JP2009012430A - Inkjet printing apparatus and inkjet printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printing method capable of performing a high quality printing without installing a plurality of kinds of print heads with different numbers of jetting holes per unit area. <P>SOLUTION: In the inkjet printing method which conveys an article to be printed with an uneven face toward an inkjet head, jets ink droplets to the uneven face passing through the neighborhood of the inkjet head from the inkjet head, and prints the uneven face, the inkjet printing method is characterized in that the conveying speed of the article to be printed is controlled in accordance with the degree of inclination of the face part to which the ink droplets are jetted among the uneven face. When the part with a high degree of inclination is printed, by lowering the conveying speed of the article to be printed, the ink droplets can sufficiently reach even the face with the high degree of inclination, and as the result, the resolution of the part with the high degree of inclination can be made high. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink jet printing apparatus and an ink jet printing method, and more particularly to an ink jet printing apparatus and an ink jet printing method for performing ink jet printing on a printed material having an uneven surface.

  2. Description of the Related Art Conventionally, as one of information output devices for devices such as copying machines, personal computers, and facsimiles, a device that prints a digital image on a printing material using an ink jet print head has been used. Since this ink jet method is a non-contact type printing method, there is an advantage that printing can be performed on an uneven surface. This inkjet printing is also used for decorating ceramic building materials such as tiles (for example, Japanese Patent Application Laid-Open No. 2004-114500).

  When printing on an uneven surface of an object to be printed by an ink jet method, for example, the object is printed by passing the object to the lower side of the print head by a conveying means such as a belt conveyor and ejecting ink from the print head onto the uneven surface. .

  FIG. 8 is a cross-sectional view for explaining a conventional printing method. FIG. 8 shows that the substrate 1 having the horizontal surface 2a and the inclined surface 2b is transported horizontally at a constant speed and passes under the ink jet head 3, and ink droplets 4 are ejected from the ink jet head 3 at regular time intervals. The state which injected is shown. The inclined surface 2b is inclined at 45 ° C. with respect to the horizontal surface 2a.

  As shown in FIG. 8, the ink droplets 4 land on the horizontal surface 2a with an interval d, whereas the ink droplets 4 land on the inclined surface 2b with an interval √2d. For this reason, the inclined surface 2b has a lower resolution than the horizontal surface 2a.

In order to solve this problem, Japanese Patent Application Laid-Open No. 9-193368 has four types of print heads with different numbers of ejection holes per unit area, and uses different print heads according to the inclination of the uneven surface. Printing is described. For example, when printing a non-tilted surface, select the print head with the fewest number of ejection holes per unit area for printing, and the higher the inclination of the surface to be printed, the more the number of ejection holes per unit area Select a print head with many prints. Thereby, it is possible to increase the printing resolution even in a portion with a high inclination.
JP 2004-114500 A Japanese Patent Laid-Open No. 9-193368

  According to the above-mentioned Japanese Patent Laid-Open No. 9-193368, since it is necessary to provide a plurality of types of print heads having different numbers of ejection holes per unit area, there is a problem that the apparatus is increased in size and complexity and the equipment cost is increased. is there.

  An object of the present invention is to provide an inkjet printing apparatus and an inkjet printing method capable of performing high-quality printing without installing a plurality of types of print heads having different numbers of ejection holes per unit area.

  The ink jet printing apparatus of the present invention (invention 1) includes an ink jet head, a transport means for transporting a printed material having an uneven surface to an ink droplet ejection area of the ink jet head, and a control means for controlling the transport speed of the transport means. The control unit is configured to pass the ink droplet ejection region according to the inclination of the surface portion of the uneven surface conveyed to the ink droplet ejection region. The conveyance speed at the time is controlled.

An ink jet printing apparatus according to a second aspect of the present invention is the ink jet printing apparatus according to the first aspect, wherein an angle formed between a perpendicular of the surface portion conveyed to the ink droplet ejection region and the conveyance direction of the conveying means is θ, and the surface portion is the ink droplet ejection When the conveyance speed when passing through the region is V, the control means controls the conveyance speed V so that the following expression is established.
V = A · sin θ (A is a constant)

  According to a third aspect of the present invention, there is provided the ink jet printing apparatus according to the first or second aspect, wherein the control means is configured to store the image data to be printed on the concavo-convex surface, and to perform the printing even when the transport speed is changed. An image processing unit configured to process the image data to be printed into image data after processing in order to print the same image as the image data on the uneven surface; The processing unit transfers the image data to be printed on the surface portion in the transport direction when the transport speed of the surface portion passing through the ink droplet ejection area is 1 / N times the reference speed in the image data to be printed. The image data enlarged N times is used as the processed image data, and the control means ejects ink droplets from the inkjet head so as to print the processed image data on the uneven surface. Is to control And wherein the door.

