# Patent

## Title
Illumination device and method for manufacturing same

## Abstract

According to one embodiment, an illumination device includes an organic light-emitting unit, a first electrode, a second electrode and an optical layer. The organic light-emitting unit includes an organic light-emitting layer, a first and a second major surface. The first electrode is provided on the first major surface. The second electrode is provided on the second major surface and includes a conductive layer, a first interconnection and a second interconnection. The first interconnection is electrically connected to the conductive layer and aligned in a first direction parallel to the first major surface. The second interconnection is electrically connected to the conductive layer and aligned apart from the first interconnection and parallel to the first interconnection. The optical layer is provided on a side of the second electrode opposite to the organic light-emitting unit and includes a low refractive index portion and a high refractive index portion.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-045673, filed on Mar. 2, 2010; the entire contents of which are incorporated herein by reference.
FIELD
Embodiments described herein relate generally to an illumination device and a method for manufacturing the same.
BACKGROUND
The practical use of organic light emitting devices in display devices, light sources, illumination, etc., is being studied. In an organic electroluminescent element, an organic thin film is provided between a cathode and an anode; a voltage is applied between the cathode and the anode; excitons are created; and the light emitted when the excitons undergo radiative deactivation is utilized. Materials having relatively low conductivities such as, for example, ITO (Indium Tin Oxide) are used as the anode.
In the case where an organic electroluminescent element is applied in large surface-area illumination and the like, problems are expected because the conductivity of the anode is low, a voltage drop may occur in the plane, and the brightness may become nonuniform.
Moreover, to increase the luminous efficacy, it is important to efficiently extract the light emitted in the organic light-emitting layer.
JP-A 2006-156400 (Kokai) discusses technology to increase the outcoupling efficiency of an organic electroluminescent element by providing a diffraction grating layer. However, in such a method, it is necessary to form a fine diffraction grating. Therefore, it is difficult to practically apply such a method in an illumination device having a large surface area.
Special technology is necessary to increase the outcoupling efficiency while suppressing the voltage drop in the plane to practically use an organic electroluminescent element in an illumination device having a large surface area.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A and FIG. 1B are schematic views illustrating the configuration of an illumination device according to a first embodiment;
FIG. 2A and FIG. 2B are schematic views illustrating the configuration of the illumination device according to the first embodiment;
FIG. 3 is a schematic view illustrating operations of the illumination device according to the first embodiment;
FIG. 4A and FIG. 4B are schematic views illustrating the configuration of another illumination device according to the first embodiment;
FIG. 5A and FIG. 5B are schematic views illustrating the configuration of the another illumination device according to the first embodiment;
FIG. 6A to FIG. 6G are schematic cross-sectional views in order of the processes, illustrating a method for manufacturing the illumination devices according to the first embodiment;
FIG. 7A to FIG. 7G are schematic cross-sectional views in order of the processes, illustrating another method for manufacturing the illumination devices according to the first embodiment;
FIG. 8A to FIG. 8C are schematic views illustrating the configuration of an illumination device according to a second embodiment;
FIG. 9A to FIG. 9C are schematic views illustrating the configuration of another illumination device according to the second embodiment;
FIG. 10A to FIG. 10C are schematic views illustrating the configuration of still another illumination device according to the second embodiment; and
FIG. 11 is a flowchart illustrating a method for manufacturing an illumination device according to a third embodiment.



DETAILED DESCRIPTION
In general, according to one embodiment, an illumination device includes an organic light-emitting unit, a first electrode, a second electrode and an optical layer. The organic light-emitting unit includes an organic light-emitting layer, a first major surface, and a second major surface. The first electrode is provided on the first major surface of the organic light-emitting unit. The second electrode is provided on the second major surface of the organic light-emitting unit. The second electrode includes a conductive layer, a first interconnection and a second interconnection. The first interconnection is electrically connected to the conductive layer and aligned in a first direction parallel to the first major surface, and the first interconnection has a conductivity higher than a conductivity of the conductive layer. The second interconnection is electrically connected to the conductive layer and aligned apart from the first interconnection and parallel to the first interconnection, and the second interconnection has a conductivity higher than the conductivity of the conductive layer. The optical layer is provided on a side of the second electrode opposite to the organic light-emitting unit. The optical layer includes a low refractive index portion and a high refractive index portion. The low refractive index portion has a portion overlapping at least one selected from the first interconnection and the second interconnection as viewed from a direction perpendicular to the first major surface. The high refractive index portion has a portion contacting the portion of the low refractive index portion, the high refractive index portion having a refractive index higher than a refractive index of the low refractive index portion.
According to another embodiment, a method for manufacturing an illumination device is disclosed. The device includes an organic light-emitting unit, a first electrode, a second electrode and an optical layer. The organic light-emitting unit includes an organic light-emitting layer, a first major surface, and a second major surface. The first electrode is provided on the first major surface of the organic light-emitting unit. The second electrode is provided on the second major surface of the organic light-emitting unit. The second electrode includes a conductive layer, a first interconnection and a second interconnection. The first interconnection is electrically connected to the conductive layer and aligned in a first direction parallel to the first major surface, and the first interconnection has a conductivity higher than a conductivity of the conductive layer. The second interconnection is electrically connected to the conductive layer and aligned apart from the first interconnection and parallel to the first interconnection, and the second interconnection has a conductivity higher than the conductivity of the conductive layer. The optical layer is provided on a side of the second electrode opposite to the organic light-emitting unit. The optical layer includes a low refractive index portion and a high refractive index portion. The low refractive index portion has a portion overlapping at least one selected from the first interconnection and the second interconnection as viewed from a direction perpendicular to the first major surface. The high refractive index portion has a portion contacting the portion of the low refractive index portion, the high refractive index portion having a refractive index higher than a refractive index of the low refractive index portion. The method can include forming a low refractive index film used to form the low refractive index portion on a major surface of a substrate. The method can include forming a high conductivity film used to form the first interconnection and the second interconnection on the low refractive index film. The method can include patterning the low refractive index film and the high conductivity film to form the low refractive index portion, the first interconnection, and the second interconnection. The method can include forming the high refractive index portion on the major surface of the substrate exposed between the low refractive index portion, the first interconnection, and the second interconnection. The method can include forming the conductive layer to cover the low refractive index portion, the first interconnection, the second interconnection, and the high refractive index portion. The method can include forming a photosensitive insulating film on the conductive layer. The method can include forming an insulating layer made of the insulating film and having a patterned configuration conforming to a patterned configuration of the first interconnection and the second interconnection by using the first interconnection and the second interconnection as a mask to irradiate light onto the insulating film through the substrate and by developing. The method can include forming the organic light-emitting unit on the insulating layer and the conductive layer. In addition, the method can include forming the first electrode on the organic light-emitting unit.
Exemplary embodiments of the invention will now be described in detail with reference to the drawings.
The drawings are schematic or conceptual; and the relationships between the configuration and width of portions, the proportions of sizes among portions, etc., are not necessarily the same as the actual values thereof. Further, the dimensions and proportions may be illustrated differently among drawings, even for identical portions.
In the specification and drawings of the application, components similar to those described in regard to a drawing thereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate.
First Embodiment
FIG. 1A and FIG. 1B are schematic views illustrating the configuration of an illumination device according to a first embodiment of the invention.
FIG. 2A and FIG. 2B are schematic views illustrating the configuration of the illumination device according to the first embodiment of the invention.
Namely, FIG. 1A is a cross-sectional view along line A1-A2 of FIG. 1B, FIG. 2A, and FIG. 2B; FIG. 1B is a cross-sectional view along line B1-B2 of FIG. 1A; FIG. 2A is a cross-sectional view along line C1-C2 of FIG. 1A; and FIG. 2B is a cross-sectional view along line D1-D2 of FIG. 1A.
As illustrated in FIGS. 1A and 1B and FIGS. 2A and 2B, the illumination device 110 according to this embodiment includes: an organic light-emitting unit 30 including an organic light-emitting layer, a first major surface 30a, and a second major surface 30b; a first electrode 10 provided on the first major surface 30a of the organic light-emitting unit 30; a second electrode 20 provided on the second major surface 30b of the organic light-emitting unit 30; and an optical layer 40 provided on the side of the second electrode 20 opposite to the organic light-emitting unit 30. In other words, the organic light-emitting unit 30 is provided between the first electrode 10 and the second electrode 20.
The organic light-emitting layer of the organic light-emitting unit 30 may include, for example, Alq3 (tris(8-hydroxyquinolinato)aluminum), and the like. However, this embodiment is not limited thereto. The organic light-emitting layer may include any material. In addition to the organic light-emitting layer, the organic light-emitting unit 30 may further include various organic films such as charge transport organic films and charge injection layers.
The first electrode 10 may include, for example, Al, Ag, and alloys of Mg:Ag, etc. However, the embodiments of the invention are not limited thereto. The first electrode 10 may include any conductive material.
Herein, a direction perpendicular to the first major surface 30a is taken as a Z-axis direction. The Z-axis direction is the stacking direction of the first electrode 10, the organic light-emitting unit 30, and the second electrode 20. For example, the direction from the second electrode 20 toward the first electrode 10 is the Z-axis direction. One direction perpendicular to the Z-axis direction is taken as an X-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is taken as a Y-axis direction. The X-axis direction is taken to be a first direction; and the Y-axis direction is taken to be a second direction.
The second electrode 20 includes a conductive layer 20b, a first interconnection 21, and a second interconnection 22.
The conductive layer 20b opposes the first electrode 10 along the Z-axis direction with the organic light-emitting unit 30 interposed therebetween. The conductive layer 20b is parallel to the first major surface 30a. 
The first interconnection 21 is electrically connected to the conductive layer 20b. The first interconnection 21 is aligned in the first direction (the X-axis direction) parallel to the first major surface 30a. The conductivity of the first interconnection 21 is higher than the conductivity of the conductive layer 20b. 
The second interconnection 22 is electrically connected to the conductive layer 20b. The second interconnection 22 is aligned apart from the first interconnection 21 and parallel to the first interconnection 21. The conductivity of the second interconnection 22 is higher than the conductivity of the conductive layer 20b. The second interconnection 22 is adjacent to the first interconnection 21 along the Y-axis direction.
In this specific example, the first interconnection 21 and the second interconnection 22 are provided on the side of the conductive layer 20b opposite to the organic light-emitting unit 30.
The conductive layer 20b may include, for example, ITO; and the first interconnection 21 and the second interconnection 22 may include, for example, a metal such as Al and Cu. This embodiment is not limited thereto. It is sufficient for the conductivities of the first interconnection 21 and the second interconnection 22 to be higher than the conductivity of the conductive layer 20b. 
The conductive layer 20b is transparent to light emitted from the organic light-emitting unit 30.
The transmittances of the first interconnection 21 and the second interconnection 22 with respect to the light emitted from the organic light-emitting unit 30 are lower than the transmittance of the conductive layer 20b with respect to the light. The first interconnection 21 and the second interconnection 22 are light-shielding with respect to the light recited above. The first interconnection 21 and the second interconnection 22 are reflective with respect to the light recited above.
The optical layer 40 includes a low refractive index portion 40a and a high refractive index portion 40b. 
The low refractive index portion 40a has a portion overlapping at least one selected from the first interconnection 21 and the second interconnection 22 as viewed from the Z-axis direction (the direction perpendicular to the first major surface 30a). In other words, the low refractive index portion 40a has a portion opposing the at least one selected from the first interconnection 21 and the second interconnection 22 along the Z-axis direction. In this specific example, the low refractive index portion 40a includes a first portion 41 opposing the first interconnection 21 and a second portion 42 opposing the second interconnection 22.
The high refractive index portion 40b has a portion contacting the portion of the low refractive index portion 40a recited above (the portion recited above overlapping the at least one selected from the first interconnection 21 and the second interconnection 22 as viewed from the Z-axis direction). The refractive index of the high refractive index portion 40b is higher than the refractive index of the low refractive index portion 40a. For example, at least a portion of the high refractive index portion 40b contacts at least a portion of the low refractive index portion 40a along the Y-axis direction.
Silicon oxide, for example, may be used as the low refractive index portion 40a. In such a case, the refractive index is, for example, about 1.4. Polyimide, for example, may be used as the high refractive index portion 40b. In such a case, the refractive index is about 1.7.
As illustrated in FIG. 1A and FIG. 1B, the second electrode 20 may include other interconnections similar to the first interconnection 21 and the second interconnection 22.
In other words, the second electrode 20 may include the conductive layer 20b and multiple interconnections 20a aligned in the X-axis direction and electrically connected to the conductive layer 20b, where the conductivities of the interconnections 20a are higher than the conductivity of the conductive layer 20b. The number of the interconnections 20a may be an arbitrary number of 2 or more. In other words, the second electrode 20 may include the multiple interconnections 20a having band configurations aligned in the X-axis direction.
The pitch between such multiple interconnections 20a is arbitrary and may have equal spacing or may be changed, for example, between the end portions and the central portion of the illumination device 110.
Hereinbelow, the case is described where the pitches between the multiple interconnections 20a are substantially equal to each other.
In this specific example as illustrated in FIG. 2A, the low refractive index portion 40a is provided in the regions where the first interconnection 21 and the second interconnection 22 are provided as viewed from the direction perpendicular to the first major surface 30a. In other words, the low refractive index portion 40a is provided along the regions where the first interconnection 21 and the second interconnection 22 are provided as viewed from the direction perpendicular to the first major surface 30a. The low refractive index portion 40a has substantially the same pattern (the pattern in the X-Y plane as viewed from the direction perpendicular to the first major surface 30a) as the interconnection 20a (the first interconnection 21 and the second interconnection 22).
The first portion 41 and the second portion 42 of the low refractive index portion 40a are aligned in the first direction.
The high refractive index portion 40b is adjacent along the second direction to the portion of the low refractive index portion 40a recited above (e.g., the first portion 41 and the second portion 42) and contacts the portion recited above along the second direction.
In other words, the high refractive index portion 40b is provided in portions where the low refractive index portion 40a is not provided. In other words, the high refractive index portion 40b is provided in regions where the interconnection 20a (the first interconnection 21 and the second interconnection 22) is not provided. Thus, it is advantageous for the pattern of the low refractive index portion 40a to substantially match the pattern of the interconnection 20a because, as described below, the low refractive index portion 40a and the interconnection 20a can be formed collectively; and the production efficiency increases.
However, this embodiment is not limited thereto. It is sufficient for the low refractive index portion 40a to have a portion overlapping the interconnection 20a (at least one selected from the first interconnection 21 and the second interconnection 22) as viewed from the Z-axis direction and for the high refractive index portion 40b to have a portion contacting the low refractive index portion 40a. 
Hereinbelow, the case is described where the low refractive index portion 40a has substantially the same pattern (the pattern in the X-Y plane) as the interconnection 20a (the first interconnection 21 and the second interconnection 22) and the high refractive index portion 40b is provided in the regions where the interconnection 20a (the first interconnection 21 and the second interconnection 22) is not provided.
As illustrated in FIG. 2B, an insulating layer 50 is provided in a region opposing the interconnection 20a along the Z-axis direction. The insulating layer 50 is provided between the organic light-emitting unit 30 and the second electrode 20 (in this case, the conductive layer 20b). In other words, the illumination device 110 further includes the insulating layer 50 provided between the second electrode 20 and the organic light-emitting unit 30, where the insulating layer 50 has a portion overlapping at least one selected from the first interconnection 21 and the second interconnection 22 as viewed from the direction perpendicular to the first major surface 30a. The insulating layer 50 may be provided as necessary and may be omitted.
As illustrated in FIG. 1A, a substrate 60 is provided on the side of the optical layer 40 opposite to the second electrode 20. The substrate 60 may include a material transparent to the light emitted from the organic light-emitting unit 30. A glass substrate, for example, may be used as the substrate 60. The substrate 60 may be provided as necessary and may be omitted. The substrate 60 may be provided on the side of the first electrode 10 opposite to the organic light-emitting unit 30. In such a case, the substrate 60 may be transparent or light-shielding.
Thus, in the illumination device 110 according to this embodiment, a voltage drop in the plane of the second electrode 20 can be suppressed by adding the interconnection 20a having a high conductivity to electrically connect to the conductive layer 20b made of ITO, etc., having a relatively low conductivity. Thereby, the electric field applied to the organic light-emitting unit 30 is uniform in the plane; and light emission uniform in the plane can be obtained.
Further, the transparency of the interconnection 20a (e.g., the first interconnection 21 and the second interconnection 22) having the high conductivity is lower than the transparency of the conductive layer 20b. Specifically, the interconnection 20a is reflective; and the low refractive index portion 40a is provided in the region where the interconnection 20a is provided. Therefore, outcoupling efficiency increases.
In other words, an object of this embodiment is to solve the problems that newly occur when putting an illumination device using an organic electroluminescent element having a large surface area into practical use, that is, to suppress the voltage drop in the plane and increase the outcoupling efficiency. Such problems can be solved by applying the combination of the conductive layer 20b and the interconnection 20a having the conductivity higher than that of the conductive layer 20b and further applying the combination of the high refractive index portion 40b and the low refractive index portion 40a. 
FIG. 3 is a schematic view illustrating operations of the illumination device according to the first embodiment of the invention.
As illustrated in FIG. 3, an electric field is applied to the organic light-emitting unit 30 when a voltage is applied between the first electrode 10 and the second electrode 20. The electric field causes the organic light-emitting unit 30 to emit light L1. The light L1 passes through the conductive layer 20b of the second electrode 20, enters the high refractive index portion 40b of the optical layer 40, and travels through the high refractive index portion 40b. Light L2, i.e., a portion of the light L1, is emitted to the external environment from the high refractive index portion 40b. In this specific example, the light L2, i.e., the portion of the light L1, is emitted to the external environment from the high refractive index portion 40b through the substrate 60.
Light L3, i.e., one other portion of the light L1, is reflected by the face of the high refractive index portion 40b on the side opposite to the second electrode 20 (in this specific example, an interface IF2 between the high refractive index portion 40b and the substrate 60) and once again travels through the interior of the high refractive index portion 40b. At this time, the low refractive index portion 40a is provided adjacent to the high refractive index portion 40b; and the light L3 enters the low refractive index portion 40a. Because the refractive index of the low refractive index portion 40a is lower than that of the high refractive index portion 40b, the angle of the optical path of the light L3 changes at an interface IF1 (corresponding to the side face of the low refractive index portion 40a) between the high refractive index portion 40b and the low refractive index portion 40a. 
In other words, an incident angle θb on the high refractive index portion 40b side and an emergence angle θa on the low refractive index portion 40a side are related by Snell's law by na·sin θa=nb·sin θb at the interface IF1, where a low refractive index na is the refractive index of the low refractive index portion 40a and a high refractive index nb is the refractive index of the high refractive index portion 40b. 
Thus, the light radiated from the organic light-emitting unit 30 (in this case, the light L3) is refracted based on the difference of the refractive index between the low refractive index portion 40a and the high refractive index portion 40b when traveling from the high refractive index portion 40b into the low refractive index portion 40a. 
Thus, the optical path of the light L3 changes at the interface IF1 (corresponding to the side face of the low refractive index portion 40a) between the high refractive index portion 40b and the low refractive index portion 40a; and the light L3 travels through the interior of the low refractive index portion 40a, is reflected by the interconnection 20a, once again passes through the low refractive index portion 40a, and is extracted to the external environment.
In the case of a comparative example in which the refractive index in the optical layer 40 is uniform (e.g., the low refractive index portion 40a is not provided and the entire optical layer 40 is the high refractive index portion 40b), the angle of the optical path of the light L3 does not change in the interior of the optical layer 40; and the light L3 undergoes multiple reflections inside the optical layer 40, is absorbed inside the optical layer 40, and is difficult to extract to the outside. Therefore, the efficiency is low in the comparative example.
Conversely, in the illumination device 110 according to this embodiment, the high refractive index portion 40b and the low refractive index portion 40a are provided in the optical layer 40. Therefore, the optical path of the light L3 changes at the interface IF1 thereof; the multiple reflections can be suppressed; and the light L3 can be easily extracted to the external environment. Thus, the efficiency is high in the illumination device 110.
Further, the low refractive index portion 40a is designed to have a portion overlapping the interconnection 20a (the first interconnection 21 and the second interconnection 22) as viewed from the Z-axis direction; and the low refractive index portion 40a opposes the interconnection 20a along the Z-axis direction. Therefore, the light L3 traveling through the low refractive index portion 40a can be efficiently reflected by the interconnection 20a; and the efficiency can be increased.
It is desirable for the refractive index of the high refractive index portion 40b to be higher than the refractive index of the organic light-emitting unit 30. Thereby, the light L1, L2, and L3 emitted in the organic light-emitting unit 30 can efficiently enter the high refractive index portion 40b from the organic light-emitting unit 30 and easily be extracted to the external environment.
Further, in this specific example, the insulating layer 50 having a portion overlapping the interconnection 20a as viewed from the Z-axis direction is provided. The insulating layer 50 opposes the interconnection 20a along the Z-axis direction. The insulating layer 50 insulates the organic light-emitting unit 30 from the portion of the conductive layer 20b opposing the interconnection 20a. Therefore, the electric field applied to the portion of the organic light-emitting unit 30 where the insulating layer 50 is provided is lower than at the other portions. As described above, the transparency of the interconnection 20a is lower than the transparency of the conductive layer 20b. Therefore, the light emitted at the portion opposing the interconnection 20a is not easily extracted to the outside. In the illumination device 110, the insulating layer 50 is provided at the portion opposing the interconnection 20a; and the emission of the light of the organic light-emitting unit 30 at the portion where it is difficult to extract the light is suppressed more than at the other portions. Therefore, the efficiency increases further.
As illustrated in FIG. 1B, a width Wa1 of the interconnection 20a along the second direction (i.e., the width of the first interconnection 21 along the Y-axis direction and the width of the second interconnection 22 along the Y-axis direction) is greater than the peak wavelength of the light emitted from the organic light-emitting unit 30. In other words, specifically, the width Wa1 is greater than 10 micrometers (μm). Thereby, the resistance of the interconnection 20a can be reduced and it is easy to obtain a uniform light emission in the plane by increasing the width Wa1 of the interconnection 20a to at least a certain amount. In the case where the width of the interconnection 20a is reduced too much, it is difficult to pattern the interconnection 20a; and the productivity may decrease.
By setting the width Wa1 of the interconnection 20a along the Y-axis direction greater than the peak wavelength of the light emitted from the organic light-emitting unit 30 and not less than 10 μm, the width of the low refractive index portion 40a provided conforming to the region where the interconnection 20a is provided can be greater than the peak wavelength of the light; the effects of the refraction recited above can be obtained; and the outcoupling efficiency increases.
Moreover, a width Wb1 of the conductive layer 20b along the Y-axis direction where the interconnection 20a is not provided is wider than the width Wa1 of the interconnection 20a along the Y-axis direction. Thereby, light can be extracted efficiently via the conductive layer 20b having the high transmittance.
For example, the pitch of the interconnection 20a along the Y-axis direction may be at least twice the width Wa1 of the interconnection 20a along the second direction. A distance Wc1 along the Y-axis direction from the center of the first interconnection 21 along the Y-axis direction to the center of the second interconnection 22 along the Y-axis direction may be at least twice the width Wa1 of the interconnection 20a along the second direction. Thereby, a high opening ratio can be ensured.
Moreover, the pitch of the interconnection 20a along the Y-axis direction may be at least 10 times the width Wa1 of the interconnection 20a along the second direction. The distance Wc1 along the Y-axis direction from the center of the first interconnection 21 along the Y-axis direction to the center of the second interconnection 22 along the Y-axis direction may be at least 10 times the width Wa1 of the interconnection 20a along the second direction. Thereby, a high opening ratio of about 80% can be ensured.
As illustrated in FIG. 2A, a width Wa2 of the low refractive index portion 40a along the second direction (i.e., the width of the first portion 41 along the Y-axis direction and the width of the second portion 42 along the Y-axis direction) may be greater than the peak wavelength of the light emitted from the organic light-emitting unit 30. Thereby, the effects of the refraction recited above are obtained; and the outcoupling efficiency increases.
A width Wb2 of the high refractive index portion 40b along the Y-axis direction is wider than the width Wa2 of the low refractive index portion 40a along the Y-axis direction. In other words, the low refractive index portion 40a is provided opposing the interconnection 20a; and the high refractive index portion 40b is provided opposing the portions of the second electrode 20 (the conductive layer 20b) where the interconnection 20a is not provided.
The pitch of the low refractive index portion 40a along the Y-axis direction may be at least twice the width Wa2 of the low refractive index portion 40a along the second direction and may be set substantially the same as the distance Wc1. In other words, a distance Wc2 along the Y-axis direction from the center of the first portion 41 along the Y-axis direction to the center of the second portion 42 along the Y-axis direction may be at least twice the width Wa2 of the low refractive index portion 40a along the second direction. The distance Wc2 may be set to be substantially the same as the distance Wc1. Thereby, a high opening ratio can be ensured.
Moreover, the pitch of the low refractive index portion 40a along the Y-axis direction may be at least 10 times the width Wa2 of the low refractive index portion 40a along the second direction and may be set to be substantially the same as the distance Wc1. In other words, the distance Wc2 along the Y-axis direction from the center of the first portion 41 along the Y-axis direction to the center of the second portion 42 along the Y-axis direction may be at least 10 times the width Wa2 of the low refractive index portion 40a along the second direction. The distance Wc2 may be set to be substantially the same as the distance Wc1. Thereby, a high opening ratio of about 80% can be ensured.
In this specific example as illustrated in FIG. 2B, a width Wa3 of the insulating layer 50 along the Y-axis direction is set to be substantially the same as the width Wa1 and the width Wa2.
A width Wb3 along the Y-axis direction between the insulating layers 50 is set to be substantially the same as the width Wb1 and the width Wb2.
A distance Wc3, i.e., the pitch of the insulating layer 50 along the Y-axis direction, may be at least twice the width Wa3 of the insulating layer 50 along the Y-axis direction and may be set to be substantially the same as the distance Wc1 and the distance Wc2. Thereby, a high opening ratio can be ensured.
Moreover, the distance Wc3, i.e., the pitch of the insulating layer 50 along the Y-axis direction, may be at least 10 times the width Wa3 of the insulating layer 50 along the Y-axis direction and may be set to be substantially the same as the distance Wc1 and the distance Wc2. Thereby, a high opening ratio of about 80% can be ensured.
The width Wa1 of the interconnection 20a along the Y-axis direction may be set to be, for example, not less than 10 μm and not more than 1000 μm. In the case where the width Wa1 is narrower than 10 μm, it may be difficult to pattern the interconnection 20a when constructing an illumination device having a large surface area. In the case where the width Wa1 is greater than 1000 μm, it is difficult to have a high opening ratio while suppressing nonuniformity due to the voltage drop in the plane.
The pitch of the interconnection 20a along the Y-axis direction (i.e., the distance Wc1 along the Y-axis direction from the center of the first interconnection 21 along the Y-axis direction to the center of the second interconnection 22 along the Y-axis direction) may be not less than 100 μm and not more than 10 mm. It is undesirable for the pitch of the interconnection 20a to be less than 100 μm because the opening ratio easily decreases. In the case where the pitch of the interconnection 20a is greater than 10 mm, the brightness may become nonuniform in the plane.
It is desirable for the width along the Y-axis direction of the portion of the low refractive index portion 40a (e.g., the first portion 41 and the second portion 42) overlapping the at least one selected from the first interconnection 21 and the second interconnection 22 as viewed from the direction perpendicular to the first major surface to be not less than 100 μm and not more than 1000 μm, that is, equal to the width of the interconnection 20a along the Y-axis direction.
As illustrated in FIG. 3, a thickness t2 of the high refractive index portion 40b along the Z-axis direction is greater than the organic light-emitting unit 30 thickness (a distance t1). The distance t1 may be set to be, for example, not less than 100 nanometers (nm) and not more than 300 nm; and the thickness t2 may be not less than 1 μm and not more than 100 μm.
FIG. 4A and FIG. 4B are schematic views illustrating the configuration of another illumination device according to the first embodiment of the invention.
FIG. 5A and FIG. 5B are schematic views illustrating the configuration of the another illumination device according to the first embodiment of the invention.
Namely, FIG. 4A is a cross-sectional view along line A1-A2 of FIG. 4B, FIG. 5A, and FIG. 5B; FIG. 4B is a cross-sectional view along line B1-B2 of FIG. 4A; FIG. 5A is a cross-sectional view along line C1-C2 of FIG. 4A; and FIG. 5B is a cross-sectional view along line D1-D2 of FIG. 4A.
As illustrated in FIGS. 4A and 4B and FIGS. 5A and 5B, the one other illumination device 111 according to this embodiment includes the first electrode 10, the second electrode 20, the organic light-emitting unit 30, and the optical layer 40 described above. However, in the illumination device 111, the second electrode 20 further includes a third interconnection 23 and a fourth interconnection 24.
The third interconnection 23 is electrically connected to the conductive layer 20b, the first interconnection 21 and the second interconnection 22. The third interconnection 23 is aligned in a third direction different from the first direction and parallel to the first major surface. The conductivity of the third interconnection 23 is higher than that of the conductive layer 20b. 
The fourth interconnection 24 is electrically connected to the conductive layer 20b, the first interconnection 21, and the second interconnection 22. The fourth interconnection 24 is aligned apart from the third interconnection 23 and parallel to the third interconnection 23. In other words, the fourth interconnection 24 is aligned in the third direction. The conductivity of the fourth interconnection 24 also is higher than that of the conductive layer 20b. 
In this specific example, the third direction is taken to be a direction orthogonal to the first direction. In other words, the third interconnection 23 is aligned in the Y-axis direction. The fourth interconnection 24 also is aligned in the Y-axis direction.
The distances along the Z-axis direction between the third interconnection 23 and the first electrode 10 and between the fourth interconnection 24 and the first electrode 10 are substantially the same as the distances along the Z-axis direction between the first interconnection 21 and the first electrode 10 and between the second interconnection 22 and the first electrode 10. In other words, the third interconnection 23 and the fourth interconnection 24 are in the same layer as the first interconnection 21 and the second interconnection 22. The material used as the third interconnection 23 and the fourth interconnection 24 may be the same material used as the first interconnection 21 and the second interconnection 22. The third interconnection 23 and the fourth interconnection 24 may be formed collectively with the first interconnection 21 and the second interconnection 22. Thereby, it is possible to efficiently construct the first to fourth interconnections 21 to 24.
Thus, in the illumination device 111, the interconnection 20a having a conductivity higher than that of the conductive layer 20b is provided in a grid along the X-axis direction and the Y-axis direction.
Thereby, even in the case where the illumination device 111 is an illumination device with a large surface area having both a long X-axis direction length and a long Y-axis direction length, the voltage drop can be suppressed in both the X-axis direction and the Y-axis direction; and it is possible to obtain a uniform brightness.
As illustrated in FIG. 5A, the low refractive index portion 40a of the optical layer 40 further has a portion overlapping at least one selected from the third interconnection 23 and the fourth interconnection 24 as viewed from the direction perpendicular to the first major surface 30a (the Z-axis direction). In other words, the low refractive index portion 40a may include a third portion 43 opposing the third interconnection 23 along the Z-axis direction. Also, the low refractive index portion 40a may include a fourth portion 44 opposing the fourth interconnection 24 along the Z-axis direction.
In this specific example, the low refractive index portion 40a is provided in the regions where the first interconnection 21, the second interconnection 22, the third interconnection 23, and the fourth interconnection 24 are provided as viewed from the direction perpendicular to the first major surface 30a. In other words, the low refractive index portion 40a is provided conforming to the regions where the first interconnection 21, the second interconnection 22, the third interconnection 23, and the fourth interconnection 24 are provided as viewed from the direction perpendicular to the first major surface 30a. The low refractive index portion 40a has substantially the same pattern (the pattern in the X-Y plane as viewed from the direction perpendicular to the first major surface 30a) as the interconnection 20a (the first interconnection 21, the second interconnection 22, the third interconnection 23, and the fourth interconnection 24).
The first portion 41 and the second portion 42 of the low refractive index portion 40a are aligned in the first direction (the X-axis direction); and the third portion 43 and the fourth portion 44 of the low refractive index portion 40a are aligned in the second direction (the Y-axis direction).
The high refractive index portion 40b has portions adjacent along the second direction to the first portion 41 and the second portion 42 of the low refractive index portion 40a to contact the first portion 41 and the second portion 42 along the second direction. Further, the high refractive index portion 40b has portions adjacent along the first direction to the third portion 43 and the fourth portion 44 of the low refractive index portion 40a to contact the third portion 43 and the fourth portion 44 along the first direction.
In other words, the high refractive index portion 40b is provided in the portions where the low refractive index portion 40a is not provided. In other words, the high refractive index portion 40b is provided in the regions where the interconnection 20a (the first interconnection 21, the second interconnection 22, the third interconnection 23, and the fourth interconnection 24) is not provided. Thus, it is advantageous for the pattern of the low refractive index portion 40a to substantially match the pattern of the interconnection 20a because, as described below, the low refractive index portion 40a and the interconnection 20a can be formed collectively; and the production efficiency increases.
Thus, the low refractive index portion 40a is provided to oppose the third interconnection 23 and the fourth interconnection 24. Thereby, the light L3 is efficiently extracted to the external environment due to the effects of the refraction described in regard to FIG. 3. Thereby, a high efficiency can be obtained. Thereby, the voltage drop in the plane can be suppressed to obtain a uniform brightness; and a highly efficient illumination device with increased outcoupling efficiency can be provided.
By further providing the insulating layer 50 to oppose the third interconnection 23 and the fourth interconnection 24 in the Z-axis direction as illustrated in FIG. 5B, the light emission of the organic light-emitting unit 30 at the portions where it is difficult to extract the light (the portions opposing the third interconnection 23 and the fourth interconnection 24) can be suppressed more than at the other portions; and the efficiency increases further.
In the illumination device 111, it is desirable to set the width of the third interconnection 23 along a fourth direction (in this case, the X-axis direction) perpendicular to the third direction and parallel to the first major surface 30a and the width of the fourth interconnection 24 along the fourth direction to be greater than the peak wavelength of the light emitted from the organic light-emitting unit 30. Thereby, the resistances of the third interconnection 23 and the fourth interconnection 24 can be set lower than a constant value; and the voltage drop in the plane can be effectively suppressed.
It is desirable to set the distance along the fourth direction from the center of the third interconnection 23 along the fourth direction to the center of the fourth interconnection 24 along the fourth direction to be not less than 10 times the width of the third interconnection 23 along the fourth direction and not less than 10 times the width of the fourth interconnection 24 along the fourth direction. Thereby, a high opening ratio can be obtained; the outcoupling efficiency can be increased; and a high efficiency is easily obtained.
An example of a method for manufacturing the illumination device 110 and the illumination device 111 according to this embodiment will now be described.
FIG. 6A to FIG. 6G are schematic cross-sectional views in order of the processes, illustrating the method for manufacturing the illumination devices according to the first embodiment of the invention.
Namely, FIG. 6A to FIG. 6G illustrate the method for manufacturing the illumination device 110 or the illumination device 111 and are cross-sectional views corresponding to the cross section along line A1-A2 of FIG. 1B or FIG. 4B.
First, as illustrated in FIG. 6A, a low refractive index film 40af used to form the low refractive index portion 40a is formed on a major surface 60a of the substrate 60 made of, for example, glass, etc.; and a high conductivity film 20af used to form the first interconnection 21 and the second interconnection 22 is formed on the low refractive index film 40af. SiO2, for example, may be used as the low refractive index film 40af. The thickness of the low refractive index film 40af may be, for example, not less than 1 μm and not more than 100 μm. The forming of the low refractive index film 40af may include any method such as vapor deposition and coating. Al, for example, may be used as the high conductivity film 20af. The thickness of the high conductivity film 20af may be, for example, not less than 20 nm and not more than 1000 nm. The forming of the high conductivity film 20af may include vapor deposition such as sputtering, etc.
Then, as illustrated in FIG. 6B, the low refractive index film 40af and the high conductivity film 20af are patterned to form the first interconnection 21 and the second interconnection (the interconnection 20a) and the low refractive index portion 40a. Such patterning may be performed using, for example, photolithography; and such patterning may be performed collectively. By appropriately designing the configuration of the mask during the photolithography, the third interconnection 23 and the fourth interconnection 24 can be collectively provided simultaneously with the low refractive index portion 40a, the first interconnection 21, and the second interconnection 22.
Then, as illustrated in FIG. 6C, the high refractive index portion 40b is formed on the major surface 60a of the substrate 60 exposed between the low refractive index portion 40a, the first interconnection 21, and the second interconnection 22.
In this specific example, a high refractive index film 40bf used to form the high refractive index portion 40b is formed to cover the low refractive index portion 40a, the first interconnection 21, the second interconnection 22, and the major surface 60a of the substrate 60. Polyimide, for example, may be used as the high refractive index film 40bf. 
Then, as illustrated in FIG. 6D, etch-back is performed on the high refractive index film 40bf to expose the first interconnection 21 and the second interconnection 22. Thus, the high refractive index portion 40b is formed.
Continuing as illustrated in FIG. 6E, the conductive layer 20b is formed to cover the low refractive index portion 40a, the first interconnection 21, the second interconnection 22, and the high refractive index portion 40b. ITO, for example, may be used as the conductive layer 20b. The thickness of the conductive layer 20b may be 50 nm to 200 nm. The forming of the conductive layer 20b may include any method such as sputtering and coating.
Then, a photosensitive insulating film 50f is formed on the conductive layer 20b. For example, a positive photosensitive acrylic resin and the like may be used as the insulating film 50f. 
Then, light 50u is irradiated onto the insulating film 50f from the face of the substrate 60 on the side opposite to the major surface 60a using the first interconnection 21 and the second interconnection 22 as a mask. Namely, light 50u is irradiated onto the insulating film 50f through the substrate 60 using the first interconnection 21 and the second interconnection 22 as a mask. The photosensitive insulating film 50f is photosensitive to energy of the light 50u. Subsequently, developing is performed. Thereby, the portions of the insulating film 50f irradiated with the light 50u are removed; and the portions that are screened by the first interconnection 21 and the second interconnection 22 and are not irradiated with the light 50u remain.
Thereby, as illustrated in FIG. 6F, the insulating layer 50 made of the insulating film 50f is formed with a patterned configuration conforming to the patterned configuration of the first interconnection 21 and the second interconnection 22.
Then, as illustrated in FIG. 6G, the organic light-emitting unit 30 is formed on the insulating layer 50 and the conductive layer 20b; and the first electrode 10 is formed on the organic light-emitting unit 30.
Thereby, the illumination device 110 or the illumination device 111 can be manufactured.
In the illumination device 110 and the illumination device 111, the low refractive index portion 40a opposes the first interconnection 21 and the second interconnection 22 along the Z-axis direction; and the first interconnection 21 and the second interconnection 22 can be formed collectively with the low refractive index portion 40a. Therefore, the productivity is high.
FIG. 7A to FIG. 7G are schematic cross-sectional views in order of the processes, illustrating another method for manufacturing the illumination devices according to the first embodiment of the invention.
Namely, FIG. 7A to FIG. 7G illustrate the method for manufacturing the illumination device 110 or the illumination device 111 and are cross-sectional views corresponding to the cross section along line A1-A2 of FIG. 1B or FIG. 4B.
First, as illustrated in FIG. 7A, the low refractive index film 40af is formed on the major surface 60a of the substrate 60; and the high conductivity film 20af is formed on the low refractive index film 40af. 
Then, as illustrated in FIG. 7B, the low refractive index film 40af and the high conductivity film 20af are patterned to form the first interconnection 21 and the second interconnection (the interconnection 20a) and the low refractive index portion 40a. In such a case as well, the patterning is performed collectively. Further, the third interconnection 23 and the fourth interconnection 24 may be collectively provided simultaneously with the low refractive index portion 40a, the first interconnection 21, and the second interconnection 22.
Continuing as illustrated in FIG. 7C, the high refractive index portion 40b is formed on the major surface 60a of the substrate 60 exposed between the low refractive index portion 40a, the first interconnection 21, and the second interconnection 22. In this specific example, a negative photosensitive material (e.g., photosensitive polyimide) is used as the high refractive index film 40bf. 
Then, light 40bu is irradiated onto the high refractive index film 40bf from the face of the substrate 60 on the side opposite to the major surface 60a using the first interconnection and the second interconnection 22 as a mask; and developing is performed. Thereby, the portions of the high refractive index film 40bf irradiated with the light 40bu remain; and the portions screened by the first interconnection 21 and the second interconnection 22 and not irradiated with the light 40bu are removed.
Thereby, as illustrated in FIG. 7D, the first interconnection 21 and the second interconnection 22 are exposed. Thus, the high refractive index portion 40b is formed.
Thus, in this specific example, the forming of the high refractive index portion 40b includes: forming the negative photosensitive high refractive index film 40bf used to form the high refractive index portion 40b to cover the low refractive index portion 40a, the first interconnection 21, the second interconnection 22, and the major surface 60a of the substrate 60; irradiating light onto the high refractive index film 40bf from the face of the substrate 60 on the side opposite to the major surface 60a using the first interconnection 21 and the second interconnection 22 as a mask; and performing developing. Thereby, the self-alignment makes positional alignment unnecessary; and the high refractive index portion 40b can be formed with high productivity.
Thereafter, as illustrated in FIG. 7E to FIG. 7G, the illumination device 110 or the illumination device 111 can be manufactured by processes similar to those described in regard to FIG. 6E to FIG. 6G.
In such a manufacturing method as well, the first interconnection 21 and the second interconnection 22 are formed collectively with the low refractive index portion 40a; and the high refractive index portion 40b is formed with self-alignment with the first interconnection 21, the second interconnection 22, and the low refractive index portion 40a. Therefore, positional alignment is unnecessary; and the high refractive index portion 40b can be formed with high productivity.
In a comparative example, a diffraction grating is used as the optical layer provided on the side of the second electrode 20 opposite to the organic light-emitting unit 30. Such a comparative example corresponds to, for example, the configuration of the organic electroluminescent element discussed in JP-A 2006-156400 (Kokai). Thus, when a diffraction grating is applied as the optical layer, the disposition pitch between the high refractive index layer and the low refractive index layer is about the same as the wavelength of the light emitted from the organic light-emitting unit 30. For example, the disposition pitch between the high refractive index layer and the low refractive index layer is about 10 nm to 1 μm. Thereby, a diffraction effect occurs. Thus, it is necessary to provide the high refractive index layer and the low refractive index layer with extremely small pitches to use the diffraction effect; and the productivity is low. Further, because the disposition pitch between the high refractive index layer and the low refractive index layer differs greatly from the disposition pitch of the first interconnection 21 and the second interconnection 22 (e.g., not less than 100 μm and not more than 10 mm), it is difficult to form the high refractive index layer and the low refractive index layer collectively with the first interconnection 21 and the second interconnection 22.
Conversely, the illumination devices 110 and 111 according to this embodiment can be used as illumination devices having large surface areas. The nonuniform brightness in the plane due to the voltage drop, which is a problem characteristic to illumination devices having large surface areas, is suppressed by the interconnection 20a (the first interconnection 21 and the second interconnection 22) having the high conductivity; and a uniform light emission in the plane can be obtained.
Also, by providing the low refractive index portion 40a to oppose the reflective interconnection 20a (the first interconnection 21 and the second interconnection 22) having the low transmittance, the refraction effect of the interface IF1 between the low refractive index portion 40a and the high refractive index portion 40b is utilized; the optical path of the light L3 is changed; multiple reflections are suppressed; and the light L3 can be efficiently extracted to the external environment. Thus, in the illumination devices 110 and 111, a refraction effect different from the diffraction effect is utilized.
Further, the high refractive index portion 40b and the low refractive index portion 40a can be formed collectively with the first interconnection 21 and the second interconnection 22; and the productivity also is high.
It may be possible to apply a method that utilizes a diffraction effect to increase the outcoupling efficiency in a display device and the like in which, for example, one pixel has a size of about 200 μm and the voltage drop in the pixel electrode is not problematic. However, based on the approaches using diffraction gratings, it is considered to be difficult to practically realize both the suppression of the nonuniform brightness and the increase of the outcoupling efficiency which are characteristically necessary for illumination devices having large surface areas.
Conversely, in the illumination devices 110 and 111 according to this embodiment, the suppression of the nonuniform brightness and the increase of the outcoupling efficiency, which are characteristically necessary for illumination devices having large surface areas, can be simultaneously realized by utilizing the refraction effect and by providing the interconnection 20a having the high conductivity and the low refractive index portion 40a opposing the interconnection 20a. Thereby, the voltage drop in the plane is suppressed to obtain a uniform brightness; and a highly efficient illumination device with increased outcoupling efficiency can be provided.
Further, by providing the low refractive index portion 40a at a position corresponding to the interconnection 20a having the high conductivity, the interconnection 20a, which suppresses the voltage drop in the plane which is characteristic to illumination devices having large surface areas, can be constructed simultaneously with the low refractive index portion 40a, which increases the outcoupling efficiency. Thereby, the voltage drop in the plane is suppressed to obtain a uniform brightness; the outcoupling efficiency can be increased; and a highly efficient illumination device can be manufactured with high productivity.
Second Embodiment
FIG. 8A to FIG. 8C are schematic views illustrating the configuration of an illumination device according to a second embodiment of the invention.
Namely, FIG. 8A is a cross-sectional view along line A1-A2 of FIG. 8B and FIG. 8C; FIG. 8B is a cross-sectional view along line B1-B2 of FIG. 8A; and FIG. 8C is a cross-sectional view along line C1-C2 of FIG. 8A.
In the illumination device 120 according to this embodiment as illustrated in FIG. 8A to FIG. 8C, the first interconnection 21 and the second interconnection 22 are provided on the organic light-emitting unit 30 side of the conductive layer 20b. 
An insulating layer is provided between the first interconnection 21 and the organic light-emitting unit 30 and between the second interconnection 22 and the organic light-emitting unit 30 and has a portion overlapping at least one selected from the first interconnection 21 and the second interconnection 22 as viewed from the Z-axis direction (the direction perpendicular to the first major surface 30a). The insulating layer 50 covers the first interconnection 21 and the second interconnection 22 and electrically insulates the first interconnection 21 and the second interconnection 22 from the organic light-emitting unit 30. Otherwise, the configuration is similar to that of the illumination device 110, and a description is therefore omitted.
The illumination device 120 according to this embodiment also suppresses the voltage drop in the plane to obtain a uniform brightness; and a highly efficient illumination device with increased outcoupling efficiency can be provided.
In the illumination device 120, the thickness of the low refractive index portion 40a along the Z-axis direction is thinner than the thickness of the high refractive index portion 40b along the Z-axis direction. In other words, the low refractive index portion 40a is covered with the high refractive index portion 40b; and the low refractive index portion 40a is buried in the high refractive index portion 40b. 
FIG. 9A to FIG. 9C are schematic views illustrating the configuration of another illumination device according to the second embodiment of the invention.
Namely, FIG. 9A is a cross-sectional view along line A1-A2 of FIG. 9B and FIG. 9C; FIG. 9B is a cross-sectional view along line B1-B2 of FIG. 9A; and FIG. 9C is a cross-sectional view along line C1-C2 of FIG. 9A.
Also in the one other illumination device 121 according to this embodiment as illustrated in FIG. 9A to FIG. 9C, the first interconnection 21 and the second interconnection 22 are provided on the organic light-emitting unit 30 side of the conductive layer 20b. An insulating layer is provided between the first interconnection 21 and the organic light-emitting unit 30 and between the second interconnection 22 and the organic light-emitting unit 30 and has a portion overlapping at least one selected from the first interconnection 21 and the second interconnection 22 as viewed from the Z-axis direction.
In the illumination device 121, the thickness of the low refractive index portion 40a along the Z-axis direction is substantially the same as the thickness of the high refractive index portion 40b along the Z-axis direction.
The illumination device 121 also suppresses the voltage drop in the plane to obtain a uniform brightness; and a highly efficient illumination device with increased outcoupling efficiency can be provided.
FIG. 10A to FIG. 10C are schematic views illustrating the configuration of still another illumination device according to the second embodiment of the invention.
Namely, FIG. 10A is a cross-sectional view along line A1-A2 of FIG. 10B and FIG. 10C; FIG. 10B is a cross-sectional view along line B1-B2 of FIG. 10A; and FIG. 10C is a cross-sectional view along line C1-C2 of FIG. 10A.
As illustrated in FIG. 10A to FIG. 10C, the still another illumination device 122 according to this embodiment also includes the first electrode 10, the second electrode 20, the organic light-emitting unit 30, and the optical layer 40. The second electrode 20 further includes the third interconnection 23 and the fourth interconnection 24. The first interconnection 21, the second interconnection 22, the third interconnection 23, and the fourth interconnection 24 are provided on the organic light-emitting unit 30 side of the conductive layer 20b. The insulating layer 50 is provided between the first interconnection 21 and the organic light-emitting unit 30, between the second interconnection 22 and the organic light-emitting unit 30, between the third interconnection 23 and the organic light-emitting unit 30, and between the fourth interconnection 24 and the organic light-emitting unit 30 and has portions overlapping the first interconnection 21, the second interconnection 22, the third interconnection 23, and the fourth interconnection 24 in the Z-axis direction.
The illumination device 122 also suppresses the voltage drop in the plane to obtain a uniform brightness; and a highly efficient illumination device with increased outcoupling efficiency can be provided.
In the illumination device 122, the thickness of the low refractive index portion 40a along the Z-axis direction is thinner than the thickness of the high refractive index portion 40b along the Z-axis direction. However, similarly to the illumination device 121, the thickness of the low refractive index portion 40a along the Z-axis direction may be set to be substantially the same as the thickness of the high refractive index portion 40b along the Z-axis direction.
Third Embodiment
A third embodiment of the invention is a method for manufacturing the illumination device. In other words, this manufacturing method is a method for manufacturing an illumination device including: the organic light-emitting unit 30 having the first major surface 30a and the second major surface 30b; the first electrode 10 provided on the first major surface 30a of the organic light-emitting unit 30; the second electrode 20 provided on the second major surface 30b of the organic light-emitting unit 30, where the second electrode 20 includes the conductive layer 20b, the first interconnection 21 electrically connected to the conductive layer 20 and aligned in the first direction parallel to the first major surface 30a, and the second interconnection 22 electrically connected to the conductive layer 20b and aligned apart from the first interconnection 21 and parallel to the first interconnection 21, the conductivities of the first interconnection 21 and the second interconnection 22 being higher than that of the conductive layer 20b; and the optical layer 40 provided on the side of the second electrode 20 opposite to the organic light-emitting unit 30, where the optical layer 40 includes the low refractive index portion 40a having a portion overlapping at least one selected from the first interconnection 21 and the second interconnection 22 as viewed from the direction perpendicular to the first major surface 30a and the high refractive index portion 40b having a portion contacting the portion of the low refractive index portion 40a recited above and having a refractive index higher than that of the low refractive index portion 40a. 
FIG. 11 is a flowchart illustrating the method for manufacturing an illumination device according to the third embodiment of the invention.
In the method for manufacturing an illumination device according to this embodiment as illustrated in FIG. 11, first, the low refractive index film 40af used to form the low refractive index portion 40a is formed on the major surface 60a of the substrate 60 (step S110).
Then, the high conductivity film 20af used to form the first interconnection 21 and the second interconnection 22 is formed on the low refractive index film 40af (step S120).
Continuing, the low refractive index film 40af and the high conductivity film 20af are patterned to form the low refractive index portion 40a, the first interconnection 21, and the second interconnection 22 (step S130).
Then, the high refractive index portion 40b is formed on the major surface 60a of the substrate 60 exposed between the low refractive index portion 40a, the first interconnection 21, and the second interconnection 22 (step S140).
Continuing, the conductive layer 20b is formed to cover the low refractive index portion 40a, the first interconnection 21, the second interconnection 22, and the high refractive index portion 40b (step S150).
Then, the photosensitive insulating film 50f is formed on the conductive layer 20b (step S160). Then, light is irradiated onto the insulating film 50f from the face of the substrate 60 on the side opposite to the major surface 60a using the first interconnection 21 and the second interconnection 22 as a mask; developing is performed; and the insulating layer 50 made of the insulating film 50f is formed with a patterned configuration conforming to the patterned configuration of the first interconnection 21 and the second interconnection 22 (step S170).
Continuing, the organic light-emitting unit 30 is formed on the insulating layer 50 and the conductive layer 20b (step S180).
Then, the first electrode 10 is formed on the organic light-emitting unit 30 (step S190).
In other words, for example, the method described in regard to FIG. 6A to FIG. 6G is implemented.
According to such a manufacturing method, the first interconnection 21 and the second interconnection 22 can be formed collectively with the low refractive index portion 40a; the voltage drop in the plane is suppressed to obtain a uniform brightness; and a highly efficient illumination device with increased outcoupling efficiency can be manufactured with high productivity.
As described above in regard to FIG. 7A to FIG. 7G, the forming of the high refractive index portion 40b may include: forming the negative photosensitive high refractive index film 40bf used to form the high refractive index portion 40b to cover the low refractive index portion 40a, the first interconnection 21, the second interconnection 22, and the major surface 60a of the substrate 60; irradiating light onto the high refractive index film 40bf from the face of the substrate 60 on the side opposite to the major surface 60a using the first interconnection 21 and the second interconnection 22 as a mask; and performing developing. Thereby, the self-alignment makes positional alignment unnecessary; and the high refractive index portion 40b can be formed with high productivity.
Hereinabove, exemplary embodiments of the invention are described with reference to specific examples. However, the invention is not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriate selections from known art, including various modifications made by one skilled in the art in regard to configurations, sizes, material qualities, arrangements, and the like of specific configurations of components included in illumination devices such as first electrodes, second electrodes, conductive layers, interconnections, organic light-emitting layers, organic light-emitting units, optical layers, high refractive index portions, low refractive index portions, insulating layers, and the like. Such practice is included in the scope of the invention to the extent that similar effects thereto are obtained.
Further, any two or more components of the specific examples may be combined within the extent of technical feasibility; and are included in the scope of the invention to the extent that the purport of the invention is included. Moreover, all illumination devices practicable by an appropriate design modification by one skilled in the art based on the illumination devices described above as embodiments of the invention also are within the scope of the invention to the extent that the purport of the invention is included.
Furthermore, various modifications and alterations within the spirit of the invention will be readily apparent to those skilled in the art. All such modifications and alterations should therefore be seen as within the scope of the invention.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.

## Claims

1. An illumination device, comprising:
a transparent substrate;
a first electrode;
an organic light-emitting unit provided between the transparent substrate and the first electrode, the organic light-emitting unit including an organic light-emitting layer, the organic light-emitting unit having a first major surface facing the first electrode;
a second electrode provided between the transparent substrate and the organic light-emitting unit, the second electrode including,
a conductive layer,
a first interconnection electrically connected to the conductive layer and extending in a first direction parallel to the first major surface, the first interconnection having a conductivity higher than a conductivity of the conductive layer, the first interconnection overlapping the organic light-emitting unit as viewed from a normal direction perpendicular to the first major surface, and
a second interconnection electrically connected to the conductive layer, being apart from the first interconnection and extending in a first direction, the second interconnection overlapping the organic light-emitting unit as viewed from the normal direction, the second interconnection having a conductivity higher than the conductivity of the conductive layer;

an optical layer provided between the transparent substrate and the second electrode, the optical layer including,
a low refractive index portion contacting the transparent substrate, the low refractive index portion overlapping the first interconnection and the second interconnection as viewed from the normal direction, and
a high refractive index portion contacting the transparent substrate and contacting the low refractive index portion, a refractive index of the high refractive index portion being higher than a refractive index of the low refractive index portion and higher than a refractive index of the transparent substrate; and

an insulating layer provided between the second electrode and the organic light-emitting unit, the insulating layer overlapping the first interconnection and the second interconnection as viewed from the normal direction, the insulating layer formed in part by using the first interconnection and the second interconnection as a mask to irradiate light onto an insulating film through the transparent substrate, the insulating film so formed serving as the insulating layer.

2. The device according to claim 1, wherein a width of the first interconnection along a second direction perpendicular to the first direction and parallel to the first major surface is greater than 10 micrometers and a width of the second interconnection along the second direction is greater than 10 micrometers.

3. The device according to claim 1, wherein a distance along a second direction perpendicular to the first direction and parallel to the first major surface from a center of the first interconnection along the second direction to a center of the second interconnection along the second direction is not less than 10 times a width of the first interconnection along the second direction and not less than 10 times a width of the second interconnection along the second direction.

4. The device according to claim 1, wherein a width along a second direction perpendicular to the first direction and parallel to the first major surface of the portion of the low refractive index portion overlapping the at least one selected from the first interconnection and the second interconnection as viewed from the direction perpendicular to the first major surface is not less than 10 micrometers.

5. The device according to claim 1, wherein the second electrode further includes:
a third interconnection electrically connected to the conductive layer, the first interconnection, and the second interconnection and aligned in a third direction different from the first direction and parallel to the first major surface, the third interconnection having a conductivity higher than the conductivity of the conductive layer; and
a fourth interconnection electrically connected to the conductive layer, the first interconnection, and the second interconnection and aligned apart from the third interconnection and parallel to the third interconnection, the fourth interconnection having a conductivity higher than the conductivity of the conductive layer.

6. The device according to claim 5, wherein the low refractive index portion further has a portion overlapping at least one selected from the third interconnection and the fourth interconnection as viewed from the direction perpendicular to the first major surface.

7. The device according to claim 5, wherein a width of the third interconnection along a fourth direction perpendicular to the third direction and parallel to the first major surface is greater than 10 micrometers and a width of the fourth interconnection along the fourth direction is greater than 10 micrometers.

8. The device according to claim 5, wherein a distance along a fourth direction perpendicular to the third direction and parallel to the first major surface from a center of the third interconnection along the fourth direction to a center of the fourth interconnection along the fourth direction is not less than 10 times a width of the third interconnection along the fourth direction and not less than 10 times a width of the fourth interconnection along the fourth direction.

9. The device according to claim 5, wherein distances along the direction perpendicular to the first major surface from the third interconnection to the first electrode and from the fourth interconnection to the first electrode are identical to distances along the direction perpendicular to the first major surface from the first interconnection to the first electrode and from the second interconnection to the first electrode.

10. The device according to claim 1, wherein
the conductive layer is translucent to a light emitted from the organic light-emitting unit, and
transmittances of the first interconnection and the second interconnection with respect to the light are lower than a transmittance of the conductive layer with respect to the light.

11. The device according to claim 1, wherein the first interconnection and the second interconnection are reflective with respect to a light emitted from the organic light-emitting unit.

12. The device according to claim 11, wherein the light emitted from the organic light-emitting unit is refracted based on a difference of refractive indexes of the low refractive index portion and the high refractive index portion in traveling from the high refractive index portion into the low refractive index portion.

13. The device according to claim 1,
wherein the first interconnection and the second interconnection are provided on a side of the conductive layer opposite to the organic light-emitting unit and the insulating layer is provided between the conductive layer and the organic light-emitting unit.

14. The device according to claim 1,
wherein the first interconnection and the second interconnection are provided on the organic light-emitting unit side of the conductive layer and the insulating layer is provided between the first interconnection and the organic light-emitting unit and between the second interconnection and the organic light-emitting unit.

15. The device according to claim 1, wherein a width of the first interconnection along a second direction perpendicular to the first direction and parallel to the first major surface is not more than 1000 micrometers and a width of the second interconnection along the second direction is not more than 1000 micrometers.

16. The device according to claim 1, wherein a distance along a second direction perpendicular to the first direction and parallel to the first major surface from a center of the first interconnection along the second direction to a center of the second interconnection along the second direction is not less than 100 micrometers and not more than 10 millimeters.

17. The device according to claim 1, wherein a width along a second direction perpendicular to the first direction and parallel to the first major surface of the portion of the low refractive index portion overlapping the at least one selected from the first interconnection and the second interconnection as viewed from the direction perpendicular to the first major surface is not less than 100 micrometers and not more than 1000 micrometers.

18. The device according to claim 1, wherein the insulating layer is buried in the organic light-emitting unit.