JPS5830579B2 - Liquid development method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method of forming an electrostatic latent image on an image carrier formed by electrophotography or electrostatic recording into a visible image using a liquid developer O.
The present invention relates to a liquid developing method including a step of removing excess developer remaining on the image carrier.

The electrostatic latent image formed on the image carrier by a latent image forming process such as exposure to charging light is turned into a visible image by being supplied with a liquid developer in a developing section.

Conventional methods for removing surplus developer from the moving image carrier while holding the developed image include a method of removing surplus developer using corona discharge, and a method of removing surplus developer using rotating rollers. It is being

However, the conventional method for removing excess developer using corona discharge has the disadvantage that the corona wire gets dirty and the effect of removing excess developer decreases significantly when used for a long time.

Further, in high-speed electrophotographic processes, a large corona discharge is required in both quantity and density, but it is extremely difficult to obtain such a corona discharge due to the structure.

For this reason, depending on the corona discharger, a sufficient effect of removing excess developer may not be obtained in some cases.

In addition, in the conventional method of removing excess developer using a roller, in order to obtain a satisfactory effect of removing excess developer, the accuracy of the roller surface, the prevention of dirt, the accuracy of the distance between the roller and the image carrier, and the stability of the rotation speed are required. A high level of adjustment is required for these factors.

Furthermore, in a high-speed electrophotographic process, when excess developer is removed by a roller, the roller is required to rotate at a high speed, resulting in various drawbacks in terms of equipment durability and cost.

The present invention provides a liquid developing method that eliminates the above-mentioned drawbacks, has the effect of removing a sufficient amount of excess developer, and enables stable removal of excess developer even during long-term use. .

Furthermore, when the liquid developing method of the present invention is applied especially to high-speed electrophotographic processes, excess developer can be removed efficiently, which was not possible with conventional methods.

A liquid developing method of the present invention which achieves the above object is a method of developing an electrostatic latent image by applying a liquid developer to an electrostatic latent image bearing surface ζ, in a contact surface with the said bearing surface. An elastic member that does not cause deformation is impregnated with the developer and pressed against the support surface, and the developer squeezed out from the member during the compression process of the member is supplied to the support surface, so that the member is in a compressed state. When developing the latent image by absorbing excess developer on the carrier into the member in the process of restoring the image, a direct current bias voltage or an alternating current of opposite polarity to the carrier liquid in the developer is applied to the member. It is characterized by applying a bias voltage.

Hereinafter, the present invention will be explained in detail according to examples.

FIG. 1a shows an example of bias application, and FIG. 2 is an explanatory diagram for explaining the principle of a method for removing excess developer using the bias effect.

In FIG. 1a, the excess developer removing roller 3 is located between the developing section 2 and the transfer section 10, and is in close proximity to or in contact with the photosensitive drum 1.

A conductive rigid body 32 made of metal or the like is provided around the rotating shaft 31 of the roller 3 .

A bias voltage 42 is applied to the rotating shaft 31 from a power source 42 through a switch 44 .

Incidentally, the DC bias or the AC bias can be arbitrarily selected by operating the above-mentioned switch.

Bearings 3 are provided at both ends of the roller 3 as shown in FIG.
9 is provided, and the rotating shaft 32 is rotatably supported with respect to a bearing 39.

A roller 38 is provided between the bearing 39 and the roller, and is set so that the photosensitive drum 1 and the roller 3 are at a certain close distance or in a certain contact state.

A spring 91 is provided between the bearing 39 and the machine frame 92 to draw the rotating shaft 32 toward the drum 1 in order to bring the roller 38 into contact with the photosensitive drum 1 with a constant pressure.

A gear 93 is fixed to one end of the rotating shaft 32 and meshes with a gear 94.

The roller 3 is rotated by applying rotational force from the motor 95 via the gear 94.

An electrostatic latent image formed on the photoreceptor drum 1 through a charging section and an exposure section (not shown) is visualized in the developing section 2.

When the photoreceptor drum 1 holding the visible image formed on its surface rotates in the direction of the arrow from the developing section 2 and leaves the developing section 2, the surface tension between the photoreceptor drum 1 and the developer, the photoreceptor drum 1 Due to factors such as the condition of surface collapse and the viscosity of the developer,
On the surface of the photosensitive drum 1, a large amount of the main liquid in the developer, that is, surplus developer, remains.

At this time, toner particles are slightly present on the photoreceptor drum 1 even in the bright areas of the image where there is no latent image along with excess developer, causing so-called fog.

Methods for removing this fog are as follows: (1) A method in which the surplus developer removal roller 1 is used to simultaneously remove the surplus developer and remove the fog.

