JP4205998B2 - Projection screen and projection display device - Google Patents

Description

【００４５】
また、全反射プリズムレンズ１１４の出光側の表面が平坦面であるとすると、全反射プリズムレンズ１１４内で映像光Ｌが進む角度θ_４と、全反射プリズムレンズ１１４から出射する映像光Ｌの出射角度θ_５との間には、次式（２）が成立する。
ｓｉｎθ_４＝ｓｉｎθ_５／ｎ … （２）
【００４６】
ここで、各単位プリズム１１３の入射面１１３ａとスクリーン面の法線とがなす角度をγとすると、
γ＝φ＋λ−π／２≧０ … （３）
であることが好ましい。
【００４７】
これは、各単位プリズム１１３の入射面１１３ａの角度γが負の場合には、各単位プリズム１１３の入射面１１３ａの形状が逆テーパ形状となり、各単位プリズム１１３を成形するための成形型の作製及び成形型による各単位プリズム１１３の成形が困難になるからである。
【００４８】
なお、各単位プリズム１１３のレンズ角度φは映像光Ｌの入射角度θ_１に関して単調減少するので、各単位プリズム１１３の入射面１１３ａの角度γは、スクリーン面のうち映像光Ｌの入射角度θ_１が大きくなる部分（同心円の中心Ｏから遠い側の部分）で負になりやすい。ここで、全反射プリズムレンズ１１４内で映像光Ｌが進む角度θ_４が略０である場合において、各単位プリズム１１３の入射面１１３ａの形状が逆テーパー形状とならないようにするための条件は、次式（４）により表される。
ｃｏｓ^−１｛ｃｏｓ（θ_１）／ｎ｝／２≦λ … （４）
【００４９】
一方、スクリーン面のうち映像光Ｌの入射角度θ_１が小さくなる部分（同心円の中心Ｏに近い側の部分）では、各単位プリズム１１３の入射面１１３ａに入射した映像光Ｌの一部が全反射面１１３ｂで全反射されずに抜けて迷光となる。
【００５０】
ここで、各単位プリズム１１３での迷光の発生態様を説明するため、単位プリズム１１３の入射面１１３ａで屈折されて丁度単位プリズム１１３の谷部へ向かう基準映像光Ｌ_０（すなわち、１つの単位プリズム１１３内で映像光Ｌが迷光となる部分と有効光となる部分との境界の位置を通過する映像光）について考察する。
【００５１】
各単位プリズム１１３の入射面１１３ａに対する映像光Ｌの入射角度をθ_２、各単位プリズム１１３の入射面１１３ａでの屈折角度をθ_３、単位プリズム１１３のプリズムピッチをｐ、各単位プリズム１１３の全反射面１１３ｂで全反射されて有効光として好適に利用される部分の幅をｅ₁ 、各単位プリズム１１３の全反射面１１３ｂで全反射されずに抜けて迷光となる部分の幅をｅ_２、各単位プリズム１１３の高さをｈ、各単位プリズム１１３の入射面１１３ａのうち映像光Ｌが迷光となる部分と有効光となる部分との境界の高さをｓとすると、映像光Ｌが有効光となる部分の幅ｅ_１は、以下の式（５）により表される。
ｅ_１＝（ｈ−ｓ）×（ｔａｎ（φ＋λ−π／２）＋ｔａｎθ_１） … （５）
【００５２】
ここで、上式（５）において、ｈ及びｓはそれぞれ以下の式（６）（７）により表すことができる。
ｈ＝ｐ×ｔａｎ（φ＋λ）×ｔａｎφ／（ｔａｎ（φ＋λ）−ｔａｎφ）… （６）
ｓ＝−ｐ×ｔａｎ（φ＋λ）／（１＋ｔａｎ（φ＋λ）×ｔａｎ（φ＋λ＋θ_３）） … （７）
なお、
θ_３＝ｓｉｎ^−１｛ｓｉｎ（θ_１＋φ＋λ）／ｎ｝ … （８）
である。
【００５３】
図３から明らかなように、プリズムピッチｐと、映像光Ｌが有効光となる部分の幅ｅ_１との間には、ｅ_１≦ｐの関係がある。また、映像光Ｌが有効光となる部分の幅ｅ_１とレンズピッチｐとの比ｅ_１／ｐは、映像光Ｌの入射角度θ_１が大きくなる程大きくなり、ある箇所でｅ_１＝ｐとなる。この場合、ｅ_１＝ｐとなる箇所に比べて映像光Ｌの入射角度θ_１が大きくなる領域では、各単位プリズム１１３の入射面１１３ａに入射した映像光Ｌは全反射面１１３ｂで全て全反射され、迷光が存在しない。
【００５４】
以上に説明したように、スクリーン面のうち映像光Ｌの入射角度θ_１が小さくなる部分（同心円の中心Ｏに近い側の部分）では、各単位プリズム１１３の入射面１１３ａに入射した映像光Ｌの一部が全反射面１１３ｂで全反射されずに抜けて迷光となるという問題があり、一方、スクリーン面のうち映像光Ｌの入射角度θ_１が大きくなる部分（同心円の中心Ｏから遠い側の部分）では、各単位プリズム１１３の入射面１１３ａの形状が逆テーパ形状となるという問題がある。
【００５５】
図４は、図１に示すプロジェクションスクリーン１１１の全反射プリズムレンズ１１４における各単位プリズム１１３の頂角λと映像光Ｌの入射角度θ_１との関係を説明するための図である。
【００５６】
図４において、線２０５は、全反射プリズムレンズ１１４内で映像光Ｌが進む角度θ_４が０（すなわち、全反射プリズムレンズ１１４から出射する映像光Ｌの出射角度θ_５が０）である場合において、上式（５）〜（８）に従って求められた、各単位プリズム１１３で迷光が発生する境界を示し、線２０６は、同様の場合において、上式（４）に従って求められた、各単位プリズム１１３の入射面１１３ａの形状が逆テーパー形状となる境界を示している。なお、線２０５，２０６を求める際には、全反射プリズムレンズ１１４の材料の屈折率ｎを１．５５としている。
【００５７】
図４において、２本の線２０５，２０６に囲まれた内側の領域は、各単位プリズム１１３の入射面１１３ａに入射した映像光Ｌの一部が全反射面１１３ｂで全反射されずに抜けて迷光となるということがなく、かつ、各単位プリズム１１３の入射面１１３ａの形状が逆テーパ形状となるということもない領域である。このため、各単位プリズム１１３の頂角λと、スクリーン面上での各単位プリズム１１３の位置に応じた映像光Ｌの入射角度θ_１とが、この領域内に存在している場合には、迷光の問題も逆テーパー形状の問題も発生しない。具体的には例えば、各単位プリズム１１３の頂角λが３５°で一定の場合を考えると、映像光Ｌの入射角度θ_１が４５〜６０°の範囲にあれば、迷光の問題も逆テーパー形状の問題も発生しない（符号２０７参照）。
【００５８】
しかしながら、近年、プロジェクションスクリーン１１１は大型化する傾向にあり、これに伴って映像光Ｌの入射角度θ_１の範囲も広くなってきているので、各単位プリズム１１３の頂角λが一定であるとすると、スクリーン面のうち映像光Ｌの入射角度θ_１が小さくなる部分及び映像光Ｌの入射角度θ_１が大きくなる部分で、線２０５，２０６に囲まれた内側の領域から外れやすくなる。
【００５９】
ここで、迷光の問題を解消するためには、線２０５により規定される映像光Ｌの入射角度θ_１の許容下限値を下げることが有効であり、このため、スクリーン面のうち映像光Ｌの入射角度θ_１が小さくなる部分（同心円の中心Ｏに近い側の部分）での各単位プリズム１１３の頂角λを小さくすることが好ましい。一方、逆テーパー形状の問題を解消するためには、線２０６により規定される映像光Ｌの入射角度θ_１の許容上限値を上げることが有効であり、このため、スクリーン面のうち映像光Ｌの入射角度θ_１が大きくなる部分（同心円の中心Ｏから遠い側の部分）での各単位プリズム１１３の頂角λを大きくすることが好ましい。
【００６０】
このため、本実施の形態においては、各単位プリズム１１３の頂角λを、スクリーン面の全面に亘ってスクリーン面のうち同心円の中心Ｏに近い側よりも遠い側の方が大きくなるように連続的に変化させるようにしている（符号２０１〜２０３参照）。これにより、映像光Ｌの入射角度θ_１の許容幅を拡げることができ、スクリーン面の全面に亘って迷光の問題及び逆テーパ形状の問題が発生しないようにすることができる。なお、図４に示す線２０１〜２０３は、各単位プリズム１１３の頂角λの変化を映像光Ｌの入射角度θ_１との関係で示したものであるが、各単位プリズム１１３の頂角λの変化を各単位プリズム１１３の位置（同心円の中心Ｏからの距離）との関係で示すことも当然可能であり、この関係は図５に示すようなものとなる。
【００６１】
なお、上述した実施の形態において、各単位プリズム１１３の入射面１１３ａは、スクリーン面に対する垂線（法線）に対して０°以上（好ましくは、１／１０００°以上）の抜け勾配（入射面１１３ａとスクリーン面の法線とがなす角度γが正である勾配）を有していることが好ましい。また、各単位プリズム１１３の入射面１１３ａの表面粗さは、スクリーン面の全面に亘って均一であることが好ましい。
【００６２】
また、上述した実施の形態においては、各単位プリズム１１３の頂角λをスクリーン面の全面に亘って連続的に変化させる場合を例に挙げて説明したが、これに限らず、各単位プリズム１１３の頂角λをスクリーン面内で段階的に変化させるようにしてもよい。
【００６３】
第２の実施の形態
次に、図６乃至図８により、本発明の第２の実施の形態に係るプロジェクションスクリーンを備えたプロジェクションディスプレイ装置について説明する。なお、本発明の第２の実施の形態は、レンチキュラーレンズの構成が異なる点、全反射プリズムレンズ及びレンチキュラーレンズを１枚のシートに一体化して形成している点を除いて、他は上述した第１の実施の形態と同様である。本発明の第２の実施の形態において、上述した第１の実施の形態と同一部分には同一符号を付して詳細な説明は省略する。
【００６４】
図６に示すように、本発明の第２の実施の形態に係るプロジェクションディスプレイ装置１００′は、プロジェクションスクリーン１１１′と、プロジェクションスクリーン１１１′に対して映像光Ｌを斜めに投射する投射光学系１１２とを備えている。
【００６５】
ここで、プロジェクションスクリーン１１１′は、背面側に配置された投射光学系１１２から斜めに投射された映像光Ｌを観察側へ向けて出射させるものであり、全反射プリズムレンズ１１４′と、全反射プリズムレンズ１１４′の観察側に設けられたレンチキュラーレンズ１１５′とを有している。
【００６６】
このうち、全反射プリズムレンズ１１４′は、投射光学系１１２から投射された映像光Ｌを屈折及び集光させるものであり、図７に示すように、ベースシート２３と、ベースシート２３の入光側の表面（映像光Ｌが入射する最入光面）に形成された複数の単位プリズム１１３とを有している。なお、上述した第１の実施の形態と同様に、各単位プリズム１１３は、入射した光を屈折させる入射面（第１の面）１１３ａと、入射面１１３ａで屈折された光を全反射する全反射面（第２の面）１１３ｂとを有している。また、各単位プリズム１１３は、スクリーン面から外れた同心円の中心Ｏ（図６参照）を基準にして同心円状に延びる円弧状プリズムとして形成されており、各単位プリズム１１３の頂角λは、スクリーン面上での当該各単位プリズム１１３の位置に応じて変化している。特に、各単位プリズム１１３の頂角λは、３０°以上４５°以下の範囲で、同心円の中心Ｏに近い側（図面下側）よりも遠い側（図面上側）の方が大きくなるように連続的に変化していることが好ましい。なお、各単位プリズム１１３の頂角λの変化の態様としては、上述した第１の実施の形態の場合と同様の態様をとることができる。
【００６７】
一方、レンチキュラーレンズ１１５′は、図７及び図８に示すように、ベースシート２３の出光側の表面に形成されており、断面が台形状の複数の台形状部分（単位レンズ）２５を有している。
【００６８】
