JP2004246178A

JP2004246178A - Optical unit, projection type video display device and polarizing plate used therein

Info

Publication number: JP2004246178A
Application number: JP2003037007A
Authority: JP
Inventors: Kazuo Hoden; 和夫鋪田; Takuya Shiaki; 卓也仕明; Eiji Yamaguchi; 英治山口
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2003-02-14
Filing date: 2003-02-14
Publication date: 2004-09-02

Abstract

<P>PROBLEM TO BE SOLVED: To secure the brightness and the contrast of a video together with the heat radiation property of a polarizing plate in a projection type video display device. <P>SOLUTION: The polarizing plate arranged on the light incident side of a video display element is constituted so that a polarizing element is held on a sapphire base plate and an angle formed by the optical axis of the sapphire base plate with the absorbing axis of the polarizing element is within the range of 90°±6° (excepting the range of ±2°) or 0°±6° (excepting the range of ±2°), and constituted so that the polarizing element is arranged on the video display element side and the sapphire base plate is arranged on a light source side. The thickness of the sapphire base plate is set to about 0.3×10<SP>-3</SP>to 1.0×10<SP>-3</SP>m. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、光源側からの光を偏光変換して映像表示素子に照射し映像信号に応じた光学像を形成して投射する投射型映像表示装置に係わり、特に、偏光板の放熱技術に関する。
【０００２】
【従来の技術】
従来より、投射型映像表示装置において、液晶パネル等の映像表示素子に入射させる光、または該映像表示素子から出射される光のうちの所定の偏光方向のものを通すための偏光板としては、偏光素子としての偏光フィルムが光源からの光の吸収による温度上昇で変形するのを防止するために、該偏光フィルムを光透過性の基板上に貼り合せた構成とする。本発明に関連し、放熱性の点から上記基板をサファイアで構成する従来技術としては、例えば特許第３０９１１８３号明細書（特許文献１）に記載されたものがある。該特許明細書には、サファイア基板として、Ｃ軸方向またはＣ軸投影線方向と透過すべき偏光透過軸とのなす角度を±２゜以内、またはＣ軸と直交する軸と透過すべき偏光透過軸とのなす角度を±２゜以内、またはＣ面と透過すべき偏光の透過方向に垂直な面とのなす角度を±２゜以内とする構成が記載されている。
【０００３】
【特許文献１】
特許第３０９１１８３号明細書
【０００４】
【発明が解決しようとする課題】
上記従来技術では、Ｃ軸方向またはＣ軸投影線方向と透過すべき偏光透過軸とのなす角度などが±２゜以内であって好ましくは±０．５゜以内と、全体的に狭い角度範囲に限定されるため、これを満足するためには高い部品精度が必要となり、製作コストの増加にもつながると考えられる。また、サファイア基板を、液晶パネル（映像表示素子）側に配した場合には、コントラストが著しく劣化するおそれもある。
本発明の課題点は、上記従来技術の状況に鑑み、サファイア基板を備えた偏光板を用いる投射型映像表示装置技術として、該偏光板において、（１）放熱性と併せ、映像の明るさ及びコントラストも確保できるようにすること、（２）部品精度を緩和できるようにして生産性の向上を可能にし、低コスト化も図れるようにすること、等である。
本発明の目的は、かかる課題点を解決できる技術の提供にある。
【０００５】
【課題を解決するための手段】
上記課題点を解決するために、本発明では、投射型映像表示装置またはその光学ユニットを構成するために、基本的に、
（１）偏光素子をサファイア基板で保持して成る偏光板であって、映像表示素子の光入射側に配する偏光板を、該偏光板内において該偏光素子を映像表示素子側に、該サファイア基板を反対側に配し、該サファイア基板の光学軸と該偏光素子の吸収軸とのなす角が９０゜±６゜（±２゜の範囲を除く）以内または０゜±６゜（±２゜の範囲を除く）以内となるようにする。
（２）偏光板を映像表示素子の光入射側と光出射側とに配し、該両偏光板をそれぞれ、サファイア基板上に偏光素子が該映像表示素子側にして保持された構成とし、うち入射側に配される偏光板を、サファイア基板の光学軸と偏光素子の吸収軸とのなす角が９０゜±６゜（±２゜の範囲を除く）以内または０゜±６゜（±２゜の範囲を除く）以内とされたものとする。
（３）偏光板を映像表示素子の光入射側と光出射側とに配し、光入射側に配される偏光板を、サファイア基板上に偏光素子が該映像表示素子側にして保持され、該サファイア基板の光学軸と該偏光素子の吸収軸とのなす角が９０゜±６゜（±２゜の範囲を除く）以内または０゜±６゜（±２゜の範囲を除く）以内とされたものとし、光出射側に配される偏光板を、偏光素子がサファイア基板の両面側に配され、該サファイア基板の光学軸と該両面側の偏光素子の吸収軸とのなす角が９０゜±０．５゜以内または０゜±０．５゜以内とされたものとする。
さらに、
（４）上記（１）〜（３）のいずれかにおいて、上記サファイア基板を、板厚が約０．３×１０^−３ｍ〜１．０×１０^−３ｍのものとする。
【０００６】
【発明の実施の形態】
以下、本発明の実施例につき、図面を用いて説明する。
図１〜図６は、本発明の実施例の説明図である。図１は、映像表示素子に対する偏光板の第１の組合わせ構成例を示す図、図２は、図１の組合わせ構成を用いた投射型映像表示装置の構成例を示す図、図３は映像表示素子に対する偏光板の第２の組合わせ構成例を示す図、図４は映像表示素子に対する偏光板の第３の組合わせ構成例を示す図、図５は、偏光板を構成するサファイア基板の結晶軸角度ズレに対する明るさ及びコントラストの関係を示す図、図６は、偏光板の温度特性の実測結果例を示す図である。
【０００７】
図１において、２０は映像表示素子としての液晶パネル、４は入射側偏光板、５は出射側偏光板、４１は入射側偏光板４の偏光素子としての偏光フィルム、４２は入射側偏光板４のサファイア基板、５１は出射側偏光板５の偏光素子としての偏光フィルム、５２は出射側偏光板５のサファイア基板、２１は、偏光変換され、かつ色分離された赤（Ｒ）、緑（Ｇ）、青（Ｂ）いずれかの色光の入射偏光光である。また、Ｘ−Ｘ’は、入射光２１の直線偏光の偏光方向である。
【０００８】
上記構成において、入射側偏光板４、出射側偏光板５とも、偏光フィルム４１、５１を液晶パネル側に配する。偏光フィルム４１と偏光フィルム５１は互いに、光の透過軸が約９０゜ずれるようにしてある。Ｐ偏光光またはＳ偏光光の入射偏光光２１は、入射側偏光板４のサファイア基板４２を通過し、偏光フィルム４１に入射する。偏光フィルム４１はＸ−Ｘ’方向を透過軸としている。該サファイア基板４２の結晶軸（光学軸）は、サファイア基板４２の結晶軸（光学軸）が偏光に影響を与えないようにするために、偏光フィルム４１の透過軸（吸収軸）と同じＸ−Ｘ’方向もしくはこれと直交する方向にしてある。該サファイア基板４２の結晶軸（光学軸）の方向が偏光フィルム４１の透過軸（吸収軸）の方向からずれるに従い、該サファイア基板４２のの複屈折による直線偏光の楕円偏光への変化量が増大し、その結果、偏光フィルム４１での光の吸収量が増加して光損失が増大し、映像の明るさやコントラストが低下するとともに、発熱量も増大する。
【０００９】
上記構成では、明るさとコントラストとを約９８％以上にするために、上記サファイア基板４２の光学軸（結晶軸）と上記偏光フィルム４１の吸収軸（透過軸）とのなす角を、９０゜±６゜以内または０゜±６゜以内となるようにしている（図５で説明）。また、サファイア基板４２の熱伝導により偏光フィルム４１の温度を下げるために、該サファイア基板４２の板厚は約０．３×１０^−３ｍ〜１．０×１０^−３ｍとしている。入射側偏光板４に対し光の透過軸を９０゜ずらせた出射側偏光板５については、サファイア基板５２の光学軸（結晶軸）と偏光フィルム５１の吸収軸（透過軸）とのなす角を、０゜±１０゜以内程度または９０゜±１０゜以内程度とすれば実用上特に問題ない。サファイア基板５２の板厚は、上記サファイア基板４２と同様、約０．３×１０^−３ｍ〜１．０×１０^−３ｍとしている。
【００１０】
図２は、上記図１の偏光板を用いて成る投射型映像表示装置の構成例である。
図２において、１は光源ユニット、６は、複数の微小なレンズセルより成り複数の２次光源像を形成する第１のアレイレンズ、７は、同じく複数の微小なレンズセルより成り上記第１のアレイレンズの個々のレンズ像を結像する第２のアレイレンズ、８は、偏光ビームスプリッタ（図示なし）と１／２波長位相差板（図示なし）から構成され、上記第２のアレイレンズ７側からの光をＰ偏光光とＳ偏光光に分離した後、該両偏光光のうちいずれか一方の偏光方向を回転してＰ、Ｓいずれかの偏光光に揃えて出射する偏光変換素子、９は集光レンズ、１２、１３は色分離用のダイクロイックミラー、１０Ｒ、１０Ｇ、１０Ｂはコンデンサレンズ、１４、１５、１６は反射ミラー、１７、１８はリレーレンズ、２０Ｒ、２０Ｇ、２０Ｂは映像表示素子としての透過型液晶パネル、４Ｒは液晶パネル２０Ｒの入射側偏光板、５Ｒは液晶パネル２０Ｒの出射側偏光板、４Ｇは液晶パネル２０Ｇの入射側偏光板、５Ｇは液晶パネル２０Ｇの出射側偏光板、４Ｂは液晶パネル２０Ｂの入射側偏光板、５Ｇは液晶パネル２０Ｇの出射側偏光板、１１は色合成用のダイクロイックプリズム、３は映像光を拡大投射するための投射レンズユニット、１９はスクリーン、２６は冷却用ファン、２７は冷却用空気の流路である。入射側偏光板４Ｒ、４Ｇ、４Ｂ及び出射側偏光板５Ｒ、５Ｇ、５Ｂはそれぞれ、上記図１に示した構成を備えているものとする。液晶パネル２０Ｒ、２０Ｇ、２０Ｂはそれぞれ、映像信号に基づき駆動回路（図示なし）により駆動され、入射された偏光光を変調して出射する。また、リレ−レンズ１７、１８は、液晶パネル２０Ｂの、光源ユニット１からの光路長が、液晶パネル２０Ｒ、２０Ｇの場合に比べて長いのを補うために設けられる。光源ユニット１から投射レンズユニット３までの上記諸要素は、投射型映像表示装置における光学ユニットを構成している。
【００１１】
かかる構成において、上記光源ユニット１から出た光（白色光）は、上記第１のアレイレンズ６で複数の２次光源像を形成した後、上記第２のアレイレンズ７で該複数の２次光源像を結像し、該結像光が、上記偏光変換素子８内で、偏光ビームスプリッタ（図示なし）でＰ偏光光とＳ偏光光とに分離され、１／２波長位相差板（図示なし）により、例えば該Ｐ偏光光が偏光方向を回転されてＳ偏光光とされ、上記偏光ビームスプリッタで分離されたＳ偏光光と併せ、集光レンズ９に入射される。集光レンズ９で集光された白色光のＳ偏光光は、ダイクロイックミラー１２に約４５゜の入射角で入射する。ダイクロイックミラー１２では、Ｒ光のＳ偏光光は反射され、Ｇ光及びＢ光のＳ偏光光は透過される。
【００１２】
上記反射されたＲ光のＳ偏光光は反射ミラー１４で反射されて光路変更し、コンデンサレンズ１０Ｒを介してＲ光用の透過型液晶パネル２０Ｒの入射側偏光板４Ｒに入射される。該Ｒ光のＳ偏光光は、該入射側偏光板４Ｒにおいて該入射側偏光板４Ｒの透過軸方向のものが透過されることで偏光方向を揃えられ、Ｒ光用の透過型液晶パネル２０Ｒに照射される。該液晶パネル２０Ｒでは、該Ｒ光のＳ偏光光が透過時に映像信号に基づいて変調され、Ｒ光のＰ偏光光となって出射される。液晶パネル２０Ｒから出射されたＲ光のＰ偏光光は、出射側偏光板５Ｒに入射され、該出射側偏光板５Ｒにおいて該出射側偏光板５Ｒの透過軸方向のものが透過されることで偏光方向を揃えられ、ダイクロイックプリズム１１に入射される。ダイクロイックプリズム１１では、そのダイクロイック面で反射され、投射レンズユニット３に入る。
【００１３】
一方、ダイクロイックミラー１２を透過したＧ光及びＢ光のＳ偏光光は、さらに、ダイクロイックミラー１３に約４５゜の入射角で入射し、該ダイクロイックミラー１３で、Ｇ光のＳ偏光光は反射され、Ｂ光のＳ偏光光は透過される。反射されたＧ光のＳ偏光光は、コンデンサレンズ１０Ｇを介してＧ光用の透過型液晶パネル２０Ｇの入射側偏光板４Ｇに入射される。
該Ｇ光のＳ偏光光は、該入射側偏光板４Ｇにおいて該入射側偏光板４Ｇの透過軸方向のものが透過されることで偏光方向を揃えられ、Ｇ光用の透過型液晶パネル２０Ｇに照射される。該液晶パネル２０Ｇでは、該Ｇ光のＳ偏光光が透過時に映像信号に基づいて変調され、Ｇ光のＰ偏光光となって出射される。液晶パネル２０Ｇから出射されたＧ光のＰ偏光光は、出射側偏光板５Ｇに入射され、該出射側偏光板５Ｇにおいて該出射側偏光板５Ｇの透過軸方向のものが透過されることで偏光方向を揃えられ、ダイクロイックプリズム１１に入射される。該Ｇ光のＰ偏光光は、ダイクロイックプリズム１１内においてダイクロイック面で反射され、投射レンズユニット３に入る。
【００１４】
また、上記ダイクロイックミラー１３を透過したＢ光のＳ偏光光は、リレーレンズ１７を経て反射ミラー１５で反射され、さらにリレーレンズ１８を経て反射ミラー１６で反射され、コンデンサレンズ１０Ｂを介してＢ光用の透過型液晶パネル２０Ｂの入射側偏光板４Ｂに入射される。該Ｂ光のＳ偏光光は、該入射側偏光板４Ｂにおいても該入射側偏光板４Ｂの透過軸方向のものが透過されることで偏光方向を揃えられ、Ｂ光用の透過型液晶パネル２０Ｂに照射される。該液晶パネル２０Ｂでは、該Ｂ光のＳ偏光光が透過時に映像信号に基づいて変調され、Ｂ光のＰ偏光光となって出射される。液晶パネル２０Ｂから出射されたＢ光のＰ偏光光は、出射側偏光板５Ｂに入射され、該出射側偏光板５Ｂにおいて該出射側偏光板５Ｇの透過軸方向のものが透過されることで偏光方向を揃えられ、ダイクロイックプリズム１１に入射される。ダイクロイックプリズム１１内において該Ｂ光のＰ偏光光はダイクロイック面で反射され、投射レンズユニット３に入る。
すなわち、上記のように、ダイクロイックプリズム１１からは、映像信号により変調されたＲ光のＰ偏光光と、Ｇ光のＰ偏光光と、Ｂ光のＰ偏光光とが互いに色合成された状態で出射され、白色光のＰ偏光光として投射レンズユニット３に入り、該投射レンズユニット３によりスクリーン１９上に映像光として拡大投射される。
【００１５】
上記構成において、各入射側偏光板４Ｒ、４Ｇ、４Ｂ及び各出射側偏光板５Ｒ、５Ｇ、５Ｂでは、それぞれの偏光フィルムの透過軸を通過できない光は、該それぞれの偏光フィルムに吸収されて熱に変り、それぞれの偏光フィルムの温度を上昇させる。サファイア基板は、その放熱特性により該偏光フィルムの熱を放熱し、該偏光フィルムと偏光板全体の温度上昇を抑える。冷却用ファン２６は、冷却用ダクト（図示なし）等により流路２７を形成し、各入射側偏光板４Ｒ、４Ｇ、４Ｂ、各出射側偏光板５Ｒ、５Ｇ、５Ｂ、各液晶パネル２０Ｒ、２０Ｇ、２０Ｂ等に送風し、これらを冷却する。
【００１６】
なお、上記構成例では偏光変換素子８からは、偏光変換の結果、Ｓ偏光光が出射されるようにしたが、これに限らず、Ｐ偏光光が出射されるようにしてもよい。この場合は、Ｒ、Ｇ、Ｂ各色光のＰ偏光光がそれぞれ、各入射側偏光板４Ｒ、４Ｇ、４Ｂを透過し、対応する液晶パネル２０Ｒ、２０Ｇ、２０Ｂに照射され、該液晶パネル２０Ｒ、２０Ｇ、２０Ｂにおいて、透過時に映像信号に基づいて変調され、Ｒ、Ｇ、Ｂ各色光のＳ偏光光となって出射され、ダイクロイックプリズム１１で色合成される。
【００１７】
図３は、映像表示素子に対する偏光板の第２の組合わせ構成例を示す図である。本構成は、偏光素子を映像表示素子側に配した偏光板を、映像表示素子の入射側に１個、出射側に２個設けた場合の例である。該２個の偏光板それぞれのサファイア基板により出射側の放熱効果を高められ、偏光素子の過度の温度上昇を抑えられる。
図３において、２０は映像表示素子としての液晶パネル、４は入射側偏光板、５ａ、５ｂは出射側偏光板、４１は入射側偏光板４の偏光素子としての偏光フィルム、４２は入射側偏光板４のサファイア基板、５ａ_１は出射側偏光板５ａの偏光素子としての偏光フィルム、５ａ_２は出射側偏光板５ａのサファイア基板、５ｂ_１は出射側偏光板５ｂの偏光素子としての偏光フィルム、５ｂ_２は出射側偏光板５ｂのサファイア基板、２１は、偏光変換され、かつ赤（Ｒ）、緑（Ｇ）、青（Ｂ）いずれかの色光に分離された入射偏光光としてのＰ偏光光またはＳ偏光光である。また、Ｘ−Ｘ’は、入射偏光光２１の直線偏光の偏光方向である。偏光フィルム５ａ_１としては偏光度の低いものを用い、偏光フィルム５ｂ_１としては偏光度の高い（ほぼ１００％）ものを用いる。
【００１８】
