JP2006264262A - Ink-jet recording method and ink-jet recording system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an image grace and a delivery reliability compatible by making dots, which are recorded for an on-paper preliminary delivery at the time of performing a bidirectional recording by an ink-jet recording apparatus, to be minimum and dispersed uniformly as far as possible within an image domain. <P>SOLUTION: In a dot pattern recorded for the on-paper preliminary delivery, the dot patterns which are recorded by an outward-trip recording scan and a return-trip one are made different. The preliminary delivery can be performed by a suitable timing and frequency against an ink flashing in nozzle varying with the progress of each recording scan. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording method and an ink jet recording system, and more particularly to an ink jet recording method and an ink jet recording system for forming an image by reciprocally scanning a recording head having a plurality of recording elements with respect to a recording medium.

  For example, as information output devices in word processors, personal computers, facsimiles, and the like, recording devices that record information such as desired characters and images on a sheet-like recording medium such as paper or film are widely used.

  Among them, an ink jet recording apparatus that ejects ink as droplets and forms an image on a recording medium has attracted attention. In particular, a serial-type inkjet recording apparatus that mounts a recording head that discharges ink according to recording information and performs recording while reciprocating the recording head in a direction intersecting the conveyance direction of a recording medium such as paper is inexpensive. In general, it is widely used because it is easy to downsize.

  Such an ink jet recording apparatus can record a high-quality image at high speed and with low noise, and can be provided with a large number of ejection ports for ejecting ink at a high density in the recording head. However, it is possible to record a large image with high resolution. In addition, it has many excellent points such as a color image can be output relatively easily.

  As a method for ejecting ink, an electric signal is applied to a heating element (electric thermal energy converter) in the vicinity of the ejection port to cause a state change accompanied by a sudden volume change (bubble generation) in the ink. Ink is ejected from the ejection port (nozzle) by a change in ink pressure due to a mechanical variation using a method of ejecting ink from the ejection port by an acting force based on this state change or an electro-mechanical conversion element such as a piezoelectric element. There is known a method of performing recording by attaching ink droplets to a recording medium.

  In an ink jet recording head using such a system, a plurality of recording elements each including an ejection port, a liquid path leading to the ejection port, and an element that generates energy for ejecting ink are arranged in a multi-density manner. In general, a plurality of nozzles are provided according to the type of ink to be applied. As ink types, in addition to basic four color inks (black, cyan, magenta, yellow, hereinafter referred to as dark ink), light inks (light cyan, There are also increasing forms of deploying light magenta, light black, and light yellow. By using light ink together with dark ink, it is possible to form a smooth and high-gradation image with little graininess.

  However, in such an ink jet recording head, although the reliability of ejection and recording has been remarkably improved due to the advancement of the ejection performance, it has been confirmed that the reliability is lowered under certain special conditions. ing. For example, in the vicinity of a finely configured discharge port, even a slight evaporation of ink cannot be ignored, and if there is a period during which recording is not performed even for a short time, the color material density of the ink near the discharge port is To rise. Then, the density of the image to be recorded immediately after the start of recording partially rises and becomes conspicuous as density unevenness.

  FIG. 1 is a schematic diagram for explaining the problem of density unevenness at the edge of the image. Here, a recording state in which a regular gradation image is formed on an A4 size recording medium 1 by a conventional general inkjet recording apparatus is shown. The error diffusion method is used as the pseudo halftone process, and by this, dot recording / non-recording at a predetermined position on the recording medium is determined. In addition, an example in which a multi-pass printing method unique to a serial-type printing apparatus is employed is shown, and here, an example of an image formed by 4-pass multi-pass printing by one-way printing scanning is shown.

  According to the figure, a phenomenon in which the recording density of the left end portion of the image of the recording medium 1 is increased is confirmed. A schematic diagram for enlarging and explaining this state is shown in the lower left of the figure. Although there is no change in the amount of discharge discharged from each nozzle of the recording head, that is, the size of the dots, in the recording scanning direction, the dots formed by the first discharge at the start of recording (first discharge) The dot has the highest density. As the second discharge, the third discharge, and the number of discharges are continued, the dot density gradually returns to the standard state.

  Such a phenomenon at the extreme end (recording scan start position) of the recorded image does not occur specifically in the gradation image as shown in FIG. It is a phenomenon that occurs in the same way whether the image is a halftone image having a uniform density or a digital photographic image.

  Factors for such phenomena include ink component characteristics, environmental conditions such as environmental temperature and humidity, and usage conditions of the recording head. For example, in an environment where the temperature is high and the humidity is low, the volatile components in the ink evaporate more rapidly than usual on the ink surface near the ejection port, and the colorant density increases. In other words, in the recording head, dots that are darker than usual are recorded by the ink ejected from the nozzles until the ink in a high color material density is discharged from the nozzles. When evaporation is further promoted, the first ejection (first ejection) itself in the recording scan becomes unstable, which develops into a problem of instability.

  Conventionally, as a countermeasure for such a problem, it has often relied mainly on ink prescription. That is, a device has been devised to suppress the variation in the color material concentration of the ink by adjusting the viscosity of the ink or adjusting the type and concentration of the color material and the solvent. However, in this case, if the ink volatility is reduced in order to suppress the variation of the color material density, the fixability (dryness) of the recorded image is impaired, and a new problem such as smear occurs. There is. Therefore, conventionally, the ink has been refined with a narrow latitude (range) in which both the fixing problem and the instability problem are satisfied to some extent.

  On the other hand, as another countermeasure for solving the problem of instability, a method of adjusting the amount of energy applied to the first discharge has been proposed as disclosed in Patent Document 1, for example. According to Patent Document 1, the width of the voltage pulse to be applied to the electrothermal transducer provided in each nozzle in order to give larger thermal energy than usual to the first ejection of each recording scan. Are set longer than the others, and a method of applying a pre-pulse with an appropriate width that does not lead to ejection is disclosed. Thus, by setting a large amount of energy to be applied for the ejection operation, a sufficient amount of ejection can be realized even with ink having an increased color material density.

