CA2377050A1 - Form of a printing element in an offset printing process - Google Patents
Form of a printing element in an offset printing process Download PDFInfo
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- CA2377050A1 CA2377050A1 CA002377050A CA2377050A CA2377050A1 CA 2377050 A1 CA2377050 A1 CA 2377050A1 CA 002377050 A CA002377050 A CA 002377050A CA 2377050 A CA2377050 A CA 2377050A CA 2377050 A1 CA2377050 A1 CA 2377050A1
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- printing element
- printing
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- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
- B41N1/00—Printing plates or foils; Materials therefor
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- General Physics & Mathematics (AREA)
- Printing Methods (AREA)
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Abstract
The form of the printing element differs within a report format surface. All printing elements of a printing dot have all around straight sides which hav e different lengths and encompass different sized angles. The clearings betwee n adjacent printing elements have a constant width around a printing element. Due to said geometric arrangement of multishaped printing elements, namely polygons, straight lines are always obtained in any given printing dot regardless of their direction on the surface. Moiré effects are also prevent ed in four-color printing.
Description
The invention relates to a form for a printing element which is one of a plurality of printing elements, separated from one another all round by lands, on a printing unit in an offset printing process such as, in particular, rotary offset printing, s the printing element being in each case of a geometric, polygonal shape.
Since printing surface production began there has been a desire in the case of the offset printing process not to use photomechanical screens and instead to imitate the old, to unscreened lithography or at least to achieve the closest possible approach to it. With the development of photolithography it became increasingly clear that though printing of relatively high quality could be obtained with screens of conventional design, it was not possible to imitate i5 the old lithographic prints. Photomechanical screens, such as the gradar screen or magenta screen for example, were very good for the recently developed photolithography and also for printing surface production but screens of this type do suffer from certain technical shortcomings such as line breakdowns, 2o moire patterns, secondary moire patterns and rosetting. There is still a desire for lithography of the original kind, that is to say printing from stone, without a screen and with the only grain being that of the surface of the stone, to be made possible as a printing element for offset printing.
2s Consequently, the first very general aim exists of producing unscreened lithographs. The first idea was to use the colour grain of a transparency as a basis and to separate out this granulation by means of colour separation and use it as a printing element. This attempt failed due to the inadequacies of 3o the photographic materials used. Some success was achieved with computer programs and PostScript page-description programs.
However since these screening programs are subject to a controlled randomness generator, there is the problem that, the finer the resolution of the units selected, the more difficult it is to calculate the particular gradation curve. Because of this problem screens of this type - such as the Cristall, Diamond or Harlequin HD screens - are not suitable for rotary s newspaper printing presses.
A return had to be made to conventional screening for offset printing. In rotary offset printing, a printing plate is mounted on a cylinder under tension. The cylinder co-operates with a further cylinder covered with a rubber blanket and the to latter co-operates in turn with an impression cylinder over which the paper to be printed on is fed. The printing points on the printing plate are prepared in such a way that they repel water and accept the greasy printing ink. The non-printing points are prepared to have an affinity for water and they repel i5 the greasy printing ink. In printing, the whole of the printing plate is first dampened, when only the non-printing points that have an affinity for water accept the water. The printing plate, which is thus damp in parts, then travels past inking rollers which transfer the grease-containing ink to the points on the 2o printing plate that are not damp. The image to be printed is then transferred to the blanket cylinder and from there to the paper to be printed on.
k' The points in a printed image which are to be inked are split up into printing elements which cannot be seen by the 2s naked eye. Each printing element is separated from the adjoining ones by lands. The lands are not inked. The greater the total area of the lands is at a dot in the image, the lighter the dot appears to be. The proportion that the inked area represents of the total area of a dot in the image defines a grey value, the 3o half-tone value of the dot, and is normally given as a percentage.
By means of a screen having a plurality of printing elements distributed over it, it is possible, by varying the size of the printing elements, to simulate different half-tone values. It is known for the printing elements to take the form of squares, semicircular areas, or elliptical or other geometrical areas. Given the fineness that is possible in s technical terms, the sharpness of the outlines in images has not been entirely satisfactory with the known forms of printing element. This is due to the fact that even when the printing elements are of only medium size, i.e. when the relevant region of the image is of medium half-tone value, there is some join-up io between the dots, thus making the sharpness of outline and the graduations of the shadows in the printed image unsatisfactory.
In the form of printing element that needs to be found, the dot join-up needs to be positioned to the "rear", in the direction where the shadow lies, as far as possible, and it needs to be i5 possible for the new form of printing element to be controlled perfectly via gradation curves.
