Note: Descriptions are shown in the official language in which they were submitted.
7~S
The present invention relates to a composite photo-
graphic reproduction material for use in industrial and scient-
. ific photography, in artistic displays and in radiography.
Conventional photographic products usually carry a
photographic silver halide emulsion coating on one side of a
transparent or reflecting base material. In radiography, most
conventional X-ray films carry such a layer on both sides of a
- transparent film base. In view of the high cost of silver, a
need exists to reduce the amount of silver required for obtain-
ing the desired photographic properties in photographic pro-
ducts without loss of image density, image quality and inform-
ation content.
. This invention seeks to provide a photographic record-
ing material carrying a light-sensitive silver halide emulsion
with a considerably reduced amount of silver halide as compared
to that of conventional products used in the areas mentioned
above, in combination with a second light-sensitive layer which
will yield photographic records of acceptable information
capacity.
Thus this invention provides a photographic element
comprising a photographic base carrying a light-sensitive
:: photographic silver halide emulsion layer capable of yielding
an image upon image-wise exposure and development and a photo-
sensitive non-silver halide layer contain.ing a light-sensitive
composition selected from the group consisting of diazotype
compositions which form azo dyes, vesicular compositions and
photosensitive polymers, and wherein said non-silver halide
: layer is capable of yielding a second visible image in direct
register with an image present in the light-sensitive silver
halide emulsion layer, after exposure and development of the
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non-silver halide layer.
In use, the silver halide emulsion layer is exposed,
developed, stabilized or fixed in a conventional manner to
produce a silver image. Following this development, the non-
silver halide photosensitive layer is exposed to suitable actinic
radiation through the developed silver image. Then the latent
image in the thus exposed non-silver halide layer is developed
to form a non-silver image. The silver and non-silver image
combine in a composite image in various ways and for various
applications, as will be described below.
United States Patents 3,567,445 and 3,578,451 have
proposed for use as lithographic plates, a lithographic
base carrying a negative working photosensitive composition
that undergoes a chemical reaction in imagewise exposed
areas which renders the exposed areas organophilic and
hydrophobic and a silver halide layer over the negative
working photosensitive composition. After formation of
a silver image in the silver halide layer, the photo-
sensitive composition is exposed and the silver image
is re~oved prior to development of the photosensitive
layer. In this application, the silver image represents
a kind of mask for producing a lithographic pattern. The
mask is removed after exposure of the underlying photo-
resist and, therefore, does not contribute to the final
image as required by the present inventionO
U. S. Patent 3,132,963 and 3,945,822 relate
to Xerothermography and similar processes. Both employ
a photoconductive layer and a silver halide layer and
rely on electrophotographic principles.
The present invention is illustrated by the
accompanying drawings in which:
Figs. 1 and 2 are schematic views of two embodiments
of the photographic recording material of the invention;
and
Fig. 3 are characteristic curves of prior art pro-
ducts and the product of the invention.
Referring to Fig. 1, a photographic recording
material 1 has a transparent film base 2 carrying a
photographic silver halide emulsion layer 4 and a layer
3 of a hydrophobic, positive working, near-ultraviolet
light-sensitive, one- or two-component diazo composition.
Fig. 2 shows an alternative embodiment of the invention
in which layers 3 and 4 are on opposite sides of the film-
base 2.
When layer 3 is exposed to actinic radiation
through a silver image formed in layer 4, the positive-
-- 3 --
~ 5
working diazonium compound is destroyed in exposed areas
of layer 3 and, upon development with an alkaline material,
forms a positive azo dye image in imagewise non-exposed
areas by coupling of the residual diazonium compound and
an azo coupler. The azo dye image thus formed in layer
3 will correspond exactly to, and be in registry with,
the silver image in layer 4.
