This invention relates in general to photo¬ graphy and in particular to photographic restorative or protective coating compositions. More specifi¬ cally, this invention relates to photographic elements, such as still film, motion picture films, paper prints, microfiche, and the like, to which a radiation-curable coating composition has been applied to eliminate defects, such as scratches, abrasion marks, and the like, which impair its. appearance or projection capabilities, and/or to provide 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 coatin ^"* compositions hav ^' 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-refleccion layers which reduce glare.

Many of the coating compositions used in the past to form protective overcoats on photographic elements have suffered from disadvantages which have greatly limited their usefulness. For example, it has been particularly difficult to formulate compositions which are fully satisfactory in providing abrasion and scratch resistance for

-2-

photographic elements which are commonly subjected to severe conditions in handling and use, such as micro¬ fiche 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. An effective solution to the problem of providing useful protective overcoats for photo¬ graphic elements, such as microfiche and motion picture films, which are subject to severe conditions of use, is disclosed in United States Patent 4,092,173, issued May 30, 1978. As described in this patent, protective overcoats are formed on photographic elements by coating the element with a radiation-curable composition, comprising- an acrylated urethane, an aliphatic ethylenically- unsaturated carboxylic acid and a multifunctional aerylate, 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 protective overcoat layer can be applied to the image-bearing side of the element or to the support side of the element or to both sides. As further described in United States Patent 4,171,979, issued October 23, 1979, the compositions of United States Patent 4,092,173 are effective photographic restorative compositions for 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. Such a restorative composition can be applied locally in the region of the defects only, to effectively eliminate them and restore the element to a substantially defect-free condition, 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.

The present invention is directed to the objective of providing an improved radiation-curable coating composition which will provide protective overcoats on photographic elements in the manner described in United States Patent 4,092,173 and/or accomplish the restoration of photographic materials in the manner described in United States Patent 4,171,979.

It has now been discovered that incorporation of a siloxy-containing polycarbinol in radiation-curable compositions comprising an acrylated urethane, an aliphatic ethylenically- unsaturated carboxylic acid and a multifunctional acrylate substantially improves their performance as coating compositions for forming protective overcoats on photographic elements and/or in treating photo¬ graphic elements which have defects such as scratches, abrasion marks, and the like. In particular, the siloxy-containing polycarbinols, and especially certain mixtures of siloxy-containing poly¬ carbinols, have been found to provide improved wetting, leveling, and coating characteristics, to provide improved adhesion to the photographic

element, and to provide improved hardness, increased scratch resistance, and reduced coefficient of friction.

Accordingly, this invention provides a photographic protective or restorative coating composition which is radiation-curable and is characterized in that the composition comprises (1) an acrylated urethane, (2) an aliphatic ethenically- unsaturated carboxylic acid, (3) a multifunctional acrylate, and (4) a siloxy-containing polycarbinol. Furthermore, this invention provides photographic supports and elements that are coated with the protective or restorative coating compositions described herein. In addition, this invention, provides methods for using such compositions to provide protective or restorative coatings over at least a part of a photographic support or element.

The radiation-curable compositions described herein can be used to provide protective overcoats and/or to treat scratches, abrasion marks, and similar defects in many different types of photo¬ graphic 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. Examples are cellulose nitrate film, cellulose acetate film, poly(vinyl acetal)

fil , polystyrene film, ρoly(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(vinyl- pyrrolidone) , acrylamide polymers, and the like. A 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. In practicing the invention, the protective overcoat can be applied only to the image-bearing side of the photographic element, only to the support side of the element or to both sides of the element. The restorative method of treatment described herein is especially advantageous with motion picture ilms. Th s, 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 ^' cceptable. 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. This method 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 radia io -curable composition 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 United States Patents 3,509,234; 3,600,539 ^* ;

3,694,415; 3,719,638 and 3,775,377 and in British Patent 1,321,372.. The acrylated urethanes are readily cross-linked by application of suitable radiation and are particularly advantageous in that they form a very hard and very abrasion-resistant material upon curing. A preferred 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-hydroxy- ethyl 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

o:

acid, 4-pentenoic acid, 2-hexenoic acid, and the like. Preferred acids are those of the formula:

I I

C = C - COOH

R ³ where R 1, R2, and R3 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 adhesion ^■ fend promote fast curing. Typical examples .of this class of acrylic monomers are: neopentylglycol diacrylate, pentaerythritol triacrylate,

1,6-hexanediol diacrylate, tri ethylolpropane 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:

⁴ 0 R ⁵ 0 R t

CH ₂ = C - C - 0 - CHg - C - CH ₂ - 0 - C - C = CH ₂

R-

where each R is a hydrogen atom or an alkyl group of 1 to 2 carbon atoms, each R is an alkyl group of 1 to 6 carbon atoms or a radical of the formula:

0 R ⁶ » t - CH ₂ - 0 - C - C = CE ₂

in which R is a hydrogen atom or an alkyl group of 1 to 2 carbon atoms .

The fourth essential ingredient of the radiation-curable composition is a siloxy-containing polycarbinol. The siloxy-containing polycarbinols, which can also be described as organofunctional silicones having carbinol functionality, are well known materials. Examples of commercially available materials of this class include Dow Corning* 193 Surfactant, Dow Corning* 1248 Fluid, Dow Corning*

C--.

XF4-3557 Fluid, Dow Corning* Q4-3667 Fluid and Dow Corning * Q2-8026 Fluid, all of which are available from Dow Corning Corporation, Midland, Michigan, U.S.A. These materials are polydi ethyl- siloxanes containing alcohol functional groups grafted onto the siloxane chain. Illustrative structural formulas of the siloxy-containing poly- carbinols are as follows:

and

CH, CH- _j t -> t J

H- _j C-Si-0- -Si-CH, CEL- CH„ where R is a hydrocarbon radical, generally containing 1 to 10 carbon atoms, and X and Y are integers, generally having a value in the range of from 2 to 100. The siloxy-containing polycarbinols are described in detail in United States Patent 4,130,708, issued December 19, 1978.

As explained herein, 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, (3) a multifunctional acrylate, and (4) a siloxy-containing polycarbinol. Mixtures of two or more acrylated urethanes, of two or more aliphatic ethylenically-unsaturated carboxylic acids . of two or more multifunctional acrylates, and of two

or more siloxy-containing polycarbinols 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-ethylhexylacrylate and hydroxy- propyl acrylate can be used to modify the viscosity of the composition, and acrylamide can be used as an adhesion promoter. Other useful viscosity modifiers include solvents such as acetone or methanol. The proportions of each of the four essential components of the radiation-curable coating composition can be varied widely, as desired. The acrylated urethane can be used in an amount of from 4 to 60% of the total composition on a weight basis, the aliphatic ethylenically-unsaturated carboxylic acid can be used in an amount of from 1 to 20% of the total composition on a weight basis, the multi¬ functional acrylate can be used in an amount of from 20 to 95% of the total composition on a weight basis, and the siloxy-containing polycarbinol can be used in an amount of from 0.5 to 8% 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 character¬ istics of the photographic element which is being coated with the radiation-curable formulation. High concentrations of the aliphatic ethylenically-unsatur¬ ated 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

-^JS.E

G__PI

resistance, flexibility and adhesion achieved therewith, are compositions comprised of an acrylated urethane, acrylic acid, a siloxy-containing polycarbinol, trimethylolpropane triacrylate and neopentylglycol diacrylate or 1,6-hexanediol diacrylate. Use of the mixture of multifunctional acrylates, namely the combination of trimethylolpropane triacrylate and neopentylglycol diacrylate or 1,6-hexanediol diacrylate, is especially advantageous in that the trimethylolpropane triacrylate is particularly effective in providing good adhesion, and the neopentylglycol diacrylate or 1,6-hexanediol 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 photo¬ graphic element. For example, the particular coating compositions which will provide optimum adhesion 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 protected with overcoat layers in accordance with

this invention are processed to form a visible image prior to being coated on the image-bearing side with the radiation-curable composition. 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 bl ach-fixing) and stabilizing, and color reversal elements in sequence comprising black-and-white negative development, followed by reversal exposure or fogging, color development, bleaching, fixing (or combined bleach-fixing) and stabilizing. An advantageous manner of utilizing the invention described herein is to modify the conventional photographic processing operation to include, as final steps in the process following -drying of" the "element, the steps of coating and curing to form the protective overcoat. The coating and curing steps can be carried out in a batch, semicontinuous or continuous manner, as desired.

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, air-knife coating, roll coating, gravure coating, extrusion coating, bead coating, curtain coating, use of wire wound coating rods, and so forth. Generally, the coating deposited on the element will be a very thin coating such as a wet coverage in the range from 2 to 20 cubic centimeters of coating composition per square meter of surface coated, more usually in the range from 3 to 10 cubic centimeters of coating composition per square meter, and preferably about 5 cubic

-13 -

centimeters of coating composition per square meter. The viscosity of the coating composition can vary widely, depending on the particular method of coating which is chosen. Satisfactory coatings can be readily formed on photographic elements from coating compositions having a viscosity 'in the range from 25 to 1000 centipoises, and more preferably in the range from 75 to 200 centipoises.

The photographic elements that are treated with the restorative compositions of 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. 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 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 practice of this invention.

The restorative composition of this invention is applied to the photographic element at least in the region of the element in which the defects are located, and is thereafter cured. 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 any of the coating procedures described hereinabove.

The viscosity of the radiation-curable composition used to treat a scratched or abraded 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. Viscosities in the range from 5 to 600 centipoises are useful for this purpose, with the preferred range being from 10 to 100 centipoises, and the most preferred range being from 30 to 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. 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. Dosages in the range of 0.2 to 50 megarads, more usually in the range from 0.5 to 20 megarads, can be 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 a scratch is completely filled in by the radiation-curable composition it remains completely filled in. after the curing step is completed. While it is not necessary to employ * solvents or diluents which are removed from the coating in the curing step, they can be employed if needed to modify the properties of the coating composition.

When the radiation-curable composition is cured by the use of ultraviolet radiation, a photo- initiator 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)benzoρhenone, 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.

Overcoating of photographic elements in the manner described herein can be advantageously carried out in appropriate cases prior to cutting the element to its final size. Thus, after the photographic element has been processed to a visible image and dried, it can be coated with the radiation-curable composition, then irradiated, and then cut to size. In some instances, it will be sufficient to coat the radiation-curable compositions only on the side of the element bearing the image-containing layer(s) or only on the support side. In other instances, it will be desirable to coat the photographic element with radiation-curable composition on both sides. For example, motion picture films and microfiche will typically be coated on both sides in view of the very severe handling that such articles are subject to in ordinary use and the need to reduce to an absolute minimum the formation of scratches on such articles. Both sides of the element can be coated simul- taneously or each side can be coated separately depending on the particular method used for coating.

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 providing protective overcoats, or 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

f

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 layer 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 can be practical with elements which comprise a photographic support, an

10 image-bearing layer and a protective overcoat layer and elements which do not include an image-bearing layer which are intended to be used in the subsequent preparation of elements having an image-bearing layer.

The invention is further illustrated by the -- ^■ --' following examples of its practice.

EXAMPLE 1

A radiation-curable coating composition was, prepared as follows: 0

Component Weight

Acrylated urethane resin^ ' 10-1 •

Trimethylolpropane triacrylate 31.2

Neopentylglycol diacrylate 42.4 5 Acrylic acid 9.6

Fluorocarbon coating aid (2 ^J . 0.2

Methyldiethanol amine 2.5

Benzophenone 4.0

100.0 0

^ 'The acrylated urethane resin had the following structure:

CH,

H-.C-C-CH- 3 t :

0

II ? ^H

^ The coating aid was Surfactant* FC-430 from

Minnesota Mining and Manufacturing Company, St. Paul, Minnesota, U.S.A.

