JPH0752390A - Recording apparatus and inkjet recording apparatus - Google Patents

Abstract

PURPOSE:To provide an inkjet recording apparatus which can reduce density irregularities and obtain sufficient image quality at all times. CONSTITUTION:Random mask patterns of a predetermined size wherein non- recording pixels and recording pixels are arranged at random are set in four kinds of mask registers 105 corresponding to recording areas. The set mask patterns are output to selectors 106 and 107 and an AND circuit, 103, whereby the recording data is thinned. The recording data is fed to a recording head. Without a cycle of patterns in the thinned data, the periodicity of density irregularities is eliminated, so that images of high quality are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device, and more particularly to an ink jet recording device for recording by ejecting ink from a recording head.

[0002]

2. Description of the Related Art A recording device such as a printer, a copying machine or a facsimile is constructed to record an image consisting of a dot pattern on a recording material such as paper or a plastic thin plate based on image information. .

The recording apparatus can be classified into an ink jet type, a wire dot type, a thermal type, a laser beam type and the like depending on the recording method. Among them, the ink jet type (ink jet recording apparatus) is one in which ink is ejected from a discharge port of a recording head. (Recording liquid) droplets are ejected and ejected, and the droplets are adhered to a recording material for recording.

In recent years, a large number of recording devices have been used, and high speed recording, high resolution, high image quality, low noise, etc. are required for these recording devices. As an example of a recording device that meets such a demand, the inkjet recording device can be cited. In this ink jet recording apparatus, since recording is performed by ejecting ink from the recording head, stabilization of ink ejection is required to satisfy the above requirements.
Stabilization of the ink ejection amount is required.

However, although the ink jet recording apparatus attempts to stabilize the ink ejection, the quality of the image to be recorded largely depends on the performance of the recording head alone. Shape of ejection port of recording head and electrothermal converter (ejection heater)
A slight difference that occurs during the manufacturing process of the recording head, such as variations in the recording head, affects the ejection amount of each ejected ink and the direction of the ejection direction, and deteriorates the image quality as density unevenness of the finally formed image. Will be.

A specific example will be described with reference to FIGS. In FIG. 11-a, reference numeral 1101 denotes a multi-head, and for simplicity, it is assumed to be composed of eight multi-nozzles (1102). Reference numeral 1103 denotes an ink droplet ejected from the multi-nozzle 1102. Normally, it is ideal that ink is ejected in a uniform direction with a uniform discharge amount as shown in this figure. If such ejection is performed, dots of uniform size are landed on the paper surface as shown in FIG. 11-b, and a uniform image without density unevenness is obtained as a whole. (11-c).

However, in reality, as described above, each nozzle has variations, and if printing is performed in the same manner as above, as shown in FIG. The size and the direction of the ink drop ejected from the nozzle of No. 2 vary, and the ink drop is landed on the paper surface as shown in 12-b. According to this figure
Area factor 1 periodically with respect to the head main scanning direction
There is a blank portion that cannot be filled with 00%, or conversely dots are overlapped more than necessary, or a white streak appears in the center of the figure. The collection of dots landed in such a state has the density distribution shown in FIG. 12-c in the nozzle arrangement direction, and as a result,
Normally, these phenomena are perceived as density unevenness as seen by human eyes.

Therefore, as a countermeasure against this density unevenness, for example, a method as disclosed in JP-A-60-107975 has been devised. The method will be described with reference to FIGS. 13 and 14.
According to this method, the multi-head 2001 is scanned three times to complete the print area shown in FIGS. 11 and 12, but the area of a half 4-pixel unit is completed in two passes. In this case, the 8 nozzles of the multi-head are divided into a group of 4 upper nozzles and 4 lower nozzles, and 1 nozzle is 1 nozzle.
The dots printed by one scan are the prescribed image data thinned to about half according to a predetermined image data array. Then, at the time of the second scan, dots are embedded in the remaining half of the image data to complete the printing of the 4-pixel unit area. The recording method as described above is hereinafter referred to as a multi-pass recording method.

When such a recording method is used, even if the same head as the multi-head shown in FIG. 12 is used, the effect on the print image peculiar to each nozzle is halved, so the printed image is shown in FIG. 12B, the black streaks and white streaks shown in FIG. 12B are less noticeable. Therefore, the density unevenness is also shown in Fig. 1.
As shown in 3-c, it is considerably relaxed as compared with the case of FIG.

When performing such recording, the first scan and the second scan
In the scan, the image data is divided in such a manner as to fill each other according to a certain array, and this image data array (thinning-out pattern) usually forms a staggered grid for each vertical and horizontal pixel as shown in FIG. It is most common to use something like this.

Therefore, in the unit printing area (here, in units of 4 pixels), printing is completed by the first scan for printing the zigzag lattice and the second scan for printing the inverse zigzag lattice.

An example of electrical control in the case of performing such thinning printing will be described below with reference to FIGS. The Head unit sets the print data Si in the 8-bit shift register with the print data synchronization clock CLKi, BEi1 *, BEi2 *, BEi3 *,
The BEi4 * signal is turned on to drive the HEAD transistor array and heat the Heater to print. Here, * indicates low active. The LATCH * signal is a control signal for latching print data, and the CARESi * signal is a reset signal for clearing the latch. One heat is Heat Trigg
er signal starts from the pulse generator BEi1 *, BEi2 *, BEi3
Outputs *, BEi4 * signals. This signal may be output while being shifted in time, but here, for simplification, they are output simultaneously.

In order to perform thinning, the flip-flop in the figure is hit with a Heat Trigger signal to change the masking signals (for example, BEi1 * and BEi3 *) alternately with each heat.
Actually, it depends on High / Low of the output signal DATAENB of the flip-flop as shown in the timing chart of FIG. He
BEi1 *, BEi2 *, BEi3 *, BEi4 * when at Trigger signal is applied
The signal goes low and each nozzle heats up. The masked timing is written with a broken line in the figure and corresponds to the DATAENB signal. Both the EVEN signal and the ODD signal are signals for initial setting of the mask pattern. If you want to print in a staggered pattern, EV before printing one line.
When the EN signal is sent, the flip-flop is preset and zigzag printing is possible. On the line where you want to perform reverse zigzag printing, the flip-flop is reset when the ODD signal is sent and the BEi2 * and BEi4 * signals are turned on first, enabling reverse zigzag printing.

