JPH09156130A - Apparatus for ink jet recording and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an ink jet recorder capable of recording a high quality character by improving character density by a method wherein in the ink jet recorder, deterioration of sharpness at an edge part of the character is prevented, and a main cause for deterioration of image quality such as oozing out or the like is removed. SOLUTION: A black character is detected to a recording data (S302). An edge of the detected black character is detected (S304). Respectively different recording methods are set up to the edge part of the character and a part excepting the edge part (S 307, S308). For example, the edge part is recorded only by one time scan, and the other part is recorded by superimposing a dot by two time scans. Thereby, oozing out is prevented for the edge part, and density can be increased for the part excepting that.

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 and a recording method for recording by ejecting ink from a recording head, and more particularly to recording of characters.

[0002]

2. Description of the Related Art The ink jet recording system has various advantages such as low noise, low running cost, downsizing of a device and easy colorization, and is used in printers, copying machines, facsimiles and the like. In this method, the color recording method generally uses three colors of cyan, magenta, and yellow, or four colors of ink with black added to perform color recording.

By the way, in ink jet recording,
In order to obtain a color image with high color development without ink bleeding, it was necessary to use a dedicated paper with an ink absorption layer in the past, but in recent years, large amounts of ink have been used in printers, copiers, etc. Various systems for improving the recording quality when recording on "plain paper" used in the above have been put into practical use. However, the recording quality on "plain paper" is still at an insufficient level. One of the most important factors is compatibility between ink bleeding between colors and black recording quality, especially black character recording quality.

Usually, when a color image is recorded on plain paper by an ink jet recording method, a quick-drying ink having a relatively high penetration speed into the plain paper is used. Therefore, it is possible to obtain an image without ink bleeding between the respective colors, but the density is low as a whole, and in the vicinity of the recording image area of each color, the ink slightly bleeds along the fibers of the paper, so-called feathering. Rings are likely to occur. Feathering is relatively unnoticeable around the color image area,
The black image area is likely to be conspicuous around the black image area, which deteriorates the recording quality. In particular, when the black image is a character, it becomes an indistinct character lacking sharpness, resulting in poor quality.

[0005]

By the way, depending on the environment in which the printer is used, most of the color images output there are mainly black text, and some of the graphs and captions are colored, or noticed. It may be the case that the part is colored in one point. In such a usage environment, the black character quality is an important factor when considering the recording quality.

However, the quick-drying ink used to obtain a color-free image on a plain paper causes the problems of density and feathering to be remarkable as described above, and is not suitable for recording black characters. Often.

Here, the feathering is relatively inconspicuous in the color image area and is easily noticeable around the black image area because the difference in lightness between the recording medium and the black ink is large and the contrast is strong. . On the other hand, the sharpness defect caused by feathering can be eliminated by increasing the difference in brightness and increasing the sharpness of the image. Then, one method for increasing the sharpness in a black image or the like is to increase the density of the image.

This image density is determined by the amount of dye or pigment in the ink that is ejected. The density of the ink itself is often determined by the specifications of the recording apparatus that normally uses it, and therefore it is not possible to increase the density by using inks of multiple densities. Therefore, it is known that, in a normal printing apparatus, double-strike printing is performed in which printing is performed twice for one pixel as a method of increasing the density.

The present invention has been made from such a point of view, and it is an object of the present invention to improve both the quality of black characters and a high-quality color image without bleeding in ink jet recording. An object is to provide an inkjet recording device and an inkjet recording method.

[0010]

According to the present invention, there is provided:
In an inkjet recording apparatus that uses a recording head to perform recording by ejecting ink from the recording head to a recording medium based on the recording data, a character detecting unit that detects a character from the recording data, and a character detected by the character detecting unit. Recording control means for controlling to increase the density and perform recording.

More preferably, the ink jet recording apparatus further comprises edge detection means for detecting an edge portion of the character detected by the character detection means, and the recording control means is arranged to detect the character detected by the character detection means. It is characterized in that the density of areas other than the edge portion detected by the edge detecting means is increased.

Further, in an ink jet recording method in which a recording head is used and recording is performed by ejecting ink from the recording head to a recording medium based on the recording data, a character is detected from the recording data and an edge portion of the detected character is detected. And increasing the density of the detected character other than the edge portion.

According to the above construction, it is possible to change the recording mode by dividing the character recording into the edge portion and the other area. For the portion other than the edge portion, for example, the ink ejection amount is increased to increase the density. Further, it is possible to secure the sharpness of the edge portion by reducing the amount of ejected ink in the edge portion.

[0014]

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

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

The carriage 101 is provided with a cartridge guide 103, and the carriage 101 is provided with a recording head 102 detachably mounted thereon as a guide and mounting means, and is movable along guide shafts 104 and 105. This allows the print head 102 to scan for printing.

After the paper 106 as a recording medium is fed to the back side of the apparatus by the paper feed roller 107, the recording is performed by the paper feed roller 108 and a pinch roller (not shown) for pressing the paper 106 against this roller. Intermittent feed is performed during scanning of the head. The paper pressing plate 109 regulates the direction of the paper, and the paper is sent toward the front of the apparatus, during which recording is performed. The above-mentioned ink cartridges are a color ink cartridge 110 and a black ink cartridge 111 that store three colors of yellow, magenta, and cyan.
The two types can be inserted into the cartridge guide 103 separately and can communicate with the recording head 102 with ink.

