WO2018207484A1 - Display device and electronic apparatus - Google Patents

Abstract

[Problem] To provide a display device and an electronic apparatus in which a leakage current between pixels is suppressed. [Solution] This display device comprises: an organic electroluminescent layer; a first electrode disposed on one primary surface side of the organic electroluminescent layer and shared by a plurality of pixels; a plurality of second electrodes disposed on the other primary surface side of the organic electroluminescent layer and disposed individually to each pixel; and a plurality of third electrodes disposed on the other primary surface side of the organic electroluminescent layer and disposed between each of the plurality of second electrodes.

Description

Display device and electronic device

This disclosure relates to a display device and an electronic device.

In recent years, there has been an increasing demand for high definition and low power consumption for display devices for mobile use.

For example, a display device using an organic electro-luminescence element (OLED) disclosed in Patent Document 1 described below is self-luminous and has low power consumption, so that it can be applied to mobile applications. Expected.

However, in such an organic electroluminescent device, since the organic electroluminescent layer is provided in common for all the light emitting devices, a leakage of drive current is likely to occur between adjacent light emitting devices.

For this reason, Patent Document 1 discloses a technique in which a relief pattern for blocking an electrode and a charge transport layer is disposed between light emitting elements. In Patent Document 2, a portion of the hole transport layer other than the light emitting region of each pixel is surface-treated with ultraviolet rays to increase a resistance value of a portion irradiated with the ultraviolet rays, thereby suppressing leakage current between the pixels. Is disclosed. Further, Patent Document 3 discloses a technique for applying a periodic drive voltage to a light emitting element to suppress leakage current.

Special table 2003-530660 gazette JP 2004-158436 A JP 2014-52617 A

By the way, in an organic electroluminescence (organic EL) display, display is generally performed by driving an organic electroluminescent element with a thin film transistor formed on a glass substrate. In applications such as displays for televisions and smartphones, amorphous silicon and polycrystalline silicon, for example, are used as channel materials for transistors.

On the other hand, for a high-definition and small-sized display device having a pixel pitch of 10 μm or less and a resolution exceeding 2500 ppi, an organic electroluminescent element is driven by a MOS (Metal-Oxide-Semiconductor) transistor formed on Si. There is a case.

The technologies disclosed in Patent Documents 1 and 2 are difficult to apply to a display device having such a high pixel pitch. Further, the technique disclosed in Patent Document 3 is very complicated in controlling the drive voltage.

Therefore, the present disclosure proposes a new and improved display device and electronic apparatus that can suppress the leakage current between pixels.

According to the present disclosure, the organic electroluminescent layer, the first electrode disposed on one main surface side of the organic electroluminescent layer and common to a plurality of pixels, and the other main surface side of the organic electroluminescent layer And a plurality of second electrodes arranged individually for each pixel, and a plurality of second electrodes arranged on the other main surface side of the organic electroluminescent layer and between the plurality of second electrodes. A third electrode is provided.

Further, according to the present disclosure, the organic electroluminescent layer, the first electrode disposed on one main surface side of the organic electroluminescent layer and common to a plurality of pixels, and the other main electroluminescent layer of the organic electroluminescent layer are disposed. A plurality of second electrodes arranged on the surface side and corresponding to each pixel individually, on the other main surface side of the organic electroluminescent layer, and between the plurality of second electrodes There is provided an electronic device including a display unit having a plurality of third electrodes disposed on the surface.

According to the present disclosure, it is possible to provide a display device and an electronic apparatus in which leakage current between pixels is suppressed. Therefore, it is possible to prevent unintentional light emission of the pixel due to the leak current and a decrease in the color gamut of the display image accompanying this.

As described above, according to the present disclosure, it is possible to provide a display device and an electronic apparatus in which leakage current between pixels is suppressed.
Note that the above effects are not necessarily limited, and any of the effects shown in the present specification, or other effects that can be grasped from the present specification, together with or in place of the above effects. May be played.

It is sectional drawing which shows typically the display apparatus which concerns on one Embodiment of this indication. It is a typical top view for demonstrating arrangement | positioning of the separate electrode of a display apparatus shown in FIG. 1, and a 3rd electrode. It is typical sectional drawing for demonstrating the structure of the separate electrode of the display apparatus shown in FIG. FIG. 2 is a schematic circuit diagram of an organic electroluminescence element included in the display device shown in FIG. 1. It is a graph which shows the relationship between the leakage current and light emission current in a display apparatus. It is a graph which shows the relationship between the brightness | luminance in a display apparatus, leakage current, and light emission current. It is a top view showing the shape and arrangement of an individual electrode and a 3rd electrode in one modification of this indication. It is a top view showing the shape and arrangement of an individual electrode and a 3rd electrode in one modification of this indication. It is a top view showing the shape and arrangement of an individual electrode and a 3rd electrode in one modification of this indication. It is a typical sectional view explaining an individual electrode and a 3rd electrode in one modification of this indication. It is a typical sectional view explaining an individual electrode and a 3rd electrode in one modification of this indication. It is a typical sectional view explaining an individual electrode and a 3rd electrode in one modification of this indication. FIG. 10 is a cross-sectional view schematically illustrating a display device according to a modification example of the present disclosure. It is a typical sectional view for explaining composition of an individual electrode in one modification of this indication. It is sectional drawing which shows typically an example of the display apparatus which does not have a 3rd electrode. FIG. 16 is a plan view illustrating an arrangement of pixels included in the display device illustrated in FIG. 15. It is a schematic diagram for demonstrating the leakage current between separate electrodes. It is a schematic diagram for demonstrating the leakage current between separate electrodes. It is a graph which shows typically the relation between the voltage and current of an organic electroluminescent layer. FIG. 16 is a schematic arrangement view of individual electrodes provided in the display device shown in FIG. 15.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol. In addition, the size of each member in the drawing is emphasized as appropriate for ease of explanation, and does not indicate actual dimensions and ratios between members.

