JP2006268331A - Printer and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve print quality to a label face of a CD, a DVD or the like. <P>SOLUTION: When a CPU 110 receives setting of print, the CPU 110 decides whether the set kind of a paper sheet is the label face or not. As a result, an ML table stored in a hard disk is acquired when the paper sheet is the label face, and an SML table is acquired when not a label. The CPU 110 performs halftone processing according to the thus acquired table. By such the printing processing, use of a small dot is restricted in time of printing to the label face, and a medium dot and a large dot are used. Accordingly, even when color of a low gradation value is printed on the label face LB, generation of banding is suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printing apparatus that forms a multi-tone image by dot distribution and prints the image on a predetermined printing medium.

  In recent years, many printing apparatuses perform printing using two or more types of dots having different sizes in order to improve image quality. In general, in such a printing apparatus, when printing a light color, small ink droplets are ejected, and when printing a highly saturated color, large ink droplets are ejected to form dots. Has been done.

  In addition, recent printing apparatuses have a function of performing printing by directly ejecting ink on a label surface of an optical disk such as a CD or a DVD as well as normal printing paper (see Patent Document 1 below). .

JP 2003-16699 A

  In general, the ink receiving layer formed on the label surface of the optical disk is inferior in water absorption compared to ordinary printing paper. Therefore, the conventional printing apparatus suppresses the occurrence of bleeding due to the overlapping of inks. Therefore, when printing on the label surface, the number of ink droplets ejected per unit area is set to 40 to 50% of that during normal printing. Printing was limited to the limit.

  In such a conventional printing apparatus, when a light color is printed on the label surface, the number of dots formed per unit area is limited, and further, small dots are formed. There was a problem that streak noise called banding was likely to occur. Banding means that dots on the same raster line are not formed in an ideal position due to a manufacturing error of the nozzle, and a gap is generated between the raster line and the adjacent raster line. It is a phenomenon.

  The present invention has been made in view of the problem that banding occurs during printing on a label surface or the like, and an object thereof is to improve the print quality in printing on a label surface or the like.

Based on the above object, the printing apparatus of the present invention is configured as follows. That is,
A printing apparatus that uses a plurality of types of dots having different sizes according to gradation values, forms a multi-gradation image according to the distribution of the dots, and prints the image on a predetermined printing medium,
Determining means for determining the type of the print medium;
When the determination means determines that the print medium is a medium having a non-fibrous print surface, the use of the smallest dot among the plurality of types of dots having different sizes is substantially prohibited. Prohibited means,
And a dot substitution unit that represents a gradation to be represented by the smallest dot when the use of the smallest dot is substantially prohibited by the prohibiting unit. And

  According to the printing apparatus of the present invention, when the printing medium to be printed is a medium having a non-fibrous printing surface, the gradation represented by the smallest dot is represented by another size dot. Can do. Therefore, even when the number of ink droplets ejected per unit area is limited when printing on a printing medium having low water absorption, the gradation that should be represented by the smallest dot is represented by the large dot. Therefore, the gap between dots can be made inconspicuous, and banding can be prevented from occurring.

  When the use of the smallest dot is substantially prohibited, the amount of use of the dot may be zero, or the amount of use may be limited to a few percent of the normal amount of use. Good.

  As a method for determining the type of the print medium by the determination unit, for example, a list of print media that can be printed by the printing apparatus is displayed on a display, and selection from the list is received by the user to determine the type. Can be. Further, an operation button for selecting a print medium may be provided in the printing apparatus, and the type of the print medium may be determined according to the operation of the operation button. Further, means for irradiating the print medium with light and a sensor for measuring the reflectance of the reflected light from the print medium may be provided, and the type of the print medium may be automatically determined according to the reflectance.

In the printing apparatus having the above configuration,
The medium having the non-fibrous printing surface can be a disk medium having an information recording surface capable of recording / reproducing data and a printing surface capable of printing with ink. Further, the use of the smallest dot may be substantially prohibited even for a print medium having a relatively low ink absorption rate, such as an OHP sheet or a film.

