JP6284858B2 - inkjet printer - Google Patents

Description

  The present invention relates to an inkjet printer.

  2. Related Art Ink jet printers that record images by ejecting ink onto recording media such as recording paper and resin films are widely known. In an inkjet printer, an image is recorded by ejecting ink while moving a recording head having a plurality of nozzles arranged along the conveyance direction of the recording medium in a direction perpendicular to the conveyance direction of the recording medium. There is something to do.

  Some recording heads of this type can record dots of different sizes on a recording medium by changing the amount of ink forming the dots. By reducing the dots, the recorded image can be improved in image quality. Also, printing can be performed at high speed by increasing the dots. In addition, printing speed may be required, and an ordinary inkjet printer is provided with a plurality of printing modes according to speed and image quality.

  However, even if the same amount of ink is ejected depending on the type of recording medium, the diameter of the recorded dots may differ, and when solid printing is performed in which pixels are filled with ink, the density depends on the degree of ink filling. Image quality defects such as unevenness and white streaks may occur. For example, in the technique described in Japanese Patent Application Laid-Open No. 10-244692, the ink ejection amount is corrected so that the recorded dot size is the same even if the paper to be used is different. In addition, a technique is disclosed in which a solid printing portion is detected, dots inside the contour portion are replaced with small-diameter dots, and printing is performed by reducing the amount of ink in the solid portion.

Japanese Patent Laid-Open No. 10-244992

  In the conventional technique, the relationship between the diameter of the ink particles ejected from the nozzle for each sheet and the diameter of the dots after the ink particles have adhered to the sheet is measured, and the relationship is stored. When a paper to be used is input, ink particles having a diameter corresponding to the paper are ejected from the nozzle.

  However, the conventional technology cannot be used for unknown paper and printing modes because the relationship between ink particles and dot diameter is unknown. In addition, it is quite difficult for the user to accurately measure the dot diameter, and there is a problem that new paper cannot be set. In addition, since dots of the same color are printed with one dot per pixel, there is a problem that finer correction cannot be performed.

An ink jet printer according to the present invention includes a plurality of nozzles, a recording head that discharges ink from the nozzles to a recording medium, a transport unit that transports the recording medium, and a transport unit that transports the recording medium by mounting the recording head. A carriage that reciprocates in a direction that intersects the direction, a platen that is disposed opposite to the lower surface of the carriage and holds the recording medium, and the ink from the recording head based on image data and a print mask. A control unit for controlling ejection; and a mask memory for storing a print mask; acquiring the print mask from the mask memory; ejecting the ink from the recording head; and recording an image on the recording medium In an inkjet printer, one of a plurality of printing modes corresponding to the image quality recorded on the recording medium is selected. Input means for inputting to select one of a plurality of types of input and the recording medium for selecting, is mounted on the carriage, and the concentration detecting means for detecting a density of the image recorded on the recording medium In the mask memory, the type of the recording medium and the print mask corresponding to the printing mode are stored in association with each other, and the type of the recording medium and the printing mode to be used are input from the input unit. Is input from the mask memory corresponding to the type of the input recording medium and the printing mode, and the recording medium is acquired based on the acquired print mask. to record the image, when using a new said recording medium type that is not stored in the mask memory, for each of the printing modes, the A test pattern including a plurality of gradation patches on a recording medium is recorded for each print mask stored in the mask memory, and the gradation recorded on the recording medium for each print mask by the density detection unit The density for each patch is detected, it is determined whether or not the detected density reaches a predetermined density, and the print mask having a predetermined high priority is extracted from the print masks that have reached the predetermined density. For each print mode, the extracted print mask is stored in the mask memory in association with the new recording medium and the print mode .

  According to the ink jet printer of the present invention, it is possible to perform solid printing suitable for an unknown paper and a printing mode, and it is possible to obtain a printed matter having a suitable image quality.

