JP2001038927A - Ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet redording apparatus capable of forming an image high in gradation properties and reducing irregularity without increasing a circuit scale or transmission data quantity to a large extent. SOLUTION: A first drive waveform forming part 102 forms drive signals capable of forming dots different in size at every unit recording cycle to supply the signal forming a dot having the size corresponding to the data from a data distributing part 108 among them to even number-th nozzles and a second drive waveform forming part 103 forms drive signals capable of forming dots having a waveform different from a first drive waveform and different in size to supply the signal forming a dot having the size corresponding to the data from the data distributing part 108 among them to odd number-th nozzles.

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 apparatus for forming an image by ejecting inks having a plurality of different dot diameters onto a recording medium, and more specifically, to ejecting different amounts of ink droplets. And a method of generating and selecting a driving waveform for performing the operation.

[0002]

2. Description of the Related Art In recent years, OA equipment such as a personal computer, a copying apparatus, and a word processor has become widespread, and an apparatus for recording digital images by an ink jet system as one type of image forming (recording) apparatus of these apparatuses. Are rapidly developing and spreading. In particular, the colorization of OA equipment has been advanced along with the enhancement of its functions, and accordingly, various color ink jet recording apparatuses have been developed.

In general, an ink jet recording apparatus includes a carriage on which recording means (print head) and an ink tank are mounted, conveying means for conveying recording paper, and control means for controlling these. A direction (main scanning direction) perpendicular to the recording paper transport direction (sub-scanning direction) with the print head that ejects ink droplets from the plurality of ejection ports.
In this case, serial scanning is performed, while intermittent conveyance is performed by an amount equal to the recording width during non-recording. Further, in the case of a color-compatible ink jet recording apparatus, a color image is formed by superimposing ink droplets ejected by a print head of a plurality of colors.

In this recording method, characters and figures are recorded by discharging ink as fine droplets from a discharge port (nozzle) onto a recording medium in accordance with a recording signal, and is non-impact. Because it has the advantages of low noise, low running cost, easy downsizing of the device, and relatively easy colorization, it is used together with a computer or word processor, etc. Or in a recording device such as a copier, a printer, a facsimile, etc. used alone,
Widely used as image forming (recording) means.

As a method of ejecting ink in an ink jet recording apparatus, a heating element (electric / thermal energy converter) is provided in the vicinity of an ejection port, and an electric signal is applied to the heating element to locally heat the ink. A thermal method in which ink is ejected from an ejection port by causing a pressure change to occur, and a piezo method in which an ink is ejected by applying a mechanical pressure to the ink using an electric / pressure converting means such as a piezo element are used. ing. Generally, the former thermal method has a feature that it is easy to increase the density of nozzles and increase the number of nozzles. On the other hand, the latter piezo method has features such as excellent ejection controllability, high ink flexibility, and a semi-permanent head life.

FIG. 16 is a block diagram showing a schematic configuration of an entire control circuit of an ink jet recording apparatus to which the present invention can be applied.

A CPU 601 in the form of a microprocessor is connected to a host 624 via an interface 605, and a ROM 602 storing a control program, an EEPROM 603 storing an updatable control program and a processing program, various constant data, and the like;
The RAM 604 for storing command signals and recording information received from the H.24 via the interface 605 is accessed, and the recording operation is controlled based on the information stored in these memories. Further, the CPU 601 moves the carriage 620 by operating the carriage motor 611 via the output port 608 and the carriage motor control circuit 610, and operates the paper feed motor 614 via the output port 608 and the paper feed motor control circuit 613. Paper transport mechanism 61 such as a transport roller.
Operate 2 Further, the CPU 601 includes a RAM 604
A desired image can be recorded on a recording medium by driving the print head 622 via the print head control circuit 621 based on the recording information stored in the recording medium. The power supply circuit 619 outputs a logic drive voltage Vcc (for example, 5 V) for operating the CPU 601 and the print head control circuit 621, various motor drive voltages Vm (for example, 24 V), a print head 622.
Is output, for example, a voltage Vh (for example, 30 V) for driving. Further, instruction information input from the operation keys 607 is transmitted to the CPU 601 via the input port 606, and when an instruction from the CPU 601 is transmitted to the LED control circuit 615 via the output port 609, the LED is turned on or the display control circuit is activated. LCD 618 when transmitted to 617
Will display a message. A CPU bus 623 connects the above-described components to each other.

In the conventional ink jet recording method, it was necessary to use a special coated paper having an ink absorbing layer in order to obtain a high color image without bleeding of the ink. A method of giving printability to plain paper used in large quantities in printers and copiers has also been put to practical use. Further, it is desired to support various recording media such as OHP sheets, cloths, plastic sheets, and the like. In order to meet such demands, recording media (recording media) having different ink absorption characteristics were selected as necessary. At this time, a recording apparatus capable of performing the best recording regardless of the type of the recording medium has been developed and commercialized. Regarding the size of the recording medium, large-sized posters for advertisements and woven fabrics such as clothing have been required. The demand for such an ink jet recording apparatus has been increasing in a wide range of industrial fields as an excellent recording means.
It can be said that there is a demand for providing even higher quality images, and a demand for higher speed is further increasing.

In general, color ink jet recording methods include cyan (Cy), magenta (Mg), and yellow (Y
e) Color recording is realized by using the three color inks and using the four color inks to which black (Bk) is added. Unlike a monochrome ink jet recording device that prints only characters, such a color ink jet recording device requires various elements such as coloring, gradation, and uniformity when recording a color image image. Becomes

However, the quality of the recorded image largely depends on the performance of the print head alone. For example, in the thermal method, a slight difference in each nozzle that occurs during a print head manufacturing process, such as a variation in the shape of a discharge port of a print head or a variation in an electric / heat converter (discharge heater), is ejected to each of the nozzles. This affects the amount and the direction of the ejection direction, and causes deterioration in image quality as density unevenness of a finally formed print image. As a result, the area and the area are periodically
A "white" portion that does not satisfy the factor of 100% exists, or conversely, dots overlap more than necessary, or white streaks occur. These phenomena are usually perceived by human eyes as density unevenness.

Therefore, a method called a multi-pass printing method has been proposed as a measure against such density unevenness. Here, for the sake of simplicity, a case where a single ink color head having 12 nozzles is used will be described as an example. The state of recording is shown in FIG.

[0012] After the staggered pattern ● is recorded in the first scan and the paper is fed by half the recording width (6 dot width), the recording is completed by recording the inverted staggered pattern ○ in the second scan. That is, by alternately performing paper feed in a unit of 6 dots and recording in a staggered / inverted staggered pattern, a recording area in units of 6 dots is completed for each scan. In this manner, by printing one line using two different nozzles, a high-quality image with reduced density unevenness can be formed. In addition, the multi-pass printing method has an effect of suppressing bleeding by printing while drying the ink, and an increase in the temperature of the print head which causes ejection failure because the number of printing dots is reduced for each scan. The effect of suppressing the
Can be achieved at the same time. Here, the description has been made in the main scanning direction, but it is possible to further improve image quality by thinning out and recording dots continuous in the sub-scanning direction.

As a method of generating pass data for each scan, a method of generating pass data by thinning out print data using a staggered / inverted zigzag pattern as described above (referred to as a fixed mask method). Or a method of generating pass data by thinning out print data using a random mask pattern in which print dots and non-print dots are randomly arranged (referred to as a table mask)
Also, by skipping only the recording dots,
A method of generating data (referred to as a data mask) is known.

[0014]

Generally, in ink-jet recording, analog gradation expression cannot be realized with one dot. Therefore, a variety of color expressions are created by optimally arranging a plurality of dots per unit area. However, there is a limit to the amount of ink that can be applied per unit area without causing ink overflow. Although it greatly varies depending on the recording medium, the total amount of ink that can be ejected per 300 dpi ^* 300 dpi is at most about 200 pl. Furthermore, if the gradation is simply increased without changing the recording dot diameter, the actual resolution will be reduced.

If the resolution of the pixels is increased, finer gradation expression can be performed. If smaller dots can be ejected, color variations that can be expressed in a unit area increase, which is advantageous in terms of image quality. Further, the reduction in the size of the dots also brings about the effect of reducing the grain state. At present, discharge control of 3 pl or less has become feasible. Therefore, by reducing the amount of ejected ink droplets to reduce the recording dot diameter, it is possible to form a high-quality image with excellent gradation properties and inconspicuous granularity in a low density region.

However, since the area that can be filled with one dot becomes small with a small dot, it is necessary to print more dots than before in order to express high density, resulting in a longer recording time. Evils occur. Generally, when a small dot having a half dot diameter is used, four times the recording time is required. In order to prevent a reduction in the recording time, it is conceivable to increase the driving frequency for ejecting ink droplets four times, or increase the number of nozzles four times, but none of these methods is easy.

As a method for avoiding this, a method using dots of a plurality of sizes has been proposed. By printing dots of a plurality of different sizes from the same nozzle, it is possible to increase the recording speed by firing large dots instead of firing many small dots in a high density area. At the same time, the use of small dots in the low-density region reduces the graininess and enhances the gradation, so that high-speed, high-quality image formation can be realized.

In the so-called bubble jet method, a plurality of large and small heaters are provided, and the size of bubbles generated according to the number or type of operating heaters can be changed to control the ink discharge amount. In the piezo inkjet method, the ejection amount can be changed by controlling the drive voltage applied to the element and finely controlling the ejection (pressure) of the ink. At present, products that can use three types of dot diameters (discharge ink droplet amounts) in both types have been commercialized.

The control of the variable ink ejection amount in the piezo ink jet system will be briefly described. The piezo ink-jet method has excellent discharge controllability because active meniscus control is possible by controlling the drive signal, and it is relatively easy to print multiple size dots in a wide range from small dots to large dots. It is possible to stably discharge (split). Furthermore, it can be said that a great advantage is that the control of the flying speed of the ejected ink droplets is also possible. The drive waveform selection control for changing the dot size in the piezo inkjet system can be roughly classified into the following two systems. One is a “time-division pulse application method”, in which a plurality of drive pulses (for example, a large dot pulse and a small dot pulse) for ejecting different ink droplet amounts are continuously generated and input within one recording cycle. ON / OFF is independently controlled for these. The other is a “pulse switching method”, which simultaneously generates and inputs a plurality of drive pulses (for example, a large dot pulse and a small dot pulse) for ejecting different ink droplet amounts, and switches and uses them according to data. It is.

FIG. 17 shows an example of the "time-division pulse application method" in which drive waveforms for realizing the ejection of large dots and small dots are inserted in a time-division manner. . In the “time division pulse application method”, a large dot pulse and a small dot pulse are provided in a unit recording cycle. Control is performed such that the flying speed of the small ink droplet by the small dot waveform is relatively higher than the flying speed of the large ink droplet by the large dot waveform. As a result, it is possible to avoid or suppress the displacement of the landing positions of the small dots and the large dots driven at different timings on the paper surface. Further, not only the large dot waveform is turned ON to form a large dot, and the small dot waveform alone is turned ON to form a small dot, but also the large dot waveform and the small dot waveform are turned ON to obtain a maximum dot. It is also possible. FIG.
Is an example of a “pulse switching method” in which drive waveforms for realizing ejection of large dots and small dots are simultaneously generated and switched.

Increasing the types of dot sizes that can be ejected in this way basically leads to an improvement in gradation expression power. However, there are many problems in selectively forming dots of many sizes for each pixel.

In order to realize various dot sizes in the thermal method, it is necessary to increase the number and types of heaters to be mounted, and there is not a limit to mounting a large number of heaters for each nozzle. In the piezo method, in the case of the above-mentioned "time-division pulse application method", not only is it difficult to accurately align the landing positions of dots of different sizes, but also the recording speed is reduced due to a large unit recording cycle. Inevitable. In the case of the above-mentioned "pulse switching method", since a switch circuit is provided for each nozzle, cost increase due to an increase in circuit scale becomes a serious problem.

Further, if the dot size is one type, the data for each pixel can be binary, but if it is selected from four types, for example, five values are required. That is, as the types of dots that can be selected for each pixel increase, the necessary data amount increases dramatically. For this reason, printing / printing from the host PC side to the inkjet recording apparatus or within the apparatus
A large amount of data must be transferred to the head, and as a result, an increase in the number of wirings and an increase in the transfer rate may be unavoidable, which causes an increase in the circuit scale / the number of components and an increase in cost.

