JP5506596B2 - Recording apparatus and recording method - Google Patents

Description

  The present invention relates to a recording apparatus and a recording method for printing by controlling the operation of a print head. In particular, the present invention relates to an ink jet recording apparatus and a recording method.

  In a recording apparatus typified by an ink jet printer, high image quality is a major point that affects its performance as well as high printing speed. In order to achieve high image quality, it is necessary to land droplets ejected from the print head accurately and uniformly on a predetermined position on the paper. In particular, in the case of a color printer, it is important to improve the landing accuracy in order to prevent a so-called color misregistration problem that the hue is changed by shifting the landing position of each color.

  However, when bi-directional printing is performed, the order in which dots are ejected and landed from each color print head in the forward pass and the return pass is changed depending on the print head arrangement order. There is a problem that so-called bidirectional color banding occurs.

  For example, Japanese Patent Laid-Open No. 2003-226004 discloses drawing based on a color swath to which a non-uniform print mask function is applied, which lowers the probability of using nozzles corresponding to the peripheral region of the edge compared to other nozzles. A technique for making bidirectional color banding inconspicuous by performing an operation is disclosed.

JP 2003-226004 A

  As described above, the cause of the bi-directional color banding is that the color stacking order differs between the forward pass and the return pass. Among them, the first scan (first scan) first drawn on the recording medium is the first scan. The contribution rate of the last scan (final scan) is high. The former is explained by the fact that the ink ejected on the paper for the first time spreads in a short time and forms large dots, and the ink ejected later forms a slightly smaller dot on the spread ink. it can. In other words, the influence of the first ejected color in the first scan and the print head color positioned in the front of the carriage traveling direction become strong. For the latter, the influence of this color is strong because the print head color located at the end of the final scan, that is, the rear of the carriage traveling direction is at the top of the print surface. An example of typical bidirectional color banding is shown in FIG. FIG. 3A shows a proper image. FIG. 3B is a diagram illustrating an example of bidirectional banding. Striped patterns appear in images with bidirectional banding, and the quality is poor compared to proper images.

  Bidirectional color banding may also occur between the left and right edges of the print area. Even within an area where the order of color overlap is the same, the time difference between the forward path and the backward path is large near the origin in the main scanning direction (direction in which the carriage scans). In other words, it takes time to draw at the beginning of the outbound trip and at the end of the return trip. On the other hand, at the end opposite to the origin, the time difference drawn from the forward path to the return path is small. This time difference causes a difference in the dry state of the dots on the paper in the immediately preceding scan, so that the nature of the ink ejected thereon naturally changes. In other words, color banding occurs due to the time difference.

  When printing a large poster or advertising material, there is a technique called tiling that arranges a plurality of small printed materials horizontally to make a large printed material. When there is color banding at the left and right ends, when tiling, the color difference between the joints of the printed matter becomes conspicuous, and the image quality may be significantly reduced.

  In Japanese Patent Laid-Open No. 2003-226004, a non-uniform print mask function is applied to color swaths for dark ink colors (for example, cyan, magenta, and black), and a uniform print mask function is applied to light ink colors (for example, yellow). This makes bidirectional color banding less noticeable.

  However, by applying a non-uniform print mask function, if attention is paid to a certain scan, the difference in nozzle use probability increases near the non-uniform end of the color swath. This is nothing but a difference between the drawing process for forming dots in a certain area and the drawing process for forming dots in another area. This is the same as the cause of the color banding due to the time difference between the left and right ends. This is more conspicuous when the print mask function uses a polygonal line or S-shaped gradation curve and has a steep slope such as 0% to 100% or 100% to 0%. Color banding corresponding to the gradation curve constituting the non-uniform print mask function will occur.

  Further, in the color swath, a difference between the non-uniform portion of the print mask function and the uniform portion may appear as color banding. This is because the non-uniform upper and lower areas of the print mask function complement each other and form a conventional dot for one scan. The number will increase. That is, a difference occurs in the time until the image is completed. This difference is exactly the cause of the color banding because it is different between the drawing process for forming dots in one area and the drawing process for forming dots in another area.

  For bidirectional color banding, instead of bidirectional printing, unidirectional printing is performed, so that the overlapping order of ink colors and the time difference can be unified over the entire drawing area. This reduces color banding, but is not practical because the printing speed is reduced by a factor of 1/2 compared to bidirectional printing. In addition, in unidirectional printing, image quality defects due to specific vibrations on the carriage travel path are accumulated every scan, which may lead to image quality defects such as vertical stripes and color unevenness.

  In addition, by mounting two or more print heads for each color so that the colors are arranged symmetrically on the carriage, it is possible to unify the color stacking order regardless of the forward or backward path. Since a double or more head is required, the cost increases such as an increase in the size and weight of the carriage and an increase in the size of an actuator for driving the carriage.

  In addition, when the positioning accuracy at the time of paper conveyance is poor or the paper conveyance amount itself is not appropriate, streaks that become darker or lighter may appear at the upper and lower ends of the color swath. These are border bandings called black stripes, white stripes, and so on. An example of this is shown in FIGS. 4 (a) and 4 (b). FIG. 4A shows an example of boundary banding. FIG. 4B is another example of boundary banding. These appear as streaks with a difference in color density between the upper and lower ends of the color swath and the other portions. In order to prevent these problems, it is necessary to adjust the sheet conveyance amount as appropriate. However, it is difficult to keep the conveyance amount constant for a long period of time.

  Boundary banding can also occur due to slow drying after ink landing on a specific paper. Inside the color swath, since ink is present with high probability around the ink, the ink becomes a wall and the movement of the ink is prevented. However, at the end of the color swath, that is, the edge, there is a space where nothing exists on one side, so that the ink easily moves. A so-called phenomenon called “mottling” occurs, and as a result, only this edge portion causes a change in hue from other regions. This phenomenon is sometimes called beading.

  Furthermore, the dot diameter after landing may be small for a specific sheet. In this case, density unevenness easily occurs due to slight deviation in landing. In general, the density strength often appears as horizontal stripes in the paper feed direction. This is a phenomenon called “hot weather”. An example of this is shown in FIG. FIG. 5 is a diagram showing an example of blurring. This is an example in which density unevenness occurs in a portion where landing deviation occurs and appears as white streaks.

  The present invention has been made in view of such circumstances, and a recording apparatus and a recording method capable of making boundary banding, beading, blurring, etc. inconspicuous, including color banding during bidirectional printing in the recording apparatus. The purpose is to provide.

The recording apparatus of the present invention ejects ink onto a recording medium while scanning the print head, and in the recording apparatus that forms an image on the recording medium, the nozzles provided in the print head are equally divided into a plurality of regions, The probability of using the nozzle for each divided area is obtained by applying a print mask function, the ink is ejected onto the recording medium, and the end of the color swath that is drawn in one scan during bidirectional printing perform drawing operation by a probability that is used for the nozzle to the nozzle corresponding to the peripheral region to apply and non-uniform the print mask function lower than the other nozzles, corresponding to a region other than the peripheral region perform drawing operation by a probability that is used for the nozzle to the nozzle to apply a uniform said print mask function, transport when the width of the peripheral region for transporting the recording medium Tsu and a positive integer multiple of the width substantially matches Ji, the conveying pitch is the width of the divided region, constitutes a probability distribution that is used in the nozzle the printmask function corresponding to the region is non-uniform The gradation curve is not steep, and the gradation curve has an edge of the print head in the peripheral area when the print mask function having a uniform use probability of the nozzle is defined as 100%. The probability that the nozzle on the part side is used is any value of 20 to 35%, the side facing the end part is any value of 65 to 80%, and the side facing the end part side The probability is 100%, and the probability is gradually increased from the end side of the print head in the peripheral area to the opposing side, and the one on the other side of the print head and the other side In the side area, the print mask function having a gradation curve symmetrical with respect to the center of the print head is applied, and the print is applied to the corresponding divided areas in the peripheral area on the one side and the other side. When the mask functions are added to each other, the print mask function in which the probability that the nozzles are used becomes uniform is applied .