In the printing apparatus having the above configuration,
A first table for converting the gradation value into an occurrence rate of at least two types of dots including the smallest dot and a larger dot, or the occurrence rate of the smallest dot is substantially Refer to the second table for converting the gradation value to the occurrence rate of at least one kind of dot including the large dots, and the gradation value of the input image data is set to each size. Gradation value conversion means for converting to the occurrence rate of dots,
The dot substitution means substitutes the second table for the gradation value conversion means when the use of the smallest dot is substantially prohibited by the prohibition means, instead of the first table. , The gradation to be represented by the smallest dot may be represented by a dot of another size.

  With such a configuration, it is possible to prohibit the use of the smallest dot when performing the process of converting the gradation value of the input image data into the occurrence rate of dots of each size.

In the printing apparatus having the above configuration,
It is good also as a thing provided with the memory | storage part which memorize | stores said 1st table and said 2nd table separately.

  With such a configuration, use of the smallest dot can be prohibited by a simple process of switching the table to be referred to.

In the printing apparatus having the above configuration,
A storage unit for storing the first table;
The dot substitution means reads out the first table from the storage unit when the use of the smallest dot is substantially prohibited by the prohibition means, and converts the first table into the second table. It is good also as a means to convert to 2 and to make the said gradation value conversion means refer to this 2nd table.

  According to such a configuration, since the table can be dynamically converted according to the type of the print medium, it is not necessary to store a plurality of tables, and the storage area can be saved.

In the printing apparatus having the above configuration,
A storage unit that stores a first table for converting the gradation value into an occurrence rate of at least two types of dots including the smallest dot and a larger dot;
The dot substitution means, when the use of the smallest dot is substantially prohibited by the prohibition means, uses the first table to change the gradation value of the image data to the occurrence rate of dots of each size. A means for converting the occurrence rate of the smallest dot to an occurrence rate of dots of other sizes larger than this when forming a multi-tone image by the distribution of the dots It is good.

  According to such a configuration, the generation rate of the smallest dot can be converted into the generation rate of dots of other sizes in the halftone process in which a multi-tone image is formed by the distribution of dots. Therefore, even with such a configuration, it is not necessary to store a plurality of tables, and the storage area can be saved.

The present invention can also be configured as a printing apparatus as follows. That is, this printing device
A printing head having a plurality of dot forming elements capable of forming dots of different sizes on a printing medium, and rastering the dots by the dots while reciprocating the printing head relative to the printing medium. A printing apparatus for forming and printing an image,
Determining means for determining the type of the print medium;
When it is determined by the determining means that the print medium is a medium having a non-fibrous print surface, among the plurality of types of dots having different sizes, a raster with a minimum dot used for printing is used. And a printing means for forming the printing head by using different dot forming elements while reciprocating at least a plurality of times with respect to the printing medium.

  According to such a printing apparatus, when the printing medium to be printed is a medium having a non-fibrous printing surface, rasters with the smallest dots are all formed by the same dot forming element. Absent. Therefore, occurrence of banding can be suppressed when there is a manufacturing error or the like in the dot forming element. The dot forming element is, for example, a nozzle that ejects ink.

  In a printing apparatus having such a configuration, as a method of forming a raster using different dot forming elements while reciprocating a printing head at least a plurality of times with respect to a printing medium, for example, a printing method called an overlap or an interface is used. A printing method called lace or a combination of both can be used.

  In addition to the configuration as the printing apparatus described above, the present invention can also be configured as a printing method or a computer program in the printing apparatus. The computer program may be recorded on a recording medium such as a flexible disk, a CD-ROM, a magneto-optical disk, or a memory card.

Hereinafter, in order to further clarify the operations and effects of the present invention described above, embodiments of the present invention will be described based on examples in the following order.
A. First embodiment:
(A1) Configuration of printing system:
(A2) Printer configuration:
(A3) Printing process:
B. Second embodiment:
C. Third embodiment:
D. Variations:

A. First embodiment:
(A1) Configuration of printing system:
FIG. 1 is a block diagram showing the overall configuration of a printing system 10 as a first embodiment. As shown in the figure, a printing system 10 according to the present embodiment prints on a computer 100 and a label surface LB (hereinafter, simply referred to as “label surface LB”) of an optical disk such as a CD or DVD having a non-fibrous printing surface. And a printer 200 capable of performing the above. As described above, the printing system constituted by the computer 100 and the printer 200 can be called a “printing apparatus” in a broad sense.

