Method for producing an ink transfer medium, in particular a printing blanket, in particular a printing blanket for offset printing, especially a printing blanket for dry offset printing

Description

[0001] Method for producing an ink transfer medium, in particular a printing blanket, in particular a printing blanket for offset printing, especially a printing blanket for dry offset printing

[0002] The present invention relates to a method for producing an ink transfer medium, in particular a printing blanket, in particular a printing blanket for offset printing, very particularly a printing blanket for dry offset printing, according to patent claim 1.

[0003] Various processes for reproducing print templates have long been known, for example, in letterpress printing, offset printing, gravure printing, flexographic printing, and screen printing, which can collectively be referred to as printing technology. These printing techniques can be used for the mass production of printed products through the repeated use of a single print template.

[0004] Offset printing is an indirect planographic printing process, the most widely used printing technique in book, newspaper, advertising, and packaging printing. In indirect printing processes, the printing plate and the printing substrate do not come into contact with each other. The ink is first transferred to a blanket cylinder and then to the substrate to be printed. This protects the printing plate and allows for printing on a wide range of substrates, such as paper, cardboard, plastic (films), glass, ceramics, and metal sheets.

[0005] A special application of offset printing is dry offset printing, an indirect relief printing process. Dry offset printing can be used to print conical or cylindrical shapes such as plastic cups, tubes, and buckets.

[0006] In offset printing, a rubber blanket, or printing blanket, is an intermediate carrier used to transfer the ink from the printing plate to the medium to be printed, such as a substrate. For this purpose, the rubber blanket is stretched over a blanket cylinder, or simply a blanket cylinder, which is positioned between the plate cylinder containing the printing plate and the impression or impression cylinder containing the substrate. In dry offset printing, instead, the rubber blanket is stretched over a blanket cylinder, which is positioned between a cliché cylinder with a relief printing form and the impression or impression cylinder containing the substrate. A distinction is made between compressible and incompressible blankets.

[0007] The blanket therefore has a significant influence on the quality of the printed product, as it transfers the printing ink to the substrate. To ensure optimal ink transfer, the thickness of the blanket, i.e., its radial thickness, must be set to a predetermined value with a very tight tolerance. For example, in the printing industry, printing blankets with a thickness of 1,950 µm and a tolerance of + / - 20 µm are used.

[0008] Typically, the thickness of the printing blanket is adjusted by grinding the radially outward-facing surface of the cover plate or the cover layer of the vulcanized printing blanket to the predetermined size.

[0009] The disadvantage here is that the radially outward-facing surface of the cover layer, as the functional layer of the printing blanket, is precisely the side that serves for ink transfer. Thus, sanding on the radially outward-facing surface of the cover layer, which can also be referred to as the printing side of the cover layer, can create a sanding structure, which can be undesirable for at least some printing applications because the sanding structure can influence ink transfer and impair the printing result.

[0010] Another disadvantage of grinding the printing side of the cover layer is that as long as this surface is ground, the printing side of the cover layer cannot be defined or embossed by other methods.

[0011] Another disadvantage is that the radially outward-facing surface of the cover layer can be damaged during sanding by hard foreign objects that can get caught between the printing blanket and the abrasive material or are embedded in the cover layer. Furthermore, during the further sanding process, the surface of the cover layer in this area can be sanded less, leaving a raised area in this area of ​​the unsanded surface of the cover layer. This can change the radially outward-facing surface of the cover layer to such an extent that no printing process can be carried out with this blanket. The blanket can then be unusable as a whole and considered scrap.

[0012] EP 0 372 719 A2 describes a laminated printing blanket construction comprising at least a base layer and a surface layer laminated to one surface thereof, and wherein the opposite surface of the base layer is substantially untextured so that, when mounted on a blanket cylinder, the pressures to which the blanket is subjected are distributed substantially over the entire surface of the blanket in contact with the cylinder.

[0013] JP 2005 125666 A describes, in order to reduce thickness unevenness of a rubber blanket surface, a manufacturing method for the rubber blanket for printing with a printing layer provided on a substrate layer, comprising a step of integrating the substrate layer with the printing layer and then a step of polishing a back surface of the substrate layer.

[0014] EP 2 789 472 A2 describes a method for producing a printing blanket of a certain thickness, which has a carrier in the form of an inextensible base layer and a structure with at least one intermediate layer and a cover layer, with the following method steps: a web-shaped carrier is provided, the web-shaped carrier is connected to a web-shaped structure so that a web-shaped composite is created, after production of the composite, a surface of the composite is ground until the composite has the desired thickness, the printing blanket is separated from the web-shaped composite.

