Image forming apparatus

• US 20040179082A1
• Filed: 03/12/2003
• Published: 09/16/2004
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Original Assignee: Toshiba Tec Corporation (Toshiba Corporation)
• Inventors: Aoki, Shinji, Hiroki, Masashi, Watanabe, Takeshi, Takahashi, Masashi
• Granted Patent: US 7,030,895 B2
• Time in Patent Office: Days
• 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

There is provided a photoreceptor cleanerless image forming apparatus capable of decreasing color mixture or an exposure error due to reverse transfer toner or untransferred toner.

An image forming apparatus 100 according to the present invention 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 intensities Iy, Ic, Im, and Ik are assumed for exposure sources of the exposure apparatuses in the image forming units which form yellow, magenta, cyan, and black images, respectively, the exposure intensities are configured to satisfy conditions of Ik≧Ic≧Im≧Iy and Ik>Iy. 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 is conditioned to decrease color mixture or exposure error with respect to at least one of an exposure intensity, an exposure resolution, a volume-based average particle diameter of toner, a light source wavelength, a layer thickness of toner to be transferred, and the weight-based average charged amount of toner.

2. The image forming apparatus according to claim 1,

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 intensities Iy, Ic, Im, and Ik are configured to satisfy conditions of Ik≧

Ic≧

Im≧

Iy and Ik>

Iy, where said exposure intensities Iy, Ic, Im, and Ik correspond to exposure sources for exposure apparatuses in image forming units to form yellow, magenta, cyan, and black images, respectively.

3. The image forming apparatus according to claim 2,

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

4. The image forming apparatus according to claim 2,

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

5. The image forming apparatus according to claim 2,

wherein said exposure source is a semiconductor laser.

6. The image forming apparatus according to claim 1,

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.

7. The image forming apparatus according to claim 6,

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

8. The image forming apparatus according to claim 6,

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

9. The image forming apparatus according to claim 6,

wherein said exposure source is a semiconductor laser.

10. The image forming apparatus according to claim 6,

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, Dm, Dc, and Dk are used for said exposure source to create an electrostatic latent image.

11. The image forming apparatus according to claim 6,

wherein said exposure resolution Ry equals said exposure resolution Rk.

12. The image forming apparatus according to claim 1,

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.

13. The image forming apparatus according to claim 1,

wherein said apparatus comprises four photoreceptor cleanerless developing apparatuses to overlappingly form yellow, magenta, cyan, and black toner images;

and

volume-based average particle diameters Pa, Pb, Pc, and Pd are configured to satisfy conditions of Pa≧

Pb≧

Pc≧

Pd and Pa>

Pd, where Pa, Pb, Pc, and Pd indicate volume-based average particle diameters of toners to be developed on a photoreceptor in the order of development.

14. The image forming apparatus according to claim 13,

wherein said image forming apparatus is configured in 4-drum tandem so that four photoreceptor cleanerless image forming units can overlappingly form yellow, magenta, cyan, and black images on a transfer material.

15. The image forming apparatus according to claim 13,

wherein said image forming apparatus is configured in accordance with a 4-rotation system so that four photoreceptor cleanerless developing apparatuses can overlappingly form yellow, magenta, cyan, and black images on an intermediate transferrer, and then these images are transferred onto a transfer material from said intermediate transferrer at a time.

16. The image forming apparatus according to claim 13,

wherein a transfer condition is so adjusted that the sum of layer thicknesses for untransferred toner and reverse transfer toner becomes 100 [g/cm²] or less during transfer of a solid image.

17. The image forming apparatus according to claim 13,

wherein said exposure source performs exposure within a red or near-infrared area whose center wavelength is 630 nm or more.

18. The image forming apparatus according to claim 13,

wherein said exposure source is a semiconductor laser.

19. The image forming apparatus according to claim 13,

wherein the weight-based average charged amounts of yellow, magenta, cyan, and black toners are configured to produce an initial difference within the range of ±

5 [C/g].

20. The image forming apparatus according to claim 1,

wherein said apparatus is a photoreceptor cleanerless image forming apparatus to overlappingly form yellow, magenta, cyan, and black toner images;

and

an exposure source used for forming an electrostatic latent image complies with a blue or blue-violet area whose center wavelength is 460 nm or less.

21. The image forming apparatus according to claim 20,

wherein said image forming apparatus is provided with a transfer condition so adjusted that the sum of layer thicknesses for untransferred toner and reverse transfer toner becomes 100 [g/cm²] or less during transfer of a solid image.

22. The image forming apparatus according to claim 20,

wherein said image forming apparatus is configured in 4-drum tandem so that four photoreceptor cleanerless image forming units can overlappingly form yellow, magenta, cyan, and black images on a transfer material.

23. The image forming apparatus according to claim 20,

wherein said image forming apparatus is configured in accordance with a 4-rotation system so that four photoreceptor cleanerless image forming units can overlappingly form yellow, magenta, cyan, and black images on an intermediate transferrer, and then these images are transferred onto a transfer material from said intermediate transferrer at a time.

24. The image forming apparatus according to claim 1,

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

an exposure source for forming a yellow electrostatic latent image complies with a red or near-infrared area whose center wavelength is 630 nm or more, and an exposure source used for forming at least a cyan electrostatic latent image out of the other electrostatic latent images in the remaining colors complies with a blue or blue-violet area whose center wavelength is 460 nm or less.

25. The image forming apparatus according to claim 24,

wherein said exposure source is a semiconductor laser.

26. The image forming apparatus according to claim 24,

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

27. The image forming apparatus according to claim 24,

wherein exposure sources for forming magenta and black electrostatic latent images comply with a red or near-infrared area whose center wavelength is 630 nm or more.

28. The image forming apparatus according to claim 24,

wherein exposure sources for forming magenta and black electrostatic latent images comply with a blue or blue-violet area whose center wavelength is 460 nm or less.

29. The image forming apparatus according to claim 1,

wherein said apparatus is a photoreceptor cleanerless image forming apparatus to overlappingly form yellow, magenta, cyan, and black toner images;

and

layer thicknesses Ta, Tb, Tc, and Td are configured to satisfy conditions of Ta≦

Tb≦

Tc≦

Td and Ta<

Td, where Ta, Tb, Tc, and Td indicate thicknesses of toner layers to be transferred to a transfer material in this order.

30. The image forming apparatus according to claim 29,

wherein a ratio between X and Y is greater than or equal to 1/25000 and is smaller than or equal to 1/10, where X indicates a layer thickness of a toner image developed on a photoreceptor during solid image formation, and Y indicates a layer thickness of toner returned to a photoreceptor from a solid toner image already transferred to a transfer material.

31. The image forming apparatus according to claim 29,

wherein said image forming apparatus is configured in 4-drum tandem so that four photoreceptor cleanerless image forming units can overlappingly form yellow, magenta, cyan, and black images on a transfer material.

32. The image forming apparatus according to claim 29,

wherein said four toner images are formed in the order of yellow, magenta, cyan, and black from upstream to downstream.

33. The image forming apparatus according to claim 29,

wherein said image forming apparatus is configured in accordance with a 4-rotation system so that four photoreceptor cleanerless image forming units can overlappingly form yellow, magenta, cyan, and black images on an intermediate transferrer, and then these images are transferred onto a transfer material from said intermediate transferrer at a time.

34. The image forming apparatus according to claim 1,

wherein said apparatus is a photoreceptor cleanerless image forming apparatus to overlappingly form yellow, magenta, cyan, and black toner images;

and

weight-based average charged amounts Qa, Qb, Qc, and Qd are configured to satisfy conditions of Qa≦

Qb≦

Qc≦

Qd and Qa<

Qd, where Qa, Qb, Qc, and Qd indicate weight-based average charged amounts of toners to be transferred to a transfer material in this order.

35. The image forming apparatus according to claim 34,

wherein volume-based average particle diameters of yellow, magenta, cyan, and black toners are configured to produce an initial difference within the range of ±

1 [m].

36. The image forming apparatus according to claim 34,

wherein volume-based average particle diameters Pa, Pb, Pc, and Pd are configured to satisfy conditions of Pa≧

Pb≧

Pc≧

Pd and Pa>

Pd, where Pa, Pb, Pc, and Pd indicate volume-based average particle diameters of toners to be developed on a photoreceptor in this order.

37. The image forming apparatus according to claim 34,

wherein layer thicknesses Ta, Tb, Tc, and Td are configured to satisfy conditions of Ta≦

Tb≦

Tc≦

Td and Ta<

Td, where Ta, Tb, Tc, and Td indicate layer thicknesses of toners to be developed on a photoreceptor in this order.