U.S. patent number 3,925,081 [Application Number 05/354,008] was granted by the patent office on 1975-12-09 for photographic products containing anti-reflection layer.
This patent grant is currently assigned to Polaroid Corporation. Invention is credited to Charles K. Chiklis.
United States Patent |
3,925,081 |
Chiklis |
December 9, 1975 |
Photographic products containing anti-reflection layer
Abstract
Photographic images, particularly multicolor images, viewed
through a transparent support, have an anti-reflection coating on
the outer surface of said support. The anti-reflection coating
comprises a quarterwave layer of a fluorinated polymer. The images
may be formed by multicolor diffusion transfer processes using dye
developers or other image dye-providing materials. In the preferred
embodiments, the photographic image is an integral
negative-positive reflection print. Abrasion resistance of the
anti-reflection coating carried by polyester transparent support is
improved by surprisingly low levels of an isocyanate.
Inventors: |
Chiklis; Charles K. (Lexington,
MA) |
Assignee: |
Polaroid Corporation
(Cambridge, MA)
|
Family
ID: |
23391517 |
Appl.
No.: |
05/354,008 |
Filed: |
April 24, 1973 |
Current U.S.
Class: |
430/14; 428/421;
428/422; 428/480; 428/483; 430/17; 430/18; 430/208; 430/220;
430/496; 430/503; 430/510; 430/533; 430/941; 430/950; 430/961 |
Current CPC
Class: |
G03C
8/52 (20130101); Y10T 428/269 (20150115); Y10T
428/261 (20150115); Y10T 428/31797 (20150401); Y10S
430/162 (20130101); Y10T 428/31786 (20150401); Y10T
428/265 (20150115); Y10T 428/266 (20150115); Y10T
428/31565 (20150401); Y10T 428/273 (20150115); Y10T
428/3154 (20150401); Y10T 428/31544 (20150401); Y10S
430/142 (20130101); Y10S 430/151 (20130101); Y10T
428/3158 (20150401) |
Current International
Class: |
G03C
8/52 (20060101); G03C 8/00 (20060101); G03C
001/76 (); G03C 003/00 (); G03C 001/40 (); G03C
001/84 () |
Field of
Search: |
;96/77,76R,76C,87R,84R,3,29D,5PL,29R,67,119R,72
;117/76F,76P,DIG.7,72R,138.8F,138.8A,161R,161UH,161UF
;428/421,422,489,483 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Smith; Ronald H.
Assistant Examiner: Schilling; Richard L.
Attorney, Agent or Firm: Mervis; Stanley H.
Claims
What is claimed is:
1. A photographic product for use in diffusion transfer processes
comprising a transparent polyester support carrying on one side
thereof an image-receiving layer, the other side of said
transparent polyester support carrying an anti-reflection coating,
said anti-reflection coating having an index of refraction less
than said polyester support and comprising a quarter-wave stratum
of a fluorinated polymer and an isocyanate in said stratum or
between said stratum and said transparent polyester support, said
isocyanate being present in a quantity effective to increase the
abrasion resistance of said fluorinated polymer stratum.
2. A photographic product as defined in claim 1, including at least
one layer containing photosensitive silver halide carried on said
first side.
3. A photographic product as defined in claim 2, including an image
dye-providing material in a layer contiguous to said silver halide
containing layer.
4. A photographic product as defined in claim 1 wherein said
image-receiving layer includes a mordant for a dye.
5. A photographic product as defined in claim 1 wherein said
image-receiving layer is a silver receptive layer containing a
silver precipitant.
6. A photographic product as defined in claim 4 wherein said dye is
a dye developer.
7. A photographic product as defined in claim 1 wherein said
transparent support has an index of refraction of at least about
1.6.
8. A photographic product as defined in claim 7 wherein said
polyester is a polyethylene terephthalate.
9. A photographic product as defined in claim 1 wherein said
anti-reflection coating has an index of refraction at least about
0.20 less than said transparent support.
10. A photographic product as defined in claim 7 wherein said
anti-reflection coating has an index of refraction of about 1.3 to
about 1.45.
11. A photographic product as defined in claim 1 wherein said image
dye-providing material is a compound which provides a diffusible
dye as a function of oxidation or color coupling.
12. A photographic product as defined in claim 2 including an
image-receiving layer, said layer of silver halide being positioned
between said support and said image-receiving layer.
13. A photographic product as defined in claim 1 wherein said
fluorinated polymer stratum includes a vinylidene fluoride
copolymer.
14. A photographic product as defined in claim 1 wherein said
fluorinated polymer stratum includes a copolymer of vinylidene
fluoride and chlorotrifluoroethylene.
15. A photographic product as defined in claim 1 wherein said
fluorinated polymer stratum includes a copolymer of vinylidene
fluoride and tetrafluoroethylene.
16. A photographic product as defined in claim 1 wherein said
fluorinated polymer stratum includes a copolymer of vinylidene
fluoride and hexafluoropropylene.
17. A photographic product as defined in claim 1 wherein said
polyester film has a thickness of about 3 to 10 mils.
18. A photographic product as defined in claim 1 wherein said
fluorinated polymer stratum includes polymethyl methacrylate.
19. A photographic product as defined in claim 1 wherein said
isocyanate is a polyisocyanate.
20. A photographic product as defined in claim 1 wherein said
isocyanate is methylene-bis-(4-phenylisocyanate).
21. A photographic product as defined in claim 1 wherein said
isocyanate is present in said fluorinated polymer stratum at a
concentration of about 0.5 to 8 percent by weight of said polymer
stratum.
22. A photographic product as defined in claim 1 wherein said
isocyanate is coated at a concentration of about 1 mg./ft..sup.2
between said polyester support and said fluorinated polymer
stratum.
23. A photographic film product comprising a first support and a
second support, at least one of said supports being a transparent
polyester support, a photosensitive layer carried on one of said
supports, and a rupturable container releasably holding a
processing composition adapted, when distributed between
predetermined layers carried by said supports, to develop said
photosensitive layer and provide an image viewable through said
transparent polyester support, the external surface of said
transparent polyester support carrying an anti-reflection coating,
said anti-reflection coating having an index of refraction less
than said polyester support and comprising a quarter-wave stratum
of a fluorinated polymer and an isocyanate in said stratum or
between said stratum and said transparent polyester support, said
isocyanate being present in a quantity effective to increase the
abrasion resistance of said fluorinated polymer stratum.
24. A photographic product as defined in claim 22 wherein both of
said supports are transparent polyester supports and each carries
said anti-reflection coating on the external surface thereof.
25. A photographic product as defined in claim 22 including an
image-receiving layer and means adapted to provide a masking layer
between said photosensitive layer and said image-receiving layer to
mask the developed photosensitive layer when the image in said
image-receiving layer is viewed through said transparent polyester
support.
26. A photographic product for forming a diffusion transfer image
in dye within a permanent laminate including at least one developed
silver halide layer, said photographic product comprising, in
combination, an image-receiving layer; at least one silver halide
emulsion, each said silver halide emulsion having associated
therewith an image dye-providing substance selected from the group
consisting of image dyes and image dye intermediates; means
providing a light-reflecting layer between said image-receiving
layer and said silver halide emulsion(s) to mask said silver halide
emulsion(s) after development thereof and to provide a white
background for viewing a dye image in said image-receiving layer; a
transparent polyester support through which image-receiving layer
may be viewed; means providing a processing composition for
developing said silver halide emulsion(s) after photoexposure and
for forming a transfer image in at least one dye in said
image-receiving layer; said product including an anti-reflection
coating on the outer surface of said transparent polyester support,
said anti-reflection coating having an index of refraction less
than said polyester support and comprising a quarter-wave stratum
of a fluorinated polymer and an isocyanate in said stratum or
between said stratum and said transparent polyester support, said
isocyanate being present in a quantity effective to increase the
abrasion resistance of said fluorinated polymer stratum.
27. A photographic film as defined in claim 26 wherein each said
dye is a dye developer.
28. A photographic film as defined in claim 26 wherein each said
image dye-providing substance is an intermediate for an image
dye.
29. A photographic product as defined in claim 26 wherein said
silver halide emulsion(s) are adapted to be exposed through said
transparent polyester support.
30. A photographic product as defined in claim 26 wherein said
means providing a light-reflecting layer comprise a white pigment
dispersed in said processing composition, and said processing
composition is contained in a rupturable container positioned to
distribute said processing composition containing said pigment
between said image-receiving layer and said silver halide
emulsion(s).
31. A photographic product as defined in claim 26 comprising a
temporary laminate including said layers confined between two
dimensionally stable supports, at least one of said supports being
a transparent polyester support, the bond between a predetermined
pair of layers being weaker then the bond between other pairs of
layers, and including a rupturable container releasably holding
said processing composition, said rupturable container being so
positioned as to distribute said processing composition between
said predetermined layers, ssaid processing composition being
adapted to provide said permanent laminate following distribution
and drying.
32. A photographic product as defined in claim 26 wherein said
transparent support has an index of refraction of at least about
1.6.
33. A photographic product as defined in claim 31 wherein said
polyester is a polyethylene terephthalate.
34. A photographic product as defined in claim 26 wherein said
anti-reflection coating has an index of refraction at least about
0.20 less than said transparent polyester support.
35. A photographic product as defined in claim 32 wherein said
anti-reflection coating has an index of refraction of about 1.3 to
1.45.
36. A photographic product comprising a first support; a
red-sensitive silver halide emulsion; a green-sensitive silver
halide emulsion; and a blue-sensitive silver halide emulsion; said
silver halide emulsions having associated therewith, respectively,
a cyan dye developer, a magenta dye developer and a yellow dye
developer; an image-receiving layer for receiving image dyes
transferred thereto by diffusion as a function of exposure and
development of said silver halide emulsion layers; a second support
which is a transparent polyester support through which said
image-receiving layer may be viewed; a rupturable container
releasably holding a processing composition adapted, upon
distribution between predetermined layers of said film to develop
said silver halide emulsions and to effect the formation of a
transfer image in dye in said image-receiving layer, said
processing composition also being adapted to provide a permanent
laminate including said developed silver halide emulsions and said
image-receiving layer; and means providing a light-reflecting layer
between said image-receiving layer and said silver halide emulsions
effective to provide a white background for viewing said transfer
image and for masking said developed silver halide emulsions; said
product including an anti-reflection coating on the outer surface
of said transparent polyester support, said anti-reflection coating
having an index of refraction less than said polyester support and
comprising a quarter-wave stratum of a fluorinated polymer and an
isocyanate in said stratum or between said stratum and said
transparent polyester support, said isocyanate being present in a
quantity effective to increase the abrasion resistance of said
fluorinated polymer stratum.
37. A photographic product as defined in claim 36 wherein said
first support is opaque.
38. A photographic product as defined in claim 36 wherein said
transparent polyester support and said image-receiving layer
comprise a separate element adapted to be brought into superposed
relationship with said silver halide emulsions.
39. A photographic product as defined in claim 36 wherein said
layers are held in fixed relationship between said supports prior
to and during exposure.
40. A photographic product as defined in claim 39 wherein said
fixed relationship is provided by a binder tape along at least two
parallel sides of said product.
41. A photographic product as defined in claim 39 wherein said
product is a laminate of said layers between said first and said
second supports, the bond between a pair of predetermined layers
being weaker than the bonds between the other layers, said
rupturable container being so positioned as to release said
processing composition for distribution between said pairs of
layers.
42. A photographic product as defined in claim 36 wherein said
silver halide emulsions are present as separate planar layers.
43. A photographic product as defined in claim 36 wherein said
silver halide emulsions are present in the form of minute elements
arranged in side-by-side relationship in a photosensitive screen
pattern.
44. A photographic product as defined in claim 42 wherein said
blue-sensitive silver halide emulsion layer is between said
image-receiving layer and said other silver halide emulsion
layers.
45. A photographic product as defined in claim 42 wherein said
blue-sensitive silver halide emulsion layer is between said first
support and said other silver halide emulsion layers, and said
first support is a transparent polyester support.
46. A photographic product as defined in claim 45 wherein said
transparent polyester first support carries an anti-reflection
coating on the outer surface thereof, said anti-reflection coating
having an index of refraction less than said polyester first
support and comprising a quarter-wave stratum of a fluorinated
polymer and an isocyanate in said stratum or between said stratum
and said transparent polyester first support, said isocyanate being
present in a quantity effective to increase the abrasion resistance
of said fluorinated polymer stratum.
47. A photographic laminate comprising (a) at least one exposed and
developed silver halide layer, (b) an image-carrying layer
containing an image in at least one dye, (c) a light-reflecting,
white layer positioned between said silver halide layer or layers
and said image-receiving layer and effective to mask said developed
silver halide layer or layers, and (d) a transparent polyester
layer through which said image may be viewed against said white
layer, said layers being permanently laminated together, said
transparent polyester layer having an anti-reflection coating on
the outer surface thereof, said anti-reflection coating having an
index of refraction less than said polyester layer and comprising a
quarter-wave stratum of a fluorinated polymer and an isocyanate in
said stratum or between said stratum and said transparent polyester
support, said isocyanate being present in a quantity effective to
increase the abrasion resistance of said fluorinated polymer
stratum.
48. A photographic image comprising a transparent polyester support
carrying on one side thereof an image-carrying layer containing an
image in dye or silver, the other side of said transparent
polyester support carrying an anti-reflection coating, said dye
image being viewable through said anti-reflection coating and said
transparent polyester support, said anti-reflection coating having
an index of refraction less than said polyester support and
comprising a quarter-wave stratum of a fluorinated polymer and an
isocyanate in said stratum or between said stratum and said
transparent polyester support, said isocyanate being present in a
quantity effective to increase the abrasion resistance of said
fluorinated polymer stratum.
49. A photographic image as defined in claim 48 wherein said
transparent polyester support has an index of refraction of at
least 1.6 and said anti-reflection coating has an index of
refraction of at least about 0.20 less than said transparent
support.
50. A photographic product as defined in claim 49 wherein said
anti-reflection coating has an index of refraction of about 1.3 to
about 1.45.
51. A photographic product as defined in claim 1 wherein said
isocyanate is present in a quantity of about 1 to 2
mg./ft..sup.2.
52. A photographic product as defined in claim 1 wherein said
isocyanate is a polyisocyanate.
53. A photographic product as defined in claim 1 wherein said
quantity of said isocyanate is also effective to increase the
adhesion of said fluorinated polymer stratum to said polyester film
base.
Description
This invention is concerned with photography and, more
particularly, with the formation of images in color or
black-and-white by diffusion transfer processing.
A number of photographic processes have been proposed wherein the
resulting photograph commprises the developed silver halide
emulsion(s) retained as part of a permanent laminate, with the
desired image being viewed through a transparent support. Of
particular significance are those processes where the image is in
color and is formed by a diffusion transfer process. If the image
is to be viewed as a reflection print, the image-carrying layer is
separated from the developed silver halide emulsion(s) in said
laminate by a light-reflecting layer, preferably a layer containing
titanium dioxide. Illustrative of patents describing such products
and processes are U.S. Pat. No. 2,983,606 issued Mar. 9, 1961 to
Howard G. Rogers, U.S. Pats. No. 3,415,644, 3,415,645 and 3,415,646
issued Dec. 10, 1968 to Edwin H. Land, U.S. Pats. Nos. 3,594,164
and 3,594,165 issued July 20, 1971 to Howard G. Rogers, and U.S.
Pat. No. 3,647,437 issued Mar. 7, 1972 to Edwin H. Land.
Referring more specifically to the aforementioned U.S. Pat. No.
3,415,644, said patent discloses photographic products and
processes employing dye developers wherein a photosensitive element
and an image-receiving layer are maintained in fixed relationship
prior to photoexposure and this fixed relationship is maintained
after processing and image formation to provide a laminate
including the processed silver halide emulsions and the
image-receiving layer. Photoexposure is made through a transparent
(support) element and application of a processing composition
provides a layer of light-relecting material to provide a white
background for viewing the image and to mask the developed silver
halide emulsions. The desired color transfer image is viewed
through said transparent support against said white background.
