Abstract:
A printing method and a printer for implementing the printing method are disclosed. When a printhead including a first end and a second end sequentially prints a first area and a second area which are adjacent to each other, the method comprises performing printing by means of the printer by relatively moving locations of the printhead and a print object in such a way that a surface printed by the second end in the first area and a surface printed by the second end in the second area face each other. The printhead rotates around a rotational axis comprising at least one point on the printhead, one end of the printhead, a center of the printhead, or both ends of the printhead.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on the 16 Feb. 2010 and there duly assigned Serial No. 10-2010-0013843. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printer and a printing method, and more particularly, to a printer and a printing method for reducing a deviation between nozzles. 
     2. Description of the Related Art 
     Generally, a display device converts data processed by a data processing device into an image. Examples of the display device include a liquid crystal display (LCD) device, an organic electroluminescent (EL) display device, and a plasma display panel (PDP). Such display devices are flat display devices which have smaller volume and weight than cathode-ray tube display devices. 
     The flat display devices commonly have a pixel pattern for displaying an image. For example, the LCD device includes various pixel patterns, such as a thin film transistor (TFT), a gate signal line, a data signal line, a pixel electrode, a black matrix, a color filter, and a common electrode. For example, the organic EL display device includes various pixel patterns, such as an anode electrode, an electron injection layer (EIL), a hole injection layer (HIL), a cathode electrode, and an organic layer. 
     SUMMARY OF THE INVENTION 
     The present invention provides a printer and a printer method for reducing a deviation between nozzles during printing. 
     According to an aspect of the present invention when a printhead including a first end and a second end sequentially prints a first area and a second area which are adjacent to each other, the printing method comprises the step of performing printing by relatively moving locations of the printhead and a print object in such a way that a surface printed by the second end in the first area and a surface printed by the second end in the second area face each other. 
     When the location of the printhead with respect to the print object switches from the first area to the second area, the printhead may rotate with respect to the print object. 
     The printhead may rotate around at least one point on the printhead constituting a rotation axis. The printhead may rotate around one end of the printhead constituting the rotation axis. The printhead may rotate around the center of the printhead constituting the rotation axis. The printhead may rotate around both ends of the printhead constituting the rotation axis. 
     A method of adjusting the locations of the printhead and the print object may comprise moving the print object with respect to the printhead. 
     A method of adjusting the locations of the printhead and the print object may comprise moving the printhead in parallel with the print object. 
     The printing method may be an inkjet printing method. 
     The printing method may be a nozzle printing method. 
     The printhead may spray a light emitting material so as to form a light emitting unit. The printhead may spray a pigment of a color filter layer so as to form a color filter layer. The printing method may be performed by using a plurality of the printheads, each spraying a pigment of a single color. 
     The printhead may be formed so as to tilt at a predetermined angle with respect to a moving direction of the print object on a print surface. 
     With respect to the print object, the printing method may further include: performing printing while moving the printhead in a first direction; moving the printhead in a second direction; rotating the printhead; performing printing while moving the printhead in a direction opposite to the first direction; moving the printhead in the second direction; and rotating the printhead. 
     The printing method may further include: performing printing while moving the print object in a direction opposite to a first direction with respect to the printhead; moving the print object in a direction opposite to a second direction; rotating the printhead; performing printing while moving the print object in the first direction with respect to the printhead; moving the print object in the direction opposite to the second direction; and rotating the printhead. 
     When the location of the printhead with respect to the print object switches from the first area to the second area, the printing method may further include controlling a location of the printhead so as to start printing in the second area, wherein the controlling of the location comprises: receiving the location of the printhead with respect to the print object, the location being received by a vision camera; and compensating the location of the printhead. 
     According to another aspect of the present invention, when a printhead including a first end and a second end sequentially prints a first area and a second area which are adjacent to each other, the printer performs printing by relatively moving locations of the printhead and a print object in such a way that a surface printed by the second end in the first area and a surface printed by the second end in the second area face each other. 
     When the location of the printhead with respect to the print object switches from the first area to the second area, the printhead may rotate with respect to the print object. 
