JP2005306014A - Liquid ejection head, liquid ejection recorder and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long liquid ejection head, a liquid ejection recorder and a liquid ejection recording method capable of outputting a high definition image at high speed with high reliability. <P>SOLUTION: An ejection opening group having a plurality of ejection opening arrays are arranged in zigzag so that impact time difference between dots being formed contiguously in the arranging direction of ejection openings while overlapping partially on a print material becomes constant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid discharge head (inkjet recording) that performs recording in a liquid discharge recording method (inkjet recording method) in which a pixel is formed on a printing material by discharging a liquid such as ink from a discharge port, and an image is formed from the pixel. The present invention relates to a head), a liquid discharge recording apparatus (inkjet recording apparatus), and a liquid discharge recording method (inkjet recording method).

  With the spread of information processing equipment such as copying machines, word processors, computers, and communication equipment, digital image recording using a liquid ejection head as one of the image forming apparatus or recording apparatus of those equipment Is rapidly spreading. With the increase in quality and color of visual information in information processing equipment and communication equipment, demands for higher image quality and color are increasing for recording devices.

  In such a recording apparatus, in order to achieve pixel miniaturization in response to the demand for higher image quality, nozzles including ejection openings and liquid passages for liquids such as ink (hereinafter simply referred to as ink) are formed with high density. Integrated liquid discharge heads have been used. Further, in order to colorize, the recording apparatus is generally provided with ink heads for ejecting ink of each color corresponding to, for example, each ink of cyan, magenta, yellow, and black. In addition, recording devices are also required to increase the number of pixels that can be formed at one time, thereby increasing the recording speed while enabling high-quality image formation and high-speed recording operations. For this purpose, the liquid discharge head has been provided with a large number of nozzles.

  In particular, a method of enabling high-speed output by making the length of the liquid discharge head about the width of the maximum printing material to be recorded and enabling execution of printing by one-pass scanning is being realized. In this case, for example, when considering an A4 landscape feed page printer, the length of the liquid discharge head is about 30 cm. If the nozzle density is 1200 dpi (dot per inch), approximately 14,000 or more nozzles are required. In order to manufacture such a liquid discharge head having many nozzles at once, a large substrate is required, which is very difficult from the viewpoint of manufacturing cost and yield.

  Further, because of the large number of nozzles, it is difficult to make all the nozzles have the same performance and maintain the same performance. For this reason, it is conceivable that unevenness in ink discharge amount and deviation in the landing position (deviation) occur between the nozzles. On the other hand, in order to prevent optical density unevenness in the recorded image, head shading correction is performed. It is known to use this technique.

  As a method of head shading, a method of measuring the optical density of the output pixel for each nozzle and feeding back the result to input image data to correct the optical density unevenness is general. For example, when the discharge amount of a certain nozzle is small for some reason and the optical density of that part is thin, correction is performed to increase the gradation value of the part of the input image corresponding to the nozzle, thereby The uniformity of image optical density in the output image is measured.

  In addition, in many nozzles, non-ejection nozzles may be generated. Complementary processing is performed for this, and non-ejection nozzle correction that enables image output even if all nozzles are not defective ( The technology of non-discharge complementation is also known.

As a method of non-discharge complementation, for example, when a certain nozzle does not discharge, instead of dots (pixels) to be formed by the nozzle, the nozzles on both sides of the nozzle are used and positioned at positions adjacent to the dot. There are known methods for forming dots, and methods for correcting image data for recording operation so that dots are formed around non-ejection nozzles instead of dots to be formed (adjacent interpolation). . In addition, a method of complementing by forming ink dots of other colors such as black in a portion where dots are to be formed by a cyan non-ejection nozzle is also known.
U.S. Pat. No. 4,723,129 U.S. Pat. No. 4,740,796 US Pat. No. 4,463,359 U.S. Pat. No. 4,345,262 U.S. Pat. No. 4,313,124 U.S. Pat. No. 4,558,333 U.S. Pat. No. 4,459,600 JP 59-123670 A JP 59-138461 A

  In a liquid discharge recording apparatus, how fast and how high-quality images are output and how this is realized at low cost is one direction of technological advancement. On the other hand, as described above, it is expensive to manufacture a liquid discharge head that is effective in forming a high-quality image at a high speed and has a long, high-density integrated nozzle. There is a problem that the yield is lowered and the performance is difficult to maintain. Further, as described above, if the head shading or discharge failure complement method is used, an image can be output even if there is a certain amount of defects in a long and high density liquid discharge head integrated with nozzles. Therefore, it is inevitable that the image quality deteriorates from the quality of the output image by the liquid discharge head having no defect.

  In view of the actual state of the above-described prior art, the present invention reduces unevenness in image density caused by a difference in landing time when dots are formed adjacent to a printing material, and achieves high speed, high image quality, and high It is an object of the present invention to provide a liquid discharge head, a liquid discharge recording apparatus, and a liquid discharge recording method that are configured to output an image with reliability.

  In order to achieve the above-described object, the liquid discharge head of the present invention includes a plurality of discharge port arrays each having a plurality of discharge port arrays in which discharge ports for discharging liquid are arranged at regular intervals, and the discharge port array In the discharge port arrays adjacent to each other in the group and between the adjacent discharge port array groups, the discharge ports belonging to each of the discharge port arrays are arranged at a first interval with respect to the direction of the discharge port array, and The discharge ports arranged at a second interval with respect to the direction intersecting the direction of the discharge port row and at the end of the discharge port row in the portion adjacent to the discharge port group in the discharge port row group The line connecting each other and the line in the adjacent discharge port array group are on the same line, and the discharge ports are arranged so as not to overlap in the intersecting direction.

  Further, in the liquid ejection method of the present invention, the ejection port array groups having a plurality of ejection port arrays in which the ejection ports for ejecting liquid are arranged at regular intervals are arranged in a staggered manner, and the above-mentioned and adjacent ones in the ejection port array group In the discharge port arrays adjacent to each other between the discharge port array groups, the discharge ports belonging to each of the discharge port arrays are arranged at a first interval with respect to the direction of the discharge port array, The adjacent discharge port arrays are arranged at a second interval with respect to a direction intersecting the column direction, and the discharge port array in the discharge port array group is located at an end portion of the discharge port group adjacent to the discharge port group. A liquid discharge head arranged such that a line connecting the discharge ports and the line in the adjacent discharge port row group are parallel and the discharge ports do not overlap in the intersecting direction, In the direction of crossing Adjacent to the ejection port row in the ejection port row group adjacent to each other in the ejection port row, the liquid is ejected and the liquid is landed on the adjacent pixel position of the print material, respectively. In the ejection port arrays adjacent to each other between the ejection port arrays, the liquid is ejected so that the time difference for ejecting the liquid and landing the liquid on the adjacent pixel positions of the print material is equal.

  According to the present invention, by arranging the ejection port groups having a plurality of ejection port arrays in a zigzag pattern, a long head as a whole can be configured to cope with higher speed. In addition, by making the landing time difference between dots formed by overlapping partially adjacent to each other in the discharge port arrangement direction of the printing material, a high quality and reliable image with little image density unevenness can be obtained. Can be formed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Liquid discharge head]
FIG. 1 is a schematic diagram of a liquid discharge head (inkjet head) 21 for discharging a liquid such as ink (hereinafter simply referred to as ink) according to the present embodiment. As shown in the figure, the liquid discharge head 21 is configured by arranging a plurality of head chips 10a, 10b,... In a zigzag shape, and works as one long liquid discharge head as a whole. In FIG. 1, only three head chips are shown for the sake of clarity, but the liquid discharge head 21 of the present embodiment may have a larger number of head chips 10. In the following description, the liquid discharge head composed of a plurality of head chips is also referred to as a multihead.

  A head chip 10 used in a multi-head according to an embodiment of the present invention is shown in a broken state in FIG. FIG. 3 is a plan view showing the nozzle structure of the head chip 10 and shows the positional relationship between the ink flow path 17 formed by the ink chamber 13 of FIG. The head chip 10 is manufactured using, for example, a Si wafer, and an elongated ink supply port 15 is formed. A top plate 19 for forming the ejection port 16 and the ink chamber 13 is provided on the Si wafer.

  Each ink supply port 15 is formed with two rows of ink chambers 13 arranged at predetermined intervals along the longitudinal direction of the ink supply port 15 so as to sandwich the ink supply port 15. Are provided with an energy generating element 14 and an ejection port 16 for ejecting ink as droplets facing the energy generating element 14.

  In this embodiment, two rows of ejection ports 16 parallel to each other across the ink supply port 15 are arranged in a so-called zigzag pattern, shifted by a half pitch, and arranged along the longitudinal direction of the ink supply port 15. The interval between the ejection ports 16 is apparently half the interval between the ink chambers 13 corresponding to the ejection ports 16 in each row. Further, an electrode wiring (not shown) that is formed of the energy generating element 14 and Al and supplies power to the energy generating element 14 is formed on the surface of the Si wafer by a film forming technique, and the terminal of the electrode wiring 17 is Au or the like. The bumps 18 are formed so as to protrude from the surface of the Si wafer.

  Although not shown in detail, the energy generating element 14 in the present embodiment is configured by a portion of the heating resistor layer formed of, for example, TaN, TaSiN, Ta—Al, or the like that is not covered by the electrode wiring. And has a predetermined sheet resistance value. The energy generating element 14 and the electrode wiring 17 are covered with a protective layer made of SiN having a predetermined thickness, and the surface of the protective layer on the energy generating element 14 is covered with Ta having a predetermined thickness. A structured anti-cavitation layer is formed.

  The ink supply port 15 described above is formed by anisotropic etching using the crystal orientation of a Si wafer used as a heat generating substrate. In other words, when the surface of the Si wafer is <100> and has a <111> crystal orientation in the thickness direction, an alkaline anisotropic etching solution such as KOH, tetramethylammonium hydroxide (TMAH) or hydrazine is used. The etching is performed to a desired depth with selectivity in the etching direction. Further, the ink chamber 13 and the ejection port 16 are formed by a photolithography technique, and by supplying power to the energy generating element 14, for example, 4 picoliter ink droplets are ejected from the ejection port 16.

  1 to 3 and the like, only a small number of energy generating elements 14 and discharge ports 16 are shown for easy understanding, but each head chip 10 can have a larger number of discharge ports 16.

[Liquid discharge recording device]
FIG. 4 is a diagram schematically illustrating a liquid discharge recording apparatus (inkjet recording apparatus) according to this embodiment to which the liquid discharge head according to the present invention can be applied. This apparatus is an apparatus that forms an image by forming dots by causing droplets to land on a print material from an ejection port while moving the liquid discharge head as described above relative to the print material. is there.