The description will be made in the following order.
1. Background and overview of the present disclosure 1.1. Problems of leakage current in display device 1.2. 1. Overview of suppression of leakage current according to the present disclosure 2. Configuration of display device 3. Verification of influence of leakage current Modification 5 Summary

<1. Background and Summary of the Disclosure>

[1.1. Problems of leakage current in display devices]
First, prior to detailed description of the present disclosure, a problem of leakage current in a display device using an organic electroluminescent element will be described. 15 is a cross-sectional view schematically showing an example of a display device that does not have a third electrode to be described later, FIG. 16 is a plan view showing the arrangement of pixels that the display device shown in FIG. 18 is a schematic diagram for explaining a leakage current between individual electrodes, FIG. 19 is a graph schematically showing a relationship between the voltage and current of the organic electroluminescent layer, and FIG. 20 is a display device shown in FIG. FIG. 3 is a schematic arrangement view of individual electrodes.

A display device 200 shown in FIG. 15 is a display device using an active matrix organic electroluminescent element. In the display device 200, the organic electroluminescent layer 210 is disposed on the interlayer insulating film 280. The organic electroluminescent layer 210 has an individual electrode 220 as an anode on the interlayer insulating film 280 side and a cathode on the opposite side. Transparent common electrode 230 is disposed. On the transparent common electrode 230, a protective insulating film 240, a color filter layer 250, a sealing resin 260, and a cover glass 270 are laminated in this order. On the other hand, in the interlayer insulating film 280, a contact 281 and a wiring 283 that connect the individual electrode 220 to a pixel drive circuit (not shown) are arranged.

The organic electroluminescent layer 210 can emit white light when a voltage is applied between the transparent common electrode 230 and the individual electrode 220, for example. White light emitted from the organic electroluminescent layer 210 passes through the transparent common electrode 230 and the protective insulating film 240 and enters the color filter layer 250. The color filter layer 250 includes a red color filter 250R, a green color filter 250G, and a blue color filter 250B that are divided corresponding to each individual electrode 220. The red color filter 250R, the green color filter 250G, and the blue color filter 250B convert incident light into red, green, and blue, respectively, and emit the light toward the sealing resin side. The emitted light further passes through the sealing resin 260 and the cover glass 270 and is emitted to the outside.

An example of the pixel array in the active matrix display device 200 is that shown in FIG. 16 in plan view. As shown in FIG. 16, the individual pixel 220 and the corresponding red color filter 250R, green color filter 250G, and blue color filter 250B form red pixels SP _R , green pixels SP _G, and blue pixels SP _B as sub-pixels. . Such a large number of red pixels SP _R , green pixels SP _G and blue pixels SP _B are capable of emitting light of the three primary colors of red, green and blue and constitute one pixel. By arranging such pixels in a matrix, a display panel that displays an image corresponding to the input signal in color is configured.

Here, the leakage current between pixels is examined. 17 and 18 are schematic diagrams for explaining the leakage current between the individual electrodes 220, and FIG. 19 is a schematic diagram showing the relationship between the voltage and current of the individual electrode (anode) 220 when a voltage is applied to the organic electroluminescent layer 210. FIG. As a result of the present inventors having prototyped and examined various display elements, a case where a leak current flowing between the individual electrodes 220 greatly increases the potential of the non-light-emitting individual electrode 220 is recognized, and the main path of the leak current is It was found that this was the lower layer portion of the organic electroluminescent layer 210 shown in FIG. Details will be described below.

In the display device 200 described above, the organic electroluminescent layer 210 is not separated for each color, and the individual electrodes 220 corresponding to the subpixels are connected below the organic electroluminescent layer 210. The organic electroluminescent layer 210 is not a good insulator in nature, and it is difficult to completely suppress the leakage current between the adjacent individual electrodes 220. That is, an organic material layer that easily injects charges such as holes is arranged on the individual electrode 220 side of the organic electroluminescent layer 210. Therefore, current flows through such an organic material layer as a leakage path. Can leak. Typically, the sheet resistance of the organic electroluminescent layer 210 is considered to be about 10 ¹² Ω / □ or less.

Considering such a leakage path of the organic electroluminescent layer 210, the resistance R _IE-IE of the portion where the leakage current between the adjacent individual electrodes 220 flows is (sheet resistance Ω / □ of the organic electroluminescent layer 210) × ( The distance between the individual electrodes 220) / (the length of one side of the individual electrodes 220) is approximately expressed. The amount of leakage current is affected by the relationship between the resistance R _SP in the thickness direction of the organic electroluminescent layer 210 and the resistance R _IE-IE between the individual electrodes 220 when a voltage is applied.

On the other hand, considering the light emission current characteristics shown in FIG. 19, the organic electroluminescent layer 210 has an extremely small light emission current when the voltage applied by the individual electrode 220 is relatively small. That is, the current-voltage characteristics are not ohmic but rise rapidly from around 3.5 V, and when the applied voltage is low, the resistance R _SP in the thickness direction of the organic electroluminescent layer 210 is large. Therefore, when display is to be performed with low luminance light emission, the resistance R _SP with respect to the resistance R _IE-IE increases, and the influence of the leakage current increases.

Therefore, in the display device 200 as shown in FIG. 15, it is difficult to suppress a leakage current that flows unintentionally between the individual electrodes 220 that feed the organic electroluminescent layer 210. Further, it was considered that the influence of the leakage current appears more remarkably when a low voltage is applied to the organic electroluminescent layer 210 in order to perform low luminance display.

The leakage current flowing between the individual electrodes 220 described above can cause a decrease in the color gamut of the display device 200. When pure blue is displayed by causing only the blue pixel SP _B to emit light, for example, a voltage may be applied between the central individual electrode 220B and the transparent common electrode 230 in FIG. it can. However, as indicated by an arrow in FIG. 20, a leak current flows to the surrounding individual electrodes 220R and 220G corresponding to the red and green pixels SP _R and SP _G adjacent thereto. As a result, the pixels SP _R and SP _G around the pixel SP _B shine red or green, so that the blue color purity displayed in the pixel SP _B falls. Since the same phenomenon occurs when other colors such as red and green are developed, the color gamut that can be displayed is narrowed.

Further, in a display device having a fine pixel pitch P _P, in particular, reduction in color reproducibility in a low luminance which is caused by the leak current is remarkable. This will be specifically described below. When refining the pitch P _P between pixels, although reasonable for roughly that miniaturized to keep similar figure the arrangement of the individual electrodes 220, for example, in the case of halving the size of the individual electrode 220 It is practical to halve the distance between the individual electrodes 220 adjacent to each other. This is because the dimensions of the individual electrodes 220 and the distance between the individual electrodes 220 are set based on the accuracy of photolithography at the time of manufacture.