As a method of avoiding these problems, a method of forming dots of different sizes in a plurality of scans of the same area by multi-pass printing can be considered. For example, as shown in FIG. 19, a printing scan for forming large dots and a printing apparatus for forming small dots are alternately executed. However, if dots of different sizes are simply formed for each printing scan, density unevenness may occur and image quality may be significantly degraded.

This phenomenon will be briefly described with reference to FIG. FIG. 20 is a schematic cross-sectional view showing the state of penetration and fixation of the ink into the recording paper when the next dot is ejected at a relatively short time interval adjacent to the previously landed dot. Generally, ink droplets ejected later penetrate in a direction perpendicular to the paper surface and in a direction along the paper surface, but do not permeate and fix in a region where the ink droplets that have landed earlier have penetrated. The ink droplets ejected later penetrate and fix further below the area where the ink droplets ejected earlier have permeated. In contrast to this, in the above-described method, only large dots or small dots can be ejected for each scan, so that depending on the density based on the image data, a significant deviation in the dot area (duty) formed for each scan is avoided. However, there is a slight difference in the final density between the area selected for scanning for forming a large dot and the area for which scanning for forming a small dot precedes. Since the difference in density exists alternately corresponding to the paper conveyance width, there is a problem that the result may be recognized as unevenness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to form dots of various sizes efficiently and to form high-quality images with excellent gradation and without uneven density. An object of the present invention is to provide an excellent ink jet recording apparatus which enables the recording.

[0027]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a recording medium based on input image information while relatively scanning a print head having a plurality of ink discharge sections on the recording medium. An ink jet recording apparatus that forms an image by ejecting ink to each of the ejection units, wherein each of the ejection units ejects at least N types (N
.Gtoreq.2) can be formed, and at least one type of selectable dot different for each pixel formation position is predetermined from the N types of dots. The recording is performed by determining the dots to be formed at each pixel formation position based on the dot.

According to the present invention, a print head having an ejection section array composed of a plurality of ink ejection sections is scanned over a recording medium, and ink is ejected onto the recording medium based on input image information to form an image. In the inkjet recording apparatus, each of the ejection sections can form dots of N types (N ≧ 2) and can select differently from the dots of the N types for each pixel forming position. At least one
Dots of various sizes are predetermined, and at least one type of size that can be selected at each pixel formation position for each of the grouped discharge units in the even-number discharge units and the odd-number discharge units. The recording is performed by determining the dot of (1).

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 3 shows the structure of the recording section of the ink jet recording apparatus according to the present invention.

Reference numeral 301 denotes a print head, which includes ink tanks in which color inks of four colors (Bk, Cy, Mg, Ye) are respectively enclosed, and four ink tanks corresponding to the respective ink tanks.
And a multi-head in which one head is integrated. A carriage 302 supports the print head 301 and moves the print head 301 together with printing. The carriage 302 is at the home position HP shown in FIG. Reference numeral 303 denotes a paper feed roller, which rotates together with the auxiliary roller 304 in the direction indicated by the arrow in FIG. Reference numeral 305 denotes a paper feed roller, which feeds the recording paper 306 and plays a role of recording simultaneously with the paper feed roller 303 and the auxiliary roller 304 and suppressing the paper 306. Here, the print head 301 is Bk,
It has 64 nozzles arranged in the paper feed direction for each of the four colors Cy, Mg, and Ye.

The basic recording operation in the above configuration will be described.

During standby, the carriage 302 at the home position HP moves in the X direction in response to a print start command and ejects ink onto the print paper 306 in accordance with print data by a plurality of nozzles of the print head 301 to perform printing. When the recording of the recording data is completed to the end of the recording paper 306, the carriage returns to the original home position. When the paper feed roller 304 rotates in the direction of the arrow, the paper is fed by a predetermined width in the Y direction, and recording in the X direction is started again. Data recording is realized by repeating such a scanning operation and a paper feeding operation.

Although not shown, the inkjet recording apparatus according to the present embodiment includes a control unit including a CPU, a ROM, a RAM, a dedicated circuit for controlling and executing recording and image processing, an external host Drives an interface unit for exchanging image information and various control information with a computer, etc., a carriage motor for driving a carriage, a feed motor for driving a feed roller, a paper transport motor for driving a paper transport, and the like. Driver for driving a print head for driving the print head, an operation panel for inputting control information by a user,
And so on.

FIG. 4 is a schematic view of the vicinity of the pressure generating chamber of the print head. 401 is a piezoelectric vibrator, 402
Reference numeral 403 denotes a vibration plate that receives the displacement of the piezoelectric vibrator, 403 denotes a pressure chamber, 404 denotes an ink supply flow path connected to an ink reservoir, and 405 denotes a nozzle flow path. It is assumed that the print head has 16 nozzles and the nozzle pitch is 600 dpi.

FIG. 1 is a schematic block diagram showing a print head drive control block for generating a drive signal for each nozzle in accordance with input image information and supplying the same to the print head. Reference numeral 101 and a position detection unit detect the position of the carriage on which the print head is mounted. 10
Reference numeral 2 denotes a first drive waveform generation unit that generates a first drive waveform at a predetermined cycle in the recording area according to the position detection unit 101 and supplies the first drive waveform to the nozzle groups belonging to the first group. 103
Denotes a second drive waveform generation unit, which generates a second drive waveform at a predetermined cycle in the recording area according to the position detection unit 101 and supplies the second drive waveform to the nozzle groups belonging to the second group. 104
Denotes an offset control unit, and the first drive waveform generation unit 102
And the position detection unit 101 in the second drive waveform generation unit 103
The offset of the drive waveform generation timing with respect to the detection position based on the output is controlled. A memory unit 105 temporarily stores image data input from outside the figure. An input control unit 106 performs a process of writing recording data to the memory unit 105. An output control unit 107 reads out image data based on the position detected by the position detection unit 101 on the recording paper surface of the print head. 108
Denotes a data distribution unit which distributes data read from the memory unit 105 to corresponding nozzles and supplies the data.
Reference numerals 110a to 110p denote switch units corresponding to the nozzles # 0 to # 15, and drive waveforms O in accordance with the input data.
N / OFF control is performed. A control unit 120 monitors the status of each unit and performs various controls related to print head driving in response to control signals from inside and outside the drawing.

