US2620285A - Process for drying photographic emulsions - Google Patents

Description

Dec. 2, 1952 C. E. ROSE PROCESS FOR DRYING PHOTOGRAPHIC EMULSIONS Filed July 18. 1951 2 SHEETS-SHEET l N www@ lnl Hf od l* N" ,iN s SN IN V EN TOR. C/ze5 ef'lfzge rielase A T TORNE Y.

DCC. 2, 1952 C, E ROSE 2,620,285

PROCESS FOR DRYING PHOTOGRAPHIC EMULSIONS Filed July 18, 1951 2 SHEETS- SHEET 2 DKYIN' G CHAJYEBE'R CSEASo/WNG CHAMBER IN VEN TOR.

Chestefgezeose A TTORNE Y.

Patented Dec. 2, 1952 PROCESS FOR DRYING PHOTOGRAPHIC EMULSIONS Chester Eugene Rose, Raritan Township, Middlesex County, N. J., assigner to E. I. du Pont de Nemours & Company, Wilmington, Del., a. corporation of Delaware Application July 18, 1951, Serial No. 237,418

8 Claims.

This invention relates to a process for setting and drying photographic silver halide emulsion coatings. More particularlyv it relates to a continuous process of setting and drying gelatino silver halide emulsion coatings on continuous supports such as flexible films or papers.

The manufacture of photographic films and papers includes the steps of depositing a coating of warm, owable colloid silver halide emulsion onto a support, the cooling of the liquid emulsion layer below its setting point to form a gelled layer, and drying to remove excess water. The setting` is accomplished by passing the support after coating into a chilled zone. After the emulsion is set, it is then dried. The drying operation must be conducted under such conditions that the emulsion layer is not remelted. The conventional methods of drying are time-consuming and require large buildings and apparatus.

An object of this invention is to provide an improved process of setting and drying gelatina silver halide emulsion coatings. A further object is to provide such a process which requires shorter drying period. A related object is to provide such a process which can be practiced in smaller apparatus and buildings. A still further object is to provide a rapid process for setting and drying gelatino silver halide emulsion layers which gives coatings of uniform quality. Still other objects will be :apparent from the following description.

The above objects are accomplished by the present invention which in its broader aspects consists in passing the support, e. g., film or paper, after it has been coated with an aqueous gelatine silver halide emulsion into a chilling zone that is maintained at a temperature below '75 F., preferably at 40 to 70 F. depending upon the gelatin content, whereby the Iemulsion is firmly and smoothly gelled. Low gelatin content emulsions require the lower temperatures. The element is then passed into a conditioning zone which is maintained yat a temperature which is from 5D to 30 F. bel-ow the melting point of the gelatine silver halide emulsion layer for la period of about i0 to 180 seconds whereby a rmer gel is formed. The element is then passed into a drying Zone and the layer is dried by means `of a high velocity current of air which is maintained at such a temperature and humidity that the emulsion is abo-ve its normal melting point without the aforementioned conditioning. The element is removed from contact with such air after the moisture content of the emulsion has been reduced to produce a water to gelatin ratio of 0.5 to 1.5 to 1.0 by weight.

(Cl. 11W-103) The drying conditions may vary widely but a dry-bulb temperature of 110 to 235 F. :and a wetbulb temperature 2 to 20 F. above the normal melting point of the gelled but unconditioned emulsion layer and va period from 30 to 180 sec. is preferably used at an air velocity of 2,000 to 15,000 feet per minute or greater, and the element so disposed that the emulsion surface is exposed to the current of air. The conditions 'being such that the rate of evaporation from a free water surface would be 0.5 to 3.0 lbs. per hour per square foot. The emulsion layer as it emerges from the high velocity zone has its water content reduced to the desired level.

It has been found that the emulsion layers and particularly those which contain a substantial amount of soluble bromides and chlorides can be further improved if they are removed from the foregoing treatment when the water to gelatin ratio is between 0.5 and 1.5 to 1.0 and passed into a curing zone where a current of air passes over the surface of the emulsion layer at a velocity of l0 to about 2,000 or more feet per minute at a dry-'bulb temperature of 70 F. to 100 F., a wetbulb temperature from 50 F. to 75 F. and a relative humidity of 30% to 60%. The conditions being such that the rate of evaporation from a free wet surface would be less than 0.5 lb. per hour per square foot and preferably less than 0.2 lb. .per hour per square foot. The emulsion layer then may be passed through a seasoning zone maintained at a still lower temperature, were the linal water to gelatin ratio is adjusted to between 0.23 and 0.34 to 1.0, prior to being wound` on suitable take-up rolls.

