Organic electroluminescence display device and method for manufacturing the same

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

In recent years, organic EL (Electro Luminescence) displays have been attracting attention as FPDs (Flat Panel Display). The organic EL display includes a display panel in which a plurality of organic EL elements serving as pixels are arranged. The display panel usually includes an element substrate on which an organic EL element is formed and a sealing facing substrate facing the element substrate. An organic EL display panel is manufactured by laminating a sealing facing substrate and an element substrate and sealing a region provided with an organic EL element.

In the conventional organic EL display, for example, a 0.7 mm thick glass substrate is used for the element substrate, and a 0.7 to 1.1 mm glass substrate is used for the sealing facing substrate. For this glass substrate, for example, non-alkali glass is used.

As a method for manufacturing a glass substrate, for example, a fusion draw method and a float method are known. The fusion draw method is a method in which molten glass is poured into a gutter, and the glass overflowing from both sides of the gutter is integrated at the lower part of the gutter to manufacture a glass plate. In the fusion draw method, since the glass surface does not come into contact with anything other than air, a very flat surface can be obtained. However, since it is difficult to increase the size of the gutter into which the molten glass is poured, it is not possible to manufacture a wider glass.

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

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

When a glass substrate formed by the float method is used as a substrate for an LCD (Liquid Crystal Display), it is known that the surface of the substrate is mechanically polished (polished) in order to obtain the flatness of the surface of the substrate. However, although relatively large irregularities such as waviness are removed from the polished glass substrate, on the other hand, minute 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. 5 (a) shows a conventional polished glass substrate 50, and FIG. 5 (b) is an enlarged cross-sectional view showing a configuration after forming an organic EL element on the glass substrate of FIG. 5 (a).

The glass substrate 50 is formed by a float method, and the surface of the substrate is polished. In this example, the upper surface of the substrate 50 in the figure is the formation surface and the polishing surface of the organic EL element. As shown in FIG. 5A, a plurality of polishing scratches 51, which are minute recesses, are formed on the polished upper surface of the substrate 50. Further, the unpolished lower surface has undulating irregularities without polishing scratches. The width of the polishing scratch 51 on the surface of the substrate 50 is, for example, several μm.

In FIG. 5B, the anode 52, the organic EL layer 53, and the cathode 54 are formed on the substrate 50. The organic EL layer 53 is laminated with, for example, a hole injection transport layer, a light emitting layer, and an electron injection transport layer. When a current is supplied to the organic EL layer 53 via the anode 52 and the cathode 54, the light emitting layer of the organic EL layer 53 self-luminesces.

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 scratch 51 on the upper surface of the substrate 50, and have a concave shape similar to the polishing scratch 51. Therefore, the amount of the anode 52, the organic EL layer 53, and the cathode 54 formed is larger in the vicinity of the polishing scratch 51 than in the other parts. Therefore, when a current is supplied to the anode 52 and the cathode 54, the voltage is concentrated in the vicinity of the polishing scratch 51, and the anode 52 and the cathode 54 are likely to be short-circuited, which causes a problem that the characteristics of the element are deteriorated.

A method of forming an insulating layer on the polished surface of a glass substrate is known (see, for example, Patent Document 1).<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2000-21563</text></patcit>

<p> As described above, the conventional organic EL display device has a problem that a short circuit between the anode and the cathode is likely to occur and the characteristics of the organic EL element are deteriorated.</p><p> The present invention has been made to solve such a problem, and an object of the present invention is to provide an organic EL display device capable of preventing a short circuit between an anode and a cathode and improving the characteristics of an organic EL element and a method for manufacturing the same. And.</p>

