US2145996A - Process of producing a screened work copy of an original to be reproduced - Google Patents

Process of producing a screened work copy of an original to be reproduced Download PDF

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Publication number
US2145996A
US2145996A US147675A US14767537A US2145996A US 2145996 A US2145996 A US 2145996A US 147675 A US147675 A US 147675A US 14767537 A US14767537 A US 14767537A US 2145996 A US2145996 A US 2145996A
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United States
Prior art keywords
negative
continuous
tone
screened
original
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US147675A
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Schupp Wilhelm
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PAUL A HENNIG
SYDNEY KOPPEL
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PAUL A HENNIG
SYDNEY KOPPEL
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Priority to US147675A priority Critical patent/US2145996A/en
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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F5/00Screening processes; Screens therefor

Definitions

  • the main or-screenednegative generally 18 not have well defined dotsfthe shadow dots (in.
  • the lightest portions of the negative must be essentially larger than normally usual and the lights (the darkest portions of the negative) must be closed a little more than in case of screened 2o negatives hitherto used in the chemigraphy.
  • the lights shall have only a delicateblackening; but within the range of this delicate blackening the lights must have an extremely high contrast.
  • This result is obtained by very short exposure of a sensitive film, the index of gradation .of which is very high (steep characteristic curve), and by utilizing a developer which automatically limits the blackening within the lightest portions.
  • the second continuous-tone negative is ob? tained from a sensitive film with a mean or less high index of gradation; whereby the film is highly super-exposed and developed by a develop er which also limits the blackening automatically.
  • the screened work copy may I. i. be produced in the following manner:
  • the three negatives an unexposed sensi-- tive film are superimposed so that in the direction of the printing light the films are lying behind each other in the sequence: first continu ous-tone negative, screened negative, second continuous-tone negative, unexposed film. Thereafter the unexposed film is exposed through the three negatives. The second continuous-tone negative is removed and the exposure repeated.
  • the twice exposed film is then developed, fixed.
  • the quality of the reproduction essentially depends upon the corrective efllciencyof the second continuous-tone negative, which controls the tone or tint values y es comprises producing a main or screened negof the screened negative'within the shadows and which therefore is responsiblefor the production of well defined contours particularly between such portions and points of the reproduction which highly contrast with each other.
  • this second continuous-tone negative it'is therefore to be considered that besides limiting the blackening the creation of light courts or halos is carefully avoided.
  • the production of the second negative is essentially simplified thereby that for its developing a developer is used which is composed of an aqueous solution of pyrocatechin and an aqueous solution of alkali carbonate (potash, sodium carbonate or mixtures thereof).
  • a developer which is composed of an aqueous solution of pyrocatechin and an aqueous solution of alkali carbonate (potash, sodium carbonate or mixtures thereof).
  • alkali carbonate potassium, sodium carbonate or mixtures thereof.
  • I have i. i. obtained very satisfying results by using a developer composed of practically equal parts ofa solution of about 5 g. pyrocatechin in 1000 ccm. water and of a solution of about 40 g. 25 potash in 1000 ccm. water.
  • the quantity of pyrocatechin in the first solution and the quantity of potash in the second solution may be varied withincertain limits. In any case, how ever, it is recommendable'to maintain the rela tion 5:40 between pyrocatechin and potash.
  • the developer is not stable; it decomposes after about 10 minutes.
  • - copy or an original to be reproduced which process comprises producing a main or screened negative of said original having the shadow dots thereon larger than normal and the lights closed more than normal, subjecting a sensitive film ,to a very short exposure to produce a first continuous-tone negative of said original, developing and fixing said negative in a developer composed of substan-v tially equal parts of a solution or 5 g. pyrocatechin in 1000 ccm. of water and a solution 01-40 g. potash in 1000 ccm. of water, subjecting a second sensitive film to high over-exposure to produce a second continuous-tone negative of said original,
  • the process for producing a screened work copy of an original to be reproduced comprises preparing a main or screened negativehaving the shadow dots thereon larger than normal and the lights closed more than normal,

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)