ここで、各台形状部分２５は、その下底部分が入光側、上底部分が出光側にくるように配置されており、隣接する各台形状部分２５の間には断面がＶ字形状のＶ字形状部分２６が設けられている。なお、各台形状部分２５は、所定の屈折率を有する材料で形成されている。また、各Ｖ字形状部分２６は、各台形状部分２５の屈折率よりも低い屈折率を有する材料が各Ｖ字形状部分２６の間に充填されることにより形成され、各台形状部分２５とその間に設けられたＶ字形状部分２６との界面により光を全反射させて映像光Ｌを拡散させることができるようになっている（図７及び図８参照）。
【００６９】
また、各Ｖ字形状部分２６は、観察側から入射した光を吸収する光吸収作用を有していることが好ましい。なお、各Ｖ字形状部分２６の材料は特に限定されないが、例えば、低屈折率の合成樹脂中に、染料、顔料又は着色された樹脂微粒子等からなる光吸収粒子を混入させることにより形成することが好ましい。
【００７０】
なお、図６乃至図８に示すプロジェクションスクリーン１１１′において、投射光学系１１２から斜めに投射された映像光Ｌは、全反射プリズムレンズ１１４′の各単位プリズム１１３の入射面１１３ａに入射する。
【００７１】
そして、このようにして各単位プリズム１１３の入射面１１３ａに入射した映像光Ｌは入射面１１３ａで屈折され、全反射面１１３ｂで全反射された後、観察側へ向けてスクリーン面に略垂直な方向に進行する。
【００７２】
その後、このようにして全反射プリズムレンズ１１４′から出射された映像光Ｌは、レンチキュラーレンズ１１５′の台形状部分２５の下底部分側から入射し、その一部の光がそのまま透過する一方で、残りの光は台形状部分２５とＶ字形状部分２６との界面で全反射され、最終的に全ての光が台形状部分２５の上底部分側から観察側へ向けて出射される。
【００７３】
このように本発明の第１及び第２の実施の形態によれば、背面側に配置された投射光学系１１２から映像光Ｌが斜めに投射されるプロジェクションスクリーン１１１，１１１′において、映像光Ｌが入射する背面側に設けられた全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ，１１４′の複数の単位プリズム１１３の頂角λを、一定の角度範囲（例えば３０°以上４５°以下の範囲）で同心円の中心Ｏに近い側よりも遠い側の方が大きくなるように変化させるようにしている。これにより、映像光Ｌの入射角度θ_１が小さくなる投射光学系１１２に近い側の部分で各単位プリズム１１３の頂角λをより小さくし、映像光Ｌの入射角度θ_１が大きくなる投射光学系１１２から遠い側の部分で各単位プリズム１１３の頂角λをより大きくすることができる。このため、迷光などの発生による映像光Ｌのロスが生じない範囲としての映像光Ｌの入射角度θ_１の許容幅を拡げることができ、表面輝度の低下やコントラストの低下がなく、投射光学系１１２から映像光Ｌを略垂直に投射した場合に得られる映像の画質と同等のレベルの高画質を映像を表示することができる、プロジェクションスクリーン１１１，１１１′及びプロジェクションディスプレイ装置１００，１００′を得ることができる。
【００７４】
また、本発明の第１及び第２の実施の形態によれば、各単位プリズム１１３の入射面１１３ａが、スクリーン面に対する垂線（法線）に対して０°以上の抜け勾配を有しているので、各単位プリズム１１３を成形するための成形型に逆テーパー形状の部分が含まれることがなく、成形型の作製が容易になり、また、レンズ成形の際における成形型からの各単位プリズム１１３の離型も容易に行うことができる。
【００７５】
さらに、本発明の第１及び第２の実施の形態によれば、各単位プリズム１１３の入射面１１３ａの表面粗さがスクリーン面の全面に亘って均一であるので、スクリーン面上で映像のむらが発生しないようにして高画質な映像が観察されるようにすることができる。
【００７６】
（他の実施の形態）
なお、本発明は、上述した第１及び第２の実施の形態に限定されるものではなく、下記の（１）〜（６）に述べるような種々の変形や変更が可能であり、それらも本発明の範囲内である。
【００７７】
（１） 上述した第１及び第２の実施の形態においては、全反射プリズムレンズ及びレンチキュラーレンズとして、全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ，１１４′及びレンチキュラーレンズ１１５，１１５′を用いているが、全反射プリズムレンズ及びレンチキュラーレンズ等の具体的な形状としては、上述した本発明の特徴を持つものであれば、これに限らず、任意の構成をとることができる。
【００７８】
（２） 上述した第１の実施の形態においては、全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ，１１４′及びレンチキュラーレンズ１１５を別々のシート（プリズムシート及びレンチキュラーレンズシート）に形成しているが、これに限らず、全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ及びレンチキュラーレンズ１１５を１枚のシートに一体化して形成してもよい。一方、上述した第２の実施の形態においては、全反射プリズムレンズ１１４′及びレンチキュラーレンズ１１５′を１枚のシートに一体化して形成しているが、これに限らず、全反射プリズムレンズ１１４′及びレンチキュラーレンズ１１５′を別々のシート（プリズムシート及びレンチキュラーレンズシート）に形成してもよい。
【００７９】
（３） 上述した第１及び第２の実施の形態において、レンチキュラーレンズ１１５，１１５′の観察側（レンチキュラーレンズ１１５，１１５′がない場合には、全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ，１１４′の観察側）には、図１及び図６に符号１１７で示すように、全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ，１１４′やレンチキュラーレンズ１１５，１１５′を通過した映像光Ｌを拡散させる拡散シートを設けるようにしてもよい。なお、拡散シートとしては、拡散剤などが混入されることにより拡散作用が与えられたものであることが好ましい。
【００８０】
（４） 上述した第１及び第２の実施の形態においては、全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ，１１４′の観察側にレンチキュラーレンズ１１５，１１５′を設けているが、レンチキュラーレンズ１１５，１１５′の代わりに、拡散剤などにより光を拡散させる拡散シートや、光の屈折により光を拡散させる複数のビーズがコーティングされたビーズスクリーン等を用いることもできる。
【００８１】
（５） 上述した第１及び第２の実施の形態において、レンチキュラーレンズ１１５，１１５′の観察側（レンチキュラーレンズ１１５，１１５′がない場合には、全反射プリズムレンズ１１４，１１４Ａ，１１４Ｂ，１１４′の観察側）には、機能性保持層を設けるようにしてもよい。なお、機能性保持層としては、各種のものを用いることができるが、例えば、反射防止層（ＡＲ層）、ハードコート層（ＨＣ層）、帯電防止層（ＡＳ層）、防眩層（ＡＧ層）、防汚層及びセンサー層などが挙げられる。
【００８２】
ここで、反射防止層（ＡＲ層）は、プロジェクションスクリーン１００，１００′の表面での光の反射を抑えるための層であり、光の反射率を抑える機能を有するフィルムをレンズ表面にラミネートしたり、レンズ表面に反射防止処理を直接施すことにより得られる。ハードコート層（ＨＣ層）は、プロジェクションスクリーン１００，１００′の表面を保護して傷付きを防止するための層であり、強度を増加させる機能を有する耐摩耗性フィルムをレンズ表面にラミネートしたり、レンズ表面にハードコート処理を直接施すことにより得られる。帯電防止層（ＡＳ層）は、プロジェクションスクリーン１００，１００′で生じる静電気を除去するための層であり、帯電防止機能を有するフィルムをレンズ表面にラミネートしたり、レンズ表面に帯電防止処理を直接施すことにより得られる。防眩層（ＡＧ層）は、プロジェクションスクリーン１００，１００′のぎらつきなどを防止するための層であり、防眩性機能を有するフィルムをレンズ表面にラミネートしたり、レンズ表面に防眩処理を直接施すことにより得られる。防汚層は、プロジェクションスクリーン１００，１００′の表面への汚れの付着を防止するための層であり、汚れの付着を防止する機能を有するフィルムをレンズ表面にラミネートしたり、レンズ表面に防汚処理を直接施すことにより得られる。センサー層は、タッチセンサー等の機能を有する層である。
【００８３】
（６） 上述した第１及び第２の実施の形態に係るプロジェクションディスプレイ装置１００，１００′においては、投射光学系１１２から出射された映像光Ｌをプロジェクションスクリーン１１１，１１１′へ向けて上方へ投射する打ち上げ方式が採用されているが、これに限らず、投射光学系１１２から出射された映像光Ｌをプロジェクションスクリーン１１１，１１１′へ向けて下方へ投射する打ち下ろし方式を採用するようにしてもよい。
【００８４】
ここで、プロジェクションディスプレイ装置１００，１００′において打ち上げ方式が採用される場合には、プロジェクションスクリーン１１１，１１１′及び投射光学系１１２は例えば、図９に示すような位置関係でキャビネット１５１内に収納される。具体的には例えば、投射光学系１１２の映像光源としてＬＣＤライトバルブを用い、５０インチのプロジェクションスクリーン１１１，１１１′に対して、スクリーン面の下端部に入射する映像光Ｌの入射角度θ_１１が４５°、スクリーン面の上端部に入射する映像光Ｌの入射角度θ_１０が６０°となるような態様で、プロジェクションスクリーン１１１，１１１′の下方から映像を投射するようにすることができる。なお、この場合、プロジェクションスクリーン１１１，１１１′と投射光学系１１２との水平距離は略８００ｍｍである。
【００８５】
一方、プロジェクションディスプレイ装置１００，１００′において打ち下ろし方式が採用される場合には、プロジェクションスクリーン１１１，１１１′及び投射光学系１１２は例えば、図１０に示すような位置関係でキャビネット１５２内に収納される。具体的には例えば、投射光学系１１２の映像光源としてＤＭＤを用い、５０インチのプロジェクションスクリーン１１１，１１１′に対して、スクリーン面の上端部に入射する映像光Ｌの入射角度θ_２０が４５°、スクリーン面の下端部に入射する映像光Ｌの入射角度θ_２１が７０°となるような態様で、プロジェクションスクリーン１１１，１１１′の上方から映像を投射するようにすることができる。なお、この場合、プロジェクションスクリーン１１１，１１１′と投射光学系１１２との水平距離は略７００ｍｍとなる。
【００８６】
なお、図９及び図１０に示すプロジェクションディスプレイ装置１００，１００′では、投射光学系１１２から出射された映像光Ｌがプロジェクションスクリーン１１１，１１１′に直接投射されているが、これに限らず、図１１に示すような位置関係でキャビネット１５３内に収納し、投射光学系１１２から出射された映像光Ｌが折り返しミラー１５５を介してプロジェクションスクリーン１１１，１１１′に投射されるようにしてもよい。
【００８７】
【実施例】
次に、上述した実施の形態の具体的実施例について述べる。
【００８８】
（実施例１）
実施例１に係るプロジェクションスクリーンとして、プリズムシート及びレンチキュラーレンズシートを有する、５０インチの背面投射型テレビ用のプロジェクションスクリーンを製造した。なお、実施例１に係るプロジェクションスクリーンは、上述した第１の実施の形態に対応するものである。
