JP5257032B2 - Printing device - Google Patents

Description

  The present invention relates to a printing apparatus.

  In an inkjet printer as a printing apparatus, a dot forming operation for forming dots on a medium such as paper by ejecting ink droplets from nozzles of a print head that moves in a predetermined movement direction, and transporting the medium across the movement direction An image is printed by alternately repeating a transport operation for transporting in the direction and arranging a plurality of dot rows (hereinafter also referred to as raster lines) along the moving direction in the transport direction on the medium.

Further, in the print head, a dark ink nozzle row that discharges dark ink droplets such as black ink and magenta ink, and a light ink nozzle row that discharges light ink droplets such as light black ink and light magenta ink, and the like. There is something with. In some cases, these light ink droplets and dark ink droplets are overlapped to form dots (see Patent Document 1).
JP 2005-193463 A

However, in that case, there is a possibility that the gloss of the dots changes depending on the landing order of the ink droplets. That is, the glossiness of the dots is more susceptible to the influence of the succeeding ink droplet than the ink droplet that has landed in advance, for example, the glossiness is higher when the succeeding ink droplet is a light ink, When the ink droplets are dark ink, the gloss tends to be low.
The effect of the gloss change due to the difference in the landing order is manifested as gloss unevenness in the printed image during bidirectional printing.

Specifically, in general, the light ink nozzle row and the dark ink nozzle row are arranged adjacent to each other in the moving direction of the print head. Therefore, when landing in the order of dark ink droplets → light ink droplets in the forward path of bidirectional printing, the landing order in the return path is reversed, that is, landed in the order of light ink → dark ink. Become. Then, the raster line formed in the forward path becomes highly glossy, and the raster line formed in the backward path becomes low in gloss. That is, a difference in gloss occurs between these raster lines, and the final printed image is completed. Some gloss unevenness (gloss banding) occurs in the moving direction.
Such gloss unevenness tends to be particularly noticeable in a dark color portion of a printed image, and black ink is frequently used in the dark color portion. That is, if the uneven glossiness associated with the black ink can be suppressed, the uneven glossiness of the image can be effectively reduced.

 The present invention has been made in view of the above problems, and an object thereof is to realize a printing apparatus that can effectively reduce uneven glossiness of an image printed on a medium.

The main invention for achieving the object is as follows:
A head having a plurality of nozzle rows in a crossing direction intersecting the transport direction, a nozzle row in which a plurality of nozzles are arranged along the transport direction of the medium;
A moving mechanism for reciprocating the head in the intersecting direction with respect to the medium,
A printing apparatus in which ink is ejected from the nozzle toward the medium while the head is moving in the forward and backward paths in the intersecting direction,
The head includes a black ink nozzle array to discharge black ink, or the first write discharges the first light black ink lighter than black ink black ink nozzle array and the second light than the first light black ink A second light black ink nozzle row for discharging light black ink ,
In the printing apparatus, the black ink nozzle row is disposed between the first light black ink nozzle row and the second light black ink nozzle row in the intersecting direction.

  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 apparent from the description of the present specification and the accompanying drawings.

A head having a plurality of nozzle rows in a crossing direction intersecting the transport direction, a nozzle row in which a plurality of nozzles are arranged along the transport direction of the medium;
A moving mechanism for reciprocating the head in the intersecting direction with respect to the medium,
A printing apparatus in which ink is ejected from the nozzle toward the medium while the head is moving in the forward and backward paths in the intersecting direction,
The head includes a black ink nozzle row that ejects black ink droplets, a first color light ink nozzle row that ejects light ink droplets of the first color that is lighter than the dark ink of the first color, and a dark color of the second color. A second color light ink nozzle row that discharges the light ink droplets of the second color lighter than ink,
The printing apparatus, wherein the black ink nozzle row is disposed between the first color light ink nozzle row and the second color light ink nozzle row in the intersecting direction.