  The computer 100 includes a CPU 110, a memory 120, a hard disk 130, a graphic controller 140, a PS / 2 interface 150, a USB interface 160, and the like. These are connected by a predetermined bus (not shown). A display 300 is connected to the graphic controller 140, and input devices such as a keyboard 400 and a mouse 500 are connected to the PS / 2 interface. Also, the printer 200 is connected to the USB interface 160.

  The CPU 110 loads and executes programs such as the application program 121, the printer driver 122, the display driver 123, and the input device driver 124 on the memory 120. These programs may be loaded from the hard disk 130 or may be loaded from various recording media such as a flexible disk and a CD-ROM.

  The application program 121 is a program for reading image data 131 stored in the hard disk 130 or the like and editing or printing the image data 131. The printer driver 122 is a program for controlling the printer 200 in accordance with a print instruction from the application program 121 and printing designated image data 131. The display driver 123 is a program for performing display control on the display 300 via the graphic controller 140. The input device driver 124 is a program for transmitting input operations with the keyboard 400 and the mouse 500 to various programs.

  The printer driver 122 includes an image data acquisition module 122a, a color conversion module 122b, a halftone processing module 122c, and a print data generation module 122d.

  The image data acquisition module 122 a is a module for acquiring image data 131 to be printed from the application program 121.

  The color conversion module 122 b converts the color of each pixel of the image data 131 represented in the RGB format into a color in the CMYKLcLm format suitable for printing by the printer 200 based on the color conversion table 132 stored in the hard disk 130. Module. The color conversion table includes a color composed of a combination of R, G, and B, and C (cyan), M (magenta), Y (yellow), K (black), and Lc (light cyan) to be expressed by a printer. A color composed of a combination of Lm (light magenta) is stored in association with each other.

  The halftone processing module 122c is for expressing the color converted by the color conversion module 122b by the distribution of two or more types of dots having different sizes based on the SML table 133 or the ML table 134 stored in the hard disk 130. It is a module. The SML table defines the usage ratios of three types of dots, small dots, medium dots, and large dots, according to the color gradation value. The ML table defines two types of medium dots and large dots. The dot usage rate is defined.

  The print data generation module 122d is a module for adjusting the data generated by the halftone processing module 122c into data in a format that can be interpreted by the printer 200.

(A2) Printer configuration:
FIG. 2 is a block diagram showing the internal configuration of the printer 200. As shown in the figure, the printer 200 has, as a mechanism for printing on the label LB, a carriage 210 on which an ink cartridge 212 is mounted, a carriage motor 220 that drives the carriage 210 in the main scanning direction, and a tray TR on which a CD or DVD is set. A paper feed motor 230 and the like are provided.

  The carriage 210 includes a total of six ink heads 211 for each color of C, M, Y, K, Lc, and Lm. An ink cartridge 212 containing these inks is mounted on the carriage 210, and the ink supplied from the ink cartridge 212 to the ink head 211 adjusts the voltage applied to a piezo element (not shown) to adjust the label surface. Discharged to LB.

  The ink head 211 adjusts the negative voltage waveform applied to the piezo element in accordance with control by the control circuit 250 described later, and changes the ink suction speed in three stages before ink droplet ejection. By doing this, the size of the ink droplets to be ejected is adjusted, and dots of three types of sizes, large dots, medium dots, and small dots can be formed.

  FIG. 3 is an explanatory diagram showing the principle of ejecting ink droplets of different sizes from the ink head 211. In the voltage waveform shown in the upper part of the figure, the waveform indicated by a broken line is a waveform when a normal dot is ejected. In a section d2 shown in this voltage waveform, once a negative voltage is applied to the piezo element PE, the piezo element PE is deformed in a direction in which the cross-sectional area of the ink passage 68 is increased. Since the ink supply speed from the ink cartridge 212 is limited, the ink supply amount is insufficient for the expansion of the ink passage 68. As a result, as shown in the state A in the lower part of FIG. 3, the ink interface Me at the tip of the nozzle Nz is recessed in a meniscus shape inside the nozzle Nz.

