Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~lile 913,771
3a3~71D~i
P~OTOCHROMIC AZIRIDINE RRCORDING MEDIA
This invention relates to media which can be
imaged by exposure to actinic radlatiorl. More partlcularly,
the invention relates to articles capable of being used f'or
irnaging or recording bas~d on photochromic aziridines, which
allow the image-formin~ operatlon t;o be reversible~ i.e., the
recorded image may be erased.
Many conventional imaglng materials undergo
lrreversible changes when exposed to actinic radiation. Thus,
erasure is impossible without physical destruction of the image
itself. Additionally, in many instances~ the ima~e formed is
latent, and subsequent development ls necessary.
Photochromes are compounds which change color
reversibly on exposure to actinic radiation. Such dlrect-
developing photochromic materials, however~ traditionally
suffer the limitation that images produced from systems con-
taining these materials have very little stability, l.e., the
image will ~ade spontaneously within a few minutes or hours
at room temperature.
It has now been ascertained that particularly
defined photochromic aæiridine compounds can be utilized for
imaging wherein the recorded image may be erased and informa-
tion may be added, the film may be re-used, etc.
~ urthermore, when the compounds are vapor
coated on a substrate, such can be utilized for high resolu-
tion, long term recording. These films can be utilized indata recording applications such as video disc or mlcrofiche,
especially ln conJunction with high densit~ data recording.
Besides being direct developing, such medla can be updated or
erased. The films can further be used as intermedlates
in photographic and/or copylng processes and as prooring
materials.
The articles can also be used, in con~unctlon
with spectral fllters, to monitor exposure to actlnic
radiatlon~
In Schleigh et al, U.S. Patent No. 3,~9LI,874,
there is described the use of aziridines in photoreductive
imaging. A reducible, image-forming compound is comblned
wlth the photochromic aziridine ln a binder on a substrate to
form a radiation-sensitive layer. Upon exposure to actlnic
radiation, followed by heating, an image may be obtained.
Furthermore, partly crystalline and partly crystallagraphlcally
aligned photochromic aziridines and oxiranes are dlsclosed as
having utility in windshields, sunglassesg and light switching
devlces in U.S. Patent No. 3,964,823.
It has now been found that by applying herein- ~
after-define~ photochromic aziridines onto a substrate, and by ~ -
utilizing an oxygen barrier material to cover the aziridine
2~ coating, the lifetime Or the image formed by exposure to
actinic radiatlon can be increased at least a thousand times
more than that of the photochromic aziridine in oxygen or air.
In accordance with the invention, there is pro-
vided a thermally stable optically erasable imaging or record- ;
ing medium comprising a substrate having on at least one
surface thereof coating or film of at least one photochromic ~;-
aziridine o~ the formula
--2
. ~
9~jj
~ N02
N N
Rl R2
whereln Rl and R2 separately are hydrogen, lower alkyl,phenyl~
or ortho or para lower alkyl or lower alkoxy substikuted
phenyl, and together are alkylene having 4 to 7 carbon atoms
inclusive 3 and overlying said coating, or in some instances
integral therewith, a substantially oxygen~lmpermeable barrier
coating which is reasonably transparent to actinic radiation.
The medium can be imaged by exposure to actinic
radiation, optically erased, and reimaged, with the image
being substantially resistant to thermal bleaching.
: 15 The photochromic azlridines utilized in this
invention are 2Rl,2R2-6tp-nitrophenyl)-4-phenyl-1,3-diazabi- ;;
cycloC3.1.0]hex-3-enes, which can be structually designated:
N02
:~ ~ H / -~ :
20 ~ -H
N N ~ ::
~: Rl 2 -
wherein Rl and R2 taken separately are hydrogen~ lower alkyl;
phenyl, or ortho or para lower alkyl or lower alkoxy substi- .
,
tuted phenyl (wherein the term "lower" designates ~rom 1 to
4 carbon atoms)~ and wherein Rl and R2 taken tog~ther are
alkylene having 4 to 7 carbon atom~ inclusive. These compound~
can be synthesized by the method dlsclosed by Heine et al in
J. Org. Chem. 32, 2708-10 (1967) and in U.S. Patent No.
3,609,165. The most preferrad compound ~or this invention
is the dimethyl derivatlve~ 2,2'-dimethyl-6(p-nitrophenyl)-ll-
phenyl-1,3-dlazabicYclo[3.l.o]hex-3-ene. Pr~ferred alkylene
derivatives include the cyclohexyl and cyclopentyl deriva-
tives.
These aziridines are colorless prior to exposure
to an electron b~am or ultraviolet radiatlon, but upon exposure,
the compounds turn various shades o~ blue depending upon the
Rl and R2 groups contalned t~lerein. If such compounds are
place~ in the dark, they agaln become colorless; hence the
color change ls reversible. Additionally, they may be bleached
thermally or by exposure to visible radiation, i.e. 3 they will
revert to their colorless condition by use of such methods.
Therefore, it is known that the colorless form of the photo-
chromic azirldine can be converted to the colored form uPon
exposure to electron beam or ultraviolet radiation, and the
reversible reaction baok to the colorless form can occur upon
exposure of the aziridine to visible light~ or when placed in ;
the dark, or thermally.
This can be deplcted by the following: ;
A _ l B
dark
--
.
wherein A represents the colorless form, B the colored ~orm~
vl is a radiation frequency limiked to the ultravlolet, ancl
V2 is a radlation frequency limited to the visible.
It has now been ascertalned that in the absence
of oxygen~ the thermal bleaching reaction can be substantially
dimlnished~ and the photochromic material can be rendered
dark-stable, i.e.
A ~ B
hv
~ ?~ ~
To illustrate this phenomenon, a vapor-deposited film of the
dlmethyl derivative was coated on a quartz substrate and
allowed to stand in air for 24 hours to become slightly
turbid, and was then irradiated to yield the deep blue color.
The sample ~las placed in an optical cell in whlch the atmos-
sphere could be controlled.
Under a nitrogen atmosphere at rsorn temperature,the transmissive optical denslty ~measured at 620 nm) oP the
colored film remained essentially constant for seven days;
however, upon introduction of oxygen, the color bleached
rapidly. These results are shown in Figure 1.
Alternatively, using the same set-up with the
film in an air atmosphere, but at 60C, exposure to ultraviolet
radiation caused the ~ilm-to color practically instantaneously,
and then thermally bleach very rapidly. The coloration-
bleach cycle was repeated six times, and then the atmospherewas changed from air to nitrogen, still maintaining the
temperature at 60C. Exposure to ultraviolet with the film
in the nitrogen atmosphere provided a stable colored form
which showed no bleaching over 180 minutes. These startling
results are illustrated ln Figure 2.
--5--
' .,
To ~urther illustrat0 the results o~ an oxygen
atmosphere on the photochromic compoundsg strips of rllter
paper were saturated with benzene solutions of various aziri-
dines of the above formula and dried. The strlps were then
irradiated with ultraviolet to generate the blue form. One
set o~ these irradiated strips was kept in a nitrogen atmos-
phere in the dark, and another set was kept in an oxy~en
atmosphere. Both sets were malntained at room temperature in
the dark. The time required to bleach to one-half of the
original optical density was estimated visually and i8 recorded
in Table I. Considerable care was taken to minimize exposure
of the samples to light during the periodic readout.
