JP4717620B2 - Inkjet recording method and inkjet recording apparatus - Google Patents

Description

  The present invention relates to an ink jet recording method and an ink jet recording apparatus for recording an image on a recording medium using an ink jet recording head having a nozzle row in which nozzles for ejecting ink are arranged at high density.

  With the spread of information processing devices such as computers and word processors and communication devices, there is an increasing demand for output devices that output digital image information processed by these devices. As one of the output devices, an ink jet recording apparatus that forms an image by ejecting ink droplets to form dots on a recording medium is rapidly spreading. In order to improve the recording speed and the resolution of a recorded image, this ink jet recording apparatus has a large number of ejection portions (hereinafter also referred to as nozzles) composed of ink ejection ports for ejecting ink droplets, liquid paths, and recording elements, An integrated and arranged recording head is used.

  In recent years, there has been an increasing demand to be able to output color recording images. For this reason, in an inkjet recording apparatus that records a color image, a recording operation is performed using a recording head that ejects a plurality of types of color inks in addition to a recording head that ejects black ink. At this time, since the recording head and the recording medium are kept in a non-contact state, the recording operation can be performed with low noise. Further, the ink jet recording apparatus can record high-resolution images at high speed by increasing the nozzle density. In addition, since there is no need to perform special processing such as development and fixing on a recording material such as plain paper, it has various advantages that a high-quality image can be obtained at a low price. In particular, an on-demand type ink jet recording apparatus is easy to color, and since the apparatus itself can be reduced in size and simplified, future demand is also promising. Further, as the demand for colorization of recorded images increases, there is a demand for higher image quality and higher speed for inkjet recording apparatuses.

  On the other hand, against the background of recent technological advances in nozzle integration, it is becoming possible to manufacture recording heads with higher density and longer length. In general, a recording head manufactured in high density and long is called a long recording head, and this long recording head has a width of an area that can be recorded on the recording medium by a single recording scan on the recording medium. Can be enlarged as compared with the case where a conventional short recording head is used. For this reason, further technical development has been promoted as an extremely useful technique capable of realizing unprecedented high-speed recording while maintaining high image quality as in the past.

However, the following problems may occur in an inkjet recording apparatus that performs a recording operation using a high-density and long recording head as described above.
That is, when a large number of ink droplets are simultaneously ejected from a long recording head in which nozzles are arranged at a high density, and a recording scan of the recording head or a scanning of the recording medium is performed at a high speed, there is a gap between the recording head and the recording medium. Irregular airflow (turbulence) is generated. As a result, there arises a problem that the landing positions of the ink droplets are disturbed. It is also known that the turbulent flow generated between the recording head and the recording medium has a great influence on the ink droplet ejection state, and this is also a factor that lowers the landing accuracy. Such fluctuations in the landing position cause streaky or vortex density unevenness in the image, which causes a problem of remarkably lowering the image quality. This realizes high-speed and high-quality image recording. It is a hindrance.

Currently, a technique disclosed in Patent Document 1 or Patent Document 2 is known as a technique for solving the above-described streaky density unevenness.
Patent Document 1 discloses a technique in which nozzle rows provided in a recording head are divided into printing and non-printing nozzle groups with a constant pitch, and further, the constant pitch is made finer. According to this technique, it is possible to make it difficult to visually recognize the generated stripe-shaped density unevenness (streaky unevenness).

  Further, Patent Document 2 discloses a mask pattern for distributing an image in the same recording area to a plurality of times of main scanning when a recording method for completing an image in the same recording area by a plurality of times of main scanning is adopted. Is disclosed. In this mask pattern, the thinning rate is set larger at the end side than at the center side of the nozzle row. By using this mask pattern, it is possible to reduce the frequency of use of the end nozzles and eliminate density unevenness caused by ejection deviation from the end nozzles.

JP 2001-18376 A JP 2002-96455 A

  However, the techniques described in each of the above patent documents still have room for improvement in terms of avoiding image degradation due to the occurrence of turbulent flow generated between the recording head and the recording medium. In other words, the turbulent flow generated between the recording head and the recording medium is not limited to the end of the nozzle row and may occur in the entire nozzle row, and the influence of the turbulent flow between the nozzle rows can be ignored. It is gone. For this reason, it is difficult to sufficiently avoid image degradation due to the occurrence of turbulence only with the conventional technique.

  In the future, what is required of an ink jet recording apparatus is to simultaneously realize higher speed and higher image quality. For this purpose, it is required to improve the deterioration of the image quality due to the turbulent flow as described above.

  The present invention can reduce turbulent flow generated between a recording head and a recording medium even when high-speed recording is performed using a recording head in which ink discharge portions are arranged at high density, and the ink droplet landing accuracy is reduced. It is an object of the present invention to provide an ink jet recording apparatus and an ink jet recording method capable of reducing the above problem.

  In order to achieve the above object, the present invention has the following configuration.

That is, the first embodiment of the present invention, the multi-valued image data corresponding to an image to be recorded on the same recording area, converting means for converting the binary image data, against the same recording area using different mask patterns corresponding to the respective scanning multiple times, and thinning means for thinning the image data of the corresponding binary to the same recording area, thinned by said thinning means in each of said plurality of scans 2 Recording control means for completing an image to be recorded in the same recording area by recording a thinned image in the same recording area based on value image data, each of the different mask patterns A first region that thins out binary image data at a relatively high thinning rate and a second region that thins out at a relatively low thinning rate are arranged in the nozzle arrangement direction. The width of the nozzle row direction of the first region may be greater than the nozzle arrangement width of the second region.

  The second aspect of the present invention is an ink jet recording which records an image on the recording medium by ejecting ink droplets from the nozzle while scanning a recording head in which a plurality of nozzles are arranged relative to the recording medium. A scanning means for relatively scanning the recording head a plurality of times with respect to the same recording area of the recording medium, and a multivalue corresponding to each pixel constituting an image to be recorded in the same recording area Binary image data corresponding to the same recording area by using conversion means for converting the image data into binary image data and different mask patterns corresponding to each of a plurality of scans on the same recording area And thinning out the same recording area based on binary image data thinned out by the thinning means in each of the plurality of scans. Recording control means for completing an image to be recorded in the same recording area by recording an image, and each of the different mask patterns includes an area allowing recording of the binary image data and the 2 An area that does not allow recording of value image data is arranged, and in the nozzle arrangement direction, the proportion of the recording allowable area is relatively high in a unit of a width that is an integral multiple of the width of the pixel. A portion and a relatively low portion are repeatedly arranged.

The third aspect of the present invention is an ink jet recording which records an image on the recording medium by ejecting ink droplets from the nozzle while scanning a recording head in which a plurality of nozzles are arranged relatively to the recording medium. A scanning step of relatively scanning the recording head a plurality of times with respect to the same recording area of the recording medium, and multivalued image data corresponding to an image to be recorded in the same recording area. , thinning the step of converting the binary image data, the binary image data using a different mask patterns corresponding to the respective scanning multiple times, corresponding to the same recording area against the same recording area Ku and as engineering, by recording the image thinning the same recording area on the basis of the binary image data drawn between Te said plural scans each odor, the same recording area And a degree Engineering of Ru to complete an image to be recorded, each of the different mask patterns are first thinned out in the first region and the relatively low thinning rate of thinning out image data at a relatively high thinning rate of the binary Two regions are arranged in the nozzle arrangement direction, and the width of the first region in the nozzle array direction is larger than the width of the second region in the nozzle arrangement direction .

  According to a fourth aspect of the present invention, ink jet recording is performed in which an image is formed on the recording medium by ejecting ink droplets from the nozzle while scanning a recording head in which a plurality of nozzles are arranged relative to the recording medium. A method of relatively scanning the recording head a plurality of times with respect to the same recording area of the recording medium; and a multivalue corresponding to each pixel constituting an image to be recorded in the same recording area The binary image data corresponding to the same recording area using a step of converting the image data into binary image data and different mask patterns corresponding to each of a plurality of scans of the same recording area A thinning image is recorded in the same recording area based on the binary image data thinned out in each of the plurality of scans. A step of completing an image to be recorded in the same recording area, wherein each of the different mask patterns does not allow the recording of the binary image data and the recording of the binary image data. In the arrangement direction of the nozzles, there are a relatively high portion and a relatively low portion in which the recording allowable area occupies a unit of an integral multiple of the pixel width in the nozzle arrangement direction. It is characterized by being repeatedly arranged.