  On the other hand, when the voltage waveform shown by the solid line in the upper part of FIG. 3 is used and a negative voltage is suddenly applied to the piezo element PE as shown in the section d1, the amount of ink supplied from the ink cartridge 212 is further insufficient. Therefore, the ink interface Me is further indented as compared with the state A as indicated by the state a. Next, when a positive voltage is applied to the piezo element PE (section d3), the ink passage 68 is narrowed and ink is ejected. At this time, from the state where the ink interface Me is not recessed inward so much (state A), large ink droplets are ejected as shown in state B and state C, and from the state where the ink interface Me is greatly recessed inside (state a). As shown in state b and state c, small ink droplets are ejected. Thus, inks having different sizes are ejected from the ink head 211.

  Returning to FIG. The carriage 210 is movably held on a sliding shaft 280 installed in parallel with the platen 270. The carriage motor 220 rotates the drive belt 260 in accordance with a command from the control circuit 250 to reciprocate the carriage 210 in a direction parallel to the platen 270, that is, in the main scanning direction.

  The paper feed motor 230 conveys the tray TR in the direction perpendicular to the platen 270 by rotating the platen 270. That is, the tray TR is conveyed by a predetermined amount in the sub-scanning direction according to the rotation angle of the platen 270.

  The printer 200 further includes a control circuit 250 for controlling the printing mechanism described above. Connected to the control circuit 250 are a USB interface 240 for connection to the computer 100, a liquid crystal display 241, an operation panel 242, a memory card slot 243, and the like.

  The control circuit 250 includes a CPU 251, a ROM 252, and a memory 253. The ROM 252 stores a control program for controlling the operation of the printer 200. The CPU 251 develops the control program in the memory 253 and executes it, thereby controlling the ink head 211, the carriage motor 220, and the paper feed motor 230 based on the print data received from the computer 100 via the USB interface 240. Then, color printing is performed on the label surface LB.

  The printer 200 according to the present embodiment can print on the label surface LB of the CD or DVD mounted on the tray TR. However, a normal printing paper can be used instead of the tray TR to set the normal printing paper. Of course, printing can also be performed on printing paper.

(A3) Printing process:
FIG. 4 is a flowchart of the printing process. Such a printing process is a process executed when the printer driver 122 is called when a user performs a printing operation in the application program 121 executed on the computer 100.

  When this printing process is executed, the CPU 110 of the computer 100 displays the setting screen of the printer driver 122 on the display 300, and accepts the printing setting by the user (step S100). The items to be set include, for example, paper type and color / monochrome designation. If printing has already been set, the setting information stored in the memory 120 or the hard disk 130 may be acquired without displaying the setting screen. Here, description will be made assuming that color printing is performed.

  When CPU 110 accepts the print setting, CPU 110 determines the type of paper selected by the user (step S110). As a result, if the selected paper is the label surface LB (step S110: Yes), the CPU 110 acquires the ML table stored in the hard disk 130 in order to substantially prohibit the formation of small dots on the label LB surface. (Step S120). On the other hand, if it is other paper, the SML table is acquired (step S130).

  When the CPU 110 acquires the SML table or the ML table, the CPU 110 acquires the color conversion table 132 stored in the hard disk 130 (step S140). Then, the image data 131 to be printed is acquired from the application program 121 (step S150).

  Next, the CPU 110 performs color conversion processing on the color of each pixel constituting the image data 131 using the color conversion table 132 acquired in step S120 (step S160). In this color conversion process, the gradation value in the RGB format is converted into the gradation value in the CMYKLcLm format. If the printer 200 does not have light cyan and light magenta inks, it may be converted into color values in the CMYK format.

  When the CPU 110 ends the color conversion process, the CPU 110 performs a halftone process for each ink color using the ML table 134 acquired in step S120 or the SML table 133 acquired in step S120 (step S170). .

  In this halftone process, first, using the ML table 134 or the SML table 133, the gradation value of each ink color converted in step S160 is converted into the occurrence rate of each dot having a different size. .

