JPH0452661A - 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 <Industrial Application Field> The present invention relates to an image forming apparatus that forms an image by electrostatically adhering a developer to a recording medium.

<Prior art> Various devices have been developed to form images according to image information, and some of these devices use conductive magnetic toner, which is a fine powder developer, to electrostatically transfer the toner to a recording medium. There is an imaging device that forms an image by depositing it.

For example, the method shown in Japanese Patent Publication No. 51-46707 has been proposed. As shown in FIG. 6, a non-magnetic cylinder 50
The conductive magnetic toner 51 on the outer periphery of the non-magnetic cylinder 50 is attached to the outer periphery of the cylinder 50 and conveyed by an alternating magnetic field of a rotating magnet 52 provided coaxially with the non-magnetic cylinder 50 . Then, the toner 51 is passed through recording electrodes 53 densely arranged along the axial direction on the outer peripheral surface of the non-magnetic cylinder 50,
When the power supply unit is in physical contact with the recording medium 54 formed by laminating the conductive layer 54b and the insulating layer (or di'f!F!Ma) from the inside, which is provided close to the non-magnetic cylinder 50, A voltage is applied by the recording electrode 55. At this time, the recording electrode 53
By applying a voltage corresponding to the image information between the insulating layer 54a of the recording medium 54 and the conductive layer 54b of the recording medium 54, the toner 51 is attached to the insulating layer 54a of the recording medium 54 to form an image.

In addition, as shown in FIG. 7, an image forming apparatus to which the above image forming method is applied is configured such that a non-woven fabric built in a developing device 57 is used for recording medium 54 conveyed by a driving conveyance roller 56a and a driven conveyance roller 56b. Toner 51 is conveyed onto a recording electrode 53 by the rotation of a rotating magnet 52 provided coaxially with the magnetic cylinder 50, and an image is formed by attaching or not attaching the toner 51 according to a signal voltage from a recording control unit 58. .

For example, the signal voltage from the recording control section 58 is +40V.
When the voltage is applied, the toner 51 adheres to the recording medium 54, and when the voltage is □V, the toner 51 does not adhere. By repeating this operation, image formation is performed.

After the image is displayed in the image display area 59, the j. Then, the electrical charge is removed in the direction of grounding, and the recording material falls onto the non-magnetic cylinder 50 and is conveyed again in preparation for the next recording. Further, the charge remaining in the recording medium 54 is removed by the charge removal brush 61 in the direction of grounding.

<Problems to be Solved by the Invention> However, in the above configuration, if recording is always repeated with the same polarity (for example, positive), as shown in FIG. Since the charge remains and accumulates, there are problems described below.

For example, if a negative charge equivalent to 15 V is accumulated in the recording medium 54, the toner 51 is attracted to it by the accumulated residual charge even though it is a white image when it passes through the developing device. There is a risk that the film may adhere to the recording medium 54 and stain the screen, resulting in so-called fog, ghost, or the like.

Furthermore, if negative charge remains and accumulates on the recording medium 54, if an attempt is made to record at +30V when the residual charge passes through the developing device, it will be different from the potential of the recording medium 54 itself by -5■. Recording was performed with an applied voltage of +35 V for contrast, and there was a risk that the image density would be high only in this area, making the image difficult to see.

An object of the present invention is to provide an image forming apparatus that solves the above-mentioned RB problem of the prior art and prevents biased charges from remaining on the recording medium by changing the polarity of the signal voltage applied to the recording electrode at least for each screen. It is about providing.

<Means for Solving the Problems> A typical means for solving the problems of the prior art described above and applied to the embodiments described below includes recording electrodes and a recording electrode for applying voltage to the developer according to image information. , a driving means for applying a signal voltage according to image information to the recording electrode, a recording medium to which the developer is attached to form an image;
The polarity of the signal voltage applied to the recording electrode by the driving means is sequentially changed at least for each screen.

<Function> According to the above configuration, by changing the polarity of the signal voltage applied to the recording electrode for each screen or for each multiple screens, it is possible to prevent charges of unbalanced polarity from remaining in the recording medium. can.

Therefore, unnecessary developer does not adhere to the recording medium during image formation, and a clear, high-quality image can be obtained.