上記において、入射側偏光板４、出射側偏光板５ａ、５ｂとも、偏光フィルム４１、５ａ_１、５ｂ_１を液晶パネル２０側に配する。偏光フィルム５ａ_１、５ｂ_１は、サファイア基板５ａ_２に対してはその両面側に配されている。偏光フィルム４１と偏光フィルム５ａ_１、５ｂ_１とは互いに、光の透過軸が約９０゜ずれるようにしてある。Ｐ偏光光またはＳ偏光光の入射偏光光２１は、入射側偏光板４のサファイア基板４２を通過し、偏光フィルム４１に入射する。偏光フィルム４１はＸ−Ｘ’方向を透過軸としている。入射側偏光板４において該サファイア基板４２の結晶軸（光学軸）は、サファイア基板４２の結晶軸（光学軸）が偏光に影響を与えないようにするために、偏光フィルム４１の透過軸（吸収軸）と同じＸ−Ｘ’方向もしくはこれと直交する方向にしてある。該サファイア基板４２の結晶軸（光学軸）の方向が偏光フィルム４１の透過軸（吸収軸）の方向からずれるに従い、該サファイア基板４２の複屈折による直線偏光の楕円偏光への変化量が増大し、その結果、偏光フィルム４１での光の吸収量が増加して光損失が増大し、映像の明るさやコントラストが低下するとともに、偏光板としての発熱量が増大し温度も上昇する。出射側偏光板５ａ、５ｂについても同様である。
【００１９】
上記構成では、偏光板４における明るさとコントラストとを約９８％以上にすべく、該サファイア基板４２の光学軸（結晶軸）と該偏光フィルム４１の吸収軸（透過軸）とのなす角を、９０゜±６゜以内または０゜±６゜以内となるようにしている。また、サファイア基板４２の熱伝導により偏光フィルム４１の温度を下げるために、該サファイア基板４２の板厚は約０．３×１０^−３ｍ〜１．０×１０^−３ｍとしている。入射側偏光板４に対し光の透過軸を９０゜ずらせた出射側偏光板５ａ、５ｂについても、明るさとコントラストとを約９８％以上にするために、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）とのなす角が所定範囲の値となるようにする。出射側偏光板５ａについては、サファイア基板５ａ_２の光学軸（結晶軸）と偏光フィルム５ａ_１の吸収軸（透過軸）とのなす角を、０゜±０．５゜以内または９０゜±０．５゜以内の値にする（図５で説明）。また、サファイア基板５ａ_２の熱伝導により偏光フィルム５ａ_１の温度を下げるために、該サファイア基板５ａ_２の板厚は約０．３×１０^−３ｍ〜１．０×１０^−３ｍとしている。出射側偏光板５ｂについても、明るさとコントラストとを約９８％以上にするために、偏光フィルム５ｂ_１の吸収軸（透過軸）と上記サファイア基板５ａ_２の光学軸（結晶軸）とのなす角が、０゜±０．５゜以内または９０゜±０．５゜以内となるようにしている。偏光フィルム５ｂ_１とサファイア基板５ｂ_２との間では、該サファイア基板５ｂ_２の光学軸（結晶軸）と該偏光フィルム５ｂ_１の吸収軸（透過軸）とのなす角を、０゜±１０゜以内程度または９０゜±１０゜以内程度としておけば実用上特に問題はない。また、サファイア基板５ｂ_２の板厚は、該サファイア基板５ｂ_２の熱伝導により偏光フィルム５ｂ_１の温度を下げるために、上記サファイア基板５ａ_２の場合と同様、約０．３×１０^−３ｍ〜１．０×１０^−３ｍとしている。
本図３に示す出射側偏光板５ａ、５ｂを、上記図２の投射型映像表示装置における出射側偏光板５Ｒ、５Ｇ、５Ｂのそれぞれに替えて用いると、偏光板の温度上昇を抑え、明るさとコントラストを改善した投射型映像表示装置を構成することができる。
【００２０】
図４は、映像表示素子に対する偏光板の第３の組合わせ構成例を示す図である。本構成は、２個の偏光素子を１枚のサファイア基板の両面上に配して成る偏光板を、映像表示素子の出射側に設けた場合の例である。
図４において、２０は映像表示素子としての液晶パネル、４は入射側偏光板、５ｃは出射側偏光板、４１は入射側偏光板４の偏光素子としての偏光フィルム、４２は入射側偏光板４のサファイア基板、５ｃ_１は、出射側偏光板５ｃ内においてサファイア基板に対し液晶パネル２０側に配された偏光素子としての偏光フィルム、５ｃ_２は出射側偏光板５ｃのサファイア基板、５ｃ_３は、出射側偏光板５ｃ内においてサファイア基板５ｃ_２に対し液晶パネル２０と反対側に配された偏光素子としての偏光フィルム、２１は、偏光変換されかつ赤（Ｒ）、緑（Ｇ）、青（Ｂ）いずれかの色光に分離された入射偏光光としてのＰ偏光光またはＳ偏光光、Ｘ−Ｘ’は、入射偏光光２１の直線偏光の偏光方向である。
【００２１】
上記において、入射側偏光板４、出射側偏光板５ｃとも、偏光フィルム４１、５ｃ_１を液晶パネル２０側に配する。出射側偏光板５ｃにおいて、偏光フィルム５ｃ_１、５ｃ_３は、サファイア基板５ｃ_２上に設けられる。偏光フィルム４１と偏光フィルム５ｃ_１、５ｃ_３とは互いに、光の透過軸が約９０゜ずれるようにしてある。Ｐ偏光光またはＳ偏光光の入射偏光光２１は、入射側偏光板４のサファイア基板４２を通過し、偏光フィルム４１に入射する。偏光フィルム４１はＸ−Ｘ’方向を透過軸としている。入射側偏光板４において該サファイア基板４２の結晶軸（光学軸）は、サファイア基板４２の結晶軸（光学軸）が偏光に影響を与えないようにするために、偏光フィルム４１の透過軸（吸収軸）と同じＸ−Ｘ’方向もしくはこれと直交する方向にしてある。該サファイア基板４２の結晶軸（光学軸）の方向が偏光フィルム４１の透過軸（吸収軸）の方向からずれるに従い、該サファイア基板４２の複屈折による直線偏光の楕円偏光への変化量が増大し、その結果、偏光フィルム４１での光の吸収量が増加して光損失が増大し、映像の明るさやコントラストが低下するとともに、偏光板としての発熱量が増大し温度も上昇する。出射側偏光板５ｃについても同様である。
【００２２】
上記構成では、入射側偏光板４における明るさとコントラストとを約９８％以上にするために、該サファイア基板４２の光学軸（結晶軸）と該偏光フィルム４１の吸収軸（透過軸）とのなす角を、９０゜±６゜以内または０゜±６゜以内となるようにしている。また、サファイア基板４２の熱伝導により偏光フィルム４１の温度を下げるために、該サファイア基板４２の板厚は約０．３×１０^−３ｍ〜１．０×１０^−３ｍとしている。入射側偏光板４に対して光の透過軸を９０゜ずらせた出射側偏光板５ｃについても、明るさとコントラストとを約９８％以上にすべく、サファイア基板５ｃ_２の光学軸（結晶軸）と偏光フィルム５ｃ_１、５ｃ_３の吸収軸（透過軸）とのなす角を、０゜±０．５゜以内または９０゜±０．５゜以内となるようにしている。また、サファイア基板５ｃ_２の板厚は、該サファイア基板５ｃ_２の熱伝導により偏光フィルム５ｃ_１、５ｃ_３の温度を下げるために、約０．３×１０^−３ｍ〜１．０×１０^−３ｍとしている。本図４に示す出射側偏光板５ｃを、上記図２の投射型映像表示装置における出射側偏光板５Ｒ、５Ｇ、５Ｂのそれぞれに替えて用いて成る投射型映像表示装置においても、偏光板の温度上昇を抑え、明るさとコントラストの改善を図ることができる。
【００２３】
図５は、上記図１、図３及び図４の構成における、サファイア基板の結晶軸（光学軸）方向と偏光フィルム（偏光素子）の透過軸（吸収軸）方向との角度ズレに対する明るさ及びコントラストの関係の説明図である。
一般に、偏光素子の偏光軸（透過軸また吸収軸）に対して角度θを成して設けられた厚さｔ、複屈折率ｎの部材における光透過率は、入射光の波長をλとするとき、
Ｉ＝Ｉ_０・ｓｉｎ^２（２θ）・ｓｉｎ^２（π・ｔ・ｎ／λ） …（数１）
で表される（例えば、特開平１０−５５００２号公報の段落００１４〜００１５参照）。
【００２４】
図５は、偏光板における明るさ及びコントラストを上記数１により計算した結果を、実測値と併せて示す。
図５において、横軸は、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）との角度ズレ、縦軸は、明るさまたコントラストである。図中、特性Ａは、偏光素子を映像表示素子側に配しサファイア基板をその反対側に配した偏光板の特性、特性Ａ_１は、特性Ａのうち、上記数１により求めた明るさ及びコントラストの計算結果、特性Ａ_２は、同じく特性Ａのうち、明るさの実測結果、特性Ａ_３は、同じく特性Ａのうち、コントラストの実測結果である。また、特性Ｂは、偏光素子をサファイア基板に対し映像表示素子とは反対の側に配した偏光板のコントラスト特性、特性Ｂ_１は、特性Ｂのうち、上記数１により求めたコントラストの計算結果、特性Ｂ_２は、同じく特性Ｂのうち、コントラスト特性の実測結果である。図１、図３及び図４における入射側偏光板４の偏光フィルム４１とサファイア基板４２と間では、上記特性Ａを有する。また、図３における出射側偏光板５ａのサファイア基板５ａ_２と出射側偏光板５ｂの偏光フィルム５ｂ_１との間では、偏光フィルム５ｂ_１が、サファイア基板５ａ_２の複屈折による乱れた偏光成分を吸収するため、コントラスト及び明るさが、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）との角度ズレに対し急激に低下し、上記特性Ｂを有する。図４における出射側偏光板５ｃのサファイア基板５ｃ_２と偏光フィルム５ｃ_３との間でも同様に、偏光フィルム５ｃ_３が、サファイア基板５ｃ_２の複屈折による乱れた偏光成分を吸収するため、コントラスト及び明るさが急激に低下し、上記特性Ｂを有する。図３における出射側偏光板５ａの偏光フィルム５ａ_１は、出射側偏光板５ｂの偏光フィルム５ｂ_１と同じ透過軸方向とされ、図４における出射側偏光板５ｃの偏光フィルム５ｃ_１は、偏光フィルム５ｃ_３と同じ透過軸方向とされる。
【００２５】
上記の結果、特性Ａにおいては、偏光板における明るさとコントラストとを例えば約９８％以上とするためには、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）との角度ズレが±６°以内であることが必要である。また、特性Ｂにおいては、偏光板におけるコントラストを例えば約９８％以上とするためには、該角度ズレが±０．５°以内であることが必要である。すなわち、図１、図３及び図４における入射側偏光板４の偏光フィルム４１とサファイア基板４２と間では、サファイア基板４２の光学軸（結晶軸）と偏光フィルム４１の吸収軸（透過軸）との角度ズレを±６°以内とし、該サファイア基板４２の光学軸（結晶軸）と該偏光フィルム４１の吸収軸（透過軸）とのなす角を、９０゜±６゜以内または０゜±６゜以内となるようにする。また、図３における出射側偏光板５ａのサファイア基板５ａ_２と出射側偏光板５ｂの偏光フィルム５ｂ_１との間、及び、図４における出射側偏光板５ｃのサファイア基板５ｃ_２と偏光フィルム５ｃ_３との間では、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）との角度ズレを±０．５°以内とし、該サファイア基板の光学軸（結晶軸）と該偏光フィルムの吸収軸（透過軸）とのなす角を、９０゜±０．５゜以内または０゜±０．５゜以内となるようにする。図３における出射側偏光板５ａの偏光フィルム５ａ_１は上記のように、出射側偏光板５ｂの偏光フィルム５ｂ_１と同じ透過軸方向とされるため、サファイア基板５ａ_２との間で、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）との角度ズレを±０．５°以内とされ、該サファイア基板の光学軸（結晶軸）と該偏光フィルムの吸収軸（透過軸）とのなす角を、９０゜±０．５゜以内または０゜±０．５゜以内とされる。図４における出射側偏光板５ｃの偏光フィルム５ｃ_１についても同様に、偏光フィルム５ｃ_３と同じ透過軸方向とされるため、サファイア基板５ｃ_２との間で、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）との角度ズレを±０．５゜以内とされ、該サファイア基板の光学軸（結晶軸）と該偏光フィルムの吸収軸（透過軸）とのなす角を、９０゜±０．５゜以内または０゜±０．５゜以内とされる。図１における出射側偏光板５の偏光フィルム５１とサファイア基板５２との間及び図３における出射側偏光板５ｂの偏光フィルム５ｂ_１とサファイア基板５ｂ_２との間では、明るさとコントラストが、光学系内において後段に配されるダイクロイックプリズム１１に依存するため、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）とのなす角の角度ズレを±６°以内にする必要はなく、±１０°程度としても問題にならない。
【００２６】
偏光板における明るさとコントラストを約９８％以上とすることは、装置の省電力化や偏光板の温度上昇阻止を図る点からも今後の１つの設計基準となり得る。例えば図２の投射型映像表示装置において、光学系における輝度の許容低下率を約１０％以内としたとき、偏光板における光の吸収量は約２％以下とすることが求められる。本図５の結果から、サファイア基板の板厚を約０．３×１０^−３ｍ〜１．０×１０^−３ｍの範囲とし、サファイア基板の結晶軸（光学軸）方向と偏光フィルム（偏光素子）の透過軸（吸収軸）方向との角度ズレを±６゜以内の値とし、サファイア基板の光学軸と偏光素子の吸収軸とのなす角を９０゜±６゜以内または０゜±６゜以内とすることで、偏光板における損失光量を約２％以下に抑えることができると考えられる。
【００２７】
図６は、偏光板の温度特性の実測結果例を示す図である。
図６において、横軸には基板の板厚を、縦軸には偏光フィルムの温度をとっている。本特性は、図２に示した投射型映像表示装置における実測値であり、測定条件は、周囲温度Ｔａは２５゜Ｃ、光源は１５５Ｗ仕様の超高圧水銀ランプ、液晶パネルは０．７インチパネル、測定対象の偏光板は、入力側偏光板４Ｇ、その偏光フィルムの寸法は縦２１．５×１０^−３ｍ、横１８．０×１０^−３ｍ、基板は、縦２３．５×１０^−３ｍ、横２０．０×１０^−３ｍのサファイア基板とガラス基板の場合、である。
【００２８】
図６の結果から明らかなように、サファイア基板、ガラス基板とも、板厚が薄いほど基板の熱伝導性が向上し偏光フィルムの温度は低くなる。熱伝導率は、ガラスが０．５５〜０．７５（Ｗ／ｍＫ）、サファイアが約４２（Ｗ／ｍＫ）である。一般に、偏光フィルムは耐用年数と熱変形による色ムラ（輝度ムラ）発生の点から７０゜Ｃ以下の温度範囲で使用するのが望ましい。周囲温度の許容上限温度の３５゜Ｃにおいて偏光フィルムの温度が７０゜Ｃになるとすると、周囲温度が常温の２５゜Ｃの場合は、偏光フィルムの温度は６０゜Ｃとなる。図６の結果では、サファイア基板の場合、板厚が１．０ｍｍでは偏光フィルムの温度は約５７゜Ｃ、板厚が０．３ｍｍでは偏光フィルムの温度は約５５゜Ｃとなり、板厚を１．０ｍｍ以下とすれば、周囲温度が許容上限温度の３５゜Ｃに達した場合にも、偏光フィルムの温度は７０゜Ｃ以下にすることができる。また、サファイア基板において、例えば加工時における平面精度や破壊強度の確保を考慮した場合、板厚０．３ｍｍは１つの下限値となる。従って、上記理由から、サファイア基板の板厚は、０．３ｍｍ〜１．０ｍｍが適切であると考えられる。
【００２９】
上記実施例構成によれば、投射型映像表示装置において、偏光板の放熱性の確保と併せ、映像の明るさ及びコントラストも確保することができる。また、一部または全部の偏光板において、サファイア基板の光学軸（結晶軸）と偏光フィルムの吸収軸（透過軸）とのなす角のズレの許容範囲を、例えば特許第３０９１１８３号明細書に記載された±２゜以内であって望ましくは±０．５゜以内という範囲に対し大幅に大きくすることができるため、部品精度や組立て精度を緩和でき、偏光板単体、光学ユニット及び投射型映像表示装置の製作性の向上と低コスト化につなげることが可能となる。
なお、上記実施例では投射型映像表示装置として映像表示素子としての液晶パネルを３個用いるものにつき説明したが、本発明はこれには限定されず、例えば液晶パネル等の映像表示素子を１個用いる構成のものであってもよい。また、偏光板としては、偏光素子とサファイア基板とが離れて配される構成のものであってもよい。さらに、偏光板の基板としては、サファイア基板に限らず、他の熱伝導率の良好な１軸性結晶体を用いることも可能である。
【００３０】
【発明の効果】
本発明によれば、投射型映像表示装置において、偏光板の放熱性の確保と併せ、映像の明るさ及びコントラストも確保することができる。また、部品精度や組立て精度を緩和でき、製作性の向上と低コスト化が可能となる。
【図面の簡単な説明】
【図１】本発明の実施例として、映像表示素子に対する偏光板の第１の組合わせ構成例を示す図である。
【図２】図１の組合わせ構成を用いた投射型映像表示装置の構成例を示す図である。
【図３】本発明の実施例として、映像表示素子に対する偏光板の第２の組合わせ構成例を示す図である。
【図４】本発明の実施例として、映像表示素子に対する偏光板の第３の組合わせ構成例を示す図である。
【図５】サファイア基板の結晶軸角度ズレに対する明るさ及びコントラストの関係を示す図である。
【図６】偏光板の温度特性の実測結果例を示す図である。
【符号の説明】
１…光源ユニット、２０Ｒ、２０Ｇ、２０Ｂ…液晶表示素子、３…投射レンズユニット、４、４Ｒ、４Ｇ、４Ｂ…入射側偏光板、４１、５１、５ａ_１、５ｂ_１、５ｃ_１、５ｃ_３…偏光フィルム、４２、５２、５ａ_２、５ｂ_２、５ｃ_２…サファイア基板、５Ｒ、５Ｇ、５Ｂ、５ａ、５ｂ、５ｃ…出射側偏光板、６…第１のアレイレンズ、７…第２のアレイレンズ、８…偏光変換素子、９…集光レンズ、１０Ｒ、１０Ｇ、１０Ｂ…コンデンサレンズ、１１…ダイクロイックプリズム、１２、１３…ダイクロイックミラー、１４、１５、１６…反射ミラー、１７、１８…リレーレンズ、１９…スクリーン、２１…光路、２６…冷却用ファン、２７…冷却用空気の流路。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a projection-type image display apparatus that converts light from a light source into a polarized light, irradiates the light to an image display element, and forms and projects an optical image in accordance with an image signal.
[0002]
[Prior art]