The recording method of the present invention is a recording method of a recording apparatus that forms an image on the recording medium by ejecting ink to the recording medium while scanning the printing head, and the nozzles provided in the printing head are equally divided into a plurality of regions. The probability that the nozzle is used for each divided area is obtained by applying a print mask function, the ink is ejected onto the recording medium, and the color drawn in one scan during bidirectional printing by probability used for the nozzle corresponding to the peripheral region of the swath ends obtains the low and non-uniform the print mask function compared to the probability that the use of other nozzle to apply the print mask function drawing operation by applying a step of performing a drawing operation, the print mask function probability is uniform used for nozzles to the nozzle corresponding to a region other than the peripheral region And performing, have a, a step of conveying to a positive integer multiple of the width of the conveying pitch substantially matches the time of transporting the width and the recording medium of the peripheral region, the conveying pitch is the divided The gradation curve that constitutes the probability distribution of the nozzles corresponding to the region where the print mask function is non-uniform is not steep, and the gradation curve is used for the nozzles. When the print mask function having a uniform probability is applied and set to 100%, the probability that the nozzles on the end side of the print head in the peripheral area are used is any value of 20 to 35%. The side facing the edge has a value of 65 to 80%, the sum of the probabilities of the edge and the opposing side is 100%, and the probability is the value of the print head in the peripheral area. Previous The print mask function is configured to gradually increase from the end side to the opposing side, and the peripheral area on one side and the other side of the print head has the print mask function whose gradation curve is symmetric with respect to the center of the print head. Applying the print mask functions to be applied to the corresponding divided areas in the peripheral area on the one side and the other side, the print mask function having a uniform use probability of the nozzles applied, characterized in Rukoto.

  According to the present invention, it is possible to suppress printing defects such as boundary banding, beading, and blurring, as well as bidirectional banding resulting from the difference in color order between the forward path and the return path.

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. FIG. 2 is a schematic view of the carriage mechanism. FIG. 3A shows a proper image. FIG. 3B is a diagram illustrating an example of bidirectional color banding. FIG. 4A and FIG. 4B are diagrams illustrating an example of boundary banding. FIG. 5 is a diagram illustrating an example of smoothness. FIG. 6 is a diagram showing the principle of drawing in a printing mode called 4-pass. FIG. 7 is a diagram showing the principle of drawing in the print mode to which an embodiment of the present invention is applied. FIGS. 8A and 8B are diagrams illustrating an example of a color swath having a large effect of suppressing boundary banding and beading to which a non-uniform print mask function is applied. FIG. 9 is a diagram illustrating an example of a color swath having a large color banding suppression effect to which a print mask function with a fixed printing rate is applied. FIG. 10A, FIG. 10B, and FIG. 10C are diagrams illustrating an example of a color swath having a large color banding suppression effect to which a non-uniform print mask function is applied. FIG. 11 is a flowchart showing an example of the operation of the embodiment. FIG. 12 is a diagram showing the principle of drawing in the print mode to which another embodiment of the present invention is applied. FIG. 13 is a diagram showing the principle of drawing in the printing mode to which still another embodiment of the present invention is applied.