  In FIG. 4, reference numerals 101a to 101d denote multi-head type ink jet recording heads (hereinafter referred to as “heads”) each of which is a long head by mounting a plurality of heads in a staggered manner. These heads are fixed and supported in parallel with each other at a predetermined interval in the arrow X direction by a holder 102. The lower surfaces of the respective heads 101a to 101d are arranged along the arrow Y direction and are provided with discharge ports facing downward, thereby enabling recording corresponding to the width of the printing material.

  These heads 101 a to 101 d are of a type that discharges recording liquid using thermal energy, and are controlled to be discharged by a head driver 120.

  The heads 101a to 101d and the holder 102 constitute a head unit, and the head unit is moved in the vertical direction by the head moving means 124.

  The caps 103a to 103d disposed adjacent to the lower portions corresponding to the heads 101a to 101d have ink absorbing members such as sponges therein. The caps 103a to 103d are fixedly supported by a holder (not shown), and a cap unit is configured by the holder and the caps 103a to 103d. The cap unit is moved by the cap moving means 125 in the direction of arrow X. It has become.

  Each of the heads 101a to 101d is supplied with ink of each color of cyan, magenta, yellow and black from the ink tanks 104a to 104d through the ink supply tubes 105a to 105d, thereby enabling color recording. This ink supply is performed by utilizing the capillary phenomenon of the head discharge port, and the liquid levels of the ink tanks 104a to 104d are set lower than the discharge port position by a certain distance.

  The belt 106 is for conveying a printing material (recording paper) 127, and is a chargeable seamless belt. The belt 106 is drawn around a predetermined path by a driving roller 107, idle rollers 109 and 109a, and a tension roller 110, and is driven by a belt driving motor 108 connected to the driving roller 107 and driven by a motor driver 121. . The belt 106 travels in the direction of the arrow X immediately below the discharge ports of the heads 101a to 101d. Here, the lower support is suppressed by the fixed support member 126.

  A cleaning unit 117 that removes paper dust and the like adhering to the surface of the belt 106 is disposed below the belt 106 in the figure.

  The charger 112 that charges the belt 106 is turned on and off by the charger driver 122, and the printed material 127 is attracted to the belt 106 by the electrostatic attraction force due to the charging.

  In front of and behind the charger 112, pinch rollers 111 and 111 a for pressing the conveyed print material 127 against the belt 106 are arranged in cooperation with the idle rollers 109 and 109 a.

  The printed material 127 in the paper feed cassette 113 is sent out one by one by the rotation of the paper feed roller 116, and is transported to the mountain guide 113 in the direction of arrow X by the transport roller 114 and the pinch roller 115 driven by the motor driver 123. The The chevron guide 113 has a chevron space that allows the printed material 127 to bend.

  The printed material 127 for which recording has been completed is discharged to the paper discharge tray 118.

  The head driver 120, the head moving unit 124, the cap moving unit 125, the motor drivers 121 and 123, and the charger driver 122 are all controlled by the control circuit 119.

  The recording operation by the liquid ejection recording apparatus of the present embodiment is performed by transporting the printing material 127 and, at this time, selectively ejecting ink from each liquid ejection head according to input image data. Each liquid ejection head is driven by selectively supplying a drive pulse voltage to each heater (energy generating element) at a predetermined timing. As a result, the ink droplets ejected from each liquid ejection head fly and adhere to a predetermined position on the printing material, thereby forming dots as recording pixels on the printing material. Thus, an image corresponding to the input image data is formed.

  In FIG. 4, the liquid discharge head has a full-line configuration having a length corresponding to the width of the maximum print material used for recording, and the liquid discharge recording apparatus includes the liquid discharge head or the print material. In this configuration, only one of the two is moved and recording is performed on the entire printing material. However, serial-type liquid ejection that performs main scanning that moves the liquid ejection head and sub-scan that moves the printing material is shown. A recording device may be used.

  The liquid discharge recording apparatus has a control system for executing the recording operation control as described above. FIG. 5 is a block diagram showing an example of the configuration of such a control system.

  In this control system, an image data input unit 41, an operation unit 42, a CPU 43, a RAM 45, and an image data processing unit 46 are connected to each other via a bus line 48 for transmitting an address signal, various data, a control signal and the like in the apparatus. Has been provided. Further, the operation mechanism such as the liquid discharge head and the belt driving motor and the detection mechanism such as a linear encoder are connected to the bus line 48. In FIG. doing.

  The CPU 43 performs predetermined various information processing based on the control program 44d, and performs overall control of the entire liquid discharge recording apparatus. The control program 44d includes a program for controlling the operation of each unit as described above, an error processing program, and the like, and is stored in a storage medium 44 such as a ROM, FD, CD-ROM, HD, memory card, or magneto-optical disk. Supplied. The CPU 43 operates by reading out the control program 44 from the storage medium 44 via the bus line 48. In some cases, the control program 44d is read by the reading device and temporarily works as a temporary storage unit 45. Etc., and is supplied to the CPU 43 from there. Further, the storage medium 44 mainly includes printing material information 44a which is information regarding the type of printing material, ink information 44b which is information regarding ink used for recording, and information regarding the environment such as temperature and humidity during the recording operation. The environment information 44d and the like may be stored as appropriate, and these information may be used for good recording control.

  The work RAM 45 is mainly used as a work area for various programs, a temporary save area for error processing, a work area for image processing, and the like. The work RAM 45 may be used by copying various tables in the storage medium 44, changing the contents of the tables as appropriate, and using them for image processing.

  The image data input unit 41 functions to input image data from an image input device such as a scanner or a digital camera, or image data stored in a hard disk of a personal computer, to the liquid discharge recording apparatus. The operation unit 42 includes various keys for an operator to perform input processing such as setting various parameters and a command for starting a recording operation.

  The image data processing unit 46, based on the image data input from the image data input unit 41, is finally composed of binary information indicating whether or not each color ink dot is to be formed at each dot position. It works to convert it into data that can be used as Such conversion can be performed using a conventionally used method.

  For example, multi-value image data is input from the image data input unit 41. The image data processing unit 46 separates the multi-value image data so as to correspond to the color of each ink ejected from each liquid ejection head 21, and quantizes it into N-value image data for each color and each pixel, An ejection pattern corresponding to the gradation value “K” in each quantized pixel is created. For example, when multi-value image data expressed in 8 bits (256 gradations) is input to the image data input unit 41, the gradation value of the output image data is 25 (= 24 + 1) values in the image data processing unit 46. Is converted to A multi-value error diffusion method can be used for such K-value processing of input gradation image data, but is not limited to this, and any intermediate method such as an average optical density storage method, a dither matrix method, or the like can be used. Tonal processing methods can be used. Based on the density information of the image, by repeating the K-value conversion process for all the pixels, data consisting of binary information indicating whether or not to form each color dot for each dot position is generated. Is done.

  Next, in describing the details of the recording operation by the liquid discharge recording apparatus of the present embodiment, first, the recording operation by the liquid discharge recording apparatus of the comparative example compared with the present embodiment will be described.

[First Comparative Example]
FIG. 6 is a diagram illustrating a recording operation by a long liquid discharge head 61 in which all the discharge ports 62 are arranged in a line as a first comparative example of the present embodiment. In the drawing, an arrow C indicates the moving direction of the liquid discharge head 61 with respect to the printing material during the recording operation, or the printing material side is moved with respect to the liquid discharging head 61 as indicated by an arrow D. You may let them. In this way, ink is selectively ejected from each ejection port 62 at a predetermined frequency while the liquid ejection head 61 and the printing material are moved relative to each other, whereby ink is printed at each dot position of the recording matrix 65 schematically shown. Are selectively attached to form a dot pattern.

  That is, by ejecting ink from the ejection port 62 having the number 1, each dot position of the recording line number 1 in the recording matrix 65 and by ejecting ink from the ejection port 62 having the number 2, recording line numbers of the recording matrix 65 are recorded. 2 is formed at each pixel position. At this time, if, for example, 1280 ejection ports 62 arranged at a pitch of 1200 dpi (approximately 21.2 μm intervals) are used as the liquid ejection head 61, the interval between the dot positions of the recording matrix 65 is approximately 21.2 μm. However, when the size of the dots formed by the ink droplets is larger than this interval, the adjacent dots overlap each other. In addition, if the size of the dots formed by the ink droplets is even larger, the dots that are obliquely adjacent to each other also overlap each other like the dot positions (1, a) and (2, b). Further, even when the ink droplet does not land at an ideal position (the center of each dot position of the recording matrix 65), it is conceivable that adjacent dots overlap each other.

  When dots are overlapped in this way, when performing interlace recording or multi-pass recording in a conventional serial type recording apparatus, as shown in FIG. It becomes the same shape as the case where it forms independently. On the other hand, when recording is performed in one pass using the liquid discharge head 61 of the comparative example, adjacent dots cooperate to form an elliptical dot as shown in FIG. Even in diagonally adjacent dots, as shown in FIG. 7B, the dot shape may change at the overlapping portion to form a gourd-like dot, or may deviate from the ideal dot shape.

  This is because, in interlace recording or multi-pass recording, there is a certain difference in the time for ink droplets to land at adjacent dot positions, whereas in this comparative example, dot positions (1, a) and (2 , A) etc., the landing times are almost the same, and between the dot positions (1, a) and (1, b) or between the dot positions (1, a) and (2, b), etc. If the driving frequency is 10 kHz, for example, the driving frequency is assumed to be due to the difference in landing time of only 0.1 msec. That is, after the ink droplets have landed, before the ink droplets are absorbed by the print material, the ink droplets land on the dot positions adjacent to each other, so that the ink droplets merge on the print material, Therefore, it is interpreted that a desirable dot shape is impaired. In other words, the absorption speed of the ink droplets to the printing material cannot keep up with the recording speed. Therefore, it is considered that this tendency becomes more prominent as the heater driving frequency is increased and the recording speed is increased.

  As described above, the present inventors consider the absorption time of the ink to the print material as described above, and when the dots are formed at adjacent dot positions, the ink is absorbed by the print material as much as possible. It has been found that it is effective to obtain high image quality in high-speed recording to form dots with a difference of more than a predetermined time.

  Here, the absorption behavior of the ink to the printing material is measured, and the point of obtaining the absorption time will be described in detail.

  A relatively common measurement method for those skilled in the art includes the “Brist method” defined in J-TAPPI. According to this method, the ink permeation rate into the printing material within a very short time after the ink contacts the surface of the printing material can be obtained as an absorption rate coefficient, that is, the ink per unit volume is printed. It is possible to obtain the time that is absorbed into the printing material in the region of the unit area of the material. By this method, the ink (BCI5C: manufactured by Canon Inc.) used in BJF850 (produced by Canon Inc.) is used as a professional photo paper (PR101: manufactured by Canon Inc.) and ink jet electrophotographic plain paper (PBPAPER: Canon Inc.). The results shown in Table 1 can be obtained by measuring the time absorbed by high-quality exclusive paper for inkjet (HR101: manufactured by Canon Inc.).

