NL2006885A - SCREEN PRINTING METHOD AND A PLATE FITTED IN ACCORDANCE WITH THIS SCREEN PRINTING METHOD. - Google Patents

Abstract

Screen printing method for applying a pattern (170) on a panel (100) and a panel (100) comprising a pattern (170) provided according to this method. In particular, an optical panel (100) of glass or quartz, having a pattern (170) of parallel lines or strips (180) with gaps (190) there between for use in parallax barrier auto stereoscopy. In particular, the lines or strips (180) are of enamel ink, preferably black enamel ink. By circumferential bevelled edges, the temperature resistance of the panel (100) is improved.

Description

Brief description: Screen printing method and a patterned plate according to this screen printing method.

PREFACE

The present application relates to a method for applying a pattern to a plate.

Screen printing, also known as silk screen printing, is a printing technique that is used for multiple graphic purposes, such as textile decoration, posters, art prints and textile printing. This technique is also used industrially for the production of, for example, printed circuit boards and solar cells.

The principle of screen printing technology is fairly simple. A piece of fine mesh of, for example, silk, polyester or steel is stretched over a frame. The screen printing frame is then typically provided with a photosensitive layer that is exposed by means of a (positive) film. The dark surfaces present on the positive are washed away during development, so that permeable spots on the screen printing frame are created, through which the ink is pressed. The ink (or soldering paste) is applied to the window and spread out with the help of a doctor blade, whereby the shape of the template is printed on the object to be printed (the image carrier). This technique can be repeated with different colors and shapes that are printed next to each other or over each other.

Screen printing ink covers well; this means that it is also possible to print on dark image carriers. This is in contrast to surface printing, relief printing and gravure printing where transparent inks are always used.

With the right printing ink or paste, almost any material can be printed with the screen printing technique, for example also round glass bottles. Nowadays, technology is used on a large scale industrially and the silk screen is also indispensable in the art world.

Ink is a liquid colorant used for writing or printing. Usually ink is black or blue, but there are also different colored inks.

In the strict sense, ink is a solution or colloidal solution of dyes. In that sense, ink differs from paint, which consists of a spread with pigments. There are different types of ink, such as printing ink, of which offset ink is a special form. These inks are in fact a paint because they contain pigments instead of dyes.

A squeegee is a kind of distributor comb for pressing ink through the screen of the screen printing frame. In screen printing, the ink is physically applied to the substrate to be printed by the still-open parts in the mesh (image) using this instrument.

There are various documents that relate to screen printing.

For example, WO 2009/106912 (A1) describes a roller for roller screen printing, in particular for decoration of ceramic products.

For example, WO 2007/124551 (A1) describes a UV serigraphy method for manufacturing FRP boards, using an unsaturated polyester resin inks on an FRP laminate and curing it in two steps.

EP 1710095 (A1) describes, for example, a method for manufacturing strong metal foil on a carrier plate and applying parts precisely with a laser.

Various documents relate to devices suitable for screen printing, specific materials used in screen printing, and so on.

The documents mentioned above relate to general and specific developments in screen printing technology.

Typically, the prior art has the drawback that patterns cannot be applied with great accuracy. This is an inherent disadvantage of the technology used and / or devices and / or materials.

Also, the prior art does not provide materials or methods that can be used at elevated temperatures.

Furthermore, the prior art does not provide a combination of techniques and / or materials that meet high optical requirements.

Thus, there is still a need for an improved screen printing method that jeopardizes one or more of the aforementioned problems and drawbacks without favorable features.

SUMMARY OF THE INVENTION

The present invention relates to a method for applying a pattern to a plate, preferably a flat plate, which plate has suitable optical properties and which plate has at least one flat side thereof around bevelled edges, comprising the steps of: providing the plate, applying a pattern with a suitable, adhesive and curable ink to the plate, wherein preferably before applying the ink the plate is washed and dried, and curing the ink.