  Hereinafter, a recording apparatus and a recording method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In this figure, the recording apparatus 1 is an ink jet printer. The recording apparatus 1 includes a control unit 20 that controls the operation of the entire apparatus. The control unit 20 includes a CPU 21 of a control unit that performs overall control of processing operations in the control unit 20, a ROM 22 of a storage unit in which programs for performing various controls and printing operations of the recording apparatus 1, and the execution of the printing operation are performed. The RAM 23 of the storage means used as a working storage area by each control unit, the EEPROM 24 of the storage means configured by a non-volatile memory for storing setting values and data immediately before the power is turned off, and the state operated in the operation panel 44 are read. At the same time, the operation panel control unit 25 that displays information on the display unit included in the operation panel 44, the print control unit 26 that is a control unit that controls the print operation by the print head 41 with respect to the recording medium, and the operation of the carriage mechanism 42 are performed. From a carriage control unit 27 as a control means for controlling, a grid roller or the like for conveying a sheet as a recording medium A sheet conveyance control unit 28 which is a control means for controlling the operation of the formed sheet conveyance mechanism 43, an image memory 30 for storing an image to be printed, and an image memory writing / reading control unit for performing writing / reading control on the image memory 30 31, a host I / F unit 29 which is an interface for inputting / outputting image data and control commands to / from a host computer.

  The print control unit 26 and the carriage control unit 27 control the printing operation while coordinating the print positions based on the carriage position read by the linear encoder 45.

  FIG. 2 is a schematic view of an example constituting the carriage mechanism. The carriage mechanism 42 is provided with means for detecting the position of the print head 41. When ejecting droplets from the print head 41 in the recording apparatus 1, a linear encoder 45 incorporating a scale sensor attached to the carriage 420 and a linear scale 421 fixed along the traveling path of the carriage 420 are used. The current position during the reciprocation of the carriage 420 is detected, and information is input to the control unit 20. The control unit 20 recognizes the position of the print head 41 and generates ink ejection timing, thereby improving the positional accuracy of the droplets that have landed on the paper 422. In this example, four color print heads 41 are mounted in the order of K (black), C (cyan), M (magenta), and Y (yellow) from the left side when viewed from the paper 422 feeding direction, that is, from the head in the forward direction. Yes. In the forward direction, ink colors are formed on the paper 422 in this order, and the reverse is the reverse direction.

  Ink jet printers using these configurations require multiple scans and bi-directional carriage scans in order to suppress the deflection and omission of the nozzles of the print head 41 and periodic unevenness due to vibration of the drive system. Usually, a certain area is drawn. This is generally called a multipath method. In the multi-pass method in which an image of a certain region is completed by n scans, the number of dots ejected in one scan is 1 / n with respect to the total dots constituting a certain region. For example, in a printing mode called 4-pass that completes an image in 4 scans, a quarter of dots constituting a certain area are ejected for each scan, and the image is completed by conveying the paper 422 each time. I will let you. In this case, the conveyance pitch of the paper 422 is approximately ¼ of the color swath constituted by the total number of nozzles of the print head 41. FIG. 6 shows this state focusing on only a certain print color. The conveyance pitch of the paper 422 is ¼ of the used nozzle range of the print head 41, and ¼ constituent dots of the image are ejected by the color swath created in one scan. It can be seen that the image is completed by taking 4 scans for each area.

  An example of a print mode to which an embodiment of the present invention is applied will be described with reference to FIG. At the time of 4-pass printing, ¼ of the used nozzle range of the head was used as the paper conveyance amount, but here, ５ of the used nozzle range is used for it. In addition, the non-uniform region of the print mask function is 1/5 each above and below the used nozzle range of the head. By matching the non-uniform area of the paper conveyance amount and the print mask function, the first scan and the final scan (in this case, the fifth scan) are complemented in the entire drawing area. As a result, there is no drawing area to which the uniform print mask function is applied in all scans, and the difference between the non-uniform portion of the print mask function and the uniform portion, which has been a problem in the past, appears as color banding. There is no problem. In addition, since the printing rates of the first scan and the final scan, which are dominant with respect to color banding, are necessarily reduced, there is an effect of suppressing bidirectional color banding. Further, since the printing rate at the end of the color swath is also reduced, there is an effect on boundary banding and beading. When printing is performed in the print mode of FIG. 7, the nozzle use efficiency of the print head is reduced to 4/5 times compared to the normal four passes. This means that the printing speed is reduced to 4/5 times.

