JP2001357979A - El element - Google Patents

El element

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JP2001357979A
JP2001357979A JP2000180165A JP2000180165A JP2001357979A JP 2001357979 A JP2001357979 A JP 2001357979A JP 2000180165 A JP2000180165 A JP 2000180165A JP 2000180165 A JP2000180165 A JP 2000180165A JP 2001357979 A JP2001357979 A JP 2001357979A
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layer
light
emitting layer
selective reflection
polarizing plate
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JP2000180165A
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Japanese (ja)
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Yuzo Hisatake
雄三 久武
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Toshiba Corp
株式会社東芝
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L51/00Solid state devices using organic materials as the active part, or using a combination of organic materials with other materials as the active part; Processes or apparatus specially adapted for the manufacture or treatment of such devices, or of parts thereof
    • H01L51/50Solid state devices using organic materials as the active part, or using a combination of organic materials with other materials as the active part; Processes or apparatus specially adapted for the manufacture or treatment of such devices, or of parts thereof specially adapted for light emission, e.g. organic light emitting diodes [OLED] or polymer light emitting devices [PLED];
    • H01L51/52Details of devices
    • H01L51/5281Arrangements for contrast improvement, e.g. preventing reflection of ambient light

Abstract

PROBLEM TO BE SOLVED: To provide an EL element with excellent contrast characteristics and display brightness characteristics.
SOLUTION: A polarizing plate 16, a quarter wavelength plate 14, a selective reflection layer 12, a light emission layer 22, and a reflection electrode 24 are successively laminated. The selective reflection layer is formed by polymerizing a cholesteric liquid crystal layer and reflects selectively the first circular polarization component of incident light. The light from outside, penetrating through the polarizing plate and the quarter wave length plate, is reflected by the reflection electrode after passing through the selective reflection layer, and absorbed at the polarizing plate after passing through the selective reflection layer again. Out of the light from the light emission layer, one of the circular polarization component passes through the selective reflection layer and the polarizing plate and is emitted to the observing side, and the other circular polarization component is reflected by the selective reflection layer and reflected further by the reflection electrode in the direction of observation side, and passes through the selective reflection layer and the polarizing plate, and emitted to the observation side.
COPYRIGHT: (C)2001,JPO

Description

【発明の詳細な説明】 DETAILED DESCRIPTION OF THE INVENTION

【0001】 [0001]

【発明の属する技術分野】この発明は、EL(エレクトロスミネセンス)素子に関し、特に、円偏光板を具備した高コントラストなEL素子に関する。 TECHNICAL FIELD The present invention relates to an EL (electro-scan Mine sensing) device, and more particularly, to a high-contrast EL device provided with the circularly polarizing plate.

【0002】 [0002]

【従来の技術】近年、有機発光材料が実用域に達していることから、EL素子は、低消費電力、広視野角、薄型軽量の表示素子として注目されている。 Since Recently, organic light emitting material has reached the practical range, EL element, low power consumption, wide viewing angle, it has attracted attention as a display device thin and light. 一般に、従来のEL素子によれば、反射電極上に発光層が設けられている。 In general, according to the conventional EL element, a light-emitting layer is provided on the reflective electrode. これは、発光層から反射電極側に向かって出射された光を反射電極で反射させて反対側に出射させることにより、点発光した光をなるべく観察者側に出射させるためである。 This may be achieved by emitted to the opposite side of the light emitted toward the reflective electrode side from the light-emitting layer is reflected by the reflective electrode, in order to emit the light spot emission light as possible on the viewer side.

【0003】しかしながら、このような構成とした場合、反射電極の反射率が高いほど、発光層を発光させない状態、つまり、黒表示としたい場合において、入射した外光が反射電極で反射してしまうため、黒表示の黒レベルが悪くなり、コントラスト特性が低下してしまう問題がある。 However, if such a configuration, the higher the reflectivity of the reflective electrode, a state not to emit light emitting layer, that is, when you want to black display, external light incident ends up reflected by the reflective electrode Therefore, the black display of the black level is deteriorated, there is a problem that the contrast characteristic is degraded.

【0004】この問題を回避する方法として、反射電極の反射率を下げるか、あるいは、偏光板および1/4波長板を設けることにより外光のみ反射成分を吸収させる方法が考えられている。 As a method to avoid this problem, reduce the reflectivity of the reflective electrode, or a method of absorbing the reflected component only the external light has been considered by providing a polarizing plate and the quarter-wave plate. 後者の方法は、次のような原理でコントストを高めるものである。 The latter method is to increase the Kontosuto with the following principle. すなわち、入射した外光は、偏光板および1/4波長板を透過することにより円偏光となる。 That is, external light incident becomes circularly polarized light transmitted through the polarizing plate and the quarter-wave plate. そして、この円偏光は、ガラス基板界面や反射電極によって反射されても、反射により円偏光の位相が180度ずれるため、再び1/4波長板を透過すると、入射したときとは直交する方向の直線偏光となり、偏光板に吸収される。 Then, the circularly polarized light, be reflected by the glass substrate interface and the reflection electrodes, since the shift phase of the circularly polarized light 180 by reflection and transmitted through the quarter-wave plate again, the direction of orthogonal to as having entered becomes linearly polarized light is absorbed by the polarizing plate. 従って、反射電極の反射率に関係なく、外光は反射電極にて反射されないの場合と同様の効果を得ることができる。 Therefore, regardless of the reflectivity of the reflective electrodes, the external light can be obtained the same effect as the not reflected by the reflection electrode.

【0005】また、後者の方法は、反射電極での反射に限らず、ガラス基板界面での誘電反射や配線電極での反射に対しても有効であり、偏光板および1/4波長板を設けない場合と比較して、著しくコントラスト特性が向上する。 Further, the latter method is not limited to the reflection by the reflective electrode, is also effective against the reflection of a dielectric reflective and wiring electrodes on the glass substrate interface, it provided a polarizing plate and the quarter-wave plate compared to the absence, improves significantly the contrast characteristics.

【0006】しかしながら、偏光板を設けた場合、発光層から出射した光のうち、少なくとも50%は偏光板で吸収されるため、表示輝度自体が低下するという問題が生じる。 However, the case of providing a polarizing plate, of the light emitted from the light emitting layer, at least 50% is absorbed by the polarizing plate, there is a problem that the display luminance itself decreases. 例えば、現在実用化されている偏光板を用いた場合、偏光板および1/4波長板を設けない場合と比較して、56%程度、表示輝度が低下する。 For example, when a polarizing plate that are currently in practical use, compared with the case without the polarizing plate and the quarter-wave plate, about 56%, the display luminance decreases.

【0007】 [0007]

【発明が解決しようとする課題】以上のように、従来のEL素子では、偏光板および1/4波長板を設けない場合、コントラスト特性が著しく低く、特に明るい環境、 As described above [0005] In the conventional EL elements, the case without the polarizing plate and the quarter-wave plate, the contrast characteristic is significantly lower, especially bright environment,
つまり外光が強い条件下での使用において大きな問題となっていた。 This means that the external light has been a major problem in the use of in the strong conditions. また、偏光板および1/4波長板を設けた場合、コントラスト特性は著しく改善されるものの、偏光板および1/4波長板を設けない場合と比較して、5 Also, the case of providing a polarizing plate and the quarter-wave plate, although the contrast characteristic is significantly improved, as compared with the case without the polarizing plate and the quarter-wave plate, 5
6%程度、表示輝度が低下するという問題がある。 About 6%, there is a problem that the display luminance decreases.

【0008】この発明は以上の問題点に鑑みなされたもので、その目的は、優れたコントラスト特性および表示輝度特性を有したEL素子を提供することにある。 [0008] The present invention has been made in consideration of the above problems, its object is to provide an EL device having excellent contrast characteristics, and a display brightness characteristic.

【0009】 [0009]

【問題を解決する手段】上記目的を達成するため、この発明に係るEL素子は、偏光板と、上記偏光板の後方に配設された1/4波長板と、上記1/4波長板の後方に配設された発光層と、上記発光層の後方に配設された反射電極と、上記1/4波長板と発光層の間に設けられているとともに、コレステリック液晶層をポリマー化して形成され、入射光の第1円偏光成分を選択的に反射する選択反射層と、を備えたことを特徴としている。 Means for solving the problems] To achieve the above object, EL element according to the present invention, the polarizer and the above and a quarter-wave plate which is disposed behind the polarizer, the quarter-wave plate a light emitting layer disposed in the rear, a reflective electrode disposed to the rear of the light emitting layer, with is provided between the quarter-wave plate and the light-emitting layer, formed a cholesteric liquid crystal layer and polymerized is, is characterized by comprising: a selective reflection layer selectively reflects first circularly polarized light component of the incident light.

【0010】また、この発明に係るEL素子によれば、 Further, according to the EL device according to the present invention,
上記発光層および反射電極は透明基板上に形成され、上記発光層は、上記透明基板と反射電極との間に位置し、 The light emitting layer and a reflective electrode is formed on a transparent substrate, the light emitting layer is located between the transparent substrate and the reflective electrode,
上記選択反射層は、上記発光層と透明基板の間に設けられている。 The selective reflection layer is provided between the light emitting layer and the transparent substrate. また、この発明に係る他のEL素子によれば、上記発光層および反射電極は透明基板上に形成され、上記反射電極は、上記透明基板と発光層との間に設けられ、上記発光層は、上記反射電極と選択反射層との間に設けられていることを特徴としている。 In accordance with another EL element according to the present invention, the light emitting layer and a reflective electrode is formed on a transparent substrate, the reflective electrode is provided between the transparent substrate and the light emitting layer, the light-emitting layer It is characterized in that provided between the reflective electrode and the selective reflective layer.

【0011】この発明に係るEL素子において、上記選択反射層は、それぞれ互いにピッチの異なる複数のコレステリック液晶層を積層して形成され、あるいは、層厚方向にピッチが連側的に変化した1層のコレステリック液晶層により形成され、可視光全域の波長に光に対し上記コレステリック層の螺旋方向と同じ方向の円偏光を反射することを特徴としている。 [0011] In EL device according to the present invention, the selective reflection layer are each formed by stacking a plurality of cholesteric liquid crystal layers having different pitches from each other, or one layer pitch has changed communicating side manner in the layer thickness direction of formed by a cholesteric liquid crystal layer, with respect to light in the wavelength of the entire visible light region is characterized by reflecting the circularly polarized light in the same direction as the spiral direction of the cholesteric layer.

【0012】上記のように構成されたEL素子によれば、偏光板および1/4波長板を通って入射した外光は円偏光となり、選択反射層により反射されず、そのまま透過する。 [0012] According to the thus constructed EL element as described above, external light incident through the polarizing plate and the quarter-wave plate becomes circularly polarized light is not reflected by the selective reflection layer, it transmits it. そして、選択反射層を透過した外光は反射電極に入射し、ここで観察側に反射される。 Then, the external light transmitted through the selective reflection layer is incident on the reflective electrode is reflected on the observation side here. その際、外光は位相が180度ずれるため、選択反射層を通過し、更に1/4波長板を透過した後、偏光板入射時とは直交する直線偏光となり、この偏光板によって吸収される。 At that time, since the external light is phase shifted 180 degrees, passes through the selective reflection layer is further passes through the quarter-wave plate, into a linearly polarized light orthogonal to that at the time of polarizer incident, absorbed by the polarizing plate . これにより、反射電極で反射された外光を吸収して外部への出射を防止でき、その結果、コントラスト特性を向上することが可能となる。 Thus, by absorbing the external light reflected by the reflective electrode can be prevented emitted to the outside, as a result, it is possible to improve the contrast characteristics.

【0013】また、発光層から出射された発光光は、非偏光であり、左円偏光、右円偏光両方の成分からなる。 Further, emission light emitted from the light-emitting layer is non-polarized, left-circularly polarized light consists of two components of the right circularly polarized light.
その内、一方の円偏光成分は選択反射層で反射されることなくこの選択反射層を透過し、1/4波長板により偏光板を透過する方位の直線偏光とされ、偏光板を透過する。 Among them, one of the circularly polarized light component is transmitted through the selective reflection layer without being reflected by the selective reflection layer, a 1/4-wave plate are linearly polarized orientation transmitted through the polarizing plate, it passes through the polarizer. 他方の円偏光成分は選択反射層により選択反射されて反射電極に入射し、再び反射電極にて位相を180度ずらして反射され逆向きの円偏光成分となり、最終的に選択反射層および偏光板を透過して観察側に出射される。 Circularly polarized light component of the other is incident on the reflective electrode is selectively reflected by the selective reflection layer, phase and becomes 180 degrees shift is reflected reverse circularly polarized component again by the reflective electrode, finally selective reflection layer and the polarizing plate transmitted to and emitted to the observation side.

【0014】そのため、上記EL素子によれば、コントラスト特性を従来に比較して大幅に向上させることができるとともに、発光層から発光された光の大部分を観察側へ出射させることが可能となり、従来と比較して2倍以上の表示輝度が得られる。 [0014] Therefore, according to the EL element, it is possible to greatly improved compared to the contrast characteristics to the conventional, it is possible to emit most of the light emitted from the light emitting layer to the observer side, conventional display luminance of more than twice compared is obtained.

【0015】 [0015]

【発明の実施の形態】以下、図面を参照しながら、この発明の実施の形態に係るEL素子について詳細に説明する。 BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, with reference to the drawings, EL element according to the embodiment of the present invention will be described in detail. まず、本実施の形態に係るEL素子の基本構成を説明する。 First, a basic structure of an EL element according to this embodiment.

【0016】図1に示すように、EL素子は、例えばガラスからなるほぼ矩形状の透明基板10を備え、この透明基板の観察側には、コレステリック液晶をポリマー化したフェルム状のコレステリック液晶層からなる選択反射層12、1/4波長板14、偏光板16が順に設けられている。 [0016] As shown in FIG. 1, EL element includes, for example, a substantially rectangular transparent substrate 10 made of glass, the observation side of the transparent substrate, a cholesteric liquid crystal from Ferme-like cholesteric liquid crystal layer which is polymerized selective reflective layer 12, 1/4-wavelength plate 14 made, polarizing plate 16 are sequentially provided. また、透明基板10の背面側には、複数の配線20がマトリクス状に形成されているとともに、画素ごとに対応して発光層22、および反射電極24が順に形成されている。 Further, on the back side of the transparent substrate 10, a plurality of wires 20 are formed in a matrix, light emitting layer 22 and the reflective electrode 24, are formed in this order so as to correspond to each pixel.

【0017】偏光板16および1/4波長板14は、例えば、入射した外光(非偏光)を左円偏光とするように光軸が配置され、入射した外光は左円偏光となる。 The polarizer 16 and the quarter-wave plate 14, for example, incident external light (unpolarized light) is arranged the optical axis such that the left circular polarized light, external light incident becomes left circularly polarized light. また、選択反射層12を構成するコレステリック液晶層の分子は、発光層22側から見て左回りの螺旋構造を有している。 Further, the molecules of the cholesteric liquid crystal layer constituting the selective reflection layer 12 has a left-handed spiral structure viewed from the light-emitting layer 22 side. これにより、選択反射層12は、その発光層2 Thus, the selective reflection layer 12, the light-emitting layer 2
2側の主面に到達する入射光のうち、左円偏光成分のみを反射し、反射する成分とは逆回りの右円偏光成分を透過するとともに、反対側の主面に到達する入射光のうち左円偏光成分のみを反射し、右円偏光成分を透過する機能を有している。 Of the incident light reaching the 2 side of the main surface, it reflects only left-circularly polarized light component, with the reflected component is transmitted through the right-handed circularly polarized light component of the opposite direction, of the incident light reaching the main surface on the opposite side of reflects only left-circularly polarized light component, and has a function of transmitting the right-handed circularly polarized light component.

【0018】上記構成のEL素子によれば、偏光板16 According to the EL device having the above structure, the polarizing plate 16
を通して入射した外光は、偏光板16および1/4波長板14を通ることにより左円偏光となり、この左円偏光は、選択反射層12により反射せず、そのまま透過する。 External light incident through becomes the left circularly polarized light by passing through the polarizing plate 16 and the quarter-wave plate 14, the left circularly polarized light is not reflected by the selective reflection layer 12, passes through it. 従って、入射した外光は、反射電極24に入射し、 Therefore, external light incident enters the reflective electrode 24,
ここで観察側に反射される。 It is reflected to the observation side here. そして、反射電極24で反射された外光は位相が180度ずれるため、選択反射層12を通過し、更に1/4波長板14を透過した後は、 Since external light reflected by the reflective electrode 24 is shifted in phase by 180 degrees, passes through the selective reflection layer 12, after further passing through the quarter-wave plate 14,
偏光板16入射時とは直交する直線偏光となるため、この偏光板16によって吸収される。 Since the orthogonal linear polarization at the time of the polarizing plate 16 enters, it is absorbed by the polarizing plate 16. 従って、EL素子の黒表示時、反射電極24で反射された外光を吸収して外部への出射を防止でき、その結果、コントラスト特性を向上することが可能となる。 Thus, by absorbing the black display of the EL device, the external light reflected by the reflective electrode 24 can prevent the emission to the outside, as a result, it is possible to improve the contrast characteristics.

【0019】これに対して、発光層22から出射された発光光は、非偏光であり、左円偏光、右円偏光両方の成分からなる。 [0019] In contrast, luminescent light emitted from the light emitting layer 22 is a non-polarized, left-circularly polarized light consists of two components of the right circularly polarized light. その内、右円偏光成分は選択反射層12で反射されることなくこの選択反射層を透過し、1/4波長板14により偏光板16を透過する方位の直線偏光とされ、偏光板を透過する。 Among them, the right circularly polarized light component is transmitted through the selective reflection layer without being reflected by the selective reflection layer 12, a 1/4-wave plate 14 is a linearly polarized light of the direction that passes through the polarizing plate 16, passes through the polarizing plate to. 一方、左円偏光成分は選択反射層12により選択反射されて反射電極24に入射し、 On the other hand, left circularly polarized light component is selectively reflected by the selective reflection layer 12 is incident on the reflective electrode 24,
再び反射電極にて位相を180度ずらして反射され右円偏光成分となり、最終的に選択反射層12および偏光板を透過して観察側に出射される。 Phases becomes 180 degrees shift is reflected right-handed circularly polarized light component by the reflecting electrode again, finally selective reflecting layer 12 and transmitted through the polarizing plate is emitted to the observation side.

【0020】以上のことから、本EL素子によれば、コントラスト特性を従来に比較して大幅に向上させることができるとともに、発光層22から発光された光の大部分を観察側へ出射させることが可能となり、従来と比較して2倍以上の表示輝度が得られる。 [0020] From the foregoing, according to this EL device, be emitted as well as being able to significantly improved compared to the contrast characteristics to the conventional, most of the light emitted from the light-emitting layer 22 to the viewing side It is possible, as compared with the conventional display brightness more than twice obtained. また、選択反射層12をそれぞれ螺旋ピッチの異なる複数のコレステリック液晶層を積層して構成し、あるいは、層厚方向に螺旋ピッチが連続的に変化した1層以上のコレステリック液晶層によって構成し、可視光全域の波長の光に対し、螺旋方向と同じ方向の円偏光線分を反射する構成とすることにより、発光色に関わらず上述した機能および効果を得ることができる。 Further, the selective reflection layer 12 each formed by stacking a plurality of cholesteric liquid crystal layers having different helical pitches, or constituted by one or more cholesteric liquid crystal layers in which the helical pitch is continuously changed in the layer thickness direction, visible for light having a wavelength of light throughout, with the configuration that reflects circularly polarized light component of the same direction as the helical direction, it is possible to obtain the above-mentioned function and effect regardless of emission colors.

【0021】次に、上記のように構成されたEL素子の具体例について説明する。 [0021] Next, a specific example of configured EL element as described above. ここでは、従来と同様の製法、材料にて有機のEL発光材料を用いてEL素子を作成した。 Here, we create the EL device using the organic EL light emitting material in the same process, material and conventional. この場合、選択反射層12として、ガラスからなる透明基板10上に螺旋ピッチがそれぞれ300、3 In this case, as the selective reflection layer 12, the helical pitch on each of the transparent substrate 10 made of glass 300,3
40、390、450、520、590nmであり、Δ Is a 40,390,450,520,590nm, Δ
nが0.1、平均屈折率nが1.6の複数のコレステリック液晶層をプレーナー配向となるように積層した。 n is 0.1, the average refractive index n was laminated such that the planar orientation of the plurality of cholesteric liquid crystal layer of 1.6.

【0022】各コレステリック液晶層の膜厚は、螺旋ピッチの約10倍とした。 [0022] The thickness of each cholesteric liquid crystal layer, was about 10 times the helical pitch. また、各コレステリック液晶層は、螺旋ピッチが各種可視光波長と実効的に一致する長さであり、螺旋ピッチに平均屈折率を乗じたnp値の波長の光のうち、液晶分子の捻れ方向と同じ向きの円偏光、つまり左円偏光を反射する。 Each cholesteric liquid crystal layer is the length of helical pitch to match the various visible light wavelength and effective, in the light of the wavelength of the np value obtained by multiplying the average refractive index in the helical pitch, the direction twist of the liquid crystal molecules circularly polarized light in the same direction, that is, reflecting the left-handed circularly polarized light. 各コレステリック液晶層の反射率は膜厚に依存し、螺旋ピッチの10倍程度の膜厚では反射率100%となる。 Reflectance of each cholesteric liquid crystal layer depends on the film thickness, 100% reflectance at a thickness of 10 times the helical pitch. 従って、各コレステリック液晶層は、左円偏光のうち螺旋ピッチに平均屈折率を乗じたnp値の波長の光を中心として、Δnと螺旋ピッチとを乗じたバンド幅の光を反射する。 Accordingly, the cholesteric liquid crystal layer, around the light having a wavelength of np value obtained by multiplying the average refractive index in the helical pitch of left-handed circularly polarized light and reflects light of bandwidth obtained by multiplying the Δn and the spiral pitch.

【0023】前述したように、螺旋ピッチの異なる6種のコレステリック液晶層を、各層で左円偏光の反射率が100%となる膜厚に作成し、各層にてΔnと螺旋ピッチとを乗じたバンド幅の反射を得ることにより、ほぼ可視光全域の波長に対して左円偏光を選択的に反射する選択反射層12を得ることができる。 [0023] As described above, the six cholesteric liquid crystal layers having different helical pitches, create reflectance of the left circularly polarized light is the film thickness becomes 100% at each layer, by multiplying the Δn and the spiral pitch at each layer by obtaining a reflection bandwidth, it is possible to obtain a selective reflection layer 12 that selectively reflects left-circularly polarized light for a wavelength of approximately the entire visible light region. このように形成したコレステリック液晶ポリマー層は、紫外線硬化、熱重合などにより硬化して、フィルムあるいは膜として取り扱えるようにした。 The so-formed cholesteric liquid crystal polymer layer, UV curing, and cured by such thermal polymerization, and can be handled as a film or membrane.

【0024】なお、選択反射層は、螺旋ピッチの異なる複数のコレステリック液晶層を積層した構成に限らず、 [0024] Incidentally, the selective reflection layer is not limited to the structure formed by laminating a plurality of cholesteric liquid crystal layers having different helical pitches,
層厚方向に沿って螺旋ピッチが連続的に変化した単一のコレステリック液晶層で構成してもよく、この場合でも上記と同様の作用効果が得られる。 May be composed of a single cholesteric liquid crystal layer in which the helical pitch is continuously changed along the thickness direction, the same effect as described above can be obtained even in this case. また、液晶ポリマーを用いず、2枚以上の基板を用いて液晶層として形成しても同様の光学的効果が得られる。 Further, without using the liquid crystal polymer, the same optical effects be formed as a liquid crystal layer by using two or more substrates can be obtained.

【0025】上記のように形成された選択反射層12上に、EL素子の長手方向に対して光軸が反時計回りに1 [0025] On the selective reflection layer 12 formed as described above, first optical axis counterclockwise with respect to the longitudinal direction of the EL element
25°の角度をなすように、アートン樹脂からなるリターデーション値140nmの位相差板を貼り合せ、更にその上に、EL素子の長手方向に対して光軸が62.5 At an angle of 25 °, bonded retardation value 140nm of the phase difference plate made of Arton resin, further thereon, the optical axis with respect to the longitudinal direction of the EL element 62.5
°の角度をなするように、アートン樹脂からなるリターデーション値270nmの位相差板を貼り合せ、1/4 ° angle as Nasr of bonding the retardation of the retardation value 270nm made of Arton resin, 1/4
波長板14を形成した。 To form a wavelength plate 14. その後、EL素子の長手方向に対して光軸が45°の角度となるように偏光板16を貼り合せた。 Thereafter, bonding the polarizing plate 16 so that the optical axis with respect to the longitudinal direction of the EL element becomes the angle of 45 °.

【0026】このようなリターデーション値が140n [0026] Such a retardation value 140n
m、270nmの位相差板および偏光板を上述した角度構成で貼り合せることにより、可視光全域の波長に対し2枚の位相差板が1/4波長板14として作用し、偏光板16を含めて左円偏光板として機能する。 m, by laminating in the above-described angle constituting a phase difference plate and the polarizing plate of 270 nm, a retardation plate of the two with respect to the wavelength of visible light region acts as a quarter-wave plate 14, including a polarizing plate 16 Te functions as a left-handed circularly polarized light plate.

【0027】以上のように構成したEL素子においても、外光の反射防止、および発光光の殆どの光を出射させるといった効果を得ることができた。 [0027] In the structure the EL element as described above, it was possible to obtain such an effect emit most of the light of the anti-reflection of external light, and emitting light. 図2は、本実施例に係るEL素子(曲線A)、偏光板のみを備えたEL 2, EL element according to the present embodiment (curve A), EL having a polarizing plate only
素子(曲線B)、並びに、偏光板および選択反射層を持たないEL素子(曲線C)のコントラスト特性を各種照度にて比較した結果を示している。 Elements (curve B), as well, and the contrast characteristic of the EL element having no polarizing plate and the selective reflection layer (curve C) shows the results of a comparison with various illuminance.

【0028】この図から分かるように、偏光板を持たないEL素子(曲線C)と、偏光板を備えたEL素子(曲線A、B)とを比較すると、偏光板を設けたほうがいずれの照度においても高いコントラスト特性を得られる。 [0028] As can be seen from this figure, the EL element having no polarizing plate (curve C), the EL element (curve A, B) having a polarization plate are compared, and any idea to provide a polarizing plate illumination obtain a high contrast characteristic in.
これは、前述したように、反射電極で反射した外光を偏光板で吸収する効果による。 This is because, as described above, due to the effect of absorbing the external light reflected by the reflective electrode by the polarizing plate.

【0029】また、偏光板を設けた2つのEL素子(曲線A、B)同士を比較すると、本実施の形態のように、 Further, two EL device having a polarizing plate (curve A, B) when compared to each other, as in this embodiment,
選択反射層を備えたEL素子の方がさらに高いコントラスト特性を得られることが分かる。 It can be seen that towards the EL element having a selective reflection layer can be obtained a higher contrast characteristic. これは、本実施の形態に係るEL素子の表示輝度は、選択反射層を持たないEL素子に比較して、略2倍となったことに起因している。 This display luminance of the EL element according to the present embodiment is different from the EL element having no selective reflection layer is due to the fact that doubled approximately.

【0030】以上のことから、本実施の形態によれば、 [0030] From the foregoing, according to this embodiment,
コントラスト特性及び高い表示輝度の双方に優れたEL Excellent EL in both the contrast characteristic and high display brightness
素子を得ることができる。 It can be obtained element. なお、この発明は上述した実施の形態に限定されることなく、この発明の範囲内で種々変形可能である。 The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention. 例えば、有機EL発光素子を例に説明したが、本発明は発光層の種類にとらわれるものではなく、無機EL発光層を用いた場合でも同様の効果が得られることはいうまでもない。 For example, has been described an organic EL device as an example, the present invention is not intended to be bound on the type of the light-emitting layer, the same effect even in the case of using an inorganic EL light-emitting layer can be obtained of course.

【0031】上述した実施の形態において、EL素子は、選択反射層と発光層との間に透明基板を持たない構成としても良く、この場合、透明基板に起因する視差をなくことができる。 [0031] In the embodiment described above, EL elements may be configured without a transparent substrate between the light-emitting layer and the selectively reflective layer, in this case, it is possible to eliminate the parallax due to the transparent substrate.

【0032】また、透明基板上に発光層および反射電極を形成したEL素子においては、発光層が透明基板と反射電極との間に位置する場合、図3に示すように、コレステリック液晶層からなる選択反射層12は、発光層2 Further, in the EL element to form a light-emitting layer and a reflective electrode on a transparent substrate, when the light-emitting layer is located between the transparent substrate and the reflecting electrode, as shown in FIG. 3, consisting of a cholesteric liquid crystal layer selective reflection layer 12, light-emitting layer 2
2と透明基板10との間に設けられていてもよい。 2 and may be provided between the transparent substrate 10. 同様に、図4に示すように、反射電極24が透明基板10と発光層22との間に位置する場合、発光層22は、反射電極と選択反射層との間に設けられてもよい。 Similarly, as shown in FIG. 4, when the reflective electrode 24 is located between the transparent substrate 10 and the light emitting layer 22, light emitting layer 22 may be provided between the reflective electrode and the selective reflective layer. このような構成によれば、発光層22からの発光光は、選択反射層12により反射された後、更に反射電極によって反射されて再び選択反射層を透過する光に変換され、最終的に偏光板を透過して観察側に出射されるもので、その際、視差を生じることなく発光光を出射することができる。 According to this structure, light emitted from the light-emitting layer 22 is reflected by the selectively reflective layer 12, it is further converted into light transmitted again selectively reflective layer is reflected by the reflective electrodes, eventually polarized It intended to be emitted to the observation side through the plate, it being possible to emit the emitted light without causing parallax.

【0033】 [0033]

【発明の効果】以上詳述したように、この発明によれば、入射光の第1円偏光成分を選択的に反射する選択反射層および偏光板を設けることにより、コントラスト特性および表示輝度がともに優れたEL素子を提供することができる。 As described above in detail, according to the present invention, by providing the selective reflection layer and the polarizing plate for selectively reflecting the first circular polarization component of the incident light, both the contrast characteristic and the display brightness it is possible to provide an excellent EL element.

【図面の簡単な説明】 BRIEF DESCRIPTION OF THE DRAWINGS

【図1】この発明の実施の形態に係るEL素子の構造及び動作を概略的に示す図。 FIG. 1 is a diagram schematically illustrating the structure and operation of the EL element according to the embodiment of the present invention.

【図2】本発明のEL素子及び従来のEL素子のコントラスト特性の照度依存性の一例を示す図。 Diagram illustrating an example of illuminance dependence of the contrast characteristic of the EL element and the conventional EL element of the present invention; FIG.

【図3】この発明の他の実施の形態に係るEL素子の構造及び動作を概略的に示す図。 Figure 3 schematically illustrates the structure and operation of the EL device according to another embodiment of the present invention.

【図4】この発明の更に他の実施の形態に係るEL素子の構造及び動作を概略的に示す図。 [4] Furthermore diagram schematically illustrating the structure and operation of the EL device according to another embodiment of the present invention.