  In addition, many ink jet recording apparatuses have been provided in which preliminary ejection unrelated to recording on a recording medium is performed before recording scanning and the like, and an ink receiver for preliminary ejection is provided.

  However, due to recent high image quality, high speed, large format, and the like, there are cases where the problem of instability cannot be solved sufficiently with only the above-described measures. For example, in order to realize even higher image quality, there is a technique for increasing the density and number of recording elements in a recording head and forming an image with higher density and speed with smaller ink droplets. Has been promoted. However, in this case, since the ratio of the surface area to which the ink of each recording element (nozzle) is exposed to the outside air is increased as compared to the conventional case, the evaporation of ink in the recording head is further increased.

  In addition, the multi-pass printing method generally adopted in the serial type ink jet printing apparatus can also improve the smoothness of the image, but it increases the number of times of printing scanning, and in one printing scanning. In terms of reducing the number of ejections, it also works in the direction of promoting the evaporation of ink from the recording head.

  Furthermore, with respect to the temperature adjustment control of the print head that is performed to stabilize the discharge state of each nozzle, the print head is warmed so as to maintain a constant temperature, and as a result, the evaporation of ink may be promoted. is there.

  Furthermore, in the situation where an image is formed on a large-sized recording medium, the distance and time that the recording head moves and scans in one recording scan also increases. In recent years, support for media having a larger width than that of the A4 size has increased, and from this point, the problem of ink evaporation in each printing scan has been recognized again. In other words, the amount of ink evaporation during the same recording scan is a non-negligible amount because the distance of one recording scan is designed to be long.

  In order to deal with such a problem of instability in a severe situation, a method of performing preliminary ejection on a recording medium on which an image is formed is disclosed (for example, Patent Document 2 or Patent Document 3). According to the above-mentioned patent document, by generating ejection data different from image data according to a predetermined pattern, the frequency of preliminary ejection can be increased without moving the recording head to a predetermined preliminary ejection port. Is described. Hereinafter, such preliminary ejection onto the recording medium is referred to as “paper surface preliminary ejection” in this specification.

  As described above, in recent ink jet recording apparatuses, by introducing various measures such as “paper surface pre-discharge”, even when a high resolution image is formed on a large format recording medium, It has been possible to suppress the adverse effects of the image due to the one-sided instability problem to some extent.

JP-A-4-39051 JP-A-55-139269 JP-A-6-40042

  By the way, when “paper surface pre-discharge” is executed, even if dots that are not related to the image are actually formed on the recording medium, the ink color is difficult to visually recognize, such as light cyan, light magenta, or yellow. If so, it will not be a problem. On the other hand, in the case of ink colors that are easily detected, such as dark cyan, dark magenta, or black, if dots become conspicuous at a position unrelated to the image, it causes deterioration in image quality. That is, even when “paper surface preliminary discharge” is executed, a device for arranging dots formed for paper preliminary discharge as inconspicuous as possible is desired. In this case, first, it is preferable that the dots are uniformly dispersed throughout the recording medium. Second, it is preferable to minimize the preliminary ejection on the paper itself.

  However, the timing at which preliminary ejection is actually required varies depending on the printing conditions. In particular, when bidirectional printing is performed, the necessity for preliminary ejection and the rate of change of the required number of shots in the scanning direction are often different between the printing scan in the forward pass and the print scan in the return pass. Further, the timing at which the preliminary ejection is required is also affected by the position where the normal preliminary ejection other than the paper surface preliminary ejection is performed. Further, even in the same print scan, the necessity for preliminary ejection increases as the scan proceeds.

  Even in various situations as described above, conventionally, it is common to perform recording for preliminary ejection on the paper surface at the same rate throughout the entire recording scan. As a result, excessive pre-discharge of the paper is necessary and the ink is wasted, or there are places where the number of pre-discharge of the paper is insufficient, causing problems with instability. Effective paper preliminary discharge has not been realized yet.

  The present invention has been made in view of the above problems, and the object of the present invention is that even when bidirectional recording is performed by an inkjet recording apparatus, dots recorded for “paper surface preliminary ejection” It is an object to provide an ink jet recording method and an ink jet recording system capable of achieving both image quality and ejection reliability by dispersing at a minimum and uniformly within an image region.

  Therefore, in the present invention, from a plurality of recording elements arranged in a predetermined direction, based on image data, or based on preliminary ejection data for maintaining the recording characteristics of the recording elements while being unrelated to the image data. In the inkjet recording method of forming an image on the recording medium using a recording head that forms dots on the recording medium by ejecting ink, first preliminary ejection data is added to the first portion of the image data The first recording data is generated by this, and the first recording for ejecting ink to the recording medium according to the first recording data while moving and scanning the recording head in the direction intersecting the predetermined direction. Different from the step, the step of transporting the recording medium in a direction intersecting the first direction, and the first portion of the image data. A step of generating second recording data by adding second preliminary ejection data to the second portion, and moving and scanning the recording head in a direction opposite to the first recording step. A second recording step of ejecting ink onto the recording medium in accordance with the recording data of 2, and a first dot pattern formed on the recording medium by the recording head based on the first preliminary ejection data, and the second spare The second dot patterns formed on the recording medium according to the ejection data are different from each other.

  Further, ink is ejected from a plurality of recording elements arranged in a predetermined direction based on image data, or based on preliminary ejection data for maintaining the recording characteristics of the recording elements irrespective of the image data. In the inkjet recording system that forms an image on the recording medium using a recording head that forms dots on the recording medium, the first preliminary ejection data is added to the first portion of the image data to add the first preliminary ejection data. Generating recording data, means for ejecting ink to the recording medium in accordance with the first recording data while moving and scanning the recording head in a direction crossing the predetermined direction, and the recording medium A second preparatory step is performed on the means for conveying the image data in a direction crossing the first direction and a second portion different from the first portion of the image data. Means for generating second recording data by adding ejection data, and ink on the recording medium in accordance with the second recording data while moving and scanning the recording head in a direction opposite to the first recording step. And a second dot pattern formed on the recording medium by the second preliminary ejection data, and a second dot pattern formed on the recording medium by the second preliminary ejection data. Are different from each other.