【００８９】
まず、ＮＣ旋盤により切削加工して得られる金型を用い、厚さ１．８ｍｍのアクリル製のベースシート上にて紫外線硬化性樹脂（硬化後の屈折率が１．５５）を硬化して成形加工することにより、一方の表面に全反射プリズムレンズが形成された、全体として厚さ２ｍｍのプリズムシートを得た。
【００９０】
ここで、プリズムシートに形成された全反射プリズムレンズは、スクリーン面から外れた同心円の中心を基準にして同心円状に延びる複数の円弧状プリズム（単位プリズム）を有するようにした。なお、各単位プリズムの円弧の半径（同心円の中心からの距離）はスクリーン面の下端部中央で８００ｍｍ、プリズムピッチは１００μｍ、プリズム高さは約１５０μｍとした。また、各単位プリズムの頂角λは、スクリーン面の下端部（最も同心円の中心に近い側の部分）で３７°、スクリーン面の上端部（最も同心円の中心から遠い側の部分）で４０°とし、３７〜４０°の範囲で変化させた（図１２参照）。なお、各単位プリズムからの映像光の出射角度θ_５は０（垂直出射）とした。
【００９１】
次に、円筒状のロール金型を用い、耐衝撃性アクリル樹脂を押し出し成形することによりレンチキュラーレンズシートを製造した。
【００９２】
ここで、レンチキュラーレンズシートに形成されたレンチキュラーレンズは、断面が半楕円形状の複数の単位レンズを有するようにした。なお、各単位レンズのレンズ横径は１４０μｍ、レンズ縦径は１００μｍとした。また、各単位レンズのレンズピッチは１４０μｍ、レンズ高さは５０μｍとした。これにより、水平拡散角が半値角で３５°、垂直拡散角が半値角で１５°の拡散特性が得られた。
【００９３】
なお、このようにしてレンチキュラーレンズシートを押出し成形する際に、耐衝撃性アクリル樹脂に極微量の黒色染料及び拡散剤を混合した。このようにして製造されたレンチキュラーレンズシートの透過率は７０％となり、外光等の反射防止効果及び拡散効果が得られた。
【００９４】
以上のようにして製造されたプリズムシートとレンチキュラーレンズシートとを組み合わせ、プロジェクションスクリーンを製造した。また、このようにして製造されたプロジェクションスクリーンを、図９に示すような打ち上げ方式のプロジェクションディスプレイ装置（背面投射型テレビ）に組み込んだ。なお、プロジェクションスクリーンの画面サイズは５０インチであり、投射光学系の映像光源としては、ＬＣＤライトバルブを用いた。ここで、投射光学系は、スクリーン面の下端部より８００ｍｍ下方の高さに配置し、プロジェクションスクリーンと投射光学系との水平距離（投射距離）は８００ｍｍとした。また、スクリーン面の下端部に入射する映像光の入射角度θ_１１を４５°、スクリーン面の上端部中央に入射する映像光の入射角度θ_１０を６０°とした。
【００９５】
（実施例２）
実施例２に係るプロジェクションスクリーンとして、全反射プリズムレンズ及びレンチキュラーレンズが一体化して形成された、５０インチの背面投射型テレビ用のプロジェクションスクリーンを製造した。なお、実施例２に係るプロジェクションスクリーンは、上述した第２の実施の形態に対応するものである。
【００９６】
まず、ＮＣ旋盤により切削加工して得られる金型を用い、厚さ１．８ｍｍのアクリル製のベースシート上にて紫外線硬化性樹脂（硬化後の屈折率が１．５５）を硬化して成形加工することにより、一方の表面に全反射プリズムレンズが形成された、全体として厚さ２ｍｍのプリズムシートを得た。
【００９７】
ここで、プリズムシートに形成された全反射プリズムレンズは、スクリーン面から外れた同心円の中心を基準にして同心円状に延びる複数の円弧状プリズム（単位プリズム）を有するようにした。なお、各単位プリズムの円弧の半径（同心円の中心からの距離）はスクリーン面の下端部中央で８００ｍｍ、プリズムピッチは１００μｍ、プリズム高さは約１５０μｍとした。また、各単位プリズムの頂角λは、スクリーン面の下端部（最も同心円の中心に近い側の部分）で３７°、スクリーン面の上端部（最も同心円の中心から遠い側の部分）で４０°とし、３７〜４０°の範囲で連続的に変化させた（図１２参照）。なお、各単位プリズムからの映像光の出射角度θ_５は０（垂直出射）とした。
【００９８】
次に、以上のようにして製造されたプリズムシートの反対側の表面に、断面が台形状の複数の台形状部分（単位レンズ）を形成し、次いで、隣接する各台形状部分の間に、光吸収粒子を含有する低屈折率樹脂を充填し、Ｖ字形状部分を形成した。なお、各台形状部分の材料としては、高屈折率のエポキシアクリレートを用いた。また、各Ｖ字形状部分の材料としては、低屈折率のウレタンアクリレートを用い、光吸収粒子としては、大日精化工業（株）製のラブコロール（登録商標）を用いた。なお、ラブコロールの平均粒径は８μｍであり、添加量は４５重量％とした。
【００９９】
ここで、各台形状部分のレンズピッチは５０μｍ、屈折率は１．５７とした。また、各Ｖ字形状部分の屈折率は１．４８とした。なお、各台形状部分の上底部分の長さと各Ｖ字形状部分の三角形の底辺部分の長さとが互いに等しくなるようにし、いわゆるブラックストライプ率を５０％とした。また、各Ｖ字形状部分の頂角は２０°とした。
【０１００】
以上のようにして全反射プリズムレンズとレンチキュラーレンズとが１枚のシートの表裏に一体化して形成されたプロジェクションスクリーンを製造した。また、このようにして製造されたプロジェクションスクリーンを、実施例１と同様に、図９に示すような打ち上げ方式のプロジェクションディスプレイ装置（背面投射型テレビ）に組み込んだ。なお、プロジェクションスクリーンの画面サイズは５０インチであり、投射光学系の映像光源としては、ＬＣＤライトバルブを用いた。ここで、投射光学系は、スクリーン面の下端部より８００ｍｍ下方の高さに配置し、プロジェクションスクリーンと投射光学系との水平距離（投射距離）は８００ｍｍとした。また、スクリーン面の下端部に入射する映像光の入射角度θ_１１を４５°、スクリーン面の上端部中央に入射する映像光の入射角度θ_１０を６０°とした。
【０１０１】
（実施例３）
実施例３に係るプロジェクションスクリーンとして、実施例２に係るプロジェクションスクリーンのレンチキュラーレンズの前側（最観察側）に、厚さが０．１ｍｍのＡＲコートフィルムをラミネートした。
【０１０２】
（比較例１）
比較例１に係るプロジェクションスクリーンとして、実施例４に係るプロジェクションにおいて、全反射プリズムレンズの各単位プリズムの頂角λを４０°で一定としたものを製造した。
【０１０３】
（評価結果）
実施例１に係るプロジェクションスクリーンでは、入射角度の許容幅が広く、表面輝度の低下やコントラストの低下もなく、高画質の映像が得られた。また、透過率が６０％、反射率が５％、ゲインが３であった。また、垂直拡散角（垂直視野角）（半値角）は１０°、水平拡散角（水平視野角）（半値角）は２５°であった。
【０１０４】
実施例２に係るプロジェクションスクリーンでは、実施例１と同様に、入射角度の許容幅が広く、表面輝度の低下やコントラストの低下もなく、高画質の映像が得られた。また、透過率が８０％、反射率が５％、ゲインが４であった。また、垂直拡散角（垂直視野角）（半値角）は１２°、水平拡散角（水平視野角）（半値角）は２５°であった。
【０１０５】
実施例３に係るプロジェクションスクリーンでは、実施例２と同様に、入射角度の許容幅が広く、表面輝度の低下やコントラストの低下もなく、高画質の映像が得られた。また、反射率は、実施例２に比べて１．５％改善した。
【０１０６】
一方、比較例１に係るプロジェクションスクリーンでは、スクリーン面の下部中央付近が、実施例１〜３に係るプロジェクションスクリーンに比べてやや暗く、また、ゴーストが観察された。
【０１０７】
【発明の効果】
以上説明したように本発明によれば、迷光などの発生による映像光のロスが生じない範囲としての映像光の入射角度の許容幅を拡げ、表面輝度の低下やコントラストの低下がなく、映像光源から映像光を略垂直に投射した場合に得られる映像の画質と同等のレベルの高画質な映像を表示することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態に係るプロジェクションスクリーンを備えたプロジェクションディスプレイ装置を示す概略斜視図。
【図２】図１に示すプロジェクションスクリーンの要部を示す斜視図。
【図３】図１に示すプロジェクションスクリーンの全反射プリズムレンズにおける映像光の光路を説明するための図。
【図４】図１に示すプロジェクションスクリーンの全反射プリズムレンズにおける各単位プリズムの頂角と映像光の入射角度との関係を説明するための図。
【図５】図１に示すプロジェクションスクリーンの全反射プリズムレンズにおける各単位プリズムの位置と頂角との関係を説明するための図。
【図６】本発明の第２の実施の形態に係るプロジェクションスクリーンを備えたプロジェクションディスプレイ装置を示す概略斜視図。
【図７】図６に示すプロジェクションスクリーンの要部を示す斜視図。
【図８】図７に示すXIII−XIII線に沿った断面図。
【図９】本発明の第１及び第２の実施の形態に係るプロジェクションスクリーンを備えたプロジェクションディスプレイ装置の第１の組立例を示す図。
【図１０】本発明の第１及び第２の実施の形態に係るプロジェクションスクリーンを備えたプロジェクションディスプレイ装置の第２の組立例を示す図。
【図１１】本発明の第１及び第２の実施の形態に係るプロジェクションスクリーンを備えたプロジェクションディスプレイ装置の第３の組立例を示す図。
【図１２】実施例１〜３における全反射プリズムレンズの各単位プリズムの位置と頂角との関係を示す図。
【図１３】一般的なフレネルレンズシートを備えたプロジェクションスクリーンの一例を示す図。
【図１４】全反射プリズムレンズを備えたプロジェクションスクリーンにおいて単位プリズムの頂角が大きい場合の映像光の光路を説明するための図。
【図１５】全反射プリズムレンズを備えたプロジェクションスクリーンにおいて単位プリズムの頂角が小さく場合の映像光の光路を説明するための図。
【符号の説明】
１００，１００′ プロジェクションディスプレイ装置
１１１，１１１′ プロジェクションスクリーン
１１２ 投射光学系
１１３ 単位プリズム
１１３ａ 入射面
１１３ｂ 出射面
１１４，１１４′ 全反射プリズムレンズ
１１５，１１５′ レンチキュラーレンズ
１１６ 単位レンズ
１１７ 拡散シート
１５１，１５２，１５３ キャビネット
１５５ 折り返しミラー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection screen, and in particular, obliquely projects and observes image light emitted from an image light source having a cell structure such as an LCD (Liquid Crystal Display) or DMD (Digital Micro-mirror Device). The present invention relates to a projection screen suitable for the above and a projection display device including the same.
