Patent Publication Number: US-7588306-B2

Title: Ink jet printing method and apparatus

Description:
This is a divisional of application Ser. No. 10/950,422, filed on Sep. 28, 2004, which is a divisional of application Ser. No. 10/214,109, filed on Aug. 8, 2002, now U.S. Pat. No. 6,866,358, issued on Mar. 15, 2005. 
    
    
     This application is based on Japanese Patent Application Nos. 2001-245030 filed Aug. 10, 2001 and 2002-225314 filed Aug. 1, 2002, the contents of which are incorporated hereinto by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink jet printing method and apparatus, and more specifically, to so called margin-less printing (hereinafter also referred as no edge blank printing), in which a printing medium such as a printing sheet is printed without forming any edge blank spaces on the printing medium. 
     2. Description of the Related Art 
     In an ink jet printing apparatus such as an ink jet printer, a platen is provided at an opposite portion to a printing head. The platen determines a positional relationship between a printing medium transported thereon and the printing head that ejects ink to the printing medium. For example, the platen has a plurality of platen ribs arranged on a top surface thereof in a scanning direction of the printing head. Supported on the tops of the platen ribs, the printing medium can be transported while maintaining a fixed distance from the printing head. 
     On the other hand, the ink jet printer can accomplish high-image-quality printing comparable to a silver salt photography. There correspondingly has been a growing demand for margin-less printing in which printing is carried out on the printing medium that is glossy like silver salt photographs. In recent years, ink jet printers having the corresponding functions for the margin-less printing have been provided. 
     When the ink jet printer is used for the margin-less printing, it is necessary that ink is essentially ejected also to an area extending out from an edge of the printing medium to prevent a blank space from occurring on an edge portion of the printing medium. That is, errors may occur while the printing medium is being transported or errors in the size of the printing medium may occur in connection with cutting accuracy. Accordingly, to allow for such errors, ink is generally ejected to an area extending out from the position of the edge of the transported printing medium (see  FIG. 11 ). 
     The ink ejected to the extending area is desirably corrected. For this purpose, for example, as shown in  FIG. 11 , a gap N 3004  is formed in the above described platen rib M 3003  so as to have a predetermined distance along a scanning range of the printing head, in a direction in which the printing medium is transported. An ink-absorbing member (not shown) is also provided at the bottom of the gap M 3003 . Further, an ink-absorbing member is provided on the platen at predetermined locations in a width direction of the printing medium corresponding to the scanning direction of the printing head, and over an area corresponding to a range within which ejection openings of the printing head are arranged. These arrangements for correcting ink enable ink ejected out from four edges of the printing medium to be corrected, thereby achieving margin-less printing to the printing medium. 
     However, when such no edge blank printing is executed notably at an edge area (including an area extending out from the edge of the printing medium in the direction in which it is transported and an area located inside this edge) located close to the edge of the printing medium, a large amount of ink mist may be generated, resulting in worse printing condition. The inventors have thus found that certain measures must be taken to reduce the amount of possible ink mist. 
     That is, when a normal area different from the edge area is printed, a distance between the printing medium, a target of ejected ink, and the printing head is relatively short, and then a distance over which the ejected ink flies is also short. Accordingly, a relatively small amount of ink mist may scatter or float without reaching the printing medium. However, when the edge area is printed, a distance between the ink-absorbing member, the target of ejected ink which is ejected out from the edge of the printing medium, and the printing head is relatively long, and then a distance over which the ejected ink flies is also long. Accordingly, a relatively large amount of ink mist may scatter or float without reaching the absorbing member. Thus, when the edge area is printed, certain measures must be taken to reduce the amount of mist. If no measures are taken for the mist, ink mist adhering to the printing medium or the platen ribs is likely to contaminate the printing medium. Further, ink mist adhering to rollers or gears is likely to disturb the normal operation of the rollers or gears. 
     SUMMARY OF THE INVENTION 
     The present invention is provided on the basis of attentions to the new technical problem, the need to reduce the amount of ink mist associated with the above described margin-less printing. It is an object of the present invention to provide an ink jet printing method and apparatus that can suppress the contamination of a printing medium or the like caused by ink or ink mist which may scatter or float inside the apparatus when margin-less printing is carried out. 
     It is another object of the present invention to provide a novel special printing method for the above-described margin-less printing. 
     In the first aspect of the present invention, there is provided an ink jet printing method of performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed for both areas of a first area of the printing medium which extends out from an edge thereof in a direction in which the printing medium is transported and a second area on the printing medium which is located inside the edge, the number of ejection openings used for one scanning operation is reduced compared to printing only for the second area. 
     In the second aspect of the present invention, there is provided an ink jet printing method of performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed for an edge area including an area located out of an edge of the printing medium in a direction in which the printing medium is transported and an area located inside the edge, the number of ejection openings used for one scanning operation is reduced compared to printing in an area on the printing medium which is other than the edge area. 
     In the third aspect of the present invention, there is provided an ink jet printing method of performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings through to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed for an edge area including an area located out of an edge of the printing medium in a direction in which the printing medium is transported and an area on the printing medium which is located inside the edge, an amount of ink ejected during one scanning operation is reduced compared to printing in an area on the printing medium which is other than the edge area. 
     In the fourth aspect of the present invention, there is provided an ink jet printing method of performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to cause the printing head to execute a plurality of times of scanning operation in the same area of the printing medium, 
     wherein a mask used to generate ejection data for each of the plurality of scanning operations, a total duty of the mask for the plurality of scanning operations being less than 100%, is used to generate ejection data for each scanning operation in an edge area including an edge of the printing medium in a direction in which the printing medium is transported and having a predetermined width, so that an amount of ink ejected to the edge area is reduced compared to an area on the printing medium which is other than the edge area. 
     In the fifth aspect of the present invention, there is provided an ink jet printing method of performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed in an edge area including an area located out of the printing medium in a direction in which the printing medium is transported and an area on the printing medium which is located inside the edge, the number of times of scanning operation by the printing head over a predetermined width along the transportation direction is reduced compared to printing in an area on the printing medium which is other than the edge area. 
     In the sixth aspect of the present invention, there is provided an ink jet printing method of performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to cause the printing head to execute a plurality of times of scanning operation in the same area of the printing medium, 
     wherein when printing is performed in an edge area including an area located out of the printing medium in a direction in which the printing medium is transported and an area on the printing medium which is located inside the edge, a mask used for generating ejection data for each of the plurality of times of scanning operation for the edge area is different from the mask used in a case of printing for an area on the printing medium which is other than the edge area. 
     In the seventh aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed for both areas of a first area of the printing medium which extends out from an edge thereof in a direction in which the printing medium is transported and a second area on the printing medium which is located inside the edge, the number of ejection openings used for one scanning operation is reduced compared to printing only for the second area. 
     In the eighth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed for an edge area including an area located out of an edge of the printing medium in a direction in which the printing medium is transported and an area located inside the edge, the number of ejection openings used for one scanning operation is reduced compared to printing in an area on the printing medium which is other than the edge area. 
     In the ninth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed for an edge area including an area located out of an edge of the printing medium in a direction in which the printing medium is transported and an area on the printing medium which is located inside the edge, an amount of ink ejected during one scanning operation is reduced compared to printing in an area on the printing medium which is other than the edge area. 
     In the tenth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to cause the printing head to execute a plurality of times of scanning operation in the same area of the printing medium, 
     wherein a mask used to generate ejection data for each of the plurality of scanning operations, a total duty of the mask for the plurality of scanning operations being less than 100%, is used to generate ejection data for each scanning operation in an edge area including an edge of the printing medium in a direction in which the printing medium is transported and having a predetermined width, so that an amount of ink ejected to the edge area is reduced compared to an area on the printing medium which is other than the edge area. 
     In the eleventh aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to eject ink from the printing head to the printing medium, 
     wherein when printing is performed in an edge area including an area located out of the printing medium in a direction in which the printing medium is transported and an area on the printing medium which is located inside the edge, the number of times of scanning operation by the printing head over a predetermined width along the transportation direction is reduced compared to printing in an area on the printing medium which is other than the edge area. 
