JP3013329B2 - Electrostatic latent image developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for developing an electrostatic latent image. INDUSTRIAL APPLICABILITY The present invention can be suitably applied to analog and digital electrocopiers, electrophotographic printers and facsimile machines.

[0002]

2. Description of the Related Art To develop an electrostatic latent image formed on a latent image carrier such as a photoconductive photoreceptor, a developing solution in which toner is dispersed in a dispersion medium is held on a peripheral surface of a developing roller. There is a developing method in which the electrostatic latent image is visualized with the toner by supplying the latent image to the surface of the latent image carrier, and as one of the developing methods, the distance between the peripheral surface of the developing roller and the surface of the latent image carrier in the developing section is considered. That is, there is known a method of performing development by making the thickness of a developing solution film formed on the peripheral surface of a developing roller thinner than the developing gap (Japanese Patent Application Laid-Open No. 55-143565). This developing method is hereinafter referred to as “non-contact liquid developing method”.

In the non-contact liquid developing system, there is a gap between the developing film formed on the peripheral surface of the developing roller and the surface of the latent image carrier, and when the electric charge constituting the electrostatic latent image reaches the developing section, Due to the action of the electric field by the charges, the developer film projects so as to “extend” toward the charges and adheres to the latent image carrier to develop the electrostatic latent image.

However, when the above-mentioned non-contact liquid developing method is actually carried out using a developing roller having a smooth peripheral surface, the developed image shows "developing unevenness" such as so-called "white spots". Appeared, indicating that a good visible image could not be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an electrostatic latent image developing apparatus capable of obtaining an extremely good visible image by a non-contact liquid developing system. Aim.

[0006]

SUMMARY OF THE INVENTION An electrostatic latent image developing apparatus according to the present invention comprises the steps of "supplying a liquid developer held on the peripheral surface of a developing roller to a latent image carrier, and forming the liquid developer on the latent image carrier. Device for visualizing an electrostatic latent image, comprising a developing roller, a developer supply unit, and a squeeze roller.

The “developing roller” has a smooth peripheral surface,
In a predetermined developing section, the liquid developer is disposed in close proximity to the surface of the latent image carrier with a developing gap therebetween, and the liquid phase developer is held in a thin film on the peripheral surface and is rotated in a predetermined direction to hold the liquid developer. The liquid developer thus developed is brought to the developing section. Here, the expression “close to” means that the size of the developing gap is 100 μm or less, preferably 50 μm or less.

The "developer supply means" supplies a liquid developer to the peripheral surface of the developing roller. The “squeeze roller” removes excess liquid developer from the liquid developer layer supplied to the developing roller by the developer supply unit, and forms a uniform liquid developer thinner than the developing gap on the peripheral surface of the developing roller. The film is formed very thin .

The direction of rotation of the developing roller may be the same or opposite to the direction of movement of the surface of the latent image carrier in the developing section.

As the liquid phase developer, a "developer in which a toner is dispersed in a dispersion medium", that is, a developer conventionally known as a developer for electrophotography can be used (claim 2).
In addition to the developer, a "printing ink", that is, an emulsion ink, a water-based ink, an oil-based ink, or the like can be used (claim 3). "Emulsion ink" is an oil phase in which a pigment is uniformly dispersed in a non-drying oil or a non-volatile oil.
So-called W / O in which about 90 to 50% of an aqueous phase is emulsified in 50%
A so-called O / W type in which an oil phase in which a pigment is uniformly dispersed is emulsified in an aqueous phase can also be used.

In the invention according to claim 2, the squeeze roller is provided with "a liquid phase developer film to the developing section.
In order to increase the toner concentration in the liquid developer, a bias voltage having the same polarity as that of the toner can be applied (claim 4). A bias voltage having a polarity opposite to that of the image charge can be applied (claim 5).

[0012]

The squeeze roller rotates in contact with the liquid developer layer formed on the developing roller, so that both ends in the thickness direction of the liquid developer layer, that is, on the peripheral surface of the developing roller and on the peripheral surface of the squeeze roller. Then, fluid velocities opposite to each other are applied to the liquid developer layer, and excess liquid developer is removed from the peripheral surface of the developing roller using the flow velocity distribution in the layer thickness direction. Therefore, unlike the conventional developer film forming method using a scraper or a coating roller, the squeeze roller and the developing roller are not in contact with each other, so that a liquid phase developer film having a desired thickness is uniformly formed on the peripheral surface of the developing roller. can do.

As the developing gap between the developing roller and the latent image carrier is "extremely small", the liquid phase developer film formed on the peripheral surface of the developing roller by the squeeze roller becomes extremely thin.