[0002]
[Prior art]
Conventionally, as a rear projection type projection display device (rear projection type television), three CRTs of red, green and blue are used as video light sources, and video light emitted from such video light sources is transmitted through the projection. 2. Description of the Related Art A projection display device that projects on the back side of a screen and observes an image from the observation side is known.
[0003]
Here, the projection screen used in such a projection display device is generally composed of a Fresnel lens sheet and a lenticular lens sheet, and forms image light emitted from an image light source on the projection screen and directivity. It can be emitted toward the observer as diffused light having
[0004]
Specifically, for example, as shown in FIG. 13, the projection screen 300 is disposed on the observation side of the Fresnel lens sheet 301, the Fresnel lens sheet 301 having a circular Fresnel lens 302 formed on the surface on the light output side, And a lenticular lens sheet 303 having a horizontal diffusion lenticular lens 304 formed on the surface on the light incident side. A light exit lens 305 and a black stripe 306 are formed on the light exit surface of the lenticular lens sheet 303.
[0005]
Among these, the Fresnel lens 302 formed on the Fresnel lens sheet 301 can be obtained by forming grooves having a predetermined angle at a predetermined pitch in a transparent resin material such as acrylic. The image light emitted in a radially diffused state from an image light source (not shown) disposed in the screen is condensed toward the observation side. The lenticular lens 304 formed on the lenticular lens sheet 303 can be obtained by forming cylindrical unit lenses so as to regularly extend in the vertical direction on one plane, and is condensed by the Fresnel lens sheet 301. The image light is mainly diffused in the horizontal direction and emitted as diffused light having directivity in the horizontal direction.
[0006]
By the way, in recent years, instead of the projection display device using the three CRTs of red, green and blue as described above, an image light source having a cell structure such as LCD or DMD is used. There is an increasing need for a single-lens projection display device that projects the emitted image light onto the back side of a transmissive projection screen and observes the image from the observation side.
[0007]
Conventionally, in such a single lens type projection display device, a method of projecting image light substantially perpendicularly to the projection screen from the back side of the projection screen has been common. However, such a method requires a depth substantially equal to that of a conventional CRT projection display device, and there is a problem that the device cannot be reduced in size.
[0008]
Under such circumstances, as one of the projection display devices, the image light emitted from the image light source is projected obliquely on the projection screen, so that the image quality is not impaired and compared with the conventional one. Thus, there has been proposed a projection display device that can realize a significant reduction in thickness (see Patent Documents 1 and 2).
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 61-208041
[Patent Document 2]
JP 2000-180967 A
[0010]
[Problems to be solved by the invention]
In such a projection display device, a unit prism group (total reflection prism lens) having a triangular cross section is provided on the light incident side surface as an optical means for condensing image light incident obliquely on the projection screen. The incident video light is refracted by the first surface (incident surface) of the unit prism and then totally reflected by the second surface (total reflection surface) to be emitted from the surface on the light output side.
[0011]
Here, in a projection screen equipped with such a total reflection prism lens, the portion closer to the image light source where the incident angle of the image light (the angle of the image light with respect to the screen surface) becomes smaller (each unit prism comes off the screen surface). In the case of extending concentrically with the center of the concentric circle as a reference, the incident surface of each unit prism 311 of the total reflection prism lens 310 is a portion close to the center of the concentric circle) as shown in FIG. A part of the image light incident on 311a is not totally reflected by the total reflection surface 311b but passes through and becomes stray light, which causes troubles such as a double image (ghost). In FIG. 14, symbol L11 indicates the optical path of the component that becomes normal light in the image light, and symbol L12 indicates the optical path of the component that becomes stray light. The stray light generated in this way increases as the apex angle (tip angle) λ of each unit prism 311 increases, and decreases as it decreases.
[0012]
On the other hand, in a projection screen equipped with such a total reflection prism lens, the part farther from the image light source where the incident angle of the image light is larger (each unit prism is concentric with respect to the center of the concentric circle off the screen surface) 15, the apex angle λ of each unit prism 311 becomes smaller, and the incident surface 311 a of each unit prism 311 has an inverse taper shape, as shown in FIG. Therefore, a part of the image light incident from the incident surface 311a of each unit prism 311 is totally reflected by the total reflection surface 311b and then reflected again by the incident surface 311a to become stray light, resulting in a loss of image light. was there. In FIG. 15, reference numeral L21 indicates the optical path of the component that becomes normal light in the image light, and reference numeral L22 indicates the optical path of the component that becomes stray light. In addition, when the incident surface 311a of each unit prism 311 has an inversely tapered shape, it becomes difficult to produce a mold for molding each unit prism 311. Also, when forming a lens, each unit prism 311 is formed from the mold. There was a problem that it was difficult to release the mold. Further, when a mold for molding each unit prism 311 is manufactured by cutting a mold material, a mold shape corresponding to the reversely tapered incident surface 311a of each unit prism 311 is obtained. The incident surface 311a of each unit prism 311 becomes a rough surface with a cutting mark. In this case, since the area where the incident surface 311a of each unit prism 311 is a mirror surface and the area where the surface is rough are present on the screen surface, the image looks different at the boundary between these areas. There was a problem that the image was observed as unevenness.
[0013]
As described above, in the conventional projection screen, the allowable range of the incident angle of the image light is narrow, and the loss of the image light due to the occurrence of stray light or the like is likely to occur. there were.
[0014]
The present invention has been made in consideration of such points, and has expanded the allowable range of the incident angle of the image light as a range in which the loss of the image light due to the occurrence of stray light or the like does not occur, thereby reducing the surface luminance and reducing the contrast. An object of the present invention is to provide a projection screen and a projection display device capable of displaying a high-quality image having a level equivalent to the image quality obtained when image light is projected substantially vertically from an image light source without deterioration. And
[0015]
[Means for Solving the Problems]
The present invention provides a projection screen that emits image light projected obliquely from a projection optical system disposed on the back side toward the observation side, and has a plurality of unit prisms provided on the back side on which the image light is incident. A total reflection prism lens, wherein each unit prism has a first surface that refracts incident light and a second surface that totally reflects light refracted by the first surface. Each of the unit prisms has an apex angle corresponding to an angle formed by the first surface and the second surface, and the apex angle of each unit prism is determined on the screen surface. A projection screen characterized by changing according to the position of a unit prism.
[0016]
In the present invention, it is preferable that each unit prism extends concentrically with reference to the center of a concentric circle deviated from the screen surface. In addition, it is preferable that the apex angle of each unit prism is changed so as to be larger on the side farther from the side closer to the center of the concentric circle. Furthermore, it is preferable that the apex angle of each unit prism changes within a range of 30 ° to 45 °. Furthermore, it is preferable that the apex angle of each unit prism continuously changes from the side closer to the center of the concentric circle to the side farther from the center.
[0017]
In the present invention, the total reflection prism lens includes a first apex angle fixing region in which an apex angle of each unit prism is constant at a predetermined first angle, and the first apex angle fixing region. A second apex angle fixing region which is located in a different area and is constant at a predetermined second angle different from the first angle; and the first apex angle fixing region and the first prism The vertical angle of each unit prism is between the first angle and the second angle, depending on the position of each unit prism on the screen surface. It is preferable to have a changing apex angle changing region.
[0018]
Here, the apex angle changing region is such that the apex angle of each unit prism changes only the angle of the first surface with respect to the screen surface without changing the angle of the second surface with respect to the screen surface. It is preferable to have a first apex angle changing portion that changes. The apex angle changing region is located between the first apex angle changing unit and the first apex angle fixing region, and the apex angle of each unit prism is the first surface and the screen surface. The second apex angle changing part that changes by changing the angle of the second surface, and the first apex angle changing part and the second apex angle fixing area, It is preferable that the apex angle of the unit prism further includes a third apex angle changing portion that changes as the angles of the first surface and the second surface with respect to the screen surface change.
[0019]
Furthermore, in the present invention, it is preferable that the first surface of each unit prism has a draft of 0 ° or more with respect to a perpendicular to the screen surface. In addition, it is preferable that the first surface of each unit prism has a uniform surface roughness over the entire screen surface.
[0020]
In the present invention, it is preferable to further include a lenticular lens that is provided on the observation side of the total reflection prism lens and diffuses light that has passed through the total reflection prism lens.
[0021]
Here, it is preferable that the lenticular lens has a plurality of unit lenses having a semi-elliptical cross section or a plurality of unit lenses having a trapezoidal cross section.
