JP4155188B2 - Liquid ejecting apparatus and liquid ejecting method - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus and a liquid ejecting method for ejecting droplets from a nozzle opening formed in a liquid ejecting head toward an object to be processed.

  A typical example of a conventional liquid ejecting apparatus is an ink jet recording apparatus provided with an ink jet recording head for image recording. As other liquid ejecting apparatuses, for example, an apparatus having a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an electrode material (conductive paste) used for forming an electrode such as an organic EL display, a surface emitting display (FED), etc. ) An apparatus equipped with an ejection head, an apparatus equipped with a bioorganic matter ejection head used for biochip production, an apparatus equipped with a sample ejection head as a precision pipette, and the like.

  An ink jet recording apparatus, which is a typical example of a liquid ejecting apparatus, is used for many printing including color printing in recent years because noise during printing is relatively low and small dots can be formed with high density. .

  Such an ink jet recording apparatus generally includes an ink jet recording head mounted on a carriage and reciprocally moved in the width direction (head scanning direction) of a recording medium such as recording paper (processing object), and the recording medium as a head. And a feed mechanism that moves in a direction (feed direction) perpendicular to the scanning direction, and is further arranged to face the recording head and supports the recording medium conveyed by the feeding mechanism from the back surface with respect to the recording head. A platen for defining the position of the recording medium is provided.

  In this ink jet recording apparatus, printing is performed by ejecting ink droplets from a recording head to a recording medium in accordance with print data. The recording head mounted on the carriage can discharge, for example, black, yellow, cyan, and magenta inks, so that not only text printing with black ink but also the discharge ratio of each ink can be achieved. By changing it, full-color printing is possible.

  In addition, the ink jet recording apparatus includes borderless printing in which printing is performed on the entire surface of the recording medium without leaving a margin in the edge portion of the recording medium, and bordering printing in which ink droplets are not applied to the edge portion of the recording medium. There are models that can be switched appropriately.

  When borderless printing is performed, printing is performed on an area slightly larger than the size of the recording medium in consideration of a margin for the positional deviation of the recording medium and the carriage.

  That is, in order to perform printing without leaving a margin at the left and right side edges (edges extending in the feeding direction) of the recording medium, the scanning range of the recording head during printing is outside the side edges of the recording medium. Therefore, the ink droplets can be ejected to a region that is laterally removed from the recording medium.

  Further, when printing is performed without leaving a margin at the front and rear edges (edges extending in the head scanning direction) of the recording medium, the printing medium deviates to the front side from the front edge at the start of printing. The area up to the area is designated as the print target area, and at the end of printing of the recording medium, the area up to the rear side of the trailing edge of the recording medium is designated as the print target area.

The ink droplets ejected toward the region outside the recording medium are absorbed by an absorbing member (sponge, bell eater, etc.) disposed on the back side of the recording medium so as to face the recording head.
JP 2002-86757 A

  As described above, when printing is performed without leaving a margin at the edge of the recording medium, ink droplets are ejected from the edge of the recording medium to a region outside the front and rear and / or left and right. There has been a problem that the ink mist that has come to the back side of the recording medium adheres to the edge of the back side of the recording medium and causes the recording medium to become dirty. In particular, it is a problem when performing double-sided printing on a recording medium or when printing on a recording medium that uses both sides, such as a postcard.

  In addition, the mist ink smudges the interior of the machine, causing malfunction due to adhesion of the ink mist to an electric circuit or a linear scale, and depositing on the ink cartridge to contaminate the user's hand.

  In general, a feeding mechanism for feeding a recording medium in a feeding direction includes rollers that are arranged to face each other so as to sandwich and feed the recording medium. One of the opposed rollers is a driving roller having a structure in which alumina is baked on the surface of the metal roller to improve the frictional force, and the other roller is a driven roller made of plastic.

  In general, contact / peeling between these rollers and the recording medium, rubbing with the next recording medium when the recording medium is supplied from the auto sheet feeder, contact with a structural member in the recording medium supply path, etc. Thus, the recording medium is charged when it is sent to the printing area. If the recording medium is charged in this way, the above-described ink mist tends to adhere to the back surface of the recording medium.

