JPH11295938A - Electrostatic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of back noise or the image expansion in a formed image, in consequence of the discharge generated between a recording head and the image carrier at the non-exposing time, in an electrostatic recording device forming the electrostatic latent image on the image carrier by performing the discharge by exposing a photoelectric conversion layer on the recording head by the exposing device, in a state of applying a voltage between the recording head and the image carrier. SOLUTION: In this electrostatic recording device forming an electrostatic latent image on a dielectric layer 13 of an image carrier surface by applying the voltage from a power source 31 to a position between a conductive layer 12 of an image carrier 10 and a conductive layer 22 of a recording head 20, and performing the exposure in accordance with the image information from an exposing device on the photoelectric conversion layer 24 of the recording head 20, the device is allowed to apply the stronger electric field on the photoelectric conversion layer between the electrode layer and the conductive layer at the non-exposing time rather than the exposing time by controlling the bias voltage applied from a bias power source 32 on an electrode layer 25 disposed on the surroundings of the discharging part on the surface of the photoelectric conversion layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic recording apparatus used for forming an electrostatic latent image on an image carrier in an image forming apparatus such as a copying machine or a printer, and more particularly to a recording head and an image forming apparatus. With a voltage applied between the recording head and the image carrier, the photoelectric conversion layer provided on the recording head is exposed by an exposure device, and an electrostatic latent image is formed on the image carrier by a discharge between the recording head and the image carrier. An electrostatic recording apparatus that forms an image is characterized in that a discharge is generated between the recording head and the image carrier during non-exposure, thereby suppressing back noise and image expansion. Have

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer using an electrophotographic system, an electrostatic latent image is formed on the surface of an image carrier such as a photosensitive member or the like. Is developed with toner to form a toner image on the surface of the image carrier, and the toner image is transferred to a recording medium to form an image.

In such a conventional image forming apparatus, when an electrostatic latent image is formed on the surface of an image carrier made of a photosensitive member, a corona discharge is performed by a charging device to make the surface of the image carrier uniform. Then, the surface of the charged image carrier is exposed according to image information to form an electrostatic latent image on the surface of the image carrier.

However, when the surface of the image bearing member is uniformly charged by performing corona discharge by the charging device as described above, a large amount of ozone or the like is generated, thereby deteriorating environmental conditions or causing the photosensitive member or the like to be degraded. There is a problem that the surface of the image carrier deteriorates and the life of the image carrier is shortened.

Therefore, in recent years, in forming an electrostatic latent image on the surface of an image bearing member, various developments have been made on an electrostatic recording apparatus in which generation of ozone is reduced.

[0006] As such an electrostatic recording apparatus, for example, as described in JP-A-9-230680 and JP-A-9-258503, a dielectric layer is formed on a conductive layer. Using a recording head having an image carrier and a photoelectric conversion layer formed on a conductive layer, the recording head is orthogonal to the moving direction of the image carrier, and the dielectric layer of the image carrier and the photoelectric conversion in the recording head are used. Layers are arranged so as to face each other, and while the image carrier is moved, a voltage is applied between the conductive layer of the image carrier and the conductive layer of the recording head. Perform exposure according to the image information, discharge between the recording head and the image carrier in the exposed portion,
There has been proposed one in which an electrostatic latent image is formed on the surface of an image carrier.

However, when an electrostatic latent image is formed on the surface of the image carrier as described above, discharge occurs between the recording head and the image carrier even in a portion where no exposure has been performed. In the background portion of the image, if a streak-like noise called back noise extending in the arrangement direction of the recording head occurs, or if an electrostatic latent image continuous in the moving direction of the image carrier is formed, the exposure is not performed. Even after finishing, there is a problem in that discharge occurs between the recording head and the image carrier in this portion, and the formed image extends in the moving direction of the image carrier.

[0008]

According to the present invention, a photoelectric conversion layer provided on a recording head is exposed by an exposure apparatus in a state where a voltage is applied between the recording head and the image carrier as described above. It is an object of the present invention to solve the above-described problems in an electrostatic recording apparatus configured to form an electrostatic latent image on an image carrier by discharging between a recording head and an image carrier, As described above, discharge occurs between the recording head and the image carrier at the time of non-exposure, so that the background noise occurs in the formed image or the formed image extends in the moving direction of the image carrier. The challenge is to prevent it.