  FIG. 5 is an explanatory diagram showing an outline of the conversion processing by the SML table 133. As shown in the figure, the SML table 133 defines the proportion of large dots, medium dots, and small dots that are used for the gradation value of each ink. For example, if the gradation value of the ink color is 255, 100% of large dots are used, and other medium dots and small dots are not used. If the tone value of the ink is 63, large dots are not used, and small dots and medium dots are used. As described above, in the conversion using the SML table 133, the gradation value of the ink color is converted into the occurrence rates of four types of dots, large dots, medium dots, small dots, and no dots.

  FIG. 6 is an explanatory diagram showing an outline of the conversion process by the ML table 134. As shown in the figure, the ML table 134 defines a ratio of using large dots and medium dots with respect to the gradation value of each ink, and the use ratio of small dots in the SML table 133 is medium dots. Defined in terms of percentage of use. For example, when the gradation value exceeds 191, only large dots are used, and only medium dots are used until the gradation value is about 120. As described above, in the conversion using the ML table 134, the smallest dot is not used, and the tone value of the ink color is converted into the occurrence rate of three types of dots, large dots, medium dots, and no dots. .

  As described above, when the gradation value of each ink color is converted into the dot occurrence rate, the CPU 110 distributes each dot according to the occurrence rate by a known technique such as a dither method or an error diffusion method, thereby increasing the number of dots. The gradation image is represented by the distribution of dots. Then, print data in which the dot distribution state is recorded is generated. The print data defines the position at which ink is ejected on the label surface LB or the printing paper, the type of ink to be ejected, and the size of the ink to be ejected.

  When the halftone process is thus completed, the CPU 110 outputs the print data generated by the halftone process to the printer 200 via the USB interface 160 (step S180). With the above processing, a series of printing processing in the computer 100 is completed. Upon receiving the print data transferred in step S180, the printer 200 performs color printing by controlling the paper feed motor 230, carriage motor 220, and ink head 211 while analyzing the received print data.

  According to the first embodiment described above, when printing on the label surface LB, the smallest dot is not used, and only the medium dot and the large dot are used for printing. Therefore, even when a color with a low gradation value is printed on the label surface LB, the gap between dots can be made inconspicuous, and the occurrence of banding is suppressed.

B. Second embodiment:
In the first embodiment described above, two types of tables, the ML table 134 and the SML table 133, are stored in the hard disk 130, and these tables are used properly according to the type of paper. In contrast, in the second embodiment, only the SML table 133 is stored in the hard disk 130.

  FIG. 7 is a block diagram showing the overall configuration of a printing system 10b as the second embodiment. As shown in the figure, the printing system 10b of this embodiment employs a configuration in which the ML table 134 is deleted from the hard disk 130 with respect to the printing system 10 shown in FIG. 1, and the other parts are the same.

  FIG. 8 is a flowchart of the printing process in the second embodiment. As shown in the drawing, the printing process of the present embodiment is the same as the printing process of the first embodiment shown in FIG. 4 except for steps S110 to S130. Therefore, detailed description of overlapping processes is omitted here.

  As shown in the figure, when this printing process is executed, first, the CPU 110 accepts printing settings (step S200) and acquires the SML table 133 stored in the hard disk 130 (step S210).

  Next, the CPU 110 determines the paper type based on the print settings received in step S200 (step S220). As a result, if the selected paper is the label surface LB (step S220: Yes). A process of converting the SML table 133 acquired in step S210 to the ML table 134 is performed (step S230). On the other hand, if it is another sheet (step S220: No), the process of step S230 is skipped.

  In the table conversion processing in step S230, the CPU 110 performs an operation for converting the occurrence rate of small dots in the SML table 133 into the occurrence rate of medium dots. This calculation can be performed based on, for example, the following equation (1). That is, assuming that the medium dot occurrence rate in the SML table 133 is MD and the small dot occurrence rate is SD, the medium dot occurrence rate MD2 after conversion is expressed as follows. However, α is a predetermined coefficient that can be calculated according to the area ratio of medium dots to small dots, and can be set to 0.25, for example.

MD2 = MD + SD × α (1)

  In the present embodiment, conversion is not performed for the occurrence rate of large dots, and the occurrence rate of large dots in the SML table 133 before conversion is applied as it is to the occurrence rate of large dots in the ML table 134 after conversion. Good.

