JP2014178560A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain images having no occurrence of leakage and sufficient gradation characteristics, when both a brush-like charging brush (charging member) 2 and a photoreceptor (image carrier) 1 having suppressed the leakage, in an imaging device of an image forming apparatus.SOLUTION: An imaging device uses a charging brush 2 that uniformly charges a photoreceptor 1 carrying images, exposes the photoreceptor 1 with laser beams LZ from a line head (3), develops electrostatic latent images on the photoreceptor 1 with a toner on a developing roller 43 of a developing device 4, and uses, as the photoreceptor 1, a photoreceptor including an undercoat layer (12) on a support (11) and a charge generating layer (13) and a charge transport layer (14) thereon. When a transit time of the developing device 4 from an exposure position P1 to a developing position P2 on the surface of the photoreceptor 1 is T (s), and the power of the laser is L (μW), the imaging device sets T and L so as to satisfy (1): L≥-333×T+217.

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer using an electrophotographic system, and an image forming apparatus used therefor.

  Examples of the image forming apparatus in the image forming apparatus include those disclosed in Japanese Patent Application Laid-Open Nos. 2003-131477 (Patent Document 1) and 2004-184909 (Patent Document 2).

  In Patent Document 1, the charging means of the image carrier is a contact charging means using conductive particles, and the supply of the conductive particles to the contact charging means is performed by externally adding the conductive particles to the developer of the developing means. Then, it is carried out from the developing means through the image carrier surface. Further, in the transfer type and cleanerless image forming apparatus, the supply of the conductive particles by the developing unit is stably performed, and the dark potential Vd maintaining property is improved while ensuring a margin for the leaked image.

  Japanese Patent Application Laid-Open No. 2004-228688 discloses a toner-less image forming apparatus in which toner is scattered on the downstream side of the charging unit and upstream of the position where the latent image forming unit forms the latent image on the image carrier. A cleanerless image forming apparatus including a member.

  Japanese Patent Application Laid-Open No. H10-228561 discloses that a countermeasure against leakage is taken in a cleanerless image forming apparatus. However, this Patent Document 1 does not use an image carrier (photoreceptor) having an undercoat layer that is effective in improving leakage, and there is a problem of leakage due to scratches that the user may inadvertently apply. Has not been resolved.

  Further, Patent Document 2 discloses that a brush is brought into contact with the photoconductor for the purpose of scattering the transfer residual toner on the photoconductor with a brush. However, the problem that the charging member and the brush can be combined to be compact and simple can not be solved.

  Japanese Patent Laid-Open No. 9-114193 discloses a charge injection method using a charging brush for magnetic particles. Japanese Patent Application Laid-Open No. 2009-69236 discloses one that uses a laser power of 21 μW (= 0.21 mW) or less. JP-A-8-6357 discloses a contact injection charging type. JP-A-8-50395, JP-A-8-0394, and JP-A-2003-57868 each disclose a charge injection method using a charging brush for magnetic particles. However, these techniques are different in configuration from the present invention.

  Further, in the image forming apparatus of the image forming apparatus, it is effective to increase the thickness of the undercoat layer of the image carrier such as a photoconductor to cope with the leakage of the brush-shaped charging member, and further carelessness of the image carrier. It is already known that there is an effect on leakage from scratches. However, the conventional image carrier having a thick undercoat layer has a problem that the sensitivity is deteriorated and the gradation of the image cannot be satisfied.

  SUMMARY OF THE INVENTION An object of the present invention is to obtain an image having sufficient gradation without causing leakage when both a brush-shaped charging member and a photoreceptor with improved leakage are used.

The image forming apparatus according to claim 1 includes an image carrier that carries an image, a brush-like charging member that uniformly charges the image carrier, an exposure unit that exposes the image carrier with laser light, and In an image forming apparatus using a developing unit that develops a latent image on an image carrier with toner, the image carrier includes an undercoat layer on a support, and a charge generation layer and a charge transport layer thereon. Using an image carrier, the passing time of the surface of the image carrier from the exposure position by the exposure means to the development position by the development means is T (s), and the laser power of the exposure means is L (μW). and when,
L ≧ −333 × Ding + 217 (1)
It is characterized by satisfying.

  According to the image forming apparatus of the first aspect, since a leak does not occur even if a flaw is caused by a brush-like charging member, in order to be able to use a photoconductor provided with an undercoat layer having a low sensitivity, the exposure position can be used. Since the conditions for the passage time of the surface of the image carrier to the development position and the exposure amount are set, stable high-quality images can be obtained.

