JP2002036519A - Ink-jet imaging device and ink-jet imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet imaging device and an ink-jet imaging method capable of avoiding a problem of having different hues in the forward path and the backward path in the movement in the main scanning direction of a carriage while improving the ink drying property, and capable of cutting back the color ink consumption amount. SOLUTION: An ink head comprises two drying promoting liquid heads 58e, 58f. In the case an ink head carriage is at the home position, the first drying promoting liquid head 58e, a black ink head 58d, and the second drying promoting liquid head 58f are disposed in this order from the scanning direction front side. In the case a black ink is ejected from the black ink head 58d at the time of moving in the forward path, a drying promoting liquid is ejected from the first drying promoting liquid head 58e prior thereto. In the case the black ink is ejected from the black ink head 58d at the time of moving in the backward path, the drying promoting liquid is ejected from the second drying promoting liquid head 58f prior thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inkjet image forming apparatus and an inkjet image forming method. In particular, the present invention relates to an improvement for improving the drying property of an ink.

[0002]

2. Description of the Related Art In general, in an ink jet type image forming apparatus (hereinafter, referred to as an ink jet printer), image formation is performed in order by discharging ink droplets toward the upper surface of a continuously fed recording sheet. The recording paper on which the image has been formed is sequentially discharged onto the discharge tray and stacked. At this time, if the succeeding recording paper is discharged in a state where the ink on the recording paper discharged earlier is not completely dried, image disturbance due to contact between the recording papers and the recording paper Dirt occurs. For this reason, in the ink jet printer, improving the drying property of the ink is an indispensable factor for improving the image quality of the image and increasing the number of images formed per unit time.

In this type of printer, a dye ink or a pigment ink is used as a black ink for forming a black image. Since pigment inks have better black reproducibility than dye inks, it is preferable to use pigment inks to form high-quality images. However, the pigment ink has a lower permeability to the recording paper than the dye ink, and thus requires a longer drying time. Therefore, if the pigment ink is directly discharged onto the recording paper as it is, there is a possibility that the image is disturbed or the recording paper is stained due to the contact of the subsequent recording paper.

In view of this point, as an improvement of an image forming operation for improving the drying property of a pigment ink,
There is one disclosed in JP-A-8-197831. According to this publication, when a black image and a color image are adjacent to each other, printing is performed at a position of some black dots with a color ink (comprising a dye ink) as a base,
Then, it is disclosed that a black dot is formed by printing a plurality of black ink droplets at the position. In this publication, some black dots are not printed in all or part of the black image, that is, dots are thinned out, and color ink is printed at the positions of the thinned black dots. It is also disclosed. That is, some of the black dots are replaced with color dots. With these methods, it is possible to shorten the drying time of the black ink while effectively suppressing bleeding due to the inflow of ink between adjacent dots or adjacent images.

[0005]

However, the technique disclosed in the above publication has the following problems. In other words, since color ink is printed as the base of black dots or some of the black dots are replaced with color dots, the consumption of color ink is significantly increased, and this color ink is effective for original color printing. It is in a situation that it is not used for.

Further, C (cyan) which is a color ink,
The drying time of the black image portion can also be shortened by superimposing each of the M (magenta) and Y (yellow) inks to express black. In this case, however, the difference in the order of superimposition causes the black hue to change. Will be different. That is, when the ink cartridges fixed on the carriage are arranged in the above order, the color ink is superimposed in the order of C, M, and Y on the outward path of the movement of the carriage in the main scanning direction, and black is expressed. On the other hand, on the return path of the movement in the main scanning direction, the color inks are superposed in the order of Y, M, and C, and black is expressed. As described above, since the order of superimposition of the respective color inks is different between the forward path and the return path, the hue of black is also different due to the different order, which may cause a problem that a desired black cannot be expressed. As a means for solving this problem, an image forming operation is performed only on the outward movement of the carriage in the main scanning direction, and the ink is not ejected on the return movement. The image formation can be performed only once, and the image forming operation cannot be speeded up.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and an object of the present invention is to improve the drying property of ink while maintaining the hue between the forward and backward movements of the carriage in the main scanning direction. It is an object of the present invention to provide an inkjet image forming apparatus and an inkjet image forming method capable of avoiding a situation in which the color image changes, and reducing the consumption of the color ink.

[0008]

Means for Solving the Problems-Summary of the Invention-In order to achieve the above object, the present invention comprises a drying promoting liquid discharging unit for discharging a drying promoting liquid for promoting drying of ink, The drying promoting liquid improves the drying property of the ink and prevents a change in hue of an image formed by the ink. Further, by improving the arrangement of the drying promoting liquid discharge section, high-speed image formation is enabled.

-Solution Means- Specifically, an ink-jet image forming apparatus which forms an image on a recording medium by discharging ink droplets from the image forming means is assumed. For this inkjet image forming apparatus,
An image forming unit is provided with an ink discharge unit that discharges ink droplets and a drying promotion liquid discharge unit that discharges a drying promotion liquid for promoting drying of the ink droplets. Further, the drying-promoting-liquid ejecting unit is disposed on both sides of the ink ejecting unit in the main scanning direction, and before the ink droplet is ejected from the ink ejecting unit, it is located at a predetermined position on the recording medium where the ink droplet is to be applied Either one of the drying promoting liquid discharge units is configured to discharge the drying promoting liquid.

According to this specific matter, when an ink having a low drying property such as a pigment-based black ink is ejected at the time of forming an image on a recording medium, a predetermined amount of the ink on the recording medium to which the ink is to be applied is preceded. The drying promotion liquid is applied to the position from the drying promotion liquid discharge unit. And
The ink is superimposed on the drying accelerating liquid and applied to the recording medium. Accordingly, the drying of the ink is promoted by the drying promoting liquid, the drying time of the ink is shortened, the disturbance of the image due to the subsequent contact of the recording medium can be prevented, and the number of images formed per unit time is increased. be able to. In addition, by arranging the drying-promoting liquid discharging units on both sides of the ink-discharging unit in the main scanning direction, it is possible to previously form the base using the drying-promoting liquid in both the forward movement and the backward movement in the main scanning direction. In other words, it is possible to form an image having excellent ink drying properties on both the forward path and the return path. Further, since the same image forming operation is performed in the forward path and the return path, the hue of the image does not differ depending on the scanning direction of the image forming unit. Furthermore,
This is not a method of shortening the time required for drying using inks of other colors (for example, using a dye color ink as a base of the pigment black ink). It is also possible to reduce.

