DISPLAY DEVICE

A display device includes a first substrate having a first surface and a second surface opposite to the first surface, a first light-emitting layer including a first polymer and an ionic liquid on the second surface, a first electrode provided on a first side surface of the first light-emitting layer, a second electrode provided on a second side surface of the first light-emitting layer opposite to the first side surface of the first light-emitting layer, and a second substrate in contact with the first light-emitting layer opposite to the first substrate.

FIELD

One embodiment of the present invention relates to a display device including a light-emitting Electrochemical Cell (LEC) and a method of manufacturing the display device.

BACKGROUND

In recent years, a light-emitting electrochemical cell has attracted attention as a light-emitting element. The light-emitting electrochemical cell has a structure in which a first electrode, a second electrode, a light-emitting layer including a light-emitting polymer and an ionic liquid are stacked, and the light-emitting layer is sandwiched between the first electrode and the second electrode. The light-emitting layer of the light-emitting electrochemical cell contains both electrons and ions and emits light by spontaneously forming a p-i-n bond by applying a voltage between the first electrode and the second electrode (see Japanese laid-open patent publication No. 2011-103234 and Japanese laid-open patent publication No. 2000-67601).

SUMMARY

A display device according to one embodiment of the present invention includes a first substrate having a first surface and a second surface opposite to the first surface, a first light-emitting layer including a first polymer and an ionic liquid on the second surface, a first electrode provided on a first side surface of the first light-emitting layer, a second electrode provided on a second side surface of the first light-emitting layer opposite to the first side surface of the first light-emitting layer, and a second substrate in contact with the first light-emitting layer opposite to the first substrate.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. However, the present invention can be implemented in many different aspects and should not be construed as being limited to the description of the embodiments exemplified below. Although the width, thickness, shape, and the like of each part are schematically represented in comparison with the actual embodiments in order to clarify the description, the drawings are merely examples and do not limit the interpretation of the present invention. In addition, in the present specification and the drawings, elements similar to those described above with respect to the above-described figures are denoted by the same symbols (or symbols denoted by A, B, and the like) and a detailed description thereof may be omitted as appropriate. Furthermore, the letters “first” and “second” with respect to each element are convenient signs used to distinguish each element, and do not have any further meaning unless otherwise specified.

In the present specification, when a member or area is described as being “above (or below)” another member or area, this includes not only the case where it is directly above (or directly below) the other member or area but also the case where it is above (or below) the other member or area, i.e., it includes the case where other components are included between the above (or below) the other members or areas. Also, in the following explanation, unless otherwise specified, in a cross-sectional view, a side on which a light-emitting electrochemical cell120is provided with respect to a first substrate is referred to as “upper” or “above”, a side viewed from “upper” or “above” is referred to as “upper surface” or “upper surface side”, and the opposite side is referred to as “lower”, “below”, “lower surface” or “lower surface side”.

First Embodiment

A display device100according to one embodiment of the present invention will be described with reference toFIG.1toFIG.8B.

First, a structure of the display device100according to one embodiment of the present invention will be described while referring toFIG.1toFIG.8B.FIG.1is an exploded view of the display device100according to one embodiment of the present invention. The display device100includes a first substrate101, an element formation layer140, a light-emitting electrochemical cell120, and a second substrate102.

The element formation layer140is provided on the first substrate101. A pixel circuit including a switching element for controlling the light-emitting electrochemical cell120is arranged in a matrix in the element formation layer140.

The light-emitting electrochemical cell120is arranged in a matrix on the element formation layer140. In addition, the light-emitting electrochemical cell120is electrically connected to the switching element and is controlled by turning the switching element on/off. The light-emitting electrochemical cell120has a structure in which a light-emitting layer including a light-emitting polymer and an ionic liquid is sandwiched between a first electrode and a second electrode. The light-emitting layer includes both electrons and ions and the light-emitting layer emits light by spontaneously forming a p-i-n bond by applying a voltage between the first electrode and the second electrode. Also, the ionic liquid refers to an organic salt that is liquid at room temperature. A structure of the light-emitting electrochemical cell120is described in detail later.

The second substrate102is provided on the light-emitting electrochemical cell120. The first substrate101and the second substrate102are bonded via an adhesive material115.

FIG.2is a cross-sectional view when the display device100shown inFIG.1is sectioned along a line A1-A2.

For example, a glass substrate or a plastic substrate is used as the first substrate101and the second substrate102. For example, an organic resin such as acryl, polyimide, polyethylene terephthalate, and polyethylene naphthalate is used as the plastic substrate. The display device100that can be bent or curved can be formed as the first substrate101and the second substrate102using a plastic substrate having flexibility.

