JP2002036515A - Recording device and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording device and a recording method capable of recording a high quality image by preventing generation of density irregularity at a joint part of recorded images in a multi-pass recording method. SOLUTION: As one of a plurality of mask patterns complementing with each other, a mask pattern having a different pixel thinning ratio in the sub scanning direction of a recording image is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus and a printing method of a so-called multi-pass printing method, and more particularly to a printing apparatus and a printing method suitable for printing an image using an ink jet printing head.

[0002]

2. Description of the Related Art As a recording apparatus, there is an ink jet recording apparatus using an ink jet recording head. This ink jet recording apparatus is configured to record an image by ejecting ink droplets from ejection ports of an ink jet recording head and attaching the ink droplets to a recording medium. Therefore, in order to print a high-quality image, the stability of the ink ejection timing and the stability of the ink ejection amount are required. The stability of the ink ejection timing
This is illustrated on the ink jet recording apparatus main body side.
However, the quality of the recorded image largely depends on the performance of the recording head alone. In other words, the ink ejection amount may vary due to slight variations that occur during the manufacture of the print head, such as variations in the shape of the ejection openings in the print head and variations in the performance of the heater when thermal energy of the heater is used as the ejection energy of ink droplets. And the ejection direction is adversely affected. As a result, density unevenness of the recorded image occurs, which may degrade the quality of the recorded image.

As a measure for preventing such density unevenness, for example, a multi-pass printing method has been proposed for a serial type printing apparatus that prints an image while moving a print head in the main scanning direction. 1 and 2 are explanatory diagrams of the multi-pass printing method.

In the case of the recording system shown in FIG. 1, an image in each of predetermined areas A, B, C,... On the recording medium is completed by the recording head H performing two recording scans. That is, a recording operation in which the recording head H ejects ink droplets while moving in the main scanning direction indicated by the arrow X, and the recording medium is conveyed in the sub-scanning direction indicated by the arrow Y by a distance equal to a half of the recording width of the recording head H. Is alternately repeated. The recording medium is transported in the sub-scanning direction by a transport roller or the like. FIG. 1 shows that the recording head H relatively moves in the direction opposite to the arrow Y due to the conveyance of the recording medium in the sub-scanning direction with respect to the recording head H. In the area A, an image is recorded by the first recording scan and the second recording scan of the recording head H. Similarly, in the area B, the second recording
An image is printed by the printing scan and the third printing scan. Thus, the image for each of the regions A, B, C,.
The printing is completed by two printing scans of the print head H. At the time of such first and second print scans, an image is printed based on print data thinned out using mask patterns that complement each other. The areas A and A are determined by the print images obtained during the first and second print scans.
Images for each of B, C,... Are completed. As mask patterns that complement each other, for example, a staggered mask pattern or a random mask pattern is used.

In the case of the recording system shown in FIG. 2, an image for each of the predetermined areas A, B,... On the recording medium is completed by the recording head H performing four recording scans. That is, a recording operation in which the recording head H ejects ink droplets while moving in the main scanning direction of arrow X, and a recording medium is conveyed in the sub-scanning direction of arrow Y by a distance of １ ／ of the recording width of the recording head H Is alternately repeated. In FIG. 2, the conveyance of the recording medium in the sub-scanning direction with respect to the recording head H causes
It is shown that the recording head H moves relatively in the direction opposite to the arrow Y. In the area A, images are recorded by the first, second, third, and fourth recording scans of the recording head H, and similarly, in the area B, the second, third, fourth, and An image is recorded by the fifth recording scan. Thus, the image for each of the areas A, B,... Is completed by the recording head H performing the recording scan four times. At the first, second, third, and fourth printing scans, an image is printed based on print data thinned out using mask patterns that complement each other. Then, the image for each of the areas A, B,... Is completed by the recorded images at the time of the four recording scans.