FIG. 1 is a diagram illustrating the configuration of an inkjet printer. FIG. 2 is a diagram illustrating a recording method of the ink jet printer. FIG. 3 is a diagram illustrating recorded dots. FIG. 4 is a diagram for explaining the test pattern. FIG. 5 is a diagram for explaining test pattern measurement results. FIG. 6 is a diagram for explaining the relationship between the test pattern and the density. FIG. 7 is a diagram illustrating the relationship between the print mask and the print mode. FIG. 8 is a block diagram of the ink jet printer. FIG. 9 is a flowchart for explaining a test operation of the ink jet printer. FIG. 10 is a flowchart illustrating the recording operation of the ink jet printer. FIG. 11 is an external view of an ink jet printer. FIG. 12 is a diagram for explaining the color measurement result of the test pattern. FIG. 13 is a flowchart for explaining a second test operation of the ink jet printer.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating the configuration of an inkjet printer. The housing 2 constitutes the exterior of the inkjet printer 1. The recording head 5 is an ink jet head that ejects ink. The recording head 5 is mounted on the carriage 4 and reciprocates over the recording medium 13 supported by the platen 6. Four recording heads 5 corresponding to inks of four colors of black, cyan, magenta, and yellow are mounted on the carriage 4. Five or more colors may be used. The recording medium 13 is intermittently conveyed while being attracted to the flat platen 6. An image is recorded by ejecting ink from the recording head 5 onto the recording medium 13 supported by the platen 6. A desired image is completed by repeating conveyance and recording while scanning.

  The carriage 4 is guided by the rail 3 which is a linear rail, and reciprocates in a direction intersecting the conveyance direction of the recording medium 13. In this example, the intersecting direction is a perpendicular direction. The carriage 4 is fixed to the belt 7. The belt 7 is wound around a pair of pulleys 9. A motor 8 is connected to one pulley 9 and reciprocatingly scans along the rail 3 by driving. The position of the carriage 4 can be detected by an encoder 11 mounted on the carriage 4 with a linear scale 10 arranged along the moving direction of the carriage 4. A density sensor 14 is mounted on the carriage 4. The density sensor 14 detects the density of the image recorded on the recording medium 13. Since the density sensor 14 is mounted on the carriage 4, the density can be detected at an arbitrary position in the main scanning direction of the recording medium 13. Further, since the recording medium 13 can be conveyed in the forward and reverse directions, the density can be detected at an arbitrary position in the sub-scanning direction.

  A colorimetric sensor 18 is mounted on the carriage 4. The colorimetric sensor 18 detects the color difference of the image recorded on the recording medium 13. Since the colorimetric sensor 18 is mounted on the carriage 4, color difference detection can be performed at an arbitrary position in the main scanning direction of the recording medium 13. Further, since the recording medium 13 can be conveyed in the forward and reverse directions, it is possible to detect a color difference at an arbitrary position in the sub-scanning direction.

  The platen 6 is provided with a plurality of suction holes and communicates with a duct at the bottom of the platen 6. The duct is connected to a fan, and air is sucked from the suction hole by the fan to lower the pressure of the duct portion. Therefore, the recording medium 13 sticks to the platen 6.

  A front paper guide and a rear paper guide are arranged before and after the platen 6. The recording medium 13 is guided and conveyed in the order of the rear paper guide, the platen 6, and the front paper guide. Between the rear paper guide and the platen 6, a plurality of transport rollers 12 are arranged along the platen 6 at regular intervals. The conveyance roller 12 is composed of a pair of rollers of a driving roller and a pinch roller pressed against the driving roller. The recording medium 13 is sandwiched between two pairs of rollers, and the recording medium 13 is conveyed by the rotation of the driving roller.