The conditions described above in the first high-velocity, high-temperature drying zone result in an extremely high rate of evaporation lof the undesired water from the gelled emulsion layer. The rapid rate of evaporation has a cooling effect on the emulsion layer and although it exhibits a tendency to melt while in this zone, because the wet-bulb temperature of the air is suc that the emulsion layer is above its normal melting point, the previous conditioning at approximately F. permits the use of high temperatu'res without any significant melting of the emulsion.

It has been found that if the passage of the gelled emulsion layer through the high-temperature, high-velocity drying zone is controlled so approximately to 95% of the water content of the Ioriginal liquid emulsion has been evaporated to produce a water to gelatin ratio of be tween 0.5 and 1.5 to 1.0 by weight, the physical and photographic properties of the layers are 3 quite satisfactory and the rapid concentration of the soluble salts in the emulsion is not disadvantageous. The residual water is then removed in the curing zone and equilibrium is brought about in the seasoning zone or chamber.

Suitable apparatus for carrying out the process described above are disclosed in the accompanying drawing which forms a part of this specincation. Referring now to the drawing:

Fig. 1 is an elevation of a suitable apparatus for carrying out the process;

Fig. l-A is a section taken along the line A-A of Fig. 1;

Fig. 2 is an elevation of a modined apparatus for carrying out the process;

Fig. 3 is an elevation of another modified apparatus for carrying out the process; and

Fig. 4 is an elevation of another modined apparatus for carrying out the process.

In Figs. 1, 2, 3, and 4 a roll of nlm I passes over guide roller I and under guide roller 8 into contact with a gelatin silver halide aqueous emulsion in coating pan 6. It then passes into a cooling tower Il over guide roller or drum I3, then into a horizontal chamber and then into a high-velocity, high-temperature drying chamber I6 which communicates with a source of hot air through a plurality of slots or openings. The nlm then passes to a rewind station.

An elongated slot or outlet I6 (as shown in Figs. 1, 2 and 3) for exhausting the hot air is provided at the sides of the drying chamber near edges of the emulsion surface or the sides may be completely open as shown in Fig. 4. Hot air having a velocity of 2,000 to 15,000 feet per minute and the wet and dry-bulb temperatures and relative humidity described above passes through the drying chamber to the outlets, e. g., in the sides of the chamber and at the top of the horizontal chamber.

The cooling tower should be of such length that the emulsion gels and is nrmly set and conditioned before it passes into the high-velocity drying chamber. In general, a unitl foot of nlm should remain in the cooling tower for a period of about one minute and in the high-temperature, high-velocity drying chamber about two minutes.

Referring now to Fig. 4 which illustrates a practical although more complex commercial apparatus, a roll of transparent nlm base I is passed over a series of guide rolls 2 and 3, the lower guide rolls 3 being mounted on a movable frame so that they can move upwardly and downwardly. The elevator construction just described is cornmon in photographic processing apparatus and, since it forms no part of the present invention, is not shown in detail. The elevator construction, however, permits one t9 start a new roll Iy through the machine without interrupting the continuous coating and drying. The series of guiding rolls 2 and 3 and elevator construction, may be mounted in a chamber 4 which can be heated or cooled so that the nlm has a uniform temperature as it passes into the coating unit 5.

