JP2004234901A - Display substrate, organic el display device, manufacturing method of display substrate and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify manufacturing process of a display substrate used for an EL display device or the like. <P>SOLUTION: This display substrate is so structured that a positive hole injection layer 3 is formed in a display region out of a surface of a glass substrate 1; and a luminescent layer 4 is formed in each region surrounded by a bank 9 formed on its upper layer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２５】
また、フッ素化ポリイミド樹脂の好ましい例として、式［２］で示される樹脂を挙げることができる。
【００２６】
【式２】

【００２７】
さらに、フッ素化アクリル樹脂の好ましい例として、式［３］で示される樹脂を挙げることができる。
【００２８】
【式３】

【００２９】
さらに、フッ素化シロキサン樹脂の好ましい例として、式［４］で示される樹脂を挙げることができる。
【００３０】
【式４】

【００３１】
上記したフッ素原子を含有する樹脂は、それ自体撥水性を有する樹脂材料として本発明において好適に用いることができる。
上記した樹脂材料を、本発明の目的達成上有用な感光性樹脂材料とするには、活性エネルギー線硬化型樹脂組成物とする通常の方法が採用され、活性エネルギー線によるパターニングによって精密で高解像度のパターンを形成することのできる感光性樹脂材料が採用される。
【００３２】
すなわち、樹脂材料単独では露光波長に対して十分な感度が得られない場合には、必要に応じて例えば、４，４’−ジアジドジフェニルメタン、４，４’−ジアジドジフェニルスルフィド等のアジド系開始剤、α，α−ジメトキシ−α−フェニルアセトフェノン等のアセトフェノン系開始剤、トリフェニルスルフォニウム塩等のカチオン系開始剤、２，６−ビス（４’−アジドベンザル）メチルシクロヘキサノン、２，６−ビス（４’−アジドベンジリデン）−ｔ−ブチルシクロヘキサノン等のビスアジド系感光剤、１−ナフチル−ビス−トリクロロメチル−２−トリアジン、１−（４−メトキシアントラセニル）−ビス−トリクロロ−２−トリアジン等のトリアジン系感光剤、のような感光剤、あるいはこれらの感光剤とペリレン、アントラセン、フェノチアジン、５−ニトロアセナフテン、Ｎ−アセチル−４−ニトロ−１−ナフチルアミン、ミヒラーズケトン、９−フルオレノン、ｐ−ニトロアニリン、ベンジル，１，２−ベンズアントラセン、ピレン、ｐ−キノン、４−ニトロ−１−ナフチルアミン、エリスロシンのような増感剤とを、通常用いられる量的範囲で併用することにより感度を向上させることができる。
上述の含フッ素感光性樹脂を用いることによって、正孔注入層３上に撥水性を有するバンク９を形成可能となる。
【００３３】
ところで、正孔注入層が無い場合と比較して、正孔注入層がある場合は発光効率が非常に高くなる。たとえば正孔注入層が無い場合の電流効率を１とすると、正孔注入層がある場合の電流効率は１０〜１００以上にもなる。これは正孔注入層にＰｏｌｙｅｔｈｙｌｅｎｄｉｏｘｙｔｈｉｏｐｈｅｎｅとＰｏｌｙｓｔｙｒｅｎｅｓｕｌｆｏｎａｔｅが含まれている場合でも、ポリアニリンとＰｏｌｙｓｔｙｒｅｎｅｓｕｌｆｏｎａｔｅが含まれている場合でもほぼ同じ特性を示す。
【００３４】
（基板１の製造方法）
次に、ディスプレイ基板１の製造方法について説明する。
図３は、製造方法のプロセスを示した図である。以下、図３に従って説明する。
（１）陽極側の処理（ステップＳａ１〜Ｓａ３）
はじめに、ガラス基板１の面のうちの表示領域にＴＦＴ１１を配設する（ステップＳａ１）。表示領域は、ガラス基板１の面のうち発光層４をパターン形成するための領域として予め決められており、たとえば、ガラス基板１の面を長方形とすると、一回り小さい長方形の領域が表示領域に相当する。
ＴＦＴ１１の配設方法は従来の方法と同様であるため、その一例（低温ポリシリコンの例）を簡単に説明する。まず、ガラス基板１（表示領域）の前処理として、ガラス基板１上に絶縁層を形成し、その上に、アモルファスのシリコン層を積層する。その後、シリコン層に対し、たとえばレーザアニール処理等の加熱処理を施すことにより、アモルファスのシリコン層を再結晶させ、結晶性のポリシリコン層を形成しておく。次に、形成されたポリシリコン層をパターニングし、半導体層（図２における１１Ｓ，１１Ｃ，１１Ｄに相当）を形成した上にゲート絶縁層１１Ｚを積層する。
【００３５】
次に、タンタルなどの材料でゲート配線およびゲート電極１１Ｇを形成した後、ＰＨ_３／Ｈ_２イオンをドーピングする。ゲート電極１１Ｇの上に第一層間絶縁層１１Ｙを形成した後、ソース電極１１Ｓ、ドレイン電極１１Ｄに導通を取るためのコンタクトホールをゲート絶縁層１１Ｚおよび第一層間絶縁層１１Ｙに形成する。その後、アルミをスパッタおよびパターニングしてアルミ電極１１Ａを形成し、その上に第二層間絶縁膜１１Ｘを形成後、陽極１４とアルミ電極１１Ａを導通させるためのコンタクトホールを形成する。
【００３６】
