CA1084338A - Halftone printing process and halftone offset printing press plates - Google Patents
Halftone printing process and halftone offset printing press platesInfo
- Publication number
- CA1084338A CA1084338A CA268,738A CA268738A CA1084338A CA 1084338 A CA1084338 A CA 1084338A CA 268738 A CA268738 A CA 268738A CA 1084338 A CA1084338 A CA 1084338A
- Authority
- CA
- Canada
- Prior art keywords
- plate
- parts
- printing
- halftone
- dot area
- 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.)
- Expired
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M1/00—Inking and printing with a printer's forme
- B41M1/10—Intaglio printing ; Gravure printing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M1/00—Inking and printing with a printer's forme
- B41M1/02—Letterpress printing, e.g. book printing
- B41M1/04—Flexographic printing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M1/00—Inking and printing with a printer's forme
- B41M1/06—Lithographic printing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M3/00—Printing processes to produce particular kinds of printed work, e.g. patterns
- B41M3/008—Sequential or multiple printing, e.g. on previously printed background; Mirror printing; Recto-verso printing; using a combination of different printing techniques; Printing of patterns visible in reflection and by transparency; by superposing printed artifacts
-
- 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
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Printing Methods (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Halftone printing is carried out by printing a first impression in entirety with a solid density of good render-ability from the middle-tone part to the light-tone part in a printed matter and printing at least a second im-pression, superposed over the first impression, with a printing plate lightly and supplementarily expressing only the parts of high dot density of the printed matter. A set of press plates for carrying out this printing process is also provided. A set of plates includes a first plate which has been contact photoprinted with a screened film made from a transparent or reflecting original and at least a second plate adapted to express somewhat lightly and supplementarily only parts of high dot densities (%) of the first plate. If desired a third plate can be used to express more lightly than the second plate and supplementarily only parts of higher dot densities (%) of the second plate.
Halftone printing is carried out by printing a first impression in entirety with a solid density of good render-ability from the middle-tone part to the light-tone part in a printed matter and printing at least a second im-pression, superposed over the first impression, with a printing plate lightly and supplementarily expressing only the parts of high dot density of the printed matter. A set of press plates for carrying out this printing process is also provided. A set of plates includes a first plate which has been contact photoprinted with a screened film made from a transparent or reflecting original and at least a second plate adapted to express somewhat lightly and supplementarily only parts of high dot densities (%) of the first plate. If desired a third plate can be used to express more lightly than the second plate and supplementarily only parts of higher dot densities (%) of the second plate.
Description
33i~
This invention re:Lates generaLly to halftone printing and more particularly to a novel halftQne printing process which can be readily prac-ticed in a simple and economical manner without requiring skilled operators to produce printed impressions having density ranges substantially equal to those of photographs. The invention also relates to advanced halftone offset machine plated or press plates which can be produced from halftone positives or halftone negatives for offset, letterpress, or gravure printing, and which produce printed impressions of density curves substantially corresponding to those of photographs.
Heretofore, the so-called "conventional" process, wherein variations in density are produced by the sizes of the halftone dots, has been generally ` ` practiced as a halftone printing process. In representing tone in this con-ventional process, however, the regions in the vicinity of the smallest dots and the largest dots of the halftone dots are often neglected with respect to `~ the techniques of photography and printing, and the highlight parts (small dot parts) and shadow parts (large dot parts) of the printed matter tend to become flat, whereby the maximum density cannot be elevated to that of a photo-graph.
For the purpose of overcoming this difficulty, the so-called "duotone"
process was developed. By this duotone process, the halftone dot angle is changed so as to prevent moiré from being produced. By this process, however, in spite of some improvement in the highlight parts of the printed matter3 ~ density gradation for representing the shadow parts, which occupy a wide - density range, is deficient, and it is not possible to fully represent tone.
Another known process is the complementary color process, in which color density is corrected by superimposing a light-color plate. By this process, also, while the tone of the color is somewhat corrected~ density gradation for representing the shadow parts of the printed matter is deficient - and is not sufficient for representing tone.
~' 43;3~ :
s In this representation of t~ne by combination with ~ight color, it is very difficult to predict beforehand the tone of the finished printed im-pression. For this reason, this is often carried out in the proof stage, and several dot angles which will not give rise to moire must be determined. At the same time, because of the difficulty of the work and the complex nature of `~ the work process, an extremely high degree of technical skill is required.
Moreover, work over a long period is necessary, and much material must also be used.
i It would appear that representation of the shadow part on the printed matter occupying a wide density range by expanding the density range is possible by increasing the ink film thickness. However, as a result of a general behavior of a printing ink, which is one kind of fluid, when the ink film thickness, that is, the solid density, is reduced, the dimensions of the dots produced by the transfer of the ink tend to undergo an overall shrinkage, whereas, when the ink film thickness, that is, the solid density, is increased, the sizes of the dots produced by the ink transfer tend to undergo an overall increase .
Consequently, when the solid density is lowered to reduce the si3e of the dots, the entire impression becomes of light color~ and the tone becomes weakO
Conversely, when the solid density is raised to increase the siæe of the dots, the entire impression becomes dark, and the tone becomes strong. As a result~
` the dot gain approaches a fill-in state, or fill in occurs, giving rise to blotching of the print~ loss of the tone render-ability~ and overall darkening.
The tone renderability for every percentage of dot density is influenced by the ink film thickness, that is, the solid density, and the ;
reproduction of the overall tone is determined by the accuracy of reproduci-bility of the individual dots. That is~ the to~e reproducibility of a printed impression depends on the accuracy of reproducibility of the size of the dots and the thickness of the ink film transferred onto these dots. This is true
This invention re:Lates generaLly to halftone printing and more particularly to a novel halftQne printing process which can be readily prac-ticed in a simple and economical manner without requiring skilled operators to produce printed impressions having density ranges substantially equal to those of photographs. The invention also relates to advanced halftone offset machine plated or press plates which can be produced from halftone positives or halftone negatives for offset, letterpress, or gravure printing, and which produce printed impressions of density curves substantially corresponding to those of photographs.