Figs. 1 and 2 illustrate one system according
to the invention. While this embodiment employed a posi-
tive working diazo material, the non-silver halide photo-
sensitive layer may be a negative-working diazotype com-
position according to special applications as will be
described below, or a vesicular system or a photosensi-
tive polymer. In each system, the principle is the same,
namely the formation of an imagewise light-absorbing
record in the non-silver layer that will be additive to,
and in registry with, the silver image. Exposure, develop-
ment and fixing of the non-silver image formed in the non-
; silver halide layer is carried out using techniques known
for such systemsO
!''` The b~se carrying the photosensitive layer~ may
be any transparent or translucent photographic base mate-
rial, such as polyester, e. g. polyethylene terephthalate,
polycarbonate, cellulose acetate, cellulose acetate buty-
rate, cellulose acetate propionate, polystyrene, poly-
vinyl chloride, polyvinyl acetate and the like.
The present invention finds utility in a wide
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variety of photographic products, and particularly those
that employ a large amount of silver, such as X-ray film.
.~ X-ray film employs silver halide layers on both sides of
a transparent base, and hence the cost of X-ray film is
~ensitive to the rising cost of silverO
For industrial X-rays of conventional design,
the X-ray radiation passing through X-ray transmitting
areas of the object being examined will directly expose
the silver halide layer. However, when taking medical
X-rays, the X-ray radiation passing through the object is
used to excite phosphor-containing intensifying screens
on either side of the X-ray film, such as calcium tung-
state or rare earth screens, the silver halide is thus
exposed ~y the X-ray radiation and by the actinic light
emitted from the phosphors of the intensifying screens,
the X-ray radiation providing 1 to 5% of the exposure
;. with the balance provided by the actinic light from the
screens~
: An X-ray photographic material of the invention
. 20 has a silver halide layer and a non-silver halide layer
;j as shown in Figs. 1 and 2. Generally~ the X-ray material
will be loaded in a cassette (not shown) as is conventional
In contrast to the conventional use of standard X-ray re-
cording materials, the X-ray material of the invention is
preferably exposed with only one inten~ifying screen in c ~
tact with the silver halide emulsion, with the cassette ar-
%~d ~ Ll~Lt~ sil~h~ide layer faces the object to be
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radiographed and the incident X-radiation. After exposure,
the latent silver image is developed and stabilized or
;~ fixed in a conventional manner to produce a negative silver
image in the silver halide emulsion layer, Following
this development, the non-silver halide photosensitive
layer of the photographic material is exposed to radiation
suitably attenuated by the silver image and actinic to
the non-silver halide layer. The latent image in the
thus exposed non-silver halide layer is developed to form
a non-silver positive image in imagewise unexposed areas.
- The silver and non-silver images cooperate to give a
combined image of such density and information capacity
as to be suitable for both medical and industrial radio-
, graphy,
The silver halide layer of the X-ray photograph~
, material of the invention may comprise any light-sensitive
:. silver halide photographic emulsion for an X-ray material,
such as a high speed silver iodo-bromide emulsion (1-3
mol % iodide, 97-99 mol % bromide). The silver halide
layer i9 coated over the transparent or translucent base,
or over the non-silver halide layer, by any suitable means,
Imagewise exposure with X-ray radiation and development
and stabilization or fixing of the silver image is also
effected using conventional technology and apparatus,
The non-silver halide photosensitive layer is
preferably a positive working, diazotype composition,
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vesicular system, or photosensitive polymer. In each
~ystem, the principle will be the same, namely the forma-
tion of a positive visible image in the non-silver halide
layer that will be additive to, and in registry with,
the silver image. Exposure, development and fixing of
the positive images formed in the non-silver halide
systems will be carried out using techniques known for
such systems.
The preferred non-silver halide system is a
positive working W -light-sensitive diazotype composition.
Diazotype compositions are known to provide dense azo
dye images of high image resolution, and hence are widely
used in microfilm. This high resolution is particularly
valuable in the present invention, especially for medical
X-ray material where high image resolution is an important
factor in diagnosis.