Here, the color ink cartridge 110
The yellow, magenta, and cyan inks stored in
In order to prevent ink bleeding at color boundaries when forming a color image, a material having a high penetration speed into recording paper is used. On the other hand, as the black ink stored in the black ink cartridge 111, one that has a relatively slower penetration speed into the recording paper than the above three types of color ink is used so that a black image has a high density. To be However, in the present embodiment, in order to achieve the effect of the present invention, the permeation rate is not necessarily limited to the slow one.

2A and 2B show the recording head 1.
FIG. 2 is a perspective view of 02 viewed from the rear and from the front.

On the front surface of the recording head 102, yellow, magenta, cyan, and black ejection port groups are arranged in a straight line. Each group has 24 discharge ports for yellow, magenta, and cyan, and 64 discharge ports for black, and there is a space equal to or larger than the discharge port pitch between the groups of each color.

Each of these ejection ports is provided with an ink liquid passage communicating with the ejection port, and a common liquid for supplying ink to these liquid passages is provided behind the portion where the ink liquid passage is provided. A room is provided. An ink path corresponding to each of the ejection ports is provided with an electrothermal converter that generates thermal energy used to eject ink droplets from the ejection port and electrode wiring for supplying electric power to the electrothermal converter. There is. These electrothermal converters (ejection heaters) and electrode wirings are formed by a film forming technique on a substrate 201 made of silicon or the like.
Further, by stacking a partition wall made of resin, a top plate, and the like on the substrate 201, the ejection port, the ink liquid path, and the common liquid chamber are formed. Further to the rear, a drive circuit for driving the electrothermal converter based on a recording signal is provided in the form of a printed board 202. In the present embodiment, the recording head 102 is configured by bonding and forming a grooved top plate integrally provided with a partition wall or a common liquid chamber for dividing a plurality of ink liquid paths, and a substrate. There is. The grooved top plate is integrally molded, and polysulfone is preferable as the integrally molded material, but other molding resin materials can also be used.

Silicon substrate 201 and printed circuit board 2
02 is a distributor 2 which is provided on the same aluminum plate 203 and is integrally molded with the grooved top plate.
From 08, the pipes 204 to 20 corresponding to each color ink
7 is protruding. The pipes 204 to 207 for connecting to the ink cartridges are in communication with the individual flow paths provided inside the distributor 208, and these flow paths are in communication with the common liquid chamber for the ink of each color. That is, the flow paths provided in the distributor 208 are 4 for yellow, magenta, cyan, and black.
There is a book, and each common liquid chamber is connected to each pipe.

In this embodiment, the color ink cartridge in which the three color ink tanks are integrated and the Bk ink cartridge are independently replaceable, but instead, the ink tank and the recording head are integrated. Inkjet cartridges of the type described above may be used.

About 40 ng of ink is ejected from the ejection openings for yellow (Y), magenta (M) and cyan (C) provided on the recording head 102, and about 40 ng of ink is ejected from the ejection openings for black (Bk). 80 ng of ink is discharged.

An example of the components of the used ink is shown below.

1. Y (yellow) C.I. I. Direct Yellow 86 3 parts Diethylene glycol 10 parts Isopropyl alcohol 2 parts Urea 5 parts Acetinol EH (Kawaken Chemical) 1 part Water balance 2. M (magenta) C.I. I. Acid Red 289 3 parts Diethylene glycol 10 parts Isopropyl alcohol 2 parts Urea 5 parts Acetylenol EH (Kawaken Chemical) 1 part Water balance 3. C (cyan) C.I. I. Direct Blue 199 3 parts Diethylene glycol 10 parts Isopropyl alcohol 2 parts Urea 5 parts Acetylenol EH (Kawaken Chemical) 1 part Water balance 4. Bk (black) C.I. I. Direct Black 154 3 parts Diethylene glycol 10 parts Isopropyl alcohol 2 parts Urea 5 parts Water balance In this way, C, M, and Y have 1% acetylenol EH.
The addition improves the permeability. In addition,
In addition to the above-mentioned acetylenol EH, other additives in the ink include other surfactants and alcohols.

FIG. 3 is a block diagram showing the control arrangement of the above-mentioned color ink jet recording apparatus.

A system controller 301 controls the entire apparatus, and a storage device (ROM) in which a control program including a microprocessor is stored, and a storage device (RAM) used when the microprocessor performs processing. Etc. are provided.

The driver 302 drives a carriage motor 304 for moving the carriage 101 in the main scanning direction, and similarly, the driver 303 drives the sheet 1 in the sub scanning direction.
The paper feed motor 305 for rotating the paper feed roller for paper feed of No. 06 is driven.

The host computer 306 supplies information to be recorded to the ink jet recording apparatus of this embodiment. The reception buffer 307 temporarily stores the data supplied from the host computer 306. Data is accumulated until it is read. The frame memory 308 has a fixed memory size required for recording by expanding data to be recorded into image data and storing the image data. In the present embodiment, the memory size is such that one sheet can be stored, but it goes without saying that the application of the present invention is not limited to this size.

The print memory 309 temporarily stores data to be printed, and its storage capacity changes depending on the number of ejection openings of the print head. The print control unit 310 controls the drive of the print head based on a command from the system controller 301, and controls the ejection timing, the transfer of ejection data, and the like. Head driver 3
Reference numeral 11 drives each of the heads 102Y, 102M, 102C and 102Bk based on a control signal from the recording control unit 310.

