JP2006093019A - Organic el display and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light extracting efficiency of an organic EL display. <P>SOLUTION: The organic EL display 1 is provided with an insulating substrate 10, a light extracting layer 30 formed on the insulating substrate 10 and provided with a first area 31 and a plurality of second areas 32 which are phase separated from it, and an organic EL device 40 formed on the light extracting layer 30. The light extracting layer 30 is formed by forming a film containing a plurality of materials on the insulating substrate 10 and by phase separating in the film. The absolute value of the difference of the refractive index of the first area 31 and the refractive index of the second areas 32 is 0.05 or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic EL (electroluminescence) display device and a manufacturing method thereof.

  Since the organic EL display device is a self-luminous display device, the viewing angle is wide and the response speed is fast. In addition, since a backlight is not necessary, it is possible to reduce the thickness and weight. For these reasons, in recent years, organic EL display devices have attracted attention as display devices that replace liquid crystal display devices.

  An organic EL element, which is a main part of an organic EL display device, includes a light-transmitting front electrode, a light-reflective or light-transmitting back electrode opposed to the front electrode, and a light-emitting layer interposed therebetween. It consists of an organic layer. An organic EL element is a charge injection type self-luminous element that emits light when electricity is passed through an organic layer.

  By the way, the luminance of the organic EL element increases in accordance with the magnitude of the current flowing therethrough. However, when the current density is increased, the power consumption is increased and the lifetime of the organic EL element is remarkably shortened. Therefore, in order to realize high luminance, low power consumption, and long life at the same time, the light emitted from the organic EL element should be extracted more efficiently to the outside of the organic EL display device, that is, the light extraction efficiency should be improved. ,is important.

  An object of the present invention is to increase the light extraction efficiency of an organic EL display device.

  According to a first aspect of the present invention, an insulating substrate, a light extraction layer formed on the insulating substrate and including a first region and a plurality of second regions phase-separated therefrom, and the light extraction layer And the light extraction layer is formed by forming a film containing a plurality of materials on the insulating substrate, and causing phase separation in the film. An organic EL display device is provided in which the absolute value of the difference between the refractive index of the second region and the refractive index of the second region is 0.05 or more.

  According to the second aspect of the present invention, by forming a film containing a plurality of materials on an insulating substrate and causing phase separation in the film, the first region and the plurality of second regions phase-separated from the first region A step of forming a light extraction layer whose absolute value of the difference between the refractive index of the first region and the refractive index of the second region is 0.05 or more, and an organic EL element on the light extraction layer The manufacturing method of the organic electroluminescence display characterized by including the process to form is provided.

  According to the present invention, the light extraction efficiency of the organic EL display device can be increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to components that exhibit the same or similar functions, and duplicate descriptions are omitted.

  FIG. 1 is a cross-sectional view schematically showing an organic EL display device according to an aspect of the present invention. FIG. 2 is a plan view schematically showing an example of a light extraction layer that can be used in the organic EL display device of FIG. In FIG. 1, the organic EL display device 1 is depicted such that its display surface, that is, the front surface or the light emitting surface faces upward, and the back surface faces downward.

  An organic EL display device 1 shown in FIG. 1 is a top emission type organic EL display device that employs an active matrix driving method. The organic EL display device 1 includes an insulating substrate 10 such as a glass substrate, for example.

  On the insulating substrate 10, a plurality of pixels are arranged in a matrix. Each pixel includes a pixel circuit and an organic EL element 40.

  The pixel circuit includes, for example, a drive control element (not shown) and an output control switch 20 connected in series with the organic EL element 40 between a pair of power supply terminals, and a pixel switch (not shown). The drive control element has a control terminal connected to a video signal line (not shown) via a pixel switch, and outputs a current having a magnitude corresponding to the video signal supplied from the video signal line to the output control switch 20. To the organic EL element 40. The control terminal of the pixel switch is connected to a scanning signal line (not shown), and the switching operation is controlled by the scanning signal supplied from the scanning signal line. Note that other structures may be employed for these pixels.

On the substrate 10, for example, a SiN _x layer and a SiO _x layer are sequentially stacked as the undercoat layer 12. On the undercoat layer 12, for example, a semiconductor layer 13, which is a polysilicon layer in which a channel and source / drain are formed, a gate insulating film 14 that can be formed using, for example, TEOS (TetraEthyl OrthoSilicate), etc., and MoW, for example, The gate electrodes 15 are sequentially stacked, and they constitute a top gate type thin film transistor (hereinafter referred to as TFT). In this example, these TFTs are used as pixel switches 20, output control switches, and drive control element TFTs. A scanning signal line (not shown) that can be formed in the same process as the gate electrode 15 is further disposed on the gate insulating film 14.

