Patent Grant
8157351
The present invention relates to an inkjet printing apparatus and an inkjet printing method.
Inkjet printing apparatuses include line-type printing apparatuses and serial-type printing apparatuses. The serial-type apparatus performs main-scanning and sub-scanning. In the main scanning, the apparatus moves a printing head relative to a print medium while causing the printing head to eject an ink. In the sub-scanning, the apparatus feeds a print medium by a predetermined amount in a direction orthogonal to a main scanning direction. The serial-type apparatus serially forms an image on the print medium by alternately repeating the main scanning and the sub-scanning.
Some of the serial-type printing apparatuses employ a multi-scan print mode in order to improve quality of images. In the multi-scan print scheme, while a printing medium having a width smaller than that of a range of an array of printing elements is transferred, the printing head performs main scanning of the printing medium plural times so as to complete the printing of an image in a predetermined region (for example a single pixel array region) on the print medium.
For the execution of the multi-scan scheme, image data to be printed in the predetermined region needs to be divided into plural image data corresponding to the plural times of main scanning. Conventionally, masks have been used for such division. A mask is, as publicly known, an aggregate of data in which data allowing image data to be printed thereon (data for not masking the image data) and data not allowing image data to be printed thereon (data for masking the image data) are previously arrayed. Then, by executing AND operations of such masks and the binary image data to be printed on the predetermined region, the binary image data to be printed on the predetermined region is divided into the plural image data corresponding to the respective times of the scanning.
Meanwhile, a dye-based ink or a pigment ink is used in an inkjet printing apparatus. The use of the pigment ink contributes to improvement of various properties needed for a printed image, such as a density, a definition, and image durability such as water resistance and light resistance.
In the case of pigment inks, however, gloss values may vary with the color and printing method in some cases. For example, in a case where an image is printed by the multi-scan printing mode by use of a cyan ink having a relatively great gloss value and a yellow ink having a relatively small gloss value, there may occur glossiness unevenness in some cases due to a gloss value difference between the cyan and yellow inks. That is, since a gloss value of a part printed with the cyan ink is greater than that of a part printed with the yellow ink, glossiness unevenness occurs due to a difference between these gloss values.
In order to reduce such glossiness unevenness as described above, there has been known a technique in which a printing rate in the last time of scanning with an ink having a relatively small glass value is set greater than a printing rate in the last time of scanning with an ink having a relatively great gloss value (for example, refer to Description of U.S. Pat. No. 7,152,950). According to this technique, an ink having a relatively small gloss value is more likely to be positioned in an outermost layer, and therefore, a dominant color of inks in an outermost layer is uniformed in an image of secondary or higher order color is uniformed, whereby glossiness unevenness is reduced.
However, the above described technique aims to reduce glossiness unevenness in an image of a secondary or higher order color obtained by inks of plural colors printed overlaying one another, and is thus insufficient for reducing glossiness unevenness occurring between single-color images respectively printed with inks of plural colors. That is, although the above described technique reduces glossiness unevenness by uniforming a dominant color of the outermost layer inks, the above technique cannot uniform a dominant color of the outermost layer inks of one color image of one color and another single color image of another color. Accordingly, even if the technique disclosed in the above patent document is employed, glossiness unevenness occurring between single-color images respectively printed with different colors cannot be reduced. Additionally, even in a case of an image of a secondary or higher order color, glossiness unevenness cannot be reduced by the above described technique if printing rates of inks with different glossiness unevennesses widely differ from each other.
The present invention was made in consideration of the above points, and provides an inkjet printing apparatus and inkjet printing method which are used to obtain a printed matter having a small degree of glossiness unevenness, when an image is printed by use of plural colors of inks having different gloss values.
In order to achieve the above object, the present invention is an inkjet printing apparatus for forming an image on a print medium by relatively scanning to the print medium a first ejection unit for ejecting a first ink and a second ejection unit for ejecting a second ink different in kind from the first ink. The inkjet printing apparatus is characterized by including a forming unit configured to form the image with the first and second inks on the print medium by a first printing mode for completing an image to be printed with the first ink to a pixel array region on the print medium by scanning the first ejection unit one time and a second printing mode for completing an image to be printed with the second ink to the pixel array region on the print medium by scanning the second ejection unit plural times, and is characterized in that a gloss value of a solid image with the second ink is greater than a gloss value of a solid image with the first ink.