Conventionally, in a projection-type image display device, as a polarizing plate for passing light incident on an image display element such as a liquid crystal panel, or light emitted from the image display element having a predetermined polarization direction, In order to prevent a polarizing film serving as a polarizing element from being deformed by a rise in temperature due to absorption of light from a light source, the polarizing film is attached to a light-transmitting substrate. In connection with the present invention, as a conventional technology in which the substrate is made of sapphire from the viewpoint of heat dissipation, there is, for example, a technology described in Japanese Patent No. 3091183 (Patent Document 1). The patent specification discloses that the angle between the C-axis direction or the C-axis projection line direction and the polarization transmission axis to be transmitted is within ± 2 °, or the polarization transmission axis to be transmitted to the axis perpendicular to the C-axis, as the sapphire substrate. A configuration is described in which the angle between the axis and the plane is within ± 2 ° or the angle between the C plane and the plane perpendicular to the transmission direction of polarized light to be transmitted is within ± 2 °.
[0003]
[Patent Document 1]
Patent No. 3091183
[0004]
[Problems to be solved by the invention]
In the above prior art, the angle formed between the C-axis direction or the C-axis projection line direction and the polarization transmission axis to be transmitted is within ± 2 °, and preferably within ± 0.5 °, so that the entire angle range is narrow. In order to satisfy this requirement, high component accuracy is required, which is considered to lead to an increase in manufacturing cost. Further, when the sapphire substrate is disposed on the liquid crystal panel (video display element) side, the contrast may be significantly deteriorated.
The problem of the present invention is to provide a projection-type image display device technology using a polarizing plate provided with a sapphire substrate in view of the above-mentioned conventional technology. (2) To be able to improve the productivity by relaxing the component accuracy and to reduce the cost, and the like.
An object of the present invention is to provide a technique capable of solving such a problem.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, in order to configure a projection type video display device or its optical unit, basically,
(1) A polarizing plate having a polarizing element held by a sapphire substrate, wherein the polarizing plate arranged on the light incident side of the image display element is disposed inside the polarizing plate such that the polarizing element is located on the image display element side. The substrate is disposed on the opposite side, and the angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is within 90 ° ± 6 ° (excluding the range of ± 2 °) or 0 ° ± 6 ° (± 2 °). (Excluding the range of ゜).
(2) Polarizing plates are arranged on the light incident side and the light emitting side of the image display element, and the two polarizing plates are each configured so that the polarizing element is held on the sapphire substrate on the image display element side. The angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is within 90 ° ± 6 ° (excluding the range of ± 2 °) or 0 ° ± 6 ° (± 2 °). (Excluding the range of ゜)).
(3) polarizing plates are arranged on the light incident side and the light emitting side of the image display element, and the polarizing plate arranged on the light incident side is held on the sapphire substrate with the polarizing element facing the image display element; The angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is within 90 ° ± 6 ° (excluding the range of ± 2 °) or 0 ° ± 6 ° (excluding the range of ± 2 °). The polarizing plate disposed on the light emitting side is provided with a polarizing element disposed on both sides of the sapphire substrate, and the angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element on the both sides is 90 °. It shall be within ± 0.5 ° or within 0 ± 0.5 °.
further,
(4) In any one of the above (1) to (3), the sapphire substrate may have a thickness of about 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 6 are explanatory diagrams of an embodiment of the present invention. 1 is a diagram showing a first configuration example of a combination of a polarizing plate and an image display element, FIG. 2 is a diagram showing a configuration example of a projection type video display device using the combination configuration of FIG. 1, and FIG. FIG. 4 is a diagram showing a second configuration example of a polarizing plate for an image display device, FIG. 4 is a diagram showing a third configuration example of a polarizing plate for an image display device, and FIG. 5 is a sapphire substrate constituting the polarizing plate FIG. 6 is a diagram showing the relationship between brightness and contrast with respect to the crystal axis angle shift, and FIG. 6 is a diagram showing an example of actual measurement results of temperature characteristics of a polarizing plate.
[0007]
In FIG. 1, reference numeral 20 denotes a liquid crystal panel as an image display element, 4 denotes an incident side polarizing plate, 5 denotes an outgoing side polarizing plate, 41 denotes a polarizing film as a polarizing element of the incident side polarizing plate 4, and 42 denotes an incident side polarizing plate 4. Substrate 51, a polarizing film 51 as a polarizing element of the output side polarizing plate 5, 52 a sapphire substrate of the output side polarizing plate 5, and 21 a polarization-converted and color-separated red (R), green (G) ) Or blue (B) incident polarized light. XX ′ is the polarization direction of the linearly polarized light of the incident light 21.
[0008]
In the above configuration, the polarizing films 41 and 51 are arranged on the liquid crystal panel side for both the incident side polarizing plate 4 and the emitting side polarizing plate 5. The polarizing film 41 and the polarizing film 51 are configured such that the light transmission axes are shifted from each other by about 90 °. The incident polarized light 21 of the P-polarized light or the S-polarized light passes through the sapphire substrate 42 of the incident-side polarizing plate 4 and enters the polarizing film 41. The polarizing film 41 has a transmission axis in the XX ′ direction. The crystal axis (optical axis) of the sapphire substrate 42 is the same as the transmission axis (absorption axis) of the polarizing film 41 in order to prevent the crystal axis (optical axis) of the sapphire substrate 42 from affecting the polarization. The direction is set to the X 'direction or a direction perpendicular thereto. As the direction of the crystal axis (optical axis) of the sapphire substrate 42 shifts from the direction of the transmission axis (absorption axis) of the polarizing film 41, the amount of change of linearly polarized light into elliptically polarized light due to birefringence of the sapphire substrate 42 increases. As a result, the amount of light absorbed by the polarizing film 41 increases, the light loss increases, the brightness and contrast of an image decrease, and the amount of heat generation also increases.
[0009]
In the above configuration, the angle between the optical axis (crystal axis) of the sapphire substrate 42 and the absorption axis (transmission axis) of the polarizing film 41 must be 90 ° ± 90% in order to make the brightness and the contrast about 98% or more. It is set to be within 6 ° or within 0 ° ± 6 ° (described in FIG. 5). Further, in order to lower the temperature of the polarizing film 41 by heat conduction of the sapphire substrate 42, the thickness of the sapphire substrate 42 is about 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m. Regarding the emission-side polarizing plate 5 whose transmission axis of light is shifted by 90 ° with respect to the incidence-side polarization plate 4, the angle between the optical axis (crystal axis) of the sapphire substrate 52 and the absorption axis (transmission axis) of the polarizing film 51 is set. , 0 ° ± 10 ° or 90 ° ± 10 °, there is no practical problem. The thickness of the sapphire substrate 52 is about 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m.
