Image forming apparatus

• US 7,265,768 B2
• Filed: 01/04/2006
• Issued: 09/04/2007
• Est. Priority Date: 03/12/2003
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Inventors: Aoki, Shinji, Hiroki, Masashi, Watanabe, Takeshi, Takahashi, Masashi
• Primary Examiner(s): Evanisko; Leslie
• Application Number:
  US11/324,229
• Publication Number:
  US 20060109334A1
• Time in Patent Office: 608 Days
• Field of Search: 347/115, 347/117, 347/118, 347/131, 347/132, 347/254
• US Class Current: 347/115
• CPC Class Codes: G03G 15/0115 and forming a half-tone image
• CPC Class Codes: G03G 15/0173 plural rotations of recording member to produce multicoloured copy, e.g. rotating set of developing units G03G15/0163 takes precedence
• CPC Class Codes: G03G 15/0189 primary transfer to an intermediate transfer belt G03G15/0184 takes precedence
• CPC Class Codes: G03G 15/0194 primary transfer to the final recording medium G03G15/0184 takes precedence
• CPC Class Codes: G03G 15/0415 and means for controlling illumination or exposure
• CPC Class Codes: G03G 21/0064 using the developing unit, e.g. cleanerless or multi-cycle apparatus
• CPC Class Codes: G03G 2215/0119 Linear arrangement adjacent plural transfer points
• CPC Class Codes: G03G 2215/0164 Uniformity control of the toner density at separate colour transfers
• CPC Class Codes: G03G 2215/0602 Developer

Abstract

A photoreceptor cleanerless image forming apparatus and method for overlappingly forming yellow, cyan, magenta, and black toner images and decreasing color mixture or an exposure error due to reverse transfer toner or untransferred toner are provided. The image forming apparatus 100 comprises four image forming units 100a, 100b, 100c, and 100d configured to be photoreceptor cleanerless in a 4-drum tandem manner. Each image forming unit includes a photoreceptor 103a, 103b, 103c, or 103d, a charger 105a, 105b, 105c, or 105d, an exposure apparatus 106a, 106b, 106c, or 106d, and a developing apparatus 109a, 109b, 109c, or 109d. When exposure resolutions Ry, Rc, Rm, and Rk are assumed for exposure sources of the exposure apparatuses in the image forming units which form yellow, cyan, magenta, and black images, respectively, the exposure resolutions are configured to satisfy the conditions of Rk≦Rc≦Rm and Rm>Rk. This decreases an exposure error (image hysteresis) in an image formed on paper.

Claims

1. A photoreceptor cleanerless image forming apparatus to overlappingly form yellow, magenta, cyan, and black toner images,

wherein said apparatus includes a control section that is configured to decrease color mixture or exposure error based on controlling an exposure resolution,

wherein said apparatus is a 4-drum tandem image forming apparatus comprising four photoreceptor cleanerless image forming units each including at least a photoreceptor, a charger, an exposure apparatus, and a developing apparatus for overlappingly forming yellow, magenta, cyan, and black images;

and

exposure resolutions Ry, Rm, Rc, and Rk are configured to satisfy conditions of Rk≦

Rc≦

Rm and Rm>

Rk, where said exposure resolutions Ry, Rm, Rc, and Rk correspond to exposure apparatuses in image forming units to form yellow, magenta, cyan, and black images, respectively.

2. The image forming apparatus according to claim 1,

wherein said image forming unit is provided with a transfer condition such that the sum of mass per unit area for untransferred toner and reverse transfer toner becomes 100[g/cm²] or less during transfer of a solid image.

3. The image forming apparatus according to claim 1,

wherein an exposure source of said exposure apparatus complies with a red or near-infrared area whose center wavelength is 630 nm or more.

4. The image forming apparatus according to claim 1,

wherein an exposure source of said exposure apparatus is a semiconductor laser.

5. The image forming apparatus according to claim 1,

wherein beam diameters Dy, Dm, Dc, and Dk are configured to satisfy conditions of Dk≧

Dc≧

Dm≧

Dy and Dk>

Dy, where said beam diameters Dy, Din, Dc, and Dk are used for said exposure source to create an electrostatic latent image, where said beam diameters Dy, Din, Dc, and Dk correspond to image forming units to form yellow, magenta, cyan, and black images, respectively.

6. The image forming apparatus according to claim 1,

wherein said exposure resolution Ry equals said exposure resolution Rk.

7. A photoreceptor cleanerless image forming apparatus to overlappingly form yellow, magenta, cyan, and black toner images,

wherein said apparatus includes a control section that is configured to decrease color mixture or exposure error based on controlling an exposure resolution,

wherein said apparatus is a 4-drum tandem image forming apparatus comprising four photoreceptor cleanerless image forming units each including at least a photoreceptor, a charger, an exposure apparatus, and a developing apparatus for overlappingly forming yellow, magenta, cyan, and black images;

and

exposure resolutions Ry, Rm, Rc, and Rk are configured to satisfy conditions of Rk≦

Rc≦

Rm≦

Ry and Ry>

Rk, where said exposure resolutions Ry, Rm, Rc, and Rk correspond to image forming units to form yellow, magenta, cyan, and black images, respectively.

8. A method of overlappingly forming yellow, magenta, cyan, and black toner images using a photoreceptor cleanerless image forming apparatus comprising four photoreceptor cleanerless image forming units each including at least a photoreceptor, a charger, an exposure apparatus, and a developing apparatus for overlappingly forming yellow, magenta, cyan, and black images, the method comprising:

decreasing color mixture or exposure error based on controlling exposure resolutions Ry, Rm, Rc, and Rk to satisfy conditions of Rk≦

Rc≦

Rm and Rm>

Rk, where said exposure resolutions Ry, Rm, Rc, and Rk correspond to exposure apparatuses in image forming units to form yellow, magenta, cyan, and black images, respectively.

9. The method according to claim 8,

wherein each of said image forming units is provided with a transfer condition such that the sum of mass per unit area for untransferred toner and reverse transfer toner becomes 100[g/cm²] or less during transfer of a solid image.

10. The method according to claim 8,

wherein an exposure source of said exposure apparatus complies with a red or near-infrared area whose center wavelength is 630 nm or more.

11. The method according to claim 8,

wherein an exposure source of said exposure apparatus is a semiconductor laser.

12. The method according to claim 8, wherein beam diameters Dy, Dm, Dc, and Dk of exposure sources of respective exposure apparatuses are configured to satisfy conditions of Dk≧

Dc≧

Dm≧

Dy and Dk>

Dy, and further comprising;

creating an electrostatic latent image using said exposure sources of said exposure apparatuses with said respective beam diameters Dy, Dm, Dc, and Dk,

where said beam diameters Dy, Dm, Dc, and Dk correspond to image forming units to form yellow, magenta, cyan, and black images, respectively.

13. The method according to claim 8,

wherein said exposure resolution Ry equals said exposure resolution Rk.

14. A method of overlappingly forming yellow, magenta, cyan, and black toner images using a photoreceptor cleanerless image forming apparatus comprising four photoreceptor cleanerless image forming units each including at least a photoreceptor, a charger, an exposure apparatus, and a developing apparatus for overlappingly forming yellow, magenta, cyan, and black images, the method comprising:

decreasing color mixture or exposure error based on controlling exposure resolutions Ry, Rm, Rc, and Rk to satisfy conditions of Rk≦

Rc≦

Rm≦

Ry and Ry>

Rk, where said exposure resolutions Ry, Rm, Rc, and Rk correspond to image forming units to form yellow, magenta, cyan, and black images, respectively.