[0014]

FIG. 1A shows an embodiment of the first aspect of the present invention. A “photoconductive photoconductor” as a latent image carrier, denoted by reference numeral 1, is formed in a drum shape, rotates in the direction of an arrow, and includes charging means and exposure means (not shown) (an original image exposure system for irradiating an original optical image). And a writing method using a light beam, etc.), and a visible image corresponding to the electrostatic latent image is formed by the electrostatic latent image developing device. The visible image is transferred onto transfer paper by a transfer unit (not shown).

The "liquid phase developer" used in this embodiment is a developer for electrophotography in which a toner is dispersed in a dispersion medium. It is also an embodiment. The visible image formed on the photoconductor 1 by development is a “toner image”.

In the embodiment of FIG. 1A, reference numeral 2 denotes a developing roller, reference numeral 6 denotes a squeeze roller, and reference numeral 5 denotes a casing. The developing roller 2 is a metal roller having a smooth peripheral surface, and is disposed very close to the peripheral surface of the photoconductor 1 via a developing gap. Development gap is 30
μm. The distal end of a scraper 4a whose base is held by the casing 5 abuts on the lower peripheral surface of the developing roller 2, and the scraper 4a and the peripheral surface of the developing roller 2 form a developing solution reservoir.

The developer 3 as a liquid developer is pumped up from a tank (not shown) through a pipe 7A and supplied from the nozzle 7 to the "developer storage". The developer 3 supplied to the developer reservoir wets the peripheral surface of the developing roller 2 to form a developer layer as a liquid developer layer, and moves with the roller peripheral surface as the developing roller 2 rotates counterclockwise. I do. That is, a pipe 7A is supplied from a tank (not shown) to the nozzle 7.
Means for pumping up the developer 3 through the scraper 4a
Constitutes "developer supply means".

A squeeze roller 6 is provided above the developing roller 2.
Is provided. The squeeze roller 6 has its peripheral surface close to the peripheral surface of the developing roller 2 with a predetermined gap therebetween, and rotates in the same direction as the developing roller 2. For this reason, in the portion where the peripheral surfaces of the developing roller 2 and the squeeze roller 6 are close to each other, the moving directions of the peripheral surfaces of the two rollers 2 and 6 are opposite to each other, and the developer layer held on the peripheral surface of the developing roller 2 is The remainder is removed. Thus, a uniform developer film having a predetermined layer thickness is formed on the peripheral surface of the developing roller 2 as a “liquid developer film”.

The thickness of the developing solution film formed on the peripheral surface of the developing roller 2 by the action of the squeeze roller 6 is determined mainly by the "rotation speed ratio" between the development roller 2 and the squeeze roller 6. It is set so that the thickness of the developer film formed as described above is smaller than the development gap (30 μm). In addition, the tip of the scraper 4b whose base is held by the casing 5 is in contact with the peripheral surface of the squeeze roller 6, thereby cleaning the peripheral surface of the squeeze roller 6.

As the developing roller 2 rotates, the developing solution film is brought to a developing portion, that is, a portion near the peripheral surface of the developing roller 2 and the peripheral surface of the photosensitive member 1. FIG. 1B shows the state of the developing unit as an explanatory diagram. The photoconductor 1 has a positive charge (+
When the developer film 10 and the peripheral surface of the photoreceptor 1 approach each other in the developing section, the developer film 10 becomes static as shown in FIG. It projects so as to extend toward the charge of the electrostatic latent image, and adheres to the peripheral surface of the photoreceptor to visualize the electrostatic latent image. FIG. 1B shows that the developing solution protruding from the developing solution film 10 is
2 shows a state immediately before adhering to the peripheral surface.

Here, the technical meaning of making the development gap and the liquid developer film extremely small will be described. FIG.
(C) shows a case where the developing gap is relatively large and the thickness of the developer film 10A as the liquid developer film is accordingly large. In such a case, if the developer film 10A protrudes so as to extend toward a part of the electrostatic latent image charge, it becomes difficult to form the protrusion of the developer film near the protruding portion.

That is, as shown, when one projection 10A1 is formed on the developing solution film 10A, the surface of the developing solution film 10A is depressed toward the peripheral surface of the developing roller 2 around the projection 10A1. Becomes In the "recessed portion", the resultant force of the surface tension acts toward the outside of the developer film 10A, so that the pressure is reduced, and the liquid phase developer around the protrusion 10A1 is drawn toward the protrusion 10A1. The projection 10A1 continues to project by taking in the liquid developer attracted in this manner. For this reason, in the portion immediately adjacent to the projection 10A1,
Another projection due to the developer film 10A is unlikely to be formed, and therefore, in the visible image obtained as a result of development, the projection 10A
In other words, a so-called “slit-through” portion occurs around the portion visualized by 1. FIG. 1C also shows a state immediately before the protrusion 10A1 extending from the developing solution film 10A comes into contact with the surface of the photoconductor 1, similarly to FIG. 1B.

