JP3719012B2 - Liquid crystal display device - Google Patents

Description

で表される。
【００１２】
この臨界角は、図６（ａ）〜図６（ｃ）に示すように、透過反射層１２および下側のガラス基板７の材料の屈折率ｎ１、ｎ２によっても変化する。また、臨界角が大きいと透過反射層１２の透過成分が多くなり、黒表示が得られる視角範囲は広がるが、反射成分が少なくなるため白表示が暗くなる。臨界角が小さいと逆の傾向を示し、視角範囲が狭くなり、十分な黒表示が得られない。このため、臨界角は、視角範囲と明るさの両方を考慮して適正に設定する必要があり、これに基づいてリニアプリズム１２の屈折率ｎ１と頂角θｔを適正に設定すれば良い。例えば、図６（ａ）に示す屈折率ｎが１．４のリニアプリズム１２では、臨界角が３０°〜５０°の範囲で、頂角が３０°〜１１０°の範囲が好ましい。また、図６（ｂ）に示す屈折率ｎが１．５のリニアプリズム１２では、臨界角が３０°〜５０°の範囲で、頂角が６０°〜１２０°の範囲が好ましい。さらに、図６（ｃ）に示す屈折率ｎが１．６のリニアプリズム１２では、臨界角が３０°〜５０°の範囲で、頂角が８０°〜１３０°の範囲が好ましい。
【００１３】
次に、このような液晶表示装置１の作用について説明する。
まず、液晶セル２の上下一対のガラス基板６、７の透明電極１０、１１間に電圧を印加しない電界非印加時には、液晶セル２の液晶層８中の液晶分子がランダムに配向されて散乱状態を呈する。このときには、液晶セル２に入射した光が液晶層８中で散乱され、液晶セル２に入射した光の進行方向に対して反対側に向かう後方散乱光が観察者側に出射され、液晶セル２に入射した光の進行方向側に向かう前方散乱光のうち、透過反射層３を透過して下側のガラス基板７から空気層４を介して光吸収層５に吸収される一部の前方散乱光を除き、これ以外の大部分の前方散乱光が透過反射層３のリニアプリズム１２の上面側の２面、および透過反射層３と下側のガラス基板７の各底面で反射されて観察者側に出射されるので、白紙のように白い所謂ペーパーホワイトの明るい白表示が得られる。このときには、透過反射層３が液晶セル２の下側のガラス基板７の内面（図１では上面）に設けられて液晶層７に密接していることにより、液晶層８と透過反射層３との間における光の損失が少なく、白表示での反射率が高くなるため、これによっても明るい白表示が得られる。
【００１４】
また、液晶セル２の上下一対のガラス基板６、７の透明電極１０、１１間に電圧を印加した電界印加時には、液晶セル２の液晶層８中の液晶分子が電界方向に整列されて透過状態を呈する。このときには、液晶セル２に入射した光が液晶セル２を透過して透過反射層３に向けて出射される。この出射光のうち、一部の出射光つまりリニアプリズム１２の臨界角よりも大きい角度でリニアプリズム１２に入射する入射光は、リニアプリズム１２の上面側の２面、および透過反射層３と下側のガラス基板７の各底面で反射されて透過反射層３から観察者側に出射されるが、液晶セル２に対して大きく傾いた角度で入射する光強度は弱く、これ以外の出射光つまり臨界角よりも小さい角度でリニアプリズム１２に入射する入射光は、リニアプリズム１２の上面側の２面から入射し、この入射光が透過反射層３および下側のガラス基板７を透過して空気層４に出射され、液晶セル２の背面に配置された光吸収層５に吸収される。このため、暗い黒表示となり、リニアプリズム１２の臨界角の範囲内で暗い黒表示が得られるとともに、広い視角範囲が確保できる。このときには、透過反射層３が液晶セル２の下側のガラス基板７の上面に設けられて液晶層８に密接しているので、液晶セル２を正面（図１では真上）から観察した際、電界が印加されていない白表示画素と電界が印加された黒表示画素とにおける白黒表示間の奥行き視差が少なくなり、また液晶セル２を斜め上方から観察した際、白表示の縁に黒表示の影ができて画像が二重に見えるという画素間視差をも防ぐことができ、これにより鮮明で明るい反射型の白黒表示が得られる。
【００１５】
なお、上記第１実施形態では、液晶セル２の下側のガラス基板７の内面に透過反射層３を直接設けたが、これに限らず、例えば図７に示すように、透過反射層３の下面に屈折層１５を設け、この屈折層１５を下側のガラス基板７の内面に設けても良い。この場合には、透過反射層３の屈折率ｎ１と、屈折層１５の屈折率ｎ３と、下側のガラス基板７の屈折率ｎ２とがすべて異なっていも良く（ｎ１≠ｎ３≠ｎ２）、また透過反射層３の屈折率ｎ１と屈折層１５の屈折率ｎ３とが等しく、下側のガラス基板７の屈折率ｎ２のみが異なっていても良い（ｎ１＝ｎ３≠ｎ２）。このようにすれば、臨界角を変えることができ、これに伴って視角範囲も変えることができる。
また、上記第１実施形態およびその変形例では、透過反射層３のリニアプリズム１２の各角部が尖った形状に形成されているが、これに限らず、例えば図３および図７に点線で示すように、頂角θｔおよび底角θｂを円弧状に丸みをもたせた形状に形成しても良く、また断面三角形である必要はなく、断面台形状に形成しても良い。
【００１６】
［第２実施形態］
次に、図８を参照して、この発明の液晶表示装置の第２実施形態について説明する。なお、図１〜図６に示された第１実施形態と同一部分は同一符号を付し、その説明は省略する。
この液晶表示装置２０は、液晶セル２の下側のガラス基板７の内面（図８では上面）に光吸収層５を設け、この光吸収層５の上面に低反射層２１を設け、この低屈折層２１の上面に透過反射層３を設け、この透過反射層３の上面に透明電極１１を配列形成した構成になっており、これら以外は第１実施形態と同じ構成になっている。この場合、低反射層２１は、透過反射層３から出射された光の反射を極力抑えて光吸収層５に入射させるものである。
このような液晶表示装置２０では、第１実施形態と同様の作用効果があるほか、特に下側のガラス基板７の内面に光吸収層５を設け、この光吸収層５の上面に低反射層２１を設けたことにより、透過反射層３から出射された光の反射を抑え、効率良く光吸収層５に入射させて吸収させることができるので、正面での黒表示およびコントラスト性能が向上する。
【００１７】
［第３実施形態］
次に、図９を参照して、この発明の液晶表示装置の第３実施形態について説明する。この場合にも、図１〜図６に示された第１実施形態と同一部分には同一符号を付し、その説明は省略する。
この液晶表示装置３０は、液晶セル２の電極構造が異なる以外は第１実施形態と同じ構成になっている。すなわち、液晶セル２の上側のガラス基板６の内面（図９では下面）には、ＩＴＯなどからなる透明な共通電極３１が表示領域の全域に亘って形成されている。また、下側のガラス基板７の内面（同図では上面）には、アクティブ素子であるＴＦＴ（薄膜トランジスタ）３２が縦横に所定間隔でマトリックス状に多数配列形成されているとともに、これらＴＦＴ３２を覆って透過反射層３が設けられている。この透過反射層３の上面には、ＩＴＯなどからなる透明な画素電極３３がＴＦＴ３２に対応して縦横に多数配列形成されている。そして、これら画素電極３３はスルーホール３４を介して各ＴＦＴ３２にそれぞれ電気的に接続されている。
このような液晶表示装置３０では、第１実施形態と同様の作用効果があるほか、特にＴＦＴ３２により液晶セル２の散乱状態と透過状態を高速で制御することができ、これにより応答速度の速い反射型の白黒表示が得られる。
【００１８】
なお、上記第３実施形態では、下側のガラス基板７の上面にＴＦＴ３２を覆って透過反射層３を設けたが、これに限らず、例えば、図１０に示す第１変形例のように、下側のガラス基板７の上面にＴＦＴ３２を覆って保護層３５を設け、この保護層３４上に第２実施形態と同様に光吸収層５を設け、この光吸収層５の上面に低反射層２１を設け、この低屈折層２１の上面に透過反射層３を設け、この透過反射層３の上面に画素電極３３を配列形成し、これら画素電極３３をスルーホール３４を介して各ＴＦＴ３２にそれぞれ電気的に接続した構成であっても良い。この場合にも、第３実施形態と同様の作用効果あるほか、低反射層２１により、透過反射層３から出射された光の反射を抑え、効率良く光吸収層５に入射させて吸収させることができるので、正面での黒表示およびコントラスト性能が向上する。
【００１９】
また、上記第３実施形態では、下側のガラス基板７の上面にＴＦＴ３２を形成したが、これに限らず、例えば、図１１に示す第２変形例のように、下側のガラス基板７の上面に透過反射層３を設け、この透過反射層３の上面に共通電極３１を形成し、上側のガラス基板６の下面に画素電極３３を縦横に配列形成するとともに、これら画素電極３３に対応させてＴＦＴ３２を配列形成した構成でも良い。このような構成でも、第３実施形態と同様の作用効果があることは言うまでもない。
さらに、図１１の第２変形例に限らず、例えば、図１２に示す第３変形例のように、下側のガラス基板７の上面に光吸収層５を設け、この光吸収層５の上面に低反射層２１を設け、この低屈折層２１の上面に透過反射層３を設け、この透過反射層３の上面に共通電極３１を形成し、上側のガラス基板６の下面に画素電極３３およびＴＦＴ３２を配列形成した構成でも良い。このようにすれば、第２実施形態と第３実施形態の両方の作用効果があることは言うまでもない。
【００２０】
［第４実施形態］
次に、図１３を参照して、この発明の液晶表示装置の第４実施形態について説明する。この場合にも、図１〜図６に示された第１実施形態と同一部分には同一符号を付し、その説明は省略する。
この液晶表示装置４０は、液晶セル２にカラーフィルタ４１を設けた構成になっており、これ以外は第１実施形態と同じ構成になっている。
すなわち、液晶セル２は、上側のガラス基板６の下面にカラーフィルタ４１が形成され、このカラーフィルタ４１の下面に透明電極１０が配列形成され、下側のガラス基板７の上面に透過反射層３が設けられ、この透過反射層３の上面に透明電極１１が配列形成され、上側のガラス基板６と下側のガラス基板７との間に液晶層８をシール材９で封止した構成になっている。
このような液晶表示装置４０では、第１実施形態と同様、電界非印加時に液晶セル２が散乱状態を呈するので、白紙のように白い所謂ペーパーホワイトの明るい白表示が得られ、電界印加時に液晶セル２が透過状態を呈するので、カラーフィルタ４１によって反射型のカラー表示が得られる。
【００２１】
なお、上記第４実施形態では、下側のガラス基板７の上面に透過反射層３を直接設けたが、これに限らず、例えば、第２実施形態と同様、下側のガラス基板７の上面に光吸収層５を設け、この光吸収層５上に低反射層２１を介して透過反射層３を設けた構成でも良い。このようにすれば、コントラストの高いカラー表示が得られる。また、これに限らず、例えば、第３実施形態およびその各変形例のように、液晶セル２にＴＦＴ３２を設けた構成でも良い。このようにすれば、高速応答が可能なカラー表示が得られる。
また、上記第１〜第４実施形態およびその各変形例では、透過反射層３のリニアプリズム１２が、その上側の２面の傾斜長さの等しい左右または前後に対称な断面２等辺三角形に形成されている場合について述べたが、これに限らず、例えば上側の２面の傾斜長さの異なる非対称な断面三角形に形成しても良い。このような透過反射層３では、リニアプリズム１２の長辺側と短辺側とで臨界角が異なるが、上記各実施形態とほぼ同様の作用効果があることは言うまでもない。
【００２２】
また、上記第１〜第４実施形態およびその各変形例では、透過反射層３の上面にリニアプリズム１２を形成した場合について述べたが、これに限らず、例えば、図１４に示すように、透過反射層３の上面に四角錐プリズム５０を液晶セル２の画素ピッチよりも小さい間隔で縦横に密接させて配列形成しても良く、また図１５に示すように、八角錐プリズム５１を同様に配列形成しても良く、さらに図示しないが、三角錐プリズム、六角錐プリズム、十角錐プリズムなどの多角錐プリズムを配列形成した構成でも良い。また、多角錐プリズムに限らず、図１６に示すように、円錐プリズム５２を同様に配列形成しても良く、また図示しないが、楕円錐プリズムを配列形成した構成も良い。このような多角錐プリズム、円錐プリズム、楕円錐プリズムを配列形成した透過反射層３を用いれば、少なくとも３方向以上の多方向からの光を反射させることができるので、より一層、明かる白表示を得ることができる。
