GB2120805A - Contact halftone screen - Google Patents
Contact halftone screen Download PDFInfo
- Publication number
- GB2120805A GB2120805A GB08314470A GB8314470A GB2120805A GB 2120805 A GB2120805 A GB 2120805A GB 08314470 A GB08314470 A GB 08314470A GB 8314470 A GB8314470 A GB 8314470A GB 2120805 A GB2120805 A GB 2120805A
- Authority
- GB
- United Kingdom
- Prior art keywords
- halftone screen
- square
- combined contact
- film
- contact halftone
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F5/00—Screening processes; Screens therefor
- G03F5/14—Screening processes; Screens therefor by contact methods
Abstract
The screen is formed by a sheet, preferably a film,comprising a system of opaque and transparent, substantially square-shaped dots in chess board arrangement. In each opaque dot is a substantially centrally situated transparent circle occupying substantially 5% of the area of the associated square-shaped dot. The screen is prepared photographically. <IMAGE>
Description
SPECIFICATION
Combined contact halftone screen
The invention relates to a combined contact halftone screen for printing and the structure ofthe printing dot for breaking up black and white and colour pictures into individual printing elements.
Combined contact halftone screens are used for obtaining reproductions in the printing industry in offset printing, i.e. printing from a planographic surface by way of a rubber-blanketed cylinder, and in letterpress, i.e. vertical printing, where the picture is created by a combination of individual printing elements Known kinds of halftone screens operate with printing elements which are sometimes elliptical or circular, but mostly square-shaped. Special halftone screens are also used with different patterns and structures such as textile imitation and the like.
Halftone screens are divided into positive and negative and according to the number of dots (lines) per 1 cm into screens with 25, 40, 48, 54, 60, 70, 80 and more dots (lines). Recently also twin halftone screens with adjacent dots ofdifferentsize are made, in order to obtain improvement in the transmission of the largest amount of information from the original for reproduction. Halftone screens of conventional type with square-shaped printing elements (dots) arranged in the form of a chess board are predominantly used. In these halftone screens the densest part of the printing element (dot) is its central part (core) and the density decreases towards the borders (fringe area). When the said halftone screen is used, the shape of the printing element is visible on the print.If details have to be clearly shown halftone screens with a density above 54 dots per 1 cm have to be used, requiring a printing paper of high quality with a very smooth surface, and a further drawback is the possibility of clogging. If a halftone screen with more than 60 dots per 1 cm is used, the contrast is reduced and printing becomes more demanding.
The aim ofthe invention is to avoid, or at least to mitigate these drawbacks.
The aim ofthe invention isto avoid, or at least mitigate these drawbacks.
The invention provides a combined contact halftone screen formed by a sheet comprising a system of opaque and transparent, substantially square-shaped dots in chess board arrangement, in each opaque dot being a substantially centrally situated transparent circle occupying substantially 5% of the area of the associated square-shaped dot. In a preferred embodimentthe sheet is a film or foil.
The invention also relates to a method of manufacture of said combined contact halftone screen wherein a first image, consisting of black and white squares of equal size in chess board arrangement, is exposed on to afilm,then a second image, consisting of black circles of equal size the area of whichis substantially 5% ofthe area of one said square, is superexposed on to said film such that one said black circle is situated substantially in the centre of each wide square, whereuponthefilm is developed and fixed.
The invention will now be described, by way of example, with referenceto the accompanying diagrammatic drawings, in which:~
Figure A shows a conventional square-shaped black dot,
Figure B shows a square-shaped black dot accord ing to the invention, Figure C is a detail of a picture with a straight-line border between a bright and dark surface,
Figure D shows a conventional contact halftone screen, Figure E shows the border of FigureCphoto- graphed through the screen shown in D,
Figure F is identical to Figure C,
Figure G shows a combined contact halftone screen according to the invention, and
Figure H shows the border of F photographed through the screen in Figure G.
The combined contact halftone printing screen expresses better the sharpness ofthe printing dots and the surface of reproduced pictures is more perfect, with a higher marginal sharpness and better design. In colour and black and white reproductions it increases the contrast and quality even when printing on a material of poor quality. A more extensive application of colour is enabled in the course of printing. The combined contact halftone screen is commonly used for printing techniques offset and letterpress. It is particularly advantageous for electronic scanning devices. The printing dot offers a considerable effect for gigantography, as for instance for advertisements, posters and the like. By the use of the combined contact halftone screen the quality of pictures in newspapers and periodicals is substantially improved.
Claims (6)
1. A combined contact halftone screen, formed by a sheet comprising a system of opaque and transparent, substantially square-shaped dots in chess board arrangement, in each opaque dot being a substantially centrally situated transparent circle occupying sub stantially 5% of the area of the associated square shaped dot.
2. Ascreen according to Claim 1, wherein the sheet is a film orfoil.
3. A combined contact halftone screen constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, Figures B, G and H of the accompanying drawings.
4. A method of manufacture of a combined contact halftone screen, wherein a first image, consisting of black and white squares of equal size in chess board arrangement, is exposed on to a film, then a second image consisting of black circles of equal size the area of each of which is substantially 5% of the area of one of said square, is superexposed on to said film such that one said black circle is situated substantially in the centre of each white square, whereupon the film is developed and fixed.
5. A method of manufacture of a combined contact halftone screen substantially as herein described with reference to Figures B, G and H of the accompanying drawing.
6. A combined contact halftone screen made by a method according to Claim 4 or 5.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CS823943A CS247260B1 (en) | 1982-05-28 | 1982-05-28 | Contact combined autotype network-raster |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8314470D0 GB8314470D0 (en) | 1983-06-29 |
| GB2120805A true GB2120805A (en) | 1983-12-07 |
| GB2120805B GB2120805B (en) | 1986-02-12 |
Family
ID=5380976
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08314470A Expired GB2120805B (en) | 1982-05-28 | 1983-05-25 | Contact halftone screen |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5957241A (en) |
| CH (1) | CH655190A5 (en) |
| CS (1) | CS247260B1 (en) |
| DE (1) | DE3302061A1 (en) |
| GB (1) | GB2120805B (en) |
| IT (2) | IT1161568B (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE958529C (en) * | 1955-06-23 | 1957-02-21 | Herbst & Illig | Contact grid |
| DE3220711C2 (en) * | 1982-06-02 | 1984-06-28 | Schumacher Kg, 6000 Frankfurt | Printing forme set for autotypical full-color image printing |
-
1982
- 1982-05-28 CS CS823943A patent/CS247260B1/en unknown
-
1983
- 1983-01-22 DE DE19833302061 patent/DE3302061A1/en active Granted
- 1983-01-24 CH CH371/83A patent/CH655190A5/en not_active IP Right Cessation
- 1983-02-08 IT IT19485/83A patent/IT1161568B/en active
- 1983-02-08 IT IT8320737U patent/IT8320737V0/en unknown
- 1983-02-14 JP JP58021748A patent/JPS5957241A/en active Pending
- 1983-05-25 GB GB08314470A patent/GB2120805B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3302061A1 (en) | 1983-12-01 |
| IT1161568B (en) | 1987-03-18 |
| JPS5957241A (en) | 1984-04-02 |
| IT8319485A0 (en) | 1983-02-08 |
| CH655190A5 (en) | 1986-03-27 |
| IT8320737V0 (en) | 1983-02-08 |
| GB8314470D0 (en) | 1983-06-29 |
| DE3302061C2 (en) | 1988-05-11 |
| GB2120805B (en) | 1986-02-12 |
| IT8319485A1 (en) | 1984-08-08 |
| CS247260B1 (en) | 1986-12-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |