JPH0333767A - Color printing system - Google Patents

Abstract

PURPOSE:To reduce the loss of a toner image and a color mixture and to improve a printing quality by impressing the bias voltage of the same polarity as the electrification of a photoconductor at the time of invertingly developing a second latent image and executing a magnetic brush development with two- component consisting of non-magnetic toner and a specific high resistance from a second and subsequent colors. CONSTITUTION:At the time of invertingly developing the second latent image, the bias voltage of the same polarity as the electrification of the photoconductor is impressed, and at the second and subsequent colors, the magnetic brush development with high resistant two-component consisting of the non-magnetic toner and a high resistance magnetic carrier at 10<4>OMEGAcm or above is executed. When the high resistance magnetic carrier is used, the attracting force of the carrier and toner is small, a electric field frequency prepared by a photoconductor 1 surface and a magnetic brush is small, in inverted electric field is held, thereby, a first toner image 12 is attracted to the photoconductor 1 surface, and simultaneously, the force to remove it by the carrier is small. Thus, the loss of the toner image and the color mixture can be reduced, and the excellent printing quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color printing method, in which an electrostatic latent image is developed and visualized using colored particles (toner) to obtain an image. Many means and methods have been proposed for recording and printing image information using electrostatic recording and electrophotographic techniques, and in recent years, printing methods for printing computer output have become widely used. It has come to be used.

However, conventional techniques generally have the disadvantage that they can only be printed in one color, such as black, and although there is a demand for printing in two or three colors, such methods have problems with printing quality. There were problems such as inferiority and the need for a high-precision drive mechanism, high-voltage power supply, and high-voltage mechanism, which hindered its practical application.

The present invention improves printing quality by reducing toner image loss and color mixing in a color printing method in which two or more colors are developed sequentially using one drum and the two or more color toner images formed are transferred simultaneously. The purpose of this invention is to provide an excellent color printing method that does not require a high-precision rotating mechanism, high-voltage power supply, or high-voltage mechanism.

A feature of the present invention according to the above is that a first latent image is formed by first exposure on a highly conductive photoreceptor, this first latent image is reversely developed, and then a second latent image is formed on the photoconductive photoreceptor. A second latent image is formed by exposure in step 2, and the process of reversing and developing this second latent image is repeated two or more times to create toner images of two or more colors on the photoreceptor, which are simultaneously transferred to recording paper. In a color printing method that creates an image of two or more colors by
When reversing and developing the latent image, a bias voltage of the same polarity as the 1iF voltage of the photoconductor is applied, and from the second color onwards, high resistance 2. The purpose is to perform component magnetic brush development.

Next, one embodiment of the present invention will be described based on the drawings.

The device according to the present invention uses an electrophotographic method for electrostatic recording, and is particularly suitable for printing in two to three colors. However, in order to make the explanation easier to understand, hereinafter, based on an example, an electrophotographic method will be used. This article will be described in terms of a method for obtaining two-color printing using a method.

Here, FIG. 1 is a schematic configuration diagram of a printing device used for two-color printing electrophotography according to an embodiment of the present invention, and FIG. 2 is an enlarged explanatory diagram showing the state of toner adhesion after development. It is.

In the figure, 1 is a photoconductive photoreceptor (hereinafter referred to as a photoconductive drum)
, 2 is a charger, 4 is a first developing device, 6 is a second developing device, 7 is a recording paper, 8 is a transfer device, and 9 is a cleaner, these constitute the printing device, and 3 and 5 are the first developing device. This shows a 1,2 light image.

Further, 10 is a first latent image, 11 is a second latent image, 12 is a first toner image, 13 is a second toner image, and 14 is a mixed color toner image.

First, general color printing using the above-mentioned configuration will be described below.

That is, the photoconductive drum 1 is uniformly charged with the charger 2,
Next, the first optical image 3 is irradiated to form a charge latent image. Then, this charge latent image is reversely developed by the first developing device 4.

Subsequently, the portions of the photoconductive drum 1 that were not irradiated with the first light image 3 are irradiated with a second light image 5.

A second charge latent image is created and reversely developed by the second developer 6 to form a two-color toner image on the photoconductive drum 1.

The toner images thus created are simultaneously transferred onto the recording paper 7 by a transfer device 8 in the presence of a transfer corona.

This transferred toner image, although not shown in the drawing, is ultimately fixed.

The toner image remaining on the photoconductive drum 1 is removed by a cleaner 9, and the same process is repeated again to continuously obtain a large number of images.

However, with the above configuration, two-color toner images can be transferred simultaneously using one photoconductive drum, so there is no reduction in printing speed or complication of the device. It is something.

FIG. 2 shows the state of a toner image formed on the photoconductive drum 1 by two successive developments in the above-described structure.

The illustrated vo indicates the charging potential on the photoconductive drum 1, and the first optical image 3 forms a first latent image 10, and the second optical image 5 forms a second latent image 11.

Then, by the first development by the first developing device 4, the first toner image 12 is placed on the first latent image 10, and the second toner image 12 is placed on the first latent image 10.
A second toner pattern 13 is formed at a location of the second WI image 11 by the second development by the developing device 6 .

However, when the first latent image 10 is developed and toner is attached, the potential vl is V, <V, and during the second development, (
Since there is a potential of V, -V, ), the second toner adheres to this portion, resulting in a mixed color toner image 14 as shown in the figure.

Another problem is that during the second development, the first toner is removed and enters the second @ imager 6, and when this accumulates, the color of the second toner image 13 deteriorates (the second developer dirt)
Sometimes.

Therefore, in order to obtain stable printing over a long period of time without mixed color images or stains of the second developer using such a system, it is necessary to do the following.

(1) The first toner image is not removed during the second development.

(2) Even if you have some problems, don't accumulate them.

It is used immediately during the second development to avoid increased color degradation.

(3) The overlapping of the second toner on the first toner image is minimized, and the color mixture is kept to an extent that does not cause any practical problems.

The present invention was developed focusing on the above-mentioned points, and each embodiment thereof will be described next.

Example 1 A photoconductive drum was positively charged to 500 to 1000 V and irradiated with a first optical image 3 to form a first latent image 10. The residual potential in the exposed area was 50V.

Next, as a first developer, a low resistance magnetic carrier of 103 Ωcm or less and a positively charged black toner are mixed in a weight ratio of 1 to 1.
Make a 5% two-component magnetic developer and add +1 to the first developer 4.
A bias voltage of 00-+500V was applied, and the first latent image 10 was developed with a magnetic brush.

At this time, the developed image density was close to the saturation density and was 1.0 or more. When the potential after development was measured, it was found to be VX2200V at the highest image density.

Next, a second light image 5 was irradiated to create a second latent image ↓l.

A high resistance magnetic carrier with a resistance of 10' Ω or more is used as the second developer, and a positively charged red toner is used at a weight ratio of 1 to 5%.
A two-component magnetic developer was prepared and magnetic brush development was performed.

I and second toner images 12.13 developed in this way
When the image was transferred onto recording paper 7 and thermally fixed, the amount of the mixed color toner image 14 was small, and the first toner image 12 was a black image that had no problem in practical use.

Further, even when the second toner image 13 was continuously printed, a red image with very little amount of the first toner mixed in was obtained.

In particular, the carrier resistance is good when it is 10'' Ω or more and the thickness of the magnetic brush is 2 to 6 on.

In terms of manufacturing the carrier, a stable product was obtained when the carrier was manufactured in a 10"Ω country.
It was obtained by creating an oxide film on the surface of iron powder with a diameter of 0/Am.

On the other hand, when the second development was carried out using the same magnetic carrier as the first development and applying almost the same bias, about half of the first toner image 12 was removed, and the second
Toner adheres to almost the same amount as the first toner, resulting in only a black image with strong red color.Furthermore, when printing continuously, black toner gets mixed into the second developer, resulting in a muddy red image. It is had.

At this time, when a bias voltage having the same polarity as the bias voltage applied to the first developing device 4 and larger than the bias voltage applied to the first developing device 4 was applied to the second developing device 6, a bias voltage was applied to the second developing device 6. Removal of the first toner image 12 is reduced;
Although the above-mentioned problems were improved, the second development was inferior to that using a high-resistance magnetic carrier, and some problems remained in terms of stable printing.

As mentioned above, the reason why such good results can be obtained when using a high-resistance magnetic carrier is that the attraction force between the carrier and toner (Coulomb force due to the charge on the toner) is small, and the force between the photoconductor surface and the magnetic brush is small. This is thought to be because the formed electric field gradient is small and an inverted electric field is maintained, so the first toner image 12 remains attracted to the photoconductor surface and the force with which it is removed by the carrier is small.

As described above, the mixed color toner image 14 is added to the first toner image 12.
According to the developing method of this embodiment with less color, not only is there less color mixing into the first toner, but the second toner image 13 is also free of color.
In the first image transferred to the recording paper 7, the chromatic toner is located below the black toner image, so the influence of the mixed color toner image 14 is as follows.
This will be extremely rare.

Example 2 In Example 1 above, when the first development was developed using the same high resistance carrier as the second development, Example 1
Similarly, good results were obtained.

At this time, the first developing bias voltage is 0 to 500V,
Good images were obtained even with non-bias (OV) development.

In order to reduce the mixed color toner copy 14 in the second development, it is necessary to perform the first development sufficiently,
For this purpose, in the first magnetic brush development, it is preferable that the magnetism is strong < L (800 to 1000 Gauss or more), and the magnetization is 10 to 30 am in order to widen the development width.

Example 3 In Examples 1 and 2 above, when the second developing capacity was made smaller than that of the first, the amount of mixed color toner 14 to the first toner image ↓2 was reduced, and black reproduction was improved. .

Although the image density of the second toner image 13 decreased slightly, it was a value that caused no problem in practical use.

As a means of reducing the developing capacity, in order to reduce the contact between the photoconductive drum 1 and the magnetic brush, the gap between the photoconductive drum 1 and the magnetic brush is made smaller than that of the first developing device 4.

Increased size by 0.1 to 0.5. In addition, the magnetic force is 100~
It was lowered by 200 Gauss.

By doing this, the effect of removing the first toner image ↓2 during the second development was slightly reduced, but in the method of the present invention in Example 1.2, this removal effect was originally small. There was no significant difference in practical effects.

Example 4 In Examples 1 to 3, when the charge amount of the toner of the second developer was made larger than that of the first developer, the amount of mixed color toner/image 14 on the first toner image 12 was reduced, and Second
Accumulation of the first toner in the developing device 6 has been reduced.

The reason for this is that when the charge is large, the toner adsorption force to the carrier is large, and the first toner image 12 is (V, -V,)
It is thought that even if the first toner is mixed into the second developer, it will not accumulate because the first toner is easier to develop.

Example 5 In Examples 1 to 4, when a low bias voltage of 50 to 200 V with the same polarity as the charging of the photoconductor was applied to the second developing device 6, the first toner image ↓2 was changed by the second development. There was no practical problem in removing or accumulating the first toner in the second developer. The reason is.

When the bias is applied, the first toner image 12 becomes the first latent image 1.
This is because the force of attraction to zero is large, and the first toner is not attracted to the carrier, but only slightly overlaps the mixed color toner images 14.

Example 6 In Examples 1 to 4, when an alternating current voltage was used for the bias voltage of the second copying device 6, the tone of the second image obtained by the second development could be made softer, and adjustment became easier. Ta.

Further, in Example 5, when an alternating current component was superimposed on the bias voltage, a similar effect was obtained.

Example 7 In Example 1, the contact between the magnetic brush and the photoconductive drum during the first development was made close so that the photoreceptor potential after development was reduced by 100 to 200 V. The mixed color toner image 14 was reduced, and black reproduction was improved.

This is because the developing ability in the second development is reduced by the amount of the potential drop, and the overlap of the second toner is reduced.

Example 8 In Examples 1 to 6, after development, the photoconductive drum 1 was uniformly exposed to weak light to lower the surface potential by 100 to 200 V, and the same effect as in Example 7 was obtained.

Example 9 In Examples 1 to 6, when printing was performed by adjusting the irradiation amount so that the residual voltage at the time of irradiation of the first optical image 3 was 100 to 300 V, color mixing of the second toner to the first toner image 12 was observed. 14
has decreased, and black reproduction has improved.

This is because the developing ability in the second development becomes relatively low due to the presence of residual voltage.

In the first development, it was better to apply a bias.

Example 10 In Examples 1, 3 to 6, and 8.9, the first development was performed using cascade development, and the second development was performed as in each of the above examples.
A similar good image was obtained when developed with a high-resistance magnetic brush.

Example 11 In Examples 1 to 4, the first latent image 10 is transferred to the first developing device 4.
When a bias was applied to sufficiently perform the first development and the amount of toner in the first toner image 12 was increased, a portion of this first toner pattern ↓2 tended to be removed during the second development. At this time, during the second development, the contact between the photoelectric drum 1 and the magnetic brush is lightened to reduce the developing ability, and then v
When developing was performed by applying a bias voltage of 100 to 200 V with the same polarity as o so that the second toner was slightly overlapped on the first toner image 12, it was found that part of the first toner image 12 was not removed. , has almost disappeared.

In addition, the Japanese Patent Application Publication No. 1983 entitled “Non-Impact Printer J”
The color printing method shown in the -83069 publication is “
The second @ image is performed using a "high resistance magnetic toner developer", and the "high resistance magnetic toner" forms a magnetic brush on a developing roll containing a built-in magnet to perform development.

However, there are problems when using the printing method described in the above publication in a two- or three-color printer. (1) Since the developer contains a large amount of black or low-brightness magnetic material, the color (2) If a chromatic color is used as the first color and a black magnetic toner is used as the second color, if even a small amount of black magnetic toner is mixed into the first color image, the coloring of the first color will deteriorate significantly. do(
3) When using a high-resistance magnetic toner developer, the gap between the photoconductive photoreceptor and the developing roll must be narrowed to about 0.5 m, so a high-precision drive mechanism is required (4)
In addition, when using a "high resistance magnetic toner developer", in order to improve the developability, the bias voltage to be applied must be set to a large value (500 to 700 V) approximately equal to the charging voltage of the photoreceptor.
This requires a high-voltage power supply and a high-voltage mechanism.

In contrast, according to one aspect of the present invention, high resistance two-component magnetic brush development is performed using a non-magnetic toner and a high resistance magnetic carrier with a resistance of 104 Ω or more for at least the second and subsequent colors. 10' Ω for second and subsequent colors
The reason for using a high resistance magnetic carrier of 0 or more, that is, the superiority in printing quality, was described in Example 1 above.

In addition, in the present invention,
Compared to the color printing method described in the publication, since a non-magnetic toner is used, any color can be printed without being limited to the colors specific to magnetic materials, such as the black of magnetite and ferrite, or the brown of magnetite. Furthermore, the gap between the photoconductive photoreceptor and the developing roll can be made large (as shown in Example 1, the optimal gap between the photoconductive photoreceptor and the developing roll is 2 to 6). ), not only does it not require a high-precision drive mechanism, but it also requires a low voltage bias, which is advantageous in terms of power supply and insulation structure. In addition, in the present invention, if the first development is black, even if other chromatic colors are mixed into the first development, the effect thereof can be practically ignored.

Furthermore, although the electrophotographic method has been described above, the present invention can be applied to an electrostatic recording method in which reversal development of a negative latent image is sequentially performed two or more times.

Furthermore, in the case shown in FIG. 1, it is effective to appropriately adopt a method of improving the transfer efficiency by uniformly irradiating the toner to eliminate static electricity or performing negative charge to recharge the toner before transfer. Furthermore, installing a magnetic carrier cleaner for removing unnecessary carriers that have adhered to the photoconductive drum after development is effective in preventing transfer omissions.

In summary, according to the present invention, in a color printing method in which two or more colors are developed sequentially using one drum and the formed toner images of two or more colors are simultaneously transferred, It provides a color printing method that reduces toner image loss and color mixing, provides excellent print quality, and does not require a high-precision drive mechanism, high-voltage power supply, or high-voltage mechanism.

It can be said that this invention has excellent effects.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a printing device used for two-color printing electrophotography according to an embodiment of the present invention, and FIG. 2 is an enlarged explanatory diagram showing the state of toner adhesion after development. DESCRIPTION OF SYMBOLS 1... Photoconductive drum, 2... TF electric appliance, 3... First optical image, 4... First developing device, 5... Second optical image, 6...
...Second developer. 7...Recording paper, 8...Transfer device, 9...Cleaner,
10...first wI image, 11...second latent image, 12...
・1st toner image, figure 11, 11th official document (spontaneous) May 11, 2000 Patent application filed April 20, 2000 (C) Name (510) Hitachi Co., Ltd. Manufacturer 4, Agent Residence (103) Nisshin Building, 2-9-5 Kayabacho, Nihonbashi, Chuo-ku, Tokyo Telephone: 03 (661) 0071 Column 6 of “Detailed Description of the Invention” of Mei JIIl, Contents of Amendment ( 1) Correct "image density" on page 11, line 18 of the specification to "both image density." ) "Mixed color ↓ 4" on page 14, line 17 of the specification is corrected to "mixed color toner image 14."

Claims (1)

[Scope of Claims] 1. A first latent image is formed on the photoconductive photoreceptor by a first exposure, this first latent image is reversely developed, and then a second latent image is formed on the photoconductive photoreceptor. forming a second latent image by the second exposure;
A color printing method in which the process of reversing and developing this second latent image is repeated two or more times to create toner images of two or more colors on the photoreceptor, and these images are simultaneously transferred to recording paper to create images of two or more colors. In this step, when reversing and developing the second latent image, a bias voltage of the same polarity as the charging of the photoconductor is applied, and from the second color onwards, a non-magnetic toner and a high resistance magnetic carrier of 10^4 Ωcm or more are applied. A color printing method characterized by high-resistance two-component magnetic brush development. 2. In the color printing method described in claim 1, the total development in which multiple colors are developed sequentially is 10^4Ωc.
A color printing method that uses high resistance two-component magnetic brush development using a high resistance magnetic carrier of m or more.