(Embodiment 1) As a first embodiment of the present invention, a recording is performed in which a character portion which is a black image area is extracted from the recording data, the edge of the black character data is further detected, and only the portion other than the edge portion is hit twice. The method will be described.

Black Character Detection Method FIG. 4 is a diagram for explaining the flow of recording data in the configuration shown in FIG.

The print data sent from the host computer 306 is stored in the receiving buffer 307 inside the printing apparatus via the interface. The reception buffer 307 has a capacity of several k to several + k bytes. The recording data stored in the reception buffer 307 is sent to the text buffer (frame memory) 308 after command analysis is performed on each of the recording data. In the text buffer 308, the record data is held as an intermediate format for one line, and the recording position of each character, the type of decoration, the size, the character (code),
Processing for adding font addresses and the like is performed. As described above, the capacity of the text buffer varies depending on each model, and the serial printer has a capacity of several lines and the page printer has a capacity of one page. Further, the print data stored in the text buffer 308 is expanded and stored in the print buffer 309 in a binarized state, and a signal is sent to the print head as ejection data, whereby printing is performed.

In the case of performing multi-pass printing in this embodiment, the binarized data stored in the print buffer 309 is thinned by a predetermined amount and then transferred to the print head. Therefore, the mask pattern can be set according to the state of 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.

In this embodiment, black character detection is performed on the binarized data stored in the print buffer 309 immediately before the data is sent to the print head. Black characters are usually 6 points (2 mm) to 24 points (8 mm), and even large characters have 72 points (24 mm).
mm). In the present embodiment, black character extraction is performed by detecting a null raster where data does not exist.

FIG. 5 is a flowchart showing the sequence of black character detection.

First, in step S1, the print buffer 3
The print data is read from 09Y, 309C, and 309Bk and temporarily stored in a memory such as a RAM.

This memory can store Bk, Y, M, and C independently, but the capacity of the memory depends on the size of the character to be extracted. For example, if characters up to 72 points are to be extracted, it is necessary to store 340 rasters or more at 360 dpi. Considering A4 vertical size, 1
It is about 122.4 kbytes per color. On the other hand, when the recording head shown in FIG. 2 is used, the ejection port array range is 160
Although it corresponds to the array length for the ejection openings, the maximum length that can be actually printed by one scan is equivalent to the Bk64 ejection openings. Therefore, a memory having a capacity that is a multiple of the maximum length that can be printed by one scan is preferable so that large characters can be sufficiently extracted. Here, the larger the capacity, the larger the size of the black character that can be discriminated, but the mainstream of the black character is 24 points or less, and in this case, about 114 rasters at 360 dpi are required. That is, it corresponds to two rows of the Bk64 ejection port. From the above point of view, in this embodiment, about 6 of 64 discharge ports are provided.
The storage medium has a capacity of 384 rasters, which corresponds to the number of rows. This is about 1.1 Mbytes per color.

Next, in step S2, it is detected whether or not there is data of each color in each raster for the read recording data. That is, before or after each raster data, a bit indicating whether or not there is data for each color data in the raster is set, and by determining the content, it is determined whether or not there is data for each color. Based on this result, it is possible to determine whether the data existing in the raster is Bk data, color data, or data in which these colors are mixed.

In step S3, a null raster is detected based on the above detection result. That is, it is determined whether or not there is a so-called null raster that does not have any color data in that raster, and if it is determined that there is no null raster, continuous data in which images are connected for the data read in step S1 above. Record that will be described later,
That is, in the present embodiment, this processing procedure is exited to perform 3-pass printing. When it is determined that a certain raster is a null raster, it is detected in step S4 whether there is a next null raster. Here, if there is no next null raster, it cannot be determined within the range being determined, so black characters are not extracted and this processing is exited. If it is determined that there is a next null raster, it is further determined in step S5 whether there is color data between the null raster detected in step S3 and the null raster detected in this step. If there is color data, it is considered that it is not text and is not extracted as a black character, and this processing procedure is exited. If there is no color data, the text is regarded as Bk data and is extracted as a black character in step S6. In the present embodiment, as an area for storing the extracted black character data, R having a capacity corresponding to the detection range is used.
A memory such as AM is used.

Edge Detection Method Next, regarding the edge detection of the extracted black character data,
This will be described with reference to FIG.

In FIG. 6, the pixel 22 is the pixel of interest for which it is determined whether or not the pixel 22 is an edge. Here, the edge portion is a portion at which a region without dots is switched to a region with dots, or vice versa. Therefore, for the pixel of interest, the surrounding pixels 11, 12, 13, 21,
If even one of 23, 31, 32, and 33 has different dots, it can be determined as an edge. For example, when the data of the pixel of interest 22 is the data in which dots are recorded, and the data in which even one of the surrounding pixels has no dots,
The pixel of interest 22 is determined to be an edge portion, and is determined not to be an edge only when all of the surrounding pixels are data to be recorded. In fact, AND data of the pixel of interest and the individual surrounding pixels is taken, and if all the results are "1", it is judged that it is not an edge portion. That is, it is data other than the edge portion of the black character data. Then, based on the data thus determined, the AND data of the inverted data of the data other than the edge part and the original data of black characters is taken,
This is the edge portion data of black characters.

