JP2004009549A - Method for driving ink jet head and ink jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accelerate a printing speed when one pixel is formed by discharging a plurality of times an ink liquid droplet without increasing a drive frequency. <P>SOLUTION: First and second nozzle arrays 35A and 35B are formed at an interval d in a sub-scanning direction on a nozzle surface of a head chip 12 of the ink jet printer. 64 ink nozzles are arranged at a pitch P in a main scanning direction in each nozzle array, and the ink nozzles are disposed in a zigzag manner between the respective nozzle arrays. The first ink nozzle 34A included in the first nozzle array 35A is driven in a predetermined drive frequency, and ink liquid droplets 61, 63 and 65 are discharged a plurality of times continuously by a predetermined drive frequency, and the second ink nozzle 34B included in the other second nozzle array 35B is driven in the same drive frequency at a time difference t, and the ink liquid droplets 62, 64 and 66 are discharged a plurality of times. Thus, the plurality of the ink liquid droplets are impacted in a state that the ink liquid droplets are slightly deviated in the main scanning direction and sub scanning direction to form a print of one pixel. Since the ink liquid droplets are discharged from the two ink nozzles to print the one pixel, the printing speed can be accelerated substantially twice without increasing the drive frequency. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for driving an ink-jet head that forms printing for one pixel by discharging ink droplets a plurality of times for the purpose of increasing recording density and the like, and to an ink-jet printer that performs printing using the driving method. .
[0002]
[Prior art]
2. Description of the Related Art There is known an inkjet printer that performs printing in a print mode in which ink droplets are ejected a plurality of times to a print area of one pixel for the purpose of increasing a recording density. For example, Japanese Patent Publication No. 4-48626, Japanese Patent No. 3219514, and the like disclose a method of ejecting a plurality of ink droplets to one pixel region, and overprinting a plurality of ink droplets with their positions shifted from each other by a predetermined amount. There has been proposed an ink jet recording apparatus for increasing the recording density.
[0003]
Such a print mode is applicable to an ink jet printer having various types of ink jet heads. For example, a static ink for discharging ink droplets by changing the volume of an ink chamber storing ink using electrostatic force. The present invention can be applied to a printer having an electrically driven ink jet head. As the electrostatic drive type ink jet head, for example, those described in JP-A-6-71882, JP-A-6-55732, and JP-A-5-50601 are known.
[0004]
[Problems to be solved by the invention]
Here, in the case where one pixel is formed by discharging ink droplets a plurality of times while maintaining a constant recording resolution (density) by driving the inkjet head, the number of ink droplet discharges for printing one pixel The printing speed decreases as the value increases. In order to increase the printing speed, it is necessary to increase the driving frequency that defines the ejection cycle of the inkjet head.
[0005]
However, since the driving frequency naturally has an upper limit, when adopting a printing mode in which one pixel is formed by discharging ink droplets a plurality of times, if the recording density is increased, the printing speed is sacrificed. If one attempts to increase the recording density, one must sacrifice the recording density. As described above, in the conventional inkjet printer, it is difficult to improve both the recording density and the printing speed by adopting the print mode in which one pixel is formed by discharging the ink droplets a plurality of times.
[0006]
In view of the above, an object of the present invention is to propose a method of driving an inkjet head which can realize an improvement in printing speed in a printing mode in which one pixel is formed by discharging ink droplets a plurality of times without increasing the driving frequency. Is to do.
[0007]
Another object of the present invention is to propose an ink jet printer that performs printing by such a method of driving an ink jet head.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention relates to a method of driving an inkjet head that performs printing of one pixel by discharging ink droplets a plurality of times.
Forming at least first and second ink nozzles on a nozzle surface of an inkjet head,
While moving the ink jet head relative to the recording medium in a direction different from the direction in which the first and second ink nozzles are arranged, the ink is ejected from the first and second ink nozzles at a predetermined drive cycle. It is characterized by performing printing for one pixel by discharging droplets.
[0009]
In the present invention, at least the first and second ink nozzles that discharge ink droplets at a predetermined driving cycle are used to discharge a plurality of ink droplets necessary for printing one pixel. I have. Therefore, compared with the case where one pixel is printed by ejecting ink droplets a plurality of times using a single ink nozzle, the time required for printing one pixel is basically reduced to 1 / the number of ink nozzles used. Can be shortened to Therefore, the printing speed in the printing mode in which one pixel is formed by discharging ink droplets a plurality of times can be improved without increasing the driving frequency of the inkjet head.