  In order to solve such a problem, a method of providing a discharging means such as a discharging brush for discharging the charged recording medium is also conceivable. In this case, the installation position of the discharging means is necessarily a pair of rollers. Therefore, the distance from the feed mechanism to the printing area is longer than that of the feed mechanism. For this reason, problems such as deterioration in the feeding accuracy of the recording medium and floating of the recording medium are likely to occur. Further, there is also a problem in that paper dust or the like is generated by rubbing a recording medium such as paper with a static elimination brush and adheres to the nozzle, thereby deteriorating ink droplet ejection performance.

  In addition, in order to meet the recent demand for higher image quality, the size of ink droplets ejected from a recording head is becoming smaller and smaller. Ink droplets of small size rapidly decrease in speed due to the viscous resistance of air, so that ink droplets ejected from the recording head toward the area outside the recording medium during borderless printing do not reach the absorbing member. There is a possibility of mist.

  Also, depending on the ejection mode, ink droplets may be ejected separately into the main part and the satellite part, and the weight difference between the main part and the satellite part may become large. Even if it is provided, a situation may occur in which the effect acts on the main portion but does not act on a satellite portion whose weight is considerably smaller than that of the main portion.

  The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a mist of droplets ejected from the liquid ejecting head toward the outer edge of the object to be processed in the edgeless processing. An object of the present invention is to provide a liquid ejecting apparatus and method that can reliably prevent the formation of the liquid.

In order to solve the above-described problem, a liquid ejecting apparatus according to the present invention includes a nozzle plate in which a nozzle opening is formed. A liquid ejecting head that ejects droplets, and a function of driving and controlling the liquid ejecting head to appropriately select a plurality of size droplets that form dots of different sizes on the object to be ejected from the nozzle openings. A potential difference between the discharge control means, a conductive member disposed in a region opposite to the liquid jet head on the back side of the object to be processed, and the nozzle plate and the conductive member. A potential difference generating means for generating, and when discharging droplets to an edge portion of the object to be processed and a region outside the edge portion, the potential difference generating means In a state in which the potential difference caused between the serial nozzle plate and the conductive member, so that the ejection control means comprises a discharge mode which do not eject droplets of the largest size in the droplet of the plurality of sizes The liquid jet head is driven and controlled.

Preferably, the discharge mode that does not discharge the largest droplet among the plurality of droplets is a discharge mode that discharges the smallest droplet.

  Preferably, the apparatus further includes switching control means for controlling on / off switching of the potential difference generating means, the switching control means for the edge portion of the object to be processed and a region outside the edge portion. The potential difference generating means is turned off so that a potential difference is not generated between the nozzle plate and the conductive member except when a droplet is discharged.

Preferably, the discharge control means switches to a discharge mode that does not discharge the largest droplet among the plurality of droplets only when the number of droplets discharged exceeds a predetermined number.

  In addition, preferably, it has an absorbing member that is disposed on the back side of the object to be processed and that can absorb the liquid droplets discharged from the nozzle opening toward a region outside the object to be processed, The conductive member constitutes the absorbing member, is formed integrally with the absorbing member, or is disposed adjacent to the absorbing member.

  Preferably, the absorbing member further includes a platen that is disposed to face the liquid ejecting head, supports the object to be processed from the back surface thereof, and defines a position of the object to be processed with respect to the liquid ejecting head. Is provided on the platen.

  Preferably, the apparatus further includes holding means for holding the workpiece to be processed in an electrically floating state.

In order to solve the above-described problem, the present invention includes a nozzle plate in which nozzle openings are formed, and causes liquid droplets to be ejected from the nozzle openings by causing pressure fluctuations in the liquid in the pressure chamber communicating with the nozzle openings. A liquid ejecting method that uses a liquid ejecting head to appropriately select a plurality of sizes of droplets that form dots of different sizes on an object to be processed and eject the liquid droplets from the nozzle opening to the object to be processed , When droplets are ejected to the edge portion of the object to be processed and the region outside the edge portion, the area facing the liquid ejecting head on the back side of the object to be processed being processed in a state where the potential difference is generated between the arranged conductive member and the nozzle plate, the liquid jet f at the discharge mode without discharging droplets of the largest size in the droplet of the plurality of sizes Discharging droplets from de.