Here, when the current-voltage characteristic of the organic electroluminescent layer 210 is approximated by a simple resistance, the resistance of the organic electroluminescent layer 210 is inversely proportional to the area of the individual electrode 220. For example, if you set the pixel pitch _{P P} 1/2, the resistance _{R SP} portion of the organic electroluminescent layer 210 corresponding to the individual electrode 220 is increased to four times.
On the other hand, the resistance R _IE-IE between the individual electrode 220, since no change is the ratio of the length of one side of the individual electrode 220 between the distance and the individual electrode 220 Changing the pixel pitch P _P, light of the above formula It seems that there is no change. Therefore, the smaller the pixel pitch _{P P,} the resistance _{R SP} portion of the organic electroluminescent layer 210 is increased in inverse proportion to the square of the pixel pitch _{P P} to the resistance _{R IE-IE} between the individual electrode 220, individual electrode 220 The influence of the leakage current between them increases. As a result, the color reproducibility of the display device 200 at a low luminance is likely to deteriorate.

[1.2. Overview of leakage current suppression according to the present disclosure]
As described above, the present inventors have specified that the occurrence of leakage current between the individual electrodes 220 passes through the organic electroluminescent layer 210. Furthermore, the present inventors have found that the leakage current affects the color reproducibility of the display device 200, particularly the color reproducibility at low luminance, and the influence of the leakage current increases as the pixel pitch _PP is reduced. It was.

For the purpose of suppressing the influence of such a leakage current, the present disclosure, as shown in FIG. 1 and FIG. 2, provides additional electrodes (a later-described first electrode) between the individual electrodes 20 (20 B, 20 G, and 20 R). 3) 90) was considered. Then, the present inventors set the potential of the third electrode 90 closer to the potential of the transparent common electrode 30 than the potential of the individual electrode 20, thereby reducing the leakage current generated in the individual electrode 20. It was found that it can be absorbed. Hereinafter, the present disclosure will be described in more detail.

<2. Configuration of display device>
Next, the display device according to the present embodiment will be described in detail. FIG. 1 is a cross-sectional view schematically showing an example of a display device according to the present embodiment, and FIG. 2 is a schematic plan view for explaining the arrangement of individual electrodes and third electrodes of the display device shown in FIG. 3 is a schematic cross-sectional view for explaining the configuration of individual electrodes of the display device shown in FIG. 1, and FIG. 4 is a schematic circuit diagram of an organic electroluminescent element provided in the display device shown in FIG. .

The display device 100 shown in FIGS. 1 to 4 is a top emission type display device provided with an active matrix organic electroluminescent element. In the display device 100, the organic electroluminescent layer 10 is disposed on the interlayer insulating film 80, and an individual electrode (second electrode) as an anode is formed on the main surface of the organic electroluminescent layer 10 on the interlayer insulating film 80 side. 20, a transparent common electrode (first electrode) 30 as a cathode is disposed on the opposite main surface. Further, a third electrode 90 is disposed between the individual electrodes 20 on the main surface of the organic electroluminescent layer 10 on the interlayer insulating film 80 side. On the transparent common electrode 30, the protective insulating film 40, the color filter layer 50, the sealing resin 60, and the cover glass 70 are laminated in this order. In the interlayer insulating film 80, a contact 81 and a wiring 83 that connect the individual electrode 20 to the pixel drive circuit, and a contact 85 and a wiring 87 that connect to the third electrode 90 are disposed. A circuit for driving the organic electroluminescent element OLED as shown in FIG. 4 is appropriately arranged in the interlayer insulating film 80 and a semiconductor substrate (not shown) below the interlayer insulating film 80.

In the present embodiment, as in the display device 200, the display device 100 includes a red pixel SP _R , a green pixel SP _G , and a blue pixel SP _B as shown in FIG. The red pixel SP _R , the green pixel SP _G , and the blue pixel SP _B are combined to form one pixel. The pixels can be arranged in a matrix to display an image.

The organic electroluminescent layer 10 includes an organic luminescent material, and is provided on the individual electrode 20 and the interlayer insulating film 80 as a continuous film common to all the organic electroluminescent elements OLED. The organic electroluminescent layer 10 emits light when an electric field is applied between the individual electrode 20 and the transparent common electrode 30.

Specifically, when an electric field is applied, holes are injected from the individual electrode 20 and electrons are injected from the transparent common electrode 30 into the organic electroluminescent layer 10. The injected holes and electrons recombine in the organic electroluminescent layer 10 to form excitons, and the exciton energy excites the organic light emitting material, so that fluorescence or phosphorescence is emitted from the organic light emitting material. generate.

Here, the organic electroluminescent layer 10 may be formed in a multilayer structure in which a plurality of functional layers are stacked. For example, the organic electroluminescent layer 10 may be formed in a structure in which a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer are sequentially stacked from the individual electrode 20 side. The organic electroluminescent layer 10 may be formed in a so-called tandem structure in which a plurality of light emitting layers are connected via a charge generation layer or an intermediate electrode.

The organic electroluminescent layer 10 is composed of a hole transport material, an electron transport material, an electric charge transport material, an organic light emitting material, or the like according to the layer configuration. Each of such materials is not limited and can be appropriately combined with known materials.
Moreover, the wavelength of the light emitted from the organic electroluminescent layer 10 can be appropriately set according to the application, and in the display device 100 according to the present embodiment, the emission wavelength is set so that the emission color is white.

Further, as described above, the organic electroluminescent layer 10 is a continuous film common to the organic electroluminescent element OLED, and is continuously formed over a plurality of pixels in a plan view. Here, in the case of an organic electroluminescence display having a pixel pitch of several tens of microns or more, an organic electroluminescent layer that emits each color of red, green, and blue is divided for each color by mask evaporation or the like. Sometimes it forms. However, in the case of a high-definition small display using Si-MOS having a pixel pitch of 10 μm or less, it is difficult to divide and form the organic electroluminescent layer for each color. Therefore, when manufacturing the display device 100 having a small pixel pitch, the organic electroluminescent layer 10 that emits white light is formed so as to cover the entire effective pixel region, and the red / green is formed by the color filter layer 50 disposed thereon.・ A system that splits each blue color is suitable.