このようにしてＴＦＴ１１を配設した後、その上に平坦化層１３を形成し、ＴＦＴ１１と陽極１４を電気的に接続するためのコンタクトホールを形成する（ステップＳａ２）。平坦化層１３は、これによりＴＦＴ１１が電気的に保護されるとともに、基板上が平坦化される。
その後、平坦化層１３の上部に、陽極１４を設ける（ステップＳａ３）。陽極１４は、ここではチタンおよびＩＴＯをスパッタし、電極形状にパターニングした物である。ここで、チタンの膜厚は５００Å以上であればよい。またＩＴＯは酸化インジウムに酸化錫を１〜５重量％ドープした透明導電膜であり、正孔注入層３に正孔を注入する電極として機能するものである。陽極１４の一部は平坦化層１３に形成されたコンタクトホールとアルミ電極１１Ａによって、ＴＦＴ１１のドレイン電極１１Ｄと電気的に接続される。
なお、図２には示さなかったが、その後必要に応じて、陽極１４の画素部分を囲うように、厚さ５０〜３００ｎｍ程度の酸化シリコン、窒化シリコンなどの無機絶縁薄膜を設けることとしてもよい。
【００３７】
（２）正孔注入層３の形成（ステップＳａ４）
次に、ガラス基板１の面のうちの表示領域全面に、正孔注入層３を形成する。具体的には、正孔注入層３形成用の液体材料（例えばＰｏｌｙｅｔｈｙｌｅｎｄｉｏｘｙｔｈｉｏｐｈｅｎｅとＰｏｌｙｓｔｙｒｅｎｅｓｕｌｆｏｎａｔｅを水に分散させた溶液（Ｂａｙｔｒｏｎ Ｐ、バイエル社商標））をスピンコートにより塗布後、２００℃のホットプレートで１０分間焼成することにより、正孔注入層３を薄膜として形成する。
正孔注入層３を形成する段階におけるガラス基板１の面は、陽極１４が平坦に形成された状態にあり、正孔注入層３を厚さが均一な薄膜として形成できる。
【００３８】
（３）バンク９の形成（ステップＳａ５）
正孔注入層３を形成した後、バンク９を形成する。バンク９は、前出の有機溶剤現像タイプの含フッ素感光性樹脂を凸状に加工した仕切部材である。正孔注入層３の層上にバンク９をパターン配置していくことにより、後に発光層４を形成するための領域を形成していく。
【００３９】
具体的な一例を以下に示す。
まず、フッ素化エポキシ樹脂（上掲式［１］で示される）２０ｇおよび１−（２−メトキシナフチル）−ビス−トリクロロメチル−２−トリアジン０．２ｇをメチルイソブチルケトン８０ｇに溶解し、含フッ素感光性樹脂溶液を調製する。次に正孔注入層３形成後のガラス基板１に、前記含フッ素感光性樹脂溶液を膜厚５μｍとなるように塗布し、溶剤を乾燥させる。その後、バンク９が形成される部分のみに光が当たるようなフォトマスクを介して露光し、メチルイソブチルケトンを用いて現像することで、バンク９を形成する。この場合、フッ素化エポキシ樹脂の重合を完結させるため、６０℃から１５０℃での加熱処理を加えても良い。
【００４０】
別の一例を以下に示す。
フッ素化ポリイミド樹脂（式［２］で示される）１０ｇを、Ｎ−メチル−２−ピロリドン９０ｇに溶解して、含フッ素感光性樹脂溶液を調整した。次に正孔注入層３形成後のガラス基板１に、前記含フッ素感光性樹脂溶液を膜厚５μｍとなるように塗布し、溶剤を乾燥させる。その後、バンク９が形成される部分のみに光が当たるようなフォトマスクを介して露光し、メチルイソブチルケトンを用いて現像することで、バンク９を形成する。この場合、フッ素化エポキシ樹脂の重合を完結させるため、２００℃から３５０℃での加熱処理を加えても良い。
【００４１】
（４）発光層４の形成（ステップＳａ６）
次に発光層４を形成する。具体的には、インクジェット塗布装置を用いて、発光層４を形成するための液体材料（発光材を有機溶媒で溶解させた発光ポリマーインク組成物）をバンク９によって囲まれた各領域に、順番に吐出させていくことになる。液体材料を吐出させた後、乾燥させることによって液体材料中の有機溶媒を除去し、これにより発光層４を形成することができる。
【００４２】
（５）陰極側の処理（ステップＳａ７〜Ｓａ９）
発光層４の上部に陰極１５を形成する（ステップＳａ７）。この陰極１５は、厚さ５ｎｍのＣａを真空蒸着した後に厚さ２００ｎｍのＩＴＯをスパッタすることにより形成する。
その後、基板保護のための保護膜として透明なバリア膜１６を形成させるとともに（ステップＳａ８）、最後に封止処理として透明な封止材１７および封止ガラス１８を設ける（ステップＳａ９）。
【００４３】
図４は、ディスプレイ基板１００の端の部分について、正孔注入層３、陰極１５、バリア膜１６および封止材１７に係る部分の断面図を示したものである。図４（ａ），（ｂ），（ｃ）に３つの例を示すように、バリア膜１６は、正孔注入層３や陰極１５を設けた領域を覆うようにして形成するのが好ましく、封止材１７は、バリア膜１６を囲うようにして形成するのが好ましい。なお、図４では陰極と導通を取るための陰極コンタクト１９も示している。
ここで、広範囲に正孔注入層３を形成した場合は、正孔注入層３を形成後、あるいはバンク９を設けた後に、正孔注入層３の一部を除去する処理を行えばよい。除去方法としては、ライン状にエキシマレーザを照射し、照射ラインと直角方向にガラス基板１を移動する方法を用いることができる。この際、除去しない正孔注入層３の部分についてはメタルマスクなどで保護しておけばよい。
【００４４】
以上述べたように、本実施形態に係るディスプレイ基板１００によれば、ガラス基板１とバンク９の間に一面に正孔注入層３を形成した構造を採っている。このため、正孔注入層３の膜厚を、スピンコート塗布により均一に形成することができる。また、バンク９を設けた後は、発光層４のみを形成すればよく、インクジェットヘッドを用いる工程がＲＧＢ各１回、合計３回で足りるため、製造工程を簡易化させることができる。
【００４５】
上述した実施形態は、発明の内容を説明するためのものに過ぎず、任意に変形を加えることができる。
