Abstract:
A method of producing and using photo media to print a glossy, photo-quality image. The image is printed onto the back of a coated transparent base. Thereafter, an opaque backing is applied to cover the printed image. The resulting print is viewed from the front, which provides the photo-quality, attractive appearance primarily because of the substantial gloss depth and uniformity attributable to the transparent base. The transparent base and backing protect the ink-receiving coating and make the resulting print very durable. The image is light fast because the ink is sandwiched between the transparent base and the backing, thereby sealing the ink from oxygen. In a preferred embodiment of the present invention, the backing is applied as a liquid using substantially the same mechanism as used for printing the image.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to techniques for producing a photograph-quality, glossy image using an ink-jet type printer.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     Ink-jet printers are popular and cost-effective devices for producing color images. The quality of color prints made by ink-jet type printers has advanced to a level such that photo-quality images can be produced. To this end, special print media, hereafter collectively referred to as “photo media,” have been developed. The photo medium usually comprises a base of white, plastic film, or bonded layers of plastic and paper. One side of the base is coated with a thin, ink-receiving coating. This ink-receiving coating provides substantially all of the photographic attributes of the medium.  
         [0003]     In addition to absorbing ink, the ink-receiving coating must be clear to enable the white base to show through. The coating must be uniformly glossy so that the same gloss level occurs in printed and non-printed portions of the image. The ink-receiving coating also must be durable so as to be handled as a photograph. This requires resistance to scuffing, scratching, and smearing. The coating should be water-fast and, preferably, designed to isolate the ink from free oxygen, to ensure the light-fastness of the image.  
         [0004]     The foregoing design demands of the photo media in general and the ink-receiving coating in particular can be met with an alternative approach, which is the subject of the present application. In particular, the present invention provides a new method of producing a glossy, photo-quality image. The image is printed onto the back of a coated transparent medium or base. Thereafter, an opaque backing is applied to cover the printed image. The resulting image or “print” is viewed from the front of the transparent base, which provides a photo-quality, attractive appearance. This is primarily because of the substantial gloss depth and uniformity, which characteristics are attributable to the transparent base.  
         [0005]     As another advantage of the present invention, the transparent base and backing protect the ink-receiving coating and make the resulting print very durable. The image is light fast because the ink is sandwiched between the transparent base and the backing, thereby sealing the ink from ambient oxygen.  
         [0006]     It will be appreciated that, because the above-mentioned design requirements of durability, uniform gloss, etc., are met by the transparent base and backing, such requirements do not apply to the ink-receiving coating, thereby simplifying the production of that coating.  
         [0007]     In a preferred embodiment of the present invention, the backing is applied as an ink-like liquid that is thereafter dried. The liquid is applied using mechanisms substantially similar to those used for printing the image.  
         [0008]     In another preferred embodiment, the backing is a sheet of material that is bonded to the coated, printed side of the transparent base. A versatile media handling system is provided for use in applying either the liquid backing or the sheet backing.  
         [0009]     Other advantages and features of the present invention will become clear upon study of the following portion of this specification and the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a cross sectional, greatly enlarged view of a photo-quality print produced in accord with the present invention.  
         [0011]      FIG. 2  is a diagram depicting in a section view the primary components of an ink-jet printer that is adapted to carry out the photo media printing of the present invention. This figure shows the printer operating to print an image onto a transparent base.  
         [0012]      FIG. 3  is a diagram like  FIG. 2  but showing the printer operating to retract the image-carrying transparent base in preparation for applying a backing to cover the image.  
         [0013]      FIG. 4  is a diagram like  FIGS. 2 and 3  but showing the printer in an alternative embodiment wherein the image-carrying transparent base is moved against and adhered to a sheet of opaque backing material. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0014]      FIG. 1  depicts the layers of a photo-quality print  20  produced in accord with the preferred embodiments of the present invention. The layers include a transparent base  22 , comprising polyethylene terephtalate (PET) film of the type commonly used as transparencies for overhead projectors and the like.  
         [0015]     A very thin (about 20 μ) ink-receiving coating  24  is applied to the base  22 . This coating can be any ink-receptive layer and is preferably a transparent, colorless alumina sol-gel that is applied by any of a variety of methods such as spinning, spraying, dipping or flowing to form a coating that is then dried and cured. Also, a silica sol-gel will suffice as the ink-receiving coating  24 . Hydrogels are also suitable as the ink-receiving coating  24 .  