The present invention is particularly suitable for making transparent plates with a pattern that makes it possible to see an image placed under the plate, also referred to as panorama, in three-dimensional, 3D form. That is, where an observer who is at a certain distance from the plate receives a three-dimensional or spatial visual impression of the actually two-dimensional, 2D image. To this end, it is necessary that the 2D image is arranged in a suitable manner. This technique is also referred to in practice as autostereoscopy.

The term "plate" in the present description and claims refers to a three-dimensional object that has a certain length, width and thickness, wherein the thickness is significantly smaller than the width and / or length and wherein this thickness is sufficient to make the plate intrinsic to provide strength against, for example, bending. Otherwise the plate can have any shape. In the light of the present invention, the plate preferably has a constant thickness.

For the best effect, in terms of a sharp and clear 3D impression, the plate has suitable optical properties. After extensive and in-depth tests, the inventor has determined that total energy absorption is an important parameter in this. This absorption is as small as possible in an example. This can be achieved, for example, by keeping the number of absorption sites (for example, taken per cm 3) in the plate as small as possible. Absorption sites are, for example, metal particles and metal ions such as Zn or Fe. The concentration thereof is in an example less than 100 ppm, more preferably less than 10 ppm, such as less than 5 ppm. These tests have also shown that direct energy transmission through the plate is as large as possible in an example, which also applies to light transmission. In order to obtain as balanced an image as possible for the 3D display in terms of colors, it has been established that the RD65 color yield in an example is as large as possible. It has further been established that the shadow coefficient in an example is as large as possible in order to obtain optimum contrast effect.

In one example, the plate is a flat plate, such as is used in shelters or the like. Alternatively, the plate in an example has a thickness variation over the surface that is as small as possible, such as less than 1/100 variation with respect to the total thickness.

After prolonged experimentation it has been established that the risk of cracking of the plate during heating and cooling is drastically reduced by providing the plate with bevelled edges on all sides. This is particularly relevant because in the present method the plate is heated relatively quickly and cooled quickly. This is necessary to be able to apply the pattern with a required accuracy. In one example, the beveled edges are polished, because polished edges are even better able to absorb stress in the plate.

In the present description and the claims, the term beveled edges also includes rounded edges or stepped edges and the like.

The ink used is an ink that adheres sufficiently to the plate. In one example, the ink allows hardly any or no light through. In one example, the ink cures well and quickly, for example at an elevated temperature. In one example, the ink obtains a hardness comparable to quartz (7 on the Mohs scale). Such an ink is sufficiently durable for use in, for example, an abri. An ink and plate can be selected such that properties thereof are such that a suitable adhesion is obtained.

The ink is then cured. Curing can take place, for example, by raising the temperature, by chemically activating a hardener present in the ink, such as by adding an activator, by applying light, such as UV radiation, by evaporating any solvent present in the ink, by using a electric field, by baking, or combinations thereof.

The present invention thus provides a method that makes it possible to apply a pattern with a particularly high accuracy. After applying a pattern of a certain width to a plate, the width hardly varies in the course of the present method, i.e. less than 1/1000 of the width, often even less than 1/10000 of the width. As an example, a line or strip with a width of 1 mm will provide a width over the entire length of the line or strip that deviates less than 1 micrometer (µm) from this width of 1 mm, or that between 0.999 mm and 1.001 mm is located. It can be said that the line has a virtually constant width. This is of great importance for obtaining an optimal 3D image.

The invention also provides a plate, in particular a plate with optical properties, provided with a pattern arranged thereon according to the method described above.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a method for applying a pattern to a plate and a plate provided with such a pattern, in particular an optical plate.

In one example, the plate is made of glass, or of quartz, preferably safety glass. Glass and quartz meet the optical properties relevant to the plate to a certain extent.

The glass or quartz is preferably safety glass that meets the EN-14179 standard and / or the EN 12600 standard for thermally tempered glass, or an equivalent material. Such a plate is extremely suitable for use in environments where possible breakage of the plate can occur, for example due to vandalism.

