WO1999052650A1

WO1999052650A1 - Method for the electron irradiation of layers on surfaces of objects and a device for carrying out the method

Info

Publication number: WO1999052650A1
Application number: PCT/DE1999/000337
Authority: WO
Inventors: Siegfried Panzer; Gösta MATTAUSCH; Siegfried Schiller; Rainer Bartel; Dieter Leffler; Tino Bobe
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 1998-04-11
Filing date: 1999-02-04
Publication date: 1999-10-21
Also published as: DE19816246C1

Abstract

The invention relates to a method for the electron irradiation of layers which are deposited on objects, or of areas of objects near the surface thereof. According to the inventive method, the physical and/or chemical properties of materials in the surface or in the areas near the surface are altered. The invention also relates to a device for carrying out the method. The preferred area of application of the invention extends to cover the hardening of coating materials, for example, paints and lacquers and of organic/inorganic composite systems which are deposited on objects having three-dimensionally formed surfaces. The device for carrying out the method is suited for robotics and can be economically used for a wide range of industrial applications.

Description

1

Process for electron irradiation of layers on surfaces of objects and device for carrying out the process

The invention relates to a method for electron irradiation of layers which are applied to objects, or of areas of the objects near the surface, in order to change the physical and / or chemical properties of the substances of the layer applied to the surface or in areas near the surface Device for carrying out the method The preferred field of application of the invention is the hardening of electron-hardenable paints, for example paints and lacquers, as well as of organic / inorganic composite systems which are applied to objects with three-dimensionally shaped surfaces. The use of the invention is particularly expedient for the finishing of highly stressed surfaces of parts of motor vehicle and aircraft construction, such as scratch-resistant coatings on curved window panes or of facade and construction elements

Methods for electron irradiation of surface layers are described, for example, in the standard work "Electron Beam Technology" by Schiller, Heisig and Panzer (Wissenschaftliche Verlagsgesellschaft Stuttgart, 1977). This describes, among other things, how the physical and / or chemical properties of substances are modified by the action of electron beams Electron irradiation is particularly widespread for the curing of printing inks, adhesives and paints.The method according to the known state of the art allows the use of solvent-free systems based, for example, on acrylate, the curing of the paint being carried out by a polymerization process initiated by the electron beam is mainly used in the production of adhesive films, for the curing of printing inks and for lacquer hardening in the furniture and woodworking industries High scratch hardness and abrasive wear resistance of the surfaces that can be achieved compared to other hard processes are valued

Surface layer to transmit an energy dose, which is dependent on the intended effect and the substances to be modified, and which lies within certain tolerances, with the electron beam 2

A device for using the method for color hardening is known, for example, from the magazine "Papιer + Kunststoff Ververarbeitung ', 1996, Issue 1, pages 8-14, in which an electron irradiation device is used for drying printing inks and lacquer. This irradiation device essentially consists of an irradiation unit with associated supply and control devices as well as means for transporting the radiation material through the electron beam field The radiation unit itself consists of an evacuated electron beam generator with a connected, vacuum-tight beam outlet window that is permeable to the electron beam.In the electron beam generator, electrons are released by a hot cathode, accelerated and in an electrical field Formed into an electron beam A linearly extended arrangement of the hot cathode and the acceleration electrode allows the generation of one which is broadly extended in one direction , curtain-like electron beam

Furthermore, a type of electron beam generator of the axial type is known in which a rotationally symmetrical electron beam is generated and scanned in a connected scanner by means of a beam deflection unit along a line for a time-linear periodic deflection function

In both of the aforementioned cases, the electron beam emerges through the beam exit window at atmospheric pressure. This creates an electron beam field, the width of which is generally large compared to its length. In summary, it can therefore be said that the beam generators known in the prior art are usually designed for an electron beam field generate that has homogeneous properties at the specified distance from the beam exit window Due to the laws of electron scattering, it is inevitable with these beam generators that the properties of the electron beam field change with increasing distance from the beam exit window, while regardless of this the property homogeneity is maintained in the beam width

The electron beam field can in principle be characterized by a

Electron density distribution, a distribution of the electron movement direction and an energy distribution With increasing distance from the beam exit window, the dispersion of the electron movement directions increases, but their mean value coincides with the direction of acceleration of the electron beam and thus defines an irradiation direction of the electron beam field 3

Electrons also increase with increasing distance from the beam exposure window, in contrast the mean value of the electron energy decreases.The consequence of this fact is that the dose transferred in the electron beam field characterized above to the surface and the adjacent penetration area of the electrons depends in a complex manner on the irradiation conditions, in particular on the Distance of the surface to the beam exposure window and the angle between the surface normal and the direction of irradiation