  Further, the above-described ink jet recording method is realized by a computer.

  Furthermore, the computer program described above is stored.

  According to the present invention, in an ink jet recording apparatus that forms an image by bidirectional recording investigation, an appropriate timing and frequency with respect to ink evaporation in the nozzle that changes in accordance with the progress of each scanning scan in the forward pass and the backward pass scan. The preliminary discharge can be executed.

  Hereinafter, in order to describe the embodiments of the present invention, the configuration of an ink jet recording apparatus applicable to each embodiment will be described first.

  FIG. 2 is an external perspective view showing a schematic configuration of an ink jet recording apparatus applicable to the present invention. In the figure, 11 is a carriage. The carriage 11 can be mounted integrally and detachably with a recording head and an ink tank for storing ink. Reference numeral 12 denotes a carriage motor. The carriage motor 12 transmits the driving force to the carriage 11 through the belt 4 and the pulleys 5a and 5b. The carriage 11 reciprocates in the recording scanning direction (main scanning direction) according to the guide support of the guide shaft 6 by the driving force of the carriage motor 12. Reference numeral 13 denotes a flexible cable for transmitting a recording signal to a recording head mounted on the carriage 11. Reference numeral 15 denotes a paper discharge cassette that can store recording media after recording in a stacked state, and 17 denotes a paper feed tray for stacking and holding the recording media before being conveyed to the recording unit.

  FIG. 3 is a configuration diagram for explaining in detail the configuration around the recording head of the inkjet recording apparatus. The recording head 22 and the ink tank 21 for supplying ink to the recording head 22 enable black (K), cyan (C), magenta (M), and yellow (Y) in order to enable high-quality color recording with photographic tone. A total of six colors of light cyan (LC) and light magenta (LM) are prepared. Reference numeral 141 denotes a cap for protecting the ejection opening of the recording head 22, and six recording heads are arranged corresponding to the ink colors. At the time of non-recording, the recording head 22 moves to the upper part of the cap 141 which is the home position, and the cap 141 caps the ejection port surface of each recording head. Thereby, evaporation from the ejection port during non-recording can be suppressed. Further, the cap 141 is connected to a suction pump (not shown), and the operation of this suction pump can appropriately suck ink in the recording head and prevent clogging of ink in the nozzle.

  Reference numeral 143 denotes a wiper blade. The wiper blade 143 moves in the direction of arrow C with respect to the discharge port surface released from the capping, thereby wiping the discharge port surface of the recording head 22 and removing excess ink and dirt. Further, although not shown here, preliminary ejection openings for receiving preliminary ejection from the recording head 22 immediately before the recording scanning are provided in the recording scanning area of the recording head on the side of the cap 141 and on the opposite side thereof. It has been. That is, it is possible to appropriately execute preliminary ejection to the preliminary ejection port immediately before the recording scanning by the forward scanning and immediately before the recording scanning by the backward scanning.

  During recording, the recording head 22 ejects ink according to a recording signal received from the flexible cable 13 while reciprocatingly scanning in the direction of arrow B, thereby forming dots on the recording medium. The ejection timing is measured when the encoder sensor 16 stretched in the main scanning direction (B direction) detects the movement position of the carriage 11. When one recording scan is completed, the recording medium 1 is transported in the direction of arrow A, which is the sub-scanning direction, by a distance corresponding to the recording width as the transport roller 3 rotates. Thereafter, the carriage is moved and scanned again to execute the next recording scan. Images are sequentially formed on the recording medium 1 by alternately repeating the recording scanning and the conveying operation.

  Here, each of the recording head 22 and the ink tank 21 is shown as a head cartridge that can be attached to and detached from the carriage 13. However, for example, the recording head and the ink tank may be configured integrally, or the ink cartridge Only the tank 22 may be configured to be independently detachable with respect to each color of the recording head 22 fixedly incorporated in the carriage 11.

  FIG. 4 is a schematic diagram for explaining the ejection port surface of the recording head 22 applicable in the following embodiment. In the recording heads 22K, 22LC, 22C, 22LM, 22M, and 22Y, 1280 ejection ports 23 are arranged at an arrangement density of 1200 dpi (dot / inch; reference value). Each ejection port 23 has an opening area adjusted so as to suppress the ejection amount as much as possible in order to realize high image quality recording. In the following embodiment, the ejection amount of ink ejected from each ejection port 23 at a time Is about 4 ng. The six recording heads 22 are mounted on the carriage 11 in a state of being arranged in parallel in the main scanning direction (B direction). Each ink path for supplying ink to each ejection port is provided with an electrothermal converter for generating thermal energy. When a predetermined voltage pulse is applied to the electrothermal transducer according to the recording signal, film boiling occurs in the ink due to rapid heat generation, and the ink is ejected as droplets by this foaming energy. Such a method using foaming energy is a particularly preferable method for realizing high density and high definition of recording.

  FIG. 5 is a block diagram for explaining a control configuration of the ink jet recording apparatus applicable to the present invention. In the figure, an image controller 210 notifies the print engine 220 of a control command in accordance with a processing command from an operation unit (not shown) of the host apparatus 200 or the recording apparatus main body. During recording, the recording data received from the host device 200 is analyzed and developed, and converted into binary data of six colors corresponding to dot recording / non-recording. The print engine 220 performs an actual recording operation based on the control command and binary data received from the image controller 210.

  The image controller 210 and the print engine 220 are connected by a dedicated interface. The command transmission from the image controller 210 to the print engine 220 is sent to the print engine 220, and the status from the print engine 220 to the image controller 210 is notified of the state change. Transmission or image data communication for transferring image data from the image controller 210 to the print engine 220 can be executed.

