KR20050024376A - Electroluminescent device with a color filter - Google Patents

Abstract

The present invention relates to a substrate 1, a porous layer 2 adjacent to the substrate 1, and at least one first electrode 3, an electroluminescent layer 4 and a second adjacent the porous layer 2. An electroluminescent device comprising a laminated body composed of electrodes 5, wherein the coloring material, preferably the ink, is at least partly related to the electroluminescent device present in the pores of the porous layer 2. The porous layer 2 can be divided, comprising a plurality of different colored materials, to obtain a black matrix structure and / or a color filter structure. The invention also relates to a method of manufacturing an electroluminescent device.

Description

Electroluminescent device having a color filter {ELECTROLUMINESCENT DEVICE WITH A COLOR FILTER}

The present invention relates to an electroluminescent device comprising a substrate and a laminated body composed of one or more first electrodes, an electroluminescent layer and a second electrode.

Various embodiments of electrically driven display systems based on different principles are known and widely used.

According to one of the above principles, an organic light emitting diode, a so-called OLED, is used as the light source. The organic light emitting diode is composed of a plurality of function layers. In the Philips Journal of Research, 1998, 51, 467, the typical structure of an OLED is described. Typical structures have an ITO (indium tin oxide) layer as a transparent electrode (anode), a conductive polymer layer, an electroluminescent layer, ie a layer of luminescent material, in particular a luminescent polymer, and a metal, preferably having a low work function Metal electrodes (cathodes). Such structures are typically provided on a substrate, generally glass. The generated light reaches the viewer through the substrate. OLEDs comprising a light emitting polymer in the electroluminescent layer are also referred to as polyLEDs or PLEDs.

To improve light output or brightness, organic LEDs include additional functional layers. Such LEDs are disclosed, for example, in US patent application 2001/0019242. The functional layer may comprise a color filter, for example.

These and other aspects of the invention will be apparent from and elucidated with reference to one embodiment of the two figures.

1 shows a cross section of an electroluminescent device.

2 shows a divided porous layer with colored material in the pores.

As shown in FIG. 1, the electroluminescent device preferably comprises a substrate 1 in the form of a transparent glass plate or a transparent polymer foil. On the substrate 1 is provided a porous layer 2 which transmits light emitted by the electroluminescent device. The porous layer 2 has a low refractive index and leads to improved light emission from the electroluminescent device, which may be based on the fact that the total internal reflection is disturbed. The layer thickness of the porous layer 2 is preferably in the range of 1 to 10 μm.

The pore size in the porous layer 2 is in the nanometer range, preferably in the range from 20 to 100 nm. The porous layer 2 is preferably a colloidal layer. That is, they are prepared from colloidal or colloidal solutions. Colloidal or colloidal solutions are heterogeneous material systems containing very small particles that are not visible under an optical microscope, wherein the particles are dispersed in a liquid or gaseous medium. These particles are characterized by very high surface-to-mass ratios. As a result, the colloidal layer 2 consists of very small particles of a colloidal solution, the size of which ranges from 1 to 400 nm. Alternatively, the porous layer 2 may comprise an aerogel.

The stack is adjacent on the porous layer 2, the stack comprising at least one transmissive electrode 3, an electroluminescent layer 4 and a second electrode 5. The first electrode 3 acts as an anode and the second electrode 5 acts as a cathode. Electrodes 3 and 5 are provided such that they form a two-dimensional array.

The first electrode 3 may comprise, for example, p-doped silicon or indium-doped tin oxide (ITO). The second electrode 5 may comprise a metal, alloy or n-doped silicon, for example aluminum, copper, silver or gold. It may be preferred that the second electrode 5 comprises two or more conductive layers. The second electrode 5 comprises a first layer of alkaline earth metal such as calcium or barium and a second layer of aluminum.

The electroluminescent layer 4 comprises a light emitting polymer or small organic molecules. Depending on the type of material used for the electroluminescent layer 4, the device is referred to as LEP (light emitting polymer) or polyLED, or SMOLED (small molecule organic light emitting diode). Preferably, the electroluminescent layer 4 comprises a light emitting polymer. In the case of light emitting polymers, for example poly (p-phenylene vinylene) (PPV), substituted PPV (eg dialkoxy-substituted PPV) or doped PPV can be used.

Alternatively, the laminate may include additional layers such as hole-transport layers and / or electron-transport layers. The hole-transport layer is arranged between the first electrode 3 and the electroluminescent layer 4. The electron-transport layer is located between the second electrode 5 and the electroluminescent layer 4. Both layers preferably comprise a conductive polymer.

The electroluminescent layer 4 can be divided into a plurality of color pixels which emit light in red, green and blue. In order to produce colored light, the material in the electroluminescent layer 4 can be doped with a fluorescent dye, or a polymer emitting colored light is used as the material in the electroluminescent layer 4. In a different embodiment, the polymer is used in the electroluminescent layer 4, which emits light in a wide range of wavelengths and the color filter structure in the porous layer 2 has three primary colors from this light: red, It is used to generate light in any one of green or blue color.

Typically, when a suitable voltage of low volts is applied to the electrodes 3 and 5, the positive and negative charge carriers are injected to move to the electroluminescent layer 4 to which they are combined to generate light. This light travels through the first transmissive electrode 3, the porous layer 2 and the substrate 1 before reaching the viewer. When the electroluminescent layer 4 is doped with a fluorescent dye, the light generated by electron-hole recombination excites the dye, which then emits light in one of three primary colors.

The pores of the porous layer 2 are at least partially provided with a coloring material. The term " colored " herein includes red, yellow, green, blue, and the like, which are conventional colors, but also include black. If the porous layer 2 comprises a coloring material, a color filter is obtained. It may be desirable for two or more coloring materials to be introduced into the pores of the porous layer. Advantageously, as shown in FIG. 2, the porous layer 2 is thereby divided into compartments to form a color filter structure. These compartments may take the form of, for example, strips and / or pixels. Preferably, the porous layer 2 comprises strip-shaped and pixelated sections, said strip-shaped sections being formed by a black material, said pixelated sections being formed by red, green or blue materials in particular. Do. In this embodiment, such partitioning produces not only the black matrix structure but also the color filter structure in the porous layer 2. The strip-shaped compartments preferably have a width of 50 to 100 μm. The pixelated compartments preferably have a size of 200 × 300 μm.

It is particularly preferable that the coloring substance is an ink. In addition to organic solvents, suitable inks typically comprise one or more binders, conductive salts, as well as additional auxiliaries and additives where necessary. In part, they are used in aqueous form. Suitable inks additionally include pigments or dyes. For dyes, for example C.I. Acid Red 118, C.I. Acid Red 254, C.I. Acid Green 25, C.I. Acid Blue 113, C.I. Acid Blue 185, C.I. Acid Blue 7, C.I. Acid Blue 7 or C.I. Acid Black 194 can be used. In pigments, for example, C.I. Pigment Red 177, C.I. Pigment Red 5, C.I. Pigment Red 12, C.I. Pigment Green 36, C.I. Pigment Blue 209 or C.I. Pigment Blue 16 is available.

The amount of dye or pigment in the ink is preferably in the range of 0.1 to 20% by weight relative to the total weight of the ink.

In order to produce a porous layer 2 comprising at least one coloring ink in the voids, ink jet printing can advantageously be used. Ink jet printing is a known method in which various substrates can be coated in a contactless manner. Ink jet printing is used for producing color filters, for example in liquid crystal display screens.

First, the substrate 1 is provided by, for example, a sol-gel process or a spin coating process, for example of a porous layer 2 of SiO ₂ or metal oxide. In case the porous layer 2 is a colloidal layer, for example, a colloidal aqueous solution is prepared first, after which the solution is applied to the substrate 1 by spin coating. After drying at a temperature in the range from 150 to 180 ° C., a porous layer 2 is obtained which is firmly adhered to the substrate 1.

Ink is provided directly on the porous layer 2, which is possible, for example, because a substrate 1 comprising the porous layer 2 is present in an ink jet printer. As a result of the capillary forces, the ink at least partially enters the voids in the porous layer 2. Depending on the layer thickness of the porous layer 2 and the amount of ink deposited on the porous layer 2 during ink jet printing, less and more pores of the porous layer 2 will comprise the ink. In addition, the accuracy of the printing process is determined by these two factors. The method has the advantage that a subsequent drying process is not necessary and therefore the coloring ink can be introduced into the pores of the porous layer 2 as a coloring material quickly and economically.

If the porous layer 2 is to have a black matrix structure and a color filter or color filter structure, black ink is first provided, preferably in such a way that the strip-shaped sections form a lattice. Subsequently, the coloring ink (s) are provided.

Depending on the wavelength of the light emitted by the electroluminescent layer 4 and the use of the electroluminescent device, the porous layer 2 may comprise one, two or three different colored materials.

Although the description of the present invention relates only to passive electroluminescent devices, the present invention may also be used in active electroluminescent devices. In an active electroluminescent device, the first electrode has a pixel structure, and each pixel electrode is driven by two or more thin film transistors and one capacitor.

It is an object of the present invention to provide an improved electroluminescent device with high light output with color filters, which can be manufactured in a simple and rapid manner.

This object is an electroluminescent device comprising a substrate, a porous layer adjacent to the substrate, and a laminate adjacent to the porous layer and comprising at least one first electrode, an electroluminescent layer and a second electrode, wherein the colored material is At least in part by an electroluminescent device present in the pores of the porous layer.

The porous layer improves the coupling of light in the electroluminescent device because the porous layer has a low refractive index and disturbs the total internal reflection. By introducing the coloring material into the pores of the porous layer, a color filter is obtained in a simple manner in which the color filter changes the emission color of the electroluminescent device and improves daylight contrast. The production of color filters is advantageous because it does not require the provision of additional layers.

Advantageous embodiments according to claim 2 allow the absorption properties to be adapted to the emission spectrum of the light emitted by the electroluminescent layer of the coloring material.

Advantageous embodiments according to any of claims 3 to 5 enable an electroluminescent device having a black matrix structure and / or a color filter structure to be obtained in a simple manner.

An advantageous use of the ink as the coloring material according to claim 6 allows the coloring material to be introduced easily and quickly into the pores of the porous layer. An additional advantage exists in that coloring material can be introduced into the porous layer in a later step. This is very cost effective and depending on the laminate used, the coloring material may be suitable for the (release) properties of the laminate.

The invention also provides a method of making an electroluminescent device comprising a substrate, a porous layer adjacent to the substrate, at least one first electrode, an electroluminescent layer, and a second electrode adjacent to the porous layer, wherein the coloring material is at least partially In the pores of the porous layer, the coloring material is introduced into the porous layer by ink jet printing.

Ink jet printing allows color filters to be manufactured in a simple, fast and economical way. In particular, this allows an electroluminescent device comprising a black matrix and pixelated color filter structure to be obtained in a simple and rapid manner.

Embodiments of the present invention will then be described to constitute examples of possible implementations.

Example

De-by diluting a colloidal solution of SiO ₂ (Levasil ^ⓒ VPAC 4056) with a particle diameter of 50㎚ using the number of ionization, to produce a colloidal solution of SiO ₂ having a SiO ₂ concentration of 5% by weight. The colloidal aqueous solution obtained is passed through a membrane filter having a pore size of 5 μm. In the substrate 1, a glass plate having a thickness of 1.1 mm was used, which was pressed in a spin coater and coated with a colloidal aqueous solution of SiO ₂ . In this process, the substrate 1 is rotated at 200 rpm, and the solution is dried by an infrared lamp in the rotating diagram. Subsequently, the coated substrate 1 is placed in an oven and exposed to a temperature of 150 ° C. The porous layer ₂ of SiO ₂ firmly attached to the substrate 1 has a layer thickness of 200 nm.

The coated substrate 1 is introduced into an ink jet printer and first black ink is provided on the porous layer 2 in such a way that a black matrix structure is obtained. Then, in addition to the black matrix structure, red, blue, and green inks are successively provided to obtain a color filter structure. A 100 nm thick ITO layer is provided on the porous layer 2 as the first electrode 3 and then constructed. Subsequently, a 200 nm thick polyethylene dioxythiophene (PDOT) layer as a hole-conducting layer, and an 80 nm thick electroluminescent layer 4 are provided. The electroluminescent layer 4 is classified into color pixels that emit light in red, green and blue. Red-emitting color pixels are poly [{9-ethyl-3,6-bis (2-cyanovinylene) carbazolylene)} alt-co- [2-methoxy-5- (2-ethylhexyloxy ) -1,4-phenylene}], the blue emitting color pixel comprises poly [9,9-dihexylfluorenyl-2,7-diyl], and the green emitting color pixel comprises poly [{ 9,9-dioctyl-2,7-divinylene-fluorenylene} -alt-co- {2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene}] Include. The red-emitting color pixel is opposite the area of the porous layer 2 containing the red ink in the voids. In addition, the green-emitting color pixels and the blue-emitting color pixels are respectively opposite the areas of the porous layer 2 comprising the green ink and the blue ink. The strip-shaped section of the porous layer 2 comprising black ink divides the pixels into triads, each three pairs having red, green and blue pixels. The electroluminescent layer 4 is provided with a second electrode 5 consisting of a layer of Ba having a thickness of 5 nm and a layer of Al having a thickness of 200 nm.

The electroluminescent device obtained exhibits improved daylight contrast and high spectral purity of primary colors.

The present invention is widely used in electroluminescent devices comprising a substrate and a laminated body composed of one or more first electrodes, electroluminescent layers and second electrodes.

Claims (7)

A substrate 1, a porous layer 2 adjacent to the substrate 1, and at least one first electrode 3, an electroluminescent layer 4 and a second electrode 5 adjacent the porous layer 2 and An electroluminescent device comprising a laminated body composed of The electroluminescent device wherein the coloring material is at least partially present in the pores of the porous layer (2). Electroluminescent device according to claim 1, characterized in that the porous layer (2) comprises at least two coloring materials. Electroluminescent device according to claim 2, characterized in that the porous layer (2) is divided. 4. Electroluminescent device according to claim 3, characterized in that the division of the porous layer (2) has a different form. 5. Electroluminescent device according to claim 4, characterized in that the division of the porous layer (2) takes the form of a strip and / or a pixel. The electroluminescent device according to any one of claims 1 to 5, wherein the coloring substance is an ink. A substrate 1, a porous layer 2 adjacent to the substrate 1, and at least one first electrode 3, an electroluminescent layer 4 and a second electrode 6 adjacent to the porous layer 2. A method of making an electroluminescent device comprising a laminated body consisting of) and wherein the coloring material is at least partially present in the pores of the porous layer 2, An electroluminescent device, characterized in that the coloring material is introduced into the porous layer (2) by ink jet printing.