GB1583547A

GB1583547A - Coated film assemblies

Info

Publication number: GB1583547A
Application number: GB3396476A
Authority: GB
Original assignee: Bexford Ltd
Current assignee: Bexford Ltd
Priority date: 1976-08-16
Filing date: 1976-08-16
Publication date: 1981-01-28

Description

(54) IMPROVEMENTS IN COATED FILM ASSEMBLIES (71) We, BEXFORD LIMITED, Imperial Chemical House, Millbank, Lohdon SWIP 3JF, a British Company do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a process for the production of a coated photographic film base and to the production of a light-sensitive photographic film by the application of a light-sensitive photographic emulsion to the film base and to the products.

It has been widely accepted in the photographic art that a light-sensitive photographic emulsion applied directly to the surface of a plastics support film does not exhibit sufficient adhesion to the support film for use in most of the usual photographic end uses. As a result, it has become common practice to interpose two or more subbing layers between the support film and the photographic emulsion. For example, when the photographic emulsion comprises a gelatinous silver halide composition, a polymeric subbing layer and then a gelatinous subbing may be applied to the surface of the support film prior to the application of the photographic emulsion to the gelatinous subbing layer.

According to the present invention, a process for the production of a photographic film base comprises coating the surface of a self-supporting plastics film with a subbing composition comprising a polymer comprising a vinyl halogenoester, molecularly orienting the coated film by stretching in at least one direction, and then subjecting the surface of the applied subbing layer to a modifying treatment by corona discharge.

The present invention also relates to a photographic film base comprising a self-supporting plastics film and a subbing layer applied to the surface of said film prior to stretching the film in at least one direction to impart molecular orientation to the film, said subbing layer comprising a polymer comprising a vinyl halogenoester, the subbing layer being adherent to the plastics film and having been subjected to a surface modifying treatment by corona discharge.

According silver halide emulsions, adhere directly to the treated copolymeric subbing layer of the base without further treatment or coating, e.g. with a gelatinous subbing layer. The application of the light-sensitive photographic emulsion directly to the surface of the treated copolymeric subbing layer avoids certain technical disadvantages which may be associated with the use of gelatinous subbing layers, for example tackiness in damp or humid conditions, high surface friction which can create winding problems, optical interference patterns on the film, static charge generation and an effect termed "ageing in contact" which results from components, such as hardening agents included in coatings on the other side of the film migrating into the gelatinous subbing layer when the coated film is wound into a reel and causing premature cross-linking of the gelatin subbing layer which impairs the adhesion of the light-sensitive emulsion to the gelatin subbing layer.

The self-supporting plastics film may consist of any suitable plastics film, such as films of polysulphones and linear polyesters which may be obtained by condensing one or more dicarboxylic acids of their lower alkyl diesters. e.g. terephthalic acid. isophthalic, phthalic, 2,5-, 2,6-. and 2,7-naphthalene dicarboxylic acid. succinic acid. sebacic acid. adipic acid, azelaic acid. diphenyl dicarboxylic acid. and hexahydroterephthalic acid or bis-p-carboxyl phenoxy ethane. optionally with a monocarboxylic acid, such as pivalic acid. with one or more glycols, e.g. ethylene glycol. 1.3-propanediol. 1,4-butanediol neopentyl glycol and 1,4 cyclohexanedimethanol. Biaxially oriented and heat-set films of polyethylene terephthalate are particularly useful for the production of the photographic films according to this invention. Such self-supporting plastics films may be transparent and light-transmitting, optionally including photographically inert dyestuffs, e.g. blue dyestuffs for X-ray films, or may be rendered opaque by the addition of additives, such as pigments and fillers, and may in particular have a white and paper-like texture which may be achieved by the addition of suitable fillers and/or by voiding. The white and paper-like films may be used as bases for photographic prints.

Preferably, the vinyl halogenoester subbing polymer comprises a homopolymer or copolymer of vinyl mono-, di- or trihalogenoacetate, especially vinyl mono-, di- or trichloroacetate.

When the subbing polymer comprises a copolymer, it may comprise a copolymer of a vinyl halogenoester, preferably one of the preferred halogenoesters mentioned above, with one or more ethylenically unsaturated copolymerisable monomers.

The subbing copolymer may comprise a copolymer of a vinyl halogenoester with one or more further monomers which yield in the final copolymer carboxyl, hydroxyl, ester, nitrile, amide, N-mono or N,N-di-substituted amide, amino or substituted amino groupings, such as those listed in Table 1.

TABLE 1 Itaconic acid Maleic acid Citraconic acid Acrylic acid Methacrylic acid Crotonic acid Di-esters and mono-esters of unsaturated dicarboxylic acids with monohydric or polyhydric alcohols Allyl alcohol Vinyl alcohol Esters of unsaturated mono-carboxylic acids with polyhydric alcohols, e.g. 2-hydroxyethyl methacrylate Vinyl acetate Acrylonitrile Acrylamide Methacrylamide N-(l.l-dimethyl-3-oxobutyl) acrylamide N-mono or N,N-di-substituted derivatives of unsaturated amides, e.g. tertiary butyl acrylamide, NN-dimethyl acrylamide, N-methylol acrylamide N-methoxy methyl acrylamide, N-acetoxy methyl acrylamide N-vinyl pyrrolidone Dimethyl-amino-ethyl methacrylate A preferred class of subbing copolymers comprises copolymers of a vinyl halogenoester with at least one ethylenically unsaturated copolymerisable monomer which functions to lower the softening temperature of the copolymer in relation to the softening temperature of the copolymer prepared in the absence of the softening temperature-lowering comonomer.

Such comonomers have an internal plasticising effect and may include alkyl acrylates, alkyl methacrylates. polyalkylene oxide itaconates and maleates, vinyl alkyl ethers, vinyl esters, alkenes, alkadiencs and alkyl styrenes, e.g. those listed in Table 2.

TABLE 2 N-Butyl acrylate 2-Ethoxyethyl acrylate Ethyl acrylate 2-Ethylhexyl acrylate Decyl methacrylate Octa decyl methacrylate 2-Ethylhexyl methacrylate Di-(polypropyleneoxy) itaconate Vinyl butyl ether Vinyl'ethyl ether Vinyl methyl ether Vinyl isobutyl ether Vinyl stearate Vinyl versatate Ethylene '1-Butene Butadiene 4-Dodecyl styrene 4-Nonyl styrene Such copolymers preferably comprise 50 to 98 mole % of the vinyl halogenoester, 2 to 30 mole % of softening temperature-lowering monomer and up to 20 mole % of one or more other copolymerisable monomers such as any of those mentioned above in Table 1.

A further preferred class of subbing copolymers comprises copolymers of a vinyl halogenoester with at least one copolymerisable carboxylic acid cyclic anhydride such as maleic anhydride or a chloromaleic anhydride, itaconic anhydride or citraconic anhydride Such copolymers may be derived from one or more additional copolymerisable monomers including those listed in Tables 1 and 2 above, the preferred comonomers being methyl acrylate, ethyl acrylate, butyl acrylate, an ethyl chloroacrylate, a chloroethyl acrylate, acrylonitrile, acrylamide acrylic acid, methyl methacrylate, maleic acid, itaconic acid, citraconic- acid, styrene. vinyl acetate, vinyl alcohol, allyl alcohol and butadiene. Such copolymer ers preferably comprise 20 to 85 mole %of the vinyl halogenoester with 1 to 15 mole %of the copolymerisable carboxylic acid cyclic anhydride and 0 to 79 mole% of one or more other copolymerisable monomers.

An alternative subbing composition comprises a copolymer of a vinyl halogenoester with a carboxylic acid cyclic anhydride as specified above in admixture with one or more polyurethane resins.