The gate insulating film 14 and the gate electrode 15 are covered with an interlayer insulating film 17 made of, for example, SiO _x formed by a plasma CVD method or the like. A source / drain electrode 21 is disposed on the interlayer insulating film 17 and is buried with a passivation film 18 made of, for example, SiN _x . The source / drain electrode 21 has, for example, a three-layer structure of Mo / Al / Mo, and is electrically connected to the source / drain of the TFT through a contact hole provided in the interlayer insulating film 17. . Further, video signal lines (not shown) that can be formed in the same process as the source / drain electrodes 21 are further arranged on the interlayer insulating film 17.

  A planarization layer 19 is formed on the passivation film 18. A reflective layer 70 is disposed on the planarization layer 19. As a material for the planarization layer 19, for example, a hard resin can be used. As a material of the reflective layer 70, for example, a metal material such as Al can be used.

  The planarizing layer 19 and the reflective layer 70 are covered with the light extraction layer 30. The light extraction layer 30 includes a first portion 31 and a plurality of second portions 32 phase-separated therefrom. The first portion 31 and the second portion 32 are light transmissive, and they have different refractive indexes.

  In the example shown in FIGS. 1 and 2, when the light extraction layer 30 is observed from a direction perpendicular to the film surface, the second portion 32 has an approximately lattice-like arrangement structure, for example, an approximately triangular lattice as shown in FIG. Each of which is generally circular. Moreover, in the example shown in FIG.1 and FIG.2, each 2nd part 32 is a substantially spherical shape.

  On the light extraction layer 30, light transmissive first electrodes 41 are juxtaposed apart from each other. Each first electrode 41 is disposed to face the reflective layer 70. In addition, each first electrode 41 is connected to the drain electrode 21 through a through hole provided in the passivation film 18, the planarization layer 19, and the light extraction layer 30.

  The first electrode 41 is an anode in this example. As a material of the first electrode 41, for example, a transparent conductive oxide such as ITO (Indium Tin Oxide) can be used.

  A partition insulating layer 50 is further disposed on the light extraction layer 30. The partition insulating layer 50 is provided with a through hole at a position corresponding to the first electrode 41. The partition insulating layer 50 is an organic insulating layer, for example, and can be formed using a photolithography technique.

  On the first electrode 41 exposed in the through hole of the partition insulating layer 50, the organic layer 42 including the light emitting layer 42a is disposed. The light emitting layer 42a is a thin film containing a luminescent organic compound whose emission color is red, green, or blue, for example. The organic layer 42 can further include layers other than the light emitting layer 42a. For example, the organic layer 42 may further include a buffer layer 42b that plays a role in mediating injection of holes from the first electrode 41 to the light emitting layer 42a. In addition, the organic layer 42 may further include a hole transport layer, a hole blocking layer, an electron transport layer, an electron injection layer, and the like.

  The partition insulating layer 50 and the organic layer 42 are covered with a light transmissive second electrode 43. In this example, the second electrode 43 is a cathode provided continuously in common with each pixel. The second electrode 43 is formed on the same layer as the video signal line through a contact hole (not shown) provided in the passivation film 18, the planarizing layer 19, the light extraction layer 30, and the partition insulating layer 50. The electrode wiring is electrically connected. Each organic EL element 40 includes the first electrode 41, the organic material layer 42, and the second electrode 43.

  In the organic EL display device 1 shown in FIG. 1, glass sealing or protective film sealing is usually performed to prevent the organic EL element 40 from deteriorating due to contact with moisture or oxygen. In the organic EL display device 1, a polarizing plate is usually disposed on the front side of the organic EL element 40.

  As described above, in the organic EL display device 1, the light extraction layer 30 is disposed adjacent to the organic EL element 40. When such a structure is adopted, the light emitted from the light emitting layer 42a of the organic EL element 40 can be taken out to the outside of the organic EL display device 1 with higher efficiency, as will be described below.

  A part of the light emitted from the light emitting layer 42a propagates in the film surface direction while being repeatedly reflected in the laminated body of the first electrode 41 and the organic layer 42. The light propagating in the film surface direction cannot be extracted outside if the incident angle with respect to the main surface of the previous laminate is large.

