US370110A - William hall walkee and geobge eastman - Google Patents

Description

(No Model.)

W. -H. WALKER & G. EASTMAN.

. PROGBSS 0F COATING PHOTOGRAPHIG PAPER.

No. 370,110. Patented Sept. 20, 1887.

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UNITED STATES PATENT EicE,

XVILLIAM HALL XVALKER AND GEORGE EASTMAN, OF ROCHESTER, NEW YORK, ASSIGNORS TO THE EASTMAN DRY PLATE AND FILM COMPANY,

OF SAME PLACE.

PROCESS OF COATING PHOTOGRAPHIC PAPER.

SPECIFICATION forming part of Letters Patent No. 370,110, dated September 20, 1887.

Original application filed October 25, 1884, Serial No. 146,449. Divided and this application filed March 5, 1887. Serial No.

To all whom it may concern.-

Be it known that we, \VILLIAM HALL XVALKER, a citizen of the United States, of Roch ester, Mon roe county, New York, temporarily residing at London, England, and GEORGE EASTMAN, of Rochester, in the county of Monroe and State of New York, have invented certain new and useful Improvements in Processes of Coating Photographic Paper; and we do to hereby declare the following to be a full, clear,

and exact description of the same.

This application is filed as a division of our prior application,No. 146,449, (patented March 8, 1887, No. 358,848,) and is designed to cover I 5 the improvement in the art of coating paper or other flexible supporting material with a uniform coating of sensitized emulsion, said improvement being described and set forth in the before-mentioned application, but not lineited in practice to the mechanism there shown.

Since the introduction of the article known as bromide paper for photographic positives and negatives numerous attempts have been made to devisea practicable method of manufacturing the material on a large scale and at less expense both in time and material; but until our present invention no material progress had been made, and the manufacture was conducted by what may be termed the 'original processesthat is to say, either by laying the sensitized material on the paper with brushes or the more common method of passing a strip of paper around rollers, uniting the ends of the strips to form an endless band, and by the rotation of the rollers causing the band to travel in contact with a body of emulsion until the entire surface had re ceived a coating, when it was suspended or left hanging until dried.

A moments consideration of the nature of the sensitized material, the conditions under which it is applied, and the changes to which the paper is subjected will serve to show why the ordinary processes of coating and the ma- 5 chinery employed areincompetent to perform the operations and at the same time preserve the necessary conditions.

The sensitized emulsion as ordinarily com- (No model.)

pounded contains as the sensitive medium silver salts dissolved or held suspended in a mixture of water and gelatine, the latter serving as the vehicle for carrying and holding the sensitive material upon the paper. The silver salts are a valuable product; hence it is desirable that the minimum quantity capable of 5 5 producing good work should be employed, and 4 for that and other reasons only sufficient gelatine is mixed in the emulsion to produce, when applied to the paper, a film or layer of just sufficient depth to retain the desired or requi- 6 site quantity of the sensitizing medium. As

is obvious, the layer or film of emulsion de posited on the paper must be as free from spots and irregularities as possible; hence any treatment of the paper or coating before, dur- 6 ing, or after the emulsion is applied which will produce or favor the formation of spots, streaks, or irregularities in the surface or thickness of the film will result in the production of defective and unsalable paper, in- Volving the loss of much valuable time, labor, and material. It must also be remembered that the emulsion is in a liquid condition when applied to the surface of the paper, that the paper becomes saturated by the water 0011- tained in the mixture, that no opportunity is afforded for a critical examination of the coating, nor can the defects in its surface be removed or remedied after the gelatine has once set, and that the entire process has necessarily to be conducted in a photographic dark-room; hence if the finished article contains the irregularities and inequalities mentioned they cannot readily be discovered or detected, even by a critical examinationthe 3 coating is so extremely thin-until the final testactual usehas been applied, and then, and not before, can the merchantable and practical value of the material be ascertained. It

will readily be understood, therefore, why the 0 ordinary processes employed for coating cloth, paper, and other materials with paint, glue, parafiine, and other substances and compounds not requiring so even and regular a surface as photographic paper, whose irregularities are 5 measured not by instruments, but by the results produced by the action of light alone why said processes and machines have not and cannot as ordinarily worked be usedin the manufacture of photographic paper.

As before stated, notwithstanding the many attempts made to produce a successful article of bromide paper by a cheaper and more practlcable method, the only process by which it was generally understood it could be successfully made, and the only one in practical use at the t1me of our invention, was that in which a belt or band of paper with its ends united was caused to pass through a bath of emul- S101], and when the band had been drawn through the liquid and the coating applied it i was either raised out of the bath and allowed 7 we have succeeded in discovering a method of manipulation whereby, by a continuous process, we are enabled to produce a commercial artlcle of bromide paper expeditiously and cheaply, in sheets of any desired dimensions, and with the minimum of waste.

Our improvement relates more particularly to the treatment of the paper after the coating has been applied; and it consists, generally stated, in so conducting the operation that after the paper has been supplied with a thin and uniform coating of the emulsion, and while the layer or film is still in a fluid state, the coated web shall, while under sufficie'nt tenslon to maintain its surface flat, be drawn or moved continuously in the same direction until the gelatine in the coating has set, after which, and as rapidly as the web is delivered, 1t 1s hung in loops upon .a frame, where it is allowed to remain until the paper has been thoroughly dried.

Various mechanical contrivances may be employed in practicing our improvement-such, forexample, as those described in the applications of George Eastman, Nos. 224,189 and- 228,746; but the preferred form, construction, and arrangement are described in our beforementioned application, No. 146,449, patented No. 358,848, of which patented machine the accompanying drawing is a representation, in which the figure is aside elevation of the ma chine.