Here, the present inventors have studied the causes of the above-mentioned background noise and image expansion, and found that the photoelectric conversion layer provided on the recording head in the above-described electrostatic recording apparatus was exposed to light. When a semiconductor laser or the like is used in an exposure device that performs exposure, weak light is guided from the exposure device to the recording head even in a portion where exposure is not performed, and the light causes a small amount of carriers to be generated in the photoelectric conversion layer of the recording head. It is considered that the carrier gradually accumulates and a discharge occurs between the recording head and the image carrier, thereby causing a back noise extending in the arrangement direction of the recording head. Further, when forming an electrostatic latent image continuous in the moving direction of the image carrier, by exposing the photoelectric conversion layer in this portion for a long time, excess carriers remaining without being discharged in this photoelectric conversion layer portion are discharged. It is considered that even after the exposure and the completion of the exposure, the excess carrier causes a discharge between the recording head and the image carrier, and the formed image extends in the moving direction of the image carrier.

[0010] The present inventors have repeated studies based on the results of such considerations to prevent the occurrence of background noise and image stretching, and have completed the present invention.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, in an electrostatic recording apparatus according to the present invention, an image carrier having a dielectric layer formed on a conductive layer and an image carrier formed on the conductive layer are provided. A recording head in which the formed photoelectric conversion layer faces the dielectric layer in the image carrier, an exposure device that performs exposure according to image information to the photoelectric conversion layer in the recording head, A voltage applying means for applying a voltage between the conductive layer and the conductive layer in the recording head, and exposing the photoelectric conversion layer by the above-described exposure apparatus in a state where the voltage is applied by the voltage applying means, and In an electrostatic recording apparatus that forms an electrostatic latent image on an image carrier by discharging between the carrier and the carrier, an electrode layer is provided around a discharge unit that performs discharge on the surface of the photoelectric conversion layer in the recording head. In both cases, a bias voltage applying means for applying a bias voltage to the electrode layer is provided, so that a stronger electric field acts on the photoelectric conversion layer between the electrode layer and the conductive layer during non-exposure than during exposure. A control device for controlling a bias voltage applied from the bias voltage applying means to the electrode layer is provided.

In the electrostatic recording apparatus according to the present invention, the voltage is applied between the conductive layer of the image carrier and the conductive layer of the recording head by the voltage applying means, and the photoelectric device of the recording head is exposed by the exposure apparatus. The conversion layer is exposed in accordance with the image information, and discharge is generated between the recording head and the image carrier in the exposed portion to form an electrostatic latent image on the image carrier. A control device controls a bias voltage applied from a bias voltage applying means to an electrode layer provided around a discharge portion that performs discharge on the surface, and at the time of non-exposure than at the time of exposure, this electrode layer and the conductive layer A strong electric field acts on the photoelectric conversion layer between the two.

Here, as described above, when a bias voltage is applied from the bias voltage applying means to the electrode layer provided around the discharge portion for performing the discharge on the surface of the photoelectric conversion layer,
When a predetermined portion of the photoelectric conversion layer is exposed for a long time from the exposure device so as to form an electrostatic latent image continuous in the moving direction of the image carrier, the portion of the photoelectric conversion layer remains without being discharged. Even if excess carriers are generated, the excess carriers move quickly toward the electrode layer due to the electric field acting on the photoelectric conversion layer between the electrode layer and the conductive layer in this recording head, and the excess carriers Flows into the electrode layer or is discharged at the boundary between the electrode layer and the discharge portion, and is discharged through the electrode layer.

For this reason, even when an electrostatic latent image continuous in the moving direction of the image carrier is formed, the discharge between the recording head and the image carrier due to the excess carrier after the completion of the exposure as in the prior art. And the formed image is prevented from extending in the moving direction of the image carrier.

Further, when applying a bias voltage to the electrode layer provided on the surface of the photoelectric conversion layer from the bias voltage applying means as in the electrostatic recording device of the present invention,
By controlling the bias voltage applied from the bias voltage applying means by the control device and applying a stronger electric field to the photoelectric conversion layer between the electrode layer and the conductive layer at the time of non-exposure than at the time of exposure, Even if carriers are generated in the photoelectric conversion layer by weak light from the exposure device,
The carriers move quickly toward the electrode layer due to the strong electric field acting on the photoelectric conversion layer, and the carriers flow into the electrode layer or are discharged at the boundary between the electrode layer and the discharge portion, and are discharged through the electrode layer. Become so.