In the electron irradiation methods according to the known state of the art, the material to be irradiated is guided through the radiation field at a constant distance from the radiation exposure window. The permissible width of the radiation material is limited by the width of the beam exit window. Surface layers of up to a few 100 g / rm are irradiated on flat supports, such as Paper or foil webs and plates The acceleration voltage for generating the electron beam is 100 to 300 kV depending on the application

In the case of the electron irradiation devices according to the prior art, the irradiation unit is mounted in a fixed position. The object to be irradiated is moved in a fixed spatial association with the irradiation unit avoids The working cabin has supply and discharge channels for the material to be irradiated, which are protected against X-ray radiation. Irradiation is usually carried out under inert conditions in the range <100 ppm O ₂ concentration. To ensure these conditions, the cabin is flushed with inert gas, for example with N ,,

The control and supply devices for the operation of the radiation device contain, among other things, means for regulating and keeping the radiation conditions constant, in particular the acceleration voltage, the beam current and the transport speed of the radiation material. The beam current is generally coupled to the speed of the radiation material in the case of radiation units with axial electron guns and Scanners, as are known, for example, from the prior art mentioned, additionally contain the supply devices a deflection generator via which the electron beam with fixed parameters and a frequency 4

is scanned in the range of 100 Hz, i.e. periodically linearly deflected, e.g. after a triangular or sawtooth function

The radiation devices known according to this prior art have in common that a stationary or, in the case of beam scanning, quasistationary electron beam field is generated with radiation conditions that are constant over the length of the beam exit window. The radiation methods bound to it thus only allow for flat products that are at a constant distance from the beam emission window the radiation field happen, radiation with homogeneous dose distribution

From the book “Electron Beam Technology” already mentioned, a method for electron irradiation with high energies in the range of 1 MeV is also known, according to which bodies with weakly curved surfaces are irradiated in electron beam fields of the type described above. This is possible because in this case the Change the properties of the radiation field over a larger area only slightly as the distance from the beam exposure window increases. The geometric limits for the surface shape of the body are set here primarily by the angle of the surface normal to the beam direction, since the local dose distribution on the surface depends approximately on the cosine of this angle For special applications of high-energy radiation, for example for the radiation crosslinking of insulating materials of high-voltage cables, it is also known to use suitable arrangements of electron backscattering bodies in the electron beam field to achieve sufficiently homogeneous radiation for such radiation goods

From the Haefer reference, "Surface and Thin Film Technology", Part II,

Surface modification by particles and quanta, Springer-Verlag, 1991, pages 131 to 134, is known to modify layers on three-dimensionally structured surfaces with electron beams. For this purpose, the electron beam is generated with a relatively high acceleration voltage of, for example, 230 kV, so that it is in the Irradiation atmosphere has a sufficiently long range of about 20 cm. The strong dispersion of the direction of movement of the electrons, especially in the second half of the available electron range, is used to irradiate surface elements with different inclinations to the beam direction sufficiently homogeneously. The overall curvature of the sufficiently homogeneously irradiable surface is therefore limited to a fraction of the electron range in the irradiation atmosphere 5

The advantage is paid for by a high acceleration voltage compared to the layer thickness that can be treated. The price is an increased outlay in terms of plant technology and reduced energy efficiency

It is also known to apply arbitrarily curved surfaces to the electron beam in such a way that the surface of the workpiece is melted. This is an edge layer refinement which leads to the hardening of the surface, for example of cams (DE 41 30 462 C 1). This solution has the disadvantage that the process has to take place in a vacuum, since the required energy input is very high due to the required thickness of the remelting layer. Furthermore, this technology is only suitable for relatively small parts with high production numbers

The disadvantage of the known methods and devices resulting from the prior art is that a transfer of the high-energy radiation to the electron beam hardening of thin surface layers on bodies with largely any three-dimensionally curved surfaces fails due to the narrow limits of the process flexibility. In addition, a high technical outlay is required who questions the economics of processes and facilities for many applications

The invention has for its object to provide a method for electron irradiation and the associated device, which makes it possible to change the physical and / or chemical properties of layers that are applied to objects or near-surface areas of objects at a defined depth Objects can be largely arbitrarily, three-dimensionally curved

The field of application of electron radiation is expanded and its cost efficiency and flexibility are increased

According to the invention, the object is achieved according to the features of claim 1. Appropriate embodiments of the method according to the invention are described in associated subclaims 2 to 10. A device for carrying out the method is implemented in accordance with the features of claim 1 1 Oeschπeben facility 6

The method according to the invention consists of irradiating layers on objects or near-surface areas of objects with a three-dimensionally formed surface within permissible tolerances in a defined manner and consequently carrying out a property modification of the surface layer such that the object is in an optimal position and orientation for the radiation, at least with regard to partial surfaces Radiation exposure window of the irradiation device is exposed to the radiation effect. By lining up such partial areas without gaps, it is possible to irradiate the entire area of the object to be irradiated

Due to electron scattering in the beam exposure window and in the gas-filled one

Working distance between the beam exposure window and the surface of the object results in a steady decrease in the radiation dose in the peripheral zones of the partial surfaces. The partial surfaces to be irradiated are therefore lined up in such a way that the energy doses transmitted in the peripheral zones from at least two radiation events add up to the required total dose Taking advantage of the fact that the intended modification effect depends exclusively or dominantly on the radiation dose, but not on the time regime of its transmission

Within the sub-area there are differences in the irradiation conditions for the individual flat elements, such as those caused by different distances from the

Beam exit windows or different angles between their surface normal and the direction of radiation, but also due to different exposure times due to different translation speeds, can be compensated for by adjusting the intensity profile in the plane of the beam exit window.Under intensity distribution, the beam current density distribution in the plane of Beam exit window understood

It is assumed that the geometric course of the surface of the object relative to the beam exit window is known and that for the exposure of a certain flat element the partial area of the electron beam emerges from a location that can be assigned to the flat element or a flat area of the beam exit window Surface geometry to calculate the required intensity profile in the plane of the beam exit window on the basis of the laws determining the electron propagation in matter or, for simplification, if necessary using empirically based or empirical ones 7

Determine methods and also implement them practically while maintaining the load capacity limits of the beam exit window

The method is carried out with a device according to claim 1 1, essentially combining a known axial beam source for an electron beam with a freely programmable wide-angle deflection for the electron beam in two axes. In contrast to the prior art, the deflection of the axial electron beam does not take place contemporary and linear, but two-dimensional and within a deflection pod with instantaneous speed or beam dwell time that can be varied within wide limits. In order to set the technologically relevant intensity profiles, a deflection unit operating in the medium frequency range is used with a beam guiding electronics adapted to it

Corresponding to the dose depth distribution of the energy absorption of electrons, with a given current density on flat elements whose distance to the beam exit window is greater than half the range of the electrons, a smaller dose is transmitted with increasing distance.This disadvantage of surface elements with a greater distance to the beam exit window can be advantageously due to an increased intensity in the assigned window area are compensated for, since this measure does not change the relative dose gradient over the layer thickness to be irradiated, the permissible dose gradient ultimately determines the maximum possible distance of a surface element to be irradiated from the beam exposure window given the acceleration voltage, the radiation exposure window and the gas between the radiation exposure window and the object surface.

A significant expansion of the process flexibility with regard to the adjustability of dose gradients, but in particular the tolerance of contour-related variations in the working distance within the current irradiation range would result if, instead of nitrogen, a gas with a lower density is used, expediently helium. For reasons of cost, it is not acceptable, however, inertizing the entire work booth with helium The device for carrying out the irradiation process is therefore equipped with a protective gas duct, which only locally inertises the area of the instantaneous radiation exposure to the surface layer to be modified with pure helium or a nitrogen-helium mixture. Another advantage of this device is it that the consumption of high purity inert gas on a 8th

The minimum is reduced and the requirement for the global oxygen concentration in the work cabin can be significantly alleviated, which in addition to the direct inert gas costs in particular also reduces the effort for the inward and outward transfer of the objects

The structural size of the surface details, to which the irradiation conditions can be adapted, is limited to small dimensions primarily by the directional dispersion of the electrons due to scattering when passing through the beam exit window and the subsequent gas path. This is the lower, the higher the electron energy and the smaller the distance of the surface element from the beam exposure window and its mass per unit area

An important element of the radiation unit according to the invention is therefore a special support grid, which can be cooled with water, for example, which enables the use of particularly thin metal foils as radiation exposure windows. With this technology, small values of the directional dispersion of the emerging electrons can be achieved even at low acceleration voltages of less than approximately 150 kV. This has the advantage that the radiation source is lighter and more compact than the prior art represented by devices with significantly higher acceleration voltages, the expenditure for radiation protection containment is lower and the radiation exposure of the object below the surface layer to be modified is low.

For the irradiation of surfaces of objects, the extent of which is large compared to an irradiable partial area, it is expedient to combine neighboring partial areas into radiation paths. The irradiation of such a path then takes place during the relative movement between the respective surface of the object and the irradiation unit. The surface of the object is aligned with the beam direction and the intensity distribution is adjusted in the plane of the beam exit window in accordance with the partial area located in the respective element in the area of action of the electron beam. It is also expedient to carry out the irradiation of the surface of the objects by stringing suitably selected radiation paths in a row

In this case, one or both can be used for the optimal positioning of the beam source and object as well as for generating the precubbing speeds necessary for the method 9

Several robots are used.For example, one robot can move the irradiation unit with respect to the object.However, it is also advantageous to use another robot to move the respective object relative to the irradiation unit before or during the irradiation while the irradiation unit is at rest or simultaneously via the first robot is aligned perpendicular to the radiation area

Another degree of technological freedom is achieved with the radiation device according to the invention in that the beam exposure window can be rotated relative to the beam source. This simplifies the implementation of a path control operation that is required for the irradiation of curvilinearly limited paths on free-form surfaces

In the previously described method variants, it has always been assumed that the contour of the surface to be irradiated is given in analytical form or as a CAD file. However, it is also possible with the invention to remove unknown or very roughly tolerated contours simultaneously and directly in connection with the irradiation process To this end, the device for carrying out the irradiation process is provided with interfaces for coupling a digitizing device. The contour data of the surface thus determined are then available online for calculating and setting the intensity distribution, the required feed and the optimal alignment of the irradiation device and object

The optimal alignment of the partial area to be irradiated with respect to the beam exit window is given when the entirety of the flat elements can be acted upon by the electrons under optimal conditions.This requirement is generally met when the distance to the beam exit window is sufficiently small and the surface normals of the partial areas form an angle less than about 45 ° to the beam direction

An expansion of the effectively irradiable angular range is achieved in the irradiation device according to the invention in that adjustable reflector diaphragms are arranged directly below the beam exit window, which reflect the emerging electron beam. With an appropriate setting of the angle of the reflector diaphragm relative to the main exit direction of the electron beams, even partial areas of surfaces can then be effectively irradiated whose surface normals are more than 45 ° are inclined against the surface normal of the plane of the beam exit window. The advantage over the known rigid reflection bodies is that the reflector diaphragms can be automatically controlled in connection with the robot movement and can thus be flexibly adapted to different contours

As a particular advantage of the present invention, it should be emphasized once again that, for example, the hardening of electron-beam hardenable lacquer layers on wear-stressed, three-dimensionally shaped surfaces of the type mentioned at the outset can be carried out. The hardening can be carried out either immediately after the lacquer application from the liquid state or after a pre-hardening UV rays occur In the case of previous UV curing, it may also be advantageous to restrict the additional electron beam curing to surface areas that are particularly exposed to wear

embodiments

The invention is explained in more detail below on the basis of exemplary embodiments and associated drawings. The drawings show: FIG. 1 a schematic illustration of the basic structure of an irradiation unit for implementing the electron irradiation method according to the invention; 2 shows the arrangement of the radiation unit on a handling device, for example on an industrial robot; Fig. 3 is a schematic representation of the irradiation process for the surface of a corrugated sheet with division into individual hardness tracks and representation of the

Paths (n-1), n and (n + 1) to be set dose distribution D _k (x), and the intensity profile ι (x, y) to be programmed for the path n in the window plane; 4a shows the arrangement of an angle plate relative to the beam opening window; 4b shows the position of a lacquer layer to be irradiated on this angular plate relative to the dose-depth distribution for pure nitrogen and pure helium as inert gas;

Fig. 5 shows the orientation of the window and object and the intensity profile using the example of

Hardening the lateral surface of a truncated cone using the feed method; 6 shows a schematic illustration of the basic features of a flash method based on the pulsed radiation of spherical caps by means of an exposure mask obtained by superimposing sub-cycles;

7 shows the irradiation of a 3D free-form surface using the flash method, the exposure mask being programmable by digitizing the contour and point by point

Dwell times of the beam was generated; 8 shows the application of the flash method for sequential pulse-shaped irradiation of complex, large-area three-dimensional contours;

8a is an illustration of the alternating radiation and

Positioning cycles; Fig. 9 shows a possibility of the contour to be irradiated by a together with the

To determine the moving digitizing device and set the substrate-specific intensity profiles online;

Fig. 10 the use of automatically pivoting reflector panels for local

Improvement of the radiation conditions on hard-to-reach areas 1 schematically shows the basic structure of an irradiation unit 1 for carrying out a method for electron irradiation of layers on surfaces of objects according to the invention.

The radiation unit 1 essentially consists of an axial beam source 11 and a beam pipe 1.2. The beam source 1 .1 has a tubular, evacuable and closable housing 2 on its top with a radially arranged turbopump 2.1 and an insulator 2.2 integrated into the housing 2 as a vacuum-tight socket, into which the high-voltage cable 3 is inserted. Within the housing 2, a cathode unit 4 is connected to the insulator 2.2 in the axial direction, which consists of a known hot cathode 4 1 and a control electrode 4.2 which regulates the beam current I of an axial electron beam 4.3 emerging from the hot cathode 4 1. The beam source 1 1 is dimensioned for an acceleration voltage of 150 kV. An anode 5 and a deflection unit 6 are arranged axially under the cathode unit 4.

The deflection unit 6 is designed such that it can deflect the axial electron beam 4.3 formed in the beam source 1.1 and running through an anode bore in the direction of the emitter tube 1.2 at a frequency of 200 Hz to 20 kHz within an axially symmetrical deflection cone 6.1 with a 50 ° tip angle. On the outside of the housing 2 there is also a mounting plate 7 for fastening the radiation unit 1 to a holder or handling device (not shown here).

Connected to the housing 2 in the axial direction is the jet pipe 1.2, which is rotatably connected to the housing 2 of the beam source 1 .1 about the central axis, that is to say polar, and is also connected to control and supply devices, not shown. The polar angle between beam source 1.1 and beam pipe 1.2 can be set with a servo motor 8 during operation. On the lower side of the drawing, the jet pipe 1.2 is closed with a vacuum-tight, water-cooled rectangular jet window 9.

The beam window 9 with a width 9 1 and a length 9.2 lies completely within the base area of the deflection cone 6.1 and essentially consists of a cooled support grid which is covered with a thin metal foil that is largely transparent to electron beams 9.3. On its outside end, the radiation window is surrounded by a protective gas guide 10 for protective gas 11. 13

2 shows the irradiation unit 1 connected to an industrial robot 20. The irradiation unit 1 and the robot 20 are located within a closed work booth, not shown in FIG. 2, which is designed as a radiation protection contour and is filled with inert gas

The industrial robot 20 is connected for the present purpose in the usual manner to a stable base 21 and a lower part 22 and has arms 23 and 24 which are mounted so as to be pivotable and rotatable. The irradiation unit 1 is fastened to the distal end of the arm 24 Connection with drive and control devices, not shown, can be moved both manually and automatically in several degrees of freedom, which are realized by rotary axes of different spatial orientations and are indicated in FIG. 2 by arrows

In Fig. 3, the implementation of the irradiation of the surface of a corrugated sheet 30 is shown in a schematic representation, which lies in a Cartesian coordinate system with the axes x, y and z. Too hard lacquer layer 31 is applied to the underside of it only because of the easier representation Electron beams 9 3 are generated with the irradiation unit 1, of which only the beam exposure window 9 is shown here to simplify the illustration, and directed against the paint layer 31. The distance between the beam exposure window 9 and the paint layer 31 is referred to as the working distance z _A

The contour of the corrugated sheet 30 is described by a function z (x, y). If z (x, y) is not constant as in the exemplary embodiment given, the local working distance z _A naturally also changes. The range of variation of this variation is called Δz _A. The edges of corrugated sheet 30 and beam exit window 9 are aligned parallel to the x or y axis. The length of the corrugated sheet 30 is measured in the y direction. It is large compared to the length 9 2 of the beam exit window 9. The width of the corrugated sheet 30 is measured in the x direction and is, in turn, greater than the width 9 1 of the beam exit window 9. By moving the irradiation unit 1 in the y direction at the feed speed v, a rectangular stripe with the width 9 1 of the beam exit window and any length is detected by the electron beams 9 3, hereinafter referred to as the irradiation path The total area of the corrugated sheet 30 is then determined by successively lining up the B radiation paths 32 irradiated in the x-direction For productivity reasons, a cell-like scanning of the surface is required, ie a passage through neighboring ones 14

Irradiation paths 32 with opposite feed direction v _k , expedient This method, which is referred to below as the feed method, is shown in FIG. 3 using the example of the (n-1) -th, n-th and (n + 1) -th path So that the individual radiation doses D _k (x) add up to the target dose D _s in the overlap region of the (n-1) -th and n-th single path, the intensity profile in the window plane is to be programmed such that one within the k-th radiation path 32 Trapezoidal dose distribution D _k (x) with edge modulation results

D _k (x) = D 1 -

1 + exp ((x - x,) / x _HIVB ) 1 + exp ((x _r - x) / x _HIVB )

The parameter x _HWB sets the slope of the flank profile, while x, the left and x represent the right boundary of the k-th irradiation path 32. As the width for an irradiation path 32, which must be less than or equal to the width 9 1 of the beam exit window 9, the area between the two maxima of the surface contour of the corrugated metal sheet is selected 30 When passing through the first and the last irradiation path 32, the x-Koordmaten the edges of the corrugated metal sheet 30 in the interval (x, + x _HWB x, -X _HWB) Add ^tO

The course of the intensity i in the plane of the beam exit window 9, which is required for realizing the dose distribution D _k (x), is also shown schematically. The intensity profile ι (x, y) takes into account that both with increasing angle between the direction of propagation of the electrons and the surface normal at the beam run ref and as the working distance z _A increases, an increase in the intensity i in the segment of the beam exit window 9 that corresponds to the beam travel reflection under consideration is required. The irradiation paths 32 are traversed at constant feed speed v in the feed direction v _k that is opposite from path to path due to the symmetry of the corrugated sheet 30 the intensity profile ι (x, y) and the beam current I constant

In order to illustrate the influence of the protective gas 10 on the specific technological embodiment of the method, the alignment of a step-shaped angle plate 33 with respect to the beam exit window 9 is shown in FIG. 4a. The angle plate 33 bears on the two surfaces, which are at a distance z _A = 10 cm and z _A + Δz _A = 20 cm from the beam window 9, a lacquer layer 31 with a mass of 60 g / m ^{2 of} beam window 9, lacquer layer 31 and angle plate 33 are not drawn to scale for reasons of better representation 4b shows the dose-depth distribution D (z) for an acceleration voltage of 150 kV, which describes the course of the energy emission of the electrons as a function of the surface mass already irradiated. The mass per unit area is by definition the product of the thickness z and density p, of the spreading medium. In this diagram, a 10 μm thick beam window 9 made of titanium, the protective gas 11 and the lacquer layer 31 on the angle plate 33, not shown here, are entered in scale with respect to the mass per unit area for the two limit traps, that as protective gas 11 pure nitrogen, on the other hand pure helium is used.

Tolerable dose gradients over the lacquer layer 31 to be modified are achieved if it is in the region of the maximum of the dose-depth distribution D (z). If 1 l of nitrogen is used as the protective gas, then a working distance z _A = 3 cm to 7 cm from the Beam window 9 acceptable. If the contour-related variation in the working distance Δz _A for the given parameters of the beam source 1 .1 is greater than approximately 4 cm, the protective gas 11 is mixed with helium to the required extent. While the given

If the contour of the angled plate 33 were to be easily hardened in a helium atmosphere, the dose differences between the two sections of the lacquer layer 31 would be unacceptably high when irradiated in a nitrogen atmosphere even when the working distance z _{A was} reduced.

In Fig. 5, the irradiation of a truncated cone 40 is shown, which with the

Angular velocity φ is rotated about the axis of rotation x '. The distance of a surface element of the truncated cone 40 at location x from the axis of rotation x 'is denoted by r (x). The working distance z _A between the lacquer layer 31 applied to the outer surface of the truncated cone 40 and the radiation window 9 does not change during the rotational movement. Since the feed rate results from v = r (x) • φ, the intensity profile ι (x, y) proportional to r (x) in the x direction is selected in order to achieve constant radiation doses in the lacquer layer 31.

The exemplary embodiments in FIGS. 3 to 5 are distinguished by the fact that the surfaces of the objects to be irradiated can be broken down into radiation paths 32 within which the contour of the surfaces does not change, or at least only slightly, over a length 9.2 of the beam exit window 9. This is generally a prerequisite for the applicability of the feed method. lo

If this requirement is not met, the energy doses required for hardening are alternatively irradiated at feed v = 0 by pulsed release of the beam current during an integer multiple of the beam deflection via the beam exit window with a stationary, two-dimensional intensity profile i (x, y), which is subsequently used as an exposure mask is designated. The described irradiation process is called the flash method in the following. Several objects can be irradiated simultaneously. The number of individual exposure masks is essentially limited only by the area of the radiation exit window 9 available.

The exposure masks can expediently be generated using two different methods, which are shown with reference to FIGS. 6 and 7.

If the substrates have certain symmetries, such as spherical or cylindrical symmetry, guiding the electron beam by means of superimposed sub-cycles is advantageous in terms of programming. The subcycle is understood to mean that the electron beam describes a simple geometric figure, such as a line, a square or a circle, at a constant speed. The overlay then exists that this basic figure is run through several times. Their size and position is chosen for each subcycle according to the geometry of the assigned object area.

6 shows the simultaneous curing of lacquer layers 31 on two spherical caps 41. The axial electron beam 4.3 is guided by the deflection unit 6, both of which are not shown here, in such a way that it describes two congruent figures made of concentric circles in the plane of the beam exit window 9 at a constant running speed. The radii of these deflection circles 42 are staggered so that the intensity stroke required for the edge region of the spherical caps 41 due to the strong inclination of the surface to be hardened relative to the main exit direction of the electron beams 9.3 results from the sum of the intensities constant on each individual circle

If the objects to be irradiated are non-symmetrical free-form surfaces, a three-dimensional discretization of their contours is first necessary.

This principle is illustrated in FIG. 7 using the example of a housing 43. The locally required intensities are then computer-aided from the j k values z _k = z (x _{ι #} y _k ) ι _{| k} = ι (x _{| (} y _k ) determined at the coordinate points (x, y _k ) and set by point-by-point programmed hold times τ = τ (x _{J (} y _k ) within a deflection grid comprising jk grid points 44. The deflection control for the electron beam is designed for 1024 x 1024 possible grid points 44. The holding times τ _k belonging to selected points are illustrated with diagram columns 45

8 illustrates the expansion of the flash method for objects whose extent is greater than the width 9 1 and length 9 2 of the beam exit window 9. For this purpose, the beam exit window 9 is positioned before the irradiation over the lacquer layer 31 applied to a free-form surface 46, that the longitudinal axis of the radiation unit 1, not shown, runs as parallel as possible to the surface normal of the surface elements of the part to be hardened and that its entire contour is within a working distance z _A limited by the tolerable dose-depth gradient. The exposure mask is applied to the contour profile of the one under the radiation window 9 partial area of the lacquer layer 31 is adapted and this is then hardened by pulse-like release of the beam current I during an integer multiple of the beam deflection period via the beam exposure window 9. After the hardening of a partial area, the radiation unit 1 is placed over an ang The delimiting, not yet hardened partial area is positioned and at the same time a new exposure mask is generated. The limitation of the elementary areas 47 is selected so that large areas are filled without gaps and with sufficient dose constancy along the overlapping seam of partial areas. Instead of the rectangular elementary areas 47 selected here, other area shapes can also be used become

FIG. 8a illustrates the flash method consisting of alternating irradiation and positioning on the basis of the time profiles of the feed speed v and the beam current I.

In the previous exemplary embodiments, it was always assumed that the course of the contour z (x, y) is known either in analytical form or as a data file at sufficiently closely spaced support points

9 shows the coupling of the irradiation unit 1, of which only the radiation exposure window 9 is indicated for simplicity, with a digitizing device 50. The digitizing device 50 takes the contour of the free-form surface 46 to be irradiated 18th

during the feed movement without contact with sensor signals 51. The required intensity profile and the optimal orientation of the radiation unit 1 are calculated either in teach-m mode or online and continuously adapted to the current site of exposure during the radiation. The technological variant shown here can be implemented for both the flash and the feed method.

In FIG. 10, the arrangement of a reflector diaphragm 52 is shown in a simplified manner laterally under the beam exposure window 9. The reflector diaphragm 52 can be pivoted about a pivot point and can be displaced parallel to the plane of the beam window 9.

The electron beams 9.3 emanating from the beam exit window 9 strike the part of the lacquer layer 31 lying parallel to the beam exit window 9 approximately perpendicularly on the surface of a carrier 53. The reflector diaphragm 52 is set such that the electrons 9.4 reflected by it now also strike the lacquer layer 31 of the fold 54 lying perpendicular to the beam exposure window 9 at a favorable angle of incidence.

19

List of the reference symbols used for the patent application "Process for electron irradiation of layers on surfaces of objects and device for carrying out the process"

1 radiation unit

1 1 beam source

1 .2 nozzle

2 housings

2.1 turbopump

2.2 isolator

3 high voltage cables

4 cathode unit

4.1 hot cathode

4.2 control electrode

4.3 axial electron beam

5 anode

6 deflection unit

6.1 Deflection cone

7 mounting plate

8 servo motor

9 beam exit window

9.1 window width

9.2 window length

9.3 electron beams

9.4 reflected electrons

10 Shielding gas routing

1 1 shielding gas

20 handling device, robot

21 base

22 lower part

23 arm

24 arm 20th

30 corrugated iron

31 lacquer layer / color layer

32 radiation path

33 angle plate

40 truncated cone

41 ball cap

42 deflection circle

43 housing

44 grid point

45 chart column

46 free-form surface

47 irradiated elementary area

50 digitizing device

51 sensor signals

52 reflector cover

53 carriers

54 folding

D _s target dose

D _k (x) dose distribution in the k-th radiation path (32)

D (z) dose-depth distribution

i intensity i ( ^χ , y) intensity profile

I beam current

J Running index k Running index r radius

S electron range t time u _B acceleration voltage

V feed speed

v _k feed direction in the kth path x coordinate direction x 'axis of rotation

Flank width of the dose distribution D _k (x) x left boundary of an irradiation path (32) right boundary of an irradiation path (32)

y coordinate direction

z Coordinate direction z _A working distance

Δz _A variation of the working distance z (x, y) surface contour

φ angular velocity p _He density of helium p _N2 density of nitrogen τ holding time per grid point (44)

Claims

claims

1 method for electron irradiation of layers on surfaces of objects or near-surface areas of objects for changing the physical and / or chemical properties of substances in the layer or in the near-surface areas at approximately atmospheric pressure by means of an irradiation unit with a radiation exposure window, characterized in that the Irradiation of the surface of the objects or their applied layer takes place in one partial area or in succession in several adjoining partial areas in such a way that the object is brought into a defined position that is optimal for irradiating the respective partial area with respect to the beam exit window (9) of the irradiation unit (1), that the irradiation of the respective partial area in locations of the beam exit window (9) assignable area elements takes place such that the intensity profile i (x, y) of an electron beam (9.3) in the plane of the beam exit window s (9) is selected in accordance with the irradiation conditions of the assigned surface elements and that the required energy dose with the electron beam (9.3) is continuously transmitted to the object moving relative to the irradiation unit (1) at a defined feed rate (v) or impulsively to the stationary object.

2. The method according to claim 1, characterized in that adjacent partial areas on the surface of the object are combined into radiation tracks (32) and that the electron irradiation of the radiation tracks (32) takes place simultaneously with the associated relative movement between the object and the radiation unit (1), wherein the alignment of the object and the radiation unit (1) and the

Intensity profile ι (x, y) in the plane of the beam exit window (9) can be selected according to the partial area of the object located in the current beam exposure area

3. The method according to claims 1 or 2, characterized in that the longitudinal axis of the beam window (9) is always aligned parallel to the feed direction (v _n ) during the irradiation of an irradiation path (32) and different dwell times of surface elements under the beam window (9) be taken into account by adapting the programming of the intensity profile ι (x, y). 23

Method according to one of claims 1 to 3, characterized in that the intensity profile (ι (x, y)) both from radiation path (32) to radiation path (32) and within an radiation path (32) in accordance with the contour of the surface of the object is adapted for continuous blasting operation

Method according to one of claims 1 to 4, characterized in that a protective gas (1 1) is used for the inertization of the irradiation site, which consists of pure nitrogen, pure helium or a mixture of nitrogen and helium, with stronger objects with a high helium content is worked.

A method according to claim 5, characterized in that the protective gas (1 1) or protective gas mixture is supplied locally to the irradiation site

Method according to one of claims 1 to 6, characterized in that the relative feed speed (v) between the irradiation unit (1) and the object and the irradiation process alternate and the dose rate required for modifying the surface layer is defined by an object-related, two-dimensional and stationary exposure mask and the in each elementary area (47) integrally radiated energy dose is set by pulse-shaped timing of the power of the electron beam

Method according to Claim 2 or 7, characterized in that the irradiation of the entire surface of the object is carried out by stringing together radiation paths (32) or irradiated elementary areas (47)

Method according to one of claims 1 to 8, characterized in that for determining a component-specific intensity profile (ι (x, y)) in the impact area between adjacent radiation tracks or irradiated elementary areas (47), the energy inputs from their previous or subsequent radiation are also taken into account

Method according to one of Claims 2 to 10, characterized in that the contour of the surface of the object to be irradiated is determined by a digitizing device (50) which is moved along before the irradiation process, and the contour data acquired in this way determines what is required in the plane of the beam exit window (9) 24

Intensity profile (ι (x, y)) can be calculated and set in teach-in mode or online.

1 1 device for electron irradiation of layers on surfaces of objects or areas close to the surface of objects for changing the physical and / or chemical properties of substances in the layer or in the areas close to the surface according to claim 1, consisting of a radiation unit with an electron beam source of the axial type at least one beam deflection unit, a beam pipe, which is closed by a beam exposure window in beam spreading direction, supply and control devices for operating the radiation unit, means for holding it and the object to be irradiated, and for realizing a relative movement between the radiation unit and the object to one another, characterized in that that the control devices contain a beam deflection control with which the local deflection speed is defined point by point in at least one beam deflection direction

Dwell time or the superposition of deflection sub-cycles of the axial electron beam (4.3) and thus the intensity profile (i (x, y)) is programmable, and that the means for receiving the radiation unit (1) and the object and for realizing the relative movement to one another are means for aligning the Contain the surface of the object or partial areas thereof to the beam exit window (9).

1 2 Device according to claim 1 1, characterized in that the jet pipe (1 .2) about the axis of the beam source (1 .1) is rotatably arranged on this.

13 Device according to claims 1 1 or 12, characterized in that the x and y axes of the intensity profile (ι (x, y)) with the polar angle of rotation between the jet pipe (1 .2) and the beam source (1 .1) in such a way can be carried along so that they always run parallel to the edges of the beam exit window (9)

14 Device according to one of claims 1 1 to 13, characterized in that the radiation window (9) consists of a light metal foil with a thickness of preferably 10 microns.

1 5 Device according to one of claims 1 1 to 14, characterized in that under the beam window (9) reflector screens (52) are arranged, which 25th

during the irradiation process are automatically pivotable relative to the main exit direction of the electrons (9 3) and displaceable parallel to the plane of the beam exit window (9)

16 Device according to one of claims 1 1 to 1 5, characterized in that a protective gas guide (10) surrounding the radiation window (9) is arranged on the radiation unit (1)

17 Device according to one of claims 1 1 to 16, characterized in that one or more robots (20) are provided for the mutual positioning, orientation and for generating the relative movement between the irradiation unit (1) and the objects to be irradiated

18 Device according to one of claims 1 1 to 17, characterized in that one of the radiation unit (1) oriented to the radiation unit window (9) on the radiation unit (1)

The surface contour of the object-detecting digitizing device (50) is arranged

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