JPH1095137A - Image forming equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming equipment which can form good images with good ion concentration and only a little fog without being influenced by environmental changes and at practical voltage by controlling the electrification of a toner just before used for image formation. SOLUTION: The percentage of a reverse-electrified toner is reduced and image force of a toner holding roller 14 and electrostatic force due to the application of ion voltage to the control electrode 4, applied to the toner 16, are balanced, and sufficient image density and low fogging are obtained, by adjusting the electrification level of the toner 16 in the range of -5 to -30μ C/g, on the toner holding roller 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus which can be used in a copying machine, a printer, a plotter, a facsimile, and the like.

[0002]

2. Description of the Related Art Conventionally, as one of image forming apparatuses, an electrode body having a plurality of apertures (hereinafter, referred to as apertures) is used to control the passage of toner particles through the apertures based on image data. A method of forming an image on a support by using toner particles passing therethrough is disclosed in, for example, US Pat.
No. 89,935.

[0003] Specifically, this image forming apparatus is composed of a thin flat plate made of an insulator, a continuous reference electrode formed on one surface of the flat plate, and a plurality of reference electrodes formed on the other surface and insulated from each other. An aperture electrode body comprising a control electrode, a plurality of apertures formed through the flat plate, the reference electrode, and the control electrode for each control electrode, and arranged in at least one row; Means for selectively providing a potential difference based on image data between the electrodes, and means for supplying charged toner particles to the aperture so that the passage of the toner particles through the aperture is controlled by the potential difference. Means for positioning the support in the flow path of the toner particles so that the support and the aperture electrode body can relatively move.

Further, US Pat. No. 4,743,926,
In each of the specifications of 4,755,837, 4,780,733 and 4,814,796, an aperture electrode body is disposed with a control electrode facing the support and a reference electrode facing the toner supply side. Image forming apparatus is disclosed.

On the other hand, US Pat.
No. 89 describes the voltage applied to the control electrode by arranging the aperture electrode body with the reference electrode facing the support and the control electrode facing the toner supply side. Of the image forming apparatus disclosed in
An image forming apparatus that can be reduced to a certain extent is described.

Here, the toner does not pass through the aperture,
The time when the toner particles are not adhered to the support, that is, the time when the white background portion of the image is formed, is hereinafter referred to as “off time”. In the reverse case, that is, the toner is allowed to pass through the aperture, and the toner is The point at which dots are formed by
Hereinafter, it will be referred to as “on”.

[0007] The voltage applied to the control electrode is hereinafter referred to as "control voltage". That is, the "control voltage at the time of ON" is applied to the control electrode in order to pass the aperture through the toner, attach the toner particles on the support, and form a dot by the toner on the support. It is voltage. Conversely, the "off-time control voltage"
A voltage applied to a control electrode in order to form a white background portion of an image on a support without allowing the toner to pass through the aperture. The voltage difference between the ON control voltage and the OFF control voltage is referred to as “drive voltage”. Further, by the image forming apparatus having the above-described configuration, an aggregate of dots made of toner, which is arranged at an arbitrary position on the support,
This is referred to as “toner image”. That is, a toner image refers to an image formed by selectively arranging dots by toner on a white background which is a base material of a support, and not only a dot portion,
A toner image is formed by the arrangement of the dot portion and the white portion.

[0008]

However, in the above-described conventional image forming apparatus, since the control electrodes are driven by circuit elements such as ICs, it is necessary to reduce the drive voltage as much as possible. Preferably, in order to use a practical and inexpensive IC, the drive voltage must be set within 50 V. However, the relationship between the control voltage and the image density (hereinafter, referred to as control voltage characteristic) is shown by a broken line in FIG. It can be seen from the curve shown in FIG. 4 that no matter how much the control voltage at the time of ON and OFF is set within the range where the driving voltage of 50 V is held, the reflection density value at the time of ON is sufficiently higher than 1.5. It has been substantially impossible to obtain image forming conditions that can simultaneously achieve a good white background without fogging with a reflection density of 0.07 or less when off.

The control voltage characteristic shown in FIG. 5 shows a case where a negatively charged toner is used as the toner.

More specifically, the control voltage characteristic indicated by the broken line in FIG. 5A has a steep slope on the high voltage side, whereas the slope on the low voltage side is gentle. Therefore, in order to obtain the on-state density, +65 V or more is required. In consideration of the safety factor, the control voltage is actually about +70 V. When the control voltage is lowered with reference to this voltage, the off state cannot be obtained even if the control voltage is lowered by 50 V from the on time to +20 V because the slope of the control voltage characteristic on the low voltage side is gentle. . In order to turn off reliably, the control voltage needs to be -20 V or less, and the drive voltage reaches 90 V.

The ideal control voltage characteristics are shown in FIG.
As shown by the solid line b, the density can be controlled in a binary manner at a certain voltage threshold, and under such conditions, the driving voltage can be extremely reduced. However, in reality, it becomes like a broken line in FIG. 5A. The most significant reason is that the charge amount of the toner supplied to the toner flow control means varies.

