JP3013330B2 - 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 an electrostatic latent image developing device. 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 carrier to the surface of the latent image carrier. 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 effectively solves the problem of uneven development such as white spots in a non-contact liquid developing system. An object of the present invention is to provide an electrostatic latent image developing device capable of obtaining a visible image.

[0006]

An electrostatic latent image developing apparatus according to the present invention comprises the steps of "supplying a liquid developer held on a peripheral surface of a rotating body 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 belt as a rotating body, a developer supply unit, a liquid film forming unit, and a spacer unit.

The “developing belt” has a smooth peripheral surface,
In a predetermined developing section, the liquid developer is disposed close to the surface of the latent image carrier with a developing gap therebetween. Bring the phase developer to the development station. Here, "in close proximity"
Means that the size of the developing gap is 400 μm or less, preferably 100 μm or less. The developing belt is provided such that the “peripheral surface portion stretched between the driving pulleys” is located in the developing unit. Then, the latent image carrier and the developing
In the direction of movement of the peripheral surface of the developing belt,
Effective development enough to prevent development unevenness such as white spots
An area is formed.

[0008] The "developer supply means" supplies the liquid developer to the peripheral surface of the developing belt. The “liquid film forming unit” removes excess liquid phase developer from the developing belt to which the liquid phase developer has been supplied by the developer supplying unit, and forms a liquid phase developer film thinner than the developing gap. The "spacer means" is means for maintaining a predetermined developing gap between the surface of the latent image carrier and the peripheral surface of the developing belt in the developing section.

The "rotation direction of the developing belt" may be the same as or opposite to the moving direction of the surface of the latent image carrier in the developing section. "Latent image carrier" includes a photoconductive photoreceptor and a thin dielectric layer formed on a conductive substrate (an electrostatic latent image can be formed by position-selective charging using a multi-needle electrode, etc.) Can be used.

As the liquid film forming means, a known doctor blade or the like can be used, and a preferable liquid film forming means is a "squeeze roller". Also, various types can be used for the `` developer supply means '', but as a desirable form, `` a storage part for storing the liquid phase developer, and immersed in the liquid phase developer in this storage part, And a liquid-phase developer supply member for holding and circulating the liquid developer and applying and supplying the held liquid-phase developer to the peripheral surface of the developing belt (claim 3). The phase developer supply member may be formed as a "porous elastic roller" and also serve as a developing belt cleaning unit (claim 4).

In the above-described electrostatic latent image developing apparatus, it is preferable that "the peripheral surface of the developing belt is made conductive and a developing bias voltage having the same polarity as that of the toner is applied to the conductive portion".
(Claim 5).

[0012] As a liquid phase developer used for development,
A developer "having toner dispersed in a dispersion medium", that is, a developer conventionally known as a developer for electrophotography can be used.In addition to the developer, "printing ink", that is,
Emulsion ink, water-based ink, oil-based ink and the like can be used. “Emulsion ink” is an oil phase in which a pigment is uniformly dispersed in a non-drying oil or a non-volatile oil.
% Of a 90% to 50% aqueous phase emulsified, or a so-called O / W type emulsified oil phase in which a pigment is uniformly dispersed in an aqueous phase. .

[0013]

In the conventional non-contact liquid developing system, the reason why unevenness in development such as the above-mentioned "white spots" occurs is considered as follows. FIG. 4D is an explanatory view showing a state of a developing unit of a conventional non-contact liquid developing system. Latent image carrier 1
Is formed with an electrostatic latent image by a positive charge (indicated by a + symbol), and a liquid-phase developer 3 and a latent image carrier, which are held as a liquid-phase developer film on the peripheral surface of a developing roller 2 in a developing section. When the peripheral surface of the liquid developer 1 approaches, the liquid developer 3 is polarized in the direction of its film thickness, and the electrostatic latent image electric field acting on the polarized charge causes the liquid developer 3 to charge the electrostatic latent image as shown in FIG. And adheres to the peripheral surface of the photoreceptor to visualize the electrostatic latent image.