[0015] WO 2017 / 144358 A1 describes a rubber blanket for a printing cylinder of a printing press, comprising at least one upper printing layer made of compact elastomeric material, at least one lower layer having a contact surface in contact with the printing cylinder, and at least one fabric reinforcement layer arranged between the upper layer and the lower layer, wherein the lower layer consists of expanded elastomeric material.

[0016] JP S63 303796 A describes that in order to obtain a printing surface efficient in the reproducibility of dot and solid printing, by a method in which a surface of a rubber layer is made into a fine uneven surface, liquid elastomer and resin are transferred onto a rubber layer by printing, or otherwise the surface of the rubber layer is made into a fine uneven surface by attaching a roller to the rubber layer by pressure, and finally bridging.

[0017] US 2008 / 057188 ​​A1 describes a method for producing a printing blanket with a textured printing surface, in which a polyurethane printing surface layer is applied to a substrate in a single pass in 100% solid form. The surface of the polyurethane layer is provided with a plurality of depressions or reservoirs of substantially uniform size to create an improved surface for receiving and transferring printing ink.

[0018] An object of the present invention is to provide an ink transfer medium, in particular a printing blanket, in particular a printing blanket for offset printing, and more particularly a printing blanket for dry offset printing, of the type described above, so that the aforementioned disadvantages can be overcome. In particular, the limitations of the surface design of the printing side of the cover layer, which can result from sanding this side, are to be reduced or even completely eliminated. At the very least, an alternative ink transfer medium is to be created.

[0019] The object is achieved according to the invention by a method for producing a color transfer medium having the features according to claim 1. Advantageous further developments are described in the subclaims.

[0020] The present invention therefore relates to a method for producing an ink transfer medium, in particular a printing blanket, in particular a printing blanket for offset printing, very particularly a printing blanket for dry offset printing, wherein the ink transfer medium has a cover layer with a printing side, wherein the cover layer is designed to transfer an ink by means of the printing side, and wherein the ink transfer medium has a contact layer with a contact side, wherein the contact layer is designed to be arranged on a surface of a flat body, wherein the contact side of the contact layer is arranged facing away from the printing side of the cover layer, wherein the cover layer and / or the contact layer has, preferably consists of, at least one elastomeric material, in particular at least one rubber.

[0021] The method according to the invention comprises at least the steps: Grinding the contact side of the contact layer and embossing the print side of the cover layer at least in sections using an embossing foil and / or embossing paper.

[0022] In this way, the previously known grinding of the ink transfer medium, which serves to set a predetermined thickness of the ink transfer medium with the smallest possible tolerance, can be shifted from the printing side to the opposite contact side. Since the contact side of the contact layer serves to establish contact with a flat body such as a printing cylinder or the like, grinding structures and the like on the surface of the contact side of the contact layer can be accepted, since this can neither impair the contact effect nor influence the printing result. The printing side can therefore remain free of the previously known grinding structures, which can offer corresponding advantages, as will be described in more detail below.

[0023] This can also make it possible to adapt the printing side of the cover layer to the medium to be printed, depending on the application-specific properties required, such as tack, roughness, ink acceptance, ink release, and the like. This option may previously have been limited or even impossible due to sanding the printing side of the cover layer.

[0024] The contact side of the contact layer can preferably be bonded to a flat body, such as a printing cylinder. This can enable the ink transfer medium to adhere securely to the flat body via the contact side of the contact layer. For this purpose, an adhesive layer can preferably be applied to the contact side of the contact layer in order to achieve contact between the contact side of the contact layer and a flat body, such as a printing cylinder, by means of adhesive bonding as simply, reproducibly, and / or cost-effectively as possible.

[0025] The present invention can be applied to any ink transfer media that can be used in printing processes. In particular, the present invention can be applied to ink transfer media used in offset printing, flexographic printing, and digital printing in order to utilize their advantageous properties.

[0026] According to one aspect of the present invention, the printing side of the cover layer is unsanded. This reliably prevents abrasive structures on the printing side of the cover layer, thus preventing their impact on the printing result. This also allows for other surface design options, as will be described further below.

[0027] According to a further aspect of the present invention, the ink transfer medium has, at least in sections, a predetermined thickness, which has been adjusted by grinding the contact side of the contact layer. Thus, the predetermined thickness of the ink transfer medium can be achieved by grinding as previously known. At the same time, the disadvantages that can result from grinding the print side of the cover layer can be avoided, as already described above.

[0028] According to the invention, the printing side of the cover layer is embossed at least in sections by means of an embossing foil and / or embossing paper. In other words, the printing side of the cover layer has a surface embossed with an embossing foil or embossing paper. This can make it possible to improve ink acceptance and / or ink release. This has previously been prevented by sanding the printing side of the cover layer, since an embossed surface of the printing side of the cover layer would be destroyed by the subsequent sanding. Thus, by shifting the sanded surface from the printing side of the cover layer to the contact side of the contact layer, new design options can be created for the printing side of the cover layer and thus for the printing process in order to improve it.

