JP2014035827A - Inorganic el element light emitting device - Google Patents
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- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 95
- 238000009792 diffusion process Methods 0.000 claims abstract description 55
- 239000000758 substrate Substances 0.000 claims abstract description 50
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 46
- 230000002265 prevention Effects 0.000 claims abstract description 31
- 230000003405 preventing effect Effects 0.000 claims abstract description 13
- 150000002500 ions Chemical class 0.000 claims description 13
- 239000013078 crystal Substances 0.000 claims description 12
- 239000002994 raw material Substances 0.000 claims description 6
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 abstract description 10
- 238000000034 method Methods 0.000 abstract description 10
- 238000010304 firing Methods 0.000 abstract description 8
- 239000010408 film Substances 0.000 description 38
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 24
- 239000000243 solution Substances 0.000 description 15
- 238000004519 manufacturing process Methods 0.000 description 13
- 239000011787 zinc oxide Substances 0.000 description 13
- 239000011248 coating agent Substances 0.000 description 9
- 238000000576 coating method Methods 0.000 description 9
- 239000000463 material Substances 0.000 description 9
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 238000003618 dip coating Methods 0.000 description 6
- 238000010587 phase diagram Methods 0.000 description 6
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical group [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 239000011777 magnesium Substances 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 4
- 239000010436 fluorite Substances 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 230000003449 preventive effect Effects 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 229910052984 zinc sulfide Inorganic materials 0.000 description 3
- 229910052693 Europium Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- -1 MgO rare earth Chemical class 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- YRKCREAYFQTBPV-UHFFFAOYSA-N acetylacetone Chemical compound CC(=O)CC(C)=O YRKCREAYFQTBPV-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 description 2
- 238000005401 electroluminescence Methods 0.000 description 2
- COTNUBDHGSIOTA-UHFFFAOYSA-N meoh methanol Chemical compound OC.OC COTNUBDHGSIOTA-UHFFFAOYSA-N 0.000 description 2
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 2
- 235000002639 sodium chloride Nutrition 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 239000011592 zinc chloride Substances 0.000 description 2
- 235000005074 zinc chloride Nutrition 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- ZOIORXHNWRGPMV-UHFFFAOYSA-N acetic acid;zinc Chemical compound [Zn].CC(O)=O.CC(O)=O ZOIORXHNWRGPMV-UHFFFAOYSA-N 0.000 description 1
- 229910002056 binary alloy Inorganic materials 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hcl hcl Chemical compound Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229940097364 magnesium acetate tetrahydrate Drugs 0.000 description 1
- XKPKPGCRSHFTKM-UHFFFAOYSA-L magnesium;diacetate;tetrahydrate Chemical compound O.O.O.O.[Mg+2].CC([O-])=O.CC([O-])=O XKPKPGCRSHFTKM-UHFFFAOYSA-L 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000005424 photoluminescence Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- YZYKBQUWMPUVEN-UHFFFAOYSA-N zafuleptine Chemical compound OC(=O)CCCCCC(C(C)C)NCC1=CC=C(F)C=C1 YZYKBQUWMPUVEN-UHFFFAOYSA-N 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000004246 zinc acetate Substances 0.000 description 1
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- Electroluminescent Light Sources (AREA)
Abstract
Description
本発明は、希土類元素を原料とする発光層から光を放射する無機ＥＬ素子発光デバイスに関する。 The present invention relates to an inorganic EL element light emitting device that emits light from a light emitting layer made of a rare earth element as a raw material.
