Inkjet recording apparatus and control method thereof

Abstract

An inkjet recording apparatus and a control method thereof. An inkjet recording apparatus which applies ink substantially uniformly to a recording medium formed with a plurality of regions arranged in a matrix, includes: a recording head having M nozzles each capable of discharging ink; an acquisition unit which acquires discharge amount information regarding a discharge amount of ink discharged per unit time from each nozzle of the M nozzles; and a control unit which controls the M nozzles to discharge ink while relatively scanning the recording head with respect to the recording medium, and applies ink to the plurality of regions. The control unit has: a classification unit which classifies, based on the discharge amount information, N (N < M) nozzles assigned to recording with respect to a region column including the plurality of regions arranged in a scanning direction, into a first group and a second group which exclusively discharge with respect to each region included in the region column; and a decision unit which decides, based on the discharge amount information, a proportion of the number of regions of the region column in which the nozzles belonging to each of the first group and the second group discharge.

Description

Technical Field

[0001] This invention relates to recording control in inkjet recording devices. Background Technology

[0002] In inkjet recording apparatuses manufacturing organic EL elements for display light-emitting elements and quantum dot color conversion layers for color conversion, stability of the ejection volume of each recording nozzle is required. For example, in the case of manufacturing a display with a large number of organic EL elements arranged on a substrate, when the ejection volume of each recording nozzle deviates, the ink droplet volume (film thickness) varies depending on the pixel, and the light-emitting characteristics become uneven. Similarly, in the case of manufacturing a quantum dot color conversion layer, when the ink droplet volume (film thickness) changes for the same reason, the optical properties of the quantum dot color conversion layer become uneven depending on the pixel and region. Japanese Patent Application Publication 2016-192407 (Patent Document 1) proposes a method to reduce the unevenness of ink droplet volume by correcting the combination of nozzles used in ink ejection, even when there are deviations in the ejection volume from each nozzle. Furthermore, Japanese Patent Application Publication Hei 10-13674 (Patent Document 2) proposes a method to reduce the unevenness of ink droplet volume by increasing or decreasing the number of dots ejected from each nozzle, even when there are deviations in the ejection volume from each nozzle.

[0003] However, in Patent Document 1, nozzles that are actually used for each scan are selectively used, resulting in nozzles that are actually usable for dispensing but are not used. Therefore, there is a problem of reduced nozzle utilization efficiency and decreased robustness to unevenness caused by factors other than dispensing volume deviations. Furthermore, in Patent Document 2, there is a possibility of ink droplet volume differences between adjacent pixels and high spatial frequency unevenness due to quantization errors. Summary of the Invention

[0004] An inkjet recording apparatus for substantially uniformly applying ink to a recording medium having multiple regions arranged in a matrix, comprising:

[0005] The recording head has M nozzles, each configured to dispense ink.

[0006] The acquisition unit acquires dispensing quantity information related to the dispensing quantity of ink from each of the M nozzles per unit number of times; and

[0007] The control unit simultaneously scans the recording head relative to the recording medium and controls the ink ejection from the M nozzles to coat the multiple areas with ink.

[0008] The control unit has:

[0009] a classifying unit, which classifies, based on the discharge amount information, N nozzles assigned for recording on a column of regions including a plurality of regions arranged in the scanning direction into a first group and a second group that discharge exclusively to each region included in the column of regions, wherein N < M; and

[0010] a determining unit that determines, based on the discharge amount information, the proportion of the number of regions in the column of regions to which nozzles belonging to each of the first group and the second group perform discharge.

[0011] A control method for an inkjet recording apparatus, for applying ink substantially uniformly to a recording medium having a plurality of regions arranged in a matrix, wherein

[0012] said inkjet recording apparatus comprises a recording head having M nozzles each configured to discharge ink,

[0013] said control method comprises:

[0014] an obtaining step of obtaining discharge amount information related to the discharge amount of ink discharged per unit number of times from each of said M nozzles; and

[0015] a control step of controlling ink discharge of said M nozzles to apply ink to said plurality of regions while causing said recording head to perform relative scanning with respect to said recording medium,

[0016] said control step comprises:

[0017] a classifying step of classifying, based on the discharge amount information, N nozzles assigned for recording on a column of regions including a plurality of regions arranged in the scanning direction into a first group and a second group that discharge exclusively to each region included in the column of regions, wherein N < M; and

[0018] a determining step of determining, based on the discharge amount information, the proportion of the number of regions in the column of regions to which nozzles belonging to each of the first group and the second group perform discharge.

[0019] The present invention reduces non-uniformity in the amount of ink droplets during recording in an inkjet recording apparatus. Description of the Drawings

[0020] Figure 1 is a diagram showing the overall structure of the recording apparatus.

[0021] Figure 2 is a block diagram showing the hardware structure related to recording control.

[0022] Figure 3 is a diagram illustrating the structure of the recording medium.

[0023] Figure 4 It is a diagram illustrating the structure of the recording head.

[0024] Figure 5 This is a flowchart of the output data generation and processing (first embodiment).

[0025] Figure 6 It is a diagram showing the relationship between the scanning of the recording head and the recording medium.

[0026] Figure 7 This is a diagram illustrating the concept of multi-nozzle and the output volume Gr.

[0027] Figure 8 This is a detailed flowchart of the determination of multiple nozzles and number of points (S004) (First Embodiment).

[0028] Figure 9 This is a diagram illustrating the record parameters for the bank column of the Y-line.

[0029] Figure 10 This is an illustrative diagram showing a recording made by multiple nozzles.

[0030] Figure 11 This is a detailed flowchart (as in previous examples) determined by the number of nozzles and points.

[0031] Figure 12 This is a diagram illustrating the record parameters for the clustered columns of row Y (previous example).

[0032] Figure 13 This is an illustrative diagram showing a recording made by multiple nozzles (a previous example).

[0033] Figure 14 This is a diagram that illustratively shows a comparison between the first embodiment and a conventional example.

[0034] Figure 15 This is a detailed flowchart of the multi-nozzle segmentation (S004-3B) (Second Embodiment).

[0035] Figure 16 It is a diagram illustrating the recorded parameters for each of the multiple nozzles. Detailed Implementation

[0036] The embodiments will now be described in detail with reference to the accompanying drawings. Furthermore, the following embodiments do not limit the invention as defined in the claims. Several features are described in the embodiments, but these features are not necessarily essential to the invention, and the features can be combined arbitrarily. In addition, the same or identical structures are given the same reference numerals in the drawings, and repeated descriptions are omitted.

[0037] (First Embodiment)

[0038] As a first embodiment of the inkjet recording apparatus according to the present invention, the following description shall take a recording apparatus for coating ink on a display substrate as an example.

[0039] <Device Structure>

[0040] Figure 1 This is a diagram showing the overall structure of the recording device 1 in the first embodiment. Furthermore, Figure 1 (a) is a top view. Figure 1 (b) is a side view; for ease of illustration, only a portion of the elements of the recording device are shown. Figure 1 The image shows a substrate 11, the object to be coated with ink, positioned at a predetermined location on a stage 10. The stage 10 is fixed to the base 9 of the apparatus.

[0041] The recording head 2 coats the substrate 11 by dispensing RGB inks in a substantially uniform manner. In the recording head 2, a plurality of recording nozzles 3 (not shown) are arranged in the direction opposite to the substrate 11, each nozzle being configured to dispense any one of the RGB inks. The recording head 2 is supported by a scanning mechanism and is configured to scan the recording nozzles 3 in a plane parallel to the XY plane at a predetermined distance from the substrate 11 in the Z direction. Specifically, the main scanning guide 5 extends along the main scanning direction (Y direction), and the sub-scanning guide 7 extends along the sub-scanning direction (X direction), both supported by support members 8.

[0042] The recording head 2 is fixed to the main scanner 4, and the recording head 2 can scan freely in a plane parallel to the XY plane. Furthermore, the recording head 2 and the substrate 11 can move relative to each other, or the recording head 2 can be fixed while the substrate 11 moves. Ink of various colors is supplied from the ink tank 101 to the sub-ink tank 123 via the dashed path. The cap 124 can temporarily receive waste ink from the recording head 2 and direct it to the waste ink tank 140. Furthermore, the dashed path conceptually represents the ink supply system and does not necessarily represent a physical connection.

[0043] Figure 2 This is a block diagram showing the hardware structure related to the recording control of the recording device 1. Furthermore, for ease of illustration, only a portion of the elements controlled by the control unit are shown.

[0044] The CPU 301 reads and executes the system control program stored in the ROM 302, and controls the entire system according to the program. At this time, the program is expanded in the RAM 312 and used as a working area. That is, the RAM 312 temporarily stores data, input data, etc., required for the processing executed by the CPU 301. In addition, the CPU 301 also controls the operation of the cleaning unit 304, the conveying assembly 303, etc. Furthermore, the CPU 301 controls the recording operation of the recording head 2 through the drive circuit 307, the binarization circuit 308, and the image processing unit 309.

[0045] The image processing unit 309 performs predetermined image processing on the recorded image data. Specifically, the image processing unit 309 performs image data transformation for each color based on information such as the pixel size, pixel spacing, and required film thickness for each pixel of the input substrate 11. The binarization circuit 308 transforms the image data transformed by the image processing unit 309 into binarized data that can be used in the ejection control of the recording head. Furthermore, the drive circuit 307 executes the ink droplet ejection operation of the recording head 2 according to the binarized data obtained by the binarization circuit 308. Although binarization processing has been described, multi-valued processing, i.e., processing that ejects multiple droplet sizes, is also possible.

[0046] In addition, in the defective nozzle compensation 310, a process for generating compensation data for defective nozzles (hereinafter referred to as compensation processing) is performed. In the defective nozzle detection unit 311, nozzles (defective nozzles) whose ink droplet ejection state in the multiple nozzles formed in the recording head 2 is inappropriate are detected. At this time, the CPU 301 reads the pattern data stored in the ROM 302 and drives the recording head 2 via the drive circuit 307 based on the data. In addition, the various units controlling the recording operation of the transport assembly 303 and the like record the defective nozzle detection pattern onto the recording medium. Then, the defective nozzle detection unit 311 reads the recorded pattern to detect defective nozzles.

[0047] Figure 3 This is a diagram illustrating the structure of the substrate 11, which serves as the recording medium. Figure 3 (a) shows a top view of the recording medium. Figure 3(b) shows its side view. The substrate 11, which serves as the recording medium, is, for example, a glass substrate facing the display, with a thickness of 0.7 mm to 1.1 mm. The agglomerate material 12 is a spacer used to prevent ink flow / mixing, and is preferably a light-shielding material. Its thickness is about 2 μm to 30 μm. Multiple regions (agglomerates) are formed on the recording medium in a matrix arrangement. Agglomerate 100 indicates the area surrounded by the substrate 11 (bottom surface) and the agglomerate material 12 (side surface), and the necessary amount of ink droplets can be injected from the opening (top side) of agglomerate 100 by inkjet injection. Agglomerates 100 are arranged in a repeating arrangement of R, G, B. In the following description, when specifically referring to agglomerates, a coordinate system such as "R[X][Y]" will sometimes be used. Hereinafter, agglomerate 100 will also sometimes be simply referred to as agglomerate. For example, in Figure 3 The cluster 100 is referred to as "B[2][0]" etc. In addition, for the sake of simplicity, not all RGB clusters are shown / illustrated, but only the B (Blue) cluster is explained.

[0048] Furthermore, the concepts of "Y-row" and "cluster column" are introduced here. Specifically, Y0 row refers to the 0th Y-row, that is, the "cluster column" composed of B[0][0], B[1][0], B[2][0], ..., B[X][0]. Specifically, in the case of an 8K resolution (7680 pixels × 4320 pixels) display, the range of X is 0 to 7679, and the range of Y is 0 to 4319, that is, there are 4320 "cluster columns", which are called Y0 row to Y4319 row. In addition, in the following explanation, the direction of "cluster column" is defined as the direction parallel to the main scanning direction in the recording scan. That is, when the recording medium (substrate 11) is rotated 90 degrees relative to the recording head 2, the clusters arranged in the direction parallel to the main scanning direction of the recording head are newly called "cluster columns". The same applies when the main scanning direction and the recording medium (substrate 11) are tilted at an angle.