[0029] According to a further aspect of the present invention, the ink transfer medium has at least one reinforcement layer, which is arranged at least partially between the cover layer and the contact layer. This can enable the transmission of forces, and in particular tensile forces, particularly in the direction of rotation of the ink transfer medium during the printing process, and thus promote the stability and durability of the ink transfer medium. Textile fabrics such as woven fabrics can preferably be used as reinforcement layers, which enable the implementation of the properties described above and can simultaneously be cost-effective, easy to process, and / or lightweight.

[0030] According to a further aspect of the present invention, the reinforcement layer comprises, preferably consists of, at least one elastomeric material, in particular at least one rubber. In this way, the corresponding material properties can be utilized to implement such a color transfer medium.

[0031] An embodiment and further advantages of the invention are explained below in conjunction with the following figures. Therein: Fig. 1 is a schematic sectional view of a color transfer medium according to the invention, and Fig. 2 is a perspective schematic view of a color transfer medium according to the invention.

[0032] The description of the above figures is given in cylindrical coordinates with a longitudinal axis X, a radial direction R perpendicular to the longitudinal direction X and a circumferential direction U perpendicular to the radial direction R.

[0033] Fig. 1 shows a schematic sectional view of a color transfer medium 1 according to the invention. Fig. 2 shows a perspective schematic representation of an ink transfer medium 1 according to the invention. The ink transfer medium 1 is designed in this embodiment as a printing blanket 1 or as a rubber blanket 1 for dry offset printing.

[0034] The printing blanket 1 has, in the radial direction R from outside to inside, a cover layer 10 as a functional layer 10 with a printing side 10a which is directed radially outwards. The printing side 10a serves to absorb ink in order to transfer it to a printing substrate. On the side of the printing layer 10 facing away from the printing side 10a, there is a strength carrier 11 which, by means of an embedded fabric, can transmit tensile forces, in particular in the circumferential direction U. Further radially inwards there is a contact layer 12 with a contact side 12a, wherein the contact side 12a of the contact layer 12 faces away from the printing side 10a of the cover layer 10. The cover layer 10 and the contact layer 12 consist of an elastomer material. The strength carrier layer 11 has an elastomer material in which the fabric is embedded.

[0035] According to the invention, the printing side 10a of the cover layer 10 is not ground, as previously known, in order to thereby bring the printing blanket 1 to a predetermined thickness in the radial direction R with the smallest possible tolerance. Instead, the contact side 12a of the contact layer 12 is ground to achieve the same result, but leaving the printing side 10a of the cover layer 10 unsanded. This can prevent grinding structures on the printing side 10a of the cover layer 10, which could have a negative impact on the printing result.

[0036] Furthermore, the printed side 10a of the cover layer 10 can be embossed at least in sections by means of an embossing foil and / or by means of an embossing paper in order to improve the ink transfer to the printed side 10a of the cover layer 10. List of reference symbols (part of the description)

[0037] Rradial direction Ucircumferential direction XLongitudinal axis 1Ink transfer medium; printing blanket; rubber blanket 10Top layer; functional layer 10aPrinting side 11Strengthening layer 12Contact layer 12aContact side

Claims

1. Method for producing an ink transfer medium (1), in particular a printing blanket (1), in particular a printing blanket (1) for offset printing, very particularly a printing blanket (1) for dry offset printing, wherein the ink transfer medium (1) has a covering layer (10) with a printing side (10a), wherein the covering layer (10) is designed to transfer an ink by means of the printing side (10a), and wherein the ink transfer medium (1) has a contact layer (12) with a contact side (12a), wherein the contact layer (12) is configured to be arranged on a surface of a flat body, wherein the contact side (12a) of the contact layer (12) is arranged so as to face away from the printing side (10a) of the covering layer (10), wherein the covering layer (10) and the contact layer (12) comprise, preferably consist of, at least one elastomeric material, in particular at least one rubber, wherein the method comprises at least the steps: • grinding the contact side (12a) of the contact layer (12), and • embossing the printing side (10a) of the covering layer (10) at least in sections by means of an embossing foil and / or an embossing paper.

2. Method according to Claim 1, characterized in that the printing side (10a) of the covering layer (10) is of unground form.

3. Method according to Claim 1 or 2, characterized in that the ink transfer medium (1) has, at least in sections, a predetermined thickness which was set by grinding the contact side (12a) of the contact layer (12).

4. Method according to one of the preceding claims, characterized by at least one reinforcement material layer (11) which is arranged at least in sections between the covering layer (10) and the contact layer (12).

5. Method according to one of the preceding claims, characterized in that the reinforcement material layer (11) comprises, preferably consists of, at least one elastomeric material, in particular at least one rubber.