JP3212975B2 - Liquid developing device and liquid developing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developing apparatus and a liquid developing apparatus which use a liquid toner in which toner particles are dispersed in a carrier liquid and perform development by causing toner particles to fly onto a latent image carrier by electrostatic force. About the method.

[0002]

2. Description of the Related Art In recent years, as a developing method in a full-color copying machine, a printer, or the like, there is a liquid developing method using a liquid developer suitable for higher speed and higher image quality than at present.

As such a liquid developing system, there is one described in, for example, JP-A-8-015993.

In this method, a developer is prepared by dispersing toner particles in an insulating liquid (isopar), and the toner particles are electrophoresed on an electrostatic latent image for development. In this case, the toner particles having a particle size of about 1 micron are positively or negatively charged in the liquid by the constituent resin and the polarity controlling agent, so that a stable dispersion suspension is performed.

FIG. 12 is a schematic diagram of an electrophotographic apparatus using such a liquid developing system. 12 includes a photosensitive drum 28, a charger 2, an exposure unit 3, a developing unit 4, a squeeze roller 5, a transfer roller 6, a pressure roller 10, a heat roller 11, a static eliminator 8, and a cleaning blade 9. ing.

The photosensitive drum 28 forms an electrostatic charge image (electrostatic latent image). The charger 2 includes a photosensitive drum 2
8 is uniformly charged on the surface. The exposure device 3 irradiates the photosensitive drum 28 with light by a laser or the like to form an electrostatic latent image.

The developing section 4 makes a liquid toner adhere to the electrostatic latent image to form a visible image. The squeeze roller 5 removes excess developer after the development in the developing unit 4. The transfer roller 6
The visible image on the photosensitive drum 28 is transferred onto the recording medium 7.

The pressure roller 10 and the heat roller 11 apply the visible image transferred onto the recording medium 7 to the recording medium 7.
Fix on top. The static eliminator 8 is provided for the photosensitive drum 2 after the transfer.
8 to remove the latent image charges. Cleaning blade 9
Removes the residual liquid toner remaining on the photosensitive drum 28 without being transferred.

The recording process is as follows. First,
The surface of the photosensitive drum 28 is uniformly charged by the charger 2.
Next, light is applied to the image area by the exposing device 3 to remove the charged charges in the light-irradiated portion. As a result, an electrostatic latent image in a form in which the charge in the image portion has been removed is formed.

In the developing section 4, toner particles 23, which are colored fine particles charged to the same polarity as the electrostatic latent image, are attached to the latent image by a developing roller 24 to form a visible image. After the visible image is formed by the developing unit 4, the excess dispersion medium on the photosensitive drum 28 is removed by the squeeze roller 5.

Next, the recording medium 7 is superimposed on this toner image,
An electric field having a polarity opposite to the charging polarity of the toner particles 23 is applied to the recording medium 7 by the transfer roller 6 disposed on the back side of the recording medium 7.

As a result, the toner image on the photosensitive drum 28 is transferred to the recording medium 7 by electrophoresis. The transferred toner image is fused to the recording medium 7 by heat or pressure by the pressure roller 10 and the heat roller 11 to be a permanent image.

On the other hand, the latent image charge on the photosensitive drum 28 after the transfer is eliminated by the light from the static eliminator 8. The residual liquid toner remaining on the latent image carrier 1 without being transferred is removed by the cleaning blade 9. By repeating a series of processes from charging to cleaning, continuous printing is performed.

As another liquid developing method, for example, in Japanese Patent Application Laid-Open No. 9-230704, printing on a recording medium is performed by causing toner to fly on an electrostatic latent image on a photosensitive member.

[0015]

However, the above-described liquid developing system has the following problems.
That is, since a large amount of the dispersion medium in the liquid developer is attached onto the photosensitive drum 28 together with the liquid toner, it is difficult to perform the squeeze operation for removing the excess dispersion medium.

In the tandem type color developing process using such a liquid developing method, since the dispersion medium adhered during the development of the first color is large, the dispersion medium of the first color moves to the toner images of the second and subsequent colors. Easy to mix and color.
This is because when a toner image is formed on the photosensitive drum 28,
This is because the dispersion medium in the liquid developer adheres to both the image area and the non-image area on the photosensitive drum 28.

Further, at the time of fixing, the dispersion medium evaporates, causing a danger due to the generation of flammable solvent gas. In this case, a recovery mechanism is required to prevent the flammable solvent gas generated by the evaporation from flowing out of the apparatus, resulting in an increase in cost. This is because when transferring the toner image on the photosensitive drum 28 to the recording medium 7, a large amount of the dispersion medium also adheres to the recording medium 7, and it is difficult to prevent the flammable solvent gas from flowing out of the apparatus. This is because

Further, the structure for performing colorization becomes complicated. This is a method for colorization.
In the cycle method, first, a first color toner image is formed on the photosensitive drum 28, and then a second color toner image is formed.
At this time, when the second liquid developer is used, the developed toner image of the first color falls to the developing device of the second color and is mixed with the liquid toner of the second color. Also, the photosensitive drum 2
8, when a second color toner image is formed with respect to the first color toner image, the first color and the second color toner are mixed.

For this reason, the toner image once developed is temporarily transferred once, and is transferred four times (Yellow, Magent
a, Cyan, Black), a structure for transferring and fixing to the recording medium 7 is required.