14-a, 14-b, and 14-c in FIG. 14 show how recording of a fixed area is completed when the zigzag and inverse zigzag patterns are used, as in FIG. This is explained using a multi-head having nozzles. First, in the first scan, printing is performed in a staggered pattern (marked with diagonal lines) using the lower four nozzles (14-a).
Next, in the second scan, the paper feed is 4 pixels (1/1 of the head length
Only 2) is performed, and an inverted zigzag pattern (white circles) is recorded (14-b). Further, in the third scan, the paper is fed again by 4 pixels (1/2 of the head length), and the staggered pattern is recorded again (14-c).

In this way, the paper is fed in units of 4 pixels in sequence,
By alternately recording zigzag and reverse zigzag patterns,
The recording area in units of 4 pixels is completed for each scan. As described above, by completing printing with two different types of nozzles in the same area, it is possible to obtain a high-quality image without density unevenness.

[0016]

However, even when such multi-pass printing is performed, the above density unevenness is not completely eliminated depending on the duty, and new density unevenness is confirmed especially in the halftone. Or The phenomenon will be described below.

Usually, the image data to be recorded in a certain area received by the printer is already regularly arranged. On the recording device side, a certain amount of that data is stocked in a buffer, and a new mask (image array pattern) such as zigzag or inverse zigzag is applied,
Only when both are turned on, the pixel is printed.

FIGS. 17 to 19 explain this situation. In FIG. 17, reference numeral 1710 denotes already-arranged data stored in the buffer, 1720 denotes a zigzag pattern mask indicating pixels that allow printing in the first pass, and 1730 denotes 2
Inverted zigzag pattern masks 1740 and 1750 showing pixels that are allowed to be printed in the first pass represent pixels to be printed in the first pass and the second pass, respectively.

In FIG. 17, the area 2 in the buffer is
When printing 5%, the arrayed data is already stocked. In general, this data is arranged in a state where the print data is scattered as much as possible in order to keep the density uniform in a specified fixed area. What kind of image arrangement these have depends on what kind of area gradation method is used at the time of image processing before being transferred to the printer main body. What is shown in 1710 is an example of a certain image array for 25% data, but for such data, 1720 and 173, respectively.
If printing is performed with a mask of 0, data is distributed and recorded in the first pass and the second pass in the state in which the data is equally divided as indicated by 1740 and 1750.

However, as shown in FIG. 18, exactly 50%
Data comes in, the data 1810 in which the images are arranged in the most scattered state and the staggered pattern mask (180
It is easy to imagine that either 2) or the reverse zigzag pattern mask (1830) will be in a completely aligned arrangement.

When this happens, the first pass (184
In 0), printing of all image data is completed, and no printing is performed in the second pass (1850). That is, all print data (1810) is printed by the same nozzle. Therefore, the effect of nozzle variation will be directly reflected in the density unevenness,
The original purpose of the divided recording method cannot be achieved.

FIG. 19 shows the printing state when the array image data with a higher duty than that of FIGS. 17 and 18 is input. In this case as well, printing is performed in the first pass and the second pass. You can see that the numbers are quite different. As described above, the density unevenness, which was improved at a high duty near 100%, appears again at the data near a low duty of about 50%.

As shown in FIG. 14, the head always prints a staggered pattern or an inverted zigzag pattern using all nozzles. Therefore, in the print area of FIG. 14, the upper 4 pixels are landed in the staggered pattern first, and then the reverse zigzag pattern is landed. After the staggered pattern is landed, the staggered pattern is landed. In other words, if this is combined with the above problem, a printing area in which a large number of dots are landed in the first pass and then a small amount of dots are landed in the second pass, and there is almost no printing in the first pass and in the second pass Areas where a large number of dots are printed will appear alternately every half the width of the head. From such a phenomenon, the following adverse effects were also caused especially at the joint portion of the ink jet recording system.

In the ink jet recording system, when another dot is superposed on a previously recorded dot, the dot hit later than the previously recorded dot sinks in the depth direction of the paper in the overlapping portion. There is a tendency.

FIG. 20 is a sectional view schematically showing it. This is because the dyes such as dyes in the ejected ink physically and chemically bond with the recording medium, but at this time, the bond between the recording medium and the dyes is finite, and thus the bonding force greatly differs depending on the type of dye. As long as there is no ink dye (cross-hatching) ejected first, the ink dye (cross-hatching) remains on the surface of the recording medium because it is preferentially bonded, and the ink dye (hatching) that is ejected later is not printed on the recording medium surface. It is thought that it is difficult to combine and sinks in the depth direction of the paper surface. Further, when considering the behavior of the ink at the fiber level inside the recording medium, the fiber once bound to the dye or the like in the ink is stronger in hydrophilicity than the state where it is not bound at all. Therefore, the ink droplet that has landed adjacent to the highly hydrophilic portion tends to be drawn in the direction in which the previous ink droplet has landed.

Further, as the previous ink droplets are not sufficiently fixed, that is, the more the water droplets are contained, the stronger the hydrophilicity is, and the ink droplets landing adjacently are easily attracted. Therefore, the print area in which a small number of dots are landed after a large number of dots are landed and the area in which a large number of dots are printed in the second pass in a state where almost no dots are printed at the beginning is half the width of the head. If they appear alternately, the dots recorded in the area adjacent to the print area where a lot of ink has landed at the boundary have a strong attraction force and are adjacent to the print area where a small amount of ink has landed. The dots recorded in the area have a weak attraction. Due to this difference, the density of the boundary between the print areas may be dark or light, resulting in uneven density. This is a halftone, which is particularly noticeable, and has a periodicity that alternates by half the width of the head.

When thinning printing is performed using a specific mask pattern, the print data and the mask pattern may have the same period. Resonance occurs when the amplitude of print density and the amplitude of print data due to the arrangement of print pixels and non-print pixels in the mask pattern overlap. The dot array of the image thus formed has a pattern with a certain specific directionality. This phenomenon is usually called moire. This is conspicuous when the image using the same mask pattern is present in a plurality of lines, and is easily recognized by the user. This moire largely depends on the periodicity of the mask pattern.

