US2327828A - Colloidal carbon antihalation layer - Google Patents

Description

COLLOIDAL CARBON ANTIHALATION LAYER Filed March 26, 1941 I (SILVER HAL/DE EMULSION.

ANT/HALAT/ON LAYER OFALKALF, 50L UBLE MATERIAL CONTAIN/N6 OISPERSED CARBON BLACK.

Nokwooo SIMMONS INVENT OR Patented Aug. 24, 1943 COLLOIDAL CARBON ANTIHALATION LAYER Norwood L. Simmons, Rochester, N. Y., assignor to. Eastman Kodak Company, Rochester, N. Y.,

a corporation of New Jersey Application March 26, 1941, Serial No. 385,277 (01. 95-8) 10 Claims.

terial, is a well recognized effect and many proposals have been made for overcoming it. A light absorbing material i usually applied to one of the surfaces of the support such as the rear surface so that the rays, which would otherwise be reflected onto the sensitive layer, are thereby absorbed. It is usually desirablefor the lightabsorb light to which the emulsion layer is sensitive and, in the case of panchromatic or multicolor elements, the anti-halation layer, should absorb as much of the visible spectrum as possible. Carbon or graphite dispersed in the backing material is especially suitable for this purpose and a colloidal carbon dispersion for use in anti-halation backings has been described in Staud & Weyerts U. Srpatent application Serial No. 343,254, filed June 29, 1940, now Patent Number 2,271,234.

In the present day manufacture of photographic materials, anti-halation layers are usually applied to photographic supports at rather high speed in continuous application machines. For this purpose, the coating solution must have the proper consistency to flow onto the support. It is necessary, therefore, to dilute the coating solution to the proper degree for coating and it has been found that the dispersions of colloidal carbon prepared as described in the Staud 8: Weyerts application Serial No. 343,254, now Patent Number 2,271,234, cannot be diluted with organic solvents without in many cases destroying the dispersion or causing the precipitation of the colloidal carbon. a

It is, therefore, the principal object of the present invention to provide an anti halation layer ofcolloidal carbon or carbon black which is finely dispersed in a coating solution and which solution may be diluted with organic liquids to proper coating consistency. A further object is to provide an anti-hala-tion layer which dissolves smoothly inphotographic developers and does not disintegrate and contaminate the developer. Other objects will appear from the following description of my invention.

These objects are accomplished by using as the absorbing material of the anti-halation layer to anti-halation layer a water-insoluble,alkali-soludispersed therein in a sufficiently fine state of subdivision that the dispersion may be diluted with organic solvents to an indefinite extent and is maintained in the dispersed state both during and after coating on a photographic support. The method of preparing such dispersionwill be -more fully described hereinafter.

In the accompanying drawing the single figure i a sectional view of a photographic film having an anti-halation layer according to my invention.

The material which I propose to use as an anti-halation backing for photographic elements comprises as a supporting material a waterinsoluble,alkali-soluble synthetic colloidal ma- ,terial, such as a cellulose ester or synthetic resin. The cellulose ester is .preferably a dicarboxylic acid ester of cellulose such as cellulose acetate phthalate, cellulose acetate maleate, cellulose acetate succinate, cellulose'acetate propionate phthalate, cellulose acetate propionate maleatc or cellulose acetate propionate succinate. The synthetic resin is preferably a polyvinyl resin such a polyvinyl phthalate or polyvinyl acetate phthalate. In this alkali-soluble material, there is dispersed colloidal carbon or carbonblack in such manner that the material assumes a plastic state and in that state is subjected to high shearing forces to bring about a fine and complete dispersion of the carbon particle in the plastic mass. f

It has been found that when attempting to disperse carbon particles in alkali-soluble vehicles, mechanical treatments such as agitation in simple containers, agitation in ball mills, colloid mills or grinding the particles into the dispersion first in a relatively fiuid condition on roller mills do not produce stable dispersions. It is only by means of a high viscosity milling technique in which the mass is subjected to extremely high shearing stresses that it is possible to accomplish the high degree of dispersion necessary to maintain the carbon particles in suspension in the vehicle during subsequent treatment and coating on photographic supports. It is not necessary, when proceeding in this manner, ,to use dispersing agents to maintain the dispersion of carbon particles in the vehicle.

I shall now describe the essential details of my process for dispersing carbon particles in alkali-soluble vehicles. The alkali-soluble dispersion medium or vehicle is mixed'with the carbon in a dry state and a small quantity of plasticizer is added. The whole is then mixed roughly by any simple method and the mixture is fed moving rolls.

between the rolls of a mill of the type commonly used in the rubber industry. It is essential that, after a short time in such a mill, the mass shall exhibit an unusually stifi consistency. It may be necessary to heat or cool the rolls of the mill to attain such consistency. This depends to some extent on the quantity of plasticizer added to the mixture. In order to increase the shearing force, it may be desirable to operate the two rolls of the mill at a differential speed of perhaps 1% to 1 as between the front and rear rolls. The more closely the rolls are held together during the milling operation, the greater is the shearing stress and consequently the more nearly perfect the degree of dispersion of the pigment in the vehicle.

