CA1078500A - Solid-state color imaging devices and method for making them - Google Patents

Abstract

SOLID-STATE COLOR IMAGING DEVICES
AND METHOD FOR MAKING THEM

Abstract of the Disclosure A color imaging device is comprised of means for sensing radiation comprising a planar array of charge-handling semiconductor photosensors, preferably at least one of the photo-sensors having a radiation sensing area with at least one dimension less than about 100 micrometers, and superimposed thereon, filter means for controlling access of radiation to the sensing means.
The filter means comprises a transparent mordant layer with a plurality of radiation intercepting means defining a planar array of filter elements lying in the mordant layer in micro-registra-tion with the sensing areas of the photosensors. The filter area of each intercepting means contains at least one mordantable dye which absorbs radiation in at least one portion of the spectrum and transmits radiation in at least one other portion of the spectrum. The color imaging device comprises an interlaid pattern having at least two sets of intercepting means, the first set having a different radiation absorption and transmission characteristic from that of the second set.

Description

~ield of the _vention The invention relates to solid-state color imaginK
devices, particularly to a solid-state photosensitive device that has a planar array Or charge-handling semiconductor photosensors in micro-registration with a multicolor planar array of filter elements. The color imaging . _ _ . .. .
devices are particularly useful for solid-state video cameras.
Description Relative to the Prior Art A reliable yet sensitive all-solid-state camera would find abundant utility, including, for example, use in television, card readers, facsimile recorders, picturephor~es, and character recognition, etc. However, in addition to the problems of the bulk of non-solid-state cameras which are further prone to drift, misalignment and short tube life, color cameras suffer from the complications of having to register separate electron bearns and to reduce the effects of electron beam lag. Thus, a relatively simple efficient color camera which overcomes these problems is still sought.
Color photosensitive devices using soLid-state image sensors of various types, for example, charge coupled devices, known as CCDs, and charge coupled imagers known as CCIs, have been proposed for and used in video cameras. To avoid optical complexity and problems with image registration, it is highly desirable that color image sensing occur at a single imaging site, e.g., at a single planar photosensitive array. Difficulty is encountered with such "single-site"
color imaging, however, because at least three distinct types of color information must be extracted in order to represent a color image in video signal form.
3~ One known approach to prov:Ldlng a ";ing:Le-sLte"

color sensing device uses a single irnage sensor of broad wavelength sensit:ivity and a cooperat:Lng filter disc which 1, .

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passes a series of color fllters through the image beam in a repeating sequence. The filter interpositions are synchro-nized to image-scanning, a filter typically being interposed during an entire field scan. Devices operating in this manner are said to produce a "field sequential" color sig-nal. One problem with this approach is that the resulting signal presents the extracted color image information in a time order which is radically different from the time order of~ say, the standard NTSC video signal. (The standard NTSC
video signal is described in Chapter 16, "Television Trans-mission", Transmission Systems for Communications, revised :'third edition, by members of the Technical Staff of Bell Telephone Laboratories, copyright 1964, Bell Telephone Laboratories, Inc.) A further disadvantage is that some of the color image information (e.g., blue image information if a blue filter is utilized) tends to be disproportionately detailed and hence wasteful of sensor capacity in consid-eration of the response characteristics of the human eye.
Certain other proposed approaches to achieving "single-site" color image-sensing call for the use of striped color filters superposed on a single image sensor. One such type of image sensor uses filter grids which are angularly superimposed on one another. (See ~S Patent 3,378,633 by Macovski issued April 16, 1968.) As a result of image-scanning, such image sensors produce a composite signal wherein chrominance information is represented in the form of modulated carrier signals. Such apparatus may be adapted to produce signals in the NTSC format or, i~ desired, the color image information can be separated by frequency domain tec~miques. In practice, however, it has proven difficult to produce such sensors economically, partlcularly where detailed image information is required.

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Striped filters whiCh transmit a repeating sequence o~ three or more spectral bands have also been proposed for use in color imaging. With this arrangement, the filters are typically aligned in one direction and scanning o~ the image is performed orthogonally to that direction. In effect, elemental sample areas are defined along the filter stripes.
With this arrangement, i~ will be appreciated that sampling for a given color is not uniform for both directions. Addi-tionally, the sampling patterns which result tend to provide a disproportionate quantity of information regarding basic color vectors to which the eye has less resolving power, e.g., "blue" information relative to "green" information.
Another approach to color imaging which has been proposed is the "dot" scanning system, as discussed in US Pat-ent 2, 683,769 by Banning issued July 13, 1954 O That approach generally uses spectrally selective sensor elements which are arranged in triads (red, green and blue elements respectively).
However, in US Patent 2,755,334 by Banning issued July 17, 1956, a repeated arrangement of four element groupings (red-, green-, blue- and white-sensitive elements, respectively) is described. Such approaches to color imaging have not been -of practical significance, in part because of the cost of fab-ricating the number of individual elements which are ~equired to provide image in~ormation having adequate detail.
Many of the problems associated with the prior art discussed above are overcome by the approach taken in US Patent 3,971,065 by Bayer issued July 20, 1976. In the Bayer approach, color imaging is effected by a single imag-ing array composed of individual luminanc0 and chrominance senslng elements which are d:lstribllted according to type (sensitivity) in repeating i.nterlaid patterns, the lumi~
nance pattern exhibiting the highest frequency of --4~
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occurrence -- and therefore the hlghest rre~uency of image sampling -- irrespective of direction across the array.
Preferably, to produce an element array according to the Bayer approach, a solid state sensor array of broad wavelength sensitivity is provided with a superposed filter array. Filters which are selectively transparent in the green region of the spectrum are preferably employed in producing luminance-type elements~ and filters selectively transparent in the red and blue spectra] regions, respectively, are preferably employed in producing chrominance-type elements.
(The term "luminance" is herein used in a broad sense to refer to the color vector which is the major contributor of luminance information. The term "chrominance" refers to those color vectors other than the luminance color vectors which provide a basis for defining an image.) Methods for providing a multicolor fi]ter array are known in the art. For example, U.S. Patent No. 3,839,039, issued October 1, 1974 to Suzuku et al shows a multicolor filter which consists of a plurality of monocolor stripe filters ~laminated together, each monocolor stripe filter made by a process comprising exposing a substrate having a photosensitive surface to light through a striped mask, converting the light image into a metallic image, forming a dichroic layer uniformly on top of the metallic image and removing the dichroic layer together with the metallic layer. U.S. Patent No. 3,771,857, issued November 13, 1973 to Thomasson et al shows another multieolor striped filter which consists of a plurality of layers of striped monocolor filters formed succe.;s:lvcly on top of eaeh other. U.S. Patent No. 3,623,794, issued November 30, 30 1971 to S.L. Brown and U.S. Patent No. 3,6:l9,~41, issued November g, 1971 to D.W. Wil:loughby show multicolor filters consisting of a lamination of monocolor Krating filters com-prising photoresist grating patterns filled with dye-vehiele 78~