For this reason, discharge is prevented from occurring between the recording head and the image carrier in a portion where no exposure is performed, and back noise does not occur in the background portion of an image formed as in the prior art. Is suppressed.

On the other hand, when an electrostatic latent image is formed on an image carrier by performing exposure, the bias voltage applied to the electrode layer from the bias voltage applying means is changed to change the voltage between the electrode layer and the conductive layer. When the electric field acting on the photoelectric conversion layer is weaker than that at the time of non-exposure, the carriers generated in the photoelectric conversion layer due to exposure by the exposure device are sufficiently discharged from the discharge portion to the surface of the image carrier, and sufficiently discharged to the surface of the image carrier. Thus, an electrostatic latent image having a high charge is formed, and an image having a sufficient image density can be obtained.

Here, the controller applies the bias voltage applying means so that a stronger electric field acts on the photoelectric conversion layer between the electrode layer and the conductive layer during non-exposure than during exposure. In controlling the bias voltage to be applied from the above, for example, a strong electric field is applied to the photoelectric conversion layer between the electrode layer and the conductive layer in an inter-image portion between image portions where an electrostatic latent image is formed. The controller controls the bias voltage to be applied to the electrode layer from the bias voltage applying means by the control device.Also, during exposure scanning for forming an electrostatic latent image, each time switching between exposure and non-exposure is performed. It is also possible to control the bias voltage applied from the bias voltage applying means to the electrode layer by the controller so that a stronger electric field acts on the photoelectric conversion layer during non-exposure than during exposure A.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrostatic recording apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

In the electrostatic recording apparatus according to this embodiment, as shown in FIG.
0 is formed in a ring shape, and the ring-shaped image carrier 10 is provided with a pair of rollers 1, 2 provided at a required distance.
, And one of the rollers 1 is rotated by a driving device (not shown) so that the image carrier 10 is
It is made to run between two. In this embodiment, the belt-shaped image carrier 10 formed as described above is used in the form of a ring, but the drum-shaped image carrier 10 is used, The body 10 may be rotated.

FIG. 2 shows an example of the image carrier 10 described above.
As shown in FIG. 2, a conductive layer 12 is formed on the surface of a dielectric substrate 11 and an insulating dielectric layer 13 is further formed on the conductive layer 12. The conductive layer 12 is grounded by a lead wire 14.

Here, in the image carrier 10, as a material constituting the base 11 and the dielectric layer 13, for example, polyimide, fluorine resin, polyethylene, polypropylene, ionomer, polyvinyl alcohol, polyvinyl acetate, ethylene acetate Vinyl copolymer, poly-4-methylpentene-1, polymethyl methacrylate, polycarbonate polystyrene, acrylonitrile methyl acrylate copolymer, acrylonitrile butadiene styrene copolymer, polyterephthalate ethylene, polyurethane elastomer, cellulose acetate, triacetic acid Cellulose, cellulose nitrate, cellulose propionate, cellulose acetate butyrate, ethyl cellulose, regenerated cellulose, nylon 6,
Nylon 66, nylon 11, nylon 12, polysulfone, polyethersulfone, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, polyvinylidene chloride, vinylidene chloride, vinyl chloride copolymer, vinyl nitrile rubber alloy, polytetrafluoroethylene, Polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyethylene tetrafluoroethylene copolymer and the like can be used.

The dielectric layer 1 of the image carrier 10
3, the electric resistivity of the dielectric layer 13 is set to 10 ¹¹ in order to prevent the potential of the charged portion from lowering.
Ω · cm or more.
The thickness may be within a range where the strength is not a problem in practical handling and durability, and is generally 2 μm.
It is considered that about m to 100 μm is appropriate.

When an electrostatic latent image is formed on the surface of the image carrier 10 running between the rollers 1 and 2 as described above, the recording head 20 faces the dielectric layer 13 on the surface of the image carrier 10. In such a manner, an exposure device 30 is provided along the width direction of the image carrier 10 orthogonal to the moving direction of the image carrier 10, and an exposure device 30 is provided behind the recording head 20. Exposure is performed in accordance with image information, and discharge is performed between the recording head 20 and the image carrier 10 in a portion thus exposed,
An electrostatic latent image is formed on the image carrier 10.

