JP2005190838A - Organic electroluminescence display device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescence display device which can improve characteristics of an organic electroluminescence element by preventing short-circuiting between an anode and a cathode, and also to provide its manufacturing method. <P>SOLUTION: This organic electroluminescence display device comprises: a substrate 10 having an undulating rugged face formed by the float method, ITO 101 formed on the undulating rugged face of the substrate 10; an organic electroluminescence layer 102 formed on the ITO 101; and the cathode 103 formed so as to sandwich the organic electroluminescence layer 102 between the ITO 101 and it. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic EL display device and a method for manufacturing the organic EL display device.

  In recent years, organic EL (Electro Luminescence) displays have attracted attention as FPD (Flat Panel Display). The organic EL display includes a display panel in which a plurality of organic EL elements serving as pixels are arranged. A display panel usually includes an element substrate on which an organic EL element is formed and a sealing counter substrate facing the element substrate. The counter substrate for sealing and the element substrate are bonded together, the region where the organic EL element is provided is sealed, and an organic EL display panel is manufactured.

  In a conventional organic EL display, for example, a glass substrate having a thickness of 0.7 mm is used for the element substrate, and a glass substrate having a thickness of 0.7 to 1.1 mm is used for the counter substrate for sealing. For example, non-alkali glass is used for the glass substrate.

  As a method for producing a glass substrate, for example, a fusion draw method or a float method is known. The fusion draw method is a method of manufacturing a glass plate by pouring molten glass into a bowl and integrating the glass overflowing from both sides of the bowl at the bottom of the bowl. The fusion draw method can obtain a very flat surface because the glass surface is not in contact with other than air. However, since it is difficult to increase the size of the bowl into which the molten glass is poured, a wider glass cannot be manufactured.

  In the float process, molten glass is poured into a bath containing a molten metal (for example, Sn) bath, adjusted to a predetermined width and thickness while advancing ribbon-like glass (glass ribbon), and a desired glass plate It is a method of manufacturing. The float process can produce a large amount of flat plate glass. In particular, since a wider glass can be produced by widening the bathtub, it is used for producing a large glass substrate.

  However, in the case of a glass substrate formed by the float process, undulation is likely to occur in the substrate. The undulation is caused by waves generated in the molten metal bath, contact with a roll carrying the glass ribbon, temperature change in the cooling process, and the like.

  When a glass substrate formed by a float process is used as a substrate for an LCD (Liquid Crystal Display), it is known that the substrate surface is mechanically polished (polished) in order to obtain flatness of the substrate surface. However, the polished glass substrate can remove relatively large irregularities such as waviness, but on the other hand, fine polishing scratches are formed on the surface of the glass substrate by polishing.

  A conventional glass substrate will be described with reference to FIG. FIG. 5A shows a conventional polished glass substrate 50, and FIG. 5B is an enlarged cross-sectional view showing a configuration after an organic EL element is formed on the glass substrate of FIG. 5A.

  This glass substrate 50 is formed by the float process, and the substrate surface is polished. In this example, the upper surface of the substrate 50 in the figure is the surface on which the organic EL element is formed and is the polished surface. As shown in FIG. 5A, a plurality of polishing flaws 51 that are minute concave portions are formed on the polished upper surface of the substrate 50. In addition, on the lower surface that is not polished, there are no polishing scratches, but undulations are formed. The width of the polishing scratches 51 on the surface of the substrate 50 is, for example, several μm.

  In FIG. 5B, an anode 52, an organic EL layer 53, and a cathode 54 are formed on the substrate 50. The organic EL layer 53 includes, for example, a hole injecting and transporting layer, a light emitting layer, and an electron injecting and transporting layer. When a current is supplied to the organic EL layer 53 through the anode 52 and the cathode 54, the light emitting layer of the organic EL layer 53 emits light.

  As shown in the figure, the anode 52, the organic EL layer 53, and the cathode 54 are formed along the shape of the polishing flaw 51 on the upper surface of the substrate 50, and have the same concave shape as the polishing flaw 51. Therefore, the formation amount of the anode 52, the organic EL layer 53, and the cathode 54 is larger in the vicinity of the polishing flaw 51 than in other portions. For this reason, when a current is supplied to the anode 52 and the cathode 54, the voltage is concentrated in the vicinity of the polishing scratches 51, the anode 52 and the cathode 54 are easily short-circuited, and there is a problem that the characteristics of the element deteriorate.

