JP2014197466A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance display quality while achieving a super long-life by suppressing current leakage between adjacent elements, without reducing the opening ratio of a pixel more than necessary, thereby reducing crosstalk caused by the leakage current, in a display device including an organic EL element.SOLUTION: First electrode interval d1 of an R light-emitting element 3R and a G light-emitting element 3G having a smallest difference of light emission threshold voltage is made narrower than the first electrode intervals d2, d3 of the G light-emitting element 3G and a B light-emitting element 3B, and of the B light-emitting element 3B and R light-emitting element 3R. A third electrode 20 is arranged in the latter, and the potential of the third electrode 20 is set to the potential of a negative electrode, i.e., the second electrode 15.

Description

  The present invention relates to a display device for full color display using an organic EL element.

  An organic EL (electroluminescence) element has a configuration in which an anode, an organic EL layer including at least a light emitting layer, and a cathode are stacked. In addition, as a color display device using an organic EL element, a red, green, and blue light emitting layer is configured to be patterned into pixel shapes of each color, and a light emitting layer that emits white and a pixel shape of each color are provided. A configuration provided with red, green, and blue color filters is used. In order to facilitate the manufacturing process, a part or all of the organic compound layer of the organic EL element used in such a color display device is continuously formed over all the two-dimensional elements. Sometimes.

  In recent years, with the increase in definition of display devices, the pixel size is reduced, and the distance between the electrodes of two adjacent elements is narrower than before. Therefore, the current leaks to the element adjacent to the element to be emitted through the organic compound layer formed continuously over all the elements, and the adjacent element emits light and crosstalk occurs. Has occurred.

  In Patent Document 1, a metal wiring is formed in a gap between adjacent elements, the metal wiring is electrically connected to an organic compound layer formed continuously, and the potential is measured when the element is not emitting light. There has been proposed a method of suppressing crosstalk by setting a potential lower than the anode potential.

JP 2012-155953 A

  However, the method of Patent Document 1 has a problem that the ratio (aperture ratio) of the light emitting region in the pixel region becomes small because the metal wiring having a certain width is formed so as to surround all the elements. There is. When the aperture ratio is small, it is necessary to increase the current density flowing in the element in order to obtain the same luminance, which causes a problem that the deterioration of the element is promoted and the lifetime of the display device is shortened.

  An object of the present invention is to suppress current leakage between adjacent elements without reducing the aperture ratio of a pixel more than necessary in a display device including an organic EL element, reduce crosstalk, and display quality. It is an object to provide a display device that is excellent in life and has a long life.

The display device of the present invention includes a plurality of organic EL elements that emit at least three different colors,
The organic EL element includes a first electrode formed for each organic EL element, a second electrode common to the plurality of organic EL elements, and an organic EL layer sandwiched between the first electrode and the second electrode. ,
The organic EL layer includes at least a light emitting layer, and a charge transport layer disposed between the light emitting layer and the first electrode and common to a plurality of organic EL elements,
The organic EL element has a light emission threshold voltage that varies depending on the light emission color.
Among the gaps between the first electrodes in the set of two adjacent organic EL elements that emit different colors, the gap between the first electrodes in the set having the smallest difference in the light emission threshold voltage emits two different neighboring colors. It is characterized by being narrower than the set of EL elements.

  According to the present invention, the interval between the first electrodes of the set of organic EL elements that are likely to generate a leak current is relatively wide, and the interval between the first electrodes is relatively narrowed for the set of organic EL elements that are difficult to generate. Thus, crosstalk due to leakage current can be suppressed without lowering the aperture ratio more than necessary. Further, by disposing the third electrode, the insulating partition wall, or the gap in the region where the interval between the first electrodes is widened, the leakage current to the adjacent organic EL elements can be further suppressed. Therefore, according to the present invention, it is possible to provide a display device with excellent display quality and longer life because crosstalk due to leakage current is suppressed.

It is a figure which shows Embodiment 1 of the display apparatus of this invention, (a) is a perspective view, (b) is the fragmentary sectional view. It is a plane schematic diagram which shows the pixel layout of Embodiment 1 of FIG. It is a plane schematic diagram which shows the structure of the peripheral circuit of the display apparatus of this invention. (A) is an equivalent circuit diagram which shows the pixel circuit of the display apparatus of this invention, (b) is a timing chart. It is a figure which shows the structure of Embodiment 2 of the display apparatus of this invention, (a) is a cross-sectional schematic diagram, (b) is a plane schematic diagram which shows a pixel layout. FIG. 6 is an equivalent circuit diagram of three adjacent pixels in the embodiment illustrated in FIG. 5. FIG. 6 is a schematic plan view showing a pixel layout different from FIG. 5. FIG. 6 is a schematic plan view showing a pixel layout different from FIG. 5. FIG. 6 is a schematic plan view showing a pixel layout different from FIG. 5. It is a cross-sectional schematic diagram which shows the structure of Embodiment 3 of the display apparatus of this invention. It is a cross-sectional schematic diagram which shows the structure of Embodiment 4 of the display apparatus of this invention. It is a cross-sectional schematic diagram which shows the structure of Embodiment 5 of the display apparatus of this invention. It is a figure which shows the color reproduction range of the display apparatus in Example 1 and Comparative Example 1 of this invention. 6 is a schematic plan view showing a pixel layout of Comparative Example 1. FIG. 10 is a schematic plan view showing a pixel layout of Comparative Example 2. FIG.

  Embodiments of the present invention will be specifically described below with reference to the drawings. In addition, the well-known or well-known technique of the said technical field is applied about the part which is not illustrated or described in particular in this specification. The embodiment described below is one embodiment of the present invention and is not limited thereto.

