JPH0355263A - Ink droplet charge control system for charge control type ink jet printer - Google Patents

Abstract

PURPOSE:To improve a recording quality by correcting charge of an ink droplet to be controlled with a predetermined charge correction amount corresponding to print presence/absence pattern of a vicinity ink droplet. CONSTITUTION:A charge correction amount Ac(P) for an ink droplet do to be noted is predetermined corresponding to a print presence/absence pattern P(dn) of a vicinity ink droplet in response to the coupling pattern P(dn, df) of the pattern P(dn) of the ink droplet dn in predetermined vicinity of the droplet dn and print presence/absence pattern (df) relative to the print presence/ absence pattern P(dn) of the vicinity ink droplet of the ink droplet df disposed remotely from the vicinity, and an injecting ink droplet is charge-controlled. In this case, the pattern P of the droplet dn in predetermined vicinity of the droplet do to be controlled is detected, and injecting ink droplet is charge correction-controlled by the predetermined amount Ac(p) corresponding to the detected pattern P. Thus, an effect equivalent to the correction considered for substantially more reference ink droplets can be obtained even in case of the charge correction considered for the less reference ink droplets.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a charge control type inkjet printer, and specifically, to a charge control type inkjet printer, specifically, a W! A charging control method for ink droplets in a charge control type inkjet printer that controls whether or not to print dots on a recording medium placed opposite a nozzle by applying an electric current and deflecting the charged ink droplets using an electric field. Regarding.

[Prior art] The basic structure of a charge control type inkjet printer is as follows.
For example, as shown in Fig.
See Publication No. 25971>.

This includes a pair of band'R electrodes 4 in front of each nozzle 41 arranged at a predetermined corner on the front surface of the ink droplet generating device 1f40.
2 is arranged, and a pair of deflection electrodes 43 are further arranged in front of it, and the ink droplets ejected from each nozzle 41 sequentially pass between the charging electrodes 42 and between the deflection electrodes 143, and are arranged opposite to the nozzle 41. It is configured such that the recording paper 45 is reached. In such an inkjet printer, voltage control is performed on the charging electrode 42 based on image information while a steady electric field is formed by the deflection electrode 43. As a result, the flying ink droplets are charged in accordance with the image information, and these charged ink droplets are
It flies toward the recording paper 45 under the deflection action according to I and the deflection electric field. That is, 14 for recording based on image information.
The dot printing position on 5 is controlled by the amount of charge on the ink droplet.

Note that charging control is performed so that the non-printing dots receive a deflection action sufficient to reach the gutter 46, and this gutter 4
The ink supplemented in step 6 is collected by the ink droplet generating device 40.

More specific charging control for the ink droplets has conventionally been carried out, for example, as follows.

For example, as shown in FIG. 4, at the moment when the ink ■ ejected from each nozzle 41 of the ink droplet generator 0 is turned into droplets by ultrasonic vibration or the like, a voltage is applied to the charged 14i42, and the ink droplet is Charging is performed on dO. The order (scanning method) of dot printing positions is determined in advance in the scanning range for each nozzle (between the stitching points SP in Figure 3), and the presence or absence of printing (image information) for each printing position according to this order is determined in advance. (correspondence), the charging member for the controlled ink droplet do is determined.

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 effect from the ink droplets before and after it. Therefore, even if the ink droplets have the same amount of charge, the printing position will shift depending on the state of the ink droplets flying forward and backward (deflection distortion). In order to prevent such deflection distortion, conventionally, the charging matrix is corrected depending on the state of the ink droplets flying forward and backward. Specifically, the amount of charge is corrected as follows.

The flight path of ink droplets is determined by the gutter 46 when printing (fl, f2, f3 in Fig. 4) and when printing.
There are various possible deflections for the deflection (f4 in FIG. 4), but the electrostatic and aerodynamic effects on other ink droplets differ depending on which path the ink droplet flies. From this, we assume different printing presence/absence patterns for ink droplets that exist in a predetermined vicinity of the ink droplet of interest, for example, about 6 drops before and 6 drops after, and in each pattern, the ink droplet of interest can achieve the desired printing. 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 advance in a memory such as a ROM.

Then, during actual printing, the printing presence/absence pattern of ink droplets in a predetermined vicinity of the controlled ink droplet is detected, the charge correction value corresponding to the detected printing presence/absence pattern is read from the memory, and the charge correction amount is Charge correction control is performed.