A method for forming an insulating layer on a polished surface of a glass substrate is known (see, for example, Patent Document 1).
JP 2000-21563 A

  As described above, the conventional organic EL display device has a problem that the anode and the cathode are easily short-circuited and the characteristics of the organic EL element are deteriorated.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an organic EL display device capable of preventing the short circuit between the anode and the cathode and improving the characteristics of the organic EL element, and a method for manufacturing the same. And

  An organic EL display device according to the present invention is formed on a glass substrate having a wavy uneven surface, a first electrode formed on the wavy uneven surface of the glass substrate, and the first electrode. A second electrode formed so as to sandwich the organic light emitting layer (for example, the organic EL layer in the present embodiment) between the organic light emitting layer and the first electrode. . Thereby, the characteristic of an element can be improved.

  In the organic EL display device described above, the substrate-side surface of the first electrode may include a concavo-convex surface derived from the undulating concavo-convex surface. Thereby, the short circuit of an anode and a cathode can be prevented.

  In the organic EL display device described above, the pitch of the irregularities on the undulating irregular surface may be wider than that of the display pixel portion. Thereby, a short circuit between the anode and the cathode can be prevented in the display pixel portion.

  The organic EL display device described above may be a passive drive type.

  The method for manufacturing an organic EL display device according to the present invention includes a step of forming a first electrode on a wavy uneven surface of a glass substrate having a wavy uneven surface, and a glass on which the first electrode is formed. Forming an organic light emitting layer on the substrate; and forming a second electrode on the glass substrate on which the organic light emitting layer is formed so as to sandwich the organic light emitting layer between the first electrode and the first electrode. And a step. As a result, an organic EL display device having excellent element characteristics can be manufactured.

  In the above-described method for manufacturing an organic EL display device, the pitch of the wavy unevenness of the glass substrate may be wider than that of the display pixel portion. Thus, an organic EL display device that does not cause a short circuit between the anode and the cathode can be manufactured.

  In the method for manufacturing the organic EL display device described above, the glass substrate may be non-alkali glass. As a result, an organic EL display device with better element characteristics can be manufactured.

  The above-described method for manufacturing an organic EL display device may further include a step of planarizing a surface of the first electrode on which the organic light emitting layer is formed. Thereby, the first electrode is flattened, and an organic EL display device with more excellent element characteristics can be manufactured.

  In the method for manufacturing an organic EL display device described above, a glass substrate formed by a float method is used as the glass substrate, and the first electrode is formed on a molten metal contact surface or a molten metal non-contact surface. Good. Thus, an organic EL display device having excellent element characteristics can be manufactured using a glass substrate formed by a float process.

  ADVANTAGE OF THE INVENTION According to this invention, the organic EL display which can prevent the short circuit of an anode and a cathode, and can improve the characteristic of an organic EL element, and its manufacturing method can be provided.

  Hereinafter, embodiments to which the present invention can be applied will be described. By the following description, this invention is not limited to the following embodiment. In order to clarify the explanation, the following description and drawings are omitted as appropriate. Further, those skilled in the art can easily change, add, and convert each element of the following embodiments within the scope of the present invention.

  A method for manufacturing the organic EL display device according to the present embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a substrate showing an outline of a method for manufacturing an organic EL display device according to the present embodiment, and FIG. 2 is a flowchart showing details of the method for manufacturing the organic EL display device according to the present embodiment. .

  The organic EL display device according to this embodiment includes an organic EL display panel in which a plurality of organic EL elements serving as pixels are arranged. In general, an organic EL display panel includes an element substrate on which an organic EL element is formed and a counter substrate disposed to face the element substrate in order to seal the organic EL element.

  A method for manufacturing the organic EL display device according to the present embodiment will be described with reference to FIG. FIG. 1 schematically shows a partial cross section of a substrate 10 which is an element substrate.

  First, as shown in FIG. 1A, a substrate 10 is formed. The substrate 10 is non-alkali glass formed by, for example, a float method. The substrate 10 has undulations on the upper and lower surfaces. However, the upper and lower surfaces of the substrate 10 do not have minute recesses such as polishing scratches. For example, the thickness of the substrate 10 is 0.7 mm. On the other hand, the typical shape of the undulation is unevenness with an undulation height of about 10 μm at an interval of 10 mm. In the present embodiment, the organic EL element is formed without mechanically polishing the substrate 10 having waviness on the surface.

  Next, as shown in FIG. 1B, ITO 101 is formed on the substrate 10. The ITO 101 is a transparent electrode serving as an anode, and is formed by sputtering, for example. At this time, a minute protrusion 101a may occur on the surface of the ITO. The protrusion 101a is caused by, for example, dust during film formation or abnormal growth.

  Next, as shown in FIG. 1C, the surface of the ITO 101 is polished. By polishing the surface of the ITO 101, the protrusions 101a are removed and the surface of the ITO 101 is flattened.

  Next, as shown in FIG. 1D, the organic EL layer 102 and the cathode 103 are formed on the ITO 101. The organic EL layer 102 and the cathode 103 are formed by, for example, coating or vapor deposition. Since there is no minute unevenness on the substrate 10, the formation amounts of the ITO 101, the organic EL layer 102, and the cathode 103 in the thickness direction are almost uniform on the substrate 10. 103 can be prevented from being short-circuited. Thereafter, the counter substrate is bonded, and sealing, cutting, and the like are performed to form an organic EL display panel.

  Next, the manufacturing method of the organic EL display device according to the present embodiment will be described in detail with reference to FIG. First, a glass substrate used for an element substrate is formed by a float method (step S101).

  In the float process, a glass raw material is made into molten glass in a melting kiln, and the molten glass flows into a float bath (molten metal bath) to form a glass ribbon which is a ribbon-like glass. For the production of glass by the float process, see Masayuki Yamane et al., “Glass Optical Handbook”, 1st edition, Asakura Shoten, July 6, 1999, p. 359-362.

  The glass ribbon formed by the float process is conveyed to a slow cooling kiln by a roll or the like and slowly cooled in the slow cooling kiln. When a sudden temperature change is applied to the glass ribbon, distortion occurs and the glass ribbon is gradually cooled while adjusting the temperature so that it does not cool at once. Then, it cut | disconnects to a desired size and becomes a glass substrate.

  Further, since a surface diffusion layer of Sn by a molten metal bath is formed on the glass substrate formed by the float process, it is washed with hydrochloric acid or the like to remove Sn (S102). The thickness of the glass substrate used as an element substrate is 0.7-1.1 mm, for example. Examples of the glass substrate thus formed include alkali-free glass (for example, AN100 manufactured by Asahi Glass Co., Ltd.) and alkali glass (ASA manufactured by Asahi Glass Co., Ltd.). In this embodiment, alkali-free glass is used. Alkali-free glass has little influence on the organic EL element because it has little elution of alkali components. The surface of the glass substrate has undulations as shown in FIG.

  ITO, which is an anode electrode material, is formed on the molten metal contact surface of the glass substrate (step S103). ITO can be formed on the entire surface of the glass substrate with good uniformity by sputtering or vapor deposition. Here, the film is formed with a film thickness of 150 nm by a DC sputtering method. An ITO pattern is formed by photolithography and etching (step S104). This ITO pattern becomes the anode. A phenol novolac resin is used as the resist, and exposure development is performed. Etching may be either wet etching or dry etching. Here, ITO was patterned using a mixed aqueous solution of hydrochloric acid and nitric acid. Monoethanolamine was used as the resist stripping material. As shown in FIG. 1B, protrusions are formed on the surface of the ITO, so that the protrusions and the like are removed and flattened by polishing the surface of the ITO (S105).