Embodiment 1
FIG. 1A is a perspective view of an embodiment of a display device of the present invention. The display device according to the present embodiment includes a plurality of pixels 100 including organic EL elements. The plurality of pixels 100 are arranged in a matrix and form a display area 101. The pixel means a region corresponding to the light emitting region of one organic EL element. In the display device of the present embodiment, one organic EL element having a luminescent color is arranged for each pixel 100. Examples of the emission color of the organic EL element include red (R), green (G), blue (B), yellow, cyan, magenta, and white. Further, the display device according to the present embodiment includes a pixel unit including a plurality of pixels having different emission colors (for example, a red light emission (R light emission) pixel, a green light emission (G light emission) pixel, and a blue light emission (B light emission) pixel). Multiple sequences are arranged. The pixel unit is a minimum unit that enables light emission of a desired color by mixing colors of pixels.

  FIG. 1B is a partial schematic cross-sectional view taken along the line A-A ′ of FIG. The pixel 100 includes a first electrode (anode) 11R, 11G, and 11B, a hole transport layer 12, a light emitting layer 13R, 13G, and 13B, an electron transport layer 14, and a second electrode (cathode) on the substrate 10. 15 and the organic EL elements 3R, 3G, 3B. Usually, each organic EL element 3R, 3G, 3B is sealed with a sealing film 16 so that external oxygen and moisture do not enter.

  The organic EL element 3R is an R organic EL element (R light emitting element), and the R light emitting layer 13R in the element emits light. Similarly, the organic EL elements 3G and 3B are a G light emitting organic EL element (G light emitting element) and a B light emitting organic EL element (B light emitting element), respectively, and an R light emitting layer 13G and a B light emitting layer in the element, respectively. 13B emits light. The hole transport layer 12, the light emitting layers 13R, 13G, and 13B and the electron transport layer 14 are collectively referred to as an organic EL layer. In the present invention, between the first electrodes 11R, 11G, and 11B and the light emitting layers 13R, 13G, and 13B, a charge transport layer (in this example, the hole transport layer 12) common to the plurality of organic EL elements 3R, 3G, and 3B. And a leakage current passing through the charge transport layer is suppressed.

  The first electrodes 11R, 11G, and 11B are formed separately for each of the organic EL elements 3R, 3G, and 3B. The hole transport layer 12, the electron transport layer 14, and the second electrode 15 are all organic EL elements. It is formed continuously over 3R, 3G, and 3B.

  The hole transport layer 12 continuously formed over all pixels is made of a material having a sheet resistance smaller than that of the light emitting layers 13R, 13G, and 13B in order to lower the driving voltage of the organic EL element. For this reason, when a current is passed through the organic EL element that is desired to emit light, the current leaks to the adjacent pixel through the hole transport layer 12, and the adjacent organic EL element also emits light. As a result, crosstalk occurs. In particular, when crosstalk occurs when adjacent organic EL elements emit different colors, the color purity of the pixel is lowered, and the color reproducibility is lowered in the color display device. Furthermore, as the distance between the first electrodes 11R, 11G, and 11B decreases, the ratio of the resistance between the organic EL elements to the in-plane direction of the substrate 10, that is, the resistance between two adjacent organic EL elements, decreases. . For this reason, current easily leaks in the in-plane direction of the substrate 10, and crosstalk appears more remarkably.

  Generally, crosstalk is alleviated by increasing the resistance between organic EL elements. For example, there is a means of forming the hole transport layer 12 with a material that does not have high carrier mobility. In addition, when the hole transport layer 12 and the electron transport layer 14 are formed for each of the organic EL elements 3R, 3G, and 3B, the resistance is higher than when they are formed in common. Therefore, the resistance between adjacent organic EL elements increases as the number of layers common to all pixels in the organic EL layer is reduced.

However, according to the study by the present inventors, it is not possible to completely prevent the crosstalk essentially by merely increasing the resistance between the organic EL elements. A case where an organic EL element β (light emission threshold voltage: V _βth ) having a low light emission threshold voltage is arranged next to an organic EL element α (light emission threshold voltage: V _αth ) having a high light emission threshold voltage is taken as an example. Here, the light emission threshold voltage is a potential difference applied between the first electrode 11R, 11G, 11B of the organic EL element 3R, 3G, 3B and the second electrode 15 when the organic EL element starts to emit light. .

When light is emitted by applying a voltage of V _alpha to the element alpha, element a voltage applied to the beta V _beta, a current leaking I _leak, and the resistance between the two pixels and R _V α -V β = RI _leak > 0 (1)
The relationship holds.

Assuming that the light emission threshold voltage V _αth is applied to the element α to emit light, no _matter how large R is, the element β has I _leak = (V _αth −V _β ) / R, V _βth <V _β <V _αth (2)
Leak current.

On the other hand, 'if the _leak, the element alpha I' the current leaking to the element alpha when light is emitted by applying a light emission threshold voltage V _Betath the element _{β I leak = (V βth -V} α) / R, V _βth <V _αth <V _α (3)
However, since this is a negative value, it means that no leakage current flows through the element α and no light is emitted. That is, it can be seen that such a leakage current I ′ _leak does not flow.

  As described above, the present inventors have intensively studied and found that the presence / absence of crosstalk is determined depending on the magnitude relationship of the light emission threshold voltage of the organic EL element, and the degree thereof is also increased or decreased. For this reason, it is preferable that the light emission threshold voltages are equally aligned between organic EL elements having different light emission colors. However, when R, G, and B organic EL elements are combined in order to realize full-color light emission, the recombination energy differs depending on the wavelength of the emitted light, so that the emission threshold voltage of each organic EL element is generally different. Is. Specifically, it is necessary to apply a large voltage to the B light emitting element having the shortest wavelength and high energy. In general, a phosphorescent material capable of obtaining high luminous efficiency needs to be applied with a larger voltage than a fluorescent material. Usually, when this is adopted only for a specific color, or for other design factors, the light emission threshold voltage of the light emitting element is different.

