JP6115016B2 - Printing apparatus, printed matter production method, and printing program - Google Patents

Description

  The present invention relates to printing.

  A line printer that is a printer having a line head is known. The line head is a print head in which ink ejection nozzles are arranged over the entire recording width. With this configuration, it is not necessary to scan the print head in a direction orthogonal to the conveyance direction of the print medium.

  Line printers enable high-speed printing, but the performance of line heads tends to be a problem. As a technique for coping with the case where the performance degradation of the line head occurs, those disclosed in Patent Documents 1 to 3 are known.

JP 2004-276387 A Japanese Patent No. 273003 JP 9-193372 A

  The problem of the prior art is that it is not possible to suppress the performance degradation of the line head. The performance degradation of the line head is caused by, for example, the performance degradation of the nozzle that ejects ink. The reduction in nozzle performance means, for example, that ink cannot be ejected appropriately temporarily. As the cause of this, for example, heat generated by ejecting ink frequently in a short time can be cited. When a nozzle with reduced performance is generated, for example, the performance of the line head is reduced in the form of a temporary decrease in printing speed and image quality.

Application Example 1: A printing apparatus that performs printing by forming dots on a print medium using a line head including a plurality of nozzles based on dot data indicating the presence or absence of dot formation for each pixel.
When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When the second density is higher than the first density, a part of the dots assigned to the first nozzle is formed by a second nozzle different from the first nozzle.

According to this application example, it is possible to suppress the performance degradation of the line head. When the dots assigned to form the first nozzle have the second density, the first nozzle is more loaded than the first density, leading to a decrease in the performance of the first nozzle. In such a case, the load on the first nozzle is reduced by the second nozzle forming part of the dots assigned to the first nozzle. As a result, the performance degradation of the line head is suppressed.
The “dot density” referred to here is the number of dots formed per unit distance in the conveyance direction of the print medium. This “unit distance” may be considered as the number of unit pixels.
The “dot data” referred to here is data generated as a result of the halftone process, and is distinguished from data in which the presence / absence of dot formation is changed by processing “dot data”.

Application Example 2: The printing apparatus according to Application Example 1,
When dots are formed according to dot data, the first assigned to the first nozzle has a third density larger than the first density and smaller than the second density. When the printing speed is, the dots are formed according to the dot data, while at the second printing speed higher than the first printing speed, a part of the dots assigned to the first nozzle is formed. The second nozzle is different from the first nozzle.

  According to this application example, it is possible to determine whether printing is performed according to dot data, which is suitable for each printing speed. From the viewpoint of suppressing deterioration in image quality, it is preferable to form dots according to dot data. Since the printing speed is low in the case of the first printing speed, even if dots are formed with the same density as compared with the case of the second printing speed, the load is smaller. Therefore, in the case of the first printing speed in the case of the third density, priority is given to suppression of deterioration in image quality by printing according to dot data. On the other hand, at the second printing speed, priority is given to reducing the load on the first nozzle. In this way, it is possible to more appropriately determine whether or not to print according to dot data.

Application Example 3: The printing apparatus according to Application Example 1 or Application Example 2,
A nozzle distance that is a distance between the first nozzle and the second nozzle in a direction orthogonal to the conveyance direction of the print medium is equal to or less than a predetermined length.

  According to this application example, even if the second nozzle forms a part of the dots assigned to the first nozzle, since the deviation of the dot formation position is less than the predetermined length, it is possible to suppress deterioration in image quality. .

Application Example 4: The printing apparatus according to Application Example 3,
When a part of the dots assigned to the first nozzle is formed by the second nozzle, the dots assigned to be formed for all the nozzles are different from each other by the nozzle distance in the orthogonal direction by the nozzle distance. Form.

  According to this application example, it is possible to suppress degradation in image quality and degradation in line head performance. By changing the assignment as described above, the dots originally assigned in the dot data and the dots whose assignment has been changed are not formed redundantly for the second nozzle and other nozzles. By avoiding such duplication, it is possible to prevent duplication of dots not specified by the dot data. As a result, deterioration in image quality is suppressed. Furthermore, since it is avoided that a load concentrates on a specific nozzle, the performance fall of a nozzle is suppressed.