【００２３】
さらに、上記第１〜第４実施形態およびその各変形例では、液晶セル２の液晶層６が高分子１０中に液晶分子１１を分散させた高分子分散型の構成になっているが、これに限らず、例えばコレステリック相とネマティック相との相転移型の液晶を用いた散乱透過型の液晶セルでも良く、また電界印加時に透過状態を呈し、電界非印加時に散乱状態を呈する液晶セル２に限らず、電界印加時に散乱状態を呈し、電界非印加時に透過状態を呈する散乱透過型の液晶セルでも良い。
【００２４】
【発明の効果】
以上説明したように、この発明によれば、液晶素子が散乱状態を呈するときには、後方散乱光が観察者側に出射するほか、透過反射層を透過して光吸収層に吸収される一部の前方散乱光を除く大部分の前方散乱光が透過反射層のプリズムで反射されて観察者側に出射するので、白表示が明るくなり、白紙のように白い所謂ペーパーホワイトの白表示が得られるばかりか、液晶素子の光出射側の基板の内面に透過反射層を設けたことにより、液晶層と透過反射層との間での光の損失が少なく、白表示での反射率が高くなるため、これによっても明るい白表示が得られる。また、液晶素子が透過状態を呈するときには、液晶素子に入射した光が液晶素子を透過して透過反射層に向けて出射され、その液晶素子の正面から所定の角度範囲で入射した光がプリズムの透過反射層を透過して光吸収層に吸収され、これ以外の範囲で入射する光はプリズムで反射されるが、液晶素子の法線から大きく傾いた方向から入射される光の強度は弱いので、十分に暗い黒表示が得られる。さらに、透過反射層が液晶セルの光出射側の基板の内面に設けられて液晶層に密接しているので、正面から観察した際、白黒表示間の奥行き視差が少なく、また斜め方向から観察した際、白表示の縁に黒表示の影ができて画像が二重に見えるという画素間視差をも防ぐことができる。
【図面の簡単な説明】
【図１】この発明の液晶表示装置の第１実施形態を示した断面図。
【図２】図１の透過反射層のリニアプリズムの要部を示した拡大斜視図。
【図３】図２の透過反射層が液晶セルの下側のガラス基板上に設けられた状態における要部の断面形状を示した拡大図。
【図４】図１の液晶表示装置の理想的な吸収反射特性を示した図。
【図５】図３のリニアプリズムの臨界角を求めるときの光路状態を示した図。
【図６】図５のリニアプリズムの屈折率に対する臨界角と頂角との関係を示し、（ａ）は屈折率が１．４の場合を示した図、（ｂ）は屈折率が１．５の場合を示した図、（ｃ）は屈折率が１．６の場合を示した図。
【図７】図３の透過反射層と下側のガラス基板との間に屈折層を設けた変形例を示した図。
【図８】この発明の液晶表示装置の第２実施形態を示した断面図。
【図９】この発明の液晶表示装置の第３実施形態を示した断面図。
【図１０】図９の第３実施形態の第１変形例を示した断面図。
【図１１】図９の第３実施形態の第２変形例を示した断面図。
【図１２】図９の第３実施形態の第３変形例を示した断面図。
【図１３】この発明の液晶表示装置の第４実施形態を示した断面図。
【図１４】透過反射層の上面に四角錐プリズムを配列形成した要部の拡大斜視図。
【図１５】透過反射層の上面に八角錐プリズムを配列形成した要部の拡大斜視図。
【図１６】透過反射層の上面に円錐プリズムを配列形成した要部の拡大斜視図。
【符号の説明】
１、２０、３０、４０ 液晶表示装置
２ 液晶セル
３ 透過反射層
５ 光吸収層
６ 上側のガラス基板
７ 下側のガラス基板
８ 液晶層
１２ リニアプリズム
２１ 低反射層
３２ ＴＦＴ
４１ カラーフィルタ
５０ 四角錐プリズム
５１ 八角錐プリズム
５２ 円錐プリズム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device.
[0002]
[Prior art]
Conventionally, in a liquid crystal display device, the structure of a liquid crystal cell is simpler than that of a TN liquid crystal element, there are few manufacturing problems, and the utilization rate of light is increased without using a polarizing plate. A scattering transmission type liquid crystal display element such as a polymer dispersion type liquid crystal display element in which a liquid crystal layer in which liquid crystal molecules are dispersed is sealed between a pair of transparent electrode substrates has been developed.
This polymer-dispersed liquid crystal display device has a scattering state in which liquid crystal molecules are randomly oriented in the liquid crystal layer when no electric field is applied between the pair of transparent electrode substrates, and the liquid crystal layer is in the liquid crystal layer when an electric field is applied. Thus, the liquid crystal molecules are aligned in the direction of the electric field and exhibit a transmission state.
[0003]
When performing black and white display with this liquid crystal display device, an optical element such as a black light absorbing plate, a scattering type reflecting plate, or a specular type reflecting plate is disposed on the back side of the polymer dispersion type liquid crystal cell. ing. When no electric field is applied between the electrode substrates of the liquid crystal cell, the liquid crystal cell exhibits a scattering state, so that white display is obtained by observing the scattered light. In addition, when an electric field is applied between the counter electrodes of the liquid crystal cell, the liquid crystal cell at the location where the electric field is applied exhibits a transmission state, so that the optical element disposed on the back side of the liquid crystal cell is directly viewed and looks black. Alternatively, by observing weak reflected light or not observing reflected light, a portion to which an electric field is applied is displayed in black.
[0004]
[Problems to be solved by the invention]
However, in such a liquid crystal display device, if a black light absorbing plate is used as an optical element in order to obtain the darkest black display, black display can be ensured, but a bright white display cannot be obtained. . This is because of the backscattered light traveling in the opposite direction to the traveling direction of the light incident on the liquid crystal cell due to the scattering state of the liquid crystal layer and the forward scattered light traveling toward the traveling direction of the light incident on the liquid crystal cell. This is because the forward scattered light is absorbed by the light absorption layer.
In addition, in a liquid crystal display device using a scattering type reflection plate as an optical element, light transmitted through the liquid crystal cell when an electric field is applied is scattered by the scattering type reflection plate, and a part of this scattered light is transmitted again through the liquid crystal cell. Therefore, there is a problem that sufficient black display cannot be secured.
Furthermore, in a liquid crystal display device using a mirror-type reflector as an optical element, high contrast is obtained under specific observation conditions. However, due to the specularity of the reflector, the viewer's own reflection may occur, or black display may occur. There are problems such as glare and a narrow viewing angle range.
[0005]
An object of the present invention is to ensure bright white display and dark black display without causing reflection or glare of black display, and to prevent parallax between pixels and depth parallax between monochrome displays.
[0006]
[Means for Solving the Problems]
The present invention relates to a scattering transmission type liquid crystal element in which a liquid crystal layer is sealed with a sealing material between a pair of transparent substrates, and is controlled in a scattering state and a transmission state in accordance with an applied electric field, and the liquid crystal element The light is provided on the inner surface of the substrate on the light emitting side, and is composed of a plurality of prisms arranged on one surface, transmits light incident at a predetermined angle range, and reflects light incident at an angle other than the predetermined angle range. And a light absorption layer that absorbs light transmitted through the transmission / reflection layer.
According to the present invention, when the liquid crystal element exhibits a scattering state, in addition to the backscattered light directed to the opposite side to the traveling direction of the light incident on the liquid crystal element, the liquid crystal element travels toward the traveling direction side of the light incident on the liquid crystal element. Of the forward scattered light, most of the forward scattered light except for some forward scattered light that is transmitted through the transmissive reflective layer and absorbed by the light absorbing layer is reflected by the prism of the transmissive reflective layer and is emitted to the viewer side. Therefore, the white display becomes brighter and white so-called white display like white paper can be obtained, and the liquid crystal layer and the transmissive reflective layer are provided by providing a transmissive reflective layer on the inner surface of the light emitting side substrate of the liquid crystal element. Since the loss of light between the two is small and the reflectance in white display is high, a bright white display can also be obtained. In addition, when the liquid crystal element is in a transmissive state, light incident on the liquid crystal element is transmitted through the liquid crystal element and emitted toward the transmission / reflection layer, and light incident in a predetermined angle range from the front surface of the liquid crystal element is emitted from the prism. Light that is transmitted through the transmission / reflection layer and absorbed by the light absorption layer and incident in a range other than the predetermined angle range is reflected by the prism, but the light incident from a direction greatly inclined from the normal line of the liquid crystal element is reflected. Since the intensity is weak, a sufficiently dark black display can be obtained. Further, since the transmission / reflection layer is provided on the inner surface of the substrate on the light emitting side of the liquid crystal cell and is in close contact with the liquid crystal layer, there is little depth parallax between black and white display when observed from the front, and the observation is performed from an oblique direction. At this time, it is possible to prevent the inter-pixel parallax that the shadow of the black display is formed on the edge of the white display and the image looks double.
[0007]
In this case, as described in claim 2, by using a prism sheet in which a plurality of linear prisms having a triangular cross-section are arranged, a range of a predetermined viewing angle with respect to two directions, upper and lower or left and right, is transmitted. Since it is absorbed by the light absorption layer and incident light other than the viewing angle is scattered and emitted to the viewer side, a bright and high-contrast reflective display can be obtained.
Further, as described in claim 3, the prism is formed of a prism sheet in which protrusions in the shape of a polygonal cone, a cone, or an elliptical cone are arranged in close contact vertically and horizontally, so that all directions in the vertical and horizontal directions are obtained. Can be used effectively, and a brighter white display can be obtained.
In addition, as described in claim 4, by providing a low reflection layer between the overreflection layer and the light absorption layer, reflection at each interface between the transmission reflection layer and the light absorption layer is reduced, and black The display can be darkened to increase the contrast.
In addition, as described in claim 5, by providing an active element corresponding to each pixel, the contrast is high, the parallax between pixels and the depth parallax between black and white displays are small, and the scattering state and transmission state of the liquid crystal element can be changed at high speed. It can be controlled, and a reflection type monochrome display having a high response speed can be obtained.
Furthermore, as described in claim 6, by providing the color filter, it is possible to obtain a reflective color display having a high contrast and a small parallax between pixels and a small depth parallax between black and white displays.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
Hereinafter, a liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view of a liquid crystal display device. The liquid crystal display device 1 includes a polymer dispersion type liquid crystal cell (liquid crystal element) 2, a transmission / reflection layer 3 provided in the liquid crystal cell 2, and an air layer 4 on the light emission side of the liquid crystal cell 2. The light absorption layer 5 is provided. The liquid crystal cell 2 has a configuration in which a liquid crystal layer 8 is sealed with a sealing material 9 between a pair of upper and lower transparent glass substrates 6 and 7. In this case, transparent electrodes 10 such as ITO are arranged on the opposing surface (the lower surface in FIG. 1) of the upper glass substrate 6 among the opposing surfaces of the pair of upper and lower glass substrates 6 and 7, and the lower side ( On the opposite surface, that is, the inner surface (upper surface in the figure) of the glass substrate 7 on the light emitting side, a transmissive reflection layer 3 is provided, and a transparent electrode 11 such as ITO is formed on the transmissive reflection layer 3 with the upper transparent electrode 10. They are arranged orthogonally. The liquid crystal layer 8 is composed of a polymer dispersed liquid crystal type (PDLC) in which liquid crystal molecules are dispersed in a polymer.
