WO1997001796A1

WO1997001796A1 - Composite sheet and methods for printing differently-transformed images using composite sheet

Info

Publication number: WO1997001796A1
Application number: PCT/US1996/010528
Authority: WO
Inventors: Eric Karl Zeise
Original assignee: Eastman Kodak Company
Priority date: 1995-06-29
Filing date: 1996-06-17
Publication date: 1997-01-16
Also published as: JPH10505300A; EP0778961A1

Abstract

A composite sheet and a method for printing differently-transformed images using a composite sheet. In the method, a composite sheet is provided that has first and second portions. The first portion defining a primary receiver having a first set of receiver spectral characteristics. A secondary receiver is selected. The secondary receiver defines a second set of receiver spectral characteristics. A set of colorants is selected. The colorants define a first set of colorant spectral characteristics for printing the first receiver and a second set of colorant spectral characteristics for printing the second receiver. The first sets of spectral characteristics, taken together, have one or more differences from the second sets of spectral characteristics. Digitized first and second images are provided. The digitized first image is normalized relative to the first sets of spectral characteristics to provide a normalized-digitized first image. The digitized second image is normalized relative to the second sets of spectral characteristics to provide a normalized-digitized second image. After the normalizing steps, the colorants are deposited on the portions of the composite sheet. The depositing on the first portion is modulated by the normalized-digitized first image to create a first colorant image. The depositing on the second portion is modulated by the normalized-digitized second image to create a second colorant image.

Description

COMPOSITE SHEET AND METHODS FOR PRINTING DIFFERENTLY- TRANSFORMED IMAGES USING COMPOSITE SHEET

Field Of The Invention The invention relates to printing methods and media. The invention more particularly relates to composite sheets having two or more different portions and methods for printing differently-transformed images on different portions of a composite sheet.

Background Of The Invention

In a number of uses it is desirable to print either matched images or images that differ from each other in a controlled manner, on two or more different receivers. For large production runs, the images can be printed independently and any differences between images on different receivers can be adjusted by any means including trial and error. The economic cost of the adjustment is minimal, on a relative basis, since the cost can be amortized over the production run. Small production runs are subject to different economic constraints. The amortized cost of an adjustment between different images can rapidly overrun the value of the product. One approach for solving this problem is to print multiple images at the same time on the same printer, then use the images separately. This approach is very practical if the receivers are all the same or very similar, but breaks down if the receivers are substantially different in terms of spectral properties.

It is therefore highly desirable to provide methods in which two or more receivers, having substantially different spectral characteristics can be printed with substantially similar colorant images using a single composite sheet.

It is also highly desirable to provide a composite sheet having a transfer portion and two or more different non-transfer portions.

Summary Of The Invention

The invention provides a composite sheet and a method for printing differently-transformed images using a composite sheet. In the method, a composite sheet is provided that has first and second portions. The first portion defines a primary receiver having a first set of receiver spectral characteristics. A secondary receiver is selected. The secondary receiver defines a second set of receiver spectral characteristics. A set of colorants is selected. The colorants define a first set of colorant spectral characteristics for printing the first receiver and a second set of colorant spectral characteristics for printing the second receiver. The first sets of receiver and colorant spectral characteristics, taken together, have one or more differences from the second sets of receiver and colorant spectral characteristics. Digitized first and second images are provided. The digitized first image is normalized relative to the first sets of receiver and colorant spectral characteristics to provide a normalized-digitized first image. The digitized second image is normalized relative to the second sets of receiver and colorant spectral characteristics to provide a normalized-digitized second image. After the normalizing steps, the colorants are deposited on the portions of the composite sheet. The depositing on the first portion is modulated by the normalized-digitized first image to create a first colorant image. The depositing on the second portion is modulated by the normalized-digitized second image to create a second colorant image. It is an advantageous effect of the invention that two or more different receivers can be printed with substantially similar colorant images using a single composite sheet and individual normalization ofthe different images.

It is an advantageous effect ofthe invention that a composite sheet is provided that has a transfer portion and two or more different non-transfer portions.

Brief Description Of The Figures

The invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying figures wherein:

Figure 1 is a schematic diagram of an embodiment of the methods of the invention.

Figure 2 is a generalized diagram of the methods of the invention. Figure 3 is a cross-sectional view of a composite transfer sheet useful in the methods of the invention.

Figure 4 is a cross-sectional view of an embodiment ofthe composite sheet of the invention.

