US1338492A - Art or method of producing photographic screens for half-tone work - Google Patents

Description

UTED STATES PATENT OFFICE.

HARRY A. GORIBETT, OF NEW YORK, N. Y.. ASS'IGNOR TO BRETT PROCESS SCREEN COMPANY, INC., OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ART OR METHOD OF PRODUCING PHOTOGRAPHIC SCREENS FOR HALF-TONE WORK.

No Drawing.

Tr, (/U 11-71 am. it may concern Be it known that I, I'IARRY A. CORBETT, a subject of the King of the United Kingdom of Great Britain and Ireland, and residing at the borough of Manhattan, in the city,-

county. and State of New York, have invented certain new and useful- Improvements in the Art or Methods of Producing Photographic Screens for Half-Tone Work,

of which the following is a specification.

My invention relates to an art or method of producing photographic screen for halftone work, and more particularly to the production of a screen of this character where in the body of the plate and the surface thereof containing" the light diffusing, retracting or projecting portions are formed of a homogeneous, integral body, by a method by which a master plate may be quickly and accurately duplicated.

l'leretofore screens in general commercial use in half-tone work have been of three general types :Ruled.screens composed of a glass plate having cut therein a large num master upon gelatin containing a light sen sitive emulsion or substance and carried by a glass plate. To these may be added a fourth type of screen such as that described in the Letters Patent of James Willard lHorris, Number 1,161,824 dated Novemher 23,]1915, wherein the operative surfaceb the" screen is composed of gelatin so treated as to produce a large number of closely juxtaposed, minute, lens-like formations thereupon.

While the effects secured by each of the types ot'commercial screens referredto,

differ radically from those secured by screens of any other type and the manner of handling eaclrtype of screen may differ from.

that of any other, these screens" have in Specification of Letters Patent.

Application filed March 28, 1916. Serial No. 87,758.

common the characteristic that each screen of a type, must be produced entirely separately, distinctly and independently of every other screen of that type, and by the same method or steps; making exactitu'de in the production of a number of similar screens practically impossible. A skilled worker in the printing arts in using a screen of any particular type can secure certain artistic effects with one screen of that type which he can not secure with another screen of the same type having theoretically identical characteristics and made by identically the same method. In other words, where each screen in itself is an original piece of work in an attempt to duplicate or reproduce, a screen, various conditions may enter into the work which will result in variances in the character of the completed article, even though the work be done by the same workman, with the same tools and in the same manner as when the original was made.

By means of the method or art of my invention, I am enabled to produce a number of photographic screens for half-tone work, each ofwhich will be an exact replica of every other, even to the most minute detail. Screens so made will have the same character of surface formation and the same degree of transparency as every other screen,-

the qualities of each screen being substan-v tially identical'with those of the master with the possible exception that with'a master screen of one type, it may be slightly more transparent and slightly more effective in diffusing, refracting or projecting of light rays.- By my improved method, a number of screens may be produced each of which may be handled by the skilled worker in the art in exactly the same manner as any other screen of the same grade, thus avoiding those difliculties resulting from the breakage of a screen now ordinarily used commercially, and the attempt to secure another screen which a worker may use under exactly the same conditions as he did the destroyed screen. This possibility growing out of my invention is of more than secondary importance, in that one of the great objections to the ordinary screen now being commercially used is that the worker'becomes accustomed to a. particular screen and in case of breakage of the screen,- finds it necessary to art of reproducing this particular screen, it

being understood however, that certain of the steps essential to the practice of my invention with this Morris type of screen are not essential in connection with the use of other screens as masters, or even in reproducing a screen made in accordance with my invention.

- Considering the invention in its broader aspects my improved method or art may be used for making a number of reproductions from any type of master screen wherein the control of the light rays is due to surface formations, as distinguished from variances in the tones or degree of transparency of said surface. Specifically my invention relates tothe reproduction of the screen described in the Letters Patent of the said James Willard Morris.

In the practice of my method or art, I apply to the surface of the master plate or screen having the depressions therein, or the elevations thereon, a superficial coating of an ammoniacal solution of nitrate of silver, precipitating the silver upon said surface in the same manner as silver is precipitated upon plate glass in the manufacture of mirrors. I have found that in this manner a continuous, electro-conductive surface may be formed upon said master screen or plate preparatory to the next step of the process. I have employed silver for the coating because of the close grain of this metal and the ease with which it may be applied to the surface of the master screen or plate. Other electro-conductive substances insoluble in an electro-platin bath, may be used in lieu thereof if desire however, although such substance must have a very close grain to give satisfactory results. Gold or platinum might be used advantageously, although I have found ordinary plumbago unsuitable for this use. Or-

dmarlly the dimensions of the depressionsand elevations which must be'so coated, are so small that a granular substance or a metal having a texture or grain coarser'than that of silver, would not exactly reproduce the master but would introduce in the re roduction made therefrom, certain pecu iarities and eccentricities which would seriously affect the operative effect of the reproduction in its use.