In the present invention, since the thickness of the liquid phase developer film is extremely small, when one projection is formed as shown in FIG. 1B, it is formed around the projection. The depression reaches the “bottom” of the liquid-phase developer film, that is, the peripheral surface of the developing roller 2, where the liquid-phase developer film is cut. For this reason, even if one protrusion is formed on the liquid developer film, the range of influence of the formation of the protrusion is narrow, and the protrusion of the liquid developer film can be generated in close proximity according to the electrostatic latent image charge. There is no development failure such as the above-mentioned "missing margin".

As shown in FIG. 1 (a), the developing solution film which has passed through the developing section by the rotation of the developing roller 2 is scraped by a scraper 4a.
As a result, it is scraped off from the peripheral surface of the developing roller 2 to the bottom of the casing 5. The developer 3 thus scraped off and flows down from the developer supply section to the bottom of the casing 5.
Is returned into a tank (not shown) by a pipe 7B.

A bias power supply 12a is provided to apply a weak bias voltage (150 V) to the developing roller 2 in order to prevent the influence of the induced voltage generated on the developing roller 2 by the surface charge of the photosensitive member 1.

FIG. 2 shows an embodiment of the present invention. In order to avoid complication, the same reference numerals as those in FIG. 1 are used in FIG.

The difference from the embodiment of FIG. 1 lies in that in the embodiment of FIG. 2, a "bias voltage of the same polarity as that of the toner" is applied to the squeeze roller 6 by the bias power supply 12b. In order to prevent the influence of the induced voltage of the developing roller 2 by the bias voltage of the squeeze roller 6, the developing roller 2
, A positive bias voltage is applied by a bias power supply 12a.

[0028] In the gap portion of the squeeze roller 6 and the developing roller 2 for bias voltage applied to the squeeze roller 6 is the same polarity as the toner, the toner of the developer layer in a liquid phase a developer layer developing roller 2 side As a result, the toner concentration in the liquid developer film formed on the developing roller 2 becomes higher than the toner concentration in the developer supplied to the developer supply unit. That is, by increasing the toner concentration in the developing solution provided as a liquid phase developer film to the developing section, efficient development becomes possible.

FIG. 3 shows a modified embodiment. In this embodiment, the rotation direction of the developing roller 2 is "clockwise", which is opposite to that in the embodiment of FIGS. As a result, the scraper 4a for cleaning the developing roller 2 comes into contact with the upper peripheral surface of the developing roller 2 and the lower peripheral surface of the developing roller 2 has a thin plate-like liquid phase developer supply member. 11 are in close proximity. To form a developer layer as a liquid developer layer on the peripheral surface of the developing roller 2, the developer supply member 1
1 is not in contact with the peripheral surface of the developing roller 2. The squeeze roller 6 is provided below the developing roller 2 to form a developing solution film.

As in this embodiment, by setting the rotation direction of the developing roller 2 to be "in a direction opposite to the moving direction of the photosensitive member 1 in the developing section", the liquid phase developer can be efficiently supplied into the developing gap. Can be sent, and development can be performed efficiently. In this embodiment as well, a bias voltage may be applied to the developing roller 2 as in the embodiment of FIG. 1, and a bias voltage having the same polarity as the toner is applied to the squeeze roller 6 as in the embodiment of FIG. be able to.

FIG. 4 shows an embodiment of the present invention. The difference from the embodiment of FIGS. 1 and 2 is that a bias voltage having the same polarity as the toner, that is, a polarity opposite to the latent image charge is applied to the developing roller 2 from the bias power supply 12c.
By doing so, the “potential difference between the photoconductor 1 and the developing roller 2 in the developing gap” increases, and the projections on the developing solution film are easily formed, so that the development can be performed efficiently. Also in this embodiment, a bias voltage having the same polarity as that of the toner may be applied to the squeeze roller 6 as in the embodiment of FIG. 2 (in this case, the bias voltage applied to the squeeze roller may be changed). (The bias voltage is higher than the bias voltage to the developing roller.) As in the embodiment of FIG.
May be reversed with respect to the moving direction.

