US2984568A

US2984568A - Photographic antihalation and protective layer comprising a nitrated styrene-maleic acid copolymer

Info

Publication number: US2984568A
Application number: US698902A
Authority: US
Inventors: Hart Rene Maurice; Roosens Laurent Pierre; Troquet Jacques Rene
Original assignee: Gevaert Photo Producten NV
Current assignee: Gevaert Photo Producten NV
Priority date: 1956-11-26
Filing date: 1957-11-26
Publication date: 1961-05-16
Anticipated expiration: 1978-05-16
Also published as: GB852141A; DE1071477B; BE552915A; FR1190631A

Description

' 2,984,568 PHOTOGRAPHIC TIVE LAYER COMPRISING A NITRATED STY- RENE-MALEIC ACID COPOLYMER Ren Maurice Hart, Wilrijk-Antwerp, and Laurent Pierre Roosens and Jacques Ren Troquet, Antwerp, Belgium, assignors to Gevaert Photo-Producten N.V., Antwerp, Belgium, a Belgian company No Drawing. Filed Nov. 26, 1957, Ser. No. 698,902

Claims priority, application Belgium Nov. 26, 1956 7 Claims. (Cl. 96-84) The present invention relates to a photographic element provided with an alkali soluble hydrophobic outer layer containing as the main constituent a layer-forming polymer, and more particularly to a photographic element provided with an antihalation backing or with a protective layer applied to the light-sensitive silver halide layer or to the layer bearing already a silver image or a color image.

It is known to provide photographic elementssuch as black-and-white films and multilayer color films with an antihalation backing in order to inhibit light reflec tion from the back side to the emulsion side. This layer generally consists of a binding agent such as gelatin or a synthetic polymer, and a substance absorbing the light rays of this region of the spectrum to which the silver halide emulsion (or, in the case of a multilayer film, the emulsion layernearest to the support) is sensitive.

It is further known to apply a protective layer (e.g. an anti-abrasive layer or a layer which absorbs the ultraviolet radiations) consisting of a layer-forming polymer to the light-sensitive layer (no the sensitive layers) or to a layer bearing already a silver image or a color image.

The polymeric products which are to be used as binding agents in outer layers such as the above-mentioned antihalation or protective layers must meet several severe requirements. Besides the particular function of these layers, they must in any case, on account of their position, possess special mechanical properties and show a resistance to outer influences such as friction, pression, water, moist air etc. so that the films, plates or photographic papers provided with such layers can be treated in the processing baths and/or in the apparatus, e.g. cameras or projection apparatus, without being damaged.

If these layers must be applied to a flexible support, the layer-forming polymers must moreover be chosen in such a way that the formed layers possess a sufiicient flexibility. Another requirement which particularly concerns the antihalation layers consists therein that neither thislayer nor a constituent thereof may be transferred onto the silver halide emulsionlayer if the emulsion layer and the backing layer come into contact e.g. when a photographic film is wound.

If it is desired that the layers are to be removed during the treatment in the usual photographic baths (e.g. in the case of antihalation layers containing a light-absorbing substance which is not or not completely decolorized in the processing baths), the polymeric binding agent must moreover be sufiiciently soluble in the developers, which frequentlyare only slightly alkaline. On the other hand, the sensitivity to the alkali must not be too high since the contact of these layers e.g. with wet hands would damage the photographic element. A further requirement is that the layers obtained from the polymeric binding agent must be become sticky in moist atmosphere. a t The derivatives of the styrene-maleic acid copolymers AN TIHALATION AND PROTEG erties. In moist atmosphere these layers become smooth provide new and improved antihalation coatings and which hitherto have been proposed as binding agent for antihalation layers do not possess the required propand sticky, which involves a transfer of the colored particles of the antihalation layer onto the emulsion layer on winding and on storing the photographic element.

It is therefore an object of the present invention to protective layers. Another object is to provide such layers the flexibility of which is perfectly adapted to that of the usual flexible photographic supports to which they are to be applied. Another object of the invention is to provide antihalation coatings and protective layers which possess outstanding mechanical properties, such as an exceptional resistance to scratching and improved gliding properties. A further object is to provide such antihalation coatings which can be removed readily by weakly alkaline solutions such as the usual photographic developers. A still further object of our invention is to provide antihalation coatings and protective layers with hydrophobic character which possess exceptional resistance to moisture.

The above objects are accomplished in accordance with the present invention when the antihalation coating or the protective layer contains as the main constituent a nitrated styrene-maleic acid copolymer.

In order to obtain antihalation layers according to the present invention, an organic dyestuff or a mixture of such dyestufis dissolved in an appropriated solvent can be incorporated in a solution of a nitrated styrene-maleic acid copolymer. Suitable antihalationdyestufis can be found e.g. among the styryl dyestuffs, the triand di-aryl methane dyestuffs and the azomethine dyestuffs. The antihalation layer can be applied to a usual support such as e.g. to a flexible light-transmitting film support or to a glass plate, which is to be provided on the other side with a light-sensitive silver halide emulsion layer.

According to another embodiment of the present in vention, antihalation layers can be prepared by starting from pigment dispersions e.g. carbon black in the polymeric binding agent. In this respect the nitrated styrenemaleic acid copolymers possess the great advantage to give stable dispersions by simply mixing, whilst stirring, the pigment with a solution of the polymer in an organic solvent such as a lower alcohol, without any addition of a dispersing agent. It is to be noted that the prepara tion of such dispersions with the polymers as used hither to for the same purposes always necessitates an intense" mechanical treatment, e.g. in a colloid mill. The black dispersion can be applied as antihalation coating toa suitable support as described hereinbefore.

When the nitrated, styrene-maleic acid copolymers are i to be applied as a protective layer on a light-sensitive emulsion layer or on a photographic image-bearing layer, especially a color image-bearing layer, ultra-violet radiation absorbing substances, such as diaminostilbene derivatives, derivatives of coumarone, pyrazoline or imidazoline, may be incorporated in the solution of the polymer. The support for the emulsion layer or for the image bearing layer can be e.g. a flexible film or a barytacoated paper.

The nitrated styrene-maleic acid copolymers are ob tained by action of nitric acid upon styrene-maleic acid copolymers. Although in general fuming nitric acid hitherto was used therefor, a great part (up to 70%) of the fuming'nitric acid can be replaced by ordinary nitric acid. In the circumstances the reaction runs very smoothly at room temperature. Also a mixture of nitric acid and sulphuric acid can be used. In the event, the reaction is better carried out whilst heating e.g. between 50 and 70 C. Also the proportion nitric acid/ sulphuric acid is of importance and the best resultsare:

estates;

attained with proportions ranging from 7/3 to 9/1. In this way about one nitrogrou'p per styrene unit is incorporated. which-theoretically corresponds with a nitrogen content'of5.3%. 9

- The degree of polymerization of the starting products is only slightly influenced by the nitration. This degree of polymerization is not of particular importance in the preparation of ordinary antihalation layers with soluble dyestuffs; but must be taken into account in the preparation of antihalation backings containing carbon black. In this case, polymers with a relatively low molecular weight are preferably used so that strongly concentrated solutions (25 to 35%) can be prepared which do not show an excessive viscosity. 4

' Hereinafter follow some examples of preparing the nitrated styrene-maleic acid copolymers. W

PREPARATION l (a Styrene-maleic, acid copolymer i 41.6 parts by weight of styrene (previously washed with a solution of sodium hydroxide and water. respectively; dried upon calcium chloride and distilled in nitrogen atmosphere under reduced pressure) are copolyme'rized with 43.1 parts by weight of maleic acid anhydride' in 730 parts by volume of toluene, previously dried upon calcium chloride. The mixture is heated at'1l0 C. for 9 hours in the presence of 0.42 part by weight of azobisisobutyronitrile as initiator. The polymerization mixture is filtered and the deposited styrenemaleic acid copolymer is'washed with hexane and dried in a desiccator at '50? 'C.