  The operation will be described using a flowchart. FIG. 11 is a flowchart showing an example of the operation of the embodiment. The operation of the process for applying the print mask function to the print head 50 will be described. The drawing is controlled by the CPU 21 based on a program stored in the ROM 22. Also, the print mask function based on the gradation curve is stored in advance in the ROM 22 and is read out from there when it is applied. The print head 50 is divided into a first area 51, a second area 52, a third area 53, a fourth area 54, and a fifth area 55 so that the widths of the areas are equally divided. A print mask function stored in the ROM 22 is applied to each area. When the non-uniform print mask function is applied to the first area 51 and the print mask function applied to the first area 51 is complemented to the fifth area 55, the non-uniform print mask function becomes 100%. Applied. The image to be drawn is an image in which the image printed in the first area 51 and the image printed in the fifth area are complemented.

  First, when the process is started, the process proceeds to step S2 when the non-uniform print mask function is used, and to step S3 when not used (step S1). In step S1, it is determined what print mask function is applied to the print head 50, and the process branches. This is a kind of selection means. Here, the RAM 23 stores a flag for determining whether or not to use the RAM 23 in advance. The flag is varied based on a user setting or a print mode setting. It is also possible to input a print mode from the operation panel 44 as input means and perform branch processing based on the input. You may branch according to the conditions decided beforehand by the program.

  Next, step S2 will be described. Here, a description will be given using an example in which the nozzle is divided into five. The nozzle row is divided into five regions as an example, and the present invention is not limited to this. When a non-uniform print mask function is used, the nozzle row is divided into five areas, and the print mask function to be used is applied to each area. A non-uniform print mask function is applied to the first area 51 and the fifth area 55, and a uniform print mask function is applied to the other areas. Whether the nozzle is used or not is determined based on the print mask function. Data for determining use and non-use is stored corresponding to each nozzle. For example, “1” data is stored in the RAM 23 corresponding to each nozzle when used, and “0” data is not used. The print mask function is stored as a table or calculation formula in which data is stored. A mask is created for each nozzle by calculating based on this print mask function. As another example, a mask to which a print mask function is applied in advance may be stored and selected and used.

  Next, step S3 will be described. If a uniform print mask function is used, the uniform print mask function is applied to each region of the segmented nozzle. Whether the nozzle is used or not is determined based on the uniform print mask function. Data for determining use or non-use is stored for each nozzle. For example, “1” data is stored in the RAM 23 corresponding to each nozzle when used, and “0” data is not used. The print mask function is stored as a table or calculation formula in which data is stored. A mask is created for each nozzle by calculating based on this print mask function. As another example, a mask to which a print mask function is applied in advance may be stored and selected and used.

  After a mask is set for the print head 50, printing is performed based on the mask and image data stored in the image memory 30.

  Similarly, a print mode in which the paper conveyance amount is set to 1/6 of the use nozzle range of the print head and the non-uniform area of the print mask function is set to 2/6 above and below the use nozzle range of the head can be considered. In this case, the effect of suppressing various banding is greater. However, the printing speed is reduced to 2/3 times. Further, as shown in FIG. 12, the paper conveyance amount is 1/8 of the used nozzle range of the print head, and the non-uniform area of the print mask function is 4/8 each above and below the used nozzle range of the head, that is, all areas. A printing mode that complements the top and bottom is also conceivable. In this case, the upper and lower four blocks each complement each other, which means that all the dots constituting the drawing area are in a complementary relationship, so the effect of suppressing various bandings is the greatest. However, the printing speed is reduced to 1/2 times. In the end, it can be said that the effect of improving the image quality increases as the non-uniform area is expanded while being matched with the carry amount, and the printing speed is lowered.

