JP2007152784A - Inkjet printer registration adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: In the case of performing resist adjustment, as the droplet size and the image quality increase, the influence of carriage vibration that occurs when an adjustment pattern group is formed by printing has become ignorable.
The vibration generated by the reciprocating movement of the carriage includes a region that is stable only in the forward direction, a region that is stable only in the backward direction, and a region that is stable in the reciprocating direction. A bidirectional adjustment pattern for calculating a reciprocal adjustment value is printed in an area where the reciprocation is stable. By arranging a pattern that can be adjusted in one direction in another area, it is possible to realize registration adjustment that is not affected by vibration during carriage reciprocation.
[Selection] Figure 5

Description

  The present invention relates to a resist adjustment technique between heads (main scanning direction) and between forward printing and backward printing in an inkjet printer.

Using a conventional ink-jet printer registration adjustment method provides a printer with high cost performance that can perform registration adjustment close to actual printing with a relatively inexpensive detection mechanism compared to the method of detecting the edge position of the adjustment pattern. be able to. (For example, see Patent Document 1)
Japanese Patent Laid-Open No. 10-329381

  However, in recent years, ink droplets have been reduced with the demand for higher image quality, and even higher accuracy has been required for this resist adjustment system, leading to the following inconveniences.

  That is, the influence on the density caused by the unique situation when the adjustment pattern group is printed, for example, the vibration of the carriage, the floating of the paper, and the like cannot be ignored when detecting the optimum resist value. Conventionally, the landing deviation that occurs under such a unique situation was relatively small compared to the ink dot size on the paper, so the influence on the density of the adjustment pattern group was very small. The relative influence increases with the miniaturization of the size, and the registration adjustment value is calculated and determined using the detection value having an error due to the landing position deviation, so that sufficient registration adjustment accuracy cannot be obtained.

  As a matter of course, as the droplet size is reduced, the mechanical accuracy is improved to ensure the quality during normal printing. However, a configuration that covers even a phenomenon under a specific situation is not preferable from the viewpoint of cost performance.

  On the other hand, since the adjustment value acquired in the registration adjustment is continuously used for normal printing, the influence becomes large even if the situation is unusual.

  Accordingly, the present invention provides a highly accurate resist adjustment method that avoids the influence of disturbances such as carriage vibration and paper floating when printing an adjustment pattern group used for resist adjustment, and an ink jet printer using the same. The purpose is to provide.

  In the present invention, there are at least two types of registration adjustment patterns of forward printing, backward printing, and reciprocating printing, and each of the registration adjusting patterns is arranged at a position where the vibration during the reciprocating movement of the carriage is not affected.

  Furthermore, for the purpose of improving the detection accuracy, the sensor has a sensor for measuring the distance between the print head and the recording material, and before printing the resist adjustment pattern, the distance is set over the entire region of the recording material in the main scanning direction. The resist adjustment pattern was printed in an area where the amount of variation was small.

  The present invention is a method for avoiding the influence of deviation of landing position due to disturbance on registration adjustment. By using this method, it is possible to eliminate the influence of the landing position deviation caused by a unique situation (disturbance) when the adjustment pattern group is printed and formed, for example, vibration of the carriage, floating of the paper, and the like. For this reason, it is possible to obtain an optimum registration adjustment value with high accuracy. Accordingly, it is possible to provide a printing apparatus that can perform printing with high registration adjustment accuracy.

  First, in order to help the understanding of the present invention, an explanation will be started from an outline of the configuration and conventional automatic registration adjustment, taking an ink jet printer suitable for application of the present invention as an example.

  FIG. 1 is a perspective view showing a configuration example of a preferred color inkjet printing apparatus in which the present invention is implemented or applied. In the figure, the front cover is removed and the inside of the apparatus is exposed.