Conventional additives may be included in the copolymeric subbing layer, e.g. adhesion promoters, such as a partially hydrolysed vinyl acetate/vinyl chloride copolymer optionally admixed with a chlorinated phenol, slip and anti-static agents.

If desired, the coating dispersion or solution may contain a cross-linking, agent which functions to cross-link the subbing copolymer thereby improving adhesion to the plastics film.

Additionally. the cross-linking agent should preferably be capable of internal cross-linking in order to provide protection against solvent penetration. Suitable cross-linking components may comprise epoxy resins, alkyd resins, amine derivatives such as hexamethoxymethyl melamine and/or condensation products of an amine, e.g. melamine. dizine, urea, cyclic ethylene urea, cyclic propylene urea. thiourea. cyclic ethylene thiourea, alkyl melamines. aryl melamines. benzo guanamines, guanamines, alkyl guanamines and aryl guanamines with an aldehyde. e.g. formaldehyde. A useful condensation product is that of melamine with formaldehyde. The condensation product may optionally be alkoxylated. The cross-linking agent may be used in amounts of up to 25 % by weight based on the weight of the polymer in the subbing composition.

A catalyst is also preferably employed to facilitate cross-linking. Preferred catalysts for cross-linking melamine formaldehyde include ammonium chloride, ammonium nitrate, ammonium thiocyanate. ammonium dihydrogen phosphate, ammonium sulphate, diammonium hydrogen phosphate. para toluene sulphonic acid, maleic acid stabilised by reaction with a base. and morpholinium para toluene sulphonate.

According to the invention the copolymeric subbing layer is applied to the plastics film during the process by which the plastics film is produced.

The procedure for applying the subbing composition may be any of the known coating techniques, such as dip coating, bead coating, reverse roller coating or slot coating and the composition may be applied as an aqueous latex or solution or as a solution in an organic solvent.

If the film is produced by a process of molecular orientation which is normally achieved by stretching in one or more directions it is convenient to apply the copolymeric subbing layer during the stretching operation. Usually, oriented films are biaxially oriented by stretching in two mutually perpendicular directions, for example as is the case with polyethylene terephthalate films. The subbing layer may be applied before the stretching operation is commenced, or more preferably between the stretching operations applied in the two perpendicular directions. Such a sequence of coating between the stretching operations is preferred for the coating of oriented polyethylene terephthalate films. The subbing layer is preferably applied as an aqueous dispersion in such an operation.

The modifying treatment applied to the subbing layer may comprise flame treatment, ion bombardment, electron beam treatment, exposure to ultra-violet light or preferably corona discharge treatment.

Corona discharge treatment may be effected in air at atmospheric pressure with conventional equipment using a high frequency, high voltage generator, preferably having a power output of from I to 20 kw at a potential of 1 to 100 kv. Discharge is conveniently accomplished by passing the film over a dielectric support roller at the discharge station at a linear speed preferably of 1.0 to 500 m per minute. The discharge electrodes may be positioned 0.1 to 10.0 mm from the moving film surface. The applied subbing layer should preferably exhibit a wetting test value after corona discharge treatment exceeding 56 dynes/cm when measured by the Union Carbide Standard Wetting Test (WC 81-3/1964) with a formamide/'Cellosolve' (registered Trade Mark) mixture, whereas the value exhibited by an untreated layer is generally in the range 35 to 45 dynes/cm. In this test, liquid mixtures having a range of surface tensions are made up using various concentrates of formamide in 'Cellosolve' (2-ethoxyl ethanol) and brushed onto the surface to be examined. The wetting test value is the surface tension of the liquid mixture having the highest surface tension which does not contract into droplets within two seconds after application onto the surface.

Copolymeric subbing layers having a coat weight in the range 0.1 to 10 mg/dm2 provide satisfactory adhesion. Coat weights in the range 1.0 to 2.0 mg/dm2 are preferred.

