JP6175816B2 - Printing apparatus and printing method - Google Patents

Description

  The present invention relates to a printing apparatus and a printing method.

  As a typical printing apparatus, there is an ink jet printer of a type that ejects ink from a nozzle using a piezoelectric element. In this type of ink jet printer, an ink chamber is provided in each nozzle, and ink is ejected from the nozzle by driving a piezoelectric element to change the volume of the ink chamber (for example, Patent Document 1).

JP 2009-73076 A

  In general, when a large amount of ink is ejected from a nozzle at a time in order to form a large-sized dot, the residual vibration of the piezoelectric element or the residual vibration of the ink in the ink chamber lasts longer. There is. Furthermore, if a large amount of ink is ejected at a time, then a large amount of ink flows into the ink chamber at a time, resulting in unstable ink ejection, for example, unintended ink ejection. There is a possibility. When high-resolution and high-resolution printing is performed, such a problem may occur more remarkably by continuously ejecting a large amount of ink at a time. In addition, in a printing apparatus, reduction of ink mist generated due to ink ejection, cost reduction, resource saving, ease of manufacture, improvement in usability, and the like have been desired.

The present invention has been made to solve at least part of the problems described above, it can be implemented deliberately following form.
The first aspect of the present invention is a printing apparatus capable of recording dots of different sizes on a print medium. This printing device
A print head comprising a plurality of nozzles capable of recording at least a first dot and a second dot larger than the first dot by discharging liquid;
A transport mechanism that transports the print medium relative to the print head at least at a first speed or a second speed higher than the first speed;
A print control unit that controls the print head and the transport mechanism and records the first dot and the second dot on the print medium in accordance with a gradation value of given image data. ,
The print control unit
An image is printed in a first mode on the print medium that is transported relatively at the first speed, and a second mode is printed on the print medium that is transported relatively at the second speed. Print the image with
The gradation value at which the second dot starts to be recorded when printing is performed in the second mode, and the gradation value at which the second dot starts to be recorded when printing is performed in the first mode. Higher than.
Further, the present invention can be realized as the following application examples.

(1) According to one aspect of the present invention, a printing apparatus capable of recording dots of different sizes on a printing medium is provided. A printing apparatus of this form is a printing apparatus capable of recording dots of different sizes on a print medium; and at least a first dot and a second dot larger than the first dot by discharging a liquid; A print head comprising a plurality of nozzles capable of recording the print medium; and a transport mechanism that transports the print medium relative to the print head at least at a first speed or a second speed higher than the first speed. A print control unit that controls the print head and the transport mechanism, and records the first dot and the second dot on the print medium according to a gradation value of given image data; The print control unit prints an image in a first mode on the print medium relatively transported at the first speed and is relatively transported at the second speed. No. for print media When the image is printed in the second mode; when the printing is performed in the second mode, the gradation value higher than the gradation value at which the second dot is recorded when the printing is performed in the first mode. The second dot is recorded. According to the printing apparatus of this aspect, in the second mode in which the printing speed is fast, the gradation value at which the second dot starts to be used instead of the first dot is higher than in the first mode. When forming a large-sized dot, the degree of change in the volume of the ink chamber is larger than when forming a small-sized dot, and residual vibration tends to continue. If the next dot is formed before the vibration is attenuated, there is a possibility that the correct amount of ink cannot be ejected. However, according to the printing apparatus of the present embodiment, when printing is performed in the second mode, the use of the second dot having a relatively large size up to a high gradation value can be suppressed. The residual vibration can be reduced as compared with the case where printing is performed. Further, when printing is performed in the second mode, the amount of ink that flows into the ink chamber at a time can be reduced to a higher gradation value than when printing is performed in the first mode. Therefore, even when ink is ejected continuously at a high printing speed, the ink can be ejected stably. Further, in the first mode in which the printing speed is slow, a second dot having a large size is recorded instead of the first dot having a relatively small size at a gradation value lower than that in the second mode. For this reason, when printing is performed at a low printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist can be reduced.