Heretofore, the so-called "conventional" process, wherein variations in density are produced by the sizes of the halftone dots, has been generally ` ` practiced as a halftone printing process. In representing tone in this con-ventional process, however, the regions in the vicinity of the smallest dots and the largest dots of the halftone dots are often neglected with respect to `~ the techniques of photography and printing, and the highlight parts (small dot parts) and shadow parts (large dot parts) of the printed matter tend to become flat, whereby the maximum density cannot be elevated to that of a photo-graph.
For the purpose of overcoming this difficulty, the so-called "duotone"
process was developed. By this duotone process, the halftone dot angle is changed so as to prevent moiré from being produced. By this process, however, in spite of some improvement in the highlight parts of the printed matter3 ~ density gradation for representing the shadow parts, which occupy a wide - density range, is deficient, and it is not possible to fully represent tone.
Another known process is the complementary color process, in which color density is corrected by superimposing a light-color plate. By this process, also, while the tone of the color is somewhat corrected~ density gradation for representing the shadow parts of the printed matter is deficient - and is not sufficient for representing tone.
~' 43;3~ :
s In this representation of t~ne by combination with ~ight color, it is very difficult to predict beforehand the tone of the finished printed im-pression. For this reason, this is often carried out in the proof stage, and several dot angles which will not give rise to moire must be determined. At the same time, because of the difficulty of the work and the complex nature of `~ the work process, an extremely high degree of technical skill is required.
Moreover, work over a long period is necessary, and much material must also be used.
i It would appear that representation of the shadow part on the printed matter occupying a wide density range by expanding the density range is possible by increasing the ink film thickness. However, as a result of a general behavior of a printing ink, which is one kind of fluid, when the ink film thickness, that is, the solid density, is reduced, the dimensions of the dots produced by the transfer of the ink tend to undergo an overall shrinkage, whereas, when the ink film thickness, that is, the solid density, is increased, the sizes of the dots produced by the ink transfer tend to undergo an overall increase .
Consequently, when the solid density is lowered to reduce the si3e of the dots, the entire impression becomes of light color~ and the tone becomes weakO
Conversely, when the solid density is raised to increase the siæe of the dots, the entire impression becomes dark, and the tone becomes strong. As a result~
` the dot gain approaches a fill-in state, or fill in occurs, giving rise to blotching of the print~ loss of the tone render-ability~ and overall darkening.
The tone renderability for every percentage of dot density is influenced by the ink film thickness, that is, the solid density, and the ;
reproduction of the overall tone is determined by the accuracy of reproduci-bility of the individual dots. That is~ the to~e reproducibility of a printed impression depends on the accuracy of reproducibility of the size of the dots and the thickness of the ink film transferred onto these dots. This is true
- 2 -- :
~8~33~3 , not only with monochrome processes but also with color processes.
It is an object of this invention to provide a halftone printing process by which the density range of the conventional printed impression is L enlarged, and printed impressions substantially identical to photographs can be obtained.
More specifically, an object of the invention is to provide a half-tone printing process by which printed impressions wherein the density tone gradation is rich, and the tone is substantially the same as that of a photo-graph can be printed in an efficient and simple manner.
It is another object of this invention to provide a set of halftone offset press plates capable of printing, in a simple manner with high work efficiency, printed matter of rich density gradation and excellent tone similar - to that of photographs.
The halftone printing process according to this invention comprises a first process step in which a first impression is printed in entirety with a solid density of good renderability from the middle-tone part to the light~
tone part in an original and at least one second process step in which - printing is carried out in superposition over the first impression with a printing plate lightly and supplementarily expressing only the parts of high dot area %J also referred to hereinafter as dot density, of said origlnal.
The apparatus of the invention consists of a set of halftone offset ;
press plates comprising a first plate which has been contact photoprinted with a screened film made from a transparent or reflecting original and at least a second plate adapted to express somewhat lightly and supplementarily only -; parts of high dot area % of said first plate, said plates being used to print superposed impressions to form a final printed matter.
By the practice of the halftone printing process according to this -~ invention~ printing is carried out in entirety in a manner to make possible .
~ faithful expression of density tone gradation from middle parts through light .' .
~ ~ 3 -:~
.-' ` --33~
parts, which has heretofore been possible, by means of an ordinary printing plate produced by contact printing a halftone screened film made from a trans-parent or reflection original copy, and superposed printing is carried out with a printing plate in which only the parts of high dot density, which have discontinuity or poor rendering, are further lightly and supplementarily ex-pressed, whereby the density tone gradation of only the parts of high dot density can be compensated for without disturbing the tone from the middle parts through the bright parts.
Since this supplementary or compensating printing is carried out with almost no variation of the solid density and with the use of a printing plate in which only the parts of high dot density are lightly and supplement-arily expressed, that is, a plate in which the area of the dots is reduced in comparison with that of a plate for overall printing, printing is possible without density curve discontinuity, moreover, with only the simple procedure of matching the register marks, and without the occurrence of moire'. Thus, an advantageous feature of this invention is that, since moire'is prevented from occurring excellent impressions can be obtained without the necessity of printing with varied dot angle.
In the use of the abovementioned set of press plates, a first im-pression is printed by means of the first plate and then at least one impression is printed by means of the second plate in superposition over the first impression only at the parts thereof ranging from middle-tone parts through shadow parts, more specifically, parts of densities above 50~. Moreover, since the corresponding dot parts of the second plate are somewhat lightly and supplementarily expressed, the density range is expanded in the shadow parts of the printed matter, and a printed matter of good tone can be printed by merely aligning the register marks and printing ~th ink of the same density.
For this reason, there is no necessity for adjustment of dot angle of screen in order to prevent moire'. Furthermore, special skills such as that for re--~ .
- .
- ~8~338 touching are not necessary, and printed matter of a width of density gradation and expanse of the density region of the same order as those of phokographs can be simply and econon~cally obtained, e~cellent renderability being posi-tively attainable at the same time.
Other advanatages and features will be more clearly apparent ~rom the following detailed description.
~ In the drawings:
``` Figure 1 is a graph indicating variation of density relative to screen dot density or screen percentage (%) of printed matter printed by the ~ ;
process and plates of this invention; and ~ -Figure 2 is a graph indicating variation of density relative to - screen dot density or screen percentage (%) of printed matter printed by plates after the second plate.
