GB2066159A

GB2066159A - An intaglio printing plate and a printing method

Info

Publication number: GB2066159A
Application number: GB8038608A
Authority: GB
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1979-12-03
Filing date: 1980-12-02
Publication date: 1981-07-08
Also published as: JPS5678991A; JPS5928479B2; GB2066159B; DE3045322C2; DE3045322A1; FR2471283B1; FR2471283A1

Abstract

An intaglio printing plate to be mounted on a plate cylinder 22 of a printing apparatus comprises a cylinder 27, e.g. of aluminium or plastics, on which is mounted a layer of elastic rubber 26 which is super-imposed by an oil-repellent layer 24 and, optionally, a photo-sensitive layer 25. Recesses 30 are formed in the oil repellent layer e.g. by utilising irradiation to which the photo-sensitive material is sensitive. The resultant intaglio printing plate can be used to print satisfactorily on a hard object 28, with thick ink films. <IMAGE>

Description

SPECIFICATION Improvements in or relating to an intaglio printing plate and to a printing method This invention relates to an intaglio printing plate, more specifically to an intaglio printing plate that facilitates thick film printing on the surface of a hard material, and to a method of printing using such a plate.

Presently utilised printing methods for thick film printing include screen printing and transfer printing utilising a rubber sheet. However, by utilising these methods it is not yet possible to control satisfactorily the film thickness of the ink forming the image, the dimensional accuracy of the image lines, and the overall pattern accuracy of the printed image. By "pattern accuracy" is meant the accuracy of the relative location of the various components of the printed image.

In screen printing a screen, for example of finemeshed silk or of wire gauze is stretched over a wooden or metal frame. A design is applied directly to the screen by printing the screen with a greasy medium, such as paint or ink, a water-soluble gun then being applied to the screen which seals the pores of the silk in the region to which the design has not been applied. The greasy paint is then washed away with a solvent so that the corresponding areas of the screen become pervious to ink. Alternatively a photographic method may be utilized to render certain regions of the screen pervious to ink and other regions impervious to ink. Printing ink can then be forced through the appropriate areas of the screen, by utilising a rubber squeegee, onto a sheet of paper or the like to be printed.This method suffers from the disadvantage that each image is not formed from a uniform body of ink, but a plurality of separate bodies of ink that have been forced through the separate meshes of the screen. The printed image thus can have an irregular edge. Also the printed image may have relatively low pattern accuracy and relatively low dimensional accuracy of the lines of the printed image since the mesh may become distorted as the ink is forced through the mesh by the squeegee.

In the above mentioned transfer printing method, in which a rubber sheet is used, initially ink is transferred to the surface of an elastic rubber sheet and is then transferred again directly onto the surface to be printed. However, this method suffers from the disadvantage that there is relatively low pattern accuracy and relatively low dimensional accuracy of the lines of the printed image, especially where a large dimensional image is printed, since the rubber sheet will be deformed elastically as the rubber sheet is pressed against the surface onto which the image is to be printed.

Afurthertype of printing that has been utilised is offset printing. This is a commonly used printing method since the printing plates can be manufactured simply. This method is applicable to thin film printing, such as printing on paper, but is not really applicable for use is connection with thick film printing. The reason is that the mechanism utilised in offset printing is such that if it is used for thick film printing the images tend to have pin holes and also the images tend to be irregular.

Figure 1 of the accompanying drawings is a schematic sectional view through part of an offset printing apparatus to illustrate the principle of the ink transfer mechanism utilised in offset printing.