(2) In the printing apparatus according to the above aspect; when printing is performed in the second mode, the maximum number of the first dots recorded per unit area is printed in the first mode. It may be more than the case. According to the printing apparatus of this aspect, in the second mode in which the printing speed is fast, the number of small dots that are recorded most per unit area is larger than in the first mode in which the printing speed is slow. That is, in the second mode, instead of using the second dots having a large size, the first dots having a small size are often used. Therefore, even when printing is performed at a high printing speed, residual vibration can be reduced and the amount of ink flowing into the ink chamber at a time can be reduced. Therefore, even when ink is ejected continuously at a high printing speed, the ink can be ejected stably. Further, in the first mode in which the printing speed is slow, the use of the first dot having a relatively small size is restricted, and the second dot having a large size is recorded instead of the first dot. For this reason, when printing is performed at a low printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist can be reduced.

(3) In the printing apparatus according to the above aspect; when printing is performed in the second mode, an intermediate gradation among a range of gradation values expressed using the first dot and the second dot In terms of value, a larger number of the first dots may be recorded than when printing is performed in the first mode. According to the printing apparatus of this aspect, when printing is performed in the second mode having a high printing speed at an intermediate gradation value, the first size having a smaller size than that when printing is performed in the first mode. Are often used. Therefore, since small dots are used instead of large dots, residual vibration can be reduced and the amount of ink flowing into the ink chamber at a time can be reduced. Therefore, even when ink is ejected continuously at a high printing speed, the ink can be ejected stably. Further, in the second mode with a slow printing speed, the use of the first dot having a small size is restricted at an intermediate gradation value. For this reason, when printing is performed at a low printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist can be reduced.

(4) In the printing apparatus of the above aspect, the nozzle can further record a third dot that is larger than the first dot and smaller than the second dot by discharging liquid; A print control unit; controls the print head and the transport mechanism, and sets the first dot, the second dot, and the third dot to the print medium according to a gradation value of the image data; When printing is performed in the second mode, the first dot is printed at a gradation value higher than the gradation value at which the third dot is recorded when printing is performed in the first mode. Three dots may be recorded. According to the printing apparatus of this aspect, even when three types of sizes of dots are recorded, in the second mode where the printing speed is fast, the third dot starts to be used compared to the first mode. The key value is high. Therefore, the use of the third dots larger than the first dots can be suppressed up to a gradation value higher than that in the first mode, so that the residual vibration is reduced as compared with the case where printing is performed in the first mode. be able to. Further, when printing is performed in the second mode, the amount of ink that flows into the ink chamber at a time can be reduced to a higher gradation value than when printing is performed in the first mode. Therefore, even when ink is ejected continuously at a high printing speed, the ink can be ejected stably. Further, in the first mode in which the printing speed is slow, the third dot is recorded instead of the relatively small first dot at a gradation value lower than that in the second mode. For this reason, when printing is performed at a low printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist can be reduced.

(5) In the printing apparatus of the above aspect; when printing is performed in the second mode, the maximum number of the third dots recorded per unit area is printed in the first mode. It may be more than the case. According to the printing apparatus of this aspect, in the second mode in which the printing speed is high, the number of the third dots recorded most per unit area is larger than in the first mode in which the printing speed is slow. That is, in the second mode, instead of using a second dot having a large size, a third dot having a smaller size than the second dot is often used. Therefore, even when printing is performed at a high printing speed, residual vibration can be reduced and the amount of ink flowing into the ink chamber at a time can be reduced. Therefore, even when ink is ejected continuously at a high printing speed, the ink can be ejected stably. Furthermore, in the first mode in which the printing speed is slow, the use of the third dot smaller than the second dot is restricted, and the second dot is recorded instead of the third dot. For this reason, when printing is performed at a low printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist can be reduced.

(6) In the printing apparatus according to the above aspect, in the second mode, the print control unit uses more nozzles than the first mode for a predetermined range of the print medium in the second mode, The dots may be recorded. According to the printing apparatus of this aspect, the number of nozzles used when recording dots in a predetermined range of the print medium in the second mode in which the printing speed is high is the number of nozzles used in the first mode. More than the number of Therefore, the amount of liquid ejected from one nozzle for recording dots within a predetermined range can be reduced, so that residual vibration is reduced and the amount of ink flowing into the ink chamber at a time is reduced. can do. Therefore, even when ink is ejected continuously at a high printing speed, the ink can be ejected stably. Furthermore, in the first mode in which the printing speed is slow, since the amount of liquid ejected from one nozzle can be increased in order to record dots within a predetermined range, the number of ink ejections is reduced. . Therefore, in the first mode where the printing speed is slow, the generation of ink mist can be reduced.