The invention also relates to a process for the production of a photographic film which comprises applying a light-sensitive photographic emulsion over the surface modified copolymeric subbing layer of a photographic film base produced as described above and to the photographic film.

Any suitable light-sensitive photographic emulsion, such as a conventional gelatinous silver halide emulsion. may be applied by conventional techniques to the surface modified subbing layer. Such an emulsion may contain any of the conventional additives. It has been found that light-sensitive emulsions bond with good adhesion, as stated above, after direct application to the surface modified layer.

The invention is further illustrated by the, following example. in which dry and wet adhesion have the following meanings and were assessed by the following tests.

Dry adhesion refers to the adhesion of a gelatinous silver halide emulsion via an underlying gelatin subbing layer. if present, to the plastics film in the final photographic film, assessed.

both before and after processing in standard photographic chemicals, by sticking a self adhcsivc tape along the torn edge of the film and rapidly separating the tape from the film.

Wet adhesion refers to the adhesion of a gelatinous silver halide emulsion via an underlying gelatin subbing layer. if present. to the plastics film in the final photographic film, assessed, after processing in the standard photographic chemicals and washing in water for 15 minutes by rubbing with a sponge over a series of lines scored in the still wet emulsion.

EXAMPLE An aqueous copolymeric subbing latex of the following formulation was prepared: A latex containing a copolymer of 78 mole % vinyl monochloroacetate.

15 mole % ethyl acrylate and 7 mole % acrylamide 10g Distilled water 90 g A polyethylene terephthalate film was melt extruded and quenched to the amorphous state on a cooled rotating drum. The resulting film was stretched in the direction of extrusion to about 3.5 times its original length. It was then coated on both sides with the aqueous dispersion described above by a roller coating technique and passed into a stenter oven where the coating was dried. The dried coated film was then stretched sideways about 3.5 times its original width and finally heat set at a temperature of about 210 C. The final thickness of the subbing layer on each side of the biaxially drawn film was about 0.3 micron, and the total thickness of the film was about 100 microns.

The copolymeric subbing layer was corona discharge treated at atmospheric pressure using a commercially available 'Vetaphone' (registered Trade Mark) 3 kw treater to prqduce a coating having Union Carbide Wetting Test value greater than 56 dynes/cm. The treatment conditions were film speed 20 fpm, power 2 kw, electrode to film distance 1.5 mm.

A conventional X-ray silver halide gelatinous photographic emulsion was applied'directly to the corona discharge treated surfaces of the subbing layers, without interposing a gelatin subbing layer. The wet and dry adhesions were satisfactory.

WHAT WE CLAIM IS: 1. A process for the production of a photographic film base, which comprises coating the surface of a self-supporting plastics film with a subbing composition comprising a polymer comprising a vinyl halogenoester, molecularly orienting the coated film by stretching in at least one direction, and then subjecting the surface of the applied subbing layer to a modifying treatment by corona discharge.

2. A process according to claim 1, in which the vinyl halogenoester subbing polymer comprises a homopolymer or copolymer of vinyl mono-, di- or trihalogenoacetate.

3. A process according to claim 2, in which the mono-, di- or trihalogenoacetate is mono-, di- or trichloroacetate.

4. A process according to claim 1, 2 or 3, in which the vinyl halogenoester subbing polymer comprises a copolymer derived from a vinyl halogenoester and one or more comonomers selected from Table 1 above.

5. A process according to any preceding claim, in which the vinyl halogenoester subbing polymer comprises a copolymer derived from a vinyl halogenoester and one or more softening temperature-lowering comonomers selected from Table 2 above.

6. A process according to claim 5, in which the subbing copolymer comprises 50 to 98 mole % of a vinyl halogenoester, 2 to 30 mole % of the softening temperature-lowering monomer(s) and up to 20 mole % of one or more other copolymerisable monomers.

7. A process according to any preceding claim, in which the vinyl halogenoester subbing polymer comprises a copolymer of a vinyl halogenoester with at least one copolymerisable carboxylic acid cyclic anhydride.