<Embodiment> An embodiment of an image forming apparatus to which the present invention is applied will be described below with reference to the drawings.

FIG. 1(a) Φ)(C)(b) is a schematic explanatory diagram of a recording medium, FIG. 2 is a cross-sectional explanatory diagram showing a schematic configuration of an image forming apparatus,
FIG. 3 is a perspective explanatory view of the recording electrode, and FIG. 4 is a partially enlarged sectional view of the recording medium.

First, the schematic structure of the image forming apparatus will be explained with reference to FIGS. 2 to 4.

In FIG. 2, reference numeral 1 denotes a recording electrode for applying a voltage to the developer according to image information. The recording electrode 1 is arranged axially on the outer peripheral surface of a non-magnetic cylinder (hereinafter referred to as "sleeve") 3 which is a developer supply means for supplying conductive magnetic developer (hereinafter referred to as "toner J") 2. are closely attached along the line.

As shown in FIG. 3, the recording electrodes 1 are densely provided on the flexible printed circuit board 1a along the axial direction. This recording electrode 1 is connected to an electrode driver IC held on a support plate 1b, and a conductor exposed portion 1d that contributes to recording is provided at the tip of the recording electrode 1. As the electrode driver IC, for example, a VFD driver (MS G1163 manufactured by Oki Electric) is used. Further, a plurality of toner through holes 1e are bored in the substrate 1a along the axial direction of the sleeve 3. The toner 2 conveyed in the direction of arrow A on the outer circumference of the sleeve 3 is
The toner is configured to pass through the toner through hole 1e and reach the conductor exposed portion 1d.

Further, 1f is a connector electrically connected to the electrode driver IC.

The toner 2 is magnetic, for example, acrylic resin, 30% to 50% Mag 2 Tight, and 2% to 10% carbon.
% of low electrical resistance is used, and the volume resistivity value is 1 x 102 to 1 x 108 (ΩC111
), and recording is possible at an applied voltage in the range of 10 to 40 inches.

A rotating magnet 4 is coaxially attached to the sleeve 3. This rotating magnet 4 is driven to rotate around a rotating shaft 4a by a drive motor (not shown), and the toner 2 is transferred to the sleeve 3 by an alternating magnetic field formed by this rotating magnet 4.
It is conveyed along the outer circumferential surface of. Said sleeve 3
The rotating magnet 4 is housed in a developing device 7 shown in FIG.

In the vicinity of the recording electrode 1, an endless belt-shaped recording sheet 5, which is a recording medium for forming an image by electrostatically adhering the toner 2, is arranged with a portion of the recording sheet 5 close to it. The recording sheet 5 is passed between a driving roller 6a and a tensile roller 6b, which are arranged in a pair above and below, and serve as a conveying means. The drive roller 6a is rotationally driven by a drive motor (not shown).
The recording sheet 5 is conveyed in the direction of arrow B in FIG.

As shown in FIG. 4, the recording sheet 5 includes a surface layer 5a made of a transparent material mainly composed of butyral resin or urethane resin, a colored inorganic substance, and a binder (acrylic resin, plastic resin). A colored layer 5b, a conductive layer 5c deposited with aluminum or ITO (indium and tin oxide) to provide conductivity, and a base material 5d made of a plastic resin such as polyethylene terephthalate, volutileno, polypropylene, etc. are polymerized. It is composed of

The surface layer 5a and the colored layer 5b constitute an electrically insulated dielectric layer, and the colored layer 5b is made of titanium oxide (TiOz), aluminum oxide (A IhOs), etc. in order to produce white as the base color of the screen. ), tin oxide (Sno
Inorganic substances such as w, ) are used.

The dielectric layer has a thickness of 2 to 40 μm and a volume resistivity of I
The conductive layer 5c has a thickness of 800 to 1000 Ω and a volume resistance of
“Ω1 or less.

The surface layer 5a has a thickness of 1 to 10 μm and a volume resistivity of lXl0h to IXl0I0Ωl, and the colored layer 5b has a thickness of 1 to 30 μm and a volume resistivity of 1×10 to I
IO”Ω1.