     In the twelfth aspect of the present invention, there is provided an ink jet printing apparatus for performing printing by repeating an operation of scanning a printing head having a plurality of ink ejection openings to a printing medium and an operation of transporting the printing medium, so as to cause the printing head to execute a plurality of times of scanning operation in the same area of the printing medium, 
     wherein when printing is performed in an edge area including an area located out of the printing medium in a direction in which the printing medium is transported and an area on the printing medium which is located inside the edge, a mask used for generating ejection data for each of the plurality of times of scanning operation for the edge area is different from the mask used in a case of printing for an area on the printing medium which is other than the edge area. 
     With the above configuration, when printing is carried out so as to leave no blank at a narrow portion adjoining an edge of a printing medium in a direction in which it is transported (what is called margin-less printing), in the case of printing is carried out both in a first area of the printing medium which extends out from the edge thereof in the transportation direction and a second area on the printing medium which is located inside the edge, the number of ejection openings used for one scanning operation is reduced compared to printing only in the second area. This reduces the amount of ink ejected to the first area, which extends out from the edge, thereby reducing the amount of scattering ink or floating ink mist. 
     Further, in another aspect of the present invention, for margin-less printing, when an edge area of a predetermined width including the edge of the printing medium in its transportation direction is printed, the amount of ink is reduced compared to printing in an area on the printing medium which is other than the edge area. This reduces the amount of ink ejected out from the printing medium for the edge area, and then the amount of scattering ink or floating ink mist can be reduced. 
     Furthermore, in another aspect of the present invention, the number of scanning operations performed by the printing head over a predetermined width in the transportation direction is reduced compared to an area other than the edge area. This reduces the time for which mist generated while the printing medium remains in the edge area adheres to the printing medium. In yet another aspect of the present invention, a mask used to generate ejection data for each of the plurality of scanning operations for printing the edge area is differentiated from a mask for an area other than the edge area so that a minimum mask unit of the mask for the edge area is greater than that of the mask for the area other than the edge area. Consequently, ink ejected out from the printing medium for the edge area becomes a fixed mass. This reduces the amount of scattering ink or floating mist. 
     The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an external construction of an ink jet printer as one embodiment of the present invention; 
         FIG. 2  is a perspective view showing the printer of  FIG. 1  with an enclosure member removed; 
         FIG. 3  is a perspective view showing an assembled print head cartridge used in the printer of one embodiment of the present invention; 
         FIG. 4  is an exploded perspective view showing the print head cartridge of  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of the print head of  FIG. 4  as seen diagonally below; 
         FIGS. 6A and 6B  are perspective views showing a construction of a scanner cartridge upside down which can be mounted in the printer of one embodiment of the present invention instead of the print head cartridge of  FIG. 3 ; 
         FIG. 7  is a block diagram schematically showing the overall configuration of an electric circuitry of the printer according to one embodiment of the present invention; 
         FIG. 8  is a diagram showing the relation between  FIGS. 8A and 8B ,  FIGS. 8A and 8B  being block diagrams representing an example inner configuration of a main printed circuit board (PCB) in the electric circuitry of  FIG. 7 ; 
         FIG. 9  is a diagram showing the relation between  FIGS. 9A and 9B ,  FIGS. 9A and 9B  being block diagrams representing an example inner configuration of an application specific integrated circuit (ASIC) in the main PCB of  FIGS. 8A and 8B ; 
         FIG. 10  is a flow chart showing an example of operation of the printer as one embodiment of the present invention; 
         FIG. 11  is a diagram showing a gap formed in a printing medium transportation path in an ink jet printer according to an embodiment of the present invention and more specifically formed in a platen rib; 
         FIG. 12  is a diagram illustrating a printing method according to a first embodiment of the present invention; 
         FIG. 13  is a diagram illustrating a printing method according to a second embodiment of the present invention; 
         FIGS. 14A-14D  are diagrams showing a relationship between the number of passes for multi-pass printing and the number of scanning operations (time) when an edge area is printed, according to the second embodiment; 
         FIG. 15  is a diagram illustrating a printing method according to a third embodiment of the present invention; 
         FIGS. 16A and 16B  are diagrams schematically showing masks used in an area other than the edge area according to the third embodiment; 
         FIG. 17  is a diagram schematically showing a mask used for the edge area according to the third embodiment; and 
         FIG. 18  is a diagram illustrating printing methods according to a fifth and sixth embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described by referring to the accompanying drawings. 
     At first, an ink jet printer as an embodiment of a ink jet printing apparatus according to the present invention, by referring to  FIGS. 1-10 . 
     In this specification, a word “print” refers to not only forming significant information, such as characters and figures, but also forming images, designs or patterns on printing medium and processing media, whether the information is significant or insignificant or whether it is visible so as to be perceived by humans. 
     The word “printing medium” include not only a paper used in common printing apparatus, but a cloth, plastic films, metal plates, glass, ceramics, wood, leather or any other material that can receive ink. 
     Further, the word “ink” should be interpreted in its wide sense as with the word “print” and refers to liquid that is applied to the printing medium to form images, designs or patterns, process the printing medium or process ink (for example, coagulate or make insoluble a colorant in the ink applied to the printing medium). 
     [Apparatus Body] 
       FIGS. 1 and 2  show an outline construction of a printer using an ink jet printing system. In  FIG. 1 , a housing of a printer body M 1000  of this embodiment has an enclosure member, including a lower case M 1001 , an upper case M 1002 , an access cover M 1003  and a discharge tray M 1004 , and a chassis M 3019  (see  FIG. 2 ) accommodated in the enclosure member. 
     The chassis M 3019  is made of a plurality of plate-like metal members with a predetermined rigidity to form a skeleton of the printing apparatus and holds various printing operation mechanisms described later. 
     The lower case M 1001  forms roughly a lower half of the housing of the printer body M 1000  and the upper case M 1002  forms roughly an upper half of the printer body M 1000 . These upper and lower cases, when combined, form a hollow structure having an accommodation space therein to accommodate various mechanisms described later. The printer body M 1000  has an opening in its top portion and front portion. 
     The discharge tray M 1004  has one end portion thereof rotatably supported on the lower case M 1001 . The discharge tray M 1004 , when rotated, opens or closes an opening formed in the front portion of the lower case M 1001 . When the print operation is to be performed, the discharge tray M 1004  is rotated forwardly to open the opening so that printed sheets can be discharged and successively stacked. The discharge tray M 1004  accommodates two auxiliary trays M 1004   a , M 1004   b . These auxiliary trays can be drawn out forwardly as required to expand or reduce the paper support area in three steps. 
     The access cover M 1003  has one end portion thereof rotatably supported on the upper case M 1002  and opens or closes an opening formed in the upper surface of the upper case M 1002 . By opening the access cover M 1003 , a print head cartridge H 1000  or an ink tank H 1900  installed in the body can be replaced. When the access cover M 1003  is opened or closed, a projection formed at the back of the access cover, not shown here, pivots a cover open/close lever. Detecting the pivotal position of the lever as by a micro-switch and so on can determine whether the access cover is open or closed. 
     At the upper rear surface of the upper case M 1002  a power key E 0018 , a resume key E 0019  and an LED E 0020  are provided. When the power key E 0018  is pressed, the LED E 0020  lights up indicating to an operator that the apparatus is ready to print. The LED E 0020  has a variety of display functions, such as alerting the operator to printer troubles as by changing its blinking intervals and color. Further, a buzzer E 0021  ( FIG. 7 ) may be sounded. When the trouble is eliminated, the resume key E 0019  is pressed to resume the printing. 
     [Printing Operation Mechanism] 
     Next, a printing operation mechanism installed and held in the printer body M 1000  according to this embodiment will be explained. 
     The printing operation mechanism in this embodiment comprises: an automatic sheet feed unit M 3022  to automatically feed a print sheet into the printer body; a sheet transport unit M 3029  to guide the print sheets, fed one at a time from the automatic sheet feed unit, to a predetermined print position and to guide the print sheet from the print position to a discharge unit M 3030 ; a print unit to perform a desired printing on the print sheet carried to the print position; and an ejection performance recovery unit M 5000  to recover the ink ejection performance of the print unit. 
     (Printing Unit) 
     Here, the print unit will be described. The print unit comprises a carriage M 4001  movably supported on a carriage shaft M 4021  and a print head cartridge H 1000  removably mounted on the carriage M 4001 . 
     [Print Head Cartridge] 
     First, the print head cartridge used in the print unit will be described with reference to  FIGS. 3 to 5 . 