[0010]
FIG. 2 is an example of the configuration of a projection type image display device using the polarizing plate of FIG.
In FIG. 2, 1 is a light source unit, 6 is a first array lens formed of a plurality of minute lens cells and forms a plurality of secondary light source images, and 7 is formed of a plurality of minute lens cells. The second array lens 8, which forms an individual lens image of the array lens, is composed of a polarizing beam splitter (not shown) and a half-wave retardation plate (not shown). A polarization conversion element that separates light from the 7 side into P-polarized light and S-polarized light, and then rotates one of the polarization directions of the two polarized lights to align it with either P or S polarized light and emits the same. , 9 are condenser lenses, 12 and 13 are dichroic mirrors for color separation, 10R, 10G, and 10B are condenser lenses, 14, 15, and 16 are reflection mirrors, 17, 18 are relay lenses, and 20R, 20G, and 20B are images. display The transmission type liquid crystal panel as a child, 4R is the incident side polarization plate of the liquid crystal panel 20R, 5R is the exit side polarization plate of the liquid crystal panel 20R, 4G is the incidence side polarization plate of the liquid crystal panel 20G, 5G is the exit side polarization of the liquid crystal panel 20G. Plate, 4B is an incident side polarizer of the liquid crystal panel 20B, 5G is an exit side polarizer of the liquid crystal panel 20G, 11 is a dichroic prism for color synthesis, 3 is a projection lens unit for enlarging and projecting image light, and 19 is a screen. , 26 are cooling fans, and 27 is a cooling air flow path. It is assumed that the incident-side polarizing plates 4R, 4G, and 4B and the outgoing-side polarizing plates 5R, 5G, and 5B each have the configuration shown in FIG. Each of the liquid crystal panels 20R, 20G, and 20B is driven by a drive circuit (not shown) based on a video signal, and modulates and emits incident polarized light. The relay lenses 17 and 18 are provided to compensate for the fact that the optical path length from the light source unit 1 of the liquid crystal panel 20B is longer than that of the liquid crystal panels 20R and 20G. The above elements from the light source unit 1 to the projection lens unit 3 constitute an optical unit in a projection type video display.
[0011]
In such a configuration, the light (white light) emitted from the light source unit 1 forms a plurality of secondary light source images with the first array lens 6 and then forms the plurality of secondary light images with the second array lens 7. A light source image is formed, and the formed light is separated into a P-polarized light and an S-polarized light by a polarizing beam splitter (not shown) in the polarization conversion element 8, and a half-wave retardation plate (shown in FIG. No), for example, the P-polarized light is rotated in the polarization direction to become S-polarized light, and is incident on the condenser lens 9 together with the S-polarized light separated by the polarization beam splitter. The white S-polarized light condensed by the condenser lens 9 is incident on the dichroic mirror 12 at an incident angle of about 45 °. The dichroic mirror 12 reflects the S-polarized light of the R light and transmits the S-polarized light of the G light and the B light.
[0012]
The reflected S-polarized light of the R light is reflected by the reflection mirror 14, changes the optical path, and is incident on the incident-side polarizing plate 4R of the transmission liquid crystal panel 20R for the R light via the condenser lens 10R. The S-polarized light of the R light is transmitted through the incident-side polarizing plate 4R in the direction of the transmission axis of the incident-side polarizing plate 4R so that the polarization directions thereof are aligned, and is transmitted to the transmissive liquid crystal panel 20R for the R light. Irradiated. In the liquid crystal panel 20R, the S-polarized light of the R light is modulated based on a video signal when transmitted, and is emitted as P-polarized light of the R light. The P-polarized light of the R light emitted from the liquid crystal panel 20R is incident on the emission-side polarizing plate 5R, and is polarized by being transmitted through the emission-side polarizing plate 5R in the transmission axis direction of the emission-side polarizing plate 5R. The directions are aligned and the light enters the dichroic prism 11. In the dichroic prism 11, the light is reflected by the dichroic surface and enters the projection lens unit 3.
[0013]
On the other hand, the S-polarized light of the G light and the B light transmitted through the dichroic mirror 12 further enters the dichroic mirror 13 at an incident angle of about 45 °, and the S-polarized light of the G light is reflected by the dichroic mirror 13. , B light is transmitted. The reflected S-polarized light of the G light is incident on the incident-side polarizing plate 4G of the transmission liquid crystal panel 20G for the G light via the condenser lens 10G.
The S-polarized light of the G light is transmitted through the incident-side polarizing plate 4G in the direction of the transmission axis of the incident-side polarizing plate 4G so that the polarization directions thereof are aligned, and is transmitted to the G-light transmissive liquid crystal panel 20G. Irradiated. In the liquid crystal panel 20G, the S-polarized light of the G light is modulated based on a video signal when transmitted, and is emitted as P-polarized light of the G light. The P-polarized light of the G light emitted from the liquid crystal panel 20G is incident on the emission-side polarizing plate 5G, and is polarized by being transmitted through the emission-side polarizing plate 5G in the transmission axis direction of the emission-side polarizing plate 5G. The directions are aligned and the light enters the dichroic prism 11. The P-polarized light of the G light is reflected by the dichroic surface in the dichroic prism 11 and enters the projection lens unit 3.
[0014]
The S-polarized light of the B light transmitted through the dichroic mirror 13 is reflected by the reflection mirror 15 through the relay lens 17, further reflected by the reflection mirror 16 through the relay lens 18, and is reflected by the condenser lens 10B. Incident on the incident side polarizing plate 4B of the transmission type liquid crystal panel 20B. The S-polarized light of the B light is transmitted through the incident-side polarizing plate 4B in the direction of the transmission axis of the incident-side polarizing plate 4B so that the polarization directions thereof are aligned, and the transmission type liquid crystal panel 20B for the B light is transmitted. Is irradiated. In the liquid crystal panel 20B, the S-polarized light of the B light is modulated based on a video signal when transmitted, and is emitted as P-polarized light of the B light. The P-polarized light of the B light emitted from the liquid crystal panel 20B is incident on the emission-side polarizing plate 5B, and is polarized by transmitting the light in the transmission axis direction of the emission-side polarizing plate 5G in the emission-side polarizing plate 5B. The directions are aligned and the light enters the dichroic prism 11. In the dichroic prism 11, the P-polarized light of the B light is reflected by the dichroic surface and enters the projection lens unit 3.
That is, as described above, from the dichroic prism 11, the P-polarized light of the R light, the P-polarized light of the G light, and the P-polarized light of the B light modulated by the video signal are color-combined with each other. The light is emitted, enters the projection lens unit 3 as P-polarized light of white light, and is enlarged and projected as image light on a screen 19 by the projection lens unit 3.
[0015]
