# US 6,103,441 A · Color toner for electrophotography

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- Number: US 6,103,441 A
- Document ID: US6103441A
- Status: Granted
- Kind: A
- Application number: 09/432,569
- Filed: 1999-11-12
- Granted: 2000-08-15
- Earliest claimed: 1998-11-12
- Assignees: Ricoh Company, Ltd.
- Inventors: Masami Tomita; Hiroyuki Fushimi; Yohichiroh Watanabe; Keiko Shiraishi
- Web page: https://patentgrep.com/patent/US6103441A

## CPC

- G03G 9/08: with toner particles
- G03G 9/0815: {Post-treatment}
- G03G 9/09708: {Inorganic compounds}
- G03G 9/09716: {treated with organic compounds}
- G03G 9/09725: {Silicon-oxides; Silicates}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

A color toner for electrophotography is made of matrix toner particles, each matrix toner particle containing a binder resin, a coloring agent, and a charge control agent, and an externally added additive which includes (a) hydrophobically treated silica particles having a primary particle size of 0.01 to 0.03 .mu.m, (b) hydrophobically treated titanium oxide particles having a primary particle size of 0.01 to 0.03 .mu.m and a specific surface area of 60 to 140 m.sup.2 /g, and (c) hydrophobically treated silica particles having a specific surface area of 20 to 50 m.sup.2 /g and a bulk density of 100 to 250 g/l.

## Claims

### Claim 1

A color toner for electrophotography comprising (i) matrix toner particles, each matrix toner particle comprising a binder resin, a coloring agent, and a charge control agent, and (ii) an externally added additive comprising:
(a) hydrophobically treated silica particles having a primary particle size of 0.01 to 0.03 .mu.m,
(b) hydrophobically treated titanium oxide particles having a primary particle size of 0.01 to 0.03 .mu.m and a specific surface area of 60 to 140 m.sup.2 /g, and
(c) hydrophobically treated silica particles having a specific surface area of 20 to 50 m.sup.2 /g and a bulk density of 100 to 250 g/l.

### Claim 2 (depends on 1)

The color toner as claimed in claim 1, wherein said externally added additive comprises 0.2 to 1.0 part by weight of said hydrophobically treated silica particles (a), 0.2 to 0.8 parts by weight of said hydrophobically treated titanium oxide particles (b), and 0.5 to 2.0 parts by weight of said hydrophobically treated silica particles (c), to 100 parts by weight of said matrix toner particles.

### Claim 3 (depends on 1)

The color toner as claimed in claim 1, wherein said externally added additive is deposited on said matrix toner particles by the steps of:
mixing said matrix toner particles, said hydrophobically treated silica particles (a) and said hydrophobically treated titanium oxide particles (b) to prepare a mixture, and
adding said hydrophobically treated silica particles (c) to said mixture.

### Claim 4 (depends on 1)

The color toner as claimed in claim 1, wherein said charge control agent comprises a metallic salt of a salicylic acid compound.

### Claim 5 (depends on 1)

The color toner as claimed in claim 1, wherein said matrix toner particles have a volume mean diameter of 4 to 10 .mu.m.