JP2621489C - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a charge control type ink jet printer, specifically, an ink droplet continuously ejected from a nozzle is charged according to image information, and the charged ink is charged. The present invention relates to a charge control type ink jet printer in which a droplet is deflected by an electric field to control the presence / absence of dot printing on a recording medium arranged opposite a nozzle. [Prior Art] The basic structure of a charge control type ink jet printer is, for example, as shown in FIG. 6 (see JP-A-57-25971). This is because a pair of charging electrodes 42 are arranged in front of the nozzles 41 arranged at a predetermined interval on the front surface of the ink droplet generating device 40, and a pair of deflecting electrodes 43 are further in front thereof.
Are arranged so that the ink droplets ejected from each nozzle 41 sequentially pass between the charging electrodes 42 and between the deflecting electrodes 43 and reach the recording paper 45 arranged opposite to the nozzles 41. In such an ink jet printer, voltage control based on image information for the charging electrode 42 is performed in a state where a steady electric field is formed by the deflection electrode 43. As a result, the flying ink droplet is charged in accordance with the image information, and the charged ink droplet flies toward the recording paper 45 under the deflecting action according to the charge amount and the deflection electric field. That is, the dot printing position on the recording paper 45 based on the image information is controlled by the charge amount for the ink droplet. The non-printing dots are subjected to charging control so as to be subjected to a deflecting action that reaches the gutter 46, and the ink captured by the gutter 46 is collected by the ink droplet generator 40. More specifically, the charging control for the ink droplets is conventionally performed, for example, as follows. For example, as shown in FIG. 7, a voltage is applied to the charging electrode 42 at the moment when the ink I ejected from each nozzle 41 of the ink droplet generating device 40 is formed into droplets by ultrasonic vibration or the like, and the ink droplet do Is charged. The order of the dot printing positions (scanning method) in the scanning range for each nozzle (between the stitching points SP in FIG. 6) is predetermined, and the presence or absence of printing at each printing position according to this order (the image information The response amount determines the charge amount for the controlled ink droplet do. In the process in which the ink droplet d charged according to the image information flies as described above, the flying ink droplet d receives an electrostatic or aerodynamic action from the preceding and following ink droplets. Therefore, even if the ink droplets have the same charge amount, their printing positions are shifted depending on the state of the ink droplets that fly back and forth (deflection distortion). In order to prevent such a deflection distortion, conventionally, the charge amount is corrected according to the state of the ink droplet flying back and forth. Specifically, the charge amount is corrected as follows. Trajectory of ink droplets, various can take in (f ₄ in FIG. _{7) (f 1, f 2,} f 3 in FIG. 7) and when deflecting the gutter 46 without printing when performing printing The electrostatic and aerodynamic effects on the other ink droplets differ depending on the ink droplets that fly in any of the paths. From this, different printing presence / absence patterns are assumed for ink droplets existing in a predetermined vicinity of the target ink droplet, for example, about six drops before and about six drops after, and in each pattern, the target printing ink droplet The charge correction amount for reaching the position is actually measured, and the relationship between each print presence / absence pattern and the charge correction amount is stored in a memory such as a ROM in advance. At the time of actual printing, a print presence / absence pattern of an ink droplet in a predetermined vicinity of the controlled ink droplet is detected, and a charge correction amount corresponding to the detected print presence / absence pattern is read from the memory, and the charge correction amount is read. Correction control is performed. In the conventional ink droplet charge control method in which the charge amount corresponding to the image information is corrected based on the printing presence / absence pattern of the nearby ink droplet, the electrostatic charge of each ink droplet is reduced by the nearby ink droplet. The influence of the target and the aerodynamic is taken into account, and the deflection distortion can be reduced. [Problems to be Solved by the Invention] By the way, with the conventional ink droplet charging control method as described above, it is difficult to realize dot printing with even less deflection distortion. It is based on the following reasons. As shown in FIG. 8, in order to reduce the deflection distortion, it is necessary to increase the number of ink droplets (reference droplets) to be considered as having an effect on the target ink droplet. However, when the number of reference ink droplets is increased, the number of print presence / absence patterns with the reference ink droplets increases, and the capacity of the memory for storing the charge correction amount in association with the print presence / absence pattern increases as shown in FIG. Would. For example, when the reference ink drops 100 drops, the indium pattern becomes two ways ^100, its storage capacity is enormous, is the realization of the real memory device becomes difficult. Furthermore, the time required to measure each data by actually reproducing the print presence / absence pattern becomes enormous, which is not practical. Therefore, an object of the present invention is to obtain an effect equivalent to a correction in which substantially more reference ink droplets are taken into consideration even in charge correction in consideration of fewer reference ink droplets. [Means for Solving the Problems] As shown in FIG. 1, the present invention is configured such that when a nozzle 1 ejects an ink droplet 2 to a plurality of printing positions within a predetermined scanning range, the nozzle 1 continuously emits the ink droplet. Spouted ink drop 2
Is controlled for each printing position in accordance with the image information I, and the charged ink droplets are deflected by an electric field to determine whether or not dot printing is to be performed at a predetermined printing position on the recording medium 3 disposed opposite the nozzle 1. It is premised on a charge control type ink jet printer that controls the ink droplet charging control realized in the ink jet printer. The presence / absence of the printing pattern P of the ink droplet dn selected according to the scanning method on the assumption that the target ink droplet do has electrostatic and aerodynamic effects.