(b) Nitrated .rt yrene-m aleic acid copolymer 80 parts by weight of a styrene-maleic acid copolymer are dissolved whilst stirring in 400 parts by volume of fuming nitric acid, whilst the temperature is kept below C. by ice-cooling. V

The clear solution is precipitated in distilled water. The precipitate is pulveriied and washed with distilled water to neutral reaction as can be controlled with indicator paper. The product is dried under vacuum at 40, C. It contains 5.6% of nitrogen.

PREPARATION 2 3 50 crnfi of strong nitric acid (d=1.42) and'l50 cm. of fuming nitric acid (ab- 152) are brought into a reac-. tion flask, and 100 g. of'styrene-maleic acid copolymer are gradually added whilst stirring at a temperature kept between 2 5 and 30 C. After standing overnight the solution is added to water and the formed precipitate is washed with water.

The product is dried under vacuum to constant weight. It contains 5.4% of nitrogen.

PREPARATION 3 A nitrated styrene-maleic acid copolyrner is prepared byv causing 1 kg. of the styrene-maleic acid copolymer to react withv 6.3 liter of strong nitric'acid (d l.42) and 9.95 liter of sulphuric acid (96%) for 8 hours at 60 C.

The formed reaction product is separated in the same way. as in the previous examples. It contains 5.5% of nitrogen. a V

The following examples illustrate the invention without limiting, however, the scope thereof.

- A EXAMPLE 1 A solution of 60 g. of a nitrated styrene-maleic acid copolymer in amixture of 300 crn. of ethanol and 300 c COf methal'l01 is prepared. This solution (hereinafter called A) is added to a solution of 22 g. of a green dyestufi (known under the denomination Bro 721 and described. in' BIOS comp. 146/2/ 382/ 30), in a mixture 015-209 cmfii of ethanol and200cm. of methanol (solution B). This solution; is coated on the rear of a cellulose aceto-butyrate' film support, the front side of.which is to. be provided with a panchromatic sensitized silver iodoare dissolved in a mixture of 200 cm. of ethanol and ns baths- ExaMPLE 2' 22 g. of a dyestufi of the following formula (IJH2-CH2QH are dissolved in a mixture of 200 cm. of ethanol and 200 cm. of methanol. This colored solution is added to solution A described in Example 1. After application to the rear of a cellulose triacetate film support which'is to be provided with an orthochromatic sensitized silver chloro-bromide emulsion, a deep-red colored layer is ob 200 cm. of methanol. This solution is added to the solution A described in Example 1. After application to a suitable support in the manner described in Example 2 an orange-colored layer is obtained which decoloriz es in the processing baths.

EXAMPLE 4 22 g. of. a dyestuff described in PB report 74174, frame 820. (US. Government, Office of Technical Services, Washington), are dissolved together with 60 g. of nitrated styrene-maleic acid copolymer in a mixture of 500. cm. of ethanol and 500 cm. of methanol. After ap; plication to a flexible support which is to be provided with three, differentially sensitized silver halide emulsion layers contining color couplers, a violet layer is obtained. This layer d'ecolorizes and dissolves in the photographic processing baths. 7

- EXAMPLES 7 g. of carbon black are added to a solution of 60 g. ofanitratedstyrene-maleic acid copolymer in 250 cm.3 of ethanol, whilst thoroughly stirring. After dispersing the carbon black, the volume is. brought to 1 liter by adding a mixture of 1 part of ethanol and 2 parts of methanol.. This solution can be cast onto a flexible support; A brown-black layer is obtained which is eas removable in photographic processing baths. The

layer, a photographic element eg a positive motion pic: ture color film, provided therewith, is free from halae tion. V V

. EXAMPLE 6 A solution of 9 g. of a nitrated styrene-maleic acid copolymerv in a mixture. of 700 cm. of ethanol and B QQ cm. -of m thanol is coated as an anti-abrasive layer onto a silver chloro-bjromide emulsion layer on a baryta-coated paper support. The photographic properties of the tlight sensitive lays .11 2 99;matlfidl she-na cremai s- 9 friction fog is periods of stockage, and moreover the light-reflection being almost completely. inhibited by considerably diminished in respect of those of a photographic emulsion without protective layer.

EXAMPLE 7 75 g. of a nitrated styrene-maleic acid copolymer and 5 g. of Teregitol NP 35 (trademark for alkylphenylpolyethylene glycol ether) are dissolved in a mixture of 600 cm. of ethanol, 160 cm. of ether, 100 cm. of isopropylalcohol and 50 cm. of methylene-glycol. This solution is mechanically applied to the image-bearing layer of an exposed and developed motion picture film of the positive type. This layer protects the film against scratching, moisture and mishandling during the treatment.

EXAMPLE 8 12 g. of Uvinul 400 (a substituted benzophenone) are added the solution of the copolymer described in Example 6. This solution is applied as protective layer on the emulsion layer of a photographic negative film. This layer protects the emulsion against ultra-violet rays.

We claim:

1. A photographic element comprising a support, at least one light-sensitive silver halide emulsion layer, and an alkali-soluble hydrophobic outer layer, said outer layer being mainly constituted by a nitrated copolymer consisting of 50 mol percent styrene monomeric units alternating with 50 mol percent maleic acid monomeric units, the copolymer containing 0.8 to 1.2 nitro groups per styrene monomeric unit.

2. A photographic element comprising a flexible lighttransmitting support, at least one light-sensitive silver halide emulsion layer on one side of said support, and an alkali-soluble hydrophobic anti-halation layer on the other side of said support, said anti-halation layer comprising a copolymer and a light-absorbing substance, said copolymer consisting of 50 mol percent styrene monomen'c units alternating with 50 mol percent maleic acid monomeric units, the copolymer containing 0.8 to 1.2 nitro groups per styrene monomeric unit.

3. The photographic element according to claim 2, wherein the light-absorbing substance is an organic dyestuff.

4. The photographic element according to claim 2, wherein the light-absorbing substance is carbon black.

5. A photographic element comprising a support, at least one light-sensitive silver halide emulsion layer on one side of said support, and an alkali-soluble hydrophobic protective layer coated on said emulsion layer, said protective layer being mainly constituted by a copolymer consisting of mol percent styrene monomeric units alternating with 50 mol percent maleic acid monomeric units, the copolymer containing 0.8 to 1.2 nitro groups per styrene monomeric unit.

6. The photographic element according to claim 5, wherein the protective layer includes an ultro-violet radiation absorbing substance.

7. A photographic element comprising a support, at least one image-bearing layer, said image having been obtained by exposing to light a light-sensitive silver halide emulsion layer on one side of said support, said element further ocmprising a. protective layer coated on said image-bearing layer, said protective layer being mainly constituted by a copolymer consisting of 50 mol percent styrene monomeric units alternating with 50 mol percent maleic acid monomeric units, the copolymer containing 0.8 to 1.2 nitro groups per styrene monomeric unit.

References Cited in the file of this patent UNITED STATES PATENTS 2,077,789 Hagedorn Apr. 20, 1937 2,173,480 Jung Sept. 19, 1939 2,274,551 Kenyon et al. Feb. 24, 1942 2,685,512 Sawdey Aug. 3, 1954 2,748,029 Spear et al. May 29, 1956 FOREIGN PATENTS 115,781 Australia Aug. 25, 1942 UNITED STATES} PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 2,984,568 May 16, 1961 Ren Maurice Hart et a1.

It is hereby certified that error apfaears in the above numbered patent requiring correction and that the said Letters Patent. should read as "corrected below.

Column 1, line 35, for "no" read or same column, line 70, for "be" read not Signed and sealed this 21st day of November 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOM M-DC-