  Therefore, as shown in FIG. 1B, the display device of the present invention is in a group (a group of 3R and 3G in this example) having the smallest difference in light emission threshold voltage among a pair of two adjacent organic EL elements. The interval between the first electrodes is set to be narrower than the interval between the other first electrodes. In this example, the distance d1 between the first electrode 11R of the R light emitting element 3R and the first electrode 11G of the G light emitting element 3G is the narrowest. The distance d2 between the first electrode 11G of the G light emitting element 3G and the first electrode 11B of the B light emitting element 3B and the distance between the first electrode 11B of the B light emitting element 3B and the first electrode 11R of the R light emitting element 3R. d3 is wider than d1. FIG. 2 is a schematic plan view showing the pixel layout of the display device shown in FIG. 1B, and shows an example in which the pixel units 30 are arranged in 2 rows × 2 columns. In FIG. 2, only the pixel unit 30 and the first electrodes 11R, 11G, and 11B are shown for convenience. As shown in FIGS. 1B and 2, the distances d2 and d3 of the first electrodes in the groups other than the group having the smallest difference in the light emission threshold voltage (the groups of 3G and 3B, 3B and 3R in this example) are the distances. Wide compared to d1. Note that d2 and d3 may be equal or different as long as they are wider than d1. Note that d2 and d3 are both set within a range of 30 μm or less.

  As described above, the resistance between the organic EL elements 3R, 3G, and 3B increases in proportion to the interval between the first electrodes 11R, 11G, and 11B. In the present invention, the difference in the light emission threshold voltage is large, and the interval between the first electrodes of the set of organic EL elements in which crosstalk occurs is widened to alleviate the crosstalk. The interval between the first electrodes of the set of organic EL elements whose influence can be ignored is narrowed. Accordingly, the light emitting region is not narrowed by unnecessarily widening the interval between the organic EL elements, and the aperture ratio can be increased, leading to a longer life of the display device. In the present invention, the voltage applied to the organic EL element is based on the potential of the fixed voltage line connected to the second electrode 15.

  Although the crosstalk generated through the hole transport layer 12 has been described, a part of the organic EL layer, that is, the charge transport layer may be formed in contact with two adjacent first electrodes 11R, 11G, and 11B. In this case, crosstalk occurs. That is, the charge transport layer formed in contact with two adjacent first electrodes 11 may be the electron transport layer 14.

  In the present embodiment, the first electrodes 11R, 11G, and 11B, the hole transport layer 12, the light emitting layers 13R, 13G, and 13B, the electron transport layer 14, and the second electrode 15 are stacked in this order from the substrate 10 side. The charge transport layer on the first electrode 11R, 11G, 11B side may be the electron transport layer 14. In that case, the hole transport layer 12 is located on the second electrode 15 side, and the first electrode 11 serves as a cathode and the second electrode 15 serves as an anode.

  The display device of the present invention may be a bottom emission type display device in which the light of the organic EL element is emitted from the substrate 10 side, or the top emission in which the light of the organic EL element is emitted from the side opposite to the substrate 10. Type display device.

  Next, each member will be specifically described.

  As the substrate 10, an insulating substrate such as quartz, glass, or plastic, a metal substrate, a silicon substrate, or the like can be used. Further, the substrate 10 may have a switching element such as a transistor or an MIM element formed on the insulating substrate or the silicon substrate. In that case, the substrate 10 may have a planarization film for planarizing the unevenness of the switching elements.

  The first electrode 11R, 11G, 11B and the second electrode 15 are made of a conductive material. Specifically, transparent oxide conductive layers such as tin oxide, indium oxide, indium tin oxide, and indium zinc oxide, and simple metals such as Al, Ag, Cr, Ti, Mo, W, Au, Mg, and Cs A metal layer made of the above alloy can be used. Furthermore, the first electrodes 11R, 11G, and 11B and the second electrode 15 may be composed of a laminated film of a transparent oxide conductive layer and a metal layer, or a laminated film of a plurality of metal layers.

  For the hole transport layer 12, a known material can be suitably used. For example, a triphenyldiamine derivative, an oxodiazole derivative, a polyphylyl derivative, a stilbene derivative, or the like can be used. In addition, oxides such as molybdenum oxide and tungsten oxide, organic substances such as 2,3,5-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), and mixtures thereof are used. be able to. The hole transport layer 12 includes a single layer or a plurality of layers of an organic compound having a hole injection property and a hole transport property. Further, if necessary, an electron blocking layer may be provided as the hole transport layer 12 in order to prevent electrons from moving from the light emitting layers 13R, 13B, and 13G to the first electrodes 11R, 11G, and 11B that are anodes. It can also be provided.

  The light emitting layers 13R, 13B, and 13G are not particularly limited and known materials can be applied. The light emitting layers 13R, 13B, and 13G may be composed of only a light emitting material, or may be a mixed layer of a light emitting dopant material and a host material. The light emitting layers 13R, 13B, and 13G may include an assist dopant material in addition to the light emitting dopant material and the host material. In the present invention, the host material means a material having the highest weight concentration among the components in the light emitting layers 13R, 13B, and 13G. Further, the light emitting material and the light emitting dopant material may be either a fluorescent material or a phosphorescent material.

  A known material can be suitably used for the electron transport layer 14, and examples thereof include an aluminum quinolinol derivative, an oxadiazole derivative, a triazole derivative, a phenylquinoxaline derivative, a silole derivative, and a phenanthroline derivative. In addition, alkali metals, alkaline earth metals, rare earth metals, and compounds thereof can be used. Moreover, the mixture of the illustrated material can also be used suitably. It consists of a single layer or a plurality of layers of an organic compound having electron injection properties and electron transport properties. In addition, a hole blocking layer can be provided as the electron transport layer 14.

  Further, as the hole transport layer 12 and the electron transport layer 14, an exciton blocking layer for suppressing diffusion of excitons generated in the light emitting layers 13R, 13B, and 13G can be provided. Note that the hole transport layer 12 and the electron transport layer 14 are not essential, and may be omitted depending on the configuration of the organic EL elements 3R, 3G, and 3B.

  The sealing film 16 has a function of preventing oxygen and moisture from entering the organic EL elements 3R, 3G, and 3B, and an inorganic material such as silicon nitride, silicon oxide, or alumina can be used. Moreover, the sealing film 16 may be comprised with the laminated film which consists of two or more layers of inorganic materials, and may be comprised with the laminated film of the inorganic material and the resin material.

  In addition, a sealing cap can be used instead of the sealing film 16 as long as the organic EL elements 3R, 3G, and 3B are sealed. As the sealing cap, a cap-shaped member such as glass or plastic can be used. In addition, the sealing cap may be configured by a plate-like member such as a glass plate and a sealant disposed around the display region 101 in order to bond the member and the substrate 10. Further, the space between the sealing cap and the second electrode 15 of the organic EL elements 3R, 3G, 3B may be filled with a gas such as nitrogen or argon, or filled with a resin material such as acrylic resin. It may be. A desiccant may be disposed in the space.

[Driving method of display device]
A method for driving the display device of the present invention will be described with reference to FIGS.

  As shown in FIG. 3, the display device of the present invention has a data line driving circuit 102 and a scanning line driving circuit in addition to a display area 101 in which pixels 100 are arranged in a two-dimensional array of m rows × n columns. 103 and a power line driver circuit 104. A video signal is input to the data line driving circuit 102 from a display panel controller (not shown), and a data voltage as gradation display data corresponding to the video signal is output from each output terminal of the data line driving circuit 102 to n data lines. 105 is output. A control signal is input to the scanning line driving circuit 103 from a display panel controller (not shown), and a control voltage for controlling the operation of the pixel 100 is output to m scanning lines 106 from each output terminal of the scanning line driving circuit 103. The Further, the power supply line driving circuit 104 applies a voltage to the power supply line 107 arranged in parallel with each scanning line 106.

  FIG. 4A shows a pixel circuit in i-th row and k-th column. The pixel circuit includes an n-type selection transistor 201, a p-type drive transistor 202, a storage capacitor 203 that holds a data voltage, and the organic EL element 3. The gate electrode of the selection transistor 201 is connected to the scanning line 106 (i), one of the source electrode and the drain electrode is connected to the data line 105 (k), and the other is connected to the gate electrode of the driving transistor 202. The scanning line 106 (i) represents the i-th scanning line 106, and the data line 105 (k) represents the k-th data line 105. One of the source electrode and the drain electrode of the driving transistor 202 is connected to the power supply line 107, and the other is connected to the organic EL element 3. The storage capacitor 203 has one terminal connected to the gate electrode of the driving transistor 202 and the other connected to the power supply line 107. Note that one end of the organic EL element 3 is connected to the drive transistor 202, while the other end is connected to the fixed voltage line 108.

  FIG. 4B is a timing chart showing a driving method of the pixel circuit of FIG. 4A and a driving method of the pixel circuit in the i−1 and i + 1 rows, and shows an example of line sequential driving. . In a certain frame, in the writing period A of the pixel in the i-th row, the control voltage P (i) applied to the i-th scanning line 106 (i) is at the H level, so that the selection transistor 201 becomes conductive. . Then, the data voltage V (i) is applied to the pixel circuit from the data line 105 (k), and the charge corresponding to the data voltage V (i) is held in the storage capacitor 203. Thereafter, the control voltage P (i) becomes L level, and the selection transistor 201 is turned off. In the light emission period B, a current corresponding to the data voltage V (i) written in the storage capacitor 203 in the writing period A flows from the power supply line 107 to the organic EL element 3 through the driving transistor 202. Then, the organic EL element 3 emits light with a luminance corresponding to the amount of current. A total of the writing period A and the light emission period B is one frame. When the light emission period B ends, the writing period A ″ for the next frame starts. Strictly speaking, the pixel circuit in FIG. 4A also emits light during the writing period A.

  The driving method of the pixel circuits in the (i−1) th and i + 1th rows is the same. The writing period of the i-1th row is a period in which the control voltage P (i-1) is at the H level in FIG. 4B, and ends before the writing period A of the ith row starts. It overlaps the light emission period B ′ of the previous frame in the i-th row. The writing period of the (i + 1) th row is a period during which the control voltage P (i + 1) is at the H level, and starts after the writing period A of the ith row, and overlaps the light emission period B of the current frame of the ith row. . In this way, the data voltage is written to each pixel in the order of the (i-1) th row, the ith row, and the (i + 1) th row, and the i-1th row, the ith row, and the i + 1th row are according to the data voltage. In order, the organic EL element emits light.

[Pixel layout]
The pixel layout of the display device according to the present embodiment is not particularly limited, and a layout known in the technical field can be used. For example, in addition to the stripe arrangement shown in FIG. One pixel unit 30 may be composed of three pixels or four pixels. In the case of four pixels, it may be composed of three color light emitting elements such as R, G, B, and G, or a four color light emitting element in which white (W) is added to R, G, and B. It may be configured.

[Embodiment 2]
FIG. 5A is a schematic cross-sectional view of one pixel unit of the display device according to this embodiment, and FIG. 5B is a schematic plan view showing the pixel layout. In FIG. 5B, only the pixel unit 30, the first electrodes 11R, 11G, and 11B, and the third electrode 20 are shown for convenience.

  This example is characterized in that, in addition to the configuration of the first embodiment, the third electrode 20 is formed in a portion where the interval between the first electrodes is wide. In this example, the gap between the first electrode 11G of the G light emitting element 3G and the first electrode 3B of the B light emitting element 3B and the gap between the first electrode 11B of the B light emitting element 3B and the first electrode 11R of the R light emitting element 3R are Three electrodes 20 are formed. The third electrode 20 is electrically connected to the hole transport layer 12 and is more than the anode potential during non-light emission of the two adjacent organic EL elements (in this example, the first electrodes 11R, 11G, and 11B). It is set to a low potential.