[0010]
Here, in the case where one pixel is formed by discharging ink droplets larger than the number of ink nozzles used for printing one pixel, the ink droplets must be discharged from each ink nozzle a plurality of times. Thus, printing for one pixel may be performed.
[0011]
In addition, since the ink nozzles used for printing one pixel are arranged at predetermined intervals in the relative movement direction of the inkjet head, by giving a predetermined time difference to the ejection time of the ink droplets of each ink nozzle, The landing positions of the ink droplets from the respective ink nozzles can be matched. That is, overprinting can be performed on the print area of one pixel. For example, in the case where the first and second ink nozzles are provided, the landing position of the ink droplet from the second ink nozzle coincides with the landing position of the ink droplet from the first ink nozzle. In such a manner, a predetermined time difference may be provided between the ejection time points of the ink droplets of the first and second ink nozzles.
[0012]
When the first and second ink nozzles are arranged along the relative movement direction of the inkjet head so as to have an interval of an integral multiple of the basic resolution, the time difference between the first and second ink nozzles The interval may be a value obtained by dividing the interval by the relative speed of the inkjet head.
[0013]
Next, in the case of performing overstrike, there is a fear that so-called strike-through may occur when a large number of ink droplets are overstruck at the same position, and the ink that has landed on the surface of the recording medium oozes out to the back side of the recording medium. . In order to reliably prevent strikethrough, the landing position of the ink droplet from the second ink nozzle is slightly different from the landing position of the ink droplet from the first ink nozzle in the relative movement direction of the inkjet head. The predetermined time difference may be provided between the ejection points of the ink droplets of the first and second ink nozzles so that the ink droplets are shifted.
[0014]
When the first and second ink nozzles are arranged along the direction of relative movement of the inkjet head so as to have an interval of an integral multiple of the basic resolution, the time difference is determined by the relative movement of the first and second ink nozzles. If the interval in the direction is set to a value larger or smaller by a predetermined amount than a value obtained by dividing the interval in the direction by the relative speed, the landing positions of the ink droplets from both ink nozzles are slightly shifted before and after in the relative movement direction of the inkjet head. Can be repeatedly struck.
[0015]
Instead, the interval between the first and second ink nozzles in the direction of relative movement of the inkjet head is set to an interval larger or smaller by a predetermined amount than an integer multiple of the basic resolution, and the time difference is set. Even when the distance between the first and second ink nozzles is divided by the relative velocity, the landing positions of the ink droplets from both ink nozzles are slightly shifted in the front and rear directions of the relative movement of the ink jet head. You can beat.
[0016]
Next, in the method for driving an ink jet head of the present invention, the first and second ink nozzles are arranged so as to be shifted by a predetermined amount in the relative movement direction of the ink jet head, and are also shifted by a predetermined amount in a direction orthogonal to the relative movement direction. It is also possible to displace them.
[0017]
With this configuration, the impact positions of the ink droplets ejected from both ink nozzles are overprinted with a slight shift in the direction of the relative movement of the ink jet head and the direction orthogonal thereto. Therefore, since the landing positions of the ink droplets for forming one pixel are integrated a plurality of times, the aggregation of the ink droplets for one pixel can be improved, and the print quality can be improved.
[0018]
For example, the first and second ink nozzles may be arranged at positions shifted by half the basic resolution in a direction orthogonal to the direction of relative movement of the inkjet head.
[0019]
Next, in general, a first nozzle row in which a plurality of first ink nozzles are arranged at regular intervals, and a plurality of second ink nozzles are arranged in regular intervals on an inkjet nozzle surface. A second nozzle row is formed. Of course, three or more nozzle rows can be formed.
[0020]
In this case, in order to accurately define the interval between the nozzle rows, it is desirable to form the nozzle rows in the same member.
[0021]
In order to form each ink nozzle with high accuracy, it is desirable to form each ink nozzle by a dry etching process using ICP.
[0022]
Next, the method for driving an ink jet head of the present invention can be applied to an electrostatically driven ink jet head that ejects ink droplets from each ink nozzle by electrostatic force.
[0023]
On the other hand, the present invention relates to an ink jet printer, and is characterized in that printing for one pixel is performed by the above-described method of driving an ink jet head according to the present invention. According to the inkjet printer of the present invention, it is possible to increase the printing speed in a printing mode in which one pixel is formed by discharging ink droplets a plurality of times without increasing the driving frequency of the inkjet head and without lowering the recording density. Can be.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an inkjet printer to which the present invention is applied will be described with reference to the drawings.