  As described above, when the table is converted, the CPU 110 acquires the color conversion table 132 and the image data 131 (step S240, step S250), and then performs a color conversion process using the color conversion table 132 (step S240). Step S260). Then, halftone processing is executed using the SML table 133 acquired in step S210 or the converted ML table 134 converted in step S230 (step S270). As a result, the generated print data is transferred to the printer. 200 (step S280).

  According to the second embodiment described above, if the paper type is the label surface LB, printing is performed after the SML table 133 is dynamically converted to the ML table 134. Therefore, it is not necessary to store a plurality of tables in the hard disk 130, and the disk capacity can be saved.

C. Third embodiment:
In the second embodiment described above, the SML table 133 is converted (step S230) prior to the color conversion process (step S260 in FIG. 8). In contrast, in this embodiment, table conversion is performed during halftone processing. The configuration of the printing system in this embodiment is the same as that of the printing system 10b of the second embodiment shown in FIG. 7, and the ML table 134 is not stored in the hard disk 130.

  FIG. 9 is a flowchart of the printing process in the third embodiment. As shown in the figure, first, when the CPU 110 receives a print setting by the user (step S300), the CPU 110 acquires the SML table 133 stored in the hard disk 130 (step S310), and further acquires the color conversion table 132 (step S310). Step S320).

  Subsequently, the CPU 110 acquires image data 131 to be printed from the application program 121 (step S330), and performs color conversion processing using the color conversion table 132 acquired in step S310 (step S340). Then, the halftone process shown in FIG. 10 is executed (step S350).

  FIG. 10 is a flowchart showing details of the halftone process in this embodiment. When such halftone processing is executed, the CPU 110 first determines the gradation values of each ink color based on the SML table 133 acquired in step S310, that is, large dots, medium dots, small dots, and no dots. The dot generation rate is converted (step S352).

  Subsequently, the CPU 110 determines whether or not the paper type is the label surface LB based on the print setting received in step S300 (step S354). If the result of this determination is that the paper type is the label surface LB (step S354: Yes), the CPU 110 performs processing to convert the small dot occurrence rate converted in step S352 to the medium dot occurrence rate. (Step S356). Also in this conversion process, the above-described equation (1) of the second embodiment can be used. On the other hand, if the paper type determined in step S354 is other than the label surface LB (step S354: No), the CPU 110 skips the process of step S356.

  Next, the CPU 110 distributes each dot by the dither method or the error diffusion method based on the dot generation rate obtained in step S352 or the dot generation rate converted in step S356, and prints. Data is generated (step S358).

  When the halftone process described above is completed, the CPU 110 outputs print data to the printer as shown in FIG. 9 (step S360).

  According to the third embodiment described above, the SML table 133 is converted in the halftone process. Even with such a configuration, it is not necessary to store a plurality of tables in the hard disk 130 as in the second embodiment, and the disk capacity can be reduced.

D. Variations:
As mentioned above, although the various Example of this invention was described, it cannot be overemphasized that this invention is not limited to these Examples, and can take a various structure in the range which does not deviate from the meaning.

  For example, the printer driver 122, the color conversion table 132, the SML table 133, and the ML table 134 illustrated in FIG. 1 are stored in the memory 253 of the printer 200 illustrated in FIG. 2, and the CPU 251 of the printer 200 performs various printing operations described above. It is good also as what performs a process. In this case, the printer 200 can accept the print settings through the operation panel 242 by displaying a screen for performing print settings on the liquid crystal display 241. Further, the image data 131 can be input from the memory card inserted into the memory card slot 243. According to such a configuration, it is possible to perform printing on the label surface LB by using the printer 200 alone without using the computer 100.

  In the various embodiments described above, the type of paper is determined by receiving print settings from the user. On the other hand, for example, the printer 200 is provided with means for irradiating the printing paper with light and a sensor for measuring the reflectance of the reflected light from the printing paper, and the type of the printing paper is automatically selected according to the reflectance. It is good also as what distinguishes.

  In the various embodiments described above, the case where printing is performed on the label surface LB of a CD or DVD has been described. However, a non-fibrous print medium having a relatively low ink absorption rate, such as an OHP sheet or film. The present invention can also be applied to printing on a printer. In this case, when determining the printing paper for the printing process, not only the label surface LB but also the OHP sheet or film is selected as the printing paper, the same processing as the printing processing for the label surface LB is performed. And it is sufficient.