[0049] Figure 4 It is a diagram illustrating the structure of the recording head. Figure 4 The record header 2a in (a) is illustrated illustratively when making a reference. Figure 6 (a) The record header used during multi-pass recording, as described later. Additionally, Figure 4 The record header 2b in (b) is illustratively shown when making a reference. Figure 6 (b) The record header used when recording a single pass, as described later.

[0050] In recording head 2a, a plurality (M) of recording nozzles 3 are arranged in the Y direction. The number of nozzles shown here is conceptual; in practice, approximately 256 to 1024 nozzles are preferably arranged in each recording head. Furthermore, the nozzle array density (resolution) is preferably approximately 600 dpi. Additionally, a pressure generating unit (not shown) is connected to the nozzles 3, enabling the dispensing of ink from the nozzles. The pressure generating unit can be a component utilizing the deformation of a piezoelectric element, a component utilizing film boiling of a heating element, etc. Here, the designed dispensing volume of the recording nozzles 3 is set to 3 [pL]. However, due to various dimensional tolerances during manufacturing, the actual dispensing volume will vary (variance) for each recording nozzle. On the other hand, recording head 2b is a recording head integrally formed by arranging 2048 (M) recording nozzles 3 in the Y direction and 10 in the X direction. Compared to recording head 2a, it has 5 to 20 times more recording nozzles.

[0051] <Summary>

[0052] In the first embodiment, a method for simultaneously achieving the following three objectives by using the group segmentation of multiple nozzles, which will be described later, will be explained.

[0053] "Objective 1": Reduce the average ink droplet volume deviation in each Y row caused by the head's ejection volume deviation.

[0054] "Objective 2": Reduce the deviation in ink droplet volume between X clusters belonging to each Y row.

[0055] "Objective 3": Use all multi-nozzles as evenly as possible.

[0056] • Regarding multi-trip recording / single-trip recording

[0057] Figure 6 It is a diagram showing the relationship between the scanning of the recording head and the recording medium. Figure 6 (a) is used in Figure 4 The diagram in (a) illustrates a recording method in which the recording head 2a performs N main scans. Multi-pass recording refers to a method in which the recording head 2 repeatedly performs main scan recording and sub-scan feeding on the recording medium (substrate 11) while recording multiple times on a region of the recording medium. Furthermore, the recording head 2 can be moved relative to the recording medium (substrate 11), or one side can be fixed.

[0058] on the other hand, Figure 6 (b) is used in Figure 4The diagram in (b) illustrates a recording method in which the recording head 2b performs single-pass recording with a main scan count of 1. Single-pass recording is a method in which the recording head 2 records an area of ​​the recording medium in only one main scan. To achieve single-pass recording, a long ruler with a recordable width equal to or greater than the length of the substrate and a number of recording nozzles required to record the amount of ink needed to record clumps in only one recording scan are required.

[0059] Regarding multi-nozzle

[0060] In this embodiment, "multi-nozzle" is defined as follows. That is, multi-nozzle (abbreviated as "MN" if necessary) refers to "individual recording nozzles actually used to record any Y rows". Additionally, when it is necessary to distinguish between multiple nozzles, a suffix is ​​sometimes added as MNX (where X is an integer greater than or equal to 0). For example, when there are 10 multiple nozzles, they are referred to as MN0, MN1, ..., MN9. Figure 6 To illustrate the concept of multiple nozzles.

[0061] First, consider Figure 6 The recording nozzle in (a) is capable of recording row Y0. As described above, Figure 6 (a) is a conceptual diagram of multi-pass recording with N main scans, where N is set to 8, i.e., 8-pass recording. However, the relationship between any Y-row and multiple nozzles depends on various factors. For example, it depends heavily on physical relationships such as the recording nozzle resolution of the recording head, the sub-scan feed rate of the recording head, and the cluster resolution in the sub-scan direction of the substrate. In addition, nozzles in the recording head that do not eject or have extremely large droplet position misalignment are practically unusable for recording, so these nozzles need to be removed from the multiple nozzles. Furthermore, it should be noted that the recording pass and multiple nozzles are not necessarily in a one-to-one correspondence. For example, when the cluster length (dimension in the Y direction) is large and the nozzle density of the recording head is high, it is possible that two or more adjacent nozzles in the same recording pass may be used as multiple nozzles.

[0062] Next, consider Figure 6 The recording nozzle in (b) is capable of recording the Y0 row. As mentioned above, Figure 5 (b) is a conceptual diagram of a single-pass recording. The recording head 2a, as previously described, consists of 10 heads, which are numbered 0 to 9 from left to right for illustration. The recording Y0 position is the fifth nozzle from the top in the Y direction of each head, and the recording scan is completed in one scan (scan number 0). That is, even in the case of a single pass, recording can be performed using the 10 nozzles MN0 to MN9.

[0063] In summary, the concept of a multi-nozzle system involves using physically different nozzles to record independently. This can be achieved either by varying the number of strokes within a single head, or by using multiple heads to record in a single operation. Alternatively, it can be a combination of both (multiple heads and multi-stroke recording). From this point forward, details regarding recording types (multiple-stroke or single-stroke recording), specific scan numbers, nozzle numbers, etc., will be omitted; the focus will be on the structure of the multi-nozzle system.

[0064] <The action of the device>

[0065] Figure 5 This is a flowchart of the output data generation process in the recording apparatus 1 according to the first embodiment. Regarding the output data generation process, the CPU 301 is the main component, reading the program from the ROM 302 and instructing associated circuits such as the image processing unit 309 to perform processing as needed. Hereinafter, the process will be described with reference to this flowchart and the accompanying drawings.

[0066] In S001, CPU 301 performs needle movement calculations. Needle movement refers to one or more relative movements accompanying the recording action of the recording head and the recording medium (substrate 11). Based on the size of the recording medium, the number of dots required for each cluster, the maximum ejection frequency of the recording head, etc., the CPU calculates the main scan count, main scan speed, sub-scan feed rate, sub-scan count, etc. of the recording head using a predetermined method.

