JPH0619612B2 - Image forming method - Google Patents

Description

The present invention relates to an image forming method used in a copying machine or the like, and in particular, on a photosensitive member irradiated with light based on an image pattern to be formed, In particular, it relates to an image forming method for forming a toner image on a dark portion (non-exposed portion) of a photoconductor.

[Conventional technology]

Conventionally, an electrophotographic recording method has been widely used as an image forming method using light. This system Fig. 4
The printing principle is shown in Fig. 4 (c) from (a). First, as shown in FIG. 4 (a), the photosensitive member 1 made of a photoconductive film such as selenium is uniformly charged in advance by the corona discharger 2, and then, as shown in FIG. 4 (b).
Arrow A based on the image pattern to be formed as shown in
The electrostatic latent image 3 is formed by irradiating a laser beam or the like from the direction. Then, as shown in FIG. 4 (c), a voltage having the same polarity as the charging polarity is applied to the magnetic brush developing device 4, and the charged toner 5 is attached to the latent image part by the electric field acting between the latent image part and the developing device. Thus, a toner image 6 which is a visible image is obtained.

[Problems to be solved by the invention]

As described above, in the conventional electrophotographic recording method, the photoconductor is first uniformly charged by using a corona discharger, and then the charging potential of the photoconductor is lowered by light to form a latent image at an image forming portion. The latent image is made visible by attaching toner charged by the magnetic brush developing device to the latent image portion. Therefore, a corona discharger for uniformly charging the photoconductor is required.

This corona discharger requires a high voltage power supply of several KV, and has a drawback that it is easy to discharge when the humidity of the atmosphere around which the corona discharger is installed is high, and it is difficult to discharge when the humidity is low. As described above, the corona discharger is liable to be affected by the humidity of the surrounding atmosphere in which the corona discharger is installed or dust, and thus has a problem of poor reliability.

In addition, when the photoconductor is charged by using this corona discharger, ozone gas is generated when the corona discharger discharges, and if a large amount of this ozone gas is generated, it adversely affects the human body, which is a problem.

[Means for solving problems]

The problems described above include a photosensitive member in which a transparent conductive film and a photoconductive film capable of being charged in both polarities are sequentially laminated on a transparent substrate, a first developing device facing the photoconductive film, and the photoconductive film. A second developing device facing each other and separated from the first developing device by a predetermined distance;
A transport mechanism for transporting the photoconductor, transports charged toner between the first developing device and the photoconductor, applies a voltage between the first developing device and the transparent conductive film, and from the base side. Light irradiation is performed over the entire surface of the photoconductor to form a charged toner layer on the photoconductive film, and after the charge of the charged toner layer is injected from the transparent conductive film to the photoconductive film, the light irradiation is stopped. By doing so, a trap charge is formed on the photoconductive film, and after the photoconductor is conveyed, a voltage having a polarity opposite to that of the first developing device is applied between the second developing device and the transparent conductive film, and it is formed from the substrate side. By exposing the photoconductive film by irradiating light according to the image pattern to be formed, by electrostatically removing only the charged toner attached to the exposed portion of the photoconductive film,
This is solved by the image forming method of the present invention that forms a toner image corresponding to an image pattern.

[Action]

That is, in the image recording method of the present invention, a photosensitive member is prepared in which a transparent conductive film and a photoconductive film that is charged in both polarities are sequentially laminated on a transparent substrate, and the photoconductive film and the first developing machine are used. While applying a developing bias between them, the entire surface of the photoconductor is exposed from the substrate side to form a charged toner layer on the photoconductive film, and the charge of the charged toner layer causes the charge from the transparent conductive film to be transferred to the photoconductive film. Injecting to form trap charges in the photoconductive film, then transporting the photoconductor, applying a voltage between the second developing device and the transparent electrode, and corresponding to the image pattern to be formed from the substrate side. The electrostatic charger removes only the charged toner adhering to the exposed part of the photoconductive film by electrostatically exposing it to form a toner image corresponding to the image pattern, and the charger operates at a high voltage like a corona discharger. Is not required, and it does not affect the ambient temperature and humidity. Sarezu, in which so as to form an image at a low voltage, and simple operation.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

The image recording principle used in the method of the present invention will be described with reference to FIGS. 1 (a) to 1 (b).

First, as shown in FIG. 1 (a), on a transparent substrate 11 made of polyethylene terephthalate, for example, a transparent conductive film 12 made of an indium-tin-oxide (ITO) layer and an organic material having both positive and negative polarities. Evaporate the photoconductive film 13 to be charged,
Alternatively, a film-shaped photoreceptor 14 formed by coating is prepared.

A first magnetic brush developing machine 15 carries a two-component developer consisting of an insulating toner and a carrier onto the photoconductive film 13, and a sleeve made of a non-magnetic material layer around the first magnetic brush developing machine 15. The DC voltage _Vb is applied between the transparent conductive film 12 and the transparent conductive film 12 so that the first magnetic brush developing machine 15 becomes positive and the transparent conductive film 12 becomes negative, and the charged toner is electrostatically charged on the photoconductive film 13. And then develop it. At this time, at the same time, a fluorescent lamp is used as a light source from the side of the substrate 11 to irradiate light in the direction of arrow B to expose the entire surface of the photoconductor 14. Then, photocarriers are generated inside the exposed photoconductive film 13, and the electrons forming the photocarriers are attracted to the charge of the charged toner layer attached on the photoconductive film 13 to cause the surface of the photoconductive film 13 to be exposed. Reach
The potentials of the transparent conductive film 12 and the photoconductive film 13 become substantially equal. That is, in the first developing process using the first developing machine 15, since the potentials of the transparent conductive film 12 and the photoconductive film 13 are substantially equal to each other, it is as if the development bias _Vb is used on the transparent conductive film 12. It will be similar. In this way, the opposite amount of electric charge (negative charge in this case) 17 having the same amount as that of the charged toner layer 16 is induced on the surface of the photoconductive film 13.

The amount of adhered toner M _i at this time is expressed by the equation (1).

M _i = δp _{[2ε 0 ε r · V b /} ρ i ] ^1/2 ... ‥ ... ‥ ...
(1) where δ is the mass of the toner, p is the packing rate per unit volume of the toner layer, ρ _i is the volume charge density of the toner layer attached to the image area, ε ₀ = vacuum dielectric constant, ε _γ indicates the relative dielectric constant of the toner layer.

This developing bias voltage V _b is applied to the first developing device and the transparent conductive film 12
When the light irradiation from the fluorescent lamp is stopped and the image exposure is stopped while the voltage is applied during the period, the resistance value of the photoconductive film 13 increases, and the photoconductive film 13 becomes a substantially perfect insulator.

Therefore, the charges 17 induced in the photoconductive film 13 become trap charges and cannot move. The surface potential on the toner layer 16 in the I developing process using the first developing machine 15 is
It becomes uniform as V _b of FIG. 1 (a), also adhering toner amount is as X _i of FIG. 1 (a).

Next, the photoconductor 14 is conveyed by a predetermined distance, and the second developing machine 18
In the II developing step as shown in FIG. 1 (b) when it is opposed to the second developing machine 18, the developing bias voltage _Vb 'is set to a reverse bias state to the I developing step. And the transparent conductive film 12 are applied. At this time, at the same time, laser light is irradiated from the side of the substrate 11 in the direction of arrow C corresponding to the image pattern to perform exposure. Then, the charged toner 16 adhered in the I-th developing step is applied with a reverse bias voltage, and
Due to the electric field generated between 18 and the transparent conductive film 12, the second
The electric charges 17 trapped on the surface of the photoconductive film 13 start to be collected in the developing machine 18 and are also irradiated with light. Move to the side. Eventually, the exposed portion of the charged toner layer disappears, and the charges trapped on the surface of the photoconductive film 13 disappear completely.

On the other hand, in the non-exposed area where the laser light is not irradiated, a part of the charged toner layer is collected in the second developing machine 18 by the action of the electric field between the second developing machine 18 and the transparent conductive film 12, film
13 Electrons trapped on the surface cannot move. Therefore, the photoconductive film acts as a capacitor according to the amount of the collected charge of the charged toner layer, and charges 20 of the same polarity are induced on the transparent conductive film 12. Since the capacitance of the photoconductive film 13 in the dark when light is not radiated is small, the surface potential on the photoconductive film 13 varies greatly even with a slight positive charge induced in the transparent conductive film 12. , The developing bias voltage V _b ′ is balanced, and the toner in the unexposed portion is no longer electrostatically collected. Then, the charged toner remains only in the non-exposed portion, and a toner image is formed.

The amount of adhered toner M _0i at this time is expressed by the equation (2) because the trap charges obtained in the I-th development process are developed with the development bias voltage V _b ′.

M _0i = δp {-(ε _γ d / ε _d ) + [(ε _γ d / ε _d ).
² + 2ε ₀ ε _r (V _b + ρ _i (2ε ₀ ε _r · V _b /
ρ _i ) ^1/2 × d / ε ₀ ε _d ) / ρ _i ] ^1/2 } (2) where d is the thickness of the photoconductive film, and the fourth term is the latent charge due to trapped charges. The image potential is shown. This latent image potential is
If the voltage is kept higher than the bias voltage _Vb 'applied to the developing machine, a sufficiently dark print can be formed. The surface potential on the toner layer 16 in the second developing process using the second developing machine 18 is as shown by V _b ′ in FIG. 1 (b), and the amount of adhered toner distribution is shown in FIG. 1 (b). Like X _2i , it adheres to the non-exposed portion that is not irradiated with laser light.

Here, more specific numbers will be used to explain the embodiment of the present invention in detail with reference to FIG.

On the transparent substrate 11 made of polyethylene terephthalate having a thickness of 75 μm described above, the transparent conductive film 12 made of an ITO layer is vapor-deposited to have a thickness of 0.2 μm, and the photoconductive film 13 made of an organic material having a thickness of 100 μm is applied thereon. Thus, the photoconductor film 14 is formed. On the photoconductive film 13 side of the photoconductor film 14, two magnetic brush developing machines 31 and 32 are installed at a predetermined interval, and are opposed to the first developing machine 31 with the photoconductor film 14 interposed therebetween. A light source 33 made of a fluorescent lamp for exposing the entire surface of the photosensitive film 14 is installed on the side where the light is applied. Output of 0.8 mW as a light source for image data exposure on the side facing the second developing machine 32 with the photoconductor film 14 interposed therebetween.
The helium-neon laser light source 34 is installed. Both the first magnetic brush developing machine 31 and the second magnetic brush developing machine 32 were sleeve rotating type developing machines, and the rotating peripheral speed of the sleeve was 30 cm / sec. Also, the photoconductor film 14
The carrier speed is 10 cm / sec, and the particle size of the developer is about 10
A two-component developer is used in which an insulating toner having a particle diameter of 10 μm and a carrier made of iron powder having a particle diameter of 10 μm to 15 μm are mixed so that the weight ratio of the toner is 10%. Here, the specific charge of the toner is set to 10 μC / g.

Next, first, a voltage of 500 V is applied as a developing bias voltage Vb to the first magnetic brush developing machine 31, and the photoconductor film 14 is developed while irradiating the photoconductor film 14 with light from the light source 33. A charged toner layer is formed on 13. In the exposed state, charges of opposite polarity corresponding to the amount of charge of the attached charged toner layer are formed in the vicinity of the surface of the photoconductive film 13, and when this exposure is stopped, the resistance value of the exposed portion increases, and the surface of the photoconductive film 13 increases. It becomes a trap charge that the charge does not move.

Next, the photosensitive member 14 is moved in the direction of arrow D, and the developing bias voltage V is applied between the second magnetic brush developing device 32 and the transparent conductive film 12.
Development is performed by applying a voltage of -100 V as _b '. At the same time, laser light is emitted from the laser light source 34 based on the image pattern to expose the photoconductor 14. Then the first developing machine
The charged toner adhered by 31 gradually begins to be collected in the second developing machine 32 by the electric field generated by the application of the reverse bias voltage. Also, the charges trapped on the surface of the photoconductive film 13 are gradually transferred to the second layer through the photoconductive film 13 having a low resistance.
Move to the ground electrode side of the developing machine. Eventually, the exposed portion of the charged toner layer disappears, and the charges trapped on the surface of the photoconductive film 13 also disappear completely.

On the other hand, in the non-exposed area, part of the charged toner layer is recovered by the action of the electric field, but the electrons trapped on the surface of the photoconductive film cannot move because the photoconductive film has high resistance.

Therefore, charges of the same polarity are induced on the transparent conductive film 12 in accordance with the amount of charges collected in the charged toner layer. Since the capacitance of the photoconductive film 13 in the dark when light is not irradiated is small, the surface potential on the photoconductive film fluctuates greatly and balances with the developing bias voltage even when a slight positive charge is induced. Then, no more charged toner is electrostatically collected. In this way, the toner image is formed only on the non-exposed portion. In the present embodiment, printing with a print density of OD of 1.0 or more was obtained.

Further, a second embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment in that one-component conductive magnetic toner (resistance value = 10 ₆ Ωcm) is used as the toner and has a thickness of 8 μm (trade name: SO-102) manufactured by Kodak Company. Is used to form a photoconductive film 13 ′, a developing bias voltage V _b = 200 V is applied to the first developing device 41, and a ground potential is applied to the second developing device 42.

First, the developing bias voltage V _b of 200 V is applied between the first developer unit 41 and the transparent conductive film 12, fluorescent lamp light source from the same time base 11 side
33 is used to develop while exposing the entire surface of the photoconductor 14. At this time, electric charges are injected into the conductive magnetic toner to become positively charged toner. This charged toner adheres to the surface of the photoconductive film 13 'to form a charged toner layer. At this time, among the photocarriers generated in the photoconductive film 13 'by light irradiation, negative charges having a polarity opposite to that of the charged toner are induced on the surface of the photoconductive film 13'.

Then, when the light irradiation is stopped, the resistance value of the photoconductive film increases,
The charges induced on the surface of the photoconductive film 13 'are trapped. Next, after the photoconductor 14 is conveyed in the direction of arrow D, the second
A ground potential is applied to the developing machine 42, and a laser light source 34 is used from the side of the substrate 11 to irradiate laser light corresponding to an image pattern to be formed. Then, for the same reason as in the first embodiment, the charged toner layer and the trapped charges disappear in the light irradiation portion irradiated with the laser beam, and the charged toner layer remains in the non-exposed portion to obtain a printed image. .

In this embodiment, the print density was 0.D. and a value of 1.0 or more was obtained, and good print without fog around the print was obtained.

Further, although the magnetic brush developing machine is used in this embodiment, the developing machine may be of any type as long as it can carry the charged toner. Further, the photoconductor may be wound around a rotating body in a roll shape.

〔The invention's effect〕

As described above, according to the image forming method of the present invention, it is not necessary to charge the surface of the photoconductor using a high voltage power source such as a corona discharger, and the influence of humidity in the atmosphere unlike a corona discharger. A printed image can be formed by a simple device and a simple process without receiving it, and the reliability at the time of image formation is improved.

[Brief description of drawings]

1 (a) and 1 (b) are conceptual diagrams for explaining the recording principle in the image forming method of the present invention, and FIG. 2 illustrates the first embodiment of the image forming method of the present invention. FIG. 3 is a conceptual diagram for explaining a second embodiment of the image forming method of the present invention, and FIG. 4 is a conceptual diagram for explaining a conventional image forming method. In the figure, 11 is a substrate, 12 is a transparent conductive film, 13 is a photoconductive film, 14 is a photoconductor film, 15, 31, 41 are first developing devices, 16 is a charged toner layer, 17 is trap charge, 18 , 32, 42 are second developing machines, 19
Is a ground electrode, 20 is an induced charge, 33 is a fluorescent lamp light source, and 34 is a laser light source.

Claims (1)

[Claims] 1. A photosensitive member comprising a transparent substrate and a photoconductive film which can be charged in both polarities sequentially laminated on a transparent substrate, a first developing device facing the photoconductive film, and the photoconductive film. The second developing device is opposed to the first developing device and is separated from the first developing device by a predetermined distance, and a transport mechanism for transporting the photosensitive member. The second developing device transports the charged toner between the first developing device and the photosensitive member. A voltage is applied between the first developing device and the transparent conductive film, and light is irradiated from the substrate side over the entire surface of the photoconductor to form a charged toner layer on the photoconductive film. ,
After the charge is injected from the transparent conductive film to the photoconductive film, the light irradiation is stopped to form trap charges in the photoconductive film, and then the photoconductor is conveyed. By applying a voltage having a polarity opposite to that of the first developing machine, and irradiating the photoconductive film with light corresponding to the image pattern to be formed from the substrate side, the exposed portion of the photoconductive film is exposed. An image forming method, wherein a toner image corresponding to an image pattern is formed by electrostatically removing only the attached charged toner.