JP7184240B2 - Creating a direct-to-mesh screen - Google Patents

Description

This application claims priority from Application No. PCT/EP2017/050214 filed on January 5, 2017.

Screen printing is a printing technique that uses a mesh to transfer ink onto a substrate except in areas made impermeable to the ink by a screen printing stencil, also called a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh openings with ink and then a reverse stroke causes the screen to momentarily contact the substrate along the contact line. This causes the ink to wet the substrate as the screen bounces off after the blade passes and pulls it away from the mesh openings.

Making a screen printing stencil is a tedious and labor intensive task. It requires many process steps, chemicals, large amounts of water, and is largely done manually. This is the least automated part of the current screen printing business.

Embodiments of the present disclosure will become apparent by reference to the following detailed description and drawings. In the drawings, similar reference numbers correspond to similar, but not identical, components. For the sake of brevity, reference numbers or reference features having previously described functions may or may not be described in relation to other drawings in which they appear.

FIG. 1 illustrates a direct-to-mesh printer according to one example of this disclosure.

FIG. 2A illustrates in cross-section elements of a process in screen printing using a direct-to-mesh screen printer, according to one example of the present disclosure. FIG. 2B illustrates in cross-section elements of a process in screen printing using a direct-to-mesh screen printer, according to one example of the present disclosure. FIG. 2C illustrates in cross-section elements of a process in screen printing using a direct-to-mesh screen printer, according to one example of the present disclosure. FIG. 2D illustrates in cross-section elements of a process in screen printing using a direct-to-mesh screen printer, according to an example of the present disclosure. FIG. 2E illustrates in cross-section elements of a process in screen printing using a direct-to-mesh screen printer, according to one example of the present disclosure.

Figure 3A schematically illustrates an emulsion on mesh, providing a comparison between current technology (Figure 3A) and the disclosure herein (Figure 3B), according to one example of the present disclosure. Figure 3B schematically illustrates an emulsion on mesh, providing a comparison between current technology (Figure 3A) and the disclosure herein (Figure 3B), according to one example of the present disclosure.

FIG. 4 is a flowchart illustrating a method of screen printing according to one example of this disclosure.

There are some examples of previous solutions for directly coating mesh to form stencils for screen printing. These will be explained.

・Mesh preparation and coating:
Direct Application of Emulsion: Direct application of emulsion is done either by machine or by hand. Both sides of the screen must be coated with emulsion to ensure proper coverage. Machines or automated versions are strictly machines that replace humans. This machine applies the exact amount of emulsion with much greater accuracy and provides uniform coverage. This machine is generally less wasteful.

Capillary Film: A capillary film is a film pre-coated with an emulsion. The mesh is supersaturated with water and the film (emulsion side down) is placed against the supersaturated mesh. The emulsion is drawn into the mesh by capillary action. This gives a more precise coating of the emulsion in both thickness and coverage. As the emulsion diffuses into the mesh, the film is peeled off.

Once the emulsion penetrates the screen mesh, the screen mesh must be dried. Once the screen mesh is dry, it is ready for image transfer or stenciling. As the emulsion dries, it shrinks and conforms to the mesh, creating a rough, uneven surface. (This rough surface accelerates aging of the squeegee during the printing process.)

Most emulsions today are activated by ultraviolet (UV) radiation (ie, UV-activated), but may be activated by visible light. Once coated, the stencil must be protected from exposure to any light (even normal visible light has enough UV to initiate the curing process). Hereafter the emulsion is considered to be UV activated/cured.

Image Transfer/Stencil Creation:
In screen printing, there is one stencil for each color, typically cyan, magenta, yellow, and black (CMYK) plus each spot color (spot colors are usually discrete colors not easily achievable with CYMK colors). is based on). Areas of the stencil that we do not want ink to pass through are blocked by an emulsion that is subsequently cured to form the stencil, and all other areas have only mesh. Any openings in the mesh may be completely blocked or partially blocked by the emulsion to form a stencil.

Film positive ink: Print a completely black UV-absorbing layer on a plastic transparency sheet. Printing is usually done by laser or inkjet printers using special film positive inks (film positive ink means high opacity black ink that completely blocks all visible and UV light). The film is then adhered to the precoated mesh and exposed to UV light. Attachment is usually done by removable tape (such as masking tape). After exposure, the film is removed and the uncured emulsion is washed away.

However, this approach is very labor intensive at all stages and it is not possible to automate many steps. In addition, errors are prone to occur during film installation using the correct film to prepare the final stencil prior to printing. It requires large amounts of consumables (inks and films) as well as large amounts of chemicals and cleaning agents.

Thermal screen:
In this method, the mesh is precoated with a heat activated emulsion. Typically, the mesh (without frame) is placed in a thermal printer where the emulsion is directly cured/activated. Once complete, the unexposed emulsion is washed off and the stencil is placed on the frame and printed.

However, this approach limits the mesh count. Also, the emulsion is not very strong. Pretreated mesh is expensive. Stencil alignment needs to be more thorough. Finally, the stencil can be damaged while being installed.

