Read-out device and procedure for its manufacture

ES 2 236 615 T3

DESCRIPTION

Display device and procedure for its manufacture.

The invention relates to a luminous character and symbol display device of a type which is integral with the surrounding surface.

Character display devices are known, which appear as black areas which are activated by turning on luminous units with a suitable model, which are hidden by the black aspect areas. Such an area can be made, for example, of dark glass through which the light of light-emitting diodes, arranged in a suitable matrix, shines. In the idle state it is not apparent that the character display device or display is present on the surface and this can be used as a feature of industrial appliance design. Devices are known which are capable of displaying characters on any surface, that is, they do not depend on the surface having a black appearance. This requires projection from a projector placed in front of the display and this is not suitable for household appliances. Additionally, various applications of glass plates as light guides are known, in which the light remaining on the edge can provide characters which can be read in the plane of the flat element. None of these constructions mentioned allows the use of, for example, a metal surface, but with respect to the apparatus, the glass surface is mandatory. There is, however, a desire to have the front of an apparatus made for example of aluminum, which can be structured by brush painting, but possibly can also be completely glossy.

In order to make an aluminum foil translucent it is necessary to drill holes and a large number of holes arranged closely together can provide a construction that, under certain light conditions, looks like an entire metal surface, in which the activation of a matrix of light emitting diodes provides luminous characters. However, under certain other lighting conditions it can be clearly seen that it is actually a matrix of holes and the luminous characters can only be seen at a narrow angle around the axis, that is almost frontally. Furthermore, this drilling creates a local destruction of the protective oxide layer on the surface and this reflects the light and makes the existence of a viewing area evident. It has been recognized that aluminum that has been vapor deposited on a transparent surface can be both translucent and appear completely reflective metallic, but the use of these techniques again requires the presence of a glassy material, which both must be adjusted within the surrounding aluminum surface as it should cover the entire surface, so the entire aluminum structural impression is destroyed.

Examples of prior art display devices are described in DE 299 24 202 U1 and GB A 2 226 796. Both documents describe display devices with a transparent plate constituting the display surface. DE 299 24 202 U1 has a synthetic top plate, while GB A 2 226 796 describes a glass top plate.

In practice, it is desirable to obtain the functionality of an apparently entire but translucent metallic surface with respect to many ferrous (such as for example a stainless steel alloy) or non-ferrous (such as for example aluminum, titanium or zinc and their alloys). It is an object of the invention to provide a display device that is not subject to the aforementioned limitations on its appearance.

This is obtained in a construction, which is particular in that a cavity is formed in the material from the back, which viewed from the front surface and towards the back comprises an integral and identical transparent or translucent protective outer layer, with respect to the touch and visual appearance, to the protective layer of the surrounding surface, a translucent layer of ferrous or non-ferrous metal and a reinforcing structure for said layers, which provides access to light sources for displaying information.

One embodiment of the invention is particular in that the transparent or translucent protective outer layer is a lacquer layer of the type that displays the expected hardness, strength and transparency of a metal layer adapted for a ferrous or non-ferrous metal in use. The actual choice of a lacquer, varnish or enamel that meets these conditions is a well-known task for those skilled in the field of metal surface treatment. Enamel can be vitreous for pure metals and alloys having a melting point above the enamel in question.

A further embodiment of the invention using aluminum is particular in that the bottom of the cavity viewed from the front surface and towards the center comprises a transparent oxide outer layer integral with the surrounding surface oxide layer and a translucent layer of aluminum.

In a further embodiment of the invention the reinforcing structure for said layers additionally serves as a carrier for the light sources.

An advantageous embodiment of the invention is particular in that the reinforcing construction is made of a dimensionally stable cast compound, which supports the outer layers and carries a fixture for the light sources so that the light is carried throughout the entire path. up to the outer layers. It is important that the casting compound does not exhibit shrinkage or expansion during hardening, as this can lead to changes in the appearance of the front of the material serving as the viewing area. The casting compound must also support the light sources so that they are arranged as close to the front as possible.

In order to have as great a temperature stability as possible in construction, materials with similar properties are used according to a further advantageous embodiment of the invention, in which the fastener is an element in the metal used for the part. cast of essentially the same dimensions, although suitably reduced, as the cavity and in that the casting compound is translucent and fills the interstices between the metal element and the cavity.

According to a simplified construction, the

ES 2 236 615 T3 which also causes less local heating of the display device, the fixture supports the ends of optical fibers which carry light from more distant light sources.

According to a further simplified construction, low power light emitting diodes are used near the front surface which functions as the display area.

The invention also relates to a process for the manufacture of the display device and is particular in that it comprises at least the following steps, not necessarily in the order listed:

1) a cavity is formed in the casting, with a shape corresponding to the final cavity and a depth that leaves enough material so that the protective layer on the front is not stressed, 2) a translucent protective layer is deposited or transparent on the front surface of the casting, 3) a chemical etching or similar process is carried out, such as removal of material by laser ablation or the like, at an atomic level at the bottom of the cavity, until adequate translucency is obtained, 4) the material remaining at the bottom is protected against oxidation, 5) a reinforcing structure is placed in the cavity, 6) a composed in the space remaining between the reinforcing structure and the cavity, 7) light sources are arranged in the reinforcing structure. In this procedure the actual process for the provision of the cavity will be decided by the person skilled in the art according to the selected material. For example, in some materials it may be convenient to use milling, turning, or grinding while others can work well with the much faster operation of calibrated partial punching, in which the material flows. Cavity formation can occur before or after providing texture to the surface (which is contemplated separately from surface protection), which can take place by brushing, blasting, or grinding. Creation of the cavity can be a multi-step process comprising electro erosion. The person skilled in the art will determine if all parts of the process comprised in the process are suitable for a particular product.

An advantageous procedure for use with a casting made of aluminum is particular in that it involves the following steps, not necessarily in the order listed:

1) a cavity is milled in the casting, with a shape corresponding to the final cavity and a depth that leaves enough material so that the oxide layer on the front is not subjected to stress, 2) a chemical etching or similar process, such as removal of material by laser ablation or the like, at an atomic level at the bottom of the cavity, until adequate translucency is obtained, 3) some of the material remaining at the bottom is electrolytically converted to aluminum oxide, 4) a fixture for light sources is fitted inside the cavity, 5) a compound is melted in the space between the fixture and the cavity .

An advantageous procedure for the controlled removal of material consists in subjecting the material to pulses of a high power laser and, in contrast to many other applications of this technology, it is feasible to control the operation by measuring the translucency by means of a sensor. adaptive light coupled to the laser control circuit from the front side of the aluminum casting, that is to say, there is no dependence on the reflection of the material directly hit by the laser. Depending on the wavelength of the high-power ablation laser, it may be advantageous to use a different light source for the translucency measurement, in particular a light source having the same wavelength distribution as the translucency source. light to be incorporated into the display.

The invention will be described in detail with reference to the drawings, in which:

Figure 1 shows the appearance of a display according to the invention;

Figure 2 shows a casting in the first stage of manufacture;

Figure 3 shows the result of a further manufacturing step;

Figure 4 shows a further manufacturing step;

Figure 5 is still a further stage of manufacture and precision of the work;

Figures 6a and 6b show two views of a finished cavity for the display device according to the invention;

Figure 6c shows the same in greater detail;

^Y Figure 7 shows a cavity fitted with a fixture for the light sources.

In figure 1 the structure of a display device according to the invention is represented. An aluminum plate 3 with an appropriate surface finish is provided with a cavity into which a casting compound 2 is fused surrounding a fixture of the light source 1. In a) the appearance of the light source is shown. display device when turned on in a model that can read ALUDISPLAY. The dimension of the circles used to indicate the dot matrix pattern is not indicative of the dimension of each point of light but of its perceived brightness. When the display device is unplugged, there is no discernible difference between the display area and the surrounding surface finish of aluminum material.

In figure 2 it is schematically represented how a milling cutter 4 prepares a cavity in the casting 6 and it is also depicted that the front surface of the casting 6 is provided with a particular surface finish by the tool 8, which can be a grinding wheel or a polishing wheel or a wire brush or a blasting operation. The order in which these mechanical operations are carried out will be determined by the person skilled in the art. The forces created by the cutting process determine how deep the milling can go, as the proof is that it should not influence the oxide layer on the front of the display device, i.e. there should be no cracking of the layer oxide which would indicate very clearly the location of the display device.

Following this the casting with the previously machined section 9 is subjected to anodizing or decorative coating / lacquering with a clear coating in order to protect the front surface before the final manufacturing steps. The

ES 2 236 615 T3 intermediate result is schematically represented in figure 3 in which 11 indicates the anodized oxide layer which has a thickness of typically 5-25 µm and 10 indicates the aluminum surface underneath.

In order to reduce the thickness of the aluminum in the viewing area without stressing the front oxide layer, a gradual removal of the material is achieved by a laser ablation process (the preferred process). In Figure 4 this is schematically represented by the laser beam 12, the laser optics 13 and the various depths the laser beam reaches. It will be noted that the anodized oxide layer 14 at the bottom of the cavity is simultaneously removed (and to the point where the process takes place in an oxidizing atmosphere and is replaced by a thin oxide layer).

Figure 5 shows a schematic representation of the final process in the provision of the appropriate cavity: in selected locations (points distributed according to some rule or in a tracer) a high power laser, such as a femtosecond laser is used. to "drill" holes that are 10-30 nm from the front surface (the transfer from metallic aluminum to decorative oxide). The drilling is supervised by means of the light sensor 17 which provides an input signal to the control of the power and the depth of the laser 15, 16. In a) it is represented in detail on a larger scale than a very thin layer of translucent aluminum remains at the bottom of each hole or void in the aluminum layer deposited on the transparent oxide layer. It will advantageously eliminate almost all aluminum in a previously defined model, as it will provide a slightly "floating" visibility of that model in ordinary lighting, while the model can also be strengthened by turning it on as described in the present application, or the model is can extinguish using a different pattern created by light sources.

Figures 6a and 6b finally show how the frame of the display device according to the invention is presented after manufacture.

Figure 7 depicts how a fixture for a number of individually steerable light sources is fitted and held in a cavity until the casting compound has hardened around it, after which the display device as such is ready to be used. The finished display device fully supports the front oxide layer and the thermal coefficient of expansion is such that it is obtained over a very wide temperature range. As long as the thermal capacity of the fixture is similar to aluminum, the surface in the viewing area will not be distinguishable from the entire aluminum, even by touch.

The invention will be further documented by means of the following example:

A 10 mm diameter thin sheet was prepared in a piece of aluminum by turning on a lathe to a thickness of 100 μιη. This was subsequently anodized to a 15 µm thickness of the oxide layer on each side. This semi-finished product was exposed to ablation laser treatment according to one aspect of the invention carried out at the Gottingen eV Laser-Laboratorium, PO Box 2619, D37016 Gottingen, Germany. A series of 1mm x 1mm square "spots" was formed on the prepared thin sheet until a translucency of 0.1% was obtained for each "spot". Each point consists of a grid of 10 x 10 micro-cavities essentially cylindrical (but in practice slightly conical) each 40 µm in diameter and a distance between centers of 100 µm. A closer inspection of a cavity displays a slightly sharp-edged cross section. A femtosecond ultraviolet excimer laser was used and a CCD camera was used on the side of the sheet that was not being treated in order to determine when the appropriate translucency was obtained for each microcavity, after which the laser beam was stopped and moved to the next location on the grid. In some cases, the final transparency of the individual micro cavities was considerably higher, due to the depletion of the aluminum due to the roughness of the surface. However, visual inspection of the front of the finished items, even under a microscope (x 100x) and illuminated at an angle from the side, did not reveal the location of these higher transparency stains and they are therefore considered insignificant. on the practical product. Figure 6c, which is not to scale, shows the plan layout of the micro cavities and reinforcing ribs in the structure at the bottom of the cavity.

A light emitting diode was fitted into the cavity on one side of the thin sheet and the other side - the front side - was observed in both daylight and dark. The pattern of the dots was clearly visible emanating from the entire aluminum surface at a 120 ° angle view, and in broad daylight a red light was clearly visible at a distance of a maximum of 3-4 meters. A blue diode was less visible, the maximum distance being only 1 meter. When the LED was turned off, there was no visible trace of the laser ablation treatment on the front surface which appeared completely uniform, even when using a hand lens.

It is within the scope of the invention to provide a seemingly whole but translucent display of various types, such as a dot matrix display, a static text or symbols display, or a dynamic text or symbols display. Type selection can influence the actual shape of translucent parts, because the bottom of the cavity can be predominantly smooth and translucent (providing apparent infinite resolution of the displayed characters or symbols) or predominantly made up of translucent islands surrounded by a structure in the form of a metal grid or ribs (for example corresponding to a display of the dot matrix type). Such a grid-like structure visible only from the back of the display provides a reinforcement of the structure and improves the bond between inserts and the metal part.