The following example illustrates the method of forming a dispersion of carbon black in the alkali-soluble material suitable for use as an anti-halation backing according to my invention.

To 500 grams of cellulose acetate phthalate, made from a cellulose acetate of 38.3% acetyl and containing 23.0% total combined phthalyl, there is added 200 grams of Peerless Brand carbon black (sold by Binney 8: Smith Company, New York city) and 200 grams of methyl car- ,bitol. The mass is mixed intimately with a paddle and is then fed rapidly into the rolls of a rubber mill, The rolls are preferably water cooled to maintain a maximum temperature of 180 F. Heat is generated during the milling operation. The rolls turn at speeds of 24 R. P. M. and 30 R. P, M. in opposite directions so as to carry the mass down between the rolls. When the raw material, which is quite dry and powdery, is dumped between the rolls, a small portion of it clings to the more rapidly moving of the two rolls while the remainder falls through the rolls. By gradually dumping the material which falls between the rolls back on top of the rolls, eventually the entire mass is m-adeto cling to the surface of the more rapidly I The material gradually assumes a plastic state and as a result of the high shearing force exerted at the surface of the two rolls the carbon is very rapidly dispersed in the cellulose acetate phthalate.

After about minutes of such milling action, the sheet of material which is wrapped completely about the faster moving roll is taken off the roll by means of a blade which is an integra1 part of the mill. The sheet of material which falls from the roll is about inch thick, and soon cools to room temperature and becomes quite brittle, breaking into chips when handled.

The efiiciency of the dispersion process may be measured by dissolving some of the chip-like vehicle for the dispersed material is an alkaliinsoluble material such as cellulose nitrate, whereas alkali-soluble material is used for the v purposes of my invention.

The method of preparing an anti-halatien layer according to my invention will now be described.

A 75 gram portion of the dispersion of carbon black in cellulose acetate phthalate prepared as described above is dissolved in 270 grams of methyl Cellosolve, 160 grams of water, 10 grams of acetone and 380 grams of ethyl alcohol. This solution is quite stable without further treatment except for a slight sedimentation which is largely due to the chemical nature of the vehicle used. The same degree of sedimentation, which diminishes to a small amount after 24 hours, takes place if the cellulose acetate phthalate is used alone without carbon black dispersed in it. In order to cleanse the solution of suspended matter which is not entirely dispersed and has not. settled out, it should be passed through a centrifuge.' After this operation, the solution, which has a viscosity of about 5 centipoises, may

be applied directly to a photographic film s'upport by any of the usual methods such as immersion or capillary bead application. This solution, when applied to a photographic fihn support, traveling at a speed of about six feet per minute gives an optical density of about 1.25 and is exceedingly uniform. When this material is immersed in ordinary photographic developers, a softening and partial solubility of the cellulose acetate phthalate occurs and solubility takes place readily in a water rinse. The carbon black disperses in the solution probably as an adsorbed material on the colloidal cellulose acetate phthalate.

My invention will now be described with particular reference to the accompanying drawing.

As shown in the drawing, a support [0 of any suitable material such as cellulose nitrate, cellulose acetate, cellulose acetate propionate or synthetic resin is coated with an emulsion layer H or with suitable subbing layers (not shown) between the support l0 and the emulsion layer II, and with the anti-halation layer l2 consisting of the alkali-soluble material containing dispersed colloidal carbon.

Coatings of carbon black dispersed in cellulose acetate phthalate or other alkali-soluble materials may be used as anti-halation layer when appled to photographic film so as to give various types of photographic film.

an optical density of from 0.1 to 2.0. dition to their use as anti-halation backings, the coatings prepared according to my invention are also useful in the preparation of leaders for motion picture film or for anti-static layers in Carbon black coatings avoid the appearance of residual dye stain which frequently results from the use of dye backings in photographic film and also decrease the electrical resistance of the film.

The specific example described above refers to the use of methyl carbitol as a plasticizer for the cellulosic vehicle. Other plasticizers such as methyl Cellosolve, triacetin, dibutyl phthalate, etc., may be used.

Although cellulose acetate phthalate is the pre ferred vehicle for the carbon dispersions used ac cording to my invention, I am not limited to this material but may use the other water-soluble, alkali-soluble materials specified herein. Ihave found that cellulose acetate phthalates made 'from cellulose acetate of from 32% to 38.3%

herein and that my invention is to be taken as limited only by the scope of the appended claims.

