JP2013215979A - Printing apparatus, printing method, and printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To flatten a surface of an auxiliary image while preventing bleeding or color mixture of an image.SOLUTION: A printing apparatus includes: a first nozzle for discharging ink for printing a main image; a second nozzle for discharging ink for printing an auxiliary image overlapped with the main image; and a control part. When the auxiliary image is printed on a material to be printed prior to the main image, the control part controls so that the auxiliary image is printed on the material to be printed by forming a dot in a size larger than the predetermined size by discharging the ink from the second nozzle to the area of the material to be printed in which a dot in the predetermined size is formed after forming the dot in the predetermined size by discharging the ink from the second nozzle to the material to be printed, and controls so that the main image is printed on the auxiliary image by discharging the ink from the first nozzle to the auxiliary image.

Description

  The present invention relates to a printing apparatus, a printing method, and a printed matter.

  As an example of a printing apparatus, there is an ink jet printer (hereinafter referred to as a printer) that prints an image on a printing material by ejecting ink from nozzles provided in a head (see, for example, Patent Document 1).

  Some printers suppress bleeding of black ink by forming dots of slow-drying black ink on top of fast-drying white ink dots (see, for example, Patent Document 2). In addition, there is a printer that prints a white layer after printing a first image on a transparent film and prints the second image on the white layer so that two types of images can be seen from both sides. (For example, see Patent Document 3). When two types of images are overlapped and printed through the white layer in this way, if the surface of the first image is uneven, the image quality of the second image is deteriorated. Therefore, a method of flattening the surface of the white layer by adjusting the thickness of the white layer according to the unevenness of the first image has been proposed.

JP 2011-56868 A JP 2001-246767 A JP 2011-164379 A

  Further, for example, there is a printer that prints a main image made of black ink or color ink on an auxiliary image made of white ink in order to improve the color development of the image. In such a printer, for example, if an auxiliary image composed of only dots of the maximum size is printed, the auxiliary image is difficult to dry, and bleeding and color mixing occur with the main image printed thereon. It will occur. On the other hand, by printing the auxiliary image with the small dots over the medium dots, the auxiliary image is easy to dry, but the surface of the auxiliary image is uneven, so the main image printed on it The image quality will deteriorate.

  Therefore, an object of the present invention is to flatten the surface of the auxiliary image as much as possible while suppressing blurring and color mixing of the image.

The main invention for solving the above problems is a first nozzle for ejecting ink for printing a main image, and a second nozzle for ejecting ink for printing an auxiliary image overlapping the main image, A printing apparatus comprising: a second nozzle capable of forming dots of a plurality of sizes; and a control unit that controls ejection of ink from the first nozzle and the second nozzle. When the auxiliary image is printed first, the control unit discharges ink from the second nozzle to the printing material to form dots of a predetermined size, and then the predetermined size of the auxiliary image is printed. An auxiliary image is printed on the printing material by ejecting ink from the second nozzle to the printing material region on which dots are formed to form dots having a size larger than the predetermined size. And controlling the main image to be printed on the auxiliary image by ejecting ink from the first nozzle to the auxiliary image. It is.
Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

1 is a block diagram illustrating an overall configuration of a printing system. FIG. 2A is a schematic perspective view of the printer, and FIG. 2B is a diagram illustrating the arrangement of nozzles provided on the lower surface of the head. FIG. 3A is a diagram illustrating an image printed in the front printing mode, and FIG. 3B is a diagram illustrating an image printed in the reverse printing mode. 4A and 4B are diagrams illustrating a printing method in the front printing mode in the comparative example. 5A to 5C are diagrams illustrating a printing method in the front printing mode according to the first embodiment. 6A is a diagram illustrating a printing method in the front printing mode according to the first embodiment, and FIG. 6B is a diagram illustrating a printing method in the back printing mode according to the first embodiment. FIG. 7 is a diagram for explaining a printing method in the front printing mode according to the second embodiment. 8A and 8B are diagrams illustrating a printing method in the front printing mode according to the third embodiment. FIG. 9 is a diagram illustrating a printing method in the front printing mode according to the fourth embodiment. 10A and 10B are diagrams illustrating a printing method according to the fifth embodiment. FIG. 11 is a diagram illustrating a printer according to the first modification.

=== Summary of disclosure ===
At least the following will become apparent from the description of the present specification and the accompanying drawings.

That is, a first nozzle that ejects ink for printing a main image and a second nozzle that ejects ink for printing an auxiliary image that overlaps the main image, which are capable of forming dots of multiple sizes. A printing apparatus including two nozzles and a control unit that controls ejection of ink from the first nozzle and the second nozzle, and prints the auxiliary image on the printing material prior to the main image. In this case, the control unit discharges ink from the second nozzle to the printing material to form dots of a predetermined size, and then the printing material on which the dots of the predetermined size are formed. In this area, ink is ejected from the second nozzle to form dots having a size larger than the predetermined size, so that an auxiliary image is printed on the printing material, and the auxiliary By ejecting ink from the first nozzle relative to the image, controlling such that the main image is printed on the auxiliary image, a printing apparatus according to claim.
According to such a printing apparatus, the surface of the auxiliary image serving as a lower layer can be flattened as much as possible while suppressing bleeding and color mixing of the image, and image quality deterioration of the image can be suppressed.

In this printing apparatus, the control unit controls the ejection of ink from the second nozzle so that the large size dot is formed on the predetermined size dot.
According to such a printing apparatus, the surface of the auxiliary image can be flattened as much as possible.

In this printing apparatus, the control unit controls the ejection of ink from the second nozzle so that the large size dot is formed between the predetermined size dots.
According to such a printing apparatus, the surface of the auxiliary image can be flattened as much as possible.

In this printing apparatus, the large size is a maximum size among the plurality of sizes, and the control unit adds the maximum size to some of the pixels defined in the printing material. Controlling the ejection of ink from the second nozzle so that dots of a size are formed.
According to such a printing apparatus, it is possible to suppress blurring and color mixing of the image.