Preferably, the discharge mode that does not discharge the largest droplet among the plurality of droplets is a discharge mode that discharges the smallest droplet.

  Preferably, no potential difference is generated between the nozzle plate and the conductive member except when droplets are ejected to an edge portion of the object to be processed and a region outside the edge portion. Like that.

Preferably, only when the number of droplets discharged exceeds a predetermined number, the mode is switched to a discharge mode in which the largest droplet size among the plurality of size droplets is not discharged.

  According to the present invention, it is possible to reliably prevent mist formation of liquid droplets discharged from the liquid ejecting head toward the outer edge of the object to be processed in the edgeless processing.

  Hereinafter, an ink jet recording apparatus and method as an embodiment of a liquid ejecting apparatus and method according to the present invention will be described.

  The ink jet recording apparatus according to the present embodiment is an ink jet recording apparatus in which the pressure generating element provided corresponding to the pressure chamber communicating with the nozzle opening causes pressure fluctuations in the ink in the pressure chamber to eject ink droplets from the nozzle opening. A recording head (a type of liquid ejecting head) is provided. As the pressure generating element, for example, a piezoelectric vibrator can be used.

  1 and 2 are perspective views showing a schematic configuration of the ink jet recording apparatus according to the present embodiment, and FIG. 3 is an enlarged view of a platen of the ink jet recording apparatus and its periphery. In FIG. 1, reference numeral 1 denotes a carriage. The carriage 1 is guided by a guide member 4 via a timing belt 3 driven by a carriage motor 2 and is reciprocated in the axial direction of the platen 5. Yes. The platen 5 supports the recording paper 6 (a kind of object to be processed) from the back surface thereof and defines the position of the recording paper 6 with respect to the recording head 12.

  The carriage 1, the carriage motor 2, the timing belt 3, and the guide member 4 constitute a scanning mechanism that scans the ink jet recording head 12 together with the carriage 1 in the head scanning direction.

  The ink jet recording head 12 has a plurality of pressure chambers 173 communicating with the plurality of nozzle openings 165, and is mounted on the side of the carriage 1 facing the recording paper 6. An ink cartridge 7 that supplies ink to the recording head 12 is detachably mounted on the carriage 1. The detailed structure of the recording head 12 will be described later.

  A cap member 13 is disposed at a home position (right side in FIG. 1) which is a non-printing area of the ink jet recording apparatus, and the recording head 12 mounted on the carriage 1 has moved to the home position. Sometimes, it is configured to be pressed against the nozzle forming surface of the recording head 12 to form a sealed space with the nozzle forming surface. A pump unit 10 for applying a negative pressure to the sealed space formed by the cap member 13 is disposed below the cap member 13.

  In the vicinity of the printing area side of the cap member 13, a wiping means 11 having an elastic plate such as rubber is disposed so as to be able to advance and retreat in the horizontal direction with respect to the movement trajectory of the recording head 12. When reciprocating toward the member 13 side, the nozzle forming surface of the recording head 12 can be wiped off as necessary.

  The ink jet recording apparatus according to the present embodiment further includes a feeding mechanism that intermittently conveys the recording paper 6 on which printing processing is performed by the recording head 12 in a feeding direction orthogonal to the head scanning direction.

  As shown in FIG. 3, the feed mechanism is opposed to each other to feed paper rollers 14 a and 14 b that are disposed opposite to each other to sandwich the recording paper 6 and feed it onto the platen 5, and to each other to discharge the printed recording paper 6. Disposed paper discharge rollers 15a and 15b are provided. The paper supply roller 14a and the paper discharge roller 15a are driven rollers, and the paper supply roller 14b and the paper discharge roller 15b are drive rollers.

  As can be seen from FIG. 3, the platen 5 includes a plurality of ink receiving longitudinal openings 5 c, 5 d, 5 e, 5 f extending in a direction parallel to the paper feeding direction (feeding direction) F, and a head orthogonal to the paper feeding direction F. A plurality of ink receiving lateral openings 5a and 5b extending in the scanning direction are formed.

  Of the plurality of ink receiving vertical openings 5c, 5d, 5e, and 5f, the pair of ink receiving openings 5c are arranged so that the left and right ends of the A3 size recording paper 6 pass directly above, respectively. The openings 5d are arranged so that the left and right ends of the B4 size recording paper 6 pass directly above, and the pair of ink receiving openings 5e allows the left and right ends of the A4 size recording paper 6 to pass right above. The pair of ink receiving openings 5f are arranged so that the left and right ends of the B5 size recording paper 6 pass right above each other.

  Further, the plurality of ink receiving lateral openings 5a and 5b include a paper feeding side ink receiving opening 5a arranged on the paper feeding side and a paper discharging side ink receiving opening 5b arranged on the paper discharging side.

  In each of the ink receiving openings 5a, 5b, 5c, 5d, 5e, and 5f, an absorbing member 16 that absorbs the ink ejected from the recording head 12 is disposed.

  FIG. 4 is a functional block diagram of the ink jet recording apparatus according to the present embodiment. As shown in FIG. 4, the recording apparatus includes a printer controller 61 and a print engine 62. The printer controller 61 includes an interface 63 that receives print data from a host computer (not shown), a RAM 64 that stores various data, a ROM 65 that stores control routines for various data processing, and a CPU. A control unit 82, an oscillation circuit 66, a drive signal generation circuit (drive signal generation means) 83 for generating a drive signal, and print data and drive signals developed in dot pattern data (bitmap data). An interface 67 for transmitting to the print engine 62 is provided.

  In addition to this, the printer controller 61 detachably holds a memory card 76 that is a kind of recording medium, a card slot 77 that functions as a recording medium holding unit, and information recorded on the memory card 76 to the control unit 82. A card interface 78 for transmission. In the memory card 76, data relating to the waveform of the drive signal is recorded. As a recording medium other than the memory card 76, for example, a floppy disk, a hard disk, a magneto-optical disk, or the like can be used.

  The control unit 82 is a kind of computer, and performs ink droplet ejection control (e.g. switching of ejection modes) with reference to waveform data of drive signals recorded in the memory card 76 and control routines recorded in the ROM 65. Do.

  The interface 63 receives, for example, print data including one or more data of a character code, a graphic function, and image data from a host computer. The interface 63 can output a busy (BUSY) signal, an acknowledge (ACK) signal, and the like to the host computer.

  The RAM 64 is used as a reception buffer, an intermediate buffer, an output buffer, a work memory (not shown), and the like. Print data from the host computer is temporarily stored in the reception buffer, intermediate code data is stored in the intermediate buffer, and dot pattern data is expanded in the output buffer.

  The ROM 65 stores various control routines executed by the control unit 82, font data, graphic functions, and the like.

  The ROM 65 stores a control routine (control program) that is continuously used without being changed. Data that is scheduled to be upgraded or changed, such as data related to the waveform of the drive signal, is recorded in the memory card 76 described above.

  Further, the control unit 82 controls the drive signal generation circuit 83 based on the data related to the waveform of the drive signal read from the memory card 76 to generate a predetermined drive signal according to the print mode.

  The print engine 62 includes a stepping motor 80 that drives the recording head 12 in the main scanning direction, a paper feed motor 81 that transfers recording paper, and an electric drive system 71 of the recording head 12. The electric drive system 71 of the recording head 12 includes a shift register 72, a latch circuit 73, a level shifter 74, a switch 75, a piezoelectric vibrator 161, and the like. The control unit 82 and the drive signal generation circuit 83 drive the piezoelectric vibrator 161 to cause pressure fluctuations in the ink in the pressure chamber 173, thereby ejecting ink droplets from the nozzle openings 165 toward the recording paper 6. The head drive means for making it correspond is comprised.

  As the control unit 82, for example, a host computer connected directly to the recording apparatus as a single unit, or one of many computers connected via a network may be used.

  In addition, the control unit 82 performs borderless printing for printing on the entire surface of the recording paper without leaving a margin at the edge of the recording paper 6 and printing with margin for not applying ink droplets to the edge of the recording paper 6. A function of switching appropriately according to input data is provided.

  FIG. 5 shows the main part of the drive circuit of the recording head 12, and the shift register 72, latch circuit 73, level shifter 74, switch 75, and piezoelectric vibrator 161 in FIG. It is comprised from the elements 72A-N, 73A-N, 74A-N, 75A-N, 161A-N corresponding to the nozzle opening 165 (refer FIG. 4). For example, when the bit data applied to each of the switch elements 75A to 75N configured as analog switches is “1”, the drive vibration is directly applied to the piezoelectric vibrators 161A to N, and each of the piezoelectric vibrators 161A to N is driven. It is deformed according to the signal waveform of the signal. Conversely, when the bit data applied to each switch element 75A to N is “0”, the drive signal to each piezoelectric vibrator 161A to N is cut off, and each piezoelectric vibrator 161A to N holds the previous charge. .

  6 is a cross-sectional view showing the structure of the recording head 12 of the ink jet recording apparatus shown in FIG.

  The recording head 12 includes a synthetic resin base 163 and a flow path unit 164 attached to the front surface of the base 163 (corresponding to the left side of the drawing). The flow path unit 164 includes a nozzle plate 166 provided with a nozzle opening 165, a vibration plate 167, a flow path forming plate 168, and a sheet 176.

  The base 163 is a block-like member provided with an accommodation space 169 that is open on the front surface and the back surface. The accommodation space 169 accommodates the piezoelectric vibrator 161 fixed to the fixed substrate 170.

  The nozzle plate 166 is a thin plate member in which a large number of nozzle openings 165 are formed along the sub-scanning direction. Each nozzle opening 165 is opened at a predetermined pitch corresponding to the dot formation density. The diaphragm 167 and the sheet 176 form an island portion 171 as a thick portion with which the piezoelectric vibrator 161 abuts, and a thin portion 172 that is provided so as to surround the island portion 171 and has elasticity. .

  A large number of island portions 171 are provided at a predetermined pitch so that one island portion 171 corresponds to one nozzle opening 165.

  The flow path forming plate 168 is provided with an opening for forming a pressure chamber 173, a common ink chamber 174, and an ink supply port 175 that connects the pressure chamber 173 and the common ink chamber 174.

  The nozzle plate 166 is disposed on the front surface of the flow path forming plate 168, and the vibration plate 167 and the sheet 176 are disposed on the back surface side. The nozzle plate 166, the vibration plate 167, and the sheet 176 serve as the flow path forming plate 168. The channel unit 164 is formed by being integrated by adhesion or the like in a state of sandwiching.

  In the flow path unit 164, a pressure chamber 173 is formed on the back side of the nozzle opening 165, and the island portion 171 of the diaphragm 167 is located on the back side of the pressure chamber 173. Further, the pressure chamber 173 and the common ink chamber 174 communicate with each other through the ink supply port 175.

  The front end of the piezoelectric vibrator 161 is in contact with the island portion 171 from the back side, and the piezoelectric vibrator 161 is fixed to the base 163 in this contact state. The piezoelectric vibrator 161 is supplied with a drive signal (COM), print data (SI), and the like via a flexible cable.

  The piezoelectric vibrator 161 in the longitudinal vibration mode has a characteristic of contracting in a direction orthogonal to the electric field when charged and extending in a direction orthogonal to the electric field when discharged. Therefore, in the recording head 12, the piezoelectric vibrator 161 contracts backward by being charged, and the island portion 171 is pulled back along with the contraction, and the contracted pressure chamber 173 expands. Along with this expansion, the ink in the common ink chamber 174 flows into the pressure chamber 173 through the ink supply port 175. On the other hand, by discharging, the piezoelectric vibrator 161 extends forward, the island portion 171 of the elastic plate is pushed forward, and the pressure chamber 173 contracts. With this contraction, the ink pressure in the pressure chamber 173 increases.

In the present embodiment, the absorbing member 16 provided on the platen 5 includes a conductive material, and is formed by foaming, for example, by mixing a conductive material such as carbon into polyethylene or polyurethane. Alternatively, the absorbing member 16 can be formed by applying a conductive material to a foamed material of polyethylene or polyurethane by plating. Alternatively, a polyethylene or polyurethane foam can be impregnated with an electrolyte liquid having ions such as Na ⁺ , K ⁺ , Cl ⁻ , HCO ₃ ⁻ . Ink may be used as the electrolyte liquid.