  FIG. 2 is a diagram illustrating a recording method of the ink jet printer. An example of printing with multiple passes is shown. In the figure, the number of nozzles is also reduced in order to explain the concept of the recording method. Also, 2 nozzles are used per block. Originally, a multi-nozzle recording head having 512 nozzles is used. In this example, the transport amount is 2.5 nozzles and 1.5 nozzles, that is, the distance between the nozzles at the ends of the block plus half the distance between the nozzles is alternately transported. This is an example, and a method of increasing the resolution in the transport direction is shown. However, the present invention is not limited to this, and a method in which intermittent transport is performed by alternately setting a distance obtained by adding or subtracting the half of the distance between the nozzles to the distance between the nozzles at the ends of the block can be used as the transport distance. Moreover, you may convey so that 2 dots or more, such as 2 dots, 3 dots, etc. can be formed between nozzles. By recording the same line in the main scanning direction of the recording medium 13 by a plurality of passes by different nozzles, it is possible to prevent image quality defects due to the characteristics unique to the nozzles. For example, when one line is completed by n nozzles, one nozzle has a 1 / n influence on the line.

  The recording head 5 is divided into eight blocks, using the same number of nozzles 28 as one block. In other words, the block is divided into eight blocks of a first block 20, a second block 21, a third block 22, a fourth block 23, a fifth block 24, a sixth block 25, a seventh block 26, and an eighth block 27. The recording medium 13 is conveyed based on the length of the block and half the distance between the nozzles. In the example, the inter-nozzle distance is 1/180 inch. dpi indicates that printing with a resolution of 180 dots per inch can be performed. The first ejection position 29 is indicated by a dotted quadrilateral for four dots when the dot resolution on the recording medium 13 is 360 dpi. That is, the first dot area 30, the second dot area 31, the third dot area 32, and the fourth dot area 33 represent one pixel with a resolution of 360 dpi. A todd corresponding to the amount of ink for four small dots is formed in one pixel.

  In the first pass, ink is ejected to the first dot area 30 and the third dot area 32 at the first ejection position 29 by the nozzles of the first block 20. The recorded dots are represented by numbers surrounded by circles, and the numbers indicate the number of passes when recorded. In this example, the image is completed in 8 passes. In the second pass, ink is ejected to the second dot area 31 and the fourth dot area 33 at the second ejection position 34 by the nozzles of the second block 21 to record dots. In the third pass, ink is ejected to the first dot area 30 and the third dot area 32 at the third ejection position 35 by the nozzles of the third block 22 to record dots. In the fourth pass, ink is ejected to the second dot area 31 and the fourth dot area 33 at the fourth ejection position 36 by the nozzles of the fourth block 23 to record dots. In the fifth pass, ink is ejected to the first dot area 30 and the third dot area 32 at the fifth ejection position 37 by the nozzles of the fifth block 24 to record dots. In the sixth pass, ink is ejected to the second dot area 31 and the fourth dot area 33 at the sixth ejection position 38 by the nozzles of the sixth block 25 to record dots. In the seventh pass, ink is ejected to the first dot area 30 and the third dot area 32 at the seventh ejection position 39 by the nozzles of the seventh block 26 to record dots. In the eighth pass, ink is ejected to the second dot area 31 and the fourth dot area 33 at the eighth ejection position 40 by the nozzles of the eighth block 27 to record dots.

In addition, the image quality to be recorded can be changed by applying a print mask in each pass and performing control so as to change the amount of ink for forming dots.
Dots are recorded by 8 passes, and are recorded at a resolution of 360 dpi, which is half the distance between nozzles. Recording can be performed with an image resolution of 720 dpi by controlling the conveyance of the recording medium 13 using a conveyance distance that is ¼ of the distance between nozzles.

  Next, the dots recorded on the recording medium 13 will be described. FIG. 3 is a diagram illustrating recorded dots. FIG. 3A is a diagram illustrating a first example of recorded dots. FIG. 3B is a diagram for explaining a second example of dots to be recorded. FIG. 3C is a diagram illustrating a third example of dots to be recorded. FIG. 3D illustrates a fourth example of dots to be recorded. The numbers enclosed in circles in the figure represent dots, and the size of the circles represents the size of the dots. The numbers indicate the number of passes when printed. A square surrounding the dot indicates a pixel. Four pixels having an image resolution equivalent to 360 dpi become pixels equivalent to 180 dpi.

