JP3633227B2

JP3633227B2 - Discharge device, illumination device, and liquid crystal display device

Info

Publication number: JP3633227B2
Application number: JP22769297A
Authority: JP
Inventors: 眞一品田; 茂生御子柴; 智一志賀; 桂子平山; 正志土屋
Original assignee: 日立ライティング株式会社
Priority date: 1997-08-25
Filing date: 1997-08-25
Publication date: 2005-03-30
Anticipated expiration: 2017-08-25
Also published as: JPH1167150A

Description

【０００１】
【発明の属する技術分野】
本発明は平面状に発光する平板型放電装置等の放電装置、たとえば液晶パネル等のバックライトが必要な表示素子を使用するテレビ、ゲーム機、カーナビゲーションシステム等の情報映像機器やワープロ等のＯＡ機器、若しくは光源を内蔵した表示システムなどにおける放電装置、放電装置を用いた照明装置および液晶表示装置に関するものである。
【０００２】
【従来の技術】
液晶パネルを有する液晶表示装置は薄型軽量でありかつ低消費電力であるため、パソコンやテレビ等各種の情報映像ディスプレイとして広く利用されているが、液晶パネル自体は発光素子でなく、表示のためには液晶パネルの背面から光を供給するバックライトが必要である。そして、通常液晶表示装置に用いられているバックライトは、細径の蛍光ランプとアクリル樹脂の導光体とを組み合わせたものが主であるが、平板型放電装置（放電ランプ）も使用されている。
【０００３】
図１０はたとえば特願平７−２７２３２２号の明細書、図面に記載されている従来の平板型放電装置を示す断面図である。図に示すように、ソーダガラス等からなる透光性の前面板１０とソーダガラス、セラミック等からなる絶縁基板２０と側板３０とがたとえば低融点ガラス（図示せず）で一体に気密封着され、扁平状の密閉容器１が構成されている。また、発光面となる前面板１０の内面には互いに平行な第１、第２の（一対の）放電電極４０、４１が設けられ、放電電極４０、４１の表面は第１の誘電体層５０で覆われている。また、絶縁基板２０の内面には蛍光体６０が塗布され、密閉容器１内の放電空間７０には水銀と始動用ガスとしてアルゴンやネオンーアルゴン等の混合ガス、またはキセノン、クリプトン、アルゴン、ヘリウム、ネオン等の希ガスの放電ガスが封入されている。
【０００４】
この平板型放電装置においては、放電電極４０、４１間に高周波の駆動電圧を印加すると、放電空間７０内に放電が発生し、放電で発生した紫外線により蛍光体６０が励起されて発光し、光が前面板１０を通して外部に放射される。
【０００５】
【発明が解決しようとする課題】
ところで、平板型放電装置を液晶表示装置のバックライトに用いるためには、調光のために駆動電圧の電圧値、周波数等を変化させる必要がある。しかし、平板型放電装置を液晶表示装置のバックライトに用いるためには発光の輝度均せい度が良好であることが重要な条件の一つとなっているにもかかわらず、従来の平板型放電装置においては、駆動電圧の電圧値、周波数を変化させると、安定に動作する電圧値領域、周波数領域が狭いから、動作中に放電が不安定になり、輝度ムラやチラツキ、陽光柱の収縮等が発生しやすく、このために発光が不均一になり、輝度均せい度が悪くなることがあり、輝度の調光範囲が狭かった。
【０００６】
本発明は上述の課題を解決するためになされたもので、安定に動作する電圧値、周波数の領域が広い放電装置、輝度の調光範囲が広い放電装置、照明装置、液晶表示装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
この目的を達成するため、本発明においては、透光性を有する前面板と絶縁基板とを組み合わせて扁平状の密閉容器を構成し、上記前面板の内面に第１、第２の放電電極を設け、上記第１、第２の放電電極の表面を覆って第１の誘電体層を設け、上記絶縁基板の内面に蛍光体を塗布し、上記密閉容器の内部に放電ガスを封入した放電装置において、上記密閉容器の上記絶縁基板または上記前面板の外面の上記第１、第２の放電電極の間にかつ上記第１、第２の放電電極とほぼ平行方向にアース電極を設ける。
【０００９】
この場合、上記アース電極として金属箔からなるものを用い、上記アース電極を上記密閉容器に接着する。
【００１０】
また、透光性を有する前面板と絶縁基板とを組み合わせて扁平状の密閉容器を構成し、上記前面板の内面に第１、第２の放電電極を設け、上記第１、第２の放電電極の表面を覆って第１の誘電体層を設け、上記絶縁基板の内面に蛍光体を塗布し、上記密閉容器の内部に放電ガスを封入した放電装置において、上記密閉容器の上記絶縁基板または上記前面板の内面の上記第１、第２の放電電極の間にかつ上記第１、第２の放電電極とほぼ平行方向にアース電極を設け、上記アース電極の表面を覆って第２の誘電体層を設ける。
【００１１】
この場合、上記前面板に設けた上記アース電極の表面を覆う上記第２の誘電体層として透光性の材料からなるものを用いる。
【００１２】
これらの場合、上記アース電極の幅を０．８ｍｍ以上にする。
【００１３】
また、上記アース電極を上記第１、第２の放電電極から８．５ｍｍ以上離して上記絶縁基板に設ける。
また、上記アース電極を上記第１、第２の放電電極から２０ｍｍ以上離して上記前面板に設ける。
また、上記第１の誘電体層の表面に保護層を設ける。
また、上記前面板に設けた上記アース電極として透明導電膜からなるものを用いる。
また、照明装置において、上記の放電装置を用いて照明するように構成する。
また、液晶表示装置において、上記の放電装置をバックライトとして用いる。
【００１９】
【発明の実施の形態】
図１は本発明に係る平板型放電装置を示す一部切断斜視図である。図に示すように、前面板１０と絶縁基板２０と側板３０とが一体に気密封着されて、扁平状の密閉容器１が構成され、前面板１０の内面に互いに平行な放電電極４０、４１が設けられ、放電電極４０、４１の表面が厚膜印刷法によって設けられた第１の誘電体層５０によって覆われ、絶縁基板２０の内面に蛍光体６０が塗布され、密閉容器１内の放電空間７０に放電ガスが封入されている。また、絶縁基板２０の外面の放電電極４０、４１の間すなわち中央部にはアース電極８０が放電電極４０、４１と平行にかつ放電空間７０の全長に渡って設けられている。
【００２０】
この平板型放電装置においては、放電電極４０、４１に図２に示すような駆動電圧を印加する。すなわち、放電電極４０に図２（ａ）に示した−Ｖ_ｈの電圧を持つ矩形波電圧Ｖ１を印加し、放電電極４１に図２（ｂ）に示した位相が矩形波電圧Ｖ１と半周期ずれた矩形波電圧Ｖ２を印加する。また、アース電極８０をアース電位に保持する。このような駆動方法により、放電空間７０内に放電が発生し、放電で発生した紫外線により蛍光体６０が励起されて発光し、光が前面板１０を通して外部に放射される。
【００２１】
このような平板型放電装置においては、絶縁基板２０の外面にアース電極８０が設けられているから、放電空間７０内に安定性、均一性の良好である放電が発生するので、蛍光体６０が安定に励起されて発光する。このため、安定に動作する矩形波電圧Ｖ１、Ｖ２の電圧値、周波数の領域が広くなるから、矩形波電圧Ｖ１、Ｖ２の電圧値、周波数を大きく変化させたとしても、動作中に放電が不安定になることがなく、輝度ムラやチラツキ、陽光柱の収縮等が発生しにくく、発光が均一になり、輝度均せい度が良好であるので、輝度の調光範囲が広くなる。しかも、動作中に放電が不安定になることがないから、長寿命になる。また、誘電体層５０を厚膜印刷法によって設けているから、誘電体層５０を簡単に設けることができる。
【００２２】
なお、アース電極８０はたとえばアルミニウム等の金属箔（リボン）を接着することで非常に簡単に設けることができるから、製造コストがほとんど増加しない。また、接着剤付の金属箔（金属テープ）を用いればさらに簡単にアース電極８０を設けることができる。また、誘電体層５０はその表面をたとえばＭｇＯ等の保護層（図示せず）で覆ってやることで、動作電圧の低下、スパッタリングの減少が可能になり、さらに長寿命の平板型放電装置を得ることができる。
【００２３】
図３は図１に示したような平板型放電装置の駆動電圧の安定動作領域を示すグラフで、このグラフは絶縁基板２０の中央部に設けたアース電極８０の幅が３ｍｍ、発光面の大きさが１１５ｍｍ×８８ｍｍであり、水銀とアルゴンが２．６６ｋＰａ封入され、矩形波電圧Ｖ１、Ｖ２のパルス幅が５μｓ一定である場合のもので、矩形波電圧Ｖ１、Ｖ２の電圧値および周波数を変化させて放電が安定になる動作領域を調べた結果を示すものであり、領域ａはアース電極８０を設けた場合の安定動作領域を示し、領域ｂはアース電極８０を設けない場合の安定動作領域を示す。このグラフから明らかなように、アース電極８０を設けた場合には、アース電極を設けない場合と比較して安定動作領域を大幅に拡大できる。すなわち、アース電極を設けない場合には、安定動作周波数範囲が１５〜３０ｋＨｚであるが、アース電極８０を設けた場合には、安定動作周波数範囲を１０〜３５ｋＨｚまで拡大することができる。つまり、アース電極８０を設けた場合には、アース電極を設けない場合と比較して安定動作周波数範囲を上下各５ｋＨｚだけ拡大することができる。また、アース電極８０を設けた場合には、動作周波数全体でほぼ一定の低い電圧値で動作することができる。なお、このグラフでは電圧値の上限が８００Ｖであるが、これは駆動回路を構成する回路素子の耐電圧の関係で実験できなかったものであり、これ以上の電圧値での測定は行なっていないが、たとえば矩形波電圧Ｖ１、Ｖ２の周波数が３０ｋＨｚのときには、上限安定動作電圧が高くなっており、アース電極８０を設けた場合には安定動作電圧値範囲も上下に拡大されることが明らかである。このように、平板型放電装置にアース電極８０を付加することで、広い電圧値範囲、周波数範囲で放電の安定化を図ることができ、しかも発光輝度は電圧値、周波数に比例して高くなるから、輝度の調光範囲を２倍近く拡大することができる。さらに、アース電極８０はアース電位に保持されており、動作中にアース電極８０にはほとんど電流が流れないから、アース電極８０を設けたとしても消費電力が増加することはない。
【００２４】
図４は図１に示したような平板型放電装置のアース電極８０の幅と最低安定動作電圧との関係を示すグラフで、このグラフは周波数を３２ｋＨｚ（この周波数ではアース電極８０が付加されないと安定に放電しない）とした以外は図３に示したグラフの場合と同様の場合のものである。このグラフから明らかなように、アース電極８０の幅を０．８ｍｍ以上にすると、所定値以上の電圧値を有する矩形波電圧Ｖ１、Ｖ２を印加すれば放電が安定になる。また、アース電極８０の幅を広くするに従い最低安定動作電圧は低下し、アース電極８０の幅が３ｍｍ以上になると、最低安定動作電圧はほぼ一定になる。したがって、アース電極８０の幅を０．８ｍｍ以上にしたときには、輝度の調光範囲を確実に広くすることができる。
【００２５】