8. A process according to claim 7, in which the subbing composition comprises a mixture of the vinyl halogenoester/anhydride copolymer and a polyurethane.

9. A process according to any preceding claim, in which the plastics film is biaxially oriented by stretching in two mutually perpendicular directions and the subbing composition is applied between the stretching operations in the two directions.

10. A process according to any preceding claim, in which the plastics film comprises a biaxially oriented and heat-set polyethylene terephthalate film.

11. A process for the production of a photographic film. which comprises applying a light-sensitive photographic emulsion directly over the surface corona discharge treated polymeric subbing layer of a photographic film base produced according to a process claimed in any preceding claim.

12. A process for the production of a photographic film base substantially as described in the Example.

13. A process for the production of a photographic film substantially as described in the Example.

14. A photographic film base. which comprises a self-supporting plastics film and a subbing layer applied to the surface of said film prior to stretching the film in at least one direction to impart molecular orientation to the film, said subbing layer comprising a polymer comprising a vinyl halogenoester. the subbing layer being adherent to the plastics film and having been subjected to a surface modifying treatment by corona discharge.

15. A photographic film base according to claim 14 in which the vinyl halogenoester subbing polymer comprises a homopolymer or copolymer of vinyl mono-, di- or trihalogenoacetate.

16. A photographic film base according to claim 15. in which the mono-, di- or trihalogenoacetate is mono-, di- or trichloroacetate.

17. A photographic film base according to claim 14. 15 or 17. in which the vinyl halogenoester subbing polymer comprises a copolymer derived from a vinyl halogenoester and one or more comonomers selected from Table I above.

18. A photographic film base according to any of claims 14 to 17. in which the vinyl halogenoester subbing polymer comprises a copolymer derived from a vinyl halogenoester and one or more softening temperature-lowering comonomers selected from Table 2 above.

19. A photographic film base according to claim 18, in which the subbing copolymer comprises 50 to 98 mole % ov vinyl halogenoester. 2 to 30 mole % of the softening

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. original width and finally heat set at a temperature of about 210 C. The final thickness of the subbing layer on each side of the biaxially drawn film was about 0.3 micron, and the total thickness of the film was about 100 microns. The copolymeric subbing layer was corona discharge treated at atmospheric pressure using a commercially available 'Vetaphone' (registered Trade Mark) 3 kw treater to prqduce a coating having Union Carbide Wetting Test value greater than 56 dynes/cm. The treatment conditions were film speed 20 fpm, power 2 kw, electrode to film distance 1.5 mm. A conventional X-ray silver halide gelatinous photographic emulsion was applied'directly to the corona discharge treated surfaces of the subbing layers, without interposing a gelatin subbing layer. The wet and dry adhesions were satisfactory. WHAT WE CLAIM IS:

1. A process for the production of a photographic film base, which comprises coating the surface of a self-supporting plastics film with a subbing composition comprising a polymer comprising a vinyl halogenoester, molecularly orienting the coated film by stretching in at least one direction, and then subjecting the surface of the applied subbing layer to a modifying treatment by corona discharge.

temperature-lowering monomer(s) and up to 20 mole % of one or more other copolymerisable monomers.

20. A photographic film base according to any of claims 14 to 19, in which the vinyl halogenoester subbing polymer comprises a copolymer of a vinyl halogenoester with at least one copolymerisable carboxylic acid cyclic anhydride.

21. A photographic film base 20 in which the subbing composition comprises a mixture of the vinyl halogenoester/anhydride copolymer and a polyurethane.

22. A photographic film base according to any of claims 14 to 21, in which the plastics film comprises a biaxially oriented and heat-set polyethylene terephthalate film.

23. A photographic film, which comprises a light-sensitive photographic emulsion applied over the surface modified polymeric subbing layer of a photographic film base according to any of claims 14 to 22.

24. A photographic film base substantially as described in the Example.

25. A photographic film substantially as described in the Example.