[0022]
The unit lenses having a trapezoidal cross section are arranged so that the lower bottom part is on the light incident side and the upper bottom part is on the light output side, and the cross section is V-shaped between the adjacent unit lenses. The unit lenses are formed of a material having a predetermined refractive index, and the portions provided between the unit lenses have a refractive index lower than the refractive index of the unit lenses. It is preferable that the light is totally reflected by an interface between each unit lens and a portion provided between the unit lenses. Moreover, it is preferable that each said part whose cross section is V-shaped has the light absorption effect | action which absorbs the light which injected from the observation side. Furthermore, it is preferable that each of the portions having a V-shaped cross section is formed by mixing light-absorbing particles in the resin.
[0023]
Furthermore, in the present invention, it is preferable that the total reflection prism lens and the lenticular lens are integrally formed on one sheet.
[0024]
Furthermore, in the present invention, diffusion is provided on the observation side of the total reflection prism lens (or the lenticular lens), and diffuses light that has passed through the total reflection prism lens (or the total reflection prism lens and the lenticular lens). It is preferable to further provide a sheet.
[0025]
Furthermore, in the present invention, it further comprises a functional retention layer including at least one layer selected from the group consisting of an antireflection layer, a hard coat layer, an antistatic layer, an antiglare layer, an antifouling layer and a sensor layer. Is preferred.
[0026]
The present invention also provides a projection display device comprising the projection screen as described above and a projection optical system that projects image light obliquely onto the projection screen.
[0027]
According to the present invention, in the projection screen on which the image light is obliquely projected from the projection optical system arranged on the back side, the total reflection prism lens having the plurality of unit prisms is provided on the back side on which the image light is incident. The optical axis of the image light projected obliquely from the projection optical system can be corrected only on the light incident surface side (back surface side), and the image can be emitted toward the observation side. At this time, in the present invention, the apex angle of each unit prism is changed in accordance with the position of each unit prism on the screen surface. Specifically, for example, in the case where each unit prism extends concentrically with reference to the center of a concentric circle deviated from the screen surface, the apex angle of each unit prism is set within a certain angular range (for example, 30 ° or more and 45 °). In a range of less than or equal to (°), the distance on the far side is larger than the side near the center of the concentric circle. That is, the vertical angle of each unit prism is made smaller at the portion closer to the projection optical system where the incident angle of the image light is smaller, and each unit prism is arranged at the portion farther from the projection optical system where the incident angle of the image light is larger The apex angle is made larger. For this reason, it is possible to widen the allowable range of the incident angle of the image light as a range in which the loss of the image light due to the occurrence of stray light or the like does not occur, and there is no decrease in the surface brightness and the contrast, and the image light is transmitted from the projection optical system. It is possible to obtain a projection screen and a projection display device capable of displaying a high-quality video having a level equivalent to that of a video obtained when projected substantially vertically.
[0028]
Further, according to the present invention, in the total reflection prism lens, the first apex angle fixed region where the apex angle of each unit prism is constant at a predetermined first angle is different from the first apex angle fixed region. A second apex angle fixing region, the apex angle of each unit prism being constant at a predetermined second angle different from the first angle, the first apex angle fixing region, and the second apex angle An apex angle that is located between the angle fixed region and the apex angle of each unit prism is changed between the first angle and the second angle in accordance with the position of each unit prism on the screen surface. By providing the change region, the apex angle of each unit prism of the total reflection prism lens can be changed only in a part thereof, not over the entire screen surface. Thereby, it becomes easy to produce a mold for molding the total reflection prism lens, and a high-quality projection screen and projection display device can be obtained at a lower cost.
[0029]
Furthermore, according to the present invention, in the apex angle changing region of the total reflection prism lens, the apex angle of each unit prism is the angle of the first surface with respect to the screen surface without changing the angle of the second surface with respect to the screen surface. Is located between the first apex angle changing portion that changes by changing only the first apex angle changing region and the first and second apex angle fixing regions, and the apex angle of each unit prism is By providing the second and third apex angle changing portions that change by changing the angles of the first surface and the second surface with respect to the screen surface, the boundary of each region can be made less noticeable. It is possible to achieve higher image quality.
[0030]
Furthermore, according to the present invention, the first surface of each unit prism has an omission gradient of 0 ° or more with respect to a normal line (normal line) to the screen surface. It is possible to prevent loss. Also, in this case, since the mold for molding each unit prism does not include a reverse-tapered portion, the fabrication of the mold becomes easy, and each unit prism from the mold during lens molding The mold release can be easily performed.
[0031]
Furthermore, according to the present invention, by making the surface roughness of the first surface of each unit prism uniform over the entire screen surface, it is possible to prevent image unevenness on the screen surface. A high-quality image can be observed.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0033]
First embodiment
First, a projection screen and a projection display apparatus including the projection screen according to the first embodiment of the present invention will be described with reference to FIGS.
[0034]
As shown in FIG. 1, the projection display apparatus 100 according to the first embodiment of the present invention includes a projection screen 111 and a projection optical system 112 that projects image light L obliquely onto the projection screen 111. ing. Note that the projection optical system 112 has an image light source such as an LCD or DMD, and an optical system for expanding image light emitted from the image light source.
[0035]
Here, the projection screen 111 emits the image light L projected obliquely from the projection optical system 112 disposed on the back side toward the observation side, and includes a total reflection prism lens 114 and a total reflection prism lens. 114 has a lenticular lens 115 provided on the observation side.
[0036]
Among these, the total reflection prism lens 114 refracts and condenses the image light L projected from the projection optical system 112, and as shown in FIG. A plurality of unit prisms 113 are provided on the surface side.
[0037]
Each unit prism 113 has an incident surface (first surface) 113a that refracts incident light, and a total reflection surface (second surface) 113b that totally reflects light refracted by the incident surface 113a. The obliquely incident video light L can be refracted and totally reflected to travel in a direction substantially perpendicular to the screen surface. Each unit prism 113 is formed as an arcuate prism that extends concentrically with reference to a center O (see FIG. 1) of a concentric circle that is off the screen surface. Specifically, for example, each unit prism 113 preferably has a prism pitch of 100 to 200 μm and a prism height of 150 to 300 μm.
[0038]
Here, each unit prism 113 has an apex angle λ corresponding to an angle formed by the incident surface 113a and the total reflection surface 113b, and the apex angle λ of each unit prism 113 corresponds to each unit prism on the screen surface. It changes according to the position of 113. In particular, the apex angle λ of each unit prism 113 is in the range of 30 ° or more and 45 ° or less and is continuous so that the side farther from the side closer to the center O of the concentric circle (lower side in the drawing) (upper side in the drawing) becomes larger. It is preferable that it changes.
[0039]
On the other hand, the lenticular lens 115 diffuses light that has passed through the total reflection prism lens 114 in the horizontal direction, and a plurality of cylindrical unit lenses 116 are provided on the light incident surface side on which the image light L is incident. . Specifically, for example, the cross section of each unit lens 116 is a semi-elliptical shape with a lens lateral diameter of 140 μm and a lens vertical diameter of 100 μm, a lens pitch of 140 μm, a lens height of 50 μm, and a horizontal diffusion angle. Is preferably 20 to 50 ° in terms of half-value angle (the angle at which the luminance when observed from a certain direction is half the luminance when observed from the front).
[0040]
As shown in FIGS. 1 and 2, the total reflection prism lens 114 and the lenticular lens 115 are formed on separate sheets (prism sheet and lenticular lens sheet). In FIGS. 1 and 2, the total reflection prism lens 114 and the lenticular lens 115 are drawn apart from actual dimensions for easy understanding.
[0041]
Next, the optical path of the image light L in the total reflection prism lens 114 of the projection screen 111 shown in FIG. 1 will be described with reference to FIG.
[0042]
As shown in FIG. 3, the image light L emitted from the projection optical system (see reference numeral 112 in FIG. 1) has different incident angles θ depending on the position on the screen surface.₁Thus, the light enters the incident surface 113a of each unit prism 113 of the total reflection prism lens 114. The incident angle θ of the image light L₁Is preferably 35 ° or more (preferably 45 ° or more) and 50 ° or less at the end of the screen surface closer to the projection optical system (side closer to the center O of the concentric circle).
[0043]
The video light L incident on the incident surface 113a of each unit prism 113 in this way is refracted by the incident surface 113a, totally reflected by the total reflection surface 113b, and then substantially perpendicular to the screen surface toward the observation side. Proceed in the direction.
[0044]
In order to realize such an optical path of the image light L, the incident angle θ of the image light L₁The shape of each unit prism 113 is determined according to the above. Specifically, the lens angle of each unit prism 113 (the angle formed by the total reflection surface 113b and the screen surface) is φ, the apex angle of each unit prism 113 is λ, and the refractive index of the material of the total reflection prism lens 114 is n. , The angle formed by the image light L after being reflected by the total reflection surface 113b of each unit prism 113 and the normal line of the screen surface is θ₄In this case, the shape of each unit prism 113 is determined by the following equation (1).
[Expression 1]

[0045]
Also, assuming that the surface on the light output side of the total reflection prism lens 114 is a flat surface, the angle θ at which the image light L travels in the total reflection prism lens 114.₄And the output angle θ of the image light L emitted from the total reflection prism lens 114₅The following equation (2) is established between
sinθ₄= Sinθ₅/ N (2)
[0046]
Here, when the angle formed between the incident surface 113a of each unit prism 113 and the normal line of the screen surface is γ,
γ = φ + λ−π / 2 ≧ 0 (3)
It is preferable that
[0047]
This is because, when the angle γ of the incident surface 113a of each unit prism 113 is negative, the shape of the incident surface 113a of each unit prism 113 becomes a reverse taper shape, and a molding die for molding each unit prism 113 is produced. This is because it is difficult to form the unit prisms 113 with a mold.
[0048]
The lens angle φ of each unit prism 113 is the incident angle θ of the image light L.₁Therefore, the angle γ of the incident surface 113a of each unit prism 113 is equal to the incident angle θ of the image light L on the screen surface.₁Tends to be negative at a portion where the value of becomes large (portion far from the center O of the concentric circle). Here, the angle θ at which the image light L travels in the total reflection prism lens 114₄Is approximately 0, a condition for preventing the shape of the incident surface 113a of each unit prism 113 from becoming an inversely tapered shape is expressed by the following equation (4).
cos^-1{Cos (θ₁) / N} / 2 ≦ λ (4)
[0049]
On the other hand, the incident angle θ of the image light L on the screen surface₁In a portion where the value becomes smaller (a portion closer to the center O of the concentric circle), a part of the image light L incident on the incident surface 113a of each unit prism 113 is not totally reflected by the total reflection surface 113b and becomes stray light. .
[0050]
Here, in order to explain how stray light is generated in each unit prism 113, the reference image light L that is refracted by the incident surface 113a of the unit prism 113 and just goes to the valley of the unit prism 113.₀(In other words, image light passing through the position of the boundary between the portion where the image light L becomes stray light and the portion where it becomes effective light in one unit prism 113) will be considered.
[0051]
The incident angle of the image light L with respect to the incident surface 113a of each unit prism 113 is θ₂, The refraction angle at the incident surface 113a of each unit prism 113 is θ₃, P is the prism pitch of the unit prism 113, and e is the width of the portion that is totally reflected by the total reflection surface 113b of each unit prism 113 and is preferably used as effective light.₁ , The width of the part which is not totally reflected by the total reflection surface 113b of each unit prism 113 and becomes stray light is e.₂When the height of each unit prism 113 is h and the height of the boundary between the portion where the image light L becomes stray light and the portion where the image light L becomes effective light in the incident surface 113a of each unit prism 113 is s, the image light L is Width e of effective light₁Is represented by the following equation (5).
e₁= (H−s) × (tan (φ + λ−π / 2) + tan θ₁(5)
[0052]
Here, in the above equation (5), h and s can be expressed by the following equations (6) and (7), respectively.
h = p × tan (φ + λ) × tanφ / (tan (φ + λ) −tanφ) (6)
s = −p × tan (φ + λ) / (1 + tan (φ + λ) × tan (φ + λ + θ)₃)) ... (7)
In addition,
θ₃= Sin^-1{Sin (θ₁+ Φ + λ) / n} (8)
It is.
[0053]
As is clear from FIG. 3, the prism pitch p and the width e of the portion where the image light L becomes effective light.₁E between₁There is a relationship of ≦ p. Further, the width e of the portion where the image light L becomes effective light₁And the ratio e of the lens pitch p₁/ P is the incident angle θ of the image light L₁Increases as the value of e increases.₁= P. In this case, e₁= Incident angle θ of image light L compared to the position where p = p₁In the region where becomes large, the image light L incident on the incident surface 113a of each unit prism 113 is totally reflected by the total reflection surface 113b, and stray light does not exist.
[0054]
As described above, the incident angle θ of the image light L on the screen surface.₁In a portion where the value becomes smaller (a portion closer to the center O of the concentric circle), a part of the image light L incident on the incident surface 113a of each unit prism 113 is not totally reflected by the total reflection surface 113b and becomes stray light. On the other hand, the incident angle θ of the image light L on the screen surface₁There is a problem that the shape of the incident surface 113a of each unit prism 113 becomes an inversely tapered shape in a portion where the distance becomes larger (portion far from the center O of the concentric circle).
[0055]
4 shows the apex angle λ of each unit prism 113 and the incident angle θ of the image light L in the total reflection prism lens 114 of the projection screen 111 shown in FIG.₁It is a figure for demonstrating the relationship.
[0056]
In FIG. 4, a line 205 indicates an angle θ that the image light L travels in the total reflection prism lens 114.₄Is 0 (that is, the emission angle θ of the image light L emitted from the total reflection prism lens 114)₅Is a boundary where stray light is generated in each unit prism 113, obtained in accordance with the above equations (5) to (8), and a line 206 is in accordance with the above equation (4) in the same case. The obtained boundary where the shape of the incident surface 113a of each unit prism 113 becomes a reverse taper shape is shown. When obtaining the lines 205 and 206, the refractive index n of the material of the total reflection prism lens 114 is set to 1.55.
[0057]
In FIG. 4, in the inner region surrounded by two lines 205 and 206, a part of the image light L incident on the incident surface 113a of each unit prism 113 passes through without being totally reflected by the total reflection surface 113b. This is a region in which stray light is not generated and the shape of the incident surface 113a of each unit prism 113 is not reversely tapered. For this reason, the apex angle λ of each unit prism 113 and the incident angle θ of the image light L according to the position of each unit prism 113 on the screen surface.₁However, if it exists in this region, neither the problem of stray light nor the problem of the inverse taper shape occurs. Specifically, for example, considering the case where the apex angle λ of each unit prism 113 is constant at 35 °, the incident angle θ of the image light L₁Is in the range of 45 to 60 °, neither the problem of stray light nor the problem of the inverse taper shape occurs (see reference numeral 207).
[0058]
However, in recent years, the projection screen 111 tends to increase in size, and accordingly, the incident angle θ of the image light L₁Therefore, if the apex angle λ of each unit prism 113 is constant, the incident angle θ of the image light L on the screen surface is₁And the incident angle θ of the image light L₁It becomes a part where becomes large, and it becomes easy to remove | deviate from the inner area | region enclosed by line 205,206.
[0059]
Here, in order to solve the problem of stray light, the incident angle θ of the image light L defined by the line 205 is obtained.₁Therefore, it is effective to lower the allowable lower limit value of the image light L. Therefore, the incident angle θ of the image light L on the screen surface is effective.₁It is preferable to reduce the apex angle λ of each unit prism 113 at a portion where the angle becomes smaller (a portion closer to the center O of the concentric circle). On the other hand, in order to eliminate the problem of the inverse taper shape, the incident angle θ of the image light L defined by the line 206 is₁Therefore, it is effective to increase the allowable upper limit value of the image light L. Therefore, the incident angle θ of the image light L on the screen surface is effective.₁It is preferable to increase the apex angle λ of each unit prism 113 in a portion where the angle becomes larger (portion far from the center O of the concentric circle).
[0060]
For this reason, in the present embodiment, the apex angle λ of each unit prism 113 is continuously extended over the entire screen surface so that the side of the screen surface farther from the side closer to the concentric circle center O is larger. (See reference numerals 201 to 203). Thereby, the incident angle θ of the image light L₁Can be widened, and the problem of stray light and the problem of the inverse taper shape can be prevented from occurring over the entire screen surface. Note that lines 201 to 203 shown in FIG. 4 indicate the change in the apex angle λ of each unit prism 113 as the incident angle θ of the image light L.₁The change in the apex angle λ of each unit prism 113 can naturally be shown in relation to the position of each unit prism 113 (distance from the center O of the concentric circle). The relationship is as shown in FIG.
[0061]
In the above-described embodiment, the incident surface 113a of each unit prism 113 has a draft (incident surface 113a) of 0 ° or more (preferably 1/1000 ° or more) with respect to a normal (normal line) to the screen surface. And an angle γ formed by the normal to the screen surface is preferably a positive slope). The surface roughness of the incident surface 113a of each unit prism 113 is preferably uniform over the entire screen surface.
[0062]
In the above-described embodiment, the case where the apex angle λ of each unit prism 113 is continuously changed over the entire screen surface is described as an example. However, the present invention is not limited to this. May be changed stepwise within the screen plane.
[0063]
Second embodiment
Next, a projection display device including a projection screen according to the second embodiment of the present invention will be described with reference to FIGS. The second embodiment of the present invention is the same as that described above except that the configuration of the lenticular lens is different and the total reflection prism lens and the lenticular lens are integrally formed on one sheet. This is the same as in the first embodiment. In the second embodiment of the present invention, the same parts as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.
[0064]
As shown in FIG. 6, a projection display device 100 ′ according to the second embodiment of the present invention includes a projection screen 111 ′ and a projection optical system 112 that projects image light L obliquely onto the projection screen 111 ′. And.
[0065]
Here, the projection screen 111 ′ emits the image light L projected obliquely from the projection optical system 112 disposed on the back side toward the observation side, and includes a total reflection prism lens 114 ′ and a total reflection. And a lenticular lens 115 ′ provided on the observation side of the prism lens 114 ′.
[0066]
Among them, the total reflection prism lens 114 ′ refracts and condenses the image light L projected from the projection optical system 112. As shown in FIG. 7, the base sheet 23 and the incident light of the base sheet 23 are used. And a plurality of unit prisms 113 formed on the side surface (the most incident light surface on which the image light L is incident). As in the first embodiment described above, each unit prism 113 includes an incident surface (first surface) 113a that refracts incident light and a total reflection that totally reflects light refracted by the incident surface 113a. And a reflecting surface (second surface) 113b. Each unit prism 113 is formed as an arc-shaped prism that extends concentrically with respect to the center O (see FIG. 6) of a concentric circle that is off the screen surface. It changes in accordance with the position of each unit prism 113 on the surface. In particular, the apex angle λ of each unit prism 113 is in the range of 30 ° or more and 45 ° or less and is continuous so that the side farther from the side closer to the center O of the concentric circle (lower side in the drawing) (upper side in the drawing) becomes larger. It is preferable that it changes. In addition, as a mode of change of the apex angle λ of each unit prism 113, a mode similar to the case of the first embodiment described above can be taken.
[0067]
On the other hand, as shown in FIGS. 7 and 8, the lenticular lens 115 ′ is formed on the surface on the light output side of the base sheet 23, and has a plurality of trapezoidal portions (unit lenses) 25 having a trapezoidal cross section. ing.
[0068]
Here, each trapezoidal portion 25 is arranged such that the lower bottom portion is on the light incident side and the upper bottom portion is on the light output side, and the cross section between the adjacent trapezoidal portions 25 is V-shaped. The V-shaped portion 26 is provided. Each trapezoidal portion 25 is made of a material having a predetermined refractive index. Each V-shaped portion 26 is formed by filling a material having a refractive index lower than the refractive index of each trapezoidal portion 25 between the V-shaped portions 26. The image light L can be diffused by totally reflecting the light by the interface with the V-shaped portion 26 provided between them (see FIGS. 7 and 8).
[0069]
Moreover, it is preferable that each V-shaped part 26 has the light absorption effect | action which absorbs the light which injected from the observation side. The material of each V-shaped portion 26 is not particularly limited. For example, the V-shaped portion 26 is formed by mixing light-absorbing particles composed of dyes, pigments, or colored resin fine particles in a low refractive index synthetic resin. Is preferred.
[0070]
6 to 8, the image light L projected obliquely from the projection optical system 112 is incident on the incident surface 113a of each unit prism 113 of the total reflection prism lens 114 ′.
[0071]
The video light L incident on the incident surface 113a of each unit prism 113 in this way is refracted by the incident surface 113a, totally reflected by the total reflection surface 113b, and then substantially perpendicular to the screen surface toward the observation side. Proceed in the direction.
[0072]
Thereafter, the image light L emitted from the total reflection prism lens 114 ′ in this way is incident from the lower bottom portion side of the trapezoidal portion 25 of the lenticular lens 115 ′, and part of the light is transmitted as it is. The remaining light is totally reflected at the interface between the trapezoidal portion 25 and the V-shaped portion 26, and finally all the light is emitted from the upper bottom portion side of the trapezoidal portion 25 toward the observation side.
[0073]
As described above, according to the first and second embodiments of the present invention, the image light L is projected on the projection screens 111 and 111 ′ on which the image light L is obliquely projected from the projection optical system 112 disposed on the back side. The apex angles λ of the plurality of unit prisms 113 of the total reflection prism lenses 114, 114A, 114B, 114 ′ provided on the back side where the light enters is concentric with a certain angle range (for example, a range of 30 ° to 45 °) It is made to change so that the side far from the side close | similar to the center O may become large. Thereby, the incident angle θ of the image light L₁The apex angle λ of each unit prism 113 is made smaller at the part closer to the projection optical system 112 where the angle of incidence becomes smaller, and the incident angle θ of the image light L₁The apex angle λ of each unit prism 113 can be made larger at a portion far from the projection optical system 112 where the angle becomes larger. Therefore, the incident angle θ of the image light L as a range in which loss of the image light L due to generation of stray light or the like does not occur.₁Can be widened, there is no decrease in surface brightness and contrast, and the image quality is equivalent to the image quality obtained when the image light L is projected substantially vertically from the projection optical system 112. The projection screens 111 and 111 ′ and the projection display devices 100 and 100 ′ can be obtained.
[0074]
Further, according to the first and second embodiments of the present invention, the incident surface 113a of each unit prism 113 has a draft of 0 ° or more with respect to a perpendicular (normal line) to the screen surface. Therefore, the molding die for molding each unit prism 113 does not include a reverse-tapered portion, making it easy to manufacture the molding die, and each unit prism 113 from the molding die during lens molding. The mold release can be easily performed.
[0075]
Furthermore, according to the first and second embodiments of the present invention, since the surface roughness of the incident surface 113a of each unit prism 113 is uniform over the entire screen surface, the image unevenness on the screen surface. A high-quality image can be observed without being generated.
[0076]
(Other embodiments)
The present invention is not limited to the above-described first and second embodiments, and various modifications and changes as described in the following (1) to (6) are possible. It is within the scope of the present invention.
[0077]
(1) In the first and second embodiments described above, total reflection prism lenses 114, 114A, 114B, 114 'and lenticular lenses 115, 115' are used as total reflection prism lenses and lenticular lenses. Specific shapes of the total reflection prism lens, the lenticular lens, and the like are not limited to those described above, and any configuration can be adopted as long as they have the characteristics of the present invention described above.
[0078]
(2) In the first embodiment described above, the total reflection prism lenses 114, 114A, 114B, 114 ′ and the lenticular lens 115 are formed on separate sheets (prism sheet and lenticular lens sheet). However, the total reflection prism lenses 114, 114A, 114B and the lenticular lens 115 may be integrally formed on one sheet. On the other hand, in the second embodiment described above, the total reflection prism lens 114 ′ and the lenticular lens 115 ′ are integrally formed on one sheet. The lenticular lens 115 ′ may be formed on separate sheets (prism sheet and lenticular lens sheet).
[0079]
(3) In the first and second embodiments described above, the observation side of the lenticular lenses 115 and 115 '(when there are no lenticular lenses 115 and 115', total reflection prism lenses 114, 114A, 114B, 114 ' 1 and FIG. 6, a diffusion sheet that diffuses the image light L that has passed through the total reflection prism lenses 114, 114 </ b> A, 114 </ b> B, 114 ′ and the lenticular lenses 115, 115 ′. May be provided. In addition, it is preferable that the diffusion sheet is provided with a diffusion action by mixing a diffusion agent or the like.
[0080]
(4) In the first and second embodiments described above, the lenticular lenses 115 and 115 'are provided on the observation side of the total reflection prism lenses 114, 114A, 114B and 114'. Instead of ′, a diffusion sheet for diffusing light with a diffusing agent or the like, a bead screen coated with a plurality of beads for diffusing light by light refraction can be used.
[0081]
(5) In the first and second embodiments described above, the observation side of the lenticular lenses 115, 115 ′ (when there is no lenticular lens 115, 115 ′, total reflection prism lenses 114, 114A, 114B, 114 ′ On the observation side, a functional retention layer may be provided. Various types of functional retention layers can be used. For example, an antireflection layer (AR layer), a hard coat layer (HC layer), an antistatic layer (AS layer), an antiglare layer (AG) Layer), an antifouling layer and a sensor layer.
[0082]
Here, the antireflection layer (AR layer) is a layer for suppressing reflection of light on the surfaces of the projection screens 100 and 100 ', and a film having a function of suppressing the reflectance of light is laminated on the lens surface. It can be obtained by directly applying an antireflection treatment to the lens surface. The hard coat layer (HC layer) is a layer for protecting the surfaces of the projection screens 100 and 100 'to prevent scratches, and a wear-resistant film having a function of increasing the strength is laminated on the lens surface. It can be obtained by directly applying a hard coat treatment to the lens surface. The antistatic layer (AS layer) is a layer for removing static electricity generated in the projection screens 100 and 100 ', and a film having an antistatic function is laminated on the lens surface, or an antistatic treatment is directly applied to the lens surface. Can be obtained. The anti-glare layer (AG layer) is a layer for preventing glare of the projection screens 100 and 100 ', and a film having an anti-glare function is laminated on the lens surface or anti-glare treatment is applied to the lens surface. Obtained by direct application. The antifouling layer is a layer for preventing dirt from adhering to the surfaces of the projection screens 100 and 100 ', and a film having a function of preventing the adhesion of dirt is laminated on the lens surface, or the lens surface is antifouling. Obtained by direct treatment. The sensor layer is a layer having a function such as a touch sensor.
[0083]
(6) In the projection display devices 100 and 100 ′ according to the first and second embodiments described above, the image light L emitted from the projection optical system 112 is projected upward toward the projection screens 111 and 111 ′. However, the present invention is not limited to this, and it is also possible to adopt a downfall method in which the image light L emitted from the projection optical system 112 is projected downward toward the projection screens 111 and 111 ′. Good.
[0084]
Here, when the launch method is adopted in the projection display devices 100 and 100 ′, the projection screens 111 and 111 ′ and the projection optical system 112 are accommodated in the cabinet 151 in the positional relationship as shown in FIG. The Specifically, for example, an LCD light valve is used as the image light source of the projection optical system 112, and the incident angle θ of the image light L incident on the lower end of the screen surface with respect to the 50-inch projection screens 111 and 111 ′.₁₁Is 45 °, the incident angle θ of the image light L incident on the upper end of the screen surface₁₀It is possible to project an image from below the projection screens 111 and 111 ′ in such a manner that the angle is 60 °. In this case, the horizontal distance between the projection screens 111 and 111 ′ and the projection optical system 112 is approximately 800 mm.
[0085]
On the other hand, when the down-sliding method is adopted in the projection display devices 100 and 100 ′, the projection screens 111 and 111 ′ and the projection optical system 112 are accommodated in the cabinet 152 in the positional relationship as shown in FIG. The Specifically, for example, the DMD is used as the image light source of the projection optical system 112, and the incident angle θ of the image light L incident on the upper end of the screen surface with respect to the 50 inch projection screens 111 and 111 ′.₂₀Is 45 °, the incident angle θ of the image light L incident on the lower end of the screen surface₂₁It is possible to project an image from above the projection screens 111 and 111 ′ so that the angle is 70 °. In this case, the horizontal distance between the projection screens 111 and 111 ′ and the projection optical system 112 is approximately 700 mm.
[0086]
9 and 10, the image light L emitted from the projection optical system 112 is directly projected onto the projection screens 111 and 111 '. However, the present invention is not limited to this. 11 may be stored in the cabinet 153 in the positional relationship as shown in FIG. 11 and the image light L emitted from the projection optical system 112 may be projected onto the projection screens 111 and 111 ′ via the folding mirror 155.
[0087]
【Example】
Next, specific examples of the above-described embodiment will be described.
[0088]
Example 1
As a projection screen according to Example 1, a projection screen for a 50-inch rear projection television having a prism sheet and a lenticular lens sheet was manufactured. Note that the projection screen according to Example 1 corresponds to the first embodiment described above.
[0089]
First, a mold obtained by cutting with an NC lathe is used to cure an ultraviolet curable resin (with a refractive index of 1.55 after curing) on a 1.8 mm thick acrylic base sheet. By processing, a prism sheet having a thickness of 2 mm as a whole, in which a total reflection prism lens was formed on one surface, was obtained.
[0090]
Here, the total reflection prism lens formed on the prism sheet has a plurality of arc-shaped prisms (unit prisms) extending concentrically with reference to the center of the concentric circle deviated from the screen surface. The radius of the arc of each unit prism (distance from the center of the concentric circle) was 800 mm at the center of the lower end of the screen surface, the prism pitch was 100 μm, and the prism height was about 150 μm. The apex angle λ of each unit prism is 37 ° at the lower end of the screen surface (the portion closest to the center of the concentric circle) and 40 ° at the upper end of the screen surface (the portion farthest from the center of the concentric circle). And changed in the range of 37 to 40 ° (see FIG. 12). In addition, the output angle θ of the image light from each unit prism₅Was 0 (vertical emission).
[0091]
Next, a lenticular lens sheet was manufactured by extruding an impact-resistant acrylic resin using a cylindrical roll mold.
[0092]
Here, the lenticular lens formed on the lenticular lens sheet has a plurality of unit lenses having a semi-elliptical cross section. Each unit lens has a lateral diameter of 140 μm and a longitudinal lens diameter of 100 μm. Each unit lens has a lens pitch of 140 μm and a lens height of 50 μm. As a result, a diffusion characteristic with a horizontal diffusion angle of 35 ° at half-value angle and a vertical diffusion angle of 15 ° at half-value angle was obtained.
[0093]
In addition, when extrusion molding the lenticular lens sheet in this way, a very small amount of black dye and a diffusing agent were mixed with the impact-resistant acrylic resin. The transmittance of the lenticular lens sheet thus manufactured was 70%, and an antireflection effect and a diffusion effect such as external light were obtained.
[0094]
A projection screen was manufactured by combining the prism sheet and the lenticular lens sheet manufactured as described above. In addition, the projection screen manufactured in this way was incorporated into a launch-type projection display apparatus (a rear projection television) as shown in FIG. The screen size of the projection screen is 50 inches, and an LCD light valve was used as the image light source of the projection optical system. Here, the projection optical system was disposed at a height of 800 mm below the lower end of the screen surface, and the horizontal distance (projection distance) between the projection screen and the projection optical system was 800 mm. Also, the incident angle θ of the image light incident on the lower end of the screen surface₁₁45 °, the incident angle θ of the image light incident on the center of the upper end of the screen surface₁₀Was 60 °.
[0095]
(Example 2)
As the projection screen according to Example 2, a projection screen for a 50-inch rear projection television in which a total reflection prism lens and a lenticular lens were integrally formed was manufactured. Note that the projection screen according to Example 2 corresponds to the second embodiment described above.
[0096]
First, a mold obtained by cutting with an NC lathe is used to cure an ultraviolet curable resin (with a refractive index of 1.55 after curing) on a 1.8 mm thick acrylic base sheet. By processing, a prism sheet having a thickness of 2 mm as a whole, in which a total reflection prism lens was formed on one surface, was obtained.
[0097]
Here, the total reflection prism lens formed on the prism sheet has a plurality of arc-shaped prisms (unit prisms) extending concentrically with reference to the center of the concentric circle deviated from the screen surface. The radius of the arc of each unit prism (distance from the center of the concentric circle) was 800 mm at the center of the lower end of the screen surface, the prism pitch was 100 μm, and the prism height was about 150 μm. The apex angle λ of each unit prism is 37 ° at the lower end of the screen surface (the portion closest to the center of the concentric circle) and 40 ° at the upper end of the screen surface (the portion farthest from the center of the concentric circle). And continuously changed in the range of 37 to 40 ° (see FIG. 12). In addition, the output angle θ of the image light from each unit prism₅Was 0 (vertical emission).
[0098]
Next, on the opposite surface of the prism sheet manufactured as described above, a plurality of trapezoidal sections (unit lenses) having a trapezoidal cross section are formed, and then, between the adjacent trapezoidal sections, A V-shaped portion was formed by filling a low refractive index resin containing light absorbing particles. In addition, as a material of each trapezoidal part, high refractive index epoxy acrylate was used. Moreover, low refractive index urethane acrylate was used as the material of each V-shaped part, and Rabcoroll (registered trademark) manufactured by Dainichi Seika Kogyo Co., Ltd. was used as the light-absorbing particles. In addition, the average particle diameter of the love color was 8 μm, and the addition amount was 45% by weight.
[0099]
Here, the lens pitch of each trapezoidal portion was 50 μm and the refractive index was 1.57. The refractive index of each V-shaped portion was 1.48. The length of the upper base part of each trapezoidal part and the length of the base part of the triangle of each V-shaped part were made equal to each other, and the so-called black stripe ratio was set to 50%. The vertex angle of each V-shaped part was 20 °.
[0100]
As described above, a projection screen in which the total reflection prism lens and the lenticular lens were integrally formed on the front and back of one sheet was manufactured. In addition, the projection screen manufactured in this way was incorporated into a launch-type projection display device (rear projection type television) as shown in FIG. The screen size of the projection screen is 50 inches, and an LCD light valve was used as the image light source of the projection optical system. Here, the projection optical system was disposed at a height of 800 mm below the lower end of the screen surface, and the horizontal distance (projection distance) between the projection screen and the projection optical system was 800 mm. Also, the incident angle θ of the image light incident on the lower end of the screen surface₁₁45 °, the incident angle θ of the image light incident on the center of the upper end of the screen surface₁₀Was 60 °.
[0101]
(Example 3)
As a projection screen according to Example 3, an AR coat film having a thickness of 0.1 mm was laminated on the front side (most observation side) of the lenticular lens of the projection screen according to Example 2.
[0102]
(Comparative Example 1)
As the projection screen according to Comparative Example 1, the projection according to Example 4 was manufactured by making the apex angle λ of each unit prism of the total reflection prism lens constant at 40 °.
[0103]
(Evaluation results)
In the projection screen according to Example 1, the allowable range of the incident angle was wide, and a high-quality image was obtained without a decrease in surface luminance and a decrease in contrast. Further, the transmittance was 60%, the reflectance was 5%, and the gain was 3. The vertical diffusion angle (vertical viewing angle) (half-value angle) was 10 °, and the horizontal diffusion angle (horizontal viewing angle) (half-value angle) was 25 °.
[0104]
In the projection screen according to Example 2, as in Example 1, the allowable range of the incident angle was wide, and a high-quality image was obtained without a decrease in surface luminance or a contrast. Further, the transmittance was 80%, the reflectance was 5%, and the gain was 4. The vertical diffusion angle (vertical viewing angle) (half-value angle) was 12 °, and the horizontal diffusion angle (horizontal viewing angle) (half-value angle) was 25 °.
[0105]
In the projection screen according to Example 3, as in Example 2, the allowable range of the incident angle was wide, and a high-quality image was obtained without a reduction in surface luminance or contrast. Further, the reflectance was improved by 1.5% compared to Example 2.
[0106]
On the other hand, in the projection screen according to Comparative Example 1, the vicinity of the lower center of the screen surface was slightly darker than the projection screens according to Examples 1 to 3, and ghosts were observed.
[0107]
【The invention's effect】
As described above, according to the present invention, the allowable range of the incident angle of the image light as a range in which the loss of the image light due to the occurrence of stray light or the like does not occur is widened, and there is no decrease in surface luminance or contrast, and the image light source Therefore, it is possible to display a high-quality video having a level equivalent to that of the video obtained when the video light is projected substantially vertically.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a projection display device including a projection screen according to a first embodiment of the invention.
FIG. 2 is a perspective view showing a main part of the projection screen shown in FIG.
3 is a view for explaining an optical path of image light in a total reflection prism lens of the projection screen shown in FIG. 1; FIG.
4 is a diagram for explaining a relationship between an apex angle of each unit prism and an incident angle of image light in the total reflection prism lens of the projection screen shown in FIG. 1;
FIG. 5 is a view for explaining the relationship between the position of each unit prism and the apex angle in the total reflection prism lens of the projection screen shown in FIG. 1;
FIG. 6 is a schematic perspective view showing a projection display device provided with a projection screen according to a second embodiment of the present invention.
7 is a perspective view showing a main part of the projection screen shown in FIG. 6. FIG.
8 is a cross-sectional view taken along line XIII-XIII shown in FIG.
FIG. 9 is a diagram showing a first assembly example of a projection display device including a projection screen according to the first and second embodiments of the present invention.
FIG. 10 is a diagram showing a second assembly example of the projection display device including the projection screen according to the first and second embodiments of the present invention.
FIG. 11 is a diagram showing a third assembly example of the projection display device including the projection screen according to the first and second embodiments of the present invention.
FIG. 12 is a diagram showing the relationship between the position of each unit prism of the total reflection prism lens and the apex angle in Examples 1 to 3;
FIG. 13 is a diagram showing an example of a projection screen provided with a general Fresnel lens sheet.
FIG. 14 is a diagram for explaining an optical path of image light when a vertex angle of a unit prism is large in a projection screen including a total reflection prism lens.
FIG. 15 is a diagram for explaining an optical path of video light when a vertex angle of a unit prism is small in a projection screen including a total reflection prism lens.
[Explanation of symbols]
100,100 'projection display device
111, 111 'projection screen
112 Projection optical system
113 unit prism
113a Incident surface
113b Outgoing surface
114, 114 'total reflection prism lens
115,115 'lenticular lens
116 unit lens
117 Diffusion sheet
151, 152, 153 cabinet
155 Folding mirror

Claims (18)

In the projection screen for emitting image light projected obliquely from the projection optical system arranged on the back side toward the observation side,
A total reflection prism lens having a plurality of unit prisms provided on the back side on which image light is incident, wherein each unit prism is refracted by a first surface that refracts incident light and the first surface. A total reflection prism lens having a second surface that totally reflects the reflected light,
Each unit prism has an apex angle corresponding to an angle formed by the first surface and the second surface, and the apex angle of each unit prism is the position of each unit prism on the screen surface. Depending on the
The apex angle of each unit prism changes so that the side farther than the side closer to the projection optical system is larger,
The projection screen according to claim 1, wherein an apex angle of each unit prism changes in a range of 30 ° to 45 ° .   2. The projection screen according to claim 1, wherein each of the unit prisms extends concentrically with a center of a concentric circle deviated from the screen surface as a reference.   The projection screen according to claim 2, wherein an apex angle of each of the unit prisms is changed to be larger on a side farther than a side closer to the center of the concentric circle. The apex angle of the unit prisms is characterized by continuously changes toward the side close to the center of the concentric circle to the far side, projection screen according to any one of claims 1 to 3 . Wherein the first surface of each unit prism is characterized in that it has a 0 ° or more draft with respect to the normal to the screen surface, projection of any one of claims 1 to 4 screen. Said first surface, characterized in that the surface roughness is uniform over the entire surface of the screen surface, projection screen according to any one of claims 1 to 5 for each of the unit prisms. The projection according to any one of claims 1 to 6 , further comprising a lenticular lens that is provided on the observation side of the total reflection prism lens and diffuses light that has passed through the total reflection prism lens. screen. The projection screen according to claim 7 , wherein the lenticular lens includes a plurality of unit lenses having a semi-elliptical cross section. The projection screen according to claim 7 , wherein the lenticular lens includes a plurality of unit lenses having a trapezoidal cross section. Each unit lens having a trapezoidal cross section is disposed such that the lower bottom portion is on the light incident side and the upper bottom portion is on the light exit side, and a section having a V-shaped cross section between the adjacent unit lenses. The unit lenses are formed of a material having a predetermined refractive index, and the portion provided between the unit lenses is made of a material having a refractive index lower than the refractive index of the unit lenses. The projection screen according to claim 9 , wherein the projection screen is formed to totally reflect light by an interface between each unit lens and a portion provided therebetween. 11. The projection screen according to claim 10 , wherein each of the portions having a V-shaped cross section has a light absorption function of absorbing light incident from the observation side. 12. The projection screen according to claim 11 , wherein each of the portions having a V-shaped cross section is formed by mixing light absorbing particles in a resin. The projection screen according to any one of claims 7 to 12 , wherein the total reflection prism lens and the lenticular lens are integrally formed on a single sheet. Wherein provided on the viewing side of the total reflection prism lens, wherein the further comprising a diffusing sheet for diffusing light passing through the total reflection prism lens, projection of any one of claims 1 to 6 screen. 14. The diffractive sheet according to claim 7 , further comprising a diffusion sheet that is provided on the observation side of the lenticular lens and diffuses light that has passed through the total reflection prism lens and the lenticular lens. Projection screen. It further comprises a functional retention layer including at least one layer selected from the group consisting of an antireflection layer, a hard coat layer, an antistatic layer, an antiglare layer, an antifouling layer and a sensor layer. Item 16. The projection screen according to any one of Items 1 to 15 . The projection screen according to any one of claims 1 to 16 , and
A projection display device comprising: a projection optical system that projects image light obliquely onto the projection screen. In the total reflection prism sheet used in the projection screen that emits the image light projected obliquely from the projection optical system arranged on the back side toward the observation side,
A total reflection prism lens having a plurality of unit prisms provided on the back side on which image light is incident, wherein each unit prism is refracted by a first surface that refracts incident light and the first surface. A total reflection prism lens having a second surface that totally reflects the reflected light,
Each unit prism has an apex angle corresponding to an angle formed by the first surface and the second surface, and the apex angle of each unit prism is the position of each unit prism on the screen surface. Depending on the
The apex angle of each unit prism changes so that the side farther than the side closer to the projection optical system is larger,
The total reflection prism sheet, wherein the apex angle of each unit prism changes in a range of 30 ° to 45 ° .

Images