JP5035204B2 - Liquid ejection apparatus and liquid ejection method - Google Patents

Description

  The present invention relates to a liquid ejection apparatus and a liquid ejection method.

2. Related Art Inkjet printers are known as liquid ejecting apparatuses that eject liquid (for example, ink) onto a medium (paper, cloth, OHP paper, etc.). In an ink jet printer, a dot forming process for ejecting ink droplets from a head by moving a carriage and a transport process for transporting paper are alternately repeated to print an image composed of dots on paper. Also, some inkjet printers are called line printers that use a head having a length corresponding to the paper width instead of moving the head by a carriage (see Patent Document 1).
JP 2007-68202 A

When expressing the darkest gradation, it is necessary to apply ink without gaps so that the background of the medium cannot be seen. For this reason, in order to be able to form dark dots on a large number of pixels, a plurality of dark nozzle rows for discharging dark ink may be prepared.
However, if the number of light nozzle rows that discharge light ink is the same as the number of dark nozzle rows, the number of nozzle rows increases, resulting in increased manufacturing costs.
An object of the present invention is to reduce the number of nozzle rows.

The main invention for achieving the above object is as follows: (1) a plurality of nozzles in a predetermined direction and a plurality of dark nozzle rows for discharging the first liquid; and (2) a plurality of nozzles in the predetermined direction. A second liquid having the same color as the first liquid and having a light density, and having a number of light nozzle rows smaller than the number of dark nozzle rows, and (3) a pixel on the medium using a plurality of the dark nozzle rows A controller that forms dark dots on a number of pixels smaller than the number of pixels on which the dark dots are formed using a number of the light nozzle rows smaller than the number of the dark nozzle rows. And a liquid ejecting apparatus.
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  At least the following matters will become clear from the description of the present specification and the accompanying drawings.

(1) a plurality of dark nozzle rows having a plurality of nozzles in a predetermined direction and discharging a first liquid; and (2) a second nozzle having a plurality of nozzles in the predetermined direction and having a lighter concentration than the first liquid. (3) forming a dark dot on a pixel on a medium by ejecting liquid and using a plurality of the dark nozzle rows less than the number of the dark nozzle rows, and the dark nozzle rows And a controller that forms light dots in a smaller number of pixels than the number of pixels in which the dark dots are formed using a number of the light nozzle rows smaller than the number of the light nozzle rows. Becomes clear.
According to such a liquid ejecting apparatus, the number of nozzle rows can be reduced.

  In such a liquid ejecting apparatus, it is desirable that when a liquid is ejected from a certain nozzle, no liquid is ejected from a nozzle adjacent to the nozzle. Thereby, when a certain nozzle discharges a liquid, it is not affected by an adjacent nozzle.

  In such a liquid ejecting apparatus, when a certain nozzle forms a dot in a certain pixel, it is desirable that the nozzle does not form a dot in a pixel that is next to the pixel. Thereby, the printing speed can be increased.

  In this liquid ejection apparatus, the plurality of dark nozzle rows include a first dark nozzle row and a second dark nozzle row, and the second dark nozzle after the first dark nozzle row forms the dark dots. A row forms the dark dot, the light nozzle row forms the light dot at a pixel where the dark dot is formed by the first dark nozzle row, and the dark dot is formed by the second dark nozzle row It is desirable not to form the light dots on the formed pixels. Thereby, bleeding can be suppressed.

  In this liquid ejecting apparatus, it is desirable that the dark dots are larger than the light dots. Thereby, it becomes easy to make the graininess of the light portion inconspicuous and to express the deep and dark portion.

  In the liquid ejecting apparatus, as the plurality of dark nozzle rows, there are a plurality of dark cyan nozzle rows that eject dark cyan ink to form dark cyan dots, and the light nozzle row ejects light cyan ink. A light cyan nozzle row for forming light cyan dots, and the liquid ejection device includes a plurality of dark magenta nozzle rows having a plurality of nozzles in a predetermined direction and ejecting dark magenta ink to form dark magenta dots. A light magenta nozzle array having a plurality of nozzle arrays in a predetermined direction and ejecting light magenta ink having a lighter density than the dark magenta ink to form light magenta dots, the number of the dark magenta nozzle arrays It is desirable that a light magenta nozzle array with a small number of light is further provided, and the light magenta dots are arranged between the light cyan dots. Thereby, the graininess is reduced and the image quality is improved.

In addition, the first liquid is discharged from a dark nozzle row having a plurality of nozzles in a predetermined direction, and the second liquid having a lighter concentration than the first liquid is discharged from a light nozzle row having a plurality of nozzles in the predetermined direction. In the liquid ejection method, a plurality of dark nozzle rows are used to form dark dots on pixels on a medium, and the number of the light nozzle rows is smaller than the number of dark nozzle rows, and the dark nozzle rows are used. A liquid ejection method is characterized in that light dots are formed on a smaller number of pixels than the number of dots.
According to such a liquid ejection method, the number of nozzle rows can be reduced.

=== Configuration of Printing System ===
Next, an embodiment of a printing system will be described with reference to the drawings. However, the description of the following embodiments includes embodiments relating to a computer program and a recording medium on which the computer program is recorded.

  FIG. 1 is an explanatory diagram showing an external configuration of a printing system. The printing system 100 includes a printer 1, a computer 110, a display device 120, an input device 130, and a recording / reproducing device 140. The printer 1 is a printing apparatus that prints an image on a medium such as paper, cloth, or film. The computer 110 is communicably connected to the printer 1 and outputs print data corresponding to the image to be printed to the printer 1 in order to cause the printer 1 to print an image.