Also, the structure becomes complicated when the first color is transferred to the recording medium as it is without intermediate transfer of the toner image once developed, and the transfer is performed four times.

For colorization, the photosensitive drum 2
In the case where four toners 8 are used and a toner image is formed on the photosensitive drum 28 for each color, the structure is also complicated.

Further, in order to perform colorization, it is necessary to form an electrostatic latent image for each color, and it is necessary to rotate the photosensitive drum 28 at least four times in a four-cycle system. This is an obstacle to increasing the printing speed on the recording medium 7.

On the other hand, in the latter liquid developing method described above,
By flying toner against the electrostatic latent image on the photoreceptor,
Although it is possible to print on transfer paper, it is difficult to perform colorization because the structure is limited to a single color.

The present invention has been made in view of such a situation, and has as its object to provide a liquid developing apparatus and a liquid developing method which can improve developing performance with a simple structure. It is.

[0025]

According to a first aspect of the present invention, there is provided a liquid developing apparatus, wherein toner particles are contained in a carrier liquid with respect to an image portion of an electrostatic latent image formed on a latent image carrier. A liquid developing device that flies a dispersed liquid toner and develops it in a non-contact manner, wherein the toner particles are formed into an ink material that is formed into a film form on a latent image carrier, and a static image is formed near the latent image carrier. A recording head for flying a group of flying particles of a predetermined color charged toward the electrostatic latent image, and a toner image on the latent image carrier when the volume concentration of the toner particles flying on the latent image carrier is less than a predetermined value. A developing unit having a squeeze roller for removing excess dispersion medium and forming toner particles adhered on the latent image carrier into a film form is provided .
The difference between the potential and the developing bias voltage
Less than the threshold voltage required for toner to fly,
The difference between the potential of the image area and the developing bias voltage is the threshold voltage
It is characterized by being made larger . Further, a plurality of developing means may be provided corresponding to each color. The developing means may include an exposure device for forming an electrostatic latent image on the latent image carrier. The developing means may include a charger for uniformly charging the latent image carrier. The exposing unit irradiates the charged charges on the latent image carrier with light, removes the charged charges and forms an image area, and the recording head operates in the same manner as the charges charged on the surface of the latent image carrier. It is possible to cause a flying particle group charged to a polarity to fly. Also,
The exposure device removes the charged charges by irradiating light to a portion other than a portion where an image portion is formed, with respect to the charges charged on the latent image carrier,
The recording head can fly a flying particle group charged on the surface of the latent image carrier with a charge different in polarity from the charge charged on the surface of the latent image carrier. The recording head has a plurality of recording electrodes having a convex discharge point, arranged in a direction perpendicular to the conveying direction of the latent image carrier, and applied with a developing bias voltage. And a liquid toner channel groove for guiding the liquid toner in the toner chamber to the discharge point side. Further, the recording head can fly the flying particle group by applying a developing bias voltage.
Further, an electrophoresis electrode for guiding the toner particles to the discharge point side by electrophoresis may be provided in the liquid toner flow channel. Further, a developing bias voltage for controlling the volume concentration of the toner particles on the latent image carrier can be changed and applied to the recording electrode. The liquid developing method according to claim 11, wherein the toner particles that are formed into a film form on the latent image carrier in a carrier liquid for an image portion of the electrostatic latent image formed on the latent image carrier. A liquid developing method for developing a non-contact development by flying a dispersed liquid toner, comprising: a first step of uniformly charging the surface of a latent image carrier; and forming an electrostatic latent image on the latent image carrier. A second process for flying the flying particles of a predetermined color charged toward the electrostatic latent image from the discharge point, and removing the excess dispersion medium on the latent image carrier,
In the third step of forming the toner particles adhered on the latent image carrier into a film form, and in the electrostatic latent image,
The difference between the potential and the developing bias voltage causes the liquid toner to fly.
Lower than the threshold voltage required for
Make the difference from the developing bias voltage larger than the threshold voltage
And a fourth step . In the second step, light is irradiated to the electric charge charged on the latent image carrier,
A step of removing the charged charges to form an image area is included. The third step includes a step of flying a flying particle group charged to the same polarity as the charges charged on the surface of the latent image carrier. Can be made. Further, the second step includes a step of irradiating light to a portion other than the portion where an image area is formed with respect to the charge charged on the latent image carrier to remove the charged charge, and the third step includes: The method may further include a step of flying a flying particle group charged on the surface of the latent image carrier with a charge different from that of the charge on the surface of the latent image carrier. In addition, the third step may include a step of flying a flying particle group of each color. Further, the third step may include a step of causing the flying particles to fly by applying a developing bias voltage. Further, the third step may include a step of guiding the toner particles to the discharge point side by electrophoresis. Further, the third step may include a step of changing the developing bias voltage in order to control the volume concentration of the toner particles on the latent image carrier. In the liquid developing device and the liquid developing method according to the present invention, for the electrostatic latent image formed on the latent image carrier, toner particles that are formed into a film form on the latent image carrier in a carrier liquid. When the dispersed liquid toner flies and is developed in a non-contact manner, the surface of the latent image carrier is uniformly charged, an electrostatic latent image is formed on the latent image carrier, and charged toward the electrostatic latent image. After causing the flying particles of the predetermined color to fly from the discharge point, for example, the excess dispersion medium on the latent image carrier is removed, and the toner particles adhered on the latent image carrier are formed into a film form. By doing so, the squeezing operation of the excess dispersion medium is facilitated, the danger due to the generation of flammable solvent gas is prevented, and one-cycle development is made possible. Color mixture when flying So as to stop.