In accordance with this invention, in a first printing step, printing is first carried out with solid density such as to obtain a printed matter in which the middle part to the light part, that iS9 the part of a dot density less than 50 percent, is as close as possible to at least the theoretical value of the density curve. The plate (first plate) used in this step must not be one in which 10% of the dots appear to have disappeared, and 90% are filled in as in an ordinary plate, but must be one which has been faithfully reproduced.
- Preferably, the printing is carried out in a manner such that the parts of ` dot density less than 80% are faithfully reproduced. -These techniques have been established in the prior art and may be - practiced by ordinary methods.
:-~
In the case where the number of screen lines is relatively coarse, and it is desired to impart forceful intensity in the region from the middle - part through the dark part, an increase in the size of the dots up to appro~i-mately ~20% is permissible.
In a second printing step following the abovedescribed first printing .
~8~33t3 step, printing is carried out by means of a second pla~e in which only the parts of dot density above 50%, preferably above 70% and more preferably only the parts of` high dot density above 90% are supplementarily expressed. A
plate which is supplemen~arily expressecl with a dot density above any poin~
?~ as a starting point may be used provided that the parts are of this dot de~sity above 50%.
In this second printing step, an impression with intensity can be prlnted by superimposed impressions with a printing plate in which only the parts above 70% are supplementarily expressed, and the density range can be expanded to that similar to a photograph with a printing plate in which only the parts above 90% are supplementarily expressed.
In this second printing step, furthermore, the printed dots are somewhat smaller in area (i.e., expressed somewhat lightly) than the dots in the first printing step in the corresponding parts, and, for this reason, a break or discontinuity in the density curve is not observable. Furthermore, it becomes possible to print with the ink density maintained constant.
While the first press plate of this invention is of a construction similar to that of a press plate of the ordinary conventional process, it differs in that it is a plate wherein the parts thereof of high dot density, e.g., over 90%, and parts thereof of low dot density, e.g., less than 10%, are not neglected but are expressed. Ordinarily, since parts of a film screen of dot density over 90~ are difficult to express on the printed matter~ it is a common practice not to form dots in these partsO In accordance with this invention, however, formation of solid parts of this character are avoided as much as possible in the first plate.
The selection of the plate material of this first plate is not limited in this invention, it being possible to use plates for ~inc plates, aluminum plates, PS plates, deep-etch plates, and the like. In the case where the first plate is to be produced from a screen positive film, a plate material .~ ' ~8~33~
for screen positive use is used. For producing the ~irst plate from a screen negative film, a plate material for screen negative use is used.~ Accordingly, in the preparation of the press plates (including the first and second plates and others,if necessary) according to this invention, either a positive or a negative screen film can be used.
The second plate differs from the first plate in that it is a plate somewhat lightly and supplementarily expressing only the parts of high dot ,- ~
density of the first plate. That is, this second plate prints only the middle-tone parts to be shadow parts in the printed matter. When the first and second plates are compared, it is observed that the parts in ~hich dots are formed of the second plate are more restricted than those of the first plate.
; More than two second printing steps can be carried out. For example, -~ in the case of two second printing steps, the second impression of the second - printing step is made with a plate on which is lightly expressed only the part ` of dot density higher than that expressed at the time of the first impression of the second printing step. For example, in the case where the first impres-;- sion of the second step has been made with a dot density higher than 70% as , . . .
the starting point, the second impression can be made with a dot density ~ higher than 80% as the starting point. In the case of more than 90% as the - 20 starting point in the first impression, the second impression can be made with ~ more than 95% as the starting point.
- Use of two or more of the second printing step in this manner pro-, . . .
duces a greater intensity, and printing of a density range equivalent to that of a photograph can be accomplished.
It is not necessary in all cases to use two or more second printing steps as described above. For example, when a solid density of 1.5 or higher - value is produced in the first printing step, and a solid density of the same or higher value is produced in the second printing step, a very good printed matter is obtained, although it is not so good as compared with the case where .
"~
i ` ' ' ~ . .: . ~. : . '. . ' ~84~8 ' two or more second printing steps are used.
In this case, furthermore7 by using a plate which lightly expresses the dots in only the parts above 80% in the second printing step and increasing the solid density thereby to produce in the maximum density part a density close to that in the case where two or more second printing steps are used, a result which is closer to the theoretical value than to the density curve of - a paper print photograph is obtained.
Thus, the number of second printing steps and the values of the solid density and the dot density to be used as the starting point in the supplementary expression of the plate are determined by the character and use of the printed material to be thus obtained and are not basically limited in the practice of this invention.
- ; For example~ when-the difficulties of trapping and offsetting are considered, a method wherein two or more second printing steps are not used in a multicolor press or a web offset printing press may be a desirable mode ~- of practice in that it affords economy in labor cost, materials cost, and production cost and speed up of the production process.
One or more plates similar to the second plate can be usedO Tha*
is, for example, a third plate in which only the parts of high dot density of the dot formed parts of the second plate are expressed somewhat more lightly than in the second plate can be used. In the case where parts of dot densi-- ties above 70% are expressed on the second plate, the third plate is prefer-ably one on which parts of dot densities above 80% are expressed more lightly than on the second plate. In this case, the printed matter will become one having a forceful appearance.
In the case where the second plate expresses the parts of dot densi- -- ties above 90%, a third plate expressing only parts of dot densities above 95%
more lightly than the second plate can be used.
The second plate~ third plate, etc., can elevate the density from _ ~ _ ~ ., , ::.: , . .. . .
33~3 ~`
the middle-tone parts to the dark parts of the printed matter ~ithout disturb-ing the expression of the tone of the entire printed matter, particularly from the middle-tone parts to be light parts, in conventional offset printing, in ~hich the density cannot be elevated l~ithout disturbance of the tone due to dot gain of the printed matter. The reason for this is that the second plate, third plate, etc., express supplementarily only the parts of high dot density which parts, moreover, are lightly expressed.
The method of producing the press plates of this invention, basically, is not ljmited. For example, on the first plate, a halftone negative or a halftone positive is produced from a transparent or reflecting original by applying a screen to a negative or a positive film similarly as in the ordin-- ary method. Any film can be used provided that it is one for screen use - Furthermore,t~e kind of screen, basically, is not limited. For example, a con~act screen or a glass screen can be used. Screens of 65~ 85, 100, 110, 120, 133, 150, 175, 200, 250, 300, etc., lines per 2.54 cm. (1 inch) can be used depending on the necessity.
` For exposure, a flash is additionally used, care being taken to obtain all dots from minimum dots to maximum dots without om~ssion. The dots particularly in the shadow parts in the halftone positive, that is, dots above 90%, must not be filled in. In the case of a halftone negative, conversely to the case of a halftone positive, the film is expressed without disappearance of the highlight parts below 10~.
Photoprinting is carried out by placing in a printing frame a plate blank which has been gr~ined and has been sensitized with the film and pri~ g by vacuum contact. For the light source, an ordinary arc lamp, a mercury lamp - or the like is used.
Each of the plates after the second plate or third plate can also be produced by making a screened film, similarly as in the case of the first plate,from a transparent or reflecting original and contact printing on a plate blank.
- g _ '~:``' ' : ' .
33t3 It is necessary, ho~iever, that this screened film be one which lightly and " supplementarily expresses only the middle-tone parts to the dark parts (pre-ferably dot densities above 50~ with a halftone positive and dot densities below 5~ Wit~l a halftone negative) on the printed matter of the plate subse-quent to the first plate or the second plate.
In the case of a halftone positive from a screened film made from a transparent or a reflecting original, the plate after the second or third plate can be produced by varying the exposure time only on parts of high dot density (parts of low dot density in the case of a halftone negative) in the lQ scraening process step to produce the screened film and carrying out printed therewith. `
, Furthermore, pre-ss plates of a number of steps can also be produced from a screened film made from a transparent or reflecting original by direct contact printing by varying the exposure time. By using an arc lamp, a mercury lamp or the like as the light source, and effecting control with the exposure time, light distance and the developing time, it is possible to produce the plates after the second plate or the third plate for supplementarily expressing only the parts of high dot density of the printed mat~er.
In each of these methods of producing the plates, a halftone positive~
~o or a halftone negative for, for example, offset, letterpress, or gravure can be used.
The sequence in which the first and second printing steps are carried ; out can be selected at will.
For example, the printing may be carried out from the third plate or it may be carried out from the second plate, the printing order being select-able at will.
The halftone printing process according to this invention is applic-able not only to offset printing but also to various other halftone printing processes such as letterpress printing and gravure printing, and the resulting _ 10 --' :~'. , ~¢~8~3~3 printed matter cannot only be used ~s an ordinary printed matter but also be substituted for a real photograph by printing on paper. ~or example, the resulting printed matter can be used as a transparency for display by illumi~
nation from the reverse side, IYhich was not possible with a conventional printed matter.
; In accordance with this invent;ion, it is possible to supplementarily express up to the darkest parts without disturbing the tone of the entire impression, to expand the density range, to attain the density of an original ` paper print photograph (reflection orginal copy) and, in some cases, to attain lo or exceed the highest density of an original positive film (transparent COpy) - More specifically, solid densities of 1.30 to 1.65 with yellow, 2.05 to 2.17 with magenta, 2.05 to 2.17 with cyan, 2.10 to 2.30 with black, and 2~30 compos-itely can be attained or even exceeded in some cases, and densities measured as transparent densities can reach or exceed in some cases the highest density of an original positive film and can exceed the highest density of an original paper print photograph.
Furthermore, in the second printing step, the density of the parts in which moire'can occur is very low, and, moreover, the dot area is smaller than that of the corresponding parts in the first prin~ing step. Therefor~, by accurately matching register marks, the occurrence of moire-can be prevented. -In parts where the dot density is higher than 90~ in the first printing step, no moire, whatsoever, is observable.
- By the practice of this invention, the density curves of the tones to be reproduced can be varied almost at will, and impressions exactly as desired can be obtainedO
` In order to indicate more fully the nature and utility of this in-vention, the following examples of practice thereof are set forth, it being understood that these examples are presented as being illustrative only and are not intended to limit the scope of the invention.
,, :~89L~3~
Examples Printing impressions were made by the process of this invention, and the densities ~rith respect to their dot densities were measured. Each printing plate was made by using a 150/2.54-cm. screen. The results were as shown in the follo~ring table.
In the following table, the reference character A designates an impression or printed matter in the case wherein it is printed by the above described first printing step, with the first plate, and the reference characters B, C7 and D designate impressions or printed matter in the case wherein they are printed by the abovedescribed second printing process, with s second, third and fourth plates respectively. Furthermore, the combined designation A+B, for example, denotes an Lmpression or printed matter printed by printing B in superposition on A. In other words A+B is printed super-posedly by the first and second plates. The same applies to other combined designations A~C, A~BtC, A~C~D, and B~C.
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~ r~ Cr~ r~ r~ Cr~ Cr~ r~ ~ r~ ~ r~ r~ r~ ~ r~ ~I (r~ r~ Cr~ Cr~ r~ r1 r . ' O O O O O O O OO O O OO O O C~ O O O O O O O
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r~ r;~ r~ r~ r~ ~ r~
p h f~ 1~
p ~ ¢ ~¢ ~ ¢
¢ ¢ ¢ ~¢ ¢ ~ ~ ~ ¢ ~ ¢ ~
r1 c~ ~~ U) ~D 1~ 0 a) O r~ In r~ ~ r~ r~ r~ r1 C~ f.
~` ' :~ -- 13 --:` ' .
:'`: : ' ~ ` , :L~8~338 ~hen these results are plotted as a graphical representation, they become as shown in Figure 1. ~y the practice of the process and by the use of the press plates according to this invention, the density range is expanded in comparison with that heretofore attainable, and the density curve is simi-- lar in shape to that of the theoretical density curve of the positive film, from ~hich it is apparent that the renderability is better than that known } heretofore. In this graph, the shaded region represents the middle-tone parts ofthe printed matter or impression, and ~A+C+D) printed with the use of the ~` press plates of the invention exhibits a dot gain which is less than that of t 10 conventional printing, indicating that good printing has been achieved. In particular (A+C~D) has no dot gain in the middle parts in comparison with those of conventional printing.
