Abstract:
An inkjet printing apparatus includes a printing assembly adapted to create inkjet images on a medium. A durability station provided in series with the printing assembly is adapted to apply direct a durability material in solution with a supercritical carbondioxide solvent onto the medium to provide an overcoat for protecting inkjet prints.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    Cross reference is made to commonly assigned co-pending U.S. patent application Ser. No. 09/684,183 filed in the names of Mark S. Janosky et al. on Oct. 6, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a inkjet apparatus for printing images, more particularly to such apparatus that coats the images with a durable material.  
         BACKGROUND OF THE INVENTION  
         [0003]    Durability is a performance criterion that is expected by consumers of photographic and other prints. This criterion includes resistance to tearing, fading, water and chemical exposure plus numerous other factors. In the current state of the art, silver halide prints demonstrate a high degree of overall durability in relation to inkjet. This fact is one of the reasons why inkjet near photographic quality printing technologies are not completely supplanting the silver halide share of the market. However, these other technologies are rapidly improving durability through the addition of materials and processes.  
           [0004]    One example of a non-silver halide printing process that produces a durable photographic quality print is the Kodak Picture Maker. The Kodak Picture Maker creates durable prints by using the same thermal dye diffusion printing process that is used to produce the image on the media. Specifically, this printing process is one in which dye is transferred from a donor ribbon to media by means of heating a thermal print head while the print head, donor ribbon and media are in mechanical contact. By performing this process in a serial fashion for three separate primary color patches (sometimes there is a fourth black patch) in a controlled manner, an image can be produced on the media. To ensure durability, this printing process is performed one more time except that instead of dye transfer, a continuous clear overcoat material is transferred to the media. This process is often referred to as peel-apart or thermal transfer overcoat (TTO).  
           [0005]    A second example of a non-silver halide printing process that produces a durable photographic quality print is the Canon Hyperphoto. Patents associated with this type of process are U.S. Pat. Nos. 4,832,984 and 4,785,313, as well as European Patents 0 858 905 A1 and 0 858 906 A1. In the Canon Hyperphoto, the original media has already been pre-coated with a special chemical layer prior to printing (actually done during the production of the media). This coating is designed such that during the inkjet printing process, the inks can penetrate the layer and stabilize on an ink-receiving layer below the special coating. The Canon Hyperphoto then uses a heated fuser to seal this top coating over the image after the print cycle is complete. This process is often referred to as incorporated since the durability material is already incorporated into the media prior to printing.  
           [0006]    Recently, inkjet printing has become a popular method for printing photographic quality images. Inkjet printing is now being developed for retail photofinishing. While the printed images are of high quality, inkjet prints suffer from a number of disadvantages relative to other hard copy out puts. In particular inkjet prints have poor water fastness, light fastness, finger print resistance, and abrasion resistance. Thus there is a need for improved dye chemistry and improved overcoats. Further more, in order to increase inkjet printing through put a fast-drying receiver is required. Fast drying receivers are porous and are low gloss. Thus, an overcoat is also useful increasing the gloss of the printed image.  
           [0007]    Overcoats could potentially provide a low cost solution because the desired protection may be packed into one layer. Hydrophobic polymers may be used to eliminate water penetration. The polymers may also be formulated to reduce the permeation of gas such as ozone that are known to bleach dyes. The overcoat may also be packed with UV screening agents to improve light fastness. Adhesion promoters such as copolymers and wetting agents may be formulated into the over coat to provide defect-free coatings that will not blister or delaminate. These ideas are being incorporated in current overcoat formulations with some success but they suffer from cost, waste, and difficulties in providing adequate protection while balancing environmental concerns at the point of use.  
           [0008]    A polymer formulation to be coated at the point of use after a print is generated requires a solvent that meets a higher environmental standard. Solvents that are odorous, flammable and hazardous will not be acceptable. Hydrophobic polymers that provide the best protection against water damage are incompatible with a water solvent. Compromises of using hydrophilic-hydrophobic copolymers would not be effective because they are not as effective against fingerprints and abrasion. Hydrophobic lattices dispersed in water could potentially be useful but coated films are prone to pinhole defects that allow water to penetrate. They also require considerable annealing to allow the lattices to coalesce and form a continuous film. This may require extra equipment such as heaters or fusing rollers, which adds to cost and detracts from high productivity.  
           [0009]    Even if water were to be used as the solvent, considerable cost would be associated with the removal of the water solvent. This requires a drying station, which adds to cost and productivity. When receivers are loaded with water, the receiver tends to cockle after drying. Therefore, some cost savings in the receiver design may be realized if the overcoat does not increase solvent burden on the receiver.  