1 is a schematic configuration diagram illustrating a main part of an image forming apparatus according to a first embodiment of an image forming apparatus to which the present invention is applied. It is a figure explaining the film | membrane structure of the photoconductor of embodiment. It is a figure explaining the sensitivity comparison of a photoconductor with an undercoat layer in the embodiment and without an undercoat layer. It is a figure explaining the area | region from the exposure position to the image development position in embodiment. It is a figure explaining the passage time and exposure amount of the surface of the photoreceptor from the development position to the exposure position in the embodiment. It is a schematic block diagram which shows the principal part of the image forming apparatus of 2nd Embodiment of the image forming apparatus to which this invention is applied.

  Hereinafter, an embodiment of an image forming apparatus in a printer as an image forming apparatus to which the present invention is applied will be described. FIG. 1 is a schematic configuration diagram illustrating a main part of the image forming apparatus according to the first embodiment. The image forming apparatus includes a photosensitive member 1 as an “image carrier”, a brush-like charging brush 2 as a “charging member”, a line head 3 as an “exposure unit”, a developing device 4 as a “developing unit”, A transfer roller 5 and the like are provided.

  The photoreceptor 1 is driven to rotate in the clockwise direction in the drawing by a driving means (not shown). The charging brush 2 uniformly charges the surface of the photoreceptor 1 that is rotationally driven in this way. The surface of the photosensitive member 1 that is uniformly charged is formed with an electrostatic latent image by the laser light LZ from the line head 3 as an exposure means, and carries this electrostatic latent image. This electrostatic latent image is developed into a toner image by a developing device 4 using toner (not shown). The developed toner image is transferred onto a recording sheet at a transfer nip portion between the photoreceptor 1 and the transfer roller 5.

  The recording paper is supplied from a paper feed cassette provided in a printer main body (not shown), and the recording paper on which the toner image is transferred is fixed to the toner image by the fixing device and discharged outside the apparatus. As described above, the image forming apparatus of the embodiment constitutes a part of a printer as an image forming apparatus.

The developing device 4 includes a hopper unit 4A that stores toner (not shown) and a developing unit 4B. In the hopper section 4A, an agitator 41 that is rotationally driven by a driving means, a toner supply roller 42 that is rotationally driven by the driving means, and the like are disposed.
The toner in the hopper portion 4 </ b> A moves toward the toner supply roller 42 while being agitated by the rotational drive of the agitator 41. The toner supply roller 42 has a metal cored bar and a roller portion made of foamed resin or the like coated on the surface thereof, and rotates while adhering the toner in the hopper portion 4A to the surface of the roller portion. To do.

  Further, in the developing unit 4B of the developing device 4, a developing roller 43 as a “developer carrying member” that rotates while being in contact with the photosensitive member 1 and the toner supply roller 42, and a thin film whose tip is in contact with the surface thereof. A layering blade 44 and the like are provided. The toner attached to the toner supply roller 42 in the hopper 4A is supplied to the surface of the development roller 43 at the contact portion between the development roller 43 and the toner supply roller 42. When the supplied toner passes through the contact position between the developing roller 43 and the thinning blade 44 as the developing roller 43 rotates, the layer thickness on the surface of the developing roller 43 is regulated.

  Then, the toner whose layer thickness has been regulated adheres to the electrostatic latent image on the surface of the photosensitive member 1 in the developing region which is a contact portion between the developing roller 43 and the photosensitive member 1. By this adhesion, the electrostatic latent image is developed into a toner image. A transfer bias is applied to the transfer roller 5 by a transfer bias power source (not shown), whereby a transfer electric field is formed between the electrostatic latent image on the photoreceptor 1 and the transfer roller 5. In place of the transfer roller 5, a transfer charger or a transfer brush may be employed.

  FIG. 2 is a view for explaining the film configuration of the photoreceptor 1 of the embodiment which is an “image carrier”. The photoreceptor 1 has a support 11 for grounding in the lowest layer, an undercoat layer 12 for preventing leakage on the support 11, and a charge generation layer 13 on the undercoat layer 12. In addition, a charge transport layer 14 is provided on the charge generation layer 13. The photoreceptor 1 has a drum shape, and the support 11 constitutes the core material.

