JP2009029146A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device which can print a high-quality image with no density variation-caused lines at high speed and which can be easily manufactured at a low cost. <P>SOLUTION: The inkjet recording device includes a first nozzle group 81 including a first nozzle array 81A and a second nozzle array 81B arranged in parallel therewith, and a second nozzle group 82 including a third nozzle array 82A and a fourth nozzle array 82B arranged in parallel therewith. A plurality of nozzles n on the end side of the first nozzle array 81A and a plurality of nozzles n on the end side of the third nozzle array 82A are arranged in the same position in an array direction Y. A plurality of nozzles n on the end side of the second nozzle array 81B and a plurality of nozzles n on the end side of the fourth nozzle array 82B are arranged in the same position in the array direction Y. Distances in a relative motion direction X between the first nozzle array 81A and the second nozzle array 81B, between the second nozzle array 81B and the third nozzle array 82A, and between the third nozzle array 82A and the fourth nozzle array 82B are set equal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs image recording using an ink jet recording head in which ink discharge ports containing a colorant are integrated and arranged. More specifically, a long recording constituted by arranging a plurality of nozzle groups each having a nozzle array in which each nozzle is alternately arranged in a staggered manner on the upstream side and the downstream side in the conveyance direction of the recording medium with respect to the recording head. The present invention relates to an ink jet recording apparatus using a head. In particular, the present invention relates to an ink jet recording apparatus suitable for so-called one-pass recording, in which a recording image is completed by scanning and recording the recording head once with respect to a recording area corresponding to the long recording head.

  The present invention is applicable to all devices that record on a recording medium made of a material such as paper, cloth, leather, nonwoven fabric, OHP paper, and metal. Specific examples of applicable equipment include office equipment such as printers, copiers, and facsimile machines, and industrial production equipment.

  With the spread of information processing devices such as copying machines, word processors, computers, and communication devices, inkjet recording devices that record digital images by the inkjet method are rapidly becoming one of the output devices for image recording of these devices. Is popular. In this ink jet recording apparatus, there is known an apparatus that performs recording using a recording head in which a plurality of recording elements (hereinafter also referred to as nozzles) are arranged in an integrated manner in order to improve the recording speed. Further, in recent years, there has been an increasing demand for colorization of recorded images, and those equipped with a plurality of types of recording heads that discharge color inks are generally used. The nozzles described in the present specification and the claims include an ink discharge port that discharges ink supplied to a common liquid chamber of a recording head, and an ink discharge port that discharges ink supplied to the common liquid chamber. And a discharge energy generating element that discharges the ink supplied into the liquid path from the ink discharge port.

  In general, an ink jet recording apparatus performs dot recording by causing ink, which is a recording liquid, to land on various recording media made of paper or the like as flying droplets (ink droplets). That is, the ink jet recording apparatus employs a non-contact method in which the recording head does not contact the recording medium, and thus has an advantage that recording can be performed with low noise. In addition, high resolution and high-speed recording are possible by increasing the density of the ink discharge nozzles, and because special processing such as phenomenon images and fixing is not required even for recording media such as plain paper, It is possible to obtain a high-quality image at a price. For this reason, in recent years, it has been widely applied to various recordings. In particular, an on-demand type inkjet printing apparatus is easy to colorize, and since the apparatus itself can be miniaturized and simplified, the demand is expected to be expected to further increase in the future. Also, as the demand for colorization of recorded images increases, higher image quality and higher speed are increasingly required.

  In addition, against the background of recent technological advances in nozzle integration, it has become possible to manufacture high-density and long recording heads. A long print head with a high density of nozzles is generally called a full multi-type long print head, and a single print scan is performed on a wide print area corresponding to the long print head. The one that completes the image is proposed and implemented. According to this ink jet recording apparatus, since both the recording speed and the image quality can be satisfied, further technical development is in progress.

Japanese National Patent Publication No. 10-508808 JP 2000-507522 A Japanese Patent Laid-Open No. 10-250059 US Pat. No. 5,923,348 US Pat. No. 6,172,689

  However, in the ink jet recording apparatus using the above-described high-density and long recording head, the following various problems occur.

  First, in the above system, when an image in a recording area is completed by recording by one recording scan (one-pass recording) or by a small number of recording scans, the ink droplets ejected from the nozzles of each recording head are shortened. It is necessary to absorb and fix the recording medium over time. For this reason, it is necessary to provide a large heating / drying means for the recording medium, or to take measures such as reducing the amount of ink required for recording, resulting in an increase in cost and a decrease in recording density or pixel density. There is a problem that only a low-quality recorded image can be realized.

  Second, if the nozzles are arranged in a line at a high density, depending on the appropriate amount of ink, ink droplets ejected from adjacent nozzles may coalesce on the recording medium to form an inappropriate shape. . In addition, when the recorded image has a high duty, the ink that cannot be absorbed on the recording medium becomes a puddle on the surface of the recording medium, which may cause image quality deterioration.

  Thirdly, artifacts having discontinuity in density occur at the sites where the nozzle groups are connected, and characteristic streaking caused by high and low density, that is, visually white lines or black lines. A streak may occur and the image quality may deteriorate.

  Therefore, a recording head having a nozzle group composed of two nozzle rows, that is, an upstream nozzle row and a downstream nozzle row, is also proposed by alternately arranging the nozzles on the upstream side and the downstream side. . Also in this case, a long head is formed by connecting a plurality of nozzle groups, and this is applied to a full line printer or the like.

  However, as described above, in an inkjet recording apparatus using a recording head configured by connecting a plurality of nozzle groups, the occurrence of white and black lines is reduced in an image formed by the same nozzle group. However, white stripes or black stripes may occur at the joints between the nozzle groups as described above, and sufficient image quality has not been achieved.

  An object of the present invention is to provide a long recording head capable of recording a high-quality image at high speed without causing streaky density unevenness, and capable of being manufactured inexpensively and easily, and using the recording head described above. Another object of the present invention is to provide an ink jet recording apparatus.