     The print head cartridge H 1000  in this embodiment, as shown in  FIG. 3 , has an ink tank H 1900  containing inks and a print head H 1001  for ejecting ink supplied from the ink tank H 1900  out through nozzles according to print information. The print head H 1001  is of a so-called cartridge type in which it is removably mounted to the carriage M 4001  described later. 
     The ink tank for this print head cartridge H 1000  consists of separate ink tanks H 1900  of, for example, black, light cyan, light magenta, cyan, magenta and yellow to enable color printing with as high an image quality as photograph. As shown in  FIG. 4 , these individual ink tanks are removably mounted to the print head H 1001 . 
     Then, the print head H 1001 , as shown in the perspective view of  FIG. 5 , comprises a print element substrate H 1100 , a first plate H 1200 , an electric wiring board H 1300 , a second plate H 1400 , a tank holder H 1500 , a flow passage forming member H 1600 , a filter H 1700  and a seal rubber H 1800 . 
     The print element substrate H 1100  has formed in one of its surfaces, by the film deposition technology, a plurality of print elements to produce energy for ejecting ink and electric wires, such as aluminum, for supplying electricity to individual print elements. A plurality of ink passages and a plurality of nozzles H 1100 T, both corresponding to the print elements, are also formed by the photolithography technology. In the back of the print element substrate H 1100 , there are formed ink supply ports for supplying ink to the plurality of ink passages. The print element substrate H 1100  is securely bonded to the first plate H 1200  which is formed with ink supply ports H 1201  for supplying ink to the print element substrate H 1100 . The first plate H 1200  is securely bonded with the second plate H 1400  having an opening. The second plate H 1400  holds the electric wiring board H 1300  to electrically connect the electric wiring board H 1300  with the print element substrate H 1100 . The electric wiring board H 1300  is to apply electric signals for ejecting ink to the print element substrate H 1100 , and has electric wires associated with the print element substrate H 1100  and external signal input terminals H 1301  situated at electric wires&#39; ends for receiving electric signals from the printer body. The external signal input terminals H 1301  are positioned and fixed at the back of a tank holder H 1500  described later. 
     The tank holder H 1500  that removably holds the ink tank H 1900  is securely attached, as by ultrasonic fusing, with the flow passage forming member H 1600  to form an ink passage H 1501  from the ink tank H 1900  to the first plate H 1200 . At the ink tank side end of the ink passage H 1501  that engages with the ink tank H 1900 , a filter H 1700  is provided to prevent external dust from entering. A seal rubber H 1800  is provided at a portion where the filter H 1700  engages the ink tank H 1900 , to prevent evaporation of the ink from the engagement portion. 
     As described above, the tank holder unit, which includes the tank holder H 1500 , the flow passage forming member H 1600 , the filter H 1700  and the seal rubber H 1800 , and the print element unit, which includes the print element substrate H 1100 , the first plate H 1200 , the electric wiring board H 1300  and the second plate H 1400 , are combined as by adhesives to form the print head H 1001 . 
     [Carriage] 
     Next, by referring to  FIG. 2 , the carriage M 4001  carrying the print head cartridge H 1000  will be explained. 
     As shown in  FIG. 2 , the carriage M 4001  has a carriage cover M 4002  for guiding the print head H 1001  to a predetermined mounting position on the carriage M 4001 , and a head set lever M 4007  that engages and presses against the tank holder H 1500  of the print head H 1001  to set the print head H 1001  at a predetermined mounting position. 
     That is, the head set lever M 4007  is provided at the upper part of the carriage M 4001  so as to be pivotable about a head set lever shaft. There is a spring-loaded head set plate (not shown) at an engagement portion where the carriage M 4001  engages the print head H 1001 . With the spring force, the head set lever M 4007  presses against the print head H 1001  to mount it on the carriage M 4001 . 
     At another engagement portion of the carriage M 4001  with the print head H 1001 , there is provided a contact flexible printed cable (see  FIG. 7 : simply referred to as a contact FPC hereinafter) E 0011  whose contact portion electrically contacts a contact portion (external signal input terminals) H 1301  provided in the print head H 1001  to transfer various information for printing and supply electricity to the print head H 1001 . 
     Between the contract portion of the contact FPC E 0011  and the carriage M 4001  there is an elastic member not shown, such as rubber. The elastic force of the elastic member and the pressing force of the head set lever spring combine to ensure a reliable contact between the contact portion of the contact FPC E 0011  and the carriage M 4001 . Further, the contact FPC E 0011  is connected to a carriage substrate E 0013  mounted at the back of the carriage M 4001  (see  FIG. 7 ). 
     [Scanner] 
     The printer of this embodiment can mount a scanner in the carriage M 4001  in place of the print head cartridge H 1000  and be used as a reading device. 
     The scanner moves together with the carriage M 4001  in the main scan direction, and reads an image on a document fed instead of the printing medium as the scanner moves in the main scan direction. Alternating the scanner reading operation in the main scan direction and the document feed in the sub-scan direction enables one page of document image information to be read. 
       FIGS. 6A and 6B  show the scanner M 6000  upside down to explain about its outline construction. 
     As shown in the figure, a scanner holder M 6001  is shaped like a box and contains an optical system and a processing circuit necessary for reading. A reading lens M 6006  is provided at a portion that faces the surface of a document when the scanner M 6000  is mounted on the carriage M 4001 . The lens M 6006  focuses light reflected from the document surface onto a reading unit inside the scanner to read the document image. An illumination lens M 6005  has a light source not shown inside the scanner. The light emitted from the light source is radiated onto the document through the lens M 6005 . 
     The scanner cover M 6003  secured to the bottom of the scanner holder M 6001  shields the interior of the scanner holder M 6001  from light. Louver-like grip portions are provided at the sides to improve the ease with which the scanner can be mounted to and dismounted from the carriage M 4001 . The external shape of the scanner holder M 6001  is almost similar to that of the print head H 1001 , and the scanner can be mounted to or dismounted from the carriage M 4001  in a manner similar to that of the print head H 1001 . 
     The scanner holder M 6001  accommodates a substrate having a reading circuit, and a scanner contact PCB M 6004  connected to this substrate is exposed outside. When the scanner M 6000  is mounted on the carriage M 4001 , the scanner contact PCB M 6004  contacts the contact FPC E 0011  of the carriage M 4001  to electrically connect the substrate to a control system on the printer body side through the carriage M 4001 . 
     [Configuration of Printer Electric Circuit] 
     Next, an electric circuit configuration in this embodiment of the invention will be explained. 
       FIG. 7  schematically shows the overall configuration of the electric circuit in this embodiment. 
     The electric circuit in this embodiment comprises mainly a carriage substrate (CRPCB) E 0013 , a main PCB (printed circuit board) E 0014  and a power supply unit E 0015 . 
     The power supply unit E 0015  is connected to the main PCB E 0014  to supply a variety of drive power. 
     The carriage substrate E 0013  is a printed circuit board unit mounted on the carriage M 4001  ( FIG. 2 ) and functions as an interface for transferring signals to and from the print head through the contact FPC E 0011 . In addition, based on a pulse signal output from an encoder sensor E 0004  as the carriage M 4001  moves, the carriage substrate E 0013  detects a change in the positional relation between an encoder scale E 0005  and the encoder sensor E 0004  and sends its output signal to the main PCB E 0014  through a flexible flat cable (CRFFC) E 0012 . 
     Further, the main PCB E 0014  is a printed circuit board unit that controls the operation of various parts of the ink jet printing apparatus in this embodiment, and has I/O ports for a paper end sensor (PE sensor) E 0007 , an automatic sheet feeder (ASF) sensor E 0009 , a cover sensor E 0022 , a parallel interface (parallel I/F) E 0016 , a serial interface (Serial I/F) E 0017 , a resume key E 0019 , an LED E 0020 , a power key E 0018  and a buzzer E 0021 . The main PCB E 0014  is connected to and controls a motor (CR motor) E 0001  that constitutes a drive source for moving the carriage M 4001  in the main scan direction; a motor (LF motor) E 0002  that constitutes a drive source for transporting the printing medium; and a motor (PG motor) E 0003  that performs the functions of recovering the ejection performance of the print head and feeding the printing medium. The main PCB E 0014  also has connection interfaces with an ink empty sensor E 0006 , a gap sensor E 0008 , a PG sensor E 0010 , the CRFFC E 0012  and the power supply unit E 0015 . 
       FIG. 8  is a diagram showing the relation between  FIGS. 8A and 8B , and  FIGS. 8A and 8B  are block diagrams showing an inner configuration of the main PCB E 0014 . Reference number E 1001  represents a CPU, which has a clock generator (CG) E 1002  connected to an oscillation circuit E 1005  to generate a system clock based on an output signal E 1019  of the oscillation circuit E 1005 . The CPU E 1001  is connected to an ASIC (application specific integrated circuit) and a ROM E 1004  through a control bus E 1014 . According to a program stored in the ROM E 1004 , the CPU E 1001  controls the ASIC E 1006 , checks the status of an input signal E 1017  from the power key, an input signal E 1016  from the resume key, a cover detection signal E 1042  and a head detection signal (HSENS) E 1013 , drives the buzzer E 0021  according to a buzzer signal (BUZ) E 1018 , and checks the status of an ink empty detection signal (INKS) E 1011  connected to a built-in A/D converter E 1003  and of a temperature detection signal (TH) E 1012  from a thermistor. The CPU E 1001  also performs various other logic operations and makes conditional decisions to control the operation of the ink jet printing apparatus. 
     The head detection signal E 1013  is a head mount detection signal entered from the print head cartridge H 1000  through the flexible flat cable E 0012 , the carriage substrate E 0013  and the contact FPC E 0011 . The ink empty detection signal E 1011  is an analog signal output from the ink empty sensor E 0006 . The temperature detection signal E 1012  is an analog signal from the thermistor (not shown) provided on the carriage substrate E 0013 . 
     Designated E 1008  is a CR motor driver that uses a motor power supply (VM) E 1040  to generate a CR motor drive signal E 1037  according to a CR motor control signal E 1036  from the ASIC E 1006  to drive the CR motor E 0001 . E 1009  designates an LF/PG motor driver which uses the motor power supply E 1040  to generate an LF motor drive signal E 1035  according to a pulse motor control signal (PM control signal) E 1033  from the ASIC E 1006  to drive the LF motor. The LF/PG motor driver E 1009  also generates a PG motor drive signal E 1034  to drive the PG motor. 
     Designated E 1010  is a power supply control circuit which controls the supply of electricity to respective sensors with light emitting elements according to a power supply control signal E 1024  from the ASIC E 1006 . The parallel I/F E 0016  transfers a parallel I/F signal E 1030  from the ASIC E 1006  to a parallel I/F cable E 1031  connected to external circuits and also transfers a signal of the parallel I/F cable E 1031  to the ASIC E 1006 . The serial I/F E 0017  transfers a serial I/F signal E 1028  from the ASIC E 1006  to a serial I/F cable E 1029  connected to external circuits, and also transfers a signal from the serial I/F cable E 1029  to the ASIC E 1006 . 
     The power supply unit E 0015  provides a head power signal (VH) E 1039 , a motor power signal (VM) E 1040  and a logic power signal (VDD) E 1041 . A head power ON signal (VHON) E 1022  and a motor power ON signal (VMON) E 1023  are sent from the ASIC E 1006  to the power supply unit E 0015  to perform the ON/OFF control of the head power signal E 1039  and the motor power signal E 1040 . The logic power signal (VDD) E 1041  supplied from the power supply unit E 0015  is voltage-converted as required and given to various parts inside or outside the main PCB E 0014 . 
     The head power signal E 1039  is smoothed by a circuit of the main PCB E 0014  and then sent out to the flexible flat cable E 0011  to be used for driving the print head cartridge H 1000 . 
     E 1007  denotes a reset circuit which detects a reduction in the logic power signal E 1041  and sends a reset signal (RESET) to the CPU E 1001  and the ASIC E 1006  to initialize them. 
     The ASIC E 1006  is a single-chip semiconductor integrated circuit and is controlled by the CPU E 1001  through the control bus E 1014  to output the CR motor control signal E 1036 , the PM control signal E 1033 , the power supply control signal E 1024 , the head power ON signal E 1022  and the motor power ON signal E 1023 . It also transfers signals to and from the parallel interface E 0016  and the serial interface E 0017 . In addition, the ASIC E 1006  detects the status of a PE detection signal (PES) E 1025  from the PE sensor E 0007 , an ASF detection signal (ASFS) E 1026  from the ASF sensor E 0009 , a gap detection signal (GAPS) E 1027  from the GAP sensor E 0008  for detecting a gap between the print head and the printing medium, and a PG detection signal (PGS) E 1032  from the PG sensor E 0010 , and sends data representing the statuses of these signals to the CPU E 1001  through the control bus E 1014 . Based on the data received, the CPU E 1001  controls the operation of an LED drive signal E 1038  to turn on or off the LED E 0020 . 
     Further, the ASIC E 1006  checks the status of an encoder signal (ENC) E 1020 , generates a timing signal, interfaces with the print head cartridge H 1600  and controls the print operation by a head control signal E 1021 . The encoder signal (ENC) E 1020  is an output signal of the CR encoder sensor E 0004  received through the flexible flat cable E 0012 . The head control signal E 1021  is sent to the print head H 1001  through the flexible flat cable E 0012 , carriage substrate E 0013  and contact FPC E 0011 . 
       FIG. 9  is a diagram showing the relation between  FIGS. 9A and 9B , and  FIGS. 9A and 9B  are block diagrams showing an example internal configuration of the ASIC E 1006 . 
     In these figures, only the flow of data, such as print data and motor control data, associated with the control of the head and various mechanical components is shown between each block, and control signals and clock associated with the read/write operation of the registers incorporated in each block and control signals associated with the DMA control are omitted to simplify the drawing. 
     In the figures, reference number E 2002  represents a PLL controller which, based on a clock signal (CLK) E 2031  and a PLL control signal (PLLON) E 2033  output from the CPU E 1001 , generates a clock (not shown) to be supplied to the most part of the ASIC E 1006 . 
     Denoted E 2001  is a CPU interface (CPU I/F) E 2001 , which controls the read/write operation of register in each block, supplies a clock to some blocks and accepts an interrupt signal (none of these operations are shown) according to a reset signal E 1015 , a software reset signal (PDWN) E 2032  and a clock signal (CLK) E 2031  output from the CPU E 1001 , and control signals from the control bus E 1014 . The CPU I/F E 2001  then outputs an interrupt signal (INT) E 2034  to the CPU E 1001  to inform it of the occurrence of an interrupt within the ASIC E 1006 . 
     E 2005  denotes a DRAM which has various areas for storing print data, such as a reception buffer E 2010 , a work buffer E 2011 , a print buffer E 2014  and a development data buffer E 2016 . The DRAM E 2005  also has a motor control buffer E 2023  for motor control and, as buffers used instead of the above print data buffers during the scanner operation mode, a scanner input buffer E 2024 , a scanner data buffer E 2026  and an output buffer E 2028 . 
     The DRAM E 2005  is also used as a work area by the CPU E 1001  for its own operation. Designated E 2004  is a DRAM control unit E 2004  which performs read/write operations on the DRAM E 2005  by switching between the DRAM access from the CPU E 1001  through the control bus and the DRAM access from a DMA control unit E 2003  described later. 
     The DMA control unit E 2003  accepts request signals (not shown) from various blocks and outputs address signals and control signals (not shown) and, in the case of write operation, write data E 2038 , E 2041 , E 2044 , E 2053 , E 2055 , E 2057  etc. to the DRAM control unit to make DRAM accesses. In the case of read operation, the DMA control unit E 2003  transfers the read data E 2040 , E 2043 , E 2045 , E 2051 , E 2054 , E 2056 , E 2058 , E 2059  from the DRAM control unit E 2004  to the requesting blocks. 
     Denoted E 2006  is an IEEE 1284 I/F which functions as a bi-directional communication interface with external host devices, not shown, through the parallel I/F E 0016  and is controlled by the CPU E 1001  via CPU I/F E 2001 . During the printing operation, the IEEE 1284 I/F E 2006  transfers the receive data (PIF receive data E 2036 ) from the parallel I/F E 0016  to a reception control unit E 2008  by the DMA processing. During the scanner reading operation, the  1284  I/F E 2006  sends the data ( 1284  transmit data (RDPIF) E 2059 ) stored in the output buffer E 2028  in the DRAM E 2005  to the parallel I/F E 0016  by the DMA processing. 
