ATTACHMENT MEANS

Abstract: Attachment means for attaching a flexographic printing form, particularly a printing form of photopolymeric material, on a plate cylinder, is provided with a flexible supporting layer and a photopolymeric layer supported by the supporting layer being fully exposed. In order to obtain a particularly effective attachement means the adherent characteristics of a photopolymeric layer are advantageously utilized. Experiments have shown that these adherent characteristics are also maintained in case of intensive use during at least 8 to 12 months. Moreover, on the one hand a good attachment of the printing form on the plate cylinder is achieved, whereas on the other hand the printing form can relatively easily be removed from the adherent photopolymeric layer and no residual photopolymeric material remains on the printing form. In this way a long lifetime of the attachment means applied on the plate cylinder is achieved, while on the other hand the printing form needs no longer undergo any cleansing treatment. Damaging of the printing form by removal is excluded as well so that the printing form is more times available for repeat order without any problem.

Description: Attachment means This invention relates to an attachment means for attaching a flexographic printing form or other printing type, particularly a printing form of photopolymeric material, on a plate cylinder or similar printing type carrier. The known attachment means of this type comprises a strip of double-sided adhesive tape, e.g. supplied from a roll, attached with the one adherent side on the plate cylinder so that on the other adherent side one or more flexographic printing forms can be attached. Such flexographic printing forms consist of a photopolymeric layer attached to a supporting layer. Through a film, on which the desired images and/or text etc. have been recorded, the photopolymeric layer is exposed and then washed out, whereafter finally the resulting printing form is subjected to a subsequent treatment. In case of using the known attachment means the problem arises that the supporting layer of the printing form adheres strongly to the adherent layer of the attachment means, due to which removal of the printing form is troublesome and moreover a residual part of the adherent layer often remains on the printing form. Consequently the attachment means generally has to be replaced after use one or several times, whereas on the other hand the printing form has to be cleansed in order to remove the adherent layer. Because the cleansing operation of the printing form is intensive the printing form is commonly thrown away. Thus in case of a repeat order a new printing form has to be produced. It is an object of this invention to provide a attachment means of the type as mentioned in the preamble, which overcomes these disadvantages in a simple, but nevertheless effective way. In accordance with the invention the attachment means is characterized by a flexible supporting layer and an adherent photopolymeric layer supported by the supporting layer being completely exposed. The invention relies on the recognition that in order to obtain a particularly effective attachment means advantageously the adherent characteristics of a photopolymeric layer can be utilized. Experiments have shown that these adherent characteristics also maintain in case of intensive use during a period of at least 8 to 12 months. Moreover, on the one hand a good attachment of the printing form on the plate cylinder is realized, whereas on the other hand the printing form can relatively easily be removed from the adherent photopolymeric layer and no residual photopolymeric material remains on the printing form. Thiε results in a long lifetime of the attachment means applied to the plate cylinder, whereas on the other hand the printing form no longer needs to undergo a cleansing operation. Damaging of the printing form by the removal is excluded as well, so that the printing form is available several times for repeat orders without any problem. Moreover, the attachment means of the invention has the advantage that the photopolymeric layer is highly resistant to the solvents present in the used inks. A further important advantage is achieved in that the photopolymeric layer as compared with the adherent layers of the known attachment means has a considerable thickness and a relatively low hardness and, according to a preferred embodiment, is of at least 1.5 mm in thickness. In this way the photopolymeric layer of the attachment means forms a kind of resilient layer between the printing form and the plate cylinder, which results in taking away the unavoidable non-circular shapes of the plate cylinder and printing forms and tolerance due to gear abrasion by the photopolymeric layer. This aspect induces a considerable lifetime increase of the moving parts of the printing press, as well as lifetime increase of the printing form. An accompanying important advantage