  In the first embodiment of the present invention, a full-line type recording head having a plurality of nozzles that eject ink and a recording medium are moved relative to each other as the recording is performed, and recording is performed by ejecting ink from the nozzles. In an ink jet recording apparatus that records an image on a medium, the recording head includes a first nozzle array including a plurality of nozzles arranged along an arrangement direction intersecting a relative movement direction with the recording medium, and the first nozzle array A first nozzle group including a second nozzle row arranged in parallel to the first nozzle group, a third nozzle row comprising a plurality of nozzles arranged along the arrangement direction, and the third nozzle row arranged in parallel. A second nozzle group including a fourth nozzle row, and a plurality of nozzles on the end portion side of the first nozzle row and a plurality of nozzles on the end portion side of the third nozzle row are in the relative movement method And the plurality of nozzles on the end side of the second nozzle row and the plurality of nozzles on the end side of the fourth nozzle row are arranged at the same position in the arrangement direction, The distance between the first nozzle row and the second nozzle row, the second nozzle row and the third nozzle row, and the third nozzle row and the fourth nozzle row in the relative movement direction is equal.

According to a second aspect of the present invention, in the first aspect, a fifth nozzle row comprising a plurality of nozzles arranged along the arrangement direction, and a sixth nozzle arranged in parallel with the fifth nozzle row. A third nozzle group including a row, wherein the first nozzle row and the fifth nozzle row are arranged at the same position in the relative movement direction, and the second nozzle row and the sixth nozzle row are It is arranged at the same position in the relative movement direction.
In the first or second embodiment, the first nozzle group, the second nozzle group, and the third nozzle group are arranged in a staggered manner in the arrangement direction.

  As described above, according to the present invention, the density of the connected dots formed by the connected dots formed by the adjacent nozzles in the nozzle group and the ink droplets ejected from the adjacent nozzles at the portion connecting the nozzle groups is more uniform. Generation of streaky density unevenness can be suppressed, and an image of good quality can be formed.

  Further, if the nozzle groups are arranged in a staggered manner, it is possible to minimize the expansion of the width in the direction of relative movement of the recording head with the recording medium.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a conceptual configuration of an ink jet recording apparatus applied to an embodiment of the present invention, and FIG. 2 is a plan view schematically showing an arrangement state of recording heads.

  The ink jet recording apparatus 1 of the present embodiment is a full line type color ink jet in which a plurality of long recording heads 2Y, 2M, 2C, and 2Bk extending in a direction orthogonal to the recording medium conveyance direction are arranged in parallel. It is a recording device. Here, 2Y is a recording head for discharging yellow ink, 2M is a recording head for discharging magenta ink, 2C is a recording head for discharging cyan ink, and 2Bk is a recording head for discharging black ink. Each recording head has substantially the same configuration, and in the following description, unless there is a particular need for distinction, these are collectively referred to as recording head 2.

  Each recording head 2 is connected to four ink tanks 3Y, 3M, 3C and 3Bk (hereinafter collectively referred to as ink tanks 3) respectively storing yellow ink, magenta ink, cyan ink and black ink. 4, each ink tank 3 is replaceable with respect to the connection pipe 4.

  The head moving means 10 for recovery processing whose operation is controlled by the control device 9 can be moved up and down in the direction facing the platen 6. The recording heads 2 are arranged at predetermined intervals along the conveying direction of the conveying belt 5 so as to face the platen 6 with the endless conveying belt 5 interposed therebetween. The recording head 2 has an ink discharge port for discharging ink, a common liquid chamber to which the ink in the ink tank 3 is supplied, and an ink described later for guiding ink from the common liquid chamber to each ink discharge port. A flow path is formed. In each ink flow path, a plurality of nozzles each including an electrothermal converter (heater) as discharge energy generating means for generating heat energy for discharging the supplied ink tank is provided. The heater is electrically connected to the control device 9 via the head driver 2a. Driving and stopping of the heater are controlled in accordance with an on / off signal (discharge / non-discharge signal) sent from the control device.

  On the other hand, on the side of each recording head 2, prior to the recording operation on the recording medium P, the thickened ink or the like intervening in the ink flow path is discharged from the ejection port of the recording head 2 to recover the recording head. The head cap 7 for performing the recording is arranged in a state shifted by a half pitch with respect to the arrangement interval of the recording heads. The head cap 7 can be moved directly below the recording head 2 by the cap moving means 8 whose operation is controlled by the control device 9, and can receive the waste ink discharged from the ink discharge port. ing.

  The conveying belt 5 that conveys the recording medium P is wound around a driving roller connected to a belt driving motor 11, and its operation is switched by a motor driver 12 connected to the control device 9. Further, on the upstream side of the transport belt 5, a charger 13 is provided for charging the transport belt 5 to bring the recording medium P into close contact with the transport belt 5. The charger 13 is turned on / off by a charger driver 13 a connected to the control device 9. A pair of feeding rollers 14 and 14 for supplying the recording medium P onto the conveying belt 5 is connected to a feeding motor 15 for driving and rotating the pair of feeding rollers 14 and 14. Yes. The operation of the feeding motor 15 is switched by a motor driver 16 connected to the control device 9.

  Therefore, when performing a recording operation on the recording medium P, first, each recording head 2 is lifted away from the platen 6. Next, after the head cap 7 is moved immediately below each recording head 2 to perform the recovery process, the head cap 7 is moved to the original standby position. Thereafter, the recording head 2 further moves to the platen side to the recording position. Then, simultaneously with the operation of the charger 13, the conveying belt 5 is driven, and the recording medium P is placed on the conveying belt by the paper feed rollers 14 and 14, and a predetermined color image is recorded by each recording head 2. Recorded on the medium P.

Next, the internal structure of the recording head will be described with reference to FIG.
In the figure, the inkjet head 2 includes a heater board 23 that is a substrate on which a plurality of heaters 22 for heating ink is formed, and a top plate 24 that covers the heater board 23. A plurality of ink discharge ports 25 are formed in the top plate 24. A tunnel-like liquid path 26 communicating with each ink discharge port 25 is formed behind each ink discharge port 25. Each liquid path 26 is commonly connected to one ink liquid chamber at the rear thereof. Ink stored in the ink tank 3 is supplied to each ink chamber through an ink supply port. The ink supplied to the ink liquid chamber is supplied to each liquid path 26.