[0009]
In this polymer-dispersed liquid crystal cell 2, the liquid crystal molecules in the liquid crystal layer 8 are randomly oriented and exhibit a scattering state when no voltage is applied between the transparent electrodes 10 and 11 of the pair of glass substrates 6 and 7. When the electric field is applied between the transparent electrodes 10 and 11 of the pair of glass substrates 6 and 7, the liquid crystal molecules of the liquid crystal layer 8 are aligned in the direction of the electric field and exhibit a transmission state. In this liquid crystal cell 2, the opposing region where the transparent electrode 10 of the upper glass substrate 6 and the transparent electrode 11 of the lower glass substrate 7 intersect with the liquid crystal layer 8 corresponds to one pixel, and this pixel is It is arranged in a matrix.
On the other hand, as shown in FIG. 2 and FIG. 3, the transmission / reflection layer 3 has an isosceles triangular linear prism 12 on the upper surface facing the liquid crystal layer 8 at a predetermined interval, that is, an interval smaller than the pixel pitch of the liquid crystal cell 2. The linear prisms 12 are configured to transmit incident light within the viewing angle range (near the front) and reflect other incident light. That is, the linear prism 12 transmits incident light in a viewing angle range (0 ° to ± 40 °) and is incident at an incident angle other than this so as to obtain an ideal absorption reflection characteristic shown in FIG. Is reflected from the lower glass substrate 7 without being emitted to the air layer 4. The light absorption layer 5 is a black film that absorbs light emitted from the lower glass substrate 7 of the liquid crystal cell 2.
[0010]
By the way, in the linear prism 12, the range of the incident angle (inclination angle with respect to the normal line of the liquid crystal cell 2) through which the incident light is transmitted through the transmission / reflection layer 3, and the lower glass substrate through which the incident light is transmitted through the transmission / reflection layer 3 The critical angle is the boundary angle with the range of incident angles reflected by 7;
This critical angle will be described with reference to FIG.
An angle formed by a light beam incident on one surface of the linear prism 12 having an isosceles triangle having a cross section shown in FIG. 5 and a normal line of the liquid crystal cell 2 is an incident angle θ1, and a refraction angle thereof is θ2. When the angle formed by the normal when exiting from the bottom surface of the linear prism 12 to the lower glass substrate 7 is the exit angle θ3 and the refraction angle is θ4, and the light incident on the glass substrate 7 is incident on the air layer 4 An angle formed with the normal line is an emission angle θ4 and a refraction angle is θ5. Further, the refractive index of the linear prism 12 is n1, the refractive index of the glass substrate 7 is n2, and an angle corresponding to the crossing angle between one surface of the upper surface of the linear prism 12 and the bottom surface in the vicinity of the apex angle θt is θp.
Under this condition, the geometric relationship of θp, θ2, and θ3 is
(90 ° −θp) + θ2 + θ3 = 90 °
θ2 = θp−θ3 (1)
And the geometrical relationship of θp, θcp, θ1 is
(90 ° −θp) + θcp + θ1 = 90 °
θcp = θp−θ1 (2)
It is.
[0011]
Also, according to the law of refraction, the relationship between θ1 and θ2 is
sin θ1 / sin θ2 = n1
sin θ1 = n1 · sin θ2
θ1 = asin (n1 · sinθ2) (3)
And the relationship between θ3 and θ4 is
n1 · sin θ3 = n2 · sin θ4
sin θ3 = (n2 / n1) sin θ4
θ3 = asin {(n2 / n1) sin θ4} (4)
And the relationship between θ4 and θ5 is
n2 · sin θ4 = sin θ5 = 1 (θ5 = 90 °)
sin θ4 = (1 / n2)
θ4 = asin (1 / n2) (5)
Is established. From these equations, the theoretical critical angle θcp is

It is represented by
[0012]
As shown in FIGS. 6A to 6C, this critical angle also varies depending on the refractive indexes n1 and n2 of the materials of the transmission / reflection layer 12 and the lower glass substrate 7. If the critical angle is large, the transmission component of the transmission / reflection layer 12 increases, and the viewing angle range in which black display can be obtained is widened, but the white display becomes dark because the reflection component decreases. When the critical angle is small, the opposite tendency is exhibited, the viewing angle range becomes narrow, and sufficient black display cannot be obtained. For this reason, it is necessary to set the critical angle appropriately in consideration of both the viewing angle range and the brightness. Based on this, the refractive index n1 and the apex angle θt of the linear prism 12 may be set appropriately. For example, in the linear prism 12 having a refractive index n of 1.4 shown in FIG. 6A, the critical angle is preferably in the range of 30 ° to 50 °, and the apex angle is preferably in the range of 30 ° to 110 °. In the linear prism 12 having a refractive index n of 1.5 shown in FIG. 6B, the critical angle is preferably in the range of 30 ° to 50 °, and the apex angle is preferably in the range of 60 ° to 120 °. Furthermore, in the linear prism 12 having a refractive index n of 1.6 shown in FIG. 6C, the critical angle is preferably in the range of 30 ° to 50 °, and the apex angle is preferably in the range of 80 ° to 130 °.
[0013]
Next, the operation of the liquid crystal display device 1 will be described.