A 35mm color print motion picture film having a pol (ethylene terephthalate) support and gelatino/silver halide emulsion layers was exposed, processed, coated on both sides with the coating composition described above, and cured by passing it under a bank of three 200 watt/2.54 cm. high intensity mercury vapor UV lamps at a distance of 30.5 cm. A sample of the coated film is referred to hereinafter as film sample A. Coating compositions B, C and D were also prepared, coated in the same manner on the same exposed and processed motion picture film, and cured in the same manner to provide film Samples B, C and D. These compositions were identical to composition A, except that composition B additionally contained 5 parts per hundred parts by weight of Dow Corning • 193 Surfactant, composition C additionally contained 5 parts per hundred parts

OM

Y/Ϊ

by weight of Dow Corning* Fluid Q4-3667, and composition D additionally contained 5 parts per hundred parts by weight of a mixture of one part by weight Dow Corning* 193 Surfactant and one part by weight Dow Corning* Fluid Q4-3667.

The coated film samples were subjected to scratch resistance and coefficient of friction .tests in accordance with procedures of the American National Standards Institute, Inc., 1430 Broadway, New York, New York, USA 10018. Specifically, the scratch resistance tests were carried out in accordance vith ANSI Test Method PHI.37 - 1977 and the coefficient of friction tests were carried out in accordance with ANSI Test Metod PHI.47 - 1972. For purposes of comparison, a sample of the uncoated film, referred to hereinafter as the control film, was tested in the same manner.

^' Results obtained are reported- in Table I below. In regard to the light transmission data, higher values for light transmission are indicative of less haze under the test conditions and thus of greater scratch resistance. In regard to the data for the "single arm scratch" test, values reported are the load in grams required to form a scratch which is visible at the indicated projection distance, with higher values at a given projection distance being indicative of greater scratch resistance. The term "plow" refers to conditions under which the stylus of the test instrument "plows" its way through substantially the entire layer.

C FI

Light Single Arm Scratch (grams) Coefficient Transmission Projected at Projected at of 4 ft. 15 ft. Plow Friction

Control Film

Emulsion Bide 20 30 40 90 0.18

Support side 30 60 70 >140 0.22

Film Sample A

Emuløion side 20 , 40 50 60 0.28

Support Bide 4o 90 100 >l4θ 0.2Θ ,

O

1

Film Sample B

Emulsion side 20 50 60 100 0.24

Support side o 90 100 >l4o 0.24

Film Sample C

Emulsion Bide 20 60 6 ₅ 115 0.14

Support side 70 110 120 >140 0.14 r

Use of Dow Corning* Surfactant 193 in coating composition B provided substantial improvement in coatability as compared with composition A, i.e., the coating was much more uniform with considerably less tendency for cratering and the formation of blemishes to occur. Use of Dow Corning* Fluid Q4-3667 in coating composition C provided a substantial improvement in scratch resistance and a substantial reduction in coefficient of friction. Use of both Dow Corning* Surfactant 193 and Dow Corning* Fluid Q4-3667 in coating composition D provided major improvements in regard to coatability, scratch resistance, and coefficient of friction.

EXAMPLE 2

•A radiation-curable coating composition was prepared as follows: Component Weight % Acrylated urethane resin of Example 1 9 , . 6

Trimethylolpropane triacrylate 29 .7

Neopentylglycol diacrylate 35. . 6

1,6-Hexanediol diacrylate 4. .8

Acrylic acid 9. .1 Fluorocarbon coating aid of Example 1 0. .2

Siloxy-containing polycarbinol 4. . 8

Methyldiethanol amine 2. .4

Benzophenone 3. , 8

100.0

^ 'A mixture of one part by weight Dow Corning* 193 Surfactant and one part by weight Dow Corning* Fluid Q4-3667.

The above described coating composition was utilized as a protective overcoat for photographic film in the same manner described in Example 1 and gave similar good results. The radiation-curable compositions described herein are highly effective in forming protective overcoat layers and in eliminating or reducing defects such as scratches, abrasion marks, and the like, in photographic elements. They have excellent wetting, leveling, and coating character¬ istics which facilitate their application to photographic elements. They adhere strongly to photographic elements and are easily cured with convenient and readily available radiation sources to form transparent, flexible and highly scratch resistant protective coatings.

-^RE-

O PI

•