JPS5935020B2 - Electrostatic latent image transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic latent image transfer device used in an electrophotographic copying machine.

In an electrostatic latent image transfer type electrophotographic copying machine, the surface potential of the photoreceptor darkly decays after being charged as shown in FIG. In the Leon mixture, it changes as shown in Figure 2.

When an electrostatic latent image is transferred, the surface potential of the photoreceptor darkly decays as shown in Figure 3a, whereas conventionally, a constant bias voltage is applied to the transferred member as shown in Figure 3a. Therefore, as shown in c in the figure, the transfer potential of the transfer member changes due to the dark decay, resulting in uneven image density. In view of these points, it is an object of the present invention to provide an electrostatic latent image transfer device that does not cause unevenness in image density.

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

As shown in FIG. 4, the original placed on the original placing table 11 is illuminated by illumination light sources 12 and 13, and the light rays from the original pass through a mirror 14, an in-prism lens 15, and a color separation filter 16. Slit exposure is performed on the photoreceptor film 17.

An optical system consisting of illumination light sources 12 and 13, a mirror 14, an in-prism lens 15, and a color separation filter 16 is a wire 1.
The color separation filter 16 is made up of a plurality of primary color or multicolor filters 20 to 23, and is driven by a motor through a motor 8 to move along a guide member 19 to scan the original. The light beams from the document are sequentially exchanged to separate the light beams into each color. The photoreceptor film 17 has one end fixed to the photoreceptor drum 24 and the other end fixed to the reel 25, and moves back and forth between the exposure position and the transfer position as the photoreceptor drum 24 and reel 25 rotate. When the photoreceptor film IT is moved to the exposure position, it is charged in advance by the charger 26 in front of it, and then exposed at the exposure position as described above to form an electrostatic latent image. Further, the photoreceptor film IT moves to the transfer position, contacts the transfer paper 28 between the photoreceptor drum 24 and the transfer drum 27, transfers the electrostatic latent image, and then is neutralized by the static eliminator 29.
A bias voltage is applied to the conductive layer of the photoreceptor film 17 by a transfer bias device 30 . This bias voltage is a voltage as shown in d in the figure, which increases in accordance with the dark decay of the surface potential of the photoreceptor film IT as shown in a in FIG. transfer paper 2
The transfer potential of No. 8 becomes uniform, and uneven image density is prevented.
The transfer paper 28 is pulled out from a roll 31 by a roller 32, cut into a suitable length by a cutter 33, and transferred to a transfer drum 27.
is clamped by a clamper 36.

When this transfer paper 28 passes between the transfer drum 27 and the photoreceptor 24, the electrostatic latent image is transferred from the photoreceptor film 17, and then it is developed with the developer from the developer tanks 37 to 40 at the development position. , unnecessary developer is absorbed by plotter roller 41 and dried by heaters 42 and 48. Further, each electrostatic latent image corresponding to each color separation of the color separation filter 16 is transferred to the transfer paper 28 in a superimposed manner every rotation of the transfer drum 27, and the developing tanks 37 to 40 are also transferred to the transfer drum 27.
The electrostatic latent image on the transfer paper 28 is sequentially moved to the transfer position every rotation, and the electrostatic latent image on the transfer paper 28 is developed with a developer of each color corresponding to the color separation, thereby reproducing a color image. When development is completed and a color image is reproduced from the transfer paper 28, the clamper 36 is removed by the clamp cam 43, and the transfer paper 28 is peeled off from the transfer drum 27 by the peeling claw 44.
It is transported by a heater 48 and a fan 49, and is dried by a cutter 50.
The transfer bias device 30 described above is configured as shown in FIG. 5, for example. That is, during transfer, switch SWl is turned on, relay RA operates, and transistors Tl, T2 and capacitor C are turned on.
1 to C3 and resistors R1 to R5 oscillates to generate a square wave, which is amplified by transistor T3. On the other hand, the capacitor C4 is short-circuited via the normally closed contact RA-b of the relay RA and the variable resistor R1, and the voltage between the terminals is O. When the relay RA operates, the current flowing through the transistor T3 and the current flowing through the resistor R6 A part of the voltage flows through the variable resistors VR2 to VR5 selected by the switch SW2 and is charged. As the charging voltage of the capacitor C4 increases, the emitter potential of the transistor T3 increases, and the square wave from the collector becomes smaller. This square wave is amplified by the transistor T4, passes through the flybutter transformer FT,
The voltage is converted into a DC voltage by a rectifier circuit consisting of a diode D, a resistor R7, and a capacitor C5. This DC voltage becomes a bias voltage as indicated by d in FIG. 3, which increases with time, and is applied to the conductive layer of the photoreceptor film 17 through the switch SW3. The switch SW3 is closed during transfer, and the switch SW2 is switched at each step of transferring each electrostatic latent image corresponding to each color separation of the color separation filter 16. Therefore, the transient characteristics of the bias voltage in each process can be adjusted by variable resistors R2 to VR5.
Further, the final value of the bias voltage can be adjusted by varying the emitter voltage of the transistor T3 using the variable resistor VRl. In addition, in FIG. 5, D2 and D3 are diodes, R
8 to Rl2 are resistors, and TH is a thermistor. Further, the present invention can also be applied to a full-surface exposure type color electronic copying machine as shown in FIG.

That is, in FIG. 4, an original on an original table 58 is illuminated by lamps 56 and 57, and an optical image from this original is exposed to the entire surface of the photoreceptor film 17 via a mirror 59, a color separation filter 60, and a mirror 61. It was designed so that In view of the above, according to the electrostatic latent image transfer device according to the present invention, a bias voltage that increases over time in accordance with the dark decay of the surface potential of the photoreceptor is applied to the conductive layer of the photoreceptor, so that transfer can be performed uniformly. It is possible to prevent uneven image density.

[Brief explanation of drawings]

Figure 1 is a dark decay characteristic diagram of the surface potential of the photoconductor after charging, Figure 2 is a diagram of the decay characteristic of the surface potential of the photoconductor from the time of charging to the time of transfer, and Figure 3 is an explanation of the transfer effect of the present invention. 4 is a schematic configuration diagram showing an example of a color electrophotographic copying machine to which the present invention is applied, FIG. 5 is a circuit diagram showing an example of a transfer bias device used in the present invention, and FIG. 6 is a circuit diagram showing an example of a transfer bias device used in the present invention. FIG. 2 is a schematic configuration diagram showing another example of a color electrophotographic copying machine to which the above-mentioned color electrophotographic copying machine is applied. 17... Photosensitive film, 24... Photosensitive drum, 27... Transfer drum, 30...
...Transfer bias device.

Claims (1)

[Claims] 1. A transfer means for sequentially bonding members to be transferred to a photoreceptor and transferring an electrostatic latent image on the photoreceptor to a transfer material, and a transfer means that transfers an electrostatic latent image on the photoreceptor to a transfer material, and an electrostatic latent image transfer device, comprising: a transfer bias device that uniformizes the transfer potential of the transfer target member by generating an increasing DC voltage and applying it to the conductive layer of the photoreceptor;