  In the present invention, “scanning” refers to the following operation. That is, ink is moved while relatively moving in a direction intersecting the nozzle arrangement direction (which may be oblique) with one nozzle row in which nozzles are arranged in a high density in a substantially row shape. Refers to an operation of recording all or a part of an image by ejecting. Therefore, when a plurality of nozzle rows are arranged in parallel in the main scanning direction, a plurality of nozzle rows and a recording medium correspond to the number of arranged nozzle rows even when the relative movement is performed once. It will be described that “scanning” is performed. In addition, even when the recording head and the recording medium repeatedly perform relative movement as in so-called multi-pass recording, it will be described that a plurality of “scans” corresponding to the number of repetitions of the relative movement have been performed. . For example, in the case where three-pass multi-pass printing is performed by a head unit having three print heads of the same color, a description will be given assuming that a total of nine “scans” have been performed.

  According to the present invention, even when recording is performed at high speed using a recording head in which ink ejection portions are arranged at high density, turbulence generated between the recording head and the recording medium is reduced, and ink droplets are reduced. The landing position can be maintained with high accuracy, and a high-quality image can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing a schematic configuration of a line type ink jet recording apparatus applicable to an embodiment of the present invention.
In FIG. 1, reference numeral 11 denotes an ink tank that stores ink used for recording, and ink containing a predetermined color material is stored in the ink tank. The ink stored in the ink tank 11 is supplied to the line head (recording head) 17 via the ink supply unit 12. The line head 17 is held by a head holding member 14 so as to be movable up and down, and an interval between the line head 17 and the recording medium 19 (hereinafter referred to as a sheet interval) can be adjusted. As will be described in detail later with reference to FIG. 2, the line head includes a plurality of ejection units (hereinafter also referred to as nozzles) that eject ink along a direction orthogonal to the width direction (X direction) of the recording medium P. And) are arranged at high density. A capping member 15 is provided so that the discharge ports of the nozzles provided in the line head 17 can be sealed and opened. The capping member 15 is installed for each line head for the purpose of preventing clogging of each nozzle due to adhesion of ink due to evaporation of the ink solvent or adhesion of foreign matters such as dust. The capping member 15 is configured so that the ink discharge port can be sealed (capped) as necessary. In addition, the recording medium P is fed to a transport mechanism having a transport roller 18 and a transport belt 16 as main components by a paper feed mechanism (not shown). The operations of the transport mechanism and the line head 17 are controlled by a controller unit (not shown). That is, the line head 17 discharges ink from each nozzle based on discharge data sent from the controller unit through the flexible cable 13, and the transport system transports the recording medium in synchronization with the ink discharge operation of the line head 17. An image is recorded on the recording medium by the conveying operation of the recording medium and the ink discharging operation.

FIG. 3 is a front view showing a schematic configuration of a serial type inkjet recording apparatus applicable to the embodiment of the present invention.
In the figure, 32 is a carriage supported by a guide shaft 27 and a linear encoder 28 so as to be capable of reciprocating along the main scanning direction (X direction). The carriage 32 reciprocates along the guide shaft 27 by driving the carriage motor 30 and moving the drive belt 29. A plurality of ink jet recording heads (hereinafter simply referred to as recording heads) 22 are detachably mounted on the carriage 32. In each recording head, a plurality of ejection units (hereinafter also referred to as nozzles) for ejecting ink are arranged along the main scanning direction. The liquid path formed in each nozzle of the recording head 21 is provided with a heating element (electrothermal converter) that generates thermal energy for discharging ink in the liquid path. An ink tank 21 supplies ink of a predetermined color to each recording head. The ink tank 21 and the recording head 22 constitute an ink cartridge.

  Further, this serial type ink jet recording apparatus is provided with a transport mechanism for transporting a recording medium P such as plain paper, high-quality exclusive paper, OHP sheet, glossy paper, glossy film, postcard and the like. This transport mechanism includes a transport roller (not shown), a paper discharge roller 25, a transport motor 26, and the like, and is transported intermittently in the sub-scanning direction (Y direction) as the transport motor 26 is driven.

  A discharge signal and a control signal sent from a controller unit, which will be described later, are sent to the recording head 22 and the transport mechanism via a flexible cable 23, and each recording head 22 and the transport mechanism are sent according to the discharge signal and the control signal. Works.

  That is, the heating element of the recording head is driven based on the position signal of the carriage 32 output from the linear encoder 28 and the discharge signal, and the ink droplets are discharged from the nozzles by the thermal energy generated at the time of driving. To land on. Further, the transport mechanism transports the recording medium by a certain amount in the sub-scanning direction between the main scanning of the recording head based on the control signal. By repeating the recording operation by the recording head and the conveying operation by the conveying mechanism, an image is formed on the entire recording medium. In addition, a recovery unit 34 having a cap portion 35 that can seal and open the ejection port formed in the recording head is installed at the home position of the carriage 32 set outside the recording area.

Next, the structure of the ejection part (nozzle) provided in the recording head of each ink jet recording apparatus described above will be described with reference to FIG.
In FIG. 6, the recording heads 17 and 22 are roughly constituted by a heater board nd, which is a substrate on which a plurality of heaters nb for heating ink are formed, and a top board ne placed on the heater board nd. ing. A plurality of discharge ports na are formed in the top plate ne, and a tunnel-like liquid path nc communicating with the discharge ports na is formed behind the discharge ports na. Each liquid path nc is connected to one ink liquid chamber in common behind it, and ink is supplied to the ink liquid chamber via an ink supply port, and this ink is supplied from the ink liquid chamber to each liquid path nc. To be supplied.

  The heater board nd and the top plate ne are positioned and joined so that each heater nb corresponds to each liquid path nc. In FIG. 6, only four heaters nb are shown, but one heater nb is arranged corresponding to each liquid path nc. When a predetermined drive pulse is supplied to the heater nb, the ink on the heater nb boils to form bubbles, and the ink in the liquid path nc is discharged as droplets from the discharge port na due to the volume expansion of the bubbles. The Further, the discharge port na, the heater nb, and the liquid path nc constitute a nozzle (discharge portion) n.

  The ink jet recording method applicable to the present invention is not limited to the method using a heating element (heater) as shown in FIG. For example, a charge control type, a divergence control type, and the like can be applied to a continuous ink jet system that continuously ejects ink droplets into particles. In addition, as long as it is an on-demand type ink jet recording system that ejects ink droplets as necessary, a pressure control system that ejects ink droplets from ejection ports by mechanical vibration of a piezoelectric vibration element can be applied.

FIG. 7 is a block diagram illustrating a configuration example of a control system of the ink jet recording apparatus according to the present embodiment.
In FIG. 7, reference numeral 71 denotes a data input unit that receives image data and control data transmitted from an external device 80 such as a host computer, and 72 denotes an operation unit that performs data input or setting operation. Reference numeral 73 denotes a CPU for performing various information processing and control operations, and 74 is a storage medium for storing various data. In this storage medium 74, a recording information storage unit 74a for storing mainly information relating to the type of the recording medium, information relating to ink, and information relating to the environment such as temperature and humidity during recording, and various control programs A program storage unit 74b for storing groups is included. Further, 75 is a RAM that temporarily stores processing data and input data of the CPU 72, and 76 is an image data processing unit that performs predetermined image processing including color conversion and binarization processing on the input image data. It is. Reference numeral 77 denotes an image recording unit that outputs an image by a recording head, a transport mechanism, and the like.

  More specifically, the external device 80 includes, for example, an image input device such as a scanner or a digital camera, or a personal computer. Multi-value image data (for example, RGB 8-bit data) output from the scanner, digital camera, or the like, or multi-value image data stored in a hard disk of a personal computer or the like is input to the image data input unit 71. The operation unit 72 also includes various keys for setting various parameters and inputting a recording start instruction. The CPU 73 controls the entire inkjet recording apparatus according to various programs in the storage medium. As a program stored in the storage medium 74, there is a program for operating the ink jet recording apparatus according to a control program or an error processing program, and all the operations of the present embodiment are executed according to this program. As the storage medium 74 for storing the program, a ROM, FD, CD-ROM, HD, memory card, magneto-optical disk, or the like can be used. The RAM 75 is used as a work area for executing various programs stored in the storage medium 74, a temporary save area for error processing, and a work area for image processing. In the RAM 75, after copying various tables in the storage medium 74, the contents of the tables can be changed, and image processing can be performed while referring to the changed tables.

The image processing unit 76 performs color separation processing for converting input multi-value image data (for example, 8-bit RGB data) into multi-value data for each ink color (for example, 8-bit CMYBk data) for each pixel. Further, the multi-value data of each color is quantized into data of K value (for example, 17 values) for each pixel, and the gradation value “K” (gradation value 0 to 16) indicated by each of the quantized pixels. The dot arrangement pattern corresponding to is set. Here, the multi-value error diffusion method is used for the K-value processing, but the present invention is not limited to this, and an arbitrary halftone processing method such as an average density storage method or a dither matrix method may be used. Is also possible. Further, after performing the above-described K-value conversion processing, each gradation is made to correspond to a dot arrangement pattern described later (this pattern may be referred to as a unit shape INDEX of an image having a dot concentration type). Dot arrangement patterning processing is performed. Then, in a plurality of print scans by the print head, a thinning process is performed on the binary print data generated by the dot arrangement patterning process to distribute the print data to each print scan using the thinning mask pattern. Note that a plurality of recording scans by the recording head include one recording scan performed by a recording head having two or more nozzle rows.
By repeating these processes, binary recording data representing ejection and non-ejection for each nozzle of the recording head is created. The image recording unit 77 then ejects ink based on the binary recording data created by the image data processing unit 76 to form a dot image on the recording medium.

Next, the arrangement state of the nozzles provided in the recording head used in each of the ink jet recording apparatuses will be described with reference to FIG. 2, FIG. 4, and FIG.
FIG. 2 is a diagram showing an arrangement state of nozzles of a recording head (line head) 17 used in the full line type ink jet recording apparatus shown in FIG.
In FIG. 2, the recording head 17 has a plurality (four in this case) of nozzle rows 17A, 17B, 17C, and 17D arranged side by side in the recording medium conveyance direction (Y direction). Each nozzle row has the same configuration, and each is a so-called connecting head in which two middle nozzle rows are connected. That is, the nozzle row 17A includes a middle nozzle row 171 and a middle nozzle row 175. The line head 17 </ b> B includes a middle nozzle row 172 and a middle nozzle row 176. The line head 17 </ b> C includes an intermediate nozzle row 173 and an intermediate nozzle row 177. Further, the line head 17D includes a middle nozzle row 174 and a middle nozzle row 177.

  Each nozzle row 17A, 17B, 17C, and 17D constituting each line head has the following configuration. In addition, since each nozzle row has the same configuration, the following description will be given taking the nozzle row 17A as an example.

  The middle nozzle row 171 constituting the nozzle row 17A is composed of a plurality (here, four) of small nozzle rows NG1 to NG4. These small nozzle rows are arranged in a staggered pattern. Further, each small nozzle row has a configuration in which the nozzle arrangement density in the sub-scanning direction is increased by arranging a plurality of nozzles n that eject ink droplets of an average of 2.5 pl in a staggered manner. . Further, the adjacent small nozzle rows in the nozzle row 171 overlap each other at the ends, so that a constant arrangement density can be obtained for the entire nozzle row. In this embodiment, the nozzle arrangement density in the nozzle row 171 is 1200 dpi.

  The nozzle array configured in this manner can perform recording of approximately 4 inches width by one recording scan by four small nozzle arrays, that is, one middle nozzle array. The nozzle rows 171 and 175 enable recording with a width of about 8 inches. The other line heads 17C, 17B, and 17D have the same configuration.

  2 shows a line head in which four nozzle rows are arranged in parallel in the sub-scanning direction (Y direction), the present invention is not limited to the line head having the above-described configuration, It is also possible to use a line head having a configuration. For example, it may be possible to eject large and small ink droplets from the same nozzle, or it may be capable of ejecting dark ink and light ink. Further, the number of nozzle rows is not limited to four, and other numbers of nozzle rows may be provided in parallel.

Next, a configuration example of a recording head used in the serial type ink jet recording apparatus shown in FIG. 3 will be described with reference to FIGS.
The recording head 22 shown in FIG. 4 has a configuration in which four nozzle rows 22A, 22B, 22C, and 22D are arranged in parallel on a single recording head constituent member. In each nozzle row, a plurality of nozzles n are arranged in a zigzag pattern at a high density along a certain arrangement direction (Y direction). In this recording head, the arrangement density of each nozzle row is 1200 dpi, and the average ink droplet amount of each nozzle is 2.5 pl.

  In the state where the recording head 22 is mounted on the carriage 32, the arrangement direction of the plurality of nozzles coincides with the sub-scanning direction (Y direction) that is the recording medium conveyance direction. Accordingly, the scanning direction of the recording head 22 is the X direction orthogonal to the sub-scanning direction.

  On the other hand, the recording head 22 shown in FIG. 5 also has a configuration in which four nozzle rows 22A, 22B, 22C, and 22D are arranged in parallel on a single recording medium constituent member, similarly to the recording head shown in FIG. Have.

  However, in the recording head 22 shown in FIG. 5, each nozzle row is a relatively long nozzle row in which two small nozzle rows are connected. That is, the nozzle row 22A includes a small nozzle row 2211 and a small nozzle row 225. The nozzle row 22B includes a small nozzle row 222 and a small nozzle row 226. The nozzle row 22C includes a small nozzle row 223 and a small nozzle row 227. The nozzle row 22D includes a small nozzle row 224 and a small nozzle row 228. Further, the two small nozzle rows constituting each nozzle row are arranged with their end portions overlapping each other.

  Furthermore, each small nozzle row arranges a plurality of nozzles n that eject ink droplets of an average of 2.5 pl in a staggered manner along the Y direction, thereby reducing the nozzle arrangement density in the sub-scanning direction (Y direction). It has a high density configuration. In the recording head 22 shown in FIG. 5, the nozzle arrangement density in each nozzle row is 1200 dpi.

  4 and 5, it is also possible to form a recording head for each nozzle row and make them detachable individually as shown in FIG.

Next, an embodiment of thinning division recording, which is a characteristic part of the present invention, will be described.
In this embodiment, by thinning out print data using a mask pattern having a low print rate area (high thinning rate area) and a high print rate area (low thinning rate area) having a predetermined width, Distribute the recording data to the nozzles. This is one of the characteristic configurations of this embodiment.

First, the principle of the present invention found out by the present inventors as a result of extensive studies by the present inventors will be described below.
In the serial type ink jet recording apparatus as shown in FIG. 3, when the scanning speed of the carriage 32 that scans the recording head 22 is slow, or when the nozzles are arranged at an extremely low density of about 150 dpi, the nozzle array The turbulence generated inside is weak. However, when the nozzles are arranged at a high density of 600 dpi or more and an image with a high recording rate is recorded at a high speed, a strong turbulent flow is generated.

  This was confirmed by the following experiment. In other words, the distance between the recording head 22 and the recording medium P is set to about 0.5 mm to 3.0 mm, and the relative scanning speed between the recording head 22 and the recording medium P exceeds 5 inches / s (sec). A main scan was performed. At this time, when a recording head having a nozzle row in which nozzles for ejecting small droplets of 6 pl or less are arranged at a high density of about 600 dpi, the region width for ejecting ink droplets simultaneously in the nozzle row is wide. It was observed that strong turbulence was generated and the landing accuracy was significantly degraded.

  In this case, in a recording medium having a relatively rough paper surface as represented by plain paper, the landing ink droplets have a large diffusion (bleeding), and therefore, a certain amount of variation in the landing position is within the allowable range for image quality. . However, when recording is performed on a recording medium with less bleeding such as coated paper or glossy paper, the landing position is disturbed and is easily recognized as density unevenness.

  As a result of repeating the experiment as described above, it was confirmed that the recording conditions in which the image deterioration appears remarkably in the ink jet recording apparatus are as follows.

That is,
(1) The nozzle rows of the recording head are arranged in a substantially single row with a density of 600 dpi or more (here, the substantially one row includes the staggered arrangement shown in FIGS. 3 and 9).
(2) The amount of ink droplets from the nozzle is a small droplet of 6 pl or less,
(3) The relative movement speed of the recording head and the recording medium, that is, the recording scanning speed is 5 inches / s or more,
(4) The distance between the recording head and the recording medium is 0.5 mm or more.

  Furthermore, it was also confirmed that the higher the recording rate during one main scan, the more noticeable the deterioration of the image. FIG. 9 schematically shows how ink droplets land at that time.