  The heater board 23 and the top plate 24 are assembled by being aligned so that each heater 22 comes to a position corresponding to each liquid path 26. Although only four heaters 22 are shown in FIG. 3, each heater 22 is arranged one by one corresponding to each liquid passage 26. When a predetermined drive pulse is supplied to the heater 22 in the assembled recording head, the ink on the heater 22 boils to form bubbles, and the ink is pushed out from the discharge port 25 by the volume expansion of the bubbles and discharged. Is done. The ink jet recording method applicable to the present invention is not limited to the so-called bubble jet (registered trademark) method using a heating element (heater) as shown in FIG. 1 and FIG. In the case of a continuous type that continuously injects particles into particles, a charge control type, a divergence control type, and the like are applicable. Further, in the case of an on-demand type that ejects ink droplets as necessary, a pressure control method that ejects ink droplets from an ink ejection port by mechanical vibration of a piezoelectric vibration element is also applicable.

FIG. 4 is a block diagram showing an example of the configuration of the control system of the ink jet recording apparatus of the present invention.
In FIG. 4, 31 is an image data input unit for inputting multi-value image data from an image input device such as a scanner or a digital camera, or multi-value image data stored in a hard disk of a personal computer, and 32 is a list of various parameters. An operation unit 33 having various keys for instructing setting and start of recording is a CPU as control means for controlling the entire recording apparatus in accordance with various programs in the storage medium. Reference numeral 34 denotes storage means for storing various data. The storage means 34 includes a recording medium information storage unit 34a mainly relating to the type of recording medium, an ink information storage unit 34b relating to ink used for printing, and an environment information storage unit 34c for storing information relating to the environment such as temperature and humidity during recording. And various control program group storage units 34d. Further, reference numeral 35 denotes a RAM used as a work area for various programs in the storage means 34, a temporary save area for error processing, and a work area for image processing. All the operations of this embodiment are performed by this program. As the storage means 34 for storing the program, ROM, FD, CD-ROM, HD, memory card, magneto-optical disk, or the like can be used. The RAM 35 can also copy various tables in the storage unit 34, change the contents of the tables, and proceed with image processing while referring to the changed tables.

  An image data processing unit 36 quantizes the input multi-valued image data into N-valued image data for each pixel and creates an ejection pattern corresponding to the gradation value “K” indicated by each quantized pixel. It is. The image data processing unit N-values the input multi-value image data, and then creates an ejection pattern corresponding to the gradation value “K”. For example, when multi-valued image data expressed in 8 bits (256 gradations) is input to the image data input unit 31, the image data processing unit 36 converts the gradation value of the output image data into a K value. Here, the multilevel error diffusion method is used for the K-value processing of the input gradation image data. However, 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 employed. Is also possible. Further, by repeating the above-described K-value conversion processing for all the pixels based on the density information of the image, a binary drive signal for ejection and non-ejection for each pixel for each ink nozzle is formed.

  An image recording unit 37 ejects ink based on the ejection pattern created by the image data processing unit 36 and forms a dot image on a recording medium. 38 transmits an address signal, data, control signal, and the like in the apparatus. It is a bus line.

  Next, the arrangement of the nozzles of the recording head, which is a characteristic part of this embodiment, will be described with reference to FIGS. In order to clarify the characteristics of the preferred embodiment of the present invention, first, the related art of the present invention will be described, and then the arrangement of the nozzles of the recording head in the present embodiment and the differences from the related art will be mainly described. The arrangement of the recording head will be described.

(Related technology of the present invention)
FIG. 5A is a diagram showing a long recording head used for a full-line type ink jet recording head, and FIG. 5B shows an image recorded using the recording head shown in FIG. 5A. FIG.
In FIG. 5, reference numerals 41 to 44 denote a head nozzle group having a total of 512 nozzles in which nozzles are alternately arranged on the left and right sides of the drawing (arranged in a staggered manner). These nozzle groups are alternately arranged in a staggered pattern on the left and right, and a long recording head is constituted by these nozzle groups 41 to 44. In FIG. 5A, a long recording head 45 having a total of 2048 nozzles is configured by connecting four nozzle groups 41 to 44. However, three or four recording heads are formed in one recording head. It is also possible to connect the above nozzle groups.

  Here, an image recording state by the ink jet recording apparatus using the long recording head 45 will be described. The recording data of the recording operation performed using the recording head 45 is created by color-separating the input image so as to correspond to each color head and binarizing the color-separated gray image by the error diffusion method. Is done.

For example, when a gray image as shown in FIG. 5B is recorded using the long recording head 45, for example, adjacent nozzles in the nozzle groups 41 and 43, depending on the ejection amount, the ink used, the recording medium, and the recording speed. Ink droplets are ejected almost simultaneously and land on the recording medium almost simultaneously to form recording areas 48A and 48C. Ink droplets are ejected from the nozzles adjacent to the nozzle groups 42 and 44 substantially simultaneously with a time difference corresponding to the distance distance L thereafter, thereby forming the recording regions 48B and 48D. At this time, streaky density unevenness (density density different from other parts) is formed in the connecting portions 49A, 49B, and 49C that connect the recording areas 48A and 48C that are recorded first and the recording areas 48B and 48D that are recorded later. In the figure, black stripes, which are stripe-shaped density irregularities with higher density than other parts, are taken as an example), and the image quality may be significantly reduced.
Hereinafter, the stripe-like density unevenness in the connecting portion of the image formed in each nozzle group is also referred to as “connecting streak”.

  In the case of a long recording head in which all nozzles are arranged in a line along the same straight line, there is no connection streak on the image as in the case of using the recording head as described above. High-quality recording is possible. However, forming such a long single-row recording head with a high-density nozzle array has a problem in that it involves many difficulties in manufacturing and increases the manufacturing cost.