  In the above-described embodiment, when the label surface LB is selected as the printing paper, the small dot occurrence rate is set to zero, and printing is performed using only medium dots and large dots. However, the occurrence rate of small dots does not need to be strictly zero. For example, the use rate may be substantially prohibited, for example, by limiting the occurrence rate to about several percent compared to the normal time.

  Further, in the various embodiments described above, banding is suppressed by restricting the use of dots of the minimum size among a plurality of types of dots having different sizes. However, for example, on normal printing paper, printing is performed by interlace processing, and on printing on the label surface, printing is performed by combining the interlacing processing and overlap processing by changing the normal printing mode and its printing mode. It is good.

  FIG. 11 is a flowchart of the printing process in such a modification. In such print processing, when the CPU 110 receives print settings (step S400), the CPU 110 acquires the SML table 133, the color conversion table 132, and the image data 131 (steps S410 to S430), and the color conversion table for the image data 131 is obtained. After performing color conversion processing using 132 (step S440), halftone processing is executed using the SML table 133 (step S450).

  Thereafter, CPU 110 determines whether or not the paper type received in step S400 is label surface LB (step S460). If the paper type is the label surface LB (step S460: Yes), print data for printing the image obtained by the halftone process is generated while performing the interlace process and the overlap process (step S470). . If the paper type is not the label surface LB (step S460: No), print data for printing is generated while only interlace processing is performed (step S480). Then, the CPU 110 outputs the print data generated in step S470 or step S480 to the printer 200 (step S490). The printer 200 interprets the print data output in this way, and controls the paper feed motor 230 and the ink head 211 while reciprocating the carriage by the carriage motor 220 to specify the specified print mode (interlace processing, overlap). Process), color printing is performed.

  Interlace processing uses an ink head having a plurality of nozzles in the sub-scanning direction, forms a plurality of rasters separated by the nozzle pitch in the sub-scanning direction, and then slightly shifts the head position in the sub-scanning direction. In this process, a new raster is formed between already formed rasters. In addition, the overlap processing is, for example, that the dots of each raster are formed in every other main scan in the first main scan and the remaining dots are formed in the second main scan. This is a process of forming a raster by movement. If printing is performed on the label surface LB by such a method, it is suppressed that adjacent dots are formed by the same nozzle, so that occurrence of banding is suppressed even if the nozzle has a manufacturing error or the like. It becomes possible to do. If the overlap processing is performed, a longer printing time than usual is required, but the printing range for the label surface LB is usually within a circle having a diameter of about 12 cm, which is greater than when printing to A4 size. Since printing is completed in a short time, it does not matter much. Further, the interlace processing and the overlap processing may be applied only to the raster formed by the smallest dot, and the raster formed by other size dots may be processed in the normal printing mode.

1 is a block diagram showing an overall configuration of a printing system as a first embodiment. FIG. 2 is a block diagram illustrating an internal configuration of a printer. It is explanatory drawing which shows the principle in which the ink droplet of a different magnitude | size is discharged from an ink head. It is a flowchart of a printing process. It is explanatory drawing which shows the outline | summary of the conversion process by a SML table. It is explanatory drawing which shows the outline | summary of the conversion process by ML table. It is a block diagram which shows the whole structure of the printing system 10b as 2nd Example. It is a flowchart of the printing process in 2nd Example. It is a flowchart of the printing process in 3rd Example. It is a flowchart which shows the detail of the halftone process in 3rd Example. It is a flowchart of the printing process in a modification.

Explanation of symbols

10, 10b ... Printing system 100 ... Computer 110 ... CPU
DESCRIPTION OF SYMBOLS 120 ... Memory 121 ... Application program 122 ... Printer driver 122a ... Image data acquisition module 122b ... Color conversion module 122c ... Halftone processing module 122d ... Print data generation module 123. Display driver 124 ... Input device driver 130 ... Hard disk 131 ... Image data 132 ... Color conversion table 133 ... SML table 134 ... ML table 140 ... Graphic controller 150 .. PS / 2 interface 160 ... USB interface 200 ... printer 210 ... carriage 211 ... ink head 212 ... ink cartridge 220 ... carriage motor 230 ... paper feed motor 240 ... USB interface 250 ... Control circuit 251 ... CPU
252 ... ROM
253 ... Memory 260 ... Drive belt 270 ... Platen 280 ... Slide axis 300 ... Display 400 ... Keyboard 500 ... Mouse