FIG. 7 is a schematic diagram showing an example of edge detection. FIG. 7 shows a character “A” composed of 24 × 18 dots, and in the drawing, a black circle represents a dot to be recorded.

Further, FIG. 8 shows a result of performing the above-mentioned edge detection on the character "A". In the figure, white circles indicate detected edge dots, and black circles indicate other dots. Although the edge portion is one dot in this embodiment, it is also possible to extract the edge portion of a plurality of dots by repeating the method described above a plurality of times or expanding the range of surrounding pixels.

FIG. 9 is a flow chart showing an example of a sequence relating to actual edge detection.

First, in step S201, the black character data extracted in the process shown in FIG. 5 is read. The amount of data to be read depends on the capacity of the memory of the printer body, but if the width that the print head can print in one scan is one line,
It is set so that it can hold several lines of data. This is the original data.

Next, in step S202, the address of the original data is shifted upward by one raster. This is stored as shift data 1. Step S
At 203, the address of the original data is shifted downward by one raster. This is stored as shift data 2. Here, the up and down directions as the shifting direction are the upward direction in the order of data transmission and the downward direction in the later order.

In step S204, the original data, the shift data 1 and the shift data 2 obtained above are respectively shifted to the left, and the shift data 3 and the shift data 3 are obtained.
Save as 4, 5. Further, in step S205, the original data, the shift data 1 and the shift data 2 are respectively shifted rightward and stored as shift data 6, 7 and 8, respectively.

In step S206, the AND data of the original data and the shift data 1 to 8 is taken to obtain data other than the edge portion of the extracted black character, that is, internal data. Further, in step S207, the AND data of the inverted data of the data other than the edge portion of the black character and the original data can be obtained to obtain the edge portion data of the black character.

Although the above-mentioned sequence has steps in eight steps, it can be performed as software processing, and since it is relatively simple processing as described above, it does not require hardware processing. It is also possible to do so. The latter configuration is advantageous from the viewpoint of processing speed.

Setting of Recording Method FIG. 10 is a flowchart showing a sequence for setting the recording method using the results of the above-described black character detection and edge detection.

The processing of steps S301 to S304 is the processing shown in FIGS. 5 and 9, and the description thereof is omitted here. In this process, when it is determined that the black character does not exist (step S303), step S3
In 09, a normal recording method is set. In this embodiment, 1-pass printing is set as a normal printing method. However, multi-pass printing may be set depending on the type of printing medium used.

On the other hand, in the above processing, when it is judged that a black character exists, edge detection is performed (step S30).
4) The black character edge data and the data other than the edge data that can be obtained by edge detection are extracted in steps S305 and S306, respectively. As described above, in the present embodiment, the edge portion can be detected by one dot, but a plurality of dots may be detected.

Next, in step S307, a recording method is set for the extracted edge portion data. In this embodiment, in order to obtain the sharpness of the edge portion, one-pass printing and 100% duty printing are performed. On the other hand, step S
At 308, a recording method is set for the data other than the extracted edge portion. That is, here, in order to increase the density of black characters, printing with a 200% duty is performed in multi-pass printing. As a method of recording 200% duty, 100% duty recording is repeated twice in two passes to eject each pixel twice (twice), or 50% duty recording is performed four times. There is a method.

The density increase ratio can be variously set within the allowable range of the recording medium. For example, O
It is also possible to set the HP sheet to about 150% and the plain paper to 200%.

After the above processing, in step S310,
It is determined whether there is data to be processed, and if there is print data, the process returns to step S301 to repeat the sequence of black character detection, edge detection, and printing method setting again. If there is no print data to be processed, this sequence ends.

According to this sequence, the edge portion of the black character and the other data can be separated and extracted, and the recording method can be set for each. This makes it possible to increase the density by hitting only the inside of the black character excluding the edge part, to prevent the sharpness from being lowered due to the feathering of the edge part, and to secure the black density above a certain level.

Next, a method of hitting twice will be described.
That is, the data other than the edge portion of the extracted black character is 2
The case of printing by scanning once will be described.

(1) Dot-on-dot FIG. 11 is a schematic diagram showing a dot-on-dot, that is, a state in which dots overlap.

Dots are added at exactly the same positions as the dots printed by the first scan. In this case, it is possible to increase the density mainly due to the increase of the dye density on the paper surface according to the ejected ink amount. Further, since dots are added at the same position, the same print data can be used as it is, and the process becomes the simplest.

(2) Shift of Half Pixel in Carriage Scanning Direction FIG. 12 is a schematic diagram for explaining a method of printing by shifting dots in the carriage scanning direction, showing another example of the double-strike method.

Here, with respect to the dots printed by the first scanning, the printing position is shifted by half a pixel in the scanning direction of the carriage to add dots. Although the ink amount is the same as that of the dot-on-dot described above, the dye is not partially collected and can be dispersed to some extent, and therefore the density is high. In this method, since the dot interval is half that in the above case, it is necessary to land with a position accuracy that is twice as great in the carriage scanning direction. Further, in this case, the recording may be performed separately in two scans, or the recording may be performed by doubling the driving frequency in one scan.

Since the above method adds dots at different positions, it is necessary to create new data whose position is shifted by half a pixel based on the data other than the edge portion of the black character. As the processing, the data other than the edge portion is expanded on a buffer having a size twice as large as the scanning direction, and when there is a dot on the left and right, the data is added and stored separately from the data other than the edge portion. To do so. The processing may be performed by software or may be performed by hardware.