According to such a printing apparatus, when a light ink droplet is superimposed on a black ink droplet to form a dot, the ink droplet is ejected in the order of the black ink nozzle row → the first color light ink nozzle row in the forward path. In the return path, ink droplets are ejected in the order of the black ink nozzle row → the second light ink nozzle row. That is, in both the forward path and the backward path, a light ink droplet is ejected after the black ink droplet and overlaps on the medium to form dots.
Therefore, the gloss difference between the dark color raster line formed in the forward pass and the dark color raster line formed in the return pass is suppressed, and as a result, the gloss unevenness in the dark color portion in the image is effectively reduced.

In such a printing apparatus,
The first color and the second color are black;
The first color light ink nozzle row is a first light black ink nozzle row that discharges first light black ink droplets lighter than the black ink droplets;
The second color light ink nozzle row is preferably a second light black ink nozzle row for discharging a second light black ink droplet lighter than the first light black ink droplet.

According to such a printing apparatus, ink droplets are ejected in the order of the black ink nozzle row → first light black ink nozzle row in the forward path, and in the order of black ink nozzle row → second light black ink nozzle array in the backward path. Ink droplets are ejected. That is, in both the forward path and the backward path, a light ink droplet related to the black ink is ejected after the black ink droplet and overlaps on the medium to form dots.
Therefore, the gloss difference between the dark color raster line formed in the forward pass and the dark color raster line formed in the return pass is suppressed, and as a result, the gloss unevenness in the dark color portion in the image is effectively reduced.

In such a printing apparatus,
The nozzles of the nozzle row are formed at a predetermined pitch in the transport direction,
Some of the nozzle rows of the nozzle rows are shifted from the reference nozzle row by a predetermined amount in the transport direction.
In the black ink nozzle row, the first light black ink nozzle row, and the second light black ink nozzle row, the positions of the nozzles are preferably aligned with respect to the transport direction.

  According to such a printing apparatus, since the black ink droplet and the first light black ink droplet ejected in the forward path land at the same position in the transport direction, it is possible to form dots by overlapping these ink droplets. it can. Further, since the black ink droplet and the second light black ink droplet ejected in the return path land at the same position in the transport direction, these ink droplets can be overlapped to form a dot. Therefore, it is possible to reliably suppress the gloss difference between the dark color raster line formed in the forward path and the dark color raster line formed in the backward path.

In such a printing apparatus,
The first color is cyan, the second color is magenta;
The head includes a first color dark ink nozzle row that discharges the dark ink droplet of the first color, and a second color dark ink nozzle row that discharges the dark ink droplet of the second color,
The black ink nozzle row, the first color dark ink nozzle row, and the second color dark ink nozzle row are between the first color light ink nozzle row and the second color light ink nozzle row in the intersecting direction. It is desirable to be disposed between.

  According to such a printing apparatus, the black ink nozzle row, the first color dark ink nozzle row, and the second color dark ink nozzle row are the first color light ink nozzle row and the second color with respect to the intersecting direction. The first color is cyan and the second color is magenta. Therefore, when the black ink droplet and the light cyan ink droplet are overlapped to form a dot in the forward pass, and the black ink droplet and the light magenta ink droplet are overlapped to form a dot in the return pass, a gloss difference between these dots is formed. As a result, the gloss unevenness of the dark color portion in the image is effectively reduced.

In such a printing apparatus,
In the forward path, the light ink droplets of the first color overlap and land at the positions where the black ink droplets land on the medium, and dots are formed on the medium.
In the return path, the second color light ink droplets overlap and land at the position where the black ink droplets land on the medium, and dots are formed on the medium.
The dot formation position on the forward path and the dot formation position on the return path are preferably different with respect to the transport direction.
According to such a printing apparatus, the difference in gloss between the dots formed in the forward pass and the dots formed in the return pass is suppressed, and as a result, the gloss unevenness in the dark part of the image is effectively reduced.

In such a printing apparatus,
It is desirable that a transport mechanism that transports the medium in the transport direction is provided between the movement operation of the head in the forward path and the movement operation of the head in the return path.
According to such a printing apparatus, the dot formation position on the forward path and the dot formation position on the return path can be made different with respect to the transport direction.