Both one-component and two-component diazotype
compositions may be usedO As is known, in order to re-
produce the image as a positive, the diazo compound must
be light-sensitive so that it will decompose to a com-
po~nd no longer capable of forming an azo dye with azo
coupling components in those areas which are exposed to
light. A diazo compound must also be able to couple
under preferably alkaline conditions by simply exposing
the diazotype layer containing it to an alkaline environ-
ment such as ammonia gas, but at the same time, in the
case of two-component systems, having the capability of
:
remaining in a dormant state so that it will not prema-
turely couple with the azo components. The ability to
resist premature coupling may be enhanced by the addition
of stabilizing agents to the two-component coating solu-
tion used in producing the diazotype layer. The use of
stabilizing agents, such as acid stabilizers, endows the
two-component diazotype layer with suitable storage
; stability.
The present invention may make use of such light-
sensitive diazonium compounds as are disclosed in U. S.
; Patent 2,501,874 and in the article by Van der Griten in
the Photographic Journal, vol. 92H, 1952, page 46 Sta-
bilized diazos derived from N-substitued-p-phenylene-
diamines are most satisfactoryO According to the usual
practice, these diazos are generally used iD the form
of salts stabilized with zinc chloride, cadmium chloride
and the like.
Azo coupling compounds are also well known in
the diazo art and include, but are not limited to, the
diazo coupling compounds disclosed at pages 220 to 248
in "Light-Sensitive Systems Chemistry and Application of
Non-Silver Halide Photographic Processes"; by Jaromir
Kosar, published by John Wiley, New York, Copyright 1965.
Acid stabilizers which are generally employed
to prevent the precoupling of the diazonium salt and
coupling component include organic acids such as citric
acid, tartaric acid, boric acid, acetic acid, etc. as
well as inorganic acid such as sulfuric acid, hydrochloric
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acid, etc. Other additives which are generally included
in the light-sensitive diazo layer to prevent precoupling
include acidic salts such as zinc chloride, magnesium
chloride, cadmium chloride, etc.
When a two-component diazotype composition is
used, the azo dye image is developed by contacting the
exposed diazotype layer with an alkaline material, such
as ammonia gas, as is known in the art When a one
component diazotype composition is used, the developing
agent will contain both an alkaline material and an azo
coupling component, as is known.
Where a one-component diazotype composition is
used, the diazotype layer cannot undergo premature coupl-
ing during development of the silver image, since no azo
coupling component is in the diazotype layer. The azo
coupler will be supplied during alkaline development of
the latent diazo image. Where a two-component system is
used, premature coupling is avoided because the hydro-
phobic diazotype layer does not imbibe sufficient alka-
line material during the brief immersion in the aqueous
alkaline silver developer to cause any significant diazo-
type development. However, the latent diazo image is
readily developed using ammonia gas or the like.
; To insure acceptable image density, it is pre-
ferred to use a total amount of silver halide in the
range of about 1 to about 15 grams per square meter and
an amount of diazomium compound of from about 0.2 to
_ g _
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about 0.9 grams per square meter, with the azo coupler
being used in an amount at least equimolar to the diazonDIm
compound. The optimum concentrations of the silver halide
and non-silver halide layers will be determined empiric- -
ally, case-by-case for each system.
When the X-ray material, according to the in-
; vention, is used for medical X-rays, in most cases only
one intensifying screen is employed, and this is placed
between the object being X-rayed and the silver halide
1~ layer. The use of a backside flourescent screen may be
valuable to achieve shorter exposures of the silver halide
layer by light emitted from this screen which must traverse
the non-silver halide layer and the filmbase. However,
sharpness and resolutioo of the final image will be
1~ significantly lower. Thus, in most cases the use of a
backside flourescent screen is not essential, especially
because of the l~w light sensitivity of diazo compounds
and for the stated reasons of loss of image quality.