According to the above configuration, by respectively printing inks having different gloss values by different printing modes, glossiness unevenness occurring due to gloss value differences between the inks can be reduced. Thereby, a printed matter having a small degree of glossiness unevenness can be obtained.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Embodiments according to the present invention will be described in detail below with reference to the drawings.
A carriage HC engages with a helical groove 104 of a lead screw 105, the lead screw 105 configured to move in synchronization with a forward and reverse rotations of a drive motor 113 and to rotate through driving force transmission gears 109 to 111. The carriage HC thus makes reciprocating movement in directions indicated by arrows a and b (in main scanning directions) while being supported by a guide rail 103. The carriage HC has an integrated inkjet cartridge IJC mounted thereon, containing a printing head IJH and an ink tank IT. Note that, the ink tank IT and the printing head IJH are integrally formed so as to constitute a replaceable ink cartridge IJC in this embodiment. However, the ink tank IT and the printing head IJH may be separated from each other.
A paper pressing plate 102 presses a print medium P against a platen 100 along a moving direction of the carriage HC. Photocouplers 107 and 108 identify existence of a lever 106 of the carriage, and detects a home position at which rotational directions of the motor 113 is switched or which is used for other purposes.
In this embodiment, the ink tanks IT contain a cyan ink (BCI-1421 C) and a yellow ink (BCI-1421 Y) at least. As will be described later by use of
A capping member 122 that caps a front face of the printing head IJH is supported by a member 116, and performs suction-based recovery of the printing head through an aperture 123 inside a cap by use of a suction apparatus 115 that sucks the inside of a cap. A cleaning blade 117 is moved frontward and backward by a member 119. The cleaning blade 117 and the member 119 are supported by a main body supporting plate 118. Additionally, the lever 121 is provided for starting suction of the suction-based recovery, and moves along with movement of a cum 120 engaging with the carriage. The movement of the lever 121 is controlled by a driving force from the drive motor, the driving force transmitted by a publicly known transmission mechanism such as clutch switching. Note that a configuration of the printing apparatus according to the present invention is fine as far as it allows desired operations of capping, cleaning and suction-based recovery to be performed at known timings.
When image data is inputted to the interface 300, the image data is converted into print-use data between the G. A. 304 and the MPU 301. The print-use data is temporarily stored in the DRAM 303 until it accumulates to a level, high enough to start driving of the printing head. Then, the printing head is driven in accordance with the print-use data having been transmitted to the head driver 305 at the same time as the motor drivers 306 and 307 are driven, whereby printing is performed.
The printing apparatus in this embodiment is configured so as to be capable of executing at least two printing modes (the first printing mode and the second printing mode). The “first printing mode” is a printing mode in which the printing head scans one pixel array region (a raster region) one time, and will be referred to as an interlace printing mode (an interlace mode) below in some cases. The “second printing mode” is a printing mode in which the printing head scans one pixel array region (a raster region) plural times, and will be referred to as a multi-scan print mode (a multi-scan mode) below in some cases.
Next, gloss value differences among inks will be described.
Note that a print duty is a ratio of plural pixels (N pixels) constituting a unit region to pixels (M pixels) on which dots are actually printed, and is expressed by N/M×100(%). For example, if the number of pixels constituting the unit region is 100, and dots are printed on 25 of the 100 pixels, a print duty is 25% in the unit region. In like manner, a print duty is 100% in a case where dots are printed on all of the 100 pixels.
As shown in this graph, in general, a gloss value widely changes in accordance with a print duty, and a great-low relationship of gloss values between two inks may be reversed in accordance with the print duty. Accordingly, in order to exclusively define relative levels of gloss values, a print duty of images used for measurement of gloss values needs to be uniquely determined previously. Therefore, in this patent description, levels of gloss values are defined in accordance of gloss values at the measurement of solid images (solid patches) at a print duty of 100%. For example, considering the cyan ink and the yellow ink, a gloss value of the cyan ink when the print duty was 100% was about 50, and a gloss value of the yellow ink when the print duty was 100% was about 28. Consequently, in this case, the cyan ink corresponds to an ink having a relatively great gloss value, and the yellow ink corresponds to an ink having a relatively small gloss value. In this embodiment, the yellow (Y) and black (K) inks are set as inks having relatively small gloss values, and the magenta (M) and cyan (C) inks are set as relatively great gloss values.