In this printing apparatus, the predetermined size is a first size and a second size that is larger than the first size, and the control unit has the first size formed on the printing material. Controlling the ejection of ink from the second nozzle so that the large size dot is formed on the first size dot among the dots and the second size dot.
According to such a printing apparatus, the surface of the auxiliary image can be flattened as much as possible.

In this printing apparatus, the control unit may print the printing material more than the number of dots constituting the auxiliary image to be printed when the auxiliary image is printed on the printing material prior to the main image. And controlling the ejection of ink from the second nozzle so that the number of dots constituting the auxiliary image to be printed is smaller when the main image is printed before the auxiliary image.
According to such a printing apparatus, it is possible to shorten the printing time when the main image is first printed on the printing material.

Further, the printing method is to print the auxiliary image over the auxiliary image, and after ejecting the ink for printing the auxiliary image on the printing material to form dots of a predetermined size, The printing target is formed by ejecting ink for printing the auxiliary image to the area of the printing material on which dots of a predetermined size are formed to form dots having a size larger than the predetermined size. Printing the main image on the auxiliary image by ejecting ink for printing the main image on the auxiliary image printed on the printing material, and a step of printing the auxiliary image on the material A printing method comprising the steps of:
According to such a printing method, the surface of the auxiliary image serving as a lower layer can be made as flat as possible while suppressing bleeding and color mixing of the image, and image quality deterioration of the image can be suppressed.

In addition, after ejecting ink for printing an auxiliary image on the printing material to form dots of a predetermined size, the region of the printing material on which the dots of the predetermined size are formed By ejecting ink for printing the auxiliary image to form dots having a size larger than the predetermined size, the auxiliary image printed on the printing material is printed over the auxiliary image. And a main image.
In such a printed matter, image blurring and color mixing are suppressed, and the main image is printed on the auxiliary image whose surface is flattened, so image quality deterioration of the image is suppressed.

=== Printing system ===
The embodiment will be described with reference to an example of a printing system in which a “printing apparatus” is an inkjet printer (hereinafter referred to as a printer) and the printer and a computer are connected.
FIG. 1 is a block diagram showing the overall configuration of the printing system. FIG. 2A is a schematic perspective view of the printer 1, and FIG. 2B is a diagram illustrating the arrangement of nozzles provided on the lower surface of the head 41. FIG. 2B is a diagram virtually showing the arrangement of nozzles when the head 41 is viewed from above.

  The printer 1 includes a controller 10, a transport unit 20, a carriage unit 30, a head unit 40, and a detector group 50. The printer 1 is communicably connected to the computer 60, and a printer driver installed in the computer 60 uses the hardware resources of the computer 60 to create print data for causing the printer 1 to print an image. Or output print data to the printer 1. Note that the printer driver may be stored in a storage medium such as a CD-ROM (Compact Disk-Read Only Memory) or downloaded via the Internet.

A controller 10 in the printer 1 is for performing overall control in the printer 1. The interface unit 11 transmits and receives data to and from the computer 60 that is an external device. A CPU 12 (Central Processing Unit) is an arithmetic processing device for performing overall control of the printer 1, and controls each unit via a unit control circuit 14. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like.
The detector group 50 is for monitoring the situation in the printer 1 and outputting the detection result to the controller 10.

The transport unit 20 feeds the printing material S such as paper, cloth, and film to a printable position, and transports the printing material S in a predetermined direction (hereinafter referred to as a transport direction).
The carriage unit 30 is for moving the head 41 mounted on the carriage 31 along the guide rail 32 in a moving direction that is a direction that intersects the conveying direction of the printing material S (in addition, intersects). The direction is generally an orthogonal direction).

  The head unit 40 is for ejecting ink onto the printing material S and has a head 41. As shown in FIG. 2B, a number of nozzles that eject ink are provided on the lower surface of the head 41, and a nozzle row is formed for each color of ejected ink. In order from the left in the moving direction, a black nozzle row Nk that discharges black ink K, a cyan nozzle row Nc that discharges cyan ink C, a magenta nozzle row Nm that discharges magenta ink M, and yellow that discharges yellow ink Y. A nozzle row Ny and a white nozzle row Nw that discharges white ink W are formed. The controller 10 (corresponding to a control unit) controls ink ejection from the nozzles provided in the head 41.

  In each nozzle row, 180 nozzles (# 1 to # 180) are arranged at a predetermined nozzle pitch D in the transport direction. For the sake of explanation, small numbers are given in order from the nozzles on the downstream side in the transport direction. Further, the ink ejection method from the nozzle may be a piezo method in which ink is ejected from the nozzle by expanding and contracting the ink chamber by applying a voltage to the driving element (piezo element), or using a heating element in the nozzle. A thermal method in which bubbles are generated and ink is ejected from the nozzles by the bubbles may be used.

  In addition, each nozzle provided in the head 41 is assumed to be a nozzle capable of forming dots of a plurality of sizes. In other words, each nozzle provided in the head 41 can eject various amounts of ink corresponding to dots of a plurality of sizes. In the present embodiment, the nozzle can form dots of three types (large dots, medium dots, and small dots).

  In the printer 1 having such a configuration, the controller 10 includes an ejection operation for ejecting ink from the nozzles while moving the head 41 in the movement direction by the carriage 31 to form dots on the pixels on the printing material S, and a transport unit. The conveyance operation of conveying the printing material S to the downstream side in the conveyance direction by 20 is alternately repeated. As a result, since dots are formed by the subsequent ejection operation at positions different from the positions of the dots formed by the previous ejection operation, a two-dimensional image is printed on the printing material S.

  Note that the pixel on the printing material S is a unit region defined on the printing material S and is a region where one dot is formed. Further, in the following description, a dot row along the moving direction of the head 41 is referred to as a “raster line”, and the image is configured by arranging a plurality of raster lines in the transport direction. One discharge operation is also referred to as “pass”.

=== Print mode ===
FIG. 3A is a diagram illustrating an image printed in the front printing mode, and FIG. 3B is a diagram illustrating an image printed in the back printing mode. The printer 1 according to the present embodiment uses white ink (W) for a “main image (color image or monochrome image)” that is printed by appropriately using four colors of ink (YMCK) of yellow, magenta, cyan, and black. Then print the “auxiliary image (background image)” to be printed. Therefore, in this embodiment, the nozzles that discharge four color inks of yellow, magenta, cyan, and black correspond to the first nozzle, and the nozzle that discharges white ink corresponds to the second nozzle, and the main image and auxiliary An image on which images are superimposed corresponds to a printed matter.

  By printing the main image on the white auxiliary image, it is possible to print the main image with good color development. Further, when the printing material S is transparent, it is possible to prevent the opposite side of the main image from being seen through. That is, the shielding property of the main image can be ensured.

  Further, the printer 1 of the present embodiment has a front printing mode and a back printing mode. As shown in FIG. 3A, the front printing mode is a mode in which the auxiliary image Pw is printed on the printing material S before the main image Pco, and the main image Pco is superimposed on the auxiliary image Pw. is there. Therefore, an image printed in the front printing mode is visually recognized from the printing surface side as indicated by an arrow in the drawing.

  On the other hand, in the reverse printing mode, as shown in FIG. 3B, the main image Pco is printed on the printing material S before the auxiliary image Pw, and the auxiliary image Pw is printed over the main image Pco. Mode. Accordingly, the image printed in the reverse printing mode is visually recognized from the side opposite to the printing surface side through the printing material S, as indicated by an arrow in the drawing. Therefore, when using a transparent printing material S such as a plastic film, the back printing mode is performed.

=== Printing Method: Comparative Example ===
4A and 4B are diagrams illustrating a printing method in the front printing mode in the comparative example. In addition, one square drawn in the printing material S in the drawing is a pixel p, and a pixel number (1 to 6) is given in the pixel p.

  In the printing method of the comparative example shown in FIG. 4A, the auxiliary image Pw is composed of only the largest large dot LD among the three types of dots (large dot, medium dot, small dot) that can be formed by the nozzles belonging to the white nozzle row W. To print. In addition, large dots LD are independently formed on all the pixels p (1 to 6) of the printing material S, and a one-layer auxiliary image Pw composed of the large dots LD is formed. Specifically, while the controller 10 in the printer 1 moves the head 41 in the moving direction, white ink in an amount corresponding to the large dot LD is supplied from the head 41 to each pixel p on the printing material S. The large dots LD are formed in each pixel p by discharging. That is, in the printing method of FIG. 4A, the raster line of the auxiliary image Pw in which single large dots LD are arranged in the moving direction is completed in one pass.

  Generally, the large dot LD is used for printing a solid image without a gap. Therefore, the large dots LD are designed to be larger than the pixels p so that the large dots LD formed on the adjacent pixels p overlap each other. Therefore, in the auxiliary image Pw printed by the printing method of FIG. 4A, the large dots LD in the vicinity are connected, and the surface of the auxiliary image Pw is flattened. Therefore, the main image Pco can be printed on the flat surface of the auxiliary image Pw, and deterioration of the image quality of the main image Pco can be suppressed.

  However, as the size of the dots formed on the printing material S increases, that is, as the amount of ink that lands on the printing material S with a single ink discharge from the nozzle increases, the solvent of the ink becomes less likely to evaporate. Dots are difficult to dry. Therefore, like the auxiliary image Pw printed by the printing method of FIG. 4A, the auxiliary image Pw composed only of the large dots LD is difficult to dry. Further, when the raster line constituting the auxiliary image Pw is completed in one pass as in the printing method of FIG. 4A, the amount of ink ejected on the printing material S in one pass increases. The image Pw becomes more difficult to dry. As a result, the main image Pco is printed on the auxiliary image Pw that is insufficiently dried, and bleeding or color mixing occurs between the auxiliary image Pw and the main image Pco.

  On the other hand, in the printing method of the comparative example shown in FIG. 4B, the auxiliary image Pw is printed by superimposing the small dots SD on the medium dots MD. That is, the auxiliary image Pw is formed by two layers in which a layer composed of small dots SD is superimposed on a layer composed of medium dots MD. Specifically, the controller 10 in the printer 1 forms the medium dot MD at each pixel p on the printing material S while moving the head 41 in the movement direction in the previous pass, and then the head in the subsequent pass. While moving 41 in the moving direction, small dots SD are formed on the medium dots MD formed in each pixel p. That is, in the printing method of FIG. 4B, the raster line of the auxiliary image Pw in which the dots in which the small dots SD are superimposed on the medium dots MD are arranged in the movement direction is completed in two passes.

  Since the smaller the size of the dots, the easier it is to dry, the auxiliary image Pw of FIG. 4B composed of medium dots MD and small dots SD is easier to dry than the auxiliary image Pw composed of only large dots LD (FIG. 4A). Become. Furthermore, in order to form a small dot SD overlaid on the medium dot MD, when the raster line constituting the auxiliary image Pw is completed in two passes, it is discharged onto the printing material S in one pass. Since the amount of ink is reduced, the auxiliary image Pw becomes easier to dry. Therefore, the main image Pco can be printed over the auxiliary image Pw in a dry state, and bleeding and color mixing between the auxiliary image Pw and the main image Pco can be suppressed.

  However, if a small dot SD is formed on the medium dot MD, that is, if a small size dot is formed after forming a large size dot, the small dot formed on the medium dot MD is formed. The SDs are not connected, and the small dots SD are fixed independently. For this reason, the small dots SD fixed in a state of being separated from each other protrude from the upper surface of the medium dot MD, and the surface of the auxiliary image Pw becomes uneven. If it does so, the main image Pco will be printed on the uneven surface of the auxiliary image Pw, and the image quality of the main image Pco will deteriorate.