たとえば、正孔注入層３の形成方法は、スピンコート以外の方法であってもよく、ディップ法やＬＳＭＣＶＤ（Ｌｉｑｕｉｄ Ｓｏｕｒｃｅ Ｍｉｓｔｅｄ ｃｈｅｍｉｃａｌ ｖａｐｏｒ ｄｅｐｏｓｉｔｉｏｎ）法等であってもよい。いずれにしても、均一な膜厚の正孔注入層３を形成することができる。
また正孔注入層を形成するための液体材料としては、
ＰｏｌｙｅｔｈｙｌｅｎｄｉｏｘｙｔｈｉｏｐｈｅｎｅとＰｏｌｙｓｔｙｒｅｎｅｓｕｌｆｏｎａｔｅを水に分散させた溶液（Ｂａｙｔｒｏｎ Ｐ、バイエル社商標）を用いたが、ポリアニリンと
Ｐｏｌｙｓｔｙｒｅｎｅｓｕｌｆｏｎａｔｅを水に分散させた溶液を用いても同等な特性（発光輝度、発光効率、寿命）を得ることが可能である。
【００４６】
また、本発明は、トップエミッション、ボトムエミッションのいずれの形式のディスプレイ基板にも適用できる。上述実施形態ではトップエミッションタイプの有機ＥＬ表示装置を想定したが、ボトムエミッションタイプの場合、平坦化層１３は不要であり、陽極１４はＩＴＯの単層膜で良く、陰極１５としては厚さ５〜１０ｎｍのＣａと厚さ２００ｎｍのアルミのような光を反射する金属膜を形成することになる。いずれにしても、正孔注入層３を形成した上部に、バンク９を設ける構造にすることにより、製造工程の簡易化、成膜均一化の効果を奏することができる。
【００４７】
以上のように本発明を用いることにより、ディスプレイ基板１００を従来よりも簡易な工程で製造することができ、膜厚不均一の問題も回避することができる。このようにして製造したディスプレイ基板１００は、広い分野に利用することができる。たとえば、当該ディスプレイ基板を用いて有機ＥＬ（エレクトロルミネッセンス）表示装置を製造することができる。また、有機ＥＬ表示装置を、各種電子機器、たとえば、携帯電話、ＰＤＡ（Ｐｅｒｓｏｎａｌ Ｄｉｇｉｔａｌ Ａｓｓｉｓｔａｎｔｓ）、ＰＣやワープロのディスプレイ、ＴＶ、ディジタルカメラの表示部、デジタルビデオカメラのファインダーおよびディスプレイといった電子機器に用いることができる。
【図面の簡単な説明】
【図１】本発明の実施形態に係るディスプレイ基板１００の斜視図である。
【図２】ディスプレイ基板１００の断面図である。
【図３】ディスプレイ基板１００の製造工程図である。
【図４】ディスプレイ基板１００の断面図である。
【図５】従来のディスプレイ基板の斜視図である。
【符号の説明】
１００…ディスプレイ基板、
１…ガラス基板、３…正孔注入層、４…発光層、９…バンク、
１１…ＴＦＴ（Ｔｈｉｎ Ｆｉｌｍ Ｔｒａｎｓｉｓｔｏｒ）、１３…平坦化層、
１４…陽極、１５…陰極、１６…バリア膜、１７…封止材、１８…封止ガラス、
１９…陰極コンタクト。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a display substrate used for a display device such as an EL (electroluminescence) device, and more particularly to a display substrate used for a polymer organic EL display device in which each functional layer is formed after dissolving a material in a solution.
[0002]
[Prior art]
2. Description of the Related Art In a display device such as an organic EL, a display substrate in which a plurality of light-emitting layers (thin films) are pattern-formed on a glass substrate surface is used. The light-emitting layer has a property of emitting light by itself when a voltage is applied. By making some light-emitting layers emit light, one image can be displayed on the entire display substrate.
FIG. 5 shows a perspective view of a conventional display substrate. As shown in FIG. 5, the display substrate is provided with a partition member called a bank 9 on the surface of the glass substrate 1. The hole injection layer 3 and the light emitting layer 4 are formed in each of the regions surrounded by the bank 9. The hole injection layer 3 is an additional layer provided to make the light emitting layer 4 easily emit light.
[0003]
A conventional process for manufacturing a display substrate is roughly as follows (see Patent Documents 1 to 3).
(1) An anode-side treatment (such as formation of an anode electrode) is performed on the surface of the glass substrate 1.
(2) The bank 9 is formed.
(3) The hole injection layer 3 is formed.
(4) The light emitting layer 4 is formed.
(5) Processing on the cathode side (forming of a cathode electrode and sealing processing for protecting the substrate).
Note that, since an end portion of the surface of the glass substrate 1 is provided with a sealing glass or the like for protection, a bank 9 and a light emitting layer 4 are actually provided in an internal region (display region) of the surface of the glass substrate 1. It is formed. In addition, in FIG. 5, illustration of portions related to the electrodes is omitted.
[0004]
[Patent Document 1]
JP 2000-355394 A
[Patent Document 2]
JP 2000-323276 A
[Patent Document 3]
JP 2000-208254 A
[0005]
[Problems to be solved by the invention]
As described above, in the conventional display substrate manufacturing process, the hole injection layer 3 and the light emitting layer 4 are formed after the bank 9 is formed on the surface of the glass substrate 1. For this reason, a liquid material (water-dispersible polymer ink composition) for forming the hole injection layer 3 is first discharged to each of the regions surrounded by the bank 9 using, for example, an inkjet head. The hole injection layer 3 is formed by drying. Next, a liquid material (light-emitting polymer ink composition) for forming the light-emitting layer 4 is further discharged, and then dried to form the light-emitting layer 4. Since the light emitting layer 4 forms each of the RGB colors separately, three ink jet steps were required. Including the formation of the hole injection layer, the inkjet process was required four times. As described above, there is a problem that the manufacturing process becomes very complicated.
[0006]
Further, while the banks 9 are provided with a positional accuracy and a dimensional accuracy of 5 microns or less, the positional accuracy of ink droplet application of various ink compositions in the ink jet process has a variation of 10 microns or more. For this reason, there has been a problem that it is difficult in terms of production technology to discharge the liquid material with high positional accuracy to all the regions surrounded by the bank 9. As a means for avoiding this problem, the glass substrate 1 after the formation of the bank 9 is subjected to CF treatment after oxygen plasma treatment. ₄ There is a means for performing a plasma treatment and performing a surface modification treatment such that the surface of the anode is compatible with the ink composition (lyophilic) and the surface of the bank 9 is repellent (lyophobic) of the ink composition. By performing such processing, even if the landing position of the ink droplet is slightly shifted in the ink jet process, a part of the ink droplet is attracted to the lyophilic anode surface and is attracted from the lyophobic bank 9 surface. Since the ink droplets are pushed, an effect is obtained in which all the ink droplets fall within the area surrounded by the bank 9.
[0007]
However, when a large number of small panels are manufactured from a large substrate, there has been a problem that it is difficult to create a uniform surface state by the above-described surface modification treatment.
For this reason, the thickness of the hole injection layer 3 formed in each region becomes uneven, and even if the thickness of the light emitting layer 4 is uniform, the amount of holes injected into the light emitting layer 4 varies. was there. As a result, there has been a problem that the luminance of the display device becomes non-uniform.
The present invention has been made in view of such a point, and can be manufactured by a simpler process than before, and as a result, the problem of non-uniform film thickness as described above does not occur. It is an object of the present invention to provide a new display substrate, a new organic EL display device, a method of manufacturing a display substrate, and an electronic device.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problem, the configuration of the present invention provides a light-emitting layer that emits light by the combination of electrons and holes in each of the regions surrounded by a partition member (bank) provided in a display region on the substrate surface. In the formed display substrate, a hole injection layer for injecting the holes into the light emitting layer is formed on the entire display region of the substrate surface, and a bank is formed on the hole injection layer. It is characterized by having.
According to such a configuration, the hole injection layer can be formed over the entire display region of the substrate surface, and the hole injection layer can be easily formed with a uniform thickness. In addition, since only the light emitting layer is formed in a region surrounded by the bank provided on the hole injection layer, the process content for manufacturing such a display substrate can be simplified.
[0009]
In the above-described configuration, the hole injection layer is at least
Polyethylenedioxythiophene and Polystyrenesulfonate may be included. Alternatively, the hole injection layer may include at least polyaniline and polystyrenesulfonate. According to such a configuration, since the hole injection performance to the light emitting layer is good, an EL display having excellent characteristics such as light emission luminance, light emission efficiency, and life can be manufactured.
[0010]
Further, according to the structure of the present invention, there is provided a method of manufacturing a display substrate in which a light-emitting layer which emits light by the combination of electrons and holes is formed in each of regions surrounded by a partition member (bank) provided in a display region on a substrate surface. Forming a hole injection layer for injecting the holes into the light emitting layer over the entire display region of the substrate surface, and forming the bank on the surface of the hole injection layer. And a step of forming the light emitting layer in each of the regions surrounded by the bank.
According to such a configuration, the hole injection layer can be formed over the entire display region of the substrate surface, and the hole injection layer can be easily formed with a uniform thickness. Further, it is sufficient to form only the light emitting layer in a region surrounded by the bank provided on the hole injection layer, so that the content of the display substrate manufacturing process can be simplified.
[0011]
In the above-described method for manufacturing a display substrate, the step of forming the hole injection layer includes forming the hole injection layer on one surface by spin-coating a liquid material for forming the hole injection layer. You may. As a result, the thickness of the hole injection layer can be made uniform.
Here, the liquid material for forming the hole injection layer may be a water-dispersible polymer material. The bank may be formed by developing a fluorine-containing photosensitive resin with an organic solvent. According to this configuration, when the bank is formed of a fluorine-containing photosensitive resin of an organic solvent development type, since the hole injection layer is made of a water-dispersible polymer material, the fluorine-containing photosensitive resin is developed with an organic solvent. However, there is no possibility that the hole injection layer dissolves / swells.
[0012]
In addition, as one of utilization forms of the above-described display substrate, there is an organic EL (electroluminescence) display device including the display substrate. The organic EL display device can be used in various electronic devices. For example, a mobile phone, a PDA (Personal Digital Assistants), a display of a PC or a word processor, a display of a TV, a digital camera, a viewfinder of a digital video camera, etc. And electronic devices such as displays.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a perspective view of a display substrate 100 according to the present embodiment. The difference from the above-described conventional display substrate is that a bank 9 is formed above the hole injection layer 3.
FIG. 2 is a cross-sectional view when focusing on one certain light emitting layer 4. In the drawings, each layer is schematically shown, and the relative thickness and the like are different from those shown in the drawings.
[0014]
The configuration of the display substrate 100 will be described in detail with reference to FIG. Starting from the lower layer side of FIG. 2, first, a TFT (Thin Film Transistor) 11 is arranged on the surface of the glass substrate 1. The TFT 11 is provided for adjusting the amount of current flowing through the light emitting layer 4, thereby adjusting the luminance of the light emitting layer 4. The illustration of the wiring associated with the TFT 11 is omitted.
A flattening layer 13 is provided as an upper layer of the TFT 11. The flattening layer 13 is a layer provided for the purpose of protecting the TFT 11 and flattening the surface of the substrate.
[0015]
An anode 14 is provided as an upper layer of the planarization layer 13. The anode 14 can be, for example, a laminated film of aluminum and ITO or a laminated film of titanium and ITO, and is electrically connected to the TFT 11.
When the anode 14 is a laminated film of aluminum and ITO, aluminum reflects light from the light emitting layer 4 toward the display surface side to increase luminance, and ITO has a function of injecting holes into the hole injection layer 3. When the anode 14 is a laminated film of titanium and ITO, the thickness of the titanium, ITO, hole injection layer, light emitting layer, and cathode 15 described later is optimized so that incident light is reflected at the interface of each layer. The light beams interfere with each other and cancel each other out, so that the display area looks black and the contrast is improved.
[0016]
The hole injection layer 3 is provided as an upper layer of the anode 14. The hole injection layer 3 is provided on the entire display area of the surface of the display substrate 100, which characterizes the structure of the display substrate 100 according to the present embodiment. Since an end portion of the surface of the glass substrate 1 is provided with a sealing glass or the like for protection later, the hole injection layer 3 is formed in an internal region (display region) of the surface of the glass substrate 1. .
[0017]
A bank (partition member) 9 is provided on the hole injection layer 3, and a light emitting layer 4 is formed in a region surrounded by the bank 9.
On the layer of the light emitting layer 4, a cathode 15 made of a laminated film of, for example, 5 nm thick Ca and 200 nm thick ITO is provided. In the cathode 15, ITO functions as a conductive layer, and Ca has a function of injecting electrons into the light emitting layer 4. Above the cathode 15, a transparent barrier film 16 as a protective film, a transparent sealing material 17, and a sealing glass 18 are sequentially provided. The sealing material 17 and the sealing glass 18 are formed so as to cover the hole injection layer 3, the bank 9, and the like.
[0018]
In the display substrate 100 shown in FIG. 2, when a predetermined voltage (about 3 V to 10 V) is applied between the anode 14 and the cathode 15, holes (holes) from the anode 14 to the light emitting layer 4 via the hole injection layer 3. ) Is injected. On the other hand, electrons are injected from the cathode 15 into the light emitting layer 4. As a result, holes and electrons are combined in the light emitting layer 4, and the bond energy generated when the holes are combined is radiated (emitted) as light energy. The emitted light exits from the sealing glass 18 side.
[0019]
(Idea of the present invention)
As described above, the display substrate 100 according to the present embodiment is structurally characterized in that the bank 9 is formed on the hole injection layer 3.
The present inventor has argued that in the conventional display device, a plurality of layers such as the hole injection layer 3 and the light emitting layer 4 must be formed after the formation of the bank 9, so that the manufacturing process, particularly the process using an inkjet head, becomes complicated. As a result, it was thought that it was difficult to make the film thickness uniform.
[0020]
Based on such a concept, the present inventor has devised a structure in which the hole injection layer 3 is provided below the bank 9 as described above. According to such a structure, since the hole injection layer 3 can be formed before the bank 9 is provided in the manufacturing process, at least the thickness of the hole injection layer 3 is easily uniform using a spin coating method or the like. Can be
After the bank 9 is provided on the hole injection layer 3, only the light emitting layer 4 needs to be formed, and it is sufficient to perform the liquid material ejection three times by the inkjet head. As described above, there is also an effect that the contents of the process using the inkjet head are simplified.
[0021]
The conventional display substrate has a structure in which the hole injection layer 3 is provided for each light emitting layer 4 (see FIG. 5), and when a voltage is applied, the hole injection layer 3 becomes adjacent to the light emitting layer. 4 functioned to inject holes. On the other hand, in the display substrate 100 according to the present embodiment, the hole injection layer 3 is provided not on each light emitting layer 4 but on the entire display region of the substrate. There may be a view that holes may be injected into the light emitting layer 4 that should not be injected. However, the present inventor needs to consider the possibility that holes move in a direction different from the direction in which the voltage is applied, because the hole injection layer 3 is sufficiently thin in the direction in which the voltage is applied. Therefore, it was considered that the above-mentioned problem did not occur.
[0022]
As described above, the display substrate 100 according to the present embodiment has the same function as the conventional hole injection layer 3, although there is a difference in structure from the conventional display substrate.
Further, the hole injection layer 3 is formed by applying and baking a solution in which Polyethylenedioxythiophene and Polystyrenesulfonate are dispersed in water (Baytron P, trade name of Bayer) or a solution in which polyaniline and Polystyrenesulfonate are dispersed in water to form a thin layer having a predetermined thickness. However, the fired hole injection layer 3 is insoluble in most organic solvents. Therefore, the structure shown in FIG. 2 can be formed by forming the bank 9 using a fluorine-containing photosensitive resin of an organic solvent development type.
The above is the point of view of the present inventors, and is the principle of the present invention.
[0023]
Examples of the fluorine-containing resin which is the main component of the above-mentioned fluorine-containing photosensitive resin include, for example, fluorinated epoxy resins, fluorinated polyimide resins, fluorinated polyamide resins, fluorinated polyurethane resins, fluorinated siloxane resins and modified resins thereof. Etc. can be used.
The fluorinated resin is not particularly limited, but preferred examples of the fluorinated epoxy resin include a resin represented by the formula [1].
[0024]
(Equation 1)

[0025]
Preferred examples of the fluorinated polyimide resin include a resin represented by the formula [2].
[0026]
[Equation 2]

[0027]
Further, as a preferred example of the fluorinated acrylic resin, a resin represented by the formula [3] can be given.
[0028]
[Equation 3]

[0029]
Further, as a preferred example of the fluorinated siloxane resin, a resin represented by the formula [4] can be given.
[0030]
(Equation 4)

[0031]
The above-mentioned resin containing a fluorine atom can be suitably used in the present invention as a resin material having water repellency itself.
In order to make the above-mentioned resin material a photosensitive resin material useful for achieving the object of the present invention, an ordinary method of forming an active energy ray-curable resin composition is adopted, and precise and high resolution is obtained by patterning with an active energy ray. A photosensitive resin material capable of forming the above pattern is employed.
[0032]
That is, if the resin material alone does not provide sufficient sensitivity to the exposure wavelength, an azide compound such as 4,4′-diazidodiphenylmethane or 4,4′-diazidediphenyl sulfide may be used, if necessary. Initiators, acetophenone-based initiators such as α, α-dimethoxy-α-phenylacetophenone, cationic initiators such as triphenylsulfonium salt, 2,6-bis (4′-azidobenzal) methylcyclohexanone, 2,6- Bisazide-based photosensitizers such as bis (4'-azidobenzylidene) -t-butylcyclohexanone, 1-naphthyl-bis-trichloromethyl-2-triazine, 1- (4-methoxyanthracenyl) -bis-trichloro-2- Photosensitizers such as triazine photosensitizers such as triazine, or these photosensitizers and perylene, anthracene, Phenothiazine, 5-nitroacenaphthene, N-acetyl-4-nitro-1-naphthylamine, Michler's ketone, 9-fluorenone, p-nitroaniline, benzyl, 1,2-benzanthracene, pyrene, p-quinone, 4-nitro- Sensitivity can be improved by using a sensitizer such as 1-naphthylamine or erythrosine in a commonly used quantitative range.
By using the above-mentioned fluorine-containing photosensitive resin, it is possible to form the water-repellent bank 9 on the hole injection layer 3.
[0033]
By the way, as compared with the case where there is no hole injection layer, the luminous efficiency becomes very high when there is a hole injection layer. For example, assuming that the current efficiency when there is no hole injection layer is 1, the current efficiency when there is a hole injection layer is 10 to 100 or more. This shows almost the same characteristics regardless of whether the hole injection layer contains Polyethylenedioxythiophene and Polystyrenesulfonate or polyaniline and Polystyrenesulfonate.
[0034]
(Method of manufacturing substrate 1)
Next, a method for manufacturing the display substrate 1 will be described.
FIG. 3 is a diagram showing a process of the manufacturing method. Hereinafter, description will be made with reference to FIG.
(1) Processing on the anode side (steps Sa1 to Sa3)
First, the TFT 11 is provided in the display area on the surface of the glass substrate 1 (Step Sa1). The display region is predetermined as a region for pattern-forming the light emitting layer 4 on the surface of the glass substrate 1. For example, if the surface of the glass substrate 1 is rectangular, a rectangular region which is slightly smaller is used as the display region. Equivalent to.
Since the method of disposing the TFT 11 is the same as the conventional method, an example (an example of low-temperature polysilicon) will be briefly described. First, as a pretreatment of the glass substrate 1 (display area), an insulating layer is formed on the glass substrate 1, and an amorphous silicon layer is stacked thereon. After that, the amorphous silicon layer is recrystallized by subjecting the silicon layer to a heat treatment such as a laser annealing treatment to form a crystalline polysilicon layer. Next, the formed polysilicon layer is patterned to form a semiconductor layer (corresponding to 11S, 11C, and 11D in FIG. 2), and a gate insulating layer 11Z is laminated.