  With this configuration, a current path from the first electrodes 11R, 11G, and 11B to the third electrode 20 through the hole transport layer 12 is created in a set having a large difference in light emission threshold voltage. As a result, the current path to the adjacent organic EL element can be eliminated, or the amount of current flowing to the adjacent organic EL element can be reduced. For this reason, the adjacent organic EL element does not emit light, and crosstalk is suppressed. By forming the third electrode 20 between organic EL elements having a large difference in light emission threshold voltage and occurrence of crosstalk, crosstalk is suppressed and the difference in light emission threshold voltage is relatively small. The third electrode is not formed between the ignorable organic EL elements. For this reason, the light emitting region is not narrowed by unnecessarily spacing the pixels, and the aperture ratio can be increased, leading to a longer life of the display device.

  “The third electrode 20 is set to a potential lower than the anode potential during non-light emission of any of the two adjacent organic EL elements” means the following setting. As shown in FIG. 5, the third electrode 20 disposed between the organic EL elements 3G and 3B has an anode potential during non-light emission of the organic EL elements 3G and 3B (in this example, the first electrodes 11G and 11B). ) Is set to a lower potential. Similarly, the third electrode 20 disposed between the organic EL elements 3B and 3R is lower than the anode potential during non-light emission of the organic EL elements 3B and 3R (the first electrodes 11B and 11R in this example). Set to potential.

  Further, all the third electrodes 20 are connected to a common voltage line (not shown), and any of the third electrodes 20 has a potential lower than the anode potential when all the organic EL elements 3R, 3G, 3B are not emitting light. May be configured. Further, the voltage applied to the third electrode 20 may be a variable voltage instead of a fixed voltage as long as the voltage is lower than the light emission threshold voltage of each of the two adjacent organic EL elements. Alternatively, all the third electrodes 20 and the second electrodes 15 may be electrically connected so that the same voltage is applied. The third electrode 20 is formed in the same layer as the first electrodes 11R, 11G, and 11B, and it is desirable to form the third electrode 20 in the same process as the patterning of the first electrodes 11R, 11G, and 11B.

[Driving method of display device]
FIG. 6 is an equivalent circuit diagram showing a pixel circuit for one pixel unit shown in FIG. In this example, the pixel circuit of each pixel is basically the same as that in FIG. 4A, but the third electrode 20 is arranged between the pixel circuits of B light emission and R light emission, and R light emission and B light emission. ing. And the 3rd electrode 20 and the 1st electrode side of organic EL element 3R, 3G, 3B become the equivalent circuit electrically connected through the resistance 300. FIG. Here, the resistor 300 is the resistance in the in-plane direction of the substrate 10 of the charge transport layer (in this example, the hole transport layer 12) formed in common contact with the two first electrodes of two adjacent organic EL elements. Represents.

  In the present invention, the third electrode 20 is provided, and the set potential of the third electrode 20 is set to a potential lower than the anode potential when the organic EL elements 3R, 3G, 3B are not emitting light, so that the leakage current is reduced to the third electrode. 20 flows. Therefore, crosstalk due to leakage current is suppressed between the organic EL elements 3R and 3B, 3G and 3B. The third electrode 20 is preferably set to a potential lower than the anode potential during non-light emission of any of the two adjacent organic EL elements while the display device is driven.

[Pixel layout]
In the present embodiment, as shown in FIG. 5B, it is preferable that the third electrodes 20 are not island-shaped but connected to each other and formed in a stripe shape. Note that the size of each pixel may be the same or different from the viewpoint of the lifetime.

  The layout of the pixel of the display device according to the present embodiment is not limited to the layout shown in FIG. 5B, and a layout known in the technical field can be used. For example, as shown in FIG. 7, one pixel unit 30 may be formed by four pixels, and may be formed in a stripe shape in the order of R light emitting pixels, B light emitting pixels, and two G light emitting pixels. In this case, the third electrode 20 is provided only between the first electrode 11B of the B light emitting pixel and the first electrodes 11Ga and 11Gb of the two G light emitting pixels.

  In the present invention, as shown in FIG. 8, R light emitting pixels, B light emitting pixels, and two G light emitting pixels may be arranged in a delta arrangement within one pixel unit 30. Also in this case, the third electrode 20 is provided only between the first electrode 11B of the B light emitting pixel and the first electrodes 11Ga and 11Gb of the two G light emitting pixels. Further, one of the two G light emitting pixels may be configured as a white light emitting W light emitting pixel. Other color combinations are possible. The R light emission pixel, the B light emission pixel, and the G light emission pixel may have the same size.

  Furthermore, as shown in FIG. 9, three pixels, that is, an R light emitting pixel, a B light emitting pixel, and a G light emitting pixel may be arranged in delta, and only the B light emitting pixel may have a large area. This configuration is preferable because the lifetime of the B light emitting pixel can be extended.

[Embodiment 3]
FIG. 10A is a schematic cross-sectional view of one pixel unit of the display device according to this embodiment. The feature of this example is that, in addition to the configuration of the first embodiment, the third electrode 20 covered with the insulating layer 40 is formed at a portion where the interval between the first electrodes is wide. In this example, the gap between the first electrode 11G of the G light emitting element 3G and the first electrode 3B of the B light emitting element 3B, and the gap between the first electrode 11B of the B light emitting element 3B and the first electrode 11R of the R light emitting element 3R, respectively. The third electrodes 20 and 20 covered with the insulating layer 40 are formed. The third electrode 20 is electrically insulated from the hole transport layer 12 through the insulating layer 40, and any anode potential (in this example, the first electrode 11R, 11G, 11B).