(dn) and the print density D (df) of the ink droplet df located farther from the nearby droplet, the charge correction amount Ac (P, D) for the target ink droplet do is determined in advance for each printing position, In performing the charge control on the droplet, the printing presence / absence pattern P of the ink droplet dn in a predetermined vicinity of the controlled ink droplet is detected, and the printing density D of the ink droplet df farther from the neighboring ink droplet dn is detected. The charge correction control for the ejected ink droplets is performed for each printing position at the predetermined charge correction amount Ac (P, D) corresponding to the detected print presence / absence pattern P and print density D. [Operation] In a state where the ink droplets 2 are continuously ejected from the nozzles 1, the ink droplets dn located in the vicinity of the current ink droplet do of interest until the ink droplet do of interest reaches the recording body 3. It has aerodynamic as well as electrostatic effects. On the other hand, the ink droplet df located at a distant place has a small electrostatic effect on the target ink droplet do and a small aerodynamic effect. This aerodynamic effect is mainly caused by disturbing the air flow around the flight path of the target ink droplet, which largely depends on the density of the ink droplet flying forward. From such a relationship, for the nearby ink droplet dn having a greater influence (both electrostatic and aerodynamic), the influence is relatively small (only aerodynamic) according to each print presence / absence pattern P (dn). For the distant ink droplet df, the printing density D (d
For patterns having the same f), the charge correction amount Ac (P, D) is determined in advance according to each printing density D (df). The charge correction amount Ac (P, D) may be considered integrally with the influence of the nearby ink droplet dn and the influence of the distant ink droplet df, or may be independently considered. When considered as one, the ink droplet is continuously fly in a state where both the nearby ink droplet dn in a certain printing presence / absence pattern and the distant ink droplet df in a predetermined printing presence / absence pattern at a certain printing density are present, The charging correction amount Ac () is measured while measuring the deviation amount of the target ink droplet do from the normal printing position (determined based on image information).