In the conventional ink droplet charge control method, in which the amount of charge corresponding to image information is corrected based on the printing/non-printing pattern of neighboring ink droplets, each ink droplet is subject to electrostatic charge caused by neighboring ink droplets. This will take into account the aerodynamic effects and reduce the deflection distortion.

[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.

This is based on the following reasons.

As shown in FIG. 5, in order to reduce the deflection distortion, it is necessary to increase the number of ink droplets (reference droplets) that should be considered as having an influence on the ink droplet of interest. However, as the number of reference ink droplets increases, the number of printing/presence patterns with the reference ink droplets increases, and the capacity of the memory that stores the charge correction amount in association with the printing/presence patterns increases as shown in FIG. I end up. For example, set the reference ink drop to 100
In the case of droplets, there are 2100 printing/non-printing patterns, and the storage capacity thereof is enormous, making it difficult to realize it in an actual memory device. Furthermore, it would take an enormous amount of time to actually reproduce the printing/non-printing pattern and measure each data, which is not practical.

Therefore, an object of the present invention is to obtain an effect equivalent to that of a correction that takes substantially more reference ink droplets into account even if the charging correction takes into account a smaller number of reference ink droplets.

[Means for Solving the Problems] As shown in FIG. 1, the present invention charges ink droplets 2 continuously ejected from a nozzle 1 according to image information I, and deflects the charged ink droplets by an electric field. The present invention is based on a charge control type inkjet printer that controls whether or not to print dots on a recording medium 3 disposed opposite the nozzle 1. , the technical means for solving the above problem is based on the printing presence/absence pattern P (dn) of the ink droplet dn located in a predetermined vicinity of the focused ink droplet do, and the printing/non-printing pattern P (dn) of the ink droplet dr located further away from the concerned ink droplet do. Combined pattern P (dn, df) with printing presence/absence pattern P (df) related to printing presence/absence pattern P (dn)
) for the relevant ink droplet do? V! The i correction m A c (P) is predetermined in association with the printing presence/absence pattern P (dn) of the nearby ink droplets, and when performing charging control on the ejected ink droplets, the ink droplets in a predetermined vicinity of the controlled ink droplet do The printing presence/absence pattern P of dn is detected, and the charging correction control for the ejected ink droplets is performed using the predetermined charging correction amount ACCP) corresponding to the detected printing presence/absence pattern P.

[Function] When ink droplets 2 are continuously ejected from the nozzle 1, each ink droplet is ejected from other ink droplets by electrostatic rll-1 due to electrostatic repulsion while flying to the recording medium 3. It is affected by aerodynamic effects such as turbulence of airflow around the route. here,
The ink droplet dn located near the ink droplet do of interest exerts both the electrostatic influence and the aerodynamic influence, whereas the ink droplet dfl. t focused ink droplet dO
There are few electrostatic influences, and most of them are aerodynamic influences.

Furthermore, when looking at general images other than images (character images, etc.), which have a particularly large variation by m degree, the pattern variation of the presence or absence of printing is small.

Because of this relationship, while considering all possible print presence/absence patterns for the nearby ink droplet dn, which has a larger influence (both electrostatic influence and aerodynamic influence), IwJ only> For distant ink droplets (H), the charge correction amount is determined by considering only the printing presence/absence pattern related to each printing presence/absence pattern of the above-mentioned nearby ink droplets dn.

That is, each printing presence/absence pattern P (d
In accordance with the combination pattern P (dn, df) of the printing presence/absence pattern of the distant ink droplet (n) and the printing presence/absence pattern of the distant ink droplet (dn, df), the charge correction suspension AC(P) for the relevant ink droplet do is determined by the printing presence/absence pattern P of the nearby ink droplet. (dn). In reality, ink droplets are continuously flown in a state in which a nearby ink droplet dn in a certain printing pattern and a distant ink droplet in a related printing pattern exist. The charge correction amount is determined while determining the amount of deviation from the print position (determined based on image information), and the charge correction value is associated with the print presence/absence pattern P (dn) of the relevant nearby ink droplet dn.

Here, the printing presence/absence pattern P (df) of distant ink droplets df, which should be taken into consideration when determining the charging correction value, is based on the nature of the image to be formed (state of density change, etc.) or the order in which dots are printed in the scanning range. Printing presence/absence pattern P (dn) of neighboring ink IDn depending on conditions such as whether to print or not (scanning method), etc.
associated with. In particular, when an image without sudden density changes is targeted, there is little variation in the overall print presence/absence pattern. It is also possible to use the same pattern as the printing presence/absence pattern P (dn). In this way, making the printing presence/absence pattern P (df) of the distant ink droplets df, which should be considered, the same as the printing presence/absence pattern P (dn) of the nearby ink ldn is based on pattern reproduction when determining the charge correction output. This is preferable because it facilitates processing such as actual measurement. The printing presence/absence pattern of the distant ink droplet is said to be the same as the printing presence/absence pattern of the nearby ink droplet when the printing presence/absence pattern of the distant ink droplet is exactly the same as the printing presence/absence button of the nearby ink droplet, and This includes any case where the same pattern as the print presence/absence pattern is repeated multiple times. This relationship is determined depending on the range to be considered as a nearby ink droplet or a distant ink droplet.