The ink jet recording apparatus according to the present embodiment employs a so-called multi-pass recording method in which an image is formed by scanning the same recording area a plurality of times. As described above, in multi-pass printing, an image is formed using a plurality of nozzles on one line, thereby suppressing density unevenness due to a slight difference in the ink ejection amount and ejection direction of each nozzle, and simultaneously performing pass printing. This is a printing method in which the print duty for each is reduced to prevent deterioration of image quality due to ink bleeding or the like. In this embodiment, two-pass printing will be described as an example. The recording resolution is 600 dpi in the main scanning direction × 600 dpi in the sub-scanning direction.

First, the driving waveform in this embodiment will be described. FIGS. 6A and 6B show the first drive waveform generated by the first drive waveform generator 102 and the second drive waveform generated by the second drive waveform generator 103, respectively. The first drive waveform generated by the first drive waveform generator 102 has a first unit recording cycle consisting of a drive signal M1 having two continuous waveform components, a waveform A1 and a waveform B1, and the subsequent unit recording cycle is continuous. And a drive signal N1 having a waveform D1 and a waveform E1, which are two waveform components,
The drive signal M1 and the drive signal N1 are alternately repeated every unit recording cycle. With the drive signal M1, three types of dots can be selectively formed. O only for waveform A1
The dot A1 is obtained by N, the dot B1 is obtained by turning ON only the waveform B1, and the dot C1 can be obtained by turning ON both the waveform A1 and the waveform B1. With the drive signal N1, dots of two types can be selectively formed. The dot D1 can be obtained by turning ON only the waveform D1, and the dot E1 can be obtained by turning ON both the waveform D1 and the waveform E1. The waveform D1 and the waveform E1 have the same waveform, and the waveform E1 is not turned ON alone. On the other hand, the second drive waveform generator 1
The second drive waveform generated in step 03 is a waveform D1 and a waveform E1 which are two continuous waveform components in the first unit recording cycle.
And a drive signal M1 having two continuous waveform components, a waveform A1 and a waveform B1, in a unit recording cycle that follows. In the second drive waveform, the recording cycle using the drive signal M1 and the drive signal N1 is opposite to the first drive waveform. Here, the unit recording cycle is 6 on the paper.
00 dpi, which is equal to the recording resolution in the main scanning direction.

Here, the dots formed by the driving waveform have the following relationship. First, the ejection ink droplet amount (dot diameter) has a relationship of dot E1> dot D1> dot C1> dot B1> dot A1. Further, with respect to the ejection ink droplet speed, the relationship of dot B1> dot A1 is satisfied in the drive signal M1, and the dots A1 and B1 (and the dot C1) land at almost the same position on the paper. On the other hand, in the drive signal M1, dot Es1> dot D
1, and the dots D1 and E1 land at approximately the same position on the paper. Here, the dot Es1 has the waveform E
1 indicates an ink droplet that forms a part of the dot E1 ejected.

In this embodiment, all 16 nozzles are divided into two groups, a first group consisting of even-numbered nozzle groups and a second group consisting of odd-numbered nozzle groups (FIG. 2). That is, the first driving waveform is the nozzle # (2
n) and the second drive waveform is nozzle # (2n + 1)
Supplied to Here, n is an integer of 0 or more. As described above, in the present embodiment, the same line is formed by two scans by two-pass printing. The two types of scan S and scan T are alternately repeated, and a half of the head width is interposed between scans.
Is carried out corresponding to the width of 8 nozzles. The offset control unit 104 controls the offset of the drive waveform generation timing in the scan S to be zero, and controls the offset in the scan T to be equivalent to one pixel (1/600 dpi). That is, the drive waveforms generated by the first drive waveform generator 102 and the second drive waveform generator 103 are shifted by one pixel between the scan S and the scan T. In the scan S, the first group is an even-numbered pixel row with a dot A1 or a dot B1 or a dot C
1. A dot D1 or a dot E1 can be formed in an odd-numbered pixel row, and a second group is a dot A1 or a dot B1 or a dot C1 in an odd-numbered pixel row, and a dot D1 in an even-numbered pixel row.
Alternatively, the dot E1 can be formed. On the contrary, in the scanning T, the first group can form the dot A1 or the dot B1 or the dot C1 in the odd-numbered pixel row, the dot D1 or the dot E1 in the even-numbered pixel row, and the second group can form the dot A1 or the dot A1 or the dot in the even-numbered pixel row. The dot B1 or the dot C1, and the dot D1 or the dot E1 can be formed by an odd pixel row.

In the scan S, the first drive waveform generator 102 and the second drive waveform generator 103 generate the first drive waveform and the second drive waveform without any offset in the main scanning direction. On the other hand, in the scan T, the first drive waveform generation unit 102 and the second drive waveform generation unit 103 offset the first drive waveform and the second drive waveform by an amount equivalent to one pixel (1/600 inch) in the main scanning direction. Generate a waveform. That is, in the scan S and the scan T, the recording cycle for generating the drive signal M1 and the recording cycle for generating the drive signal N1 are reversed. In the previous scan, the drive signal M1,
Coordinates (pixel position) at which the drive signal N1 is supplied in a later scan
And the drive signal N1 in the previous scan and the drive signal M1 in the subsequent scan
Are provided in a zigzag pattern. FIG. 5 shows the state of this printing scan. Here, since the paper transport amount is equivalent to 8 (even number) pixels, the scan S and the scan T with an offset are alternately repeated. However, if the paper transport amount is equivalent to odd pixels, the scan S is always performed. , Substantially the same printing scan can be performed.

Next, the image data format and the transfer direction will be briefly described. In the present embodiment, during the printing scan, all image data necessary for the next printing scan is transferred from the host PC and temporarily stored in the memory unit 104 via the input control unit 106. The image data stored in the memory unit 105 is 2-bit data per pixel. In each printing scan, the data stored in the memory unit 105 is printed by the output control unit 107 and printed by the position detection unit 101.
It is output based on the detection position of the head on the recording paper.