     The printhead may rotate around at least one point on the printhead constituting a rotation axis. The printhead may rotate around one end of the printhead constituting the rotation axis. The printhead may rotate around the center of the printhead constituting the rotation axis. The printhead may rotate around both ends of the printhead constituting the rotation axis. 
     The printhead may include a plurality of nozzles. 
     The printer may perform printing using an inkjet printing method. 
     The printer may perform printing using a nozzle printing method. 
     When the location of the printhead with respect to the print object switches from the first area to the second area, the printer may further include a control system for controlling a location of the printhead to start printing in the second area, wherein the control system may include: a vision camera for receiving the location of the printhead with respect to the print object; and a compensator for compensating the location of the printhead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1  is a conceptual schematic diagram illustrating movement of a printhead moving with respect to a print object according to a parallel movement when viewed from above according to an embodiment of the present invention; 
         FIG. 2  is a conceptual schematic diagram illustrating a printhead switching from a first area to a second area according to a rectilinear movement and a rotary movement according to an embodiment of the present invention; 
         FIG. 3  is a diagram comparing discharge rates in a cross-section taken along a line III-III of  FIG. 1  and a cross-section taken along a line III-III of  FIG. 2 ; 
         FIG. 4  is a conceptual schematic diagram illustrating movement of a printhead on a print object when viewed from above according to a modified example of the embodiment of  FIG. 2 ; 
         FIG. 5  is a schematic perspective view illustrating a printer having a printhead moving with respect to a print object; 
         FIG. 6  is a flowchart of movement of the printhead of  FIG. 5 ; 
         FIG. 7  is a schematic perspective view illustrating a print object in a parallel movement and a printer including a printhead in a rotary movement; 
         FIG. 8  is a flowchart of movements of the print object and the printhead of  FIG. 7 ; 
         FIG. 9  is a schematic perspective view illustrating the printhead of  FIG. 5  for describing location compensation of the printhead; 
         FIG. 10  is a flowchart of movement and location compensation of the printhead of  FIG. 9 ; 
         FIG. 11  is a conceptual schematic diagram illustrating movement of a printhead on a print object when viewed from above according to another modified example of the embodiment of  FIG. 2 ; 
         FIG. 12  is a conceptual schematic diagram illustrating movement of a printhead on a print object when viewed from above according to another modified example of the embodiment of  FIG. 2 ; 
         FIG. 13  is a conceptual schematic diagram illustrating movement of a printhead on the print object when viewed from above according to another example of the embodiment of  FIG. 2 ; 
         FIG. 14  is a conceptual schematic diagram illustrating movement of a printhead on a print object when viewed from above according to another example of the embodiment of  FIG. 2 ; and 
         FIG. 15  is a conceptual schematic diagram illustrating a plurality of printheads used to print red, green, and blue, respectively, on a print object when viewed from above according to the embodiment of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the present invention will be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
       FIG. 1  is a conceptual schematic diagram illustrating movement of a printhead moving with respect to a print object according to a parallel movement when viewed from above according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the print object  1  includes a first area and a second area. The printhead H 1  may print the first area while rectilinearly moving in a direction opposite to a Y-axis direction. After printing the first area, the printhead H 1  moves below the print object  1  so as to move to the second area, and then moves to the second area in parallel with an X-axis. After moving to the second area in parallel with the X-axis, the printhead H 1  prints the second area while rectilinearly moving in the Y-axis direction. Here, the printhead H 1  may include a plurality of nozzles. For example, in  FIG. 1 , the printhead H 1  includes a total of 6 nozzles, namely from a first nozzle N 1  through a sixth nozzle N 6 . 
     The number and locations of the nozzles on the printhead H 1  are not limited to the embodiment of  FIG. 1 , and may vary. 
     According to the current embodiment of the present invention, the first area is sequentially printed in the X-axis direction from the first nozzle N 1  to the sixth nozzle N 6 , and the second area is also sequentially printed in the X-axis direction from the first nozzle N 1  to the sixth nozzle N 6 . Accordingly, adjacent surfaces of the first and second areas are printed by using different nozzles. 