           [0010]    Supercritical carbondioxide has been studied as alternative solvent for organic materials such as high molecular weight polymers, hydrophobic polymers, surfactant copolymers, and drugs. It has been suggested as an environmentally friendly solvent.  
         SUMMARY OF THE INVENTION  
         [0011]    It is a feature of the present invention that supercritical carbondioxide be used as solvent in providing overcoats for protecting inkjet prints. The advantages of using supercritical carbondioxide include the following: 
           [0012]    1. The range of polymers can be used is be greater than if water were the solvent because supercritical carbondioxide is a better solvent than water. For example, the permissible polymers include high molecular weight hydrophobic materials. In particular, polymeric components include vinyl, acrylic, styrenic, siloxane, urethane monomers and interpolymers of the base vinyl, acrylic and styrenic, siloxane and urethane monomers; poly(methylmethacrylate), organo-silane, cellulosic esters, polyesters, and fluorinated polymers may potentially be used with a supercritical carbondioxide solvent.  
           [0013]    2. Supercritical carbondioxide is environmentally friendly.  
           [0014]    3. Using supercritical carbondioxide as solvents eliminates the need of a drying station because supercritical carbondioxide rapidly converts to a gas. The risk of receiver cockle is reduced or eliminated.  
           [0015]    4. Supercritical carbondioxide dries rapidly improving productivity. 
           [0016]    The above and other objects, advantages and novel features of the present invention will become more apparent from the accompanying detailed description thereof when considered in conjunction with the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings in which:  
         [0018]    [0018]FIG. 1 is a photofinishing apparatus block diagram;  
         [0019]    [0019]FIG. 2 is a post-print treatment processor block diagram;  
         [0020]    [0020]FIG. 3 shows a top view of a preferred embodiment of the apparatus of the invention;  
         [0021]    [0021]FIG. 4 shows a side view of the preferred embodiment of the apparatus of the invention; and  
         [0022]    [0022]FIG. 5 is a detailed view of a portion of the photofinishing apparatus of FIGS.  1 - 4 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    The present description will be directed in particular to elements forming part of, or in cooperation more directly with, the apparatus in accordance with the present invention. It is understood that elements not specifically shown or described may take various forms well known to those skilled in the art.  
         [0024]    Referring now to the drawings, wherein like reference numerals represent similar or corresponding parts throughout the several views. FIG. 1 illustrates a block diagram of a generic photofinishing apparatus  10 . Photofinishing apparatus  10  is partitioned into five major subsystems. These subsystems include a film processor  12 , a film scanner  14 , an image data manager  16 , an inkjet printer  18 , and a finisher or post-print treatment processor  20 . The basic functions of each of these systems are described as follows. Film processor  12  chemically processes rolls of film  22  (orders) into negatives  24 . Scanner  14  digitizes negatives  24  or other printed images  26  into raw digital image data  28 . Image data manager  16  performs image processing on raw digital image data  28  (either from an outside source or from film scanner  14 ) and converts this raw digital image data  28  into processed digital image data  30 . Inkjet printer  18  then uses this processed digital image data  30 , image materials (inks)  32  (including ink) and media  34  to produce printed media  36 . Finally, finisher or post-print treatment processor  20  performs any operation following printing (such as back printing, drying, durability application of a durability material  38 , cutting, and/or print sorting) which results in durable prints  40 .  
         [0025]    There are three basic formats of printed media  36  as it leaves printer  18 . The first format is printed media  36  that is already cut into prints  40 . The second format is printed media  36  that have a plurality of images on a media segment  46  (FIGS. 2 and 3). The third and final format is printed media  36  that is continuous or in a roll form (not shown).  
         [0026]    While each format demonstrates some advantages over the others, and the present invention is applicable to all formats, the illustrative embodiment of the present invention will be the media segment  46  format which includes multiple images on a print, as well as borders along the edges and between the images.  
         [0027]    [0027]FIG. 2 illustrates a block diagram of the illustrative embodiment of post-print treatment processor  20 . Post-print treatment processor  20  is partitioned into four major process stations. These process stations include a drying station  50 , a durability station  52 , a cutting station  54 , and a sorting station  56 . The machine control of these stations is performed by a control computer (CPU)  58  and control electronics  60 .  
         [0028]    Drying station  50  performs any necessary drying prior to any durability application or fixing that will take place. Durability station  52  performs the function of applying a liquid overcoat of durability material  38  to media segment  46  to produce a durable media segment  62 . Cutting station  54  performs the function of converting durable printed media  62  into durable prints  40 . Finally, sorting station  56  performs the function of taking durable prints  40  from cutting station  54  and organizing them in a way that the photofinisher can return the durable prints  40  to a customer as sorted durable prints  40 ′.  