  With this configuration, an electric field component from the third electrode 20 toward the second electrode 15 is generated between the first electrodes in a set having a large difference in the light emission threshold voltage. The electric field component weakens the electric field in the in-plane direction of the substrate 10 and hinders the movement of carriers (holes) in the in-plane direction of the substrate 10, thereby preventing current leakage to the adjacent organic EL element. Can be reduced. For this reason, the adjacent organic EL element does not emit light, and crosstalk is suppressed. The third electrode 20 is formed between the pixels having a large difference in the light emission threshold voltage and the occurrence of crosstalk, thereby suppressing the crosstalk. The difference in the light emission threshold voltage is relatively small, and the influence of the crosstalk is ignored. The third electrode 20 covered with the insulating layer 40 is not formed between the pixels that may be formed. As a result, the light emitting region is not narrowed with an interval between pixels more than necessary, leading to a longer life of the display device.

  In the present embodiment, since there is the insulating layer 40, holes are not injected from the third electrode 20 into the hole transport layer 12.

  “The third electrode 20 is set to a potential higher than any anode potential at the time of light emission of two adjacent organic EL elements” means the following setting. In this example, as shown in FIG. 10A, any light emission threshold value of the G light emitting element 3G and the B light emitting element 3B is applied to the third electrode 20 disposed between the G light emitting element 3G and the B light emitting element 3B. Apply a voltage higher than the voltage. Similarly, a voltage equal to or higher than the light emission threshold voltage of either the B light emitting element 3B or the R light emitting element 3R is applied to the second electrode 20 disposed between the B light emitting element 3B and the R light emitting element 3R.

  Further, all the third electrodes 20 are connected to a common voltage line (not shown), and any third electrode 20 has a potential higher than the anode potential at the time of light emission of all the organic EL elements 3R, 3G, 3B. It is good also as composition set up. The third electrode 20 is preferably set to a potential higher than the anode potential corresponding to the maximum value of display luminance of any two adjacent organic EL elements. The reason is that an electric field from the third electrode 20 toward the second electrode 15 is generated between the first electrodes 11R, 11G, and 11B, and the electric field in the in-plane direction of the substrate 10 disappears on the third electrode 20. For this reason, the movement of carriers (holes) in the in-plane direction of the substrate 10 can be made sufficiently small. The potential set for the third electrode 20 is not fixed and may be varied as long as it is higher than the anode potential at the time of light emission of each of the two adjacent organic EL elements. Moreover, the electric potential set to the 3rd electrode 20 is set to below the withstand voltage between wiring of a display apparatus.

  The third electrode 20 is formed in the same layer as the first electrodes 11R, 11G, and 11B, and is preferably formed in the same material and the same process as the patterning of the first electrodes 11R, 11G, and 11B. The third electrode 20 does not have to be equidistant from the two adjacent first electrodes 11R, 11G, and 11B, and may be between the two adjacent first electrodes 11R, 11G, and 11B.

  Further, as shown in FIG. 10B, the third electrode 20 may be formed inside the substrate 10 on which the first electrodes 11R, 11G, and 11B are formed. Moreover, the 1st electrode 11 may be covered with the one part insulating layer (not shown) of the board | substrate 10, for example. The same material as that of the insulating layer 40 can be used for this insulating layer.

[Pixel layout]
Also in the display device according to this embodiment, the pixel layout is not particularly limited, and a layout known in the technical field can be used. The third electrode 20 in the second embodiment is covered with the insulating layer 40 or formed on a part of the substrate 10 is the third embodiment, and all the pixel layouts shown in the second embodiment can be applied.

[Embodiment 4]
FIG. 11A is a schematic cross-sectional view of one pixel unit of the display device according to this embodiment. The feature of this example is that, in addition to the configuration of the first embodiment, an insulating partition 50 is formed in a portion where the interval between the first electrodes is wide. In this example, the gap between the first electrode 11G of the G light emitting element 3G and the first electrode 3B of the B light emitting element 3B, and the gap between the first electrode 11B of the B light emitting element 3B and the first electrode 11R of the R light emitting element 3R, respectively. An insulating partition 50 is formed. In this example, the hole transport layer 12 is formed so as to cover the first electrodes 11R, 11G, and 11B and the partition 50 in common to all the organic EL elements 3R, 3G, and 3B.

  With this configuration, the organic EL layer including the hole transport layer 12 is formed so as to wrap around the partition 50 in a set having a large difference in light emission threshold voltage. It has become. Organic EL that has a large difference in light emission threshold voltage and reduces crosstalk by increasing the resistance between organic EL elements where crosstalk occurs, and the effect of crosstalk is negligible because the difference in light emission threshold voltage is relatively small. A partition wall 50 is not formed between the elements. For this reason, the light emitting region is not narrowed by unnecessarily spacing the pixels, and the aperture ratio can be increased, leading to a longer lifetime of the display device.

  Further, as shown in FIG. 11B, the height of the partition wall 50 may be adjusted so that the organic EL layer such as the hole transport layer 12 is disconnected on the partition wall 50 and is electrically insulated. Alternatively, the organic EL layer formed on the partition wall 50 may be removed after the organic EL layer such as the hole transport layer 12 is formed on the partition wall 50. The method for removing the organic EL layer is not limited. For example, a method of wiping, a method of contacting with an adhesive substance, or laser ablation may be used. By doing in this way, a leak current can be interrupted more effectively and crosstalk can be suppressed.

  Hereinafter, the process of forming the partition 50 will be described. First, a photosensitive insulating resin is applied on the substrate 10 on which the first electrodes 11R, 11G, and 11B are formed. Next, this photosensitive insulating resin is subjected to pattern exposure and developed to form a pattern of the partition walls 50. After baking this, it is hydrophilized by light irradiation or the like to form the partition 50. The photosensitive resin used as the partition wall 50 may be either a positive resist or a negative resist, and an insulating photosensitive resin is used. Specific examples include polyimide, acrylic resin, novolac resin, and fluorene, but are not limited thereto.

[Pixel layout]
Also in the display device according to the present embodiment, the layout of the pixels is not particularly limited, and a layout known in the technical field can be used. In Embodiment 4, the third electrode 20 in Embodiment 2 is replaced with a partition wall 50, and the pixel layout shown in Embodiment 2 can be applied.