filter materials hav~ng preferential ahsorption in diff'erent regions of the visible spectrum.
As can be seen by the above-described patents, prior art multicolor filters comprise multiple layers of monocolor filter patterns stacked sequentially on t,op of each other in order to obtain multicolor filter arrays. However, it is desirable for each element in the filter array to be as close as possible to the surface of the underlying photosensor element or elements in the array. This result is most desirably 10 accomplished by producing a relatively thin, single ],ayer multicolor filter array superimposed on the surface of the image sensor. A single layer multicolor filter array substantially reduces the possibility that light rays which pass through a filter element at an angle to the optical axis wil], strike a photosensor element beneath an adjacent filter element. ~urther, higher resolution can be obtained by reducing the depth of focus requirements for the optics.

Summary of the Invention In accordance with the present invention a color ~', imaging device is provided which comprises means for sensing radiation comprising a planar array of charge-handling semicon-ductor photosensors, preferably at least some of the photosensors having at least one dimension that is less than about 100 micro-meters, more preferably each of the photosensors having a radiation sensing area less than 10 4 square centimeters, and superimposed thereon, filter means for controlling access Or radiation to the sensing means. The filter means comprises a transparent mordant layer and a plurality of radiation intercepting means defLninlr a planar array of fl,lter elements lyi,ng in the mordant ]ayer ln micro-registration with the sensing area or areas of the photo-sensors. The filter area of each intercepting means contains at least one mordantable dye which absorbs radiatlon in at least one 1~3~8~
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portion of the spectrum and transrnits radiation in at least one other portlon of the spectrum.
Color imaging devices of thls invention have an interlaid pattern of filter elements made of at least two sets of intercepting means, each set having a common ra~iation absorption and transmission characteristic different from each other set. The photosensors lying immediately beneath each set of intercepting means will respond to radiation transmitted by the overlying filter elements.
The color imaging devices of the present invenjtion are formed by superimposing the filter means on the sensing means so that each filter element of the filter means is in micro-registration with the underlying photosensor of the sensing means. Generally, it is desirable to have the filter means contiguous with the sensing means; however, in certain embodiments where the filter means are formed on a thin transparent layer of film base (for example, as a substrate), the filter means can be separated from the sensing means by the thin film layer when superimposed on the sensing means (in other words, the thin film support layer can be considered an integral part of the filter means in such embodiments). Even so, for these embodiments, -it is preferred to superimpose the filter means on the sensing means with the filter means closest to the sensing means and the transparent substrate on the outer side. The filter means is provided by forming a transparent mordant layer on a substrate.
The substrate can be the sensing means itself, a transparent support material which can be superimposed on the sensing means, or a support from which the filter means can be transferred to and superimposed on the sensing means.
A plurality of radiation interceptin~r means de~lning an array of filter elements is formed ln the transparent mordant layer by:
A. forming a transparent mordant layer on a substrate;
B. coating a layer of photoresist over the mordant layer;

3~7~5130 C. exposing the photoresist to a pattern representing a set of filter elements and developing the photoresist ~o obtain window areas in the photoresist layer corresponding to said pattern;
D. imbibing a dye into the mordant layer through the window areas to fix the dye in the mordant layer by reason of the lateral restraint to dye migration exhibited by the mordant layer, thus forming dyed filter elements corresponding to said pattern;
E. removing the rernaining portions of the photoresist to yield a first set of dyed filter elements in a planar array in the mordant layer; and F. repeating steps (B) through (E) at least once to form another set of dyed filter elements in the mordant layer in an interlaid pattern with the first set, each repetition of the steps yielding an additional set Or dyed rilter elements in an interlaid pattern with the prior sets, each set having a common light absorption and transmission characteristic which differs from each other set.
Brief Description of the Drawings Fig. lA is a cross-sectional representation, in part, of a color lmaging device depicting a filter element in which dye is imbibed into a layer without a mordant;
Fig. lB is a cross-sectional representation, in part, of a color imaging device depicting a filter element in which dye is imbibed into a layer containing a mordant;
Fig. 2A is a pictoria]. representat:l.on of a mult:L-color filter array formed ln accord wi~h a preferred embodiment of the invention, Fig. 2B is an exploded pictorlal representatio corresponding to the array depicted in Fig. 2A;

Fig. 3A is a cross-sectional representation, in part, of a row Or sensing elements Or a color imaging device having a ~78S~
planar filter array f'ormed in accordance w~th the present invention;
Fig. 3B is a cross-sectional representation, in part, of a row of sensing elements ad~acent the row represented in Fig. 3A;
Fig. 4 is a perspective representation showing a basic arrangement of elements for a camera system using a color imaging device according to the invention; and Figs. 5A through 5F depict a sequence of steps in a preferred implementation for forming one color pattern in the filter array in accord with the invention.
Detailed Description of the Invention In accordance with the present invention, a color imaging device is provided which has filter means comprising a plurality of radiation intercepting means defining a planar array of filter elements superimposed on an array of solid-state photosensors. The solid-state photosensors useful in this invention are charge-handling image sensors examples of which include, for instance, charge-coupled devices (also known as charge-coupled imagers, charge-transfer devices, charge-transfer imagers), charge-injection devices, bucket brigade devices, diode arrays, combin-ations of these, and the like. Each filter element is in micro-registration with the radiation sensing area of the underlying photosensor or photosensors. As used herein the term "micro-registration" means that def'ined areas having at least one dimension less than about 100 micrometers, for example, the filter areas and sensing areas described herein, are allgned so that, on a micro-meter scale, the f'ilter area and underlying sensln~ area or areas are substantially coextensive with each other and the boundaries 30- of such areas are ~ubstantlally superlmposed. Thus a single filter element havlng at least one dlmenslon less than about 100 micro-meters may be superlmposed over one sensing area or a group of $ - 9 -- ~C37~

sensing areas in accord with the particular embodirnent of the invention.
The filter means comprises sets of d~ed filter elements each set having common light absorption and transmission character-istics made by imbibing a mordantable dye into a transparent mordant layer having a mordant for the dyes being used. The mordant layer can also comprise a binder reSin to which the mordant is added. The filter means comprises at least two different sets of light intercepting means. The filter elements of each set of light intercepting means are imbibed with a dye or dyes having radiation absorption and transmission in a different region of the spectrum from that of each other set.