(3) Shifting Half-Pixel in Carriage Scanning Direction + Paper Feeding Direction FIG. 13 shows still another example of the double hitting method, in which dots are shifted in the carriage scanning direction and the paper feeding direction for recording. It is a schematic diagram for explaining.

For the dots printed in the first scan,
Dots are added by shifting the driving position by half a pixel in the carriage scanning direction and the paper feeding direction, respectively. Since the landing points are periodically dispersed in the same manner as the half-pixel shift in the carriage scanning direction, the density is high. According to the above method,
2 on the midpoint of the diagonal line of the dots printed in the first scan
Recording will be performed in the second scan. Compared to the dot-on-dot described above, double accuracy is required in the carriage scanning direction and the paper feeding direction, but the density can be most effectively improved.

As described above, in the present embodiment, the black character detection and the edge detection are performed, and the portion other than the edge portion of the black character, that is, the internal data is hit twice to increase the density. Due to this increase in density, it is possible to enhance the contrast with the background and improve the quality of black characters. Furthermore, the edge data is not struck twice and the occurrence of unnecessary feathering is minimized. It is possible to realize an ink jet recording apparatus capable of improving the recording quality of the above.

The present embodiment focuses on black characters which are considered to be an important parameter in the image to be recorded, but the sequence and recording method performed in this embodiment are not limited to black characters, and all characters, In other words, it goes without saying that it can be applied to color characters.

(Embodiment 2) As a second embodiment of the present invention, a case will be described in which after performing black character extraction and edge detection, dots are added by different scanning except for the edge portion of the black character.

As described above, depending on the environment in which the printer is used, when a color image is recorded, it is almost the case that one-point color, that is, some color graphics are present in black characters, which is a pictograph. There may be few real images. It can be said that high-speed recording of black characters in such a case is an important parameter for the performance of the inkjet recording apparatus. Therefore. In the present embodiment, printing is performed in two passes in both directions so as not to slow down the printing speed, as compared with normal one-pass printing in one direction.

Normally, when performing bidirectional printing, it is necessary to make carriage control with sufficiently high accuracy to reduce the deviation of the landing position of ejected ink droplets on the forward and return paths of the carriage. This can be dealt with by, for example, controlling the position of the carriage and controlling the ejection timing by using an encoder or the like, but there is a risk of increasing the cost. In this case, when the inkjet recording apparatus is applied to a high-priced product, there is a margin in cost, but in the case of a low-priced product, such control cannot be adopted.

In this embodiment, the recording method which does not require the highly accurate position control as described above is used. That is, in the forward pass, which is the first scan, the edge portion of the black character and the inside thereof are normally recorded, and in the return pass, which is the next scan, only the portion other than the edge of the black character, that is, the inside of the black character is recorded. Therefore, dots are already printed around the dots printed by the second scan. Here, the positional accuracy of the dots printed in the second scan may be such that the dots are present inside the dots printed in the first scan.

In the case of the dot-on-dot described in the first embodiment and when the edge portion is one pixel, a state in which printing is performed by two scans will be described with reference to the drawings.

FIG. 14 shows a case where dots recorded in the backward path overlap dots already recorded in the outward path other than the edge portion. In this case, only 2 inside
The edge portion is printed once, and recording is performed by one scan.

On the other hand, in the state shown in FIG. 15, the dots recorded on the return pass are displaced by a half pixel in the landing position. However, even in such a case, the dots do not protrude outside the edge dots, and the sharpness of the edges can be maintained.

Further, in FIG. 16, the dots printed on the return pass are displaced by one pixel from the landing position. In this case, the edge in the displaced direction is hit twice, and this cannot maintain the sharpness of the edge portion.

From the above, it is necessary that the accuracy of the landing position on the return path be within ± 1 pixel. That is, the sharpness of the edge portion can be realized by the bidirectional recording having the landing position accuracy equal to or less than the width of the detected edge portion, and the black character with high density can be recorded.

FIG. 17 is a flow chart showing a sequence for realizing the recording of this embodiment.

First, in steps S401 to S404, black character detection and edge detection are performed as in the above embodiments. Thereafter, the edge portion data of the black character and the data other than the edge portion, which can be obtained by the edge detection as in the above-described embodiment, are respectively processed in steps S405 and S406.
Extract with The edge portion may be detected by one dot, or a plurality of dots may be detected.

On the other hand, the data in which the black character could not be extracted in step S403 and the edge portion data extracted in step S305 are used for the recording method setting by the forward scan in step S308. On the other hand, the data other than the edge portion extracted in step S306 is processed in step S
This is used for setting the printing method by the backward scan performed in 307.

According to the above-mentioned sequence, the data other than the edge portion of the black character and the other data can be separated and extracted, and the scanning direction for printing can be set for each, so that only in the return path. It is possible to increase the density by striking the data inside the black characters twice.

As described above, by using the results of the black character detection and the edge detection, the data other than the edge portion of the black character is recorded in the backward path of the bidirectional recording so that the sharpness can be achieved without lowering the recording speed. It is possible to record black characters with high density.

The present embodiment focuses on black characters which are considered to be an important parameter in the image to be recorded, but the sequence and recording method performed in this embodiment are not limited to black characters, and all characters, In other words, it goes without saying that it can be applied to color characters.

(Third Embodiment) As a third embodiment, a case where the ratio of density increase of data inside black characters and the complement ratio of edge portion data are changed according to a recording medium (hereinafter, also simply referred to as medium) to be used. Will be described.

