JP2009104859A - Organic el element, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element capable of reducing short-circuits between the lower part electrode and the upper part electrode. <P>SOLUTION: In the organic EL element including the lower part electrode 12, the upper part electrode 19, and an organic EL material layer (positive hole injection layer 13) formed by a coating between the electrodes, between banks 14 formed on a substrate 11, the organic EL material layer (positive hole injection layer 13) covers a part of the banks 14, and an insulating layer 15 is formed between the organic EL material layer (positive hole injection layer 13) and the upper part electrode 19 on the banks 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic EL element and a method for manufacturing the same.

  In recent years, a color display device in which a light emitting material such as an organic fluorescent material is dissolved in an organic solvent to form an ink, and the ink (composition) is formed on a substrate by patterning between an anode and a cathode. Research and development is actively conducted. As an application method, an inkjet method (Patent Document 1), a printing method (Patent Document 2), a nozzle printing method (Patent Document 3), and the like are known.

  In particular, research on an “organic EL (electroluminescence) display device” using an organic EL material as a light-emitting material is active (Patent Document 1).

  FIG. 14 is a schematic cross-sectional view showing a conventional organic EL display device in which an organic EL material is applied and formed using an inkjet method.

First, a pixel electrode (lower electrode) 62 is formed on the substrate 61 by patterning, and a partition wall (bank) 64 for pixel separation is patterned by photolithography so as to cover the edge of the light emitting element. Forming. The bank 64 is a liquid-repellent resin containing a fluororesin or the like, or by applying liquid repellency to the surface of the resin by CF ₄ plasma treatment or the like, the ink applied between the banks (in the groove) The trouble of getting over and mixing in adjacent pixels is prevented.

  On the lower electrode 62, at least a hole injection layer 63 and a light emitting layer 67 are applied and formed in this order as an organic EL material layer. Subsequently, an electron transport layer 68 and an upper common electrode 69 are deposited in this order as a cathode (upper electrode).

  In an organic EL display device in which a conventional organic EL material is applied and formed by an inkjet method or the like, an organic EL material layer is formed by applying a sufficient amount of application ink between banks, but drying an organic solvent, although not shown. Is forming. As shown in FIG. 15, the meniscus (hole injection layer 531 and light emitting layer 571) of the organic EL material layer is formed on the bank sidewall portion after drying. Here, a particular problem is that an organic EL material layer is left in an extremely small amount on the bank side wall portion. In particular, the hole injection layer has a low electric resistance, and when a hole injection material is present on the bank side wall, a leak path 70 is formed between the lower electrode 62 and the upper electrodes 68 and 69, and the organic EL element is short-circuited. There was a problem.

  In order to prevent this, conventionally, as shown in FIG. 15, it has been proposed to form a first bank 60 for the purpose of insulation under a resin bank (second bank) (Patent Document). 4).

Japanese Patent No. 3036436 JP 2005-310400 A JP 2001-189192 A JP 2003-249375 A

  An object of this invention is to provide the organic EL element which can reduce the short circuit of a lower electrode and an upper electrode, and its manufacturing method.

As means for solving the above problems, the present invention provides:
In an organic EL element comprising a lower electrode and an upper electrode between a bank formed on a substrate and an organic EL material layer formed by coating between the electrodes,
The organic EL material layer covers a part of the bank, and an insulating layer is formed between the organic EL material layer on the bank and the upper electrode.

  According to the present invention, since the “insulating layer” is formed between the “organic EL material layer (hole injection layer)” and the “upper electrode”, “lower electrode” → “organic EL material layer (hole injection layer)” Layer) ”→” Leak path of “upper electrode” can be easily cut off. Therefore, a short circuit between the lower electrode and the upper electrode can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. Since each layer and each member have a size that can be recognized in the drawings, the scale is different from the actual scale.

  As illustrated in FIG. 1A, the lower electrode 12 is formed on the substrate 11. The substrate 11 is glass, a polymer film, or a metal foil, and the thickness is not particularly limited. The lower electrode 12 may be a transparent conductive film such as ITO, IZO, or IZWO, and the film thickness is preferably 50 to 500 nm.

  A bank 14 made of a liquid repellent resin for pixel separation is formed between the lower electrodes 12. As the bank (partition wall) 14, a photosensitive resin such as polyimide or acrylic can be used. The shape of the bank 14 is preferably a stripe shape or a lattice shape having a groove width of 50 to 300 μm, a bank width of 5 to 50 μm, a bank height of 0.3 to 5 μm, and a taper angle of 30 ° to 90 °. Incidentally, if the upper surface of the bank 14 is made liquid-repellent, the coating solution is repelled on the upper surface of the bank and the coating solution can be prevented from being mixed into adjacent pixels.

  A hole injection layer 13 is formed as an organic EL material layer by coating between the banks 14. At this time, the hole injection layer 13 forms a meniscus 131 so as to cover a part of the bank 14.

  As the hole injection layer 13, in addition to a PEDOT system (PEDOT-PSS; poly (3,4-ethylenedithiothiophene) -poly- (styreneenesulfonate)), a cyclohexane system or the like can be used. The thickness of the hole injection layer 13 is preferably 10 to 150 nm.

  As the coating method, in addition to the nozzle printing method, a general dispensing method, an inkjet method, a printing method, or the like can be used. The same applies to the light emitting layer 17 which will be described later by the coating method.

  Subsequently, as illustrated in FIG. 1B, a photomask 16 having a transparent portion having a size including the meniscus 131 of the coating film on the bank sidewall portion is prepared, and the insulating layer 15 is formed using a photo-CVD apparatus. As described above, SiN is formed only on the portion irradiated with the light 10. As a result, the insulating layer (SiN film) 15 sufficiently covers the meniscus 131 of the hole injection layer (PEDOT-PSS) 13.

  The insulating layer 15 may be organic or inorganic, or a laminate thereof. As the inorganic insulating layer, Si—N, Si—O, Si—O—N or the like is preferable, and as the organic insulating layer, for example, a Teflon (registered trademark) resin is preferable. The film thickness may be insulative, but is preferably 10 to 500 nm, for example. Since the material of the insulating layer 15 is a general-purpose product, the cost of the material can be reduced, and the insulating layer 15 can be applied to make it flexible.

  The insulating layer 15 can be formed by a sputtering method, a vapor deposition method, a photolithography method or the like in addition to the above-described photo-CVD method. At this time, the temperature of the substrate hardly rises and there is almost no damage to the hole injection layer 13 and the like.

  The insulating layer 15 may be formed between the hole injection layer 13 in the vicinity of the bank and the upper electrode 19, and there is no particular problem even if a light emitting layer or an electron transport layer intervenes between them. Further, an auxiliary electrode or the like may be provided.

  Subsequently, as illustrated in FIG. 1C, the light emitting layer 17 is applied and formed in the grooves between the banks 14. The light emitting layer 17 is not particularly limited as long as it can be applied from a polymer to a medium molecular or low molecular structure and may be a coating type organic EL material. The film thickness is preferably in the range of 20 to 200 nm.

Subsequently, as shown in FIG. 2, an electron transport layer (Cs ₂ CO ₃ ) 18 is formed on the light-emitting layer 17 formed by coating, and an upper electrode (Al) 19 is further formed and sealed. An organic EL element (not shown) was used. Incidentally, the upper electrode 19 is formed so as to straddle adjacent pixels.

  The organic EL element obtained in this manner is an organic EL formed by coating between the lower electrode 12 and the upper electrode 19 and the electrodes 12 and 19 between the banks 14 formed on the substrate 11. And a material layer (hole injection layer 13). The organic EL material layer (hole injection layer 13) covers a part of the bank 14, and the organic EL material layer (hole injection layer 13) on the bank 14 and the upper electrode 19 An insulating layer 15 is formed between them.

