JP2574261B2 - Color electrophotographic apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic apparatus which can be used for a color hard copy apparatus such as a color copying machine or a color printer.

2. Description of the Related Art Conventionally, a plurality of toner images of different colors are formed in advance on an electrophotographic photosensitive member (hereinafter, referred to as a photosensitive member) by repeating charging, exposure, and development a plurality of times, and then the toner images are collectively transferred to paper. There have been proposed various color electrophotographic methods for obtaining a color image.

FIG. 2 shows a conventional example of an apparatus using such a color electrophotographic method. In the figure, 1 rotates in the direction of the arrow
Se-Te photoreceptor, 2 is a corona charger for uniformly charging the surface of photoreceptor 1, 3 is a laser beam scanner, 4 to 7 are yellow (Y), magenta (M), cyan (C), respectively. A developing process in which black (Bl) developer is separately contained, 8 is plain paper, 9 is a neutralization lamp for facilitating electrostatic transfer of a toner image to plain paper 8, and 10 is a static image on a plain paper. A corona charger for electrotransfer; 11 a heating and fixing device; 12 a cleaning blade for electrostatically transferring a toner image onto plain paper 8 and removing toner remaining on the photoreceptor 1; 13 a surface of the photoreceptor This is a static elimination lamp for setting a potential to an initial state.

Next, a method of forming a color image using the above-described color electrophotographic apparatus will be described. First, after the photoconductor 1 is positively charged by the corona charger 2, the laser beam scanner 3
Scans the yellow image signal to form a negative electrostatic latent image (an electrostatic latent image in which the image portion is exposed and the surface potential of the photoreceptor is attenuated). Then, the electrostatic latent image is subjected to negative / positive reversal development by the developing device 4 containing the Y toner to form a yellow toner image on the photoreceptor 1. At this time, only the developing unit 4 containing the Y toner is set to the developing condition in which the toner flies, but the other developing units 5 to 7 are adjusted so that the toner does not fly. After developing with the Y toner, the entire surface of the photoreceptor 1 is irradiated with the charge removing lamp 13 to light remove the yellow electrostatic latent image.

Next, by the same method as the method for forming the yellow toner image, the steps of charging, exposure, development, and light removal are repeated,
The Y, M, C and Bl toner images are formed on the photoreceptor 1.
After the formation of all the toner images is completed, the static elimination lamp 9 is set in advance.
Then, the electrostatic latent image is optically neutralized, and the corona charger 2 electrostatically transfers the toner image to plain paper 8. The toner image transferred to the plain paper 8 is heated and fixed by the heat fixing unit 11. On the other hand, after the electrostatic transfer, the toner remaining on the photoconductor 1 is removed by the cleaning blade, and one cycle of color image formation is completed.
(For example, JP-A-60-95456).

2. Problems to be Solved by the Invention As described in the previous section, when a photoreceptor is subjected to light elimination in a conventional apparatus, depending on an erasing lamp used, toner on the photoreceptor scatters and a phenomenon in which an image is blurred was found. Such a phenomenon was not known at all.

Then, when the cause was investigated, the following was found. FIG. 3 shows the toner scattering mechanism.

Yellow toner once developed on photoconductor (Se-Te) 1
When the toner 14 is charged again, the positively charged toner adheres to the positively charged photoconductor 1 as shown in FIG. 3A. At this time, for example, when the entire surface is illuminated with blue neutralization light,
The potential of the bare photoreceptor drops quickly. However, since the yellow toner does not transmit the blue light at the portion where the yellow toner is attached, the potential below the toner remains high. Therefore, the toner scatters around the newly generated image along the lines of electric force at the periphery of the image (FIG. 3B), and the blur of the image occurs.

Accordingly, it is an object of the present invention to provide a color electrophotographic apparatus capable of obtaining a clear color print without blurring of an image.

Means for Solving the Problems The present invention is directed to a color electrophotographic apparatus that forms a plurality of toner images having different colors on a photoreceptor by repeating a charging / exposure / development cycle a plurality of times. Is a color electrophotographic apparatus in which the wavelength of the neutralization light for neutralizing the toner is at least the wavelength that passes through the first toner used.

According to the present invention, since the wavelength of the neutralizing light of the photoconductor uses the wavelength that passes through the toner used first, the photoconductor potential under the recharged first color toner can be easily changed to light. Decay. For this reason, no new lines of electric force are generated in the peripheral portion of the image, and the toner does not scatter to the periphery, and the image does not bleed.

In addition, it is essential that the static elimination light that can be used in the present invention penetrates the toner to be developed first among toners of different colors. Although white light contains all wavelength components, it is not preferable because the energy is too strong and the light decay rates of the naked photoconductor and the photoconductor under the toner are different. Therefore, the colors of the static elimination light are green or red when Y is used first, blue or red when M is used, and C
When it is blue or green.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.

Developing units 15, 16 and 17 are non-contact non-magnetic one-component developing units that fly toner with a DC electric field. A thin layer of toner is formed on aluminum developing rollers 18, 19 and 20 by blade 21. Configuration. The developing unit 15 contains yellow (Y), the developing unit 16 contains magenta (M), and the developing unit 17 contains cyan (C) insulating toner. Then, the developing devices 18, 19, 20 and the photoconductors 22 were provided with a fixed gap (developing cap), and the respective developing devices were installed to face each other around the photoconductors 22. Each developing device is provided with a separation / contact mechanism that is close to the photoconductor during development and separated during non-development. The specifications of the developing device, the developing conditions, and the physical properties of the toner are shown below.