Grouping of inks applicable to this embodiment is not limited to the above manner. Only the yellow ink may be set as an ink having a relatively small gloss value, the other three inks may be set inks having relatively great gloss values. Alternatively, in contrast, while only the magenta ink may be set as an ink having a relatively great gloss value, the other three inks may be set inks having relatively small gloss values. That is, the number of inks having relatively small gloss values may be one or plural, and, likewise, the number of inks having relatively great gloss values may be one or plural.
Next, a printing method of this embodiment will be described.
In each of unit regions, a mask X-1 is used in the first pass, a mask X-2 is used in the second pass, a mask X-3 is used in the third pass, and a mask X-4 is used in the fourth pass. These masks are previously stored in the ROM 302, and are read out from the ROM when used.
In a first unit region, by using the mask X-1 in the first pass, printing is performed on one raster region through a nozzle of the nozzle number 13. By using the mask X-2 in the second pass, printing is performed on one raster region through a nozzle of the nozzle number 10. In like manners, by using the mask X-3 in the third pass, and by using the mask X-4 in the fourth pass, printing is performed on raster regions through nozzles of the nozzle number 7 and the nozzle number 4, respectively. By thus constraining the number of nozzles usable for printing on one raster region to only one, printing on one raster region is performed with one scanning pass. A dot image printed with one scanning pass has high surface flatness and smoothness, and tends to have a great gloss value. Accordingly, in order to obtain a great gloss value, it is preferable that the interlace mode such as one shown in
In each of unit regions, a mask Y-1 is used in the first pass, a mask Y-2 is used in the second pass, a mask Y-3 is used in the third pass, and a mask Y-4 is used in the fourth pass. These masks are previously stored in the ROM 302, and are read out from the ROM when used. By use of such masks as those, the number of nozzles usable for printing on one raster region is increased to 4, whereby printing on one raster region is executed with four scanning passes. A dot image printed with multiple scanning passes has lower surface flatness and smoothness, and tends to have a smaller gloss value, than the above dot image printed with one scanning pass. Accordingly, in the multi-scan mode shown in
Although the same mask set (X-1 to X-4 or Y-1 to Y-4) is used for all of the unit regions in each of
One set is randomly selected from such plural mask sets for each unit region, and printing with four scanning passes is performed on the unit region by use of the selected one mask set.
More specifically, the MPU randomly selects one set from the plural mask sets stored in the ROM. The MPU sets, in the RAM, the thus selected mask set as a mask set used for a unit region. On the other hand, image data to be printed on the unit regions are stored in a print buffer. There, image data stored in the print buffer is singly picked based on the mask pattern being set in the RAM, and printing is performed in accordance with this picked image data. The above described selection of a mask set is performed for every unit region, whereby a mask set to be used is changed for each unit region.
This random selection of a mask set for each unit region enables unique setting of a mask set for each of the unit regions. Thereby, cyclic unevenness occurring over plural unit regions which are aligned side by side in the sub scanning direction can be reduced as compared to a case where one mask set is used continuously over the plural unit regions.
Note that, while seven varieties of mask sets are prepared in
The yellow and black inks are printed by the interlace mode in accordance with the mask patterns shown in
Reference (a) of
First of all, when a print paper sheet is transferred and reaches a predetermined print start position, printing in the first pass is started. In the first pass, the yellow ink is ejected from ejection orifices 25 and 29 while the printing head moves in the main scanning direction. The yellow ink ejected from the ejection orifice 25 is continuously printed on the raster a, and the yellow ink ejected from the ejection orifice 29 is continuously printed on the raster e. After the completion of printing in the first pass, the print paper sheet is transferred in the sub scanning direction by an amount corresponding to a width of the one block.