  When the light extraction layer 30 is disposed adjacent to the organic EL element 40, the traveling direction of the light emitted from the light emitting layer 42a can be changed. Therefore, the light emitted from the light emitting layer 42a can be extracted to the outside of the organic EL display device 1 with higher efficiency.

  This effect cannot be remarkably obtained when the absolute value of the difference between the refractive index of the first portion 31 and the refractive index of the second portion 32 is small. Therefore, in this aspect, the absolute value of the difference between the refractive index of the first portion 31 and the refractive index of the second portion 32 is set to 0.05 or more.

  The refractive index of the first portion 31 may be larger than the refractive index of the second portion 32. Alternatively, the refractive index of the first portion 31 may be smaller than the refractive index of the second portion 32. In either case, the above effect can be obtained.

  The light extraction layer 30 used in the organic EL display device 1 can be formed by the following method, for example.

  First, an organic layer is formed on the planarization layer 19. For example, the organic layer is formed by applying a coating solution obtained by dissolving a diblock copolymer of polystyrene (PS) and polymethyl methacrylate (PMMA) in a solvent such as propylene glycol monomethyl ether acetate (PGMEA) on the planarizing layer 19. It is formed by removing the solvent from the resulting coating film.

  Next, the previous organic layer is annealed to cause phase separation. This annealing is performed within the range of the glass transition temperature to the order-disorder transition temperature of the block copolymer. If it carries out like this, PMMA which comprises a block copolymer will approach, the island-like area | region which consists of PMMA, and the sea-like area | region which consists of PS will arise in an organic substance layer. In this manner, the light extraction layer 30 including the first region 31 that is a sea-like region and the second region 32 that is an island-like region is obtained.

  If the block copolymer having a small variation in the molecular weight of PMMA is used, the island-like regions are substantially spherical or substantially cylindrical, and the dimensions thereof are substantially constant. Further, the dimensions of the island regions can be controlled according to the PMMA molecular weight, and the arrangement pitch thereof can be controlled according to the PMMA molecular weight and the PS molecular weight. When the molecular weight of PMMA and PS and the ratio thereof are appropriately set, the island-like regions having a substantially spherical shape or a substantially cylindrical shape are regularly arranged. Typically, the line connecting the centers thereof forms a substantially equilateral triangle. Can be arranged to form.

  According to this method, as described above, the size of the second region 32 and the distance between the centers thereof can be controlled according to the molecular weight of PMMA or PS. That is, the dimensions of the second regions 32 and their arrangement can be controlled at the molecular level.

  In this method, a photomask or the like is not used, but self-assembly of a block copolymer is used. When an extremely fine pattern is formed, it is difficult to manufacture the photomask by the method using the photomask. When an extremely fine pattern is formed, it is difficult to transfer the photomask pattern with high accuracy by a method using a photomask. In particular, with a large substrate, it is difficult to form a large mask with a fine pattern. On the other hand, these problems can be avoided in the method using the self-assembly of the block copolymer.

  In general, since the organic EL element has a thin film multilayer structure, if the light extraction layer has irregularities, a short circuit between the electrodes may occur due to the irregularities. Therefore, it is necessary to provide a planarizing layer between the light extraction layer that is not formed by the above method and the organic EL element. On the other hand, the light extraction layer 30 obtained by the previous method is excellent in flatness. Therefore, it is not necessary to arrange a planarizing layer between the light extraction layer 30 and the organic EL element 40.

  In addition, when a planarization layer is disposed between the light extraction layer 30 and the organic EL element 40, variation in light extraction efficiency may occur due to variation in the thickness of the planarization layer. Therefore, it is advantageous also in this point that the arrangement of the planarizing layer on the light extraction layer 30 is unnecessary.

  In the above embodiment, the structure of FIGS. 1 and 2 is adopted for the light extraction layer 30, but other structures may be adopted for the light extraction layer 30.

  3 to 5 are perspective views schematically showing modifications of the light extraction layer. FIG. 6 is a plan view of the light extraction layer of FIG. FIG. 7 is a plan view schematically showing another modification of the light extraction layer.

  In the light extraction layer 30 of FIG. 3, the second regions 32 are randomly arranged in the first region 31. Each second region 32 has a substantially spherical shape, and therefore has a substantially circular shape when the light extraction layer 30 is observed from a direction substantially perpendicular to the main surface thereof. Such a light extraction layer 30 functions as a light scattering layer.

  In the light extraction layer 30 of FIG. 4, each second region 32 has a substantially cylindrical shape, and therefore has a substantially circular shape when the light extraction layer 30 is observed from a direction substantially perpendicular to the main surface thereof. In the light extraction layer 30, the second region 32 may form a substantially lattice-like arrangement structure in the first region 31, for example, a substantially triangular lattice-like arrangement structure as shown in FIG. They may be arranged at random. When the second region 32 forms a substantially grid-like arrangement structure, the light extraction layer 30 functions as a diffraction grating. On the other hand, when the second regions 32 are randomly arranged, the light extraction layer 30 functions as a light scattering layer.

  In the light extraction layer 30 of FIGS. 5 and 6, each second region 32 is layered, and its main surface is substantially perpendicular to the main surface of the light extraction layer 30. The first region 31 and the second region 32 form a stripe when the light extraction layer 30 is observed from a direction substantially perpendicular to the main surface thereof. The light extraction layer 30 functions as a diffraction grating.

  In the light extraction layer 30 of FIG. 7, the first region 31 and the second region 32 form a schlieren-like pattern when the light extraction layer 30 is observed from a direction substantially perpendicular to the main surface. The light extraction layer 30 functions as a diffraction grating and / or a light scattering layer.

  The structure of the light extraction layer 30 can be changed according to, for example, the composition of the coating liquid, the annealing temperature, and the time described above. For example, when the material of the first region 31 contained in the coating liquid used to obtain the structure of FIG. 3 is increased, the structure of FIG. 4 can be obtained, and when the material of the first region 31 is further increased, The structure of FIG. 5 is obtained.

  In the above embodiment, the organic EL display device 1 is a top emission type, but the organic EL display device 1 may be a bottom emission type. For example, the reflective layer 70 may be omitted and the second electrode 43 may be light reflective.

  In addition, when adopting a configuration in which full color display is performed using the organic EL elements 40 whose emission colors are red, green, and blue, in consideration of the luminance balance of red, green, and blue, light is emitted only to the pixel portions of some colors. An extraction layer 30 may be provided.

  In the case of adopting a configuration in which a white light emitting organic EL element 40 and a color filter are combined to perform full color display, the light extraction layer 30 may be provided in all the pixel portions, or light is emitted only to the pixel portions of some colors. An extraction layer 30 may be provided.

  Further, when a high molecular material is used for the organic EL element 40, the glass transition temperature thereof is 130 ° C. or higher, which is higher than that of the low molecular material, and therefore a light extraction layer may be provided on the organic EL element 40.

  Examples of the present invention will be described below.

(Example)
In this example, the organic EL display device 1 shown in FIG. 1 was produced by the following method.

  First, film formation and patterning are repeated on the surface of the glass substrate 10 on which the undercoat layer 12 is formed in the same manner as a normal TFT formation process, so that the TFT 20, interlayer insulating film 17, electrode wiring (not shown), source -The drain electrode 21 and the passivation film 18 were formed.

  Next, as shown in FIG. 3, a planarizing layer 19 made of a hard resin was formed on the passivation film 18. Subsequently, a reflective layer 70 made of Al was formed on the planarizing layer 19 by mask sputtering.

  Next, on the planarizing layer 19, a coating solution obtained by dissolving a diblock copolymer of PS and PMMA in PGMEA was spin-coated. Here, the concentration of the block copolymer in PGMEA was 2% by weight. Then, the solvent was removed from the coating film by baking at 110 ° C. Further, the organic material layer thus obtained was annealed at 210 ° C. for 4 hours in a nitrogen atmosphere, and subsequently annealed at 135 ° C. for 40 hours. Thereby, the light extraction layer 30 shown in FIG. 2 was obtained. In the light extraction layer 30, the absolute value of the difference between the refractive index of the first region 31 and the refractive index of the second region 32 is about 0.09.

  Next, a first electrode 41 was obtained by depositing ITO on the light extraction layer 30 using a mask sputtering method.

Next, a photosensitive resin is applied to the surface of the substrate 11 on which the first electrode 41 is formed, and the resulting coating film is subjected to pattern exposure and development, whereby water repellency having an opening corresponding to the light emitting portion of each pixel. The partition insulating layer 50 was formed. The substrate 10 on which the partition insulating layer 50 was formed was subjected to a surface treatment using CF ₄ / O ₂ plasma gas to fluorinate the surface of the partition insulating layer 50.

  Next, a liquid film was formed by discharging the ink for forming the buffer layer into each liquid reservoir formed by the partition insulating layer 50 by an ink jet method. Subsequently, these liquid films were heated to a temperature of 120 ° C. for 3 minutes to obtain a buffer layer 42b.

  Thereafter, the light emitting layer forming ink was ejected onto the buffer layer 42b by an ink jet method to form a liquid film. Then, the light emitting layer 42a was obtained by heating these liquid films to the temperature of 90 degreeC for 1 hour.

  Next, Mg and Ag were sequentially vacuum-deposited on the surface of the substrate 11 on which the light emitting layer 42a was formed, and then ITO was deposited by sputtering. Thereby, a second electrode 43 having a multilayer structure was obtained. Furthermore, the organic EL display device 1 shown in FIG. 1 was completed by performing a sealing process and the like.

  The light extraction layer 30 of the organic EL display device 1 was observed from a direction perpendicular to the film surface. As a result, the light extraction layer 30 is composed of a first region 31 and a plurality of second regions 32 dispersed therein, and these second regions 32 form a substantially lattice-like arrangement structure. I was able to confirm. In addition, the shape of each second region 32 when the light extraction layer 30 was observed from the direction perpendicular to the film surface was substantially circular.

(Comparative example)
The organic EL display device 1 was produced by the same method as described in the above example except that the light extraction layer 30 was not provided.

  Next, for the organic EL display devices 1 according to Examples and Comparative Examples, the amount of light taken out to the outside was measured under the same conditions. As a result, the amount of light obtained by the organic EL display device 1 according to the example was about 1.4 times the amount of light obtained by the organic EL display device 1 according to the comparative example. That is, it was confirmed that the organic EL display device 1 according to the example had higher luminous efficiency than the organic EL display device 1 according to the comparative example.

1 is a cross-sectional view schematically showing an organic EL display device according to one embodiment of the present invention. FIG. 2 is a plan view schematically showing an example of a light extraction layer that can be used in the organic EL display device of FIG. 1. The perspective view which shows the modification of a light extraction layer roughly. The perspective view which shows the modification of a light extraction layer roughly. The perspective view which shows the modification of a light extraction layer roughly. The top view of the light extraction layer of FIG. The top view which shows roughly the other modification of a light extraction layer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Organic EL display device, 10 ... Insulating substrate, 12 ... Undercoat layer, 13 ... Semiconductor layer, 14 ... Gate insulating film, 15 ... Gate electrode, 17 ... Interlayer insulating film, 18 ... Passivation film, 19 ... Flattening layer 20 ... output control switch, 21 ... source / drain electrodes, 30 ... light extraction layer, 31 ... first part, 32 ... second part, 40 ... organic EL element, 41 ... first electrode, 42 ... organic layer, 42a ... light emitting layer, 42b ... buffer layer, 43 ... second electrode, 50 ... partition insulating layer, 70 ... reflective layer.

Claims (8)

An insulating substrate;
A light extraction layer formed on the insulating substrate and including a first region and a plurality of second regions phase-separated from the first region;
An organic EL element formed on the light extraction layer,
The light extraction layer forms a film containing a plurality of materials on the insulating substrate, and causes phase separation in the film,
An organic EL display device, wherein an absolute value of a difference between a refractive index of the first region and a refractive index of the second region is 0.05 or more.   2. The organic EL display device according to claim 1, wherein the material of the first and second regions is organic.   2. The organic EL display device according to claim 1, wherein each of the plurality of second regions is substantially circular when the light extraction layer is observed from a direction substantially perpendicular to a main surface thereof.   2. The organic EL display device according to claim 1, wherein each of the plurality of second regions is substantially spherical.   2. The organic EL according to claim 1, wherein the first region and the plurality of second regions form stripes when the light extraction layer is observed from a direction substantially perpendicular to a main surface thereof. Display device.   2. The schlieren-like pattern is formed in the first region and the plurality of second regions when the light extraction layer is observed from a direction substantially perpendicular to a main surface thereof. Organic EL display device.   2. The organic EL display device according to claim 1, wherein each of the plurality of second regions has a layer shape, and a main surface thereof is substantially perpendicular to a main surface of the light extraction layer. A film containing a plurality of materials is formed on an insulating substrate, and phase separation is caused in the film, thereby providing a first region and a plurality of second regions phase-separated from the first region. Refraction of the first region Forming a light extraction layer whose absolute value of the difference between the refractive index and the refractive index of the second region is 0.05 or more;
And a step of forming an organic EL element on the light extraction layer.

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