Nearby ink droplets dn and distant ink droplets d to be considered above
It is better to have as many f as possible, but in reality, depending on the required performance (allowable deflection distortion), etc., the number of ink droplets dn should be set within a range where the electrostatic influence cannot be ignored. The distance ink droplet df is determined within a range where the aerodynamic influence cannot be ignored.

As described above, the charge correction I for the ink droplet of interest do
When performing charging control on ejected ink droplets in a state where A cfP) is predetermined, in addition to charging control based on basic image information I, the printing presence/absence pattern P (dn) of neighboring ink droplets dn is detected. Then, the predetermined charge correction amount A corresponding to the detected printing presence/absence pattern P
Charge correction control is performed at c(P). In this charging control of ejected ink droplets, the bartan of the ink droplets dn in the vicinity of the target υJllll ink drop do is actually detected, but the ink droplets in the distance are not actually considered a problem. Therefore, the actual printing presence/absence pattern of distant ink droplets does not necessarily match the printing presence/absence pattern assumed when determining the above-mentioned charge correction amount. However, the printing presence/absence pattern assumed when determining the above-mentioned charge correction amount is determined based on the actual printing conditions such as the properties of the image to be formed (density distribution, etc.), scanning method, etc. in relation to the printing presence/absence pattern of nearby ink droplets. Therefore, if the printing presence/absence pattern of the nearby ink droplets is detected, the actual printing presence/absence pattern of the distant ink droplets df will not differ significantly from the printing presence/absence pattern assumed when determining the above charge correction amount. Therefore, the actual aerodynamic influence on the controlled ink droplet do is not significantly different from that assumed when determining the charge correction function.

[Example] Embodiments of the present invention will be described below based on the drawings.

The basic structure of the entire printer is similar to that shown in FIG. In addition, the recording conditions are dot density...24 dots/order Ink droplet size...30μ droplet formation speed...25 Q Ktlz ink droplet initial velocity...20m/sec Deflection width...2.5 order Number of dots: Assuming 60 dots/scan.

A control system for the charging electrode 42 is, for example, as shown in FIG.

In the figure, 10 is an image data processing device 1, and this image data processing device 10 converts image data from an image reading device 12 such as an image scanner or an image data generating device 14 constituted by a computer or the like to the printer. It converts into dot print data (image information) that conforms to the .

Reference numeral 16 denotes a serial-in/parallel-out shift 1-register, and this shift register 16 stores dot print data sequentially output serially from the image data processing device RA10. Print data is stored for each ink droplet in the range (-3λ to +18λ) between 3v4 and 18 front drops (hereinafter, the rear is represented by + and the number of drops is represented by λ). Among the parallel outputs of the shift register 16, the shift register 16 and the register are arranged so that only dot print data corresponding to ink droplets that are expected to have a particularly large electrostatic and aerodynamic influence on the ink droplet of interest are stored in the register 17. 17 is connected. The dot print data to be stored in this register 17 differs depending on the scanning method in the main scanning direction, but
For example, according to the interlaced scanning method as shown in FIG. 7, -3λ to +3λ, +5λ, +7λ, +8λ, . +
10λ, +13λ. ◆Dot print data corresponding to 18λ (total 121*) is selected. This is −3λ~+
The 3λ ink droplet flies very close to the ink droplet of interest, and the +5λ. ◆7λ, +8λ, +10λ, +1
This is because the flight path of the ink droplets of 3λ and +18λ is close to the flight path of the ink droplet of interest when the interlaced scanning method is followed. Furthermore, Figure 7 shows the order of generation of ink droplets.
This figure shows the relationship between the drop numbers (1 to 60) and their printing positions (dot positions: 1 to 60), where the numbers outside the parentheses indicate the drop numbers and the numbers in the parentheses indicate the dot positions.