  The print engine 220 is controlled by an MPU (Micro Processor Unit) 221 in accordance with a program recorded in the ROM 227. The RAM 228 is used as a work area for the MPU 221 or an area for temporarily storing data. The MPU 221 controls the carriage drive system 223, the transport drive system 224, the recovery drive system 225, and the head drive system 226 via an ASIC (Application Specific Integrated Circuit) 222. Further, the MPU 221 can read / write data from / to the print buffer 229 and the mask buffer 230 via the ASIC 222.

  The print buffer 229 is an area for temporarily storing image data converted into a format that can be transferred to the recording head. The mask buffer 230 is an area for temporarily storing a mask pattern when executing multi-pass printing. A plurality of types of mask patterns prepared for a plurality of recording modes are stored in the ROM 227 in advance. When the recording mode is determined during actual recording, the corresponding mask pattern is read from the ROM 227 and stored in the mask buffer 230 each time. The paper preliminary discharge buffer 260 stores a paper preliminary discharge pattern corresponding to each recording scan.

  The control flow during recording will be described below. When a recording start command is input to the host device 200, image data is transferred from the host device 200 to the image controller 210 together with information such as the recording mode, the number of recordings, and the type of recording medium. The image controller 210 analyzes the received image data, generates information necessary for recording such as recording quality and margin information, further analyzes and develops the image data, and starts conversion processing to binary data for each color To do. Detailed expansion processing will be described later. Among the generated information, information necessary for setting the recording operation in the print engine 220 such as recording quality and margin information is notified to the print engine 220 as it is.

  Information notified to the print engine 220 is processed by the MPU 221 via the ASIC 222 and then held in the RAM 228. This information is appropriately referred to when necessary thereafter, and is used for separation of processing. Further, a mask pattern is written into the mask buffer 230 as necessary.

  When the notification of necessary information is completed, the image controller 210 starts to transfer binary image data of each color converted from the image data to the print engine 220. The print engine 220 writes the transferred image data in the print buffer 229. By repeating the image transfer from the image controller 210, in the print engine 220, transfer data to the head is successively accumulated in the print buffer 229.

  When a predetermined amount of data accumulated in the print buffer 229 is accumulated, a corresponding mask pattern is read from the mask buffer 230 and AND (logical product) processing is performed on the image data. Thereafter, ejection data as pre-discharge of the paper surface generated in advance corresponding to the printing scan is called from the pre-discharge surface discharge buffer 260 and added by OR (logical sum) processing. In the conventional paper preliminary discharge, it is generally added to the data stored in the print buffer. However, in the present invention, in order to give a characteristic to the paper preliminary discharge pattern provided for each recording scan. Further, the preliminary ejection data on the paper is added to the binary data after the AND process with the mask data.

  When the ejection data to be recorded in the next recording scan is determined in this way, the MPU 221 transports the recording medium by the transport driving system 224 via the ASIC 222 and moves the carriage 11 by the carriage driving system 223. . In addition, the recovery system is driven by the recovery drive system 225 to perform necessary recovery processing on the recording head 22 before the recording operation. Further, the image output position and the like are set in the ASIC 222, the carriage 11 is driven, and the recording operation is started.

  When the carriage 11 moves and reaches the recording start position set in the ASIC 222, the image data on which the above-described preliminary paper ejection pattern is ORed in accordance with the ejection timing is sequentially read from the print buffer 229. Thereafter, the completed binary data is transferred to the recording head 22. Under the control of the head drive system 226, the recording head 22 executes ejection by driving the recording head in accordance with the transferred data. The recording operation is realized by repeating the processing from the reception of the image from the image controller 210 to this step.

  FIG. 6 is a diagram for explaining an image processing process inside the host apparatus 200 and the recording apparatus 240. In the figure, the host device 200 receives 600 × 600 dpi RGB (red, green, blue) or KCMY (black, cyan, magenta, yellow) format multi-value data (here, 8 bits each) via the printer driver 250. It is generated and transferred to the recording apparatus main body. When the received data is in the RGB format, the image controller 210 performs RGB to R′G′B ′ color conversion processing 500 in order to obtain a color space that matches the recording apparatus. Next, in order to match the ink color used in the printing apparatus, multi-valued data of 600 × 600 dpi K, LC, LM, C, M, and Y (in this case, each 8 bits) is used from R′G′B ′ 8-bit data. Color separation processing 510 to (bit).

  On the other hand, when the data received by the image controller 210 is in the KCMY format, the color separation process 510 is performed without performing the color conversion process 500. In the color conversion process 500 and the color separation process 510, data conversion is performed using a predetermined color conversion lookup table. The lookup table may be stored in advance in the ROM data of the recording apparatus main body, or may be transferred from the host apparatus 200 together with the image data.

  Subsequently, quantization processing 520 from 8-bit (255 gradation) data of K, LC, LM, C, M, and Y to 4 bits (5 gradations) for each color is performed. As the quantization processing 520, a known multilevel error diffusion method or dither method is applied. The quantized 4-bit (5-gradation) data of K, LC, LM, C, M, and Y is subjected to an index expansion process 530, which will be described later, and 1 bit for each color of K, LC, LM, C, M, and Y It is converted into (2 gradations) data. Such index expansion is employed for the purpose of reducing the processing load on RGB multi-valued data and improving both the gradation and the speed and image quality. In the index expansion of the following embodiment, it is assumed that processing for expanding 600 dpi 4-bit (5 gradations) data into 1200 dpi 1-bit (2 gradations) data is executed using a predetermined matrix pattern.

  FIG. 7 is a schematic diagram for explaining an index pattern for a certain color. In the drawing, the input data given to each pixel of 600 dpi is shown on the left side. On the right side, output data converted based on the value of each input data is shown. In the output data, an area represented by four 2 × 2 areas corresponds to one pixel of 600 dpi, and each area represents a 1200 dpi area in which dot recording / non-recording is determined. In each output data, a black area is an area where dots are recorded, and a blank area is an area where dots are not recorded. It can be seen that the area in which dots are recorded increases as the value of the input data increases. In the index expansion processing 530, 600 dpi 4-bit data is converted into 1200 dpi 1-bit data according to the pattern shown here. Such a setting pattern may be common to each color, or may be prepared independently. Further, it may be stored in the ROM in the recording apparatus main body in advance, or may be downloaded from the host apparatus together with the recording data. The converted binary data is transferred to the print engine 220.