The quality of black characters greatly differs depending on the recording medium. For example, in the case of plain paper, the landed ink often spreads along the fibers of the paper to cause feathering. Further, since it is relatively hard for ink to remain on the surface, a certain amount of ink is required to increase the density, but there is a problem such as feathering, so it is not possible to eject an extremely large amount of ink. Further, in the OHP sheet, although depending on the coating agent, only the ink amount within the allowable range of the ink absorbing ability of the ink receiving layer forming the surface can be ejected. Further, coated paper has a relatively large bleeding rate and a high density, but feathering is likely to occur. Each of the media used in this way has its own characteristics, and black characters must be processed accordingly.

FIG. 18 is a flow chart showing a sequence of performing black character detection and edge detection, and setting a print duty (density increase rate) for each of the edge portion and the data other than the edge portion of the black character.

First, after extracting the data other than the edge portion or the edge portion data as in the above-described embodiments, the recording duty is set for the edge portion data extracted in step S507 and the recording method according to this is set. To set. Further, the recording duty and the recording method thereof are set for the data other than the edge portion extracted in step S507. The recording duty of each is shown in FIG.
It is determined by the table schematically shown in FIG. In FIG. 19, the recording duty is set according to various media, but in order to obtain sharpness at the edge portion, 1 is set.
The duty is set to 00% or less, and the inner data is recorded at 120 to 200% in order to increase the density of black characters.

Specifically, the medium 1 is assumed to be a standard medium, and the density is set to be relatively high. Media 2 is supposed to be very easy to blur,
The density inside the black characters is not increased so much, and in order to further suppress the blurring at the edge part, the duty is lowered to change the data complementation rate. Also,
The media 3 and 4 have no problem such as bleeding, but the density increase rate inside the black characters is changed assuming a medium in which the ink ejection amount is limited.

According to the above sequence, the edge portion of the black character and the other data can be separated and extracted, and the recording duty corresponding to the medium can be set for each, whereby the inside of the black character is hit twice. When increasing the density by doing so, it is possible to select a density increasing rate suitable for the medium. Further, for media in which bleeding or the like is a problem, a reduction in the complementation ratio of the data in the edge portion is suppressed to suppress a decrease in the sharpness of the edge portion.

As described above, the black character detection and the edge detection are performed, and the recording duty is set and recorded for the data inside and the edge portion of the black character, respectively, so that it is suitable for the medium used for recording. It is possible to perform the recording in which the density increase of the black character and the blurring of the edge portion are suppressed.

In the present embodiment, the recording duty is determined by using the medium as a parameter, but the setting of the medium is instructed by the host side and sent to the printer. Specifically, the information of the medium set by the printer driver or the like is used, and the information is reflected in the sequence based on the information. It is also possible to recognize the medium by setting a DIP switch or the like provided on the printer body or the like.

Although the present embodiment focuses on black characters which are considered to be important parameters in the image to be recorded, the sequence and recording method shown above are not limited to black characters, and all characters, that is, color It goes without saying that it can be applied to letters.

(Embodiment 4) As a fourth embodiment, a recording method will be described in which the sharpness of the edge portion is further improved and the density of black characters is further increased by controlling the direction in which the deposited ink bleeds.

In the ink jet recording system, when another dot is superposed on a previously recorded dot, the dot of the dot printed after the previously recorded dot is sunk in the depth direction of the paper in the overlapping portion. There is a tendency. FIG.
FIG. 4 is a cross-sectional view schematically showing it.

This is because the dyes such as dyes in the ejected ink are physically and chemically bound to the recording medium, but at this time, the binding between the recording medium and the dyes is finite, and therefore the binding force depends on the kind of the dyes. As long as there is no significant difference between the two, the amount of ink dye ejected earlier will remain on the surface of the recording medium due to the priority being given to the recording medium. This is because it is considered that it sinks in the depth direction and is dyed.

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 more hydrophilic than the state where it is not bonded 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 ink droplets are contained, the stronger the hydrophilicity is, and the ink droplets that have landed adjacently are easily attracted. Therefore, if there is nothing around the edge, the ink dots that have landed will spread in all directions, but if dots have already been formed in adjacent pixels, then the landed ink will have already formed dots. Will be drawn to the side.

The present embodiment utilizes such a feature. That is, black character detection and edge detection are performed on the data to be recorded to extract the edge part of the black character, and the inner edge part is extracted one more level. The edge portion extracted first is the outer edge, and the edge portion extracted next is the inner edge. For the edges thus extracted, the driving order is such that the inner edge is recorded and then the outer edge is recorded. Then, the internal data of black characters is printed in the manner of increasing the density as in the above embodiment, and the printing is completed.

A state in which such recording is performed will be described with reference to FIG.

In FIG. 21, dots on the inner edge portion are first printed. Next, the outer edge portion is driven in. At this time,
The ink on the outer edge dots is attracted to the inner edge dots that have been hit previously. This weakens the force of the outer edge dots to spread outward,
A sharper edge can be formed. Furthermore, the density of the black character internal dots is increased and recording is performed, but when the black character internal dots land, the inner edge dots have already been formed and the black character internal dots are also attracted to the inner edge dots. Go. Therefore, the finally formed black character is a high-quality black character in which the density of the inner edge portion is high, the edge portion is sharp, and the density of the entire black character is also high.