[0026]

Embodiments of the present invention will be described below. In the drawings described below, FIG.
The same reference numerals are given to the parts common to.

(First Embodiment) FIG. 1 is a schematic view showing a first embodiment of a liquid developing apparatus according to the present invention, and FIG.
1 is a perspective view showing details of the recording head of FIG. 1, FIG. 3 is an enlarged perspective view of a portion A of FIG. 2, and FIGS. 4 (a) and 4 (b) are arrows B and B of the recording head of FIG. Plan view and front view showing C,
FIG. 5 is a cross-sectional view showing the head end of the recording head of FIG. 2, and FIGS. 6 to 9 are diagrams for explaining the operation of the liquid developing device of FIG.

The liquid developing apparatus shown in FIG. 1 includes a latent image carrier 1, a charger 2, developing units 4a to 4d, a transfer roller 6, a heat roller 11, and a static eliminator 8.

The latent image carrier 1 forms an electrostatic charge image (electrostatic latent image). The charger 2 uniformly charges the surface of the latent image carrier 1.

The developing units 4a to 4d have four colors (Yellow).
w, Magenta, Cyan, Black) (tandem system). Each developing section 4a-
4d is an exposure unit 3, a squeeze roller 5, and a recording head 1.
3 is provided. The developing units 4b to 4d include the charger 2.

The exposing device 3 irradiates the latent image carrier 1 with a laser or the like to form an electrostatic latent image. The squeeze roller 5 removes the excess dispersion medium on the latent image carrier 1 and turns the toner particles into a film form.

The ink material to be formed into a film form is described in US Pat. No. 5,650,253 (Colu).
mn 10 Line 8-Column 13 Line 14) and US
Details are shown in P5,698,616.

The recording head 13 causes the flying particle group 22 charged to the same polarity as the charge on the surface of the latent image carrier 1 to fly toward the latent image carrier 1.

The transfer roller 6 transfers the visible image on the latent image carrier 1 onto the recording medium 7. The heat roller 11 fixes the visible image transferred on the recording medium 7 on the recording medium 7. The static eliminator 8 neutralizes the latent image charge on the latent image carrier 1 after the transfer.

Details of the recording head 13 are shown in FIGS. The recording head 13 shown in these figures includes a liquid toner chamber 14, a migration electrode 16, a recording electrode 17, a liquid toner channel groove 29, and a channel wall 20.

The liquid toner chamber 14 contains liquid toner. The migration electrode 16 transports the toner particles by electrophoresis. A plurality of recording electrodes 17 are arranged side by side in a direction orthogonal to the transport direction of the latent image carrier 1 in FIG. At the tip of each recording electrode 17, a convex discharge point 30 for discharging the toner particles transported by the migrating electrode 16 is provided.

The liquid toner flow channel 29 guides the liquid toner to the discharge point 30. The flow channel wall 20 is provided to divide the liquid toner flow channel 29.

Here, the liquid toner chamber 14 has a liquid toner supply port 18 and a liquid toner discharge port 19, and is connected to a liquid toner tank via a tube (not shown). The liquid toner chamber 14 applies a back pressure to the liquid toner and forces the liquid toner in the liquid toner chamber 14 to circulate.

FIGS. 4A and 4B show the vicinity of the discharge point 30 of the latent image carrier 1 and the recording head 13. FIG. FIG.
As shown in (a) and (b), an ejection opening 15 is provided between the recording electrodes 17 of the recording head 13. Between the discharge points 30 of each recording electrode 17, the toner particles 2
A third meniscus 27 is formed. The formation of the meniscus 27 will be described later.

A flow path wall 20 is provided between the recording electrodes 17.
A liquid toner channel groove 29 is provided. Then, the flying particle group 22 from the convex ejection point 30 flies toward the latent image carrier 1.

FIG. 5 shows the details of the head end portion of the recording head 13. As shown in FIG. 5, the liquid toner 21 supplied from the liquid toner supply port 18 in FIG. 2 flows through the individual liquid toner flow channel 29 and goes to each part where the discharge point 30 is formed. The migration electrode 1 is provided on the substrate 31 on which the liquid toner flow channel 29 is formed so as to be in contact with the liquid toner 21.
6 is patterned.

A migration voltage Vep is applied to the migration electrode 16. The recording electrode 17 is patterned inside the insulating coating member 32 forming the liquid toner channel groove 29 to the vicinity of the tip of the discharge point 30. A developing bias voltage Veb is applied to the recording electrode 17.
Then, the toner particles 23 in the liquid toner 21 gradually move on the free surface by the migration voltage Vep and concentrate toward the ejection point 30.

Voltage applied to recording electrode 17 and latent image carrier 1
The upper potential distribution is shown in FIG. As shown in FIG. 6A, a constant developing bias voltage Veb is applied to the recording electrode 17 such that toner particles are not discharged.

As shown in FIG. 6D, the latent image carrier 1 is uniformly charged with Vo (about 600 to 650 V). Then, as shown in FIG. 6 (c), when light is irradiated to the portion to be an image by the exposure device 3 of FIG. 1, the charged charge in the light-irradiated portion is removed. At this time, as shown in FIG. 6B, the surface potential of the image portion on the latent image carrier 1 is Vi.
(50-100V), and the surface potential other than the image area is
Voi (about 550 to 600 V).

Next, the ejection principle will be described with reference to FIGS. First, the relationship between the voltages applied to the recording electrode 17 and the counter electrode 26 necessary for discharging the toner particles will be described.

In order to discharge toner particles, a certain amount of applied voltage difference is required between the recording electrode 17 and the counter electrode 26. Here, the minimum applied voltage difference at which the toner particles can be discharged is defined as a threshold voltage Vth.

Therefore, when the voltage difference between the recording electrode 17 and the counter electrode 26 is equal to or greater than Vth, toner particles are ejected from the recording electrode 17. When the voltage difference between the recording electrode 17 and the counter electrode 26 is smaller than Vth, the toner particles are not ejected.

Here, as shown in FIG. 8A, a voltage Vep is applied to the migration electrode 16 in FIG. 5 in order to transport the toner particles to the discharge point 30 in FIG. 4 by electrophoresis.
At this time, as shown in FIGS. 8B and 8C, an applied voltage difference (Veb) between the applied voltage (development bias voltage) Veb to the recording electrode 17 and the applied voltage (Vd1) to the counter electrode 26.
−Vd1) is equal to or higher than the threshold voltage Vth.

As a result, the toner particles move toward the leading end of the recording electrode 17, and an electrostatic force for discharging the toner particles is obtained. The toner particles overcome the meniscus force, the surface tension and the viscous force of the liquid toner by the electrostatic force, and become fine flying particles 22 to form a discharge point 30 of the recording electrode 17.
Fly from. At this time, toner particles are supplied. By repeating such an operation, the toner particles are continuously discharged from the recording electrode 17.

When the applied voltage difference (Veb-Vd) between the applied voltage (developing bias voltage) Veb to the recording electrode 17 and the applied voltage (Vd) to the counter electrode 26 does not exceed the threshold voltage Vth, the toner particles Does not provide the electrostatic force required for ejection. Therefore, no toner particles are discharged from the recording electrode 17.

FIG. 9 shows a state of the meniscus 27 near the discharge point 30 when the developing bias voltage Veb is applied to the recording electrode 17.

The toner particles 2 in the liquid toner chamber 14
3 moves to the ejection point 30 side by the electrostatic force generated by the migration voltage Vep and the developing bias voltage Veb. This is the ejection preparation stage. In this state, since the voltage has not reached the threshold voltage Vth yet, the flying particle group 22
Does not occur. At this time, a meniscus 27 of the toner particles 23 is formed in each ejection opening 15.

Next, the operation of the liquid developing apparatus having the above configuration will be described. First, as described in FIG.
The surface of the latent image carrier 1 is uniformly charged by the charger 2. Next, light is applied to a portion of the latent image carrier 1 where an image area is to be formed by the exposure device 3 to remove the charged charges. As a result, a negative electrostatic latent image in which the charge of the image portion has been removed is formed.

The potential on the latent image carrier 1 at this time is shown in FIG.
The distribution shown in FIG. At this time, first, Yellow
It is assumed that the voltage Vep is applied to the migration electrode 16 of the recording head 13 of w. Thereby, the toner particles 23 are conveyed to the discharge opening 15.

The recording bias voltage V is applied to the recording electrode 17.
When eb (for example, about 1000 V) is applied, a meniscus 27 at the tip of the recording electrode 17 is formed as shown in FIG. When the latent image carrier 1 moves to a position facing the recording head 13, the potential Vi of the image portion (for example, about 50 to 100 V) and the voltage Veb of the recording electrode 17 are obtained.
The difference Veb-Vi from the threshold voltage Vth (for example, 6
(About 00 to 800 V).

For this reason, as described with reference to FIGS. 7 and 9, Yel
The low flying particle group 22 flies. The yellow flying particle group 22 flies toward the image area, and the latent image carrier 1
By attaching to the upper side, a yellow toner image is formed.

On the other hand, the potential V other than the image portion described with reference to FIG.
oi (for example, about 500 to 600 V) and the recording electrode 17
Veb (eg, about 1000 V)
-Voi is the threshold voltage Vth (for example, 600 to 80
0V) or less. Therefore, the flying particle group 22 does not fly except for the image portion.

When the yellow toner image is formed on the latent image carrier 1 and a yellow toner image is formed, pressure is applied by the squeeze roller 5 shown in FIG. 1 to remove the excess dispersion medium. As a result, the toner particles are formed into a film form on the latent image carrier 1. Then, a yellow toner image formed into a film form is formed on the latent image carrier 1.

In the squeeze operation by the squeeze roller 5, it has become clear from experiments that when the toner volume concentration becomes, for example, 53% or more, the toner images of the second and subsequent colors are not affected. ing. Further, it is clear from experiments that when the toner volume concentration is, for example, 53% or more, even if the squeezing operation by the squeezing roller 5 is unnecessary, it does not affect the toner images of the second and subsequent colors.

