Method of treating scratched or abraded photographic elements with radiation-curable compositions comprising an acrylated urethane, an aliphatic ethylenically-unsaturated carboxylic acid and a multifunctional acrylate

Photographic elements, such as still films, motion picture films, paper prints, microfiche, and the like, which have defects such as scratches, abrasion marks and the like, which impair the appearance or projection capabilities of the element are treated with a restorative composition which fills in the defects so as to effectively eliminate them and restore the element to a substantially defect-free condition. The restorative composition which is applied to the photographic element is a radiation-curable composition comprising an acrylated urethane, an aliphatic ethylenically-unsaturated carboxylic acid and a multifunctional acrylate. It is applied to the element, at least in the region of the defect being treated, and, is then subjected to radiation, such as, for example, ultraviolet light irradiation or high energy electron bombardment, sufficient to bond it to the element and cure it to a transparent, flexible, scratch-resistant, cross-linked polymeric material.

This invention relates in general to the photographic art and in particular 
to a method of treating a photographic element, having defects therein 
which impair its appearance or projection capabilities, to restore the 
element to a substantially defect-free condition. More specifically, this 
invention relates to the application of a radiation-curable composition to 
photographic elements, such as still films, motion picture films, paper 
prints, microfiche, and the like, having defects such as scratches, 
abrasion marks, and the like, on one or both sides thereof, to fill in 
such defects and thereby effectively eliminate them. The radiation-curable 
composition can be applied locally in the region of the defects only or it 
can be applied over the entire surface of the element to both eliminate 
the defects and form a protective overcoat layer that is capable of 
providing protection against subsequent scratching or abrasion. 
Photographic elements having protective overcoat layers are well known and 
a wide variety of different coating compositions have been proposed in the 
past for use as protective overcoats. Such overcoats serve a number of 
different purposes, such as to provide protection against fingerprints, 
abrasion and scratching, to protect against water spotting, to provide a 
particular surface texture such as a matte surface, to provide protection 
against blocking, and to act as anti-reflection layers which reduce glare. 
Layers of a temporary nature which are intended to be removed after they 
have served their purpose and layers which are permanently bonded to the 
photographic element have been described in the prior art. Protective 
overcoats can be applied to photographic elements by coating solutions or 
dispersions of film-forming agents in organic solvents such as are 
described, for example, in U.S. Pat. Nos. 2,259,009; 2,331,746; 2,706,686; 
3,113,867; 3,190,197 and 3,415,670; by coating of aqueous film-forming 
compositions such as are described, for example, in U.S. Pat. Nos. 
2,173,480; 2,798,004; 3,502,501 and 3,733,293; by coating of compositions 
containing discrete, transparent, solid particles of submicroscopic size 
as described in U.S. Pat. No. 2,536,764; by coating of plasticized polymer 
compositions as described in U.S. Pat. No. 3,443,946; by coating of 
polymerized perfluorinated olefins as described in U.S. Pat. No. 
3,617,354; and by lamination of a protective layer as described, for 
example, in U.S. Pat. Nos. 3,397,980 and 3,697,277. 
Protective overcoats known heretofore have suffered from various 
disadvantages which have greatly limited their usefulness. For example, 
though numerous types of overcoats have been proposed, none has been fully 
satisfactory in providing abrasion and scratch resistance for photographic 
elements which are commonly subjected to severe conditions in handling and 
use, such as microfiche and motion picture films. Protective overcoats for 
such elements must meet exacting requirements with respect to factors such 
as transparency and flexibility as well as abrasion resistance and scratch 
resistance, and must be very strongly bonded to the underlying material to 
avoid the possibility of delamination. Protective overcoats meeting all of 
these requirements have long been sought without success. Moreover, many 
of the compositions proposed heretofore for use as overcoats are not 
effective as restorative compositions for treating elements which have 
been subjected to scratching or abrasion in use. 