Referring to Figure 1 a cylinder 11, which is termed an impression cylinder acts to urge an object 12, which is to be printed, into firm contact contact with the outer periphery of a blanket cylinder 13, the blanket cylinder being formed with an outer periphery formed from rubber or similar resilient material. As is well known ink 14, in the form of an image to be printed, is transferred from a plate cylinder (not shown) on to a portion of the outer periphery of the blanket cylinder 13. As can be seen the applied ink 14 is in the form of a line of ink having a total heigh H. As the blanket cylinder 13 rotates in the direction of the arrow the periphery of the blanket cylinder, which is pressed into firm contact with the upper surface of the object 12 to be printed, is deformed.It will be appreciated that the ink 14 is at least partially transferred onto the object 12 to be printed, but as can be seen during this actual printing step the ink applied to the object 12 can be considered to be divided into three parts. The first part 1 5a is the ink that is retained on the periphery of the blanket cylinder and which eventually becomes the correct printed image, a part of which may remain on the blanket cylinder. The second part 1 Sb is the ink which is forced out of the image position along the boundary between the blanket cylinder 13 and the object 12, which causes irregular reproduction. The third part 1 sic is the ink absorbed and fixed into the object 12 to be printed.It is to be appreciated therefore that when attempts are made to effect thick film printing by such a process one result is irregular reproduction because the ink is subjected to the printing pressure which is proportional to the illustrated distance P1 while it is on the blanket cylinder 13. The thicker the printed image required the higher the height H of ink to be transferred onto the blanket cylinder 13. It will be appreciated that the higher the height of ink H the greater quantity of ink available to spread away from the intended image area during the actual printing step, and thus the lower the quality of the printing.

It is to be appreciated that when the object to be printed is of a non-absorbing nature, such as metal or glass the resultant reproduction will be be even more irregular because the ink part 1 5c cannot be absorbed into the object 12. To reduce such irregular reproduction of the intended image lines attempts have been made to make the ink harder or more viscous and also attempts have been made to reduce the overall printing pressure by controlling the printing speed. However even when such procedural steps are adopted it has been found that the resultant printed matter has many pin holes and is blurred when attempts are made to produce a thick printed film. Thus it will be appreciated that offset printing is not really practicable for use when a faithful image is to be printed as a thick film.

For thick film printing it is essential that the quantity of ink can be controlled freely depending upon the precise purpose of the printing. Screen printing or intaglio printing processes are the only presently available methods that provide this facility.

As has been mentioned above, however, screen printing has the disadvantages that the printing accuracy is not stable since the screen may be deformed as the ink is applied to the paper to be printed by the squeegee. In intaglio printing, however, it is at present impossible to print directly onto hard materials, such as metal or glass, since the printing plate is made of a hard metallic material.

Thus, at the present time, when it is desired to print a thick film onto a hard material there is no alternative but to employ an indirect method in which the ink is transferred from a printing plate onto a rubber sheet or rubber coated blanket cylinder, the image then being printed onto the object in question. It will be appreciated that this has all the disadvantages specifically described above with reference to offset printing.

The present invention seeks to provide a printing plate that will enable the clear printing of a thick film with no irregular reproduction and blurring, and the invention also seeks to provide a printing plate that can enable the printing of a thick film onto a hard surface, such as metal or glass.

According to this invention there is provided an intaglio printing plate adapted to have recesses formed on the surface thereof, which recesses correspond to image lines, said plate comprising an elastic layer superimposed by either oil-repellent layer or an oil-repellent layer laid on a photosensitive layer, said layers being laminated in order, the arrangement being such that sections of at least the outer layer can be selectively removed to form said recesses.

Preferably said elastic layer comprises an elastic rubber layer, and may be from 100 Ci to 1000 CL in thickness and from 300 to 900 in hardness on the Shore scale A.

Conveniently said rubber layer is supported by a plate located on the side thereof remote from said oil-repellant layer.

The plate may be in the form of a cylinder or roller.

Preferably parts of said oil repellent layers are removed to form said recesses, and said recesses have a depth of from 5 11 to 20 . Conveniently said oil-repellent and said photo-sensitive layer, if provided, are elastic.

In one embodiment the oil-repellent layer is made of silicone rubber containing a photo-sensitive material or a rubber material containing a fluorine compound and a photo-sensitive material, which is mounted directly on said elastic rubber layer, the image line section of the oil repellent layer being removed by a process which involves irradiation of selected areas of the surface of the oil repellent layer with radiation to which said photo-sensitive material is sensitive.