  When the electrical characteristics of the organic EL element having the above configuration were measured, the “leakage current” caused by the organic EL material layer remaining on the bank side wall portion was almost eliminated. In addition, since the insulating layer 15 is formed on the bank 14, it is possible to prevent oxygen and moisture generated from the bank 14 from entering the light emitting layer 17 and the electron transport layer 18, and thus the high luminance of the organic EL display device. And longer life.

  As described above, the organic EL element shown in FIGS. 1 and 2 shows only one bank for pixel separation and its periphery. However, when an organic EL display device is configured, it is two-dimensional as shown in FIG. A plurality are arranged in a shape. That is, the above-described organic EL element can be used as one light emitting point and used as an exposure light source for an organic EL display device, an illumination device, or an electrophotographic image forming apparatus.

  FIG. 3 is a schematic cross-sectional view showing the arrangement of the organic EL element 111 on the substrate, the drive circuit 112 and the data line 116 arranged outside thereof. The drive circuit includes a TFT and a storage capacitor.

  FIG. 4 shows details of the configuration of the drive circuit shown in FIG. The drive circuit shown in FIG. 4 has a typical circuit configuration called a current programming method. The driving circuit of the present invention is not limited to this.

  The drive circuit 112 includes a drive transistor T1 (113), a switching transistor T2 (114), a storage capacitor Ch (115), and an organic EL element (111). In addition, since it is a known circuit configuration, description of the details of the operation is omitted.

  Next, a case where the organic EL element is used in an organic EL display device will be described. FIG. 5 schematically shows a state where a plurality of organic EL elements and drive circuits shown in FIGS. 3 and 4 are two-dimensionally arranged in the same plane as one pixel, that is, arranged in a matrix. This pixel is connected to a gate driver and a source driver through a wiring, and enters a light emitting state or a non-light emitting state when a driving pulse is supplied.

  A region where a plurality of such organic EL elements are arranged in the same plane as pixels is a display region of the organic EL display device. That is, the organic EL element according to this embodiment can be used in a display area of an organic EL display device.

  For example, as shown in FIG. 7, the organic EL display device may be in any form as long as it is a television 152, a display device for PC, or a device having an image display portion. For example, a portable display device may be used. Alternatively, the organic EL display device according to this embodiment can be mounted on an electronic imaging device such as a digital camera or the display unit of the mobile phone 151.

  FIG. 6 shows a configuration in which the organic EL display device shown in FIG. 5 is made into a panel module. The panel module means a configuration in which components necessary for connection to an external device such as an interface driver and a connection terminal are integrated in a casing in addition to the configuration shown in FIG.

  Next, embodiments of the present invention will be described with reference to the drawings.

<Example 1>
As shown in FIG. 1A, an ITO film having a thickness of 100 nm was formed on the glass substrate 11 having a thickness of 0.7 mm as the lower electrode 12 by photolithography.

  A bank 14 made of a liquid repellent resin for pixel separation was formed between the lower electrodes 12 by photolithography. The banks (partitions) 14 were patterned and formed in a stripe shape having a height of 3 μm, a width of 20 μm, and a groove width of 80 μm by using a photosensitive resin such as polyimide or acrylic.

  An organic EL material layer was formed between the banks 14 by coating. Specifically, as the hole injection layer 13, PEDOT-PSS was applied and formed in a groove between the banks 14 using a nozzle printing device. Immediately after the application, the PEDOT-PSS solution was sufficiently accumulated between the banks 14, but after the solvent water evaporated and dried, the film thickness was about 40 nm, and the meniscus was formed on the bank side wall. It was observed that 131 was formed.

  Next, as shown in FIG. 1B, a photomask 16 having a transparent portion having a size including the meniscus 131 of the coating film on the bank side wall portion is prepared, and the insulating layer 15 is formed using a photo-CVD apparatus. As a result, SiN was formed to a thickness of 100 nm only on the portion irradiated with the light 10. At this time, the temperature of the substrate hardly increased, and the hole injection layer 13 was hardly damaged. Moreover, according to cross-sectional observation, it was confirmed that the insulating layer 15 sufficiently covered the meniscus 131 of the hole injection layer (PEDOT-PSS) 13.