P, D). In addition, when considering independently, the first charge correction amount is determined while measuring the printing position of the target ink droplet do in a state where only the neighboring ink droplet dn in a certain printing presence / absence pattern is present, and further, a certain printing density is determined. Distant ink droplets in a predetermined print pattern at
In the state where only df exists, the second charge correction amount is determined while measuring the printing position of the target ink droplet do, and the final charge correction amount is determined by the sum of the first charge correction amount and the second charge correction amount. Ac (P, D) is determined. It is preferable that the number of the adjacent ink droplets dn and the far ink droplets df to be considered is as large as possible. However, as a practical problem, depending on the required performance (permissible deflection distortion) and the like, it is preferable that For the droplet dn, the electrostatic effect is determined within a range that cannot be ignored, and for the distant ink droplet df, the aerodynamic effect is determined within a range that cannot be ignored. As described above, when the charge control is performed on the ejected ink while the charge correction amount Ac (P, D) for the target ink droplet do is predetermined, the charge control based on the basic image information I is performed together with the charge control based on the basic image information I. The print presence / absence pattern P (dn) of the ink droplet dn and the print density D (df) of the distant ink droplet df are detected, and the predetermined charge correction amount Ac (P, D) corresponding to the detected print presence / absence pattern and print density is detected. The charge correction control is performed in (). [Example] Hereinafter, an example of the present invention will be described with reference to the drawings. The basic structure of the entire printer is the same as that shown in FIG. The recording conditions are as follows: dot density: 24 dots / mm ink droplet size: 30 μm dropletization speed: 250 KHz initial ink droplet speed: 20 m / sec deflection width: 2.5 mm number of dots: 60 dots / scan. A control system for the charging electrode 42 is, for example, as shown in FIG. In FIG. 1, reference numeral 10 denotes an image data processing device, which adapts image data from an image reading device 12 such as an image scanner or an image data generating device 14 composed of a computer or the like to the printer. Is converted into dot print data (image information). Reference numeral 16 denotes a serial-in / parallel-out shift register. The shift register 16 stores dot print data sequentially output from the image data processing apparatus 10 in serial. The print data is stored for ink droplets in the range (−3λ to + 13λ) between and the front 13 droplets (hereinafter, the rear is represented by −forward and + is represented by λ). The shift register described above stores only the dot print data corresponding to the ink droplet expected to have a large electrostatic and aerodynamic effect on the ink droplet of interest among the parallel outputs of the shift register 16 in the register 17.
The wiring between 16 and the register 17 is separated. The dot print data to be stored in the register 17 differs depending on the scanning method in the main scanning direction. For example, according to the interlaced scanning method shown in FIG. 10, -3λ to + 3λ, + 5λ, Dot print data corresponding to each ink droplet of + 7λ, + 10λ, and + 13λ (a total of 10 droplets) is selected. This is because the ink droplet of -3λ to + 3λ flies very close to the target ink droplet.
Also, the ink droplets of + 5λ, + 7λ, + 10λ, and + 13λ have their trajectories close to the trajectory of the target ink droplet when the interlaced scanning method is used. FIG. 10 shows the relationship between the order in which ink droplets are generated (drop numbers: 1 to 60) and their printing positions (dot positions: 1 to 60). The numbers indicate the dot positions. Reference numeral 20 denotes a hexadecimal counter, and reference numeral 22 denotes a ROM that outputs position data corresponding to the count value of the counter 20, and the position data output from the ROM 22 is set in a register 24. The position data generation circuit is configured by the counter 20, the ROM 22, and the register 24. The contents of the ROM 22 are
The print position data according to the interlaced scanning method corresponding to each count value, such as the first print position and the second print position, is stored. Since the stored position data is printed at 60 dots between the stitching points SP (see recording conditions), it corresponds to the count value from 0 to 59 one-to-one. The shift register 16 and the counter 20 perform a shift operation and a count operation according to a timing clock from the timing controller 18, and the timing clock from the timing controller 18 is synchronized with the dropping timing in the ink drop generator 40. ing. On the other hand, reference numeral 26 denotes a density detector for detecting the print density of the ink droplet farther than the above 13λ with respect to the target ink droplet. The density detector 26 specifically detects the print density of 64 droplets from 14λ to 77λ. For example, as shown in FIG. 3, a timing controller 27 and a 6-bit up / down counter 29 are used. It consists of. The timing controller 27 has two operation modes, an initial setting mode Mi and a detection mode Ms. As shown in FIG. 4, the initial setting mode Mi (mode switching) from the start until 64 drops are ejected is started. At the signal H level, the dot print data sequentially output from the shift register 16 in synchronization with the dropping clock is “1” (
When the dot print data is "1", an up-count signal is output when the dot print data is "1" in the detection mode Ms (mode switching signal L level) which is switched after the ejection of 64 drops. While the dot print data is "0"
When "" (corresponding to no printing), a down-count signal is output.