  In the figure, 1000 is a replaceable ink jet cartridge, and 2 is a carriage unit for detachably holding the ink jet cartridge. Reference numeral 3 denotes a holder for fixing the ink jet cartridge 1000 to the carriage unit 2. When the ink jet cartridge 1000 is mounted in the carriage unit 2 and the cartridge fixing lever 4 is operated, the ink jet cartridge 1000 is interlocked with the carriage unit 2. 2 is pressed. In addition, positioning of the ink jet cartridge 1000 is performed by the press contact, and at the same time, a contact between a required signal transmission electrical contact provided on the carriage unit 2 and an electrical contact on the ink jet cartridge 1 side is performed. Reference numeral 5 denotes a flexible cable for transmitting an electric signal to the carriage unit 2.

  In the figure, reference numeral 30 denotes a reflective optical sensor. This functions to detect the density of the adjustment pattern group printed on the paper in the automatic registration adjustment system of the present invention. The density of the adjustment pattern group printed on the paper can be arbitrarily detected by the cooperative action of the paper feeding and the scanning of the carriage to which the optical sensor 30 is attached. Further, it may also be used as a sheet edge detection means.

  A carriage motor 6 serves as a drive source for reciprocally scanning the carriage unit 2 in the main scanning direction, and a carriage belt 7 transmits power to the carriage unit 2. Reference numeral 11 denotes a guide shaft which exists in the main scanning direction and supports the carriage unit 2 and guides its movement. Reference numeral 9 denotes a transmissive photocoupler attached to the carriage unit 2, and 10 denotes a light shielding plate provided near the carriage home position. A home position unit 12 includes a recovery system such as a cap member that caps the front surface of the inkjet head, suction means that sucks the inside of the cap, and a member that wipes the front surface of the head.

  Reference numeral 13 denotes a discharge roller for discharging the print medium. The print medium is sandwiched in cooperation with a spur roller (not shown), and is discharged outside the printing apparatus. Reference numeral 14 denotes a line feed unit, which conveys a print medium in a predetermined amount in the sub-scanning direction.

  FIG. 2A is a perspective view showing details of the head cartridge 1000. Here, 15 is an ink tank containing black ink, and 16 is an ink tank containing cyan, magenta and yellow inks, which can be attached to and detached from the ink jet cartridge body. Reference numeral 17 denotes a connection port of each color ink stored in the ink tank 16 to the ink supply tube 20 on the ink jet cartridge main body side, and 18 denotes a black ink connection port similarly stored in the ink tank 15, which is held in the ink jet cartridge main body by the connection. Ink can be supplied to the print head 1. Reference numeral 19 denotes an electrical contact portion, which can receive an electrical signal from the printing apparatus main body control portion via a flexible cable in accordance with the contact with the electrical contact portion provided in the carriage unit 2.

  In this example, the Bk ink ejection unit in which nozzles for ejecting Bk ink are arranged, and the nozzle groups for ejecting Y, M, and C inks, respectively, are integrated and correspond to the Bk ejection port arrangement range inline. The head in which the color ink ejection units arranged in parallel are arranged side by side is used.

  FIG. 2B is a schematic perspective view partially showing the main structure of the print head unit 1 of the head cartridge 1000.

  2B, a plurality of discharge ports 22 are formed at a predetermined pitch on the discharge port surface 21 facing the print medium 8 with a predetermined gap (for example, about 0.5 to 2.0 mm). An electrothermal converter (such as a heating resistor) 25 for generating energy used for ink discharge is disposed along the wall surface of each liquid path 24 connecting the common liquid chamber 23 and each discharge port 22. ing. In this example, the head cartridge 1000 is mounted on the carriage 2 in such a positional relationship that the ejection ports 22 are arranged in a direction intersecting the scanning direction of the carriage 2. In this way, the corresponding electrothermal converter (hereinafter also referred to as “ejection heater”) 25 is driven based on the image signal or the ejection signal to cause the ink in the liquid path 24 to boil, which is generated at that time. The print head 1 is configured to eject ink from the ejection port 22 by the pressure of the bubbles.