Due to the adverse effects described above, in multi-pass printing which is performed to correct nozzle variations and the like, it is not always possible to obtain sufficient image quality with respect to density unevenness. These adverse effects of density unevenness have a periodicity that appears alternately in a print area of a certain width, and therefore promote human vision that is recognized as density unevenness.

Therefore, an object of the present invention is to provide a recording apparatus and an inkjet recording apparatus which can always obtain sufficient image quality by reducing uneven density.

[0030]

In order to achieve the above-mentioned object, the present invention makes a recording head having a plurality of ink ejecting sections to scan the same recording area of a recording medium a plurality of times, and in each scanning. In an ink jet recording apparatus for forming a thinned image according to a thinning pattern to complete an image, non-printing pixels and printing pixels are randomly arranged, and a generating means for generating a plurality of random mask patterns of a predetermined size, and this generating means. The random mask pattern thus generated is used as a thinning pattern for the respective recording areas, and thinning means for thinning print data is provided.

[0031]

According to the above construction, by forming an image with the print pixels according to the random mask mask pattern, the pattern period of the thinning array is not provided, and the same nonuniformity in the conventional multipass printing method is eliminated. By eliminating the periodicity of the density unevenness, the adverse effect of the density unevenness, which occurs due to the number of print pixels in the multi-pass printing of the print area several times, is overcome.

[0032]

EXAMPLES Examples of an ink jet recording apparatus of the present invention will be described in detail below with reference to the drawings.

21 to 25 are preferred ink jet unit IJU, ink jet head IJH, ink tank IT, ink jet cartridge IJC, ink jet recording apparatus main body IJRA, and carriage HC to which the present invention is applied or applied. FIG. 6 is an explanatory diagram for explaining the relationship between the two. Hereinafter, the configuration of each part will be described with reference to these drawings.

(I) General Description of Apparatus Main Body FIG. 21 is an example of a schematic view of an ink jet recording apparatus IJRA applied to the present invention. In the figure, the driving force transmission gear 501 is interlocked with the forward and reverse rotations of the drive motor 5013.
Lead screw 500 rotating through 1,5009
The carriage HC that engages with the spiral groove 5004 of No. 5 has a pin (not shown) and is reciprocated in the directions of arrows a and b. The carriage HC is equipped with an ink jet cartridge IJC. Reference numeral 5002 denotes a paper pressing plate that holds the paper in the platen 500 in the carriage moving direction.
Press against 0. Reference numerals 5007 and 5008 denote photo couplers, which are home position detecting means for confirming the existence of the carriage lever 5006 in this region and switching the rotation direction of the motor 5013. Reference numeral 5016 is a member for supporting a cap member 5022 for capping the front surface of the recording head. Reference numeral 5015 is a suction means for sucking the inside of the cap to perform suction recovery of the recording head via the inside-cap opening 5023. 5017 is a cleaning blade.
Reference numeral 019 denotes a member that allows this blade to move in the front-rear direction, and these members are supported by the main body support plate 5018. Needless to say, a well-known cleaning blade can be applied to this example instead of this form.

Reference numeral 5012 is a lever for starting suction for suction recovery, and a cam 5020 for engaging with the carriage.
And the driving force from the drive motor is controlled by known transmission means such as clutch switching.

The capping, cleaning, and suction recovery are configured so that the desired processing can be performed at their corresponding positions by the action of the lead screen 5005 when the carriage comes to the home position side area. Any desired operation can be applied to this example if desired operation is performed at the timing.

Ink Jet Cartridge IJ in this Example
In C, the ink storage ratio is high, and the tip of the ink jet unit IJU slightly protrudes from the front surface of the ink tank IT. This ink jet cartridge IJC is a type that is fixed and supported by the above-mentioned positioning means of the carriage HC mounted on the ink jet recording apparatus main body IJRA and the electrical contacts, and is removable from the carriage HC. is there.

(Ii) Description of Ink Jet Unit IJU The ink jet unit IJU is of a type in which recording is performed by using an electrothermal converter which generates thermal energy for causing film boiling to the ink in response to an electric signal. It is a unit.

(Iii) Description of Heater Board FIG. 22 is a schematic view of the heater board 100 of the head used in this embodiment. The temperature adjustment (sub) heater 8d for controlling the temperature of the head, the ejection portion array 8g in which the ejection (main) heater 8c for ejecting the ink is arranged, and the drive element 8h are positioned as shown in FIG. Because of this, they are formed on the same substrate. By arranging each element on the same substrate in this manner, the head temperature can be detected and controlled efficiently, and the head can be made compact and the manufacturing process can be simplified. The figure also shows the positional relationship of the cross section 8f of the outer peripheral wall of the top plate, which is divided into a region where the heater board is filled with ink and a region where it is not. The discharge heater 8d side of the outer peripheral wall cross section 8f of the top plate functions as a common liquid chamber. In addition, the liquid passage is formed by the groove portion formed on the discharge portion row 8g of the outer peripheral wall cross section 8f of the top plate.

(Iv) Description of Control Configuration Next, a control configuration for executing recording control of each unit of the above-described apparatus configuration will be described with reference to the block diagram shown in FIG. In the figure showing the control circuit, 10 is an interface for inputting a recording signal, 11 is an MPU, 1
Reference numeral 2 is a program ROM that stores a control program executed by the MPU 11. Reference numeral 13 is a dynamic RAM that stores various data (the above-mentioned recording signals and recording data supplied to the head). The number of times the recording head is replaced can also be stored. 14 is a recording head 1
8 is a gate array for controlling supply of recording data to the interface 8, interface 10, MPU 11, RAM 13
It also controls the transfer of data between them. Reference numeral 20 is a carrier motor for carrying the recording head 18, and 19 is a carrying motor for carrying the recording paper. Reference numeral 15 is a head driver for driving the head, and 16 and 17 are motor drivers for driving the carry motor 19 and the carrier motor 20, respectively.

