Particles and device for displaying image

• US 20050001810A1
• Filed: 09/19/2002
• Published: 01/06/2005
• Est. Priority Date: 09/19/2001
• Status: Active Grant

• Current Assignee: Bridgestone Corporation
• Original Assignee: Bridgestone Corporation
• Inventors: Murata, Kazuya, Takagi, Koji, Nihei, Norio, Kitano, Hajime, Masuda, Yoshitomo, Yakushiji, Gaku, Kawagoe, Takahiro
• Granted Patent: US 7,525,719 B2
• Time in Patent Office: Days
• US Class Current: 345/107
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02F 1/1671 involving dry toners
• CPC Class Codes: G02F 1/16757 Microcapsules

Abstract

The present invention intends to provide particles for displaying images used in an image display device capable of displaying and eliminating repeatedly accompanied by flight and movement of particles utilizing Coulomb force, being superior in stability, particularly in repetition durability, memory characteristic stability, adaptability for temperature change, having capability of regulating charge amount, and accordingly, favorable images with sufficient contrast should be stably obtained. The present invention provides particles coated with a resin; specifying Span of particle diameter distribution, charge attenuation property, thermal change of the surface hardness, tensile break strength, Izod impact strength (with a notch), abrasion loss (Taber), tensile elastic modulus, flexural elastic modulus, or tear strength. The present invention also proposes about the structure of the particles.

Claims

1. Particles for displaying images used in an image display device which displays images by flying and moving at least one group of particles enclosed between a pair of facing substrates of which at least one is transparent and across the substrates, an electric field being applied, wherein the ingredients for the particles satisfy at least one requirement among the following:

(1) they are coated with a resin;

(2) Span of particle diameter distribution defined by the following equation is less than 5;

Span=(d_0.9−

d_0.1)/d_0.5

wherein d_0.1 represents a particle diameter (μ

m) of the particles whose ratio of particles equal to or less than it is 10%, d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this, d_0.9 represents a particle diameter of the particles whose ratio of particles equal to or smaller than it is 90% each in the particle diameter distribution;

(3) in the case where the surfaces of the particles are charged by applying a voltage of 8 kV onto a Corona generator deployed at a distance of 1 mm from the surface of the particles, a surface potential of the particle 0.3 second after the discharge is greater than 300 V;

(4) a ratio between a surface hardness at 0°

C. and a surface hardness at 100°

C. is 1.7 or smaller;

(5) tensile break strength is 20 MPa or greater;

(6) Izod impact strength (with a notch) is 100 J/m or greater;

(7) abrasion loss (Taber) is 22 mg or less;

(8) tensile elastic modulus is 24.5 MPa or greater;

(9) flexural elastic modulus is 44.1 MPa or greater;

(10) tear strength is 100 kg/cm or greater;

(11) they are a group of combined particles comprising mother particles whereon many child particles of at least one kind adhere;

(12) they are obtained by surface treating fine particles by the use of a solution of charge control agent;

(13) they are coated with a resin by spraying a solution prepared by dissolving resin;

(14) at least one resin layer is formed as an outer layer over a spherical central component by coating a resin comprising a component whose index of refraction is different from that of the central component;

(15) they involve an indefinite particles around which at least one resin layer is formed by coating a resin comprising a component whose index of refraction is different from that of the indefinite particle;

or

(16) they contain a resin component prepared by polymerizing at least one kind of monomer selected from acrylic monomer, methacrylic monomer and styrenic monomer.

2. A group of particles containing a mixture obtained by blending at least two kinds of said particles according to claim 1 different in both color and charge characteristics.

3. The particles according to claim 1, whose solvent-indissoluble ratio in a solvent defined by the following equation is 50% or greater:

Solvent-indissoluble ratio (%)=(B/A)×

100

wherein A represents the weight of said particles before they are immersed into the solvent, and B represents the weight of said particles after immersing them in a non-defective solvent for 24 hours at the temperature of 25°

C.

4. The particles according to claim 1, which are spherical.

5. The particles according to claim 1, whose water absorption is 3% by mass or less.

6. The particles according to claim 1, whose average particle diameter d_0.5 is 0.1 to 50 μ

m;

wherein d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this.

7. The particles according to claim 1, whose surface charge density measured and calculated by the use of a carrier and in accordance with blow-off method is within the range of 2 to 150 μ

C/m² in an absolute value and whose average particle diameter d_0.5 is 0.1 to 50 μ

m;

wherein d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this.

8. The particles according to claim 1, whose color is at least one selected from white or black.

9. The particles according to claim 1, whose surface hardness measured at the temperature of 25°

C. in accordance with JIS K7215 is at least 40 degrees.

10. The group of particles according to claim 2, which have a difference between each surface charge density measured and calculated by the use of a carrier and in accordance with blow-off method within the range of 2 to 150 μ

C/m² in an absolute value and whose average particle diameter d_0.5 is 0.1 to 50 μ

m;

wherein d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this.

11. The group of particles according to claim 2, which have a difference between each surface potential in the case where the surfaces of the particles are charged by applying a voltage of 8 kV onto a Corona generator deployed at a distance of 1 mm from the surface of each particle is 100 V or smaller at 0.3 second after the discharge.

12. The group of particles according to claim 2, which have a ratio (A/B) between the maximum average particle diameter (A) of d_0.5 and the minimum average particle diameter (B) of d_0.5 is 50 or smaller,

wherein d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this.

13. The particles according to claim 1, at least whose surface are formed with a resin obtained by adding a charge control agent.

14. The particles according to claim 13, wherein said charge control agent is at least one kind of chemical compound selected from nigrosine compound, resin acid modified azine, resin acid modified azine compound, the fourth grade ammonium salt, salicylic acid-based metal complex, phenolic condensate, metal-containing azo compound and triphenylmethanes delivertives.

15. The particles according to claim 1, which are obtained by surface treating fine particles with a solution of charge control agent and wherein said charge control agent is at least one kind of chemical compound selected from nigrosine compound, resin acid modified azine, resin acid modified azine compound, the fourth grade ammonium salt, salicylic acid-based metal complex, phenolic condensate, metal-containing azo compound and triphenylmethanes delivertives.

16. The particles according to claim 1, which is obtained by surface treating fine particles with a solution of charge control agent and wherein said surface treatment is adding the fine particles into the solution prepared by dissolving the charge control agent in a solvent and then, drying said fine particles after separating them by filtration.

17. The particles according to claim 1, wherein said particles are coated with a resin and wherein the coating amount of said resin is 0.01 to 30% by weight of the amount of said particles.

18. The particles according to claim 1, wherein said particles are coated with a resin and wherein, defining the average particle diameter d_0.5 before coating resin as r_a and defining the average particle diameter d_0.5 after coating resin as r_b, a changing factor:

R=r_b/r_a is 5 or smaller,

wherein d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this.

19. The particles according to claim 1, wherein the ingredients for the particles are a group of combined particles comprising mother particles whereon many child particles of at least one kind adhere;

and the ratio (B/A) between the average particle diameter d_0.5 (B) of the child particles and the average particle diameter d_0.5 (A) of the mother particles is 20 or greater,

wherein d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this.

20. The particles according to claim 1, wherein the ingredients for the particles are a group of combined particles comprising mother particles whereon many child particles of at least one kind adhere;

and the average particle diameter d_0.5 of the child particles is 1 μ

m or smaller, wherein d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this.

21. The particles according to claim 1, wherein the ingredients for the particles are a group of combined particles comprising mother particles whereon many child particles of at least one kind adhere;

and

Span of particle diameter distribution defined by the following equation is less than 5;

Span=(d_0.9−

d_0.1)/d_0.5

wherein d_0.1 represents a particle diameter (μ

m) of the particles whose ratio of particles equal to or less than it is 10%, d_0.5 represents a particle diameter (μ

m) defining that 50% of the particles are greater than this, and another 50% of the particles are smaller than this, d_0.9 represents a particle diameter of the particle whose ratio of particles equal to or smaller than it is 90% each in the particle diameter distribution.

22. The particles According to claim 1, wherein the ingredients for the particles are a group of combined particles comprising mother particles whereon many child particles of at least one kind adhere;

and both the mother particles and the child particles are conjugated by any one of mechano-chemical method, mechano-fusion method, and grafting method.

23. The particles according to claim 1, wherein at least one resin layer is formed as an outer layer over a spherical central component by coating a resin comprising a component whose index of refraction is different from that of the central component, and which are white.

24. The particles according to claim 1, wherein said particles involve an indefinite particles Around which at least one resin layer is formed by coating a resin comprising a component whose index of refraction is different from that of the indefinite particles and which are white.

25. The particles according to claim 1, which are insulating particles with volume specific resistance of 1×

10¹⁰ Ω

·

cm or greater.

26. An image display device which displays images by flying and moving at least one kind of particles enclosed between a pair of facing substrates of which at least one is transparent and across the substrates, an electric field being applied, wherein said particles are the particles According to claim 1.

27. The image display device according to claim 26, wherein the volume population of said particles in the space between said substrates is 10 to 80%.

28. The image display device according to claim 26, wherein cavities between said substrates are saturated with the air having relative humidity of 60% RH or smaller at the temperature of 25°

C.

29. The image display device according to claim 26, comprising plural of display cells formed by partition walls positioned between said substrates.

30. The image display device according to claim 29, wherein said partition walls are formed by any one of screen printing method, sandblast method, photosensitive paste method or additive method.

31. The image display device according to claim 29, wherein said partition walls are with single rib structure.