Here, as shown in FIGS. 2 and 3, the recording head 20 includes a light-transmitting conductive layer 22, a charge injection preventing layer 23, and a charge generating material on a light-transmitting substrate 21. And a charge transfer layer 24b containing a charge transport material, and an electrode layer 25 in which a discharge portion 25a for performing discharge is formed in a slit shape.
Are sequentially stacked.

As a voltage applying means 31 for applying a voltage between the conductive layer 12 of the image carrier 10 and the conductive layer 22 of the recording head 20, a power supply is applied to the conductive layer 22 of the recording head 20. 31 are connected.

As a bias voltage applying means 32 for applying a bias voltage to the electrode layer 25 of the recording head 20, a bias power supply 32 is connected to the electrode layer 25, and the bias power supply 32 applies a voltage to the electrode layer 25. A control device 33 for controlling the bias voltage is provided. The controller 33 controls the bias voltage applied from the bias power supply 32 to the electrode layer 25 to the photoelectric conversion layer 24 between the electrode layer 25 and the conductive layer 22 during non-exposure rather than during exposure. A strong electric field is applied.

Here, a transparent glass plate is generally used as the translucent substrate 21 in the recording head 20, and a transparent ITO film is generally used as the translucent conductive layer 22.

The photoelectric conversion layer 24 is a function-separated type in which the charge generation layer 24a containing the charge generation material and the charge transfer layer 24b containing the charge transport material are laminated as described above. The invention is not limited thereto, and any structure may be used as long as it is configured similarly to the photosensitive layer in the electrophotographic photosensitive member, and a so-called single-layer type photoelectric conversion layer 24 may be used. The charge generation material, charge transport material, binder resin, additives and the like used in the photoelectric conversion layer 24 may be selected from known materials similar to those used in the photosensitive layer of the electrophotographic photosensitive member according to the purpose. Can be selected and used.

Examples of the material constituting the electrode layer 25 provided on the photoelectric conversion layer 24 include metal materials such as aluminum, chromium, titanium, magnesium, gold, and platinum; tin oxide, indium oxide, and ITO. A conductive oxide film, a conductive paste, a conductive ink, or the like can be used, and a surface protective layer (not shown) can be provided on the electrode layer 25. When a surface protection layer is not provided on the electrode layer 25, it is preferable to use a material that is not easily oxidized by the discharge in the discharge unit 25a as a material for forming the electrode layer 25.

Further, the discharge unit 25 which performs the discharge as described above
When providing the electrode layer 25 in which a is formed in the shape of a slit, for example, a mask member (not shown) corresponding to the discharge unit 25a is arranged on the photoelectric conversion layer 24,
The electrode layer 25 is formed by a method such as vapor deposition, ion plating, sputtering, or printing, or after the electrode layer 25 is formed, a part of the electrode layer 25 is removed in a slit shape by photolithography or the like, and discharge is performed. Part 25
A method such as providing a can be used.

When the electrode layer 25 is provided on the photoelectric conversion layer 24 in this manner, the electrode layer 25 is sufficiently adhered to the photoelectric conversion layer 24 and no problem is caused in handling and durability. In general,
The thickness of the electrode layer 25 is set in the range of 0.03 μm to 5 μm. In addition, in the slit-shaped discharge portion 25a, the slit width L is generally set in a range of 10 μm to 150 μm so that the discharge is appropriately performed.

In this embodiment, a spacer 26 is provided between the recording head 20 and the image carrier 10 as shown in FIG. The dielectric layer 13 of the carrier 10 is opposed to the carrier 10 at a required interval.

Here, the material forming the spacer 26 has a small coefficient of friction with the image carrier 10,
Any material that does not easily scratch the surface of 0, for example,
Fluororesin or the like can be used.

As described above, the spacer 26 is provided between the recording head 20 and the image carrier 10, and the recording head 2
When the image carrier 10 is not brought into contact with the image carrier 10, the surface of the recording head 20 is not contaminated by the foreign material even if the foreign material is transported as the image carrier 10 travels.

