JP4255250B2 - Electroluminescent element - Google Patents

Description

【０１１４】
その後、発光層として、下記化学式（２）に示すアルミニウムキノリノール金属錯体（Ａｌｑ_３）を厚み８０ｎｍ蒸着し、最後に電子注入層兼スパッタリング保護層として、下記化学式（３）に示すバソキュプロイン（ＢＣＰ）とＬｉの共蒸着層を２０ｎｍ成膜した。モル比率がＢＣＰ：Ｌｉが１：２になるように成膜速度を調節した。
【０１１５】
【化２】

【０１１６】
【化３】

【０１１７】
成膜条件は、真空度５×１０^−５Ｐａ、各層の有機材料は成膜速度２〜５Å／ｓｅｃで成膜した。成膜条件としてスパッタガスはＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝５０：１）、圧力０．１Ｐａ、ＲＦ出力１００Ｗ、ＤＣ出力１５０Ｗとした。成膜速度２〜５Å／ｓｅｃでガス圧５．５×１０^−２Ｐａの条件下で１５０ｎｍの透明電極層を形成し発光エリア２ｍｍ×２ｍｍの有機ＥＬ素子を作製した。
【０１１８】
その後、透明電極層上に低屈折率層としてＭｇＦ_２を真空蒸着法にて５０ｎｍ形成し、最後にバリア層としてＳｉＯ_２、ＳｉＮの組合せからなる膜を５μｍ成膜した。成膜条件はマグネトロンスパッタリングにてターゲットＳｉＯｘＮｙを使用し、スパッタガスはＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝３０：１）、圧力０．２Ｐａ、ＲＦ出力１５０Ｗ、ＤＣ出力２００Ｗとした。バリア層の形成はプラズマＣＶＤ法でも形成可能である。透明電極層のシート抵抗は１０Ω／□であった。得られた有機ＥＬ素子の発光エリアは２ｍｍ×２ｍｍであり、陽極の成膜からバリア層までの工程はすべて真空下で行った。
【０１１９】
Ａｌを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は１０Ｖ印加時の電流密度は１１０ｍＡで、３０００ｃｄ／ｍ^２であった。
【０１２０】
［比較例１］
光導波防止層を形成しない有機ＥＬ素子を実施例１と同様の工程で作製した。Ａｌを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は１０Ｖ印加時の電流密度は２０ｍＡで、２００ｃｄ／ｍ^２であった。
【０１２１】
［比較例２］
光導波防止層としてＩＴＯを使用し、表面粗さを５ｎｍとし、膜厚を１００ｎｍとした有機ＥＬ素子を実施例１と同様の工程で作製した。陽極としてＡｌ、光導波防止層としてＩＴＯを形成した膜について四探針法により表面抵抗値を調べたところ０．６Ω／□であった。Ａｌを陽極とした有機ＥＬ素子は１０Ｖ印加時の電流密度は１００ｍＡで、２６００ｃｄ／ｍ^２であった。
【０１２２】
［実施例２］
基材として、縦横２５ｍｍ×２５ｍｍで、厚みが１．１ｍｍの透明ガラスを洗浄後、マグネトロンスパッタリング法にて膜厚１００ｎｍのＡｌもしくはＣｒからなる陽極を成膜した。スパッタガスとしてＡｒを用い、圧力０．１５Ｐａ、ＤＣ出力２００Wとした。その上に光導波防止層として１０ｎｍのＩＴＯをマグネトロンスパッタリング法にて形成した。スパッタガスとして、ＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝５０：１）、圧力０．１Ｐａ、ＤＣ出力１５０Ｗとした。成膜時は金属マスクを使用し発光エリア２ｍｍ×２ｍｍが４ヶ所できるように陽極のパターニングを行った。その後、基材を酸素プラズマ下に曝した。Ａｌ／ＩＴＯの陽極の場合、酸素プラズマ処理を行った後、大気中で仕事関数を測定した結果４．９ｅＶから５．７ｅＶとイオン化ポテンシャルが低下した。ＩＴＯが形成されていない場合、仕事関数の値は変わらなかった。
【０１２３】
次いで、形成した光導波防止層上に正孔注入輸送層として、下記化学式（４）に示すポリエチレンジオキシチオフェン（ＰＥＤＯＴ）をスピンコートにより厚み８０ｎｍ形成し加熱乾燥させた。以下に、（ＰＥＤＯＴ（ＰＳＳ））の化学式を示す。
【０１２４】
【化４】

【０１２５】
その後、酸素濃度が１ｐｐｍまでの低酸素条件下および湿度が１ｐｐｍまでの低湿度条件下であるグローブＢＯＸ中にて発光層として、下記化学式（５）に示すポリ（ジオクチルフルオレン−ｃｏ−アントラセン）（ＰＦ）を厚み８０ｎｍに成膜し、最後に電子注入層兼スパッタリング保護層としてバソキュプロイン（ＢＣＰ）とＬｉの共蒸着層を２０ｎｍ成膜した。モル比率がＢＣＰ：Ｌｉが１：２になるように成膜速度を調節した。以下に、ＰＦの化学式について示す。
【０１２６】
【化５】

【０１２７】
成膜条件は、真空度５×１０^−５Ｐａ、ＢＣＰの成膜速度２Å／ｓｅｃで成膜した。電子注入層を成膜後、透明電極層としてＩＴＯ、ＩＺＯをスパッタリングにより１５０ｎｍ形成した。電子注入層へのスパッタダメージを軽減するため、対向ターゲット式マグネトロンスパッタ装置で成膜した。成膜条件としてスパッタガスはＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝５０：１）、圧力０．１Ｐａ、ＲＦ出力１００Ｗ、ＤＣ出力１５０Ｗとした。成膜速度２〜５Å／ｓｅｃでガス圧５．５×１０^−２Ｐａの条件下で１５０ｎｍの透明電極層を形成し発光エリア２ｍｍ×２ｍｍの有機ＥＬ素子を作製した。
【０１２８】
その後、透明電極層上に低屈折率層としてＭｇＦ_２を真空蒸着法にて５０ｎｍ形成し、最後にバリア層としてＳｉＯ_２、ＳｉＮの組合せからなる膜を５μｍ成膜した。成膜条件はマグネトロンスパッタリングにてターゲットＳｉＯｘＮｙを使用し、スパッタガスはＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝３０：１）、圧力０．２Ｐａ、ＲＦ出力１５０Ｗ、ＤＣ出力２００Ｗとした。
【０１２９】
Ａｌを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は８Ｖ印加時の電流密度は２００ｍＡで、９０００ｃｄ／ｍ^２であった。Ｃｒを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は８Ｖ印加時の電流密度は２２０ｍＡで、６０００ｃｄ／ｍ^２であった。
【０１３０】
［比較例３］
光導波防止層を形成しない有機ＥＬ素子を実施例２と同様の工程で作製した。Ａｌを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は１０Ｖ印加時の電流密度は２０ｍＡで、２００ｃｄ／ｍ^２であった。Ｃｒを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は８Ｖ印加時の電流密度は６０ｍＡで、７００ｃｄ／ｍ^２であった。
【０１３１】
［実施例３］
基材として、縦横２５ｍｍ×２５ｍｍで、厚みが１．１ｍｍの透明ガラスを洗浄後、マグネトロンスパッタリング法にて膜厚１００ｎｍのＡｌもしくはＣｒからなる陽極を成膜した。スパッタガスとしてＡｒを用い、圧力０．１５Ｐａ、ＤＣ出力２００Wとした。その上に光導波防止層として１０ｎｍのＩＴＯをマグネトロンスパッタリング法にて形成した。スパッタガスとして、ＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝５０：１）、圧力０．１Ｐａ、ＤＣ出力１５０Ｗとした。
【０１３２】
次いで、形成した光導波防止層上に正孔注入輸送層としてポリエチレンジオキシチオフェン（ＰＥＤＯＴ）をスピンコートにより厚み８０ｎｍ形成し加熱乾燥させた。その後、酸素濃度が１ｐｐｍまでの低酸素条件下および湿度が１ｐｐｍまでの低湿度条件下であるグローブＢＯＸ中にて発光層としてポリ（ジオクチルフルオレン−ｃｏ−アントラセン）（ＰＦ）を厚み８０ｎｍに成膜し、最後に電子注入層としてＬｉＦを０．５ｎｍ成膜した。更にその上にＣａを１０ｎｍ蒸着した。を２０ｎｍ成膜した。成膜条件は、真空度５×１０^−５Ｐａ、ＬｉＦの成膜速度０．１Å／ｓｅｃ、Ｃａの成膜速度１．０Å／ｓｅｃで成膜した。電子注入層を成膜後、透明電極層としてＩＴＯ、ＩＺＯをスパッタリングにより１５０ｎｍ形成した。発光層へのスパッタダメージを軽減するため、対向ターゲット式マグネトロンスパッタ装置で成膜した。成膜条件としてスパッタガスはＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝５０：１）、圧力０．１Ｐａ、ＲＦ出力１００Ｗ、ＤＣ出力１５０Ｗとした。成膜速度２〜５Å／ｓｅｃでガス圧５．５×１０^−２Ｐａの条件下で１５０ｎｍの透明電極層を形成し発光エリア２ｍｍ×２ｍｍの有機ＥＬ素子を作製した。
【０１３３】
その後、透明電極層上に低屈折率層としてＭｇＦ_２を真空蒸着法にて５０ｎｍ形成し、最後にバリア層としてＳｉＯ_２、ＳｉＮの組合せからなる膜を５μｍ成膜した。成膜条件はマグネトロンスパッタリングにてターゲットＳｉＯｘＮｙを使用し、スパッタガスはＡｒとＯ_２の混合ガス（体積比Ａｒ：Ｏ_２＝３０：１）、圧力０．２Ｐａ、ＲＦ出力１５０Ｗ、ＤＣ出力２００Ｗとした。
【０１３４】
Ａｌを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は８Ｖ印加時の電流密度は３００ｍＡで、１２０００ｃｄ／ｍ^２であった。Ｃｒを陽極としＩＴＯを透明電極層とした有機ＥＬ素子は８Ｖ印加時の電流密度は３３０ｍＡで、８０００ｃｄ／ｍ^２であった。
【０１３５】
【発明の効果】
本発明によれば、上述したように電荷注入層としての機能を有し、かつ、光の導波を抑制する機能も保持する光導波防止層が金属電極層上に設けられているので、金属電極層に用いる金属の種類に関わらず、ダークスポット等を生じさせることが少なく、さらに、光の導波を抑制することから光の損失を抑えることができるため、良好な光の取り出し効率を有するＥＬ素子とすることができるという効果を奏する。
【図面の簡単な説明】
【図１】本発明のＥＬ素子の一例を示す概略断面図である。
【図２】本発明のＥＬ素子の製造方法の一例を示す工程図である。
【符号の説明】
１ … 基材
２ … 陽極
３ … 光導波防止層
４ … 正孔輸送層
５ … 発光層
６ … 電子注入輸送層
７ … 陰極
８ … 低屈折率層
９ … バリア層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electroluminescent element having good luminous efficiency (hereinafter, electroluminescent may be abbreviated as EL) element.
[0002]
[Prior art]
EL elements using electroluminescence are highly visible due to self-emission and are completely solid elements, so they have features such as excellent impact resistance, so they are attracting attention as light emitting elements in various display devices. Has been.
[0003]
Such EL elements include an inorganic EL element using an inorganic compound as a light emitting material and an organic EL element using an organic compound. Among these, since organic EL elements can be easily miniaturized with a significantly reduced driving voltage, practical research has been actively conducted as next-generation display elements. The structure of the organic EL element is basically a laminate of an anode / light emitting layer / cathode, and a structure in which a transparent anode is formed on a substrate using a glass plate or the like is usually employed. In this case, the emitted light is extracted to the substrate side.
[0004]
As such an EL element, an attempt has been made in recent years to extract light emission from the cathode side by making the cathode transparent. Thus, when light emission is taken out from the cathode side, it is possible to manufacture a transparent EL element as a whole by making the anode transparent together with the cathode. Such a transparent EL element can employ any color as a background color, and can be a colorful display other than during light emission. Further, when black is used as the background color, there is an advantage that the contrast at the time of light emission can be improved. Furthermore, when a color filter or a color conversion layer is used, since these can be placed on the EL element, it is not necessary to consider the color filter or the color conversion layer in the manufacturing stage of the EL element. When forming the anode, the substrate temperature can be increased and the resistance value of the anode can be lowered.
[0005]
As an example of an EL device having such advantages, Japanese Patent Application Laid-Open No. 10-162959 discloses that a cathode is formed of an electron-injecting metal layer and an amorphous transparent conductive layer having a very thin film thickness. A technique for extracting light emission from a light source is disclosed. Further, it is disclosed that a metal having a work function of 4.8 eV or higher, a transparent conductive film, or a combination thereof is used for the anode, and examples of suitable metals include Au, Pt, Ni, and Pd. Yes. However, since these metals do not have good adhesion to the organic EL layer formed on the anode metal, there is a risk of generating dark spots (non-light emitting points) and non-uniform light emission. Therefore, as a means for solving such problems, a method using a metal having a work function of less than 4.8 eV such as chromium, molybdenum, tungsten, tantalum or the like as a metal used for the anode metal is disclosed in Japanese Patent Application Laid-Open No. 2001-43980. Is disclosed. As described above, by using a metal of 4.8 eV, it is possible to suppress the generation of dark spots, but on the other hand, new disadvantages such as a decrease in current density and a decrease in light emission efficiency at the same applied voltage occur. I was allowed to.
[0006]
Furthermore, as a means for solving such a problem, a method of laminating a transparent conductive film called a modified electrode on the anode metal has been proposed, but also in this method, light loss due to the transparent conductive film is proposed. There is a problem that the light extraction efficiency is greatly inferior.
[0007]
Therefore, it is desired to develop a means for solving all these problems in an EL element that extracts light emission from the transparent cathode side.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and an EL element capable of improving light extraction efficiency without causing inconveniences such as dark spots regardless of the type of metal in the metal electrode layer. The main purpose is to provide
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a metal electrode layer, an organic EL layer including a light emitting layer formed on the metal electrode layer, and the organic EL layer as described in claim 1. An EL device having at least a formed transparent electrode layer is characterized in that an optical waveguide preventing layer that functions as a charge injection layer and suppresses light loss is provided on the metal electrode layer. An EL device is provided.
[0010]
In the present invention, as described above, the optical waveguide preventing layer that functions as a charge injection layer and also retains the function of suppressing light guiding is provided on the metal electrode layer. Regardless of the type of metal used in the layer, there are few dark spots and the like, and since light loss can be suppressed because light waveguide is suppressed, an EL that has good light extraction efficiency It can be an element.
[0011]
In the invention described in claim 1, as described in claim 2, the optical waveguide prevention layer preferably has a surface roughness in the range of 10 nm to 30 nm. Thus, by forming the surface of the optical waveguide prevention layer roughly within the above range, when the light generated in the organic EL layer is guided in the optical waveguide prevention layer, the vicinity of the surface of the optical waveguide prevention layer. The light is irregularly reflected by the roughness of the light, and the waveguide of light can be suppressed. As a result, loss due to light guiding can be suppressed, so that the light extraction efficiency can be improved.
[0012]
In the invention described in the second aspect, as described in the third aspect, it is preferable that an average film thickness of the optical waveguide preventing layer is in a range of 0.1 nm to 30 nm. This is because an optical waveguide prevention layer having an average film thickness within the above range can sufficiently function as a charge injection layer.
[0015]
Claims 1 to above 3 In the invention described in any of the preceding claims, the claims 4 As described in, an organic material having conductivity can be used as the material used for the optical waveguide prevention layer. Claims 5 As described above, the optical waveguide prevention layer may be formed of an inorganic oxide containing indium. Furthermore, in this case the claim 6 It is preferable that it is ITO as described in. This is because ITO has a high light transmittance and a low resistance, so that the drive voltage of the EL element can be lowered and the luminous efficiency can be improved.
[0016]
Claims 1 to above 6 In the invention described in any of the preceding claims, the claims 7 As described above, the light reflectance of the metal electrode layer is preferably 30% or more within the visible region of 380 to 780 nm. This is because by setting the light reflectance of the metal electrode layer in the above range, light generated in the light emitting layer is reflected by the metal electrode layer, and light can be efficiently extracted from the transparent electrode layer side.
[0017]
Claims 1 to above 7 In the invention described in any of the preceding claims, the claims 8 As described above, the thickness of the metal electrode layer is preferably in the range of 40 nm to 500 nm. If the film thickness is thinner than the above range, light may pass through the metal electrode layer. On the other hand, if the film thickness is thicker than the above range, the smoothness as the EL element is impaired, and the transparent electrode layer or the like This is because inconvenience such as disconnection may occur.
[0018]
Claims 1 to above 8 In the invention described in any of the preceding claims, the claims 9 As described above, the light transmittance of the transparent electrode layer is preferably 50% or more within a visible region of 380 to 780 nm. This is because light generated in the light emitting layer can be efficiently extracted from the transparent electrode layer side if the transparent electrode layer has a light transmittance within the above range.