     In other words, referring to  FIG. 1 , the adjacent surfaces of the first and second areas are respectively printed by the sixth nozzle N 6  and the first nozzle N 1 . 
     At this point, since the printhead H 1  includes the plurality of nozzles N 1  through N 6 , there may be a deviation between nozzles due to different discharge rates, or the like. Such a deviation may occur irregularly or regularly, and if the deviation occurs gradually, a difference between accumulated discharge rates of the first and sixth nozzle N 1  and N 6 , respectively, may be higher than a difference between discharge rates of the adjacent first and second nozzles N 1  and N 2 , respectively. Such a discharge rate deviation between the first and sixth nozzles N 1  and N 6 , respectively, eventually generates a light emitting deviation which is easily perceived. 
     In order to decrease a deviation between nozzles, when a printhead H 2  including a first end and a second end sequentially prints a first area and a second area, locations of the printhead H 2  and the print object  1  may be adjusted in such a way that a surface printed by the second end in the first area and a surface printed by the second end by the second area face each other. 
       FIG. 2  is a conceptual schematic diagram illustrating the printhead switching from the first area to the second area according to a rectilinear movement and a rotary movement according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the printhead H 2  includes a first end where a first nozzle N 1  is located and a second end where a sixth nozzle N 6  is located. When the printhead H 2  sequentially prints the first area and the second area, the printhead H 2  may be rotated so that the surface printed by the second end, where the sixth nozzle N 6  is located, in the first area and the surface printed by the second end, where the sixth nozzle N 6  is located, in the second area face each other. 
     As shown in  FIG. 2 , the printhead H 2  may be rotated based on a predetermined point so that adjacent surfaces of the first and second areas are printed by the same nozzle. Here, a surface printed by the second end denotes a surface on the first or second area which is printed by the second end. Similarly, a surface printed by the first end denotes a surface on the first or second area which is printed by the first end. 
     The effect of printing adjacent surfaces by using the same nozzle as shown in  FIG. 2  will now be described with reference to  FIG. 3 . 
       FIG. 3  is a diagram comparing discharge rates in a cross-section taken along a line III-III of  FIG. 1  and a cross-section taken along a line III-III of  FIG. 2 . 
       FIG. 3  illustrates a first straight line I showing discharge rates of the nozzles N 1  thru N 6  of  FIG. 1  and a second straight line II showing discharge rates of the nozzles N 1  thru N 6  of  FIG. 2 . Here, it is assumed that the discharge rates of the first and sixth nozzles N 1  and N 6 , respectively, of the printhead H 1  or H 2  are different from each other by Δx. In addition, looking at the first straight line I, the difference between the discharge rates is Δx at each adjacent point A. 
     On the other hand, looking at the second straight line II, there is no difference between the discharge rates at each adjacent point B, and only a deviation Δn between adjacent nozzles gradually occurs. Accordingly, a printing method or a printer may use the printhead H 2  having the deviation Δn to reduce a deviation between nozzles on adjacent surfaces by printing the adjacent surfaces by using the same nozzle. 
     When a printhead including a first end and a second end sequentially prints a first area and a second area, a printing method according to an embodiment of the invention includes performing printing by adjusting locations of the printhead and a print object in such a way that a surface printed by the second end in the first area and a surface printed by the second end in the second area face each other, and this method will now be described with reference to  FIGS. 4  thru  6 . 
       FIG. 4  is a conceptual schematic diagram illustrating movement of a printhead on a print object when viewed from above according to a modified example of the embodiment of  FIG. 2 ,  FIG. 5  is a schematic perspective view illustrating a printer having the printhead moving with respect to the print object, and  FIG. 6  is a flowchart of movement of the printhead of  FIG. 5 . 