On the other hand, the above-described exposure device 40 that performs exposure on the recording head 20 according to image information includes:
For example, a laser device, an LED device, various optical shutter array devices, and the like can be used.

In the electrostatic recording apparatus according to this embodiment, when the electrostatic latent image is formed on the surface of the image carrier 10, the recording head 20 is supplied from the power source 31.
A voltage is applied between the conductive layer 22 of the image carrier 10 and the conductive layer 12 of the image carrier 10 to apply an electric field between the recording head 20 and the image carrier 10. The corresponding light is guided to the recording head 20 through an exposure slit 27 provided in the recording head 20, and this light is applied to the slit-shaped portion of the photoelectric conversion layer 24 provided with the discharge portion 25a.

As described above, the exposure device 40 transfers the photoelectric conversion layer 2
4 is irradiated with light, carriers are generated in the photoelectric conversion layer 24, and the carriers are applied to a discharge portion 25 a facing the image carrier 10 by an electric field acting between the recording head 20 and the image carrier 10. The discharger 25a moves and the electric field rises in the discharge portion 25a to generate a discharge.
0, an electrostatic latent image is formed on the surface.

In the case where discharge is performed by irradiating light from the exposure device 40 as described above, and in the case where discharge is not performed without irradiating light, the electrode layer 25 of the recording head 20 is supplied from the bias power supply 32. Is controlled by the control device 33, and when no discharge is performed, a stronger electric field is applied to the photoelectric conversion layer 24 between the electrode layer 25 and the conductive layer 22 than when a discharge is performed. To do.

As described above, when the exposure device 40 performs long-time exposure to the photoelectric conversion layer 24 at a certain portion from the exposure device 40 to form an electrostatic latent image continuous in the moving direction of the image carrier 10 as described above. Even if excess carriers remain without being discharged in the photoelectric conversion layer 24, the excess carriers are quickly released through the electrode layer 25, and after the exposure, the excess
The occurrence of discharge between the photoconductor and the image carrier 10 is suppressed, and weak light is guided from the exposure device 40 to the photoelectric conversion layer 24 in the non-exposed portion. Even if a carrier is generated, the carrier is released through the electrode layer as in the case described above, thereby preventing a discharge from occurring between the recording head 20 and the image carrier 10 in a non-exposed portion.

After the electrostatic latent image is formed on the surface of the image carrier 10 in this manner, the static latent image formed on the surface of the image carrier 10 is formed in the same manner as in a commonly used image forming apparatus. The toner 51 is supplied from the developing device 50 to the electro-latent image,
A toner image corresponding to the electrostatic latent image is formed on the surface of the image carrier 10.

Here, in the developing device 50, the toner 51 is accommodated in the toner accommodating section 52, and a developing sleeve 53 is provided so as to face the image carrier 10. 51 is supplied to a developing sleeve 53 by a supply roller 54, and the toner 51 thus supplied is guided to the image carrier 10 by the developing sleeve 53, and the developing sleeve 53 is transferred to the image carrier 10.
And a toner image corresponding to the electrostatic latent image formed on the surface of the image carrier 10 is formed.

After the toner image corresponding to the electrostatic latent image is formed on the surface of the image carrier 10 in this way, the image carrier 10
The recording paper 61 is moved between the transfer roller 60 and the image carrier 10 in synchronization with the toner image being guided to the position of the transfer roller 60 provided so as to face one of the rollers 2 for running the recording paper 61. The transfer roller 60 guides the toner image formed on the surface of the image carrier 10 to the recording paper 61.
To be transferred.

Next, an experiment was conducted using the electrostatic recording apparatus according to the above-described embodiment, and when an image was formed using the electrostatic recording apparatus according to the embodiment satisfying the conditions of the present invention, occurrence of back noise occurred. It will be clarified with reference to a comparative example that an image having a sufficient image density can be obtained while being prevented.

Here, in this experiment, the thickness of the image carrier 10 in the above-mentioned electrostatic recording apparatus was 50 μm.
m, a conductive layer 12 is formed on a substrate 11 made of a polyimide film having a width of 25 cm and a peripheral length of 30 cm.
The dielectric layer 13 having a thickness of 0 μm was used.