First, when no electric field is applied between the transparent electrodes 10 and 11 of the pair of upper and lower glass substrates 6 and 7 of the liquid crystal cell 2, the liquid crystal molecules in the liquid crystal layer 8 of the liquid crystal cell 2 are randomly oriented and scattered. Presents. At this time, the light incident on the liquid crystal cell 2 is scattered in the liquid crystal layer 8, and the backscattered light directed to the opposite side to the traveling direction of the light incident on the liquid crystal cell 2 is emitted to the viewer side. Of the forward scattered light traveling in the traveling direction of the light incident on the light, a part of the forward scattered light that is transmitted through the transmission / reflection layer 3 and absorbed by the light absorption layer 5 from the lower glass substrate 7 through the air layer 4 Except for light, most of the other forward scattered light is reflected on the two upper surfaces of the linear prism 12 of the transmission / reflection layer 3 and the bottom surfaces of the transmission / reflection layer 3 and the lower glass substrate 7 to observe the viewer. Since the light is emitted to the side, white white so-called paper white bright white display can be obtained. At this time, the transmission / reflection layer 3 is provided on the inner surface (upper surface in FIG. 1) of the glass substrate 7 on the lower side of the liquid crystal cell 2 and is in close contact with the liquid crystal layer 7. Light loss during the period is small, and the reflectance in white display is high, so that a bright white display can be obtained.
[0014]
When an electric field is applied between the transparent electrodes 10 and 11 of the pair of upper and lower glass substrates 6 and 7 of the liquid crystal cell 2, the liquid crystal molecules in the liquid crystal layer 8 of the liquid crystal cell 2 are aligned in the direction of the electric field and transmitted. Presents. At this time, the light incident on the liquid crystal cell 2 passes through the liquid crystal cell 2 and is emitted toward the transmission / reflection layer 3. Of the emitted light, a part of the emitted light, that is, incident light that is incident on the linear prism 12 at an angle larger than the critical angle of the linear prism 12, the two surfaces on the upper surface side of the linear prism 12, the transmission / reflection layer 3 and the lower side. Although the light is reflected from the bottom surface of the glass substrate 7 on the side and emitted from the transmission / reflection layer 3 to the viewer side, the intensity of light incident on the liquid crystal cell 2 at a greatly inclined angle is weak, and other emitted light, that is, Incident light incident on the linear prism 12 at an angle smaller than the critical angle is incident from two surfaces on the upper surface side of the linear prism 12, and the incident light passes through the transmission / reflection layer 3 and the lower glass substrate 7 to be air. The light is emitted to the layer 4 and absorbed by the light absorption layer 5 disposed on the back surface of the liquid crystal cell 2. For this reason, a dark black display is obtained, a dark black display is obtained within the critical angle range of the linear prism 12, and a wide viewing angle range can be secured. At this time, since the transmission / reflection layer 3 is provided on the upper surface of the glass substrate 7 below the liquid crystal cell 2 and is in close contact with the liquid crystal layer 8, the liquid crystal cell 2 is observed from the front (directly above in FIG. 1). The depth parallax between the black and white display between the white display pixel to which the electric field is not applied and the black display pixel to which the electric field is applied is reduced, and when the liquid crystal cell 2 is observed obliquely from above, the black display is performed at the edge of the white display. It is possible to prevent the inter-pixel parallax that the image appears double and the image looks double, thereby obtaining a clear and bright reflective monochrome display.
[0015]
In the first embodiment, the transmission / reflection layer 3 is directly provided on the inner surface of the glass substrate 7 on the lower side of the liquid crystal cell 2. However, the present invention is not limited to this. For example, as shown in FIG. A refractive layer 15 may be provided on the lower surface, and the refractive layer 15 may be provided on the inner surface of the lower glass substrate 7. In this case, the refractive index n1 of the transmission / reflection layer 3, the refractive index n3 of the refractive layer 15, and the refractive index n2 of the lower glass substrate 7 may all be different (n1 ≠ n3 ≠ n2). The refractive index n1 of the transmission / reflection layer 3 may be equal to the refractive index n3 of the refractive layer 15, and only the refractive index n2 of the lower glass substrate 7 may be different (n1 = n3 ≠ n2). In this way, the critical angle can be changed, and the viewing angle range can be changed accordingly.
Moreover, in the said 1st Embodiment and its modification, although each corner | angular part of the linear prism 12 of the transmission / reflection layer 3 is formed in the pointed shape, it is not restricted to this, For example, FIG. 3 and FIG. As shown in the figure, the apex angle θt and the base angle θb may be formed in a circular arc shape, or may be formed in a trapezoidal cross section, not necessarily a triangular cross section.
[0016]
[Second Embodiment]
Next, a second embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same part as 1st Embodiment shown by FIGS. 1-6, and the description is abbreviate | omitted.
The liquid crystal display device 20 is provided with a light absorption layer 5 on the inner surface (upper surface in FIG. 8) of the glass substrate 7 below the liquid crystal cell 2, and a low reflection layer 21 is provided on the upper surface of the light absorption layer 5. The transmission / reflection layer 3 is provided on the upper surface of the refractive layer 21, and the transparent electrodes 11 are arranged on the upper surface of the transmission / reflection layer 3, and the other configurations are the same as those in the first embodiment. In this case, the low reflection layer 21 is made to enter the light absorption layer 5 while suppressing reflection of the light emitted from the transmission reflection layer 3 as much as possible.
Such a liquid crystal display device 20 has the same effects as the first embodiment, and in particular, the light absorption layer 5 is provided on the inner surface of the lower glass substrate 7, and the low reflection layer is formed on the upper surface of the light absorption layer 5. By providing 21, reflection of light emitted from the transmission / reflection layer 3 can be suppressed, and the light can be efficiently incident on the light absorption layer 5 and absorbed, thereby improving the black display and contrast performance in the front.
[0017]
[Third Embodiment]
Next, a third embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. Also in this case, the same parts as those in the first embodiment shown in FIGS.
The liquid crystal display device 30 has the same configuration as that of the first embodiment except that the electrode structure of the liquid crystal cell 2 is different. That is, a transparent common electrode 31 made of ITO or the like is formed over the entire display area on the inner surface (lower surface in FIG. 9) of the glass substrate 6 on the upper side of the liquid crystal cell 2. In addition, a large number of TFTs (thin film transistors) 32 as active elements are arranged in a matrix at predetermined intervals on the inner surface (upper surface in the figure) of the lower glass substrate 7 and cover these TFTs 32. A transmission / reflection layer 3 is provided. A large number of transparent pixel electrodes 33 made of ITO or the like are arranged on the upper surface of the transmission / reflection layer 3 in the vertical and horizontal directions corresponding to the TFTs 32. The pixel electrodes 33 are electrically connected to the TFTs 32 through through holes 34, respectively.
Such a liquid crystal display device 30 has the same effects as those of the first embodiment, and in particular, the TFT 32 can control the scattering state and transmission state of the liquid crystal cell 2 at high speed. A black and white display of the mold is obtained.
[0018]
In the third embodiment, the transmission / reflection layer 3 is provided on the upper surface of the lower glass substrate 7 so as to cover the TFT 32. However, the present invention is not limited thereto. For example, as in the first modification shown in FIG. A protective layer 35 is provided on the upper surface of the lower glass substrate 7 so as to cover the TFT 32, and the light absorbing layer 5 is provided on the protective layer 34 in the same manner as in the second embodiment. 21, the transmission / reflection layer 3 is provided on the upper surface of the low refractive layer 21, the pixel electrodes 33 are arranged on the upper surface of the transmission / reflection layer 3, and the pixel electrodes 33 are respectively connected to the TFTs 32 through the through holes 34. An electrically connected configuration may be used. In this case, in addition to the same effects as the third embodiment, the low-reflection layer 21 suppresses the reflection of the light emitted from the transmissive reflection layer 3 and efficiently enters the light absorption layer 5 to be absorbed. Therefore, the black display and contrast performance in the front are improved.
[0019]
Moreover, in the said 3rd Embodiment, although TFT32 was formed in the upper surface of the lower glass substrate 7, it is not restricted to this, For example, like the 2nd modification shown in FIG. The transmission / reflection layer 3 is provided on the upper surface, the common electrode 31 is formed on the upper surface of the transmission / reflection layer 3, and the pixel electrodes 33 are vertically and horizontally arranged on the lower surface of the upper glass substrate 6, and correspond to the pixel electrodes 33. The TFT 32 may be arranged in an array. Needless to say, this configuration has the same effects as those of the third embodiment.
Further, not limited to the second modification example of FIG. 11, for example, as in the third modification example shown in FIG. 12, the light absorption layer 5 is provided on the upper surface of the lower glass substrate 7, and the upper surface of the light absorption layer 5 is provided. Is provided with a low reflection layer 21, a transmission reflection layer 3 is provided on the upper surface of the low refraction layer 21, a common electrode 31 is formed on the upper surface of the transmission reflection layer 3, and the pixel electrode 33 and the lower surface of the upper glass substrate 6 are formed. A configuration in which the TFTs 32 are arranged may be used. If it does in this way, it cannot be overemphasized that there exists an effect of both 2nd Embodiment and 3rd Embodiment.
[0020]
[Fourth Embodiment]
Next, a fourth embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. Also in this case, the same parts as those in the first embodiment shown in FIGS.
The liquid crystal display device 40 has a configuration in which a color filter 41 is provided in the liquid crystal cell 2, and the other configuration is the same as that of the first embodiment.
That is, in the liquid crystal cell 2, the color filter 41 is formed on the lower surface of the upper glass substrate 6, the transparent electrodes 10 are arranged on the lower surface of the color filter 41, and the transmissive reflection layer 3 is formed on the upper surface of the lower glass substrate 7. The transparent electrodes 11 are arranged and formed on the upper surface of the transmission / reflection layer 3, and the liquid crystal layer 8 is sealed with a sealing material 9 between the upper glass substrate 6 and the lower glass substrate 7. ing.
In such a liquid crystal display device 40, as in the first embodiment, since the liquid crystal cell 2 exhibits a scattering state when no electric field is applied, white white so-called white light like white paper is obtained. Since the cell 2 exhibits a transmissive state, the color filter 41 can provide a reflective color display.
[0021]
In the fourth embodiment, the transmission / reflection layer 3 is directly provided on the upper surface of the lower glass substrate 7. However, the present invention is not limited to this. For example, the upper surface of the lower glass substrate 7 is the same as in the second embodiment. Alternatively, the light absorption layer 5 may be provided, and the transmission / reflection layer 3 may be provided on the light absorption layer 5 via the low reflection layer 21. In this way, a color display with high contrast can be obtained. For example, the liquid crystal cell 2 may be provided with the TFT 32 as in the third embodiment and its modifications. In this way, a color display capable of high-speed response can be obtained.
Further, in the first to fourth embodiments and the modifications thereof, the linear prism 12 of the transmission / reflection layer 3 is formed in an isosceles triangle having a symmetrical cross section in the left-right or front-back direction where the two upper surfaces have the same inclination length. However, the present invention is not limited to this. For example, the upper two surfaces may be formed in asymmetric cross-sectional triangles having different inclination lengths. In such a transmission / reflection layer 3, the critical angle differs between the long side and the short side of the linear prism 12, but it goes without saying that there are almost the same functions and effects as in the above embodiments.
[0022]
In the first to fourth embodiments and the modifications thereof, the case where the linear prism 12 is formed on the upper surface of the transmission / reflection layer 3 is described. However, the present invention is not limited to this, for example, as shown in FIG. The quadrangular pyramid prisms 50 may be arranged on the upper surface of the transmission / reflection layer 3 so as to be closely and vertically aligned at an interval smaller than the pixel pitch of the liquid crystal cell 2, and as shown in FIG. An array may be formed, and although not shown, a configuration in which polygonal pyramid prisms such as a triangular pyramid prism, a hexagonal pyramid prism, and a decagonal pyramid prism are arrayed may be employed. In addition to the polygonal pyramid prism, as shown in FIG. 16, the conical prisms 52 may be similarly formed, and although not shown, an elliptical pyramid prism may be arranged. By using the transmission / reflection layer 3 in which such polygonal pyramid prisms, conical prisms, and elliptical cone prisms are arranged, it is possible to reflect light from at least three directions, so that a brighter white display is achieved. Can be obtained.
[0023]
Furthermore, in the first to fourth embodiments and the modifications thereof, the liquid crystal layer 6 of the liquid crystal cell 2 has a polymer dispersion type structure in which the liquid crystal molecules 11 are dispersed in the polymer 10. For example, the liquid crystal cell 2 may be a scattering transmission type liquid crystal cell using a phase transition type liquid crystal of a cholesteric phase and a nematic phase, and the liquid crystal cell 2 that exhibits a transmission state when an electric field is applied and exhibits a scattering state when no electric field is applied. Not limited to this, a scattering transmission type liquid crystal cell that exhibits a scattering state when an electric field is applied and exhibits a transmission state when no electric field is applied may be used.
[0024]
【The invention's effect】
As described above, according to the present invention, when the liquid crystal element exhibits a scattering state, in addition to the backscattered light being emitted to the observer side, a part of the light that is transmitted through the transmission reflection layer and absorbed by the light absorption layer. Most of the forward scattered light except the forward scattered light is reflected by the prism of the transmission / reflection layer and is emitted to the viewer side, so that the white display becomes brighter, and a white so-called white display like white paper can be obtained. Or, by providing a transmission / reflection layer on the inner surface of the substrate on the light emitting side of the liquid crystal element, there is less loss of light between the liquid crystal layer and the transmission / reflection layer, and the reflectance in white display is increased. This also provides a bright white display. When the liquid crystal element is in a transmissive state, the light incident on the liquid crystal element is transmitted through the liquid crystal element and emitted toward the transmission / reflection layer, and the light incident on the prism in a predetermined angle range from the front of the liquid crystal element. Light that is transmitted through the transmission / reflection layer and absorbed by the light absorption layer and is incident in other ranges is reflected by the prism, but the intensity of light incident from a direction greatly inclined from the normal line of the liquid crystal element is weak. A sufficiently dark black display can be obtained. Further, since the transmission / reflection layer is provided on the inner surface of the substrate on the light emitting side of the liquid crystal cell and is in close contact with the liquid crystal layer, there is little depth parallax between black and white display when observed from the front, and the observation is performed from an oblique direction. At this time, it is possible to prevent the inter-pixel parallax that the shadow of the black display is formed on the edge of the white display and the image looks double.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first embodiment of a liquid crystal display device of the present invention.
2 is an enlarged perspective view showing a main part of a linear prism of the transmission / reflection layer of FIG. 1;
3 is an enlarged view showing a cross-sectional shape of a main part in a state in which the transmission / reflection layer of FIG. 2 is provided on a glass substrate on the lower side of the liquid crystal cell.
4 is a diagram showing ideal absorption reflection characteristics of the liquid crystal display device of FIG. 1. FIG.
5 is a diagram showing an optical path state when a critical angle of the linear prism of FIG. 3 is obtained.
6 shows the relationship between the critical angle and the apex angle with respect to the refractive index of the linear prism of FIG. 5, (a) shows the case where the refractive index is 1.4, and (b) shows the refractive index of 1. FIG. The figure which showed the case of 5, (c) is the figure which showed the case where a refractive index is 1.6.
7 is a view showing a modification in which a refractive layer is provided between the transmission / reflection layer of FIG. 3 and the lower glass substrate.
FIG. 8 is a cross-sectional view showing a second embodiment of the liquid crystal display device of the present invention.
FIG. 9 is a cross-sectional view showing a third embodiment of the liquid crystal display device of the present invention.
10 is a sectional view showing a first modification of the third embodiment in FIG.
FIG. 11 is a cross-sectional view showing a second modification of the third embodiment in FIG. 9;
12 is a cross-sectional view showing a third modification of the third embodiment in FIG. 9;
FIG. 13 is a cross-sectional view showing a fourth embodiment of the liquid crystal display device of the present invention.
FIG. 14 is an enlarged perspective view of a main part in which quadrangular pyramid prisms are arrayed on the upper surface of a transmission / reflection layer.
FIG. 15 is an enlarged perspective view of a main part in which octagonal pyramid prisms are arrayed on the upper surface of a transmission / reflection layer.
FIG. 16 is an enlarged perspective view of a main part in which conical prisms are arranged on the upper surface of the transmission / reflection layer.
[Explanation of symbols]
1, 20, 30, 40 Liquid crystal display device
2 Liquid crystal cell
3 Transmission / reflection layer
5 Light absorption layer
6 Upper glass substrate
7 Lower glass substrate
8 Liquid crystal layer
12 Linear prism
21 Low reflection layer
32 TFT
41 Color filter
50 square pyramid prism
51 Octagonal pyramid prism
52 Conical Prism

Claims (6)

A scattering transmission type liquid crystal element, wherein a liquid crystal layer is sealed with a sealing material between a pair of transparent substrates, and is controlled in a scattering state and a transmission state according to an applied electric field;
This liquid crystal element is provided on the inner surface of the substrate on the light emitting side, and is composed of a plurality of prisms arranged on one surface. A transmissive reflective layer that reflects light;
A liquid crystal display device comprising: a light absorption layer that absorbs light transmitted through the transmission / reflection layer. The liquid crystal display device according to claim 1, wherein the prism is a prism sheet in which a plurality of linear prisms having a triangular cross section are arranged. 2. The liquid crystal display device according to claim 1, wherein the prism is a prism sheet in which a plurality of protrusions in the shape of a polygonal cone, a cone, or an elliptical cone are arranged in close contact vertically and horizontally. The liquid crystal display device according to claim 1, wherein a low reflection layer is provided between the transmission reflection layer and the light absorption layer. The liquid crystal display device according to claim 1, wherein the liquid crystal element includes an active element corresponding to each pixel. The liquid crystal display device according to claim 1, wherein the liquid crystal element includes a color filter.

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