The first substrate101has a first surface101aand a second surface101bfacing the first surface101a. In addition, the second substrate102has a first surface102aand a second surface102bfacing the first surface102a. The first surface102aof the second substrate102is a surface from which light emitted from a light-emitting layer123is emitted, and the first surface102apreferably has a light diffusion effect. For example, the first surface102apreferably has a minute unevenness formed by an antiglare treatment. In addition, in the case where the light emitted from the light-emitting layer123is also emitted from the first surface101aof the first substrate101, the first surface101apreferably has a light diffusion effect. The first surface101apreferably has a minute unevenness formed by an antiglare treatment. The light emission of the light-emitting electrochemical cell120may be emitted from the first surface102aside of the second substrate102or may be emitted from the first surface101aside of the first substrate101. In addition, the light emission of the light-emitting electrochemical cell120may be emitted from both the first surface102aof the second substrate102and the first surface101aof the first substrate101.

The element formation layer140is provided on the first surface101aof the first substrate101, and the light-emitting electrochemical cell120is provided on the element formation layer140. In the present embodiment, light-emitting electrochemical cells120R,120G, and120B having different emission spectrum peaks are used as the light-emitting electrochemical cell120. In the present embodiment, the light-emitting electrochemical cell120R emits red, the light-emitting electrochemical cell120G emits green, and the light-emitting electrochemical cell1208emits blue. In the following explanation, when the light-emitting electrochemical cells120R,120G, and120B are not distinguished, they are simply referred to as the light-emitting electrochemical cell120. In addition, the same applies to each component of the light-emitting electrochemical cells120R,120G, and120B.

The light-emitting electrochemical cell120R has a structure in which a light-emitting layer123R including a light-emitting polymer and an ionic liquid is sandwiched between a first electrode121R and a second electrode122R. That is, a side surface123Rc of the light-emitting layer123R is in contact with the first electrode121R, and a side surface123Rd is in contact with the second electrode122R. Therefore, the light-emitting layer emits light by spontaneously forming a p-i-n bond by applying a voltage between the first electrode121and the second electrode122. Similarly, the light-emitting electrochemical cell120G has a structure in which a light-emitting layer123G including a light-emitting polymer and an ionic liquid is sandwiched between a first electrode121G and a second electrode122G. A first side surface123Gc of the light-emitting layer123G is in contact with the first electrode121G, and a second side surface123Gd is in contact with the second electrode122G. The light-emitting electrochemical cell120B has a structure in which a light-emitting layer123B including a light-emitting polymer and an ionic liquid is sandwiched between a first electrode121B and a second electrode122B. The first side surface123Bc of the light-emitting layer123B is in contact with the first electrode121B, and the second side surface123Bd is in contact with the second electrode122B.

The first electrode121and the second electrode122include at least one of an oxide conductive layer and a metal conductive layer. For example, an indium-oxide-based transparent conductive layer (for example, ITO) or a zinc-oxide-based transparent conductive layer (for example, IZO, ZnO) is used as the oxide conductive layer. In addition, an MgAg thin film may be used as the conductive layer having light transmittance instead of the oxide conductive layer. For example, a single layer or a stacked layer of copper, titanium, molybdenum, tantalum, tungsten, or aluminum is used as the conductive layer. In the present embodiment, the case where the oxide conductive layer is used as the first electrode121and the second electrode122will be described. In addition, in the present embodiment, although the hatching of the first electrode121and the hatching of the second electrode122are illustrated by different hatching, they have the same conductive material when the first electrode121and the second electrode122are formed of the same conductive film. Also, the first electrode121and the second electrode122may be formed of different conductive films. In this case, the first electrode121and the second electrode122may have different conductive materials. The thickness of each of the first electrode121and the second electrode122is, for example, 50 nm or more and 150 nm or less.

The light-emitting layer123includes a light-emitting polymer and an ionic liquid. The light-emitting layer123R, the light-emitting layer123G, and the light-emitting layer1238have different light-emitting polymers. When the thickness of the light-emitting layer123is increased, an electric field is less likely to be applied between the first electrode121and the second electrode122, and when the thickness is decreased, the first electrode121and the second electrode122are shorted. Therefore, the thickness of each of the light-emitting layers123R,123G, and123B is preferred to be 50 nm or more and 150 nm or less, for example. The thickness of the light-emitting layer123may be appropriately set within the above-described range according to the thicknesses of the first electrode121and the second electrode122.

An insulating layer125is provided between the second electrode122R and the first electrode121G. The insulating layer125electrically insulates the second electrode122R and the first electrode121G. The insulating layer125may have light transmittance and may be an inorganic material such as silicon oxide or silicon nitride, or an organic material such as polyimide, polyamide, acryl, or epoxy. A non-light transmittance film such as a metal film may be arranged on the side surface of the insulating layer125. According to this structure, it is possible to suppress unintentional mixing of lights of different colors emitted from the adjacent light-emitting layer123R, the light-emitting layer123G, and the light-emitting layer123B.

The adhesive material115is provided so as to surround peripheral edges of the first substrate101and the second substrate102. As a result, the first substrate101and the second substrate102are bonded. Since the light-emitting layer123deteriorates by moisture, the adhesion between the first substrate101and the second substrate102is preferably high.

AlthoughFIG.2shows the second surface102bof the second substrate102and the light-emitting electrochemical cell120are illustrated as being in contact with each other, the structure is not limited thereto. An insulating film may be provided between the second surface102bof the second substrate102and the light-emitting electrochemical cell120. The insulating film is provided on a side of the second surface102bof the second substrate102. The insulating film may be an inorganic material such as silicon oxide or silicon nitride, or an organic material such as polyimide, polyamide, acryl, or epoxy.

According to conventional light-emitting electrochemical cells, a total thickness of the light-emitting electrochemical cells was increased because the light-emitting electrochemical cells were formed by stacking the first electrode, the light-emitting layer, and the second electrode. In addition, since a metal conductive layer such as aluminum is used for at least one of the stacked first electrode or the second electrode, it is difficult to emit the light emission of the light-emitting electrochemical cell from both the upper substrate and the lower substrate.

The display device100according to one embodiment of the present invention, the light-emitting electrochemical cell120includes the first electrode121, the second electrode122, and the light-emitting layer123on the element formation layer140, and they are not stacked. The thicknesses of the first electrode121, the second electrode122, and the light-emitting layer123are substantially the same. As a result, the thickness of the light-emitting electrochemical cell120can be made smaller than when the first electrode121, the second electrode122, and the light-emitting layer123are stacked in this order. As a result, the total thickness of the display device100can be reduced. In addition, since the first electrode121and the second electrode122are not stacked on the light-emitting layer123, the light emission from the light-emitting layer123is not blocked by the first electrode121and the second electrode122even if the metal conductive layer is used for the first electrode121and the second electrode122. Therefore, the light emitted from the light-emitting layer123can be emitted from both the first substrate101side and the second substrate102side.

<Plan View of Element Formation Layer>

FIG.3is a plan view showing an outline of the element formation layer140. As shown inFIG.3, a display area103is provided on the first substrate101, and a peripheral area104is provided around the display area103. A plurality of pixel circuits109is arranged in a matrix in the display area103. Each of the pixel circuits109arranged in a matrix overlap each of the light-emitting electrochemical cells120. Although not shown inFIG.3, the switching element included in the pixel circuit109is electrically connected to the light-emitting electrochemical cell120. The light emission of the light-emitting electrochemical cell120is controlled by the switching element.

In addition, scan line drive circuits105aand105bare provided in the peripheral area104so as to sandwich the display area103, and a plurality of terminals107is provided at an end portion (end portion of the first substrate101) in the peripheral area104. A driver IC106is provided between the plurality of terminals107and the display area103. In addition, the plurality of terminals107is connected to a flexible printed circuit board108.

The scan line drive circuits105aand105bare connected to a gate wiring111which is connected to the pixel circuit109. The driver IC106is connected to a data wiring112which is connected to the pixel circuit109. AlthoughFIG.3shows an example in which a signal line drive circuit is incorporated in the driver IC is shown, the signal line drive circuit is provided on the first substrate101separately from the driver IC106. The driver IC106may be arranged on the first substrate101in the form of an IC chip or may be arranged on the flexible printed circuit board108.

In addition, although not shown, the pixel circuit109has a switching element, a gate of a switching element130is connected to the gate wiring111, and a source or drain of the switching element130is connected to the data wiring112.

Next, the pixel circuit109and the light-emitting electrochemical cell120included in the display device100will be described with reference toFIG.4andFIG.5.FIG.4is a layout of the light-emitting electrochemical cell120.FIG.4shows not only the light-emitting electrochemical cell120, but also data wirings112R,112G, and112B, and common wirings138R,138G, and138B formed in the element formation layer140. Although not shown, the common wirings138R,138G, and138B are electrically connected in the peripheral area104.

As shown inFIG.4, the first electrode121has a straight portion extending at least along a first direction D1. Specifically, the first electrode121has a straight portion extending along the first direction D1and a straight portion bent in a second direction D2intersecting the first direction D1. The second electrode122has a straight portion extending at least along the first direction D1. Specifically, the second electrode122has a straight portion extending along the first direction D1and a straight portion bent in the second direction D2intersecting the first direction D1. That is, the first electrode121has a shape opposite to an L-shape (the same shape as when the line-symmetrical shape of the L-shape is rotated 180° to the left with respect to the rotation center), and the second electrode122has an L-shape (the line-symmetrical shape of the L-shape). The first electrode121and the second electrode122face each other, and the light-emitting layer123is provided in an area surrounded by the first electrode121and the second electrode122.

A side surface123Ra and a side surface123Rb of the light-emitting layer123R face each other, and the side surface123Rc and the side surface123Rd face each other. The side surface123Ra and the side surface123Rc of the light-emitting layer123R are in contact with the first electrode121R, and the side surface123Rb and the side surface123Rd of the light-emitting layer123R are in contact with the second electrode122R. Therefore, the light-emitting layer123R can be made to emit light by applying a voltage between the first electrode121in contact with the side surface123Ra and the second electrode122in contact with the side surface123Rb, and between the first electrode121in contact with the side surface123Rc and the second electrode122in contact with the side surface123Rd.

The first electrode121R is electrically connected to the data wiring112R, and the second electrode122R is electrically connected to the common wiring138. The first electrode121G is electrically connected to the data wiring112G, and the second electrode122G is electrically connected to the common wiring138. The first electrode121B is electrically connected to the data wiring112B, and the second electrode122B is electrically connected to the common wiring138. The light-emitting electrochemical cell120controls the emission intensity of the light-emitting layer123by applying a voltage corresponding to the signal input to the data wiring112to the first electrode121and applying the voltage applied to the common wiring138to the second electrode122.

FIG.5is a cross-sectional view along a line B1-B2of the layout of the light-emitting electrochemical cell shown inFIG.4. InFIG.5, a detailed structure of the element formation layer140and the light-emitting electrochemical cell120will be described.

Switching elements130R and130G are provided on the first surface101aof the first substrate101via an under layer insulating film131. Specifically, the switching elements130R and130G are transistors. For example, the switching element130R includes a semiconductor layer132, a gate insulating film133, a gate electrode134, an interlayer insulating film135, and a source electrode or drain electrode136a,136b. Also, the under layer insulating film131is provided to prevent impurities from entering the semiconductor layer132from the first substrate101. The semiconductor layer132is provided on the under layer insulating film131, the gate insulating film133is provided on the semiconductor layer132, and the gate electrode134is provided to overlap the semiconductor layer132via the gate insulating film. The interlayer insulating film135is provided to cover the gate electrode134, and the source electrode or drain electrode136a,136bis provided on the interlayer insulating film135. The source electrode or drain electrode136a,136bis connected to the semiconductor layer132via contact holes formed in the interlayer insulating film135. The source electrode or drain electrode136ais a part of the data wiring112.

An interlayer insulating film137is provided on the interlayer insulating film135and the source electrode or drain electrode136a,136b, and the common wiring138is provided on the interlayer insulating film137. An insulating film139is provided on the interlayer insulating film137and the common wiring138.

Amorphous silicon, polysilicon, or an oxide semiconductor can be used as the semiconductor layer132. In addition, copper, titanium, molybdenum, tantalum, tungsten, and aluminum can be used as the gate electrode134, the source electrode or drain electrode136a,136b, and the common wiring138in a single layer or stacked layer. In addition, an inorganic material such as silicon oxide or silicon nitride can be used as the under layer insulating film131, the gate insulating film133, the interlayer insulating film135, and the interlayer insulating film137. In addition, the insulating film139is preferred to have a planarization function, and an organic material such as polyimide, polyamide, acryl, or epoxy can be used as the insulating film139.

The first electrode121R, the second electrode122R, and the light-emitting layer123are provided on the insulating film139as the light-emitting electrochemical cell120R. The first electrode121R is electrically connected to the source electrode or drain electrode136bvia a contact hole formed in the interlayer insulating film137and the insulating film139. Although not shown inFIG.5, the second electrode122R is electrically connected to the common wiring138via the contact hole formed in the insulating film139. In addition, the insulating layer125is provided between the second electrode122R and the first electrode121G.

<Method of Manufacturing Display Device>

Next, a method of manufacturing the display device100according to one embodiment of the present invention will be described while referring toFIG.6AtoFIG.8B.

FIG.6Ais a diagram illustrating the process of forming the element formation layer140on the first substrate101. The first substrate101has the first surface101aand the second surface101bfacing the first surface101a. The first surface101aof the first substrate101is subjected to an antiglare treatment. In addition, the thickness of the display device100can be reduced by setting the thickness of the first substrate101to 0.1 mm to 0.3 mm. Also, in the case where a diffuser or a reflector is separately provided on the first surface101aside, the antiglare treatment may not be performed on the first surface101a. The element formation layer140is formed on the second surface101bof the first substrate101. The under layer insulating film131, the switching element130, the interlayer insulating film137on the switching element130, the common wiring138, and the insulating film139included in the element formation layer140are formed using a known method.

FIG.6Bis a diagram illustrating a process of forming the first electrodes121R,121G, and121B and the second electrodes122R,122G, and122B on the element formation layer140. First, the contact hole reaching the source electrode or drain electrode136bis formed in the interlayer insulating film137and the insulating film139of the element formation layer140and the contact hole reaching the common wiring138is formed in the insulating layer139. Next, an oxide conductive film having light transmittance is formed on the element formation layer140(the insulating film139), and the first electrode121and the second electrode122are formed by a photolithography process. As a result, the first electrode121and the source electrode or drain electrode136bare electrically connected, and the second electrode122and the common wiring138are electrically connected. Also, in the present embodiment, although the case where the first electrode121and the second electrode122are formed in the same process will be described, they may be formed in different processes if the first electrode121and the second electrode122are formed of different conductive materials.

FIG.7Ais a diagram illustrating the process of forming the insulating layer125between the first electrode121and the second electrode122. For example, the insulating layer125is provided between the second electrode122R and the first electrode121G, and the insulating layer125is provided between the second electrode122G and the first electrode121B. The insulating layer125may be a material having light transmittance. For example, the insulating layer125may be formed using an inorganic material such as silicon oxide or silicon nitride, or an organic material such as polyimide, polyamide, acryl, or epoxy. For example, in the case where the insulating layer125is formed using an organic material, the insulating layer125may be formed by coating using an ink-jet method. In the case where the insulating layer125is formed by the ink-jet method, the insulating layer125may be selectively formed in an area between the first electrode121and the second electrode122.

FIG.7Bis a diagram illustrating the process of forming the light-emitting layers123R,123G,123B on the element formation layer140. For example, a light-emitting material that emits red light is applied by the ink-jet method to an area where the side surface of the first electrode121R and the side surface of the second electrode122R face each other. A light-emitting material that emits green light is applied by the ink-jet method to an area where the side surface of the first electrode121G and the side surface of the second electrode122G face each other. A light-emitting material that emits blue light is applied by the ink-jet method to an area where the side surface of the first electrode121B and the side surface of the second electrode122B face each other. Also, it is preferred to apply the insulating layer125and the light-emitting material by the ink-jet method because they can be formed at the same time. In addition, the light-emitting layers123R,123G, and123B can be randomly arranged by forming the light-emitting material by the ink-jet method as shown in the layout ofFIG.4.

The light-emitting material includes a light-emitting polymer, an ionic liquid, and an organic solvent. Examples of the light-emitting polymer include various 7-conjugated polymers. Specific examples thereof include paraphenylenevinylene, fluorene, 1,4-phenylene, thiophene, pyrrole, paraphenylene sulfide, benzothiadiazole, biotifin, or a polymer of a derivative obtained by introducing a substituent thereto, or a copolymer containing the same. The type of light-emitting polymer may be changed depending on the light-emitting layers123R,123G, and123B. In addition, the ionic liquid is a substance that is an ionic species and maintains a liquid state at room temperature. Although the examples thereof include a substance using a phosphonium system as a raw material, other raw materials may be used. The ionic liquid and the light-emitting polymer are efficiently mixed and used to ensure a reasonable viscosity in order to apply the organic solvent on the element formation layer140. For example, at least one selected from a group consisting of toluene, benzene, tetrahydrofuran, carbon disulfide, dimethyl chloride, chlorobenzene, and chloroform is preferred to be used as the organic solvent. In this case, only one of these compounds or only a combination of two or more of these compounds can be used as the organic solvent.

Next, the light-emitting material applied to the element formation layer140is annealed. The annealing process is preferred to be performed at a temperature at which the light-emitting material does not deteriorate, for example, 120° C. or lower. The annealing process may be performed in the atmosphere or in a vacuum. The light-emitting layers123R,123G, and123B having the light-emitting polymer and the ionic liquid are formed by evaporating the organic solvent contained in the light-emitting material by annealing.

FIG.8Ais a diagram illustrating the process of drawing the adhesive material115on the first surface101aof the first substrate101. For example, the adhesive material115is drawn on the first surface101aof the first substrate101so as to surround the peripheral portion of the first electrode121using a light-hardening resin.

FIG.8Bis a diagram illustrating a process of bonding the second substrate102on the first substrate101. The first surface102aof the second substrate102is subjected to the antiglare treatment. In addition, the thickness of the display device100can be reduced by setting the thickness of the second substrate102to 0.1 mm to 0.3 mm. Also, in the case where a diffuser or a reflector is separately provided on the first surface102aside, the antiglare treatment may not be performed on the first surface102a. The bonding of the first substrate101and the second substrate102may be performed in the atmosphere or in a vacuum. After the first substrate101and the second substrate102are bonded, the adhesive material115is cured by irradiating the adhesive material115with light, it is possible to adhere the first substrate101and the second substrate102.