[0006]

However, even when the above-described multi-pass printing method is performed, periodic density unevenness may occur in a printed image depending on the density of print data. For example, in the multi-pass printing method of FIG. 1, two operations of transporting the recording medium in the sub-scanning direction by a transport roller or the like between the image recording by the first recording scan and the image recording by the third recording scan. Then, the passage of time enters. Due to these factors, a streak-like connecting streak may be generated at a joint between the image printed by the first print scan and the image printed by the third print scan, that is, at the boundary between the areas A and B. Such connecting streaks are
Since the recording medium appears in the form of a band at each period of the conveyance operation of the recording medium by the conveyance roller or the like, it appears to human eyes as density unevenness. The same applies to the case of the multi-pass printing method of FIG.

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing apparatus and a printing method capable of printing high-quality images by preventing occurrence of density unevenness at a joint portion of print images in a so-called multi-pass printing method. is there.

[0008]

A recording apparatus according to the present invention uses a recording head having a plurality of recording elements, and forms an image of a predetermined width on a recording medium while moving the recording head in the main scanning direction. A recording operation for recording, and a transport operation for transporting the recording medium in a sub-scanning direction that intersects the main scanning direction,
In a printing apparatus that sequentially prints images on the recording medium, pixels of a predetermined print image are thinned out using a plurality of complementary mask patterns, and the transport operation is performed at least once. A plurality of mask patterns, wherein the plurality of mask patterns are divided into a plurality of scans, and the plurality of mask patterns are different in the sub-scanning direction of the recorded image. It is characterized by including a pattern.

A recording method according to the present invention uses a recording head having a plurality of recording elements and records an image of a predetermined width on a recording medium while moving the recording head in the main scanning direction. And a transport operation of transporting the recording medium in a sub-scanning direction that intersects with the main scanning direction. In the recording method of sequentially recording images on the recording medium, a plurality of mask patterns complement each other. A plurality of scans of the print head which involves the transport operation at least once, printing the pixels of the thinned print image, and printing the plurality of masks. The pattern includes a mask pattern in which the pixel thinning rate differs in the sub-scanning direction of the recorded image.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. This embodiment is an application example as an ink jet recording apparatus and an ink jet recording method.

(Basic Configuration) First, an example of a basic configuration of a recording apparatus to which the present invention can be applied will be described.

FIG. 12 is a schematic perspective view of an ink jet recording apparatus 300 to which the present invention can be applied. In the printing apparatus 300, the carriage 400 is slidably guided in the main scanning direction indicated by an arrow X by two guide shafts 314 and 315 extending in parallel. The carriage 400 is reciprocated in the main scanning direction by a driving force of a motor transmitted through a driving force transmission mechanism such as a belt. An ink jet recording head and an ink tank 151 for supplying ink ejected from the recording head are mounted on the carriage 400. Reference numeral 316 denotes a sheet as a recording medium. After the sheet is inserted from the insertion port 311 and its conveyance direction is reversed, the conveyance roller 319 is used.
Is transported in the sub-scanning direction indicated by arrow Y. Then, ink droplets are ejected from the ejection openings of the recording head onto the sheet 316 on the platen 318. The recording head is
A configuration including an electrothermal converter that generates thermal energy to discharge ink can be provided. In this case, the electrothermal transducer generates heat by applying an electric pulse according to the recording data, and the thermal energy causes film boiling in the ink. Then, the ink is ejected from the ejection port with the generation of bubbles in the ink due to the film boiling. Reference numeral 310 denotes a recovery unit that performs operations such as capping the ejection openings of the recording head at the time of a recording operation and recovering ink from the ejection openings.

FIG. 3 is a diagram for explaining the flow of print data. The recording data sent from the host computer (host device) is stored in the reception buffer 303 of the recording device 300 via the interface 302. The command analysis of the recording data stored in the reception buffer 303 is performed by the command analysis unit 304.
The result is sent to the raster buffer 305. The print data stored in the raster buffer 305 is expanded by the data expansion unit 306 and stored in the print buffer 307 as binarized data. Then, a print signal corresponding to the print data is sent from the print buffer 307 to the print head 308, whereby an image is printed.

