JPH0629995B2 - Development method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for obtaining a multicolor print by one transfer, and in particular, toner of another color is mixed in a developing device for the second and subsequent colors. The present invention relates to a method for developing an electrostatic latent image, which prevents the occurrence of the above.

Conventional technology Development to obtain a multicolored print in one transfer operation
Although various transfer devices have been proposed, an example of the development transfer process for obtaining a multicolor print in this so-called one pass will be described with reference to FIG.

The surface of the electrostatic latent image carrier 2 is uniformly charged by the charger 1, the electrostatic latent image forming means 3 forms an electrostatic latent image for the first color, and the electrostatic latent image is developed by the developing device 4. To develop with the first color toner. Next, the electrostatic latent image forming means 5 forms an electrostatic latent image for the second color, and the electrostatic latent image is developed by the developing device 6.
To develop with the second color toner. These developments are transferred onto the paper sent from the paper feed tray 7 by the transfer device 8, and the transferred image is fixed by the fixing device 9. On the other hand, when the toner remaining on the electrostatic latent image carrier 2 is removed by the cleaner 10, the next developing / transferring cycle is started thereafter.

Problems to be Solved by the Invention However, in the conventional developing method, the second color developing device 6 is used.
At the time of development by, the toner of each development of the first color may be mixed into the developing device 6 of the second color.

As a measure for preventing the toner of the first color from being mixed in the developing device 6 of the second color, a developing method of developing by non-contact development as disclosed in JP-A-55-18659 has been proposed. Since this developing method is non-contact development, the first color development is not mechanically peeled off to cause color mixture, but in this method, the developer is held between the developer carrier and the electrostatic latent image carrier. Reciprocates regardless of whether it is an image portion or a non-image portion, so that color mixing still occurs in the developing device.

The present invention has been made to eliminate the above-mentioned drawbacks, and an object thereof is to prevent color mixture to a developing device by devising a developing bias applied in non-contact development.

Means for Solving the Problems In the developing method according to the present invention, at least two or more electrostatic latent image forming means are arranged around the electrostatic latent image carrier, and each of the electrostatic latent image forming means is provided. In a developing method in which the electrostatic latent image is visualized by a developing means provided on the downstream side in the rotation direction of the electrostatic latent image carrier, a non-magnetic one-component developer is used for at least the developing means for the second and subsequent colors, A bias voltage in which the electrostatic latent image carrier and the developer carrier are arranged in a non-contact state to face each other, and the developer carrier is superimposed with direct current and alternating current,
The maximum value of the voltage is V _MAX , the minimum value is V _MIN , the potential of the non-image portion of the electrostatic latent image carrier is V _BKG , the surface potential of the image portion developed by the developing means in the preceding stage is V _DDP , V _TH is a predetermined potential difference required for the developer of the image portion developed by the developing means to fly back from the electrostatic latent image carrier to the developer carrier, and in the case of regular development, V _MAX <V _Apply a bias voltage set so that _DDP + V _TH V _MAX -V _BKG ≈ V _BKG -V _MIN, and in the case of reversal development, V _MIN > V _DDP + V _TH V _MAX -V _BKG ≈ V _BKG -V _MIN To do. To configure.

Action According to the present invention, the force for separating the developer from the electrostatic latent image carrier onto the electrostatic latent image carrier is applied to the potential of the developer and the developer carrier of the developing means. Depending on the potential difference from the developing bias, if V _MAX -V _DDP is smaller than V _{TH in} the case of regular development, V _MIN -V _{DDP in} the case of reversal development.
Is larger than V _TH , the developer in the image area developed by the developing means in the former stage does not return and fly from the electrostatic latent image carrier to the developer carrier.

Therefore, in the present invention, by applying the bias voltage set as described above to the developer carrying member, the developer in the image portion developed by the developing unit in the preceding stage does not fly back.

Embodiment An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows an embodiment in which the present invention is applied to a two-color printer.

As the electrostatic latent image carrier 11, a Mylar (trade name) wound around an aluminum drum with a thickness of 50 μm is used, and the electrostatic latent image forming means uses ion flow control as shown in FIG. The mold writing heads 13 and 14 were used. The ion flow control type write heads 13 and 14 have an aperture 15
The flow of ions is turned on / off depending on the direction of the electric field applied to the electrostatic latent image carrier 11 to form an electrostatic latent image. In the figure, 16 is a dielectric, 17 and 18 are electrodes, 19 is a wire, 20 is a high-voltage power supply, 21 is a shield, and 22 is an ion flow control pulse.

The process will be described in order. First, the precharge scorotron 12 uniformly charges the Mylar surface of the electrostatic latent image carrier 11 to -1600V. Next, the electrostatic latent image for the first color is formed by the ion flow control type write head 13. The image portion potential is -800V. Then, the electrostatic latent image is developed with the first color toner of the first color by the developing device 4 on the downstream side of the ion flow control type writing head 13. In this embodiment, two-component magnetic brush development (black)
However, the developing method may be any method. In this case, the surface potential of the image area after development is about -900V, as shown in FIG.

Then, an electrostatic latent image is written on the Mylar surface by the ion flow control type writing head 14 for the second color. At this time, the image portion potential is −800V. This electrostatic latent image is developed by the developing device 6 with the second color toner of the second color. Second
A non-magnetic one-component developer (blue) is used as the developer of the color toner, and the developer layer thickness on the developing roll 26 is set to about 1 to 2 layers by the pressing blade 23 as shown in FIG.
The developer is negatively charged. The developer layer thickness is 4 layers or more (about 50
If it is more than 1 μm), the charging property will be deteriorated, so the developer layer thickness is preferably 3 layers or less. Reference numeral 24 is a developer, 25 is a housing, 27 is a rotating direction of the developing roll, and 28 is a bias power source.

Development bias is AC1.6kVp-p, DC-at 2kHz.
The one with 1600V superimposed is used. Frequency is 1k
If it is less than Hz, fogging occurs on the back, and if it exceeds 3 kHz, the cost of the power source and the like increases, so that it is desirable to be between 1 kHz and 3 kHz. The peak value of the developing bias is applied in the state shown in FIG.

Thus, the peak value of the developing bias a is set to a value lower than the voltage (threshold) applied to the electrostatic latent image carrier 11. That is, as shown in FIG. 5, the maximum value of the voltage of the developing roller 26 with the back electrode of the electrostatic latent image carrier 11 as a reference is V _MAX , the minimum value is V _MIN , and the image portion developed in the previous stage is Let V _{DDP be} the potential, V _{BKG be the} non-image part, and V _TH be the potential difference at which the developer returns from the electrostatic latent image carrier 11 to the developing roll 26, then V _MAX <V _DDP + V _TH V _MAX −V Set so that _BKG ≈ V _BKG -V _MIN . In this case, the regular development,
In the case of inversion, it is set such that V _MIN > V _DDP + V _TH V _MAX −V _BKG ≈V _BKG −V _MIN .

At this time, the second-color blue developer is developed during the first-color development, but black is lost to black in the fixed image.
There are few problems with fixed images. Further, the blue developer attached to the background portion of the electrostatic latent image carrier 11 contains the developer carrier 2
Since the electric field pulled back to 6 acts, the electrostatic latent image carrier 1
Fogging of the background portion of 1 hardly occurs.

The peripheral speed of the developing roll 26 is the same as the process speed of the electrostatic latent image carrier 11 such as 1 cm / sec.
Is rotated in the opposite direction to the electrostatic latent image carrier 11. It is not preferable to set the peripheral speed of the developing roller 26 to 1.5 times or more the peripheral speed of the electrostatic latent image carrier 11 because the image quality is deteriorated. If the peripheral speed of the developing roller 26 is slower than that of the electrostatic latent image carrier 11, the toner will be insufficient and the developing density will not be produced.

The gap between the developing roller 26 and the electrostatic latent image carrier 11 is 200 μm.
It is set to m. This is because if the distance is 50 μm or less, it is difficult to maintain the distance, and if it is 400 μm or more, the image quality is deteriorated due to the defective flying of the developer.

After completion of development with the two color toners on the electrostatic latent image carrier 11, the development is transferred onto the paper sent from the paper feed roll 30 by the transfer device 8, and the transferred image is transferred downstream. It is fixed by the fixing device 9 on the side.

The developer remaining on the electrostatic latent image carrier 11 is cleaned by the cleaner 10.
Then, the electrostatic latent image carrier 11 is ready for the next print cycle.

In this embodiment, no color mixture was found in the blue developing device 6 even after printing 10,000 sheets. In this embodiment, the developing bias in the case of regular developing (see FIG. 5) has been described.
It goes without saying that the present invention may be applied to the developing bias in the case of reversal development, and in this case, the developing bias as shown in FIG. 6 can be set.

FIG. 7 shows another embodiment of the present invention, which has three developing units of cyan, magenta and yellow, and as shown in Table 1, black, red, yellow and a total of three colors are provided. A print sample is obtained.

In FIG. 7, 32 is a developing device for cyan, 33 is a developing device for magenta, 34 is a developing device for yellow, and 35, 36, and 3.
Reference numeral 7 is an ion flow control type write head corresponding to each developer, and since the other components are substantially the same as those in FIG. 2, the same reference numerals are given and their description is omitted.

The application states of the developing biases of the developing devices for the second and subsequent colors, that is, the developing device 33 for magenta and the developing device 34 for yellow in this case are the same as those in the embodiment shown in FIG.

The present invention is not limited to the above-described embodiments, and for example, a photoconductor may be used for the electrostatic latent image carrier and a laser may be used for the electrostatic latent image forming means. .

EFFECTS OF THE INVENTION By adopting the developing method according to the present invention, it is possible to reliably prevent the developer of the image portion developed by the developing device of the first stage from flying and mixing into the developing device of the second and subsequent stages. Like

[Brief description of drawings]

FIG. 1 is a graph showing a state of a developing bias in an embodiment of the present invention, FIG. 2 is a schematic configuration view showing an embodiment of a two-color printer to which the present invention is applied, and FIG. 3 is its ion flow control type writing. FIG. 4 is a schematic perspective view showing a head, FIG. 4 is a schematic configuration view showing a developing device, FIGS. 5 and 6 are graphs showing the state of the developing bias in the case of normal development and reversal development, and FIG. 7 is a book. FIG. 8 is a schematic configuration diagram showing another embodiment of the invention, and FIG. 8 is a schematic configuration diagram showing a conventional example. 4, 6 ... Developing device, 8 ... Transfer device, 9 ... Fixing device, 11 ... Electrostatic latent image carrier, 13, 14 ... Ion flow control type writing head, 26 ... Developing roll (developer carrier), 28 ... Bias power supply.

Claims (1)

[Claims] 1. At least two or more electrostatic latent image forming means are arranged around the electrostatic latent image carrier, and each electrostatic latent image forming means is provided on the downstream side in the rotation direction of the electrostatic latent image carrier. In the developing method for visualizing the electrostatic latent image by the developing means provided,
A non-magnetic one-component developer is used for at least the developing means for the second and subsequent colors, and the electrostatic latent image carrier and the developer carrier are arranged opposite to each other in a non-contact state, and a direct current is applied to the developer carrier. And a bias voltage superposed with an alternating current, the maximum value of which is V _MAX , the minimum value of which is V _MIN , the potential of the non-image portion of the electrostatic latent image carrier is V _BKG , and the developing means of the preceding stage is used for development. Let V _{DDP be} the surface potential of the image area, and V _{TH be the} predetermined potential difference required for the developer of the image area developed by the developing means in the preceding stage to fly back from the electrostatic latent image carrier to the developer carrier. In the case of regular development, V _MAX <V _DDP + V _TH V _MAX −V _BKG ≈V _BKG −V _MIN, and in the case of reversal development, V _MIN > V _DDP + V _TH V _MAX −V _BKG ≈V _BKG −V A developing method characterized by applying a bias voltage set to be _MIN .