While such processes provide very useful and good quality images,
it has been found that the full potential quality of the image is
not obtained because the transparent support through which the
image is viewed in fact reflects "white" light to the viewer's
eyes. Furthermore, this property of reflecting some of the light
incident on the surface of the transparent support adversely
affects the ability of the film to record a subject when
photoexposure is effected through such a transparent support.
In accordance with the copending application of Edwin H. Land,
Stanley M. Bloom and Howard G. Rogers, Ser. No. 276,979 filed Aug.
1, 1972, now U.S. Pat. No. 3,793,022 issued Feb. 19, 1974 the
above-noted problems are substantially, if not completely,
eliminated by the provision of an anti-reflection layer through
which the image is viewed and/or photoexposure is effected. The
present invention is directed toward improvements in the products
and processes disclosed and claimed in said Ser. No. 276,979, and,
in its more specific embodiments, provides novel anti-reflection
coatings.
It is, therefore, a primary object of this invention to provide
novel photographic products and processes which provide color or
black-and-white images as part of a permanent laminate, said
laminate exhibiting substantially less surface reflection of
incident light.
It is a further object of this invention to provide diffusion
transfer images, particularly multicolor transfer images, which are
viewed through a transparent element the outer surface of which
carries an improved anti-reflection coating.
Yet another object of this invention is to provide diffusion
transfer films which are exposed through a transparent support, the
outer surface of which carries an anti-reflection coating of
improved scratch resistance.
Further objects of this invention include the provision of novel
anti-reflection coatings and of transparent supports carrying said
anti-reflection coatings, such supports being particularly useful
for carrying photographically useful layers.
Other objects of this invention will in part be obvious and will in
part appear hereinafter.
The invention accordingly comprises the product possessing the
features, properties and relation of components and the process
involving the several steps and the relation and order of one or
more of such steps with respect to each of the others which are
exemplified in the following detailed disclosure, and the scope of
the application of which will be indicated in the claims.
For a fuller understanding of the nature and objects of the
invention, reference should be had to the following detailed
description of the invention taken in conjunction with the
accompanying drawings wherein:
FIGS. 1 and 2 are diagrammatic, enlarged cross-sectional views of
two embodiments of film units embodying the present invention,
illustrating the arrangement of layers during the three illustrated
stages of a monochrome diffusion transfer process, i.e., exposure,
processing and final image;
FIG. 3 is a diagrammatic, enlarged cross-sectional view of another
film unit embodying the present invention;
FIG. 4 is a diagrammatic, enlarged cross-sectional view of a
transparent sheet, adapted for use as a support for an
image-carrying element, including an anti-reflection coating in
accordance with the present invention.
As noted above, this invention is particularly concerned with color
diffusion transfer processes wherein the layer containing the
diffusion transfer image, i.e., the image-receiving layer, is not
separated from the developed photosensitive layers after processing
but both components are retained together as part of a permanent
laminate. Film units particularly adapted to provide such diffusion
transfer images have frequently been referred to as "integral
negative-positive" film units. The resulting image may be referred
to as an "integral negative-positive reflection print" and as so
used this expression is intended to refer to a reflection print
wherein the developed photosensitive layers have not been separated
from the image layer, i.e., the layer containing the transfer dye
image. A light-reflecting layer between the developed
photosensitive layer(s) and the image layer provides a white
background for the dye image and masks the developed photosensitive
layer(s). These layers are part of a permanent laminate which
usually includes dimensionally stable outer or support layers, the
transfer dye image being viewable through one of said supports.
This invention is particularly concerned with improving the
aesthetic qualities of such integral negative-positive reflection
prints.
The present invention is applicable to a wide variety of diffusion
transfer processes. The arrangement and order of the individual
layers of the film used in such processes may vary in many ways as
is known in the art, provided the final photograph is a laminate
wherein the desired image is viewed through a transparent support,
e.g., an integral negative-positive reflection print as described
above. For convenience, however, the more specific descriptions of
the invention hereinafter set forth will be by use of dye developer
diffusion transfer color processes and of integral
negative-positive film units of the type contemplated in the
previously mentioned patents, particularly U.S. Pats. Nos.
3,415,644 and 3,594,164. It will be readily apparent from such
descriptions that other image-forming reagents may be used, e.g.,
color couplers, coupling dyes or dyes (couplers) which release a
dye or dye intermediate as a result of coupling or oxidation.
When such integral negative-positive reflection prints are viewed
under ordinary lighting conditions, a small but significant amount
of light is reflected from the external surface of the transparent
support. The effect of this reflection of incident light is to
limit the clarity with which the image may be seen except when the
viewer's eyes are "just right", i.e., good viewing may be highly
directional, in that the print may have to be "tilted" with respect
to the viewer's line of vision to avoid obscuring image detail.
This problem becomes more acute when several persons try to view
the same image, as those not directly in front of the print will
experience substantial glare, with the amount of glare increasing
as the angle of view becomes more oblique. In addition, the
color(s) of a color image may appear less saturated.
If photoexposure is effected through such a transparent support,
reflection of light from the surface of the transparent support has
been found to have several undesirable results. One result is a
reduction in the exposure index or "speed" of the film, due to the
fact that some of the light which has passed through the camera
lens will be reflected before it can reach the photosensitive
layer(s) and the thus reflected light will not participate in the
recording of the photographed subject matter. Furthermore, such
reflected light has a tendency to "bounce" within the camera, and
may cause flare and reduced contrast and resolution in the final
image. If photoexposure is effected through the transparent support
in a camera which includes an image-reversing mirror in the optical
path, light reflected from the surface may cause a "ghost" image of
a particularly bright object within the scene to be superposed on
another portion of the scene in the resulting photograph.
As noted earlier, the copending application of Land, et al., Ser.
No. 276,979 teaches that such undesirable reflection from the
transparent support may be substantially reduced, if not completely
eliminated, by modifying the external surface of such transparent
supports so as to provide a controlled change in the index of
refraction to which incident light is subjected as it passes from
air into the transparent support.
The present invention is directed towards perfecting the advantages
provided by the teachings of Ser. No. 276,979 by providing improved
anti-reflection coatings for use, e.g., on the external surface of
the transparent support of a photographic element. In accordance
with the present invention, the adhesion of an anti-reflection
coating comprising a quarter-wave stratum of a fluorinated polymer,
i.e., a stratum having an optical thickness of one-quarter of
substantially the same, predetermined wavelength of light, carried
by a high refractive index, transparent synthetic polyester sheet
or support, is improved by the presence of an isocyanate.
The principles of physics by which anti-reflection coatings
function are well known and may be used to special advantage in the
present invention. Thus, it is well known that application of a
single layer transparent coating will reduce surface reflection
from a transparent layer (support) if the refractive index of said
coating is less than that of the transparent layer to which it is
applied and the coating is of appropriate optical thickness. In the
photographic products with which this invention is concerned, the
anti-reflection coating will normally be in optical contact with
air. Under these circumstances, and because the index of refraction
of air is 1, the applicable principles of physics give the
following rule: if the index of refraction of the coating material
(anti-reflection layer) is exactly equal to the square root of the
index of refraction of the substrate (transparent support), then
all surface reflection of light will be eliminated for that
wavelength at which the product of the refractive index times
thickness is equal to one-quarter of that wavelength. At other
wavelengths the destructive interference between light reflected
from the top and bottom surfaces of the anti-reflection coating is
not complete but a substantial reduction in overall reflectivity is
obtained. By selecting the optical thickness of the anti-reflection
coating to be one-quarter of a wavelength for approximately the
midpoint of the visible light wavelength range (i.e., one-quarter
of 5500 Angstroms or about 1400 Angstroms), the reduction in
reflectivity is optimized. The term "optical thickness" as used
herein refers to the product of the physical thickness of the
coating times the refractive index of the coating material. Unless
otherwise indicated, as used herein the expression "quarter-wave"
refers to coatings having an optical thickness of one-quarter of a
predetermined wavelength of light, said wavelength being 5500
Angstroms.
The anti-reflection coating should be optically clear and provide
an essentially uniform layer.