Next, the surface of the latent image carrier 1 is uniformly charged by the charger 2 of Magenta. The exposing device 3 irradiates a portion of the latent image carrier 1 where an image portion is to be formed with light to remove the charged charges. As a result, a negative electrostatic latent image in which the charge of the image portion has been removed is formed. At this time, the potential on the latent image carrier 1 has a distribution shown in FIG.

Since the voltage Vep is applied to the migration electrode 16 of the recording head 13 of Magenta, the toner particles 23 are conveyed to the ejection opening 15. Further, by applying the developing bias voltage Veb to the recording electrode 17,
The meniscus 27 at the tip of the recording electrode 17 is formed as shown in FIG.

When the latent image carrier 1 moves to the upper part of the recording head 13, the difference Veb-Vi between the potential Vi of the image portion and the voltage Veb of the recording electrode 17 becomes higher than the threshold voltage Vth. Therefore, the flying particles 22 of Magenta fly from the ejection point 30 toward the latent image carrier 1. Then, the flying particle group 22 of Magenta flies toward the image area and adheres on the latent image carrier 1, whereby Mag
The toner image of enta is formed.

On the other hand, as described above, the flying particle group 22 does not fly in areas other than the image portion because the voltage is equal to or lower than the threshold voltage Vth. When the toner image of Magenta adheres to the latent image carrier 1 and a toner image of Magenta is formed, pressure is applied by the squeeze roller 5 shown in FIG. 1 to remove an excess dispersion medium.

As a result, the toner particles 23 of Magenta are formed into a film form on the latent image carrier 1. At this time, since the yellow toner particles have already been formed into a film form, the yellow toner image does not fall due to the squeezing operation of Magenta.

Further, since the toner particles 23 of each color are formed into a film form on the latent image carrier 1, the previously formed toner image may drop to the developing units 4 b to 4 d in the next step. There is no color mixing because there is no color.
In this way, a film-formed toner image of Magenta is formed on the latent image carrier 1 following the yellow toner image.

For Cyan and Black, this Y
The same operation as that of “ello” and “Magenta” is repeated. As a result, Yellow, Ma on the latent image carrier 1
Genta, Cyan, and Black are formed into a film-formed toner image.

Next, the toner image on the latent image carrier 1 is transferred onto the transfer roller 6 shown in FIG. Further, the toner image transferred on the transfer roller 6 is transferred to the recording medium 7. At this time, heat and pressure are applied to the recording medium 7 by the transfer roller 6 and the heat roller 11, so that the toner image is fused to the recording medium 7 to be a permanent image.

On the other hand, the charge on the latent image carrier 1 after the transfer is eliminated by the light from the static eliminator 8. By repeating a series of processes from charging to static elimination, color printing is continuously performed.

As described above, in the first embodiment, the flying particle group 22 of the toner particles 23 from the recording head 13 is
The latent image is charged to the same polarity as the charge on the latent image carrier 1 so as to fly only to the image portion which is an electrostatic latent image, and the flying particles 22 are not caused to fly to the non-image portion. The squeezing operation for removing the excess dispersion medium on the carrier 1 is facilitated.

In the tandem-type color developing process of the first embodiment, since the dispersion medium adhered during the development of the first color is small, the movement of the dispersion medium of the first color to the toner images of the second and subsequent colors is difficult. Since the number of toner images is reduced, it is possible to prevent color mixture between the first color toner image and the second and subsequent color toner images.

Further, in the first embodiment, by increasing the toner volume concentration of the toner image on the latent image carrier 1,
It is possible to eliminate the need for squeezing in colorization in the tandem system or the 4-cycle system.

Here, in order to increase the toner volume concentration of the toner image, the toner concentration of the liquid toner is increased, or the voltage of the electrophoretic electrode 16 is increased to increase the amount of the toner particles 23 concentrated at the tip of the discharge opening 15. Or increasing the developing bias voltage by the recording electrode 17.

Furthermore, in the first embodiment, the flying particle group 2 is applied only to the image portion which is an electrostatic latent image on the latent image carrier 1.
2 is made to fly to reduce the adhesion of the dispersion medium onto the latent image carrier 1, so that the recording medium 7
Dispersion medium when transferring the toner image to
It is possible to avoid the danger caused by the evaporation of the dispersion medium when the toner image is fixed on the recording medium 7.

Further, since the amount of the dispersion medium adhering to the latent image carrier 1 is extremely small, a mechanism for collecting the dispersion medium is not required, and the cost of the apparatus can be prevented from increasing.

Further, since the toner image on the latent image carrier 1 is formed into a film form by the squeezing operation for each color, the previous toner image is not peeled off at the time of the squeezing operation for each color, so that there is no complicated structure. Colorization can be easily realized.

Further, the electrostatic latent image on the latent image carrier 1 is colored by the toner particles 23 flying in each of the developing sections 4a to 4d in order, so that it takes one cycle. Since development is possible, the development speed can be increased.

Further, the flying particle groups 22 of each color fly from the recording electrode 17 of the recording head 13 corresponding to each color, and adhere to the latent image carrier 1 to form a film form. The developed toner image is transferred to the developing unit 4b in the next process.
There is no color mixing since it does not fall to ~ 4d. This eliminates the need for a structure such as an intermediate transfer, so that the structure for performing colorization can be simplified.