One solution to this problem is known from the form of printing element detailed in EP A 0 825 490. The imaginary screen cells are arranged in a chessboard pattern and in each of 2o them is a arranged a printing element, so that, if a tonal value, whatever it may be, remains constant across the screen cells, the shortest distance to the adjoining printing element is of at least approximately the same size for all points on the boundary lines of a printing element. In this case the printing 2s element is to have a substantially rhomboid area, the boundary lines of which extend in curves in such a way that they form two diagonally opposed acute angles and two diagonally opposed rounded or obtuse angles.
The advantage that this form of printing element and its 3o arrangement in the screen has is that, purely in theory, join-up between the dots does not take place until a half-tone value of 100%. The only disadvantage of this figuration of printing element is the Moir~ pattern that cannot be avoided in four colour printing. This phenomenon can only be avoided if the printing elements are rotated about their centres from their normal arrangement, which is a very laborious operation in the regulating software. With this form of printing element there is also no way of preventing lines which are straight but run in an oblique direction from being shown not as such but as slightly zigzag lines.
The obj ect on which the invention is based is to develop a new form of printing element with which even sharper to reproduction and even finer, softer graduations in the shadows are possible, but in particular with which Moire patterns can easily be avoided and even oblique straight lines and edges can be reproduced sharply. A way of partly achieving this object has been found in the prior art in the form of the frequency-i5 modulated, or the stochastic, screen. This screen cannot however be used in practice. Only sometimes is the image obtained with this screen very good and very poor image resolution may equally well be obtained so that, as described, this type of screen has, in 'the end, been rejected.
2o To achieve the stated object, provision is made in accordance with the invention for the new printing element to be of a geometrically clearly defined form and to be bounded solely by straight lines, namely by more than six sides in each case.
It is particularly advantageous in this case if all the printing 2s elements in a defined region of a printing dot are different from one another, i.e. if each printing element differs from that adjoining it in respect of its figuration. It is no contradiction of the principle of adjoining printing elements always being different if this defined region, which may for 3o example comprise 15 printing elements of different figurations, is repeated, at the size of a printing dot, in a sort of repeat pattern. The only prerequisite is that here too the adjoining printing element should in each case differ from the previous one. This can for example easily be accomplished if the repeated area occurs again no earlier than after a second, differing printing element.
The printing elements are to be defined by more than six s sides, and preferably by 9 - 11 sides. These sides are also of different lengths and follow on from one another at corners which form an acute or else an obtuse angle. It is even possible for a side of an adjoining printing element to begin at any point along the length of the immediately adjoining side. This to too ensures that the figuration of the printing elements and their distribution over the area of a printing dot are irregular. The individual printing elements should however all have printed areas which are not substantially different from one another in terms of size.
i5 "Printing element" or unscreened printed image is the most suitable term for this type of printing element which in each case differs from its neighbouring elements but is clearly definable in geometrical terms. It can be used to any fineness capable of being calculated and is thus suitable for all offset 2o printing processes from high-quality newspaper printing to high-quality floor-fed printing. For the first time, printing element forms of this type which differ from those in their neighbourhood, hold out the possibility of printing similar to lithography.
2s So that the printed image can have different graduations of lightness, i.e. a varying tonal value, the printing elements need to be separated from the adjoining ones by an area which is not inked. In the layout envisaged by the present idea, these (white) areas are always in the form of lands, in such a way 3o that the printing elements which are arranged next to one another in the screen - without being arranged in a chessboard pattern - are so associated with one another that, at any tonal value, and even when the tonal value varies, the distances between two printing elements, or between a plurality of adjoining straight sides along the length of a side and the next printing element, is constant along the length of the straight side. This arrangement is a prerequisite for dot join-up between s the printing elements which in each case adjoin one another not to occur until a half-tone value of approximately 100%. The result of this arrangement is soft differences in lightness and outlines of optimum sharpness in images.
The present printing elements, which each differ from the to adjoining printing element, are of advantage not only for black and white reproduction in newspaper, web-fed or sheet-fed offset printing but also for four-colour printing. Each printing element in this diversified figuration or even just a specific group of printing elements can be inked in one of the four is colours. No Moir~ pattern is produced in this case nor can any zigzag lines, regardless of inclination or length, be seen.
