Method and device for producing a printing plate

Abstract

A method serves for producing a printing plate (15, 15') for use in a porous printing process, in particular for screen printing, and comprises the steps of: providing (S1) a carrier element (6) and forming (S2) at least one first region (20, 20a, 20b) and at least one second region (30) in the carrier element (6), wherein the at least one first region (20, 20a, 20b) is permeable to a printing ink to be used in the porous printing process, and the at least one second region (30) is impermeable to the printing ink to be used in the porous printing process, wherein the at least one first region is formed by irradiating the carrier element (6) with at least one energy beam.

Description

[0001] Method and device for producing a printing form

[0002] The present invention relates to a method and a device for producing a printing form for use in a through-printing process, a printing form for use in a through-printing process, and a through-printing process using such a printing form.

[0003] In printing technology, a printing ink is transferred to a material to be printed using a printing form in accordance with a desired print image. Various printing processes are known for this. One printing process is the through-printing process, particularly screen printing. Here, a screen or fine-mesh fabric is used as the printing form (screen printing form), the areas where, according to the print image, no printing ink is to be transferred to the material to be printed are made impermeable to the printing ink. The printing form used in screen printing therefore has image areas that are designed as a screen or fabric and are thus permeable to the printing ink, and non-image areas where the printing form is impermeable to the printing ink. In the screen printing process, the printing ink is then applied to the printing form using a squeegee, with the printing ink only passing through the image areas onto the material to be printed, which is arranged beneath the printing form.

[0004] To produce the printing form for screen printing, a rectangular grid of threads is traditionally stretched over a frame to form the screen or mesh. Depending on the requirements of the print image, different threads can be stretched onto a frame. The threads can be selected according to their thickness, for example, or their surface texture, such as smooth or fibrous. Depending on the spacing of the parallel threads in the perpendicular X and Y directions, the desired small or large holes are created, through which the printing ink is later pressed using a squeegee.

[0005] A further layer is then applied to the stretched mesh screen, closing all the holes in the mesh screen. The image to be printed is then applied to this layer. Various processes are then used to wash out the image on the layer, exposing the holes for the image to create the image areas on the printing form. For this purpose, processes using a film to be exposed and a light source, e.g., a UV light source (photomechanical processes) are known. The layer is then washed out and hardened after exposure.

[0006] Also well-known is the CTS process (CTS stands for "Computer to Screen"), in which the image, or non-image areas, are applied to the layer sealing the holes of the mesh screen using a laser or other light source. No film layer is required.

[0007] According to known methods for producing a printing form for screen printing, the screen or fine-mesh fabric is first prepared, and then the non-image areas are covered with an additional layer, similar to forming a stencil on the screen. The non-image areas where the printing form is to be impermeable to the printing ink are thus added to the screen (additive manufacturing of the printing form).

[0008] This can have the disadvantage that the mesh size and thread thickness of different areas on a screen printing form (printing form) are always the same, since the screen printing form is formed by stretching a thread and thus does not allow for different mesh sizes / thread counts for different areas of a printing form. Furthermore, the production of such a screen printing form is costly, energy-intensive, and time-consuming, as a complete cycle, including screen reprocessing, requires many different manufacturing steps, including coating, drying, exposure, washing, drying, decoating, degreasing, and drying. These processes require a lot of water, chemicals, energy, and time.

[0009] It is therefore an object of the present invention to provide an alternative or improved method for producing a printing form for use in a through-printing process, or an alternative or improved device for producing a printing form for use in a through-printing process, or an alternative or improved printing form for use in a through-printing process, and an alternative or improved through-printing process.

[0010] This object is achieved by a manufacturing method according to claim 1, a manufacturing device according to claim 10, a printing form according to claim 14, and a printing method according to claim 15. Further developments of the invention are specified in the dependent claims. The methods can also be further developed by the features of the devices specified below or in the dependent claims, and vice versa. Likewise, the features of the devices or methods can also be used for further development among themselves.

[0011] A method according to the invention serves to produce a printing form for use in a screen printing process, in particular for screen printing. The method comprises the following steps: providing a carrier element and forming at least one first region and at least one second region in the carrier element, wherein the at least one first region is permeable to a printing ink to be used in the screen printing process, and the at least one second region is impermeable to the printing ink to be used in the screen printing process, wherein the at least one first region is formed by irradiating the carrier element with at least one energy beam.