In U.S. patent application Ser. No. 737,445 filed Nov. 1, 1976, of which 
the present application is a continuation-in-part, there is disclosed a 
photographic element having on one or both sides thereof a protective 
overcoat that has been formed by coating the element with a 
radiation-curable composition comprising an acrylated urethane, an 
aliphatic ethylenically-unsaturated carboxylic acid and a multifunctional 
acrylate, and irradiating the coating to bond it to the element and cure 
it to form a transparent, flexible, scratch-resistant, cross-linked 
polymeric layer. The present application relates to utilization of this 
radiation-curable composition to treat a photographic element having 
defects therein which impair its appearance or projection capabilities, 
such as scratches, abrasion marks, and the like, to effectively eliminate 
them and restore the element to a substantially defect-free condition. The 
radiation-curable composition can be applied to the element locally in the 
region of the defects only. Alternatively, it can be applied over the 
entire surface of the element to both eliminate the defects and form a 
protective overcoat layer that is capable of providing protection against 
subsequent scratching or abrasion. In either case, radiation curing of the 
composition by, for example, the use of ultraviolet radiation or high 
energy electrons, results in the formation of a transparent, flexible, 
scratch-resistant, cross-linked polymeric material which is strongly 
bonded to the photographic element. 
The radiation-curable compositions disclosed in application Ser. No. 
737,445 can be used in treating scratches, abrasion marks, and similar 
defects in many different types of photographic elements. For example, the 
photographic elements can be still films, motion picture films, paper 
prints, or microfiche. They can be black-and-white elements, color 
elements formed from a negative in a negative - positive process, or color 
elements formed directly by a reversal process. Radiation curing of the 
composition has been found, quite surprisingly, to provide strong bonding 
to all of these different types of photographic element without in any way 
adversely affecting the element itself. The photographic elements can 
comprise any of a wide variety of supports. Typical supports include 
cellulose nitrate film, cellulose acetate film, poly(vinyl acetal) film, 
polystyrene film, poly(ethylene terephthalate) film, polycarbonate film, 
glass, metal, paper, polymer-coated paper, and the like. The image-forming 
layer or layers of the element typically comprise a radiation-sensitive 
agent, e.g., silver halide, dispersed in a hydrophilic water-permeable 
colloid. Suitable hydrophilic vehicles include both naturally-occurring 
substances such as proteins, for example, gelatin, gelatin derivatives, 
cellulose derivatives, polysaccharides such as dextran, gum arabic, and 
the like, and synthetic polymeric substances such as water-soluble 
polyvinyl compounds like poly(vinylpyrrolidone), acrylamide polymers, and 
the like. A particularly common example of an image-forming layer is a 
gelatino/silver halide emulsion layer and the compositions described 
herein provide excellent results in treating defects in and providing 
protective overcoats for such emulsion layers. 
The method of treatment described herein is especially advantageous with 
motion picture films. Thus, for example, motion picture print film often 
becomes badly scratched after it has been run through projectors many 
times. It must then be discarded even though other characteristics may 
still be acceptable. Use of the restorative coating compositions described 
herein is highly effective in alleviating scratches that would blemish the 
projected image and thus the scratched film can be restored to useful 
service. The method of this invention is particularly effective with 
scratches on the support side, which is where scratches most frequently 
occur on motion picture film. However, the restorative coating 
compositions described herein will also provide significant improvement 
with regard to scratches on the image side if such scratches are not too 
deep. 
The first essential ingredient in the radiation-curable compositions 
employed in the practice of this invention is an acrylated urethane. The 
acrylated urethane can be a monomer, oligomer or polymer, or mixtures 
thereof. The acrylated urethanes are well known materials which have been 
used heretofore in radiation-curable compositions. Materials of this type 
are described, for example, in U.S. Pat. Nos. 3,509,234; 3,600,539; 
3,694,415; 3,719,638 and 3,775,377 and in British Pat. No. 1,321,372. The 
acrylated urethanes are readily cross-linked by application of suitable 
radiation and are particularly advantageous in the coating compositions of 
this invention in that they form a very hard and very abrasion-resistant 
material upon curing. In a preferred embodiment of the invention, the 
acrylated urethane is prepared by reaction of a diisocyanate, such as 
tolylene diisocyanate, with a saturated aliphatic diol, such as 1,4-butane 
diol or neopentylglycol, and then with an unsaturated alcohol, such as 
2-hydroxyethyl acrylate. 
The second essential ingredient of the radiation-curable composition is an 
aliphatic ethylenically-unsaturated carboxylic acid. Acids of this type 
act as effective adhesion promoters in the compositions employed herein. 
Typical examples of this class of acids are acrylic acid, methacrylic 
acid, 3-chloro-2-methyl acrylic acid, 3-butenoic acid, 4-pentenoic acid, 
2-hexenoic acid, and the like. Preferred acids are those of the formula: 
##STR1## 
where R.sup.1, R.sup.2 and R.sup.3 are hydrogen atoms or alkyl groups of 1 
to 3 carbon atoms; while acrylic acid is especially preferred. 