  Subsequently, as shown in FIG. 1C, a polyfluorene polymer light-emitting layer 17 is applied in a groove between the banks 14 to a thickness of about 80 nm using a nozzle printing device. Formed.

Subsequently, as shown in FIG. 2, an electron transport layer (Cs ₂ CO ₃ ) 18 is deposited on the light-emitting layer 17 that has been formed by coating to a thickness of 3 nm and an upper electrode (Al) 19 is deposited to a thickness of 100 nm. The organic EL device was sealed (not shown).

  When the electrical characteristics of the organic EL element thus obtained were measured, almost no “leakage current” caused by the organic EL material layer remaining on the bank side wall portion. In addition, since the insulating layer 15 is formed on the bank 14, it is possible to prevent oxygen and moisture generated from the bank 14 from entering the light emitting layer 17 and the electron transport layer 18, and thus the high luminance of the organic EL display device. And longer life.

<Example 2>
As shown in FIG. 8A, ITO was formed as a lower electrode 22 on a glass substrate 21 having a thickness of 0.7 mm to a thickness of 100 nm by a photolithography method. A liquid repellent bank 24 for pixel separation was formed between the lower electrodes 22 by photolithography. The bank 24 was striped with a height of 3 μm, a width of 10 μm, and a groove width of 130 μm.

  An organic EL material layer was formed between the banks 24 by coating. Specifically, PEDOT-PSS as the hole injection layer 23 was formed in a groove between the banks 24 by using a nozzle printing apparatus. Immediately after application, the PEDOT-PSS solution was accumulated between the banks 24, but after the organic solvent and water evaporated and dried, the film thickness was about 40 nm. It was observed that meniscus 231 was formed.

  Next, as shown in FIG. 8B, a metal mask 26 having an opening having a size including the meniscus 231 of the coating film on the bank side wall portion was prepared. Then, a Teflon (registered trademark) -based resin (PFPE) was formed to a thickness of 50 nm as the insulating layer 25 using a vapor deposition method (vapor deposition source 20). According to the cross-sectional observation, it was confirmed that the insulating layer 25 sufficiently covered the meniscus 231 on the bank side wall portion of the hole injection layer (PEDOT-PSS) 23.

  Subsequently, as shown in FIG. 8C, a polyfluorene polymer light-emitting layer 27 is applied in a groove between the banks 24 to a thickness of about 80 nm using a nozzle printing apparatus. Formed. In this embodiment, since Teflon (registered trademark) resin is used as the insulating layer 25, the liquid repellency of the surface of the insulating layer 25 is given again before the light emitting layer 27 is applied. Met. That is, when the light emitting layer 27 is applied, the surface of the insulating layer 25 has a high liquid repellency and is very effective for separating pixels of the three types (R / G / B) of the light emitting layer ink 27.

Subsequently, as shown in FIG. 9, an electron transport layer (Cs ₂ CO ₃ ) 28 is deposited on the coated light emitting layer 27 to a thickness of 3 nm and an upper electrode (Al) 29 is deposited to a thickness of 100 nm. The organic EL device was sealed (not shown).

  When the electrical characteristics of the organic EL element thus obtained were measured, almost no “leakage current” caused by the organic EL material layer remaining on the bank side wall portion. In addition, since the insulating layer 25 is formed on the bank, it is possible to prevent the oxygen and moisture generated from the bank 24 from entering the light emitting layer 27 and the electron transport layer 28, and to increase the luminance of the organic EL display device. Long life was achieved.

<Example 3>
As shown in FIG. 10A, ITO was formed as a lower electrode 32 on a glass substrate 31 having a thickness of 0.7 mm to a thickness of 100 nm by a photolithography method. A liquid repellent bank 34 for pixel separation was formed between the lower electrodes 32 by photolithography. The bank 34 was striped with a height of 3 μm, a width of 20 μm, and a groove width of 100 μm.

