JP2010123286A - Laminated organic el display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated organic EL display device capable of achieving a longer life. <P>SOLUTION: In the organic EL display device, one pixel consists of two sub pixels. One sub pixel has a first organic layer and a second organic layer laminated via a common transparent electrode and the other sub pixel has the first organic layer and a third organic layer laminated via the common transparent electrode, and the first, second and third organic layers are different in luminescent color. The luminescent area of the second organic layer of each pixel is different from the luminescent area of the third organic layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic EL display device using an organic EL element as a light source, and more particularly to a stacked organic EL display device configured by stacking organic EL elements.

  2. Description of the Related Art A display device configured by arranging organic EL elements of a plurality of colors is known.

  Patent Document 1 describes a passive matrix organic EL display device in which a plurality of organic EL elements are stacked on an insulating substrate in one unit pixel.

  Patent Document 2 describes an organic EL display device that includes a plurality of subpixels in which one pixel is arranged in parallel, and each of the plurality of subpixels is formed by stacking organic layers that emit light of different colors. Has been. In the first subpixel, a first organic layer, a common electrode, a second organic layer, and a second electrode are sequentially stacked on the first electrode. In a second subpixel, the third organic layer and the common electrode are stacked on the first electrode. The second organic layer and the second electrode are sequentially stacked.

In the organic EL display device of Patent Document 2, when the first and third organic layers are caused to emit light, a positive voltage is applied to the first electrode and a negative voltage is applied to the common electrode. When the second organic layer is caused to emit light, a negative voltage is applied to the first electrode and a positive voltage is applied to the common electrode. That is, the organic EL display device disclosed in Patent Document 2 operates by time-division driving. In order to obtain a mixed color, it is necessary to apply an AC voltage between the first electrode and the common electrode.
Japanese National Patent Publication No. 10-503878 Japanese Patent Laid-Open No. 2005-174639 JP 2001-290441 A

  Although organic materials used in organic EL elements are progressing day by day, problems still remain in terms of light emission efficiency (which means luminance characteristics with respect to voltage applied to the element) and lifetime. In particular, blue organic materials currently have lower luminous efficiency and lifetime than red and green organic materials. In order to solve such a problem of characteristics according to the luminescent color, in the organic EL display device disclosed in Patent Document 3, the light emitting area is varied for each luminescent color, and the element lifetime based on the difference in luminous efficiency. A configuration for reducing adverse effects on the device is disclosed.

  However, the cited document 3 has no suggestion about application to a stacked organic EL display device.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a multilayer organic EL display device capable of improving the element lifetime.

The organic EL display device of the present invention has at least one pixel, and the pixel is composed of at least two subpixels. In one subpixel, the second organic layer is shared by the first organic layer. In another one of the subpixels, an organic EL display device in which a third organic layer is stacked on the first organic layer via a common transparent electrode,
The light emitting area of the second organic layer and the light emitting area of the third organic layer in the subpixel are different from each other.

  In the present invention, since the light emitting areas of the second organic layer and the third organic layer are different from each other, even in a stacked organic EL display device, layout of each color element according to the light emission efficiency is possible. . As a result, it is possible to provide a stacked organic EL display device with improved element lifetime.

  The organic EL display device according to the present invention includes at least one pixel, and the pixel includes at least two subpixels. In one subpixel, the second organic layer is included in the first organic layer. In another organic EL display device, the third organic layer is stacked on the first organic layer via the common transparent electrode, and the third organic layer is stacked on the first organic layer. The light emitting area of the second organic layer and the light emitting area of the third organic layer in the sub-pixel are different from each other.

  The organic EL display device of the present invention is composed of at least one pixel. Since each pixel has a first organic layer, a second organic layer, and a third organic layer, it has at least three unit elements. These unit elements emit different luminescent colors. Each pixel is composed of at least two subpixels, and one subpixel is formed by stacking a unit element having a first organic layer and a unit element having a second organic layer. ing. Another sub-pixel is formed by stacking a unit element having a first organic layer and a unit element having a third organic layer.

  The unit element is composed of a pair of electrodes and an organic layer sandwiched between the electrodes. The electrodes arranged between the unit elements stacked one above the other function as a transparent electrode common to the upper and lower unit elements.