In the first embodiment, the case where the electrostatic latent image on the latent image carrier 1 is of a negative type has been described. The latent image may be of a positive type. In this case, the flying particle group 22 of the toner particles 23 from the recording head 13 is charged to a polarity different from the charge of the electrostatic latent image on the latent image carrier 1, so that the latent image carrier 1 The flying particles 22 can fly toward the electrostatic latent image.

(Second Embodiment) FIG. 10 is a schematic view showing a liquid developing apparatus according to a second embodiment of the present invention.
In the second embodiment, the liquid developing device of the present invention is applied for a single color.

That is, the liquid developing device shown in FIG.
The apparatus includes a latent image carrier 1, a charger 2, a single-color developing unit 4 e, a transfer roller 6, a heat roller 11, and a static eliminator 8. The single-color developing section 4e includes an exposure device 3, a squeeze roller 5, and a recording head 13.

The single-color developing section 4e includes an exposing device 3, a squeeze roller 5, and a recording head 13. Recording head 1
As described above, the flying particle group 22 charged to the same polarity as the charge on the surface of the latent image carrier 1
Fly towards.

Next, the operation of the liquid developing apparatus having such a configuration will be described.

First, as described with reference to FIG. 6, the surface of the latent image carrier 1 is uniformly charged by the charger 2.
Next, light is applied to a portion of the latent image carrier 1 where an image area is to be formed by the exposure device 3 to remove the charged charges. This allows
A negative-type electrostatic latent image in which the charge of the image portion is removed is formed.

The potential on the latent image carrier 1 at this time is as shown in FIG.
The distribution shown in FIG. At this time, the recording head 13
It is assumed that the voltage Vep is applied to the migration electrode 16 (see FIGS. 3 and 5). As a result, the toner particles 23 are transported to the discharge opening 15 (see FIG. 9).

The recording electrode 17 (see FIGS. 3 and 5)
To the developing bias voltage Veb (for example, about 1000 V)
Is applied, the meniscus 2 at the tip of the recording electrode 17 is
7 are formed as shown in FIG.

When the latent image carrier 1 moves to the position facing the recording head 13, the difference Veb-Vi between the potential Vi of the image portion (for example, about 50 to 100 V) and the voltage Veb of the recording electrode 17 is obtained. The threshold voltage Vth (for example, 60
0 to 800 V) or more.

For this reason, as described with reference to FIGS. 7 and 9, the flying particle group 22 flies from the ejection point 30 toward the latent image carrier 1. The flying particle group 22 flies toward the image area and adheres to the latent image carrier 1 to form a toner image.

On the other hand, the potential V other than the image portion described with reference to FIG.
oi (for example, about 500 to 600 V) and the recording electrode 17
Veb (eg, about 1000 V)
-Voi is the threshold voltage Vth (for example, 600 to 80
0V) or less. Therefore, the flying particle group 22 does not fly except for the image portion.

When the toner image is formed on the latent image carrier 1 and a toner image is formed, pressure is applied by the squeeze roller 5 shown in FIG. 1 to remove the excess dispersion medium. As a result, the toner particles are formed into a film form on the latent image carrier 1. Then, a toner image formed into a film form is formed on the latent image carrier 1.

Experiments have shown that when the toner volume concentration is, for example, 53% or more, even if the squeeze operation by the squeeze roller 5 is unnecessary, it does not affect the subsequent image forming process.

As described above, in the second embodiment, the flying particle group 22 of the toner particles 23 from the recording head 13 of the monochromatic developing section 4e is charged to the same polarity as the charged charge on the latent image carrier 1. In this case, only the image portion which is an electrostatic latent image is made to fly, and the flying particle group 22 is made not to fly to the non-image portion. The squeezing operation for removing the excess dispersion medium on the body 1 is facilitated.

In the same manner as described above, the flying particles 22 are caused to fly only to the image portion which is an electrostatic latent image on the latent image carrier 1 so as to reduce the adhesion of the dispersion medium onto the latent image carrier 1. Therefore, the amount of the dispersion medium when transferring the toner image from the latent image carrier 1 to the recording medium 7 is extremely reduced, and the danger due to evaporation of the dispersion medium when fixing the toner image onto the recording medium 7 is avoided. can do.

In the second embodiment, the case where the exposing unit 3 is incorporated in the monochromatic developing unit 4e has been described. However, the present invention is not limited to this example, and the exposing unit 3 is provided outside the monochromatic developing unit 4e. It can also be.

(Third Embodiment) FIG. 11 is a schematic view showing a liquid developing apparatus according to a third embodiment of the present invention.
In the third embodiment, the exposure unit of each developing unit is omitted.

That is, the liquid developing device shown in FIG.
The image forming apparatus includes a latent image carrier 1, a charger 2, developing units 4f to 4i, a transfer roller 6, a heat roller 11, a static eliminator 8, and a retract mechanism 33.

The developing units 4f to 4i have four colors (Yellow).
w, Magenta, Cyan, Black) (tandem system). Each developing unit 4f ~
4i includes a squeeze roller 5 and a recording head 13. The retract mechanism 33 performs an operation of moving the transfer roller 6 up and down.

Next, the operation of the liquid developing apparatus having such a configuration will be described.

First, as described with reference to FIG. 6, the first rotation of the latent image carrier 1
Is formed into a film form on the latent image carrier 1. Then, Yel formed into a film form on the latent image carrier 1
A low toner image is formed.