Figure 5 is a diagrammatical view of an embodiment of the apparatus of the invention. Detailed Description of the Invention

In the methods of the invention two or more colorant images are printed onto two or more different receivers, using a composite sheet having two or more portions with differing compositions. The colorant images are printed from digitized images individually normalized to eliminate or minimize differences in the spectral characteristics ofthe different receivers and differences in the spectral characteristics of the colorants when printed on the different receivers. The term "colorant" is used herein to refer generically to finely divisible materials that can be affixed to another object to modify its spectral characteristics. Specific examples of colorants are solid and liquid inks and electrophotographic toners. Typically these materials include one or more dyes or pigments and a binder or solvent. "Colorant" is not limited here to colored materials, but also includes materials that alter other spectral characteristics; for example, light-scattering agents. The terms "deposit", "depositing" and the like are used herein to refer generically to processes in which a colorant is moved from a source to an initial receiving surface on an image-wise basis; that is, the colorant is moved to the surface so as to form a desired colorant image. The terms "transfer", "transferring", and the like are used herein to refer generically to processes in which a previously formed colorant image is moved from an initial receiving surface to a final receiving surface. The terms "print", "printing", and the like are used herein to refer generically to one step or multi-step procedures by which a colorant image is formed and permanently affixed to a receiving surface. For example, in electrophotographic printing, a latent or charge image is formed on a photoconductor, the latent image is developed by the deposit of toner, and the resulting toner image is subsequently fused to a receiver to provide a permanent or print image. If desired, the toner image can initially be formed on a transfer surface and can then later be moved to and permanently affixed to a secondary receiving surface.

An embodiment of the methods of the invention is shown, in summary form, in Fig. 1. The composite sheet 10 has three portions 12,14,16.

The first portion 12 defines a first receiver. A first colorant image 20 is deposited and affixed, that is printed, onto the first portion 12. In the particular embodiment shown, the first portion 12 is a piece of substantially opaque material, such as a certificate, suitable for displaying a print image under front lighting. The term "front lighting" is used herein to refer to illumination that is predominantly reflective from the surface of a colorant image or reflective from a substantially opaque surface disposed behind and substantially contiguous with a colorant image. Front lighting can be considered to have a point of origin in front of the colorant image, , on the same side of the colorant image as the viewer. The term "back lighting" is used herein to refer to illumination that is predominantly transmissive through a colorant image.. Back lighting can be considered to have a point of origin behind the colorant image, that is, on the side of the colorant image opposite the viewer.

The second receiver is a plaque 18. The corresponding second portion 14 of the composite sheet 10 is transfer material. The second colorant image 22 is initially deposited on this second or transfer portion 16 and then later fixed to the plaque 18. For many colorants, fixing requires the application of heat and pressure, symbolized by arrows 19. In the embodiment ofthe invention shown in Fig. 1, the plaque 18 is opaque. For example, the plaque 18 can be reflective metal. The plaque 18 and the fixed second colorant image 22^* are -Uluminated by front lighting.

The third receiver is defined by the third portion 16 of the composite sheet 10. A third colorant image 24 is deposited and affixed, that is, printed onto the third portion 24. In the particular embodiment shown, the third portion 16 is a piece of substantially transparent material, suitable for displaying a print image under back lighting, in a lighted holder 26 or the like. (The first portion 12 and third portion 16 are also referred to collectively herein as "non- transfer portion". This same term also applies to the first portion 12 of a composite sheet 10 having only first and second portions.)

The different portions 12,14,16 of the composite sheet 10 can provide substantially uniform images or can be varied for artistic effect For example, the certificate 12, plaque 18, and display 26 could each have the same color pictorial background in combination with text, line art, and additional color pictorial infoπnation, respectively.

The general features of the methods of the invention are further illustrated in Figure 2. (As a matter of convenience, the following and most discussion herein are directed to embodiments ofthe invention having only two different receivers. It will be understood, however, particularly with reference to Figure 1, that various embodiments ofthe invention can have two, three, or more different portions like the portions discussed in detail herein.) Differently- transformed images are printed on primary and secondary receivers, using a composite sheet having two or more portions. First, the composite sheet is provided (30) and a secondary receiver is selected (32). A first portion of the sheet is the primary receiver and defines a first set of receiver spectral characteristics. The secondary receiver is selected from either a second portion of the composite sheet or an extraneous object. In the latter case, the second portion of the composite sheet is referred to herein as a transfer portion, since a colorant image is deposited on the second portion and then later transfened to the secondary receiver.

A very wide variety of objects can be used for such a secondary receiver, subject to the limitation that the object must be capable of accepting the colorant image. Examples of secondary receivers include: clothing, china, glass wear, and compact digital discs.

