JP3979568B2 - Multicolor image display method and apparatus - Google Patents

Description

等が挙げられる。
【００２２】
発色状態における極大吸収波長が５００〜６００ｎｍの範囲にあるフォトクロミック化合物として、熱不可逆型としては、例えば、
１，２−ビス（３−（２−メチル−６−（２−（４−メトキシフェニル）エチニル）ベンゾチエニル））−３，３，４，４，５，５−ヘキサフルオロシクロペンテン、
１，２−ビス（５−メチル−２−フェニルチアゾール）−３，３，４，４，５，５−ヘキサフルオロシクロペンテン、
１−（１，２−ジメチル−３−インドリル）−２−（２−メチル−３−ベンゾチエニル）−３，３，４，４，５，５−ヘキサフルオロシクロペンテン、
２−［１−（２，５−ジメチル−１−フェニルピラゾリル）エチリデン］−３−イソプロピリデンコハク酸無水物
等が、
熱可逆型としては例えば
【００２３】
【化２】

等が挙げられる。
【００２４】
発色状態における極大吸収波長が６００〜７００ｎｍの範囲にあるフォトクロミック化合物として、熱不可逆型としては、例えば、
１−（５−メトキシ−１，２−ジメチル−３−インドリル）−２−（５−シアノ−２，４−ジメチル−３−チエニル）−３，３，４，４，５，５−ヘキサフルオロシクロペンテン、
１−（５−メトキシ−１，２−ジメチル−３−インドリル）−２−（６−カルボキシル−２−メチル−３−ベンゾチエニル）−３，３，４，４，５，５−ヘキサフルオロシクロペンテン、
１−（６−シアノ−２−メチル−３−ベンゾチエニル）−２−（５−メトキシ−１，２−ジメチル−３−インドリル）−３，３，４，４，５，５−ヘキサフルオロシクロペンテン、
２−［１−（１，２，５−トリメチル−３−ピロリル）エチリデン］−３−イソプロピリデンコハク酸無水物
等が、
熱可逆型としては、例えば、
【００２５】
【化３】

等が挙げられる。
【００２６】
発色状態における極大吸収波長が大きく異なり、ほぼイエロー、マゼンタ、シアンに認識されるこれらのフォトクロミック化合物は、所定の混合比で均一に混合されて色素及びバインダー材料とともに単一層の感光層を形成してもよいし、またそれぞれのフォトクロミック化合物とバインダー材料とからなる感光層を積層して複数層の感光層を形成してもよい。後者の場合、各層に含有させて用いてもよいし、例えば熱可逆型フォトクロミック化合物を含む層のみに含有させて用いてもよい。または、フォトクロミック化合物を含む各層と別に色素を含む層を形成してもよい。
【００２７】
本発明の第（３）の特徴は、発色状態における極大吸収波長が４００〜５００ｎｍの範囲にあるフォトクロミック化合物を熱不可逆型とし、発色状態における極大吸収波長が５００〜６００ｎｍの範囲にあるフォトクロミック化合物が熱可逆型とし、発色状態における極大吸収波長が６００〜７００ｎｍの範囲にあるフォトクロミック化合物を熱不可逆型としたことである。
【００２８】
例えば全て熱不可逆型のフォトクロミック化合物を用いて感光層を形成した場合、それぞれの化合物の可視域における吸収帯の重なりがある程度大きい場合、可視光の照射によって特定のフォトクロミック化合物を消色しようとした際に他のフォトクロミック化合物もある程度消色してしまうため、所望の色が得られにくくなってしまう。
これに対し、本発明における熱不可逆型と熱可逆型の組み合わせでフォトクロミック化合物を用いて感光層を形成した場合、可視光によって消色すべき、発色状態における極大吸収波長が４００〜５００ｎｍの範囲にあるフォトクロミック化合物と、発色状態における極大吸収波長が６００〜７００ｎｍの範囲にあるフォトクロミック化合物の可視域における吸収帯の重なりはほとんどないため、上述のような問題が生じない。発色状態における極大吸収波長が５００〜６００ｎｍの範囲にあるフォトクロミック化合物については赤外光の照射による色素の発熱により選択的に消色できる。この場合の赤外光の波長域については、前述の発色状態における極大吸収波長が６００〜７００ｎｍの範囲にある熱不可逆型フォトクロミック化合物を消色させないように設定することが好ましい。
【００２９】
本発明の第（４）の特徴は、感光層の表面に保護層を形成したことである。保護層の材料としては、透明性が高く、硬度が高い点でシリコーン樹脂またはアクリル樹脂が好適に用いられる。保護層を形成することにより感光層は水分や特定のガス等による、感光層を構成する化合物の、必要な機能の発現に関わる反応に対する悪影響を低減することが可能となり、また機械的損傷からも有効に保護されて耐久性が向上する。
【００３０】
本発明の第（５）の特徴は、紫外光照射が画像表示部全面に対して行なわれることである。画像表示媒体に紫外光照射を行なう場合、表示しようとする画像における灯樗部（感光層が無色になるべき部分）には紫外光照射による発色も、そして可視光照射や赤外光照射による消色も行なわず、それ以外の部分に紫外光を選択的に照射する方法もあるが、この場合には、画素に対応した微小な領域ごとに照射のオン／オフが制御できる発光部を連続して並べて形成した紫外光源アレイなどが必要になるし、そしてそれ以前に感光層に含まれる全種類のフォトクロミック化合物を消色させるために、表示部全面に可視光および赤外光を照射する工程が必要になる。一方、紫外光照射を画像表示部全面に対して行なう場合、紫外光を照射する光源としては、例えば画素に対応した微小な領域ごとに照射のオン／オフが制御できる発光部を連続して並べて形成した光源アレイなどである必要はなく、例えば安価なランプ光源を用いることができる。このようにランプ光源を用いるほうがコスト的にも有利であるし、照射強度の確保も容易である。また、感光層に含まれる全種類のフォトクロミック化合物を消色させるために、表示部全面に可視光および赤外光を照射する工程も不要になる。
【００３１】
本発明の第（６）の特徴は、紫外光の照射強度を可変とすることである。紫外光の照射量により感光層に含有されるフォトクロミック化合物の発色の程度は変化する。つまり紫外光の照射量により積極的に発色の程度を調整することが可能である。したがって画像全体の濃度を調整したい場合や、あるいは表示すべき画像において必要とされる最大の発色濃度が、予め画像信号の読み取りなどからわかっていれば、必要な画像濃度に必要充分な発色を生じさせるだけの照射量で紫外光を照射することにより、可視光照射による消色の程度を最小限にすることができるので、消費エネルギーの低減が可能となるし、また材料の発色・消色の繰り返し耐久性の点においても有利になる。紫外光光源自体の発光強度を制御するための制御機構、あるいは光源の外部において、光源から照射された紫外光の強度を調整する方法等により、紫外光の照射強度を可変として照射量を調整することにより、照射時間に関する条件は任意に設定できるため、例えば光源系と画像表示媒体とを相対的に移動させながら画像を形成する方法においては、前記移動の速度の制御が最も簡単になるように設定できるため（例えば一定速度、２つの速度の単純繰り返し等）、光源系と画像表示媒体との相対的移動に関するメカニカルな機構構成および制御が容易になる。
【００３２】
本発明の第（７）の特徴は、紫外光の照射時間を可変とすることである。紫外光の照射量により感光層に含有されるフォトクロミック化合物の発色の程度は変化する。つまり紫外光の照射量により積極的に発色の程度を調整することが可能である。したがって画像全体の濃度を調整したい場合や、あるいは表示すべき画像において必要とされる最大の発色濃度が、予め画像信号の読み取りなどからわかっていれば、必要な画像濃度に必要充分な発色を生じさせるだけの照射量で紫外光を照射することにより、可視光照射による消色の程度を最小限にすることができるので、消費エネルギーの低減が可能となるし、また材料の発色・消色の繰り返し耐久性の点においても有利になる。例えば光源系と画像表示媒体とを相対的に移動させながら画像を形成する方法においては、前記相対的な移動速度を調整することにより照射時間を制御して結果として照射量を調整することになる。例えば画像濃度を小さめに調整したい場合、前記相対的な移動速度を大きくすることで照射時間を短くすると、紫外光照射による発色濃度が小さくなるが、同様に可視光による消色の程度も小さくなり、発色と消色のバランスを保ちつつ全体の画像濃度の調整が可能となる。照射強度は一定にすればよいため、紫外光光源自体の発光強度を制御するための制御機構、あるいは光源の外部において、光源から照射された紫外光の強度を調整する部材等を設ける必要がなく、構成が容易になる。
【００３３】
本発明の第（８）の特徴は、可視光および赤外光の照射強度を可変とすることである。すでに説明したが、画像表示媒体の表示面に紫外光を照射すると、照射された部分の感光層に含まれる全種類のフォトクロミック化合物が発色する。ついで、各熱不可逆型フォトクロミック化合物の発色状態での可視域吸収帯に対応した波長域（極大吸収波長付近の波長域）の光の照射および赤外光の照射により、対応する特定のフォトクロミック化合物を消色させて、画像表示媒体の表示面上の所望の領域に、用いたフォトクロミック化合物の発色の有無の組み合わせによる複数の色が得られる。これにおいて、前記可視光の照射量により感光層に含有される熱不可逆型フォトクロミック化合物の消色の程度は変化し、また赤外光の照射量によって熱可逆型フォトクロミック化合物の消色の程度は変化する。つまり可視光の照射量および赤外光の照射量により対応する各熱不可逆型フォトクロミック化合物および熱可逆型フォトクロミック化合物の発色濃度を調整することが可能となり、各色の階調表示が可能となって、各色の組み合わせにより多色表示が可能となる。可視光の照射強度および赤外光の照射強度を可変として照射量を調整することにより、照射時間に関する条件は任意に設定できるため、例えば光源系と画像表示媒体とを相対的に移動させながら画像を形成する方法においては、前記移動の速度の制御が最も簡単になるように設定できるため（例えば一定速度、２つの速度の単純繰り返し等）、光源系と画像表示媒体との相対的移動に関するメカニカルな機構構成および制御が容易になる。
【００３４】
本発明の第（９）の特徴は、可視光の照射時間および赤外光の照射時間を可変とすることである。上記で説明したように、可視光の照射量および赤外光の照射量により対応する各熱不可逆型フォトクロミック化合物および熱可逆型フォトクロミック化合物の発色濃度を調整することが可能となり、各色の階調表示が可能となって、各色の組み合わせにより多色表示が可能となる。例えば前述のアレイ光源を用い、これらと画像表示媒体とを相対的に移動させながら画像を形成する方法においては、各単位発光面の照射のオン／オフを制御することにより照射時間を制御して結果として照射量を調整することになる。照射強度はそれぞれ一定にすればよいため、発光強度を制御するための制御機構を設ける必要がなく、構成が容易になる。