[0025]
(Overall configuration of inkjet printer)
FIG. 1 is a schematic configuration diagram showing a main part of the ink jet printer of the present embodiment. The ink jet printer of this example is of a serial type, and a head unit 4 is mounted on a carriage 3 that can reciprocate in a sub-scanning direction indicated by an arrow X along a guide shaft 2. The ink is supplied to the head unit 4 from the ink tank 5 disposed at a fixed position via flexible ink tubes 6 (6 (1), 6 (2)). A platen roller 7 is arranged parallel to the guide shaft 2, and printing is performed on the surface of the recording medium 8 conveyed in the main scanning direction Y by the platen roller 7 by the head unit 4 moving in the sub-scanning direction X. .
[0026]
(Structure of head chip)
FIG. 2 is a sectional view showing the head unit 4. The head unit 4 of the present example includes a rectangular parallelepiped unit cover 11 having an opening on the rear surface side, and head unit components are stored in the unit cover 11. In the unit cover 11, a head chip 12, a unit substrate 13, a damper rubber film 14, a damper retainer 15, and a relay substrate 16 are stacked in this order from the front side. The unit substrate 13 and the damper rubber film 14 form two damper chambers 21 (1) and 21 (2). The front ends of the ink supply pipes 22 (1) and 22 (2) communicate with the respective damper chambers 21 (1) and 21 (2), and the rear ends of the ink supply pipes 22 (1) and 22 (2). Communicates with each of the ink tubes 6 (1) and 6 (2). The damper chambers 21 (1) and 21 (2) are formed in the head chip 12 via the ink supply ports 23 (1) and 23 (2) (only the ink supply port 23 (1) is shown in the drawing). Two ink intake ports 24 (1) and 24 (2) (only the ink intake port 24 (1) is shown in the figure).
[0027]
The head chip 12 has a flat rectangular parallelepiped shape, and the front surface 12a is an ink nozzle surface, and the ink nozzle surface 12a is exposed from the front opening 11a of the unit cover 11. The flexible wiring boards 25 (1) and 25 (2) for power supply are drawn out from the respective side surfaces of the head chip 12, and are drawn out rearward along the insides of the respective side surfaces of the unit cover 11 to form a relay board. 16 is connected to the rear surface. Head driver ICs 26 (1) and 26 (2) are attached to portions of each of the flexible wiring boards 25 (1) and 25 (2) facing each side surface of the unit cover 11.
[0028]
FIG. 3A is a perspective view showing a part of the head chip 12 of the present example, and FIG. 3B is an exploded perspective view thereof. The head chip 12 of this example is an inkjet head of an electrostatic drive type, and two sets of inkjet heads 12A and 12B having the same structure are formed in a symmetrical manner.
[0029]
One ink jet head 12A has a flow path substrate 31 made of a semiconductor such as silicon sandwiched therebetween, a nozzle substrate 32 also made of a semiconductor made of silicon or the like disposed above the flow path substrate 31, and a glass electrode glass placed below the nozzle substrate 32. The configuration is such that the substrate 33 and the substrate 33 are laminated and joined. On the nozzle substrate 32, a nozzle row 35A in which a plurality of ink nozzles 34A are arranged in a row at a constant pitch is formed. The direction of the nozzle row 35A is the main scanning direction Y orthogonal to the moving direction of the carriage 3, that is, the sub-scanning direction X that is the moving direction of the inkjet head.
[0030]
A plurality of ink pressure chambers 36A corresponding to each ink nozzle 34A, one common ink chamber 37A, and each ink pressure chamber 36A communicate with the common ink chamber 37A between the flow path substrate 31 and the nozzle substrate 32. A plurality of ink orifices 38A are formed. The bottom surface of each ink pressure chamber 36A is a vibration plate 39A that can vibrate in an out-of-plane direction. On the surface of the electrode glass substrate 33, there are formed recesses 40A necessary for each diaphragm 39A to vibrate in an out-of-plane direction. On the bottom surface of each recess 40A, an individual electrode 41A made of ITO or the like is formed. The individual electrodes 41A corresponding to the vibration plates 39A face each other at a predetermined interval.
