# US 12,181,804 B2 · Cleanerless image forming apparatus with toner containing 1.8% by mass or less an external additive having a diameter of 5-50 nanometers

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- Number: US 12,181,804 B2
- Document ID: US12181804B2
- Status: Granted
- Kind: B2
- Application number: 18/183,326
- Filed: 2023-03-14
- Published: 2023-09-21
- Granted: 2024-12-31
- Earliest claimed: 2022-03-18
- Assignees: Ricoh Company, Ltd.
- Applicants: Shogo Kezuka; Yasuhide Matsuno; Akihiro Kawasaki; Yutaro Kaku
- Inventors: Shogo Kezuka; Yasuhide Matsuno; Akihiro Kawasaki; Yutaro Kaku
- Web page: https://patentgrep.com/patent/US12181804B2

## CPC

- G03G 15/0815: {characterised by the developer handling means after the developing zone and before the supply, e.g. developer recovering roller}
- G03G 9/0825: {characterised by their structure; characterised by non-homogenuous distribution of components (microcapsular toners G03G9/093)}
- G03G 15/0258: {provided with means for the maintenance of the charging apparatus, e.g. cleaning devices, ozone removing devices G03G15/0225, G03G15/0291 takes precedence}
- G03G 9/09708: {Inorganic compounds}
- G03G 21/0064: {using the developing unit, e.g. cleanerless or multi-cycle apparatus}
- G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY

## Abstract

An image forming apparatus includes an image bearer, a charger, a developing device, and a transferor. The charger is disposed in contact with the image bearer to charge the image bearer. The developing device supplies toner to the image bearer to form a toner image on the image bearer. The transferor transfers the toner image on the image bearer to a recording medium or an intermediate transferor. The developing device collects transfer residual toner remaining on the image bearer after transfer of the toner image. The toner contains base particles and an external additive. The external additive has a volume average particle diameter of 5 nm or more and 50 nm or less. A content of the external additive is 1.8% by mass or less in the toner.

## Claims

### Claim 1

An image forming apparatus, comprising:
an image bearer;
a charger disposed in contact with the image bearer to charge the image bearer;
a developing device configured to supply toner to the image bearer to form a toner image on the image bearer; and
a transferor configured to transfer the toner image on the image bearer to a recording medium or an intermediate transferor,
the developing device configured to collect transfer residual toner remaining on the image bearer after transfer of the toner image,
the toner containing base particles and an external additive,
the external additive having a volume average particle diameter of 5 nm or more and 50 nm or less,
a content of the external additive being 1.8% by mass or less in the toner,
the external additive containing fine inorganic particles,
the fine inorganic particles having a plurality of peaks in a particle size range of 5 nm or more and 50 nm or less in a particle size distribution of primary particles, and
when among the plurality of peaks, a highest peak is denoted by n1, a second highest peak is denoted by n2, a particle size in unit of nm of a vertex of the peak n1 is denoted by n1d, a particle size in unit of nm of a vertex of the peak n2 is represented by n2d, a height of the vertex of the peak n1 is represented by n1h, and a height of the vertex of the peak n2 is represented by n2h, all of the following formulas (1) to (3) being satisfied:
n1d>n2d (1);
10<(n1d+n2d) (2);
and
30≤{(n2h/n1h)×100}<100 (3).

### Claim 2 (depends on 1)

The image forming apparatus according to claim 1,
wherein the charger is a charging rubber roller.

### Claim 3 (depends on 2)

The image forming apparatus according to claim 2,
wherein the charger has a roughness Rz of 2 μm or more and 20 μm or less, measured by JIS B0601-2001.

### Claim 4 (depends on 2)

The image forming apparatus according to claim 2,
wherein the charger has a resistance of 1×104 Ω or more and 1×107 Ω or less.

### Claim 5 (depends on 1)

The image forming apparatus according to claim 1, further comprising a collector that collects the toner adhering to the charger.