  In FIG. 3A, one pixel is formed by 4 dots per pixel of an image resolution equivalent to 360 dpi for small dots formed with a small discharge amount in each of the first to eighth passes. In FIG. 3B, one pixel is formed with 2 dots per pixel of image resolution equivalent to 360 dpi for medium dots formed with a medium discharge amount in each of the first to eighth passes. . In FIG. 3C, the first, second, fifth and sixth passes are printed with large dots formed with a large discharge amount, and the third, fourth, seventh and eighth passes are printed with small dots formed with a small discharge amount, and 360 dpi. One pixel is formed of 2 dots in total, one large dot and one small dot per pixel of a pixel having a considerable image resolution. In FIG. 3D, the first, second, third, and fourth passes are printed with medium dots formed with a medium discharge amount, and the fifth, sixth, seventh, and eighth passes are printed with small dots formed with a small discharge amount. One pixel is formed by a total of three dots, one medium dot and two small dots per pixel of pixels having an image resolution equivalent to 360 dpi. At this time, when ejecting small dots, the dots are continuously ejected to adjacent pixels in the main scanning direction. A medium dot is formed with an ink amount corresponding to two small dots, and a large dot is formed with an ink amount corresponding to three small dots.

  For example, there are four types of methods as described above for forming dots by ejecting an amount of ink of 4 dots in small dots per pixel. Such an ejection method can be classified according to image data and a print mask applied to each nozzle of the recording head 5. A pass for ejecting ink from the nozzle and a non-ejection pass are controlled by the print mask.

  If the type of recording medium to be printed is different, the behavior of ink droplets after landing is also different, so the dot sizes are not the same. Even with the same number of drops, a print mask that drops small droplets many times has a higher solid filling performance than a mask that drops large droplets a few times. However, on the other hand, a mask that drops large droplets with a small number of times is more tolerant of the conveyance accuracy of the recording medium. Smaller dots increase the possibility of poor image quality unless the feed accuracy is increased. This conflicting characteristic requires an optimization act that balances across various types of recording media. On the other hand, there is a method using a print mask that is the greatest common divisor, but in the case of a recording medium that does not match this, solid filling may be incomplete and blurring or white stripes may occur.

  Next, test pattern printing performed for each different print mask will be described. FIG. 4 is a diagram for explaining the test pattern. FIG. 5 is a diagram for explaining test pattern measurement results. As described above, there are four types of printing methods, which are controlled by different print masks. For each different print mask, the gradation density which is the density of each gradation patch, that is, the printing density is increased from 10% by 10%, and solid printing is performed to 100%. The gradation density may be referred to as printing density. In this way, by using a test pattern including a gradation patch having a predetermined printing density, it is possible to evaluate the filling degree of solid printing for each print mask. The test pattern for each printing density is also called a gradation patch.

  The test patterns written as mask 1, mask 2, mask 3, and mask 4 in FIG. 4 are as shown in FIGS. 3 (a), 3 (b), 3 (c), and 3 (d), respectively. Represents a print mask of a different printing method. After printing this test pattern, the density of the pattern for each print density recorded with the mask 1, mask 2, mask 3, and mask 4 is measured, and the result is shown in FIG. The measurement results of the mask 1, the mask 2, the mask 3, and the mask 4 correspond to the measurement density graph 41, the measurement density graph 42, the measurement density graph 43, and the measurement density graph 44, respectively. It can be seen that the larger the number of small dots, the better the solid filling.

  In the case where the density in the graph is saturated, it is considered that the solid is filled when printing is performed at a printing density that has started to saturate. For example, this is the case where the print density of the measured density graph 41 is 90% or more. That is, solid printing can be performed by recording with the mask 1 at a printing density of 90% or more. If it is 90% or more, the measured density is the same even at 100%, for example, and ink is wasted.

  Further, the density indicated by the one-dot chain line in FIG. 5 is a predetermined density threshold. There is also a method in which the solid is filled when this concentration is exceeded. In this case, the print density of the measured density graph 41 is 75% or more and the print density of the measured density graph 42 is 90% or more. This means that there is also a method for judging that the concentration is subjectively filled even if the concentration is not saturated. In the example of FIG. 5, there are two cases depending on how to determine whether or not the density is saturated: only the mask 1 is completely filled, and mask 1 and the mask 2 are completely filled.