On the other hand, the organic electroluminescent layer 10 is considered to have a tendency that leakage current tends to flow between pixels because there is no layer breakage. However, in the display device 100 according to the present embodiment, since the leakage current flows to the third electrode 90 described later, the movement of the leakage current between the pixels is suppressed.

The transparent common electrode 30 functions as a cathode of the organic electroluminescent element OLED. Therefore, when a voltage is applied to the organic electroluminescent layer 10, the potential of the transparent common electrode 30 is smaller than the potential of the individual electrode 20 described later. The transparent common electrode 30 is provided on the organic electroluminescent layer 10 as a continuous film common to all the light emitting elements. The transparent common electrode 30 may be formed as a light transmissive electrode with a material having a high light transmittance and a small work function. For example, the transparent common electrode 30 may be formed of a transparent conductive material such as indium tin oxide, indium zinc oxide, zinc oxide, aluminum-doped zinc oxide, or gallium-doped zinc oxide, and may include aluminum (Al), magnesium (Mg ), Silver (Ag), calcium (Ca), or sodium (Na) or other metal alloy may be formed as a thin film (eg, 30 nm or less) that is thin enough to have optical transparency. Further, the transparent common electrode 30 may be formed by laminating a plurality of films made of the metal or alloy described above.

The individual electrode 20 is provided on the interlayer insulating film 80 for each pixel and functions as an anode of the organic electroluminescent element OLED. As shown in FIG. 2, in plan view, the individual electrodes 20 are disposed at equal intervals on the basis of a predetermined pixel pitch P _P corresponding to the arrangement and shape of the pixel. Specifically, an individual electrode 20R corresponding to a red pixel, an individual electrode 20G corresponding to a green pixel, and an individual electrode 20B corresponding to a blue pixel are repeatedly arranged with a boundary region having a predetermined interval therebetween. Further, in the present embodiment, the individual electrodes 20 each have a hexagonal shape in plan view.

The individual electrode 20 may be formed of a material having a high light reflectance and a large work function as a light reflecting electrode. For example, the individual electrode 20 may be formed of a simple substance or an alloy of a metal such as Cr, Au, Pt, Ni, Cu, Mo, W, Ti, Ta, Al, Fe, or Ag. May be formed by laminating a plurality of layers. Among them, Al has a high reflectance of visible light of 90% or more, and can have both power supply and a function as a reflector at the same time. When Al is used as the individual electrode 20, a trace amount of Cu may be added.

Further, as shown in FIG. 3, the individual electrode 20 may be formed by laminating an electrode 201 and a light reflecting layer 202 having conductivity. In this case, the electrode 201 can be made of a material suitable for injecting holes into the organic electroluminescent layer 10. Alternatively, the electrode 201 may be formed as a transparent electrode using a transparent conductive material such as indium zinc oxide or indium tin oxide. The light reflecting layer 202 can be made of a single metal or an alloy of metal such as Cr, Au, Pt, Ni, Cu, Mo, W, Ti, Ta, Al, Fe, or Ag.

Further, as shown in FIG. 1, a plurality of third electrodes 90 are arranged in a boundary region between the plurality of individual electrodes 20 so as to be in contact with the main surface of the organic electroluminescent layer 10. Further, as shown in FIG. 2, in the present embodiment, the plurality of third electrodes 90 are regularly arranged so as to be equidistant from the adjacent individual electrodes 20R, 20G, and 20B in plan view. Has been. From another point of view, the plurality of third electrodes 90 are arranged so as to be separated from the individual electrodes 20R, 20G, and 20B by a predetermined distance in a plan view and to surround them.

The plurality of third electrodes 90 are connected to the internal circuit of the display device 100 through contacts 85 and wirings 87, and are set to a constant potential in common. Specifically, when a voltage is applied to the organic electroluminescent layer 10, the potential of the third electrode 90 is a value obtained by adding the threshold voltage of the organic electroluminescent layer 10 to the potential of the transparent common electrode 30. Is set to be smaller.

Thus, even when a voltage is applied to the organic electroluminescent layer 10 by the transparent common electrode 30 and the individual electrode 20 and a leakage current is generated from the applied individual electrode 20 due to this, the third A leakage current can flow preferentially through the electrode 90. For this reason, leakage current is prevented from flowing from the applied individual electrode 20 to the adjacent individual electrode 20. As a result, it is possible to prevent the organic electroluminescent layer 10 from emitting light due to a voltage caused by a leakage current between the unintended individual electrode 20 and the transparent common electrode 30.

Specifically, for example, as shown in FIG. 2, when a voltage is applied to the organic electroluminescent layer 10 between the central individual electrode 20B and the transparent common electrode 30, a leakage current generated in the individual electrode 20B. Flows preferentially to the surrounding third electrode 90 (arrow in the figure). As a result, the leakage current is prevented from flowing through the surrounding individual electrodes 20B and 20G, and the surrounding green and red pixels are prevented from emitting light. As a result, a decrease in color purity of the blue pixel corresponding to the individual electrode 20B is prevented, and an image can be displayed in a wide color gamut on the display device 100.

The potential of the third electrode 90 as described above is preferably equal to or lower than the potential of the transparent common electrode 30. Thereby, the leak current generated in the individual electrode 20 can preferentially flow to the surrounding third electrode 90 more reliably. In the present embodiment, the individual electrode 20 is an anode, and can have a positive potential when a voltage is applied. Therefore, in this case, the potential of the third electrode 90 can be set to 0 V or less, for example.

Furthermore, the potential of the third electrode 90 is preferably the same as the potential of the transparent common electrode 30. Thereby, the setting of the potential of the third electrode 90 described above can be achieved more easily, and the configuration of the display device 100 becomes simple. That is, the third electrode 90 and the transparent common electrode 30 can be connected by wiring or the like, and the potential can be managed in the same wiring. For example, when the potential of the transparent common electrode 30 as the cathode is set to 0V, the potential of the third electrode 90 can also be set to 0V. Further, for example, when the transparent common electrode 30 is set to a negative potential and the potential difference with the anode is increased to increase the luminance of the organic electroluminescent element OLED, the potential of the third electrode 90 can also be a negative potential.