The secondary receiver defines a second set of receiver spectral characteristics. A set of colorants is selected (34), which define first and second sets of colorant spectral characteristics. Digitized first and second images are provided (36), (37), respectively . The digitized first image is normalized (38) relative to the first sets of spectral characteristics. The digitized second image is normalized (39) relative to the second set of spectral characteristics. The normalized, digitized images then modulate the formation (40) of colorant images on respective portions ofthe composite sheet. The portions are then separated (42).

The composition ofthe different portions ofthe composite sheet can be varied to meet the requirements of a particular use. Suitable materials for non-transfer portions ofthe sheet are those materials that are suitable for use as receivers for the colorants used. For example, using electrophotographic printing methods, the colorants are electrophotographic toners and the receivers are electrophotographic receivers, such as bond paper and electrophotographic transparency material. Similarly, using ink jet printing methods, the colorants are inkjet inks and the receivers are opaque or substantially opaque ink jet papers or plastic receivers or ink jet transparencies. The different portions can be joined together in a variety of ways. For example, adjoining portions can be adhered together at an overlap or scarf joint. The invention is not limited to composite sheets having a particular geometry. For example, different portions can be continuous areas joined together at contiguous margins or, as illustrated in Figure 1, one or more portions can be surrounded by a matrix of other material. In a particular embodiment of the methods of the invention, the differently-transformed images are printed on a type of composite sheet referred to herein as a "partial transfer sheet". Particular partial transfer sheets, useful in the method ofthe invention, are disclosed in a PCT Patent Application No. filed concurrently with this application, entitled: "TRANSFER SUPPORT AND METHOD FOR FUSING A TRANSFERABLE IMAGE TO A DIGITAL DISC", which is hereby incorporated herein by reference.

Referring now to Fig. 3, the composite or partial transfer sheet 10 is substantially planar and has a front or receiving surface 46 and a back surface 48. The partial transfer sheet 10 has a support layer 50 and a transfer layer 52. The support layer 50 is a substantially planar electrophotographic receiver, that is, a sheet of copy paper or transparency material or other sheet material which can receive an electrophotographic toner image and to which the electrophotographic toner image can be permanently fused. The support layer 50 can be uniform in composition or can have a multilayer structure.

The transfer layer 52 overlies part of the the support layer 50. The partial transfer sheet 10 thus has a transfer portion 14, which includes both support and transfer layers 50,52, and a non-transfer portion 12, which includes only the support layer 50. The relative sizes ofthe non-transfer and transfer portions 12,14 are determined by the ultimate uses of the respective portions. The transfer layer 52 is a low surface energy material that has an adhesive strength, relative to the transferable colorant image 22, that is within a selected range that allows the transfer layer 52 to retain and then release the transferable colorant image 22 as required by the method of the invention. This adhesive strength is expressed herein as a peel force, (peel forces herein are as measured at 90°). The transfer layer 52 has a surface energy that is insufficient to retain a transferable colorant image 22 subject to a peel force of greater than 550 Newtons/meter. In a preferred embodiment ofthe invention, the transfer layer 52 has a surface energy that is insufficient to retain a transferable colorant image 22 subject to a peel force of from 3 to 15 Newtons/meter. The transfer portion 14 is preferably substantially free of "bare spots" or other artifacts in the transfer layer 52 which would cause fenotyping.

In particular embodiments ofthe invention, the low surface energy material of the transfer layer is selected from the group consisting of alkyl fluorophosphonates and amorphous perfluorocarbons. In some embodiments, the invention is directed to the transfer of a toner image from such a transfer support to an article, such as a digital disc or other digital media. In a particular embodiment of the invention, the low surface energy material of the transfer layer is an alkyl fluorophosphonate having the general structure:

( F— ( CF₂ ) — ( CH₂ ) — O ) ( OR ) ₃ _.

where j is 1 or 2; m is from about 3 to about 8; n is from about 1 to about 6; and R is selected from the group consisting of NH4 and OH. One example of a commercially available alkyl fluorophosphonate is identified by the general structure:

^F— < ^F ₂ ) — < ^CH2 ) — P ( ONH₄ ) ₂

where m is from 3 to 8. This material is available from E.I. du Pont de Nemours and Co. of Wilmington, Delaware, under the designation: "Zonyl™ FSE". Zonyl™ FSE has a surface energy of from 16 to 20 dynes/cm. Another commercially available alkyl fluorophosphonate is identified by the general structure:

( F — ( CF, ) ( CH 2, )- 2 -0 ) _j— P- ( OH ) 3, - j

where m is from 3 to 8 and j is 1 or 2. This material is available from E.I. du Pont de Nemours and Co. under the designation: "Zonyl™ UR". Zonyl™ UR has a surface energy of from 16 to 20 dynes/cm. In another particular embodiment of the invention, the low surface energy layer material of the transfer layer is an amorphous perfluorocarbon having the general structure:

where R represents the atoms and electrons necessary to complete a perfluoro ring having a total of 5 carbons and heteroatoms, and d and e are mole fractions having a sum of 1. Some specific examples of a commercially available amoφhous perfluorocarbons are identified by the general structure:

F F

( ) „ ( CF, CF,

where a and b are mole fractions having the sum of 1. An amoφhous perfluorocarbon having this structure where a = 0.65 and b = 0.35 is available from E.I. du Pont de Nemours and Co under the designation: "Teflon™ AF 1600. Another amoφhous perfluorocarbon having this structure where a = 80 and b = 20 is available from E.I. du Pont de Nemours and Co under the designation: "Teflon™ AF 2400". Teflon™ AF 1600 and Teflon™ AF 2400 are aqueous or non-aqueous copolymerization products of tetrafluoroethene and 2,2- bis(trifluoromethyl)-4,5-difluoro-l,3-dioxolane. The glass transition temperamre (Tg) of Teflon™ AF materials is a function of the relative mole fractions of a and b. Teflon™ AF 1600 has a T_g of 160°C. Teflon™ AF 2400 has a T_g of 240°C. Suitable T_g's for the material of the transfer surface 14 are in the range of about 35°C to about 300°C.

The partial transfer sheet can include a visible indicator (not shown) to aid an operator in properly orienting the sheets in the paper supply of the printer. The visible indicator can be located on the back or in a "waste" section of the sheet

The partial transfer sheets just described are suitable for use with a conventional electrophotographic printer or copier. A prefened electrophotographic printer suitable for use in the method of the invention is a Kodak ColorEdge™ printer, Model 1550+, marketed by Eastman Kodak

Company of Rochester, New York. In an electrophotographic printer or copier, a latent charge image is formed and then developed with discrete particles of toner to form a toner image, which is then fused, commonly by the use of both heat and pressure. If a toner image on a partial transfer sheet is developed and fused in an electrophotographic printer or copier, the toner image on the non-transfer portion fuses with the support layer to provide what is refened to herein as a "fused toner image". On the transfer portion, the toner image is "unfused" and is described herein as being a "transferable toner image" or a "transferable image". The term "unfused" is slight misnomer. In the transfer portion of the partial transfer sheet toner particles forming the transferable image are fused to each other, but the transferable toner image is not so adhered to the transfer portion that it will not transfer to a secondary receiver, for example, an electrophotographic receiver placed in contact with the transferable toner image under conditions substantially the same as those in the fusing system of the electrophotographic printer. The term "secondary receiver" is used herein to designate an item to which the transfenable image is permanently fused. There is sufficient adherence of the transferable toner image to the transfer portion so as to prevent significant offset, that is, retention of a portion of toner image on the fusing system of the printer.

The partial transfer sheet can be printed by a non- electrophotographic printer, for example, an ink jet printer. The ink used and transfer layer material can be adjusted to allow transfer to a secondary receiver and a fusable pigment can be used in the ink to permit fusing of the colorant image to the secondary receiver. In other embodiments of the methods ofthe invention, the differently-transformed images are printed on a type of composite sheet also referred to herein as a "paper-transparency sheet". The composite sheet has a first portion of paper and a second portion of transparency material. Referrmg now to the embodiment shown in Figure 4, the composite sheet 100 of the invention includes multiple or non-transfer portions 12,16 and at least one transfer portion 14. The support layer 50 can have an opaque subportion 64 that is composed of substantially opaque electrophotographic receiver material, for example, copier paper. The support layer 50 also has a transparent subportion 66 composed of substantially transparent electrophotographic receiver material, for example, electrophotographic transparency material. The two subportions 64,66 are joined together; for example, the two portions can be adhered together at an overlap or scarf joint 68. The transfer layer 52 overlies part of the opaque subportion 64, defining the transfer portion 14. The materials described above in relation to the composite sheet 10 are suitable for the composite sheet 100 of the invention.

The selection of a composite sheet and the selection of a set of colorants are dictated by the requirements of a particular use; such as, the number of receivers, the types of receivers, and the desired visual and physical characteristics of the print images.

Colorants and receivers are described herein in relation to their spectral characteristics as printed on respective receivers. This takes into account receiver-colorant interactions and changes in spectral characteristics resulting from the printing process. For example, changes in gloss due to fenotyping during electrophotographic printing depend upon the surface in contact with a toner image during fusing. A first print image produced by depositing and heat and pressure fusing toner to a first portion of the composite sheet will have a gloss determined largely by the surface characteristics of a fuser roll or other fusing mechanism. A second print image produced by depositing toner on a second, transfer portion of the sheet converting the toner into a transferable image, then transferring and fusing the transferable image to a second receiver, will have the surface characteristics of the transfer sheet Similarly, the different procedures used to prepare the different print images can alter respective colorants and receivers in different ways. In the procedure just discussed, the colorant of the first print image was subjected to fusing conditions, typically elevated temperature and pressure, in a single fusing step. The colorant of the second print image was subjected to fusing conditions twice, once for the conversion of toner into the transferable image, and a second time, for the fusing ofthe transferable image to the secondary receiver. Any alteration or degradation of colorant resulting from fusing conditions will differ between the first and second print images. In the methods of the invention, there is thus a single set of colorants, but multiple sets of colorant spectral characteristics, representing the characteristics of the colorants as images printed of the different receivers.

The methods of the invention are directed to producing on different receivers, images that are either substantially -uniform in appearance or differ in a controlled manner. To do so, the methods of the invention take into account differences between the first sets of spectral characteristics, taken collectively, and the second sets of spectral characteristics, necessarily also taken collectively. This difference in spectral characteristics can be restated. The spectral characteristics of the first receiver in combination with the spectral characteristics of the set of colorants, as modified by printing steps required for the first receiver, differ from the spectral characteristics of the second receiver in combination with the spectral characteristics of the set of colorants, as modified by printing steps required for the second receiver. The two sets of receiver spectral characteristics can differ and the two sets of colorant spectral characteristics can be the same. Alternatively, the two sets of receiver spectral characteristics can be the same and the two sets of colorant spectral characteristics can differ. In still another alternative, the two sets of receiver spectral characteristics can differ and the two sets of colorant spectral characteristics can differ. The receiver and colorant differences are not offsetting, that is, the receiver and colorant differences do not compensate for each other.

The methods of the invention can be used in applications in which the first sets of spectral characteristics, taken collectively, are the same as the second sets of spectral characteristics; however, there is no advantage to doing so, except as a matter of convenience. For example, the methods of the invention could be used to print multiple images on ordinary paper in alternation with the printing of composite sheets ofthe invention.

The colorant images originate, for the puφoses of the methods of the invention, as digitized images within the digital memory of a computing device. The digital images used can, for example, be created by graphics, or computer- aided-design programs, or can be the product of an image capture device. The digital images can be created in one computing device and be transferred to another by electronic or other means.

The specific format for the digitized images is not critical and can be varied to meet the requirements of particular computing devices and printers. A convenient form for a digitized image is a bit map of the pixels of the image. For a binary black and white printer, the pixel specification is either 0 or 1. For a continuous tone, three-color printer, the pixel specification is typically a set of three eight-bit values (representing the decimal values of 0 to 255) for each of cyan, magenta, and yellow colorants. The digitized images are generally discussed herein as separate and discrete items of digital information. The digitized images are not limited to that format The digitized first and second images could, alternatively, take the form of a bit map for the first image, and instructions on the manipulation of that bit map for the second image. For example, the same bit map could be used for both first and second images, or a bit map could be used in a normal manner for the first image and the minor-reversal of that bit map could be used for the second image, or different bit map manipulations for both images.

Digitized images, as a matter of convenience, are discussed herein in geometric terms. Mathematical transformations equivalent to the geometric transformations discussed herein, and suitable for manipulation of digitized images, are well known to those skilled in the art Since the composite sheet defines a substantially two-dimensional surface for the deposit of the colorant images, the digital images must finally be expressed in terms of two-dimensional geometry. Prior to that time, however, the digital images can be manipulated as three- dimensional images or the like. For example, a two dimensional image can be mapped onto a three dimensional surface representing the shape of a particular secondary receiver and then be mapped onto a two dimensional projection of the surface, or these steps can be combined in a single mapping operation.

In addition to any geometric manipulation, the digitized images are each normalized relative to the spectral characteristics of a respective receiver and colorant set The terms "normalize" and "normalization" and the like are used herein to describe the mapping of a respective set of standardized specifications of visual perceptions for a particular receiver and colorant set to a set of control parameters used in printing. The normalization includes the mapping of a respective set of color specifications to a set of printer control values. The set of color specifications is a standarized representation, such as NTSC, RGB, CIELAB or CIE tristimulus values, for visual stimuli from the respective combination of receiver and colorant spectral characteristics in a particular viewing environment. A separate map is used for each combination of receiver and colorant spectral characteristics, that is for each colorant image. Maps of color specifications can be predetermined, or, less desirably, can be determined as needed as a part of the methods of the invention.