When the liquid developer 3 protrudes so as to extend toward a part of the electrostatic latent image charge, it becomes difficult for the liquid developer to protrude near the protruding portion. That is, as shown, when one projection 3A is formed on the liquid phase developer 3, the surface of the liquid phase developer film around the projection 3A is depressed toward the peripheral surface of the developing roller 2. However, since the resultant force of the surface tension acts toward the outside of the liquid developer film in the “depressed portion”, the pressure is reduced, and the liquid phase developer 3 around the projection 3A is drawn to the projection 3A side.

The projection 3A continues to grow by taking in the liquid developer 3 attracted as described above. However, in the portion immediately adjacent to the projection 3A, the liquid developer 3 is strongly attracted to the projection 3A side. Therefore, in a visible image obtained as a result of the development, a so-called “white spot” occurs around the part visualized by the projection 3A, or the electrostatic latent image is a so-called “solid part”. In some cases, the white spots appear in a "mottled" shape, resulting in uneven development.
FIG. 4D shows a state immediately before the protrusion 3 </ b> A comes into contact with the surface of the latent image carrier 1.

FIG. 4A shows a state in which the developing roller 2 holding the liquid phase developer 3 on the peripheral surface is close to the surface of the latent image carrier 1. The size of the developing gap in which the non-contact liquid developing method is possible is about 400 μm or less, and FIG.
In the state (1), the width D ₀ of the developing region in which the non-contact liquid development is possible is at most only about several mm due to the curvature of the surfaces of the latent image carrier 1 and the developing roller 2. Width of development area: When D ₀ is about several mm, the frequency at which protrusions are formed in the vicinity of the same position of the liquid phase developer film while the liquid phase developer 3 passes through the width of several mm is at most Degree, and it is impossible to form the projections as many times as the "white spots" can be eliminated.

In the present invention, as shown in FIG.
The liquid phase developer 3 is held on the peripheral surface of the developing belt 20 wound around the driving pulleys 27 and 28 and is brought to the developing unit.
Since the portion of the developing belt 20 stretched on the driving pulleys 27 and 28 is located in the developing section, the curvature of the surface of the developing belt in the developing section is 0. Therefore, the width of the developing area in which the non-contact liquid development can be performed: D ₁ is allowed several 10mm to 10 carbon mm. With such a width, when the latent image carrier passes through the developing area, the protrusions of the liquid phase developer are formed a sufficient number of times in the vicinity of the same position of the liquid phase developer film. The development is performed so that the "missing" is effectively compensated for each other, and the uneven development such as white spots is effectively eliminated.

As shown in FIG. 4C, spacers 1A are formed at both ends of the peripheral surface of the latent image carrier 1 in the width direction (the direction perpendicular to the drawing), and the developing belt is driven by driving pulleys 27 and 28. 20 is pressed against the latent image carrier 1 so that the developing belt 20 between the driving pulleys 27 and 28 is
If the developing gap is kept close to the surface of the latent image carrier 1 while maintaining the developing gap, the width of the developing area can be set large as necessary. In this case, the spacer 1A and the driving pulley 27,
28 constitutes the spacer means.

[0019]

FIG. 1 shows an embodiment of the present invention according to the first, second and fifth aspects 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 developer" used in this embodiment is a developer 3 for electrophotography in which a toner is dispersed in a dispersion medium (Isoper: trade name) and is formed on the photoreceptor 1. The visible image thus obtained is a “toner image”.

In the embodiment of FIG. 1, reference numeral 20 denotes a developing belt, reference numeral 21 denotes a squeeze roller, and reference numeral 5 denotes a casing. Reference numeral 24 denotes a storage unit for storing the developer, and reference numeral 26 denotes a pump.

The developing belt 20 is formed by depositing a metal film on the outer peripheral surface of an endless belt made of a resin film, has a smooth peripheral surface, is wound around drive pulleys 27 and 28, and is 100 μm or less by a “spacer means” described later. The photosensitive member 1 is disposed in close proximity to the peripheral surface of the photosensitive member 1 via a small developing gap. The distal end of a scraper 23 whose base is held by the casing 5 abuts on a peripheral surface portion below the developing belt 20, and the scraper 23 and the peripheral surface of the developing belt 20 form a “developer liquid reservoir”.

