JP3976947B2 - Electrophoretic display device - Google Patents

Description

ここで、第１電極４の露出面積Ｓ₁ とは、第１電極４が前記泳動用分散液２に対向（露出）している部分の面積Ｓ₁ をいい、第２電極５の露出面積Ｓ₂ とは、第２電極５が前記泳動用分散液２に対向（露出）している部分の面積Ｓ₂ をいう。
に大きく依存し、該露出面積比が大きい程コントラストが小さくなり、該露出面積比が小さい程コントラストが大きくなる。したがって、コントラストを大きくする観点からは露出面積Ｓ₁ ，Ｓ₂ の差を大きくすれば良いが、露出面積Ｓ₁ ，Ｓ₂ の差が大きすぎると、帯電泳動粒子３を実効面積の大きな電極側に移動させた際に被覆率の低下を招くおそれがある。そこで、この露出面積比を１／２〜１／２０又は２０／１〜２／１程度にすると良い。
【００３０】
また、第２電極５の幅は、上記条件を満たす範囲内で狭くしても良いが、帯電泳動粒子３の粒径よりも広いことが望ましい。
【００３１】
なお、図１(a) においては、第１電極４が基板１ａの全面に配置されると共に第２電極５が第１電極４に重なるように配置されているが、もちろんこれに限る必要はなく、前記第１電極４を基板１ｂの全面にではなく部分的に配置すると共に両電極４，５を重ならないように配置しても良い。ここで、両電極４，５を重なるように配置した場合には、両電極４，５の間に絶縁層６を配置して両電極４，５の絶縁を確保すると良い。
【００３２】
一方、第１電極４及び第２電極５は、一方の基板１ｂの側に支持されていれば足り、
＊ 基板１ｂに直接接着されていても、
＊ 何らかの部材や膜を介して基板表面に接着されていても、
良い。すなわち、図１(a) において、第１電極４は基板１ｂに直接接着されているが、何らかの膜を介して接着されていても良く、逆に第２電極５は基板１ｂに直接接着されていないが、第１電極４と重ならないように配置する場合には基板１ｂに直接接触するように配置しても良い。
【００３３】
また、上述した第１電極４及び第２電極５の少なくとも一方には不図示の電圧印加手段が接続されており、正極性又は負極性の電圧を印加できるようになっている。
【００３４】
また一方、前記一対の基板１ａ，１ｂの間隙には、図１(a) に示すように隔壁部材７を配置して、前記泳動用分散液２や前記帯電泳動粒子３の該間隙からの漏れを防止すれば良いが、この隔壁部材７を、図１(b) に示すように碁盤の目状に配置して、前記一対の基板１ａ，１ｂの間隙を該基板１ａ，１ｂの面に沿った複数の画素８に分割すると共に、各画素８に、上述した電極４，５や泳動用分散液２や帯電泳動粒子３をそれぞれ配置すると良い。
【００３５】
また、前記第２電極５の表面に電極保護層９を形成しても良い。
【００３６】
さらに、画素と画素との間にブラックマトリクスパターンを形成して遮光を施しても良く、両基板１ａ，１ｂを接着剤（図６(e) の符号１０参照）にて接着しても良い。
【００３７】
一方、表示装置は透過型としても良く反射型としても良い。但し、表示装置を透過型にする場合には、上述した領域Ｓ₁ において基板１ａ，１ｂや第１電極４や絶縁層６等を透光性のものにする必要がある。また、表示装置を反射型にする場合には、上述した領域Ｓ₁ において基板１ｂや第１電極４や絶縁層６等の少なくとも１つを非透光性にする必要がある。
【００３８】
また、帯電泳動粒子３には、ポリスチレンやポリエチレンなどのポリマー樹脂を主成分とし、これにカーボンなどの着色剤を混ぜ合わせたものを用いることができる。この帯電泳動粒子３は、正又は負の極性に帯電すれば良く、必要に応じて荷電制御剤等を混ぜ合わせると良い。この帯電泳動粒子３の粒径は０．１〜５０μｍが好ましい。
【００３９】
さらに、泳動用分散液２には、帯電泳動粒子３が良好に帯電しかつ低粘度の液体を使用すると良く、具体的には、シリコーンオイル、キシレン、トルエン、アイソパーなどを用いれば良い。
【００４０】
また、基板１ａ，１ｂには一般的なガラスを使用できるが、表示装置をフレキシブルなものにするには、ポリエチレンテレフタレート（ＰＥＴ）やポリエーテルスルフォン（ＰＥＳ）等のプラスチックフィルムを使用すれば良い。なお、表示装置を透過型にするには両方の基板１ａ，１ｂを透光性にし、表示装置を反射型にするには少なくとも一方の基板１ｂを非透光性とする必要がある。
【００４１】
さらに、第１電極４には、表示装置を透過型とする場合にはＩＴＯ（インジウム・ティン・オキサイド）等の透明電極を用い、表示装置を反射型とする場合にはＡｌなどの金属電極を用いれば良い。また、第２電極５には、ＡｌやＴｉ等の金属材料を用いれば良いが、好ましくは色の黒い材料、例えばＴｉＣなどが好ましく用いられる。
【００４２】
またさらに、絶縁層６には、アクリル樹脂やポリイミド樹脂等の有機材料を用いれば良く、表示装置を反射型とする場合には、アルミナ等の白色微粒子を混入して散乱層としての機能を付与しても良い。
【００４３】
また、隔壁部材７には、シリコーンゴム、フッ素ゴム、アクリルゴム等、その他の感光性材料を用いれば良い。
【００４４】
次に、表示装置の駆動方法について説明する。
【００４５】