Description

Patented Feb. 7,1939- PATENT OFFICE ri'cocass or raonucme a scaannnn .womr corr or AN oamnnn To an PRODUCED Wilhelm SchIlIlP,
Berlin, Germany one-third to Paul A. Hennlg, Hohokna, N. 1.; and one-third to Sydney Kopp New Ifork,
No Drawing. Application June 11, 1937,
Serial No. 14'L675 4 Claims. (01. 95-5).
For reproducing'black-white drawings, pictures etc. I have already proposed to use a positive or negative screened work copy of the originalwhich copy is photographically transferred to a print- 5 ing plate and whicli'has been obtained by the aid of a screened negative and two continuous-tone negatives; the continuous-tone negatives serve as controlling means and compensate the flattening of the tint values due to the subdivision of the screened negative into dots. Inthis process films are preferably used assensitive carriers.
With regard to the three mentioned negatives the following conditions are to be considered. The main or-screenednegative generally 18 not have well defined dotsfthe shadow dots (in.
the lightest portions of the negative) must be essentially larger than normally usual and the lights (the darkest portions of the negative) must be closed a little more than in case of screened 2o negatives hitherto used in the chemigraphy.
In the first continuous-tone negative the lights shall have only a delicateblackening; but within the range of this delicate blackening the lights must have an extremely high contrast. This result is obtained by very short exposure of a sensitive film, the index of gradation .of which is very high (steep characteristic curve), and by utilizing a developer which automatically limits the blackening within the lightest portions. The second continuous-tone negative is ob? tained from a sensitive film with a mean or less high index of gradation; whereby the film is highly super-exposed and developed by a develop er which also limits the blackening automatically.
From the three negatives thus obtained the screened work copy may I. i. be produced in the following manner:
The three negatives an unexposed sensi-- tive film are superimposed so that in the direction of the printing light the films are lying behind each other in the sequence: first continu ous-tone negative, screened negative, second continuous-tone negative, unexposed film. Thereafter the unexposed film is exposed through the three negatives. The second continuous-tone negative is removed and the exposure repeated.
The twice exposed film is then developed, fixed.
toned down, until the highest lights are free from dots, and finally treated by means of an intensifier, so that the finest dots are suillciently covered or blackened for the purpose of printing.
In the described method the quality of the reproduction essentially depends upon the corrective efllciencyof the second continuous-tone negative, which controls the tone or tint values y es comprises producing a main or screened negof the screened negative'within the shadows and which therefore is responsiblefor the production of well defined contours particularly between such portions and points of the reproduction which highly contrast with each other. In producing this second continuous-tone negative it'is therefore to be considered that besides limiting the blackening the creation of light courts or halos is carefully avoided.
I have found that the production of the second negative is essentially simplified thereby that for its developing a developer is used which is composed of an aqueous solution of pyrocatechin and an aqueous solution of alkali carbonate (potash, sodium carbonate or mixtures thereof). As such adeveloper not only avoids the creation of halos but also limits the blackening of the negative, it can also be'utilized with great advantage. for developing the first continuous-tone negative which controls the tone or tint values of the screened negative within the lights.
I have i. i. obtained very satisfying results by using a developer composed of practically equal parts ofa solution of about 5 g. pyrocatechin in 1000 ccm. water and of a solution of about 40 g. 25 potash in 1000 ccm. water. The quantity of pyrocatechin in the first solution and the quantity of potash in the second solution may be varied withincertain limits. In any case, how ever, it is recommendable'to maintain the rela tion 5:40 between pyrocatechin and potash.
It is to be considered that the developer is not stable; it decomposes after about 10 minutes.
. Therefore it is n that the developer is What I claim is:
1. The process for producing a screened work copy of an original to be reproduced; which proc- 40 ative of said original having. the shadow dots thereon vlarger than normal and the fights closed more than normal, subjecting a sensitive film to a very short exposure to produce a first continuous-tone negative of said original, developing and fixing said first continuous-tone negative in a developer composed of an aqueous solution of pyrosensitive film to high over-exposure to produce a second continuous-tone negative of said original, developing and fixing said last mentioned negative, and superimposing the three negatives upon a sensitive film and exposing the negatives upon said sensitive film. v
2. The process for producing a screened work I.
- catechin and an alkali carbonate, subjecting a; r
- copy or an original to be reproduced, which process comprises producing a main or screened negative of said original having the shadow dots thereon larger than normal and the lights closed more than normal, subjecting a sensitive film ,to a very short exposure to produce a first continuous-tone negative of said original, developing and fixing said negative in a developer composed of substan-v tially equal parts of a solution or 5 g. pyrocatechin in 1000 ccm. of water and a solution 01-40 g. potash in 1000 ccm. of water, subjecting a second sensitive film to high over-exposure to produce a second continuous-tone negative of said original,
developing and fixing said last mentioned negative, and superimposing the three negatives upon j a sensitive film and exposing the negatives upon said sensitive film.
3. The process for producing a screened work copy of an original to be reproduced, which proc-' ess comprises preparing a main or screened negativehaving the shadow dots thereon larger than normal and the lights closed more than normal,
" subjecting asensitive film to very short exposure to produce a first continuous-tone negative wherein the lights have a delicate blackening, de-
, veloping and fixing said continuous-tone nega tive, preparing a second continuous-tone'nega tive by over-exposing a sensitive film, developing and fixing the second continuous-tone negative in a developer composed of an aqueous solution of pyrocatechin and an alkali carbonate, super imposing the three negatives thus produced up n normal and the lights closed more than normal,
subjecting a sensitive film to very short exposure to produce a first continuous-tone negative wherein the lights have a delicate blackening, developing and fixing said continuous-tone negative, preparing a second continuous-tone negative by over-exposing a sensitive film, developing and fixing the second continuous-tone negative in a developer essentially comprising substantially equal parts of a solution of 5 g. pyrocatechin in 1000 com. 01 water and a solution of 40 g. potash in 1000 com. or water, superimposing the three negatives thus produced upon an unexposed film,
with the screened negative intermediate the continuous-tone negatives, exposing the unexposed film through the superimposed negatives, removing the second continuous-tone negative and again exposing the superimposed negatives, de-
veloping, fixing and toning down the twice exposed film. I
WILHELM SCHUPP.
US147675A 1937-06-11 1937-06-11 Process of producing a screened work copy of an original to be reproduced Expired - Lifetime US2145996A (en)

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