DE102018102527A1 - Device for irradiating objects - Google Patents

Abstract

The invention relates to a device for irradiating objects (12), in particular for a photochemical modification of object surfaces, with a laser device (16) for generating radiation and one formed from a bundle of flexible optical fibers (24) on a coupling side with the laser device (16 ) coupled and on a coupling-out side to the object to be irradiated (12) aligned or alignable light guide assembly (18). According to the invention, it is proposed that the laser device (16) has a plurality of laser emitters (22), and that each laser emitter (22) is coupled to an associated optical fiber (24) of the optical waveguide arrangement (18), wherein an output radiation of the respective laser emitter (22) enters the associated optical fiber (24).

Description

The invention relates to a device for irradiating objects, in particular for a photochemical modification of object surfaces, with a laser device for generating radiation and one formed from a bundle of flexible optical fibers, coupled on a coupling side with the laser device and aligned on a coupling-out side to the object to be irradiated or alignable light guide assembly.

The curing or polymerization or a photochemical change of radiation-curable, polymerizable or photochemically changeable materials such as printing inks or coatings or adhesives or molding compositions with electromagnetic radiation, for example with UV radiation is known and industrially, for example, in the printing of packaging materials or in the bonding of components or used in the production of moldings, for example in 3D printing. For this purpose, powerful UV radiation sources such as mercury lamps or LED lamps are used whose optical output power is in the relevant for the curing spectral range of about 200 nm to 400 nm, the total radiation power is often in the range of several kilowatts. The reason for this is that, as a rule, large surfaces have to be exposed within a short time with sufficient optical radiation power and radiant energy in order to achieve a high production output.

When using mercury lamps, such UV aggregates generally consist of a cylindrical UV lamp and corresponding reflector devices, which are arranged on the side facing away from the working plane, whereby the radiated UV radiation directed away from the working plane is deflected onto the working plane and so increases the overall efficiency. Due to the extensive light source used in this case, however, it is only partially possible to intensively irradiate a narrowly limited irradiation surface, so that a large part of the UV radiation can not be used in the desired manner.

The increasingly industrially used UV LED systems in this case have more favorable properties, since LEDs emit their radiation only in a half-space and thus can account for back reflectors. A disadvantage, however, is the still too large radiation angle of about 120 °, so that additional optical elements such as lenses and mirror elements are required for intensive and spatially limited illumination of the working level. In particular, when using UV-LED units for industrial purposes, for example, for curing UV printing inks and paints, which are usually applied over a large area on a substrate, very high overall performance is required, so it is necessary, many individual LEDs Arranging in an array and at the same time to direct the available radiation power as completely as possible on the work plane. In addition, it is often necessary or desired to concentrate the available radiation power homogeneously in a surface area in order to allow the most effective curing process possible.

From the DE 38 28 753 An apparatus for drying printed products in a printing machine is known in which a laser beam from a laser tube is directed onto an optical fiber cable whose individual fiber ends are arranged so that they form a transverse to the transport direction of a sheet extending line. It is also proposed to cover several wavelengths by a multiple laser. In any case, it is problematic here that only a fraction of the laser radiation enters the fiber cores in the case of total irradiation of a light-conducting cable, so that the power required on the outlet side can not be coupled in at all without overloading the cable thermally. In addition, there are intensity distributions over the beam cross section, which lead to an inhomogeneous irradiation. Such systems could therefore not be put into practice over a long period of 30 years.

Proceeding from this, the object of the invention is to remedy the disadvantages which have arisen in the prior art and to provide a system which ensures flexible and efficient light guidance to a desired work surface with a high total radiant power. Further aspects are to easily adapt the size and shape of an irradiation area and to allow a variable exposure pattern in the irradiation area.

To solve this problem, the feature combination specified in claim 1 is proposed. Advantageous embodiments and modifications of the invention will become apparent from the dependent claims.

The invention is based on the idea of compactly and precisely combining a large number of laser light sources via an optical fiber bundle at an irradiation site. Accordingly, the invention proposes that the laser device has a plurality of laser emitters or laser radiation sources, and that each laser emitter is coupled to an associated optical fiber of the optical fiber arrangement, wherein an output radiation of the respective laser emitter in the associated optical fiber enters. This makes it possible to use a high overall power of the laser radiation without thermally overloading the optical fiber cable. As a result, it is also possible to couple the output radiation of the respective laser emitter with high efficiency and thus with very little loss into the associated optical fiber. At the same time it can be achieved at the decoupling side of the optical fibers targeted pinpoint resolution at the irradiation site. Another advantage is that on the side of the radiation generation a large space can be used, while on the use side, an irradiation head may be flexibly integrated even in a cramped machine environment.

Advantageously, the laser emitters are designed as preferably continuously or quasi-continuously operating or pulsed semiconductor diodes, so that a high integration density and variable triggering with high overall power is possible.

In order to achieve effective curing or polymerization of the irradiated materials, it is favorable if the output radiation of the laser emitters is in the wavelength range from 100 nm to 500 nm.

In this context, it is also advantageous if at least some laser emitters operate at mutually different wavelengths, so that a specific photochemical change adapted to the particular substance to be hardened is possible.

Advantageously, the outcoupling-side ends of the optical fibers are held in a line-type or planar arrangement on an irradiation head which can be aligned with a region to be irradiated, so that variable alignment with an object contour is also possible.

A further particularly preferred embodiment provides that the auskoppelseitigen ends of the optical fibers are combined in at least one holder element. Such holder elements can then be preconfigured in a modular manner and assembled in order to cover a desired irradiation area as required.

A further improvement provides that a plurality of holder elements are modularly combined with one another on an irradiation head, so that a variable area coverage is achieved, wherein the irradiation head is virtually freely positionable due to the flexible light guide arrangement.

In this context, it is also advantageous if a plurality of holder elements are connected to one another in a flush arrangement at the outlet ends of the optical fibers, so as to realize a homogeneous irradiation grid.

For a simple cascading, it is advantageous if the number of optical fibers on each holding element is in the range from 1 to 1000, preferably in the range from 10 to 100.

According to yet another particularly preferred embodiment, the laser device has a control unit connected to the laser emitters, wherein the laser emitters are independent of each other in their performance adjustable and / or individually switchable via the control unit. As a result, it is possible to achieve spot-on and temporally and performance-adaptive irradiation in a process area, whereby even existing tolerances can be compensated.

In this context, it is also advantageous if the laser emitters are controllable via the control unit in accordance with a desired radiation distribution or pattern on the optionally irradiated object in the pass.

To avoid radiation losses and achieve a high irradiation efficiency, it is advantageous if the laser emitters are focused on a core region of the associated optical fiber, so that the coupling efficiency of each laser emitter into the optical fiber is more than 70% of its output radiation.

In order to separate the building units for generating radiation and the working area spatially suitable, it is advantageous if the bundle of optical fibers has a length in the range of 0.1m to 100m, preferably in the range of Im to 20m.

A further advantageous embodiment provides that the irradiation head is provided with optical elements for radiation steering and / or radiation shaping, so that a high point accuracy and / or area delineation of the irradiation in a process area is achieved.

To simplify handling on site, it is advantageous if the laser emitters are optionally arranged together with a device for power supply and / or for cooling and / or control as a supply unit in a common housing or unit.

In order to facilitate the coupling into the associated optical fibers, the size of the individual laser emitters should be in the range of 0.1 mm to 10 mm.

A particular application possibility is that the laser emitters are aligned to a delimited object area, and that the object area is coated with radiation-curing materials, in particular special colors for the production of optical effects.

• 1 ein Blockschaltbild eines Laser-basierten Bestrahlungssystems zur photochemischen Veränderung von Objektoberflächen;
• 2 und 3 mehrere modulartig miteinander kombinierbare Halterelemente für Lichtleitfasern des Bestrahlungssystems in perspektivischer Darstellung;
• 4 einen aus den Halterelementen zusammengesetzten Bestrahlungskopf in perspektivischer Darstellung.

In the following the invention will be explained in more detail with reference to the embodiment shown schematically in the drawing. Show it:

• 1 a block diagram of a laser-based irradiation system for the photochemical change of object surfaces;
• 2 and 3 a plurality of modularly combinable holder elements for optical fibers of the irradiation system in a perspective view;
• 4 a composite of the holder elements irradiation head in a perspective view.

The irradiation system shown in the drawing 10 allows efficient steering of laser radiation on objects to be irradiated 12 , which are exposed to radiation-curable, polymerizable or generally photochemically changeable materials such as printing inks or paints or adhesives or molding compositions and, if necessary, in transit on a transport device 14 are irradiated.

For this purpose, the irradiation system includes 10 a control unit 14 , a laser unit 16 and a light guide assembly 18 extending over a compact radiation head 20 flexible on the object 12 align. The laser unit 16 includes a variety of laser emitters 22 as individual radiation sources, each with an optical fiber 24 the light guide assembly 18 are optically coupled to the coupling of laser radiation.

The control unit 14 is about data connections 26 with an external computer 28 or computer network. An encoder 32 and a trigger unit 34 are via control lines 30 connected to capture object-related information or signals and trigger targeted irradiation operations in accordance with a desired radiation distribution or pattern.

The laser unit 16 includes an interface 36 that has a first control line 38 with the control unit 14 and via a second control line 40 with a driver circuit 42 is connected to the individual laser emitters 22 independently of each other to switch or adjust in their performance.

The laser emitters 22 are formed by semiconductor laser diodes which emit radiation at a wavelength in the range of 100 nm to 500 nm, with possibly some of the laser emitters 22 work at mutually different wavelengths. The size of the individual laser diodes can be in the millimeter range, with a corresponding number of radiators depending on the desired number of irradiation points 22 and fibers 24 be used.

The optical fibers 24 have a substantially round overall cross-section, which is constructed of two concentrically arranged regions with a round cross-section. The inner smaller area - the core - consists of an optically transparent material such as glass or quartz, whose optical refractive index is higher than that of the surrounding optically transparent material, the so-called cladding. The core then acts as a waveguide in that a light beam coupled into it is guided at the boundary layer between the core and cladding due to total internal reflection.

Due to the small emission area in the range of a few μm ² required for semiconductor lasers and the narrow solid angle of the emission, a high coupling efficiency into the optical fiber, which can be in the region of 70% and more, is possible at a short distance. Of course, it is also possible for the laser radiation to be coupled into the optical fiber by means of a coupling-in optical system 44 to realize.

The control unit 14 and the laser unit 16 are together with a not shown power supply and cooling in a common housing or control cabinet 46 housed in a suitable location while the compact irradiation head 20 can be positioned in a remote work area, for example in a printing press. It is possible via the light guide arrangement 18 even larger distances between installation site and work area are variably bridged. The fiber optic fibers 24 may have a length of more than 100m, since the optical losses in the fiber are very low when selecting a suitable fiber material and thereby the total losses occur substantially at the input and output surfaces due to reflections. Optionally, the fiber ends can each be provided with an optimized for the wavelength used anti-reflection coating.

It may be advantageous for the irradiation head 20 with optical elements 48 is equipped to at the decoupling fiber ends of the optical fibers 24 to shape the emerging radiation and, for example, to the object 12 to focus.

As in 2 to 4 illustrates, the irradiation head 20 a plurality of holder elements 50 which are modularly combined with each other around the exit ends 52 the optical fibers 24 to hold over a desired area in line or areal arrangement. It is expedient here also over the joints across a seamless, regular configuration of the outlet ends 52 respected.

How best 2 can be seen, the holder elements 50 with formations 54 be provided for mutual positive positioning. For fixation on the irradiation head 20 allow cross holes 56 the engagement of connecting means not shown, for example fastening screws. Around the end sections of the individual optical fibers 24 defined to position, is a comb-like groove structure 58 on each holder element 58 intended. The number of optical fibers 24 on each holder element 50 is suitably in the range of 10 to 100, so that a desired work area is covered by appropriate cascading.

3 shows in perspective exploded view additional holder elements 50 ' as intermediate elements to a multi-row arrangement of optical fibers 24 to accomplish. The rows of optical fibers 24 can be held in an offset to each other, so that the outlet ends are arranged in the intermediate row in the gaps of the underlying or overlying row.

4 shows the assembled configuration with a deck row of holder elements 50 '' resulting in four superimposed rows or rows of exit ends 52 the optical fibers 24 be realized in flush arrangement. It is possible, the individual laser emitters 22 so that, if necessary, during a relative movement of object 12 and radiation head 20 a desired dot pattern is exposed with high resolution and irradiance.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3828753 [0005]

Claims (17)

Device for irradiating objects (12), in particular for a photochemical modification of object surfaces, with a laser device (16) for generating radiation and one of a bundle of flexible optical fibers (24), coupled to a coupling side with the laser device (16) and on a decoupling side on the object (12) to be irradiated aligned or alignable light guide assembly (18), characterized in that the laser device (16) has a plurality of laser emitters (22), and that each laser emitter (22) with an associated optical fiber (24) the light guide assembly (18) is coupled, wherein an output radiation of the respective laser emitter (22) enters the associated optical fiber (24). Device after Claim 1 , characterized in that the laser emitters (22) are designed as preferably continuous or quasi-continuously operating or pulsed Hableiter laser diodes. Device after Claim 1 or 2 , characterized in that the output radiation of the laser emitter (22) is in the wavelength range of 100 nm to 500 nm. Device according to one of Claims 1 to 3 , characterized in that at least some laser emitters (22) operate at mutually different wavelengths. Device according to one of Claims 1 to 4 , characterized in that the outcoupling-side ends (52) of the optical fibers (24) are held in a line-shaped or planar arrangement on an irradiation head (20) which can be aligned with a region to be irradiated. Device according to one of Claims 1 to 5 , characterized in that the outlet ends (52) of the optical fibers (24) are combined in at least one holder element (50). Device after Claim 6 , characterized in that at the irradiation head (20) a plurality of holder elements (50) are combined in a modular manner. Device after Claim 6 or 7 , characterized in that a plurality of holder elements (50) in a flush arrangement at the outlet ends (52) of the optical fibers (24) are interconnected. Device according to one of Claims 6 to 8th , characterized in that the number of optical fibers (24) on each holding element (50) is in the range of 1 to 1000, preferably in the range of 10 to 100. Device according to one of Claims 1 to 9 , characterized in that the laser device (16) has a with the laser emitters (22) connected control unit (14), and that the laser emitters (22) via the control unit (14) independently of each other in their performance adjustable and / or individually switchable. Device after Claim 10 , characterized in that the laser emitters (22) are controllable via the control unit (14) in accordance with a desired radiation distribution or pattern on the object possibly irradiated in the passage. Device according to one of Claims 1 to 11 , characterized in that the laser emitters (22) are focused on a core region of the associated optical fiber (24), so that the coupling efficiency of each laser emitter (22) into the optical fiber is more than 70% of its output radiation. Device according to one of Claims 1 to 12 , characterized in that the bundle of optical fibers (24) has a length in the range of 0.1m to 100m, preferably in the range of Im to 20m. Device according to one of Claims 1 to 13 , characterized in that the irradiation head (20) is provided with optical elements (48) for radiation steering and / or radiation shaping. Device according to one of Claims 1 to 14 , characterized in that the laser emitters (22) are optionally arranged together with a device for power supply and / or for cooling and / or control in a common housing (46) or unit. Device according to one of Claims 1 to 15 , characterized in that the size of the individual laser emitter (22) is in the range of 0.1mm to 10mm. Device according to one of Claims 1 to 16 , characterized in that the laser emitters (22) are aligned with a delimited object area, and that the object area is coated with radiation-curing materials, in particular special colors for the production of optical effects.

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