Magnetophoretic display panel

• US 5,151,032 A
• Filed: 07/12/1990
• Issued: 09/29/1992
• Est. Priority Date: 07/13/1990
• Status: Expired due to Term

• Current Assignee: Pilot Corporation (Berkshire Hathaway Incorporated)
• Original Assignee: Kabushiki Kaisha Pilot Corporation
• Inventors: Igawa, Tatsuya
• Primary Examiner(s): Apley, Richard J.
• Assistant Examiner(s): Richman, Glenn E.
• Application Number:
  US07/551,345
• Time in Patent Office: 810 Days
• Field of Search: 434/309, 434/409, 346/74.3, 346/74.7, 428/309, 40/449, 446/132
• US Class Current: 434/409
• CPC Class Codes: B43L 1/008 with magnetic action
• CPC Class Codes: G02F 1/094 based on magnetophoretic effect
• CPC Class Codes: G09F 9/375 the position of the elements being controlled by the application of a magnetic field

Abstract

A magnetophoretic display panel comprising a plurality of cells that are sandwiched between two substrates and each of which is filled with a liquid dispersion comprising magnetic particles, a dispersion medium, a colorant and, optionally, a thickener. The magnetic particles are such that:

(A) at least 90 wt. % of them have a particle size of 10-150 μm;

(B) they have an apparent density of 0.5-1.6 g/cm³ ; and

(C) they have a saturation magnetization of 40-150 emu/g.

Claims

1. A magnetophoretic display panel comprising;

a pair of substrates, a plurality of cells sandwiched between said substrates, each of said cells filled with a liquid dispersion comprising magnetic particles, a dispersion medium, and a colorant;

at least 90 wt % of said magnetic particles have a particle size in the range of 10-150 μ

m;

said magnetic particles have an apparent density in the range of 0.5-1.6 g/cm³ ; and

said magnetic particles have a saturation magnetization in the range of 40-150 emu/g.

2. A magnetophoretic display panel according to claim 1 wherein said magnetic particles comprise porous black iron oxide particles produced by reduction with hydrogen.

3. A magnetophoretic display panel according to claim 1 wherein said magnetic particles are coated with a resin.

4. A magnetophoretic display panel according to claim 1, wherein said magnetic particles comprise a magnetic material mixed with a resin and pulverized.

5. A magnetophoretic display panel according to claim 1, wherein said magnetic material is selected from the group consisting of ferrite, γ

-hematite, γ

-ferrite oxide, barium ferrite and black iron oxide.

6. A magnetophoretic display panel according to claim 3, wherein said resin comprises a thermoplastic resin.

7. A magnetophoretic display panel according to claim 3, wherein said resin comprises a thermosetting resin.

8. A magnetophoretic display panel according to claim 3, wherein said coating is multi-layered.

9. A magnetophoretic display panel according to claim 8;

wherein said multi-layered coating comprises a first resin coating and a second resin coating, and said first resin is different than said second resin.

10. A magnetophoretic display panel according to claim 1 further comprising a thickener.

11. A magnetophoretic display panel comprising;

a pair of substrates, a plurality of cells between said substrates, each of said cells is filled with a liquid dispersion comprising magnetic particles, a dispersion medium, and a thickener, wherein, at least 90 wt % of said magnetic particles have a particle size in the range of 10-150 μ

m;

said magnetic particles have an apparent density in the range of 0.5-1.6 g/cm³ ; and

said magnetic particles have a saturation magnetization in the range of 40-150 emu/g.

12. A magnetophoretic display panel according to claim 11, wherein said magnetic particles comprise porous black iron oxide particles produced by reduction with hydrogen.

13. A magnetophoretic display panel according to claim 11 further comprising a colorant.

14. A magnetophoretic display panel according to claim 11, wherein said magnetic particles are coated with a resin.

15. A magnetophoretic display panel according to claim 14, wherein said magnetic particles comprise a magnetic material mixed with a resin and pulverized.

16. A magnetophoretic display panel according to claim 14, wherein said resin comprises a thermoplastic resin.

17. A magnetophoretic display panel according to claim 14, wherein said resin comprises a thermosetting resin.

18. A magnetophoretic display panel according to claim 14, wherein said coating is multi-layered.

19. A magnetophoretic display panel according to claim 14;

wherein said multi-layered coating comprises a first resin coating and a second resin coating, and said first resin is different than said second resin.

20. A magnetophoretic display panel according to claim 11, wherein said magnetic material is selected from the group consisting of ferrite, γ

-hematite, γ

-ferrite oxide, barium ferrite and black iron oxide.