     Referring to  FIG. 4 , the printhead H 3  may sequentially include first thru sixth nozzles N 1  thru N 6 , respectively, arranged in a direction from a first end to a second end. Here, in operation S 110  of  FIG. 6 , the printhead H 3  may move in a direction opposite to a Y-axis direction while printing the first area. Then, the printhead H 3  may move along an X-axis direction in operation S 120 . Next, the printhead H 3  may rotate based on one point on the printhead H 3  as a central axis P 1  in operation S 130 . For example, the central axis P 1  may be the center of the printhead H 3 , as shown in  FIG. 4 . The printhead H 3 , which is rotated based on the central axis P 1 , may print the second area while moving in the Y-axis direction in operation S 140 . When the second area is printed as such, a deviation between the adjacent surfaces of the first and second areas due to different discharge rates is reduced since the adjacent surfaces are printed by the sixth nozzle N 6 . When the printhead H 3  passes through the print object  1  in the Y-axis direction after printing the second area, the printhead H 3  may move in the X-axis direction in operation S 150 . The printhead H 3  may then rotate based on the central axis in operation S 160 . 
     Next, operations S 110  thru S 160  of  FIG. 6  may be repeated so as to print the print object  1 . In other words, the printhead H 3  may print a third area while moving in the direction opposite to the Y-axis direction. Here, as shown in  FIG. 4 , adjacent surfaces of the second and third areas are printed by the first nozzle N 1 , and thus there is no deviation between nozzles in each area. Such a printing method may be performed by the printer  100  of  FIG. 5 , wherein the print object  1  is fixed, and the printhead H 3  moves along the X-axis or the Y-axis with respect to the print object  1  or rotates based on the central axis P 1 . However, the device for performing the printing method of  FIG. 4  is not limited to the printer  100 . 
     A modified example of the printer  100  will now be described with reference to  FIGS. 7 and 8 . 
       FIG. 7  is a schematic perspective view illustrating a printer which moves a print object in a straight line or rotates a printhead based on a central axis, and  FIG. 8  is a flowchart of movements of the print object and the printhead of  FIG. 7 . 
     The printer  200  of  FIG. 7  is configured to move the print object  1  in a straight line and rotate the printhead H 3  based on the central axis P 1 . In order to print a first area of the print object  1 , the print object  1  may move in a Y-axis direction in operation S 210 . Then, the print object  1  may move in a direction opposite to an X-axis direction in operation S 220 . Next, the printhead H 3  may rotate based on the central axis P 1  in operation S 230 . Then, the print object  1  may move in a direction opposite to the Y-axis direction while the printhead H 3  prints a second area in operation S 240 . Next, the print object  1  may move in a direction opposite to the X-axis direction so as to print a third area in operation S 250 . Then, the printhead H 3  may be rotated in operation S 260 . Operations S 210  thru S 260  of  FIG. 8  may be repeated to print the print object  1 . In other words, the printhead H 3  may print the third area while moving the print object  1  in the Y-axis direction. 
     The structure of the printer  100  or  200  and the printing method are not limited thereto. For example, the printer  100  may adjust a relative distance between the printhead H 3  and the print object  1  by fixing the printhead H 3  and moving the print object  1  in a straight line and rotating the print object  1  based on the central axis P 1 . Alternatively, the relative distance between the printhead H 3  and the print object  1  may be adjusted by moving the printhead H 3  and the print object  1  in a straight line and rotating the printhead H 3  and the print object  1  based on the central axis P 1 . Alternatively, the printer  100  may adjust a relative distance between the printhead H 3  and the print object  1  by fixing the printhead H 3  and moving the print object  1  along a direction perpendicular to printhead. 
     A control system for compensating for the location of the printhead H 3  by compensating a rotation angle θ of the printhead H 3  may be used to precisely adjust a relative distance between the printhead H 3  and the print object  1  while changing locations of the nozzles N 1  thru N 6  by rotating the printhead H 3 . Location compensation of the printhead H 3  will now be described with reference to  FIGS. 9 and 10 . 
       FIG. 9  is a schematic perspective view illustrating the printhead of  FIG. 5  for describing location compensation of the printhead, and  FIG. 10  is a flowchart of movement and location compensation of the printhead of  FIG. 9 . 