<p> The 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 102 in the present embodiment) between the organic light emitting layer and the first electrode is provided. .. Thereby, the characteristics of the element can be improved.</p><p> In the above-mentioned organic EL display device, the surface of the first electrode on the substrate side may have an uneven surface derived from the wavy uneven surface. This makes it possible to prevent a short circuit between the anode and the cathode.</p><p> In the above-mentioned organic EL display device, the pitch of the unevenness of the wavy uneven surface may be wider than that of the display pixel portion. This makes it possible to prevent a short circuit between the anode and the cathode in the display pixel portion.</p><p> The above-mentioned organic EL display device may be a passive drive type.</p><p> 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 concavo-convex surface of a glass substrate having a wavy concavo-convex surface, and a glass on which the first electrode is formed. A second electrode is formed on the glass substrate on which the organic light emitting layer is formed and the step of forming the organic light emitting layer on the substrate so as to sandwich the organic light emitting layer between the first electrode and the first electrode. It is equipped with steps. This makes it possible to manufacture an organic EL display device having excellent device characteristics.</p><p> In the method for manufacturing an organic EL display device described above, the pitch of the wavy irregularities on the glass substrate may be wider than that of the display pixel portion. This makes it possible to manufacture an organic EL display device in which a short circuit between the anode and the cathode does not occur.</p><p> In the method for manufacturing an organic EL display device described above, the glass substrate may be non-alkali glass. This makes it possible to manufacture an organic EL display device having better device characteristics.</p><p> The method for manufacturing an organic EL display device described above may further include a step of flattening the surface of the first electrode on which the organic light emitting layer is formed. As a result, the first electrode becomes flat, and an organic EL display device having better element characteristics can be manufactured.</p><p> In the above-mentioned manufacturing method of the organic EL display device, the first electrode may be formed on the molten metal contact surface or the molten metal non-contact surface by using the glass substrate formed by the float method on the glass substrate. Good. This makes it possible to manufacture an organic EL display device having excellent device characteristics by using the glass substrate formed by the float method.</p>

<p> According to the present invention, it is possible to provide an organic EL display device capable of preventing a short circuit between an anode and a cathode and improving the characteristics of an organic EL element and a method for manufacturing the same.</p>

Hereinafter, embodiments to which the present invention can be applied will be described. By the following description, the present invention is not limited to the following embodiments. For the sake of clarification of 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 of manufacturing the organic EL display device according to the present embodiment will be described with reference to FIGS. 1 and 2. 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 a method for manufacturing an organic EL display device according to the present embodiment. ..

The organic EL display device according to the present embodiment includes an organic EL display panel in which a plurality of organic EL elements serving as pixels are arranged. The organic EL display panel usually includes an element substrate on which an organic EL element is formed and an opposing substrate arranged to face the element substrate in order to seal the organic EL element.

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

First, as shown in FIG. 1A, the substrate 10 is formed. The substrate 10 is, for example, non-alkali glass formed by the float method. The substrate 10 has undulating irregularities on the upper surface and the lower surface. However, the upper surface and the lower surface 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 swell is unevenness in which the height of the swell is about 10 μm at intervals 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, ITO 101 is formed on the substrate 10 as shown in FIG. 1 (b). ITO101 is a transparent electrode serving as an anode, and is formed by, for example, sputtering. At this time, minute protrusions 101a may be formed on the surface of the ITO. The protrusion 101a is due to, for example, dust during film formation or abnormal growth.

Then, as shown in FIG. 1 (c), the surface of ITO 101 is polished. By polishing the surface of ITO101, the protrusion 101a is removed and the surface of ITO101 is flattened.

Next, as shown in FIG. 1 (d), 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 are no minute irregularities on the substrate 10, the amount of each of the ITO 101, the organic EL layer 102, and the cathode 103 formed in the thickness direction is almost uniform on the substrate 10, so that the voltage is not concentrated and the ITO 101 and the cathode are not concentrated. It is possible to prevent a short circuit of 103. After that, the facing substrates are bonded, sealed, cut, and the like 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, the glass substrate used for the element substrate is formed by the float method (step S101).

In the float method, the 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-shaped glass. The production of glass by the float method is described in Masayuki Yamane et al., "Glass Optical Handbook", 1st Edition, Asakura Shoten, July 6, 1999, p.359-362.

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

Further, since a surface diffusion layer of Sn is formed on the glass substrate formed by the float method by the molten metal bath, it is washed with hydrochloric acid or the like to remove Sn (S102). The thickness of the glass substrate used as the element substrate is, for example, 0.7 to 1.1 mm. Examples of the glass substrate thus formed include non-alkali glass (for example, AN100 manufactured by Asahi Glass Co., Ltd.) or alkaline glass (AS manufactured by Asahi Glass Co., Ltd.), and in the present embodiment, non-alkali glass is used. Non-alkali glass has less influence on the organic EL element because the elution of the alkaline component is small. The surface of this glass substrate has undulations as shown in FIG. 1 (a).

ITO, which is an anode electrode material, is formed on the molten metal contact surface of this glass substrate (step S103). ITO can be uniformly formed on the entire surface of a glass substrate by sputtering or vapor deposition. Here, a film is formed with a film thickness of 150 nm by the DC sputtering method. An ITO pattern is formed by photolithography and etching (step S104). This ITO pattern serves as the anode. Phenolic novolak resin is used as the resist, and exposure development is performed. The etching may be either wet etching or dry etching, but here, ITO is patterned using a mixed aqueous solution of hydrochloric acid and nitric acid. Monoethanolamine was used as the resist stripping material. As shown in Fig. 1 (b), protrusions are formed on the surface of ITO. Therefore, by polishing the surface of ITO, protrusions and the like are removed and flattened (S105).