FIG. 9A shows the flying direction of ink droplets and the state of dots formed on a recording medium when ink droplets are ejected from a nozzle row in which nozzles are arranged in approximately one row at a density of 1200 dpi. The recording conditions at this time were set as follows.
The relative movement speed (recording scanning speed) between the recording head and the recording medium was set to a very low speed of 2.5 inches / s. The drive frequency of each nozzle was set to 3 kHz. The recording rate was set to 100% (state in which ejection was performed from all nozzles in the nozzle row). The separation distance between the recording head and the recording medium was set to 0.4 mm.
Under such recording conditions, as shown in the figure, the ink droplets ejected from each nozzle row fly in substantially the same direction as indicated by the arrows in the figure, and therefore, the landing positions of the ink droplets are disturbed. There was nothing, and an image having no uneven density was formed.

On the other hand, in FIG. 9B, the recording scanning speed is set to a high speed of 15 inches / s as the recording conditions, the distance between the recording head and the recording medium is set to 1.5 mm, and the other conditions are the same as in FIG. 9A. In this state, ink droplets are ejected.
In this case, a turbulent flow is generated between the recording head and the recording medium. As a result, the flying directions of the ink droplets ejected from the nozzles are non-uniform, and the landing position is disturbed. Due to the disturbance of the landing position, density unevenness, white stripes, and black stripes occurred in the formed image.

  FIG. 9C shows a case where the 3-nozzle-width region HN and the 6-nozzle-width region LN are alternately set in the same nozzle row as in FIGS. 9A and 9B. Here, the region HN having a width of 3 nozzles is a high recording rate region for recording at a high recording rate, and the region LN having a width of 6 nozzles is a low recording rate region for recording at a low recording rate. In this case, even when the recording scanning speed was set to 15 inches / s, the landing position of the ink droplets was not disturbed.

  In FIG. 10, in the nozzle array arranged at a density of 1200 dpi, similarly to the above-described FIG. 9C, a low recording rate region Ln with 6 nozzles and a high recording rate region Hn with 3 nozzles are alternately set. It shows a state in which an image is formed by repeating scanning and recording three times. FIG. 10A shows the flying state of the ink droplets ejected during the first scan and the landing state on the recording medium. FIG. 10B shows the flying state of the ink droplets ejected during the second scanning and the landing state on the recording medium. FIG. 10C shows the flying state of the ink droplets ejected during the third scan and the landing state on the recording medium. FIG. 10D shows a dot formation state by a total of three scans of FIGS. 10A to 10C.

  As shown in FIG. 10, even in this case, the ink landing position is not disturbed, and a good image can be formed. In the example shown in FIG. 10, for convenience, the case where ink is not ejected from the low recording rate area is shown. However, it is not essential as a recording condition that ejection is not performed at all. It is also confirmed that there is. For convenience, FIG. 10 shows a case in which all ejections (100% recording rate) are performed from the high recording rate area, but the ratio can be changed according to the ejection state of the low recording rate. . Note that the level of the recording rate in the nozzle row depends on the level of the thinning rate of the mask pattern M for thinning out the recording data. Accordingly, the thinning rate of the mask pattern corresponding to the high recording rate region Hm in the nozzle row is set low, and the thinning rate of the mask pattern corresponding to the low recording rate region Lm in the nozzle row is set high.

FIGS. 11 to 15 conceptually show mask patterns for performing thinning processing on print data so as to alternately set the high print rate area Hn and the low print rate area Ln in the nozzle row as described above. It is a figure.
A mask pattern 110 shown in FIG. 11 is a pattern in which low recording rate regions (high thinning rate regions) Lm and high recording rate regions (low thinning rate regions) Hm are alternately arranged. The low recording rate area (high thinning rate area) is an area where the recording data binarized by the image processing unit 76 is thinned out at a high thinning rate. The high recording rate region (low thinning rate region) Hm is a region where the binarized recording data is thinned out at a low thinning rate. Each of the regions Lm and Hm is a strip-like region extending linearly along the main scanning direction.

  The mask pattern thinning rate refers to the ratio of the non-recording area indicating the thinned-out portion of the total area of the mask pattern composed of a predetermined recording allowable area and a non-recording area. On the other hand, the mask pattern recording rate refers to the ratio of the recording allowable area to the total area of the mask pattern composed of the predetermined recording allowable area and the non-recording area. The mask pattern recording rate and the thinning rate The opposite is true. Therefore, the low thinning rate region and the high recording rate region, and the high thinning rate region and the low thinning rate region have the same meaning. Further, the thinning rate and recording rate of the mask pattern are predetermined values, and neither is a value affected by the image data.

  When this mask pattern 110 is used, even when recording is performed by performing high-speed scanning with a recording head of a nozzle array in which nozzles are arranged at high density as shown in FIGS. Such a good flying state of ink droplets can be obtained. This makes it possible to form a good image with little landing error.

  For example, by thinning the print data with the mask pattern 110, the nozzle row is in a state as shown in FIG. 9C and FIG. That is, the nozzle row has a region (high recording rate region) Hn where the number of ejected ink droplets tends to increase and a region (low recording rate region) Ln where the number of ejected ink droplets tends to decrease. It becomes the state divided | segmented alternately. In other words, the width of the high recording rate area Hn in the nozzle row direction is divided by the low recording rate area Ln. As a result, the level of turbulence generated in the gap between the recording head and the recording medium is reduced, and fluctuations in the landing position are made uniform over the entire nozzle array, and an image with good quality can be obtained.

Here, although the reason (mechanism) of reducing the above-described displacement of the landing position by using the mask pattern in which the high thinning rate region and the low thinning rate region are alternately arranged is the inventor's estimation, To do.
In order to complete an image in a short time in a serial type or full line type inkjet printer, it is necessary to perform high-speed relative scanning at a high recording rate. At this time, as described above, the turbulence of the airflow occurs in the gap between the recording head and the recording medium. The amount of the generated air flow and how it is disturbed largely depend on the scanning speed and the recording rate, but the air flow disturbance is suppressed by configuring the thinning rate distribution in the mask pattern as in the present invention.
That is, a large air flow is generated from the recording head head side to the subsequent side in the relative scanning direction by high-speed relative scanning between the recording head and the recording medium. This is the airflow generated in the gap between the recording head and the recording medium described above. Ink droplets are ejected at a high density from the recording head in a direction substantially perpendicular to the air flow, but the air current is disturbed by the high density ink ejection. Specifically, an air flow is generated so as to bypass the wall of the high density discharged ink. Then, the discharge direction of the ink droplets is changed by the detour airflow, which leads to the landing position deviation.
However, if mask patterns arranged alternately such that the thinning rate in the nozzle arrangement direction is high, low, high, and low are used, gaps are generated in the walls of high-density ejected ink. Specifically, the portion corresponding to the high thinning rate region of the mask pattern becomes the gap, and therefore, an alternating gap is generated in the nozzle arrangement direction on the wall of the ejected ink. As a result, the airflow is removed from the gap, and the amount of the detour airflow is reduced accordingly. As a result, the landing position deviation due to the detour airflow is also suppressed.

Note that the image formed by one scan of the recording head depends on the recording data, but it tends to correspond to the mask pattern shown in FIG. Areas recorded at a rate are alternately formed.
In the serial type ink jet recording apparatus as shown in FIG. 3, a plurality of complementary mask patterns in which the positions of the high recording area and the low recording area are changed are prepared, and this is switched for each scan. To the recording head. As a result, an image of the same color can be completed by a plurality of recording scans for the same scanning area.

  In a full-line type recording apparatus as shown in FIG. 1, when a recording operation is performed using the mask pattern, a line head having a plurality of nozzle arrays for ejecting ink of the same color is provided and a serial printer is provided. Similarly, a plurality of complementary mask patterns are prepared. Then, the image data thinned out by each mask pattern is supplied to each nozzle row to perform a recording operation. Thus, the same recording area is substantially scanned a plurality of times to complete the same color image.

  A mask pattern 120 shown in FIG. 12 is a pattern in which a low recording rate region Lm and a high recording rate region Hm having a strip shape are alternately arranged like the mask pattern 110 shown in FIG. However, in the mask pattern shown here, the boundary between the high recording rate region Hm and the low recording rate region Lm continuously changes (swells) in the nozzle arrangement direction. In this case, as in the case shown in FIG. 11, image quality deterioration due to airflow can be reduced. Furthermore, since one nozzle in the nozzle row performs recording at a high recording rate and recording at a low recording rate in one scan, it is possible to make the usage frequency of the nozzles uniform. . Therefore, the mask pattern 120 has an advantage that the life of each nozzle can be made uniform and the life of the entire recording head can be increased. In addition, by causing the strip-like regions to have a waveform undulation as described above, it is possible to reduce the occurrence of stripe irregularities between the regions.