Figure 2 is a graph showing density curves of impressions or printed ~ ;
matter printed bytheprinting of only the second printing step of this in-r vention. There are shown the density curves for plates B and C together with the curve for plates B~C. From this5 it will be apparent that B has been printed with 63% as the starting point, C with 80%, and D with 95~.
~, . : ' . .
.. ~ . . . .
.. . . ...
~8~33~3 , not only with monochrome processes but also with color processes.
It is an object of this invention to provide a halftone printing process by which the density range of the conventional printed impression is L enlarged, and printed impressions substantially identical to photographs can be obtained.
More specifically, an object of the invention is to provide a half-tone printing process by which printed impressions wherein the density tone gradation is rich, and the tone is substantially the same as that of a photo-graph can be printed in an efficient and simple manner.
It is another object of this invention to provide a set of halftone offset press plates capable of printing, in a simple manner with high work efficiency, printed matter of rich density gradation and excellent tone similar - to that of photographs.
The halftone printing process according to this invention comprises a first process step in which a first impression is printed in entirety with a solid density of good renderability from the middle-tone part to the light~
tone part in an original and at least one second process step in which - printing is carried out in superposition over the first impression with a printing plate lightly and supplementarily expressing only the parts of high dot area %J also referred to hereinafter as dot density, of said origlnal.
The apparatus of the invention consists of a set of halftone offset ;
press plates comprising a first plate which has been contact photoprinted with a screened film made from a transparent or reflecting original and at least a second plate adapted to express somewhat lightly and supplementarily only -; parts of high dot area % of said first plate, said plates being used to print superposed impressions to form a final printed matter.
By the practice of the halftone printing process according to this -~ invention~ printing is carried out in entirety in a manner to make possible .
~ faithful expression of density tone gradation from middle parts through light .' .
~ ~ 3 -:~
.-' ` --33~
parts, which has heretofore been possible, by means of an ordinary printing plate produced by contact printing a halftone screened film made from a trans-parent or reflection original copy, and superposed printing is carried out with a printing plate in which only the parts of high dot density, which have discontinuity or poor rendering, are further lightly and supplementarily ex-pressed, whereby the density tone gradation of only the parts of high dot density can be compensated for without disturbing the tone from the middle parts through the bright parts.
Since this supplementary or compensating printing is carried out with almost no variation of the solid density and with the use of a printing plate in which only the parts of high dot density are lightly and supplement-arily expressed, that is, a plate in which the area of the dots is reduced in comparison with that of a plate for overall printing, printing is possible without density curve discontinuity, moreover, with only the simple procedure of matching the register marks, and without the occurrence of moire'. Thus, an advantageous feature of this invention is that, since moire'is prevented from occurring excellent impressions can be obtained without the necessity of printing with varied dot angle.
In the use of the abovementioned set of press plates, a first im-pression is printed by means of the first plate and then at least one impression is printed by means of the second plate in superposition over the first impression only at the parts thereof ranging from middle-tone parts through shadow parts, more specifically, parts of densities above 50~. Moreover, since the corresponding dot parts of the second plate are somewhat lightly and supplementarily expressed, the density range is expanded in the shadow parts of the printed matter, and a printed matter of good tone can be printed by merely aligning the register marks and printing ~th ink of the same density.
For this reason, there is no necessity for adjustment of dot angle of screen in order to prevent moire'. Furthermore, special skills such as that for re--~ .
- .
- ~8~338 touching are not necessary, and printed matter of a width of density gradation and expanse of the density region of the same order as those of phokographs can be simply and econon~cally obtained, e~cellent renderability being posi-tively attainable at the same time.
Other advanatages and features will be more clearly apparent ~rom the following detailed description.
~ In the drawings:
``` Figure 1 is a graph indicating variation of density relative to screen dot density or screen percentage (%) of printed matter printed by the ~ ;
process and plates of this invention; and ~ -Figure 2 is a graph indicating variation of density relative to - screen dot density or screen percentage (%) of printed matter printed by plates after the second plate.
In accordance with this invention, in a first printing step, printing is first carried out with solid density such as to obtain a printed matter in which the middle part to the light part, that iS9 the part of a dot density less than 50 percent, is as close as possible to at least the theoretical value of the density curve. The plate (first plate) used in this step must not be one in which 10% of the dots appear to have disappeared, and 90% are filled in as in an ordinary plate, but must be one which has been faithfully reproduced.
- Preferably, the printing is carried out in a manner such that the parts of ` dot density less than 80% are faithfully reproduced. -These techniques have been established in the prior art and may be - practiced by ordinary methods.
:-~
In the case where the number of screen lines is relatively coarse, and it is desired to impart forceful intensity in the region from the middle - part through the dark part, an increase in the size of the dots up to appro~i-mately ~20% is permissible.
In a second printing step following the abovedescribed first printing .
~8~33t3 step, printing is carried out by means of a second pla~e in which only the parts of dot density above 50%, preferably above 70% and more preferably only the parts of` high dot density above 90% are supplementarily expressed. A
plate which is supplemen~arily expressecl with a dot density above any poin~
?~ as a starting point may be used provided that the parts are of this dot de~sity above 50%.
In this second printing step, an impression with intensity can be prlnted by superimposed impressions with a printing plate in which only the parts above 70% are supplementarily expressed, and the density range can be expanded to that similar to a photograph with a printing plate in which only the parts above 90% are supplementarily expressed.
In this second printing step, furthermore, the printed dots are somewhat smaller in area (i.e., expressed somewhat lightly) than the dots in the first printing step in the corresponding parts, and, for this reason, a break or discontinuity in the density curve is not observable. Furthermore, it becomes possible to print with the ink density maintained constant.
While the first press plate of this invention is of a construction similar to that of a press plate of the ordinary conventional process, it differs in that it is a plate wherein the parts thereof of high dot density, e.g., over 90%, and parts thereof of low dot density, e.g., less than 10%, are not neglected but are expressed. Ordinarily, since parts of a film screen of dot density over 90~ are difficult to express on the printed matter~ it is a common practice not to form dots in these partsO In accordance with this invention, however, formation of solid parts of this character are avoided as much as possible in the first plate.
The selection of the plate material of this first plate is not limited in this invention, it being possible to use plates for ~inc plates, aluminum plates, PS plates, deep-etch plates, and the like. In the case where the first plate is to be produced from a screen positive film, a plate material .~ ' ~8~33~
for screen positive use is used. For producing the ~irst plate from a screen negative film, a plate material for screen negative use is used.~ Accordingly, in the preparation of the press plates (including the first and second plates and others,if necessary) according to this invention, either a positive or a negative screen film can be used.
The second plate differs from the first plate in that it is a plate somewhat lightly and supplementarily expressing only the parts of high dot ,- ~
density of the first plate. That is, this second plate prints only the middle-tone parts to be shadow parts in the printed matter. When the first and second plates are compared, it is observed that the parts in ~hich dots are formed of the second plate are more restricted than those of the first plate.
; More than two second printing steps can be carried out. For example, -~ in the case of two second printing steps, the second impression of the second - printing step is made with a plate on which is lightly expressed only the part ` of dot density higher than that expressed at the time of the first impression of the second printing step. For example, in the case where the first impres-;- sion of the second step has been made with a dot density higher than 70% as , . . .
the starting point, the second impression can be made with a dot density ~ higher than 80% as the starting point. In the case of more than 90% as the - 20 starting point in the first impression, the second impression can be made with ~ more than 95% as the starting point.
- Use of two or more of the second printing step in this manner pro-, . . .
duces a greater intensity, and printing of a density range equivalent to that of a photograph can be accomplished.
It is not necessary in all cases to use two or more second printing steps as described above. For example, when a solid density of 1.5 or higher - value is produced in the first printing step, and a solid density of the same or higher value is produced in the second printing step, a very good printed matter is obtained, although it is not so good as compared with the case where .
"~
i ` ' ' ~ . .: . ~. : . '. . ' ~84~8 ' two or more second printing steps are used.
In this case, furthermore7 by using a plate which lightly expresses the dots in only the parts above 80% in the second printing step and increasing the solid density thereby to produce in the maximum density part a density close to that in the case where two or more second printing steps are used, a result which is closer to the theoretical value than to the density curve of - a paper print photograph is obtained.
Thus, the number of second printing steps and the values of the solid density and the dot density to be used as the starting point in the supplementary expression of the plate are determined by the character and use of the printed material to be thus obtained and are not basically limited in the practice of this invention.
- ; For example~ when-the difficulties of trapping and offsetting are considered, a method wherein two or more second printing steps are not used in a multicolor press or a web offset printing press may be a desirable mode ~- of practice in that it affords economy in labor cost, materials cost, and production cost and speed up of the production process.
One or more plates similar to the second plate can be usedO Tha*
is, for example, a third plate in which only the parts of high dot density of the dot formed parts of the second plate are expressed somewhat more lightly than in the second plate can be used. In the case where parts of dot densi-- ties above 70% are expressed on the second plate, the third plate is prefer-ably one on which parts of dot densities above 80% are expressed more lightly than on the second plate. In this case, the printed matter will become one having a forceful appearance.
In the case where the second plate expresses the parts of dot densi- -- ties above 90%, a third plate expressing only parts of dot densities above 95%
more lightly than the second plate can be used.
The second plate~ third plate, etc., can elevate the density from _ ~ _ ~ ., , ::.: , . .. . .
33~3 ~`
the middle-tone parts to the dark parts of the printed matter ~ithout disturb-ing the expression of the tone of the entire printed matter, particularly from the middle-tone parts to be light parts, in conventional offset printing, in ~hich the density cannot be elevated l~ithout disturbance of the tone due to dot gain of the printed matter. The reason for this is that the second plate, third plate, etc., express supplementarily only the parts of high dot density which parts, moreover, are lightly expressed.
The method of producing the press plates of this invention, basically, is not ljmited. For example, on the first plate, a halftone negative or a halftone positive is produced from a transparent or reflecting original by applying a screen to a negative or a positive film similarly as in the ordin-- ary method. Any film can be used provided that it is one for screen use - Furthermore,t~e kind of screen, basically, is not limited. For example, a con~act screen or a glass screen can be used. Screens of 65~ 85, 100, 110, 120, 133, 150, 175, 200, 250, 300, etc., lines per 2.54 cm. (1 inch) can be used depending on the necessity.
` For exposure, a flash is additionally used, care being taken to obtain all dots from minimum dots to maximum dots without om~ssion. The dots particularly in the shadow parts in the halftone positive, that is, dots above 90%, must not be filled in. In the case of a halftone negative, conversely to the case of a halftone positive, the film is expressed without disappearance of the highlight parts below 10~.
Photoprinting is carried out by placing in a printing frame a plate blank which has been gr~ined and has been sensitized with the film and pri~ g by vacuum contact. For the light source, an ordinary arc lamp, a mercury lamp - or the like is used.
Each of the plates after the second plate or third plate can also be produced by making a screened film, similarly as in the case of the first plate,from a transparent or reflecting original and contact printing on a plate blank.
- g _ '~:``' ' : ' .
33t3 It is necessary, ho~iever, that this screened film be one which lightly and " supplementarily expresses only the middle-tone parts to the dark parts (pre-ferably dot densities above 50~ with a halftone positive and dot densities below 5~ Wit~l a halftone negative) on the printed matter of the plate subse-quent to the first plate or the second plate.
In the case of a halftone positive from a screened film made from a transparent or a reflecting original, the plate after the second or third plate can be produced by varying the exposure time only on parts of high dot density (parts of low dot density in the case of a halftone negative) in the lQ scraening process step to produce the screened film and carrying out printed therewith. `
, Furthermore, pre-ss plates of a number of steps can also be produced from a screened film made from a transparent or reflecting original by direct contact printing by varying the exposure time. By using an arc lamp, a mercury lamp or the like as the light source, and effecting control with the exposure time, light distance and the developing time, it is possible to produce the plates after the second plate or the third plate for supplementarily expressing only the parts of high dot density of the printed mat~er.