I have found that when e'oatinga screen esa-tea having a gelatin surface as described in the said Letters Patent of James Willard Morris, it is extremely difficult to form a superficial coating upon the entire area of the master screen or plate, by reason of the tendency of the silver when precipitated to penetrate the gelatin to a depth sufiicient to interrupt. the continuity of the superficial metallic coating through isolated areas of the screen surface. To 'check this tendency, I have found it necessary to apply a water insoluble coating to the surface of the gelatin portion of the screen before coating with the electro-conductive material in a manner to protect the screen from the action of the silver solution. I have found that a thin coating of celluloid dissolved in ether or alcohol or other suitable solvent, will not only impart acoating to the gelatin which will protect it in the manner referred to, but that this solution apparently closes the pores of the gelatin in a manner 'to make the reproduction of this screen more perfect as to the lens-like formations than the master screen or plate. I attribute this to the probability that, while the lens-like formations upon the surface of the gelatin of the master screen or plate are themselves minute, nevertheless, the porosity of the gelatin results in the presence upon these lenslike formations of still smaller depressions which might and probably would have the effect of modifying the operative effect of some or all of-the lens-like formations in their entirety.

When the protecting coating above referred to, has been applied to the gelatin surface of the master screen or plate the superficial coating of the electro-conductive material is applied in the manner above referred to.

After the master plate has been thus coated, I form thereon by electro-deposition, a matrix of copper or other suitable metal, exercising the ordinary precautions used in the art of electro-plating to insure uniformity in the deposition of copper or other metal uponthe metallized surface of said master screen or plate.

When this matrix has been deposited to the required thickness, it is separated from Y the masterscreen or plate, the silver or other After the glass has been so formed, the under side thereof may be ground and 01- ished to bring the product to the deslred thickness and transparency and the edges having been trimmed, there will remain a solid glass screen, one surface of which w1ll have reproduced thereon all of the surface formations found in the master screen or plate. The matrix is not injuriously affected when used to press or roll glass in the manner described, and thematrix having once been formed may be used repeatedly to produce a large number of glass screens, each of which will be an exact duplicate of every other.

If it be desired to reproduce one of these glass screens that surface thereof having the operative surface formations, may be coated in the manner above referred to, to provide it with an electro-conductive superficial coating and the above. operation may be used to accurately reproducethis reproduction Without varying in any substantial detail the characteristics of. the screen made from this reproduction. It will be observed that when the matrixis made from a master having a glass surface provided with lenslike formations, or other means for dilfusing, refracting or projecting light rays, the use of the celluloid solution, or other sur-. face coating to prevent the metal of the electro-conductive coating penetrating this surface, is unnecessary. A screen made in accordance with my invention has the characteristics that the minute indentations or depressed formations therein are inclined to have rounded edges instead of ragged or sharp edges, and that the surface will be a substantially continuous surface as distinguished from one interrupted by cutting or erosion. This continuity of the surface gives mechanically, a stronger screen or small surface imperfections, is reduced to a minimum. The most important result of my improved method or art is that by means thereof a number of screens having identical qualities may be produced, and that the cost of producing these screens as compared with that of producing the master'is lower.

I have heretofore stated that when reproducing a screen whereinv the surface formations are upon gelatin, the reproduction will be superior to the master because of eliminating the porosity'of the lens-like formations, and a slightly greater volume of light rays are permitted to pass through the screen. In other words the homogeneous glass screen will be quicker than the gelatin master from which it was developed.

While I have found that the application of the superficial coating of electro-conductive material may be satisfactorily appliedto the master screen by following the practice ordinarily used in silverin a mirror, it is not my intention to limit t e invention,

considered in its broader aspects to this.

method. I have found that the coating methods ordinarily employed in electro-typing are not adapted for use in the practice of my method or art because the granular formation of the plumbago used did not form a continuous surface such as that required in producing minute formations upon the surface of the screen and because the plumbago does not form a smooth surface coating upon the matrix made therefrom. I believe it to be necessary to secure the desired accuracy of reproduction upon the plate or glass to press the matrix against the plastic glass, because if the glass is merely flowed over the matrix it would not result in surface formations of suflicient exactitude. I believe it to be broadly new to produce a number of screen elevations and depres- ,sions forming the operative surface thereof,

from a master screen, by a duplicating of the method or art and to secure the best results therefrom.

Having described the invention, what I coating of electro-conductive 'material to av master plate or screen having a plurality of closely juxtaposed, minute surface formations thereon, said material being of a texture or grain sufficiently fine not to modify the character of said surface formations, forming a matrix by the electro-deposition of metal upon said electro-conductive surface and impressing the design appearing in intaglio on said matrix upon plastic material.