The image data at a certain coordinate (pixel position) is transferred from the host PC after being divided into two times according to the two scans. In one scan, it is drive instruction information for the drive signal M1, and in the other scan, it is drive instruction information for the drive signal N1. Specifically, for the drive signal M1,
In data 3, both the waveform A1 and the waveform B1 are turned on to form a dot C1, in data 2, only the waveform B1 is turned on to form a dot B1, and in data 1, only the waveform A1 is turned on.
To form the dot A1. Data 0
Turns off all waveforms and does not form any dots.
With respect to the drive signal N1, in the data 2, both the waveform D1 and the waveform E1 are turned ON to form the dot E1, and the data 1
Means that only the waveform D1 is turned on to form the dot D1. Data 0 turns off all waveforms and does not form any dots.

Thus, in the scanning S, three types of dots A1
Alternatively, pixels in which dots B1 or dots C1 can be selectively formed and pixels in which two types of dots D1 or dots E1 can be selectively formed are arranged in a zigzag pattern. As a result, it is possible to selectively form five types of dots A1 or B1 or C1 or D1 or E1 in all pixels. In addition, each pixel in each scan needs only data for one of the drive signal M1 and the drive signal N1, and the amount of transfer data from the host PC to the print head can be reduced.

In addition, since a dot size duty to be formed is not easily deviated during a single printing scan or between printing scans and the uniformity of pixel formation is excellent, a high quality image without density unevenness is formed. Can be.

Further, when a plurality of ink droplets ejected in a single scan are connected on the paper surface, the bleeding becomes uneven, the roundness is reduced, and the image quality is deteriorated. Such a phenomenon,
If a large-size dot is to be formed at a close coordinate position, it tends to occur inevitably. Compared with the case where the same waveform is supplied to each nozzle group to form multi-size dots in the same arrangement, the dot arrangement is different for each of the first and second groups of even / odd nozzles, thereby achieving a single scan. In this case, large-size dots are formed in the same column, which is effective for improving the quality of an image.

That is, a first drive waveform composed of a plurality of continuous drive waveforms for ejecting ink droplets of different weights,
A first drive waveform and a second drive waveform in which the order of the plurality of drive waveforms is different are generated to form a first nozzle group including even-numbered nozzles and a second nozzle group including odd-numbered nozzles. Supply. Further, the offset is changed in the main scanning direction for each scan, and the first drive waveform and the second
Generate a drive waveform. As a result, it is possible to efficiently form dots having different sizes within and between scans while reducing the amount of transfer data. And high quality image formation excellent in gradation is realized.

In this embodiment, three types of dots (A1, B1, C1) can be selected with two waveforms by a drive signal M1 applied in a unit print cycle, and two dots can be selected by a drive signal N1. Two types of dots (D1, E
1) shows an example in which selective formation is possible. In addition, the drive signal N1 and the drive signal M1 are supplied to all the pixel coordinates by the two-pass printing, and it is possible to form dots of five sizes. However, the number of waveforms inserted in each unit printing cycle is not limited to two, and may be one or three or more. Also, the combination of size types that can be formed is not limited to this. In addition, it is also possible to perform the overstrike by ejecting the two scans together. Further, the present invention can be applied to multi-pass printing with three or more printing passes. By selecting the optimal parameters according to the required image quality and throughput, it is possible to efficiently realize multi-tone image formation.

As described in detail above, a plurality of drive signals for generating a plurality of drive waveforms for ejecting ink droplets of different weights are generated in a different order, and supplied to each of the nozzle groups divided into groups. In combination with the waveform selection based on the data for ON and ON / OFF control, it is possible to form multi-size dots having a different arrangement for each nozzle group. An excellent ink jet recording apparatus capable of efficiently forming dots of various diameters and realizing high-quality image formation with high gradation without unevenness without increasing the circuit scale or the amount of transfer data can be realized.

(Second Embodiment) In the first embodiment, two types of driving waveforms are supplied to two nozzle groups to perform multi-pass printing (in the first embodiment, two-pass printing is performed).
Pass printing) has been described in detail. In the present embodiment, a case will be described in which four types of driving waveforms are supplied to four nozzle groups and an image is formed by one-pass printing.

Hereinafter, the second embodiment will be described in detail with reference to the drawings. The basic configuration of the entire apparatus is the same as in the first embodiment. Print and print in this embodiment
The head also has 16 nozzles for each color. The recording resolution is 600 dpi in the main scanning direction × 600 dpi in the sub-scanning direction.

FIG. 7 is a schematic block diagram showing a print head drive control block for generating a drive signal for each nozzle according to input image information and supplying the drive signal to the print head. A position detection unit 701 detects the position of the carriage on which the print head is mounted. 70
Reference numeral 2 denotes a first drive waveform generation unit that generates a first drive waveform at a predetermined cycle in the recording area according to the position detection unit 701 and supplies the first drive waveform to the nozzle groups belonging to the first group. 703
Is a second drive waveform generation unit that generates a second drive waveform at a predetermined cycle in the recording area according to the position detection unit 701 and supplies the second drive waveform to the nozzle groups belonging to the second group. 704
Denotes a third drive waveform generation unit that generates a third drive waveform at a predetermined cycle in the recording area according to the position detection unit 701 and supplies the third drive waveform to the nozzle groups belonging to the third group. 705
Is a fourth drive waveform generation unit that generates a fourth drive waveform at a predetermined cycle in the recording area according to the position detection unit 701 and supplies the fourth drive waveform to the nozzle groups belonging to the fourth group. 706
Denotes a memory unit for temporarily storing image data input from outside the figure. 707, an input control unit;
Then, a process of writing the recording data to No. 6 is performed. An output control unit 708 reads out image data based on the position detected by the position detection unit 701 on the recording paper surface of the print head. A data distribution unit 709 distributes the data read from the memory unit 706 to corresponding nozzles and supplies the data. 710a and 710p are nozzle # 0
And # 15, which performs ON / OFF control of the drive waveform in accordance with the input data. A control unit 720 monitors the state of each unit and performs various controls related to print head driving in response to control signals from inside and outside the drawing.