The letter A designates the hang-up or drying frame; B, the supporting or carrying: rollers; O, the immersion-roller; D, the trough or receptacle for the liquid emulsion or coating material; E, the paper-feeding rolls, and F the roll of paper. For a more full description of the mechanism reference may be had to our before-mentioned patent.

The dotted lines G represent a tank or re larly and form in streaks on the paper.

the paper as it rises from the level surface of the liquid may carry only so much of the emulsion as adheres to its surface, the surplus flowing back into the receptacle. It is to be observed, moreover, that after the coating has been evenly applied to the web, and while the latter bearing the fluid coating is continued in motion to preserve and maintainitsuniformity, it is essential that the coated face be unobstructed-that is to say, it must be held and maintained out of contact with any foreign substancesuch as pressing-rolls, scrapers, or other devices-which, if permitted to so much as touch the coating, would defeat the purpose of the process by destroying the uniform character of the film and render the latter unfit for photographic purposes. The paper as it passes through the emulsion takes up a large quantity of water, which acts to expand andsoften the web;hence it becomes necessary to apply sufficient tension to draw it flat over the rollers or other supporting devices. The tension on the paper must, however, be so regulated that,

' while serving to maintain the web flat and 1 move it at a uniform speed, it shall not producewrinkles by the unequal strain upon the now weakened and expanded paper, for if such wrinkles or other irregularities in the surface occur the still fluid coating will run irregu- The movement of the web after the coating material has been evenly applied, and which is continued until the coating has set or stiffened so as to prevent running, is a progressive movement, the travel being at all times forward; but in order that the flow of the material may be regulated and the uniformity of the coating maintained it is desirable that the direction i. e., the angle or inclination-of the Web during its progressive movement should at times be reversed or altered, so that at one point it will travel upward and subsequently downward, or vice versa, thereby arresting or changing the direction of the flow, if any takes place, of the liquid coating upon the traveling web. Thus in the machine illustrated the web as it emerges from the coating device is caused to move first upward, then horizontally, downward, horizontally, and again upward to the delivery-roller.

The rate of motion and distance intervening between the coating devices and thehang up frame vary with the state of the atmos phere and the quality of the. emulsion. Or

dinarily, in using a machine such as described in our application No. 146,449, the rollers are driven at such speed as will advance the paper twenty feet a minute, and with the temperature of the room maintained at about 65 Fahrenheit the hang-up is located about thirty feet distant that is to say, the paper is maintained in motion for about one to two minutes after leaving the coating-bath before it is deposited upon the slat of the dryingframe. The time and distance must of course be adjusted and regulated according to the temperature and state of the atmosphere,and, if desired, artificial cooling and drying devices may be employed; but under all circumstances, in order to prevent blemishes when practicing the continuous process, the coated web must be kept in motion and fiat until the gelatine has set, so as to be incapable offurther movement on the surface of the paper, and when this stage has been reached (but not'before) it can be suspended in loops upon the drying-frame and remain there until the moisture has evaporated without injury to the coating.

Under certain circumstances, as when it is desired to use a thin emulsion, or in warm weather, the setting of the coated film may be facilitated by reducing its temperature as it passes from the coating apparatus to the hangup machine. This artificial coolingof the coated web may be accomplished by the use of a current of cold air, or by causing the web to pass over a surface the temperature of which is kept down, as by a current of cold air, water, or a cooling mixture or compound. A fanblower or other suitable device may be employed to produce a current of air, which is cooled by passing over ice or in any other preferred manner, the air being carefully strained from dust.

It is obvious that the process herein described is adapted to the coating of webs or strips of fabric with a surface-coating of any material which has a tendency to run and streak after its application and which possesses the property of setting or stiffening gradually while the web is maintained in motion to preserve the uniform surface of the coating.

\Ve do not claim herein the cooling of the coating, nor that portion of the process embracing the treatment of the paper after the coating has set or stiffened, as said subjectmatter is claimed in another division of this application, filed August 18, 1887, and numbered 247,492.

upon the face of the web and in changing the flow of the coating upon the web to regulate and maintain its uniformity, and maintaining the web in motion and its coated surface unobstructed by contact with foreign bodies until the coating has set or hardened suficiently to prevent running, substantially as described.

2. Theherein-described improvementin the art of producing photographic paper, which consists in applying to one face ofa web of paper a thin uniform coating or surface of fluid gelatino argentic emulsion by causing the paper to emerge from the level surface of abody of emulsion, and subsequently maintaining the coated web flat and in motion continuously and uniformly in the same direction, and the surface of the coating undisturbed by contact with foreign substances until the gelatine has set or stiffened sufficiently to prevent running, substantially as and for the purpose set forth.

3. The herein-described process of producing gelatino-argentic fabric for photographic reproductions, consisting in applying to a moving. continuous web of fabric a uniform layer of sensitive gelatino-argentic emulsion, keeping said web in motion and the coated side unobstructed until the coated gelatine is set or stiffened sufficiently to prevent flowing, and finally drying said coating.-

4. The herein-described method of producing uniform coatings upon continuous webs or strips of fabric,which consists in applying the coating material in a fluid condition evenly upon the face of the web, and subsequently maintaining the web in motion and its coated surface unobstructed by contact with foreign bodies until the coating has set or hardened sufficiently to prevent running, substantially as described.

WVILLIAM HALL WALKER. GEO. EASTMAN.

\Vitnesses to signature of VIII. H. Walker:

ALFRED J. BOULT, \VALTER J. SKERTEN.

\Vitnesses to signature of Geo. Eastman:

GEO. B. SELDEN, H. S. Bacon.

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