The diversified forms in a printing element dot according to the invention are shown by way of example in the drawings. In the drawings:
2o Fig.l is a diagrammatic section through the cylinders of a known offset printing unit, Fig.2 is a plan view to a very much enlarged scale of a single complete printing element having a plurality of other printing elements, each of different figurations, surrounding 25 1t, Fig.3 shows a number of printing dots to a somewhat reduced scale, in the repeat area shown in Fig.2 of the same tonal value, Fig.4 shows, to a very much enlarged but smaller scale, a 3o number of printing elements of different sizes, i.e. which are situated at varying distances from one another and are thus of varying tonal value, Fig.5 shows a printing dot similar to that shown in Fig.2 having a larger number of different and in particular complete printing elements within the printing dot, Fig.Sb showing a complete printing element and Fig.5a showing only part of one, s Fig.6 is a view to a reduced scale of a plurality of printing dots in the repeated area in Fig.5, all of the same tonal value, and Fig.7 shows a printing dot following the principle of the invention, but not having one single complete printing element to within the imaginary quadrilateral.
The offset printing unit shown in Fig.l employs a plate cylinder l on which a printing plate 2 is mounted under tension.
Plate cylinder 1 co-operates on the one hand with a blanket cylinder 3 and the latter in turn with an impression cylinder 5 is against which is held a print substrate to be printed on, such as paper 4, and on the other hand with the inking system 6 and damping system 7. The printing ink 60 is transferred to the printing plate 2 by the inking system 6 via a number of pressure rol'ler~s 8. The water 70 is transferred by the damping system 7 2o via a number of further transfer rollers 9. All the rollers and cylinders operate in the opposite direction from one another, as -- is indicated for some of them by the arrows.
The damping system 7 transfers water 70 to non-printing points 10 on the printing plate 2, whereas the printing points 2s 11 on printing plate 2 remain free of water. The damp points 10 repel the printing ink 60 at the points 12 at which contact is made with the contacting pressure rollers 8 while printing points 11 accept the printing ink. The printing ink is then transferred from printing plate 2 to blanket cylinder 3 and 3o there forms inked points 11' which are finally printed onto the print substrate 4. ' The printing points 11 or inked points 11' are printing elements as shown in Figs.2 and 3. They are very small and cannot be distinguished from one another with the naked eye.
Fig.2 is a very much enlarged view of such a printing element in the multi-sided figuration according to the invention, at the centre of a printing dot defined as a repeated area or of an s imaginary quadrilateral. Each printing element, whether the printing element A the whole of whose area is shown in Fig.2 or the peripheral printing elements B to G, are of approximately the same size in the printed area but are each of a basically different figuration. This can be seen from Fig.2, but io particularly from Fig.3 because there all the types of printing element are shown in their whole-area figuration.
Though printing elements A - G each have straight lines of different lengths forming their sides, they are in each case bounded by nine to eleven sides and thus also each have a is plurality of corners each with different included angles of from 40 to 320°. Not only are the printing elements always of the same basic area but the individual ones, which differ from one another, are arranged immediately next to one another in such a way that the distances between given sides and the corresponding 2o sides of whichever are the adjoining printing elements in the given case are always constant. The non-printing lands 18 are always of the same width. This is the prerequisite for avoiding dot join-up even at tonal values which are less than 100%. In the case of printing elements A - G, which are distributed over 2s the area of a printing dot with no regard whatever for a chessboard-type layout, there is never any dot join-up unless the particular printing dot is to be printed absolutely black.
Though each printing element A - G is different from the others and the lands 18 separating them are all of a constant 3o and equal width when the tonal value remains the same, these printing elements A - G are repeated, at the area of a fairly large printing dot, in a repeat the area of which can be seen from Fig.2.
Further to the above, reference should be made to Fig.4, where the printing elements A - G, each of which is different, are shown unchanged but the individual distances between the printing elements, i.e. the lands 18, vary in width over the s area of Fig.4 or of the printing dot. Hence the tonal value varies as well. What is shown becomes lighter towards the bottom of the image. The widening of the lands can take place continuously, as seen at the top, or in fairly large percentage steps, as seen at the bottom. The percentage step in the bottom io part of the image is only fairly large so as to make it more clearly apparent on this scale.
Fig.5 shows better resolution within a printing dot which has a plurality of differently figured complete printing elements A1 - A14 with the imaginary quadrilateral. Within its i5 area, each printing element A1 - A14 has a centre Mp, shown as a white dot, from which lines can be drawn to the corners Ep as shown in Figs.Sa and 5b. The triangles which are produced in each case in this way are not congruent but are always clearly figured as triangles. Working from the centre Mp, which is 2o defined within a printing dot as shown in Fig.S by its co ordinates, the size of the inking area of the printing elements or the width of the lands 18 is determined. Each printing r element A1 - A14 is thus constructed mathematically from its centre Mp.