Table I
Time Required to Bleach to
_ One-ha_~ Optical De _ity
Aziridine Derivative 2 Atmosphere N? Atmosphere
1 R2 CH3 40 mlnutes >1 year
(Rl ~ R2) = cyclopentyl3 hours>3 months
(Rl + R2) - cyclohexyl10 hours~2 months ~ ;
Rl = CH3, R2 C6~510 minutes~3 months
Rl = H, R2 C3 7 10 hours 1 month
Rl = R2 = C2H520 minutes 3 days
Rl = CH35 R2 = CH(CH3)210 minutes3 weeks
Rl = H, R2 C6H5~10 minutes 2 days
Rl = H, R2 = o-methoxyphenyl<10 minutes 15 hours
It has been further determined~ however, that
even in an inert atmosphereg such as nitrogen, initially opti- ;~
cally clear thin vapor deposited films of the aziridine com-
pounds become turbid or cloudy after a period of tlme, e.g.,
-6-
,,
24 hours. It is believed that such a condition ls due to
crystal growth of the compound.
Tnitlally optically clear films were examined
within one hour after deposition with a scanning electron
microscope. The resulting micrographs revealed a uniform
array of non-crystalline hillocks, less than one mlcrometer
in the longest dimension o~ the base of the hillocks. A
similar sample was stored in nitro~en for 24 hours and under-
went a vlsible change from a transparent fllm to a turbid ~ilm.
Scanning ~lectron micrographs o~ the turbid ~ilm revealed
that the hlllocks had grown substantially and ba~es o~ the
hillocks were irregular. Many of the hillocks had ~oined
together to ~orm three or more peaks. The regular arra~ had
essentially disappeared. Therefore~ maintaining a nitrogen,
argon, neon, etc. inert atmosphere around the photochromic
coating will serve to inhibit thermal bleaching o~ the colored
form, but will not prevent the inltlally clear film from
becoming turbid, which will decrease image resolution. While
such a condition is not preferred, even such turbid films
have utility as an imaging medlum.
It has been found that by utilizing a ~ilm-
~orming barrier coating over the thin aziridine fllm, which is
substantially impermeable to oxygen, the image stability, i.e.
resistance to thermal bleaching, and the ~ilm transparency,
i.e., image resolution capability, can be ef~ectively main-
tained. Exemplary and preferred materials which are substan-
tially impermeable to oxygen and inert toward the aziridine,
i.e., crystal growth inhibiting~ such as polyvinyl alcohol or
gelatin, applied as thin ~ilms over the photochromic ~ilm,
can effectively prevent crystal growth and also act as an
, .
. ~ . .
oxygen barrler to minlmize bleaching. Imaged fil~ coated wlth
polyvlnyl alcohol, for example, have maintained their clarity
and image density for periods exceeding one year.
In the case where the azlrldlne is simply
coated from a solvent solutlon, the dried coatlng will be
mlcrocrystalline ln nature. Obviously~ the turbidity, crystal
growth, etc. is unlmportant ln that instance.
The barrier coating should o~ course be reason-
ably transparent to actinic radiatlon. To mlnlmize crystalli-
zation of the photochromlc azirldine and therefore turbidity,the barrler coating should be applled as soon a~ter azlridlne
deposition as po~sible and before imaging.
Dyes can be added to the barrier coat to select
wavelengths that cause coloration of the aziridine. ~or
example, A]izarine Yellow dye can be added to the polyvinyl
alcohol coating to minimize backgroulld coloration from incan-
descent room lighting, but still allow imaging with, for
example, the 325 nm llne from a helium-cadmium laser.
Since moisture wlll adversely effect the oxy~en-
barrier properties Or polyvlnyl alcohol~ lt would be desirable
in a practical recording device to incorporate a radiation
transparent moisture barrier elther in intimate contact with
the article or surrounding it, e.g., films of a copolymer
vinylidene chloride and vinyl chloride.
In the case of vapor deposition ~or high resol-
ution imaging, the temperature of the recelving substrate, for
condensation of the photochromic aziridine thereon, ls critical~
If the substrate is either too cold or too warm, a non-uniform
coating deposlts and the thln aziridine film will appear to
be turbid and/or blotchy. In contrast, a transparent, uniform
8~
,, : ; ~ , , ,
homogeneous coating is attained lf the temperature of the
receiving substrate is about ~120 to -140C.
Scanning electron microscopic examination of
the blotchy films at lOOX magnification revealed that the
aziridine depo~its in the form of islands. The clear, trans-
parent films and the turbid films were further examined with
scanning electron mlcroscope at 7000X to lO,OOOX magnlrication.
The micrographs of clear9 transparent films illustrated a
uniform array of non-particulate hillocks. The valleys
between the hillocks were of minimal area compared to the area
of the hillocks; and the longest dimenslon of the hillocks was
less than one ~m. The thickness of the film was about o.6 ~m.
Although the hillocks had rounded tops, the bases of the
hillocks were not necessarlly round. Some appeared to be
oval, ellipsoidal and somewhat irregular, although the~ were
predominantly clrcular.
The scanning electron micrographs of the turbid
films revealed a similar hillock structure, but the hillocks
grew together to show an unmistakably dendrltic structure.
The tree-like structure would have branches of ten to twenty
micrometers or more.
The turbid and/or blotchy visual appearance
provides light scattering and hence a severe reduction in the
resolution of images produced with such films. In contrast,
the clear, transparent films provide minimal llght scattering
and high resolution of images.
The following tables are included for the indl-
cated sublimation conditions, wherein material was deposited
on quartz microscope slides. In Table II~the dimethyl aziri
dine derivative, i.e.~ wherein Rl = R2 = CH3 was utili~ed.
~6~V~i
For Table III, an aziridlne wher~ln Rl - H and R2 = n-C3H7
was utillz~d. In Table IV~ the aziridlne wherein Rl ~ R2 =
cyclohexyl was utillzed.
Table II
5Quartz
Receptor Time of
Bath Tem~. ~ ~ Comments
140C 25C 2.5 min. Blotchy~ non-unl~orm films
visible; at lOOX, islands
of' deposits are indicated;
at lO,OOOX, d~ndritlc
effect i~ clearly shown.
140C -75C 2,5 minO Vlsibly turbid ~ilm; at
7000X, dendrltic effect
predominates.
140C-l2goc 2.5 min. Vlsibly transparent, clear
film; at lO,OOOX, regular
array of hillocks less than
one ~m dlameter; film
thickness 0.6 ~m.
140C-153C 2.5 min. Visibly turbld film; at
lO,OOOX extensive
dendritic effect.
140C-168C 2.5 min. Visibly non-uni~orm~
turbid film; at lO,OOOX,
predomlnant dendritic
structure with somewhat
larger hillocks.