本実施の形態において、第１電極４又は第２電極５に所定極性の電圧を選択的に印加すると、帯電泳動粒子３はその極性に応じて第１電極４又は第２電極５に吸着される。これによって種々の表示を行うことができる。
【００４６】
なお、印加電圧は、帯電泳動粒子３の帯電量や、第２電極５の形状等によって異なるが、通常は、数十Ｖ程度が必要である。
【００４７】
次に、本実施の形態の効果について説明する。
【００４８】
本実施の形態によれば、前記第２電極５は、前記第１電極４の少なくとも一部を囲むような形状である。したがって、電極幅Ｗ１，Ｗ２を適切なものとすることにより該第２電極５の端縁であって前記第１電極４に対向する端縁の長さ（２ａ＋２ｂ）を、図７に示すような従来のもの（２ｃ）と比べて長くできる。その結果、第２電極５の端縁と第１電極４との間に発生する電場が従来のものより大きくなり、印加電圧を大きくしなくとも帯電泳動粒子３の移動速度を速くできる。このため、動作不良（表示不良）を抑制できる。
【００４９】
また、印加電圧は小さくても良く、消費電力の低減を図ることができる。
【００５０】
【実施例】
以下、実施例に沿って本発明を更に詳細に説明する。
【００５１】
（実施例１）
本実施例においては、図１に示す反射型の表示装置Ｄ₁ を、図６に示す方法によって製造した。
【００５２】
すなわち、図１(a) に示すように、第１電極４は一方の基板１ｂの表面全面に直接接着し、その第１電極４の表面には絶縁層６や第２電極５や電極保護層９を順に形成した。また、第２電極５は、同図(b) に示すような額縁状とし、寸法Ｌ１＝Ｌ２＝１５０μｍとし、寸法Ｗ１＝Ｗ２＝１２．５μｍとし、第１電極４及び第２電極５の露出面積比が１／２．３になるようにした。さらに、第１電極４は接地し、第２電極５には正極性又は負極性の電圧を選択的に印加できるようにした。またさらに、基板１ａ，１ｂの間隙には隔壁（隔壁部材）７を碁盤の目状に配置し、多数の画素８に区画した。また、両基板１ａ，１ｂの接着は接着剤１０によって行った。
【００５３】
ところで、基板１ａ，１ｂにはポリエチレンテレフタレート（ＰＥＴ）を使用し、第１電極４には、反射層としての機能を兼用させるためにＡｌを用いた。また、絶縁層６には、アルミナ微粒子を混入して散乱層としての機能を付与したアクリル樹脂を用い、第２電極５には、暗黒色を呈するＴｉＣを用いた。さらに、帯電泳動粒子３には、カーボン及び荷電制御剤を含んだポリスチレン樹脂粒子（粒径２μｍ）を用い、泳動用分散液２には透明のシリコーンオイルを使用した。
【００５４】
次に、表示装置Ｄ₁ の製造方法について、図６を参照して説明する。
【００５５】
表示装置Ｄ₁ を製造するに際しては、一方の基板１ｂの表面全体に第１電極４を形成し、該電極４の表面には絶縁層６を形成した（同図(a) 参照）。さらに、絶縁層６の表面にはＴｉＣ被膜を形成し、パターニングして第２電極５を形成した。さらに、第２電極５の表面には電極保護層９を形成した（同図(b) 参照）。
【００５６】
その後、電極保護層９の表面に隔壁７を形成し（同図(c) 参照）、ここに帯電泳動粒子３を泳動用分散液２に分散させた液体を均一に散布した（同図(d) 参照）。
【００５７】
さらに、他方の基板１ａの端縁部に接着剤１０を塗布し、両基板１ａ，１ｂを貼り合わせた（同図(e) 参照）。
【００５８】
以上のようにして作成した表示装置Ｄ₁ を、４０Ｖの電圧を第２電極５に印加して駆動したところ、コントラストが５であって応答速度が２０ｍｓｅｃの良好な表示が得られた。また、画素間の濃度ばらつきは観察されず、均一であった。
【００５９】
（比較例）
本比較例においては、第２電極を図７に符号５５で示すような形状（但し、寸法Ｌ１＝Ｌ２＝１５０μｍ、寸法Ｗ１＝Ｗ２＝２５μｍで、第１電極４及び第２電極５５の露出面積比は１／２）とした。その他の構成は実施例１と同様とした。
【００６０】
以上のようにして作成した表示装置を、４０Ｖの電圧を第２電極５５に印加して駆動したところ、一部に表示動作不良が観察された。印加電圧を６０Ｖにしたところ、コントラストが５であって応答速度が２０ｍｓｅｃの良好な表示が得られた。
【００６１】
（実施例２）
本実施例においては、第２電極を図２に符号１５で示すような形状（但し、寸法Ｌ１＝Ｌ２＝１５０μｍ、寸法Ｄ＝１４０μｍで、第１電極４及び第２電極１５の露出面積比は１／２．２）とした。その他の構成は実施例１と同様とした。
【００６２】
以上のようにして作成した表示装置を、４０Ｖの電圧を第２電極１５に印加して駆動したところ、コントラストが５であって応答速度が２０ｍｓｅｃの良好な表示が得られた。また、画素間の濃度ばらつきは観察されず、均一であった。
【００６３】
（実施例３）
本実施例においては、第２電極を図４に符号３５で示すような形状（但し、寸法Ｌ１＝Ｌ２＝１５０μｍ、寸法Ｗ１＝Ｗ２＝２５μｍ、寸法Ｓ１＝Ｓ２＝３１．２５μｍで、第１電極４及び第２電極３５の露出面積比は１／２．３）とした。その他の構成は実施例１と同様とした。
【００６４】
以上のようにして作成した表示装置を、２５Ｖの電圧を第２電極５に印加して駆動したところ、コントラストが５であって応答速度が２０ｍｓｅｃの良好な表示が得られた。また、画素間の濃度ばらつきは観察されず、均一であった。
【００６５】