  Accordingly, the printer 1 of the present embodiment aims to flatten the surface (printing surface) of the auxiliary image serving as a lower layer while suppressing blurring and color mixing of the image when the front printing mode is performed.

=== Printing Method: Example 1 ===
5A to 5C and FIG. 6A are diagrams for explaining a printing method in the front printing mode in the first embodiment, and FIG. 6B is a diagram for explaining a printing method in the back printing mode in the first embodiment. In addition, the left figure of FIG. 5 is a figure which shows the nozzle used for printing. For simplicity of explanation, the number of nozzles belonging to one nozzle row is reduced to 12 (# 1 to # 12). In addition, the nozzle rows (Ny, Nm, Nc, Nk) that respectively eject yellow, magenta, cyan, and black inks are collectively referred to as “color nozzle row Nco”. Further, the diagram on the right side of FIG. 5 is a diagram showing how dots are formed in the pixels p on the printing material S. For the sake of explanation, small column numbers L1, L2, L3,... Are added in order from the pixel p located on the downstream side in the transport direction.

<Front print mode>
In the first embodiment, when the front printing mode is set (FIGS. 5 and 6A), the controller 10 (corresponding to the control unit) in the printer 1 first applies the white nozzle row Nw to the printing material S. After ejecting white ink from the nozzles to form small dots SD (corresponding to dots of a predetermined size), the white nozzle row Nw is again applied to the area of the printing material S on which the small dots SD are formed. Control is performed so that the auxiliary image Pw is printed first on the printing material S by ejecting white ink to form medium dots MD larger in size (larger diameter) than the small dots SD. Thereafter, the controller 10 appropriately discharges the four-color ink (KCMY) from the color nozzle array Nco according to the print data on the auxiliary image Pw printed on the printing material S, and thereby onto the auxiliary image Pw. Control is performed so that the main image Pco is printed. In the first embodiment, the controller 10 uses the white ink from the white nozzle row Nw so that the medium dots MD (large size dots) are formed on the small dots SD (dots of a predetermined size). To control the discharge.

  Note that the auxiliary image Pw (FIG. 4A) composed of large dots LD and the auxiliary image Pw composed of small dots SD and medium dots MD as in the first embodiment per unit area of the printing material S. It is assumed that the amount of white ink ejected is equal, and the density of the auxiliary image Pw and the degree of filling of the printing material S with the white ink are equal.

  A specific printing method according to the first embodiment will be described with reference to FIG. In FIG. 5, in order to form the medium dots MD on the small dots SD, one raster line constituting the auxiliary image Pw is completed in two passes by two nozzles, and the main image Pco Is completed in one pass by one nozzle. Therefore, 1/3 nozzles # 1 to # 4 (hereinafter, downstream nozzle group) on the downstream side of the color nozzle row Nco in the carrying direction are used as nozzles for printing the main image, and the white nozzle row Nw is carried. Auxiliary images are printed on 1/3 nozzles # 5 to # 8 (hereinafter, center nozzle group) in the center in the direction and 1/3 nozzles # 9 to # 12 (hereinafter, upstream nozzle group) on the upstream side in the transport direction. The nozzle used to do this.

  The controller 10 first discharges white ink from the upstream nozzle groups # 9 to # 12 of the white nozzle row Nw while moving the head 41 in the movement direction in pass 1 shown in FIG. Small dots SD are formed on all the pixels p of L1 to L4.

  Next, the controller 10 transports the printing material S to the downstream side in the transport direction. In FIG. 5, it is assumed that raster lines of other passes are not printed between raster lines printed in a certain pass. Therefore, the conveyance amount of the printing material S in one conveyance operation is 1/3 of the nozzle row.

  Then, in the pass 2 (FIG. 5B), the controller 10 moves the head 41 in the moving direction to form the middle dots MD in the central nozzle groups # 5 to # 8 of the white nozzle row Nw, and the upstream nozzle group. Small dots SD are formed in # 9 to # 12. At this time, small dots SD are already formed in the pixels p where the central nozzle groups # 5 to # 8 form the medium dots MD. Therefore, in the pixels p of the column numbers L1 to L4, the medium dots MD are formed so as to overlap the small dots SD, and a raster line constituting the auxiliary image Pw is completed.

  Thereafter, the controller 10 again conveys the printing material S to the downstream side in the conveyance direction, and in pass 3 (FIG. 5C), the head 41 is moved in the movement direction, and the central nozzle group # of the white nozzle row Nw # 5 to # 8 and upstream nozzle groups # 9 to # 12 are formed with dots in the same manner as in pass 2, and dots having sizes corresponding to the print data are formed on the downstream nozzle groups # 1 to # 4 of the color nozzle array Nco. Let Therefore, in the pixels p of the column numbers L5 to L8, the medium dots MD are formed so as to overlap the small dots SD, and the raster line constituting the auxiliary image Pw is completed. Further, in the pixels p of the column numbers L1 to L4, the raster line that constitutes the main image Pco is formed on the raster line that constitutes the auxiliary image Pw.

  As described above, in Example 1, first, small dots SD of white ink are formed on the printing material S as shown in the upper diagram of FIG. 6A. However, since the small dot SD has a small dot diameter, the small dots SD in the vicinity are not connected to each other and are fixed independently. Therefore, the image surface is uneven at this stage. Thereafter, as shown in the central view of FIG. 6A, medium dots MD of white ink are formed on the small dots SD so as to overlap each other. Since the amount of ink for forming the medium dot MD is larger than the amount of ink for forming the small dot SD, the ink for forming the medium dot MD is between the small dots SD fixed in a state of being separated from each other. Can be filled. Therefore, the medium dots MD formed from above the small dots SD are connected, and the surface of the auxiliary image Pw is flattened. Therefore, the main image Pco can be printed over the flat surface of the auxiliary image Pw, and deterioration of the image quality of the main image Pco can be suppressed.