[0035]
Next, after forming a gate wiring and a gate electrode 11G with a material such as tantalum, the PH ₃ / H ₂ Doping ions. After forming the first interlayer insulating layer 11Y on the gate electrode 11G, contact holes for establishing conduction with the source electrode 11S and the drain electrode 11D are formed in the gate insulating layer 11Z and the first interlayer insulating layer 11Y. After that, aluminum is sputtered and patterned to form an aluminum electrode 11A, a second interlayer insulating film 11X is formed thereon, and then a contact hole for conducting the anode 14 and the aluminum electrode 11A is formed.
[0036]
After arranging the TFT 11 in this manner, a planarizing layer 13 is formed thereon, and a contact hole for electrically connecting the TFT 11 and the anode 14 is formed (Step Sa2). As a result, the TFT 11 is electrically protected by the planarizing layer 13 and the substrate is planarized.
Thereafter, the anode 14 is provided on the flattening layer 13 (Step Sa3). The anode 14 is formed by sputtering titanium and ITO and patterning it into an electrode shape. Here, the thickness of titanium may be 500 ° or more. ITO is a transparent conductive film in which tin oxide is doped with 1 to 5% by weight of indium oxide, and functions as an electrode for injecting holes into the hole injection layer 3. A part of the anode 14 is electrically connected to the drain electrode 11D of the TFT 11 through the contact hole formed in the planarization layer 13 and the aluminum electrode 11A.
Although not shown in FIG. 2, if necessary, an inorganic insulating thin film such as silicon oxide or silicon nitride having a thickness of about 50 to 300 nm may be provided so as to surround the pixel portion of the anode 14. .
[0037]
(2) Formation of hole injection layer 3 (step Sa4)
Next, the hole injection layer 3 is formed on the entire display area of the surface of the glass substrate 1. Specifically, a liquid material for forming the hole injection layer 3 (for example, a solution in which Polyethylenedioxythiophene and Polystyrenesulfonate are dispersed in water (Baytron P, a trademark of Bayer AG)) is applied by spin coating, and then coated on a hot plate at 200 ° C. for 10 hours. By firing for a minute, the hole injection layer 3 is formed as a thin film.
The surface of the glass substrate 1 at the stage of forming the hole injection layer 3 is in a state where the anode 14 is formed flat, and the hole injection layer 3 can be formed as a thin film having a uniform thickness.
[0038]
(3) Formation of Bank 9 (Step Sa5)
After forming the hole injection layer 3, a bank 9 is formed. The bank 9 is a partition member obtained by processing the aforementioned organic solvent developing type fluorine-containing photosensitive resin into a convex shape. By arranging the banks 9 in a pattern on the hole injection layer 3, a region for forming the light emitting layer 4 is formed later.
[0039]
A specific example is shown below.
First, 20 g of a fluorinated epoxy resin (represented by the above formula [1]) and 0.2 g of 1- (2-methoxynaphthyl) -bis-trichloromethyl-2-triazine are dissolved in 80 g of methyl isobutyl ketone to obtain a fluorine-containing resin. Prepare a photosensitive resin solution. Next, the fluorine-containing photosensitive resin solution is applied to the glass substrate 1 after the hole injection layer 3 is formed so as to have a thickness of 5 μm, and the solvent is dried. Thereafter, the bank 9 is formed by exposing through a photomask in which light is applied only to the portion where the bank 9 is to be formed, and is developed using methyl isobutyl ketone. In this case, a heat treatment at 60 ° C. to 150 ° C. may be added to complete the polymerization of the fluorinated epoxy resin.
[0040]
Another example is shown below.
10 g of a fluorinated polyimide resin (represented by the formula [2]) was dissolved in 90 g of N-methyl-2-pyrrolidone to prepare a fluorinated photosensitive resin solution. Next, the fluorine-containing photosensitive resin solution is applied to the glass substrate 1 after the hole injection layer 3 is formed so as to have a thickness of 5 μm, and the solvent is dried. Thereafter, the bank 9 is formed by exposing through a photomask in which light is applied only to the portion where the bank 9 is to be formed, and is developed using methyl isobutyl ketone. In this case, a heat treatment at 200 ° C. to 350 ° C. may be added in order to complete the polymerization of the fluorinated epoxy resin.
[0041]
(4) Formation of Light Emitting Layer 4 (Step Sa6)
Next, the light emitting layer 4 is formed. Specifically, a liquid material (a light-emitting polymer ink composition in which a light-emitting material is dissolved in an organic solvent) for forming the light-emitting layer 4 is sequentially applied to each region surrounded by the bank 9 by using an inkjet coating device. Will be discharged. After discharging the liquid material, the organic solvent in the liquid material is removed by drying, whereby the light emitting layer 4 can be formed.
[0042]
(5) Cathode-side processing (steps Sa7 to Sa9)
The cathode 15 is formed on the light emitting layer 4 (Step Sa7). The cathode 15 is formed by vacuum-depositing 5 nm thick Ca and then sputtering 200 nm thick ITO.
Thereafter, a transparent barrier film 16 is formed as a protective film for protecting the substrate (step Sa8), and finally, a transparent sealing material 17 and a sealing glass 18 are provided as a sealing process (step Sa9).