【発明の効果】
以上説明したように、本発明によると、前記第２電極は、前記第１電極の少なくとも一部を囲むような形状である。したがって、該第２電極の端縁であって前記第１電極に対向する端縁の長さを、従来のものと比べて長くできる。その結果、第２電極の端縁と第１電極との間に発生する電場が従来のものより大きくなり、印加電圧を大きくしなくとも帯電泳動粒子の移動速度を速くできる。このため、動作不良（表示不良）を抑制できる。
【００６６】
また、印加電圧は小さくても良く、消費電力の低減を図ることができる。
【図面の簡単な説明】
【図１】本発明に係る電気泳動表示装置の構造の一例を示す図であり、(a) は断面図、(b) は、第２電極の形状の一例を示す模式図。
【図２】第２電極の形状の一例を示す模式図。
【図３】第２電極の形状の一例を示す模式図。
【図４】第２電極の形状の一例を示す模式図。
【図５】第２電極の形状の一例を示す模式図。
【図６】本発明に係る電気泳動表示装置の製造方法の一例を示す図。
【図７】第２電極の従来の形状の一例を示す模式図。
【図８】電気泳動表示装置の従来構造の一例を示す断面図。
【図９】電気泳動表示装置の従来構造の他の例を示す断面図。
【符号の説明】
１ａ，１ｂ 基板
２ 泳動用分散液
３ 帯電泳動粒子
４ 第１電極
５ 第２電極
１５ 第２電極
２５ 第２電極
３５ 第２電極
４５ 第２電極
Ｄ₁ 電気泳動表示装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophoretic display device that performs display by moving charged electrophoretic particles.
[0002]
[Prior art]
(1) In recent years, with the development of information equipment, the amount of data of various types of information has been steadily expanding, and the output of information has been made in various forms. Such information output forms are generally
* Display on a display screen using a cathode ray tube or liquid crystal,
* Hard copy display on paper with a printer,
Can be broadly divided.
[0003]
(2) Although the above-mentioned cathode ray tube and liquid crystal have various advantages, they have several drawbacks, and hard copy displays without such drawbacks are still frequently used. Hereinafter, this point will be described in detail.
[0004]
Regarding display screens, there is an increasing need for low power consumption and thin display devices, and liquid crystal display devices are being actively developed and commercialized as display devices that can meet such needs. However, current liquid crystal display devices still have a sufficient resolution of the visual burden caused by the angle at which the screen is viewed and the reflected light making it difficult to see the characters on the screen and the flickering and low brightness of the light source. There is a disadvantage of not. CRTs have sufficient contrast and brightness compared to liquid crystal displays, but cannot be said to have sufficient display quality compared to hard copy displays described later, such as flickering. Moreover, since the apparatus is large and heavy, portability is extremely low.
