Ink jet recorder

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Field of Technology to which the Invention belongs]

The present invention relates to a color mixing prevention technique for an inkjet recording apparatus that performs color printing by ejecting ink droplets of different colors from a plurality of nozzle opening rows.

【0002】

[Conventional technology]

An inkjet recording device capable of color printing is equipped with an inkjet recording head having a plurality of rows of ink droplets of different colors independently ejected, usually four or more rows of nozzle openings, mounted on a carriage, and the recording head is mounted. It is configured to repeat the operation of ejecting ink droplets corresponding to the print data while moving in the main scanning direction and feeding the print position by a predetermined pitch at the stage when printing for one scan is completed. ..

【0003】

Since the print quality of color printing is greatly affected by the position accuracy of each dot that constitutes a pixel, in a recording device, at least the nozzle openings 2, 2, 2, 2 of each nozzle opening row that ejects ink droplets during color printing ... As shown in Fig. 10 (a), .. is arranged so that they are located on the same scanning line between each color to ensure the relative position accuracy of the dots formed on the recording medium. ..

【0004】

However, in color printing, since dots with inks of different colors are printed, there is a disadvantage that they are easily mixed with inks of other colors. In order to solve such a problem, as seen in Japanese Patent Application Laid-Open No. 4-118250, nozzle opening rows 2, 2, 2 .... That eject different ink droplets are provided at intervals of 4 printing pitches. Using an inkjet recording head (Fig. 10 (b)) in which C, M, Y, and K are shifted by one print pitch between the nozzle opening rows, dots of ink of each color formed by one main scan are formed. A printing method has been proposed to prevent color mixing by avoiding simultaneous formation on the same line.

【0005】

[Problems to be Solved by the Invention]

However, in addition to the problem of partial color mixing because the dots forming adjacent lines come into contact with the dots of other lines during the same scanning, 1 for forming dots of other colors in each line. Since two types of paper feed are required, one for the print line and the other for the large print height of the recording head for changing the print area, the paper feed error varies, resulting in banding and banding. There is a problem that white spots are caused and as a result, improvement in print quality cannot be expected. The present invention has been made in view of such a problem, and an object of the present invention is to prevent color mixing of different ink droplets and perform color printing with high print quality without causing banding or whiteout. It is to provide an inkjet recording apparatus capable of capable.

【0006】

[Means for solving problems]

In order to solve such a problem, in the present invention, an inkjet recording head in which a plurality of nozzle opening rows for independently ejecting ink droplets of different inks are arranged in the main scanning direction is moved in the main scanning direction. In an inkjet recording device that feeds a recording medium on paper in the sub-scanning direction when one scanning is completed, the recording head has a plurality of nozzle openings constituting each nozzle opening row having at least four printing pitches in the sub-scanning direction. Each nozzle opening row is divided into at least two groups, the nozzle opening rows belonging to each group are located on the same main scanning direction line, and at least 2 in the sub-scanning direction between the groups. It is arranged so that the print pitch shifts, and color data is printed in an inkjet manner.

【0007】

[Action]

When the dots of different groups do not come into contact with each other when the ink does not dry out and the printing of one scanning line is completed, the printing pitch of the recording medium equal to the numerical aperture of the nozzle is used as the paper feed amount, and the paper feed error. Keep the amount as constant as possible.

【0008】

BEST MODE FOR CARRYING OUT THE INVENTION

Therefore, the details of the present invention will be described below based on the illustrated examples. FIG. 1 shows an embodiment of an inkjet recording head used in the present invention in the form of an array of nozzle opening rows, in which reference numerals K, C, M, and Y are black, cyan, and magenta, respectively. , A nozzle opening row of the recording head 1 that independently ejects yellow ink droplets, each nozzle opening row has the number of array pitches of the nozzle openings 2 and, in this embodiment, 4 printing pitch intervals and nozzles. The number of arrangement pitches of openings 2, 2, 2 .... and the number of nozzles that are mutually exclusive. In this embodiment, five nozzle openings 2 are arranged in the sub-scanning direction, that is, in the paper feed direction.

【0009】

The nozzle opening rows C, M, and Y that eject cyan, magenta, and yellow ink droplets are located on the same line, and the nozzle opening rows K that eject black ink droplets are sub-scanned by two printing pitches. It is arranged so that it shifts in the direction.

【0010】

The recording head 1 configured in this way is moved by the carriage in the main scanning direction, that is, in the width direction of the recording paper at a constant speed, and is moved to the pressure generating chambers communicating with the nozzle openings 2, 2, 2 ...., respectively. When a drive signal is supplied to a pressure generating means such as an independently provided piezoelectric vibrator or Joule heat generating element, dots due to black ink droplets (in the figure) as shown in FIG. 2 by the first main scan. , Hatched circles) are on the line extending in the main scanning direction, and the second group of cyan, magenta, and yellow dots ( marks in the figure) are the black ink droplet dot formation lines. Is printed at two print pitch intervals.

【0011】

As a result, at least the black in the first group and the dots in the color ink in the second group do not come into contact with each other during the same main scanning, and the color mixing between black and the color ink, which is greatly affected by the color mixing, is completely prevented. It is possible to clearly print dots in cyan, magenta, and yellow. Although the cyan, magenta, and yellow dots are printed on the same scanning line, they do not pose a practical problem as compared with the deterioration of image quality due to color mixing with black.

【0012】

When the printing of one scanning line is completed, the recording medium is fed with a printing pitch equal to the number of nozzle openings, that is, five printing pitches, and then printing is executed in the same manner as the first scanning line. The first and second groups of ink dots are formed between the dots printed at intervals of two print pitches.

【0013】

Of course, at the time when printing of the second scanning line is started, the dots formed in the first scanning line are dried to such an extent that the ink due to the next dot formation is not blurred, so that printing is performed by the first scanning. A second group of colored ink dots is formed adjacent to the black dots, and black dots are formed adjacent to the second group of colored ink dots printed by the first scan. Even if the boundary regions of the dots overlap, the colored ink dots and the black dots do not mix.

【0014】

Hereinafter, printing is continued while executing paper feeds equal to the numerical apertures of the nozzles constituting each nozzle opening row and having a constant printing pitch of 5 prints. By executing the paper feed at a constant pitch in this way, the amount of error during the paper feed can be maintained as constant as possible, and printing can be executed without causing banding or whiteout.

【0015】

By adopting such a printing form, paying attention to the boundary area indicated by the cross line as shown in FIGS. 3 (a) to 3 (e), the first group, black dots, and the second group. Since the dots due to the color ink come into contact after a time difference of at least one scanning period, color mixing does not occur at the vertical boundary and the horizontal boundary between the black dots and the dots of the color ink (in addition, the figure). Medium S indicates the number of scans).

【0016】

FIG. 4 shows a second embodiment of the inkjet recording head used in the present invention in the form of an arrangement of nozzle opening rows, in which reference numerals K, C, M, and Y are black, cyan, and Cyan, respectively. Nozzle opening rows of recording head 1 that independently eject magenta and yellow ink droplets, each nozzle opening row has the number of array pitches of nozzle openings 2, and in this embodiment, an interval of 8 printing pitches. The number of array pitches of nozzle openings 2 and the number that is prime for 8 in this example, 5 nozzle openings 2, 2, 2 .... are printed 2 each other in the sub-scanning direction in this example. It is arranged so that it is shifted by the pitch.

【0017】

When printing is executed while the recording head 1 configured in this way is moved by the carriage in the main scanning direction at a constant speed, the first main scanning causes the first group of black dots (as shown in FIG. 5). In the figure, the hatched circles), the second group cyan dots (x circles in the figure), the third group magenta dots ( in the figure), and the fourth group yellow. Dots (marked with a circle in the figure) are printed on lines separated by two printing pitches in the sub-scanning direction.

【0018】

As a result, color mixing between black and all color inks is completely prevented, and dots of color inks can be printed clearly.

【0019】

When the printing of one scanning line is completed, the recording medium is fed with a printing pitch equal to the number of nozzle openings, that is, five printing pitches, and printing is executed in the same manner as the first scanning line according to the interless method. Then, dots are formed between the dots printed at intervals of two print pitches in the first scan.

【0020】

Of course, at the time when printing on the second scanning line is started, the ink of the dots formed on the first scanning line is dried to such an extent that bleeding does not occur even if it comes into contact with the dots to be printed next. Even if dots of each color ink are formed adjacent to the dots of each ink printed by the first scan and some overlap occurs in the boundary region of each dot, color mixing does not occur.

【0021】

Hereinafter, printing is continued while executing paper feed for a constant 5 printing pitches equal to the numerical aperture of the nozzles in this way. By executing the paper feed at a constant pitch in this way, the amount of error during paper feed can be maintained as constant as possible, and color printing is performed with high print quality without causing banding or whiteout. be able to.

【0022】

By adopting such a printing form, paying attention to the boundary area indicated by the cross line as shown in FIGS. 6 (a) to 6 (i), the dots of the inks of each color are separated by at least one scanning period. Therefore, black dots and dots of all color inks do not cause color mixing at the vertical boundary and the horizontal boundary (S in the figure indicates the number of scans).

【0023】

FIG. 7 shows a third embodiment of the present invention suitable for printing color printing with a total of 6 colors using light and shade inks, in which reference numerals K, C, M, and Y are used. It is a nozzle opening row of the recording head 1 that independently ejects black, dark cyan, dark magenta, and yellow ink droplets, respectively, and the symbols c and m independently eject light cyan and light magenta ink droplets. In this embodiment, the nozzle opening rows of the recording head 1 are spaced by 4 print pitches, and the number of arrangement pitches of the nozzle openings is equal to the number of the nozzle openings. In this embodiment, 63 nozzle openings 2 are sub-scanned. It is arranged in a direction.

【0024】

The nozzle opening rows K, C, M, and Y that independently eject black, dark cyan, dark magenta, and yellow ink droplets are the first group, and light cyan and light magenta ink droplets are independently ejected. With the nozzle opening rows c and m as the second group, the nozzle opening rows of the first and second groups are shifted in the sub-scanning direction by two printing pitches.

【0025】

In this embodiment, when printing is executed while the recording head 1 is moved by the carriage in the main scanning direction at a constant speed, the first main scanning causes black, dark cyan, and dark as in the first embodiment described above. Dots of magenta and yellow ink droplets ( mark with hatching in the figure) are on independent lines, and the second group of light cyan and light magenta dots ( mark in the figure) are the first. It is printed two print pitches apart from one group of dot formation lines.

【0026】

This completely prevents the mixing of black, dark cyan, dark magenta, and yellow dots with the dots of light cyan and light magenta ink droplets, and the light cyan and light magenta dots greatly contribute to the improvement of color tone. Can be printed clearly. Although the light cyan and light magenta dots are printed on the same line, the color change affects the print quality more than when mixed with black, dark cyan, dark magenta, and yellow inks, which have high color density. I won't come.

【0027】

When the printing of one scanning line is completed, the recording paper is fed by the number of printing pitches equal to the number of nozzle openings, that is, 63 printing pitches, and printing is executed in the same manner as the first scanning line according to the interless method. , Dots are formed between the dots printed at intervals of 2 print pitches in the first scan.

【0028】

Of course, when the printing of the second scanning line is started, the ink of the dots formed in the first scanning line is dried to the extent that bleeding does not occur, so that the dark color ink printed by the first scanning is used. Light-colored second group dots are formed adjacent to the first group ink dots, and dark-colored inks are adjacent to the light-colored color ink dots printed by the first scan. Even if the dots are formed and the outer peripheral regions of the dots are overlapped with each other, the color of the dots of the light-colored ink does not change with the dark-colored ink because the color mixing does not occur.

【0029】

Hereinafter, since printing is continued while executing paper feed for a constant 63 print pitches equal to the numerical aperture of the nozzles in this way, paper feed at a constant pitch such as 63 print pitches is always executed. The amount of error during feeding can be kept constant, and printing can be executed without causing banding or whiteout at the boundary line of each scanning area.

【0030】

By adopting such a printing form, even in the boundary area shown by the cross line as shown in FIG. 3 above, dots with dark color ink, which is the first group (hatched in FIG. 3). The dots (corresponding to the mark) and the dots made of the second group of light-colored ink (corresponding to the mark in Fig. 3) come into contact after at least one scanning period, so the dots of the light-colored ink and the dots of the dark-colored ink are in contact with each other. The ink does not mix at the vertical and horizontal boundaries.

【0031】

In the above-described embodiment, the case of preventing the mixing of black, dark cyan, dark magenta, and yellow ink droplet dots with the light cyan and light magenta inks has been described as an example. To prevent color mixing of dark cyan and dark magenta with light cyan, light magenta and yellow ink dots, the dark colors black, dark magenta and dark are as shown in Fig. 7 (b). The nozzle opening rows K, M, and C for ejecting cyan ink droplets are the first group, and the nozzle opening rows Y, m, and c for ejecting light-colored yellow, light magenta, and light cyan ink droplets are the first group. In addition to dividing into two groups, each nozzle opening row has nozzle openings 2, 2, 2 .... formed at intervals of 4 printing pitches, and 2 printings are performed between the nozzle opening rows of the first group and the second group. Arrange them by shifting the pitch. This makes it possible to prevent color mixing of black, dark magenta, and dark cyan with light cyan, light magenta, and yellow ink droplets as described above.

【0032】

Further, in the above-described embodiment, the arrangement pitches of the nozzle openings 2, 2, 2 .... That eject the ink of each color are the same, but the text data is the main print data as in the office recording device. In this case, as shown in FIG. 8, the nozzle opening rows for ejecting black ink droplets are arranged in multiple rows K1, K2, K3, K4 minutes with a constant pitch shift in the sub-scanning direction so as to have one printing pitch. , Nozzle opening rows K1, K2, K3, K4 are all used for text printing, and nozzle opening rows M, C for ejecting dark ink during color printing. By using K4 and nozzle opening rows Y, m, and c that eject light-color ink, text is printed with high dot density to ensure print quality and high speed, and color data is light-colored. It is possible to perform color printing with high print quality without causing color mixing between the ink of Nozzle and dark color ink.