First, the driving waveform in this embodiment will be described. The first drive waveform generated by the first drive waveform generator 702, the second drive waveform generated by the second drive waveform generator 703, the third drive waveform generated by the third drive waveform generator 704, and the fourth drive waveform Drive waveform generator 70
5 and the fourth drive waveform generated by
10 to 10d. The first drive waveform includes a drive signal K2 including a waveform A2, a drive signal L2 including a waveform C2, a drive signal M2 including a waveform B2, and a waveform D for each unit recording cycle.
Four cycles are repeated in the order of the drive signal N2 consisting of two. In the drive signal K2, the dot A is turned on by turning on the waveform A2.
2 are obtained, and similarly, the dot C2,
A dot B2 can be obtained with the drive signal M2 and a dot D2 can be obtained with the drive signal N2. The second drive waveform, the third drive waveform, and the fourth drive waveform each have a different drive signal order in four continuous cycles, and the second drive waveform includes a drive signal L2, a drive signal M2, a drive signal N2, and a drive signal K2. In the third driving waveform, the driving signal M2, the driving signal N2,
The drive signal K2 and the drive signal L2 are in this order. In the fourth drive waveform, the drive signal N2, the drive signal K2, the drive signal L2,
The drive signal M2 is in that order. That is, in the first to fourth drive waveforms, the drive signal K2 to the drive signal N2
Are all different in the arrangement of the recording cycle. Here, the unit recording cycle is equivalent to 600 dpi on the paper surface, which is equal to the recording resolution in the main scanning direction.

Thus, in the first group, the dot A2 in the (4x) pixel row, the dot C2 in the (4x + 1) pixel row,
A dot B2 can be formed in a (4x + 2) pixel row and a dot D2 can be formed in a (4x + 3) pixel row. The second group is a dot C2 in a (4x) pixel row, a dot B2 in a (4x + 1) pixel row, and a dot B2, (4x + 2) pixel. Dot D2, (4x +
2) A dot A2 can be formed in a pixel row, and a third group includes a dot B2 in a (4x) pixel row, a dot D2 in a (4x + 1) pixel row, a dot A2 in a (4x + 2) pixel row,
The dot C2 can be formed in the (4x + 3) pixel row, and the fourth group is the dot D2, (4
The dot A2 can be formed in the (x + 1) pixel row, the dot C2 can be formed in the (4x + 2) pixel row, and the dot B2 can be formed in the (4x + 3) pixel row.

Here, the dots formed by the driving waveform have the following relationship. First, the ejection ink droplet amount (dot diameter) has a relationship of dot D2> dot C2> dot B2> dot A2. Further, regarding the ejection ink droplet speed, basically, dot A2 = dot B2
= Dot C2 = dot D2.

In this embodiment, all 16 nozzles are divided into four groups using the remainder obtained by dividing the nozzle number by four. Assuming that n is an integer of 0 or more, the four groups include a first group including a nozzle group having a nozzle number (4n), a second group including a nozzle group having a nozzle number (4n + 1), and a nozzle group having a nozzle number (4n + 2). ) And a nozzle group (4n
+3) is a fourth group of nozzle groups (FIG. 8). In all scans, the first drive waveform is supplied to nozzle # (4n) and the second drive waveform is supplied to nozzle # (4n).
+1), and the third driving waveform is nozzle # (4n +
2) and the fourth drive waveform is nozzle # (4n + 3)
Supplied to As described above, in this embodiment, one-pass printing is performed, and paper conveyance corresponding to a head width of 16 nozzles is performed between scans. FIG. 9 shows this printing scan.

Next, the image data format and the transfer method will be briefly described. In the present embodiment, during the printing scan, all image data necessary for the next printing scan is transferred from the host PC, and is transferred to the memory unit 7 via the input control unit 707.
06 is temporarily stored. The image data stored in the memory unit 706 is one bit data per pixel. In each print scan, the data stored in the memory unit 706 is output by the output control unit 708 based on the position detected by the position detection unit 701 on the recording paper surface of the print head.

Image data at a certain coordinate (pixel position) is transferred from the host PC only once in correspondence with one scan.
This is drive instruction information for the drive signal K2, drive signal L2, drive signal M2, or drive signal N2 supplied to each coordinate. Specifically, data 1 is applied to drive signal K2.
Then, the waveform A2 is turned on to form a dot A2. For the driving signal L2, the waveform B2 is turned on for the data 1 to form a dot B2. For the driving signal M2, the waveform C2 is formed for the data 1. ON to form a dot C2 and drive signal N
For data 2, data 1 means that waveform D2 is turned on to form dots D2, and data 0 means that no dots are formed in all cases.

Thus, the pixel coordinates at which the dot A2 can be formed, the pixel coordinates at which the dot B2 can be formed, the pixel coordinates at which the dot C2 can be formed, and the pixel coordinates at which the dot D2 can be formed are arranged in different columns for each nozzle. As a result, the formed dot size is less likely to be deviated, bleeding is suppressed, and high-quality image formation excellent in uniformity can be realized.

That is, with respect to a plurality of continuous drive waveforms for ejecting ink droplets of different weights, a first drive waveform, a second drive waveform, a third drive waveform, and a fourth drive waveform having different orders are generated. , A first nozzle group consisting of nozzles represented by nozzle number # (4n) and a second nozzle group consisting of nozzles represented by nozzle number # (4n + 1)
The nozzle group is supplied to a third nozzle group consisting of nozzles represented by nozzle number # (4n + 2) and a fourth nozzle group consisting of nozzles represented by nozzle number # (4n + 3). As a result, it is possible to efficiently form dots having different sizes while reducing the amount of transfer data, and to avoid the occurrence of density unevenness without causing an increase in cost and circuit scale. High quality image formation with excellent performance is realized.

As described in detail above, by generating a plurality of drive signals in which a plurality of drive waveforms for ejecting ink droplets of different weights are generated in different orders and supplying the generated drive signals to each of the grouped nozzle groups, It is possible to form a multi-size dot having a different arrangement for each nozzle group. An excellent ink jet recording apparatus capable of efficiently forming dots of various diameters and realizing high-quality image formation with high gradation without unevenness without increasing the circuit scale or the amount of transfer data can be realized.