The following is another example of the configuration relating to the arrangement of the drying promoting liquid discharge section. That is, for an ink jet image forming apparatus that forms an image on a recording medium by discharging ink droplets from an image forming unit, an ink discharge unit that discharges ink droplets and a drying promoting liquid that promotes drying of ink droplets are used. A drying-promoting-liquid discharging unit to be discharged is provided in the image forming unit. Further, the drying-promoting-liquid discharging unit is disposed only on the front side of the ink discharging unit in the moving direction when the image forming unit moves from the home position in the main scanning direction. Further, before the ink ejection section ejects ink droplets in the forward path and the backward path in the main scanning direction, the drying promoting liquid ejecting section is located at a predetermined position on the recording medium where the ink droplet is to be applied in the forward path and the backward path. The drying promotion liquid is discharged during the outward movement.

According to this specific matter, at the time when the forward movement of the image forming means is completed, ink droplets are applied on the drying accelerating liquid at predetermined positions where ink droplets are to be applied on the outward movement, and the drying property is excellent. In addition to the image formation, the drying promoting liquid has already been applied to the position where the ink is to be applied during the subsequent backward movement. That is, two lines of the drying accelerating liquid are applied during the forward movement. Then, when the image forming means moves backward, the image is formed with excellent drying properties only by applying ink on the drying promoting liquid. As described above, by simply arranging the drying-promoting-liquid ejecting unit on one side of the ink ejecting unit, it is possible to form an image with excellent drying properties on both the forward path and the backward path. For this reason, the size of the image forming unit in the main scanning direction can be reduced.

The following are specific examples of the drying accelerating liquid. That is, the drying accelerating liquid is formed of a colorless liquid having a color that does not change the hue of the ink when the ink is applied thereon.

According to this specific matter, even if the drying accelerating liquid and the ink are applied on the recording medium in a superimposed manner, the reproducibility of the ink can be ensured well, the ink drying time can be shortened, and the image quality can be improved. Can be compatible.

The following is a specific example of an ink-jet image forming method in an ink-jet image forming apparatus in which two lines of a drying-promoting liquid are applied by a drying-promoting-liquid ejecting unit during the forward movement. That is, prior to the ink ejecting unit ejecting ink when the image forming unit moves in the main scanning direction from the home position, the image forming information is acquired at the time of the outward movement and at the time of the backward movement in the main scanning direction. Then, the image information at the time of the backward movement is subjected to the inversion processing of the image information, and then, based on the image information at the time of the forward movement and the inverted image information at the time of the backward movement, the forward movement and the backward movement are performed during the forward movement. The drying operation of the drying promoting liquid for the two rows is performed by the drying promoting liquid discharging unit.

By performing the image information reversing process on the image information at the time of the backward movement, a drying accelerating liquid application position as a base for image formation on the backward movement (a position coincident with the ink application position with low drying property). ) Can be set accurately, and the reliability of shortening the ink drying time is improved.

The following is a specific configuration of the arrangement of the ink nozzles for discharging ink and the drying promoting liquid nozzles for discharging the drying promoting liquid. In other words, the plurality of drying promotion liquid nozzles formed in the drying promotion liquid ejection unit are moved one by one in the sub-scanning direction with respect to the ink nozzles formed in the ink ejection unit.
/ 2 pitches, and the interval between the drying promoting liquid nozzles adjacent to each other is set to be twice as long as the interval between the ink nozzles.

As a specific image forming method,
Prior to the image forming unit moving in the main scanning direction and the ink ejection unit ejecting ink, adjacent “2n−1” -th and “2n” lines arranged in the sub-scanning direction in one row.
When at least one pair of image information of a dot pair is read (n is an integer of 1 or more) and ink is ejected from an ink nozzle to at least one of the pair of dots based on the image information, the pair of dots is read. The drying promotion liquid is discharged from the “n-th” drying promotion liquid nozzle corresponding to.

By these specific items, the number of the drying promoting liquid nozzles is only half the number of the ink nozzles, so that the structure of the image forming means can be simplified and the consumption of the drying promoting liquid can be reduced. it can.

Other specific configurations of the arrangement of the ink nozzles for discharging ink and the drying promoting liquid nozzles for discharging the drying promoting liquid include the following. That is, a plurality of drying promoting liquid nozzles formed in the drying promoting liquid discharge unit and a plurality of ink nozzles formed in the ink discharging unit form nozzle rows extending in the sub-scanning direction.
The position of the nozzle row of the drying accelerating liquid is shifted from the ink nozzle by (d + 1/1/5) of the scanning pitch of the ink nozzle in the main scanning direction.
2) It is arranged at a position having a distance twice (d is an integer of 1 or more).

As a specific image forming method,
Prior to the image forming unit moving in the main scanning direction and the ink discharge unit discharging ink, adjacent “2m−1” -th and “2m” lines arranged in the main scanning direction in one row.
When at least one pair of image information of the third dot pair is read (m is an integer of 1 or more) and ink is ejected to at least one of the dot pairs based on the image information, the main scanning direction of the image forming unit The drying promotion liquid is ejected from the drying promotion liquid nozzle corresponding to the above-mentioned dot pair every two pitch movements.

According to these specific items, one drying promotion liquid dot corresponds to two dots of ink, so that the consumption of the drying promotion liquid can be reduced.

The following configuration is a combination of the above two specific configurations relating to the arrangement of the ink nozzle for discharging ink and the drying promotion liquid nozzle for discharging the drying promotion liquid. That is, a plurality of drying promoting liquid nozzles formed in the drying promoting liquid discharge unit and a plurality of ink nozzles formed in the ink discharging unit form a nozzle row extending along the sub-scanning direction. Further, each drying accelerating liquid nozzle is halved with respect to each ink nozzle in the sub-scanning direction.
The nozzles are arranged so as to be shifted by the pitch, and the interval between the drying promoting liquid nozzles adjacent to each other is set to be twice as long as the interval between the ink nozzles. On the other hand, the position of the nozzle row of the drying accelerating liquid is arranged at a distance from the ink nozzle that is (d + ／) times (d is an integer of 1 or more) the scanning pitch of the ink nozzle in the main scanning direction. ing.

