Image forming apparatus

Patent metadata

Field	Value
Publication number	US-9904225-B2
Application number	US-201715461760-A
Country	US
Kind code	B2
Filing date	Mar 17, 2017
Priority date	Mar 22, 2016
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

In a first image formation mode, an image is formed with a first development contrast C1 and a specific dot pattern is formed with a second development contrast C2, which is lower than the first development contrast C1; in a second image formation mode, an image is formed with a third development contrast C3 and a specific dot pattern is formed with a fourth development contrast C4, which is lower than the third development contrast C3; and when ΔC1 (=C2/C1) denotes a ratio between the second development contrast C2 and the first development contrast C1, and ΔC2 (=C4/C3) denotes a ratio between the fourth development contrast C4 and the third development contrast C3, ΔC2<ΔC1 is satisfied.

First claim

What is claimed is:

1. An image forming apparatus, comprising:
a rotatable image bearing member on which an electrostatic image is formed;
a rotatable developer bearing member that supplies a developer to the image bearing member and develops the electrostatic image; and
processing portion that processes image information so as to add a specific dot pattern to an image to be formed on recording material, wherein the image forming apparatus executes: a first image formation mode in which an image is formed based on the image information by setting a peripheral velocity ratio Vd/Vdr between a peripheral velocity Vd of the developer bearing member and a peripheral velocity Vdr of the image bearing member to a first peripheral velocity ratio ΔVI; and
a second image formation mode in which an image is formed based on the image information by setting the peripheral velocity ratio Vd/Vdr to a second peripheral velocity ratio ΔV2, which is higher than the first peripheral velocity ratio ΔVI,
in the first image formation mode, the image forming apparatus forms an image with a first development contrast CI and forms the specific dot pattern with a second development contrast C2, which is lower than the first development contrast CI,
in the second image formation mode, the image forming apparatus forms an image with a third development contrast C3 and forms the specific dot pattern with a fourth development contrast C4, which is lower than the third development contrast C3, and when ΔC1 (=C2/C1) denotes a ratio between the second development contrast C2 and the first development contrast CI, and ΔC2 (=C4/C3) denotes a ratio between the fourth development contrast C4 and the third development contrast C3,
ΔC2<ΔC1 is satisfied.

2. The image forming apparatus according to claim 1 , wherein by setting density of the specific dot pattern to or below a prescribed density, the specific dot pattern becomes invisible.

3. The image forming apparatus according to claim 1 , wherein in the second image formation mode, the specific dot pattern is made less visible by setting density of the specific dot pattern lower than density of the specific dot pattern in a case where density of an entire image including the specific dot pattern is increased by the second image formation mode.

4. The image forming apparatus according to claim 3 , further comprising
an exposing apparatus that forms the electrostatic image on the image bearing member by exposing the image bearing member, wherein
on the image bearing member, density of the specific dot pattern to be developed is lowered by adjusting exposure of an electrostatic image corresponding to the specific dot pattern by the exposing apparatus.

5. The image forming apparatus according to claim 4 , further comprising
a storage portion that stores prescribed information, wherein exposure of the specific dot pattern in the first image formation mode and exposure of the specific dot pattern in the second image formation mode are stored in the storage portion in advance.

6. The image forming apparatus according to claim 4 , wherein in the second image formation mode, when forming an image on a recording medium, exposure of the specific dot pattern is lowered so that a potential of a portion corresponding to the specific dot pattern on the image bearing member becomes lower than a potential of a portion on the image bearing member corresponding to the specific dot pattern in a case where density of an entire image including the specific dot pattern is increased by the second image formation mode.

7. The image forming apparatus according to claim 6 , wherein on the image bearing member, density of the specific dot pattern is lowered by making a difference between a potential of a portion on the image bearing member corresponding to the specific dot pattern and a potential of the developer bearing member smaller than a difference between a potential of a portion on the image bearing member corresponding to the specific dot pattern in a case where density of an entire image including the specific dot pattern is increased by the second image formation mode and the potential of the developer bearing member.

8. The image forming apparatus according to claim 7 , wherein in the first image formation mode, the exposure of a portion corresponding to the specific dot pattern on the image bearing member is kept unchanged by adding first information, which does not change the exposure of the portion corresponding to the specific dot pattern, to the image information formed on the recording medium.

9. The image forming apparatus according to claim 8 , wherein in the second image formation mode, the exposure of a portion corresponding to the specific dot pattern on the image bearing member is changed by adding second information, which changes the exposure of the portion corresponding to the specific dot pattern, to the image information formed on the recording medium.

10. The image forming apparatus according to claim 1 , wherein density of the specific dot pattern formed in the second image formation mode is 60% or lower of density of a dot pattern of the image other than the specific dot pattern, which is formed in the second image formation mode.

11. The image forming apparatus according to claim 1 , wherein in the second image formation mode, the image forming apparatus enlarges a color gamut of an image formed on a recording medium as compared to the first image formation mode by increasing the peripheral velocity Vd of the developer bearing member relative to the peripheral velocity Vdr of the image bearing member so as to increase the second peripheral velocity ratio ΔV2.

12. The image forming apparatus according to claim 11 , wherein in the second image formation mode, the image forming apparatus increases the second peripheral velocity ratio ΔV2 by keeping the peripheral velocity Vdr of the image bearing member constant and only increasing the peripheral velocity Vd of the developer bearing member.

13. The image forming apparatus according to claim 1 , further comprising control a unit that executes the first image formation mode and the second image formation mode.

14. An image forming apparatus, comprising:
a rotatable image bearing member on which an electrostatic image is formed;
a rotatable developer bearing member that supplies a developer to the image bearing member and develops the electrostatic image; and
processing portion for processing image information so as to add a specific dot pattern to an image to be formed, wherein the image forming apparatus executes: a first image formation mode in which an image is formed based on the image information by setting a peripheral velocity ratio Vd/Vdr between a peripheral velocity Vd of the developer bearing member and a peripheral velocity Vdr of the image bearing member to a first peripheral velocity ratio ΔVI; and
a second image formation mode in which an image is formed based on the image information by setting the peripheral velocity ratio Vd/Vdr to a second peripheral velocity ratio ΔV2, which is higher than the first peripheral velocity ratio ΔVI,
in the first image formation mode, the image forming apparatus forms an image with a first development contrast CI and forms the specific dot pattern with a second development contrast C2 which is lower than the first development contrast CI,
in the second image formation mode, the image forming apparatus forms an image with a third development contrast C3 and forms the specific dot pattern with a fourth development contrast C4 which is lower than the third development contrast C3, and when ΔC1 (=|C2−CI|) denotes an absolute va

Assignees

• Canon Kk

Inventors

• Hirota Yusuke
• Nakahara Hisashi
• Uchiyama Akihiko

Classifications

• B41M3/14

  Security printing {(securities B42D25/29)} · CPC title

• G03G15/5037

  the characteristics being an electrical parameter, e.g. voltage · CPC title

• B41J29/40

  Means for printing fixed, i.e. unchanging, matter in addition to selectable matter · CPC title

• G03G15/06

  for developing · CPC title

• H04N1/4072

  dependent on the contents of the original · CPC title