  Next, a non-uniform print mask function will be described. An example of the gradation curve constituting the probability distribution of the nozzles applied to the print mask function will be described. Steepening the gradient curve gradient in a non-uniform region of the drawing results in color banding within this region, so it is desirable that the gradient be as gentle as possible. On the other hand, since the high printing rate at the end of the color swath causes boundary banding and beading, an appropriate gradation curve that balances these must be set. FIG. 8A is a diagram showing linear gradation curves 60 and 61 that have been conventionally used. FIG. 8B is a diagram showing gradation curves 62 and 63 having an S shape, which has been conventionally used. In these conventional gradation curves, the printing rates of the start point and the end point are connected from 0% to 100%. These are curves in which the printing rate changes from 0% to 100%, and it can be said that the inclination is steep. As described above, these are effective for boundary banding and beading, but color banding in a non-uniform region tends to occur. FIG. 9 is a diagram showing an example in which the distribution of the printing rate is fixed to 50%. The gradation curves 64 and 65 are the most gradual examples, and the print rate of the upper and lower complementary areas is fixed at 50%. Although the occurrence of color banding can be suppressed to the maximum, the edge printing rate is reduced to only 50%, so boundary banding is likely to occur. FIG. 10A is a diagram illustrating a first example of the gentle gradation curves 66 and 67. FIG. 10B is a diagram showing a second example of gentle gradation curves 68 and 69. FIG. 10C is a diagram showing a third example showing a gentle gradation curve. Even if a gradation curve with a straight line or an S-shape is used, since the inclination becomes gentle by connecting the printing rate of the start point and the end point from 30% to 70%, the occurrence of color banding can be suppressed. The edge printing rate is also 30%, and the occurrence of boundary banding is suppressed. It is preferable that the low side of the printing rate can be varied in the range of 20% to 35% and the high side correspondingly can be varied in the range of 65% to 80%. For example, a gradation curve is used in which the print rate is gradually changed with the start point being the low print rate side of 30% and the corresponding end point high side being 70%. Boundary banding and color banding can be effectively suppressed. When the low printing rate side is 20% or less and the corresponding high side is 80% or more, the gradation curve is steep and banding is likely to occur. In addition, the shape combining the circular arcs can make the gradient curve slope of a wide range of non-uniform areas gentle, and can also suppress the occurrence of color banding. In addition, since the printing rate of the start point and the end point is connected from 0% to 100%, the occurrence of boundary banding can be suppressed. Further, the gradation curves 70 and 71 that are substantially gentle are realized by narrowing the width of the region where the printing rate is a value in the vicinity of 0% or 100%. In this case, it is desirable to suppress the width of the portion where the printing rate is 20% or less or 80% or less to 5% or less of the paper feed width. However, the steeper the effect.

  However, the selection of the shape of these gradation curves and the setting of the printing rate for the start and end points differ depending on the width of the non-uniform area, and the effect varies depending on the image to be printed. It is preferable to change depending on the application.

  As described above, by increasing the width of the non-uniform region of the print mask function, the printing speed is slowed down, but high image quality can be obtained accordingly. That is, the basic four-pass print mode (referred to as standard print mode) is used as a base, the width values of the non-uniform areas of the print mask function are tabulated, and any value in the table can be entered from the operation panel 44. By allowing the user to make a selection, a combination of printing speed and printing image quality according to the user's application can be realized. A print mode can be selected based on an input from the operation panel 44. For example, this table is called “image quality improvement mode”, and weights from 1 to 3 are assigned. If you want to output printed matter that does not place much importance on image quality, it is more productive to select `` Image quality improvement mode 1 '' that reduces the width of the non-uniform area of the print mask function and increases the printing speed as much as possible, If you want to output printed matter that emphasizes image quality, you can select "Image quality improvement mode 3" with a larger width of the non-uniform area of the print mask function and obtain high image quality even if productivity is reduced. When it is desired to balance these, “image quality improvement mode 2” may be selected.