  FIG. 6 is a diagram for explaining the relationship between the test pattern and the density. In the drawing, mask 1, mask 2, mask 3, and mask 4 represent print masks of the printing method as shown in FIGS. 3A, 3B, 3C, and 3D, respectively. . As for the characteristics of each print mask, the mask 1 has a large number of small droplets, and as it goes down, there are few small droplets and large droplets are added. For example, in the case of FIG. 6, in the case of the medium 1, the mask 1 indicates that the solid is filled at the time of solid printing, and the others are not filled. In the case of the medium 2, the mask 1, the mask 2, and the mask 3 indicate that the solid is filled and the others are not filled. Here, media 1 and media 2 indicate the types of recording media. The relationship between the type of recording medium and recording based on a pre-stored print mask is shown.

  As described above, depending on the type of the recording medium, there may be a mask in which the solid is filled and a mask in which the solid is not filled. Therefore, based on the measurement result of the test pattern, an optimal print mask is set for the type of recording medium to be used, so that suitable printing can be performed. At this time, when there are a plurality of masks filled with solids, the smaller the number of small droplets, the better the image quality in the feeding direction, so a mask with few small droplets is set. For example, in the case of FIG. 6, mask 2 is selected and set for media 1 and mask 3 is selected and set for media 2. In addition, by selecting and setting a print mask having the lowest print density at the time of saturation, it is possible to eliminate wasted ink.

  FIG. 7 is a diagram illustrating the relationship between the print mask and the print mode. The print mode differs in the resolution of the image to be recorded, the printing speed, and the like. Depending on the print mode, even if the same recording medium and the same print mask are used, some may be buried when solid printing is performed, and some may not be buried. Therefore, it is preferable to select and use an optimal print mask when these print modes are changed. The print mode includes a difference in distance from the recording medium 13 to the nozzle surface of the recording head 5. This is because the dot size and landing accuracy formed by this distance change and affect the image quality. FIG. 7 is an example showing the result of solid filling when recording is performed by changing the print mode based on a certain print mask using a certain recording medium.

  The example of FIG. 7 is an example of modes with different printing speeds. When the printing mode is the highest speed or high speed, any mask is not used for solid printing. The mask 2 is the optimum print mask in the case of standard, the mask 3 in the case of high image quality, and the mask 4 in the case of the highest image quality. When the print mode is the fastest or fastest, a test pattern is printed, and a print mask that can print at the highest density as a result of density measurement is used. In such a case, the deterioration of image quality is minimized by selecting a print mask that can be printed at the highest density.

  FIG. 8 is a block diagram of the ink jet printer. The control circuit 50 is a control circuit that controls the entire inkjet printer 1. The I / F 51 is an interface with an external device. For example, it connects to a host PC and inputs data such as image data. In addition, a command is transmitted from the host PC to the inkjet printer 1 to be operated. The recording means 55 is a means for recording an image on the recording medium 13, including the recording head 5 and a mechanism for reciprocally scanning the recording head 5 in the width direction of the recording medium 13, that is, the main scanning direction. The recording means 55 is controlled by the control circuit 50. The recording means 55 includes a mechanism for moving the carriage 4 up and down, and the distance between the recording medium 13 and the recording medium 13 to be used can be varied. This distance is controlled by the control circuit 50. The media transport unit 56 includes a transport roller 12 and is a mechanism that transports the recording medium 13. The media transport means 56 is controlled by the control circuit 50. The position detection means 57 includes a linear scale 10 and an encoder 11 and detects the positions of the carriage 4 and the recording head 5. The detection result is output to the control circuit 50, and the control circuit 50 calculates the positions of the carriage 4 and the recording head 5. The position detection means 57 is controlled by the control circuit 50. The density detection means 54 includes a density detection sensor 11 provided in the carriage 4, detects the density of the image recorded on the recording medium 13, and outputs it to the control circuit 50. The density detection means 54 is controlled by the control circuit 50. The color measurement means 59 includes a color measurement sensor 18 provided in the carriage 4, detects a color difference between images recorded on the recording medium 13, and outputs the color difference to the control circuit 50. The color measuring means 59 is controlled by the control circuit 50. The image processing unit 60 can acquire printer information via the I / F 51. Moreover, a suitable printing result can be obtained by performing processing suitable for printing on the image data.

