Patent Application
20150162494
The present invention relates to a light-emitting device and a method of manufacturing a light-emitting device, in detail, relates to a light-emitting device and the like having high brightness uniformity and using an electroluminescent element with a configuration in which a light-emitting layer including a light-emitting material is sandwiched with a pair of electrodes.
An electroluminescent element has a configuration in which a light-emitting layer including a light-emitting material is sandwiched between an anode electrode and a cathode electrode, and is provided with a characteristics that a light-emission with high brightness is available with a low driving voltage. Therefore, the electroluminescent element is expected to be applied to an electro-optical device such as a display or an illumination.
In recent years, for a purpose of improving a performance as an illumination usage, researches have been conducted on improving a light extraction efficiency or making a light-emitting surface larger in area size. For example, in Patent Document 1, it is disclosed that the light extraction efficiency is improved with a light-emitting element in which a dielectric layer is formed between an anode electrode layer and a cathode electrode layer, a cavity (a concave portion) extends through at least one of the dielectric layer and the electrode layers and an inside surface of the cavity is covered with an electroluminescence coating material. Here, when numeral cavities are arranged inside of electrode surfaces and a size of each cavity and a gap between cavities are small enough, the light emission is visible as a surface light emission.
In an electroluminescent element, in general, a transparent electrode such as indium tin oxide (ITO) is used for one of the anode electrode and the cathode electrode in order to gain a high light-emitting efficiency, while a light-reflecting electrode such as a metal or the like is used for the other. A sheet resistance of ITO is higher compared to that of a metal. Therefore, between a portion near a terminal of the ITO electrode and a portion far from the terminal in the light-emitting surface, the voltage between the anode electrode and the cathode electrode comes to be different due to a voltage drop. Accordingly, when the light-emitting area is made large, a brightness distribution in the light-emitting surface becomes non-uniform.
To address such a problem, in Patent Documents 2 and 3, electroluminescent elements are disclosed in which a non-light-emitting portion is provided in a light-emitting surface with a method of arranging an insulating material between the electrodes or the like so that an area rate of the non-light-emitting portion is made smaller as a distance from a terminal of the electrode gets farther. Namely, by making an area of a substantial light-emitting portion larger at a region far from the terminal of the electrode, a brightness distribution in the light-emitting surface becomes uniform.
In the case of the electroluminescent element described in Patent Document 1, when the cavities having the same size are arranged with a constant gap, the voltage drop occurs due to an electrical resistance of the electrodes, thereby the brightness distribution in the light-emitting surface tends to be non-uniform. Further, as in the case of the electroluminescent elements described in Patent Documents 2 and 3, making a size of a cavity, which is provided at a position far from the terminal of the electrode, larger compared to a cavity provided near the terminal may cause a brightness distribution in the light-emitting surface to be more non-uniform in some cases.
The problem to be addressed of the present invention is to provide a light-emitting device in which a brightness distribution in the light-emitting surface is uniform and a light extraction efficiency is high in an electroluminescent element including plural cavities.
The present inventors have identified the cause of the above problem that, in the light-emitting device having plural cavities, a light-emitting brightness distribution in each of the cavities is non-uniform, and addressed the problem with a solution shown below.
According to the present invention, a light-emitting device is provided, the light-emitting device including, a substrate, a first electrode layer that is formed on the substrate, a dielectric layer that is formed directly on the first electrode layer or formed on the first electrode layer with another layer interposed therebetween, a second electrode layer that is formed directly on the dielectric layer or on the dielectric layer with another layer interposed therebetween, plural concave portions that pass through the dielectric layer and at least one of the first electrode layer and the second electrode layer, a light-emitting region that contacts the first electrode layer and the second electrode layer and includes a light-emitting portion formed to contact at least the first electrode layer and the dielectric layer in the concave portions, and a terminal that is formed outside of the light-emitting region and connects one of the first electrode layer and the second electrode layer having larger sheet resistance to a power supply, wherein, in the light-emitting region, the plural concave portions are formed so that a sum, per unit area, of a contour length of planar shapes of the concave portions on an upper surface of the dielectric layer is increased from a region near the terminal to a region far from the terminal, is provided.
In the present invention, it is preferable that in the light-emitting region, all of the planar shapes of the plural concave portions at the upper surface of the dielectric layer are the same.
In the light-emitting region, it is preferable that the planar shapes of the plural concave portions at the upper surface of the dielectric layer are formed to be similar.
In the light-emitting region, it is preferable that the planar shapes of the plural concave portions at the upper surface of the dielectric layer include at least two shapes that are different from each other.
In the light-emitting region, it is preferable that each area that is occupied with each planar shape of the plural concave portions at the upper surface of the dielectric layer is substantially the same in an arbitrary region in the light-emitting region.
In the present invention, it is preferable that in the case where a distribution state of the concave portions that are formed nearest the terminal is regarded as a basic pattern, the plural concave portions are formed in plural regions into which the light-emitting region is divided in accordance with a distance from the terminal, by use of a reduced pattern of the basic pattern as the distance from the terminal becomes increased; and, in two of the plural regions that are adjacent to each other, the plural concave portions are formed so that a reduction rate of the reduced pattern in the region relatively far from the terminal becomes smaller compared to a reduction pattern in the region relatively near the terminal.
In the light-emitting region, it is preferable that the maximum width of each of the concave portions at an upper surface of the dielectric layer is 10 μm or less.
In the light-emitting region, it is preferable that the concave portions are formed 102 to 108 per 1 mm square.
Further, according to the present invention, a method of manufacturing a light-emitting device is provided, the method including, a first electrode layer forming process in which a first electrode layer and a dielectric layer are formed on a substrate in order, a concave portion forming process in which a photoresist layer formed on the dielectric layer is performed a photolithography which includes an exposure by use of a photomask of a predetermined pattern to form plural concave portions that pass through the first electrode layer and the dielectric layer, a light-emitting portion forming process in which a light-emitting portion is formed so as to fill at least a part of each of the concave portions and to cover surfaces of the first electrode layer and the dielectric layer that are exposed in each of the concave portions, a second electrode layer forming process in which a second electrode layer is formed on the light-emitting portion, a terminal forming process in which, of the first electrode layer and the second electrode layer, a terminal that connects the electrode layer having larger sheet resistance to a power supply is formed; wherein, in the concave portion forming process, in the case where a surface of the photoresist layers is divided into plural regions in accordance with a distance from the terminal and the photomask corresponding to a distribution state of the concave portions that are formed nearest the terminal is regarded as a basic pattern, by use of a reduced pattern of the basic pattern as the distance from the terminal becomes increased, in two of the plural regions that are adjacent to each other, a reduction ratio of the reduced pattern in the region relatively far from the terminal becomes smaller compared to a reduction pattern in the region relatively near the terminal is provided.