Computer-to-screen (CtS) printing:
In this method, the coated mesh is printed directly onto an emulsifying screen with high opacity black ink. This is similar to film positive ink without film. All processes are the same.

However, these machines require high opacity inks, which are more expensive than regular inkjet inks.

CtS_Wax:
This method is closely related to CtS printing, but uses wax to block UV light. Everything else is the same.

However, due to the use of molten wax, these machines can be difficult to handle. Additionally, the wax requires heating to apply to the mesh.

CtS direct exposure:
This technique uses a UV laser to directly expose the emulsion.

However, the machines used in this technique are typically very expensive. Furthermore, this process does not work well with coarser grade meshes. Finally, UV lasers are still very expensive if replacement is required.

Each of the above methods requires some post-processing/follow-up. Except for heat activation and CtS direct exposure, all stencils must be exposed after image blocking has been applied (either film or CtS print and wax). This process takes about 1-2 minutes per screen using aggressive developer.

All screens should be rinsed of excess emulsion. Care must be taken to keep the emulsion out of the drainage system. After washing, the screen must be dried.

For film and heat activation methods, the finished stencil must be fine-tuned when placed on the carousel to ensure proper alignment.

The desirability of a simpler approach using less chemicals and less water is evident from the foregoing description of the current technology.

As disclosed and claimed herein, a direct-to-mesh (DtM) approach to forming stencils uses inkjet technology to spread an emulsion onto a screen. direct application to and activation/exposure. Specifically, according to the disclosure herein, a DtM screen printer includes:
a frame for holding the pre-stretched mesh in place while applying the jettable emulsion;
a fixture for holding the frame;
a platen for holding the stripper solution against one side of the pre-stretched mesh;
- a stripper dispenser that supplies the stripper onto the platen or mesh;
• A printer carriage that supports a print head for printing jettable emulsion on the side of the pre-stretched mesh opposite the platen.

FIG. 1 shows a block diagram of a direct-to-mesh (DtM) printer 100. As shown in FIG. The DtM printer 100 includes a mesh support system 110 comprising a pre-stretched mesh 112 held in place by a frame 114 . Frame 114 is held by fixtures 116 . Fixtures 116 rigidly hold frame 114 with pre-stretched mesh 112 in place during application of the jettable emulsion.

As used herein, mesh 112 is made from connected strands of fabric, fiber, metal, or other flexible/ductile material, here woven in a criss-cross pattern. The material from which the mesh is constructed can be any number of fabrics (silk, polyester), metals such as stainless steel, plastics such as polypropylene, polyethylene, nylon, polyvinyl chloride (PVC) or polytetrafluoroethylene (PTFE), or Any glass fiber may be used. The strand diameter can be any diameter common in screen printing, and the mesh size can be any size common in screen printing. A coarser mesh is usually woven with strands of larger diameter (gauge), which requires a thicker application of emulsion.

The DtM printer 100 further includes a platen support system 120 containing stripper fluid 122 held to one side of the pre-stretched mesh 112 by a platen 124 . Platen 124 holds stripper solution 122 firmly against the bottom of pre-stretched mesh 112 . The platen 124 is configured to be as smooth as possible, impervious to liquids, and resistant to dents and cracks. Platen 124 also functions to disperse energy from UV light source 208 (shown in FIG. 2D, not FIG. 1).

The stripper solution 122 may be applied directly to the platen 124 or to the mesh 112 positioned on the platen prior to applying the jettable emulsion. For example, a liquid dispenser 126 that introduces or applies stripper liquid 122 to platen 124 may have one or more sprayers 126 . The spray 126 may have a conventional atomizer or spray-type element.

By not reacting with the cured emulsion, the stripper liquid 122 suppresses dot gain, which is the effect of the printing fluid spreading into the print medium. After jetting the emulsion liquid, curing occurs so quickly that dot gain needs to be suppressed only for a short period of time.

Finally, the DtM printer 100 includes an inkjet printer 130 that includes a printhead 132 mounted on a printer carriage 134 . The printhead 132 is configured to print a jettable emulsion on the side of the pre-stretched mesh 112 opposite the platen 124 . Printer carriage 134 is a high-precision printer carriage that is accurate in both the X and Y directions in a Cartesian coordinate system and assists in precise drop placement over one or more passes during deposition of the jettable emulsion. . In fact, emulsions can be "built up" to fit a wide range of mesh gauges, from very fine to very coarse. Lamination can be used to maintain high resolution when depositing emulsions.