  Further, the smaller the size of the dots formed on the printing material S, the more easily the solvent of the ink evaporates and the dots are more likely to dry. Therefore, the auxiliary image Pw composed of small dots SD and medium dots MD as in the first embodiment is easier to dry than the auxiliary image Pw of the comparative example composed of only large dots LD (FIG. 4A). Become. Further, in the first embodiment, in order to complete the raster lines constituting the auxiliary image Pw in two passes in order to form the medium dots MD on the small dots SD, the comparative example (FIG. 4A) is used. In comparison, the amount of ink ejected to the printing material S in one pass is reduced, and the auxiliary image Pw becomes easier to dry. Therefore, the main image Pco can be printed over the auxiliary image Pw in a dry state, and bleeding and color mixing between the auxiliary image Pw and the main image Pco can be suppressed.

  That is, according to the printing method in the front printing mode in the first embodiment, the surface of the auxiliary image serving as a lower layer can be flattened while suppressing bleeding and color mixing of the image, and image quality deterioration of the image can be suppressed. .

<Backprint mode>
When the reverse printing mode is set (FIG. 6B), the lower layer main image Pco is formed on the flat surface of the printing material S. Even if the upper surface (printing surface) of the main image Pco has an uneven shape, the image quality of the auxiliary image Pw formed thereon is not affected. Accordingly, when printing the lower layer main image Pco in the reverse printing mode, it is not necessary to form a large dot on a small dot, and a dot of a size corresponding to the print data may be formed. .

  In addition, the auxiliary image Pw as the upper layer is not printed with the image superimposed thereon, and can be dried after being discharged from the printing area. Therefore, the auxiliary image Pw that is the upper layer in the reverse printing mode does not need to be easily dried or the surface of the image is flattened as much as the auxiliary image Pw that is the lower layer in the front printing mode.

  Therefore, in the reverse printing mode (FIG. 6B), the auxiliary image Pw composed of only a single large dot is printed. That is, the controller 10 sets the back printing mode rather than the number of dots (the total number of small dots SD and medium dots MD) constituting the auxiliary image Pw printed when the front printing mode is set. In this case, the ejection of white ink from the white nozzle row Nw is controlled so that the number of dots (the number of large dots LD) constituting the auxiliary image Pw to be printed becomes smaller.

  Specifically, when the reverse printing mode is set, the controller 10 first causes the head 41 to move in the moving direction and appropriately discharge four colors of ink (KCMY) from the head 41 according to the print data. Thus, the main image Pco is printed on the printing material S. Thereafter, the controller 10 causes the white ink (W) to be ejected from the head 41 toward the main image Pco on the printing material S while moving the head 41 in the moving direction, and a single large dot LD is formed on each pixel p. By forming the auxiliary image Pw, the auxiliary image Pw is printed on the main image Pco.

  By doing so, the auxiliary image Pw is configured as compared to the front printing mode (FIG. 6A) in which the raster line forming the auxiliary image Pw is completed in two passes in order to overlap the medium dots MD on the small dots SD. In the reverse printing mode in which the raster line to be completed is completed in one pass, the printing time can be shortened. In the reverse printing mode, the number of nozzles for printing the main image Pco and the number of nozzles for printing the auxiliary image Pw can be made equal.

=== Printing Method: Example 2 ===
FIG. 7 is a diagram illustrating a printing method in the front printing mode according to the second embodiment. In the second embodiment, when the auxiliary image Pw in the front printing mode is printed, the center position of the small dot SD and the center position of the medium dot MD constituting the auxiliary image Pw are shifted. That is, the controller 10 controls the ejection of white ink from the white nozzle row Nw so that medium dots are formed between the small dots SD.

  For example, as shown in FIG. 7, when the center position of the small dot SD and the center position of the medium dot MD constituting the auxiliary image Pw are shifted in the movement direction, the controller 10 controls the ejection timing of ink from the nozzles. More specifically, the controller 10 controls the ink ejection timing from the nozzles so that the center of the small dot SD is aligned with the center of the pixel p of the printing material S in the previous pass, and in the subsequent pass. The ink ejection timing from the nozzles is controlled so that the centers of the medium dots MD are aligned with the boundaries of the pixels p.

  Also in this case, it is possible to fill the space between the small dots SD previously formed in a state independent from each other with the ink for forming the medium dots MD. Can be connected through. Therefore, the surface of the auxiliary image Pw can be flattened, and deterioration of the image quality of the main image Pco printed thereon can be suppressed. Also, the auxiliary image Pw is printed with medium dots MD and small dots SD smaller than the large dot LD, and the raster line constituting the auxiliary image Pw is completed in two passes, so that the auxiliary image Pw is easily dried. Can do. Therefore, it is possible to suppress bleeding and color mixing of the image.

  When the center position of the small dot SD and the center position of the medium dot MD constituting the auxiliary image Pw are shifted in the transport direction (not shown), the transport amount of the printing material S is adjusted, or the nozzle position is the transport direction. It is preferable to provide the head 41 with two white nozzle rows Nw that are displaced from each other.

=== Printing Method: Example 3 ===
8A and 8B are diagrams illustrating a printing method in the front printing mode according to the third embodiment. In the third embodiment, after forming the small dots SD on the printing material S, the auxiliary image Pw in the front printing mode is formed by forming the large dot LD which is the maximum size among the dots that can be formed by the white nozzle row Nw. To print. However, if large dots LD are formed on all the pixels p determined on the printing material S, the auxiliary image Pw becomes difficult to dry like the auxiliary image Pw of the comparative example shown in FIG. Bleeding or color mixing occurs between them.

  Therefore, in the third embodiment, after the small dots SD are formed on the printing material S, the large dots LD are formed on some of the pixels p defined in the printing material S. The controller 10 controls the discharge of white ink from the white nozzle row Nw. That is, the auxiliary image Pw is printed by thinning out the large dots LD, and the number of large dots constituting the auxiliary image Pw of the third embodiment is larger than the number of large dots constituting the auxiliary image Pw (FIG. 4A) of the comparative example. Reduce. In addition, the number of large dots constituting the auxiliary image of the third embodiment is made smaller than the number of medium dots constituting the auxiliary image Pw (FIGS. 6 and 7) of the first and second embodiments.

  Specifically, as shown in FIG. 8A, the controller 10 forms small dots SD in all the pixels p (1 to 7) on the printing material S in the first pass, and then in the subsequent pass. Then, large dots LD are formed on every other pixel p (1, 3, 5, 7) arranged in the moving direction on the printing material S.

  Further, as shown in FIG. 8B, small dots SD and large dots LD may be alternately formed in the moving direction. That is, after the controller 10 forms the small dots SD on the even-numbered pixels p (2, 4, 6) on the printing material S in the previous pass, the odd-numbered pixels on the printing material S in the subsequent pass. Large dots LD may be formed at p (1, 3, 5, 7).

  Also in these cases, the space between the small dots SD previously formed in an independent state can be filled with ink for forming the large dots LD, and the surface of the auxiliary image Pw can be flattened. . In addition, the auxiliary image Pw is printed using large dots LD that are difficult to dry, but because the large dots LD are thinned out, the printing material S is printed in one pass compared to the comparative example (FIG. 4A). The amount of ink ejected per unit area can be reduced. Therefore, the auxiliary image Pw of the third embodiment is easier to dry than the auxiliary image Pw (FIG. 4A) of the comparative example, and it is possible to suppress bleeding and color mixing of the image.

  In FIG. 8, the auxiliary image Pw is configured by the small dots SD and the large dots LD. However, the auxiliary image Pw may be configured by, for example, the medium dots MD and the large dots LD. The medium dot MD has a larger dot diameter than the small dot SD, and the adjacent medium dots MD are easily connected to each other. However, the medium dot MD is filled with ink by forming the large dot LD after the medium dot MD. And the surface of the auxiliary image Pw can be flattened more reliably.

=== Printing Method: Example 4 ===
FIG. 9 is a diagram illustrating a printing method in the front printing mode according to the fourth embodiment. In Example 4, after forming small dots SD and medium dots MD on the printing material S (that is, after forming two types of dots having different sizes), large dots larger than the small dots SD and medium dots MD. By forming the LD, the auxiliary image Pw in the surface printing mode is printed. However, since the large dots LD are difficult to dry, the large dots LD are formed by thinning out as in the third embodiment (the large dots LD are formed on some pixels p defined on the printing material S).

  In this case, since the dot diameter of the small dot SD is small at the stage where the small dot SD and the medium dot MD are formed on the printing material S, as shown in the upper diagram of FIG. Are not connected, and the image surface is uneven. Further, the pixel p on which the small dots SD are formed is less filled with white ink than the pixel p on which the medium dots MD are formed.

  Therefore, in Example 4, the small dots SD (corresponding to the first size dots) and the medium dots MD (corresponding to the second size dots) were formed on the printing material S, and then formed on the printing material S. Of the dots (small dot SD and medium dot MD), the controller 10 causes the white ink from the white nozzle row Nw so that the large dot LD is formed on the smaller dot (small dot SD). To control the discharge.

  More specifically, the controller 10 first forms the small dots SD on the even-numbered pixels p (2, 4, 6) of the printing material S in the previous pass, and the odd-numbered pixels p ( 1, 3, 5 and 7), medium dots MD are formed. Thereafter, the controller 10 causes a large dot LD to be formed in the pixels in which the small dots SD are formed, that is, even-numbered pixels p (2, 4, 6) in a subsequent pass.

  By doing so, it is possible to improve the filling of the white ink in the pixels p in which the small dots SD are formed, and the space between the small dots SD and the medium dots MD is filled with the ink for forming the large dots LD. be able to. Therefore, the surface of the auxiliary image Pw can be flattened, and deterioration of the image quality of the main image Pco printed thereon can be suppressed. Further, since the auxiliary image Pw is printed by using the small dots SD and the medium dots MD and thinning out the large dots LD, the auxiliary image Pw of the fourth embodiment is compared with the auxiliary image Pw of the comparative example (FIG. 4A). It becomes easy to dry. Therefore, it is possible to suppress bleeding and color mixing of the image. In FIG. 9, the small dots SD and the medium dots MD are alternately formed. However, the present invention is not limited to this. For example, the small dots SD and the medium dots MD may be formed every plural pixels p.

=== Printing Method: Example 5 ===
10A and 10B are diagrams illustrating a printing method according to the fifth embodiment. A main image Pco (for example, a character image or a monochrome image) with a small amount of ink ejected per unit area of the printing material S is a main image Pco (with a large amount of ink ejected per unit area of the printing material S. For example, compared to a photographic image or a color image, deterioration in image quality is less conspicuous, and bleeding and color mixing are less likely to occur between the auxiliary image Pw. Therefore, in the fifth embodiment, when the front printing mode is set, the amount of ink (maximum value or average value) ejected per unit area of the printing material S for printing the main image Pco is equal to or greater than a threshold value. The auxiliary image Pw is made different between when it is and when it is not.

  FIG. 10 is a diagram illustrating a case where two types of images are printed on the printing material S in the front printing mode. One of the two types of images, the first main image Pco (1), is printed on the printing material S. The amount of ink ejected per unit area (maximum value or average value) is an image whose value is less than the threshold, and the other second main image Pco (2) is ink ejected per unit area of the printing material S. An image whose amount is equal to or greater than a threshold. In this case, as shown in FIG. 10A, the controller 10 controls the first auxiliary image Pw (1) of one layer composed only of the medium dots MD to be printed under the first main image Pco, Control is performed so that two layers of the second auxiliary image Pw (2) in which the medium dots MD are superimposed on the small dots SD are printed below the second main image Pco (2).

  Therefore, the raster line constituting the second auxiliary image Pw (2) is completed in two passes, whereas the raster line constituting the first auxiliary image Pw (1) is completed in one pass. Can do. Therefore, it is possible to shorten the printing time of the first auxiliary image Pw (1) and the first main image Pco (1). More specifically, as shown in FIG. 10B, the second main image Pco (2) is printed by the nozzle n (co) belonging to 1/3 of the downstream side of the head 41 in the transport direction, whereas the head 41 The first main image Pco (1) can be printed with the nozzle n (co) belonging to 1/2 of the downstream side in the transport direction. Therefore, when printing images having the same length in the transport direction, the first main image Pco (1) is more than the number of passes for printing the second main image Pco (2) and the second auxiliary image Pw (2). In addition, the number of passes for printing the first auxiliary image Pw (1) is reduced, and the printing time can be shortened.

  Note that the first auxiliary image Pw (1) formed only with the medium dots MD is not connected to the neighboring medium dots MD compared to the second auxiliary image Pw (2) in which the small dots SD and the medium dots MD are overlapped. The flatness of the printing material S may not be good, or the printing material S may not be well filled with white ink. However, the first main image Pco (1) printed on the first auxiliary image Pw (1) has a small amount of ink ejected per unit area of the printing material S, and image quality deterioration is difficult to notice. There is no.

  Alternatively, the first auxiliary image Pw (1) may be printed using only the large dots LD. In this case, the first auxiliary image Pw (1) is difficult to dry, but the first main image Pco (1) printed on the first auxiliary image Pw (1) is per unit area of the printing material S. There is no problem because the amount of ejected ink is small and bleeding and color mixing are unlikely to occur. In FIG. 10A, the second auxiliary image Pw (2) is printed by superimposing the medium dots MD on the small dots SD. However, the present invention is not limited to this, and the second auxiliary image P2 as in the second to fourth embodiments. The auxiliary image Pw (2) may be printed.

=== Modification ===
<Modification 1>
FIG. 11 is a diagram illustrating the printer 70 according to the first modification. In the above-described embodiment (FIG. 2), the printer 1 in which the ejection operation for ejecting ink while the head 41 moves in the movement direction and the conveyance operation for conveying the printing material S in the conveyance direction are taken as an example. However, it is not limited to this.

  For example, as shown in FIG. 11, ink is ejected from a fixed head 73 toward a printing material S that is transported downstream in the transport direction by a transport belt 72 that is rotated by the rotation of transport rollers 71 a and 71 b. The printer 70 may be used. In the printer 70, the first head 73 (1) that discharges white ink, the second head 73 (2) that also discharges white ink, and the fourth color ink (KCMY) are discharged from the upstream side in the transport direction. Three heads 73 (3) and a fourth head 73 (4) for discharging white ink are arranged in this order. A number of nozzles are provided on the lower surface of each head 73 along the width direction orthogonal to the transport direction. Therefore, when the printing material S passes under each head 73, the head 73 ejects ink toward the printing material S, whereby a two-dimensional image is printed on the printing material S.

  When the front printing mode is set, the controller of such a printer 70, for example, forms a small dot SD on the first head 73 (1) and then applies a medium dot MD on the second head 73 (2). The auxiliary image Pw is printed by forming, and then the main image Pco is printed on the auxiliary image Pw by the third head 73 (3). On the other hand, when the reverse printing mode is set, the controller prints the main image Pco by the third head 73 (3), and then prints the auxiliary image Pw on the main image Pco by the fourth head 73 (4). Let

  Also, for example, by repeating the ejection operation of ejecting ink while the head moves in the X direction with respect to the printing material positioned in the printing region and the moving operation of moving the head in the Y direction, printing of the printing region is performed. A printer (not shown) may be used that prints a two-dimensional image on a material, and then conveys the printing material in the X direction and conveys a new portion of the printing material to a printing region.

  Further, for example, a printer (not shown) having a head provided with white nozzle rows Nw at positions upstream and downstream in the transport direction of a color nozzle row that discharges four-color ink (KCMY) may be used.

<Modification 2>
In the above embodiment, when the reverse printing mode is set (FIG. 6B), the auxiliary image Pw composed only of the large dots LD is printed, but this is not restrictive. For example, similarly to the auxiliary image Pw in the front printing mode, the auxiliary image Pw in the reverse printing mode may be printed by superimposing the medium dots MD on the small dots SD.

  In the above-described embodiment (FIG. 5C), the raster lines constituting the main image Pco are completed in one pass, but the present invention is not limited to this. For example, as with the auxiliary image Pw, the raster line constituting the main image Pco may be completed by a plurality of passes or may be completed by a plurality of nozzles.

Further, in the above embodiment (FIG. 5), the raster line constituting the auxiliary image Pw is completed in two passes by two different nozzles, but the present invention is not limited to this.
The raster line constituting the auxiliary image Pw may be completed in two passes by the same nozzle. In that case, for example, after the small dots SD are formed by a certain nozzle, the medium dots MD may be formed by using the same nozzle in the next pass without conveying the printing material S.
Further, the raster line constituting the auxiliary image Pw may be completed in one pass. In that case, for example, two white nozzle rows Nw are provided in the head 41, and after the small dot SD is formed by one nozzle row Nw of the two white nozzle rows Nw in the same pass, the other nozzle row A medium dot MD may be formed with Nw.
Further, the raster line constituting the auxiliary image Pw may be completed in three or more passes. In that case, the dot size formed in the last pass should be larger than the dot size formed in the previous pass.

<Modification 3>
In the above embodiment, for example, as shown in FIG. 5, the main image and the auxiliary image are overlaid and printed by shifting the nozzle for printing the main image and the nozzle for printing the auxiliary image in the transport direction. Not limited to. For example, every time an image is printed, the printing material S may be reversely conveyed upstream in the conveying direction (may be back-fed). For example, when the front printing mode is set, the controller first forms small dots SD using all the nozzles belonging to the white nozzle row Nw, and then reversely conveys the printing material S upstream in the conveying direction. . After that, the controller 10 forms the medium dot MD using all the nozzles belonging to the white nozzle row Nw while conveying the printing material S to the downstream side in the conveying direction again, and after completing the auxiliary image Pw, The printing material S is reversely conveyed upstream in the conveyance direction. Thereafter, the controller 10 superimposes the main image Pco on the auxiliary image Pw using all the nozzles belonging to the nozzle row that prints the main image Pco while transporting the printing material S downstream in the transport direction again. Print.

=== Other Embodiments ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About ink>
In the above embodiment, the auxiliary image using white ink and the main image using four color inks (YMCK) of yellow, magenta, cyan, and black are printed in an overlapping manner, but the present invention is not limited to this. For example, in order to print an image having a metallic luster, an auxiliary image using a metallic ink containing a metal pigment or the like and a main image may be printed in an overlapping manner. Further, the auxiliary image is not limited to printing with white ink, but the auxiliary image may be printed with other color inks, and the white color is adjusted by appropriately using the four color inks (YMCK) together with the white ink. The supplementary image may be printed. Further, white ink may be used for printing the main image. In addition to an image obtained by superimposing the auxiliary image and the main image, a single image using white ink or a single image using four-color ink (YMCK) may be printed on the same substrate.

In this specification, “white” is not limited to white in the strict sense that is the surface color of an object that reflects 100% of all wavelengths of visible light, but is commonly used as a so-called “white”. It shall include a color called white. For example, “white” means (1) color measurement mode: spot colorimetry, light source: D50, backing: Black, printing medium: transparent film, using a colorimeter eye-one Pro manufactured by x-rite When the colorimetry is performed, the Lab-based mark is on the a ^* b ^* plane within the circumference of the radius 20 and the inside thereof, and the color is within the hue range represented by L ^* being 70 or more. (2) When the color is measured with the color mode CM2022 manufactured by Minolta in the measurement mode D502 ° field of view, SCF mode, and white background, the label in the Lab system is on the circumference of the radius 20 on the a ^* b ^* plane and inside Or a color within the hue range represented by L ^* of 70 or more, or (3) the color of the ink used as the background of the image as described in JP-A-2004-306591, If it is used, it is not limited to pure white.

1 Printer, 10 Controller, 11 Interface section,
12 CPU, 13 memory, 14 unit control circuit,
20 transport unit, 30 carriage unit, 31 carriage,
32 guide rails, 40 head units, 41 heads,
50 detector groups, 60 computers, Pco main image, Pw auxiliary image,
70 printer, 71a transport roller, 71b transport roller,
72 Conveyor belt, 73 heads

Claims (8)

A first nozzle that ejects ink for printing a main image;
A second nozzle that ejects ink for printing an auxiliary image that overlaps the main image, the second nozzle being capable of forming dots of a plurality of sizes;
A control unit for controlling ejection of ink from the first nozzle and the second nozzle;
A printing apparatus comprising:
When the auxiliary image is printed on the printing material prior to the main image,
The control unit discharges ink from the second nozzle to the printing material to form dots of a predetermined size, and then controls the region of the printing material on which the dots of the predetermined size are formed. On the other hand, ink is ejected from the second nozzle to form dots having a size larger than the predetermined size, thereby controlling the auxiliary image to be printed on the printing material. Controlling the main image to be printed on the auxiliary image by discharging ink from the first nozzle;
A printing apparatus characterized by the above. The printing apparatus according to claim 1,
The control unit controls the ejection of ink from the second nozzle so that the large size dot is formed on the predetermined size dot;
A printing apparatus characterized by the above. The printing apparatus according to claim 1,
The control unit controls the ejection of ink from the second nozzle so that the large size dots are formed between the predetermined size dots;
A printing apparatus characterized by the above. The printing apparatus according to any one of claims 1 to 3, wherein
The large size is the maximum size among the plurality of sizes,
The control unit controls the ejection of ink from the second nozzle so that the dots of the maximum size are formed on some of the plurality of pixels defined on the printing material;
A printing apparatus characterized by the above. The printing apparatus according to any one of claims 1 to 4, wherein:
The predetermined size is a first size and a second size larger than the first size,
The control unit is configured such that, among the first size dots and the second size dots formed on the printing material, the large size dots are overlapped on the first size dots. And controlling the ejection of ink from the second nozzle,
A printing apparatus characterized by the above. The printing apparatus according to any one of claims 1 to 5, wherein
The control unit is configured to precede the auxiliary image on the printing material with respect to the number of dots constituting the auxiliary image to be printed when the auxiliary image is printed on the printing material before the main image. Controlling the ejection of ink from the second nozzle so that the number of dots constituting the auxiliary image printed when the main image is printed on is reduced.
A printing apparatus characterized by the above. A printing method in which a main image is printed over an auxiliary image.
After ejecting ink for printing the auxiliary image onto the printing material to form dots of a predetermined size, the auxiliary to the area of the printing material on which the dots of the predetermined size are formed A step of printing an auxiliary image on the printing material by ejecting ink for printing an image to form dots having a size larger than the predetermined size;
Printing the main image on the auxiliary image by ejecting ink for printing the main image on the auxiliary image printed on the printing material;
A printing method characterized by comprising:   After the ink for printing the auxiliary image on the printing material is ejected to form dots of a predetermined size, the auxiliary image is applied to the area of the printing material on which the dots of the predetermined size are formed. The auxiliary image printed on the printing material and the main image printed over the auxiliary image are formed by ejecting ink for printing the ink to form dots having a size larger than the predetermined size. A printed matter comprising an image.

Images