JPS58102249A - Two-color electrophotographic method - Google Patents

Abstract

PURPOSE:To obtain sharp two-color copies by performing secondary development with an another developer having the developing threshold potential larger than the potential after finishing of primary development. CONSTITUTION:A photoreceptor 10 produced by laminating a photoconductive layer 2 and a transparent insulation layer on a conductive substrate 1 is subjected to primary charging with a Corotron 7 and at the same instant of primary exposure through a filter 5 of a complimentary color to the specific color to be reproduced, the secondary charging of the polarity reversed from that of the primary charging is applied thereupon with a Corotron 8. The photoreceptor is subjected to secondary exposure through a filter 6 that permits the transmission of only the specific color to be reproduced with the Corotron 8, and only the specific color is developed primarily with a developing machine 9. The photoreceptor 10 which is finished of the primary development is subjected to tertiary exposure with a lamp 11 for full surface exposure then to the secondary development with an another developer having the threshold potential larger than that of the potential after finishing of the primary development in a developing machine 12.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a two-color electrophotographic method for producing a photoreceptor in which a photoconductive layer and a transparent insulating layer are laminated on a conductive support.

One method conventionally known as grosses, which uses a photoreceptor with a three-layer structure to obtain a two-color copy from an original consisting of two colors, such as black and red, has been described using a photoconductive layer of PII for convenience.
About the case of obtaining a two-color copy from a two-color original consisting of red and black! Beak.

(1) A photoreceptor formed by successively laminating a conductive support 1, a photoconductive layer 2, and a transparent insulating layer 3 is first negatively charged as shown in FIG. 111.

G? ) Next, red cut filter (blue filter)
Positive charging (secondary charging) at the same time as performing image exposure through 5
(See Figure 2). The red color is cut off by the blue filter, so only the white color is exposed. That is, in the white portion, the photoconductive layer becomes conductive, and the positive charges of the photoconductive layer are discharged to the conductive layer 111. Therefore, the secondary charging is performed to such an extent that the charge on the white portion disappears. At this time, in the red and black areas, the secondary charge is positive, so some of the negative charges on the transparent insulating layer are neutralized, and as a result, the apparent potential of the surface area becomes photoconductive. It becomes positive due to the influence of the number of positive charges in the layer.

0) Next, secondary image exposure is performed through the red filter 6 (see FIG. 3). As a result, light passes through the red part, the photoconductive layer becomes conductive, and supersaturated positive charges are discharged to the conductive layer side relative to the negative charges on the transparent insulating layer.
The numbers of positive and negative charges match, and the influence of negative charges near the surface ImK increases, so the apparent surface potential of the red portion becomes a turtle.

In the steps 0) to C) above, when the potentials of the black and red parts are based on the white part (zero potential), the black part has a positive potential and the red part has a negative potential, resulting in the senkumetry curve shown in Figure 4. It will be done.

(4) Next, the latent image obtained in steps 0) to 0) is developed.The developing method involves uniformly exposing the entire surface to light after developing with a positively charged red toner. A known method is to invert the surface potential of a material from positive to negative and develop it with a black toner having a positive charge. In this method, first, development is performed with a red toner having a positive charge. As a result, as shown in FIG. 5, the surface potential of the red portion is neutralized by the red toner, and the state changes from the solid line to the broken line.

Next, the entire surface is uniformly exposed. Due to the uniform exposure of the entire surface, the surface potential of the black area is reversed from positive to negative as shown in Figure 6.
Next, development is performed using a black toner having a positive charge.

Next, transfer is performed.

Since the polarity of the red and black toners are both positive, the negative D
Transfer with a C corotron.

The above is an overview of conventional glosses, but there were problems with the conventional methods when developing with black toner. In other words, if we consider the development bias when developing with black toner and the area developed with red toner, the red toner that is developed in the final stage has a positive charge, whereas in the case of conventional When a 3jl1m agent having a development sensitivity (power, TO7 potential) corresponding to the charge of this red toner is used, the red toner having completed the KiA image is attracted to the negatively charged carrier of this IIL developer, As a result, the area developed with red toner is cleaned, and the development threshold potential for black development is V in FIG.
If the value of C is closer to hll than the value of C, black toner is additionally developed in the red area, making it impossible to obtain a clear two-color copy.

The present invention aims to solve the problems of such conventional methods.

The purpose of the present invention is to (1) uniformly charge (-order charge) a photoreceptor formed by laminating a Wako conductive layer and a transparent insulating layer on a conductive support, and Q) charge a complementary color to a specific color to be reproduced. Simultaneously with image exposure (-missing exposure) through a filter, the above-mentioned -
C) perform image exposure (secondary exposure) through a filter that transmits only the specific color to be reproduced; (4) develop only the specific color; (5) After the end of the first development T, the entire surface of the photoreceptor is uniformly exposed (tertiary exposure); (6) After the end of the first development with the specific color toner. This can be achieved by a two-color electrophotographic method characterized by development (secondary development) with another 1jtfII agent having a development threshold potential (absolute value) greater than the potential (absolute value) of .

Hereinafter, for convenience, the present invention will be described with a specific color as red and another specific color as black. (1) Apply negative uniform charging (-order charging), (2))
Positive charging (secondary charging) is applied at the same time as image exposure (-missing exposure) through a blue filter, O) Secondary exposure is applied through a red filter, (4)
) Develop the # area corresponding to red with red toner (not necessarily red, but other color toners are also acceptable) (-next development), (5) After uniformly exposing the entire surface, the red color of the developed area It consists of developing (secondary development) with a positively charged black toner having a vh development threshold (power, to7 potential) larger than the electrostatic contrast of the white part and the white part.

In other words, the present invention uses a threshold potential (power,
This method solves the above-mentioned problems by performing secondary development using a developer having a diameter of 7 mm. To explain more specifically with reference to FIG. 7, if the development threshold potential of the developer used for secondary development is set higher than Vc on the negative side, the red toner after primary development becomes electrically 17-ning during secondary development. Moreover, no additional development occurs in the red area, and a good two-color copy can be obtained.

Incidentally, such Vc can be obtained by adjusting the amount of charge of a two-component toner, but this is particularly difficult if a toner containing, for example, 35 weight of magnetite is used.

The present invention will be explained below with reference to Examples.

Using the apparatus schematically shown in Example No. 1, after developing a red color using a two-component red developer using sensitometry as shown in Figure 9, uniform exposure of the entire surface is carried out, and the surface potential of the photoreceptor becomes It looked like the 1θ diagram.

A black developer consists of a conductive carrier with a particle size of 1 GG and a widely used insulating toner (non-magnetic toner), and a conductive carrier with a particle size of 100 m and magnetite with a 35-fold weight. Two types of toners were made. FIG. 11 shows the development characteristics of two types of fAgII agents. A copy test was conducted using these two types of developers as black developer agents.

In the case of a developer containing ordinary insulating toner, the black development bias voltage is set to 15 ov or more in order to prevent the white part from overlapping when developing the black part, and -200 V when considering low density reproduction. Although it was necessary to do this, the red image was subjected to a considerable cleaning action.

On the other hand, in the case of the developer containing magnetic toner, a good two-color copy was obtained without applying a black bias voltage, without additional development, and with no cleaning of the red area.

As described above, in two-color electrophotography by the method of the present invention! - A novel method has been provided that can obtain a second lm1g1 without causing the first, JJ-obtained image to be misprinted.

Note that the direction of charging in the present invention is due to the photoconductor, and there is no problem even if the direction is opposite to that described in this specification.

[Brief explanation of drawings]

Figures 1 to 3 are explanatory diagrams when forming a red corresponding agR in red/black two-color electrophotography, Figure 4 is a seven-knot metrology line of a red corresponding latent image, and Figure 5 is a graph showing potential curves before (solid line) and after development (broken line) of a red-corresponding latent image, FIG. 6 is a potential curve before secondary development, and FIG. 7 is a potential curve after secondary development. Start developing the developer when carrying out I! Fig. 8 is a schematic diagram of the apparatus used in the method of the present invention, and Figs.
FIG. 11 is also an explanatory diagram of an embodiment of the method of the present invention. Reference numeral 21 in the figure: Conductive support: 2: Photoconductive layer; 3: Transparent insulating layer; 4: Original; 5: Blue filter; 6
... Red filter; 7.8... Charging corotron; 9... Red developing device; lO... Photoreceptor; ll...
Full exposure rung; 12...Black developing machine; 13...
Bre transfer corotron; 14... transfer corotron; 15...-recording paper; 16... static elimination corotron;
17... Cleaning device: 18... Static elimination rung. Figure 1611 Figure 2 1311 Figure 5 Figure 7 m 1118 Figure 11 WJ

Claims (1)

[Scope of Claims] A photoreceptor formed by laminating a photoconductive layer and a transparent insulating layer on a conductive support is: 0) uniformly charged (-order charging); e) complementary color to the 11 specific colors to be reproduced; (3) Image exposure through a filter that transmits only the specific color to be reproduced. Simultaneously with image exposure (-missing exposure) through a filter, charging with the opposite polarity to the above-mentioned secondary charging (secondary charging) is performed. (Secondary exposure), (4) Develop only the specific color (-Next development, process) After the completion of the first development, uniformly expose the entire surface of the photoreceptor (Third exposure), (6 ) Developed with another OIA developer having a potential greater than the potential after the completion of the first development (second development II).
) A two-color electrophotographic method.