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The ~ransparent mordant layer is a very essential feature of the inventionO When imbibing a dye into an area of a dye receiving layer of a non-mordantable type, the dye will travel both into the layer and also laterally in the layer. As depicted by Fig. lA, the lateral diffusion of the dye will affect the photosensitivity of adjacent photosensors in a color imaging device. When imbibing the same quantity of dye into a mordant layer, however, the mordant layer will fix or substantially immobilize the dye molecules and thus restrict the amount of lateral diffusion, as depicted in Fig. lB. As used herein, the terms "fix" and "immobilize" mean to effectively restrict mobibility or to substantially lessen the tendency for diffusion such that dyes fixed or immobilized in a mordant layer will not diffuse sufficiently to substantially affect the sensitivity of adjacent photosensors (including total immobility as the most desirable embodiment.) Thus~ the use of a mordant provides for better edge definition of the dyed filter area.
The importance of fixing the dye molecules to restrict lateral diffusion is readily apparent when one considers the very small size of the sensing areas of the photosensors in a useful color imaging device and thus the correspondingly small size of the superposed filter elements. It has been suggested by one reference that a color imaging device will consist of an array of over 10,000 photosensors in an area 3X 5 mm2 (see "Charge-coupling Improves its Image, Challenging Video Camera Tubes" by Tompsett et al at pages 166-167 of Electronics, January 18, 1973, pages 162-169). Useful color imaging devices of this invention will general1y comprise photosensors havinLr sensing areas with at least one dlmenslon less than abou~ 100 micrometers and, preferably, having sensing areas of a slze less than about 10 4 square centimeters, and even more preferably less )78513~

than about 2.5 X 10 5 square centirneters. :[n an especially pre-~erred embodiment each sensing area will be rectangular in shape and have dimensions Or 30 by 40 microns. Sensing areas in this preferred embodiment are separated by guard bands approximately 4 microns or less in width. Thus sharp edge definition of filter elements and micro-registration of each filter elernent with the underlying photosensor or photosensors are important.
An example of a three-color filter 8 having a planar array of filter elements is illustrated in Figs. 2A and 2B. Three sets of filter elements 2, 4 and 6 form an interlaid pattern to provide the three-color filter array 8, Each set of f`ilter elements 2, 4 and 6 has a common light absorption and transmission characteristic which is different from each other set. In a preferred color imaging device of the invention, the filter 8 is superposed on an array of photosensors so that each indivi~ual filter element C is in micro-registration with an individual photosensor. As a result of this arrangement, an image can be sampled for all three color vectors by selecting appropriate dyes for use in the three sets of color patterns 2, 4 and 6 of the filter 8.
As illustrated by Figs. 3A and 3B, a preferred color , imaging device of the present invention employs a solid-state imaging array 20 comprised of individual charge-coupled photosensors (e.g., photosensor 22 extending between the dashed lines of Fig. 3A). A filter 8, wherein the Cl, C2 and C3 of Fig. 2A and 2B are now G, R and B, respectively, is superposed on the imaging array 20. The filter 8 includes individual fllter elements 24 which are aligrned in one-to-one micro-registration with indi,vidual photo~en~ors (e.g., pho~oserlsor 22) of the imaging array 20 to rorrn a color imaglng dev:Lce of' the invention. Ind:Lvidual rllter elernents 24 of' the fllter ~ are of the selectively transmitting type and are~ arrange(l in patterns as described above with ref'erence to '~igs. 2A and 2B, The letters G~ ~ and B on individual filter areas 24 serve to 37~Sq3~

indicate selective green, red, and blue light transmission characteristics, respectively~ of the individual filter elements, as would be employed in accordance with the presently pre~erred embodiment - lla -iL~7i 3~

o~ a color imaging device of the invention. A prererred color imaging device of the invention comprises an array of color imaging elements 26, each comprising an individual filter element 24 combined with an individual photosensor such as photosensor 22, the combination being selectively sensitive to a particular region o~ the spectrum.
The filter 8 comprises a transparent mordant layer into which dyes have been imbibed to form patterns 2, 4 and 6 of indivldual filter areas 24. The mordant layer can take any convenient conventional form. In a preferred form, the mordant layer can be a conventional receiver layer o~ the type employed in dye image-transfer photographic elements which typically comprise a polymeric mordant. Examples of mordants and mordant layers useful in the present invention are described in the following US Patents: 2,548,564 by " Sprague and Brooker issued April 10, 1951; 2,548,575 by Weyerts issued April 10, 1951; 2,675,316 by Carroll and Kenyon issued April 13, 1954, 2,713,305 by Yutzy and Carroll issued July 19, 1955; 2,756,149 by Saunders et al issued July 24, 1956; 2,768,078 by Reynolds and Kenyon issued October 23, 1956; 2,839,401 by Gray and Webers issued June 17, 1958; 2,882,156 by Minsk issued April 14, 1959; 2,940,849 by Whitmore and Williams issued June 14, 1960; 2,945,006 by Minsk issued July 12, 1960; 2,952,566 by Condax issued September 13, 1960; 3,016,306 by Mader et al issued January 9, 1962; 3,048,487 by Minsk and Cohen issued August 7, 1962;
3,184,309 by Mlnsk and Cohen issued May 18, 1965; 3,271,147 by Bush issued September 6, 1966; 3,271,1ll8 by ~hitmore issued September 6, 1966; 3,282,699 by Jones and Milton issued November 1, 1966; 3,408,193 by Wol~ and Beckett issued October 29, 1968; 3,488,706 by Cohen and Mlnsk issued January 6, 1970; 3,557,o66 by Cohen and King issued January , . .