The coating unit includes a coating pan 6 which is continuously supplied with an aqueous gelatino silver halide emulsion maintained at a constant level. The nlm I passes over guide roller 1 and under guide roller 8 disposed in the pan where it comes into contact with the surface of the coating solution and picks up a thin layer of silver halide emulsion. Ihe coated nlm then passes upwardly through a cooling or setting chamber 9 which is maintained at a temperature of 40 to 60 F. by means of cool air which passes from a large plenum chamber I0 through a piurality of orinces or slots so that it sweeps over the emulsion surface as well as the back of the coated nlm. The nlm then passes through an elongated conditioning tower I I that is provided at its upper end with a chamber I2 which surrounds it and is provided with communicating orinces or slots. The cool air from the cooling tower passes through said orinces or slots into chamber I2 where it is withdrawn from the system or cooled and recirculated through chamber I0. If cold air is fed to chamber I0 in order to obtain quick setting, as is desirable for dilute aqueous gelatino silver halide emulsion coating solutions then warmer air is used in tower Il. This warmer air should, however, be 2 F. to 10 F. below the melting point of the coating in order to condition it in as short a time as possible.

At the top of the tower II there is provided a guide roller or drum and a closely-ntting baille I4 which leaves a narrow opening at the end of the tower for the passage of the nlm with its nrmly-set and conditioned gelatino silver halide emulsion layer into horizontal chamber I5, which in this case is a drying chamber connecting with vertical drying chamber I6. These chambers are provided with a plurality of spaced slots which communicate with large air ducts II and II and- I8 and I8', respectively, whereby warm drying air impinges upon or flows over one or both surfaces of the coated nlm element. This air is withdrawn at the sides of chamber I6 which are open as shown in Fig. 4 or may have elongated slots like I6 as shown in Figs. 1, 2 and 3. The air is also withdrawn from the sides of chamber I5 which are open or provided with elongated slots disposed parallel to and just above the path of the emulsion surface of the nlm.

The coated nlm then passes over guide roller I9 downwardly through vertical chamber I6 and under similar guide roller 20 past another closely ntting baille I4' then upwardly through a curved curing Zone 2l in contact with a series of spaced rollers 22 then over roller 23 and downwardly through a curved curing zone 2|' which communicates freely with said curing zone 2l. A series of rollers 24 guide the nlm during its passage through chamber 2l. A series of slots are provided in the wall of the nrst curved section of the curing chamber opposite the emulsion surface of the nlm'which communicate with a large duct 25 through which warm air is supplied. This air then passes through the second curved chamber 2l and is exhausted through side openings 2l". The end of this chamber is provided with baffles I4 to prevent passage of air into seasoning chamber 26. The nlm passes under a roller 21 disposed at the entrance end to chamber 26 and then over a series of upper and lower rollers 28 and 29. A few of such rollers can be provided with an elevator mechanism to permit changing spools 30 without stopping the dryer. The seasoning chamberl 26 has a wet and dry-bulb temperature lower than those in the previous drying zone and these nnal temperatures are determined by the desired nnal moisture in the nlm.

It has been found that a gelatino silver halide emulsion which is coated on a support is adequately conditioned against remelting if it is in the conditioning tower for a period of about 10 to 180 seconds depending on the gelatin concentration of the emulsion. When the air flows over the wet side only, the element should remain in the high-temperature. high-velocity air drying chambers I and I6 for about 30 to 180 seconds. The dry-bulb temperature should be from 110 F. to 235 F., the Wet-bulb temperature should be from 68 F. to 100 F., and the dew point from 40 F. to 70 F. The combination of conditions is such that the rate of evaporation from a free wet surface is 0.5 to 3.0 pounds per hour per square foot. The film should remain in curing chamber 2| for a period of 30 to 1'50 seconds at the lm speed of 20 to 60 feet per minute with the dry-bulb temperature about 75 F. to 90 F. and the wet-bulb temperature about 65 F. to 75 F. and the air velocity adjusted to give a rate of evaporation from a free wet surface of 0.1 to 0.5 pounds per hour per square foot. The final conditioning zone should be designed so that the unit length of film remains in it from 4 to 12 minutes at a dry-bulb temperature of 70 F. to 90 F. and a wet-bulb temperature of 60 F. to 75 F. a humidity of 30-60% and the air velocity adjusted to give a rate of evaporation from a free wet surface of 0.1 to 0.3 pounds per hour per square foot. The inveniton, of course, is not limited to such film speeds. To the contrary, the rate of travel may vary over a very wide range, e. g., l0 to 200 feet per minute or more.