Application Example 5: The printing apparatus according to any one of Application Example 1 to Application Example 4,
A dot whose assignment is changed from the first nozzle to the second nozzle is a unit of a set of dots formed on one print medium.

  According to this application example, by changing the allocation with a set of dots formed on one print medium as a unit, the boundary does not appear in one print medium and is difficult to be visually recognized. As a result, deterioration in image quality is suppressed.

Application Example 6: The printing apparatus according to any one of Application Example 1 to Application Example 5,
When the same image is continuously printed on a plurality of print media, when dots are formed according to dot data, when the dots assigned to the first nozzle have the second density, the first A part of dots assigned to the nozzle is formed by the second nozzle.

According to this application example, the printing speed is improved. Even when the same image is not continuously printed on a plurality of print media, that is, when different images are printed on each of the plurality of print media, it is unlikely that high density dots are assigned to the first nozzle in each of the different images. . Therefore, when printing different images on each of the plurality of print media, it can be considered that “a high-density dot is not assigned to the first nozzle in each different image”. Therefore, in this application example, the change in assignment is limited to the case where the same image is continuously printed on a plurality of print media. Thus, when different images are printed on each of the plurality of print media, it is possible to omit the determination regarding the dot density. As a result, the printing time is shortened by the time required for the determination, and the printing speed is improved.
“Continuous printing” means that no other image is printed after printing one image until the next image is printed. After printing one image, It is not intended to prescribe the time until the image is printed. Furthermore, “image printing” here does not include ink ejection that is not intended to form an image, for example, flushing.

Application Example 7: A method of producing a printed matter by forming dots on a print medium using a line head having a plurality of nozzles, using dot data indicating the presence or absence of dot formation for each pixel,
When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When the second density is higher than the first density, a part of the dots assigned to the first nozzle is formed by a second nozzle different from the first nozzle.
According to this application example, an effect equivalent to that of the application example 1 can be obtained.

Application Example 8: In a printing apparatus that performs printing by forming dots on a printing medium using a line head having a plurality of nozzles, using dot data indicating the presence or absence of dot formation for each pixel.
When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When the second density is higher than the first density, a part of the dots assigned to the first nozzle is formed by a second nozzle different from the first nozzle. Printing program to let you.
According to this application example, an effect equivalent to that of the application example 1 can be obtained.

1 is a configuration diagram of a printing system 10. FIG. 6 is a flowchart showing print data generation processing. 6 is a flowchart illustrating printing processing.

1. Printing system 10 (FIG. 1):
FIG. 1 shows the configuration of the printing system 10. The printing system 10 includes a host computer 200 and a printer 300. The host computer 200 and the printer 300 are connected to each other by a USB cable 120. The host computer 200 transfers data for printing (hereinafter referred to as “print data”) to the printer 300. The printer 300 prints an image on a sheet based on the print data transferred from the host computer 200. This print data includes dot data obtained by converting display image data by a printer driver. The dot data is data generated as a result of the halftone process, and is data indicating the presence / absence of dot formation for each color for each pixel. The display image data is for displaying an image on the display device 215 provided in the host computer 200.

  The host computer 200 includes a CPU 201, a RAM 203, a ROM 205, a display device controller 207, a keyboard controller 209, a memory controller 211, a hard disk drive (HDD) 213, and a communication interface (I / F) 220. These components are connected to each other via a bus 230. A display device 215 is connected to the display device controller 207. A keyboard 217 is connected to the keyboard controller 209, and an external memory 219 is connected to the memory controller 211. A USB cable 120 is connected to the communication I / F 220. The CPU 201 reads out the program stored in the HDD 213 to the RAM 203 and executes it in order to control the operation of the entire host computer 200.

  On the other hand, the printer 300 is a line printer that employs a line head as a print head, conveys A4 paper vertically, and prints at a resolution of 720 × 720 dpi. The printer 300 includes a CPU 301, a RAM 303, a ROM 305, a printing unit interface (I / F) 307, a memory controller 309, an operation panel 313, and a communication interface (I / F) 320. These components are connected to each other by a bus 330. A printing unit 311 is connected to the printing unit I / F 307, and an external memory 315 is connected to the memory controller 309.

  The CPU 301 reads a program stored in the ROM 305 to the RAM 303 and executes it in order to control the operation of the entire printer 300. The printing unit 311 is hardware such as an ink cartridge that stores ink, a line head, a platen, and the like for performing printing by discharging ink onto paper. In this line head, a number of nozzles are arranged over a distance slightly longer than the width of A4. The hues of ink mounted on this line head are C (cyan), M (magenta), Y (yellow), K (black), Lc (light cyan), and Lm (light magenta).

  The nozzles eject ink by a thermal method. Here, the thermal method is a method in which bubbles are generated in the ink by heating and the ink is ejected. This nozzle is arranged so that dots of the above hue can be formed in each column. A column is a set of pixels in series in the transport direction with a width of one pixel. The nozzles that discharge each hue are arranged in a zigzag pattern. By adopting this zigzag arrangement, it is possible to increase the distance between adjacent nozzles, which facilitates the production of the line head.

  The operation panel 313 is a user interface for a user to issue an instruction related to printing such as print cancellation. This user interface includes various buttons for inputting information and a display for outputting information.

2. Print data generation processing (FIG. 2):
FIG. 2 is a flowchart showing print data generation processing. The execution subject of this processing is the CPU 201 provided in the host computer 200. The trigger for starting this process is that a print instruction is input through the keyboard 217.

  First, the CPU 201 acquires display image data in RGB format indicating a print image (step S410). Subsequently, the sorting information indicating the sorting order and the speed information indicating the printing speed are acquired (step S415). The sort order is the order in which images are printed when there are multiple types of images to be printed on each sheet. Specific examples of the sort order include the well-known “unit unit” and “page unit”. As the printing speed, high speed (120 ppm), medium speed (86.6 ppm, balance printing mode) and low speed (60 ppm, high image quality printing mode) are prepared. ppm means the number of printed sheets per minute. Information on the sort order and printing speed is acquired based on an input to the keyboard 217.

  Next, the display image data is color-converted from the RGB format to the CMYKLcLm format with reference to the lookup table stored in the ROM 205 (step S420). Subsequently, halftone processing is executed using the dither mask stored in the ROM 205 (step S430). As a result of this halftone process, dot data is generated.

  Next, an interlace process is executed on the generated dot data (step S440). Finally, the data generated as a result of the interlace process, the sort information, and the speed information are transferred as print data to the printer 300 (step S450), and the print data generation process ends.

3. Printing process (Figure 3):
FIG. 3 is a flowchart showing the printing process. The execution subject of this process is the CPU 301 provided in the printer 300. The trigger for starting this process is that the printer 300 has received print data transfer.

  First, the CPU 301 determines whether a plurality of images to be printed next are designated to be printed in the print data (step S510). For example, when printing a plurality of images for only one page, or when printing a plurality of images for a plurality of pages, “page unit” is designated, in step S510 before printing the first page. It determines with YES. Unlike in such a case, when it is not designated to print a plurality of images to be printed next (step S510, NO), the image is printed according to the dot data (step S520).

  After the printing, it is determined whether an image to be printed remains (step S570). “An image to be printed” means that unprinted print data is stored in the RAM 303 of the printer 300 regardless of whether it is included in one print job. If an image to be printed remains (step S570, YES), the process returns to step S510.

  On the other hand, when a plurality of images to be printed are designated to be continuously printed (step S510, YES), it is determined which printing speed is designated in the print data (step S530). If the speed is low (step S530, low speed), it is determined whether there is a column whose dot density is 80% or more (step S540). This “dot density” is a value indicating the ratio of the number of pixels with dots in each column in the printing area (area excluding margins) of one sheet of paper, and is a value calculated for each ink color. . That is, for any combination of column and ink color, if the ratio of the number of pixels with dots is less than 80%, it is determined that “no column has a dot density of 80% or more”. Conversely, if the ratio of the number of pixels with dots is 80% or more for any combination of columns and ink colors, it is determined that “there is a column with a dot density of 80% or more”.

