JP2919640B2 - Inkjet recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording method for forming a clear image in a recording apparatus using an ink jet head having a plurality of nozzles.

[0002]

2. Description of the Related Art A so-called multi-droplet system in which a plurality of ink droplets are landed on substantially the same location on a recording member to form one pixel, and gradation is expressed by changing the number of ink droplets landed is known. , Inkjet recording,
In particular, it is effective as a method of expressing gradation in bubble jet printing in which it is difficult to greatly modulate the size of each ink droplet itself.

[0003]

However, in the conventional multi-droplet system, one pixel is formed by a plurality of ink droplets ejected from one nozzle. There has been a problem that streaks and density unevenness occur in a recorded image that should be uniform. In particular, there is a problem that, when the nozzle has a deviation, an overlapping portion occurs between adjacent dots, and a streak occurs, thereby greatly deteriorating the image quality. FIG. 8 schematically shows the occurrence of black streaks and white streaks in a recorded image in the case where the nozzle has a deviation. The circles in the figure indicate ink droplets that have landed on the recording member, and the portions where adjacent ink droplets overlap are black streaks. If the interval between adjacent ink droplets is too large, white streaks are formed.

In order to avoid these problems, in the conventional multi-droplet system, the head must be manufactured very precisely in order to suppress the variation in the volume of the ejected ink droplets between nozzles and the deviation thereof, resulting in cost reduction. There have been problems such as an increase in manufacturing cost and a decrease in manufacturing yield. Also, as a method of softly eliminating the density unevenness, a method of changing the number of ejected ink droplets so as to cancel out a small amount of ink droplets between nozzles by using image processing such as an error diffusion method is effective. There is a problem that the cost of the system is increased by incorporating a complicated image processing. Further, even if this image processing method is used, it is necessary to readjust ink droplets to be ejected when the ink droplet volume changes over time, and there is a problem that maintenance is poor.

An object of the present invention is to provide an ink jet recording method which solves the above problems.

[0006]

According to the present invention, there is provided an ink jet recording method for forming a gradation image using a head having a plurality of nozzles, the method comprising: Including scanning, a gradation image is formed by ejecting ink from different nozzles to one pixel in at least two sub-scans.

[0007]

According to the present invention, since one pixel is formed by ink droplets ejected from a plurality of nozzles, the variation in the ink droplet volume between the nozzles is reduced, and a recorded image in which streaks due to twisting are less likely to be obtained. .

Further, according to the present invention, one pixel is continuously recorded by m main scans and recorded by different m nozzles. For example, when the variation between the nozzles of the ink droplet volume is normally distributed with a standard deviation σ, the variation between the pixels per pixel is reduced to σ / √m in order to form one pixel with m different nozzles. The variation in ink capacity between pixels is recognized as the variation in pixel density. However, the variation in pixel density does not need to be “0” in order for the image to be clearly visible, and it is simpler than in the past because the variation in pixel density need only be small to some extent. With a simple system configuration, it is easy to obtain a clear image without unevenness and streaks.

[0009]

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

Embodiment 1 FIG. 1 is a schematic perspective view of an ink jet recording apparatus provided in each embodiment of the present invention.
In FIG. 1, reference numeral 11 denotes a recording head in which, for example, 42 (128 or 512 other) ink ejection ports are arranged at a density of 16 / mm. Each of the ejection ports has a liquid passage communicating therewith. An electric converter for generating discharge energy is provided. The electrical transducer generates heat in response to the applied electrical pulse, thereby causing film boiling in the ink,
Ink is ejected from the ejection port as bubbles grow due to the film boiling. In this example, the discharge frequency at each discharge port, that is, the drive frequency of the electric converter is 2 kHz.
It is. Reference numeral 4 denotes a carriage for mounting and moving the recording head, and the carriage 4 is moved while being guided by two guide shafts 5A and 5B which are slidably engaged at a part thereof. Reference numeral 6 denotes an ink supply tube for supplying ink to the recording head 11 by an ink tank (not shown). Reference numeral 7 denotes recording data from a control unit (not shown) to a head driving circuit provided in a part of the recording head 11. This is a flexible cable for transmitting a drive signal and a control signal based on the above. Both the ink supply tube 6 and the flexible cable 7 are formed of flexible members so as to follow the movement of the carriage 4. The carriage 4 is stretched in parallel with the guide shafts 5A and 5B and is connected to a part of a belt (not shown) for moving the carriage 4, and the belt is driven by a carriage motor (not shown). The carriage 4 can be moved. 3, the longitudinal direction is the guide shaft 5A,
A platen extends in parallel with 5B, and 2 is a recording member. The head 11 can perform recording by discharging ink to a portion facing the discharge port of the recording paper 2 as the carriage 4 moves.