  In the ink jet printing method of the present invention (claim 4), a substrate having a concavo-convex surface is transported to an ink droplet ejection region of an ink jet head, and ink is ejected from the ink jet head to the concavo-convex surface passing through the ink droplet ejection region. In the ink jet printing method for printing the uneven surface by ejecting droplets, the surface portion defines the ink droplet ejecting region according to the inclination of the surface portion of the uneven surface conveyed to the ink droplet ejecting region. It is characterized by controlling the conveyance speed when passing.

The ink jet printing method according to claim 5 is the ink jet printing method according to claim 4, wherein an angle formed by a perpendicular of a surface portion of the concavo-convex surface on which ink droplets are ejected and a transport direction of the substrate is θ, and the substrate is transported. When the speed is V, the conveyance speed V is controlled so that the following expression is established.
V = A · sin θ (A is a constant)

  According to a sixth aspect of the present invention, there is provided an ink jet printing method using the ink jet printing apparatus according to any one of the first to third aspects.

  In the ink jet printing apparatus and the ink jet printing method of the present invention, the conveyance speed of the printing material is controlled according to the inclination of the surface portion of the concavo-convex surface on which the ink droplets are ejected. For this reason, when printing a portion with a high degree of inclination, it is possible to sufficiently land ink droplets on the surface with the high degree of inclination by slowing the conveyance speed of the printing material. The resolution can be increased even in a high part.

In the present invention, if the angle formed by the perpendicular of the surface portion of the concavo-convex surface on which ink droplets are ejected and the conveyance direction of the printing material is θ and the conveyance speed of the printing material is V, the following equation is established. The conveyance speed V may be controlled as described above.
V = A · sin θ (A is a constant)

  By controlling in this way, it is possible to sufficiently increase the resolution of the portion with a high inclination.

  In the present invention, the control unit includes a storage unit that stores image data to be printed on the uneven surface, and an image processing unit that processes the image data, and the image processing unit is to perform the printing. In the image data, when the transport speed of the surface portion passing through the ink droplet ejection area is 1 / N times the reference speed, the image data to be printed on the surface portion is enlarged N times in the transport direction. The image data is preferably processed image data. Thereby, even if a change occurs in the conveyance speed of the printing material, it is possible to prevent a figure, a character, or the like to be drawn on the uneven surface of the printing material from being partially enlarged or reduced in the conveyance direction.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view showing an example of an ink jet printing apparatus used in the method of the present invention, in which (a) is a plan view of the ink jet printing apparatus 10 and (b) is a side view of the ink jet printing apparatus 10.

  The ink jet printing apparatus 10 mainly includes a belt conveyor 11 and a head unit 13 provided in the upper part of the belt conveyor 11 in the conveying direction.

  A pair of guides 14 and guides 15 are provided on the upper surface side of the belt conveyor 11. The guide 14 is movable by a cylinder 16 in a direction toward and away from the guide 15.

  A head unit 13 is provided on the downstream side of the guides 14 and 15 in the belt conveyor 11. The head unit 13 includes four types of inkjet heads 13a to 13d having different colors arranged in this order in the transport direction. These inkjet heads 13 a to 13 d are provided so as to eject ink droplets perpendicularly to the upper surface of the belt conveyor 11. The head unit 13 is disposed in the head cover 12.

  An optical sensor 19 for detecting the front end of the printing material 20 is provided in the nearest part upstream of the head unit 13 in the transport direction. The sensor 19 is composed of, for example, a CCD camera, and is configured to detect that the front end of the printing material 20 has reached the vertically lower side of the sensor 19 based on a change in imaging data.

  In the head cover 12, control means 17 is provided for controlling the ejection of ink droplets from the head unit 13 and the transport speed of the belt conveyor 11. The detection signal of the sensor 19 is input to the control means 17.

  FIG. 2 shows the printed material 20 after printing. (A) is a side view of the printed material 20, and (b) is a plan view of the printed material 20.

  As shown in FIG. 2 (a), the printed material 20 has one end side in the longitudinal direction thicker than the other end side, and the center side is inclined. The upper surface of the printing material 20 includes a first horizontal plane 21 on one end side in the longitudinal direction, a second horizontal plane 23 on the other end side in the longitudinal direction, and an inclined surface 22 between the horizontal planes 21 and 23. Yes. Reference numerals 60 and 61 are graphics printed on the upper surface of the substrate 20. 20A denotes a front end in the transport direction, 20B denotes a bending point between the horizontal surface 21 and the inclined surface 22, 20C denotes a bending point between the inclined surface 22 and the horizontal surface 23, and 20D denotes a rear end in the transport direction.