That is, since the electrostatic force on the toner is naturally different when the charge amount is different, if the control voltage characteristic is as shown in FIG. Of course, the voltage threshold is also different, and a horizontal translation of FIG. 5b is obtained. As described above, the control voltage characteristic of the toner having the charge amount distribution is obtained by superimposing the curves in FIG. 5B for the different charge amounts with the charge amount distribution, and as a result, the broken line in FIG. 5A is obtained.

Although such a charge amount distribution of the toner may be caused by a distribution of the particle diameter, the most important reason is that the toner is not uniformly saturated and charged. That is, the toner has a wide distribution from a toner that is sufficiently charged to a toner that is hardly charged. Therefore, it is most preferable that the toner be uniformly charged with saturation. To this end, the time of frictional charging of the toner may be lengthened to increase the chance of frictional charging of the toner.

However, in the conventional image forming apparatus, the charging of the toner by the toner supply unit is performed between the toner carrier and the toner supply unit, which are components of the toner supply unit, and between the toner carrier and the toner supply unit. It has been performed by friction applied to the toner between the charging of the layer regulating blade and the toner, however, these were not enough. An image forming apparatus configured to press a body has been proposed in Japanese Patent Application Laid-Open No. 6-155798.

In this image forming apparatus, since the toner can be frictionally charged even between the aperture and the toner carrier, the charge of the toner reaches a saturation value. , The toner rolls on the surface of the toner carrier, the adhesive force between the toner and the surface of the toner carrier due to electrostatic image force or the like is weakened, and the toner is Discharge from the aperture is promoted, and furthermore, the distance between the toner carrier surface, which is a toner supply point to the aperture, and the control electrode of the electrode body is close to the particle diameter of the toner,
The effect of suppressing the passage of the toner flow through the aperture at the time of OFF is improved, and the driving voltage can be reduced.

However, in this image forming apparatus, the pressing force between the electrode body and the toner carrier increases the stress such as the shearing force applied to the toner, so that several to several tens of A4 paper sheets are used. After the formation time has elapsed,
The toner is thermally fused to the electrode body, and the fused material hinders the supply of the toner to the aperture, resulting in a problem that the density of the formed image is reduced, and in the worst case, the image cannot be formed.

Therefore, it is very difficult to charge the toner uniformly and to saturation without damaging the toner, especially with a non-magnetic one-component toner, and it is difficult to charge the toner due to environmental changes such as temperature and humidity. The amount fluctuated greatly and image formation was not stable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and by controlling the charging of toner immediately before it is provided for image formation, a good image with good ON density and little fogging can be obtained. It is an object of the present invention to provide an image forming apparatus which can be formed with a practical voltage without being affected by environmental changes.

[0019]

In order to achieve this object, an image forming apparatus according to the first aspect of the present invention comprises a toner flow control means for controlling the flow of charged toner, and the toner flow control means. Toner supply means for supplying toner to the
Charge amount adjusting means for adjusting the absolute value of the charge amount of the toner when the toner is supplied from the toner supply means to the toner flow control means so as to be about 5 to 30 μC / g; It is characterized by having.

That is, the charge amount adjusting means adjusts the charge amount of the toner when the toner is supplied from the toner supply means to the toner flow control means.
Adjusted to fall within the range of 5 to -30 μC / g,
The toner whose charge amount has been adjusted is supplied from the toner supply unit to the toner flow control unit, and the toner flow control unit
The flight onto the support is controlled according to the image data.

According to a second aspect of the present invention, in the image forming apparatus, a charge amount detecting means for detecting a charge amount of the toner supplied from the toner supply means to the toner flow control means, and the charge amount detecting means detects the charge amount. Control means for controlling the charge amount adjusting means in accordance with the charged amount. That is, the charge amount detection means detects the charge amount of the toner supplied from the toner supply means to the toner flow control means, and the charge amount adjustment means detects the toner flow from the toner supply means in accordance with the detected charge amount. For example, when the toner is negatively charged, the charge amount of the toner supplied to the control unit is adjusted in a range of about −5 to −30 μC / g.

According to a third aspect of the present invention, in the image forming apparatus, the toner flow control unit and the toner supply unit are in contact with each other via a charged toner. That is, when the toner is supplied from the toner supply unit to the toner flow control unit, the toner is sandwiched between the two, and is used for image formation while being rolled between them.

The image forming apparatus according to a fourth aspect is characterized in that a non-magnetic one-component toner is used as the toner.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below.
An embodiment will be described with reference to the drawings.

First, the overall configuration of the image forming apparatus 50 will be described with reference to FIG.

The image forming apparatus 50 according to the present embodiment has the configuration shown in FIG.
A toner supply device 10 as a toner supply means is provided on the right side in FIG. 1, and an aperture electrode body 1 as a toner flow control means is provided on the left side of the toner supply device 10.
Is provided, and the toner 16 is supplied to the aperture electrode body 1 by the toner supply device 10.

Further, by a gap holding means (not shown),
To the left of the aperture electrode body 1 in FIG.
A back electrode 22 is provided while maintaining a gap of 0.1 to 1 mm from the aperture electrode body 1. An image recording medium 20 on which an image is to be formed is inserted in the gap between the aperture electrode body 1 and the back electrode 22 in the direction indicated by arrow C by rotating the conveying roller 19 in the direction indicated by arrow D in FIG. Is done. Further, forward of the image recording medium 20 in the conveyance direction after passing through the aperture electrode body 1, an image formed by the toner 16 on the aperture electrode body 1 is fixed on the image recording medium 20. A fixing device 26 is provided. The fixing device 26 includes a pressure roller 26a having a surface layer of a rubber having a releasable surface such as silicon or fluorine, a releasable coating such as a fluororesin on the surface, and a halogen lamp, a heating wire and the like inside. And the like, and a heat roller 26b having a heater, etc., and fixes an image with the toner 16 on the image recording medium 20 by a so-called heat fixing method.

Next, details of each section of the image forming apparatus 50 will be described.

As shown in FIG. 1, the toner supply device 10 has a toner case 11 which also serves as a housing of the toner supply device 10 as a whole, and is provided in the toner case 11 and rotates in the direction of the arrow in FIG. It is composed of a supply roller 12, a toner carrying roller 14, and an agitator 17, which are rotatably supported, and a holder pedestal 18c, a blade holder 18b, and a toner layer regulating blade 18 supported inside the toner case 11. And toner 1
6 is stored in the toner case 11.

The holder pedestal 18c and the blade holder 18b constitute the charge amount adjusting means of the present invention.

The toner carrying roller 14 is a roller member having a circular cross section. In order to carry the toner 16 and transport it to the aperture electrode body 1, an arrow B in FIG.
It is rotatably supported in the toner case 11 in the direction.

The toner carrying roller 14 is formed by forming a surface layer made of rubber, resin or the like having a low resistivity around a conductive core made of metal or the like. It is desirable that the surface roughness is as rough as not losing the adhesive force for carrying the toner and as smooth as not burying one toner. If the volume average particle diameter of the toner 16 is about 9 μm, the surface roughness is Ra0 It is desirable that the thickness be 0.5 μm or more and 5 μm or less.

The surface layer may be formed as a single layer, or may be formed as a two-layer structure in which a low-resistivity layer is further formed on a low-resistivity layer. Examples of the material include butyl, urethane, silicon, EPDM, and fluorine-based rubber materials mixed with a conductivity-imparting compound such as carbon black or a dye, or nylon, polyethylene, polypropylene, ABS, polyester, polyimide, PEEK, or the like. A material obtained by blending a similar conductivity-imparting compound with a plastic or the like can be used as the surface layer or a coat layer constituting the surface layer.

The supply roller 12 is a roller member having a circular cross section. In order to supply the toner 16 stored in the toner case 11 to the toner carrying roller 14, the toner carrying roller 12 shown in FIG. The toner case 1 is disposed at a position diagonally below and to the right of the roller 14 so that the toner case 1
1 is pivotally supported.

The supply roller 12 has a surface having appropriate irregularities for transporting the toner 16 toward the toner carrying roller 14, for example, a sponge such as silicon or urethane around a conductive core rod. Those having a layer are mainly used.

The agitator 17 is constructed by mounting a resin wing or a stirrer made of wire or the like on a grounded metal center shaft, and the toner 16 in the toner case 11 is fluidized. The toner 16 is applied to the surface of the supply roller 12 while being stirred so as to have fluidity as described above.
In the direction of the arrow in FIG.

The supply roller 12 and the toner carrying roller 14 are arranged such that their central axes are parallel to each other and at least the generatrix of their cylindrical surfaces is in contact with each other. Preferably, the sponge-like surface layer of the supply roller 12 is elastically deformed by receiving a pressing force from the toner carrying roller 14, and the sponge-like surface layer is provided so as to be in planar contact. At the contact portion, the supply roller 1
The toner 16 is charged by rubbing between the surface of the toner carrier 2 and the toner carrying roller 14.

Further, the toner layer regulating blade 18 is
In order to adjust the amount of the toner 16 carried by the toner carrying roller 14 to be uniform on the surface of the toner carrying roller 14, the toner carrying roller 14 in the toner case 11 in FIG. It is provided above.

In FIG. 1, the toner layer regulating blade 18 is held by a blade holder 18b which is a plate-like member bent at an angle K, and the blade holder 18b is further moved through a holder pedestal 18c. The toner layer regulating blade 18 held by the toner case 11
Is held so that one end thereof is pressed against the toner carrying roller 14.

The toner layer regulating blade 18 includes a metal plate, a resin plate, a rubber plate, a rubber chip formed at the tip thereof, and at least the toner carrying roller 14.
One having a low-resistance resin or rubber coating layer formed on the surface in contact with the substrate may be used.

Here, a method of adjusting the charge amount of the holder pedestal 18c and the blade holder 18b as the charge amount adjusting means will be described below.

By changing the bending angle K of the blade holder 18b and the dimensions X and H of the holder pedestal 18c, the angle and pressure of the toner layer regulating blade 18 pressed against the toner carrying roller 14 are adjusted. Thereby, the charge amount of the toner 16 formed in a thin layer on the toner carrying roller 14 can be adjusted.