FIG. 22 is a flow chart showing a sequence for realizing this embodiment.

When the edge portion data of black characters and the data other than the edge portion which can be obtained by edge detection are extracted in steps S605 and S606, respectively,
At 607, the extracted edge data is set as an outer edge portion for post-printing.

In step S608, edge detection is performed again on the extracted data other than the edge portion.
Edge portion data and data other than the edge portion that can be obtained by edge detection are extracted in steps S609 and S610, respectively. Next, step S6
In 12, the pre-recording is set as the inner edge portion for the extracted edge portion data. In step S613, the density increase recording is set by using the data other than the extracted edge portion as the internal data of the black character.

According to the above-described sequence, the edge portion of the black character is extracted in two steps, and the pre-printing recording and the post-printing recording are set for each of them, and the density-up recording is set for the internal data of the black character. Is possible. as a result,
By using the results of black character detection and two edge detections, the inner edge is printed first, the outer edge is printed later, and the inside of the black character is printed with increased density to spread the ink in the black character. The direction can be controlled, the sharpness of the edge portion can be improved, and high density black characters can be recorded.

Although the present embodiment focuses on black characters which are considered to be important parameters in the image to be recorded, the above-described sequence and recording method are not limited to black characters, and all characters, that is, color characters, can be used. It goes without saying that it can be applied.

(Others) In particular, the present invention is provided with a means (for example, an electrothermal converter or a laser beam) for generating thermal energy as energy used for ejecting ink, especially in the ink jet recording system. The present invention brings about excellent effects in a recording head and a recording apparatus of the type in which the state of ink is changed by the heat energy. This is because according to such a method, it is possible to achieve higher density and higher definition of recording.

With regard to its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method is a so-called on-demand type,
Although it can be applied to any type of continuous type, in particular, in the case of the on-demand type, it can be applied to a sheet holding liquid (ink) or an electrothermal converter arranged corresponding to the liquid path. By applying at least one drive signal corresponding to the recorded information and giving a rapid temperature rise exceeding the nucleate boiling, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the recording head. Liquid (ink) corresponding to this drive signal on a one-to-one basis.
This is effective because air bubbles inside can be formed. The liquid (ink) is ejected through the ejection opening by the growth and contraction of the bubble to form at least one droplet. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the 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 Japanese Patent No. 59600 is also included in the present invention. In addition, Japanese Unexamined Patent Publication No. 59-123670 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 is provided. The effect of the present invention is effective even if the configuration corresponding to the ejection portion is disclosed in JP-A-59-138461. That is, according to the present invention, recording can be surely and efficiently performed regardless of the form of the recording head.

Further, the present invention can be effectively applied to a full line type recording head having a length corresponding to the maximum width of a recording medium which can be recorded by the recording apparatus. Such a recording head may have a configuration that satisfies the length by a combination of a plurality of recording heads or a configuration as one recording head integrally formed.

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

Further, as the constitution of the recording apparatus of the present invention, it is preferable to add the ejection recovery means of the recording head, the preliminary auxiliary means and the like because the effects of the present invention can be further stabilized. If these are specifically mentioned, the recording head is heated using capping means, cleaning means, pressurizing or suction means, an electrothermal transducer, another heating element or a combination thereof. Pre-heating means for performing the pre-heating and pre-discharging means for performing the discharging other than the recording can be used.

Regarding the type or number of recording heads to be mounted, for example, only one is provided corresponding to a single color ink, or a plurality of inks having different recording colors and densities are supported. A plurality of pieces may be provided. That is, for example, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but it may be either the recording head is integrally formed or a plurality of combinations may be used. The present invention is also extremely effective for an apparatus provided with at least one of full-color recording modes by color mixing.

In addition, in the above-described embodiments of the present invention, the ink is described as a liquid, but an ink that solidifies at room temperature or lower and that softens or liquefies at room temperature may be used. Or, in the inkjet method, it is common to control the temperature of the ink itself within the range of 30 ° C. or more and 70 ° C. or less to control the temperature so that the viscosity of the ink is within the stable ejection range. Sometimes, a liquid ink may be used. In addition, the temperature rise due to thermal energy is positively prevented by using it as the energy of the state change from the solid state of the ink to the liquid state, or in order to prevent the evaporation of the ink, it is solidified and heated in the standing state. You may use the ink liquefied by. In any case, by applying heat energy such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In this case, the ink is
JP-A-54-56847 or JP-A-60-7
As described in Japanese Patent Publication No. 1260, it is also possible to adopt a form in which the sheet is opposed to the electrothermal converter in a state where it is held as a liquid or solid substance in the concave portion or through hole of the porous sheet. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

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

[0114]

As is apparent from the above description, according to the present invention, it is possible to change the printing mode by dividing the character recording into the edge portion and the area other than the edge portion. For example, it is possible to increase the density by increasing the amount of ejected ink and to reduce the amount of ejected ink for the edge portion to secure the sharpness of the edge portion.

Thus, for a character, which is an important parameter in ink jet recording density, for example, it is possible to prevent deterioration of the image quality such as bleeding while preventing the deterioration of the sharpness of the edge portion, and further improve the character density. You can As a result, it is possible to realize an inkjet recording device capable of high-quality character recording.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an inkjet recording apparatus to which the present invention can be applied.

2A and 2B are perspective views showing a mechanism of a recording head used in the inkjet recording apparatus.