従来、ＥＬ（Electroluminescence）の一種として、無機蛍光体を発光層として使用する無機ＥＬ素子が周知である。無機ＥＬ素子は、例えば一対の電極の間に発光層が設けられ、一対の電極の間に電圧を印加して発光層が光ることにより、周囲を照明する。無機ＥＬは、コストが安く、発光に発熱を伴わないという利点があり、今後の普及が期待されている。無機ＥＬ素子蛍光体としては、酸化亜鉛に希土類元素を添加して直流駆動無機ＥＬ発光層として利用した技術が周知である（非特許文献１等参照）。 Conventionally, an inorganic EL element using an inorganic phosphor as a light emitting layer is well known as a type of EL (Electroluminescence). Inorganic EL elements, for example, are provided with a light emitting layer between a pair of electrodes, and a voltage is applied between the pair of electrodes to light the light emitting layer, thereby illuminating the surroundings. Inorganic EL is advantageous in that it is low in cost and does not generate heat in light emission, and is expected to spread in the future. As the inorganic EL element phosphor, a technique in which a rare earth element is added to zinc oxide and used as a direct-current driven inorganic EL light emitting layer is well known (see Non-Patent Document 1, etc.).
ところで、希土類元素（例えばEu3＋）は、イオン半径的に見ると、発光層（例えば４配位のZnO）の結晶中にいるよりも、基板（例えば８配位のZrO2）の結晶中にいる方が結晶構造的に居心地がよいという場合がある。よって、発光層に含まれる希土類元素が基板に拡散してしまうので、結果として、特定の発光色（拡散した希土類元素が発光する色）の発光強度が低下してしまう問題があった。よって、これが発光色の輝度ムラに繋がるので、何らかの対策が必要であった。 By the way, the rare earth element (for example, Eu 3+ ) is not present in the crystal of the light emitting layer (for example, 4-coordinate ZnO), but in the crystal of the substrate (for example, 8-coordinate ZrO 2 ) in terms of ionic radius. In some cases, the crystal structure is more comfortable. Therefore, since the rare earth element contained in the light emitting layer diffuses into the substrate, as a result, there is a problem that the emission intensity of a specific emission color (the color from which the diffused rare earth element emits light) is lowered. Therefore, this leads to luminance unevenness of the luminescent color, and some measures are necessary.
本発明の目的は、発光の輝度ムラを少なく抑えることができる無機ＥＬ素子発光デバイスを提供することにある。 An object of the present invention is to provide an inorganic EL element light emitting device that can suppress uneven luminance of light emission.
前記問題点を解決するために、本発明では、希土類元素を原料とする発光層から光を放射する無機ＥＬ素子発光デバイスにおいて、無機ＥＬ素子の基板と前記発光層との間に、前記希土類元素が前記基板へ拡散することを抑制する希土類拡散防止膜を設けたことを要旨とする。 In order to solve the above problems, in the present invention, in an inorganic EL element light emitting device that emits light from a light emitting layer made of a rare earth element as a raw material, the rare earth element is interposed between the substrate of the inorganic EL element and the light emitting layer. The gist of the invention is that a rare earth diffusion preventive film that suppresses the diffusion of sapphire into the substrate is provided.
本発明の構成によれば、発光層の希土類元素が希土類拡散防止膜によってブロックされて、基板に拡散し難くなる。このため、発光層の希土類元素が減少し難くなるので、発光層として必要となる希土類元素が確保される。よって、発光の輝度ムラを少なく抑えることが可能となる。 According to the configuration of the present invention, the rare earth element in the light emitting layer is blocked by the rare earth diffusion preventing film, and is difficult to diffuse into the substrate. For this reason, rare earth elements in the light emitting layer are difficult to decrease, so that the rare earth elements necessary for the light emitting layer are secured. Therefore, it is possible to suppress the luminance unevenness of light emission.
本発明では、前記希土類拡散防止膜は、前記発光層及び前記基板のいずれとも異なる結晶構造をとることを要旨とする。この構成によれば、希土類拡散防止膜を発光層及び基板のいずれとも異なる結晶構造としたので、高い拡散防止効果を得ることが可能となる。 The gist of the present invention is that the rare earth diffusion prevention film has a crystal structure different from that of either the light emitting layer or the substrate. According to this configuration, since the rare earth diffusion prevention film has a different crystal structure from both the light emitting layer and the substrate, a high diffusion prevention effect can be obtained.
本発明では、前記希土類拡散防止膜は、自身に含まれるイオンの半径が前記希土類元素のイオン半径よりも小さく形成されていることを要旨とする。この構成によれば、希土類拡散防止膜に含まれるイオンの半径を希土類元素のイオン半径よりも小さくしたので、イオン半径の大きさの違いによって希土類元素の拡散が抑制される。よって、高い拡散防止効果を得ることが可能となる。 The gist of the present invention is that the rare earth diffusion prevention film is formed such that the radius of ions contained therein is smaller than the ion radius of the rare earth element. According to this configuration, since the radius of the ions contained in the rare earth diffusion prevention film is made smaller than the ion radius of the rare earth element, the diffusion of the rare earth element is suppressed by the difference in the size of the ion radius. Therefore, a high diffusion preventing effect can be obtained.
本発明では、前記発光層及び前記基板は、熱膨張係数が同じとなるように形成されていることを要旨とする。この構成によれば、発光層及び基板を同じ熱膨張係数としたので、無機ＥＬ素子発光デバイスの製造時に熱処理を加える過程で、これらを割れ難くすることが可能となる。 The gist of the present invention is that the light emitting layer and the substrate are formed to have the same thermal expansion coefficient. According to this configuration, since the light emitting layer and the substrate have the same thermal expansion coefficient, it is possible to make them difficult to break in the process of applying heat treatment during the manufacture of the inorganic EL element light emitting device.
本発明によれば、無機ＥＬ素子発光デバイスにおいて、発光の輝度ムラを少なく抑えることができる。 According to the present invention, in the inorganic EL element light emitting device, luminance unevenness of light emission can be reduced.
以下、本発明を具体化した無機ＥＬ素子発光デバイスの一実施形態を図１〜図６に従って説明する。
図１に示すように、本例の薄膜型無機ＥＬ素子１は、発光の材料として希土類元素が使用されている。本例の無機ＥＬ素子１は、基板２及び発光層３の各層が設けられ、これら層の間に希土類拡散防止膜４が介装されている。発光層３は、ZnOに希土類元素（RE）が含有されたRE−ZnO層からなり、本例の場合、希土類元素としてユーロピウムEuを添加したバリスタ型酸化亜鉛薄膜からなる。発光層３のZnOの粒界相には、希土類元素イオンであるRE3＋が偏析する。基板２は、例えばジルコニアZrO2を使用した基板（YSZ基板）であって、ZnOと熱膨張係数が一致するように形成される。これは、YSZ基板とZnO相との相性を確保することで、これらを割れ難くするためである。
Hereinafter, an embodiment of an inorganic EL element light-emitting device embodying the present invention will be described with reference to FIGS.
As shown in FIG. 1, the thin film inorganic EL element 1 of this example uses a rare earth element as a light emitting material. In the inorganic EL element 1 of this example, a substrate 2 and a light emitting layer 3 are provided, and a rare earth diffusion prevention film 4 is interposed between these layers. The light emitting layer 3 is composed of a RE-ZnO layer in which a rare earth element (RE) is contained in ZnO. In this example, the light emitting layer 3 is composed of a varistor type zinc oxide thin film to which europium Eu is added as a rare earth element. In the grain boundary phase of ZnO in the light emitting layer 3, RE 3+ that is a rare earth element ion is segregated. The substrate 2 is a substrate (YSZ substrate) using, for example, zirconia ZrO 2 and is formed so that the thermal expansion coefficient coincides with ZnO. This is because the compatibility between the YSZ substrate and the ZnO phase is ensured to make them difficult to break.
希土類拡散防止膜４は、希土類元素に比較してイオン半径の小さい材料で形成することにより、希土類元素の拡散防止膜として形成され、例えばMgO層が使用されている。希土類拡散防止膜４は、発光層３のRE3＋が焼成工程で基板２中へ拡散するのを防ぐ役目を有する。MgO層の場合、Mg2＋はイオン半径が小さいので、このイオン半径の大小の違いにより、基板２側への希土類元素の拡散が抑制される。希土類拡散防止膜４は、基板２の表面全域に亘り形成される。 The rare earth diffusion preventive film 4 is formed as a rare earth element diffusion preventive film by using a material having a smaller ionic radius than that of the rare earth element. For example, an MgO layer is used. The rare earth diffusion preventing film 4 has a function of preventing RE 3+ of the light emitting layer 3 from diffusing into the substrate 2 in the firing step. In the case of the MgO layer, Mg 2+ has a small ionic radius, and the diffusion of rare earth elements to the substrate 2 side is suppressed by the difference in the ionic radius. The rare earth diffusion prevention film 4 is formed over the entire surface of the substrate 2.
発光層３の表面には、例えばITO透明電極と金電極とからなる一対の電極５が形成されている。これら電極５の間に電圧を印加すると、発光層３から光が放射される。なお、電極５に印加する電圧は、直流又は交流のいずれを使用してもよい。 On the surface of the light emitting layer 3, a pair of electrodes 5 made of, for example, an ITO transparent electrode and a gold electrode is formed. When a voltage is applied between these electrodes 5, light is emitted from the light emitting layer 3. Note that the voltage applied to the electrode 5 may be either direct current or alternating current.
次に、無機ＥＬ素子１の製造手順を、図２〜図６を用いて説明する。
［希土類拡散防止膜の製造方法］
図２に示すように、ジルコニア材の基板２にMgOの希土類拡散防止膜４を形成するには、酢酸マグネシウム四水和物Mg(CH3COO)2・4H2Oの0．29mol／Lのメタノール溶液に、ゾル安定剤としてジエタノールアミンDEA（20mLの溶液に対し0．9mL添加）を加えた溶液をコート液とし、ディップコート法により成膜する。ディップコート法は、液中にワークを浸漬し、液中の粘性力、表面張力及び重力による力と速度とを調整してワークを引き上げ、これを所定回数繰り返す製法である。ワークの引き上げ速度は、必要とする膜厚に応じて制御する。引き上げ後の焼成は、例えば500℃／5分間で、コートが８回繰り返される。
Next, the manufacturing procedure of the inorganic EL element 1 will be described with reference to FIGS.
[Method of manufacturing rare earth diffusion prevention film]
As shown in FIG. 2, in order to form the MgO rare earth diffusion prevention film 4 on the zirconia substrate 2, the magnesium acetate tetrahydrate Mg (CH 3 COO) 2 .4H 2 O of 0.29 mol / L A solution obtained by adding diethanolamine DEA (0.9 mL to 20 mL of solution) as a sol stabilizer to a methanol solution is used as a coating solution to form a film by dip coating. The dip coating method is a manufacturing method in which a workpiece is immersed in a liquid, the workpiece is pulled up by adjusting the viscosity force, surface tension, and force and speed due to gravity in the liquid, and this is repeated a predetermined number of times. The workpiece lifting speed is controlled according to the required film thickness. The firing after the pulling is repeated, for example, at 500 ° C./5 minutes for 8 times.
ちなみに、希土類拡散防止膜４は、基板２と反応（それほど反応）せず、希土類元素の拡散を抑制することができる条件を満たせばよい。また、基板２は、ディップコート法による熱処理の際に変質せず、熱膨張係数がZnO発光層に近いという条件を満たせばよい。このように、基板２及び希土類拡散防止膜４は、前述の条件を満たせば、様々な種類の組み合わせが可能である。 Incidentally, the rare earth diffusion preventing film 4 does not react with the substrate 2 (react so much), and it is only necessary to satisfy a condition capable of suppressing the diffusion of the rare earth element. Further, the substrate 2 only needs to satisfy the condition that the thermal expansion coefficient is close to that of the ZnO light emitting layer without being deteriorated during the heat treatment by the dip coating method. As described above, the substrate 2 and the rare earth diffusion prevention film 4 can be combined in various types as long as the above-described conditions are satisfied.
なお、ディップコート法では、５面（ぶら下がる金具が付いている面は液に浸らない）にコーティングを行うことになるが、片面へのコーティングのための前処理は実施しておらず、液のコートは全面でも、その後の熱処理等の過程により、ほぼ表の１面のみしか成膜されない。これは、電気炉で焼成する際に、コートした液に含まれる原料が一旦蒸発し、空気に触れて酸化することで基板２上に生成されるプロセスを踏むからである。 In the dip coating method, coating is performed on 5 surfaces (surfaces with hanging metal fittings are not immersed in the liquid), but no pretreatment for coating on one side is performed, Even on the entire surface, only one surface of the surface is formed by the subsequent heat treatment or the like. This is because, when firing in an electric furnace, the raw material contained in the coated liquid once evaporates and steps on a process generated on the substrate 2 by being oxidized by contact with air.
［発光層の製造方法］
図３に示すように、希土類拡散防止膜４が成膜された基板２には、前述のディップコート法により発光層３が形成される。この場合、亜鉛（酢酸亜鉛／塩化亜鉛）を溶解したコーティング溶液（メタノール溶液前駆体）に、希土類拡散防止膜４が成膜された基板２を浸して引き上げる作業を所定回数繰り返すことにより、希土類拡散防止膜４の表面に発光層３が成膜される。ちなみに、１回のコート当たり、発光層３が約10〜20nmの成膜となっている。
[Method for producing light emitting layer]
As shown in FIG. 3, the light emitting layer 3 is formed on the substrate 2 on which the rare earth diffusion preventing film 4 is formed by the dip coating method described above. In this case, rare earth diffusion is performed by repeating the operation of immersing and lifting the substrate 2 on which the rare earth diffusion prevention film 4 is formed in a coating solution (methanol solution precursor) in which zinc (zinc acetate / zinc chloride) is dissolved. The light emitting layer 3 is formed on the surface of the prevention film 4. Incidentally, the light emitting layer 3 is formed to a thickness of about 10 to 20 nm per one coat.
図４に、コーティング溶液の製造手順を示す。ここでは、希土類元素としてEuを使用した例を示す。まず、希土類酸化物を用意し、これに塩酸HClを加える。そして、希土類酸化物と塩酸との混合物をウォーターバスで溶解し、ホットプレートで蒸発乾固する。続いて、この材料にメタノールMeOH及びアセチルアセトンを加えることにより、希土類原料溶液を製造する。 FIG. 4 shows a manufacturing procedure of the coating solution. Here, an example in which Eu is used as the rare earth element is shown. First, a rare earth oxide is prepared, and hydrochloric acid HCl is added thereto. A mixture of rare earth oxide and hydrochloric acid is dissolved in a water bath and evaporated to dryness on a hot plate. Subsequently, a rare earth material solution is produced by adding methanol MeOH and acetylacetone to this material.
一方、別工程において、塩化亜鉛ZnCl2又は酢酸亜鉛二水和物Zn(CH3COO)2・2H2Oに、メタノールMeOH及びジエタノールアミンDEAを加えて、前駆体溶液を製造する。そして、希土類原材料溶液と前駆体溶液とを混合して、コーティング溶液を製造する。なお、コーティング溶液のEuの濃度は、例えば５％を基準とし、広義として0．01〜50％の範囲内の値であればよい。 On the other hand, in a separate step, methanol MeOH and diethanolamine DEA are added to zinc chloride ZnCl 2 or zinc acetate dihydrate Zn (CH 3 COO) 2 .2H 2 O to produce a precursor solution. Then, the rare earth raw material solution and the precursor solution are mixed to produce a coating solution. The concentration of Eu in the coating solution may be a value within a range of 0.01 to 50% in a broad sense with 5% as a reference.
［希土類元素の拡散について］
ZrO2からなる基板２への希土類元素（例えばEu）の拡散は、イオン半径のみで決まるものではなく、例えば酸化数及び母酸化数の結晶構造で決まる。即ち、ある希土類元素が他の結晶中に固溶するかどうかは、イオン半径とともに、酸化数及び母酸化数の結晶構造が強く影響する。
[Diffusion of rare earth elements]
The diffusion of rare earth elements (for example, Eu) into the substrate 2 made of ZrO 2 is not determined only by the ion radius, but is determined by, for example, the crystal structure of the oxidation number and the mother oxidation number. That is, whether a certain rare earth element is dissolved in another crystal is strongly influenced by the crystal structure of the oxidation number and the mother oxidation number as well as the ionic radius.
図５に、Eu2O3−ZrO2系の相図を示す。ZrO2は、基本的に蛍石型構造をとる（室温では格子がかなり歪んでいる）。一方、コーティング溶液中のEu2O3は、相図によれば、室温では希土類Ｃ型と呼ばれる結晶構造をとり、これは蛍石関連型構造であるため、両者の構造的親和性は非常に高いという特徴がある。そのため、ZrO2はEuを始めとする希土類元素を固溶する能力が非常に高く、相図によれば、ZrO2−Eu2O3擬二成分系では28mol％Eu2O3−ZrO2までZrO2ベースの蛍石型構造の固溶体を形成する。 FIG. 5 shows a phase diagram of the Eu 2 O 3 —ZrO 2 system. ZrO 2 basically has a fluorite structure (the lattice is considerably distorted at room temperature). On the other hand, according to the phase diagram, Eu 2 O 3 in the coating solution has a crystal structure called rare earth C-type at room temperature, and this is a fluorite-related type structure. It is characterized by being expensive. Therefore, ZrO 2 has a very high ability to solid solution of rare earth elements, including Eu, according to the phase diagram, in the ZrO 2 -Eu 2 O 3 pseudo binary system up to 28mol% Eu 2 O 3 -ZrO 2 Form a solid solution of ZrO 2 based fluorite structure.
発光層３のZnOは、四面体４配位のウルツ鉱型構造をとる。これは、イオン半径が大きく、立方体型配位構造を好むEu3＋にとって非常に居心地の悪い構造ということになる。そのため、RE−ZnO／YSZというデバイス構成で高温焼成すると、REは居心地のよいYSZ基板、つまり本例で言えば基板２側へ移動することになってしまう。一方、希土類拡散防止膜４であるMgOは、岩塩型八面体をとり、ウルツ鉱型、希土類Ｃ型、蛍石型のいずれとも、全く異なる結晶構造となる。Mg2＋は、Eu3＋を始めとする希土類金属の陽イオンに比べて非常に小さいため、基本的に希土類元素は、MgOの中に固溶することができない。即ち、希土類元素の基板２への拡散が抑制可能であることが分かる。 ZnO of the light emitting layer 3 has a tetrahedral and tetracoordinate wurtzite structure. This is a very uncomfortable structure for Eu 3+ , which has a large ionic radius and prefers a cubic coordination structure. Therefore, when firing at a high temperature with a device configuration of RE-ZnO / YSZ, the RE moves to a comfortable YSZ substrate, that is, the substrate 2 in this example. On the other hand, MgO as the rare earth diffusion preventing film 4 takes a rock salt type octahedron and has a completely different crystal structure from any of the wurtzite type, rare earth C type, and fluorite type. Since Mg 2+ is very small compared to cations of rare earth metals such as Eu 3+ , basically rare earth elements cannot be dissolved in MgO. That is, it can be seen that diffusion of rare earth elements into the substrate 2 can be suppressed.
図６に、Euの隣のMgO−Gd2O3系の相図を示す。同図に示されるように、MgOを母相とする固溶体は形成されず、基本的には不純物以上の濃度には取り込まれないことが分かる。
本実施形態の構成によれば、以下に記載の効果を得ることができる。
FIG. 6 shows a phase diagram of the MgO—Gd 2 O 3 system next to Eu. As shown in the figure, it can be seen that a solid solution containing MgO as a matrix is not formed, and basically it is not incorporated at a concentration higher than the impurity.
According to the configuration of the present embodiment, the following effects can be obtained.
（１）希土類元素を用いた無機ＥＬ素子１において、ジルコニア材を材質とする基板２と希土類元素を含有した発光層３との間に、発光層３の希土類が基板２側に拡散することを抑制する希土類拡散防止膜４を設けた。このため、発光層３に含有される希土類元素が焼成等の工程で減少し難くなるので、発光層３として必要となる希土類元素が確保される。よって、無機ＥＬ素子１の発光の輝度ムラを少なく抑えることができる。 (1) In the inorganic EL element 1 using a rare earth element, the rare earth of the light emitting layer 3 diffuses toward the substrate 2 between the substrate 2 made of a zirconia material and the light emitting layer 3 containing the rare earth element. A rare earth diffusion prevention film 4 to be suppressed was provided. For this reason, since the rare earth elements contained in the light emitting layer 3 are difficult to decrease in a process such as firing, the rare earth elements necessary for the light emitting layer 3 are ensured. Therefore, luminance unevenness of light emission of the inorganic EL element 1 can be suppressed to a small extent.
（２）MgOを成分とする希土類拡散防止膜４は岩塩型八面体であるので、ウルツ型構造の発光層３や蛍石型構造の基板２のいずれに対しても、種類の異なる結晶構造となる。よって、希土類拡散防止膜４を拡散防止効果の高いものとすることができる。 (2) Since the rare earth diffusion prevention film 4 containing MgO as a component is a rock salt type octahedron, different types of crystal structures are used for both the wurtzite type light emitting layer 3 and the fluorite type structure substrate 2. Become. Therefore, the rare earth diffusion preventing film 4 can have a high diffusion preventing effect.
（３）希土類拡散防止膜４に含まれるMg2＋は、希土類元素のイオン半径よりも小さい。このように、希土類拡散防止膜４に含まれるイオンの半径を、希土類元素のイオン半径よりも小さくすれば、希土類元素が希土類拡散防止膜４を通過し難くなるので、高い拡散防止効果を得ることができる。 (3) Mg 2+ contained in the rare earth diffusion prevention film 4 is smaller than the ion radius of the rare earth element. Thus, if the radius of the ions contained in the rare earth diffusion prevention film 4 is made smaller than the ion radius of the rare earth element, the rare earth element will not easily pass through the rare earth diffusion prevention film 4, thereby obtaining a high diffusion prevention effect. Can do.
（４）基板２及び発光層３を同じ熱膨張係数としたので、無機ＥＬ素子１の作製時に熱処理を加える過程（焼成工程）で、これらを割れ難くすることができる。
（５）仮に、MgOそのものを基板２に使用すると、焼成工程−冷却工程の過程でZnO層にクラックが生じ、電気伝導が損なわれる。しかし、本例のように希土類拡散防止膜４を別の層で設けるようにすれば、基板２にクラックが生じるようなことがないので、この点で効果が高い。なお、希土類拡散防止膜４は基板２及び発光層３と熱膨張係数が異なるので、基板２で希土類拡散防止膜４の熱膨張を抑制する。
(4) Since the substrate 2 and the light emitting layer 3 have the same thermal expansion coefficient, they can be made difficult to crack in the process of applying heat treatment (firing process) when the inorganic EL element 1 is manufactured.
(5) If MgO itself is used for the substrate 2, cracks are generated in the ZnO layer in the course of the firing step and the cooling step, and electrical conduction is impaired. However, if the rare earth diffusion prevention film 4 is provided as a separate layer as in this example, the substrate 2 is not cracked, and this is highly effective. Since the rare earth diffusion prevention film 4 has a different thermal expansion coefficient from the substrate 2 and the light emitting layer 3, the substrate 2 suppresses the thermal expansion of the rare earth diffusion prevention film 4.
なお、実施形態はこれまでに述べた構成に限らず、以下の態様に変更してもよい。
・希土類拡散防止膜４の厚さは、特に限定されず、必要な膜厚が確保されていればよい。
Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
The thickness of the rare earth diffusion preventing film 4 is not particularly limited as long as a necessary film thickness is secured.