As a specific image forming method,
Prior to the image forming means moving in the main scanning direction and the ink ejection unit ejecting ink, at least image information of four ink dots adjacent to each other around a specific position is read, and based on the image information, When ejecting ink to at least one of the four ink dots,
The drying promoting liquid is ejected to the specific position, which is the center position of one ink dot.

According to these specific items, one drying promotion liquid dot corresponds to four dots of ink, so that the consumption of the drying promotion liquid can be further reduced.

The following is a method of controlling the timing of discharging the ink and the drying promotion liquid. That is, the image forming unit is moved in the main scanning direction, and the clock control is performed to control the ejection timing of the ink and the drying promotion liquid.

According to this specific matter, the configuration of the scanning mechanism can be simplified, and high-precision dot formation control can be performed.

Specific examples of the ink targeted in the above specific items, that is, the ink whose drying property is improved by a drying accelerating liquid, include a pigment-based black ink. This type of ink has good black reproducibility compared to a dye-based black ink, but has low permeability to a recording medium (such as paper), and thus requires a long drying time. Was. By applying the above-described method to the image formation using the pigment-based black ink, the drying time can be shortened, the image can be prevented from being disturbed by the subsequent contact with the recording medium, and the image per unit time can be reduced. The number of formed sheets can be increased.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) -Description of Configuration of Printer- First, the configuration of a color inkjet printer 1 as an inkjet image forming apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a perspective view showing the appearance of the color inkjet printer 1. FIG. 2 is a diagram showing the internal structure of the color inkjet printer 1.

The color ink jet printer 1 is provided with a paper feed tray 3 on the front side of the cabinet 2 (the right side in FIG. 1), and a paper discharge tray 4 above the paper feed tray 3 on the front side. Provided. On the paper feed tray 3, recording paper S as a loaded recording medium
A positioning member 31 for positioning the sheet feeding position is provided.

On the other hand, as shown in FIG.
, From the paper feed tray 3 to the paper discharge tray 4,
A pickup roller 11, a paper feed roller 12, a substantially U-shaped transport path 13, a PS roller 14, an ink jet mechanism 5, and a paper discharge roller 15 are provided in this order.

The ink jet mechanism 5 includes a guide shaft 52 extending in the main scanning direction of the ink head carriage 51, as shown in FIG. The ink head carriage 51 has an insertion hole 51a through which the guide shaft 52 is inserted.
The ink head carriage 51 is slidably supported in the extension direction of the guide shaft 52 by inserting the guide shaft 52 through the guide shaft 52.

A drive motor 53 is provided on one side in the main scanning direction. A timing belt pulley 54 is rotatably attached to an output shaft 53a of the drive motor 53, and a similar timing belt pulley 55 is provided on the other side in the main scanning direction.
A timing belt 56 is stretched between the timing belt pulleys 54 and 55, and a part of the timing belt 56 is connected to the ink head carriage 51.
It is fixed to. For this reason, the ink head carriage 51 can move in the main scanning direction by the travel of the timing belt 56 accompanying the driving of the drive motor 53. The movement of the ink head carriage 51 is reciprocated (forward movement, backward movement) according to the rotation direction of the drive motor 53.

The ink head carriage 51 holds an ink head 57 as an image forming means and has an ink tank and a drying promoting liquid tank (not shown) mounted thereon. Specifically, the ink head carriage 5
Reference numeral 1 designates each of the inks Y (yellow), M (magenta), C (cyan), and Bk (black) which are individually stored.
The individual ink tanks are mounted side by side in the main scanning direction, and a drying promoting liquid tank containing a drying promoting liquid for promoting drying of the black ink is mounted.

The drying accelerating liquid is a dye-based material, and does not change the hue of black when mixed with the black ink, or has such a color that the change in hue of black is invisible to human eyes. Liquid or a colorless liquid. As the black ink, a pigment-based ink having good black reproducibility is employed.

The ink head 57 includes yellow, magenta, cyan, and black ink heads (ink discharge units) 58a to 58d and a plurality of nozzles provided with a plurality of nozzles individually connected to these tanks via supply paths (not shown). Drying promotion liquid heads (drying promotion liquid discharge sections) 58e, 58f
(See FIG. 4). These heads 58a-5
As the arrangement state of 8f, the ink head carriage 51
Is located at the home position (print start position), the first drying promoting liquid head 58e, the black ink head 58d, and the like from the front side in the scanning direction (right side in FIG. 4).
Second drying promoting liquid head 58f, cyan ink head 5
8c, a magenta ink head 58b, and a yellow ink head 58a. The nozzles formed in each of the ink heads 58a to 58d are provided at a plurality of positions, respectively, and are arranged in the paper transport direction (arrow II in FIG. 4).
Nozzles for ejecting ink of the same color are arranged in a straight line along (I direction). Further, nozzles formed in each of the drying promoting liquid heads 58e and 58f for discharging the drying promoting liquid are also arranged in a straight line along the sheet transport direction. Each nozzle row is composed of, for example, 64 nozzles and has a resolution of 600 dpi.

As shown in FIG. 2, the color ink jet printer 1 has a control device 6 for controlling each part. The processing and operations of the color inkjet printer 1 described below are performed by the control device 6 unless otherwise specified.
Shall control.

-Description of Printing Operation- When the printing operation of the color ink jet printer 1 is started, first, one sheet of the recording paper S placed on the paper feed tray 3 is taken out by the pickup roller 11, and The sheet is guided to the conveyance path 13 by the sheet feeding roller 12. After that, the recording paper S is conveyed to the image forming position 16 facing the ink head 57 with the leading end of the paper being aligned with the image information by the PS roller 14. Then, when the recording paper S passes through the image forming position 16, each of the ink heads 58 a to 58 d and each of the nozzles provided in the drying promoting liquid heads 58 e and 58 f, based on the position of the recording paper S and image information, Image formation is performed on the upper surface of the recording paper S by ejecting the ink droplets and the drying promotion droplets individually.