     Designated E 2007  is a universal serial bus (USB) I/F which offers a bi-directional communication interface with external host devices, not shown, through the serial I/F E 0017  and is controlled by the CPU E 1001  through the CPU I/F E 2001 . During the printing operation, the universal serial bus (USB) I/F E 2007  transfers received data (USB receive data E 2037 ) from the serial I/F E 0017  to the reception control unit E 2008  by the DMA processing. During the scanner reading, the universal serial bus (USB) I/F E 2007  sends data (USB transmit data (RDUSB) E 2058 ) stored in the output buffer E 2028  in the DRAM E 2005  to the serial I/F E 0017  by the DMA processing. The reception control unit E 2008  writes data (WDIF E 2038 ) received from the  1284  I/F E 2006  or universal serial bus (USB) I/F E 2007 , whichever is selected, into a reception buffer write address managed by a reception buffer control unit E 2039 . 
     Designated E 2009  is a compression/decompression DMA controller which is controlled by the CPU E 1001  through the CPU I/F E 2001  to read received data (raster data) stored in a reception buffer E 2010  from a reception buffer read address managed by the reception buffer control unit E 2039 , compress or decompress the data (RDWK) E 2040  according to a specified mode, and write the data as a print code string (WDWK) E 2041  into the work buffer area. 
     Designated E 2013  is a print buffer transfer DMA controller which is controlled by the CPU E 1001  through the CPU I/F E 2001  to read print codes (RDWP) E 2043  on the work buffer E 2011  and rearrange the print codes onto addresses on the print buffer E 2014  that match the sequence of data transfer to the print head cartridge H 1000  before transferring the codes (WDWP E 2044 ). Reference number E 2012  denotes a work area DMA controller which is controlled by the CPU E 1001  through the CPU I/F E 2001  to repetitively write specified work fill data (WDWF) E 2042  into the area of the work buffer whose data transfer by the print buffer transfer DMA controller E 2013  has been completed. 
     Designated E 2015  is a print data development DMA controller E 2015 , which is controlled by the CPU E 1001  through the CPU I/F E 2001 . Triggered by a data development timing signal E 2050  from a head control unit E 2018 , the print data development DMA controller E 2015  reads the print code that was rearranged and written into the print buffer and the development data written into the development data buffer E 2016  and writes developed print data (RDHDG) E 2045  into the column buffer E 2017  as column buffer write data (WDHDG) E 2047 . The column buffer E 2017  is an SRAM that temporarily stores the transfer data (developed print data) to be sent to the print head cartridge H 1000 , and is shared and managed by both the print data development DMA CONTROLLER and the head control unit through a handshake signal (not shown). 
     Designated E 2018  is a head control unit E 2018  which is controlled by the CPU E 1001  through the CPU I/F E 2001  to interface with the print head cartridge H 1000  or the scanner through the head control signal. It also outputs a data development timing signal E 2050  to the print data development DMA controller according to a head drive timing signal E 2049  from the encoder signal processing unit E 2019 . 
     During the printing operation, the head control unit E 2018 , when it receives the head drive timing signal E 2049 , reads developed print data (RDHD) E 2048  from the column buffer and outputs the data to the print head cartridge H 1000  as the head control signal E 1021 . 
     In the scanner reading mode, the head control unit E 2018  DMA-transfers the input data (WDHD) E 2053  received as the head control signal E 1021  to the scanner input buffer E 2024  on the DRAM E 2005 . Designated E 2025  is a scanner data processing DMA controller E 2025  which is controlled by the CPU E 1001  through the CPU I/F E 2001  to read input buffer read data (RDAV) E 2054  stored in the scanner input buffer E 2024  and writes the averaged data (WDAV) E 2055  into the scanner data buffer E 2026  on the DRAM E 2005 . 
     Designated E 2027  is a scanner data compression DMA controller which is controlled by the CPU E 1001  through the CPU I/F E 2001  to read processed data (RDYC) E 2056  on the scanner data buffer E 2026 , perform data compression, and write the compressed data (WDYC) E 2057  into the output buffer E 2028  for transfer. 
     Designated E 2019  is an encoder signal processing unit which, when it receives an encoder signal (ENC), outputs the head drive timing signal E 2049  according to a mode determined by the CPU E 1001 . The encoder signal processing unit E 2019  also stores in a register information on the position and speed of the carriage M 4001  obtained from the encoder signal E 1020  and presents it to the CPU E 1001 . Based on this information, the CPU E 1001  determines various parameters for the CR motor E 0001 . Designated E 2020  is a CR motor control unit which is controlled by the CPU E 1001  through the CPU I/F E 2001  to output the CR motor control signal E 1036 . 
     Denoted E 2022  is a sensor signal processing unit which receives detection signals E 1032 , E 1025 , E 1026  and E 1027  output from the PG sensor E 0010 , the PE sensor E 0007 , the ASF sensor E 0009  and the gap sensor E 0008 , respectively, and transfers these sensor information to the CPU E 1001  according to the mode determined by the CPU E 1001 . The sensor signal processing unit E 2022  also outputs a sensor detection signal E 2052  to a DMA controller E 2021  for controlling LF/PG motor. 
     The DMA controller E 2021  for controlling LF/PG motor is controlled by the CPU E 1001  through the CPU I/F E 2001  to read a pulse motor drive table (RDPM) E 2051  from the motor control buffer E 2023  on the DRAM E 2005  and output a pulse motor control signal E 1033 . Depending on the operation mode, the controller outputs the pulse motor control signal E 1033  upon reception of the sensor detection signal as a control trigger. 
     Designated E 2030  is an LED control unit which is controlled by the CPU E 1001  through the CPU I/F E 2001  to output an LED drive signal E 1038 . Further, designated E 2029  is a port control unit which is controlled by the CPU E 1001  through the CPU I/F E 2001  to output the head power ON signal E 1022 , the motor power ON signal E 1023  and the power supply control signal E 1024 . 
     [Operation of Printer] 
     Next, the operation of the ink jet printing apparatus in this embodiment of the invention with the above configuration will be explained by referring to the flow chart of  FIG. 10 . 
     When the printer body M 1000  is connected to an AC power supply, a first initialization is performed at step S 1 . In this initialization process, the electric circuit system including the ROM and RAM in the apparatus is checked to confirm that the apparatus is electrically operable. 
     Next, step S 2  checks if the power key E 0018  on the upper case M 1002  of the printer body M 1000  is turned on. When it is decided that the power key E 0018  is pressed, the processing moves to the next step S 3  where a second initialization is performed. 
     In this second initialization, a check is made of various drive mechanisms and the print head of this apparatus. That is, when various motors are initialized and head information is read, it is checked whether the apparatus is normally operable. 
     Next, steps S 4  waits for an event. That is, this step monitors a demand event from the external I/F, a panel key event from the user operation and an internal control event and, when any of these events occurs, executes the corresponding processing. 
     When, for example, step S 4  receives a print command event from the external I/F, the processing moves to step S 5 . When a power key event from the user operation occurs at step S 4 , the processing moves to step S 10 . If another event occurs, the processing moves to step S 11 . 
     Step S 5  analyzes the print command from the external I/F, checks a specified paper kind, paper size, print quality, paper feeding method and others, and stores data representing the check result into the DRAM E 2005  of the apparatus before proceeding to step S 6 . 
     Next, step S 6  starts feeding the paper according to the paper feeding method specified by the step S 5  until the paper is situated at the print start position. The processing moves to step S 7 . 
     At step S 7  the printing operation is performed. In this printing operation, the print data sent from the external I/F is stored temporarily in the print buffer. Then, the CR motor E 0001  is started to move the carriage M 4001  in the main-scanning direction. At the same time, the print data stored in the print buffer E 2014  is transferred to the print head H 1001  to print one line. When one line of the print data has been printed, the LF motor E 0002  is driven to rotate the LF roller M 3001  to transport the paper in the sub-scanning direction. After this, the above operation is executed repetitively until one page of the print data from the external I/F is completely printed, at which time the processing moves to step S 8 . 
     Processing for print data with suppressing the number of used ejection openings and processing of generating print data with a mask process, for printing an edge area of a printing medium, are executed by a printer driver in a host apparatus through an outer interface and control processing for transporting the printing medium with suppressing the number of the ejection openings is executed by printing control in step S 7 . These processing will be explained referring to  FIG. 12  and succeeding drawings as the embodiments of the present invention. 
     At step S 8 , the LF motor E 0002  is driven to rotate the paper discharge roller M 2003  to feed the paper until it is decided that the paper is completely fed out of the apparatus, at which time the paper is completely discharged onto the paper discharge tray M 1004 . 
     Next at step S 9 , it is checked whether all the pages that need to be printed have been printed and if there are pages that remain to be printed, the processing returns to step S 5  and the steps S 5  to S 9  are repeated. When all the pages that need to be printed have been printed, the print operation is ended and the processing moves to step S 4  waiting for the next event. 
     Step S 10  performs the printing termination processing to stop the operation of the apparatus. That is, to turn off various motors and print head, this step renders the apparatus ready to be cut of f from power supply and then turns off power, before moving to step S 4  waiting for the next event. 
     Step S 11  performs other event processing. For example, this step performs processing corresponding to the ejection performance recovery command from various panel keys or external I/F and the ejection performance recovery event that occurs internally. After the recovery processing is finished, the printer operation moves to step S 4  waiting for the next event. 
     An embodiment to which the present invention is effectively applied is a form of a printing head that ejects ink by a pressure of a bubble from a film boiling generated by utilizing thermal energy generated from an electro-thermal converter. 
     Embodiment 1 
     Description will be given of a first embodiment of margin-less printing executed by the ink jet printer of this embodiment, described above with reference to  FIGS. 1 to 10 . 
       FIG. 11  is a side view showing a portion of a printing area in which the printing head performs a scanning operation, within printing medium transportation path in a printer of this embodiment. This figure is showing that a trailing edge area of a printing medium P is subjected to margin-less printing. The margin-less printing according to this embodiment is similarly applicable whether the trailing or leading edge area of the printing medium is printed, as is apparent from the description below. In this regard, the term “edge” or “edge area” refers both printing areas relating to the leading and trailing edge areas of the printing medium, unless otherwise specified. 
     As shown in  FIG. 11 , a platen rib M 3003  is provided with a gap M 3004 . The gap M 3004  extends in a scanning direction (the direction perpendicular to the sheet of the drawing) of a printing head H 1001 , and an ink absorbing member is provided inside the gap. Thus, the ink absorbing member, provided inside the gap corrects most of the ink ejected out of the printing medium when an edge area located close to an edge of the printing medium P is printed through scanning operations performed by the printing head H 1001 . 
     In a transportation path, a transportation roller M 3001  and a pinch roller M 3002  that presses the printing medium P against the transportation roller M 3001  to exert transportation force are provided on an upstream side of the platen rib M 3003 . Further, a sheet discharging roller M 2003  and a spur M 2004  exerting transportation force similarly are provided on a downstream side of the platen rib M 3003 . When the printing medium P is held by both pairs of rollers, which are provided across a printing area of the printing head, a specified transportation accuracy or higher is ensured. In this specification, an area, defined as an area on the printing medium P, in which the specified transportation accuracy or higher is ensured is called a “normal area”. In contrast, when the printing medium P is held by only the pair including the transportation roller M 3001  and not by the pair including the sheet discharging roller M 2003 , i.e. a leading portion of the printing medium P is printed, or when a trailing portion, held by only the pair including the sheet discharging roller M 2003 , is printed as shown in the figure, the transportation accuracy decreases. In this specification, this area is called a “low-accuracy area”. Furthermore, in an area, the transportation accuracy may be low in connection with printing of an edge area of the printing medium P, as in the low-accuracy area, and ink may be ejected out from the printing medium P for margin-less printing. In this specification, this area is called an “edge area”. More specifically, the edge area includes both an area extending out from the edge of the printing medium in its transportation direction (a first part) and an area on the printing medium which is located inside this edge (a second part). 
     More specifically, for the above areas (normal, low-accuracy, and edge areas), a boundary position or a width of area of each area relative to the printing head H 1001  is managed according to an amount of rotations of a transportation motor driving the transportation roller M 3001  to a reference of what is called head determining process or detection of the leading head of the printing medium. In particular, the edge area is defined as an area of a size equal to a value obtained by adding a transportation error and a size error in the printing medium, for both the upstream and downstream side of the transportation direction, to the position of the edge of the printing medium, which is at a predetermined position relative to the printing head H 1001 . The errors added for the upstream and downstream sides of the transportation direction need not be equal. Of course, these values depend on possible transportation errors in the printer or errors in the size of the printing medium used. 
     For margin-less printing, ink must be also ejected out of the printing medium in a width direction of the transported printing medium P, i.e. in the scanning direction of the printing head. For this purpose, although not shown in  FIG. 11 , an ink absorbing member is also provided at respective positions corresponding to edges of the printing medium P in its width direction, which is transported on the platen. Further, in this embodiment, extra printing data is generated which corresponds to the printing out of the printing medium in its width direction. In this regard, the original print data may be simply enlarged so as to extend out from the printing medium. On the other hand, printing data corresponding to the edge area, described above for margin-less printing, is shown below. 
       FIG. 12  is a diagram illustrating a printing method according to the first embodiment of the present invention. In particular, this figure shows ranges of the ejection openings (shaded and other non-white parts) in the printing head H 1001  which are used when the normal area {circle around (3)}, low-accuracy area {circle around (2)}, and edge area {circle around (1)}, described above, are printed, respectively. 
     As shown in this figure, in this embodiment, what is called multi-pass printing of two-pass is carried out, in which the same pixel row in each area is completed by causing the printing head to scan this pixel row twice. In this case, to print the same pixel row using different ejection openings, the printing medium is transported in the transportation direction between scanning operations so that the different ejection openings correspond to the same pixel row during the respective scanning operations. In the figure, a position of the printing head is shown varying with the scanning operation. However, this is for simplification of illustration. Actually, the position of the printing head H 1001  is fixed in its transportation direction, and the printing medium P moves in a printing medium transportation direction (a direction crossing at right angles to the scanning direction of the printing head) by amounts corresponding to the ranges of ejection openings used, shown by the shaded and other non-white parts. 
     As is apparent from  FIG. 12 , in this embodiment, in the respective areas, the printing medium is transported by different amounts and different numbers of ejection openings (ranges of ejection openings used) are used for one scanning operation performed by the printing head. More specifically, when the normal area {circle around (3)} is printed, all ejection openings are used for one scanning operation. In contrast, when the edge area {circle around (1)} is printed, one-fourth of all ejection openings are used for one scanning operation. That is, when the edge area {circle around (1)} is printed, a smaller number of ejection openings than that used when the normal area {circle around (3)} is printed are used for one scanning operation. Further, for the amount by which the printing medium is transported between scanning operations, the transportation amount in the normal area {circle around (3)} corresponds to half the entire width of the ejection opening row, whereas the transportation amount in the edge area {circle around (1)} corresponds to one eighth of the entire width of the ejection opening row. That is, the transportation amount in the edge area {circle around (1)} is one-fourth of that in the normal area {circle around (3)}. Thus, the transportation amount decreases consistently with the number of ejection openings used. 
     Thus, a decrease in number of ejection openings used for one scanning operation in the edge area reduces the amount of ink ejected out of the printing medium during one scanning operation. This in turn reduces the amount of ink mist that may scatter or float without being captured by the ink absorbing member in the gap. This is particularly effective because if the size of or the positional relationship between the elements of the printer such as the platen is such that scattering ink or floating mist may adhere to these elements or the printing medium in a relatively short time, the amount of scattering ink or ink mist itself can be reduced. 
     Ink mist may be generated not only in the edge area but also in the normal area. Accordingly, if priority is given to a reduction in ink mist, it is assumed that a small number of ejection openings as few as those used to print the edge area are desirably used to print the normal area. However, this embodiment does not employ such an arrangement but an arrangement in which the number of ejection openings used in the edge area is reduced compared to those used to print the normal area. The reason is shown below. 
     As previously described, a method in which a small number of ejection openings as few as those used to print the edge area are used to print the normal area may be excellent in a reduction in amount of mist. However, in this method, because of the small number of ejection openings used in the normal area, printing speed decreases. Since the printing speed is an important factor of the printer, a decrease in printing speed should be minimized. On the other hand, for the printing speed, printing is preferably carried out using as many ejection openings as possible whether the normal or edge area is printed. However, this method may increase the amount of ink mist. As is apparent from the above description, the printing speed decreases if printing is carried out using a smaller number of ejection openings in order to reduce the amount of mist. On the other hand, the amount of mist increases if printing is carried out using a larger number of ejection openings in order to increase the printing speed. Accordingly, there is a tradeoff relationship between a reduction in amount of mist and an increase in printing speed. Consequently, it has been assumed to be difficult to simultaneously meet these inconsistent requirements, a reduction in amount of mist and an increase in printing speed. 