[0012] Preferably, in the method, only the locations of the carrier element corresponding to the at least one first region are irradiated with the at least one energy beam. Preferably, in the method, the locations of the carrier element corresponding to the at least one first region are selectively irradiated.

[0013] Preferably, the carrier element is a medium or element impermeable to the printing ink. By irradiating the locations corresponding to the at least one first region with the at least one energy beam, the at least one first region can be made permeable to the printing ink, whereas the locations corresponding to the second region remain impermeable to the printing ink, in accordance with the property of the carrier element being impermeable to the printing ink.

[0014] The fact that the at least one first region is permeable to a printing ink to be used in the printing process preferably means that the printing ink can pass from an upper side of the carrier element or the printing form, to which the printing ink is applied during the printing process, through the printing form to the underside of the carrier element or the printing form. Accordingly, the expression that the at least one second region is impermeable to a printing ink to be used in the printing process preferably means that the printing ink applied to the upper side of the carrier element or the printing form cannot pass to the underside of the carrier element or the printing form.

[0015] The at least one first region can, in particular, represent image areas of the printing form that are permeable to the printing ink. The at least one second region can, in particular, represent non-image areas of the printing form that are impermeable to the printing ink.

[0016] This method can, for example, provide a subtractive manufacturing process for producing a printing form. Since essentially no additional materials and substances are required other than the carrier element itself, the printing form can be produced in a simple and / or cost-effective and / or energy-efficient manner.

[0017] Preferably, the at least one first region is formed by irradiating the carrier element with energy radiation, more preferably using laser radiation in the infrared spectral range, even more preferably with a wavelength between 300 nm and 1 mm, in particular substantially 980 nm. By using laser radiation, it is possible, for example, to vary the detail resolution of the transmission structure for the different regions of the printing form. Preferably, a spot size of the at least one energy beam on the carrier element is in the range from 1 p to 200 p. More preferably, the focus size of the energy beam on the carrier element is adjustable. This makes it possible, for example, to achieve any desired grating structures and screenings in the at least one first region.

[0018] Preferably, by irradiating the carrier element with the at least one energy beam in the at least one first region, a number of holes are formed, in particular burned in, in the carrier element, wherein more preferably the number of holes form a structure in the carrier element that is permeable to the printing ink. The holes can in particular form a lattice structure, a screen, a honeycomb structure and / or a screen. Preferably, the lattice structure, screen, honeycomb structure and / or the screen is formed by the holes together with the webs separating the holes. Webs are understood here to be the locations in the at least one first region in which the material of the carrier element has not been removed. In this way, permeability for the printing ink can be achieved, for example.

[0019] Preferably, the at least one first region forms a support structure for the at least one second region. This makes it possible, for example, to also represent non-image areas (corresponding to the at least one second region of the printing form) that are completely and / or seamlessly enclosed by image areas (corresponding to the at least one first region of the printing form), as is the case, for example, with the letter "0" or the number "0."

[0020] Preferably, a plurality of holes are formed in the carrier element in the at least one first region, wherein the plurality of holes form a structure, and wherein the structure is more preferably designed differently in a size of the holes and / or a geometric shape of the holes and / or a geometric arrangement of the holes in at least two partial regions of the at least one first region. This can, for example, provide a freely selectable support structure. Preferably, the carrier element is a plate or a film, more preferably a plastic film, in particular a PET film. Alternatively or additionally, the carrier element preferably has a thickness in the range from 25 μm to 150 μm, for example substantially 50 μm.The thickness of the carrier element refers in particular to its extension from a top side of the printing form, to which printing ink is applied in a printing process, to a bottom side of the printing form, which faces the material to be printed in the printing process. Preferably, the carrier element is clamped in a frame before forming the at least one first and at least one second region. This makes it possible, for example, to provide a carrier element that can be easily irradiated with the energy beam to form the at least one first region.

[0021] A device according to the invention serves to produce a printing form for use in a through-printing process, in particular for screen printing. The device has a carrier platform designed to receive a carrier element of the printing form, and an irradiation unit designed to generate at least one energy beam for irradiating the carrier element arranged on the carrier platform. The irradiation unit is designed and / or controlled such that by irradiating the carrier element with the at least one energy beam, at least a first region and at least a second region are formed in the carrier element, such that the at least one first region is permeable to a printing ink to be used in the through-printing process, and the at least one second region is impermeable to the printing ink to be used in the through-printing process.This makes it possible, for example, to achieve the effects described above with regard to the manufacturing process also with a manufacturing device.