For example, the bending angle K of the blade holder 18b is reduced, or the holder pedestal 1
8c, the pressing angle of the toner layer regulating blade 18 (including the tangent line between the toner layer regulating blade 18 and the toner carrying roller 14; Layer regulation blade 1
The angle formed by 8. When the angle M in FIG. 9 is increased (that is, when the toner layer regulating blade 18 stands up against the toner carrying roller 14), the charge amount increases.

Conversely, the bending angle K of the blade holder 18b is increased, or the holder pedestal 18c
Of the toner layer regulating blade 18
When the pressing angle of is reduced, the charge amount decreases.

However, when the bending angle K of the blade holder 18b and the X dimension of the holder pedestal 18c are changed, the tip of the toner layer regulating blade 18 is separated from the toner carrying roller 14 or is pressed in reverse. The H dimension of the holder pedestal 18c is adjusted appropriately so as not to go too far.

When the H dimension of the holder base 18c is increased and the pressing pressure of the toner layer regulating blade 18 is increased, the charge amount is slightly increased.

Whether the charge amount adjusted as described above is about -5 to -30 .mu.C / g is measured by suctioning the toner 16 by a Faraday cage described later, or Using a surface potentiometer, it can be obtained by calculation or the like from the measured potential. In particular,
At the time of inspection in a production line, a method of measuring the amount of charge of the toner 16 by the above-described method, and replacing the holder pedestal 18c or the blade holder 18b with a different size based on the result can be used. In this case, the sampling inspection is sufficient instead of the 100% inspection, so that the manufacturing cost does not increase. Note that, as described later, the charge amount can be automatically adjusted.

Next, the aperture electrode 1 as a toner flow control means will be described with reference to the drawings.

As shown in FIG. 2, the aperture electrode body 1 has a polyimide insulating sheet 2 having a thickness of 25 to 100 μm as a base material, and the insulating sheet 2 has an opening corresponding to a circle having a diameter of 30 to 250 μm. A plurality of apertures 6 having an area are formed in a line in the longitudinal direction of the aperture electrode body 1. In addition, a thickness of 0.1 mm is provided around the aperture 6.
A control electrode 4 made of copper foil and having a width of 10 μm to 15 μm and a width of 10 μm to 50 μm is formed for each aperture 6. Further, a plurality of driver ICs 3 are fixed on the surface of the aperture electrode body 1 on which the control electrodes 4 are formed by an adhesive or the like, and each output terminal of the driver IC 3 is connected to each control electrode 4. The application of a voltage to the control electrode 4 is controlled by the driver IC 3.

Next, a method of applying a control voltage to the control electrode 4 will be described.

As shown in FIG. 1, a control circuit 8 is connected to the driver IC 3. The control circuit 8
An image signal is received from a personal computer, a scanner, or the like (not shown), and a power supply voltage for a control voltage to be applied to the control electrode 4 when on and off, and an output terminal of each driver IC 3 based on the image signal Image data for instructing whether to apply an on or off voltage to each driver I
Supply to C3.

For example, when a control voltage of 0 V is applied at the time of off and +50 V at the time of on using negatively charged toner, the control circuit 8 sends the control voltage according to the 0 V and +50 V power supply voltage lines and the image signal to be recorded. First, second, third
The image data lines for transmitting the image data formed as 1, 0, 1,... To the control electrodes 4 of the numbers are connected to the respective driver ICs 3, and are connected to the power supply voltage and the image data. Is supplied to each driver IC 3, for example, the first control electrode 4 has +
A voltage of 50 V is applied to the second control electrode 4, that is, 0 V, which is a voltage at the time of OFF.

As the image data signal, in the above example, a logical value of "1" is given for ON and a logical value of "0" is given for OFF, but the reverse is also possible. As the image data signal, a signal coded in hexadecimal is normally transmitted and received.

By the way, when a control voltage of 0 V at the time of off and +50 V at the time of on is applied by using the negatively charged toner as in the above example, the driving voltage becomes 50 V. Inexpensive I with low withstand voltage
C can be used, and the cost of the image forming apparatus can be reduced. When the thickness of the insulating sheet 2, the thickness of the control electrode 4, the supply density of the toner 16 carried on the toner carrying roller 14, the charge amount, and the like change, the appropriate driving voltage, The control voltage at the time of ON and at the time of OFF also changes.

Further, a back voltage applying circuit 24 is connected to the back electrode 22, and the back voltage applying circuit 24 is connected to the back electrode 22 with respect to the back electrode 22.
A predetermined high voltage is applied according to the width of the gap between the aperture and the aperture electrode body 1. For example, when the above-described negatively charged toner is used and the width of the gap is 1 mm, about +1 kV is applied to the back electrode 22.

Next, the aperture 6 of the aperture electrode body 1 will be described.
The positional relationship between the toner carrying roller 14 and the toner carrying roller 14 will be described in detail. As shown in FIG. 3, a plurality of apertures 6 formed in a line have a center line 30 corresponding to the toner carrying roller in FIG. It is arranged so as to pass through the left end of the peripheral surface of the roller 14 and the central axis 32 of the toner carrying roller 14. According to this arrangement, the apertures 6 are evenly arranged on the left and right with reference to the left end of the peripheral surface of the toner carrying roller 14 in FIG. 3, so that the distribution of the toner 16 passing through each aperture 6 is Becomes uniform over the entire area of the aperture 6.

