JPS632079A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] An electrostatic latent image is formed by exposing an endless photoreceptor in which a transparent substrate, a transparent conductive layer, and a photosensitive layer are successively laminated from the transparent substrate side. In an image forming apparatus that forms a toner image on the layer side, the capacitance of the photoreceptor is set to 0.1 to 6.5.
ttF/rIL", it was possible to obtain stable and dark printing without fogging.

[Industrial application field]

The present invention relates to a 1-image forming apparatus that forms a toner image on a photoreceptor at the same time as image exposure and performs display or transfer.

? Currently, optical printers and copiers use electrophotography? It is common to perform digital recording, and recording is performed through steps such as charging, exposure, development, and transfer.

The charging process uses a corotron that performs charging by corona discharge, requires high voltage, and has the problem of generating excessive ozone.

Therefore, there is a need for an image forming method that does not generate harmful ozone and can form images at low voltage.

FIG. 7 is a diagram for explaining an image forming method that does not use a corona charger, which does not generate ozone and can form images at low voltage.

In this image forming method, as shown in FIG. 7, a transparent conductive layer 112 made of ITO or the like is provided on a transparent substrate 111, and a photoreceptor 113f made of CdS or the like having a thickness of 65 μm is provided thereon. Furthermore, a conductive magnetic toner developing device 116 is disposed opposite to a recording film 115 provided with a white insulating layer 114 having a resistance value of a certain degree, and this developing device 11
6 and the transparent conductive layer 112, a light source 117 consisting of a semiconductor laser or the like, a polygon scanner 1
18, image exposure is performed from the transparent substrate 111 side using an fθ lens 119 or the like.

Through this image exposure, a voltage is applied between the developing device 116 and the transparent conductive layer 112 of the recording film 115, and the toner is transferred to the portion of the photoreceptor layer 113 where the resistance value has decreased due to the irradiation with light. Deposited electrostatically. - On the other hand, since the thickness of the insulating layer 114 is sufficiently thick in the area that is not irradiated with light, the electrostatic adhesion force between the toner and the toner is weak, and the toner remains on the recording film 115. Therefore, a toner image 120 corresponding to image exposure is formed.

After image formation, the charges induced by light irradiation and the charges induced in the toner are discharged through the surface layer within one cycle of image display, and are magnetically attracted and collected in the developing device 116 during the next image formation. be done. In this case, since the image exposure is performed from the transparent substrate 111 side of the recording film 115, toner recovery, image exposure, and development can be performed simultaneously.

Such an image forming method is disclosed in Japanese Patent Application Laid-Open No. 57-119375.
It is publicly known in the publication No.

However, as shown in Fig. 7, the conventional image type sole &
Although this method has the advantage of not using a corona discharger, image formation is performed using the difference in Coulomb force acting on the toner between exposed and non-exposed areas, so the photoreceptor layer 113
must be made thicker. However, the thick photoreceptor layer 11
3 to have a uniform thickness is difficult. Further, by increasing the thickness of the photoreceptor layer, there is a drawback that the amount of material used increases, resulting in an increase in cost. Plus, a photoreceptor! 11
As the film 13 becomes thicker, it is necessary to increase the voltage applied between the transparent conductive film 112 of the recording film 115 and the developing device 116, and there is a drawback that the photosensitivity decreases.

[Conventional technology]

Therefore, a new image forming method has been proposed that improves all of the above-mentioned conventional drawbacks and is capable of forming images at low voltage, high sensitivity, and even on thin photoreceptors without using corona discharge gain. This image forming method can also be applied to a photoreceptor with a relatively high mobility, such as a non-polluting and inexpensive organic photoreceptor. , for example, high-speed type organic photoreceptors,
This method can be applied to SE photoreceptors, CDS photoreceptors, etc.

First, an outline of the proposed principle shown in FIG. 8 will be explained.