  In addition, when the recording head is attached obliquely, there is generally a concern that unevenness occurs in the formed image. However, this problem can be solved by increasing the head mounting accuracy. In particular, in the full multi-line printer, the head is fixed to the printing apparatus and the recording medium is conveyed, so that the influence on printing is small compared to the serial type.

The mask pattern 130 shown in FIG. 13 shows an example in which the widths in the nozzle row direction of the low recording rate region Lm and the high recording rate region Hm are configured at unequal intervals. Here, a mask pattern used when an image in the same recording area is completed by two recording scans is shown. In the figure, 130a indicates a mask pattern used in the first scan, and 130b indicates a mask pattern used in the second scan.
Even in this case, if the width of the high recording rate area is equal to or smaller than the predetermined area width, a turbulent flow generated between the recording head and the recording medium can be reduced, so that a good image can be formed. . Also, if the nozzle row is relatively long, an air flow distribution occurs at a position corresponding to the nozzle row, and the area width of the high recording ratio should be designed according to the position in the nozzle row. Is preferred.

FIG. 14 shows a mask pattern used when an image is completed by four recording scans. Even in this case, if the high recording rate area width is equal to or smaller than the predetermined area width, it is possible to make it difficult to be adversely affected by the air current, and a good image can be formed.
In addition, when recording in the same recording area is completed by four scans (when recording is performed at a recording rate of 100%), when recording is performed at an equal recording rate, the recording rate in each scan is 25. %become. For this reason, there is a case where the influence of the turbulent flow on the ink droplets is reduced without using a mask pattern in which the width of the high recording rate area is set to a very narrow width as described above. However, as shown in FIG. 15, if the width of the high recording rate area is set wide, it is not desirable because density unevenness tends to appear at a pitch that can be visually recognized easily.

  Further, when an image is completed by many recording scans, the recording rate in one scanning is low and turbulent flow is not generated for the above-described reason. You may not need to set That is, the present invention is effective when the recording matrix has a resolution of 600 dpi or higher and an image is to be completed with the number of scans of about 4 or less. In particular, a more prominent effect appears when an image is completed by two scans. This is not limited to the serial type ink jet recording apparatus, and as described above, the full line type ink jet recording apparatus has two or more nozzle rows that discharge the same color ink in parallel, and each nozzle row completes the same color image. The same applies to the case.

  As described above, as a result of intensive studies, the present inventors have made the high recording ratio area and the low recording ratio area appear alternately in the same recording scan regardless of the periodicity or aperiodicity, and the high recording ratio. It has been confirmed that it is effective to arrange the rate regions within a predetermined region width. In other words, if the recording ratio is set as described above, turbulence generated between the recording head and the recording medium is reduced even when high-speed recording is performed using a recording head having nozzles arranged at high density, and the landing position is reduced. It can be experimentally confirmed that the fluctuation of is reduced over the entire nozzle array. It was also confirmed that when the strip width of the high recording ratio area is widened, turbulence is generated inside the high recording area and the image quality cannot be maintained. Furthermore, from the viewpoint of reducing the influence of turbulent flow, it is desirable that the strip width of the low recording rate area is wide. However, when the low recording rate area is widened, it is necessary to perform recording scanning to inevitably complete an image. It is necessary to increase the number of times. For this reason, it is desirable to set the width of the low recording rate area to an appropriate width. For example, when the printing is completed by two printing scans, the total of the low printing rate areas in the nozzle row is required to be equal to the total of the high printing rate areas. In addition, since it is necessary to complete the image by thinning and dividing the image, in the present invention, a plurality of printing scans (multiple scans) are performed so that the total width of the low recording rate area is equal to the total width of the high recording rate area. It is necessary to perform multiple scans by passes or multiple scans by multiple heads).

In addition, the results confirmed by experiments will be explained in detail.
A recording head having a nozzle arrangement density of 600 dpi was used, the interval between the recording head and the recording medium was set to 1.5 mm, and the recording operation was performed at a scanning speed of 15 inches / s.

  In this case, a strip-shaped thinning mask pattern in which a high recording rate region Hm having a width of 2.4 mm by 64 nozzles and a low recording rate region Lm in which recording is almost not performed at intervals of 2.4 mm was used. In this case, the landing of the ink droplets ejected from the high recording area Hn of the nozzle row was disturbed due to turbulent flow.

  When the strip width of the high recording rate region Hm is gradually reduced and set to a width of 1.2 mm corresponding to 32 nozzles, the uneven density of the image due to turbulent flow is reduced to such a level that the image quality does not become a problem. It was done. Therefore, it has been clarified that if the strip width of the high recording rate region is set to 1.2 mm or less, high-speed recording can be performed while suppressing image deterioration in a normal inkjet recording apparatus.

  Further, as recording conditions, the scanning speed was 5 to 50 inches / s, the distance between the recording head and the recording medium was 0.5 to 3.0 mm, and the volume of ejected droplets was 6 pl or less. In this case, as described above, image quality deterioration can be reduced by setting the high recording rate area to a very fine strip width. Such an image quality deterioration reduction effect is achieved by providing a full line type ink jet recording apparatus in which two or more nozzle rows are arranged side by side and recording is performed by relative movement between the line head and the recording medium, and a serial type that performs recording scanning of two or more passes. The same was obtained in any of the inkjet recording apparatuses.

In addition, even when the width of the high recording rate area is increased from 1.2 mm, the occurrence of turbulence can be reduced to some extent, but streaks with a predetermined width pitch tend to be noticeable, and the image quality is not very favorable. It was.
That is, when an image is completed in three recording scans for the same recording area, the recording ratio in each scan is one third of the total recording ratio of the three recording scans, and four times. When an image is completed by recording scanning, it becomes a quarter. For this reason, the turbulent flow generated in each scan is reduced. That is, it is possible to obtain a good recording result even if the high recording rate width set by the mask pattern exceeds 1.2 mm as described above. For example, in 4 passes, the maximum recording rate in charge of recording in each recording scan corresponds to half of the case where an image is completed in 2 recording scans, so the predetermined width of the high recording rate area is widened to a maximum of 2.4 mm. However, the influence of turbulent flow can be reduced. However, if the width of the high recording area exceeds 1.2 mm, as described above, recording is performed with a period in which it is easy to visually recognize the stripe unevenness, which is not desirable.

  Also, when performing high-speed recording, the influence of minute turbulence may remain depending on the type of recording medium. For example, when glossy paper PR101 manufactured by Canon Inc. is used, there is a case where the influence of minute turbulence remains on the image. However, as a result of intensive studies by the present inventors, it is possible to use the area gradation method in which an image is represented by a unit shape as a pseudo halftone processing method in order to reduce the influence of the above-described minute turbulence. I found it effective. Specifically, it has been found that it is effective to adopt a binarization process using a dot concentration type area gradation method as a pseudo halftone processing method. At this time, it has become clear that the image quality can be improved by forming a strip of a high recording ratio area in a width that is an integral multiple of the unit shape of a dot-concentrated image.

Next, creation of recording data in the embodiment of the present invention will be described.
The recording data using the recording head is created by a method used in a normal ink jet printer. In this embodiment, as shown in FIG. 8, input multi-value image data (for example, 8-bit RGB data) is converted into color multi-value data (for example, 8-bit CMYBk data) corresponding to each color head for each pixel (color (Step S1). Thereafter, the color-separated color multi-value data is quantized into K values (for example, 17 values) by an error diffusion method (step S2), and a dot arrangement pattern corresponding to the quantized K values is selected. The binarization process is performed to generate binary recording data (step S3). Thereafter, the binary print data is divided by the thinning mask pattern, and the divided data is distributed to the print head (step S4). It is also possible to directly binarize the color-separated multi-value data without going through the quantization step and use this binary data as print data for driving the print head.

    FIG. 26 shows an example of processing for converting multi-value data of each color into binary print data. Here, the multi-value data of each color quantized to 17 values is converted into a dot-concentrated area gradation pattern with a recording matrix (also referred to as a dot arrangement pattern) composed of 4 × 4 cells as a unit, By assigning this to each pixel, binary data is obtained. The dot arrangement pattern shown here is a pattern generated for the purpose of forming a halftone image. Note that the squares in the figure are virtually shown to clarify the formation positions of the dots, and the squares have a resolution of 1200 dpi. This one cell corresponds to one area in the mask pattern.