50~

19, 1971; 3,625,694 by Cohen et ~l issued December 7, 1971;
3,639,357 by Cohen issued February l, 1972; 3,709,690 by Cohen et al issued January 9, 1973; 3,758,445 by Cohen et al issued September 11, 1973; 3,770~439 by Taylor issued Novem-ber 6, 1973; 3,788,855 by Cohen et al issued January 29, 1974; 3,944,424 by Cohen et al issued March 16, 1976.
Any mordantable dye can be used in the practice of this invention. Preferred dyes include any conventional mordantable dye employed in dye image-transfer photographic elements. Typical examples of such mordantable dyes are described in the above patents. Some specific examples . include, for example, Anthracene Yellow GR (400% pure Schultz No 177~, Fast Red S Conc (Color Index 176), PontacylTM
Green SN Fx (Color Index 737), Acid blue black (Color Index 246~, Acid Magenta O (Color Index ~92), Naphthol Green B
Conc (Color Index 5), Brilliant Paper Yellow Ex Conc 125%

(Color Index 364), Tartrazine (Color Index 640), MetanilTM
Yellow Conc (Color Index 138), PontacylTM Carmine 6B Ex Conc (Color Index 57), PontacylTM Scarlet R Conc (Color Index 20 487) and PontacylTM Rubine R Ex Conc (Color Index 179).
Color imaging devices having a mutlicolor filter layer according to the invention are produced by coating a mordant layer as described above on a planar array of pho-tosensors, e.g., a charge-handling semiconductor device or, alternatively, coating a mordant layer on a suitable sub-strate which can be superposed on the array of photosensors or from which the mordant layer can be transferred to the array of photosensors. ~yes are then iMblbed into the mordant layer in predetermlned patterns to obtain a filter 30 layer having the required color transmission and ab~orption characteristlcs for, say, NTSC video image reproduction.

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To produce the multicolor filter layer ~n ~ccord with one embodiment of the invention~ a semiconductive substrate having a mordant layer (Fig 5A) is first over-coated with a photoresist (Fig 5B). Any suitable photo-resist can be used. Suitable photoresists are selected so that they are compatible with the mordant layer and are soluble in a solvent system different from the dyes to be imbibed into the mordanting layer. Both positive-working and negative-working photoresists may be used in general, although the particular photoresist should be selected for the particular mordant and dye system being used. Examples of photoresists suitable for the practice of this invention are described in US Patent nos 2,610,120 by Minsk and Robertson issued September 9, 1952, 2,670,285 by Minsk and Robertson issued February 23, 1954, 2,670,286 by by Minsk and Robertson issued February 23, 1954, 2,670,287 by Minsk and Robertson issued February 23, 1954, 2,725,372 by Minsk issued November 29g 1955, and 3,046,125 by Wainer issued July 249 1962.
The photoresist is exposed to a pattern which 20 corresponds to a set of filter elements (e.g., pattern 2) as illustrated by Fig 5C. The photoresist is developed to leave an open area in the photoresist corresponding to each filter element in the set. (See Fig 5D. ) A solution o~ a dye is applied and the dye is imbibed into the mordant layer. ~See Fig 5E. ) The remaining photoresist is dis-solved away from the mordant layer and the sequence is repeated for each additional set of filter elements required.
By repeating the sequence of steps twice, i.e., exposin~ to additional patterns such as patterns 4 and 6 ( one in each 30 sequence of steps) and imbibing a different dye in each sequence, a multicolor filter element 8 as illustrated by Fig 2A can be produced.

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I~ the substrate used for coating the mordant layer is a charge-handlin~ semiconductor device, khe above sequence of steps for rorming a multicolor ~ilter array produce a color imaging device in accord with the present invention. I~ the ~ilter layer is formed on another sub-strate such as film base or the like, the filter layer can be stripped from the substrate and superposed on the charge-handling device such that each filter element is in micro- -~
registration with a photosensor, or the filter layer and substrate combination can be so superposed on the charge-handling device, provided that the substrate is transparent to the radiation used to activate the photosensors.
Preferred color imaging devices of this invention are those having filters which selectively transmit green, red and blue light to respective patterns of photosensors.
These devices can be made by imbibing green, red and blue dyes in appropriate patterns according to the steps described above. Alternatively, these devices can be made using subtractive primary dyes, i.e.g yellow, magenta and cyan dyes. In any given filter element, an appropriate combi-nation of two of these dyes would be present to provide a green, red or blue filter. The above-described procedure for making the color filter would then require that two dyes be imbibed into the mordant layer to form a set of filter elements during each masking-exposure sequence. Alterna-tively, a single subtractive primary dye can be imbibed into the mordant layer for two of the three sets of filter layers during each masking-exposure sequence. Two additional sequences would complete the three-color filter. Obviouslyg various combinations of these procedures can be used depend-ing upon the characteristics of the dyes which are bein~
used.

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Referring to Fig L~, a color imagging device 30 accordlng to the invention i~ shown in a simplified camera environment. Image inf'ormation from indlvidual rows of photosensors, such as a row 32 7 iS transferred to a shift register 34 (generally formed "on board" the imaging chip) in response to signals from an interrogating apparatus such as a line scan clock 36. Such operation is well-known7 and apparatus for performing same is described in literature and patents regarding charge-handling devices such as CCD and CID arrays. It is also generally known to process the output signal of the register by means of a circuit 3~.
Using color imaging arrays according to the invention, how-ever7 information for the various base color vectors is interspersed as a result of the intermixed sensitivities of the color array elements. Accordingly, a switching network 40 is provided to separate the image signal sequence to a usable form, for example, to parallel green, red and blue video signals.
In such form, the signals are conveniently con-verted to NTSC format using a conversion matrix 42. This is especially convenient if the numbe-r of rows in the array corresponds to the number of visible lines in a field scan (approximatly 250) or the number of' visible lines in a frame (approximately 500) comprised of interlaced fields.
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 eff'ected within the splrit and scope of the inven-tion.