According to the present invention, a light-emitting device using an electroluminescent element which has a high luminous efficiency, has a uniform brightness distribution in the light-emitting area and is easy to be manufactured is provided.
Hereinbelow, an exemplary embodiment according to the present invention will be described in detail. It should be noted that the present invention is not limited to the following exemplary embodiment, but may be practiced as various modifications within the scope of the gist of the invention. Further, each of the figures to be used indicates a specific example for illustration of the exemplary embodiment, and does not represent an actual size thereof.
In the light-emitting device 10, a substrate 11, an anode layer 12 as a first electrode layer for injecting holes, which is formed on the substrate 11 in the case where the substrate 11 side is assumed to be the downside, and a dielectric layer 13 that is formed on the anode layer 12 and has an insulating property are stacked in order. Moreover, a concave portion 16 that passes through the anode layer 12 and the dielectric layer 13 is formed. Further, a light-emitting portion 17 that is formed successively from an upper surface of the dielectric layer 13 to an inner surface of the concave portion 16 and includes a light-emitting layer emitting light with application of voltage is provided.
In the present exemplary embodiment, a configuration is employed in which a cathode layer 14 as a second electrode layer for injecting electrons is stacked at an upper part of the light-emitting portion 17. A light-emitting region of the light-emitting device 10 is a region that includes a configuration of the above-described anode layer 12, the dielectric layer 13, the light-emitting portion 17 and the cathode layer 14 and includes all the plural concave portions 16. Moreover, at an outside of the light-emitting region on the substrate 11, an anode electrode terminal 15 as a terminal that is electrically connected to the anode layer 12 and connects the anode layer 12 with a power supply (not shown in the figure) is formed. It should be noted that the cathode layer 14 is illustrated with a dotted line in
As shown in
Next, other exemplary embodiments of partial cross-sectional shapes of the light-emitting device 10 will be described. Same symbols are assigned to configurations same as those in
In a partial cross-sectional shape 10a shown in
In a partial cross-sectional shape 10b shown in
In a partial cross-sectional shape 10c shown in
In a partial cross-sectional shape 10d shown in
The substrate 11 is a base material that serves as a support body for forming the anode layer 12, the dielectric layer 13, the cathode layer 14 and the light-emitting portion 17. For the substrate 11, a material that satisfies mechanical strength required for the light-emitting device 10 is used.
The material for the substrate 11 is, in the case where the light is to be extracted from the substrate 11 side of the light-emitting device 10, required to be transparent to the visible light. It should be noted that, in the present exemplary embodiment, “transparent to the visible light” means that the visible light emitted from the light-emitting portion 17 with a constant wavelength range can be transmitted, therefore, it is not necessary to be transparent at a whole region of the visible light. However, in the present exemplary embodiment, it is preferable that the substrate 11 is transmitted by the light in the wavelength range of 450 nm to 700 nm as the visible light. Moreover, in a wavelength with a maximum light-emitting intensity, the transmittance is preferably 50% or more, and more preferably 70% or more.
As the material for such a transparent substrate 11 to satisfy the requirements, specific examples include: glasses such as sapphire glass, soda glass and quartz glass and the like; transparent resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyester resins, nylon resins and the like, silicon; metallic nitride such as aluminum nitride and the like; and transparent metallic oxide such as alumina and the like. In the case of using, as the substrate 11, a resin film or the like made of the aforementioned transparent resins, it is preferable that permeability to gas such as moisture and oxygen is low. In the case of using a resin film or the like having high permeability to gas, a thin film having a barrier property for inhibiting permeation of gas is preferably formed within a scope which does not impair the light transmission.
In the case where it is not necessary to extract the light from the substrate 11 side of the light-emitting device 10, the material for the substrate 11 is not limited to the ones which are transparent to the visible light, and may be opaque to the visible light. Specific examples of the material of the substrate 11 include: in addition to the above-described materials, simple substances such as copper (Cu), silver (Ag), gold (Au), platinum (Pt), tungsten (W), titanium (Ti), tantalum (Ta) and niobium (Nb); alloys thereof; stainless steel or the like. The thickness of the substrate 11 depends on the required mechanical strength, is arbitrarily selected and not particularly limited. In the present exemplary embodiment, the thickness of the substrate 11 is preferably 0.1 mm to 10 mm, and more preferably 0.25 mm to 2 mm.
The anode layer 12 injects holes from the anode layer 12 to the light-emitting portion 17 upon application of voltage between the anode layer 12 and the cathode layer 14. A material used for the anode layer 12 is not particularly limited as long as it has an electric conductivity. It is preferable that the material has a large work function, and specifically, the work function is preferably not less than 4.5 eV. In addition, it is preferable that the electric resistance is not notably changed for an alkaline aqueous solution. As the material satisfying such requirements, metal oxides, metals or alloys can be used.
In the light-emitting device 10 of the present exemplary embodiment, the concave portion 16 is formed to pass through the anode layer 12 and the dielectric layer 13. Therefore, since the light emitted from the light-emitting portion 17 can be extracted from the substrate 11 side through the concave portion 16, the material used for the anode layer 12 may be transparent one or opaque one.
As a transparent material used for forming the transparent electrode, for example, specific example includes: indium oxide, zinc oxide, tin oxide, indium tin oxide (ITO) and indium zinc oxide (IZO) which are complexes thereof, or the like. Among these materials, ITO, IZO and tin oxide are preferable. Moreover, a transparent conductive film composed of organic substances such as polyaniline or a derivative thereof and polythiophene or a derivative thereof.
As a transparent material used for forming the opaque electrode, for example, specific example includes: copper (Cu), silver (Ag), gold (Au), platinum (Pt), aluminum (Al), tungsten (W), titanium (Ti), tantalum (Ta) and niobium (Nb) or the like. Further, alloys thereof and stainless steel or the like may be used.
The thickness of the anode layer 12 is, in the case of using the opaque electrode, preferably 2 nm to 2 mm, and more preferably 2 nm to 2 μm, and in the case of using the transparent electrode, preferably 2 nm to 300 nm since high light transmission is required. Note that, the work function can be measured by, for example, an ultraviolet photoelectron spectroscopy.
In the present exemplary embodiment, from a viewpoint of facilitating the injection of holes from the anode layer 12 to the light-emitting portion 17, as an anode surface modification layer, a layer with a thickness of 1 nm to 200 nm composed of molybdenum (MO) oxide, amorphous carbon and carbon fluoride or the like or a layer with an average thickness of not more than 10 nm composed of metal oxide, metal fluoride or the like may be provided at a surface on a side of the anode layer 12 that contacts with the light-emitting portion 17.