The lower limit value of the potential of the third electrode 90 is not particularly limited as long as the reverse current does not substantially flow through the organic electroluminescent layer 10. For example, the potential of the third electrode 90 may be about 10 V smaller than the potential of the transparent common electrode 30. However, even if the potential of the third electrode 90 is set to a potential that is significantly lower than the potential of the transparent common electrode 30, for example, a potential that is 5 V or more lower, the above-described effect of suppressing the leakage current is not significantly improved. The effect of suppressing the leakage current described above can be sufficiently obtained by making the potential of the third electrode 90 2 V lower than the potential of the transparent common electrode 30.

In the present embodiment, the plurality of third electrodes 90 is an island-shaped electrode group having a smaller area than the individual electrodes 20. Thus, by arranging a plurality of third electrodes 90 in the form of dots, the area required for installation of the third electrode 90 can be reduced, and the area of the individual electrode 20 can be made relatively large. Thereby, the area used for light emission of the organic electroluminescent layer 10 can be increased, and even when the organic electroluminescent layer 10 emits light with the same luminance and the same current, the organic electroluminescent layer 10 The current density inside can be made relatively small. In this case, deterioration of the organic electroluminescent layer 10 can be suppressed, and the lifetime of the display device 100 can be extended.

The area of each third electrode 90 is not particularly limited as long as the connection with the contact 85 is ensured, and can be reduced according to the accuracy of the manufacturing process of the display device 100. For example, the area of each third electrode 90 can be 5% or less, preferably 3% or less of the area of each individual electrode 20.

Further, the distance between each third electrode 90 and the adjacent individual electrode 20 is not particularly limited, and the third electrodes 90 are arranged so as to be separated from each other so as not to cause a short circuit between the third electrode 90 and the individual electrode 20. .

Further, the third electrode 90 is disposed in the same layer as the individual electrode 20. That is, the third electrode 90 is simultaneously formed by the same process at the time of manufacture. Accordingly, the third electrode 90 can be easily and reliably disposed between the individual electrodes 20, and the third electrode 90 can be reliably disposed in contact with the organic electroluminescent layer 10.

Further, the material and the layer configuration of the third electrode 90 can be the same as the material and the layer configuration of the individual electrode 20.

The protective insulating film 40 is provided on the transparent common electrode 30 and protects the organic electroluminescent element OLED from the external environment, and in particular prevents moisture and oxygen from entering the organic electroluminescent layer 10. The protective insulating film 40 is made of, for example, a material having high light transmittance and low water permeability such as silicon oxide (SiO _x ), silicon nitride (SiN _x ), aluminum oxide (AlO _x ), or titanium oxide (TiO _x ). May be provided.

The color filter layer 50 is provided on the protective insulating film 40, and color-divides the light generated by the organic electroluminescent element OLED for each pixel. Specifically, the color filter layer 50 includes a red color filter 50R, a green color filter 50G, and a blue color filter 50B that are divided corresponding to each individual electrode 20. The red color filter 50R, the green color filter 50G, and the blue color filter 50B convert incident light from the organic electroluminescent layer 10 side into red, green, and blue, respectively, and emit them toward the sealing resin 60 side. The color filter layer 50 may be a resin layer that selectively transmits light in the visible light wavelength band corresponding to red light, green light, or blue light.

Sealing resin 60 is disposed on the color filter layer 50 and seals each member below the color filter layer 50. The cover glass 70 is disposed on the sealing resin 60 and protects the display unit of the display device 100.

The interlayer insulating film 80 is disposed under the organic electroluminescent layer 10 and carries the individual electrode 20 and the third electrode 90. At the same time, the interlayer insulating film 80 accommodates a contact 81 and a wiring 83 that connect the individual electrode 20 to a pixel drive circuit (not shown), and a contact 85 and a wiring 87 that connect the third electrode 90 to an external circuit. The interlayer insulating film 80 can also accommodate other wirings, elements, and the like as necessary. The interlayer insulating film 80 is formed of, for example, insulating silicon oxynitride. The wirings 83 and 87 are made of a conductor such as copper (Cu) or aluminum (Al), and connect the individual electrode 20 and the third electrode 90 to an external circuit.

As described above, the display device 100 has a drive circuit for driving the organic electroluminescence element of the display device 100 on a semiconductor substrate (not shown) or the like. The drive circuit is usually formed by being divided into pixels by a MOS process. Here, an example of a circuit constituting one pixel of the display device 100 will be described. FIG. 4 is a circuit diagram illustrating an example of a circuit that constitutes one pixel of the display device 100.

As shown in FIG. 4, the circuit constituting one pixel of the display device 100 includes an organic electroluminescent element OLED, a driving transistor DTr, a capacitive element C, and a selection transistor STr.

The organic electroluminescent element OLED is a self-luminous light emitting element in which the individual electrode 20, the organic electroluminescent layer 10, and the transparent common electrode 30 are laminated as described above. The individual electrode 20 of the organic electroluminescent element OLED is connected to the power supply line PL via the drive transistor DTr, and the transparent common electrode 30 of the organic electroluminescent element OLED is connected to the ground line that is at the ground potential. Yes. The organic electroluminescent element OLED functions as one pixel of the display device 100.

The drive transistor DTr is, for example, a field effect transistor. One of the source and the drain of the driving transistor DTr is connected to the power supply line PL, and the other of the source and the drain is connected to the individual electrode 20 of the organic electroluminescent element OLED. The gate of the drive transistor DTr is connected to one of the source and drain of the selection transistor STr. The driving transistor DTr is connected in series with the organic electroluminescence device OLED, and controls the current flowing through the organic electroluminescence device OLED according to the magnitude of the gate voltage applied from the selection transistor STr, thereby organic electroluminescence. The element OLED is driven.

The selection transistor STr is, for example, a field effect transistor. One of the source and the drain of the selection transistor STr is connected to the gate of the drive transistor DTr, and the other of the source and the drain is connected to the signal line DL. The gate of the selection transistor STr is connected to the scanning line SL. The selection transistor STr controls the signal voltage applied to the gate of the drive transistor DTr by sampling the voltage of the signal line DL and applying it to the gate of the drive transistor DTr.

Capacitance element C is, for example, a capacitor. One end of the capacitive element C is connected to the gate of the drive transistor DTr, and the other end of the capacitive element C is connected to the power supply line PL. The capacitive element C maintains the voltage between the gate and the source of the driving transistor DTr at a predetermined voltage.