・希土類拡散防止膜４の材質は、希土類拡散を抑制できるものであれば、他の材料に適宜変更可能である。
・基板２は、ジルコニア材から形成されることに限らず、他の材質に適宜変更可能である。
The material of the rare earth diffusion preventing film 4 can be appropriately changed to other materials as long as the rare earth diffusion can be suppressed.
-The board | substrate 2 is not restricted to being formed from a zirconia material, and can be suitably changed into another material.
・希土類拡散防止膜４の製造方法は、ディップコート法以外の他の製法を採用可能である。なお、これは、発光層３の製造方法でも同様に言える。
・希土類元素は、Eu以外の他の希土類を使用してもよい。
-The manufacturing method of the rare earth diffusion prevention film 4 can employ a manufacturing method other than the dip coating method. This is also true for the manufacturing method of the light emitting layer 3.
-Rare earth elements other than Eu may be used as the rare earth element.
・無機ＥＬ素子１は、例えば一対の電極が発光層３を挟み込むように配設される構造をとってもよい。即ち、無機ＥＬ素子１は、図１に述べた層構造をとることに限定されず、種々のタイプが採用可能である。 The inorganic EL element 1 may have a structure in which, for example, a pair of electrodes are disposed so as to sandwich the light emitting layer 3. That is, the inorganic EL element 1 is not limited to the layer structure described in FIG. 1, and various types can be employed.
次に、上記実施形態及び別例から把握できる技術的思想について、それらの効果とともに以下に追記する。
（イ）希土類元素を原料とする発光層から光を放射する無機ＥＬ素子発光デバイスの製造方法において、無機ＥＬ素子の基板の表面に、前記希土類元素が前記基板へ拡散することを抑制する希土類拡散防止膜を形成するステップと、前記希土類拡散防止膜が成膜された前記基板の表面に前記発光層を形成するステップとを備えた。この構成によれば、請求項１と同様の作用効果を得ることが可能である。
Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.
(A) In a method for manufacturing an inorganic EL element light emitting device that emits light from a light emitting layer made of a rare earth element as a raw material, rare earth diffusion that suppresses diffusion of the rare earth element to the substrate on the surface of the substrate of the inorganic EL element Forming a prevention film, and forming the light emitting layer on the surface of the substrate on which the rare earth diffusion prevention film is formed. According to this configuration, it is possible to obtain the same effect as that of the first aspect.
１…無機ＥＬ素子、２…基板、３…発光層、４…希土類拡散防止膜。 DESCRIPTION OF SYMBOLS 1 ... Inorganic EL element, 2 ... Substrate, 3 ... Light emitting layer, 4 ... Rare earth diffusion prevention film
Claims (4)
無機ＥＬ素子の基板と前記発光層との間に、前記希土類元素が前記基板へ拡散することを抑制する希土類拡散防止膜を設けた
ことを特徴とする無機ＥＬ素子発光デバイス。 In an inorganic EL element light emitting device that emits light from a light emitting layer made of a rare earth element as a raw material,
An inorganic EL element light emitting device comprising a rare earth diffusion preventing film for suppressing diffusion of the rare earth element into the substrate between a substrate of the inorganic EL element and the light emitting layer.
ことを特徴とする請求項１に記載の無機ＥＬ素子発光デバイス。 The inorganic EL element light emitting device according to claim 1, wherein the rare earth diffusion prevention film has a crystal structure different from any of the light emitting layer and the substrate.
ことを特徴とする請求項１又は２に記載の無機ＥＬ素子発光デバイス。 The inorganic EL element light-emitting device according to claim 1, wherein the rare earth diffusion prevention film is formed such that a radius of ions contained in the rare earth diffusion prevention film is smaller than an ion radius of the rare earth element.
ことを特徴とする請求項１〜３のうちいずれか一項に記載の無機ＥＬ素子発光デバイス。 The inorganic EL element light emitting device according to any one of claims 1 to 3, wherein the light emitting layer and the substrate are formed to have the same thermal expansion coefficient.
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