     However, the inventors focused on the point that these inconsistent requirements must be simultaneously met, i.e. the amount of mist must be sufficiently reduced while minimizing a decrease in printing speed, in order to improve image quality while increasing printing speed. The inventors thus conducted wholehearted studies in order to simultaneously meet these inconsistent requirements. As a result, first, the inventors found that when the edge area is printed, a large amount of mist is generated, requiring measures to be taken to reduce the amount of mist, as previously described, but that when the normal area is printed, only a small amount of mist is generated, eliminating the need to take measures to reduce the amount of mist. Then, the inventors minimized a reduction in number of ejection openings used to print the normal areas, for which no measures need to be taken to reduce the amount of mist, so as to minimize a decrease in printing speed. On the other hand, the inventors reduced the number of ejection openings used to print the edge area, for which measures must be taken to reduce the amount of mist, so as to sufficiently reduce the amount of mist. According to the arrangement of this embodiment, the amount of mist can be sufficiently reduced in the edge area, in which the ink mist problem is likely to occur. Consequently, the amount of mist can be reduced in the entire print area including the edge area and the normal area. Further, in the edge area, the number of ejection openings used is reduced and thus the printing speed decreases slightly. However, in the normal area, the number of ejection openings is not reduced and the printing speed does not decrease. Overall, the printing speed does not decrease significantly. That is, this method serves to simultaneously meet the inconsistent requirements, i.e. sufficiently reduce the amount of mist while minimizing a decrease in printing speed. 
     In  FIG. 12 , the number of ejection openings used is reduced not only in the edge area {circle around (1)} but also in the low-accuracy area {circle around (2)} compared to the normal area {circle around (3)} (half of all ejection openings). This is to reduce the transportation amount and thus the magnitude of transportation errors. This enables a reduction of positional deviation of ink dots formed in the low-accuracy area. 
     Further, in the above description, the number of ejection openings used and the transportation amount is varied between the low-accuracy area {circle around (2)} and the edge area {circle around (1)}. However, these may be the same in both areas. That is, in this embodiment, it is only necessary that the number of ejection openings used and the transportation amount for one scanning operation in the edge area {circle around (1)} are smaller than those in the normal area {circle around (3)}. The number of ejection openings used and the transportation amount {circle around (2)} may be the same as those in the edge area {circle around (1)}. 
     Furthermore, the illustrated example relates to a margin-less printing method, executed at the leading edge area of the printing medium. However, it can be easily understood that this method can be similarly executed at the trailing edge area by, for example, reversing the transportation direction in the figure so that a leading edge of the printing medium is placed at the position of a trailing edge, vice versa. 
     According to this embodiment, described above, the number of ejection openings used (the range of ejection openings used) is reduced in the edge area, in which ink mist is likely to occur, compared to the normal area, in which ink mist is relatively unlikely to occur. Accordingly, the amount of mist can be sufficiently reduced while minimizing a decrease in printing speed. 
     Variation of Embodiment 1 
     In the first embodiment, to reduce the amount of ink ejected to the edge area during one scanning operation below the amount of ink ejected to the normal area during one scanning operation, the number of ejection openings used for one scanning operation in the edge area is reduced compared to the normal area. In this case, what is called multi-pass printing of two-pass is carried out, in which the same pixel row in each area is completed by causing the printing head to scan this pixel row twice. That is, the same two-pass printing is carried out in both edge area and normal area. 
     However, the amount of ink ejected to the edge area during one scanning operation can also be reduced by increasing the number of passes in the edge area compared to the normal area. In this embodiment, to reduce the amount of ink ejected to the edge area during one scanning operation below the amount of ink ejected to the normal area during one scanning operation, i) the number of ejection openings used for one scanning operation in the edge area is reduced compared to the normal area, and ii) the number of passes required to complete the same pixel row in the edge area is increased compared to the normal area. 
     Then, an example of this variation will be described. First, the restrictions on the number of ejection openings used (the range of ejection openings used) in i) may be similar to those described in the first embodiment. The number of ejection openings used for the edge area is limited to one-fourth of the number of ejection openings used for the normal area. Then, for the number of passes in ii), the same pixel row in the normal area is completed using two passes, whereas the same pixel row in the normal area is completed using four passes. This is accomplished by reducing the transportation amount in the edge area {circle around (1)} to one-eighth of the transportation amount in the normal area {circle around (3)}. In this arrangement, the number of passes in the low-accuracy area {circle around (2)} may be two as with the normal area {circle around (3)} or four as with the edge area {circle around (1)}. 
     Further, the number of passes may increase from the normal area {circle around (3)} through the low-accuracy area {circle around (2)} to the edge area {circle around (1)}. For example, two passes may be executed in the normal area {circle around (3)}, four passes, in the low-accuracy area {circle around (2)}, and eight passes, in the edge area {circle around (1)}. 
     According to the arrangement of the above described variation, in the edge area, the number of ejection openings used is reduced, with the number of passes increased. This reduces the amount of ink ejected to the edge area during one scanning operation. This in turn efficiently suppresses the occurrence of ink mist in the edge area. 
     Embodiment 2 
     In this embodiment, the number of scanning operations in the edge area is reduced compared to the other areas, thereby reducing the time required to print the edge area. Thus, compared to the case in which more scanning operations are performed, the total amount of ink ejected remains the same, but the time for which mist floats, which results from ink ejected out of the printing medium during printing of the edge area, is reduced. This also reduces the time for which the printing medium remains in a space in which such mist floats. 
       FIG. 13  is a diagram illustrating a printing method according to this embodiment. As shown in this figure, four scanning operations are required to complete printing each of the normal area {circle around (3)} and the low-accuracy area {circle around (2)}, whereas only two scanning operations are required to complete printing the edge area {circle around (1)}. In the illustrated example, the time required to print the edge area {circle around (1)} corresponds to four scanning operations and is half the time required to print an area of the same size in the other areas. This reduces the possibility that floating mist or the like is further diffused, for example, owing to air currents or the like caused by a scanning operation of the printing head or that mist adheres to the printing medium. In particular, the printing medium is charged because of friction or the like, whereas ink mist is also slightly charged, so that the mist is often attracted and adheres to the printing medium owing to static electricity. However, when the number of scanning operations in the edge area is reduced as described above, the time for which the printing medium remains in the space in which mist floats is shortened to reduce the amount of mist adhering to the printing medium. 
       FIGS. 14A-14D  are diagrams showing the number of passes for multi-pass printing and the total number of scanning operations (time) used when a predetermined width A in the edge area is printed. As shown in this figure, the time required to print the edge area increases linearly with the number of passes for multi-pass printing. 
     In this embodiment, control is provided to reduce the range of ejection openings used in order to reduce the positional deviation of dots in the low-accuracy area, as in the case of Embodiment 1. 
     Embodiment 3 
     In this embodiment, the amount of floating mist is reduced by using a mask different from the one used for the normal area and low-accuracy area, to subject the edge area to multi-pass printing. 
       FIG. 15  is a diagram illustrating a printing method according to this embodiment. As shown in this figure, multi-pass printing of four-pass is carried out in each area (normal area, low-accuracy area, and edge area). However, mask processing executed to generate print data for each range of ejection openings used varies between the edge area {circle around (1)} and both low-accuracy area {circle around (2)} and normal area {circle around (3)}.  FIGS. 16A and 16B  show thinning masks used to distribute print data to two scanning operations and are formed so that a mask used for the first pass ( FIG. 16A ) and a mask used for the second pass ( FIG. 16B ) are complementary to each other and then the corresponding print areas are 100% complementary to each other. Further,  FIG. 17  shows a thinning mask used to distribute print data to two scanning operations. In this case, only the mask used for the first pass is shown, whereas a mask used for the second pass is omitted. However, the mask used during the second pass is complementary to the mask used during the first pass. 