The anti-reflection coatings of this invention are used with
polyester art known polymeric film base materials. Such film bases
typically have a thickness of about 3 to 10 mils (0.003 to 0.010
inch). Particularly useful polyester film bases have a thickness of
about 3 to 6 mils. Polyester films have higher refractive indices
than cellulose acetate, and the resultant greater incidence of
surface reflected light as compared with cellulose acetate would
normally be considered to be a disadvantage of using such materials
in integral negative-positive reflection or other prints in which
the image is viewed through a transparent base. (Indeed, the
greater surface reflection resulting in greater glare, and the
resultant need for more directional viewing, exhibited by polyester
films as compared with cellulose acetate is well known from the
commonly used protective transparent covers for notebook pages.)
These higher indices of refraction make it much more possible to
provide anti-reflection coatings which practically eliminate all
reflectivity, whereas reflectivity can only be reduced when using
cellulose acetate.
Particularly useful transparent supports are films of polyethylene
terephthalate, such as those commercially available under the
trademarks "Mylar" (E.I.DuPont de Nemours & Co.) and "Ester"
(Eastman Kodak Co.) Such polyester films have an index of
refraction on the order of about 1.66. A number of materials
suitable for anti-reflection coatings, e.g. fluorinated polymers,
have indices of refraction of about 1.35 to 1.40 which is close to
the 1.29 ideal index of refraction, i.e., the geometric mean of the
indices of refraction of the polyethylene terephthalate and the
surrounding air, or, because the index of refraction of air is 1,
the square root of the 1.66 index of refraction of polyethylene
terephthalate. Furthermore, the fact that the difference of about
0.3 in the indices of refraction between air and the
anti-reflection coating is close to the approximate 0.3 difference
in the indices of refraction of the anti-reflection coating and the
polyethylene terephthalate support means that maximum benefit will
be obtained from the anti-reflection coating; the amplitude of the
light entering the anti-reflection coating will more closely match
the amplitude of the light reflected back from the interface of the
polyethylene phthalate and the anti-reflection coating, and more
effectively cancel out the thus reflected light.
Reference is now made to the accompanying drawings wherein a
plurality of embodiments of this invention are illustrated and
wherein like numbers, appearing in the various figures, refer to
like components. For ease of understanding, these embodiments
illustrate the formation of a monochrome image using a single dye
developer. The illustrated embodiments include appropriate means of
opacification to permit the processing of the film unit outside of
a dark chamber, i.e., the film unit is intended to be removed from
the camera prior to image completion and while the film is still
photosensitive. Opacifying systems are described in the previously
noted patents and per se form no part of the present invention
which is equally applicable to film units intended to be processed
within a dark chamber.
In the discussion of FIGS. 1,2 and 3, reference to the
anti-reflection coating 26 is to be understood as referring to the
anti-reflection coating provided by stratum 26 of FIG. 4.
A particularly useful opacifying system for film units of the type
shown in FIGS. 1 and 3 utilizes a color dischargeable reagent,
preferably a pH-sensitive optical filter agent or dye, sometimes
referred to as an indicator dye, as is described in detail in the
aforementioned U.S. Pat. No. 3,647,437. In film units of the type
shown in FIG. 2, photoexposure is effected from the side opposite
the side from which the image is viewed. An opague layer to protect
the exposed silver halide from further exposure may be provided by
including a light-absorbing opacifying agent, e.g., carbon black,
in the processing composition which is distributed between the
photosensitive layer(s) and a transparent support or spreader
sheet. In such film units, it may be desirable to include a
preformed opaque layer, e.g., a dispersion of carbon black in a
polymer permeable to the processing composition, between a
preformed light-reflecting layer and the silver halide emulsion(s).
Such opacifying systems are shown and described in the
aforementioned U.S. Pats. Nos. 3,594,164 and 3,594,165.
Referring to FIG. 1, Stages A,B and C show in diagrammatic
cross-section, respectively, imaging, processing, and the finished
print in one embodiment of this invention. In Stage A, there is
shown a photosensitive element 30 in superposed relationship with
an image-receiving element 32, with a rupturable container 16
(holding an opaque processing composition 17) so positioned as to
discharge its contents between said elements upon suitable
application of pressure, as by passing through a pair of pressure
applying rolls or other pressure means (not shown). Photosensitive
element 30 comprises an opaque support 10 carrying a layer 12 of a
dye developer over which has been coated a silver halide emulsion
layer 14. The image-receiving element 32 comprises a transparent
support 24 carrying, in turn, a polymeric acid layer 22, a spacer
layer 20 and an image-receiving layer 18. An anti-reflection
coating 26 is present on the outer surface of the transparent
support 24. Photoexposure of the silver halide emulsion layer is
effected through the anti-reflection coating 26 and the transparent
support 24 and the layers carried thereon, i.e., the polymeric acid
layer 22, the spacer layer 20 and the image-receiving layer 18
which layers are also transparent, the film unit being so
positioned within the camera that light admitted through the camera
exposure or lens system is incident upon the outer surface of the
anti-reflection coating 26. After exposure the film unit is
advanced between suitable pressure-applying members, rupturing the
container 16, thereby releasing and distributing a layer 17a of the
opaque processing composition between the photosensitive element 30
and the image-receiving element 32. The opaque processing
composition contains a film-forming polymer, a white pigment and
has an initial pH at which one or more optical filter agents
contained therein are colored; the optical filter agent (agents) is
(are) selected to exhibit light absorption over at least a portion
of the wavelength range of light actinic to the silver halide
emulsion. As a result, ambient or environmental light within that
wavelength range incident upon transparent support 24 and
transmitted through said transparent support and the transparent
layers carried thereon in the direction of the photoexposed silver
halide emulsion 14a is absorbed thereby avoiding further exposure
of the photoexposed and developing silver halide emulsion 14a. In
exposed and developed areas, the dye developer is oxidized as a
function of the silver halide development and immobilized.
Unoxidized dye devoloper associated with undeveloped and partially
developed areas remains mobile and is transferred imagewise to the
image-receiving layer 18 to provide the desired positive image
therein. Permeation of the alkaline processing composition through
the image-receiving layer 18 and the spacer layer 20 to the
polymeric acid layer 22 is so controlled that the process pH is
maintained at a high enough level to effect the requisite
development and image transfer and to retain the optical filter
agent (agents) in colored form, after which pH reduction effected
as a result of alkali permeation into the polymeric acid layer 22
is effective to reduce the pH to a level which "discharges" the
optical filter agent, i.e., changes it to a colorless form.
Absorption of the water from the applied layer 17a of the
processing composition results in a solidified film composed of the
film-forming polymer and the white pigment dispersed therein, thus
providing the reflecting layer 17b which also serves to laminate
together the photosensitive element 30 and the image-receiving
element 32 to provide the final laminate (Stage C). The positive
transfer image in dye developer present in the image-receiving
layer 18a is viewed through the transparent support 24 and the
intermediate transparent layers against the reflecting layer 17b
which provides an essentially white background for the dye image
and also effectively masks from view the developed silver halide
emulsion 14b and dye developer immobilized therein or remaining in
the dye developer layer 12.
The optical filter agent is retained within the final film unit
laminate and is preferably colorless in its final form, i.e.,
exhibiting no visible absorption to degrade the transfer image or
the white background therefor provided by the reflecting layer 17b.
The optical filter agent may be retained in the reflecting layer
under these conditions, and it may contain a suitable "anchor" or
"ballast" group to prevent its diffusion into adjacent layers.
Alternatively, if the optical filter agent is initially diffusible,
it may be selectively immobilized on the silver halide emulsion
side of the reflecting layer 17b, e.g., by a mordant coated on the
surface of the silver halide emulsion layer 14; in this embodiment
the optical filter in its final state may be colorless or colored
so long as any color exhibited by it is effectively masked by the
reflecting layer 17b.
The reflecting layer provided in the embodiment of this invention
shown in FIG. 1 is formed by solidification of a stratum of
pigmented processing composition distributed after exposure. It is
also within the scope of this invention to provide a preformed
pigmented layer, e.g., coated over the image-receiving layer 18,
and to effect photoexposure therethrough, in accordance with the
teachings of U.S. Pat. No. 3,615,421 issued Oct. 26, 1971 to Edwin
H. Land.
In the embodiment illustrated in FIG. 1, photo-exposure is effected
through the image-receiving element. While this is a particularly
useful and preferred embodiment, it will be understood that the
image-receiving element may be initially positioned out of the
exposure path as illustrated in FIG. 3 and superposed upon the
photosensitive element after photoexposure, in which event the
processing and final image stages would be the same as in FIG.