[0067] The following is a specific example of needle movement calculation. If the number of multi-strokes (described later) is determined, it is determined by sub-scan feed rate = total length of the recording head ÷ number of multi-strokes. If the sub-scan feed rate is determined, it is determined by the number of main scans of the recording head = (total length of the recording medium + total length of the recording head) ÷ sub-scan feed rate. Regarding the nozzle resolution and recording blob height of the recording head, refer to the design values ​​and use the aforementioned sub-scan feed rate to determine the number of nozzles that can be used for each blob per multi-stroke. Additionally, the number of points required for each blob is determined by blob opening height × blob opening width × blob height ÷ designed ejection rate. If the number of points required for each blob is determined, regarding the maximum ejection frequency of the recording head, refer to the design values ​​and reduce the main scan speed of the recording head or change (increase) the number of multi-strokes until the necessary number of points for each blob can be recorded using the aforementioned usable nozzles.

[0068] In S002, within CPU 301, Y = 0 (Y0 row) is set as the initial value. In the loop described later, the calculations required for all Y rows are performed.

[0069] In S003, CPU 301 performs calculations for the multiple nozzles in each Y row. Figure 7 This is a diagram illustrating the concept of multiple nozzles and the output volume Gr. Specifically, Figure 7 (a) and Figure 7 and (b) are respectively calculation results based on S003 for multi-pass recording and single-pass recording, and the table shows which multiple nozzles are used for recording in the Y0 row of the block column. Multiple nozzles are associated one-to-one with recording head numbers, nozzle numbers, scan numbers, ejection amounts, and the ejection amount group (Gr) described later. For example, MN0 in the Y0 row corresponds to head number 0, nozzle number 510, scan number 0, ejection amount 2.91 [pL], and low ejection amount Gr.

[0070] In S004, the CPU 301 determines the multiple nozzles and the number of dots to be used in recording (ink ejection) for each X block in the Y row. Figure 8 is a detailed flowchart of the determination of multiple nozzles and the number of dots (S004).

[0071] In S004-1, the CPU 301 reads ejection amount information of each multiple nozzle. The ejection amount information is the ink ejection amount per unit number of ejections from each nozzle. For example, values obtained by measuring the recording head when leaving the factory can be stored in the storage unit in advance. Of course, a configuration may also be adopted in which an unillustrated ejection amount measuring unit is provided in the recording apparatus to measure and obtain the ejection amount information. Here, as Figure 7 described in (a) and (b), the number of MN is 10 (N (N < M)), and among MN0 to MN9, the ejection amount is set to have a variation within the range of 2.91 pL to 3.13 pL.

[0072] In S004-2, the CPU 301 reads the target block filling amount, that is, the required ink filling amount per block. It is determined according to various factors such as block resolution, block volume, required film thickness, and fixing conditions. The target block filling amount is about 10 pL to 300 pL. Here, the target block filling amount is set to 37.5 pL. In addition, in the present embodiment, calculation is performed such that the average ink droplet amount of each Y row matches the aforementioned target block filling amount.

[0073] In S004-3, the CPU 301 divides (classifies) the multiple nozzles into large ejection amount Gr and low ejection amount Gr. Specifically, here, after reordering the multiple nozzles in ascending order based on their ejection amount information, the multiple nozzles are divided into two groups with the median ejection amount as the boundary. Specifically, here, as Figure 7 described in (a) and (b), multiple nozzles with ejection amounts from 2.91 [pL] to 2.99 [pL] are defined as "low ejection amount Gr", and multiple nozzles with ejection amounts from 3.02 [pL] to 3.13 [pL] are defined as "large ejection amount Gr". At this time, the average ejection amount of low ejection amount Gr is 2.95 [pL], and the average ejection amount of large ejection amount Gr is 3.05 [pL].

[0074] In S004-4, CPU 301 calculates the ratio of the number of regions exclusively recorded by Gr with large output volume to the number of regions exclusively recorded by Gr with small output volume (clump ratio). Before the calculation method, "exclusive recording" and "clump ratio" are explained.

[0075] First, "exclusive recording" means that "for any cluster arranged in the X direction within a Y row, the nozzles belonging to a certain output volume Gr exclusively occupy all the points required to record each cluster." In other words, it means that "nozzles belonging to different output volumes Gr exist together for each cluster without recording any points." For example, when 5 nozzles belonging to the large output volume Gr are assigned to B[0][0], recording for B[0][0] is performed only through the 5 nozzles on the left. When 5 nozzles belonging to the small output volume Gr are assigned to B[1][0], recording for B[1][0] is performed only through the 5 nozzles on the left.

[0076] Next, the "clump ratio" will be explained. For example, suppose 500 clumps are arranged in the X direction in a Y row. If the discharge volume Gr exclusively records 300 of the 500 clumps on the left, the clump ratio of the discharge volume Gr becomes 300 / 500 = 0.6. On the other hand, the remaining clumps are recorded by the discharge volume Gr, so the clump ratio of the discharge volume Gr is (500-300) / 500 = 0.4. The clump ratio can also be expressed as a decimal such as 0.6:0.4 and the total is 1. Alternatively, it can be expressed as an integer ratio such as 1:2 and the total is not 1. The clump ratio is preferably close to discharge volume: discharge volume = 1:1. The reason is that from the point of view of nozzle durability, it is preferable to use an equal ratio. The calculation of the clump ratio that is exclusively recorded uses mathematical formula (1).

[0077] TargetInkVolume=Vd_UpperGr×N×ratio+Vd_LowerGr×(N+1)×(1-ratio)···(1)

[0078] On the left side of mathematical formula (1), TargeInkVolume is the target ink volume, which is 37.5 [pL] as mentioned above. Vd_UpperGr in the first term on the right is the average ejection volume of large ejection volume Gr, which is 3.08 [pL] herein. N is the number of dots exclusively recorded by large ejection volume Gr in each X block, which is set to "12 shots" herein. ratio is the proportion of blocks exclusively recorded by large ejection volume Gr in Y0 row, which can be in the range of 0<ratio<1. Vd_LowerGr in the second term on the right is the average ejection volume of small ejection volume Gr, which is 2.95 [pL]. N+1 is the number of dots exclusively recorded by small ejection volume Gr in each X block; since N=12, N+1=13 shots. 1-ratio is the proportion of blocks in this Y row that are undertaken by small ejection volume Gr, which can be in the range of 0<ratio<1. Herein, only ratio is an unknown value and the value to be obtained, and when solving this linear equation, ratio=0.61 is obtained.