(2) A method in which fog removal is performed before excess developer is removed.

(3) A method in which a bias voltage having a polarity opposite to that of the toner particles is applied to the developing section I to remove fog in the developing section before removing excess developer.

There is.

FIG. 1A shows a method in which the roller 3 removes excess developer and removes fog at the same time, that is, method (1) above.

The electrostatic latent image formed on the photosensitive drum 1 6 has a positive polarity in the dark part of the image and a negative polarity latent image in the bright part, and is visualized in the developing section 2 .

Furthermore, a photosensitive drum 1 holding a visible image formed on its surface
rotates in the direction of the arrow and comes into contact with or approaches the rows and rollers 3.

The roller 3 has a structure in which a conductive rigid body 32 made of metal or the like is provided around a rotating shaft 31.

The rotational direction of the roller 3 is in the forward direction of the rotational direction of the photosensitive drum 1, that is, in the direction of the arrow.

The bias voltage 42 applied to the roller 3 has a polarity opposite to that of the carrier liquid in the developer, and in order to prevent fogging, the toner particles are applied to the photoreceptor drum as shown in FIG. It is sufficient to apply a bias voltage that forms an electric field that does not move the latent image No. 1 toward the bright portion.

In FIG. 2a, the upper part shows the potentials of the bright and dark parts of the latent image on the photosensitive drum 1, and the lower part shows the movement of toner particles and carrier liquid.

This bias voltage range means that, as explained with reference to FIG. This is the range to be moved.

This is a DC voltage between the bright area potential and zero potential, or an AC voltage in which the effective voltage of a component with a polarity opposite to that of the carrier liquid takes a value within the range.

A bias voltage based on direct current or alternating current can be arbitrarily selected, or a bias voltage based on a superimposition of direct current and alternating current may be used.

These bias voltages are applied to the roller 3 through the switch 4.

In FIG. 2a, the direction of the electric field between the drum 1 and the roller 3 is indicated by an arrow, the toner particles are indicated by e, the carrier liquid is indicated by C1, and the charge of the liquid is indicated by ▪.

Due to the electric field effect caused by the above bias voltage, the photoreceptor drum 1
The toner particles of the upper bright latent image move to the roller 3, and the fog is completely removed by the movement of the toner particles.

Further, the carrier liquid C remaining on the photoreceptor drum 1 after development is attracted to the photoreceptor drum 1 by the Coulomb force and electric field effect of the bias voltage of opposite polarity to the carrier liquid applied to the roller 3. removed from the top of the drum 1.

The photosensitive drum 1 holding the visible image and having the excess developer removed rotates in the direction of the arrow.

Then, in the transfer section 10, the developed image on the photosensitive drum 1 is transferred onto a transfer paper.

In the above configuration, if a bias voltage of the same polarity as that of the carrier liquid is applied to the roller 3 as in the conventional case as shown in FIG. be done.

However, in this case, since the carrier liquid and the removal roller 3 have the same polarity, Coulomb force does not act, and the effect of removing excess developer becomes weak.

FIG. 1 shows a case where fog removal is performed independently of excess developer removal.

The electrostatic latent image formed on the photoreceptor drum 1 is developed into a visible image in the developing section 2 .

Conventionally, the fog in the bright latent image on the photoreceptor drum 1 has been removed using the above-mentioned method (2), that is, as shown in FIG. Alternatively, although not shown, the electrostatic latent image is removed by applying a direct current bias having a polarity opposite to that of the toner particles to the developing section 2 at the same time as the electrostatic latent image is visualized in the developing section 2.

The fog removal roller 5 is in close proximity to or in contact with the photoreceptor drum 1 and rotates in the forward direction of the movement of the photoreceptor drum 1, that is, counterclockwise, or in the opposite direction of the movement of the photoreceptor drum 1, that is, clockwise. It's rotating.

In other words, the fog removal effect is not influenced in any way by the direction of rotation of the fog removal roller.

The fog removal roller 5 is made of a conductive rigid body, for example, metal.

By applying a bias voltage 43 having a polarity opposite to that of the toner particles in the developer to the fog removal roller 5, a Coulomb force and an electric field effect are generated between the photosensitive drum 1 and the fog removal roller 5.

Due to the above two effects, the toner particles in the bright latent image on the photoreceptor drum 1 are moved by the fog removal roller 51 for the same reason as explained above.

The surface of the fog removal roller 5, which has toner particles adhered to the roller surface, is cleaned by a cleaning blade 6, and the adhered toner particles are scraped off.

The photoreceptor drum 1, which holds the visible image and the fog-free visible image, further rotates in the direction of the arrow and reaches the position of the roller 3.