~,
Table III
Quartz
Recep~or Time of
Temp~ Comren'~
102C-130C 3 min. No coating
111C132C 8 min. No coating
128C-130C 5 min. Light unlform ~ilm
132C-132C 6.5 mln. Clear, kransparent ~llm
131C-169C 6.5 min. Turbid film with spots
131C25~C 6.5 mln. Non-uniform, turbid
coatlng
--10--
.:
Table IV
__
Quartz
Receptor l'ime of
Bath Temp. ~ De~osltlon Comments
131C -133C 6O5 min. Light~ uniform film
148C 133C 6.5 mln. Clear, transparent ~llm
150C -166C 605 min. Somewhat turbld ~ilm with
poor adherence to substrate
150C -75C 6.5 min. Fair film, but poor
adherence to substrate
150C 25C 6.5 min. F:Llm does not adhere to
substrate
From the foregoing tables~ it can be seen that
the intermediake condensation temperature would appear to be
preferably in the range of about -120C to about -140C, at
least when the dimethyl derivatiYe is utilized. This conden-
sation temperature, as is indicated in Tables III and IV, may
vary sQmewhat depending on the particular aziridine utilized
to form the film.
Where vapor depositlon is unnecessary in pre-
paring the recording medium~ the aziridines can be simply
dissolved in an organic solvent, e.g.~ benzene, at a concen-
tration sufficient to provlde a uniform microcrystalllne coat-
lng, applied to the substrate surface, and dried. In this
instance it ls preferred to use saturated solutions to maxi-
mize coloration on porous substrates, e.g., paper. Following
this~ the film-formlng oxygen barrier material can be coated
over the microcrystalline aziridine layer ln a single coating
operation or, preferably as multiple coatings to maximize
lmage stability.
Alternatively, the aziridines can be coated
from dispersions with a film~forming blnder material, such as
cellulose nitrate, polyacrylonitrile3 polyvinyl alcohol, etc.
, ." , . ., , ,~ .
.,
It is imperative that 9 in this lnstance, the aziridlne~ be
in microcrystalline form on the substrate to ~unctlon ln khe
inventlon, and therefore binder compound~ in which the
aziridines are ~oluble should be avoided. Concentration of
the particulate azlrldlnes ln the dlspersion should be
su~flcient to provide a uniform mlcrocrystalline aziridine
coating on the substrate.
In this latter case, lt is preferred to utillze
rllm-forming binder compounds which in themselves are sub
stantially impermeable to oxy~en, e.g., polyvlnyl alcohol as
a separate oxyg~n barrier overcoat may become unnecessary.
To maximlze image stability~ however, again it is pre~erred
to utilize one or more subsequent barrier coatings of a sub-
stantially oxygen impermeable material.
The receptor ~ubstrates utilized ln the present
invention may be ~lexible or rigid, and may be reflectlve,
opaque, or transparent, and when slmply solution coated,
porous as well. High quality images can be produced on
azirldine-coated substrates such as glass, quartz, polycarbod-
limide-primed polyester film, tin oxlde-coated quartz and
glass, and polyester which has been vapor coated with alumi~
num. The physlcal properties o~ the substrate surface will,
of course, affect the structure of the thin photochromlc ~ilm.
If, for example, vapor depositlon is undertaken on a quartz ;;
substrate having rough pollshing marks, the striations due to
such polishlng can be clearly observed on the ~ilm
Readable lmages may be produce~ by relatively
low inkensity ultraviolet exposure. For example~ when the
dimethyl derivative is utilized, exposure in the range of
about 10 to about 20 milli~oyles/square centimeter ~at 325 nm)
-12-
will produce images having excellent resolution. Readable
images can be obtained at an exposure as low as 5 milli~oules
per square centimeter.
Samples of the photochromic recording medla
have been made utillzing as substrates Kodak KTFR photore~lsts
and electron beam resists, e.g., epoxidlzed polybutadiene and
polymethylmethacrylate. These substrates were slmply vapor
coated with photochromlc aziridine and subsequently overcoatecl
with polyvinyl alcohol. Thls construction allows for instant
"read-after-write" checking of in~ormatlon ln making such
article~ as video disc masters, wh~re it is desired to record
error-correction codes. The constructlon is also use~ul in
checking image quality in lithographic and printing plates
prior to development o~ the flnal relie~ image. The aziri-
dlne and polyvinyl alcohol layers can be simply removed alongwith the unpolymerized resist material following the checking
procedure.
This aspect o~ the lnvention will now be more
speciflcally described with the aid Or th~ following non-
limiting examples~ wherein all parts are by weight unless
otherwise specified. In all cases, preparation of the photo-
chromic film was carried out in a laboratory equipped with
yellow sa~e lights to eliminate extraneous ultraviolet radia-
tlon.
Sublimations were carried out in a glass labor-
atory apparatus. The apparatus consists of a heavy-walled
outer chamber that can be connected through a three-way stop-
cock to a vacuum pump or dry nitrogen or air line. Inside
this chamber is a detachable cold ~inger which can be cooled
by passing cold dry nitrogen through its lnner walls. The
~- -13-
temperature of th~ cold finger was det2rmined with a th~rmo-
couple. The sample to be sublimed was placed in th~ bottom
of the outer chamber and the substrate was attached in
intimate contact to the cold finger so as to maximlze thermal
contact.
A small amount tO.25 gm) Or 2,2'-dime~,hyl-6(p~
nitrophenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-3-ene was
placed in the bottom of the subllmation apparatus. A clean,
2 mm thick quartz substrate was firmly attached to the flat
cold finger o~ the sublimaklon tube with conductive adheslve
tape. The apparatus was assembled and evacuated to about
0.15 Torr. Cold dry nitrogen was passed through the ~acket
of the cold flnger until the temperature o~ the exit gas was
15steady at about -130C. At this point, a hot oil bath (140C)
was utilized to warm the aziridine and sublime it onto the
quartz substrate.
Under these conditions, a transparent aziridine ~ -
film of about o.6 micron thickness was deposited in two minutes.
The oil bath was removed and the cold nitrogen line replaced
by a room temperature compressed air line to warm the cold
finger rapldly to room temperature. At that point, air was
admitted to the chamber and the aziridine-f~lmed substrate -;
removed. It was optically clear. The substrate was then
dipped immediately into a 4 percent by weight aqueous solution
of polyvinyl alcohol to provide the oxygen barrier and to pre-
vent further crystal growth o~ the photochromic aziridine.
The substrate wa~ then dried and dipped again to lnsure a
uni~orm coatlng o~ the entlre area.
14-
Electron micrographs kaken o~ ~reshly deposlted
aziridine ~llms (prior to coatin~ wlth polyvinyl alcohol~ show
these to be typically about o.6 micron thick, and having
unl~orm structure. Films that have been allowed to stand in
alr or nitrogen (without a polyvinyl alcohol overcoat) change
~rom optically clear to turbld within 24 hours.
A clear, sharp blue image on a colorless trans-
parent background was obtained using 15 mllliJoules/square
B centimeter from a Sylvanla F4T5/BLB black llght when the sample
was contact prlnted using a photographic negative. Following
exposure, the sample was stored in the dark in air at room
temperature. Over a one year period, the lmage ~delity has
substantially remained. Only on the sample edges, where the
polyvinyl alcohol coating thickness decreases, or in blemished
coatlng spots, has the lmage bleached.
A similar aziridine-filmed substrate was imaged
as described above. Thèn the imaged substrate was placed in
a light-tight box which had a window made ~rom an ultraviolet
cutof~-visible transmitting filter (Kodak CS-3-6~). The box,
20 containlng ~he plate, was set out ln sunlight ~or about one- -
half hour. The box was ~ubsequently opened in a dark room
under yellow light. The image had been completely blaached,
i.e., erased. The plate was reexposed with ultraviolet as
descrlbed before and a clear~ sharp image was agaln obtained.