The third essential ingredient of the radiation-curable composition is a 
multifunctional acrylate, i.e., an acrylic monomer comprising at least two 
acrylic ester groups. Monomers of this class function in the 
radiation-curable compositions to increase hardness of the coating, 
improve adehsion and promote fast curing. Typical examples of this class 
of acrylic monomers are: 
neopentylglycol diacrylate, 
pentaerythritol triacrylate, 
1,6-hexanediol diacrylate, 
trimethylolpropane triacrylate 
tetraethylene glycol diacrylate, 
1,3-butylene glycol diacrylate, 
trimethylolpropane trimethacrylate, 
1,3-butylene glycol dimethacrylate, 
ethylene glycol dimethacrylate, 
pentaerythritol tetraacrylate, 
tetraethylene glycol dimethacrylate, 
1,6-hexanediol dimethacrylate, 
ethylene glycol diacrylate, 
diethylene glycol diacrylate, 
glycerol diacrylate, 
glycerol triacrylate, 
1,3-propanediol diacrylate, 
1,3-propanediol dimethacrylate, 
1,2,4-butanetriol trimethacrylate, 
1,4-cyclohexanediol diacrylate, 
1,4-cyclohexanediol dimethacrylate, 
pentaerythritol diacrylate, 
1,5-pentanediol dimethacrylate, and the like. 
Preferred multifunctional acrylates are those of the formula: 
##STR2## 
where each R.sup.4 is independently selected from the group consisting of 
a hydrogen atom and an alkyl group of 1 to 2 carbon atoms, each R.sup.5 is 
independently selected from the group consisting of an alkyl group of 1 to 
6 carbon atoms and a radical of the formula: 
##STR3## 
in which R.sup.6 is a hydrogen atom or an alkyl group of 1 to 2 carbon 
atoms. 
As explained hereinabove, the radiation-curable compositions used in the 
practice of this invention are compositions containing (1) an acrylated 
urethane, (2) an aliphatic ethylenically-unsaturated carboxylic acid, and 
(3) a multifunctional acrylate. Mixtures of two or more acrylated 
urethanes, of two or more aliphatic ethylenically-unsaturated carboxylic 
acids and of two or more multifunctional acrylates can be used, if 
desired, and may be advantageous in particular instances. Other 
ingredients can also be incorporated in the radiation-curable composition, 
for example, monoacrylates such as ethyl acrylate, butyl acrylate, 
2-ethylhexyl acrylate and hydroxypropyl acrylate can be used to modify the 
viscosity of the composition, and acrylamide can be used as an adhesion 
promoter. 
The proportions of each of the three essential components of the 
radiation-curable coating compositions can be varied widely, as desired. 
Typically, the acrylated urethane is used in an amount of from about 4 to 
about 60% of the total composition on a weight basis, the aliphatic 
ethylenically-unsaturated carboxylic acid is used in an amount of from 
about 1 to about 20% of the total composition on a weight basis, and the 
multifunctional acrylate is used in an amount of from about 20 to about 
95% of the total composition on a weight basis. The optimum amounts to use 
in a particular instance will depend upon the particular compounds 
involved and upon the characteristics of the photographic element which is 
being coated with the radiation-curable formulation. High concentrations 
of the aliphatic ethylenically-unsaturated carboxylic acid should usually 
be avoided in any coating composition which is to be in contact with a 
gelatin-containing layer of a photographic element as they can adversely 
affect such layers since the acid may attack the gelatin. Particularly 
preferred compositions, in view of the excellent combination of 
transparency, hardness, scratch resistance, abrasion resistance, 
flexibility and adhesion achieved therewith, are compositions comprised of 
an acrylated urethane, acrylic acid, trimethylolpropane triacrylate and 
neopentylglycol diacrylate. Use of the mixture of multifunctional 
acrylates, namely the combination of trimethylolpropane triacrylate and 
neopentylglycol diacrylate, is especially advantageous in that the 
trimethylolpropane triacrylate is particularly effective in providing good 
adhesion and the neopentylglycol diacrylate is particularly effective as a 
hardening monomer which gives increased scratch resistance without 
sacrificing flexibility. 
In the practice of this invention, the particular ingredients and 
proportion of ingredients in the coating composition that will provide the 
best results is dependent on the composition of the photographic element. 