(7) In the printing apparatus according to the above aspect; the plurality of nozzles that discharge liquid may be arranged in the print head along a direction that intersects a conveyance direction of the print medium. According to the printing apparatus of this embodiment, even when printing is performed at a relatively high speed with a so-called line head type printing apparatus, residual vibration is reduced and the amount of ink flowing into the ink chamber at a time is reduced. Therefore, the ink can be ejected stably. Further, even when printing is performed at a slow printing speed with a line head type printing apparatus, the number of ink ejections is reduced, so that the occurrence of ink mist can be reduced.

  A plurality of constituent elements of each embodiment of the present invention described above are not essential, and some or all of the effects described in the present specification are to be solved to solve part or all of the above-described problems. In order to achieve the above, it is possible to appropriately change, delete, replace with another new component, and partially delete the limited contents of some of the plurality of components. In order to solve some or all of the above-described problems or achieve some or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

  For example, one embodiment of the present invention can be realized as an apparatus including one or more elements of a print head, a transport mechanism, and a print control unit. That is, this apparatus may or may not have a print head. Further, this apparatus may or may not have a transport mechanism. In addition, this apparatus may or may not have a print control unit. Such an apparatus can be realized as, for example, a printing apparatus, but can also be realized as an object other than the printing apparatus. According to such a form, it is possible to solve at least one of various problems such as ink mist reduction, image quality improvement, cost reduction, resource saving, manufacturing ease, usability improvement and the like. Any or all of the technical features of the above-described embodiments can be applied to this product.

  The present invention can also be realized in various forms other than the printing apparatus. For example, the present invention can be realized in the form of a printing method, a printing device manufacturing method, a printing device control method, a computer program for realizing the functions of these methods, devices or systems, a recording medium on which the computer program is recorded, and the like. it can.

1 is a diagram illustrating a schematic configuration of a printer as a printing apparatus according to an embodiment of the present invention. It is a flowchart of a printing process. It is a figure which shows the recording rate table memorize | stored in the memory | storage part. It is a figure which shows the recording rate table memorize | stored in the memory | storage part. It is a figure which shows another example of the recording rate table memorize | stored in the memory | storage part. It is a figure which shows another example of the recording rate table memorize | stored in the memory | storage part.

A. First embodiment:
FIG. 1 is a diagram illustrating a schematic configuration of a printer 10 as a printing apparatus according to an embodiment of the present invention. The printer 10 of this embodiment is a so-called line head type printer that performs printing without main scanning of the print head. The printer 10 includes a control unit 100, a line head unit 200, and a transport mechanism 300.

  The line head unit 200 includes a plurality of print heads 210. The print heads 210 are arranged in a staggered manner so that the spacing between adjacent nozzles is constant over the maximum print width. The print head 210 includes a plurality of nozzles. The plurality of nozzles constitutes a nozzle row arranged in a staggered manner in the medium width direction x intersecting the transport direction y of the print medium RM. The plurality of nozzles constituting each nozzle row need not be arranged in a staggered manner along the nozzle row direction, and may be arranged, for example, in a straight line along the nozzle row direction.

  The nozzles eject ink stored in an ink cartridge (not shown) connected to the line head unit 200. The print head 210 includes a piezoelectric element for applying pressure to an ink chamber and an ink passage inside the nozzle. The piezoelectric element controls the amount of ink droplets ejected from each nozzle according to the voltage applied to the piezoelectric element. Thus, by changing the amount of ink droplets per discharge, the printer 10 can form dots of different types on the print medium RM. In the present embodiment, the printer 10 can form two sizes of dots, small dots and large dots. A small dot corresponds to the “first dot” of the present application, and a large dot corresponds to the “second dot” of the present application.

  The transport mechanism 300 includes a medium feed motor (not shown) and a transport belt (not shown). The medium feed motor drives the conveyor belt. The conveying belt conveys the printing medium RM from the upstream side to the downstream side within the maximum printing width of the line head unit 200 by driving by the medium feeding motor.

  The control unit 100 includes a CPU, a ROM, a RAM, and an EEPROM (all not shown) connected to each other via a bus. The control unit 100 controls the operation of each unit of the printer 10 such as the transport mechanism 300 and the line head unit 200 by developing a program stored in the ROM or EEPROM into the RAM and executing the program. The control unit 100 also functions as an image acquisition unit 102, a color conversion unit 104, a recording rate data generation unit 106, and a formation unit 108. Processing performed by each of these functional units will be described later. Note that at least a part of the functions realized by the CPU may be realized by an electric circuit included in the control unit 100 operating based on the circuit configuration. The control unit 100 corresponds to the print control unit of the present application.

Next, a printing process for performing printing using the above-described printer 10 will be described.
FIG. 2 is a flowchart of the printing process. At the start of the printing process, the user designates a printing mode associated with the printing speed (step S10). In the present embodiment, the user can designate one of the first print mode and the second print mode. The second print mode is a mode in which printing is performed at a faster speed than the first print mode. For example, the user can designate the second print mode if importance is attached to the printing speed, and can designate the first print mode if importance is attached to the resolution.

  When the print mode is designated by the user, the CPU performs RGB processing from the personal computer (not shown) connected to the printer 10 or a memory card (not shown) inserted into the printer 10 as processing of the image acquisition unit 102. Image data is acquired (step S20).

  When the image data is acquired, the CPU uses the color conversion lookup table (not shown) provided in the EEPROM as processing of the color conversion unit 104, and uses cyan C and magenta for using the RGB format image data in the printer 10. Conversion into multi-gradation data representing the gradation values of M, yellow Y, and black K (step S30).

  Next, the CPU selects a recording rate table from the storage unit 110 as a process of the recording rate data generation unit 106 based on the selected print mode (step S40). The recording rate table is a table that converts the ink amount data of each ink into dot recording rate data of a plurality of types of dots having different sizes. The “dot recording rate” is a value indicating the ratio of dots recorded per unit area. In step S40, the recording rate data generation unit 106 selects the first recording rate table 111 when the first printing mode is selected (step S50), and the second printing mode is selected. If so, the second recording rate table 112 is selected (step S60).

  Next, the CPU refers to the selected recording rate table as processing of the recording rate data generation unit 106 and converts the multi-gradation data into recording rate data representing the recording rates of small dots and large dots ( Step S70).

  FIG. 3 is a diagram illustrating a recording rate table stored in the storage unit 110. In each recording rate table, a ratio of using small dots and large dots is defined for the gradation value of each ink corresponding to the image data. 3A shows the relationship between the gradation value and the dot recording rate in the first recording rate table 111, and FIG. 3B shows the gradation value and the dot recording rate in the second recording rate table 112. FIG. Shows the relationship. The profile SD in FIG. 3 represents the recording rate of small dots, and the profile LD represents the recording rate of large dots.

  The tone value L1 shown in FIG. 3A is a tone value at which large dots start to be used in the first mode using the first recording rate table 111, and the tone value shown in FIG. L2 is a gradation value at which large dots start to be used in the second mode using the second recording rate table 112. In other words, only small dots are recorded up to the gradation value L1 in the first mode, and only small dots are recorded up to the gradation value L2 in the second mode.

  Comparing FIG. 3A and FIG. 3B, the gradation value L2 in the second recording rate table 112 is greater than the gradation value L1 in which the large dots start to be used in the first recording rate table 111. high. The maximum value (peak) SP2 of the small dot recording rate in the second recording rate table 112 is approximately 100%, whereas the peak SP1 of the small dot dot recording rate in the first recording rate table 111 is Approximately 50%. That is, the small dot recording rate peak SP2 in the second recording rate table 112 is higher than the small dot recording rate peak SP1 in the first recording rate table 111. Therefore, when the gradation values where the largest number of small dots are recorded are compared per unit area, more small dots are recorded in the second print mode than in the first print mode.