FIG. 2 shows a schematic configuration of a control system circuit of the apparatus according to the embodiment of the present invention. Reference numeral 201 denotes a main controller that controls the entire apparatus such as a discharge timing.
A one-chip microprocessor or the like incorporating a U (central processing unit), a program ROM (read only memory), a work RAM (random access memory) and the like is usually used. The main controller 201 transmits an image data signal to a host computer 203 such as an image reader.
, And stores it in the frame memory 205 for the buffer in frame units. At the time of recording, the main controller 201 controls the drive of the carriage feed motor 209 through the motor driver 207 and controls the drive of the paper feed motor 213 through the motor driver 211.
At the same time, the image data signal read from the frame memory 205 is converted into gradation data according to the present system (printing apparatus), and the ejection control of the head 11 is performed via the driver controller 215 and the head driver 217 according to the present invention. , So that high-quality image recording can be obtained.

A case where four gradations are recorded using this apparatus will be described. That is, recording is performed while changing one pixel within the range of 0 to 3 ink droplets.

FIG. 3 is a conceptual diagram for explaining the recording method of this embodiment. Numeral 11 schematically shows a recording head, in which 42 nozzles are arranged in the vertical direction in the figure. For convenience, the nozzle numbers are changed from top to bottom in the figure # 1, #
2, # 3 to # 42. Further, the 42 nozzles are divided into 14 blocks of 3 nozzles, and each block is designated as A to A.
N, nozzles of each block are represented by a to c. In the case of this embodiment, for one pixel, image data 1 or more is recorded by the nozzle a of each block, image data 2 or more is recorded by the nozzle b, and image data 3 is recorded by the nozzle c. When recording on recording paper, first, recording is performed while moving the carriage using nozzles # 3 to # 42 (indicated by A in FIG. 3).
As a result, pixels at positions 1 to 40 in the vertical direction (sub-scanning direction) from above the recording paper are recorded with 0 or 1 ink droplets.

Next, the recording paper is fed upward by one pixel (in the figure, the head is relatively moved downward for convenience, and is shown at a position shifted in the main scanning direction for convenience). Recording is performed using nozzles # 2 to # 42 (in FIG. 3,
B). As a result, the nozzles # 2 to 41 record the pixels at the positions 1 to 40 recorded last time, and the nozzle # 42 (nozzle c) newly records the pixels at the position 41. Next, the recording paper is further advanced by one pixel, and recording is performed using nozzles # 1 to # 42 (shown by C in FIG. 3; # 41 (nozzle b)).
Is the pixel at position 41, and # 42 (nozzle c) is a new 4
The recording of the pixel at position 2 is performed). As a result, # 1 to # 40
Nozzles record 1 to 40 pixels recorded in the previous time and the previous time and form an image of 0 to 3 dots (for example, the pixel at the position 40 is # 42 (nozzle c) and # 41 (nozzle b)
And # 40 (nozzle a) in this order).

Next, the recording paper for 40 pixels is fed upward and # 1 to # 4.
Recording is performed with 42 nozzles (shown by D in FIG. 3; #
1 (nozzle a) is # (nozzle b) of the pixel at position 41
Performs recording of the pixel at the position 42). Next, the recording paper is further advanced by one pixel (indicated by E in FIG. 3).
Recording is performed using the nozzle No. 42, the recording paper for one pixel is further fed upward, recording is performed using the nozzles # 1 to # 42, and then the recording paper is fed upward for 40 pixels. Do. When the recording is repeated in this manner, the pixels at any positions are recorded by the nozzles c, b, and a.
An image with four gradations can be obtained over the entire screen.

At the lowermost end of the image, # 42
An image is formed by stopping the recording with the nozzles # 41, # 40 and # 40.

Paying attention to the image thus obtained, the first pixel (at position 1) is recorded by nozzles # 1, 2, 3 and the second pixel is recorded by nozzles # 2, 3, 4. Thus, since each pixel is continuously recorded by three different nozzles,
The variation in the ink droplet volume of each nozzle is averaged. Further, as shown in FIG. 3, the pixels at the positions 2, 3, and 4 in the main scanning direction are formed of only the # 4 nozzle for the image data 1, so that even if the # 5 nozzle is distorted, the effect does not appear. . Regarding the image data 2 and 3, if the # 5 nozzle is distorted, it affects the pixels at the positions 3, 4, and 5 in the main scanning direction. However, when the # 5 nozzle is used, the # 4 nozzle is always used.
Since the nozzles are used, the effects are averaged out and reduced.