FIG. 31 shows an example of a pattern representing 17 gradations by a dot concentration type area gradation method in a 4 × 4 recording matrix. The illustrated pattern is a pattern in which dots are recorded in a grid closer to the center in 16 matrices each time the gradation value to be expressed increases by one gradation. In FIG. 31, only 16 patterns are shown. At first glance, there are 16 gradations. Actually, however, there are patterns with gradation value 0 that do not form any dots other than these patterns. Accordingly, 17 gradations can be expressed with a total of 17 patterns obtained by adding the pattern of gradation value 0 to the 16 patterns shown in the figure.
FIG. 27 is a diagram showing a state in which the image data represented by the dot concentration type area gradation pattern shown in FIG. Here, a unit shape corresponding to one pixel is constituted by a recording matrix composed of 4 × 4 cells, and the entire image has a configuration in which this unit shape is repeated. Note that the X direction in the figure indicates the direction in which the recording head scans the recording medium while ejecting ink droplets, and the Y direction indicates the arrangement direction of the nozzle rows provided in the recording head. Further, in the figure, the area where the inside of the grid is painted black indicates the data for ejecting ink droplets.
When the recording operation is performed by the full line type ink jet recording apparatus shown in FIG. 1 or the serial type ink jet recording apparatus shown in FIG. 3, the image data shown in FIG. 26 is displayed using the mask pattern in this embodiment. As shown in FIG. 17, distribution is performed for each scan.

  In this case, a recording head having first to fourth nozzle arrays that discharge the same color is prepared, and the recording operation is sequentially performed by each nozzle array. That is, the pattern data recording (first scanning) shown in FIG. 27A is performed by the first nozzle row located on the most upstream side in the scanning direction (printing medium conveyance direction). Subsequently, pattern data recording (second scanning) shown in FIG. 27B is performed by the second nozzle row. Subsequently, the pattern data recording (third scan) shown in FIG. 27C is performed by the third nozzle row. Finally, pattern data recording (fourth scanning) shown in FIG. 27D is performed by the fourth nozzle row. Thus, an image for one color is completed.

  When the image data shown in FIG. 26 is recorded by the serial type ink jet recording apparatus shown in FIG. 3, two nozzle rows (left column and right column) for recording the same color are arranged as the recording head. A nozzle is used and an image is recorded by two main scans using these nozzle arrays. That is, in the first main scan, pattern data recording (first scan) shown in FIG. 27A is performed by the left column, and pattern data recording (second scan) shown in FIG. 27B is performed by the right column. Next, in the second main scan, pattern data recording (third scan) shown in FIG. 27C is performed in the left column, and pattern data recording (fourth scan) shown in FIG. 27C is performed in the right column. Thus, an image for one color is completed.

  An example of the mask pattern M for dividing the image data as described above is shown in FIG. Note that the circled numbers 1, 2, 3, and 4 in the figure indicate positions that can be recorded by the first scan, the second scan, the third scan, and the fourth scan in FIG. By using the mask pattern to perform divided recording as described above, the level of turbulence generated between the recording head and the recording medium can be reduced in both the full-line type and serial type ink jet recording apparatuses. Is possible. As a result, the landing position of the ink droplet can be maintained with high accuracy, and a high-quality image can be formed.

  Thus, in any type of ink jet recording apparatus, recording is performed for each region (high recording rate region) for a unit shape having a width of 0.08 mm. In addition, between the areas having a width corresponding to the unit shape that is simultaneously recorded, there is an area (low recording rate area) having a width (0.24 mm width) corresponding to three unit shapes that are not recorded. For this reason, the turbulent flow generated between the recording head and the recording medium is greatly reduced, and the landing position of the ink droplet is maintained with high accuracy. Further, the mask pattern M shown in FIG. 28 has an arrangement in which each unit shape adjacent in the main scanning direction is shifted up and down by 2 dots in the sub-scanning direction. The boundary between and continuously changes in the nozzle arrangement direction (swells). For this reason, the frequency of use of the nozzles can be made uniform in one scan, the life of the entire recording head can be increased, and the occurrence of uneven stripes between the regions can be reduced.

  On the other hand, FIG. 29 is a diagram showing another example in which the image data for the dot concentration type area gradation shown in FIG. 26 is divided into four recording scans. Also in this case, the cell has a resolution of 1200 dpi, the unit shape of the image is 4 × 4, and the high recording rate area is 0.08 mm corresponding to 4 nozzle rows. For this reason, a turbulent flow level can be reduced and a good quality image can be recorded.

  The present invention also provides an inkjet recording apparatus using a recording head that discharges a plurality of types of ink having substantially the same hue and different densities, and a recording head in which nozzles that discharge ink droplets of different ink amounts are arranged. The present invention can also be applied to an inkjet recording apparatus to be used. In any case, the high recording rate region and low recording to be set in the nozzle row according to the number of nozzle rows to be used, the type of ink, the type of recording medium, the recording speed, the amount of ink droplets to be recorded, etc. The width of the rate area may be set.

As an example, a model in which a recording operation is performed using a recording head in which nozzles that discharge 6 pl (large nozzles) and nozzles that discharge 1 pl (small nozzles) are alternately arranged and the arrangement density is 1200 dpi. The figure is shown in FIG. Here, a total of four nozzles of two large nozzles and two small nozzles are set as the high recording rate area Hn. Similarly to the high recording rate region Hn, the low recording rate region Ln is set by a total of four large and small nozzles, and thus an image is completed by a total of two scans.
Also in this case, since the high recording rate region Hn is 0.08 mm, recording at a low turbulence level is possible, and a good image can be recorded.

  By the way, as an ink jet recording method that can realize the above-described high-density nozzle row relatively easily and at low cost, for example, a recording head that forms recording by using thermal energy and performs recording is used. There is an ink jet recording method used. However, the present invention is not particularly limited to this.

Next, the present invention will be described more specifically with reference to the following examples.
<Example 1>
In the full-line type ink jet recording apparatus shown in FIG. 1, a recording operation was performed using the ink jet recording head shown in FIG. At this time, as the ink ejected from the recording head, commercially available ink BCI6 black for BJF900 (manufactured by the present applicant) was used. Each ink droplet was ejected at 2.5 ± 0.5 pl.
In addition, as a recording medium, photo glossy paper dedicated to inkjet (Pro Photo Paper, PR101: manufactured by the present applicant) was prepared.

FIG. 17 is a diagram schematically showing a nozzle array and a mask pattern M of the recording head used in this embodiment. The recording head shown in FIG. 17 actually has the configuration shown in FIG. 2, but here, for convenience, the nozzles arranged in a staggered pattern shown in FIG. .
The upstream first nozzle row 17A composed of the nozzle rows (medium nozzle rows) 171 and 175 of FIG. 2 records the recording data at the positions indicated by the round numbers 1 and 5 in FIG. 17B. Note that FIG. 17B shows a mask pattern M for performing a thinning process.

  Subsequently, the second nozzle row 17B composed of 172 and 176 in FIG. 2 records data at positions indicated by the circled numbers 2 and 6 in FIG. Similarly, the third nozzle row 171C records data at positions indicated by circle numbers 3 and 7, and the fourth nozzle row 171D records data at positions indicated by circle numbers 4 and 8.

  In FIG. 17A, a region composed of nozzles with double circles in the nozzle row 171 is a high recording rate region. The high recording area is a strip-shaped area having a density of 1200 dpi and an area width of 4 nozzles, that is, a width of 0.08 mm. Further, a nozzle in which only a circle is written is a low recording ratio area. Here, ink is not ejected in the low recording area.

  Further, in the nozzle rows 171A and 171D, the two middle nozzle rows 171 and 175, and 174 and 178 constituting each of them are connected with their end portions overlapped, which corresponds to the connecting portion. The nozzles to be used are in a high recording area in each nozzle row. Thereby, the image deterioration of a joint part can be reduced.

  As recording conditions in the recording operation, an image was formed with an ejection frequency of 30 kHz and a relative movement speed of the recording head and the recording medium of 25 inches / s. As a result, image degradation (density unevenness) that appears to be the effect of turbulence was reduced, and a high-quality image could be obtained.