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SUPPLEM~NTARYDISCLOSIJR
Particularly preferred mordants are polymeric mordants which have a plurality of pendant reactive groups which are capable of forming covalent bonds with the dye used. While khe exact reason for the improved edge sharp~
ness which results from these mordants in comparison with ionic mordants is not completely understood, it has been found that edge sharpness between 1 and 2 microns can be obtained for these covalently mordanted dye deposits.
The covalently bonding polymeric mordants useful in the practice of this invention have pendant reactive groups. These reactive groups can be selected from benzyl halide groups, sulfonyl groups and the like. These pendant reactive groups ~orm a covalent bond with certain mordan-table dyes such as amine dyes, phenol dyes and the like which are useful in the practice of this invention.
The covalently bonding polymeric mordants can be prepared from any ~,~-ethylenically unsaturated addition polymerizable monomer or a mixture of such polymerizable monomers. The polymeric mordant can be a homopolymer, copolymer, terpolymer or the like. Typical unsaturated -comonomers useful for polymerizing with the monomers con-taining pendant reactive groups described herein are, for example, styrene; acrylamide; acrylic and methacrylic acid, acrylic and methacrylic esters such as butyl acrylate, ethyl methacrylate and the like; olefins such as ethylene, pro-pylene, butadiene and the like; 2-acrylamido-2-methylpropane sulfonic acid; vinylbenzyl chloride; maleic anhydride;
divinylbenzene; and the like. These polymeric mordants can be made by methods which are well-known in the art.
Particularly preferred covalently bonding poly-meric mordants are polymers wherein the pendant reactive group is a benzyl halide. Polymeric mordants of this type are descrlbed in US Patent 3,944,424 by Cohen et al issued March 169 1976. The mordants of Cohen et al cannot only contain the benzyl halide reactive group, but also a pen-dant benzyl quaternary ammonium salt group. Thus, these mordants can mordant both covalently bonding dyes and ionic-ally bonding dyes. The preferred polymers of Cohen et al for use in the present invention include terpolymers com-prised of repeating units having the following structure:
-CHz-CH-I. ~ ~ (ionic bonding group) 0N~R2An~ R~
wherein Rl, R2 and R3 are individually selected from a hydrogen atom and a substituted or unsubstituted alkyl group having from about 3 to about 14 carbon atoms, with the proviso that not more than one o~ Rl, R2 and R3 is a hydro-gen atom, and An~ is an anion;

II. I ~ (covalently bondtng ~t/ group) Q

where Q is a halide such as chloride, and III. ~ ~ (cros~l inking group) -CH-CH~-Another preferred-mordant group is that deacribed in Canadian Application Serial No 300,506 by Campbell et al .. .. . .. . . . ......

.
.. . .

filed April 5, 1978. These mordants also covalently bond with certain dyes and are nonionic, anionic or cationic homopolymers or copolymers containing recurring units having the formula selected from the group consisting of:

(1) ~CH2-C~ and (2) ~CH2-C~
( L) n X ( L) n W--CHz CHR1 W--CH=CHR1 wherein R2 is hydrogen or alkyl; n = 0 or 1; R1 is hydrogen, alkyl or aryl; L is a bivalent linking group providing a linkage between the vinyl group and W; W is an electron-withdrawing group and X is a leaving group which can be displaced by a nucleophilie or eliminated in the ~orm of HX
by treatment with alkali.
When R2 is alkyl, it preferably contains from 1-6 carbon atoms such as methyl, ethyl and the like.
Rl can be hydrogen, alkyl preferably containing from 1-12 carbon atoms as described above for R , or aryl preferably containing from 6-13 carbon atoms such as phenyl, naphthyl, tolyl, xylyl and the like.
It is understood that, throughout this speci-fication wherever alkyl, aryl or alkylene are described, the terms are meant to include isomers thereof and substituted alkyl, aryl or alkylene wherein the substituent does not adversely affect the covalent bonding of the dye to the polymer.
The linking group L can be selected from the group consisting of alkylene, preferably containing ~rom about 1 to about 6 carbon ator~s such as methylene, lsopropylene, hexylene and the like; arylene preferably containing from about 6 to about 10 carbon atoms such as phenylene, naph-~. ~

. - .

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thalene and the like; arylenealkylene preferably containing from about 7 to about 11 carbon atoms such as benzyl; cooR3;
and CoNHR3 wherein R3 is selected f'rom the group consisting of arylene, alkylene or arylenealkylene such as described above.
X is a leaving group which can be displaced by elimination in the form of HX under alkaline conditions such as hydroxy, chloro, bromo, iodo, alkyl and arylsulfonyloxy (-OS02P~l), ammonio, sulfato (-OS03-) and the like.
The electron-withdrawing group W stabilizes an ~-carbanion which facilitates ~he elimination of HX resulting in an electron-deficient double bond. W can be selected from the group consisting of -S02-, -C0-, -S0-, lR1 R~
-OC-, ~NCtm and -NSO2-, O O
wherein m is 1 or 2 and Rl is as described above.
When n = 0 in formulas tl) or (2), then W is -S02-or o --OC-- -A highly preferred class of polymers according to the structure described above has repeating units having the ; formulae:
RZ ~R2 ~CHz-C~ or ~CHz-C~
(I)n I (I)n SO2CH2-CH~R1 SOzCH2=CHR1 wherein Rl, R2, L, n and X are as described above. Examples of these polymers are poly(vinylbenzyl 2-chloroethyl sul-fone), poly(vinylbenzyl vinyl sulfone) and the like. A

... ' ' . :
.

85~3 descriptlon o~ the preparation of these polymers can be found in Canadian Application Serial No 310,751 by Campbell filed September 6, 1978.
The polymers containing the recurring units descrlbed above preferably comprise anionic, cationic or nonionic polymers comprised of the above units and units derived from copolymerlzable ethylenically unsaturated monomers. Although the preferred copolymerizable monomers form units which act as mordants for dyes in themselves, basically any polymer-izable monomer may be used to form the polymeric mordant.
Cationic polymers can be formed by copolymerizing monomers forming the units described above in formulas (1) and (2) and monomers which form repeating units such as:
~CH2-CH~
~1, ~9X I 0 CHz-Q-R M

wherein Q is N or P, P.4 to R6 are independently carbocyclic or alkyl groups, and M is an anion such as described in US
Patent 3,958,995 by Campbell et al issued May 25, 1976, and other cationic units such as N-(methacryloyloxyethyl)-N,N,N-trimethylammonium methosulfate, N-(methacryloaminopropyl)-N~N,N-trimethylammonium chloride and the like.
Anionic polymers can be formed by copolymerizing with the monomers ~orming the units described ln ~ormulas (1) and (2), monomers which form repeating units such as sodium-2-sul~oethyl methacrylate, sodium 2-acrylamido-2-methylpropanesul~onatel sodium vinylbenzylsulfonate, sodium vinylbenzenesul~onate, and the like.
Nonionic polymers can be ~ormed by copolymerizlng with the units o~ ~ormulas (1) and (2), monomers which form .. . . . , . .... ,, . .. , ~ . . .. . . .. .. .
.