Next, in the second pass, the yellow ink is ejected from ejection orifices 18, 22, 26 and 30 while the printing head moves in the main scanning direction. The yellow ink ejected from the ejection orifices 18, 22, 26 and 30 is continuously printed on the rasters b, f, j and an unillustrated raster n, respectively. After the completion of printing in the second pass, the print paper sheet is transferred in the sub scanning direction by the amount corresponding to the width of the one block.
Likewise, in the third pass, the yellow ink is ejected from ejection orifices 11, 15, 19, 23, 27 and 31, and is continuously printed on the rasters c, g and k and unillustrated rasters o, s and w, respectively. Thereafter, the print paper sheet is transferred in the sub scanning direction by the amount corresponding to the width of the one block.
With the completion of printing in the fourth pass, the printing head have scanned the same print region of the print paper sheet four times, whereby printing on the same print region (a region corresponding to the rasters a to h) ends.
Reference (b) of
In contrast, in the multi-scan mode, such as one described in connection with
As has been described above, in this embodiment, an ink having a relatively small gloss value is printed by the interlace mode suitable for enhancing a gloss value of an image. On the other hand, an ink having a relatively great gloss value is printed by the multi-scan mode in which a gloss value of an image tends to become smaller. Thereby, a difference between a gloss value of an image printed with an ink having a relatively small gloss value and a gloss value of an image printed with an ink having a relatively great gloss value can be reduced. As a result, when a printed image is printed by use of plural inks having different gloss values, a printed matter having a small degree of glossiness unevenness can be obtained.
Note that, although a case of using four inks that are CMYK has been exemplified above, inks applicable in this embodiment are not limited to the above. This embodiment only needs to use at least two inks, and this embodiment is also applicable, for example, in a case where a monochrome mode using two black-based inks, a black ink and a gray ink, is executed. In this case, for example, the black ink is set as an ink (the first ink) having a relatively small gloss value, and the gray ink is set as an ink (the second ink) having a relatively great gloss value, whereby, while the black ink is printed by the interlace mode, the gray ink is printed by the multi-scan mode.
The first embodiment is configured to simultaneously execute the interlace printing mode and the multi-scan printing mode. However, the present invention is not limited to such an embodiment, and may be configured to selectively execute the interlace printing mode and the multi-scan printing mode.
The printing apparatus according to this embodiment is configured so that the interlace printing mode and the multi-scan printing mode may be selectively executable. More specifically, the printing apparatus according to this embodiment selects, for printing an image, one of the interlace printing mode and the multi-scan printing mode, in accordance with the numbers of dots of inks constituting the image.
In step S102, the number of dots of inks having greater gloss values and the number of dots of inks having smaller gloss values are counted, and then compared to each other. In this embodiment, the numbers of dots of a cyan ink and a yellow ink are counted. The cyan ink in this embodiment has a greater gloss value than the yellow ink. Therefore, if the number of dots of the cyan ink is larger than the number of dots of the yellow ink, printing is performed by the multi-scan printing mode (step S103). On the other hand, if the number of dots of the cyan ink is smaller than that of the yellow ink, printing is performed by the interlace printing mode (step S104).
If two or more images exist in the same page in step S101, the step proceeds to step S105. In step S105, judgment is made whether or not the plural images judged to be present in step 101 are partly located on the same raster. If the plural images are not partly located on the same raster, that is, if all of the images are separate from one another in a transferring direction of a print medium, the step proceeds to step S106.
In step S106, for each of the plural images, the number of dots of inks having greater gloss values and the number of dots of inks having smaller gloss values are counted, and then compared to each other. If the number of dots of the cyan ink is larger than the number of dots of the yellow ink, printing is performed by the multi-scan printing mode from the beginning of a line in which the each of the images exists (step S107). On the other hand, if the number of dots of the cyan ink is smaller than the number of dots of the yellow ink, printing is performed by the interlace printing mode from the beginning of the line in which the each of the images exists (step S108).
If judgment is made in step S105 that the plural images judged to be present in step S101 are partially located on the same raster, that is, if any two or more of the plural images are not separate from one another in the transferring direction of a print medium, the step proceeds to step S109.