The image forming operation will be specifically described.
When the recording paper S is conveyed to the image forming position 16, the ink head carriage 51 moves from the home position (left end position in FIG. 3) in the direction of arrow I in FIG. The ink and the drying promotion liquid are discharged from the nozzles 58a to 58f toward the recording paper S, thereby forming an image on the recording paper S (the discharge timing of the drying promotion liquid will be described later). When the ink head carriage 51 moves to one end of the recording sheet S, the recording sheet S is moved (conveyed) by a predetermined amount (after being moved in the sub-scanning direction indicated by the arrow III in FIG. 3) and then stopped. Then, the ink head carriage 51 is moved in the direction of arrow II in FIG. 3 (return direction in the main scanning direction).
The image formation is performed in the same manner as described above while moving to.
In this manner, the image forming operation by the reciprocating movement of the ink head carriage 51 and the feeding operation of the recording paper S are performed alternately, and the image is formed on the entire recording paper S.

The recording paper S on which an image is formed over substantially the entire area of the front surface is discharged toward the discharge tray 4 by the discharge rollers 15. As a result, the recording sheet S on which a predetermined image has been formed is discharged to the discharge tray 4 in a face-up state (a state in which the image forming surface faces upward).

The operation characteristic of this embodiment is an operation for forming black pixels (black dots) on the recording paper S. In forming the black pixels, first, the drying accelerating liquid is applied to the recording paper S, and then the black ink is applied thereon.

Specifically, the ink head carriage 51
When moving from the home position, that is, when moving in the forward direction in the main scanning direction, the black ink should be applied before the black ink is applied to the recording paper S from the nozzles of the black ink head 58d. The drying promotion liquid is applied to the position from the nozzle of the first drying promotion liquid head 58e located on the front side (the right side in FIG. 4) in the forward direction. When the drying accelerating liquid is applied, the liquid permeates the recording paper S, and assists the permeation and drying of the subsequently applied black ink to the recording paper S. This makes it possible to shorten the drying time of the black ink after the black ink is applied.

Similarly, when the ink head carriage 51 moves in the backward direction in the main scanning direction, when the black ink is applied to the recording paper S from the nozzles of the black ink head 58d, the black ink is supplied prior to the application. Is applied from the nozzle of the second drying promotion liquid head 58f located on the front side (the left side in FIG. 4) in the return path direction. Also in this case, as in the case described above, the penetration and drying of the black ink into the recording paper S are assisted by the drying promoting liquid, and the drying time of the black ink can be reduced.

Further, as described above, since the drying promoting liquid is a material which does not change the hue of black even when mixed with the black ink, the drying promoting liquid and the black ink are superposed on the recording paper S in this manner. Even when applied, the reproducibility of black color is well ensured. When a black ink is applied using a color ink as a base as in the related art, there is a possibility that the hue of the black changes and the desired black cannot be expressed. In this embodiment, the change in hue of black does not occur, so that desired black can be expressed with good reproducibility.
Further, in the case of the present embodiment, the black hue in each case is the same even when the above-mentioned case where the drying promoting liquid is used and the case where it is not used are mixed. Therefore, a desired black color can be expressed with good reproducibility on the entire recording paper S, and high-quality image formation can be performed.

Further, since the formation of the base with the drying promoting liquid can be performed in advance in both the forward path and the backward path in the main scanning direction, the hue of black is not different between the forward path and the backward path. This also enables the desired black color to be expressed with good reproducibility on the entire recording paper S, and high-quality image formation can be performed.

Further, since the color ink is not used to shorten the time required for drying the black ink, it is possible to greatly reduce the consumption of the color ink while improving the drying property of the black ink. Higher image quality can be achieved. In particular, when facsimile printing is performed, only black printing is performed. Therefore, there is a problem in that the consumption of color ink is extremely increased in the related art. In the present embodiment, this problem can be solved, the consumption of the color ink can be significantly reduced, and the color ink can be effectively used for the original color image formation.

Further, in the conventional method of expressing black by superimposing color inks, there is a possibility that the order of superimposition of each color ink is different between the forward path and the return path, and the hue of black is different. This embodiment does not adopt a method of expressing black by overlapping color inks.
Accordingly, the desired black color can be expressed with good reproducibility on the entire recording paper S, and a high-quality image can be formed. Also, this can reduce the consumption of the color ink.

(Second Embodiment) Next, a second embodiment of the present invention will be described. This embodiment is a modification of the discharge mode of the drying promotion liquid. Other configurations and operations are the same as those of the above-described first embodiment. Therefore, here, only the ejection form of the drying accelerating liquid will be described.

FIG. 5 shows the arrangement of the ink heads 58a to 58d and the drying promoting liquid head 58e. As shown in this figure, in the present embodiment, the drying promoting liquid head 58e is provided only at the forefront position in the main scanning direction when the ink head 57 moves from the home position in the forward direction. The length of the drying promoting liquid head 58e in the sub-scanning direction (the length in the vertical direction in the drawing) is set to be twice the length of the black ink head 58d in the sub-scanning direction. More specifically, a front head portion (region A in FIG. 5) located on the side of the black ink head 58d, and extends upstream from the front head portion A in the sheet conveyance direction (upward in the drawing). And a rear head portion (region B in FIG. 5). That is,
When the ink head 57 is moving in the forward scanning direction in the main scanning direction, the drying promoting liquid head 58e dries to a portion where black pixels are formed by the black ink from the black ink head 58d during the forward scanning direction. To the other ink heads 58a to 58d, the application of the accelerating liquid and the application of the drying accelerating liquid to the portion where the black pixels are formed by the black ink from the black ink head 58d during the subsequent backward movement can be performed at the same time. On the other hand, the dimension in the sub-scanning direction is formed longer. That is, the front head portion A applies the drying accelerating liquid to the portion where the black pixels are formed by the black ink from the black ink head 58d during the forward movement, and the black ink from the black ink head 58d during the backward movement. Thus, the rear head portion B applies the drying accelerating liquid to a portion where a black pixel is formed. Thus, when the ink head 57 moves in the forward path, the bases for the forward path and the return path (substrates by the drying promoting liquid) are formed simultaneously. The arrangement order of the ink heads 58a to 58d is the same as that of the first embodiment.

Hereinafter, the operation of forming a black pixel in the present embodiment will be described. First, when the ink head 57 moves from the home position in the forward scan direction in the main scanning direction, before the black ink from the black ink head 58d is applied onto the recording paper S, the control unit 6 performs the forward scan and the return scan. The formation position information of each black pixel is read from a storage device such as a memory. Then, based on the read information, a process of inverting the printing order of the black pixels on the return path is performed, and after the processing, the drying promotion liquid ejection control of the drying promotion liquid head 58e based on the image information on the return path and the image information on the forward path is performed. . That is, at the time of image formation on the outward path, from the head portions A and B on the front side and the rear side of the drying promotion liquid head 58e,
The discharge operation of the drying promoting liquid for two lines (for the forward path and the return path) is performed based on the above information.

Thereafter, the black ink for the outward path is applied to a predetermined position from the black ink head 58d, and the image forming operation of the outward path is performed. On the other hand, during the subsequent return movement, since the drying promoting liquid has already been applied on the recording paper S, the black ink for the return movement is applied onto the recording paper S from the black ink head 58d so as to be superimposed thereon. The return image forming operation is performed. The operation at the time of the outward movement and the operation at the time of the backward movement are performed alternately, and the image formation on the entire recording paper S is performed.

As described above, also in this embodiment, when the black ink is applied to the recording sheet S from the nozzles of the black ink head 58d, the drying promotion liquid head 58e is moved to the position where the black ink is to be applied prior to the application. A drying accelerating liquid is applied from a nozzle. For this reason, the penetration and drying of the black ink into the recording paper S are assisted, and the drying time of the black ink can be reduced.

Further, in the present embodiment, the application of the drying promotion liquid prior to the application of the black ink can be performed on both the forward path and the return path only by providing one drying promotion liquid head 58e. Therefore, the configuration of the ink head 57 can be simplified and the length of the ink head 57 in the main scanning direction can be reduced as compared with the first embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described. This embodiment is also a modification of the discharge mode of the drying promotion liquid. Other configurations and operations are the same as those of the above-described first embodiment. Therefore, here, only the discharge mode of the drying accelerating liquid will be described.

FIG. 6 shows the arrangement of the black ink head 58d and the drying promoting liquid head 58e. As shown in this drawing, a plurality of nozzles 59d-a, 59d-b,..., 59e-s, 59e-
are formed. Black ink head 58d
Black nozzles 59d-a, 5
A nozzle row composed of 9d-b,.
e, a plurality of drying promoting liquid nozzles 59e-
.. extend in the sub-scanning direction (vertical direction in the drawing) and are parallel to each other.

Each of the drying promoting liquid nozzles 59e-s, 5
The formation position of 9e-t,.
a, 59d-b,... are not opposed to each other in the main scanning direction (horizontal direction in the figure). In particular,
The position at which each of the drying promoting liquid nozzles 59e-s, 59e-t,... Is formed with respect to the position at which the black nozzles 59d-a, 59d-b,.
.. Are formed at positions shifted in the sub-scanning direction by half the distance between the nozzles of -b,..., And the nozzle intervals of the drying promoting liquid nozzles 59e-s, 59et,. 59d-b,... Are set to twice the nozzle interval. That is, one drying promotion liquid nozzle 59
e-s is two adjacent black nozzles 59d-a,
59d-b, the two black nozzles 59d
When the black ink is ejected from at least one of -a and 59d-b, the drying promotion liquid as a base thereof is discharged from the corresponding drying promotion liquid nozzle 59e-s. Thereby, the drying promotion liquid nozzle 59e
The number of −s, 59e−t,...
a, 59d-b,... are set to half.

In the black pixel forming operation in this embodiment, first, before the black ink from the black ink head 58d is applied onto the recording paper S, the control unit 6 changes the dot arrangement in the main scanning direction. Assuming that "m" and the arrangement of dots in the sub-scanning direction are "n", the first dot {coordinate position (2n-1, m)} and the second dot {coordinate position (2n) in the sub-scanning direction in one row , M)} is read from a storage device such as a memory. When black ink is to be applied to at least one of the first dot and the second dot based on the read information, the black ink nozzle (the nozzle in FIG. 6) that forms the first dot 59d-a) and a black ink nozzle (nozzle 59d-b in FIG. 6) forming the second dot when viewed from the main scanning direction, a first drying promoting liquid nozzle (FIG. 6). The drying accelerating liquid is discharged from the nozzle 59e-s).

Similarly, the third dot {coordinate position (2 (n + 1) -1, m)} and the fourth dot {coordinate position (2 (n + 1), m)} in the sub-scanning direction in one row are shown. Is read from a storage device such as a memory. When black ink is to be applied to at least one of the third dot and the fourth dot based on the read information, the black ink nozzle (the nozzle in FIG. 6) that forms the third dot is used. 59d-c) and 4
When viewed from the main scanning direction with the black ink nozzle (nozzle 59d-d in FIG. 6) that forms the second dot, the second drying-promoting liquid nozzle (nozzle 59e- The drying promotion liquid is discharged from t).

Thereafter, similarly, it is determined whether or not the drying promotion liquid is ejected from the n-th drying promotion liquid nozzle based on the image information of the 2n-1st dot and the 2nth dot. The drying promoting liquid is discharged from the drying promoting liquid nozzle 59e.

In this embodiment, as described above, the number of the drying promoting liquid nozzles 59e-s, 59et,... Is set to half the number of the black nozzles 59d-a, 59d-b,. Therefore, the manufacturing cost of the ink head can be reduced, and the consumption of the drying promotion liquid can be reduced.

The configuration of this embodiment can be applied to both the first and second embodiments.
When applied to the first embodiment, the present invention may be applied to only one of the drying promoting liquid heads, or may be applied to both of the drying promoting liquid heads.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. This embodiment is also a modification of the discharge mode of the drying promotion liquid. Other configurations and operations are the same as those of the above-described first embodiment. Therefore, here, only the discharge mode of the drying accelerating liquid will be described.

FIG. 7 shows the arrangement of the black ink head 58d and the drying promoting liquid head 58e. As shown in this figure, a plurality of nozzles are formed in each of the heads 58d and 58e. A plurality of black nozzles 59d, 59d,... Formed on the black ink head 58d.
Are formed in the sub-scanning direction, and are parallel to each other, in the sub-scanning direction. Further, each of the drying promoting liquid nozzles 59e, 59e,.
Are formed at positions facing the black nozzles 59d, 59d,... In the main scanning direction.

As a feature of the present embodiment, the interval between the black nozzle row and the drying promoting liquid nozzle row is set to “(d + ／) P”, where P is the print dot pitch in the main scanning direction. d is an integer of 1 or more).

In this embodiment, one dot of the drying promoting liquid is ejected corresponding to two dots of black ink in the main scanning direction, and the consumption of the drying promoting liquid is further reduced. It is possible.

Before the ink head 57 moves in the forward direction and discharges black ink, the control unit 6 determines the image information of the black pixels of the first dot and the second dot in the main scanning direction in one row. Read from a storage device such as a memory. When applying black ink to at least one of the first dot and the second dot based on the read information, a black ink nozzle for forming the first dot and the second dot is provided. The drying promotion liquid is discharged from the drying promotion liquid nozzle at the same position in the main scanning direction. The black ink nozzles forming the first dot and the second dot may be the same nozzle, or may be individual nozzles (when a plurality of black ink nozzles are arranged in the main scanning direction). There may be.

Next, the whole of the ink head 57 moves by one pitch in the main scanning direction to move the black ink nozzle 59d.
, The black ink of the first dot is ejected. At this time, the black dots are formed such that the centers thereof are shifted from the dot centers of the drying promoting liquid by about a half pitch in the main scanning direction.
In the above-described nozzle arrangement in the third embodiment, the drying promotion liquid is ejected every time the ink head 57 moves by one pitch. However, in the present embodiment, the drying promotion liquid is ejected once every two pitch movements. The drying promotion liquid may be discharged. Thereafter, the entire ink head 57 further moves by one pitch in the main scanning direction, and the black ink of the second dot is ejected from the black ink nozzle. At this time, the black dots are formed such that the centers thereof are shifted from the dot centers of the drying promoting liquid by about a half pitch in the main scanning direction.

Next, the control unit 6 reads the image information of the black pixels of the third dot and the fourth dot in the main scanning direction in one row from a storage device such as a memory. Then, for the subsequent dots, the “2m−1” -th dot and “2m−1”
Based on the image information of the “m” th dot, it is determined whether to discharge the “m” th drying promotion liquid from the drying promotion liquid nozzle, and the same image forming operation as described above is performed.

As described above, since one dot of the drying promotion liquid corresponds to two dots of the black ink in the main scanning direction, the consumption of the drying promotion liquid can be further reduced. Can be. Note that the nozzle arrangement in this embodiment can be applied to both the first embodiment and the second embodiment described above. When applied to the first embodiment, the present invention may be applied to only one of the drying promoting liquid heads, or may be applied to both of the drying promoting liquid heads.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described. This embodiment is also a modification of the discharge mode of the drying promotion liquid. Specifically, the configuration is a combination of the configuration of the third embodiment and the configuration of the fourth embodiment. Other configurations and operations are the same as those of the above-described first embodiment. Therefore, here, only the discharge mode of the drying accelerating liquid will be described.

FIG. 8 shows the arrangement of the black ink head 58d and the drying promoting liquid head 58e. As shown in this figure, each of the drying promoting liquid nozzles 59e, 59e,.
Are formed at positions shifted in the sub-scanning direction by half the nozzle spacing of the black nozzles 59d, 59d,... With respect to the formation positions of the black nozzles 59d, 59d,. Accelerating liquid nozzles 59e, 5
The nozzle intervals of 9e,...
are set to twice the nozzle interval of d,. That is,
One drying promoting liquid nozzle 59e corresponds to two adjacent black nozzles 59d, 59d, and when at least one of the two black nozzles 59d, 59d discharges black ink, the drying promoting liquid as a base thereof Is discharged from the drying promoting liquid nozzle 59.

The interval between the black nozzle row and the drying promoting liquid nozzle row is set to (d + ／) P, where P is the print dot pitch in the main scanning direction (d is 1).
Integer greater than or equal to).

That is, the black ink 2 in the main scanning direction
The configuration is such that one dot of the drying promoting liquid is ejected corresponding to each dot.

With this configuration, two dots of black ink in the main scanning direction and two dots of black ink in the sub-scanning direction are used.
The configuration is such that one dot of the drying promotion liquid is ejected in correspondence with a total of four dots including the individual dots, so that the consumption of the drying promotion liquid can be significantly reduced.

In the black pixel forming operation according to the present embodiment, first, before the black ink from the black ink head 58d is applied onto the recording paper S, the control unit 6 changes the arrangement of the dots in the main scanning direction. Assuming that “m” and the arrangement of dots in the sub-scanning direction are “n”, the first dot in the main scanning direction within one row ｛coordinate position (2n−1, 2m−
1)} and the second dot {coordinate position (2n-1, 2
m)｝ and the second dot in the same row in the sub-scanning direction as the first dot in the main scanning direction (hereinafter, referred to as a third dot)
{Coordinate position (2n, 2m-1)} and second dot in the same row in the sub-scanning direction as the second dot in the main scanning direction (hereinafter referred to as fourth dot) {Coordinate position (2n, 2m-1)}
m) Read the image information of the black pixel with｝ from a storage device such as a memory. Then, based on the read information,
When applying black ink to at least one of the first to fourth dots, the black ink nozzle forming the first dot and the black ink nozzle forming the third dot are viewed from the main scanning direction. Then, the drying promotion liquid is discharged from the first drying promotion liquid nozzle located between them. Next, the entire ink head moves by one pitch in the main scanning direction and moves from the black ink nozzle by one pitch.
The black ink of the third or third dot is ejected. Thereafter, the entire ink head further moves by one pitch in the main scanning direction, and the black ink of the second or fourth dot is ejected from the black ink nozzle.
In the above-described nozzle arrangement in the third embodiment, the drying promotion liquid is ejected every time the ink head moves by one pitch. However, in the present embodiment, one drying acceleration liquid is ejected every two pitch movements. What is necessary is just to discharge the drying accelerating liquid.

Then, "4n
-3 "th dot {coordinate position (2n-1, 2m-
1) {, "4n-2" th dot {coordinate position (2n-
1, 2m)}, "4n-1" th dot {coordinate position (2n, 2m-1)}, "4n" th dot {coordinate position (2n, 2m)} It is determined whether or not to discharge the (n, m) th drying promotion liquid from 59e, and the same image forming operation as described above is performed.

In this embodiment, as described above, since one dot of the drying promotion liquid corresponds to four dots of the black ink, the consumption of the drying promotion liquid is greatly reduced. Can be achieved. In addition, the manufacturing cost of the ink head can be reduced as the number of nozzles is reduced. Note that the nozzle arrangement in this embodiment can be applied to both the first embodiment and the second embodiment described above. When applied to the first embodiment, the present invention may be applied to only one of the drying promoting liquid heads, or may be applied to both of the drying promoting liquid heads.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described. This embodiment is a modification of the ejection control of each ink head.

In the above embodiment, the ink head 57
The operation control in the main scanning direction of the ink head 5 is performed one pitch at a time.
This was done by sending 7 mechanically. In this embodiment,
The clock control is performed while the ink head 57 is continuously moved in the main scanning direction to control the ejection timing of the ink and the drying promotion liquid.

FIG. 9A shows a state in which a predetermined basic clock is specified, and the time interval between the drying promotion liquid ejection pulse and the black ink ejection pulse is determined by scanning the ink head 57 and the drying promotion liquid. 6 is a timing chart in a mode in which the time interval between discharges of black ink is set to L times (L is an integer of 1 or more).

On the other hand, FIG. 9B shows a state in which a predetermined basic clock is specified, and the time interval between the drying promotion liquid ejection pulse and the black ink ejection pulse is determined by scanning the ink head and the drying promotion liquid. 6 is a timing chart of a mode in which the time interval between ejection of black ink and black ink is set to (L + Ｌ) times.

Such control makes it possible to simplify the configuration of the scanning mechanism and to perform control with high dot position accuracy. In this embodiment, FIG.
A variety of controls can be implemented by arbitrarily selecting the control methods (a) and (b).

-Other Embodiments- In each of the above-described embodiments, the discharge mode of the drying accelerating liquid relating to the formation of black pixels has been described. This is because an example using a pigment-based black ink which requires a long time for drying is given as an example. The present invention is not limited to this,
When there is a demand to shorten the drying time of the color ink by using the drying accelerating liquid, the same operation as the above embodiments may be applied as an image forming method using the color ink.

[0085]

As described above, according to the present invention, the ink jet image forming apparatus is provided with the drying promoting liquid discharging section for discharging the drying promoting liquid for promoting the drying of the ink droplets. By arranging the sections on both sides of the ink discharge section in the main scanning direction, one of the drying promoting liquid discharging sections discharges the drying promoting liquid to a predetermined position on the recording medium to which the ink droplet is to be applied. I have. For this reason, the drying time of the ink is shortened, the disturbance of the image due to the subsequent contact of the recording medium can be prevented, the number of images formed per unit time can be increased, and the performance of the inkjet image forming apparatus can be improved. be able to. Further, since the same image forming operation is performed in the forward path and the return path, high-quality image formation can be realized without the image hue being different depending on the scanning direction of the image forming unit. Furthermore, since it is not a method of shortening the time required for drying using inks of other colors, it is possible to greatly reduce the consumption of inks of other colors, and to reduce the consumption of other colors. The ink can be effectively used for original image formation.

Further, the drying-promoting liquid ejecting section is disposed only on one side of the ink ejecting section, and the drying-promoting liquid is ejected to a predetermined position on the recording medium where ink droplets are to be applied in the forward path and the return path during the forward movement. In this case, the size of the image forming unit in the main scanning direction can be reduced, which contributes to the overall size of the apparatus.

When the drying accelerating liquid is made of a colorless liquid having a color that does not change the hue of the ink when the ink is applied thereon or a colorless liquid, the reproducibility of the ink is improved. As a result, the ink drying time can be shortened and the image quality can be improved, and the practicality of the inkjet image forming apparatus can be improved.

Further, a plurality of drying promoting liquid nozzles formed in the drying promoting liquid discharge section are arranged so as to be shifted by a half pitch in the sub-scanning direction with respect to the ink nozzles formed in the ink discharging section. When the distance between the adjacent drying promoting liquid nozzles is set to be twice as long as the distance between the ink nozzles, the above-described effect can be obtained even though the number of the drying promoting liquid nozzles is half the number of the ink nozzles. Thus, the configuration of the image forming unit can be simplified, and the consumption of the drying promoting liquid can be reduced.

In addition, the position of the nozzle row of the drying promoting liquid is
When the ink nozzle is arranged at a distance of (d + ／) times the scanning pitch of the ink nozzle in the main scanning direction, one drying promoting liquid is provided for two dots of ink. Since the dots correspond to each other, the consumption amount of the drying promoting liquid can also be reduced.

By combining the arrangement of these two nozzles, it becomes possible to make one dot of the drying promoting liquid correspond to four dots of ink, and the consumption of the drying promoting liquid is greatly reduced. The frequency of replenishment of the drying accelerating liquid can be reduced, and the running cost of the apparatus can be reduced.

As a method of controlling the ejection timing of the ink and the drying promotion liquid, when the image forming means is moved in the main scanning direction and the clock control is performed to control the ejection timing of the ink and the drying promotion liquid, The configuration of the scanning mechanism can be simplified, control with high dot position accuracy can be performed, and higher-quality image formation can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an appearance of a color inkjet printer according to an embodiment.

FIG. 2 is a diagram illustrating the internal structure of a color inkjet printer.

FIG. 3 is a perspective view showing an ink jet mechanism.

FIG. 4 is a diagram schematically illustrating an arrangement state of each head according to the first embodiment.

FIG. 5 is a diagram schematically illustrating an arrangement state of each head according to a second embodiment.

FIG. 6 is a diagram schematically illustrating a nozzle arrangement state of each head according to a third embodiment.

FIG. 7 is a diagram schematically illustrating a nozzle arrangement state of each head according to a fourth embodiment.

FIG. 8 is a diagram schematically illustrating a nozzle arrangement state of each head according to a fifth embodiment.

FIG. 9 is a timing chart illustrating ejection timings of a black ink and a drying accelerating liquid according to a sixth embodiment.