[0019]
Claims 1 to above 9 In the invention described in any of the preceding claims, the claims 10 As described above, the metal electrode layer is preferably an anode. This is because a configuration in which the metal electrode layer is an anode and the transparent electrode layer is a cathode is a preferable aspect in terms of work function and the like.
[0020]
Claims above 10 In the invention described in claim 1, the claims 11 As described above, in the relationship between the work function value WFa of the metal electrode layer and the work function value WFb of the optical waveguide prevention layer, the work function value preferably satisfies WFa <WFb. This is because by making the work function value of the optical waveguide prevention layer higher than that of the metal electrode layer, the injection of holes into the light emitting layer is stabilized and the light emission efficiency can be improved.
[0021]
Claims above 10 Or claims 11 In the invention described in claim 1, the claims 12 As described above, the work function value of the transparent electrode layer is preferably 5.0 eV or less. This is because by using a transparent electrode layer having a work function value in the above range as a cathode, injection of electrons into the light emitting layer is stabilized and light emission efficiency can be improved.
[0022]
Claims 1 to above 12 In the invention described in any of the preceding claims, the claims 13 As described above, the sheet resistance of the metal electrode layer portion composed of the metal electrode layer and the optical waveguide preventing layer is preferably 1Ω / □ or less. This is because by setting the sheet resistance of the metal electrode layer portion within the above range, the resistance can be lowered, so that the drive voltage can be lowered and the light emission efficiency can be improved.
[0023]
Claims 1 to above 13 In the invention described in any of the preceding claims, the claims 14 As described above, a low refractive index layer having a refractive index of 1.7 or less and a light transmittance of 70% or more in the visible region of 380 nm to 780 nm is preferably laminated on the transparent electrode layer. Since the low refractive index layer provided on the transparent electrode layer has a refractive index and light transmittance in the above-mentioned range, the EL element due to the difference in refractive index of the organic EL layer, the transparent electrode layer, etc. This is because light can be prevented from being trapped and light extraction efficiency can be improved.
[0024]
Claims 1 to above 14 In the invention described in any of the preceding claims, the claims 15 As described above, it is preferable to laminate a barrier layer made of a combination of silicon oxide and silicon nitride and protecting the organic EL layer from the influence of water vapor and oxygen on the transparent electrode layer. The organic EL layer and the like may be deteriorated by exposure to water vapor and oxygen. However, by providing a barrier layer having such characteristics, the organic EL layer can be protected from those effects. This is because the lifetime of the element can be extended.
[0025]
Claims 1 to above 15 In the invention described in any of the preceding claims, the claims 16 As described above, the metal electrode layer is preferably formed on a substrate. This is because the strength of the EL element can be improved by forming a metal electrode layer or the like on the substrate.
[0026]
The invention also includes claims. 17 And forming a metal electrode layer as an anode, and using an inorganic oxide containing indium on the metal electrode layer so that the surface roughness is within a range of 10 nm to 30 nm. A step of forming a wave preventing layer, a step of subjecting the optical waveguide preventing layer to ultraviolet ozone or oxygen plasma, and performing a plasma treatment to change a work function value of the optical waveguide preventing layer by 0.2 eV or more, and the plasma treatment Provided is a method for manufacturing an EL element, comprising at least a step of forming an organic EL layer on a later optical waveguide prevention layer and a step of forming a transparent electrode layer as a cathode on the organic EL layer. .
[0027]
In the present invention, as described above, by forming the surface of the optical waveguide prevention layer roughly within the above range, it is possible to suppress light loss due to light guided in the optical waveguide prevention layer. By applying plasma treatment to the optical waveguide prevention layer, it is possible to form a suitable difference from the work function value of the metal electrode layer that is the anode, so that the injection of holes into the light emitting layer is stabilized, and the light emission efficiency is improved. It has the advantage that it can be improved.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the EL element of the present invention and the manufacturing method thereof will be described. First, the EL element will be described.
[0029]
I. EL element
The EL element of the present invention is an EL element having at least a metal electrode layer, an organic EL layer formed on the metal electrode layer, and a transparent electrode layer formed on the organic EL layer. Further, an optical waveguide preventing layer that functions as a charge injection layer and suppresses light loss is provided.
[0030]
Usually, in an EL element, in order to improve luminous efficiency, a layer having a function as a charge injection layer for stabilizing charge injection into the organic EL layer is often provided. Also in the present invention, an optical waveguide preventing layer is provided on the metal electrode layer as a layer having such a function. However, the layer having such a function may cause a loss of light due to the incident light being guided in the inside thereof, which may cause a decrease in light extraction efficiency. Therefore, in the present invention, in addition to the function as a charge injection layer, by using an optical waveguide prevention layer that retains such a function of suppressing light guide, the light extraction efficiency can be increased in addition to the light emission efficiency. Can also be improved.
[0031]
The structure of the EL element of the present invention having such advantages will be described in detail.
[0032]
1. Optical waveguide prevention layer
The optical waveguide preventing layer in the present invention serves as a charge injection layer that stabilizes the injection of charges into the organic EL layer, and light incident on the optical waveguide preventing layer is guided in the optical waveguide preventing layer. It also has a function of suppressing the loss of light caused by doing so.
[0033]
By providing the optical waveguide preventing layer having such a function on the metal electrode layer, the injection of charges from the metal electrode layer is performed without delay, so that the light emission efficiency is improved and the loss of light is further suppressed. Therefore, the extraction efficiency from the transparent electrode layer side of the light generated in the organic EL layer can also be improved. The shape and material of the optical waveguide preventing layer of the present invention that exerts such an action will be described in detail.
[0034]
(1) About the shape of the optical waveguide prevention layer
First, the shape of the optical waveguide preventing layer will be described. As described above, the optical waveguide preventing layer in the present invention is a layer having a function as a charge injection layer and also having a function of suppressing light loss. Therefore, the shape of the optical waveguide preventing layer in the present invention is not particularly limited as long as it does not impair the function as the charge injection layer and can suppress the loss of light. Specifically, a method of forming a rough surface of the optical waveguide prevention layer and a method of forming the optical waveguide prevention layer in an island shape can be exemplified. Hereinafter, both methods will be described.
[0035]
(1) When forming a rough surface
First, a case where the surface of the optical waveguide prevention layer is roughened so that the optical waveguide prevention layer has a function of suppressing light loss will be described. By roughening the surface of the optical waveguide prevention layer in this way, light loss in the optical waveguide prevention layer can be suppressed in the vicinity of the roughly formed surface of the optical waveguide prevention layer. This is because the incident light is irregularly reflected, so that the waveguide of incident light can be suppressed. Accordingly, this reduces light loss and improves the light extraction efficiency from the transparent electrode side.
[0036]
The surface roughness of the optical waveguide preventing layer that exerts such an action is not particularly limited as long as it is a surface roughness capable of irregularly reflecting incident light near the surface. Specifically, it is preferably in the range of 10 nm to 30 nm, preferably in the range of 15 nm to 30 nm, and particularly preferably in the range of 20 nm to 30 nm. If the surface roughness is smaller than the above range, the irregular reflection of incident light does not occur sufficiently, and the effect of suppressing light guiding may not be obtained sufficiently. On the other hand, the surface is less than the above range. If the roughness is large, the smoothness of the organic EL layer formed on the optical waveguide preventing layer may be impaired.
[0037]
The surface roughness referred to here is a value obtained by measuring the average surface roughness of the film surface using Nanopics 1000 manufactured by Seiko Instruments Inc.
[0038]
Furthermore, the average film thickness of the optical waveguide preventing layer in the present invention is preferably in the range of 0.1 nm to 30 nm, and more preferably in the range of 0.1 nm to 10 nm. If the average film thickness is made thinner than the above range, the role of the optical waveguide prevention layer as the charge injection layer is not fully exhibited. On the other hand, if the average film thickness is made thicker than the above range, the light generated in the light emitting layer This is because light is guided in the optical waveguide preventing layer without being scattered, and thus the light extraction efficiency is lowered.
[0039]
Incidentally, the rough formation of the surface in the present invention not only means a state in which the surface of the film-like layer has irregularities within a certain range, but also a state in which no film is uniformly formed, That is, the case where the optical waveguide preventing layer is formed in an island shape on the metal electrode layer and, as a result, has the above-described surface roughness is included.
[0040]
(2) In case of island shape
Next, a case where the optical waveguide prevention layer is formed in an island shape will be described. In the optical waveguide prevention layer formed in an island shape, light incident from the shape is guided through the inside and is not emitted from the side surface of the EL element, thereby suppressing light loss due to light guiding. It can be done.