No ghosts were detectable. This process could be repeated
over and over with~ut visible loss in quality o~ the resulting
lmage.
Resolutlon of the aziridine-filmed quartz plate
was determlned by recording and then reading out a standing-
wave grating. Under yellow safe lights, a fringe pattern
f
--1 5
. ' . , ` ~ , . . ~
D~
was formed by interferrlng two expanded beam~ ~rom the 325 nmline of a helium~cadmium laser, The sample was exposed to 17
milliJoules per square centlmeter. An image o~ 1020 line
pairs per millimeter was recorded. The ~act that this grating
had been recorded was confirmed by passing ~ helium-neon laser
beam (633 nm) through the imaged sample and obser,ving spots
dlffracted from the zero order beam~ The ratio o~ intensity
of the first ord~r beam to that o~ the ~ero order beam was 0.4
percent.
Re5ponse time o~ the polyvinyl alcohol-coated
azirldine-filmed quartz plate was determined by measuring the
change in its transmittance at 633 nm as a functlon o~ time
after exposure to a ten nanosecond UV-nitrogen laser pulse
(345 nm). The response time to a one mllli~oule laser pulse
(25 milli~oules per square centlmeter) was less than the 200
nanosecond response time of the photomultiplier tube used to
make the measurement. The sample was found to color in le~s
than 200 nanoseconds. ,
Thermal stability of the exposed blue form was
~o determined in two experiments. In the first, the azirldlne-
fllmed substrate was placed in a special optical sample chamber
and kept in 52C in air. After ultravlolet irradiation with
a Xenon source, absorbance of the 620 nm peak was monitored
as a function of time. The sample showed no detectable change
in 60 mlnukes. Films with no polyvinyl alcohol barrier coat-
l~g bleached completely withln 30 minutes.
In a second experiment, one o~ the samples was
imaged and then stored in the dark at room temperature for one
year. Only at the edge o~ the sample, where the barrier layer
was thin, was there any noticeable thermal bleaching.
-16-
Measurements were made of the rate of optical
bleaching of an exposed polyvinyl alcohol-coated photochromic
aziridine film by the bleachlng action o~ red (633 nm) light.
The previously exposed (blue) sample was placed ln the path
of an expanded beam ~rom a holium-neon laser. The lntensity
o~ that beam at the sample plane was measured with a Gamma
Scientific 820A photometer. Small portions o~ the beam lnci-
dent on the ~ilm and the beam exlttlng from the ~ilm were
samples by means of beam splitters. Thus, the change ~n tran~-
mlttance o~ that beam could be ~ollowed as the sample bleached.An exposure Or approximately 350 milli~oules per square centi~
meter was required to bleach the sample from a transmissive
optlcal density of 0.65 to one o~ 0.325.
~ .:
Two clean, 2 mm thlck quartz substrates were
coated with 2,2'dimethyl-6 (p-nitrophenyl) 4-phenyl-1,3-diaza- -
bicyclo[3.1.0]hex-3-ene as described in Example 1. The coated `~ ;
substrates were immediately dipped into a 4 percent by weight
aqueous solution of polyvinyl alcohol and dried. The poly
20 vinyl alcohol coating procedure was repeated several times to ~ ~ -
provide dry polyvinyl alcohol coatlngs of about 2 ~m thlckness.
One sample was exposed (in vacuo) to an electron
beam for 0.232 seconds having an accelerating potential of 26
kilovolts, a beam current o~ 10 microamps and a beam area of
2.88 square centimeters (21 milli~oules per square centimeter).
The sample developed an erasable image which had a trans-
missive optical density o~ about 0.5. The second sample
was given a 2 second 0xposure (in vacuo) to an electron beam
having an accelerating potentlal o~ 165 kilovolts, a beam
current of 5 milliamps and beam area o~ 225 square centimeters
-17-
.
. ~.
(7.3 ~oules per square centlmeter). A hlgh quality image
was ob~ained whlch was erasable by exposure to vi~ible light.
Strips o~ filter paper were dipped ln a sa~ur-
ated benzene solution o~ 2,2' dimethyl-6(p-nltrophenyl)-4-
phenyl-1,3-diazabicyclo[3.1.0]hex-3-ene and dried. The
resulting strlps were subsequently dlp-coated in a 4 percent
by weight aqueous polyvinyl alcohol solution and dried with a
heat gun. One strip wa8 dipped in the polyvinyl alcohol and
dried once, another three times and another five times. These
strips and an uncoated strip were then exposed to ultraviolet
radiation from a Sylvanla F4T5/BLB black light to bring them
to a reflective optical density of about 0.90 and then stored
in air in the dark in a 50C oven. A second set was stored
in air in the dark in a 0C refrigerator. At various inter-
vals the samples were removed and re~lective optical density
measurements were made. These measurements are illustrated
in Tables V and VI below.
Table V - Darlc Storage in Air at 50C
:
Re~lective Optical Density
No. of Coatings 0 200 400 600 800 1000
Polyvinyl Alcohol min. min. min. min. min. min.
O . 9 0 . 1 ---- ~
1 0.9 0O47 0.4 0O3~ .3 0.25
~ 0.90.73 o.68 o.65 0.63 0.62
0.9 n.78 0.75 0.7ll 0.73 0O73
-18-
:
:''' ' ~ , , .:
-
Table VI - Dark ~tora~ in Air at 0~C
Reflective Optical Den~ity
No~ of Coatings 0 200 400 600 800 looo
Polvvinyl Alcohol min. min. min~ min. min. mln.
~ _ _ _ _ _ _
0 0.9 o.63 0 55 0.48 0.44 o.36
1 0.9 0.~ 0 77 0.71l 0.72 0.69
3 o.g o.36 0,.~5 o.84 0.83 0.82
0.9 0.~8 0.87 0.8~ 0.85 o.84
At the end of this experiment the samples were
bleached optically by a one-half hour exposure to a 100 watt
yellow General ~lectric "Rug Lite" at a distance of slx inchesO
The samples were reimaged and there was no apparent loss in
sensitivity, nor were ghost patterns preserlt.
Example 4
A 1.0 gram sample of 2,2'-dimethyl-6(p-nltro-
phenyl)-4-phenyl-1,3-diazabicyclo[3.1.0]hex-3-ene was ground
to a fine particle size in a mortar and pestle. Ten grams of
a 4 percent by weight aqueous polyvinyl alcohol solution were
added to the aziridine and the-mixture was then ~round for a
20 few minutes to achieve a uniform dispersion. The dispersion -
:
was applied by brush to white cardboard and dried with a heat
gun. The entire substrate was then dipped in a 4 percent by
weight aqueous polyvinyl alcohol solution and dried with a
heat gun. Dipping and drying was repeated three more times
to insure a complete seal of the aziridine from air.
This medium was then contact-printed from a
negative by exposing it for five seconds to the mercury lamp
in a "Colite'1 exposure unit. A clear, sharp blue image on
white background was produced. The image was bleached out by
exposing the sample for one-half hour to a yellow incandescent
... ., . . , . ., ~
L6(D~
General Electric "Bug Lite" at a distance of slx inches.
When it was reimaged, there were no ghost images or apparent
105s 0~ sensiti~ity. This lmaged sample was stored in the
dark with no image deterloration over a perlod of one week.