FIG. 24 is a circuit diagram showing the details of each part of FIG. The gate array 14 includes a data latch 141,
It has a segment (SEG) shift register 142, a multiplexer (MPX) 143, a common (COM) timing generation circuit 144, and a decoder 145. The recording head 18 has a diode matrix configuration, and a drive current flows through the ejection heaters (H1 to H64) where the common signal COM and the segment signal SEG match, and the ink is heated and ejected.

The decoder 145 decodes the timing generated by the common timing generation circuit 144 and selects any one of the common signals COM1 to COM8. The data latch 141 latches the recording data read from the RAM 13 in 8-bit units, and the multiplexer 143 stores the recording data in the segment shift register 1
According to 42, it outputs as segment signals SEG1-8. The output from the multiplexer 143 can be variously changed according to the contents of the shift register 142, such as 1 bit unit, 2 bit unit, or all 8 bits as described later.

The operation of the above control structure will be described. When a recording signal is input to the interface 10, the recording signal is converted between the gate array 14 and the MPU 11 into recording data for printing. Then, the motor drivers 16 and 17 are driven, and the recording head is driven according to the recording data sent to the head driver 15 to perform printing.

Next, FIG. 25 shows a block diagram for explaining the flow of print data inside the printing apparatus. The print data sent from the host computer is stored in the receiving buffer inside the printing apparatus via the interface. The reception buffer has a capacity of several k to several tens of kbytes. Command analysis is performed on the recorded data stored in the reception buffer, and then the data is sent to the text buffer. In the text buffer, the recorded data is held as an intermediate format for one line,
A process is performed in which the print position of each character, the type of modification, the size, the character (code), the address of the font, etc. are added. The capacity of the text buffer varies depending on each model,
A serial printer has a capacity of several lines, and a page printer has a capacity of one page. Further, the print data stored in the text buffer is expanded and stored in the print buffer in a binarized state, and a signal is sent to the print head as print data for printing. In this embodiment, the binary data stored in the print buffer is multiplied by mask pattern data (random mask) described later, and then the signal is sent to the print head. Therefore, it is also possible to set the mask pattern data after observing the data stored in the print buffer. Depending on the type of recording device, there is also a device which does not have a text buffer and expands the recording data accumulated in the reception buffer simultaneously with command analysis and writes it in the print buffer.

Specific examples of the present invention will be described below using such an apparatus.

(Embodiment 1) As a first embodiment, an example using a thinning pattern by a random mask of an ink jet recording apparatus will be described below with reference to the drawings.

How to generate a random mask will be described with reference to FIG. In this embodiment, 2 used for 4-pass printing
A 4 × 4 mask pattern with 5% duty thinning is used. In FIG. 1, whether or not to print a 4 × 4 mask pattern is set for each print pixel.
Numbers are displayed on each pixel like the matrix display of 4 rows. Further, there is a column setting corresponding to each column, and the columns are column 1, column 2, column 3, and column 4 in order from the first column. The setting of the random mask in this mask pattern will be described step by step.

First, in column 1, one is randomly selected from pixel 11, pixel 21, pixel 31, and pixel 41. In this embodiment, the pixel 11 is selected. The selection method is such that a random number is generated and the position of the pixel is determined according to the value. Similarly, in column 2, column 3, and column 4, one is selected from four pixels. In the above process, the mask pattern of 25% duty thinning: A-1
To complete.

Next, in column 1, a mask pattern: A
Three pixels other than the pixel 11 used in −1 (pixel 21,
One is randomly selected from the pixels 31 and 41). In this embodiment, the pixel 21 is selected. Similarly, in column 2, column 3, and column 4, one is randomly selected from the three pixels. The mask pattern: A-2 is completed as described above.

Next, one of the two pixels in each of column 1, column 2, column 3 and column 4 is selected to be a mask pattern: A-3. Finally, a mask pattern: A-4 consisting of the remaining pixels in each column is set. As described above, four types of random mask patterns with 25% duty thinning are set.

By performing printing with these four mask patterns, the printing area can be complemented by 100% in four passes. In this embodiment, a 25% duty thinning 4 × 4 mask pattern is used.
12% of 8-pass printing, thinning 50% duty of pass printing.
It supports 5% thinning random mask pattern, 6x6 mask pattern and 8x8 mask pattern, and the setting of the random mask pattern is 100% complementary to the print area by the number of passes. You can do it.

Next, the timing for setting the random mask pattern will be described. FIG. 2 shows a 4-pass random mask pattern setting sequence. This sequence is a sequence when print data is sent.
After confirming the transmission of print data, the carriage is ramped up at step-1. A counter such as a CPU is used to manage the number of generated random mask patterns, and if the carriage ramp-up is performed, step
-2 resets the counter. Next, step
The mask pattern is generated at -3, and the contents of the mask pattern generation are shown in FIG.

In FIG. 3, first, at step-1, the information of the mask pattern that has already been generated and stored for the print data is checked, and if there is a mask pattern that has already been generated, then FIG. As described above, the random mask is set by a random number from the pixels excluding the selected pixel. First, the column 1 is set, then the columns 2, 3, and 4 are set, one mask pattern is created, and the process is terminated (step-2 to step).
-6).

Returning to the sequence of FIG. 2, step-4
Store (store) the mask pattern generated in. Storage is performed using NV (nonvolatile) RAM, memory, or the like. When the storage is completed, the count is counted up at step-5 and the sequence returns to the mask pattern generation sequence. After completing four mask patterns in this way, step-6
Then, the generation of the random mask pattern is finished, and step-
In step 7, the mask pattern is set in the buffer such as DRAM of FIG. When setting, the generated mask pattern (4 × 4 in FIG. 1) is repeated a plurality of times so that the random mask pattern is applied to the entire print area (for example, 64 × 1 line).

The print data stored in the print buffer is masked (and) according to the random mask pattern set in the buffer, and printing is performed according to the masked print data in step-8. And finally st
The random mask pattern printed in ep-9 is erased, leading to printing in the next pass.

The random mask pattern once generated does not need to be held until it is completely complemented in the printing area, and the mask pattern once used for printing is erased after the printing is completed. However, if the next print data is transmitted and a random mask pattern is generated before the print area is 100% complemented, a random mask pattern is created independently of the random mask pattern being complemented. Can be generated and stored.