The invention will be further illustrated but it is not intended to be limited by the following examples:

Example I A gelatino-silver iodo-bromide emulsion containing approximately 0.097% silver iodide, 4.903% silver bromide, 6.34% gelatin and 88.66% Water by Weight is coated onto a sheet of cellulose acetate film base at the rate of 18 grams of liquid emulsion per sq. ft. The coated film is passed into a setting zone and a conditioning zone where it is subjected to a concurrent stream of air at 60 F. for 130 seconds. It is then passed into the turbulent air drying zone where jets of air at 120 F. dry bulb and 75 F. Wet bulb impinge against the surface at a velocity of 8000 feet per minute for 120 seconds through slots 1%; inch wide extending completely across the film spaced 6 inches apart and spaced 2 to 6 inches from the web. The drying rate was 1.1 pounds of Water per hour per square foot of free wet surface. The lm next passes into a curing Zone, having a dry bulb temperature of 85 F., a Wet bulb temperature of 70 F. and an air velocity of 40 feetA per minute parallel to the surface of the web, for 120 seconds and then passes into a seasoning zone, having a dry bulb temperature 84 F., a wet bulb temperature of 70 F. and an air velocity of ten feet per minute for 480 seconds. The drying rate in the curing zone was 0.02 pound and that in the seasoning zone 0.01 pound of water per hour per square foot of free Wet surface. At the end of this final period the moisture content of the film is 2.48%.

Example II A gelatine-silver halide emulsion containing about 4.7% silver halide, 4.6%v gelatin and 90.7% water by weight is coated onto a cellulose acetate film at a rate of- 14.0` grains of liquid emulsion per sq. ft. The coated film is passed into a setting and conditioning zone where it is subjected to a concurrent stream of air atl 55 F. for 110 seconds. It is then passedV into a vturbulent air drying zone where jets of air at 110 F. dry bulb and 72 F. wet bulby impingev against the surface at a velocity of 8000 feet per minute for a period of 180 seconds through slots T31; inch wide extending completely across the film spaced 6 inches apart and spaced 2 to 6 inches from the Web. The drying rate was 1.0 pound of water per hour per square foot of free wet surface. The gelatino silver halide layer was sufficiently dried at theend of this period and the emulsion had a moisture content below 2.5%.

Ezvample III A gelatino-silver iodo-bromide emulsion containing approximately 0.059% silver iodide, 4.64% silver bromide, 4.55% gelatin and 90.8% Water by Weight is coated onto a cellulose acetate film base at the rate of 13.8 grams per sq. ft. The coated lm is passed into a setting and conditioning zone Where it is subjected to a concurrent stream of air at 55 F. for 110 seconds. It is then passed into the turbulent air drying zone where jets of air at 110 F. dry bulb and 72 F. wet bulb impinge against the surface at a velocity of l3000 feet per minute for a period of 105 seconds through slots inch wide extending completely across the film spaced 6 inches apart and spaced 2 to 6 inches from the web. The drying rate was 1.0i pound of water per hour per square foot of free wet surface. It next passes into a curing zone, having a dry bulb temperature of F., a wet bulb temperature of 71 F. and an air velocity of 40 feet per minute parallel to the surface of the web, for two minutes and passes into a seasoning zone, having a dry bulb temperature of 84 F., a wet bulb temperature of 70 F. and an air velocity of ten feet per minute parallel to the surface of the web for eight minutes. At the end of this final period, the moisture content of the film is 1.8%. The drying rate in the curing zone was 0.04 pound and that in the seasoning zone 0.01 pound of water per hour per square foot of free wet surface.

Example IV A gelatino-silver bromo-chloride emulsion containing approximately 1.96% silver bromide, 3.57% silver chloride, 3.92% gelatin and 90.55% water is coated onto a sheet of cellulose acetate lm base at the rate of 13.6 grams per sq. ft. The coated lm is then passed into a setting and conditioning Zone where it is subjected to a concurrent stream, of air at 40 F. for 180 seconds, then passed into the turbulent air drying zone where jets of air at F. dry bulb and 70 F. wet bulb impinge against the surface at a velocity of 4200 feet per minute for seconds through slots Tse inch Wide extending completely across the film spaced 6 inches apart and spaced 2 to 6 inches from the web. The drying rate Was 0.6 pound of water per square foot of free wet surface. It next passed into -a curing zone, having a dry bulb temperature of 85 F., a wet bulb temperature of 70 F. and an air velocity of 40 feet per minute parallel to the surface of the web for two minutes. It next passes into a seasoning zone, having a dry bulb temperature 82 F., a wet bulb temperature of 70 F. and an air velocity of ten feet per minute parallel to the surface of the web for eight minutes. At the end of this final period the moisture content of the film is 1.78%. The drying rate in the curing zone was 0.03 pound and. that in the seasoning zone 0.01 pound of water per hour per square foot of free wet surface.