(First Embodiment) Next, referring to FIGS. 4 to 6, a first embodiment of the present invention having the above-described basic configuration will be described.
An embodiment will be described.

In the case of the present embodiment, a recording head 308 having 64 ejection ports (hereinafter, also referred to as "nozzles") formed in the sub-scanning direction is used.
The image is recorded on the sheet 316 by the same multi-pass recording method as described above.

That is, a recording operation in which the recording head 308 ejects ink droplets while moving in the main scanning direction indicated by the arrow X;
The transport operation of transporting the paper 316 in the sub-scanning direction indicated by the arrow Y by a distance of 1/2 of the recording width of the recording head 308 (width of 32 nozzles) is alternately repeated. FIG. 4 shows that the recording head 308 relatively moves in the direction opposite to the arrow Y due to the conveyance of the sheet 316 with respect to the recording head 308 in the sub-scanning direction. In the area B, the (n-1) th printing scan of the printing head 308 and the nth printing scan are performed.
The image is recorded by the recording scan of the recording head 308. Similarly, in the area C, the n-th recording scan of the recording head 308 and the (n + 1) th
The image is recorded by the recording scan of. Thus, the image for each of the areas A, B, C,.
08 is completed by two recording scans.

At the time of the first and second printing scans, an image is printed based on print data thinned out using mask patterns that complement each other. In the case of this example, the binarized data stored in the print buffer 307 is thinned using the mask patterns A and B, and the thinned data is sent to the print head 308 as a print signal.

Hereinafter, the mask patterns A and B will be described. In the following description, regarding the 64 nozzles in the recording head 308, the first nozzle, the second nozzle,..., The 64th nozzle are arranged in order from the upper side to the lower side in FIG.
Nozzle.

From the first nozzle of the recording head 308 to the 32nd nozzle
The print data for the nozzles up to the nozzle is thinned out using the mask pattern A. The mask pattern A is
As shown in FIG. 5A, this is a pattern in which the thinning rate gradually decreases from the first nozzle to the 32nd nozzle. FIG.
7 is a specific explanatory diagram of the mask pattern A. FIG. In FIG. 6, white circles are pixel portions thinned out by the mask pattern A, that is, mask portions, and black circle portions are pixel portions not thinned out by the mask pattern A. In the case of this example, the thinning rate decreases at a constant rate from the first nozzle to the 32nd nozzle.

On the other hand, print data for the nozzles No. 33 to No. 64 of the print head 308 is thinned out using the mask pattern B. The mask pattern B is, as shown in FIG.
This is a pattern in which the thinning rate gradually increases toward the nozzle. As the mask pattern B, the white circle part and the black circle part in the mask pattern A of FIG.
A pattern assigned from the nozzle to the 64th nozzle can be used.

Such mask patterns A and B may be stored in a ROM or a RAM in advance, or may be created using a random number table or the like at the start of recording. Further, the mask pattern used for each of the regions A, B, C,... May be changed by offsetting the read position of the mask pattern. For example, as shown in FIG. 6, in the case of a mask pattern A that is periodically repeated in the horizontal direction in FIG. 6 with the movement of the print head 308 in the main scanning direction, the data of the mask pattern A is Are read periodically from the predetermined read start position in the horizontal direction in FIG. In this case, by shifting the reading start position of the mask pattern A, the mask pattern A used for each of the regions A, B, C. In that case, the thinning rate of the mask pattern A does not change.

As described above, by thinning out the pixels of the recorded image using the mask patterns A and B, as shown in FIG.
The connection between the images printed by the (n-1) th printing scan and the (n + 1) th printing scan has a low density. Then, the image of the low density connection portion is complemented by the high density printing by the n-th printing scan. As a result, it is possible to print a high-quality image while suppressing the occurrence of streak-like connecting streaks at a connecting portion of a recorded image.

(Second Embodiment) Next, a second embodiment of the present invention having the above-described basic configuration will be described with reference to FIGS.