In one example the plate has bevelled edges on a flat side and preferably on both flat sides (top and bottom) which have an angle with the normal on the plane of the plate of between 30 and 60 degrees, preferably between 40 and 50 degrees , such as 45 degrees. After experimentation it has been found that an angle between 30 and 60 degrees gives the best results in terms of the risk of breakage and / or damage to the plate. A 45-degree angle gives the best results.

In one example, the ink is an enamel ink, preferably a black enamel ink. Such an ink is scratch-resistant after curing, which is desirable for durability and optical properties. In one example, the ink obtains a hardness comparable to quartz (from 6 to 8 on the Mohs scale). Such an ink furthermore transmits little or no light, which is extremely desirable. Such an ink can be obtained from companies such as Pemco, Ferro, and Johnson Matthey.

The ink may further be an accelerator, a retarder, a diluent, an antifoam, an antifoam, an equalizer, a hardener, an adhesive, a thickener, a mattifying powder, a plasticizer, an antistatic, or a combination of these.

In one example, the ink has a viscosity of 1000-5000 mPa.sec, more preferably of 2000-4000 mPa.sec. It is very important to adjust the viscosity of the ink correctly. Too low a viscosity causes the applied pattern to flow too much, while too high a viscosity does not yield any clean lines, for example of the same thickness and width over the entire line. After prolonged experimentation, the inventors have succeeded in determining a suitable viscosity range. Parameters that co-determine a suitable viscosity are type of powder particles in the ink, type of screen used, type of diluent, thickness of the final layer, etc.

In one example, when applying the ink, a screen is used with more than 75 threads per cm, preferably more than 100 threads per cm, such as 120 threads per cm, preferably a screen with plastic or metal threads and preferably a metal window, such as an aluminum window. Such a screen has a high quality value, such as T120, with which, for example, lines can be placed next to each other as accurately as possible. With such a screen, among other things, the above-mentioned advantages can be obtained, such as the non-flow of lines during application and curing. In one example, the screen itself has sufficient pressure to enable ink to be applied with a doctor blade.

In one example, the ink is applied with a doctor blade, which doctor blade exerts a pressure of more than 0.1 kPa, more preferably between 0.1 and 100 kPa, such as 2 kPa, on the ink. The pressure of the doctor blade is greater than the pressure of an applied screen. The pull is typically adjustable

In an example, the thickness of the ink applied is determined with a doctor blade to a thickness of between 10-200 µm, preferably between 20-100 µm, more preferably between 50-90 µm, such as 70-80 µm. This thickness is measured wet. Typically, the thickness will be as small as possible to save material. On the other hand, the layer will be sufficiently thick to allow (virtually) no light through. Moreover, a dried ink is, for example, sufficiently scratch-resistant.

In one example, the plate is washed and dried before applying the ink. Washing can, for example, take place with the aid of water, for example with a low oxygen content. Drying typically takes place in air, whether or not at elevated temperature, reduced pressure, with venting, or a combination thereof. A clean surface is thus obtained, to which the ink adheres better. Among other things, this benefits the durability and hardness of the ink.

In one example, the ink cartridge comprises parallel or parallel lines or strips in a first direction, which lines or strips have one and the same constant width. Typically, the first direction is a vertical direction, seen during use of the plate. By applying the present invention, lines or strips with a very constant width are obtained. Even after performing the present method with possible optional steps, the variation in width is less than 1/1000 of the average width, even less than 1/10000.

In an example, the number of lines or strips is between 0.2 and 250 per cm, preferably between 0.5 and 100 per cm, more preferably between 1 and 50 per cm, even more preferably between 2 and 10 per cm, such as between 4 and 8 per cm. The number of lines or strips per centimeter is partly determined by the number of image lines used per centimeter when forming an image to be placed under the plate, or these two numbers are related to each other. It has now been found that the number of lines or strips per centimeter should not be too high, because then too little light can pass through the plate. If the number of lines is too small, the 3D effect will disappear. In an example, the number of lines is 2 per centimeter, 4 per centimeter or 8 per centimeter. This optimizes the amount of light and the resulting 3D effect as well.