is that the thickness of the printing form itself can be considerably less than the required thickness, because of the fact that the relatively thick photopolymeric layer of the attachment means already provides an important part of the required total height of the printing thickness above the plate cylinder. It will be understood that application of relatively thin printing forms will induce a considerable economy of 25-40%. Moreover, not only a reduction of cost but also a better printing quality in case of printing on relatively rough materials iε achieved. According to a particularly advantageous embodiment the attachment means of the invention is provided with reference markers on the photopolymeric layer or the supporting layer. Advantageously the transparent characteristicε of the photopolymeric material for poεitioning the printing form in the correct position on the plate cylinder are utilized herein. In this way positioning the printing form(s) on the plate cylinder can take place rapidly and precisely, no expensive auxiliary apparatus for recording different printing forms on subsequent plate cylinders being necessary. The invention will be explained more in detail by means of the drawings, which illustrate highly schematically an exemplary embodiment of the attachment means of the invention. Figure 1 represents a perspective view of the end of a sheet of an embodiment of the attachment means of the invention applied to a roll (not shown) . Figure 2 represents a perspective view of the one end of a plate cylinder, on which a printing form by means of a piece of attachment means of figure 1 is applied. In figure 1 the end of a sheet of attachment means 1 is illustrated in a perspective view on a much enlarged scale. It will be understood that in a practical embodiment the attachment means 1 will have a considerably higher width than the width εhown in figure 1. The attachment means 1 includeε a flexible supporting or stabilizing layer 2 conεiεting of e.g. a polyester material. This εupporting layer supportε a photopolymeric layer 3 covered by a protective layer 4. For example, thiε protective layer 4 can consist of polyester as well. In the exemplary embodiment illustrated in figure 1 the supporting layer 2 is provided on both sides with an adherent layer 5 and 6 respectively, the adherent layer 5 connecting the photopolymeric layer 3 with the supporting layer 2 and the adherent layer 6 serving to attach the attachment means 1 on a plate cylinder partly visible in figure 2. Alternatively the supporting layer 2 can be embodied without the adherent layerε 5, 6, the photopolymeric layer being united with the εupporting layer 2 in another way and the attachment meanε being attached on the plate cylinder 7 in another way, e.g. by a commonly uεed double-sided adhesive tape. In a convenient embodiment of the protective layer 4 a εeparate protective layer for the adherent 6 can be omitted when the attachment meanε 1 iε supplied on a roll. Alternatively it iε of course posεible to apply a separate removable protective layer on the adherent layer 6. When applying the photopolymeric layer 3 in the attachment means 1 aε described above the characteristic of the photopolymeric material being sticky or adherent is utilized advantageously. In case of application of photopolymeric material for producing flexographic printing forms in a conventional way, after washing out the printing form a εubεequent treatment of the printing form iε carried out in order to diεεolve the εtickiness of the exposed photopolymeric material. The present invention relies on the recognition that this sticky or adherent characteristic of the photopolymeric material makes a photopolymeric layer particularly suitable for application as an adherent layer in the attachment means as described above. The photopolymeric layer 3 is expoεed completely, which reεultε in a further changing of the structure of the photopolymer. In figure 2 the one end of the plate cylinder 7, on which a piece of the attachment meanε 1 of fig. 1 iε applied, iε illuεtrated in a perεpective view. The photopolymeric layer 3 iε partially broken away εo that the supporting layer 2 is partially visible. Furthermore a printing form 8 is illustrated, on which highly schematically pictures 9 and text 10 are indicated. This printing form 8 is embodied in a conventional way with a photopolymeric layer and a supporting layer, on which pictures 9 and text 10 are shaped by way of exposure through a film, then waεhing out and finally a εubsequent treatment in the photopolymeric layer. Due to the application of the completely exposed photopolymeric layer 3, the attachment means 1 aε deεcribed above haε the advantage that on the one hand the printing form 8 can be attached correctly upon the plate cylinder 7 and on the other hand it can eaεily be removed aε well. In thiε way no reεidual photopolymeric material remainε on the supporting layer 8 of the printing form so that this printing form 8 