  An auxiliary wiring material is deposited on the ITO pattern (step S106). The auxiliary wiring material can be formed by sputtering or vapor deposition using a low-resistance metal material such as Al or Al alloy. Further, in order to improve adhesion to the base or prevent corrosion, a barrier layer such as TiN or Cr may be formed on the lower layer or upper layer of the Al film to form the auxiliary wiring in a laminated structure. This barrier layer can also be formed by vapor deposition or sputtering. Here, a Cr / Al / Cr laminated film or a MoNb / Al / MoNb laminated film having a total thickness of 450 nm is formed as an auxiliary wiring material by DC sputtering.

  The auxiliary wiring material is patterned by photolithography and etching to form an auxiliary wiring pattern (step S107). For the etching, an etching solution made of a mixed aqueous solution of phosphoric acid, acetic acid, nitric acid or the like can be used. It is also possible to form the anode material and the auxiliary wiring material in order, and then pattern the auxiliary wiring material and the anode material in order. A signal is supplied to the anode or the cathode by the auxiliary wiring pattern.

  Next, an opening insulating film is formed (step S108). As the insulating film, photosensitive polyimide is spin-coated, patterned after a photolithography process, and then cured to form an opening insulating film having a pixel opening in a pixel. At the same time, a contact hole between the cathode and the auxiliary wiring is formed. For example, the pixel opening is formed with a size of about 300 μm × 300 μm, and the contact hole between the cathode and the auxiliary wiring is formed with a size of about 200 μm × 200 μm. Since the glass substrate has waviness at a wider interval than the pixel opening, the surface shape of the glass substrate is almost flat in the pixel opening.

  Next, a cathode barrier is formed (step S109). For the cathode partition, for example, novolac resin is used. A novolak resin is spin-coated, patterned by a photolithography process, and then photoreacted to form cathode barrier ribs. It is preferable to use a negative type photosensitive resin so that the cathode partition has an inversely tapered structure. When a negative photosensitive resin is used, when light is irradiated from above, the photoreaction becomes insufficient at deeper locations. As a result, when viewed from above, the cross-sectional area of the cured portion has a structure that is narrower on the lower side than on the upper side. This means that it has an inverted taper structure. With such a structure, the cathodes can be separated from each other because the portions that are shaded when viewed from the vapor deposition source during vapor deposition of the cathodes do not reach the vapor deposition. Further, oxygen plasma or ultraviolet light may be irradiated in order to modify the surface of the ITO layer in the opening.

  Next, an organic EL element is formed on the pixel opening (step S110). For example, an organic EL layer and a cathode are deposited using a deposition apparatus. The organic EL layer often includes an interface layer, a hole transport layer, a light emitting layer, an electron injection layer, and the like as constituent elements. However, it may have a different layer structure. The thickness of the organic EL layer is usually about 100 to 300 nm. Copper phthalocyanine (CuPc) is 10 nm thick as the interface layer, and N, N′-di (naphthalen-1-yl) -N, N′-diphenyl-benzidine (α-NPD) is 60 nm thick as the hole transport layer, Alq is deposited to a thickness of 50 nm as a light emitting layer, and LiF is deposited to a thickness of 0.5 nm as an electron injection layer. In the above structure, a triphenylamine-based material such as triphenyldiamine (TPD) can be used for the hole transport layer instead of α-NPD.

  Al is often used for the cathode, but alkali metals such as Li, Ag, Ca, Mg, Y, In, and alloys containing them can also be used. The thickness of the cathode is usually about 50 to 300 nm, and here it is Al having a thickness of 200 nm. In addition, the cathode can be formed by physical vapor deposition (PVD) such as sputtering or ion plating. Thereby, an organic EL element is formed.

  Through these steps, a large element substrate on which a plurality of organic EL elements are formed is manufactured. Usually, a plurality of organic EL display panels having a plurality of organic EL elements are formed on one substrate. Then, by cutting and separating each organic EL display panel, a plurality of organic EL display panels can be obtained from one mother glass. This process will be described later. The manufacturing process of the organic EL element substrate described above is an example of a manufacturing process of an element substrate used in a typical organic EL display device, and is not limited to the manufacturing process described above.

  Next, a manufacturing process of the counter substrate for sealing the organic EL element will be described. Since the organic EL element deteriorates due to moisture in the air, it is sealed using a counter substrate. A glass substrate having a thickness of 0.7 to 1.1 mm is formed as a counter substrate by a float method (step S201) and washed with hydrochloric acid or the like (step S202). As the glass substrate, the same substrate as the element substrate may be used, or a polished substrate may be used. Then, the counter substrate is processed to provide a water catching material storage unit for placing a water catching material that captures moisture (step S203). The water catching material storage part is formed, for example, by digging a part of the counter substrate by etching or sandblasting. A water catching material is disposed in the water catching material storage unit (step S204). As the water catching material, calcium oxide powder, water catching tape or the like is used.

  And a sealing material is apply | coated to the surface which provided the water catching material accommodating part of the opposing board | substrate using dispenser (step S205). A sealing material is provided so as to surround the organic EL display region and seal the organic EL element. Further, a scattering prevention seal is provided between the organic EL display regions to prevent the cut end material cut from the display panel from being scattered during cutting. As the sealing seal, a photosensitive epoxy resin is preferable. For example, a cationic photopolymerization type epoxy resin can be used and functions as an adhesive for bonding the element substrate and the counter substrate. The same material can be used for the anti-scattering seal. Thereby, a manufacturing process can be simplified. A sealing substrate (counter substrate) is manufactured by the above manufacturing process. The above manufacturing process is a typical example, and the present invention is not limited to this.

  Next, the element substrate and the counter substrate are bonded together to seal the organic EL element (step S111). The subsequent steps will be described with reference to FIGS. FIG. 3 is a plan view showing the configuration of the substrate, and FIG. 4 is a cross-sectional view showing the configuration of the substrate after sealing. 3 and 4, 10 is an element substrate, 11 is an organic EL display region, 12 is an auxiliary wiring, 20 is a counter substrate, 21 is a water catching material storage unit, 22 is a water catching material, 23 is a sealing seal, Reference numeral 25 denotes a scattering prevention seal.

  The element substrate 10 is provided with an organic EL display region 11 formed by the above-described steps S101 to S110 and including a plurality of organic EL elements, and an auxiliary wiring 12 for supplying a signal to each element. As shown in FIG. 3, the element substrate 10 is provided with six organic EL display regions 11, and the organic EL display panel 30 is formed by cutting and separating the substrate. On the counter substrate 20 slightly smaller than the element substrate 10, a water catching material storage portion 21 is formed for each organic EL display region 11, and a water catching material 22 is arranged. The counter substrate 20 is provided with a sealing seal 23 surrounding each organic EL display region 11. Further, scattering prevention seals 25 are provided between the sealing seals 23 corresponding to the respective organic EL display regions 11.

  Positioning is performed so that the element substrate 10 and the counter substrate 20 face each other, both substrates are pressurized, and each sealing material is irradiated with UV light. As a result, the two substrates are bonded as shown in FIG. Each organic EL display region 11 provided on the element substrate 10 is surrounded by a sealing seal 23 as shown in FIG. A water catching material 22 is disposed in a space surrounded by both substrates and the sealing seal 23 to prevent deterioration of the organic EL element due to moisture remaining or entering the sealed space. The organic EL element is sealed with a pair of substrates including the element substrate 10 and the counter substrate 20. Since the auxiliary wiring 12 is connected to an external drive circuit, a part of the sealing seal 23 is bonded across the auxiliary wiring 12.

  Further, the outer surfaces of the element substrate 10 and the counter substrate 20, that is, the opposite surface of the element substrate 10 on which the organic EL element is provided and the opposite surface of the counter substrate 20 on which the water capturing material 22 is provided are polished. Accordingly, the substrate may be thinned. For example, when each substrate is thinned to a thickness of 0.5 mm, an organic EL display panel 30 having a total thickness of 1.0 mm is obtained.

  The sealed substrate is cut to separate each organic EL display panel 30 (step S112). For example, the cutting position is different between the element substrate 10 and the counter substrate 20. The counter substrate 20 is cut so as to surround the periphery of the sealing seal 23. The element substrate 10 is cut so as to surround the periphery of the sealing seal 23 and the end of the auxiliary wiring 12. Therefore, the element substrate 10 is cut outside the organic EL display region 11 from the counter substrate 20 by the amount of the auxiliary wiring 12 provided outside the sealing seal 23. Thereby, each organic EL display panel 30 can be divided.