The developer 3 as a liquid developer is stored in the storage 2
Then, the solution is pumped up from the inside of the tube 25 by the pump 26 and supplied to the developing solution reservoir. The developer 3 supplied to the developer reservoir is supplied to the peripheral surface of the developing belt 20, and moves with the peripheral surface of the developing belt 20 as the developing belt 20 rotates counterclockwise. That is, the storage unit 24, the pipe 25, and the pump 26
, The scraper 23 and the developing belt 20 constitute "developer supply means".

In the casing 5, the developing belt 20
The squeeze roller 21 disposed near the upper portion of the developing belt 20 has its peripheral surface close to the peripheral surface of the developing belt with a predetermined minute gap therebetween, rotates counterclockwise at a predetermined rotational speed, and The excess developer is scraped off to the developer reservoir.

That is, the squeeze roller 21 rotates to form a flow velocity distribution of the developing solution 3 between the peripheral surface of the developing belt and the peripheral surface of the squeeze roller. It forms a film. Thus, the excess liquid phase developer is removed from the developing belt 20 by the squeeze roller 21 as “liquid film forming means”,
A liquid developer film thinner than the developing gap is formed.

The distal end of a scraper 22 whose base is held by the casing 5 abuts on the peripheral surface of the squeeze roller 21 to constantly clean the peripheral surface of the squeeze roller 21. The developing solution film formed on the developing belt 20 is brought to the developing unit as the developing belt 20 rotates.

As described above, the outer peripheral surface of the developing belt 20 is conductive due to the metal film formed on the outer peripheral surface, and the conductive portion has a negative polarity (a polarity opposite to the latent image charge) from the DC voltage power supply 12. A developing bias voltage is applied.

Referring to FIG. 3A, the developing belt 20
Spacers 20A and 20B are formed at both ends in the width direction of the outer peripheral surface of the belt over the entire circumference of the belt. Spacer 20
A and 20B have a "thickness equal to the developing gap" and are formed by attaching a mylar film or the like.

As shown in FIG. 3B, the developing belt 20 has the spacers 20A and 20B in contact with the peripheral surface of the photosensitive member 1 at both ends in the width direction (direction orthogonal to the drawing) of the photosensitive member 1. Accordingly, the developing belt 20 and the surface of the photoconductor 1 approach each other with a predetermined developing gap in the developing section. That is, the spacers 20A and 20B constitute spacer means in this embodiment.

Returning to FIG. 1, the developing film held on the peripheral surface of the developing belt 20 is brought to the developing section by the rotation of the developing belt 20, and the electrostatic latent image is visualized by non-contact liquid development. Since the effective development area, that is, the “width of the development portion in the moving direction of the peripheral surface of the photoconductor 1” has a sufficient size, good development without uneven development such as “white spots” can be performed as described above. is there.

Since the developing bias voltage has a polarity opposite to that of the latent image charge, an electric field for promoting the developing electric field by the electrostatic latent image is formed in the developing section, and the formation of projections on the developing solution film is promoted. A high-visibility image can be obtained.

The developing solution film that has passed through the developing section by the rotation of the developing belt 20 is scraped off from the peripheral surface of the developing belt 20 to the storage section 24 by the scraper 23 as shown in FIG. The surplus developer is also supplied from the developer reservoir to the reservoir 24.
Runs down inside.

FIG. 2 shows a first embodiment of the present invention.
An example is shown. In FIG. 2, the same reference numerals as those in FIG. 1 are used for those which are considered to be free from confusion to avoid complication.

In this embodiment, the bottom of the casing 5A forms a storage section for storing the developer 3, and the elastic roller 30, which is a liquid developer supply member, is provided in the storage section. Is immersed in the developer 3.

The elastic roller 30 is formed of a porous material such as a sponge, and rotates while rotating while holding the developing solution 3 while being in pressure contact with the developing belt 20. At the same time, the peripheral surface of the developing belt 20 that has passed through the developing unit is cleaned.

The bottom of the casing 5A constituting the storage section and the elastic roller 30 constitute developer supply means. In the case of this embodiment, since the liquid supply developer assembling means such as a pump is not required in the developer supply means, the configuration of the developer supply means is simple, and there is no need to provide a dedicated cleaning device for the developing belt 20. Of course, also in this embodiment, it goes without saying that the developing belt 20 may be made conductive and a developing bias voltage having a polarity opposite to that of the latent image charge may be applied.