【００３５】
本発明の第（１０）の特徴は、白色光および赤外光を画像表示部全面に照射する工程を含むことである。発色させた全種類のフォトクロミック化合物を、画像表示部全面にわたってすべて消色して全消去したい場合、各熱不可逆型フォトクロミック化合物の発色状態での可視域吸収帯に対応した波長の光を照射するアレイ光源および赤外光のアレイ光源を用いて、光照射による消色を各熱不可逆型フォトクロミック化合物、そして熱可逆型フォトクロミック化合物について行なうことになるが、表示部全面に効率よく照射できる白色光光源および赤外光源を設けることにより、短時間での表示画像の全消去が可能となる。前記白色光光源および赤外光光源は、例えば画素に対応した微小な領域ごとに照射のオン／オフが制御できる発光部を連続して並べて形成した光源アレイなどである必要はなく、安価なランプ光源を用いることができる。このようにランプ光源を用いるほうがコスト的にも有利であるし、照射強度および熱量の確保も容易である。
【００３６】
本発明の第（１１）の特徴は、各波長の可視光光源が、白色光源と光学フィルターから構成されることである。可視光光源の各波長は、使用する熱不可逆型フォトクロミック化合物の発色体の可視域吸収帯に対応させて設定されるが、さらに詳細には、極大吸収波長付近に設定したり、あるいは光反応収率の波長依存を考慮したり、または他のフォトクロミック化合物の発色体の可視域吸収帯の波長域との関係を考慮して、より短波長側にあるいはより長波長側に設定することがある。このように可視光光源の好ましい波長の設定は使用するフォトクロミック化合物により様々であるが、可視光光源を白色光源と光学フィルターから構成すれば、光学フィルターの形成条件、または交換設置等により、波長の調整が容易にできる。
【００３７】
本発明の第（１２）の特徴は、各波長の可視光光源が、例えばＬＥＤやＬＤ等のような、それぞれが特定の発光波長域をもつ発光素子から構成されることである。この場合は光の利用効率が高く、照射強度の確保も容易になるし、消費エネルギーの低減も可能となる。
【００３８】
本発明の第（１３）の特徴は、ライン状の紫外光光源と可視光光源、および赤外光光源を備え、画像表示媒体と前記光源類とを相対的に移動させながら、画像を形成する装置を構成することである。ここで、ライン状というのは厳密に直線状に限られるものではなく、例えばある長さの光源ユニットがいわゆる千鳥状に互い違いに配列して全体的にラインを形成しているようなものも含むものであるし、また微小な領域ごとに照射のオン／オフが制御できる発光面を連続して並べて形成した光源アレイ等に関しても、同一波長の光源を構成する発光面の配列が一列でなく、複数列であってもよい。また、発光波長が異なるそれぞれの光源アレイが一つの構造体に組み込まれていてもよいし、独立した構造体として構成されてもよい。
本発明の多色画像表示方法を用いて画像表示装置を作製する場合は、光源の種類や構成などにより様々な構成を考えることができ、用途に応じて適宜選択すればよい。ただし、高解像度・高速書き込み・小型化・低コストなどが要求される場合は、各光源類をライン状に構成、配置し、これらと画像表示媒体とを相対的に移動させながら画像を形成する方法がより好ましい。
【００３９】
以下、実施例により、本発明を具体的に説明する。
【実施例】
（実施例１）
フォトクロミック化合物として、熱不可逆型である、２−［１−（２−メチル−５−ジエチルアミノスチリル−３−チエニル）メチリデン］−３−イソプロピリデンコハク酸無水物（以下ＰＣ１と呼ぶ）、および熱可逆型である
【００４０】
【化４】

（以下ＰＣ２と呼ぶ）
を用いた。ポリスチレン１００重量部に対しＰＣ１を１０重量部添加して溶媒に溶解させ、石英基板上にキャスト膜を作成した。ＰＣ２についても同様に石英基板上にキャスト膜を作成した。これらの光照射前の吸収スペクトルを測定したところ、ＰＣ１、ＰＣ２いずれも３００ｎｍ〜４００ｎｍ弱の範囲に吸収帯が認められ、いずれも無色であった。これらに高圧水銀ランプから取り出した３６６ｎｍの紫外光を照射したところ、ＰＣ１、ＰＣ２はそれぞれ青紫、マゼンタに発色し、吸収スペクトルの極大吸収波長はそれぞれ５９５ｎｍ、５３０ｎｍであった。
ＰＣ１については上と同様の処方によるキャスト膜を白色ＰＥＴ（ポリエチレンテレフタレート）基板（１２５μｍ）上に形成した。またＰＣ２については上の処方に対し、ＰＣ２が１０重量部に対しシアニン系色素である
【００４１】
【化５】

（以下Ｄ１と呼ぶ）
を５重量部添加した処方によるキャスト膜を同様に白色ＰＥＴ基板上に形成した。
またこれらとは別に、ＰＣ１を含むキャスト膜（１０μｍ）を形成後、ＰＶＡによる分離膜（２μｍ）を介してその上に前述のＰＣ２およびＤ１を含むキャスト膜（１０μｍ）を形成した。ＰＣ１のみを含む感光層、ＰＣ２およびＤ１を含む感光層、そして両者を積層させて形成した感光層はいずれも無色であり、基板の色が白であるため、観察者には白と認識された。
積層感光層全面に３６６ｎｍの紫外光を照射したところ、ＰＣ１、ＰＣ２の両者が発色し、両者が単独で発色した色の中間的な色を呈した。この状態の積層感光層に７８０ｎｍの発光波長のＬＤの赤外光を照射したところ、ＰＣ１のみが発色したのと同様の青紫色を呈した。またこれに再び３６６ｎｍの紫外光を照射したあと、ＬＥＤにより６００ｎｍの光を照射したところ、ＰＣ２のみが発色したのと同様のマゼンタ色を呈した。
【００４２】
（比較例１）
フォトクロミック化合物としてＰＣ２の代わりに、熱不可逆型である、２−［１−（５−メチル−２−ｐ−ジメチルアミノスチリル−４−オキサゾリル）エチリデン］−３−イソプロピリデンコハク酸無水物（以下ＰＣ３と呼ぶ）を用い、実施例１と同様の操作を行なった。ＰＣ３の吸収スペクトルの極大吸収波長はＰＣ２と同様で５３０ｎｍであった。実施例１と同様に形成した積層感光層全面に３６６ｎｍの紫外光を照射したところ、ＰＣ１、ＰＣ３の両者が発色し、両者が単独で発色した色の中間的な色を呈した。この状態の積層感光層に７８０ｎｍの発光波長のＬＤの赤外光を照射したが、照射により色は変化しなかった。この状態の積層感光層にＬＥＤにより６００ｎｍの光を照射したところ、ＰＣ３のみが発色したのと同様のマゼンタ色にはならず、かなり淡いマゼンタ色を示した。
【００４３】
フォトクロミック化合物として、熱不可逆型である１，２−ビス（２−フェニル−４−トリフルオロメチルチアゾール）−３，３，４，４，５，５−ヘキサフルオロシクロペンテン（以下ＰＣ４と呼ぶ）、熱可逆型である前記のＰＣ２、および熱不可逆型である１−（５−メトキシ−１，２−ジメチル−３−インドリル）−２−（５−シアノ−２，４−ジメチル−３−チエニル）−３，３，４，４，５，５−ヘキサフルオロシクロペンテン（以下ＰＣ５と呼ぶ）を用いた。ポリスチレン１００重量部に対しＰＣ４を１０重量部添加して溶媒に溶解させ、石英基板上にキャスト膜を作成した。ＰＣ２、ＰＣ５についても同様に石英基板上にキャスト膜を作成した。これらの光照射前の吸収スペクトルを測定したところ、ＰＣ４、ＰＣ２、ＰＣ５いずれも３００ｎｍ〜４００ｎｍ弱の範囲に吸収帯が認められ、いずれも無色であった。これらに高圧水銀ランプから取り出した３６６ｎｍの紫外光を照射したところ、ＰＣ４、ＰＣ２、ＰＣ５はそれぞれイエロー、マゼンタ、シアンに発色し、吸収スペクトルの極大吸収波長はそれぞれ４２０ｎｍ、５３０ｎｍ、６６５ｎｍであった。
ＰＣ４について上と同様の処方によるキャスト膜を白色ＰＥＴ（ポリエチレンテレフタレート）基板（１２５μｍ）上に形成し、さらにＰＶＡによる分離膜（２μｍ）を介してその上に、上と同様の処方に対し、ＰＣ２が１０重量部に対しさらにＤ１を５重量部添加した処方によるキャスト膜（１０μｍ）を形成し、やはりＰＶＡによる分離膜（２μｍ）を介してさらにその上にＰＣ５を含むキャスト膜（１０μｍ）を形成し、さらに保護層としてＰＶＡ膜（２μｍ）を形成した。このようにして形成した積層型の感光層は無色であり、基板の色が白であるため、観察者には白と認識された。
感光層全面に３６６ｎｍの紫外光を照射したところ、ＰＣ４、ＰＣ２、ＰＣ５すべてが発色し、濃灰色を呈した。この状態の感光層に、各波長の可視光および赤外光を照射したところ、様々な色の変化が生じたが、その様子を以下に示す。
【００４４】
（実施例２）
感光層の一部分にＬＥＤにより４７０ｎｍの光を照射したところ、照射部が青紫色を呈した。
【００４５】
（実施例３）
感光層の別の部分にＬＤにより７８０ｎｍの赤外光を照射したところ、照射部が緑色を呈した。
【００４６】
（実施例４）
感光層の別の部分にＬＥＤにより６６０ｎｍの光を照射したところ、照射部が赤色を呈した。
【００４７】
（実施例５）
実施例２で青紫色を呈した部分にさらにＬＤにより７８０ｎｍの赤外光を照射したところ、照射部がシアン色を呈した。
【００４８】
（実施例６）
実施例３で緑色を呈した部分にさらにＬＥＤにより６６０ｎｍの光を照射したところ、照射部が黄色を呈した。
【００４９】
（実施例７）
実施例２で青紫色を呈した部分にさらにＬＥＤにより６６０ｎｍの光を照射したところ、照射部がマゼンタ色（赤紫色）を呈した。
【００５０】
（実施例８）
実施例７でマゼンタ色（赤紫色）を呈した部分にさらにＬＤにより７８０ｎｍの赤外光を照射したところ、照射部が無色になり、基板の白色が見えた。
【００５１】
実施例２〜８で用いたのと同様の感光層を作製した。ただし３６６ｎｍの紫外光を照射する際、実施例２〜８で用いた感光層の場合と、照射時間は同一だが、半分の照度において照射を行なったところ、感光層は灰色を呈した。
【００５２】
（実施例９）
この感光層の一部分にＬＥＤにより４７０ｎｍの光を実施例２と同様に照射したところ、照射部が淡い青紫色を呈した。
【００５３】
（実施例１０）
この感光層の別の部分にＬＤにより７８０ｎｍの赤外光を実施例３と同様に照射したところ、照射部が淡い緑色を呈した。
【００５４】
（実施例１１）
この感光層の別の部分にＬＥＤにより６６０ｎｍの光を実施例４と同様に照射したところ、照射部が淡い赤色を呈した。
【００５５】
実施例２〜８で用いたのと同様の感光層を作製した。ただし３６６ｎｍの紫外光を照射する際、実施例２〜８で用いた感光層の場合と、照度は同一だが、半分の照射時間において照射を行なったところ、感光層は灰色を呈した。
【００５６】
（実施例１２）
この感光層の一部分にＬＥＤにより４７０ｎｍの光を実施例２と同様に照射したところ、照射部が淡い青紫色を呈した。
【００５７】
（実施例１３）
この感光層の別の部分にＬＤにより７８０ｎｍの赤外光を実施例３と同様に照射したところ、照射部が淡い緑色を呈した。
【００５８】
（実施例１４）
この感光層の別の部分にＬＥＤにより６６０ｎｍの光を実施例４と同様に照射したところ、照射部が淡い赤色を呈した。
【００５９】
実施例２〜８で用いたのと同様の感光層を作製し、さらに３６６ｎｍの紫外光の照射も同一の条件で行なった。感光層は全面、濃灰色を呈した。
【００６０】
（実施例１５）
この感光層の一部にＬＥＤにより４７０ｎｍの光を実施例２の場合の半分の照度で照射し（照射時間は同様）、その部分にさらにＬＤにより７８０ｎｍの赤外光を実施例３と同様に照射したところ、照射部がシアンと緑の中間的な色を呈した。
【００６１】
（実施例１６）
この感光層の別の部分にＬＥＤにより４７０ｎｍの光を実施例２と同様に照射し、その部分にさらにＬＤにより７８０ｎｍの赤外光を実施例３の場合の半分の照度で照射（照射時間は同様）したところ、照射部がシアンと緑の中間的な色を呈した。
【００６２】
（実施例１７）
この感光層の別の部分にＬＤにより７８０ｎｍの赤外光を実施例３の場合の半分の照度で照射（照射時間は同様）し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４と同様に照射したところ、照射部がオレンジ色を呈した。
【００６３】
（実施例１８）
この感光層の別の部分にＬＤにより７８０ｎｍの赤外光を実施例３と同様に照射し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４の場合の半分の照度で照射（照射時間は同様）したところ、照射部が黄緑色を呈した。
【００６４】
（実施例１９）
この感光層の別の部分にＬＥＤにより４７０ｎｍの光を実施例２の場合の半分の照度で照射（照射時間は同様）し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４と同様に照射したところ、照射部が赤とマゼンタの中間的な色を呈した。
【００６５】
（実施例２０）
この感光層の別の部分にＬＥＤにより４７０ｎｍの光を実施例２と同様に照射し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４の場合の半分の照度で照射（照射時間は同様）したところ、照射部が青紫とマゼンタの中間的な色を呈した。
【００６６】
（実施例２１）
この感光層の一部にＬＥＤにより４７０ｎｍの光を実施例２の場合の半分の照射時間で照射し（照度は同様）、その部分にさらにＬＤにより７８０ｎｍの赤外光を実施例３と同様に照射したところ、照射部がシアンと緑の中間的な色を呈した。
【００６７】
（実施例２２）
この感光層の別の部分にＬＥＤにより４７０ｎｍの光を実施例２と同様に照射し、その部分にさらにＬＤにより７８０ｎｍの赤外光を実施例３の場合の半分の照射時間で照射（照度は同様）したところ、照射部がシアンと緑の中間的な色を呈した。
【００６８】
（実施例２３）
この感光層の別の部分にＬＤにより７８０ｎｍの赤外光を実施例３の場合の半分の照射時間で照射（照度は同様）し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４と同様に照射したところ、照射部がオレンジ色を呈した。
【００６９】
（実施例２４）
この感光層の別の部分にＬＤにより７８０ｎｍの赤外光を実施例３と同様に照射し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４の場合の半分の照射時間で照射（照度は同様）したところ、照射部が黄緑色を呈した。
【００７０】
（実施例２５）
この感光層の別の部分にＬＥＤにより４７０ｎｍの光を実施例２の場合の半分の照射時間で照射（照度は同様）し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４と同様に照射したところ、照射部が赤とマゼンタの中間的な色を呈した。
【００７１】
（実施例２６）
この感光層の別の部分にＬＥＤにより４７０ｎｍの光を実施例２と同様に照射し、その部分にさらにＬＥＤにより６６０ｎｍの光を実施例４の場合の半分の照射時間で照射（照度は同様）したところ、照射部が青紫とマゼンタの中間的な色を呈した。
【００７２】
（実施例２７）
上述の実施例１〜２６で用いたような画像表示媒体に対して画像の書き込みを行なう、画像表示装置を作製した。図１にその構成の概要を示す。
実施例２７において作製した装置には画像表示媒体（１）を装置内に導入するための挿入口（２）が設けられている。そこから画像表示媒体（１）が挿入されると、搬送ローラ（３）により、画像表示媒体は書き込みのための光源部に搬送されていく。光源部は紫外光光源（４）と、４７０ｎｍの発光波長を有するＬＥＤアレイ（５）、５６０ｎｍの発光波長を有するＬＥＤアレイ（６）、６６０ｎｍの発光波長を有するＬＥＤアレイ（７）、ライン状の白色ＬＥＤ（８）、赤外ＬＤアレイ（９）および赤外ランプ（１０）で構成される。実施例２７では紫外光光源は水銀ランプと光学フィルタで構成し、３６６ｎｍ付近の波長の紫外光を照射できるようになっている。また前記各可視波長を発光するＬＥＤアレイおよび赤外ＬＤアレイは、画素に対応した微小な領域ごとに照射のオン／オフが制御できるように構成されている。これらの各光源類はその発光強度の調整が可能であり、さらに画像表示媒体の搬送速度も調整が可能となっている。これらの光源部を通過して画像の書き込みがなされた画像表示媒体は排紙トレー（１１）に排出される。
【００７３】
【発明の効果】
以上、詳細かつ具体的な説明から明らかなように、本発明の請求項１により、発色状態における極大吸収波長が大きく異ならず、吸収帯の重なりが大きな２つのフォトクロミック化合物間においても、消色の選択性が向上する。
また、本発明の請求項２により、カラー表示に必要な３原色（イエロー、マゼンタ、シアン）が得られるため、画像信号に従い、画像表示媒体上の所望の位置に所定の波長の可視光を照射し、および所望の位置に赤外光を照射することにより、多色表示が可能となる。
また、本発明の請求項３により、イエロー発色化合物／マゼンタ発色化合物間、およびマゼンタ発色化合物／シアン発色化合物間では、発色状態における極大吸収波長が比較的近く、吸収帯の重なりがある場合が多いが、可視光と赤外光により良好な選択性をもって消色が可能となり、またイエロー発色化合物／シアン発色化合物間では、発色状態における極大吸収波長が離れており、吸収帯の重なりはほとんどない場合が多いのでやはり良好な選択性をもって消色が可能となる。したがって所望の色が忠実に表示され、表示品質が高い多色表示が可能となる。
また、本発明の請求項４により、水分や特定のガス等による、感光層を構成する化合物の、必要な機能の発現に関わる反応に対する悪影響を低減することが可能となり、耐久性が向上し、信頼性が高い多色画像表示方法が得られる。
また、本発明の請求項５により、紫外光の光源として、画素サイズに対応した微細なスポット単位での照射は不要となり、光源素子の構成が容易になり、コスト的にも有利になる。
また、本発明の請求項６により、発色の程度が調整できるので、表示すべき画像において必要とされる発色濃度に必要充分な発色を生じさせることにより、可視光照射および赤外光照射による消色の程度を低減することができるので、消費エネルギーの低減が可能となるし、材料の発色・消色の繰り返し耐久性の点においても有利になる。
また、本発明の請求項７により、発色の程度が調整できるので、表示すべき画像において必要とされる発色濃度に必要充分な発色を生じさせることにより、可視光照射および赤外光照射による消色の程度を低減することができるので、消費エネルギーの低減が可能となるし、また材料の発色・消色の繰り返し耐久性の点においても有利になる。紫外光の照射時間を可変として制御することにより、照射強度は一定にすればよいため、紫外光光源自体の発光強度を制御するための制御機構、あるいは光源の外部において、光源から照射された紫外光の強度を調整する部材等を設ける必要がなく、構成が容易になる。
また、本発明の請求項８により、各色について発色濃度の調整が可能となり、したがって階調表示が可能となり、画像表示媒体上の画像としては多色表示が可能となる。可視光および赤外光の照射時間に関する条件は任意に設定できるため、例えば光源系と画像表示媒体とを相対的に移動させながら画像を形成する方法においては、前記移動の速度の制御が最も簡単になるように設定できるため（例えば一定速度、２つの速度の単純繰り返し等）、前記移動に関するメカニカルな機構構成および制御が容易になる。
また、本発明の請求項９により、各色について階調表示が可能となり、画像表示媒体上の画像としては多色表示が可能となる。可視光および赤外光の照射時間を可変として制御することにより、照射強度については一定にすればよいため、可視光光源および赤外光光源自体の発光強度を制御するための制御機構、あるいは光源の外部において、光源から照射された可視光の強度を調整する部材等を設ける必要がなく、構成が容易になる。
また、本発明の請求項１０により、各フォトクロミック材料を選択的に消色させるための各波長の可視光光源および赤外光光源とは別に、表示部全面に効率よく照射できる白色光光源および赤外光光源を設けることにより、短時間での表示画像の全消去が可能となる。
また、本発明の請求項１１により、白色光源と光学フィルターにより、各フォトクロミック材料を選択的に消色させるための可視光光源を構成するため、光学フィルターの形成条件、または交換設置等により、波長の調整が容易にできる。
また、本発明の請求項１２により、特定の発光波長域をもつ発光素子を用いる場合は、光の利用効率が高く、照射強度の確保も容易になるし、消費エネルギーの低減も可能となる。
更にまた、本発明の請求項１３により、所望の色を忠実に表示できる、高表示品質の書き換え型の多色表示装置が実現できる。
【図面の簡単な説明】
【図１】本発明において用いた画像表示装置の構成の概略図である。
【符号の説明】
１ 画像表示媒体
２ 挿入口
３ 搬送ローラ
４ 紫外光光源
５ ＬＥＤアレイ
６ ＬＥＤアレイ
７ ＬＥＤアレイ
８ 白色ＬＥＤ
９ 赤外ＬＤアレイ
１０ 赤外ランプ
１１ 排紙トレー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image display method and apparatus, and more particularly to an image display method and apparatus capable of repeatedly writing and erasing a color image by light irradiation.
[0002]
[Prior art]
Although proposals have been made for rewritable display media using photochromic compounds that exhibit reversible color changes upon irradiation with light, no proposal has been found for a practical method and apparatus that can rewrite full-color images many times. .
[0003]
As a method for forming a color image using a photochromic compound, for example, in JP-A-5-271649, yellow-orange is irradiated with ultraviolet light at 254 nm, red is irradiated with ultraviolet light at 313 nm, and blue-violet is irradiated with ultraviolet light at 365 nm. There has been proposed a method in which three types of photochromic diarylethene compounds that develop color are mixed to form a photosensitive layer on a substrate and irradiated with ultraviolet light of each wavelength. In order to form a full-color image, it is necessary to control the extinction / color development of three or more kinds of photochromic compounds that develop three primary colors (blue, green, red or yellow, magenta, and cyan) with light. Therefore, it is necessary to select the presence or absence of coloring of each material in three types of ultraviolet light wavelength regions, that is, three or more types of photochromic compounds that do not overlap in the absorption band in the ultraviolet region are necessary. Must exhibit the three primary colors in the colored state, but no such compound system is actually found. For practical use, it is necessary to consider not only the coloring properties but also the repeated durability and heat / humidity stability, and it seems very difficult to develop a material that satisfies all of these.
[0004]
In JP-A-7-199401, a photosensitive layer is formed on a substrate using three types of photochromic fulgide compounds showing yellow, magenta, and cyan in a colored state, and all photochromic compounds are formed using ultraviolet light at 366 nm. A method for selectively erasing a specific material by irradiating a photosensitive layer with light having a specific wavelength after color development has been proposed. Although this method has the advantage that there is only one type of ultraviolet light, for example, the light emitted to decolor the magenta color developing material also erases the yellow color developing material and the cyan color developing material. There is a problem that a desired color cannot often be obtained accurately.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention has been made in view of the above-described state of the art and problems, and provides a rewritable multicolor display method and apparatus with high display quality capable of faithfully displaying a desired color. This is intended to improve the decolorization selectivity between two photochromic compounds in which the maximum absorption wavelength in the colored state is not greatly different and the overlap of the absorption bands is large. Another object is to obtain three primary colors (yellow, magenta, cyan) necessary for color display, irradiate a desired position on the image display medium with visible light of a predetermined wavelength according to the image signal, and This is to enable multicolor display by irradiating the position with infrared light. Another object is to improve the selective decoloring property, display a desired color faithfully, and enable multicolor display with high display quality. Another object is to obtain a highly reliable multicolor image display method with improved durability. Another object is to simplify the structure of the light source element and to make it advantageous in terms of cost. Another purpose is to adjust the degree of color development, and to generate color development necessary and sufficient for the color density required in the image to be displayed. It is possible to reduce energy consumption. Another object is to enable gradation display by adjusting the color density for each color, thereby enabling multicolor display of an image on an image display medium. Another object is to make it possible to completely erase a display image in a short time. Another object is to facilitate ensuring the irradiation intensity of a visible light source for selectively decoloring each photochromic material, and to reduce energy consumption. Another object is to realize a rewritable multicolor display device of high display quality that can faithfully display a desired color.
[0006]
[Means for Solving the Problems]
The above-mentioned problems include (1) “a thermally irreversible photochromic compound and a thermoreversible photochromic compound, and a maximum absorption wavelength in a colored state. Each other At least ultraviolet light irradiation is applied to an image display medium in which a photosensitive layer containing two or more kinds of photochromic compounds including different substances and at least one of a naphthalocyanine dye and a cyanine dye is formed on a support substrate. Process for coloring all types of photochromic compounds contained in the photosensitive layer , Departure A process for selectively erasing each thermally irreversible photochromic compound by irradiating a desired region with visible light in a wavelength region corresponding to the maximum absorption wavelength of each colored thermally irreversible photochromic compound. About And a method of selectively erasing the thermoreversible photochromic compound by irradiating a desired region with infrared light. (2) “The photochromic compound has a maximum absorption wavelength in the range of 400 to 500 nm in the colored state, a photochromic compound in which the maximum absorption wavelength in the colored state is in the range of 500 to 600 nm, and the maximum in the colored state.” The multicolor image display method as described in (1) above, which contains all photochromic compounds having an absorption wavelength in the range of 600 to 700 nm, (3) “maximum absorption wavelength in a colored state” Is a heat irreversible photochromic compound in which the maximum absorption wavelength in the colored state is in the range of 500 to 600 nm is a thermoreversible type, and the maximum absorption wavelength in the colored state is 600 to 700 nm. The photochromic compounds in the range of (4) “A protective layer is formed on the surface of the photosensitive layer.” (1) to (1), (3) The multicolor image display method according to any one of items 3), (5) “Ultraviolet light irradiation is performed on the entire surface of the image display unit”, (1) to (4) The multicolor image display method according to any one of the items 1) to (6), wherein any one of the items (1) to (5) is characterized in that the irradiation intensity of ultraviolet light is variable. The multicolor image display method according to any one of Items (1) to (5), wherein the irradiation time of ultraviolet light is variable. Method ”, (8)“ Multicolor according to any one of items (1) to (5), wherein the irradiation intensity of visible light and infrared light is variable ” Image display method ”, (9)“ Multicolor image display according to any one of items (1) to (5), wherein the irradiation time of visible light and infrared light is variable ” Method ”, (10)“ Multicolor according to any one of items (1) to (9), including a step of irradiating the entire surface of the image display unit with white light and infrared light ” Image display method ”, (11)“ A visible light source of each wavelength is composed of a white light source and an optical filter, ”according to any one of (1) to (10), Multicolor image display method ”, (12)“ Visible light source of each wavelength is composed of light emitting elements each having a specific light emission wavelength range ”(1) to (10) This is achieved by the “multicolor image display method according to any one of items”.
[0007]
Further, the above-mentioned problem is (13) of the present invention, comprising “a linear ultraviolet light source, a visible light source, and an infrared light source, and moving the image display medium and the light sources relative to each other while moving the image display medium and the light sources relatively. This is achieved by a “multicolor image display device characterized by forming an image using the method according to any one of items (1) to (12)”.
[0008]
Hereinafter, the present invention will be described in detail.
The feature (1) of the present invention includes a thermally irreversible photochromic compound and a thermoreversible photochromic compound, and has a maximum absorption wavelength in a colored state. Each other At least ultraviolet light irradiation is applied to an image display medium in which a photosensitive layer containing two or more kinds of photochromic compounds including different substances and at least one of a naphthalocyanine dye and a cyanine dye is formed on a support substrate. Process for coloring all types of photochromic compounds contained in the photosensitive layer , Departure A process for selectively erasing each thermally irreversible photochromic compound by irradiating a desired region with visible light in a wavelength region corresponding to the maximum absorption wavelength of each colored thermally irreversible photochromic compound. About And a step of selectively erasing the thermoreversible photochromic compound by irradiating a desired region with infrared light.
[0009]
Photochromic compounds are classified into heat irreversible photochromic compounds and thermoreversible photochromic compounds. In the heat irreversible type, a decoloring reaction from a colored state to a decolored state occurs only by light irradiation, and hardly occurs thermally. On the other hand, in the thermoreversible type, a decoloring reaction occurs to some extent even by light irradiation, but proceeds greatly by heat. Therefore, for example, even in a photosensitive layer containing both, even if the maximum absorption wavelength in both color development states is almost the same, only the thermoreversible photochromic compound can be selectively decolored by heating, and the maximum absorption Irradiation with visible light in a region corresponding to the wavelength can selectively erase the thermally irreversible photochromic compound to some extent. Further, when the maximum absorption wavelength in the colored state is different to some extent, only the compound can be selectively decolored by irradiation with visible light in a region corresponding to the maximum absorption wavelength in the colored state of the thermally irreversible photochromic compound. .
[0010]
It is convenient that the absorption band (ultraviolet region) in the decolored state of the plurality of photochromic compounds to be used has a large overlap. In that case, even if the emission wavelength region of the ultraviolet light source is quite narrow, all kinds of photochromic compounds contained in the photosensitive layer can be colored if the wavelength is in the overlapping portion of the absorption band. Even if the absorption band (ultraviolet region) overlap in the decolored state is small or non-overlapping, it should have sufficient spectral characteristics to induce color reaction of all photochromic compounds used by the ultraviolet light source. Good.
The difference in the maximum absorption wavelength in the colored state means that the color to be recognized is different, but this maximum absorption wavelength may be set according to the color to be used for display, and the photochromic compound The type may be set to be equal to or greater than the number of colors desired for display.
[0011]
Moreover, it is preferable that all the photochromic compounds to be used have the same color developing sensitivity and decoloring sensitivity.
In addition to the photochromic compound, the material constituting the photosensitive layer includes a binder material and a dye. First, the binder material does not adversely affect the photochromic function of the photochromic compound, and is compatible with the photochromic compound. It is preferable to use a resin material that can form a film and is excellent in transparency after curing. Examples of such a material include polystyrene, polyester, polymethyl methacrylate, vinyl chloride-vinylidene chloride copolymer, polyvinyl chloride, polyvinylidene chloride, and polyvinyl acetate. Examples of the dye include naphthalocyanine dyes and cyanine dyes as dyes having absorption in the infrared region. Since these have absorption in the infrared region of 700 nm or more, they have sensitivity even for LDs of 780 nm or 830 nm.
[0012]
Examples of the material for the support substrate include transparent materials such as polyethylene terephthalate, polyethersulfone, and polycarbonate, and opaque materials such as paper.
[0013]
As a method for forming the photosensitive layer, a vapor deposition method can be mentioned in addition to the coating method, but the coating method is simple, and both the photochromic compound and the binder material are dissolved in a solvent, and a method such as a printing method or a spin coating method is used. The film may be formed by coating and drying. The photosensitive layer may be either a single layer or a plurality of layers, but when forming a plurality of layers, it is preferable to form a separation layer between the layers so that adjacent layers do not mix. The separation layer can be formed by applying a film-forming solution using a solvent that does not dissolve the binder material and photochromic compound in the photosensitive layer.
[0014]
As a light source for irradiating ultraviolet light, a mercury lamp or a xenon lamp may be used in combination with an optical filter to extract ultraviolet light in a desired wavelength range, or light emission that emits light in a specific wavelength range such as an LED or LD. An element may be used. For example, in the case of manufacturing a display device in which a light source system for writing / erasing is made as compact as possible, a light emitting element such as an LED is preferable, and light emission that can control on / off of irradiation for each minute region is preferable. You may comprise the light source array formed by arranging the surface continuously.
[0015]
As a light source for irradiating visible light, lamps having a configuration in which an optical filter is combined with a white light source may be used, or a light emitting element that emits light in a specific wavelength region such as an LED or an LD may be used. For example, in the case of manufacturing a display device in which a light source system for writing / erasing is made as compact as possible, a light emitting element such as an LED is preferable, and light emission that can control on / off of irradiation for each minute region is preferable. You may comprise the light source array formed by arranging the surface continuously. Alternatively, a light source array may be configured by combining the lamps and light valve elements such as a liquid crystal shutter array. In particular, when irradiating only a desired region, the irradiation of each light emitting surface of the light source array is turned on / off while relatively moving the light source array and the image display medium having the photosensitive layer formed on the support substrate. This can also be achieved by controlling off.
[0016]
As a light source for irradiating infrared light, lamps having a combination of an infrared lamp and an optical filter for cutting light in an unnecessary wavelength range may be used, or a specific wavelength range such as an LED or LD may be used. A light-emitting element that emits light may be used. For example, in the case of manufacturing a display device in which a light source system for writing / erasing is made as compact as possible, a light emitting element such as an LED is preferable, and light emission that can control on / off of irradiation for each minute region is preferable. You may comprise the light source array formed by arranging the surface continuously. Alternatively, a light source array may be configured by combining the lamps and light valve elements such as a liquid crystal shutter array. In particular, when irradiating only a desired region, the irradiation of each light emitting surface of the light source array is turned on / off while relatively moving the light source array and the image display medium having the photosensitive layer formed on the support substrate. This can also be achieved by controlling off.
[0017]
In the present invention, as a method for displaying a desired image, first, when the display surface of the image display medium is irradiated with ultraviolet light, all kinds of photochromic compounds contained in the irradiated photosensitive layer are colored. Then, by irradiating light in a wavelength region corresponding to the visible region absorption band in the colored state of each thermally irreversible photochromic compound (a wavelength region near the maximum absorption wavelength), the corresponding specific thermally irreversible photochromic compound is erased. To color. Furthermore, by irradiating a specific area on the display surface of the image display medium with infrared light, the naphthalocyanine dye or cyanine dye contained in the exposed photosensitive layer absorbs the infrared light and generates heat. Therefore, the thermoreversible photochromic compound in that region is selectively decolored. Using this method, it is possible to form a desired image by generating a color development state of some desired photochromic compounds in a desired region on the display surface of the image display medium. When all types of photochromic compounds contained in the photosensitive layer are colored, when the same region is irradiated with visible light having a plurality of wavelengths, they may be irradiated simultaneously or sequentially. Moreover, when irradiating sequentially separately, the order of the wavelength to irradiate may be arbitrary. Further, the order of irradiation with visible light and irradiation with infrared light may be arbitrary.
[0018]
The second feature of the present invention is that the photosensitive layer has a photochromic compound having a maximum absorption wavelength in the range of 400 to 500 nm in a colored state, and a photochromic compound having a maximum absorption wavelength in the range of 500 to 600 nm in the colored state. In other words, it contains all the photochromic compounds having a maximum absorption wavelength in the colored state in the range of 600 to 700 nm.
[0019]
The colors recognized in the colored state of each of the photochromic compounds substantially correspond to yellow, magenta, and cyan, and these constitute three primary colors, so that multicolor display is possible by the above-described image display method.
[0020]
As a photochromic compound having a maximum absorption wavelength in the range of 400 to 500 nm in a colored state,
1,2-bis (2-phenyl-4-trifluoromethylthiazole) -3,3,4,4,5,5-hexafluorocyclopentene,
Dimethyl 2,3-di (2-methylbenzothienyl) maleate,
1,2-bis (5-ethoxy-2-methylthiazole) -3,3,4,4,5,5-hexafluorocyclopentene,
2- [1- (3,5-Dimethyl-4-isoxazolyl) ethylidene] -3-isopropylidene succinic anhydride
Etc.
As a thermoreversible type, for example,
[0021]
[Chemical 1]

Etc.
[0022]
As a photochromic compound having a maximum absorption wavelength in the range of 500 to 600 nm in a colored state, as a heat irreversible type, for example,
1,2-bis (3- (2-methyl-6- (2- (4-methoxyphenyl) ethynyl) benzothienyl))-3,3,4,4,5,5-hexafluorocyclopentene,
1,2-bis (5-methyl-2-phenylthiazole) -3,3,4,4,5,5-hexafluorocyclopentene,
1- (1,2-dimethyl-3-indolyl) -2- (2-methyl-3-benzothienyl) -3,3,4,4,5,5-hexafluorocyclopentene,
2- [1- (2,5-Dimethyl-1-phenylpyrazolyl) ethylidene] -3-isopropylidene succinic anhydride
Etc.
As a thermoreversible type, for example
[0023]
[Chemical formula 2]

Etc.
[0024]
As a photochromic compound having a maximum absorption wavelength in the range of 600 to 700 nm in a colored state, as a heat irreversible type, for example,
1- (5-Methoxy-1,2-dimethyl-3-indolyl) -2- (5-cyano-2,4-dimethyl-3-thienyl) -3,3,4,4,5,5-hexafluoro Cyclopentene,
1- (5-Methoxy-1,2-dimethyl-3-indolyl) -2- (6-carboxyl-2-methyl-3-benzothienyl) -3,3,4,4,5,5-hexafluorocyclopentene ,
1- (6-Cyano-2-methyl-3-benzothienyl) -2- (5-methoxy-1,2-dimethyl-3-indolyl) -3,3,4,4,5,5-hexafluorocyclopentene ,
2- [1- (1,2,5-Trimethyl-3-pyrrolyl) ethylidene] -3-isopropylidene succinic anhydride
Etc.
As a thermoreversible type, for example,
[0025]
[Chemical 3]

Etc.
[0026]
These photochromic compounds, which are recognized as yellow, magenta, and cyan, differ greatly in the maximum absorption wavelength in the colored state, and are uniformly mixed at a predetermined mixing ratio to form a single photosensitive layer together with the dye and the binder material. Alternatively, a plurality of photosensitive layers may be formed by laminating a photosensitive layer made of each photochromic compound and a binder material. In the latter case, it may be used by being contained in each layer, or may be used by being contained only in a layer containing a thermoreversible photochromic compound, for example. Alternatively, a layer containing a pigment may be formed separately from each layer containing a photochromic compound.
[0027]
The feature (3) of the present invention is that a photochromic compound having a maximum absorption wavelength in the range of 400 to 500 nm in a colored state is a heat irreversible type, and a photochromic compound having a maximum absorption wavelength in the range of 500 to 600 nm in a colored state. It is a thermoreversible type, and a photochromic compound having a maximum absorption wavelength in a colored state in the range of 600 to 700 nm is a heat irreversible type.
[0028]
For example, when a photosensitive layer is formed using a photochromic compound that is irreversibly heat irreversible, when the overlap of absorption bands in the visible region of each compound is somewhat large, when a specific photochromic compound is erased by irradiation with visible light In addition, since other photochromic compounds are also decolored to some extent, it becomes difficult to obtain a desired color.
On the other hand, when a photosensitive layer is formed using a photochromic compound in a combination of a thermally irreversible type and a thermoreversible type in the present invention, the maximum absorption wavelength in a colored state that should be decolored by visible light is in the range of 400 to 500 nm. Since there is almost no overlap of the absorption band in the visible region between a certain photochromic compound and a photochromic compound having a maximum absorption wavelength in the range of 600 to 700 nm, the above-described problem does not occur. A photochromic compound having a maximum absorption wavelength in the color development state in the range of 500 to 600 nm can be selectively erased by heat generation of the dye by irradiation with infrared light. In this case, it is preferable to set the wavelength range of the infrared light so that the thermally irreversible photochromic compound having the maximum absorption wavelength in the color development state in the range of 600 to 700 nm is not decolored.
[0029]
The fourth feature of the present invention is that a protective layer is formed on the surface of the photosensitive layer. As a material for the protective layer, a silicone resin or an acrylic resin is preferably used in terms of high transparency and high hardness. By forming the protective layer, the photosensitive layer can reduce adverse effects on the reaction related to the expression of necessary functions of the compound constituting the photosensitive layer due to moisture, specific gas, etc., and also from mechanical damage. Effectively protected to improve durability.
[0030]
The fifth feature of the present invention is that the entire surface of the image display unit is irradiated with ultraviolet light. When the image display medium is irradiated with ultraviolet light, the lantern (portion where the photosensitive layer should be colorless) in the image to be displayed is colored by ultraviolet light irradiation, and is extinguished by visible light irradiation or infrared light irradiation. There is also a method of selectively irradiating ultraviolet light to other portions without performing color, but in this case, a light emitting unit that can control on / off of irradiation for each minute region corresponding to a pixel is continuously provided. In order to decolorize all types of photochromic compounds contained in the photosensitive layer, a process of irradiating the entire surface of the display with visible light and infrared light is necessary. I need it. On the other hand, when the ultraviolet light irradiation is performed on the entire surface of the image display unit, as a light source for irradiating the ultraviolet light, for example, a light emitting unit that can control irradiation on / off for each minute region corresponding to the pixel is continuously arranged It is not necessary to be a formed light source array, and an inexpensive lamp light source can be used, for example. Thus, it is advantageous in terms of cost to use a lamp light source, and it is easy to ensure irradiation intensity. Further, in order to decolorize all kinds of photochromic compounds contained in the photosensitive layer, a step of irradiating visible light and infrared light to the entire display portion is not necessary.
[0031]
A sixth feature of the present invention is that the irradiation intensity of ultraviolet light is variable. The degree of color development of the photochromic compound contained in the photosensitive layer varies depending on the irradiation amount of ultraviolet light. That is, it is possible to positively adjust the degree of color development according to the irradiation amount of ultraviolet light. Therefore, if you want to adjust the density of the entire image, or if the maximum color density required for the image to be displayed is known in advance from reading the image signal, etc., sufficient and sufficient color development will occur for the required image density. By irradiating with ultraviolet light at an irradiation amount that can be reduced, the degree of decoloration due to visible light irradiation can be minimized, so energy consumption can be reduced, and coloring and decoloring of materials can be reduced. This is also advantageous in terms of repeated durability. Adjust the irradiation amount by changing the irradiation intensity of the ultraviolet light by using a control mechanism for controlling the emission intensity of the ultraviolet light source itself, or by adjusting the intensity of the ultraviolet light emitted from the light source outside the light source. As a result, the conditions relating to the irradiation time can be arbitrarily set. For example, in the method of forming an image while relatively moving the light source system and the image display medium, the speed of the movement is controlled most easily. Since it can be set (for example, constant speed, simple repetition of two speeds, etc.), mechanical mechanism configuration and control relating to relative movement between the light source system and the image display medium are facilitated.
[0032]
A seventh feature of the present invention is that the irradiation time of ultraviolet light is variable. The degree of color development of the photochromic compound contained in the photosensitive layer varies depending on the irradiation amount of ultraviolet light. That is, it is possible to positively adjust the degree of color development according to the irradiation amount of ultraviolet light. Therefore, if you want to adjust the density of the entire image, or if the maximum color density required for the image to be displayed is known in advance from reading the image signal, etc., sufficient and sufficient color development will occur for the required image density. By irradiating with ultraviolet light at an irradiation amount that can be reduced, the degree of decoloration due to visible light irradiation can be minimized, so energy consumption can be reduced, and coloring and decoloring of materials can be reduced. This is also advantageous in terms of repeated durability. For example, in a method of forming an image while relatively moving the light source system and the image display medium, the irradiation time is controlled by adjusting the relative moving speed, and the irradiation amount is adjusted as a result. . For example, if you want to adjust the image density to a smaller value, if you shorten the irradiation time by increasing the relative movement speed, the color density due to ultraviolet light irradiation will decrease, but the degree of decoloration due to visible light will also decrease. The overall image density can be adjusted while maintaining the balance between coloring and decoloring. Since the irradiation intensity only needs to be constant, there is no need to provide a control mechanism for controlling the emission intensity of the ultraviolet light source itself, or a member for adjusting the intensity of the ultraviolet light emitted from the light source outside the light source. Easy to configure.
[0033]
The eighth feature of the present invention is that the irradiation intensity of visible light and infrared light is variable. As described above, when the display surface of the image display medium is irradiated with ultraviolet light, all types of photochromic compounds contained in the irradiated photosensitive layer are colored. Next, the corresponding specific photochromic compound is obtained by irradiation with light in the wavelength range corresponding to the visible absorption band in the color development state of each heat irreversible photochromic compound (wavelength range near the maximum absorption wavelength) and infrared irradiation. By decoloring, a plurality of colors can be obtained in a desired region on the display surface of the image display medium by combining the presence or absence of coloration of the used photochromic compound. In this, the degree of decoloration of the thermally irreversible photochromic compound contained in the photosensitive layer varies depending on the amount of visible light irradiation, and the degree of decoloration of the thermoreversible photochromic compound varies depending on the amount of infrared light irradiation. To do. In other words, it is possible to adjust the color density of each thermally irreversible photochromic compound and thermoreversible photochromic compound corresponding to the irradiation amount of visible light and the irradiation amount of infrared light, and gradation display of each color is possible. Multi-color display is possible by combining each color. By adjusting the irradiation amount by making the irradiation intensity of visible light and the irradiation intensity of infrared light variable, the conditions relating to the irradiation time can be arbitrarily set. For example, while moving the light source system and the image display medium relatively, the image In the method of forming a mechanical structure, the speed of the movement can be set so as to be the simplest (for example, a constant speed, a simple repetition of two speeds, etc.). Easy mechanism configuration and control.
[0034]
The ninth feature of the present invention is that the irradiation time of visible light and the irradiation time of infrared light are variable. As explained above, it is possible to adjust the color density of each thermally irreversible photochromic compound and thermoreversible photochromic compound corresponding to the irradiation amount of visible light and the irradiation amount of infrared light, and gradation display of each color Thus, multicolor display is possible by combining each color. For example, in the method of forming an image using the above-described array light source and relatively moving these and the image display medium, the irradiation time is controlled by controlling on / off of irradiation of each unit light emitting surface. As a result, the dose is adjusted. Since it is only necessary to make the irradiation intensity constant, it is not necessary to provide a control mechanism for controlling the emission intensity, and the configuration becomes easy.
[0035]
A tenth feature of the present invention is that it includes a step of irradiating the entire surface of the image display unit with white light and infrared light. An array that irradiates light with a wavelength corresponding to the visible light absorption band in the colored state of each thermally irreversible photochromic compound when it is desired to erase all of the developed photochromic compounds over the entire image display area. Using a light source and an array light source of infrared light, decoloring by light irradiation is performed on each thermally irreversible photochromic compound and thermally reversible photochromic compound. By providing the infrared light source, it is possible to completely erase the display image in a short time. The white light source and the infrared light source do not need to be a light source array in which light emitting units capable of controlling on / off of irradiation are continuously arranged for each minute region corresponding to a pixel, for example, and an inexpensive lamp A light source can be used. Thus, it is advantageous in terms of cost to use a lamp light source, and it is easy to secure irradiation intensity and heat quantity.
[0036]
The (11) feature of the present invention is that the visible light source of each wavelength is composed of a white light source and an optical filter. Each wavelength of the visible light source is set in accordance with the visible region absorption band of the chromophore of the heat irreversible photochromic compound to be used, but more specifically, it is set near the maximum absorption wavelength or photoreaction absorption. In consideration of the wavelength dependence of the rate, or in consideration of the relationship with the wavelength region of the visible region absorption band of the color former of another photochromic compound, it may be set to a shorter wavelength side or a longer wavelength side. As described above, the setting of the preferred wavelength of the visible light source varies depending on the photochromic compound to be used.If the visible light source is composed of a white light source and an optical filter, the wavelength of the visible light source can be changed depending on the formation conditions of the optical filter or replacement installation. Adjustment is easy.
[0037]
The (12) feature of the present invention is that the visible light source of each wavelength is composed of light emitting elements each having a specific emission wavelength region, such as an LED or LD. In this case, the light use efficiency is high, the irradiation intensity can be easily secured, and the energy consumption can be reduced.
[0038]
According to a thirteenth feature of the present invention, a linear ultraviolet light source, a visible light source, and an infrared light source are provided, and an image is formed while relatively moving the image display medium and the light sources. Is to configure the device. Here, the line shape is not strictly limited to a straight line shape, and includes, for example, a case in which light source units having a certain length are arranged in a staggered pattern so as to form a line as a whole. In addition, even for light source arrays that are formed by continuously arranging light emitting surfaces that can control the on / off of irradiation for each minute region, the arrangement of light emitting surfaces that constitute light sources of the same wavelength is not a single row, but a plurality of rows. It may be. Moreover, each light source array from which light emission wavelength differs may be integrated in one structure, and may be comprised as an independent structure.
When an image display device is manufactured using the multicolor image display method of the present invention, various configurations can be considered depending on the type and configuration of the light source, and may be appropriately selected depending on the application. However, when high resolution, high-speed writing, miniaturization, low cost, etc. are required, each light source is configured and arranged in a line, and an image is formed while moving these and the image display medium relatively. The method is more preferred.
[0039]
Hereinafter, the present invention will be described specifically by way of examples.
【Example】
Example 1
As a photochromic compound, 2- [1- (2-methyl-5-diethylaminostyryl-3-thienyl) methylidene] -3-isopropylidene succinic anhydride (hereinafter referred to as PC1), which is a heat irreversible type, and thermoreversible Is a type
[0040]
[Formula 4]

(Hereafter referred to as PC2)
Was used. 10 parts by weight of PC1 was added to 100 parts by weight of polystyrene and dissolved in a solvent to prepare a cast film on a quartz substrate. Similarly, a cast film was formed on a quartz substrate for PC2. When these absorption spectra before light irradiation were measured, both PC1 and PC2 showed an absorption band in the range of 300 to 400 nm, and both were colorless. When these were irradiated with 366 nm ultraviolet light extracted from a high-pressure mercury lamp, PC1 and PC2 developed blue-violet and magenta, respectively, and the maximum absorption wavelengths of the absorption spectrum were 595 nm and 530 nm, respectively.
For PC1, a cast film having the same formulation as above was formed on a white PET (polyethylene terephthalate) substrate (125 μm). PC2 is a cyanine dye for 10 parts by weight of PC2
[0041]
[Chemical formula 5]

(Hereinafter referred to as D1)
Similarly, a cast film having a formulation with 5 parts by weight added was formed on a white PET substrate.
Separately, a cast membrane (10 μm) containing PC1 was formed, and then a cast membrane (10 μm) containing PC2 and D1 was formed thereon via a PVA separation membrane (2 μm). The photosensitive layer containing only PC1, the photosensitive layer containing PC2 and D1, and the photosensitive layer formed by laminating both were colorless and the substrate color was white. .
When the entire surface of the laminated photosensitive layer was irradiated with ultraviolet light of 366 nm, both PC1 and PC2 developed color, and both exhibited an intermediate color between the developed colors. When the laminated photosensitive layer in this state was irradiated with infrared light of LD having an emission wavelength of 780 nm, the same blue-purple color as that in which only PC1 was colored was exhibited. When this was again irradiated with ultraviolet light of 366 nm and then irradiated with light of 600 nm by the LED, the same magenta color as that of only PC2 was developed.
[0042]
(Comparative Example 1)
As a photochromic compound, 2- [1- (5-methyl-2-p-dimethylaminostyryl-4-oxazolyl) ethylidene] -3-isopropylidene succinic anhydride (hereinafter referred to as PC3) is a heat irreversible type instead of PC2. The same operation as in Example 1 was performed. The maximum absorption wavelength of the absorption spectrum of PC3 was 530 nm as in PC2. When the entire surface of the laminated photosensitive layer formed in the same manner as in Example 1 was irradiated with ultraviolet light of 366 nm, both PC1 and PC3 developed color, and both exhibited an intermediate color between the developed colors alone. The laminated photosensitive layer in this state was irradiated with LD infrared light having an emission wavelength of 780 nm, but the color did not change by irradiation. When the laminated photosensitive layer in this state was irradiated with light of 600 nm by the LED, it did not have the same magenta color as that of the PC 3 alone, but showed a rather light magenta color.
[0043]
As a photochromic compound, 1,2-bis (2-phenyl-4-trifluoromethylthiazole) -3,3,4,4,5,5-hexafluorocyclopentene (hereinafter referred to as PC4) which is a heat irreversible type, heat PC2 as reversible type and 1- (5-methoxy-1,2-dimethyl-3-indolyl) -2- (5-cyano-2,4-dimethyl-3-thienyl)-as heat irreversible type 3,3,4,4,5,5-hexafluorocyclopentene (hereinafter referred to as PC5) was used. 10 parts by weight of PC4 was added to 100 parts by weight of polystyrene and dissolved in a solvent to prepare a cast film on a quartz substrate. For PC2 and PC5, cast films were similarly formed on a quartz substrate. When the absorption spectrum before light irradiation was measured, all of PC4, PC2, and PC5 showed an absorption band in the range of 300 nm to slightly less than 400 nm, and all were colorless. When these were irradiated with 366 nm ultraviolet light extracted from a high-pressure mercury lamp, PC4, PC2 and PC5 were colored yellow, magenta and cyan, respectively, and the maximum absorption wavelengths of the absorption spectrum were 420 nm, 530 nm and 665 nm, respectively.
For PC4, a cast film having the same formulation as above is formed on a white PET (polyethylene terephthalate) substrate (125 μm), and further on a PVA separation membrane (2 μm). Formed a cast membrane (10 μm) with a formulation in which 5 parts by weight of D1 was further added to 10 parts by weight, and a cast membrane (10 μm) containing PC5 was further formed on the PVA separation membrane (2 μm). Further, a PVA film (2 μm) was formed as a protective layer. The laminated photosensitive layer formed in this way was colorless and the substrate color was white, so that the observer recognized it as white.
When the entire surface of the photosensitive layer was irradiated with 366 nm ultraviolet light, all of PC4, PC2 and PC5 were colored and dark gray. When the photosensitive layer in this state was irradiated with visible light and infrared light of each wavelength, various color changes occurred. This is shown below.
[0044]
(Example 2)
When a part of the photosensitive layer was irradiated with light of 470 nm by an LED, the irradiated part was bluish purple.
[0045]
(Example 3)
When another portion of the photosensitive layer was irradiated with infrared light of 780 nm by LD, the irradiated portion was green.
[0046]
Example 4
When another portion of the photosensitive layer was irradiated with light of 660 nm by the LED, the irradiated portion was red.
[0047]
(Example 5)
When the infrared light of 780 nm was further irradiated to the part which showed the bluish purple color in Example 2 by LD, the irradiated part showed cyan color.
[0048]
(Example 6)
When the part which exhibited green in Example 3 was further irradiated with light of 660 nm by the LED, the irradiated part exhibited yellow.
[0049]
(Example 7)
When the portion having the bluish purple color in Example 2 was further irradiated with light at 660 nm by the LED, the irradiated portion exhibited a magenta color (red purple).
[0050]
(Example 8)
When the magenta (red purple) portion of Example 7 was further irradiated with infrared light of 780 nm by LD, the irradiated portion became colorless and the substrate was white.
[0051]
Photosensitive layers similar to those used in Examples 2 to 8 were produced. However, when irradiating with ultraviolet light of 366 nm, the irradiation time was the same as in the case of the photosensitive layer used in Examples 2 to 8, but when the irradiation was performed at half the illuminance, the photosensitive layer became gray.
[0052]
Example 9
When a portion of this photosensitive layer was irradiated with light of 470 nm by an LED in the same manner as in Example 2, the irradiated portion exhibited a light blue-purple color.
[0053]
(Example 10)
When another portion of this photosensitive layer was irradiated with infrared light of 780 nm by LD in the same manner as in Example 3, the irradiated portion exhibited a light green color.
[0054]
(Example 11)
When another portion of this photosensitive layer was irradiated with 660 nm light by an LED in the same manner as in Example 4, the irradiated portion exhibited a light red color.
[0055]
Photosensitive layers similar to those used in Examples 2 to 8 were produced. However, when irradiating with ultraviolet light of 366 nm, the illuminance was the same as in the case of the photosensitive layer used in Examples 2 to 8, but when the irradiation was performed in half the irradiation time, the photosensitive layer became gray.
[0056]
(Example 12)
When a portion of this photosensitive layer was irradiated with light of 470 nm by an LED in the same manner as in Example 2, the irradiated portion exhibited a light blue-purple color.
[0057]
(Example 13)
When another portion of this photosensitive layer was irradiated with infrared light of 780 nm by LD in the same manner as in Example 3, the irradiated portion exhibited a light green color.
[0058]
(Example 14)
When another portion of this photosensitive layer was irradiated with 660 nm light by an LED in the same manner as in Example 4, the irradiated portion exhibited a light red color.
[0059]
Photosensitive layers similar to those used in Examples 2 to 8 were prepared, and irradiation with 366 nm ultraviolet light was performed under the same conditions. The photosensitive layer was dark gray on the entire surface.
[0060]
(Example 15)
A part of this photosensitive layer is irradiated with light of 470 nm by an LED at half the illuminance in the case of Example 2 (irradiation time is the same), and infrared light of 780 nm is further applied to that part by LD as in Example 3. When irradiated, the irradiated area exhibited an intermediate color between cyan and green.
[0061]
(Example 16)
The other part of the photosensitive layer is irradiated with light of 470 nm by an LED in the same manner as in Example 2, and further, the part is irradiated with infrared light of 780 nm by LD at half the illuminance as in Example 3 (irradiation time is Similarly, the irradiated part exhibited an intermediate color between cyan and green.
[0062]
(Example 17)
Another portion of this photosensitive layer was irradiated with infrared light of 780 nm by LD at half the illuminance in the case of Example 3 (irradiation time was the same), and further light of 660 nm was applied to that portion by LED as in Example 4. When irradiated, the irradiated part was orange.
[0063]
(Example 18)
The other part of this photosensitive layer was irradiated with infrared light of 780 nm by LD in the same manner as in Example 3, and the light of 660 nm was further irradiated by that LED by LED at half the illuminance in Example 4 (irradiation time was In the same manner, the irradiated part was yellowish green.
[0064]
Example 19
The other part of the photosensitive layer is irradiated with light of 470 nm by the LED at half the illuminance in the case of Example 2 (the irradiation time is the same), and the part is further irradiated with light of 660 nm by the LED as in Example 4. As a result, the irradiated part exhibited an intermediate color between red and magenta.
[0065]
(Example 20)
The other part of the photosensitive layer is irradiated with light of 470 nm by the LED in the same manner as in Example 2, and further, the light of 660 nm is further irradiated by LED by the LED at half the illuminance in Example 4 (the irradiation time is the same). As a result, the irradiated part exhibited an intermediate color between violet and magenta.