The display device100according to one embodiment of the present invention can be manufactured by the above-described processes.

According to the method of manufacturing the conventional light-emitting electrochemical cell, since the light-emitting electrochemical cell is formed by stacking the first electrode, the light-emitting layer, and the second electrode, processes for forming each of them are required.

According to the method of manufacturing the light-emitting electrochemical cell120of the present embodiment, the first electrode121and the second electrode122can be formed on the element formation layer140in the same process by forming and processing the oxide conductive film. In addition, even when different light-emitting materials are used, the light-emitting layers123R,123G, and123B can be formed in the same process by applying different light-emitting materials by the ink-jet method. Further, the light-emitting layers123R,123G, and123B, and the insulating layer125can be formed in the same process by applying the light-emitting material and the organic material by the ink-jet method. As a result, the manufacturing process of the display device100can be simplified.

In the present embodiment, although the case where one display device100is manufactured for one substrate, the present invention is not limited thereto. A large substrate can also be used to manufacture a plurality of display devices100at once. In this case, a plurality of light-emitting electrochemical cells120may be formed on the first substrate101, and the first substrate101and the second substrate102are bonded by the adhesive material115and then separated for each of the plurality of display devices100.

Second Embodiment

In the present embodiment, a display device100A having a structure partially different from the display device100will be described with reference toFIG.9toFIG.11.FIG.9is a cross-sectional view when the display device100A is cut across a plurality of light-emitting electrochemical cells150.

The element formation layer140is provided on the first surface101aof the first substrate101, and the light-emitting electrochemical cell150is provided on the element formation layer140. The light-emitting electrochemical cell150includes an auxiliary electrode126and an auxiliary electrode127in addition to the first electrode121, the second electrode122, and the light-emitting layer123. The auxiliary electrode126is provided between the element formation layer140and the light-emitting layer123, and the auxiliary electrode127is provided between the second surface102band the light-emitting layer123of the second substrate102. The auxiliary electrode126is electrically connected to the first electrode121, and the auxiliary electrode127is electrically connected to the second electrode122. An area in contact with the light-emitting layer123can be increased by providing the auxiliary electrode126.

In addition, the auxiliary electrode126and the auxiliary electrode127preferably do not overlap each other. This is because a voltage is applied in the thickness direction of the display device100A by overlapping the auxiliary electrode126and the auxiliary electrode127. In addition, the area where the auxiliary electrode126is in contact with the light-emitting layer123and the area where the auxiliary electrode127is in contact with the light-emitting layer123are preferably substantially equal. Brightness unevenness can be suppressed in the light-emitting layer123by making the area where the auxiliary electrode126contacts the light-emitting layer123and the area where the auxiliary electrode127contacts the light-emitting layer123substantially equal.

The auxiliary electrode126and the auxiliary electrode127have the oxide conductive layer. For example, ITO and IZO having light transmittance are used as the oxide conductive layer. In addition, an MgAg thin film may be used as the conductive layer having light transmittance instead of the oxide conductive layer. In addition, in the present embodiment, although the hatching of the first electrode121and the hatching of the auxiliary electrode126are illustrated by different hatching, the first electrode121and the auxiliary electrode126may be formed of the same conductive material. Similarly, although the hatching of the second electrode122and the hatching of the auxiliary electrode127are illustrated by different hatching, the second electrode122and the auxiliary electrode127may be formed of the same conductive material. In addition, the thickness of each of the auxiliary electrode126and the auxiliary electrode127is preferred to be smaller than the thickness of the first electrode121and the second electrode122. For example, the thicknesses of the auxiliary electrode126and the auxiliary electrode127are set to be smaller than the thicknesses of the first electrode121and the second electrode122within a range of 50 nm or more and 150 nm.

FIG.10is a layout of the display device100A. The layout shown inFIG.10is different from the layout shown inFIG.4in that the auxiliary electrode126and the auxiliary electrode127are provided in the first electrode121and the second electrode122.

As shown inFIG.10, in a light-emitting electrochemical cell150R, the first electrode121R has an auxiliary electrode126R electrically connected to the first electrode121R, and the second electrode122R has an auxiliary electrode127R electrically connected to the second electrode122R. The shape of the auxiliary electrode126R is shown by dashed lines because the auxiliary electrode126R is provided below the light-emitting layer123R.

FIG.11is a cross-sectional view along a line C1-C2of the layout of the light-emitting electrochemical cell shown inFIG.10. A detailed structure of the element formation layer140and the light-emitting electrochemical cell150will be described inFIG.11. Also, since a structure of the switching element130is the same as that of the switching element130shown inFIG.5, a detailed explanation thereof is omitted.

The interlayer insulating film137is provided on the interlayer insulating film135and the source electrode or drain electrode136a,136b, and the common wiring138is provided on the interlayer insulating film137. The insulating film139is provided on the interlayer insulating film137and the common wiring138. An organic insulating film having a planarization function is preferably used as the insulating film139.

The light-emitting electrochemical cell150is provided on the insulating film139. The auxiliary electrode126is provided between the element formation layer140and the light-emitting layer123. The auxiliary electrode126is electrically connected to the source electrode or drain electrode136bvia the contact hole formed in the interlayer insulating film137and the insulating film139. The first electrode121is provided on the auxiliary electrode126.

The auxiliary electrode127is provided between the second substrate102and the light-emitting layer123. Although not shown inFIG.11, the second electrode122is electrically connected to the common wiring138via the contact hole formed in the insulating film139. The auxiliary electrode127is electrically connected to a common wiring128via the second electrode122.

<Method of Manufacturing Display Device>

Next, a method of manufacturing the display device100A according to one embodiment of the present invention will be described while referring toFIG.12AandFIG.14.

FIG.12Ais a diagram illustrating the process of forming the element formation layer140and the auxiliary electrode126on the first substrate101. The element formation layer140is formed on the second surface101bof the first substrate101by a known method. Next, the contact hole reaching the source electrode or drain electrode136bis formed in the element formation layer140and the insulating film139. In addition, the contact hole reaching the common wiring138is formed in the insulating film139. Next, an oxide conductive film is formed on the element formation layer140(the insulating film139), and the auxiliary electrode126is formed by the photolithography process. As a result, the auxiliary electrode126and the source electrode or drain electrode136bare electrically connected.

FIG.12Bis a diagram illustrating the process of forming the first electrode121and the second electrode122on the element formation layer140. First, a metal conductive film is formed on the element formation layer140(the insulating film139), and the first electrode121and the second electrode122are formed by the photolithography process. As a result, the first electrode121is provided on the auxiliary electrode126. In addition, the second electrode122is electrically connected to the common wiring138via the contact hole formed in the insulating film139. Also, in the present embodiment, although an example in which the second electrode122is directly connected to the common wiring138is shown, one embodiment of the present invention is not limited thereto. For example, the second electrode122may be connected to the common wiring138via a conductive layer made of the same conductive material as the auxiliary electrode126. It is preferred to use the oxide conductive film as the auxiliary electrode126and the metal conductive film as the first electrode121and the second electrode122because the processing of the auxiliary electrode126and the first electrode121is facilitated.

FIG.13Ais a diagram illustrating the process of forming the insulating layer125and the light-emitting layers123R,123G, and123B. The insulating layer125is formed between the first electrode121and the second electrode122. Next, the light-emitting material that emits red light is applied by the ink-jet method to the area where the side surface of the first electrode121R and the side surface of the second electrode122R face each other. The light-emitting material that emits green light by the ink-jet method to the area where the side surface of the first electrode121G and the side surface of the second electrode122G face each other. The light-emitting material that emits blue light is applied by the ink-jet method to the area where the side surface of the first electrode121B and the side surface of the second electrode122B face each other. It is preferred to apply the insulating layer125and the light-emitting material by the ink-jet method because they can be formed at the same time.

Next, the light-emitting material applied to the element formation layer140is annealed. The annealing temperature is preferably a temperature at which the light-emitting material does not deteriorate, for example, 120° C. or lower. The annealing atmosphere may be air or vacuum. The light-emitting layers123R,123G, and123B having the light-emitting polymer and the ionic liquid are formed by evaporating the organic solvent contained in the light-emitting material by annealing.

FIG.13Bis a diagram illustrating the process of forming the auxiliary electrode127on the second surface102bof the second substrate102. An oxide conductive film is formed on the second surface102bof the second substrate102, and the auxiliary electrode127is formed by the photolithography process.

FIG.14is a diagram illustrating the process of bonding the second substrate102on the first substrate101. The first substrate101and the second substrate102are bonded so that each of the auxiliary electrodes127R,127G, and127B formed on the second surface102bof the second substrate102contacts each of the second electrodes122R,122G and122B. As a result, the first substrate101and the second substrate102can be bonded so that each of the auxiliary electrodes122R,122G and1228is in contact with each of the auxiliary electrodes127R,127G, and127B. The bonding of the first substrate101and the second substrate102may be performed in the atmosphere or in a vacuum. After the first substrate101and the second substrate102are bonded, the adhesive material115is cured by irradiating the adhesive material115with light, and it is possible to adhere the first substrate101and the second substrate102.

The display device100A according to one embodiment of the present invention can be manufactured by the above-described processes.