【符号の説明】 DESCRIPTION OF SYMBOLS

10…透明基板 12…選択反射層 14…1/4波長板 16…偏光板 22…発光層 24…反射電極 10 ... transparent substrate 12 ... selective reflection layer 14 ... 1/4-wave plate 16 ... polarizing plate 22 ... light-emitting layer 24 ... reflective electrode

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl. 7識別記号 FI テーマコート゛(参考) H05B 33/12 H05B 33/12 Z 33/14 33/14 A Fターム(参考) 2H049 BA02 BA03 BA05 BA07 BA42 BB03 BB61 BC21 3K007 AB02 BA06 CB01 CC01 DA01 DB03 EB00 5C094 AA06 AA10 BA27 DA13 EB02 ED11 ED14 ED20 FA02 5G435 AA02 AA03 AA04 BB05 BB16 DD12 FF03 FF05 FF14 ────────────────────────────────────────────────── ─── of the front page continued (51) Int.Cl. 7 identification mark FI theme Court Bu (reference) H05B 33/12 H05B 33/12 Z 33/14 33/14 a F -term (reference) 2H049 BA02 BA03 BA05 BA07 BA42 BB03 BB61 BC21 3K007 AB02 BA06 CB01 CC01 DA01 DB03 EB00 5C094 AA06 AA10 BA27 DA13 EB02 ED11 ED14 ED20 FA02 5G435 AA02 AA03 AA04 BB05 BB16 DD12 FF03 FF05 FF14

Claims (5)

    【特許請求の範囲】 [The claims]
  1. 【請求項1】偏光板と、 上記偏光板の後方に配設された1/4波長板と、 上記1/4波長板の後方に配設された発光層と、 上記発光層の後方に配設された反射電極と、 上記1/4波長板と発光層の間に設けられているとともに、コレステリック液晶層をポリマー化して形成され、 And 1. A polarizing plate, the and a quarter-wave plate which is disposed behind the polarizer, a light emitting layer disposed behind the quarter-wave plate, distribution to the rear of the light emitting layer and set the reflected electrode, with is provided between the quarter-wave plate and the light emitting layer is formed by a cholesteric liquid crystal layer was polymerized,
    入射光の第1円偏光成分を選択的に反射する選択反射層と、 を備えたことを特徴とするEL素子。 EL element characterized in that and a selective reflection layer selectively reflects first circularly polarized light component of the incident light.
  2. 【請求項2】上記発光層および反射電極は透明基板上に形成され、 上記発光層は、上記透明基板と反射電極との間に位置し、上記選択反射層は、上記発光層と透明基板の間に設けられていることを特徴とする請求項1に記載のEL素子。 Wherein said light emitting layer and a reflective electrode is formed on a transparent substrate, the light emitting layer is located between the transparent substrate and the reflective electrode, the selective reflection layer, the light-emitting layer and the transparent substrate EL element according to claim 1, characterized in that provided between.
  3. 【請求項3】上記発光層および反射電極は透明基板上に形成され、 上記反射電極は、上記透明基板と発光層との間に設けられ、上記発光層は、上記反射電極と選択反射層との間に設けられていることを特徴とする請求項1に記載のEL Wherein said light emitting layer and a reflective electrode is formed on a transparent substrate, the reflective electrode is provided between the transparent substrate and the light emitting layer, the light emitting layer, the above reflective electrode and the selective reflective layer EL according to claim 1, characterized in that provided between the
    素子。 element.
  4. 【請求項4】上記選択反射層は、それぞれ互いにピッチの異なる複数のコレステリック液晶層を積層して形成され、可視光全域の波長に光に対し上記コレステリック液晶層の螺旋方向と同じ方向の円偏光を反射することを特徴とする請求項1ないし3のいずれか1項に記載のEL Wherein said selective reflecting layer are each formed by stacking a plurality of cholesteric liquid crystal layers having different pitches from each other, the same direction of the circularly polarized light for light in the wavelength of visible light range and the spiral direction of the cholesteric liquid crystal layer EL according to any one of claims 1 to 3, characterized in that reflects
    素子。 element.
  5. 【請求項5】上記選択反射層は、層厚方向にピッチが連側的に変化した1層のコレステリック液晶層により形成され、可視光全域の波長に光に対し上記コレステリック液晶層の螺旋方向と同じ方向の円偏光を反射することを特徴とする請求項1ないし3のいずれか1項に記載のE Wherein said selective reflecting layer pitch is formed by the cholesteric liquid crystal layer of the continuous side varying the first layer in the layer thickness direction, and the spiral direction of the cholesteric liquid crystal layer to light in the wavelength of the visible light region E according to any one of claims 1 to 3, characterized in that reflect circularly polarized light in the same direction
    L素子。 L element.
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