In the case of this example, the recording head 308 of 64 nozzles similar to that of the first embodiment is used, and the paper 316 is basically formed by the multi-pass recording method similar to that of FIG. Record the image in

That is, a recording operation in which the recording head 308 ejects ink droplets while moving in the main scanning direction indicated by the arrow X;
The transport operation of transporting the sheet 316 in the sub-scanning direction indicated by the arrow Y by a distance of １ ／ of the recording width of the recording head 308 (width of 16 nozzles) is alternately repeated. FIG. 7 shows that the recording head 308 relatively moves in the direction opposite to the arrow Y due to the conveyance of the sheet 316 with respect to the recording head 308 in the sub-scanning direction. In the area A, the (n-2) th, (n-1) th,
An image is recorded by the n-th and (n + 1) -th recording scans. Similarly, the recording head 308 is located in the area B.
(N-1), n-th, (n + 1), and (n +
An image is printed by the four printing scans of 2). As described above, the image for each of the areas A, B,... Is completed by the recording head 308 performing the recording scan four times.

At the time of the first, second, third and fourth printing scans, an image is printed based on print data thinned out using mask patterns that complement each other. In the case of this example, the mask patterns A, B,
Using C and D, the binarized data stored in the print buffer 307 is thinned out and sent to the print head 308 as a print signal.

Hereinafter, the mask patterns A, B, C, D
Will be described. In the following description, the recording head 3
Regarding the 64 nozzles at 08, the first nozzle, the second nozzle,
... the 64th nozzle.

From the first nozzle of the recording head 308 to the sixteenth nozzle
The print data for the nozzles up to the nozzle is thinned out using the mask pattern D, the print data for the nozzles from the 17th nozzle to the 32nd nozzle is thinned out using the mask pattern C, and the 33rd nozzle is replaced with the 48th nozzle. Print data for the nozzles up to the nozzle is thinned out using the mask pattern B, and print data for the nozzles from the 49th nozzle to the 64th nozzle is thinned out using the mask pattern A.

The mask patterns A and C are shown in FIG.
7C, the pattern in which the thinning rate gradually increases from the upper nozzle to the lower nozzle in FIG. 7 of the recording head 308, that is, from the 49th nozzle to the 64th nozzle, and from the 17th nozzle to the 32nd nozzle. It is. FIG.
7 is a specific explanatory diagram of a mask pattern A. FIG. In FIG. 9, white circles are pixel portions thinned out by the mask pattern A, that is, mask portions, and black circle portions are pixel portions not thinned out by the mask pattern A.
The mask pattern C can be set similarly to the mask pattern A. Conversely, mask pattern B,
D indicates the recording head 308 as shown in FIGS. 8B and 8D.
7, the thinning rate gradually decreases from the upper nozzle to the lower nozzle, that is, from the 33rd nozzle to the 48th nozzle, and from the 1st nozzle to the 16th nozzle. As the mask patterns B and D, a pattern obtained by inverting the white circle portion and the black circle portion in the mask pattern A of FIG. 9 and assigning them to the 33rd nozzle to the 48th nozzle and the 1st nozzle to the 16th nozzle can be used. .

Such mask patterns A, B, C, D
Is similar to the case of the first embodiment described above,
It may be stored in M or RAM, or may be created at the start of recording by using a random number table or the like. Alternatively, the mask pattern read position may be offset to change the mask pattern used for each of the regions A, B,. For example, as shown in FIG.
In the case of the mask pattern A which is periodically repeated in the horizontal direction in the figure with the movement of the recording head 308, the data of the mask pattern A is accompanied by the movement of the recording head 308 in the main scanning direction. , From the predetermined read start position in the horizontal direction in FIG. In this case, by shifting the reading start position of the mask pattern A, the mask pattern A used for each of the regions A, B,.
Can be slightly different. In that case, the thinning rate of the mask pattern A does not change.

As described above, the mask patterns A, B, C,
By thinning out the pixels of the recorded image using D, as shown in FIG. 7, the connection portion of the image printed by the (n-2) th printing scan and the (n + 2) th printing scan has low density. Then, the image of the low-density connection portion is (n)
This is complemented by high density printing by the -1) printing scan and the (n + 1) th printing scan. As a result, the occurrence of streak-like streaks at the stitch portion of the recorded image is suppressed,
High quality images can be recorded.