A second porkion o~ this sample was dip-coated
and dried twice from a solutlon of 0.15 gram Alizarine Yellow
dye in 25 milliliters of a ll percent by weight aqueous poly-
vinyl alcohol solution. This sample was exposed for 60
seconds to the l'Collte'l unit through a ne~ative. A sharp,
green image on yellow background was obtained. The back-
ground in thls image came up only slightly a~tar 30 minutes
exposure to overhead IlCool White" ~luorescent lights.
When the aziridines are utlllzed to monitor
radiation, ~ilt~ means are disposed between the aziridine
compound and the source o~ actlnic radiation to allow only
radiation of the character being monitored to reach the aziri~
dine compound. At least one color standard is provided wlth
which to compare the color developed by the aziridine compound. ~`
In the preferred embodiment, the color standard ls separate
from the aziridine comopund, e.g., as the background color
of the substrate. When the color developed by the aæiridine
compound matches the appropriate color standard, the user is
informed that the preselected amount of radiation exposure
has been reached.
The amount of radiation causing the specific
aziridine to develop the color of the color standard may be
accurately determined by measuring the lntensity of the lamp
output with a photometer at the sample plane and the time of
exposure. The product of the intensity and exposure time
gives the exposure (e.g., Joules/cm2)O The visual match between
-2n-
the color of the patch and the color standard 1Y deflned as
the "end point". Several di~ferent patches of one speclfic
aziridine may be us0d wlth a given reference color. Each
patch may be covered by a dlfferent filter to attenuate the
amount o~ radiation to which the aziridlne compound is exposed.
Then3 each patch is calibrated so t;hat a user wlll be informed
as to the amount of radiation required to color match each
patch with the reference color. Alternatively, a speci~ic
azlridine may be color matched wlth several different stan-
dards. Again, each color match wlll represent a differentprecalibrated exposure. However, it is preferable to use a
single color standard.
Where more than one discrete patch of azirldine
compound are present and the patches have different sensitiv-
ities to the actinic radiation being monitored (by overlaylngthe patches with attenuating layers of differing strengths),
a separate color standard is not required~ In such a monitor,
the aziridine patches themselves can serve as a means of com-
parison to alert the user that the predetermlned amount of
radiation has been reached. Since optical density at satur-
ation (deepest blue color possible~ of each photochromic
aziridine is relatively constant, a saturated patch may be
used as a color standard for another unsaturated patch.
The patch with the filter which attenuates the
least w111 reach saturation first, and the filter which atten-
uates the most will reach saturation last. Thus, with photo-
metric calibration, the exposure for saturation may be deter~
mined for each patch. Hence, it is possible to use a monitor
containing a series of patches, which encompass at some lnter-
mediate level a predetermined critical level of exposure. For
..:: , :: .
s , :: , : .,
example~ if the permissible eight hours dose is 3.0 milli-
joules/cm , a monitor havlng patches which reach saturation
at 1.0, 2.0, 3.0, 4.0 and ~.0 milli~oules/cm2 could be used.
The user would note that the first patch colors and reache.s
saturation first~ and then the second will follow suit. At
this point, the user has been exposed to two MilliJoules/cm2.
The third patch is becoming blue and the fourth patch is
lighter blue. Scme time prior to the third patch becoming
the same color as the first and second patches, the user
should leave the actinic radiation area to avoid becominp
expost~d to the permisslble limit.
The monitor of this aspect of the present
invention is especially useful in the treatment of psoriasis,
where a patient receives a photoactive drug and is periodically
exposed to ultraviolet radiation. An article by Parrish et a]
in the l~ew ~n~land Journal of rledicine 291, 1207-11 (1974)
described psoriasis photochemotherapy. The patient is first
treated with a photoactive drugr (e.g.~ 8-methoxypsoralen) by
oral or topical adrninistration, followed by exposure to
specific actinic radiation. Generally, the near UV radiation
in the range of 320 to 390 nanometers is utilized. l'he quan-
tity of radiation required varies between about 1 and 20
joules/cm2 and is dependent upon patient tolerance and response
to the drug. The procedure is expected to involve an initial
intensive treatment phase L ollo~Jed by a long term maintenance
program. Each patient is initially "titrated" to deterrnine
tolerance and effectiveness of treatment. Since the amount of
UV exposure utilized in the treatment is critical to both the
efficacy of the photoactive drug and the minimization of toxic
reactlons such as er~thema, an accurate monitoring of radia~ion
-22-
,
: .. , :
, . . ~ :.
6~ S
exposure is important.
Currently, expensive electronic integratln~
devices are bein~ utili~ed and developed to monitor the
radiation dosage. The inex~ensive, easlly rabrlcated, reli-
able, accurate and reusable monitor of the present lnventlonis well suited ~or use ln this treatment method.
The monltor can also be utilized as a sun
exposure monitor, although for this use it ls desirable to
add an additlonal filter to prevent color bleachlng from the
large amount o~ vislble radiation present ln sunlight. The
device may be used by a sunbather or those concenred about
sensitivity to the solar radiation, and the approPriate chan~e
ln color of the aziridine compound indicates the amount o~
exposure to erythemal radiation. The monitor may also be used
to lndicate necessary adJustments for solar collector panels
by comparlng the rate of change of the color wlth panel posi-
tion.
Since the photochromic a~lridinesused in this
invention respond to actinic radiation as far out as about 450
nanometers; the device, with appropriate filters, ma~ be used
to monltor the exposure received by plant life. Cumulative
light exposure around 435 nanometers ~blue) is indicated by
the change ~rom colorless to blue 9 and alternatively exposure
around h75 nanometers (red) can be correlated with the extent
of optical bleaching ~rom blue to colorless. Thus, light
exposure which af~ects processes such as chlorophyll forma-
~ . ~
tion, photomorphogenesis, phototropism, etc. can be monitored.
The device may also be used to monltor ultra-
violet therapy given to infants undergoing treatment for
jaundice. Another use for the device is in monitoring exposure
- 23
by industrial workers to ultraviolet light and electron beam
radiation used in various manu~acturing processes.
Example 5
_ _
Psoriasis Treatment Monitor
The aziridlne compound, 2 a Z ~ -dirnethyl-~(p-
nitrophenyl)~4-phenyl-1,3-diazabicyclo[3.1,0]hex-3-~ne ~0.25 g),
was ground to a flne particle slze in a mortar and pestle.
Aqueous polyvinyl alcohol (PVA) solution (3 g o~ solution)
was added to the azlridine compound and the mixture was ground
rO~ a ~ew mlnutes to achleve a uniform dispersion. The disper-
sion was applied by brush to bond paper and drled with a heat
gun. The entlre substrate was then dipped in an a~ueous 4%
PVA solution and dried with a heat gun. Dipping and drying
were repea~ed three more times to completely seal the aziridine -
compound from oxygen.
Patches o~ the aziridine coated substrate (about
0.25 cm2) were attached to a color standard sheet. The color
standard sheet was bond paper coated with blue Ben,~amln Moore
Formulation 9-31 Flat Latex paint~ This paint was s01ected
because of the visual match between it ~nd the colored form of
the aziridine dispersion at a reflective optlcal density of
0.8ll when viewed throu~h the ~ilter s~stem (described below).
Five patches of aziridine coated substrate were attached to
strips o~ the color standard sheet about 1.5 cm x 7.5 cm so
that the patches were completely surrounded by the colored
background. The entire strip was then coated with a 4%
aqueous soIution of PVA.