=== Configuration of Printing Apparatus 1 ===
Hereinafter, as a printing apparatus 1 according to the present embodiment, a serial ink jet printer (hereinafter referred to as printer 1) will be described as an example.
FIG. 1 is a block diagram of the system configuration of the printer 1. 2A is a perspective view of the internal configuration of the printer 1, and FIG. 2B is a longitudinal sectional view thereof.

 The printer 1 is used by being connected to a computer 60 that is an external device. The printer 1 that has received the print data from the computer 60 controls each unit (conveyance unit 20, carriage unit 30, head unit 40) by the controller 10, and forms an image on a sheet S as a medium. At that time, the situation in the printer 1 is monitored by the detector group 50, and the controller 10 controls each unit 20, 30, 40 based on the detection result.

  The controller 10 includes an interface unit 11, a CPU 12, and a memory 13. The interface unit 11 transmits and receives data between the computer 60 and the printer 1. The CPU 12 is an arithmetic processing unit that controls the entire printer 1, and controls each unit 20, 30, 40 via the unit control circuit 14. The memory 13 secures an area for storing the program of the CPU 12, a work area, and the like.

  The transport unit 20 (corresponding to a transport mechanism) feeds the paper S to a printable position and transports the paper S by a predetermined transport amount in the transport direction during printing. The paper feed roller 21 and the transport motor 22 are transported. A transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 sends the paper S to be printed to the transport roller 23. When the paper detection sensor 51, which is one of the detector groups 50, detects the leading edge of the paper S sent toward the transport roller 23, the controller 10 rotates the transport roller 23 to move the paper S to the print start position. Position to. When the paper S is positioned at the print start position, at least some of the nozzles on the lower surface of the print head 41 face the paper S. The platen 24 is provided at a position that can face the lower surface of the print head 41, and supports the paper S being printed from below.

  The carriage unit 30 reciprocates the print head 41 in an intersecting direction (hereinafter referred to as a carriage movement direction) intersecting the transport direction. The carriage 32 on which the print head 41 is mounted, a guide rail 36, and a carriage motor 33. And a pulley 34 and a timing belt 35. The guide rail 36 guides the carriage 32 so as to be capable of reciprocating along the carriage movement direction. The timing belt 35 is connected to the carriage motor 33 via the pulley 34 and a part of the timing belt 35 is connected to the carriage 32, and the carriage 32 is reciprocated in the movement direction by the rotation of the carriage motor 33. As a result, the print head 41 is reciprocated in the carriage movement direction with respect to the paper S.

  The head unit 40 includes a print head 41 for ejecting ink droplets onto the paper S. A plurality of nozzles are provided on the lower surface of the print head 41, and each nozzle is provided with an ink chamber containing ink and a piezo element as a drive element for changing the volume of the ink chamber to eject ink droplets. It has been. The nozzle arrangement will be described later.

  In the serial printer 1 having such a configuration, a dot forming operation for intermittently ejecting ink droplets from the print head 41 moving in the carriage movement direction to form dots on the paper S, and transporting the paper S are performed. The conveyance operation of conveying in the direction is repeated alternately. By doing so, the dot row is formed at a position different from the dot row (raster line) formed by the previous dot forming operation in the transport direction, and the image is completed. The printer 1 can perform bidirectional printing, that is, forms an image by ejecting ink droplets toward the paper S in the forward and backward paths in the carriage movement direction. During the forward and backward dot forming operations, the sheet S is transported as described above, whereby raster lines are formed at different positions in the transport direction in the forward and backward dot forming operations.

=== Regarding the nozzle arrangement of the print head 41 ===
FIG. 3 is a nozzle arrangement diagram of the print head 41. On the lower surface of the print head 41, black (K), light black (LK), light light black (LLK), cyan (C), light cyan (LC), magenta (M), light magenta (LM), yellow (Y ), A nozzle row N composed of a plurality of (for example, 180) nozzles is provided. The nozzles of each nozzle row N are linearly arranged at a predetermined nozzle pitch P (for example, 180 dpi) along the transport direction of the paper S. The nozzle rows N are arranged in parallel to each other with an interval in the carriage movement direction. Further, in any nozzle row N, the positions of the nozzles in the transport direction are aligned with each other. Note that light black is lighter than black, and light light black is lighter than light black. Light cyan is lighter than cyan, and light magenta is lighter than magenta.

  Here, according to the present embodiment, the black ink nozzle row N (K) is sandwiched between the light black ink nozzle row N (LK) and the light light black ink nozzle row N (LLK) in the carriage movement direction. Are arranged. This is for suppressing uneven glossiness of an image formed by bidirectional printing. Details are as follows.

  For example, as in the print head 41 of the comparative example of FIG. 4, the black ink nozzle row N (K) is more moved in the carriage direction than the light black ink nozzle row N (LK) and the light light black ink nozzle row N (LLK). When a dot is formed by overlaying a light black ink droplet or a light light black ink droplet on a black ink droplet in order to print a dark-colored image using the print head 41. As shown in FIG. 5A, in the forward path of bidirectional printing, the ink is landed in the order of black ink droplets → light black ink droplets (or light light black ink droplets). Landed in the order of ink droplets (or light light black ink droplets) → black ink droplets.

 Then, since the subsequent ink droplets are light-colored light black ink droplets in the forward path, the glossiness of the dots formed in the forward path is high, but in the backward path, the subsequent ink droplets are dark black ink droplets. Therefore, the gloss of dots formed on the return path is low. In other words, the raster line formed in the forward path has high gloss, the raster line formed in the backward path has low gloss, and in the final printed image, gloss unevenness (gloss in the carriage movement direction) Banding).

 On the other hand, as in the present embodiment of FIG. 3, the black ink nozzle row N (K) has the light black ink nozzle row N (LK) and the light light black ink nozzle row N (LLK) in the carriage movement direction. 6A, as shown in FIG. 6A, the ink is landed in the order of black ink droplets → light light black ink droplets in the forward path of bidirectional printing, and in the return path, black ink droplets → light. Landed in the order of black ink drops. That is, in both the forward path and the backward path, a light ink droplet (light black ink droplet or light light black ink droplet) is ejected after the black ink droplet, and dots are formed on the paper S so as to overlap. Therefore, the gloss of both the dark raster line formed in the forward path and the dark raster line formed in the backward path is increased, and the gloss difference between these rice lines is decreased, and as a result, in the image. Gloss unevenness in dark parts is effectively reduced.

 In the description of FIGS. 5A to 6B described above, a so-called band printing, that is, a printing method for printing an image portion corresponding to the head height (= number of nozzles × nozzle pitch P) for each dot forming operation is illustrated. The printing method is not limited to this, and so-called interlaced printing or the like may be used. Incidentally, interlaced printing is a printing method in which an image is printed by forming dot rows at a pitch smaller than the nozzle pitch P. Among them, there is a printing method in which a dot row formed by a nozzle different from the nozzle is sandwiched between a pair of dot rows formed by nozzles adjacent to each other in one dot forming operation. is there.

  FIG. 7 is an example of a dot generation rate table according to the present embodiment. This dot generation rate table is used in halftone processing performed when the computer 60 generates print data. In the halftone process, CMYK image data having color values converted from RGB image data and having gradation values in multiple levels (for example, 256 levels) is converted into gradation values in small levels that can be expressed by the printer 1 for each pixel. For example, based on the dot generation rate table of FIG. 7, there are four stages of “dot non-formation”, “small dot formation”, “medium dot formation”, and “large dot formation”. Convert to any one of gradations. The dot generation rate on the vertical axis is the conversion probability at that time, and the gradation value on the horizontal axis is a multi-level (256 levels) gradation value before conversion.

  Here, as shown in FIG. 7, the dot rate generation table relating to K (black) of the present embodiment includes a dot generation rate related to black, a dot generation rate related to light black, and a dot generation rate related to light light black. In addition, the generation ratio of small dots and medium dots of light black and light light black ink is a positive value over the entire range of gradation values from 0 to 255. Therefore, the light black ink droplet is ejected after the black ink droplet in the above-described outbound path, and the light light black ink droplet is ejected after the black ink droplet in the inbound path, that is, either the outbound path or the inbound path of bidirectional printing. In this case, the light ink droplet is ejected after the black ink droplet.

  In the example of FIG. 3, the light black ink nozzle row N (LK) and the light light black ink nozzle row N (LLK) are located at both ends in the carriage movement direction. , N (LLK) is not limited to this as long as the black ink nozzle row N (K) is sandwiched between them, that is, both the nozzle rows N (LK) and N (LLK) are arranged at positions other than both ends. May be.

 In the embodiment of FIG. 3, when attention is paid to the nozzle row N (K), the nozzle row N (LK), and the nozzle row N (LLK), N (K) is changed to N (LK) and N ( LLK) are positioned in the order of being sandwiched between them, and in the monochrome printing mode in which printing is performed using these three nozzle rows, there is an effect that the difference in gloss can be reduced. However, even in a printing mode in which printing is performed using nozzle rows other than these three nozzle rows in combination, the same effect can be obtained as long as the printing mode mainly uses these three nozzle rows. Further, even in a print mode in which nozzle rows other than these three nozzle rows are used in combination, there is an effect of reducing a gloss difference caused by black ink (K, LK, LLK).

  Further, in the embodiment of FIG. 3, when attention is paid to the magenta ink and the cyan ink of other nozzle rows, the nozzle row N (M) and the nozzle row N (C) are changed to the nozzle row N (LC) and the nozzle row. Since the order is also sandwiched between the columns N (LM), the effect of reducing the gloss difference caused by the magenta ink and the cyan ink can also be obtained in the color printing mode using these. However, as described above, the difference in gloss caused by the black ink can be prevented by setting at least the black ink nozzle row in the order shown in FIG.

=== Regarding the Other Nozzle Arrangement of the Print Head 41 ===
FIG. 8 is an explanatory diagram of a first modification of the nozzle arrangement. In the above-described embodiment (FIG. 3), the positions of the nozzle rows N of the print head 41 in the transport direction of the nozzles are aligned over all the nozzle rows N. In the first modification of FIG. It is different in that it is. That is, in the illustrated example, the predetermined nozzle row N is shifted from the reference nozzle row N by a predetermined amount (for example, half the nozzle pitch P) in the transport direction.

  However, at least the black ink nozzle row N (K), the light black ink nozzle row N (LK), and the light light black ink nozzle row N (LLK) that should form dots by overlapping ink droplets are transported. It is preferable to align the nozzle positions in the direction (see FIG. 8). By doing so, gloss unevenness when dots are formed with black ink during bidirectional printing can be surely reduced. For nozzle rows other than black, the order is such that N (M) and N (C) are sandwiched between N (LC) and N (LM), and uneven gloss due to these inks can be reduced. The nozzles of the black ink nozzle row and the magenta ink cyan ink nozzle row are displaced from each other in the transport direction by a distance that is half the nozzle pitch P of the nozzle row. In the forming operation, these ink dots are formed on the same raster line. Since the other points are generally the same as those in the above-described embodiment, the description thereof is omitted.

 FIG. 9 is an explanatory diagram of a second modification of the nozzle arrangement. In the above-described embodiment (FIG. 3), as the nozzle row N, the black ink nozzle row N (K), the light black ink nozzle row N (LK), the light light black ink nozzle row N (LLK), and the cyan ink nozzle row N (C), a light cyan ink nozzle row N (LC), a magenta ink nozzle row N (M), a light magenta ink nozzle row N (LM), and a yellow ink nozzle row N (Y) were provided. The second modification 9 is different in that the light black ink nozzle row N (LK) and the light light black ink nozzle row N (LLK) are not provided, and black dots are formed in accordance with this difference. At this time, the light magenta ink droplet and the light magenta ink droplet are superimposed on the black ink droplet.

Therefore, the black ink nozzle row N (K) according to the second modified example is disposed between the light cyan ink nozzle row N (LC) and the light magenta ink nozzle row N (LM) in the carriage movement direction. Has been. As a result, in the forward path of bidirectional printing, the ink is landed in the order of black ink droplets → light cyan ink droplets. The gloss difference between the raster line and the raster line formed in the return path is suppressed.
Therefore, the difference in gloss is reduced in the color printing mode in which printing is performed using these nozzle rows.