Further, in the above recording head 20,
As the substrate 21, a transparent glass plate having a thickness of 3 mm, a length in the width direction facing the image carrier 10 of 25 cm, and a length in the moving direction of the image carrier 10 of 30 mm was used. A conductive layer 22 made of an ITO film having a thickness of about 0.2 μm is formed on the surface of the conductive layer 22 by a known ion plating method.
m of the charge injection prevention layer made of a polyamide resin layer
3 was formed by a tipping method. The area resistance of the ITO film forming the conductive layer 22 is about 100Ω / □.
Met.

In providing the photoelectric conversion layer 24 on the charge injection preventing layer 23, first, 1 part by weight of τ-type metal-free phthalocyanine is added to a polyvinyl butyral resin (acetylation degree 3 mol% or less, butylation 2), 100 parts by weight of tetrahydrofuran were dispersed in a ball mill pot, and these were dispersed for 24 hours to prepare a coating solution for a charge generation layer. The liquid was applied on the charge injection preventing layer 23 by using a tipping method to form a charge generation layer 24a having a thickness of 0.4 μm after drying. In addition, the viscosity of the above-mentioned coating liquid for charge generation layers was 15 cP at 20 ° C.

Next, 8 parts by weight of the hydrazone compound represented by the following chemical formula 1, 0.1 part by weight of the orange dye, and 10 parts by weight of the polycarbonate resin were added to a solvent consisting of 180 parts by weight of tetrahydrofuran. The coating solution for the charge transfer layer is prepared by dissolving the solution, the coating solution for the charge transfer layer is coated on the charge generation layer 24a by using a tipping method, and dried to form a charge having a thickness of 15 μm. A transfer layer 24b is formed, and the charge generation layer 24a and the charge transfer layer 24 are formed.
b) is provided.

[0049]

Embedded image

Then, aluminum is vapor-deposited in a state where a mask member is disposed on the surface of the photoelectric conversion layer 24,
An electrode layer 25 having a thickness of 0.1 μm is provided.
Removing the mask member to expose the photoelectric conversion layer 24;
A discharge part 25a having a slit width L of 90 μm was formed.

The recording head 20 formed as described above
A spacer 26 is provided between the photoconductor 10 and the image carrier 10, and the distance between the discharge unit 25 a and the dielectric layer 13 of the image carrier 10 is set to 20 μm by the spacer 26.

The exposing device 40 for exposing the recording head 20 according to image information includes a semiconductor laser generator, a collimating lens, a polygon mirror,
An optical element provided with an Fθ lens, a reflection mirror, and the like is used to transmit a laser beam generated by a semiconductor laser generator through an exposure slit 27 provided in the recording head 20 and a discharge section 25 a formed in the slit shape. The light is guided to the conversion layer 24, and is scanned by the polygon mirror along the slit-like discharge portion 25a. In this experiment, scanning exposure at 300 dpi was performed.

When forming an electrostatic latent image on the surface of the image carrier 10 using the recording head 20 and the exposure device 40, the moving speed of the image carrier 10 is set to 3.
At the same time, the voltage of +1600 V was applied to the conductive layer 22 of the recording head 20 from the power supply 31.

In applying a bias voltage to the electrode layer 25 of the recording head 20 from the bias power supply 32, in the first to seventh embodiments, as shown in FIG. The bias voltage Vp ₁ during the formation of an A4 size electrostatic latent image by performing exposure according to the signal and the bias voltage Vp ₂ in the inter-image portion where the electrostatic latent image is not formed are described above. Control device 3
3 by was changed as shown in Table 1 below, and lower than the bias voltage Vp ₁ while the bias voltage Vp ₂ of between images portions not forming the electrostatic latent image to form an electrostatic latent image, electrostatic In the portion between images where no latent image is formed, the electrode layer 2
A strong electric field acts on the photoelectric conversion layer 24 between the conductive layer 5 and the conductive layer 22.

In Examples 8 to 11, as shown in FIG. 5, the bias voltage Vp ₁ at the time when light was irradiated from the exposure device 40 in accordance with the image signal during one exposure scan, and the light irradiation was performed. The bias voltage Vp ₂ at the point in time when not performed is controlled by the controller 33 as shown in Table 1 below.
It was changed as shown in, and the bias voltage Vp ₂ at which light is not irradiated lower than the bias voltage Vp ₁ of the time the light is irradiated, when the light is not irradiated,
The photoelectric conversion layer 24 between the electrode layer 25 and the conductive layer 22
A strong electric field is applied to the device.