When drying thin reversible colloid layers, it has been found the rate of evaporation depends upon many factors: (l) the air velocity, (2) the lmanner of directing the air against the material,

(3) the temperature of the air, (4) the humidity of the air, the rate at which the moisture diffuses through the material. The first four items relate to drying conditions and can be specied or rated by the pounds of water which would be evaporated per sq. ft. in one hour from the surface of a container `of water or a free wet 'surface Item (5) is a function of the material being dried, its moisture content and the rate of drying.

In describing drying conditions, I prefer to specify them by the amount of water which would be evaporated from a free wet surface. For a given rate of evaporation the temperature and humidity may be varied over wide ranges provided compensating changes are made in air velocity.

Thus in the drying step of the invention e. g., in the rst section of the apparatus of Fig. 4 one may use conditions which will produce rates of evaporation as high as 1.0 to 3.0 lbs. of water per hour per sq. ft. It is in some cases desirable to reduce the drying conditions after 90 to 95% of the water has been evaporated. Thus in the case of aqueous gelatino-silver emulsions it is desirable to reduce the drying conditions when the water content is between 50% and 150% of the gelatin content. At this point the conditions are changed to give a curing condition wherein a drying rate from a free wet or water surface of less than 0.5 lb. per hour per square foot and preferably less than 0.2 pound per hour per square foot until the water to gelatin ratio reaches a value between .23 and .34 to 1.0.

Reducing the drying rate as specied above appears to permit the electrolyte salts present in the emulsion to distribute uniformly through the layer and act to conduct away any static electricity generated. If the conditions producing high drying rates are continued throughout the entire period of drying and curing the electrolytes act as though they were buried below the surface, they will not conduct away the static electricity. As a consequence the static builds up until a spark discharge is produced causing static marking of the photographic films.

The conditioning step of the invention which takes place immediately after passing through the setting chamber and before the high velocity air drying is an important feature of the invention. The period t of conditioning before drying may be represented by the following empirical formula:

(WB-69) C5N3S2 TZJB t=conditioning time in seconds C=percent gelatin in emulsion N :gelatin Viscosity S :gelatin gel strength T=conditioning temperature-JF. WB=wet bulb temperature in dryer- T.

This equation, while not exact for very dilute or very concentrated aqueous colloid solutions, applies for aqueous colloid concentrations between 4% and 6% gelatin. The formula does, however, indicated the complex nature of the operation and how the higher setting temperatures permit higher drying temperatures.

It is obvious that the process of this invention can be carried out in apparatus which vary considerably from that shown in the accompanying drawings. Additional coating units and high- Velocity drying units can be used in series to coat a plurality of gelatin-containing layers on a lm.

The process is not limited to the coating of gelatino silver halide emulsion layers but can be used in drying other set or gelled colloid silver halide emulsions and other types of layers, e. g., gelatin sublayers, gelatin filter layers, etc. Liquid layers of colloids which gel or whose changes in viscosity lag or do not follow immediately changes in temperature, or whose melting point increases with holding time, can be dried as described above at such a rate that the coating is dry before it melts or is reduced in Viscosity sufiiciently tol flow. A series of coated sheets or plates, e. g., photographic plates on a moving belt can be dried in a manner similar to that described above.

This applicationis a continuation-impart of my copending application Ser. No. 25,867, led May 8, 1948, now abandoned.

The invention has the advantage that it provides a practical commercial process for drying gelatin silver halide emulsion layers. A further advantage is that it requires small size apparatus and buildings. Still other advantages are: The lm is exposed for less time in moist condition to contaminant dust. Less material is being processed at one time so that smaller losses occur in the event of equipment failure. It obviates the need for long festoon driers, or tenter frames for supporting the lm or paper. By means of this invention it is possible to use air having a higher moisture content than has been customary in the art. As a result, dehumidifying equipment can be much reduced and less expensive.

As many widely different embodiments of this invention can be made without departing from the spirit and scope thereof,v it is to be understood that the invention is not to be limited except as defined by the claims.

What is claimed is:

1. The process which comprises coating an aqueous gelatino-silver halide emulsion onto a moving flexible web support, chilling the coated layer from 40 vto 75 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coatedweb through a zone maintained at a temperature from 5'to 30 F. below the melting point of the emulsion for a period of 10 to 180 seconds, then passing the coated web through a drying zone while exposing the emulsion layer to a high velocity current of air maintained at a dry bulb temperature of 110 F. to 235 F., a wet bulb temperature of 68 F. to F. and an air velocity of 2000 to 15,000 feet per minute so that the rate of evaporation from a free wet surface is 0.5 to 3.0 pounds per hour per sq. ft.

2. The process which lcomprises coating an aqueous gelatino-silver halide emulsion onto a continuous, moving, exible, web support, chilling the coated layer with air at a temperature from 40 F. to 70 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coated web through a zone maintained at a temperature from 5 to 30 F. below the melting point of the emulsion for a period of 10 to 180 seconds, then passing the coated web through a drying zone while exposing the emulsion layer to ahigh velocity current of air having a dry bulb temperature of F. to 235 F., a'wet bulb temperature of 68 F. to 100 F. and an air velocity of V2000 to 15,000 feet per minute so that the emulsion is 2 F. to 20 F. above its normal melting point, and removing said coated web from the drying zone after the moisture content has been reduced to 0.5 to 1.5 times the gelatin conltent of the coated layer.

3. The process which comprises coating an aqueous gelatine-silver halide emulsion onto a continuous, moving, flexible, paper sheet, chilling the coated layer with air at a temperature from 40 F. to 70 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coated sheet through a zone maintained at a temperature from 5 to 30 F. below the melting point of the emulsion for a period of to 180 seconds, then passing the coated sheet through a drying zone while exposing the emulsion layer to a high velocity current of air hav ing a dry bulb temperature of 110 F. to 235 F., a wet bulb temperature of 68 F. to 100 F. and an air velocity of 2000 to 15,000 feet per minute so that the emulsion is 2 F. to 20 F. above its normal melting point, and removing said coated sheet from the drying zone after the moisture content has been reduced to 0.5 to 1.5 times the gelatin consent of the coated layer.

4. The process which comprises coating an aqueous gelatino-silver halide emulsion onto a continuous, moving, iiexible, hydrophobic lm, chilling the coated layer with air at a temperature from 40 F. to '70 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coated lm through a zone maintained at a temperature from 5 to 30 F. below the melting point of the emulsion for a period of 10 to 180 seconds, then passing the coated film through a drying Zone while exposing the emulsion layer to a high velocity current of air having a dry bulb temperature of 110 F. to 235 F., a Wet bulb temperature of 68 F. to 100 F. and an air velocity of 2000 to 15,000 feet per minute so that the emulsion is 2 F. to 20 F. above its normal melting point, and removing said coated lm form the drying zone after the moisture content has been reduced to 0.5 to 1.5 times the gelatin content of the coated layer.

5. The process which comprises coating an aqueous gelatino-silver halide emulsion onto a continuous, moving, flexible, web support, chilling the coated layer with air at a temperature from 40 F. to '70 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coated web through a zone maintained at a temperature from 5 to 30 F. below the melting point of the emulsion for a period of 10 to 180 seconds, then passing the coated web through a drying zone while exposing said layer to a current of air having a velocity of 2,000 to 15,000 feet per minute, a dry bulb temperature of 110 F. to 235 F. and a wet bulb temperature 2 to 20 F. above the normal melting point of the gelled emulsion layer, for a period of 30 to 180 seconds.

6. The process which comprises coating an aqueous gelatine-silver halide emulsion onto a continuous, moving, exible web support, chilling the coated layer with air at a temperature from 40 F. to '70 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coated web through a zone maintained at a temperature from 5 to 30 F. below the melting point of the emulsion for a period of 10 to 180 seconds, passing the conditioned web through a drying zone while exposing said layer to a current of air having a velocity of 2,000 to 15,000 feet per minute, a dry bulb temperature of 110 F. to 235 F. and a wet bulb temperature 2 to 20 F. above the normal melting point of the gelled emulsion layer for a period of 30 to 180 seconds, then passing the coated web into a curing zone while exposing the emulsion layer to a current of air having a velocity of to about 2,000 feet per minute, a dry bulb temperature of '70 F. to 100 F., a wet bulb temperature from 50 to '75 F. and a relative humidity of 30% to 60% so that the rate of evaporation from a free wet surface will be less than 0.5 pound per square foot per hour.

7. The process which comprises coating an aqueous gelatino-silver halide emulsion onto a continuous, moving, exible paper sheet, chilling the coated layer with air at a temperature from 40 F. to '70 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coated sheet through a Zone maintained at a temperature from 5 to 30 F. below the melting point of the emulsion for a period of 10 to 180 seconds, passing the conditioned sheet through a drying zone while exposing said layer to a current of air having a velocity of 2,000 to 15,000 feet per minute, a dry bulb temperature of F. to 235 F. and a wet bulb temperature of 68 F. to 100 F. so that it is 2 to 20 F. above the normal melting point of the gelled emulsion layer for a period of 30 to 180 seconds, then passing the coated sheet into a curing Zone While exposing the emulsion layer to a current of air having a velocity of 40 to about 2,000 feet per minute, a dry bulb temperature of 70 F. to 100 F., a Wet bulb temperature from. 50 to r75" F. and a relative humidity of 30% to 60% so that the rate of evaporation from a free wet surface will be less than 0.5 pound per sq. ft. per hour.

8. The process which comprises coating an aqueous gelatina-silver halide emulsion onto a continuous, moving, flexible hydrophobic film, chilling the coated layer with air at a tempera.- ture from 40 F. to '70 F. to form a gelled emulsion layer, conditioning the gelled emulsion layer by passing the coated lm through a zone maintained at a temperature from 5 to 30 F. below the melting point of the emulsion for a period of 10 to 180 seconds, passing the conditioned film through a drying zone while exposing said layer to a current of air having a velocity of 2,000 to 15,000 feet per minute, a dry bulb temperature of 110 F. to 235 F. a wet bulb temperature of 68 F. to 100 F. so that it is 2 to 20 F. above the normal melting point of the gelled emulsion layer for a period of 30 to 180 seconds, then passing the coated lm into a curing zone while exposing the emulsion layer to a current of air having a velocity of 40 to about 2,000 4feet per minute, a dry bulb temperature of '70 F. to 100 F., a Wet bulb temperature from 50 F. to '75 F. and a relative humidity of 30% to 60% so that the rate of evaporation from the free wet surface will be less than 0.5 pound per sq. ft. per hour.

CHESTER EUGENE ROSE.

No references cited.

Claims (1)

1. THE PROCESS WHICH COMPRISES COATING AN AQUEOUS GELATINO-SILVER HALIDE EMULSION ONTO A MOVING FLEXIBLE WEB SUPPORT, CHILLING THE COATED LAYER FROM 40* TO 75* F. TO FORM A GELLED EMULSION LAYER, CONDITIONING THE GELLED EMULSION LAYER BY PASSING THE COATED WEB THROUGH A ZONE MAINTAINED AT A TEMPERATURE FROM 5* TO 30* F. BELOW THE MELTING POINT OF THE EMULSION FOR A PERIOD OF 10 TO 180 SECONDS, THEN PASSING THE COATED WEB THROUGH A DRYING ZONE WHILE EXPOSING THE EMULSION LAYER TO A HIGH VELOCITY CURRENT OF AIR MAINTAINED AT A DRY BULB TEMPERATURE OF 110* F. TO 235* F., A WET BULB TEMPERATURE OF 68* F. TO 100* F. AND AN AIR VELOCITY OF 2000 TO 15,000 FEET PER MINUTE SO THAT THE RATE OF EVAPORATION FROM A FREE WET SURFACE IS 0.5 TO 3.0 POUNDS PER HOUR PER SQ.FT.

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