  The common electrode is formed in common over all the pixels. However, this common transparent electrode is an electrode divided in units of pixels when adopting a mode in which unit elements stacked in the upper and lower directions are driven in a time division manner as disclosed in JP-A-2005-174039. Also good.

  The organic layers facing each other through the common transparent electrode are independently driven, that is, can emit light. As a result, the upper limit of the duty ratio of each organic layer can be set to 100% at the maximum.

  Here, the duty ratio of the organic layer is a duty ratio that is a driving condition for a unit element in which the organic layer is disposed between the pair of electrodes.

  The polarities of the organic layers stacked via the common transparent electrode are opposite to each other. That is, the polarity of the first organic layer and the polarity of the second organic layer are opposite to each other, and the polarity of the first organic layer and the polarity of the third organic layer are also opposite to each other. Here, the polarity direction means a direction in which supplied carriers, that is, electrons or holes flow. For example, when attention is paid to holes among carriers, and the first electrode in FIG. 1 is an anode and the common transparent electrode is a cathode, the direction in which holes flow can be referred to as a positive direction.

  In addition, when the form which drives the unit element laminated | stacked on the upper and lower sides by time division disclosed by Unexamined-Japanese-Patent No. 2005-174439 is employ | adopted, a 1st organic layer, a 2nd organic layer, a 3rd organic The polarities of the layers are in the same direction.

  As shown in FIG. 1, the first organic layer is disposed between the first electrode and the common transparent electrode. The second organic layer is disposed between the common transparent electrode and the second electrode. The third organic layer is disposed between the common transparent electrode and the third electrode.

  For example, when the first organic layer is disposed on the substrate side, the second and third organic layers are each disposed on the first organic layer. More specifically, the second and third organic layers are arranged side by side in the plane. In addition, as shown in FIG. 5, the structure which arrange | positions a 2nd and 3rd organic layer on the board | substrate side, and arrange | positions a 1st organic layer on it may be sufficient.

  The light emitting area of each organic layer is determined by the area of the region in which the organic layer is directly sandwiched between the pair of electrodes without using other members such as a partition wall. The light emission area can be changed for each unit element by changing the area of the electrode other than the common transparent electrode in each unit element. In the embodiment shown in FIG. 1, the emission area of the unit element having the first organic layer> the emission area of the unit element having the third organic layer> the emission area of the unit element having the second organic layer.

  The element lifetime can be improved by allocating a large light emitting area in the order of the organic layers having the low luminous efficiency. In an embodiment to be described later, as an example, a blue light emitting organic layer, a red light emitting organic layer, and a green light emitting organic layer are arranged in order of poor lifetime, and the light emitting areas are allocated as shown in FIG. However, the assignment is not limited to this as long as the luminous efficiency varies depending on the material used.

  The common transparent electrode is a component common to all unit elements. The common transparent electrode is connected to the reference potential outside the display area composed of pixels. Accordingly, one electrode of each unit element has the same potential. When the time-division driving disclosed in Japanese Patent Application Laid-Open No. 2005-174639 is adopted, the common transparent electrode is divided for each sub-pixel as described above. In this case, in the configuration of FIG. 1, the first electrode is formed in common over all the pixels, and the second and third electrodes are formed in common over all the pixels as one electrode, and are mutually referenced outside the display area. It becomes the structure connected to an electric potential.

  The common transparent electrode is transparent to light emitted from each unit element, that is, light emitted from each organic layer. In the configuration of FIG. 1, the second electrode and the third electrode, which are electrodes on the light extraction side, are also transparent.

  When the unit element is provided on a substrate that does not transmit light, light can be extracted from the side opposite to the side where the substrate is disposed with respect to the common transparent electrode, that is, the side opposite to the substrate.

  The material of the substrate is not particularly limited. It may be organic or inorganic. In the case of an organic material, it can be used as a flexible substrate, for example. In the case of an inorganic material, for example, glass can be used. It does not matter whether the substrate is a member that transmits light from the organic layer or a member that does not transmit light. The light extraction side may be a substrate using a member that transmits light. Alternatively, a light-transmitting member such as glass having a switching element such as a TFT for driving the unit element, and further providing another member, the substrate becomes a substantially light-impermeable article. May be.