     More specifically, basically, in the low-accuracy area {circle around (2)} and normal area {circle around (3)}, masks (in  FIGS. 16A and 16B , masks for two pass printing are shown for simplification) are used such that print data is distributed for one pixel unit (an area corresponding to a square composed of 1 dot size×1 dot size in the figure) corresponding to one ink dot to execute printing during two scanning operations, as shown in  FIGS. 16A and 16B . On the other hand, in this embodiment, as shown in  FIG. 17 , masks used are such that during a single scanning operation, for example, an eight-pixel unit (an area corresponding to a square composed of 8 dot size×8 dot size), which is larger than one pixel, is used for printing and that print data is distributed over two scanning operations. This mask processing is executed for eight pixels as a minimum unit to generate print data. Ink ejection based on this processing serves to increase the number of ink droplets flying very nearby compared to the mask processing shown in  FIGS. 16A and 16B . Thus, the group of ink droplets are attracted to one another owing to air currents generated by themselves. This reduces the amount of scattering or floating ink or ink mist. 
     In the normal area or low-accuracy area, when cluster size (minimum mask unit) is increased in order to reduce the amount of floating mist or for another reason, non-uniformity of colors because of the reciprocating scanning operations or a granular appearance may occur in a print image. To avoid this, a one-pixel unit or a minimum unit close thereto is used. 
     Further, in the above description, as shown in  FIG. 17 , the cluster size of the mask (minimum mask unit) that enables ink ejection to concentrate in a predetermined area during the same pass is shaped like a square. However, the present invention is not limited to this aspect, but a rectangular may also be used. That is, in the above description, the minimum management unit of the mask is an area corresponding to a square composed of 8×8 pixels. However, the minimum management unit of the mask may be an area corresponding to a rectangle composed of for example 2×4 pixels. 
     According to this embodiment, described above, in the edge area, in which ink mist is likely to occur compared to the normal area, a mask with a large minimum management unit is used to enable ink ejection to concentrate in a predetermined area during the same pass, thereby reducing the amount of ink mist in the edge area. 
     Embodiment 4 
     In a fourth embodiment of the present invention, masks used for multi-pass printing in the edge area are such that a printed image has a density decreasing toward the edge and that the entire image has a lower density. 
     More specifically, when four-pass multi-pass printing is carried out in the edge area, masks used to print data corresponding to this edge area are such that the mask for the first scanning operation has a ⅛ duty, the mask for the second scanning operation has a ⅙ duty, the mask for the third scanning operation has a ¼ duty, the mask for the fourth scanning operation similarly has a ¼ duty, and the total duty is less than 100% (in this case, (⅛+⅙+¼+¼)×100=about 79% duty) and that the duty of each scanning operation decreases toward the edge. 
     In this manner, the multi-pass printing operations in the edge area are not perfectly complementary to one another. This reduces the amount of ink ejected to the edge area, thereby reducing the amount of floating ink mist as described in Embodiment 1. Further, since the masks are such that the duty decreases toward the edge of the printing medium, the amount of ink likely to be ejected out of the printing medium is reduced, thereby similarly reducing the amount of floating ink mist. 
     Instead of the masks causing the duty to decrease toward the edge, those which uniformly thin data in the edge area may be used to reduce the amount of ink ejected throughout the multi-pass printing as long as the masks are not perfectly complementary to one another. 
     Further, an edge portion may be gradated to white as a result of the above mask processing. However, the width of the edge area to which ink is also ejected out from the edge of the printing medium is determined under the assumption of the worst conditions for the transportation accuracy or errors in printing medium size as previously described. Consequently, these conditions are unlikely to occur, and thus the above described gradation printing rarely occurs. Further, even if the duty for the edge area, i.e. the amount of ink landing the printing medium is reduced to about 79% as described above, this is insignificant in relation to the print image as a whole. 
     Embodiment 5 
     Basically, in this embodiment, the amount ink mist is reduced by decreasing the number of ejection openings used for the edge area as with Embodiment 1. Further, a mask pattern used for multi-pass printing is the same as or similar to that used for the normal area or low-accuracy area. 
       FIG. 18  shows areas in which different printing control is provided. This figure shows an edge area at a leading end of the printing medium (upper edge area {circle around (1)}), a low-accuracy area also at the leading end (low-accuracy upper edge area {circle around (2)}), a normal area {circle around (3)}, a low-accuracy area at a trailing end of the printing medium (low-accuracy lower edge area {circle around (4)}), and an edge area at the trailing end (lower edge area {circle around (5)}). 
     In the normal area and the low-accuracy areas, masks are used which cause the amount of ink ejected to decrease at an end portion of the area printed during each scanning operation of multi-pass printing and which are perfectly complementary to each other during the passes in which that area is printed, i.e. the masks causing the duty to decrease toward the end portion. 
     On the other hand, in the edge area, the number of ejection openings used is reduced as in Embodiment 1, and the distribution of the duty of the masks used is the same as or similar to that used for the normal area and others. This prevents a difference in density from occurring before or after one of the areas {circle around (1)} to {circle around (5)} shown in  FIG. 18  changes to another. 
     Embodiment 6 
     Basically, in this embodiment, the number of ejection openings used is reduced as with Embodiment 5, described above, and the same or similar masks are used in the areas {circle around (1)} to {circle around (5)}, shown in  FIG. 18 . More specifically, the masks with the concentrated dot size (cluster size) distribution shown in Embodiment 3 are used in the normal area or low-accuracy area. 
     A change in mask cluster size may cause a change in tone such as reciprocation non-uniformity attributed to the order of landing color inks. This change may be marked depending on the type of the printing medium. Thus, in this embodiment, for printing of the edge area, the number of ejection openings used is reduced and the mask cluster size used is the same as or similar to that used in the normal area or low-accuracy area. This prevents a noticeable tone or density difference from occurring where one area changes to another. 
     Other Embodiments 
     Embodiments 1 and 2 or 2 and 3 may be combined together. This also reduces the amount of floating ink mist or the like or the amount of mist adhering to the printing medium. 
     Further, in Embodiments 1 to 3, control of printing of the low-accuracy area {circle around (2)} may be the same as that of the edge area {circle around (1)} or normal area {circle around (3)}. 
     Further Embodiments 
     As described above, the present invention is applicable either to a system comprising plural pieces of device (such as a host computer, interface device, a reader, and a printer, for example) or to an apparatus comprising one piece of device (for example, a copy machine or facsimile terminal device). 
     Additionally, an embodiment is also included in the category of the present invention, wherein program codes of software such as those shown in  FIGS. 12-18 , for example, which realize the above described embodiments, are supplied to a computer in an apparatus or a system connected to various devices to operate these devices so as to implement the functions of the above described embodiments, so that the various devices are operated in accordance with the programs stored in the computer (CPU or MPU) of the system or apparatus. 
     In this case, the program codes of the software themselves implement the functions of the above described embodiments, so that the program codes themselves and means for supplying them to the computer, for example, a storage medium storing such program codes constitute the present invention. 
     The storage medium storing such program codes may be, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a non-volatile memory card, or a ROM. 
     In addition, if the functions of the above described embodiments are implemented not only by the computer by executing the supplied program codes but also through cooperation between the program codes and an OS (Operating System) running in the computer, another application software, or the like, then these program codes are of course embraced in the embodiments of the present invention. 
     Furthermore, a case is of course embraced in the present invention, where after the supplied program codes have been stored in a memory provided in an expanded board in the computer or an expanded unit connected to the computer, a CPU or the like provided in the expanded board or expanded unit executes part or all of the actual process based on instructions in the program codes, thereby implementing the functions of the above described embodiments. 
     As is apparent from the above description, according to one embodiments of the present invention, for what is called margin-less printing, when printing is carried out for an edge area including both an area located out from an edge of a printing medium in a direction in which it is transported and an area located inside this edge, the amount of ink ejected to this area is reduced compared to an area other than the edge area (for example, a normal area). This reduces the amount of ink ejected out of the printing medium in the edge area. Further, in another embodiment, the number of scanning operations performed by the printing head over a predetermined width in the transportation direction is reduced compared to an area other than the edge area. This reduces the time for which mist generated while the printing medium remains in the edge area adheres to the printing medium. In yet another embodiment, a mask used to generate ejection data for each of the plurality of scanning operations for printing the edge area is differentiated from a mask for an area other than the edge area so that a minimum mask unit of the mask for the edge area is greater than that of the mask for the area other than the edge area. Consequently, ink ejected out of the printing medium in the edge area becomes a fixed mass. This reduces the amount of scattering ink or floating mist. 
     As a result, the contamination of elements of the apparatus or the printing medium caused by ink mist or the like which may scatter or float in the apparatus when margin-less printing is carried out. 
     The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.