Therefore, in the four passes of this embodiment, the NVR
When generating four new random mask patterns, the AM, the memory, etc. may store the mask patterns generated in the past three scans. Since the printed mask pattern has been erased, the total number of masks is four newly generated mask patterns, three mask patterns generated in the past first print scan, and the second mask scan in the past. Two mask patterns, past three
This is the sum of one mask pattern generated in the print scan of the first time, and the total is 10 mask patterns. The NVRAM, memory, etc. are configured so as to have a capacity for storing such mask patterns.

As described above, in the multi-pass printing method in which the ink jet printing apparatus is used to perform printing by a plurality of movements and printing scans, a plurality of random mask patterns corresponding to the number of printing scans (passes) are formed. It can be set, and printing can be completed with a plurality of random mask patterns for one printing area. Further, it is possible to generate a random mask pattern so that one print area can be complemented without fail. Further, it is possible to independently generate and store a random mask pattern for different print areas.

Therefore, since each print area is printed with a unique random mask pattern, it is possible to eliminate the periodicity that appears alternately in the print area having the density unevenness, rather than suppressing the density unevenness itself. Becomes possible,
It is possible to record high-quality images.

Since the mask pattern itself does not have periodicity in the random mask pattern, in principle, it does not synchronize with any dither pattern of print data. Although it is extremely small in probability, even if the period is partially the same, it is a very small portion and is not recognized by the user as density unevenness due to the difference in the number of print dots.
Further, since there is no periodicity of the mask pattern, moire that depends on the periodicity of the mask pattern does not occur.
Therefore, by using the random mask pattern, it is possible to eliminate the periodicity of density unevenness and perform high-quality image recording.

(Embodiment 2) Next, as a second embodiment, RO
A 4-pass printing method in which a mask pattern is stored in advance in M, RAM or the like and a mask pattern is randomly selected from the mask pattern and used for printing will be described.

FIG. 4 shows a sequence for randomly selecting a mask pattern. This sequence is a sequence in which print data has been sent. In step-1, transmission of print data is confirmed and the carriage is ramped up. CP during step-2 during carriage ramp up
U is a plurality of 25% d recorded in ROM, RAM, etc.
One set is randomly selected from the mask patterns for thinning out. Since it is a mask pattern of 25% duty thinning,
The four mask patterns can be complemented 100%, and these four mask patterns form one set.
In the random selection, a random number is generated and one mask pattern can be arbitrarily selected from a plurality of mask patterns. The randomly selected mask pattern is s
In step-3, a plurality of mask patterns are stored in a rewritable storage area which is different from the area where the mask patterns are stored in advance. st
At ep-4, the stored mask pattern is set in the buffer. The print data in the print buffer is masked according to the mask pattern, and printing is performed according to the print data in step-5.

FIG. 5 shows a specific mask pattern. In FIG. 5, seven types of mask patterns A to G are shown. These mask patterns are stored in ROM, RAM, etc. in advance.
It may be set by using the random mask pattern generating method as shown in the first embodiment at N hours or the like, and does not necessarily have to be a fixed mask pattern. Further, although seven types of mask patterns are shown in this embodiment, the larger the number is, the wider the selection number becomes, and the more random the mask pattern selection becomes. Each of A to G is a set of four mask patterns, and each of the four mask patterns can be 100% complemented.

As described above, in the multi-pass printing method in which the ink jet printing apparatus is used to print by a plurality of movements and printing scans, the mask pattern is randomly selected for one printing area. A unique mask pattern can be set for each print area. As a result, it is possible to eliminate the periodicity that appears alternately in the print area having a width with density unevenness that occurs when recording is performed using the fixed mask pattern.

(Third Embodiment) Next, as a third embodiment, a printing method using a random mask pattern of m rows and n columns will be described.

FIG. 6 shows a sequence for setting a random mask pattern. Similar to the first and second embodiments, this sequence is also a sequence in a state in which print data is sent. When the print data is confirmed to be sent in step-1, the carriage is ramped up and the random mask is used. The pattern is set. In step-2, the random mask pattern is set in the buffer, in step-3, the print data in the print buffer is masked according to the mask pattern, and in step-4, printing is performed according to this print data.

FIG. 7 shows a random mask pattern of m rows and n columns. In this embodiment, m columns and n rows are not set by dividing each column (row) into random settings as in the first embodiment.
A mask pattern is generated by using random numbers in the entire row region. For example, when making a mask pattern for thinning 25% duty for 4-pass printing, the probability of random number generation is set to 1/4.
Set to. All four mask patterns may be set by using only random numbers, but they cannot be 100% complemented. Therefore, in this embodiment, the first three mask patterns are set with completely random numbers, and the last fourth mask pattern is printed on the pixels that are not complemented by the previous three mask patterns. Make sure to set the mask pattern.

With this, 100% complementation is possible,
The fourth mask pattern is a thinning pattern for printing 25% duty or more. Since the above three mask patterns are generated by completely random numbers, the same pixel may be set to be printed in the three mask patterns although the probability is small. Therefore, 100% or more printing is performed.

Normally, when the recording scan is performed a plurality of times, the way the ink bleeds or penetrates into the recording medium is different from the case where the recording is performed once, so that the optical density tends to be slightly lowered. . In this embodiment, it is possible to reduce the decrease in density by using a mask pattern that is randomly generated.

As described above, in the multi-pass printing method in which the ink jet printing apparatus is used to print by a plurality of movements and printing scans, printing is performed by setting a random mask pattern of m rows and n columns. As a result, the periodicity of density unevenness can be eliminated as in the first and second embodiments. This embodiment is particularly effective when a relatively large mask pattern is used.

(Embodiment 4) Next, as a fourth embodiment, a third embodiment
A printing method in which the random mask pattern of m rows and n columns described in the embodiment is combined with the random selection of the fixed mask pattern of the second embodiment will be described.

FIG. 8 shows a sequence for combining a random mask pattern and a fixed mask pattern. In this embodiment, a 25% duty thinning mask pattern for 4-pass printing is used.