  A printer driver is installed in the computer 110. The printer driver is a program for causing the display device 120 to display a user interface and converting image data output from the application program into print data. This printer driver is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. Alternatively, the printer driver can be downloaded to the computer 110 via the Internet. In addition, this program is comprised from the code | cord | chord for implement | achieving various functions.

  The “printing apparatus” means an apparatus that prints an image on a medium, and corresponds to the printer 1, for example. The “printing control device” means a device that controls the printing device, for example, a computer in which a printer driver is installed. The “printing system” means a system including at least a printing apparatus and a printing control apparatus.

=== Configuration of Printer ===
<Inkjet printer configuration>
FIG. 2 is a block diagram of the overall configuration of the printer 1. FIG. 3A is a cross-sectional view of the printer 1. FIG. 3B is a perspective view for explaining a conveyance process and a dot formation process of the printer 1. The basic configuration of the line printer that is the printer of this embodiment will be described below.

  The printer 1 of this embodiment includes a transport unit 20, a head unit 40, a detector group 50, and a controller 60. The printer 1 that has received the print data from the computer 110 as an external device controls each unit (the transport unit 20 and the head unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 110 and prints an image on paper. The situation in the printer 1 is monitored by a detector group 50, and the detector group 50 outputs a detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 20 is for transporting a medium (for example, paper S) in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes a paper feed roller 21, a transport motor (not shown), an upstream transport roller 23 </ b> A and a downstream transport roller 23 </ b> B, and a belt 24. The paper feed roller 21 is a roller for feeding the paper inserted into the paper insertion slot into the printer. When a transport motor (not shown) rotates, the upstream transport roller 23A and the downstream transport roller 23B rotate, and the belt 24 rotates. The paper S fed by the paper feed roller 21 is conveyed by the belt 24 to a printable area (area facing the head). When the belt 24 transports the paper S, the paper S moves in the transport direction with respect to the head unit 40. The paper S that has passed through the printable area is discharged to the outside by the belt 24. The paper S being conveyed is electrostatically attracted or vacuum attracted to the belt 24.

  The head unit 40 is for ejecting ink onto the paper S. The head unit 40 ejects ink onto the paper S being conveyed, thereby forming dots on the paper S and printing an image on the paper S. The printer of this embodiment is a line printer, and the head unit 40 can form dots for the paper width at a time. The configuration of the head unit 40 will be described later.

  The detector group 50 includes a rotary encoder (not shown), a paper detection sensor 53, and the like. The rotary encoder 53 detects the rotation amount of the upstream side conveyance roller 23A and the downstream side conveyance roller 23B. Based on the detection result of the rotary encoder 53, the transport amount of the paper S can be detected. The paper detection sensor 53 detects the position of the leading edge of the paper being fed.

  The controller 60 is a control unit (control unit) for controlling the printer. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 which is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63. In particular, the controller 60 controls the transport operation by the transport unit 20 and the ink discharge operation (dot formation operation) by the head unit 40, thereby performing dot formation with a dot arrangement as described later.

<Configuration of head unit 40>
FIG. 4A is an explanatory view of the arrangement of the plurality of nozzle rows on the lower surface of the head unit 40 as seen from above. Seven nozzle rows are provided on the lower surface of the head unit 40. The seven nozzle rows are arranged in order from the upstream side in the transport direction, the first dark cyan nozzle row (C1), the second dark cyan nozzle row (C2), the first dark magenta nozzle row (M1), and the second dark magenta nozzle row. (M2), a yellow nozzle row (Y), a light cyan nozzle row (LC), and a light magenta nozzle row (LM). The length of each nozzle row in the paper width direction is the length corresponding to the A4 size paper width.

  FIG. 4B is an enlarged view of a portion X surrounded by a dotted line in FIG. 4A, and is an enlarged view of the left end of each color nozzle row. As shown in the drawing, each nozzle row is configured by arranging a plurality of nozzles at a predetermined nozzle pitch (in this case, 1/1600 inch) along the paper width direction. Each nozzle is provided with a heater (not shown), and ink is ejected from the nozzle by heat generated from the heater. Here, each nozzle in each nozzle row is numbered sequentially from the left in the figure. As shown in the drawing, the positions in the paper width direction of the nozzles # 1 of the nozzle rows of the respective colors are aligned. Also, the nozzles of other numbers are aligned in the paper width direction.

5A and 5B are explanatory diagrams of nozzle arrangement.
In order to increase the printing resolution, it is desirable that the nozzle pitch is narrow. On the other hand, the interval between adjacent nozzles may not be narrowed due to design constraints. Therefore, the nozzles may be arranged in a staggered pattern as shown in FIG. 5A. In the following description, even when the nozzles are arranged in a staggered pattern as shown in FIG. 5A, the description will be made assuming that the nozzles are arranged in a line as shown in FIG.
In the line printer, it is necessary to prepare a nozzle row having a length corresponding to the paper width. On the other hand, the length of the nozzle row may not be increased due to design restrictions. Therefore, as shown in FIG. 5B, nozzle rows may be added to form a nozzle row having a length corresponding to the paper width. In the following description, the case where the nozzle rows are added as shown in FIG. 5B will be described assuming that the nozzles are arranged in a row as shown in FIG. 4B for the sake of simplicity.

