Particle use for image display media, image display panel using the particles, and image display device

• US 7,236,291 B2
• Filed: 04/02/2004
• Issued: 06/26/2007
• Est. Priority Date: 04/02/2003
• Status: Expired due to Fees

• Current Assignee: Bridgestone Corporation
• Original Assignee: Bridgestone Corporation
• Inventors: Murata, Kazuya, Machida, Kunio, Tamura, Hajime, Yamazaki, Hirotaka, Arai, Toshiaki, Kobayashi, Taichi, Sakurai, Ryo, Masutani, Maki, Kaga, Norihiko, Yakushiji, Gaku, Kobayashi, Yoneji, Nishimuro, Yoichi, Anzai, Hiroyuki, Tazawa, Hare
• Primary Examiner(s): Thompson; Timothy
• Assistant Examiner(s): FANG, JERRY C
• Application Number:
  US10/552,283
• Publication Number:
  US 20060146394A1
• Time in Patent Office: 1,180 Days
• Field of Search: 359/295, 359/296, 345/105, 345/84, 430/126
• US Class Current: 359/296
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1671 involving dry toners
• CPC Class Codes: G02F 2001/1678 characterised by the composition or particle type

Abstract

An image display device, in which image display media are sealed between opposed substrates, at least one of two substrates being transparent, and in which the image display media, to which an electrostatic field is applied, are made to move so as to display an image. A construction of particles used as the image display media is improved (the first, second, fourth, fifth, sixth, eighth and ninth aspects of the invention), and a material of the particles used as the image display media is improved (the third, seventh and tenth aspects of the invention). Whiteness of the particles and a liquid powder using the particles is improved, particle agglutination is prevented, and the charge property is controlled. Moreover, durability is improved such that a contrast of the image display during a repetition display is not decreased. As a result, an excellent image display can be achieved.

Claims

1. Particles used for image display media in an image display panel, comprising at least two groups of the image display media sealed between opposed substrates, at least one of two substrates being transparent, and in which the image display media, to which an electrostatic field generated between two electrodes having different potentials is applied, are made to move so as to display an image, wherein one of the two groups of the particles having different charge characteristics and different optical reflectance included in the at least two groups of the image display media has a surface on which a macroscopic concavo-convex portion exists, and the other of the two groups of the particles has a surface on which no macroscopic concavo-convex portion exists and on which fine particles are adhered in an electrostatic manner;

and

wherein, among the two groups of the particles having different charge characteristics and different reflectance, the fine particles adhered to the surface of the particles, on which no macroscopic concavo-convex portion exists, have a reverse charge polarity with respect to a charge polarity of the particles having the surface, on which no macroscopic concavo-convex portion exists, and, the fine particles do not change a charge polarity of the particles having the surface, on which no macroscopic concavo-convex portion exists, after being adhered.

2. The particles used for the image display media according to claim 1, wherein, among the two groups of the particles having different charge characteristics and different optical reflectance, the particles having the surface, on which the macroscopic concavo-convex portion exists, are obtained by crushing a resin agglomerate.

3. The particles used for the image display media according to claim 1, wherein, among the two groups of the particles having different charge characteristics and different optical reflectance, the particles having the surface, on which the macroscopic concavo-convex portion exists, are obtained by firmly adhering fine particles on a surface of mother particles.

4. The particles used for the image display media according to claim 3, wherein the adhering between the mother particles and the fine particles is performed by utilizing a mechanical impact strength.

5. The particles used for the image display media according to claim 1, wherein, among the two groups of the particles having different charge characteristics and different optical reflectance, the particles having the surface, on which no macroscopic concavo-convex portion exists, are substantially circular particles obtained by polymerizing a resin monomer.

6. The particles used for the image display media according to claim 1, wherein, among the two groups of the particles having different charge characteristics and different optical reflectance, the particles having the surface, on which no macroscopic concavo-convex portion exists, are substantially circular particles obtained by smoothing the surface under such a condition that crushed particles are exposed at a temperature higher than a melting point of the particles.

7. The particles used for the image display media according to claim 1, wherein an average particle diameter of the two groups of the particles having different charge characteristics and different optical reflectance is 0.5–

50 μ

m.

8. The particles used for the image display media according to claim 6, wherein an average particle diameter of the fine particles adhered in an electrostatic manner to the surface of the particles, on which no concavo-convex portion exists, is 20–

200 nm.

9. An image display panel comprising the image display media utilizing the particles set forth in claim 1, wherein a volume occupying rate of the at least two groups of the image display media tilled between the substrates is in a range of 5–

70 vol %.

10. An image display device comprising the image display panel set forth in claim 9.

11. The particles used for the image display media according to claim 1, wherein an average particle diameter of the fine particles adhered in an electrostatic manner to the surface of the particles on which no concavo-convex portion exists, is 20–

200 nm.