In FIG. 8, a random mask pattern of m rows and n columns is generated and set when the carriage is ramped up. The setting method is the same as in the third embodiment (step-1).
~ Step-2). However, in this embodiment, the duty is 50%.
The thinning mask pattern is used. The set random mask pattern is temporarily stored in NVRAM, a memory or the like in step-3. With respect to the stored random mask pattern, the random selection of the mask pattern described in the second embodiment is used to set the thinned fixed mask pattern of 50% duty in step-4, and the two kinds of mask patterns are combined. As a result, a thinning mask pattern of 25% duty is generated. Furthermore, this 25% du
The thinned mask pattern of ty is rewritten and stored in the storage area such as NVRAM or memory at step-5, and the stored random fixed mask pattern is set in the buffer at step-6, and the print data of the print buffer is set according to the mask pattern. Is masked, and printing is performed according to the print data in step-7.

FIG. 9 shows the flow of the mask pattern. First, a random mask pattern of 50% duty and m rows and n columns is generated by random numbers. Two 5s on this random mask
Fixed mask of 0% duty is applied and two 25%
A random mask pattern of m rows and n columns of duty is set. Furthermore, although not shown, the initial 50% dut
By applying the same fixed mask to the inversion pattern of the random mask pattern of y rows and m columns, the remaining two 25%
By setting a random mask pattern of m rows and n columns of duty, a total of four mask patterns can be set.

By using this embodiment, it is possible to generate different print duty mask patterns from two types of mask patterns, a random mask and a fixed mask. Moreover, the randomness of the random mask pattern,
It is possible to set a random fixed mask pattern having each characteristic of certainty in dividing the printing duty of the fixed mask pattern. When a mere random mask pattern is used, there may be some graininess on the image depending on the pattern, but by multiplying the random mask with a fixed mask, the graininess on the image may be reduced. The feeling can be suppressed.

It should be noted that, instead of using the fixed mask pattern, a random mask pattern expanded in the row direction or the column direction may be used to suppress the graininess on the image.

(Embodiment 5) Next, a pattern check mechanism for a random mask pattern will be described.

In this embodiment, a mechanism for preventing the mask pattern from becoming a pattern that is easily synchronized with the print data when the mask pattern is generated using random numbers will be described. FIG. 10 shows a sequence when the pattern check mechanism is used. This sequence is obtained by adding a pattern check mechanism to the sequence shown in FIG.

Descriptions other than the pattern check mechanism will be omitted. In the pattern check, immediately after the mask pattern is generated in step-3, it is checked whether it is the same as the preset prohibited mask pattern before the mask pattern is stored in step-4, and if it is the same, The mask pattern is generated again by returning to before the generation of the mask pattern. The prohibited mask pattern is a pattern that is easy to synchronize with the print data, such as the zigzag and inverse zigzag patterns described with reference to FIG. Thereby, when a random mask pattern is generated, its randomness can be more surely ensured.

(Embodiment 6) FIG. 26 is a block diagram showing the structure of a data transfer circuit embodying the present invention. In the figure, 101 is a data register connected to a memory data bus for reading out and temporarily storing print data stored in a print buffer 130 in the memory, and 102 is a data register for storing the data stored in the data register 101. A parallel-serial converter for converting to serial data, 103 is an AND gate for masking serial data, and 104 is a counter for managing the number of data transfers.

Reference numeral 105 denotes a CPU via a CPU data bus.
A register connected to 110 for storing a mask pattern, a selector 106 for selecting a digit position of the mask pattern, and a selector 107 for selecting a row position of the mask pattern. Reference numeral 111 is a counter for managing the digit position.

The data transfer circuit shown in FIG.
In response to a print command signal sent from 10, 128-bit print data is serially transferred to the print head.
The print data stored in the print buffer 130 in the memory is temporarily stored in the data register 101 and converted into serial data by the parallel-serial converter 102. The converted serial data is AN
After being masked by D-gate 103, it is transferred to the printhead. The transfer counter 104 counts the number of transfer bits, and when it reaches 128, ends the data transfer.

The mask register 105 is composed of four mask registers A, B, C and D, and stores the mask pattern written by the CPU 110. Each register stores a mask pattern of vertical 4 bits × horizontal 4 bits. The selector 106 selects the mask pattern data corresponding to the digit position by using the value of the column counter 111 as a selection signal. Further, the selector 107 selects the mask pattern data corresponding to the row position by using the value of the transfer counter 104 as the selection signal. Selector 1
The transfer pattern is masked using the AND gate 103 by the mask pattern data selected by 06 and 107.

Although the masked transfer data is directly supplied to the print head in this embodiment, it may be temporarily stored in the print buffer.

(Embodiment 7) Next, a printing method in which a random mask pattern is set for each print area and the mask is shifted for each pass will be described.

FIG. 27 shows a random mask pattern used in this embodiment. In this embodiment, a mask pattern having a size of 32 kbytes (column direction: 4 bytes × raster direction: 8 k) is used, and a case of using for 4-pass printing will be described. The random mask pattern of this embodiment is 4
Since it is for pass, it is divided into areas: A, B, C, and D, respectively, but the four masks are connected to form one mask pattern. This random mask pattern is recorded in the RAM, and the read position (pointer)
Can be set freely. Further, the pointer can be shifted for each print area and used.

FIG. 28 shows the recording head for each print area and the mask pattern used. Printing is performed with the mask: A1 in the first print scan, and printing is performed with masks B1, C1, and D1 in the subsequent scans to complete the print. Here, a mask: A1 indicates a mask indicating the position of the pointer 1 in the area A in FIG. Similarly, B1, C1, and D1 are masks in which the pointer position is 1 in each area. Masks A2, B2, C2 and D2 are used in the next print area. The pointer is offset from the mask used in the previous print area. The amount of deviation can be set arbitrarily, but in the present embodiment, one area is shifted by 256 columns. The pointer comes to the same position in the ninth recording scan. Therefore, when viewed in the adjacent print areas, it looks as if different mask patterns are used. By this mask shifting, it is possible to obtain the same effect as using different mask patterns by simply shifting the pointer from one mask.

Next, a method of generating a random mask will be described. FIG. 29 shows a block diagram of creating a random mask pattern. In this embodiment, the case of 4-pass printing will be described. First, a mask having a specific size is set, and the mask is filled with the same number of four parameters (a, b, c, d). Then, randomly select from the parameters in it,
Replace (replace). This is repeated multiple times to create a mask in which each parameter is randomly arranged. The number of times of replacement is arbitrary as long as the mask has randomness, but in the present embodiment, it is 25000 ×.
I have done it 15 times.