  The first to third organic layers may have different compositions and layer configurations.

  In the present embodiment, a switching element is provided corresponding to each unit element. This switching element is, for example, a TFT, and is formed on a substrate by a known semiconductor process. The organic EL display device of the present invention is preferably driven by active matrix, but may be driven by simple matrix.

  Such organic EL display devices are used for displays such as personal computers, mobile phones, and digital cameras.

  Hereinafter, embodiments of the organic EL display device of the present invention will be described with reference to the drawings.

(First embodiment),
FIG. 1 is a schematic view showing a part of a stacked organic EL display device according to this embodiment. The stacked organic EL display device according to the present embodiment is configured by arranging one pixel composed of two sub-pixels in a matrix.

  The subpixel is formed by laminating a plurality of organic layers each emitting light of a different color. For example, the first subpixel includes a blue organic EL element and a green organic EL element, and the second subpixel includes a blue organic EL element. It consists of an EL element and a red organic EL element. And the polarity (diode characteristic) of the organic layer of a blue organic EL element and the polarity of the organic layer of a green organic EL element and a red organic EL element are mutually reverse directions. Moreover, the electrode provided between the organic layer of a blue organic EL element, a green organic EL element, and a red organic EL element is comprised with the common transparent electrode.

  Further, as shown in FIG. 4, the light emission area of the blue organic EL element> the light emission area of the red organic EL element> the light emission area of the green organic EL element. Therefore, the area of the first electrode> the area of the second electrode> the area of the third electrode is configured.

  Organic layer is single layer type (light emitting layer), two layer type (hole transport layer / light emitting layer), three layer type (hole transport layer / light emitting layer / electron transport layer), four layer type (hole injection layer) / Hole transport layer / light emitting layer / electron injection layer), and any of the five-layer type (hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer). FIG. 2 is an xy plan view of the electrode according to the present embodiment, and FIG. 3 is a cross-sectional view taken along lines A-A ′, B-B ′, and C-C ′ of FIG. FIG. 2 shows an electrode arrangement of a first subpixel composed of a blue organic EL element and a green organic EL element, and a second subpixel composed of a blue organic EL element and a red organic EL element. One pixel consists of two sub-pixels and displays a full color. In FIG. 2, a glass substrate 101 (not shown) disposed in the back of the drawing is shown in FIG. An active pixel circuit using a thin film transistor (hereinafter referred to as TFT) 200 as an active element is disposed on the main surface of the glass substrate corresponding to each unit element. An interlayer insulating film 120 is formed on the upper layer of the pixel circuit.

  As shown in the A-A ′ cross-sectional view of FIG. 3, in order to construct the TFT 200, the Poly-Si 104 is formed on the substrate 101, and the source region 102 and the drain region 103 of the Poly-Si 104 are formed. Further, a gate electrode 105 and a drain electrode 110 connected to the drain region 103 are formed on the Poly-Si 104, and an interlayer insulating film 120 is provided so as to cover the drain electrode 110. 106 and 107 are insulating films. The TFT 200 is not limited to the illustrated top gate type, and may be a bottom gate type. The characteristics of the TFT 200 may be either p-type or n-type. Note that the anode (first, second, and third electrodes) of each unit element (hereinafter referred to as an organic EL element) is connected to the TFT 200 at the electrode contact portion of FIG. In FIG. 2, reference numeral 400 denotes a first electrode contact portion, 500 denotes a second electrode contact portion, and 600 denotes a third electrode contact portion.

  Further, as shown in the AA ′ cross-sectional view of FIG. 3, a first electrode 300 as a reflective electrode is provided on the drain electrode 110, and a blue organic layer 310 and a common transparent electrode 320 are sequentially stacked to form a blue organic EL. An element is formed. At that time, when the TFT 200 is p-type, the blue organic layer 310 is preferably laminated in the order of hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer. The blue organic layer 310 is preferably formed in common over the entire display region, that is, all pixels, by vapor deposition or the like.

  As the reflective electrode, in addition to the electrode itself being a member that reflects light, a laminated body such as a reflective film such as AlSi on the base and a transparent conductive film such as ITO on the base can be included in the meaning.