In step S109, for each of the plural images, the number of dots of inks having greater gloss values and the number of dots of inks having smaller gloss values are counted, and then compared to each other. If the number of dots of the cyan ink is larger than the number of dots of the yellow ink, printing is performed by the multi-scan printing mode from a position at which the corresponding images exists (step S110). On the other hand, if the number of dots of the cyan ink is smaller than the number of dots of the yellow ink, printing is performed by the interlace printing mode from the position in which the corresponding images exists (step S111). That is, even if the image starts in the middle of a line, the image forming is started from the starting position of an image with a corresponding printing mode by switching between the multi-scan printing mode and the interlace mode.
As has been described above, if the number of dots of inks having greater gloss values is larger, printing is performed by the multi-scan printing mode, whereas, if the number of dots of inks having greater gloss values is smaller, printing is performed by the interlace mode. By thus performing printing with a corresponding printing mode by switching between the multi-scan printing mode and the interlace printing mode, reduction of glossiness unevenness can be achieved.
In this embodiment, whether the multi-scan printing mode or the interlace printing mode is used in performing printing is judged by counting, and comparing to each other, the number of dots of inks having greater gloss values and the number of dots of inks having smaller gloss values. However, this embodiment is limited to a configuration in which the judgment is made by comparison between the numbers of dots of inks. This embodiment only needs to have a configuration in which the judgment is made by comparison between amounts of ink ejected in a unit area in which an image is printed.
Although a case of using the cyan ink and the yellow ink has been exemplified above, this embodiment is not limited to these inks. That is, inks having different gloss values are applicable. For example, a magenta ink and a black ink can be applied. The magenta ink has a relatively great gloss value as compared to the black ink. Therefore, if judgment is made that the number of dots of the magenta ink is larger, printing is performed by the multi-scan printing mode. On the other hand, if the number of dots of the black ink is larger, printing is performed by the interlace printing mode. Thereby, even in a case where printing is performed with the magenta ink and the black ink which have different gloss values, a printed matter having a small degree of glossiness unevenness can be obtained.
In the above embodiments, description has been given of cases where the multi-scan printing mode and the interlace printing mode are executed by use of a printing head in which an array density of ejection orifices used for ejecting an ink having a relatively great gloss value, and an array density of ejection orifices used for ejecting an ink having a relatively small gloss value are the same. However, the present invention is not limited to such embodiments. This third embodiment is characterized in that the multi-scan printing mode and the interlace printing mode are simultaneously executed by use of a printing head in which an array density of ejection orifices used for ejecting an ink having a relatively great gloss value, and an array density of ejection orifices used for ejecting an ink having a relatively small gloss value are different.
A printing method according to this embodiment will be described below. In this embodiment, in the same manner as in the first embodiment, a cyan ink having a relatively great gloss value is printed by the multi-scan printing mode, and a yellow ink having a relatively small gloss value is printed by the interlace mode. However, one difference from the first embodiment is, as will be described later, in that an ejection orifice array density of a yellow ink ejection unit (
First of all, when a print paper sheet is transferred and reaches a predetermined print start position, printing in the first pass is started. In the first pass, the yellow ink is ejected from ejection orifices 8 and 9 while the yellow ink ejection unit moves in the main scanning direction. The yellow ink ejected from the ejection orifice 8 is continuously printed on the raster a, and the yellow ink ejected from the ejection orifice 9 is continuously printed on the raster e. After the completion of printing in the first pass, the print paper sheet is transferred in the sub scanning direction by a length corresponding to a width equal to a nine ejection-orifice distance of the cyan ink ejection unit.
Next, in the second pass, the yellow ink is ejected from ejection orifices 6 and 7 while the yellow ink ejection unit moves in the main scanning direction. The yellow ink ejected from the ejection orifices 6 and 7 is continuously printed on the rasters b and f, respectively. After the completion of printing in the second pass, the print paper sheet is transferred in the sub scanning direction by the length corresponding to the width equal to the nine ejection-orifice distance of the cyan ink ejection unit.
Likewise, in the third pass, the yellow ink is ejected from ejection orifices 4 and 5, and is continuously printed on the rasters c and g, respectively. Thereafter, the print paper sheet is transferred in the sub scanning direction by the length corresponding to the width equal to the nine ejection-orifice distance of the cyan ink ejection unit.