Next, the surface of the latent image carrier 1 is uniformly charged by the charger 2. The exposing device 3 irradiates a portion of the latent image carrier 1 where an image portion is to be formed with light to remove the charged charges. As a result, a negative electrostatic latent image in which the charge of the image portion has been removed is formed. By the same operation as the image forming process of Magenta in the previous color, the toner particles 23 of Magenta are transferred to the latent image carrier 1 at the second rotation of the latent image carrier 1.
Formed on film foam. And the latent image carrier 1
A toner image of Magenta formed into a film form is formed thereon.

For Cyan and Black, this Y
The same operation as that of “ello” and “Magenta” is repeated. That is, a cyan toner image is formed on the latent image carrier 1 at the third rotation of the latent image carrier, and a black toner image is formed on the latent image carrier 1 at the fourth rotation of the latent image carrier. Thus, Yellow, Magenta,
A toner image in the form of a film of Cyan or Black is formed.

At the fourth rotation, the transfer roller 6 is lowered by the retract mechanism 33, and comes into contact with the latent image carrier 1.
The first to third rotations are performed by the retract mechanism 33.
Since the transfer roller 6 is in the raised state, it does not contact the latent image carrier 1.

Next, the toner image on the latent image carrier 1 is transferred onto the transfer roller 6. Further, the toner image transferred on the transfer roller 6 is transferred to the recording medium 7. At this time, heat and pressure are applied to the recording medium 7 by the transfer roller 6 and the heat roller 11, so that the toner image is fused to the recording medium 7 to be a permanent image.

As described above, in the third embodiment, each time the latent image carrier 1 is rotated, the toner particles 23 of each color are formed into a film form on the latent image carrier 1 and the toner particles 23 of the next color are formed. Before the film 23 is formed into a film form on the latent image carrier 1, an image portion that is an electrostatic latent image is formed by the single charger 2 and the exposure device 3. In addition to the effects, simplification of the configuration of the liquid developing device for performing colorization in the tandem system or the four-cycle system and reduction in cost can be realized.

In the third embodiment, the case where the electrostatic latent image on the latent image carrier 1 is a negative type has been described. However, the present invention is not limited to this example. The latent image may be of a positive type. In this case, as described above, the flying particle group 22 of the toner particles 23 from the recording head 13 is
By charging the electrostatic latent image on the latent image carrier 1 with a polarity different from that of the electrostatic latent image, the flying particle group 22 can fly toward the electrostatic latent image on the latent image carrier 1.

In the third embodiment, the case where the squeeze roller 5 is incorporated in each of the developing units 4f to 4i has been described. However, the present invention is not limited to this example. It is also possible to adopt a configuration in which

[0106]

As described above, according to the liquid developing apparatus and the liquid developing method of the present invention, the toner particles adhering to the latent image carrier are formed into a film form, and the squeezing operation of the excess dispersion medium is facilitated. At the same time, the danger due to the generation of flammable solvent gas is also prevented, and one-cycle development is made possible. Furthermore, color mixing is prevented when flying particles of each color fly with colorization. So
With a simple structure, development performance can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of a liquid developing device of the present invention.

FIG. 2 is a perspective view illustrating details of a recording head in FIG. 1;

FIG. 3 is an enlarged perspective view showing a portion A in FIG. 2;

4A is a plan view showing the recording head in FIG. 2 as viewed in the direction of arrow B, and FIG. 4B is a front view showing the recording head in FIG.

FIG. 5 is a sectional view showing a head end of the recording head of FIG. 2;

6 is a diagram showing a voltage applied to a recording electrode of FIG. 4 and a potential distribution on a latent image carrier.

FIG. 7 is a view for explaining the ejection principle of the recording head of FIG. 1;

FIG. 8 is a diagram for explaining the ejection principle of the recording head of FIG. 1;

FIG. 9 is a diagram illustrating a state of a meniscus near an ejection point of the recording head of FIG. 3;

FIG. 10 is a schematic view showing a second embodiment of the liquid developing device of the present invention.

FIG. 11 is a schematic view showing a third embodiment of the liquid developing device of the present invention.

FIG. 12 is a schematic view showing an electrophotographic apparatus using a conventional liquid developing system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 2 Charger 3 Exposure unit 4 Developing unit 4a-4d Developing unit 4e Monochromatic developing unit 4f-4i Developing unit 5 Squeeze roller 6 Transfer roller 7 Recording medium 8 Static eliminator 9 Cleaning blade 10 Pressure roller 11 Heat roller 13 Recording head 14 Liquid toner chamber 15 Discharge opening 16 Electrophoresis electrode 17 Recording electrode 18 Liquid toner supply port 19 Liquid toner discharge port 20 Flow path wall 21 Liquid toner 22 Flying particle group 23 Toner particles 24 Developing roller 26 Counter electrode 27 Meniscus 28 Photosensitive Body drum 29 Liquid toner channel groove 30 Discharge point 31 Substrate 32 Insulating coating member 33 Retract mechanism

Continued on the front page (72) Inventor Toshihiko Watari 7546 Yasuda, Kashiwazaki City, Niigata Prefecture Inside Niigata Nippon Electric Co., Ltd. Inventor Yoshihiro Hagiwara 7546 Yasuda, Kashiwazaki City, Niigata Prefecture Niigata Nippon Electric Co., Ltd. 7546 Yasuda, Kashiwazaki, Niigata, Japan Niigata Nippon Electric Co., Ltd. (72) Inventor Hitoshi Takemoto 7546, Yasuda, Oji, Kashiwazaki, Niigata Niigata Nippon Electric Co., Ltd. (56) References JP-A-4-166873 (JP, A) JP-A-9-6081 (JP, A) US Patent 5,650,253 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/10-13/11 G03G 15/10-15/11

Claims (17)

(57) [Claims] 1. A liquid developing apparatus for flying a liquid toner in which toner particles are dispersed in a carrier liquid and developing it in a non-contact manner with respect to an image portion of an electrostatic latent image formed on a latent image carrier. An ink material which is formed into a film form on the latent image carrier, and flying particles of a predetermined color charged toward the electrostatic latent image are provided near the latent image carrier. A recording head for flying the group, and, when the volume concentration of the toner particles flying on the latent image carrier is less than a predetermined value, removing the excess dispersion medium on the latent image carrier and removing the latent image on the latent image carrier. Developing means comprising a squeeze roller for forming toner particles adhered on the body into a film form, wherein, in the electrostatic latent image, a potential of a non-image portion and a developing bias voltage to the recording head are different. The difference is that the liquid toner flies Wherein the difference between the potential of the image area and the developing bias voltage is made larger than the threshold voltage. 2. A liquid developing apparatus according to claim 1, wherein a plurality of said developing means are provided corresponding to each color. 3. The liquid developing apparatus according to claim 2, wherein said developing means includes an exposure device for forming an electrostatic latent image on said latent image carrier. 4. The liquid developing apparatus according to claim 3, wherein the developing unit includes a charger for uniformly charging the latent image carrier. 5. The exposure device irradiates light to the electric charge charged on the latent image carrier, removes the electric charge, and forms an image portion, and the recording head comprises a surface of the latent image carrier. 4. The liquid developing apparatus according to claim 3, wherein the flying particle group charged to the same polarity as the upper charge is caused to fly. 6. The exposure device according to claim 1, wherein the exposing unit irradiates the charge on the latent image carrier with light to a portion other than a portion where an image area is formed to remove the charged charge. 4. The liquid developing apparatus according to claim 3, wherein the flying particle group charged to a different polarity from the charge charged on the surface of the carrier is caused to fly. 7. A recording head having a plurality of recording heads having a convex ejection point, arranged in a direction orthogonal to a conveying direction of the latent image carrier, and applied with a developing bias voltage. The liquid developing device according to claim 1, further comprising: an electrode; a toner chamber that stores liquid toner; and a liquid toner flow channel that guides the liquid toner in the toner chamber to the ejection point side. 8. The liquid developing apparatus according to claim 1, wherein the recording head flies the flying particle group by applying a developing bias voltage. 9. The liquid developing device according to claim 7, wherein an electrophoresis electrode for guiding the toner particles to the discharge point side by electrophoresis is provided in the liquid toner flow channel. . 10. The recording electrode according to claim 7, wherein a developing bias voltage for controlling a volume concentration of toner particles on the latent image carrier is changed and applied to the recording electrode.
The liquid developing device according to item 1. 11. A liquid toner in which toner particles to be formed into a film on the latent image carrier are dispersed in a carrier liquid for an image portion of an electrostatic latent image formed on the latent image carrier. A non-contact liquid developing method, comprising: a first step of uniformly charging the surface of the latent image carrier; and a first step of forming an electrostatic latent image on the latent image carrier. (2) flying flying particles of a predetermined color charged toward the electrostatic latent image from an ejection point, removing excess dispersion medium on the latent image carrier, and removing the latent image carrier; A third step of forming the toner particles adhered on the body into a film form; and in the electrostatic latent image, the difference between the potential of the non-image portion and the developing bias voltage is not necessary for the liquid toner to fly. Less than the threshold voltage, the potential of the image area and the current Fourth the difference between the bias voltage is greater than the threshold voltage
And a liquid developing method. 12. The second step includes a step of irradiating the charged charges on the latent image carrier with light and removing the charged charges to form an image area. The third step 12. The liquid developing method according to claim 11 , further comprising a step of flying the flying particle group charged to the same polarity as the charge charged on the surface of the latent image carrier. 13. The method according to claim 12, wherein the second step includes a step of irradiating light on a portion of the charge on the latent image carrier other than a portion where an image portion is to be formed to remove the charge. 12. The liquid developing apparatus according to claim 11 , wherein the third step includes a step of flying the flying particle group charged to a different polarity from the charge charged on the surface of the latent image carrier. Method. 14. The method of claim 13, wherein the third step, claims, characterized in that includes the step of flying the flying particles of each color
12. The liquid developing method according to 11 . 15. The liquid developing method according to claim 11 , wherein the third step includes a step of causing the flying particles to fly by applying a developing bias voltage. 16. The liquid developing method according to claim 11 , wherein said third step includes a step of guiding said toner particles to said discharge point side by electrophoresis. The method according to claim 17 wherein said third step, wherein the included step of changing the developing bias voltage to control the volume density of the toner particles on the latent image carrier 請
A liquid developing method according to claim 11 .