The viewing environments used for each map should conelate with expected viewing conditions for the respective colorant image. The different colorant images can each, of course, be normalized utilizing sets of colorant specifications conesponding to different viewing environments.

A set of colorant specifications determined in one viewing environment can be used, as a rough approximation, to normalize for all viewing environments. It is highly prefened, however, that a nominal viewing environment be designated for each colorant image prior to normalization of the respective digitized image and that the normalization utilize a set of colorant specifications conesponding to that nominal viewing environment. The nominal viewing environment can be limited to what is refened to herein as a "primary viewing environment". This term designates spectral characteristics of the illumination source or sources and the iUumation and viewing geometry. These parameters can be standardized and the selection of the nominal viewing environment can be reduced to a few choices in the same manner as the selection of a film type in professional photography. For example, the primary viewing environment can be designated as an illuminant selected from standard illuminants such as daylight, incandescent lighting or office fluorescent illumination with a standardized viewing geometry, such as 45° viewing/0° illumination.

If desired, the specification of the nominal viewing environment can be expanded to what is refened to herein as a "secondary viewing environment". This term is used to describe viewing parameters that are inclusive of the primary viewing environment and also include differences in ambient conditions, such as dim or dark sunound. In this case the map is produced by combining the map as defined for the primary viewing environment with an additional transformation to accomodate the visual adaptation occurring for these differing ambient conditions. Referring to Figure 1, the first and second receiver could be mapped for the secondary conditions of normal sunound, cool-white fluorescent front lighting illumination at 0° and a displacement of 6 to 10 feet with a viewing angle of 45°. The third receiver could be mapped for the secondary conditions of dim sunound, back lighting iUumination by incandescently lit diffuse white panel at 0° with a viewing angle of 0°.

Normalization based upon a nominal viewing environment has the shortcoming that if the colorant spectral characteristics are not broad or if measuring and viewing illuminants are substantially different measurement results may not accurately predict the perception ofthe colorant image under actual viewing conditions. An approach that can compensate for viewing differences is to use a map of color specifications generated by measuring the receivers and colorant set with illuminants representative of the actual viewing environment for the colorant image or measure spectroradiometric values of receiver, colorant set, and illuminant rather than tristimulus values of the receiver and colorants under a given illuminant

A map of color specifications can be based upon an analytical (theoretical) or empirical approach. The map can take a variety of forms: a mathematical function, a set of mathematical values in an anay, a neural network, or the like. In the theoretical approach, the map of color specifications is created from a physical model ofthe printing process, the parameters of which are populated by specific measurements ofthe process involved. A mathematical model is then derived which accurately describes printing device behavior for each of the portions of the composite sheet. Reasonably accurate theoretical models are very complex, as are mathematical functions describing those models. Given the large number of pixels typically processed to print a page (about 35 million pixels for an 8.5 inch by 11 inch page printed at a resolution of 600 pixels/inch) it is often more convenient to form a computationally simple representation of the composite model. A 3 dimensional look-up-table, relating individual color specifications to specific printer control values, is an example of such a computationally simple representation which can describe a fairly complex functional form. A suitable three dimensional look-up table is disclosed, for example, in Schreiber US-A- 4,500,919.

In the empirical approach, the map of color specifications for a particular receiver and colorant, in a particular viewing environment, is generated by iteratively printing color patches and relating measurements of those patches to specific control values required to produce a given color specification in that viewing environment. The map can be expanded, as desired for other primary or secondary viewing environments. More specifically, a procedure like the following can be undertaken for each of the portions ofthe composite sheet:

1) Print a sufficient number of patches at known colorant levels to allow reasonable estimation of colorant and receiver spectral characteristics.

2) Measure the visual properties of the patches.

3) Construct an accurate model, such as a three dimensional look-up table, of the device colorant behavior relating printed patch visual properties to requested colorant levels. 4) Create an accurate model, such as a three dimensional look-up table, ofthe visual adaptation mechanisms ocuπing between the viewing conditions of the colorant images in one or more nominal viewing environments and the viewing environment used for measuring the printed patch samples. 5) Combine the models of steps (4) and (5) into a single composite model, such as a composite three dimensional look-up table, which accurately describes required colorant levels required to provide a given visual stimulus from the printed and transfened region when viewed under intended nominal viewing conditions. The result of the calibration process is an accurate map which can either be used directly to calculate the bitmap image required to drive a printer and create the proper visual stimuli on the receivers, or to populate a computationally simple calculational procedure which can be utilized at great speed to derive the bitmap image required to drive a printer and create the proper visual stimuli on the receivers.