  At this time, in Pro Photo Paper PR101, the ink absorption layer is a void type, and therefore the time until the ink droplet is absorbed by the ink absorption layer is relatively long. When dots are formed on the ProPhoto Paper with the above ink, the landing time difference between the ink droplets at positions adjacent to each other is 8 msec and 20 ml / square meter if the amount of ink droplets to be attached is 10 ml / square meter. If it is set to 28 msec or more, the deformation of the formed dots can be reduced.

[Second Comparative Example]
Next, a liquid ejection head 70 of a second comparative example is shown in FIG.

  The liquid discharge head 70 is a multi-head configured by arranging a plurality of head chips 75a, 75b,... As in the present embodiment. In the figure, only three head chips are shown for easy understanding, but the liquid discharge head 70 may be configured by arranging a larger number of head chips 75 side by side.

  In FIG. 8, the direction perpendicular to the ejection port array is the main scanning direction of the liquid ejection head 70, or the relative movement direction of the liquid ejection head 70 and the printing material when the full line type liquid ejection head 70 is used ( Hereinafter, “main scanning direction”). The head chips are alternately arranged in the main scanning direction and are arranged in a direction orthogonal to the main scanning direction.

  In the entire liquid discharge head 70, there are discharge port lines 71, 72, 73, 74 at equal intervals in parallel to the column direction of the discharge port row (direction orthogonal to the main scanning direction), and each head is on this discharge port line. It is arranged so that the discharge port array of the chip is located.

  The lower part of FIG. 8 shows a time-series formation dot pattern when the liquid ejection head 70 forms dots arranged in a direction orthogonal to the main scanning direction of the printing material.

  First, dots are formed by droplets (ink droplets) discharged from the discharge ports 76 on the discharge port line 71 at time a. At this time, since the pitch of the ejection ports 76 in each ejection port array is twice the pitch of the formed dots, each dot formed on the print material is almost independent and hardly overlaps. Similarly, dots are formed by ink droplets ejected from the ejection port line 72 at time b, the ejection port line 73 at time c, and the ejection port 76 positioned at the ejection port line 74 at time d. In FIG. 8, for easy understanding, the dots 33 formed at each time are hatched, and the dots 34 formed before the time are indicated by white circles.

At this time, the time interval t of the times ab, bc, and cd is the discharge port line interval (discharge port array interval) L, and the recording speed, that is, the liquid discharge head 70 during main scanning. If the relative speed with the printing material is F,
t = L / F (1)
It becomes.

  For example, the driving frequency of the heater in each nozzle is 10 kHz, the recording density in the main scanning direction (recording matrix resolution) is the same as the density of each discharge port 72, and 1200 dpi (therefore, each dot area of the recording matrix is approximately 20 μm square). ), The recording speed F is 0.2 mm / msec. When dots are formed by landing ink droplets of 10 ml / square meter on Pro Photo Paper (PR101) as a printing material, the ink droplet absorption time T is 8 msec from Table 1, so the time a , B, c, d interval t can be used as this absorption time, and the discharge port line interval Lpr is 1.6 mm (corresponding to about 80 dots) from equation (1). Further, when dots are formed by landing ink droplets of 20 ml / square meter on Pro Photo Paper (PR101) as a printing material, the absorption time T of the ink droplets is 28 msec, so the times a, b, c , D can be the absorption time, and the discharge line interval Lpr is 5.6 mm (corresponding to about 265 dots).

  In the liquid discharge head 70 of this comparative example, the distance between the discharge port lines 71, 72, 73, and 74 is the distance Lpr at which dots can be formed after the ink droplets are absorbed by the print material with adjacent dots during the recording operation. It is set to be close to. That is, the interval E between the two ejection port arrays of each head chip is set to a value close to Lpr. Further, the head chips (for example, 75a and 75b) shifted in the main scanning direction are arranged so that the interval F between the two adjacent ejection port arrays is the same as the interval E. By doing so, it is possible to suppress the formation of elliptical or gourd-shaped dots between dots that are partially overlapped and formed adjacent to each other in a direction orthogonal to the main scanning direction.

  The meaning of the above Lpr value will be described repeatedly. This ink is based on the time that the ink is absorbed in the printing material when a certain amount of ink is stretched in the unit area. This is the interval between the discharge port lines 71, 72, 73, 74 necessary for the ink from the adjacent discharge ports 72 to land on the printing material after the time when the ink is absorbed. Therefore, the Lpr value varies depending on the amount of ink ejected from each ejection port 72 during the recording operation. Usually, it is preferable to use the total amount of ejected ink for all colors to calculate Lpr. However, when the distance between colors is sufficiently separated, the amount of ejected ink in each color unit is used to calculate Lpr. It may be used.

  Moreover, although the absorption time K used for calculating this Lpr has been shown as an example obtained by the “Brist method” in the above, it is determined whether another absorption method for defining the absorption rate is used or whether the absorption time is absorbed visually. You may ask for it. Alternatively, the absorption time may be estimated by forming dots by changing the landing time difference between adjacent dot positions and observing the shape of the dots formed thereby. That is, when ink droplets land on adjacent dot positions before the ink droplets are absorbed by the printing material and coalescence of the ink droplets occurs, the dot shape is, for example, as shown in FIG. As shown in FIG. 7 (b), it may become a gourd shape or an elliptical shape as shown in FIG. 7 (c). From this, it is possible to estimate the time during which the ink droplets are absorbed by the printing material.