  The purpose of step S540 is to determine whether or not there is a possibility that the performance degradation of the nozzle is caused. In other words, it is regarded that “the ink ejection that achieves a dot density of 80% or more has a large load on the nozzle and is likely to cause a performance drop”, and the step for leveling the load (step S560 described later) is executed. To do.

  If there is no column with a dot density of 80% or more (step S540, NO), the process proceeds to step S520, and printing according to the dot data is executed for the designated number of sheets, and then the process proceeds to step S570. The reason for printing in this manner is that in step S540, it is considered that “there is a low possibility of causing nozzle performance degradation even if printing is performed according to dot data”.

  On the other hand, if there is a column where the dot density is 80% or more (step S540, YES), the dot data is processed to shift the left and right one dot at a time in order to level the load as described above. Printing is performed (step S560). Specifically, the first sheet is printed according to dot data, the second sheet is printed for one dot for all dots, shifted to the left or right, and the third sheet is one dot for all dots, which is the opposite of the second sheet All the dots are shifted to the left and right in a cycle of 3 sheets, for example, printing is performed by shifting the direction, and the fourth sheet is printed according to dot data. The left and right directions referred to here are directions orthogonal to the paper transport direction.

  On the other hand, when the printing speed is medium speed (step S530, medium speed), it is determined whether there is a column having a dot density of 60% or more (step S550). The reason why the reference value of the dot density is set lower than in the low speed case in the medium speed is that the higher the printing speed, the greater the load on the nozzle. Therefore, by reducing the reference value of the dot density, the number of cases in which “there is a high possibility of causing performance degradation” is increased.

  Step S550 is the same as step S540 except for the reference value of dot density. That is, if there is no column having a dot density of 60% or more (step S550, NO), the process proceeds to step S520. If there is a column having a dot density of 60% or more (step S550, YES), the process proceeds to step S560.

  On the other hand, when the printing speed is high (step S530, high speed), the process proceeds to step S560 regardless of the dot density, and printing is performed by shifting one dot left and right one by one. Here, the purpose of not considering the dot density is to give priority to increasing the printing speed. If the step of determining the dot density is omitted, the printing speed is improved accordingly. In addition, since “the printing speed is high, even if the dot density is low, there is a high possibility of causing a drop in nozzle performance”, step S570 is performed without considering the dot density. It is reasonable to perform

  When the above steps are repeated and printing is completed (NO in step S570), the printing process is finished.

4). Effect:
With the printing process according to the present embodiment, it is possible to suppress a decrease in nozzle performance without greatly reducing the image quality. The performance degradation referred to here includes, in addition to temporary performance degradation, non-temporary performance degradation, that is, performance degradation due to approaching the product life. Specific examples of performance degradation include: a) heat generation caused by ink ejection at a high frequency in a short period of time, which makes it impossible to perform proper ink ejection, resulting in a decrease in printing speed and / or image quality, and b) high frequency over a long period of time. The ink discharges at the end of its life earlier than other nozzles, and c) the ink discharge is infrequent, the ink dries and the viscosity of the ink increases, making it impossible to discharge the ink properly. Is at least one of these. Since the thermal method involves heating, the above a) is particularly remarkable in the thermal method.

  As described above, when it is considered that “printing according to dot data is likely to cause a decrease in nozzle performance”, printing is performed by shifting one dot to the left and right one by one. This printing disperses the uneven usage frequency of the nozzles. Therefore, it is possible to prevent a specific nozzle from deteriorating in performance. In addition, at 720 dpi, the width of one pixel is 1/720 inch = 35.3 μm, and therefore, the displacement of one dot to the left and right is hardly visible. Therefore, it is possible to minimize the degradation of image quality.

  The above effect is particularly exerted when an image that is not a natural image, for example, a character or a straight line (for example, a ruled line) is printed. In particular, when the direction of the straight line coincides with the paper transport direction, the use of the nozzles becomes prominent, and thus the above effect is exhibited.