  As shown in FIG. 7, the ink jet recording apparatus according to the present embodiment includes the potential difference generating means 30, and a positive voltage from the power source 20 of the potential difference generating means 30 is applied to the absorbing member 16. It has become. The nozzle plate 166 is grounded via the wiring 22. Therefore, a potential difference is formed between the nozzle plate 166 and the absorbing member 16 by applying a voltage to the absorbing member 16 by the power supply 20.

  Further, in the present embodiment, a holding unit 50 is provided for holding the recording paper 6 being processed in an electrically floating state. Specifically, as shown in FIG. 7, the holding unit 50 includes insulating members 18a and 18b provided on at least the surfaces of the members that contact the recording paper 6 being processed, for example, the paper feed rollers 14a and 14b. Have.

  Thus, the recording paper 6 being processed is brought into an electrically floating state by the holding means 50 made of the insulating materials 18a and 18b, so that the recording paper 6 simply acts as a dielectric. For this reason, when the recording paper 6 is inserted between the nozzle plate 166 and the absorbing member 16, the lines of electric force starting from the absorbing member 16 extend to the nozzle plate 166 without being blocked by the recording paper 6.

  In this way, by applying a positive voltage to the absorbing member 16 by the potential difference generating means 30 and grounding the nozzle plate 166, a positive charge is induced in the absorbing member 16 and the nozzle plate 166 is shown in FIG. A negative charge is induced in As a result, electric lines of force from the absorbing member 16 toward the nozzle plate 166 are generated as indicated by arrows in FIG.

  In addition, when negative charges are induced in the nozzle plate 166, negative charges are also induced in the ink meniscus portion of the nozzle openings 165. This amount of charge can be easily calculated using the parallel plate capacitor equation. The ink droplet is discharged from the nozzle opening 165 with a negative charge corresponding to the area of the nozzle opening 165, and the Coulomb force in the direction of the absorbing member 16 is generated by the electric field generated between the nozzle plate 166 and the absorbing member 16. Receive F.

  For this reason, it is possible to surely land the ink droplets that are released from the edge portion of the recording paper 6 and ejected toward the absorbing member 16 during borderless printing, thereby preventing the ink droplets from becoming mist. can do.

  This embodiment will be further described with reference to FIG. 4. In this embodiment, print mode information related to selection of borderless printing or bordered printing and target region information related to ink droplet ejection target regions are received from the control unit 82. , And sent to the switching control unit 41 of the switching control means 40. As shown in FIG. 7, the potential difference generating means 30 is provided with a switch 42 for switching on and off, and the switching control unit 41 is switched according to the information received from the control unit 82 in FIG. 7. The indicated switch 42 is switched.

  Specifically, the switching control means 40 determines whether the process performed on the recording paper 5 is a borderless process or a bordered process. If the process is a bordered process, the switch 42 is opened. As a state, the potential difference generating means 30 is turned off.

  On the other hand, when the processing applied to the recording paper 6 is borderless processing, and the ink droplet ejection target area is an edge portion of the recording paper 6 and an area outside the edge portion, the switch 42 is used. Is closed and the potential difference generating means 30 is turned on.

  Further, in the present embodiment, when the area where the ink droplets are to be ejected is the edge part of the recording paper 6 and the area outside the edge part in the borderless process, the potential difference generating means 30 is turned on as described above. At the same time, the control unit 82 drives and controls the recording head 12 so as to be in the ejection mode in which the weight difference between the main portion and the satellite portion of the ink droplet is small.

  Specifically, the control unit 82 has a function of driving and controlling the recording head 12 to appropriately select and eject ink droplets of a plurality of sizes that form dots of different sizes on the recording paper 6. The ejection mode in which the difference in weight between the main portion and the satellite portion of the ink droplet is small is a mode in which ink droplets other than the largest ink droplet are ejected. Preferably, this ejection mode is a mode in which the ink droplet of the smallest size is ejected.

  According to the present embodiment, it is possible to reliably land the ink droplets that are ejected outward from the edge of the recording paper 6 toward the absorbing member 16 during borderless printing on the absorbing member 16. It is possible to surely prevent droplets from becoming mist.