Here, when the apertures 6 are arranged in a row as shown in FIG. 2, the inner wall surface of the aperture 6 and the flying direction of the toner 16 are parallel as shown in FIG. The wall surface does not hinder the toner 16 from flying, so that the toner 16 can fly stably.

Further, as shown in FIG. 3, the aperture electrode body 1 itself is pressed against the toner carrying roller 14 so as to bend left and right about the aperture 6. Thereby, the contact area between the aperture electrode body 1 and the toner carrying roller 14 can be increased, and
Wrinkles do not occur in the peripheral portion of the aperture 6 and uniform pressing can be performed, so that the occurrence of uneven density of the toner 16 can be suppressed.

The image forming apparatus 50 of the present embodiment includes an external computer (not shown), image signals from an image reading device, an image communication device, and the like, and the external computer,
An image formation start signal transmitted from a predetermined key operation or a switch in an image reading device, an image communication device, or the like is received by a control circuit 8, and the control circuit 8 includes the supply roller 12, the toner carrying roller 14, A motor (not shown) arranged to rotationally drive the conveying roller 19, the pressure roller 26a, the heat roller 26b, etc., a halogen heater built in the heat roller 26b, a driver I
The image forming is performed by controlling the driving of C3, the back voltage applying circuit 24 and the like.

Next, the image forming operation of the image forming apparatus 50 will be described with reference to the drawings. In the following description of the operation, the toner is described as having a negative charge. However, the present invention is not limited to this. Naturally, a positive charge toner may be used. The polarity of each applied voltage is reversed. In the following description of the operation, the distance between the aperture electrode body 1 and the back electrode 22 is 1 mm, the opening of the aperture 6 is a circle having a diameter of 60 μm, and the control electrode 4 is a representative one. Thickness 4
The values of the various applied voltages described below were determined for a copper foil of μm, but if any of these dimensions were changed within the above range, the various applied voltages would change accordingly.

In FIG. 1, the supply roller 12 has an arrow A
The toner 16 stored in the toner case 11 is conveyed toward the toner carrying roller 14. Then, the transported toner 16 is rubbed between the supply roller 12 rotating in the direction of arrow A and the toner carrying roller 14 rotating in the direction of arrow B, and is charged to a negative polarity to charge the toner carrying roller 14. Carried on top. After the toner 16 carried by the toner carrying roller 14 is conveyed with the rotation of the toner carrying roller 14 in the direction of arrow B, the toner 16 is thinned by the toner layer regulating blade 18 and the charge is made uniform. Is transported toward the aperture electrode body 1.

Here, as described above, the charge amount of the toner 16 formed in a thin layer on the toner carrying roller 14 greatly affects the image forming characteristics. By adjusting the bending angle K of the blade holder 18b supporting the toner layer regulating blade 18 and the dimensions X and H of the holder base 18c, the pressure contact angle and the pressure contact of the toner layer regulating blade 18 with respect to the toner carrying roller 14 are adjusted. This is done by adjusting the pressure.

For example, the bending angle K of the blade holder 18b is reduced, or the holder base 1
8c, the pressing angle of the toner layer regulating blade 18 (the tangent plane including the generatrix on the surface of the toner carrying roller 14 in contact with the toner layer regulating blade 18, the toner layer regulating blade 18 When the angle formed by the toner layer is increased (that is, when the toner layer regulating blade 18 stands up against the toner carrying roller 14), the charge amount increases.

On the contrary, the bending angle K of the blade holder 18b is increased, or
c, the X dimension of the toner layer regulating blade 1 is increased.
When the pressing angle of No. 8 is reduced, the charge amount is reduced.

The toner 16 on the toner carrying roller 14 is supplied below the aperture 6 while being rubbed by the insulating sheet 2 of the aperture electrode body 1.

The toner 16 is carried on the surface of the toner carrying roller 14 with an appropriate force by an electrostatic image force due to its own charge and an adhesive force such as van der Waals force. It is difficult to separate the toner 16 from the surface of the toner carrying roller 14 and fly it toward the image recording medium 20 by the electrostatic field alone, but the toner 16 may be rubbed against the insulating sheet 2 of the aperture electrode body 1. Accordingly, the toner 16 can be rolled on the toner carrying roller 14 by a mechanical action, and a driving force for releasing the toner 16 from the above-mentioned mirror image and adhesion can be applied to the toner 16.

At this time, electric charges due to friction between the toner carrying roller 14 and the toner 16 are accumulated on the surface of the insulating sheet 2 of the aperture electrode body 1, and the toner 16 is attracted to the electric charges by electrostatic force. An antistatic coating is applied to the surface so as not to adhere firmly, or the insulating sheet 2 constituting the aperture electrode body 1 has a surface resistance of 10 ^{9 to} 10 ¹¹ Ω /.
The one adjusted to cm ² may be used.

Such an adjustment is performed by adding an ink such as polyimide, acrylic, or a known ultraviolet or thermosetting resin to which carbon black, an additive such as a dye is added, and the like.
It is performed by a method of applying and curing by screen printing, spin coating, bar coating, spraying, or the like, a method of blending a conductive filler into the insulating sheet 2 itself, or a method of depositing carbon on the surface.

The aperture electrode 1 having been adjusted as described above.
Since no electric charge is accumulated on the surface, the toner 16 does not adhere and the toner 16 to the aperture 6 is not hindered.

In response to the image signal sent from a personal computer or a scanner (not shown), the control circuit 8 applies a control voltage of +50 V or 0 V to the control electrode 4 at a position corresponding to the image data through the driver IC 3. I do. As a result, the aperture 6 in the control electrode 4 to which the control voltage of +50 V is applied has a potential difference between the control electrode 4 and the surface of the toner carrying roller 14 which is grounded. An electric field is formed toward. Due to the electric field, the negatively charged toner receives an electrostatic force in a high potential direction, and the toner carrying roller 14
It is pulled out from above through the aperture 6 to the control electrode 4 side. The extracted toner 16 is applied to the image recording medium 20 by an electric field formed between the image recording medium 20 and the aperture electrode body 1 by the voltage of +1 kV applied to the back electrode 22 by the back voltage applying circuit 24. It flies toward and is deposited on the image recording medium 20 to form pixels.

In the aperture 6 in the control electrode 4 to which the control voltage of 0 V is applied, there is no potential difference between the control electrode 4 and the grounded toner carrying roller 14.
The light does not pass through the aperture 6 and no dot is formed on the image recording medium 20.

When pixels of the image recording medium 20 corresponding to one row of the apertures 6 formed by the toner 16 passing through the apertures 6 are formed on the surface facing the aperture electrode body 1, the apertures 6 are transported by a not-shown transport unit. Is transported by one pixel in the direction perpendicular to the column. Then, the toner image is formed on the surface of the image recording medium 20 by repeating the image forming process. After that, the formed toner image is
The sheet is transported to the fixing device 26 by a transport device (not shown),
The image is fixed on the image recording medium 20 by the fixing device 26. In the present embodiment, the fixing device 26 is of a heat fixing type, but may be of a pressure fixing type.

Further, in the image forming apparatus 50 of the present embodiment, since the insulating sheet 2 of the aperture electrode body 1 is directed to the toner carrying roller 14 side, the insulative sheet such as running out of toner or the like is low. Resistance toner carrying roller 1
Even when the toner 16 is not present on the surface of the toner carrier 4, the control electrode 4 and the surface of the toner carrying roller 14 are in direct contact with each other and are electrically short-circuited.

The amount of charge of the toner 16 depends on the toner layer regulating blade 18 and the toner carrying roller 1 as described above.
4, the amount of toner 16 per unit area on the toner carrying roller 14 also changes, which affects the image density. Therefore, while the positional relationship between the toner layer regulating blade 18 and the toner carrying roller 14 is fixed, the following six types of toners 16 are used to change the charge amount of the toner 16 and adjust the toner 16 to be adjusted. An evaluation test was performed on the range of the charge amount.

The composition of the toner 16 will be described below.

Binder resin (polyester made by Mitsubishi Rayon) 100 parts by weight Colorant (conductive carbon black made by Mitsubishi Chemical) 20 parts by weight WAX (polypropylene made by Sanyo Chemical) 5 parts by weight Charge control agent (metallic dye made by Orient Chemical) 1 part by weight, kneaded using a continuous single-screw extruder, cooled, pulverized, and classified to obtain a negatively charged black toner A having an average particle diameter of 9 μm. The charge amount of the toner A on the toner carrying roller 14 was −3 μC / g by a measuring method described later. The charge amounts described for the various toners described below were also measured in the same manner.

Binder resin (polyester made by Mitsubishi Rayon) 100 parts by weight Colorant (conductive carbon black made by Mitsubishi Chemical) 20 parts by weight WAX (polypropylene made by Sanyo Chemical) 5 parts by weight Charge control agent (metallic dye made by Orient Chemical) 2 parts by weight, kneaded using a continuous single-screw extruder, cooled, pulverized, and classified to have an average particle size of 9 μm and a charge amount of −5 μm.
C / g negatively charged black toner B was obtained.

Binder resin (polyester made by Mitsubishi Rayon) 100 parts by weight Colorant (conductive carbon black made by Mitsubishi Chemical) 13 parts by weight WAX (polypropylene made by Sanyo Chemical) 5 parts by weight Charge control agent (metal-containing dye made by Orient Chemical) 2 parts by weight, kneaded using a continuous single-screw extruder, cooled, pulverized, and classified to have an average particle size of 9 μm and a charge amount of −10.
μC / g of a negatively charged black toner C was obtained.

Binder resin (polyester made by Mitsubishi Rayon) 100 parts by weight Colorant (carbon black made by Mitsubishi Chemical) 13 parts by weight WAX (polypropylene made by Sanyo Chemical) 5 parts by weight Charge control agent (metallic dye made by Orient Chemical) 2 parts by weight , Kneaded using a continuous single screw extruder, cooled, pulverized and classified to obtain an average particle size of 9 μm and a charge amount of −20.
A negatively charged black toner D of μC / g was obtained.