<Comparative example 1>
Using the same ink jet recording apparatus as that used in Example 1, divided recording was performed using a mask pattern M (see FIG. 18B) that uniformly thins out image data for the nozzle rows as shown in FIG. 18A. In this case, density unevenness that appears to be an effect of turbulent flow occurred, and only low-quality images were obtained.

<Example 2>
Using the same ink jet recording apparatus as in Example 1, divided recording was performed in which a high recording rate region and a low recording rate region were set as shown in FIG. At this time, the width of the high recording ratio area was increased to a width of 16 nozzles (0.32 mm) with a nozzle row having a density of 1200 dpi. As a result of recording in this way, a high-quality image was obtained without causing density unevenness that was considered to be caused by turbulence.

<Example 3>
In the divided recording in which the high recording rate region and the low recording rate region are set as shown in FIG. 17 using the same ink jet recording apparatus as in Example 1, the width of the high recording rate region is further widened and the density is 1200 dpi. Recording was performed with a nozzle row having a width of 64 nozzles (1.2 mm). Also in this case, the density unevenness considered to be influenced by the airflow was reduced, and a high-quality image was obtained. However, a slight amount of stripe irregularity with a predetermined width pitch was visually recognized.

<Comparative example 2>
In the divided recording in which the high recording ratio area and the low recording ratio area are set as shown in FIG. 17 using the same recording apparatus as in the first embodiment, the width of the high recording ratio area is further expanded and the density of 1200 dpi is obtained. The width of the nozzle row was 128 nozzles (2.4 mm). In this case, streaks with a predetermined width pitch appear remarkably, and it is difficult to say that the image is a high-quality image. This is presumably due to the occurrence of density unevenness that appears to be influenced by the airflow within a predetermined width.

<Example 4>
While using the same recording apparatus as in the first embodiment, image data is obtained using a mask pattern M in which a strip-like high recording ratio area extending in the main scanning direction undulates in the conveyance direction of the recording medium as shown in FIG. 19B. Thinning and division recording were performed by the line head 17 shown in FIG. 19A. As a result, high-quality images were obtained with no density unevenness that might be caused by turbulence.

<Example 5>
As the ink jet recording head, a recording head 22 having a nozzle row in which 768 nozzles that discharge an average of 2.5 pl as shown in FIG. 4 are arranged at 1200 dpi is prepared, and this is the serial type ink jet recording apparatus shown in FIG. Attached to and recorded. Each ink droplet was ejected at 2.5 ± 0.5 pl. As the ink, commercially available ink BCI6 black for BJF900 (manufactured by the present applicant) was used.

  As a recording medium, photo glossy paper dedicated to inkjet (Pro Photo Paper, PR101: manufactured by the present applicant) was used.

Here, FIG. 20 shows a state of divided recording in which an image is completed by two scans in the same recording area. The recording head shown in FIG. 20 actually has the configuration shown in FIG. 4, but here, for convenience, the nozzles arranged in a staggered pattern shown in FIG. .
In this recording operation, the data at the position indicated by the circled numeral 1 in FIG. 20 is recorded in the first scan. Subsequently, data at a position indicated by a circled number 2 in FIG. 20 is recorded by the second scan. Subsequently, in the third scan, the position indicated by the circled numeral 3 in FIG. 20 was recorded, and the above operation was repeated to complete the image. Here, a double circle added to the square of the nozzle row indicates a high recording rate area, and is set to a width of 12 nozzles (0.25 mm) at 1200 dpi. The same applies to the low recording rate area. The recording conditions were an ejection frequency of 30 kHz and a relative movement speed of the recording head and the recording medium of 25 inches / s.
As a result of performing the recording operation under such recording conditions, high-quality images were obtained without causing density unevenness that was considered to be caused by turbulence.

<Comparative Example 3>
Using the same ink jet recording apparatus as in Example 5 above, the recording data was uniformly distributed to the nozzle rows of the recording head 22 by the thinning mask pattern shown in FIG. As a result, density unevenness that seems to be affected by turbulence occurred, and only low-quality images were obtained.

<Example 6>
Using the same ink jet recording apparatus as in Example 4, the image data is obtained using a thinning mask pattern having a gradient in the recording ratio at the boundary between the high recording rate region and the low recording rate region as shown in FIG. Thinning and division recording were performed by the recording head 22. As a result, the density unevenness considered to be influenced by turbulent flow did not occur, and a high-quality image was obtained.

<Example 7>
Using the same ink jet recording apparatus as in Example 4 above, image data is thinned out using a thinning mask pattern M in which a high recording rate region is undulated as shown in FIG. went. As a result, the density unevenness considered to be influenced by turbulent flow did not occur, and a high-quality image was obtained.

<Example 8>
Using the same ink jet recording apparatus as in Example 4, as shown in FIG. 24, a high recording rate region with a recording rate of 90% and a recording rate of 10% are arranged in a nozzle array in which nozzles are arranged at a density of 600 dpi. And a low recording rate area. Further, divided recording was performed with the width of the high recording rate area being 1.2 mm. As a result, the degradation of the image, which appears to be affected by turbulence, was reduced, and a high-quality image was obtained.

<Example 9>
Using the same ink jet recording apparatus as in Example 4 above, the width of the high recording ratio area is set to 0.08 mm as shown in FIG. 25, and the image data is acquired using the thinning mask pattern M distributed to four scans. Thinning and division recording were performed by the recording head 22. As a result, high-quality images were obtained with no density unevenness that might be caused by turbulence.

<Example 10>
Using the inkjet recording apparatus of Example 4, the binary image data having the area gradation shown in FIG. 31 is developed as shown in FIG. 27, and according to the image data of the first scan to the fourth scan shown in FIG. 4-pass multipass recording was performed. In this case, the recording matrix, which is the unit shape of the image, is composed of 4 × 4 cells, and each cell is set to a density of 1200 × 1200 dpi. For this reason, image recording was repeated in units of 0.08 mm in the nozzle row direction, and the high recording rate area was formed in a strip shape having a width of 0.08 mm. As a result, the recorded image was not affected by the turbulent flow and good quality could be obtained.

<Example 11>
Using the same ink jet recording apparatus as in Example 4, the binary image data having the area gradation shown in FIG. 31 is developed as shown in FIG. 27, and the first to fourth scan images shown in FIG. 29 are developed. According to the data, 4-pass multipass recording was performed. Also in this case, the recording matrix, which is the unit shape of the image, is composed of 4 × 4 cells, and each cell is set to a density of 1200 × 1200 dpi. Thereby, the image recording was repeated in units of 0.08 mm in the nozzle row direction, and the high recording rate area was formed in a strip shape having a width of 0.08 mm. Therefore, even in this case, the recorded image was not affected by the turbulent flow, and good quality could be obtained.

<Example 12>
Using the same ink jet recording apparatus as in Example 8, recording was performed according to image data having a recording matrix composed of 4 × 4 squares as a unit shape as shown in FIG. In this case, the thinning mask pattern M was set so as to include a low recording rate area that is an integral multiple of the unit shape between the high recording rate areas, and two-pass multipass recording was performed. In each pass, recording was performed in accordance with the positions of the high recording ratio area and the low recording ratio area in FIG. The recording matrix was composed of 4 × 4 cells, and each cell was set to a density of 1200 × 1200 dpi. Thereby, the image recording is repeated in units of 0.08 mm in the nozzle row direction, and the high recording rate area is set to a strip shape having a width of 0.32 mm. As a result, the influence of turbulent flow was reduced, and good image quality could be obtained.

  As described above, according to the present invention, when performing division recording such as multi-pass printing in a serial type recording apparatus using a recording head in which relatively short nozzle rows are arranged, a plurality of long nozzle rows are arranged in parallel. This is effective when recording is performed by a full-line type recording apparatus. That is, in any recording method, the fluctuation of the landing position of the ink droplet due to the turbulent flow generated between the recording head and the recording medium can be remarkably improved, and a high-quality recorded product can be obtained at high speed. it can. In addition, the present invention can be appropriately used for dot-concentrated area gradation method recording, and high-speed recording is possible while maintaining gradation reproducibility.

The present invention is applicable to all devices using recording media such as paper, cloth, leather, non-woven fabric, OHP paper, and metal. Specific examples of applicable equipment include office equipment such as printers, copiers, and facsimile machines, and industrial production equipment.
The present invention is suitable when an area gradation method called a cluster type or a dot concentration type and widely known as a “halftone gradation method” is realized by an ink jet printer. Printers that realize the area gradation method include proof-use printers that are widely used in the printing industry.
This application claims priority based on Japanese Patent Application No. 2004-360514 filed on Dec. 13, 2004, which is hereby incorporated by reference.