In the above configuration, in each of the incident-side polarizing plates 4R, 4G, and 4B and each of the outgoing-side polarizing plates 5R, 5G, and 5B, light that cannot pass through the transmission axis of each of the polarizing films is absorbed by the corresponding polarizing film and becomes heat. And raise the temperature of each polarizing film. The sapphire substrate radiates the heat of the polarizing film due to its heat radiation characteristics, and suppresses the temperature rise of the polarizing film and the polarizing plate as a whole. The cooling fan 26 forms a flow path 27 by a cooling duct (not shown) or the like, and each of the incident side polarizing plates 4R, 4G, 4B, each of the emitting side polarizing plates 5R, 5G, 5B, and each of the liquid crystal panels 20R, 20G. , 20B, etc. to cool them.
[0016]
In the above configuration example, the polarization conversion element 8 emits S-polarized light as a result of polarization conversion. However, the present invention is not limited to this, and P-polarized light may be emitted. In this case, the P-polarized light of each of the R, G, and B color lights passes through each of the incident-side polarizing plates 4R, 4G, and 4B, and irradiates the corresponding liquid crystal panels 20R, 20G, and 20B. At 20G and 20B, the light is modulated based on the video signal at the time of transmission, is emitted as S-polarized light of each of R, G, and B color lights, and is color-combined by the dichroic prism 11.
[0017]
FIG. 3 is a diagram illustrating a second configuration example of a combination of a polarizing plate and an image display element. This configuration is an example in which one polarizing plate having a polarizing element disposed on the image display element side is provided on the incident side of the image display element and two on the output side. The sapphire substrate of each of the two polarizing plates enhances the heat radiation effect on the emission side, and suppresses an excessive rise in temperature of the polarizing element.
In FIG. 3, reference numeral 20 denotes a liquid crystal panel as an image display element, 4 denotes an incident side polarizing plate, 5a and 5b denote outgoing side polarizing plates, 41 denotes a polarizing film as a polarizing element of the incident side polarizing plate 4, and 42 denotes an incident side polarized light. Sapphire substrate of plate 4, 5a ₁ Denotes a polarizing film as a polarizing element of the output-side polarizing plate 5a, 5a ₂ Denotes the sapphire substrate of the output side polarizing plate 5a and 5b ₁ Denotes a polarizing film as a polarizing element of the output side polarizing plate 5b, 5b ₂ Is a sapphire substrate of the output-side polarizing plate 5b, and 21 is P-polarized light or S-polarized light as incident polarized light that has been polarization-converted and separated into red (R), green (G), or blue (B) color light. It is polarized light. XX ′ is the polarization direction of the linearly polarized light of the incident polarized light 21. Polarizing film 5a ₁ As the polarizing film 5b ₁ Used is one having a high degree of polarization (almost 100%).
[0018]
In the above description, the polarizing films 41 and 5a are used for both the incident-side polarizing plate 4 and the emitting-side polarizing plates 5a and 5b. ₁ , 5b ₁ Is disposed on the liquid crystal panel 20 side. Polarizing film 5a ₁ , 5b ₁ Is the sapphire substrate 5a ₂ Are arranged on both sides. Polarizing film 41 and polarizing film 5a ₁ , 5b ₁ And the light transmission axes are shifted from each other by about 90 °. The incident polarized light 21 of the P-polarized light or the S-polarized light passes through the sapphire substrate 42 of the incident-side polarizing plate 4 and enters the polarizing film 41. The polarizing film 41 has a transmission axis in the XX ′ direction. The crystal axis (optical axis) of the sapphire substrate 42 in the incident-side polarizing plate 4 is set so that the crystal axis (optical axis) of the sapphire substrate 42 does not affect the polarization. Axis) or the direction orthogonal thereto. As the direction of the crystal axis (optical axis) of the sapphire substrate 42 deviates from the direction of the transmission axis (absorption axis) of the polarizing film 41, the amount of change of linearly polarized light into elliptically polarized light due to birefringence of the sapphire substrate 42 increases. As a result, the amount of light absorbed by the polarizing film 41 increases, the light loss increases, the brightness and contrast of an image decrease, and the amount of heat generated by the polarizing plate increases, and the temperature also increases. The same applies to the emission-side polarizing plates 5a and 5b.
[0019]
In the above configuration, the angle between the optical axis (crystal axis) of the sapphire substrate 42 and the absorption axis (transmission axis) of the polarizing film 41 is set so that the brightness and the contrast of the polarizing plate 4 are about 98% or more. It is set to be within 90 ° ± 6 ° or within 0 ° ± 6 °. Further, in order to lower the temperature of the polarizing film 41 by heat conduction of the sapphire substrate 42, the thickness of the sapphire substrate 42 is about 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m. The emission-side polarization plates 5a and 5b whose light transmission axes are shifted by 90 ° with respect to the incidence-side polarization plate 4 also have an optical axis (crystal axis) of the sapphire substrate that is about 98% or more in brightness and contrast. The angle between the polarizing film and the absorption axis (transmission axis) is set to a value within a predetermined range. For the emission-side polarizing plate 5a, the sapphire substrate 5a ₂ Optical axis (crystal axis) and polarizing film 5a ₁ Is set to a value within 0 ° ± 0.5 ° or within 90 ° ± 0.5 ° (described with reference to FIG. 5). The sapphire substrate 5a ₂ Film 5a by heat conduction of ₁ The sapphire substrate 5a ₂ Is about 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m. The output side polarizing plate 5b is also provided with a polarizing film 5b in order to make the brightness and contrast about 98% or more. ₁ Absorption axis (transmission axis) and the sapphire substrate 5a ₂ Are made to be within 0 ° ± 0.5 ° or within 90 ° ± 0.5 °. Polarizing film 5b ₁ And sapphire substrate 5b ₂ Between the sapphire substrate 5b ₂ Optical axis (crystal axis) and the polarizing film 5b ₁ There is no practical problem if the angle between the above and the absorption axis (transmission axis) is set to about 0 ° ± 10 ° or about 90 ° ± 10 °. The sapphire substrate 5b ₂ Of the sapphire substrate 5b ₂ Film 5b by heat conduction of ₁ In order to lower the temperature of the sapphire substrate 5a, ₂ About 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m.
When the output-side polarizing plates 5a and 5b shown in FIG. 3 are used in place of the output-side polarizing plates 5R, 5G and 5B in the projection-type image display device shown in FIG. And a projection-type image display device with improved contrast.
[0020]
FIG. 4 is a diagram illustrating a third configuration example of a combination of a polarizing plate and an image display element. This configuration is an example in which a polarizing plate having two polarizing elements arranged on both surfaces of one sapphire substrate is provided on the emission side of the image display element.
4, reference numeral 20 denotes a liquid crystal panel as an image display element, 4 denotes an incident side polarizing plate, 5c denotes an outgoing side polarizing plate, 41 denotes a polarizing film as a polarizing element of the incident side polarizing plate 4, and 42 denotes an incident side polarizing plate 4. Sapphire substrate, 5c ₁ Are polarizing films 5c as polarizing elements disposed on the liquid crystal panel 20 side with respect to the sapphire substrate in the output side polarizing plate 5c. ₂ Denotes the sapphire substrate of the output side polarizing plate 5c, 5c ₃ Is a sapphire substrate 5c in the output side polarizing plate 5c. ₂ In contrast, a polarizing film 21 as a polarizing element disposed on the side opposite to the liquid crystal panel 20 is an incident polarized light that has been polarization-converted and separated into one of red (R), green (G), and blue (B) color lights. P-polarized light or S-polarized light as light, XX ′, is the polarization direction of the linearly polarized light of the incident polarized light 21.
[0021]
In the above, both the incident side polarizing plate 4 and the exit side polarizing plate 5c are polarizing films 41 and 5c. ₁ Is disposed on the liquid crystal panel 20 side. In the output side polarizing plate 5c, the polarizing film 5c ₁ , 5c ₃ Is the sapphire substrate 5c ₂ Provided above. Polarizing film 41 and polarizing film 5c ₁ , 5c ₃ And the light transmission axes are shifted from each other by about 90 °. The incident polarized light 21 of the P-polarized light or the S-polarized light passes through the sapphire substrate 42 of the incident-side polarizing plate 4 and enters the polarizing film 41. The polarizing film 41 has a transmission axis in the XX ′ direction. The crystal axis (optical axis) of the sapphire substrate 42 in the incident-side polarizing plate 4 is set so that the crystal axis (optical axis) of the sapphire substrate 42 does not affect the polarization. Axis) or the direction orthogonal thereto. As the direction of the crystal axis (optical axis) of the sapphire substrate 42 deviates from the direction of the transmission axis (absorption axis) of the polarizing film 41, the amount of change of linearly polarized light into elliptically polarized light due to birefringence of the sapphire substrate 42 increases. As a result, the amount of light absorbed by the polarizing film 41 increases, the light loss increases, the brightness and contrast of an image decrease, and the amount of heat generated by the polarizing plate increases, and the temperature also increases. The same applies to the emission-side polarizing plate 5c.
[0022]
In the above configuration, the optical axis (crystal axis) of the sapphire substrate 42 and the absorption axis (transmission axis) of the polarizing film 41 are formed so that the brightness and contrast of the incident-side polarizing plate 4 are about 98% or more. The angle is set to be within 90 ° ± 6 ° or 0 ° ± 6 °. Further, in order to lower the temperature of the polarizing film 41 by heat conduction of the sapphire substrate 42, the thickness of the sapphire substrate 42 is about 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m. The sapphire substrate 5c is also used for the output-side polarizing plate 5c whose transmission axis is shifted by 90 ° with respect to the input-side polarizing plate 4 so that the brightness and the contrast are about 98% or more. ₂ Optical axis (crystal axis) and polarizing film 5c ₁ , 5c ₃ Is made within 0 ° ± 0.5 ° or 90 ° ± 0.5 °. The sapphire substrate 5c ₂ Of the sapphire substrate 5c ₂ Film 5c by heat conduction of ₁ , 5c ₃ About 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m. The projection-type image display device in which the emission-side polarizing plate 5c shown in FIG. 4 is used instead of each of the emission-side polarization plates 5R, 5G, and 5B in the projection-type image display device of FIG. Temperature rise can be suppressed, and brightness and contrast can be improved.
[0023]
FIG. 5 shows the brightness and the brightness with respect to the angular deviation between the crystal axis (optical axis) direction of the sapphire substrate and the transmission axis (absorption axis) direction of the polarizing film (polarizing element) in the configurations of FIGS. 1, 3 and 4 described above. FIG. 4 is an explanatory diagram of a relationship between contrasts.
Generally, the light transmittance of a member having a thickness t and a birefringence n provided at an angle θ with respect to the polarization axis (transmission axis or absorption axis) of the polarizing element is represented by the wavelength of the incident light being λ. When
I = I ₀ ・ Sin ² (2θ) · sin ² (Π · t · n / λ) (Equation 1)
(For example, refer to paragraphs 0014 to 0015 of JP-A-10-55002).
[0024]
FIG. 5 shows the results of calculating the brightness and the contrast of the polarizing plate according to the above equation 1 together with the actually measured values.
In FIG. 5, the horizontal axis represents the angle deviation between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film, and the vertical axis represents brightness or contrast. In the figure, the characteristic A is the characteristic and characteristic A of the polarizing plate in which the polarizing element is arranged on the image display element side and the sapphire substrate is arranged on the opposite side. ₁ Is the calculation result of the brightness and the contrast obtained by the above equation 1 among the characteristics A, ₂ Is the brightness measurement result of the characteristic A, the characteristic A ₃ Is the measurement result of the contrast in the characteristic A. The characteristic B is a contrast characteristic and a characteristic B of a polarizing plate in which the polarizing element is disposed on the side opposite to the image display element with respect to the sapphire substrate. ₁ Is the calculation result of the contrast obtained by the above equation 1 among the characteristics B, ₂ Is an actual measurement result of the contrast characteristic of the characteristic B. The characteristic A described above is provided between the polarizing film 41 of the incident side polarizing plate 4 and the sapphire substrate 42 in FIGS. Further, the sapphire substrate 5a of the output side polarizing plate 5a in FIG. ₂ And polarizing film 5b of output side polarizing plate 5b ₁ Between the polarizing film 5b ₁ Is the sapphire substrate 5a ₂ Absorbs the polarized component disturbed by the birefringence of the above, the contrast and the brightness decrease sharply with respect to the angular deviation between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film. It has characteristic B. Sapphire substrate 5c of emission-side polarizing plate 5c in FIG. ₂ And polarizing film 5c ₃ Similarly, the polarizing film 5c ₃ Sapphire substrate 5c ₂ Absorbs the polarized component disturbed by the birefringence of the above, the contrast and brightness are sharply reduced, and has the characteristic B. Polarizing film 5a of output-side polarizing plate 5a in FIG. ₁ Is the polarizing film 5b of the output side polarizing plate 5b ₁ 4. The polarizing film 5c of the output side polarizing plate 5c in FIG. ₁ Is a polarizing film 5c ₃ And the same transmission axis direction.
[0025]
As a result, in the characteristic A, in order to make the brightness and contrast of the polarizing plate about 98% or more, for example, the angle between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film. The deviation must be within ± 6 °. In the characteristic B, in order to make the contrast in the polarizing plate, for example, about 98% or more, the angle deviation needs to be within ± 0.5 °. That is, the optical axis (crystal axis) of the sapphire substrate 42 and the absorption axis (transmission axis) of the polarizing film 41 between the polarizing film 41 of the incident side polarizing plate 4 and the sapphire substrate 42 in FIGS. And the angle between the optical axis (crystal axis) of the sapphire substrate 42 and the absorption axis (transmission axis) of the polarizing film 41 is within 90 ° ± 6 ° or 0 ° ± 6 °. Within ゜. Further, the sapphire substrate 5a of the output side polarizing plate 5a in FIG. ₂ And polarizing film 5b of output side polarizing plate 5b ₁ And the sapphire substrate 5c of the output side polarizing plate 5c in FIG. ₂ And polarizing film 5c ₃ The angle deviation between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film is within ± 0.5 °, and the optical axis (crystal axis) of the sapphire substrate and the polarization axis The angle between the film and the absorption axis (transmission axis) should be within 90 ° ± 0.5 ° or within 0 ° ± 0.5 °. Polarizing film 5a of output-side polarizing plate 5a in FIG. ₁ Is the polarizing film 5b of the output side polarizing plate 5b as described above. ₁ Sapphire substrate 5a ₂ Between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film is within ± 0.5 °, and the optical axis (crystal axis) of the sapphire substrate is The angle between the polarizing film and the absorption axis (transmission axis) is 90 ° ± 0.5 ° or 0 ° ± 0.5 °. Polarizing film 5c of output side polarizing plate 5c in FIG. ₁ Similarly, the polarizing film 5c ₃ Sapphire substrate 5c ₂ Between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film is within ± 0.5 °, and the optical axis (crystal axis) of the sapphire substrate and the The angle between the polarizing film and the absorption axis (transmission axis) is 90 ° ± 0.5 ° or 0 ° ± 0.5 °. 1. Between the polarizing film 51 of the output side polarizing plate 5 and the sapphire substrate 52 in FIG. 1 and the polarizing film 5b of the output side polarizing plate 5b in FIG. ₁ And sapphire substrate 5b ₂ Since the brightness and the contrast depend on the dichroic prism 11 arranged at a later stage in the optical system, the angle formed between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film. Does not need to be within ± 6 °, and there is no problem even if it is about ± 10 °.
[0026]
Making the brightness and contrast of the polarizing plate about 98% or more can be one of the design criteria in the future from the viewpoint of power saving of the device and prevention of temperature rise of the polarizing plate. For example, in the projection type image display device shown in FIG. 2, when the allowable reduction rate of the luminance in the optical system is set within about 10%, the amount of light absorbed by the polarizing plate is required to be about 2% or less. From the results shown in FIG. 5, the thickness of the sapphire substrate was set to about 0.3 × 10 ^-3 m ~ 1.0 × 10 ^-3 m, and the angle deviation between the crystal axis (optical axis) direction of the sapphire substrate and the transmission axis (absorption axis) direction of the polarizing film (polarizing element) is within ± 6 °. By setting the angle between the element and the absorption axis within 90 ° ± 6 ° or 0 ° ± 6 °, it is considered that the amount of light loss in the polarizing plate can be suppressed to about 2% or less.
[0027]
FIG. 6 is a diagram illustrating an example of a measurement result of temperature characteristics of a polarizing plate.
In FIG. 6, the horizontal axis represents the thickness of the substrate, and the vertical axis represents the temperature of the polarizing film. This characteristic is an actual measurement value in the projection type image display device shown in FIG. 2, and the measurement conditions are as follows: ambient temperature Ta is 25 ° C., light source is an ultra-high pressure mercury lamp of 155W specification, and liquid crystal panel is 0.7 inch panel. The polarizing plate to be measured is the input-side polarizing plate 4G, and the size of the polarizing film is 21.5 × 10 ^-3 m, width 18.0 × 10 ^-3 m, substrate is 23.5 × 10 vertically ^-3 m, width 20.0 × 10 ^-3 m for a sapphire substrate and a glass substrate.
[0028]
As is clear from the results of FIG. 6, the thinner the sapphire substrate and the glass substrate, the higher the thermal conductivity of the substrate and the lower the temperature of the polarizing film. The thermal conductivity is 0.55 to 0.75 (W / mK) for glass and about 42 (W / mK) for sapphire. Generally, it is desirable to use a polarizing film in a temperature range of 70 ° C. or less from the viewpoint of the service life and the occurrence of color unevenness (luminance unevenness) due to thermal deformation. Assuming that the temperature of the polarizing film becomes 70 ° C. at 35 ° C. which is the allowable upper limit temperature of the ambient temperature, the temperature of the polarizing film becomes 60 ° C. when the ambient temperature is 25 ° C. which is normal temperature. In the result of FIG. 6, in the case of a sapphire substrate, when the plate thickness is 1.0 mm, the temperature of the polarizing film is about 57 ° C., and when the plate thickness is 0.3 mm, the temperature of the polarizing film is about 55 ° C. When the thickness is set to 0.0 mm or less, even when the ambient temperature reaches the allowable upper limit temperature of 35 ° C., the temperature of the polarizing film can be set to 70 ° C. or less. Further, in the sapphire substrate, for example, in consideration of securing planar accuracy and breaking strength during processing, a plate thickness of 0.3 mm is one lower limit. Therefore, for the above reason, it is considered that the thickness of the sapphire substrate is suitably from 0.3 mm to 1.0 mm.
[0029]
According to the configuration of the above embodiment, in the projection type image display device, the brightness and the contrast of the image can be ensured in addition to the heat radiation of the polarizing plate. Further, in some or all of the polarizing plates, the allowable range of the angle deviation between the optical axis (crystal axis) of the sapphire substrate and the absorption axis (transmission axis) of the polarizing film is described in, for example, Japanese Patent No. 3091183. Within ± 2 ° and preferably ± 0.5 ° within the specified range, the accuracy of parts and assembly can be relaxed, the polarizing plate alone, the optical unit and the projection type image display It is possible to improve the manufacturability of the device and reduce the cost.
In the above embodiment, the projection type video display device is described using three liquid crystal panels as video display elements. However, the present invention is not limited to this, and for example, one video display element such as a liquid crystal panel is used. The configuration used may be used. Further, the polarizing plate may have a configuration in which the polarizing element and the sapphire substrate are separated from each other. Furthermore, the substrate of the polarizing plate is not limited to the sapphire substrate, and other uniaxial crystals having good thermal conductivity can be used.
[0030]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, in a projection type video display apparatus, while ensuring the heat dissipation of a polarizing plate, the brightness and contrast of an image can also be ensured. In addition, the accuracy of parts and the accuracy of assembly can be relaxed, so that manufacturability can be improved and cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a first combination configuration example of a polarizing plate for an image display device as an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration example of a projection type video display device using the combination configuration of FIG. 1;
FIG. 3 is a diagram showing a second configuration example of a combination of a polarizing plate and an image display device as an embodiment of the present invention.
FIG. 4 is a diagram illustrating a third combination configuration example of a polarizing plate for an image display element as an embodiment of the present invention.
FIG. 5 is a diagram showing a relationship between brightness and contrast with respect to a crystal axis angle shift of a sapphire substrate.
FIG. 6 is a diagram showing an example of a measurement result of temperature characteristics of a polarizing plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light source unit, 20R, 20G, 20B ... Liquid crystal display element, 3 ... Projection lens unit, 4, 4R, 4G, 4B ... Incident side polarizing plate, 41, 51, 5a ₁ , 5b ₁ , 5c ₁ , 5c ₃ ... Polarizing film, 42, 52, 5a ₂ , 5b ₂ , 5c ₂ ... Sapphire substrate, 5R, 5G, 5B, 5a, 5b, 5c ... Outgoing side polarizing plate, 6 ... First array lens, 7 ... Second array lens, 8 ... Polarization conversion element, 9 ... Condenser lens, 10R , 10G, 10B ... condenser lens, 11 ... dichroic prism, 12, 13 ... dichroic mirror, 14, 15, 16 ... reflection mirror, 17, 18 ... relay lens, 19 ... screen, 21 ... optical path, 26 ... cooling fan, 27 ... Cooling air flow path.

Claims

An optical unit for a projection-type image display device that irradiates light from a light source side to an image display element and modulates the light based on an image signal to form an optical image,
A polarization conversion element that aligns the polarization direction of light from the light source side to form predetermined polarized light,
The polarizing element is disposed on the sapphire substrate on the light incident side with respect to the image display element, the polarizing element is held on the sapphire substrate side, and the angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is 90 °. Each of the R, G, and B color light incident from the polarization conversion element side is set to within ± 6 ° (excluding the range of ± 2 °) or within 0 ° ± 6 ° (excluding the range of ± 2 °). A polarizing plate that allows light having a predetermined polarization direction to pass through and enters the image display device,
An optical unit comprising:

An optical unit for a projection-type image display device that irradiates light from a light source side to an image display element and modulates the light based on an image signal to form an optical image,
A polarization conversion element that aligns the polarization direction of light from the light source side to form predetermined polarized light,
A color separation unit that separates R, G, and B color lights from the polarized light;
A polarizing plate disposed on the light incident side and the light emitting side with respect to the image display element, both polarizing plates each having a configuration in which the polarizing element is held on the sapphire substrate with the image display element side, The angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is within 90 ° ± 6 ° (excluding the range of ± 2 °) or 0 ° ± 6. (Excluding the range of ± 2), and the polarized light of each of the R, G, and B color lights incident from the color separation unit side is incident on the image display element through the polarized light having a predetermined polarization direction. A polarizing plate having a configuration;
An optical unit comprising:

An optical unit for a projection-type image display device that irradiates light from a light source side to an image display element and modulates the light based on an image signal to form an optical image,
A polarization conversion element that aligns the polarization direction of light from the light source side to form predetermined polarized light,
A color separation unit that separates R, G, and B color lights from the polarized light;
A polarizing plate arranged on the light incident side with respect to the image display element, wherein the polarizing element is held on the sapphire substrate on the image display element side, and the optical axis of the sapphire substrate and the absorption axis of the polarizing element Is within 90 ° ± 6 ° (excluding the range of ± 2 °) or 0 ° ± 6 ° (excluding the range of ± 2 °), and R, which is incident from the color separation unit side, An incident-side polarizing plate that allows the polarized light of each color of G and B to enter the image display device through a polarized light having a predetermined polarization direction;
A polarizing plate arranged on the light emission side with respect to the image display element, wherein the polarizing elements are arranged on both sides of the sapphire substrate, and the optical axes of the sapphire substrate and the absorption of the polarizing elements arranged on both sides. The angle with the axis is within 90 ° ± 0.5 ° or within 0 ° ± 0.5 °, and is a predetermined one of the polarized light of each color of R, G, and B modulated and emitted by the image display device. An exit-side polarizing plate that allows the polarization direction of
An optical unit comprising:

The above polarizing plate, the optical unit according to claim 1, 2 or 3 the thickness of the sapphire substrate is about ^{^{0.3 × 10 -3 m~1.0 × 10 -3}} m.

A projection-type image display device that irradiates light from a light source side to an image display element and projects an optical image formed based on an image signal,
A polarization conversion element that aligns the polarization direction of light from the light source side to form predetermined polarized light,
A color separation unit that separates R, G, and B color lights from the polarized light;
The polarizing element is disposed on the sapphire substrate on the light incident side with respect to the image display element, the polarizing element is held on the sapphire substrate side, and the angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is 90 °. Each of the R, G, and B color lights incident from the color separation unit side is within ± 6 ° (excluding the range of ± 2 °) or within 0 ° ± 6 ° (excluding the range of ± 2 °). A polarizing plate that allows light having a predetermined polarization direction to pass through and enters the image display device,
A driving circuit for driving the video display element based on a video signal,
A projection lens unit that projects the optical image formed by the video display element,
A projection type video display device characterized by comprising:

A projection-type image display device that irradiates light from a light source side to an image display element and projects an optical image formed based on an image signal,
A polarization conversion element that aligns the polarization direction of light from the light source side to form predetermined polarized light,
A color separation unit that separates R, G, and B color lights from the polarized light;
A polarizing plate disposed on the light incident side and the light emitting side with respect to the image display element, both polarizing plates each having a configuration in which the polarizing element is held on the sapphire substrate with the image display element side, The angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is within 90 ° ± 6 ° (excluding the range of ± 2 °) or 0 ° ± 6. (Excluding the range of ± 2), and the polarized light of each of the R, G, and B color lights incident from the color separation unit side is incident on the image display element through the polarized light having a predetermined polarization direction. A polarizing plate having a configuration;
A driving circuit for driving the video display element based on a video signal,
A projection lens unit that projects the optical image formed by the video display element,
A projection type video display device characterized by comprising:

A projection-type image display device that irradiates light from a light source side to an image display element and projects an optical image formed based on an image signal,
A polarization conversion element that aligns the polarization direction of light from the light source side to form predetermined polarized light,
A color separation unit that separates R, G, and B color lights from the polarized light;
A polarizing plate arranged on the light incident side with respect to the image display element, wherein the polarization element is held on the sapphire substrate on the image display element side, and the optical axis of the sapphire substrate and the absorption axis of the polarization element R, G incident from the color separation unit side are within 90 ° ± 6 ° (excluding the range of ± 2 °) or 0 ° ± 6 ° (excluding the range of ± 2 °). , An incident-side polarizing plate that allows the polarized light of each color of B to enter the image display device through a polarized light having a predetermined polarization direction;
A polarizing plate arranged on the light emitting side with respect to the image display element, wherein the polarizing elements are arranged on both sides of the sapphire substrate, and form an optical axis of the sapphire substrate and an absorption axis of the polarizing elements on both sides. The angle is within 90 ° ± 0.5 ° or 0 ° ± 0.5 °, and a predetermined direction of polarization of the R, G, B polarized light modulated and emitted by the image display device is emitted. An exit-side polarizing plate through which an object passes;
A driving circuit for driving the video display element based on a video signal,
A projection lens unit that projects the optical image formed by the video display element,
A projection type video display device characterized by comprising:

The above polarizing plate, the projection type image display device according to claim 5, 6 or 7 the thickness of the sapphire substrate is about ^{^{0.3 × 10 -3 m~1.0 × 10 -3}} m.

A polarizing plate for a projection-type image display device that converts light from a light source into a polarized light and irradiates the image display element to form an optical image according to an image signal,
The polarizing element is held on a sapphire substrate having a thickness of about 0.3 × 10 ⁻³ m to 1.0 × 10 ⁻³ m, and the angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element is 90 °. When within ± 6 ° (excluding the range of ± 2 °) or within 0 ° ± 6 ° (excluding the range of ± 2 °), and polarized light of each of R, G, and B light is incident, A polarizing plate having a configuration in which a polarized light having a predetermined polarization direction is allowed to pass through the image display device.

A polarizing plate for a projection-type image display device that converts light from a light source into a polarized light and irradiates the image display element to form an optical image according to an image signal,
Polarizing elements are arranged on both sides of a sapphire substrate having a thickness of about 0.3 × 10 ⁻³ m to 1.0 × 10 ⁻³ m, and the angle between the optical axis of the sapphire substrate and the absorption axis of the polarizing element. Is within 90 ° ± 0.5 ° or within 0 ° ± 0.5 °, and when polarized light of each of R, G, and B light emitted from the image display device is incident, the polarized light is A polarizing plate having a configuration in which light having a predetermined polarization direction passes therethrough.