  Further, as shown in FIGS. 3A and 3B, in this embodiment, the gradation value of the image data can be expressed by using small dots and large dots. For an intermediate gradation value H that is half of the representable gradation value, the small dot recording rate in the second recording rate table 112 is larger than the small dot recording rate in the first recording rate table 111. That is, when the second print mode is selected, more small dots are recorded for the intermediate gradation value H than in the first print mode. As described above, in the conversion to the recording rate data using the recording rate table, the multi-gradation data is converted into three types of recording rate data of large dots, small dots, and no dots.

  When the conversion to the recording rate data is performed, the CPU performs a halftone process by a systematic dither method as a process of the forming unit 108 (step S80). Specifically, dot arrangement data representing the dot arrangement state is generated from the recording rate data generated in step S70.

  Next, the CPU performs an interlacing process for rearranging the dot arrangement data according to the nozzle arrangement of the printer 10, the transport amount of the print medium RM, and the like as the process of the forming unit 108 (step S90).

  When the interlacing process is performed, the CPU controls the medium feed motor, the print head 210, and the like as the process of the forming unit 108, and performs printing by discharging ink from the nozzles of the print head 210 (step S100). By performing a series of printing processes as described above, the printer 10 forms a print image.

  Generally, in order to eject ink from a nozzle, for example, when a voltage is applied to a piezoelectric element using a drive signal, at least one of the piezoelectric element, an ink chamber, and an ink flow path connected to the ink chamber In this case, residual vibration occurs. When a large voltage is applied to the piezoelectric element, the degree of change in the volume of the ink chamber increases, and a relatively large amount of ink is ejected, thereby recording a large size dot. Also grows. For this reason, in the case where dots of a large size are continuously formed at a high printing speed, there is a possibility that ink ejection becomes unstable.

  However, in the printer according to the present embodiment, large dots begin to be used in the second mode in which high-speed printing is performed at a higher gradation value than in the first mode in which low-speed printing is performed. Thus, for example, an image that can be formed with one large dot is formed with four small dots at a high gradation value, so that the residual vibration that occurs with the formation of the large dot is reduced and the ink chamber is moved to. The amount of ink that flows in at once is reduced. Therefore, ink can be ejected continuously and stably even at a high printing speed. In the first mode with a slow printing speed, large dots are recorded instead of small dots at a lower gradation value than in the second mode with a fast printing speed. For this reason, when printing is performed at a slow printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist is reduced. Therefore, according to the printer of the present embodiment, dots of a more appropriate size are used according to the printing speed, so that a good printed image can be obtained at both a high printing speed and a low printing speed. Furthermore, since the ink mist adhering to the printer and the ink cartridge can be reduced at a slow printing speed, for example, problems caused by the ink mist adhering to the printer and the ink cartridge can be reduced.

  Further, in the printer 10 of the present embodiment, when the printing speed is high, the peak of the small dot recording rate is higher than when the printing speed is low. At the intermediate gradation value H, small dots are used instead of large dots when the printing speed is high compared to when the printing speed is low. Therefore, when the printing speed is fast, printing can be performed using many first dots of small size. Therefore, even when printing is performed at a high printing speed, residual vibration can be reduced and the amount of ink flowing into the ink chamber at a time can be reduced. Therefore, ink can be ejected continuously and stably even at a high printing speed. In the first mode with a slow printing speed, large dots are recorded instead of small dots at a lower gradation value than in the second mode with a fast printing speed. For this reason, when printing is performed at a slow printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist is reduced.

  In addition, the line head type printer 10 as in the present embodiment is often used particularly for printing an image at a high speed. However, in the second printing mode in which printing is performed at a high printing speed, as described above, dots of small size are used as much as possible to reduce residual vibration and to reduce the amount of ink flowing into the ink chamber at a time. Printing is performed. Therefore, even when high-speed printing is performed by the line head type printer 10, ink can be ejected continuously and stably.

B. Second embodiment:
In the above-described embodiment, when printing is performed by recording dots of two types, small dots and large dots, ink can be ejected continuously and stably in high-speed printing, and ink mist in low-speed printing. The printer 10 that can reduce the occurrence of the problem and the printing process performed in the printer 10 have been described. In this embodiment, even when printing is performed by recording dots of three different sizes, ink can be ejected continuously and stably in high-speed printing, and the occurrence of ink mist can be reduced in low-speed printing. A simple printer.