The attenuating filters were prepared by rirst
making a master mix and then successively dlluting it to
achieve various concentrations. The master mix was prepared
-2~-
as ~ollows: ~lylene WS (53.5 g - DuPont 4,4~ methylenebls-
cyclohexyllsocyanate) was charged to a 250 ml three~neck flask
nd stirred and heated to 50C. Polycaprolactone polyol (83.o
g - molecular weight about 530) was added and the temperature
rose to 84~C. A~ter two hours of stirrlng~ the temperature
had decreased to 65C. Dibutyltin dilaurate (0.24 g) was
then added. Hydroxyethyl methacrylate (HEMA, 37.4 ~) was
slowly added to the stirred mixture and allowed to react ror
about 45 minutes. The resulting syrupy mixture was designated
10 Oligomer "A"~ Oligomer "A" (5.05 g) was mixed with 5.05 g of
V-Pyrol~ monomer (N~vlnyl-2-yyrrolldone ~rom GAF Corp.). To
this mixture, anisoin ethyl ether (0.5 g) and ~,a-diethoxy-
acetophenone (0.1 g) were added. To the resulting solution,
Genacryl Yellow 3G (C.I. #4~055, 2.0 ~), 2,4 dihydroxybenæo-
15 phenone (0.424 g) and Alizarine Yellow 5GS (C.I. #14055,
o.o386 g) were added sequentially and stirred until dissolved.
This solution was addad to a mixture o~ Oligomer 7'A" (43.3 g)
HEMA (43.3 g) and a,a-diethoxyacetophenone (o.86~ g) to form
the ~aster mixO The master mix was dlluted with various
amounts of a diluent made o~ 1:1 Oligom~r l'A":HEMA ~ 1 wt %
a,a-dlethoxyacetophenone as shown in Table VII.
Table VII
19.9997
210.0002 o.5798
37.9999 1.2223
47.0002 1.7830 -
5S.9999 2.8716 ~ ;
Each of these solutions was coated onto Mylar
with a ~44 Meyer bar and exposed under a nitrogen atmosphere
to a bank o~ Sylvania F15T 8/BL lamps rOr 2.5 minutes on the
~ ~J~
~25-
,: , . ~
.6~
coated side, 10 minutes on the back side, and then an addi
tional 5 minutes on the coated side, The resultlng cured
films provlde a relatively ~lat spectral response to near UV
radiation.
The cured films are 0asily removed from the
Mylar and cut into the appropriate size to fit over the photo-
chromic azlridine patches. The most concentrated mixture fllm
is conveniently attached to the patch at one end of the sub-
strate, wlth a systematlc decrease in concentratlon over the
other patches,
The spectral response shaping ~ilter was ~re
pared by dissolving the followlng ingredients in 4~.5 g of a
1:1 mixture of Oligomer "A" and HEMA:
0.750 g Genacryl Yellow 3G (C.I, #48055);
0.0782 g dihydroxybenzophenone;
0.213 g phenylsallcYlate;
0.252 g anisoln ethyl ether; and
0.260 g ~,a-diethoxYacetophenone.
The resulting solutlon was coated on Mylar with a R44 Meyer
bar and cured in a nitrogen atmosphere with a bank of Sylvania
F15T 8/BL lamps. The coated side was exposed for ten minutes
and the backside for five minutes, The resulting film was
peeled from the Mylar and was o.o68 mm thick, A portion of
thls film 1.5 cm x 7.5 cm was attached to the attenuating
filters. The entire assembly was covered by a layer of Mylar
to form a monitor, The monitor was exposed to a pair of
Sylvania FR 40 BL-235 lamps. These lamps have an emission
spectrum similar to the lamps used in treat~ng psoriasis. As
the monltor was exposed to the radiation~ the photochromic
aziridine chan~ed to a blue color. The patch under the
-26-
attenuatlng ~ilter 5 ~irst matched the color o~ the color
standard followed by 4 through l as the length Or time of
exposure increased. By the kime that the patch under filter
1 matched the color o~ the standard, the other patches were
darkened 80 thak lt was ver~ easy to visually determlne that
their "end-points" had been passed.
At the point where the color o~ the photo-
chromic azlrldine patch matched the color standard, the reflec-
tlve optical denslty (herelnafter re!ferred to as "optical
density") was o.88 through the monltor's ~ilters as measured
by a MacBeth RD~519 Vensitometer with cyan ~ilter.
A monitor- was exposed to the Sylvania FR40BL-235
lamps until the color of all patches hadpassed the "end-point".
The optlcal density of each patch was determlned and the moni-
tor was then placed in the dark for 72 hours. At the end ofthls time, the optical density was measured agaln. The data is
recorded in Table VII. There was little change in optlcal
density following 72 hours in the dark. The monitor was then
exposed to a yellow GoE~ ~'Bug Llte" at a distance of 15 cm for
two hours. The optlcal density was determined. The results
(also shown in Table VIII) lndicate that the bleaching under
visible radiation is substantial, and that the monitors ma~
be reused.
Table VIII
Optical_Density
Sample 1 ? 3 4 5 ::
Immedlately a~ter exposure to UV loO0 1~12 1.34 1032 1.39
After 72 hours in dark o.961.09 1.29 1.28 1. 39
A~ter exposure to visible light 0.26 0.26 0.2G 0.26 0.26
-27-
. .
,.
6~
Comparlson of the spectral response of this
device and the phyRiological response of human skin following
ingestion of 8-methoxypsoralen indlcates that it would be a
sllperior monitor for determining the radiatlon exposure in
psoriasis treatment.
~ ' '
The aziridine compound, 2,2'-dimethyl~6(p-
nitrophenyl)-4-phenyl-1,3-diazabicycloC3.1.0]hex-3-ene was
dispersed in an aqueous polyvlnyl alcohol solution. 'rhe
solution was applied to white cardboard and completely sealed
ln PVA as descrlbed in Example 5.
The monitor was then prepared as follows:
The entire light sensltive substrate was covered
with masking tape. The masking tape was cut and removed in
areas where the color standard is to be applied. The entire
surface was covered with Ben~amin Moore 9-31 Flat Latex paint.
The masking tape (in areas of light-sensltive patches) was
then removed. -
The entire substrate was then dip-coated in 4%
PV~ and dried (repeated three tlmes).
Filters (combining the spectral response shap-
ing filter and the attenuating filter into one) to be placed
over the individual patches were prepared in the following
manner.
A master dye mixture was prepared ~y addin8 the
following ingred~ents to 1324 g of 20.5% mod. cell. acetate
in acetone solution:
14.8391 g Genacryl Yellow (Berncolors~ Inc. -
Bernacryl Yellow, 4G);
.
1.4298 g Allzarine Yellow (Berncolors, Inc. -
Bernachrome Yellow 6G);
2.3421 g dihydroxybenzophenone, and
2.0992 g phenyl salicylate.
The mixture was warmed and stirred t;o dlssolve the dyes and
then passed through a pressure filter.
A serie~ o~ dilutlons of this master mlxture was
made by adding various amounts of 20.5% mod. cell. ac~tate/
acetone solution. Samples of these solutions were knife-coated
at wet thicknesses of 3.65 mm and then air dried in an oven at
80C (0.0457 mm dry). Samples were selected that gave repre
sentative endpoints of each film when placed over the aziri-
dine dispersion and exposed with theFR40BL-23~ lamps. The
dllutions u~ed in this example are given below.