In the display device 100 according to the present embodiment described above, the third electrode 90 is disposed between the individual electrodes 20, and the potential of the third electrode 90 is equal to the potential of the transparent common electrode 30. It is smaller than a value obtained by adding a threshold voltage for the layer 10. Thus, even when a voltage is applied to the organic electroluminescent layer 10 by the transparent common electrode 30 and the individual electrode 20 and a leakage current is generated from the applied individual electrode 20 due to this, the third A leakage current can flow preferentially through the electrode 90. For this reason, leakage current is prevented from flowing from the applied individual electrode 20 to the adjacent individual electrode 20. As a result, it is possible to prevent the organic electroluminescent layer 10 from emitting light due to a voltage caused by a leakage current between the unintended individual electrode 20 and the transparent common electrode 30. In addition, unintentional light emission of pixels corresponding to other surrounding colors is prevented, and the display device 100 can display an image in a wide color gamut.

In addition, as described above, the influence of the leakage current is larger as the pixel pitch is smaller. In order to realize a fine pixel pitch of 10 μm or less, it is suitable to arrange a continuous white organic electroluminescent layer and perform color conversion by the color filter layer. Even in the organic electroluminescent layer, the influence of the leakage current is large. The display device 100 according to the present embodiment described above can sufficiently suppress the influence of leakage current between pixels even when such a fine pixel pitch is employed.

<3. Verification of influence of leakage current>
Next, the display device 100 and the display device 200 are compared, and the influence of the leakage current due to the presence or absence of the third electrode 90 is verified. Here, the power supply line related to light emission of the display device 100 and the display device 200 is set to a positive voltage, for example, 8V, and the potential of the anode (individual electrodes 20, 220) can be used up to about 6V by turning on the drive transistor DTr. Was set as follows. This is a design in which a potential drop of about 2 V at the maximum occurs between the source and drain of the drive transistor DTr. On the other hand, the potential of the cathode (transparent common electrodes 30, 230) was set to the ground potential (0V).

First, based on the current-voltage characteristics of the organic electroluminescent layer 210 shown in FIG. 19, the results of estimating the emission current and the leakage current that flows to the adjacent individual electrode 220 in the absence of the third electrode 90 are shown. FIG. 5 is shown. In addition, FIG. 5 shows the result of measuring the emission current in the display device 100 and the leakage current that flows to the adjacent individual electrode 20 together. The numerical values in the graph of FIG. 5 indicate the voltage values of the individual electrodes 20 and 220 when light is emitted.

When the light emission current shown on the horizontal axis, that is, the current flowing through the organic electroluminescent layer 210 is 10 ⁻¹² A or less, the leak current no longer reaches 1/10 or more of the light emission current, and when it is 10 ⁻¹³ A or less, light emission occurs. It becomes almost equal to the current. On the other hand, in the display device 100 in which the third electrode 90 is set to 0 V, the leakage current is suppressed to about 1/10 of that of the display device 200, and in particular, the leakage current suppressing effect on the low voltage side of 3 V or less. Was remarkable. Further, in the display device 100 in which the third electrode 90 is set to −2V, the leakage current can be suppressed to 1/100 or less of the display device 200.

Further, FIG. 6 shows a value obtained by subtracting from 1 a value obtained by dividing the leakage current flowing in the adjacent individual electrodes 20 and 220 by the light emission current when various voltages are applied to one individual electrode 20 and 220. Since the value on the vertical axis in this graph indicates the relationship between the light emission current and the leakage current, it is a measure of the width of the color gamut of the display devices 100 and 200. The horizontal axis of FIG. 6 represents luminance. Specifically, the individual electrodes 20 and 220 of all the sub-pixels of the organic electroluminescent element OLED, that is, all the red, green, and blue sub-pixels belonging to all the pixels are illuminated with a predetermined voltage. Brightness in the case of

As shown in FIG. 6, in the display device 200 that does not have the third electrode 90, the color gamut reduction due to the leakage current between the individual electrodes 220 cannot be ignored at 1 nit, which is a sufficiently visible luminance. In the actual prototype panel, color gamut reduction was observed and improvement was necessary.

On the other hand, in the display device 100 having the third electrode 90, the leakage current that causes color mixing is 1/10 or less of the light emission current even at a luminance as low as 0.001 nit that is not visible. The drop in the area could only be around 10%. However, as shown in FIG. 6, in view of the wide color gamut, the effect of setting the potential of the third electrode 90 to a voltage (−2V) that is lower than the potential 0V of the transparent common electrode 30 is not dramatic. It was. On the other hand, when the third electrode 90 is set lower than the potential of the transparent common electrode 30, the power consumption of the entire display device 100 may increase. Therefore, it is considered that the potential of the third electrode 90 is made lower than the potential of the transparent common electrode 30 when it is necessary to suppress the leakage current between the individual electrodes 20 to the limit.

In the display device 100, the third electrode 90 is arranged as a dot having a small area. However, as described above, the leakage current can be sufficiently suppressed. The area of the individual electrode 20 in such a display device 100 is only about 12% smaller than the area of the individual electrode 220 in the display device 200 shown in FIG. It was also possible to suppress the influence of.

<4. Modification>
The embodiment of the present disclosure has been described above. Hereinafter, some modified examples of the embodiment of the present disclosure will be described. Each modified example described below may be applied to the above-described embodiment of the present disclosure alone, or may be applied to the above-described embodiment of the present disclosure in combination. Each modification may be applied instead of the configuration described in the embodiment of the present disclosure, or may be additionally applied to the configuration described in the embodiment of the present disclosure.

First, in the above-described embodiment, the transparent common electrode 30 is a cathode and the individual electrode 20 is an anode. However, the present disclosure is not limited thereto. The transparent common electrode 30 may be an anode, and the individual electrode 20 may be a cathode. In this case, when a voltage is applied to the organic electroluminescent layer 10, the potential of the transparent common electrode 30 is larger than the potential of the individual electrode 20. The potential of the third electrode 90 is larger than the value obtained by subtracting the threshold voltage for the organic electroluminescent layer 10 from the potential of the transparent common electrode 30. Thereby, the effect of suppressing the leakage current between the individual electrodes 20 can be obtained.