  This effect will be further described. In the case where the electric potential difference generating unit 30 applies a charge to the ink droplet and discharges it, if the ink droplet is separated into the main portion and the satellite portion, the charge in the satellite portion becomes the charge in the main portion. May have the opposite polarity. In this case, since the charge of the satellite portion has the same polarity as the charge of the absorbing member 16, the satellite portion cannot be drawn toward the absorbing member 16 by the electric field.

  Therefore, in the present embodiment, when the area where the ink droplets are to be ejected is an edge portion of the recording paper 6 and an area outside the edge portion in the marginless process, the main portion and the satellite portion of the ink droplet are The recording head 12 is driven and controlled by the control unit 82 so as to be in an ejection mode in which the weight difference is small, so that the ink droplets are reliably prevented from becoming mist.

  As a modification of the above-described embodiment, the switching control means 40 can also turn on the potential difference generating means 30 by closing the switch 42 even in the bordered process. Further, the switching control means 40 also performs the borderless process in the case where the ink droplet ejection target area is the edge part of the recording paper 6 and a part other than the area outside the edge part (the central part of the print target area). The potential difference generating means 30 can be turned on by closing the switch 42.

  As another modification, as shown in FIGS. 9 and 10, a grid member 25 made of a conductive material is disposed adjacent to the upper surface of the absorbing member 16, and the power source 20 is connected to the grid member 25. A positive voltage can be applied. The grid member 25 has a conductive portion 25a extending along the head scanning direction and a conductive portion 25b extending along the feed direction.

  In the case of this modification, it is not always necessary to include a conductive material in the absorbing member 16, and the absorbing member 16 can be formed of, for example, a sponge or a bell eater. Further, the conductive absorbing member 16 and a member made of a conductive material may be used in combination. In this case, the member made of a conductive material does not need to be in a lattice shape, and may be in a wire shape. Moreover, you may arrange | position adjacent to the lower surface instead of the upper surface of the absorption member 16. FIG.

  Also in the present modification, when the area where the ink droplets are to be ejected is the edge part of the recording paper 6 and the area outside the edge part in the borderless process, the potential difference generating means 30 is turned on and the ink is discharged. The recording head 12 is controlled by the control unit 82 so that the ejection mode in which the weight difference between the main portion and the satellite portion of the droplet is small is set.

  Also in this modification, the same effect as the above embodiment can be obtained.

  Further, in the above-described embodiment and each of the modifications described above, as shown in FIG. 11, the absorbing member 16 instead of the nozzle plate 166 is grounded by the wiring 22 and a negative voltage is applied to the nozzle plate 166 by the power source 20. good.

  In the above embodiment and each modification, the direction of the electric field generated by the potential difference generating means 30 can be reversed. That is, the nozzle plate 166 side can be set to a positive potential and the absorbing member 16 side can be set to a negative potential.

1 is a perspective view illustrating a schematic configuration of an ink jet recording apparatus as an embodiment of a liquid ejecting apparatus according to the invention. FIG. 9 is another perspective view showing a schematic configuration of an ink jet recording apparatus as an embodiment of the liquid ejecting apparatus according to the invention. The figure which expanded and showed the platen of the ink jet type recording apparatus shown in FIG.1 and FIG.2, and its periphery. 2 is a functional block diagram of the ink jet recording apparatus shown in FIG. FIG. 2 is a circuit diagram illustrating a main part of a recording head driving circuit of the ink jet recording apparatus illustrated in FIG. 1. FIG. 2 is a cross-sectional view illustrating a structure of a recording head of the ink jet recording apparatus illustrated in FIG. 1. FIG. 3 is an enlarged cross-sectional view of a potential difference generating unit and its periphery of the ink jet recording apparatus shown in FIGS. 1 and 2. FIG. 3 is a diagram showing a state of lines of electric force generated by a potential difference generating unit of the ink jet recording apparatus shown in FIGS. 1 and 2. The top view which showed the modification of embodiment shown in FIG. The longitudinal cross-sectional view which showed the modification shown in FIG. The top view which showed the other modification of embodiment shown in FIG.