[0005]
On the other hand, hard copy display is thought to be unnecessary due to the digitization of information, but in reality, a huge amount of hard copy output is still being performed. The reason is that when the information is displayed on the display screen, in addition to the above-mentioned problems related to the display quality, the resolution is generally about 120 dpi at the maximum, compared with the printout on paper (usually 300 dpi or more). Is quite low. Therefore, the display on the display screen imposes a greater visual burden than hard copy display. As a result, even if it can be confirmed on the display, hard copy output is often performed once. In addition, the hard-copy information is arranged in large numbers without limiting the display area to the size of the display screen as in the display screen display, or rearranged without performing complicated device operations, and confirmed in order. The fact that the hard copy display can be used together is also a great reason. Furthermore, the hard copy display does not require energy for holding the display and has excellent portability that information can be confirmed anytime and anywhere as long as the amount of information is not extremely large.
[0006]
(3) By the way, the above-mentioned hard copy display has the above-mentioned various advantages but has a drawback of consuming a large amount of paper. Therefore, recently, as an alternative to this hard copy display, the development of a rewritable recording medium (a recording medium that can record and erase images with high visibility many times and does not require energy to maintain the display) has been developed. It is being actively promoted. This is called a paper-like display of the third rewritable display method that inherits the characteristics of such hard copy.
[0007]
The necessary conditions for this paper-like display are that it is rewritable, does not require energy to maintain display, or is sufficiently small (memory property), has excellent portability, and has excellent display quality. And so on.
[0008]
(4) A conventional example of such a paper-like display will be described for reference.
[0009]
At present, as a display method that can be regarded as a paper-like display, for example, an organic low molecular weight / high molecular resin matrix system that records and erases with a thermal printer head (for example, Japanese Patent Laid-Open Nos. 55-154198 and 57-82086). And a reversible display medium using Japanese Laid-open Patent Publication No. This system is partly used as a display part of a prepaid card, but has a problem that the contrast is not so high and the number of recording / erasing repetitions is relatively small, such as about 150 to 500 times.
[0010]
(5) Another conventional example of the paper-like display described above will be described for reference.
[0011]
In addition, as a display method usable as another paper-like display, Harold D. et al. An electrophoretic display device (US Pat. No. US Pat. No. 3,612,758) proposed by Lee et al. Is known. In addition, an electrophoretic display device is disclosed in Japanese Patent Laid-Open No. 9-185087.
[0012]
FIG. 8 is a diagram showing the structure and operating principle of the electrophoretic display device. The display device D ₂ includes a pair of substrates 1a and 1b arranged with a predetermined gap between them. In the gap between the substrates, a dispersion liquid 2 for electrophoresis and a large number of charged electrophoretic particles 3 charged to a negative polarity are arranged. In addition, electrodes 64 and 65 are formed on the substrates 1a and 1b so as to sandwich the dispersion liquid 2 for electrophoresis. Further, the charged electrophoretic particles 3 and the electrophoretic dispersion liquid 2 are colored in different colors so as to have different optical characteristics.
[0013]
In such a display device D ₂ , when a negative polarity voltage is applied to the lower electrode 65 and the upper electrode 64 is grounded as shown in FIG. The charged electrophoretic particles 3 are adsorbed by the upper electrode 64 in the figure, and the color of the charged electrophoretic particles 3 is recognized when observed from the direction A in the figure. Further, as shown in FIG. 6B, when a positive polarity voltage is applied to the lower electrode 65 in the figure, the charged electrophoretic particles 3 are adsorbed on the lower electrode 65 in the figure and observed from the direction of the arrow A. The color of the dispersion liquid 2 for electrophoresis is recognized. By performing such driving in units of pixels, an arbitrary image is displayed by a large number of pixels.
[0014]
In such an electrophoretic display device, the response time (time required for pixel writing or erasing) is relatively fast, such as several tens of ms or less, and the number of rewrites can be 10 ⁸ times or more. In addition, the colored charged electrophoretic particles deposited on the electrodes by applying a voltage are stable over a long period of time even when the driving voltage is removed, so that no power is required during display. That is, it has a memory property. Furthermore, since it is a reflective display device, eye fatigue caused by flickering of the light source can be suppressed.
[0015]
However, it has several problems. That is,
First, it was essential to color or opacify the electrophoresis dispersion. For this reason, it is difficult to form a dispersion for electrophoresis with a single component, and a coloring material such as a dye or ion must be mixed in the dispersion for electrophoresis. The presence of such a colorant tends to act as an instability factor in the electrophoresis operation in order to bring in a new charge and transfer, and may deteriorate the performance, life and stability of the display device. Secondly, if the combination of the dispersion for electrophoretic dispersion is small but the lightness of the colored charged electrophoretic particles is not used, observation is performed even when the colored charged electrophoretic particles are far from the observer side. In some cases, the color of the colored charged electrophoretic particles may be observed through the dispersion liquid for electrophoresis. Therefore, the selection of the optimum colors for the electrophoretic dispersion and the colored charged electrophoretic particles is limited, and it has been difficult to realize multicolor display.
[0016]
(6) On the other hand, an electrophoretic display device as shown in FIG. 9 is disclosed in Japanese Patent Application Laid-Open No. 49-5598 and Japanese Patent Application No. 10-005727. Hereinafter, the electrophoretic display device will be described in detail.
[0017]
The electrophoretic display device D ₃ shown in FIG. 9 has substantially the same structure as the electrophoretic display device D ₂ shown in FIG. 8, but both electrodes 74 and 75 (hereinafter referred to as “first electrode 74” and “second electrode”). The difference is that the electrode 75 ″ is disposed on the same substrate 1b side. In the apparatus D ₃ , the charged electrophoretic particles 3 are assumed to be positively charged.
[0018]
In the display device D ₃ , when a negative polarity voltage is applied to the second electrode 75 and a positive polarity voltage is applied to the first electrode 74 as shown in FIG. The charged electrophoretic particles 3 are adsorbed by the second electrode 75, and the color of the first electrode 74 is recognized when observed from the direction A shown in the figure. Further, as shown in FIG. 5B, when a positive polarity voltage is applied to the second electrode 75 and a negative polarity voltage is applied to the first electrode 74, the charged electrophoretic particles are charged positively. 3 is adsorbed by the first electrode 74, and the colors of the second electrode 75 and the charged electrophoretic particles 3 are recognized when observed from the direction A shown in the figure. By performing such driving in units of pixels, an arbitrary image is displayed by a large number of pixels.
[0019]
[Problems to be solved by the invention]
However, in the electrophoretic display device D ₃ shown in FIG. 9, the electric field for moving the charged electrophoretic particles 3 is mainly the end of the second electrode 75 (see reference numeral 75a in FIG. 9B) and the first electric field. A leakage electric field is formed between the electrode 74 and the second electrode 75 on the side of the surface portion (see reference numeral 75b in FIG. 7B).
[0020]
[Formula 1]
u = DζE / 4πη
D: Dielectric constant ζ of electrophoretic dispersion zeta zeta potential E of colored electrophoretic particles; electric field strength η; moving speed u of charged electrophoretic particles 3 expressed by the viscosity of electrophoretic dispersion is shown in the electrophoretic display shown in FIG. lower than that of the device D _2, as the case was also a possibility that malfunction (display defect) occurs.
[0021]
In order to prevent such a decrease in moving speed and the occurrence of malfunction, it is sufficient to apply a sufficient voltage between the electrodes. In such a case, there is a problem of an increase in power consumption.
[0022]
Accordingly, an object of the present invention is to provide an electrophoretic display device that prevents malfunction and the like.
[0023]
[Means for Solving the Problems]
The present invention has been made in consideration of the above circumstances, and a pair of substrates disposed in a state where a predetermined gap is provided, a dispersion liquid for electrophoresis disposed in a gap between these substrates, and the dispersion liquid for electrophoresis A plurality of charged electrophoretic particles dispersed in a movable manner, and a first electrode and a second electrode supported on one substrate side and arranged to face the dispersion liquid for electrophoresis and the charged electrophoretic particles; An electrophoretic display that performs display by moving the charged electrophoretic particles by an electric field generated between an edge of the second electrode and the first electrode and adsorbing the charged electrophoretic particles to the first electrode or the second electrode In the device
The second electrode has a shape surrounding at least a part of the first electrode, and an exposed area ratio between the first electrode and the second electrode is 1/2 to 1/20 or 20/1 to 2 /. It has the width | variety which becomes 1. It is characterized by the above-mentioned.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0025]
First, the structure of an electrophoretic display device according to the present invention will be described with reference to FIGS.
[0026]
The electrophoretic display device according to the present invention, as shown by reference numeral D ₁ in FIG. 1 (a), a pair of substrates 1a arranged with a predetermined spacing, 1b and, the substrates 1a, 1b gap The electrophoretic dispersion 2 disposed in the electrophoretic dispersion, a plurality of charged electrophoretic particles 3 dispersed in the electrophoretic dispersion, and the electrophoretic dispersion 2 and the electrophoretic dispersion 2 supported on one substrate 1b side. A first electrode 4 and a second electrode 5 are provided so as to face the charged electrophoretic particles 3.
[0027]
Here, the second electrode 5 has a shape surrounding at least a part of the first electrode 4. FIG. 1 (b) shows a frame shape surrounding the square portion of the first electrode 4 as a specific shape of the second electrode 5. However, the shape is not limited to this. For example,
* As indicated by reference numeral 15 in FIG. 2, the frame may have a frame shape surrounding the circular portion of the first electrode 4,
* As shown by the reference numeral 25 in FIG. 3, even in a shape surrounding each of a plurality of square portions of the first electrode 4,
* As shown by reference numeral 35 in FIG.
* As shown by reference numeral 45 in FIG. 5, arranged so as to form a concentric circle,
It may be. The second electrodes 5, 15, 25, 35, and 45 are arranged so as to form a loop without being cut in the middle, but needless to say, the first electrode 4 is not limited to this. As long as at least a part of the second electrode 5 is surrounded, a part of the second electrode 5 may be cut.
[0028]
By the way, the display contrast in the electrophoretic display device having such a structure is as follows.
[0029]
[Formula 2]

Here, the exposed area S ₁ of the first electrode 4, refers to the area S ₁ of the portion where the first electrode 4 faces (exposed) to the dispersion liquid 2, the exposure area S of the second electrode 5 ₂ means the area S ₂ of the portion where the second electrode 5 faces (exposes) the dispersion liquid 2 for electrophoresis.
The contrast decreases as the exposed area ratio increases, and the contrast increases as the exposed area ratio decreases. Therefore, from the viewpoint of increasing the contrast, the difference between the exposed areas S ₁ and S ₂ may be increased. However, if the difference between the exposed areas S ₁ and S ₂ is too large, the charged electrophoretic particles 3 are placed on the electrode side having a large effective area. There is a possibility of causing a decrease in the coverage when moved to. Therefore, this exposed area ratio is preferably about 1/2 to 1/20 or about 20/1 to 2/1.
[0030]
In addition, the width of the second electrode 5 may be narrow within a range satisfying the above conditions, but is desirably wider than the particle diameter of the charged electrophoretic particles 3.
[0031]
In FIG. 1 (a), the first electrode 4 is disposed on the entire surface of the substrate 1a and the second electrode 5 is disposed so as to overlap the first electrode 4. Of course, the present invention is not limited to this. The first electrode 4 may be disposed not on the entire surface of the substrate 1b but partially so that the electrodes 4 and 5 do not overlap. Here, when the electrodes 4 and 5 are arranged so as to overlap, it is preferable to secure insulation between the electrodes 4 and 5 by arranging the insulating layer 6 between the electrodes 4 and 5.
[0032]
On the other hand, it is sufficient that the first electrode 4 and the second electrode 5 are supported on the one substrate 1b side,
* Even if directly bonded to the substrate 1b
* Even if it is bonded to the surface of the substrate through some member or film,
good. That is, in FIG. 1 (a), the first electrode 4 is directly bonded to the substrate 1b, but may be bonded via some film, and conversely, the second electrode 5 is bonded directly to the substrate 1b. However, when it is arranged so as not to overlap the first electrode 4, it may be arranged so as to be in direct contact with the substrate 1b.
[0033]
In addition, a voltage applying means (not shown) is connected to at least one of the first electrode 4 and the second electrode 5 described above so that a positive or negative voltage can be applied.
[0034]
On the other hand, a partition member 7 is disposed in the gap between the pair of substrates 1a and 1b as shown in FIG. 1 (a), so that the dispersion 2 for electrophoresis and the charged electrophoretic particles 3 leak from the gap. This partition member 7 is arranged in a grid pattern as shown in FIG. 1 (b), and the gap between the pair of substrates 1a and 1b extends along the surfaces of the substrates 1a and 1b. In addition, the pixel 8 is divided into a plurality of pixels 8, and the electrodes 4, 5, the electrophoretic dispersion liquid 2, and the charged electrophoretic particles 3 may be disposed in each pixel 8.
[0035]
Further, an electrode protective layer 9 may be formed on the surface of the second electrode 5.
[0036]
Further, a black matrix pattern may be formed between the pixels to shield the light, and both the substrates 1a and 1b may be bonded with an adhesive (see reference numeral 10 in FIG. 6 (e)).
[0037]
On the other hand, the display device may be a transmissive type or a reflective type. However, in the case of the transmission type display device, it is necessary to substrate 1a in the region S ₁ described above, 1b and the first electrode 4 and the insulating layer 6 and the like to those of the translucent. The display in the case of the device in reflective type, it is necessary to non-light-transmitting at least one such substrate 1b, the first electrode 4 and the insulating layer 6 in the region S ₁ described above.
[0038]
In addition, as the electrophoretic particles 3, particles obtained by mixing a polymer resin such as polystyrene or polyethylene as a main component and a colorant such as carbon can be used. The charged electrophoretic particles 3 may be charged to a positive or negative polarity, and a charge control agent or the like may be mixed as necessary. The particle diameter of the charged electrophoretic particles 3 is preferably 0.1 to 50 μm.
[0039]
Further, as the electrophoretic dispersion liquid 2, it is preferable to use a liquid in which the charged electrophoretic particles 3 are well charged and have a low viscosity. Specifically, silicone oil, xylene, toluene, isopar, or the like may be used.