  In FIG. 2 (a), θ represents an angle formed between the perpendicular 30 of the inclined surface 22 and the first horizontal plane 21.

  In FIG. 1, for ease of explanation, the length of the head unit 13 in the transport direction is drawn large. In practice, however, the length of the head unit 13 in the transport direction is the first horizontal plane 21, The length in the conveying direction of the inclined surface 22 and the second horizontal surface 23 is extremely small.

  Next, an example of the printing method of the present invention using the inkjet printing apparatus 10 will be described.

  First, the cylinder 16 is actuated so that the distance between the guide 14 and the guide 15 is equal to or slightly larger than the length in the short direction of the substrate 20. Next, the printed material 20 is placed on the belt conveyor 11 and conveyed into the head cover 12, and ink droplets are ejected from the inkjet heads 13 a to 13 d of the head unit 13 to print on the upper surface of the printed material 20.

  At this time, the conveying speed of the printing material 20 is controlled by the control means 17 in accordance with the inclination of the surface portion of the upper surface of the printing material 20 existing in the ink droplet ejection region of the head unit 13. The time at which the front end 20A, each bending point 20B, 20C, and the rear end 20D of the substrate 20 reaches the ink droplet ejection area is the time at which the sensor 19 detects the front end 20A of the substrate 20, the conveyance speed of the conveyor 11, and the point 20A. ˜20B, points 20B to 20C, and points 20C to 20D are calculated from the horizontal distances between them. The horizontal distance is input to the control means 17 in advance.

  In the present embodiment, the conveyance speed of the belt conveyor 11 when printing on the first horizontal plane 21 and the second horizontal plane 23 is the same speed, and the conveyance speed of the belt conveyor 11 when printing on the inclined surface 22 is the horizontal plane. The conveyance speed of the belt conveyor 11 is controlled by the control means 17 so as to be slower than when printing on 21 and 23. In this way, the figures 60 and 61 are printed on the upper surface of the substrate 20 (FIG. 2 (b)).

  FIG. 3 is an enlarged plan view of a portion III in FIG. 2B after printing, and FIG. 4 is an enlarged plan view of a portion IV in FIG. 2B after printing. In FIG. 3, reference numeral 32 denotes an ink droplet.

As shown in FIGS. 3 and 4, when the substrate 20 is viewed from directly above (vertical direction), the interval between the ink droplets 32 in the longitudinal direction (conveying direction) of the substrate 20 is the interval L _{1 on the} inclined surface 22. Is smaller than the interval L ₂ in the horizontal plane 21. The reason for this is that, as described above, the conveyance speed when printing the inclined surface 22 is slower than the conveyance speed when printing the horizontal surfaces 21 and 23. Since the same head unit 13 is used for printing on the horizontal surface 21 and the inclined surface 22, the interval between the ink droplets 32 in the direction perpendicular to the transport direction (the short direction of the substrate 20) is the interval on the inclined surface 22. W ₁ and the interval W ₂ in the horizontal plane 21 are the same.

  As described above, since the conveyance speed at the time of ejecting ink droplets onto the inclined surface 22 is controlled to be slow, by adjusting this conveyance speed, the portion drawn on the inclined surface 22 of the figures 60 and 61. Can be made as high as the resolution of the portions drawn on the horizontal planes 21 and 23.

  Next, a specific method for adjusting the conveying speed of the belt conveyor and an example of a printing method at the conveying speed will be described.

[Determination of transport speed]
The transport speed of the belt conveyor 11 when printing the first horizontal plane 21 and the second horizontal plane 23 is the standard speed V, and the transport speed of the belt conveyor 11 when printing the inclined surface 22 is slower than the standard speed V / V / The conveying speed of the belt conveyor 11 is controlled by the control means 17 so as to be N.

  In the present embodiment, N = 1 / sin θ (refer to FIGS. 2A and 7 for θ). The reason is as follows.

  That is, as described above, as shown in FIG. 8, when printing is performed on the printing material 1 with the transport speed and the ink droplet ejection speed (the number of ink droplets ejected from the inkjet head per unit time) being constant, the inclined surface The interval between the ink droplets 4 in 2b is larger than the interval between the ink droplets 4 in the horizontal plane 2, and the dot density of the ink droplets 4 is reduced. As is clear from this, when a graphic is printed on the inclined surface and the horizontal plane at the same conveyance speed, the graphic printed on the inclined surface is lighter than the graphic printed on the horizontal plane.