<Restrictions due to crosstalk between nozzles>
In the nozzle row of this embodiment, nozzles are formed with a narrow nozzle pitch of 1/1600 inch. In such a case, when ink is supplied from a supply path to a large number of nozzles in the nozzle row (when the supply path is configured in common), ink from a certain nozzle is supplied. The ejection may affect the ejection of ink from a nozzle adjacent to the nozzle (adjacent nozzle). For example, the ejection of ink from nozzle # 2 affects the ejection of ink from nozzle # 1 and nozzle # 3. The reason for this is considered that the pressure fluctuation of the ink in the nozzle # 2 when ink is ejected from the nozzle # 2 is transmitted to the nozzle # 1 and the nozzle # 3. Further, it is considered that the ink supply to the nozzle # 2 affects the ink supply to the nozzle # 1 and the nozzle # 3. In this way, mutual influence between adjacent nozzles is called “crosstalk between nozzles”.

  Due to crosstalk between nozzles, the amount of ink when a certain nozzle ejects ink may vary depending on whether or not adjacent nozzles eject ink. For example, when nozzle # 1 or nozzle # 3 does not eject ink, even if ink droplets of an ideal size are ejected from nozzle # 2, nozzle # 1 or nozzle # 3 ejects ink. There is a possibility that only a small ink droplet is ejected from the nozzle # 2.

  For this reason, in the present embodiment, when ink is ejected from a certain nozzle, it is restricted not to eject ink from an adjacent nozzle.

=== Dot Forming Method of the First Embodiment ===
<About cyan>
FIG. 6 is an explanatory diagram of the dot forming method of the first embodiment. FIG. 7A is an explanatory diagram of a dark dot forming method using the first dark cyan nozzle row in the first embodiment. FIG. 7B is an explanatory diagram of a dark dot forming method using the second dark cyan nozzle row in the first embodiment. FIG. 7C is an explanatory diagram of a light dot forming method using a light cyan nozzle row in the first embodiment. Here, attention is paid only to cyan, and description of nozzle rows of other colors is omitted. In the explanatory text, “cyan” is also omitted if it is not necessary, and for example, “dark cyan nozzle row” may be referred to as “dark nozzle row”.

  On the upper side in the figure, the first dark nozzle row (C1), the second dark nozzle row (C2), and the light nozzle row (LC) are shown. Thus, in the present embodiment, the number of light nozzle rows is smaller than the number of dark nozzle rows.

  On the lower side in the figure, dots formed on pixels arranged in a square lattice are shown. The hatched dots are dark dots. The dark dots are formed by dark ink ejected from the dark nozzle row. Dots without hatching indicate light dots. The light dots are formed by the light ink ejected from the light nozzle row. As will be described later, dark dots and light dots are formed so as to overlap each other. Therefore, in FIG. 6, white light dots are shown on the dark dots indicated by hatching.

  Here, for convenience of explaining the arrangement of dots, a state in which the most dots are formed is shown in the drawing. For this reason, when dots are formed as shown in the figure, the cyan gradation (density) expressed by the dark cyan dots and the light cyan dots is the darkest gradation. Originally, the cyan gradation differs depending on the image to be printed, and some dots are not formed according to the cyan gradation.

First, a state of forming dots (raster) arranged in the paper width direction will be described.
As shown in FIG. 7A, when the first dark nozzle row (C1) faces the odd-numbered raster, dark ink is ejected from the odd-numbered nozzles in the first dark nozzle row, and dark dots are formed in the odd-numbered pixels. It is formed. For example, when the first raster faces the first dark nozzle row (C1), dark ink is ejected from the odd nozzles of nozzles # 1, 3, 5,. Is formed. When the first dark nozzle row (C1) faces the even-numbered raster, dark ink is ejected from the even-numbered nozzles in the first dark nozzle row, and dark dots are formed in even-numbered pixels. For example, when the pixels of the second raster face the first dark nozzle row (C1), dark ink is ejected from the even nozzles of nozzles # 2, 4, 6,. Is formed. In this way, by ejecting ink from one of the odd nozzles or even nozzles and not ejecting ink from the other nozzle, ink is not ejected from adjacent nozzles. The problem of crosstalk between nozzles is avoided.

  As shown in FIG. 7B, when the second dark nozzle row (C2) faces the odd-numbered raster, dark ink is ejected from the even-numbered nozzles in the second dark nozzle row, and dark dots are formed in the even-numbered pixels. It is formed. For example, when the first raster faces the second dark nozzle row (C2), dark ink is ejected from the even nozzles of nozzles # 2, 4, 6,. Is formed. When the second dark nozzle row (C2) faces the even-numbered raster, the dark ink is ejected from the odd-numbered nozzles in the second dark nozzle row, and dark dots are formed in the odd-numbered pixels. For example, when the pixels of the second raster face the second dark nozzle row (C2), dark ink is ejected from the odd nozzles of nozzles # 1, 3, 5,. Is formed. In this way, by ejecting ink from one of the even nozzles or odd nozzles and not ejecting ink from the other nozzle, the ink is not ejected from adjacent nozzles. The problem of crosstalk between nozzles is avoided.

  As shown in FIG. 7C, when the light nozzle row (LC) faces the odd-numbered raster, light ink is ejected from the odd-numbered nozzles of the light nozzle row, and light dots are formed in the odd-numbered pixels. For example, when the pixels of the first raster face the light nozzle row (LC), light ink is ejected from the odd nozzles of nozzles # 1, 3, 5,. It is formed. Further, when the light nozzle row (LC) faces the even-numbered raster, light ink is ejected from the even-numbered nozzles of the light nozzle row, and light dots are formed at even-numbered pixels. For example, when the pixels of the second raster face the light nozzle row (LC), light ink is ejected from the even nozzles of nozzles # 2, 4, 6,. It is formed. That is, the light nozzle row (LC) forms light dots in the same arrangement as the dark dots formed by the first dark nozzle row (C1). Even in the light nozzle row, ink is ejected from one of the odd nozzles or even nozzles, and ink is not ejected from the other nozzle, so that ink is not ejected from adjacent nozzles. Therefore, the problem of crosstalk between nozzles is avoided.