In the above case, the potential of the third electrode 90 is preferably equal to or higher than the potential of the transparent common electrode 30, and more preferably the same as the potential of the transparent common electrode 30. Furthermore, the upper limit of the potential of the third electrode 90 is not particularly limited, and may be in a range where a reverse current does not substantially flow through the organic electroluminescent layer 10. However, the effect of suppressing the leakage current described above can be sufficiently obtained by making the potential of the third electrode 90 2 V larger than the potential of the transparent common electrode 30.

In the above-described embodiment, the shapes of the pixels and the individual electrodes 20 are hexagons, but the present disclosure is not limited to this. Further, the arrangement of the third electrodes around the individual electrodes may be appropriately changed according to the shape of the individual electrodes and the use thereof.

Examples of changing the shape of the individual electrodes and the arrangement of the third electrodes are shown in FIGS. In FIG. 7, the individual electrodes 21R, 21G, and 21B corresponding to red, green, and blue have a rectangular shape according to the shape of the pixel, and are arranged in stripes. The third electrode 90A is arranged on the extension line of the corners of the individual electrodes 21R, 21G, and 21B so as not to be short-circuited with the individual electrodes 21R, 21G, and 21B.

In FIG. 8, the individual electrodes 22R, 22G, and 22B corresponding to red, green, and blue form a square according to the shape of the pixel. Further, the third electrode 90B is arranged on the extension line of the corners of the individual electrodes 22R, 22G, and 22B so as not to be short-circuited with the individual electrodes 22R, 22G, and 22B. However, the third electrode 90B is not arranged on the extension line of one corner of each individual electrode 22R, 22G, 22B. As described above, the third electrodes 90B are regularly arranged, and some of the third electrodes 90B may not be arranged as necessary. In addition, the third electrode may be disposed around the individual electrode that is easily affected by the leak current, while the third electrode may not be disposed around the other individual electrode.

FIG. 9 shows the arrangement of the individual electrodes 23R, 23G, 23B, and 23W when the color filter layer has white pixels that do not use a color conversion member. The individual electrodes 23R, 23G, 23B, and 23W corresponding to red, green, blue, and white form a square according to the shape of the pixel. Further, the third electrode 90C is arranged on the extension line of the corners of the individual electrodes 23R, 23G, 23B, and 23W so as not to be short-circuited with the individual electrodes 23R, 23G, 23B, and 23W. When such a white pixel is employed, it is advantageous for improving the maximum luminance.

In the embodiment and the modification described above, the third electrode is described as a point-like one, but the present disclosure is not limited to this. For example, the third electrode can take various shapes, for example, a linear electrode extending between the individual electrodes. Further, the third electrode may have a mesh shape extending between the individual electrodes.

Also, the arrangement of the individual electrode and the third electrode on the interlayer insulating film can be appropriately changed according to these forming methods. In FIG. 10, the interlayer insulating film 80 </ b> A has a convex portion 803, and the individual electrode 24 and the third electrode 90 </ b> D are disposed on the convex portion 803. The interlayer insulating film 80A, the individual electrode 24, and the third electrode 90D form an anode and a new common electrode on the interlayer insulating film used in a general LSI (large-scale integrated circuit) wiring. Then, it can be obtained by processing using known photolithography and dry etching.

In FIG. 11, an interlayer insulating film 80B is further embedded in the gap region between the individual electrode 25 and the third electrode 90E. In such a case, since the plane formed by the individual electrode 25, the third electrode 90E, and the interlayer insulating film 80B is relatively smooth, a thin portion is locally formed when the organic electroluminescent layer is formed. Can be prevented. As a result, uniform light emission is possible regardless of the portion. Such a structure can also be realized by using a known general LSI manufacturing process or TFT (thin-film-transistor) manufacturing process.

In FIG. 12, the interlayer insulating film 80C has a convex portion 803A, and the individual electrode 26 and the third electrode 90F are arranged on the convex portion 803A. An insulating film 805 is formed on the individual electrode 26 and the third electrode 90F. In this case, the organic electroluminescent layer in the opening region of the insulating film 805 emits light, and the effective area of the individual electrode 26 is the area of the opening surrounded by the insulating film 805. Such a structure can be formed by further forming an insulating film on the electrode and then removing a part of the insulating film so as to form an opening with respect to the structure in FIG.

Further, as a wiring for supplying power to the third electrode, for example, as shown in FIG. 13, a light shielding layer 88 made of metal may be used instead. The light shielding layer 88 is disposed in the interlayer insulating film 80, blocks light emitted from the organic electroluminescent layer 10, and protects pixel driving MOS transistors and TFTs in lower layers. The light shielding layer 88 is continuously formed in the entire display portion of the display device 100, and can be formed of a metal layer having low reflectance and transmittance, such as titanium nitride or tungsten. By connecting the light shielding layer 88 and the third electrode 90 with the contact 87A and connecting the light shielding layer 88 to an external circuit, the potential of the third electrode 90 can be set.

In the above-described embodiment, the individual electrode 20 has a function as a reflector, but the present disclosure is not limited to this. For example, as shown in FIG. 14, the individual electrode 27 is formed as a transparent electrode using a transparent conductive material such as indium zinc oxide or indium tin oxide. On the other hand, a reflector 89 such as a metal film is disposed below the individual electrode 26 in the interlayer insulating film 80D.

In addition, the display device according to the present disclosure may be a bottom emission type. In this case, the individual electrode is a transparent electrode, and the reflector in the interlayer insulating film is omitted.

Further, in the above-described embodiment, the organic electroluminescent layer is continuously formed over a plurality of pixels, but is not limited thereto, and the organic electroluminescent layer emits red, green, and blue colors. The electroluminescent layer may be formed separately for each color by mask vapor deposition or the like. When such a pixel pitch is relatively large such as several tens of microns or more, a method of dividing the organic electroluminescent layer for each color is suitable. Such a configuration is also possible when the display device is driven by a thin film transistor made of amorphous silicon, polycrystalline silicon, oxide semiconductor, or the like. As described above, the organic electroluminescent layer is divided for each color, and the display device according to the present disclosure having the third electrode can preferably suppress the leakage current between the pixels.

The circuit configuration used for driving the light emission of the display device is not limited to that shown in FIG. 4, and various known circuits can be employed. In addition, various pixel driving methods having a correction operation for improving the uniformity of image quality within the panel have been devised, but the technology of the present disclosure can be widely applied regardless of these detailed pixel driving methods. However, in some cases, the voltage applied to the third electrode is not always maintained at a constant value, and a transistor installed between the constant potential line and the third electrode during a period when the contribution to light emission is small, such as a correction operation. Control such as turning off the switch may be adopted.