     When the location of the printhead H 3  switches from a first area to a second area with respect to the print object  1 , the control system controls a location of the printhead H 3  so as to start printing on the second area. Here, the current embodiment of the present invention is described in the situation where the printhead H 3  switches from the first area to the second area, but the invention is not limited thereto, and the printhead H 3  may switch to any adjacent area. Referring to  FIG. 9 , the printhead H 3  includes a vision camera C. Also, since an align mark M is marked on the print object  1  or a surrounding stage, the vision camera C may read the align mark M and adjust the rotation angle θ of the printhead H 3  so as to compensate for the location of the printhead H 3 . Accordingly, the control system may receive the location of the printhead H 3  with respect to the print object  1  (operations S 231  and S 261  of  FIG. 10 ), and compensate for the location of the printhead H 3  (operations S 232  and S 262 ). Since operations S 231  and S 232 , and operations S 261  and S 262 , are performed before moving the printhead H 3  along a Y-axis direction after rotating the printhead H 3 , operations S 231  and S 232 , and operations S 261  and S 262 , may be performed between rotation of the printhead H 3  and movement of the print object in the Y-axis direction, as illustrated in the flowchart of  FIG. 8 . In other words, referring to  FIG. 10 , in order to print the first area of the print object  1 , the print object  1  may move in a Y-axis direction in operation S 210 . Then, the print object  1  may move along a direction opposite to an X-axis direction in operation S 220 . Next, the printhead H 3  may be rotated based on a central axis P 1  in operation S 230 . Then, the location of the printhead H 3  with respect to the print object  1  may be received in operation S 231 . Next, the location of the printhead H 3  may be compensated for in operation S 232 . Then, the second area may be printed while moving the print object  1  in a direction opposite to the Y-axis direction in operation S 240 . Next, in order to print a third area, the print object  1  may be moved in the direction opposite to the X-axis direction in operation S 250 . Then, the printhead H 3  may be rotated in operation S 260 . Next, the location of the printhead H 3  with respect to the print object  1  may be received in operation S 261 . Then, the location of the printhead H 3  may be compensated for in operation S 262 . Next, operations S 210  thru S 262  of  FIG. 10  may be repeated so as to print the print object  1 . In other words, the third area may be printed while moving the print object  1  in the Y-axis direction. 
       FIGS. 11  thru  14  are various modified examples of  FIG. 2 . 
     In  FIGS. 11  thru  14 , a print object  1  is fixed and a print head H 4 , H 5 , H 6 , or H 7  is moved, but an embodiment of the present invention is not limited thereto, and at least one of the print object  1  and the print head H 4 , H 5 , H 6 , or H 7  may be moved. In other words, the print object  1  may move in a straight line and the print head H 4 , H 5 , H 6 , or H 7  may rotate based on the central axis P 1 , or both the print object  1  and the print head H 4 , H 5 , H 6 , or H 7  may move in a straight line and rotate based on the central axis P 1 . Also, when the print head H 4 , H 5 , H 6 , or H 7  or the print object  1  rotates, a location of the print head H 4 , H 5 , H 6 , or H 7  may be additionally compensated as described with reference to  FIGS. 9 and 10 . 
       FIG. 11  is a conceptual schematic diagram illustrating movement of the printhead on the print object when viewed from above according to another modified example of the embodiment of  FIG. 2 . 
     Referring to  FIG. 11 , the printhead H 4  includes first thru sixth nozzles N 1  thru N 6 , respectively, a first rotation axis P 2  on a first end of the printhead H 4  where the first nozzle N 1  is located, and a second rotation axis P 3  on a second end where the sixth nozzle N 6  is located. A first area may be printed while moving the printhead H 4  in a direction opposite to a Y-axis direction. Then, the printhead H 4  may be rotated based on the second rotation axis P 3 . Next, a second area may be printed while moving the printhead in the Y-axis direction. Then, the printhead H 4  may be rotated based on the first rotation axis P 2 . Next, a third area may be printed while moving the printhead H 4  in the direction opposite to the Y-axis. Such processes may be repeated so as to print the print object  1 . 