  FIG. 3 is a schematic diagram for explaining the reflective optical sensor 30 used in the apparatus of FIG. The reflective optical sensor 30 includes a light emitting unit 31 and a light receiving unit 32. The light Iin 35 emitted from the light emitting unit 31 is reflected by the printing medium 8, and the reflected light Iref 37 can be detected by the light receiving unit 32. The detection signal is transmitted as information on the electric board of the printing apparatus.

  In order to detect the density of the adjustment pattern group equal to the visual appearance, the incident angle and the reflection angle are made different to detect irregularly reflected light.

  In order to perform registration adjustment for all heads in charge of discharging each color of C, M, Y, and K, the white LED or three-color LED is used for the light emitting unit and the visible light is used for the light receiving unit. It is assumed that a photodiode is used. However, in the case of the present invention in which the relationship between the relative printing position and the density is detected, and when adjusting between different colors, a three-color LED is used because a color with high detection sensitivity can be selected. It is preferable.

  By the way, even if it says density detection, it is not necessary to detect the absolute value as the detection performance of the sensor, and within each pattern belonging to the adjustment pattern group (one pattern included in the adjustment pattern is hereinafter referred to as a patch). What is necessary is just to have the performance which can detect a relative density difference. With respect to the stability of the detection system, it is sufficient that the optical sensor system has a degree of stability that does not affect the detected density difference until the detection of the set of adjustment patterns. For sensitivity adjustment, for example, the optical sensor 30 is moved to a non-printing portion of the paper, and the LED current is adjusted so that the detection level becomes the upper limit at this location, or the gain of the detection amplifier is adjusted, Adjust the sensitivity. Although sensitivity adjustment is not essential, it is a desirable process for improving the S / N ratio and increasing detection accuracy.

  In such a configuration, conventional resist adjustment is performed as follows.

  First, the head to be aligned is selected, and the first adjustment pattern group is printed on the first adjustment pattern group during the forward pass and the second adjustment pattern group is overlapped with the first adjustment pattern group during the return pass using the head. . For example, the first and second adjustment pattern groups are formed by arranging a plurality of 10 mm square patch shapes in the main scanning direction. However, the printing position between the first and second patches is mainly set in each patch. It is designed to be different by one dot in the scanning direction. The purpose of this adjustment pattern group printing process is to make the printing positions of the patches different for each patch. For example, the same first and second adjustment pattern groups are used, and each patch is used for return printing. The basic idea is to shift the ejection timing of the head in accordance with the printing, but it is usually sufficient to detect patches that are shifted in units of one dot, in which case the dots are shifted by one dot. It is easier to construct an adjustment pattern group and print it.

  Next, the paper is moved in the sub-scanning direction to adjust the position so that the optical sensor can scan each patch as the carriage moves.

  Then, while scanning the carriage at a constant speed, the density of each patch is read by the optical sensor, and the detected value is transmitted to the circuit board. In the circuit board, the detected signal is A / D converted and stored as the density value of each patch. The reason for scanning at a constant speed is to stabilize the posture of the carriage to ensure reading accuracy and to perform spatial filtering on each patch simultaneously by detecting while scanning.

  Finally, the alignment condition of the patch having the lowest density among the patches is adopted as the optimum resist adjustment value. However, depending on how the offsets are given in the first and second adjustment pattern groups, the alignment condition of the patch with the highest density may be adopted, or interpolation / calculation is performed from the alignment conditions of the preceding and following patches. In some cases, an optimum value is obtained.

  The outline of the conventional automatic registration adjustment has been described above based on the configuration of the ink jet printer. From here, the implementation method of this invention is demonstrated.

  A method for arranging the vibration in the carriage reciprocating motion shown in claim 1 at a position where the adjustment pattern printing is not affected will be described.

  The landing position of the droplet is affected by carriage vibration.