1.
In the embodiment illustrated in FIG. 1, photo-exposure and viewing
of the final image both are effected through the transparent
support 24. Accordingly, the advantages of the anti-reflection
coating 26 are obtained twice, i.e., first, by minimizing failure
of the film unit to record light passed by the camera lens and
second, by minimizing glare during viewing.
It will be noted in the embodiment illustrated in FIG. 1 that the
image-viewing layer 18 is temporarily bonded to the silver halide
emulsion layer 14 prior to exposure. The rupturable container or
pod 16 is so positioned that upon its rupture the processing
composition 17 will delaminate the film unit and distribute itself
between the image-receiving layer 18 and the silver halide emulsion
layer 14. The distributed layer of processing composition 17a upon
solidification forms a layer 17b which bonds the elements together
to form the desired permanent laminate. Procedures for forming such
prelaminated film units, i.e., film units in which the several
elements are temporarily laminated together prior to exposure, are
described, for example, in U.S. Pat. No. 3,625,281 issued to Albert
J. Bachelder and Frederick J. Binda and in U.S. Pat. No. 3,652,282
to Edwin H. Land, both issued Mar. 28, 1972. A particularly useful
and preferred prelamination utilizes a water-soluble polyethylene
glycol as described and claimed in the copending application of
Edwin H. Land, Ser. No. 247,023 filed Apr. 24, 1972 (now U.S. Pat.
No. 3,793,023 issued Feb. 19, 1974).
The use of such temporarily laminated film units maximizes the
beneficial effects obtained in the photoexposure stage from having
the exposure effected through the anti-reflection coating 26, since
the preclamination eliminates any other layer-to-air interface
which could also reflect light and thus reduce the amount of light
recorded by the photosensitive layer(s).
It will be recognized that the transfer image formed following
exposure and processing of film units of the type illustrated in
FIG. 1 will be a geometrically reversed image of the subject.
Accordingly, to provide geometrically nonreversed transfer images,
exposure of such film units should be accomplished through an image
reversing optical system, such as in a camera possessing an image
reversing optical system utilizing mirror optics, e.g., as
described in U.S. Pat. No. 3,447,437 issued June 3, 1969 to Douglas
B. Tiffany. As noted above, when photoexposure is effected in such
an image reversing optical system, photoexposure through an
anti-reflection layer provides additional advantages in preventing
the reflection of light which might cause the formation in the
final image of a reflected or ghost image of one part of the
photographed scene superposed upon another part of the scene.
If desired, the photosensitive element 30 may utilize a transparent
support instead of the opaque support 10 shown in FIG. 1. In this
alternative embodiment, the film unit should be processed in a dark
chamber or an opaque layer, e.g., pressure-sensitive, should be
superposed over said transparent support to avoid further exposure
through the back of the film unit during processing outside of the
camera.
FIG. 2 illustrates another film structure adapted to provide an
integral negative-positive reflection print and wherein
photoexposure and viewing are effected from opposite sides. In this
embodiment, a photosensitive element 34 comprises a transparent
support 24 carrying a layer 22 of a polymeric acid, a spacer 20, an
image-receiving layer 18, a light-reflecting layer 60 (e.g., of
titanium dioxide), an opaque layer 62 (e.g., of carbon black), a
dye developer layer 12, and a silver halide emulsion layer 14.
After photoexposure, a processing composition 17 is applied by
rupturing a pod 16 and distributing the processing composition
between a cover or spreader sheet 64 and silver halide emulsion
layer 14. The cover sheet 64 may be transparent as illustrated in
FIG. 2 and described in detail in the above noted U.S. Pat. No.
3,594,165, in which event photoexposure may be effected through it
while it is held in place, e.g., by a binder tape around the edges
of the film unit or by temporary lamination prior to photoexposure,
as discussed above. In this embodiment, an anti-reflection coating
26 is provided on the outer or exposure surface of the transparent
cover sheet 64. (Alternatively, cover sheet 64 may be opaque in
which event it is positioned out of the exposure path prior to
photoexposure, as described in detail in the above noted U.S. Pat.
No. 3,594,164.) The opaque processing composition 17 contains
suitable opacifying agents, e.g., carbon black, titanium dioxide,
etc. The light-reflecting layer 60 preferably includes a white
pigment, such as titanium dioxide, to provide a white background
against which the transfer image may be viewed. The opaque layer
62, e.g., a layer of carbon black in gelatin, provides the
requisite light protection while assuring an aesthically pleasing
white background for the final image.
Processing of film units of the types described above is initiated
by distributing the processing composition between predetermined
layers of the film unit. In exposed and developed areas, the dye
developer will be immobilized as a function of development. In
unexposed and undeveloped areas, the dye developer is unreacted and
diffusible, and this provides an imagewise distribution of
unoxidized dye developer, diffusible in the processing composition,
as a function of the point-to-point degree of exposure of the
silver halide layer. The desired transfer image is obtained by the
diffusion transfer to the image-receiving layer of at least part of
this imagewise distribution of unoxidized dye developer. In the
illustrated embodiments, the pH of the photographic system is
controlled and reduced by the neutralization of alkali after a
predetermined interval, in accordance with the teachings of the
above noted U.S. Pat. No. 3,615,644, to reduce the alkalinity to a
pH at which the unoxidized dye developer is substantially insoluble
and non-diffusible. As will be readily recognized, the details of
such processes form no part of the present invention but are well
known; the previously noted U.S. patents may be referred to for
more specific discussion of such processes.
The film units illustrated in FIGS. 1,2, and 3 have, for
convenience, been shown as monochrome films. Multicolor images may
be obtained by providing the requisite number of differentially
exposable silver halide emulsions, and said silver halide emulsions
are most commonly provided as individual layers coated in
superposed relationship. Film units intended to provide multicolor
images comprise two or more selectively sensitized silver halide
layers each having associated therewith an appropriate image
dye-providing material providing an image dye having spectral
absorption characteristics substantially complementary to the light
by which the associated silver halide is exposed. The most commonly
employed negative components for forming multicolor images are of
the "tripack" structure and contain blue-, green-, and
red-sensitive silver halide layers each having associated therewith
in the same or in a contiguous layer a yellow, a magenta and a cyan
image dye-providing material, respectively. Interlayers or spacer
layers may, if desired, be provided between the respective silver
halide layers and associated image dye-providing materials or
between other layers. Integral multicolor photosensitive elements
of this general type are disclosed in U.S. Pat. No. 3,345,163
issued Oct. 3, 1967 to Edwin H. Land and Howard G. Rogers as well
as in the previously noted U.S. patents, e.g., in FIG. 9 of the
aforementioned U.S. Pat. No. 2,983,606.
A number of modifications to the structures described in connection
with the figures will readily suggest themselves to one skilled in
the art. Thus, for example, the mulitcolor multilayer negative may
be replaced by a screen-type negative as illustrated in U.S. Pat.
No. 2,968,554 issued Jan. 17, 1961 to Edwin H. Land and in the
aforementioned U.S. Pat. No. 2,983,606 particularly with respect to
FIG. 3 thereof.
The image dye-providing materials which may be employed in such
processes generally may be characterized as either (1) initially
soluble or diffusible in the processing composition but are
selectively rendered non-diffusible in an imagewise pattern as a
function of development; or (2) initially insoluble or
non-diffusible in the processing composition but which are
selectively rendered diffusible or provide a diffusible product in
an imagewise pattern as a function of development. These materials
may be complete dyes or dye intermediates, e.g., color couplers.
The requisite differential in mobility or solubility may, for
example, be obtained by a chemical action such as a redox reaction
or a coupling reaction.
As examples of initially soluble or diffusible materials and their
application in color diffusion transfer, mention may be made of
those disclosed, for example, in U.S. Pat. Nos. 2,774,668;
2,968,554; 2,983,606; 2,087,817; 3,185,567; 3,230,082; 3,345,163;
and 3,443,943. As examples of initially non-diffusible materials
and their use in color transfer systems, mention may be made of the
materials and systems disclosed in U.S. Pat. Nos. 3,185,567;
3,443,939; 3,443,940; 3,227,550; and 3,227,552. Both types of image
dye-providing substances and film units useful therewith also are
discussed in the aforementioned U.S. Pat. No. 3,647,437 to which
reference may be made.