Claims (10)

A printing apparatus that uses a plurality of types of dots having different sizes according to gradation values, forms a multi-gradation image according to the distribution of the dots, and prints the image on a predetermined printing medium,
Determining means for determining the type of the print medium;
When the determination means determines that the print medium is a medium having a non-fibrous print surface, the use of the smallest dot among the plurality of types of dots having different sizes is substantially prohibited. Prohibited means,
A printing apparatus comprising: a dot substitution unit that, when the use of the smallest dot is substantially prohibited by the prohibition unit, represents a gradation to be represented by the smallest dot by a dot of another size. The printing apparatus according to claim 1,
A first table for converting the gradation value into an occurrence rate of at least two types of dots including the smallest dot and a larger dot, or the occurrence rate of the smallest dot is substantially Refer to the second table for converting the gradation value to the occurrence rate of at least one kind of dot including the large dots, and the gradation value of the input image data is set to each size. Gradation value conversion means for converting to the occurrence rate of dots,
The dot substitution means substitutes the second table for the gradation value conversion means when the use of the smallest dot is substantially prohibited by the prohibition means, instead of the first table. A printing apparatus in which the gradation to be represented by the smallest dot is represented by dots of other sizes. The printing apparatus according to claim 2,
A printing apparatus comprising a storage unit that individually stores the first table and the second table. The printing apparatus according to claim 2,
A storage unit for storing the first table;
The dot substitution means reads out the first table from the storage unit when the use of the smallest dot is substantially prohibited by the prohibition means, and converts the first table into the second table. A printing apparatus comprising: means for converting the second table to the gradation value conversion means. The printing apparatus according to claim 1,
A storage unit that stores a first table for converting the gradation value into an occurrence rate of at least two types of dots including the smallest dot and a larger dot;
The dot substitution means, when the use of the smallest dot is substantially prohibited by the prohibition means, uses the first table to change the gradation value of the image data to the occurrence rate of dots of each size. After the conversion to the above, when forming a multi-tone image by the distribution of the dots, there is provided means for converting the occurrence rate of the smallest dot to the occurrence rate of dots of other sizes larger than this printing apparatus. A printing head having a plurality of dot forming elements capable of forming dots of different sizes on a printing medium, and rastering the dots by the dots while reciprocating the printing head relative to the printing medium. A printing apparatus for forming and printing an image,
Determining means for determining the type of the print medium;
When it is determined by the determining means that the print medium is a medium having a non-fibrous print surface, among the plurality of types of dots having different sizes, a raster with a minimum dot used for printing is used. A printing unit configured to form the printing head using different dot forming elements while reciprocating the printing head at least a plurality of times. The printing apparatus according to any one of claims 1 to 6,
The medium having a non-fibrous printing surface is a disk medium having an information recording surface capable of recording / reproducing data and a printing surface capable of printing with ink. A printing method in which a plurality of types of dots having different sizes according to gradation values are selectively used, a multi-gradation image is formed by the distribution of the dots, and the image is printed on a predetermined printing medium,
Determining the type of the print medium;
When it is determined that the determined print medium is a medium having a non-fibrous print surface, the use of the smallest dot among the plurality of types of dots having different sizes is substantially prohibited. ,
A printing method in which the gradation to be represented by the smallest dot is represented by dots of other sizes. A computer program for properly using a plurality of types of dots having different sizes according to gradation values, forming a multi-gradation image according to the distribution of the dots, and printing the image on a predetermined print medium,
A discrimination function for discriminating the type of the print medium;
When the discrimination function determines that the print medium is a medium having a non-fibrous print surface, the use of the smallest dot among the plurality of types of dots having different sizes is substantially prohibited. Prohibited functions,
When the use of the smallest dot is substantially prohibited by the prohibition function, the computer realizes a dot replacement function that represents a gradation to be represented by the smallest dot by a dot of another size. Computer program for.   The computer-readable recording medium which recorded the computer program of Claim 9.

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