  Here, attention is focused on dark dots arranged in the paper width direction. When forming dots of a certain raster (when forming dots aligned in the paper width direction), the first dark nozzle row (C1) does not use even nozzles or odd nozzles and forms dark dots every other pixel in the paper width direction. On the other hand, in the second dark nozzle row (C2), the odd nozzles or even nozzles are formed so that dark dots are formed between the dark dots formed every other pixel by the first dark nozzle row in the paper width direction. Are not used, and dark dots are formed every other pixel in the paper width direction. Thereby, the dark dots formed by the first dark nozzle row (C1) and the dark dots formed by the second dark nozzle row (C2) are alternately arranged in the paper width direction, and the dark ink is applied without a gap. Can do. If the dark dots formed by the first dark nozzle row (C1) and the dark dots formed by the second dark nozzle row (C2) are formed on the same pixel, the gap where dark ink is not applied is formed. This makes it easier to see the background of the paper when it is desired to paint with cyan.

  Next, paying attention to the relationship between dark dots and light dots arranged in the paper width direction, as can be seen from FIGS. 7A and 7C, the light dots are superimposed on the dark dots formed by the first dark nozzle row (C1). Is formed. The reason is as described below. Since the first dark nozzle row (C1) is provided on the upstream side in the transport direction from the second dark nozzle row (C2), the first dark nozzle row (C1) is more than the second dark nozzle row (C2). First, dark dots are formed. For this reason, when the light nozzle row is opposed to the pixel in which the dark dots are formed, the dark dot formed by the first dark nozzle row (C1) is darker than the dark dot formed by the second dark nozzle row (C2). The ink is absorbed by the paper and dried rather than the dots. In consideration of such a dry state of the dark dots, in the present embodiment, the light dots are formed so as to overlap the dark dots formed by the first dark nozzle row (C1). If the light dots are formed not on the first dark nozzle row (C1) but on the dark dots formed by the second dark nozzle row (C2), the ink tends to spread.

Next, how dots are formed in the carrying direction will be described.
As shown in FIG. 7A, the odd-numbered nozzles in the first dark nozzle row (C1) eject dark ink every time they face the odd-numbered raster to form dark dots every other pixel in the transport direction. To do. For example, the nozzle # 1 ejects dark ink each time it faces the first, third, fifth,... Raster, and forms dark dots every other pixel in the transport direction. In this way, the odd-numbered nozzles in the first dark nozzle row (C1) form dark dots on odd-numbered raster pixels, and dots on even-numbered raster pixels that are next to the pixels. do not do. The even-numbered nozzles in the first dark nozzle row (C1) eject dark ink every time they face the even-numbered raster, and form dark dots every other pixel in the transport direction. For example, nozzle # 2 ejects dark ink each time it faces the second, fourth, sixth,... Raster, and forms dark dots every other pixel in the transport direction. In this way, the even-numbered nozzles in the first dark nozzle row (C1) form dark dots on even-numbered raster pixels and dots on odd-numbered raster pixels that are next to the pixels. do not do.

  As shown in FIG. 7B, the odd-numbered nozzles in the second dark nozzle row (C2) discharge dark ink every time they face the even-numbered raster to form dark dots every other pixel in the transport direction. To do. For example, nozzle # 1 ejects dark ink each time it faces the second, fourth, sixth,... Raster, and forms dark dots every other pixel in the transport direction. In this way, the odd-numbered nozzles in the second dark nozzle row (C2) form dark dots on even-numbered raster pixels, and dots on odd-numbered raster pixels next to that pixel. do not do. Further, the even-numbered nozzles in the second dark nozzle row (C2) discharge dark ink every time they face the odd-numbered raster to form dark dots every other pixel in the transport direction. For example, nozzle # 2 ejects dark ink each time it faces the first, third, fifth,... Raster, and forms dark dots every other pixel in the transport direction. In this way, the even-numbered nozzles in the second dark nozzle row (C2) form dark dots at odd-numbered raster pixels and dots at even-numbered raster pixels that are next to the pixels. do not do.

  As shown in FIG. 7C, the odd-numbered nozzles in the light nozzle row (LC) discharge light ink every time they face the odd-numbered raster to form light dots every other pixel in the transport direction. For example, nozzle # 1 ejects light ink each time it faces the first, third, fifth,... Raster, and forms light dots every other pixel in the transport direction. Thus, the odd-numbered nozzles form light dots on the odd-numbered raster pixels, and do not form dots on the even-numbered raster pixels that are next to the pixels. The even-numbered nozzles in the light nozzle row (LC) discharge light ink each time they face the even-numbered raster, and form light dots every other pixel in the transport direction. For example, nozzle # 2 discharges light ink each time it faces the second, fourth, sixth,... Raster, and forms light dots every other pixel in the transport direction. That is, the light nozzle row (LC) forms light dots in the same arrangement as the dark dots formed by the first dark nozzle row (C1). In this way, even-numbered nozzles form light dots on even-numbered raster pixels and do not form dots on odd-numbered raster pixels that are next to the pixels.

  Here, attention is focused on dark dots arranged in the transport direction. When forming dots in pixels arranged in the transport direction, the first dark nozzle row (C1) forms dark dots every other pixel in the transport direction, while the second dark nozzle row (C2) The dark dots are formed every other pixel so that the dark dots are formed in the transport direction of the dark dots formed every other pixel by the nozzle row. Thereby, the dark dots formed by the first dark nozzle row (C1) and the dark dots formed by the second dark nozzle row (C2) are alternately arranged in the transport direction, and the dark ink is applied without a gap. Can do. If the dark dots formed by the first dark nozzle row (C1) and the dark dots formed by the second dark nozzle row (C2) are formed on the same pixel, the gap where dark ink is not applied is formed. This makes it easier to see the background of the paper when it is desired to paint with cyan.