  Next, a drive circuit and the like are mounted (step S113). On the element substrate 10, the auxiliary wiring 12 is extended outside from the region surrounded by the sealing seal 23. A terminal portion is formed at the outer end portion of the auxiliary wiring 12, and an anisotropic conductive film (ACF) is attached to the terminal portion to connect a TCP (Tape Carrier Package) provided with a drive circuit. Specifically, ACF is temporarily crimped to the terminal portion. ACF uses Hitachi Chemical Anisolm 7106U. The temporary pressure bonding temperature is 80 ° C., the pressure bonding pressure is 1.0 MPa, and the pressure bonding time is 5 seconds. Next, the TCP with the built-in drive circuit is finally bonded to the terminal portion. The main pressure bonding temperature is 170 degrees, the pressure bonding pressure is 2.0 MPa, and the pressure bonding time is 20 seconds. Thus, the drive circuit is mounted. The organic EL display panel 30 is attached to the housing, and the organic EL display device is completed (step S114).

  Thus, the characteristics of the organic EL element can be improved by using a glass substrate that has undulations and does not have minute irregularities such as polishing scratches. In particular, since there are no polishing scratches on the glass substrate, a short circuit between the anode and the cathode can be prevented as compared with a polished glass substrate. Further, since the interval between the undulations of the glass substrate is larger than that of the display pixel, the glass substrate is flat in the display pixel, and the undulation does not affect the characteristics of the element.

  In the above description, alkali-free glass is used for the substrate. However, the present invention is not limited to this, and low alkali glass, soda-lime glass, quartz glass, or the like may be used. In the above description, the float method is used. However, the present invention is not limited to this, and a roll-out method or the like may be used.

It is sectional drawing of the board | substrate which shows the manufacturing method of the organic electroluminescent display apparatus concerning this invention. It is a flowchart which shows the manufacturing method of the organic electroluminescence display concerning this invention. It is a top view which shows the structure of the organic electroluminescent display apparatus concerning this invention. It is sectional drawing which shows the structure of the organic electroluminescent display apparatus concerning this invention. It is sectional drawing of the conventional glass substrate.

Explanation of symbols

10 Substrate 101 ITO
102 organic EL layer 103 cathode 11 organic EL display region 12 auxiliary wiring 20 counter substrate,
21 Water catching material storage 22 Water catching material 23 Seal for sealing 25 Seal for preventing scattering 30 Display panel

Claims (9)

A glass substrate having a wavy uneven surface;
A first electrode formed on the wavy uneven surface of the glass substrate;
An organic light emitting layer formed on the first electrode;
A second electrode formed so as to sandwich the organic light emitting layer between the first electrode,
An organic EL display device comprising:   2. The organic EL display device according to claim 1, wherein a substrate-side surface of the first electrode includes an uneven surface derived from the wavy uneven surface.   3. The organic EL display device according to claim 1, wherein a pitch of the unevenness of the undulating uneven surface is wider than that of the display pixel portion.   The organic EL display device according to claim 1, which is a passive drive type. Forming a first electrode on the wavy uneven surface of the glass substrate provided with the wavy uneven surface;
Forming an organic light emitting layer on the glass substrate on which the first electrode is formed;
Forming a second electrode on the glass substrate on which the organic light emitting layer is formed so as to sandwich the organic light emitting layer with the first electrode;
A method for manufacturing an organic EL display device comprising:   The method for manufacturing an organic EL display device according to claim 5, wherein the pitch of the undulating unevenness of the glass substrate is wider than that of the display pixel portion.   The method for manufacturing an organic EL display device according to claim 5, wherein the glass substrate is alkali-free glass.   The method of manufacturing an organic EL display device according to claim 5, further comprising a step of planarizing a surface of the first electrode on which the organic light emitting layer is formed. 9. The organic material according to claim 5, 6, 7 or 8, wherein a glass substrate formed by a float method is used as the glass substrate, and the first electrode is formed on a molten metal contact surface or a molten metal non-contact surface. Manufacturing method of EL display device.

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