Then, the up / down counter 29 is activated by the up count signal and the down count signal from the timing controller 27, and the count value n is the printing density, that is,
This corresponds to a print density (n / 64) of printing n drops out of 64 drops. The upper three bits of the count value of the up / down counter 29 are set in the register 28. That is, in this density detection, the print density of 64 distant droplets is classified into eight levels. The up / down counter 29 is configured so that carry-over processing at a count value of 64 or more and borrow processing at a count value of 0 or less are performed according to a general method. As described above, dot print data (10 bits) corresponding to the 10 drops near the target ink droplet set in the register 17, the print position data (6 bits) of the target ink droplet set in the register 24, and the register 28 The print density data (3 bits) of the distant ink droplets of 14λ to 77λ with respect to the target ink droplets set in is input to the address of the ROM 30 in parallel. The ROM 30 previously stores the charge amount for the target ink droplet, and the read charge data is passed through a charge data processing device 32 for performing processing such as correction for each nozzle, and further through a D / A converter 34 so as to obtain the actual voltage. Converted to output,
The conversion output is applied to the charging electrode 42. The contents of the ROM 30 are as follows. As the charge amount, data determined based on actual measurement is stored in association with each address input. Eight levels of the print presence / absence pattern (two patterns) of 10 drops (-3λ to + 3λ, + 5λ, + 7λ, + 10λ, and + 13λ) in the vicinity of the target ink drop, and ink drops of + 14λ to + 77λ at a further distance the test pattern print density representative to place print presence pattern (2 ^triplicate) constant bound and 2 ¹⁰ × 2 ³ = 8192 types of each stage performing actual measurement. As a pre-measurement step, one ink droplet is caused to fly over the scanning range
The amount of charge (applied voltage to the charging electrode 42) for reaching the zero-point printing position is obtained in advance, for example, theoretically or experimentally. In the actual measurement, first, ink droplets are caused to fly in each of the test patterns, and charge control is performed so that the target ink droplet has a predetermined charge amount based on the position to be printed as described above (no correction). At this time, a deviation between a position to be printed on the recording paper 45 and an actually printed position is measured. This measurement is performed by an image measuring device including a microscope, a CCD camera, a CRT, a computer, and the like. Then, a specific charge correction amount is obtained from the deflection amount necessary to eliminate the deviation, and the charge correction amount is added to the charge amount determined based on the print position (considering the sign), the print position and the pattern are corrected. Is generated (voltage value applied to the charging electrode 42) corresponding to. This charged data is stored in each printing position (for example, 60 points) at each printing presence / absence pattern (for example, 81
The print position and the print presence / absence pattern (corresponding to the print presence / absence pattern of nearby ink droplets and the print density of distant ink droplets) are stored in the ROM 30. In addition, it took about 8 hours to perform the process from the measurement of the deviation in all the patterns for all the printing positions to the generation of the charging data. The above configuration is for one nozzle in the ink droplet generator 40,
Actually, a charging control system having a configuration similar to the above is provided for each nozzle. However, strictly speaking, the contents of the ROM 30 must be changed for each nozzle,
Actually, there is almost no difference in the printing state even though the contents in the ROM 30 corresponding to each nozzle are the same. When actually performing charging control on the charging electrode 42 for the ink droplet ejected from each nozzle 41 of the ink droplet generating device 40, the controlled ink droplet is controlled based on the dot print data stored in the register 17 from the shift register 16. , While the print density of 64 distant droplets from 14λ of the controlled ink droplet is detected by 3-bit data stored in the register 28 via the density detector 26. . And
When data on the printing position of the controlled ink droplet is set in the register 24,
The ROM 30 is accessed based on the position data, the printing presence / absence data of the above-described nearby droplets, and the printing density data of the distant droplets, and the applied voltage of the charging electrode 42 is controlled based on the corresponding charging data. Then, the controlled ink droplet is charged with an amount corresponding to the electric field strength when passing between the charging electrodes 42, and undergoes a deflecting action according to the charging amount when passing between the deflecting electrodes 43. The ink reaches the recording paper 45 while being subjected to an electrostatic action or an aerodynamic action from each ink droplet in the vicinity of the flight path. At this time, since the charge amount of the controlled ink droplet is determined in consideration of the electrostatic and aerodynamic effects of the nearby ink droplet and the predetermined distant ink droplet in the flight system of the ink droplet, the amount of charge on the recording paper 45 is determined. Is substantially the same as the target printing position based on the image information. Looking at the specific effects of variations in the printing position, the variations at each printing position between linear printing and solid printing are controlled by only position data (image information) (
(Without correction), a variation of 120 μm at the maximum was confirmed. On the other hand, when the charge was corrected in consideration of only the printing presence / absence pattern of the nearby 10 drops, the variation was at most 70 μm.
μm, and when the charge was corrected in consideration of the print density of 64 droplets farther than 14λ as in the above-described embodiment, the above variation was 10 μm or less. In addition, the number of charged data stored in the ROM 30 is 60 × 2 ¹⁰ × 2 ³ = 491520 despite the consideration of 10 drops of nearby ink drops and 64 drops of distant ink drops. In the above embodiment, the charging data read from the ROM 30 takes into account the basic factors of the printing position, but when determining the charging data in the ROM 30, the charging data in the ROM 30 depends on the printing presence / absence pattern of nearby ink droplets and the printing density of distant ink droplets. The charge correction control based on this is considered. Therefore, it is also possible to adopt a configuration in which the charge amount based on the print position is corrected based on the print presence / absence pattern in the actual charge control. FIG. 5 is a diagram showing another embodiment of the charging control system. In this example, a ROM that stores charging data determined based on printing position data and a printing presence / absence pattern of nearby ink droplets and a ROM that stores charging correction data determined based on the printing density of distant ink droplets are separated. It is for the body. In such a mode, the influence of the distant ink droplet on the target ink droplet (mainly aerodynamic effect) occurs to some extent independently of the influence of the nearby ink droplets (electrostatic effect and aerodynamic effect), and This is based on the premise that it does not depend much on the printing position. In FIG. 5, a ROM 30a storing charging data determined based on the printing position data of the ink droplet of interest and the printing presence / absence pattern of ink droplets in the vicinity thereof is determined based on the printing density of the distant ink droplet of the ink droplet of interest. R storing charge data
OM30b. The ROM 30a is accessed by the print position data of the controlled ink droplet set in the register 24 and the print presence / absence pattern data of the neighboring ink droplet set in the register 17, while the ROM 30b is accessed by the register 28.
Is accessed by the print density data of the distant ink droplet set in the
The charge data read out from 30a and 30b is added by the arithmetic unit 31, and the added charge data forms the basis for controlling the voltage applied to the charging electrode. In this embodiment, RO
The configuration before M30a and M30b and the configuration after the operation unit 31 are the same as those shown in FIG. The charging data to be stored in the ROMs 30a and 30b is determined as follows. Ink droplets are caused to fly in each of the printing presence / absence patterns (2 ¹⁰ = 1024 patterns) that can be taken by the 10 ink droplets in the vicinity of the target ink droplet, and the printing position and the printing position are determined based on the deviation from the printing position, as in the above embodiment. The charging data corresponding to the presence / absence pattern is determined.
On the other hand, the charging data relating to the influence of the distant ink droplets is 8 for the representative print presence / absence pattern of 10 drops in the vicinity of the target ink drop to be printed at a position represented by 60 points and for the further distant ink drops + 14λ to + 77λ. It is determined by actually measuring 2 ³ = 8 test patterns obtained by combining predetermined printing presence / absence patterns representing the printing density of each stage. That is, the flying is performed in each test pattern, and the charging control is performed so that the target ink droplet has a charging amount determined in accordance with the representative printing position and the representative printing presence / absence pattern of the neighboring ink droplet (only the neighboring ink droplet is considered). At this time, a deviation between the position to be printed on the recording paper 45 and the actually printed position is measured, and charging data is determined based on the deviation amount. As a result, charging data corresponding to only the influence of the distant ink droplet is obtained. In the case of the above embodiment, the effect is that printing is performed under the same conditions as in the example shown in FIG. 2, and the variation in the printing position is 15 μm or less, and compared with the above-described embodiment (control system in FIG. 2). No significant deterioration that could cause a problem in image quality was observed. Further, in this case, the number of data in the ROM 30a is 60 × 2 ¹⁰ = 61440,
Since the number of data of 30b is 2 ³ = 8 (491520) as compared with the previous embodiment, the number of charged data to be stored extremely is reduced and the data measurement man-hour is also reduced. Although the respective charging data from the ROM 30a and the ROM 30b are added to obtain the final charging data, other operations such as subtraction and multiplication may be adopted in consideration of the actual recording state. In the case of the above embodiment, when determining the charging data in the ROM 30a, charging correction control based on the printing presence / absence pattern of the neighboring ink droplets is taken into consideration.