  FIG. 3 is a diagram for explaining a sensitivity comparison of the photoreceptors with and without the undercoat layer. The measurement conditions are such that the laser beam is light having a constant wavelength, irradiation is performed for a fixed irradiation time, and the moving speed of the surface of the photosensitive member is set to a fixed speed. Then, the surface potential value was measured by changing the intensity of the laser power for the photoreceptor having an undercoat layer and the photoreceptor having no undercoat layer. A photoreceptor with an undercoat layer is duller in surface potential attenuation than a photoreceptor without an undercoat layer.

  FIG. 4 is a diagram illustrating an area from the exposure position to the development position in the embodiment. The line head 3 and the developing roller 43 (developing device 4) are installed so that the exposure position P1 and the developing position P2 are arranged in this order from the downstream side with respect to the rotation direction of the photoconductor 1 in the clockwise direction. The surface of the photoreceptor 1 moves between the exposure position P1 and the development position P2 with a constant passage time by the rotation of the photoreceptor 1 itself. If the sensitivity of the photoconductor 1 is poor, the surface potential of the photoconductor 1 after the exposure is not sufficiently lowered to a predetermined potential. Therefore, this can be dealt with by ensuring a sufficient amount of time on the surface of the photoreceptor 1 from the exposure position P1 to the development position P2 or by increasing the exposure amount.

FIG. 5 is a diagram for explaining the passage time and exposure amount of the surface of the photoreceptor 1 from the development position P1 to the exposure position P2. The photoreceptor 1 with the undercoat layer has a lower surface potential sensitivity than the photoreceptor without the undercoat layer. Therefore, it is necessary to set a longer exposure time and a longer exposure time from the exposure position P1 to the development position P2. Therefore, when the passing time from the exposure position P1 to the development position P2 is T (s: second) and the laser power of the line head 3 as the exposure means is L (μW),
L ≧ −333 × T + 217 (1)
Set to satisfy the following formula. As a result, the photoconductor without an undercoat layer has good gradation, and the photoconductor with an undercoat layer has poor tone. it can.

  FIG. 6 is a schematic configuration diagram showing a main part of the image forming apparatus of the second embodiment. In addition, the same code | symbol as FIG. 1 is attached to the element similar to 1st Embodiment, and a corresponding element. In the printer according to the second embodiment, the photosensitive member 1 and the developing device 4 are configured as a process cartridge 10 supported as a single image forming unit on a common support. If the process cartridge 10 needs to be replaced due to deterioration of the photoconductor 1 or the developing device 4 with time, it can be taken out as shown in FIG. That is, the process cartridge 10 can be taken out upward (in the direction of arrow A in the figure) by opening the paper discharge tray 9 which is an opening / closing member provided on the upper surface of the printer main body 20.

  Similar to the first embodiment, the photosensitive member 1 is driven to rotate in the clockwise direction in the drawing by a driving unit (not shown). The charging brush 2 uniformly charges the surface of the photoreceptor 1 that is driven to rotate. An electrostatic latent image is formed on the surface of the uniformly charged photoreceptor 1 by the laser light L from the line head 3 as an exposure means, and this electrostatic latent image is carried. This electrostatic latent image is developed into a toner image by a developing device 4 using toner (not shown). The developed toner image is transferred onto a recording sheet at a transfer nip portion between the photoreceptor 1 and the transfer roller 5. The recording paper is conveyed from a paper feed cassette 7 provided at the lower part of the printer main body 20 toward a transfer nip portion between the photoreceptor 1 and the transfer roller 5 by a paper feed roller 7a, a registration roller (not shown), or the like. Is done. Further, the recording paper onto which the toner image has been transferred is conveyed to the fixing device 8 where the toner image is fixed and discharged outside the apparatus.

  The developing device 4 includes a hopper portion 4A that stores toner and a developing portion 4B, and a toner supply roller 42 that is rotationally driven by a driving unit is disposed in the hopper portion 4A. The toner in the hopper 4A moves toward the toner supply roller 42 while being agitated, and the toner supply roller 42 rotates while adhering the toner in the hopper 4A to the surface of the roller. Further, in the developing unit 4B, a developing roller 43 as a “developer carrying member” that rotates while contacting the photoreceptor 1 and the toner supply roller 42, and a thinning blade 44 whose tip is in contact with the surface thereof. Etc. are arranged. The toner attached to the toner supply roller 42 is supplied to the surface of the development roller 43 at a contact portion between the development roller 43 and the toner supply roller 42, and the supplied toner is developed with the rotation of the development roller 43. The layer thickness is regulated by the thinning blade 44.