2s As well as by the complete printing elements as shown in Fig.5b, a printing dot, is also defined by partial printing elements B, C, D, such as the element B shown in Fig.5a whose centre Mp lies on a line belonging to the imaginary quadrilateral. To become a complete printing element B, a 3o partial printing element of this kind pairs off, as shown in Fig.6, with a sister element identified by the same letter at the edge of the adjoining printing dot.
1~
Figs.7a to 7c in turn show another printing element which has a different figuration but where there is no departure from the basic idea underlying the invention. As shown in Fig.7a, a printing dot comprises four partial printing elements M, N, O
s and P whose centres Mp are situated not on a line belonging to the imaginary quadrilateral but at its corners. For this purpose reference should be made to Fig.7b. The polygonal figuration of a printing element having the plurality of corners Ep can be seen in particular from Fig.7c, in which partial printing io elements M, N, O and P are shown turned through 90 ° . As in all the other figurations, the white lines represent the lands 18, which are wider as dictated by the desired tonal value. The figuration of the printing element which is adopted as a principle, with its plurality of sides 18, remains unchanged.
Since printing surface production began there has been a desire in the case of the offset printing process not to use photomechanical screens and instead to imitate the old, to unscreened lithography or at least to achieve the closest possible approach to it. With the development of photolithography it became increasingly clear that though printing of relatively high quality could be obtained with screens of conventional design, it was not possible to imitate i5 the old lithographic prints. Photomechanical screens, such as the gradar screen or magenta screen for example, were very good for the recently developed photolithography and also for printing surface production but screens of this type do suffer from certain technical shortcomings such as line breakdowns, 2o moire patterns, secondary moire patterns and rosetting. There is still a desire for lithography of the original kind, that is to say printing from stone, without a screen and with the only grain being that of the surface of the stone, to be made possible as a printing element for offset printing.
2s Consequently, the first very general aim exists of producing unscreened lithographs. The first idea was to use the colour grain of a transparency as a basis and to separate out this granulation by means of colour separation and use it as a printing element. This attempt failed due to the inadequacies of 3o the photographic materials used. Some success was achieved with computer programs and PostScript page-description programs.
However since these screening programs are subject to a controlled randomness generator, there is the problem that, the finer the resolution of the units selected, the more difficult it is to calculate the particular gradation curve. Because of this problem screens of this type - such as the Cristall, Diamond or Harlequin HD screens - are not suitable for rotary s newspaper printing presses.
A return had to be made to conventional screening for offset printing. In rotary offset printing, a printing plate is mounted on a cylinder under tension. The cylinder co-operates with a further cylinder covered with a rubber blanket and the to latter co-operates in turn with an impression cylinder over which the paper to be printed on is fed. The printing points on the printing plate are prepared in such a way that they repel water and accept the greasy printing ink. The non-printing points are prepared to have an affinity for water and they repel i5 the greasy printing ink. In printing, the whole of the printing plate is first dampened, when only the non-printing points that have an affinity for water accept the water. The printing plate, which is thus damp in parts, then travels past inking rollers which transfer the grease-containing ink to the points on the 2o printing plate that are not damp. The image to be printed is then transferred to the blanket cylinder and from there to the paper to be printed on.
k' The points in a printed image which are to be inked are split up into printing elements which cannot be seen by the 2s naked eye. Each printing element is separated from the adjoining ones by lands. The lands are not inked. The greater the total area of the lands is at a dot in the image, the lighter the dot appears to be. The proportion that the inked area represents of the total area of a dot in the image defines a grey value, the 3o half-tone value of the dot, and is normally given as a percentage.
By means of a screen having a plurality of printing elements distributed over it, it is possible, by varying the size of the printing elements, to simulate different half-tone values. It is known for the printing elements to take the form of squares, semicircular areas, or elliptical or other geometrical areas. Given the fineness that is possible in s technical terms, the sharpness of the outlines in images has not been entirely satisfactory with the known forms of printing element. This is due to the fact that even when the printing elements are of only medium size, i.e. when the relevant region of the image is of medium half-tone value, there is some join-up io between the dots, thus making the sharpness of outline and the graduations of the shadows in the printed image unsatisfactory.
In the form of printing element that needs to be found, the dot join-up needs to be positioned to the "rear", in the direction where the shadow lies, as far as possible, and it needs to be i5 possible for the new form of printing element to be controlled perfectly via gradation curves.