  Further, the application of the present invention has been described so far for the standard print mode. Of course, this application is also possible for other print modes. In the draft printing mode where the number of scans has been reduced with emphasis on productivity, deterioration of image quality has been regarded as a problem in the past, but by applying the “image quality improvement mode” to this as well, the printing speed is faster than the standard printing mode. Therefore, the image quality can be improved compared to the conventional draft printing mode. In the high image quality printing mode in which the number of scans is increased with emphasis on image quality, a higher image quality can be expected by applying the “image quality improvement mode”. In other words, by adding an additional “image quality improvement mode” function to the existing print mode, the user can select the print mode from the operation panel 44 in a matrix manner. Fine-tuned operation is possible.

  Further, in the print mode in which the print head is divided into the upper block and the lower block as shown in FIG. 12 and is completely complemented by the upper and lower blocks, the effect of suppressing various printing defects is very large, which is preferable. However, in this embodiment, the print mask function itself applied to the color swath has a complementary relationship up and down. That is, for the color swaths in which the upper 4 blocks are generated by a certain print mask function, the lower 4 blocks only have a complementary relationship therewith. As a result, strictly speaking, the color swath drawn in one scan may cause mask mismatch due to different print mask functions at the joint between the upper and lower blocks. As a result, banding may occur in the central portion of the color swath, although only slightly. This is remarkable when a color swath is generated using an FM screen mask or the like.

  A printing mode shown in FIG. 13 is conceivable as a more preferable form that solves this problem. First, consider a print mask function that covers the entire used nozzle width of the color swath. Here, this is referred to as “mask A”. Since the color swath to which the mask A is applied has no complementary relationship between the upper and lower blocks, there is no joint. That is, slight banding does not occur in the drawing result to which the mask A is applied. Next, a completely complementary print mask function that complements the mask A is prepared. Then, the upper and lower half areas of the print mask function are respectively replaced, and this is called “mask A ′”. As a result, the upper block of the mask A and the lower block of the mask A ′, and the lower block of the mask A and the upper block of the mask A ′ are in a complementary relationship. The mask A ′ has a joint because the upper and lower blocks are interchanged. Here, as shown in FIG. 13, 1 to 4 scans draw a color swath to which the mask A is applied, and 5 to 8 scans draw a color swath to which the mask A ′ is applied. This is repeated after the ninth scan. As a result, the probability that the mask A ′, which may cause mask mismatch at the joint, is reduced to ½ of the whole, so that the occurrence of slight banding can be suppressed.

  As described above, the non-uniform print mask function is applied to reduce the probability that the nozzle corresponding to the peripheral area of the color swath edge is used as compared with the other nozzles. In addition to bidirectional banding, which is caused by the color stacking order differing between the forward path and the return path, printing defects such as border banding, beading, and blurring are suppressed by making the width of the correct area approximately match the paper transport amount. be able to. As a result, it can be expected to stably achieve high print image quality.

  The present invention can be used in a recording apparatus such as an ink jet printer.

DESCRIPTION OF SYMBOLS 1 ... Recording device, 20 ... Control part, 21 ... CPU, 22 ... ROM, 23 ... RAM, 24 ... EEPROM, 25 ... Operation panel control part, 26 ... Print control unit, 27 ... carriage control unit, 28 ... paper conveyance control unit, 29 ... host I / F unit, 30 ... image memory, 31 ... image memory write / read control unit , 41 ... print head, 42 ... carriage mechanism, 43 ... paper transport mechanism, 44 ... operation panel, 45 ... linear encoder

Claims (4)