Printhead 132 is an inkjet printhead such as a thermal inkjet, piezoelectric inkjet, drop-on-demand inkjet, or other suitable jetting printhead capable of jetting fluid, including the jettable emulsions disclosed herein. may be

Screen mesh 112 , which may be of any type, expensive or inexpensive, and of any gauge, is stretched over frame 114 . Frame 114 is placed in inkjet printer 130 with stripper 122 placed on platen 124 . A jettable emulsion is then applied to the masked area by an inkjet printer 130 and substantially simultaneously exposed to a high intensity UV lamp or other suitable UV source such as a UV light emitting diode (LED). UV lamps (or LEDs) can be matched to the reaction range of the jettable emulsion for optimum performance. For the jettable emulsion disclosed herein, the emulsion responds at a wavelength of 395 nanometers (nm). Other jettable emulsions may have other response wavelengths, including below 395 nm. For coarse mesh, the application may be a multi-pass operation to build up the emulsion to the required thickness. By "coarse mesh" is meant a mesh that has a looser weave and thus a larger gap between strands than a fine mesh screen. For example, 335 mesh count is considered a fine mesh, while 110 mesh count is considered a coarse mesh. Here mesh count is the number of thread crossings per square inch.

The direct-to-mesh method disclosed herein is made possible by the recent development of low viscosity jettable emulsions. By "low viscosity" is meant a range from about 4 centipoise (cP) to about 15 cP (about 4 millipascal-seconds to 15 millipascal-seconds). These new jettable emulsions are used to create embossed effects on a wide variety of materials using UV printers. These new jettable emulsions are also more elastic and therefore can be used more easily as replacements for previous emulsions. Any color can be used in the jettable emulsion, including transparent or clear, but a light cyan or light magenta can be used to provide a slight contrast for verifying the stencil. Any color can be used in the jettable emulsion, including transparent or clear, but a light cyan or light magenta can be used to provide a slight contrast for verifying the stencil.

An example of a jettable emulsion that can be suitably used in the process disclosed herein is a UV-activated acrylate monomer that has elastomeric properties after curing. The jettable emulsion is a special embossed "varnish" polymer that quickly deposits and cures on the substrate to form both highly durable and highly resistive layers. The cured polymer is also durable and flexible/elastic (if the polymer is hard it will crack easily during use rendering the stencil useless). VersaUV (Roland DG) technology is one example of materials that may be useful in the practice of the present disclosure.

Stripper liquid 122 is configured to provide a smooth, non-reactive printing surface under mesh 112 . It also serves to limit the dot gain of the printed emulsion. Dot gain occurs when the ejected droplet (ie dot) expands or spreads before UV exposure. This is especially important when halftones are employed, ie when the entire space within the mesh is not filled with emulsion. However, UV curing occurs very quickly after the emulsion is jetted, so dot gain needs to be suppressed only for a short period of time.

The release liquid 122 is a dot gain control liquid that does not react with the curing emulsion so that the emulsion does not lift or separate from the mesh 112 . The fluid for the stripper solution 122 can be modified by altering certain properties including, but not limited to, surface tension, ionic mixture, polar or non-polar components, or changing whether the fluid is aqueous or non-aqueous. , can be modified or adjusted for jettable emulsions.

The stripper solution 122 may be aqueous (eg, distilled water), or may include water alone or at least one emulsifier in an amount sufficient to prevent evaporation of the stripper solution. Examples of emulsifying agents include, but are not limited to, emulsifying agents known as surfactants, including polysorbates, glycerin, and glycols such as butylcellulose. In some embodiments, the emulsifier may be present in an amount of at least 3% to 5% by volume to prevent evaporation of stripper solution 122 . Other examples of stripper solution 122 also include water-based varnishes such as butyl acetate, xylene, xylol, dimethylbenzene, and combinations thereof.

The stripper solution 122 is deposited directly onto the platen 124 or onto the mesh 112 after the mesh is placed on the platen 124 . In most current technology formulations, the emulsion can be quite coarse, often caused by the emulsion becoming conformal to the mesh during the drying process. However, this rough emulsion surface wears on the squeegee and can require reshaping or replacement of the squeegee blade. However, in the direct-to-mesh process, the stripper liquid 122 ensures a very smooth surface once the jettable emulsion is deposited within the mesh. See, eg, FIG. 3B and the discussion that accompanies it.

Since the emulsion applied to the mesh 112 is only in the blocked areas, there is no overshoot or overexposure due to reflection of UV light onto the masked areas. This provides a much smoother, cleaner image. (These overshoot and overexpose areas can produce spots or droplets inside the image, especially around the edges, which are the "flips" of pinholes.)

The platen 124 provides a smooth, hard, impermeable surface for the stripper solution 122 and gently holds the mesh 112 taut to ensure a good, even, flat surface for applying the emulsion. push. In some embodiments, the platen 124 does not absorb the stripper solution 122, does not interact chemically or physically with the stripper solution 122, and is planar (±0.05 mm/m). By "smooth" is meant that the surface of platen 124 is a regular surface that can be either polished/glossy or matte/matte, so long as the surface is regular.

Exemplary steps of the direct-to-mesh process are illustrated in FIGS. 2A-2E, which are cross-sectional views of the DtM device.