One solution to this problem is known from the form of printing element detailed in EP A 0 825 490. The imaginary screen cells are arranged in a chessboard pattern and in each of 2o them is a arranged a printing element, so that, if a tonal value, whatever it may be, remains constant across the screen cells, the shortest distance to the adjoining printing element is of at least approximately the same size for all points on the boundary lines of a printing element. In this case the printing 2s element is to have a substantially rhomboid area, the boundary lines of which extend in curves in such a way that they form two diagonally opposed acute angles and two diagonally opposed rounded or obtuse angles.
The advantage that this form of printing element and its 3o arrangement in the screen has is that, purely in theory, join-up between the dots does not take place until a half-tone value of 100%. The only disadvantage of this figuration of printing element is the Moir~ pattern that cannot be avoided in four colour printing. This phenomenon can only be avoided if the printing elements are rotated about their centres from their normal arrangement, which is a very laborious operation in the regulating software. With this form of printing element there is also no way of preventing lines which are straight but run in an oblique direction from being shown not as such but as slightly zigzag lines.
The obj ect on which the invention is based is to develop a new form of printing element with which even sharper to reproduction and even finer, softer graduations in the shadows are possible, but in particular with which Moire patterns can easily be avoided and even oblique straight lines and edges can be reproduced sharply. A way of partly achieving this object has been found in the prior art in the form of the frequency-i5 modulated, or the stochastic, screen. This screen cannot however be used in practice. Only sometimes is the image obtained with this screen very good and very poor image resolution may equally well be obtained so that, as described, this type of screen has, in 'the end, been rejected.
2o To achieve the stated object, provision is made in accordance with the invention for the new printing element to be of a geometrically clearly defined form and to be bounded solely by straight lines, namely by more than six sides in each case.
It is particularly advantageous in this case if all the printing 2s elements in a defined region of a printing dot are different from one another, i.e. if each printing element differs from that adjoining it in respect of its figuration. It is no contradiction of the principle of adjoining printing elements always being different if this defined region, which may for 3o example comprise 15 printing elements of different figurations, is repeated, at the size of a printing dot, in a sort of repeat pattern. The only prerequisite is that here too the adjoining printing element should in each case differ from the previous one. This can for example easily be accomplished if the repeated area occurs again no earlier than after a second, differing printing element.
The printing elements are to be defined by more than six s sides, and preferably by 9 - 11 sides. These sides are also of different lengths and follow on from one another at corners which form an acute or else an obtuse angle. It is even possible for a side of an adjoining printing element to begin at any point along the length of the immediately adjoining side. This to too ensures that the figuration of the printing elements and their distribution over the area of a printing dot are irregular. The individual printing elements should however all have printed areas which are not substantially different from one another in terms of size.
i5 "Printing element" or unscreened printed image is the most suitable term for this type of printing element which in each case differs from its neighbouring elements but is clearly definable in geometrical terms. It can be used to any fineness capable of being calculated and is thus suitable for all offset 2o printing processes from high-quality newspaper printing to high-quality floor-fed printing. For the first time, printing element forms of this type which differ from those in their neighbourhood, hold out the possibility of printing similar to lithography.
2s So that the printed image can have different graduations of lightness, i.e. a varying tonal value, the printing elements need to be separated from the adjoining ones by an area which is not inked. In the layout envisaged by the present idea, these (white) areas are always in the form of lands, in such a way 3o that the printing elements which are arranged next to one another in the screen - without being arranged in a chessboard pattern - are so associated with one another that, at any tonal value, and even when the tonal value varies, the distances between two printing elements, or between a plurality of adjoining straight sides along the length of a side and the next printing element, is constant along the length of the straight side. This arrangement is a prerequisite for dot join-up between s the printing elements which in each case adjoin one another not to occur until a half-tone value of approximately 100%. The result of this arrangement is soft differences in lightness and outlines of optimum sharpness in images.
The present printing elements, which each differ from the to adjoining printing element, are of advantage not only for black and white reproduction in newspaper, web-fed or sheet-fed offset printing but also for four-colour printing. Each printing element in this diversified figuration or even just a specific group of printing elements can be inked in one of the four is colours. No Moir~ pattern is produced in this case nor can any zigzag lines, regardless of inclination or length, be seen.