In another embodiment the oil-repellent layer is made of silicone rubber or rubber material containing a fluorine compound, and the photo-sensitive layer comprises a photo-adhesive material, the non-image line sections of both layers being made to adhere together by irradiation, the non-exposed areas of the rubber layer then being removed.

In a further embodiment the oil-repellent layer is made of silicone rubber or rubber material containing a fluorine compound, and the photo-sensitive layer is made of photo-destructive material, the two layers initially being adhered together, the adhesion being between the layers being broken by irradiation of preselected areas, the exposed section of the rubber layer subsequently being removed.

Preferably informing said recesses, in addition through a moving part of the oil repellent layer, at least part of the photo-sensitive layer is also removed, and preferably in addition to removing part of the oil repellent layer and the photo-sensitive layer, part of the elastic rubber is also removed forming said recesses.

According to another aspect of this invention there is provided, a method of thick film printing onto a hard object comprising the steps of applying ink to a intaglio printing plate, said plate comprising an intaglio printing plate having recesses formed on the surface thereof, which recesses correspond to image lines, said plate comprising an elastic layer superimposed by either oil-repellent layer or an oil repellent layer laid on a photo-sensitive layer, said layers being laminated in order and applying ink from the intaglio printing plate to said hard object.

This invention also relates to an item when printed by a process according to the invention.

In order that the invention may be more readily understood, and sothatfurtherfeaturesthereof may be appreciated, the invention will now be described by way of example with reference to Figures 2 to 7 of the accompanying drawings in which: Figure 2 is a diagrammatic cross sectional view of part of a printing apparatus incorporating an intaglio printing plate in accordance with the present invention; Figure 3 is a diagrammatic cross sectional view of the printing plate shown in Figure 2; Figure 4 is a cross sectional view of part of the periphery of the printing plate shown in Figures 2 and 3; and Figures 5to 7 are respectively cross sectional views of parts of the periphery of further intaglio printing plates in accordance with the invention.

Referring initially to Figure 2 of the accompanying drawings, which shows part of a printing apparatus utilising an intaglio printing plate in accordance with the invention, a distributing cylinder 20 and form roller 21 are utilised to supply ink onto a printing plate 23 in accordance with the present invention (the printing plate being in the form of a cylinder) as the printing plate 23 rotates in contact with the form roller 21. The printing plate 23 comprises an outer layer 24 of elastic oil-repellent material, this layer having a thickness of six to 201l. Immediately under this outer layer there is an elastic photo-sensitive layer 25, and underneath that layer there is an elastic rubber layer 26 having a thickness of 100 F to 1000 Ce and having a hardness of 30 degrees to 90 degrees on the Shore scale A. These layers are supported by a support plate 27 which is made of aluminium or a plastics material body and which, in this embodi ment, has cylindrical configuration. It will be appreciated that the described intaglio plate can thus readily be supported in position on the plate cylinder 22 of a printing apparatus in the same way that a presensitized plate can be located in position.

In utilising the illustrated apparatus in a printing process ink 29 which is to form the eventual printed image on an object 28 which is to be printed is initially present in a distributed condition 29a on the distributing cylinder 20. The ink is then transferred to form an even film 29b on the form roller 21, and from there the ink is transferred to recesses 30 formed in the outer periphery of the printing plate 23. The ink is held in position 29e remains in position on the printed object, but a portion of the ink 29f remains in the recess 30.

Reference has been made to recesses 30 formed in the outer periphery of the plate, and these recesses 30 can be formed by several alternative methods, although the precise structure of the printing plate 23 may differ slightly depending upon which particular method is to be utilised. In the case of a printing plate having a structure as illustrated in Figure 2 the oil repellent layer 24 may be made of silicone rubber, or rubber material incorporating a fluorine compound, and the photo-sensitive layer 25 may be made of a photo-adhesive material. The outer surface of the plate may be exposed to a predetermined pattern of irradiation, the exposed regions of the oil-repellent layer being bonded to the photosensitive layer. The un-exposed regions may then be removed by swelling dissolution.