  As in the embodiment of FIG. 7, a predetermined amount of light cyan ink is used even in the high gradation value region of cyan so that light cyan ink and light magenta ink are used even when printing a high density image. It is preferable to set a dot generation rate of a predetermined amount of light magenta ink even in a high tone value region of magenta color. This also applies to the embodiments of FIGS. 3 and 8.

=== Other Embodiments ===
The above-described embodiments are for facilitating the understanding of the present invention, and are 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.

  In the above-described embodiment, the piezoelectric effect method using a piezo element is exemplified as the ink discharge method. However, the present invention is not limited to this. For example, the ink is heated from the nozzles by bubbles generated in the ink. A thermal jet method may be used.

1 is a block diagram of a system configuration of a printer 1. FIG. 2A is a perspective view of the internal configuration of the printer 1, and FIG. 2B is a cross-sectional view thereof. FIG. 4 is a nozzle arrangement diagram of the print head 41. It is a nozzle arrangement figure of a comparative example. FIG. 5A is an explanatory diagram of the gloss of the image portion printed in the forward path in the case of the nozzle arrangement of the comparative example, and FIG. 5B is an explanatory diagram of the gloss of the image portion printed in the same pass. FIG. 6A is an explanatory diagram of the gloss of the image portion printed in the forward path in the case of the nozzle arrangement according to the present embodiment, and FIG. 6B is an explanatory diagram of the gloss of the image portion printed in the backward path. It is an example of the dot production rate table concerning this embodiment. It is explanatory drawing of the 1st modification of a nozzle arrangement | sequence. It is explanatory drawing of the 2nd modification of a nozzle arrangement.

Explanation of symbols

1 Inkjet printer (printing device), 10 controller,
11 interface section, 13 memory, 14 unit control circuit,
20 transport unit, 21 paper feed roller, 22 transport motor,
23 transport roller, 24 platen, 25 discharge roller,
30 Carriage unit, 32 Carriage, 33 Carriage motor,
34 pulley, 35 timing belt, 36 guide rail,
40 head units, 41 print heads,
50 detector groups, 51 paper detection sensors, 60 computers,
S paper (medium), N nozzle row,
N (K) black ink nozzle row,
N (LK) light black ink nozzle row,
N (LLK) light light black ink nozzle row,
N (C) Cyan ink nozzle row,
N (LC) light cyan ink nozzle row,
N (M) Magenta ink nozzle row,
N (LM) light magenta ink nozzle row,
N (Y) Yellow ink nozzle row

Claims (4)

A head having a plurality of nozzle rows in a crossing direction intersecting the transport direction, a nozzle row in which a plurality of nozzles are arranged along the transport direction of the medium;
A moving mechanism for reciprocating the head in the intersecting direction with respect to the medium,
A printing apparatus in which ink is ejected from the nozzle toward the medium while the head is moving in the forward and backward paths in the intersecting direction,
The head includes a black ink nozzle array to discharge black ink, or the first write discharges the first light black ink lighter than black ink black ink nozzle array and the second light than the first light black ink A second light black ink nozzle row for discharging light black ink ,
The printing apparatus according to claim 1, wherein the black ink nozzle row is disposed between the first light black ink nozzle row and the second light black ink nozzle row in the intersecting direction. The printing apparatus according to claim 1 ,
The nozzles of the nozzle row are formed at a predetermined pitch in the transport direction,
Some of the nozzle rows of the nozzle rows are shifted by a predetermined amount in the transport direction with respect to the positions of the nozzles .
The printing apparatus, wherein the black ink nozzle row, the first light black ink nozzle row, and the second light black ink nozzle row are aligned with each other in the transport direction. The printing apparatus according to claim 1 or 2,
In the forward path, to the position where the black-in click landed in the medium, dots are formed on the first light black ink is the medium landed overlap,
And in the return path, to the position where the black-in click landed in the medium, dots are formed on the second light black ink is the medium landed overlap,
The printing apparatus, wherein the dot formation position on the forward path and the dot formation position on the return path are different with respect to the transport direction. The printing apparatus according to claim 3,
A printing apparatus comprising: a transport mechanism that transports the medium in the transport direction between the forward movement operation of the head and the backward movement operation of the head.