The dielectric layer 13 is provided between the anode layer 12 and the cathode layer 14 to separate and insulate the anode layer 12 and the cathode layer 14 with a predetermined gap therebetween and to form the concave portion 16 where the light-emitting portion 17 contacts the anode layer 12 inside thereof. Thus, it is necessary for the dielectric layer 13 to be made of a material having high resistivity. The electric resistivity thereof is required to be not less than 108 Ωcm, and preferably not less than 1012 Ωcm.
Specific examples of the material for forming the dielectric layer 13 include: silicon nitride, boron nitride and metal nitride such as aluminum nitride; silicon oxide (silicon dioxide) and metal oxide such as aluminum oxide. In addition, polymer compounds such as polyimide, polyvinylidene fluoride and parylene can be used.
The thickness of the dielectric layer 13 is preferably not more than 1 μm in order that the entire thickness of the light-emitting device 10 may not become too thick. In the present exemplary embodiment, thickness of the dielectric layer 13 is preferably 10 nm to 500 nm, more preferably 50 nm to 200 nm. Since the voltage necessary to emit light is lower as the space between the anode layer 12 and the cathode layer 14 is narrower, the dielectric layer 13 is preferably thinner from this viewpoint. However, if the dielectric layer 13 is too thin, dielectric strength becomes possibly insufficient against the voltage for driving the light-emitting device 10.
The cathode layer 14 injects electrons into the light-emitting portion 17 upon application of voltage between the anode layer 12 and the cathode layer 14. In the exemplary embodiment, since the concave portion 16 is filled with the light-emitting portion 17 as will be described later, the cathode layer 14 is formed above the dielectric layer 13 as a successive film that is not passed through by the concave portion 16.
The material used for the cathode layer 14 is not particularly limited as long as, similarly to that of the anode layer 12, the material has electrical conductivity. In the exemplary embodiment, it is preferable that the material has a small work function and is chemically stable. Considering the chemical stability, the work function of the material used for the cathode layer 14 is preferably not less than 2.5 eV.
Specific examples of the material used for the cathode layer 14 include Al, MgAg alloy and alloys of Al and alkali metals such as AlLi and AlCa. The thickness of the cathode layer 14 is preferably in the range of 10 nm to 1 μm, and more preferably 50 nm to 500 nm.
In the case of the light-emitting device 10 to which the exemplary embodiment is applied, light emitted from the light-emitting portion 17 is extracted from the substrate 11 side. Therefore, the cathode layer 14 may be formed by an opaque material. In this case, the opaque material for forming the cathode layer 14 preferably has a high light reflectivity.
In general, a sheet resistance of a thin film with thickness of 100 nm composed of the transparent conductive material of metal oxides such as ITO is, 5Ω per square to 100Ω per square, and a sheet resistance of a thin film with thickness of 100 nm composed of the opaque metal material is 0.1Ω per square to 1Ω per square. The value of the sheet resistance depends on the film thickness, and the sheet resistance becomes smaller as the film thickness becomes thicker. Besides, the value of the sheet resistance varies due to existence or non-existence of fine holes such as concave portion 16. In many cases, though not able to generalize, the sheet resistance of the transparent electrode film is larger than that of the metal electrode film. In the light-emitting device 10 of the present exemplary embodiment, typical specific examples of the anode layer 12 and the cathode layer 14 include an ITO film with a thickness of 150 nm and an Al film with a thickness of 130 nm, respectively. In this case, since the sheet resistance of the anode layer 12 is larger than that of the cathode layer 14, the terminal of the present invention is an anode electrode terminal 15 that is electrically connected to the anode layer 12.
In the light-emitting device 10 of the present exemplary embodiment, the light emitted from the light-emitting portion 17 can be extracted from the cathode layer 14 side by forming the cathode layer 14 with ITO or the like, which is the transparent electrode. When forming the cathode layer 14 with ITO, for the purpose of lowering the electron injection barrier to the light-emitting portion 17, it is preferable to form a layer composed of a material used for the above cathode layer 14 between the cathode layer 14 and the light-emitting portion 17 with a thin thickness with which light can be transmitted, and the thickness thereof is preferably 1 nm to 30 nm.
In the light-emitting device 10 of the present exemplary embodiment, a first electrode layer formed to contact the substrate 11 is the anode layer 12, and a second electrode layer formed above the light-emitting portion 17 is the cathode layer 14, however, the anode layer 12 and the cathode layer 14 may be reversed each other. That is, the first electrode layer may be a cathode layer and the second electrode layer may be an anode layer. As materials for forming the anode layer and the cathode layer in this case, the same materials for the above anode layer 12 and the cathode layer 14 can be used, respectively.
Note that, the direction of extracting the light emitted from the light-emitting portion 17 to the outside of the light-emitting device 10 may be toward the anode layer 12 side or the cathode layer 14 side, and toward both the anode layer 12 side and the cathode layer 14 side.
In the light-emitting device 10 of the present exemplary embodiment, the concave portion 16 is formed to pass through the anode layer 12 and the dielectric layer 13 formed on the substrate 11.
In the present exemplary embodiment, in the concave portion 16, the light-emitting portion 17 including a light-emitting material described later is formed. In the light-emitting portion 17, the holes injected from the anode layer 12 and the electrons injected from the cathode layer 14 are recombined in the region therebetween, thereby the light-emitting material emits the caused energy as light. Therefore, light emission tends to occur at a region where a distance from both the anode layer 12 and the cathode layer 14 is short.
Next, light emission of the light-emitting portion 17 in the concave portion 16 will be described.
As shown in
In the light-emitting device 10 of the present exemplary embodiment, in the light-emitting portion 17, the edge region 17b is easier to emit light compared to the center portion 17a and the outer portion 17c. Therefore, in the present exemplary embodiment, the edge region 17b of the light-emitting portion 17 is the light-emitting site, and the center portion 17a and the outer portion 17c are the non-light-emitting sites. Thus, when a proportion of the edge region 17b occupied in the light-emitting region is made larger, the light is emitted with high brightness because the light-emitting sites are increased. On the other hand, when a proportion of the center portion 17a or the outer portion 17c is made larger, the light is hard to be emitted with high brightness because the non-light-emitting sites are increased.
Here, the “edge region 17b” in the light-emitting device 10 to which the present exemplary embodiment is applied is, viewed from a light extraction direction of the substrate 11, a terminal that contacts the anode layer 12 and the dielectric layer 13 in the light-emitting portion 17 formed in the concave portion 16.