  For example, consider a case where the distance between the head and the paper is about 1.6 mm and the carriage speed is 30 inches / s.

  If the distance between the head and the paper fluctuates by 0.3 mm due to the influence of vibration, the landing position will be shifted by 30 μm from the ideal position.

  In the case of printing with fine droplets, the diameter of the landed droplet is about 30 μm (which is a representative value because it is affected by the state of the media). Therefore, the deviation of 30 μm corresponds to one dot of the droplet, and the adjustment pattern printing at the position where the carriage vibrates is not desirable for realizing high image quality.

  The carriage requires the most power when transitioning from the stopped state to the constant speed state. On the other hand, in the constant speed region, since it is power for stabilizing the speed, it is smaller than that at the time of transition. Therefore, the vibration of the carriage from the stop state to the constant speed region becomes larger than the carriage vibration in the constant speed region.

  FIG. 4 shows a measurement example of the speed fluctuation in the CR direction and the carriage position.

  The upper diagram of FIG. 4 shows speed fluctuations in forward driving (drive from HP to BP), and the lower chart shows speed fluctuations in backward driving (drive from BP to HP).

  As shown in FIG. 4, in an inkjet printer that prints while reciprocating the carriage in the main scanning direction, in the drive of the carriage, in the area where only the forward direction vibrates, the area where only the backward direction vibrates, There is an area (the center of the sheet) that is stable both in the reciprocating direction.

  For this reason, if all the adjustment patterns are printed in a region where both reciprocations are stable, an optimum registration adjustment value can be obtained without being affected by vibration.

  However, it is desirable to print all the adjustment patterns at a position with little vibration (the center of the paper), but in this case, the amount of media consumption in the paper transport direction increases.

  Incidentally, there are three types of adjustment in automatic registration adjustment in a typical ink jet printer. The three types are registration adjustment between nozzles in the same color (hereinafter referred to as even / odd adjustment), registration adjustment between chips of other colors (hereinafter referred to as color adjustment), and registration adjustment in reciprocal printing (hereinafter referred to as bidirectional adjustment). .

  Of these three types of registration adjustment, even / odd adjustment and inter-color adjustment can be adjusted by printing in one direction to adjust the state of the nozzle. On the other hand, bidirectional adjustment requires bidirectional printing in order to correct landing position deviations in the forward direction and the backward direction. Therefore, a resist adjustment pattern is arranged as shown in FIG.

  By printing a bidirectional adjustment pattern in a region where carriage vibration is stable during both reciprocations (position B shown in FIG. 5), optimal bidirectional adjustment can be realized.

  On the HP side (position A shown in FIG. 5), an even / odd or inter-color adjustment pattern is printed only by backward printing. When the backward drive is used, since the carriage vibration on the HP side is small, adjustment with little influence of vibration can be realized. Similarly, an adjustment pattern is printed on the BP side only by forward printing (position C shown in FIG. 5).

  With this arrangement of the adjustment patterns, it is possible to realize registration adjustment that avoids the influence of carriage vibration in all three types of registration adjustment patterns in a typical ink jet printer.

  A method for measuring the distance between the head and the paper over the entire main scanning direction and printing the resist adjustment pattern in an area with a small amount of variation will be described.

  By the above method, it is possible to realize registration adjustment that avoids the influence of carriage vibration. The vibration state can be measured by measuring at the time of shipment, but it is not possible to define the change over time and the state of the adjustment medium.

  Therefore, before the adjustment pattern is printed, the carriage vibration state and media state of the adjustment pattern printing area are measured, and the adjustment pattern is printed in the stable area, thereby obtaining an optimum registration adjustment value.

The main cause of the landing position deviation is that the distance between the head and the paper fluctuates.
Therefore, the variation in the distance between the head and the paper is measured.