  However, it is preferable that there is no deviation even with one dot. Therefore, if it is considered that “there is no possibility of causing a drop in nozzle performance even if printing according to dot data is performed”, printing is performed according to dot data without shifting left and right by one dot.

  In addition, by changing the criterion of “whether or not the possibility of causing nozzle performance degradation is high or low” according to the print mode, it is possible to achieve printing that is more in line with user requirements with respect to printing speed and image quality. .

5. Other embodiments:
Embodiments of the invention are not limited to the above-described embodiments, and various forms within the technical scope of the invention can be adopted. For example, additional components in the embodiment can be omitted from the embodiment. The additional components referred to here are elements corresponding to matters not specified in the substantially independent application example. For example, the following embodiments may be used.

  As described above, when printing a straight line in the same direction as the paper transport direction, the dot shifting method may be changed according to the width of the straight line. For example, the dots may be shifted by the width of the straight line. That is, if it is a straight line having a width of 2 dots, it is shifted by 2 dots, and if it is a straight line having a width of 3 dots, it is shifted by 3 dots. Such a technique can further reduce the uneven use of the nozzle.

  As described above, when the dots are shifted by a distance corresponding to the width of the straight line, if the straight line is thick, it is conceivable that the misalignment is likely to be visually recognized and the image quality is degraded. Therefore, when printing a straight line having a predetermined width or more, for example, a width of 5 dots or more, the number of dots corresponding to a distance shorter than the width of the straight line may be shifted by, for example, one dot.

  A part of the printing process may be executed by the host computer 200. For example, after the interlace process (step S440), the host computer 200 makes a determination corresponding to step S510 and steps S530 to S550. If the determination result corresponds to YES in step S530 or step S540 in the printing process, the dot data generated as a result of the halftone process is processed, and the data generated as a result of the processing is sent to the printer 300. It may be transferred. In this way, the printer 300 only needs to form dots according to the transferred data.

  A dedicated hardware RIP may be used. For example, the hardware RIP executes halftone processing on data transferred from a computer, and transfers dot data generated thereby to a printer. At the time of this transfer, the “part of printing process” described above as a modified example may be executed.

  The definition of dot density may be different from that of the embodiment. For example, the length of the column serving as the denominator of the dot density may be longer or shorter than the print area of one sheet. For example, it may be half the print area of one sheet. In this case, for example, the dot density may be calculated for each of the divided areas, and it may be determined whether both areas are less than the reference value or at least one is more than the reference value. Alternatively, instead of fixing the half-length region, the half-length region is moved pixel by pixel from one end to the other end to determine whether the dot density is equal to or higher than the reference value. Also good.

  The numerical values exemplified in the embodiment may be changed. The numerical value is, for example, a reference value of dot density or a printing speed. In addition, when shifting the dots to the left and right, it is possible to shift a plurality of dots instead of shifting one by one.

  Even when images to be continuously printed are different, printing shifted to the left and right may be executed. For example, the dot density of each column may be calculated for each image, and when there is a column having a dot density equal to or higher than a reference value common to both images, printing shifted to the left and right may be executed.

The printer 300 may execute all or part of the print data generation process. For example, the printer 300 may execute color conversion processing and / or halftone processing.
The determination regarding the dot density may be the same regardless of the printing speed.
Any number of printing speeds may be used. For example, one type may be used.
Instead of the dither method, dot data may be generated by an error diffusion method.
The ink ejection method is not limited to the thermal method, but may be a piezo method, for example.

DESCRIPTION OF SYMBOLS 10 ... Printing system 120 ... USB cable 200 ... Host computer 201 ... CPU
203 ... RAM
205 ... ROM
207 ... Display device controller 209 ... Keyboard controller 211 ... Memory controller 213 ... HDD
215 ... Display device 217 ... Keyboard 219 ... External memory 220 ... Communication I / F
230 ... Bus 300 ... Printer 301 ... CPU
303 ... RAM
305 ... ROM
307 ... Printing section I / F
309 ... Memory controller 311 ... Printing section 313 ... Operation panel 315 ... External memory 330 ... Bus

Claims (9)