  In view of this, it has been proposed and implemented to manufacture a long recording head easily and at low cost by adopting a configuration in which relatively short nozzle groups are alternately arranged on the left and right. That is, by forming a plurality of short nozzle rows that can be manufactured at a relatively low cost by a known technique, and arranging them alternately while shifting, the nozzle rows that are manufactured individually are manufactured by a longer recording head. Compared to the case where they are bonded together, it is easy in terms of accurately manufacturing the nozzle position, and is excellent in cost. An example is shown in FIG.

The recording head 50 shown in FIG. 6 is configured such that each nozzle group is integrated, and the nozzle groups are arranged in a staggered manner to constitute a long recording head that is applied to a full-line inkjet recording apparatus. It has become. In the following, X indicates the conveyance direction of the recording medium relative to the recording head, and Y indicates the direction orthogonal to the conveyance direction of the recording medium.
In the following description, the X direction refers to the case where the recording medium is conveyed in a fixed direction in one pass with respect to the full line type ink jet recording head fixed at the time of recording, or conversely Considering the case where the recording medium is intermittently conveyed with respect to the inkjet recording head that is serially moved, it is also referred to as the relative movement direction of the recording head and the recording medium.

  In this recording head 50, two nozzle rows in which nozzles are arranged at the same density along the Y direction are formed on the upstream side and the downstream side in the X direction, and one nozzle row 51A, 51B is used to form one nozzle row. A nozzle group 51 is formed. The nozzles in the downstream nozzle row 51B are arranged so as to be located in the middle in the Y direction with respect to the nozzles in the upstream nozzle row 51A. Thereby, in one nozzle group, the upstream nozzle and the downstream nozzle are adjacent to each other in the Y direction that is the arrangement direction thereof, and the arrangement pitch is 5C. In other words, the nozzles are arranged in a staggered manner by two nozzle rows in one nozzle group. As a result, a high-density head in the Y direction is formed in one nozzle group, and substantially the same density as when nozzles are formed in a row at an arrangement pitch of 5C can be obtained.

  The recording head 50 shown here includes a total of four nozzle groups, the nozzle group 51 and nozzle groups 52, 53, and 54 having the same configuration as the nozzle group 52, on the upstream side and the downstream side in the X direction. They are sequentially connected along the Y direction while being shifted alternately. The nozzle groups 51 and 53 are arranged at the same position in the X direction, and the nozzle groups 52 and 54 are arranged at the same position in the X direction.

  Here, L1, L2, and L3 indicate distance intervals in the X direction of the nozzle rows. Here, L1 is the distance between the upstream nozzle rows 51A, 53A of the upstream nozzle groups 51, 53 and the upstream nozzle rows 52A, 54A of the downstream nozzle groups 52, 54, and L2 is the upstream in each nozzle group. L3 is the distance interval between the side nozzle row and the downstream nozzle row, L3 is the downstream nozzle row 51B, 53B of the upstream nozzle group 51, 53 and the upstream nozzle row 52A, 54A in the downstream nozzle group 52, 54. The distance interval (also referred to as the distance between nozzle groups) is shown.

  In the recording head 50 configured as described above, the distance L2 between the nozzle rows in each nozzle group and the distance interval L3 between the nozzle groups are greatly different. For this reason, among the dots that have landed on the recording medium, the density at the connecting portion of the image formed by each nozzle group is different from the density at the other portions, resulting in streak-like density unevenness in the entire image, resulting in deterioration in image quality. Problem arises. This is presumably due to the following reasons.

  That is, when a recording operation is performed by the long recording head 50, two adjacent dots formed by landing ink droplets ejected from nozzles adjacent in the Y direction (hereinafter referred to as adjacent nozzles) on the recording medium are as follows. , The one end is overlapped and connected to each other. This state is shown in FIG.

As the connected dots, for example, as shown in FIGS. 13 (a) and 13 (b), when forming a gourd on the recording medium, and when forming an oval as shown in FIG. 13 (c) There is.
Among these, FIG. 13 (a) shows a case where two adjacent dots have landed with a relatively large time difference, and the optical density of the overlapping part of the connected dots forming the gourd type is higher than that of the other part. Is also clearly higher. FIG. 13B shows a case where the difference in landing time between two adjacent dots is shorter than the case shown in FIG. There is almost no difference between the optical density of the overlapping part of the two dots and the optical density of the other part. Furthermore, FIG. 13C shows a case where the difference in landing time between two adjacent dots is shorter than that shown in FIGS. When the ink droplets land, the inks mix with each other and become an oval rather than a gourd.

  As described above, the dots formed on the recording medium have different densities and shapes depending on the time difference between adjacent dots. When such connected dots are continuously formed in one image in the X direction, depending on the variation state of the landing position of the ink dot, it may be a density such as a streaky white stripe or black stripe. It appears as unevenness (a connecting stripe).

  In the recording head 50 described above, the ink droplet landing time difference is a relatively short time difference corresponding to L2 in the adjacent nozzles in each nozzle group. For this reason, connected dots as shown in FIG. 13B or FIG. 13C are formed, whereas in the joint portion of the nozzle group, the landing time difference between the ink droplets of adjacent nozzles corresponds to L3. Due to the large time difference, connected dots as shown in FIG. 13A are formed. As a result, portions having different densities are formed at the connecting portions of the image, and this becomes uneven density and is formed in a stripe shape.

  As another related technique, a recording head 60 as shown in FIG. 7 has been proposed. The recording head 60 includes two sets of long head portions 61 and 62 that are connected in the Y direction by shifting substantially one row of nozzle rows alternately along the X direction to the upstream side and the downstream side. It is arranged on the downstream side. Each nozzle of the long recording head 62 on the downstream side is in the Y direction with respect to each nozzle of the long recording head unit 61 on the upstream side by a pitch 6C that is ½ of the arrangement pitch of the nozzles in each nozzle row. It is arranged to shift to. Therefore, in the overall configuration of the recording head 60, the pitch of the nozzles adjacent in the Y direction is 6C, and substantially the same density as when the nozzles are formed in a line at the arrangement pitch 6C is obtained. It has become a thing.