Another application of the X-ray film of the
invention lies in medical radiography in the diagnosis of
low contrast subject matter, e. g. in mamography and in
the radiography of lungs. Here, highest contrast and
highest resolution are required for the detection of the
low density differences between cancerous tissue and
pulmonary nodules and the surrounding tissue. For such
applications, the use of single-side X-ray film with only
one front screen has been advocated because its defect
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detection is superior to the use of a double-side coated
film and two intensifying screens. Although the advent
of new, more efficient fluorescent screens has overcome
the speed loss due to the use of only one-sided X-ray
- 5 films~ contrast is still sacrificed, and thus a loss of
information capacity has to be toleratedO This loss of
contrast for the radiography of low-contrast subject mat-
ter is a serious deficiency in the present state of the
art. The use of a single-sided silver halide X-ray film
of the present invention in combination with the non-
silver halide layer represents a distinct advantage be-
cause it
a) significantly increases the contrast so badly
needed for the detection of cancerous tissue or of pul-
monary nodules, without the use of heavier silver-halide
- coating,
b) does not increase the patient dosage as compared
to that applied in customary single-sided X-ray films, and
c) does not sacrifice resolution, and yields greater
information capacity because of its higher contrast than
that of a customary single-sided X-ray filmO
Still another aspect of the invention is the
application in industrial radiography. Here the use of
high-energy X - or gamma radiation required for penetrat-
ing thick metal parts frequently yield low image contrast
because of the low subject contrast. To counteract this,
industrial X-ray films often are coated with silver halide
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emulsion which carry as much as three times the amount
of silver as a medical X-ray film to insure an image con-
trast sufficient for defect detection. Also, if higher
resolution is required, single-side coated X-ray-films
are used. However, this means sacrifice of contrast and
thus a sacrifice of information capacity. The image-
recording system of the invention, using a front-side
silver halide emulsion and positive non-silver halide
layer, e. g. a diazo layer, coated either underneath the
silver-halide emulsion or on the back side of the film
base, increases the contrast so badly needed in high-
energy industrial radiography, without increase in silver
content and without loss of speed as compared to that of
a customary single-coated X-ray film.
The X-ray photographic material according to
the invention is adapted to conventional machine process-
ing Thus, the photographic material can be developed,
after imagewise X-ray radiation exposure, in a continuous
processor, eOg. of the type described in U. S. Patent
3,545,971, such as an "X-0-Mat Processor'~. The photo-
graphic material carrying the silver image may then be
exposed through the silver image and the latent azo dye
image developed by means of a conventional diazo processor,
such as an Ozalid ~ machineO For sharper images the light
source and optical arrangement of the conventional diazo
processor may be replaced with an optical arrangement to
`- provide collimated light such as is known in the art.
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Development time in the X-ray processor and exposure and
development times in the diazo processor are determined
empirically.
Another aspect of the invention is the use of
a silver halide layer and a positive-working non-silver
halide layer on a photographic base as a variable-contrast
recording medium. It is emphasized that this readily
enables a reduction of silver by an amount of some 50b
or more for conventional recording films, since the con-
trast of the combined image can be selected by the degree
of exposure of the non-silver halide layer. This is
achieved by selecting the actinic exposure level of the
non-silver halide positive-working layer, eO g. a diazo
layer. At a degree of exposure insufficient to destroy
all the diazonium salt in the image area, fog will be
high. At increasing exposure levels, the fog level will
~ decrease, the maximum density will remain constant and,
; therefore, the contrast will increase. However, at in-
creasing degrees of over-exposure of the diazo layer,
the maximum density and contrast of the developed image
will be decreased. Thus, the contrast will go through a
maximum. Therefore, the choice of the expo~ure for the
diazo layer enables a variable contrast image with dif-
ferent degrees of maximum density and contrast without
` 2S significant change in fog level or background density
; (except, of course, if the exposure of the positive-
working diazo layer were completely omitted and followed
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by its development).
For some uses, the non-silver halide layer can
be a negative working photosensitive material. Thus,
using a silver-halide layer on the front-side of the base
(i.e. facing the camera lens or the incident radiation
for contact printing of an original transparency) and a
photosensitive negative-working layer, e.gO a diazo layer,
; on the backside, it is possible to obtain a recording
material for line-recordsO This product is used as fol-
lows. First, a sharply focused silver image is recorded
on the silver-halide layer in any conventional manner.
After processing, the resulting silver image is exposed
with heavily diffused light onto the negative diazo layer.