In an alternative method, which is used to form a plate as illustrated in Figure 5, the steps described above with reference to Figure 4 are repeated, save that the photo-sensitive layer 25 which is exposed at the bottom of the recess 30 is also dissolved.

In an alternative method portions of the oilrepellent layer 24 and the photo-sensitive layer 25 may be removed by initially making selected portions of these layers soluble to a solvent by exposure to irradiation. In such a case the photo-sensitive layer 25 may be made of a diazophoto-sensitive material and the oil-repellent layer 24 may include a diazonium salt. After induction of photolysis of the diazonium salt by irradiation the selected parts of the oil-repellent layer and the photo-sensitive layer are removed by means of an appropriate solvent. The resultant plate has an appearance similar to the plate shown in Figure 5.

Alternatively the oil-repellent layer 24 may be made of silicone rubber or a rubber material incorporating fluorine compound, and the photosensitive layer 25 may be made of a photodestructive material. After exposure to a predetermined pattern of radiation the adhesion between the oil-repellent layer and the photo-sensitive layer is destroyed in the areas corresponding to the desired image lines. This enables the selected parts of the oil-repellent layer to be readily removed together, optionally, with at least part of the underlying photo-sensitive layer. This again results in the production of a plate having the appearance illustrated in Figure 5.

In a further method, the method steps immediately described above are utilised, but part of the elastic rubber layer 26 is also removed by utilising an appropriate organic solvent. This results in a plate having the appearance illustrated in Figure 6. Finally a separate photo-sensitive layer 25 may be omitted and thus the oil-repellent layer 24 may be made of silicone rubber, or rubber material incorporating a fluorine compound, and a photo-sensitive radical.

The arrangement is such that when the plate has been exposed to appropriate radiation the oilrepellent layer can be peeled off in the areas corresponding to the desired image lines. This provides a plate having the appearance illustrated in Figure 7.

In all the above described embodiments the elastic rubber layer 26 which lies immediately under the photo-sensitive layer 25 (or, in the case of Figure 7) immediately under the oil-repellent layer 24, can have a hardness within the range of 30 degrees to SO degrees as measured on the Shore scale A, and this layer can have a thickness of from 100 it to 1000 it Thus the elastic rubber layer 26 is such that it can be compressed easily at printing stage and it also has the stability of a supported rubber elastic body.

The support plate 27 may be made of such materials as aluminium plate or a plastics material body to provide a satisfactory degree of strength to the whole printing plate. Thus the printing plate 23 can be easily fixed or removed from the plate cylinder 22, as mentioned above.

The surface of the printing plate 23 consists of the convex part of the oil-repellent layer 24, together with the various recesses 30 defined within that surface. Ink is supplied only to the recesses 30 provided in the oil-repellent layer 24, as described above, each recess 30, when filled with ink, proceeds to the printing position as the plate cylinder 22 rotates.

For thick film printing to be accomplished satisfactorily the following conditions should be met. Each recess 30 in the printing plate must hold a greater quantity of ink than is necessary to provide a film of the required thickness on the object 28 to be printed since part of the ink always remains within the recess 30 after the printing process. Also, of course, when the ink that is transferred on to the object 28 dries the film thickness will be reduced. The dimensions of the recess 30 should therefore be determined with these factors in mind. It is to be noted that the ink has fluidity, a specific viscosity and is, generally speaking, non-compressible.