20 is a sexagesimal counter, 22 is a ROM that outputs position data corresponding to the count value of the counter 20;
Position data output from the OM 22 is set in the register 24. Counter 20, ROM2
2. The register 24 constitutes a position data generation circuit. The contents of the ROM 22 include printing position data according to the interlaced scanning method corresponding to each count value, such as the -Itth printing position, the second printing position, etc. Since 60 dots are printed between each stitching point SP (see recording conditions), this stored position data has a one-to-one correspondence with the count values from 0 to 59. The register 16 and the counter 20 perform a shift operation and a counting operation based on a timing clock from a timing controller 18, and the timing clock from the timing controller 18 is synchronized with the droplet formation timing in the ink droplet generator 40. ing.

As described above, the dot print data (12 bits) corresponding to 12 droplets near the ink droplet of interest set in the register 17 and the print position data (6 bits) of the ink droplet of interest set in the register 24 are parallelized. This is the address input for the ROM 30. This ROM 30 stores in advance the amount of charge for the ink droplet of interest, and the read charge data is transferred to a charge data processing device 32 that performs processing such as correction for each nozzle, and then to a D/A converter 34 before being converted into reality. is converted into a voltage output, and this converted output is applied to the charging electrode 42.

The contents of the ROM 30 are as follows.

For charging data, data determined based on actual measurements is stored in association with each address input.

12 droplets near the ink droplet of interest (-3λ to +3λ, +5λ.
+7λ. +8λ. +10λ. Regarding the 2 12 = 4 0 9 6 test patterns that combine the printing presence/absence pattern of +13λ, +18λ) and the printing presence/absence pattern in which the printing presence/absence pattern of the neighboring ink droplet is repeated four or more times with ink droplets further away. Perform actual measurements.

In the pre-measurement step, the charging voltage (voltage applied to the band 'l1i electric viA42) for making the ink droplet fly at 1 wA and reach each of the 60 printing positions within the scanning range on the recording paper 45 is calculated, for example, theoretically. Alternatively, it can be experimentally determined in advance.

In the actual measurement, first, ink droplets are made to fly according to each of the above test patterns, and charging control is performed so that the ink droplet of interest has a predetermined band II amount based on the position to be printed as described above (no correction). At that time, the deviation between the position to be printed and the position actually printed on the recording paper 45 is measured. This measurement can be performed using a microscope, COD camera, or CRT.
This is carried out using an image measuring device composed of a computer or the like.

Then, calculate the specific charge correction amount from the deflection point necessary to eliminate this deviation, add the charge correction period to the band W1 determined based on the above print position (considering the positive and negative), and add the charge correction amount to the print position and Charging data corresponding to the pattern (charging electrode 4
2). This charging data is used for each printing position (for example, 60 points) and each printing presence/absence pattern (for example, 4 points).
096 ways), and the corresponding printing position [(6 bits)
and the print presence/absence pattern (12 bits) of nearby ink droplets and are stored in the ROM 30.

The above configuration is the ink droplet generator fl! This is for one nozzle in 40, and in reality, a charging control system having the same configuration as above is provided corresponding to each nozzle.

However, strictly speaking, the contents of the ROM 30 must be changed for each nozzle, but in reality, the R
Even though the contents of OM30 are the same, there is almost no difference in the printing condition.

When the charging electrode 42 actually controls the charging of the ink droplets ejected from each nozzle 41 of the ink droplet generating device 140, the controlled ink droplets are determined based on the dot printing data stored in the register 17 from the shift register 16. neighborhood 12
The print pattern of droplets cannot be detected. Then, when the data regarding the printing position of the controlled ink droplet is set in the register 24, the ROM 30 is accessed based on this position data and the printing presence/absence pattern data of the neighboring droplet.
The voltage applied to the charging electrode 42 is controlled based on the corresponding charging data.

Then, when the controlled ink droplet passes between the charging electrodes 42, it is charged in an amount corresponding to the electric field strength, and when it passes between the deflection electrodes 43, it is deflected according to the amount of charge, and further The ink drops reach the recording paper 45 while receiving electrostatic or aerodynamic action from each ink droplet near the flight path. At this time, the charge base of the controlled ink droplet is determined by the electrostatic charge of the nearby ink droplet and the distant ink droplet in the flight system of the ink droplet.
Since this is determined in consideration of aerodynamic effects, the actual printing position on the recording paper 45 is approximately the same as the intended printing position based on the image information.