For example, the particular coating compositions which will provide 
optimum adehsion depend on the particular binder used in the image-bearing 
layer(s) or, if the element is to be coated on the support side, the 
particular material used as a support. Generally speaking, it is much 
easier to obtain adequate adhesion to the support than to obtain adequate 
adhesion to the image-bearing layer(s). A few simple experiments may be 
found to be necessary to formulate an optimum coating composition for any 
particular photographic element. 
The photographic elements which are treated in accordance with this 
invention are elements which have been exposed and processed to form a 
visible image and which, during exposure or processing or more usually 
during subsequent use, have been abraded or scratched or otherwise treated 
in a manner to impart defects which impair their appearance or projection 
capabilities. Such processing can be carried out in any suitable manner. 
For example, black-and-white elements are typically processed in a 
sequence of steps comprising developing, fixing and washing, color prints 
in a sequence comprising color developing, bleaching, fixing (or combined 
bleach-fixing) and stabilizing, and color reversal elements in a sequence 
comprising black-and-white negative development, followed by reversal 
exposure or fogging, color development, bleaching, fixing (or combined 
bleach-fixing) and stabilizing. While scratches or abrasion marks can be 
incurred in exposure and/or processing, the more typical situation is a 
gradual accumulation of such defects as a result of use of the element. 
Thus, the normal use of exposed and processed elements, for example, use 
of a motion picture film in a projector or of a microfiche in a reader, 
commonly results in the formation of the kinds of defects which can be 
removed or at least diminished by the method of this invention. 
As disclosed hereinabove, in carrying out the method of this invention the 
radiation-curable composition is applied to the photographic element at 
least in the region of the element in which the defects are located. It 
can be applied only to such region, since local application to the defects 
by suitable means such as a brush or other type of applicator can be 
utilized, if desired. It will usually be much easier and more convenient, 
since there will be many small scratches and abrasion marks on the 
photographic element, to apply the radiation-curable composition over the 
entire surface or surfaces of the element where the defects appear. In 
following the latter procedure, coating of the photographic element with 
the radiation-curable composition can be carried out in any convenient 
manner. For example, it can be carried out by dip coating, airknife 
coating, roll coating, gravure coating, extrusion coating, bead coating, 
curtain coating, use of wire wound coating rods, and so forth. Typically, 
the coating deposited on the element will be a very thin coating such as a 
wet coverage in the range from about 2 to about 20 cubic centimeters of 
coating composition per square meter of surface coated, more usually in 
the range from about 3 to about 10 cubic centimeters of coating 
composition per square meter, and preferably about 5 cubic centimeters of 
coating composition per square meter. 
The viscosity of the radiation-curable composition used to treat the 
photographic element must be sufficiently low that it is able to fill in 
the scratch or other defect. In other words, the viscosity must not be so 
high that the composition applied bridges over a scratch with the result 
that the scratch will remain as a visible defect beneath the transparent 
cured polymeric material. The optimum viscosity will depend on numerous 
factors such as the type of element being treated, the method of 
application of the composition, and the width and depth of the scratch. 
Typically, viscosities in the range from about 5 to about 600 centipoises 
are useful, with the preferred range being from about 10 to about 100 
centipoises, and the most preferred range being from about 30 to about 40 
centipoises. 
Apparatus and methods for curing of radiation-curable compositions by 
subjecting them to suitable forms of radiation are well known and any 
suitable radiation curing process can be used in carrying out this 
invention. For example, curing can be carried out by the application of 
ultraviolet radiation of suitable intensity. High energy ionizing 
radiation such as X-rays, gamma rays, beta rays and accelerated electrons 
can also be used to accomplish curing of the coating. Typically, the 
radiation used should be of a sufficient intensity to penetrate 
substantially all the way through the coated layer. The total dosage 
employed should be sufficient to bring about curing of the 
radiation-curable composition to form a solid plastic. Typically, dosages 
in the range of about 0.2 to about 50 megarads, more usually in the range 
from about 0.5 to about 20 megarads, are employed. The coating 
compositions used in this invention are substantially completely 
convertible to a solid product so that the removal of solvent or diluents 
during the curing step is not necessary. Furthermore, they undergo little 
or no shrinkage upon curing. Accordingly, when the scratch is completely 
filled in by the radiation-curable composition it remains completely 
filled in after the curing step is completed. 