Normalization can be simplified by the use of receivers and colorant sets having standarized spectral characteristics. Nominal values of spectral characteristics can then be used for normalization. If desired, the normalization process can include a step of selecting from a series of predetermined standardized maps representing particular combinations of colorant set receiver, and standarized viewing conditions.

The maps utilized in the normalization process can take into account the physical hmitations of the printing process. For example, color reproduction can be poor when a light colored transparent colorant is used with a dark colored receiver. The map can delete the use of any colorant in such areas. The methods of the invention are generally discussed herein in terms of three-color images. Colorant sets are not limited to three colorants. In the previous example, a map could provide for a white undercolorant where hght colored colorant overlay dark colored receiver.

The normalized, digitized images are used to print the colorant images on respective receivers. More specifically, the normalized, digitized images modulate the deposit of colorant on respective portions of the composite sheet. The resulting images may be subject to additional steps, such as fusing, or transfer and fusing, to produce final colorant images. Normalization may or may not be completed prior to the printing of a respective colorant image. Included as a part of printing is any additional conversion or manipulation of the digital images required by a particular printer. For example, resolution ofthe image (number of pixels) can be decreased to the resolution level of the printer or apparent resolution of an image can be increased. Suitable algorithms for this and similar p poses are well known to those of skill in the art. After any necessary conversion or manipulation, the digitized images are used to modulate the deposit of colorant on the composite sheet. Colorant amounts are typically controlled by pixel color specifications. For a black and white binary printer, the pixel specifications are either 0 or 1 (0 may represent no deposit of colorant and 1 may represent full colorant coverage ofthe pixel area). For a continuous tone, three color printer, pixel specifications are provided for each colorant. Typically pixel specifications are 8-bit values (0 to 255) for cyan, magenta and yellow colorants, defining three bit mapped planes composed of a rectilinear array of pixels. (Such an array is 5100 elements wide and 6600 pixels high to represent an 8.5 inch by 11 inch at a resolution of 600 pixels/inch) The three bit mapped planes modulate the depositing of colorants by the printer.

A typical printing process (here, more accurately, a "colorant deposition process") requires data in pixel sequential order delivered to a deposition head (that is, ink jet head, LED anay, rasterized laser, or the like) synchronously with the position of the deposition head on the composite sheet The methods of the invention require different normalizations, that is, different pixel processing procedures, for the different portions of the composite sheet. The bitmap of processed pixels for the deposition head to deposit can either be formed ahead and stored as a precached or buffered store of pixel data which can be provided to the printer as fast as the printer requires or as a sequential stream of processed pixels which are processed as needed by the printer. If a precached store of pixel data is used, then normalization and any additional conversion or manipulation ofthe digitized images (refened to collectively herein as "pixel processing" and, referring to the processed digitized images, as "processed pixels") is completed prior to colorant deposition. Otherwise, pixel processing and colorant deposition occur stepwise, one pixel at a time. In an intermediate case, pixel processing and colorant deposition, are stepwise not fbrjndividual pixels, but for a region or band of composite sheet at a time.

The appropriately processed pixels must be supphed to the deposition head for each of the different portions of the composite sheet that is, different portions of the composite sheet require different pixel processing procedures. For example, if the deposition head is actuated in a raster fashion for a two portion composite sheet, then the pixel processing required switches back and forth as portion boundaries are crossed by the deposition head.

The required switching between different pixel processing procedures can be provided by an architecture in which pixel processing, in effect switches from one look-up-table to another as portion boundaries are crossed. If printing is done from a precached bitmap, the switching of pixel processing can be accomplished by loading a single LUT processer with the values appropriate for that portion and then processing data for each portion in turn. If printing requires individual pixels to be processed sequentially, all LUT processors can be loaded simultaneously. Switching can be provided by choice of LUT processor. Pixels can also be processed by all LUT processors and switching can be reduced to choosing whichever value is appropriate for a particular composite sheet portion.

If all colorants are applied for a pixel (rather than all pixels for each colorant in turn as in color frame sequential printing, then the processors for each colorant have to be paralleled.

The precached bitmap can be smaller than a full page if the color processing can keep up with the printer throughput on average. In this case, bands of pixels are processed in turn with one of the architectures described above. This can be used to save on memory requirements for the bitmap cache. After printing, the different portions are separated and mounted in holders or otherwise processed for a particular use. Transfer portions are brought into contact with an appropriate receiver and then fused. Fusing is illustrated in Figure 1. A transfer portion is disposed within a press with the transferable colorant image and a surface of a secondary receiver juxtaposed. The press forces transferable image and surface together and heats transferable image and surface to a fusing temperature appropriate for the materials ofthe colorants used. The used transfer portion is discarded or recycled, if appropriate (not shown).