1 is a perspective view showing a schematic configuration of a full-line type ink jet recording apparatus applied to an embodiment of the present invention. It is explanatory drawing which shows an example of the line head used for the inkjet recording device shown in FIG. 1 is a plan view showing a schematic configuration of a serial type ink jet recording apparatus applied to an embodiment of the present invention. It is explanatory drawing which shows an example of the recording head used for the inkjet recording device shown in FIG. It is explanatory drawing which shows the other example of the recording head used for the inkjet recording device shown in FIG. 2 is an explanatory perspective view showing an internal structure of a recording head used in the ink jet recording apparatus. FIG. 1 is a block diagram illustrating a schematic configuration of a control system of an ink jet recording apparatus according to an embodiment of the present invention. It is a flowchart explaining the image processing in embodiment of this invention. It is explanatory drawing explaining the principle of the ink discharge operation | movement in embodiment of this invention. It is explanatory drawing which shows an example of the ink discharge operation | movement in the embodiment of this invention, and the landing state of an ink drop. It is explanatory drawing which shows an example of the mask pattern in embodiment of this invention. It is explanatory drawing which shows the other example of the mask pattern in embodiment of this invention. It is explanatory drawing which shows the other example of the mask pattern in embodiment of this invention. It is explanatory drawing which shows the other example of the mask pattern in embodiment of this invention. It is explanatory drawing which shows the mask pattern which expanded the width | variety of the high recording rate area | region of the mask pattern shown in FIG. It is explanatory drawing which shows the other example of the ink discharge operation | movement in the embodiment of this invention, and the landing state of an ink drop. It is a figure which shows typically the other example of the nozzle row used in the 1st Example of this invention, and the landing state of an ink drop. It is a figure which shows typically the other example of the nozzle row used by the comparative example with respect to the Example of this invention. It is a figure which shows typically the other example of the nozzle row used in the 4th Example of this invention. It is a figure which shows typically the other example of the nozzle row and mask pattern which are used in the 5th Example of this invention. It is a figure which shows typically the other example of the nozzle row and mask pattern which are used by the comparative example with respect to the Example of this invention. It is a figure which shows typically the other example of the nozzle row and mask pattern which are used in the 6th Example of this invention. It is a figure which shows typically the other example of the nozzle row and mask pattern which are used in the 7th Example of this invention. It is a figure which shows typically the other example of the nozzle row and mask pattern which are used in the 8th Example of this invention. It is a figure which shows typically the other example of the nozzle row and mask pattern which are used in the 9th Example of this invention. It is explanatory drawing which shows an example of the image data recorded using the dot concentration type area | region gradation method in embodiment of this invention. FIG. 27 is an explanatory diagram showing an example in which the image data shown in FIG. 26 is divided corresponding to each scan of divided recording. It is explanatory drawing which shows the mask pattern for dividing | segmenting the image data shown in FIG. 26 into each image data shown in FIG. It is explanatory drawing which shows the other example which divided | segmented the image data shown in FIG. 27 corresponding to each scanning of division | segmentation recording. It is explanatory drawing which shows the other example of the image data recorded using the dot concentration type area | region gradation method in embodiment of this invention. It is explanatory drawing which shows the dot arrangement pattern corresponding to each gradation value by a dot concentration type area gradation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Full line type inkjet recording device 2 Serial type inkjet recording device 17 Line head 17A-17D Nozzle row 22 Recording head 22A-22D Nozzle row 71 Data input part 73 CPU
75 RAM
74 Storage Medium 76 Image Processing Unit 77 Image Recording Unit 110 Mask Pattern 120 Mask Pattern 130 Mask Pattern 140 Mask Pattern 150 Mask Pattern M Mask Pattern n Nozzle P Recording Medium

Claims (9)

An inkjet recording apparatus that records an image on the recording medium by ejecting ink droplets from the nozzle while scanning a recording head in which a plurality of nozzles are arranged relative to the recording medium,
Scanning means for scanning the recording head relative to the same recording area of the recording medium a plurality of times;
Conversion means for converting multivalued image data corresponding to an image to be recorded in the same recording area into binary image data;
And thinning means for thinning the binary image data using a different mask patterns corresponding to the respective scanning multiple times, corresponding to the same recording area against the same recording area,
An image to be recorded in the same recording area is completed by recording a thinned image in the same recording area based on the binary image data thinned out by the thinning means in each of the plurality of scans. Recording control means,
In each of the different mask patterns, a first region where the binary image data is thinned out at a relatively high thinning rate and a second region where the binary image data is thinned out at a relatively low thinning rate are arranged in the nozzle arrangement direction. An inkjet recording apparatus, wherein a width of the first region in the nozzle array direction is larger than a width of the second region in the nozzle array direction . An inkjet recording apparatus that records an image on the recording medium by ejecting ink droplets from the nozzle while scanning a recording head in which a plurality of nozzles are arranged relative to the recording medium,
Scanning means for scanning the recording head relative to the same recording area of the recording medium a plurality of times;
Conversion means for converting multivalued image data corresponding to each pixel constituting an image to be recorded in the same recording area into binary image data;
Thinning means for thinning out binary image data corresponding to the same recording area using different mask patterns corresponding to each of a plurality of scans for the same recording area;
An image to be recorded in the same recording area is completed by recording a thinned image in the same recording area based on the binary image data thinned out by the thinning means in each of the plurality of scans. Recording control means,
Each of the different mask patterns includes a first region that thins out the binary image data at a relatively high thinning rate and a second region that thins out at a relatively low thinning rate in the nozzle arrangement direction. An ink jet recording apparatus, wherein the ink jet recording apparatus is repeatedly arranged in a unit of a width that is an integral multiple of the width of.   The inkjet recording apparatus according to claim 2, wherein the conversion unit converts the multivalued image data into the binary image data by assigning a dot concentration type dot arrangement pattern to the pixels. .   The inkjet recording apparatus according to claim 2, wherein a position of a boundary between the first area and the second area in the arrangement direction of the nozzles differs according to a position in the scanning direction.   The inkjet recording apparatus according to claim 4, wherein the position of the boundary is displaced stepwise along the scanning direction.   The inkjet recording apparatus according to claim 1, wherein the position of the boundary is displaced in a waveform along the scanning direction.   3. The mask pattern includes a plurality of types of first regions having different widths in the nozzle arrangement direction and a plurality of types of second regions having different widths in the nozzle arrangement direction. 2. An ink jet recording apparatus according to 1. An inkjet recording method for recording an image on the recording medium by ejecting ink droplets from the nozzle while scanning a recording head in which a plurality of nozzles are arranged relative to the recording medium,
A scanning step of relatively scanning the recording head a plurality of times with respect to the same recording area of the recording medium;
Converting multi-value image data corresponding to an image to be recorded in the same recording area into binary image data;
Using different mask patterns corresponding to the respective scanning multiple times against the same recording area, and the more thinning rather Engineering image data of the corresponding binary to the same recording area,
By recording an image thinning the same recording area on the basis of the binary image data drawn between Te said plural scans each odor, as engineering of Ru to complete an image to be recorded on the same recording area And
In each of the different mask patterns, a first region where the binary image data is thinned out at a relatively high thinning rate and a second region where the binary image data is thinned out at a relatively low thinning rate are arranged in the nozzle arrangement direction. An ink jet recording method, wherein a width of the first region in the nozzle array direction is larger than a width of the second region in the nozzle array direction . An inkjet recording method for forming an image on the recording medium by ejecting ink droplets from the nozzle while scanning a recording head having a plurality of nozzles arranged relative to the recording medium,
Scanning the recording head relative to the same recording area of the recording medium a plurality of times;
Converting multi-value image data corresponding to each pixel constituting an image to be recorded in the same recording area into binary image data;
Thinning out binary image data corresponding to the same recording area using different mask patterns corresponding to each of a plurality of scans for the same recording area;
Recording a thinned image in the same recording area based on the thinned binary image data in each of the plurality of scans, thereby completing an image to be recorded in the same recording area; Prepared,
Each of the different mask patterns includes an area in which recording of the binary image data is allowed and an area in which recording of the binary image data is not allowed, and the pixels are arranged in the nozzle arrangement direction. An ink jet recording method, wherein a portion having a relatively high ratio and a portion having a relatively low ratio occupied by the permissible recording area are repetitively arranged in a unit of a width that is an integral multiple of the width.

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