When the radiation-curable composition is cured by the use of ultraviolet 
radiation, a photoinitiator should be included in the composition. Many 
photoinitiators which are useful for such purpose are known to the art, 
for example, butyl benzoin ether, isobutyl benzoin ether, ethyl benzoin 
ether, benzophenone, benzoin, acetophenone dimethyl quinoxiline, 
4,4'-bis(dimethylamino)benzophenone, and the like. Such photoinitiators 
may be used singly or in combination. The use of photoinitiators is not 
necessary when curing is carried out with high energy electrons. 
The radiation-curable compositions described herein adhere strongly to both 
the image-bearing side and the support side of photographic elements, and, 
accordingly, are effective in treating scratches, abrasion marks, and 
other defects on either or both of the image-bearing side and the support 
side. They are effective in providing adhesion to materials with which it 
is ordinarily difficult to achieve adhesion, such as the cellulose 
triacetate or poly(ethylene terephthalate) which are commonly used as 
support materials for photographic elements and the gelatino/silver halide 
emulsion layers or gelatin protective layers commonly employed on the 
image-bearing side of photographic elements. Irradiation of the 
composition to cure it to a transparent, flexible, scratch-resistant, 
cross-linked polymeric material can be carried out with no significant 
detrimental effect on the image-bearing layer(s), even with color elements 
in which the images are dye images.

The invention is further illustrated by the following examples of its 
practice. 
EXAMPLE 1 
An acrylated urethane was prepared by dissolving tolylene diisocyanate 
(TDI) and neopentylglycol (NPG) in neopentylglycol diacrylate and heating 
the resulting solution at 65.degree. C. for 4 hours, then adding 
2-hydroxyethyl acrylate (HEA) and reacting for 6 hours in the presence of 
dibutyl tin dilaurate as a catalyst. The molar ratio of TDI:NPG:HEA was 
1.0:0.5:0.8. The acrylated urethane produced by this method has the 
following structure: 
##STR4## 
A radiation-curable coating composition containing the acrylated urethane 
described above was prepared with the following composition: 
______________________________________ 
Component Weight % 
______________________________________ 
Acrylated urethane 10.1 
Neopentylglycol diacrylate 
42.4 
Trimethylolpropane triacrylate 
31.2 
Tetraethyleneglycol diacrylate 
2.4 
Acrylic acid 7.2 
Fluorocarbon coating aid 
0.2 
Methyldiethanol amine 2.5 
Benzophenone 4.0 
______________________________________ 
A 35 mm color print motion picture film having a poly(ethylene 
terephthalate) support and gelatino/silver halide emulsion layers was 
exposed and processed to a visible image and then scratched on the support 
side with a synthetic fiber cleaning pad to give a random distribution of 
scratches of different lengths, widths and depths. The scratched side of 
the film was coated over its entire surface with the radiation-curable 
composition described above. Curing of the coating was carried out by 
passing the film at a rate of 45 feet per minute through a curing oven 
containing three 200 watt/inch high intensity medium pressure mercury 
vapor UV lamps. Curing of the coating resulted in the formation of a 
transparent, flexible, scratch-resistant, cross-linked polymeric layer 
which was strongly bonded to the support. The coating completely filled in 
the scratches so they were no longer visible. The coefficient of friction 
of the cross-linked polymeric coating was substantially the same as that 
of the poly(ethylene terephthalate) support. To evaluate the effectiveness 
of the coating, the coated film was run through a motion picture projector 
and the overall appearance of the projected image was found to be 
excellent, with the scratches no longer being visible. 
EXAMPLE 2 
A color print motion picture film having a cellulose triacetate film 
support and gelatino/silver halide emulsion layers was exposed and 
processed to a visible image and then scratched on the support side in the 
same manner as described in Example 1. Both sides of the film were then 
coated with the following radiation-curable composition: 
______________________________________ 
Component Weight % 
______________________________________ 
Acrylated urethane of Example 1 
8.7 
Trimethylolpropane triacrylate 
38.4 
Acrylic acid 9.6 
Neopentylglycol diacrylate 
37.2 
Benzophenone 3.8 
Methyldiethanol amine 2.3 
______________________________________ 
Curing of the coatings was carried out by passing the film under a bank of 
three 200 watt/inch high intensity mercury vapor UV lamps at a distance of 
12 inches and resulted in the formation of transparent, flexible, 
scratch-resistant, cross-linked polymeric layers strongly bonded to both 
the support side and the image side of the motion picture film. The 
coating on the support side completely filled in the scratches so they 
were no longer visible. To evaluate the effectiveness of the coating, the 
coated film was run through a motion picture projector and the overall 
appearance of the projected image was found to be excellent, with the 
scratches no longer being visible. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.