JPS6349776A - Dichroic electrophotographic copying method - Google Patents

Abstract

PURPOSE:To obtain an image with high resolving power without any reduction in copying speed by charging photoconductive layers of a composite photosensitive body electrostatically to the mutually opposite polarities and performing dichroic exposure, and charging the photoconductive layers to the same polarity and performing B-color exposure while cutting off light of color A. CONSTITUTION:When a dichroic copy of, for example, red and black is taken, photoconductive layers 10B and 10C are charged electrostatically to the opposite polarities as shown in a figure (c) and the dichroic exposure is performed by red exposure and secondary electrostatic charging. Consequently, charges at a black part disappear, and a latent image corresponding to a red part is formed on the surface of the photosensitive body and developed with red toner TR. In a black process, the photoconductive layers are charged to the negative polarity integrally as shown in a figure (g) and exposed while red light is cut off by a red filter to form a latent image of the black part on the surface, the image is developed with black toner TN and both images are superposed one over the other. Consequently, latent images are all surface latent images and the quantity of light is used sufficiently to obtain a high-resolution image without any reduction in copying speed.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a two-color electrophotographic reproduction method.

(Prior art) A composite photoreceptor in which two photoconductive layers with different spectral sensitivities are laminated on a conductive substrate at a temperature of ℃? A two-color electrophotographic copying method for copying 12-color manuscripts using
No. 348], and Multi-color Copying Method (July 1986)
Patent application (5) dated May 21st is known.

However, in the former two-color electrophotographic copying method, the secondary M electric process on the surface of the photoreceptor is caused by the light I8! The image (M
There was a drawback that the K-light simultaneous reverse charging process was complicated and the demolition ability was reduced.

On the other hand, the latter multi-color copying method was proposed to eliminate the above-mentioned drawbacks, but the photoconductive layer 1-2 of the composite photoreceptor is on the longer wavelength side of color A in the visible wavelength range. Since it does not have photosensitivity to half or the short wavelength side, only half the amount of light of color A can be used when forming the latent image, and while resolution is improved, the copying speed is halved. was there.

(Objective) An object of the present invention is to provide a two-color electrophotographic copying method that can obtain a copying channel with high resolution without reducing the copying speed.

(Structure) The non-invention is the eleventh point of the above composite photoreceptor. After charging the photoconductive layers of spear 2 to opposite polarities and approximately equal potential, a two-color original consisting of A and B colors was subjected to backlighting to form an electrostatically deposited image corresponding to the CA color image. A that forms and develops this #electronic latent image.
After the color development process and the second photoconductive layer are charged to the same polarity, the two-color original image IX! is passed through a color A filter that blocks light from the color A image. An 8-color development process in which an electrostatic latent image corresponding to a B-color image is formed by exposure, and this latent image is developed while applying a bias voltage that cancels out the residual potential of the photoconductive layer of the tooth 2. The special feature is that it has .

Here, the composite photoreceptor (hereinafter simply referred to as photoreceptor) is:
A first photoconductive layer and a second photoconductive layer are laminated in this order by VC on a conductive substrate at a temperature of .degree. The first photoconductive layer has panchromatic photosensitivity to at least A color. The photoconductive layer of Spear 2 has no photosensitivity to A-color VC.

Here, color A indicates one of the chromatic colors (usually red, back, green, etc.) that forms the image of the two-color original that is exposed to image 1.

Further, the color B indicates another chromatic color or an achromatic color (usually black) that forms an image other than the color A of the two-color original.

On the other hand, the city images obtained by the A-color development process and the 8-color development process are different in color from each other, and are sequentially transferred onto the same transfer paper by aligning their relative positions.

Here, the colors of each of the above visible images are generally matched to the colors of the image of the two-color original, but depending on your preference,
The color should be a different color from the color of the original image.

In addition, when the development in each development process is performed by a dry development method, the town fl! A fixing step is required to fix the image. This fixing of the visible image is performed sequentially each time one of the visible images (color A or color B) is transferred.
Alternatively, it may be performed at once after transferring both visual images.

Further, as for the A-color original image process and the 8-color original image process, whichever process is performed first may be carried out at any temperature.

Hereinafter, the present invention will be specifically described based on an illustrated embodiment.

℃, the photoreceptor 10 has a first photoconductive layer 10B on a conductive substrate 10A, and a photoconductive layer 10C on the second photoconductive layer.
The temperature becomes ℃. As will be explained later with reference to FIG. 5, the photoreceptor 10 is normally formed in the shape of a drum, but in FIG. 1, it is shown as a flat plate to simplify the explanation.

Note that the photoreceptor 10 is formed into a belt shape and has a good temperature.

In this example, the conductive substrate 10A was an aluminum drum.

The first photoconductive layer 10B is required to have panchromatic spectral sensitivity, and its materials include Se-Te alloy, A
s25e3 etc. can be used, but in non-example,
As25e3 is deposited on the conductive substrate 10A to a thickness of 60 mm.
It was formed by μmVC vacuum evaporation.

The second photoconductive layer 10C has a two-layer structure of a general KCGL (carrier generation layer) and a CTL (carrier transport layer).
Color A can be selected by using C and selecting a CGL pigment, and in this example, azo pigment / polyester resin =
371 (wt ratio) with tetrahydrofuran to a thickness of 0.1
A 20 μm thick VC coating was formed using tetrahydrofuran with a carrier transport substance/boccal carbonate resin = 171 (wt ratio) at 1 μm on the first photoconductive layer 10B. It was formed by overcoating with a dipping method via an intermediate layer made of resin.

Therefore, the temperature of the first photoconductive layer 10B in this example is
has a panchromatic spectral sensitivity as shown, for example, by curve 2-1 at °C in Figure 2.

In addition, the photoconductive layer 10C of the spear 2 is
As shown in 2-2, it has photosensitivity to light of K 400 to 580 nm, and as shown in curve 2-5') vc
It has a spectral sensitivity and spectral transmittance that transmits 90% or more of light with a longer wavelength than that of 500 plates.

As is clear from Figure 2, the second photoconductive layer 10C is
It has no photosensitivity to long wavelength light, that is, red light. The color A in this example is red, and the color B in this example is red.
Colors can be chromatic or achromatic colors other than red. Hereinafter, the above color A is red and the color B is black, and a red developing step of developing a red image of a two-color original with red toner;
A black developing process in which a black image of a two-color original is developed with black toner will be described as an example.

In the red developing process, first the photoreceptor 10? , while being exposed to red light, it is charged to a negative polarity (hereinafter referred to as primary charging).

As a result, as shown in FIG. 1(a)K, the negative charge is
uniformly distributed on the surface of the photoconductive layer 10C17).

Here, the first photoconductive layer 10B is normally positively charged and the second photoconductive layer IOC is negatively charged; It is possible. This is because red light generates carriers in all layers of the first photoconductive layer 10B.

Further, the intermediate layer is a blocking layer, which blocks carriers in a weak electric field or leaks carriers in a high electric field. The carriers blocked here are trapped and create a reverse electric field in degrees Celsius, and do not move even in degrees Celsius.

On the other hand, due to the above-mentioned primary charging and red exposure, holes are easily injected from the conductive substrate 10A into the first light 4 to layer 10B and move through the first photoconductive layer 10B.
．． Spear 2 Light Guide'4. Holes balanced by the negative charge on the surface of /*10c are induced at the boundary between the first photoconductive layer 10B and the photoconductive layer 10C of the fang 2 and are etranoped.

As a result, an electric double layer of positive and negative charges π is formed through the photoconductive layer 10C of the spear 2 at ℃. If we compare this state to a capacitor, we say that the second photoconductive l11ioc is charged. In this state, the charging potential appears as the photoreceptor surface potential in °C. In this example, the charging potential due to primary charging was set to -2200 cm.

Next, the photoreceptor 10 is positively charged (hereinafter referred to as secondary charging). The positive charge imparted by this cancels out the negative charge on the surface of the photoreceptor, so the holes dragged to the boundary between the first photoconductive layer 10B and the photoconductive layer 10C of the spear 2 are transferred to the photoreceptor. The negative charges, which are in excess of the negative charges on the surface and balanced by the excess positive charges, form the conductive substrate 10A and the conductive layer 1. It is induced at the boundary between OB and °. (Figure 1(b)).

This state includes the 1,1'F10 element conductive layer 10B and the 1?
A state in which an electrical double layer is formed through the second photoconductive layer 10C, that is, the first and second photoconductive layers 10B, 10
Both photoconductive layers 10B and IOC' are charged, but the directions of the electric fields in each photoconductive layer are opposite to each other. It is said that it was done. In this example, the charging potential in the queen state is +800V for the first photoconductive layer 10B and +800V for the second photoconductive layer 10B.
C & -700V. Here, j! 2 photoconductive layer i
The potential of oc is the first and second photoconductive layers 10B and 1oet.
Among the c-blocked holes, -holes leak without being trapped, so even if the absolute values of the potentials of these photoconductive layers are added together, they do not equal the potential at the time of primary charging. The surface potential of the photoreceptor at this time is +100VVc.

Continuing with "C5" As shown in FIG. 1 (C) VC, the light image of the two-color original O is used to illuminate the photoreceptor 10 with "CC image". Here, since the photoreceptor surface potential corresponding to the black image (including gray and non-red images) of the two-color original O has the same optical comfort as the first and second photoconductive layers 10B and IOC, The charge disappears at the same rate, +100 V~Ov
It became. In addition, the white background area (non-image area) of the two-color original ◯ [the corresponding photoreceptor surface potential was −50 V because there was a large residual potential in the photoconductive layer 10B of 21. Furthermore, the photoreceptor surface potential corresponding to the red image of the two-color original O is such that the first photoconductive layer 10B has no photosensitivity to red light, and only the photoconductive layer of the fang 2 loses its charge. It became -600V.

In this way, according to the position distribution of -600V,
An electrostatic latent image corresponding to the red image & IVC is formed.

By developing this electrostatic latent image with positively charged red toner TR (Fig. 1 (d)), a visible red image on the surface of the photoreceptor 10 is obtained.

In this example, the town tax statue above? : Vc transfer on transfer paper S (
(Fig. 1 (f)
) L-C1 red copy imager R.

On the other hand, the photoreceptor 10 undergoes a static elimination and cleaning process at
111 preparations are made for the next black development process.

In the black color development step, first, the photoreceptor 10 is primarily charged to a negative polarity without being exposed to red light. yi, photoconductive layer 10B of spear 2
, 10C as one unit, and the photoreceptor surface potential is -1200V.
(Fig. 1 [g]) At this time, some of the holes are injected from the conductive substrate 10A to the first photoconductive layer 10BVC, but most of the holes are blocked at the interface. Ru.

Next, as shown in FIG. 1(h) VC, image exposure is performed using the light image of the two-color original O through the red filter F. Here, the second photoconductive layer 10C has a temperature curve 2 in Figure 2.
Since it has a spectral transmittance as shown by −3, the surface potential of the photoreceptor corresponding to the white background portion and red image of the two-color original O is canceled due to the charged state of the second photoconductive layer 10C. The voltages were -600V and -650V, respectively. In addition, the photoreceptor surface potential corresponding to the black image of two-color original O is approximately zero)
Since it was in a light state, the voltage was -1150v.

At this time, since the photoconductive layer 10C of the fang 2 has no photosensitivity to red light, the residual potential on the surface of the photoreceptor exhibits a relatively large value.

Therefore, as shown in FIG. 1(i) Ic, the electrostatic latent image corresponding to the black picture card formed by the surface potential distribution of -1150 . A visible black image is obtained on the surface of the photoreceptor 100 by developing with the positively charged black toner TN while applying a bias voltage of . By transferring this visible image onto the transfer paper S (FIG. 1(j)) and then fixing it [FIG. 1(k)], a black copy image (, I N) is obtained.

In the above-mentioned example, copy images with high resolution of 5 lines/dragon or more were obtained for both the red copy image maintenance R and the black copy image IN.

FIG. 6 illustrates a specific copying apparatus for carrying out the above process.

In FIG. 16, a drum-shaped photoreceptor 10 is rotatably supported by the main body of the apparatus, and is rotated at a constant speed in the direction of the arrow by a drive device (not shown) during copying.

The photoreceptor 10 is negatively charged by the lamp charger 11VC so that the surface potential becomes -2200V.

At this time, a discharge voltage of -7,000V is applied to the charger 12, and the pipe 16 is turned on.

After a while, the charger 141 to which a discharge voltage of +5.0 KV was applied (the surface potential of the photoconductor 10 became +
Charged to 100 ■, continued ℃, two-color original ○
The image is exposed by a known exposure optical system 15 that exposes a light image. Further, the red filter F is arranged so as to be able to enter and exit the exposure light beam by a known appropriate means, and is withdrawn from the exposure light beam during the image exposure. As described above, the silent ts image formed by this image exposure is an a image corresponding to a red image, and this electrostatic latent image is developed with red toner by a red developing device ffi 16Vc. The red visible image formed on the photoreceptor 10 is transferred onto the transfer paper S using this red toner. In other words, the transfer paper S is fed from a cassette (not shown) by a well-known paper feeding means, and is fed by registration rollers 17 to a transfer section 18 that is synchronized with the movement of the red discharged image, and then transferred to the transfer unit 18. The negative polarity corona discharge of 19 causes electrostatic transfer of the red visible image.

The transfer paper S on which the red visible image is transferred is transferred to the fixing device 20 2. After one visible red image has been fixed, it is stocked in the °C stocker 22 through the return sub-transport path 21.

On the other hand, the photoreceptor 10 that has undergone the above-described copying process is neutralized by a static eliminator 23 and then cleaned by a cleaning device 24 to prepare for the next process.

This photoreceptor 10 has a lamp charger 1iVc.
It is negatively charged so that the surface potential becomes -1200V.

At this time, a discharge potential of -5.7 KV is applied to the charger 12, and the lamp 16 is turned off.

℃, the photoreceptor 10 receives image exposure of the light image of the two-color original 0. At this time, the red filter F enters into the exposure light flux, and as a result, an electrostatic charge a ('iA) corresponding to a black image is formed at a temperature of ℃ and as per the spinning speed. A black toner is developed from a black developing device 25Vc while applying a bias mineral pressure of 700V.The black visible image formed on the photoreceptor 10 by this black toner is different from the red visible image. The transfer paper S that is transferred onto the fixed transfer paper S, that is, the transfer paper S that has been stocked in the stacker 22, is transferred by the paper feed roller 26 to the sub-conveyance w521.
℃, the registration roller 171/C direction is fed again, and from this registration roller 17Vc, it is sent to the transfer unit 18 in synchronization with the movement of the black town inspection team, and the transfer unit 1
9, a black visible image is transferred by the negative corona discharge.

The transfer paper S on which the black visible image has been transferred is transferred to the king conveyance path 27.
After the black OJ visual image is fixed by the fixing machine 20, it is discharged from the copying machine. On the other hand, the photoreceptor 10
As described above, after going through the static elimination and cleaning processes, the series of copying processes is completed in preparation for the next copying.

In the above embodiment, if there is VC rectification between the conductive substrate 10A of the photoreceptor 10 and the first photoconductive layer 10B, red exposure, In other words, the lamp 16 does not have to be turned on.

(Effect) As is clear from the process, static 11LMI&! corresponding to one mound of each color. is formed by one surface latent image, and a sufficient amount of light can be obtained when forming the latent image, so a copied image with high release force can be obtained without reducing the copying speed.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining one embodiment of the two-color electrophotographic copying method according to the present invention, and FIG. 2 is a diagram showing the spectral sensitivity and spectral transmittance of the composite photoreceptor in the above embodiment. FIG. 6 is a schematic diagram of a copying apparatus showing an example of a device for carrying out the copying method in the above embodiment. 1u...The photoreceptor, Q...2-color original, F...filter, S...transfer paper, IOA...conductive substrate,
10B... First photoconductive layer, 10C... Spear 2 photoconductive layer, 11... Lamp charger, 14... Charger, 15... Exposure optical system, 16... Red current. 17... Registration roller, 19... Transfer device,
TR...Red toner, TN...Black toner. % (2

Claims (1)

[Scope of Claims] A first photoconductive layer having photosensitivity to at least color A is provided on a conductive substrate, and the first photoconductive layer also has photosensitivity to color A. A two-color electrophotographic copying method using a composite photoreceptor having a second photoconductive layer having a second photoconductive layer, the first and second photoconductive layers of the composite photoreceptor having polarities opposite to each other and approximately equal to each other. After being charged to a potential, the two-color document consisting of the A color and B color is imagewise exposed to form an electrostatic latent image corresponding to the A color image, and this electrostatic latent image is developed. After charging the first and second photoconductive layers of the composite photoreceptor to the same polarity, the two-color original is image-exposed through an A-color filter that blocks the A-color image to form a B-color image. a B color development step of forming an electrostatic latent image corresponding to the second photoconductive layer and developing this electrostatic latent image while applying a bias voltage that cancels out the residual potential of the second photoconductive layer; A two-color electrophotographic copying method comprising a transfer step of sequentially transferring visible images of different colors obtained by a color development step onto the same transfer paper while adjusting their relative positions.