Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
  • H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
  • H05B33/145—Arrangements of the electroluminescent material
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
  • H05B33/22—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
  • H05B33/26—Light sources with substantially two-dimensional radiating surfaces characterised by the composition or arrangement of the conductive material used as an electrode
  • H05B33/28—Light sources with substantially two-dimensional radiating surfaces characterised by the composition or arrangement of the conductive material used as an electrode of translucent electrodes

Definitions

• the present invention relates to a multicolor electroluminescent element and a method for its production.
• Electroluminescence technology has recently become increasingly important. It enables the realization of almost any size, glare-free and shadow-free, homogeneous illuminated surfaces. The power consumption and depth (in the order of a millimeter and below) are extremely low.
• the typical application also includes the backlighting of transparent films which are provided with lettering and / or image motifs.
• Electroluminescence is the direct luminescence excitation of luminescent pigments or luminophores by an alternating electrical field.
• Electroluminescent elements based on the so-called thick-film technology with inorganic luminous pigments or luminophores and AC excitation have largely become established. Compared to thin-film EL elements, thin-film EL elements are less complex and therefore less expensive to manufacture.
• the luminous pigments or luminophores are embedded in a transparent, organic or ceramic binder.
• the starting materials are mostly zinc sulfides, which depend on the doping or co-doping and the preparation process generate different, relatively narrow-band emission spectra. The focus of the spectrum determines the respective color of the emitted light.
• the exciting AC voltage field generally has a frequency of a few hundred Hertz, the effective value of the operating voltage often being in a range from approximately 50 to 150 volts.
• a higher luminance can generally be achieved, which is usually in a range from approximately 50 to approximately 200 candelas per square meter.
• Increasing the frequency usually causes a color shift towards lower wavelengths.
• both parameters must be coordinated to achieve a desired lighting impression.
• ITO indium tin oxide electrodes
• plastic films plastic films. They are very thin (some 100 ⁇ ) and offer the advantage of high transparency with a relatively low surface resistance (approx. 60 to 600 ohms). However, they cannot be applied to structured surfaces with steps, are not deformable, and cannot be applied to substrates that easily outgas in a vacuum.
• printing pastes with ITO or ATO (antimony tin oxides, antimony tin oxide) or intrinsically conductive transparent polymer pastes can be used. With a thickness of approx. 5 to 20 ⁇ m, such electrodes only offer less transparency with a high surface resistance (up to 50 kOhm). However, they can largely be applied in any structure, even on structured surfaces. They also offer relatively good laminatability and limited deformability.
• the lifespan of an EL element is limited. It mainly depends on the level and frequency of the AC voltage applied, but also on environmental influences, in particular the effects of moisture and UV radiation.
• the service life of an EL element is usually given as the half-life of the luminescent pigments. This is the time after which the luminance under the influence of the electric field has decreased by half of the initial value under unchanged operating conditions. In practice, the luminance is roughly within 2000 to 3000 operating hours to half of the original value.
• the emission color of an EL element can be adapted to the desired color impression by a variety of possible measures. These include the doping and co-doping of the luminous pigments, the mixture of two or more EL pigments, the addition of one or more organic and / or inorganic color-converting and / or color-filtering pigments, the coating of the EL pigment with organic and / or inorganic color-converting and / or color-filtering substances, the incorporation of colorants into the polymer matrix in which the luminous pigments are dispersed, and the incorporation of a color-converting and / or color-filtering layer or film into the structure of the EL element.
• Luminophores which emit a pure white, are not yet available. For this reason, whitish-glowing EL elements are often produced using a mixture of at least two luminescent pigments, the emissions of which add up to (almost) white. In order to obtain pure white, it is usually necessary to use an organic conductive varnish with a light blue color. However, the different aging of the two luminescent pigments causes a change in the color impression over the course of the service life, which is often very disruptive or unacceptable for the planned application. Furthermore, there are almost white luminophores, which, however, contain toxic zinc selenides and are therefore reluctant to use them.
• Corresponding EL elements are referred to as multicolor electroluminescent elements.
• Multi-color electroluminescent elements are known, inter alia, from EP-A-104561 8. It describes a multi-colored EL lamp in which different colors result from additive color mixing, in that at least two electroluminescent layers lying one above the other and containing luminescent pigments are appropriately controlled by means of at least three electrode layers.
• the first electrode is produced by vapor deposition of ITO on a PET substrate, whereas all further layers, that is to say also all further electrodes, are produced by means of screen printing.
• EP-A-0998171 also describes a multi-layer EL element with different patterns and many luminescent colors.
• the first transparent electrode is produced by vapor deposition or sputtering onto a PET film. All other electrodes are produced by printing optically transparent pastes.
• a multi-color EL element is known from EP-A-0973358, which has a plurality of transparent electrode layers and a plurality of luminescent layers with different colors. According to this document too, a multi-layer printing technology is implemented.
• the multicolor electroluminescent element which, depending on the electrical control, can assume different luminous colors and yet can be produced in a high quality with reasonable effort. Associated with this is the task of providing a suitable manufacturing process for multi-color EL elements, which enables high product quality with little waste. According to one aspect of the present invention, this object is achieved by a multicolor electroluminescent element according to claim 1. Contrary to the prior art, according to which multicolor electroluminescent elements are designed as a multilayer screen printing structure on a film, the multicolor electroluminescent element according to the invention is constructed from at least two electroluminescent films, each with a luminescent layer.
• An electroluminescent film is to be understood as a coherent film body with a certain dimensional stability, which stems from the fact that the luminous layer of the electroluminescent film is applied to a stable film substrate (as a support) and / or itself consists of a preferably cast film, in the matrix of which the dispersed Luminophores are stored.
• a stable film substrate as a support
• / or itself consists of a preferably cast film, in the matrix of which the dispersed Luminophores are stored.
• Different colors are generated by additive color mixing, in that each luminescent layer, each emitting in a different color, is excited differently by a separately controlled alternating electric field.
• a separately controlled alternating electric field With three electroluminescent foils in the colors red, green and blue, the entire color spectrum including white can be displayed with appropriate control.
• the object is achieved by a method for producing a multicolor electroluminescent element according to claim 23.
• a method for producing a multicolor electroluminescent element according to claim 23 Contrary to the state of the art, not all individual layers of the EL element are applied sequentially, so to speak "from bottom to top", one above the other in terms of printing technology, but at least two prefabricated electroluminescent films, for example by lamination, assembled.
• the problems described above with the wiring of the electrodes are largely eliminated.
• the connections of the electrodes on the individual electroluminescent foils can be produced separately prior to assembly according to controllable techniques that are common for conventional single-color electroluminescent elements.
• 1 a to 1 k show different basic arrangement variants in the layer structure of multicolor electroluminescent elements according to the invention, in each case once before joining the electroluminescent films and afterwards. Any additional insulating or adhesion promoter layers contained in the structure are not shown.
• FIG. 2 shows an example of a multicolor electroluminescent element composed of three electroluminescent foils, in each case before the electroluminescent foils are joined together and afterwards, each electroluminescent foil having a stable foil substrate.
• FIG. 3 shows an example of a multicolor electroluminescent element composed of three electroluminescent films, in each case before the electroluminescent films are joined together and afterwards.
• the structure is similar to that in FIG. 2, but the middle electroluminescent film does not have a film substrate, but its film property stems from the cast matrix of the luminescent layer.
• 4 shows the structure of an electroluminescent film of a particularly preferred multicolor electroluminescent element according to the invention.
• Three (possibly also two) similar electroluminescent films of the type shown, which differ only in their luminous color, are combined with one another.
• FIGS. 1 a to 1 k show examples of various fundamentally possible arrangement variants of the layer structure of multicolor electroluminescent elements according to the invention.
• the partial representation on the left in each case shows the electroluminescent films 1, 2, 3 before the assembly, and the partial representation on the right shows the layer structure of the multicolor electroluminescent element which has subsequently formed.
• further layers, in particular dielectric or insulating or adhesion promoter layers can be contained in the respective structure, which are not shown for the sake of clarity.
• the adhesion promoter layers serve to connect the electroluminescent films to one another.
• Color filtering or color converting layers and imprints (not shown) can also be included in order to produce a desired color impression. These can also be provided only over part of the area in order to achieve certain graphic designs.
• Each electroluminescent film 1, 2, 3 has a luminescent layer 1 1, 1 2, 1 3 with disperse electroluminophores 4, which are preferably cast films in whose film matrix 6 the electroluminophores 4 are embedded. Extruded foils are also possible, but these are less advantageous due to the often less favorable distribution of the electroluminophores.
• the representation of the electroluminophores 4 is to be understood purely schematically. In practice, efforts are made to obtain particles that approximate the spherical shape. Electroluminophores are usually sensitive to the effects of moisture. For this reason, additional layers are usually integrated into the layer structure of conventional electroluminescent elements, which take on the function of a moisture barrier or vapor barrier.
• Corresponding layers can also be integrated into the structure of the multicolor electroluminescent element according to the invention. However, these can largely be eliminated, in particular, if micro-encapsulated electroluminophores 4 are used.
• the microencapsulation is usually oxidic or nitridic, however, organic microencapsulation or diamond-like carbon encapsulation ("diamond-like carbon") is also conceivable.
• the first electroluminescent film 1 has a Qe, largely transparent or reflectively opaque) electrode layer 21 and a largely transparent back electrode layer 31, depending on the application. Together with the first luminous layer 11 arranged in between, they form a first electroluminescent capacitor.
• the second luminescent layer 1 2 belonging to the second electroluminescent film is provided with only one largely transparent electrode layer 22. In the fully assembled multicolor electroluminescent element, the electrode layer 22 and the second luminescent layer 12 together with the back electrode layer 31 of the first electroluminescent film 1 form a second electroluminescent capacitor.
• the multicolor electroluminescent element shown in FIG. 1b is largely constructed like the multicolor electroluminescent element in FIG. 1a. However, in order to achieve better controllability, the second luminescent layer 1 2 also has its own back electrode layer 32. Back electrode layer 32 and electrode layer 22 can also be interchanged.
• the structure shown in FIG. 1b makes it necessary to provide an insulating layer 42 on the connection surface between the first electroluminescent film 1 and the second electroluminescent film 2 in order to avoid short circuits.
• 1 c and 1 d each show a multicolor electroluminescent element with three electroluminescent films 1, 2, 3.
• Each of the luminescent layers 11, 12, 13 emits with a different color due to different electroluminophores 4, so that the variety of colors that can be achieved by means of additive color mixing is even greater.
• red electroluminophores 4 it is possible in principle to display the entire color spectrum.
• red electroluminophores are usually not used because they contain cadmium, which is toxic.
• a red fluorescent color can also be achieved by means of color-converting or color-filtering substances.
• the at least four electrodes required for a "three-color" structure can be distributed differently before being joined together.
• an electrode layer 22 and a back electrode layer 32 can also be arranged on the second electroluminescent film 2, as shown in FIG. 1 c, while the third, middle electroluminescent film 3 does not necessarily have its own electrode layer is needed. Or the second electroluminescent film 2 does not have a back electrode layer 32, for this the third electroluminescent film 3 is provided with its own electrode layer 23.
• the structure shown in Fig. 1 e or Fig. 1 f corresponds essentially to the structure shown in Fig. 1 a.
• the first electroluminescent film 1 (FIG. 1e) or the second electroluminescent film 2 (FIG. 1f) has a stable film substrate 51, 52.
• the corresponding electrode layer 21, 22, preferably made of ITO (indium tin oxide), can then be sputtered or vapor-deposited onto the film substrate 51, 52, for example by vacuum technology.
• the transparent or at least partially transparent film substrate 51, 52 consists of a polymeric or copolymeric film, for example made of polycarbonate (PC) or polyalkylene terephthalates or polyamide (PA) or polyacrylate or polymethacrylate or polymethyl methacrylate (PMMA) or polyurethane (PUR) or polyoxymethylene (POM) or ABS graft polymers or polyolefins, such as polyethylene (PE) or polypropylene (PP), or polystyrene (PS) or polyvinyl chloride (PVC) or polyimide (Pl) or polyetherimides (PEI) or polyether or polyether ketones (PEK) or polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVdF) or similar films which have high transparency in the optically visible wavelength range.
• PC polycarbonate
• PA polyalkylene terephthalates
• PA polyamide
• PMMA polymethacrylate or polymethyl methacrylate
• the film substrate 51, 52 acts as a stabilizing support, the corresponding luminescent layer 1 1, 1 2 no longer necessarily requires particular intrinsic stability, so that the luminescent layer 1 1, 12 is not only designed as a (cast) film, but instead also as a screen printing layer or the like can be.
• FIG. 1 g and 1 h show a structure corresponding to FIG. 1 c and FIG. 1 d, the first electroluminescent film 1 having a film substrate 51 of the type described above.
• the structure of the multicolor electroluminescent element shown in FIG. 1 i largely corresponds to the structure shown in FIG. 1 b, wherein both electroluminescent films 1, 2 have a film substrate 51, 52 of the type described above. It is thus possible to use two almost identical electroluminescent films 1, 2, which differ only in the color of their electroluminophores 4. By adding a third electroluminescent film (not shown) that differs only in its luminescent color, an RGB arrangement for displaying the entire color spectrum is also possible.
• FIG. 1j and 1k show a structure corresponding to FIG. 1g and FIG. 1h, wherein in addition to the first electroluminescent film 1, the second electroluminescent film 2 also has a film substrate 52 of the type described above.
• the (rear) electrode layers 21, 22, 23, 31, 32, 33 are generally contacted over the entire edge of the electrode surface by means of conductors which are guided in a ring around the electrode surface. This has the advantage that, despite the not inconsiderable surface resistance of the thin electrode layers 21, 22, 23, 31, 32, 33, there are no excessively large potential differences across the surface, and therefore the homogeneous lighting effect is supported. Furthermore, individual electroluminescent films 1, 2, 3, but also the entire multicolor electroluminescent element can be divided into segments, with individual segments are each separately electrically contacted and can also be controlled separately in order to be used as a segment display for displaying different patterns or graphics or else characters.
• FIG. 2 A somewhat more detailed illustration of a "three-color" (RGB) emitting multicolor electroluminescent element is shown in FIG. 2.
• the left partial illustration shows the electroluminescent films 1, 2, 3 before the assembly, and the right partial illustration shows the layer structure of the multicolor electroluminescent element which has subsequently been created.
• a pressure-sensitive adhesive layer 7 is provided on the first, lowermost electroluminescent film 1 for simplified attachment to a base. Otherwise, the individual electroluminescent films 1, 2, 3 are largely the same and essentially constructed in accordance with FIG. 1 i (only the luminescent layers 1 1, 1 2, 1 3 naturally emit in a different color, expediently red, blue and green):
• ITO indium tin oxide
• This electrode layer 21, 22, 23 can be structured conventionally by means of a scratch-cut plotter or by means of etching or by laser action in accordance with the desired formation of several segments and the corresponding connection wiring, or can be used over the entire area. It is also possible to partially ablate the electrode layer 21, 22, 23 in the finished or semi-finished electroluminescent film 1, 2, 3 or even in the finished or semi-finished multi-color electroluminescent element, so to speak, to structure and thus contour it.
• bus bars i.e. more conductive wiring elements
• Silver conductive pastes and / or copper conductive pastes and / or carbon conductive pastes are produced.
• the respective luminescent layer 11, 1, 13 is preferably produced by screen printing in the form of electroluminophores 4 or EL pigments 4 dispersed in a transparent polymer matrix 6 in the desired graphic configuration.
• suitable EL pigments 4 or EL pigment mixtures 4 are used and / or suitable color-converting and / or color-filtering substances are added to the binder of the matrix 6.
• color-converting and / or color-filtering effects can also be brought about by applying a corresponding layer 61, 62, 63 to the top of the substrate 51, 52, 53 and / or laminating a corresponding film by means of further printing.
• a dielectric layer 41, 42, 43 it may be expedient to apply a dielectric layer 41, 42, 43 to the luminescent layer 1 1, 1 2, 1 3. If a screen printing process is used, a second dielectric layer 81, 82, 83 is advantageously applied, as a result of which small imperfections and / or micro-air inclusions are covered and the insulation property is improved.
• transparent polymeric dielectric layers 41, 42, 43, 81, 82, 83 are preferably used according to the invention, whereby the smallest possible layer thickness must be taken into account, since usually no additions which increase the relative dielectric constant can be added, since such , for example consisting of fine barium titanate pigments, admixtures would have a very strong influence on the transparency and would usually bring about an undesired opacity with strong reflection.
• the (largely) transparent back electrode 31, 32, 33 is preferably produced by means of screen printing in the form of an intrinsically conductive polymer layer and / or a layer with metal oxides, for example indium tin oxides (ITO) or antimony tin oxides (ATO).
• ITO indium tin oxides
• ATO antimony tin oxides
• the back electrode 31, 32, 33 can be designed largely freely in graphic and functional terms. Since conventional electrically conductive screen printing pastes do not have good surface conductivity, so-called bus bars (not shown) are printed bordering or bordering, especially in the case of larger areas, by means of well electrically conductive pastes. These bus bars can also be used for the execution of the electrical connections are used.
• the back electrode 31, 32, 33 can also be produced over the entire surface by means of doctor blades, roller coating, curtain casting, spraying and the like.
• adhesion promoter layers 72, 73 can be applied which bring about and / or improve the bond between the individual electroluminescent films 1, 2, 3.
• An adhesion promoter layer 71, 72, 73 is primarily understood to mean a transparent polymeric connecting layer. This can create a connection in the cold adhesive process after peeling off a protective film and application by means of pressure. However, hot-melt adhesive coatings can also be used, which bring about an adhesive bond under temperature and pressure. Since a composite that is as optically transparent as possible is required, the adhesive layer 71, 72, 73 must be transparent and the composite must be designed free of air inclusions. Furthermore, the adhesion promoter layer 72, 73 is also intended to compensate for unevenness in the preceding layers.
• connection of the electroluminescent films 1, 2, 3 by means of cold lamination and / or hot lamination can take place flat or element-wise.
• connection can also be made only at points or in strips, since if necessary the three electroluminescent films 1, 2, 3 are fixed together when installed in a corresponding application.
• the dielectric layers 41, 81 and the back electrode 31 of the lowermost electroluminescent film must be made largely transparent, while one or more of the layers mentioned are preferably designed to be opaque or reflective for one-sided light emission upwards, and the back electrode 31 additionally takes on various wiring functions can.
• the arrangement blue-red-green, with green being arranged on the light exit side was very efficient for generating one as large a variety of colors as possible, and in particular to produce the color white.
• the EL pigments 4 or the combinations of EL pigments 4 and the use of corresponding color-converting and / or color-filtering substances other arrangements or a different sequence can also be used.
• the luminescent layer 1 1, 1 2, 1 3 can be formed from an EL cast film.
• EL cast films are understood to mean thin films produced from the solution by means of casting processes, in which the electroluminescent pigments with a diameter of less than 30 ⁇ m, preferably less than 20 ⁇ m, particularly preferably less than 15 ⁇ m, are embedded.
• Such EL cast films are relatively dimensionally stable and can preferably be coated in a roll-to-roll process with electrode layers 21, 22, 23 by means of vacuum technology or screen printing or knife coating or roll coating or spraying or curtain casting.
• the application of the dielectric layers 41, 42, 43, 81, 82, 83 can be dispensed with and thus very good transparency and electrical dielectric strength and excellent surface planicity can be achieved.
• the disadvantage of this method lies in the full-surface design of the luminescent layers 1 1, 1 2, 1 3 and thus the higher costs due to an increased proportion of EL pigments 4.
• FIG. 3 shows an alternative embodiment, the reference numbers of corresponding layers being retained compared to FIG. 2.
• the middle electroluminescent film 3 can be formed using an EL cast film as the luminescent layer 13.
• the other electroluminescent films 1, 2 can in principle be designed without the film substrate 51, 52 if the luminescent layers 11, 12 are produced accordingly.
• An advantage of the arrangement shown in FIG. 3 is the saving of one or two electrode layers.
• a mirror-image structure of the upper and lower electroluminescent films 1, 2 is shown, and the middle electroluminescent film 3 is with cast luminescent layer 1 3 and two Dielectric layers 43, 83 executed.
• These two dielectric layers 43, 83 can alternatively also be arranged on both sides of the luminescent layer 1 3 and can furthermore be used for promoting adhesion and contain color-converting and / or color-filtering admixtures.
• the adhesive layers 71, 72 of the upper and lower electroluminescent films 1, 2 can be omitted, and the back electrodes 31, 32 of the upper and lower electroluminescent films 1, 2 form the electrodes for the middle EL capacitor.
• an electroluminescent film 1 shown in FIG. 4 has proven to be a particularly favorable compromise of reliable function and good manufacturability.
• Three (possibly also two) similar electroluminescent films of the type shown, which differ only in their luminous color, are combined with one another to form a multicolor electroluminescent element according to the invention.
• Electroluminescent film 1 essentially consists of a film substrate 51 made of PET or other plastic, onto which the electrode layer 21 is vapor-deposited or sputtered, a luminescent layer 11 and a transparent back electrode 31 applied by screen printing, which is laminated by means of the insulating film 91.
• substrates are also conceivable which do not consist of a plastic film but of a ceramic material, for example glass.

Landscapes

• Electroluminescent Light Sources (AREA)
• Illuminated Signs And Luminous Advertising (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34223111

Family Applications (1)

Country Status (5)

Families Citing this family (3)

Family Cites Families (12)

• 2003
  • 2003-08-21 DE DE10338502A patent/DE10338502A1/de not_active Ceased
• 2004
  • 2004-07-28 EP EP04763573A patent/EP1656818B1/fr not_active Expired - Lifetime
  • 2004-07-28 US US10/568,921 patent/US20060255717A1/en not_active Abandoned
  • 2004-07-28 AT AT04763573T patent/ATE487357T1/de active
  • 2004-07-28 WO PCT/EP2004/008462 patent/WO2005022960A1/fr active Application Filing
  • 2004-07-28 DE DE502004011855T patent/DE502004011855D1/de not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events