Binder resin (polyester made by Mitsubishi Rayon) 100 parts by weight Colorant (carbon black made by Mitsubishi Chemical) 13 parts by weight WAX (polypropylene made by Sanyo Chemical) 5 parts by weight Charge control agent (metallic dye made by Orient Chemical) 4 parts by weight , Kneaded using a continuous single screw extruder, cooled, pulverized and classified to obtain an average particle size of 9 μm and a charge amount of −35.
A μC / g negatively charged black toner E was obtained.

Binder resin (polyester made by Mitsubishi Rayon) 100 parts by weight Colorant (carbon black made by Mitsubishi Chemical) 8 parts by weight WAX (polypropylene made by Sanyo Chemical) 5 parts by weight Charge control agent (metallic dye made by Orient Chemical) 4 parts by weight , Kneaded using a continuous single screw extruder, cooled, pulverized and classified to obtain an average particle diameter of 9 μm and a charge amount of −41.
A negatively charged black toner F of μC / g was obtained.

Binder resin (polyester made by Mitsubishi Rayon) 100 parts by weight Colorant (carbon black made by Mitsubishi Chemical) 5 parts by weight WAX (polypropylene made by Sanyo Chemical) 5 parts by weight Charge control agent (metallic dye made by Orient Chemical) 4 parts by weight And kneading using a continuous single-screw extruder, cooling, pulverizing, and classifying to obtain an average particle size of 9 μm and a charge amount of −52.
A μC / g negatively charged black toner G was obtained.

Using the above seven kinds of toners, an image formation evaluation test was performed, and an ON density of +50 V and an OFF fogging density of 0 V were measured and evaluated.

The charge amount shown above is measured by the following method.

First, toner is put into the image forming apparatus 50,
The toner carrying roller 1 is removed for 5 seconds after the aperture electrode body 1 is removed.
4. The supply roller 12 and the agitator 17 are rotated.

Next, the toner 1 on the toner carrying roller 14
Blot 6 using a Faraday cage.

In the Faraday cage, KEITHLEY
The company's electrometer is connected, the charge amount when the toner is sucked into the Faraday cage is read by the electrometer, and the value is divided by the weight of the sucked toner,
Calculate the charge amount.

The concentration is measured by the following method.

The test pattern for image evaluation is a test pattern in which square ON portions each having a side of several cm are arranged at several places on A4 paper, and +50 V is applied to the ON portion, and 0 V control voltage is applied to the OFF portion. Is applied and R made by MACHBETH
The ON portion and the OFF portion were measured at several points each using a D914 reflection densitometer, and the average value was defined as each density.

When measured as described above, it is practically desirable that the ON density is 1.5 or more and the OFF fog density is 0.10 or less.

Table 1 shows the results of image formation evaluation performed under the above conditions.

[0092]

[Table 1]

As is clear from Table 1, the charge amount is about-
The toners B to E in the range of 5 to -30 μC / g are
At a driving voltage of 50 V, an on-concentration that can withstand practical use is obtained, and the off-state fogging can be suppressed well.

On the other hand, the toner A having the charge amount smaller than the above-mentioned range can obtain the ON density, but is extremely fogged and is not suitable for practical use. This is because the toner A has a weak mirror image force on the toner carrying roller 14 and is in a state in which it is very easy to fly. Further, since the charge amount is low, the toner having the opposite polarity, that is, the positively charged toner also increases. It is.

Further, when the charge amount is larger than the range E to G, the fogging can sufficiently withstand practical use, but the ON concentration is low. This is because the toners E to G are
This is because the mirror image power is strong and it is very difficult to fly.

As described above, regardless of whether or not the charge of the toner 16 is saturated, the toner 1 immediately before being supplied to the aperture electrode body 1 as the toner flow control means.
The charge amount of No. 6 was adjusted to about -5 to-
By adjusting to the range of 30 μC / g, good image recording can be performed stably with respect to environmental changes.
From Table 1, it is most preferable that the charge amount is about −20 μC / g. The control voltage characteristic when the toner 16 having such a charge amount is used is as shown by a solid line in FIG.
The required and sufficient contrast is obtained with the driving voltage of, and a circuit element such as an inexpensive IC having a low withstand voltage can be used as the driving circuit 8, so that an inexpensive image forming apparatus can be provided. Becomes

The present invention is not limited to the embodiment described in detail above, and various changes can be made without departing from the gist of the present invention.

In the second embodiment described below, the same reference numerals are used for components having the same functions as those in the first embodiment.

For example, in the first embodiment, the holder pedestal 18c and the blade holder 18b are used as the charge amount adjusting means. Specifically, the bending angle K of the blade holder 18b and the holder pedestal 18c
The measurement was performed by adjusting the dimensions X and H, and adjusting the pressure contact angle and pressure of the toner layer regulating blade 18 against the toner carrying roller 14. In this case, more specifically, several types of blade holders 18b and holder pedestals 18c having different dimensions of K, X, and H are prepared and combined.