(Third Embodiment) Next, a third embodiment of the present invention having the above-described basic configuration will be described with reference to FIGS.

In the case of this example, a print head 308 of 64 nozzles similar to that of the first embodiment is used, and a part of an image is printed by two print scans of the print head 308 (multi-pass printing). The other part of the image is recorded by one recording scan of the recording head 308.

That is, a recording operation in which the recording head 308 ejects ink droplets while moving in the main scanning direction indicated by the arrow X;
Paper 3 for a distance corresponding to the width of 48 nozzles of recording head 308
And the transport operation of transporting P.16 in the sub-scanning direction of arrow Y is alternately repeated. In FIG. 10, the recording head 30
It is shown that the recording head 308 relatively moves in the direction opposite to the arrow Y by the conveyance of the sheet 316 with respect to the sheet 8 in the sub-scanning direction. In the area A, the recording head 30
An image is printed by a total of two print scans using the 49th to 64th nozzles in the (n-1) th print scan and the 1st to 16th nozzles in the nth print scan. . Similarly, in the area C, the recording head 30
Using the 49th to 64th nozzles in the 8th nth printing scan and the 1st to 16th nozzles in the (n + 1) th printing scan, an image is printed by a total of two printing scans. On the other hand, in the area B, the recording head 308
An image is printed by one printing scan using the 17th nozzle to the 48th nozzle in the nth printing scan. In this manner, the images of the areas A and C are
8 is completed by two recording scans, and the image of the area B is completed by one recording scan of the recording head 308.

At the time of printing scanning of such areas A and C, an image is printed based on print data thinned out using mask patterns that complement each other. In this case,
Using the mask patterns A and B, the print buffer 30
7 is thinned out and sent to the printhead 308 as a print signal.

The first to sixteenth nozzles of the recording head 308
The print data for the nozzles up to the nozzle is thinned out using the mask pattern A, and the print data for the nozzles from the 49th nozzle to the 64th nozzle is thinned out using the mask pattern B. The print data for the 17th nozzle to the 48th nozzle does not use a mask pattern and does not thin out. The mask pattern A is a pattern in which the thinning rate gradually decreases from the first nozzle to the sixteenth nozzle of the recording head 308 as shown in FIG. On the other hand, the mask pattern B is a pattern that gradually increases from the 49th nozzle to the 64th nozzle of the recording head 308 as shown in FIG.

The mask patterns A and B are set in advance in the same manner as in the first and second embodiments described above.
It may be stored in an OM or a RAM, or may be created at the start of recording using a random number table or the like.
Further, similarly to the first and second embodiments described above, the readout position of the mask pattern may be offset to change the mask pattern used for each of the recording areas A and C.

As described above, by thinning out the pixels of the print image using the mask patterns A and B, the print data is printed by the (n-1) th print scan and the (n + 1) th print scan as shown in FIG. There is no joint in the image. Further, the density of the connecting portion between the image printed by the (n-1) th printing scan and the image printed by the nth printing scan changes so as to complement each other. It is possible to record a high-quality image while suppressing the occurrence of streak-like streaks at the stitch portion. The same applies to a connection portion between an image printed by the n-th printing scan and an image printed by the (n + 1) -th printing scan.

In the case of this example, it is possible to record a high-quality image as described above, and it is possible to set a large transport amount of the sheet 316 per unit time. Thus, high-speed recording can be realized.

(Other Embodiments) The number of nozzles in the print head is not limited to 64 in the above-described embodiment, but is arbitrary, and a mask pattern corresponding to the number of nozzles is used. In that case, an optimal mask pattern may be generated or selected according to the number of nozzles in the print head. Also, when printing an image using only specific nozzles among all the nozzles in the print head according to the type of print image, an optimum mask pattern is generated according to the number of nozzles used for the printing. Alternatively, it may be selected.