  The printer according to the present embodiment has two types of small dots and large dots by controlling the amount of ink droplets ejected from each nozzle according to the voltage applied to the piezoelectric element by the printer 10 according to the first embodiment. In contrast, dots of three sizes, small dots, medium dots, and large dots, are formed. The medium dot corresponds to the “third dot” in the present application. Whereas the storage unit 110 included in the printer 10 of the first embodiment stores the first recording rate table 111 and the second recording rate table 112, the storage unit of the printer of the present embodiment 3 recording rate table 113 and fourth recording rate table 114 are stored. Since other configurations of the printer of the present embodiment are the same as those of the printer 10 of the first embodiment, description and illustration are omitted.

  Further, in the printing process using the printer 10 of the present embodiment, the difference from the first embodiment is that the recording rate data generation unit 106 has a third recording rate when the first printing mode is selected. When the table 113 is selected and the second printing mode is selected, the fourth recording rate table 114 is selected. Other processes performed in the printing process are the same as those in the first embodiment, and thus the description thereof is omitted.

  FIG. 4 is a diagram showing a recording rate table stored in the storage unit in the present embodiment. Each recording rate table defines the proportion of small dots, medium dots, and large dots that are used for the gradation value of each ink corresponding to the image data. 4A shows the relationship between the gradation value and the dot recording rate in the third recording rate table 113, and FIG. 4B shows the gradation value and the dot recording rate in the fourth recording rate table 114. FIG. Shows the relationship. A profile SD in FIG. 4 represents a small dot recording rate, a profile MD represents a medium dot recording rate, and a profile LD represents a large dot recording rate.

  A gradation value M3 shown in FIG. 4A is a gradation value at which medium dots start to be used in the first mode using the third recording rate table 113, and a large dot is used as the gradation value L3. The tone value to start with. The gradation value M4 shown in FIG. 4B is a gradation value at which medium dots start to be used in the second mode using the fourth recording rate table 114, and the gradation value L4 uses large dots. The tone value to start with. In other words, in the first mode using the third recording rate table 113, only small dots are recorded up to the gradation value M3, and only small dots and medium dots are recorded up to the gradation value L3. In the second mode using the fourth recording rate table 114, only small dots are recorded until the gradation value M4, and only small dots and medium dots are recorded until the gradation value L4.

  Comparing FIG. 4A and FIG. 4B, the gradation value L4 in the fourth recording rate table 114 is higher than the gradation value L3 in the third recording rate table 113. The gradation value M4 at which the medium dot starts to be used in the fourth recording rate table 114 is higher than the gradation value M3 at which the medium dot starts to be used in the third recording rate table 113.

  Furthermore, the small dot recording rate peak SP4 in the fourth recording rate table 114 is approximately 100%, whereas the small dot recording rate peak SP3 in the third recording rate table 113 is approximately 50%. . The medium dot recording rate peak MP4 in the fourth recording rate table 114 is approximately 100%, whereas the medium dot recording rate peak MP3 in the third recording rate table 113 is approximately 50%. . That is, the small dot recording rate peak SP4 in the fourth recording rate table 114 is higher than the small dot recording rate peak SP3 in the third recording rate table 113. The medium dot recording rate peak MP4 in the fourth recording rate table 114 is higher than the medium dot recording rate peak MP3 in the third recording rate table 113. Therefore, when the gradation values where the largest number of small dots are recorded are compared per unit area, more small dots are recorded in the second print mode than in the first print mode. Further, when comparing the gradation values in which the largest number of medium dots are recorded per unit area, more medium dots are recorded in the second print mode than in the first print mode.

  As shown in FIGS. 4A and 4B, in the present embodiment, the gradation value of the image data can be expressed by using small dots, medium dots, and large dots. The recording rate of small dots in the fourth recording rate table 114 is larger than the recording rate of small dots in the third recording rate table 113 for an intermediate gradation value H that is half of the representable gradation values. That is, as in the first embodiment, when the second print mode is selected, more small dots are recorded per unit area than in the first print mode for the intermediate gradation value H. The As described above, in the conversion to the recording rate data using the recording rate table, the multi-gradation data is converted into the recording rates of four types of dots, large dots, medium dots, small dots, and no dots.