S~63 repeating units such a.s acrylamide, M-vinylpyrrolidinone, N-isopropylacrylamide, and the like.
The polymers can be either homopolymers having the repeating units of formulas (1) and (2) or copolymers of these with other cationic, anionic or nonionic ethylenically unsaturated monomers. Preferred cationic copolymers are poly[m- and p-vînylbenzyltrimethylammonium chloride-co-m-and p-vinylbenzyl 2-chloroethyl sulfone] (1:1 w) and poly[m-and _-vinylbenzyltrimethylammonium chloride-co-_- and p-vinylbenzyl vinyl sulfone-co-divinylbenzene] (49:49:2 w). A
preferred anionic copolymer is poly[m-and p-vinylbenzyl 2 chloroethyl sulfone-co-sodium 2-sulfoethyl methacrylate]

(1: 1 w~ .
A preferred nonionic copolymer dye mordant of this type is poly[acrylamide-co-vinylbenzyl 2-chloroethyl sul-~one] (80:20 w). Preferably, the copolymers comprise from about 10 to about 90 weight percent of the repeating units of formulas (1) and (2).
The homopolymers or copolymers can be formed by free radical polymerization of the corresponding monomers and by optionally treating the resulting polymers with alkali.
Dyes which are particularly useful in the practice :
of this inVention in combination with the preferred covalently bonding polymeric mordants described above are those dyes having a reactive amine group having the formula:
R~ R7 -SO2N- (:CH2) r,-NH

wherein each of R6 and R7 is a substituted or unsubstituted lower alkyl group and n is an integer from 1 to about 5.

7~5~

Some examples of such dyes havlng a reactive amine group which is not part of the chromophore of the dye include:

l-hydroxy-5-methylsulfamyl-4-{m-C2-(n-methylamino)-ethyl-n-methyl sulfamyl phenyl~azo}naphthalene;
l-hydroxy 5-{m-[2-(n-methylamino)ethyl-n-methyl sulfamyl]phenyl sul~amaonamido}-4-{[2-(methylsul-fonyl)-4-nitrophenyl]azo}naphthalenej and 2-cyano-4-{m-[2-(n-methylamino)ethyl-n-methyl sul-famyl~phenylazo}phenol.
l~ Particularly preferred photoresis~s for use with the preferred benzyl chloride-containing polymeric mordants described above are the polyvinyl cinnamate resists.
Unless otherwise specified, the following con-ditions apply to the examples which follow.
Gelatin suspensions of the polymeric mordants were made up for coating the specimen on polyester film base or glass. Where the coatings were made on polyester film, a .006-mil blade was used, the polyester was subbed with a copolymer of methylacrylate, vinylidene chloride and itaconic acid according to the teachings of US Patent 3,271,345 by Nadeau et al issued September 6, 1966, to improve adhesion of the mordant layer to the polyester, and the dried coating of gelatin-polymer was about 10 ~m thick.
Resist coatings were prepared on a Headway Research EC 101~ spinner operating at 2500 RPM for 20 seconds. The coatings were then dried in an oven at 75-80 C for 15-20 minutes.
Exposure masks were prepared and contained one pattern for each of the colors. The patterns corresponded to the patterns in Fig 2A. The pattern on the mask was a single lO0 x lO0 array, centered in the 2-l/2-inch~square mask, and o~ the same dimensions as the CCD array with which the filter pattern was to be eventually Jolned.

, .. .. . . .

5~

Exposure and mask allgnment was accomplished on a silicon-wafer aligner made by Photo-Lithographic Systems, Fort Washington, Pa.
The following examples are presented.
Example l:
A substrate material of subbed 3-mil polyester film was coated with a thin layer of a polymer mordant composition having a structure comprised of:
(l) 49% by weight -CH2-CH-~1, CHz Cl +N-(C6H13) 3 (2) 49% by weight -CHz-CH- , and ~1\
f n CH
Cl (3~ 2% by weight -CH2-CH-in a gelatin binder (2% gelatin, o.o6% polymer, .01% for-maldehyde, weight percents). This polymer mordant has the proper surface characteristics (the resist laying down readily and with good adhesion, little or no dye penetration ocurring through the adhering resist to the protected poly-mer, yet the polymer itself reacting readily with the dye solution, and the resist processing sequence having no adverse effect upon the polymer) so that it was possible to lay down a thin layer of protective photoresist.

~ SD 23 ~ ~"~
': : ' , ~73~5~

A layer o~ polyvinyl cinnamate resist available as KPR~ Photoresist from Eastman Kodak Company was coated on the mordant layer and dried. The first exposure was made through a chromium mask so that only the polymer mordant under the unexposed areas of the resist would accept magenta dye (dye #l~ af`ter development. Exposure was made for 6 sec in a Photo-Lithographic Systems silicon-wafer handler and exposure using the built~in 200-watt mercury-arc source.
The resist was developed for 30 sec by spraying with Kodak Photoresist Developer~. A dip in dye #l solution (made basic by ammonia with 50 mg dye/100 ml water) dyed the area left unmasked by the resist. The remaining resist was stripped with dichloroethane on a cotton swab. The process of resist coating, exposure, dyeing and stripping was then repeated two more times substituting a different exposure mask and solutions of dye ~2 and dye #3 were used each time to provide the desired three-color pattern. The sequence of dye application has no ef`fect upon subsequent dyeing in a previously masked area. The resolution obtained was more than sufficient to give quite sharp edges to the dyed areas which were 30 microns x 40 microns and there was distinct differentiation between ad~acent dyed areas. Edge sharpness of` the dyed areas was measured at about 1-3 microns by microdensitometer tracings.