A printing apparatus that performs printing by forming dots on a printing medium using a line head having a plurality of nozzles, using dot data indicating the presence or absence of dot formation for each pixel,
When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When having a second density greater than the density of 1, forming a portion of the dots assigned to the first nozzle by a second nozzle different from the first nozzle ;
When dots are formed according to dot data, the first assigned to the first nozzle has a third density larger than the first density and smaller than the second density. When the printing speed is, the dots are formed according to the dot data, while at the second printing speed higher than the first printing speed, a part of the dots assigned to the first nozzle is formed. A printing apparatus formed by a second nozzle different from the first nozzle . A printing apparatus that performs printing by forming dots on a printing medium using a line head having a plurality of nozzles, using dot data indicating the presence or absence of dot formation for each pixel,
When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When having a second density greater than the density of 1, forming a portion of the dots assigned to the first nozzle by a second nozzle different from the first nozzle;
A printing apparatus, wherein a nozzle distance, which is a distance between the first nozzle and the second nozzle in a direction orthogonal to the conveyance direction of the print medium, is a predetermined length or less . The printing apparatus according to claim 2 ,
When a part of the dots assigned to the first nozzle is formed by the second nozzle, the dots assigned to be formed for all the nozzles are different from each other by the nozzle distance in the orthogonal direction by the nozzle distance. Forming printing device. A printing apparatus according to any one of claims 1 to 3 , wherein
The dot whose assignment is changed from the first nozzle to the second nozzle is a printing apparatus in which a set of dots formed on one print medium is a unit. A printing apparatus according to any one of claims 1 to 4 , wherein
When the same image is continuously printed on a plurality of printing media, and when dots formed according to dot data are assigned to the first nozzle and have the second density, the first density A printing apparatus that forms a part of dots assigned to the nozzles by the second nozzle. A method of producing a printed matter by forming dots on a print medium using a line head having a plurality of nozzles, using dot data indicating the presence or absence of dot formation for each pixel,
When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When having a second density greater than the density of 1, forming a portion of the dots assigned to the first nozzle by a second nozzle different from the first nozzle ;
When dots are formed according to dot data, the first assigned to the first nozzle has a third density larger than the first density and smaller than the second density. When the printing speed is, the dots are formed according to the dot data, while at the second printing speed higher than the first printing speed, a part of the dots assigned to the first nozzle is formed. A printed matter production method in which the second nozzle is different from the first nozzle .   A method of producing a printed matter by forming dots on a print medium using a line head having a plurality of nozzles, using dot data indicating the presence or absence of dot formation for each pixel,
  When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When having a second density greater than the density of 1, forming a portion of the dots assigned to the first nozzle by a second nozzle different from the first nozzle;
  A nozzle distance that is a distance between the first nozzle and the second nozzle in a direction orthogonal to the conveyance direction of the print medium is equal to or less than a predetermined length.
  Print production method. In a printing apparatus that performs printing by forming dots on a printing medium using a line head equipped with a plurality of nozzles, with dot data indicating the presence or absence of dot formation for each pixel,
When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When having a second density greater than the density of 1, forming a portion of the dots assigned to the first nozzle by a second nozzle different from the first nozzle ;
When dots are formed according to dot data, the first assigned to the first nozzle has a third density larger than the first density and smaller than the second density. When the printing speed is, the dots are formed according to the dot data, while at the second printing speed higher than the first printing speed, a part of the dots assigned to the first nozzle is formed. A printing program for realizing formation by a second nozzle different from the first nozzle .   In a printing apparatus that performs printing by forming dots on a printing medium using a line head equipped with a plurality of nozzles, with dot data indicating the presence or absence of dot formation for each pixel,
  When dots are formed according to dot data, when dots assigned to the first nozzles included in the plurality of nozzles have a first density, dots are formed according to dot data, while the first When having a second density greater than the density of 1, forming a portion of the dots assigned to the first nozzle by a second nozzle different from the first nozzle;
  A nozzle distance that is a distance between the first nozzle and the second nozzle in a direction orthogonal to the conveyance direction of the print medium is equal to or less than a predetermined length.
  A printing program to achieve this.

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