Amount of
Amount of20.5% Mod. Cell.
Sample # Master Mix (~Acetate in ~cetone (~)
100 0
2 93.5 8.7
3 85.o 15.0
4 76.o 2l~.0
85.0 33
Samples of these films were cut to size and ;;
fixed to the aziridine patches with Dow Corning SII,ASTIC 732
B 25 RTV adheslve. A layer of 2 mil Mylar was then glued over all
five filters with the SILASTIC adhesive, and the entire assembly
was allowed to cure under pressure for 24 hours.
The monitor was exposed to a palr of FR 40
BL-235 lamps at the rate of 2.08 milliwatts/cm2 (measured with
a Gamma Scientific 820A Photometer) until each of the endpoints
had been reached. The sample was then optically bleached with
J~ "~
-29-
.
o~
a G.E. "~ug Lite". Thl~ cycle was repeated two more time~.
On ths fourth cycle, the optlcal density Or
each of the patches was measured periodically (throu~h the
filters) with an RD-100 densitometer. The sample was sub-
sequently bleached optically and a ~l~th cycle of UV exposuregiven. At the end of the fi~th exposure 3 the sample was
placed in the dark and left for 69 hours at room temperature.
Optical density readings were then taken. These data are
summarized below.
The underllned readings, ln each sample, were
the prevlGusly ~udged visual "endpoints". Thus, in these ten
determinations the visual endpoints varied with optlcal denslty
between 0.89 and o.g2 t< 3~), and the extent of bleaching in
the dark was minimal~
4th Exposure Cycle
Exposure
(J!cm2) Optical Density of Sample #
1 2 3 4 5
O 28 .27 .30 .28 .26 ;~
~196 .45 D 39 .36 32 .31
.595 ~62 ~56 .46 .40 .36 -
1.2~~83 .73 ~55 .48 .42
1.58 .92 .80 .60 .52 .~6
2.18 .92 .68 .62 .52
4.05 .85 .76 .67
; 1~-75 ~91 o~l .70
5.74 .87 .76
6~72 ^89 .77
9.87 t90
. .
- -3-
Expos~re
Optica ~
_ 2 3 4 5_
0 .29 .2~ .31 .28 .28
.196 .1~4 .37 .34 .34 o 29
.595 .62 .53 .42 .41 .34
1.49 .91 .78 .5~ ~52 .46
2.18 .92 .70 .61 .52
3.96 .88 .78 .68
4.45 .~9 .79 .~8
5.75 .86 .73
6.72 .9~ .78 -
8.90 .~5
10.6 . go
Optical Density :
A~ter Standing in Dark 69 Hours
.86 .88 .88 .82 .86
Example 7
20Psorlasis Treatment Monitor - :;
The radiation sensitive.substrate was prepared
by coating an aziridine-PVA dispersion to a thickness o~
approximately 0~ 025 mm on phenyl-terminated polycarbodiimide- .
::: primed polyester and subsequently coating with PVA as described .
~ 25 in Example 5. A color standard background was prepared by .
,
: coating primed polyester with the latex paint described in :~
Example 5. Ten holes (about 0O 25 cm2) were punched in ~his
: reference strip, and transparent double-coated pressure sensi- ~:
tive adhesive tape was attached to the uncoated side over the
hole!s. Patches of the light sensitive substrate were then
pressed into the holes in the reference-strip and held in .~ .;
position with the pressure sensitive adhesive. A strip of
tracing paper (Crane - 100% cotton from American Pad and -
Paper Co.) (1.5 cm x 7.5 cm) was placed over the painted sur-
face.
:
. . . , , , .. ~ ;; :
rllhe ~ilter s,ystem for the exposure side con-
sisted of a layer Or t,he spectral response shapin~ ~llter o~
Example 5 and a neutral density step wed~e rllter (Stouffer
#95). The neutral density step wedge filter was placed over
the spectral response shaping filter wlth each step covering
a ~ifrerent light sensitlve patch. The readout side was covered
with visible transmitting UV-absorbing filters made up o~ the
spectral response shaping ~llter plus a filter of the cur~d
master mix o~ Example 5 and held in place by the double-
coated pressure sensitive adheslve tape,
The assembled monitor was exposed for 16 minutesto th0 FR 40 ~L-235 lamps of Example 5 at the rate of 1.8 x
10 3 watts/cm2 and the difference in the color intensity of
the various segments could be easily distinguished visually.
Reflectance O.D. measurements were subsequently made through
the filters of the readout side using a MacBeth RD-51~ dens~to-
meter with a cyan filter. The results are shown in Table IX.
Table IX
Optical Density
l 1.10
2 1.12
3 1.02
4 1.00
.88
6 .82 ;
7 .79
~ .7l
9 .6~
.64 ~,
~ackground1.03
": .
.
~ 6~ S
~ Monitor
The Yellow dYe, Setoflavin T (C.I ~49005,
0.0225 g), was dissolved in 7 cc o~ a 4% aqueous PVA solution.
This dyed PVA solutlon was then mlxed with the azlridine com-
pound (().25 g) to make the light-sensitlve substrate as
described in Example 5.
Alizarine Yellow (C.I. #14055, 0.0345 ~) was
dissolved in one ml o~ 1:1 ethanol:acetone. This solution was
mixed with 2.83 g of 39% mod cell. acetate in acetone and then
coated onto a Mylar web usin~ a #44 Meyer Bar (drled film
thlckness - 0.01 mm).
Films o~ the Aliæarine Yellow/mod. cell. acetate
were then laid over patches o~ the Seto~lavin-aziridine sub-
strates. The flrst patch was covered by one ~llm, and thesecond by two. A CS-7-54 (Corning ~lass Works - Corning Glass
#9363) UV-transmitting, visible-blocking filter was placed over
all o~ the segments.
This assembly was exposed outside to ~ull
(~innesota winter) sunlight. After 25 minuteæ exposure, the
light sensitlve patch under a single ~ilm was considerably
darker, but only slightly darker under two film~. Reflectance
O.D. readings were made through the Ali7arine Yellow (C.I.
#14055)-mod. cell. acetate ~ilm using a MacBeth RD-519 densito-
meter (cyan ~ilter). The data is recorded in Table X.
Table X
Time O.D.
1 Film 2 Fllms
Start .23 .23
~xpose 2:lQ-2:35 p.m. 1.40 .29
Expose 2:50-4:20 p.m. 1.51 54
-33-
. .
O~
Transmittance measurements as a runct,ion o~
wavelength were made of a combination of two layers of the
3.1% Alizarine Yellow-mod. cell, acetate and a 0,015 mm film
of 3.2% Seto~lavin/PVA. These tran~mlttance values and the
azirldine-PVA response values were multlplied to get the
approximate device spectral response.
~9
Three dispersions of aziridine compound ln PVA
were prepared as in Example 5, each havlng a different
aziridine/PVA ratio. These were coated to approximately 0.05
mm l;hickness onto cardboard. A spectral response shaping
filter (~xample 5) was placed over samples of each of the
dispersions. They were then exposed to the blacklights of
Example 5 and optical density readings were taken. The read- -
ings (Table XI~ illustrate that it is possible to obtain a
spread of endpoints by using a common ~ilter9 but different
loadings of aziridine in the light sensitlve substrate, and
these differences can be observed visually.