Explanation of symbols

1 Carriage 5 Platen 6 Recording paper (object to be processed)
12 Inkjet recording head (liquid jet head)
14a, 14b Feed roller 16 Absorbing member 18a, 18b Insulating material 20 Power supply 22 Wiring 25 Conductive grid member 30 Potential difference generating means 40 Switching control means 41 Switching control section 42 Switch 50 Holding means 82 Control section 83 Drive signal generating circuit 161 Piezoelectric vibrator (pressure generating element)
165 Nozzle opening 166 Nozzle plate 173 Pressure chamber

Claims (11)

A liquid ejecting head that has a nozzle plate in which a nozzle opening is formed, causes a pressure fluctuation in a liquid in a pressure chamber communicating with the nozzle opening, and discharges droplets from the nozzle opening;
A discharge control unit having a function of appropriately selecting a plurality of droplets of a plurality of sizes forming different size dots on the object to be driven by controlling the liquid ejecting head;
A conductive member disposed in a region facing the liquid jet head on the back surface side of the workpiece to be processed;
A potential difference generating means for generating a potential difference between the nozzle plate and the conductive member,
When discharging droplets to an edge portion of the object to be processed and a region outside the edge portion, a potential difference is generated between the nozzle plate and the conductive member by the potential difference generating means. In this state, the liquid ejecting apparatus that drives and controls the liquid ejecting head so that the ejection control unit is in an ejection mode that does not eject the largest droplet among the plurality of droplets . Wherein the plurality of sizes ejection mode without discharging droplets of the largest size in the droplets is the smallest size of the liquid ejecting apparatus according to claim 1, wherein the liquid droplet is ejected mode to eject. A switching control means for switching on and off the potential difference generating means;
The switching control means turns off the potential difference generating means and turns off the nozzle plate and the conductivity except when discharging droplets to an edge portion of the object to be processed and a region outside the edge portion. the liquid ejecting apparatus according to claim 1 or 2 so as not to generate a potential difference between the members. Said ejection control means, any number of ejected droplets only when more than a predetermined number, of claims 1 to 3 switched to discharge mode which do not eject droplets of the largest size in the droplet of the plurality of sizes The liquid ejecting apparatus according to claim 1. An absorbing member that is disposed on the back side of the object to be processed, and that can absorb liquid droplets discharged from the nozzle opening toward a region outside the object to be processed;
It said conductive member, a liquid injection according to any one of the absorbing member constitutes the or the formed absorption member integrally or said absorbent claims being disposed adjacent to the member 1 to 4 apparatus. A platen that is disposed to face the liquid ejecting head, supports the object to be processed from its back surface, and defines a position of the object to be processed with respect to the liquid ejecting head;
The liquid ejecting apparatus according to claim 5 , wherein the absorbing member is provided on the platen. Liquid ejecting apparatus according to any one of claims 1 to 6 further comprising a holding means for holding the state of the object to be treated the electrically floating during processing. A liquid ejecting head having a nozzle plate in which nozzle openings are formed and causing pressure fluctuations in the liquid in a pressure chamber communicating with the nozzle openings to discharge liquid droplets from the nozzle openings is formed on the object to be processed. A liquid ejecting method for appropriately selecting a plurality of size droplets that form dots of different sizes and discharging the droplets from the nozzle openings to the object to be processed ,
When droplets are ejected to the edge portion of the object to be processed and the region outside the edge portion, the area facing the liquid ejecting head on the back side of the object to be processed being processed The liquid ejecting head in a discharge mode in which the largest droplet among the plurality of droplets is not discharged in a state where a potential difference is generated between the conductive member disposed in the nozzle and the nozzle plate A liquid ejecting method for discharging droplets from a liquid. The liquid ejecting method according to claim 8 , wherein the discharge mode in which the largest droplet among the plurality of droplets is not discharged is a discharge mode in which the smallest droplet is discharged. A potential difference is prevented from being generated between the nozzle plate and the conductive member except when droplets are discharged to an edge portion of the object to be processed and a region outside the edge portion. The liquid ejecting method according to 8 or 9 . Number of ejected droplets only when more than a predetermined number, according to any one of claims 8 to 10 switches to the plurality of sizes discharge mode which greatest not eject droplets of size in the droplet Liquid injection method.

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