The photoreceptor 124 includes a transparent substrate 121, a transparent conductive film 22, and a photoconductive layer 123, all of which are laminated in this order.The transparent conductive layer 123 is connected to ground. Reference numeral 125 denotes a first developing (solid toner developing) means, and specifically, it has a structure in which a non-magnetic sleeve is provided on the surface of a magnetic roller, and a carrier made of conductive magnetic toner or conductive iron powder is applied to this. This is a so-called magnetic brush developing machine, in which a two-component developer mixed with an insulating toner is charged. A developing bias voltage is applied by a power source 126 between the sleeve of this developing device and the transparent conductive film. 127 is a uniform solid toner layer formed in the shape of a photoreceptor. 128 is an image exposure means, specifically an LED array optical system consisting of a cell-hoc lens and an IJD array. 129 is a photocarrier near the surface of the photoreceptor r@, which becomes a latent image charge. 130 is toner in the exposed area. Reference numeral 131 denotes a second developing (contrast developing) means for collecting the toner in the non-exposed area, and specifically, it is a magnetic brush developing device similar to that used to form a uniform solid toner layer.

A voltage having a polarity opposite to the developing bias voltage of the first developing machine is applied to this second developing machine by a power supply 132.
33 is a toner image from which toner in non-exposed areas has been removed.

Next, the image forming procedure will be described.

In FIG. 8, a uniform petatoner layer is formed on the surface of the photoreceptor by applying a developing bias to the developing device 125 and conveying the toner.

The transparent substrate side of the photoreceptor 124 is image exposed using an image exposure device [128]. In the exposed area, among the photocarriers generated in the photoconductive layer, carriers having a polarity opposite to that of the petatoner layer 127 move toward the interface and become latent image charges.

Next, the developing machine 131 connected to the reverse bias voltage
5. The toner is completely transported, and the toner 134 in the non-exposed area is collected into the developing device 131 by electrostatic force. At this time, the toner 130 in the image area is also slightly collected, but the latent image charge 129
Due to the electrostatic binding force between the toner charge and the toner charge, most of the toner remains on the photoreceptor, and a toner image is formed.

On this toner image, if necessary, a conventional transfer means 135
After the latent image charge on the photoconductor is transferred to a recording paper 136, the latent image charge on the photoreceptor is removed by a full-light static eliminator 137 or the like, and collected in the first developing machine.

At the same time as this residual toner is collected, the next image formation is performed. Continuous recording is performed by repeating the above process.

Next, an outline of the second proposed principle shown in FIG. 9 will be explained.

The difference between FIG. 9 and FIG. 8 is that an image exposure and development process is employed in which solid toner development and image exposure are performed simultaneously. For this reason, during image exposure and development, the capacity of the photoreceptor appears to increase in the exposed area, so the amount of toner adhering to the exposed area increases, resulting in a toner image with a certain degree of contrast between the exposed area and the non-exposed area. is obtained.

It can be seen that the method shown in FIG. 9 is advantageous for photoreceptors that move quickly.

[Problem that the invention seeks to solve]

However, in the image forming method as shown in FIG. 8 and FIG. I'm trying to collect it inside.

Therefore, the toner 134 in the exposed area on the photoconductor 124 is also collected into the developing device 131, resulting in a problem that the print density becomes low.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide an image forming apparatus lt capable of obtaining a toner image without fog and a sufficiently high print density.

[Means for solving problems]

The above problem is that the transparent substrate, transparent conductive layer, and photosensitive layer are
An endless photoreceptor formed by laminating N layers, and a first developing means disposed on the photoconductive layer side of the photoreceptor.

a second developing means; a first developing means on the transparent substrate side of the photoreceptor;
an image exposing means disposed at a position facing the developing means or between the first and second developing means, and simultaneously with or after the formation of a uniform petatoner layer by the first developing means. , an image forming apparatus in which the image exposure means performs full image exposure, and then the toner adhering to the non-exposed area is collected in the second developing and imaging means to form a toner image on the photoreceptor; This problem is solved by an image forming apparatus characterized in that the electrostatic capacitance of the body is between 0.1 μF/m and 6.5 μF/m'.

[Effect]

Here, first, regarding the conventional image forming method explained using FIGS. 8 and 9, using a model at the time of image formation,
This will be explained in more detail.

By the way, in the method shown in FIG. 8 in which image exposure is performed after uniform peta development, considering an ideal situation, of the carriers generated by light irradiation, the amount of carriers equal to the amount of charge in the charged toner layer is Only the charge reaches the surface of the photoreceptor, and this becomes a latent image charge. -If we consider the case where image exposure and development are performed at fi1 as shown in FIG. 9, the relationship between carrier movement time and image exposure time becomes important. Typically, the image exposure time is the carrier movement time within the photoreceptor, t. It's shorter.

Therefore, in this case, the simultaneous exposure and development process is substantially the same as the process shown in FIG. 8, in which uniform solid development, nine-image exposure, and contrast development are separated, respectively.

Therefore, the image forming process explained using FIG. 8 will be mainly explained below.

An ideal development model is shown in FIG.

In the figure, 1 is a photoreceptor, which is a transparent substrate 1a.

A transparent conductive layer 1b and a photoreceptor 41c are sequentially laminated, 2 is a first developing means, 3 is a second developing means, 5F'
i image exposure means, 6 is a toner image, A is a latent image charge, B is an induced charge, and C is a charged toner. FIG. 5A is a diagram showing a uniform petatoner development process, and the adhered toner fMb at this time is expressed by the following equation.

Figure (b) is a diagram showing the light irradiation process. Of the light carriers generated by light irradiation, an amount of charge Q equal to the amount of toner charge during uniform petatoner development moves to the surface of the photoreceptor, causing static 'W! The latent image charge Q is expressed by the following equation.

FIG. 5C is a diagram showing a contrast development process, which is a process in which the electrostatic latent image charge Q is developed with a current bias voltage vb2. The adhering toner amount Mc at this time is expressed by the following formula.

As is clear from equation (3), as the reverse bias voltage increases, the amount of adhered toner Mc decreases.

Therefore, regarding the reverse bias voltage required for fog removal,
We examined it centrally.

Figure 3 shows that the amount of developer is 1 fathom! Using the mixing ratio of magnetic toner and insulating toner as a parameter, reverse bias voltage V
The relationship between b2 and fog density is determined. The conductive magnetic toner has a resistance value of 10'G.

The magnetic powder content is 80% and acts as a carrier.

- 10,000, the insulating toner has a resistance value of 1015 Ω·α or more and a magnetic powder content of 10 to 30%. As for the experimental conditions, a functionally separated organic photoreceptor with a film thickness of 10 μm was used, and a recording speed of 5
cwt/B, and developing bias voltage vbl=500■. From No. 3 (2), it was found that in both cases where the mixing ratio is in the range of 0 to 40%, a region with no fog exists in which the reverse bias voltage vbl is in the range of about 20 to 30 V.

Therefore, the reverse bias voltage vbz, which is the center value of the area where no fogging occurs, is set to 25V, and the electrostatic capacitance of the photoconductor is
FIG. 1 is a graph of the relationship between ikC and the amount of adhered toner Me.

In FIG. 1, the developing bias voltage Vb1 is 300 V, which is a typical developing bias voltage when using conductive magnetic toner, and the developing bias voltage Vb1 is 300 V, which is a typical developing bias voltage when using conductive magnetic toner, and conductive magnetic toner and insulating magnetic toner are mixed at a weight ratio of 40 cm. Two examples of a typical development bias voltage of 600 V when mixed toners are used are shown. In addition, the numerical value used in the calculation is the practical value of the toner volume charge density of 6.6 C/771" (
Toner specific charge q/, m = 10 μC/g), toner layer relative permittivity εr = 2.2°, toner volume charge density δ
=t, xg/m. Here, the adhesion toner amount Me for obtaining a light-dense printing quality is 6 g/m'. This target value is shown in FIG. 1 by a broken line. From this figure, vbyu = 60
At 0 V, dark printing can be obtained when the photoreceptor capacitance is in the range of 0.1 μF/m' to 6.5 μF/m'', and vb1=
At 300v, the capacitance is 0.25ztF/m' to 4
．． It can be seen that a dark print can be obtained in the range of 1 μF/m'.

〔Example〕

Figure M4 is a diagram showing the first embodiment of the present invention.

The recording drum has a transparent conductive film 1 on a transparent glass drum 1a.
The photoreceptor drum 1 has an organic photoreceptor 1c made of a 7-thalocyanine type organic photoreceptor 1c laminated thereon to a thickness of about 15μ, corresponding to a capacitance of 1.7μF/m''.

On the outer periphery of the photoreceptor drum 1, a first magnetic brush developing device 2,
A second magnetic brush developing device 3, a transfer means 4 consisting of a conductive rubber roller, and an IJD array bar 7 which is an optical static elimination means.
Place it as shown in the figure, and also put 24
0dpl LED array and selfoc lens (S
LA-20] LED array optical system 5f! : Established.

A magnetic brush developing machine has a structure in which a non-magnetic sleeve is provided on a magnet roller. As the developer, a two-component developer containing an insulating magnetic toner and a conductive magnetic toner mixed at a total height ratio of 30 cm was used.

The insulating magnetic toner is charged to about -10 tr C/g by frictional charging with the conductive magnetic toner.

A negative voltage of -500V is applied by a power supply 8 to the magnetic brush developing machine 2 which is the first developing means, and a positive voltage of +30V is applied by the power supply 9 to the magnetic brush developing machine 3 which is the second developing means. ing. Further, a positive voltage of +500V is applied by a power source 12 to the conductive rubber roller 4, which is a transfer means. The transparent conductive layer 1bFi is grounded.

Next, the image forming means will be explained below.

First, this recording drum is rotated steadily in the direction of the arrow. Next, while conveying the negatively charged toner to the first magnetic brush developing device 2 in a direction opposite to the running direction of the recording medium, the negatively charged toner is deposited on the photoreceptor, and petatoner development is performed. after that,
The image exposure means 5 exposes the image according to the image pattern.

In the exposure section, photocarriers generated inside the photoreceptor move to the surface of the photoreceptor and become trapped charges 11. This is the latent image charge. Next, like the first magnetic brush developing machine, the second magnetic brush developing machine 3 also electrostatically removes the charged toner in the non-exposed area adhering to the photoconductor while conveying it in the opposite direction to the running direction of the recording medium. toner image 6 is obtained. Thereafter, the toner image is electrostatically transferred onto the recording paper 12 by a conductive rubber roller 4. After the transfer, it is fixed on the recording M12 by the fixing means 13 to form a permanent image 14. After the transfer, the photoreceptor is neutralized using an LED arrayper, which is an optical charge removal means, using approximately 1.5 times the half-reduced exposure energy of the photoreceptor.

As a result, the residual charge on the photoreceptor and the latent image charge paired with the charge of the residual toner are removed, and the bond between the residual toner and the latent image charge is weakened. Next, petatoner development is performed again using the first magnetic brush developing device 2. At this time, the residual toner remaining without being transferred is easily collected by the first magnetic brush developing machine because the electrostatic binding force is weakened by the LED arrayper.

The above process is repeated as described above, and continuous printing is performed.

In this way, in this embodiment, the print density is 0. D.

= 1.1 or more, fog density 0. D, = 0102 or below, dark prints with no blur and density unevenness were stably obtained.

Also, in comparison with the conventional image forming method shown in FIG. 7, in this example,
Therefore, the manufacturing cost of the photoreceptor film can be reduced.

■Thinner photoreceptors have higher photosensitivity.

■ Insulating toner can be used and transfer to plain paper is easy.

It has various characteristics such as.

FIG. 5 is a diagram showing a second embodiment of the present invention. Fourth
The difference from the figure is that the image exposure means 5 is arranged opposite the first developing means 2. This is an application of the present invention to an image forming process in which petatoner development and image a source are simultaneously performed as shown in FIG. This method has the advantage that since a constant electric field is always applied between the photoreceptor and the first developing device, the efficiency of using photocarriers generated by image exposure to form a latent image is high. FIG. 6 is a diagram showing a third embodiment of the present invention. The difference from FIG. 5 is that the first developing means and the second developing means are integrated into one developing machine. The developing machine has a non-magnetic fixed sleeve 26 on a rotatable magnet row 222.
A developing electrode 24 serving as a first developing means is provided thereon via an insulating film 25, and a developing bias voltage 8 is applied to this developing electrode, thereby making the entire sleeve 26 a second developing means, This is the point where a reverse bias voltage 9 was applied to the developing sleeve 26.

This method has the advantage that the developing machine can be made smaller.

Also number 1. In the second and third examples, a two-component developer in which an insulating toner and a conductive toner were mixed at a weight ratio of 30% was used as the developer, but a one-component developer containing only a conductive magnetic toner was used. Of course, it is possible to apply In this case, it becomes easier to remove the charge from the residual toner by photostatic discharge, and it becomes extremely easy to recover the residual toner to the first developing device.

Furthermore, the first. In the second and third embodiments, a photosensitive drum was used as the recording medium, but it goes without saying that a photosensitive belt may also be used.

In this case, the device can be made more compact.

The above has described a cleanerless recording process in which residual toner is collected into the first developing machine, but it goes without saying that the present invention can also be applied to a process in which residual toner is removed by a fur brush cleaner or a blade cleaner. .

Further, in the above embodiment, a single layer structure g consisting of only a photoconductive layer was used as the photosensitive layer 1c, but of course a two-layer structure in which an insulating layer is provided on the photoconductive layer can also be used. . In this case, since the photoconductive layer is protected by the insulating layer, there is an advantage that the life of the photoconductive layer can be extended. Further, when the photosensitive layer 1c is only a photoconductive layer, the latent image charge (trapped charge) and the charge of the charged toner developed with petatoner may be combined, and this combined charged toner is transferred to the photosensitive layer 1c. The electrostatic force attached to the film may weaken and be recovered during contrast development. On the contrary,
When the photoconductive layer is protected with an insulating layer, the latent image charge and the charged toner form a complete electrical double layer, resulting in a more uniform toner image than when using only the photoconductive layer. There are advantages.

〔Effect of the invention〕

According to the present invention, since there is no need to use a corona discharger, high voltage is not required, and reliability is improved because it is less susceptible to the influence of humidity φ dust and the like. In addition, compared to the image forming method already disclosed in Japanese Patent Application Laid-open No. 119375/1983 as a method that does not use a corona discharger, a thinner photoreceptor can be used, resulting in improved photosensitivity and lower manufacturing costs. It has the advantage of being measurable. Furthermore, the present invention has the advantage that stable, dark printing can be obtained.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the electrostatic capacitance of the photoreceptor and the amount of layered toner, Figure 2 is an explanatory diagram of an ideal development model, and Figure 3 is a diagram showing the relationship between reverse bias voltage and degree of fog. , FIG. 4 is an explanatory diagram of the first embodiment, FIG. 5 is an explanatory diagram of the second embodiment,
FIG. 6 is an explanatory diagram of the third embodiment, FIG. 7 is an explanatory diagram of the image forming method without using a corona charger, FIG. 8 is an explanatory diagram of the first conventional example, and FIG. 9 is an explanatory diagram of the second conventional example. It is an explanatory diagram of a conventional example. In the figure, 1 is a photoreceptor, 1a is a transparent substrate, 1b is a transparent conductive layer, 1c is a photosensitive layer, 2 is a first developing means, and 3 is a second developing means.
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Claims (1)

[Claims] Transparent substrate (1a), transparent conductive layer (1b), photosensitive layer (1c)
), and a first developing means (2) and a second developing means (3) arranged on the photoconductive layer side of the photoreceptor (1). and the photoreceptor (1
) and an image exposing means (5) disposed at a position facing the first developing means (2) or at a position between the first and second developing means on the transparent substrate side, Simultaneously or after the formation of a uniform petatoner layer by the developing means (2), image exposure is performed by the image exposing means (5), and then the toner adhering to the non-exposed area is exposed to the second layer.
The toner image (6) is collected into the developing means (3) of the photoreceptor (
1) In an image forming apparatus that forms an image on the photoreceptor (
1) Increase the capacitance from 0.1μF/m^2 to 6.5μF/
An image forming apparatus characterized in that the image forming apparatus is between m^2.