【0033】

By the way, as described above, by dividing into a plurality of groups and shifting by two or more printing pitches, bleeding can be suppressed almost completely, but the order of ink droplet ejection between different groups cannot be taken into consideration. In other words, taking Fig. 5 as an example, each raster is scanned and printed by the dots represented by the hatched circles, the hatched circles, the marks, and the circles. Some rasters have hatched dots printed first, while others have x circles and and dots printed first.

【0034】

In such a case, as described above, bleeding at the color boundary can be completely prevented, but when dots are formed at the same position with inks of different colors and colors are expressed by color superposition (for example, cyan C dots). And yellow Y dots are overlapped to form green dots), and the composition of the ink of each color is different. Therefore, in actual printing, which ink dot is formed first (in the case of green, in the case of green). Depending on the method of printing cyan first and yellow later, or printing yellow first and cyan later), the hue (color) changes and the graininess changes. Due to such circumstances, depending on the background on which the color inks are printed and the combination, it is necessary to arrange them in the same group and always form dots in the same order.

【0035】

Fig. 9 (a) is for dealing with such a problem, and the nozzle opening rows c, C, K, m, M, Y of light cyan, dark cyan, black, light magenta, dark magenta, and yellow are used. , In this order, light cyan nozzle opening row c and dark cyan nozzle opening row C have 3 print pitches, and black nozzle opening row K and light magenta nozzle opening row m have 3 print pitches. It is arranged so that the nozzle opening row M of dark magenta and the nozzle opening row Y of yellow are shifted by 3 printing pitches.

【0036】

According to this embodiment, cyan and yellow are arranged in the same group, cyan is arranged first, and magenta and light cyan are arranged in the same group, and light cyan is printed first. In addition to preventing the increase, black and yellow, which tend to bleed, can be arranged in different groups to completely prevent color mixing.

【0037】

Further, in the embodiment shown in FIG. 9 (b), light magenta, dark cyan, black, light cyan, dark magenta, and yellow nozzle opening rows m, C, K, c, M, and Y are arranged in this order. At the same time, the light magenta nozzle opening row m and the dark cyan nozzle opening row C have a printing pitch of 3, and the black nozzle opening row K and the light cyan nozzle opening row c have a printing pitch of 3 and the dark magenta nozzle opening. It is arranged so that the printing pitch is shifted by 3 between the row M and the yellow nozzle opening row Y.

【0038】

According to this embodiment, by arranging cyan, pale cyan, and yellow in the same group and printing cyan and pale cyan first, it is possible to suppress an increase in graininess due to exudation, and black, yellow, etc., which are easily exuded. Can be placed in different groups to completely prevent color mixing.

【0039】

[Effect of the invention]

As described above, in the present invention, in the recording head, the plurality of nozzle openings constituting each nozzle opening row have at least an interval of 4 printing pitches or more in the sub-scanning direction, and each nozzle opening row is at least. It is divided into two groups, and the nozzle opening rows belonging to each group are located on the same main scanning direction line, and the groups are arranged so as to be offset by at least two printing pitches in the sub-scanning direction between the groups. Since the data is printed by the interless method, it is possible to feed the paper with a certain amount of paper feed, and the ink dots that change color due to color mixing are printed after a dry time. It is possible to print in a state where color mixing, banding, and whiteout do not occur, and color printing can be performed with high print quality.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows one Example of the recording head used in this invention in the arrangement form of a nozzle opening.

[Figure 2]

It is a figure which shows the print form of this invention divided by the number of times of a main scan.

[Fig. 3]

Figures (a) to (e) show the temporal changes in which the vertical and horizontal boundaries between the dots of the first group and the dots of the second group printed by the same printing form are formed. Is.

[Fig. 4]

It is a figure which shows one Example of the recording head used in this invention in the arrangement form of a nozzle opening.

[Fig. 5]

It is a figure which shows the print form of this invention divided by the number of times of a main scan.

[Fig. 6]

FIGS. (A) to (2) are diagrams showing temporal changes in which the vertical boundaries and the horizontal boundaries of the dots of the first to fourth groups printed by the same printing form are formed.

[Fig. 7]

FIGS. (A) and (B) are diagrams showing an embodiment of the recording head used in the present invention in the form of an array of nozzle openings.

[Fig. 8]

It is a figure which shows the other embodiment of the inkjet type recording head which can be used in this invention in the arrangement form of a nozzle opening.

[Fig. 9]

FIGS. (A) and (B) are diagrams showing another embodiment of the inkjet recording head that can be used in the present invention in the form of an array of nozzle openings.

[Fig. 10]

FIGS. (A) and (B) are diagrams showing an example of a conventional recording head in an array form of nozzle openings.

[Explanation of symbols]

1 Inkjet recording head 2 Nozzle opening K, C, M, Y Nozzle opening row c, m Nozzle opening row