The charge correction control based on the print presence / absence pattern of the nearby ink droplet and the print density of the distant ink droplet is considered in the entire charge data from b. [Effects of the Invention] As described above, according to the present invention, when a nozzle ejects ink droplets to a plurality of printing positions within a predetermined scanning range, ink droplets continuously ejected from the nozzles are ejected. In accordance with image information, control is performed for each printing position to charge the ink, and the charged ink droplet is deflected by an electric field to control the presence or absence of dot printing at a predetermined printing position on a recording medium arranged opposite to the nozzle. In the charge control type inkjet printer described above, the charge correction amount for the target ink droplet is determined in advance for each printing position from the printing presence / absence pattern of the nearby ink droplet and the printing density of the distant ink droplet selected according to the scanning method. In the actual charge control, the controllable ink droplet is charged with the predetermined charge correction amount corresponding to the print presence / absence pattern of the nearby ink droplet and the print density of the distant ink droplet. Since the charge correction is performed for each printing position, it is possible to perform charge correction control substantially sufficiently considering the influence of the distant ink droplet without increasing the number of reference ink droplets at a distant place. As a result, dot printing with less deflection distortion can be realized without particularly increasing the capacity of a memory for storing data relating to the charge correction amount, and the recording image quality can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing an example of the basic configuration of a charging control device employing an ink droplet charging control method according to the present invention, and FIG. FIG. 4 is a diagram showing a specific configuration example of the density detector, FIG. 4 is a timing chart showing an operation example of the density detector, FIG. 5 is a diagram showing another embodiment of the charging control device, and FIG. FIG. 7 is a diagram showing an example of a basic configuration of a control type ink jet printer, FIG. 7 is a diagram showing an example of a flight path of an ink droplet, FIG. 8 is a diagram showing a relationship between a reference ink droplet and an effect of reducing deflection distortion, and FIG. FIG. 10 is a diagram showing a relationship between a reference ink droplet and a required memory capacity, and FIG. 10 is a diagram showing an example of interlaced scanning. [Description of Signs] 1 ... Nozzle, 2 ... Ink droplet, 3 ... Recorded body, 10 ... Image data processing device, 16 ... Shift register, 17, 24, 28 ... Register, 18 ... Timing controller, 20 ... Counter, 22
... ROM (for position data), 26 ... Density detector, 30 ... ROM (for charging data), 32
... Charging data processor, 34 ... D / A converter, 42 ... Charging electrode.

Claims (1)

Claims: When a nozzle (1) ejects an ink droplet (2) to a plurality of printing positions within a predetermined scanning range,
Mark in accordance ink droplets are continuously ejected from the nozzle (1) and (2) the image information (I)
It controls and charges each character position, deflects the charged ink droplet by an electric field, and controls the presence or absence of dot printing at a predetermined printing position on a recording medium (3) arranged opposite to the nozzle (1). there thus charge control type inkjet printer was, Ri predetermined vicinity near the focused ink droplets (do), and static with respect to the focused ink droplets (do)
Ink drops selected according to the scanning method assuming that electrical and aerodynamic effects are expected
(dn) print presence / absence pattern {P (dn)} and the ink droplet (d
f) print density {D (df)} and the charge correction amount {Ac (
P, D)｝ is predetermined for each printing position , and when charging control is performed for the ejected ink droplet, the printing presence / absence pattern (P) of the ink droplet (dn) in the predetermined vicinity of the controlled ink droplet (do)
And the print density (D) of the ink droplet (df) farther than the above-mentioned nearby ink droplet (dn) is detected, and the print density (D) corresponding to the detected print presence / absence pattern (P) and the print density (D) is detected. A charge control method for an ink droplet in a charge control type ink jet printer, wherein charge correction control for a jetted ink droplet is performed for each printing position with a predetermined charge correction amount {Ac (P, D)}.