[0043]
FIG. 4 is a cross-sectional view of a portion related to the hole injection layer 3, the cathode 15, the barrier film 16, and the sealing material 17 at an end portion of the display substrate 100. As shown in FIGS. 4A, 4B and 4C, the barrier film 16 is preferably formed so as to cover the region where the hole injection layer 3 and the cathode 15 are provided. The sealing material 17 is preferably formed so as to surround the barrier film 16. FIG. 4 also shows a cathode contact 19 for establishing conduction with the cathode.
Here, when the hole injection layer 3 is formed over a wide range, a process of removing a part of the hole injection layer 3 may be performed after forming the hole injection layer 3 or after providing the bank 9. As a removing method, a method of irradiating an excimer laser in a line shape and moving the glass substrate 1 in a direction perpendicular to the irradiation line can be used. At this time, the portion of the hole injection layer 3 that is not removed may be protected by a metal mask or the like.
[0044]
As described above, the display substrate 100 according to the present embodiment has a structure in which the hole injection layer 3 is formed on the entire surface between the glass substrate 1 and the bank 9. Therefore, the thickness of the hole injection layer 3 can be made uniform by spin coating. After the bank 9 is provided, only the light-emitting layer 4 needs to be formed, and the process using an ink-jet head is performed only once for each of RGB, three times in total, so that the manufacturing process can be simplified.
[0045]
The embodiments described above are merely for explaining the contents of the invention, and can be arbitrarily modified.
For example, the hole injection layer 3 may be formed by a method other than spin coating, such as a dipping method or an LSMCVD (Liquid Source Chemical vapor deposition) method. In any case, the hole injection layer 3 having a uniform thickness can be formed.
Further, as a liquid material for forming the hole injection layer,
A solution (Baytron P, trade name of Bayer Corporation) in which Polyethylenedioxythiophene and Polystyrenesulfonate were dispersed in water was used.
The same characteristics (luminance, luminous efficiency, lifetime) can be obtained even by using a solution in which Polystyrenesulfonate is dispersed in water.
[0046]
In addition, the present invention can be applied to both types of display substrates, top emission and bottom emission. In the above embodiment, the top emission type organic EL display device is assumed. However, in the case of the bottom emission type, the flattening layer 13 is unnecessary, the anode 14 may be a single-layer film of ITO, and the cathode 15 has a thickness of 5 mm. A metal film that reflects light such as Ca of 10 to 10 nm and aluminum with a thickness of 200 nm is formed. In any case, by adopting a structure in which the bank 9 is provided above the hole injection layer 3 formed, the effects of simplifying the manufacturing process and uniforming the film formation can be obtained.
[0047]
As described above, by using the present invention, the display substrate 100 can be manufactured by a simpler process than before, and the problem of non-uniform film thickness can be avoided. The display substrate 100 manufactured as described above can be used in a wide range of fields. For example, an organic EL (electroluminescence) display device can be manufactured using the display substrate. In addition, the organic EL display device is used for various electronic devices such as mobile phones, PDAs (Personal Digital Assistants), displays of PCs and word processors, TVs, display units of digital cameras, viewfinders and displays of digital video cameras, and the like. be able to.
[Brief description of the drawings]
FIG. 1 is a perspective view of a display substrate 100 according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the display substrate 100.
FIG. 3 is a manufacturing process diagram of the display substrate 100.
FIG. 4 is a cross-sectional view of the display substrate 100.
FIG. 5 is a perspective view of a conventional display substrate.
[Explanation of symbols]
100 ... display substrate,
DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 3 ... Hole injection layer, 4 ... Light emitting layer, 9 ... Bank,
11: TFT (Thin Film Transistor), 13: flattening layer,
14 ... anode, 15 ... cathode, 16 ... barrier film, 17 ... sealing material, 18 ... sealing glass,
19 ... Cathode contact.

Claims (9)

In a display substrate in which a light emitting layer which emits light by a combination of electrons and holes is formed in each of regions surrounded by a partition member (bank) provided in a display region on a substrate surface,
A hole injection layer for injecting the holes into the light emitting layer is formed on the entire display region of the substrate surface, and a bank is formed on the hole injection layer. Display board. The display substrate according to claim 1,
A display substrate, wherein the hole injection layer includes at least Polyethylenedioxythiophene and Polystyrenesulfonate. The display substrate according to claim 1,
A display substrate, wherein the hole injection layer contains at least polyaniline and polystyrene sulfate. An organic EL (electroluminescence) display device comprising the display substrate according to claim 1. In a method for manufacturing a display substrate, a light-emitting layer that emits light by the combination of electrons and holes is formed in each of regions surrounded by a partition member (bank) provided in a display region on a substrate surface.
Forming a hole injection layer for injecting the holes into the light emitting layer over the entire display region of the substrate surface;
Forming the bank on a surface of the hole injection layer;
Forming the light emitting layer in each of the regions surrounded by the bank. The method for manufacturing a display substrate according to claim 5,
The method of manufacturing a display substrate, wherein the step of forming the hole injection layer comprises spin-coating a liquid material for forming the hole injection layer to form the hole injection layer. The method for manufacturing a display substrate according to claim 6,
A method for manufacturing a display substrate, wherein the liquid material forming the hole injection layer is a water-dispersible polymer material. The method for manufacturing a display substrate according to any one of claims 5 to 7,
The method for manufacturing a display substrate, wherein the bank is formed by developing a fluorine-containing photosensitive resin with an organic solvent. An electronic apparatus comprising the organic EL display device according to claim 4.

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