The “light-emitting site” is, among the light-emitting portion 17, a region where the light is substantially emitted viewed from the light extraction direction of the substrate 11. The “non-light-emitting site” is, among the light-emitting portion 17, a region where the light is hardly emitted in substance viewed from the light extraction direction of the substrate 11.
Further, with respect to the concave portion 16 formed in a particular region at the upper surface of the dielectric layer 13 in the light-emitting region, a value calculated by dividing a sum of a contour length (perimeter) of a planar shape (a concave shape) of the concave portion 16 with an area of the particular region is defined as an “edge density” in the particular region.
In the present exemplary embodiment, when a width of the concave portion 16 is made smaller, the non-light-emitting sites in the center portion 17a of the concave portion 16 is relatively reduced, thereby the light-emitting brightness is easy to be increased. Note that, the “width of the concave portion 16” is a diameter of a minimum circle surrounding the planar shape.
Moreover, in the light-emitting region where the plural concave portions 16 are formed, when a gap between the adjacent concave portions 16 is made small and a density of the concave portions 16 is made large, the non-light-emitting sites of the outer portion 17c that is a region sandwiched with the dielectric layer 13 and the cathode layer 14 is reduced, thereby the light-emitting brightness is easy to be increased. Specifically, the gap between the adjacent concave portions 16 is preferably not more than 10 μm. Here, the gap between the adjacent concave portions 16 is a distance from a center of gravity of the concave portion 16 to a center of gravity of another concave portion 16 that is located nearest.
Note that,
The arrangement of the plural concave portions 16 (16a to 16o) may be, other than the arrangement with lattice pattern shown in
The planar shape of one concave portion 16 (16a to 16o) is not particularly limited. In the present exemplary embodiment, from a viewpoint of facilitating the design and the production, circular shape or polygonal shape is preferable. The maximum width of one concave portion 16 (16a to 16o) is preferably not more than 10 μm, more preferably 0.1 μm to 5 μm, further preferably 0.1 μm to 1 μm. Moreover, the concave portions 16 (16a to 16o) are preferably formed 102 to 108 per 1 mm square in an arbitrary surface of the substrate 11.
In the light-emitting device 10 (100a to 100e) to which the present exemplary embodiment is applied, the edge region 17b relatively emits more light compared to the center portion 17a and the outer portion 17c. Therefore, the light-emitting intensity is increased by increasing the edge density.
As a method of increasing the edge density, for example, methods (1) to (3) shown below are exemplified to vary the distribution of the concave portions 16 (16a to 16o).
(1) To increase a number of the concave portions 16 (16a to 16o) per unit area without changing the shape and the size of the concave portions 16 (16a to 16o).
(2) To reduce the size and gap of the concave portions 16 (16a to 16o) with the same proportion without changing the shape of the concave portions 16 (16a to 16o).
(3) To use the shape of the concave portions 16 (16a to 16o) that include more edge region.
In the light-emitting device 10, non-uniform light-emission in the light-emitting region tends to be resolved by increasing the edge density successively or gradually from a position near the anode electrode terminal 15 to a position far from the anode electrode terminal 15. Hereinbelow, for the convenience of expression,
As described above, the light-emitting device 10a is designed from a viewpoint that the number of the concave portions 16a to 16c per unit area is increased. Thereby, in a part relatively far from the anode electrode terminal 15, the edge density of the concave portions 16c is increased compared to the concave portions 16a, accordingly, the effect of the voltage drop is offset, then an element that uniformly emits light is gained.
The concave portions 16d to 16f in the light-emitting device 100b are formed so that the areas occupied with each planar shape thereof are substantially the same. The depressed polygonal shape can have a longer perimeter compared to the minimum circle surrounding the depressed polygonal shape. Therefore, when using the concave portions 16e and 16f, the edge density can be set higher than using the concave portions 16d with a circular shape.
The light-emitting device 100b shown in
Since the edge density is easy to be high by increasing a number of points of concave polygons which have an inner angle of more than 180 degrees, it is preferable that the concave polygons with more number of points are used as the distance from the anode electrode terminal 15 becomes far. Further, even if the number of points of the concave polygons is the same, the edge density can be high by making the inner angle of less than 180 degrees smaller. Thereby, in a part far from the anode electrode terminal 15, the edge density of the concave portions 16e and 16f is increased compared to the concave portions 16d, accordingly, the effect of the voltage drop is offset, then an element that uniformly emits light is gained.
In the case of the light-emitting device 100b shown in
Moreover, in the case where the number of the concave portions 16 (16d to 16f) per unit area is the same, when the concave portions 16 (16d to 16f) are formed so that respective areas occupied with the planar shape of the concave portions 16 (16d to 16f) per unit area at the upper surface of the dielectric layer 13 (refer to
Next, other than the light-emitting device 100b shown in
Note that, it is preferable that every shape at the upper surface of the dielectric layer 13 (refer to
All of the plural concave portions 16i to 16l formed on the dielectric layer 13 (refer to
In the light-emitting device 100d, the number of the concave portions 16j per unit area in a region j is more than the number of the concave portions 16i per unit area in a region i that is adjacent to the region j and nearest the anode electrode terminal 15. Further, the number of the concave portions 16k per unit area in a region k that is adjacent to the region j and relatively far from the anode electrode terminal 15 compared to the region j is more than the number of the concave portions 16j per unit area in the region j. Still furthermore, the number of the concave portions 16l per unit area in a region l that is adjacent to the region k and relatively farthest from the anode electrode terminal 15 is more than the number of the concave portions 16k per unit area in the region k.
Moreover, the concave portions 16i to 16l are formed so that the width of the concave portions 16j in the region j smaller than the width of the concave portions 16i in the region i, the width of the concave portions 16k in the region k smaller than the width of the concave portions 16j in the region j, and the width of the concave portions 16l in the region l smaller than the width of the concave portions 16k in the region k.
Furthermore, the concave portions 16 are formed to make a similar pattern in which the shape of the concave portions 16 and the ratio of the width of the concave portions 16 and the gap between of the concave portions 16 in each area are the same, thus the edge density in each area is sequentially increased from the region i that is nearest the anode electrode terminal 15 to the region l that is the farthest from the anode electrode terminal 15.
In the light-emitting device 100d, for example, the width of the concave portions 16l in the region l that is relatively far from the anode electrode terminal 15 is made smaller compared to that of the concave portions 16i in the region i that is nearest the anode electrode terminal 15, and the density of the concave portions 16l in the region l is made increased compared to that of the concave portions 16i in the region i, thereby the difference in the edge density in the light-emitting region of the light-emitting device 100d can be increased compared to the case where the concave portions 16 have the same size.
As described above, it is preferable in manufacturing that the plural concave portions 16 form a pattern that is repeatedly formed in a predetermined region, and that a pattern of the region relatively far from the anode electrode terminal 15 and a pattern of the region relatively near the anode electrode terminal 15 are the similar pattern in which the shape of the concave portions 16 and the ratio of the width of the concave portions 16 and the gap between of the concave portions 16 are the same.
In the light-emitting device 100e, the planar shapes of the concave portions 16m (a region m), the concave portions 16n (a region n) and the concave portions 16o (a region o) are the same or similar to each other. Compared to the concave portions 16m formed in the region m that is the edge portion of the light-emitting region near the anode electrode terminal 15, the concave portions 16o formed in the region o that is the center portion of the light-emitting region relatively far from the anode electrode terminal 15 have a narrower width, and the number of the concave portions 16o per unit area in the region o is more than the number of the concave portions 16m per unit area in the region m.
Further, the concave portions 16o in the region o are formed to make a similar pattern in which the shape of the concave portions 16m and the ratio of the width of the concave portions 16m and the gap between the concave portions 16m in the region m are the same. Thereby, the edge density in the region o can be higher than that in the region m.
The concave portions 16n formed in the region n that is farther from the anode electrode terminal 15 than the region m and nearer than the region o are middle in size and number per unit area between the concave portions 16m and the concave portions 16o, and the shape of the concave portions 16n and the ratio of the width of the concave portions 16n and the gap between the concave portions 16n in the region n are formed to be same as those of the concave portions 16m and 16o in the regions m and o. Therefore, the edge density in the region n is larger than that in the region m and smaller than that in the region o.
A pattern 30 shown in
The pattern 30 shown in
Here, the total area of the concave portions 16A (the number thereof is 16) in the pattern 30 is 16πR2, the total area of the concave portions 16B (the number thereof is 4) in the pattern 31 is 16πR2, the summation of the contour length of the concave portion 16A (the number thereof is 16) in the pattern 30 is 32πR, and the summation of the contour length of the concave portion 16B (the number thereof is 4) in the pattern 31 is 16πR. As described, when using the reduction patterns in which the planar shape of the concave portions 16A and 16B and the proportion of the gap between the concave portions 16A and 16B are similar, the edge density is increased since the size in each concave portion becomes small although the area occupied with the concave portions 16A and 16B is same.
Those patterns are preferable because they are easy to be manufactured only by changing the reduction ratio at the time of patterning with mask exposure. Moreover, it is preferable in manufacturing since it is easy to form the concave portions 16 so that the area occupied with the shape of the concave portion 16 per unit area at the upper surface of the dielectric layer 13 is substantially same in an arbitrary region.
In the present exemplary embodiment, the light-emitting portion 17 includes a light-emitting material that emits light by application of voltage and current supply, and is formed by applying the material so as to be in contact with an inner surface of the concave portion 16. In particular, in the case where the light-emitting portion 17 is formed with plural layers including a layer composed of an organic compound, the layer including the light-emitting material is called a light-emitting layer. In the light-emitting portion 17, holes injected from the anode layer 12 and the electrons injected from the cathode layer 14 are recombined, and light emission occurs.
As the material of the light-emitting material, either an organic material or an inorganic material may be used. In the case where an organic material is used as the light-emitting material (a luminescent organic material), either a low molecular compound or a high molecular compound may be used. Specific examples may include luminescent low-molecular compound and luminescent high-molecular compound described in Oyo Butsuri (Applied Physics), Vol. 70, No. 12, pages 1419-1425 (2001) written by Yutaka Ohmori.
As the luminescent organic material, a phosphorescent organic compound and a metal complex are preferable. Among the metal complexes, there exist ones that show phosphorescence, and such metal complexes are also preferably used. In the present exemplary embodiment, in particular, it is exceptionally desirable to use cyclometalated complexes in terms of improving light emission efficiency. As the cyclometalated complexes, complexes of Ir, Pd, Pt and the like including ligands such as 2-phenylpyridine derivatives, 7,8-benzoquinoline derivatives, 2-(2-thienyl)pyridine derivatives, 2-(1-naphthyl)pyridine derivatives, 2-phenylquinoline derivatives are provided, and iridium (Ir) complexes are especially preferred. The cyclometalated complexes may include ligands other than the ligands required to form the cyclometalated complexes. Note that the cyclometalated complexes are preferable in terms of improving light emission efficiency because compounds that emit light from triplet exciton are included therein.
As the high molecular compound, specific examples include; poly-p-phenylenevinylene (PPV) derivatives such as MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenykenevinylene]); polymer compounds of a n-conjugated system such as polyfluorene derivatives and polythiophene derivatives; polymers introducing low-molecular pigments and tetraphenyldiamine or triphenylamine to a main chain or a side chain and the like. The light-emitting polymer compounds and light-emitting low-molecular compounds can be used in combination.
The light-emitting layer includes the light-emitting material and a host material, and the light-emitting material is dispersed in the host material in some cases. It is preferable that the host material has charge transporting properties, and it is also preferable that the host material is a hole-transporting compound or an electron-transporting compound.
In the present exemplary embodiment, the light-emitting portion 17 may include a hole-transporting layer to receive a hole from the anode layer and transport the hole to the light-emitting layer. As the hole-transporting materials for forming the hole-transporting layer, publicly known materials can be used. Specific examples thereof include low molecular triphenylamine derivatives such as: TPD (N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′ diamine); α-NPD (4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl); and m-MTDATA (4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine). In addition, examples also include: polyvinylcarbazole; and triphenylamine derivative-based high-molecular compound polymerized by introducing a polymerizable functional group. The above hole-transporting materials may be used solely or by mixing two or more, and may be used by laminating different hole-transporting materials.
To mediate a hole injection barrier, a hole injection layer may be provided between the above hole-transporting layer and the anode layer 12. As a material for forming the hole injection layer, publicly known materials such as copper phthalocyanine, a mixture of poly-ethylendioxythiophene (PEDOT) and polystyrene sulfonate (PSS) (PEDOT:PSS), fluorocarbon and silicon dioxide may be used, and a mixture of the hole-transporting materials used for the above hole-transporting layer and electron acceptors such as 2,3,5,6-tetrafluorotetracyano-1,4-benzoquinodimethane (F4TCNQ) may be used.
Further, in the present exemplary embodiment, the light-emitting portion 17 may include an electron transporting layer for transporting an electron from the cathode layer 14 to the light-emitting layer. The material which can be used for the electron transporting layer includes; quinolinic derivatives, oxiadiazole derivatives, perylene derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro displacement fluorene derivatives or the like. More specifically, tris(8-quinolinolato) aluminium (abbreviated expression: Alq), bis[2-(2-hydroxyphenyl)benzothiazolato]zinc, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazol can be used.