Thus, all sharp density edges in the silver layer will
be recorded as unsharp edges. This procedure, particu~rly
if used with a, say, 7 mil thick film base, reduces
greatly the macro contrast in the combined image, but
enhances the micro contrast of samll and large details.
Obviously, the resulting image will display a high back-
, .
i~; 20 ground density. This, however, is overcome by a high-
intensity viewer, known to the art, or by adjusting ex-
posure time if printing of this record is desired. Print-
; ing the combined images of the recording system of the
invention onto a negative- or a positive-working high
; 25 contrast recording material (e. g. graphic arts silver
halide film, high contrast diazo electrophotographic
; layers) will yield a line record showing either a white
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line record on a dark background, or a dark line record
on a light background, respectively.
The use of a unit-gamma non-silver halide back
layer in combination with its diffuse exposure through
the developed silver image displays a uniform background
density in the combined image Thus, only edge contrasts
will be displayed. This feature adds considerably to the
detection of small details, irrespective of the macro-
contrast of surrounding imagP areas.
The selection of differently colored azo dyes
to be formed in the photosensitive diazo layer can result
in various rolor displays. In particular, both single
color and multiple color displays can be generated. As
;~ for multiple color displays, it is advantageous to select
diazos of different "speed" or coupling rates which
results in suitable color separation of the individual
components. In addition, one or more negative-working
diazos may be added to one or more positive-working diazos
of different "speed" or coupling rates. This will ensure
still better color separation and greater color discrimi-
nation. For highly saturated color displays, bleaching
of the silver-image subsequent to the diazo development
is reco~mended. An advantage of the availability of a
variety of colors lies in the fact that it is known that
radiograms may be taken with X-rays of different wave-
lengths (energies). Thus, monochrome pictures in dif-
ferent colors could be easily produced by taking two or
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or three exposures of the same subject using the films of
this invention using different wavelength X-rays. The
~ resulting monochromes could then be superposed to make a
- single color picture (see "Color X-ray Images and Enhanced
Contrast", R. S. Mackay and C. C. Collins, J. Biological
Photo Ass'n., 25, No. 3, p. 114-118, August, 1957).
Other applications of this invention will be-
come apparent to those skilled in the art.
The present invention i5 illustrated by the
following Examples. In the specification and appended
claims, all parts and proportions are by weight unless
otherwise stated~
Example 1
Polyester filmbase, 7 mil, was lacquered on one
side with a solution containing cellulose acetate butyrate
`; and imbibed with a diazo formulation containing 2,5-
dibutoxy-4-morpholino-benzene diazonium chlorozincate and
.'! 3,3'-dihydroxy-2-naphthanilide, which give a bright blue
color on ammonia development. The opposite side was coa~d,
in sequence, with (l)a ~riming composition of vinylidene
chloride/maleic anhydride and vinyl acetate in a solventof
methyl ethyl ketone and methyl isobutyl ketone,(2) a ge~ti~
containing subbing layer, (3) a high speed gelatino
bromiodide ammonia-type medical X-ray emulsion of aver-
age crystal size, 1.3 - 1.4~um, at 4.3 g. silver/m2, and
(4) a thin protective gelatin-containing surface layer
This coated material was placed emulsion-side-up in an
aluminum ront vacuum cassette with CaWO4 Par-Speed
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screens, exposed to an X-ray source operated at 65 kv by
modulating the beam using a calibrated aluminum stepwedge,
processed through an Eastman Kodak M6 ~ processing system
to obtain a silver image and then, without interim room
light exposure, further processed through an Ozalid OM 30
diazo copier, silver image side up, at a dial (speed)
~etting of 35 for the exposure, 10 for the development.
The exposed material was processed in the Ozalid
copier as such without recourse to any further protection
of the diazo layer. In this fashion a silver stepwedge
image was formed on one side of the base with its positive
diazo copy on the reverse side. The characteristic curve
appears in Figure 3 designed as the "silver plus diazo
image",
A second sample was similarly exposed and the
silver image developed, but the diazo latent image was
bleached clear with light instead of being processed to
a visible image. The characteristic curve of this sample
is labeled "silver image" in Figure 3. A simulated two-
sided silver image film was obtained by doubling the den-
sity points of the "silver image" curve and its character-
istic curve plotted and labeled "silver image 2X" in
Figure 3.