         [0016]     Coated transparent base layers of the type considered here are readily available as supplies for ink-jet printers. An exemplary one of the many suitable types is that available from Hewlett-Packard Company of Palo Alto Calif., and designated as Premium Inkjet Transparency Film, product number C3828A.  
         [0017]     As will be explained, the image is printed onto the ink-receiving coating  24 . The side of the base carrying the ink-receiving coating  24  is designated, for the purposes of this description, as the “back” of the transparent base. In accord with preferred embodiments of the present invention, the printed image is then covered with an opaque, white backing  26  that is applied in a way to provide an intimate, gap-free bond with the ink-receiving coating  24 . The finished print  20  is viewed through the front of the transparent base  22 , which, as noted, provides a uniform, deep glossy surface for a photo-quality print.  
         [0018]     In a preferred embodiment the backing  26  is “painted” over the ink-receiving coating  24 . Any number of mechanisms may be employed for this painting task. Described next is an embodiment that employs the mechanisms of an ink-jet printer for both printing the image and for applying the backing  26  after the image is printed on the ink-receiving coating  24 .  
         [0019]      FIG. 2  depicts the primary components of an ink-jet printer that, in addition to printing the image, is adapted for applying the backing  26  as mentioned above. The printer includes an input tray  32  into which is stacked several sheets of transparent media  30 , each sheet being the combination of the transparent base  22  and ink-receiving coating  24  ( FIG. 1 ).  
         [0020]     As the print operation commences, a sheet of media  30  is pulled by a pick roller  34  and directed as indicated by directional arrow  36  through a path  38  that is defined between the pick roller  34  and two guide members: a lower guide member  42  and an upper guide member  40 . It is noteworthy here that although only individual rollers and guide surfaces appear in  FIGS. 2-4 , a number of such rollers and surfaces are provided, spaced apart across the width of the media sheet (i.e., in a direction normal to the plane of  FIGS. 2-4 ).  
         [0021]     Upon entering the passage  38 , the leading edge  44  of the media sheet passes through the nip of an idler  46  and the pick roller  34  to contact a lightweight lower gate  48 . The lower gate  48  is pivotally attached at one end to the printer chassis and weighted so that it normally moves under the force of gravity into a position where its free end fits between two adjacent pick rollers  34 . The contact by the leading edge  44  of the media sheet  30  causes the gate  48  to swing open (counterclockwise in the figures) into the position shown in dashed lines of  FIG. 2 , thereby to permit the media sheet  30  to continue through the passage  38 .  
         [0022]     The media sheet  30  continues around the pick roller  34  and slips beneath an edge-detect roller  50 , which moves slightly away from the pick roller  34  to accommodate the thickness of the media sheet. The edge-detect roller  50  carries a transducer that provides a signal to a microprocessor-based print controller  80  in response to the movement of the detector away from the pick roller  34 . This edge information is saved in the controller memory.  
         [0023]     The sheet  30  is guided into the nip of a pinch roller  52  and a feed roller  54 . The feed roller  54  includes a position encoder that provides metering signals to the print controller, which signals correlate to the length of sheet  30  moved relative to the roller.  
         [0024]     Near the pinch roller  52  there is mounted a container of ink, commonly known as an ink-jet cartridge  60 , for printing an image onto the coated side of the media sheet  30 . The cartridge  60  is removably mounted to a carriage  62 . The carriage  62  is slidable along a support rod  64  that is housed within the printer. The rod extends across the printer, oriented perpendicularly to the direction the media sheet  30  is advanced through the printer. Bushings  65  may be fit into the carriage  62  to facilitate sliding.  
         [0025]     In the present embodiment, four cartridges  60  are preferred (although only the outer one is shown in the figures) for color printing. The cartridges contain black, cyan, yellow, and magenta inks for this purpose. Each cartridge  60  includes a plastic body that comprises a liquid ink reservoir shaped to have a downwardly depending snout  66 . A print head  68  (the size of which is greatly enlarged in the drawing for clarity) is attached to the end of the snout. The print head is a thermal type, formed with minute nozzles that align with chambers of ink. Each chamber has a heat transducer in it, which is driven (heated) as needed to create a vapor bubble that ejects an ink droplet through a print zone  70  onto the sheet  30 .  
         [0026]     The cartridge  60  has a circuit mounted to it (not shown) that includes exposed contacts that mate with contacts of a circuit carried inside the carriage  62 . The carriage is connected, as by a flexible, ribbon-type multi-conductor to the print controller  80 , which provides to the cartridges control signals for precisely timed ejection of ink droplets. The droplets render the image on the advancing sheet  30  as the carriage  62  is reciprocated across the printer.  