  In the printer according to the present embodiment, in the second mode in which high-speed printing is performed, medium dots and large dots start to be recorded at higher gradation values than in the first mode in which low-speed printing is performed. In the second mode, the maximum value of the small dot recording rate and the maximum value of the medium dot recording rate are higher than those in the first mode. Therefore, when performing high-speed printing, printing can be performed using many small dots and medium dots. Further, in the first mode that performs low-speed printing, medium dots and large dots are recorded at lower gradation values than in the second mode that performs high-speed printing, so the number of ink ejections can be reduced. it can. Therefore, the same effect as that of the first embodiment is obtained. Therefore, even when printing is performed using a plurality of dots such as small dots, medium dots, and large dots, according to the printer of this embodiment, ink is continuously and stably ejected in high-speed printing. In the low-speed printing, the generation of ink mist can be reduced.

C. Variations:
The embodiment described above can be variously modified as follows.

・ Modification 1:
In the first embodiment described above, the CPU of the printer 10 has the first recording rate table 111 shown in FIG. 3A stored in the storage unit of the printer 10 as the processing of the recording rate data generation unit 106. The multi-tone data is converted into the recording rate data by referring to the second recording rate table 112 shown in FIG. 3B according to the print mode. On the other hand, the recording rate table to be referred to may be different from the recording rate table shown in FIGS.

  FIG. 5 is a diagram illustrating another example of the recording rate table stored in the storage unit 110. The recording rate table 111a shown in FIG. 5A is another example of the first recording rate table referred to in the first mode, and the recording rate table 112a shown in FIG. It is another example of the 2nd recording rate table referred in a mode. As described above, in the second mode with a high printing speed, the large dots start to be used from a higher gradation value than in the first mode, and the peak SP2a of the maximum dot recording rate of the small dots is higher than the peak SP1a in the first mode. However, if a higher recording rate table is used, residual vibration that occurs with the formation of large dots is reduced, and the amount of ink that flows into the ink chamber at a time is reduced. Therefore, ink can be ejected continuously and stably even at a high printing speed. In addition, when printing is performed at a slow printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist is reduced.

Modification 2
In the second embodiment described above, the CPU of the printer 10 has the third recording rate table 113 shown in FIG. 4A stored in the storage unit of the printer 10 as the processing of the recording rate data generation unit 106. Referring to the fourth recording rate table 114 shown in FIG. 4B according to the print mode, the multi-gradation data is converted into recording rate data. On the other hand, the recording rate table to be referred to may be different from the recording rate table shown in FIGS.

  FIG. 6 is a diagram illustrating another example of the recording rate table stored in the storage unit. The recording rate table 113a shown in FIG. 6A is another example of the third recording rate table referred to in the first mode, and the recording rate table 114a shown in FIG. It is another example of the 4th recording rate table referred in a mode. In the recording rate table 114a shown in FIG. 6B, medium dots and large dots start to be used from a higher gradation value than in the first mode, and the maximum recording rate peak SP4a of small dots is the peak in the first mode. Higher than SP3a. Further, the peak MP4a of the medium dot maximum recording rate is higher than the peak MP3a in the first mode. If such a recording rate table 114a is used in the second mode with a high printing speed, residual vibrations that occur with the formation of large dots are reduced, and the amount of ink that flows into the ink chamber at a time is reduced. Is done. Therefore, ink can be ejected continuously and stably even at a high printing speed. In addition, when printing is performed at a slow printing speed, the number of ink ejections is reduced, so that the occurrence of ink mist is reduced.

・ Modification 3:
In the various embodiments described above, the printer 10 is a line head type ink jet printer. On the other hand, the printer 10 may be a so-called serial head type printer in which the print head ejects ink while reciprocating along the width direction of the print medium RM.

-Modification 4:
In the various embodiments described above, the ink ejection method for ejecting ink from the nozzles of the print head 210 of the printer 10 is based on driving of a piezoelectric element. On the other hand, as the ink discharge method, various methods such as a thermal method in which bubbles are generated in the nozzle using a heating element and ink is discharged by the bubbles may be used. That is, if the ink ejection method in the printing apparatus is a method in which pressure (vibration) is applied to the ink flow path, the ink chamber, or a member connected thereto, the residual vibration occurs, and therefore the present invention can be applied.