[0031]
Each individual electrode 41A is connected to an individual electrode lead terminal 42A that is drawn out to the side, and is electrically connected to the head driver IC 26 (1) via the aforementioned flexible wiring board. A common electrode terminal 43A is also attached to the flow path substrate 31, and this common electrode terminal 43A is also connected to the head driver IC 26 via a flexible wiring board.
[0032]
When a voltage is applied between the individual electrodes 41A and each of the diaphragms 39A functioning as the common electrode 43A, the diaphragm 39A vibrates due to an electrostatic force generated therebetween. In response to this vibration, the volume of each ink pressure chamber 36A fluctuates to generate ink ejection pressure, and ink droplets are ejected from each ink nozzle 34A. Such an electrostatically driven ink droplet ejection mechanism is known, and a detailed description thereof will be omitted.
[0033]
Note that an ink intake port 24 (1) for supplying ink to the common ink chamber 37A is formed in the bottom surface of the common ink chamber 37A and the electrode glass substrate 33, and the ink tank is provided via the ink tube 6 (1). 5 supplies ink.
[0034]
Since the other ink jet head 12B has the same structure as the ink jet head 12A, the corresponding portions are indicated by the same numerals with B added thereto, and their description is omitted.
[0035]
(Nozzle arrangement)
FIG. 4 is an explanatory diagram showing an ink nozzle array formed on the nozzle surface 12a of the head chip 12 when viewed from the recording medium side. As shown in this figure, in the head chip 12 of this example, two nozzle rows 35A and 35B are formed along a paper feed direction (main scanning direction) Y orthogonal to the ink jet head moving direction (sub-scanning direction) X. Is formed. The nozzle row 35A is a nozzle row including a plurality of, for example, 64 first ink nozzles 34A (1) to 34A (64) arranged in the main scanning direction Y. The other nozzle row 35B is also a nozzle row including 64 second ink nozzles 34B (1) to 34B (64) arranged in the main scanning direction Y.
[0036]
More specifically, the first ink nozzles 34A (1) to 34A (64) forming the first nozzle row 35A are linearly arranged at a constant pitch P, for example, at an interval equivalent to 180 dpi (= 0.141 μm). The second ink nozzles 34B (1) to 34B (64) which are arranged on the upper side and constitute the second nozzle row 35B are also arranged at the same pitch P. However, the second ink nozzles 34B (1) to 34B (64) forming the second nozzle row 35B have a half pitch P / 2 as a whole, for example, 360 dpi (= 70 μm). It is arranged at a position relatively shifted in the direction. Therefore, the first ink nozzles 34A (1) to 34A (64) and the second ink nozzles 34B (1) to 34B (64) are staggered from each other by P / 2. I have.
[0037]
In this example, the interval between the first and second nozzle rows 35A and 35B, that is, the nozzle row interval d in the sub-scanning direction is set to a value that is an integral multiple of the basic resolution (pitch P). For example, it is set to 0.56 mm (= 141 μm × 4), which is four times the basic resolution.
[0038]
The head chip 12 of the present example is of a face eject type in which ink droplets are ejected from ink nozzles provided on the upper surface of a nozzle substrate. An edge eject type in which ink is ejected from an ink nozzle provided at an end may be used.
[0039]
Further, two nozzle rows 34A and 34B are formed on the nozzle substrate 32 as described above. In order to accurately form the intervals between the nozzle rows and the respective ink nozzle pitches, as in this example, the nozzle substrate 32 is a single common nozzle substrate commonly used for each of the inkjet heads 12A and 12B, and the same nozzle substrate is used. It is desirable to form both ink nozzles simultaneously by an etching process.
[0040]
Further, in order to form an ink nozzle having a target cross-sectional shape on a nozzle substrate which is a semiconductor substrate, it is desirable to form the ink nozzle by dry etching using ICP.
[0041]
(Drive control device)
Next, FIG. 5 is a schematic block diagram illustrating an example of a drive control device of the inkjet printer 1 of the present embodiment. The drive control device 51 of the present example has an ink jet head control unit 52 mainly composed of a CPU. Print information is supplied to the CPU from an external device 53 via a bus, and a ROM, a RAM, and a character generator 54 are connected via an internal bus.