Table XI
-- .
Optical Densit~
llelght__ Weight Ratio
Aziridine 4% PVA Aziridine~PVA 0 10 m~/cm2 40 rn~/cm2
.0186 g .178 g 2.6.12 .26 .88
.oo70 g .17~ g 9~ o12 .22 .59
25.0018 g .178 g .25.12 .15 .27
In carrying out the above measurements, the
spectral response shaping filter was removed prior to deter-
minin~ the optical density.
.
- -34-
. : . . ,; .
"~
. , ~:
~1~6~
s
Plant Lighting Indlcator ~or Red Llght Respon~e
.__ (~ )
Filter paper was dlpped in a saturated benzene
solutlon Or the Rl = R2 = C~f3 derivative and the solvent evap-
orated. This strip was coated with 4% PVA and dried wlth a
heat gun. The PVA coatin~ was repeated three more tlmes. The
sample was irradlated to an optical denslty o~ .70 (RD 100
densitometer).
Strips of 3M brand infrared transparency ~ilm
Type ~577 were stacked to varlous thicknesses over the irradi- ;
ated aziridine to makè a step wedge attenuating filter for red
llght. A CS 3-69 UV cut-of'f, visible transmitting filter was
placed over this wedge. The entire assembly was taped to a
cardboard backing.
One o~ these indicators was placed in a window
with northern exposure and one with a southern exposure (both
inclined 45). They were exposed from sunrlse to sunset on a
cloudy-bright January day. There was significantly more bleach-
ing in the sample given southern exposure.
The experiment was repeated on a totally cloudy
January day. ~oth samples showed equal bleaching, but consid-
erably less bleaching than that ~ound in the monltors exposed
on the cloudy-brlght day.
The experiment was repeated on a totally sunny
day. For the sample given a southern exposure, complete
bleachin~ occurred at all positions having up to lO layers of
the blue transparency material over them. For the sample le~t
in the northern exposure, only a trace o~ bleachlng occurred
under the area with 4 layers. No noticeable bleaching occurred
in areas co~ered with more than 4 layers.
., - , - ..
, , : , " ., .
. ",, :
- . - -~
~601~
Exam~
Plant Ll~htin~ Indlcakor for Blu~ Llr~ 9C~e
A substrate was prepared as described in
Exam~le 6. Alizarine Yellow (4.0 g~ of` Bernchrome Yellow) and
4.0 g Or tetrahydroxybenzophenone were dissolved ln a solution
of 14.5~ mod. cell, acetate in acet;one. Thls served as the
master solution used to make ~he combined spectral shaping and
attenuating filters. Thls solutiorl was diluted with 14.5% mod.
cell. acetate to malce representative samples. These samples
were coated to .38 mm wet (.o56 mm dry) by a knife coating and
dried two hours ln an 80C oven. From these films, two samples
were selected.
Baslc Blue 7 (C.I. ~42595, 0.362 g) was dissolved
ln 159.4 g of 24.2% mod. cell. acetate in acetone and coated
wlth a knife coater to 0.305 mm wet~ 0.046 mm dry). This
f`ilter, which is to be removed during readout, attenuates
visible light in the red region of the spectrum where the
azlridine is most easily optically bleached. (It is, however,
essentially transmitting in the near- W and far visible
region.)
Samples of the Alizarine Yellow/tetrahydroxy-
benzophenone in mod. cell. acetate fllters were placed over
the indicators and then a layer o~ 0.05 mm Mylar placed over
that. A layer o~ the Basic Blue 7 fllm was laid temporarlly
over the entire assembly. These lndicators were then placed
7 cm f`rom a pair of G.E. #40CW Cool White Fluorescent lamps
(3.24 milliwatts/cm2 total output at sample plane). Reflective
optical density readings of the aziridine/PVA layer were taken
periodically (through the filters) with a MacBeth RD-100 densi-
tometer (yellow f`ilter position). These readings are givenin Table XII.
-36-
Table XII
__
Optlcal Densit,y After
# Grams~ GramsTotal Exposure of
Master14.5% Mod.Cell. (Joul~s/cm2)
5Sam~le # MixtureAcetate/Acetone 0 9.72 23.3 65 2
l 100 0 .44 .82 1.00 1.15
2 80 20 ,52 .96 1.12 1.32
The Basic Blue 7 Filter was removecl and the sample was bleached
with a G.E. "Bug Lite".
~,
~lectron Beam Radiation Monitor
The a~lridine, 2,2'-dimethyl-6(p-nitrophenyl)-
4-phenyl~1,3-diazabicyclo[3.1.~hex-3-ene (0.25 ~m), was ground
to a fine particle size in a mortar and pestle. Aqueous poly-
vinyl alcohol (PVA) solution (3 gm of 4% solution) was added to
the aziridine and the mixture was then ground for a few minutes ;
to achieve a uni~orm dispersion. The dispersion was applied
by brush to bond paper and dried with a heat gun. The entire
substrate was then dipped in an aqueous 4% PVA solution and
dried with a heat gun. Dipplng and drying was repeated three
more tlmes to completely seal the aziridine from alr. Patches ~ ~
of this material were attached to the comparison sheet ln the ~'
manner Or Example 5 and the entire substrate was dip-coated ln
4~ PVA solution and dried. The entire monitor substrate was ;
2~ covered with a single layer of the UV-attenuatin~, visible
transmlttlng film prepared for the psoriasls treatment monitor
of Example 5, Sample l (.o68 mm) to prevent coloration by room
light. Dif~erent thicknesses of Mylar were then stacked over
each of the light sensitive patches to provide step-wise atten-
~30 uation of the electron beam.
,:
'': :'
-37- '
Thls a~sembly was ~ixed to a cardboard backing
and passed through the purged exposure chamber of an Energy
Sciences Electrocurtaln Systems hlgh energy electron beam
radiatlon curing unit (acceleratlng potential 175 Kev, beam
current - 4.32 x lO 6 amps/cm2, l.ll second exposure (.84
Joules/cm2). After exposure, reflective optical densities
were measured for each Or the patches of the monitor (through
the filters) using an AD-~19 densitometer (blue filter
position).
The sample was then re-exposed under the same
conditions (cumulative electron beam exposure l. 68 Joules/
cm2). The e~fects of these exposures on the optical densities
of the various segments is shown in Table XIII.
Table XIII
Total
Thickness
of Beam
Attenuating
Layers 0 D O.D-. Af~er Electron
and Mylar Before
Segment Filter)~xposure .84 Joules/cm2 1.68 Joules/cm2
~ .
l .094 mm.18 1,28 --
2 .129 mm. 221.03 1.23
25 3 .170 ~m.24 .34 .40
4 .221 mm. 34 .34 .33
.246 mm.38 .38 .37
6 .272 mm. 36 .36 .36
7 .297 mm. 39 .42 .42
30 8 .322 mm. 35 .39 .36
,
This sample was optically bleached with a ~.E. "Bug Lite" and
re-~maged. The sample showed little or no loss of sensiti~ity.
In addition to the above appllcation of the
monltor as an indicator of cumulative exPosure, the monitor
35 substrate could be used as a beam penetration indicator.
- 3~ -
