JP2004268361A - Inkjet recording device and its color shift correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a color shift due to extension and shrinkage of paper sheets in an inkjet recording device, by a simple method without taking a complicated arrangement such as printing of a special mark or a detecting means. <P>SOLUTION: A driving period of each printing head is changed from extension and shrinkage characteristics of a paper sheet prepared beforehand, according to the number of drying parts incorporated in the inkjet recording device, and the number of drying parts present at a rear stage of the printing head. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an office and industrial inkjet recording apparatus and a method for correcting color misregistration thereof.
[0002]
[Prior art]
In a conventional color misregistration correction method, an alignment mark is formed at a predetermined position on each page by a first printing device, and the alignment mark is detected by a mark detection device of a second printing device. The paper transport speed is controlled so that the phase between the timing of the mark detection signal and the timing of the paper feed control signal is constant (for example, see Patent Document 1).
[0003]
Some print a test pattern, measure the color with a color detector to determine the hue, and detect the relative misregistration of each color from the hue value to determine the recording start timing for each color head. (For example, see Patent Document 2).
[Patent Document 1]
JP 2002-187660 A [Patent Document 2]
JP-A-8-160704, p12, FIGS. 32-33)
[0004]
[Problems to be solved by the invention]
However, in the color misregistration correction method using the above-described detection device, a detection device and a control circuit for analyzing the detection signal and performing correction are required, which makes the device complicated and expensive.
[0005]
The present invention proposes a printing apparatus and method for correcting color misregistration of an inkjet recording apparatus at low cost without taking the above-described complicated configuration.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has a plurality of printing apparatuses each including an image forming unit that forms an image by ejecting ink from a print head and a drying unit that dries ink printed on paper. In an ink jet recording apparatus that forms a final image by arranging apparatuses in series and performing a printing / drying process a plurality of times, each of the print heads is driven at a driving cycle corresponding to the expansion / contraction characteristics of a sheet prepared in advance. It is characterized by the following.
[0007]
Further, there is provided a means for changing and printing the drive cycle according to the number of drying sections incorporated in the ink jet recording apparatus and the number of drying sections existing at the subsequent stage of each print head. .
[0008]
Further, the printing is performed by changing the driving cycle according to the number of drying sections incorporated in the ink jet recording apparatus and the number of drying sections existing at the subsequent stage of each print head.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a schematic configuration diagram of an ink jet recording apparatus used in the present invention.
[0011]
The first printing device 1 prints yellow, the second printing device 2 prints magenta, the third printing device 3 prints cyan, and the fourth printing device 4 prints black. The paper is fed in the direction of the arrow, and finally passes through four printing devices to finally record a color image.
[0012]
FIG. 2 is a schematic configuration diagram of the first printing apparatus 1 in FIG.
[0013]
Here, the second, third, and fourth printing apparatuses have the same configuration, and the difference is the color of the ink ejected from the print head. The paper 5 sent to the printing apparatus 1 is heated and dried by the heater 8 to evaporate the water of the ink after an image is formed on the platen 7 by the ink discharged from the print head 6.
[0014]
Therefore, for example, in an ink jet recording apparatus using four colors, the paper is repeatedly expanded and contracted by printing four times until the color image is completed. If printing is performed without taking the expansion and contraction of the paper into account, the printing position of the latter stage will be shifted with respect to the printing of the previous stage, and an appropriate color image will not be obtained. However, in the color misregistration correction method using the detection device, a detection device and a control circuit for analyzing a detection signal and performing correction are required, which makes the device complicated and expensive. Therefore, it is desirable to perform the correction without using a special device.
[0015]
The present invention, in order to eliminate the color shift due to the expansion and contraction of the paper, from the expansion and contraction characteristics of the paper prepared in advance, the drive cycle of each print head, the number of drying units incorporated in the inkjet recording apparatus, and the print head It is characterized in that it is changed depending on the number of drying sections present in the latter stage.
[0016]
FIG. 3 shows expansion and contraction of the paper used in the present invention due to a change in moisture.
[0017]
As shown in FIG. 3, the paper width changes by 1% in the paper width direction and the paper size changes by 0.1%. This change is plastic expansion and contraction. Return.
[0018]
On the other hand, the flow direction shows plastic expansion and contraction. For example, when looking at the moisture content of 7%, with respect to the initial paper size, it contracts by 0.94% once with moisture absorption / drying, contracts by 2.30% with moisture absorption / drying twice, and 2.91 with moisture absorption / drying three times. % Shrinkage, 3.43% shrinkage after 4 times of moisture absorption / drying, and the amount of shrinkage differs depending on the number of times of moisture absorption / drying even if the original moisture content is restored. This is related to the method of making paper.When the paper is stretched, pressed and squeezed, and then dried with a dryer, it is dried and fixed with distortion inside in the flow direction, so it is released by moisture absorption. In order to return to the original state, the flow direction gradually contracts.
[0019]
Since a line head is used as a print head in a high-speed inkjet recording apparatus, the pitch of print dots in the paper width direction depends on the nozzle pitch of the print head, and it is difficult to change the print dot pitch in accordance with contraction of the paper. . However, since the paper width direction is plastic expansion and contraction, it is possible to prevent the color shift due to the expansion and contraction of the paper by always drying the paper so as to have a constant moisture content.