The configuration of the roller 3 is the same as the roller 3 shown in FIG. 1a.

The bias voltage 42 applied to the roller 3 is a DC voltage or an AC voltage with a polarity opposite to that of the carrier liquid, and this bias voltage is applied to the roller 3 through a switch 44.

Symbols, etc. in Figure 2 are in the order of Figure 2a.

In this roller 3, as described above in FIG. Move to.

Further, at this time, a bias voltage having the same polarity as that of the toner particles is applied at the same time, and the effect of fixing the toner particles on the photoreceptor drum 1 can also be obtained due to the bias voltage.

The photosensitive drum 1 holding the microscope image further rotates in the direction of the arrow.

Then, the developed image on the photosensitive drum 1 is transferred to a transfer paper in the transfer section 10.

In this case, since excess developer removal and fog removal are performed using separate structures, that is, excess developer removal roller 3 and fog removal roller 5, voltages under optimal conditions can be applied to each. The effects of removing excess developer and removing fog are particularly large.

Further, in this case, it is also possible to adopt a configuration in which fog is removed after removing excess developer.

As described above, by simply applying a bias voltage, it is possible to remove excess developer stably for a long period of time.

Further, even in a high-speed electrophotographic process, a sufficient effect of removing excess developer can be obtained by increasing the bias voltage.

Moreover, it is also possible to obtain good images without fog.

Next, another example of bias application will be described.

This case in FIG. 4 is characterized in that a uniform insulating coating 33 is applied around the mouth collar 3 shown in FIG. 1a.

According to the above-described structure, when the roller 3 contacts the photoreceptor drum 1, the contact is made through the coating 33, so that the surface of the photoreceptor drum 1 is not damaged, and the insulating coating 3
By selecting the material (non-adhesive) used in step 3, it is possible to prevent toner particles from adhering to the surface of the roller 3;
and - the cleaning of the roller 3 is also facilitated.

Further, it is of course possible to provide the turnip removal roller shown in FIG. 1 in this embodiment as well.

The case shown in FIG. 5a is characterized in that the roller 3 shown in FIG. 1 is covered with a conductive net 34 around it.

However, the rigid body 30 within the conductive mesh 34 may be electrically conductive or non-conductive.

When the excess developer is removed, since the surface of the roller 3 is mesh-like, the excess developer enters the gaps between the meshes, so that the removal of the excess developer can be carried out quickly and efficiently. .

FIG. 5 is characterized in that the roller 3 shown in FIG. 1 is covered with an insulating mesh 35.

Incidentally, the developer that has entered the mesh may be removed by absorbing it with a sponge or the like.

This configuration has the effect of quickly and efficiently removing excess developer.

The structure of the roller 3 in the embodiment of the present invention shown in FIG. It is characterized by the fact that it is provided.

In the developing section 2, the electrostatic latent image on the photoreceptor drum 1 is visualized.

The photosensitive drum 1 holding this visible image rotates in the direction of the arrow and comes into contact with the roller 3 .

The roller 3 is connected to the photoreceptor drum 1 in a forward direction, that is, in FIG. 6a.
Now rotate in the counterclockwise direction of the arrow.

When the photosensitive drum roller and the roller 3 come into contact with each other, the elastic open cell 36 of the roller 3 forms a contact surface having a certain width in the rotation direction due to its elasticity.

The size of this contact surface is uniquely determined by determining the configuration and shape of the roller 38 shown in FIG. 3 and the roller 3, and the diameter of the photosensitive drum 1.

Although the bias voltage applied to the roller 3 is not shown in FIG. When the fog is removed,
It is a DC voltage or an AC voltage with a polarity opposite to that of the carrier liquid.

On the other hand, when the roller 3 is used to remove fog, the polarity is opposite to that of the carrier liquid, and the dark potential and bright potential of the electrostatic latent image on the photoreceptor drum 1 are set to upper and lower limits, or lower and upper limits, respectively. This is a DC voltage that takes a value within the range, or an AC voltage where the effective voltage of a component with a polarity opposite to that of the carrier liquid takes a value within the range.

Incidentally, these voltages may also be bias voltages obtained by superimposing direct current and alternating current.

At the contact surface, the carrier liquid is removed due to the electric field effect and Coulomb force caused by the bias voltage. In the case of the embodiment, the electric field effect and Coulomb force are particularly strong, and the removal effect is extremely large.

When the photoreceptor drum 1 and the roller 3 are separated, the carrier liquid on the photoreceptor drum 1 is removed from the net due to the elastic restoring force of the compressed elastic open cell 36 of the excess developer removing roller. It is further absorbed into the interior of the elastic open cell through the gap.