  The ROM 52 is a non-volatile memory, and stores a program for controlling the ink jet printer 1, initial setting values, and the like. In addition, a print mask corresponding to the type of recording medium to be used and the type of printing mode can be stored in association with each other, searched by the control circuit 50, and a print mask corresponding to the type of recording medium can be obtained. The control circuit 50 operates according to this program. The RAM 53 is a memory used for work memory of the control circuit 50, temporary storage of data, and the like.

  The temperature detection means 58 is a temperature sensor that is disposed in the housing 2 and detects the temperature. The detection result is output to the control circuit 50. The temperature detected by the temperature detecting means 58 is used to measure the temperature when the test pattern is recorded and derive the relationship between the print mask, the print density, and the temperature. That is, the temperature is varied in a thermostatic bath, a test pattern is recorded at the varied temperature, and the concentration is detected. By doing so, an optimal mask for each temperature can be derived. The optimum print mask for each recording medium is stored in the ROM 52 for each temperature, the temperature at the time of actual printing is measured, and the optimum print mask for the recording medium to be used at that temperature is obtained and applied, Print the image. Although not shown, input means such as a touch panel is connected to the control circuit 50 and performs various inputs such as mode selection and recording medium selection. Various inputs may be performed from an external device via the I / F 51.

  FIG. 9 is a flowchart for explaining a test operation of the ink jet printer. The control circuit 50 operates according to the program and setting values stored in the ROM 52. First, the recording medium 13 to be newly used is set in the ink jet printer (step S1). At this time, test printing is executed, and a mode for acquiring an optimum print mask is selected.

Next, since it is necessary to record and measure the test pattern on the recording medium 13 for all usable printing modes, a printing mode that has not yet been recorded is set (step S2). The print mode is set according to a predetermined order.
Next, a test pattern is recorded for each print mask on the set recording medium (step S3). Available print masks are stored in the ROM 52 in advance.

  Next, the density measurement unit 54 measures the density of the test pattern printed on the recording medium. The medium conveying means 56 is controlled to rewind the recording medium, and the density of the pattern recorded by the density detection sensor 11 mounted on the carriage 4 is detected (step S4).

  Next, a test pattern is printed in the all print mode, and it is determined whether the density measurement has been completed. If all of the patterns have not been completed, the process proceeds to step S2, and if completed, the process proceeds to step S6 (step S5).

  Next, for each print mode, for each print mask, a density curve is calculated when the horizontal axis represents the print density to be darkened every 10% of the test pattern and the vertical axis represents the detected value (step S6). Although it is preferable to obtain an approximate curve by the least square method, any other method may be used as long as it is data that can be used to determine whether a solid is filled by solid printing. For example, a method such as whether it can be divided into two by using a threshold value or can be divided by inclination can be considered.

  Next, it is determined whether the detected concentration is saturated based on the obtained approximate curve. For example, a point at which the slope of the approximate curve is below a predetermined slope, for example, when the rate of change is 1% or less is calculated (step S7). Do this for each print mask. Here, instead of the saturation start point, a threshold value of a predetermined measured density value may be determined in advance, and it may be determined whether or not the value is equal to or greater than that value.

  Next, for each printing mode, it is determined whether or not the print mask is saturated, and among the saturated print masks, a print mask having an ejection method with less small droplet ejection is selected as the optimum print mask for the print mode and the recording medium. (Step S8). In other words, a high priority condition for selecting a predetermined print mask is selected. Then, for each print mode, the optimum print mask is stored in association with the recording medium (step S9). Here, also when the determination is made using the threshold value, it is preferable that a print mask of an ejection method with less ejection of small droplets be the optimum print mask. As another example, it is conceivable to select a print mask having a saturation point with the lowest print density.