In one example, an opening between the lines or strips is between 1/10 and 1/2 of the width of the lines, preferably between 1/5 and 1/3 of the width. With a proper ratio between, respectively, the width of lines or strips, the number of lines or strips per centimeter, and the width of openings, desired 3D properties can be obtained with a suitable panorama ghost. This is described in detail in a patent application NL2004797, filed by the applicant, "Method and device for manufacturing a panorama ghost for providing an autostereoscopic image", with reference to the present inventor. For further details, reference is therefore made to this application, which application is incorporated herein by reference.

In one example, width and thickness of the lines or strips and width of the openings are optically checked, preferably with a laser and a camera. A laser emits a beam of light that is completely or partially blocked by a line or strip. With an optical system, such as a camera, the width of a line can then easily be determined. The thickness of a line or strip can also be determined. The quality of the method can thus be easily monitored and adjusted if necessary. A more or less continuous inspection of lines and openings can take place by moving one (or more) laser (s) perpendicular to the lines on the plate. The relative position of lines and openings between them can also be determined in this way. A product that does not meet quality specifications can also be rejected.

In one example, the curing takes place at a temperature of more than 500 ° C, preferably more than 600 ° C, preferably for a time of more than 15 minutes, such as more than 20 minutes, after which the plate is preferably cooled quickly. , preferably faster than 40 ° C / minute, more preferably faster than 75 ° C / minute, such as faster than 100 ° C / minute. Too low a temperature causes ink to flow out slightly, as a result of which the above-mentioned quality requirements cannot be met. Too high a temperature causes too much stress in the plate, resulting in an increased risk of breakage. A temperature of 500 ° C to 700 ° C is preferred. Cooling typically occurs to room temperature. Fast cooling has the advantage that an optimum quality and hardness of glass and ink is obtained. In addition, the pattern as applied is also substantially obtained after curing, for example in terms of accuracy.

In one example, the plate moves back and forth during curing at a speed of between 0.1 and 5 meters / minute, more preferably between 0.2 and 3 meters / minute, even more preferably between 0.5 and 2 meters / minute, such as 1 meter / minute. This ensures that stress in the plate flows away as much as possible. Care is also taken to ensure that the plate does not flow too much, because, for example, a part of the plate becomes too hot, for example to a temperature close to a flow temperature.

In an example the plate has a size of more than 80 x 100 cm 2, preferably more than 100 x 125 cm 2, preferably more than 110 x 150 cm 2, such as more than 120 x 180 cm 2, and a thickness of preferably 1-10 mm, preferably 3 -7 mm, such as 5 mm. Plates of various sizes can thus be manufactured which represent a 2D image of a comparable size as a 3D image. The plates obtained may be considerably larger than methods obtainable with prior art.

In one example, the plate has a light transmission (τν) in the visible light of more than 89%, such as more than 90%, such as more than 91%, and preferably has a total energy absorption (ae) of less than 10%, preferably less than 5%, such as less than 3%, such as 2%, and preferably has a direct energy transmission (xe) of more than 85%, preferably more than 87%, such as more than 88%, such as 89% or 90%, and preferably a Shading Coefficient (SC) of more than 0.97, preferably more than 1.00, such as more than 1.02, such as 1.03, and preferably a color rendering - RD65 (Rd) has more than 99, such as 100 (all according to EN-410, with a thickness of 6 mm). After extensive experimentation, it has been found that the best results are obtained, in terms of imaging, contrast, brightness, distortion, 3D display, when plates with the above-mentioned optical characteristics are used.