On the other hand, the image forming apparatus 52 shown in FIG.
And a charge amount detecting means 18a for detecting the charge amount of the toner 16 on the surface of the toner carrying roller 14, and the toner layer regulating blade 18 and the blade holder 18b in accordance with a signal obtained from the charge amount detecting means 18a. An arithmetic unit 18e and a position adjusting unit 18f as a control unit for adjusting the position of and setting the charge amount to a predetermined value;
It may be used as charge amount adjusting means. A known surface voltmeter can be used as the charge amount detection means 18a, and the charge amount is measured with good reproducibility by calibrating the surface charge in advance. As the position adjusting unit 18f, a moving stage such as an XZ two-axis stage or an XYZ three-axis stage, or a rotating unit such as a rotary stage or a motor can be used alone or in an appropriate combination.

For example, as the position adjusting means 18f, X for moving the blade holder 18b and the toner layer regulating blade 18 in the vertical and horizontal directions in FIG.
By combining a Z2-axis stage with a θ stage for rotating the blade holder 18b and the toner layer regulating blade 18 clockwise or counterclockwise in FIG. 12, K, X in FIG. , H dimensions can be produced.

Further, if the X, Z, and θ coordinates of the XZ two-axis stage and the θ stage for setting an arbitrary angle M in FIG. 9 are stored in the arithmetic unit 18e, for example, The angle M was initially 45 degrees,
In the course of image formation, if it is determined by the arithmetic unit 18e that the charge amount is too high based on the measurement result from the charge amount detection unit 18a, the angle M is slightly reduced, for example, by 40. As you set
Based on the data stored in the arithmetic unit 18e, the XZ two-axis stage and the θ stage of the position adjusting unit 18f are driven to adjust the angle M to 40 degrees. Then, while monitoring the measurement result from the charge amount detecting means 18a again, the above-described process is repeated until the target charge amount is obtained.

The image forming apparatus according to the second embodiment described above maintains the charge amount set to an arbitrary reference value in the range of -5 to -30 μC / g.
The control means automatically adjusts the charge amount of the toner. Therefore, even if the remaining amount of toner fluctuates due to a long-term image forming operation, it is possible to maintain good image forming characteristics without any modification. Is possible. In this case, the most suitable charge amount in the image evaluation result was about-
Control may be performed so as to be set to 20 μC / g.

Further, in the two embodiments described above, the toner is all negatively charged, but the same applies to the case where the toner is positively charged.

[0105]

As is apparent from the above description, in the image forming apparatus according to the first aspect of the present invention, the charge amount of the toner immediately before being supplied to the toner flow control means by the charge amount adjusting means. Is adjusted so as to be about 5 to 30 μC / g, so that there is no fogging at the time of OFF and a high-contrast image with a high density at ON can be formed. Further, with respect to such a charge amount of the toner, on / off control can be performed with a low driving voltage, and an inexpensive image forming apparatus capable of forming a good image can be provided.

According to the image forming apparatus of the second aspect,
Since the charge amount of the toner is automatically adjusted by the control unit so as to maintain the charge amount in the above range, even if the remaining amount of toner fluctuates due to a long-term image forming operation, no action is required. Therefore, it is possible to maintain good image forming characteristics. It should be noted that it is also possible to make adjustment so that the charge amount is set to the most suitable arbitrary reference value in the above range.

In the image forming apparatus according to the third aspect, since the toner flow control means and the toner supply means are in contact with each other via the toner, the binding force to the toner supply means is released. From above, the toner can be supplied to the passage section, and high contrast can be achieved at a low voltage.

The image forming apparatus according to the fourth aspect of the invention can provide a small and inexpensive image forming apparatus with a simple configuration by using a non-magnetic one-component toner as the toner.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of an aperture electrode body used in the image forming apparatus.

FIG. 3 is a diagram schematically showing a positional relationship between an aperture electrode body and a carrying roller in the image forming apparatus.

FIG. 4 is a sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram for explaining voltage control characteristics of image density in the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aperture electrode body 4 Control electrode 6 Aperture 10 Toner supply device 14 Toner carrying roller 16 Toner 18 Toner layer regulating blade 18b Blade holder 18c Holder pedestal 18a Charge amount detecting means 18e Arithmetic device 18f Position adjusting means 20 Image recording medium

Claims (4)

[Claims] 1. An image forming apparatus comprising: a toner flow control means for controlling a flow of charged toner; and a toner supply means for supplying toner to the toner flow control means, wherein the toner is supplied from the toner supply means. An image forming apparatus comprising: a charge amount adjusting unit for adjusting an absolute value of a charge amount of the toner when supplied to the toner flow control unit to be about 5 to 30 μC / g. apparatus. 2. A charge amount detection means for detecting a charge amount of toner supplied from the toner supply means to the toner flow control means, and the charge amount according to the charge amount detected by the charge amount detection means. The image forming apparatus according to claim 1, further comprising a control unit that controls the adjustment unit. 3. The image forming apparatus according to claim 1, wherein the toner flow control unit and the toner supply unit are in contact via a charged toner. 4. The image forming apparatus according to claim 1, wherein the toner is a non-magnetic one-component toner.