With the completion of printing in the fourth pass, the printing head has scanned the same print region of the print paper sheet four times, whereby printing on the same print region (here, a region corresponding to the rasters a to h) ends.
Reference (b) of
On the other hand, the cyan ink is printed by the multi-scan printing mode by means of the cyan ink ejection unit having a total of 36 ejection orifices at positions indicated by the circles and by the crossbars in (a). A transferring distance of a print paper sheet is set so as to be equal to the above described nine ejection-orifice distance. Then, printing is performed by use of ejection orifices 28 to 36 in the first pass, by use of ejection orifices 19 to 27 in the second pass, by use of ejection orifices 11 to 18 in the third pass, and by use of ejection orifices 1 to 9 in the fourth pass. Thereby, at the same time as printing is performed with four scanning passes on the same print region (here, the region corresponding to the rasters a to h), printing is performed with four scanning passes on each single raster region. As a result, an image printed of cyan dots printed on the same raster through four-times scanning has relatively large irregularities. Therefore, a gloss value of the cyan image can be reduced.
As has been described above, even the yellow ink ejection unit and in the cyan ink ejection unit has different ejection orifice array densities, the ink having a relatively great gloss value can be printed by the multi-scan printing mode, and the yellow ink having a relatively small gloss value can be printed by the interlace mode. As a result, a gloss value difference between a gloss value of an image printed with the ink having a relatively small gloss value and that having a relatively great gloss value can be reduced, whereby glossiness unevenness attributable to a gloss value difference between the inks can be reduced.
In this example, a cyan ink (BCI-1421 C) and a yellow ink (BCI-1421 Y) were alternately printed to be in bands of cyan, yellow, cyan, yellow and so on, so as to form a solid image, the bands each having a width of about several millimeters. Here, in accordance with the method described in the first embodiment, the yellow ink having a relatively small gloss value was printed by the interlace mode, and the cyan ink having a relatively great gloss value was printed by the multi-scan printing mode. Then, glossiness of the solid image thus printed was visually examined, and glossiness unevenness was not perceived.
In this example, printing was performed in accordance with the method described in the second embodiment by use of a magenta ink (BCI-1421 M) and a black ink (BCI-1421 Bk). The magenta ink has a relatively great gloss value as compared to the black ink. Therefore, when the number of dots of the magenta ink was judged to be larger than that of the black ink, printing was performed by the multi-scan printing mode, whereas, when the number of dots of the black ink was judged to be larger than that of the magenta ink, printing was performed by the interlace mode. Then, glossiness of each image thus printed was visually examined, and glossiness unevenness was not perceived.
In this example, a cyan ink (BCI-1421 C) and a yellow ink (BCI-1421 Y) were alternately printed to be in bands of cyan, yellow, cyan, yellow and so on, so as to form a solid image, the bands each having a width of about several millimeters. Here, in accordance with the method described in the third embodiment, the yellow ink having a relatively small gloss value was printed by the interlace mode, and the cyan ink having a relatively great gloss value was printed by the multi-scan printing mode. Then, glossiness of the solid image thus printed was visually examined, and glossiness unevenness was not perceived.
With a cyan ink (BCI-1421 C) and a yellow ink (BCI-1421 Y), solid printing at a duty of 100% was performed on glossy paper LFM-GP421R by the multi-scan printing mode by use of the random mask patterns shown in
A print pattern was printed so as to form a solid image, in the same manner as in Example 1 described above, using a cyan ink (BCI-1421 C) and a yellow ink (BCI-1421 Y) alternately printed to be in bands of cyan, yellow, cyan, yellow and so on, the bands each having a width of about several millimeters. Then, glossiness of this pattern was visually examined. As a result, glossiness unevenness considered to be attributable to a gloss value difference between cyan and yellow is concerned, and a glossiness feel thereof brought discomfort.
The above examination results of Examples 1 to 3 and Comparable Example can be summarized in a table as follows.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2008-106078, filed Apr. 15, 2008, which is hereby incorporated by reference herein in its entirety.
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| 2008-106078 | Apr 2008 | JP | national |
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| Number | Date | Country | |
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