       FIG. 12  is a conceptual schematic diagram illustrating movement of the printhead on a print object when viewed from above according to another modified example of the embodiment of  FIG. 2 . 
     Referring to  FIG. 12 , the printhead H 5  includes first thru sixth nozzles N 1  through N 6 , respectively, and a first rotation axis P 2  on a first end of the printhead H 5  where the first nozzle N 1  is located. A first area may be printed while moving the printhead H 5  in a direction opposite to a Y-axis direction. Then, the printhead H 5  may be rotated based on the first rotation axis P 2 . Here, the printhead H 5  may rotate clockwise or counterclockwise. Next, the printhead H 5  may move in an X-axis direction. Then, a second area may be printed while moving the printhead H 5  in the Y-axis direction. Next, the printhead H 5  may again be rotated based on the first rotation axis P 2 . Here, the printhead H 5  may not move in the X-axis direction, and a third area may be printed while again moving the printhead H 5  in the direction opposite to the Y-axis direction. The print object  1  may be printed by repeating the above processes. The printhead H 4  of  FIG. 11  includes two rotation axes P 2  and P 3 , whereas the printhead H 5  of  FIG. 12  includes one rotation axis P 2  to change directions. 
       FIG. 13  is a conceptual schematic diagram illustrating movement of the printhead on the print object when viewed from above according to another example of the embodiment of  FIG. 2 . 
     Referring to  FIG. 13 , the printhead H 6  includes first thru sixth nozzles N 1  through N 6 , respectively, and a second rotation axis P 3  on a second end of the printhead H 6  where the sixth nozzle N 6  is located. A first area may be printed while moving the printhead H 6  in a direction opposite to a Y-axis direction. Then, the printhead H 6  may be rotated based on the second rotation axis P 3 . Next, a second area may be printed while moving the printhead H 6  in the Y-axis direction. Then, the printhead H 6  may be rotated again based on the second rotation axis P 3 . Next, the printhead H 6  may be moved in the X-axis direction so as to adjust alignment of the printhead H 6  and the print object  1 . Then, a third area may be printed while moving the printhead H 6  in the direction opposite to the Y-axis direction. The print object  1  may be printed by repeating the above processes. 
       FIG. 14  is a conceptual schematic diagram illustrating movement of the printhead on the print object when viewed from above according to another example of the embodiment of  FIG. 2 . 
       FIG. 14  shows that the printhead H 7  may tilt in any direction. For example, the printhead H 2  of  FIG. 2  may have a high right and a low left with respect to a moving direction, and the printhead H 7  of  FIG. 14  may have a low right and a high left with respect to a moving direction. 
     The print object  1  to be printed according to the printing methods and the printers  100  and  200  of  FIGS. 2  thru  14  is not limited, and any printable object may be used. For example, the print object  1  may be a substrate  10 , including a plurality of pixel regions PR. 
     A method of printing the substrate  10  will now be described with reference to  FIG. 15 . 
       FIG. 15  is a conceptual schematic diagram illustrating a plurality of printheads used to print red (R), green (G), and blue (B), respectively, on a print object when viewed from above according to the embodiment of  FIG. 2 . 
     The plurality of pixel regions PR may be formed in a matrix on the substrate  10 . A pixel pattern may be formed in the pixel region PR so as to display an image. For example, when the resolution of the substrate  10  is 1024×768, about 1024×768×3 pixel regions PR may be formed on the substrate  10 . Here, each pixel region PR may be filled with a light emitting material of R, G, or B. In addition, the printhead H 8  may spray the light emitting material of R. Also, the printhead H 9  may spray the light emitting material of G, and the printhead H 10  may spray the light emitting material of B. Here, the printheads H 8 , H 9 , and H 10  may form a color filter by respectively spraying an R color filter material, a G color filter material, and a B color filter material, wherein the R, G, and B color filter materials each emit a single color light by filtering a white light. 
     The printing method may be an inkjet printing method or a nozzle printing method. 
     According to the embodiments of the present invention, a light emitting deviation is reduced by reducing a deviation between nozzles during printing. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.