  Also in the recording head 60 configured as described above, the distance intervals in the X direction of adjacent nozzles are different in the connecting portions E61, E62, and E63 at the ends of the nozzle rows. For this reason, there arises a problem that density differences occur in the connected dots to be formed, and a connecting stripe is generated. That is, in the connecting portion E61, after dots are formed by ink droplets ejected from the nozzles located at the lower end of the nozzle row 61A, the Y2 side in the Y direction of the nozzle row 62A passes through a time corresponding to the distance interval L1. Dots are formed by the ink droplets ejected from the nozzles at the ends, and further, the dots are ejected by the ink droplets ejected from the nozzles located at the Y1 side end in the Y direction of the nozzle row 61B through the time interval corresponding to the distance interval L3. Is formed. Thereafter, dots are formed by ink droplets ejected from the position of the Y1 side end in the Y direction of the nozzle row 62B through a time interval corresponding to the distance interval L1.

  In the connecting dots formed in the connecting portion E61 of the nozzle row in this way, there is a slight difference between the time interval corresponding to the distance interval L1 and the time interval corresponding to the distance interval L3. For this reason, it is formed by the dots formed by the ink droplets ejected from the Y2 side end nozzle in the Y direction of the nozzle row 62A and the ink droplets ejected from the Y1 side end nozzle in the Y direction of the nozzle row 61B. The density of the connection portion with the dot is lower than that of the connection portion of other adjacent dots. When the connected dots are continuously formed in the X direction, stripe-like density unevenness (joint stripes) appears in the X direction. In addition, it is known that the ink dot landing positions are likely to be disturbed at the end of the nozzle row, so that the Y2 side end in the Y direction of the nozzle row 61A and the Y1 side end in the Y direction of the nozzle row 61B The number of cases of coalescence increases, and connecting stripes due to this coalescence tend to occur. Such density unevenness similarly occurs in the other connecting portions E62 and E63.

Further, another related technique shown in FIG. 8 has been proposed.
The recording head 70 shown here has two recording heads formed by connecting four nozzle rows in a staggered manner in the same manner as the recording head 60 shown in FIG. However, in this related technology, the distance in the X direction between the downstream nozzle rows 71B and 71D of the upstream long recording head 71 and the upstream nozzle rows 72A and 72C of the downstream long recording head 72. The interval is sufficiently widened. According to this, in any of the connecting portions E71, E72, E73 of each nozzle row, each dot overlaps with an adjacent dot in a sufficiently fixed state. For this reason, all the connected dots formed are in the state shown in FIG. 13A, and a relatively good image can be obtained. However, this recording head 70 has a new problem that the signal lines are complicated for the reasons described above, the width in the X direction becomes too large, and the recording apparatus is increased in size.

(First embodiment of the present invention)
In order to solve the problems existing in the related art as described above, in the first embodiment of the present invention, the recording head used in the full line type ink jet recording apparatus shown in FIG. 1 is configured as shown in FIG. .
In FIG. 9, reference numerals 81, 82, 83, 84 denote nozzle groups composed of odd nozzle rows and even nozzle rows. These nozzle groups are sequentially arranged along the Y direction while being alternately shifted to different positions in the X direction, that is, upstream and downstream. These nozzle groups 81 to 84 constitute a long recording head 80 extending in the Y direction. The nozzle groups 81 and 83 are arranged at the same position in the X direction, and the nozzle groups 82 and 84 are arranged at the same position in the X direction. In FIG. 9, a long recording head 80 is configured by connecting four nozzle groups 81 to 84. However, three or four or more nozzle groups are arranged in one recording head. It is also possible to do.

  Each nozzle group has the same configuration. For example, the nozzle group 81 is located at an odd number from the upper end among the plurality of nozzles n arranged at a predetermined pitch along the Y direction Y. It has an odd nozzle row 81A composed of nozzles and an odd nozzle row 81B located evenly (including 0th) from the upper end among the plurality of nozzles n. Each nozzle n in the even nozzle row 81B is arranged so as to be located in the middle in the Y direction with respect to each nozzle n in the odd nozzle row 81A. Thereby, in one nozzle group, the nozzles in the odd nozzle group and the nozzles in the even nozzle group are adjacent to each other in the Y direction as the arrangement direction thereof, and the arrangement pitch is 8C. Accordingly, in this nozzle group 81, nozzles n are arranged in a staggered manner by two nozzle rows 81A and 81B, thereby forming a high-density head. That is, substantially the same density as in the case where the nozzles are formed in a line at the arrangement pitch 8C can be obtained. Each nozzle row 81A, 81B is formed on a substrate, and each substrate P1, P2 is integrally supported by a support plate P.

  Here, L1, L2, and L3 indicate distance intervals in the X direction of the nozzle rows, and L1 is an even number of the odd nozzle rows 81A and 83A of the upstream nozzle groups 81 and 83 and the downstream nozzle groups 82 and 84. The distance between the nozzle rows 82A and 84A, L2 is the distance between the odd nozzle rows and the even nozzle rows in each nozzle group, and L3 is the odd nozzle rows 81B and 83B of the upstream nozzle groups 81 and 83 and the downstream side. The distance intervals (referred to as the distance between the nozzle groups) of the nozzle groups 82 and 84 with the even nozzle rows 82A and 84A are shown. In FIG. 9, E81, E82, and E83 indicate connecting portions of the nozzle groups.

  When a solid image is formed by the recording head 80, the dots formed by the ink droplets ejected from the Y2 side end nozzle in the Y direction of the nozzle row 81A and the nozzle row 81B of the nozzle row 81A are formed in the nozzle portion 81A. Dots formed by ink droplets ejected from the Y2 side end nozzle in the Y direction, dots formed by ink droplets ejected from the Y1 end nozzle in the Y direction of the nozzle row 82A, Y direction of the nozzle row 82B The dots formed by the ink droplets ejected from the nozzle on the Y1 side end are sequentially formed in the Y direction.