In FIG. 2A, frame 114 surrounds platen 142 . Fixtures 116 for supporting frame 114 are omitted in FIGS. 2A and 2B-2E. Frame fixtures 116 are similar to those currently used in the art. One or more elements or sprays 126 spray a layer of stripper solution 122 onto an upper surface 126 a of platen 124 . Spray 126 may be fixed in place or configured to traverse platen 124 . Of course, the ejected liquid can be applied by various methods such as spraying, wiping or brushing.

In FIG. 2B, mesh 112 is placed across the top of frame 114 . Below the mesh 112 is a platen 124 having a thin, uniform coating of stripper solution 122 supported on the platen's surface 124a. In some embodiments, the stripper solution 122 has a thickness of about 20 micrometers (μm), but in any case less than the gauge of the mesh and planar within ±0.5 μm. Stripping solution 122 backs up mesh 112 when applied to provide good coverage of the jettable emulsion. The stripper solution 122 is formulated to avoid sticking of the jettable emulsion to the platen 124 . The formulation of stripper solution 122 prevents the emulsion from binding, reacting, or otherwise sticking to the platen. In some cases, the emulsion may react with stripper 122, but generally does not adhere to platen 124 due to said interaction/reaction. If the adhesion of the emulsion to the platen 124 is stronger than the adhesion of the emulsion to the mesh 112, the emulsion may debond/peele from the mesh. This can lead to pinholes and bare patches. In the worst case, it causes the mesh to break or tear.

In FIG. 2C, the platen 124 is moved with the stripper solution 122 onto the mesh 112, tensioning the mesh and forcing the stripper solution against the back of the mesh. This provides a smooth, tensioned and flat printing surface. Movement of platen 124 is indicated by arrow 202 .

In FIG. 2D, a print head 132 translatable by a printer carriage 134 (not shown in FIG. 2D, but shown in FIG. 1) moves a block image or stencil 206 (shown in FIG. 2E). is printed directly onto the mesh 112, where the block image is the inverse, or negative, of the actual image to be printed or screen printed. Printhead 132 moves laterally in the direction indicated by arrow 204 to form screen stencil 206 on mesh 112 . The “ink” is essentially the UV curable jettable emulsion described above that is UV cured when applied by the UV light source 208 . In one example, the UV source moves laterally in the direction indicated by arrow 210 . This is similar to what happens with conventional UV printers. FIG. 2D shows printhead 132 and UV light source 208 moving across mesh 112 . However, the mesh support system, including mesh 112 and frame 114 (and fixture 116 ), can be translated relative to printhead 132 and UV light source 208 . The UV light sources 208 may be fixed to either side of the printhead 132 so that the mesh 112 can be printed from both directions.

In FIG. 2E, stencil 206 has been removed from the printer and is ready for use without further preparation or processing.

In some embodiments, layer 128 may be placed on surface 124a of platen 124 prior to applying stripper solution 122 thereon. Layer 128 is referred to herein as the "background type." The platen 124 was held at a constant height and a "background" 128 was placed. Background types 128 include 4 mm mirror, 2 mm clear glass, 2X glass (top), polyethylene white, glass (top)/mirror (bottom), 4 mm glass (top), 3 mm mirror. For example, using a 4 mm mirror, the printed surface was 2 mm higher than the 2 mm clear glass. Different results were obtained with the "bipartite" background. For example, "2X glass" consists of two sheets of clear glass. "Glass (top)/mirror (bottom)" was a 2mm piece of glass on a 2mm/4mm mirror. It is believed without particular theory that the use of two plates causes light reflection/refraction where the two surfaces meet in-between. "Polyethylene White" was a sheet of white polyethylene.

A comparison of results according to one example is shown in FIGS. 3A-3B. Both figures show the emulsion applied to mesh 112 .

3A, in combination 300 of conventional spreadable emulsion 302 and mesh 112, the emulsion conforms to the warp and weft threads (strands 112a and 112b) of the mesh, including both the top of the mesh and the bottom of the mesh. Follow target. This conformality occurs as the spreadable emulsion 302 air dries on the mesh 112 . In particular, FIG. 3A shows how a conventionally applied emulsion 302 shrinks as it dries on mesh 112 after being applied either by hand or by an applicator machine. This shrinkage is inevitable as the water component dries. Emulsion 302 is commonly used in the art.

In FIG. 3B, in combination 350 of jettable emulsion 302′ and mesh 112 of the present disclosure, jettable emulsion is flattened by smooth surface 124a of platen 124 (and stripper 122 thereon). bottom surface 302'a. It can be seen that the top surface 302'b of the jettable emulsion 302' is less conformal to the warp and weft threads of the mesh 112 than the current emulsion 302. (The lower surface 302'a is where the screen ink is applied with a squeegee and pressed during the actual screen printing process). In DtM, the mesh 112 has stripper liquid 122 supported by a smooth platen 124, so the lower surface 302'a of the emulsion 302' is flatter or flatter. This is also the result of essentially immediate curing by UV radiation.

This process is called direct-to-mesh (DtM) and requires additional processing both before application of the emulsion (i.e., application of emulsion) and after application (washing of unexposed emulsion and ink). (computer to screen). The DtM process does not require additional processing before or after application of the jettable emulsion 302', thus simplifying the creation of the stencil 206.