         [0029]    The process thread that holds these stations together is the basic media transport that occurs throughout post-print treatment processor  20 . This transport encompasses a further feature of the invention. FIGS. 3 and 4 illustrate the detailed architecture of a preferred embodiment of post-print treatment processor  20  that pertains to this invention. These figures illustrate the top and side view perspectives, and can be referenced along with FIG. 2 for the rest of the description.  
         [0030]    As noted, printer  18  can use any preferred printing technology but should be able to produce a media segment  46  that has a plurality of printed images  44  (FIG. 3). The plurality of images  44  may be tiled or positioned on media segment  46  in numerous combination forms with borders between the images and/or along the edges of the images. These combinations are mainly a function of the geometry of media segment  46 , the print formats that can be worked with by the overall photofinishing apparatus  10 , and the statistical image makeup of film or digital orders being processed by photofinishing apparatus  10 .  
         [0031]    Drying station  50  receives media segment  46  as follows. The lead edge of a media segment  46  feeds onto a front platen  64  from printer  18  and an entrance detection sensor  68  detects it. This detection allows control computer  58  to begin the control of the drying and transport functions through control electronics  60 . First, a dryer  66  is set to an appropriate temperature. Next, a set of urge rollers  72  that are used to transport media segment  46  through drying station  50  are sped up to the appropriate speed. This speed is set so as to allow the desired amount of drying to take place as media segment  46  passes under dryer  66  and moves toward durability station  52 .  
         [0032]    Next, the same urge rollers  72  that provide the basic forward motion transport are used in combination with a front platen edge guide  74  and a front platen alignment mechanism  76  to perform an alignment function for upstream cutting station  54 . Basically, urge rollers  72  use conical shaped rollers that provide forward and lateral motion simultaneously. By designing the frictions and loads between urge rollers  72 , media segment  46  and front platen  64  correctly, media segment  46  will straighten out and ride with one side edge against front platen edge guide  74 . At this point, the alignment now is dependent on the alignment of front platen  64  and durability station  52 . This is accomplished by using front platen alignment mechanism  76  that is adapted to allow all or some of the six rigid body degrees-of-freedom of front platen  64  to be adjusted.  
         [0033]    Exiting drying station  50 , media segment  46  will trigger an exit detection sensor  70  within drying station  50 . The signal generated by exit detection sensor  70  will be used by control computer  58  and control electronics  60  to start the durability treatment process as the media segment  46  approaches the entrance of durability station  52 . Referring to FIG. 5, the entrance to durability station  52  is a nip created by a pair of rollers  78 . Before entrance of a media segment, durability station  52  has been placed in an idle mode to minimize waste.  
         [0034]    Exiting the nip of rollers  78 , media segments  46  are transported below a nozzle head  80  having an array of spray nozzles, not shown, spaced (but not necessarily aligned) across the path of the media segments. The nozzle head is in fluid communication via a conduit  82  with reservoir  38  of durability material in solution with a supercritical carbondioxide solvent. Conduit  82  is valved at  84  under the control of CPU  58 . Durable media segments  62  exit durability station  52  through a nip created by a second pair of rollers  86 .  
         [0035]    The durability material may be pure, such that a powdery material may be deposited on the media segment upon conversion of the supercritical carbondioxide to a gas. It is possible that an additional step would be needed to fuse the powder. Alternatively, a second, co-solvent may be carried by the durability material so that a fusing step is not required. Such a co-solvent might, for example, be a ketone, an alcohol, a glycol ether, a hydrocarbon, etc.  
         [0036]    After station  52 , media segment  46  is ready to go through a two-axis cutting process within cutting station  54 . Cutting station  54  is comprised of a slitting station  90 , a pull roller set  92 , a segment chopping station  114 , a rear platen  96  (including urge rollers  72   a ), a rear platen right edge guide  98 , a rear platen left edge guide  100 , and a print chopping station  102 . Slitting station  90  is further broken down into a right edge slitter  104 , a left edge slitter  106 , a center slitter  108 , an edge slitter position mechanism  110  and a center slitter retract mechanism  112 . Segment chopping station  114  is further broken down into a segment detection sensor  116 , a waste control mechanism  118 , and a waste drawer  120   a . Print chopping station  102  is further broken down into a print chopper  122 , a lead edge metering roller set  124 , a lead edge sensor  126 , a trail edge metering roller set  128 , a trail edge sensor  130 , a metering roller retract mechanism  132  and another waste drawer  120   b.    