  Among these, in the adjacent nozzle n in each of the nozzle groups 81 and 82, the landing time difference between the adjacent dots is a time difference corresponding to the distance interval L2. This time difference is set so that a gourd-shaped connecting dot obtained by overlapping a part of two adjacent landing dots as shown in FIG. 13A or FIG. 13B is formed. Further, in the connecting portion E81 of the nozzle groups 81 and 82, the positional relationship of the landing of the ejected ink is set as follows because the nozzles are adjacent to each other in the X direction. That is, dots formed by ink droplets ejected from the Y2 side end nozzle in the Y direction of the nozzle row 81B and dots formed by ink droplets ejected from the Y1 side end nozzle in the Y direction of the nozzle row 82A. Are adjacent to each other and partially overlap each other to form a connected dot. The difference in landing time between these two dots is a time difference corresponding to the distance interval L3. This distance interval L3 is set to a distance interval substantially the same as the distance interval L2 when the recording medium is conveyed at a constant speed at a position facing the recording head that is performing recording. Similarly to the connection dots formed before that, the connection dots formed in step 1 are gourd-type connection dots as shown in FIG. 13 (a) or (b).

Here, “substantially the same” is a form in which the recording is executed under a single pass of relative movement between the recording head and the recording medium, and the recording head and the recording medium are within or between the nozzle groups. The ink ejected from the two nozzles adjacent in the relative movement direction (X direction) is a landing dot (a gourd-shaped connection as shown in FIG. This indicates that the dots are “identical” within a range in which dots can be formed.
Therefore, the connecting portion E81 and the connected dots formed by the nozzles in the nozzle groups 81 and 82 exhibit almost the same shape and density in the overlapping portion of the dots. As a result, streaky density unevenness does not occur and a good image can be formed.

  Moreover, the structure which made the edge part of each nozzle group overlap (overlap) can also be taken. This case is illustrated. In the connecting portion E82 between the nozzle groups 82 and 83, the respective nozzle rows are overlapped with each other in the Y direction. That is, in the joint portion E82, among the four nozzle rows, several nozzles located at the lower end portion of the nozzle row 82A and several nozzles located at the upper end portion of the nozzle row 83A are the same in the Y direction. Several nozzles located at the lower end of the nozzle row 82B and several dots located at the upper end of the nozzle row 83B are present at the same position in the Y direction.

In the connecting portion E82, the dots formed by the ink droplets ejected from the Y1 side nozzles in the Y direction of the nozzle row 83A, and the inks ejected from the Y1 side nozzles in the Y direction of the nozzle row 83B. Dots formed by droplets, dots formed by ink droplets ejected from nozzles near the lower end of the nozzle row 82A, dots formed by ink droplets ejected from nozzles near the lower end of the nozzle row 82B, They are formed so as to be sequentially adjacent in the Y direction. In this case, among the nozzles at the lower end in the nozzle rows 82A and 82B, the nozzles that overlap with the nozzle rows 83A and 83B in the Y direction include used nozzles and unused nozzles, and only the used nozzles are arbitrarily selected. Select to use. That is, the nozzles for forming the four dots in the connecting portion E82 are sequentially adjacent to each other through the pitch 8C in the Y direction, and the nozzles are selected so that the two ink droplets do not land at the same position in one dot. I do. As a result, the landing time difference of the four ink droplets can be made the time difference corresponding to L2 and L3 also in the connecting portion E82, and the stripe-shaped density unevenness does not occur.
It is to be noted that the occurrence of density unevenness can be prevented in the connecting portion E83 as in the connecting portion E81.

  As described above, according to the first embodiment, an image can be formed at a high speed by the long recording head 80, and the occurrence of streaky density unevenness in the formed image is reliably suppressed. be able to. Further, since the long recording head in the first embodiment is configured by arranging short nozzle groups in a staggered manner, it can be manufactured inexpensively and easily.

(Second embodiment of the present invention)
Next, a second embodiment of the present invention will be described with reference to FIG.
The recording head 90 in the second embodiment has a plurality of nozzle groups (here, four nozzle groups 91, 92, 93, 94) having the same configuration as in the first embodiment, which are staggered. The long recording heads are arranged in the same manner. However, the recording head 90 shown here is different in the two nozzle rows constituting each nozzle group.
Now, taking the nozzle group 91 as an example, each nozzle row 91A, 91B of the nozzle group 91 has a plurality of nozzles constituting each arranged in a staggered manner.

That is, the nozzle rows 91A are arranged in a staggered manner by nozzle row components 91A1 and 91A2 that are alternately arranged along two straight lines arranged with a minute distance interval L4 in the X direction. Similarly to this nozzle row 91A, a nozzle row 91B constituted by two nozzle row components 91B1 and 91B2 is formed in parallel with the nozzle row 91A, and the adjacent nozzles in each nozzle row are formed. The pitch is 9B. Further, each nozzle of the nozzle row 91B is arranged at an intermediate position between the nozzles of the other nozzle row 91B. Therefore, the pitch of the adjacent nozzles in the Y direction viewed from the entire nozzle group 91 is 9C (= 9B × 1/2). The other nozzle groups are similarly configured.
In addition, each nozzle row component of the nozzle group 91 and each nozzle row component of the nozzle group 93 are arranged on the same straight line parallel to the Y direction, and each nozzle row component and nozzle group of the nozzle group 92 are arranged. 94 nozzle array components are arranged on the same straight line parallel to the Y direction.

  In FIG. 10, L1 indicates the upstream nozzle row components 91A1 and 93A1 of the nozzle groups 91 and 93 located upstream in the X direction, and the upstream nozzle row of the nozzle groups 92 and 94 located downstream. The distance between the component elements 92A1 and 94A1 in the X direction is indicated, L2 indicates the distance distance between adjacent nozzles in each nozzle group, and L3 indicates the nozzle array component 91B2 on the downstream side of the upstream nozzle groups 91 and 93. 93B2 indicates the distance interval in the X direction between the upstream nozzle array components 92A1 and 94A1 of the downstream nozzle groups 92 and 94 (hereinafter, this distance interval is also referred to as the distance between nozzle groups in the X direction). ing. The distance intervals L2 and L3 are set to substantially the same distance interval.

  In the second embodiment, in the joint portion E91 between the nozzle group 91 and the nozzle group 92, the nozzles n1, n2, n3, and n4 located at the lower end portions of the nozzle array components 91A1, 91B1, 91A2, and 91B2 are provided. They are sequentially adjacent in the Y direction. Further, following the nozzle n4 at the lower end of the nozzle row component 91B2, nozzles n5, n6, n7, and n8 located at the upper ends of the nozzle row configurations 92A1, 92B1, 92A2, and 92B2 are sequentially adjacent in the Y direction. ing. Then, dots are sequentially formed by ink droplets ejected from these eight nozzles, and adjacent dots partially overlap each other to form connected dots.

  The distance intervals in the X direction between adjacent nozzles in the same nozzle group are all L2, and the landing time difference of ink droplets ejected from each nozzle is uniform. For this reason, the connected dots to be formed are gourd-shaped connected dots as shown in FIG. 13 (a) or (b). The distance interval between the nozzle n4 located at the lower end of the nozzle row component 91B2 and the nozzle n5 located at the upper end of the nozzle row component 92A1 is L3, and this distance interval L3 is substantially the same as the distance interval. They are set the same. Accordingly, the landing time difference between the ink droplets ejected from the adjacent nozzles n4 and n5 is substantially the same as the landing time difference between the ink droplets ejected from the other adjacent nozzles.

  For this reason, all the connected dots formed by the ink droplets ejected from the nozzles n1 to n8 are gourd-shaped connected dots as shown in FIG. 13A or 13B, and the density of the overlapping portion is It becomes uniform. Therefore, streaky density unevenness does not occur in the formed image.

  Moreover, it is also possible to take the structure of overlap like the above-mentioned. As an example, in the connecting portion E92, several nozzles located at the lower end of each nozzle row component 93A1, 93A2, 93B1, 93B2 of the nozzle group 93 and the upper end of each nozzle row component 92A1, 92A2, 92B1, 92B2 Several nozzles located in the section are formed so as to partially overlap in the Y direction. As a nozzle for forming eight dots in the joint portion E92, a recording operation is performed by selecting nozzles that are sequentially adjacent to each other through the pitch 9C in the Y direction and that do not land two ink droplets at the same position. I do. Thereby, also in the joint portion E92, the landing time difference of the eight ink droplets can be made the time difference corresponding to the substantially same distance intervals L2 and L3, and this causes the occurrence of streaky density unevenness. Disappear.

  In the connecting portion E93, the occurrence of density unevenness can be prevented similarly to the connecting portion E91. When the nozzle rows are arranged at high density as in this embodiment, the amount of ink ejected from each nozzle is recorded with a smaller ejection amount than when the nozzle rows are arranged at low density. . Specifically, an ink discharge amount that has a dot diameter of about pitch × √2 with respect to the nozzle pitch is selected.

(Third embodiment of the present invention)
FIG. 11 is a diagram showing a third embodiment of the present invention. The recording head 100 shown here is obtained by further arranging the nozzle group of the first embodiment shown in FIG. 9 side by side in the X direction. By this, the same effect as in the above embodiment can be expected and adjacent dots can be expected. The dot shape can be stably obtained as shown in FIG. 13A.

(Fourth embodiment of the present invention)
FIG. 12 (please replace it because the drawing was pasted at the end of this document) is a diagram showing a fourth embodiment of the present invention. The recording head 110 shown here is constituted by a single nozzle row in which each nozzle group is arranged in a straight line. Each nozzle row is opposed to each other via a distance interval L2, and the nozzles in the two opposed nozzle rows are arranged so as to be shifted from each other in the Y direction by a pitch of 11C. The two rows of nozzle rows are arranged in a staggered manner at positions shifted from the upstream side and the downstream side, and the two rows of nozzle rows located on the upstream side and the nozzle rows 2 located on the downstream side. A set of nozzle rows is arranged such that its upper and lower ends overlap in the Y direction.

  Also in this embodiment, since adjacent nozzles are sequentially formed through time intervals corresponding to substantially the same distance intervals L2 and L3, continuous dots of uniform density can be formed, and a high-quality image can be formed. Can be formed.

(Other embodiments)
In the above embodiment, the case where a full-line type recording head is used has been described as an example. However, the present invention performs a recording operation while moving the recording head in a direction intersecting the conveyance direction of the recording medium. The present invention can also be applied to a so-called serial printer type ink jet recording apparatus. In this case, not only one-pass recording in which an image in the recording area is completed by one recording scan (pass) but also so-called multi-pass recording in which an image in one recording area is completed by a plurality of recording scans. However, the present invention is effective.

  In the above embodiment, an example of an ink jet recording apparatus using a recording head having a nozzle that ejects a fixed amount of ink droplets has been described. However, a recording head having nozzles that can eject ink droplets of different ink amounts has been described. In addition, the present invention is applicable. Further, the present invention can be applied to a recording head that discharges light and dark inks having different densities in the same hue in addition to yellow, cyan, magenta, and black.

  INDUSTRIAL APPLICABILITY The present invention provides a particularly excellent effect in a recording apparatus using an inkjet recording head that performs recording by ejecting ink in nozzles as flying ink droplets using thermal energy among inkjet recording methods. It is.

  Furthermore, as a serial printer type ink jet recording apparatus, a recording head is fixed to the apparatus main body, or an electrical connection with the apparatus main body and ink from the apparatus main body are mounted by attaching the recording head to the apparatus main body. Are known which have various configurations, such as a replaceable chip type that enables supply of ink, or a cartridge type recording head in which an ink tank is provided integrally with the recording head itself. However, the present invention is effective in any case.

(Example)
Hereinafter, the present invention will be described more specifically with reference to examples.

<Example 1>
In Example 1, a recording operation was performed on the inkjet recording head shown in FIG. 1 using the long recording head 80 shown in FIG. In the long recording head 80, the upstream nozzle row and the downstream nozzle row constituting each nozzle group are each configured with a density of 600 dpi. Specifically, a head chip mounted on a commercially available BJF850 (manufactured by Canon Inc.) was bonded together, and printing was performed as a long head by using only nozzle groups arranged as shown in FIG. Therefore, each nozzle group is configured to have 256 nozzles at a nozzle pitch of 1200 dpi, and four nozzle groups are arranged in a staggered manner with the nozzle groups being alternately shifted to the upstream side and the downstream side.