I claim: I 1. The method of p'reparing anti-halations for photographic supports,-which comprises mixing a carbon pigment witha water-insoluble, al-

Kali-soluble, synthetic .colloidal material, subjecting the mixture to vigorous shearing forces while in the condition of a highly viscous, plastic mass, so that a dispersion of the carbon pigment in the colloidal material'is formed which may be diluted with organic liquids without precipitating the carbon pigment from the dispersion, diluting said dispersion with an organic liquid, .and coating it on a photographic support.

2. The method of preparing anti-halation backings for photographic supports, which comprises mixing a carbon pigment with a dicarboxylic acid ester of cellulose, subjecting the mixture to vigorous shearing forces while in the condition of a highly viscous, plastic mass, so that a dispersion of the carbon pigment in the colloidal material is formed which may be diluted with organicliquids without precipitating the carbon pigment from the dispersion, diluting said dispersion with an organic liquid, and coating it on a photographic support.

3. The method of preparing anti-hala'tion backings for photographic supports, which comprises mixing a carbon pigment with cellulose acetate phthalate, subjecting the mixture to vigorous shearing forces while in the condition of a highly viscous, plastic mass, so that a dispersion of the carbon pigment in the colloidal material is formed which may be diluted with organic liquids without precipitating the carbon pigment from the dispersion, diluting said dispersion with an organic liquid, and coating it on a photographic support,

4. The method of preparing anti-halation backings for photographic supports, which comprises mixing acarbon pigment with cellulose acetate propionate phthalate, subjecting the mixture to vigorous shearing forces while in the condition of a highly viscous, plastic mass, so that a dispersion of the carbon pigment in the colloidal material is formed which maybe diluted with organic liquids without precipitating the carbon pigment from the dispersion, diluting said dispersion with an organic liquid, and coating it on a photographic support.

5. The method of preparing anti-halation backings for photographic supports, which comprises mixing a carbon pigment with cellulose acetate propionate succinate, subjecting the mixture to vigorous shearing forces while in the condition of a highly viscous, plastic mass, so that a dispersion of the carbon pigment in the colloidal material is formed which may be diluted with organic liquids without precipitating the carbon pigment from the dispersion, diluting said dispersion with an organic liquid, and coating it on a photographic support,

6. The method of preparing anti-halation.

jecting the mixture to vigorous shearing forces while in the condition of a highly viscous, plastic mass, so that a dispersion of the carbon pigment in the colloidal material is formed which may be diluted with organic liquids without precipitating. the carbon pigment from the dispersion, diluting said dispersion with an organic liquid, and coating it on a photographic support.

7. A photographic element comprising a support having thereon a sensitive emulsionlayer and an anti-halation layer consisting of a waterinsoluble, alkali-soluble, synthetic colloidal material and colloidal carbon which has been dispersed in said colloidal material by the action of high shearing forces applied to the material while it is in the condition of a highly viscous plastic mass and to such an extentthat dilution of the dispersion by organic liquids causes no precipitation of carbon pigment from the dispersion, and which is in a sufilciently fine state of subdivision that a dispersion is maintained upon dilution of the material with an organic liquid and during and after coating.

8. A photographic element comprising a support having thereon a sensitive emulsion layer and an anti-halation layer consisting of a dicarboxylic acid ester of cellulose and colloidal carbon which has been dispersed in said cellulose ester .by the action of high shearing forces applied to the cellulose ester while it is in the condition of a highly viscous plastic mass and to such an extent that dilution of the dispersion by organic liquid causes no precipitation of carcondition of a highly viscous plastic mass and to such an extent that dilution of the dispersion by organic liquids causes no precipitation of carbon pigment from the dispersion, and which is in a suificiently fine state of sub-division that a dispersion is maintained upon dilution of the 'resin with an organic liquid and during and after coating.

10. A photographic element comprising a support having thereon a sensitive emulsion layer and an anti-halation layer consisting of a cellulose acetate phthalate and colloidal carbon which has been dispersed in said cellulose acetate phthalate by the action of high shearing forces applied to said cellulose acetate phthalate while it is in the condition of a highly viscous plastic mass and to such an extent that dilution of the dispersion by organic liquids causes no precipitation of carbon pigment from the dispersion, and which is in a suiiiciently fine state of subdivision that a dispersion is maintained upon dilution of the cellulose acetate phthalate with an organic liquid and during and after coating.

NORWOOD L. SIMMONS.

CERTIFICATE OF CORBECTIIQN." P e N ,5 7,.8 8- g s ;,v 915'- NORWOOD L. SIMMONS.

It is hereby certified that error appeare in the printed specification of the above numbered patent requiring correction as follows: Page 5, first eolumn, lines 5 'and 6, claim 1,, for "ant-i halati'ons for read -anti-ha1ation baokinga for; and that theeaid Letters Patent ehouldbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this lth da of November, A. D. 1915.

Henry Van Aredale, V .(g Acting. commieioner. of Patents.

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