Dye #l - Magenta OH
~0\ ,1~

NH N=~ CH3 CH3 S02 e~ ~I-SO2NHCH2CH2NH

l-hydroxy-5-methylsulf'amyl-ll-{m-[2-(n-methylamino)-ethyl-n-methyl sulf'amyl phenylJazo}naphthalene SD~4 ... .
:

Dye #2 - Cyan OH

NH N=N~e-NO2 o~o ~ `8 I H3 CH3 ~ / -SO2NHCH2CHzNH

l-hydroxy-5-{m-[2-(n-methylamino)ethyl-n-methyl sulfamyl]phenyl sulfamaonamido}-4-{[2-(methyl sul-fonyl)-4-nitrophenyl]azo}naphthalene.
Dye #3 - Yellow OH
\n-C=N ..
t :
N=N

~ / -SO2NCH2CH2NH

2-cyano-4-{m-[2-(n-methylamino)ethyl-n-methyl sul-famyl]phenyl}azo phenol Each of these dyes was mordanted by vlrtue of a covalent bond forming between the phenol portion of the dye and the benzyl chloride pendant group of the polymer mordant.
Example 2:
Example 1 was repeated except that the cyan and magenta dyes were replaced with dye solutions ~ and #5, respectively, which are solwtions of anionic dyes. Dye #3 described above was used to complete the third color of the mask. (Dye #3 was made basic with sodium hydrogen carbonate rather than ammonia.) A three-color array was produced.
The mordanting of the anionic dye~ demonstrates that the quaternary ammonium sites on the polymer mordant are avalla-ble for rnordanting lonic dyes. The edge sharpness ln thecase of the covalently bonding dyes is superior to that of the anionic dye mixtures when using the same amount of -~, SD 25 .
, .

polymeric mordant. The edge sharpness o~ the mordanted anionic dye deposits was measured at about 20-50 microns.
Dye Solution #4:
27 cc of 1% alkali Fast Green lOG C142170 30 cc of 1% Rapid Filter Yellow in water to 200 cc Dye Solution #5:
0.16 g Sorultra A
1,0 g Tartrazine CI19140 0.34 g Eosine Extra Yellowish CI 45380 o . L15 g Xylene Red B CI45100 in water to 200 cc :

Claims (27)

We claim:
1. A color imaging device comprising:
A. means for sensing radiation comprising a planar array of charge-handling semiconductive photosensors having sensing areas sensitive to radiant energy and superimposed thereon, B. filter means for controlling access of radiation to said sensing means, said filter means comprising

1. a transparent mordant layer and 2. a plurality of radiation intercepting means defining a planar array of filter elements lying in said mordant layer in micro-registration with the sensing areas of said photosensors, the filter area of said intercepting means having at least one mordantable dye which absorbs radiation in at least one portion of the spectrum and transmits radiation in at least one other portion of the spectrum, said intercepting means being in micro-registration with the underlying sensing area of said photosensors by reason of the lateral restraint to dye migration exhibited by said mordant layer, said filter means having at least two sets of inter-cepting means, one set having a common radiation absorption and transmission characteristic that is different from another set.

2. A color imaging device as described in claim 1 wherein said filter means comprises three sets of radiation intercepting means, the filter elements of all intercepting means of each set selectively transmitting light of a different primary color.

3. A color imaging device as described in claim 1 wherein at least some of said photosensors have at least one dimension less than about 100 micrometers.

4. A color imaging device as described in claim 1 wherein at least some of said photosensors have a radiation sensing area less than about 10-4 square centimeters.

5. A color imaging device as described in claim 1 wherein each of said filter elements has at least one dimension that is less than about 100 micrometers.

6. A color imaging device as described in claim 1 wherein said filter means comprises three sets of radiation intercepting means, the filter areas of all intercepting means of each set selectively transmitting light of a different primary color, and wherein said transparent mordant layer comprises a binder resin and a mordant.

7. A color imaging device comprising:
A. means for sensing radiation comprising a planar array of charge-handling semiconductive photosensors, at least some of said photosensors having a radiation sensing area less than 2.5 X 10-5 square centimeters; and superimposed thereon, B. filter means for controlling access of radiation to said sensing means, said filter means comprising 1. a transparent mordant layer and 2. a plurality of radiation intercepting means defining a planar array of filter elements lying in said mordant layer in micro-registration with the sensing areas of said photosensors, the filter area of said intercepting means having at least one mordantable dye which absorbs radi-ation in at least one portion of the spectrum and transmits radiation in at least one other portion of the spectrum, said filter means comprising three sets of said intercepting means, one set having filter elements that selectively transmit green light, a second set having filter elements that selectively transmit red light, and a third set having filter elements that selectively transmit blue light, said intercepting means being in micro-registration with the underlying sensing area of said photosensors by reason of the lateral restraint to dye migration exhibited by said mordant layer.

8. A color imaging device as described in claim 7 wherein each of said filter elements has at least one dimension that is less than about 100 micrometers.

9. A color imaging device comprising:
A. means for sensing radiation within the visible spectrum comprising a planar array of charge-coupled semiconductive photosensors, at least some of said photosensors having a visible radiation sensing area less than 10-4 square centimeters; and, superimpose thereon, B. filter means for controlling access of visible radiation to said sensing means, said filter means comprising (1) a transparent mordant layer, (2) a plurality of light intercepting means defining a planar array of filter elements lying in said mordant layer in micro-registration with the sensing areas of said photosensors, the filter area of said intercepting means con-taining at least one mordantable dye which absorbs light in at least one portion of the visible spectrum and transmits light in at least one other portion of the visible spectrum, said intercepting means being in micro-registration with the underlying sensing area of said photosensors by reason of the lateral restraint to dye migration exhibited by said mordant layer, (3) a first set of said light intercepting means having a common light absorption and transmission characteristic wherein light is absorbed in one portion of the visible spectrum and transmitted in another portion of the visible spectrum, and (4) a second set of light intercepting means having a common light absorption and transmission characteristic which differs from that of said first set of light intercepting means, said first and second set of light intercepting means forming an interlaid pattern.

10. A color imaging device as described in claim 9 wherein said first set of light intercepting means is superim-posed over a greater total sensing area of said sensing means than said second set.

11. A color imaging device as described in claim 9 wherein said filter means comprises three sets of light inter-cepting means, the filter elements of all intercepting means of each set selectively transmitting light of a different primary color.

12. A color imaging device as described in claim 11 wherein each of said photosensors have a visible radiation sensing area less than about 2.5 X 10-5 square centimeters.