In each of these methods of producing the plates, a halftone positive~
~o or a halftone negative for, for example, offset, letterpress, or gravure can be used.
The sequence in which the first and second printing steps are carried ; out can be selected at will.
For example, the printing may be carried out from the third plate or it may be carried out from the second plate, the printing order being select-able at will.
The halftone printing process according to this invention is applic-able not only to offset printing but also to various other halftone printing processes such as letterpress printing and gravure printing, and the resulting _ 10 --' :~'. , ~¢~8~3~3 printed matter cannot only be used ~s an ordinary printed matter but also be substituted for a real photograph by printing on paper. ~or example, the resulting printed matter can be used as a transparency for display by illumi~
nation from the reverse side, IYhich was not possible with a conventional printed matter.
; In accordance with this invent;ion, it is possible to supplementarily express up to the darkest parts without disturbing the tone of the entire impression, to expand the density range, to attain the density of an original ` paper print photograph (reflection orginal copy) and, in some cases, to attain lo or exceed the highest density of an original positive film (transparent COpy) - More specifically, solid densities of 1.30 to 1.65 with yellow, 2.05 to 2.17 with magenta, 2.05 to 2.17 with cyan, 2.10 to 2.30 with black, and 2~30 compos-itely can be attained or even exceeded in some cases, and densities measured as transparent densities can reach or exceed in some cases the highest density of an original positive film and can exceed the highest density of an original paper print photograph.
Furthermore, in the second printing step, the density of the parts in which moire'can occur is very low, and, moreover, the dot area is smaller than that of the corresponding parts in the first prin~ing step. Therefor~, by accurately matching register marks, the occurrence of moire-can be prevented. -In parts where the dot density is higher than 90~ in the first printing step, no moire, whatsoever, is observable.
- By the practice of this invention, the density curves of the tones to be reproduced can be varied almost at will, and impressions exactly as desired can be obtainedO
` In order to indicate more fully the nature and utility of this in-vention, the following examples of practice thereof are set forth, it being understood that these examples are presented as being illustrative only and are not intended to limit the scope of the invention.
,, :~89L~3~
Examples Printing impressions were made by the process of this invention, and the densities ~rith respect to their dot densities were measured. Each printing plate was made by using a 150/2.54-cm. screen. The results were as shown in the follo~ring table.
In the following table, the reference character A designates an impression or printed matter in the case wherein it is printed by the above described first printing step, with the first plate, and the reference characters B, C7 and D designate impressions or printed matter in the case wherein they are printed by the abovedescribed second printing process, with s second, third and fourth plates respectively. Furthermore, the combined designation A+B, for example, denotes an Lmpression or printed matter printed by printing B in superposition on A. In other words A+B is printed super-posedly by the first and second plates. The same applies to other combined designations A~C, A~BtC, A~C~D, and B~C.
'' :- ~ ,' ' : ... :.. ,, ` , .. '. ' ' ~n ~
33~3 .
U) ~ ~ r~ r~ ~ ~ r~ ~ ~ ~ O C~ O u~
~ i i; r;r~ riri c~ r;r;r;r; ~ iri ri r; ,i,i ~
a) I~ ~ o ~, ~D ~5, 0 G~) r~ O a~ cc) ~ 0 o ,~ 9 ~ ~ O
,~, a ,_i,i ,; ,; ,;,;,; ,; ,~ ,j,j,; ~ C`l C`; C`i r-i r;r;ri r; r;r-i r~ ~i ri ri ri ri d~ ~ r~ ~ cn o a~ ~ U) 1~ t- ~n ,~ o o r~) d ~ o o u) ~ ,~ u) oo ,~ rl C-, i ri ri ri ri ri ri r;~i ri ri ri ~ C`l C~ i r; ri ri ri ri ri ri O ri ~--1 ri ri ri ~ ~ 9 1~ C~ r~ 1~ 0rl ~) r~U) 1~ 0 0 ~C) 5) r~ O ~ ~ O d- U) C~ 10 O ~ ~ ~ a o o o ~ ~~ ~ ~ ~ r~
ri O O O ri ri r,i ri ri ri ri ri ri r; r; ri ri ri ri ri r; Fi r~ O O O O O O
~ ~ tO OD r~ OO ~D OD ~cr) d- r~ r~ ~ r~ r') O 1~ C~3 0 ~9 ~ d ~ D
" ~ ri O O O O O O O ri ri ri ri ri r~ ri ri O O O O O O O O I O O O O
o o u) c~ ~~ ~) r~ O O O O O
r~ O O O O O O OO O O OO O O O O O O O O O O O O O O O
h ~" - ,1 ~ ~ o c~ d ~1~ O d~ d~~5) cn GO Cl~ r~ ~ o ~ r~
o ~ Do ~
O o o o o o o oo o o oo o o o o o O O O O O O O O O O
, O O O O O O O OO O O OO O O O O O O O O O O
i, O O O O O O O OO O O OO O O O O O O O O O O
- h C~> o 1~ C~ O c~ O r~ ~ O CSl ao r~ O
O O O O O O O O O O O O O O O O O O O O O O O
~ o o o o o o o oo o o oo o o o o o o o o o o f. ~ O C~i r~ r1 r~ r~ r~ r~ r~ l C`l C~l C`l C~ l rl r~ r~ r~ r~ ~I r~
,.- O O O O O O O OO O O OO O O O O O O O O O O
~ r~ Cr~ r~ r~ Cr~ Cr~ r~ ~ r~ ~ r~ r~ r~ ~ r~ ~I (r~ r~ Cr~ Cr~ r~ r1 r . ' O O O O O O O OO O O OO O O C~ O O O O O O O
U~ o o o o o o o o o o o o o o o o o o o o o o o OooO ~ooO Oooo oooo oooo ooo o o o o o o o o o o o o o o o o o o o o o o o O o o o o o o o o o o o o o o o o o o o o o o .
r~ r;~ r~ r~ r~ ~ r~
p h f~ 1~
p ~ ¢ ~¢ ~ ¢
¢ ¢ ¢ ~¢ ¢ ~ ~ ~ ¢ ~ ¢ ~
r1 c~ ~~ U) ~D 1~ 0 a) O r~ In r~ ~ r~ r~ r~ r1 C~ f.
