The invention relates generally to dye transfer or thermal printers. More particularly, the invention relates to the problem of creases or wrinkles being formed in the dye transfer areas of a dye donor web during dye transfer printing. Crease formation in a dye transfer area can result in an undesirable line artifact being printed on a dye receiver.
A typical multi-color dye donor web that is used in a dye transfer or thermal printer is substantially thin and has a repeating series of three different rectangular-shaped color sections or patches such as a yellow color section, a magenta color section and a cyan color section. In addition, there may be a transparent colorless laminating section immediately after the cyan color section.
Each color section of the dye donor web consists of a dye transfer area which is used for dye transfer printing and a pair of opposite longitudinal edge areas alongside the dye transfer area which often are not used for printing. The dye transfer area may be about 152 mm wide and the two longitudinal edge areas may each be about 5.5 mm wide, so that the total web width is approximately 163 mm.
To make a multi-color image print using a thermal printer, a motorized donor web take-up spool draws a longitudinal portion of the dye donor web off a donor web supply spool in order to successively move an unused single series of yellow, magenta and cyan color sections over a stationary liner array (bead) of selectively heated resistive elements on a thermal print head between the supply and take-up spools. Respective color dyes within the yellow, magenta and cyan color sections are successively heat-transferred line-by-line, via the selectively heated resistive elements, onto a dye receiver medium such as a paper or transparency sheet or roll, to form the color image print. The selectively heated resistive elements often extend across the entire width of a color section, i.e. across the dye transfer area and the two longitudinal edge areas comprising that color section. However, only those resistive elements that contact the dye transfer area are selectively heated. Those resistive elements that contact the two longitudinal edge areas are not heated. Consequently, the dye transfer occurs from the dye transfer area to the dye receiver medium, but not from the two longitudinal edge areas to the dye receiver medium.
As each color section is drawn over the selectively heated resistive elements, it is subjected to a longitudinal tension particularly by the forward pulling force of the motorized donor web take-up spooi. Since the dye transfer area in the color section is heated by the resistive elements, but the two longitudinal edge areas alongside the dye transfer area are not, the dye transfer area is significantly weakened and therefore is vulnerable to being longitudinally stretched as compared to the two edge areas. Consequently, the longitudinal tension will stretch the dye transfer area relative to the two longitudinal edge areas. This stretching causes the dye transfer area to become thinner than the non-stretched edge areas, which in turn causes some creases or wrinkles to develop in the dye transfer area, most acutely in those regions of the dye transfer area that are close to the non-stretched longitudinal edge areas. The creases or wrinkles occur most acutely in the regions of the dye transfer area that are close to the non-stretched edge areas because of the sharp, i.e. abrupt, transition between the stretched (thinner) transfer area and the non-stretched (thicker) edge areas.
As the dye donor web is pulled by the motorized donor web take-up spool over the selectively heated resistive elements, the creases or wrinkles tend to spread from a trailing (rear) end portion of a used dye transfer area at least to a leading (front) end portion of the next dye transfer area to be used. A known problem that can result is that the creases in the leading (front) end portion of the next dye transfer area to be used will cause undesirable line artifacts to be printed on a leading (front) end portion of the dye receiver medium. The line artifacts printed on the dye receiver medium, although they may be relatively short, are quite visible.
The question presented therefore is how to solve the problem of the creases or wrinkles being created in an unused dye transfer area so that no line artifacts are printed on the dye receiver medium during the dye transfer.
The Cross-Referenced Application
The cross-referenced application discloses a thermal printer capable of preventing crease formation in successive dye transfer areas of a dye donor web that can cause line artifacts to be printed on a dye receiver during dye transfer from each dye transfer area to the dye receiver. To prevent crease formation, there is provided a crease-preventing roller for supporting a dye transfer area of the dye donor web and two edge areas of the dye donor web alongside the dye transfer area. The roller has respective helical ribs that spiral inwardly from coaxial opposite ends of the roller and that are resilient to be deformed towards the opposite ends of the roller due to longitudinal tensioning of the dye transfer area and two edge areas. When deformed, the ribs urge the dye transfer area and two edge areas to spread in opposition to crease formation during dye transfer from the dye transfer area to the dye receiver. Thus, crease formation can be prevented even though the dye transfer area is heated by the print head, but the two edge areas are not.
According to one aspect of the invention, a thermal printer capable of preventing crease formation in successive dye transfer areas of a dye donor web that can cause line artifacts to be printed on a dye receiver during dye transfer from each dye transfer area to the dye receiver, comprises:
a thermal print head for heating a dye transfer area of the dye donor web sufficiently to effect dye transfer from the dye transfer area to the dye receiver, but not heating two opposite edge areas of the dye donor web alongside the dye transfer area sufficiently to allow dye transfer from the two edge areas to the dye receiver, so that crease formation can occur at least in respective regions of the dye transfer area adjacent the two edge areas; and
a crease-preventing roller for supporting at least the dye transfer area and two edge areas, having an elastic cover layer that can be stretched towards coaxial opposite ends of the roller to spread at least the regions of the dye transfer area in which crease formation can occur in order to oppose crease formation, and having respective movable members (such as the helical ribs in the cross-referenced application) moving to stretch the elastic cover layer towards the opposite ends of the roller.
The addition of the elastic cover layer to the crease-preventing roller (as compared to the crease-preventing roller without the elastic cover layer in the cross-referenced application) ensures a uniform contact of the roller with the dye transfer area and two edge areas.
According to another aspect of the invention, a method in a thermal printer of preventing crease formation in successive dye transfer areas of a dye donor web that can cause line artifacts to be printed on a dye receiver during dye transfer from each dye transfer area to the dye receiver, comprises:
heating a dye transfer area of the dye donor web sufficiently to effect dye transfer from the dye transfer area to the dye receiver, but not heating two opposite edge areas of the dye donor web alongside the dye transfer area sufficiently to allow dye transfer from the two edge areas to the dye receiver, so that crease formation can occur at least in respective regions of the dye transfer area adjacent the two edge areas; and
stretching an elastic cover layer on a crease-preventing roller that supports at least the dye transfer area and two edge areas towards the opposite ends of the roller, so that the elastic cover layer spreads at least the regions of the dye transfer area in which crease formation can occur in order to oppose crease formation.
Each yellow, magenta or cyan color section 2, 3 and 4 of the dye donor web 1 consists of a yellow, magenta or cyan dye transfer area 5 which is used for printing and a pair of similar-colored opposite longitudinal edge areas 6 and 7 alongside the dye transfer area which often are not used for printing. Preferably, the dye transfer area 5 is about 152 mm wide and the two edge areas 6 and 7 are each about 5.5 mm wide, so that the total web width W is approximately 163 mm.
Initialization
Beginning with
In
Successive Yellow, Magenta and Cyan Dye Transfers
To make a multi-color image print, respective color dyes in the dye transfer areas 5 of a single series of yellow, magenta and cyan color sections 2, 3 and 4 on the dye donor web 1 must be successively heat-transferred in superimposed relation onto the dye receiver sheet 12. This is shown beginning in
In
When the yellow color section 2 of the dye donor web 1 is pulled forward over the print head 48 in
A known heat activating control 74, preferably including a suitably programmed microcomputer using known programming techniques, is connected individually to the resistive elements 49A, 49A, ***, 49B, 49B, ***, 49A, 49A, ***, to selectively heat those resistive elements 49B that make pressured print-line-contact with the dye transfer area 5, and preferably not heat (or only slightly heat) those resistive elements 49A that make pressured contact with the two edge areas 6 and 7 alongside the dye transfer area. See
As the yellow color section 2 of the dye donor web 1 is used for dye transfer line-by-line, it is pulled forward from the print head 48 and over the second stationary donor web guide bar or stripper 52 in
Then, the dye transfer onto the dye receiver sheet 12 is repeated line-by-line in
Once the magenta dye transfer onto the dye receiver sheet 12 is completed, the platen roller 42 is shifted via the rotated cam 44 and the platen lift 46 from adjacent the print head 48 to separate the platen roller from the print head, and the motorized capstan 28 and the pinch roller 30 are reversed to advance the dye receiver sheet rearward, i.e. trailing (rear) edge 26 first, partially into the rewind chamber 40. See
Then, the dye transfer onto the dye receiver sheet 12 is repeated line-by-line in
Once the cyan dye transfer onto the dye receiver sheet 12 is completed, the platen roller 42 is shifted via the rotated cam 44 and the platen lift 46 from adjacent the print head 48 to separate the platen roller from the print head, and the motorized capstan roller 28 and the pinch roller 30 are reversed to advance the dye receiver sheet rearward, i.e. trailing (rear) edge 26 first, partially into the rewind chamber 40. See
Final
Finally, as shown in
Typically in prior art dye transfer, as each yellow, magenta and cyan color section 2, 3 and 4, including its dye transfer area 5 and the two edge areas 6 and 7 alongside the transfer area, is pulled or drawn forward over the linear array (bead) of selectively heated resistive elements 49A, 49A, ***, 49B, 49B, ***, 49A, 49A, ***, the color section is subjected to a longitudinal tension imposed substantially by a forward pulling force F of the motorized donor web take-up spool 54. See
As the dye donor web 1 is pulled by the motorized donor web take-up spool 54 over the linear array (bead) of selectively heated resistive elements 49A, 49A, ***, 49B, 49B, ***, 49A, 49A ***, the slanted creases or wrinkles 62 tend to spread rearward from a trailing (rear) end portion 66 of a used dye transfer area 5 at least to a leading (front) end portion 68 of the next dye transfer area to be used. See
The question presented therefore is how to solve the problem of the slanted creases or wrinkles 62 being created in an unused transfer area 5 so that no line artifacts 70 are printed on the dye receiver sheet 12 during the dye transfer.