[0041]
The optical waveguide prevention layer formed in an island shape having such an action is within a range of 1% to 99%, preferably 10% with respect to a region where the organic EL layer on the metal electrode layer is formed. It is preferable to be provided so as to cover a region within a range of ˜90%, and particularly within a range of 30% to 80%.
[0042]
This is because, if the optical waveguide prevention layer is formed in a wider range than the above range, the film has a shape close to a film shape, so that the effect of suppressing the waveguide of light obtained by forming the island shape cannot be obtained. On the other hand, if the region is narrower than the above range, the function as the charge injection layer is not sufficiently exhibited, and the light emission efficiency is lowered.
[0043]
(2) Materials for optical waveguide prevention layer
Next, materials for forming the optical waveguide prevention layer will be described. The material for forming the optical waveguide preventing layer in the present invention is not particularly limited as long as it can satisfactorily inject charges from the metal electrode layer into the organic EL layer. For example, an organic material having conductivity and an inorganic material having conductivity can be given. Hereinafter, these materials will be described.
[0044]
(1) Conductive organic material
Examples of the organic material having conductivity for forming the optical waveguide preventing layer in the present invention include materials used for the hole injection layer when the metal electrode layer is an anode. When using as a cathode, the material used for an electron injection layer can be mentioned. For example, the material used for the hole injection layer is not particularly limited as long as it can stabilize the injection of holes from the metal electrode layer to the organic EL layer. Specifically, a conductive polymer such as doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, and polyacetylene, or an electron donating compound such as tetrathiofulvalene and tetramethylphenylenediamine, and tetracyanoquino The organic material etc. which form the charge transfer complex which consists of electron-accepting compounds, such as dimethane and tetracyanoethylene, can be mentioned. Furthermore, when it is set as the optical waveguide prevention layer which has a function as an electron injection layer, if it is the material which stabilizes the injection | pouring of the electron from a metal electrode layer, it will not specifically limit. Specifically, a conductive polymer such as doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, and polyacetylene, or an electron donating compound such as tetrathiofulvalene and tetramethylphenylenediamine, and tetracyanoquino The organic material etc. which form the charge transfer complex which consists of electron-accepting compounds, such as dimethane and tetracyanoethylene, can be mentioned. Moreover, the metal dope layer with an alkali metal or alkaline-earth metal is mentioned. Suitable electron transport materials and metal dope materials include BCP (bathocuproin) or Bphen (bassophenantrone) and metal dopes such as Li, Cs, Ba, Sr.
[0045]
(2) Conductive inorganic oxide
Next, an inorganic material having conductivity as a material for forming the optical waveguide prevention layer will be described. The inorganic oxide having conductivity in the present invention is not particularly limited as long as it is a material that stabilizes charge injection into the organic EL layer. Specific examples of such an inorganic material having conductivity include In—Zn—O, In—Sn—O (ITO), ZnO—Al, Zn—Sn—O, In—O, Sn—O, Zn-O, Cd-O, Cd-In-O, Cd-Sn-O, Mg-In-O, Ca-Ga-O system or TiO ₂ , TiN, ZrN, HfN, LaB ₆ Etc. Among these, an inorganic oxide containing indium is preferable. Among them, it is particularly preferable to use ITO. This is because ITO has high conductivity and light transmittance and low resistivity, so that the light extraction efficiency can be improved and the driving voltage of the EL element can be lowered.
[0046]
▲ 3 ▼ Other
In the present invention, in addition to the materials described above, amorphous semiconductors such as α-Si, α-SiC, α-C, microcrystals such as μ-C-Si, μ-C-C-Si, and the like The optical waveguide prevention layer can also be formed by the above.
[0047]
2. Organic EL layer
Next, the organic EL layer used in the present invention will be described. In general, examples of the organic EL layer include a light emitting layer, a buffer layer, a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer. As such an organic EL layer in the present invention, it is essential to include a light emitting layer. Moreover, it is also possible to combine the light emitting layer and each of the above layers into an organic EL layer composed of a plurality of layers.
[0048]
In addition, the method for forming the organic EL layer in the present invention is not particularly limited as long as the method enables high-definition patterning because of the necessity of patterning. For example, a method of forming an organic EL layer in a pattern by a vapor deposition method, a printing method, an ink jet method or the like, a method of applying a material for forming an organic EL layer as a coating liquid, such as a spin coating method, a casting method, a dipping method Examples thereof include coating methods such as a coating method, a bar coating method, a blade coating method, a roll coating method, a gravure coating method, a flexographic printing method, and a spray coating method. Among these, in this invention, it is preferable to form an organic EL layer using a vapor deposition method.
[0049]
Hereinafter, the light emitting layer which is an essential component in such an organic EL layer will be described.
[0050]
(Light emitting layer)
In the EL element, the light emitting layer is an essential layer, and is a layer that requires patterning when manufacturing full-color and multi-color displays. As a material for forming such a light emitting layer, a dye-based, metal complex-based, or polymer-based light-emitting material can be generally used. Hereinafter, a light emitting material will be described as a material for forming such a light emitting layer.
[0051]
(1) Dye-based materials
Examples of dye materials include cyclopentamine derivatives, tetraphenylbutadiene derivatives, triphenylamine derivatives, oxadiazol derivatives, pyrazoloquinoline derivatives, distyrylbenzene derivatives, distyrylarylene derivatives, silole derivatives, thiophene ring compounds, pyridine rings. Examples thereof include compounds, perinone derivatives, perylene derivatives, oligothiophene derivatives, trifumanylamine derivatives, oxadiazole dimers, pyrazoline dimers, and the like.
[0052]
(2) Metal complex materials
As metal complex materials, aluminum quinolinol complex, benzoquinolinol beryllium complex, benzoxazole zinc complex, benzothiazole zinc complex, azomethylzinc complex, porphyrin zinc complex, europium complex, iridium metal complex, platinum metal complex, etc. Examples include metal complexes having a rare earth metal such as Al, Zn, Be, etc., or Tb, Eu, Dy, etc., and having an oxadiazole, thiadiazole, phenylpyridine, phenylbenzimidazole, quinoline structure, etc. as a ligand. it can.
[0053]
(3) Polymeric materials
Polymer materials include polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, the above dye bodies, and metal complex light emitting materials. Can be mentioned.
[0054]
3. Metal electrode layer
The material for forming the metal electrode layer in the present invention is not particularly limited as long as it is conductive. Specifically, Au, Ta, W, Pt, Ni, Pd, Cr, Al alloy, Ni alloy, Cr alloy, etc. can be mentioned.
[0055]
Furthermore, the light reflectance of the metal electrode layer is preferably 30% or more, more preferably 50% or more, within the visible region of 380 to 780 nm. This is because the EL element of the present invention extracts light from the transparent electrode layer side, so that light generated in the organic EL layer is reflected within the above range, thereby suppressing light loss.
[0056]
In addition, the reflectance in this invention shows the value measured by room temperature and the air | atmosphere using the ultraviolet visible spectrophotometer (Shimadzu Corporation make, UV-2200A).
[0057]
The film thickness of such a metal electrode layer is preferably in the range of 40 nm to 500 nm, and more preferably in the range of 100 nm to 300 nm. If the film thickness is made thinner than the above range, the resistance value may increase, which is not preferable. On the other hand, if the film thickness is thicker than the above range, it is difficult to obtain smoothness as the entire EL element when the metal electrode layer is formed in a pattern, and furthermore, at the end of the metal electrode layer. The step with the base material is not preferable because it may cause inconveniences such as disconnection or disconnection of the transparent electrode layer formed on the metal electrode layer.
[0058]
Further, when the metal electrode layer and the member made of the optical waveguide prevention layer formed on the metal electrode layer are a metal electrode layer portion, the sheet resistance of the metal electrode layer portion is 1Ω / □ or less, It is preferably 0.6Ω / □ or less. This is because by reducing the sheet resistance of the metal electrode layer portion in this way, it is possible to reduce the driving voltage and improve the light emission efficiency.
[0059]
Here, the sheet resistance is a numerical value obtained by dividing a DC voltage applied between two electrodes on the surface of a test piece by a current flowing through the surface, and in the present invention, it is measured by a four-probe method. Value.
[0060]
4). Transparent electrode layer
Since the EL element of the present invention takes out light generated in the light emitting layer from the transparent electrode layer side, the material for forming the transparent electrode layer is not particularly limited as long as it is a transparent conductive material. However, an inorganic oxide containing indium is preferable. This is because they have high transparency and low resistance, and thus have high light transmittance and can reduce driving voltage. Specifically, In—Zn—O (IZO), In—Sn—O (ITO), ZnO—Al, Zn—Sn—O, and the like can be given. Among these, ITO is particularly preferable in the present invention.
[0061]
In addition, the light transmittance of the transparent electrode layer is preferably 50% or more, more preferably 80% or more, within the visible region of 380 nm to 780 nm. This is because light can be extracted well from the transparent electrode layer side as long as it is a transparent electrode layer having a light transmittance within the above range.
[0062]
In addition, the transmittance | permeability in this invention shows the value measured by room temperature and the air | atmosphere using the ultraviolet visible spectrophotometer (Shimadzu Corporation make, UV-2200A).
[0063]
Furthermore, the film thickness of the transparent electrode layer is preferably in the range of 10 nm to 500 nm, and more preferably in the range of 50 nm to 300 nm. If the film thickness is smaller than the above range, the conductivity becomes insufficient and the function as an electrode may not be exhibited, which is not preferable. On the other hand, if the film thickness is thicker than the above range, the light transmittance may be lowered. Further, when the EL element is slightly deformed, the flexibility is inferior and cracks are generated in the transparent electrode layer. Since it may become easy, it is not preferable.
[0064]
5. Charge injection transport layer
Next, the charge injection transport layer will be described.
[0065]
In the present invention, a charge injecting and transporting layer can be provided between the organic EL layer and each electrode layer. The charge injecting and transporting layer here has a function of stably transporting the charge from the electrode to the organic EL layer, and by providing such a charge injecting and transporting layer between the organic EL layer and the electrode. In addition, the injection of charges into the light emitting layer in the organic EL layer is stabilized, and the light emission efficiency can be increased.
[0066]
As such a charge injecting and transporting layer, a hole injecting and transporting layer for transporting holes injected from the anode into the light emitting layer, and an electron injecting and transporting similarly for transporting electrons injected from the cathode into the light emitting layer. There is a layer. Hereinafter, both charge injection transport layers will be described.
[0067]
(1) Hole injection transport layer
The hole injecting and transporting layer in the present invention is not particularly limited as long as it is a layer capable of transporting holes injected from the anode into the light emitting layer. For example, a hole injection layer having a function of stably injecting holes injected from the anode into the light emitting layer, and a hole transport layer having a function of transporting holes injected from the anode into the light emitting layer When it consists of either one, when it consists of those combinations, it may be the case where it consists of a layer which has these both functions.
[0068]
Furthermore, the thickness of the hole injecting and transporting layer is not particularly limited as long as its function is sufficiently exerted, but it is within the range of 10 nm to 300 nm, and particularly within the range of 30 nm to 100 nm. preferable.
[0069]
Such a hole injecting and transporting layer is not particularly limited as long as it is a material that stably transports holes injected from the anode to the light emitting layer. Specifically, N- (1-naphthyl) -N-phenylbedidine (α-NPD), 4,4,4-tris (3-methylphenylphenylamino) triphenylamine (MTDATA), and higher molecular weight Examples of the material include polyvinyl carbazole (PVCz), poly3,4 ethylene dioxythiophene (PEDOT), polyphenylene vinylene derivatives, and the like.
[0070]
(2) Electron injection transport layer
Next, the electron injecting and transporting layer will be described. The electron injecting and transporting layer in the present invention includes an electron injecting layer having a function of stably injecting electrons injected from the cathode into the light emitting layer, and an electron transporting layer having a function of transporting electrons into the light emitting layer. When it consists of either one, when it consists of those combinations, it may be the case where it consists of a single layer which has these both functions.
[0071]
First, the electron injection layer will be described. The material for forming the electron injection layer is not particularly limited as long as it can stabilize the injection of electrons into the light emitting layer. Examples of such materials include alkali metalated or alkaline earth metal oxides or fluorides. Among these, an alkaline earth metal fluoride is preferable. This is because the alkaline earth metal fluoride has a high melting point and can improve heat resistance. Specifically, MgF ₂ , CaF ₂ , SrF ₂ , BaF ₂ Etc. The thickness of the electron injection layer made of such a material is preferably in the range of 0.2 nm to 10 nm.
[0072]
Further, when a transparent oxide conductive material such as indium oxide is used as the cathode, these work functions are 4.6 eV or more, and therefore electrons using a material having a work function of 4.0 eV or less are used. It is preferable to form an injection layer. Under a low driving voltage, it is difficult to inject electrons directly from the cathode formed of indium oxide having a work function of 4.6 eV or more into the light emitting layer, but a work function of 4.0 eV or less is interposed between these layers. This is because the electron injection is facilitated by providing the electron injection layer having the above. Specifically, Ba, Ca, Li, Cs, Mg, etc. are mentioned. When the electron injection layer is formed of such a material, the film thickness is preferably 0.2 nm to 50 nm, and more preferably 0.2 nm to 20 nm. In this case, since a transparent oxide conductive material is used as the cathode, transparency is required for the electron injection layer when light is extracted from the cathode side.
[0073]
Next, a material for forming the electron transport layer is not particularly limited as long as it is a material capable of transporting electrons injected from the cathode or the electron injection layer into the light emitting layer. Specifically, examples of the electron-transporting organic material include BCP (vasocupron) and Bpehn (vasophenanthroline).
[0074]
In addition, in the case of a layer having both the function as an electron injection layer and the function as an electron transport layer, an alkali metal or an alkaline earth metal as a doping material is mixed with an electron transporting organic material. Electrons can be stably injected into the light emitting layer and transported. Examples of such a metal dope material include Li, Cs, Ba, and Sr. In this case, the molar ratio between the electron transporting organic material and the metal-doped material is preferably in the range of 1: 1 to 1: 3, and more preferably in the range of 1: 1 to 1: 2. Furthermore, the film thickness in this case is preferably in the range of 5 nm to 1000 nm, and more preferably in the range of 10 nm to 100 nm. This is because the electron mobility is increased by adding the metal-doped material, and the transmittance is higher than that of a single metal.
[0075]
5. Other
In addition, the layers that can constitute the EL element of the present invention in addition to the above layers will be described.
[0076]
(1) Low refractive index layer
In the present invention, the low refractive index layer can be formed on the transparent electrode layer. Usually, since each layer has a different refractive index, light may be confined in the element due to such a difference in refractive index. Therefore, in the present invention, by forming the low refractive index layer between the cathode and the barrier layer described later, light loss due to the barrier layer can be reduced, and the light extraction efficiency can be further improved. It can be done.
[0077]
Such a low refractive index layer has high transparency because it is provided on the transparent electrode layer in the light extraction direction, and further has a refractive index of 1.7 or less, of which 1.5 or less. It is preferable that This is because by setting the refractive index within the above range, light loss due to the difference in refractive index between the transparent electrode layer and the barrier layer is suppressed, and the light extraction efficiency from the transparent electrode layer side is improved.
[0078]
The refractive index referred to here is a value obtained by forming a film on a Si wafer using a spectroscopic ellipsometer (manufactured by Jovin Yvon) and refraction at visible wavelengths.
[0079]
In addition, the light transmittance of the low refractive index layer is preferably 70% or more, and more preferably 80% or more, in the visible region of 380 nm to 780 nm, for the purpose of improving the light extraction efficiency. In addition, the transmittance | permeability here is obtained by the measurement mentioned above.
[0080]
Furthermore, the film thickness of the low refractive index layer is not particularly limited as long as it is a film thickness that can maintain the light transmittance, but is preferably in the range of 10 nm to 10000 nm.
[0081]
As a material for forming such a low refractive index layer, porous SiO ₂ , MgF ₂ , SiO ₂ , MgO and the like.
[0082]
(2) Barrier layer
Next, the barrier layer used in the present invention will be described. The barrier layer in the present invention is a layer that plays a role of protecting the organic EL layer including the light emitting layer from the influence of water vapor and oxygen. When the light emitting layer or the like is exposed to water vapor, oxygen, or the like, the deterioration thereof is promoted, resulting in a disadvantage that the element life of the EL element is shortened. In view of this, the lifetime of the device is extended by providing a barrier layer that prevents permeation of water vapor and oxygen into the device.
[0083]
The water vapor transmission rate of such a barrier layer is 0.001 g / m. ² / Day or less, of which, 0.0001 g / m ² / Day or less is preferable.
[0084]
Further, the oxygen transmission rate is 0.001 g / m. ² / Day or less, of which, 0.0001 g / m ² / Day or less is preferable. This is because the oxygen and water vapor transmission rates within the above ranges can suitably prevent the transmission of both into the device.
[0085]
In addition, the oxygen permeability in this invention is measured on condition of 23 degreeC and 90% Rh using the oxygen gas permeability measuring apparatus (the MOCON company make, OX-TRAN 2/20). The water vapor transmission rate was measured under the conditions of 37.8 ° C. and 100% Rh using a water vapor transmission rate measuring device (manufactured by MOCON, PERMATRAN-W 3/31).
[0086]
In the present invention, since the barrier layer is provided in the light extraction direction, the light transmittance in the visible region of 380 nm to 780 nm is preferably 60% or more, and more preferably 80% or more. This is because if the transmittance is lower than the above range, light absorption by the barrier layer is increased, and the light extraction efficiency from the transparent electrode layer is reduced. The light transmittance measurement method here is the same as described above.
[0087]
Furthermore, the film thickness is not particularly limited as long as it is a film thickness that can sufficiently block the transmission of water vapor and oxygen as a barrier layer, but it is 0.1 μm to 100 μm in relation to the light transmittance. It is preferable to be within the range.
[0088]
The material for forming such a barrier layer is not particularly limited as long as it is a material that can suitably prevent permeation of water vapor and oxygen and is excellent in transparency. For example, silicon oxide or silicon nitride may be used, and a combination thereof may be used.
[0089]
In the present invention, the low refractive index and barrier layer may be formed of a protective layer having the functions of both layers. Such a protective layer is particularly limited as long as the refractive index is within the range of the refractive index of the low refractive index layer, and the water vapor transmission rate and the oxygen transmission rate are within these ranges of the barrier layer. Not. Moreover, since it is provided on a transparent electrode layer, it is preferable that transparency is high.
[0090]
(3) Base material
Furthermore, in this invention, you may form an EL element on a base material. This is because when EL elements are formed on a substrate, the strength of the EL elements can be improved. A material that can be used as such a substrate is not particularly limited as long as it is a material having self-supporting properties. Moreover, since a base material is provided under a metal electrode layer, it does not need to have transparency in particular. For example, quartz, glass, silicon wafer, and polymer base materials include polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyimide (PI), and polyamideimide (PAI). , Polyethersulfone (PES), polyetherimide (PEI), polyetheretherketone (PEEK), and the like. Among these, quartz (glass), silicon wafer, or super engineering plastics such as polyimide (PI), polyamideimide (PAI), polyethersulfone (PES), polyetherimide (PEI), and polyetheretherketone (PEEK) are preferable. . This is because they have a heat resistance of 200 ° C. or higher and can increase the substrate temperature in the production stage.
[0091]
6). Specific embodiment of EL device of the present invention
Next, specific embodiments of the EL element of the present invention will be described.
[0092]
FIG. 1 illustrates an example of a specific embodiment of the EL element of the present invention. In the EL element shown in FIG. 1, a base material 1 and an anode 2 are formed on the base material 1. In this embodiment, the anode 2 is the metal electrode layer described above. Further, an optical waveguide preventing layer 3 having a rough surface is provided on the anode 2 as the metal electrode layer, and holes are transported to the light emitting layer on the anode 2 having the optical waveguide preventing layer 3. A hole transport layer 4 having a function to perform is formed. In this embodiment, since the anode 2 is composed of the above-described metal electrode layer, the optical waveguide prevention layer 3 has a function as a hole injection layer, and the holes injected from the optical waveguide prevention layer 3 are The positive hole transport layer 4 quickly transports it into the light emitting layer 5. Furthermore, a light emitting layer 5 is laminated on the hole transport layer 4. The light emitting layer 5 is usually formed in a pattern, and when a full color EL element is formed, the light emitting layers of a plurality of colors are each patterned. Further, an electron injection / transport layer 6 for injecting and transporting electrons from the cathode is formed on the light emitting layer 5, and a cathode 7 is formed on the electron injection / transport layer 6. In this embodiment, since the anode 2 is the above-described metal electrode layer, the cathode 7 is the above-described transparent electrode layer, and light is extracted from the cathode 7 side which is the transparent electrode layer. In this embodiment, in order to further improve the light extraction efficiency from the cathode 7 side, the low refractive index layer 8 is formed on the cathode 7, and the light emitting layer 5 and the like are further protected from the influence of oxygen and water vapor. A protective barrier layer 9 is formed on the low refractive index layer 8.
[0093]
Hereinafter, each structure is demonstrated about the EL element of this invention in such an aspect. This embodiment is an embodiment in which the metal electrode layer described above is used as an anode and the transparent electrode layer is used as a cathode, and the organic EL layers such as the optical waveguide prevention layer and the light emitting layer are the same as described above. The description here is omitted.
[0094]
(electrode)
This embodiment is characterized in that the metal electrode layer described above is used as an anode and the transparent electrode layer is used as a cathode.
[0095]
Thus, in this embodiment using the metal electrode layer as an anode, when the work function of the optical waveguide prevention layer is WFb and the work function of the anode is WFa, the relationship between the two is
WFa <WFb
It is preferable that
[0096]
Here, the work function of the optical waveguide preventing layer is preferably 4.8 eV or more, more preferably 5.0 eV or more, in view of the stability of hole injection into the organic EL layer. By forming the optical waveguide prevention layer having the work function in such a range on the anode having the work function and the work function within the range of the above formula, the injection of holes from the anode is further stabilized. This is because the luminous efficiency can be improved.
[0097]
Moreover, the transparent electrode layer becomes a cathode by using the metal electrode layer as an anode. In this case, the work function of the cathode is preferably 5.0 eV or less, and more preferably 4.8 eV or less. Furthermore, the sheet resistance of the cathode made of the transparent electrode layer is preferably 20Ω / □ or less.
[0098]
The work function here is a numerical value measured in the atmosphere using a surface analyzer AC-1 manufactured by Riken Keiki Co., Ltd.
[0099]
II. Manufacturing method of EL element
Next, the manufacturing method of the EL element of the present invention will be described. The EL device manufacturing method of the present invention includes a step of forming a metal electrode layer as an anode, and an inorganic oxide containing indium on the metal electrode layer, and the surface roughness is in the range of 10 nm to 30 nm. A step of forming an optical waveguide prevention layer so that the optical waveguide prevention layer is exposed to ultraviolet ozone or oxygen plasma, and a plasma treatment is performed to change the work function value of the optical waveguide prevention layer by 0.2 eV or more. The method includes at least a step of forming an organic EL layer on the optical waveguide prevention layer after the plasma treatment and a step of forming a transparent electrode layer as a cathode on the organic EL layer.
[0100]
FIG. 2 shows an example of a method for manufacturing an EL element of the present invention having such characteristics. Hereinafter, the manufacturing method of the EL element of the present invention will be specifically described with reference to FIG.
[0101]
First, as shown in FIG. 2A, an anode 2 made of a metal electrode layer is prepared, and an optical waveguide preventing layer 3 made of the above-described material is formed on the anode 2. At this time, the optical waveguide preventing layer 3 is formed so that its surface roughness is in the range of 10 nm to 30 nm. By forming the optical waveguide prevention layer in such a shape, light is prevented from being guided in the optical waveguide prevention layer, thereby reducing the loss of light and improving the light extraction efficiency. It can be made.
[0102]
In addition, as a method of forming the surface roughness of the optical waveguide prevention layer as a shape within the range of 10 nm to 30 nm, it is possible to form by using any one of corona treatment, etching, sand plast, or a combination thereof. it can.
[0103]
The “surface roughness” here means not only the state in which the surface of the film-like layer is formed to have irregularities within a certain range as described above, but also the film is uniformly formed. It includes a state where it is not formed. That is, in addition to forming the optical waveguide prevention layer in a film shape, it may be formed in an island shape to have the above-described surface roughness.
[0104]
Further, as shown in FIG. 2B, the work function of the optical waveguide prevention layer 3 is changed by 0.2 or more by exposing the optical waveguide prevention layer 3 having a rough surface to ultraviolet ozone or oxygen plasma. Plasma treatment is performed. In such plasma treatment, when the work function value of the anode 2 made of the metal electrode layer is WFa and the work function value of the optical waveguide prevention layer 3 is WFb, the relationship between the two is
WFa <WFb
It is preferable to perform plasma treatment so that By performing such a plasma treatment, the work function value of the optical waveguide preventing layer 3 can be controlled so that the work function between the anode 2 and the optical waveguide preventing layer 3 has a suitable difference. This is because holes can be injected stably.
[0105]
Next, an organic EL layer is formed on the anode 2 having the optical waveguide prevention layer 3 that has been subjected to plasma treatment and set to a suitable work function value. The organic EL layer has at least the light emitting layer 5, but here, as shown in FIG. 2C, the hole transport layer 4 that plays a role of transporting holes from the anode 2 is optically guided. FIG. 2D shows a case where a light-emitting layer 5 which is an essential layer in the EL element is provided on the hole-preventing layer 3 as shown in FIG. In addition, as shown in FIG. 2E, an electron injection transport layer 6 that stabilizes and transports electrons to the light emitting layer 5 can be stacked on the light emitting layer 5 as the organic EL layer. . On such an organic EL layer, a cathode 7 made of a transparent electrode layer is provided as shown in FIG.
[0106]
Thereafter, as described above, the barrier layer that protects the organic EL layer from the effects of water vapor and oxygen, and further, the low refractive index that eliminates the trapping of light into the device due to the difference in refractive index between the cathode and the barrier layer. A layer may be provided.
[0107]
By manufacturing in this way, an EL element that can emit light from the upper surface of the figure can be obtained.
[0108]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.
[0109]
【Example】
The following examples further illustrate the invention.
[0110]
[Example 1]
As a substrate, transparent glass having a length and width of 25 mm × 25 mm and a thickness of 1.1 mm was washed, and then an anode made of Al or Cr having a thickness of 100 nm was formed by a magnetron sputtering method. Ar was used as the sputtering gas, the pressure was 0.15 Pa, and the DC output was 200 W. On top of that, 10 nm ITO was formed as an optical waveguide prevention layer by magnetron sputtering. As sputtering gas, Ar and O ₂ Gas mixture (volume ratio Ar: O ₂ = 50: 1), pressure 0.1 Pa, DC output 150 W. When the surface resistance value of the film formed with Al as the anode and ITO as the optical waveguide preventing layer was examined by the four-probe method, it was 0.5Ω / □.
[0111]
During film formation, a metal mask was used, and anodes were formed in a pattern by photolithography so that four light emitting areas of 2 mm × 2 mm could be formed. Thereafter, the substrate was exposed to oxygen plasma. In the case of the Al / ITO anode, after performing oxygen plasma treatment, the work function was measured in the atmosphere. As a result, the ionization potential was reduced from 4.9 eV to 5.7 eV. When ITO was not formed, the work function value did not change. When the surface of ITO on Al was observed by SEM, it was confirmed that it was formed in an island shape rather than a uniform film at 25 nm or less.
[0112]
Next, bis (N-naphthyl) -N-phenylbenzidine (α-NPD) represented by the following chemical formula (1) is formed on the formed optical waveguide prevention layer as a hole injecting and transporting layer by a vacuum heating vapor deposition method with a thickness of 80 nm. A hole injection transport layer was formed. The chemical formula of this α-NPD is shown below.
[0113]
[Chemical 1]

[0114]
Then, as a light emitting layer, the aluminum quinolinol metal complex (Alq shown to following Chemical formula (2)). ₃ ) Was deposited to a thickness of 80 nm, and finally, a vapor deposition layer of bathocuproine (BCP) and Li represented by the following chemical formula (3) was deposited to a thickness of 20 nm as an electron injection layer / sputtering protective layer. The film formation rate was adjusted so that the molar ratio of BCP: Li was 1: 2.
[0115]
[Chemical formula 2]

[0116]
[Chemical 3]

[0117]
The film forming conditions are as follows: degree of vacuum 5 × 10 ^-5 Pa and the organic material of each layer were formed at a film formation rate of 2 to 5 cm / sec. As film formation conditions, sputtering gas is Ar and O. ₂ Gas mixture (volume ratio Ar: O ₂ = 50: 1), pressure 0.1 Pa, RF output 100 W, DC output 150 W. Gas pressure 5.5 × 10 at deposition rate 2-5Å / sec ^-2 A transparent electrode layer having a thickness of 150 nm was formed under the conditions of Pa to produce an organic EL device having a light emitting area of 2 mm × 2 mm.
[0118]
Then, MgF as a low refractive index layer on the transparent electrode layer ₂ Is formed to 50 nm by a vacuum deposition method, and finally SiO2 is formed as a barrier layer. ₂ A film made of a combination of SiN and 5 μm was formed. The deposition conditions are magnetron sputtering using a target SiOxNy, and sputtering gases are Ar and O. ₂ Gas mixture (volume ratio Ar: O ₂ = 30: 1), pressure 0.2 Pa, RF output 150 W, DC output 200 W. The barrier layer can also be formed by a plasma CVD method. The sheet resistance of the transparent electrode layer was 10Ω / □. The light emitting area of the obtained organic EL element was 2 mm × 2 mm, and all processes from the anode film formation to the barrier layer were performed under vacuum.
[0119]
The organic EL device using Al as the anode and ITO as the transparent electrode layer has a current density of 110 mA when 10 V is applied, and is 3000 cd / m. ² Met.
[0120]
[Comparative Example 1]
An organic EL element in which an optical waveguide prevention layer was not formed was produced in the same process as in Example 1. The organic EL device using Al as the anode and ITO as the transparent electrode layer has a current density of 20 mA when 10 V is applied, and is 200 cd / m. ² Met.
[0121]
[Comparative Example 2]
An organic EL device having ITO having a surface roughness of 5 nm and a film thickness of 100 nm was produced in the same process as in Example 1 using ITO as the optical waveguide preventing layer. When the surface resistance value of the film in which Al was formed as the anode and ITO was formed as the optical waveguide preventing layer was examined by the four probe method, it was 0.6Ω / □. The organic EL element using Al as an anode has a current density of 100 mA when 10 V is applied, and is 2600 cd / m 2. ² Met.
[0122]
[Example 2]
As a substrate, transparent glass having a length and width of 25 mm × 25 mm and a thickness of 1.1 mm was washed, and then an anode made of Al or Cr having a thickness of 100 nm was formed by a magnetron sputtering method. Ar was used as the sputtering gas, the pressure was 0.15 Pa, and the DC output was 200 W. On top of that, 10 nm ITO was formed as an optical waveguide prevention layer by magnetron sputtering. As sputtering gas, Ar and O ₂ Gas mixture (volume ratio Ar: O ₂ = 50: 1), pressure 0.1 Pa, DC output 150 W. During film formation, the anode was patterned using a metal mask so that four light emitting areas of 2 mm × 2 mm were formed. Thereafter, the substrate was exposed to oxygen plasma. In the case of the Al / ITO anode, after performing oxygen plasma treatment, the work function was measured in the atmosphere. As a result, the ionization potential was reduced from 4.9 eV to 5.7 eV. When ITO was not formed, the work function value did not change.
[0123]
Next, polyethylenedioxythiophene (PEDOT) represented by the following chemical formula (4) was formed as a hole injection transport layer on the formed optical waveguide prevention layer by spin coating to a thickness of 80 nm and dried by heating. The chemical formula of (PEDOT (PSS)) is shown below.
[0124]
[Formula 4]

[0125]
Thereafter, poly (dioctylfluorene-co-anthracene) represented by the following chemical formula (5) as a light emitting layer in a globe BOX under low oxygen conditions with an oxygen concentration of up to 1 ppm and under low humidity conditions with a humidity of up to 1 ppm ( PF) was deposited to a thickness of 80 nm, and finally a vapor deposition layer of bathocuproine (BCP) and Li was deposited to a thickness of 20 nm as an electron injection layer / sputtering protective layer. The film formation rate was adjusted so that the molar ratio of BCP: Li was 1: 2. The chemical formula of PF is shown below.
[0126]
[Chemical formula 5]

[0127]
The film forming conditions are as follows: degree of vacuum 5 × 10 ^-5 The film was formed at a deposition rate of 2 Pa / sec for Pa and BCP. After forming the electron injection layer, ITO and IZO were formed as a transparent electrode layer by sputtering to a thickness of 150 nm. In order to reduce the sputter damage to the electron injection layer, the film was formed with an opposed target type magnetron sputtering apparatus. As film formation conditions, sputtering gas is Ar and O. ₂ Gas mixture (volume ratio Ar: O ₂ = 50: 1), pressure 0.1 Pa, RF output 100 W, DC output 150 W. Gas pressure 5.5 × 10 at deposition rate 2-5Å / sec ^-2 A transparent electrode layer having a thickness of 150 nm was formed under the conditions of Pa to produce an organic EL device having a light emitting area of 2 mm × 2 mm.
[0128]
Then, MgF as a low refractive index layer on the transparent electrode layer ₂ Is formed to 50 nm by a vacuum deposition method, and finally SiO2 is formed as a barrier layer. ₂ A film made of a combination of SiN and 5 μm was formed. The deposition conditions are magnetron sputtering using a target SiOxNy, and sputtering gases are Ar and O. ₂ Gas mixture (volume ratio Ar: O ₂ = 30: 1), pressure 0.2 Pa, RF output 150 W, DC output 200 W.
[0129]
The organic EL device using Al as the anode and ITO as the transparent electrode layer has a current density of 200 mA when 8 V is applied, and is 9000 cd / m. ² Met. The organic EL element using Cr as the anode and ITO as the transparent electrode layer has a current density of 220 mA when 8 V is applied, and is 6000 cd / m. ² Met.
[0130]
[Comparative Example 3]
An organic EL element in which an optical waveguide preventing layer was not formed was produced in the same process as in Example 2. The organic EL device using Al as the anode and ITO as the transparent electrode layer has a current density of 20 mA when 10 V is applied, and is 200 cd / m. ² Met. The organic EL element using Cr as the anode and ITO as the transparent electrode layer has a current density of 60 mA when 8 V is applied, and is 700 cd / m. ² Met.
[0131]
[Example 3]
As a substrate, transparent glass having a length and width of 25 mm × 25 mm and a thickness of 1.1 mm was washed, and then an anode made of Al or Cr having a thickness of 100 nm was formed by a magnetron sputtering method. Ar was used as the sputtering gas, the pressure was 0.15 Pa, and the DC output was 200 W. On top of that, 10 nm ITO was formed as an optical waveguide prevention layer by magnetron sputtering. As sputtering gas, Ar and O ₂ Gas mixture (volume ratio Ar: O ₂ = 50: 1), pressure 0.1 Pa, DC output 150 W.
[0132]
Next, polyethylene dioxythiophene (PEDOT) as a hole injecting and transporting layer was formed on the formed optical waveguide prevention layer by spin coating to a thickness of 80 nm and dried by heating. Thereafter, poly (dioctylfluorene-co-anthracene) (PF) is formed to a thickness of 80 nm as a light emitting layer in a globe BOX under low oxygen conditions with an oxygen concentration of up to 1 ppm and under low humidity conditions with a humidity of up to 1 ppm. Finally, 0.5 nm of LiF was deposited as an electron injection layer. Further, 10 nm of Ca was deposited thereon. Was deposited to a thickness of 20 nm. The film forming conditions are as follows: degree of vacuum 5 × 10 ^-5 Films were formed at a deposition rate of 0.1 Pa / sec for Pa and LiF and a rate of 1.0 cm / sec for Ca. After forming the electron injection layer, ITO and IZO were formed as a transparent electrode layer by sputtering to a thickness of 150 nm. In order to reduce the sputter damage to the light emitting layer, the film was formed with an opposed target type magnetron sputtering apparatus. As film formation conditions, sputtering gas is Ar and O. ₂ Gas mixture (volume ratio Ar: O ₂ = 50: 1), pressure 0.1 Pa, RF output 100 W, DC output 150 W. Gas pressure 5.5 × 10 at deposition rate 2-5Å / sec ^-2 A transparent electrode layer having a thickness of 150 nm was formed under the conditions of Pa to produce an organic EL device having a light emitting area of 2 mm × 2 mm.
[0133]
Then, MgF as a low refractive index layer on the transparent electrode layer ₂ Is formed to 50 nm by a vacuum deposition method, and finally SiO2 is formed as a barrier layer. ₂ A film made of a combination of SiN and 5 μm was formed. The deposition conditions are magnetron sputtering using a target SiOxNy, and sputtering gases are Ar and O. ₂ Gas mixture (volume ratio Ar: O ₂ = 30: 1), pressure 0.2 Pa, RF output 150 W, DC output 200 W.
[0134]
The organic EL device using Al as the anode and ITO as the transparent electrode layer has a current density of 300 mA when 8 V is applied, and 12000 cd / m. ² Met. The organic EL element using Cr as the anode and ITO as the transparent electrode layer has a current density of 330 mA when 8 V is applied, and is 8000 cd / m. ² Met.
[0135]
【The invention's effect】
According to the present invention, as described above, the optical waveguide prevention layer that functions as a charge injection layer and also retains the function of suppressing light guiding is provided on the metal electrode layer. Regardless of the type of metal used for the electrode layer, there are few dark spots, etc., and further, since light loss can be suppressed because light waveguide is suppressed, it has good light extraction efficiency. There exists an effect that it can be set as an EL element.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of an EL element of the present invention.
FIG. 2 is a process diagram showing an example of a method for producing an EL element of the present invention.
[Explanation of symbols]
1 ... Base material
2… Anode
3 ... Optical waveguide prevention layer
4 ... Hole transport layer
5 ... Light emitting layer
6 ... Electron injection transport layer
7… Cathode
8 ... Low refractive index layer
9… Barrier layer

Claims (17)

A metal electrode layer; an optical waveguide preventing layer formed on the metal electrode layer and having irregularities on a surface; an organic electroluminescent layer formed on the optical waveguide preventing layer and including a light emitting layer; An electroluminescent device having at least a transparent electrode layer formed on the luminescent layer,
The optical waveguide prevention layer has a function as a charge injection layer, and has a function of suppressing light loss caused by light incident on the optical waveguide prevention layer being guided through the optical waveguide prevention layer. Yes, and
An electroluminescent element characterized in that light generated in the light emitting layer is reflected by the metal electrode layer and light is extracted from the transparent electrode layer side . 2. The electroluminescent layer according to claim 1, wherein the optical waveguide preventing layer has an average surface roughness of 10 nm to 30 nm measured using Nanopics 1000 manufactured by Seiko Instruments Inc. Nescent element.   The electroluminescent device according to claim 2, wherein an average film thickness of the optical waveguide preventing layer is in a range of 0.1 nm to 30 nm.   4. The electroluminescent device according to claim 1, wherein the material used for the optical waveguide prevention layer is an organic material having conductivity. 5.   The electroluminescent device according to any one of claims 1 to 3, wherein the optical waveguide preventing layer is formed of an inorganic oxide containing indium.   The electroluminescent device according to claim 5, wherein the inorganic oxide containing indium is indium tin oxide.   The electroreflectance according to any one of claims 1 to 6, wherein the metal electrode layer has a light reflectance of 30% or more in a visible region of 380 to 780 nm. Nescent element.   8. The electroluminescent device according to claim 1, wherein the metal electrode layer has a thickness in a range of 40 nm to 500 nm.   9. The electroluminescence according to claim 1, wherein the light transmittance of the transparent electrode layer is 50% or more within a visible region of 380 to 780 nm. Nescent element.   The electroluminescent device according to any one of claims 1 to 9, wherein the metal electrode layer is an anode.   11. The electroluminescent device according to claim 10, wherein the work function value is WFa <WFb in the relationship between the work function value WFa of the metal electrode layer and the work function value WFb of the optical waveguide preventing layer.   The work function value of the said transparent electrode layer is 5.0 eV or less, The electroluminescent element of Claim 10 or Claim 11 characterized by the above-mentioned.   The electroluminescence according to any one of claims 1 to 12, wherein a sheet resistance of the metal electrode layer portion including the metal electrode layer and the optical waveguide prevention layer is 1 Ω / □ or less. Cent element.   14. A low refractive index layer having a refractive index of 1.7 or less and a light transmittance of 70% or more in a visible region of 380 nm to 780 nm is laminated on the transparent electrode layer. The electroluminescent device according to claim 1.   15. A barrier layer made of a combination of silicon oxide and silicon nitride is formed on the transparent electrode layer, and a barrier layer protecting the organic electroluminescent layer from the influence of water vapor and oxygen is laminated. The electroluminescent device according to claim 1.   The electroluminescent element according to claim 1, wherein the metal electrode layer is formed on a base material. Forming a metal electrode layer as an anode;
On the metal electrode layer, an inorganic oxide containing indium is used, and optical waveguide prevention is performed so that the average surface roughness of the film surface measured using Nanopics 1000 manufactured by Seiko Instruments Inc. is in the range of 10 nm to 30 nm. Forming a layer;
Exposing the optical waveguide layer to ultraviolet ozone or oxygen plasma, and performing a plasma treatment to change the work function value of the optical waveguide layer by 0.2 eV or more;
Forming an organic electroluminescent layer on the optical waveguide preventing layer after the plasma treatment;
Forming a transparent electrode layer as a cathode on the organic electroluminescent layer;
At least have a, the light generated in the light emitting layer is reflected by the metal electrode layer, the electroluminescent device, characterized in that to produce the electroluminescent element in which light is taken out from the transparent electrode layer side Production method.

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