On the other hand, in Comparative Examples 1 to 4, constant bias voltages shown in Table 1 below were applied to the electrode layers 25 of the recording head 20 from the bias power supply 32, respectively.

Then, as shown in the above Examples 1 to 11 and Comparative Examples 1 to 4, the surface of the image carrier 10 was extended on the surface of the image carrier 10 as shown in FIG. A band-shaped electrostatic latent image of a book was formed.

After forming the respective electrostatic latent images on the surface of the image carrier 10 in this manner, the developing device 50 converts the electrostatic latent images formed on the surface of the image carrier 10 into the electrostatic latent images. The toner 51 was supplied to form a toner image corresponding to the electrostatic latent image on the surface of each image carrier 10.

Here, in the developing device 50,
The toner 51 has an average particle size of 10 μm obtained by kneading, pulverizing, and classifying a mixture containing a bisphenol A type polyester resin and carbon black as main components by a known method.
In addition to using a negatively charged m, a suitable developing bias voltage is applied to the developing sleeve 53 to prevent background fogging.

Next, the toner image thus formed on each image carrier 10 is transferred to the recording paper 61 by the transfer roller 60 as described above, and the occurrence of background noise and the image density in each formed image are performed. Was evaluated, and the results are shown in Table 1 below.

Here, the situation of occurrence of the back noise is shown in FIG. 6 in the case of the A4 recording paper 61 on which the image is formed.
The number of black streaks extending in the direction orthogonal to the band-shaped image portion in the white image portion corresponding to the range shown in (a) is counted, and the results are shown in Table 1.

Regarding the image density, the image density in the band-shaped image area was measured with a commercially available densitometer (trade name: Sakura Densitometer PDA). ◎, the image density is 0.9 ~
When there is no practical problem in 1.2, the symbol "O" indicates that the image density is 0.
Table 1 shows the case where there is a practical problem when the value is less than 9.

[0063]

[Table 1]

As a result, when an image was formed using the electrostatic recording devices of Comparative Examples 1 to 3 in which a constant bias voltage of 200 V or more was applied from the bias power supply 32 to the electrode layer 25 of the recording head 20. In the case where back noise occurs in the formed image and the image is formed using the electrostatic recording apparatus of Comparative Example 4 in which the bias voltage applied to the electrode layer 25 in the recording head 20 is set to 0 V, The image density in the resulting image was low. On the other hand, when an image is formed using the electrostatic recording devices of Examples 1 to 11 satisfying the conditions of the present invention, the generation of the background noise is prevented and the image having the sufficient image density is obtained. was gotten. Further, when an image was formed using these electrostatic recording devices, the occurrence of image elongation was also suppressed.

Here, in the above experiment, when the bias voltage applied to the electrode layer 25 of the recording head 20 from the bias power supply 32 is set to 500 V or more, the electrode layer 25 always discharges to the image carrier 10. ,
The bias voltage applied from the bias power supply 32 is 500
If the bias voltage applied from the bias power supply 32 is set to -100 V or less, sufficient discharge from the recording head 20 to the image carrier 10 at the time of forming a latent image may not be performed, or conversely, Since a discharge is generated from the surface of the image carrier 10 on which the electrostatic latent image is formed toward the electrode layer 25 and the formed image is whitened, the bias voltage Vp ₁ during the formation of the latent image and Examples 8 to 1
The bias voltage Vp ₂ in 1 had to be a voltage higher than -100 V.

In the electrostatic recording device according to the first embodiment, the exposure device 40 is provided behind the recording head 20, and light corresponding to image information is provided from the exposure device 40 to the recording head 20. Although guided to the photoelectric conversion layer 24 through the slit 27, the belt-shaped image carrier 10 is formed in a ring shape as shown in FIG. 3, the space inside the image carrier 10 is increased, and an exposure device 40 is provided inside the image carrier 10 so as to face the recording head 20 via the image carrier 10. Photoelectric conversion layer 2 provided on recording head 20 from device 40
Exposure according to the image information can be performed on the portion 4. In this case, since the light emitted from the exposure device 40 is guided to the recording head 20 through the image carrier 10,
The image carrier 10 needs to be made of a translucent material, while the conductive layer 22
Need not be formed of a translucent material.