  Next, paying attention to the relationship between dark dots and light dots arranged in the transport direction, as can be seen from FIGS. 7A and 7C, the light dots are superimposed on the dark dots formed by the first dark nozzle row (C1). Is formed. The reason is that when the light nozzle row is opposed to the pixel in which the dark dots are formed, the dark dot formed by the first dark nozzle row (C1) is formed by the second dark nozzle row (C2). This is because the ink is absorbed by the paper and dried rather than the dark dots.

  By the way, due to the design of the nozzle, there is a limit to the period (ejection period) in which ink droplets can be ejected continuously from the nozzle. If dots are formed in pixels that are continuous in the transport direction, the paper can be transported only by a distance corresponding to one pixel during the ejection cycle, and the transport speed is slowed down and the printing speed is slowed down. . On the other hand, in the first embodiment, since each nozzle forms a dot every other pixel in the transport direction, paper can be transported at a distance of two pixels during the ejection cycle, and the printing speed can be increased. Can be fast.

  According to the first embodiment described above, dark dots are formed in a checkered pattern by the first dark nozzle row (C1) (see FIG. 7A), and the second so that dots are formed between the dark dots. Dark dots are formed in a checkered pattern by the dark nozzle row (C2) (see FIG. 7B), and as a result, dark dots are formed in all pixels. In contrast, the light dots are only formed in a checkered pattern by one light nozzle row (see FIG. 7C), and light dots are not formed in all the pixels (see FIG. 6). The reason for this will be described below.

  The light dots are originally formed for the purpose of expressing a light color with a smooth gradation. For this reason, the light dots need only be formed sparsely in the light color portion of the printed image, and it is not necessary to form the light dots densely. To express the same density (intermediate color) as forming light dots on all pixels, if you form dark dots sparsely instead of light dots (or mix light dots and dark dots) ) And similar concentrations can be expressed. That is, the necessity for arranging light dots at a high density is low. On the other hand, the dark dot is used when expressing a dark color, and is particularly used when expressing a dark gradation by painting a pixel. If there is a gap where dark ink is not applied, the background of the paper becomes easy to see, and a sufficiently dark gradation cannot be expressed. When printing a character, dark dots are mainly used because the character portion has a high density. And in order to make the edge of a character easy to see, it is necessary to arrange dark dots with high resolution. That is, it is highly necessary to arrange dark dots at a high density. For this reason, dark dots are formed on all pixels even though light dots are formed in a checkered pattern.

  Since the light dots need only be formed in a checkered pattern and need not be formed in all pixels, in the first embodiment, the number of light nozzle rows is larger than the number of dark nozzle rows. Less. For this reason, according to the first embodiment, since the number of nozzle rows of the head unit can be reduced as compared with the case where the number of light nozzle rows is the same as the number of dark nozzle rows, the manufacturing cost can be reduced.

In the first embodiment, the size of the dark dot is larger than the size of the light dot. The reason for this will be described below.
The light dots are originally formed for the purpose of expressing a light color with a smooth gradation. For this reason, if the light dot becomes a large dot, the graininess becomes conspicuous in the light portion of the printed image, which is not desirable. For this reason, it is desirable that the light dots are small. On the other hand, if the size of the dark dots is reduced, a gap where dark ink is not applied is generated, and the background of the paper becomes easy to see even when it is desired to paint with a single cyan color. For this reason, it is advantageous that the dark dot is larger than the same size as the light dot. For this reason, in the first embodiment, the size of the dark dots is larger than the size of the light dots.

<About inks other than cyan>
Also for magenta, two dark nozzle rows (M1, M2) and one light nozzle row (LM) are prepared (see FIGS. 4A and 4B). For this reason, if the two dark nozzle rows (M1, M2) and one light nozzle row (LM) of magenta also form dots in the same manner as in the case of cyan, the same effect as cyan can be obtained. Can do. As a result, the number of nozzle rows of the head unit can be reduced as compared with the case where the number of light magenta nozzle rows is the same as the number of dark magenta nozzle rows, so that the manufacturing cost can be reduced.

  It is desirable that the pixels on which magenta light dots are formed and the pixels on which cyan light dots are formed are different pixels. That is, cyan light dots are formed in a checkered pattern, and magenta light dots are also formed in a checkered pattern so that magenta light dots are formed between cyan light dots formed in a checkered pattern. It is desirable. As a result, cyan light dots and magenta light dots are dispersed and arranged in a light portion of the print image, so that the granularity of the print image is reduced and the image quality is improved.

  For yellow, light and dark inks having different densities are not ejected. This is because the dots are less noticeable in yellow compared to cyan and magenta, so the problem of graininess is less likely (in contrast, cyan and magenta cause the problem of graininess because dots are more noticeable. Because it is easy, light ink is prepared). For this reason, only one nozzle row for discharging yellow ink is prepared (see FIGS. 4A and 4B).

  The yellow nozzle row (Y) forms dots in a checkered pattern. Accordingly, when ink is ejected from a certain nozzle, it is possible to restrict the ink from being ejected from an adjacent nozzle, and the problem of crosstalk between nozzles is avoided. Further, since each nozzle forms a dot every other pixel in the transport direction, the paper can be transported at a distance of two pixels during the ejection cycle, and the printing speed can be increased.

=== Second Embodiment ===
FIG. 8 is an explanatory diagram of the dot forming method of the second embodiment. FIG. 9A is an explanatory diagram of a dark dot forming method using the first dark cyan nozzle row in the second embodiment. FIG. 9B is an explanatory diagram of a dark dot forming method using the second dark cyan nozzle row in the second embodiment. FIG. 9C is an explanatory diagram of a light dot forming method using a light cyan nozzle row in the second embodiment.

  As shown in FIG. 9A, when the first dark nozzle row (C1) faces each raster, dark ink is ejected from odd-numbered nozzles in the first dark nozzle row, and dark dots are formed in odd-numbered pixels. The As shown in FIG. 9B, when the second dark nozzle row (C2) faces each raster, dark ink is ejected from the even-numbered nozzles of the second dark nozzle row, and dark dots are formed in even-numbered pixels. It is formed. Further, as shown in FIG. 9C, when the light nozzle row (LC) faces each raster, light ink is ejected from the odd-numbered nozzles of the light nozzle row, and light dots are formed in the odd-numbered pixels. In this way, each nozzle row discharges ink from one of the odd nozzles or even nozzles, and does not discharge ink from the other nozzle, so that ink is not discharged from adjacent nozzles. Therefore, the problem of crosstalk between nozzles is avoided.

  Also in the second embodiment, since the light dots do not have to be formed in all the pixels, the number of light nozzle rows can be made smaller than the number of dark nozzle rows. For this reason, also in the second embodiment, the number of nozzle rows of the head unit can be reduced as compared with the case where the number of light nozzle rows is the same as the number of dark nozzle rows, so that the manufacturing cost can be reduced.

  However, in the second embodiment, the first dark nozzle row and the second dark nozzle row form dots in pixels that are continuous in the transport direction. The light nozzle row also forms dots on pixels that are continuous in the transport direction. For this reason, since the paper can be transported only by a distance of one pixel during the ejection cycle, the transport speed is slower and the print speed is slower in the second embodiment than in the first embodiment. .

=== Third Embodiment ===
FIG. 10 is an explanatory diagram of the dot forming method of the third embodiment. FIG. 11A is an explanatory diagram of a dark dot forming method using the first dark cyan nozzle row in the third embodiment. FIG. 11B is an explanatory diagram of a dark dot forming method using the second dark cyan nozzle row in the third embodiment. FIG. 11C is an explanatory diagram of a light dot forming method using a light cyan nozzle row in the third embodiment.

  As shown in FIG. 11A, each nozzle of the first dark nozzle row (C1) ejects dark ink when facing an odd-numbered raster, and does not eject dark ink when facing an even-numbered raster. Dark dots are formed every raster. Further, as shown in FIG. 11B, each nozzle of the second dark nozzle row (C2) ejects dark ink when facing the even-numbered raster, and does not eject dark ink when facing the odd-numbered raster. Dark dots are formed every other raster. Further, as shown in FIG. 11C, each nozzle of the light nozzle row (LC) ejects light ink when facing an odd-numbered raster, and does not eject light ink when facing an even-numbered raster. Light dots are formed every raster. Thus, since each nozzle forms a dot every other pixel in the transport direction, paper can be transported at a distance of two pixels during the ejection cycle, and the printing speed can be increased. .

  Also in the third embodiment, since light dots do not have to be formed in all pixels, the number of light nozzle rows can be made smaller than the number of dark nozzle rows. For this reason, also in the third embodiment, since the number of nozzle rows of the head unit can be reduced as compared with the case where the number of light nozzle rows is the same as the number of dark nozzle rows, the manufacturing cost can be reduced.

  However, in the third embodiment, ink is also ejected from adjacent nozzles, which causes a problem of crosstalk between nozzles.

=== Comparative Example ===
FIG. 12A is an explanatory diagram of a dot forming method of a comparative example. FIG. 12B is an explanatory diagram of a dark dot forming method in a comparative example. FIG. 12C is an explanatory diagram of a light dot forming method in a comparative example. Again, the figure shows a state where the most dots are formed.

  The comparative example is different from the first to third embodiments in that the number of dark nozzle rows and the number of light nozzle rows is the same (in the first to third embodiments, the number of light nozzle rows is larger than the number of dark nozzle rows. Few).

  In the comparative example, when the most dots are formed (when the cyan gradation (density) is the darkest gradation), dark dots and light dots are formed in all the pixels. In order to form dots in this way, in the comparative example, dark dots are formed on all pixels by two dark nozzle rows. Specifically, the first dark nozzle row (C1) forms dark dots in a checkered pattern as shown in FIG. 12B, and the second dark nozzle row (C2) places dark dots in the remaining checkered pattern pixels. Form. Similarly, in the comparative example, the light nozzle row also forms light dots on all pixels by the two light nozzle rows. Specifically, the first light nozzle row (CL1) forms light dots in a checkered pattern as shown in FIG. 12C, and the second light nozzle row (CL2) forms dark dots on the remaining checkered pattern pixels. Form.

  In the comparative example, since it is necessary to prepare two deep nozzle rows and two light nozzle rows, the number of nozzle rows of the head unit increases, and the number of light nozzle rows is reduced as in the above-described embodiment. Compared to the case, the manufacturing cost is increased.

  In the comparative example, the number of pixels that are formed by overlapping dots of the same color (here cyan) is large. For this reason, the density of the first embodiment is set so that the cyan density when dots are formed as shown in FIG. 12A and the cyan density when dots are formed as shown in FIG. Assuming that the colors of the ink and light ink and the dark ink and light ink of the comparative example are adjusted, respectively, the change in cyan density with respect to the amount of ink applied is smaller in the comparative example than in the first embodiment. As a result, in the comparative example, the amount of cyan ink ejected when printing an image is larger than in the first embodiment described above.