Moreover, for the purpose of suppressing holes from passing through the light-emitting layer and efficiently recombining holes and electrons in the light-emitting layer, a hole-block layer may be provided between the above electron transporting layer and the light-emitting layer. In order to form the above hole-block layer, publicly known materials such as a triazine derivative, an oxadiazole derivative, a phenanthroline derivative or the like may be used. This hole-block layer may be considered as one of layers included in the light-emitting portion 17.
The thickness of each layer configuring the light-emitting portion 17 can be arbitrarily selected considering charge mobility, charge injection balance, interruption of emitted light and the like, therefore it is not generally limited. In the present exemplary embodiment, the thickness is preferably in the range of 1 nm to 1 μm, more preferably 2 nm to 500 nm, further preferably 5 nm to 200 nm. Moreover, the thickness of the light-emitting portion 17 summed up with thickness of each layer is, between the anode layer 12 and the cathode layer 14, preferably in the range of 30 nm to 1 μm, more preferably 50 nm to 500 nm.
To lower the barrier for the electron injection from the cathode layer 14 into the light-emitting portion 17 and thereby to increase the electron injection efficiency, a cathode buffer layer may be provided adjacent to the cathode layer 14. The cathode buffer layer is required to have a lower work function than the cathode layer 14. Metal materials are preferably used for forming the cathode buffer layer. Specifically, for example, the material thereof includes alkali metals (Na, K, Rb and Cs), magnesium (Mg), alkaline earth metals (Ca, Sr and Ba), rare earth metals (Pr, Sm, Eu and Yb), one selected from fluoride, chloride and oxide of these metals and mixture of two or more selected therefrom. The thickness of the cathode buffer layer is preferably in the range of 0.05 nm to 50 nm, more preferably 0.1 nm to 20 nm, and still more preferably 0.5 nm to 10 nm.
For the light-emitting device 10 in the present exemplary embodiment, the inorganic material can be used as the light-emitting body as described above. An electroluminescent element using the inorganic material can be considered as an inorganic electroluminescent element. As the inorganic material, for example, an inorganic phosphor is exemplified. The specific example of the inorganic phosphor and the configuration and manufacturing method of the electroluminescent element is exemplified by the ones described in the Japanese Patent Application Laid-Open Publication No. 2008-251531.
The anode electrode terminal 15 is electrically connected to the anode layer 12, thereby connects the anode layer 12 to a power supply (not shown in the figure). In the present exemplary embodiment, the anode electrode terminal 15 is connected to the anode layer 12 as a first electrode layer that shows higher property in sheet resistance compared to the cathode layer 14 as second electrode layer.
Next, a method of manufacturing a light-emitting device 10 will be explained with reference to the drawings.
First, as shown in
Next, the concave portions 16 are formed with a method using a photolithography (a concave portion forming process).
First, as shown in
Thereafter, as shown in
Here, for example, by performing a same magnification exposure such as a contact exposure or proximity exposure and the like, the pattern of the concave portions 16 having the same magnification with the mask pattern of the resist layer 71 is formed. Moreover, for example, by performing a reduced magnification exposure such as a projection exposure and the like, the pattern of the concave portions 16 having the reduced magnification with respect to the mask pattern of the resist layer 71 (reduced pattern) is formed.
In the present exemplary embodiment, the exposure is performed to a certain region of the resist layer 71 by using a photomask of a pattern (basic pattern) having been formed in advance. Further, a reduced magnification exposure is performed by using the same photomask, then the pattern (reduced pattern) corresponding to the plural concave portions 16 is formed on the whole surface of the light-emitting region. With this method, the pattern corresponding to a desired light-emitting device can be easily formed, which is preferable in productivity.
As described above, in the manufacturing method to which the present exemplary embodiment is applied, in the light-emitting device 10, when forming the pattern of the concave portions 16 at a region relatively far from the anode electrode terminal 15, the mask pattern (basic pattern) of the photomask used in forming the pattern at a region near the anode electrode terminal 15 is used by reducing (reduced pattern). Thereby, the patterning with high edge density can be easily performed. Moreover, the area occupied with the shapes of the concave portions 16 per unit area becomes the same at an arbitrary portion in the light-emitting region.
Then, as shown in
Subsequently, as shown in
Next, as shown in
Note that, by controlling etching conditions (a process time, gases to be used, pressure, and a substrate temperature) in performing the etching, the plural layers having been formed on the substrate 11 can be removed at the same time so that the concave portions 16 are in a state of being passed through. For example, it is possible that the resist layer 71 and the dielectric layer 13 are removed at the same time, or the resist layer 71, the dielectric layer 13 and the anode layer 12 are removed at the same time.
Next, as shown in
Next, as shown in
By the aforementioned processes, the light-emitting device 10 can be manufactured. In the present exemplary embodiment, a protective layer or a protective cover (not shown in the figure) for stably using the light-emitting device 10 for long periods and protecting the light-emitting device 10 from outside may be mounted. As the protective layer, polymer compounds, metal oxides, metal fluorides, metal borides, silicon nitrides and silicon oxides may be used. A lamination thereof may also be used.
As the protective cover, glass plates, plastic plates with a surface treated with low hydraulic permeability, or metals may be used. The protective cover may be bonded to the substrate 11 by using a thermosetting resin or a photo-curable resin to be sealed. At this time, spacers may be used so that predetermined spaces are maintained, thus the prevention of scratches on the light-emitting device 10 is facilitated. Filling the spaces with inert gases such as nitrogen, argon and helium prevents the oxidation of the cathode layer 14 on the upper side. Especially, in a case of using helium, high thermal conductivity thereof enables heat generated from the light-emitting device 10 upon application of voltage to be effectively transmitted to the protective cover. In addition, by putting desiccants such as barium oxide in the spaces, the light-emitting device 10 is easily prevented from being damaged by moisture absorbed in the sequence of the aforementioned manufacturing processes.
In the present exemplary embodiment, the case where an organic light-emitting element is used as a light source is explained as a specific example, however, the light-emitting element may be manufactured by replacing the light source with another one with the same size.
In a light-emitting device 20 shown in
Specific explanation on each configuration above in the light-emitting device 20 is the same as that on each configuration corresponding to the light-emitting device 10 (refer to
In the light-emitting device 20, a cathode electrode terminal 25 as a terminal which is electrically connected to the cathode layer 24 and connects the cathode layer 24 to a power supply (not shown in the figure) is formed outside of the light-emitting region. That is, the light-emitting device 20 is different from the light-emitting device 10 in the point that a sheet resistance of the cathode layer 24 as the second electrode layer is larger than that of the anode layer 22 as the first electrode layer and that the terminal in the light-emitting device 20 is the cathode terminal that connects the cathode layer 24 as the second electrode layer to a power supply. As a specific example of the light-emitting device 20, a light-emitting device in which the anode layer 22 is composed of a opaque metal film, the cathode layer 24 is a conductive film composed of metal oxide such as ITO, and the light emitted from the light-emitting portion 27 is extracted from the cathode layer 24 side is exemplified. As described above, when the film thickness is similar, the sheet resistance of ITO film is usually larger than that of metal film.
In the light-emitting device 20, a first electrode layer formed to contact the substrate 21 is the anode layer 22, and a second electrode layer formed above the light-emitting portion 27 is the cathode layer 24, however, the anode layer 22 and the cathode layer 24 may be reversed each other. Moreover, the direction of extracting the light emitted from the light-emitting portion 27 to the outside of the light-emitting device 20 may be toward the anode layer 22 side or the cathode layer 24 side, and toward both the anode layer 22 side and the cathode layer 24 side.
Hereinafter, the present invention will be described further in detail with reference to examples. However, the present invention is not limited to the following examples as long as the scope of the gist thereof is not exceeded.
A phosphorescent light-emitting polymer compound (A) was prepared in accordance with the method disclosed in the paragraph [0077] of International Publication No. WO2010-016512. The weight-average molecular weight of polymer compound (A) was 52000, and molar ratio of each repeating unit was k:m:n=6:42:52.
A light-emitting material solution (hereinafter, also referred to as “solution A”) was prepared by dissolving 3 parts by weight of the light-emitting polymer compound prepared (A) in 97 parts by weight of toluene.
A light-emitting device 1 having the similar cross-sectional shape as shown in
A glass substrate (=the substrate 11: 110 mm square, 1 mm in thickness) in which ITO film (=the anode layer 12: 150 nm in thickness, sheet resistance 10Ω per square) with a pattern that corresponds to the light-emitting region of 100 mm square was formed on the surface thereof was performed an ultrasonic cleaning in the order of surface acting agent, pure water and isopropanol. The glass substrate with ITO after cleaning was mounted to the inside of a plasma generation device, and oxygen plasma was irradiated for 5 seconds in the condition that the pressure in the device was 1 Pa and the supplied power was 50 W. Note that, the anode electrode terminal 15 (refer to
Next, the glass substrate with ITO was placed in a sputtering device, and a silicon dioxide layer (SiO2) in film thickness of 50 nm (=the dielectric layer 13) was formed on a whole light-emitting region by sputtering method.
Subsequently, a photoresist (AZ1500 manufactured by AZ Electronic Materials) of about 1 μm in film thickness was formed by a spin coating method, thereby the resist layer 71 (refer to
Next, on a quartz (having a thickness of 3 mm) as a substrate, a mask A corresponding to a pattern in which circles are arranged in a cubic lattice was produced, and exposure was performed with respect to the region p with 20 mm width from the anode electrode terminal 15 of the light-emitting region, in a reduction ratio of 10/50 by use of a stepper exposure device. Then, exposure was performed with respect to the region q with 20 mm width adjacent to the exposed region p in a reduction ratio of 9/50, then exposure was performed with respect to the region r with 20 mm width adjacent to the exposed region q in a reduction ratio of 8/50, then exposure was performed with respect to the region s with 20 mm width adjacent to the exposed region r in a reduction ratio of 7/50, then exposure was performed with respect to the region t with 20 mm width adjacent to the exposed region s in a reduction ratio of 6/50, thereby a whole region of 100 mm square was exposed. Subsequently, development was executed with 1.2 mass % aqueous solution of TMAH (tetramethyl ammonium hydroxide: (CH3)4NOH) for patterning the resist layer 71. Thereafter, heat at a temperature of 130° C. was applied for 10 minutes.
Next, by use of a reactive ion etching device (RIE-200iP manufactured by SAMCO Inc.), dry etching process was performed for patterning the SiO2 layer. As an etching condition, trifluoromethane (CHF3) was used as a reactant gas, and the reaction was executed for 16 minutes under conditions of a pressure of 0.3 Pa and output bias/ICP=60/100 (W).
Then, by removing the residue of the resist by the resist removing solution, patterning of the ITO film was performed by dry etching with the above reactive ion etching device. Here, as an etching condition, a mixed gas of Chlorine (Cl2) and silicon tetrachloride (SiCl4) was used as a reactant gas, and the reaction was executed for 7 minutes under conditions of a pressure of 1 Pa and output bias/ICP=180/100 (W).
Subsequently, the reactant gas was replaced with CHF3 gas, and the reaction was executed for 20 minutes under conditions of a pressure of 0.3 Pa and output bias/ICP=120/100 (W) as an etching condition.
Next, the SiO2 layer was cleaned by showering pure water thereto, then dried by use of a spin dry device.
As a result, the plural concave portions 16p with 2 μm diameter were formed in the region p with 20 mm width adjacent to the anode electrode terminal 15, the plural concave portions 16q with 1.8 μm diameter were formed in the region q with 20 mm width adjacent to the region p, the plural concave portions 16r with 1.6 μm diameter were formed in the region r with 20 mm width adjacent to the region q, the plural concave portions 16s with 1.4 μm diameter were formed in the region s with 20 mm width adjacent to the region r, and the plural concave portions 16t with 1.2 μm diameter were formed in the region t with 20 mm width adjacent to the region s, and the depth of the concave portions 16p to 16t was all 170 nm (among this, the SiO2 layer was etched by 30 nm at the time of etching).
Values regarding the plural concave portions 16p to 16t in the regions p to t of the light-emitting device 1 are shown in Table 1.
As shown in Table 1, in the light-emitting device 1, the plural concave portions (the concave portions 16p to 16t) are formed so that the edge density of the concave portions (mm/mm2) are increased gradually from the region p near the anode electrode terminal 15 to the region t far from the anode electrode terminal 15. On the other hand, the occupation ratio (%) of the concave portions is shown to be equal in each region. Note that, the occupation ratio (%) of the concave portions in each region p to t is a proportion with respect to the whole area of each region p to t.
Next, on the electrode substrate in which the above concave portions 16p to 16t were formed, the solution A was applied by the spin coating method (spin rate: 3000 rpm) and was left under a nitrogen atmosphere at the temperature of 140° C. for an hour to be dried, thereby the light-emitting portion 17 was formed. Thereafter, on the light-emitting portion 17, a sodium fluoride layer (thickness of 4 nm) as the cathode buffer layer and an aluminum layer (thickness of 130 nm, sheet resistance of 0.5Ω per square) as the cathode layer 14 were formed in order by a deposition method (not shown in the figure), thereby the light-emitting device 1 was produced.
When voltage was applied to the light-emitting device 1 produced as described above and light was emitted near the anode electrode terminal 15 with brightness of 100 cd/m2, brightness was 100 cd/m2 also at the region relatively far from the anode electrode terminal 15 and unevenness in brightness could not be visually recognized.
In accordance with the following operation, a light-emitting device 2 having a similar cross-sectional shape with
By the similar operation with Example 1, after forming a silicon dioxide (SiO2) layer on a glass substrate with ITO, the silicon dioxide layer and ITO film were patterned and dried by a spin dry device.
Next, the glass substrate with ITO was mounted to a reactive ion etching device (RIE-200iP manufactured by SAMCO Inc.). Thereafter, AC voltage was applied to the oxygen gas introduced in the device to discharge an electrical current, and the generated oxygen plasma was irradiated to the glass substrate. Here, an amount of oxygen gas flowed into the device was adjusted, and the reaction was executed for 30 seconds under conditions of a pressure of 1 Pa and an applied electrical power of 150 W. Then, the gas to be introduced was replaced with the CHF3 gas. Here, an amount of the flowed gas was adjusted, and the pressure was set to be 7 Pa. Further, the reaction was executed for 10 seconds under conditions of a PE mode and an applied electrical power of 300 W.
As a result, the plural concave portions 16 with 2 μm diameter were formed in a region 1 with 20 mm width adjacent to the anode electrode terminal 15, the plural concave portions 16 with 1.8 μm diameter were formed in a region 2 with 20 mm width adjacent to the region 1, the plural concave portions 16 with 1.6 μm diameter were formed in a region 3 with 20 mm width adjacent to the region 2, the plural concave portions 16 with 1.4 μm diameter were formed in a region 4 with 20 mm width adjacent to the region 3, and the plural concave portions 16 with 1.2 μm diameter were formed in a region 5 with 20 mm width adjacent to the region 4, and the depth of the concave portions 16 was 200 nm (among this, the depth of a bored part 16b was 30 nm, and the SiO2 layer was etched by 30 nm at the time of etching). Note that the distribution of the plural concave portions 16 in the light-emitting device 2 (not shown in the figure) is same as that of the light-emitting device 1 produced in Example 1 (refer to
Thereafter, by the same operation with that in Example 1, the light-emitting portion 17, the cathode buffer layer and the cathode layer 14 were formed in order (not shown in the figure), thereby the light-emitting device 2 was produced.
When voltage was applied to the light-emitting device 2 produced as described above and light was emitted near the anode electrode terminal 15 with brightness of 100 cd/m2, brightness was 100 cd/m2 also at the other side and unevenness in brightness could not be visually recognized.
In accordance with the following operation, a light-emitting device 3 having a similar cross-sectional shape with
By use of the same mask A used in producing the light-emitting device 1, plural concave portions 16u with a circular shape were formed in a region u with 33 mm width from the anode electrode terminal 15 in a reduction ratio of 1/5 of the mask A by use of a stepper exposure device. Thereafter, in a region v with 33 mm width adjacent to this region u, plural concave portions 16v were formed with a mask B that is different from the mask A. The mask B has a quartz (having a thickness of 3 mm) as a substrate, and corresponds to a pattern in which depressed dodecagonal shape was arranged in a square lattice. In the depressed dodecagonal shape, the edge length is 1.25 times of that in the circular shape with the same width. By use of a stepper exposure device, the plural concave portions 16v with a depressed dodecagonal shape were formed in the region v in a reduction ratio of 1/5 of the mask B.
Subsequently, in a region w with 33 m width adjacent to the region v, the plural concave portions 16w was formed by use of a mask C that is different from the mask B. The mask C has a quartz (having a thickness of 3 mm) as a substrate, and corresponds to a pattern in which depressed dodecagonal shape was arranged in a square lattice. In the depressed dodecagonal shape, the edge length is 1.50 times of that in the circular shape with the same width. By use of a stepper exposure device, the plural concave portions 16w with a depressed dodecagonal shape were formed in the region w in a reduction ratio of 1/5 of the mask C.
Values regarding the plural concave portions 16u to 16w in the regions u to w of the light-emitting device 3 are shown in Table 2.
As shown in Table 2, in the light-emitting device 3, the plural concave portions (the concave portions 16u to 16w) are formed so that the edge density of the concave portions (mm/mm2) are increased gradually from the region u near the anode electrode terminal 15 to the region w far from the anode electrode terminal 15. On the other hand, the occupation ratio (%) of the concave portions is gradually decreased.
Thereafter, by the same operation with that in Example 1, the light-emitting portion 17, the cathode buffer layer and the cathode layer 14 were formed in order (not shown in the figure), thereby the light-emitting device 3 was produced.
When voltage was applied to the light-emitting device 3 produced as described above and light was emitted near the anode electrode terminal 15 with brightness of 100 cd/m2, brightness was 90 cd/m2 at the other side and unevenness in brightness was visually in a small range. The maximum brightness was 105 cd/m2, and the difference from the minimum brightness was 15 cd/m2.
By the same operation with that in Example 1, after forming the SiO2 layer on the glass substrate with ITO, a photoresist layer was formed on the SiO2 layer. Next, by use of the same mask A as in Example 1, exposure was repeatedly performed to a region of 10 mm square in a reduction ratio of 1/5 of the mask A by a stepper exposure device, thereby whole of the light-emitting region was exposed. Thereafter, by the same operation with that in Example 1, the light-emitting portion 17, the cathode buffer layer and the cathode layer 14 were formed in order (not shown in the figure), thereby the light-emitting device 4 was produced.
When voltage was applied to the light-emitting device 4 produced as described above and light was emitted near the anode electrode terminal 15 with brightness of 100 cd/m2, brightness was 60 cd/m2 at the other side and unevenness in brightness was visually recognized.
By the same operation with that in Example 1, a light-emitting device 5 having a similar cross-sectional shale as that of
Note that, the concave portions 16α to 16∈ were all formed to have a depth of 170 nm (the SiO2 layer was etched by 30 nm at the time of etching). Further, by the same operation with that in Example 1, the light-emitting portion 17, the cathode buffer layer and the cathode layer 14 were formed in order (not shown in the figure).
When voltage was applied to the light-emitting device 5 produced as described above and light was emitted near the anode electrode terminal 15 with brightness of 100 cd/m2, brightness was 10 cd/m2 at the other side and unevenness in brightness was visually recognized. Values regarding the plural concave portions 16α to 16∈ in the regions α to ∈ of the light-emitting device 5 are shown in Table 3.
As shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-245831 | Nov 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2012/078489 | 11/2/2012 | WO | 00 |