         [0037]    As media segment  62  is pulled through slitting station  90 , right edge slitter  104 , left edge slitter  106 , and center slitter  108  are engaged. As pull rollers  92  pull media segment  62  through slitting station  90 , media segment  62  is actually split into two new media segments, a right split media segment  134  and a left split media segment  136  (FIG. 3). The waste material generated by the slitting operation is deposited into waste drawer  120   a.    
         [0038]    Pull rollers  92  push right split media segment  134  and left split media segment  136  between the respected sets of urge rollers  72   a  and rear platen  96 . A set of spring fingers  140  aids this guidance action. This pushing action continues until segment detection sensor  116  detects the media segment trail edge of the right split media segment  134  and left split media segment  136 . The signal from this detection is used by the intelligence of control computer  58  and control electronics  60  to drive right split media segment  134  and left split media segment  136  until their trail edge is just slightly downstream of segment chopper  114 .  
         [0039]    At this point, the entire transport system of post-print treatment processor  20  is shutdown and durability station  52  is put into an idle mode again. As the right split media segment  134  and left split media segment  136  rest on rear platen  96 , segment chopper  114  is activated and a single cut is made. The two split media segments are now completely independent of one another.  
         [0040]    Once the right split media segment  134  and left split media segment  136  (FIG. 3) are separated from one another, they need to be aligned for the final print chopping process. This alignment process begins by allowing urge rollers  72   a  associated with right split media segment  134  to drive the segment toward print chopping station  102 . The alignment occurs in the exact same manner as was described for front platen  64 . Beginning with the right side, urge rollers  72   a  use their conical shape to laterally move the right split media segment toward the rear platen right edge guide  98  while simultaneously moving the right split media segment  134  toward print chopping station  102 . This same action can occur in parallel or in series between the left split media segment  136  and the rear platen left edge guide  100 . At this point, either the right split media segment  134  or left split media segment  136  is ready to be chopped into durable prints  40 .  
         [0041]    Right split media segment  134  and left split media segment  136  are ready to be print chopped. FIG. 4 illustrates the use of single print chopper  122  such as a known guillotine or rotary chopper. Two print choppers would allow the overall throughput to be improved. With single print chopper  122 , the act of cutting right split media segment  134  and left split media segment  136  into durable prints  40  occurs as follows. Urge rollers  72   a  feed split media segment  134  forward so that the lead edge enters the nip of lead edge metering rollers  124 . Lead edge metering rollers  124  are already accelerated to a constant velocity and after they grab right split media segment  134  it essentially has taken the transport control away from urge rollers  72   a . Lead edge metering rollers  124  transports right split media segment  134  forward until the media lead edge within the segment is detected by lead edge sensor  126 . Since the location of the plurality of images  44  are known relative to this lead edge, lead edge metering rollers  124  begin to position right split media segment  134  within print chopper  122 . There are two basic cutting processes that can be used at this point. One process is to perform the entire cut in one cutting stroke. The second process is to perform the required cut by using a series of small cuts and metering jogs. Using either method results in the waste media falling into waste drawer  120   b  below print chopper  122 .  
         [0042]    Once the waste media is trimmed off from the lead edge of the first image, lead edge metering rollers  124  transport right split media segment  134  towards trail edge metering rollers  128 . At this point, trail edge retract mechanism  132  has opened the nip of trail edge metering rollers  128 . This is done in order that the lead edge of right split media segment  134  can easily be pushed through this nip and positioned such that the trail edge of the image can be chopped. Once positioned, trail edge retract mechanism  132  closes and print chopper  122  is activated. This action now separates a finished print  40  from the rest of right split media segment  134 . Finished print  40  is now transported to one of entrance chutes  142  on sorting station  56 . The same print chopping cycle is repeated for the plurality of images  44  on the rest of the right split media segment  134 . Once complete, the exact same process can be performed for the left split media segment  136 .  
         [0043]    As noted trail edge metering rollers  128  act as the transport mechanism for moving durable prints  40  into sorting station  56 . Sorting station  56  is the final process and is composed of a set of entrance chutes  142 , an elevator mechanism  144 , a set of exit trays  146  additional urge rollers (not shown). As noted before, sorting station  56  is functionally the mechanism that accepts durable prints  40  and stacks them in an appropriate manner which makes it easy for the photofinisher to get the durable prints  40  back to the customer. As with some of the other systems in this description, sorting station  56  in its own right is very complicated and is not the focus of this invention. However, the embodiment used in this invention simply allows elevator mechanism  144  to raise entrance chutes  142  such that a given finished print can be transported into one of the chutes. The finished print then slides down the chute due to gravity and is allowed to be transported to a selected exit tray  146  by means of urge rollers (not shown) associated with that exit tray. This process is controlled under the intelligence of control computer  58  and control electronics  60 .  
         [0044]    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.