In this embodiment, the excess developer is removed very quickly and efficiently due to the electric field effect caused by the bias voltage, the Coulomb force, and the absorption power of the elastic open cell 36.

The embodiment of the present invention shown in FIG. 6 is characterized in that the structure of the roller 3 is such that an electrically conductive elastic open cell 37 is covered with an insulating net 35.

In this embodiment as well, due to the restoring force due to the elasticity of the elastic open cell body 37, the carrier liquid on the photosensitive drum 1 is further absorbed into the inside of the elastic open cell body through the mesh.

Moreover, the excess developer is effectively removed very quickly and efficiently by the Coulomb force of the electric field effect caused by the bias voltage and the absorption power of the elastic open cell body 3γ.

In addition, as another embodiment, a combination with a conductive mesh as well as a conductive foam is also possible.

The embodiment shown in FIG. 7a is characterized in that the roller shown in FIG. 6a also functions as a developing roller.

In the figure, the photosensitive drum 1 on which the electrostatic latent image has been formed rotates in the direction of the arrow t and comes into contact with the roller 7, forming a certain contact surface.

The roller 7 is in pressure contact with the photosensitive drum 1 while moving in the forward direction, that is, in the direction of the arrow in FIG. 7a.

A bias voltage 8 applied to the roller 7 is a DC voltage or an AC voltage having a polarity opposite to that of the carrier liquid, and is applied to the roller 7 through a switch 44 .

The developer contained in the elastic open cells 72 of the roller 7 moves to the contact surface as the roller rotates.

Due to compression from the photoreceptor drum, the developer passes from inside the elastic open cell through the openings of the conductive net 73 and visualizes the electrostatic latent image on the photoreceptor drum 1 .

The excess developer is effectively removed by the electric field effect and Coulomb force effect by applying a bias voltage to the conductive network 73.

Further, since the bias voltage has the same polarity as that of the toner particles, the bias voltage has the effect of fixing the toner particles on the photoreceptor drum.

That is, the roller simultaneously performs three functions on the contact surface: (1) developing, (2) removing excess developer, and (3) fixing the toner particle image.

When the roller 7 separates from the photoreceptor drum 1, the restoring force of the deformed elastic open cell body 72 allows the excess developer on the photoreceptor drum 1 to effectively pass through the openings of the conductive net 73 and into the elastic open cell body. It is absorbed into the body.

The photosensitive drum 1 holding the visible image and having the excess developer removed moves in the direction of the arrow and then approaches the fog removal roller.

The toner particles in the bright part of the latent image on the photoreceptor drum are
The fog is removed by the roller 5ζ, which has a fog removing function as shown in the figure.

According to this embodiment as well, the developer can be removed efficiently and an image without fog can be obtained.

The embodiment shown in FIG. 7 is characterized in that the roller 3 shown in FIG. 6 also functions as a developing roller.

The bias voltage applied to the roller 7 is a DC voltage or an AC voltage with a polarity opposite to that of the carrier liquid.

Of course, both the bubbles 74 and the mesh 75 may be made of electrically conductive materials.

The embodiment shown in FIG. 8a is characterized in that the roller 7 shown in FIG. 7a is used not only to develop, remove excess developer, and fix toner particles on the photosensitive drum, but also to remove fog.

As mentioned in the explanations of FIGS. 1a and 2a above, the bias voltage applied to the roller 7 has a polarity opposite to that of the carrier, and has a dark potential that is equal to the bright potential of the electrostatic latent image on the photoreceptor drum 1. It is a direct current voltage that takes a value within a range defined as an upper limit and a lower limit, or a lower limit and an upper limit, respectively, or an alternating voltage that takes a value within the range where the effective voltage of a component with a polarity opposite to that of the carrier liquid.

In this configuration, by applying a DC voltage or an AC voltage within the area, fog adhering to the bright area can be noticeably removed without removing toner powder adhering to the dark area potential.
This can be removed.

Therefore, it is possible to obtain an image without fogging.

Furthermore, in the embodiment shown in FIG. 8, the roller 7 shown in FIG. Features.

The bias voltage applied to the roller 7 has a polarity opposite to that of the carrier liquid, and has a value within a region that rubs the bright area potential and dark area potential of the electrostatic latent image on the photoreceptor drum 1 by the upper limit and the lower limit, or the lower limit and the upper limit, respectively. This is a direct current voltage that takes a value within this range, or an alternating voltage that has an effective voltage of a component with a polarity opposite to that of the carrier liquid that takes a value within the range.

Below, we will show experimental results showing that applying a bias voltage of opposite polarity to the carrier liquid as in the present invention is more effective.