[0042]
The inkjet head control unit 52 uses the storage area in the RAM as a work area, executes a control program stored in the ROM, and, based on character information generated from the character generator 54, controls a control signal for driving the inkjet head. Generate The control signal becomes a drive control signal corresponding to the print information via the logic gate array 55 and the drive pulse generating circuit 56, and via the connector 57, the head driver IC 26 (26 (1 (1)) formed on the head substrate 58. ), 26 (2)). The head driver IC 26 is also supplied with a drive voltage pulse signal V3, a control signal LP, and a polarity inversion control signal REV.
[0043]
In the head driver IC 26, a driving voltage pulse to be applied to each diaphragm of the head chip 12 (12A, 12B), that is, a common electrode, is supplied based on the above-mentioned signals supplied and the driving voltage Vp supplied from the power supply circuit 60. A drive voltage pulse to be output from the common output terminal COM and to be applied to each counter electrode (individual electrode) corresponding to each of the ink nozzles 34A and 34B is output from the number of individual output terminals SEG corresponding to each individual electrode. The potential difference between the output of the common output terminal COM and the output of the individual output terminal SEG is applied between each of the vibration plates 39A and 39B corresponding to each of the ink nozzles 34A and 34B and the individual electrode facing each other. A driving potential difference waveform in a designated direction is applied during driving (when ink droplets are ejected), and no driving potential difference is applied when not driving.
[0044]
The drive pulse generation circuit 56 generates a drive signal having a predetermined pulse width and a control signal LP for forming one print pixel with the determined number of ejections, and outputs the control signal LP to the head driver IC 26.
[0045]
(Printing operation)
In the inkjet head drive control device 1 of the present embodiment, it is possible to perform print control in a plurality of print modes. For example, 2 shot (shot) / dot (dot) driving for forming one printing pixel by discharging ink droplets at a maximum of two consecutive times, and 3 shot / dot forming at a maximum of three consecutive ink droplets to be discharged. Printing can be performed by driving, 4 shot / dot driving formed by discharging ink droplets up to 4 times continuously, and 6 shot / dot driving formed by discharging ink droplets up to 6 times continuous. I have.
[0046]
Further, in each driving state, it is possible to control the gradation of each pixel by changing the number of ejections of ink droplets in one pixel printing period.
[0047]
The print mode in each of the above-described drive modes can be selectively switched by an input from the external device 3 side.
[0048]
FIG. 6 shows a signal waveform of each part in the print mode by 6 shot / dot drive. In each figure, a drive voltage pulse signal V3, a control signal (latch pulse) LP, a polarity inversion control signal REV, a COM output which is an output of the common terminal COM, and an individual terminal are supplied from the inkjet head control unit 52 to the head driver IC 26. The SEG output, which is the output of the SEG, and the COM-SEG potential difference, which is the potential difference (nozzle driving voltage waveform) generated between the common electrode (diaphragm) and the individual electrodes, are shown.
[0049]
In the print mode by the 6 shot / dot drive, one pixel of print is formed by continuously discharging ink droplets up to six times. In this print mode, seven gradation printing can be performed by performing shot modulation of seven gradations. In other words, the first grayscale having the highest density is obtained by performing six consecutive shots in the one-pixel printing period T, the second grayscale is obtained by performing five shots, and the third grayscale is obtained. The gray scale is obtained by performing four shots, the fourth gray scale is obtained by performing three shots, the fifth gray scale is obtained by performing two shots, and the sixth gray scale is obtained. Can be obtained by performing one shot, and the seventh gradation can be obtained by setting the non-drive state.
[0050]
Here, the head chip 12 of the present example includes two nozzle rows 35A and 35B extending in the main scanning direction. In the multi-shot print mode, the first nozzle included in both nozzle rows 35A and 35B. Ink droplets are ejected using both the ink nozzles 34A (1) to 34A (64) and the second ink nozzles 34B (1) to 34B (64).
[0051]
As an example, a printing operation of 6 shots / dot using the first ink nozzle 34A (1) and the corresponding second ink nozzle 34B (1) will be described.
[0052]
In this case, as shown in FIG. 7A, ink droplets for six shots are ejected to a print area of one pixel. That is, the first, third, and fifth shots 61, 63, and 65 are ejected from the first ink nozzle 34A (1) at the timing shown in FIG. 6, and the landing position of each shot is determined by the drive voltage pulse V3. Assuming that Td is the driving cycle and v is the scanning speed of the carriage, v (CR) is shifted in the sub scanning direction at intervals of α = Td × v (CR).
[0053]
On the other hand, the second ink nozzle 34B (1) is also driven at the timing shown in FIG. 6, but the drive timing is provided with a predetermined time difference. In this example, d / v (CR) + Δt is adopted as the time difference t. d is the nozzle row interval in the sub-scanning direction X as described above, and v (CR) is the carriage scanning speed. At is used to shift the landing position of the second ink nozzle 34B (1) by a small distance β in the carriage scanning direction X with respect to the landing position of the first ink nozzle 34A (1).
[0054]
As a result, the second, fourth, and sixth shots 62, 64, and 66 continuously ejected from the second ink nozzle 34B are different from the first, third, and fifth shots 61, 63, and 65, respectively. At a position shifted by P / 2 in the main scanning direction Y, the ink droplet lands at a position shifted by a distance α in the carriage scanning direction. In addition, the first and third shots 61, 63, and 65 land at positions shifted by a distance β in the carriage scanning direction.
[0055]
As described above, printing of one pixel is performed by ink droplets of three shots continuously discharged from the first and second ink nozzles 34A (1) and 34B (1). As a result, the time required for one-pixel printing is (T + Δt), which is approximately half of the time width 2T for ejecting ink droplets for six shots from each ink nozzle. Therefore, it is possible to reduce the recording density without increasing the driving frequency as compared with the conventional case where a single ink nozzle is used to discharge one pixel by discharging ink droplets a plurality of times. And the printing speed can be approximately doubled.
[0056]
In this example, the landing positions of the ink droplets for six shots are slightly shifted in the sub-scanning direction and the main scanning direction. There is no fear of omission.
[0057]
Furthermore, since the ink nozzles of the first nozzle row 35A and the second nozzle row 35B are staggered, the landing position of the first ink nozzle and the landing position of the second ink nozzle are determined in the main scanning direction. The state is shifted to Y. Therefore, compared with the case where a plurality of ink droplets are overprinted while being shifted only in the sub-scanning direction X, there is obtained an advantage that a plurality of dots forming one pixel are better grouped.
[0058]
In this example, two nozzle rows 35A and 35B are arranged. However, the present invention is also applicable to a case where an inkjet head having a configuration in which three or more nozzle rows are arranged at predetermined intervals in the sub-scanning direction is provided. . In this case, if the number of nozzle rows is N, the time required for printing one pixel can be substantially reduced to 1 / N. In other words, the printing speed can be increased N times.
[0059]
Further, in this example, the landing position of the ink droplet of the second ink nozzle 34B81) is set to β in the sub-scanning direction X with respect to the landing position of the ink droplet of the first ink nozzle 34A (1). In this case, the time difference t between the drive timings is set to t = d / v (CR) + Δt. It is also possible to eject ink droplets from the ink nozzles at a time difference t '= d / v (CR) where Δt is omitted. In this case, the landing position of the ink droplet from the first ink nozzle and the landing position of the ink droplet from the second ink nozzle are the same in the sub-scanning direction X, as shown in FIG. Position. In this manner, one-pixel printing can be performed.
[0060]
Here, the ink droplets are ejected from both the ink nozzles by the time difference t ′ in which Δt is omitted to form a state in which the landing position is shifted in the sub-scanning direction X as shown in FIG. To do so, the nozzle row interval d (interval in the sub-scanning direction X) between the first nozzle row 35A and the second nozzle row 35B may be set as follows.
d = N × P ± Δd
Here, Δd is a value smaller than the pitch P (basic resolution), and N is a positive integer.
[0061]
(Another example of nozzle arrangement)
FIG. 8A is an explanatory diagram showing an example of a nozzle array to which the present invention can be applied, and corresponds to FIG. 4 in the above example. In the nozzle arrangement shown in FIG. 8A, the nozzle row interval d between the first and second nozzle rows 35A and 35B and the interval P between the ink nozzles are the same as in the above example. However, the first ink nozzles 34A included in the nozzle row 35A and the corresponding second ink nozzles 34B included in the nozzle row 35B are formed at the same position in the main scanning direction Y.
[0062]
When the first ink nozzle 35A and the second ink nozzle 35B are driven with a time difference t (= d / v (CR) + Δt) by adopting the nozzle arrangement of this configuration, as shown in FIG. Ink droplets of six shots land in a state of being shifted by α / 2 in the sub-scanning direction X, and one-pixel printing is formed. The first, third, and fifth shots 61, 63, and 65 are ejected from the first ink nozzle 34A (1), and the second, fourth, and sixth shots 62, 64, and 66 are the second ink nozzles. 34B (1).