In one example, the plate is provided with a pattern for forming a so-called parallax barrier for use with a panorama ghost for a 3D representation of an image. That is, image and plate are made in accordance with the principles of the parallax barrier autostereoscopy.

The invention will now be further elucidated on the basis of examples, which in no way limit the scope of protection. The scope of protection is given by the claims.

SHORT FIGURE DESCRIPTION

Figure 1a, b schematically shows an example of the present method, in the form of a representation with mutually spaced parts.

Figure 2 shows diagrammatically a sectional view along the line II-II in Figure 1a of a fragment of a plate manufactured according to the example of Figure 1a, b.

EXTENDED FIGURE DESCRIPTION

Figure 1a, b schematically shows an example of the present method.

A screen printing method is shown in Figure 1a. Ink (130) is passed over a pattern image (120) on a screen printing frame with a doctor blade through a screen (110). A pattern corresponding to the pattern image (120) thus results on a plate (100).

Figure 1b schematically shows a partial fragment (circled) of a pattern on the plate (100). This schematic illustration relates in one example to a pattern (170) consisting of parallel or parallel lines or strips (180) having a certain width (231), with openings (190) between these lines or strips (180) having a certain width width (233), which lines or strips (180) (and openings 190) have a certain density (235), which is expressed in number of lines or strips per cm (or number of lines or strips per inch). Although not explicitly shown, the pattern (170) extends substantially over the entire surface of the plate (100).

EXAMPLES

Some typical values for glass are included below for comparison.

Table 1 gives specific characteristics for different types of glass, with different thicknesses thereof. Both Planibel and Matelux Clearvision are trademarks of AGC Europe.

Table 1. Glass characteristics

In one example, a flat plate (100) of 120 x 180 cm 2 of the Matelux Clearvision type is provided. The thickness of the plate is 5 mm. First of all, the edges or edges of the plate on both flat sides (140, 150) are chamfered (200, 210) at an angle α of 45 degrees with the normal (160) on the surface of the plate (200, 210) and polished, as shown schematically in Figure 2, which is a sectional view of a fragment of the plate (100) along the line 11-1 in Figure 1a. If necessary, the plate is sandblasted, provided with holes and / or notches and further finished in the light of a final application.

To prevent impurities during further processing, the plate is then passed through a washing and drying tunnel on a conveyor belt, the plate being washed with water containing a surfactant, and then dried in air at 60 ° C for 2 minutes. After this, an enamel layer (black, from the company Pemco) is applied to one side of the plate by means of screen printing. The enamel layer or ink is balanced, meaning that there is virtually no shrinkage or expansion during further processing. The ink used has a viscosity of 2000 mPa.sec. The screen used (110) has an aluminum frame and plastic wires (120 per centimeter). The pressure on the doctor blade is approximately 0.2 Pa, the lead time of the plate is approximately 30 seconds. This makes 8 lines per centimeter with an opening between the lines of which the width is 1/5 of the of the lines. The thickness of the lines is approximately 80 μηπ. The lines may be squeezed slightly, for example with a few thousandth of a millimeter towards each other, so that image strips coincide with the density of the 2D image.

In an oven, the plate is then heated to 650 ° C for 20 minutes with the enamel ink being baked on the glass surface. The plate rolls back and forth in the oven at a speed of 0.5 meter / minute. Optionally, a special conveyor belt ensures that the hardening takes place without further distortion of the glass surface. With very strong blowers, the hot glass is cooled to room temperature at 130 ° C / minute. This creates stresses between the inner core and outer layers of the glass, which stresses are discharged through the beveled edges. As a result, a mechanically very strong glass plate is obtained, among other things. The quality of the lines applied is checked with a laser and a camera. The hardness of the ink is also checked by means of a scratch test.

The invention is of course not limited to the example described above. Various embodiments are possible for a person skilled in the art on the basis of the foregoing description, all of which are understood to fall within the scope of the following claims.