The diversified forms in a printing element dot according to the invention are shown by way of example in the drawings. In the drawings:
2o Fig.l is a diagrammatic section through the cylinders of a known offset printing unit, Fig.2 is a plan view to a very much enlarged scale of a single complete printing element having a plurality of other printing elements, each of different figurations, surrounding 25 1t, Fig.3 shows a number of printing dots to a somewhat reduced scale, in the repeat area shown in Fig.2 of the same tonal value, Fig.4 shows, to a very much enlarged but smaller scale, a 3o number of printing elements of different sizes, i.e. which are situated at varying distances from one another and are thus of varying tonal value, Fig.5 shows a printing dot similar to that shown in Fig.2 having a larger number of different and in particular complete printing elements within the printing dot, Fig.Sb showing a complete printing element and Fig.5a showing only part of one, s Fig.6 is a view to a reduced scale of a plurality of printing dots in the repeated area in Fig.5, all of the same tonal value, and Fig.7 shows a printing dot following the principle of the invention, but not having one single complete printing element to within the imaginary quadrilateral.
The offset printing unit shown in Fig.l employs a plate cylinder l on which a printing plate 2 is mounted under tension.
Plate cylinder 1 co-operates on the one hand with a blanket cylinder 3 and the latter in turn with an impression cylinder 5 is against which is held a print substrate to be printed on, such as paper 4, and on the other hand with the inking system 6 and damping system 7. The printing ink 60 is transferred to the printing plate 2 by the inking system 6 via a number of pressure rol'ler~s 8. The water 70 is transferred by the damping system 7 2o via a number of further transfer rollers 9. All the rollers and cylinders operate in the opposite direction from one another, as -- is indicated for some of them by the arrows.
The damping system 7 transfers water 70 to non-printing points 10 on the printing plate 2, whereas the printing points 2s 11 on printing plate 2 remain free of water. The damp points 10 repel the printing ink 60 at the points 12 at which contact is made with the contacting pressure rollers 8 while printing points 11 accept the printing ink. The printing ink is then transferred from printing plate 2 to blanket cylinder 3 and 3o there forms inked points 11' which are finally printed onto the print substrate 4. ' The printing points 11 or inked points 11' are printing elements as shown in Figs.2 and 3. They are very small and cannot be distinguished from one another with the naked eye.
Fig.2 is a very much enlarged view of such a printing element in the multi-sided figuration according to the invention, at the centre of a printing dot defined as a repeated area or of an s imaginary quadrilateral. Each printing element, whether the printing element A the whole of whose area is shown in Fig.2 or the peripheral printing elements B to G, are of approximately the same size in the printed area but are each of a basically different figuration. This can be seen from Fig.2, but io particularly from Fig.3 because there all the types of printing element are shown in their whole-area figuration.
Though printing elements A - G each have straight lines of different lengths forming their sides, they are in each case bounded by nine to eleven sides and thus also each have a is plurality of corners each with different included angles of from 40 to 320°. Not only are the printing elements always of the same basic area but the individual ones, which differ from one another, are arranged immediately next to one another in such a way that the distances between given sides and the corresponding 2o sides of whichever are the adjoining printing elements in the given case are always constant. The non-printing lands 18 are always of the same width. This is the prerequisite for avoiding dot join-up even at tonal values which are less than 100%. In the case of printing elements A - G, which are distributed over 2s the area of a printing dot with no regard whatever for a chessboard-type layout, there is never any dot join-up unless the particular printing dot is to be printed absolutely black.
Though each printing element A - G is different from the others and the lands 18 separating them are all of a constant 3o and equal width when the tonal value remains the same, these printing elements A - G are repeated, at the area of a fairly large printing dot, in a repeat the area of which can be seen from Fig.2.
Further to the above, reference should be made to Fig.4, where the printing elements A - G, each of which is different, are shown unchanged but the individual distances between the printing elements, i.e. the lands 18, vary in width over the s area of Fig.4 or of the printing dot. Hence the tonal value varies as well. What is shown becomes lighter towards the bottom of the image. The widening of the lands can take place continuously, as seen at the top, or in fairly large percentage steps, as seen at the bottom. The percentage step in the bottom io part of the image is only fairly large so as to make it more clearly apparent on this scale.
Fig.5 shows better resolution within a printing dot which has a plurality of differently figured complete printing elements A1 - A14 with the imaginary quadrilateral. Within its i5 area, each printing element A1 - A14 has a centre Mp, shown as a white dot, from which lines can be drawn to the corners Ep as shown in Figs.Sa and 5b. The triangles which are produced in each case in this way are not congruent but are always clearly figured as triangles. Working from the centre Mp, which is 2o defined within a printing dot as shown in Fig.S by its co ordinates, the size of the inking area of the printing elements or the width of the lands 18 is determined. Each printing r element A1 - A14 is thus constructed mathematically from its centre Mp.
