JPH07132620A - Color ink jet recording method - Google Patents

Abstract

PURPOSE:To prevent the blur of the contour of an image pattern by eliminating the color mixture of dots having different ink colors by ejecting same color ink droplets of selected average quantity to a medium to be recorded at a substantially same place. CONSTITUTION:When image data is inputted to a recording apparatus (S100), pixels are selected (S101) and the total amt. of the liquid droplets of the selected pixels is calculated (S102). Next, it is judged whether the adjacent pixels are the same color (S103) and, when the pixels are not the same color, S104 is executed to calculate the total amt. of the liquid droplets of the adjacent pixels. In the case of the same color, S109 is executed to perform the calculation and comparison of the total amt. of the liquid droplets of adjacent pixels. After calculation is completed (S104), the comparison of the measured result is performed (S105) and it is judged whether the total amt. of the liquid droplets of the adjacent pixels is magnitude generating blur (S106). In the case of YES, the alteration of the total amt. of the liquid droplets of the adjacent pixels (S107) and the combination selection of the number of liquid droplets (S108) are performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color ink jet recording method capable of high-quality color recording, a recording apparatus for executing the method, and an information processing system equipped with the recording apparatus as output means.

[0002]

2. Description of the Related Art Conventionally, paper, cloth, plastic sheet, O
A recording apparatus for recording on a recording medium such as a HP sheet (hereinafter also simply referred to as recording paper) can be equipped with recording heads of various recording methods, for example, a wire dot method, a thermal method, a thermal transfer method, and an inkjet method. It has been proposed as a form.

However, in such a recording apparatus, as a low noise non-impact recording, an ink jet type recording head for recording on a recording paper by ejecting ink from an ejection port (nozzle) arranged on a recording element. Since the recording apparatus equipped with the recording device is capable of high-density and high-speed recording operation, an output unit of the information processing system, for example, a copying machine,
Facsimile, electronic typewriter, word processor,
A printer as an output terminal such as a workstation, a personal computer, a host computer,
It is used and commercialized as a handy or portable printer provided in an optical disc device, a video device, and the like. In this case, the inkjet recording apparatus has a configuration corresponding to the function, usage pattern, etc. peculiar to these apparatuses.
Generally, an inkjet recording apparatus includes a carriage on which a recording unit (recording head) and an ink tank are mounted, a conveying unit that conveys recording paper, and a control unit that controls these. Then, the recording head for ejecting ink droplets from the plurality of ejection ports is serially scanned in the direction (main scanning direction) orthogonal to the recording paper conveyance direction (sub-scanning direction), while the recording paper is set to the recording width when not recording. The same amount is intermittently conveyed. This recording method is one in which ink is ejected onto a recording sheet in accordance with a recording signal to perform recording, and the running cost is low and it is widely used as a quiet recording method. Further, by using a recording head in which a large number of nozzles for ejecting ink are arranged in a straight line in the sub-scanning direction, the recording head scans the recording paper once to perform recording with a width corresponding to the number of nozzles. It Therefore, it is possible to speed up the recording operation.

The recording element, that is, an energy generating means for generating energy for ejecting ink, uses an electromechanical transducer such as a piezo element, or radiates electromagnetic waves such as a laser to generate heat. There is a method of discharging liquid droplets by the action of, or a method of heating the liquid by an electrothermal conversion element having a heating resistor.

Among them, the recording head of the type that discharges liquid by utilizing thermal energy (so-called valve jet type) can perform high resolution recording because the liquid discharge ports can be arranged at high density. It is possible. Among them, the recording head using the electrothermal converting element as the energy generating means is easy to be made compact, and has the advantages of the IC technology and the microfabrication technology, which have been remarkably improved in technology and reliability in the recent semiconductor field. This is advantageous because it can be used in two parts, high-density mounting is easy, and the manufacturing cost is low.

Further, in the case of a color-compatible ink jet recording apparatus, pixels are formed on a recording medium with inks such as black (B), cyan (C), magenta (M) and yellow (Y), It has excellent advantages as a means for high-definition image output and high-speed printing.