  The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each form described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Printer 100 ... Control unit 102 ... Image acquisition part 104 ... Color conversion part 106 ... Recording rate data generation part 108 ... Formation part 110 ... Storage part 111, 111a ... 1st recording rate table 112, 112a ... 2nd recording Rate table 113, 113a ... Third recording rate table 114, 114a ... Fourth recording rate table 200 ... Line head unit 210 ... Print head 300 ... Conveying mechanism y ... Medium conveying direction x ... Medium width direction H ... Intermediate floor Tone value SP1, SP2, SP3, SP4, SP1a, SP2a, SP3a, SP4a ... Small dot recording rate peak MP3, MP4, MP3a, MP4a ... Medium dot recording rate peak L1, L2, L3, L4, L1a, L2a, L3a, L4a ... Tone values at which large dots begin to be used M3, M4, M3a, M4a ... Medium Gradation value RM ... print media Tsu door starts to be used

Claims (8)

A printing apparatus capable of recording dots of different sizes on a print medium,
A print head comprising a plurality of nozzles capable of recording at least a first dot and a second dot larger than the first dot by discharging liquid;
A transport mechanism that transports the print medium relative to the print head at least at a first speed or a second speed higher than the first speed;
A print control unit that controls the print head and the transport mechanism and records the first dot and the second dot on the print medium in accordance with a gradation value of given image data. ,
The print control unit
An image is printed in a first mode on the print medium that is transported relatively at the first speed, and a second mode is printed on the print medium that is transported relatively at the second speed. Print the image with
The gradation value and the second dot starts to be recorded when the printing was performed in the second mode, the first when said printing was conducted in the mode of the second gradation dots that began to be recorded not high than the value,
Printing device. The printing apparatus according to claim 1,
When printing is performed in the second mode, the maximum number of the first dots recorded per unit area is larger than that when printing is performed in the first mode. The printing apparatus according to claim 1 or 2, wherein
When printing is performed in the second mode, printing is performed in the first mode at an intermediate gradation value in a range of gradation values expressed using the first dot and the second dot. A printing apparatus in which a larger number of the first dots are recorded than in the case of performing. A printing apparatus according to any one of claims 1 to 3, wherein
The nozzle can further record a third dot that is larger than the first dot and smaller than the second dot by discharging a liquid;
The print control unit
Controlling the print head and the transport mechanism, and recording the first dot, the second dot, and the third dot on the print medium according to the gradation value of the image data;
The gradation value and the third dot starts to be recorded when the printing was performed in the second mode, the third gray dots that started to be recorded in the case of performing printing in the first mode not high than the value, the printing device. The printing apparatus according to claim 4,
When printing is performed in the second mode, the maximum number of the third dots recorded per unit area is larger than that when printing is performed in the first mode. A printing apparatus according to any one of claims 1 to 5, comprising:
In the second mode, the printing control unit records the dots using a larger number of nozzles than that used in the first mode for a predetermined range of the printing medium. A printing apparatus according to any one of claims 1 to 6, comprising:
The printing apparatus, wherein the plurality of nozzles that eject liquid are arranged in the print head along a direction that intersects a conveyance direction of the print medium. A printing method capable of recording dots of different sizes on a print medium,
For a print head comprising a plurality of nozzles capable of recording at least a first dot and a second dot larger than the first dot by discharging liquid, the print medium is at least at a first speed or Conveying relatively at a second speed that is faster than the first speed;
A control mechanism that controls the print head and a transport mechanism that relatively transports the print medium at the first speed or the second speed that is faster than the first speed. Recording the first dot and the second dot on the print medium according to the gradation value of the image data obtained,
In the step of performing the printing,
An image is printed in a first mode on the print medium that is transported relatively at the first speed, and a second mode is printed on the print medium that is transported relatively at the second speed. Print the image with
Gradation value and the second dot starts to be recorded in the case of printing with the second mode, than the gradation value and the second dots that started to be recorded in the case of printing with the first mode high not, printing method also.

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