In the embodiment shown in FIGS. 1 (a), 2, 3 and 4, instead of the above-mentioned developing solution, a "printing ink" is used as the liquid layer developer, that is, the above-mentioned emulsion ink or oily / aqueous solution. Ink and the like can be used.

[0033]

As described above, according to the present invention, a novel electrostatic latent image developing device can be provided. In the electrostatic latent image developing device of the present invention, as described above, the “liquid-phase developer film” having a very small developing gap and being thinner than the developing gap.
Is uniformly formed by the squeeze roller, so that good development can be performed without development failure such as "development unevenness" due to white spots or the like which has been a problem in conventional non-contact liquid development.

When a developer for electrophotography is used as the liquid layer developer as in the second aspect of the invention, in order to compensate for toner consumption during development, toner is replenished in the developer to reduce the toner concentration. It is necessary to make adjustments. However, if printing ink is used as the liquid layer developer as in the third aspect of the present invention, the ink is consumed as the ink itself and there is no change in solid components in the ink. ”Does not require any coordination action.

In the electrostatic latent image developing device according to the fourth aspect, the toner concentration in the developing solution film formed on the developing roller is higher than the toner concentration in the developing solution supplied to the developer supply section. In particular, efficient development becomes possible without using a developer having a high toner concentration.

In the electrostatic latent image developing device according to the fifth aspect, the potential difference in the developing gap is effectively increased, and the formation of projections in the liquid phase developer film is facilitated, so that efficient development can be performed. .

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one embodiment of the invention described in claims 1 and 2;

FIG. 2 is a diagram for explaining one embodiment of the invention described in claim 4;

FIG. 3 is a diagram for explaining a modified example.

FIG. 4 is a diagram for explaining one embodiment of the invention described in claim 5;

[Explanation of symbols]

 Reference Signs List 1 latent image carrier 2 developing roller 3 liquid phase developer 4a, 4b scraper 6 squeeze roller 7 nozzle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koji Ono Nakamei Ichimido, Shimada-cho, Shibata-cho, Miyagi Prefecture No. 3 ・ Tohoku Ricoh Co., Ltd. (72) Inventor Takashi Ito Shimada, Shibata-cho, Miyagi No. 3 in 1 Shinmei-do, Tohoku Ricoh Co., Ltd. (72) Inventor Yoshiyuki Araseki Nakano, Nakata, Shibata-machi, Shibata-gun, Miyagi Prefecture No. 3 in 1 Tohoku Ricoh Co., Ltd. (72) Inventor Takayoshi Kudo, Miyagi Shinmei-do, Shimada-cho, Shibata-cho, Shibata-gun No.3, 1 ・ Tohoku Ricoh Co., Ltd. (56) References JP-A-6-194965 (JP, A) JP-A-6-222677 (JP, A) Tokubo Sho57 -18184 (JP, B2) JP-B-58-30579 (JP, B2)

Claims (5)

(57) [Claims] An apparatus for supplying a liquid developer held on a peripheral surface of a developing roller to a latent image carrier to visualize an electrostatic latent image formed on the latent image carrier, comprising: It has a peripheral surface, and is disposed in close proximity to the surface of the latent image carrier at a predetermined developing section with a developing gap therebetween, and holds the liquid phase developer in a thin film on the peripheral surface in a predetermined direction. A developing roller that brings the held thin film-shaped liquid phase developer to the developing section by rotating, a developer supply unit that supplies the liquid phase developer to the peripheral surface of the development roller, and a developer supply unit To remove the excess liquid developer from the liquid developer layer supplied to the developing roller, and to form a very thin uniform liquid developer film thinner than the developing gap on the peripheral surface of the developing roller. Having a squeeze roller provided in non-contact with the developing roller Electrostatic latent image developing device of the non-contact liquid developing method according to claim and. 2. A latent electrostatic image developing device according to claim 1, the liquid-phase developer, an electrostatic non-contact liquid developing method, which is a developer prepared by dispersing toner in a dispersion medium Latent image developing device. 3. A latent electrostatic image developing device according to claim 1, non-contact, wherein the liquid phase the developer is a printing ink
An electrostatic latent image developing device of a liquid touch type . 4. The electrostatic latent image developing device according to claim 2, wherein the squeeze roller has the same polarity as the toner in the squeeze roller in order to increase the concentration of the toner in the liquid phase developer provided as a liquid phase developer film to the developing section. non characterized by applying a bias voltage
An electrostatic latent image developing device of a contact liquid developing type . 5. A non-contact liquid developing system according to claim 1, wherein a bias voltage having a polarity opposite to that of the latent image charge is applied to the developing roller . An electrostatic latent image developing device.