[0040]
Moreover, although general glass can be used for the substrates 1a and 1b, a plastic film such as polyethylene terephthalate (PET) or polyether sulfone (PES) may be used to make the display device flexible. In order to make the display device transmissive, it is necessary to make both the substrates 1a and 1b translucent. To make the display device reflective, it is necessary to make at least one substrate 1b non-translucent.
[0041]
Further, the first electrode 4 is a transparent electrode such as ITO (Indium Tin Oxide) when the display device is a transmissive type, and a metal electrode such as Al when the display device is a reflective type. Use it. The second electrode 5 may be made of a metal material such as Al or Ti, but a black material such as TiC is preferably used.
[0042]
Furthermore, the insulating layer 6 may be made of an organic material such as acrylic resin or polyimide resin. When the display device is a reflective type, white particles such as alumina are mixed to provide a function as a scattering layer. You may do it.
[0043]
For the partition member 7, other photosensitive materials such as silicone rubber, fluorine rubber, and acrylic rubber may be used.
[0044]
Next, a method for driving the display device will be described.
[0045]
In the present embodiment, when a voltage having a predetermined polarity is selectively applied to the first electrode 4 or the second electrode 5, the charged electrophoretic particles 3 are adsorbed to the first electrode 4 or the second electrode 5 according to the polarity. . As a result, various displays can be performed.
[0046]
The applied voltage varies depending on the charge amount of the charged electrophoretic particles 3, the shape of the second electrode 5, and the like, but usually requires about several tens of volts.
[0047]
Next, the effect of this embodiment will be described.
[0048]
According to the present embodiment, the second electrode 5 has a shape surrounding at least a part of the first electrode 4. Accordingly, by making the electrode widths W1 and W2 appropriate, the length (2a + 2b) of the edge of the second electrode 5 opposite to the first electrode 4 is as shown in FIG. It can be made longer than the conventional one (2c). As a result, the electric field generated between the edge of the second electrode 5 and the first electrode 4 becomes larger than the conventional one, and the moving speed of the charged electrophoretic particles 3 can be increased without increasing the applied voltage. For this reason, a malfunction (display defect) can be suppressed.
[0049]
Further, the applied voltage may be small, and power consumption can be reduced.
[0050]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0051]
Example 1
In this example, the reflective display device D ₁ shown in FIG. 1 was manufactured by the method shown in FIG.
[0052]
That is, as shown in FIG. 1 (a), the first electrode 4 is directly bonded to the entire surface of one substrate 1b, and the insulating layer 6, the second electrode 5, and the electrode protective layer are formed on the surface of the first electrode 4. 9 were formed in order. Further, the second electrode 5 has a frame shape as shown in FIG. 5B, the dimension L1 = L2 = 150 μm, the dimension W1 = W2 = 12.5 μm, and the exposure of the first electrode 4 and the second electrode 5 The area ratio was set to 1 / 2.3. Further, the first electrode 4 is grounded, and a positive or negative voltage can be selectively applied to the second electrode 5. Furthermore, partition walls (partition wall members) 7 are arranged in a grid pattern in the gap between the substrates 1a and 1b and partitioned into a large number of pixels 8. The both substrates 1a and 1b were bonded with an adhesive 10.
[0053]
By the way, polyethylene terephthalate (PET) was used for the substrates 1a and 1b, and Al was used for the first electrode 4 in order to share the function as a reflective layer. The insulating layer 6 was made of an acrylic resin mixed with alumina fine particles and provided with a function as a scattering layer, and the second electrode 5 was made of TiC exhibiting a dark black color. Further, polystyrene resin particles (particle diameter 2 μm) containing carbon and a charge control agent were used for the charged electrophoretic particles 3, and transparent silicone oil was used for the electrophoretic dispersion 2.
[0054]
Next, a manufacturing method of the display device D ₁ will be described with reference to FIG.
[0055]
In the production of display apparatuses D ₁ is the first electrode 4 is formed on the entire surface of one substrate 1b, the surface of the electrode 4 to form an insulating layer 6 (see FIG. (A)). Further, a TiC film was formed on the surface of the insulating layer 6 and patterned to form the second electrode 5. Furthermore, an electrode protective layer 9 was formed on the surface of the second electrode 5 (see FIG. 5B).
[0056]
Thereafter, a partition wall 7 is formed on the surface of the electrode protection layer 9 (see FIG. 10C), and a liquid in which the charged electrophoretic particles 3 are dispersed in the dispersion liquid 2 is uniformly dispersed (see FIG. See)).
[0057]
Furthermore, the adhesive 10 was applied to the edge portion of the other substrate 1a, and the two substrates 1a and 1b were bonded together (see FIG. 5E).