[0022] Preferably, the irradiation unit is designed to direct the at least one energy beam exclusively onto the locations corresponding to the at least one first region of the carrier element. Preferably, the irradiation unit and the carrier platform are arranged in the device so as to be movable relative to one another. Preferably, the irradiation unit comprises a number of laser diodes, more preferably a plurality of laser diodes arranged in an array, in particular a number of laser diodes that emit laser light in the infrared spectral range, preferably with a wavelength between 300 nm and 1 mm, in particular substantially 980 nm. The laser diodes are preferably cooled.

[0023] A printing form according to the invention is intended for use in a through-printing process, in particular for screen printing, and comprises a carrier element having at least one first region and at least one second region, wherein the at least one first region is permeable to a printing ink to be used in the through-printing process, and the at least one second region is impermeable to the printing ink to be used in the through-printing process, and wherein the at least one first region is formed by irradiating the carrier element with at least one energy beam.

[0024] Preferably, the printing form is a printing form produced by a production method described above and / or a printing form produced in a production device described above. Preferably, the first region is in the form of a grid structure, a screen, a honeycomb structure, and / or a screen and / or has a number of holes that are permeable to the printing ink. Preferably, the first region is formed by at least partially removing material from the carrier element.

[0025] A printing process according to the invention is carried out using the printing form described above. The printing form is placed on a material to be printed, and printing ink is applied to the printing form using a doctor blade. The material to be printed can be, for example, paper, cardboard, plastic, textiles, ceramics, metal, wood, or glass, or any other printable material. Examples of printing inks that can be used include water-based inks, plastisol inks, UV inks, varnish inks, adhesives, conductive pastes, etc.

[0026] Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the accompanying figures. Fig. 1 shows a schematic, perspective view of an apparatus for producing a printing form according to an embodiment of the present invention.

[0027] Fig. 2a and 2b show a schematic, perspective view of a printing form according to an embodiment of the present invention, wherein Fig. 2b shows an enlarged section of the printing form shown in Fig. 2a, which section is marked in Fig. 2a by a dashed circle,

[0028] Fig. 3 shows schematic steps of a method for producing a printing form according to an embodiment of the present invention, and

[0029] Fig. 4 shows a schematic perspective view of a printing form according to another embodiment of the present invention.

[0030] A device for producing a printing form according to an embodiment of the present invention is described below with reference to Fig. 1. The production device 1 shown in Fig. 1 is designed as a plotter and comprises a base plate 2, a support platform in the form of a support plate 3, and an irradiation unit 4.

[0031] The base plate 2 has a linear guide device, e.g., in the form of two rails 5a, 5b, which are arranged parallel to each other and extending in a first direction x on an upper side of the base plate 2. The carrier plate 3 is arranged on the rails 5a, 5b such that it is movable relative to the base plate 2 in the first direction x.

[0032] The carrier plate 3 is designed to accommodate a carrier element 6 of the printing form. For this purpose, the carrier plate 3 has a frame 7 on its side facing away from the base plate 2, into which the carrier element 6 can be clamped.

[0033] Above the carrier plate 3 and at a distance therefrom, the production device 1 has a holder 8, for example in the form of a beam, wherein the holder extends in a second direction y. The holder 8 can, for example, be attached to the base plate 2 at its ends spaced apart in the second direction y by means of feet 9a, 9b. The irradiation unit 4 is arranged on the holder 8 such that it is movable along the holder 8 in the second direction y.

[0034] The first direction x, along which the carrier plate 3 is provided for movement relative to the base plate 2, and the second direction y, along which the irradiation unit 4 is provided for movement relative to the base plate 2, are provided at an angle to each other, preferably at right angles to each other. In Fig. 1, the two directions x, y are each parallel to a plane formed by the base plate 2 and are horizontal directions, respectively.