In the embodiment shown in FIGS. 1 and 2, a "printing ink", that is, the above-described emulsion ink, oil-based or water-based ink can be used as the liquid phase layer developer instead of the developer. Further, as the developing belt, a metal belt or a conductive rubber belt can be used instead of the above-described embodiment. If these metal belts or conductive rubber belts are used as the developing belt, the entire developing belt is conductive, so that the application of the developing bias voltage is easy when the invention of claim 5 is implemented.

[0038]

As described above, according to the present invention, a novel electrostatic latent image developing device can be provided. Claims 1-5
Since the electrostatic latent image developing device of the invention described above has the above-described configuration, good development without developing failure such as “developing unevenness” due to white spots or the like which has been a problem in conventional non-contact liquid development. It can be performed.

When a developer for electrophotography is used as the liquid phase developer as in the case of the above embodiment, the toner is replenished in the developer to compensate for the consumption of toner during development, and the toner concentration is adjusted. However, if a printing ink is used as the liquid phase developer, the ink is consumed as the ink itself and there is no change in the solid component in the ink, so that an adjusting action such as "toner density adjustment" is not required.

The "spacer means" is not limited to the above-described one, and any means can be used as long as it can maintain a predetermined developing gap between the surface of the latent image carrier and the peripheral surface of the developing belt in the developing section. Any appropriate one can be used.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the invention described in claims 1, 2 and 5;

FIG. 2 is a diagram for explaining one embodiment of the invention described in claims 1, 2 and 4;

FIG. 3 is a view for explaining spacer means in the embodiment.

FIG. 4 is a diagram for explaining the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 3 Liquid phase developer (developer) 20 Developing belt 20A, 20B Spacer

Continuation of front page (56) References JP-A-53-137154 (JP, A) JP-A-1-237578 (JP, A) JP-A-2-284175 (JP, A) JP-A-62-47075 (JP) , A) JP-B-51-22819 (JP, B2) JP-B-49-10259 (JP, B2)

Claims (5)

(57) [Claims] 1. An apparatus for supplying a liquid developer held on a peripheral surface of a rotating body 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 close to the surface of the latent image carrier at a predetermined developing section with a development gap therebetween, and holds the liquid phase developer in a thin film on the peripheral surface and rotates in a predetermined direction. By doing so, a developing belt that brings the retained liquid-phase developer to the developing section, a developer supply unit that supplies the liquid-phase developer to the peripheral surface of the developing belt, and an excess liquid-phase developer from the developing belt A liquid film forming means for removing and forming a liquid phase developer film thinner than the developing gap; and, in the developing section, a predetermined developing gap between the surface of the latent image carrier and the peripheral surface of the developing belt. And a spacer means for maintaining the developing belt, between the driving pulleys of the developing belt. By positioning the stretched peripheral portion at the developing portion, it is possible to prevent development unevenness such as white spots or the like in the moving direction of the peripheral surface of the developing belt in the opposing portion between the latent image carrier and the developing belt. An electrostatic latent image developing device of a non-contact liquid developing type, wherein an effective developing area is formed to a sufficient extent. 2. The electrostatic latent image developing device according to claim 1, wherein the liquid film forming means is a squeeze roller.
Non-contact liquid developing type electrostatic latent image developing device. 3. An electrostatic latent image developing apparatus according to claim 1, wherein said developer supply means stores a liquid phase developer, and is immersed in said liquid phase developer in said storage section. A non-contact liquid developing type electrostatic latent device, comprising: a liquid phase developer supply member that holds the developer and rotates cyclically, and applies and supplies the held liquid phase developer to the peripheral surface of the developing belt. Image developing device. 4. A latent electrostatic image developing device according to claim 3, non of the liquid phase developer supplying member, an elastic roller of porous, characterized in that it also serves as a developing belt cleaning means
An electrostatic latent image developing device of a contact liquid developing type . 5. The electrostatic latent image developing device according to claim 1, wherein the peripheral surface of the developing belt is conductive, and a developing bias voltage having a polarity opposite to that of the latent image charge is applied. Characteristic non-contact
Liquid developing type electrostatic latent image developing device.