[0063]
Also in this case, the time required for one-pixel printing can be made approximately half the time width T for ejecting ink droplets for six shots from each ink nozzle. Therefore, it is possible to reduce the recording density without increasing the driving frequency as compared with the conventional case where a single ink nozzle is used to discharge one pixel by discharging ink droplets a plurality of times. And the printing speed can be approximately doubled.
[0064]
Further, in this example, the landing positions of the ink droplets for six shots are slightly shifted in the sub-scanning direction X, so that there is a possibility of strikethrough when a plurality of ink droplets land at the same position. Not even.
[0065]
In this case, the present invention is also applicable to a case where an inkjet head having a configuration in which three or more nozzle rows are arranged at predetermined intervals in the sub-scanning direction is provided. In this case, if the number of nozzle rows is N, the time required for printing one pixel can be substantially reduced to 1 / N. In other words, the printing speed can be increased N times.
[0066]
Further, the landing position of the ink droplet of the second ink nozzle 34B (1) is shifted by β in the sub-scanning direction X with respect to the landing position of the ink droplet of the first ink nozzle 34A (1). For this reason, the time difference t between the drive timings is set to t = d / v (CR) + Δt. It is also possible to eject ink droplets from the ink nozzles at a time difference t '= d / v (CR) where Δt is omitted. In this case, as shown in FIG. 7B, the landing positions of the ink droplets 61, 63, and 65 from the first ink nozzle and the ink droplets 62 and 62 from the second ink nozzle. The landing positions 64 and 66 are the same. In this manner, one-pixel printing can be performed.
[0067]
Further, in this case, the ink droplets are ejected from both the ink nozzles by the time difference t ′ in which Δt is omitted to form a state in which each of the six shots is shifted as shown in FIG. 8B. In this case, the nozzle interval d (interval in the sub-scanning direction X) between the first nozzle row 35A and the second nozzle row 35B may be set as follows.
d = N × P ± Δd
Here, Δd is a value smaller than the pitch P (basic resolution), and N is a positive integer.
[0068]
【The invention's effect】
As described above, in the ink jet head driving method of the present invention, a plurality of ink nozzles arranged at a predetermined interval are moved relative to the recording medium in a direction different from the arrangement direction, and By discharging ink droplets from a plurality of ink nozzles, printing of one pixel is formed by discharging ink droplets a plurality of times.
[0069]
Therefore, compared with the case where a single ink nozzle is driven at a predetermined driving frequency to discharge ink droplets a plurality of times to perform one-pixel printing, the printing speed is substantially reduced by the number of used ink nozzles. Can be doubled. Also, since one pixel is printed by a plurality of ink nozzles, it is possible to increase the maximum density (maximum ink ejection amount) and reduce the number of levels of gradation expression without lowering the driving frequency. . Furthermore, since the ejection of the ink droplets is shared by the plurality of ink nozzles when printing one pixel by ejecting the ink droplets a plurality of times, it is advantageous for the durability of the ink jet head.
[0070]
Next, by employing the inkjet driving method according to the present invention, the printing speed can be increased without increasing the driving frequency and without decreasing the recording density, so that the time required for printing is reduced, and the printing result is reduced. Can realize a beautiful inkjet printer.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an ink jet printer to which the present invention is applied.
FIG. 2 is a sectional view showing a head unit in the ink jet printer of FIG.
3A and 3B are views showing a head chip mounted on the head unit of FIG. 2, wherein FIG. 3A is a perspective view showing a part of the head chip in cross section, and FIG. 3B is an exploded perspective view thereof.
FIG. 4 is an explanatory diagram showing an arrangement state of ink nozzles formed on a nozzle surface of the head chip of FIG. 3;
FIG. 5 is a schematic block diagram illustrating an inkjet head drive control device in the inkjet printer of FIG. 1;
6 is a signal waveform diagram showing an operation of each part of the inkjet head drive control device of FIG. 5, which is an example in which one pixel is formed in a 6 shot / dot mode.
FIGS. 7A and 7B are explanatory diagrams showing two examples of landing positions of ink droplets when printing one pixel in a 6 shot / dot mode.
FIG. 8A is an explanatory view showing another example of the nozzle arrangement, and FIG. 8B is an explanatory view showing an example of the landing position of each ink droplet in the 6 shot / dot mode in the case of the nozzle arrangement. It is.