The state of the parameters of this random array is stored in the ROM. From there, create thinning masks for each. For example, parameters: a, b, c, d
Correspond to masks A, B, C, and D respectively, and a mask is created by setting bits only at positions where the corresponding parameters are present. Since the positions of the respective parameters are originally randomly arranged, the created mask also has a random mask pattern having a random arrangement. Moreover, since it is originally created from one mask, it is 100% sure
It becomes a complementary random mask pattern. This operation is performed by the CPU, and the created mask is stored in the RAM for use.

FIG. 30 shows the relationship between the CPU, ROM and RAM. In the case of the printer main body, data of a random array is stored in the ROM, the above-described random mask is created at the timing of turning on the power, and the mask state is stored in the RAM. When the carriage is ramped up for each recording scan, it is read from the RAM and ANDed with the print data in the print buffer to perform printing.

Therefore, when creating a random mask, it is possible to change the random mask according to the print mode. For example, a random mask pattern for 2-pass printing, 4-pass printing, 8-pass printing can be created from the data of the same random array. This is determined by the number of types of parameters of random array data (four types in FIG. 29), but if there are 24 types (for example, 0 to 23) of parameters, there will be as many paths as there are divisors. Can be adapted. In other words, if two masks are created corresponding to 0 to 11 and 12 to 23, it corresponds to two passes.
If three masks are created corresponding to 7, 8 to 15 and 16 to 23, it corresponds to 3 passes. In the same way, 4,
It is possible to support 6, 8, 12, and 24 paths.

Further, instead of associating one parameter with one mask, by associating a plurality of parameters with one mask, 100% or more complementation or double printing at a certain ratio is performed. It is possible to set the rate of increase by the number of parameters to be set. In the above example, if two masks are created corresponding to 0 to 15 and 8 to 23, it becomes 133%, and 0 to 17,
150% if you create 2 masks corresponding to 6-23
become.

As described above, the ROM of this embodiment
A random mask is created from the random array data stored in the RAM and stored in the RAM.
Read from and use. Further, by shifting the read position for each print area, it is possible to use a different random mask pattern in the proximity print area. This allows the random mask pattern to be used more effectively in terms of non-synchronization with the print data.

(Others) The present invention brings excellent effects particularly in a recording head and a recording apparatus of a system which utilizes thermal energy among ink jet recording systems.

Regarding its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4740.
What is done using the basic principles disclosed in 796 is preferred. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, liquid (ink)
By applying at least one drive signal to the electrothermal converter arranged corresponding to the sheet or liquid path in which the is held, which corresponds to the recorded information and gives a rapid temperature rise exceeding nucleate boiling, This is effective because heat energy is generated in the electrothermal converter to cause film boiling on the heat acting surface of the recording head, and as a result, bubbles can be formed in the liquid (ink) in one-to-one correspondence with this drive signal. The liquid (ink) is ejected through the ejection openings by the growth and contraction of the bubbles to form at least one droplet. It is more preferable to make the driving signal into a pulse shape because bubbles can be grown and contracted immediately and appropriately, and thus a liquid (ink) with excellent responsiveness can be ejected. This pulse-shaped drive signal is disclosed in U.S. Pat. No. 4,463,359 and No. 43.
Those as described in 45262 are suitable. If the conditions described in US Pat. No. 4,313,124, which is an invention relating to the rate of temperature rise on the heat acting surface, are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the ejection port, the liquid passage, and the electrothermal converter (the linear liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned respective specifications. US Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which a heat acting portion is arranged in a bending region.
A configuration using the specification of No. 459600 is also included in the present invention. In addition, Japanese Laid-Open Patent Publication No. 123670/1984 discloses a configuration in which a common slit is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters, and an opening for absorbing a pressure wave of thermal energy. The present invention is also effective as a configuration based on Japanese Patent Laid-Open No. 138461/1984, which discloses a configuration that corresponds to the discharge portion.

In addition, as the form of the ink jet recording apparatus of the present invention, other than the one used as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and a facsimile apparatus having a transmission / reception function can be used. It may be a form or the like.

The present invention is not limited to ink jet recording, but can be applied to general recording devices such as heat sensitive recording, heat transfer recording, wire dot recording, etc., and when a random mask pattern is used in a serial printer. The effect will be described.

As described above, the divided (multi-pass) recording is performed by printing with a plurality of different recording elements (elements) on one raster, thereby making it possible to determine the characteristics (deviation, dot size, etc.) of the recording elements. The unevenness is averaged to make it difficult to see the density unevenness in one recording area.
With respect to the effect of this divided recording, if the print data and the mask pattern are synchronized and the recording elements used are biased as described above, the characteristics are likely to appear in one raster. Therefore, by using the random mask, the synchronism with the data is lost, and the divided printing can be effectively performed.

This is common to all dot matrix printers. In the case of producing a pseudo gradation property by two values of ON / OFF of dots, it is necessary to uniformly control the characteristics of this recording element, and division printing using a random mask is effective.

Further, in the case of a recording apparatus (heat transfer or the like) which performs printing by utilizing heat, the division printing is effective in the sense that the temperature rise of the recording head is suppressed. In this case as well, the print data and the thinning-out mask are synchronized with each other, which causes unevenness in the head temperature rise, and uneven density (nonuniformity of dot diameter) occurs due to heat distribution in the recording head. Against this, divided recording using a random mask pattern is effective.

Further, in a color recording apparatus having a plurality of recording heads arranged side by side in the scanning direction of the carriage, the color tone changes depending on the order in which dots are printed. The synchronization between the print data and the thinning mask appears in the color tone, and an image having a color tone different from the color desired by the user may be recorded. For example, in the case of thermal transfer recording, if the previously printed dots (ink layer) exist on the recording medium, the dots to be transferred next are difficult to be transferred. On the other hand, in ink jet recording, when a highly penetrating ink is used, the dye of the previously printed ink is adsorbed on the ink holding layer or the fiber of the recording medium first, and the dye of the next printed ink is difficult to be adsorbed.
Therefore, the color tone of the previously printed dots becomes strong. Further, in the case of ink having low penetrability, the post-printing dye may not flow and may be overlaid on the upper layer. Divided recording using a random mask pattern is also effective for these phenomena.