         [0027]     As an alternative to the four-cartridge configuration just described, the present invention may be implemented with a single cartridge containing discrete reservoirs of the four inks, wherein each ink color is channeled to a discrete nozzle set on a single print head. Also, as will become clear, the invention may be implemented in a system that employs two interchangeable cartridges: one containing black ink and the other containing three ink colors.  
         [0028]     Inasmuch as the present invention calls for printing of one side of the media sheet  30  for viewing through another side, one of ordinary skill will appreciate that the image data provided by the print controller  80  to the ink cartridge will be ordered in a way to print a mirror image of the image that is viewed.  
         [0029]     In addition to controlling the ink ejection from the ink cartridge  60 , the print controller  80  provides signals suitable for controlling a drive motor  82 , which, via a gear transmission  84 , controls the rotational speed and direction of the rollers in the printer. In this regard, the transducer carried on the edge-detect roller  50  provides a signal to the print controller  80  in response to the movement of the detector toward the pick roller  34 , which movement occurs as the trailing edge  56  of the sheet  30  passes from between those rollers  50 ,  54  in the feed direction shown by arrow  58 . Once the trailing edge  56  of the sheet  30  is detected, the print controller is apprised of the length of the media sheet  30  (as a result of a comparison of the metering signals corresponding to the opposing edges of the sheet) and drives the feed roller  54  by an amount sufficient to allow printing of the image to the margin of the sheet.  
         [0030]     After the image is printed, the feed roller  54  is paused while the sheet  30  is supported, as by edge shelves  88 , to permit partial drying of the ink. After the pause, the rotational directions of the feed roller  54  and pick roller  34  are reversed to retract the sheet  30  in preparation for “painting” the printed image with the backing  26 .  
         [0031]     As shown in  FIG. 3 , the sheet  30  is retracted in a direction (arrow  90 ) opposite to the direction the sheet moved (arrow  58 ,  FIG. 2 ) during printing. The edge  56  of the sheet  30  follows the pick roller  34  until engaging the gate  48 , which is in the closed position ( FIG. 3 ). The dashed arrow  92  shows the path of the retracted sheet, which moves into contact with a retraction roller  94  that is driven by the drive motor  82  as discussed above. Idler rollers associated with the retraction roller are omitted for clarity.  
         [0032]     In a preferred embodiment, the edge  56  of the retracted sheet  30  moves away from the retraction roller  94  in the printer such as shown by arrow  95  into a space between a back guide surface  96  and two or more guide rollers  98 . The retracted sheet  30  does not contact the roll  100 , the significance of which is described more fully below.  
         [0033]     The sheet  30  is fully retracted when the leading edge  44  of the sheet is moved into the print zone  70 . At this time, the backing is applied. To this end, one of the ink cartridges, the black ink cartridge, is swapped with a backing container  102  such as shown in  FIG. 3 . This container  102  holds the backing in liquid form and is shaped to match the configuration of the ink cartridges  60  (hence, easily fitting into the carriage  62 ).  
         [0034]     As to the make-up of the liquid backing, any liquid that dries as an opaque, preferably white, layer will suffice, provided that the image is unaffected by the application of the backing or its application.  
         [0035]     In the preferred embodiment, the backing liquid is a composition much like black ink used in ink-jet printing, except for the substitution of titania particles for carbon black. More particularly, the backing liquid is a solution of 5 to 10% by weight polyvinyl alcohol (5% being preferred) and 2 to 10% by weight titania particles (2% preferred) having a maximum size of less than about 100 nanometers. In order to ensure complete coating of the titania particles, the solution is subjected to ultrasonication for at least 10 minutes.  
         [0036]     Without undue experimentation one could certainly arrive at other formulations for the backing liquid. For example, one concerned with ensuring the liquid is absolutely opaque may use titania in an amount more than 10% by weight. In any event, the backing liquid can be considered a white paint that is opaque when dry and thereby provides an effective photo-media backing.  
         [0037]     The backing liquid of the present embodiment is applied in a manner analogous to printing. In this regard, a print head  104  is connected to the backing container  102  in a manner and location that matches the print head  68  of an ink cartridge  60 . The print head is a thermal type, as described above, although one could employ any drop-on-demand type print heads, such as a piezoelectric type.  