  The print engine 220 applies a mask pattern thinning process 540 to 1-bit (2-gradation) data of each color of K, LC, LM, C, M, and Y, and a binary image recorded in each recording scan. Data is determined.

  After recording / non-recording is determined for each recording scan, preliminarily generated preliminary ejection data (two values) for preliminary ejection on the paper is added to each recording scan data by OR (logical sum) processing. (Paper surface preliminary discharge addition processing 550). The present invention is characterized in that different ejection data is added depending on whether the recording scan is the forward scan or the backward scan.

  FIG. 8 is a diagram showing an example of recording positions of dots that are actually added by the paper preliminary ejection addition processing 550. Here, for the sake of explanation, the number of ejection ports of the recording head is 16. Reference numeral 300 denotes a recording head, and reference numerals 310 to 325 denote 16 discharge ports provided in the recording head 300. The resolution of the pattern is equal to the resolution of the binarized data, and is 1200 dpi in both the ejection port alignment direction (Y direction) and the print head scanning direction (X direction). The squares shown in the figure indicate individual recording pixels, and it is determined whether or not each pixel is a recording pixel for preliminary ejection.

  Reference numeral 360 denotes the origin (X0, Y0) of the pixel of interest. When this pixel of interest is a recording pixel for preliminary ejection, a dot is applied to this position by the ejection port 310. A pixel 361 located at coordinates (X0 + X1, Y0 + 1) moved by X1 dot in the X direction and 1 dot in the Y direction from the origin 360 is a pixel in which dots are recorded by the ejection port 311. Similarly, a pixel 362 located at coordinates (X0 + 2 × X1, Y0 + 2) moved by X1 dot in the X direction and 1 dot in the Y direction from the pixel 361 is a pixel in which dots are recorded by the ejection port 312. Further, a pixel 363 located at coordinates (X0 + 3 × X1, Y0 + 3) moved by X1 dot in the X direction and 1 dot in the Y direction from the pixel 362 is a pixel in which dots are recorded by the ejection port 313. Here, if Y0 + 3 = Y1-1, the above-described arrangement is similarly repeated as (X0 + 1, Y1) for the pixel 364 in which dots are recorded by the next ejection port 314.

  By using the regular pattern as described above, pixels in which dots for preliminary ejection on the paper surface are recorded are determined in the recording scan focusing on all 16 ejection openings, and the pattern is determined in the X direction. Can be used as a repetitive pattern having a cycle of 4 × X1 dots and 4 × Y1 dots in the Y direction.

  According to the paper preliminary ejection pattern, each pixel position can be indicated by using the four parameters of the origins X0 and Y0 and the inter-dot distances X1 and Y1. However, such a paper preliminary discharge pattern is an example, and a parameter may be added to realize another paper preliminary discharge pattern, or a parameter may be deleted for simplification. The pattern can be changed for each color and each recording mode by appropriately changing parameters or preparing a plurality of types. Further, the parameters may be changed stepwise within the same printing scan.

  In the above description, the paper preliminary ejection pattern is added to the binary data after the index development. However, in the present invention, it is possible to add the paper preliminary and data at the level of 4 bits and 5 values. is there.

  FIG. 14 is a diagram for explaining image processing steps in the host device 200 and the recording device 240 when the paper surface preliminary ejection addition processing is executed before the index development processing 530. In this case, the paper surface preliminary ejection addition processing 540 is performed on 4-bit data of K, LC, LM, C, M, and Y quantized to five gradations. Specifically, among the five levels of data from 0000 to 0100 shown in FIG. 7, for example, a data value of a part of a pixel whose input data is “0000” is converted to “0001” according to a predetermined rule. . The input data to which the paper preliminary discharge is added is converted into data of 1 bit (2 gradations) for each color of K, LC, LM, C, M, and Y by performing index development processing 530.

  FIG. 15 is a diagram showing an example of an index pattern for the input level “0001” after the paper preliminary ejection data is added. Here, two types of output patterns 900 and 910 are prepared for the same input level “0001”. In this way, by preparing two types of patterns in advance and alternately switching and outputting them, it is possible to reduce the bias of the discharge ports that perform discharge. The 1-bit (two gradations) data converted by the index development process 530 is transferred to the printer engine 220 in a state in which the pre-discharge data on the page is included.

  As described above, 1-bit data in a state including the preliminary ejection data on the paper is used as data for forward scanning and for backward scanning according to the mask pattern when used for reciprocal recording during recording. As a result, the added preliminary ejection data is distributed to either forward scanning or backward scanning, and ink is ejected onto the paper surface according to the data. That is, the added preliminary ejection data is distributed to the forward scan and the backward scan.

  Each embodiment in which the ink jet recording apparatus described above is used and a feature of the pre-discharge pattern on the paper surface is specifically described below.

(First embodiment)
In this embodiment, when bi-directional multi-pass printing is performed, the area on which dots are recorded for preliminary ejection on the paper is differentiated between forward scanning and backward scanning. Control is performed so that dots recorded for ejection are uniformly dispersed.

  FIG. 9 shows an arrangement state of dots recorded for preliminary ejection on the paper in each printing scan when two-pass multi-pass printing is performed in both directions. In the figure, in forward scanning (hereinafter also simply referred to as forward scanning), recording is performed while moving the recording head in the direction of the arrow in the figure. At this time, the recording for preliminary ejection on the paper surface is not performed up to approximately the center position of the recording scan, but is performed in a uniform pattern in the area beyond the center position. After the end of the forward scanning, the recording medium is conveyed by an amount corresponding to 640 nozzles, which is half the number of nozzles 1280, and then backward scanning (simply referred to as backward scanning) is performed.

  In the subsequent backward scanning, recording is performed while moving the recording head in the direction of the arrow in the figure. At this time, the recording for preliminary ejection on the paper surface is not performed up to approximately the center position of the recording scan, but is performed in a uniform pattern in the area beyond the center position.