It will be understood that dye transfer images which are neutral or
black-and-white instead of monochrome or multicolor may be obtained
by use of a single dye or a mixture of dyes of the appropriate
colors in proper proportions, the transfer of which may be
controlled by a single layer of silver halide, in accordance with
known techniques. It is also to be understood that "direct
positive" silver halide emulsions may also be used, depending upon
the particular image dye-providing substances employed and whether
a positive or negative color transfer image is desired.
It will also be understood that the present invention may be
utilized with films wherein the final image is in silver, and
photoexposure and/or viewing is effected through a transparent
support which is provided with an anti-reflection coating in
accordance with the teachings of this disclosure. Indeed, the
transfer of silver may be utilized to provide a silver image or to
provide a dye image by silver dye bleach processing.
In the preferred embodiments, the layers comprising the individual
film units are secured in fixed relationship prior to, during, and
after photoexposure and processing to provide the desired integral
negative-positive image. Film units of this type are well known in
the art and are illustrated, for example, in the above cited U.S.
Pat. Nos. 3,415,644; 3,467,437; and 3,594,165, as well as in other
patents. In general, a binding member is provided extending around,
for example, the edges of the composite structure and securing the
elements thereof in fixed relationship. The binding member may
comprise a pressure-sensitive tape securing and/or maintaining the
layers of the structure together at its respective edges. If the
edge tapes are also opaque, edge leakage of actinic radiation
incident on the film unit will be prevented. The edge tapes also
will act to prevent leakage of the processing composition from the
laminate during and after processing. The rupturable pod is so
positioned as to discharge its contents between predetermined
layers; e.g., between the image-receiving layer 18 and the silver
halide emulsion layer 14 of FIG. 1; these layers may be temporarily
bonded to each other with a bond strength less than that exhibited
by the interface between the opposed surfaces of the remaining
layers, as described above. The binding member may also serve to
provide a white mask or border for the final image. The manufacture
of such film units or packets is well described in the above-noted
and other patents and need not be set forth in any detail here.
Rupturable container 16 may be of the type shown and described in
any of U.S. Pats. Nos. 2,543,181; 2,634,886; 3,653,732; 2,723,051;
3,056,492; 3,056,491; 3,152,515; and the like. In general, such
containers will comprise a rectangular blank of fluid- and
air-impervious sheet material folded longitudinally upon itself to
form two walls which are sealed to one another along their
longitudinal and end margins to form a cavity in which processing
composition 17 is retained. The longitudinal marginal seal is made
weaker than the end seals so as to become unsealed in response to
the hydraulic pressure generated within the fluid contents 17 of
the container by the application of compressive pressure to the
walls of the container, e.g., by passing the film unit between
opposed pressure applying rollers.
The rupturable container 16 is so positioned as to effect
unidirectional discharge of the processing composition 17 between
predetermined layers, e.g., the image-receiving layer 18 and the
silver halide layer 14 next adjacent thereto, upon application of
compressive force to the rupturable container 16. Thus, the
rupturable container 16, as illustrated in FIG. 1, is fixedly
positioned and extends transverse a leading edge of the
prelaminated film unit with its longitudinal margin seal directed
toward the interface between the image-receiving layer 18 and the
silver halide emulsion layer 14. The rupturable container 16 is
fixedly secured to this laminate by a tape extending over a portion
of one wall of the container, in combination with a separate
retaining member or tape extending over a portion of the laminate's
surface generally equal in area to about that covered by said
tape.
A preferred opacification system to be contained in the processing
composition 17 to effect processing outside of a camera is that
described in the above-mentioned U.S. Pat. No. 3,647,437, and
comprises a dispersion of an inorganic light-reflecting pigment
which also contains at least one light-absorbing agent, i.e.,
optical filter agent, at a pH above pKa of the optical filter agent
in a concentration effective when the processing composition is
applied, to provide a layer exhibiting optical transmission density
> than about 6.0 density units with respect to incident
radiation actinic to the photosensitive silver halide and optical
reflection density < than about 1.0 density units with respect
to incident visible radiation.
In lieu of having the light-reflecting pigment in the processing
composition, the light-reflecting pigment used to mask the
photosensitive strata and to provide the background for viewing the
color transfer image formed in the receiving layer may be present
initially in whole or in part as a preformed layer in the film
unit. As an example of such a preformed layer, mention may be made
of that disclosed in U.S. Pat. No. 3,615,421 issued Oct. 26, 1971
and in U.S. Pat. No. 3,620,724 issued Nov. 16, 1971, both in the
name of Edwin H. Land. The reflecting agent may be generated in
situ as is disclosed in U.S. Pats. Nos. 3,647,434 and 3,647,435,
both issued Mar. 7, 1972 to Edwin H. Land.
The dye developers (or other image dye-providing substances) are
preferably selected for their ability to provide colors that are
useful in carrying out subtractive color photography, that is, the
previously mentioned cyan, magenta and yellow. They may be
incorporated in the respective silver halide emulsion or, in the
preferred embodiment, in a separate layer behind the respective
silver halide emulsion. Thus a dye developer may, for example, be
in a coating or layer behind the respective silver halide emulsion
and such a layer of dye developer may be applied by use of a
coating solution containing the respective dye developer
distributed, in a concentration calculated to give the desired
coverage, of dye developer per unit area, in a film-forming
natural, or synthetic, polymer, for example, gelatin, polyvinyl
alcohol, and the like, adapted to be permeated by the processing
composition.
Dye developers, as noted above, are compounds which contain the
chromophoric system of a dye and also a silver halide developing
function. By "a silver halide developing function" is meant a
grouping adapted to develop exposed silver halide. A preferred
silver halide development function is a hydroquinonyl group. Other
suitable developing functions include ortho-dihydroxyphenyl and
ortho-and para-amino substituted hydroxyphenyl groups. In general,
the development function includes a benzenoid developing function,
that is, an aromatic developing group which forms quinonoid or
quinone substances when oxidized.
The image-receiving layer may comprise one of the materials known
in the art, such as polyvinyl alcohol, gelatin, etc. It may contain
agents adapted to mordant or otherwise fix the transferred images
dye(s). Preferred materials comprise polyvinyl alcohol or gelatin
containing a dye mordant such as poly-4-vinylpyridine, as disclosed
in U.S. Pat. No. 3,148,061, issued Sept. 8, 1964 to Howard C.
Haas.
In the various color diffusion transfer systems which have
previously been described, and which employ an aqueous alkaline
processing fluid, it is well know to employ an acid-reacting
reagent in a layer of the film unit to lower the environmental pH
following substantial dye transfer in order to increase the image
stability and/or to adjust the pH from the first pH at which the
image dyes are diffusible to a second (lower) pH at which they are
not. For example, the previously mentioned U.S. Pat. No. 3,415,644
discloses systems wherein the desired pH reduction may be effected
by providing a polymeric acid layer adjacent the dyeable stratum.
These polymeric acids may be polymers which contain acid groups,
e.g., carboxylic acid and sulfonic acid groups, which are capable
of forming salts with alkali metals or with organic bases; or
potentially acid-yielding groups such as anhydrides or lactones.
Preferably the acid polymer contains free carboxyl groups.
Alternatively, or in addition, an acid-reacting reagent may be
provided in a layer adjacent to the silver halide layer most
distant from the image-receiving layer, as disclosed in U.S. Pat.
No. 3,573,043 issued Mar. 30, 1971 to Edwin H. Land. Another system
for providing an acid-reacting reagent is disclosed in U.S. Pat.
No. 3,576,625 issued Apr. 27, 1971 to Edwin H. Land.
An inert interlayer or spacer layer may be and is preferably
disposed between the polymeric acid layer and the dyeable stratum
in order to control or "time" the pH reduction so that it is not
premature and thus interfere with the development process. Suitable
spacer or "timing" layers for this purpose are described with
particularity in U.S. Pat. Nos. 3,362,819; 3,419,389; 3,421,893;
3,455,686; and 3,575,701.