Since the above-mentioned ink jet recording apparatus can be configured to be capable of relatively large-size recording such as A1 relatively easily, a reader for reading an image is connected to copy an original document.
A printing device compatible with 1-color printing, such as a plotter such as a printer for CAD output, has been commercialized. In addition, on the other hand, various usages have been demanded, and there is an increasing demand for recording on an OHP film which can be projected for presentations at conferences, lectures and the like. Therefore, when a recording medium having different ink absorption characteristics is selected as needed, a recording apparatus capable of performing the best recording regardless of the type of the recording medium has been developed and commercialized.

As a method of producing gradation in the ink jet recording apparatus, one pixel of an image signal is made to correspond to one pixel of binary recording, and this is binarized by a predetermined threshold value to express gradation. Method (dither method), or as in JP-A-59-207265 and JP-A-57-160654, the size of dots is formed by forming a coalesced droplet of a plurality of droplets and landing it on a recording medium. Method (droplet modulation method), as in Japanese Patent Laid-Open No. 63-53052, a plurality of droplets are landed at the same position on a recording medium to form one dot, and the number of landed droplets is reduced. There is a method of obtaining gradation (multi-droplet method). Among these, the dither method is accompanied by a decrease in image resolution, and the droplet modulation method is in a practical range such as the distance between sheets of a recording device.
There is a drawback that it is difficult to obtain a wide gradation range. On the other hand, the multi-droplet method is excellent as a method capable of performing high-resolution and high-gradation printing by selecting an inkjet head having small droplets.

FIG. 6 illustrates pixel formation by the multi-droplet method. As described above, the multi-droplet method forms a single pixel by depositing a plurality of droplets at substantially the same position and landing one droplet, but one droplet also forms one pixel. It may be considered as a pixel.

Generally, it takes several hundred msec or more for the ink to permeate even when the droplets land on the recording medium. Therefore, when the preceding droplets land on the recording medium 605, hemispherical droplets 601 are formed on the recording medium. Therefore, a larger hemispherical droplet 603 can be formed on the recording material by overlapping and landing the succeeding droplet 602 on the preceding droplet 600 on the recording medium. It is possible to control the size of the pixel 604 by changing.

The recording speed may be reduced by increasing the number of droplets to be overlapped in order to obtain a wider gradation range. However, the droplet modulation method described above and Japanese Patent Publication No. 63-502261 have been disclosed. It is possible to solve this problem by using a combination of a method in which liquid droplets having different volumes ejected from different nozzles are landed on the recording material in an extremely short time by using the inkjet head described in 1 above. it can.

A conventional recording method will be described below with reference to the drawings.

FIG. 7 is a diagram for explaining a schematic structure of a recording head of an ink jet recording apparatus to which a conventional recording method is applied and its periphery.

The recording head 701 is removably mounted on the carriage 702. The carriage 702 is slidably engaged with two guide shafts 703a and 703b, and is reciprocated in the direction of arrow A (main scanning direction) by a driving means (not shown) while being guided by these guide shafts 703a and 703b. Moving.

The recording head 701 is composed of monochromatic recording heads Bk (corresponding to black), C (corresponding to cyan), M (corresponding to magenta), and Y (corresponding to yellow) in order to form a full-color image. Each recording head has a predetermined density, for example, a density of 400 dpi, facing the recording paper, and has orifices arranged in a direction perpendicular to the moving direction of the carriage. Recording media such as paper and OHP film (hereinafter,
The recording paper 704 is sandwiched by a pair of conveyance rollers and a pair of tension rollers (not shown), and is conveyed in the direction of arrow B (sub-scanning direction). Reference numeral 705 is a platen whose longitudinal direction is parallel to the conveying roller pair, and sucks the recording paper 704 by suction means (not shown) in order to prevent the recording paper 704 from floating and wrinkling.