Referring again to Figure 2 when a printing plate manufactured as described above is utilised in the printing process as described above a pressure P1, schematically indicated in Figure 2, is applied to the plate cylinder by means of an impression cylinder (not illustrated) which is located underneath the object 28 on which an image is to be printed. In the portions of the periphery of the plate 23 where no recess 30 is provided the printing pressure P1 is equal to the compression of the printing plate 23, that is to say the compression of the oil-repellent layer 24, the photo-sensitive layer 25 (if provided) and the elastic rubber layer 26, since the plate cylinder 22 and the support plate 27 are both rigid bodies. The applied pressure is maintained substantially constant from the beginning of the printing process to the end of the printing process.Thus when an image line is actually being printed the ink in the recess 30 and the part of the printing plate located under the recess 30 are subjected to the printing pressure P1. Since the ink is substantially non-compressible as mentioned above, the portion of the printing plate beneath the recess 30 must be compressed through the ink. Since the layer 26 is formed of resilient material this layer can be compressed and thus the ink in the recess 30 is accurately deposited onto the object 28 to be printed, without any blurring of the printed image and without distortion of the printed image.

It will be appreciated that whilst, during a printing process utilising a plate in accordance with the invention the actual impression mechanism utilises the elasticity of the printing plate 23 in a manner which is similar to that utilised in connection with off-set printing, as described above, in utilising the plate according to the invention ink is prevented from being forced out of the recess to the sides of the recess. Thus, the intaglio printing plate of the present invention is compressed while keeping the ink within the recess 30. Compared with off-set printing in which the printing plate is compressed, with the ink consequently being exposed, the ink is not forced out of the image position easily, and thus, in use, the intaglio printing plate described above serves to prevent any ink from being forced out to the sides of the recess.In the embodiments shown in Figures 5 and 6 the ink held in the photo-sensitive layer 25 and/or the elastic rubber layer 26 is discharged by virtue of the elasticity of the printing plate because the holding limit of the photosensitive layer and/or the elastic rubber layer is exceeded. It has been found that for accurate printing it is desirable to keep the printing pressure such that the deformation of the exterior of the plate 23 (P) is greater than the thickness of the film within the recesses 30 (H).

Referring now to Figure 3 of the accompanying drawings, when printing, a pressure, schematically indicated as pressure P2, is applied, and when the recess 30, which corresponds to the image line is pressed against the object 28 to be printed, it is believed that the condition illustrated in Figure 3 exists. Thus it is believed that the deformation of the essentially elastic material defining the periphery of the recess 30 is greater in the region "T" than in the region that initially comes into contact with the body 28. Thus the thickness of the ink in the region f' of the recess, which is close to the boundary g' which defines the side wall of the recess 30 (which is the first side wall of the recess to come into contact with the body 28) is less than the thickness of the ink in the remaining part f of the recess 30 adjacent the other boundary g.Thus, in zone f' the ink is pressed against the body to be printed, whereas in zone fthe ink acts in the same manner as the layers forming the plate in the non-image sections of the plate, that is to say the oil repellent layer 24 the photo-sensitive layer 25 and the elastic rubber layer 26, and in the non-image section are forced upwards. The upward movement of the various layers adjacent the recess 30 is believed to be reduced gradually in proportion as the second boundary g is brought into firm contact at the body 28 and the first boundary g' is thus moved away from the body 28. During this process the ink pocket Tt is formed to prevent ink from being forced out to the sides of the recess 30.

As has been described above the ink present in the recess 30 will divide into two parts, one part comprising the ink 29e that is transferred onto the object 28 to be printed, the other part comprising the residual ink 29 f that is left within the recess 30. The residual ink 29 f serves to make the next feeding of ink into the recess 30 quite smooth. The depth of the ink in the recess 30 can be selected depending upon the precise nature of the printing to be performed, but practically speaking the depth of the recess 30 for usual intaglio printing is preferably in the range of from 5 u to 20 u.

By utilising an intaglio printing plate according to the present invention, printing onto a comparatively rough surface or a hard surface can be accomplished without spoiling the image quality because of the nature of the printing plate.