FIG. 3 is a block diagram showing a configuration of a control circuit of the inkjet recording apparatus.

FIG. 4 is a diagram illustrating a flow of print data in the inkjet printing apparatus.

FIG. 5 is a flowchart showing a sequence of black character detection performed in an embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating edge detection performed in an embodiment of the present invention.

FIG. 7 is a schematic diagram showing a character composed of 24 × 18 dots for explaining the edge detection.

FIG. 8 is a schematic diagram showing a character in which an edge portion has been extracted by performing the edge detection.

FIG. 9 is a flowchart showing a sequence of edge detection performed in an embodiment of the present invention.

FIG. 10 is a flowchart showing a sequence for setting a black character detection, edge detection and recording method performed in the first embodiment of the present invention.

FIG. 11 is a diagram illustrating dot-on-dot, which is one of the means for increasing the density of black characters in the first embodiment.

FIG. 12 is a diagram for explaining half-pixel shifting in the carriage scanning direction, which is one of means for increasing the density of black characters.

FIG. 13 is a diagram for explaining half-pixel shift in the carriage scanning direction + paper feed direction, which is one of the means for increasing the density of black characters.

FIG. 14 is a diagram illustrating a state in which bidirectional recording is performed according to the second embodiment of the present invention, and is a schematic diagram illustrating a case where the landing positions of the forward pass and the return pass are not displaced.

FIG. 15 is a diagram similarly illustrating a state in which bidirectional recording is performed, and is a schematic diagram illustrating a case where the landing positions on the forward pass and the return pass are displaced by half a pixel.

FIG. 16 is a diagram similarly illustrating a state in which bidirectional recording is performed, and is a schematic diagram illustrating a case where the landing positions of the forward pass and the return pass are deviated by one pixel.

FIG. 17 is a flowchart showing a sequence of black character detection, edge detection, and recording direction setting performed in the second embodiment.

FIG. 18 is a flowchart showing a sequence for setting black character detection, edge detection and recording duty, which is performed in the third embodiment of the present invention.

FIG. 19 is a schematic diagram showing a table for setting a recording duty according to the medium used in the third embodiment.

FIG. 20 is a schematic cross-sectional view for explaining penetration into a recording medium when two dots land at a time interval.

FIG. 21 is a schematic diagram for explaining the drawing of ink at the edge portion according to the fourth embodiment of the present invention.

FIG. 22 is a flow chart showing a sequence for setting black character detection, edge detection, and driving order, which is performed in the fourth embodiment.

[Explanation of symbols]

101 carriage 102, 102Y, 102M, 102C, 102Bk
Recording head 103 Cartridge guide 104 Guide shaft 105 Guide shaft 106 Recording paper 107 Paper feed roller 108 Paper feed roller 109 Paper pressing plate 110 Color ink cartridge 111 Black ink cartridge 201 Silicon substrate 202 Printed circuit board 203 Aluminum plate 204 to 207 Pipe 208 Distributor 301 System controller 302 Carriage motor driver 303 Paper feed motor driver 304 Carriage motor 305 Paper feed motor 306 Host computer 307 Reception buffer 308Y, 308M, 308C, 308Bk Frame memory 309Y, 308M, 308C, 308Bk Print buffer 310 Recording control unit 311 Head driver

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiharu Inami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hitoshi Sugimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Fumihiro Goto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (11)

[Claims] 1. An ink jet recording apparatus which uses a recording head to perform recording by ejecting ink from the recording head to a recording medium based on the recording data, and a character detecting means for detecting a character from the recording data, and the character detecting means. An ink jet recording apparatus comprising: a recording control unit that controls to increase the density of a character detected by the unit to perform recording. 2. The ink jet recording apparatus further comprises edge detecting means for detecting an edge portion of the character detected by the character detecting means, and the recording control means detects the edge of the character detected by the character detecting means. The ink jet recording apparatus according to claim 1, wherein the density of portions other than the edge portion detected by the means is increased. 3. The ink jet recording apparatus according to claim 1, wherein the recording control unit increases the density of the detected character by scanning the recording head a plurality of times. 4. The ink jet recording apparatus according to claim 1, wherein the recording control unit increases the density of the detected character according to the type of recording medium used for recording. 5. The inkjet recording apparatus according to claim 2, wherein the recording control unit performs recording on at least a part of the detected character other than the edge portion before the edge portion. 6. The edge detecting means detects a multi-stage edge portion by performing edge detection a plurality of times, and the recording control means records the inner edge portion of the multi-stage edge portion first. The ink jet recording apparatus according to claim 5, further comprising a control to perform. 7. An ink jet recording method using a recording head to perform recording by ejecting ink from the recording head to a recording medium based on the recording data, wherein a character is detected from the recording data and an edge portion of the detected character is detected. Is detected, and the density of the detected characters other than the edge portion is increased, and each step is included. 8. The ink jet recording method according to claim 7, wherein the density of the detected character is increased by scanning the recording head a plurality of times. 9. The ink jet recording method according to claim 7, wherein the density of the detected character is increased according to the type of recording medium used for recording. 10. The ink jet recording method according to claim 7, wherein recording is performed on at least a part of the detected character other than the edge portion before the edge portion. 11. The method according to claim 10, wherein a multi-step edge portion is detected by performing edge detection a plurality of times, and an inner edge portion is recorded first in the multi-step edge portion. Inkjet recording method.