<5. Summary>
As described above, according to the present disclosure, it is possible to suppress the influence of leakage current between individual electrodes in a display device having an organic electroluminescent element. Accordingly, unintentional light emission of pixels corresponding to other surrounding colors is prevented, and an image can be displayed in a wide color gamut in the display device.

Note that the display device described above can also be used as a display unit of various electronic devices that display an input image signal or an internally generated image signal as a still image or a moving image. Examples of such an electronic device include a music player having a storage medium such as a semiconductor memory, an imaging device such as a digital camera and a video camera, a notebook personal computer, a game device, and a portable information terminal such as a mobile phone and a smartphone. Can be illustrated.

The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that it belongs to the technical scope of the present disclosure.

In addition, the effects described in this specification are merely illustrative or illustrative, and are not limited. That is, the technology according to the present disclosure can exhibit other effects that are apparent to those skilled in the art from the description of the present specification in addition to or instead of the above effects.

The following configurations also belong to the technical scope of the present disclosure.
(1)
An organic electroluminescent layer;
A first electrode disposed on one main surface side of the organic electroluminescent layer and common to a plurality of pixels;
A plurality of second electrodes arranged on the other main surface side of the organic electroluminescent layer and individually for each pixel;
A display device comprising: a plurality of third electrodes disposed on the other main surface side of the organic electroluminescent layer and between the plurality of second electrodes.
(2)
When a voltage is applied to the organic electroluminescent layer, the potential of the first electrode is smaller than the potential of the second electrode, and the potential of the third electrode is the first electrode. The display device according to (1), which is smaller than a value obtained by adding a threshold voltage of the organic electroluminescent layer to the potential of the organic electroluminescent layer.
(3)
The display device according to (2), wherein the potential of the third electrode is equal to or lower than the potential of the first electrode.
(4)
When a voltage is applied to the organic electroluminescent layer, the potential of the first electrode is greater than the potential of the second electrode, and the potential of the third electrode is the first electrode. The display device according to (1), which is larger than a value obtained by subtracting a threshold voltage of the organic electroluminescent layer from the potential of the organic electroluminescent layer.
(5)
The display device according to any one of (2) to (4), wherein the potential of the third electrode and the potential of the first electrode are the same.
(6)
The display device according to any one of (1) to (5), wherein the third electrode is arranged in an island shape in plan view.
(7)
The third electrode according to any one of (1) to (6), wherein the third electrode is arranged so as to be equidistant from the plurality of second electrodes adjacent to each other in plan view. Display device.
(8)
The display device according to any one of (1) to (7), wherein the second electrode and the third electrode are arranged in the same layer.
(9)
The display device according to any one of (1) to (8), wherein the organic electroluminescent layer is formed continuously over the plurality of pixels in a plan view.
(10)
An organic electroluminescent layer;
A first electrode disposed on one main surface side of the organic electroluminescent layer and common to a plurality of pixels;
A plurality of second electrodes disposed on the other main surface side of the organic electroluminescent layer and corresponding to each pixel individually;
An electronic apparatus comprising: a display unit having a plurality of third electrodes arranged on the other main surface side of the organic electroluminescent layer and between the plurality of second electrodes.

10, 210 Organic electroluminescent layer 20, 20B, 20G, 20R, 21B, 21G, 21R, 22B, 22G, 22R, 23B, 23G, 23R, 23W, 24, 25, 26, 27, 220, 220B, 220G, 220R Individual electrode 201 Electrode 202 Light reflection layer 30, 230 Transparent common electrode 40, 240 Protective insulating film 50, 250 Color filter layer 50R, 250R Red color filter 50G, 250G Green color filter 50B, 250B Blue color filter 60, 260 Sealing resin 70, 270 Cover glass 80, 80A, 80B, 80C, 80D, 280 Interlayer insulating film 81, 85, 87A, 281 Contact 83, 87, 283 Wiring 88 Light shielding layer 89 Reflector 90, 90A, 90B, 90C, 90D, 90E, 90F Third electrode 100, 200 Display device

Claims (10)

1. An organic electroluminescent layer;
   A first electrode disposed on one main surface side of the organic electroluminescent layer and common to a plurality of pixels;
   A plurality of second electrodes arranged on the other main surface side of the organic electroluminescent layer and individually for each pixel;
   A display device comprising: a plurality of third electrodes disposed on the other main surface side of the organic electroluminescent layer and between the plurality of second electrodes.
2. When a voltage is applied to the organic electroluminescent layer, the potential of the first electrode is smaller than the potential of the second electrode, and the potential of the third electrode is equal to that of the first electrode. The display device according to claim 1, wherein the display device is smaller than a value obtained by adding a threshold voltage of the organic electroluminescent layer to a potential.
3. The display device according to claim 2, wherein the potential of the third electrode is equal to or lower than the potential of the first electrode.
4. 3. The display device according to claim 2, wherein the potential of the third electrode and the potential of the first electrode are the same.
5. The display device according to claim 1, wherein the third electrode is arranged in an island shape in plan view.
6. The display device according to claim 1, wherein the third electrode is disposed so as to be equidistant from the plurality of second electrodes adjacent to each other in a plan view.
7. The display device according to claim 1, wherein the second electrode and the third electrode are disposed in the same layer.
8. The display device according to claim 1, wherein the organic electroluminescent layer is formed continuously over the plurality of pixels in a plan view.
9. When a voltage is applied to the organic electroluminescent layer, the potential of the first electrode is larger than the potential of the second electrode, and the potential of the third electrode is equal to that of the first electrode. The display device according to claim 1, wherein the display device is larger than a value obtained by subtracting a threshold voltage of the organic electroluminescent layer from a potential.
10. An organic electroluminescent layer;
    A first electrode disposed on one main surface side of the organic electroluminescent layer and common to a plurality of pixels;
    A plurality of second electrodes disposed on the other main surface side of the organic electroluminescent layer and corresponding to each pixel individually;
    An electronic apparatus comprising: a display unit having a plurality of third electrodes arranged on the other main surface side of the organic electroluminescent layer and between the plurality of second electrodes.

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