A final sample was treated to givethe silver
image and diazo image, but the silver halide emulsion
layer was removed by enzymatic treatment The character-
istic curve of the resultant diazo image was labeled
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"diazo image" in Figure 3
A tabulation of all sensitometric data is given
in Table I. The exposure is expressed in roentgens to
give a net density of loO~ Densitometric measurements
were made through a visual (Wrattan 106~ filter. Grada-
tion was measured from net density 0 25 to 2.0
TABLE I
Sensitometric Data
Fog Exposure (r) Gradation D-max
Silver plus 19 0.00329 1.82 2.67
diazo image
Silver image 15 0.00827 -- 1 72
` Silver image 2X 27 0.00353 2 23 3.41
.~
Example 2
Polyester filmbase was coated as in Example 1
to give a material having the diazo layer on one side and
a subbed layer on the opposite side suitable for receiv-
ing a silver halide emulsion. A low-speed bormoiodide
industrial X-ray emulsion of ultrafine grain, average
crystal Rize of 0.3~um, was coated at 4.5 g silver/m2 on
the subbed side and overcoated with a thin protective
gelatin-containing surface layer. The coated material
was placed with the silver halide emulsion side up in
a cassette and exposed to an X-ray source operated at
65 KV by modulating the beam using a calibrated aluminum
stepwedge. Processing was done in "Liquadol" ~ developer
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. . . .
for 5 mins. with shortstop and fixation in "Liquafix" R.
Subsequent diazo development was done as in Example 1.
In this fashion a silver stepwedge image was formed on
one side of the base with its positive blue diazo copy
on the reverse side. The sensitometry of this image is
referred to as the silver plus diazo image in Table IIo
A second sample was similarly treated except
that the diazo latent image was bleached clear with light
instead of being processed to a visible image, A simu-
lated two-sided silver image film was obtained by doubling
the density points of the silver image and the resulting
sensitometry referred to as silver image 2X in Table II.
; The exposure is expressed in roentgens to give a net
den#ity of 1.5, the gradation is measured from net density
1.5 - 2.5. A comparison was made with a two-sided GAF
100 industrial X-ray control coating.
TABLE II
Sensitometric Data
~ Exposure (r)Gradation
Silver plus diazo image 11 1.94 4.45
Silver image 2X 9 1.81 3.09
GAF 100 Industrial 15 1.81 4.37
X-ray image
Exsmple 3
A number of strips of the X-ray product prepared
in Example 1 were placed emulsion-side-up in an aluminum
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front vacuum cassette with CaWO4 Par-Speed screens,
exposed to an X-ray source operating at 65 KV through a
calibrated aluminum stepwedge and processed in an Eastman
Kodak M6 ~ processing system to obtain the same silver
image on each strip. Single strips were fed through the
exposure section of an Ozalid OM300 ~ diazo copier with
the silver image side up at differing transport speeds
as controlled by the dial settings on the copierO All
~` strips were put through the ammonia development section
at a dial setting of lO. The fog level remained un-
changed over the 10-30 setting range but iDcreased to
0.38 over the 40-60 setting range. Gradation went through
a distinct maximum at a setting of 20, somewhat higher
than the silver image 2X. Shoulder density was essen-
~5 tially maximized at a setting of 20.
Example 4
: Polyester filmbase, 7 mil, was lacquered on one
side with a cellulose acetate butyrate-containing solu-
tion and imbibed with the diazo composition of Example 1,
This layer was subsequently overcoated with (1) a gelatin-
containing subbing layer, (2) a high speed bromoiodide
ammonia-type medical X-ray emulsion at 5.5 g. silver/m2
and (3) a 1,3~um protective gelatin-containing surface
layer.
The X-ray material was exposed and developed
as in Example 1 with similar results.
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