FIG. 8 is a view for explaining the schematic structure of the orifice arrangement surface of the recording head 801 mounted on the carriage 803. The orifice arrangement surface 802 is 2
The two orifice rows R1 and R2 are arranged with a spacing of 0.635 μm. Orifice rows R1 and R
In 2, the orifices are arranged at 0.0635 μm intervals. The orifices Mi of the orifice row R1 and the orifices Ni of the orifice row R2 are at the same level in the inkjet head. The orifices in the orifice row R1 are designed to eject droplets (D1) with a volume of about 5 pl, and the orifices in the orifice row R2 are designed to eject droplets (D2) with a volume of about 10 pl.

By depositing a predetermined number of droplets D1 and D2 on substantially the same position on the recording paper, the size of the pixel on the recording paper can be controlled. For example, the minimum ejection time interval of droplets is 2.5 msec, the moving speed of the carriage is 63.5 mm / sec, and the orifices Mi, N
i, the total amount of ink is 25 at almost the same position on the recording paper.
To form a pixel by overlapping pl droplets, the signal of the chart of FIG. 9 is applied to the droplet ejection means, and one droplet D1 is discharged from the orifice Mi and droplet D2 is discharged from the orifice Ni.
It is only necessary to discharge two of each.

FIG. 10 shows an example of pixel formation by the multi-droplet method using the ink jet recording apparatus having the structure shown in FIGS. Pixels of seven types from P1 to P7 can be freely obtained by stacking five droplets D1 and D2 in total. n1 and n2 are the numbers of the droplets D1 and D2, respectively, which are superposed at substantially the same location. According to a study made by the present inventor, the reflection density of a pixel pattern arranged at a pixel density of 400 dpi was measured using an ink and a recording paper having the following compositions, and it was 0.4 or less for P1 and 1.4 for P7. The above is the result, and a large difference value could be obtained.

(Ink) Diethylene glycol 30.0% by weight Water 67.5% by weight Dye (CI.FB2) 3.0% by weight (Recording paper) Mitsubishi Paper, IJ matte coated paper In the conventional multi-droplet method, one pixel is used. When a large number of liquid droplets are formed, that is, when liquid droplets of different ink colors, which have become large droplets on the recording paper, are adjacent to and in contact with each other, pixel color mixing occurs. In particular, when the difference in brightness between adjacent ink colors is large, such as when the yellow and black monochromatic regions are adjacent to each other, the image quality due to sensory deterioration is significantly reduced.

FIG. 11 shows a yellow single color area 1107 and a black single color area 11 as a comparative example of the embodiment described later.
Adjacent yellow pixel 1109 at the border of 06
The formation of the black pixels 1108 on the recording paper will be described. Here, nb1 and nb2 are the numbers of droplets D1 and D2 that land on substantially the same position on the recording material to form one black pixel, respectively, and ny
1, ny2 are droplets D1, which are landed at substantially the same position on the recording paper to form one pixel of yellow color.
It is the number of D2.

In the area indicated by the broken line in FIG. 11A, nb1 + nb is set to the extent that adjacent droplets on the recording paper do not come into contact with each other.
2, when ny1 + ny2 is small, for example, FIG.
When nb1 = ny1 = 1 as in (b) or when both droplets do not contact as in FIG. 11 (c),
The monochrome pixels 1111 and 1110 are formed, respectively. However, nb1 + nb2 and ny1 are enough to contact adjacent droplets.
When both + ny2 are large, for example, in the case of FIG. 11 (d), both are in contact with each other before or during the permeation process, and the colors are mixed. Generally, ink permeation begins several hundred msec or more after a droplet has landed on the recording material, but color mixing is much faster than this due to the surface tension of the ink. Pixel 111
It becomes 2. At the boundary between the black and yellow monochromatic regions of the image, such mixed color pixels are formed with a width of a plurality of pixels, the outline of the image is blurred, and the image quality is degraded.