Additional procedures can be provided as a part of transfer. For example, the fused colorant image can be varnished to modify gloss or covered by a protective layer. Gloss can also be modified by fenotyping, that is, selecting a transfer portion that can "mold" a desired surface finish on the fused image.

An embodiment of the apparatus 70 of the invention is illustrated schematically in Figure 5. A controller 72 supplies processed pixels to a printer 74 having a supply 76 of composite sheets. (Composite sheets 10 are shown, however, the same apparatus 70 could be illustrated utilizing composite sheets 100.) Colorant images 20,22 are deposited by a deposition head 80 (an ink jet head, or latent image formation and toner transfer system, or the like) of the printer 74 using a set of colorants supplied by a colorant source 82 (an ink cartidge, a series of developer stations or the like). Although it is not considered desirable, different colorant sources could be used for different portions of the sheet Each colorant source would include the same colorant set.

Portions 12,14 of the composite sheet 10 are then detached by a separator 84 (illustrated as a knife edge). A first non-transfer portion 12 is then complete and is removed from the apparatos 70. A second, transfer portion 14 is ahgned with a secondary receiver 18 in a fuser 86. The fuser has fuser members 88 complementary in shape to the secondary receiver 18. After fusing, the used transfer poition is discarded (not shown) and the secondary receiver 18, bearing the fused second colorant image 22' is removed from the apparatus 70. Movement of the composite sheet 10, portions, 12,14, and so on, between different parts of the apparatus 70 can be provided manually or by automated means well known to those skilled in the art.

Composite Sheet List

composite sheet 10 colorant image 20 first portion 12 secondary receiver 18 second portion 14 second colorant image 22 third portion 16 third colorant image 24 lighted holder 26 composite sheet 30 secondary receiver 32 colorants 34 digitized first image 36 digitized second image 37 digitized first image normahzed 38 digitized second image normalized 39 modulated images 40 separated portions 42 transfer sheet 10 receiving surface 46 back surface 48 support layer 50 transfer layer 52 transfer portion 14 non-transfer portion 12 composite sheet 100 transparent subportion 66 scarf joint 68 opaque subportion 64 controller 72 printer 74 apparatus 70 deposition head 80 colorant source 82 separator 84 secondary receiver 18 fuser 86

Claims

What Is Claimed Is:

1. A method for printing differently-transformed images using a composite sheet said method comprising the steps of: providing a composite sheet having first and second portions, said first portion defining a primary receiver having a first set of receiver spectral characteristics; selecting a secondary receiver defining a second set of receiver spectral characteristics; selecting a set of colorants, said colorants defining a first set of colorant spectral characteristics for printing said first receiver and a second set of colorant spectral characteristics for printing said second receiver, said first sets of receiver and colorant spectral characteristics, taken together, having one or more differences from said second sets of receiver and colorant spectral characteristics; providing digitized first and second images; normalizing said digitized first image relative to said first sets of receiver and colorant spectral characteristics; normalizing said digitized second image relative to said second sets of receiver and colorant spectral characteristics; and after said normalizing steps, depositing said colorants on said portions of said composite sheet said depositing on said first portion being modulated by said normahzed digitized first image to create a first colorant image, said depositing on said second portion being modulated by said normalized digitized second image to create a second colorant image.

2. The method of claim 1 further comprising, after said depositing, separating said first and second portions.

3. The method of claim 1 wherein said secondary receiver has different spectral characteristics than said primary receiver.

4. The method of claim 3 wherein said first portion of said sheet is further characterized as a non-transfer portion and said second portion of said sheet is further characterized as a transfer portion; and further comprising transferring said second colorant image from said second portion to said secondary receiver.

5. The method of claim 4 further comprising, prior to said depositing, minor reversing said digitized second image.

6. The method of claim 1 further comprising, prior to said forming, defining a set of geometric parameters of said secondary receiver, and mapping said digitized second image onto an imaginary geometric surface defined by said set of geometric parameters.

7. The method of claim 1 wherein said second portion defines said secondary receiver and said first and second portions have different spectral characteristics.

8. The method of claim 1 further characterized as: after said normalizing steps, electrostatographically printing said digitized images.

9. A composite sheet comprising: a support layer of electrophotographic receiver material, said support layer having a substantially opaque section and a substantially transparent section, said sections being bonded together; and a transfer layer overlying a portion of said support layer.

10. The composite sheet of claim 9 wherein said substantially opaque section is paper, said substantially transparent section is transparency material and said transfer layer has a surface energy that is insufficient to retain a transferable electrophotographic toner image subject to a peel force at 90 degrees of about 550 Newtons/meter.