  On the other hand, FIG. 7 is an enlarged cross-sectional view for explaining a state in which printing is performed on the printing material 20 by changing the conveyance speed. In FIG. 7, as described above, the transport speed when printing on the horizontal planes 21 and 23 is the standard speed V, and the transport speed when printing on the inclined surface 22 is V / N (N = 1 / sin θ), constant. A state in which printing is performed at the ink droplet ejection speed is shown. As described above, the ink droplet 31 on the horizontal surfaces 21 and 23 is obtained by setting the transport speed when printing on the inclined surface 22 to 1 / N (N = 1 / sin θ) times the transport speed when printing the horizontal surface 21. The distance d between the ink drops 31 and the distance d between the ink droplets 31 on the inclined surface 22 are the same. Accordingly, the dot density of the ink droplets on the inclined surface 22 and the dot density on the horizontal surfaces 21 and 23 are the same, and the color density of the figure is the same on the inclined surface 22 and the horizontal surfaces 21 and 23.

  In this way, N = 1 / sin θ so that the color density is the same regardless of whether the graphic is printed on either the inclined surface 22 or the horizontal surfaces 21 and 23.

  In addition, as the conveyance speed is changed between the inclined surface 22 and the horizontal planes 21 and 23 as described above, it is necessary to process the image stored in the control unit 17 so as to correspond to the conveyance speed. This will be described below.

[Image processing]
FIG. 5 (a) is an image 40A before processing, and FIG. 5 (b) is an image 40B after processing this image 40A. In FIG. 5, the code | symbol 41 has shown the boundary line of the part which should be drawn on the 1st horizontal surface 21, and the part which should be drawn on the inclined surface 22 among these images 40A and 40B.

  Data of the image 40A to be printed is stored in the storage unit of the control unit 17. The processed image 40B is obtained by stretching the data of the portion to be printed on the inclined surface 22 of the image 40A (that is, the portion on the left side of FIG. 5A from the boundary line 41) N times in the transport direction. The data is shown in FIG. 5 (b). At this time, the stretching process is performed so that the darkness of the color of the stretched portion is the same before and after stretching. Here, the same color density means that the dot intervals of the ink droplets in the stretching direction are the same before and after stretching, and therefore the dot density of the ink droplets is the same.

  The creation of this data is performed by the image processing unit of the control means 17.

  The reason for processing the image in this way is as follows.

  FIG. 6 is a plan view of the substrate 20 when printing is performed based on the stored data of the image 40A. Here, as described above, the conveyance speed is controlled to be the standard speed V when printing on the horizontal surfaces 21 and 23 and V / N when printing on the inclined surface 22.

  As described above, when the image 40A is printed by controlling the conveyance speed as described above, the graphic 60A printed on the substrate 20 is the image 40A to be printed, as described in the section “Determining the conveyance speed”. Will be visualized in the same color intensity. However, since the conveyance speed when printing on the inclined surface 22 is 1 / N times the conveyance speed when printing on the horizontal surface 21, the portion printed on the inclined surface 22 in the figure 60A is compared with the image 40A. The size is reduced to 1 / N times in the transport direction.

  Thus, in order to avoid the portion of the graphic 60A printed on the inclined surface 22 from being reduced in the transport direction, the data of the processed image 40B is created as described above.

  That is, in the image 40B, the portion to be printed on the inclined surface 22 is stretched N times in the transport direction as compared to the image 40A. On the other hand, the conveyance speed when printing the inclined surface 22 is 1 / N times the conveyance speed when printing the horizontal surface 21. Therefore, when the image 40B is printed under the condition of the conveyance speed, the portion of the image 40B to be printed on the inclined surface 22 is reduced by 1 / N times in the conveyance direction, and as a result, the image is printed on the substrate 22. A figure having the same shape as 40A is printed.

  The color intensity of the image 40B is the same as that of the image 40A. For this reason, as described in the above-mentioned “determination of the conveyance speed”, the graphic when printed on the substrate 20 is visually perceived as having the same color density as the image 40A. .

[Print]
The substrate 20 is conveyed by the belt conveyor 11. At this time, the first horizontal plane 21 and the second horizontal plane 22 are conveyed at the standard speed V, and the inclined plane 22 is conveyed at the conveyance speed V / N.

  Thus, while the printing material 20 is conveyed, ink droplets are sprayed from the inkjet heads 13a to 13d to the printing material based on the data of the image 40B. As a result, the figure 60 having the same shape and color density as the image 40 </ b> A is printed on the surface of the printing material 20.

