JP2003205622A - Inkjet recorder and method of inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder and a method of inkjet recording capable of maintaining a condition of a recording head for proper ejection of ink without lowering the recording speed and the image quality. <P>SOLUTION: In the case where a color pixel 22 is formed on a recording medium by ejecting ink from an ejection nozzle which does not eject the ink for a time period not less than a predetermined ejection rest time period, a white pixel 23 is formed on the color pixel 22 to allow the color pixel to be inconspicuous. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording apparatus and an inkjet recording method for recording using a plurality of colors of ink.

[0002]

2. Description of the Related Art An ink jet recording system uses a single color ink or a plurality of color inks corresponding to color recording to eject onto a recording material (paper, cloth, OHP paper, printed circuit board, etc.) to form an image. Is a method of forming. An inkjet recording apparatus that employs this recording method includes, for example, a carriage that mounts a recording head and an ink tank, a conveyance unit that conveys a recording material, and a control unit that controls these.

In such an ink jet recording apparatus, the recording head is serially scanned in a direction (main scanning direction) intersecting the recording material conveying direction (sub scanning direction),
An operation of ejecting ink droplets from a plurality of ejection ports in the recording head, an operation of conveying the recording material in the sub-scanning direction,
By repeating the step, recording is sequentially performed on the recording material. This recording method is already widely used as a high-speed, easy, and inexpensive recording method because ink is directly ejected onto a recording material according to a recording signal, and furthermore, it has an advantage that recording can be performed on plain paper. In addition, its future is highly expected.

Further, by providing a recording head for ejecting ink of a plurality of colors, it is easy to deal with recording of a full-color image. In the case of such a full-color ink jet recording apparatus, generally, there are four types of recording heads corresponding to four color inks including three primary colors of yellow (Y), magenta (M) and cyan (C), including black (B). Needed.

By the way, in the ink jet recording apparatus,
During suspension of ink ejection, water or the like, which is a solvent of ink, may evaporate from an ink ejection port forming a nozzle of a recording head. In that case, the viscosity of the ink at the tip of the nozzle increases, and the ink is no longer ejected during the recording operation.
Ink droplets may not be able to be ejected at the original size and speed. Further, the refilling speed of the ink into the nozzle after the ink is discharged becomes slow, and air bubbles may be mixed in the nozzle, which may prevent the ink from being discharged. As a countermeasure against this, a recovery process of the recording head is performed. As the recovery process, the recording head is guided to the ejection recovery section provided at a position not facing the recording material before the start of the recording operation or during the recording operation, and the recording head is driven by the ink pump provided in the recovery section. There is a suction recovery process for recovering the ejection performance of the recording head by sucking the ink whose viscosity has changed in the nozzle. Furthermore, as other recovery processing,
There is a preliminary ejection process in which the recording head is guided to a position that does not face the recording material, and ink that does not contribute to image recording is ejected from the recording head (Japanese Patent Laid-Open No. 11-334096). However, during such recovery processing, it is not possible to eject ink from the recording head onto the recording material, so if such recovery processing is performed frequently,
Higher recording speed cannot be achieved.

As a method for maintaining good ejection performance of the recording head without reducing the recording speed, there is so-called preliminary ejection on paper. In this preliminary ejection on paper, ink is ejected (preliminary ejection) from a nozzle that has not been ejected for a long time toward a pixel already formed on a recording material (hereinafter, referred to as “formation pixel”). This is a method in which a pixel formed by the ink is made inconspicuous by superimposing it on a previously formed pixel (JP-A-4-361048). This method
Preliminary ejection can be performed without guiding the carriage to a position where it does not face the recording material, so the recording speed is not reduced.

[0007]

However, in a high-definition color ink jet recording apparatus, when a color pixel formed by preliminarily ejected color ink is superposed on the color pixel formed previously, the OD (optical density) value is It may change and deteriorate the image quality.

It is an object of the present invention to provide an ink jet recording apparatus and an ink jet recording method capable of maintaining a good ink ejection state of a recording head without lowering the recording speed and the image quality.

[0009]

An inkjet recording apparatus of the present invention is an inkjet recording apparatus for recording on a recording medium by using recording heads capable of ejecting ink of a plurality of colors from different ejection ports. Ink is ejected from an ejection port that does not eject the ink for a period longer than the ejection suspension time to form pixels of inconspicuous color on the recording medium.