Looking at the specific effect on the variation in printing position, the variation in each printing position between straight printing and solid printing is as follows.
When controlling only with position data (image information) (no correction), a maximum variation of 120 μm was confirmed, whereas when charging was corrected by considering only the print presence/absence pattern of 12 nearby drops, the above variation was reduced. 70 μm door, and furthermore, when charging was corrected by taking into consideration the printing/non-printing pattern of nearby ink droplets and the distant ink droplets in the same pattern (repeated 4 times) as in the above example, the above variation became 10 μm or less. .

However, in areas where the image angle of 81 degrees suddenly changes (parts such as characters), the above fluctuation is 15 μml! i! However, this difference is almost invisible to the naked eye and is at a level that is practically unacceptable.

Also, the number of charging data stored in ROM'30 is 60X
2"245760, which is the same as when only 12 nearby ink droplets are considered.

In the above embodiment, the charging data read from the ROM 30 takes into account the basic factors of the print position, but when determining the charging data in the ROM 30, the printing presence/absence pattern of nearby ink droplets and the pattern of distant ink are used. This takes into account charge correction control based on a combined pattern of droplet print/absence patterns. Therefore, in actual charging control, it is also possible to adopt a configuration in which the amount of charging based on the printing position is corrected based on the printing presence/absence variation.

[Effect of the Invention J As explained above, according to the present invention, the printing presence/absence pattern of neighboring ink droplets and the printing presence/absence pattern of ink droplets located further away from the neighboring ink droplets related to the printing presence/absence pattern of the neighboring ink droplets are determined. The charge collection amount for the ink droplet of interest is determined in advance in accordance with the combination pattern with the pattern, in correspondence with the printing presence/absence pattern of the neighboring ink droplets, and during actual charging control, the amount of charge collection for the focused ink droplet is determined in advance in correspondence with the printing presence/absence pattern of the neighboring ink droplets. Since the charge correction for the controlled ink droplet is performed using the above predetermined charge correction amount, the charge can be substantially sufficiently taken into account the influence of the distant ink droplet, even without increasing the number of reference droplets particularly far away. Correction control becomes possible. As a result, dot printing with less deflection distortion can be realized without particularly increasing the capacity of the memory that stores data regarding the charge correction amount, and the quality of recorded images can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the structure of the present invention, FIG. 2 is a diagram showing an example of the basic configuration of a band N control device adopting the ink droplet charging control method according to the present invention, and FIG. 3 is a diagram showing the charging control method. Figure 4 is a diagram showing an example of the flight path of an ink droplet, Figure 5 is a diagram showing the relationship between a reference ink droplet and the effect of reducing deflection distortion, and Figure 6 is a diagram showing an example of the basic structure of an inkjet printer. 7 is a diagram showing the relationship between reference ink droplets and necessary memory capacity, and FIG. 7 is a diagram showing an example of the state of interlaced scanning. [Description of symbols] 1... Nozzle 2... Ink droplet 3... Recording body 10... Image data processing device 16... Shift register 17.24... Register 18... Timing controller 20... Counter 22... ROM (for position data) 30... ROM (for charging data) 32... Charge data processing device 34... D/A converter 42... Band m electrode

Claims (2)

[Claims] (1) Ink droplets (2
) is charged in accordance with image information (I), and the charged ink droplets are deflected by an electric field to control whether or not dots are printed on a recording medium (3) placed opposite the nozzle (1). In a charge-controlled inkjet printer, an ink droplet (dn
) and the printing presence/absence pattern {P(df)} related to the printing presence/absence pattern P(dn) of the neighboring ink droplet (df) located further away from the neighboring ink droplet (df). The bonding pattern with {P(dn, df)
}, the charge correction amount {Ac(P)} for the ink droplet of interest (do) is predetermined in association with the printing presence/absence pattern {P(dn)} of the neighboring ink droplets, and charge control is performed for the ejected ink droplet. When performing this, an ink drop (d) in a predetermined vicinity of the controlled ink drop (do)
n) is detected, and the charge correction control for the ejected ink droplets is performed using the predetermined charge correction amount {AC(P)} corresponding to the detected print presence/absence pattern (P). Characteristic charge control method for ink droplets in a charge control type inkjet printer. (2) When predetermining the charge correction amount {Ac(P)}, the ink droplet (dn
) of the printing presence/absence pattern {P(dn)} and the same printing presence/absence pattern of the ink droplet (df) located in the vicinity of the ink droplet (df) located further away from the said neighborhood {P(dn)
, df)}, the charge correction amount {Ac(P)} for the ink droplet of interest (do) is set as the neighboring ink droplet (dn).
2. A charge control method for ink droplets in a charge control type inkjet printer according to claim 1, characterized in that the method is determined in association with a printing presence/absence pattern {P(dn)}.