[0022]

By the way, in the case of a color image by an ink jet recording apparatus, there is a problem that the contour of the image is blurred and the print quality is deteriorated due to the bleeding due to the color mixture of the ink before fixing, especially at the boundary of the monochromatic area. .
On the other hand, in the method of modulating the pixel area such as the dither method, a dedicated paper having a coat layer having good water absorption is used as a recording medium as a color mixing prevention method in units of dots, or as a method of preventing units in pixels, There are known a method in which dots of different colors are arranged in a staggered pattern, and a method in which the same line is printed by scanning a plurality of times (Japanese Utility Model Publication No. 63-321155). However, for the multi-droplet method, a color mixing prevention method that makes use of its high resolution and high gradation is not yet known, and even when any of the above three prevention methods is used as it is, The running cost of image output becomes high,
There are drawbacks peculiar to each method, such as a decrease in pixel density due to a staggered arrangement of dots and a decrease in printing speed due to multiple scans.

[0023]

In order to solve the above problems, a color ink jet recording method according to the present invention uses a plurality of colors for performing color recording of input image information by ejecting ink droplets onto a recording medium. In the method of forming one pixel by using a plurality of ink jet recording heads corresponding to the above, and further, when ejecting ink droplets, a plurality of ink droplets of the same color are landed at substantially the same location on the recording medium. A step of setting at least two types of average amount per droplet of the ink droplet, which is represented as a ratio of the total amount of the ink droplets of the same color landed on the substantially same spot, and the total number of the ink droplets; , An average amount is selected for each of a plurality of colors, and the selected average amount of the same color ink droplets is landed at substantially the same location on the recording medium to perform color recording. And having a flop.
Preferably, it has an electrothermal converter that generates thermal energy that causes film boiling in the ink in order to eject the ink.

A color ink jet recording apparatus according to the present invention is characterized in that color recording is performed based on the color ink jet recording method.

Further, an information processing system according to the present invention is characterized by including the color ink jet recording device as an output means.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the color ink jet recording method according to the present invention will be described below with reference to the drawings.
The schematic configuration of the inkjet recording apparatus to which the present invention is applied is the same as the apparatus described in the conventional example (see FIGS. 7 and 8).

Generally, in droplet ejection, a plurality of secondary droplets (satellite droplets) are ejected together with a main droplet by the application of one ejection signal, but these droplets are usually landed on substantially the same position on the recording medium. However, since one pixel is formed, there is no particular problem even if these main droplets and satellite droplets are combined and expressed as one droplet. Therefore, in the following, for simplification of description, it is assumed that one droplet is ejected by applying one ejection signal.

FIG. 1 is a diagram for explaining a schematic structure of a circuit of a control system of an ink jet recording apparatus applied to an embodiment of a method according to the present invention. The main controller 2 receives the pixel data signal of each ink color from the host computer 1 such as an image reader, and stores the pixel data signal in the frame memory 3 for buffer in units of one frame. When recording,
The main controller 2 controls the drive of the carriage feed motor 8 through the motor driver 7 and the drive of the paper feed motor 10 through the motor driver 9, and also stores the image data for each ink color read from the frame memory 3. In addition, the ejection control of the ink jet head 6 is performed at the timing of the present invention via the driver controller 4 and the head driver 5, whereby high-quality image recording can be obtained.

FIG. 2 is a flow chart showing the flow of the recording method according to the present invention.

First, when the image information is input to the recording device in S (step) 100, first, in steps 101 and 1.
In 02, the pixel selection and the total droplet amount of the selected pixel are calculated. Next, it is determined whether adjacent pixels have the same color (step 103). If it is determined that they are not the same color, the process proceeds to step 104, and the total droplet amount of adjacent pixels is calculated. On the other hand, if it is determined that the colors are the same, the process proceeds to step 109, and the calculation and comparison of the total droplet amount of adjacent pixels are not performed. When the calculation is completed in step 104, the process proceeds to step 105 to compare the calculation results. In step 106, it is determined whether the total amount of droplets of adjacent pixels causes bleeding. Here, if YES is determined, the total droplet amount of the adjacent pixels is changed (step 107) and the combination of the droplet numbers is selected (step 108). On the other hand, if NO is determined in step 106, such a change or selection is not made, and the process proceeds to step 109. When all the data are analyzed by repeating steps 100 to 109, the process proceeds to step 110, and the recording operation by the inkjet recording head is started.