Claims (17)

A method for applying a pattern to a plate, preferably a flat plate, which plate has suitable optical properties and which plate has at least one flat side thereof around bevelled edges, comprising the steps of: providing the plate, applying a pattern with a suitable, adhesive and curable ink to the plate, the plate being preferably washed and dried prior to applying the ink, and curing the ink. Method according to claim 1, wherein the plate is made of glass or quartz, preferably safety glass, and wherein the plate preferably complies with the Standard EN-14719 for safety glass and / or with the Standard EN-12600 for thermally tempered glass. Method according to one or more of claims 1-2, wherein the ink is an enamel ink, preferably a black enamel ink. A method according to any one of claims 1-3, wherein the ink has a viscosity of 1000-5000 mPa.sec, more preferably of 2000-4000 mPa.sec. Method according to one or more of claims 1-4, wherein in applying the ink a screen is used with more than 75 threads per cm, preferably more than 100 threads per cm, such as 120 threads per cm, preferably a sieve with plastic or metal wires and preferably a metal window, such as an aluminum window. A method according to claim 5, wherein the ink is applied with a doctor blade, which doctor blade exerts a pressure of more than 0.1 kPa, more preferably between 0.1 and 100 kPa, such as 2 kPa, on the ink. A method according to any one of claims 5-6, wherein thickness of the ink applied is determined with a doctor blade to a thickness of between 10-200 µm, preferably between 20-100 µm, more preferably between 50-90 µm, such as 70-80 pm. A method according to any one of claims 1-7, wherein the ink cartridge comprises parallel lines or strips in a first direction, which lines or strips have one and the same constant width, the number of lines or strips preferably being between 0.2 and Is 250 per cm, preferably between 0.5 and 100 per cm, more preferably between 1 and 50 per cm, even more preferably between 2 and 10 per cm, such as between 4 and 8 per cm. The method of claim 8, wherein an aperture between lines or strips is between 1/10 and 1/2 of the width of the lines or strips, preferably between 1/5 and 1/3 of the width. Method according to one or more of claims 7-8, wherein width and thickness of the lines or strips and openings are optically checked, preferably with a laser and a camera. Method according to one or more of claims 1-10, wherein the curing takes place at a temperature of more than 500 ° C, preferably more than 600 ° C, preferably for a time of more than 15 minutes, such as more than 20 minutes, after which the plate is preferably cooled rapidly, preferably faster than 40 ° C / minute, more preferably faster than 75 ° C / minute, such as faster than 100 ° C / minute. Method according to one or more of claims 1-11, wherein the plate moves back and forth during curing at a speed of between 0.1 and 5 meters / minute. Method according to one or more of claims 1-12, wherein the plate has a size of more than 80 x 100 cm 2, preferably more than 100 x 125 cm 2, preferably more than 110 x 150 cm 2, such as 120 x 180 cm 2, and a thickness of preferably 1-10 mm, preferably 3 -7 mm, such as 5 mm. Method according to one or more of claims 1-13, wherein the plate preferably has a light transmission (τν) in the visible light of more than 89%, such as more than 90%, and preferably has a total energy absorption (ae) less than 10%, preferably less than 5%, such as less than 3%, and preferably has a direct energy transmission (xe) of more than 85%, preferably more than 87%, such as more than 88%, and at preferably has a Shading Coefficient (SC) of more than 0.97, preferably more than 1.00, such as more than 1.02, and preferably a color rendering - RD65 (Rd) of more than 99, such as 100 (all according to EN-410, with a thickness of 6 mm). Method according to one or more of claims 1-14, wherein the plate has beveled edges that have an angle with the normal of the plate of between 30 and 60 degrees, preferably between 40 and 50 degrees, such as 45 degrees. Method according to one or more of claims 1-14, wherein the plate is provided with a pattern of parallel lines or strips for use in parallax-barrier autostereoscopy. A plate provided with a pattern manufactured according to the method according to one or more of the preceding claims.