The ink jet recording method of the present invention is an ink jet recording method for recording on a recording medium by using recording heads capable of ejecting inks of a plurality of colors from different ejection ports. Ink is ejected from an ejection port that does not eject to form pixels of inconspicuous color on the recording medium.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a perspective view of an inkjet recording apparatus as an embodiment of the present invention. The recording material (recording medium) set in the paper feed tray 1 is conveyed downward at the start of a recording job, and after an image is formed by ink applied from an inkjet recording head (not shown), the recording material is ejected. The paper is discharged to the paper tray 2.

FIG. 2 is a perspective view of the main part of the ink jet recording apparatus of FIG. The carriage 11 is moved in the main scanning direction indicated by arrow A by the carriage driving motor 13 via the carriage driving belt 14. The main scanning direction is orthogonal to the sheet passing direction (sub scanning direction) of the recording material 12 indicated by the arrow B. The recording material 12 is conveyed by a paper feed motor (not shown), and the paper feed motor and the carriage drive motor 13 are controlled by a control circuit (not shown). The discharge recovery unit 16 includes a discharge recovery pump (not shown). When the inkjet recording head 18 mounted on the carriage 11 moves to a position facing the ejection recovery unit 16 and the recording head 18 comes into contact with the ejection recovery unit 16, suction recovery processing can be performed. That is, the suction recovery process can be performed by sucking the ink into the discharge recovery section 16 from the discharge port forming the nozzle of the recording head 18 by the suction force of the discharge recovery pump. Further, by ejecting ink that does not contribute to image recording from the recording head 18 toward the ejection recovery unit 16, recovery processing by preliminary ejection can be performed. Reference numeral 15 is a carriage drive rail for guiding the carriage 11 so as to be movable in the main scanning direction, and 17 is a conveyance roller for the recording material 12. 20
Is an image recorded on the recording material 12 with ink.

FIG. 3 is an enlarged view of the carriage 11 portion. The ink droplet is ejected from the ejection port of the nozzle 19 provided in the inkjet recording head 18. In this example, five recording heads 18 are provided for ejecting black, yellow, magenta, cyan, and white inks, and a nozzle 19 is provided for each recording head 1.
In 64, 64 are provided each. The row of nozzles 19 (nozzle row) extends in a direction intersecting the main scanning direction of arrow A. In the case of this example, the nozzle row extends orthogonally to the main scanning direction and along the sub scanning direction. In the recording head 18, various ejection methods for ejecting ink from the nozzles 19 can be adopted. For example, a method of ejecting ink by using thermal energy generated from the electrothermal converter may be used. In that case, the heat of the electrothermal converter causes film boiling in the ink, and the foaming energy at that time allows the ink to be ejected. Further, it is also possible to adopt a method of ejecting ink by utilizing mechanical displacement of an electromechanical transducer such as a piezo element.

In the recording apparatus of this example, an operation of moving the recording head 18 together with the carriage 11 in the main scanning direction while ejecting ink from the recording head 18 based on image data, and a recording material 12 in the sub scanning direction. An image is formed on the recording material 12 by repeating the operation of feeding to the recording material 12.

FIG. 12 is a schematic block configuration diagram of a control system in the recording apparatus.

The CPU 100 executes control processing and data processing of the operation of the printing apparatus of this example. ROM101 is
Programs such as those processing procedures are stored, and RA
M102 is used as a work area or the like for executing those processes. The ink is ejected from the recording head 18 by the CPU 100 supplying drive data (image data) such as an electrothermal converter and a drive control signal (heat pulse signal) to the head driver 18A. The CPU 100 controls a carriage drive motor 13 for driving the carriage 11 in the main scanning direction via a motor driver 13A, and a paper feed motor 104 for conveying the recording material 12 in the sub scanning direction by a motor driver 104A. Control through.

FIG. 4 is an explanatory diagram of nozzle numbers assigned to the nozzles 19 by forming 64 lines for each recording head 18. The nozzle number is represented by (x, y),
The recording head 18 for ejecting white ink is x = 0, the recording head 18 for ejecting black ink is x = 1, the recording head 18 for ejecting yellow ink is x = 2, and the recording head 18 for ejecting magenta ink is x =. 3. The recording head 18 for ejecting cyan ink has x = 4. In each recording head 18, 64 nozzles 19 have y = 1 to
64 is attached. Therefore, as shown in FIG. 4, the nozzle number of the second nozzle 19 from the top in the print head 18 for ejecting white ink is (0, 2), and the print head 18 for ejecting cyan ink is shown in FIG. The sixth nozzle 19 from the top has a nozzle number (4, 6)
Becomes

FIG. 5 is a flow chart for explaining the control of the recording head 18. This control flow is processed in parallel with the image forming flow, the carriage control flow, and the time measuring flow, which are not shown. The time measurement flow updates the discharge pause time T for each nozzle 19. The discharge pause time T is associated with the nozzle number by T (x, y),
That is, T (0-4, 1-64). Further, in the present example, white plain paper or the like is assumed as the recording material 12.

In the flow of FIG. 5, first, in step S1, the ejection pause time TA until the recovery process is required is set based on the recording job designated by the user. As the time TA, in the nozzle 19 of the recording head 18 that ejects the type of ink most likely to cause a drop in ejection performance, set a continuous ejection pause time at which the ejection performance may deteriorate in the nozzle 19. Is effective. In the next step S2, movement of the carriage 11 is controlled by the carriage control flow, and the carriage 11 is opposed to a portion on the recording material 12 where recording is not performed (so-called blank portion). After guiding the carriage 11 to a position facing the blank portion, step S
Go to 3.

In step S3, the discharge pause time T (0 to 4, 1 to 64) of all nozzles is compared with the time TA. When all of the nozzle discharge pause times T (0, 4, 1 to 64) are shorter than the time TA, the process proceeds to step S4, while at least one of the nozzle discharge pause times T (0, 4, 1 to 64) is performed. If at least the time TA is exceeded, the process proceeds to step S5. In step S5, the recording head 18 is moved to a position facing the ejection recovery unit 16, and the ejection recovery unit 16 performs the recovery process (recovery process by suction and / or preliminary ejection) of the recording head 18, and then proceeds to Step S6. move on. In step S6, the nozzle discharge pause time T (0-4, 1-
All of 64) are reset to "0", and then the process proceeds to step S10.

In step S4, the nozzles 19 other than the nozzles 19 for ejecting white ink, that is, the nozzles 1 for ejecting black, yellow, magenta, and cyan inks are used.
The discharge pause time T (1 to 4, 1 to 64) of 9 and the preliminary discharge time TB are compared. The preliminary discharge time TB is the time T
A time sufficiently shorter than the time obtained by subtracting the time required for the carriage 11 to move across the recording material 12 from A is set. Discharge pause time T (1 to 4, 1 to 6
When all of 4) are shorter than the preliminary ejection time TB, the process proceeds to step S10. On the other hand, the discharge pause time T (1 to 4, 1
~ 64), even if the preliminary ejection time TB or more, the process proceeds to step S7.

In step S7, ink is ejected from the nozzle (x, y) judged to satisfy T (1 to 4, 1 to 64) ≧ TB in step S4 to the blank portion of the recording material 12, Go to step S8. In step S8, white ink ejection nozzles (0, y) located in the same row y as the nozzles that ejected ink in step S7.
Then, the white ink is ejected. As a result, as shown in FIG. 6, on the colored pixels (pixels formed with black, yellow, magenta, and cyan ink) 22 formed in the margin of the recording material 12 in step S7,
White pixels (pixels formed with white ink) 23 are formed. In FIG. 6, for convenience of description, the pixels 22 and 2 are
The formation position of 3 is shifted. In this example, since the white recording material 12 is assumed, the white pixels 23 make the colored pixels 22 inconspicuous on the recording material 12. Naturally, those pixels 22, 23 do not participate in the recording of the image. When a plurality of nozzles that eject ink are located in the same row y in step S7, a plurality of colored pixels 22 are formed at the same position on the recording material 12. In the subsequent step S9, the ejection pause times T (x, y) and T (0, y) of the nozzles that ejected the ink in the previous steps S7 and S8 are set to "0", and then the process proceeds to step S10. .

As described above, the preliminary ejection on the paper is performed for the nozzles 19 for ejecting the black, yellow, magenta, and cyan inks by the processing of steps S7 to S9.

In step S10, the discharge pause time T (0, 1 to 64) of the nozzle 19 for discharging the white ink,
The preliminary ejection time TB is compared. Discharge pause time T
When all of (0, 1 to 64) are shorter than the preliminary ejection time TB, the process is ended. On the other hand, the discharge pause time T (0,
1 to 64), even if the preliminary discharge time TB or more,
It proceeds to step S11. In step S11, the white ink is ejected from the nozzle (0, y) determined to satisfy T (0, 1 to 64) ≧ TB in step S10 to the blank portion of the recording material 12, and then the process proceeds to step S12. . In this example, since the white recording material 12 is assumed, the white pixel formed by the white ink is
It is inconspicuous on the recording material 12. Naturally, that pixel does not participate in the recording of the image. In step S12, the ejection suspension time T (0, y) of the nozzle that ejected the white ink in step S11 is set to "0", and then the process ends.

Thus, steps S11 and S12
By this processing, preliminary ejection on the paper is performed for the nozzles 19 for ejecting white ink.

(Second Embodiment) FIG. 7 shows a second embodiment of the present invention.
FIG. 3 is a perspective view of a main part of the inkjet recording apparatus as the embodiment of FIG.

In this example, an identification device 21 for identifying the color of the recording material 12 is provided at a position upstream of the recording material 12 in the conveying direction. A light source is provided inside the identification device 21, and the color of the recording material 12 conveyed to a position facing the identification device 21 is identified. The configuration is the same as that of FIG. 2 described above except that the identification device 21 is provided, and thus the description thereof is omitted. The configuration of the carriage 11 in this example is also the same as that in FIG. 3 described above.

FIG. 8 is a flow chart for explaining the color identifying operation of the recording material 12 in this example. This identification flow is started when the recording material 12 starts to be conveyed. First, in step S11, the recording material 12 is placed at a position where the recording material 12 faces the identification device 21.
Wait until it is transported by 7. When the recording material 12 is conveyed to the position facing the identification device 21, the process proceeds to step S12. Then, in step S12, the color of the recording material 12 is identified by the identifying device 21, and then the process ends.

FIG. 9 is a flow chart for explaining the control of the recording head 18. This control flow is processed in parallel with the image forming flow, the carriage control flow, and the time measuring flow, which are not shown. The time measurement flow updates the discharge pause time T for each nozzle 19. The ejection rest time T is T (x, y), that is, T (0-4, 1-6) in association with the nozzle number, as in the above-described embodiment.
4).

In the flow of FIG. 9, steps S1 to S8 are the same as those in the above-described embodiment of FIG.
Descriptions thereof are omitted. In step S8, the white pixel 23 of white ink is formed on the colored pixel 22 formed in the blank portion of the recording surface in step S7, and then the process proceeds to step S13. In step S13, depending on the color of the recording material 12 identified in the identification flow of FIG. 8 (also referred to as “paper color”), it is located in the same row y as the nozzle that ejected the ink in previous step S7. Nozzle (1
~ 4, y), at least one of black, yellow, magenta, and cyan ink is ejected. That is, depending on the color of the recording material 12, black, yellow, magenta,
By ejecting at least one of the cyan inks,
Colored pixels 24 are formed as shown in FIG.
The color adjustment is performed so that the white pixels 23 are not noticeable on the recording material 12. Of course, those pixels 22, 23, 2
4 is not involved in recording the image. In FIG. 10, for convenience of explanation, the formation positions of the pixels 22, 23, and 24 are shifted. When a plurality of nozzles for ejecting ink are located in the same row y in step S7, the recording material 1
A plurality of colored pixels 22 are formed at the same position on 2. Then, it progresses to step S9.

Steps S9, S10 and S11 are the same as those in the embodiment of FIG. 5 described above. In step S11, T (0,1 to 64) ≧ TB in the previous step S10
After the white ink is ejected from the nozzle (0, y) determined to be the blank area of the recording material 12 to step S
Proceed to 14. In step S14, according to the color of the recording material 12 identified in the identification flow of FIG.
At least one of black, yellow, magenta, and cyan ink is ejected from the nozzles (1 to 4, y) located in the same row y as the nozzle that ejected the ink in 1. That is, by ejecting at least one of black, yellow, magenta, and cyan inks according to the color of the recording material 12, the colored pixels 24 are formed as shown in FIG. Adjust the color so that it is not noticeable at the top. Naturally, those pixels 23, 24 do not participate in the recording of the image. In FIG. 11, for convenience of explanation, the pixel 2
The formation positions of 3, 24 are shifted. After that, the process proceeds to step S15, and the ejection pause times T (1 to 4, y) and T (0, y) of the nozzles that ejected the ink in the previous steps S11 and S14 are set to "0", and then the process ends. .

