JPS5880656A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic method utilizing a laser printer without dropping charging potential when a photoreceptor is used repeatedly, by irradiating destaticizing light uniformly prior to electrostatic charging of the photoreceptor. CONSTITUTION:The surface of a photoreceptor 10 is electrostatically charged positive by a corona discharger 11 for electrostatic charging and is irradiated with laser light 12 which is modulated according to a printing signal. The latent image is visualized by reversal developing with a developing device 13 and the visualized toner image is transferred on paper 15 by a corona discharger 14 for transfer. A destaticizer 16 irradiates destaticizing light for the purpose of erasing the electric charge remaining on the photoreceptor 10. The residual toner is removed by a cleaning device 17. If a semiconductor laser of 700- 900nm wavelength is used as a laser light source in the stage of forming the latent images, an illuminating device which is cut off >=600nm light is used for the destaticizer 16.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method of forming an electrostatic latent image on a photoreceptor by performing charging and imagewise exposure, and particularly to a laser printer using laser light for imagewise exposure. Concerning the electrophotographic method that can be taught.

In electrophotography using a copying machine, etc., the surface of a photoreceptor is uniformly charged, image exposure is performed on the surface to form an electrostatic latent image, and then
The toner and charge remaining on the surface of the photoreceptor after development and transfer are removed by cleaning means and static eliminating means, and the photoreceptor can be used repeatedly. In addition to copying machines, there are laser printers that utilize electrophotography using such an image-forming process.

However, a laser printer cannot use the same photoreceptor as a copying machine as it is, and is characterized by the photoreceptor structure shown in FIG. 1, for example.

In the figure, a photoreceptor 3 is constructed by forming a multilayered photoconductive layer made of Se, 5e-Te, etc. on a conductive base material. The photoconductive layer has a layer thickness of about 10 pm.
It has a three-layer structure in which a 5e-Te layer 2-2 with a layer thickness of about /μm is interposed between an e layer-7-1 and a Se layer-13 with a layer thickness of about 6em.

In the photoreceptor for a laser printer shown in Fig. 1, the role of each layer is clear. The Se layer 2-1, which is a layer that reacts to generate charges, is a layer for transporting charges.

In the Se-TeMii Co2, the content of Te is adjusted in order to absorb the irradiated laser light and generate electric charge. For example, semiconductor lasers are characterized by highly directional monochromatic light, and (GaA)) As is 7θθn
The wavelength ranges from m to 700 nm. In other words, (GaA
)) When using an As semiconductor laser, the 5e-Te layer coco-2 has a thickness of 700 nm to 900 nm by increasing the Te content.
It is wavelength sensitized to have sensitivity in nm.

Therefore, to explain the image forming process when using the photoreceptor 3 shown in FIG. 1, first, as shown in FIG. to be charged. At this time, positive charges are held in the Se layer, 2-3,
The negative (-) charge is transferred through the conductive substrate/Se layer--l
is induced at the interface of

In this state, when a laser beam is irradiated, positive and negative charges are generated at <S e -T e jil , 2-z, as shown in Fig. 2 (b). That is, the laser beam passes through the upper Se layer-13, is absorbed by the 5e-Te layer and 2-2, and generates respective charges. Therefore, the 5e-Te layer, 2-
The positive charge generated in 2 combines with the negative charge induced through the Se layer of the charge transport layer, 2-1, by the electric field of the charged charge between the surface and the base material l, and the negative charge is The positive charge t on the charge retention layer 5eliJ-3 is attracted and combined with that charge. Therefore, the potential of the surface of the photoreceptor in the region irradiated with the laser beam is greatly attenuated as shown in FIG.

This electrostatic latent image is visualized by a developing device and then transferred onto paper. However, unlike the electrostatic latent image produced by a general copying machine, the electrostatic latent image has a low potential at the latent image portion, so that reversal development is performed in a developing device. The toner and charges remaining on the surface of the photoreceptor are then removed through a cleaning process and a charge removal process, and the photoreceptor is prepared for the next image formation and used repeatedly. In the static elimination step, the photoreceptor is generally uniformly irradiated once using a white light source. As mentioned above, since the photoreceptor for laser printers has a three-layer structure as shown in FIG. 1, it has the following drawbacks.

When charging and exposure are repeated (multi-copying) using a light source with a wavelength of 1100 nm or more, such as a laser beam, the difference in Te content in the 5e-Te layer and 2-2 increases δ
As a result, the increase in dark current (dark decay) within that layer becomes significant. Therefore, even if charging is performed in the charging step, the amount of charge will be reduced due to dark current. This is because all the positive or negative charges generated in the 5e-Te layer 2-2 by the laser beam due to image exposure do not combine with the charges caused by the charging process, and some of the charges are 5e-Te. Trapped within the Te layer 2-2. This trapped charge increases rapidly as the light is repeatedly used.

The charges trapped in the above 5e-TeiiJ-2 are excited by a high electric field due to the next uniform charging, and the trap 1- is released and combines with the charged charges (dark current), so that the charging potential (charging ability) decreases.

If the charged potential decreases, the potential of the portion irradiated with the laser beam will not decrease much even after the first exposure, and the contrast will decrease, causing image fogging and the like, making it impossible to obtain a clear image. In order to irradiate white light in the static elimination process, 5e-
The Te layer 2-2 is also irradiated with light to generate charges, which are combined with residual charges to eliminate static from the photoreceptor. However, it is trapped in the 5e-T'e layer, 2-2.

The present invention provides an electrophotographic method using a laser printer in which the dark current is minimized and the charging potential does not decrease when the photoreceptor is repeatedly used as described above.

In particular, the present invention is an electrophotographic method that includes steps of charging, exposing, developing, transferring, cleaning, and eliminating static electricity from a photoconductor, and is characterized in that it eliminates static electricity from the photoconductor, and the photoconductor is reused in this static elimination process. In this case, the dark current in the photoconductive layer is suppressed to prevent the subsequent charging potential from decreasing.

The electrophotographic method according to the present invention will be explained in detail below with reference to the drawings. FIG. 3 is a diagram showing the image forming process of the electrophotographic method according to the present invention. In the figure, reference numeral 10 denotes a photoreceptor having a structure as shown in FIG. Laser light irradiates the body, /3 is a developing device that performs reversal development to visualize the electrostatic latent image, /g is a transfer corona discharge device for transferring the visualized image onto paper /j, / Reference numeral Z denotes a static eliminating device in the present invention, which irradiates static eliminating light to eliminate charges remaining on the photoreceptor io. Further, /2 is a cleaning device for removing residual toner. Although not shown in this figure, the paper 15 is peeled off from the photoreceptor after the transfer process, passes through a fixing section, the toner image is fixed, and the paper is printed out.

In the image forming process shown in FIG. 3, when a semiconductor laser having a wavelength in the range of 700 nm to θOn m is used as the laser light source, the static eliminator/2 has a wavelength of 110 nm.
A lighting device that cuts off light with wavelengths of 0n or longer is used. For example, if you use a blue filter as a white light source,
n or more is cut, and the photoreceptor 10 is irradiated after the transfer process. The static eliminator irradiates the photoreceptor 10 with light cut at 1100 nm or more as described above, and this light is absorbed by the charge retention layer 2-3 of the photoconductive layer, and the charge is stored in this layer. generate. This leaves a charge (positive) on the surface of the photoreceptor.
combines the charges (negative) generated in the charge retention layer-13,
It will take a while to remove the static electricity.

As mentioned above, the residual charge on the photoreceptor io is removed by the light irradiation from the above-mentioned static eliminator t/J, and the remaining charge is removed by the next cleaning device/J.
At step 7, the surface of the photoreceptor 10 is cleaned and prepared for the next image formation. Here, the 5e-Te layer 1-2 of the photoconductive layer does not absorb the light when irradiated with the neutralizing light, so no charge is generated, and an increase in dark current is suppressed. That is, conventionally, in order to remove the residue on the photoreceptor IO, a white light source was used as it is as static elimination light to irradiate the photoreceptor /θ. Therefore, charges are generated in the 5e-Te layer 2-2, and dark current increases due to repeated use of laser light. However, as in the present invention, the Se layer, 2-
By generating and removing charges in 3, an increase in dark current in the 5e-Te layer 2-2 is suppressed, and a decrease in charging ability in the next charging process can be suppressed. Compared to the 5e-Te layer and 2-2, the Se layer here exhibits stable characteristics with very little increase in dark current even when charging and exposure are repeated by irradiating laser light or neutralizing light. Therefore, the charge on the photoreceptor IO is removed by irradiating the charge removal light, thereby charging the photoreceptor IO.

Even if exposure is repeated, there is almost no decrease in charging ability due to dark current in the Se layer, 2-3, and the 5e-Te layer, 2
-2 optical fatigue can be suppressed and the photoreceptor 10 can be used repeatedly.

The above static elimination light, tA, was described using a white light source with a blue filter to cut out light of 1100 nm or more, but the point is to avoid irradiating light that is absorbed by the 56-Te layer. Nisukan is good, at least 110
It is sufficient to use light whose wavelength is cut from 0n to 11000n. Furthermore, the static eliminator/l is not limited to being placed at the position shown in FIG.
It is sufficient to place the photoreceptor IO before it is uniformly charged at /.

Next, examples will be described.

・Example/ The image forming process shown in Fig. 3 was used, and the light source of the static eliminator/g was 10 Toshiba fuse type light bulbs of /coV and 200 mA, which were connected in series. are connected in parallel in j sets and a voltage of -F(V) is applied to them. Then, the light from this light source is filtered through a Toshiba colored glass filter, monochromatic series filter (v-y, z> or (B-
Multi-copying was performed using static eliminating light that passed through the yl).

By using the above-mentioned neutralizing light, fluctuations in the potential charged on the photoreceptor '10 by the corona discharge device// were suppressed, making it possible to always obtain clear images.

Example 3 As the image forming process, the one shown in FIG. 3 is used as in Example. As a light source for static elimination light, the peak wavelength is 4.
A Toshiba cold cathode fluorescent lamp (F, L, 2G-T), which emits blue light of 1/, f nm, is used. This lamp is as shown in FIG. 5
The light is turned on via the Ω/W Pariscoder at 0. This fluorescent lamp was placed at a distance of approximately /field to /θ1 from the surface of the photoreceptor 70, and multi-copying was performed.

In this case, the surface potential after charging by the corona discharge device was stable with almost no fluctuation.

And I was always able to obtain clear images with no fog.

As explained above, in the electrophotographic method of the present invention, in the static elimination step, by using static elimination light whose wavelength is cut from laser light, dark current increases due to trapping of charges generated by laser light irradiation. The surface of the photoreceptor can be uniformly and stably charged at all times, and clear images without fog can be obtained.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing an example of a photoreceptor structure using a laser printer, Figures 1 (,) (b) and (c) are diagrams provided to explain image formation by the photoreceptor of a laser printer, and Figure 3. The figure shows an image forming process by the electrophotographic method of the present invention, and FIG. 7 is a drive circuit diagram showing an example of driving a lamp for static elimination light according to the present invention. /: Conductive base material, - binary conductive layer, 2-1: Se layer (charge transport layer), M! 2:5e-Te layer (charge generation layer) 1.2-3:S
e layer (charge retention layer), /θ: photoreceptor, //: charging corona discharge device, /, 2: laser light, /3: developing device, /
ri: corona discharge device for transfer, 7g: static eliminator, /2: cleaning device. Boiling I 42 Figure jQ- 4 Figure 3

Claims (1)

[Claims] 1. In an electrophotographic method using a laser printer in which a photoreceptor is charged and exposed to laser light to form an electrostatic latent image on the photoreceptor, before the photoreceptor is charged. An electrophotographic method characterized in that a photoreceptor is uniformly irradiated with static eliminating light having a wavelength shorter than that of a laser beam, and the photoreceptor is charged and exposed to laser light, and the photoreceptor is repeatedly used. 2. The electrophotographic method according to claim 1, wherein the photoreceptor has a structure in which a charge retention layer, a charge generation layer, and a charge transport layer are laminated in this order. 3. The electrophotographic method according to claim 2, wherein the static eliminating light has a wavelength that is absorbed by the charge retention layer of the photoreceptor. 4. The static elimination light is a white light source and is passed through a filter that cuts wavelengths equivalent to laser light.
The electrophotographic method described in Section 2 or Section 2 or Section gJ3.