2s As well as by the complete printing elements as shown in Fig.5b, a printing dot, is also defined by partial printing elements B, C, D, such as the element B shown in Fig.5a whose centre Mp lies on a line belonging to the imaginary quadrilateral. To become a complete printing element B, a 3o partial printing element of this kind pairs off, as shown in Fig.6, with a sister element identified by the same letter at the edge of the adjoining printing dot.
1~
Figs.7a to 7c in turn show another printing element which has a different figuration but where there is no departure from the basic idea underlying the invention. As shown in Fig.7a, a printing dot comprises four partial printing elements M, N, O
s and P whose centres Mp are situated not on a line belonging to the imaginary quadrilateral but at its corners. For this purpose reference should be made to Fig.7b. The polygonal figuration of a printing element having the plurality of corners Ep can be seen in particular from Fig.7c, in which partial printing io elements M, N, O and P are shown turned through 90 ° . As in all the other figurations, the white lines represent the lands 18, which are wider as dictated by the desired tonal value. The figuration of the printing element which is adopted as a principle, with its plurality of sides 18, remains unchanged.
Claims (21)
1. Printing element for simulating tonal values on a printing substrate, having a plurality of printing elements distributed over the area of the screen, characterised in that the individual printing element (A - G; A1- A14; M - P) has a geometrically clearly defined form and is bounded by straight lines alone, namely by more than six sides in each case.
2. Printing element according to claim 1, characterised in that the printing element (A - G; A1 - A14; M - P) is bounded by 9 to 11 sides.
3. Printing element according to claim 1 or 2, characterised in that the printing element (A - G; A1 - A14; M - P) is bounded by sides of unequal length.
4. Printing element according to one of the foregoing claims, characterised in that it is a polygon (A - G; A1 - A14;
M - P) with sides of any desired different lengths which meet one another at angles of any desired different sizes.
M - P) with sides of any desired different lengths which meet one another at angles of any desired different sizes.
5. Printing element according to claim 4, characterised in that the angles between the sides at the corners (Ep) of the polygon are between 5° and 175° or at least are not more than 180°.
6. Printing element according to claim 4 or 5, characterised in that sides of a printing element (A - G; A1 - A14; M - P) that meet include first an acute angle and then an obtuse angle.
7. Printing element according to one of the foregoing claims, characterised in that each printing element (A - G; A1 -A14; M - P) differs from the adjoining one in respect of its figuration.
8. Printing element according to one of the foregoing claims, characterised in that only a part (A - D; M - P) of a printing element bounded by a plurality of sides is arranged within an imaginary quadrilateral which represents a printing dot.
9. Printing element according to claim 8, characterised in that the imaginary quadrilateral is filled by only parts (M - P) of a printing element.
10. Printing element according to one of the foregoing claims, characterised in that a printing element (A) bounded completely by sides all round is arranged within the imaginary quadrilateral.
11. Printing element according to claim 10, characterised in that more than one and preferably six printing elements (A1 -A14) bounded completely by sides all round are arranged within the imaginary quadrilateral.
12. Printing element according to one of the foregoing claims, characterised in that the figuration of the always differing printing elements (A - G; A1 - A14; M - P) is repeated as a repeat area (Figs.2, 6) which corresponds to the imaginary quadrilateral.
13. Printing element according to one of claims 10 to 12, characterised in that a printing element (A4, A8) adjoining said complete printing element has at least one boundary edge parallel to the imaginary quadrilateral.
14. Printing element according to one of the foregoing claims, characterised in that one side of an adjoining printing element (A, C) starts along the length of the side of an adjoining printing element (B).
15. Printing element according to one of the foregoing claims, characterised in that the printing areas of all the printing elements (A - G, A1- A14; M - P) are substantially the same despite the fact that their figurations are in each case entirely different from one another.
16. Printing element according to one of the foregoing claims, characterised in that defined in each printing element there is a centre (Mp) whose position within the imaginary quadrilateral does not change when the tonal value changes.
17. Printing element according to claim 16, characterised in that the imaginary lines from the centre (Mp) to the corners (Ep) of the polygon enclose clearly bounded triangles, and the triangles are therefore not congruent.
18. Printing element according to claim 17, characterised in that the centre (Mp) of a printing element is situated on the imaginary line of the quadrilateral (Figs.5a, 7b).