[0035] The irradiation unit 4 is designed to generate at least one energy beam in the form of laser radiation 11 for irradiating the carrier element 6 arranged on the carrier plate 3. For this purpose, the irradiation unit 4 can, for example, have one or more laser diodes, for example a plurality of laser diodes arranged in an array. For example, between 16 and 128 laser diodes can be arranged in an array. The laser diodes emit laser light, e.g., in the infrared spectral range, preferably with a wavelength between 300 nm and 1 mm, in particular substantially 980 nm.

[0036] Due to the mobility of the carrier plate 3 relative to the base plate 2 and thus also to the holder 8 in the first direction x, as well as the mobility of the irradiation unit 4 relative to the base plate 2 and thus also to the carrier plate 3 in the second direction y, the laser radiation 11 generated by the irradiation unit 4 can be selectively directed onto any point of the carrier element 6 arranged on the carrier plate 3.

[0037] A method for producing a printing form according to an embodiment of the present invention is described below with reference to Figures 2a, 2b and 3. The method can be carried out, for example, in the production device 1 described above or shown in Figure 1. In a first step S1, a carrier element 6 for the printing form is provided. In the present embodiment, the carrier element 6 is designed as a film, for example a PET film. The carrier element 6 is impermeable to a printing ink to be used in a through-printing process. The thickness of the carrier element 6 can be, for example, 50 μm. In the present embodiment, the carrier element 6 is clamped in a frame 7, for example in the frame 7 mentioned above with reference to Figure 1.

[0038] In a second step S2, first regions 20 are formed in the carrier element 6, which are permeable to a printing ink to be used in a through-printing process, and second regions 30 are formed, which are impermeable to the printing ink to be used in the through-printing process. According to one embodiment of the present invention, the first regions 20 are formed by selectively irradiating the locations of the carrier element 6 that correspond to the first regions 20 with at least one energy beam. For this purpose, for example, the laser radiation 11 generated in the production device 1 by the irradiation unit 4, as described above with reference to Fig. 1, can be used. The irradiation unit 4 can be moved in the first direction x and the second direction y such that the laser radiation 11 is directed exclusively onto the locations corresponding to the first regions 20 of the carrier element.If the irradiation unit 4 passes over locations of the carrier element 6 which correspond to the second regions 30, the laser radiation 11 can, for example, be switched off or the energy emitted per unit of time can at least be reduced.

[0039] Fig. 2a shows, purely by way of example, a carrier element 6 in which two first regions 20 are formed in the form of two spaced-apart and differently sized squares, surrounded by a second region 30 of the carrier element 6.

[0040] In order to achieve permeability of the first regions 20 for the printing ink, the locations of the carrier element 6 corresponding to the first regions 20 are irradiated with the energy beam or the laser radiation 11 in such a way that holes 21 are formed, e.g. burned in, in the carrier element 6, as shown schematically in the enlarged illustration in Fig. 2b. In other words, by irradiating the locations of the first region 20 with the energy beam or the laser radiation 11, material of the carrier element 6 is partially removed, so that the holes 21 are formed. The holes 21, together with the webs 22 separating them, in which the material of the carrier element 6 has not been removed, form a structure permeable to the printing ink, for example similar to a fabric or screen.

[0041] The holes 21 are preferably arranged in the first region 20 at regular intervals in the form of a grid, and each have the same geometric shape and size, as shown in Fig. 2b.

[0042] According to a further development of the method according to the invention, the holes 21 of the first regions 20 can be designed differently in different sub-regions in order to achieve different grids in the different sub-regions. For this purpose, for example, the size of the holes 21 in a first sub-region and a second sub-region can be selected differently, as shown schematically in Fig. 2b: Fig. 2b shows a first sub-region 20a of the first region 20, which corresponds to the larger of the two squares (in Figures 2a, 2b the square at the top right), and a second sub-region 20b of the first region 20, which corresponds to the smaller of the two squares (in Figures 2a, 2b the square at the bottom left), as well as a circular sub-region within a circular ring, which is provided as a second region 30 in the larger square. The smaller square (second sub-region 20b) also has a circle designed as a second region 30.In the first partial region 20a, the holes 21 formed by irradiation with the laser radiation 11 are larger to achieve a coarser grid. In the second partial region 20b, the holes 21 are smaller than in the first partial region 20a to achieve a smaller grid.

[0043] As shown in Fig. 2b, the first region 20 (or the first and second partial regions 20a, 20b) forms a support structure for the annular or circular second regions 30, which are completely and seamlessly enclosed by the first region 20.

[0044] The carrier element 6 formed in the method described above with the first regions 20 or 20a, 20b, and the second region 30 together form a printing form 15. This is suitable for use in a through-printing process, in particular in a screen printing process.

[0045] Fig. 4 shows a further embodiment of a printing form 15' in the form of a carrier element 6 within a frame 7. In the present embodiment, the carrier element 6 is rectangular, with an outer rectangle being designed as a second region 30, i.e. a region impermeable to the printing ink, and an inner rectangle provided in the outer rectangle being designed as a first region 20a with a first, coarse screening, i.e. as a region permeable to the printing ink. In the inner rectangle (first region 20a), a star-shaped second region 30 is formed, i.e. a region impermeable to the printing ink, in which second region 30, i.e. a region permeable to the printing ink, is formed. The star-shaped first region 20b has a smaller screening than the first region 20a forming the inner rectangle.This allows, for example, the detailed jagged edges of the small star to be better represented. The first region 20a forming the inner rectangle forms a support structure for the star-shaped second region 30, which is not connected to the second region 30 forming the outer rectangle, but is completely and seamlessly enclosed by the first region 20a (inner rectangle).

[0046] To use the printing form 15 or 15' described above with reference to Fig. 2a, 2b or Fig. 4 in a through-printing process, in particular a screen printing process, the printing form 15, 15' is placed on a material to be printed, e.g. paper. A printing ink is then applied to the printing form 15, 15' using a squeegee. The printing ink only reaches the material to be printed (image areas) at the points where the first regions 20 or 20a, 20b are formed in the printing form. The second regions 30 of the printing form 15, 15' are impermeable to the printing ink and thus prevent printing ink from reaching the material to be printed at the points corresponding to the second regions (non-image areas). Water-based ink, for example, can be used as the printing ink.

[0047] The present invention is not limited to the embodiments described above. Rather, modifications of the described embodiments are possible within the scope of the present invention.

[0048] For example, the figures show a rectangular support element 6 clamped in a rectangular frame 7. However, any other geometric shapes of the support element and / or the frame element are also possible, such as round or oval shapes, or the shape of a regular or irregular polygon, etc. The same applies to the components of the manufacturing device shown in Fig. 1, in particular to the base plate 2 and the support plate 3.

[0049] The printing form can have one or more first and / or second regions, wherein the first regions can be provided with the same or different screening. The at least one first and at least one second region are preferably selected according to a print image to be achieved. The holes forming the screening of the at least one first region can be, for example, square or circular, or have any other shape. The screening, for example defined by a shape and size of the holes, as well as a distribution of the holes and webs separating the holes, is preferably selected such that a printing ink used in the through-printing process can penetrate the holes.

[0050] In the above embodiments, the carrier element is formed as a film, for example, a PET film. Another carrier element, for example, a (thin) plate, can also be used as the carrier element. Preferably, the carrier element is selected in terms of its shape, dimensions, and material such that it is impermeable to a printing ink to be used in a through-printing process and becomes permeable to the printing ink at least in certain regions when the corresponding first regions are selectively irradiated with the at least one energy beam.

[0051] The present invention is also not limited to the manufacturing method and the manufacturing device described above. The device shown in Fig. 1, for example, has a linear guide device on its base plate, which serves to move the carrier plate in the first direction x, and the irradiation unit is provided on the holder so that it can move along the second direction y. Alternatively, the carrier plate can also be fixed in the manufacturing device, and the irradiation unit can be provided so that it can move in both the first direction x and the second direction y, or vice versa.

[0052] It is also possible to use a line exposure unit with a plurality of individually controllable irradiation elements, e.g., laser diodes or groups of laser diodes, as the irradiation unit. The line exposure unit extends across the entire width (e.g., in the second direction y) of the area to be exposed and is provided so as to be movable relative to the carrier plate in a direction perpendicular to the width of the area to be exposed (e.g., in the first direction x). By switching the individually controllable irradiation elements of the line exposure unit on and off, a desired intensity profile can be achieved on the carrier element corresponding to the first areas to be exposed.

[0053] Furthermore, it is possible to use an irradiation unit which generates at least one energy beam, in particular a laser beam, which is directed selectively onto the locations of the carrier medium corresponding to the at least one first region by a deflection optic, such as one or more optical elements such as a deflectable mirror.

