JP7198882B2 - light emitting device - Google Patents

Description

The present invention relates to light emitting devices.

An organic EL element is one of the light sources of the light emitting device. An organic EL element has a structure in which an organic layer is arranged between a first electrode and a second electrode which are transparent electrodes. When the first electrode is a transparent electrode, metal is often used for the second electrode. When the first electrode, the second electrode, and the organic layer are formed over a wide area, the organic EL device becomes a surface emitting device.

On the other hand, in order for people to use the mirror, it is necessary to arrange light sources around the mirror. For example, in Patent Document 1, by not forming the first electrode in the central portion of the substrate, the central portion of the organic EL element can be used as a non-light-emitting portion, and the second electrode located in this non-light-emitting portion can be used as a mirror. Are listed.

Further, in Patent Document 2, by not forming the first electrode and the organic layer in the central part of the substrate, the central part of the organic EL element is used as a non-light-emitting part, and the second electrode located in this non-light-emitting part is used as a mirror. It is stated that

JP-A-2000-41807 Japanese Patent Application Laid-Open No. 2003-217868

In the structures of Patent Documents 1 and 2, the first electrode made of a transparent electrode material is not formed in the central portion of the substrate. However, since the transparent electrode material has higher resistance than metal, the parasitic resistance of the first electrode increases in the structures of Patent Documents 1 and 2. For this reason, the brightness of a region of the organic EL element away from the terminal connected to the first electrode is lower than that of the other regions.

The problem to be solved by the present invention is to allow a part of the organic EL element to function as a mirror as a non-light-emitting portion while improving the conductivity to the first electrode, and as a result, the luminance distribution in the organic EL element is improved. One example is to prevent it from happening.

A first invention includes a first electrode having a light transmissive property,
a second electrode having a smaller work function than the first electrode;
an organic layer located between the first electrode and the second electrode;
an intermediate layer located between the first electrode and the organic layer and electrically connected to the first electrode;
with
at least one of the intermediate layer and the second electrode has light reflectivity;
The light-emitting device includes a first region that does not overlap with the intermediate layer and in which the first electrode and the second electrode overlap with each other with the organic layer interposed therebetween.

A second invention includes a first electrode having a light transmissive property,
a second electrode having a smaller work function than the first electrode;
an organic layer located between the first electrode and the second electrode;
an intermediate layer positioned between the first electrode and the organic layer and having a lower work function than the first electrode;
with
The first electrode and the second electrode have a first region that is a region that does not overlap with the intermediate layer and that overlaps with each other,
The first region is a light emitting device smaller than the intermediate layer.

1 is a plan view of a light emitting device according to an embodiment; FIG. It is the figure which removed the 2nd electrode from FIG. FIG. 3 is a view of FIG. 2 with an organic layer removed; FIG. 4 is a view of FIG. 3 with an intermediate layer removed; FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1; FIG. 2 is a cross-sectional view taken along the line BB of FIG. 1; It is the figure which looked at the light-emitting device when a voltage is applied between the 1st electrode and the 2nd electrode from the 2nd surface side of a board|substrate.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

FIG. 1 is a plan view of a light emitting device 10 according to an embodiment. FIG. 2 is a diagram of FIG. 1 with the second electrode 130 removed. 3 is a view of FIG. 2 with the organic layer 120 removed, and FIG. 4 is a view of FIG. 3 with the intermediate layer 160 removed. 5 is a sectional view taken along line AA of FIG. 1, and FIG. 6 is a sectional view taken along line BB of FIG.

The light emitting device 10 according to the embodiment has a first electrode 110 , an organic layer 120 , a second electrode 130 and an intermediate layer 160 . The first electrode 110 has a property of transmitting visible light (optical transparency). The organic layer 120 is located between the first electrode 110 and the second electrode 130 . The second electrode 130 is made of a material whose work function is smaller than that of the first electrode 110 . The intermediate layer 160 is located between the first electrode 110 and the organic layer 120 and electrically connected to the first electrode 110 . The intermediate layer 160 is made of, for example, a material whose work function is smaller than that of the first electrode 110 . At least one of the intermediate layer 160 and the second electrode 130 has light reflectivity. Having light reflectivity here means, for example, reflecting visible light. The light emitting device 10 also has a first region 142 . The first region 142 is a region that does not overlap with the intermediate layer 160 and is a region where the first electrode 110 and the second electrode 130 overlap each other with the organic layer 120 interposed therebetween. A detailed description will be given below.

If the light emitting device 10 is of a bottom emission type, which will be described later, the substrate 100 is made of a translucent material such as glass or translucent resin. However, if the light-emitting device 10 is of a top-emission type, which will be described later, the substrate 100 may be made of a material that does not transmit light. The shape of the substrate 100 is appropriately selected according to the shape of the light emitting device 10, such as a polygon such as a rectangle, or a circle. Here, the substrate 100 may have flexibility. When the substrate 100 has flexibility, the thickness of the substrate 100 is, for example, 10 μm or more and 1000 μm or less. In particular, when the substrate 100 is made of a glass material and has flexibility, the thickness of the substrate 100 is, for example, 200 μm or less. When the substrate 100 is made of a resin material and has flexibility, the material of the substrate 100 may include, for example, PEN (polyethylene naphthalate), PES (polyether sulfone), PET (polyethylene terephthalate), or polyimide. formed. Further, when the substrate 100 contains a resin material, an inorganic barrier film such as SiN _x or SiON is formed on at least the light emitting surface (preferably both surfaces) of the substrate 100 in order to suppress moisture from penetrating the substrate 100. ing. When the substrate 100 has flexibility, it may further have a fixing base material for fixing the light emitting device 10 in a bent state.

A light-emitting portion 140 is formed on the first surface 102 of the substrate 100 . The light emitting section 140 has a structure for emitting light, such as an organic EL element. This organic EL element has a structure in which a first electrode 110, an organic layer 120, and a second electrode 130 are laminated in this order. The first electrode 110 is, for example, an anode, and the second electrode 130 is, for example, a cathode.

The first electrode 110 is a transparent electrode having optical transparency. The transparent conductive material constituting the transparent electrode is a material containing a metal, for example, a metal oxide such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), IWZO (Indium Tungsten Zinc Oxide), or ZnO (Zinc Oxide). be. The thickness of the first electrode 110 is, for example, 10 nm or more and 500 nm or less. The first electrode 110 is formed using, for example, sputtering or vapor deposition. The first electrode 110 may be a carbon nanotube or a conductive organic material such as PEDOT/PSS.

The second electrode 130 is made of, for example, a metal selected from the first group consisting of Al, Au, Ag, Pt, Mg, Sn, Zn, and In, or an alloy of metals selected from the first group. Contains a metal layer. In this case, the second electrode 130 has light shielding properties and reflects light from the organic layer 120 . The thickness of the second electrode 130 is, for example, 10 nm or more and 500 nm or less. However, the second electrode 130 may be formed using the material exemplified as the material of the first electrode 110 . The second electrode 130 is formed using, for example, sputtering or vapor deposition. The work function of the material forming the second electrode 130 is smaller than the work function of the material forming the first electrode 110 .

The organic layer 120 has, for example, a structure in which a hole injection layer, a light emitting layer, and an electron injection layer are laminated in this order. A hole transport layer may be formed between the hole injection layer and the light emitting layer. An electron transport layer may be formed between the light emitting layer and the electron injection layer. Also, the organic layer 120 may have a multi-photon structure having a plurality of light-emitting layers such as a so-called tandem structure. The organic layer 120 may be formed by a vapor deposition method. Also, at least one layer of the organic layer 120, for example, the layer in contact with the first electrode, may be formed by a coating method such as an inkjet method, a printing method, or a spray method. In this case, the remaining layers of the organic layer 120 are formed by vapor deposition. Also, all layers of the organic layer 120 may be formed using a coating method.

The intermediate layer 160 is located between the first electrode 110 and the organic layer 120 . Specifically, the intermediate layer 160 is in contact with the first electrode 110 and is made of a material having a work function smaller than that of the first electrode 110 . This material is, for example, a metal selected from the first group consisting of Al, Au, Ag, Pt, Mg, Sn, Zn, Nd, Cu, Bi, Pd, and In, or a metal selected from the first group. a metal layer made of an alloy of metals that The intermediate layer 160 may be formed using the same material as the second electrode 130 . In this case, since the intermediate layer 160 can be formed using the same device as the second electrode 130, the manufacturing cost of the light emitting device 10 can be reduced. The intermediate layer 160 is formed using, for example, a sputtering method or a vapor deposition method. Note that the thickness of the intermediate layer 160 is, for example, 1 nm or more and 500 nm or less.

Moreover, although there is a possibility that a convex portion such as a burr is formed on the edge of the intermediate layer 160, the intermediate layer 160 is short-circuited to the second electrode 130 because the edge of the intermediate layer 160 is covered with the organic layer 120. is suppressed.

Also, there is one region on the substrate 100 where the intermediate layer 160 and the first electrode 110 overlap. The intermediate layer 160 does not partially cover the first electrode 110 . In the example shown in FIGS. 2 and 3, the first electrode 110 is substantially rectangular except for the portion that will become the first terminal 112 . The intermediate layer 160 does not cover the regions along the two sides of the first electrode 110 facing each other. In this region (first region 142 ), first electrode 110 is in direct contact with organic layer 120 . As will be described later, the first region 142 of the light emitting section 140 emits light. On the other hand, since the region (second region 144) overlapping with the intermediate layer 160 does not emit light, when the intermediate layer 160 has a thickness of 50 nm or less, the intermediate layer 160 transmits light and the light is reflected by the second electrode 130. If the thickness of the intermediate layer 160 is greater than that, the intermediate layer 160 itself has light reflectivity and can be used as a mirror. In the examples shown in FIGS. 1-6, two first regions 142 sandwich a second region 144 . However, the planar layout of the first area 142 and the second area 144 is not limited to the examples shown in FIGS.

Note that the area of the first region 142 is smaller than the area of the second region 144 . In a cross section parallel to one side of the substrate 100 and passing through the center of the light emitting section 140, the width w ₁ of the first region 142 (see FIG. 5) is equal to the width w ₂ of the second region 144 (see FIG. 5), that is, the intermediate layer less than 160 width. Width _w1 is, for example, shorter _than width w2. In addition, in the example shown in FIG. 1, this cross section is substantially the same as the cross section shown in FIG. 5 or FIG.

An edge of the first electrode 110 may be covered with an insulating layer. In this case, the insulating layer is made of, for example, a photosensitive resin material such as polyimide, and surrounds a portion of the first electrode 110 that serves as the light emitting region of the light emitting section 140 . By providing the insulating layer, short-circuiting between the first electrode 110 and the second electrode 130 at the edge of the first electrode 110 can be suppressed. The insulating layer is formed by applying a resin material that will form the insulating layer and then exposing and developing the resin material. This step is performed, for example, after forming the first electrode 110 and before forming the organic layer 120 .

The light emitting device 10 has a first terminal 112 and a second terminal 132 . The first terminal 112 is electrically connected to the first electrode 110 and the second terminal 132 is electrically connected to the second electrode 130 . In the examples shown in FIGS. 1-4, the first terminal 112 and the second terminal 132 are arranged along the same side of the substrate 100 . However, the positions of the first terminal 112 and the second terminal 132 are not limited to this. The first terminal 112 has a layer made of the same material as the first electrode 110, and the second terminal 132 has a layer made of the same material as the second electrode 130. . In other words, the first terminal 112 is integrated with the first electrode 110 and the second terminal 132 is integrated with the second electrode 130 .

The light emitting section 140 is sealed with a sealing section (not shown). The sealing portion is made of, for example, glass, metal such as aluminum, or resin, and has a shape with a recess in the center. The edge of the sealing portion is fixed to the substrate 100 or a film formed thereon with an adhesive. As a result, the space surrounded by the sealing portion and the substrate 100 is sealed. And the light emitting part 140 is located in this sealed space.

The sealing portion may be a sealing film. The sealing film is formed using, for example, an ALD (Atomic Layer Deposition) method. In this case, the step coverage of the sealing film is enhanced. Further, in this case, the sealing film may have a multilayer structure in which a plurality of layers are laminated. In this case, it may have a structure in which a first sealing layer made of a first material (for example, aluminum oxide) and a second sealing layer made of a second material (for example, titanium oxide) are repeatedly laminated. . The bottom layer may be either the first sealing layer or the second sealing layer. Also, the uppermost layer may be either the first sealing layer or the second sealing layer. Also, the sealing film may be a single layer in which the first material and the second material are mixed. However, the sealing film may be formed using other film forming methods such as CVD or sputtering. In this case, the sealing film is formed of an insulating film such as SiO ₂ or SiN, and its film thickness is, for example, 10 nm or more and 1000 nm or less.

In the examples shown in FIGS. 1 to 6, the first region 142 of the light emitting device 10 is a bottom emission type organic EL element. However, the first region 142 may be a top emission type organic EL element. In this case, the light emitted from the light emitting device 10 does not pass through the substrate 100 . When the first region 142 is a top emission type organic EL element, the stacking order of the first electrode 110 and the second electrode 130 is opposite to that of the bottom emission type. That is, on the substrate 100, the second electrode 130, the organic layer 120, the intermediate layer 160, and the first electrode 110 are laminated in this order. However, the structure of the organic EL element is not limited to the above two examples.

Next, a method for manufacturing the light emitting device 10 will be described. First, the first electrode 110 is formed on the substrate 100 . A first terminal 112 is also formed in this step. Next, the intermediate layer 160, the organic layer 120, and the second electrode 130 are formed in this order. Next, the light emitting section 140 is sealed using a sealing section.

After that, a conductive member (eg, bonding wire, lead member, or FPC (Flexible Printed Circuit)) is connected to the first terminal 112 and the second terminal 132 .

FIG. 7 shows the light emitting device 10 when a voltage is applied between the first electrode 110 and the second electrode 130, viewed from the second surface 104 side of the substrate 100 (that is, the surface opposite to the light emitting section 140). It is a diagram. The intermediate layer 160 is not formed between the first electrode 110 and the organic layer 120 in the first region 142 of the light emitting section 140 . Therefore, the organic layer 120 in the first region 142 emits light.

On the other hand, the intermediate layer 160 is positioned between the first electrode 110 and the organic layer 120 in the second region 144 . The intermediate layer 160 has a smaller work function than the first electrode 110 . Therefore, the carrier (hole) injection barrier between the intermediate layer 160 and the organic layer 120 is increased, and as a result, carriers are hardly injected from the intermediate layer 160 into the organic layer 120 . Therefore, the organic layer 120 located in the second region 144 hardly emits light. Also, the intermediate layer 160 reflects visible light. Therefore, the second region 144 functions as a mirror.

As described above, the light emitting device 10 has a configuration in which the first regions 142, which are light emitting elements, are arranged on both sides of the second region 144, which is a mirror. Further, no opening is formed in the first electrode 110 and the intermediate layer 160 is formed on the first electrode 110 . Therefore, the parasitic resistance of the first electrode 110 is reduced, and as a result, the luminance distribution of the first region 142 can be suppressed.

Also, by changing the shape pattern of the intermediate layer 160, the shapes of the first region 142 and the second region 144 can be changed. Therefore, the shapes of the first region 142 and the second region 144 can be easily changed.

In addition, since the second region 144 does not emit light, it also functions as a heat radiator that dissipates heat generated in the first region 142 . Therefore, it is possible to prevent the temperature of the first region 142, the light emitting section 140, and the light emitting device 10 from increasing.

In addition, as described above, the second electrode 130 is formed using a material that reflects light. Therefore, if the second electrode 130 is also formed outside the light emitting unit 140, the portion of the second electrode 130 located outside the light emitting unit 140 can be used as a mirror.

Further, the intermediate layer 160 may have a structure in which a first layer made of a conductive material that reflects light and a second layer made of an insulating material are laminated. In this case, it is not necessary to limit the work function of the conductive material forming intermediate layer 160 . The second layer may or may not transmit light. Also, the second layer may be formed by treating the surface of the first layer (eg, oxidation treatment, reduction treatment). Moreover, when the first layer is formed by introducing an impurity into a semiconductor material, the second layer may be formed by introducing an impurity of the opposite conductivity type into the surface layer of the first layer.

Although the embodiments and examples have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than those described above can be adopted.

10 Light emitting device 100 Substrate 110 First electrode 120 Organic layer 130 Second electrode 140 Light emitting part 142 First region 144 Second region 160 Intermediate layer

Claims (2)

a first electrode having optical transparency;
a second electrode having a smaller work function than the first electrode;
an organic layer located between the first electrode and the second electrode;
an intermediate layer located between the first electrode and the organic layer and electrically connected to the first electrode;
with
the work function of the intermediate layer is smaller than the work function of the first electrode;
at least one of the intermediate layer and the second electrode has light reflectivity;
Having a first region that is a region that does not overlap with the intermediate layer and in which the first electrode and the second electrode overlap with each other with the organic layer interposed therebetween;
The first regions are located on both sides of the intermediate layer,
The light-emitting device, wherein the width of the first region is smaller than the width of the intermediate layer in the arrangement direction of the first region and the intermediate layer. The light emitting device according to claim 1 ,
The light-emitting device, wherein the intermediate layer is rectangular.

Images