JPS607444A - Electrophotographic printing method - Google Patents

Abstract

PURPOSE:To improve the sharpness of an image by executing electrostatic charging to a specific polarity, exposure, corona discharging to the polarity opposite to that of the charging, and development on the surface of a photographic sensitive body, then performing the 2nd photoscanning exposure and the 2nd development. CONSTITUTION:The surface of the photosensitive drum 1 is discharged by a lamp 2 and a discharger 3 and electrified to about 1,200V by an electrifier 4, then while the 1st scanning exposure L1 is carried out with a laser beam, the surface is discharged to about 100V by an electrifier 5 which generates coronas. The 1st electrostatic latent image of a format part is formed in said exposure process and scanning exposure is performed with the laser beam L1. Then, the 2nd scanning exposure is executed by an optical modulator 11, rotary mirror 12, and image-forming lens 13 with a laser beam L2 corresponding to an electric signal to form the 2nd electrostatic latent image of a print part. Then, the photosensitive drum surface is exposed entirely. Further, said 1st latent image is developed by using the 2nd developing device 16. Consequently, red toner sticks the exposed part with the laser beam L1, and a low-potential part corresponding to the part of the scanning exposure L1 is also developed to improve the sharpness of the image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method, and more particularly to an image forming method for obtaining images based on different latent images.

Conventionally, two different types of latent images (
For example, the main proposal is to form a combination of a format frame, text information, or black text information, a red mark, and a seal (AS), and develop these with different color developers to create an image (1). has been done.

However, there are disadvantages in that color mixing occurs between different images, and furthermore, the previously formed phenomenon image is disturbed during subsequent development.

Figure 1 explains an example of the conventional portrait forming process, in which (■) to (V) indicate each culm, and L at each degree.
The side shows the surface potential of the photoreceptor at that time, and the previous state of the photoreceptor is shown on the side.

In the 11th step (I) of the 4th step, a photoconductive layer a of Se, etc.
, to the photoreceptor with the layer a2 provided with the corona (H;
IU+! :'; CTE, for example, +800 Vi, : Charging sequence, then the first exposure L of the image information of the former 71-, etc. at the second (II) I' level.

The surface potential of the exposed portion is attenuated to, for example, +50 V, and a first static latent image is formed.

Next, in step (III) L, a bias voltage (e.g., +400V (indicated by a broken line) is applied to reversely develop the exposed area.

In the step (IV) after the first development, a second exposure L2 of image information such as characters is performed on the photoconductor A, and the potential of the exposed area is attenuated to, for example, +50V, thereby forming a second electrostatic latent image. do. Next, in step (V), a bias voltage (for example, +40
0V + (indicated by a broken line) is applied to reversely develop the second exposed area.

In the above process, the red toner T (
Color mixing of black toner T(B) was likely to occur in the area developed with R). This is because even after the first exposed area was developed with red toner, the surface potential of that area was lower than that of the unexposed area, and therefore, the black toner was developed in the second development.

For example, when the unexposed area is +800V and the exposed area is +50V, after the first development, the potential of the exposed area increases by 2 due to the toner charge and becomes around +150V. Next, after the FF52 latent image is formed, when a +400V developing bias is applied and second development is performed, the second exposed area is sufficiently developed, but at the same time, a considerable amount of black toner is also developed in the first exposed area. . During this second development, set the development bias voltage sufficiently low so that the first exposed area is not developed (for example, ++5 (IV), the development of the second exposed area will be insufficient. Also, carriers may be present in the unexposed area. wear occurs.

Furthermore, the problem with the process shown in FIG.
(R) is the point that is taken as kakii^. This is because, in the second development, the magnetic brush formed by the second-order developer mechanically moves the red toner developing area tF71? What to do is L1 SuJ, but is it also A1 to the minus in the developer? The fact that the red toner with positive polarity is electrostatically attracted to the charged carrier also has an effect.

As a countermeasure to this problem, the developing bias voltage was changed to
1'? It has been proposed to increase the bias during the second development, but in order to prevent the above-mentioned black phenomenon in the red toner development area, there is a restriction on making the second development bias sufficiently high. , no satisfactory effect was obtained.

The present invention has been made in view of the above points, and provides an image forming method that can satisfactorily obtain images based on different latent images.

The following is a detailed explanation of the present invention.
I will explain as I go along.

FIG. 2 is an explanatory diagram of an example of an image forming apparatus that implements the method of the present invention.

1 is a conductive layer a3.1 made of aluminum or the like. It is a photosensitive drum having an electrophotographic photosensitive member on its surface, which basically consists of a photoconductive layer a2 such as CCTs and a surface insulating layer a1 such as polyester, and rotates in the direction of the arrow.

The surface of the photosensitive drum 1 is charged in advance by a lamp 2 and an AC static eliminator 3, and then charged to about +1,200 by a primary charger 4.
After being charged to V (Fig. 3 (1)), the first scanning exposure 1 is performed using a laser beam, and at the same time, the voltage is reduced to about -100 V by a secondary charger 5 that generates alternating current or negative polarity corona. It is removed (Figure 3 (2)).

In this secondary charging and simultaneous exposure step, a first electrostatic latent image of the format portion is formed. Scanning exposure using the laser beam L1 is performed by a laser light source 6, an optical modulator 7 that modulates the laser beam in accordance with a recorded image signal, a rotating mirror 8, and an imaging lens 9.

Next, the light 1jlO/LEDB 1 is converted into an electric signal t) by an optical modulator 11, a rotating mirror 12, and an imaging lens 13, which modulate the light 1jlO/LEDB 1 in accordance with another recorded image signal other than the above-mentioned signal. A second scanning exposure is performed using the corresponding laser beams 1 and 2, and a second electrostatic latent image of the printed portion is formed. The surface potential of the scanning exposure section is approximately +400V (Fig. 3 (
3)).

Of the two latent images obtained with this method, the second 1h image is first processed using a known secondary magnetic brush method in which a secondary developer TI consisting of a black toner of negative polarity and an iron powder carrier is used. 19 images are produced by the first developing device 1TO, which is a developing device.

As a result of this development, a black color I/N is deposited on the exposed area according to Zahi J.T. 7 (Figure 3 (4)).

Incidentally, the developer 111 of the developing device 14 has a holding body 1, for example, a sleeve 1.
4. DC power supply 14. The bias voltage applied from +4
A voltage between 00V and -100V is selected. This may be at ground potential.

Next, the entire surface of the photosensitive drum 1 is exposed to light by the lamp 15. With this full-surface exposure, 1c')? The potential of the scan-exposed part of the ff image becomes about -80 V, and the potential of the non-scan-exposed part becomes about +400 V (FIG. 3 (5)).

Next, the above-mentioned first latent image is transferred to a second developer J having an insulating II which is a red non-magnetic toner having a positive polarity and a developer T2. A developing method as described in JP-A No. 54-43038 (
Development is performed using a developing method in which an alternating voltage is applied as a bias voltage to a developer 11 carrier, such as a sleeve, and the developer is caused to fly back and forth between the developer carrier and the photoreceptor. As a result of this development, the red toner T2 adheres to the portion exposed by the laser beam L1 (FIG. 3(6)).

Second developer sleeve 16. The distance between the sleeve 16 and the photosensitive drum 1 is approximately 300 pLm, and a bias voltage is applied to the sleeve 16 by a power supply 162.
1.50011z・1,500Vp-p (530Vr,
1! , S) A DC component of r''300V is superimposed.

Due to the action of the alternating type W, the red I and the ner'I' move back and forth between the sleeve drums, and at this time, during scanning exposure, the areas where the potential is low are sufficiently developed. - The toner polarity of the black toner developing section T1 is negative, and C is also
The surface of the black toner developing section is raised to approximately +320V, which repels the positively charged red toner/long-earth effect?!), preventing color mixing.Also, black toner development There is a red toner in the area, like a brush.
Since there is no rubbing, there is no need to scrape off black toner.

Note that the sleeve 16 of the second developing device. The DC component value of the voltage to be applied to is between +320V and -aOV, preferably a value v close to +320V (Fig. 953 (6)).

When the second development is completed, the red and black two-color toner images on the photosensitive drums /, 1t: are charged to negative polarity (or positive polarity) by the pre-transfer charger 17, and then charged to positive polarity (or negative polarity). The images are simultaneously transferred onto a transfer material 19 by a transfer charger 18 of different polarity.

The untransferred toner on the photosensitive drum 2 is cleaned by a blade cleaner 20.

On the other hand, the toner on the transfer material 19 is fixed by a fixing device (not shown).

It goes without saying that the color combinations of the above-mentioned developers can be selected as desired.

3 (1) to (6) explain the process steps of the above-mentioned embodiment apparatus, and in each step, the upper side shows the charge state of the photoreceptor, and the lower side shows the surface potential of the photoreceptor. It is a schematic diagram.

In the step (1), conductive layer a3-CdS etc. cr) N J
Il! v) Photoreceptor A consisting of photoconductive layer a2 and insulating layer al is charged to about +1,200'V by primary charger 4.

In step (2), first scanning exposure L1 is performed based on information such as the format, and at the same time, corona radiation of alternating current or negative polarity is performed by the secondary charger 5 to form a first latent image. At this time, the surface potential of the photoreceptor A becomes approximately -100V in both the exposed and non-exposed areas.

(3) I: A second scanning exposure L2 is performed on the culm based on information such as characters, and -2? i? form an image. The latent image potential of this exposed area is about +400V.

At t5 (approximately 4LI), the second development is performed using negative polarity black toner 1. For convenience, the surface charge of the photoreceptor is expressed as 1° of toner.

In step (5), the entire surface is exposed. Here f(S(2)l
The potential of the exposed part of the first latent image formed by the culm is approximately -80V.
, and the other parts excluding the black I/toner developing area are approximately 4 FIOV.

In Step (6) 1, a second development is performed using the red toner 'I'2 of positive polarity by applying an alternating debris flow superimposed with a +300V DC bias current 1F to the developing sleeve.

In this way, a clear two-color image with no color or image disturbance is obtained.

In addition, in the example 1- below, +iζ is an example in which a τN type light guiding layer is used, but a selenium)'P type one may also be used, in which case the polarity of the toner/latent image potential during charging is This is the opposite of the above.

As described above in detail in the specific examples, the present invention is capable of forming images based on different latent images in good condition.

[Brief explanation of the drawing]

FIGS. 1(I) to (V) are explanatory diagrams of each step to explain a conventional image forming process, FIG. 2 is an explanatory diagram of a specific example of an image forming apparatus that implements the method of the present invention, and FIG. FIGS. (1) to (6) are explanatory views of each step of the image forming process of the present invention. 1 is a photosensitive drum, 4 is a primary charger, 5 is a secondary charger, 6
・lO is a laser light source, 7-11 is a light modulator, 8-12 is a rotating mirror, 9-13 is an imaging lens, 1 is a first developing device, 15 is a full-surface exposure lamp, 2nd developing device is above and below, 17 is a pre-transfer charger, 18 is a transfer charger, and 19 is a transfer paper. Patent Applicant Canon Inc. Company No. 1 Ro Figure 3 Figure 4 Foil Figure 2

Claims (1)

[Claims] (1) Conductive Layer/Photoconductive Layer Using an electrophotographic photoreceptor whose basic structure is an insulating layer, the surface of the photoreceptor is charged with a predetermined polarity, and a first optical scanning exposure is performed on the surface of the photoreceptor. At the same time, a step of applying a corona discharge having a polarity component opposite to the polarity,
Step of performing second light scanning exposure on the surface of the photoreceptor, t7','
A first development step in which the electrostatic latent image formed by the light scanning exposure of 1 is developed with a T1 color developer; 12 of polarity
4. Having a second development step of developing with a color developer
．． An electrophotographic printing method with ν characteristics.