needs not undergo any special cleanεing operation and does not damage. As a result the printing form 8 maintains its availability for repeat orders. Furthermore the attachment means 1 has the advantage that when removing the printing form 8 the photopolymeric layer 3 does not get damaged so that the attachment means has a long lifetime. Experiments have shown that this lifetime amounts at least 8 to 12 months. For the user of the attachment means of the invention this means a considerable economy, since when using a conventional attachment meanε it generally has to be replaced after removal of a printing form one or more times, whereas as a result of the remaining of glue residues on the printing form it mostly has to be thrown away. As appears from the drawings the photopolymeric layer 3 haε a conεiderable thickneεε with reεpect to the adherent layerε 5, 6. Thiε reεults in advantageous utilization of the resilient characteristic of the photopolymeric layer 3, as a consequence of which the non-circular shape of the plate cylinder and the bearings of the plate cylinder can be taken away and a considerable noise reduction and a lifetime increase of the printing press are achieved. Moreover a relatively resilient support of the printing form 8 is realized, which increases the lifetime of the printing form. The quality of the printed matter is also improved, particularly in case of printing on rough material. Furthermore, applying of the relatively thick photopolymeric layer 3 on the attachment means 1 has the advantage that the thickneεε of the printing form 8 can be leεε εo that a conεiderable economy of 25 to 40% on material coεtε for producing the printing formε can be realized. As indicated εchematically in figureε 1 and 2 reference markers 11 are provided to the photopolymeric layer 3 εo that before applying the printing forms on the plate cylinder after applying the attachment meanε 1 upon the plate cylinder 7 reference markerε for poεitioning the printing for ε are available. In this way the user can rapidly and preciεely locate printing formε on the deεired place. Alternatively it is possible to print the reference markerε 11 on the εupporting layer 2 in caεe of a suitable embodiment of the connection between the supporting layer and the photopolymeric layer. The photopolymeric layer 3 can have various thicknesses ranging from e.g. 1 to 4 mm, dependent on the desire of the user. The thickneεε to be applied is dependent on the required height of the printing form for the relative printing press. The photopolymeric material has the advantage that it is reεiεtant to the solvents present in the used inks, as well aε to the influence of ozone. Although in the foregoing the invention iε explained by means of an application for attaching the printing formε on a print cylinder it will be understood that the attachment means of the invention can alεo be applied for mounting and positioning of characters, numbers and pictures on other printing apparatuε, amongst which encoding apparatus, stamping apparatus etc. Furthermore it haε to be noted that for applying the attachment meanε on a magnetic plate cylinder the attachment meanε can be provided with a thin metallic sheet. Alternatively the attachment means can be laminated with a magnetic foil. The invention is not limited to the exemplary embodiment as described in the foregoing, which can be varied in several ways within the εcope of the invention.

Claims: CLAIMS 1. Attachment means for attaching a flexographic printing form, particularly a printing form of photopolymeric material, on a plate cylinder, characterized by a flexible supporting layer and an adherent photopolymeric layer supported by the εupporting layer being completely exposed. 2. Attachment means according to claim 1, characterized by reference markers preferably attached to the photopolymeric layer. 3. Attachment means according to claim 1 or 2 , characterized in that the supporting layer iε provided on the side backing the photopolymeric layer with an adherent layer for attaching the attachment means on the plate cylinder. 4. Attachment meanε according to claim 1 or 2 , characterized by a thin metallic εheet for attaching the attachment means on the plate cylinder. 5. Attachment means according to claim 1 of 2, characterized by a thin magnetic foil for attaching the attachment means on the plate cylinder. 6. Attachment means for attaching a flexographic printing form, particularly a printing form of photopolymeric material, on a plate cylinder, characterized by reference markerε. 7. Method for producing a attachment meanε according to anyone of the preceding claimε, wherein a photopolymeric layer iε applied to a εupporting layer, characterized in that the photopolymeric layer iε completely expoεed.

Inventors: GOOVAARD JAN, GOOVAARD, JAN
Applicants: GOOVAARD JAN, J M J HOUTSTRA HOLDING B V, GOOVAARD, JAN, J.M.J. HOUTSTRA HOLDING B.V.
Application year: 1995
Main classification: B41N10
IPC codes: B41F27, B41N6