When various images are recorded by using the above-described recording method, a clear image with very few streaks and unevenness can be obtained as compared with the conventional method of recording one pixel with a plurality of ink droplets ejected from the same nozzle. Obtained.

Embodiment 2 FIG. 4 shows a second embodiment of the present invention. The head 11 is a recording head in which 42 ink ejection ports are arranged at a density of 16 nozzles / mm, similarly to the first embodiment. In such a case, the nozzle arrangement of a, b, and c of each block is changed to b, c, and a.
The image data 2 or more is formed by the nozzle a, the image data 3 is formed by the nozzle b, and the image data 1 or more is formed by the nozzle c. The feed in the sub-scanning direction is the same as in the first embodiment. With such a configuration, the streak generated at the network of the blocks A and B was eliminated, and a good image was obtained.

[Embodiment 3] A method of printing 17 gradations using the print head 11 shown in FIG. 1 having 128 nozzles will be described. That is, printing is performed by changing the number of ink droplets per pixel in the range of 0 to 16.

FIG. 5 is a conceptual diagram for explaining the recording method of the third embodiment. Numeral 11 schematically shows a recording head, in which 128 nozzles are arranged in the vertical direction in the figure. For convenience, the nozzle No. Are # 1, 2, 3, ... 128 from top to bottom in the figure.

When recording on a recording paper, first, a step # 123 is performed.
Printing is performed while moving the carriage using only six nozzles of 128 to 128. As a result, 1 to 1
The pixel at the position 6 is recorded with 0 or 1 ink droplet.

Next, the paper is fed upward by 10 pixels (the head is relatively moved downward for convenience in the drawing). Recording is performed using nozzles # 113 to # 128.
As a result, the nozzles of # 113 to # 120 were changed to # 123 to # 1 of the previous time.
Pixels at positions 1 to 6 recorded by nozzles 28 are recorded, and nozzles # 119 to # 128 newly record pixels at positions 7 to 16. Therefore, the pixels at the positions 1 to 6 are 1
Recording is performed with 0 to 2 ink droplets per pixel.

Next, the paper is again moved up by 6 pixels, and
Recording is performed using nozzles 7 to 128. When such recording is sequentially repeated, when the 16th recording is completed, 1
Pixels at positions 8 are recorded with ink of 0 滴 16 drops, and an image of 17 gradations is obtained. If the recording is repeated in the same manner as above from the 17th time onwards, 17
A gradation image is obtained. In addition, at the lowermost end of the image, the recording is sequentially and repeatedly stopped from the lower side for 6 nozzles and 10 nozzles for each scan to form an image.

Focusing on, for example, the pixel at the position 1 in the image obtained in this way, the nozzles # 1, 11, 1
7, 27, 33, 43, 49, 59, 65, 75, 8
1, 91, 97, 107, 113, and 123 (the order of recording is reversed). Since the ink droplets are formed from a total of 16 nozzles, variations in the ink droplet volume of each nozzle are averaged, and streaks, unevenness, etc. Will be obtained.

When various images were recorded using the above-described recording method, compared with a conventional recording method in which one pixel was recorded by a plurality of ink droplets ejected from the same nozzle, an extremely sharp image having no stripes or unevenness was obtained. Can be obtained.

FIG. 6 shows a fourth embodiment of the present invention. 11 is 5
This is a recording head in which 12 ink ejection ports are arranged at a density of 16 nozzles / mm.
This figure shows a method of printing 13 gradations by sequentially repeating these with 8 pixels and 16 pixels.

FIG. 7 shows a fifth embodiment of the present invention. 11 is 4
A method of printing four gradations using a print head having eight ink ejection ports arranged at a density of 16 / mm will be described. For the 11 recording heads, 48
Nozzles are provided, and for convenience, nozzle No. Are # 1, 2, 3,... 48 from the top of the figure to the bottom.

When recording on recording paper, first, # 21 to # 21
Printing is performed while moving the carriage in the main scanning direction using only the 48 nozzles (indicated by A in the figure). At this time, the positions of pixels 1 to 20 from above the recording paper (nozzles # 21 to # 21)
40), that is, in the portion where x = 2 (x: the number of overlaps) in the figure, recording is performed with max 2 shots / pixel, and 20 to 2 pixels from the top of the recording paper.
At the position of 8 pixels (nozzle Nos. 41 to 48), that is, the portion where the number of overlaps is 3 in the figure, printing is performed with max one shot / pixel.