Auxiliary wiring material is formed on the ITO pattern (step S106). As the auxiliary wiring material, a low resistance metal material such as Al or Al alloy is used, and a film can be formed by sputtering or vapor deposition. Further, in order to improve the adhesion with the substrate or prevent corrosion, a barrier layer such as TiN or Cr may be formed in the lower layer or the upper layer of the Al film to form an 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 having a total thickness of 450 nm or a MoNb / Al / MoNb laminated film is formed as an auxiliary wiring material by a DC sputtering method.

This auxiliary wiring material is patterned by photolithography and etching to form an auxiliary wiring pattern (step S107). An etching solution consisting of a mixed aqueous solution of phosphoric acid, acetic acid, nitric acid and the like can be used for etching. It is also possible to form a film of 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 cathode by this auxiliary wiring pattern.

Next, an open insulating film is formed (step S108). As the insulating film, a photosensitive polyimide is spin-coated, patterned in a photolithography step, and then cured to form an aperture insulating film having pixel openings in the pixels. At the same time, a contact hole is formed between the cathode and the auxiliary wiring. For example, the pixel opening is formed to be about 300 μm × 300 μm, and the contact hole between the cathode and the auxiliary wiring is formed to be about 200 μm × 200 μm. Since the swells of the glass substrate are present at intervals wider than the pixel openings, the surface shape of the glass substrate is substantially flat at the pixel openings.

Next, the cathode partition wall is formed (step S109). For the cathode partition wall, for example, novolak resin is used. The novolak resin is spin-coated, patterned in a photolithography process, and then photoreacted to form a cathode bulkhead. It is preferable to use a negative type photosensitive resin so that the cathode partition has a reverse taper structure. When a negative type photosensitive resin is used, when light is irradiated from above, the deeper the place, the more insufficient the photoreaction becomes. As a result, when viewed from above, the cured portion has a structure in which the cross-sectional area of the cured portion is narrower in the lower part than in the upper part. This means that it has a reverse taper structure. With such a structure, the cathodes can be separated from each other because the vapor deposition does not reach the portion that is hidden from the vapor deposition source when the cathodes are vapor-deposited. Further, oxygen plasma or ultraviolet rays may be irradiated to modify the surface of the ITO layer of 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 vapor-deposited using a thin-film 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) with a thickness of 10 nm as the interface layer, N, N'-di (naphthalene-1-yl) -N, N'-diphenyl-benzidine (α-NPD) with a thickness of 60 nm 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. With the above configuration, a triphenylamine-based substance such as triphenyldiamine (TPD) can be used for the hole transport layer instead of α-NPD.

Al is often used as 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. The cathode can also be formed by physical vapor deposition (PVD) such as sputtering and ion plating. As a result, 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 step will be described later. The above-mentioned manufacturing process of the organic EL element substrate is an example of the manufacturing process of the element substrate used in a typical organic EL display device, and is not limited to the above-mentioned manufacturing process.

Next, the manufacturing process of the opposed 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 facing substrate. A glass substrate having a thickness of 0.7 to 1.1 mm is formed as a facing substrate by the float method (step S201), and washed with hydrochloric acid or the like (step S202). As the glass substrate, the same one as the element substrate may be used, or a polished substrate may be used. Then, the facing substrate is processed to provide a water catching material storage portion for arranging the water catching material that traps water (step S203). The water catching material storage portion is formed by digging a part of the facing substrate by, for example, etching or sandblasting. The water catching material is placed in this water catching material storage part (step S204). Calcium oxide powder, water catching tape, etc. are used as the water catching material.

Then, a sealing material is applied to the surface of the facing substrate provided with the water catching material storage portion using a dispenser (step S205). A sealing material is provided so as to surround the organic EL display area and seal the organic EL element. Further, a shatterproof seal for preventing the cut scraps cut from the display panel during cutting is provided between each organic EL display area. A photosensitive epoxy resin is preferable as the sealing seal. For example, a photocationically polymerized epoxy resin can be used, which functions as an adhesive for bonding the element substrate and the opposing substrate. The same material can be used for the shatterproof seal. This makes it possible to simplify the manufacturing process. A sealed substrate (opposed substrate) is manufactured by the above manufacturing process. The above-mentioned manufacturing process is a typical example, and is not limited to this.