[Embodiment 5]
FIG. 12 is a schematic cross-sectional view of one pixel unit of the display device according to this embodiment. The feature of this example is that, in addition to the configuration of the first embodiment, the gap 60 is formed in a portion where the interval between the first electrodes is wide. In this example, the gap between the first electrode 11G of the G light emitting element 3G and the first electrode 3B of the B light emitting element 3B, and the gap between the first electrode 11B of the B light emitting element 3B and the first electrode 11R of the R light emitting element 3R, respectively. An insulating gap 60 is formed. In this example, the hole transport layer 12 is formed so as to cover the first electrodes 11R, 11G, 11B and the gap 60 in common to all the organic EL elements 3R, 3G, 3B.

  As a means for forming the gap, there is a means for forming the light emitting layers 13R, 13G, 13B or the electron transport layer 14 and then cutting the organic EL layer located between specific pixels by laser ablation. Further, when the organic EL layer is formed by a mask vapor deposition method, a means for separately forming a film so that specific pixels are not electrically connected may be used. Further, by using the photolithography method, the hole transport layer 12 to the light emitting layer 13 or the electron transport layer 14 are formed for each organic EL element of each color, and the film is formed so that specific pixels are not electrically connected. Means may be used.

  Since the air gap 60 is insulative, it is possible to obtain an effect of suppressing crosstalk by suppressing leakage current. Even if a film forming material enters the gap 60 during the film formation of the electron transport layer 14, the electron transport layer 14 is not an insulator, but the contact resistance with the hole transport layer 12 and the light emitting layer 13 is increased, so that crosstalk. Can be suppressed. Furthermore, it is more effective if the electron transport layer 14 is a layer having a higher resistance than the hole transport layer 12 and the light emitting layer 13.

  With this configuration, in a set having a large difference in light emission threshold voltage, an organic EL layer such as the hole transport layer 12 is not in contact with each other, so that leakage current can be suppressed. The configuration in which the organic EL elements having a large difference in light emission threshold voltage and crosstalk are not electrically connected is suppressed to suppress the occurrence of crosstalk, and the difference in light emission threshold voltage is relatively small. No structure is formed between the organic EL elements whose influence can be ignored. For this reason, the light emitting region is not narrowed by unnecessarily spacing the pixels, and the aperture ratio can be increased, leading to a longer life of the display device.

[Pixel layout]
Also in the display device according to the present embodiment, the layout of the pixels is not particularly limited, and a layout known in the technical field can be used. Embodiment 5 is obtained by replacing the third electrode 20 in Embodiment 2 with a gap 60, and all the pixel layouts shown in Embodiment 2 can be applied.

  As Example 1, a display device having a configuration corresponding to Embodiment 2 of the present invention was manufactured. First, a pixel circuit (not shown) was formed on a silicon substrate, and an interlayer insulating film made of silicon oxide was formed thereon, so that the substrate 10 shown in FIG. A Ti film having a thickness of 50 nm was formed on the substrate 10 by sputtering. Subsequently, the Ti film was patterned for each pixel to form the first electrodes (anodes) 11R, 11G, 11B and the third electrode 20. A plurality of first electrodes 11B constituting the B light emitting element 3B, a first electrode 11G constituting the G light emitting element 3G, and a plurality of first electrodes 11R constituting the R light emitting element 3R were formed. The third electrode 20 is not formed between the first electrode 11R of the R light emitting element 3R and the first electrode 11G of the G light emitting element 3G. This is because when the light emission threshold voltages of the organic EL elements of the respective colors were compared, the R light emitting element 3R was about 2.4V, the G light emitting element 3G was about 2.4V, and the B light emitting element 3B was about 2.7V. is there. The pixel layout is as shown in FIG. 5B. The size of the pixel unit 30 is L1 = L2 = 94.5 μm, the sizes of the first electrodes 11R, 11G, and 11B are L3 = 70.0 μm, L4 = 15.8 μm. It was. In addition, the distance between the first electrodes was set to the narrowest distance between 11R and 11G, d1 = 7 μm, and between 11G and 11B, and between 11B and 11R, d2 = d3 = 20 μm.

  On the substrate surface on which the patterned first electrode 11 was formed, an organic EL layer composed of a plurality of organic compound layers including the B light emitting layer 13B was formed by vacuum deposition. In order to form a film only on the substrate surface on which the first electrode 11B constituting the B light emitting element 3B was formed, a hole transport layer 12 was first formed. The hole transport layer 12 includes a first hole transport layer and a second hole transport layer. The first hole transport layer was formed by doping the host material shown in the following compound 1 with 0.5% by mass of NDP9 (manufactured by NOVALED) and having a thickness of 15 nm. On the 1st positive hole transport layer, the material of the compound 1 was formed into a film with a thickness of 20 nm, and the 2nd positive hole transport layer was formed. Thereafter, the B light emitting layer 13B was sequentially formed with a thickness of 30 nm.

  Next, an organic EL layer composed of a plurality of organic compound layers including the R light emitting layer 13R was formed by a vacuum deposition method. In order to form a film only on the substrate surface on which the first electrode 11R constituting the R light emitting element 3R was formed, the position of the shadow mask used for forming the organic EL layer of the B light emitting element 3B was moved. After forming the first and second hole transport layers with the same material as the first and second hole transport layers of the B light emitting element 3B with film thicknesses of 15 nm and 40 nm, respectively, R emission including a known red light emitting material The layer 13R was formed with a film thickness of 30 nm.

  Next, an organic EL layer composed of a plurality of layers including the G light emitting layer 13G was formed by a vacuum deposition method. The shadow mask used to form the organic EL layer of the R light emitting element 3R was moved in order to form a film only on the substrate surface on which the first electrode 11G constituting the G light emitting element 3G was formed. After forming the first and second hole transport layers with the same material as the first and second hole transport layers of the R light emitting element 3R with thicknesses of 15 nm and 30 nm, respectively, G light emission including a known green light emitting material The layer 13G was formed with a film thickness of 30 nm.