[0020]
On the other hand, in the paper feeding (flow) direction, even if the moisture content is constant, the amount of shrinkage varies depending on the number of times of moisture absorption and drying. Therefore, it is necessary to change the drive cycle of each print head so that the dot pitch of each color is the same. There is.
[0021]
FIG. 4 shows, for example, a drive cycle when a color image of 600 dots / inch for each color is formed at a paper feed speed of 100 inch / sec on the sheet having the expansion / contraction characteristics of FIG.
[0022]
Looking at the print head of the first printing apparatus, the paper finally shrinks by 3.43% after printing by the print head of the first printing apparatus because the drying step is performed four times after printing by the first printing apparatus. I do.
[0023]
Therefore, it is necessary to print at 579.4 dots / inch so as to shrink by 3.43% to 600 dots / inch, and the driving cycle is 57.94 kHz at a paper feed speed of 100 inches / sec. Regarding the print head of the second printing device, the paper has already shrunk 0.94% from the initial state at the time of printing by the second printing device, and after the printing in this shrunk state, the drying step is performed. After three passes, the paper eventually shrinks by 3.43%.
[0024]
Therefore, 2.49%, which is obtained by subtracting 0.94% from 3.43%, is the amount that finally contracts after printing by the second printing apparatus, so that it contracts by 2.49% and becomes 600 dots / inch. Needs to be printed at 585.1 dots / inch, and the driving cycle is 58.51 kHz at a paper feed speed of 100 inches / sec.
[0025]
By similarly considering the third and fourth printing apparatuses, the driving cycle of the print head in the third printing apparatus is 59.32 kHz, and the driving cycle of the print head in the fourth printing apparatus is 59.69 kHz. can get.
[0026]
In the above embodiment, the case where the initial moisture content of the paper is 7% has been described. However, since the initial moisture content varies depending on the type of the paper, the present invention is used for the internal or external storage device of the printing apparatus. For each sheet / sheet feed speed, for example, a graph of expansion and contraction due to a change in moisture of the sheet in FIG. 3 and combination data of expansion and contraction characteristics of the sheet and a driving cycle as shown in FIG. 4 are prepared. Then, by selecting the paper / paper feed speed on a panel or the like of the apparatus, each print head is printed at the drive cycle stored in the storage device, thereby eliminating color misregistration.
[0027]
The combination data may be stored in an external host (such as a personal computer) connected directly to the printing apparatus or via a network. Further, the combination data may have a configuration (a configuration including a rewritable storage device) that can be added or updated as needed by communication (telephone line, Internet, etc.) or distribution of media (FD, CD-ROM, etc.) (of course). If the paper to be used is limited, a configuration in which data is stored in the ROM and used without updating is also possible.)
[0028]
Further, the present invention can be applied to both cut paper and continuous paper, but it is preferable to use paper that is stored in a place with appropriate temperature and humidity as much as possible. In the case of continuous paper, there are two types of supply types, box type and roll type. In the case of box type, the paper is folded alternately at perforations, wrapped in a plastic bag, and put in a cardboard box. Have been. When stored for a long time after use halfway, the moisture content does not change much because it is wrapped in vinyl again. In the case of the roll type, when the roll is used after being used halfway, the moisture content on the roll surface slightly changes, but the inside hardly changes.
[0029]
As described above, the driving cycle of each print head is set according to the data for each sheet / sheet feed speed prepared for the printing apparatus in advance, the number of drying units incorporated in the inkjet recording apparatus, and the subsequent stage of the print head. By changing each according to the number of drying sections present, it is possible to eliminate the color shift of the ink jet recording apparatus without using the alignment mark forming means, the color shift detecting means, etc., and it is possible to reduce the cost of the apparatus. .
[0030]
【The invention's effect】
According to the present invention, without providing a special mark formation and detection device, by the data prepared for the printing device in advance, the drive cycle of each print head, the number of drying units incorporated in the inkjet recording device, In addition, the color shift of the ink jet recording apparatus can be eliminated by changing the number depending on the number of drying sections existing downstream of the print head, and the cost of the apparatus can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of the configuration of an ink jet recording apparatus used in the present invention.
FIG. 2 is a schematic configuration diagram of a printing apparatus used in the present invention.
FIG. 3 is a graph showing expansion and contraction of a sheet used in the present invention with a change in moisture.
FIG. 4 is a table showing the driving cycle of each print head based on the expansion and contraction characteristics of the paper used in the present invention.
[Explanation of symbols]
1 is a first printing device, 2 is a second printing device, 3 is a third printing device, 4 is a fourth printing device, 5 is a sheet on which an image is formed, 6 is a print head, 7 is a platen, 8 is a heater and 9 is a roll.

Claims (3)

A printing / drying process in which a plurality of printing apparatuses including an image forming section for forming an image by ejecting ink by a print head and a drying section for drying ink printed on paper are provided, and each printing apparatus is arranged in series. A plurality of times to form a final image in the ink jet recording apparatus,
An ink jet recording apparatus, wherein each of the print heads is driven at a drive cycle corresponding to the expansion / contraction characteristic of a sheet prepared in advance. The apparatus according to claim 1, further comprising means for changing and printing the driving cycle depending on the number of drying units incorporated in the ink jet recording apparatus and the number of drying units existing downstream of each print head. 2. The ink jet recording apparatus according to 1. 2. The ink jet printing method according to claim 1, wherein the driving cycle is changed according to the number of drying units incorporated in the ink jet recording apparatus and the number of drying units existing downstream of each of the print heads. A color misregistration correction method for a recording apparatus.

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