(Third Embodiment) In the first and second embodiments, the piezo-type ink jet recording in which ink droplets are ejected by pressure generated by a vibrator that expands and contracts according to the input drive voltage waveform. The device has been described. In the third embodiment, a bubble jet method (thermal method) in which ink is locally heated by applying an electric signal to a heating element provided in the vicinity of a discharge port to cause a pressure change to discharge the ink. The ink jet recording apparatus will be described.

Hereinafter, the third embodiment will be described in detail with reference to the drawings. The basic configuration of the entire apparatus is the same as in the first embodiment.

FIG. 11 is a schematic view showing the vicinity of the heater of the print head. Reference numerals 1101 and 1102 denote a small heater and a large heater which generate different amounts of heat. Here, the positions are shifted from each other in the vertical direction and the horizontal direction. 1103 is an ink supply channel connected to the ink reservoir, and 1104 is a nozzle channel. Print·
It is assumed that the head has 16 nozzles and the nozzle pitch is 600 dpi.

When only the small heater 901 closer to the ejection port is driven to generate heat, ink droplets of an amount corresponding to the formation of the dot A3 are ejected, and the small heater 901 and the large heater 902 are ejected.
Are simultaneously driven to generate heat to eject ink droplets in an amount sufficient to form the dot B3. At each coordinate position in a single print scan, a small dot A3 is formed by driving the small heater 1101 or the small heater 1101 and the large heater 11 are driven.
The formation of the large dot B3 by the 02 drive can be selectively executed. Here, the unit recording cycle is 600 d on the paper.
pi, which is equal to the recording resolution in the main scanning direction.

In this embodiment, similarly to the first embodiment, all 16 nozzles are divided into a first group consisting of even-numbered nozzle groups and a second group consisting of odd-numbered nozzle groups (FIG. 2). ). As described above, in the present embodiment, the same line is formed by two scans by two-pass printing. The two types of scanning S and scanning T are alternately repeated, and a paper conveyance corresponding to an 8-nozzle width which is １ ／ of the head width is performed between the scannings. In the scanning S and the scanning T, the following dot formation is performed. First, in scan S, the first
In the group, the ON / OFF control of the small heater is performed based on the data in the printing cycle corresponding to the even pixel row (the large heater is
FF) to form a small dot A3, and in a printing cycle corresponding to an odd pixel row, ON / OFF of a large heater and a small heater is controlled based on data to form a large dot B3. In the second group, on the contrary to the first group, the large heater B and the small heater are turned on / off based on the data in the printing cycle corresponding to the even-numbered pixel row to form a large dot B3, and the printing corresponding to the odd-numbered pixel row is performed. In the cycle, ON / OFF of the small heater is controlled based on the data (the large heater is OFF) to form a small dot A3. Next, in the scan T, in the first group, a large dot B3 is formed in a recording cycle corresponding to an even pixel row, and a small dot A3 is formed in a recording cycle corresponding to an odd pixel row. In the second group, an even pixel row is formed. A small dot A3 is formed in a recording cycle corresponding to the above, and a large dot B3 is formed in a recording cycle corresponding to the odd pixel row. That is, one scan (S)
In the scan (T), the small dots A3 can be arranged in a staggered manner and the large dots B3 can be arranged in an inverted staggered manner.
Can be arranged in a zigzag pattern, and the small dots A3 can be arranged in a zigzag pattern. FIG. 12 shows this printing scan. Here, since the paper transport amount is equivalent to 8 (even number) pixels, the scan S and the scan T are alternately repeated. However, if the paper transport amount is equivalent to the odd pixel, the scan S (or the scan T) is always performed. ), Substantially the same printing scan can be performed.

The image data is 1-bit data per pixel, and data 1 at a coordinate position where a small dot A3 can be formed.
Means small heater ON, large heater OFF, large dot B
At the coordinate position where 3 can be formed, data 1 means that the small heater and the large heater are ON. Data 0 means that the small heater and the large heater are both turned off in both cases.

As a result, not only the amount of data transferred from the host PC to the print head can be reduced, but also the dot size and duty formed during a single print scan or between print scans are less likely to be biased, and the uniformity of image formation is reduced. In addition, it is possible to form an image excellent in gradation without density unevenness by suppressing bleeding due to overlapping of dots in scanning.

That is, the first nozzle consisting of the even-numbered nozzles
By changing the combination order of ON / OFF control for each recording cycle of a plurality of heaters for ejecting ink droplets of different weights between the nozzle group and the second nozzle group including the odd-numbered nozzles, the transfer data amount is changed. It is possible to efficiently form dots having different sizes within a scan and between scans while reducing the number of dots, without causing an increase in cost and circuit scale, and avoiding the occurrence of density unevenness. High quality image formation with excellent gradation is realized.

As described above in detail, by making the recording cycle for ejecting ink droplets of different weights different for each group of nozzles, it is possible to form multi-size dots having a different arrangement for each nozzle group. Become. An excellent ink jet recording apparatus capable of efficiently forming dots of various diameters and realizing high-quality image formation with high gradation without unevenness without increasing the circuit scale or the amount of transfer data can be realized.

(Other Embodiments) In the first and third embodiments, the nozzle number # (2n) and the nozzle #
(2n + 1), and in the second embodiment, nozzle # (4n), nozzle # (4n + 1), nozzle # (4n + 2), nozzle # (4
The description has been given by taking as an example a case where the image data is divided into first, second, third, and fourth groups each including (n + 3). The number of groups is not limited to two groups or four groups. Further, the grouping is not limited to the case where the uniform nozzle intervals are set to the same group, and a group of nozzles selected at random may be grouped, or a group may be grouped for each sheet conveyance width according to multi-pass printing.

In the first and third embodiments, two
In the second embodiment, a case where one-pass printing is performed has been described as an example, but it is apparent that the present invention can be applied to any multi-pass printing of three or more passes.

In the first embodiment, the "time-division pulse application method" is adopted as the drive waveform switching method in the pixel. However, the "pulse switching method" may be used. They may be used in combination. Further, the waveform may not be selected for each pixel as in the second embodiment.

In the third embodiment, the case where two large and small heaters are mounted and small dot formation by a small heater and large dot formation by a large and small heater are selected and executed has been described as an example. Many types of heaters may be mounted. The arrangement of the heater is not limited to this.

In the above embodiment, four colors (B
(k, Cy, Mg, Ye), an ink tank in which color inks are respectively enclosed, and an ink jet recording apparatus equipped with a multi-head in which four heads corresponding to the respective ink tanks are integrated. And a multi-head composed of independent one-color heads may be mounted. Further, the ink colors are not limited to four colors, and L-Cy and L-Mg
For example, a configuration using a plurality of inks having different densities using light colors may be used. The number of nozzles is not limited to 16. Furthermore, the inkjet recording apparatus that records one dot per pixel for each ink color has been described.
The same ink may be overprinted.

The number of print heads to be mounted is not limited to one set (one for each color).
The present invention can also be applied to an ink jet recording apparatus having two or more heads. FIG. 13 is a schematic diagram showing a configuration of a recording unit of an ink jet recording apparatus equipped with two sets of print heads. The carriage 302 has a first print head 301 and a second print head 307 mounted thereon, and has six colors (Bk, Cy, Mg, Y, L-Cy,
L-Mg) ink. FIG. 14 is a diagram showing an example of the ink arrangement of the two sets of print heads. Here, the ink arrangement is configured to be symmetric.

The form of the ink jet recording apparatus according to the present invention is not limited to the one provided integrally or separately as an image output apparatus of an information processing apparatus such as a computer or a word processor, and may be combined with a reading apparatus. It may be a copying machine or a facsimile machine having a communication function.

[0078]

According to the present invention, it is possible to efficiently form dots of various diameters, and to form a high-quality image with high gradation and little unevenness without greatly increasing the circuit scale and the amount of transferred data. It has an excellent effect that an ink jet recording apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a print head drive control block according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a manner of grouping nozzles included in a print head according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an ink jet recording apparatus according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram of a print head according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a state of print scanning according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating two types of drive waveform signals according to the first embodiment of the present invention.

FIG. 7 is a schematic block diagram of a print head drive control block according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a manner of grouping nozzles included in a print head according to a second embodiment of the present invention.

FIG. 9 is a diagram illustrating a state of print scanning according to a second embodiment of the present invention.

FIG. 10 is a diagram showing four types of driving waveforms according to the second embodiment of the present invention.

FIG. 11 is a diagram illustrating a print / print operation in a third embodiment of the present invention.
It is a schematic diagram of a head.

FIG. 12 is a diagram illustrating a state of print scanning according to a third embodiment of the present invention.

FIG. 13 is a schematic view showing an ink jet recording apparatus according to another embodiment of the present invention.

FIG. 14 is a diagram illustrating an example of an ink arrangement of a two-unit print head according to another embodiment of the present invention.

FIG. 15 is a schematic diagram illustrating a state of multi-pass printing.

FIG. 16 is a schematic block diagram illustrating a configuration example of an overall control circuit of the inkjet recording apparatus.

FIG. 17 is a schematic diagram illustrating a “time-division pulse application method”.

FIG. 18 is a schematic diagram illustrating a “pulse switching method”.

FIG. 19 is a diagram illustrating an example of a driving waveform switching method for multi-pass printing.

FIG. 20 is a schematic diagram illustrating the state of penetration and fixing when the difference in landing time of ink droplets that form adjacent dots is short.

[Explanation of symbols]

 Reference Signs List 101 Position detection unit 102 First drive waveform generation unit 103 Second drive waveform generation unit 104 Offset control unit 105 Memory unit 106 Input control unit 107 Output control unit 108 Data distribution unit 110 Switch unit 120 Control unit 622 Print head

Claims (10)

[Claims] An ink jet recording apparatus that forms an image by ejecting ink to a recording medium based on input image information while relatively causing a print head having a plurality of ink ejection sections to scan over the recording medium. Wherein each of the ejection sections can form dots of N types (N ≧ 2) by ejecting ink droplets having at least different weights,
At least one type of selectable dot different from each of the N types of dots for each pixel formation position is predetermined, and the dots to be formed at each pixel formation position are determined and recorded based on the image information. An inkjet recording apparatus. 2. The ejection unit according to claim 1, wherein the plurality of ejection units are grouped into a plurality of ejection unit groups, and at least one type of dot predetermined for each pixel formation position is different for each ejection unit group. Item 3. An ink jet recording apparatus according to Item 2. 3. The image forming apparatus according to claim 1, wherein the print head scans the same area of the recording medium a plurality of times to form an image, and each scan of the same area uses different types of dots for printing. Item 3. The ink jet recording apparatus according to item 1 or 2. 4. The printing apparatus according to claim 1, wherein the plurality of ejection unit groups are constituted by ejection unit groups having an equal interval among a plurality of ejection units arranged in a conveying direction of a recording medium. The inkjet recording device according to any one of the above. 5. The discharge unit group according to claim 1, wherein the plurality of discharge unit groups are formed by a discharge unit group having a length corresponding to a transport amount of the recording medium among the plurality of discharge units arranged in the transport direction of the recording medium. The inkjet recording apparatus according to claim 3, wherein 6. The discharge unit group according to claim 1, wherein the plurality of discharge unit groups are formed by a plurality of discharge unit groups arranged in a random manner among a plurality of discharge units arranged in a conveying direction of a recording medium. The inkjet recording device according to any one of the above. 7. An ink jet recording method in which a print head having an ejection section array including a plurality of ink ejection sections is scanned over a recording medium, and ink is ejected onto the recording medium based on input image information to form an image. In the apparatus, each of the discharge units is capable of forming N types of dots (N ≧ 2), and at least one type of the N types of dots that can be selected for each pixel forming position. Are determined in advance, and at least one of the even-numbered ejection unit groups and the odd-numbered ejection unit groups that can be selected at each pixel formation position for each of the grouped ejection unit groups
An ink jet recording apparatus for performing recording by determining dots of various sizes. 8. The image forming apparatus according to claim 7, wherein the print head scans the same area of the recording medium a plurality of times to form an image, and in each scan, different types of dots can be selected. Ink jet recording device. 9. The ink jet recording apparatus according to claim 1, wherein the print head ejects ink droplets by causing a state change in the ink using thermal energy. 10. The ink jet recording apparatus according to claim 1, wherein the print head ejects ink droplets by operating a piezo element.