JP3040503B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a first electrostatic latent image formed on an image carrier, which is developed by a first developing device with a first toner, and then a second electrostatic latent image is formed. The present invention relates to an image forming apparatus that forms an image by developing with a second toner by a second developing device.

[0002]

2. Description of the Related Art In order to form an image using an image forming apparatus such as an electrophotographic copying machine or a printer, first, the surface of a photoreceptor, which is an image carrier, is uniformly charged, and the original image is exposed to the charged image. An electrostatic latent image is formed. Next, a toner is supplied to the surface of the photoreceptor having the electrostatic latent image by a developing device to form a visible image,
The obtained toner image is transferred and fixed on a transfer material such as paper.

In this case, in a copier, a printer, or the like using a two-color developing method, the first electrostatic latent image is first developed using the first toner as described above, and then the first electrostatic latent image is developed to the same polarity as the first toner. Similarly, the second electrostatic latent image is developed with the charged second toner. However, in such a two-color or multi-color developing method, the toner adhered to the surface of the photoreceptor in the first development is scraped off by the magnetic brush ears in the second development, and is gradually introduced into the second developer. mixing. Due to this mixing, "mixed colors" in which the first toner is mixed in the image developed with the second toner as the number of copies increases, and the first toner image is disturbed by the magnetic brush of the second developing device. Causes a problem that an abnormal image is generated.

[0004] By the way, several proposals have conventionally been made as a developing method. For example, a method of forming a thin layer of magnetic or non-magnetic toner on a sleeve and developing the toner by an electric field of DC + AC, a method of providing an electrode for generating an alternating electric field in the sleeve and flying the toner by the principle of an electric field curtain, and the like. is there. However, these methods
In an image forming apparatus that requires an expensive AC bias power supply and obtains a multicolor image by developing the first and second developing devices by a contact method, the above-mentioned problems have not been solved.

On the other hand, non-magnetic toners have conventionally been used as color toners. This is because in a color toner containing a magnetic material, the magnetic material does not have transparency, causing a phenomenon that the color becomes turbid, and a so-called pure color cannot be obtained. However, if a non-magnetic color toner is used for the first color, in the two-color developing method, problems occur due to color mixing and disturbance of the toner image as described above.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and the first aspect of the present invention relates to a first color mixing method in which the first toner is mixed into the second toner and a second developing device. It is an object to provide an image forming apparatus in which a toner image is not disturbed and an abnormal image is prevented from being generated.

[0007] The invention of claim 2 or 3 provides, in addition to the above,
It is an object to provide an image forming apparatus capable of obtaining a color image with improved color purity when a color toner is used as the first toner and the second toner.

[0008]

According to the present invention, there is provided an image forming apparatus comprising: a first developing device for transferring a first electrostatic latent image formed on an image carrier to a first toner; In the image forming apparatus which forms a second electrostatic latent image after developing with the second developing device and forms the image by developing the second electrostatic latent image with the second toner using the second developing device, the entire surface of the image carrier has a magnetic attraction force. Wherein the first toner is a magnetic toner,
The second toner is a non-magnetic toner, and the invention of claim 2 is characterized in that, in addition to the above, the first toner contains an organic magnetic material. In addition to the features of the second aspect, the organic magnetic material is a condensed polycyclic polynuclear aromatic type ferromagnetic resin.

[0009]

According to the first aspect of the present invention, since the first toner is a magnetic toner, it is strongly attracted to the electrostatic latent image portion of the image carrier, while the second toner is non-magnetic. Since the toner is a magnetic toner, the force of scraping the image of the first toner developed by the first developing device is weak, so that color mixing and image disturbance do not occur in the second development.

According to the second aspect of the present invention, in addition to the above-mentioned functions, the first toner contains an organic magnetic material, so that the transparency of the magnetic material is improved. Purity is improved.

According to the third aspect of the present invention, the condensed polycyclic polynuclear aromatic type ferromagnetic resin as the organic magnetic substance has particularly high transparency, so that the color purity of a color image is further improved.

[0012]

FIG. 1 shows the structure of an image forming section of an image forming apparatus such as a copying machine or a printer. On the peripheral surface of the image carrier 1, a first charging device 2, a first developing device 3, a second charging device 4, a second developing device 5, a transfer device 6, and the like are arranged in the order of rotation indicated by arrows. Have been.

The image carrier 1 uniformly charged by the first charging device 2 is exposed by a first exposure 7 by a first exposure means (not shown) in accordance with first image information of a document, and a first exposure is performed thereon. An electrostatic latent image is formed, and the first electrostatic latent image is developed by the first developing device 3 with the first toner. Subsequently, the image carrier 1 is charged again by the second charging device 4, and is exposed by a second exposure by a second exposure unit (not shown) based on the second image information of the same document. An electrostatic latent image is formed, and the second electrostatic latent image is developed by the second developing device 5 with the second toner.

The toner image thus formed on the image carrier 1 is transferred by a normal image forming process onto a recording sheet P sent from a sheet feeding device (not shown) under the action of a transfer device 6. After the image is transferred to the recording paper P and fixed by a fixing device (not shown), the recording paper P is discharged to complete the image.

Here, the first developing device 3 comprises a developing section 3a and a toner replenishing section 3b. A developing sleeve 31 and a paddle 3 are arranged in the developing section 3a from the image carrier 1 side.
2. A separator 34 having fins 33 and a horizontal stirring screw 35 are provided.

The carrier constituting the developer is contained in the developing section 3a. On the other hand, the first toner is agitated by the agitator 36 of the toner replenishing section 3b and supplied to the developing section 3a by the toner replenishing roller 37. You. In this embodiment, the first toner is a magnetic toner.

In the developing section 3a, a developer comprising a carrier and a magnetic toner is supplied to a developing sleeve 31 by a paddle 32.

The developing sleeve 31 has a rotating sleeve on the outer surface and a magnet inside, and the carrier and the magnetic toner supplied by the action of the magnet are adsorbed and carried on the surface, and these are doctor blades. After being regulated to an appropriate amount by 38, the toner is conveyed to a developing position close to the image carrier 1, a magnetic brush of developer is formed, and the first electrostatic latent image on the image carrier 1 is changed to the first toner. Is developed. In this case, in the present embodiment, the image carrier 1 is formed by forming a thin film of an organic magnetic material on the surface and magnetized with multipolarity. Therefore, the entire surface of the image carrier has a magnetic material attracting force, The first toner, which is a toner, can be strongly held on the surface of the electrostatic latent image portion.

The separator 34 and the horizontal stirring screw 35 provided in the developing unit 3a allow the excess toner and carrier regulated by the doctor blade 38 to pass through, and at that time, a part of them is dropped into the inside, and Stir in the width direction.

Next, the structure of the second developing device 5 is the same as the structure of the first developing device 3, and the description thereof is omitted.
For the second developing device 5, a non-magnetic toner is used. For this reason, when the first toner image is held on the image carrier 1 and enters the second developing area, the second toner is non-magnetic and has a weak force to scrape off the first toner. Development with the second toner is performed without disturbing the toner,
The second electrostatic latent image based on the second image information can be visualized with toner without generating an abnormal image.

FIG. 2 shows a state in which an image is formed by the above method. Image carrier 1 formed with organic magnetic thin film 1a
On the first, the first electrostatic latent image A is developed with the magnetic toner T ₁ in the first development, and the second electrostatic latent image B is formed with the non-magnetic toner T ₂ in the second development without being disturbed. Has been developed.

Next, when a multicolor image is formed using a color toner as the first toner, an organic magnetic toner is used as the first toner. Examples of the organic magnetic material include a ferrocene polymer of an organometallic polymer, a ferromagnetic resin of a polymer magnetic material of COPNA (condensed polycyclic polynuclear aromatic) type, and the like.

Since these organic magnetic materials have high transparency,
By using an organic magnetic material as the first toner as the magnetic toner, a pure-color multicolor image without color turbidity can be obtained.

An example of the configuration of the organic magnetic toner is as follows.
The yellow toner is composed of 63 parts by weight of a styrene-n-butyl methacrylate copolymer, 30 parts by weight of a ferrocene-benzaldehyde condensation polymer, 2 parts by weight of a quaternary ammonium salt, and 5 parts by weight of benzine yellow. Other color toners, such as magenta and cyan, are also composed of the same organic magnetic toner.

[0025]

As described above, according to the present invention, in the first aspect of the present invention, the first toner (for example, black toner) is a magnetic toner, so that it is strongly attracted to the electrostatic latent image portion of the image carrier. On the other hand, since the second toner is a non-magnetic toner, the power of scraping the image of the first toner developed by the first developing device is weak. Therefore, the first toner is also removed by the magnetic brush in the second development. It is not scraped off, and the occurrence of color mixing and image disturbance can be prevented.

According to the second aspect of the present invention, in addition to the above effects, since the first toner contains an organic magnetic material, the transparency of the magnetic material is improved. Can be improved.

According to the third aspect of the present invention, the condensed polycyclic polynuclear aromatic type ferromagnetic resin as the organic magnetic substance has particularly high transparency, so that the color purity of a color image can be further improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an image forming unit of an image forming apparatus according to an embodiment.

FIG. 2 is an explanatory diagram showing a state of toner adhesion by first and second developments.

[Explanation of symbols]

Reference Signs List 1 image carrier 3 first developing device 5 second developing device T ₁ magnetic toner T ₂ non-magnetic toner

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisao Murayama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Fumihiko Ishikawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor J. Mizuishi 1-3-6 Nakamagome, Ota-ku, Tokyo, Japan Ricoh Co., Ltd. (56) References JP-A-58-136055 (JP, A) JP-A-57- 101852 (JP, A) JP-A-3-33866 (JP, A) JP-A-62-288856 (JP, A) JP-A-56-69657 (JP, A) JP-A-62-245272 (JP, A) JP-A-58-135654 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 15/08-15/095

Claims (3)

(57) [Claims] 1. A first electrostatic latent image formed on an image carrier is developed with a first toner by a first developing device, and then a second electrostatic latent image is formed. The second electrostatic latent image is formed by a second developing device. An image forming apparatus that forms an image by developing with two toners, wherein the entire surface of the image carrier has a magnetic attraction force, the first toner is a magnetic toner, and the second toner is a magnetic toner.
An image forming apparatus, wherein the toner is a non-magnetic toner. 2. The image forming apparatus according to claim 1, wherein the first toner contains an organic magnetic material. 3. The image forming apparatus according to claim 2, wherein the organic magnetic material is a condensed polycyclic polynuclear aromatic type ferromagnetic resin.