Patent Application
20060216095
This invention relates in general to methods of printing and printers and in particular to methods of borderless printing and printers for providing borderless prints.
Many photographers use digital cameras to capture images. Unlike conventional wet processing of silver halide film and papers, digital images can be printed directly onto sheets of paper. Color images may be printed using ink jet printers, multicolor transferable toner printers, heat sensitive coated paper printers, or thermal dye transfer printers. Many mass-market retail establishments have user-friendly kiosks where shoppers may make color prints. A large number of these kiosks use thermal dye transfer printers. Because the kiosks use large amounts of paper, the images may be printed on a continuous web of paper. The images are later separated from each other and from the web by a suitable cutter or knife. Such prints have dye images that bleed to the edges in the latitudinal and longitudinal directions. These prints are known as borderless prints and are the most popular prints with consumers.
Thermal dye transfer printers generate very high quality images. As such, a number of photographers want their own thermal dye transfer printer. However, it is impractical and not cost effective to supply continuous web paper for the images. It would also be expensive to supply built-in paper cutters and knives to provide borderless prints. To meet the demand for borderless prints, there are known methods of bleeding the latitudinal edges so that there is no border on the tops and bottoms of prints. See, for example, U.S. Pat. Nos. 5,441,353; 5,196,863; and 5,499,880. However, those techniques cannot provide prints that bleed to the longitudinal borders.
To solve this problem and provide full borderless prints, others use special manufactured sheets of paper that carry perforated longitudinal leading and trailing borders. The leading edge and the trailing edge of the paper are perforated to let the user remove them from the finished print. In this way, the printed image may slightly exceed the area between the perforations. The excess portion of the image is removed with the perforated leading and trailing edge to provide the user with a borderless image.
A key drawback of the existing solution is the requirement for special paper with perforations on the leading and trailing edges. Such paper is expensive to manufacture and has little or no other market outside of printing digital images. In addition customers are dissatisfied with the requirement for tearing off the perforated edges of the printed images. However, conventional printers are not configured to use ordinary paper and provide borderless prints.
In a conventional thermal printer, paper is clamped between a capstan roller and a pinch roller and pulled through a nip between a thermal print head and the platen. The capstan and pinch rollers are driven by a stepper motor that provides both precise movement and control of the paper sheet. The print head and platen capture a web of donor material with dye and press it against the paper. The platen spins freely while the web and receiver are pulled past the print head. Heat from the thermal head transfers dye from the donor web onto the receiver paper to create an image.
An example of a prior art thermal dye transfer printer 600 that provides monotone, multi-tone or full color printing is shown in
The invention provides both a method and apparatus for borderless printing. In the apparatus, the invention provides a print head that is moveable toward and away from a donor web. The donor web is disposed between supply and take-up reels. The print head is on one side of the donor web; on the other side is a cylindrical platen. The sheet of paper is fed by urge rollers toward a nip between the print head and the platen. The paper travels along a path from a supply bin to an exit bin. A sensor is located in the path of the paper for detecting the edge of the paper as it approaches and leaves the print head. The sensor may also align the lead edge of the paper. Upon detecting the lead edge of the paper, the apparatus then drives the lead edge along a path to a location that will dispose the lead edge in the nip of the print head and the platen when the print head is lowered. The sensor provides the information for the stepper motor to precisely position the lead edge of the paper in a predetermined position for borderless printing. That position places the lead edge proximate to and just short of the corresponding position of the linear array of thermal printing elements disposed in the print head. Then the print head and/or platen move relative to each other in order to clamp the lead edge of the paper between the print head and the platen. The platen is then driven and the print head is energized in order to provide a full bleed print from the leading edge to trailing edge. The sensor senses the trailing edge of the sheet. The sheet is driven to carry its trailing edge past the linear array of printing elements and then the sheet is returned to its initial position for printing the next color. Thus, the invention may provide single, dual or full-color prints.