Claims

1. An intaglio printing plate adapted to have recesses formed on the surface thereof, which recesses correspond to image lines, said plate comprising an elastic layer superimposed by either oil-repellent layer or an oil-repellent layer laid on a photo-sensitive layer, said layers being laminated in order, the arrangement being such that sections of at least the outer layer can be selectively removed to form said recesses.

2. A printing plate according to claim 1 wherein said elastic layer comprises an elastic rubber layer.

3. An-intaglio printing plate according to claim 1 or claim 2 wherein said elastic layer is from 100 it to 1000 IL in thickness and from 300 to 900 in hardness on the Shore scale A.

4. An intaglio printing plate according to any one of claims 1 to 3 in which the rubber layer is supported by a plate located on the side thereof remote from said oil-repellent layer.

5. An intaglio printing plate according to any one of the preceding claims in the form of a cylinder or roller.

6. An intaglio printing plate according to any one of the preceding claims wherein parts of said oil-repellent layer are removed to form said recesses.

7. An intaglio printing plate according to any one of the preceding claims wherein said recesses have a depth of from 5 u to 20 u.

8. An intaglio printing plate according to any one of the preceding claims wherein said oil-repellent layer, and said photo-sensitive layer, if provided, are elastic.

9. An intaglio printing plate according to any one of claims 1 to 8 wherein the oil-repellent layer is made of silicone rubber containing a photo-sensitive material or a rubber material containing a fluorine material, which is mounted directly on said elastic rubber layer, the image line section of the oilrepellent layer being removed by a process which involves irradiation of selected areas of the surface of the oil-repellent layer with radiation to which said photo-sensitive material is sensitive.

10. An intaglio printing plate according to any one of claims 1 to 8 in which the oil-repellent layer is made of silicone rubber or rubber material containing a fluorine compound, and the photo-sensitive layer comprises a photo-adhesive material, the non-image line sections of both layers being made to adhere together by irradiation, the non-exposed areas of the rubber layer then being removed.

11. An intaglio printing plate according to any one of claims 1 to 8 in which the oil-repellent layer is made of silicone rubber or rubber material containing a fluorine compound, and the photo-sensitive layer is made of photo-destructive material, the two layers initially being adhered together, the adhesion being between the layers being broken by irradiation of preselected areas, the exposed section of the rubber layer subsequently being removed.

12. An intaglio printing plate according to any one of claims 1 to 8 or 10 or 11 in which a photo-sensitive layer is provided wherein in forming said recesses, in addition through a moving part of the oil-repellent layer, at least part of the photosensitive layer is also removed.

13. An intaglio printing plate according to claim 12 wherein in addition to removing part of the oil-repellent layer and the photo-sensitive layer, part of the elastic rubber is also removed in forming said recesses.

14. A method ofthickfilm printing onto a hard object comprising the steps of applying ink to a intaglio printing plate, said plate comprising an intalgio printing plate having recesses formed on the surface thereof, which recesses correspond to image lines, said plate comprising an elastic layer superimposed by either oil-repellent layer or an oil-repellent layer laid on a photo-sensitive layer, said layers being laminated in order and applying ink from the intaglio printing plate to said hard object.

15. A method of thick film printing according to claim 14 wherein said plate comprises a plate according to any one of claims 1 to 13.

16. An intaglio printing plate substantially as herein described with reference to and as shown in Figures 2 to 4 of the accompanying drawings.

17. An intaglio printing plate substantially as herein described with reference to and as shown in Figures 2 to 4 as modified by Figure 5 of the accompanying drawings.

18. An intaglio printing plate substantially as herein described with reference to and as shown in Figures 2 to 4 as modified by Figure 6 of the accompanying drawings.

19. An intaglio printing plate substantially as herein described with reference to and as shown in Figures 2 to 4 as modified by Figure 7 of the accompanying drawings.

20. A thick film printing process substantially as herein described with reference to the accompanying drawings.

21. An item when printed by a process according to any one of claims 14, or 20.

22. Any novel feature or combination of features disclosed herein.