[0079] That is, in Y0 row, when block X is set as 500 blocks, the 5 multi-nozzles belonging to large ejection volume Gr record 305 blocks, accounting for 61% of the total. In addition, it means that the 5 multi-nozzles belonging to small ejection volume Gr record 195 blocks, accounting for 39% of the total. Thereby, the average in-block ink droplet amount of Y0 row can be made to reach 37.5 [pL], which is the target value.

[0080] Herein, the definitions of "large block" and "small block" are explained. A "large block" refers to a block in which the ink droplet amount within the block is set to be relatively large in a Y row, and a "small block" refers to a block in which the ink droplet amount within the block is set to be relatively small. In this embodiment, a large block refers to "a block where N+1 dots are recorded by small ejection volume Gr", and a small block refers to "a block where N dots are recorded by large ejection volume Gr". Specifically, the ink droplet amount of a large block is 2.95 [pL] × 13 [shots] = 38.4 [pL], and the ink droplet amount of a small block is 3.08 [pL] × 12 [shots] = 37.0 [pL].

[0081] Herein, the features of this embodiment are organized and explained. A relatively larger number of dots are recorded by small ejection volume Gr, and a relatively smaller number of dots are recorded by large ejection volume Gr. Thereby, the difference between the ink droplet amounts of large blocks and small blocks is 38.4 [pL] - 37.0 [pL] = 1.4 [pL]. This difference is smaller than the designed ejection volume of 3 [pL] for 1 droplet. Generally, the difference in ink droplet amount between adjacent blocks in a Y row becomes a film thickness difference, that is, a difference in optical characteristics such as brightness and chrominance, which may be visually recognized. However, according to the method of this embodiment, the average ink droplet amount of the Y row can be made to conform to the target value, and at the same time, the difference in ink droplet amount between adjacent blocks can be reduced.

[0082] In S004-5, CPU 301 is configured with large and small clusters in the X direction. In S004-4, the ratio of large to small clusters is determined to be 0.36:0.64, so the arrangement in the X direction can be determined here. As the simplest method, it is assumed that the clusters are rearranged according to random numbers following the ratio on the left. The method of rearranging with random numbers has the advantage of lower computational load. As another method, the configuration method can be determined by considering factors such as frequency characteristics in a discontinuous configuration of large and small points. Alternatively, S004-4 and S004-5 can be integrated to apply error diffusion methods, dithering methods, etc.

[0083] Figure 9 This diagram illustrates the record parameters for the cluster columns (region columns) of row Y. Specifically, it shows the configuration method of large / small clusters X0 to X4 in row Y0. Furthermore, this also continues after X5, with the ratio described above being large cluster: small cluster = 61:39.

[0084] In S005, the CPU 301 also determines the MN within the cluster and the point configuration (drop address (DA)) in the X direction within the cluster. That is, in S004, even which output quantity Gr records which point in which cluster X, while in S005, the remaining recording parameters are determined. DA is the address that can be recorded in the X direction, i.e., the main scan direction, and can be calculated based on the highest output frequency of the recording head [kHz], the relative movement speed of the recording head and the recording medium (substrate), the cluster width (X direction), the recording dot diameter, etc. Here, in each cluster, each MN can record a maximum of 4 points, DA0 to 3.

[0085] Figure 10 This is an illustrative diagram showing recording performed by multiple nozzles. Furthermore, in Figure 10 In the diagram, the physical configuration is shown horizontally (X-direction). However, it's important to note that the MN numbers used vertically do not necessarily represent the physical configuration. For example, regarding X0·Y0, since it's a small cluster, 12 records are needed, recorded using only 5 nozzles (MN5-9) with a high output (Gr). Similarly, regarding X1·Y0, since it's a large cluster, 13 records are needed, recorded using only 5 nozzles (MN0-4) with a low output (Gr). Furthermore, since it's MN5 nozzles × DA4 points, a maximum of 20 records can be made. That is, 12 records can be selected from the maximum 20 recordsable addresses. Here, the selection method is determined by random numbers. In addition, to ensure the nozzle usage is as even as possible, the nozzles used can be rotated, and various other methods can be used to determine the configuration.

[0086] In S006, CPU 301 determines whether processing for all Y rows is complete. If complete, the process ends. Figure 5 In the case of incomplete Y-rows, the incomplete Y-rows are set (e.g., Y-rows are incremented), and the process returns to S003.

[0087] Through the above processing, the average value of the Y row is completely consistent with the target injection volume. Then, the CPU 301 and the binarization circuit 308 convert the image data transformed by the image processing unit 309 into binarized data that can be used in the ejection of the recording head. Then, the drive circuit 307 executes the ejection operation of ink droplets from the recording head 2 according to the binarized data obtained by the binarization circuit 308.

[0088] Summarizing the process in the first embodiment, the multiple MNs belonging to row Y are rearranged in ascending order of output volume, and the central value is used as a boundary to divide them into two groups (large output volume Gr and small output volume Gr). Small clusters (N shots) are assigned to the large output volume Gr, and large clusters (N+1 shots) are assigned to the small output volume Gr (i.e., one more shot). Furthermore, the cluster ratio (ratio of large to small clusters) is determined by making the average ink droplet volume of row Y the target ink droplet volume. Small clusters are recorded by the large output volume Gr, and large clusters are recorded by the small output volume Gr.

[0089] <Effect>

[0090] With the above structure, in the first embodiment, all three objectives (objectives 1 to 3) can be achieved simultaneously. This differs from the point-count correction structure of previous examples ( Figures 11-13 The effects of the first embodiment will be explained by comparison.

[0091] Figure 11 This is a detailed flowchart illustrating the determination of multiple nozzles and the number of points, as in the conventional embodiment. Specifically, it shows the process compared to the first embodiment (…). Figure 8 This corresponds to the processing in previous examples.

[0092] S004-1, 2, and 5 are the same as in the first embodiment, so their description is omitted. The processing of the conventional examples corresponding to S004-3 and 4 will be described as S004-3A and 4A.

[0093] In S004-3A, CPU 301 calculates the average output of MN from row Y. That is, it calculates... Figure 7 (a) shows the average output of the 10 MNs. Specifically, the average output of MN0 to MN9 is calculated as 2.91 [pL] to 3.13 [pL]. Here, the average output is 3.01 [pL]. That is, in the first embodiment (S004), instead of calculating individual averages by dividing the output into large output Gr and small output Gr, in the conventional example, the average output of all MNs is calculated.

[0094] In S004-4A, the CPU 301 calculates the ratio of large clusters to small clusters. For example, the calculation uses mathematical formula (2).

[0095] TargetInkVolume=Vd_Average×N×ratio+Vd_Average×(N+1)×(1-ratio)···(2)

[0096] TargetInkVolume on the left-hand side of mathematical formula (2) is the target ink volume, which is 37.5 [pL]. Vd_Average in the first term on the right-hand side is the average ejection volume, which is 3.02 [pL] herein. N is the number of dots recorded in each X-cluster, which is set as 12 shots herein (hereinafter, a cluster of N shots is referred to as a small cluster). ratio is the proportion of small clusters in row Y0, and can range as 0<ratio<1. In the second term on the right-hand side, N is 12 shots, so N+1 is 13 shots (hereinafter, a cluster of N+1 shots is referred to as a large cluster). 1-ratio is the proportion of large clusters recorded in this Y row. ratio can range as 0<ratio<1. Herein, only ratio is an unknown, and when solving this linear equation, ratio=0.58 is obtained.

[0097] That is, when there are 500 clusters X in row Y0, it means that 10 multi-nozzles record 12 shots (large clusters) in 290 clusters, accounting for 58% of the total, and similarly, 10 multi-nozzles record 210 clusters (small clusters), accounting for 42% of the total. Thereby, the average ink droplet volume within clusters in row Y0 can reach the target value of 37.5 [pL].

[0098] Figure 12 This is a diagram illustrating recording parameters for a cluster row for Y rows in a conventional example. Compared with the first embodiment ( Figure 9 ), it can be seen that the difference in ink droplet volume between adjacent clusters is approximately 3 [pL].

[0099] Figure 13 This diagram exemplarily shows conventional recording by multi-nozzles. In addition, same as Figure 10 , the physical configuration is shown in the horizontal direction (X direction). On the other hand, it should be noted that the vertical direction is represented by MN numbers, which does not necessarily represent the physical configuration. Only five clusters X0 to X4 are shown by extraction, but different from the first embodiment ( Figure 10 ), it can be seen that in each cluster, all 10 MNs are used substantially equally.

[0100] Figure 14This diagram illustrates a comparison between the first embodiment and a conventional example. Specifically, it shows the results obtained by simulating the amount of ink droplets in 500 clumps in the X direction and 500 clumps in the Y direction. The output amount of the recording head was calculated as a normal distribution with an average output amount (center value) of 3 [pL] and a standard deviation of 3%. Furthermore, the target ink droplet amount for each clump was 37.5 [pL].

[0101] Figure 14 (a) illustratively shows the result obtained by the method of the first embodiment. Figure 14 (b) illustratively shows the results obtained by the method of the previous examples. Additionally, Figure 14 (c) is a diagram depicting the ink droplet distribution in row Y150 for both the method of the first embodiment (solid line) and the method of the conventional example (dashed line). (Refer to...) Figure 14 From (c), it can be seen that the average value becomes 37.5 [pL] of the target ink droplet amount in both methods, and the dot count correction is effective. On the other hand, it can be seen that the difference between the ink droplet amount of each agglomerate and the target ink droplet amount is clearly small in the first embodiment. That is, Figure 14 (a) compared to Figure 14 (b) has less deviation, in Figure 14 In (c), the amplitude of the solid line is smaller than that of the dashed line.

[0102] As explained above, according to the first embodiment, in recording performed by multiple nozzles, each nozzle of the recording head is classified into high-output Gr and low-output Gr. Based on this, high-output Gr is assigned to small clumps with N points, and low-output Gr is assigned to large clumps with N+1 points. With this structure, the above three objectives (objectives 1 to 3) can be achieved simultaneously.

[0103] (Second Implementation)

[0104] In the second embodiment, the following method is described: instead of simply dividing the output amount into two parts using the center value, the method involves dividing the output amount into a large output Gr and a small output Gr, for example, based on a random number, calculating the difference in ink amount between the large and small clumps, and repeating the experiment to reduce this difference. In the second embodiment, only the processing of S004-3 in the first embodiment is different, while everything else is the same. Hereinafter, to avoid repetition, only the differences from the first embodiment will be described.

[0105] <Topic>

[0106] In the first embodiment, as a method for dividing the large and small discharge volumes Gr, a simple 2-division is performed using the median value of the discharge volume, assigning the upper half as the large discharge volume Gr and the lower half as the small discharge volume Gr. However, when the variance of the discharge volume of the multiple nozzles allocated to the Y-row is large (i.e., the discharge volume deviation is large), the difference between the "average value of the large discharge volume Gr" and the "average value of the small discharge volume Gr" gradually increases. That is, as the variance of the discharge volume within the multiple nozzles allocated to the Y-row increases, large clumps become smaller than small clumps, and the difference gradually widens. Therefore, reducing the difference between large and small clumps is important, but when the variance of the discharge volume within the multiple nozzles is large, the method of 2-dividing using the median value of the discharge volume sometimes becomes insufficient.

[0107] <The action of the device>

[0108] Therefore, in the second embodiment, the processing method for the multi-nozzle segmentation (S004-3) in the first embodiment is changed. Hereinafter, the multi-nozzle segmentation processing in the second embodiment will be described as S004-3B. Figure 15 This is a detailed flowchart of the multi-nozzle segmentation (S004-3B) in the second embodiment.

[0109] In S004-3B-1, CPU 301 generates random number permutations. For example, the number (ratio) of 0 and 1 is 5 each, and the order of 0 and 1 is randomized.

[0110] In S004-3B-2, CPU 301 generates random numbers corresponding to multiple nozzles. Specifically, in the corresponding method, when the number of multiple nozzles in the Y row is 10, the values ​​of the arrangement MN

[10] = {0, 0, 1, 1, 0, 1, 0, 1, 1, 0} are assigned to the small output Gr if the value is 0, and to the large output Gr if the value is 1. For example, the small output Gr is due to MN[0] = 0, and the large output Gr is due to MN1 = 1.

[0111] In S004-3B-3, CPU 301 calculates the average output Vd_UpperGr of the large output Gr and the average output Vd_LowerGr of the small output Gr. In S004-3B-4, CPU 301 calculates the ink volume of large and small clumps. In S004-3B-5, CPU 301 calculates the difference in ink volume within large and small clumps. Specifically, the difference in ink volume is set as ΔInkVolume using mathematical formula (3), with the number of points in the large clump set to N+1 points and the number of points in the small clump set to N points.

[0112] ΔInkVolume=Vd_UpperGr×N-Vd_LowerGr×(N+1)···(3)

[0113] In S004-3B-6, CPU 301 calculates the ratio of large clumps to small clumps. Similar to the first embodiment, the ratio of large clumps to small clumps can be calculated using mathematical formula (1).

[0114] In S004-3B-7, CPU 301 uses two evaluation criteria to evaluate the grouping of large and small ink output clumps (Gr and Gr). The first evaluation criterion is that the difference in ink volume ΔInkVolume between large and small clumps is small (preferably the smallest). The smaller ΔInkVolume is (but it needs to be above 0), the smaller the difference in ink volume with adjacent clumps becomes, and the lower the visual recognizability, so it is preferred. The second evaluation criterion is that the ratio falls within a certain range (target ratio). For example, when the ratio = 0.1, it is not desirable to use a ratio that is extremely biased towards a certain group, such as the ratio of large output Gr: small output Gr = 1:9 in the Y row.

[0115] The rationale is that when a recording nozzle with a high ejection rate (Gr) occasionally stops ejecting, the impact of this non-ejection texture becomes significant, and the balance of recording nozzle durability deteriorates when the usage ratio of recording nozzles is uneven. Therefore, the ratio of the number of clumps used needs to be limited to some extent. Here, the target is to enter a range of 1:2 to 2:1 between high ejection rate (Gr): low ejection rate (Gr). Specifically, when converted to raito, the target value becomes 0.33. <ratio<0.66。

[0116] Based on satisfying the second evaluation criterion ratio, the smaller the first evaluation criterion ΔInkVolume, the better. If neither the first nor the second condition is satisfied, return to S004-3B-1 and start again after generating other random numbers. If both conditions are satisfied, proceed to S004-3B-8. In S004-3B-8, CPU 301 temporarily saves the optimal segmentation method.

[0117] In S004-3B-9, CPU 301 determines whether to terminate the specified number of iterations. For example, if 10,000 iterations are specified, the optimal partitioning method can be calculated within the specified computation time.

[0118] <Effect>

[0119] Figure 16 This is a graph illustrating the recorded parameters for each of the multiple nozzles. Specifically, Figure 16(a) shows the result obtained by group segmentation through the first embodiment. Figure 16 (b) shows the result obtained through group segmentation using the second embodiment. Figure 16 (a) and Figure 16 In (b), the ejection volume is the same in each of the multiple nozzles (MN0-9). As shown in the figure, the ejection volume deviation in MN0-9 is relatively large, ranging from 2.34 to 3.50 [pL]. Therefore, as... Figure 16 As shown in (a), when the central value is simply used as the boundary for 2-division, the ink droplet volume of the large agglomerate is 35.0 [pL] and the ink droplet volume of the small agglomerate is 39.89 [pL], and the size relationship is reversed.

[0120] On the other hand, Figure 16 In (b), the ink droplet size Gr is divided by multiple iterations based on random numbers. Therefore, the ink droplet size of the large clump is 37.93 [pL], and the ink droplet size of the small clump is 37.18 [pL], with the difference converging to 0.76 [pL]. Furthermore, the ratio of the proportions of the large and small clumps in the X direction becomes 0.57:0.43, a good ratio close to 1:1.

[0121] As explained above, according to the second embodiment, group segmentation is performed based on random numbers. Therefore, even when the output deviation is relatively large, it is possible to simultaneously achieve the three objectives (objectives 1 to 3) shown in the first embodiment.

[0122] (Third Implementation)

[0123] In the third embodiment, other methods of processing S004-2, S004-3B-4, and S004-3B-5 in the first and second embodiments will be described. All other processes are the same, so to avoid repetition, only the differences from the first and second embodiments will be described below.

[0124] <Topic>

[0125] In the first and second embodiments described above, it is assumed that a natural ejection volume deviation (variance) exists in the multi-nozzle system. Therefore, the smaller the ejection volume deviation (variance) of the multi-nozzle system, the smaller the difference in ink droplet volume with adjacent clumps becomes, and the effect of reducing high spatial frequency non-uniformity is reduced. Although it is not likely to occur in reality, when the ejection volume deviation (variance) of the multi-nozzle system is 0, the difference in ink droplet volume with adjacent clumps results in the same outcome as in the conventional examples. That is, high spatial frequency non-uniformity is generated.

[0126] <The action of the device>

[0127] First, let's explain S004-2, which is the first change point in the third embodiment. In the first and second embodiments described above, the target injection volume was set to 37.5 [pL]. 37.5 [pL] cannot be achieved as an integer multiple of the average ejection volume of the recording head, which is 3 [pL]. Therefore, 12.5 shots are virtually achieved by using approximately equal amounts of 12 shots × 3 [pL] = 36 [pL] and 13 shots × 3 [pL] = 39 [pL] in the X direction. Generally, the average number of injection shots per Y row is (2N+1) / 2 shots.

[0128] In the third embodiment, the target ink volume is made to be an integer multiple of the average ejection volume of the recording head, i.e., N times. For example, if N = 13, the target ink volume becomes 39 [pL]. As a result, recording can be performed at an integer multiple of the average ejection volume of the recording head, thus having the advantage that even when the ejection volume deviation (variance) of multiple nozzles is small, the difference in ink droplet volume with adjacent clumps is also reduced.

[0129] Next, we will use mathematical formula (4) to explain S004-3B-4 as the second change point. The difference between mathematical formula (4) and mathematical formula (1) is that the N+1 points in the second term on the right are changed to N points (i.e., the number of times they are spit out is equal). In addition, the second change point is accompanied by the first change point, and it is not the second change point that has an effect on its own.

[0130] TargetInkVolume=Vd_UpperGr×N×ratio+Vd_LowerGr×N×(1-ratio)…(4)

[0131] Finally, let's use mathematical formula (5) to explain S004-3B-5 as the third change point. The difference between mathematical formula (5) and mathematical formula (3) is that the N+1 points in the second term on the right are changed to N points. In addition, the third change point is associated with the first change point, and does not have an effect on its own.

[0132] ΔInkVolume=Vd_UpperGr×N-Vd_LowerGr×N…(5)

[0133] As explained above, according to the third embodiment, the target ink quantity is achieved using N pulses without requiring dot count correction. Therefore, even with small deviations in the ejection volume, the difference in ink droplet quantity between adjacent clumps can be reduced.

[0134] (Modified Example)

[0135] In the above embodiment, it is described that the output amount Gr is divided into 2 parts, but the same effect is obtained by dividing it into 3 parts, 4 parts, ..., N parts.

[0136] (Other embodiments)

[0137] This invention can also be implemented by supplying a program that performs one or more functions of the above embodiments to a system or device via a network or storage medium, and having the program read and executed by one or more processors in the computer of the system or device. Alternatively, it can also be implemented by a circuit (e.g., an ASIC) that performs one or more functions.

[0138] Other embodiments

[0139] The embodiments of the present invention can also be implemented by providing software (programs) that perform the functions of the above embodiments to a system or device via a network or various storage media, and the computer or central processing unit (CPU) or microprocessor unit (MPU) of the system or device reads out and executes the program.

[0140] The invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the claims are appended to disclose the scope of the invention.

Claims

1. An inkjet recording apparatus for substantially uniformly coating ink onto a recording medium having multiple regions arranged in a matrix, characterized in that, have: The recording head has M nozzles, each configured to dispense ink. The acquisition unit acquires dispensing quantity information related to the dispensing quantity of ink ejected per unit number of times from each of the M nozzles; as well as The control unit simultaneously scans the recording head relative to the recording medium and controls the ink ejection from the M nozzles to coat the multiple areas with ink. The control unit has: The classification unit, based on the ejection volume information, classifies the N nozzles allocated to the records for a column of regions arranged in the scanning direction into a first group and a second group that exclusively eject from each region contained in the column of regions. <M; as well as The decision unit determines, based on the discharge volume information, the proportion of the number of regions in the region column that are discharged by nozzles belonging to each of the first and second groups.

2. The inkjet recording device according to claim 1, characterized in that, The classification unit, based on the discharge volume information, uses the median value of the discharge volume of the N nozzles as a boundary to classify the N nozzles into a first group with relatively small discharge volumes and a second group with relatively large discharge volumes.

3. The inkjet recording device according to claim 2, characterized in that, The amount of ink in the first region recorded by nozzles belonging to the first group is less than the amount of ink in the second region recorded by nozzles belonging to the second group.

4. The inkjet recording device according to claim 3, characterized in that, The first number of times ink is ejected from the first region by nozzles belonging to the first group is greater than the second number of times ink is ejected from the second region by nozzles belonging to the second group.

5. The inkjet recording apparatus according to claim 4, characterized in that, The first number of times is one more than the second number of times.

6. The inkjet recording apparatus according to claim 1, characterized in that, The classification unit calculates, among a plurality of randomly set combinations of the first group and the second group, combinations where the ratio satisfies a predetermined target ratio and the difference between the first ink amount recorded by nozzles belonging to the first group and the second ink amount recorded by nozzles belonging to the second group in the first region is relatively small, and classifies the N nozzles in the calculated combinations into the first group with a relatively small average output and the second group with a relatively large average output.

7. The inkjet recording apparatus according to claim 6, characterized in that, The classification unit calculates the combination in which the ratio satisfies a predetermined target ratio and the difference between the first ink amount recorded by the nozzles belonging to the first group of nozzles and the second ink amount recorded by the nozzles belonging to the second group of nozzles is minimized.

8. The inkjet recording apparatus according to claim 1, characterized in that, further comprising a setting unit configured to set a target ink amount for each region included in the region column so that the target ink amount is an integer multiple of an average discharge amount of the M nozzles, wherein the classification unit classifies the N nozzles into the first group having a relatively small average discharge amount and the second group having a relatively large average discharge amount, a first number of ink discharges performed for a first region recorded by nozzles belonging to the first group is equal to a second number of ink discharges performed for a second region recorded by nozzles belonging to the second group.

9. A control method for an inkjet recording apparatus, which applies ink substantially uniformly to a recording medium having a plurality of regions arranged in a matrix formed thereon, characterized in that, the inkjet recording apparatus includes a recording head having M nozzles each configured to be capable of discharging ink, the control method comprises: an acquiring step of acquiring discharge amount information related to a discharge amount of ink discharged per unit number of times from each of the M nozzles; and a controlling step of controlling ink discharge from the M nozzles while causing the recording head to relatively scan the recording medium, to apply ink to the plurality of regions, the controlling step comprises: a classifying step of, based on the discharge amount information, classifying N nozzles allocated for recording a region column including a plurality of regions arranged in the scanning direction into a first group and a second group that exclusively perform discharge for each region included in the region column, wherein N<M; and a determining step of determining, based on the discharge amount information, a ratio of the number of regions in the region column for which discharge is performed by nozzles belonging to each of the first group and the second group.

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