  An organic EL material layer was formed between the banks 34 by coating. Specifically, PEDOT-PSS as the hole injection layer 33 and a polyfluorene-based polymer material as the light emitting layer 37 were applied and formed in this order in the grooves between the banks 34 using a nozzle printing device. Immediately after the application, each solution was accumulated between the banks 34, but after the solvent such as water or an organic solvent evaporated and dried, the film thickness of the hole injection layer (PEDOT-PSS) 33 was increased. Was about 40 nm, and the thickness of the light emitting layer 37 was about 80 nm. Furthermore, it was observed that meniscus 331 and 371 were formed on the bank side wall portion.

  Next, as shown in FIG. 10B, a photomask 36 having a transparent portion having a size including the meniscus 331 and 371 of the coating film on the bank side wall portion was prepared. And using the photo-CVD apparatus, as the insulating layer 35, SiON was formed in a film thickness of 100 nm only on the portion irradiated with the light 30. At this time, the temperature of the substrate hardly increased, and the hole injection layer 33 and the light emitting layer 37 were hardly damaged. Further, according to cross-sectional observation, it was confirmed that the insulating layer 35 sufficiently covered the meniscus 331 and 371 on the bank side wall portion.

Subsequently, as shown in FIG. 11, an electron transport layer (Cs ₂ CO ₃ ) 38 is deposited on the light emitting layer 37 that has been formed by coating to a thickness of 3 nm and an upper electrode (Al) 39 is deposited to a thickness of 100 nm. The organic EL device was sealed (not shown).

  When the electrical characteristics of the organic EL element thus obtained were measured, almost no “leakage current” caused by the organic EL material layer remaining on the bank side wall portion. In addition, by forming the insulating layer 35 on the bank, it is possible to prevent oxygen and moisture generated from the bank 34 from entering the electron transport layer 38, and to increase the luminance and life of the organic EL display device. I was able to.

<Example 4>
As shown in FIG. 12A, ITO was formed on the glass substrate 41 having a thickness of 0.7 mm as the lower electrode 42 to a film thickness of 100 nm by a photolithography method. A liquid-repellent bank 44 for pixel separation was formed between the lower electrodes 42 by photolithography. The bank 44 was striped with a height of 3 μm, a width of 20 μm, and a groove width of 100 μm.

  An organic EL material layer was formed between the banks 44 by coating. Specifically, PEDOT-PSS as the hole injection layer 43 and a polyfluorene-based polymer material as the light emitting layer 47 were applied and formed in the grooves between the banks 44 in this order. Immediately after the application, these solutions were accumulated between the banks 44, but after the solvent such as an organic solvent or water was evaporated and dried, the film thickness of the hole injection layer (PEDOT-PSS) 43 was increased. Was about 40 nm, and the thickness of the light emitting layer 47 was about 80 nm. Furthermore, it was observed that meniscus 431 and 471 were formed on the bank side wall portion.

  Subsequently, bathophenanthroline was deposited on the light emitting layer 47 as an electron transport layer 48 to a thickness of about 20 nm. Since the electron transport layer (vasophenanthroline film) 48 is an organic layer, the light emitting layer 47 and the hole injection layer 43 formed thereunder can be protected. Therefore, the insulating layer 45 formed thereon can be formed by photolithography. That is, as shown in FIG. 12B, SiN was formed as an insulating layer 45 on the entire surface of the electron transport layer 48 by sputtering. Subsequently, a resist was applied over the entire surface, and a SiN film was patterned and formed only on the bank 44 by photolithography (see FIG. 12C. 46 is a photomask, 40 is light for exposure). According to the cross-sectional observation, it was confirmed that the insulating layer 45 sufficiently covered the meniscuses 431 and 471 on the bank sidewall portions of the hole injection layer 43 and the light emitting layer 47.

  Subsequently, as shown in FIG. 13, an upper electrode (Al) 49 was formed on the electron transport layer 48 by vapor deposition, and sealed to obtain an organic EL element.

  When the electrical characteristics of the organic EL element thus obtained were measured, almost no “leakage current” caused by the organic EL material layer remaining on the bank side wall portion.

  The present invention provides an element structure and a manufacturing method thereof for the purpose of preventing leakage of an organic EL light emitting device formed by applying an organic EL material layer. However, the present invention can also be applied to other display devices and electronic devices having a problem of leakage that occurs due to the organic EL material layer remaining on the side wall portion of the element isolation film.

It is the figure which showed the element structure of the display apparatus of Embodiment of this invention and Example 1, and its manufacturing method. It is the figure which showed the element structure of the display apparatus of embodiment and Example 1 of this invention. It is a typical sectional view showing an organic EL element concerning the embodiment of the present invention, its drive circuit, and wiring. It is a figure which shows the detail of the drive circuit of FIG. FIG. 5 is a schematic diagram showing a state in which an organic EL display device is configured by arranging the organic EL elements and the drive circuit shown in FIGS. 3 and 4 as a pixel in a matrix. It is a schematic diagram which shows the structure which made the organic EL display apparatus shown in FIG. 5 into the panel module. It is a schematic diagram which shows the apparatus carrying the organic electroluminescent display apparatus shown in FIG. It is the figure which showed the element structure of the display apparatus of Example 2 of this invention, and its manufacturing method. It is the figure which showed the element structure of the display apparatus of Example 2 of this invention. It is the figure which showed the element structure of the display apparatus of Example 3 of this invention, and its manufacturing method. It is the figure which showed the element structure of the display apparatus of Example 3 of this invention. It is the figure which showed the element structure of the display apparatus of Example 4 of this invention, and its manufacturing method. It is the figure which showed the element structure of the display apparatus of Example 4 of this invention. It is the figure which showed the element structure of the conventional display apparatus. It is the figure which showed the element structure of the conventional display apparatus.

Explanation of symbols

11, 21, 31, 41, 51, 61 Substrate 12, 22, 32, 42, 52, 62 Lower electrode (pixel electrode)
13, 23, 33, 43, 53, 63 Hole injection layer 14, 24, 34, 44, 54, 64 Bank 15, 25, 35, 45 Insulating film 16, 26, 36, 46 Mask 17, 27, 37, 47, 57, 67 Light emitting layer 18, 28, 38, 48, 58, 68 Electron transport layer 19, 29, 39, 49, 59, 69 Upper electrode 131, 231, 331, 431, 531, 631 of hole injection layer Meniscus 371, 471, 571, 671 Meniscus 10, 30 light of light emitting layer (photo CVD apparatus)
40 light (exposure equipment)
20 Evaporation source 111 Organic EL element 112 Drive circuit 113 Drive transistor T1
114 Switching transistor T2
115 Retention capacity Ch
116 Data line 151 Mobile phone 152 TV

Claims (6)

In an organic EL element comprising a lower electrode and an upper electrode between a bank formed on a substrate and an organic EL material layer formed by coating between the electrodes,
The organic EL material layer covers a part of the bank, and an insulating layer is formed between the organic EL material layer on the bank and the upper electrode. .   2. The organic EL element according to claim 1, wherein a lower electrode, a hole injection layer as an organic EL material layer, an insulating layer, and an upper electrode are formed in this order on the bank.   An organic EL display device comprising a plurality of the organic EL elements according to claim 1 and a drive circuit for the organic EL elements.   A panel module comprising an interface between the organic EL display device according to claim 3 and an external device.   A portable display device comprising the organic EL display device according to claim 3. In a method of manufacturing an organic EL element comprising a lower electrode and an upper electrode between a bank formed on a substrate and an organic EL material layer formed by coating between the electrodes,
Forming a bank so as to cover the edge of the lower electrode formed on the substrate;
Forming an organic EL material layer by coating between the banks;
Forming an insulating layer on the organic EL material layer covering a part of the bank;
Forming an upper electrode so as to straddle adjacent pixels;
The manufacturing method of the organic EL element characterized by having.

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