Next, the recording paper is fed upward by 20 pixels (in the drawing, the head is relatively moved downward for convenience), and printing is performed using all the nozzles (in the drawing,
B). At this time, the nozzles # 1 to # 28 are max
Recording is performed with one shot / pixel, and the nozzles # 29 to # 40 are ma
x2 shots / pixel, and the remaining portion (nozzles # 41 to # 4)
8) is recorded with max1 shots / pixel.

Next, the paper is again sent upward by 20 pixels, and nozzles # 1 to 28 max 1 shot / pixel, nozzles # 29 to 40
To perform recording with two shots / pixel and nozzles # 41 to 48 with one shot / pixel (indicated by C in the figure).

Such recording (paper is fed upward by 20 pixels, recording is performed at one shot / pixel by nozzles # 1 to 28 and 41 to 48, and recording is performed at 2 shots / pixel by nozzles # 29 to 40) is sequentially repeated. Thus, each pixel of the recording paper is recorded with the number of ink droplets of 0 to 3, and an image of four gradations can be obtained. In addition, at the lowermost end of the image, recording is performed by max. 1 shot / pixel by the nozzles # 1 to 20 to form an image.

Summarizing the above, when max 3 shots / pixel are set, pixels are formed by ink droplets of 0 to 2 in the first scan, and pixels are formed in the second scan by 0 in the first scan. A pixel is composed of １1 ink droplets. On the other hand, in the portion where the number of superpositions is three, pixels are constituted by 0 to 1 ink droplets every scan. When various images were formed using the above-described recording method, stripes and stripes were formed in comparison with a conventional method in which one pixel was recorded using a plurality of ink droplets ejected from the same nozzle.
It is possible to obtain an extremely clear image without unevenness.

(Others) It should be noted that the present invention includes a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for performing ink ejection, particularly in an ink jet recording system. An excellent effect is obtained in a recording head and a recording apparatus of a type in which the state of ink is changed by the thermal energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
It can be applied to any type of continuous type, but especially in the case of on-demand type, it can be applied to the sheet holding liquid (ink) or the electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. As a result, the liquid (ink)
This is effective because air bubbles can be formed inside. The liquid (ink) is ejected through an ejection opening (ejection port) through the process of growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. US Pat. No. 4,463,335 discloses a pulse-shaped drive signal.
No. 9 and No. 4,345,262 are suitable. Further, if the conditions described in US Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

As the configuration of the recording head, in addition to the combination configuration (a linear liquid flow path or a right-angled liquid flow path) of a discharge port, a liquid path, and an electrothermal converter as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333 and U.S. Pat.
A configuration using the specification of Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. 59-123670 discloses a configuration having a discharge section having a common slit as a discharge opening for a plurality of electrothermal transducers, and an aperture for absorbing pressure waves of thermal energy. The effect of the present invention is effective even if the configuration is based on JP-A-59-138461, which discloses a configuration in which is provided corresponding to a discharge unit. That is, according to the present invention, recording can be reliably and efficiently performed regardless of the form of the recording head.

In addition, even in the case of the serial type as described above, a recording head fixed to the apparatus main body, or an electric connection with the apparatus main body or ink from the apparatus main body by being attached to the apparatus main body. The present invention is also effective when a replaceable chip-type recording head that can be supplied or a cartridge-type recording head in which an ink tank is provided integrally with the recording head itself is used.

Further, it is preferable to add ejection recovery means for the recording head, preliminary auxiliary means, and the like as the configuration of the recording apparatus of the present invention since the effects of the present invention can be further stabilized. To be more specific, capping means for the print head, cleaning means, pressurizing or suction means, an electrothermal transducer or a heat generating element for generating thermal energy for discharging ink droplets necessary for printing. Preheating means for performing preheating using a different heating element or a combination thereof may be used, and predischarge means for performing discharge different from recording.

The type and number of recording heads to be mounted are, for example, not only one provided for single color ink, but also a plurality of inks having different recording colors and densities. A plurality may be provided. That is, for example, the printing mode of the printing apparatus is not limited to a printing mode of only a mainstream color such as black, but may be any of integrally forming a printing head or a combination of a plurality of printing heads. The present invention is also very effective for an apparatus provided with at least one of the recording modes of full color by color mixture.

In addition, the number of discharge ports is not limited to one, but a plurality of rows (for example, a configuration in which one row has 20 discharge ports and four rows are arranged) can be used.