Developing device specifications and developing conditions Developing roller diameter: 16 mm Image roller peripheral speed: 150 mm / s Toner layer thickness on developing roller: 30 μm Developing roller rotation direction: opposite to photoconductor 22 Developing gap: 150 μm during development , Non-developed 700 μm Toner physical properties Toner charge: +3 μC / g Average particle size: 10 μm Amorphous Se-Te photoreceptor drum 2 having a diameter of 100 mm as a photoreceptor
2, and charged at a surface potential of +800 V by a charger 23 (corona voltage: 7 kV) while rotating at a peripheral speed of 150 mm / s. Next, a light emitting diode 24 having an output of 7 μW and a wavelength of 670 nm was made to emit light, and a negative yellow signal was exposed on the photoreceptor 22 through the rod lens array 25 to form an electrostatic latent image. The contrast potential of the latent image was 750V. The yellow developing device 15 in a developed state in which +700 V is applied to the developing roller 18 with the latent image.
Then, the photoreceptor 22 was passed through the magenta developing device 16 and the cyan developing device 17 in a non-developed state to form a yellow toner image. After the development, the entire surface was irradiated with a red light emitting diode 26 to erase the latent image.

Next, again the corona charger 23 (corona voltage: +7.3 kV)
To charge the photoconductor 22 to + 850V. Next, the photosensitive member 22 was exposed to signal light corresponding to magenta by the light emitting diode 24 to form a magenta electrostatic latent image. Here, the surface potential of the image area formed on the Y toner image was +100 V, and the contrast potential of the latent image was 750 V. Next, the photoreceptor 22 is passed through a yellow developing unit 15 in a non-developing state, a magenta developing unit 16 in a developing state in which +800 V is applied to a developing roller 19, and a cyan developing unit 17 in a non-developing state to form a magenta toner image. Was formed. After the development, the entire surface was irradiated with a red light emitting diode 26 to erase the latent image. Since the red light is transmitted through the yellow toner, the photoreceptor under the recharged yellow toner is also quickly subjected to light elimination, and no toner scattering occurs.

Next, the corona charger 23 (corona voltage: +7.5 kV) again
As a result, the photosensitive member 22 was charged to + 950V. Next, signal light corresponding to cyan was exposed by the light emitting diode 24 to form an electrostatic latent image of cyan. Here, the surface potential of the image portion formed on the M toner image is +100 V, and the surface potential of the image portion formed on the image in which the Y toner and the M toner are superimposed is +200 V. Had a contrast potential of 750V. Next, the photoreceptor 22 was passed through a yellow developing unit 15 in a non-developing state, a magenta developing unit 16, and a developing unit 17 in a developing state in which +900 V was applied to the developing roller 20 to form a cyan toner image.

The color toner image thus obtained on the photoreceptor 22 was transferred onto paper 28 by the transfer charger 27, and then heat-fixed. On the other hand, after the transfer, the fur brush 29 was pressed against the photoreceptor 22 for cleaning.

As a result, the color density of the composite color of red, green and blue is 1.5 or more,
Further, the Y, M, and C three-color superposition density was 1.7 or more, and the toner did not scatter around the image, and a clear color image without ground fog was obtained.

Comparative Example 1 Using the same apparatus as in Example 1, the static elimination lamp 26 was changed to a tungsten lamp having a blue filter. The photoconductor 22 was charged by the charger 23 while rotating at a peripheral speed of 150 mm / s. Next, the light emitting diode 24 was caused to emit light, and a negative yellow signal was exposed on the photoreceptor 22, thereby forming an electrostatic latent image. Thereafter, the latent image was reversal-developed by the yellow developing unit 15 in a developed state.
After the development, the latent image was erased by irradiating the entire surface with a blue lamp 26.

Next, the photoconductor 22 was charged again by the corona charger 23. Thereafter, the photosensitive member 22 was exposed to signal light corresponding to magenta from the light emitting diode 24 to form a magenta electrostatic latent image. The photoreceptor 22 was passed through a yellow developing unit 15 in a non-developed state, a developing unit 16 in a developing magenta, and a cyan developing unit 17 in a non-developing state to form a magenta toner image. After the development, the latent image was erased by irradiating the entire surface with a blue discharging lamp 26. At this time, the recharged yellow portion toner scattered around the image, and the image became unclear.

Comparative Example 2 When white light was used in place of the static elimination lamp used in Comparative Example 1, similarly, the Y toner scattered around the image, and the image became unclear.

According to the present invention, it is possible to obtain a color electrophotographic apparatus capable of obtaining a clear color print without blurring of an image.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of a color electrophotographic apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the principle of a conventional color electrophotographic apparatus, and FIG. FIG. 4 is a conceptual diagram illustrating blurring development of an image line to be developed. 22 ... Photoconductor, 23 ... Charger, 24 ... Light source, 15, 16, 17
…… Developer, 26 …… Static lamp

Claims (1)

(57) [Claims] 1. A process of repeating corona charging, image exposure and development of each color of yellow, magenta and cyan a plurality of times in this order, superimposing toner images to form a color powder toner image on a photoreceptor, and then receiving paper. A color electrophotographic apparatus, wherein the static elimination light for neutralizing the photoreceptor from above the color powder toner image between each color process is red light passing through yellow and magenta. .