(Other Embodiments) In the above-described embodiment, the ink used for forming the inconspicuous pixels on the recording medium can be variously selected according to the color of the recording medium. And is not limited to the above-described embodiment. The point is that at least an inconspicuous pixel can be formed on the recording medium by ejecting ink from an ejection port that does not eject ink for a predetermined ejection pause time or longer.

The present invention can be widely applied to various recording apparatuses capable of recording color images by combining inks of different colors. Therefore, the present invention can be applied to not only the serial scan type recording apparatus described above but also a full line type recording apparatus using a recording head extending over the entire recording width of the recording material 12.

[0035]

As described above, according to the present invention, at least an inconspicuous pixel is formed on a recording medium by ejecting ink from an ejection port that does not eject ink for a predetermined ejection pause time or longer. In addition, it is possible to maintain a good ink ejection state of the recording head without lowering the recording speed and the image quality.

[Brief description of drawings]

FIG. 1 is a perspective view of a recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the recording apparatus of FIG.

3 is an enlarged perspective view of a carriage portion in the recording apparatus of FIG.

4 is an explanatory diagram of a nozzle array of a recording head in the recording apparatus of FIG.

5 is a flow chart for explaining control of a print head in the printing apparatus of FIG.

FIG. 6 is an explanatory diagram of a pixel formation example in step S5 of FIG.

FIG. 7 is a perspective view of a recording apparatus according to a second embodiment of the present invention.

8 is a flowchart for explaining a color identification procedure of a recording material in the recording apparatus of FIG.

9 is a flow chart for explaining control of a print head in the printing apparatus of FIG.

FIG. 10 is an explanatory diagram of a pixel formation example in step S13 of FIG.

FIG. 11 is an explanatory diagram of a pixel formation example in step S14 of FIG.

12 is a block configuration diagram of a control system in the recording apparatus of FIG.

[Explanation of symbols]

1 Paper tray 2 Output tray 11 carriage 12 Recording material (recording medium) 13 Carriage drive motor 14 Carriage drive Benoleto 15 Carriage drive rail 16 Discharge recovery unit 17 Conveyor roller 18 recording head 19 nozzles 20 images 21 Identification device 22 colored pixels 23 white pixels 24 colored pixels

Claims (12)

[Claims] 1. An inkjet recording apparatus for recording on a recording medium by using a recording head capable of ejecting inks of a plurality of colors from different ejection ports, at least from ejection ports that do not eject ink for a predetermined ejection pause time or longer. An inkjet recording apparatus comprising means for ejecting ink to form inconspicuous color pixels on the recording medium. 2. The ink jet recording apparatus according to claim 1, wherein the inconspicuous color pixels do not participate in image recording. 3. The inconspicuous pixel is formed by ejecting ink of different colors from a plurality of ejection openings including at least ejection openings that do not eject ink for a predetermined ejection suspension time or longer. Item 3. The inkjet recording device according to Item 1 or 2. 4. The ink jet recording apparatus according to claim 3, wherein the different color inks include at least any one of yellow ink, magenta ink, cyan ink, black ink, and white ink. 5. The ink jet recording apparatus according to claim 3, wherein the inks of different colors include white inks and inks of colors that make the pixels formed by the white inks inconspicuous. 6. The inkjet recording according to claim 5, wherein the ink that makes the pixels formed of the white ink inconspicuous is at least one of yellow ink, magenta ink, cyan ink, and black ink. apparatus. 7. The inkjet recording apparatus according to claim 1, wherein the ink for forming the inconspicuous pixels is selected according to the color of the recording medium. 8. The ink jet recording apparatus according to claim 7, further comprising means for detecting the color of the recording medium. 9. The ink jet recording apparatus according to claim 1, wherein the inconspicuous pixel is formed in a blank portion where an image is not recorded on the recording medium. 10. A first moving unit that relatively moves the recording head and the recording medium in a main scanning direction; and a sub-scanning direction that intersects the recording head and the recording medium in the main scanning direction. The inkjet recording apparatus according to any one of claims 1 to 9, further comprising: a second moving unit that relatively moves. 11. The inkjet recording apparatus according to claim 1, wherein the recording head includes an electrothermal converter that generates thermal energy for ejecting ink. 12. An inkjet recording method for recording on a recording medium using a recording head capable of ejecting ink of a plurality of colors from different ejection ports, wherein at least ejection ports for which ink is not ejected for a predetermined ejection pause time or more are used. An ink jet recording method comprising ejecting ink to form inconspicuous color pixels on the recording medium.