[0066]
(Example 21)
A part of this photosensitive layer is irradiated with light of 470 nm by an LED for half the irradiation time in the case of Example 2 (illuminance is the same), and infrared light of 780 nm is further applied to that part by LD as in Example 3. When irradiated, the irradiated area exhibited an intermediate color between cyan and green.
[0067]
(Example 22)
The other part of the photosensitive layer is irradiated with light of 470 nm by an LED in the same manner as in Example 2, and the part is further irradiated with infrared light of 780 nm by LD in half the irradiation time of Example 3 (illuminance is Similarly, the irradiated part exhibited an intermediate color between cyan and green.
[0068]
(Example 23)
Another portion of this photosensitive layer was irradiated with infrared light of 780 nm by LD in half the irradiation time in the case of Example 3 (illuminance is the same), and light of 660 nm was further applied to that portion by LED as in Example 4. When irradiated, the irradiated part was orange.
[0069]
(Example 24)
The other part of the photosensitive layer was irradiated with infrared light of 780 nm by LD in the same manner as in Example 3, and the light of 660 nm was further irradiated by LED on the part in half the irradiation time of Example 4 (illuminance was In the same manner, the irradiated part was yellowish green.
[0070]
(Example 25)
The other part of the photosensitive layer is irradiated with light of 470 nm by the LED in half the irradiation time in the case of Example 2 (illuminance is the same), and the part is further irradiated with light of 660 nm by the LED as in Example 4. As a result, the irradiated part exhibited an intermediate color between red and magenta.
[0071]
(Example 26)
The other part of the photosensitive layer is irradiated with light of 470 nm by the LED in the same manner as in Example 2, and the part is further irradiated with light of 660 nm by the LED in half the irradiation time of Example 4 (the illuminance is the same). As a result, the irradiated part exhibited an intermediate color between violet and magenta.
[0072]
(Example 27)
An image display device for writing an image on the image display medium as used in Examples 1 to 26 was manufactured. FIG. 1 shows an outline of the configuration.
The device manufactured in Example 27 is provided with an insertion port (2) for introducing the image display medium (1) into the device. When the image display medium (1) is inserted from there, the image display medium is conveyed to the light source unit for writing by the conveying roller (3). The light source section includes an ultraviolet light source (4), an LED array (5) having an emission wavelength of 470 nm, an LED array (6) having an emission wavelength of 560 nm, an LED array (7) having an emission wavelength of 660 nm, It comprises a white LED (8), an infrared LD array (9) and an infrared lamp (10). In Example 27, the ultraviolet light source is composed of a mercury lamp and an optical filter, and can irradiate ultraviolet light having a wavelength near 366 nm. Further, the LED array and the infrared LD array that emit each visible wavelength are configured to be able to control on / off of irradiation for each minute region corresponding to a pixel. Each of these light sources can adjust the light emission intensity, and can also adjust the conveyance speed of the image display medium. The image display medium on which an image has been written after passing through these light source sections is discharged to a paper discharge tray (11).
[0073]
【The invention's effect】
As described above, as is clear from the detailed and specific description, according to claim 1 of the present invention, the maximum absorption wavelength in the colored state is not significantly different, and even between two photochromic compounds having a large overlap of absorption bands, Selectivity is improved.
According to the second aspect of the present invention, the three primary colors (yellow, magenta, and cyan) necessary for color display can be obtained. Therefore, visible light having a predetermined wavelength is irradiated on a desired position on the image display medium according to the image signal. In addition, by irradiating the desired position with infrared light, multicolor display becomes possible.
Further, according to claim 3 of the present invention, the maximum absorption wavelength in the colored state is relatively close between the yellow coloring compound / magenta coloring compound and between the magenta coloring compound / cyan coloring compound, and there are many cases where there is an overlap of absorption bands. However, it is possible to decolorize with good selectivity by visible light and infrared light, and the maximum absorption wavelength in the colored state is separated between the yellow coloring compound / cyan coloring compound, and there is almost no overlap of the absorption bands. Since there are many, decoloring is possible with good selectivity. Therefore, a desired color is displayed faithfully, and multicolor display with high display quality is possible.
Further, according to claim 4 of the present invention, it becomes possible to reduce the adverse effect on the reaction related to the expression of necessary functions of the compound constituting the photosensitive layer due to moisture, specific gas, etc., and durability is improved. A highly reliable multicolor image display method can be obtained.
Further, according to the fifth aspect of the present invention, it is not necessary to irradiate a fine spot unit corresponding to the pixel size as an ultraviolet light source, and the configuration of the light source element is facilitated, which is advantageous in terms of cost.
Further, according to the sixth aspect of the present invention, the degree of color development can be adjusted. Therefore, by generating a color sufficiently necessary and sufficient for the color density required for an image to be displayed, it is possible to erase by visible light irradiation and infrared light irradiation. Since the degree of color can be reduced, energy consumption can be reduced, and it is advantageous in terms of repeated durability of coloring and decoloring of the material.
Further, according to the seventh aspect of the present invention, the degree of color development can be adjusted. Therefore, by generating sufficient color development for the color density required in the image to be displayed, the extinction by visible light irradiation and infrared light irradiation can be achieved. Since the degree of color can be reduced, it is possible to reduce energy consumption, and it is advantageous in terms of repeated durability of coloring and decoloring of the material. By controlling the irradiation time of the ultraviolet light as variable, it is only necessary to make the irradiation intensity constant. Therefore, the control mechanism for controlling the emission intensity of the ultraviolet light source itself, or the ultraviolet light emitted from the light source outside the light source. There is no need to provide a member for adjusting the intensity of light, and the configuration becomes easy.
Further, according to the eighth aspect of the present invention, the color density can be adjusted for each color, so that gradation display is possible, and multi-color display is possible as an image on the image display medium. Conditions regarding the irradiation time of visible light and infrared light can be arbitrarily set. For example, in the method of forming an image while moving the light source system and the image display medium relatively, the speed of the movement is most easily controlled. (For example, constant speed, simple repetition of two speeds, etc.), the mechanical mechanism configuration and control relating to the movement are facilitated.
According to the ninth aspect of the present invention, gradation display can be performed for each color, and multicolor display can be performed as an image on the image display medium. By controlling the irradiation time of visible light and infrared light as variable, the irradiation intensity may be made constant. Therefore, a control mechanism for controlling the emission intensity of the visible light source and the infrared light source itself, or the light source It is not necessary to provide a member or the like for adjusting the intensity of visible light emitted from the light source outside, and the configuration becomes easy.
Further, according to the tenth aspect of the present invention, a white light source and a red light that can efficiently irradiate the entire display unit separately from the visible light source and infrared light source of each wavelength for selectively decoloring each photochromic material. By providing the external light source, it is possible to completely erase the display image in a short time.
According to claim 11 of the present invention, a visible light source for selectively decoloring each photochromic material is constituted by a white light source and an optical filter. Can be adjusted easily.
Further, according to the twelfth aspect of the present invention, when a light emitting element having a specific emission wavelength region is used, the light use efficiency is high, the irradiation intensity can be easily secured, and the energy consumption can be reduced.
Furthermore, according to the thirteenth aspect of the present invention, a rewritable multicolor display device with high display quality capable of faithfully displaying a desired color can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a configuration of an image display device used in the present invention.
[Explanation of symbols]
1 Image display medium
2 insertion slot
3 Transport roller
4 Ultraviolet light source
5 LED array
6 LED array
7 LED array
8 White LED
9 Infrared LD array
10 Infrared lamp
11 Output tray

Claims (13)

And a thermally irreversible photochromic compound and thermally reversible photochromic compounds, and comprising a photochromic compound of two or more, including a maximum absorption wavelength are different from each other in the colored state, further naphthalocyanine dyes, at least one cyanine dye the image display medium obtained by forming a photosensitive layer on a support substrate, at least, the step of coloring all types of photochromic compound contained in the photosensitive layer by ultraviolet light irradiation, each thermally irreversible photochromic compound by color heat by irradiating it with industrial as you and infrared light selectively decolorizing with visible light in a wavelength region which corresponds to the maximum absorption wavelengths irradiated in a desired area of each thermally irreversible photochromic compounds to a desired region It is characterized by performing a process of selectively erasing the reversible photochromic compound. Multi-color image display method. The photosensitive layer has a photochromic compound having a maximum absorption wavelength in the range of 400 to 500 nm in a colored state, a photochromic compound having a maximum absorption wavelength in the range of 500 to 600 nm, and a maximum absorption wavelength in the colored state of 600 to 700 nm. 2. The multicolor image display method according to claim 1, comprising all the photochromic compounds in the range. A photochromic compound having a maximum absorption wavelength in the range of 400 to 500 nm in the colored state is a heat irreversible type, a photochromic compound having a maximum absorption wavelength in the range of 500 to 600 nm in the colored state is a thermoreversible type, and a maximum in the colored state 3. The multicolor image display method according to claim 2, wherein the photochromic compound having an absorption wavelength in the range of 600 to 700 nm is a heat irreversible type. 4. A multicolor image display method according to claim 1, wherein a protective layer is formed on the surface of the photosensitive layer. The multicolor image display method according to claim 1, wherein the ultraviolet light irradiation is performed on the entire surface of the image display unit. 6. The multicolor image display method according to claim 1, wherein the irradiation intensity of ultraviolet light is variable. 6. The multicolor image display method according to claim 1, wherein the irradiation time of ultraviolet light is variable. 6. The multicolor image display method according to claim 1, wherein the irradiation intensity of visible light and infrared light is variable. 6. The multicolor image display method according to claim 1, wherein the irradiation time of visible light and infrared light is variable. The multicolor image display method according to any one of claims 1 to 9, further comprising a step of irradiating the entire surface of the image display unit with white light and infrared light. The multicolor image display method according to any one of claims 1 to 10, wherein the visible light source of each wavelength includes a white light source and an optical filter. The multicolor image display method according to any one of claims 1 to 10, wherein the visible light source of each wavelength is composed of light emitting elements each having a specific light emission wavelength region. A linear ultraviolet light source, a visible light source, and an infrared light source are provided, and the method according to any one of claims 1 to 12 is used while relatively moving the image display medium and the light sources. Forming a multi-color image display device.

Images