Although the display device according to one embodiment of the present invention is described above, the above-described embodiments can be combined with or replaced with each other. In addition, in each of the above-described embodiments, at least some of them can be modified as follows.

(1) In the first embodiment, although the structure in which the first electrode121and the second electrode122have the straight portions extending in the first direction D1and the straight portions bent in the second direction D2intersecting the first direction D1is described, the shape of the first electrode121and the second electrode122is not limited thereto. The first electrode121and the second electrode122may have at least the straight portion extending in the first direction D1or the straight portion extending in the second direction D2.FIG.15is a diagram in which the first electrode121has the straight portion extending in the second direction D2and the second electrode122has the straight portion extending in the second direction D2. The side surface123Rc of the light-emitting layer123R is in contact with the first electrode121R, and the side surface123Rd is in contact with the second electrode122R. The light-emitting layer123R can be made to emit light by applying a voltage between the first electrode121and the second electrode122. Although not shown, the first electrode121has the straight portion extending in the first direction D1, and the second electrode122has the straight portion extending in the first direction D1. The side surface123Ra of the light-emitting layer123R is in contact with the first electrode121R, and the side surface123Rb may cause the light-emitting layer123R to emit light by the side surface123Rb in contact with the second electrode122R and by being applied with a voltage between the first electrode121and the second electrode122.

(2) In the second embodiment, although the structure in which the shape of the auxiliary electrode126and the auxiliary electrode127is provided as a triangle is described, the shape of the auxiliary electrode126and the auxiliary electrode127is not limited thereto. The auxiliary electrode126may have a plurality of areas extending in the first direction D1, and the auxiliary electrode127may have a plurality of areas extending in the first direction D1.FIG.16is a diagram in which the auxiliary electrode126has a plurality of areas126Ra,126Rb, and126Rc extending in the first direction D1, and the auxiliary electrode127has a plurality of areas127Ra,127Rb, and127Rc extending in the first direction D1. The plurality of areas126Ra,126Rb, and126Rc may be electrically connected to the first electrodes121. Therefore, the plurality of areas126Ra,126Rb, and126Rc may be separated or connected. Similarly, the plurality of areas127Ra,127Rb, and127Rc may be electrically connected to the second electrodes122. Therefore, the plurality of areas127Ra,127Rb, and127Rc may be separated or connected.

(3) In the second embodiment, although the structure in which the auxiliary electrode127is provided between the second surface102bof the second substrate102and the light-emitting layer123is described, the position at which the auxiliary electrode127is arranged is not limited thereto. Similar to the auxiliary electrode126, the auxiliary electrode127may be provided between the element formation layer140and the light-emitting layer123.FIG.17is a light-emitting electrochemical cell partially different from the light-emitting electrochemical cell shown inFIG.16.FIG.17is different fromFIG.16in that the plurality of areas127Ra,127Rb, and127Rc of the auxiliary electrode127is provided between the element formation layer140and the light-emitting layer123. The plurality of areas127Ra,127Rb, and127Rc of the auxiliary electrode127can be formed in the same process as the plurality of areas126Ra,126Rb,126Rc of the auxiliary electrode126by providing the plurality of areas127Ra,127Rb, and127Rc of the auxiliary electrode127between the element formation layer140and the light-emitting layer123R. Although not shown, the plurality of areas126Ra,126Rb, and126Rc of the auxiliary electrode126and the plurality of areas127Ra,127Rb, and127Rc of the auxiliary electrode127may be provided between the second surface102bof the second substrate102and the light-emitting layer123.

(4) In the second embodiment, although the structure in which the auxiliary electrode126is provided between the element formation layer140and the light-emitting layer123, and the auxiliary electrode127is provided between the second surface102bof the second substrate102and the light-emitting layer123is described, the position where the auxiliary electrode126and the auxiliary electrode127are arranged is not limited thereto. The auxiliary electrode126may be provided between the second surface102bof the second substrate102and the light-emitting layer123, and the auxiliary electrode127may be provided between the element formation layer140and the light-emitting layer123.FIG.18shows a light-emitting electrochemical cell partially different from the light-emitting electrochemical cell shown inFIG.11. InFIG.18, the auxiliary electrode126is provided between the second surface102bof the second substrate102and the light-emitting layer123R, and the auxiliary electrode127is provided between the element formation layer140and the light-emitting layer123R. Although not shown inFIG.18, the auxiliary electrode127is connected to the common wiring138via the contact hole formed in the insulating film139.

Within the scope of the present invention, it is understood that various modifications and changes can be made by those skilled in the art and that these modifications and changes also fall within the scope of the present invention. For example, the addition, deletion, or design change of components, or the addition, deletion, or condition change of processes as appropriate by those skilled in the art based on each embodiment are also included in the scope of the present invention as long as they are provided with the gist of the present invention.