19. Printing element according to one of the foregoing claims, characterised in that the printing elements (A - G; A1 -A14; M - P) which are arranged next to one another in the screen - without being arranged in a chessboard pattern - are so associated with one another that, preferably at any tonal value and even when the tonal value changes, the distances between two adjoining straight sides (18) and the next printing element is constant along the length of the straight sides (18).
20. Printing element according to claim 19, characterised in that the size of the polygon from its centre (Mp) to the corners (Ep) changes regularly as a function of the tonal value being aimed at and at the same time the distances of uniform width to whichever is the adjoining side (18) of the adjoining printing element increase or decrease equally all round.
21. Printing element according to one of the foregoing claims, characterised in that the adjoining printing elements (A
- G; A1 - A14; M - P) which are each created in a different figuration can be inked in any desired colour.
- G; A1 - A14; M - P) which are each created in a different figuration can be inked in any desired colour.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19929904.8 | 1999-06-29 | ||
| DE19929904A DE19929904A1 (en) | 1999-06-29 | 1999-06-29 | Form of a printing element in the offset printing process |
| PCT/EP2000/005662 WO2001000420A1 (en) | 1999-06-29 | 2000-06-20 | Form of a printing element in an offset printing process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2377050A1 true CA2377050A1 (en) | 2001-01-04 |
Family
ID=7913014
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002377050A Abandoned CA2377050A1 (en) | 1999-06-29 | 2000-06-20 | Form of a printing element in an offset printing process |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP1196295B1 (en) |
| CN (1) | CN1365319A (en) |
| AT (1) | ATE236019T1 (en) |
| AU (1) | AU5533800A (en) |
| CA (1) | CA2377050A1 (en) |
| DE (2) | DE19929904A1 (en) |
| RU (1) | RU2002102064A (en) |
| WO (1) | WO2001000420A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8462391B2 (en) | 2009-03-13 | 2013-06-11 | Heidelberger Druckmaschinen Ag | Method for producing a pseudo-stochastic master surface, master surface, method for producing a cylinder cover, cylinder cover, machine processing printing material, method for producing printed products and method for microstamping printing products |
| DE102020128450A1 (en) | 2020-10-29 | 2022-05-05 | Koenig & Bauer Ag | Method of operating an ink jet printing machine |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1382265A (en) * | 1962-11-05 | 1964-12-18 | Kodak Pathe | New weft and process for its manufacture |
| DE2917242C2 (en) * | 1979-04-27 | 1983-04-14 | Fogra Deutsche Forschungsgesellschaft für Druck- und Reproduktionstechnik e.V., 8000 München | Grid point contour |
| DE3711838A1 (en) * | 1986-04-30 | 1987-11-05 | Schumacher Kg | AUTOTYPICAL SCREENED PRINTING FORMS WITH HONEYCOMBED GRID ELEMENTS |
| JPH06205221A (en) * | 1991-08-13 | 1994-07-22 | Megadot Syst Ltd | Preparation of half-tone image |
| DE19633288C1 (en) * | 1996-08-19 | 1998-01-15 | Nationalzeitung Und Basler Nac | Raster on a printing unit in the offset printing process |
-
1999
- 1999-06-29 DE DE19929904A patent/DE19929904A1/en not_active Withdrawn
-
2000
- 2000-06-20 AT AT00940389T patent/ATE236019T1/en not_active IP Right Cessation
- 2000-06-20 DE DE50001637T patent/DE50001637D1/en not_active Expired - Fee Related
- 2000-06-20 CN CN00810987A patent/CN1365319A/en active Pending
- 2000-06-20 EP EP00940389A patent/EP1196295B1/en not_active Expired - Lifetime
- 2000-06-20 AU AU55338/00A patent/AU5533800A/en not_active Abandoned
- 2000-06-20 WO PCT/EP2000/005662 patent/WO2001000420A1/en active IP Right Grant
- 2000-06-20 CA CA002377050A patent/CA2377050A1/en not_active Abandoned
- 2000-06-20 RU RU2002102064/12A patent/RU2002102064A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| CN1365319A (en) | 2002-08-21 |
| DE50001637D1 (en) | 2003-05-08 |
| ATE236019T1 (en) | 2003-04-15 |
| AU5533800A (en) | 2001-01-31 |
| WO2001000420A1 (en) | 2001-01-04 |
| RU2002102064A (en) | 2003-09-10 |
| EP1196295B1 (en) | 2003-04-02 |
| DE19929904A1 (en) | 2001-01-04 |
| EP1196295A1 (en) | 2002-04-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |