EP1338349B1 - Device for presenting information - Google Patents

Abstract

An arrangement for displaying information on surfaces, e.g. road signs or advertisements, comprises a surface with a base structure (16) and further structures (18) which are self cleansing. The structure has a capillary action and the quotient of capillary work (K) and adhesion (A) is greater than 1. An arrangement for displaying information on surfaces, e.g. road signs or advertisements, comprises a surface with a base structure (16) and further structures (18) which are self cleansing. The structure has a capillary action and the quotient of capillary work (K) and adhesion (A) is greater than 1. The surface comprises e.g. polyvinyl chloride (PVC), polyethylene terephthalate, poly methylmethacrylate (PMMA) or polyamide (PA).

Description

The invention relates to a device for presenting information content on detection areas, such as road signs, signposts, Advertising signs, number plates, etc. according to the characteristics of Preamble of claim 1.

These devices are regularly exposed to environmental influences, especially in the form of soiling, which is especially In areas of road traffic applies, which sooner or later to the impairment the readability of the respective information leads. Especially in the field of safety-related information is therefore from time to time a cleaning of the respective device needed, what with a corresponding Time and cost associated. It would therefore be desirable if such devices could clean themselves to To help avoid the mentioned maintenance costs.

EP-B-0 772 514 discloses self-cleaning surfaces of articles known to be an artificial surface structure of elevations and recesses of a kind, wherein the distance between the Elevations in the range of 5 microns to 200 microns and the height of the surveys in the range of 5 microns to 100 microns. In addition, it should at least the elevations of hydrophobic polymers or durable hydrophobicized Materials are made and the bumps are not water or be removable by water with detergents.

The known solution in this respect shows a surface with these surveys for repelling pollution, being artificially a lotus leaf structure is modeled, of which it is known that they in the sense self-cleaning does not pollute and even commercial adhesives be rejected by the biological structure. Despite considerable Results in terms of a self-cleaning effect are the effect known surfaces only limited use, since either the area the materials to be used in the manufacture is severely limited or the surface is reworked consuming in terms of hydrophobing must become. Accordingly, pertinent surfaces apply in the facade design or as exterior wall paint. It has, however shown in practice that the then artificially manufactured Surfaces with "lotus effect" often do not have the desired results in the With regard to self-cleaning.

From EP-A-0 933 388 there is a structured surface with hydrophobic and / or oleophobic properties known with low surface energies. These known surfaces have large with water Widen angle on and are difficult to moisten and have water therefore a self-cleaning effect. To achieve this, one will artificially manufacturable basic structure with two different types of surveys provided as another structure on the surface, with a kind smaller elevations attached to a superstructure are in the form of geometrically larger elevations adjacent to each other directly nudge. For producing the known elevations and the superstructure as a different kind of surveys, these are taken simultaneously or successively mechanically imprinted in the surface material, by lithographic Process etched or applied by shaping processing or obtained by casting. In the mechanical stamping process is acted upon from the back according to the surface, those on their opposite side then the aforementioned two species of structural elevations ausformt. The used for this purpose Casting, embossing, Einätz- and application methods are not suitable in large-scale production of large quantities of structured Surfaces available, although this known solution very good results in the self cleaning, which, moreover, in the Nature in the form of the leaf surface of nasturtium their equivalent place.

From DE 199 23 175 A is a method for coating a plastic carrier plate known with the following process steps: Applying a stamping foil at least on a viewer facing Side surface of the plastic carrier plate, wherein the stamping foil has an adhesive layer, a surface layer and a cover sheet, joining the Embossing foil with the plastic carrier plate under the influence of pressure and Heat in a stamping process and peel off the cover sheet, so that the coated surface of the plastic carrier plate through the surface layer is formed, wherein the surface layer with hydrophobic and / or hydrophobized material existing structural elements in one Height of up to 100 microns and a distance of up to 200 microns to each other is trained. Furthermore, the known solution relates to a display element, comprising a coated carrier plate described above, the surface layer being a self-cleaning surface, which is preferably additionally scratch-resistant and / or anti-reflection properties having. The pertinent method and the associated production the display element are complicated and therefore costly.

By DE-A-199 43 299 is a surface for an object with an artificially produced basic structure from a first type of surveys known, the first type of surveys to form demarcated areas is part of a second type of survey, to which the first kind of surveys is arranged. The second kind of surveys is convex, so that a self-cleaning surface is created, which is a very good repellency for contamination having. The structures mentioned can be manufactured preferably obtained via structural rolls, but with a corresponding Expense is connected, which leads to high production costs.

EP-A-1 063 071 discloses a polymer article, in particular vehicle tires, known with a textured surface that is visible, either at least a part of the surface is corrugated in such a way that the Distance from Riffelgrat to Riffelgrat between 4 microns and 40 microns or at least a part of the surface is knobbed in such a way that the Distance from nub tip to nub tip between 5 μm and 60 μm is. Due to the known microscopic shape of surfaces with Micro surveys - corrugations or burls - one is capable of one to ensure very good self-cleaning effect. This effect is primarily based on the special dimensioning and in such a way on the well-known Microelevations. This adjusts the effect that dirt particles in the known solution only on the tips or ridges of the micro surveys come to sit and thus very little contact, say Adhesive surface, have to the ground.

Nevertheless, one comes only to very rough microstructures what adversely affects the desired cleaning.

Based on this prior art, the invention has the object based on creating a surface with a respect to the known Solutions improved cleaning grade for soiling and the In addition, in a cost effective manner their production in the large industrial Scale allows such devices for presenting informational content on detection surfaces from permanent contamination to protect. A task solves a surface with the features of claim 1 in its entirety.

Characterized in that according to the characterizing part of claim 1 the respective structure is formed of a stem part, at its free End of at least one capillary flows into the open, and has or develops a capillary action at the quotient of capillary K and Adhesion work A is greater than 1 is thus an elevated Abreinigungsgrad achievable over the known solutions, and Nevertheless, the pertinent device can be very cost-effective Received manner.

In the device according to the invention have the capillary structures with their capillaries a so-called. Negative heights rise on, i. Liquid is forced out of the capillaries. This is especially true for liquids whose contact angle is on the structured surface between 90 ° and 180 °. The effect of the Capillaries at the surface is through the capillary work K and the adhesion work A described. Since the capillary work K drops the structure draws; the adhesion work A, on the other hand, admits the drop in the structure Hold searches, allows the choice of the quotient for the two mentioned Work greater than 1, that the drop, as far as he wetting in the capillary opening penetrates, an opposite force undergoes the self-cleaning allows.

In a preferred embodiment of the device, the respective structure has or forms a capillary whose average capillary radius r _{K is} smaller than the radius r _{T of} the smallest water drop occurring in the environment, in particular raindrops.

In addition, since different droplet sizes occur in the application of the self-cleaning structured surface, it is important for design of the patterned self-cleaning surface that the selected capillary radii r _{K be} smaller than the radius of the smallest environmentally occurring raindrop r _T. For this purpose, the drop of rain falling raindrop is considered, which can break or burst on impact on any surface in several small drops.

From this point of view, the capillary radius r _{K of} the self-cleaning structured surface must be r _k <r _T , so that a small drop does not fall into the structure and thus no negative rise in the capillaries is achieved. For different liquids such as oil, water, chemical liquids, etc., different capillary radii then result due to the corresponding liquid properties. If the capillary action is generated by other geometric structures than tubes, such as by pyramidal, conical or frustoconical supernatants, a mean or average capillary radius r _{K is} to be determined for these structures in their interpretation.

In a further preferred embodiment of the Device consists at least in part of hydrophilic materials, in particular of plastic materials, such as thermoplastics and thermosets, in particular in the form of polyvinyl chloride, polyterephthalate, polymethylmethacrylate or polyamide. Compared to the known solutions to increase the degree of soil repellency instead of hydrophobic or oleophobic surfaces used hydrophilic material, with the would be more surprising to one of ordinary skill in the art Way to achieve a higher level of soil repellency than with the known structures mentioned. The fact that the basic structure for the Surface is formed of a hydrophilic plastic material, that is Material attracts water and absorbs moisture, so that due to the Water molecules or moisture in the material a kind of protective or Separating layer is formed on the surface, with improved dirt-repellent Properties.

In a further preferred embodiment of the Device is the surface with the detection surface over a transparent Adhesive can be connected together. Preferably come here Adhesives in question such as hotmelts based on rubber or polyolefins. Further Acrylates which are suitable both from aqueous dispersion or from. are suitable the solution can be applied. Preferably used as adhesives are also monomers and oligomers which are radiation-crosslinkable.

There is also the possibility of the recognition surface directly in the Form the type of surface shown, in which case the recognition content to be applied to the thus modified recognition surface, for example, by spraying, knife coating, printing and the like more.

Also, a plurality of capillaries can be introduced into the free ends of the respective stem part. If the stem parts are so close to each other that capillaries are likewise formed by the intermediate spaces thus obtained, an increased degree of cleaning can be achieved in this way. It may also be sufficient to introduce the respective capillary only into the basic structures.

Fig.1

eine Vorrichtung zum Darbieten eines Informationsinhaltes, hier in Form eines Wegweisers "Zum Patentamt";

Fig.2 bis 4

verschiedene Ausführungsformen von selbstabreinigenden und schmutzabweisenden Oberflächen.

In the following the device will be explained in more detail with reference to various embodiments according to the drawing.
This show in principle and not to scale representation of the

Fig.1

a device for presenting an information content, here in the form of a signpost "Zum Patentamt";

2 to 4

various embodiments of self-cleaning and dirt-repellent surfaces.

In Fig. 1 is an apparatus for presenting information contents represented on a recognition surface in the form of a signpost, the Inventor points the way to the Patent Office. Is the pertinent signpost now exposed to environmental pollution is at least long term with it to calculate that his information content is not or only difficult recognizable, so that an inventor then not only has problems with the complex Patent law, but does not even find its way to the Patent Office. Although it is possible from time to time to find the relevant signpost, for example, by hand, to clean off; the latter is however with appropriate Costs and efforts connected. Here is now the inventive Teaching that offers a possibility that the signpost and thus the device for presenting information content on recognition surfaces can cleanse oneself.

For this purpose, it is proposed that the recognition area 10 of the signpost 12 to be provided with a surface 14, as they are the subject of representation 2 to 6 is. Another possibility is the recognition surface 10 immediately as the surface 14 with the dirt-repellent To train the effect. For this purpose, the surface 14 is an artificially produced Basic structure 16 and is provided with further structures 18, which act self-cleaning, wherein the respective structure 18 has a capillary action has or unfolds at which the quotient of capillary work K and adhesion work A is greater than 1.

The lateral side view of the surface shown in FIG. 2 particularly comprises the artificially producible structure 16 with structures 18 arranged thereon, which are formed in the manner of cylindrical stem parts 20. In the respective stem part 20, a capillary 22 is centrally introduced, which opens with its capillary 24 into the open air. The mentioned stem parts 20 as structures 18 can be close to each other in a plurality of arrangements on the base structure 10 and are connected to this preferably einstükkig. Furthermore, the basic structure 16 may be formed in the manner of a film, preferably in a flexible embodiment. If the pertinent film structure is made correspondingly thin, the film can also biaxially stretch or stretch and can also assume their original position due to their elasticity. In this way, the surface 14 can also be defined on complex-shaped three-dimensional objects of any kind. The surface 14 shown in FIG. 2 is reproduced greatly enlarged and both the basic structure 16 and the further structures 18 can form microstructures, also in the nanometer range. The respective structure 18 having a capillary 22 has, from the side of the capillary opening 24, a capillary radius r _K which is smaller than the radius r _{T of} the smallest water drop occurring in the environment, in particular raindrops.

The structured surface 14 shown in FIG. 1 is self-cleaning. The structuring is described as an arrangement of individual capillary 22. For the desired action of the capillaries, a negative rise height in the capillaries 22 must be achieved, ie, liquid is forced out of the capillaries 22. This applies to liquids whose contact angle on the structured surface 14 is between 90 ° and 180 °. Mathematically, the effect of the capillaries on the surface can be described by the capillary work K and the adhesion work A. The capillary work K pulls the drop out of the structure; the adhesion work A holds the drop in the structure. The aim of the structure design is that by the appropriate choice of Kapillarradius R _K, the quotient K / A> 1. If r _{T is} greater than r _K , then the drop is distributed over several capillaries, so that: r T r K , K A > 1

For capillary work, K = πh _K ² · r _K ² · g · ρ
For the work of adhesion A for cylindrical capillaries, the following applies: A = (Σ lg + σ sg - σ sl ) 8th 3 π. r T 3 r K With σ surface tensions r _K capillary σ _lg liquid-gas h _K Rising height in the capillary σ _sg solid-gas ρ Density of the liquid σ _sl solid-liquid G Gravitational acceleration (9.81 ms ^-2 ). r _T Radius of the drop

The aforementioned capillary-like further structures can be opposite to Representation of FIG. 2 in the basic structure 16 also recessed or be part of concave and / or convex surveys relative to the basic structure 16.

σ_lg:

Oberflächenspannung der Flüssigkeit

g:

Erdbeschleunigung (9,81 ms^-2)

ρ:

Dichte der Flüssigkeit

v:

Fallgeschwindigkeit.

Since different droplet sizes occur in the application of the self-cleaning structured surface, it is additionally important for a design of this surface that the capillary radii r _{K are} smaller than the radius of the smallest rain droplet r _T occurring in the environment. For this purpose, the impact of free falling raindrops is considered. This drop shatters on impact on any surface into several small drops, including the impact on a self-cleaning structured surface with capillary action. For the radius of the smallest resulting droplet r _{T, the} following applies: r T = 6σ lg ρ G ρ v 2 6σ lg ρ G 6σ lg + 1 With:

σ _lg :

Surface tension of the liquid

G:

Gravitational acceleration (9.81 ms ^-2 )

ρ:

Density of the liquid

v:

Fall speed.

Fall A: Flüssigkeit wird in eine Kapillare hinein gezogen (Steighöhe h_K positiv)

Fall B: Flüssigkeit wird aus der Kapillare herausgedrückt (Steighöhe h_K negativ), Kapillardepression.

From this consideration, the capillary radius r _{K of} the self-cleaning structured surface r _K <r _{T must be considered} , so that a small drop does not fall into the structure and thus no negative rise in the capillaries is achieved, which makes self-cleaning possible. For different liquids, the corresponding liquid properties result in different capillary radii.
If the capillaries 22 are used as structures, the effect of the capillary forces on a liquid in both directions can be observed:

Case A: liquid is drawn into a capillary in (rising height h _K positive)

Case B: Liquid is forced out of the capillary (height of rise h _K negative), capillary depression.

If the drop lies on the structured surface, the drop lies over capillaries 22 and for self-cleaning case B is interesting, in which the liquid against the force of gravity up from the Capillary 22 is pressed in the raised drops.

σ:

Oberflächenspannungen

σ_lg:

flüssig-gas

σ_sg:

fest-gas

σ_sl:

fest-flüssig

:

Kontaktwinkel zwischen Flüssigkeit und Festkörperoberfläche

ρ:

Dichte der Flüssigkeit

g:

9,81 ms^-2 (Erdbeschleunigung)

r_K:

Radius der Kapillare 22.

As a rise height h _K in a capillary 22, this results in: H K = 2 σ lg cos pi K = 2 (σ sg -σ sl ) pi K because: σ _lg · cos = σ _sg - σ _sl (Young's equation)
With:

σ:

surface tensions

σ _lg :

liquid-gas

σ _sg :

solid-gas

σ _sl :

solid-liquid

:

Contact angle between liquid and solid surface

ρ:

Density of the liquid

G:

9.81 ms ^-2 (gravitational acceleration)

r _K :

Radius of the capillary 22.

The rise height h _K in the capillary 22 has a negative value in case B. All sizes in the formula for the rise are positive. Only the cosine of the contact angle  becomes negative for the condition: 90 ° < <180 °.

':

Kontaktwinkel der rauhen Oberfläche

:

Kontaktwinkel der glatten Oberfläche

k:

Rauhigkeitskoeffizient (> 1).

In principle, the mentioned contact angles must be greater than 90 °, so that the desired effect arises at all that the liquid is forced out of the structures by capillary forces. For surface roughness: cos  '= k cos  With

 ':

Contact angle of rough surface

:

Smooth surface contact angle

k:

Roughness coefficient (> 1).

Essential for the effect of capillary forces in structured surfaces In addition, the relationship between the radius of the structures is and the adhesion forces. Because it acts against adhesion forces here Capillary forces on the capillary wall.

In equilibrium, the capillary force acting on the liquid is opposite equal to the weight of the displaced liquid column. For the calculation fictitiously a cylinder can be assumed, the height of which corresponds to the calculated height of rise in the capillaries (for example here: Δh _K = 10.157 mm, for water with  = 110 °, ρ = 998.2 kgm ^-3 and r _K = 0 , 5 mm).
For computational comparison not the forces but capillary work and adhesion work are calculated.

The capillary work K is equal to the product of volume, gravitational acceleration g, density ρ and the height of rise h: K = πh K 2 R K 2 · G · ρ

Adhesion work in a straight circular cylinder A:

Adhesion work A over the contact surface F: A = (σ lg + σ sg - σ sl ) 8th 3 π r T 3 r k

The above formula applies to a radius r _T , the raindrops occurring in the lowest region of the water droplet size distribution in the environment in the case of a multiplicity of capillaries used.

The capillary work must be greater than the adhesion work, so that the drop not touched the capillary, but the drop from the wells is sucked and rests on the surface, which is the most advantageous Self-cleaning results. To compare the orders of magnitude of capillary work K and Adhäsionsarbeit A, the quotient K / A is calculated.

Particularly good Selbstabreinigungseffekte have emerged, provided that Surface consists of hydrophilic materials, in particular of plastic materials in the form of polyvinyl chloride, polyterephthalate, polymethylmethacrylate or polyamide. The pertinent hydrophilic materials draw moisture into the basic structure and thus form a protective layer against the impact of aqueous contaminants. In The mentioned plastic materials can also be other networked structures, especially in the form of acrylate material or those materials that prove to be biodegradable.

The surface starting material according to Figure 2 can be by the method obtained according to DE 198 28 856 C1. To the stem parts 20 in the desired Forming way, in the known method is a mold required in the manner of a screen roller, with the very large number the openings of the screen by etching, electroplating or by laser processing is obtained. The sieve is placed on a sieve or a structure roll applied and a Gegenhaltewalze, the rotates counter to the structure of roller, a so-called. Chill-roll process can be perform in which an extruded plastic material through the gap is guided between the two rollers and the stem parts 20 arise in the openings of the screen roller. To make the capillary openings 24 to be able to displace the plastic material accordingly, for example in the form of introduced mandrel parts in Siebwalzengrund. Stem parts 20 can be packed in a very high packing density with the mentioned method arrange on the basic structure 16 and otherwise very small-scale form.

Another method of manufacturing the surface 14 according to the embodiments After Fig.2ff can be achieved by the structure of individual Finest plastic material droplets, which at selected locations one after the other be deposited, with virtually any small format sizes or achieve packing densities without a corresponding complicated training of molds would be required. So can be controlled by the locations of the deposits of plastic droplets, which by corresponding relative movements between applicator and a substrate carrying the deposit, preferably computer-controlled takes place without difficulty, with any geometries can be generated. Furthermore, it is possible to produce shapes that are common Forming tools such as screen rollers, hardly or not at all feasible. Furthermore, the respective method can be readily determined by the method Generate capillary opening 24 in the stem sub-material.

The applicator used here are nozzle assemblies that are in the high-speed process are able to carry out the material order. Only droplets the size of a few Piktolitern are on the sheet-like base structure material 16 applied. Furthermore let During the order process, clock frequencies of several kHz can be achieved and The structure takes place successively, by the respective preceding, applied Plastic material is cured directly, for example by means of UV radiation or the like. The pertinent droplet application method is in the subsequently published DE 101 06 705.4 described in detail.

With the structured surface according to the invention with capillary action is achieved a very high self-cleaning effect and the pertinent Structures 18 can be obtained inexpensively on an industrial scale and for a variety of applications. The basic structure 16 with its further structures 18 may be in the nature of a sheet material be trained; but there is also the immediate possibility of the capillaries 22 in the film-like surface 14 at least from one side contribute. Furthermore, there is the possibility of the recognition surface 10 even form in the manner of the described surface 14, wherein then the dahankende recognition surface 10 finally with the information content to be provided, for example by a conventional application device, like spraying or the like ..

The aforementioned capillaries 22 with their capillary openings 24 can be also obtained via a removal process, for example by means of laser or Waterjet cutting. Also a mechanical entry via drills od. Like. is possible.

The surface 14 is preferably transparent and is with the top of the recognition surface 10 by means of a conventional transparent Adhesive connected. Preferably, rubber-based hotmelts are used or polyolefins application. Furthermore, acrylates can be applied be applied both from aqueous dispersion or from the solution are. Furthermore, the use of monomers and oligomers possible, which are radiation crosslinkable.

In the following embodiments according to the Fig.3ff the same Components provided with the same reference numerals and the various Embodiments are explained only insofar as they themselves differ significantly from the embodiment of FIG. 2.

In the embodiment of Figure 3 are a plurality of capillaries 22 frontally introduced into the respective stem part 20 and also on The reason of the basic structure 16 between the respective stem parts 20 are corresponding capillary 22 introduced.

In the embodiment according to the Fig.4 are frontally the respective Stem parts 20 provided with a plurality of conically extending capillaries 22 and on the side of the base structure 16 facing the stem parts 20 has these in an alternating sequence cylindrical capillary 22 and tapered. In the related embodiments is make sure that the smaller conical capillaries 22 in the sum in any case give a total capillary whose mean Kapillarradius is chosen such that the resulting therefrom quotient Capillary work K and adhesion work A in any case greater than 1, to the To ensure self-cleaning.

The basic structure 16 preferably has a thickness of 10 .mu.m to 50 .mu.m and the capillary depth is preferably greater than 5μm. The capillary radius is preferably chosen larger than 5μm.

As capillaries (hair tubes) within the meaning of the invention are all tubes or elongated voids (pores) with very small inside diameters suitable. As a manufacturing plastic material are also particularly crosslinkable polyacrylates.

Claims (10)

1. Means for displaying information content of display surfaces (10) such as traffic signs, road signs, advertising signs, number plates etc., whereby the relevant means is equipped with a surface (14) with an artificially produced base structure (16) and with further structures (18), or in itself forms such a surface (14) which is self-cleaning, characterised in that the relevant structure (18) is formed from a stem section (20) at the free end of which at least one capillary (22) opens out into free space, and has or develops a capillary effect, whereby the quotient of capillary effect K and adhesion effect A is greater than 1.
2. Means according to Claim 1, whereby the relevant structure (18) incorporates or forms a capillary (22), the central capillary radius of which is smaller than the radius of the smallest water droplet occurring in nature in the form of a rain drop.
3. Means according to Claim 1 or 2, whereby the surface (14) consists at least in part of hydrophilic materials.
4. Means according to Claim 3, whereby the hydrophilic materials consist of thermoplastics and duroplastics.
5. Means according to Claim 4, whereby the thermoplastics and duroplastics consist of polyvinyl chloride, polyterephthalate, polymethyl methacrylate, or polyamide.
6. Means according to one of the Claims 1 to 5, whereby the surface (14) is connected with the display surface (10) by means of a clear adhesive.
7. Means according to Claim 6, whereby the following serve as the adhesive

   hot smelts based on india rubber or polyolefines,

   acrylate, or

   monomers and oligomers.
8. Means according to one of the Claims 1 to 7, whereby several capillaries (22) are inserted into the relevant facing free end of the stem section (20).
9. Means according to one of the Claims 1 to 8, whereby the stem sections (20) are positioned so closely that the gaps produced in this way also form the capillaries (22).
10. Means according to one of the Claims 1 to 9, whereby the base structure (16) also incorporates capillaries (22).

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