Next, a specific description will be given with reference to FIG.

In this embodiment, a combination of n3 = 2 and n2 = 2 and n1 are set as the numbers of the droplets D1 and D2 to be landed on the recording medium (recording paper) at substantially the same position to form the maximum number of pixels. = 5 and n2 = 0 are preset, and the average volume of the liquid droplets superposed on substantially the same place is about 7 pl and about 5 pl, and the combination is selectively used for each ink color, and at least different from each other. At the boundary of the single-color region and its vicinity, the average volume at the time of maximum pixel formation of the droplets that are superposed at substantially the same location is set to about 5 pl, which is smaller than the normally used value of about 7 pl, for at least one ink color. This is a limited color inkjet recording method.

That is, when a maximum pixel is formed by combining droplets of n1 = 3 and n2 = 2 on an image for both black and yellow, the black area and the yellow area as shown in FIG. 2 are in contact with each other. When the image area having the highest density of ink color is obtained by both, n is set in the black area.
A combination of b1 = 3 and nb2 = 2 is selected and the average volume of the droplet is set to about 7 pl, and the maximum pixel 310 is formed. On the other hand, the yellow color has ny1 = 3 and ny2 = in other areas.
The maximum number of pixels is formed by the combination of 2, but in this area n
A combination of y1 = 5 and ny2 = 0 is selected, and the average volume of the droplet is set to about 5 pl to form the pixel 311. At this time, in the vicinity of the boundary between the two color regions, pixels having no color mixture can be formed after the permeation of the droplets.

As described above, when the droplets on the recording paper are enlarged to the extent that the droplets of different ink colors before the completion of the permeation on the recording paper come into contact with each other according to the original image information,
That is, in this embodiment, when the combination of n1 = 1 and n2 = 2 is used for both the black color and the yellow color, the ratio of the total number of liquid droplets and the number of liquid droplets superposed at substantially the same location for at least one ink color. One of the droplets represented as
By selecting an average amount per droplet that is smaller than a normally used value and using it as a signal applied to the inkjet head, it is possible to obtain an image without blurring at the boundary between different ink colors and without deterioration in quality.

In FIG. 3, the combination of the numbers of the droplets D1 and D2 is changed only for the yellow color, but as shown in FIG. 4, the droplets D1 and D2 for both the black color and the yellow color are changed.
3 is changed, or conversely to the method of FIG. 3, ny1 = 3, n for yellow as shown in FIG.
y2 = 2, and for black color, nb1 = 5, nb2 = 0
It is also possible to

Although the case where the black and yellow monochromatic areas are in contact with each other has been described above, it is not necessary to limit the use of the method of the present invention to only the boundary of the monochromatic area and its vicinity.

In the present embodiment, when the bleeding of different ink colors is likely to occur, such as at the boundary of a single color area of an image, the total amount of droplets landed at substantially the same location and the number of droplets are determined. This is a recording method for temporarily changing the average amount v of the liquid droplets expressed as a ratio, which is usually used. However, the average amount per liquid droplet set in advance is determined individually for each ink color. Good. Further, in addition to the normal average amount v1 for one droplet for one ink color, the average amounts v2, v3, ... For a plurality of droplets are determined, and the bleeding rate of the recording paper and the bleeding due to the image are likely to occur. V2, depending on
You may use v3 etc. selectively.

It should be noted that the present invention is not limited by the combination of ink colors or numerical values in each of the above embodiments. Furthermore, the recording method according to the present invention may be selectively used only when bleeding occurs on an image due to the number of overlapping droplets for one pixel for each ink color. Further, the present invention does not particularly limit the arrangement pattern of the pixels on the recording paper and can obtain a predetermined effect.