While the acid layer and associated spacer layer are preferably
contained in the positive component employed in systems wherein the
dyeable stratum and photosensitive strata are contained on separate
supports, e.g., between the support for the receiving element and
the dyeable stratum; or associated with the dyeable stratum in
those integral film units, e.g., on the side of the dyeable stratum
opposed from the negative components, they may, if desired, be
associated with the photosensitive strata, as is disclosed, for
example, in U.S. Pats. Nos. 3,362,821 and 3,573,043. In film units
such as those described in the aforementioned U.S. Pats. Nos.
3,594,164 and 3,594,165, they also may be contained on the spreader
sheet employed to facilitate application of the processing
fluid.
As is now well known and illustrated, for example, in the
previously cited patents, the liquid processing composition
referred to for effecting multicolor diffusion transfer processes
comprises at least an aqueous solution of an alkaline material, for
example sodium hydroxide, potassium hydroxide, and the like, and
preferably possessing a pH in excess of 12, and most preferably
includes a viscosity-increasing compound constituting a
film-forming material of the type which, when the composition is
spread and dried, forms a relatively firm and relatively stable
film. The preferred film-forming materials comprise high molecular
weight polymers such as polymeric, water-soluble ethers which are
inert to an alkaline solution such as, for example, a hydroxyethyl
cellulose or sodium carboxymethyl cellulose. Additionally, other
film-forming materials or thickening agents whose ability to
increase viscosity is substantially unaffected if left in solution
for a long period of time are capable of utilization. The
film-forming material is preferably contained in the processing
composition in such suitable quantities as to impart to the
composition a viscosity in excess of 100 cps, at a temperature of
approximately 24.degree. C. and preferably in the order of 100,000
cps. to 200,000 cps. at that temperature.
In particularly useful embodiments of this invention, the
transparent support contains a small quantity of a pigment, e.g.,
carbon black, to prevent fog formation due to light-piping by
internal reflection within the transparent support of actinic light
incident upon an edge thereof; such elements are described and
claimed in the copending application of Edwin H. Land Ser. No.
194,407 filed Nov. 1, 1971 now abandoned in favor of a
continuation-in-part application, Ser. No. 419,808 filed Nov. 28,
1973. Similarly, fog from such light-piping may be avoided by
incorporating an alkali-dischargeable dye in a suitable layer,
e.g., the image-receiving layer, in accordance with the disclosure
of the copending application of Howard G. Rogers, Ser. No. 194,406
filed Nov. 1, 1971 now abandoned in favor of a continuation-in-part
application, Ser. No. 408,052 filed Oct. 19, 1973. The transparent
support advantageously may include an ultraviolet light absorber,
as taught in the copending application of Ronald F. Cieciuch and
Herbert N. Schlein, Ser. No. 214,600 filed Jan. 3, 1972 now
abandoned in favor of a continuation-in-part application, Ser. No.
300,277 filed Oct. 24, 1972.
While it is generally desirable to provide the anti-reflection
coating as part of the transparent support prior to applying the
photographically used layers and subsequent assembly of the film
unit, it is within the scope of this invention to apply the
anti-reflection coating at any stage of the manufacture process
that is best suited for the particular materials and
components.
As discussed above, the anti-reflection coating or stratum should
comprise a material having an index of refraction less than that of
the transparent support. The optimum index of refraction to be
exhibited by the anti-reflection coating may be readily calculated
by the principles of physics previously discussed, but it is not
essential that such optimum value be used in order to obtain very
beneficial results. In the preferred embodiments of this invention,
the transparent support is formed of a polyester having a high
index of refraction, e.g., of about 1.6 or higher. The
anti-reflection coating preferably has an index of refraction at
least 0.20 less than, and more preferably at least 0.20 to 0.3 less
than, the index of refraction of the transparent support. Since the
polyester transparent supports will have an index of refraction of
about 1.6 or higher, the preferred anti-reflection coatings will
exhibit an index of refraction of about 1.3 to 1.45.
The fluorinated polymer may be selected from among the many
well-known and readily synthesizable fluorinated polymers. The
index of refraction typically decreases as the degree of
fluorination is increased. Fluorinated polymers having indices of
refraction of about 1.3 to 1.45 are preferred.
As stated above, the specific anti-reflection coatings with which
this invention is concerned comprises one-quarter wave strata of a
fluorinated polymer or blends of the same on a polyester
transparent support. It has now been found that is possible to
improve the abrasion resistance and/or adhesion of such fluorinated
polymer layers carried by polyester supports by having an
isocyanate included in the fluorinated polymer layer or disposed
between the fluorinated polymer layer and the polyester support.
The isocyanate has been found to be effective in quite small
quantities, and to be effective with fluorinated polymers which are
not crosslinked by the isocyanate. The suitability of any given
isocyanate for use with any given fluorinated polymer, and the
amount of isocyanate which will give useful improvements in
abrasion resistance and/or adhesion to a polyester support may be
determined by routine testing. Some isocyanates, particularly at a
given level, may provide improved abrasion resistance with limited
or no increase in the adhesion to the polyester support.
Generally speaking, the quarter-wave anti-reflection coating 26
will have an optical thickness of about 0.08 to about 0.2 micron
and more preferably from about 0.12 to about 0.15 micron, or a
preferred physical thickness of about 0.09 to about 0.11
micron.
The following examples are illustrative of the preparation of an
element of the type shown in FIG. 4.
EXAMPLE 1
A transparent 4 mil polyethylene terephthalate film base was coated
with a 0.2 weight percent solution of Hylene M-50 (trademark of E.
I. du Pont de Nemours for a 50% by weight solution of undistilled
methylene-bis-(4-phenyl-isocyanate) in monochlorobenzene in dry
(less than 0.1% water) methyl ethyl ketone to provide a dry
coverage of about 1 mg./ft..sup.2 of the isocyanate. Drying was
effected at about 250.degree. F. a quarter-wave fluorinated polymer
coating was applied over this "subcoat" by applying a solution
comprising, by weight, 112 parts of methyl ethyl ketone (dry), 28
parts of methyl isobutyl ketone (dry), 2.25 parts of Kynar 7201
(tradename of Pennwalt Chemical Co. for a copolymer of vinylidene
fluoride and tetrafluoroethylene) and 0.4 parts of polymethyl
methacrylate to give a dry coverage of about 15 mg./ft..sup.2. This
coating also was dried at about 250.degree. F. The resultant
anti-reflection coating exhibited markedly greater resistance to
abrasion, as compared with a similar control coating which did not
have the isocyanate subcoat, when rubbed vigorously with a dry
tissue, such as a Kleenex brand facial tissue. (This abrasion test
procedure has been found to be severe enough to cause scratching of
uncoated polyethylene terephthalate.) The fluorinated polymer
coating also exhibited no separation from the polyester base, as
compared with the control coating which did separate, in a
cellophane tape adhesion test. (In this test, a cellophane tape
such as that sold by 3M Company under the tradename "Scotch" tape
is placed on the subject coating, rubbed about 20 to 30 times to
insure uniform contact with the coating and then pulled off. This
is considered to be a rather rigorous test of adhesion.) While
isocyanates are known to be useful as cross-linking agents and
adhesion aids, it was surprising to discover that the Hylene M-50
was effective to increase abrasion resistance and adhesion at such
low levels. Solubility tests showed that no cross-linking had
occurred.
EXAMPLE 2
The procedure described in Example 1 was repeated except that the
quantity of the Hylene M-50 was 0.4 weight percent. The abrasion
resistance also was greater than the control and the fluorinated
polymer coating was not removed in the adhesion test.
EXAMPLE 3
The procedure described in Example 1 was repeated omitting the
isocyanate subcoat and adding the Hylene M-50 (approximately 2
weight percent based upon polymer content) to the fluorinated
polymer coating solution. The abrasion resistance was not quite as
good as that obtained in Examples 1 to 2 but still much greater
than a control in which no isocyanate was present. Adhesion of the
fluorinated polymer coating to the polyester film base was
comparable to that obtained in Examples 1 and 2. Use of dry methyl
propyl ketone as the solvent was found to give even better
results.