  The optical sensor having the shape shown in FIG. 3 is a relatively simple sensor for measuring the density, but the amount of acquired light varies substantially constant according to the height variation of the sensor and the measurement target. Therefore, the adjustment pattern printing area is scanned using this sensor. An example of a measured waveform is shown in FIG.

  From the measurement waveform of FIG. 6, a region where the sensor output fluctuation is large (a region where the head-paper distance fluctuation is large) is determined, and this region is set as an adjustment pattern printing NG region.

  As the determination means, for example, the following method is used.

  The paper width is divided based on the adjustment pattern width. The number of divisions varies depending on the paper width.

  FIG. 7 shows a dividing method when the measurement waveform of FIG. 6 is obtained. The numbers (1) to (6) at the bottom of FIG. 7 indicate the division according to the adjustment pattern width. (1) to (6) Data of a plurality of points is acquired in each area. The standard deviation [Equation 1] of the acquired signal is calculated.

  Further, 3% of the average value of all measurement data on the paper surface is set as the reference value of the reflected light amount.

  When the standard deviation is higher than the reference value, the area is set as the adjustment pattern printing NG area, and the adjustment pattern is not printed. In the measurement example of FIG. 7, the standard deviation is higher than the reference value in the areas (1) and (4). Therefore, as shown in the upper part of FIG. 7, by arranging the adjustment pattern, it is possible to realize registration adjustment that avoids the influence of fluctuation.

  (A: Even-odd adjustment, B: Bidirectional adjustment, C: Intercolor adjustment)

1 is a schematic configuration example of an inkjet printing apparatus according to an embodiment of the present invention. FIG. 4A is a perspective view showing a configuration example of a head cartridge of an ink jet apparatus, and FIG. The schematic diagram for demonstrating the optical sensor mounted in an inkjet apparatus. FIG. 6 is a schematic diagram of carriage vibration during forward driving and backward driving. An example of resist adjustment pattern arrangement that is not easily affected by carriage vibration. An example of the measurement result of the carriage-to-paper variation. FIG. 6 is an example of a resist adjustment pattern arrangement based on a measurement result of carriage paper interval variation. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Print head 2 Carriage unit 3 Carriage unit holder 4 Cartridge fixing lever 5 Flexible cable 6 Carriage motor 7 Carriage belt 8 Medium to be printed 9 Photocoupler 10 Light shielding plate 12 Home position unit including recovery system 13 Discharge roller 15 Black ink storage ink tank 16 Color ink storage tank 17 Connection port for ink supply tube 20 on the main body side of each color ink 18 Connection port for ink supply tube 20 on the main body side of black ink 19 Electrical contact portion 20 Ink supply tube 21 Ejection port surface 22 Ejection port 23 Common Liquid chamber 24 Liquid path 25 Electrothermal converter 30 Reflective optical sensor 31 Sensor light emitting part 32 Sensor light receiving part 35 Irradiation light 37 Reflected light from the printing medium 1000 Head cartridge

Claims (2)

An image is formed by having two or more print heads each having a plurality of print nozzles for discharging ink, and a carriage on which the plurality of print heads are mounted reciprocates in the main scanning direction with respect to the recording material to discharge ink. An inkjet printer for printing
It has a function of adjusting the landing position of the ink on the recording material, and the adjustment of the landing position records a plurality of resist adjustment patterns with different ink ejection timings on the recording material, and the plurality of registered resist adjustment patterns In an ink jet printer that performs by detecting ink and determining the ink discharge timing from the detection result,
A resist adjustment method comprising at least two types of resist adjustment patterns of forward pass printing, return pass printing, and reciprocating printing, and arranging each resist adjustment pattern at a position where vibration during carriage reciprocation does not affect.   It has a sensor that measures the distance between the print head and the recording material, measures the distance over the entire main scanning direction of the recording material before printing the resist adjustment pattern, and in a region where the amount of variation is small 2. The resist adjustment method according to claim 1, wherein a resist adjustment pattern is printed.

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