[0054] In general, an irradiation unit can be used which is designed and / or controlled in such a way that it is designed for selectively irradiating exclusively the locations corresponding to the at least one first region of the carrier element with at least one energy beam, so that the first region is permeable to a printing ink to be used in the printing process after irradiation.

Claims

Claims 1 . A method for producing a printing form (15, 15') for use in a screen printing process, in particular for screen printing, comprising the steps: Providing (S1) a carrier element (6) and Forming (S2) at least one first region (20, 20a, 20b) and at least one second region (30) in the carrier element (6), wherein the at least one first region (20, 20a, 20b) is permeable to a printing medium to be used in the printing process, and the at least one second region (30) is impermeable to the printing ink to be used in the printing process, wherein the at least one first region is formed by irradiating the carrier element (6) with at least one energy beam.

2. The method according to claim 1, wherein the at least one first region (20, 20a, 20b) is formed by irradiating the carrier element with laser radiation (11).

3. Method according to claim 2, wherein laser radiation (11) is used in the infrared spectral range, and / or with a wavelength between 300 nm and 1 mm, in particular essentially 980 nm.

4. Method according to one of claims 1 to 3, wherein by irradiating the carrier element (6) with the at least one energy beam in the at least one first region (20, 20a, 20b) a number of holes (21) are formed, in particular burned, in the carrier element, wherein preferably the number of holes (21) form a structure in the carrier element (6) that is permeable to the printing ink.

5. Method according to one of claims 1 to 4, wherein by irradiating the carrier element (6) with the at least one energy beam in the at least one first region (20, 20a, 20b), a plurality of holes (21) is formed in the carrier element, wherein the plurality of holes form a grid, and wherein the grid is designed differently in a size of the holes (21) and / or a geometric shape of the holes (21) and / or a geometric arrangement of the holes (21) in at least two partial regions (20a, 20b) of the at least one first region.

6. Method according to one of claims 1 to 5, wherein the carrier element (6) is a plate or a film.

7. The method according to claim 6, wherein the film is a plastic film, preferably a PET film.

8. Method according to one of claims 1 to 7, wherein the carrier element (6) has a thickness in the range of 25 p to 150 p, in particular substantially 50 pm.

9. Method according to one of claims 1 to 8, wherein the carrier element (6) is clamped in a frame (7) before the formation of the at least one first and the at least one second region.

10. Device for producing a printing form (15, 15') for use in a through-printing process, in particular for screen printing, comprising: a carrier platform (3) designed to receive a carrier element (6) of the printing form, and an irradiation unit (4) designed to generate at least one energy beam for irradiating the carrier element (6) arranged on the carrier platform (3), wherein the irradiation unit (4) is designed and / or controlled such that by irradiating the carrier element (6) with the at least one energy beam, at least a first region (20, 20a, 20b) and at least one second region (30) are formed in the carrier element (6), such that the at least one first region is permeable to a printing ink to be used in the through-printing process, and the at least one second region is impermeable to the printing ink to be used in the through-printing process.

11. Device according to claim 10, wherein the irradiation unit (4) is designed to direct the at least one energy beam exclusively onto the locations corresponding to the at least one first region (20, 20a, 20b) of the carrier element.

12. Device according to claim 10 or 11, wherein the irradiation unit (4) and the carrier platform (3) are arranged in the device (1) so as to be movable relative to one another.

13. Device according to one of claims 10 to 12, wherein the irradiation unit (4) comprises a number of laser diodes, preferably a plurality of laser diodes arranged in an array, in particular a number of laser diodes which emit laser light in the infrared spectral range and / or with a wavelength between 300 nm and 1 mm, in particular substantially 980 nm.

14. Printing form for use in a through-printing process, in particular for screen printing, comprising: a carrier element (6) with at least one first region (20, 20a, 20b) and at least one second region (30), wherein the at least one first region is permeable to a printing ink to be used in the through-printing process, and the at least one second region is impermeable to the printing ink to be used in the through-printing process, wherein the at least one first region (20, 20a, 20b) is formed by irradiating the carrier element (6) with at least one energy beam.

15. A printing method using a printing form according to claim 14, wherein the printing form (15, 15') is placed on a material to be printed, and printing ink is applied to the printing form (15, 15') by means of a doctor blade.

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