~` ' :~ -- 13 --:` ' .
:'`: : ' ~ ` , :L~8~338 ~hen these results are plotted as a graphical representation, they become as shown in Figure 1. ~y the practice of the process and by the use of the press plates according to this invention, the density range is expanded in comparison with that heretofore attainable, and the density curve is simi-- lar in shape to that of the theoretical density curve of the positive film, from ~hich it is apparent that the renderability is better than that known } heretofore. In this graph, the shaded region represents the middle-tone parts ofthe printed matter or impression, and ~A+C+D) printed with the use of the ~` press plates of the invention exhibits a dot gain which is less than that of t 10 conventional printing, indicating that good printing has been achieved. In particular (A+C~D) has no dot gain in the middle parts in comparison with those of conventional printing.
Figure 2 is a graph showing density curves of impressions or printed ~ ;
matter printed bytheprinting of only the second printing step of this in-r vention. There are shown the density curves for plates B and C together with the curve for plates B~C. From this5 it will be apparent that B has been printed with 63% as the starting point, C with 80%, and D with 95~.
~, . : ' . .
.. ~ . . . .
.. . . ...
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A halftone printing process comprising a first process step in which a first impression is printed in entirety with a solid density of good renderability from the middle-tone part to the light-tone part in an original and at least one second process step in which printing is carried out in superposition over the first impression with a printing plate lightly and supplementar-ily expressing only the parts of high dot area % of said original.
2. A halftone printing process as claimed in claim 1 in which the first impression is printed in a manner such that the parts of dot area % less than 50% are faithfully reproduced and print-ing in the second printing step is carried out by means of a second plate in which only the parts of dot area % above 50% are supplementarily expressed.
3. A halftone printing process as claimed in claim 2 in which the second step is made with a dot area % above 70% as the start-ing point and further a second impression is said step is carried out, said impression being made with a dot area % above 80% as the starting point.
4. A halftone printing process as claimed in claim 2 in which the second step is made with a dot area % above 90% as the start-ing point and further a second impression in said step is carried out, said impression being made with a dot area % above 95% as the starting point.
5. A halftone printing process as claimed in any one of claims 1 to 3 in which the sequence in which the first and second print-ing steps are carried out can be selected at will.
6. A set of halftone offset press plates comprising a first plate which has been contact photoprinted with a screened film made from a transparent or reflecting original and at least a second plate adapted to express somewhat lightly and supplemen-tarily only parts of high dot area % of said first plate, said plates being used to print superposed impression to form a final printed matter.
7. A set of halftone offset press plates as claimed in claim 6 in which the parts of said first plate of high dot area % of the order of 90% and higher and parts thereof of low area % of the order of 10% and lower are not neglected but are expressed, and said second plate is adapted to print only middle-tone parts to the shadow parts of the original, having dots in only parts of dot area % higher than 50%.
8. A set of halftone offset press plates as claimed in claim 7 in which parts of dot area % above 70% of the original are expres-sed on the second plate, and there is further provided a third plate on which parts of dot area % above 80% are expressed more lightly than on the second plate.
9. A set of halftone offset press plates as claimed in claim 7 in which parts of dot area % above 90% of the original are expres-sed on the second plate, and there is provided a third plate on which parts of dot area % above 95% are expressed more lightly than on the second plate.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP156,913/1975 | 1975-12-26 | ||
JP156,912/1975 | 1975-12-26 | ||
JP15691275A JPS5280908A (en) | 1975-12-26 | 1975-12-26 | Halfftone printing method |
JP15691375A JPS5280903A (en) | 1975-12-26 | 1975-12-26 | Halfftone offset plate |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1084338A true CA1084338A (en) | 1980-08-26 |
Family
ID=26484538
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA268,738A Expired CA1084338A (en) | 1975-12-26 | 1976-12-24 | Halftone printing process and halftone offset printing press plates |
Country Status (7)
Country | Link |
---|---|
CA (1) | CA1084338A (en) |
CH (1) | CH614160A5 (en) |
DE (1) | DE2658277C3 (en) |
GB (1) | GB1565380A (en) |
HK (1) | HK68780A (en) |
IT (1) | IT1065739B (en) |
NL (1) | NL172524C (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5742047A (en) * | 1980-08-28 | 1982-03-09 | Toppan Printing Co Ltd | Halftone gravure plate making method |
GB8802274D0 (en) * | 1988-02-02 | 1988-03-02 | Spectrum Arts Ltd | Paintings |
DE4427403A1 (en) * | 1994-08-03 | 1996-08-22 | Bse Printtechnologie | Method for colour offset printing |
ES2119529T3 (en) * | 1996-04-19 | 1998-10-01 | Schablonentechnik Kufstein Ag | HALF-TONE TEMPLATE, AS WELL AS A PROCEDURE AND DEVICE FOR ITS MANUFACTURE. |
-
1976
- 1976-12-17 GB GB5288376A patent/GB1565380A/en not_active Expired
- 1976-12-21 CH CH1613976A patent/CH614160A5/en not_active IP Right Cessation
- 1976-12-22 DE DE19762658277 patent/DE2658277C3/en not_active Expired
- 1976-12-24 NL NL7614404A patent/NL172524C/en not_active IP Right Cessation
- 1976-12-24 CA CA268,738A patent/CA1084338A/en not_active Expired
- 1976-12-24 IT IT3085476A patent/IT1065739B/en active
-
1980
- 1980-12-04 HK HK68780A patent/HK68780A/en unknown
Also Published As
Publication number | Publication date |
---|---|
CH614160A5 (en) | 1979-11-15 |
IT1065739B (en) | 1985-03-04 |
NL172524C (en) | 1983-09-16 |
DE2658277A1 (en) | 1977-07-14 |
HK68780A (en) | 1980-12-12 |
GB1565380A (en) | 1980-04-16 |
NL7614404A (en) | 1977-06-28 |
DE2658277C3 (en) | 1980-05-08 |
DE2658277B2 (en) | 1979-08-23 |
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