Referring now to
The entrance urge rollers 15, 16 are disposed at one end of the paper guides 13, 14. Entrance urge 15, 16 rollers are biased together by a suitable spring or other biasing structure, not shown, so that rotary motion imported to one roller is transmitted to the other. Roller 15 is a pinch roller and roller 16 is driven by stepper motor 17 and transmission 18. Transmission 18 is shown as a belt but may be any suitable transmission known in the art that can be used to connect the rotary motion of motor 17 to roller 16. Sheet 8 exits the nip of urge rollers 15, 16 and is supported by thermal head guide 19. The body of thermal head guide 19 has an edge sensor 40. Edge sensor 40 is any suitable sensor for identifying the leading edge 8.1 or trailing edge 8.2 of sheet 8. Edge sensor 40 may be optical, mechanical, or a combination optical/mechanical device that senses the leading and trailing edges of the sheet. Edge sensors 40 are well-known in printers and photocopiers and any suitable, conventional edge sensor 40 may be used. In addition, edge sensor 40 may be combined with a suitable gate (not shown).
Edge sensor 40 is disposed so that it can detect lead edge of sheet 8 when sheet 8 is at a known distance from the array of heat elements (heat line) 44. Distance D is the offset of a leading edge 8.1 of sheet 8 from the heat line 44 when sheet 8 is in its initial position. Edge sensor 40 is also coupled to control circuit 60. In response to edge sensor 40 detecting leading edge 8.1 of sheet 8, control circuit 60 drives urge stepper motor 17 a predetermined number of steps in order to move sheet 8 toward heat line 44 and to stop sheet 8 with its lead edge 8.1 at a distance D from heat line 44. The initial position is a distance D just short of heat line 44 and is close enough to heat line 44 that lead edge 8.1 of sheet 8 will be captured in the nip between web 21 and platen 50.
Urge rollers 15, 16 drive sheet 8 to the initial position that is shown in more detail in
Turning now to
However, in other embodiments, sheet 8 is precisely positioned and repositioned by one or more of the stepper motors that operate the pairs of urge rollers 15, 16 and exit urge rollers 56, 57 and the platen 50. In a preferred embodiment, only platen 50, urge rollers 15, 16 or exit urge rollers 56, 57 moves sheet 8 at any one time. Thus, in this embodiment, urge rollers 15, 16 control movement of sheet 8 past edge sensor 40 to heat line 44. Platen 50 controls movement of sheet 8 beneath heat line 44. Exit urge rollers 56, 57 control return of sheet 8 toward its initial position and its final discharge from printer 10. The exit urge rollers 56, 57 release control of sheet 8 at a predetermined distance after a trailing edge 8.2 (see
Control circuit 60 operates urge rollers 15, 16 to move leading edge 8.1 of sheet 8 beyond print head guide 19 and into the space between print head 25 and platen 50. Urge rollers 15, 16 may be permanently engaged or may be selectively engaged. To selectively engage urge rollers 15, 16, an upper urge roller 15 may be spring biased away from a driver urge roller 16 and an actuator (not shown) controlled by control circuit 60 is operable to move urge roller 15 into or out of engagement with urge roller 16. Exit urge rollers 56, 57 may be similarly constructed. If urge rollers 15, 16 and exit urge rollers 56, 57 are permanently engaged, then they will be actuated as described above.
After positioning lead edge 8.1 of sheet 8 as shown in
After a color or clear laminate is transferred to sheet 8, control circuit 60 stops sheet 8 in the position shown in
Donor web 21 can have multiple, sequential sections of different colors or a clear laminate and the single printing cycle described above is repeated for each color and for the clear laminate. A typical color print operation includes serial printing from section of yellow, magenta, cyan dyes and then transferring a clear, protective layer on sheet 8. After each color or clear section is printed, sheet 8 is returned to its initial position for printing the next color from the donor web.
The invention achieves borderless printing on a single sheet by precisely locating the leading edge of the sheet of paper. Edge sensor 40 senses the leading edge 8.1 of a sheet 8. Stepper motors precisely drive sets of exit urge rollers 15, 16 and platen 50 to precisely position the paper at its initial position for each printing cycle. Exit urge rollers 56, 57 may be driven by ordinary motors because it is not necessary to precisely control the passage of sheet 8 between those rollers. In this way, thermal-dye transfer material may be transferred from leading edge 8.1 of sheet 8 to trailing edge 8.2 of sheet 8, thereby eliminating any border on the leading and trailing edges.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