[Explanation of symbols]

1 Color Inkjet Printer (Inkjet Image Forming Apparatus) 57 Ink Head (Image Forming Means) 58d Black Ink Head (Ink Discharge Unit) 58e, 58f Drying Acceleration Liquid Head (Drying Acceleration Liquid Discharge Unit) 59d Black Nozzle 59e Drying Acceleration Liquid Nozzle S Recording paper (recording medium)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Ogasawara 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Japan Inside Sharp Corporation (72) Inventor Mikihiro Hayashi 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Co., Ltd. F-term (reference) 2C056 EB58 EE17 HA22 HA42

Claims (12)

[Claims] 1. An ink jet image forming apparatus for forming an image on a recording medium by discharging ink droplets from an image forming means, the image forming means comprising: an ink discharge section for discharging ink drops; A drying-promoting-liquid ejecting unit for ejecting a drying-promoting solution for accelerating the ink. The drying-promoting-liquid ejecting unit is disposed on both sides of the ink ejecting unit in the main scanning direction. An ink jet recording apparatus, wherein one of the drying promoting liquid discharging units discharges the drying promoting liquid to a predetermined position on a recording medium to which the ink droplet is to be applied before the droplet is discharged. Image forming device. 2. An ink jet image forming apparatus for forming an image on a recording medium by discharging ink droplets from an image forming means, the image forming means comprising: an ink discharge section for discharging ink drops; A drying-promoting-liquid ejecting unit that ejects a drying-promoting solution for accelerating the ink. A predetermined position on the recording medium to which ink droplets are to be applied in the forward path and the backward path before the ink discharge section ejects the ink droplets in the forward path and the backward path in the main scanning direction. An ink jet image forming apparatus configured to discharge a drying promoting liquid during the outward movement. 3. The ink jet image forming apparatus according to claim 1, wherein the drying accelerating liquid has a color that does not change the hue of the ink when the ink is applied thereon, or is colorless. An ink-jet image forming apparatus comprising a liquid. 4. An ink jet image forming method in an ink jet image forming apparatus according to claim 2, wherein the ink discharge unit discharges ink before the image forming unit moves in a main scanning direction from a home position in a forward movement. Then, image formation information is acquired for each of the forward movement and the backward movement in the main scanning direction, and the image information at the time of the backward movement is inverted. An ink jet image forming method for causing a drying-promoting-liquid discharging unit to perform a drying-promoting-liquid discharging unit for two lines on the outward path and the returning path during the outward path, based on the reverse-processed image information at the time of the returning path. Method. 5. The ink jet image forming apparatus according to claim 1, wherein the plurality of drying promotion liquid nozzles formed in the drying promotion liquid discharge unit are arranged in a sub-scanning direction with respect to the ink nozzles formed in the ink discharge unit. Wherein the interval between the drying-promoting liquid nozzles adjacent to each other is set to be twice as long as the interval between the ink nozzles. apparatus. 6. An ink jet image forming method in an ink jet image forming apparatus according to claim 5, wherein one line is formed before the image forming means moves in the main scanning direction and the ink discharge section discharges ink. "2n-1" th and "2n" adjacent to each other in the sub-scanning direction
Reading at least one pair of image information of a pair of dots (n is an integer of 1 or more); and discharging ink from at least one of the pair of dots from an ink nozzle based on the image information. An ink jet image forming method comprising: discharging a drying promotion liquid from an “n-th” drying promotion liquid nozzle corresponding to the above. 7. The ink jet image forming apparatus according to claim 1, wherein the plurality of drying promoting liquid nozzles formed in the drying promoting liquid discharge section and the plurality of ink nozzles formed in the ink discharging section are:
A nozzle row extending in the sub-scanning direction is formed, and the position of the nozzle row of the drying promoting liquid is shifted from the ink nozzle to the scanning pitch of the ink nozzle in the main scanning direction by (d + 1 /
2) An ink-jet image forming apparatus, wherein the ink-jet image forming apparatus is disposed at a position having a distance twice (d is an integer of 1 or more). 8. An ink jet image forming method in the ink jet image forming apparatus according to claim 7, wherein one line is formed before the image forming unit moves in the main scanning direction and the ink discharge unit discharges ink. "2m-1" th and "2m" adjacent to each other in the main scanning direction
Reading at least one pair of image information of the third dot pair (m is an integer of 1 or more), and ejecting ink to at least one of the dot pairs based on the image information, in the main scanning direction of the image forming unit. An ink-jet image forming method comprising: discharging a drying-promoting liquid from a drying-promoting liquid nozzle corresponding to the above-mentioned dot pair every two pitch movements of the ink. 9. The ink jet image forming apparatus according to claim 1, wherein the plurality of drying promoting liquid nozzles formed in the drying promoting liquid discharge section and the plurality of ink nozzles formed in the ink discharging section are:
A nozzle row extending in the sub-scanning direction is formed, and each of the drying promoting liquid nozzles is arranged to be shifted by a half pitch in the sub-scanning direction with respect to each of the ink nozzles. The interval between the nozzles is set to be twice as long as the interval between the ink nozzles. On the other hand, the position of the nozzle row of the drying accelerating liquid is shifted from the ink nozzle by the scanning pitch of the ink nozzle in the main scanning direction. d + 1 /
2) An ink-jet image forming apparatus, wherein the ink-jet image forming apparatus is disposed at a position having a distance twice (d is an integer of 1 or more). 10. The ink jet image forming method in the ink jet image forming apparatus according to claim 9, wherein the image forming unit moves in the main scanning direction and the ink discharging unit discharges the ink before the specific position. When at least image information of four ink dots adjacent to each other around the ink dots are read, and ink is ejected to at least one of the four ink dots based on the image information, the center position of the four ink dots is An inkjet image forming method, comprising discharging a drying promoting liquid to a specific position. 11. An ink jet image forming method in the ink jet image forming apparatus according to claim 1, wherein the image forming means is moved in the main scanning direction, and clock control is performed to discharge the ink and the drying promoting liquid. An inkjet image forming method, wherein timing is controlled. 12. The ink-jet image forming apparatus according to claim 1, wherein the ink applied on the recording medium in superposition with the drying accelerating liquid is a pigment black. An ink jet image forming apparatus, which is an ink.