In addition, in the embodiments of the present invention described above, the ink is described as a liquid. However, even if the ink is solidified at room temperature or lower, it can be softened or liquefied at room temperature. Since it can be used in liquid form when recording is performed, it can be used in the present invention. Alternatively, in the ink jet system, in some cases, the temperature is adjusted so that the ink itself is kept within a range of 30 ° C. or more and 70 ° C. or less, and the temperature is controlled so that the viscosity of the ink is in a stable ejection range. 30 ° C in this case
An ink that is liquid at a temperature of 70 ° C. or lower can be used. In addition, the ink is liquefied for the first time by heating in order to positively prevent the temperature of the ink itself from rising due to thermal energy or to prevent the ink from evaporating by using the energy as the energy of the state change from the solid state to the liquid state of the ink. May be used. In any case, the application of heat energy causes the ink to be liquefied by the application of the heat energy according to the recording signal and the liquid ink to be ejected, or to start solidifying when it reaches the recording medium. The present invention is also applicable to a case where an ink having a property of liquefying for the first time is used. In such a case, the ink
JP-A-54-56847 or JP-A-60-7
It may be used for recording while being held as a liquid material or a solid material in concave portions or through holes of a porous sheet as described in JP-A-1260. In the present invention, it is most effective to execute the above-described method of causing film boiling for each ink.

In addition, the form of the ink jet recording apparatus according to the present invention is not only one used as an image output terminal of an information processing apparatus such as a computer, but also a copying apparatus combined with a reader or the like, and further, a facsimile having a transmission / reception function. It may be in the form of an apparatus.

[0043]

As described above, according to the present invention, 1
Since one pixel is recorded by a plurality of nozzles, variations in the ink droplet volume between the nozzles are averaged, so that a clear image without streaks and unevenness can be obtained.

Further, since one pixel is formed by ink droplets ejected from a plurality of nozzles, variations in the ink droplet volume among the nozzles can be reduced, so that the production yield is increased and the cost is thereby reduced. .

Further, according to the present invention, the variation in the ink droplet volume between the nozzles is averaged, and the same image data is handled by the same nozzle in each block. Is effective.

Further, since it is not necessary to keep the sub-scanning amount constant, there is an advantage that the number of nozzles and the nozzle pitch are not restricted.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an ink jet recording apparatus to which the present invention is applied.

FIG. 2 is a circuit block diagram of the recording apparatus.

FIG. 3 is a conceptual diagram illustrating a recording method according to the first embodiment of the present invention.

FIG. 4 is a conceptual diagram illustrating a recording method according to a second embodiment of the present invention.

FIG. 5 is a conceptual diagram illustrating a recording method according to a third embodiment of the present invention.

FIG. 6 is a conceptual diagram illustrating a recording method according to a fourth embodiment of the present invention.

FIG. 7 is a conceptual diagram illustrating a recording method according to a fifth embodiment of the present invention.

FIG. 8 is a schematic view showing a streak generated when a nozzle has a twist in a conventional method.

[Explanation of symbols]

 2 Recording Material 3 Platen 4 Carriage 5A, 5B Guide Shaft 6 Ink Supply Tube 7 Flexible Cable 11 Recording Head 201 Main Controller 205 Frame Memory

Claims (5)

(57) [Claims] 1. An ink jet recording method for forming a gradation image using a head having a plurality of nozzles, the method comprising a plurality of sub-scans having at least one feed amount different from each other,
An ink jet recording method comprising forming a gradation image by ejecting ink from nozzles different from each other in at least two sub-scans for one pixel. 2. The method according to claim 2, wherein the number of nozzles is n, 1,
Assuming that the maximum number of droplets per pixel is m (m ≧ 2), the same amount of feed in the sub-scanning direction as (m−1) nozzle pitches and one (n−m + 1) * nozzle pitch 2. The ink jet recording method according to claim 1, wherein (m + 1) gradation pixels are formed by alternately performing the same amount of feeding in the sub-scanning direction. 3. In the sub-scanning, when the number of nozzles is n, the nozzle pitch is P, and the maximum number of droplets per pixel is m (m ≧ 2), the feed amount in each sub-scanning direction is N _1. × P, N ₂ × P, ..., N _m × P where n = N ₁ + N ₂
+ ... + inkjet recording method according to claim 1, characterized in that the N _m. 4. An ink jet recording method for forming a gradation image using a head having a plurality of nozzles, wherein the gradation image is formed by ejecting ink from a different nozzle to one pixel by a plurality of sub-scans. When forming, when the number of nozzles is n and the number of overlapping ink ejected by each nozzle is x, the feed amount in the sub-scanning direction is constant every time, and the number of overlapping x
Is different depending on the location. 5. The ink jet recording method according to claim 1, wherein the head discharges the ink by thermal energy.