[Explanation of symbols]
1 Inkjet printer
3 carriage
4 Head unit
5 Ink tank
8 Recording media
12 Head chip
12A, 12B inkjet head
26 Head Driver IC
31 Flow path substrate
32 nozzle substrate
33 electrode glass substrate
34A (1) to 34A (64), 34B (1) to 34B (64) Ink nozzles 35A, 35B Nozzle rows
36A ink pressure chamber
37A Common ink chamber
39A diaphragm
41A individual electrode
51 Inkjet head drive control device
52 Inkjet head controller
56 Drive pulse generation circuit
LP control signal
V3 drive voltage pulse signal
REV polarity inversion control signal
61, 63, 65 Ink droplets ejected from ink nozzle 34A
62, 64, 66 Ink droplets ejected from ink nozzle 34B
X Sub-scanning direction
Y main scanning direction

Claims (14)

In a method of driving an ink jet head for performing printing of one pixel by discharging ink droplets a plurality of times,
Forming at least first and second ink nozzles on a nozzle surface of an inkjet head,
While moving the ink jet head relative to the recording medium in a direction different from the direction in which the first and second ink nozzles are arranged, the ink is ejected from the first and second ink nozzles at a predetermined drive cycle. A method for driving an ink-jet head, characterized by performing printing for one pixel by discharging droplets. In claim 1,
A method for driving an ink-jet head, characterized in that a plurality of ink droplets are respectively ejected from the first and second ink nozzles to perform printing for one pixel. In claim 1 or 2,
The positions of the ink droplets of the first and second ink nozzles are adjusted such that the positions of the ink droplets from the first ink nozzle match the positions of the ink droplets from the second ink nozzle. A method for driving an ink jet head, characterized in that a predetermined time difference is provided between ejection times. In claim 3,
Along the relative movement direction of the inkjet head, the first and second ink nozzles are arranged so as to have an interval of an integral multiple of a basic resolution,
The method according to claim 1, wherein the time difference is a value obtained by dividing the interval between the first and second ink nozzles by the relative speed. In claim 1 or 2,
The first and the second ink nozzles are arranged such that the landing positions of the ink droplets from the second ink nozzles are shifted by a predetermined amount in the direction of relative movement of the inkjet head with respect to the landing positions of the ink droplets from the first ink nozzles. A method for driving an ink-jet head, characterized in that a predetermined time difference is provided between the ejection points of ink droplets from a second ink nozzle. In claim 5,
Along the relative movement direction of the inkjet head, the first and second ink nozzles are arranged so as to have an interval of an integral multiple of a basic resolution,
A method of driving an ink jet head, wherein the time difference is set to a value larger by a predetermined amount or smaller than a value obtained by dividing the interval between the first and second ink nozzles by the relative speed. In claim 5,
Along the relative movement direction of the inkjet head, the first and second ink nozzles are arranged so as to have a predetermined amount larger interval or a predetermined amount smaller interval than an integer multiple of the basic resolution,
The method according to claim 1, wherein the time difference is a value obtained by dividing the interval between the first and second ink nozzles by the relative speed. In any one of claims 1 to 7,
A method for driving an ink-jet head, wherein the first and second ink nozzles are arranged at positions shifted by a predetermined amount in a direction orthogonal to the direction of relative movement of the ink-jet head. In claim 8,
A method of driving an ink-jet head, wherein the first and second ink nozzles are arranged at positions shifted by a half of a basic resolution in a direction orthogonal to a relative movement direction of the ink-jet head. In any one of claims 1 to 9,
A first nozzle row in which a plurality of the first ink nozzles are arranged at regular intervals, and a second nozzle row in which a plurality of the second ink nozzles are arranged at regular intervals on the nozzle surface of the ink jet. A method for driving an ink jet head, comprising forming a nozzle row. In claim 10,
A method for driving an ink-jet head, wherein the first and second nozzle rows are formed in the same member. In claim 10 or 11,
A method of driving an ink jet head, wherein each ink nozzle constituting the first and second nozzle rows is formed by a dry etching process using ICP. In any one of claims 1 to 12,
The method of driving an inkjet head, wherein the inkjet head is an electrostatically driven inkjet head that ejects ink droplets from each ink nozzle by electrostatic force. 14. An ink-jet printer which performs printing for one pixel by the method for driving an ink-jet head according to claim 1.

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