[0058]
The display apparatuses D _1, which is created as described above, was driven by applying a voltage of 40V to the second electrode 5, the response speed to a contrast 5 were obtained good indication of 20 msec. Further, the density variation between the pixels was not observed and was uniform.
[0059]
(Comparative example)
In this comparative example, the second electrode has a shape as indicated by reference numeral 55 in FIG. 7 (however, the dimensions L1 = L2 = 150 μm, the dimensions W1 = W2 = 25 μm, and the exposed areas of the first electrode 4 and the second electrode 55) The ratio was 1/2). Other configurations were the same as those in Example 1.
[0060]
When the display device produced as described above was driven by applying a voltage of 40 V to the second electrode 55, a defective display operation was observed in part. When the applied voltage was 60 V, a good display with a contrast of 5 and a response speed of 20 msec was obtained.
[0061]
(Example 2)
In this embodiment, the second electrode is shaped as shown by reference numeral 15 in FIG. 2 (however, the dimension L1 = L2 = 150 μm, the dimension D = 140 μm, and the exposed area ratio between the first electrode 4 and the second electrode 15 is 1 / 2.2). Other configurations were the same as those in Example 1.
[0062]
When the display device produced as described above was driven by applying a voltage of 40 V to the second electrode 15, a good display with a contrast of 5 and a response speed of 20 msec was obtained. Further, the density variation between the pixels was not observed and was uniform.
[0063]
(Example 3)
In the present embodiment, the second electrode has a shape as indicated by reference numeral 35 in FIG. 4 (however, the dimension L1 = L2 = 150 μm, the dimension W1 = W2 = 25 μm, the dimension S1 = S2 = 31.25 μm, 4 and the exposed area ratio of the second electrode 35 were 1 / 2.3). Other configurations were the same as those in Example 1.
[0064]
When the display device produced as described above was driven by applying a voltage of 25 V to the second electrode 5, a good display with a contrast of 5 and a response speed of 20 msec was obtained. Further, the density variation between the pixels was not observed and was uniform.
[0065]
【The invention's effect】
As described above, according to the present invention, the second electrode has a shape surrounding at least a part of the first electrode. Therefore, the length of the edge of the second electrode that faces the first electrode can be made longer than that of the conventional one. As a result, the electric field generated between the edge of the second electrode and the first electrode becomes larger than that of the conventional one, and the moving speed of the charged electrophoretic particles can be increased without increasing the applied voltage. For this reason, a malfunction (display defect) can be suppressed.
[0066]
Further, the applied voltage may be small, and power consumption can be reduced.
[Brief description of the drawings]
1A and 1B are diagrams illustrating an example of a structure of an electrophoretic display device according to the present invention, in which FIG. 1A is a cross-sectional view, and FIG. 1B is a schematic diagram illustrating an example of a shape of a second electrode.
FIG. 2 is a schematic diagram showing an example of the shape of a second electrode.
FIG. 3 is a schematic diagram showing an example of the shape of a second electrode.
FIG. 4 is a schematic diagram showing an example of the shape of a second electrode.
FIG. 5 is a schematic diagram showing an example of the shape of a second electrode.
FIG. 6 is a diagram showing an example of a method for manufacturing an electrophoretic display device according to the present invention.
FIG. 7 is a schematic diagram showing an example of a conventional shape of a second electrode.
FIG. 8 is a cross-sectional view illustrating an example of a conventional structure of an electrophoretic display device.
FIG. 9 is a cross-sectional view showing another example of a conventional structure of an electrophoretic display device.
[Explanation of symbols]
1a, 1b Substrate 2 Electrophoretic dispersion 3 Charged electrophoretic particle 4 First electrode 5 Second electrode 15 Second electrode 25 Second electrode 35 Second electrode 45 Second electrode D ₁ Electrophoretic display device

Claims (4)

A pair of substrates arranged in a state where a predetermined gap is opened, a dispersion liquid for electrophoresis disposed in a gap between these substrates, and a plurality of charged electrophoretic particles dispersed in the migration dispersion liquid, A first electrode and a second electrode supported on the substrate side and arranged to face the dispersion liquid for electrophoresis and the charged electrophoretic particles, and an edge of the second electrode and the first electrode In the electrophoretic display device for performing display by moving the charged electrophoretic particles by an electric field generated between the first and second electrodes and adsorbing the charged electrophoretic particles to the first electrode or the second electrode ,
The second electrode has a shape surrounding at least a part of the first electrode, and an exposed area ratio between the first electrode and the second electrode is 1/2 to 1/20 or 20/1 to 2 /. An electrophoretic display device characterized by having a width of 1 . The second electrode is arranged in a frame shape with respect to the first electrode,
The electrophoretic display device according to claim 1. The second electrode has a lattice shape;
The electrophoretic display device according to claim 1. The second electrodes are arranged to form concentric circles;
The electrophoretic display device according to claim 1.

Images