13. A color imaging device comprising:
A. means for sensing radiation within the visible spectrum comprising a planar array of charge-coupled semi-conductive photosensors, at least some of said photosensors having a visible radiation sensing area less than about 2.5 X 10-5 square centimeters, and superimposed thereon, B. filter means for controlling access of visible radiation to said sensing means, said filter means comprising (1) a transparent mordant layer, (2) a plurality of light intercepting means defining a planar array of filter elements lying in said mordant layer in micro-registration with the sensing areas of said photosensors, the filter area of said intercepting means containing at least one mordantable dye which absorbs light in at least one portion of the visible spectrum and transmits light in at least one other portion of the visible spectrum, said intercepting means being in micro-registration with the underlying sensing area of said photosensors by reason of the lateral restraint to dye registration exhibited by said mordant layer, (3) a first set of said light intercepting means having a common light absorption and transmission characteristic wherein light is absorbed in one portion of the visible spectrum and transmitted in another portion of the visible spectrum, (4) a second set of light intercepting means having a common light absorption and transmission characteristic which differs from that of said first set of light intercepting means, and (5) a third set of light intercepting means having a common light absorption and transmission charact-eristic which differs from that of both the first and the second set of light intercepting means, said first, second and third sets of light intercepting means forming an interlaid pattern.

14. A color imaging device as described in claim 13 wherein said first set of light intercepting means is super-imposed over a greater total sensing area of said sensing means than either said second set or said third set.

15. A color imaging device as described in claim 14 wherein said first set of light intercepting means selectively transmits green light, said second set of light intercepting means selectively transmits red light, and said third set of light intercepting means selectively transmits blue light.

16. A method for making a color imaging device which comprises means for sensing radiation comprising a planar array of charge-handling semiconductive photosensors having sensing areas similar to radiant energy, and filter means for controlling access of radiation to said sensing means, said filter means comprising a plurality of radiation intercepting means defining a planar array of filter elements lying in micro-registration with the sensing areas of said photosensors; said method comprising:
superimposing on the array of photosensors the filter means such that the filter elements of the intercepting means are in micro-registration with the underlying sensing area of the photosensors, the filter means being formed by a method com-prising:
A. forming a transparent mordant layer on a substrate;
B. coating a layer of photoresist over the mordant layer;
C. exposing the photoresist to a pattern representing a set of filter elements and developing the photoresist to obtain window areas in the photoresist layer corresponding to said pattern;
D. imbibing a dye into the mordant layer through the window areas to fix the dye in the mordant layer by reason of the lateral restraint to dye migration exhibited by the mordant layer, thus forming dyed filter elements corresponding to said pattern;
E. removing the remaining portions of the photoresist to yield a first set of dyed filter elements in a planar array in the mordant layer; and F. repeating steps (B) through (E) at least once to form another set of dyed filter elements in the mordant layer in an interlaid pattern with the first set, each repetition of the steps yielding an additional set of dyed filter elements in an interlaid pattern with the prior sets, one set having a common light absorption and transmission characteristic that differs from another set.

17. A method for making a color imaging device as described in claim 16 wherein said method includes the step of stripping said filter means from said substrate and laminating said filter means onto said array of photosensors so that the filter elements are in micro-registration with underlying sensing area of the photosensors.

18. A method for making a color imaging device as described in claim 16 wherein steps (B) through (E) are performed three times, each time forming a set of dyed filter elements having a different primary color from each other set.

19. A method for making a color imaging device which comprises means for sensing radiation comprising a planar array of charge-handling semiconductive photosensors, at least some of the photosensors having a radiation sensing area with at least one dimension less than about 100 micrometers; and filter means for controlling access of radiation to said sensing means, said filter means comprising a plurality of radiation intercepting means defining a planar array of filter elements lying in micro-registration with the sensing areas of said photosensors; said method comprising:
superimposing on the array of photosensors the filter means such that the filter elements of the intercepting means are in micro-registration with the underlying sensing area of the photosensors, the filter means belong formed by a method com-prising:

A. forming a transparent mordant layer on a substrate;
B. coating a layer of photoresist over the mordant layer;
C. exposing the photoresist to a pattern representing a set of filter elements and developing the photoresist to obtain window areas in the photoresist layer corresponding to said pattern;
D. imbibing a dye into the mordant layer through the window areas to fix the dye in the mordant layer by reason of the lateral restraint to dye migration exhibited by the mordant layer, thus forming dyed filter elements corresponding to said pattern;
E. removing the remaining portions of the photoresist to yield a first set of dyed filter elements in a planar array in the mordant layer; and F. repeating steps (B) through (E) at least once to form another set of dyed filter elements in the mordant layer in an interlaid pattern with the first set, each repetition of the steps yielding an additional set of dyed filter elements in an interlaid pattern with the prior sets, one set having a common light absorption and transmission characteristic that differs from another set.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

20. A color imaging device as described in Claim 1 wherein said transparent mordant layer comprises a poly-meric mordant which has a plurality of pendant reactive groups which are capable of forming a covalent bond with said mordantable dye.

21. A color imaging device as described in Claim 20 wherein the edge sharpness of each of said filter ele-ments is less than about 4 microns.

22. A color imaging device as described in Claim 20 wherein said mordant is a polymer containing recurring units having the formula selected from the group consisting of:

( 1 ) and (2) wherein R2 is hydrogen or alkyl; n = 0 or 1; R1 is hydrogen, alkyl or aryl; L is a bivalent linking group providing a linkage between the vinyl group and W; W is an electron-withdrawing group; and X is a leaving group which can be displaced by a nucleophile or eliminated in the form of HX
by treatment with alkali.

23. A color imaging device as described in Claim 22 wherein said mordantable dye has a reactive amine group having the formula:

wherein each of R6 and R7 is a substituted or unsubstituted lower alkyl group and n is an integer from 1 to about 5.

24. A color imaging device as described in Claim 9 wherein said transparent mordant layer comprises a poly-meric mordant which has a plurality of pendant reactive groups which are capable of forming a covalent bond with said mordantable dye.

25. A color imaging device as described in Claim 13 wherein said transparent mordant layer comprises a poly-meric mordant which has a plurality of pendant reactive groups which are capable of forming a covalent bond with said mordantable dye.

26. A method for making a color imaging device as described in Claim 16 wherein said transparent mordant layer comprises a polymeric mordant which has a plurality of pendant reactive groups which are capable of forming a covalent bond with said mordantable dye.

27. A method for making a color imaging device as described in Claim 19 wherein said transparent mordant layer comprises a polymeric mordant which has a plurality of pendant reactive groups which are capable of forming a covalent bond with said mordantable dye.