8 is a recording control section for applying a voltage to the recording electrode 1 according to image information. This recording control section 8 is
A signal voltage corresponding to image information is applied to the conductive layer 5c of the recording sheet 5 to cause the toner 2 to adhere to the surface layer 5a to form an image.

9 is an image display section for externally displaying the image formed on the recording sheet 5; 10 is a back plate 11 of the main body of the apparatus;
This is a cleaning member attached to via a support member 11a. This cleaning member 10 is composed of a cleaning member main body 10a and a soft, conductive brush 10b, and by rubbing the recording sheet 5 with the brush 10b at an appropriate angle and distance, the recording sheet 5 can be cleaned.
This is to scrape off the toner 2 adhering to the sleeve 3. As the cleaning member 10, materials such as carbon fibers, flexible plastics (polyethylene, polypropylene) that have conductivity due to composites, urethane rubber, or silicone are used.

Further, the main body 10a of the cleaning member 10 is grounded, and when the recording sheet 5 is rubbed, the toner 2 band ii
This is to eliminate the i charge in the direction of ground.

Further, a non-magnetic member 12 and a magnet 13 for supporting the recording sheet 5 are disposed at a position facing the cleaning member 10 with the recording sheet 5 interposed therebetween.

Reference numeral 14 denotes a static eliminating brush that comes into contact with the recording sheet 5 to erase charges remaining within the recording sheet 5. As shown in FIG. 4, the static eliminating brush 14 comes into contact with a material with a low electrical resistance value, such as carbon paste 5e, coated on the conductive layer 5C of the recording sheet 5 to erase residual charges. .

The toner 2 attached to the outer periphery of the sleeve 3 by the rotating magnet 4 and conveyed passes through the hole 1d of the substrate 1a and is conveyed onto the recording electrode 1. At this time, by applying a voltage to the recording electrode 1 according to the image information, the toner 2 can be attached to the recording sheet 5 to form an image. still,
The toner 2 that did not contribute to image formation on the recording electrode 1 was
It will not fall from the sleeve 3 and affect the image formed on the recording sheet 5.

The image formed on the recording sheet 5 is transferred to the drive roller 6
By the rotation b, the recording sheet 5 is conveyed in the direction of arrow B in FIG. 2, and when it passes through the image display section 9, it is displayed on the outside. The recording sheet 5 that has passed through the image display section 9 has its residual charge erased by the charge eliminating brush 14, and the adhering toner 2 is stripped off by the cleaning member 10, and the toner 2 is transferred to the sleeve 3. It falls to the top and is transported again to prepare for the next recording.

Next, referring to FIGS. 1(a), (b), (C), and (b), the image forming operation on the recording sheet 5 will be explained in detail. In FIG. When recording is performed with a signal voltage of +30 V, the toner 2 has a positive charge, and a negative charge commensurate with the above-mentioned positive charge is induced in the dielectric layer inside the recording channel 5.

Next, in FIG. 1(b), when one screen's worth of toner 2 adheres to the recording sheet 5 to form an image, one screen's worth of toner 2 is simultaneously scraped off by the cleaning member 10. At this time, the positive charge that the toner 2 has is discharged in the direction toward the ground by the cleaning member 1o, while the negative charge remaining in the recording sheet 5 is eliminated in the direction toward the ground through the discharge brush 14.

However, when the static electricity is removed by the static elimination brush 14, the negative charges within the recording sheet 5 may not completely leak out, and there is a possibility that residual charges may still exist.

Therefore, as shown in FIG. 1C, by applying a negative signal voltage to the recording electrode 1 on the third screen, for example, a negative charge is injected into the toner 2. As a result, positive charges are induced in the dielectric body of the recording sheet 5, contrary to FIGS. 1(a) and 1(b).

As a result, as shown in FIG. 1(d), when the toner 2 recorded with a negative signal voltage is erased by the cleaning member 10, the negative charge in the toner is removed via the cleaning member 10, The uncharged toner 2 is
It falls into the developing device 7.

Further, the positive charge induced in the recording sheet 5 leaks from the static elimination brush 14, but does not leak completely and some of the charge remains. In this sale, the negative charges remaining in FIG. 1 (0)) and the positive charges remaining in FIG. 1 (cl) attract each other in the recording sheet 5 and disappear.