2. The herein described method or art of making photographic screens for half tone work consisting in applying a metallic solution to the surface ,of a master plate or screen having surface formations thereon, I

precipitating the metal of said solution upon said surface, forming a matrix by the electro-deposition of metal upon said metallized surface and impressing the design appearing in intaglio upon said matrix upon plastic glass.

3. The herein described method or art of work consisting inapplying anammoniacal solution of'nitrate of silver to the surface of a master latevor screen having surface formations t ereon, precipitating the silver of making photographic screens for half tonework consisting 1n applying a superficial coating of electro-conductive material to a master plate or screen having a lurality of closely juxtaposed,-minute sur ace formations thereon, said material being of a taxture or grain sufficiently fine not to modify the character of said surface formations, forming a' matrix by the electro-deposition of copper upon saidelectro-conductive surface and impressing the design appearing in intaglio on said matrix upon plastic material.

5. The herein described method or art of making photographic screens for half tone Work consisting in applying a metallic solution to the surface of the master plate or screen having surface formations thereon, precipitating the metal of said solution upon said surface, forming a matrix by the electro-deposition' of copper upon said metallized surface and impressing the design ap earin in intaglio upon said matrix upon F astic g ass.

6. he herein described method or art of making photographic screens for half tone work consisting in applying an ammoniacal solution of nitrate of silver to the surface of a master plateor screen having surface formations thereon, precipitating the silver of said solution upon said surface, forming a matrix by the eIectro-deposition of coper upon said silvered surface and impressing the design in intagliqupon said matrix upon lastic lass.

1 7.. he herein described method or art of making photographic. screens for half tone work consisting in applying a water insoluble coating to the gelatinous surface of a master plate or screen having therein a multiplicity of minute surface formations, thereafter su erimposing upon said water insoluble sur ace a superficial coating of an eIectro-conductive material, forming a matrix by the electro-deposition of metal upon said electro-con'ductive surface and impressing the design appearing in intaglio on said matrix upon plastic material. v

8 The herein described method or art of making photographic screens forhalf tone work consisting in applying a water insoluble coating to the gelatinous surface of a master plate or screen having thereon a multiplicity of minute formations, thereafter applying a metallic solution to said coating, precipitating the metal of said solution, forming a matrix by the electrodeposition of metal upon said metallized surface and impressing the design appearing in intaglio upon said matrix upon plastic glass.

9. The herein described method or art of making photographic screens for half tone work consisting 1n applying a water insoluble coating to the gelatinous surface of a master plate-or screen havin thereon a multiplicity of minute format1ons, thereafter applying an ammoniacal solution of nitrate of silver to said coating, precipitating the silver of said solution, forming a matrix b the electro-deposition of metal upon sai metallized surface and impress ing the design appearing in intaglio upon said matrix upon plastic glass.

10. The herein described method or art of making photographic screens for half tone work consisting in applying a water insoluble coating to the gelatinous surface of a master plate or screen having therein a multiplicity of minute surface formations, thereafter superimposing upon said water insoluble surface a superficial coating of an electro-conductive material, forming a matrix by the electro-deposition of copper upon said electro-conductive surface and impressing the design appearing in intaglio on said matrix upon plastic material.

11. The herein described method or art of-making photographic screens for half tone work consisting in applying a water insoluble coating to the gelatinous surface of a master plate or screen having thereon a multiplicity of minute formations, there-- after applying a metallic solution to said coating, precipitating the metal of said solution, forming a matrix by the electrodeposition of copper upon said metallized surface and impressing the design appear ing in intaglio upon said matrix upon plastic glass.

12. The herein described method or art of making photographic screens for half tone work consisting in applying a water insoluble coating to the gelatinous surface of a master plate orscreen having thereon a multiplicity of minute formations, thereafter applying an ammoniacal solution of nitrate of silver to said coating, precipitating the silver of said solution, forming a matrix by the electro-deposition of copper upon said metallized surface and impressing the design appearing in intaglio upon said matrix upon plastic glass.

13. The herein described method or art of making photographic screens for half tone work consisting in applying a coating of celluloid in solution to the gelatinous surface of a master plate or screen having thereon a multiplicity of minute formations whereby a water insoluble surface is formed, there It witness whereof I hereunto aflix my after applying an ammoniacal solution of signature in the presence of two subscribing 10 nitrate of silver to said coating, preeipitatwitnesses this 11th day of February, 1916.

ing the silver of. said solution forming a 4 matrix by the electro-depositioii of copper HARRY CORBETT upon said metallize l surface and impress- Witnesses:

ing the design appearing in intaglio upon JUDITH PARDEE,

said matrix upon plastic glass. I CLARIOE FRANGK.