The number of printing scans for completing an image in the multi-pass printing method is not limited to two or four as in the above-described embodiment, but is arbitrary, and is optimal according to the number of printing scans. A suitable mask pattern may be generated or selected.

The present invention can be widely applied as a recording apparatus and a recording method of various recording methods other than the ink jet recording method. The point is that it is a serial type printing apparatus and printing method as long as an image can be printed by a multi-pass printing method.

[0043]

As described above, according to the present invention, in a so-called multi-pass printing method, as one of a plurality of mask patterns complementary to each other, a mask pattern in which the pixel thinning rate differs in the sub-scanning direction of a printed image. Is used, it is possible to prevent the occurrence of density unevenness at a joint portion of a recorded image and to record a high-quality image.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a conventional multi-pass printing method.

FIG. 2 is an explanatory diagram of another example of a conventional multi-pass printing method.

FIG. 3 is a block diagram for explaining a print data processing system according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a recording method according to the first embodiment of the present invention.

FIGS. 5A and 5B are explanatory diagrams of a mask pattern used in the recording method of FIG. 4;

FIG. 6 is an explanatory diagram of a specific configuration example of a mask pattern A in FIG.

FIG. 7 is an explanatory diagram of a recording method according to a second embodiment of the present invention.

FIGS. 8A, 8B, 8C, and 8D are explanatory diagrams of mask patterns used in the recording method of FIG.

FIG. 9 is an explanatory diagram of a specific configuration example of the mask pattern A of FIG.

FIG. 10 is an explanatory diagram of a recording method according to a third embodiment of the present invention.

FIGS. 11A and 11B are explanatory diagrams of a mask pattern used in the recording method of FIG.

FIG. 12 is a perspective view of an ink jet recording apparatus to which the present invention can be applied.

[Explanation of symbols]

 300 Inkjet recording device 301 Host computer 302 Interface 303 Receive buffer 304 Command analysis unit 305 Raster buffer 306 Data development unit 307 Print buffer 308 Recording head

Claims (7)

[Claims] A recording operation for recording an image of a predetermined width on a recording medium while moving the recording head in a main scanning direction using a recording head having a plurality of recording elements; By repeating the transport operation of transporting in the sub-scanning direction that intersects with the main scanning direction, in a printing apparatus that sequentially prints images on the recording medium, a plurality of mask patterns that complement each other are used. The pixels of the recorded image are thinned out, and the transport operation is performed by at least one.
Controlling the recording head to record the pixels of the thinned-out recording image in a plurality of scans of the recording head, the plurality of mask patterns having a pixel thinning rate of the sub-scanning of the recording image. A printing apparatus comprising mask patterns that differ in direction. 2. A plurality of recording elements in the recording head are arranged substantially along the sub-scanning direction, and the plurality of mask patterns are thinned out by pixels recorded by the recording elements near an end of the arrangement. The printing apparatus according to claim 1, wherein the printing apparatus includes a mask pattern having a high ratio. 3. The printing apparatus according to claim 1, further comprising means for generating the mask pattern in accordance with the number of the printing elements used for printing an image. 4. The printing apparatus according to claim 1, further comprising a unit configured to generate the mask pattern in accordance with the number of times the print head scans a plurality of times. 5. The recording apparatus according to claim 1, wherein the recording element of the recording head is capable of discharging an ink droplet from an ink discharge port. 6. The recording apparatus according to claim 5, wherein the recording element has an electrothermal converter that generates heat energy as ejection energy of the ink droplet. 7. A recording operation for recording an image of a predetermined width on a recording medium while moving the recording head in a main scanning direction by using a recording head having a plurality of recording elements; In a recording method of sequentially recording images on the recording medium by repeating a transport operation of transporting in a sub-scanning direction that intersects with the main scanning direction, a predetermined number of mask patterns are used using a plurality of complementary mask patterns. The pixels of the print image are thinned out, divided into a plurality of scans of the print head accompanied by the transport operation at least once, and the pixels of the thinned print image are printed. A printing method, wherein a thinning rate includes a mask pattern different in the sub-scanning direction of a print image.