[0103]

According to the present invention, for each print area,
By generating a plurality of random mask patterns in which non-print pixels and print pixels are randomly arranged or randomly selecting mask patterns, it is possible to obtain a conventional pattern in an image to be formed without giving a pattern cycle of thinning arrangement. It is possible to realize high-quality image formation by eliminating the periodicity of density unevenness that occurs due to the number of print pixels in multi-pass printing in the same print area, which was uneven in the multi-pass printing method.

[Brief description of drawings]

FIG. 1 is a diagram showing setting of a random mask pattern in an inkjet recording apparatus for explaining the basic concept of the present invention.

FIG. 2 is a diagram showing a sequence in which a random mask pattern is set and printing is performed using the mask pattern.

FIG. 3 is a diagram showing a sequence for generating a random mask pattern.

FIG. 4 is a diagram showing a sequence for randomly selecting a mask pattern and performing printing using the mask pattern.

FIG. 5 is a diagram showing a plurality of mask patterns in a storage area randomly selected.

FIG. 6 is a diagram showing a sequence in which a random mask pattern is set and printing is performed using the mask pattern.

FIG. 7 is a diagram showing a random mask pattern of m rows and n columns.

FIG. 8 is a diagram showing a sequence of generating a random mask pattern, randomly selecting from the mask pattern, and performing printing using the mask pattern.

FIG. 9 is a diagram illustrating setting of a random fixed mask pattern.

FIG. 10 is a diagram showing a sequence having a mask pattern check mechanism.

FIG. 11 is a diagram showing an ideal printing state of an inkjet printer.

FIG. 12 is a diagram showing a printing state of an inkjet printer having uneven density.

FIG. 13 is a diagram illustrating division printing in a conventional example.

FIG. 14 is a diagram illustrating division printing of a conventional example.

FIG. 15 is a diagram showing an electric circuit for generating a thinning pattern according to a conventional example.

FIG. 16 is a timing chart of a heat pulse according to a conventional example.

FIG. 17 is a diagram showing 25% data and print dots in conventional divided printing.

FIG. 18 is a diagram showing 50% data and print dots in conventional divided printing.

FIG. 19 is a diagram showing 63% data and print dots in conventional divided printing.

FIG. 20 is a cross-sectional view of landing two dots.

FIG. 21 is an explanatory diagram showing an inkjet recording apparatus main body to which the present invention is applied.

FIG. 22 is a diagram illustrating a heater board.

FIG. 23 is a block diagram showing a control circuit.

FIG. 24 is a block diagram showing a control configuration.

FIG. 25 is a configuration diagram illustrating a flow of print data.

FIG. 26 is a block diagram showing a configuration of a data transfer circuit showing an embodiment of the present invention.

FIG. 27 is a diagram showing a random mask pattern.

FIG. 28 is a diagram showing a recording head for a print area and a mask pattern to be used.

FIG. 29 is a block diagram showing random mask pattern creation.

FIG. 30 is a block diagram showing a relationship between a CPU, a ROM, and a RAM.

[Explanation of symbols]

 103 AND gate 105 Mask register 106 Selector 110 CPU 130 Print buffer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B41J 2/485 B41J 3/04 103 B 3/12 (72) Inventor Atsushi Arai Shimomaruko Ota-ku, Tokyo 3-30-2 Canon Inc. (72) Inventor Admiral Iwasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo In Canon Inc. (72) Daigoro Kanematsu 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 within Canon Inc. (72) Inventor Kazuhiro Nakata 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc.

Claims (7)

[Claims] 1. Ink jet recording for completing an image by scanning a recording head having a plurality of ejection portions for ejecting ink a plurality of times with respect to the same recording area of a recording medium and forming a thinned image according to a thinning pattern in each scan. In the apparatus, non-recording pixels and recording pixels are randomly arranged and generating means for generating a plurality of random mask patterns of a predetermined size, and the random mask pattern generated by the generating means is thinned out for each recording area. An ink jet recording apparatus comprising: a thinning means for thinning out print data as a pattern. 2. The ink jet recording apparatus according to claim 1, further comprising a storage unit that stores a plurality of the random mask patterns. 3. Ink jet recording for completing an image by causing a print head having a plurality of ejecting sections for ejecting ink to scan the same print area of a print medium a plurality of times and forming a thinned image according to a thinning pattern in each scan. In the apparatus, a non-recording pixel and a recording pixel are arranged, and a selection unit that randomly selects a plurality of mask patterns of a predetermined size, and the mask pattern selected by the selection unit is a thinning pattern for each recording region. An ink jet recording apparatus comprising: a thinning means for thinning recording data. 4. An ink jet recording in which a recording head having a plurality of ejection portions for ejecting ink is made to scan the same recording area of a recording medium a plurality of times, and a thinned image is formed in accordance with a thinning pattern in each scan to complete the image. In the apparatus, a non-recording pixel and a recording pixel are randomly arranged to generate a plurality of random mask patterns of a predetermined size, and a non-recording pixel and a recording pixel are arranged to form a plurality of mask patterns of a predetermined size. Selecting means for selecting at random, and synthesizing means for synthesizing thinning patterns having different thinning rates based on the mask pattern selected by the selecting means and the random mask pattern generated by the generating means, The thinning pattern synthesized by the means is used as the thinning pattern for each recording area. An ink jet recording apparatus characterized by comprising a thinning means for thinning the recording data. 5. The ink jet recording apparatus according to claim 1, further comprising a check unit that does not use the random mask pattern as a thinning pattern when the random mask pattern is a predetermined pattern. 6. The ink jet recording apparatus according to claim 1, wherein the recording head ejects ink by heat. 7. A printing apparatus for scanning a same print area of a print medium a plurality of times by a print head having a plurality of print units, forming a thinned image according to a thinning pattern in each scan, and completing the image. Pixels and print pixels are arranged in a random number, generating means for generating a plurality of random mask patterns of a predetermined size, and the random mask pattern generated by the generating means is used as thinning pattern for each of the recording areas to record data. A recording device comprising thinning-out means.