=== Other Embodiments ===
Although a printer or the like as one embodiment has been described, the above embodiment is for facilitating understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<Number of nozzle rows>
In the above-described embodiment, there are two dark nozzle rows and one light nozzle row. However, the number of nozzle rows is not limited to this. For example, the number of light nozzle rows may be plural.

  FIG. 13 is an explanatory view of the arrangement of the plurality of nozzle rows on the lower surface of the head unit 40 according to another embodiment as seen from above. Fourteen nozzle rows are provided on the lower surface of the head unit 40.

  When paying attention to cyan, four dark nozzle rows and two light nozzle rows are provided. Although not shown here, the first dark nozzle row (C1) and the second dark nozzle row (C2) of this embodiment are dark dots formed by the first dark nozzle row (C1) of the first embodiment, respectively. Half of (see FIG. 7A) is formed, and the two dark nozzle rows of this embodiment form checkered dark dots formed by the first dark nozzle row (C1) of the first embodiment. . Similarly, the two dark nozzle rows of the third dark nozzle row (C3) and the fourth dark nozzle row (C4) of this embodiment form the second dark nozzle row (C1) of the first embodiment. A checkered pattern of dark dots (see FIG. 7B) is formed. Further, the two light nozzle rows of the first light nozzle row (LC1) and the second light nozzle row (LC2) of this embodiment are in a checkered pattern shape formed by the light nozzle row (LC) of the first embodiment. Light dots (see FIG. 7C) are formed. Each light nozzle row forms light dots in the same arrangement as the dark dots formed by the first dark nozzle row (C1) and the second dark nozzle row.

  Also in such an embodiment, since the light dots need not be formed in all the pixels, the number of light nozzle rows can be made smaller than the number of dark nozzle rows. For this reason, since the number of nozzle rows of the head unit can be reduced as compared with the case where the number of light nozzle rows is the same as the number of dark nozzle rows, the manufacturing cost can be reduced.

<About line printers>
In the above-described embodiment, a line printer that performs printing by discharging ink from a nozzle row having a length corresponding to the width of the paper while conveying the paper is described. However, the technique is not limited to such a printer, and the same technique as that of the present embodiment can be applied to another printer.

FIG. 14A is an explanatory diagram of another printer. This printer is provided with a carriage unit 30 including a carriage 31 and a carriage motor 32. A head 41 is provided under the carriage.
FIG. 14B is an explanatory view of the arrangement of the plurality of nozzle rows on the lower surface of the head 41 as seen from above. Seven nozzle rows are arranged on the lower surface of the head 41 along the moving direction. When paying attention to cyan, there are two dark nozzle rows but one light nozzle row. Each nozzle row includes a plurality of nozzles arranged at a predetermined nozzle pitch along the transport direction.

  The printer controller (not shown) controls the carriage unit 30, the head unit including the head 41, and the transport unit, and performs a dot forming operation for ejecting ink from the nozzle rows moving in the moving direction, The printing is performed by alternately repeating the carrying operation for carrying the sheet in the carrying direction.

  FIG. 15 is an explanatory diagram of a dot forming method by this printer. The figure shows a dot forming operation performed during the carrying operation. As shown in the drawing, the first dark nozzle row (C1) forms dark dots in a checkered pattern, and the second dark nozzle row (C2) is formed in a checkered pattern by the first dark nozzle row (C1). The dark dots are formed in a checkered pattern between the dark dots, and the light nozzle row (LC) forms the light dots in a checkered pattern. Even if it does in this way, the effect similar to the above-mentioned 1st Embodiment can be acquired.

<Relationship between cyan and magenta light dots>
In the above-described embodiment, the pixels on which magenta light dots are formed and the pixels on which cyan light dots are formed are different pixels, but the present invention is not limited to this. The pixel on which the magenta light dot is formed and the pixel on which the cyan light dot is formed may be the same pixel. In this way, if the positions of the light dots are shifted from the ideal position, the deterioration of the graininess is less noticeable in the light part of the printed image. Further, in the dark portion of the printed image, if cyan light dots are not formed in pixels where magenta light dots are formed, the pixels are color-shifted to the magenta side. In addition, if cyan light dots are formed in a pixel where a magenta light dot is not formed, the pixel is color-shifted to the cyan side. If a certain pixel shifts to the magenta side and another pixel shifts to the cyan side, the image quality deteriorates when black or gray is expressed. For this reason, the magenta light dot and the cyan light dot may be arranged in the same pixel. Thereby, when black or gray is expressed, the color shift is reduced and the image quality is improved.

  Here, when cyan and magenta light dots are arranged in the same pixel, it is desirable that yellow dots are also arranged in the same pixel as cyan and magenta light dots. Pixels with cyan and magenta light dots are darker than cyan and magenta compared to pixels without light dots, so when you create gray by forming yellow dots on such pixels In addition, color misregistration can be reduced. If a yellow dot is placed on a pixel where cyan or magenta light dots are not placed, the pixel where the yellow dot is placed will be misaligned to the yellow side, and a pixel where cyan or magenta light dots will be placed on the cyan side Or color shifts to the magenta side.

<About liquid ejection device>
In the above-described embodiment, an ink jet printer is described as an example of a liquid ejecting apparatus that ejects liquid. However, the liquid ejecting apparatus is not limited to a printer. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied. These methods and manufacturing methods are also within the scope of application.

<Nozzle>
In the above-described embodiment, ink is ejected using a heater. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of ejecting ink using a piezo element may be used.