First, a developed image is transferred from a photoreceptor drum onto a high-quality paper whose weight has been accurately weighed, and how much of the carrier liquid in the developer, that is, Isopar H (trade name) is carried out onto the paper is shown in Figure 8. FIG. 9 shows the results of actual experiments using the example.

The graph in Figure 9 has A4 size (JIS) on the vertical axis.
The weight of the transferred carrier liquid per sheet of high-quality paper is shown.

Also, the horizontal axis shows the bias voltage.

The above graph shows that the smaller the amount of liquid carried out, the greater the effect of removing excess developer.

Therefore, as is clear from the above graph, it can be seen that the bias voltage has a significant effect on the removal of excess developer.

Also, from this graph, it can be seen that when applying a bias voltage of the same polarity as the carrier liquid, that is, positive (+) in this experiment, the amount of excess developer removed per unit voltage increase is greater than that of the carrier liquid, that is, the amount of excess developer removed per unit voltage increase. It can be seen that the amount of excess developer removed per unit voltage increase when bias voltage is applied is larger.

This is because only the electric field effect acts on carrier liquid removal when a positive bias voltage is applied.

However, when a negative (→) bias voltage is applied, two forces act: the electrolytic effect and the Coulomb force.

For this reason, it is thought that the amount of excess developer removed per unit voltage when a negative (-) bias voltage is applied is larger than the amount of excess developer removed per unit voltage when a positive (→bias voltage is applied). It will be done.

In the above experiment, the diameter of the roller 7 was φ50, the contact area between the photoreceptor drum 1 and the roller 7 was 22.5 mm, the thickness of the insulating net was 100 μm, and the paper was A4 size (Jim).
), at a speed of 18 Qg/sec in the circumferential direction of the photoreceptor drum.

As described above, in the present invention, removal of excess developer can be carried out extremely rapidly and stably for a long period of time with a simple configuration of applying a bias voltage.

In this way, since the removal of excess developer is carried out quickly and stably for a long period of time, a liquid developing method suitable for high-speed electrophotographic processes has been made possible.

Further, it is possible to apply a voltage to the developing roller under optimal conditions for removing excess developer and removing fog, and therefore the effects of removing excess developer and fog are particularly large.

In addition, especially in the case of a developing roller having a structure in which an elastic foam is covered with a mesh, a contact surface with a certain width is formed due to the elasticity of the elastic foam, and the restoring force of the elastic foam allows the carrier liquid to flow through the mesh. It is further absorbed into the interior of the elastic foam through the gap, and has a particularly great effect on removing excess developer.

[Brief explanation of the drawing]

Figures 1a and 1 are front views of the excess developer removing device, Figures 2a, 2a', and 2 are bias effects.The principles of the excess developer removal method are explained below. An explanatory diagram for FIG. 3 is a side view showing the mechanism of the excess developer removing device shown in FIG. 1a. Figures 4, 5a and 5 are side views showing the mechanism of other excess developer removing devices, Figures 6a and 6b, Figure γa and γb, and Figure 8 Figures a and 8 are front views of other embodiments of the invention. FIG. 9 is a diagram showing changes in the amount of carrier liquid taken out by the transfer paper with respect to changes in bias voltage. 1...Photosensitive drum, 2...Developing section,
3... Surplus developer removal roller, 30...
... Rigid body, 31 ... Rotation axis, 32 ...
Conductive rigid body, 33... Insulating coating, 34...
...Conductive mesh, 35...Insulating mesh, 36...
...Elastic open cell, 37... Conductive elastic open cell, 38... Coro 39...
Bearing, 41... Capacitor 42...
・Bias power supply, 43...Bias power supply, 44
...Switch, 5...Conductive electrode roller, 6...Cleaning blade, 7...
...Development and residual developer removal roller, 71...
... Rotating shaft, 73 ... Conductive net, 72 ...
...Elastic open cell, 74...Conductive elastic open cell, γ5...Insulating net, 8...Bias power supply, 91...Spring , 92...
Fixed member, 93...Gear, 94...Gear 95...Motor 96...Developer unit.

Claims (1)

[Claims] 1. In a method of developing an electrostatic latent image by applying a liquid developer to the electrostatic latent image bearing surface, an elastic continuous layer containing open cells and absorbing and squeezing out liquid by elastic deformation. A roller having a foam and a net member provided on the surface of the foam is pressed against the surface of the carrier to deform and drive the elastic open foam, and a direct current having a polarity opposite to that of the carrier liquid of the developer is applied. Or a liquid developing method characterized by applying an alternating current bias voltage to the roller.