In a recording apparatus that ejects ink onto a recording medium while scanning the print head, and forms an image on the recording medium,
The nozzles provided in the print head are equally divided into a plurality of areas, the probability of using the nozzles for each of the divided areas is obtained by applying a print mask function, and the ink is ejected onto the recording medium. ,
Probability of use of the nozzle to the nozzle corresponding to the peripheral region of the color swath edge is drawing in one scan to apply and non-uniform the print mask function lower than the other nozzles during bidirectional printing Drawing operation,
A drawing operation is performed by applying the print mask function with a uniform probability that the nozzles are used for nozzles corresponding to areas other than the peripheral area,
The width of the peripheral area substantially coincides with the width of a positive integer multiple of the transport pitch when transporting the recording medium ,
The transport pitch is the width of the divided area,
The shape of the gradation curve constituting the probability distribution used for the nozzle corresponding to the region where the print mask function is non-uniform is not steep,
The gradation curve has a probability that the nozzles on the end side of the print head in the peripheral area are used when the print mask function with a uniform use probability of the nozzles is defined as 100%. Any value of 20-35%, the side facing the end is any value of 65-80%, the sum of the probabilities of the end and the opposing side is 100%, The probability is configured to gradually increase from the end side of the print head in the peripheral area to the opposing side;
The print mask function having a gradation curve symmetric with respect to the center of the print head is applied to the peripheral area on one side and the other side of the print head, and the correspondence in the peripheral area on the one side and the other side is applied. The recording apparatus is characterized in that the print mask function is applied so that the probability that the nozzles are used becomes uniform when the print mask functions to be applied to the divided areas are added to each other .   A set of a gradation curve that forms a probability distribution of nozzles corresponding to the width of the peripheral area and the area corresponding to the area where the print mask function is non-uniform has a plurality of print modes with different image quality. The width of the peripheral area and the gradation curve corresponding to the selected printing mode are acquired in association with the acquired printing mode, and the gradation curve is applied to the nozzle corresponding to the acquired width of the peripheral area. The recording apparatus according to claim 1, wherein the print mask function based on the image is applied.   A plurality of gradation curves each constituting a probability distribution of the use of nozzles corresponding to the width of the peripheral area and the area where the print mask function is non-uniform, and the width of the peripheral area and the gradation curve are stored Each of them is stored in a table prepared in the means, the width of the peripheral area and the gradation curve are acquired from the table based on the input of the input means, and the nozzle corresponding to the acquired width of the peripheral area is obtained. The recording apparatus according to claim 1, wherein the print mask function based on the gradation curve is applied.   In a recording method of a recording apparatus for ejecting ink to a recording medium while scanning a print head and forming an image on the recording medium,
  The nozzles provided in the print head are equally divided into a plurality of areas, the probability of using the nozzles for each of the divided areas is obtained by applying a print mask function, and the ink is ejected onto the recording medium. ,
  The print mask function in which the probability of being used for the nozzle corresponding to the peripheral region of the end portion of the color swath drawn in one scan at the time of bidirectional printing is lower and non-uniform than the probability of using the other nozzles. Obtaining and applying a print mask function to perform a drawing operation;
  A step of performing a drawing operation by applying the print mask function having a uniform probability of being used for nozzles corresponding to regions other than the peripheral region;
  A step of conveying the width of the peripheral area and a width that is a positive integer multiple of a conveyance pitch when conveying the recording medium,
Have
  The transport pitch is the width of the divided area,
  The shape of the gradation curve constituting the probability distribution of use of nozzles corresponding to the region where the print mask function is non-uniform is not steep, and the gradation curve is the print mask with the uniform use probability of the nozzles. When the function is set to 100%, the probability that the nozzles on the end side of the print head in the peripheral area are used is any value of 20 to 35%, and faces the end. The side is any value of 65 to 80%, the sum of the probabilities of the end side and the opposing side is 100%, and the probability is the counter value from the end side of the print head in the peripheral area. Configured to gradually increase toward the
  The print mask function having a gradation curve symmetric with respect to the center of the print head is applied to the peripheral area on one side and the other side of the print head, and the correspondence in the peripheral area on the one side and the other side is applied. The printing method is characterized in that the print mask function having a uniform use probability of the nozzles is applied when the print mask functions applied to the divided areas are added to each other.