In FIG. 2 (c), three (28A, 28B, 28C) which are a part of many channels 28 are shown. One end of the channel 28 (hereinafter referred to as a nozzle end) is connected to a nozzle 23 formed in the nozzle forming member 22, and the other end (hereinafter referred to as a manifold end) is connected to an ink tube 21 through an ink supply port 25. It is connected to an ink tank (not shown).

  Electrodes 29A, 29B, and 29C are formed on the surface of the partition wall 27 of each channel 28 from above the partition walls 27 to the bottom surface of the substrate 26. The electrodes 29A, 29B, and 29C are connected to the drive pulse generating means 100. Has been. When a drive signal is applied to the electrodes 29A, 29B, and 29C formed on the surface of each partition wall 27, an ink droplet is ejected from the nozzle 23 by an operation described later.

  Next, a method for manufacturing the recording head 2 will be described. First, two piezoelectric materials 27a and 27b having different polarization directions are bonded to each other on the substrate 26 via an adhesive, and a plurality of channels 28 serving as channels 28 are formed from the upper piezoelectric material 27a side by a diamond blade or the like. All grooves are cut in parallel with the same shape. As a result, adjacent channels 28 are partitioned by partition walls 27 polarized in the direction of the arrow. The channel 28 includes a deep groove portion 28a on the outlet side (nozzle end side) of the channel 28 and a shallow groove portion 28b that gradually decreases from the deep groove portion 28a toward the inlet side (manifold end side) of the channel 28. Have.

  Each partition wall 27 is composed of two piezoelectric materials 27a and 27b having different polarization directions as indicated by arrows in FIG. 2C, but the piezoelectric material may be only a portion indicated by reference numeral 27a, for example. It suffices if it is at least part of the partition wall 27.

  A metal electrode 29 is formed in each channel 28 from both side surfaces to the bottom surface, and the metal electrode 29 extends to the rear side surface of the piezoelectric material 27a through the shallow groove portion 28b. The flexible cable 6 is bonded to each metal electrode 29 via an anisotropic conductive film 78 on the rear side surface. By applying a driving pulse from the driving pulse generating means 100 to each metal electrode 29, the partition wall 27 is applied. The ink in the channel 28 is ejected from the nozzle 23 by the pressure at the time of deformation.

  On the upper surface of the piezoelectric material 27a, the cover plate 24 is adhered with an adhesive so as to cover the deep grooves 28a over the entire channels 28, and ink is introduced into the channels 28 on the shallow grooves 28b of the respective channels 28. An ink inflow port 77 to be introduced is formed.

  After the cover plate 24 is bonded, the single nozzle forming member 22 provided with the nozzle 23 is bonded to the partition wall 27 and the front surface of the cover plate with an adhesive.

  As the piezoelectric material used for the piezoelectric materials 27a and 27b, the material of the cover plate 24 and the substrate 26, and the material of the nozzle forming member 23, known materials, for example, materials described in Patent Document 3 can be used.

  The shear mode type recording head 2 can be manufactured easily because the main part of the head can be formed simply by forming the channels 28 in the piezoelectric materials 27a and 27b and forming the metal electrodes 29 on the partition walls 27 as described above. Since a large number of channels 28 can be arranged with high density, this is a preferable mode for recording high-definition images.

  FIG. 3 is a diagram schematically showing a drive pulse (right side of the figure) and a channel deformation (left side of the figure) due to the drive pulse of the first drive method according to the present invention. In FIG. 3, a first drive pulse P1 and a second drive pulse P2 for expanding the channel 28 to which ink droplets are to be ejected are sequentially applied. The first drive pulse P1 is applied only to the partition on one side of the channel 28. The second drive pulse P2 deforms the partition walls on both sides of the channel 28 to expand the channel volume. In order to deform the partition, different voltages are applied to the electrodes of the channels on both sides of the partition, and the piezoelectric material constituting the partition is caused to shear by the potential difference.

  FIG. 3A shows a state in which no voltage is applied to any electrode, and the drive pulse at this time is 0 (v). To deform only the partition wall 27B on one side of the middle channel 28B from this state (the state shown in FIG. 3B), the electrode 29A of the channel 28A is grounded, and the electrodes 29B and 29C of the channels 28B and 28C are grounded. + Von1 (v) is applied. The electrode of the channel on the right side of the channel 28C is grounded. As a result, an electric field in a direction perpendicular to the polarization direction is generated in the piezoelectric materials 27a and 27b constituting the partition wall 27B by the application of the first drive pulse P1, and the joint surface is deformed and the partition wall 27B is moved outward. On the other hand, since the potentials on both sides of the partition wall 27C are the same, the partition wall 27C is not deformed. Therefore, the volume of the channel 28B expands small. As a result, a negative pressure is generated in the ink in the channel 28B, and the ink flows.

  The first drive pulse P1 is applied with a pulse width of about 1AL, and when the channel volume expands at the rising edge of the pulse, a pressure wave is generated in the channel.

  Since the pressure wave in the channel 28B repeats inversion every 1 AL time, when the potential is returned to 0 after about 1 AL time has elapsed from the rise of the drive pulse P1 (this time is the end of the first drive pulse). The partition wall 27B returns from the expanded state to the neutral state shown in FIG. 3A, and pressure is applied to the ink in the channel 28B.

  Note that AL (Acoustic Length) is ½ of the acoustic resonance period of the channel. In this AL, when the velocity of the ejected ink droplet is measured while applying a rectangular wave pulse having a constant voltage value to the partition wall 27 and changing the pulse width of the rectangular wave, the flying speed of the ink droplet becomes maximum. It is obtained as the pulse width. In the drive pulse schematic diagram on the right side of FIG. 3, the unit of the horizontal axis is AL.

  Since the voltage Von1 of the first drive pulse P1 is low enough not to eject ink, ink is not ejected, but the pressure wave generated by the application of the first drive pulse P1 slightly vibrates the nozzle meniscus, Thus, the thickened ink in the vicinity of the meniscus surface is stirred with new ink, so that the ink is easily ejected.

  When this neutral state is maintained for about 2AL, the pressure wave in the channel 28B repeats reversal and becomes positive after about 2AL has elapsed. At this time, the second drive pulse P2 shown by hatching in FIG. 3C is applied to expand the volume of the channel 28B. The second drive pulse P2 is a pulse for ejecting ink, but the micro-vibration pressure wave is canceled by the negative pressure generated at the rising edge of the second drive pulse P2.

  As described above, the meniscus is slightly vibrated by the application of the first drive pulse P1 to cancel the ink thickening, and the pressure wave of the minute vibration is canceled by the neutral state of about 2AL, and the meniscus vibration for ink ejection is canceled. As a result, stable injection is improved.

  The second drive pulse P2 for ejecting ink is applied to deform the partition walls 27B and 27C on both sides of the channel 28B outward. That is, + Von2 (v) is applied to the electrode 29B of the channel 28B, and the electrodes 29A and 29C of the channels 28A and 28C on both sides thereof are grounded.

  When the partition walls 27B and 27C are deformed outward and the volume of the channel 28B expands, a negative pressure is generated in the ink in the channel 28B and the ink flows (Draw).

  The second driving pulse P2 is applied with a pulse width of about 1 AL, and when the channel volume expands at the rising edge of the pulse (this time is the start of the second driving pulse), a pressure wave is generated in the channel.

  The pressure wave in the channel 28B is repeatedly inverted every 1 AL time, and when the potential is returned to 0 after about 1 AL time has elapsed from the rise of the drive pulse P2, the partition walls 27B and 27C are shown in FIG. Returning to the neutral state, high pressure is applied to the ink in the channel 28B, and the ink is ejected (Release).

  The above driving method is a so-called DR system (Draw-Release).

  The pulse width of the first drive pulse P1 is 1AL in the above description, but is preferably in the range of 0.7AL to 1.3AL. When the negative pressure wave due to the expansion of the channel 28 at the start of application of the first drive pulse P1 is reversed and becomes a positive pressure, the positive pressure wave due to the contraction of the channel volume (expanded state → neutral state) is also generated. Since they are added together, the most efficient vibration can be applied.

  The pulse width of the second drive pulse P2 is also 1AL in the above description, but is preferably in the range of 0.7AL to 1.3AL. When the negative pressure wave due to the expansion of the channel 28 at the start of application of the first drive pulse P1 is reversed and becomes a positive pressure, the positive pressure wave due to the contraction of the channel volume (expanded state → neutral state) is also generated. Since they are added together, the most efficient discharge can be performed. Outside this range, the ejection efficiency due to pressure waves decreases, and the drive voltage must be increased.

  By setting the distance L between the end of the first drive pulse P1 and the start of the second drive pulse P2 to 1.5AL to 2.5AL, the fine vibration generated by the first drive pulse P1 is cancelled. After the ink discharge, the ink is ejected by the second drive pulse P2, so that the pressure wave of slight vibration does not adversely affect the pressure wave of ink ejection, and the ink ejection property is stabilized.

  Further, when the drive voltage of the first drive pulse P1 is Von1 (V) and the drive voltage of the second drive pulse P2 is Von2 (V), 0.2 ≦ | Von1 | / | Von2 | ≦ 0.8 It is preferable that Thereby, a moderate fine vibration is obtained.

  Next, in the above-described first embodiment, three adjacent channels are set as one set, three channels in each set are sequentially driven, and a plurality of drive pulses are applied within the same drive cycle to generate a plurality of inks. FIG. 4 and FIG. 5 show channel states and drive pulses in the case of continuous ejection, respectively. That is, in FIG. 4, channels A1, B1, C1, Channels A2, B2, C2, Channels A3, B3, C3... Are grouped as a set, and the A phase (channels A1, A2, A3,. ..) is first driven, then B phase (channels B1, B2, B3...), Then C phase (channels C1, C2, C3. . In addition, the driving of each phase is illustrated as ejecting two ink droplets within one driving cycle.

  FIG. 4 shows a state of channel deformation when ink droplets are ejected from the B phase. First, the first drive pulse P1 of FIG. 4 (b) is applied from the neutral state of FIG. 4 (a). Then, when the first drive pulse P1 falls, the state returns to the neutral state of FIG. 4 (a), and the second drive pulse deforms both walls of FIG. 4 (c). After the state where P2 is applied (both wall expansion state), the neutral state returns to FIG. 4A, and this is repeated twice.

  Each drive pulse at this time is shown in FIG. First, the first drive pulse P1 is applied to cause a slight vibration in the meniscus, but the first drive pulse P1 deforms only the left partition of the channels B1, B2, B3. On the other hand, the potential difference between 0 (v) of the A phase and Von1 (v) of the B phase, and for the right partition, the potential difference of Von1 (v) of the B phase and Von1 (v) of the C phase, That is, 0 (v).

  On the other hand, the second drive pulse P2 applied to eject ink droplets from the B-phase channel deforms the partition walls on both sides of the channels B1, B2, B3. As described above, the deformation of the partition wall is due to the potential difference between the voltages applied to the electrodes on both sides. Therefore, the potential difference between the A phase 0 (v) and the B phase Von2 (v), and the B phase Von2 (v) This is performed by the potential difference from 0 (v) of the C phase. The driving pulse in the present invention refers to a potential difference formed by a combination of voltages applied to these phases. Similarly, C-phase channel discharge and A-phase channel discharge are sequentially performed in the same manner.

  The first embodiment described above is a so-called DR system (Draw-Release). However, the present invention applies a contraction pulse (third drive pulse) after the second drive pulse P2. It can also be applied to the DRR method (Draw-Release-Reinforce).

  FIG. 6 shows the state of the channel when the recording head 2 of FIG. 2 is driven by the DRR method, and the state of the drive pulse at that time.

  The first drive pulse P1 is applied from the neutral state in FIG. 6 (a) to deform the partition on one side of the channel 28B, return to the neutral state after about 1AL, and then apply the second drive pulse P2 after about 2AL. This is the same as the DR system until the partition walls on both sides of the channel 28B are deformed. When the second drive pulse P2 falls at about 1AL, a third drive pulse P3 (negative voltage) for contracting the volume of the channel 28B is applied immediately after that. This state is shown in FIG. 6D, and when the negative pressure wave due to the expansion of the channel at the start of application of the second drive pulse P2 is inverted by about 1 AL and becomes a positive pressure, the third drive pulse By applying P3 (shrinkage pulse), a positive pressure wave due to shrinkage is added in a combined form, so that the discharge pressure (discharge speed) of the droplets increases and the most efficient discharge force is obtained.

  When about 1 AL has passed from the start of application of the third drive pulse P3 and the pressure wave is reversed and the inside of the channel becomes negative pressure, the force to pull back the ejected meniscus acts to narrow the extruded ink column. The action works. When the application of the third drive pulse P3 is finished before or after this, the channel expands (contracted state → neutral state), and the force for pulling back the meniscus further acts to further narrow the ink column, so that the ink column is removed from the meniscus. It is separated early and satellite droplets are less likely to occur. In other words, it is possible to suppress the length of the tail of the ink column from being elongated and to reduce satellite drops. The satellite droplet is a minute droplet formed following the leading ink droplet (hereinafter referred to as a main droplet) when ink is ejected from a channel nozzle and separated into ink droplets. When the satellite droplets land with a deviation from the landing position of the main droplet, the image quality deteriorates. In order to improve the image quality, it is important to reduce the satellite droplets as much as possible.

  The pulse width of the third drive pulse P3 is preferably 0.3 AL to 1.5 AL. As a result, the attenuation of the pressure wave generated from the beginning of the second drive pulse P2 can be kept small, the meniscus can be greatly shaken, and the satellite reduction effect is increased.

Furthermore, when the drive voltage of the first drive pulse P1 is Von1, and the drive voltage of the third drive pulse P3 is Voff,
| Von1 | = | Voff |
By doing so, both pulses can be generated by one power source, and the power source cost can be reduced.

  In the description of FIG. 6, a negative voltage is applied to the third drive pulse P3, but the deformation of the partition is determined by the difference between the voltages applied to both sides of the partition, so the third drive pulse P3 is set to a positive voltage. You can also.

  FIG. 7 shows channel states when all drive pulses are positive voltages, the A, B, and C3 phases are driven in three cycles and ink droplets are ejected from the B phase. FIG. 8 shows each drive at that time. Indicates the state of the pulse.

  The first drive pulse P1 is applied from the neutral state in FIG. 7A (FIG. 7B), and only the partition wall on one side of the B-phase channel is deformed to expand the channel volume to a small extent. Causes slight vibration. Next, after a neutral state of about 2AL, the second drive pulse P2 is applied (FIG. 7C), and the channel volume is expanded by deforming the partition walls on both sides. Immediately after the fall of the second drive pulse P2, the third drive pulse P3 is applied (FIG. 7D) to contract the channel volume.

  The application of the drive pulse at this time is a combination of positive voltages as shown in FIG. The case where ink droplets are ejected from a B-phase channel will be described as an example. In the first drive pulse P1, a positive voltage of Von1 is applied to the B-phase and C-phase channel electrodes, and the A-phase channel electrode is applied. Ground. As a result, the partition wall on one side of the B-phase channel is deformed outward to expand the channel volume to a small extent.

  The second drive pulse P2 applies a positive voltage of Von2 to the B-phase channel electrode, and grounds the A-phase and C-phase channel electrodes. Thereby, the partition walls on both sides of the B-phase channel are deformed outward.

  Next, in the third drive pulse P3, a positive voltage of Voff is applied to the A-phase and C-phase channel electrodes, and the B-phase channel electrode is grounded. As a result, the partition walls on both sides of the B-phase channel are deformed inward to contract the B-phase channel.

[Second Embodiment Recording Head]
Next, the recording head 2 and the driving method thereof according to the second embodiment of the present invention will be described. 9A and 9B are diagrams illustrating a schematic configuration of the recording head 2, wherein FIG. 9A is a perspective view showing a partial cross section, and FIG. 9B is a cross-sectional view showing a state in which an ink supply unit is provided. The recording head shown in FIG. 9 is a dummy channel type recording head in which ink discharge channels and dummy channels (air channels) are alternately arranged. Since the dummy channel type recording head does not affect other adjacent channels even if the channel partition wall is deformed, it is not necessary to perform time-division driving, and driving becomes easy.

  In FIG. 9, the dummy channels 128 are alternately arranged with the ink discharge channels 28, and the cover plate 24 forms an ink supply port 77 by grinding or cutting a portion corresponding to the ink discharge channels 28. A portion corresponding to 128 is not cut and covered with the cover plate 24 so that ink is not supplied. The nozzle forming member 22 has nozzles 23 formed only at portions corresponding to the ink discharge channels 28. Other configurations are the same as those in FIG.

  FIG. 10 is a diagram schematically showing a method of driving the dummy channel type recording head. In the figure, A1, A2, A3... Indicate ink discharge channels, and d1, d2, d3. In the neutral state of FIG. 10A, the electrodes of all the channels are grounded.

  10B, the positive voltage of Von1 is applied to one dummy channel d2 and its adjacent ink ejection channels A2 and A3 in the one-wall expansion state by the first drive pulse P1, and the adjacent dummy channel d3. Is a ground, and then a positive voltage of Von1 is applied to one dummy channel d4 and the ink ejection channels A4 and A5 adjacent to the dummy channel d4, and this is repeated thereafter.

  Further, in the double wall expansion state by the second drive pulse P2, as shown in FIG. 10C, a positive voltage of Von2 is applied to the electrodes of the ink discharge channels A1, A2, A3,. The electrodes d2, d3... are grounded.

  When the channel volume is contracted by applying the third drive pulse P3, the electrode of the ink discharge channel is grounded and a positive voltage is applied to the electrode of the dummy channel, or a negative voltage is applied to the ink discharge channel. It is sufficient to apply the voltage and ground the dummy channel electrode.

  As described above, the driving method of the present invention can be applied to a dummy channel type recording head, and it is not necessary to perform time-division driving. Therefore, driving control is easy.

  In the present invention, the viscosity of the ink is preferably 5.0 mPa · s to 50 mPa · s at 25 ° C. In the present invention, in the case of a high-viscosity ink having a large solid component content in the ink, the effect of improving the intermittent ejection property is great.

  As the content of the polymer compound with respect to the total amount of the ink, in the case of 3 to 15% by mass, the effect of improving the intermittent ejection property is large. When the volatile components of the ink are volatilized from the nozzle surface, the polymer compound may form a network structure. Even in such a case, the present invention improves the intermittent ejection property at high speed driving.

  Examples of such inks include water-based inks, non-water-based inks (solvent inks), and ultraviolet curable inks containing a polymer compound.

  Examples of the polymer compound contained in the non-aqueous inkjet ink include acrylic resins, polyester resins, polyurethane resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymer resins, and the like.

  Specifically, acrylic resins such as John Crill (manufactured by Johnson Polymer Co., Ltd.), ESREC P (manufactured by Sekisui Chemical Co., Ltd.), polyester resins such as Elitel (manufactured by Unitika Ltd.) and Byron (manufactured by Toyobo Co., Ltd.), Byron UR ( Toyobo Co., Ltd.), NT-Hilamic (Daiichi Seika Co., Ltd.), Crisbon (Dainippon Ink Chemical Co., Ltd.), Nipporan (Nippon Polyurethane Co., Ltd.) and other polyurethane resins, SOLBIN (Nisshin Chemical Co., Ltd.), Vinyl Blanc (Nissin Chemical Industry Co., Ltd.), Saran Latex (Asahi Kasei Chemicals Co., Ltd.), Sumielite (Sumitomo Chemical Co., Ltd.), Sekisui PVC (Sekisui Chemical Co., Ltd.), UCAR (Dow Chemical Co., Ltd.) Can be mentioned.

  As a solvent contained in the non-aqueous inkjet ink, as specific compounds, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, ethylene glycol diacetate, propylene glycol diacetate, diethylene glycol monoethyl ether, Alkylene glycol monoalkyl ethers such as triethylene glycol monomethyl ether, dipropylene glycol monomethyl ether and tripropylene glycol monomethyl ether, alkylene glycol dialkyl ethers such as ethylene glycol dibutyl ether and tetraethylene glycol dimethyl ether, ethylene glycol monobutyl ether Alkylene glycol monoalkyl ether acetates such as Seteto like.

  On the other hand, the polymer compound contained in the water-based inkjet ink includes resin fine particles and water-soluble resin. Examples of the resin fine particles include polyurethane, polystyrene-acrylic, polystyrene-butadiene, polystyrene-maleic acid, polyester, polyether, polycarbonate, polyamide, polyacrylonitrile, polystyrene, polybutadiene, polyacrylic acid, polymethacrylic acid, polyvinyl chloride, Resin fine particles composed of polyvinylidene chloride, polyvinyl acetate, acrylic modified silicone resin, acrylic modified fluororesin, etc., or resin fine particles composed of copolymers and salts thereof, preferably polyurethane, polystyrene-acrylic, Examples thereof include a copolymer selected from at least one of polystyrene-butadiene and polystyrene-maleic acid. Examples of water-soluble resins include styrene-acrylic acid-acrylic acid alkyl ester copolymers, styrene-acrylic acid copolymers, styrene-maleic acid copolymers, styrene-maleic acid-acrylic acid alkyl ester copolymers, and styrene. -Methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, etc. It is done.

  As the solvent contained in the water-based inkjet ink, an aqueous liquid medium is preferably used, and a mixed solvent such as water and a water-soluble organic solvent is more preferably used. Examples of water-soluble organic solvents that are preferably used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, Triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene Glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol Nomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol Monophenyl ether, propylene glycol monophenyl ether), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetra) , Tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2 -Pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) and the like.

  The effects of the present invention are illustrated below by examples.

[Ink: solvent ink]
(Ink adjustment method)
20 parts of Pigment Red 122, 10 parts of Dispersbyk-161 (manufactured by Big Chemie Japan) as a pigment dispersant, 7.8 parts of 1,3-dimethyl-2-imidazolidinone, and 62. of propylene glycol diacetate. 2 parts were mixed and dispersed using a horizontal bead mill (Ashizawa Co., Ltd., System Zeta Mini) filled with zirconia beads having a diameter of 0.5 mm at a volume ratio of 60%, and then the zirconia beads were removed to obtain a pigment dispersion. . 6 parts of pigment dispersion, 4 parts of polymer compound (Byron UR8300, manufactured by Toyobo Co., Ltd.), and finally mixed with 2 kinds of 1,3-dimethyl-2-imidazolidinone and propylene glycol diacetate as solvents The resulting ink was adjusted and mixed so that the viscosity was 10 mPa · s, and the obtained ink was filtered through a 0.8 μm filter to obtain an ink.

[Ink: Water-based ink]
(Ink adjustment method)
C. I. Pigment Blue 15: 3 100g
DEMAL C 63g
Diethylene glycol 100g
125g of ion exchange water
And then dispersed using a horizontal bead mill (system zeta mini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60%, and then centrifuged at 20,000 rpm for 30 minutes to obtain a pigment. A dispersion was obtained.
And
120 g of pigment dispersion
Latex 4 (Sparfrex 460, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 52.6 g
200g ethylene glycol
120 g of triethylene glycol monomethyl ether
Olfin 1010 (Nisshin Chemical Co., Ltd.) 4g
Proxel GXL (Zeneca) 2g
Was finished to 1000 g with ion-exchanged water, passed through a Millipore filter having a pore size of 1 micron twice to prepare an ink, and the final viscosity was 7 mPa · s.

[Recording head]
Experiments were conducted under the conditions shown in Table 1, using a recording head having the structure shown in FIG. 2 as the recording head and having a nozzle hole diameter of 20 μm, a driving frequency of 10 kHz, and a number of nozzles of 128.

〔Evaluation item〕
<Evaluation of injection stability>
In an environment of 20 ° C. and 30% RH, each ink set is mounted on an ink jet printer equipped with a piezo-type head having a nozzle hole diameter of 20 μm, a driving frequency of 10 kHz, and the number of nozzles of 128. The state after continuous discharge for 1 hour without cleaning was visually observed, and the injection stability was evaluated according to the criteria shown below.

◎: Normal emission from all nozzles ○: 1 to 3 nozzles are clogged, but recovered by one suction cleaning from nozzle surface ×: Clogging that cannot be recovered by one suction cleaning occurs <Evaluation of intermittent injection>
In an environment of 20 ° C. and 30% RH, each ink set is mounted on an ink jet printer equipped with a piezo-type head having a nozzle hole diameter of 20 μm, a driving frequency of 10 kHz, and the number of nozzles of 128. (1) Continuous discharge for 10 seconds, (2) After stopping discharge for a predetermined time, (3) Continuous discharge for 10 seconds was performed again. At this time, the length of the pause time in (2) is changed in steps of 0.5 seconds from 0.5 seconds to 5 seconds, and there is no disturbance in the discharge direction at the beginning of the re-discharge in (3). A pause time during which stable re-discharge can be performed was obtained, and intermittent discharge stability was evaluated according to the following criteria.

      A: Ejected stably even when the rest time was 5 seconds.

○: Stable ejection in the range of 2.5 to 4.5 seconds pause time, but 5 seconds or more
Then, discharge disturbance occurred in some nozzles.

      X: Discharge disturbance occurred even when the rest time was 2 seconds or less.

[Comparative example]
The same ink and recording head as in the example were used, the driving method was the DR method, and the first driving pulse was applied so as to expand both the walls of the channel.

  As is clear from Table 1, the driving method of the present invention obtained good results in both injection stability and intermittent injection, but in Comparative Example 1 performed by the conventional driving method, both injection stability and intermittent injection were obtained. It was not enough.

DESCRIPTION OF SYMBOLS 1 Inkjet recording apparatus 2 Recording head 23 Nozzle 27 Partition 28 Channel (ink discharge channel)
128 dummy channel 29 electrode 100 drive pulse generating means P1 first drive pulse (one-side expansion pulse)
P2 Second drive pulse (bilateral expansion pulse)
P3 Third drive pulse (contraction pulse)

Claims (11)

At least a part is formed of a piezoelectric material, has partition walls facing each other, and is composed of a plurality of channels that expand or contract by application of a drive pulse to electrodes formed on the partition walls. A method of driving an ink jet recording head that discharges ink from a nozzle,
Immediately before ink is ejected, a first drive pulse is applied to deform only one wall of the channel to eject ink and expand the volume of the channel,
Subsequently, the second drive pulse that expands the volume of the channel by deforming both walls of the channel is applied to eject ink.
An ink jet recording head driving method, wherein an interval between the end of the first drive pulse and the start of the second drive pulse is 1.5 AL to 2.5 AL.   The piezoelectric material is a material that is deformed in a shear mode, and the channel is controlled so that a plurality of channels adjacent to each other is set as one set, and the channels in each set are sequentially driven to discharge ink. The method for driving an ink jet recording head according to claim 1. It consists of a plurality of channels separated from each other by partition walls formed at least partly of piezoelectric material. These channels are alternately arranged between a dummy channel having no nozzle and an ink ejection channel having a nozzle and ejecting ink. An ink jet recording head driving method in which the volume of each channel is expanded or contracted by applying a driving pulse to an electrode formed on a partition wall, and ink in an ink discharging channel is discharged from a nozzle. ,
Immediately before ink is ejected, a first drive pulse is applied to deform only one wall of the channel to eject ink and expand the volume of the channel,
Subsequently, the second drive pulse that expands the volume of the channel by deforming both walls of the channel is applied to eject ink.
An ink jet recording head driving method, wherein an interval between the end of the first drive pulse and the start of the second drive pulse is 1.5 AL to 2.5 AL.   4. The pulse width of the first drive pulse is 0.7AL to 1.3AL (AL is 1/2 of the acoustic resonance period of the channel). A method for driving the ink jet recording head according to claim 1.   5. The pulse width of the second drive pulse is 0.7 AL to 1.3 AL (AL is 1/2 of the acoustic resonance period of the channel), 5. A method for driving the ink jet recording head according to claim 1. When the drive voltage of the first drive pulse is Von1, and the drive voltage of the second drive pulse is Von2,
0.2 ≦ | Von1 | / | Von2 | ≦ 0.8
The method of driving an ink jet recording head according to claim 1, wherein:   6. The method of driving an ink jet recording head according to claim 1, wherein a third driving pulse for contracting both walls of the channel is applied subsequent to the second driving pulse. . When the drive voltage of the first drive pulse is Von1, and the drive voltage of the third drive pulse is Voff,
| Von1 | = | Voff |
The method of driving an ink jet recording head according to claim 7, wherein:   The ink jet recording head according to claim 1, wherein a plurality of sets of the driving pulses are provided and ink droplets are ejected a plurality of times within the same driving cycle of a channel for ejecting ink. Driving method.   The ink jet recording head driving method according to claim 1, wherein the ink has a viscosity at 25 ° C. of 5.0 mPa · s to 50 mPa · s.   The ink-jet recording head drive according to any one of claims 1 to 10, wherein the ink contains a polymer compound, and the content thereof is 3 mass% or more and 15 mass% or less. Method.

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