図５は図１に示すような放電電極４０とアース電極８０との距離Ｌ_１と最低安定動作電圧との関係を示すグラフであり、このグラフは放電電極４０、４１の内側間隔が７６ｍｍ、アース電極８０の幅が３ｍｍで、アース電極８０は絶縁基板２０の外面に設けてあり、また動作条件は図４に示したグラフの場合と同様であり、矩形波電圧Ｖ１、Ｖ２の周波数は３２ｋＨｚ、パルス幅は５μｓである場合のものである。このグラフから明らかなように、アース電極８０を放電電極４０から次第に離していき、距離Ｌ_１が８．５ｍｍ以上になると、所定値以上の電圧値を有する矩形波電圧Ｖ１、Ｖ２を印加すれば放電が安定になる。この場合、最低安定動作電圧は約５００Ｖとほぼ一定である。しかし、距離Ｌ_１が８．５ｍｍ未満であると、すなわちアース電極８０が８．５ｍｍより放電電極４０に近いと、電圧条件を変化させても安定な放電は得られない。また、距離Ｌ_１が６４．５ｍｍを超えると、すなわちアース電極８０と放電電極４１との距離が８．５ｍｍ未満であると、電圧条件を変化させても安定な放電は得られない。したがって、アース電極８０を放電電極４０、４１から８．５ｍｍ以上離して絶縁基板２０に設けたときには、広い安定動作領域が得られ、均一性の良い発光が得られるから、輝度の調光範囲を確実に広くすることができる。
【００２６】
図６は本発明に係る他の平板型放電装置を示す断面図である。図に示すように、絶縁基板２０の内面の中央部にアース電極８１が放電電極４０、４１と平行にかつ放電空間７０の全長に渡って設けられ、放電空間７０にアース電極８１が露出しないように、アース電極８１が第２の誘電体層５１で覆われ、絶縁基板２０と誘電体層５１との表面に蛍光体６０が塗布されている。
【００２７】
この平板型放電装置においては、放電電極４０とアース電極８１との距離と最低安定動作電圧との関係は図１に示した平板型放電装置の場合と同様である。したがって、アース電極８１を放電電極４０、４１から８．５ｍｍ以上離して絶縁基板２０に設けたときには、広い安定動作領域が得られ、均一性の良い発光が得られるから、輝度の調光範囲を確実に広くすることができる。
【００２８】
なお、この実施の形態においては、アース電極８１のみを誘電体層５１で覆ったが、絶縁基板２０の全面を第２の誘電体層で覆ってもよい。
【００２９】
図７は本発明に係る他の平板型放電装置を示す断面図である。図に示すように、放電電極４０、４１の表面が第１の誘電体層５２で覆われ、前面板１０の外面の中央部にＩＴＯ膜、ネサ膜等の透明導電膜からなるアース電極８２が放電電極４０、４１と平行にかつ放電空間７０の全長に渡って設けられている。
【００３０】
この平板型放電装置においては、前面板１０の外面に透明導電膜からなるアース電極８２が設けられているから、アース電極８２による輝度の減少がなく、輝度均せい度も良好である。
【００３１】
図８は図７に示すような放電電極４０とアース電極８２との距離Ｌ_２と安定動作電圧との関係を示すグラフであり、このグラフは放電電極４０、４１の内側間隔が７６ｍｍ、アース電極８２の幅が３ｍｍで、動作条件は図４に示したグラフの場合と同様であり、矩形波電圧Ｖ１、Ｖ２の周波数は３２ｋＨｚ、パルス幅は５μｓである場合のものである。このグラフから明らかなように、アース電極８２を放電電極４０から次第に離していき、距離Ｌ_２が２０ｍｍ以上になると、所定値以上の電圧値を有する矩形波電圧Ｖ１、Ｖ２を印加すれば均一で安定な放電が発生するが、距離Ｌ_２が２０ｍｍ未満の場合には、電圧条件を変化させても安定な放電は得られない。また、距離Ｌ_２が５３ｍｍを超えると、すなわちアース電極８２が放電電極４１から２０ｍｍ未満であると、電圧条件を変化させても放電が不安定になる。したがって、アース電極８２を放電電極４０、４１から２０ｍｍ以上離して前面板１０に設けたときには、輝度の調光範囲を確実に広くすることができる。
【００３２】
図９は本発明に係る他の平板型放電装置を示す断面図である。図に示すように、たとえばガラス板を熱成形で作った箱形容器すなわち側板と一体になった絶縁基板２１と前面板１０とが一体に気密封着され、扁平状の密閉容器２が構成され、前面板１０の放電電極４０、４１間にＩＴＯ膜、ネサ膜等の透明導電膜からなるアース電極８３が放電電極４０、４１と平行にかつ放電空間７０の全長に渡って設けられ、透光性の材料からなりかつ第１、第２の誘電体層を兼ねる誘電体層５３によって放電電極４０、４１およびアース電極８３が覆われ、誘電体層５３の表面にも蛍光体６０が塗布されている。
【００３３】
この平板型放電装置においては、側板と一体になった絶縁基板２１と前面板１０とにより密閉容器２が構成されているから、組立が簡単になるので、製造コストが安価になる。また、アース電極８３が透光性の材料からなる誘電体層５３によって覆われているから、輝度が低下することがない。この平板型放電装置においても、図８に示した実験結果と同様の実験結果が得られた。したがって、アース電極８３を放電電極４０、４１から２０ｍｍ以上離して前面板１０に設けたときには、輝度の調光範囲を確実に広くすることができる。
【００３４】
また、照明装置において、図１、図６、図７、図９に示した平板型放電装置を用いて照明するように構成すれば、輝度の調光範囲が広くなるとともに、寿命が長くなる。
【００３５】
また、液晶表示装置において、図１、図６、図７、図９に示した平板型放電装置をバックライトとして用いれば、輝度の調光範囲が広くなるとともに、バックライトの寿命が長くなる。
【００３６】
なお、上述実施の形態においては、平板型放電装置について説明したが、他の放電装置に本発明を適用することができる。また、上述実施の形態においては、アース電極８０〜８３を放電電極４０、４１と平行に設けたが、アース電極を第１、第２の放電電極とほぼ平行にすなわちアース電極を第１、第２の放電電極に対して多少傾斜させて設けてもよい。また、上述実施の形態においては、第１、第２の放電電極４０、４１を設けたが、放電電極４０、４１以外の放電電極を設けてもよい。
【００３７】
【発明の効果】
本発明に係る放電装置においては、安定に動作する電圧値、周波数の領域が広くなる。
【００３８】
また、透光性を有する前面板と絶縁基板とを組み合わせて扁平状の密閉容器を構成し、前面板の内面に第１、第２の放電電極を設け、第１、第２の放電電極の表面を覆って第１の誘電体層を設け、絶縁基板の内面に蛍光体を塗布し、密閉容器の内部に放電ガスを封入した放電装置において、密閉容器の絶縁基板または前面板の外面の第１、第２の放電電極の間にかつ第１、第２の放電電極とほぼ平行方向にアース電極を設けたときには、安定に動作する電圧値、周波数の領域が広くなるから、輝度の調光範囲が広くなる。
【００３９】
また、アース電極として金属箔からなるものを用い、アース電極を密閉容器に接着したときには、アース電極を簡単に設けることができるから、製造コストがほとんど増加しない。
【００４０】
また、透光性を有する前面板と絶縁基板とを組み合わせて扁平状の密閉容器を構成し、前面板の内面に第１、第２の放電電極を設け、第１、第２の放電電極の表面を覆って第１の誘電体層を設け、絶縁基板の内面に蛍光体を塗布し、密閉容器の内部に放電ガスを封入した放電装置において、密閉容器の絶縁基板または前面板の内面の第１、第２の放電電極の間にかつ第１、第２の放電電極とほぼ平行方向にアース電極を設け、アース電極の表面を覆って第２の誘電体層を設けたときには、安定に動作する電圧値、周波数の領域が広くなるから、輝度の調光範囲が広くなる。
【００４１】
また、前面板に設けたアース電極の表面を覆う第２の誘電体層として透光性の材料からなるものを用いたときには、輝度が低下することがなく、輝度均せい度が良好である。
【００４２】
また、アース電極の幅を０．８ｍｍ以上にしたときには、輝度の調光範囲を確実に広くすることができる。
【００４３】
また、アース電極を第１、第２の放電電極から８．５ｍｍ以上離して絶縁基板に設けたときには、輝度の調光範囲を確実に広くすることができる。
また、アース電極を第１、第２の放電電極から２０ｍｍ以上離して前面板に設けたときには、輝度の調光範囲を確実に広くすることができる。
また、第１の誘電体層の表面に保護層を設けたときには、動作電圧の低下、スパッタリングの減少が可能になり、長寿命にすることができる。
また、前面板に設けたアース電極として透明導電膜からなるものを用いたときには、輝度均せい度が良好である。
また、本発明に係る照明装置、液晶表示装置においては、輝度の調光範囲が広くなる。
【図面の簡単な説明】
【図１】本発明に係る平板型放電装置を示す一部切断斜視図である。
【図２】図１に示した平板型放電装置の駆動電圧波形図である。
【図３】平板型放電装置の駆動電圧の安定動作領域を示すグラフである。
【図４】アース電極の幅と最低安定動作電圧との関係を示すグラフである。
【図５】放電電極とアース電極との距離Ｌ_１と最低安定動作電圧との関係を示すグラフである。
【図６】本発明に係る他の平板型放電装置を示す断面図である。
【図７】本発明に係る他の平板型放電装置を示す断面図である。
【図８】放電電極とアース電極との距離Ｌ_２と最低安定動作電圧との関係を示すグラフである。
【図９】本発明に係る他の平板型放電装置を示す断面図である。
【図１０】従来の平板型放電装置を示す断面図である。
【符号の説明】
１…密閉容器
２…密閉容器
１０…前面板
２０…絶縁基板
２１…絶縁基板
４０…第１の放電電極
４１…第２の放電電極
５０…第１の誘電体層
５１…第２の誘電体層
５２…第１の誘電体層
５３…誘電体層
６０…蛍光体
８０…アース電極
８１…アース電極
８２…アース電極
８３…アース電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge device such as a flat plate-type discharge device that emits light in a flat form, for example, an OA such as a television, a game machine, a car navigation system, or other information video equipment or a word processor that uses a display element such as a liquid crystal panel. The present invention relates to a discharge device in a display system including a device or a light source, an illumination device using the discharge device , and a liquid crystal display device .
[0002]
[Prior art]
A liquid crystal display device having a liquid crystal panel is thin and lightweight and has low power consumption, so it is widely used as various information video displays such as personal computers and televisions. However, the liquid crystal panel itself is not a light emitting element and is used for display. Requires a backlight to supply light from the back of the liquid crystal panel. In general, the backlight used in the liquid crystal display device is mainly a combination of a small-diameter fluorescent lamp and an acrylic light guide, but a flat discharge device (discharge lamp) is also used. Yes.