Next, the element substrate and the facing substrate are bonded together to seal the organic EL element (step S111). Subsequent steps will be described with reference to FIGS. 3 and 4. 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. In FIGS. 3 and 4, 10 is an element substrate, 11 is an organic EL display area, 12 is an auxiliary wiring, 20 is an opposite substrate, 21 is a water catching material storage part, 22 is a water catching material, and 23 is a sealing seal. 25 is a shatterproof seal.

The element substrate 10 includes an organic EL display region 11 formed by steps S101 to S110 described above 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, six organic EL display regions 11 are provided on the element substrate 10, and the organic EL display panel 30 is formed by cutting and separating the substrates. A water catching material accommodating portion 21 is formed for each organic EL display area 11 on the opposing substrate 20 which is slightly smaller than the element substrate 10, and the water catching material 22 is arranged. The facing substrate 20 is provided with a sealing seal 23 that surrounds each organic EL display area 11. Further, a shatterproof seal 25 is provided between the sealing seals 23 corresponding to the respective organic EL display areas 11.

The element substrate 10 and the facing substrate 20 are aligned so as to face each other, both substrates are pressurized, and each sealing material is irradiated with UV light. As a result, both substrates are bonded to each other as shown in FIG. As shown in FIG. 3, each organic EL display area 11 provided on the element substrate 10 is surrounded by a sealing seal 23. The water catching material 22 is arranged in the space surrounded by both substrates and the sealing seal 23 to prevent deterioration of the organic EL element due to moisture remaining or invading in the sealed space. The organic EL element is sealed with a pair of substrates consisting of the element substrate 10 and the facing substrate 20. Since the auxiliary wiring 12 is connected to an external drive circuit, a part of the sealing seal 23 is adhered across the auxiliary wiring 12.

Further, the outer surfaces of the element substrate 10 and the opposing 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 opposing substrate 20 on which the water catching material 22 is provided are polished. As a result, the substrate may be made thinner. For example, if 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 can be obtained.

The sealed substrate is cut to separate each organic EL display panel 30 (step S112). For example, the cutting positions of the element substrate 10 and the facing substrate 20 are different. The facing 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 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 with respect to the facing substrate 20 by the amount of the auxiliary wiring 12 provided outside the sealing seal 23. As a result, it can be divided into each organic EL display panel 30.

Next, the drive circuit and the like are mounted (step S113). Auxiliary wiring 12 is extended to the outside of the area surrounded by the sealing seal 23 on the element substrate 10. A terminal portion is formed at the outer end of the auxiliary wiring 12, and an anisotropic conductive film (ACF) is attached to this 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 Kasei Anisorum 7106U. The temporary crimping temperature is 80 ° C, the crimping pressure is 1.0MPa, and the crimping time is 5 seconds. Then, TCP with a built-in drive circuit is main crimped to the terminal part. The main crimping temperature is 170 degrees, the crimping pressure is 2.0MPa, and the crimping time is 20 seconds. This implements the drive circuit. The organic EL display panel 30 is attached to the housing to complete the organic EL display device (step S114).

As described above, the characteristics of the organic EL element can be improved by using the glass substrate which has waviness and does not have minute irregularities such as polishing scratches. In particular, since there are no polishing scratches on the glass substrate, it is possible to prevent a short circuit between the anode and the cathode as compared with the polished glass substrate. Further, since the interval between the undulations of the glass substrate is larger than that of the display pixels, the glass substrate is flat in the display pixels, and the undulations do not affect the characteristics of the element.

In the above description, non-alkali glass is used as the substrate, but the present invention is not limited to this, and low-alkali glass, soda-lime glass, quartz glass and the like may be used. Further, in the above description, it is formed by the float method, but the present invention is not limited to this, and a rollout method or the like may be used.

<figref num="1">It is sectional drawing of the substrate which shows the manufacturing method of the organic EL display device which concerns on this invention.</figref><figref num="2">It is a flowchart which shows the manufacturing method of the organic EL display device which concerns on this invention.</figref><figref num="3">It is a top view which shows the structure of the organic EL display device which concerns on this invention.</figref><figref num="4">It is sectional drawing which shows the structure of the organic EL display device which concerns on this invention.</figref><figref num="5">It is sectional drawing of the conventional glass substrate.</figref>

Code description

10 Substrate 101 ITO102 Organic EL layer 103 Cathode 11 Organic EL display area 12 Auxiliary wiring 20 Opposing board, 21 Water catching material storage part 22 Water catching material 23 Sealing seal 25 Anti-scattering seal 30 Display panel