  The above embodiment is an example of the present invention, and the present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, only the transport speed is changed according to the inclination of the printing surface. However, in addition to the transport speed, the ink droplet continuous spray speed (ink droplets ejected per unit time) in the inkjet heads 13a to 13d. May be changed.

  The printed material may be a building material such as a tile. An example of a tile having an uneven front surface is a hanging type tile (Japanese Patent Laid-Open No. 6-248780, etc.) 50 shown in FIG. The tile 50 has a main surface 53, a step surface 51 parallel to the main surface 53, and an inclined surface 52 inclined from the main surface 53 to the step surface 51. A tile 50 shown in FIG. 9 is described in FIG. 7 of JP-A-6-248780, and is hooked on a tile construction base plate as shown in FIG.

  FIG. 9 shows a posture in which the tile 50 is placed on the belt conveyor so as to perform ink jet decoration on the front surface of the tile 50. In this state, the main surface 53 and the step surface 51 are horizontal, and the tile 50 is transported in the direction of the arrow S, and ink jet printing is performed by controlling the transport speed as described above.

  By printing according to the method of the present invention, the main surface 53, the step surface 51, and the inclined surface 52 can be decorated so as to have the same color.

It is a figure which shows an example of the inkjet printing apparatus used for this invention method, (a) is a top view of the inkjet printing apparatus 10, (b) is a side view of the inkjet printing apparatus 10. The printed material 20 after printing is shown, (a) is a side view of the printed material 20, and (b) is a plan view of the printed material 20. FIG. 3 is an enlarged plan view of a portion III of the printing material 20 in FIG. FIG. 4 is an enlarged plan view of an IV portion of the substrate 20 in FIG. (A) is an image 40A before processing, and (b) is an image 40B after processing. It is a top view which shows the reference example at the time of printing on the to-be-printed material 20 based on the image 40A before a process. It is an expanded sectional view explaining the state printed on to-be-printed material 20 by changing conveyance speed. It is sectional drawing explaining the conventional printing method. It is a perspective view of a tile.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet printing apparatus 11 Belt conveyor 12 Head cover 13 Head unit 14, 15 Guide 16 Cylinder 17 Control means 20 Printed object 21 1st horizontal surface 22 Inclined surface 23 2nd horizontal surface 40A, 40B Image data 50 Tile 51 Main surface 52 Inclined surface 53 Step surface 60, 60A, 61 figure

Claims (6)

An inkjet head;
Transport means for transporting a substrate having an uneven surface to an ink droplet ejection region of the inkjet head;
An ink jet printing apparatus having control means for controlling the transport speed of the transport means,
The control means controls the conveyance speed when the surface portion passes through the ink droplet ejection region according to the inclination of the surface portion conveyed to the ink droplet ejection region of the uneven surface. Inkjet printing apparatus. 2. The transport speed degree when the surface portion passes through the ink droplet ejection region according to claim 1, wherein an angle formed by a perpendicular of the surface portion transported to the ink droplet ejection region and the transport direction of the transport means is θ. Is an ink jet printing apparatus, wherein the control means controls the conveying speed V so that the following equation is established.
V = A · sin θ (A is a constant) The control means according to claim 1 or 2,
A storage unit for storing image data to be printed on the uneven surface;
In order to print the same image as the image data to be printed on the uneven surface even if the conveyance speed is changed, the image data to be printed is processed and processed image data And an image processing unit to
In the image data to be printed, the image processing unit obtains image data to be printed on the surface portion when the transport speed of the surface portion passing through the ink droplet ejection area is 1 / N times the reference speed. What is enlarged N times in the transport direction is used as the processed image data,
The ink jet printing apparatus, wherein the control means controls ejection of ink droplets from an ink jet head so as to print the processed image data on the uneven surface. Ink jet for printing the uneven surface by transporting a printed material having an uneven surface to an ink droplet ejecting region of an ink jet head and ejecting ink droplets from the ink jet head to the uneven surface passing through the ink droplet ejecting region In the printing method,
An ink jet printing method comprising: controlling a transport speed when the surface portion passes through the ink droplet ejection region according to an inclination of the surface portion of the uneven surface transported to the ink droplet ejection region. . In claim 4, when an angle formed by a perpendicular of a surface portion of the concavo-convex surface on which ink droplets are ejected and a conveyance direction of the printing material is θ, and a conveyance speed of the printing material is V, the following expression The inkjet printing method is characterized in that the conveyance speed V is controlled so that
V = A · sin θ (A is a constant)   An ink jet printing method, wherein ink jet printing is performed using the ink jet printing apparatus according to claim 1.

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