In particular, in the examples of the present specification, the method described in Japanese Patent Publication No. 63-502261 was used as a method for modulating the volume of the discharged droplets, but the recording method of the present invention is disclosed in Japanese Patent Publication No.
It is not only achieved by the combination with 3-502261, but the droplet volume can be adjusted before landing on the recording material by the method described in JP-A-59-207265 and JP-A-57-160654. The effect of the present invention can also be realized by a combination with a modulation method.

[0040]

As described above, in the color ink jet recording method based on the present invention, a plurality of ink jets corresponding to a plurality of colors for performing color recording of input image information by ejecting ink droplets onto a recording medium. In a method of forming one pixel by using a recording head and landing a plurality of ink droplets of the same color at substantially the same location on the recording medium when ejecting the ink droplets, in the substantially same location on the recording medium. A step of setting at least two types of average amount per ink droplet, which is expressed as a ratio of the total amount of the same color ink droplets landed on the ink droplets and the total number of the ink droplets, prior to color recording; Selecting an average amount and landing the selected average amount of the same color ink droplets at substantially the same location on the recording medium to perform color recording. In the multi-droplet method, it is possible to prevent mixing of dots of different ink colors and prevent deterioration of image quality due to blurring of the outline of the image in the multi-droplet method, and to achieve high-quality color recording. Is possible.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a control system of a recording apparatus to which a color inkjet recording method according to the present invention is applied.

FIG. 2 is a flowchart for explaining a color inkjet recording method according to the present invention.

FIG. 3 is a diagram for explaining pixel formation based on the color inkjet recording method of the present invention.

FIG. 4 is a diagram for explaining pixel formation based on the color inkjet recording method of the present invention.

FIG. 5 is a diagram for explaining pixel formation based on the color inkjet recording method of the present invention.

FIG. 6 is a diagram for explaining a multi-droplet method.

FIG. 7 is a schematic perspective view for explaining a schematic configuration of an inkjet recording apparatus to which the present invention can be applied.

FIG. 8 is a schematic perspective view for explaining a schematic configuration of an inkjet recording head to which the present invention can be applied.

FIG. 9 is a diagram for explaining an example of signals for driving the inkjet recording apparatus.

FIG. 10 is a diagram for explaining pixel formation based on a conventional method.

FIG. 11 is a diagram for explaining a color mixing state of pixels.

[Explanation of symbols]

 1 Host Computer 2 Main Controller 3 Frame Memory 4 Driver Controller 5 Head Driver 6 Inkjet Recording Head 310 Pixel 311 Pixel 410 Pixel 411 Pixel 510 Pixel 511 Pixel 600 Preceding Droplet 601 Hemispherical Preceding Droplet 602 Subsequent Droplet 603 Large Droplet 604 Pixel 605 Recording medium (recording paper) 701 Inkjet recording head 702 Carriage 703 Guide shaft 704 Recording medium (recording paper) 705 Platen 801 Inkjet recording head 802 Orifice surface 803 Carriage

Claims (4)

[Claims] 1. A plurality of ink jet recording heads corresponding to a plurality of colors for performing color recording of input image information by ejecting ink droplets on a recording medium, and further a plurality of the same color when ejecting the ink droplets. In a color inkjet recording method for forming one pixel by landing ink droplets on substantially the same location on the recording medium, the total amount of the same color ink droplets landing on substantially the same location on the recording medium. And setting the average amount of each ink drop expressed as a ratio of the total number of the ink drops and at least two types prior to the color recording.
Selecting the average amount for each of the plurality of colors and landing the selected average amount of the same color ink droplets at substantially the same location on the recording medium to perform color recording. Color inkjet recording method. 2. The method according to claim 1, wherein the ink jet recording head has an electrothermal converter that generates thermal energy that causes film boiling of the ink in order to eject the ink. Color inkjet recording method. 3. A color inkjet recording apparatus, wherein color recording is performed based on the color inkjet recording method according to claim 1. 4. An information processing system comprising the color ink jet recording apparatus according to claim 3 as output means.