  In the paper preliminary ejection pattern recorded by repeating the forward scanning and the backward scanning and the conveyance of the recording medium as described above, the half recording area and the half non-recording area are overlapped on the recording medium and connected to each other. It will be in such a state. Therefore, in the completed image, the preliminary ejection pattern is in a uniformly dispersed state, and adverse effects caused by unevenly arranged dots can be avoided.

  FIG. 10 shows an example of an output image when the paper preliminary ejection is not performed in order to explain the adverse effects improved by the present embodiment. In the figure, the recording medium is A2 size, and a plurality of patterns using six colors of ink are formed. As a recording method, as in the present embodiment, bi-directional recording by 2-pass multi-pass recording is employed. Here, a similar pattern is arranged as a uniform halftone image on the upper left and lower right of the image. In the central portion, halftone images and characters having a density different from the above are arranged. Since these halftone images are images for detecting the problem of instability, they are recorded at a halftone image density where the density of dots is easily confirmed.

  According to the figure, in the halftone image arranged at the upper left, there is no density unevenness (dark dot area) on the left side of the image edge, whereas density unevenness (dark dot density) is on the right side of the image edge. It can be confirmed that (part) has occurred. Since the home position is located on the left side of the recording medium during recording, and preliminary ejection is performed here before the start of each recording scan, density unevenness (darker portions of dots) is present on the left side of the image edge. Is not confirmed. On the other hand, when recording the right part of the image by backward scanning, the ink is discharged in the nozzle where the number of ejections is small while the recording head scans from the right end of the recording medium to the right end of the halftone image. Evaporation is promoted to some extent. Therefore, an area that is recorded with dark dots for a while is generated, and density unevenness is recognized by alternately arranging the dark areas in the sub-scanning and the normal density areas in the forward scanning. It will be done. The same applies to the halftone image arranged in the lower right part of the image.

  On the other hand, when recording according to the preliminary ejection pattern of the present embodiment as described with reference to FIG. 9 is performed, such density unevenness is not confirmed. This is because the preliminary ejection on the paper surface is executed from the vicinity of the recording head where the color material density changes due to the evaporation of ink in the vicinity of the ejection port, beyond the central position of the recording scanning path. This is because the time during which ejection is not performed is shortened, and an increase in color material density can be suppressed.

  In addition, in the conventional preliminary ejection on the paper surface, recording for preliminary ejection is generally performed uniformly on the entire surface of the recording medium, but actually, immediately after ejection at the home position or the preliminary ejection port. In many cases, preliminary ejection is unnecessary for the recording head, and in this case, excessive preliminary ejection has occurred. On the other hand, according to the present embodiment, since the actual paper preliminary discharge is started at an appropriate timing when the necessity of the preliminary paper discharge occurs, the ink is consumed or the image is disturbed by excessive preliminary discharge. There is nothing to do. At the same time, the dots recorded by the preliminary ejection on the paper are also overlapped in the forward direction and the backward direction, and as a result, they are uniformly dispersed. Pre-discharge can be realized.

  It should be noted that, as with the ink jet recording apparatus employed in the present embodiment, two preliminary discharge ports are provided so that preliminary discharge can be performed both before the start of forward scanning and before the start of backward scanning. Although it is a preferable configuration, the effect of the present embodiment can be obtained without such a configuration. Even in a configuration in which preliminary ejection can be performed only before either recording scan, the preliminary ejection effect is sufficiently obtained because the preliminary ejection on the paper surface is executed until just before the previous recording scan. . In this case, the position (timing) for starting the preliminary ejection on the paper surface may be adjusted in each of the forward scan and the backward scan in consideration of such conditions.

  In this embodiment, the case where multipass printing is executed by two reciprocating scans has been described as an example. However, even when multipass printing is performed by more than two reciprocating scans, the effect of this embodiment is achieved. Can get. In this case, since the number of times that the recording head ejects ink in one recording scan is further reduced, the effects of the present invention can be obtained more remarkably.

  As described above, according to the present embodiment, in the paper preliminary discharge when performing bidirectional multi-pass printing, both the forward scan and the backward scan are configured to execute the preliminary discharge from the middle of the recording scan. Thus, it is possible to more efficiently suppress the problem of instability without degrading the image quality.

(Second Embodiment)
The second embodiment of the present invention will be described below. The ink jet recording apparatus employed in the present embodiment is configured such that preliminary ejection outside the recording area can be executed only on the home position side. In this embodiment, when bidirectional multi-pass printing is performed, the recording rate for recording dots for preliminary ejection on the paper surface is made different between forward scanning and backward scanning. The dots recorded for preliminary ejection on the paper are controlled so as to be uniformly dispersed.

  FIG. 11 shows an arrangement state of dots recorded for preliminary ejection on the paper in a reciprocal recording scan when two-pass multi-pass recording is performed in both directions. In the figure, in the forward scanning, recording is performed while moving the recording head in the direction of the arrow in the figure. At this time, about 35% of dots recorded for preliminary ejection on the paper surface are recorded by this forward scanning. In the forward scanning, the recording scanning is performed immediately after the preliminary ejection is performed on the home position side. Therefore, it is not necessary to record so many dots in order to maintain the color material density in the nozzle. After the forward scanning is completed, the recording medium is conveyed by an amount corresponding to 640 nozzles, which is half the number of nozzles 1280, and then backward scanning is performed.

  In the subsequent backward scanning, recording is performed while moving the recording head in the direction of the arrow in the figure. At this time, among the dots recorded for preliminary ejection on the paper, the remaining dots corresponding to about 65% are recorded by this forward scanning. In the backward scanning, since the preliminary ejection at the non-home position side is performed without being executed, it is necessary to record more dots in order to eject ink with high density in the nozzle. is there.

  The paper preliminary ejection pattern recorded by repeating the forward scan, the backward scan, and the conveyance of the recording medium as described above is a recording rate 100 in which the recording rate 35% in the forward scanning and the recording rate 65% in the backward scanning are combined. % State.