  According to the configuration of the comparative example in FIG. 8, the ink droplets that have landed on the dot positions adjacent to each other in the direction orthogonal to the main scanning direction are merged before being absorbed by the print material and the dot shape is disturbed. And image quality can be improved.

  However, when the image quality formed by Comparative Example 8 was observed in detail, it was found that the optical density unevenness partially occurred in the direction orthogonal to the main scanning direction, and a high optical density portion was formed in a streak shape. As a result of investigations by the present inventors, it has been found that the optical density of the overlapping portion of the dots varies depending on the landing time difference of the ink droplets between the overlapping dots. This will be described below.

  FIG. 9 shows an optical density distribution when dots having overlapping portions adjacent to each other are formed. As can be seen from the figure, the optical density is highest in the overlapping portion and gradually decreases toward the periphery.

  When the change of the maximum optical density (Max OD) due to the landing time difference was measured, the maximum optical density changed sharply with the change of the landing time difference until the landing time difference of about 50 ms. It can be seen that the maximum optical density settles to a certain value. In addition, this result was recorded on BJF850 (manufactured by Canon Inc.) using BCI5C (manufactured by Canon Inc.) as an ink and on Pro Photo Paper (PR101: manufactured by Canon Inc.) while changing the landing time difference. This was obtained by measuring the optical density after a sufficient time.

  Accordingly, in the dot formation pattern by the liquid ejection head 70 in FIG. 8 of the comparative example, the dots adjacent to each other are almost all, for example, the dots adjacent to the dots formed at time a are formed at time b. The dot adjacent to the dot formed at time b is formed at time c. That is, since the intervals E and F are arranged to be the same, the landing time difference is equal between the times ab, bc, and cd. However, in FIG. 8, it can be seen that the landing time difference is different only for the portion indicated by α. That is, the portion indicated by α is a portion where a dot formed at time a and a dot formed at time d overlap. Thus, it can be seen that the portion indicated by α has a long landing time difference with respect to the landing time difference between other adjacent dots. For this reason, when high optical density recording is performed, it is considered that the dot α portion has a different optical density from the other portions and appears to be streak-like.

Embodiment 1
In the configuration of the above-described comparative example, the dot landing time difference formed adjacently in the direction orthogonal to the main scanning direction (discharge port array direction) on the printing material is partially different, and thus formed. It was found that streaks appear in the image.

  Therefore, in the following embodiments, a head will be described in which the time difference of landing between dots formed by overlapping partially adjacent to each other in the ejection port arrangement direction is constant.

  A liquid discharge head 21 of this embodiment is shown in FIG.

  Head chips 10a, 10b, 10c,... Each having ejection port array groups 6a, 6b, 6c each having two ejection port arrays 5 in which ejection ports 16 for ejecting liquid are arranged at regular intervals are provided in the main scanning direction. They are alternately shifted (in a direction orthogonal to the discharge port array) and arranged in a staggered manner in a direction orthogonal to the main scanning direction.

  The liquid discharge head 21 as a whole has discharge port lines 1, 2, 3, and 4 parallel to the direction perpendicular to the main scanning direction, and is arranged so that the discharge port row of each head chip is located on the discharge port line. ing. The interval between the adjacent discharge port rows in the discharge port row group (the interval between the discharge port lines 1, 2, 3, and 4) is indicated by A, and the interval between the adjacent discharge port rows (discharge ports) between the adjacent discharge port row groups. The distance between the outlet lines 2 and 3) is indicated by B. In the present embodiment, the interval A and the interval B are equal.

  The intervals A and B indicate the ink after the ink droplets that have landed before at the dot positions adjacent to each other in the direction orthogonal to the main scanning direction (ejection port array direction) are absorbed by the print medium during the recording operation. It is preferable to set the distance to be close to the landing distance Lpr. Accordingly, it is possible to reduce the ink droplets coalesced on the printing material between the dots adjacent to each other in the direction orthogonal to the main scanning direction, thereby reducing the dot shape and improving the quality of the formed image. In this configuration, as in the above-described PR101, a printing material having an ink absorption layer having a gap type tends to have a longer ink absorption time than plain paper or high-quality exclusive paper. This is particularly effective when using a printing material.

  In the present embodiment, the discharge ports involved in recording are indicated by black circles in FIG. The ejection ports indicated by white circles in the head chip are nozzles that do not participate in recording. In the present embodiment, the ejection port that is involved in recording only needs to have the above-described configuration, and may be a dummy nozzle that does not participate in recording in other portions. Of course, it is not necessary to form discharge ports that are not originally related to discharge.

  Hereinafter, the arrangement of the discharge ports involved in recording will be described. In the ejection port array group in each head chip, the ejection ports belonging to the adjacent ejection port arrays are arranged with an interval C in the ejection port array direction. Also, in the discharge port rows adjacent between the adjacent discharge port row groups (6a and 6b, 6b and 6c), the discharge ports belonging to each row are arranged with an interval C in the direction in which the discharge ports are arranged. ing. That is, the discharge ports contributing to printing of the liquid discharge head 21 are all arranged at intervals C in the direction in which the discharge ports are arranged, and do not overlap (not at the same position) in the direction perpendicular to the discharge port array. Is arranged. Furthermore, the line connecting the discharge ports at each end of the discharge port array in the discharge port array group and the line (j and k, m and n) in the adjacent discharge port array group are on the same line. .

  In the lower part of FIG. 1, as in FIG. 8, time-series formation is performed when dots arranged in a direction orthogonal to the main scanning direction of the printing material are formed using the liquid ejection head 21 of this embodiment. A dot pattern is shown.

  Similarly to FIG. 8, dots are formed by droplets ejected from the ejection ports on the ejection port line 1 at time a. Dots are formed by droplets from the discharge ports located at the discharge port line 2 at time b, the discharge port line 3 at time c, and the discharge port line 4 at time d. The dots 31 formed at each time are hatched, and the dots 32 formed at the previous time are indicated by white circles.

  As described above, when dots are formed side by side in a direction orthogonal to the main scanning direction with the relative speed between the printing material and the head being constant using the above-described head, according to the present embodiment, FIG. As can be seen from FIG. 1, the formation of dots adjacent to each other is performed with the same landing time difference corresponding to the time intervals ab, bc, and cd in each case. For this reason, it is possible to reduce the uneven optical density of the formed image due to the difference in landing time difference between adjacent dots.

  As described above, in this embodiment, the liquid discharge head 21 is formed from a plurality of head chips 10. Therefore, a relatively long liquid discharge head 21 can be formed by using a relatively short head chip 10, and at this time, the relatively short head chip 10 has a long length, in particular, a print material 24. Unlike the case where a full-line type head having a length corresponding to the width is formed on one substrate, there is no difficulty in manufacturing and management, and low cost, high yield, high performance, high Reliable ones can be manufactured and used, and therefore the liquid discharge head 21 as a whole can be made to have high performance and high reliability even with a long configuration.

[Embodiment 2]
The liquid discharge head of this embodiment is shown in FIG. Description of the same parts as those in the first embodiment is omitted.

  As in the first embodiment, the ejection ports 82 contributing to printing of the liquid ejection head 80 are arranged at intervals C in the direction in which the ejection ports are arranged, and are arranged so as not to overlap in the direction perpendicular to the ejection port array. Has been. In the liquid discharge head 80 of FIG. 10, the interval G between the discharge port arrays of each head chip 81 and the interval H between the adjacent discharge port columns of the head chips adjacent in the main scanning direction are different. In the head chip, the line connecting the ejection ports at each end of the ejection port array, and the line in the adjacent ejection port array group, (j 'and k', m 'and n') are parallel.

  When the head as shown in FIG. 10 is used, in order to make the landing time difference between the dots formed partially overlapping adjacent to each other in the arrangement direction of the ejection openings, The appropriate speed may be adjusted according to the intervals G and H. As a result, optical density unevenness in the landing time recorded image can be reduced, and high-quality image recording can be performed.

  Further, in each of the above-described embodiments, a small head chip having discharge port arrays is arranged in a staggered manner to form a long head as a whole, but a long head that originally has discharge ports formed on a long base. A chip may be used.

(Liquid discharge method)
In the above-described embodiment, among the liquid discharge recording methods (inkjet recording methods), a liquid discharge method liquid discharge is performed in which a heater is used as an energy generating element and flying droplets are formed using thermal energy to perform recording. A configuration using the head 21 is shown.

  About this typical structure and principle, what is performed using the basic principle currently disclosed by patent document 1 and patent document 2, for example is preferable. This method can be applied to both the so-called on-demand type and continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). By applying at least one drive signal corresponding to the recording information and giving a rapid temperature rise exceeding nucleate boiling to the electrothermal transducer, the thermal energy is generated in the electrothermal transducer, and the recording head This is effective because film boiling occurs on the heat acting surface, and as a result, bubbles in the liquid (ink) corresponding to the drive signal can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable that the drive signal has a pulse shape, since the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve discharge of a liquid (ink) having particularly excellent responsiveness. As this pulse-shaped drive signal, those described in Patent Document 3 and Patent Document 4 are suitable. If the conditions described in Patent Document 5 of the invention relating to the temperature rise rate of the heat acting surface are employed, further excellent recording can be performed.

  As the configuration of the liquid discharge head, in addition to the combined configuration (straight liquid flow path or right-angle liquid flow path) of the discharge port, the liquid path, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, The structure using the patent document 6 and the patent document 7 which disclose the structure arrange | positioned in the area | region where an action part bends can also be used.

  In addition, for a plurality of electrothermal transducers, Patent Document 8 discloses a configuration in which a common slit is used as an ejection portion of the electrothermal transducer, and an opening that absorbs a pressure wave of thermal energy is associated with the ejection portion. It is good also as a structure based on the patent document 9 which discloses a structure. That is, recording can be performed reliably and efficiently regardless of the form of the liquid ejection head.

  As a liquid discharge head, even a liquid discharge head fixed to the apparatus main body can be connected to the apparatus main body to enable electrical connection with the apparatus main body and supply of ink from the apparatus main body. The head can also be used. Further, a cartridge type liquid discharge head in which an ink tank is provided integrally with the liquid discharge head may be used.

  A bubble jet (BJ) type liquid discharge head using a heating element (heater) as such an energy generating element is preferable because it can realize a large number of nozzle groups relatively easily and at low cost. The liquid discharge head that can be used in the liquid discharge recording apparatus of the invention is not limited to this. For example, in the case of a continuous type in which ink droplets are continuously ejected into particles, a charge control type, a divergence control type, etc., and in the case of an on-demand type in which ink droplets are ejected as required, a piezoelectric vibration element It is also possible to apply a pressure control method that ejects ink droplets from an orifice by mechanical vibration.

  Further, as a configuration of the liquid discharge recording apparatus of the present invention, it is possible to further stabilize the effect of the present invention by adding the recovery means of the liquid discharge head and other preliminary auxiliary means as described above. This is preferable. Specifically, heating is performed using a capping unit, a cleaning unit, a pressurizing or suction unit, an electrothermal transducer, a heating element different from this, or a combination thereof. Examples include a preliminary heating unit for performing the discharge and a preliminary discharge unit for performing discharge different from the recording.

FIG. 2 is a schematic diagram of a liquid ejection head according to a first embodiment of the present invention viewed from the ejection port surface side, and a schematic diagram of a dot pattern formed using the same. FIG. 2 is a partially broken perspective view of a head chip constituting the liquid ejection head of FIG. 1. FIG. 3 is a plan view schematically showing a nozzle structure of the head chip in FIG. 2. FIG. 2 is a schematic diagram of a liquid discharge recording apparatus including the liquid discharge head of FIG. 1. FIG. 5 is a block diagram schematically showing a control system of the liquid discharge recording apparatus of FIG. 4. FIG. 6 is a schematic diagram of a liquid ejection head according to a first comparative example viewed from the ejection port surface side, and a diagram illustrating a recording matrix for explaining dot positions formed using the liquid ejection head. The figure which shows a dot shape when a dot is formed in the mutually adjacent dot position. The schematic diagram seen from the discharge port surface side of the liquid discharge head of the 2nd comparative example, and the schematic diagram of the dot pattern formed using this. The figure which shows the optical density distribution of the part formed by the dot overlapping. FIG. 6 is a schematic diagram of a liquid discharge head used in a liquid discharge apparatus according to a second embodiment of the present invention.

Explanation of symbols

5 Discharge port array 6a, 6b, 6c Discharge port array group 16, 76 Discharge port
10a, 10b, 10c 75a, 75b, 75c Head chip 21, 70 Liquid ejection head 31, 33 Dots formed on the printing material at each time 32, 34 Dots formed on the printing material at the previous time

Claims (5)

A plurality of discharge port arrays each having a plurality of discharge port arrays in which liquid discharge ports are arranged at regular intervals are arranged in a staggered manner,
In the discharge port arrays adjacent to each other in the discharge port array group and between the adjacent discharge port array groups, the discharge ports belonging to each of the discharge port arrays have a first interval with respect to the direction of the discharge port array. And arranged at a second interval with respect to a direction intersecting the direction of the discharge port array,
In the discharge port array group, the line connecting the discharge ports at the end portion of the discharge port array adjacent to the discharge port group and the line in the adjacent discharge port array group are on the same line. And
The liquid discharge head, wherein the discharge ports are arranged so as not to overlap in the intersecting direction.   2. The liquid ejection head according to claim 1, wherein each of the ejection port array groups is formed on a substrate provided with an energy generation element that generates energy used for ejecting liquid. 3. A liquid ejection head according to claim 2;
Means for relatively moving the printing material and the liquid ejection head in the intersecting direction;
A liquid discharge recording apparatus comprising: A plurality of discharge port arrays each having a plurality of discharge port arrays in which liquid discharge ports are arranged at regular intervals are arranged in a staggered manner,
In the discharge port arrays adjacent to each other within the discharge port array group and between the adjacent discharge port array groups, the discharge ports belonging to each column are arranged at a first interval with respect to the direction of the discharge port array,
The discharge port rows adjacent in the discharge port row group are arranged at a second interval with respect to the direction intersecting the direction of the discharge port row,
In the discharge port array group, the line connecting the discharge ports at the end portion of the discharge port array adjacent to the discharge port group is parallel to the line in the adjacent discharge port array group. Yes,
A liquid discharge head disposed so that the discharge ports do not overlap in the intersecting direction;
Move relative to the print material in the intersecting direction,
In the ejection port arrays adjacent in the ejection port array group, a time difference for ejecting the liquid and landing the liquid on adjacent pixel positions of the printing material,
In the adjacent ejection port arrays between the adjacent ejection port array groups, a time difference for ejecting the liquid and landing the liquid on the adjacent pixel positions of the printing material, and
A liquid discharge recording apparatus characterized in that the two are equal. A plurality of discharge port arrays each having a plurality of discharge port arrays in which liquid discharge ports are arranged at regular intervals are arranged in a staggered manner,
In the discharge port arrays adjacent to each other in the discharge port array group and between the adjacent discharge port array groups, the discharge ports belonging to each of the discharge port arrays have a first interval with respect to the direction of the discharge port array. Arranged,
The discharge port rows adjacent in the discharge port row group are arranged at a second interval with respect to the direction intersecting the direction of the discharge port row,
In the discharge port array group, the line connecting the discharge ports at the end portion of the discharge port array adjacent to the discharge port group is parallel to the line in the adjacent discharge port array group. Yes,
Moving the liquid discharge head arranged so that the discharge ports do not overlap in the intersecting direction relative to the print material in the intersecting direction;
In the ejection port arrays adjacent in the ejection port array group, a time difference for ejecting the liquid and landing the liquid on adjacent pixel positions of the printing material,
In the adjacent ejection port arrays between the adjacent ejection port array groups, a time difference for ejecting the liquid and landing the liquid on the adjacent pixel positions of the printing material, and
A liquid discharge recording method, wherein the liquid is discharged so as to be equal to each other.

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