FIG. 4 shows a flowchart of an exemplary DtM process 400 according to this disclosure for preparing a stencil for screen printing. In process 400, a direct-to-mesh printer 100 is provided (405). As noted above, DtM screen printer 100 includes fixtures 116 for holding frame 114, which holds pre-stretched mesh 112 in place during application of jettable emulsion 302'. configured to hold A platen 124 of the DtM screen printer 100 is for holding a stripper solution 122 to one side of the pre-stretched mesh 112 . Finally, the DtM screen printer 100 includes a printer carriage 134 that supports a print head 118 for printing the jettable emulsion 302' on the side of the prestretched mesh 112 opposite the platen 124.

DtM process 400 continues with step 410 of placing frame 114 in fixture 116 . Fixture 116 is part of printer 100 and is adapted to receive frames 114 of various sizes. Fixtures 116 are configured to precisely fix frame 114 in place such that printer carriage 134 is precisely aligned with mesh 112 .

DtM process 400 continues to apply stripper solution 122 to platen 124 either directly or through mesh 112 (process 415). Application of the stripper solution 122 may be as effective if applied directly to the mesh 112 as if it had been previously applied to the platen 124 . This can be important for very large stencils or very high dot densities, such as 5,000 DPI, which can have time to evaporate even if the stripper solution 122 contains a good emulsifier.

In any event, a platen 124 coated with stripper solution 122 is brought into contact with mesh 112 (or platen 124 is brought into contact with mesh 112 and stripper solution 122 is applied to the mesh). In some embodiments, platen 124 may be raised from about 1 millimeter (mm) to about 2 mm above the level of mesh 112 to impart tightness to mesh 112 .

DtM process 400 ends with process 425 of curing jettable emulsion 302' using UV radiation. Any common UV source can be used to cure the jettable emulsion 302'.

The DtM process 400 continues with the application (420) of the jettable emulsion 302' onto the mesh 112. FIG. As described above, the jettable emulsion 302' is applied to the mesh 112 by the inkjet printer 130, where the inkjet printhead 132 jets the jettable emulsion 302'.

The DtM process 400 includes curing 425 the jettable emulsion 302' using UV. Any conventional UV source can be used to cure jettable emulsion 302'.

As a result of the DtM process 400, a stencil 206 is formed, cured, and ready to be used to screen print colors onto a suitable printing surface, such as clothing. In particular, the jettable emulsion, after curing, forms a screen stencil whose openings are used to print images on the printing surface.

[Example 4]
Four series of examples were performed. The following definitions are given in the examples and tables.

"Mesh resolution" refers to the number of threads per centimeter (cm), and the mesh resolution includes letters indicating the diameter of the thread, such as S (small diameter), T (medium diameter), and HD (large diameter). can include For example, "43T" is a mesh with 43 threads per centimeter of medium diameter.

"Frame type" indicates the type of frame 114 used, which may be a roller frame, aluminum, or big roller frame. The "aluminum" frame was a fixed square metal aluminum frame to which the mesh was glued with a certain tension before starting. A typical value for tension was about 26 Newtons (N). A "roller frame" was a re-stretchable frame that allowed the tension of the mesh to be varied after the stencil was stretched. Roller frames are much more expensive than standard square frames, but they hold the tension right and are much easier to re-deploy. The Big Roller Frame was slightly larger than the Roller Frame.

The metal mesh was a stainless steel, nickel plated mesh. This type of mesh is often used for rotary screens, screens exposed to aggressive liquids, or long runs (many prints/presses) from the same stencil.

"Unit Resolution" is the Dot Density Interweave (DPI) being ejected from the printhead.

"Pulse Count" refers to the number of firing pulses delivered to an individual nozzle.

The printhead used had eight rows of nozzles. The heading "ink channel" means how many rows were used to eject fluid, "all" means all eight rows, and the notation "11100111" means that the middle two rows were not fired. , which gives the effect of a "gap" between the injections.

“UV %” refers to the intensity of UV radiation emitted by adjustable UV LED light source 208 . The intensity of the UV LED light source 208 was modulated with a PMW (Pulse Width Modulator) to control the intensity of the generated UV light. The maximum on the UV light source 208 employed was 100 W/cm ² . For example, the 60% notation means that 60% of the UV light was modulated to 60% of full intensity.

“Stripping solution” refers to the composition of the stripping solution 122 applied to the platen 124 .

“Background type” refers to that used on the surface of platen 124 . The platen 124 was held at a constant height and then a "background" was placed on top of the platen. Background types include 4mm mirror, 2mm clear glass, 2X glass (two pieces of 2mm clear glass), "glass (up)/mirror (down)" (2mm clear glass on 2mm/4mm mirror), and "polyethylene white". (white polyethylene sheet).