  Then, the toner whose layer thickness has been regulated adheres to the electrostatic latent image on the surface of the photosensitive member 1 in the developing region which is a contact portion between the developing roller 43 and the photosensitive member 1. By this adhesion, the electrostatic latent image is developed into a toner image. Note that a transfer bias is applied to the transfer roller 5 by a transfer bias power source (not shown), whereby a transfer electric field is formed between the electrostatic latent image on the photoreceptor 1 and the transfer roller 5. In place of the transfer roller 5, a transfer charger or a transfer brush may be employed.

  The film configuration of the photoreceptor 1 of the embodiment which is the “image carrier” of the second embodiment is the same as that of the photoreceptor 1 of the first embodiment shown in FIG. Further, the relationship between the passage time from the exposure position P1 to the development position P2 on the surface of the photoreceptor 1 as T (s) and the laser power of the line head 3 as the exposure means as L (μW) is the same as in the first embodiment. Is set to satisfy the previous equation (1). The effect by these structures is the same as that of 1st Embodiment.

  In the image forming apparatus according to the second embodiment, the exposure position P1 by the line head 3 as an exposure unit is opposed to the developing roller 43 as a developer carrier with the photoconductor 1 as an image carrier interposed therebetween. It is characterized by its location. Therefore, as shown in FIG. 6B, the line head 3 as the exposure means is fixed to the main body, and the process cartridge 10 as a part of the image forming apparatus can be removed. Thereby, the exposure position P1 can be adjusted with high accuracy, so that a detailed latent image can be formed. Further, a more detailed latent image can be formed by using the line head 3 that performs line-like writing. In addition, since the charging brush 2 as a charging member is fixed to the main body and the process cartridge 10 can be removed, it is not necessary to replace the charging brush 2 with a life other than the charging brush 2, and the charging brush 2 can be used up to the life of the charging brush 2 alone. Can be used.

  In each embodiment, the undercoat layer 12 of the photoreceptor 1 has a thickness of 2 μm or more. Thereby, there is an effect of preventing leakage.

  In each embodiment, the thickness of the charge transport layer 14 of the photoreceptor 1 is 17 μm or more. This makes it difficult to leak.

  Further, in each embodiment, the transfer residual toner on the photoreceptor 1 which is an “image carrier” is collected by the developing roller 43 which is a “developer carrier”. This eliminates the cleaner blade and enables compactness.

  In each embodiment, an AC voltage waveform (AC waveform) is applied to the charging brush 2 that is a “charging member”. Thereby, a fine latent image can be formed.

  In each embodiment, the line head 3 that performs line-like writing (exposure) is used. Thereby, a more detailed latent image can be formed.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

1 Photoconductor (image carrier)
DESCRIPTION OF SYMBOLS 11 Support body 12 Undercoat layer 13 Charge generation layer 14 Charge transport layer 2 Charging brush (charging member)
3 Line head (exposure means)
4 Developing device (Developing means)

JP 2003-131477 A JP 2004-184909 A

Claims (9)

An image carrier that carries an image, a brush-like charging member that uniformly charges the image carrier, an exposure unit that exposes the image carrier with laser light, and a latent image on the image carrier that is a toner. In the image forming apparatus using the developing means for developing by
As the image carrier, an image carrier comprising an undercoat layer on the support, a charge generation layer and a charge transport layer thereon, and from an exposure position by the exposure means to a development position by the development means When the passing time on the surface of the image carrier is T (s) and the laser power of the exposure means is L (μW),
L ≧ −333 × Ding + 217 (1)
An image forming device characterized by satisfying   The image forming apparatus according to claim 1, wherein the undercoat layer is 2 μm or more.   The image forming apparatus according to claim 1, wherein the charge transport layer has a thickness of 17 μm or more.   The image forming apparatus according to claim 1, wherein a transfer residual toner on the image carrier is collected by a developer carrier of the developing unit.   The image forming apparatus according to claim 1, wherein an AC waveform is applied to the charging member.   6. The image forming apparatus according to claim 1, wherein the exposure position is a portion facing the developer carrier of the developing unit with the image carrier interposed therebetween. .   The image forming apparatus according to claim 1, wherein a line head that performs line-like writing is used as the exposure unit.   The image forming apparatus according to claim 1, wherein the charging member is fixed to the main body, and a process cartridge including the image carrier and the developing unit can be removed.   An image forming apparatus comprising the image forming apparatus according to claim 1.

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