[0003]
FIG. 10 is a cross-sectional view showing a conventional flat plate discharge device described in the specification and drawings of Japanese Patent Application No. 7-272322, for example. As shown in the figure, a translucent front plate 10 made of soda glass or the like, an insulating substrate 20 made of soda glass, ceramic, or the like and a side plate 30 are integrally hermetically sealed with, for example, low-melting glass (not shown). A flat airtight container 1 is configured. Further, first and second (a pair of) discharge electrodes 40 and 41 parallel to each other are provided on the inner surface of the front plate 10 serving as a light emitting surface, and the surfaces of the discharge electrodes 40 and 41 are the first dielectric layer 50. Covered with. A phosphor 60 is applied to the inner surface of the insulating substrate 20, and mercury and a mixed gas such as argon or neon-argon as a starting gas, or xenon, krypton, argon, helium are applied to the discharge space 70 in the sealed container 1. A rare gas discharge gas such as neon is enclosed.
[0004]
In this flat plate type discharge device, when a high frequency driving voltage is applied between the discharge electrodes 40 and 41, a discharge is generated in the discharge space 70, and the phosphor 60 is excited by the ultraviolet rays generated by the discharge to emit light. Is radiated to the outside through the front plate 10.
[0005]
[Problems to be solved by the invention]
By the way, in order to use the flat type discharge device for the backlight of the liquid crystal display device, it is necessary to change the voltage value, frequency, etc. of the drive voltage for dimming. However, in order to use the flat plate discharge device for the backlight of the liquid crystal display device, it is one of the important conditions that the luminance uniformity of light emission is good. In this case, if the voltage value and frequency of the drive voltage are changed, the voltage value region and the frequency region that operate stably are narrow, so that the discharge becomes unstable during operation, causing uneven brightness, flickering, contraction of the positive column, etc. Occurrence is likely to occur, resulting in non-uniform light emission, resulting in poor brightness uniformity, and the brightness dimming range is narrow.
[0006]
The present invention has been made to solve the above-described problems, and provides a discharge device having a wide voltage range and frequency range, a discharge device having a wide luminance dimming range , a lighting device, and a liquid crystal display device that operate stably. For the purpose.
[0007]
[Means for Solving the Problems]
In order to achieve this object, in the present invention, a flat sealed container is formed by combining a transparent front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate. A discharge device comprising: a first dielectric layer covering the surfaces of the first and second discharge electrodes; a phosphor coated on the inner surface of the insulating substrate; and a discharge gas enclosed in the sealed container In the above, an earth electrode is provided between the first and second discharge electrodes on the outer surface of the insulating substrate or the front plate of the sealed container and in a direction substantially parallel to the first and second discharge electrodes.
[0009]
In this case, the ground electrode is made of a metal foil, and the ground electrode is bonded to the sealed container.
[0010]
Further, a flat airtight container is formed by combining a translucent front plate and an insulating substrate, first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharges are provided. In the discharge device in which the first dielectric layer is provided to cover the surface of the electrode, the phosphor is applied to the inner surface of the insulating substrate, and the discharge gas is sealed in the sealed container, the insulating substrate of the sealed container or A ground electrode is provided between the first and second discharge electrodes on the inner surface of the front plate and in a direction substantially parallel to the first and second discharge electrodes, and covers a surface of the ground electrode to form a second dielectric. A body layer is provided.
[0011]
In this case, the second dielectric layer covering the surface of the ground electrode provided on the front plate is made of a translucent material.
[0012]
In these cases, the width of the ground electrode is set to 0.8 mm or more.
[0013]
The ground electrode is provided on the insulating substrate at a distance of 8.5 mm or more from the first and second discharge electrodes.
The ground electrode is provided on the front plate at a distance of 20 mm or more from the first and second discharge electrodes.
A protective layer is provided on the surface of the first dielectric layer.
The ground electrode provided on the front plate is made of a transparent conductive film.
Moreover, in an illuminating device, it comprises so that it may illuminate using said discharge device.
In the liquid crystal display device, the above discharge device is used as a backlight.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a partially cut perspective view showing a flat plate type discharge device according to the present invention. As shown in the figure, the front plate 10, the insulating substrate 20, and the side plates 30 are integrally hermetically sealed to form a flat sealed container 1, and discharge electrodes 40 and 41 parallel to each other on the inner surface of the front plate 10. The surfaces of the discharge electrodes 40 and 41 are covered with the first dielectric layer 50 provided by the thick film printing method, the phosphor 60 is applied to the inner surface of the insulating substrate 20, and the discharge in the hermetic container 1 is performed. A discharge gas is sealed in the space 70. In addition, a ground electrode 80 is provided between the discharge electrodes 40 and 41 on the outer surface of the insulating substrate 20, that is, in the central portion, in parallel with the discharge electrodes 40 and 41 and over the entire length of the discharge space 70.
[0020]
In this flat plate type discharge device, a driving voltage as shown in FIG. 2 is applied to the discharge electrodes 40 and 41. That is, the rectangular wave voltage V1 having the voltage −V _h shown in FIG. 2A is applied to the discharge electrode 40, and the phase shown in FIG. A shifted rectangular wave voltage V2 is applied. Further, the ground electrode 80 is held at the ground potential. By such a driving method, a discharge is generated in the discharge space 70, the phosphor 60 is excited by the ultraviolet rays generated by the discharge and emits light, and the light is emitted outside through the front plate 10.
[0021]
In such a flat type discharge device, since the ground electrode 80 is provided on the outer surface of the insulating substrate 20, a discharge having good stability and uniformity is generated in the discharge space 70. It emits light when excited stably. For this reason, since the voltage value and frequency regions of the rectangular wave voltages V1 and V2 that operate stably become wide, even if the voltage value and frequency of the rectangular wave voltages V1 and V2 are greatly changed, discharge does not occur during operation. Without being stable, luminance unevenness, flickering, positive column contraction, etc. are unlikely to occur, light emission is uniform, and the luminance uniformity is good, so the luminance dimming range is widened. Moreover, since the discharge does not become unstable during operation, the service life is extended. Moreover, since the dielectric layer 50 is provided by the thick film printing method, the dielectric layer 50 can be provided easily.
[0022]
The ground electrode 80 can be provided very simply by bonding a metal foil (ribbon) such as aluminum, so that the manufacturing cost hardly increases. Further, the ground electrode 80 can be provided more simply by using a metal foil (metal tape) with an adhesive. Further, the dielectric layer 50 is covered with a protective layer (not shown) such as MgO so that the operating voltage can be reduced and the sputtering can be reduced. Can be obtained.
[0023]
FIG. 3 is a graph showing the stable operation region of the driving voltage of the flat plate type discharge device as shown in FIG. 1. This graph shows that the width of the ground electrode 80 provided in the central portion of the insulating substrate 20 is 3 mm and the light emitting surface is large. Is 115 mm x 88 mm, mercury and argon are sealed in 2.66 kPa, and the pulse widths of the rectangular wave voltages V1 and V2 are constant 5 μs. The voltage value and frequency of the rectangular wave voltages V1 and V2 are changed. 3 shows the result of examining the operating region where the discharge becomes stable, where region a shows the stable operating region when the earth electrode 80 is provided, and region b shows the stable operating region when the earth electrode 80 is not provided. Indicates. As is clear from this graph, when the ground electrode 80 is provided, the stable operation region can be greatly expanded as compared with the case where the ground electrode is not provided. That is, when the ground electrode is not provided, the stable operating frequency range is 15 to 30 kHz. However, when the ground electrode 80 is provided, the stable operating frequency range can be expanded to 10 to 35 kHz. In other words, when the ground electrode 80 is provided, the stable operating frequency range can be expanded by 5 kHz above and below compared to the case where the ground electrode is not provided. Further, when the ground electrode 80 is provided, it is possible to operate at a substantially constant low voltage value over the entire operating frequency. In this graph, the upper limit of the voltage value is 800 V, but this was not possible due to the withstand voltage of the circuit elements constituting the drive circuit, and no measurement was performed at a voltage value higher than this. However, for example, when the frequency of the rectangular wave voltages V1 and V2 is 30 kHz, the upper limit stable operating voltage is high, and it is clear that when the ground electrode 80 is provided, the stable operating voltage value range is expanded vertically. is there. Thus, by adding the ground electrode 80 to the flat plate type discharge device, it is possible to stabilize the discharge in a wide voltage value range and frequency range, and the emission luminance increases in proportion to the voltage value and frequency. Therefore, the luminance dimming range can be expanded nearly twice. Furthermore, since the earth electrode 80 is held at the earth potential and almost no current flows through the earth electrode 80 during operation, even if the earth electrode 80 is provided, power consumption does not increase.
[0024]
FIG. 4 is a graph showing the relationship between the width of the ground electrode 80 of the flat plate type discharge device as shown in FIG. 1 and the lowest stable operating voltage. This graph shows a frequency of 32 kHz (at this frequency, the ground electrode 80 is not added). The case is the same as the case of the graph shown in FIG. 3 except that the discharge is not stable. As is apparent from this graph, when the width of the ground electrode 80 is 0.8 mm or more, the discharge becomes stable when the rectangular wave voltages V1 and V2 having a voltage value of a predetermined value or more are applied. Further, as the width of the ground electrode 80 is increased, the minimum stable operating voltage is lowered. When the width of the ground electrode 80 is 3 mm or more, the minimum stable operating voltage becomes substantially constant. Therefore, when the width of the ground electrode 80 is 0.8 mm or more, the luminance dimming range can be surely widened.
[0025]
Figure 5 is a graph showing the relationship between the distance L ₁ and the lowest stable operating voltage of the discharge electrode 40 and the ground electrode 80 as shown in FIG. 1, the inner space of the graph discharge electrodes 40, 41 76 mm, ground The width of the electrode 80 is 3 mm, the ground electrode 80 is provided on the outer surface of the insulating substrate 20, and the operating conditions are the same as in the graph shown in FIG. 4, and the frequencies of the rectangular wave voltages V1 and V2 are 32 kHz, The pulse width is for 5 μs. As is apparent from this graph, will release gradually the ground electrode 80 from the discharge electrode 40, the distance L ₁ is equal to or greater than 8.5 mm, by applying a square wave voltage V1, V2 having a voltage value equal to or larger than a predetermined value Discharge becomes stable. In this case, the lowest stable operating voltage is almost constant at about 500V. However, the distance _{L 1} is less than 8.5 mm, that is, the ground electrode 80 is close to the discharge electrode 40 than 8.5 mm, no stable discharge can be obtained even by changing the voltage conditions. Further, the distance _{L 1} is more than 64.5 mm, i.e. the distance between the ground electrode 80 and the discharge electrode 41 is less than 8.5 mm, no stable discharge can be obtained even by changing the voltage conditions. Therefore, when the ground electrode 80 is provided on the insulating substrate 20 at a distance of 8.5 mm or more from the discharge electrodes 40 and 41, a wide stable operation region can be obtained and light emission with good uniformity can be obtained. It can surely be widened.
[0026]
FIG. 6 is a sectional view showing another flat plate type discharge device according to the present invention. As shown in the figure, a ground electrode 81 is provided at the center of the inner surface of the insulating substrate 20 in parallel with the discharge electrodes 40 and 41 over the entire length of the discharge space 70 so that the ground electrode 81 is not exposed to the discharge space 70. The ground electrode 81 is covered with the second dielectric layer 51, and the phosphor 60 is applied to the surfaces of the insulating substrate 20 and the dielectric layer 51.
[0027]
In this flat plate type discharge device, the relationship between the distance between the discharge electrode 40 and the ground electrode 81 and the lowest stable operating voltage is the same as in the case of the flat plate type discharge device shown in FIG. Accordingly, when the ground electrode 81 is provided on the insulating substrate 20 at a distance of 8.5 mm or more from the discharge electrodes 40 and 41, a wide stable operation region can be obtained and light emission with good uniformity can be obtained. It can surely be widened.
[0028]
In this embodiment, only the ground electrode 81 is covered with the dielectric layer 51. However, the entire surface of the insulating substrate 20 may be covered with the second dielectric layer.
[0029]
FIG. 7 is a cross-sectional view showing another flat plate type discharge device according to the present invention. As shown in the figure, the surfaces of the discharge electrodes 40 and 41 are covered with a first dielectric layer 52, and a ground electrode 82 made of a transparent conductive film such as an ITO film or a nesa film is formed at the center of the outer surface of the front plate 10. It is provided in parallel with the discharge electrodes 40, 41 and over the entire length of the discharge space 70.
[0030]
In this flat plate type discharge device, since the ground electrode 82 made of a transparent conductive film is provided on the outer surface of the front plate 10, there is no decrease in luminance due to the ground electrode 82, and the luminance uniformity is good.
[0031]
Figure 8 is a graph showing the relationship between the distance L ₂ stable operating voltage of the discharge electrode 40 and the ground electrode 82 as shown in FIG. 7, the graph inner space of the discharge electrodes 40, 41 76 mm, the ground electrode The width of 82 is 3 mm, the operating conditions are the same as in the case of the graph shown in FIG. 4, the frequency of the rectangular wave voltages V1 and V2 is 32 kHz, and the pulse width is 5 μs. As is apparent from this graph, will release gradually the ground electrode 82 from the discharge electrode 40, the distance L ₂ is equal to or greater than 20 mm, uniform by applying a square wave voltage V1, V2 having the predetermined value or more voltage values Although stable discharge occurs, if the distance L ₂ is less than 20mm is not stable discharge is obtained even by changing the voltage conditions. The distance L ₂ is more than 53 mm, i.e. when the ground electrode 82 is less than 20mm from the discharge electrode 41, also by changing the voltage condition discharge becomes unstable. Therefore, when the ground electrode 82 is provided on the front plate 10 at a distance of 20 mm or more from the discharge electrodes 40 and 41, the luminance dimming range can be reliably widened.
[0032]
FIG. 9 is a sectional view showing another flat plate type discharge device according to the present invention. As shown in the figure, for example, a box-shaped container made of a glass plate by thermoforming, that is, an insulating substrate 21 integrated with a side plate and a front plate 10 are hermetically sealed together to form a flat sealed container 2. A ground electrode 83 made of a transparent conductive film such as an ITO film or a nesa film is provided between the discharge electrodes 40 and 41 of the front plate 10 in parallel with the discharge electrodes 40 and 41 and over the entire length of the discharge space 70. The discharge electrodes 40 and 41 and the ground electrode 83 are covered with a dielectric layer 53 made of a conductive material and also serving as the first and second dielectric layers, and the phosphor 60 is also applied to the surface of the dielectric layer 53 Yes.
[0033]
In this flat plate type discharge device, since the sealed container 2 is constituted by the insulating substrate 21 and the front plate 10 integrated with the side plate, the assembly is simplified and the manufacturing cost is reduced. Further, since the ground electrode 83 is covered with the dielectric layer 53 made of a translucent material, the luminance is not lowered. Also in this flat plate type discharge device, the same experimental result as the experimental result shown in FIG. 8 was obtained. Therefore, when the ground electrode 83 is provided on the front plate 10 at a distance of 20 mm or more from the discharge electrodes 40 and 41, the luminance dimming range can be reliably widened.
[0034]
Further, if the illumination device is configured to illuminate using the flat plate discharge device shown in FIGS. 1, 6, 7, and 9, the luminance dimming range is widened and the lifetime is extended.
[0035]
In the liquid crystal display device, when the flat plate discharge device shown in FIGS. 1, 6, 7, and 9 is used as a backlight, the luminance dimming range is widened and the lifetime of the backlight is extended.
[0036]
In the above-described embodiment, the flat plate discharge device has been described. However, the present invention can be applied to other discharge devices. In the above-described embodiment, the ground electrodes 80 to 83 are provided in parallel to the discharge electrodes 40 and 41. However, the ground electrode is substantially parallel to the first and second discharge electrodes, that is, the ground electrodes are the first and first electrodes. It may be provided with a slight inclination with respect to the two discharge electrodes. In the above-described embodiment, the first and second discharge electrodes 40 and 41 are provided. However, discharge electrodes other than the discharge electrodes 40 and 41 may be provided.
[0037]
【The invention's effect】
In the discharge device according to the present invention, the range of voltage value and frequency for stable operation is widened.
[0038]
In addition, a flat airtight container is configured by combining a translucent front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. In a discharge device in which a first dielectric layer is provided so as to cover the surface, a phosphor is applied to the inner surface of the insulating substrate, and a discharge gas is sealed inside the sealed container, the first of the outer surface of the insulating substrate or the front plate of the sealed container When a ground electrode is provided between the first and second discharge electrodes and in a direction substantially parallel to the first and second discharge electrodes, a stable voltage value and frequency region is widened. The range becomes wider.
[0039]
In addition, when an earth electrode made of a metal foil is used and the earth electrode is bonded to a sealed container, the earth electrode can be easily provided, so that the manufacturing cost hardly increases.
[0040]
In addition, a flat airtight container is configured by combining a translucent front plate and an insulating substrate, and first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. In a discharge device in which a first dielectric layer is provided so as to cover the surface, a phosphor is applied to the inner surface of an insulating substrate, and a discharge gas is sealed inside the sealed container, the first surface of the inner surface of the insulating substrate or the front plate of the sealed container. Stable operation when a ground electrode is provided between the first and second discharge electrodes and in a direction substantially parallel to the first and second discharge electrodes, and a second dielectric layer is provided to cover the surface of the ground electrode. Since the range of voltage value and frequency to be widened, the dimming range of luminance is widened.
[0041]
Further, when the second dielectric layer covering the surface of the ground electrode provided on the front plate is made of a translucent material, the luminance does not decrease and the luminance uniformity is good.
[0042]
Further, when the width of the ground electrode is 0.8 mm or more, the luminance dimming range can be surely widened.
[0043]
Further, when the ground electrode is provided on the insulating substrate at a distance of 8.5 mm or more from the first and second discharge electrodes, the luminance dimming range can be surely widened.
Further, when the ground electrode is provided on the front plate at a distance of 20 mm or more from the first and second discharge electrodes, the luminance dimming range can be surely widened.
In addition, when a protective layer is provided on the surface of the first dielectric layer, the operating voltage can be reduced and the sputtering can be reduced, and the life can be extended.
Further, when the ground electrode provided on the front plate is made of a transparent conductive film, the brightness uniformity is good.
Further, in the illumination device and the liquid crystal display device according to the present invention, the luminance dimming range is widened.
[Brief description of the drawings]
FIG. 1 is a partially cut perspective view showing a flat plate type discharge device according to the present invention.
FIG. 2 is a drive voltage waveform diagram of the flat plate type discharge device shown in FIG. 1;
FIG. 3 is a graph showing a stable operation region of a driving voltage of a flat plate discharge device.
FIG. 4 is a graph showing the relationship between the width of the ground electrode and the lowest stable operating voltage.
5 is a graph showing the relationship between the distance L ₁ and the lowest stable operating voltage of the discharge electrode and the ground electrode.
FIG. 6 is a cross-sectional view showing another flat plate type discharge device according to the present invention.
FIG. 7 is a sectional view showing another flat plate type discharge device according to the present invention.
8 is a graph showing the relationship between the distance L ₂ and the lowest stable operating voltage of the discharge electrode and the ground electrode.
FIG. 9 is a cross-sectional view showing another flat plate type discharge device according to the present invention.
FIG. 10 is a cross-sectional view showing a conventional flat plate type discharge device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sealed container 2 ... Sealed container 10 ... Front plate 20 ... Insulating substrate 21 ... Insulating substrate 40 ... 1st discharge electrode 41 ... 2nd discharge electrode 50 ... 1st dielectric material layer 51 ... 2nd dielectric material layer 52 ... first dielectric layer 53 ... dielectric layer 60 ... phosphor 80 ... earth electrode 81 ... earth electrode 82 ... earth electrode 83 ... earth electrode

Claims

A flat airtight container is configured by combining a translucent front plate and an insulating substrate, first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. In the discharge device in which the first dielectric layer is provided to cover the surface, the phosphor is applied to the inner surface of the insulating substrate, and the discharge gas is sealed in the sealed container, the insulating substrate or the front of the sealed container is provided. A discharge device characterized in that a ground electrode is provided between the first and second discharge electrodes on the outer surface of the face plate and in a direction substantially parallel to the first and second discharge electrodes.

2. The discharge device according to claim 1, wherein the ground electrode is made of a metal foil, and the ground electrode is bonded to the sealed container.

A flat airtight container is configured by combining a translucent front plate and an insulating substrate, first and second discharge electrodes are provided on the inner surface of the front plate, and the first and second discharge electrodes are provided. In the discharge device in which the first dielectric layer is provided to cover the surface, the phosphor is applied to the inner surface of the insulating substrate, and the discharge gas is sealed in the sealed container, the insulating substrate or the front of the sealed container is provided. A ground electrode is provided between the first and second discharge electrodes on the inner surface of the face plate and in a direction substantially parallel to the first and second discharge electrodes. The second dielectric layer covers the surface of the ground electrode. A discharge device characterized by comprising:

4. The discharge device according to claim 3, wherein the second dielectric layer covering the surface of the ground electrode provided on the front plate is made of a translucent material.

The discharge device according to any one of claims 1 to 4, wherein a width of the ground electrode is 0.8 mm or more.

The discharge device according to claim 1, wherein the ground electrode is provided on the insulating substrate at a distance of 8.5 mm or more from the first and second discharge electrodes.

The discharge device according to claim 1, wherein the ground electrode is provided on the front plate at a distance of 20 mm or more from the first and second discharge electrodes.

The discharge device according to claim 1, wherein a protective layer is provided on the surface of the first dielectric layer.

9. The discharge device according to claim 1, wherein the ground electrode provided on the front plate is made of a transparent conductive film.

An illuminating device configured to illuminate using the discharge device according to claim 1.

A liquid crystal display device using the discharge device according to claim 1 as a backlight.