  Also in this embodiment, the same effects as those of the first embodiment described with reference to FIG. 10 can be obtained.

  Note that the recording rate in forward scanning and backward scanning is adjusted according to the environmental conditions in which the recording device is installed, the position of the preliminary ejection port, the number of passes for multi-pass recording, the applied recording head and ink ejection characteristics, etc. May be. In an extreme case, the recording rate in the forward scanning may be 0% and the recording rate in the backward scanning may be 100%.

  As described above, according to the present embodiment, an ink jet having a configuration in which the preliminary discharge port is provided only on one side of the recording scan by changing the dot recording rate for the preliminary discharge on the paper surface in the forward scanning and the backward scanning. Even when reciprocating multi-pass recording is performed by the recording apparatus, it is possible to more efficiently suppress the problem of instability of the emission without degrading the image quality.

(Third embodiment)
The third embodiment of the present invention will be described below. In the ink jet recording embodiment employed in this embodiment, when bidirectional multi-pass printing is performed, the recording rate for recording dots for preliminary ejection on the paper surface is gradually increased as the recording scan proceeds. In an image completed by forward scanning and backward scanning while taking the form, the dots recorded for preliminary ejection on the paper surface are controlled to be uniformly dispersed.

  FIG. 12 shows an arrangement state of dots recorded for preliminary ejection on the paper in a reciprocal recording scan when two-pass multi-pass recording is performed in both directions. In the figure, in the forward scanning, recording is performed while moving the recording head in the direction of the arrow in the figure. At this time, the dots recorded for preliminary ejection on the paper surface gradually increase as the recording scan progresses. Here, the recording rate at the beginning of the recording scan is 35%, and the recording rate at the end of the recording scan is 65%. After the forward scanning is completed, the recording medium is conveyed by an amount corresponding to 640 nozzles, which is half the number of nozzles 1280, and then backward scanning is performed.

  In the subsequent backward scanning, recording is performed while moving the recording head in the direction of the arrow in the figure. At this time, the recording rate of dots recorded for preliminary ejection on the paper surface gradually increases as the recording scan progresses, as in the forward scan. Here, the recording rate at the beginning of the recording scan is 35%, and the recording rate at the end of the recording scan is 65%. The reason why the recording rate for preliminary ejection on the paper surface is gradually increased in this manner is that ink evaporation at nozzles that are not ejected gradually becomes a problem as the recording scan progresses.

  In the preliminary ejection on the paper recorded by repeating the forward scanning and the backward scanning and the conveyance of the recording medium as described above, the recording in the forward scanning and the recording in the backward scanning overlap each other. % Dots are recorded.

  Also in this embodiment, the same effects as those of the first embodiment described with reference to FIG. 10 can be obtained.

  In this embodiment as well, forward scanning and backward scanning are performed according to the environmental conditions in which the printing apparatus is installed, the position of the preliminary ejection port, the number of passes of multi-pass printing, the applied print head and ink ejection characteristics, and the like. The recording rate and the degree of increase thereof may be adjusted. For example, the recording rate at the beginning of the recording scan may be 0%, and the recording rate immediately before the end of the recording scan may be 100%. Further, even if the recording rate at the start of the recording scan is set higher than that at the time of recording immediately before the end of the recording scan, the present invention can be used as long as the intended effect can be obtained. It is included in the category of the invention.

  As described above, according to the present embodiment, in the preliminary ejection on the paper surface when performing bidirectional multi-pass printing, by changing the dot recording rate for preliminary ejection on the paper surface along with scanning, It has become possible to more efficiently suppress the problem of instability without degrading image quality.

  In the embodiment described above, the ink color that causes the preliminary ejection on the paper is not mentioned. The above configuration may be adopted for all ink colors or a part of ink colors, and for each ink color, a recording rate, a recording area, The recording patterns may be set different from each other. For example, a configuration may be adopted in which pre-discharge on the paper surface is more actively executed for yellow or light ink in which recorded dots are difficult to visually confirm. Further, these conditions may be separated according to an ink in which the ink solvent is volatile and an ink that is relatively less volatile. Further, when using a large-sized recording medium such as A0 size, for example, the dots recorded for preliminary ejection on the paper surface tend to be visually inconspicuous. In such a case, it is possible to positively execute paper preliminary ejection even with ink having a relatively high density. Of course, the type of ink applied to the recording is not limited to the six colors shown in the above embodiment, but only the basic four colors of black, cyan, magenta and yellow may be used. Even in the case of recording, the effect of the present invention can be obtained similarly.

  Further, in the above embodiment, as described with reference to FIG. 5, the image controller 210 provided in the recording apparatus main body 240 has been described as performing various image processing. However, in order to realize the present invention. The configuration of is not limited to this.

  FIG. 13 is a block diagram illustrating a case where image processing up to quantization processing is executed by the printer driver of the host device instead of the printing apparatus main body. In the case of such a configuration, various processes are performed by the software of the host device, so that there is a concern that the processing speed is reduced as compared with the case of FIG. However, since it is not necessary to mount an image controller having a large structure in the recording apparatus main body, it is possible to reduce the cost of the recording apparatus itself.

  Furthermore, the system for realizing the present invention does not have to be composed of a host device and a recording device. For example, a system realized by various devices such as an interface device, a reader, and a scanner, or a system realized by one device may be used.

  The inkjet recording head of the embodiment described above has been described with a configuration in which each nozzle is provided with an electrothermal conversion element, but the actual ejection method is not limited to this. However, the method applied in the above embodiment is particularly preferable in realizing high density and high definition of recording, and the effect of the present invention can be sufficiently exhibited.