As previously mentioned, before each yellow, magenta or cyan dye transfer from a dye transfer area 5 to the dye receiver sheet 12, the platen roller 42 is shifted via the rotated cam 44 and the platen lift 46 to adjacent the print head 48. This causes both the dye receiver sheet 12 and an unused yellow, magenta or cyan color section 2, 3 or 4 (comprising a dye transfer area 5 and two edge areas 6 and 7) of the donor web 1 to be intimately held together between the platen roller 42 and the print head 48. The platen roller 42 shown in
According to a preferred embodiment of the invention,
The crease-preventing roller 76 can be used in place of the platen roller 42 or the donor web guide bar 51 in
The crease-preventing roller 76 has opposed helical grooves 78 and 80 that are spiraled inwardly in respective directions from coaxial opposite ends 82 and 84 of the roller to form resilient helical ribs or projections 86 and 88. The helical ribs 86 and 88 meet midway between the roller ends 82 and 84 and they are covered with a single, cylindrical, elastic cover layer 90. The elastic cover layer 90 is secured to the helical ribs 86 and 88.
As indicated in
During the dye transfer, the helical ribs 86 and 88 are temporarily deformed or bent towards the opposite roller ends 82 and 84 by the longitudinal tensioning of the dye transfer area 5 and two edge areas 6 and 7 at the print head 48. Such longitudinal tensioning is imposed by the forward pulling force F of the motorized take-up spool 54. The helical ribs 86 and 88, when deflected towards the roller ends 82 and 84, cause the elastic cover layer 90 to be stretched towards the roller ends. In turn, the elastic cover layer, when stretched, causes at least the regions 64 of the dye transfer area 5 in which the slanted creases 62 can form to spread in opposition to crease formation, so that the line artifacts 70, shown in
The elastic cover layer 90 is an elastomeric material having a modulus of elasticity preferably within the range of 1 Mega Pascal (1×106 Pascal)-20 Mega Pascal (20 ×106 Pascal) and a hardness preferably within the range of 20 Shore A–90 Shore A. The elastomer material preferably can be constructed of either styrene-butadiene rubber, polyisoprene rubber, polybutadiene rubber, silicon rubber, ethylene-propylene rubber, urethane rubber, or fluorocarbon rubber.
The invention has been described in detail with particular reference to certain preferred and alternate embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. For example, the crease-preventing roller 76 instead of being used in place of the platen roller 42 in
This application is a continuation-in-part of commonly assigned, application Ser. No. 10/426,591, entitled PREVENTING CREASE FORMATION IN DONOR WEB IN DYE TRANSFER PRINTER THAT CAN CAUSE LINE ARTIFACT ON PRINT, and filed Apr. 30, 2003 now U.S. Pat. No. 6,768,503 in the names of Po-Jen Shih, Zhanjun J. Gao, and Robert F. Mindler.
Number | Name | Date | Kind |
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6757003 | Gao et al. | Jun 2004 | B1 |
Number | Date | Country |
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59-68282 | Apr 1984 | JP |
60-157889 | Aug 1985 | JP |
60184864 | Sep 1985 | JP |
07-178993 | Jul 1995 | JP |
Number | Date | Country | |
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20040218030 A1 | Nov 2004 | US |
Number | Date | Country | |
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Parent | 10426591 | Apr 2003 | US |
Child | 10812547 | US |