EXAMPLE 4
The procedure described in Example 3 was repeated using dry methyl
propyl ketone and a mixture of Kynar 7201, Kel F Elastomer 3700,
and polymethyl methacrylate in a weight ratio of about 51 to 21 to
28. (Kel F Elastomer 3700 is a tradename of 3M Company for a 50/50
copolymer of chlorotrifluoroethylene and vinylidene fluoride.) The
coating solution contained about 5% Hylene M-50 based on polymer
solids. Excellent resistance to abrasion and excellent adhesion
were observed in the previously stated tests.
EXAMPLE 5
The procedure described in Example 4 was repeated using each of the
following in the same weight percent as the isocyanate in the
Hylene M-50: phenyl isocyanate; phenyl isothiocyanate;
3,3-dimethyoxy-4,4-biphenyl diisocyanate; hexamethylene
diisocyanate; hexyl isocyanate; n-butyl isothiocyanate; and butyl
isocyanate. In each instance, resistance to scratch resistance was
greater than the same coating without the isocyanate. Adhesion,
however, was not as good as in Examples 1-4 in that portions of the
fluorinated polymer layer were removed by the cellophane tape.
As noted in Example 1, Hylene M-50 is sold as an undistilled
methylene p-phenyl diisocyanate dissolved in monochlorobenzene.
When a comparable solution prepared from purified methylene
p-phenyl diisocyanate was used, the abrasion resistance and
adhesion were not as good. It is believed that the greater abrasion
resistance may be due to the presence of Hylene M-50 of some
isocyanate oligomers and, indeed Hylene M-50 is described by the
manufacturer as a polyisocyanate. Coating fluids containing the
fluorinated polymer Hylene M-50 showed the same improvements in
abrasion resistance and in adhesion even though stored at room
temperature for long periods, e.g., a week, before coating.
It will be apparent from the above examples that a variety of
isocyanates (aliphatic and aromatic) have been found to be useful,
including diisocyanates and isothiocyanates and the term
"isocyanates" is used herein to include such compounds. The
quantity of isocyanate used should not be so great as to adversely
affect the index of refraction of the anti-reflection layer. In
general, the isocyanate is used in a ratio of about 2.5 to 7.5
weight percent based upon polymer solids, and the polymer coating
solution preferably contains about 1-2% solids. The solvents used
in the coating solution should be "dry", i.e., substantially free
of water, and otherwise non-reactive to avoid undesirable reactions
with the isocyanate. (The methyl propyl ketone used in the above
examples contained about 0.02 to 0.08% water, and this minute
amount of water was not found to be detrimental.) Ketonic solvents
are particularly useful. Coating may be effected using a variety of
techniques, including dipping, roller application, slot coating,
etc.
The desired effects obtained with the Hylene M-50 do not appear to
be dependent upon the presence of cross-linkable groups in the
coating.
In some instances, it has been found desirable to include a minor
proportion of a non-fluorinated polymer, particularly an acrylic
polymer such as polymethyl methacrylate, to improve the adhesion,
scratch resistance or other properties of the fluorinated polymer.
If such a non-fluorinated polymer is included, its proportion
should not be so great as to undesirably increase the index of
refraction of the fluorinated polymer coating; if, for example, it
is desirable to include polymethyl methacrylate, it has been found
that it may be present in up to about 30% weight percent of the
polymer blend.
Although the above examples have utilized mixtures or blends of
polymers in providing the fluorinated polymer anti-reflection
layer, it should be understood that such mixtures are not
necessary. Also, it should be understood that the proportions of
the blended polymers may vary depending upon the properties desired
of the final coating and upon the conditions and method of coating.
Thus, for example, the Kynar 7201 may be used alone or in blends
with polymethyl methacrylate in ratios, respectively, of 100-70%
and 0-30% used in Example 4 may be varied over the range 0-25 parts
Kel F Elastomer 3700, 100-45 parts Kynar 7201, and 0-30 parts
polymethyl methacrylate.
Other fluorinated polymers whose abrasion resistance and adhesion
have been increased by the presence of the Hylene M-50 when used
alone or in blends include polyvinylidene fluoride,
dehydrofluorinated polyvinylidene fluoride, Fluoropolymer B
(tradename of E. I. du Pont de Nemours for a 70/20/10 copolymer of
vinylidene fluoride, tetrafluoroethylene and vinylbutyrate), and
Vitron A (tradename of E. I. du Pont de Nemours for a 30/70
copolymer of hexafluoro propylene and vinylidene fluoride.
Polyethylene terephthalate film bases coated with anti-reflection
fluorinated polymer layers as described in the above examples were
used as supports for image-receiving elements of the type shown as
element 32 in FIG. 1, and integral negative-positive multicolor
reflection prints was prepared in accordance with the procedure
described in Example 2 of the copending application of Edwin H.
Land, Stanley M. Bloom, and Howard G. Rogers, Ser. No. 246,669,
filed Apr. 24, 1972 now U.S. Pat. No. 3,801,318 issued Apr. 2,
1974. Good anti-reflection properties were obtained. The general
format of the resultant integral negative-positive reflection print
was similar to that shown in FIG. 1 of the above-mentioned U.S.
Pat. No. 3,415,644. Good anti-reflection properties were
obtained.
The product shown in FIG. 4 has utility apart from use as a
photographic film support. One such use is as a protective sheet
laminated, anti-reflection coating outermost, to the surface of a
processed photographic image, e.g., a diffusion transfer image, in
accordance with the teachings of U.S. Pat. No. 2,798,021 issued
July 2, 1957 to Edwin H. Land.
It will be recognized by those of ordinary skill in the art that
the solvent of choice for a particular material, and the
concentration of the material in the coating solution, may be
readily determined by routine experimentation. Obviously the
solvent should be one which will not adversely affect, mechanically
or optically, the transparent support upon which it is coated.
The transparent support advantageously has a moisture permeability
rate adapted to accelerate "drying" of the layers forming the
integral negative-positive reflection prints of the preferred
embodiments. Reference may be made to U.S. Pat. No. 3,573,044
issued Mar. 30, 1971 to Edwin H. Land for a detailed description of
dimensionally stable, transparent polyester supports, e.g.,
microporous polyesters, having suitable permeability rates, and
said description is hereby incorporated herein for convenience. It
will be understood that selection of an anti-reflection coating
should not adversely affect the desired moiture transmission rate
of the transparent support(s).
While the image dye-providing material is generally carried on the
same support as the photosensitive silver halide, it will be
understood that this initial location is not essential, as in
forming monochromes the image dye-providing material may initially
be contained in the processing composition or in a layer of the
image-receiving element as is taught, for example, in the use of
dye developers in the previously mentioned U.S. Pat. No.
2,983,606.
The provision of an anti-reflection coating provides a number of
advantages. In the absence of the anti-reflection coating, the
optimum angle for viewing an image through the transparent support
is very specific and limited, if the viewer is to avoid to the
maximum possible extent seeing specular reflection from the surface
of the transparent support of light from the illumination source.
Such anti-reflection coating have been found to substantially
reduce or prevent such specular reflection, thus greatly improving
viewing. The resulting images exhibit increased color saturation
and density and "cleaner" whites, i.e., reduced minimum densities.
The avoidance of light loss during photoexposure is useful also in
films wherein exposure is effected through a transparent support
but the final image is separated and not viewed through a
transparent support. The reduction in surface reflection (glare)
simplifies copying prints and aids in obtaining truer copy prints;
light polarizers are customarily used to eliminate surface glare
during copying.
Where the expression "positive image" has been used, this
expression should not be interpreted in a restrictive sense since
it is used primarily for purposes of illustration, in that it
defines the image produced on the image-carrying layer as being
reversed, in the positive-negative sense, with respect to the image
in the photosensitive emulsion layers. As an example of an
alternative meaning for positive image, assume that the
photosensitive element is exposed to actinic light through a
negative transparency. In this case, the latent image in the
photosensitive emulsion layers will be a positive and the dye image
produced on the image-carrying layer will be a negative. The
expression positive image is intended to cover such an image
produced on the image-carrying layer.
Since certain changes may be made in the above product and process
without departing from the scope of the invention herein involved,
it is intended that all matter contained in the above description
or shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
* * * * *