As described above, by switching the signal voltage applied to the recording electrode to positive or negative every two screens,
The charge remaining in the recording sheet 5 is reduced, and excess toner 2 can be prevented from adhering to the recording sheet 5. Therefore,
Clear, high-quality images can be obtained.

In the above embodiment, the application to the recording electrode 1 was changed every two screens, but it is also possible to change it every 10 screens. In addition, by counting the number of screens, it is possible to freely change the polarity of the recording voltage, so that when the recording sheet 5 becomes dirty due to excess toner 2 adhesion, the polarity of the recording voltage can be changed. A clear image can be maintained by changing the image.

<Other Embodiments> In the embodiments described above, the polarity of the recording voltage was changed at least for each screen by counting the number of screens. In contrast, in this embodiment, a case will be described in which the polarity of the recording voltage is changed by detecting the time from one recording to the next recording and the environmental humidity.

For example, as shown in the graph in Figure 5, if the environmental humidity value detected by a humidity sensor (not shown) installed in the device is 40%, the next screen will be recorded within one minute after recording one screen. When recording, it indicates that the polarity of the recording voltage is changed, and when it is within 100 minutes, it indicates that the polarity of the recording voltage is not changed. That is, the shaded area in FIG. 5 indicates that the polarity of the recording voltage is changed, and the other areas indicate that the polarity of the recording voltage is not changed.

In this case, the time t for the residual charge in the recording sheet 5 to leak is determined by the resistance value R and the capacitance 1c of the dielectric layer, and is expressed as t=RXC, and as the leakage time elapses, the residual charge decreases. be able to.

<Effects of the Invention> As described above, the present invention changes the polarity of the signal voltage applied to the recording electrode for each screen or for each multiple screens, thereby preventing charges of unbalanced polarity from remaining in the recording medium. It can be prevented.

Therefore, during image formation, unnecessary developer does not adhere to the recording medium, and a clear, high-quality image can be obtained.

[Brief explanation of the drawing]

1(a), (b), (C), and (b) are schematic explanatory diagrams of a recording medium, FIG. 2 is a cross-sectional explanatory diagram showing a schematic configuration of an image forming apparatus, and FIG. 3 is a perspective explanatory diagram of a recording electrode. FIG. 4 is a partially enlarged sectional view of a recording medium, FIG. 5 is a graph showing the relationship between humidity and leak time, and FIGS. 6 to 8 are illustrations of conventional examples. 1 is a recording electrode, 1a is a flexible printed circuit board, 1b
is a recording element, 1c is a drive element, 1d is a conductor exposed part, le
is a toner through hole, 1f is a connector, 1g is a polyethylene film, 2 is a toner, 3 is a non-magnetic cylinder, 4 is a rotating magnet, 5 is a recording sheet, 5a is a surface layer, 5b is a colored layer, 5c
is a conductive layer, 5d is a base material, 6a is a tensigon roller, 6b
1 is a drive roller, 7 is a developer, 8 is a recording control unit, 9 is an image display unit, 10 is a cleaning member, 10a is a cleaning member body, 10b is a brush, 11 is a back plate, lla is a support member, 12 is a non-magnetic The members 13 are magnets, and 14 are static eliminating brushes. Figure 1 (a) (b) (C) (d)

Claims (4)

[Claims] (1) A recording electrode for applying a voltage to a developer according to image information, a driving means for applying a signal voltage to the recording electrode according to the image information, and an image by attaching the developer to the recording electrode. An image forming apparatus comprising: a recording medium for forming an image; and a polarity of a signal voltage applied to the recording electrode by the driving means is changed at least for each screen. (2) The image forming apparatus according to claim 1, wherein the polarity of the signal voltage applied to the recording electrode by the driving means is changed according to environmental humidity. (3) The image forming apparatus according to claim 1, wherein the recording medium sequentially includes a surface transparent resin layer, a colored inorganic substance, and a conductive layer. (4) The image forming apparatus according to claim 3, wherein the image formed on the recording medium is a display device that is used by displaying the image on a display section.