FIG. 10 is a flowchart illustrating the recording operation of the ink jet printer.
When an image is recorded by the inkjet printer 1, a medium to be used, that is, a recording medium is set first. In step S13, the type of the set recording medium is input.

Next, the print mode is input (step S14).
Next, a print mask corresponding to the type of the input recording medium is acquired (step S15). Printing is performed using the acquired print mask (step S16). Further, in step S13, the temperature may be further detected, and an optimum print mask may be searched and acquired from the temperature and the recording medium, and recording may be performed using the print mask in consideration of the temperature in step S16.

  FIG. 11 is an external view of an ink jet printer. The ink jet printer 1 supports the housing 2 with legs 17. The legs 17 are fixed to both ends of the lower surface of the housing 2. Along the front paper guide 15, the recording medium 13 is ejected from the gap between the front paper guide 15 and the window portion 16 in the direction indicated by the arrow.

  FIG. 12 is a diagram for explaining the color measurement result of the test pattern. Changing the mask means changing the ejection method, and as a result of giving priority to solid filling, there is a possibility that the gradation expression is lost. Therefore, the colorimetric means 59 measures the color of the test pattern after the saturation of the print mask that has the lowest print density at the time of saturation. Further, the colorimetric means 59 measures the color of the test pattern after the time when the other print mask is saturated. FIG. 12 is a diagram showing the color difference detected by the colorimetric means 59. As the color measurement method, for example, the carriage 4 and the recording medium 13 are moved so that the color measurement unit 59 comes on the test pattern, and the color measurement unit 59 starts color measurement at a certain sampling period. In this state, the recording medium 13 can be relatively conveyed in the scanning direction and the sub-scanning direction, and the test pattern can be measured in multiple points. A color difference delta E is obtained from the colorimetric values of the reference color and the measured colorimetric values of the test pattern.

  At this time, the interval between the two dashed lines in FIG. 12 is set as a predetermined allowable color difference threshold, and it is determined whether or not the measured value is exceeded. In FIG. 12, it is determined whether or not delta E is in the range of 0.7 to 1.3. The range of ± 0.3 is an example, but this range is stored in advance as an allowable range for the reference color. The color measurement is performed in the order of the test pattern that is considered to be the optimal from the test pattern that is optimal in the density measurement result, and the color difference is within the threshold value. Further, after all colorimetry is performed, a test pattern having a color difference delta E closest to 1.0 may be selected.

  In FIG. 12, six points are measured, but the value at the left end is 1.0, which is the result of color measurement for the reference test pattern. The other five points are the test patterns corresponding to the gradation densities 80%, 90% and 100% of the measured density graph 41 and the tests corresponding to the gradation densities 90% and 100% of the measured density graph 42, respectively, from the left. It is the result of the color measurement in a pattern. Of the test patterns corresponding to the gradation densities 80%, 90% and 100% of the measured density graph 41, the measured value of 90% is 1.4, which is out of the range. Others are in range. Therefore, it can be seen that printing with the mask 1 is not suitable. It can be seen that the mask 2 can be suitably printed. A test pattern print mask in which all colorimetric values fall within the threshold range is set as the optimum print mask. In this way, the selection conditions are programmed in advance, and the selected print mask is stored in association with the type of the recording medium, and is recalled and used at the time of use. If there is no mask in which all measurement values fall within the threshold range, the measurement values outside the range may be selected in order from the print mask that is close to the range.

  FIG. 13 is a flowchart for explaining a second test operation of the ink jet printer. The control circuit 50 operates according to the program and setting values stored in the ROM 52. Steps S1 to S7 are the same as those in FIG.

  In step S20, for each print mode, the print masks are ranked in a predetermined order from among the saturated print masks, for example, in order from an ejection method with less ejection of small droplets. Next, the colorimetric means 59 performs colorimetry on the test pattern selected with the uppermost print mask.