  In addition, an object of the present invention is to supply a storage medium (or recording medium) in which software program codes for realizing the functions of the above-described embodiments are recorded to a system or apparatus, and a computer (or CPU or CPU) of the system or apparatus. Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

It is a schematic diagram for demonstrating the problem of the density nonuniformity of an image edge part. 1 is an external perspective view showing a schematic configuration of an ink jet recording apparatus applicable to the present invention. It is a block diagram for explaining in detail the configuration around the recording head of the ink jet recording apparatus. FIG. 4 is a schematic diagram for explaining a discharge port surface of a recording head applied in an embodiment of the present invention. It is a block diagram for demonstrating the structure of control of the inkjet recording device applicable to this invention. FIG. 4 is a diagram for explaining an image processing process inside a host device and a recording device. It is a schematic diagram for demonstrating the index pattern about one certain color. FIG. 6 is a diagram showing recording positions of dots that are actually added by the paper preliminary ejection addition process. FIG. 5 is a diagram illustrating an arrangement state of dots recorded for preliminary ejection on the paper in each recording scan when two-pass multi-pass recording is performed in both directions. It is a figure showing an example of an output image at the time of not performing a paper surface preliminary discharge in order to explain a problem to be improved. FIG. 6 is a diagram illustrating an arrangement state of dots recorded for preliminary ejection on a paper surface in a reciprocal recording scan when two-pass multi-pass recording is performed in both directions. FIG. 6 is a diagram illustrating an arrangement state of dots recorded for preliminary ejection on a paper surface in a reciprocal recording scan when two-pass multi-pass recording is performed in both directions. FIG. 6 is a block diagram illustrating a case where image processing up to quantization processing is executed by a printer driver of a host device. FIG. 10 is a diagram for explaining an image processing process in the host device and the recording apparatus when the paper surface preliminary ejection addition processing is executed before the index development processing. It is the figure which showed the example of the index pattern with respect to input level "0001" after paper space preliminary discharge data is added.

Explanation of symbols

200 Host device 210 Image controller 220 Print engine 221 MPU
227 ROM
228 RAM
222 ASIC
223 Carriage drive system 224 Transport drive system 225 Recovery drive system 226 Head drive system 229 Print buffer 230 Mask buffer 240 Printer main body 250 Reception buffer 260 Paper pre-discharge buffer 500 Color conversion process 510 Color separation process 520 Quantization process 530 Index development process 540 Mask pattern thinning processing 550 Pre-discharge additional processing on paper

Claims (16)

By ejecting ink from a plurality of recording elements arranged in a predetermined direction based on image data or based on preliminary ejection data for maintaining the recording characteristics of the recording elements while being unrelated to the image data In an inkjet recording method for forming an image on a recording medium using a recording head for forming dots on the recording medium,
Generating first recording data by adding first preliminary ejection data to the first portion of the image data;
A first recording step of ejecting ink onto the recording medium according to the first recording data while moving and scanning the recording head in a direction intersecting the predetermined direction;
Transporting the recording medium in a direction intersecting the first direction;
Generating second print data by adding second preliminary ejection data to a second portion different from the first portion of the image data;
A second recording step of ejecting ink to the recording medium in accordance with the second recording data while moving and scanning the recording head in a direction opposite to the first recording step;
The first dot pattern formed on the recording medium by the first preliminary ejection data and the second dot pattern formed on the recording medium by the second preliminary ejection data are different from each other. Inkjet recording method.   2. The ink jet recording method according to claim 1, further comprising a step of ejecting ink at a position different from the recording medium immediately before the first recording step and immediately before the second recording step.   The inkjet recording method according to claim 2, wherein the number of dots is different between the first dot pattern and the second dot pattern.   2. The ink jet recording method according to claim 1, wherein at least one of the first dot pattern and the second dot pattern has a dot arrangement density that changes in a moving scanning direction of the recording head.   The inkjet recording method according to claim 4, wherein a region having the arrangement density of 0 exists.   The inkjet recording method according to claim 4, wherein the first dot pattern and the second dot pattern have an array density that changes symmetrically with respect to a moving scanning direction of the recording head.   7. The ink jet recording method according to claim 1, wherein the dot pattern synthesized by the first dot pattern and the second dot pattern is uniformly arranged on the recording medium. .   The method further includes a step of converting the image data from multi-value data to binary data, wherein the first preliminary discharge data and the second preliminary discharge data are added to the converted binary data. The ink jet recording method according to claim 1, wherein the binary data is   The method further includes a step of converting the image data into low-level multi-value data, wherein the first preliminary discharge data and the second preliminary discharge data are added to the converted multi-value data. The inkjet recording method according to claim 1, wherein the inkjet recording method is multi-value data.   The inkjet recording method according to claim 9, further comprising a step of converting the first recording data and the second recording data into binary data.   The recording head discharges black, cyan, magenta, and yellow dark ink and at least one of light black, light cyan, light magenta, and light yellow whose recording density is lower than the dark ink. The inkjet recording method according to claim 1, wherein the inkjet recording method is prepared.   The ink jet recording method according to claim 1, wherein the recording head is prepared for ejecting black, cyan, magenta, and yellow ink.   The ink jet recording method according to claim 1, wherein the recording element ejects ink by applying a voltage pulse to an electrothermal energy converter provided therein. By ejecting ink from a plurality of recording elements arranged in a predetermined direction based on image data or based on preliminary ejection data for maintaining the recording characteristics of the recording elements while being unrelated to the image data In an inkjet recording system that uses a recording head that forms dots on a recording medium and forms an image on the recording medium,
Means for generating first print data by adding first preliminary ejection data to the first portion of the image data;
Means for ejecting ink onto the recording medium according to the first recording data while moving and scanning the recording head in a direction intersecting the predetermined direction;
Means for transporting the recording medium in a direction intersecting the first direction;
Means for generating second print data by adding second preliminary ejection data to a second portion different from the first portion of the image data;
Means for ejecting ink to the recording medium according to the second recording data while moving and scanning the recording head in a direction opposite to the first recording step;
The first dot pattern formed on the recording medium by the first preliminary ejection data and the second dot pattern formed on the recording medium by the second preliminary ejection data are different from each other. Inkjet recording system.   A computer program for causing a computer to realize the ink jet recording method according to claim 1. A storage medium storing the computer program according to claim 15.

Images