It is explanatory drawing which showed the external appearance structure of the printing system. 1 is a block diagram of an overall configuration of a printer 1. FIG. FIG. 3A is a cross-sectional view of the printer 1. FIG. 3B is a perspective view for explaining a conveyance process and a dot formation process of the printer 1. FIG. 4A is an explanatory view of the arrangement of the plurality of nozzle rows on the lower surface of the head unit 40 as seen from above. FIG. 4B is an enlarged view of a portion X surrounded by a dotted line in FIG. 4A, and is an enlarged view of the left end of each color nozzle row. 5A and 5B are explanatory diagrams of nozzle arrangement. It is explanatory drawing of the dot formation method of 1st Embodiment. It is explanatory drawing of the formation method of the dark dot by the 1st dark cyan nozzle row in 1st Embodiment. It is explanatory drawing of the formation method of the dark dot by the 2nd dark cyan nozzle row in 1st Embodiment. It is explanatory drawing of the formation method of the light dot by the light cyan nozzle row | line | column in 1st Embodiment. It is explanatory drawing of the dot formation method of 2nd Embodiment. It is explanatory drawing of the formation method of the dark dot by the 1st dark cyan nozzle row in 2nd Embodiment. It is explanatory drawing of the formation method of the dark dot by the 2nd dark cyan nozzle row in 2nd Embodiment. It is explanatory drawing of the formation method of the light dot by the light cyan nozzle row | line | column in 2nd Embodiment. It is explanatory drawing of the dot formation method of 3rd Embodiment. It is explanatory drawing of the formation method of the dark dot by the 1st dark cyan nozzle row in 3rd Embodiment. It is explanatory drawing of the formation method of the dark dot by the 2nd dark cyan nozzle row in 3rd Embodiment. It is explanatory drawing of the formation method of the light dot by the light cyan nozzle row | line | column in 3rd Embodiment. It is explanatory drawing of the dot formation method of a comparative example. It is explanatory drawing of the dark dot formation method in a comparative example. It is explanatory drawing of the light dot formation method in a comparative example. It is explanatory drawing which permeate | transmitted the arrangement | positioning of the several nozzle row in the lower surface of the head unit 40 in another embodiment from the top. FIG. 14A is an explanatory diagram of another printer. FIG. 14B is an explanatory view of the arrangement of the plurality of nozzle rows on the lower surface of the head 41 as seen from above. It is explanatory drawing of the dot formation method by another printer.

Explanation of symbols

1 printer,
20 transport unit, 21 paper feed roller,
23A upstream conveying roller, 23B downstream conveying roller, 24 belt,
30 Carriage unit, 31 Carriage, 32 Carriage motor,
40 head units, 41 heads,
60 controller, 61 interface unit, 62 CPU,
63 memory, 64 unit control circuit 100 printing system, 110 computer,
120 display device, 130 input device, 140 recording / reproducing device

Claims (7)

(1) A plurality of dark nozzle rows having a plurality of nozzles in a predetermined direction and discharging the first liquid;
(2) having a plurality of nozzles in the predetermined direction, discharging a second liquid having the same color as the first liquid and having a light density, and having a number of light nozzle rows smaller than the number of the dark nozzle rows;
(3) Using the plurality of dark nozzle rows to form dark dots on pixels on the medium,
A controller that forms light dots in a smaller number of pixels than the number of pixels in which the dark dots are formed using a number of the light nozzle rows smaller than the number of the dark nozzle rows;
A liquid ejection apparatus comprising: The liquid ejection device according to claim 1,
A liquid ejecting apparatus, wherein when a liquid is ejected from a certain nozzle, the liquid is not ejected from a nozzle adjacent to the nozzle. The liquid ejection device according to claim 1 or 2, wherein
When a certain nozzle forms a dot in a certain pixel, the nozzle does not form a dot in a pixel that faces the next pixel. The liquid ejection device according to any one of claims 1 to 3,
As the plurality of dark nozzle rows, there are a first dark nozzle row and a second dark nozzle row,
After the first dark nozzle row forms the dark dot, the second dark nozzle row forms the dark dot,
The light nozzle row forms the light dot in a pixel in which the dark dot is formed by the first dark nozzle row, and forms the light dot in a pixel in which the dark dot is formed by the second dark nozzle row. A liquid ejecting apparatus that does not. A liquid ejection apparatus according to any one of claims 1 to 4,
The liquid ejecting apparatus according to claim 1, wherein the dark dot is a dot larger than the light dot. A liquid ejection device according to any one of claims 1 to 5,
As the plurality of dark nozzle rows, there are a plurality of dark cyan nozzle rows that form dark cyan dots by discharging dark cyan ink,
As the light nozzle row, there is a light cyan nozzle row that discharges light cyan ink to form a light cyan dot,
The liquid ejection device includes:
A plurality of dark magenta nozzle rows having a plurality of nozzles in a predetermined direction and discharging dark magenta ink to form dark magenta dots;
A light magenta nozzle array having a plurality of nozzle arrays in a predetermined direction and ejecting light magenta ink having a lighter density than the dark magenta ink to form light magenta dots, the number of the dark magenta nozzle arrays A small number of light magenta nozzle rows,
Further comprising
The liquid ejecting apparatus, wherein the light magenta dots are arranged between the light cyan dots. Discharging the first liquid from the dark nozzle row having a plurality of nozzles in a predetermined direction;
A liquid ejection method for ejecting a second liquid having the same color as the first liquid and a light concentration from a light nozzle row having a plurality of nozzles in the predetermined direction,
Using the plurality of dark nozzle rows to form dark dots on the pixels on the medium,
A liquid ejection method, wherein light dots are formed in a smaller number of pixels than the number of pixels in which the dark dots are formed by using a smaller number of light nozzle rows than the number of dark nozzle rows.

Images