"TEM" is an abbreviation for Total Emulsion Measure, which is a measure of the thickness of an emulsion. Often the term EoM (emulsion over mesh) is used, which is the ratio of the emulsion thickness divided by the mesh thickness. Here, the number in μm refers to the total thickness including the thickness of the emulsion plus the thickness of the mesh.

"Smoothness" refers to the smoothness of the stencil. On the platen side, the surface should be very smooth to the touch and have no discernible roughness. On the print side, the surface should be smooth to the touch. A slight roughness (similar to what can be experienced with frosted glass) was considered "acceptable". Generally sandpaper-like surfaces were considered "unacceptable" from the test results.

Smoothness results are based on subjective ratings where 1 is acceptable, 2 is marginally acceptable, 3 is marginally unacceptable, and 4 is unacceptable.

"Result" refers to a subjective assessment of the overall outcome of an experiment. Again, we use the same subjective rating scale described for smoothness.

"A4 print time" is the time required to print a screen of size A4 paper (21.0 cm x 29.7 cm).

[Example 1]
In Example 1, six experiments were performed. Details are shown below in Table 1A (test parameters) and Table 1B (results). All experiments used an experimental ink, UV Superflex 100 ink, as the jettable emulsion. The mesh color in each case was white. The frame type was various roller frames, aluminum or big roller frames, as described in Table IA. The unit resolution in each case was 1440 DPI. The printing speed for each experiment was 300 cm/sec. The number of pulses was as described in Table IA. In the first four experiments, all eight ink channels were fired, but in the last two experiments the middle two nozzle rows of the printhead were not fired, leaving a gap. The UV in each case was 60% of the total intensity. The stripper solution in all six experiments was 100% distilled water. The background type in the first three experiments was a 4mm mirror, while in the last three experiments it was a 2mm clear glass.

As seen in Table 1B, the TEM ranged from 10 μm to 22 μm (Experiments 1, 4, 5, 6). No TEM was obtained in Experiments 2 and 3 due to the lack of a sealed mesh. For Experiment 1, the smoothness and results were acceptable, but the mesh stuck to the mirror and the resulting 22 μm TEM was judged to be oversized. Runs 4, 5, and 6 yielded acceptable smoothness, results and sealed mesh.

A 2 mm clear glass gave better results than a 4 mm mirror, and 2 pulses appeared to give better results than 1 pulse. It is also noted that the frames used in experiments 2 and 3 were aluminum.

Table 1A DtM test, mesh = 43T, unit resolution = 1440 DPI test parameters.

Table 1B DtM test, mesh = 43T, unit resolution = 1440 DPI results

[Example 2]
In Example 2, 12 experiments were performed. Details are shown below in Table 2A (test parameters) and Table 2B (results). All experiments used UV Superflex 100 ink as the jettable emulsion. The color of the mesh in each experiment was yellow. The frame type in each experiment was aluminum. The unit resolution in each experiment was 1080 DPI. The printing speed was 375 cm/sec. The number of pulses was as shown in Table 2. All eight ink channels were fired in all experiments. UV was 60% of full intensity in all experiments except experiment 11 where UV was 40% of full intensity. The stripper solution 122 was as described in Table 2A. Background types were those listed in Table 2A.

As seen in Table 2B, the TEM ranged from 7 μm to 20 μm and no TEM was obtained in Experiment 5. For runs 1-4, 6, and 12, smoothness and results were acceptable. For runs 7 and 8, smoothness and results were marginally acceptable. For experiments 5, 9, 10, and 11, neither the smoothness nor the results were acceptable. As shown in Table 2, these experiments resulted in adhesion of the mesh to the printing surface on the platen.

The only difference between experiments 4 and 5 was the type of background used, 2x glass (top) versus polyethylene. The former seems to give better results than the latter.

The only difference between Run 4 and Runs 7-8 was the type of background used, 2× glass (top) versus 4 mm glass (top). The former seems to have yielded better results than the latter.

Regarding experiments 9, 10, and 11, these were the only experiments using a liquid containing 95% distilled water and 5% ANODAL ASL (Gedacolor). Other liquids such as 100% distilled water, 80% distilled water + 20% Dead Sea salt, 80% distilled water + 20% alcohol, and 50% distilled water + 25% window cleaner + 25% isopropanol are all acceptable or marginally acceptable. Smoothness and results are given.

Table 2A DtM test, mesh = 43T, unit resolution = 1080 DPI test parameters.

Table 2B DtM test, mesh = 43T, unit resolution = 1080 DPI results

[Example 3]
In Example 3, five experiments were performed. Details are shown below in Table 3A (test parameters) and Table 3B (results). All experiments used UV Superflex 100 UV ink as the jettable emulsion. The color of the mesh in each experiment was yellow. The frame type in each case was aluminum. Unit resolution in each experiment was either 1080 DPI or 1440 DPI. The print speed was either 300 cm/sec or 375 cm/sec as described in Table 2A. The number of pulses was as per Table 3A. In all experiments, the middle two nozzle rows of the printhead were not fired, leaving a gap ("11100111"). UV was 60% of full intensity. The stripper solution 122 in all six experiments was 100% distilled water. The background type in all experiments was a 4 mm mirror.

As seen in Table 3B, the TEM ranged from 3 μm to 45 μm. Smoothness was acceptable for all experiments, but for experiments 3, 4, and 5 the results were acceptable. For experiments 1 and 2, the results were slightly unacceptable due to slight sticking of the mesh.

In experiments 1 and 2, the number of pulses was the same in both (2), but in experiments 3, 4 and 5 the number of pulses was different (1). This difference appears to have made Experiments 1 and 2 slightly unacceptable.

Table 3A DtM test, mesh = 120T, 43T test parameters

Table 3B DtM test, mesh = 120T, 43T results

Example 4 was performed. Details are shown in Table 4A (test parameters) and Table 4B below. The mesh resolution in all experiments was 195 (US standard). All experiments used UV Super Flex 100 UV ink as the jettable emulsion. The mesh color was gray/metallic in each experiment. The frame type was metal. The unit resolution in each case was 1440 DPI. The printing speed was 300 cm/sec. The number of pulses was 1 in all experiments. In all experiments, the middle two nozzle rows of the printhead were not fired, leaving a gap ("11100111"). In runs 1-3, UV was 60%, 40%, 30% of full intensity, while in run 4, UV was 30% of full intensity. The stripping solution in Experiments 1-3 was distilled water, and in Experiment 2 no stripping solution was used. The background type in both experiments was a 3 mm mirror.

TEM was 14 μm for all experiments, as seen in Table 4B. For Experiments 1-3, both the smoothness and results were unacceptable, while for Experiment 4, the smoothness and results were acceptable.

In Runs 2 and 3 of Example 1 above, the frame was aluminum and both runs had unacceptable smoothness and results using 100% distilled water as the liquid. In Experiment 1 of Example 4, where the frame was metal, similar unacceptable results were obtained. On the other hand, in Experiment 2 of Example 4, the frame was also metal, but no liquid was used and acceptable smoothness and results were observed. Apparently, the combination of fluid and frame is one of the factors in obtaining acceptable smoothness and results. It has been found that under certain conditions, having no release fluid or backing paper gives better results. Based on the above tests, it is possible to formulate an emulsion that works without any backing surface.

Table 4A DtM Test, Mesh = 195 (U.S. Standard) Test Parameters

Table 4B DtM Test, Mesh = 195 (US Standard) Results

From the above examples, the results are: liquid (emulsion and stripper), platen configuration (e.g. single glass, double glass, glass + mirror, etc.), cure strength (20%-100% UV), dot It appears to be influenced by some very complex interactions such as density (1080, 1440), pulse number, etc. From an analytical point of view, the combinations seem almost infinite. Currently, the only method for evaluation of sets of parameters must be pragmatic, ie, test each set based on the teachings herein. However, such tests are not considered excessive.

Advantages of the DtM process 400 include the complete elimination of both stencil making and post-processing as follows.

No machines such as emulsion applicators, dryers or separate exposure units are required.

Most chemicals (except degreasers) and over 80% of water usage are reduced.

All processes can be performed without a special low UV lighting room. In fact, the DtM process can be performed in normal factory/office lighting or daylight. The jettable emulsion is kept inside a UV-protected cartridge or bag during handling. The jettable emulsion is exposed to daylight or ultraviolet light only when it is jetted onto mesh 112 .

Because the processes disclosed herein can use conventional, less expensive mesh 112, stripping the mesh from the frame 114 and re-meshing is less expensive than water, chemicals, and special cleaning stations. can often be more efficient and cheaper than mesh cleaning, which requires

The raw material, raw screen, or mesh 112 is placed on the direct-to-mesh printer 100 and the ready-to-use stencil 206 is removed from the screen and directly onto the carousel for printing the image on the printing surface. can be placed.

A further advantage of the DtM process 400 is that each stencil 206 is so precisely registered on the mesh 112 that micro-registration can be omitted when mounted on the carousel. Because the DtM process 400 positions each stencil 206 accurately (both absolutely and relatively) on the frame 106, no adjustments are necessary or required. This is accomplished through the use of frame fixtures 116 . The stencil frame is typically provided with registration holes or points. Each different carousel manufacturer has its own registration system. The frame fixture 116 is provided with the same alignment system (or possibly a differently designed auxiliary alignment system). Frame fixtures 116 allow for precise alignment of stencil frame 114 . To achieve this, a test print is made in 4 colors (or 6 or more) and then the carousel is fine-tuned. If no carousel changes are made (or the carousel goes out of alignment) and all stencils are produced on the same printer, the stencils will be correctly aligned.

The DtM process 400 disclosed herein significantly reduces either or both process time and complexity, labor and capital equipment (including specialized lighting equipment), as well as process chemicals and water. It will be appreciated that it can be reduced to

The DtM process 400 can also be used for rotary screen printing. Rotary screen printing is used in some narrow but frequently repeated printing processes such as labeling (wallpaper, linear linoleum, etc.). Rotary screen printing is very fast for those applications where each of the four colors (and any spot color) is placed on a cylinder and the material is passed underneath. Rotary screen printing typically uses a stainless steel mesh 112 for durability and stability.

Today many rotary stencils are made by large service bureaus (there are about 3 in Europe). Each stencil can cost over 100 euros, and the annual cost of replacing stencils can be in the hundreds of thousands of euros. This doesn't even take into account the inconvenience of using it in a service bureau. Many businesses are able to recoup the cost of the machines in a few quarters while reducing their reliance on expensive service bureaus.

It will be appreciated that in the foregoing description numerous specific details are set forth to provide a thorough understanding of the embodiments. However, it is understood that the embodiments may be practiced without being limited to these specific details. In other instances, well-known methods and structures may not be described in detail to avoid unnecessarily obscuring the description of the embodiments. Also, the embodiments may be used in combination with each other.

It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It will be appreciated that the foregoing description sets forth numerous specific details in order to provide a thorough understanding of the embodiments. However, it is understood that practice may be made without being limited to these specific details. In other instances, well-known methods and structures have not been described in detail to avoid unnecessarily obscuring the description of the embodiments. Also, embodiments may be used in combination with each other. Further, when "about" is used to describe a value, this is meant to include minor variations (up to ±10%) from the stated value, such as may be induced by manufacturing variations. .

Additionally, the order of the process steps in the claims may be interchanged as appropriate. For example, dispensing the stripper solution 122 onto the platen 124 or mesh 112 may include dispensing the stripper solution onto the platen and then bringing the platen and mesh together. Alternatively, the platen and mesh may be brought together and the stripper solution distributed over the mesh.

While a limited number of examples are disclosed, it should be understood that numerous modifications and variations exist therefrom. For example, the "orientation" of the printer bed/table may be changed from horizontal to vertical due to new high/ultra-fast printhead technologies that may allow jetting onto vertical surfaces.

Claims (15)

A direct-to-mesh screen printer for making screen stencils, comprising:
a frame for holding the pre-stretched mesh in place while applying the jettable emulsion;
a fixture for holding the frame;
a platen for holding stripper solution on one side of the pre-stretched mesh;
- a stripping liquid dispenser that supplies the stripping liquid onto the platen or the mesh;
- a printer carriage supporting a printhead for printing a jettable emulsion on the side of the pre-stretched mesh opposite said platen;
A direct-to-mesh screen printer comprising: 2. The direct-to-emulsion of claim 1, wherein the fixture is configured to rigidly hold the frame with the pre-stretched mesh in place during application of the jettable emulsion. Mesh screen printer. 2. The direct-to-mesh screen printer of claim 1, wherein the platen is configured to hold the stripper liquid firmly against the bottom of the pre-stretched mesh. 4. The direct-to-mesh screen printer of claim 3, wherein said platen is smooth, rigid, impermeable to said stripper solution, and resistant to dents and cracks. The stripper solution is applied very thinly and evenly to the platen or directly to the mesh when the mesh is placed on the platen so that the mesh is applied to the platen during application of the jettable emulsion. The direct-to-mesh screen printer according to claim 1, which prevents sticking. 2. The direct-to-mesh screen of claim 1, wherein the stripper is configured to suppress dot gain while at the same time providing a smooth, non-reactive surface to the jettable emulsion after curing. • Printers. 2. The direct-to-mesh screen printer of claim 1, wherein said stripper liquid comprises water and at least one emulsifier in sufficient amount to prevent evaporation of said stripper liquid. The direct-to-mesh screen printer of claim 1, wherein said jettable emulsion has a low viscosity of about 4 cP to about 15 cP and is both durable and flexible/elastic. 9. The direct-to-mesh screen printer of claim 8, wherein said jettable emulsion is a UV-activated acrylate monomer having elastomeric properties after curing. The direct-to-mesh screen printer of claim 1, further comprising a UV source for curing said jettable emulsion and forming a stencil for screen printing. A fixture for holding a frame configured to hold the pre-stretched mesh in place during application of the jettable emulsion and stripper solution against one side of the pre-stretched mesh and a printer carriage supporting a print head for printing a jettable emulsion on a side of the pre-stretched mesh opposite the platen. - providing a screen printer;
placing the frame in the fixture;
- applying a stripping solution to the platen or mesh;
- tensioning the platen and the mesh;
- applying the jettable emulsion to a mesh;
- curing the jettable emulsion using UV radiation;
process including. 12. The process of claim 11, wherein the cured emulsion forms a screen stencil and the openings in this screen stencil are used to form the image on the surface. 12. The process of claim 11, wherein the stripper solution is configured to inhibit dot gain while not adhering to the jettable emulsion after curing. 12. The process of claim 11, wherein the stripper solution comprises water and at least one emulsifier in an amount sufficient to prevent evaporation of the stripper solution. 12. The process of Claim 11, wherein said jettable emulsion is a UV-activated acrylate monomer that has elastomeric properties after curing.

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