A first electron transport layer and a second electron transport layer were formed in common over all the pixels as the electron transport layer 14 on the B light emitting layer, the R light emitting layer, and the G light emitting layer. A first electron transport layer made of the material shown in Compound 2 was formed at 20 nm. In addition, the second electron transporting layer was formed by co-evaporating a host material shown in Compound 2 and Cs ₂ CO ₃ with a compound having a cesium concentration of 8.0% by mass in the layer at 10 nm. . In this example, several materials are illustrated, but the present invention is not limited to this, and the hole transport layer, the light emitting layer, and the electron transport layer can be selected from known materials.

  On top of that, indium zinc oxide was formed as a second electrode 15 with a thickness of 500 nm, and a silicon nitride sealing film 30 was formed on the second electrode 15 with a thickness of 4 μm.

  The display device manufactured as described above was driven to display a predetermined image. The pixel circuit of each pixel of this display device is as shown in FIG.

  When the organic EL elements 3R, 3G, and 3B emit light, the first electrodes 11R, 11G, and 11B are applied with a predetermined voltage that is equal to or higher than the light emission threshold voltage according to the luminance, and are driven to the organic EL elements 3R, 3G, and 3B. A current flowed through the transistor 202. On the other hand, when the organic EL elements 3R, 3G, and 3B do not emit light, the supply of current to the pixel circuit is cut off.

  The second electrode 15 is formed in common over all the pixels, and 0 V was always applied while the display device was driven.

  The third electrode 20 is connected to the second electrode 15 outside the display area, and is always set to 0 V, that is, a potential lower than the anode potential when any of the organic EL elements 3R, 3G, 3B is not emitting light.

  FIG. 13 shows the result of the color reproducibility of the display device when the third electrode 20 is set to a potential lower than the anode potential when any of the organic EL elements 3R, 3G, 3B is not emitting light as described above. It is. Specifically, first, among the organic EL elements 3R, 3G, and 3B, only the B light emitting element 3B was caused to emit light with a desired luminance, and the chromaticity was measured when the other two elements 3R and 3G were not allowed to emit light. . The chromaticity was measured at a predetermined luminance from low luminance to high luminance. Next, the chromaticity was similarly measured for the R light emitting element 3R and the G light emitting element 3G. From the chromaticity data for each color and a plurality of luminances, the NTSC color coordinate system was taken as 100%, and the ratio to that was calculated to obtain the result of FIG.

  Further, as Comparative Example 1, as shown in FIG. 14, the third electrode 20 is not provided, and the intervals d1, d2, and d3 of the first electrodes 11R, 11G, and 11B are all set equal to 7.1 μm. A display device having the same size as that of Example 1 was constructed, and the same color reproducibility was calculated and plotted in FIG.

  From FIG. 13, it can be seen that the color reproducibility of the display device of Example 1 is suppressed at any luminance as compared to the display device of Comparative Example 1. In addition, the display device of Example 1 kept the color reproducibility almost constant at any luminance. These are considered to be a result of suppression of crosstalk occurring between pixels.

  As Comparative Example 2, as shown in FIG. 15, a display device having the same size as that of Example 1 is provided except that the third electrode 20 is provided between all the pixels and d1, d2, and d3 are equally 20.0 μm. The aperture ratio for each pixel size was compared. As a result, the aperture ratio of Example 1 is 37%, and the aperture ratio of Comparative Example 2 is 27%. It can be seen that Example 1 is more advantageous in terms of the aperture ratio. For this reason, when the display device is driven with the same luminance, the current density flowing through the organic EL element is reduced by about 30% in Example 1, and therefore the display device shown in Example 1 has a longer life. I can say that.

  3R, 3B, 3G: organic EL element, 11R, 11G, 11B: first electrode, 13R, 13G, 13B: light emitting layer, 15: second electrode, 20: third electrode, 40: insulating layer, 50: partition, 60: Air gap

Claims (8)

A plurality of organic EL elements that emit at least three different colors;
The organic EL element includes a first electrode formed for each organic EL element, a second electrode common to the plurality of organic EL elements, and an organic EL layer sandwiched between the first electrode and the second electrode. ,
The organic EL layer includes at least a light emitting layer, and a charge transport layer disposed between the light emitting layer and the first electrode and common to a plurality of organic EL elements,
The organic EL element has a light emission threshold voltage that varies depending on the light emission color.
Among the gaps between the first electrodes in the set of two adjacent organic EL elements that emit different colors, the gap between the first electrodes in the set having the smallest difference in the light emission threshold voltage emits two different neighboring colors. A display device characterized by being narrower than a set of EL elements.   In a group excluding the group having the smallest difference in light emission threshold voltage, a third electrode electrically connected to the charge transport layer is disposed in the gap between the first electrodes, and the potential of the third electrode is set to be an organic EL element. The display device according to claim 1, wherein the display device is set to a potential lower than an anode potential when no light is emitted. In a group excluding the group having the smallest difference in the light emission threshold voltage, a third electrode covered with an insulating layer is provided in the gap between the first electrodes,
The display device according to claim 1, wherein the third electrode is set to a potential higher than an anode potential at the time of light emission of the two adjacent organic EL elements. In the set excluding the set having the smallest difference in the light emission threshold voltage, there is a gap in the gap between the first electrodes,
The display device according to claim 1, wherein the charge transport layer is electrically insulated between two adjacent organic EL elements provided with the gap.   The display device according to claim 1, wherein an insulating partition is provided in a gap between the first electrodes in a group excluding the group having the smallest difference in light emission threshold voltage.   The display device according to claim 5, wherein the charge transport layer is blocked between two organic EL elements by the partition.   The display device according to claim 1, wherein a distance between the first electrodes of the two adjacent organic EL elements is 30 μm or less.   8. The set of organic EL elements having the smallest difference in light emission threshold voltage is a set of red light emitting organic EL elements and green light emitting organic EL elements. The display device described.

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