  Further, the green organic layer 330 is stacked on the common transparent electrode 320, and the second electrode 340 for driving the green organic EL element is stacked. The second electrode 340 is formed by removing the blue organic layer 310, the common transparent electrode 320, and the green organic layer 340 with a laser as shown in the AA ′ cross-sectional view of FIG. Through 500, it is preferable to make electrical contact with the TFT. At that time, when the TFT 200 is p-type, the green organic layer 340 is preferably laminated in the order of electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole injection layer.

  Similarly, a red organic layer 350 is stacked on the common transparent electrode 320, and a third electrode 360 for driving the red organic EL element is stacked. The third electrode 360 is a third electrode formed by removing the blue organic layer 310, the common transparent electrode 320, and the red organic layer 350 with a laser, as shown in the AA ′ cross-sectional view of FIG. It is preferable to make electrical contact with the TFT through the contact portion 600. At that time, when the TFT 200 is p-type, the red organic layer 350 is preferably laminated in the order of electron injection layer / electron transport layer / light emitting layer / hole transport layer / hole injection layer. In the above description, the green organic layer 330 and the red organic layer 350 are known so as to be formed only in a necessary region for each organic light emitting element, as can be seen from the cross-sectional views of FIGS. 2 and 3E-E ′. They are formed separately using a mask vapor deposition technique.

  With the above configuration, each organic EL element in one pixel can be driven independently. Since the light emission area of each organic layer, that is, the light emission area of the organic EL element is made different according to the light emission efficiency of the organic layer, the current density during driving in the organic layer having low light emission efficiency can be reduced. The lifetime of the EL element can be improved.

Schematic diagram showing a stacked organic EL display device according to an embodiment of the present invention. Xy top view which shows electrode arrangement | positioning in 1 pixel of the multilayer organic electroluminescence display which concerns on embodiment of this invention. Cross-sectional schematic diagram corresponding to the A-A 'line, B-B' line, and C-C 'line of FIG. Schematic diagram showing the size relationship of the light emitting area in one pixel of the stacked organic EL display device according to the embodiment of the present invention. Schematic diagram showing a stacked organic EL display device according to another embodiment of the present invention.

Explanation of symbols

101 Glass substrate 102 Source region 103 Drain region 104 Poly-Si
105 Gate electrode 106 Gate insulating film 107 Interlayer insulating film 110 Drain electrode 120 Interlayer insulating film 200 TFT
300 reflective first electrode 310 first color organic layer 320 common transparent electrode 330 second color organic layer 340 second electrode 350 third color organic layer 360 third electrode 400 first electrode contact portion 500 second electrode Contact portion 600 Third electrode contact portion

Claims (7)

The pixel includes at least one pixel, and the pixel includes at least two subpixels. In one subpixel, the second organic layer is stacked on the first organic layer via a common transparent electrode. In another one of the subpixels, in the organic EL display device in which the third organic layer is stacked on the first organic layer via a common transparent electrode.
The organic EL display device, wherein a light emission area of the second organic layer and a light emission area of the third organic layer in the sub-pixel are different.   The organic EL display device according to claim 1, wherein the common transparent electrode is formed in common over all pixels. The polarity of the first organic layer and the polarity of the second organic layer are opposite to each other,
The organic EL display device according to claim 2, wherein the polarity of the first organic layer and the polarity of the third organic layer are opposite to each other.   The organic EL display device according to claim 1, wherein the first organic layer is formed in common over all pixels.   Furthermore, it has a board | substrate provided with the pixel circuit formed corresponding to each said pixel in order to drive each of the said pixel, and said 1st organic layer is said 2nd organic layer and 3rd organic layer The organic EL display device according to claim 1, further formed on the substrate side.   Furthermore, it has a board | substrate provided with the pixel circuit formed corresponding to each said pixel in order to drive each of the said pixel, and said 2nd organic layer and 3rd organic layer are said 1st organic layer The organic EL display device according to claim 1, further formed on the substrate side.   The light emission efficiency of the second organic layer is better than the light emission efficiency of the third organic layer, and the light emission area of the third organic layer is larger than the light emission area of the second organic layer. 1. The organic EL display device according to 1.

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