This long recording head was used in an ink jet recording apparatus, and ink droplets containing a predetermined colorant were ejected to land dots on a recording medium, thereby performing a recording operation. Each ink droplet was driven to be ejected at 4.5 ± 0.5 pl. As the ink containing the coloring material, a commercially available ink for BJF850 (manufactured by Canon Inc.) was used.
As a recording medium, photo glossy paper dedicated to inkjet (Pro Photo Paper, PR101: manufactured by Canon Inc.) was prepared.
Further, the ejection drive frequency of the ink droplets ejected from each nozzle of the recording head was 8 kHz.

  When the long recording head 80 is used and image data is recorded by one scan of the recording head, an image recorded by the joint portion arranged by shifting the nozzle group and an image recorded by another portion are recorded. A difference in density was not recognized, and an image having a uniform density could be formed.

<Example 2>
Using the above four long recording heads, the gradation step pattern is set to 200% (using up to two 4.5 pl ink dots for a 1200 dpi recording matrix) with a full color image as the maximum upper limit ink amount. As a result of recording, as in Example 1, no change in density was observed between the image recorded by the connecting portion of the nozzle group and the image recorded by the other portion.

<Comparative example 1>
Instead of the long recording head used in Example 1, a recording operation was performed by one scan using the long recording head shown in FIG. 5A. In this case, streaky density unevenness was observed in the image recorded by the connecting portion of each nozzle group, and the quality of the recorded image was deteriorated.
As described above, according to this embodiment described in detail, it is possible to fundamentally solve the conventional problems in the recording operation using the long recording head configured by combining the nozzle groups composed of relatively short nozzle rows. it can. That is, it is possible to uniformize the density of the connected dots formed by the adjacent nozzles in the nozzle group and the connected dots formed by the ink droplets ejected from the adjacent nozzles at the portion connecting the nozzle groups. The occurrence of unevenness can be suppressed, and an image with good quality can be formed.
Further, if the arrangement of each nozzle row and each nozzle group is arranged in a staggered manner, the nozzles of the recording head can be formed with high density, and each nozzle group can be formed on the substrate as compared with the case where the nozzle groups are individually arranged on the substrate. The nozzle position can be accurately manufactured in the nozzle group, and the signal line connected to the nozzle group can be easily routed to minimize the expansion of the recording head in the width direction of the recording medium. It becomes possible. Further, compared with the case where high-density nozzles are arranged in a row, the manufacture thereof becomes extremely easy and the manufacturing cost can be greatly reduced.

It is a figure which shows the conceptual structure of the inkjet recording device applied to embodiment of this invention. FIG. 3 is a plan view schematically showing an arrangement state of recording heads. FIG. 2 is an exploded perspective view showing an internal structure of a recording head in an embodiment of the present invention. It is a block diagram which shows an example of a structure of the control system of the inkjet recording device of this invention. (A) is a figure which shows an example of the nozzle arrangement | sequence of the long recording head in the related technology of this invention, (b) is a figure which shows the image recorded using the recording head shown to the same figure (a). . It is a figure which shows the other example of the arrangement | sequence of the nozzle of the elongate recording head in the related technology of this invention. It is a figure which shows the other example of the arrangement | sequence of the nozzle of the elongate recording head in the related technology of this invention. It is a figure which shows the other example of the arrangement | sequence of the nozzle of the elongate recording head in the related technology of this invention. FIG. 3 is a diagram illustrating an arrangement of nozzles of a long recording head according to the first embodiment of the present invention. It is a figure which shows the arrangement | sequence of the nozzle of the elongate recording head in the 2nd Embodiment of this invention. It is a figure which shows the arrangement | sequence of the nozzle of the elongate recording head in the 3rd Embodiment of this invention. It is a figure which shows the arrangement | sequence of the nozzle of the elongate recording head in the 4th Embodiment of this invention. FIG. 6 is a diagram illustrating connected dots formed by two ink droplets ejected from two adjacent nozzles of a recording head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Recording head 22 Heater 23 Heater board 24 Top plate 25 Discharge port 26 Liquid path 31 Image data input part 32 Operation part 33 CPU
34 storage means 35 RAM
36 Image data processing section 37 Image recording section 38 Bus 80 Long recording head 81-84 Nozzle group 81A-84A Upstream nozzle array 81B-84B Downstream nozzle array 90 Long recording head 91-94 Nozzle group 91A-94A Upstream Nozzle arrays 91B to 94B Downstream nozzle array 100 Long recording head 110 Long recording head

Claims (3)

Inkjet recording in which a full-line type recording head having a plurality of nozzles that eject ink and a recording medium are moved relative to each other as recording is performed, and an image is recorded on the recording medium by ejecting ink from the nozzles. In the device
The recording head includes a first nozzle array composed of a plurality of nozzles arranged along an arrangement direction intersecting a relative movement direction with respect to the recording medium, and a second nozzle array arranged in parallel with the first nozzle array. A first nozzle group including:
A second nozzle group including a third nozzle row composed of a plurality of nozzles arranged along the arrangement direction and a fourth nozzle row arranged in parallel with the third nozzle row, and
The plurality of nozzles on the end portion side of the first nozzle row and the plurality of nozzles on the end portion side of the third nozzle row are arranged at the same position in the relative movement direction, and the end portion of the second nozzle row A plurality of nozzles on the side and a plurality of nozzles on the end side of the fourth nozzle row are arranged at the same position in the arrangement direction,
An ink jet recording apparatus, wherein the first nozzle row and the second nozzle row, the second nozzle row and the third nozzle row, and the third nozzle row and the fourth nozzle row have the same distance in the relative movement direction.   A third nozzle group including a fifth nozzle row composed of a plurality of nozzles arranged along the arrangement direction and a sixth nozzle row arranged in parallel with the fifth nozzle row; And the fifth nozzle row are arranged at the same position in the relative movement direction, and the second nozzle row and the sixth nozzle row are arranged at the same position in the relative movement direction. The ink jet recording apparatus according to claim 1.   The inkjet recording apparatus according to claim 1, wherein the first nozzle group, the second nozzle group, and the third nozzle group are arranged in a staggered manner in the arrangement direction.

Images