  Next, it is determined whether or not the color difference delta E of the measured test pattern is within the threshold range (step S21). If it is within the threshold range, the print mask is associated with the recording medium and stored as the optimum print mask (step S22). ). If it is outside the threshold, the next-order print mask is selected and colorimetry is performed again (step S24). After storing the optimal print mask, the image processing means is notified of the selected print mask, and the image processing conditions are changed to those suitable for the print mask (step S23). For example, by making the variable dot curve suitable for the selected ejection method, not only the solid portion but also the gradation can be expressed smoothly. Further, if the saturation of solid filling starts from a value with a low gradation density, it may be changed to image data that does not eject excess ink. In addition, the image data in a range where the solid filling is saturated may be changed to image data in which the delta E has a gradation density closest to 1.0. By doing so, the color reproducibility is improved and the quality of the image recorded on the recording medium is improved.

  The present invention can be used in an ink jet printer. In particular, the present invention can be used for a large ink jet printer that records on a wide recording medium.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Case 3 Rail 4 Carriage 5 Recording head 6 Platen 7 Belt 8 Motor 9 Pulley 10 Linear scale 11 Encoder 12 Transport roller 13 Recording medium 14 Leg part 15 Front paper guide 16 Window part

Claims (7)

A recording head having a plurality of nozzles and discharging ink from the nozzles to a recording medium;
Conveying means for conveying the recording medium;
A carriage mounted with the recording head and reciprocating in a direction intersecting the recording medium conveyance direction;
A platen disposed opposite to the lower surface side of the carriage and holding the recording medium;
Control means for controlling ejection of the ink from the recording head based on image data and a print mask;
A mask memory for storing print masks;
In an inkjet printer that acquires the print mask from the mask memory, ejects the ink from the recording head, and records an image on the recording medium,
Mounted on the carriage, an input means for selecting one of a plurality of printing modes corresponding to the image quality recorded on the recording medium and an input for selecting one of a plurality of types of the recording medium And a density detecting means for detecting the density of the image recorded on the recording medium ,
In the mask memory, the type of the recording medium and the print mask corresponding to the print mode are stored in association with each other,
When the type of the recording medium to be used and the print mode are input from the input unit, the control unit displays the print mask corresponding to the input type of the recording medium and the print mode as the mask. Acquired from a memory, and recorded an image on the recording medium based on the acquired print mask ,
When a new recording medium of a type not stored in the mask memory is used, a test pattern including a plurality of gradation patches is stored in the mask memory for each printing mode. Recording is performed for each print mask, and the density detection unit detects the density for each gradation patch recorded on the recording medium for each print mask, and determines whether or not the detected density reaches a predetermined density. Then, the print mask having a predetermined high priority is extracted from the print masks that have reached the predetermined density, and the extracted print mask is added to the new recording medium and the print medium for each print mode. An ink jet printer characterized by being stored in the mask memory in association with a print mode . The recording head can form dots of a plurality of sizes according to the amount of ink ejected,
In order to record one pixel, the ink is ejected from the nozzles different for each of the passes by a plurality of passes,
The inkjet printer according to claim 1, wherein the print mask controls whether or not to eject from the nozzle for each pass and the amount of the ink when ejected. 3. The ink jet printer according to claim 1, wherein the priority order is an order in which the number of the dots having the smallest size among the plurality of sizes is used in ascending order. 3. The ink jet printer according to claim 1, wherein the priority is higher as the solid print density of the gradation patch is lower. 4. The predetermined density is a density of a saturated portion obtained by performing an operation of estimating a relational expression between a gradation of the gradation patch and the detected density, and obtained based on the relational expression. The inkjet printer according to any one of claims 1 to 4. The inkjet printer according to any one of claims 1 to 4, wherein the predetermined density is a predetermined density value. Color measurement means for detecting a color difference is further provided, the color difference of the gradation patch of the test pattern corresponding to the print mask having reached the predetermined density is detected, and the detection result is within a predetermined color difference range. Determining whether or not to enter, and selecting the print mask according to a predetermined order from the print masks corresponding to the test pattern that falls within the color difference range based on the determination result, and the selected The inkjet printer according to any one of claims 1 to 6, wherein a print mask is stored in the mask memory in association with the new recording medium.