[0067]

As described in detail above, in the electrostatic recording apparatus of the present invention, the voltage is applied between the conductive layer of the image carrier and the conductive layer of the recording head by the voltage applying means. An exposure device is provided around a discharge unit that performs discharge on the surface of the photoelectric conversion layer when performing exposure according to image information to the photoelectric conversion layer in the recording head to form an electrostatic latent image on the image carrier. A bias voltage is applied to the electrode layer from the bias voltage applying means, and the bias voltage is controlled by a control device.
A stronger electric field acts on the photoelectric conversion layer between the electrode layer and the conductive layer during non-exposure than during exposure.

As a result, in the electrostatic recording apparatus of the present invention, when an electrostatic latent image was formed continuously in the moving direction of the image carrier, excess carriers which were not discharged and remained in the photoelectric conversion layer were generated. Even so, the excess carriers are quickly released through the electrode layer, and after completion of the exposure as in the conventional case, no discharge is caused by the excess carriers, and the formed image is likely to elongate. This prevented the problem and provided accurate images.

In the electrostatic recording apparatus according to the present invention, even if carriers are generated in the photoelectric conversion layer by weak light from the exposure apparatus during non-exposure, the carriers are generated by the strong electric field acting on the photoelectric conversion layer. It is quickly released through the electrode layer to suppress the generation of background noise in the background portion of the formed image, and at the time of exposure, an electric field acting on the photoelectric conversion layer between the electrode layer and the conductive layer. Is weakened, the carriers generated by the exposure are sufficiently discharged from the discharge portion to the surface of the image carrier, an electrostatic latent image having a sufficient charge is formed on the surface of the image carrier, and the image has a sufficient image density. Images can now be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a state where an image is formed using an electrostatic recording device according to an embodiment of the present invention.

FIG. 2 is a partial explanatory view showing a state in which a recording head is provided so as to face an image carrier in the electrostatic recording apparatus of the embodiment.

FIG. 3 is a front view showing a state in which an electrode layer provided with a slit-shaped discharge portion is provided on a recording head in the electrostatic recording device of the embodiment.

FIG. 4 shows Examples 1 to 3 using the electrostatic recording apparatus of the embodiment.
FIG. 7 is a timing chart showing a state in which the control device switches the bias voltage applied to the electrode layer of the recording head at 7.

FIG. 5 shows Examples 8 to using the electrostatic recording apparatus of the embodiment.
FIG. 11 is a timing chart showing a state in which the control device switches the bias voltage applied to the electrode layer of the recording head at 11.

FIG. 6 is a diagram illustrating a state of an electrostatic latent image formed on an image carrier in Examples and Comparative Examples.

FIG. 7 is a schematic explanatory view showing a state in which an image is formed using an electrostatic recording device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image carrier 12 Conductive layer of image carrier 13 Dielectric layer 20 Recording head 22 Conductive layer of recording head 24 Photoelectric conversion layer 25 Electrode layer 25a Discharge part 31 Voltage application means (power supply) 32 Bias voltage application means (bias power supply) 33 Control device 40 Exposure device

Claims (1)

[Claims] An image carrier having a dielectric layer formed on a conductive layer; and a recording head having a photoelectric conversion layer formed on the conductive layer facing the dielectric layer of the image carrier. An exposure device for performing exposure according to image information to the photoelectric conversion layer of the recording head; and voltage applying means for applying a voltage between the conductive layer of the image carrier and the conductive layer of the recording head. Exposure of the photoelectric conversion layer by the above-described exposure apparatus in a state where a voltage is applied by means,
In an electrostatic recording apparatus that forms an electrostatic latent image on an image carrier by a discharge between a recording head and an image carrier, an electrode is provided around a discharge portion that performs discharge on the surface of the photoelectric conversion layer in the recording head. A bias voltage applying means for applying a bias voltage to the electrode layer, and a stronger electric field acts on the photoelectric conversion layer between the electrode layer and the conductive layer during non-exposure than during exposure. As described above, the electrostatic recording device is provided with the control device for controlling the bias voltage applied from the bias voltage applying means to the electrode layer.