         [0038]     The print controller  80  controls the carriage  62  and backing container print head  104  to eject the backing liquid by an amount sufficient to cover the printed image as the media sheet  30  is advanced through the printer in a manner described above in connection with  FIG. 2 . Once the backing is applied and dried, the edge shelves  88  are moved to permit the finished print to drop into an output tray (not shown).  
         [0039]     It is contemplated that the backing container  102  can be mounted independently of the ink cartridge(s)  60 , thus obviating the need for swapping one for the other. For instance, the overall carriage size could be increased to carry a fifth container, the backing liquid container  102 . Also, a separate carriage assembly could be provided sufficiently downstream (i.e., relative to arrow  58 ,  FIG. 2 ) to apply the backing without the need for retracting the sheet  30  as described above. This downstream support of a backing liquid container is depicted in dashed lines of  FIG. 4 , with the backing container shown at  103  and the separate carriage (or extension of the same carriage  62 ) shown at  63 . Also, in such an embodiment, a page-wide array of backing liquid print heads could be provided for eliminating the need for a reciprocating carriage having backing-liquid containers. These alternative approaches would increase throughput.  
         [0040]     As noted earlier, another embodiment of the present invention employs as a backing  26  of the print  20  ( FIG. 1 ) a sheet of material that is bonded to the coated side of the transparent base  22 . The media handling system just described in connection with the prior embodiment, however, can be employed in applying either the liquid backing or the sheet backing.  
         [0041]     This alternative embodiment is described with reference to  FIG. 4 . In short, the media sheet  30  carrying the printed image is retracted by the retraction roller  94  (along the direction indicated by arrow  95 ) by an amount such that the edge  56  of the sheet  30  engages the nip between a pressure roller  102  and a roll of backing material  100 .  
         [0042]     The backing material  100  comprises a white plastic film that is coated with a transparent, pressure-sensitive adhesive, which adhesive faces outwardly to contact the ink-receiving coating  24  of the sheet  30 . The adhesive-coated film  100  can be considered as a pressure-sensitive tape. The geared drive motor  82  drives the pressure roller  102  such that the backing tape is bonded to the sheet as the sheet advances between the roller  102  and roll  100 .  
         [0043]     It is noteworthy here that best results are obtained when the sol-gel of the ink-receiving layer  24  is prepared to be translucent or “milky” in appearance, thereby to effectively hide any adhesive that may appear on non-printed portions of the image. This translucence in the sol-gel can be accomplished by blending titania into the sol-gel mixture before it is applied as the ink-receiving coating  24 .  
         [0044]     As the edge  56  of the sheet  30  is directed to the pick roller  34  (in the direction of arrow  108 ) it encounters a lightweight upper gate  49 . That gate  49  is pivotally attached at one end to the printer chassis and is weighted so that it normally moves under the force of gravity into a position (See  FIG. 2 ) where its free end prevents any media sheets from moving toward the roller in a direction opposite arrow  108  ( FIG. 4 ). The contact by the edge  56  of the media sheet  30  causes the gate  49  to swing open (clockwise in the figures) into the position shown in  FIG. 4 , thereby to permit the media sheet  30  to continue in the direction of arrow  108  through the passage toward the pick roller  34 .  
         [0045]     After the edge detect roller  50  contacts the edge  56  of the advancing, backed sheet  30 , the print controller  80  controls the pick roller  34  and pressure roller  102  so that the edge  44  of the sheet is stopped at a location (shown as dashed line  104 ) just past the nip of the pressure roller  102  and roll  100 . The user is then prompted to open the rear cover  106  of the printer to sever the tape at the location  104 . When the tape is severed, the printed advances the backed sheet to the output tray.  
         [0046]     As yet another alternative embodiment, the white, opaque backing can be prepared as individual sheets and applied, using a conventional lamination process, to the image printed as described in connection with  FIG. 2 . Such an approach would obviate the need for the above-described mechanisms for retracting the printed image.  
         [0047]     Irrespective of which backing embodiment is selected (liquid “painting,” separate sheets, etc.) in one or more embodiments of the present invention, the backing, transparent base  22 , or both, may be waterproof. Additionally, in one or more embodiments of the present invention, the backing, transparent base, or both, may be constituted to provide scratch resistance, ultraviolet (UV) radiation protection, and/or fluorescence.  
         [0048]     Although preferred and alternative embodiments of the present invention have been described, it will be appreciated by one of ordinary skill that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.